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সকালের নাশতা বা ব্রেকফাস্ট সারা দিনের সুস্থতার জন্য গুরুত্বপূর্ণ। সকালে আমাদের মেটাবলিজম বা বিপাকক্রিয়ার শুরু, এ সময় সব ধরনের হরমোনও থাকে সক্রিয়।

সকালের স্বাস্থ্যকর খাবার দিয়ে শুরু হবে দিনটা। সকালের নাশতা বাদ দিলে বা সময়মতো না খেলে সারা দিন ক্লান্ত লাগতে পারে। স্ট্যামিনা কমে যেতে পারে কাজের। কিন্তু ওদিকে আপনি হয়তো ডায়েট কন্ট্রোল করছেন, ক্যালরি মেপে খাচ্ছেন। তাহলে কেমন হওয়া উচিত আপনার স্বাস্থ্যকর নাশতা?: যাঁরা ডায়েট করতে চান, তাঁদের উচিত হবে সকালের নাশতায় ২০০ থেকে ৩০০ ক্যালরি পরিমাণ খাবার গ্রহণ করা। এই খাবারে জটিল শর্করা ও আমিষ থাকতেই হবে। চর্বি বা তেল খুব কম পরিমাণে। সঙ্গে একটি তাজা ফল থাকা ভালো।

: বাড়িতে তৈরি রুটি এবং বাজারের গোটা শস্যের তৈরি ব্রাউন ব্রেড বা সিরিয়ালের চেয়ে পরোটা, নানরুটি বা সাদা পাউরুটিতে ক্যালরি ও চর্বির মাত্রা অনেক বেশি।

: সকালের নাশতায় খানিকটা আঁশ বা ফাইবার থাকলে কোষ্ঠকাঠিন্য দূর করা সহজ হবে। সকালের দিকেই কোষ্ঠ পরিষ্কার হবে।

স্বাস্থ্যকর নাশতা কেমন হতে পারে তার উদাহরণ



দুটি হাতে বেলা ছোট রুটি বা চাপাতি (প্রতিটি ৮০ ক্যালরি = ১৬০ ক্যালরি)

এক বাটি সবজি (১৫০ গ্রাম = ৮০ ক্যালরি)

অর্ধেক কলা (৬০ ক্যালরি)



১টা রুটি বা চাপাতি (৮০ ক্যালরি)

১টা ডিম (১৬০ ক্যালরি)

আধা বাটি ডাল (৮০ ক্যালরি)



এক বোল পরিজ দুধ: ২১৭ ক্যালরি



১ কাপ দুধ (১৫০ ক্যালরি)

২ স্লাইস ব্রাউন ব্রেড (১৫৫ ক্যালরি)
source: ebanglahealth

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রান্নাঘরে থাকা শতাব্দী প্রাচীন দুই পণ্য ঘি ও মাখন। এই দুটিই খাদ্য হিসেবে ভারতবর্ষের মানুষের কাছে খুবই জনপ্রিয়। কিন্তু, ঘি মাখনের মধ্যে কোনটা বেশি স্বাস্থ্যকর, তা নিয়ে বিতর্ক চিরকালীন। তবে, চলুন আজ জেনে নেওয়া যাক এই দ্বন্দ বা বিতর্কের জয়ী আসলে কে। মাখন না ঘি?
ঘি ভারত ও মধ্য প্রাচ্যের রান্না, বিভিন্ন ধর্মীয় অনুষ্ঠান এবং ঔষধগুলিতে ব্যবহৃত একটি সাধারণ পণ্য। অন্যদিকে, মাখন হল দুধ ও ক্রিম দ্বারা প্রস্তুত একটি সাধারন দুগ্ধজাত পণ্য। অনেকেই ঘি-কে সুপারফুড হিসেবে বিবেচনা করে। কারণ, এতে ভাল ফ্যাট থাকে যা, শরীর ও ত্বকের জন্য খুবই উপকারি। কিন্তু, মাখনে ফ্যাট ও ভিটামিনের পরিমান কম থাকে বলে এতে ক্যালোরি কম থাকে। আসুন উভয়ের সম্পর্কে আরও বিস্তারিত জেনে নেওয়া যাক।
ঘি এবং মাখনের মধ্যে পার্থক্য বেশ কয়েকটি দিকের উপর ভিত্তি করে ঘি এবং মাখনের পার্থক্য করা হয়েছে। এখানে কয়েকটি কারণ রয়েছে যা, আপনাকে দুটোর মধ্যে পার্থক্য বুঝতে এবং আপনার স্বাস্থ্যের জন্য কোনটি সেরা তা জানাতে সহায়তা করবে। ১) পুষ্টির মান প্রতি ১০০ গ্রাম ঘি-তে ০.২৪ গ্রাম জল এবং ৮৭৬ কিলো ক্যালোরি শক্তি থাকে। এটিতে ০.২৮ গ্রাম প্রোটিন, ৪ মিলিগ্রাম ক্যালসিয়াম, ৩ মিলিগ্রাম ফসফরাস, ২২.৩ মিলিগ্রাম কোলিন, ৮৪০ মাইক্রো গ্রাম(এমসিজি) ভিটামিন-এ, ৮২৪ মাইক্রো গ্রাম রেটিনল(ভিটামিন-এ১), ২.৮ মিলিগ্রাম ভিটামিন-ই, ৮.৬ মাইক্রো গ্রাম ভিটামিন-কে, ১৯৩ মাইক্রো গ্রাম ক্যারোটিন(বিটা)সাথে রয়েছে ভিটামিন-বি ১২, ভিটামিন-বি৬ এবং ভিটামিন-বি৩। ঘি-এর গুরুত্বপূর্ণ উপাদান হল ফ্যাটি অ্যাসিড যা শরীরের বিপাক ক্রিয়াকে উন্নত করতে সহায়তা করে।
২) কীভাবে তৈরি করা হয়

ঘি প্রস্তুত ঘি এবং মাখন উভয়ই গরুর দুধ থেকে প্রাপ্ত। দুধের মালাই বা ক্রিম থেকে খুব সহজেই ঘরে ঘি তৈরি করা যায়। মালাইকে কম তাপমাত্রায় দীর্ঘক্ষণ নাড়ুন যাতে শক্ত অংশ(বাটারফ্যাট) এবং তরল অংশ(বাটার মিল্ক) পৃথক করা যায়। বাজারের আনসল্টেড মাখন থেকেও ঘি তৈরি করা যায়। কম তাপমাত্রায় মাখনকে গলিয়ে নিন। ঘি-এর মত তরলটি আলাদা না হওয়া পর্যন্ত এবং দুধের সলিডগুলি নীচে জড়ো না হওয়া পর্যন্ত ফোটাতে থাকুন। নিচে জমা হওয়া দুধের বাটারফ্যাট গুলি বাদামি না হওয়া পর্যন্ত অপেক্ষা করুন যতক্ষণ না পর্যন্ত ঘি-এর রঙ এবং গন্ধ বেরোয়। মাখন প্রস্তুত সেন্ট্রিফিউগেশন নামক প্রক্রিয়াটির মাধ্যমে গরুর দুধকে ক্রিমে রূপান্তরিত করে মাখন প্রস্তুত করা হয়। যেখানে একটি মেশিনের সাহায্যে দুধ ও মালাইকে উচ্চ গতিতে ঘোরানো হয়। ক্রিম উৎপাদিত হওয়ার পর তাকে ঘন করা হয়। কখনও কখনও এতে লবণ ও সুগন্ধিও ব্যবহার করা হয়। ক্রিমের তরল অংশ(বাটার মিল্ক) আলাদা করা হয় এবং শক্ত অংশটিকে মাখনে পরিনত করা হয়। ৩) অ্যালার্জি যাদের ল্যাকটোজ যুক্ত খাবারে এলার্জি তাদের জন্য ঘি সেরা হিসেবে বিবেচিত হয়। মাখনে দুগ্ধ প্রোটিন(কেসিন)উপস্থিত থাকে যা, অ্যালার্জির কারণ হতে পারে। এছাড়াও ফুসকুড়ি, চুলকানি এবং হাঁপানির মতো লক্ষণও দেখা দিতে পারে।

