(PhysOrg.com) — The U.S. Navy is getting ready to run flight tests using an assortment of biofuels. The tests will be run using an F/A-18 Super Hornet. The tests are scheduled to begin taking place at Patuxent River, Md. by spring or summer 2010. The idea is to create a drop-in system so that those in the field won’t know the difference. The biofuels being tested are camelina, jatropha and algae. Navy.mil reports on the process expected to be used:For the upcoming static and flight tests, the biofuels will be mixed in a 50-50 blend with conventional petroleum-derived jet fuel to provide the necessary specification properties. Biofuels are not as dense as conventional jet fuel, have less lubricating ability and contain no aromatic compounds, a group of chemical compounds able to penetrate the rubberlike materials that make up gaskets and seals.The Navy hopes to test properties and chemistry, seeing how the fuels react in the environments associated with high-speed military plans. The tests should be able to determine whether or not it is feasible to use biofuels as part of the fuel source for jet planes. The hope is that the most promising candidates will be available by 2013.© 2009 PhysOrg.com 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. Explore further
More information: A preprint of the article is available at arxiv.org/abs/0909.2445v2 . (PhysOrg.com) — Laboratory experiments in the last few decades have shown that some things can appear to move faster than light without contradicting Einstein’s special theory of relativity, but now astrophysicists have seen real examples of superluminal speeds in the form of radio pulses from a pulsar. Superluminal, or faster than light, speeds are associated with anomalous dispersion, which is a process in which the refractive index of a medium increases with the wavelength of light passing through it. If a light pulse (consisting of a group of light waves at different wavelengths) passes through such a medium, the group velocity of the pulse can increase to a velocity greater than any of the waves within the pulse, but the energy of the pulse still travels at the speed of light, which means information is transmitted in accordance with Einstein’s theory.Astrophysicists, led by Frederick Jenet of the University of Texas at Brownsville, have been monitoring a pulsar, PSR B1937+21, which is about 10,000 light years from Earth. They used the Arecibo Observatory in Puerto Rico to obtain radio data over three days at 1420.4 MHz with a bandwidth of 1.5 MHz. They found that pulses closer to the center arrived earlier than the normal timing, which suggests they had travelled faster than the speed of light.A pulsar is a neutron star that is spinning rapidly and emitting a rotating beam of radio radiation as it spins, which is observed on Earth at regular intervals rather like light from a lighthouse. The pulses of radiation can be affected by several factors as they travel through the interstellar medium (ISM). Their polarization can be rotated if they pass through a magnetic field, for example, and they can be scattered if they encounter free electrons, and can be absorbed by neutral hydrogen in the ISM. Jenet and his colleagues think anomalous dispersion also affects the pulses.According to Jenet and colleagues, the pulses from the pulsar traveled through a cloud of neutral hydrogen, which has a resonance of 1420.4 MHz — the exact center of the bandwidth studied. Passing through the cloud caused anomalous dispersion that resulted in a superluminal group velocity, and pulses with frequencies closest to the resonance frequency arrived earlier than other pulses. The scientists believe the pulses appear to travel faster than light because of an “interplay between the time scales present in the pulse and the time scales present in the medium.” The faster-than-light pulses do not violate Einstein’s theory because technically the pulse carries no information. The effect has been known in laboratory experiments, but these observations were the first in an astrophysical context.The findings, to be published in the Astrophysical Journal, could help astronomers gain a more complete understanding of the composition of space in the regions between stars, and in particular the properties of neutral hydrogen clouds in our galaxy. Explore further Astronomers weigh ‘recycled’ millisecond pulsar A diagram of a pulsar, showing its rotation axis and its magnetic axis. Image: NASA © 2010 PhysOrg.com Citation: Radio pulses from pulsar appear to move faster than light (2010, January 14) retrieved 18 August 2019 from https://phys.org/news/2010-01-radio-pulses-pulsar-faster.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.
