Quantum dots selftune their color for ultraefficient nano lasers

first_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The laser, one of the most valuable scientific instruments, is getting smaller and more efficient. Scientists have designed a miniature laser, whose nanoscale dimensions and low optical losses will be instrumental in future developments of integrated photonic circuits. Compared with a regular flashlight, a laser emits a very intense and strongly collimated beam of monochromatic light. These properties arise from an interaction between the gain medium and an optical cavity. In order for a laser to generate its tiny colored spot, the active gain medium, which amplifies the beam, must provide photons that are all emitted at the same wavelength in a process called “stimulated emission.” While generating sufficient stimulated emission usually requires a great deal of gain material, scientists have discovered a method to create a nano laser with only a few tiny objects called “quantum dots.” Physicists from UC Santa Barbara and the University of Pavia in Italy have designed a new nano-device that works with only two to four quantum dots. The design, which provides ultra-efficient lasing performance, is published in a recent Physical Review Letters. “While conventional quantum dot lasers require many layers with thousands of dots, this new design takes advantage of a quantum dot property that effectively self-tunes the dots’ photon emission wavelength into resonance with the cavity,” explained co-author Stefan Strauf to PhysOrg.com. When the gain medium resonates with the cavity, a laser can be created.” Individual quantum dots have very sharp transition energy, and a large number of dots will display a broad emission bandwidth due to their natural size variations. While this broad emission makes them an ideal gain material for large volume lasers, device miniaturization presents a challenge since the sharp transitions of a few quantum dots no longer resonate with the laser cavity.The team of scientists found a way out of this dilemma by embedding the dots in a photonic crystal nano cavity, which enables light to be confined in a very small volume. A photonic crystal can be made by drilling many holes within a thin membrane of a semiconductor material such as GaAs (see figure). This particular design provides a finely tuned distribution of the electromagnetic field inside the nanocavity, which optimizes the overlap of the embedded quantum dots with the field profile and increases the quality of the cavity. ‘Connecting the dots’ for quantum networks Fig. A. In this design of the ultra-efficient photonic crystal nano laser, a top-view electron microscope image shows the drilled hole pattern in a GaAs membrane. The three missing holes in a row at the center define the nano cavity, which confines the light. To finely tune the electromagnetic field, a waveguide (w) has been inserted and neighboring holes have been resized and shifted. Photo Credit: Stefan Strauf. Explore furthercenter_img “This optimization process is a lot like the skillful fine-tuning of a violin producing resonance tones, but for light instead of sound,” said Strauf. This design drastically inhibits the emission of the dots at their natural sharp energies and forces them to interact with electronic carriers in their immediate surroundings. Because this interaction provides additional energy, the dots can self-tune their emission color into resonance with the cavity. Since this is a very pronounced interaction, the nano lasers display a hundredfold improvement of their lasing threshold values compared with any other semiconductor laser. In addition to the record low lasing threshold produced with a couple of quantum dots, the scientists found a much higher optical efficiency than exhibited in high density quantum dot devices. Measuring the optical efficiency with the spontaneous emission coupling factor (which has a theoretical limit of 1.0), the team found that the new method exhibited a value of 0.85, while multi-layer quantum dot lasers have a factor ranging from 0.1-0.2. “The record low lasing thresholds combined with the high efficiencies make these nano lasers useful for future applications in integrated photonic circuits on a chip and for bio sensing of individual molecules,” said Strauf. “Such nano lasers may now be formed with only a few or even a single quantum dot.”Citation: Strauf, S. et al. Self-Tuned Quantum Dot Gain in Photonic Crystal Lasers. Physical Review Letters 96, 127404 (2006).By Lisa Zyga, Copyright 2006 PhysOrg.com Fig. B and C. (B) This image shows a close-up of the resulting field profile around the tuned nano cavity region, where the yellow-white color is the highest field strength. (C) This atomic-force microscope image shows a typical layer of the low-density quantum dot gain material that is embedded underneath the surface of the membrane. The bright spots are individual InAs quantum dots, about 20 nm in size. The dashed blue circles indicate that there are on average only a few dots spatially positioned within the field profile of the nano cavity. Photo Credit: Stefan Strauf. Citation: Quantum dots self-tune their color for ultra-efficient nano lasers (2006, April 14) retrieved 18 August 2019 from https://phys.org/news/2006-04-quantum-dots-self-tune-ultra-efficient-nano.htmllast_img read more