ঘি-এর স্বাস্থ্যকর উপকারিতা ১) ক্যান্সার প্রতিরোধ করে ঘি-তে ভিটামিন-ই রয়েছে। এটি অন্যতম শক্তিশালী অ্যান্টি-অক্সিড্যান্ট যা, দেহে জারণ চাপ কমাতে সহায়তা করে এবং ক্যান্সারের বিরুদ্ধে লড়তে সাহায্য করে। ২) ল্যাকটোজ কম একটি সমীক্ষায় দেখা গেছে যে, ঘি-তে অনেক কম পরিমাণে ল্যাকটোজ রয়েছে। কারণ, ঘি এমনভাবে প্রস্তুত করা হয় যাতে দুধের অংশটি তার থেকে আলাদা হয়ে যায় অর্থাৎ, দুধে থাকা ল্যাকটোজ বেরিয়ে যায়। ফলে, ল্যাকটোজে অ্যালার্জি রয়েছে এমন ব্যক্তিদের জন্য এটি অত্যন্ত উপকারি। ৩) হার্টের জন্য ভাল আমেরিকান হার্ট অ্যাসোসিয়েশনের সমীক্ষা অনুসারে, ঘি এর অল্প ব্যবহারই (৭ শতাংশ এর কম) হৃদরোগজনিত সমস্যা প্রতিরোধ করতে সহায়তা করতে পারে। গবেষণায় আরও বলা হয়েছে যে, ১০ শতাংশ পর্যন্ত ডায়েটরি ঘি কোলেস্টেরল এবং লাইপো-প্রোটিনের মাত্রা হ্রাস করতে সহায়তা করে। ৪) হাড়ের গঠনে ঘি-য়ে থাকা ভিটামিন-কে ক্যালসিয়ামের সঙ্গে মিলে হাড়ের স্বাস্থ্যকে ঠিক রাখতে এবং হাড়ের গঠনে সহায়তা করে।
মাখনের স্বাস্থ্যকর উপকারিতা ১) পরিপাক ক্রিয়া উন্নতি করে বাটারে গ্লাইকোস-ফিংগোলিপিডস নামে একটি বিশেষ ধরণের ফ্যাটি অ্যাসিড থাকে যা, ব্যাকটিরিয়া সংক্রমণ এবং অন্যান্য বিভিন্ন অসুবিধাগুলির বিরুদ্ধে লড়াই করে পরিপাক ক্রিয়াকে ঠিক রাখতে সহায়তা করে। ২) থাইরয়েড থেকে রক্ষা করে শরীরে ভিটামিন-এ এর অভাবজনিত কারণে অনেকেই থাইরয়েডের সমস্যার মুখোমুখি হন। মাখন ভিটামিন-এ সমৃদ্ধ হওয়ায় তা থাইরয়েড গ্রন্থি দ্বারা নিঃসৃত হরমোনগুলির সঠিক কার্যকারিতা এবং নিঃসরণে সহায়তা করে। ৩) আর্থ্রাইটিস প্রতিরোধ করে বাটারে ওলজেন ফ্যাক্টর নামে একটি বিশেষ যৌগ রয়েছে, যা অ্যান্টি-স্টিফনেস ফ্যাক্টর হিসেবেও পরিচিত। এটি বাত এবং স্পাইনাল গ্রন্থির ক্যালসিকিফিকেশন থেকে রক্ষা করে।

কোনটি বেছে নেবেন? ঘি এবং মাখন উভয়ের পুষ্টিগুণই প্রায় একরকম। তবে, ঘি কিছু দিক থেকে স্বাস্থ্যের পক্ষে ভাল এবং মাখন অন্যান্য দিক থেকে সেরা। তারা দু'জনেই খুব সামান্য পার্থক্যের সঙ্গে নিজস্বতার দিক থেকে রাজা। অতএব, মাখন বা ঘি পছন্দ করা সম্পূর্ণরূপে একজন ব্যক্তির উপর নির্ভর করে।





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আমাদের শরীরে হিমোগ্লোবিন উৎপাদনের জন্য আয়রন একটি প্রয়োজনীয় খনিজ এবং এটি দেহের অন্যান্য গুরুত্বপূর্ণ প্রক্রিয়াতেও ভূমিকা রাখে। কোনও ব্যক্তির দেহে অপর্যাপ্ত আয়রন থাকার ফলে আয়রনের ঘাটতিজনিত রক্তাল্পতা(Iron Deficiency Anaemia) হয়। এর ফলে, দেহে পর্যাপ্ত স্বাস্থ্যকর লাল রক্তকণিকার অভাব হয়। রক্তাল্পতা প্রতিরোধ থেকে শুরু করে দেহের শক্তি বাড়াতে, এই খনিজটির প্রচুর উপকারিতা রয়েছে। আয়রনের স্বাস্থ্য উপকারিতা সম্পর্কে জানতে আর্টিকেলটি পড়ুন। আয়রনের স্বাস্থ্য উপকারিতা

১) রক্তাল্পতা প্রতিরোধ করে হিমোগ্লোবিনের উৎপাদন বৃদ্ধির জন্য একটি মানবদেহে আয়রন প্রয়োজন হয়। আয়রন রক্তস্বল্পতাজনিত রোগের চিকিৎসা ও প্রতিরোধে সহায়ক, যা হিমোগ্লোবিনের মাত্রা কম হওয়ার ফলে হয় এবং এর বিভিন্ন লক্ষণ হল - ক্লান্তি, খারাপ মেজাজ, শ্বাসকষ্ট, ইত্যাদি। হিমোগ্লোবিন এমন একটি প্রোটিন যা, লোহিত রক্তকণিকায় উপস্থিত থাকে। এই প্রোটিন লাল রক্ত ​​কণিকাকে ফুসফুস থেকে শরীরের অন্যান্য অংশে অক্সিজেন বহন করতে সহায়তা করে।

২) প্রতিরোধ ক্ষমতা বাড়ায় আয়রন প্রতিরোধ ক্ষমতা বাড়াতে গুরুত্বপূর্ণ ভূমিকা পালন করে। এটি ক্ষতিগ্রস্থ কোষ, টিস্যু এবং অঙ্গগুলিতে হিমোগ্লোবিনের মাত্রা বাড়ায়। এছাড়াও, বিভিন্ন সংক্রমণের সাথে লড়াই করতে এবং রোগ প্রতিরোধে সহায়তা করে।
৩) ফোকাস এবং একাগ্রতা উন্নত করে ডায়েটে আয়রন অন্তর্ভুক্ত করার আরেকটি কারণ হল, ফোকাস এবং একাগ্রতা উন্নত করা। দেহে আয়রনের মাত্রা কম হওয়া আমাদের জ্ঞান ভিত্তিক ক্রিয়াকে অনেকাংশে প্রভাবিত করে, যার ফলে কোনও কিছুতে মনোযোগ কম হয়, স্মৃতি লোপ পায়।

৪) শক্তি বাড়ায় অপর্যাপ্ত পরিমাণ আয়রন গ্রহণের ফলে ক্লান্তি আসে যা, একজন ব্যক্তির প্রতিদিনের ক্রিয়াকলাপে হস্তক্ষেপ করে। সুতরাং, আপনার দেহে যত বেশি আয়রন থাকবে আপনি তত বেশি শক্তিশালী বোধ করবেন কারণ, আয়রন পেশী এবং মস্তিষ্কে অক্সিজেন বহন করে যা, শারীরিক এবং মানসিক উভয় কার্যকারিতার জন্য অত্যন্ত গুরুত্বপূর্ণ।

৫) স্বাস্থ্যকর গর্ভাবস্থা গর্ভাবস্থায়, রক্তের পরিমাণ এবং লাল রক্ত কণিকার উৎপাদন খুব দ্রুত হারে বৃদ্ধি পায়। যদি গর্ভাবস্থায় আয়রনের মাত্রা কম থাকে তবে, অকাল জন্ম, জন্মের সময় ওজন কম, শিশুদের মধ্যে প্রতিবন্ধী আচরণ এবং জ্ঞান ভিত্তিক ক্রিয়ার ঝুঁকি বাড়ায়।