It has been noted by scientists that asteroids and comets tend to strike the Earth in a cyclic pattern that occurs approximately every 35 million—as evidenced by telltale craters. But why such a cycle might occur is still up to conjecture. Some have suggested it’s due to a mysterious planet hidden from our view, or perhaps the presence of an as yet undiscovered companion star. In this new effort, the research duo suggests it might be due to the gravitational pull of a dark matter disk residing in the Milky Way Galaxy plane.This is not the first time that scientists have suggested such a disk might exist—it’s been suggested that a dark matter a disk would explain why our galaxy doesn’t spin apart. It is the first time, however, that such a disk has been proposed as an answer to why our planet gets bombarded periodically with asteroids or comets.In their paper, Randall and Reece note that the conventional view of the material that makes up dark matter, wouldn’t work as a means of pulling other bodes from where they currently reside, it’s evident in their name—weakly interacting massive particles. They suggest that some dark matter could be made instead of what they describe as “strong electromagnetic-like interactions among dark matter particles” which by their nature would exert a greater gravitational pull. And if that were the case, then it would seem plausible that as our solar system circles around the center of our galaxy, most particularly as we move closer to the Oort cloud, some of those bodies that exist there, could be jostled, which in turn could cause some of them to wind up on a collision course with our planet.This new theory by the research pair has some problems—it assumes the periodicity of crater creation has been firmly established, which it hasn’t, and, scientists aren’t even sure which craters on the Earth’s surface were cause by what sort of object. In any event, the theory is expected to gain or lose credence as the European Space Agency’s Gaia mission gets underway—it’s supposed to give us a better view of the Milky Way Galaxy than ever before. Explore further More information: Dark Matter as a Trigger for Periodic Comet Impacts, Phys. Rev. Lett. 112, 161301 – Published 21 April 2014. journals.aps.org/prl/abstract/ … ysRevLett.112.161301ABSTRACTAlthough statistical evidence is not overwhelming, possible support for an approximately 35×106 yr periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed. Such a disk is motivated by a novel dark matter component with dissipative cooling that we considered in earlier work. We show how to evaluate the statistical evidence for periodicity by input of appropriate measured priors from the galactic model, justifying or ruling out periodic cratering with more confidence than by evaluating the data without an underlying model. We find that, marginalizing over astrophysical uncertainties, the likelihood ratio for such a model relative to one with a constant cratering rate is 3.0, which moderately favors the dark disk model. Our analysis furthermore yields a posterior distribution that, based on current crater data, singles out a dark matter disk surface density of approximately 10M⊙/pc2. The geological record thereby motivates a particular model of dark matter that will be probed in the near future. 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.
Explore further A ten-year study of grapevine hardiness in the face of drought has been conducted by a team led by researchers at the French National Institute for Agricultural Research. In their paper published on the open access site Science Advances, they report that the wine industry does not appear to be in imminent danger due to global warming, as some have suggested. © 2018 Phys.org Credit: CC0 Public Domain Overlooked plants defy drought More information: Guillaume Charrier et al. Drought will not leave your glass empty: Low risk of hydraulic failure revealed by long-term drought observations in world’s top wine regions, Science Advances (2018). DOI: 10.1126/sciadv.aao6969AbstractGrapevines are crops of global economic importance that will face increasing drought stress because many varieties are described as highly sensitive to hydraulic failure as frequency and intensity of summer drought increase. We developed and used novel approaches to define water stress thresholds for preventing hydraulic failure, which were compared to the drought stress experienced over a decade in two of the world’s top wine regions, Napa and Bordeaux. We identified the physiological thresholds for drought-induced mortality in stems and leaves and found small intervarietal differences. Long-term observations in Napa and Bordeaux revealed that grapevines never reach their lethal water-potential thresholds under seasonal droughts, owing to a vulnerability segmentation promoting petiole embolism and leaf mortality. Our findings will aid farmers in reducing water use without risking grapevine hydraulic integrity.