Scientists develop algorithm for ultrasecret security technique

first_img Healthy blood vessels may be the answer to Alzheimer’s prevention Using a security technique called “optical Fresnel image hiding,” scientists can hide a secret image (such as the woman on the right) using algorithm keys that modulate the image’s light amplitude from a host image (such as the tower on the left). In contrast to other optical image hiding methods, the secret image is not embedded into the host image, decreasing the risk of hacking. Image credit: Yishi Shi et al. Information theft has become one of the most feared types of theft due to the vast power that comes with possessing certain information. Our numbers – social security numbers, credit card numbers, passwords, bank accounts, etc. – give authorization to access private documents and assets, and attempts to hack such accounts are ongoing. Optical security, which consists of hiding a secret image and includes methods such as holography and virtual optics, has been a growing field in security over the last few years. Until now, optical techniques have required the embedment of a secret image in a host image. Although a logical hiding procedure, embedded images can often be found in watermarked images, jeopardizing the security of the system. (Watermarks are the visible but difficult-to-replicate marks used to protect against fraud, while the host image is the visible, normally printed image covering the secret information.) To address this problem of finding the secret image in the watermark, scientists have developed a new optical security method that doesn’t require embedment. Instead, the technique uses a phase retrieval algorithm to generate specific optical and phase keys that extract the secret information when applied. The optical keys contain information and are distributed to an individual through a personal identification number (PIN). The information contained in the phase keys (the main source for determining extraction) is distributed to the individual separately.“The phase keys, designed by the phase retrieval algorithm, modulate the amplitude of the input [host] image into the amplitude of the secret image by the two Fresnel transformations,” Yishi Shi, coauthor of the paper in a recent issue of Journal of Optics A, told PhysOrg.com. “The phase keys are the main keys for the extraction of the secret image. The second type of key, the additional optical keys (which include the wavelength key and the mask position key) are also employed in our Fresnel system, which help to achieve a higher security level than can be achieved by Fourier systems.”This technique, which the scientists call “optical Fresnel image hiding (OFIH)”, satisfies “the three most important requirements in image hiding,” according to the team. Because no embedding occurs – meaning that the secret image cannot be found in the watermarked image – the method satisfies the so-called “imperceptibility requirement.” Since the watermarked image contains no secret information, and the phase keys are the main method for extraction, the OFIH method also satisfies the “robustness requirement.” Finally, since the secret image is the same size as the host image, this method also satisfies the “capacity requirement.”Another advantage of this optical technique is that one host image can hide several different secret images. In addition, one secret image can be hidden in different host images. These multiple variations further enhance the flexibility and robustness of the system.“This system is designed as a fragile system that may be used for authentication, and also could be designed as a robust or semi-fragile system for the purpose of image hiding or digital watermarking,” said Shi. “If we adopt the pure digital method to apply the Fresnel system, its realization will much easier. Thus, the flexibility of the designs for different application purposes is also obtained in the OFIH, allowing us to implement the system either by pure digital method or the opt-digital method.”Citation: Shi, Yishi, Situ, Guohai and Zhang, Jingjuan. Optical image hiding in the Fresnel domain. Journal of Optics A: Pure and Applied Optics. 8 (2006) 569-577.By Lisa Zyga, Copyright 2006 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Explore further To achieve a high capacity security system that is exceedingly robust to attacks, scientists have developed a set of instructions to unlock secret information, avoiding the need for embedding images and the risks involved. Citation: Scientists develop algorithm for ultra-secret security technique (2006, June 13) retrieved 18 August 2019 from https://phys.org/news/2006-06-scientists-algorithm-ultra-secret-technique.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Researchers show increased risk of predators can evoke adaptive response in birds

