Method for measuring luminous efficacy of LEDs

Researchers at Aalto Univ. and VTT Technical Research Centre of Finland have succeeded in developing a method which helps to improve the relative uncertainty in measuring the luminous efficacy of LEDs from the approximate five percent of today to one per cent in the future. The results were published in Light: Science & Applications journal.

Thus far, solutions based on incandescent lamps have been used in photometry, for example, in measuring light detected by the human eye, explains Tomi Pulli, a doctoral student at Aalto Univ.

The photometers that lamp manufacturers use for calibrating their devices have been produced and calibrated for incandescent lamps, which results in errors when measuring the efficacy of LEDs. In our research, we used a LED lamp with a well-defined spectrum and a PQED detector, which we developed together with VTT MIKES Metrology and European partners, and whose spectral responsivity can be determined highly accurately. Therefore, there was no need for the problematic optical filters used in applications based on incandescent lamps. Indeed, accurately determining and analyzing the spectrum of the LED was the most challenging and crucial part of the research, he reveals.

From a dot to a sphere
The detector used in measurements by Pulli and his co-researchers measures the illuminance of LEDs in a very small area. According to Professor Erkki Ikonen, the head of research, the next step will be to move onto measurements corresponding to real-life conditions for lighting.

Move Over Gatorade

Take a seat Gatorade, there’s another performance-enhancing beverage in the limelight: beet juice.

Two studies, one from the Univ. of Exeter and the other from Washington Univ. In St. Louis, have found the high nitrate content in concentrated beet juice has beneficial effects on both athletes and heart failure patients, particularly when it comes to muscle power.

“It’s a small study, but we see robust changes in muscle power about two hours after patients drink the beet juice,” said Linda R. Peterson, senior author of Washington Univ.’s study and an associate professor of medicine. “A lot of the activities of daily living are power-based—getting out of a chair, lifting groceries, climbing stairs.”

“We want to help make people more powerful because power is such an important predictor of how well people do, whether they have heart failure, cancer or other conditions. In general, physically more powerful people live longer,” she added.

Published in Circulation: Heart Failure, the study showed patients, two hours after ingesting beet juice, demonstrated a 13% increase in power muscles that extend the knee. While changes were noted in quick, power-based actions, longer tests showed no substantial improvement in muscle performance.

Blue Crabs Tolerate Low Oxygen, Still at Risk to Warming Temperatures

In 2015, the Gulf of Mexico dead zone—an area of water so low or absent in oxygen that it threatens the area’s marine life—sprawled outwards along the coasts of Louisiana and Texas, measuring 6,474 square miles. According to the National Oceanic and Atmospheric Administration (NOAA), the Gulf of Mexico boasts the second largest human-caused dead zone in the world.

With more than 550 dead zones occurring annually worldwide, scientists are attempting to discover the long-term effects dead zones will have on local species.

Bucking previous research, scientists from the Virginia Institute of Marine Science found adult blue crabs are more resilient to low-oxygen water levels than previously thought. “The notion that blue crabs are relatively intolerant of oxygen-poor waters was counterintuitive, because this species often occupies estuarine environments that can become hypoxic even in the absence of human activities,” said Rich Brill, a fishery biologist with NOAA’s National Marine Fisheries Service  

Excessive nutrients, such as nitrogen and phosphorous, and waterbody stratification prompt algal growth in dead zones. “As dead algae decompose, oxygen is consumed in the process, resulting in low levels of oxygen in the water,” according to the Environmental Protection Agency (EPA). Dead zone increases are attributed to nitrogen from fertilizers and sewage, among other human resources.

“Because coastal hypoxia can significantly impact the movements, distribution, growth and reproduction of inshore fish and invertebrate species, understanding their ability to tolerate hypoxia is becoming crucial; especially in species of ecological and commercial importance,” said Brill.

Physicists catch magnetic wave that offers promise for energy-efficient computing

A team of physicists has taken pictures of a theorized but previously undetected magnetic wave, the discovery of which offers the potential to be an energy-efficient means to transfer data in consumer electronics.

The research, which appears in Physical Review Letters, was conducted by scientists at New York Univ., Stanford Univ. and the SLAC National Accelerator Laboratory.

"This is an exciting discovery because it shows that small magnetic waves—known as spin-waves—can add up to a large one in a magnet, a wave that can maintain its shape as it moves," explains Andrew Kent, a professor of physics at NYU and the study's senior author. "A specialized x-ray method that can focus on particular magnetic elements with very high spatial resolution enabled this discovery and should enable many more insights into this behavior."

"Magnetism has been used for navigation for thousands of years and more recently to build generators, motors, and data storage devices," adds co-author Hendrik Ohldag, a scientist at the Stanford Synchrotron Radiation Laboratory (SSRL), where the soliton was discovered. "However, magnetic elements were mostly viewed as static and uniform. To push the limits of energy efficiency in the future we need to understand better how magnetic devices behave on fast timescales at the nanoscale, which is why we are using this dedicated ultrafast x-ray microscope."

These magnetic waves are known as solitons—for solitary waves—and were theorized to occur in magnets in the 1970s. They form because of a delicate balance of magnetic forces—much like water waves can form a tsunami. However, these magnetic waves are not destructive; they could potentially be harnessed to transmit data in magnetic circuits in a way that is far more energy efficient than current methods that involve moving electrical charge.

Computers Judge Personality Better than Humans

Your Facebook likes allow computer models to judge your personality better than your coworkers, friends and family, according to study published in Proceeding of the National Academy of Sciences.

People leave digital footprints daily: from browsing history and online purchases to GPS locations and social media accounts.

According to the study, this allows machines to gauge human personalities without usual social-cognitive skills. In the study, the computer only needed 10 likes to beat a person’s work colleague, 70 likes to be more accurate than a person’s friend and 250 likes to beat a spouse.

That 250 number isn’t staggering either. According to the researchers, the average Facebook user likes around 227 pages. Facebook likes indicate a positive association with both online and offline entities, including products, activities, movies, books, sports, musicians, Websites and restaurants, among others.

Traits measured in the study and compared between the judgement of a human and a computer model included openness, conscientiousness, extraversion, agreeableness and neuroticism, referred to as the big five personality dimensions.

New insights into HIV-1 vaccine design

Scientists at Los Alamos National Laboratory have created a computational model that could change the way that researchers look at possibilities for an HIV-1 vaccine.

“An effective HIV-1 vaccine has proven elusive, partly due to the difficulty of causing an immune response that can neutralize the diverse viral strains circulating in the human population,” said Alan Perelson, of Los Alamos’ Theoretical Biology and Biophysics Group. “Harnessing the power of broadly neutralizing antibodies, which emerge years into a chronic HIV infection, could help overcome this challenge.”

Shishi Luo and Perelson, published their findings in the paper “Competitive exclusion by autologous antibodies can prevent broad HIV-1 antibodies from arising.”

They used a mathematical model to examine how broadly neutralizing antibodies coevolve with HIV. By simulating the co-evolution of multiple viral strains and antibody populations, Perelson and Luo show that broadly neutralizing antibodies emerge late in infection due to competition from the highly specific antibody response to the dominant viral species in an infected person.

In their model, broadly neutralizing antibodies emerge earlier, and face less competition, in infections caused by multiple distinct strains of HIV compared with single strains. The findings support the view that a vaccine containing a mixture of diverse viral strains might reduce this competition, reduce the number of antibody mutations and elicit broadly neutralizing antibodies earlier in infection.