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News Article | April 15, 2016
Site: www.nanotech-now.com

Abstract: An international team of physicists has directly observed some unique characteristics of a superconductor for the first time, according to a paper published Wednesday in the journal Nature. Michael Lawler, a theoretical physicist at Binghamton University, contributed to the research, which he considers a great achievement for the experimentalists on the team. The researchers use a very small tool, bringing its tip close to a sample of material they want to examine. They then apply a voltage between them and try to drive a current. In this experiment, Lawler explained, they were able to change the tip by picking up a nano-sized "flake" of a material with a normal metallic tip so they could apply voltage from one superconductor to another. Superconductors are materials -- either "conventional" or "bad" metals at ambient temperatures -- that conduct electricity without resistance below a certain temperature. For decades, it was thought that these materials could conduct electricity only at temperatures far below freezing. Since the mid-1980s, however, scientists have discovered several compounds that superconduct at much higher temperatures. Lawler and his colleagues study a class of materials called cuprate superconductors, compounds including copper and oxygen that superconduct at relatively high temperatures (below 90-150 Kelvin). This particular experiment operated at about 50 millikelvin, which is about as cold as the research group can go, to reduce noise in the measured current. "This is a better and different way of looking at these cuprate materials than has previously been possible," says Lawler, who compared the new technique to the difference between looking at stars with a telescope and looking at the X-rays stars produce. Scanning tunneling microscopes (STM) with a superconducting tip allowed the group to observe the surface of these materials in a completely new way. "Before now, what we've known is that there are lots of waves present in these materials. You can think of the charge changing in a wavelike pattern, where the wave is 4 atoms across." In this experiment, the team was able to look at the superconductivity at the atomic scale for the first time. "They're observing that superconductivity can have waves in itself," Lawler says. "And that's the first time that's ever been observed." If you look at the amplitude of the wave, it's relatively modest. "It didn't surprise me, though people were hoping for something more dramatic," Lawler says. These experiments suggest that other materials -- "tuned" with different amounts of oxygen -- could produce different results, possibly more dramatic waves. In principle, a room-temperature superconductor could allow electricity to travel with zero energy loss from power plants to houses and make possible advanced high-speed trains and cell phone towers. Physicists are still working to understand the origin of high-temperature superconductivity. "I'm excited about seeing this wave that we can now probe directly," Lawler says. "We can find out if there are materials where this dramatic wave happens. They would be different kinds of superconductors than we typically study." ### In addition to Binghamton University, the team included scientists from Harvard University, Cornell University, University of St. Andrews, Seoul National University, the Institute of Basic Science in Seoul, the Institute of Advanced Industrial Science and Technology in Japan, the University of Tokyo, the Max Planck Institute for Chemical Physics of Solids and Brookhaven National Laboratory. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


Dwivedi A.,Institute of Basic science
High Temperatures - High Pressures | Year: 2015

A generalized version of the free volume theory of the Grüneisen parameter has been used here to derive expressions for the second order and third order Grüneisen parameters at extreme compression (volume tends to zero). The method adopted in the present study makes use of some basic principles of calculus. The results obtained are free from any assumptions and thus represent identities in terms of pressure derivatives of bulk modulus for materials at infinite pressure. © 2015 Old City Publishing, Inc.


Jain M.,Indian Institute of Technology Roorkee | Gupta R.,Institute of Basic Science
Computers and Industrial Engineering | Year: 2013

The present investigation deals with the reliability analysis of a repairable system consisting of single repairman who can take multiple vacations. The system failure may occur due to two types of faults termed as major and minor. When the system has failed due to minor faults, it is perfectly recovered by the repairman. If the system failure is due to major faults, there are some recovery levels/procedures that recover the faults imperfectly with some probability. However, the system cannot be repaired in 'as good as new' condition. It is assumed that the repairman can perform some other tasks when either the system is idle or waiting for recovery from the faults. The life time of the system and vacation time of the repairman are assumed to be exponential distributed while the repair time follows the general distribution. By assuming the geometric process for the system working/vacation time, the supplementary variable technique and Laplace transforms approach are employed to derive the reliability indices of the system. We propose the replacement policy to maximize the expected profit after a long run time. The validity of the analytical results is justified by taking numerical illustrations. © 2013 Elsevier Ltd. All rights reserved.


Jain M.,Indian Institute of Technology Roorkee | Gupta R.,Institute of Basic Science
International Journal of Reliability, Quality and Safety Engineering | Year: 2011

The redundancy is a widely spread technology of building computing systems that continue to operate satisfactorily in the presence of faults occurring in hardware and software components. The principle objective of applying redundancy is achieve reliability goals subject to techno-economic constraints. Due to a plenty of applications arising virtually in both industrial and military organizations especially in embedded fault tolerance systems including telecommunication, distributed computer systems, automated manufacturing systems, etc., the reliability and its dependability measures of redundant computer-based systems have become attractive features for the systems designers and production engineers. However, even with the best design of redundant computer-based systems, software and hardware failures may still occur due to many failure mechanisms leading to serious consequences such as huge economic losses, risk to human life, etc. The objective of present survey article is to discuss various key aspects, failure consequences, methodologies of redundant systems along with software and hardware redundancy techniques which have been developed at the reliability engineering level. The methodological aspects which depict the required steps to build a block diagram composed of components in different configurations as well as Markov and non-Markov state transition diagram representing the structural system has been elaborated. Furthermore, we describe the reliability of a specific redundant system and its comparison with a non redundant system to demonstrate the tractability of proposed models and its performance analysis. © 2011 World Scientific Publishing Company.