first_imgA juvenile Eurasian Sparrowhawk in Betuwe, Netherlands. Image credit: Wikipedia. © 2010 PhysOrg.com Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. More information: Predation risk affects offspring growth via maternal effects, Michael Coslovsky, Heinz Richner, Functional Ecology, Article first published online: 1 March 2011. DOI: 10.1111/j.1365-2435.2011.01834.xvia Nature. To get these results, Coslovsy and Richner went out into Bremgartenwald forest, near Bern and chose a group of great tits to use as a study group. They then exposed part of the group of mothers (during ovulation) to stuffed sparrow hawks and audio recordings of their calls; the control group was exposed to song thrushes. Two days after the nestlings hatched, they (both groups) were captured, tagged and carted off to another part of the forest to be raised by adoptive parents. As they grew, they were all monitored and it was then the researchers discovered that the offspring of stressed mothers were in fact smaller, as expected, but they also grew their wings at an unusually brisk pace, and grew them longer (1.8 millimeters on average) than other birds from the control group.Prior to this research, it’s been assumed that smaller growth in bird offspring is generally a negative effect brought about by a buildup of the stress hormone corticosterone. Now, with the news that smaller offspring also produce wings at an earlier age, and grow them longer, it might be argued that all three changes are nature’s way of helping the nestlings survive in a more hostile than normal environment; less weight, combined with longer wings at an earlier age, would seem to increase the nestling’s ability to fly away at a younger age, and to do so more speedily to ward off attacks.Of course, the results shown by Coslovsy and Richner are just one study, and have only been done on one species of bird; many more field trials will have to be made before any definitive conclusions can be drawn. Scientists shake Darwin’s foundation — chickens inherited parents’ stress symptoms (PhysOrg.com) — Evolutionary ecologists Michael Coslovsky and Heinz Richner of the University of Bern in Switzerland, have published a study in Functional Ecology where they show that when a female bird is exposed to more stress from predators, such as hawks, when ovulating, they tend to produce offspring that are smaller, which isn’t a surprise as stressed offspring in many species wind up smaller than average; the surprise is that the smaller offspring also grew their wings both faster and longer than what would be considered normal for their species. Citation: Researchers show increased risk of predators can evoke adaptive response in birds (2011, March 28) retrieved 18 August 2019 from https://phys.org/news/2011-03-predators-evoke-response-birds.htmllast_img read more