৬) পেশী শক্তি বৃদ্ধি করে পর্যাপ্ত পরিমাণ আয়রন দেহের পেশীগুলির শক্তি এবং স্থিতিস্থাপকতার জন্য প্রয়োজনীয় পরিমাণে অক্সিজেন সরবরাহ করে। এটি অ্যাথলেটিকদের পারফরম্যান্স আরও ভাল করতে সহায়তা করে। আয়রনের মাত্রা কম হলে পেশীর দুর্বলতা দেখা দেয়।



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কিউই, নামটি হয়তো শুনে থাকবেন। এটি অত্যন্ত সুস্বাদু একটি ফল। স্বাদের মতোই এর গুনাগুণও অঢেল। কয়েক দশক আগে এই ফলের প্রচলন ভারতবর্ষে সে ভাবে দেখা যায়নি। তবে, বর্তমানে ভারতের কিছু জায়গায় ফলটি পাওয়া যায় এবং এর গুনাগুণ সম্পর্কে প্রায় অনেকেই ওয়াকিবহাল।এশিয়া এবং অস্ট্রেলিয়ায় এই ফল জনপ্রিয়তা পেলেও ভারতের বহু জায়গায় এখনও দেখা যায় না এই ফল। খাস কলকাতাতেও প্রায় দেখা যায় না বললেই চলে। তবে জিটিএ সূত্রে খবর, দার্জিলিং, সিকিম সহ পার্শ্ববর্তী এলাকায় কিউই চাষের পরিকল্পনা শুরু হয়েছে। সাফল্যও পাওয়া গেছে সিকিম ও রঞ্জু ভ্যালিতে। স্বাদে ভরপুর এই ফলের স্বাস্থ্য উপকারিতাও কিন্তু প্রচুর। একটি ফল খেলেই পাবেন হাজারো সমস্যা থেকে মুক্তি। তবে চলুন জেনে নেওয়া যাক কিউই-এর স্বাস্থ্য উপকারিতা সম্পর্কে।উৎপত্তি ও কোন দেশে বেশি প্রচলন কিউই মূলত চিন দেশের ফল, যেটি দেখতে অনেকটা লেবুর মত। ফলের বাইরের রঙ গোল্ডেন ব্রাউন এবং ভেতরে সবুজ রঙের হয়। চিন দেশে গুজবেরি ও ইয়াং টাও নামেও পরিচিত এই ফলটি। তবে বর্তমানে ‘কিউই' হিসেবেই বেশি পরিচিতি লাভ করেছে। কিউই একটি অত্যন্ত সুস্বাদু বেরি, যা চীন থেকে নিউজিল্যান্ডে ২০ শতকের গোড়ার দিকে আনা হয়েছিল। ঐতিহাসিকভাবে, এটি নিউজিল্যান্ডের জাতীয় ফল হিসেবেও পরিচিত। ইউরোপ, আমেরিকা, ক্যালিফোর্নিয়া এবং গ্রিসেও বেশ জনপ্রিয়। বর্তমানে দক্ষিণ ভারতের কিছু কিছু জায়গায় মাঝেমাঝে এই ফলের প্রচলন দেখা যায়।

১) হার্টকে সুস্থ রাখে কিউই ফল ভিটামিন-সি এবং পটাসিয়াম সমৃদ্ধ, যা কার্ডিওভাসকুলার স্বাস্থ্যের জন্য খুবই ভাল। একটি সমীক্ষায় দেখা গেছে যে, প্রতিদিন এক থেকে দুটি করে কিউই ফল খেলে অক্সিডেটিভ স্ট্রেস হওয়ার সম্ভাবনা হ্রাস পায় যা, হৃদরোগসহ বিভিন্ন স্বাস্থ্য সমস্যাকে দূর করতে সাহায্য করে। এটি খেলে রক্তে ফ্যাটের পরিমাণ কমানো যায়, ফলে ব্লকেজ প্রতিরোধ করা সম্ভব হয়। এছাড়া, কিউইতে থাকা ম্যাগনেসিয়াম হার্ট ভাল রাখতে সাহায্য করে।


২) রোগ প্রতিরোধ ক্ষমতাকে শক্তিশালী করে কিউই ফলে থাকা ভিটামিন-সি ও অ্যান্টি অক্সিডেন্ট রোগ প্রতিরোধ ক্ষমতা বাড়াতে এবং রোগ প্রতিরোধে সহায়তা করে। কানাডিয়ান জার্নাল অফ ফিজিওলজি অ্যান্ড ফার্মাকোলজিতে প্রকাশিত হওয়া একটি সমীক্ষায় দেখা গেছে যে, কিউই ফলগুলি রোগ প্রতিরোধ ক্ষমতাকে জোরদার করে এবং ঠান্ডা বা ফ্লু-এর মতো অসুস্থতার সম্ভাবনাকে হ্রাস করে।

৩) হজমে সহায়তা করে কিউই ফলে অ্যাক্টিনিডিন(Actinidin) নামক এনজাইম থাকে যা, প্রোটিন-দ্রবীভূত বৈশিষ্ট্যের জন্য পরিচিত। কিউইতে থাকা ফাইবার হজমে সহায়তা করে। একটি সমীক্ষায় দেখা গেছে যে, কিউই দ্বিগুণ পরিমাণ হজমশক্তি বাড়িয়ে তুলতে পারে এবং হজমের সমস্যাগুলিকে ঠিক করে তোলে।

৪) চোখ ভাল রাখে ও দৃষ্টিশক্তি বৃদ্ধি করে কিউই ফল ফাইটোকেমিক্যালের একটি ভাল উৎস, যা ম্যাকুলার অবক্ষয় প্রতিরোধে সহায়তা করে। কিউই ফলের মধ্যে উপস্থিত ভিটামিন-এ এবং ফাইটোকেমিক্যাল চোখের ছানি এবং বয়সজনিত কারণে চোখের বিভিন্ন সমস্যা প্রতিরোধ করতে সাহায্য করে।

৫) হাড় ও দাঁত ভাল রাখে কিউই-তে থাকে ভিটামিন-এ, ভিটামিন-সি, বি-৬, বি-১২, পটাসিয়াম, ক্যালসিয়াম, লোহা এবং ম্যাগনেসিয়ামের মতো ভিটামিন ও খনিজ পদার্থ, যা শরীরের রক্ত সঞ্চালনকে ঠিক রাখে এবং হাড় ও দাঁতকে ভালো রাখতে সাহায্য করে।



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It was predicted 30 years ago, now the effect was measured for the first time by scientists at TU Wien (Vienna): The neutron spin exhibits inertial effects.

Let’s assume we are dancing on a meadow, quickly spinning about our own axis. At some point we hop on a rotating carousel. We may end up hurting ourselves when both rotations add up and angular momentum is transferred. Are similar phenomena also present in quantum mechanical systems?

After years of preparation, a team at the TU Wien managed to conduct an experiment where the spin of a neutron traverses through a region with a rotating magnetic field. A special kind of coil had to be developed to produce this rotating magnetic field. Although the neutron spin does not carry any mass and can only be described quantum mechanically, it exhibits an inertial property. These results have now been published in “Nature Partner Journal Quantum Information”.

The Inertia of Rotation: Big Wheels Keep on Turning
“Inertia is a ubiquitous feature,” Stephan Sponar of the Institute of Atomic and Subatomic Physics at TU Wien illustrates. “When we sit on a train which moves at constant speed, we cannot tell the difference to a train parked at the station. Only when changing the frame of reference, e.g. when jumping off the train, we are decelerated. We feel forces due to the inertia of our mass.”

When rotations are considered, things are similar: the angular momentum of a rotating object is conserved as long as no external torque is applied. But when considering quantum particles, things become more complicated: “Particles like neutrons or electrons feature a special kind of angular momentum – the spin”, says Armin Danner, lead author of the newly published paper.

