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. Copyright 2010 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. “Mm-wave frequency allocation around 57-66 GHz can deliver bandwidths in excess of 1 Gb/s compared to few Mb/s offered by current third generation mobile systems or 100 Mb/s offered by Wi-Fi systems,” Lim told PhysOrg.com. “There are even higher mm-wave frequencies which have much larger bandwidths available. However, the technologies for these are not yet matured and over time, the mm-wave band could be exploited to give bandwidths in excess of 10 Gb/s over short-range wireless.“Due to the short transmission distances associated with mm-wave frequencies, applications in personal area networking would be the most appropriate,” she said. “Providing fast wireless connectivity between your hi-def display screens and video content on a storage device, for example, or connecting a range of devices such as laptops, media storage and displays for entertainment and business interactivity applications, to name a few, will soon require bandwidths in excess of 100 Mb/s connectivity.”Transportation and integration optionsRegarding the basic architecture of a Fi-Wi system, the researchers looked at three possible approaches for transporting mm-wave wireless signals over optical fibers. The simplest scheme, called RF-over-fiber, involves directly transporting the wireless signals, so that no frequency translation is required at the base stations. The second method involves downconverting the mm-wave wireless signals to a lower intermediate frequency (IF) at the central office before optically transmitting the signals to the base station where they are upconverted, which is called IF-over-fiber. The third method, called baseband-over-fiber, involves transporting the wireless signals as very low-frequency baseband signals over optical fibers from the central office to the base station, and then upconverting the information to the mm-wave frequency at the base station. Ultimately, there is a tradeoff between simplicity and robustness in the three methods: while the RF-over-fiber method is the simplest, the signals are more susceptible to various impairments as they propagate along the optical fiber. Many research teams have been working on a number of strategies to overcome these impairments. The authors of the current study emphasize that these improvements are necessary for achieving good signal quality and overall system performance. Another requirement is for fiber-wireless systems to be integrated with the existing optical infrastructure. The engineers explain that the rising level of optical fiber infrastructure deployment close to residential premises provides an ideal opportunity to interconnect the wireless with fixed wired networks. This integration would enable fiber-wireless systems to take advantage of current technologies such as wavelength-division-multiplexing (WDM), which combines multiple signals on a single optical fiber by using different wavelengths. Previous research has demonstrated that WDM can significantly increase the capacity and success rates of fiber-wireless systems. In addition, research has shown that there are a range of technology options that support such integration cost-effectively without compromising the performance required of these very high-speed networks.Overall, mm-wave fiber-wireless technology has the potential to open up the wireless spectrum as the use of small, portable communication devices continues to grow. Serving as a short-distance technology, the wireless portion can cover the “last mile” of data transmission to customers, as well as in-building networking, with the potential for faster speeds and lower costs. For these reasons, fiber-wireless systems would make the most sense in densely populated areas, and also for disaster recovery environments where wired communication lines are unavailable. As Lim explained, fiber-wireless could be deployed in the near future.“We feel that fiber-wireless could be commercially ready in 3-5 years with immediate applications to new base station installations,” she said. “The adoption of Fi-Wi technologies to 3G and 4G wireless will be the most likely market in the immediate term. As the fiber deployment extends to buildings and premises, mm-wave Fi-Wi will take off.” This congestion problem was not unanticipated by electrical engineers, who, for the past two decades, have been developing new wireless technologies that use different parts of the electromagnetic spectrum. Specifically, these wireless technologies are exploiting the large, unused bandwidths of extremely high frequency (EHF) microwaves in the millimeter-wave (mm-wave) frequency region. One particular area of interest is the unlicensed 60 GHz frequency band, which has 5-mm wavelengths. (In contrast, the heavily burdened lower microwave regions have frequencies of 2-4 GHz, corresponding to wavelengths of 7.5-15 cm.) However, the 60 GHz frequency band is not without challenges, either. Since wireless signals at 60 GHz frequencies have inherently high propagation losses, they are targeted toward short-range, in-building, high-speed applications. To maintain strong incoming wireless signals for buildings, many antenna base stations must be built near customers. These base stations, in turn, would receive broadband signals from a smaller number of