Fusion and friction and fields Oh my The rich and ubiquitous world

first_img Idealized structure of turbulent flow: coherent structures, each of near-maximal helicity, are separated by vortex sheets which are each subject to Kelvin-Helmholtz instability. Copyright © PNAS, doi:10.1073/pnas.1400277111. (Source: Moffatt HK (1985), Magnetostatic equilibria and analogous Euler flows of arbitrarily complex topology. 1. Fundamentals. J Fluid Mech 159: 359378m doi:10.1017/S0022112085003251) Fluid dynamics – a subset of the area of physics known as fluid mechanics – is concerned with the motion, or flow, of liquids and gases. Within fluid dynamics, a vortex is a region within a fluid where the flow is essentially a spinning motion about an imaginary straight or curved axis. In this context, helicity represents the degree of linkage of the flow’s vortex lines, conserved when these are frozen in the fluid. Conversion of writhe to internal twist; during this deformation, Wr decreases continuously from 1 to 0, and Ƭ + N increases continuously from 0 to 1; the central curve passes at some instant through an inflexional configuration, and at this instant Ƭ decreases by unity and N increases from 0 to 1. Copyright © PNAS, doi:10.1073/pnas.1400277111. (Source: Moffatt HK, Ricca RL (1992) Helicity and the Calugareanu invariant. Proc R Soc Lond A 439:411-429. doi:10.1098/rspa.1992.0159) A critical aspect of fluid dynamics is turbulence and, in relation to helicity, what’s known as depleting nonlinearity in the Navier-Stokes equations that describe the motion of fluid substances.) More specifically, the nonlinearity of the Navier-Stokes equations arises from transport of the vorticity, or spin vector, of the fluid by the associated velocity field. This nonlinearity is minimized in any region where vorticity and velocity are parallel – which happens to be precisely those regions where helicity magnitude is maximized. “It’s therefore reasonable,” Moffatt notes, “to conjecture that helicity has a significant influence on the nonlinearity that is responsible for the transfer of energy from large to ever-smaller scales at which viscosity, however weak, ultimately can dissipate the turbulent energy.”When it came to addressing these challenges, Moffatt’s first insight was recognizing that helicity is a measure of the degree of knottedness and/or linkage of the vortex lines of the flow. “This established a bridge between classical fluid mechanics and topology,” he explains. “This insight, coupled with the technique of magnetic relaxation, led to the idea that one could unambiguously associate an energy spectrum with any knotted or linked structure. In the context of dynamo theory, recognition of helicity as a key property of turbulence provided a firm foundation for kinematic theory, and opened the door to a more ambitious fully dynamic theory of dynamo action, with saturation of the exponential growth provided by suppression of helicity by the growing magnetic field.” Kinematics – often referred to as the geometry of motion – is the branch of classical mechanics which describes the motion of points, objects and groups of objects without considering the causes of that motion.In his paper, Moffatt describes how slow viscous flows have relevance for a number of applications, one being the design of micro- and nanofluid devices. “Micro-fluid devices operate at very low Reynolds numbers due to the very small scales involved,” he explains. (The Reynolds number is a dimensionless quantity used to help predict similar flow patterns in different fluid flows.) “The properties of fluid flow in such devices need to be understood in the interests of design optimization. My theory of flow near any sharp corner, now 50 years old,” he notes, “is relevant for such devices, which frequently involve 2- or 3-dimensional flows in corner regions.”Slow viscous flows also increase the understanding of mixing processes in chemical engineering geophysics. “Mixing of fluids is at the heart of chemical engineering processes, in which the promotion of chemical interaction may be desirable,” Moffatt tells Phys.org. “For this purpose the contact area of two fluids – assumed to be immiscible, or unable to be mixed or blended – needs to be maximized.” Vigorous stirring mechanisms achieve this result, says Moffatt, frequently through the break-up of one of the fluids into small droplets – and at a microscopic level, this involves topological changes that occur despite the opposing effect of surface tension, which tends to reduce the contact area. “My focus,” he adds, “has been on the mechanism of such topological change, which occurs at singular points or curves within the flow.” Another issue is the determination of stable knotted minimum-energy magnetostatic structures. (Knots and links play a fundamental role in a wide range of fields, including quantum and classical plasmas and fluids. In fluids, the fundamental knottedness-carrying excitations occur in the form of linked and knotted vortex loops.) “Stable knotted minimum energy structures can in principle be determined by the above relaxation procedure,” Moffatt says. “These are knotted magnetic flux tubes, within which the field lines may be twisted into helical form, this contributing to the overall helicity of the structure. The challenge here is to determine the minimum magnetic energy function m(h) for any given knot K, and to thereby establish a bridge with the purely geometric theory of so-called tight knots.” Citation: Fusion, and friction, and fields! Oh, my! The rich and ubiquitous world of fluid dynamics (2014, February 26) retrieved 18 August 2019 