Spin is the intrinsic orbital angular momentum of an elementary particle. There are similarities to the rotation of a planet rotating about its axis, but in many regards this comparison does not hold: the spin is a property of pointlike particles. With a classical mindset, they cannot rotate about any axis. “Spin can be regarded as the angular momentum of an object which is constricted to a point,” Armin Danner says. The properties of such a spin are not to be found in our everyday life. But the formalism of quantum mechanics can give us an intuitive idea how things work for some cases.   

Coupling Between Spin and Magnetic Field
“Way back in 1988, colleagues already predicted how a neutron should behave when it is suddenly exposed to rotation”, Prof. Yuji Hasegawa, head of the neutron interferometry group, explains. “A coupling between the neutron spin and a rotating magnetic field was predicted. But until now, no one could directly demonstrate this coupling in its quantum mechanical form. It also took us a few years of work and several attempts to do that.”

Similar to a dancer which has spin and crosses a rotating carousel, the neutron is exposed to a rotating magnetic field. This field manipulates the spin, however, the spin orientations before and after the magnetic field are the same. After traversing the region with the magnetic field, the angular momentum of the neutron is exactly the same as before. The only thing that “happened” to the neutron is that it experienced effects of inertia, which are detectable by means of quantum mechanics.

In the experimental setup, the neutron beam is split into two separated partial beams. One of them is exposed to a rotating field while the other is unaffected. Both partial beams are then recombined. Following the rules of quantum mechanics, the neutron travels along both paths simultaneously. In the first path, effects of inertia locally change the wavelength of the particle-wave. This determines how the partial waves amplify and extinguish each other.

The biggest challenge was the design of the magnetic coil which produces the magnetic field. A small window inside the coil is needed for the neutron beam to pass through. However, the field properties must comply with the strict conditions to induce the desired field. A suitable geometry was identified with the help of computer simulations. The system was developed and tested at the neutron source of the TU Wien in the Viennese Prater while the final measurements were conducted at the ILL in Grenoble, France.

“It is fascinating that we induced a pure quantum effect which at first cannot be understood classically,” Armin Danner points out. “Our intuition should therefore not help us here at all. But we could demonstrate for a very specific case that the classical concept of inertia is still valid for the neutron spin.”
source:scitechdaily

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At least 26 percent of our oceans need urgent conservation attention to preserve Earth’s marine biodiversity, a University of Queensland-led international study has found.

Dr. Kendall Jones said the international community needed to rapidly increase marine conservation efforts to maintain the health of the world’s oceans.

“Preserving a portion of habitat for all marine species would require 8.5 million square kilometers of new conservation areas,” Dr. Jones said.

“Currently one-third of all marine species have less than 10 percent of their range covered by protected areas.

“Conserving the areas we’ve identified in our study would give all marine species a reasonable amount of space to live free from human impacts like fishing, commercial shipping or pesticide runoff.”

The authors mapped more than 22,000 marine species habitats and applied a mathematical approach to identify the minimum area required to capture a portion of each species range.

They also included areas of international importance for biodiversity (known as Key Biodiversity Areas), and areas where human impacts on the ocean are extremely low (known as marine wildernesses).

They found that the total ocean area required for conservation varied from 26-41 percent, depending on the proportion of each species range conserved.

Key regions for conservation included the Northern Pacific Ocean near China and Japan, and the Atlantic between West Africa and the Americas.

Director of Science at the Wildlife Conservation Society and UQ scientist Professor James Watson said the findings demonstrated the need for greater worldwide conservation efforts.

“The world’s nations will be coming together in China this year to sign an agreement that will guide global conservation for the next ten years,” Professor Watson said.

“This science shows that governments must act boldly, as they did for the Paris Agreement on climate change, if we are to stop the extinction crisis facing many marine species.”

Professor Watson said it was crucial that global conservation strategies involved rapid action to protect endangered species and ecosystems, combined with approaches to sustainably manage the ocean in its entirety.

“This isn’t just about strict marine protected areas,” he said.

“We need to use a broad range of strategies such as no-fishing zones, community marine reserves and broad-scale policies to put an end to illegal and unsustainable commercial fishing operations.”

The authors stress that ocean conservation was essential for people and biodiversity.

“Millions of people around the world depend on marine biodiversity as a crucial source of food and income,” Professor Watson said.

“A well-designed global conservation agreement will help preserve these livelihoods into the future.”

37
What if solar cells worked at night? That’s no joke, according to Jeremy Munday, professor in the Department of Electrical and Computer Engineering at UC Davis. In fact, a specially designed photovoltaic cell could generate up to 50 watts of power per square meter under ideal conditions at night, about a quarter of what a conventional solar panel can generate in daytime, according to a concept paper by Munday and graduate student Tristan Deppe. The article was published in, and featured on the cover of, the January 2020 issue of ACS Photonics.

Munday, who recently joined UC Davis from the University of Maryland, is developing prototypes of these nighttime solar cells that can generate small amounts of power. The researchers hope to improve the power output and efficiency of the devices.
Munday said that the process is similar to the way a normal solar cell works, but in reverse. An object that is hot compared to its surroundings will radiate heat as infrared light. A conventional solar cell is cool compared to the sun, so it absorbs light.

Space is really, really cold, so if you have a warm object and point it at the sky, it will radiate heat toward it. People have been using this phenomenon for nighttime cooling for hundreds of years. In the last five years, Munday said, there has been a lot of interest in devices that can do this during the daytime (by filtering out sunlight or pointing away from the sun).

Generating power by radiating heat
There’s another kind of device called a thermoradiative cell that generates power by radiating heat to its surroundings. Researchers have explored using them to capture waste heat from engines.

“We were thinking, what if we took one of these devices and put it in a warm area and pointed it at the sky,” Munday said.

This thermoradiative cell pointed at the night sky would emit infrared light because it is warmer than outer space.

“A regular solar cell generates power by absorbing sunlight, which causes a voltage to appear across the device and for current to flow. In these new devices, light is instead emitted and the current and voltage go in the opposite direction, but you still generate power,” Munday said. “You have to use different materials, but the physics is the same.”

The device would work during the day as well, if you took steps to either block direct sunlight or pointed it away from the sun. Because this new type of solar cell could potentially operate around the clock, it is an intriguing option to balance the power grid over the day-night cycle.



38
MIT engineers devise a decision map to identify the best mission type to deflect an incoming asteroid.
On April 13, 2029, an icy chunk of space rock, wider than the Eiffel Tower is tall, will streak by Earth at 30 kilometers per second, grazing the planet’s sphere of geostationary satellites. It will be the closest approach by one of the largest asteroids crossing Earth’s orbit in the next decade.

Observations of the asteroid, known as 99942 Apophis, for the Egyptian god of chaos, once suggested that its 2029 flyby would take it through a gravitational keyhole — a location in Earth’s gravity field that would tug the asteroid’s trajectory such that on its next flyby, in the year 2036, it would likely make a devastating impact.

Thankfully, more recent observations have confirmed that the asteroid will sling by Earth without incident in both 2029 and 2036. Nevertheless, most scientists believe it is never too early to consider strategies for deflecting an asteroid if one were ever on a crash course with our home planet.

Now MIT researchers have devised a framework for deciding which type of mission would be most successful in deflecting an incoming asteroid. Their decision method takes into account an asteroid’s mass and momentum, its proximity to a gravitational keyhole, and the amount of warning time that scientists have of an impending collision — all of which have degrees of uncertainty, which the researchers also factor in to identify the most successful mission for a given asteroid.

The researchers applied their method to Apophis, and Bennu, another near-Earth asteroid which is the target of OSIRIS-REx, an operational NASA mission that plans to return a sample of Bennu’s surface material to Earth in 2023. REXIS, an instrument designed and built by students at MIT, is also part of this mission and its task is to characterize the abundance of chemical elements at the surface.

In a paper appearing this month in the journal Acta Astronautica, the researchers use their decision map to lay out the type of mission that would likely have the most success in deflecting Apophis and Bennu, in various scenarios in which the asteroids may be headed toward a gravitational keyhole. They say the method could be used to design the optimal mission configuration and campaign to deflect a potentially hazardous near-Earth asteroid.