distant central offices. The signals between central offices and base stations would be transmitted through long-range optical fibers. Since such a system uses both optical fibers and mm-wave wireless transmission, the technology is called “fiber-wireless” (Fi-Wi). The advantage of bimodal Fi-Wi systems is that they can enjoy the strengths of both optical and wireless technologies – specifically, the inherently large bandwidth of optical fiber and the large, unused bandwidth in the mm-wave wireless spectrum. For this reason, a hybrid system has the potential to provide very high data transmission rates with minimal time delay.Recently, a team of electrical engineers working on fiber-wireless technologies has analyzed the progress made in this field over the past two decades. In a paper published in the Journal of Lightwave Technology, Christina Lim, from the University of Melbourne, and her coauthors have presented an overview of the many different techniques proposed to optically transport mm-wave wireless signals and overcome some of the challenges involved. (PhysOrg.com) — By looking at the latest electronic communication devices that have emerged over the past few years, it’s clear that the trend of smaller, portable devices is strong and expected to continue. Yet while all these notebooks, netbooks, and tablet PCs are becoming more and more popular, their explosive growth also poses a problem: these wireless devices are hogging the already congested lower microwave frequency region of the wireless spectrum. CSIRO designs world’s best mm-wave chips for communications and security More information: Christina Lim, et al. “Fiber-Wireless Networks and Subsystem Technologies.” Journal of Lightwave Technology. Vol. 28, No. 4. February 15, 2010. Doi:10.1109/JLT.2009.2031423 Citation: Fiber-wireless (Fi-Wi) to provide ultra-high-speed, short-range communication (2010, March 9) retrieved 18 August 2019 from https://phys.org/news/2010-03-fiber-wireless-fi-wi-ultra-high-speed-short-range.html Explore further A mm-wave Fi-Wi network. An optical fiber backbone (red) provides broadband connections between the central offices and antenna base stations. Then, the base stations wirelessly transmit 5-mm-wave (60 GHz) signals to customers. Within buildings and homes, the short-range wireless signals can provide high-speed connectivity (faster than 1 Gb/s) for a variety of wireless, high-bandwidth communication devices. Credit: Lim, et al.
A prototype holographic drive system designed by GE researchers in the Applied Optics Lab at GE Global Research in Niskayuna, NY. Citation: GE announces 500 GB holographic disc writer that runs at Blue-Ray speed (2011, July 21) retrieved 18 August 2019 from https://phys.org/news/2011-07-ge-gb-holographic-disc-writer.html (PhysOrg.com) — GE’s technology research group has announced the development of an optical disc writer capable of writing 500 GB of data onto a disc the same physical size as a DVD, at roughly the same speed as Blue Ray technology. This comes two years after announcing the holographic technology that was used to first imprint the discs with 25 times as much data as a Blue Ray Disc can hold. Explore further By making an announcement about an advancement in what most see as a dying technology, GE is taking somewhat of a risk, but Peter Lorraine, Manager at GE Global Research, who will be presenting today at the IEEE’s Joint International Symposium on Optical Memory & Optical Data Storage meeting is expected to pooh-pooh such notions and instead explain how the new technology could be used for long term storage for data, that the company says, will last for a hundred years (presumably if stored in ideal conditions).The technology works by initially stamping millions of tiny holographic images into a polycarbonate (a type of thermoplastic polymer) material, then a laser (which uses the same wavelength as Blue Ray technology) is used to erase parts of the holograms to encode data. Write speeds are 4-5 megabytes per second, which is on a par with Blue Ray (4.5 Mbytes/s). With this process the entire surface of the disc can be used, rather than just the four layers on the surface of the disc that Blue Ray is able to use, which is why it can hold so much more.And while critics point out that at such a rate it would take something like a whole day to fill the disc, GE counters by saying that since its primary purpose would be for archival storage, creating specialized writers that use multiple heads could very well be an option; and If such multiple read/write head drives could be created, it seems plausible to believe that such discs would be capable of carrying not just HD/3-D movies, but something even better, such as movies in a super HD (holographic?) format that hasn’t even been discovered yet.GE also points out that because the new writer uses the same wavelength as Blue Ray, its conceivable drives could be made for the new technology that would be backwards compatible, minimizing risk for both developers and end users. The company is expected to begin building arrangements with interested parties to license the new technology in just the new few months, so actual products appearing on the market can’t be too far off. More information: Press release © 2010 PhysOrg.com General Electric Develops a 500GB Optical Disc 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.