from https://phys.org/news/2014-02-fusion-friction-fields-rich-ubiquitous.html Relaxation of the trefoil knot to a tight minimum-energy state; two representations of the knot are shown (T2;3 and T3;2) indicating the existence of two distinct minimum-energy states. Copyright © PNAS, doi:10.1073/pnas.1400277111. (Source: Moffatt HK (1990) The energy spectrum of knots and links. Nature 347: 367-369) This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Journal information: Proceedings of the National Academy of Sciences Improving methods used to analyze and model fluid dynamics More information: Helicity and singular structures in fluid dynamics, Proceedings of the National Academy of Sciences, Published online before print on February 11, 2014, DOI: 10.1073/pnas.1400277111 Fluid dynamics has wide utility, with applications as diverse as human physiology (physiological fluid dynamics), the flight of insects, birds and aircraft (aerodynamics), the recovery of oil through porous media, the dynamics of ocean and atmosphere (geophysical fluid dynamics), the design of future fusion reactors (plasma dynamics and magnetohydrodynamics), and the understanding of astrophysical processes in stars and galaxies (astrophysical fluid dynamics). Recently, Prof. H. Keith Moffatt – an applied mathematician at the University of Cambridge, UK, with decades of seminal contributions in the field of fluid dynamics – published a paper reviewing several properties of helicity, including cosmological magnetic fields, topological flows, turbulence energy cascades, fusion reactor magnetic field configuration.Prof. Moffatt discussed the paper he published in Proceedings of the National Academy of Sciences with Phys.org, beginning with the main challenges to determining the role of helicity in the areas he reviewed. “Helicity in a turbulent flow of a conducting fluid usually arises from a combination of convection and Coriolis effects,” Moffatt tells Phys.org. (In physics, the Coriolis effect is a deflection of moving objects when viewed in a rotating reference frame. “These processes, acting in conjunction, can break the so-called reflectional symmetry of turbulence statistics – and helicity is a measure of the resulting lack of reflectional symmetry. Moreover,” he continues, “it’s now firmly established that under these circumstances, a magnetic field will grow spontaneously on a scale that can be much larger than the scale of the underlying turbulence – an example of what is referred to as order out of chaos.” The magnetic fields of stars and planets are generated ordinarily by this process, as are the time-dependent evolution of these fields – for example, random reversals of the Earth’s magnetic polarity. “This dynamo excitation of magnetic fields in cosmic systems,” Moffatt adds, “continues to pose major challenges for theoreticians.”Another challenge, he points out, is determining the role of helicity in so-called Euler flows of arbitrarily complex streamline topology. “There’s an exact analogy between steady Euler flows of an ideal incompressible fluid and magnetostatic equilibria in a perfectly conducting medium.” (In fluid dynamics, the Euler equations govern inviscid, or zero viscosity, flow – and assuming an ideal incompressible flow simplifies the resulting flow equations.) “The latter may be determined by a relaxation procedure dependent on the invariance of magnetic helicity, and are stable within the limits of the perfect conductivity assumption. The analogy can then be exploited to demonstrate the existence of Euler flows of arbitrary topological complexity. Unfortunately the analogy does not extend to stability considerations, and such flows are in fact almost invariably unstable due to the presence within them of vortex sheets which are subject to the classical Kelvin-Helmholtz instability.” © 2014 Phys.org. All rights reserved. Explore further At an atmospheric or oceanic scale, Moffatt continues, the Reynolds number is extremely large, and low Reynolds number results are less relevant. “However,” he adds, “chaos in flows, which is identified through the exponential separation of particle paths, is relevant to the spread of pollutants – for example, from oil spills in the ocean or from volcanic eruptions in the atmosphere. The fact that such chaos can occur even for low Reynolds number steady flow in a closed domain is an indication of the universality of this phenomenon.”Moving forward in terms of the next steps in his fluid dynamics research, Moffatt say, “It’s hard to predict the future! At present I’m working on a revision of my 1978 monograph on dynamo theory, and am also collaborating with colleagues on a study of topological transitions that can occur for a soap film on a deforming wire frame.” The latter, he notes, is a topic related “in spirit” to other situations, such as vortex reconnection, where topological transitions occur.As might be expected, a range of other applications and areas of research stand to benefit from Moffatt’s study. “Fluid mechanics is relevant to natural phenomena on all scales,” Moffatt tells Phys.org, “from the scale of the human cell up to the scale of distant galaxies. In particular,” he concludes, “my low Reynolds number studies are relevant to the smallest scales, while my studies in magnetohydrodynamics and dynamo theory are relevant in planetary and astrophysical contexts, as well as to thermonuclear fusion devices.” The latter includes, Moffatt adds, the International Thermonuclear Experimental Reactor (ITER), the latest generation and largest Tokomak fusion reactor, under construction in Cadarache, France.last_img read more

