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Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:38am

What is the UV index? 

You've probably seen the UV index in the day's weather forecast, and you know it tells you when you need to cover up and wear sunscreen.

The Sun showers Earth with light at a huge spectrum of different wavelengths, and each wavelength can have a slightly different effect on human skin.

An important part of the spectrum is ultraviolet or UV radiation: light with wavelengths too short for our eyes to see, from around 400 nanometres to 10 nanometres.

There are two important kinds of UV radiation: UV-A, with wavelengths from 400–315 nanometres, and UV-B with wavelengths from 315–280 nanometres. (Shorter wavelengths are called UV-C, but are mainly blocked by the atmosphere so we don't need to worry about it.)

UV-A and UV-B both contribute to skin damage, aging and skin cancer. But UV-B is the more dangerous: it is the major cause of sunburn, cataracts and skin cancer.

The UV index tells you how much ultraviolet radiation is around at ground level on a given day, and its potential to harm your skin.

UV radiation is a component of sunlight that can cause tanning and sunburn in the short term. In the longer term, too much exposure to UV can cause cataracts and skin cancer.

In 2002, the World Health Organization devised the UV index in an effort to make people around the world more aware of the risks.

The index boils down several factors into a single number that gives you an idea of how careful you need to be in the sun. A score of 1 or 2 is low, 3–5 is moderate, 6 or 7 is high, 8–10 is very high, and 11 and above is extreme.

Part 1

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:34am

No mountain is high enough for microplastics

From Mount Everest to the Mariana Trench, microplastics are everywhere—even high in the Earth's troposphere where wind speeds allow them to travel vast distances, a study showed recently. 

Microplastics are tiny fragments—measuring less than 5 millimeters—that come from packaging, clothing, vehicles and other sources and have been detected on land, in water and in the air.

Scientists sampled air 2,877 meters above sea level at the Pic du Midi Observatory in the French Pyrenees, a so-called "clean station" because of the limited influence exerted on it by the local climate and environment.

There they tested 10,000 cubic meters of air per week between June and October of 2017 and found all samples contained microplastics.

Using weather data they calculated the trajectories of different air masses preceding each sample and discovered sources as far away as North Africa and North America.

The study's main author Steve Allen of Dalhousie University in Canada told AFP that the particles were able to travel such distances because they were able to reach great altitudes.

The research also points to microplastic sources in the Mediterranean Sea and the Atlantic Ocean.

Once in the air or ocean, it is moving around and around in an indefinite cycle.

Steve Allen, Evidence of free tropospheric and long-range transport of microplastic at Pic du Midi Observatory, Nature Communications (2021). DOI: 10.1038/s41467-021-27454-7. www.nature.com/articles/s41467-021-27454-7

https://phys.org/news/2021-12-microplastic-pristine-pyrenees-mounta...

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:24am

The researchers modeled various scenarios in close detail, such as a situation where passengers in different seats were pronouncing a vowel for a few seconds. By creating detailed representation of the flow field and tracking every single droplet, they were able to reconstruct their ventilation paths.

In the future, the team will reproduce conditions that more closely represent the diverse human activity on public transport vehicles to help inform actions, design, and operation of future ventilation systems for safer environments.

"These high-resolution simulations were focused on public transportation vehicles, but they could be extended to commercial or residential buildings, health care facilities, offices, or schools.

"Numerical investigation of droplets in a cross-ventilated space with sitting passengers under asymptomatic virus transmission conditions" Physics of Fluids, DOI: 10.1063/5.0070625

https://phys.org/news/2021-12-seat-exposure-exhaled-droplets.html?u...

Part 3

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Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:23am

When it comes to preventing risk of infection, this is precisely what makes it difficult to contain."

The researchers analyzed what happens when speech droplets are exhaled from a row of sitting passengers in a ventilated space, like those in public transportation vehicles. In some of these systems, air is injected at the top and extracted at the bottom through the vents near the window seats.

This generates an internal recirculation to enhance thermal comfort and remove contaminants, but the researchers were interested in whether certain seat positions affect the circulation adversely.

The team found droplets from the window seat rose more and invaded the space of other passengers to a lesser extent shortly after exhalation. Moreover, droplets released from the middle seat contaminated the aisle passengers more, indicating the downward flow of personal ventilation in aisle seats could move droplets down and increase the risk of infection.

