1,875 research outputs found
Simultaneous solution of non-linear algebraic equations Technical memorandum no. 163
Digital computer program for nonlinear equation sets characteristic of filter circuit analysi
Enhanced Critical parameters of nano-Carbon doped MgB2 Superconductor
The high field magnetization and magneto transport measurements are carried
out to determine the critical superconducting parameters of MgB2-xCx system.
The synthesized samples are pure phase and the lattice parameters evaluation is
carried out using the Rietveld refinement. The R-T(H) measurements are done up
to a field of 140 kOe. The upper critical field values, Hc2 are obtained from
this data based upon the criterion of 90% of normal resistivity i.e. Hc2=H at
which Rho=90%Rho; where RhoN is the normal resistivity i.e., resistivity at
about 40 K in our case. The Werthamer-Helfand-Hohenberg (WHH) prediction of
Hc(0) underestimates the critical field value even below than the field up to
which measurement is carried out. After this the model, the Ginzburg Landau
theory (GL equation) is applied to the R-T(H) data which not only calculates
the Hc2(0) value but also determines the dependence of Hc2 on temperature in
the low temperature high field region. The estimated Hc(0)=157.2 kOe for pure
MgB2 is profoundly enhanced to 297.5 kOe for the x=0.15 sample in MgB2-xCx
series. Magnetization measurements are done up to 120 kOe at different
temperatures and the other parameters like irreversibility field, Hirr and
critical current density Jc(H) are also calculated. The nano carbon doping
results in substantial enhancement of critical parameters like Hc2, Hirr and
Jc(H) in comparison to the pure MgB2 sample.Comment: 25 pages with 9 Figs:
comments/suggestions([email protected]
Calculation of Band Edge Eigenfunctions and Eigenvalues of Periodic Potentials through the Quantum Hamilton - Jacobi Formalism
We obtain the band edge eigenfunctions and the eigenvalues of solvable
periodic potentials using the quantum Hamilton - Jacobi formalism. The
potentials studied here are the Lam{\'e} and the associated Lam{\'e} which
belong to the class of elliptic potentials. The formalism requires an
assumption about the singularity structure of the quantum momentum function
, which satisfies the Riccati type quantum Hamilton - Jacobi equation, in the complex plane. Essential
use is made of suitable conformal transformations, which leads to the
eigenvalues and the eigenfunctions corresponding to the band edges in a simple
and straightforward manner. Our study reveals interesting features about the
singularity structure of , responsible in yielding the band edge
eigenfunctions and eigenvalues.Comment: 21 pages, 5 table
Electronic data sources for kinetic models of cell signaling
Functional understanding of signaling pathways requires detailed information about the constituent molecules and their interactions. Simulations of signaling pathways therefore build upon a great deal of data from various sources. We first survey electronic data resources for cell signaling modeling and then based on the type of data representation the data sources are broadly classified into five groups. None of the data sources surveyed provide all required data in a ready-to-be-modeled fashion. We then put forward a wish list for the desired attributes for an ideal modeling centric database. Finally, we close with perspectives on how electronic data sources for cell signaling modeling have developed. We suggest that future directions in such data sources are largely model-driven and are hinged on interoperability of data sources
Kinetic measurement of ribosome motor stalling force
We measure the ribosome motor stalling forces to unzip mRNA polymers during gene expression. An approach of using the changes in the reaction rate constants to determine the molecular motor forces is presented. Specific antisense DNA oligomers complementary to mRNA templates are used as kinetic barriers for estimating the ribosome forces using real time bioluminescence detection of luciferase gene expression. The rate constants are determined by comparing the experimental data with numerical simulation of gene expression to deduce the ribosome force (26.5±1 pN) required to unzip mRNA polymers. Understanding the forces generated by the ribosome may also enable the construction of information-based artificial nanoscale machines
Anomalous thermoelectric power of Mg1-xAlxB2 system with x = 0.0 to 1.0
Thermoelectric power, S(T) of the Mg1-xAlxB2 system has been measured for x =
0.0, 0.1, 0.2, 0.4, 0.6, 0.8 and 1.0. XRD, resistivity and magnetization
measurements are also presented. It has been found that the thermoelectric
power is positive for x = 0.4 and is negative for x = 0.6 over the entire
temperature range studied up to 300 K. The thermoelectric power of x = 0.4
samples vanishes discontinuously below a certain temperature, implying
existence of superconductivity. In general, the magnitude of the thermoelectric
power increases with temperature up to a certain temperature, and then it
starts to decrease towards zero base line. In order to explain the observed
behavior of the thermoelectric power, we have used a model in which both
diffusion and phonon drag processes are combined by using a phenomenological
interpolation between the low and high temperature behaviors of the
thermoelectric power. The considered model provides an excellent fit to the
observed data. It is further found that Al doping enhances the Debye
temperature.Comment: 19 pages Text + Figs.
suggestions/comments([email protected]
Superconductivity of non- stoichiometric intermetallic compound NbB2
We report the synthesis, magnetic susceptibility and crystal structure
analysis for NbB2+x (x = 0.0 to 1.0) samples. The study facilitates in finding
a correlation among the lattice parameters, chemical composition and the
superconducting transition temperature Tc. Rietveld analysis is done on the X-
ray diffraction patterns of all synthesized samples to determine the lattice
parameters. The a parameter decreases slightly and has a random variation with
increasing x, while c parameter increases from 3.26 for pure NbB2 to 3.32 for
x=0.4 i.e. NbB2.4. With higher Boron content (x>0.4) the c parameter decreases
slightly. The stretching of lattice in c direction induces superconductivity in
the non- stoichiometric niobium boride. Pure NbB2 is non-superconductor while
the other NbB2+x (x>0.0) samples show diamagnetic signal in the temperature
range 8.9-11K. Magnetization measurements (M-H) at a fixed temperature of 5K
are also carried out in both increasing and decreasing directions of field. The
estimated lower and upper critical fields (Hc1 & Hc2) as viewed from M-H plots
are around 590 and 2000Oe respectively for NbB2.6 samples. In our case,
superconductivity is achieved in NbB2 by varying the Nb/B ratios, rather than
changing the processing conditions as reported by others.Comment: 14 pages TEXT+Figs; comments/suggestions
([email protected]). ACCEPTED: Solid State Communications (2008
Intraoral dermoid cyst- how common are they in a paediatric population? A retrospective case series
Oral dermoid cysts are rare especially in the paediatric population. They can rapidly enlarge causing dysphagia and airway compromise. We present a case series of paediatric oral dermoid cysts in our centre over the past 5 years and suggest a predisposition to tongue tie procedures. All our cases required surgical intervention and we suggest that all clinicians consider this important diagnosis when presented with a child with an intraoral swelling
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