Tornados happen in many places, but because of its unique geography, the U.S. has more than any other country—mainly due to the lack of a large mountain dividing east and west. There has been speculation recently, that global warming is causing more tornados to occur—though it has also been suggested it only seems that way because of how quickly information about tornadic events disseminates in the modern era. The trio at NOAA decided to let hard facts tell the story. They collected weather data from the national storm database, which goes back to 1954, to see if they could coax out any patterns (they only included tornados at least as strong as an F1).As it turns out, the trio did find a pattern, they say the data shows very clearly that the U.S. actually has a trend of having fewer days in which there is a tornado over the past two decades—that’s the good news. The bad news is that on days when there is a tornado, there are more than there used to be. The data shows that back in the 1970’s there were just .6 days a year that had 30 or more tornados—after the turn of the century, that number had risen to 3 days per year. Curiously, the numbers suggest that the country still experiences on average, the same number of tornadoes each year, approximately 1,200—they’re just spread out differently. They also noted that the beginning and end of the tornado “season” in recent years has fluctuated more wildly than the years prior to that.The researchers cannot say of course why the spread of tornados has changed in the U.S., though some might suggest it’s due to global warming or even changes in atmospheric conditions in parts of the country due to pollution or other unknown factors. What is clear, is that something is causing a change, and there is now evidence of it, providing a path for moving forward for better understanding what is really going on. Magazine reporting below average numbers of tornados in 2013 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. Image: U.S. National Oceanic and Atmospheric Administration, via Wikimedia Journal information: Science More information: Science 17 October 2014: Vol. 346 no. 6207 pp. 349-352. DOI: 10.1126/science.1257460 © 2014 Phys.org Citation: Data shows fewer tornado days in U.S. but more per event over past couple decades (2014, October 17) retrieved 18 August 2019 from https://phys.org/news/2014-10-tornado-days-event-couple-decades.html Explore further A trio of researches with the U.S.’s National Oceanic and Atmospheric Administration (NOAA) has found that though there are fewer total days per year when tornados occur in the U.S., the number that occur on days when there are tornados has increased over the past couple of decades. In their paper published in the journal Science, Harold Brooks, Gregory Carbin and Patrick Marsh describe how they studied weather data over the past half century and what they found when looking for trends.
Figure 2 | AFM and piezoresponse images of CIPS with different thicknesses. (a–c) AFM topography (a) PFM amplitude (b) and PFM phase (c) for CIPS flakes ranging from 100 to 7 nm thick, on doped Si substrate. Scale bar in a, 1 μm. (d,e) AFM topography (d) PFM amplitude (e) and phase (f) of 2–4 layer thick CIPS on Au coated SiO2/Si substrate. Scale bar in d, 500 nm. (g) the height (black) and PFM amplitude (blue) profile along the lines shown in d and e, respectively. L, Layers. Credit: Liu F, et al. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes. Nature Communications 7, Article number: 12357 (2016). Copyright © 2016, Rights Managed by Nature Publishing Group. Creative Commons Attribution 4.0 International License. Wang describes the ways in which the researchers addressed these challenges. “To characterize ferroelectricity at nanoscale, the most widely used technique is called piezoresponse force microscopy, or PFM, which utilizes the converse piezoelectric effect.” (In the converse piezoelectric effect, materials become strained when an electric field is applied.) This is a technique that can be implemented using a commercially available atomic force microscope (AFM), in which AC bias can be applied to the AFM probe that serves as a moving electrode on top of the sample. The resulting AC electric field will cause the periodic oscillation of the ferroelectric sample due to this converse piezoelectric effect. The oscillation signal can then be detected by the AFM. “The amplitude of the oscillation represents the piezoelectric response that is proportional to the ferroelectric polarization,” Wang explains, “while the phase of the oscillation represents the direction of the polarization.” In their study, the scientists employed a state-of-the-art approach known as Dual AC Resonance Tracking (DART) PFM developed by Asylum Research to amplify the piezoelectric response by taking advantage of the resonance enhancement. The scientists