The energetic origins of life

first_img © 2014 Phys.org When it comes to origin of life discussions the so-called “RNA World” often comes to mind. While fascinating, that set of ideas is not what is under discussion here. According to the authors, it’s all about the acetogens, the methanogens, and the chemical transformations that were key to their evolution. These microorganisms synthesize ATP using electrons from H+ to reduce CO2. In the process they generate either acetate or methane. The shared backbone in the energy metabolism of these microorganisms is the most primitive CO2-fixing pathway we know of—the acetyl-coenzyme A pathway. This pathway is generally referred to as the hub of metabolism as is links glycolytic energy production in the cell with oxidative energy production in its endosymbionts, the mitochondria.While most acetogens are classified as bacteria, the methanogens belong to kingdom Archaea. This domain was only recently classified as distinct from bacteria and eukaryotes in 1977 by the late Carl Woese. Methogens are key to a bold leap of thought primarily made by Martin, which has come to be known as the “hydrogen hypothesis”. Martin had seen a slide at a lecture which showed clusters of methogens inside eukarytoic cells nestled up right against hydrogenosomes, presumably feeding off the hydrogen they generate. Hydrogenosomes are similar to mitochondria in that they generate energy, put they are a paired-down version in that they do not contain any genome of their own. Martin imagined that this cozy relationship he observed could have existed billions of years ago—only not as parasitic residents of a host eukaryotic cell, but rather as free residents at niche energy-producing locations within host earth. The host that then acquired what was to become the future mitochondrion was not a eukaryote with a fully-formed nucleus, but instead a prokaryotic and hydrogen-dependant methanogen. The future mitochondria then, was a facultative (as opposed to obligate) anaerobic eubacterium that in alternate incarnations also become the hydrogenosome. The key feature and prediction of the theory is that the mitochondria created the nucleus, and therefore eukaryotes. This processes entailed massive transfer of most of the mitochondria’s own genetic material to the host, which swelled the original genetic rank and congealed as chromosomes, simultaneously evolving the cyctoskeletal provisions for a complicated division cycle. The theory also neatly explains the lack of mitochondria in several eukaryotes through their loss, rather than as a failure to ever acquire them. The bio-existential question of whether the host “stole” the genes from the symbiont, or whether the parasite donated them becomes one of relativity and viewpoint. It is the same dichotomy as whether to say engulf or infect, or perhaps whether the assorted neurotransmitter packages dispensed by neurons are wastes, gifts or irritants. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Journal information: Science Explore further More information: Energy at life’s origin, Science 6 June 2014: Vol. 344 no. 6188 pp. 1092-1093. DOI: 10.1126/science.1251653 Few researchers have done more than co-author Nick Lane towards uncovering the role of mitochondria in nearly every major process of the cell. He has summed up many of these ideas in his book Power, Sex, Suicide: Mitochondria and the Meaning of Life. In it he observes many things that like the hydrogen hypothesis, are now becoming accepted reality. Of note, he maintains that using those few genes preserved as local copies in the mitochondrial genome, different regions of the cell can rapidly tailor