Pre-disturbance forest type. (A) Reference pre-disturbance type for sampled pixels identified as forest loss. (B) National estimates of 2000-2014 forest loss area by re-disturbance forest type. Area estimates expressed in ha along with SEs are presented table S2A. Credit: Tyukavina et al., Sci. Adv. 2018;4: eaat2993 A team of researchers from the University of Maryland and the State University of New York has found that smallholder clearing is the dominant driver of forest loss in the Congo Basin. In their paper published in the journal Science Advances, the group describes the techniques they used to assess forest loss in the area over the period from 2000 to 2014 and what they found. The Congo Basin includes forests in the Democratic Republic of Congo, the Republic of Congo, Gabon and Equatorial Guinea—it comprises the second largest rainforest in the world (the Amazon basin is the largest). And like the Amazon basin, it is being cut down. In this new effort, the researchers sought to learn more about the entities that are cutting down the forest as a means toward targeting efforts to reduce or eliminate such cutting.To better understand what is happening in the basin, the researchers studied satellite data over the years 2000 to 2014, noting changes in tree cover. They also used remote sensing technology to analyze forest changes and deforestation drivers. They then compared what they learned with information provided by outside experts on the area. More information: Alexandra Tyukavina et al. Congo Basin forest loss dominated by increasing smallholder clearing, Science Advances (2018). DOI: 10.1126/sciadv.aat2993 The researchers also noted that the United Nations has estimated that the human population in the Congo Basin will be five times higher than it is today by the end of the century. They suggest that if conditions in the area do not improve, the entire basin could lose all its native forests over the same time period. The researchers found that the Amazon Basin lost forest area approximately the size of Bangladesh over the span of just 15 years. They also found that logging was not the biggest culprit—it was small-time clearing done by hand by subsistence farmers. In all, 80 percent of forest loss was due to what the researchers describe as smallholder clearing. The researchers suggest the reason for such massive smallholder clearing is poverty. Unable to make a living, many people turn to farming. They cut down a swath of forest and plant crops. But the soil is quickly depleted, forcing the farmers to cut down new areas periodically. Faith leaders, Pygmies join forces in fight for Congo forest © 2018 Science X Network Expansion of small-scale agriculture into recently undisturbed forests and woodlands (lines), and population growth in the region by country (bar chart). Solid lines connect the annual forest loss area estimates and dashed lines represent the linear trend based on ordinary least squares regression. Forest clearing for small-scale rotational agriculture includes clearing for charcoal production, the contribution of which does not exceed 10% of the class area. Error bars on the area estimates represent one standard error. Credit: Tyukavina et al., Sci. Adv. 2018;4: eaat2993 3-year moving average of annual forest loss area for the major disturbance categories in all countries. Each major disturbance category contributes >0.5 Mha to the total 2000-2014 forest loss area. Forest clearing for small-scale rotational agriculture includes clearing for charcoal production, the contribution of which does not exceed 10% of the class area. Error bands represent ± SE. Annual area estimates along with SEs are presented in table S2B. Abbreviations: Prim. – “Primary”, Sec. – “Secondary”, HTF – “Humid Tropical Forests”, Woodl. – “Woodlands”. Credit: Tyukavina et al., Sci. Adv. 2018;4: eaat2993 Citation: Smallholder clearing found to be dominant reason for forest loss in the Congo Basin (2018, November 8) retrieved 18 August 2019 from https://phys.org/news/2018-11-smallholder-dominant-forest-loss-congo.html 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. Journal information: Science Advances Three-year moving average of annual forest loss area for the major disturbance categories in all countries. Credit: Tyukavina et al., Sci. Adv. 2018;4: eaat2993
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. Transparency as a function of material skin depth. (a) The effective index of a square array of nanocylinders, composed of aluminum, gold, silver, and titanium. Inset: the skin depth of each metal, calculated using the Lorentz–Drude model of permittivity. (b) At a fixed wavelength, it is the ratio of the particle diameter to the skin depth of the metal that determines whether the particles behave as quasi-static dipoles or perfect conductors. The effective index is remarkably constant for d ≲ δs. Credit: Nature Communications, doi: 10.1038/s41467-019-09939-8 An illustration of how metals, dielectrics, and effective dielectrics respond to a slowly varying electric field. Within in each system, the applied field is opposed by an induced electric field generated by the buildup of surface charges. (a) In metals, the electrons are free to move until the applied and induced fields cancel in the bulk. In dielectrics (b) and effective dielectrics (c), the surface charge is generated by the polarization of the (meta-)atoms or (meta-)molecules, and the induced field is weaker than the applied