“People have mostly considered strategies of last-minute deflection, when the asteroid has already passed through a keyhole and is heading toward a collision with Earth,” says Sung Wook Paek, lead author of the study and a former graduate student in MIT’s Department of Aeronautics and Astronautics. “I’m interested in preventing keyhole passage well before Earth impact. It’s like a preemptive strike, with less mess.”

Paek’s co-authors at MIT are Olivier de Weck, Jeffrey Hoffman, Richard Binzel, and David Miller.

Deflecting a planet-killer
In 2007, NASA concluded in a report submitted to the U.S. Congress that in the event that an asteroid were headed toward Earth, the most effective way to deflect it would be to launch a nuclear bomb into space. The force of its detonation would blast the asteroid away, though the planet would then have to contend with any nuclear fallout. The use of nuclear weapons to mitigate asteroid impacts remains a controversial issue in the planetary defense community.

The second best option was to send up a “kinetic impactor” — a spacecraft, rocket, or other projectile that, if aimed at just the right direction, with adequate speed, should collide with the asteroid, transfer some fraction of its momentum, and veer it off course.

“The basic physics principle is sort of like playing billiards,” Paek explains.

For any kinetic impactor to be successful, however, de Weck, a professor of aeronautics and astronautics and engineering systems, says the properties of the asteroid, such as its mass, momentum, trajectory, and surface composition must be known “as precisely as possible.” That means that, in designing a deflection mission, scientists and mission managers need to take uncertainty into account.

“Does it matter if the probability of success of a mission is 99.9 percent or only 90 percent? When it comes to deflecting a potential planet-killer, you bet it does,” de Weck says. “Therefore we have to be smarter when we design missions as a function of the level of uncertainty. No one has looked at the problem this way before.”

Closing a keyhole
Paek and his colleagues developed a simulation code to identify the type of asteroid deflection mission that would have the best possibility of success, given an asteroid’s set of uncertain properties.

The missions they considered include a basic kinetic impactor, in which a projectile is shot into space to nudge an asteroid off course. Other variations involved sending a scout to first measure the asteroid to hone the specs of a projectile that would be sent up later, or sending two scouts, one to measure the asteroid and the other to push the asteroid slightly off course before a larger projectile is subsequently launched to make the asteroid miss Earth with near certainty.

The researchers fed into the simulation specific variables such as the asteroid’s mass, momentum, and trajectory, as well as the range of uncertainty in each of these variables. Most importantly, they factored in an asteroid’s proximity to a gravitational keyhole, as well as the amount of time scientists have before an asteroid passes through the keyhole.

“A keyhole is like a door — once it’s open, the asteroid will impact Earth soon after, with high probability,” Paek says.

The researchers tested their simulation on Apophis and Bennu, two of only a handful of asteroids for which the locations of their gravitational keyholes with respect to Earth are known. They simulated various distances between each asteroid and their respective keyhole, and also calculated for each distance a “safe harbor” region where an asteroid would have to be deflected so that it would avoid both an impact with Earth and passing through any other nearby keyhole.

They then evaluated which of the three main mission types would be most successful at deflecting the asteroid into a safe harbor, depending on the amount of time scientists have to prepare.

For instance, if Apophis will pass through a keyhole in five years or more, then there is enough time to send two scouts — one to measure the asteroid’s dimensions and the other to nudge it slightly off track as a test — before sending a main impactor. If keyhole passage occurs within two to five years, there may be time to send one scout to measure the asteroid and tune the parameters of a larger projectile before sending the impactor up to divert the asteroid. If Apophis passes through its keyhole within one Earth year or less, Paek says it may be too late.

“Even a main impactor may not be able to reach the asteroid within this timeframe,” Paek says.

Bennu is a similar case, although scientists know a bit more about its material composition, which means that it may not be necessary to send up investigatory scouts before launching a projectile.

With the team’s new simulation tool, Peak plans to estimate the success of other deflection missions in the future.

“Instead of changing the size of a projectile, we may be able to change the number of launches and send up multiple smaller spacecraft to collide with an asteroid, one by one. Or we could launch projectiles from the moon or use defunct satellites as kinetic impactors,” Paek says. “We’ve created a decision map which can help in prototyping a mission.”
source: scitech daily

39
Faculty Forum / Top 10 science anniversaries in 2020
« on: February 20, 2020, 04:45:49 PM »
2020, the International Year of Good Vision, is also a good year for scientific anniversaries.

As usual, there are the birthday anniversaries, offering an opportunity to recognize some of the great scientists of the past for their contributions to humankind’s collective knowledge. And there are the anniversaries of accomplishments, discoveries or events that left the world a different place than it had been before. There’s even an Einstein anniversary, which there almost always is.

What’s more, by selecting the Top 10 anniversaries carefully, you can illustrate how often key scientific concepts are intertwined — neutrons with bombs, for example, or magnetism with X-rays with DNA. So here, without any deep meaning to the order of presentation, are the Top 10 Science Anniversaries in 2020:

10. Roger Bacon, 800th birthday
Nobody knows for sure exactly when Bacon was born, but a passage in his writings suggests that it was around 1220. He was among the premier natural philosophers of his day; he studied first at Oxford and then lectured at the University of Paris. He became a Franciscan monk but often got in trouble for breaking the order’s rules.

Bacon was among the first to advocate for the importance of experiment in investigating nature. He especially emphasized the status of optics as a fundamental science. Bacon also understood the necessity of applying math when explaining natural phenomena. “The power of mathematics is capable of unfolding the causes of all things, and of giving a sufficient explanation of human and divine phenomena,” he wrote. Bacon thought that many big-name philosophers of his era were dolts, but revered the philosopher-theologian Robert Grosseteste, and developed some of his ideas more fully, including the role of mathematics and the notion that “laws of nature” governed natural phenomena.

9. Bose-Einstein condensate, 25th anniversary
No scientist has made more news after their death than Albert Einstein. From lasers to black holes to gravitational waves, multiple major modern discoveries have merely verified predictions from decades earlier rooted in Einstein’s imagination. One such example came in 1995 when physicists produced a new weird wavy form of matter called a Bose-Einstein condensate. In this case Einstein’s imagination was inspired by the Indian physicist Satyendra Bose.In 1924 Bose sent Einstein a paper describing (mathematically) light as a gas of particles (what we now call photons). Around that time Einstein read a paper by Louis de Broglie contending that matter particles (such as electrons) could be construed as waves. Einstein mashed up de Broglie with Bose and ended up describing matter with Bose’s math. Einstein envisioned wavy “boson” atoms that would merge into a kind of cloud of unified matter.

Making such a Bose-Einstein condensate cloud requires special conditions (it must be extremely cold, for one thing), and it took seven decades before physicists overcame the technical challenges and proved Einstein right, once again.

8. The Great Debate, centennial
Forget politics, the greatest debate of the 20th century took place on April 26, 1920, when astronomers Harlow Shapley and Heber Curtis faced off at the Smithsonian Museum of Natural History in Washington, D.C. Or at least that is the standard scientific lore.

Actually, the debate was pretty boring. Shapley read a paper about the current understanding of the Milky Way galaxy, which he believed to constitute the whole universe. Curtis read a paper contending that spiral-shaped nebulae visible through telescopes were in fact distant island universes comparable to the Milky Way. The winner of the debate was not announced until 1924, when Edwin Hubble showed that Curtis was right. Shapley conceded and for a while referred to the new cosmos of multiple galaxies as a multiverse.

7. Discovery of electromagnetism, bicentennial
Usually it’s not a good idea to play around with electricity. But two centuries ago, scientists didn’t know very much about it and curiosity got the better of them. Good thing, because that curiosity led to a discovery of unexaggeratable importance for the future of civilization.

A first step was Alessandro Volta’s primitive battery, invented in 1800. It launched a frenzy of electrical experimentation. Over the next 20 years many researchers investigated possible links between electricity and magnetism. Among them was Hans Christian Oersted at the University of Copenhagen, a chemist-physicist who had originally been trained as a pharmacist. Oersted had long suspected that electricity and magnetism shared a deep unity. During a lecture in the spring of 1820, he noticed that a current caused a nearby compass needle to move.