Droplets released from the aisle were dragged down by the ventilation system immediately.

Part 2

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:23am

Your seat on public transportation determines level of exposure to exhaled droplets

The COVID-19 pandemic has revealed the urgency of understanding how public transportation ventilation systems transmit viruses and how exhaled droplets evolve in ventilated spaces. Researchers have wondered if those ventilation systems can be improved to mitigate virus transmission.

In Physics of Fluids, researchers at IBM Research Europe developed a model with an unprecedented level of detail and focused on conditions that are more characteristic of asymptomatic transmission. The multiphysics model involved air and droplet dynamics, heat transfer, evaporation, humidity, and effects of ventilation systems.

"By visualizing the droplets and the flow, you realize the number of physical phenomena taking place around us that go unnoticed, such as the complex interactions between natural body plumes, exhalation, and ventilation.

Part 1

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Comment by Dr. Krishna Kumari Challa on December 21, 2021 at 11:39am

Bacteriostatic antibiotics promote CRISPR-Cas adaptive immunity by enabling increased spacer acquisition, Cell Host Microbe, 2021.

https://phys.org/news/2021-12-closer-harnessing-viruses-bacteria-an...

Part 3

Comment by Dr. Krishna Kumari Challa on December 21, 2021 at 11:38am

The new study by the University of Exeter, published in Cell Host Microbe, has cast new light on how to best combine antibiotics and phage therapy. Researchers conducted laboratory experiments on Pseudomonas aeruginosa a bacterium which causes disease in immunocompromised and cystic fibrosis patients. They exposed the bacterium to eight types of antibiotics—and found differences in the mechanisms by which the bacteria evolve resistance to phages, which affect how harmful they are.

Viruses penetrate molecules on the cell surface to infect bacteria. Like the human immune system, bacteria have their own CRISPR defense system, made up of proteins that fight off infection. As in human immune responses, this means that the virus infects the bacteria, and is then killed. In the process, the bacteria's CRISPR system learns to recognize and attack the virus in future.

However, the bacteria have a second defense option. They can also change their own cell surface to ward off infection, losing the receptor to which phages normally attach. This option comes with a cost to bacteria—the bacteria become less virulent, meaning they no longer cause disease, or the disease becomes less severe.

In the study, four of the eight antibiotics tested caused a dramatic increase in the levels of CRISPR-based immunity. These antibiotics are all bacteriostatic—they do not directly kill cells  but act by slowing down cell growth.

 Phage therapy could be an important part of the toolkit, in reducing antibiotic use, and in using them in combination to increase their efficiency. We found that by changing the type of antibiotics that are used in combination with phage, we can manipulate how bacteria evolve phage resistance, increasing the chances that treatment is effective. These effects should be considered during phage-antibiotic combination therapy, given their important consequences for pathogen virulence.

The researchers show that the effect of bacteriostatic antibiotics triggering CRISPR-Cas immunity results from slower phage replication inside the cell, which provides more time for the CRISPR-Cas system to acquire immunity and clear the phage infection. The research therefore identifies the speed of phage replication as a crucial factor controlling the possibility for CRISPR-Cas systems to defend against viruses.

Part 2

Comment by Dr. Krishna Kumari Challa on December 21, 2021 at 11:36am

Harnessing viruses to fight bacteria and reduce antibiotic use

New research has moved a step closer to harnessing viruses to fight bacterial infection, reducing the threat of antibiotic resistance.

A growing number of infections, including pneumonia, tuberculosis, gonorrhea, and salmonellosis, are developing antibiotic resistance, which means they becoming harder to treat, resulting in higher death rates, longer hospital stays and higher costs.

Phage therapy is the concept of using viruses (known as phage) that are harmless to humans to kill bacteria. Phage therapy can be used in combination with antibiotics to cure infections more effectively, and reduce the opportunity for bacteria to develop antibiotic resistance. However, bacteria can also evolve resistance to phages.

Part 1

Comment by Dr. Krishna Kumari Challa on December 21, 2021 at 10:59am

Chasing an Asteroid's Shadow

Comment by Dr. Krishna Kumari Challa on December 19, 2021 at 1:29pm

Fuel Cell Cars

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