their energy output. In the case of the extended trees of neurons, this might also contribute to structural alterations and perhaps even memory.As far as the origins of life, we need to turn back into the opposite direction now to try to un-create what might have happened prior to the eukaryotic merger, or at least led to it. In 2012 Martin and Lane published their thought-advances in imagining some of the geochemical processes which were later sped up, compacted, and made more efficient inside cells. These include how ion-gradients were set up at hydrothermal vents, bandied about, and later swapped H+ ions for Na+ ions as both the carriers and composers. One such process they detail in their new paper is known as serpentinization. In this sequence of geochemical reactions, seawater percolating through submarine crust exothermically oxidizes Fe2+ to Fe3+ along with the release of H2 and energy. Serpentinization taking place at the Lost City formation, for example, generates a strongly reducing environment (reducing CO2), and it also makes the effluent alkaline with a pH of around 10, essentially controlling the fluid composition of the vent. Natural proton gradients are spontaneously set up with the same magnitude and orientation as occurs inside modern autotrophes (self-nourishing, producing cells).What were the first ion-pumping mechanisms?These vent features make them naturally chemiosmotic. In chemiosmosis, as also occurs in mitochondria, ions flow down natural gradients which can potentially be harnessed to produce energy. In the case of life, which universally employs multi-tool pumps known as ATP-ases, this energy is deposited as phosphate bonds in ATP. If the primordial ATP-ase harnessed these alkaline vent gradients, a first step could have involved a simple H+/Na+ antiporter. This kind of a device (now also protein-based like the ATP-ase) could have converted the initial vent gradient into the Na+ gradient the acetogens and methanogens use today. These complexes still use iron-sulfer clusters and methyl groups as substrates, and could have enabled the emergence of free-living prokaryotes. Our understanding of chemiosmosis today is still incomplete. The so-called “proton-motive force” which couples proton and electron transfer across nebulous barriers still defies exact quantification. The flow of electrons through proteins, and the membranes which house them, continues to be one of the most exciting areas both in the origins of life, and in the creatures later evolved. Citation: The energetic origins of life (2014, June 12) retrieved 18 August 2019 from https://phys.org/news/2014-06-energetic-life.html Origin of life emerged from cell membrane bioenergetics (Phys.org) —Imagination is perhaps the most powerful tool we have for creating the future. The same might be said when it comes to creating the past, especially as it pertains to origin of life. Under what conditions did the energetic processes of life first evolve? That question is the subject of a remarkable perspective piece just published in Science. Authors William Martin, Filipa Sousa, and Nick Lane come to the startling conclusion that the energy-harvesting system in ancient microbes can best be understood if it is viewed a microcosm of the larger-scale geochemical processes of the day. In particular, they imagine a process by which natural ion gradients in alkaline hydrothermal vents, much like the “Lost City” ecosystem still active in the mid-Atlantic today, ignited the ongoing chemical reaction of life. Alkaline hydrothermal vents, like the Lost City, may have been key to origins of life. Credit: commons.wikimedia.orglast_img read more

