Lifeboat Foundation

The majority of quantum dot (QD) blinking studies have used a model of switching between two distinct fluorescence intensity levels, “on” and “off”. However, a distinct intermediate intensity level has been identified in some recent reports – a so-called “grey” or “dim” state, which has brought this binary model into question. While this grey state has been proposed to result from the formation of a trion, it is still unclear under which conditions it is present in a QD. By performing shell-dependent blinking studies on CdSe QDs, we report that the populations of the grey state and the on state are strongly dependent on both the shell material and its thickness. We found that adding a ZnS shell did not result in a significant population of the grey state. Using ZnSe as the shell material resulted in a slightly higher population of the grey state, although it was still poorly resolved. However, adding a CdS shell resulted in the population of a grey state, which depended strongly on its thickness up to 5 ML. Interestingly, while the frequency of transitions to and from the grey state showed a very strong dependence on CdS shell thickness, the brightness of and the dwell time in the grey state did not. Moreover, we found that the grey state acts as an on-pathway intermediate state between on and off states, with the thickness of the shell determining the transition probability between them. We also identified two types of blinking behavior in QDs, one that showed long-lived but lower intensity on states and another that showed short-lived but brighter on states that also depended on the shell thickness. Intensity-resolved single QD fluorescence lifetime analysis was used to identify the relationship between the various exciton decay pathways and the resulting intensity levels. We used this data to propose a model in which multiple on, grey and off states exist whose equilibrium populations vary with time that give rise to the various intensity levels of single QDs, and which depends on shell composition and thickness.

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In the past, traditional methods to understand the behavior of quantum interacting systems have worked well, but there are still many unsolved problems. To solve them, Giuseppe Carleo of ETH Zurich, Switzerland, used machine learning to form a variational approach to the quantum many-body problem.

Before digging deeper, let me tell you a little about the many-body problem. It deals with the difficulty of analyzing “multiple nontrivial relationships encoded in the exponential complexity of the many-body wave function.” In simpler language, it’s the study of interactions between many quantum particles.

If we take a look at our current computing power, modeling a wave function will need lot more powerful supercomputers. But, according to Carleo, the neural networks are pretty good at generalizing. Hence, they need only limited information to infer something. So, fiddling with this idea, Carleo and Matthias Troyer created a simple neural network to reconstruct such multi-body wave function.

UPS has successfully tested a drone that launches from the top of a UPS truck and autonomously delivers packages. http://abcn.ws/2lsyjjM

Interestingly, Seager, who studies bio signatures in exoplanet atmospheres, has suggested that two inhabited planets could reasonably turn up during the next decade, based on her modified version of the Drake equation, Space.com notes. Her equation focuses on the search for planets with biosignature gases — gases produced by life that can accumulate in a planet atmosphere to levels that can be detected with remote space telescopes.

Continue reading “NASA announces Wed. news conference on ‘discovery beyond our solar system’” »

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We may be about to meet some strange new worlds beyond our solar system.

NASA will hold a news conference Wednesday to make an announcement on exoplanets, planets that orbit a star other than our own sun. You can tune in at 1 p.m. ET and stick around for a Reddit Q&A with the researchers at 3 pm.

Currently in human trials in the U.S.

Russian and Swedish scientists have used an artifical antioxidant to slow the aging process is lab mice. The compound, known as SkQ1, targets mitochondria. ROBERT F. BUKATY AP File.

NASA has enlisted a professor from the University of Central Florida (UCF) in order to find a way of 3D printing structures on Mars.

Pegasus Professor Sudipta Seal, interim chair of UCF’s Materials Science and Engineering program is looking at how metals can be extracted from Martian soil. Speaking about the project, Seal said,

It’s essentially using additive-manufacturing techniques to make constructible blocks. UCF is collaborating with NASA to understand the science behind it.

Continue reading “3D printing houses on Mars with NASA and the University of Central Florida” »

Karl Schab

Pulling uranium out of seawater could be a cost-effective way to source nuclear fuel, scientists have found, and the technique could pave the way for coastal countries to switch to nuclear power.

With the International Atomic Energy Agency currently predicting an increase of up to 68 percent in nuclear power production over the next 15 years, finding a new, more environmentally friendly source of uranium — the most critical ingredient in nuclear power — could give this alternative to fossil fuels a boost.

Continue reading “We’re One Step Closer to Pulling Nuclear Fuel Straight Out of the Ocean” »