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n Saturday I headed to Oxford for a one-day meeting about big science in physics that was organised by the St Cross Centre for the History and Philosophy of Physics at Oxford University. Held in the Martin Wood Lecture theatre at the Department of Physics, the meeting covered the past, present and future of big science. The audience was made up of academics as well as the general public, with 200 people having registered to attend.

First up was Helge Kragh from the Niels Bohr Institute in Copenhagen, who gave a fascinating talk about what we define as big science and how that term has changed over the past century. Kragh’s focus was on the Manhattan atomic-bomb project and what followed regarding the development of large particle accelerators.

Continuing the particle-physics theme was Isabelle Wingerter-Seez from the Laboratoire d’Annecy-le-Vieux de Physique des Particules, which belongs to the French National Centre for Scientific Research, who spoke about the beginnings of CERN and the discovery of the Higgs boson in 2012 at the lab’s Large Hadron Collider.

Frank Close from Oxford University
Leading by example: going green in the lab

One common theme in questions from the audience (of which there were many) was how big-science facilities could become, well, more green. There are some facilities that are working towards this, notably the SESAME synchrotron in Jordan and the ESS, both of which use or will use renewable energy to power the accelerator complex.

But given that big science is getting bigger and ever-more important, energy sustainability needs to become a much greater consideration for those planning, designing and building these future facilities.

Want to read more?

Faculty Sections / Smart band-aid senses and treats bacterial infections
« on: February 26, 2020, 04:29:08 PM »
Antimicrobial resistance is a serious threat to global health, a phenomenon that is largely driven by incorrect treatment regimens, which result in misuse and overuse of antibiotics. Therefore, it is important to develop rapid and cheap ways of detecting bacteria, along with their sensitivity or resistance to antibiotics. This would allow rapid diagnosis of infections, tailored prescription of drugs and, in turn, a more informed and sustainable use of antibiotics.

In response to these demands, a team of researchers from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, has developed a paper-based adhesive plaster, or band-aid, based on a “sense and treat” approach. The plaster senses the presence of bacteria by changing its colour and releases antibiotics when necessary. In addition, the paper is able to distinguish between certain drug-susceptible and drug-resistant bacteria, therefore informing the best disinfection strategy (ACS Cent. Sci. 10.1021/acscentsci.9b01104).

The plaster works like a traffic light. It appears green under normal conditions, while it turns yellow in the presence of drug-sensitive bacteria and automatically releases antibiotics to kill them. If the bacteria are drug-resistant, the paper becomes red and photodynamic therapy (PDT) can be used instead. PDT is performed by shining 628 nm light onto the plaster, which induces the production of reactive oxygen species that kill or weaken the resistant bacteria.

Ad-hoc chemistry
The plaster exploits chemical compounds that change colour in the presence of bacteria. In particular, the material is soaked in bromothymol blue, a pH indicator that turns from green to yellow when exposed to the acidic environment created by bacterial metabolism. The paper also contains a pH-sensitive metal–organic framework, a compound that acts as a cage containing antibiotic molecules. Upon increased acidity, the framework breaks open and the encapsulated antibiotic is released.

A wide class of resistant bacteria produce β-lactamase, an enzyme that destroys certain types of antibiotic molecules. In response to this, the plaster is also equipped with nitrocefin, an antibiotic that shows a distinct colour change from yellow to red when interacting with β-lactamase, hence signalling the presence of drug-resistant bacteria and the need for a therapy other than antibiotics.

Based on these principles, the researchers have shown that the plaster accelerates wound healing in mice infected with both sensitive and resistant bacteria. They monitored the status of the wound over three days, and clearly observed improved tissue regeneration following the disinfecting action of either antibiotics or PDT.

The team also demonstrated the potential of the paper device in a fruit preservation model, in which it was attached onto an infected tomato that successfully recovered after three days of sensing and treatment.

The future of diagnosis and treatment
The team’s novel adhesive plaster offers great potential for the future of diagnosing and treating wound infections. It is cheap, easy to use, and effective against certain types of bacterial infections. Extending the method to practical and point-of-care applications will be the next challenge towards widespread use. Technologies like this could contribute significantly to the fight against antimicrobial resistance.

Electrical Machine / Re: Starting Of Squirrel Cage Motors
« on: February 25, 2020, 05:31:21 PM »

Thanks for sharing.

Electrical Machine / Re: Starting Of Slip-Ring Motors
« on: February 25, 2020, 05:31:10 PM »
Informative post.

Informative post.

Power System and Renewable Energy / Re: Principle of Alternators
« on: February 25, 2020, 05:29:56 PM »

Thanks for sharing.


Thanks for sharing.

Self-assessment Process Flow / Re: Self-Assessment Process Flow
« on: February 25, 2020, 05:20:29 PM »

thanks for sharing.

Communication Engineering / Re: why technology is also not a curse!!!
« on: February 25, 2020, 05:18:59 PM »
Informative post.

Computer System, Programming and Simulation / Skin Depth Calculator
« on: February 25, 2020, 05:15:37 PM »
The skin effect is a phenomenon whereby alternating electric current does not flow uniformly with respect to the cross-section of a conductive element, such as a wire. The current density is highest near the surface of the conductor and decreases exponentially as distance from the surface increases.

"Skin depth" refers to the point at which the current density reaches approximately 37% of its value at the surface of the conductor. Calculating skin depth requires the frequency of the AC signal and the resistivity and relative permeability of the conductive material. To use this calculator, just select the material type and enter the signal frequency. The resistivity and relative permeability of the chosen material will be automatically given.

Applications of Skin Depth
Skin depth is a convenient way to identify the region of the conductor in which the majority of current will flow. It is unnecessary (or in some cases wasteful) to use a wire with a radius that is significantly larger than the skin depth, because most of the current flows in the skin-depth region regardless of the size of the conductor.

The concept of skin depth might be better appreciated with the help of a real-world example. Consider RF signals for WiFi or Bluetooth, which operate at 2.4 GHz. Using the calculator, we see that the skin depth with a copper conductor is 1.331 micrometers. This means that even with a very thin (e.g., 30 AWG) wire, only a tiny fraction of the wire is carrying a significant amount of current.

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