are planning to study the pyroelectric properties of CuInP2S6 at its two-dimensional limit and apply their findings to developing energy harvesting devices. To that end, he adds, because mechanically exfoliated 2D materials are usually small and unsuitable for device applications, chemical vapor deposition growth of atomically thin CuInP2S6 is under development.”Ferroelectric properties are also very interesting for solar cell applications because of efficient ferroelectric polarization-driven carrier separation,” Liu concludes, “so 2D ferroelectricity-based solar cells could be very interesting, In its liquid phase, 2D ferroelectric CuInP2S6 could be easily hybridized with semiconductor 2D or organic materials – and a solar cell based on these hybrids would be very promising.” Figure 5 | Electric characterization of the vdW CIPS/Si diode. (a) The I–V curves from the typical vdW CIPS/Si diode with 30 nm thick CIPS, by sweeping the bias from 2.5 to −2.5 V, and then back to 2.5 V. Inset is the schematic of the device. (b) Resistance-switching voltage hysteresis loop of the diode measured at a bias voltage of −1.3 V. The schematic representations of the ON and OFF states with respect to the polarization direction are shown in the bottom-left and top-right insets, respectively. (c) Out-of-plane PFM amplitude (black) and phase (blue) measurements on the same diode device shown in a. Credit: Fucai Liu, Lu You, Kyle L. Seyler, Xiaobao Li, Peng Yu et al. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes. Nature Communications 7, Article number: 12357 (2016). Copyright © 2016, Rights Managed by Nature Publishing Group. Creative Commons Attribution 4.0 International License. Journal information: Nature Communications More information: Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes, Nature Communications 7, Article number: 12357 (2016), doi:10.1038/ncomms12357Related:1. Subatomic deformation driven by vertical piezoelectricity from CdS ultrathin films, Science Advances 01 Jul 2016, Vol. 2, no. 7, e1600209, doi:10.1126/sciadv.16002092. Picoscale precision though ultrathin film piezoelectricity, Phys.org (10 August 2016), http://phys.org/news/2016-08-picoscale-precision-ultrathin-piezoelectricity.html Citation: Cool Constructs: Room temperature out-of-plane ferroelectricity at ultrathin atomic limit (2016, September 5) retrieved 18 August 2019 from https://phys.org/news/2016-09-cool-room-temperature-out-of-plane-ferroelectricity.html , Science Advances 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 Figure 1 | Crystal structure and characterization of CIPS. (a,b) The side view (a) and side view (b) for the crystal structure of CIPS (CuInP2S6) with vdW gap between the layers. Within a layer, the Cu, In and P–P form separate triangular networks. The polarization direction is indicated in by the arrow. (b) The ferroelectric hysteresis loop of a 4-μm-thick CIPS flake. (c) AFM image of the CIPS flakes with different thicknesses. Scale bar, 2 μm. (d) The height profile along the line shown in c. Clear step height of 0.7 nm corresponding to single layer thickness of CIPS can be observed. L, Layers. Credit: Liu F, et al. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes. Nature Communications 7, Article number: 12357 (2016). Copyright © 2016, Rights Managed by Nature Publishing Group. Creative Commons Attribution 4.0 International License. (Phys.org)—Optoelectronic devices that combine electronics and photonics are incorporating two-dimensional (2D) materials for a range of applications. At the same time, cooperative phenomena – in which a system’s individual components appear to act as a single entity rather than independently – have yet to be widely investigated, an important example being ferroelectricity (spontaneous electric polarization that can be reversed by an electric field) in the 2D limit. Recently, however, scientists at Nanyang Technological University, Singapore have demonstrated room-temperature out-of-plane ferroelectricity (that is, orthogonal to the 2D material) in 2D CuInP2S6 (copper indium thiophosphate) with a ~320 K transition temperature, as well as switchable polarization in 4 nm CuInP2S6 flakes. The researchers state that their findings create the possibility of sensors, actuators, non-volatile memory devices, various van der Waals heterostructures (devices made from layers of dissimilar 2D crystals in which forces are based on molecular attraction or repulsion rather than covalent or ionic bonds), and other novel applications based on 2D ferroelectricity. Finally, in demonstrating a non-volatile memory device with an on/off ratio of ~100 in a CuInP2S6/Si ferroelectric diode, Liu notes that this investigation is just a preliminary demonstration of the possible applications of the 2D ferroelectric material. “A lot of work needs to be done to fully understand the transport mechanisms