field. Credit: Nature Communications, doi: 10.1038/s41467-019-09939-8 Journal information: Nature Communications The scientists then compared different types of metals (aluminum, silver, gold and titanium) to show that materials with longer skin depths produced the most transparent and least dispersive nanoparticle arrays. Palmer et al. showed that at a fixed wavelength, the ratio of the particle diameter to the skin depth of the metal determined if the particle would behave as quasiparticle dipoles or as perfect conductors. In addition to high transparency, the scientists could tune the system by controlling the size, shape and space of the particles. For instance, Palmer et al. controlled the aspect ratio of arrays of elliptical cylinders to show that the anisotropic response of the material could be tuned. The numerical results showed that the effective index could be easily tuned to vary by more than 50 percent when the system was rotated. Thereby the scientists were able to tune the effective index by fixing the particle positions and tuning their sizes. Scientists can tune the local refractive indices of such materials by altering the size, shape and spacing of nanoparticles to design gradient-index lenses that guide and focus light on the microscale. The electric field can be strongly concentrated in the gaps between metallic nanoparticles for the simultaneous focusing and ‘squeezing’ of the dielectric field to produce strong, doubly enhanced hotspots. Scientists can use these hotspots to boost measurements made using infrared spectroscopy and other non-linear processes across a broad frequency range. In a recent study now published in Nature Communications, Samuel J. Palmer and an interdisciplinary research team in the departments of Physics, Mathematics and Nanotechnology in the U.K., Spain and Germany, showed that artificial dielectrics can remain highly transparent to infrared radiation and observed this outcome even when the particles were nanoscopic. They demonstrated the electric field penetrates the particles (rendering them imperfect for conduction) for strong interactions to occur between them in a tightly packed arrangement. The results will allow materials scientists to design optical components that are achromatic for applications in the mid-to-infrared wavelength region. Palmer and colleagues were able to tune the local refractive index of these components by altering the size, shape and spacing of nanoparticles with sensitivity to the local refractive index of the surrounding environment. The scientists enhanced the electric field in the gaps between the metallic nanoparticles in the array and simultaneously exploited their transparency, tunability and high metallic filling fraction to design a gradient-index lens. The work focused light on the microscale and squeezed the electric field in the nanoscale to produce the doubly enhanced electric field hotspot throughout the infrared (IR) region. The scientists envision that the new work will boost measurements made using IR spectroscopy and other nonlinear processes across a broad-range of frequencies. , Optics Express More information: Samuel J. Palmer et al. Extraordinarily transparent compact metallic metamaterials, Nature Communications (2019). DOI: 10.1038/s41467-019-09939-8 J. B. Pendry et al. Extremely Low Frequency Plasmons in Metallic Mesostructures, Physical Review Letters (2002). DOI: 10.1103/PhysRevLett.76.4773 D. R. Smith. Metamaterials and Negative Refractive Index, Science (2004). DOI: 10.1126/science.1096796 Seungwoo Lee. Colloidal superlattices for unnaturally high-index metamaterials at broadband optical frequencies, Optics Express (2015). DOI: 10.1364/OE.23.028170 Tiny particles with varied shapes scatter light in useful and unusual ways To highlight this potential to tune the local effective index, Palmer et al. then constructed a gradient-index (GRIN) lens using triangular lattices of gold cylinders and varied the diameters of the cylinders with position. Using the GRIN lens, the scientists were able to simultaneously focus light on the microscale and then ‘squeeze’ light on the nanoscale to produce the intense, ‘doubly enhanced’ electric field hotspots. Unlike plasmonic enhancements, the effect did not rely on lossy resonances, demonstrating broadband and low-loss properties. They showed that the focal point of the GRIN lens had to coincide with the region of closest packing to maximize squeezing of the electric field. Unlike magnetic fields that were continuous across the air-metal interfaces in the study, the electric field strongly localized in the gaps. As a result, squeezing a 2 µm wavelength into 2 nm gaps produced strong hotspots of high intensity in the study.In this way, Palmer et al. constructed low-loss, effective dielectrics from arrays of metallic nanoparticles. The scientists obtained highly transparent arrays that exceeded the transparency of real dielectrics such as germanium; renowned for their transparency to low energy radiation. They were also able to locally tune and control the size, shape and space of the particles forming the new metamaterials. The scientists showed the effective index to be essentially constant for all wavelengths greater than 2 µm. This work will allow materials scientists to design and engineer sophisticated optical devices with metamaterials that guide or enhance light across a broad range of frequencies, essentially without an upper bound on wavelength.