By July Oersted had conducted (get it?) thorough experiments enabling him to announce the discovery of electromagnetism — the generation of a magnetic emanation outside a wire carrying an electric current. About a decade later Michael Faraday showed the opposite, that moving a magnet around a wire induces an electric current. That established the principle behind electric power generation on large scales.

6. Discovery of X-rays, 125th anniversary
When Wilhelm Röntgen discovered X-rays in 1895, they were almost immediately put to use in medical practice. But they had a scientific significance just as great as their truly revolutionary importance for medicine.

For one thing, they bolstered the relatively recent realization that light was just one of several forms of electromagnetic radiation. (Only a few years earlier Heinrich Hertz had demonstrated the existence of radio waves, verifying James Clerk Maxwell’s suspicion that light was not the only form of electromagnetic waves.) “There seems to exist some kind of relationship between the new rays and light rays; at least this is indicated by the formation of shadows,” Röntgen wrote in his first report of the discovery. Ironically, later experiments on X-rays showed that electromagnetic “waves” sometimes behave as particles.

Eventually, X-rays transformed not only medicine but also astronomy and even biology, as they provided the tool that revealed the architecture of the molecules of life. See item 5.

5. Rosalind Franklin, 100th birthday
Franklin, born in July 25, 1920, in London, showed an early interest in science and trained as a chemist, becoming an expert on coal and other carbon-based materials. She earned a doctorate from the University of Cambridge in 1945. She then worked in Paris, developing skills at using X-ray crystallography to study crystalline structures, before moving to King’s College London, where Maurice Wilkins had been studying the molecular structure of DNA. Franklin took up DNA studies and produced exceptional X-ray images. She came close to determining DNA’s double-helix structure, but didn’t get it quite right.

Meanwhile James Watson, who had been following her research, was shown one of her X-ray images by Wilkins in early 1953, enabling Watson and Francis Crick to deduce the correct DNA architecture. Franklin saw that the Watson-Crick model was consistent with her work, but didn’t immediately accept that the model would ultimately turn out to be right in detail. She died in 1958, and so was not eligible for the Nobel Prize, awarded four years later to Watson and Crick. Wilkins also shared the prize, but there is no doubt that had she still been alive, Franklin would have deserved it more than he did.

4. John Graunt, 400th birthday
Born on April 24, 1620, in London, Graunt became a successful and influential merchant after taking over his father’s drapery business. Around age 40, for some reason he became interested in the weekly “Bills of Mortality” that enumerated deaths in the city. It occurred to him to also collect records of births and diseases to create tables that showed trends or patterns. He subjected the data to mathematical analyses, revealing insights such as women live (on average) longer than men, and death rates were higher in cities than rural areas.

Graunt’s work earned him election to the Royal Society, but the Great Fire of London in 1666 burned down his house, damaging his business and sending him straight into poverty. Graunt was later recognized as the pioneer of drawing scientific conclusions from the analysis of statistical information; his work is considered a cornerstone in the foundation of the modern sciences of statistics and demography.

3. Florence Nightingale, 200th birthday
Nightingale was born to a British family in Florence, Italy, (coincidence? no) on May 12, 1820. Her family moved back to England while she was still an infant. She is best known as the most famous nurse of the 19th century, the lady with a lamp. But she was also an innovative practitioner of applied statistics; she developed sophisticated statistical analyses to support her views on hygiene and health.

She went to nursing school in Germany, and in 1854 she led a team of nurses to aid wounded British soldiers during the Crimean War. Finding horrifyingly unsanitary conditions, she instituted a cleanliness regimen that reduced the death rate among hospitalized soldiers, and she returned to England to wide acclaim. She had single-handedly elevated the social status of the nursing profession and soon she started her own nursing school. She became an expert in interpreting health statistics, and her methods influenced the development of the science of epidemiology. She presented much of the statistical evidence for the benefits of proper health standards in graphical form, earning her a reputation as a pioneer of data visualization. (Her skill at communicating the statistical evidence was instrumental in getting policy makers to adopt her recommendations.)

Sadly, at age 38, she became mostly bedridden from a debilitating disease she had contracted during her Crimean War work. But she continued working from her home for decades, consulting with governments in various countries on how to best implement sanitation and other health-related policies.

2. Prediction of the neutron, centennial
After Ernest Rutherford discovered the atomic nucleus, in 1911, scientists spent years trying to understand how the nucleus was put together. It clearly required constituents with a positive electric charge. From later experiments Rutherford deduced that the basic nuclear particle carrying positive charge was identical to a hydrogen atom’s nucleus, and he named it the proton. Heavier atoms contained multiple protons.

But the number of protons needed to account for an atom’s mass gave the nucleus more positive electric charge than the negative charge of the atom’s orbiting (nearly massless) electrons. Since atoms are electrically neutral, it seemed that the nucleus must contain some electrons to cancel out the excess positive charge. Rutherford surmised that some of those electrons in the nucleus merged with protons to make a new particle that he later called the neutron. He considered it a new kind of atom, with zero electric charge. “In consequence it should be able to move freely through matter,” he said in a lecture delivered June 3, 1920, making it capable, physicists realized two decades later, of initiating nuclear fission chain reactions.

In 1932, experiments by the British physicist James Chadwick confirmed the existence of the neutron, surprising many physicists who had not believed Rutherford. But one scientist not surprised was the American chemist William Harkins, who had made a similar proposal and was actually first to use the term “neutron” in print, in 1921.

1. Atomic bomb, 75th anniversary
It’s hard to overstate the significance for science, or for all of history, of the atomic bomb, first exploded 75 years ago in July at Alamogordo, N.M. It represents a technological discontinuity comparable to the invention of electromagnetism, gunpowder or (the control of) fire itself. The atomic bomb’s main influence on society has been via its mere existence as a weapon in waiting, potentially ready to initiate Armageddon.

But it also still serves as a symbol of the power of science: Physicists probing the unseeable realm of the innards of atoms harnessed knowledge capable of destruction on a scale previously unimaginable. Applying the same knowledge to benefit society through the production of energy has not lived up to its advanced billing, through a combination of ineptness on the part of its proponents and lack of perspective on the part of its opponents. In any case, the bomb’s reminder of science’s importance to society will never fail to persist in the future, if any.
source:sciencenews

40
Faculty Forum / কেটে গেলে কী করবেন?
« on: February 20, 2020, 04:42:41 PM »
ব্লেড, ছুরি, চাকু, ভাঙা গ্লাস কিংবা যেকোনো ধারালো বস্তু দিয়ে যেকোনো সময় হাত বা পা বা শরীরের বাইরে কোথাও কেটে যেতে পারে। এই জন্য রক্তপাত ঘটে। অনেকেই সেই রক্ত দেখে দিশেহারা হয়ে পড়েন। এতে রোগী অল্প সময়ে প্রচুর রক্তপাতের শিকার হয়। শরীর থেকে বেশি রক্ত বেরিয়ে গেলে তা বিপদের কারণ হয়ে দাঁড়ায়। তাই হাত-পা কেটে গেলে দ্রুত তার ব্যবস্থা নেওয়া উচিত।

কাটাস্থান থেকে ধীর গতিতে রক্ত বের হলে

কাটাস্থানটি তালু দিয়ে কিংবা দুআঙ্গুল দিয়ে চিমটির মতো করে চেপে ধরবেন।
কাটাস্থানটি যতটা সম্ভব উপরে তুলে ধরবেন, এতে সেই স্থানের রক্তচাপ কমে গিয়ে রক্ত পড়াও কমে যাবে।
এ সময়ে একটি পরিষ্কার কাপড় কিংবা জীবাণুমুক্ত গজ দিয়ে প্যাড তৈরি করে যত তাড়াতাড়ি সম্ভব কাটা স্থানের ওপর সেটা চেপে ধরতে হবে।
ক্ষতস্থানটি নাড়াচাড়া করা যাবে না। প্যাডটি রক্তে ভিজে গেলে তা না খুলে বরং তার ওপরে আরো গজ তুলা পেঁচিয়ে ব্যান্ডেজ করে রোগীকে যত তাড়াতাড়ি সম্ভব ধারের কাছের হাসপাতালে নিয়ে যেতে হবে।
source:bdhealth

41
Researchers from UNIGE and the University of Manchester have discovered structures based on two-dimensional materials that emit tailor-made light in any color you could wish for.