and how it is coupled to the ferroelectric switching,” he acknowledges. Tunable and mechanically robust ferroelectric ionic plastic crystals Prof. Zheng Liu and Prof. Junling Wang discussed the challenges that they and their colleagues encountered in conducting their study published in Nature Communications. “With reduced dimension, ferroelectricity – namely, long-range electric-dipole order – becomes fragile owing to the depolarization field that is opposing its own electric polarization,” Liu tells Phys.org. “The depolarization field inherently arises in ferroelectric materials due to the imperfect screening of bound charges,” that is, those bound to molecules and so cannot move in response to an external electromagnetic force. The difficulty lies in maintaining a precise geometry, Liu adds, because when the ferroelectric material’s thickness is reduced to its two-dimensional limit, the depolarization field can increase by orders of magnitude. At that point, the depolarization field may place the ferroelectric material into a paraelectric state, the result being disordered electric dipoles with a temporary polarization only when in the presence of an electric field. Therefore, the electrical boundary conditions are extremely important when exploring ferroelectricity at the material’s 2D limit. Moreover, he adds, reporting the experimental observation of switchable polarization in CuInP2S6 films down to 4 nm at room temperature, thickness reduction will greatly weaken the out-of-plane ferroelectric polarization. “This makes characterization of the ferroelectricity very difficult. Moreover, the large ionic conductivity of this material makes the polarization switching quite challenging. We therefore had to choose a small electric field that is just above the coercive field to avoid unwanted ionic motion.”Other concerns include demonstrating the potential of this 2D ferroelectric material by preparing a van der Waals ferroelectric diode formed by CuInP2S6/Si heterostructure. “In the case of CuInP2S6, the chemical composition and phase stability also play a role in stabilizing ferroelectric states – and in the 2D limit, it is difficult to determine the ferroelectricity with traditional methods, such as the time-dependent ferroelectric hysteresis loop measurement, due to large leakage current,” lead author Liu Fucai points out. Regarding potential, he explains that due to the relatively large band gap and thus weak light absorption, few-layer CuInP2S6 appears almost transparent on silicon (Si) substrate. “This situation makes the fabrication of the van der Waals heterostructure quite challenging during the lithography process.” Figure 3 | Ferroelectric polarization switching by PFM for CIPS flakes with different thicknesses. (a) The I–V curves from the typical vdW CIPS/Si diode with 30 nm thick CIPS, by sweeping the bias from 2.5 to −2.5 V, and then back to 2.5 V. Inset is the schematic of the device. (b) Resistance-switching voltage hysteresis loop of the diode measured at a bias voltage of −1.3 V. The schematic representations of the ON and OFF states with respect to the polarization direction are shown in the bottom-left and top-right insets, respectively. (c) Out-of-plane PFM amplitude (black) and phase (blue) measurements on the same diode device shown in a. Credit: Fucai Liu, Lu You, Kyle L. Seyler, Xiaobao Li, Peng Yu et al. Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes. Nature Communications 7, Article number: 12357 (2016). Copyright © 2016, Rights Managed by Nature Publishing Group. Creative Commons Attribution 4.0 International License. “By driving the AC field at the first harmonic contact resonance,” Wang continues, “the piezoelectric oscillation signal can be greatly enhanced. Thus, the small ferroelectric polarization of the ultrathin CuInP2S6 flakes can still be detected by the AFM, as the signal has been amplified by orders of magnitude. This advanced PFM technique helps us to image the fine domain structure with nanometer lateral resolution and picometer vertical resolution, and thereby realize local ferroelectric switching using an AFM probe.”The paper discusses novel applications, including sensors, actuators, non-volatile memory devices, and various van der Waals heterostructures based on 2D ferroelectricity. “By virtue of the piezoelectric effect, ferroelectric materials always have the piezoelectric and pyroelectric properties that allow the use of atomically-thin CuInP2S6 as a strain sensor with high flexibility, such as electric skin monitoring human body motion,” Liu tells Phys.org. “By using the pyroelectric effect, 2D CuInP2S6 could also be used for thermal energy harvesting, and as we know, commercially available ferroelectric random access memory, or FeRAM” – random-access memory similar to DRAM – “with fast writing speed and low-power consumption, but with destructive