Bullet Space Were Still Kickin

first_img Photo Courtesy: http://andrewcastrucci.com by George Bodarky Audio PlayerYour browser version does not support the audio element00:0000:0000:00Use Up/Down Arrow keys to increase or decrease volume. 8.28.19 6:00am New York City is home to a variety of alternative art spaces, but perhaps none have a story like this.In the mid-Eighties, a group of squatters took over an abandoned building on Manhattan’s Lower East Side. They broke in using a sledgehammer and made the place their own, even putting on art shows and plays in the space. They called the location Bullet Space — and you can find out why in this episode of “Cityscape.”Andrew Castrucci and Alexandra Rojas are artists and residents of Bullet Space. Castrucci has been living there for over 30 years and was one of the original squatters. Castrucci and Rojas recently took “Cityscape” on a tour of the building, and explained why Bullet Space is far from just another transformed tenement in the concrete jungle. Bullet Space: ‘We’re Still Kickin’!’ last_img read more

from hungary with love

first_imgThe Hungarian Information and Cultural Centre, presents international artworks exhibition Cocos Nuciferas by MD Deleep from France-Switzerland and Spirit and Matter – Three Artists – Three Generation by Ilona Lovas, Anna Makovecz and Villo Turcsány from Hungary, organised by Anna Bagyó , curated by Katalin Keserü. The two exhibitions will be inaugurated by Szilvezster Bus, Ambassador of Hungary, in the presence of François Richier, Ambassador of France. Also Read – ‘Playing Jojo was emotionally exhausting’The artworks by MD Deleep are an attempt to translate and share spiritual and ethnic emotions, sensations through these intermediaries. Thus, it is important that there exists barely any distance between the viewer and the work. With such participation, there is enough scope for the individuals to enter the specific work-scope and create new relationships between creation, creator and spectator. The artist’s aim is to work in interaction with the public, resulting in a timeless piece, which everyone can interpret in his/ her own way. An exhibition-cum-performance, curated by art historian, writer and curator Katalin Keserü, organised by art consultant Anna Bagyó, with the participation of three Hungarian woman artists: Ilona Lovas, Anna Makovecz and Villo Turcsány. The three artists, representing three different generations, coexist well with each other. Their works examine the metamorphosis of matter, body and spirit. These evergreen topics of art are translated into the language of contemporary mediums and will be presented as installations, photos and videos.When: January 27 – February 28 Where: HICC Garden and Exhibition Hall.last_img read more

S Machendranathan is new AERA chairman

first_imgS Machendranathan took over as chairperson of Airports Economic Regulatory Authority of India on Monday.   Machendranathan who hails from Tirunelveli District, Tamil Nadu had a distinguished  academic career. After completing MBA from Cochin University, he joined the Indian Police Service (IPS) in 1977 and thereafter the Indian Administrative Service (IAS) in 1979. An IAS officer of the Tamil Nadu cadre, S Machendranathan held several important positions in the Government of Tamil Nadu and in the Government of India.   Also Read – I-T issues 17-point checklist to trace unaccounted DeMO cashIn the Government of Tamil Nadu, he worked as Collector of Thanjavur District; Commissioner/ Secretary to the Government of Tamil Nadu in the Departments of Transport, Food, Cooperation and Consumer Protection; Chairman of Tamil Nadu Electricity Board.  And in the Government of India, he worked as Chairman of Tuticorin Port Trust; Additional Secretary & Financial Advisor in the Ministry of Steel as well as in the Ministry of Civil Aviation and finally as Secretary (Coordination) in Cabinet Secretariat, before superannuating from the Government Service in March, 2014.  He has also served as Government Director in several Public Sector companies such as Air India, Airports Authority of India, Steel Authority of India Limited, Rashtriya Ispat Nigam Limited, Kudremukh Iron Ore Company Limited and Metallurgical & Engineering Consultants (India) Limited.last_img read more

Traditional homes are more sustainable

first_imgAlthough people around the world want the kind of houses seen in Europe and North America, rather than those they grew up with, traditional homes can be more sustainable, says an Indian-origin engineer.Industrial building materials are often scarce and expensive and alternative, locally sourced, sustainable materials are often a better choice, said Khanjan Mehta, assistant professor of engineering design at the Pennsylvania State University.“People want to build a good house, everyone wants to have a good house. But what makes a good house? Is it wood, steel, concrete or bamboo? It all depends on the context,” Mehta said.Individuals can use locally available but scarce materials to build their individual homes, but that strategy will not build all the houses in a city or village because it cannot be scaled up to meet the demand.“People see western stuff as better, more modern and therefore they think it is good,” said Mehta.“Traditional homes can be just as cool, and maybe more sustainable,” he said.Mehta shared his thoughts at the annual meeting of the American Association for the Advancement of Science in Washington DC on Friday.last_img read more