Kolkata: In a word of advice to the trade union leaders, state Power minister and Indian National Trinamool Trade Union Congress (INTTUC) leader Sobhandeb Chattopadhyay said on Tuesday that the former should not indulge in lockouts of factories or companies, in order to claim their rights. “You have to press for your rights but not at the cost of keeping the gates of your company closed. You have to continue the flow of work. Your slogan should be Struggle is Our Right, Struggle for Better Living, Production is our Target,” Chattopadhyay said, addressing the 42nd meeting of Kolkata Municipal Corporation Employees and Workers Union. Also Read – Heavy rain hits traffic, flightsThe minister slammed the previous Left Front unions, for pursuing destructive movements to claim their rights and reiterated that INTTUC should not demand for their rights at the cost of stalling work. He stressed that the union should work for betterment of the people working in the unorganised sector, as more than 50 crore people in the country work in this sector, in comparison to 4 crore labourers working in the organised sector.Meanwhile, state Labour minister Moloy Ghatak reiterated the various steps taken by the Mamata Banerjee government, for betterment of the living standards of workers in the unorganised sector. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killed”During the Left Front rule, the jute mill workers got a meagre Rs 100 as daily wage. Now, they are getting Rs 257 a day and Dearness Allowance (DA) every six months. Not a single jute mill in the state is closed,” Ghatak said.He slammed the Narendra Modi government at the Centre, for its indifferent attitude towards the labourers. Central PSUs like Burn Standard and Hindustan Cables have closed down and many people have lost their jobs. “Now, the Centre is trying to close down 21 coal blocks in Asansol. But we will not let them do so,” the Labour minister said.
Kolkata: In an attempt to combat the dearth of doctors at various state-owned hospitals, the Bengal government is considering a proposal to make it mandatory for the doctors from the private establishments to provide voluntary service at the government hospitals.The matter is, however, in the primary level and the state Health department has been mulling if the doctors from private hospitals could be roped in. It has been learnt from the sources that during her recent meeting with the senior health officials at Nabanna, Chief Minister Mamata Banerjee also instructed the officials to explore the possibilities on how the doctors from private hospitals can be utilised in government hospitals, if there is a need. Also Read – Heavy rain hits traffic, flightsThe state Health department is contemplating how the private doctors can be engaged for giving voluntary service at the state run-hospitals. The move is aimed at ensuring proper and timely medical care to those undergoing treatment at various hospitals, particularly in the multi super-speciality ones that have come up in various parts of the state.It may be mentioned here that after coming to power, the Mamata Banerjee government has set up around 42 multi super-speciality hospitals in the districts. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedVarious modalities like determining the consultation fee of these doctors or their fixed honorarium will be worked out, most likely on the basis of the number of patients they attend. The matter is, however, up to the government.The senior Health department officials may chalk out an elaborate plan for engaging private doctors for voluntarily devoting time ato treat patients at district hospitals, as well as the multi super-speciality hospitals, sources said. The present government has increased the number of medical seats in the state. According to sources in the state Health department, the combined number of MBBS and BDS seats have increased from 2,205 to 3,750, while the number of post-graduate medical seats have increased from 880 to 1,297.The number of post-doctoral seats has also increased to 147 from 107. Around 93 tutor-demonstrators were appointed by the Health department, bringing the total number of such appointments to 2,095.Despite the initiatives taken by the state government, there is a dearth of doctors at government establishments, as the number of medical seats were not increased for a long time.According to a senior government official, the plan is at the preliminary level. The decision will be taken after considering all aspects relating to the proposal.”There is a proposal regarding the utilisation of the private doctors, which is under the consideration of the government,” the official said.