readout could be improved by employing a ferroelectric diode to achieve non-destructive readout of the information. Considering the quasi-freestanding nature of 2D materials, ferroelectric diodes, or even ferroelectric tunnel junctions with an atomically thin ferroelectric layer may have a much higher ON/OFF ratio, providing the possibility of high-density ferroelectric memories with non-destructive readout.”Regarding the relationship between, and potential applications deriving from, ferro- and piezoelectric effects and van der Waals heterostructure interactions, Liu notes that vertically stacking of different 2D materials with van der Waals force have revealed unusual properties and have been investigated for the application of tunneling transistors, light emitting diodes, and light harvesting devices. “Incorporating ferroelectricity to the van der Waals heterostructure could demonstrate new functionality, such as ferroelectric field transistors and optoelectronic memory, by combining CuInP2S6 with 2D semiconductors.” © 2016 Phys.org
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 How the motility structure of the unicellular archaea is fixed to their surface Citation: Viruses found to attack ocean archaea far more extensively than thought (2016, October 17) retrieved 18 August 2019 from https://phys.org/news/2016-10-viruses-ocean-archaea-extensively-thought.html Archaea, short for archaebacteria, are microorganisms similar to bacteria, but which have different molecular structures. Many of them exist in the oceans alongside bacteria living off organic matter.The researchers began their study by focusing on viruses that infect prokaryotes, which include both bacteria and archaea—they started with the assumption that most prokaryote deaths in the ocean are due to viral infections, and that, they note, would make the viruses responsible for the release of approximately 0.37 to 0.63 gigatons of carbon into the atmosphere every year. To learn more and to back up their assumptions, the researchers obtained 500 sea bottom soil samples from multiple areas around the world, each of which was rife with prokaryotes. Prior research has shown that bacteria are more common than archaea both on land and in shallow waters, but archaea become much more numerous in deeper water—the researchers found they made up approximately 12 percent on average of prokaryotes in such areas—though in some regions they ran as high as 32 percent.To learn more about the impact of viruses on prokaryotes, the researchers studied the infection rates of prokaryotes using a variety of methods, one which of which was a molecular analysis that revealed genes released by viruses when causing infections. They found that bacteria were infected at an average rate of 1 to 2.2 percent per day, while archaea were infected at nearly double that rate—2.3 to 4.3 percent. This shows, the team claims, that archaea are far more susceptible to viral than bacterial infection. They then calculated that archaea deaths due to viral infection accounted for approximately 15 to 30 percent of all carbon emissions from prokaryote deaths. They sum up their analysis by suggesting that archaea play a more vital role in the life-cycle of the deep sea than has been thought. (Phys.org)—A team of researchers with members from Italy, Australia, the U.S. and Japan has found that viruses are the main culprit in killing archaea in the deep sea. In their paper published in the journal Science Advances, the researchers describe the techniques they used to study archaea in soil samples from multiple deep ocean locations, what they found and what it could mean for global warming. More information: R. Danovaro et al. Virus-mediated archaeal hecatomb in the deep seafloor, Science Advances (2016). DOI: 10.1126/sciadv.1600492AbstractViruses are the most abundant biological entities in the world’s oceans, and they play a crucial role in global biogeochemical cycles. In deep-sea ecosystems, archaea and bacteria drive major nutrient cycles, and viruses are largely responsible for their mortality, thereby exerting important controls on microbial dynamics. However, the relative impact of viruses on archaea compared to bacteria is unknown, limiting our understanding of the factors controlling the functioning of marine systems at a global scale. We evaluate the selectivity of viral infections by using several independent approaches, including an innovative molecular method based on the quantification of archaeal versus bacterial genes released by viral lysis. We provide evidence that, in all oceanic surface sediments (from 1000- to 10,000-m water depth), the impact of viral infection is higher on archaea than on bacteria. We also found that, within deep-sea benthic archaea, the impact of viruses was mainly directed at members of specific clades of Marine Group I Thaumarchaeota. Although archaea represent, on average, ~12% of the total cell abundance in the top 50 cm of sediment, virus-induced lysis of archaea accounts for up to one-third of the total microbial biomass killed, resulting in the release of ~0.3 to 0.5 gigatons of carbon per year globally. Our results indicate that viral infection represents a key mechanism controlling the turnover of archaea in surface deep-sea sediments. We conclude that interactions between archaea and their viruses might play a profound, previously underestimated role in the functioning of deep-sea ecosystems and in global biogeochemical cycles. © 2016 Phys.org Journal information: Science Advances Credit: Tiago Fioreze / Wikipedia