Finding new semiconductor materials that emit light is essential for developing a wide range of electronic devices. But making artificial structures that emit light tailored to our specific needs is an even more attractive proposition. However, light emission in a semiconductor only occurs when certain conditions are met. Today, researchers from the University of Geneva (UNIGE), Switzerland, in collaboration with the University of Manchester, have discovered an entire class of two-dimensional materials that are the thickness of one or a few atoms. When combined together, these atomically thin crystals are capable of forming structures that emit customizable light in the desired color. This research, published in the journal Nature Materials, marks an important step towards the future industrialization of two-dimensional materials.

Semiconductor materials capable of emitting light are used in sectors as diverse as telecommunications, light-emitting devices (LEDs) and medical diagnostics. Light emission occurs when an electron jumps inside the semiconductor from a higher energy level to a lower level. It is the difference in energy that determines the color of the emitted light. For light to be produced, the velocity of the electron before and after the jump must be exactly the same, a condition that depends on the specific semiconducting material considered. Only some semiconductors can be used for light emission: for example, silicon — used to make our computers — cannot be employed for manufacturing LEDs.

“We asked ourselves whether two-dimensional materials could be used to make structures that emit light with the desired color,” explains Alberto Morpurgo, a professor in the Department of Quantum Matter Physics, at the UNIGE Faculty of Science. Two-dimensional materials are perfect crystals which, like graphene, are one or a few atoms thick. Thanks to recent technical advances, different two-dimensional materials can be stacked on top of each other to form artificial structures that behave like semiconductors. The advantage of these “artificial semiconductors” is that the energy levels can be controlled by selecting the chemical composition and thickness of the materials that make up the structure.

“Artificial semiconductors of this kind were made for the first time only two or three years ago”, explains Nicolas Ubrig, a researcher in the team led by professor Morpurgo. “When the two-dimensional materials have exactly the same structure and their crystals are perfectly aligned, this type of artificial semiconductor can emit light. But it’s very rare.” These conditions are so strict that they leave little freedom to control the light emitted.

Custom light
“Our objective was to manage to combine different two-dimensional materials to emit light while being free from all constraints”, continues professor Morpurgo. The physicists thought that, if they could find a class of materials where the velocity of the electrons before and after the change in energy level was zero, it would be an ideal scenario which would always meet the conditions for light emission, regardless of the details of the crystal lattices and their relative orientation.

A large number of known two-dimensional semiconductors have a zero-electron velocity in the relevant energy levels. Thanks to this diversity of compounds, many different materials can be combined, and each combination is a new artificial semiconductor emitting light of a specific color. “Once we had the idea, it was easy to find the materials to use to implement it”, adds professor Vladimir Fal’ko from the University of Manchester. Materials that were used in the research included various transition metal dichalcogenides (such as MoS2, MoSe2 and WS2) and InSe. Other possible materials have been identified and will be useful for widening the range of colors of the light emitted by these new artificial semiconductors.

Tailor-made light for mass industrialization
“The great advantage of these 2D materials, thanks to the fact that there are no more preconditions for the emission of light, is that they provide new strategies for manipulating the light as we see fit, with the energy and color that we want to have”, continues Ubrig. This means it is possible to devise future applications on an industrial level, since the emitted light is robust and there is no longer any need to worry about the alignment of atoms.

The collaboration between UNIGE and the University of Manchester took place within the framework of the EU Graphene Flagship Project.
source:scitechdaily

42
Renewable device could help mitigate climate change, power medical devices.
Scientists at the University of Massachusetts Amherst have developed a device that uses a natural protein to create electricity from moisture in the air, a new technology they say could have significant implications for the future of renewable energy, climate change and in the future of medicine.

As reported today in Nature, the laboratories of electrical engineer Jun Yao and microbiologist Derek Lovley at UMass Amherst have created a device they call an “Air-gen,” or air-powered generator, with electrically conductive protein nanowires produced by the microbe Geobacter. The Air-gen connects electrodes to the protein nanowires in such a way that electrical current is generated from the water vapor naturally present in the atmosphere.

“We are literally making electricity out of thin air,” says Yao. “The Air-gen generates clean energy 24/7.” Lovely, who has advanced sustainable biology-based electronic materials over three decades, adds, “It’s the most amazing and exciting application of protein nanowires yet.”The new technology developed in Yao’s lab is non-polluting, renewable and low-cost. It can generate power even in areas with extremely low humidity such as the Sahara Desert. It has significant advantages over other forms of renewable energy including solar and wind, Lovley says, because unlike these other renewable energy sources, the Air-gen does not require sunlight or wind, and “it even works indoors.”

The Air-gen device requires only a thin film of protein nanowires less than 10 microns thick, the researchers explain. The bottom of the film rests on an electrode, while a smaller electrode that covers only part of the nanowire film sits on top. The film adsorbs water vapor from the atmosphere. A combination of the electrical conductivity and surface chemistry of the protein nanowires, coupled with the fine pores between the nanowires within the film, establishes the conditions that generate an electrical current between the two electrodes.

The researchers say that the current generation of Air-gen devices are able to power small electronics, and they expect to bring the invention to commercial scale soon. Next steps they plan include developing a small Air-gen “patch” that can power electronic wearables such as health and fitness monitors and smart watches, which would eliminate the requirement for traditional batteries. They also hope to develop Air-gens to apply to cell phones to eliminate periodic charging.Yao says, “The ultimate goal is to make large-scale systems. For example, the technology might be incorporated into wall paint that could help power your home. Or, we may develop stand-alone air-powered generators that supply electricity off the grid. Once we get to an industrial scale for wire production, I fully expect that we can make large systems that will make a major contribution to sustainable energy production.”

Continuing to advance the practical biological capabilities of Geobacter, Lovley’s lab recently developed a new microbial strain to more rapidly and inexpensively mass produce protein nanowires. “We turned E. coli into a protein nanowire factory,” he says. “With this new scalable process, protein nanowire supply will no longer be a bottleneck to developing these applications.”

The Air-gen discovery reflects an unusual interdisciplinary collaboration, they say. Lovley discovered the Geobacter microbe in the mud of the Potomac River more than 30 years ago. His lab later discovered its ability to produce electrically conductive protein nanowires. Before coming to UMass Amherst, Yao had worked for years at Harvard University, where he engineered electronic devices with silicon nanowires. They joined forces to see if useful electronic devices could be made with the protein nanowires harvested from Geobacter.

Xiaomeng Liu, a Ph.D. student in Yao’s lab, was developing sensor devices when he noticed something unexpected. He recalls, “I saw that when the nanowires were contacted with electrodes in a specific way the devices generated a current. I found that that exposure to atmospheric humidity was essential and that protein nanowires adsorbed water, producing a voltage gradient across the device.”

In addition to the Air-gen, Yao’s laboratory has developed several other applications with the protein nanowires. “This is just the beginning of new era of protein-based electronic devices” said Yao.

Reference: “Power generation from ambient humidity using protein nanowires” by Xiaomeng Liu, Hongyan Gao, Joy E. Ward, Xiaorong Liu, Bing Yin, Tianda Fu, Jianhan Chen, Derek R. Lovley and Jun Yao, 17 February 2020, Nature.
source:scitechdaily

43
Study finds eating more at breakfast instead of dinner could prevent obesity.
Eating a big breakfast rather than a large dinner may prevent obesity and high blood sugar, according to new research published in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism.

Our body expends energy when we digest food for the absorption, digestion, transport, and storage of nutrients. This process, known as diet-induced thermogenesis (DIT), is a measure of how well our metabolism is working, and can differ depending on mealtime.

