4,139 research outputs found
PdTe a 4.5K Type II BCS Superconductor
We report on the structure and physical properties of bulk Palladium
Tellurium superconductor, which is synthesized via quartz vacuum encapsulation
technique at 750 C. The as synthesized compound is crystallized in hexagonal
crystal structure. Magnetization and Magneto-transport measurements provided
the values of lower and upper critical field to be 250 and 1200 Gauss
respectively at 2 Kelvin. The Coherence length and GL parameter are estimated
from the experimentally determined upper and lower critical fields, which are
45 nm and 1.48 respectively. The jump in Cp(T) at Tc is found to be 1.33 and
the Debye temperature and electronic specific heat constant are 203 Kelvin and
6.01mJ/mole-K2 respectively.Comment: 13 pages Text + Figs: Accepted in Sup. Sci. and Tec
Micromegas TPC studies at high magnetic fields using the charge dispersion signal
The International Linear Collider (ILC) Time Projection Chamber (TPC)
transverse space-point resolution goal is 100 microns for all tracks including
stiff 90 degree tracks with the full 2 meter drift. A Micro Pattern Gas
Detector (MPGD) readout TPC can achieve the target resolution with existing
techniques using 1 mm or narrower pads at the expense of increased detector
cost and complexity. The new MPGD readout technique of charge dispersion can
achieve good resolution without resorting to narrow pads. This has been
demonstrated previously for 2 mm x 6 mm pads with GEMs and Micromegas in cosmic
ray tests and in a KEK beam test in a 1 Tesla magnet. We have recently tested a
Micromegas-TPC using the charge dispersion readout concept in a high field
super-conducting magnet at DESY. The measured Micromegas gain was found to be
constant within 0.5% for magnetic fields up to 5 Tesla. With the strong
suppression of transverse diffusion at high magnetic fields, we measure a flat
50 micron resolution at 5 Tesla over the full 15 cm drift length of our
prototype TPC.Comment: 7 pages, 3 figure
Magnetoelectric effect due to local noncentrosymmetry
Magnetoelectrics often possess ions located in noncentrosymmetric
surroundings. Based on this fact we suggest a microscopic model of
magnetoelectric interaction and show that the spin-orbit coupling leads to
spin-dependent electric dipole moments of the electron orbitals of these ions,
which results in non-vanishing polarization for certain spin configurations.
The approach accounts for the macroscopic symmetry of the unit cell and is
valid both for commensurate and complex incommensurate magnetic structures. The
model is illustrated by the examples of MnWO4, MnPS3 and LiNiPO4. Application
to other magnetoelectrics is discussed.Comment: 11 pages, 2 figures, 2 table
Quantum phase transition in quantum wires controlled by an external gate
We consider electrons in a quantum wire interacting via a long-range Coulomb
potential screened by a nearby gate. We focus on the quantum phase transition
from a strictly one-dimensional to a quasi-one-dimensional electron liquid,
that is controlled by the dimensionless parameter , where is the
electron density and is the characteristic length of the transverse
confining potential. If this transition occurs in the low-density limit, it can
be understood as the deformation of the one-dimensional Wigner crystal to a
zigzag arrangement of the electrons described by an Ising order parameter. The
critical properties are governed by the charge degrees of freedom and the spin
sector remains essentially decoupled. At large densities, on the other hand,
the transition is triggered by the filling of a second one-dimensional subband
of transverse quantization. Electrons at the bottom of the second subband
interact strongly due to the diverging density of states and become
impenetrable. We argue that this stabilizes the electron liquid as it
suppresses pair-tunneling processes between the subbands that would otherwise
lead to an instability. However, the impenetrable electrons in the second band
are screened by the excitations of the first subband, so that the transition is
identified as a Lifshitz transition of impenetrable polarons. We discuss the
resulting phase diagram as a function of .Comment: 18 pages, 8 figures, minor changes, published versio
An optimization model for a monopolistic firm serving an environmentally conscious market: Use of Chemical Reaction Optimization Algorithm