© 2018 Phys.org Virus cause of more than 170 dolphin deaths in Brazil Explore further Climate change is expected to have an impact on wildlife across the globe. As temperatures creep upward, researchers study various species to better understand how this might affect them. In this new effort, the researchers sought to learn more about the food intake needs of bottlenose dolphins living off the coast of Florida in Sarasota Bay.To understand how much food a wild dolphin requires to live, the team looked at ocean temperatures, various states of dolphin activity and most particularly at the dolphins themselves. They noted that dolphins, like other mammals, require energy to fuel brain activity and to keep up with busy muscles—and also to keep warm. Because of this, they require different amounts of food depending on how active they are and how cold the water is.To calculate the caloric needs of the dolphins, the researchers started with data from prior studies, which have shown that the daily metabolic rate for many species averages out to approximately three to six times that of their resting rate. For the dolphins, that meant capturing several specimens and measuring their metabolic rate while they were kept at rest and then multiplying by three to six to get their average rates.The team reports that they found that the dolphins under study (with an average weight of 200 kg) required approximately 16,500 to 33,000 calories each day, which they further note translated to approximately 10 to 25 kg of fish each day. As part of the study, the group also tested lung function in the dolphins, which has been found to be a marker of environmental health in marine species.The researchers suggest studies like theirs will help with conservation efforts as the planet changes—if dolphins begin to require less food, for example, due to warmer water, that could lead to an increase in fish populations. More information: A. Fahlman et al. Field energetics and lung function in wild bottlenose dolphins, Tursiops truncatus , in Sarasota Bay Florida, Royal Society Open Science (2018). DOI: 10.1098/rsos.171280AbstractWe measured respiratory flow rates, and expired O2 in 32 (2–34 years, body mass [Mb] range: 73–291 kg) common bottlenose dolphins (Tursiops truncatus) during voluntary breaths on land or in water (between 2014 and 2017). The data were used to measure the resting O2 consumption rate (V˙O2V˙O2, range: 0.76–9.45 ml O2 min−1 kg−1) and tidal volume (VT, range: 2.2–10.4 l) during rest. For adult dolphins, the resting VT, but not V˙O2V˙O2, correlated with body mass (Mb, range: 141–291 kg) with an allometric mass-exponent of 0.41. These data suggest that the mass-specific VT of larger dolphins decreases considerably more than that of terrestrial mammals (mass-exponent: 1.03). The average resting sV˙O2sV˙O2 was similar to previously published metabolic measurements from the same species. Our data indicate that the resting metabolic rate for a 150 kg dolphin would be 3.9 ml O2 min−1 kg−1, and the metabolic rate for active animals, assuming a multiplier of 3–6, would range from 11.7 to 23.4 ml O2 min−1 kg−1.absbreak Our measurements provide novel data for resting energy use and respiratory physiology in wild cetaceans, which may have significant value for conservation efforts and for understanding the bioenergetic requirements of this species. Citation: Measuring metabolism in dolphins to calculate their caloric needs (2018, January 17) retrieved 18 August 2019 from https://phys.org/news/2018-01-metabolism-dolphins-caloric.html Bottlenose Dolphin – Tursiops truncatus. A dolphin surfs the wake of a research boat on the Banana River – near the Kennedy Space Center. Credit: Public Domain A team of researchers from several institutions in the U.S. and one in Spain has measured the metabolism of wild bottlenose dolphins in an effort to better understand their caloric needs. In their paper published in the journal Royal Society Open Science, the group describes measuring the dolphins, what they found, and explain how their findings can help with conservation efforts. Journal information: Royal Society Open Science 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.