Kolkata/Barasat: A day after a Trinamool Congress (TMC) delegation was detained at Silchar airport in Assam, a section of the party’s supporters today blocked rail and road traffic in pockets of Kolkata and its suburban areas to protest against the incident. Train services were partially affected at the Sealdah Division of Eastern Railway (ER) this morning when a group of people blocked the tracks at Dhubulia and Guma stations. Five trains were delayed due to the protest over a “non-railway issue”, an ER spokesperson said. Also Read – Rain batters Kolkata, cripples normal life “At Dhubulia, the protesters blocked the tracks for over an hour, delaying two passenger trains. Three EMU locals were also held up at Guma station in the morning,” he added. An eight-member TMC delegation which reached Silchar yesterday to assess the situation in Assam in the wake of publication National Register of Citizens (NRC) draft was not allowed to leave the airport. The party supremo and West Bengal Chief Minister Mamata Banerjee claimed that the delegation members were manhandled at the airport and accused the BJP of imposing “super emergency” in the country. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killed In North 24 Parganas district, The All India Matua Mahasangha, a religious organization representing the backward classes, put up road blockades around 10am, condemning yesterday’s incident, a senior police officer said. TMC MP Mamatabala Thakur is the chairperson of the organization. “The members of Matua Mahasangha blocked the Habra-Bashirhat Road at two places — Pairagachhi and Kashipur – to protest against the alleged manhandling of Mamatabala Thakur at Silchar airport,” the officer said. The blockade was, however, lifted after half-an-hour following police intervention, he added. On Wednesday, too, the Matuas had squatted on railway tracks at many stations in Barasat district, protesting the exclusion of over 40 lakh people from Assam’s complete draft of National Register of Citizens (NRC).
Kolkata: State minister for Technical Education, Training & Skill Development Purnendu Basu urged handloom societies across the state to join hands and create massive awareness of its products and compete with the power loom products.”The products that you are producing are limited to a closed society. You need to come up with a strategy to create an open society for handloom products. You have to go for advertisements or showcase your products. You can take slots in radios and explore other means to reach more consumers,” Basu said at a programme organised by the Weavers’ Service Centre to mark the occasion of World Handloom Day. Also Read – Rain batters Kolkata, cripples normal lifeHe emphasised that the same is true for jute products which is also seen as a more fashionable product but whose utilization is much below potential. Stressing on the need to create a powerful society for popularization of handloom and jute products Basu said: “The government alone cannot spoon feed you to keep the traditional handlooms alive. The responsibility is upon you to create a form of movement and knock at the door of the governments both the Centre and the state so that they are compelled to give more importance to this sector,” he added. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedHe regretted that the businessmen associated with the sale of handloom products are focusing more on products of other states for their own petty interests. “If we can ensure selling of only those products that are manufactured by the people of our own state, we can give create a robust market for handloom products. Don’t join hands with the businessmen of Gujarat and keep more and more products produced by our own handloom weavers,” he maintained. Basu further urged the societies to have a proper market study regarding the sales of the handloom products and work towards diversification of products.”There should be a database of semi-skilled, skilled, highly-skilled and unskilled labourers associated with the production of handloom and jute products. Proper project plan for revival of the industry should be in place before you approach the government for assistance or beneficial schemes in this regard,” advised Basu.