Upadhyay A.K.,Institute of Basic science | Sharma B.S.,Institute of Basic science
Indian Journal of Pure and Applied Physics | Year: 2011

Sound velocities and elastic moduli of some minerals viz MgO, MgAl 2O4, Al2O3, Y3Al 2(AlO4)3 and pyrope (Mg3Al 2Si3O12) up to a pressure of 200 GPa have been studied. The pressure-density relationships have been determind using the Hama-Suito theory of equation of state based on the augmented plane wave (APW) and quantum statistical methods. The elastic moduli such as bulk modulus, shear modulus, Young's modulus and Poisson's ratio have been calculated as a function of pressure. The relationships between sound velocities and elastic moduli have been used to obtain values of compressional wave velocity and shear wave velocity. The results are found to present close agreement with the available experimental data. Both compressional and shear velocities are in good agreement with the available experimental data.


Singh P.K.,Institute of Basic science
Indian Journal of Pure and Applied Physics | Year: 2011

K-primed equations of state for solids are more advantageous than the conventional pressure-volume relationships for studying higher derivatives of bulk modulus and thermoelastic properties. The reciprocal K-primed quadratic equation is consistent with the first-principles results determined from the augmented plane wave method for metals, non-metals and diatomic solids, has been studied in the present paper. The values of pressure, bulk modulus and its pressure derivative based on the first-principles in case of different solids are found to satisfy the reciprocal K-primed quadratic equation.


Singh P.K.,Institute of Basic science
Indian Journal of Pure and Applied Physics | Year: 2010

Pressure P, bulk modulus K and its first and second pressure derivatives K′ and K″, and the Grüneisen parameter y and its volume derivative q for NaCl crystal down to a compression, V/Vo = 0.65 have been studied. These properties have been calculated along different isotherms at selected temperatures in the range 300-1050 K using Holzapfel AP2 equation of state. The results obtained have been found to be in good agreement with the data reported in the literature. A reciprocal üf-primed equation, quadratic in PIK, has been found to satisfy the relationship between P, K and K' along with different isotherms, and is also consistent with the values of K" at different compressions and temperatures. Volume dependence of the Grüneisen parameter has been discussed in terms of the existing recent formulations.


Singh P.K.,Institute of Basic science
Indian Journal of Physics | Year: 2012

We have studied high derivative thermoelastic properties such as the pressure derivatives of bulk modulus and the volume dependence of the Grüneisen parameter in case of MgO for a wide range of pressures down to compression V/V0 = 0.6, and temperatures up to 3,000 K approaching the melting temperature. We have used the isothermal pressure- volume equation of state (EOS) based on the adapted polynomial expansion of second order (AP2) due to Holzapfel. The results for the P-V-T relationships and high derivative properties have been obtained using the Holzapfel AP2 EOS. The pressure derivatives of bulk modulus and volume derivatives of the Grüneisen parameter have been determined using the free volume theory. A relationship between the pressure derivative of bulk modulus and the ratio of pressure and bulk modulus has been found to hold good. © 2012 IACS.


Singh B.P.,Institute of Basic science | Singh K.S.,P.A. College
Solid State Sciences | Year: 2012

The pressure-volume-temperature relationships have been studied for the pyrope mineral. Values of volumes at simultaneously elevated temperatures and pressures have been evaluated using the Rydberg-Vinet equation of state for isothermal compression and the Singh-Suzuki equation for isobaric thermal expansion. It has been found that the results obtained from these two conventional equations can be reproduced very well by a single equation of state which covers both temperature and pressure changes in solids namely the Hartmann equation of state. Values of volumes at melting temperatures corresponding to elevated pressures have been obtained and found to compare well with the experimental values. It is also found that there exists a simple linear relationship between relative change in melting volume and melting temperature in case of pyrope at different pressures. This is supported by the earlier findings of Anderson in case of forsterite mineral. © 2011 Elsevier Masson SAS. All rights reserved.


Dwivedi A.,Institute of Basic science
High Temperatures - High Pressures | Year: 2016

We make use of some basic principles of calculus for an analysis of thermodynamic identities at extreme compression given by Stacey. The thermal expansivity of materials becomes zero at infinite pressure or extreme compression. The validity of this result originally due to Stacey has been proved in the present study in a simple manner. Higher order thermoelastic properties obtained from the derivatives of thermal expansivity have been investigated in the limit of infinite pressure. The most important results found in the present study reveal that temperature derivatives of bulk modulus become independent of pressure, and second pressure derivatives of bulk modulus become independent of temperature for materials at extreme compression. ©2016 Old City Publishing, Inc.

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