“Our results show that a meal eaten for breakfast, regardless of the amount of calories it contains, creates twice as high diet-induced thermogenesis as the same meal consumed for dinner,” said the study’s corresponding author, Juliane Richter, M.Sc., Ph.D., of University of Lübeck in Germany. “This finding is significant for all people as it underlines the value of eating enough at breakfast.”The researchers conducted a three-day laboratory study of 16 men who consumed a low-calorie breakfast and high-calorie dinner, and vice versa in a second round. They found identical calorie consumption led to 2.5 times higher DIT in the morning than in the evening after high-calorie and low-calorie meals. The food-induced increase of blood sugar and insulin concentrations was diminished after breakfast compared with dinner. The results also show eating a low-calorie breakfast increased appetite, specifically for sweets.

“We recommend that patients with obesity as well as healthy people eat a large breakfast rather than a large dinner to reduce body weight and prevent metabolic diseases,” Richter said.

Reference: “Twice as High Diet-Induced Thermogenesis After Breakfast Versus Dinner on High Calorie as Well as Low-Calorie Meals” 19 February 2020, Journal of Clinical Endocrinology & Metabolism.

Other authors include: Nina Herzog, Simon Janka, Thalke Baumann, Alina Kistenmacher and Kerstin M. Oltmanns of the University of Lübeck.
source: scitechdaily

44
Science Discussion Forum / Scientists unravel mystery of photosynthesis
« on: February 20, 2020, 02:23:51 PM »
Plants have been harnessing the sun's energy for hundreds of millions of years.

Algae and photosynthetic bacteria have been doing the same for even longer, all with remarkable efficiency and resiliency.

It's no wonder, then, that scientists have long sought to understand exactly how they do this, hoping to use this knowledge to improve human-made devices such as solar panels and sensors.

Scientists from the U.S. Department of Energy's (DOE) Argonne National Laboratory, working closely with collaborators at Washington University in St. Louis, recently solved a critical part of this age-old mystery, homing in on the initial, ultrafast events through which photosynthetic proteins capture light and use it to initiate a series of electron transfer reactions.

"In order to understand how biology fuels all of its engrained activities, you must understand electron transfer," said Argonne biophysicist Philip Laible. "The movement of electrons is crucial: it's how work is accomplished inside a cell."

In photosynthetic organisms, these processes begin with the absorption of a photon of light by pigments localized in proteins.

Each photon propels an electron across a membrane located inside specialized compartments within the cell.

"The separation of charge across a membrane -- and stabilization of it -- is critical as it generates energy that fuels cell growth," said Argonne biochemist Deborah Hanson.

The Argonne and Washington University research team has gained valuable insight on the initial steps in this process: the electron's journey.

Nearly 35 years ago, when the first structure of these types of complexes was unveiled, scientists were surprised to discover that after the absorption of light, the electron transfer processes faced a dilemma: there are two possible pathways for the electron to travel.

In nature, plants, algae and photosynthetic bacteria use just one of them -- and scientists had no idea why.

What they did know was that the propulsion of the electron across the membrane -- effectively harvesting the energy of the photon -- required multiple steps.

Argonne and Washington University scientists have managed to interfere with each one of them to change the electron's trajectory.

"We've been on this trail for more than three decades, and it is a great accomplishment that opens up many opportunities," said Dewey Holten, a chemist at Washington University.

The scientists' recent article, "Switching sides -- Reengineered primary charge separation in the bacterial photosynthetic reaction center," published in the Proceedings of the National Academy of Sciences, shows how they discovered an engineered version of this protein complex that switched the utilization of the pathways, enabling the one that was inactive while disabling the other.

"It is remarkable that we have managed to switch the direction of initial electron transfer," said Christine Kirmaier, Washington University chemist and project leader. "In nature, the electron chose one path 100 percent of the time. But through our efforts, we have been able to make the electron switch to an alternate path 90 percent of the time. These discoveries pose exciting questions for future research."

As a result of their efforts, the scientists are now closer than ever to being able to design electron transfer systems in which they can send an electron down a pathway of their choosing.

"This is important because we are gaining the ability to harness the flow of energy to understand design principles that will lead to new applications of abiotic systems," Laible said. "This would allow us to greatly improve the efficiency of many solar-powered devices, potentially making them far smaller. We have a tremendous opportunity here to open up completely new disciplines of light-driven biochemical reactions, ones that haven't been envisioned by nature. If we can do that, that's huge."
source:dailyscience

45
Generating electricity from raindrops efficiently has gone one step further. A research team led by scientists from the City University of Hong Kong (CityU) has recently developed a droplet-based electricity generator (DEG), featured with a field-effect transistor (FET)-like structure that allows for high energy-conversion efficiency and instantaneous power density increased by thousands times compared to its counterparts without FET-like structure. This would help to advance scientific research of water energy generation and tackle the energy crisis.

The research was led together by Professor Wang Zuankai from CityU's Department of Mechanical Engineering, Professor Zeng Xiao Cheng from University of Nebraska-Lincoln, and Professor Wang Zhong Lin, Founding Director and Chief Scientist from Beijing Institute of Nanoenergy and Nanosystems of Chinese Academy of Sciences. Their findings were published in the latest issue of journal Nature.

Efficiency of electrical energy conversion greatly improved

Hydropower is nothing new. About 70% of the earth's surface is covered by water. Yet low-frequency kinetic energy contained in waves, tides, and even raindrops are not efficiently converted into electrical energy due to limitations in current technology. For example, a conventional droplet energy generator based on the triboelectric effect can generate electricity induced by contact electrification and electrostatic induction when a droplet hits a surface. However, the amount of charges generated on the surface is limited by the interfacial effect, and as a result, the energy conversion efficiency is quite low.

In order to improve the conversion efficiency, the research team has spent two years developing the DEG. Its instantaneous power density can reach up to 50.1 W/m2, thousands times higher than other similar devices without the use of FET-like design. And the energy conversion efficiency is markedly higher.

Professor Wang from CityU pointed out that there are two crucial factors for the invention. First, the team found that the continuous droplets impinging on PTFE, an electret material with a quasi-permanent electric charge, provides a new route for the accumulation and storage of high-density surface charges. They found that when water droplets continuously hit the surface of PTFE, the surface charges generated will accumulate and gradually reach a saturation. This new discovery helped to overcome the bottleneck of low charge density encountered in previous work.

Unique field-effect transistor-like structure

Another key feature of their design is a unique set of structures similar to a FET, which is a Nobel Prize in Physics winning innovation in 1956 and has become the basic building block of modern electronic devices nowadays. The device consists of an aluminium electrode, and an indium tin oxide (ITO) electrode with a film of PTFE deposited on it. The PTFE/ITO electrode is responsible for the charge generation, storage, and induction. When a falling water droplet hits and spreads on the PTFE/ITO surface, it naturally "bridges" the aluminium electrode and the PTFE/ITO electrode, translating the original system into a closed-loop electric circuit.

With this special design, a high density of surface charges can be accumulated on the PTFE through continuous droplet impinging. Meanwhile, when the spreading water connects the two electrodes, all the stored charges on the PTFE can be fully released for the generation of electric current. As a result, both the instantaneous power density and energy conversion efficiency are much higher.

"Our research shows that a drop of 100 microlitres (1 microlitre = one-millionth litre) of water released from a height of 15 cm can generate a voltage of over 140V. And the power generated can light up 100 small LED light bulbs," said Professor Wang.

He added that the increase in instantaneous power density does not result from additional energy, but from the conversion of kinetic energy of water itself. "The kinetic energy entailed in falling water is due to gravity and can be regarded as free and renewable. It should be better utilized."

Their research also shows that the reduction in relative humidity does not affect the efficiency of power generation. Also, both rainwater and seawater can be used to generate electricity.

Facilitates the sustainability of the world

Professor Wang hoped that the outcome of this research would help to harvest water energy to respond to the global problem of renewable energy shortage. "Generating power from raindrops instead of oil and nuclear energy can facilitate the sustainable development of the world," he added.

He believed that in the long run, the new design could be applied and installed on different surfaces, where liquid in contact with solid, to fully utilize the low-frequency kinetic energy in water. This can range from the hull surface of ferry, coastline, to the surface of umbrellas or even inside water bottles.
source:sciencedaily

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