This work considers a monopolist firm which faces the following twin challenges of serving an environmentally sensitive market. The first challenge is the demand׳s elasticity to emissions and price. To entice its emission conscious customers and generate higher demand, the firm incrementally invests in cleaner production technologies. It also adopts a voluntary limit on its emissions from transportation. However, such investments and penalty lead to the second challenge of reduced net profit. To address above trade-off, a Non-Linear Programming (NLP) model with a maximization quadratic profit function has been formulated. Recently developed, Chemical Reaction Optimization algorithm, with superior computational performance, has been adopted to solve the NLP. The output of the model provides near optimal monopolistic price, best attainable reduction in manufacturing emissions through proportional investment and makes a choice of suitable mode of transportation for each type of product offered by the firm. Three types of sensitivity analyses were performed by varying contextual parameters: customers׳ emission elasticity, penalty charged per unit emission and investment coefficient. The results, underpin the importance of investments in cleaner technologies and the need of financial aids for profit maximizing firms operating in cleaner markets. This work provides a decision making tool to determine the near optimal degree of each of the above dimension in multiple business fronts
Effect of naloxone on the plasma levels of LH, FSH, prolactin and testosterone in Beetal bucks
Abstract Ten adult male Beetal goats were used for the study to elucidate the modulation of gonadotrophin, prolactin and testosterone secretion by endogenous opioid peptides. An indwelling catheter was placed in the jugular vein of each buck 20 h before the onset of the experiment. Bucks were divided randomly into two groups: Group I (n 5) received naloxone at a dose rate of 1 mg/kg body weight (BW) and Group II (n 5) received naloxone at a dose rate of 2 mg/kg BW intravenous. Blood samplings were done from 2 h before treatment until 2 h after treatment at 15 min intervals. Blood samples were quanti®ed for plasma LH, FSH and prolactin concentration using a heterologous double antibody radioimmunoassay (RIA) and testosterone concentration was quanti®ed by coat-a-count RIA kit. The mean plasma LH levels during pretreatment phase were 0.41 AE 0.03 ng/ml in Group I and 0.44 AE 0.02 ng/ml in Group II which signi®cantly (p < 0.05) increased to 0.91 AE 0.05 ng/ml in Group I and 1.53 AE 0.07 ng/ml in Group II. The mean plasma FSH levels did not show a difference in pre-and posttreatment animals in both groups. A signi®cant (p < 0.05) increase in plasma testosterone concentration was observed in both groups after naloxone treatment, whereas, a decrease (p < 0.05) was observed in plasma prolactin levels after naloxone treatment. Thus, it can be concluded that endogenous opioids do play an important role in modulating plasma LH, prolactin and testosterone concentrations in male goats.
Z_N Phases in Hot Gauge Theories
We argue that the \zn phases of hot gauge theories cannot be realized as a
real system with an Hermitean density matrix.Comment: 7 page
Spatial Resolution of a Micromegas-TPC Using the Charge Dispersion Signal
The Time Projection Chamber (TPC) for the International Linear Collider will
need to measure about 200 track points with a resolution close to 100 m. A
Micro Pattern Gas Detector (MPGD) readout TPC could achieve the desired
resolution with existing techniques using sub-millimeter width pads at the
expense of a large increase in the detector cost and complexity. We have
recently applied a new MPGD readout concept of charge dispersion to a prototype
GEM-TPC and demonstrated the feasibility of achieving good resolution with pads
similar in width to the ones used for the proportional wire TPC. The charge
dispersion studies were repeated with a Micromegas TPC amplification stage. We
present here our first results on the Micromegas-TPC resolution with charge
dispersion. The TPC resolution with the Micromegas readout is compared to our
earlier GEM results and to the resolution expected from electron statistics and
transverse diffusion in a gaseous TPC.Comment: 5 pages, 8 figures, to appar in the Proceedings of the 2005
International Linear Collider Workshop (LCWS05), Stanford, 18-22 March 200
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