Kolkata: A writ petition was filed at Calcutta High Court on Wednesday, pointing out the errors in the Bengali translation of the National Eligibility cum Entrance Test (NEET) question paper this year. Apala Debnath, a medical aspirant, had filed the petition, drawing the attention of the court to the ambiguity and mistakes that had occurred in the examination. It was mentioned in the petition that there were 180 mistakes out of 180 questions in the Bengali version of the NEET question paper. Also Read – Heavy rain hits traffic, flightsThe medical aspirants who appeared for the examination with Bengali as the medium were confused by the ambiguity, meaningless and incomplete Bengali translation. Most of these students became nervous and hence could not answer the questions which were known to them.It was not possible for the Bengali version students to finish all answers within 3 hours. The petitioner had also raised questions on the role of CBSE, which conducted the examination. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedThe petition also stated that the students of Bengal were compelled to appear for the examination with xerox copies of question paper and OMR answer sheet. Such incidents were reported on the day of examination as well. The petitioner pointed out that such activities were the result of absolute negligence on the part of CBSE.The petitioner moved to Calcutta High Court, seeking its intervention as neither the Centre nor the CBSE took any initiatives in this regard, particularly after Bengal Chief Minister Mamata Banerjee wrote to the Union Human Resources Development Ministry, calling for a re-examination.Following the incident, the city doctors had also written to the Chief Minister and Prime Minister, seeking their intervention.
The Australian Government has come up with an exhibition
Uber Technologies Inc have chosen Bangkok, known for its chaotic traffic, as the first city in Southeast Asia to introduce a one-day free trial for its helicopter service, after launching it in key global metro cities, including Bangalore. Chan Park, Uber’s regional general manager for Southeast Asia, said Bangkok is one of the worst cities in the world for traffic congestion.”This provides high potential for alternative transport platforms,” Bangkok Post quoted him as saying on Thursday. Thailand is among its three fastest-growing markets for its taxi app service in Southeast Asia, it said. Uber Technologies Inc, the smartphone-based cab service company will offer free helicopter rides on demand to Bangkok customers on Sunday from
Kolkata: Mystery shrouds the death of an elderly woman and her daughter whose charred bodies were found inside their apartment in Dum Dum on Friday evening.Police said the victims, identified as Dipti Mukherjee (72) and her daughter Sathi Mukherjee (54) were alone in the flat when the incident happened. Police suspect after preliminary investigation that fire from the gas cylinder led to their death but it is yet to be discovered as to how the charred bodies reached the bedroom. The police have initiated an unnatural death case in this connection and are trying to find out the exact reason. Also Read – Rain batters Kolkata, cripples normal lifeA police officer said that a plumber, who was working in another flat, noticed smoke billowing out of the victims’ flat on the first floor of a multi-storeyed building in the housing complex. The incident took place at around 5.30 pm on Friday. He informed others and the state Fire and Emergency Service department was contacted. Fire fighters reached the spot and broke open the door of the flat to find the charred bodies. The bodies have been sent for an autopsy. Police came to know that three persons — Sathi, her husband and her mother — used to live in the flat. Sathi’s husband was not in the flat when theincident took place.