12,155 research outputs found
Critical properties of the double exchange ferromagnet Nd0.4Pb0.4MnO3
Results of a study of dc-magnetization M(T, H), performed on a Nd0.6Pb0.4MnO3
single crystal in the temperature range around T_C (Curie temperature) which
embraces the critical region | epsilon | = |T -T_C |/T_C <= 0.05 are reported.
The magnetic data analyzed in the critical region using the Kouvel-Fisher
method give the values for the T_C =156.47 +/- 0.06 K and the critical
exponents, beta = 0.374 +/- 0.006 (from the temperature dependence of
magnetization), and gamma = 1.329 +/- 0.003 (from the temperature dependence of
initial susceptibility). The critical isotherm M(T_C, H) gives delta = 4.547
+/- 0.1. Thus the scaling law gamma+beta=delta beta is fulfilled. The critical
exponents obey the single scaling-equation of state M(H, epsilon) = epsilon^b
f_+/- (H/epsilon^(beta + gamma)) where, f_+ for T > T_C and f_- for T< T_C. The
exponent values are very close to those expected for the universality class of
3D Heisenberg ferromagnets with short-range interactions.Comment: 19 pages, including 6 figure
Colossal electroresistance in ferromagnetic insulating state of single crystal NdPbMnO
Colossal electroresistance (CER) has been observed in the ferromagnetic
insulating (FMI) state of a manganite. Notably, the CER in the FMI state occurs
in the absence of magnetoresistance (MR). Measurements of electroresistance
(ER) and current induced resistivity switching have been performed in the
ferromagnetic insulating state of a single crystal manganite of composition
NdPbMnO (NPMO30). The sample has a paramagnetic to
ferromagnetic (Curie) transition temperature, Tc = 150 K and the ferromagnetic
insulating state is realized for temperatures, T <~ 130 K. The colossal
electroresistance, arising from a strongly nonlinear dependence of resistivity
() on current density (j), attains a large value () in the
ferromagnetic insulating state. The severity of this nonlinear behavior of
resistivity at high current densities is progressively enhanced with decreasing
temperature, resulting ultimately, in a regime of negative differential
resistivity (NDR, d/dj < 0) for temperatures <~ 25 K. Concomitant with
the build-up of the ER however, is a collapse of the MR to a small value (<
20%) even in magnetic field, H = 7 T. This demonstrates that the mechanisms
that give rise to ER and MR are effectively decoupled in the ferromagnetic
insulating phase of manganites. We establish that, the behavior of
ferromagnetic insulating phase is distinct from the ferromagnetic metallic
(FMM) phase as well as the charge ordered insulating (COI) phase, which are the
two commonly realized ground state phases of manganites.Comment: 24 pages (RevTeX4 preprint), 8 figures, submitted to PR
Evidence for long-term variability in the ultra high energy photon flux from Cygnus X-3
A time-correlation analysis of atmospheric Cerenkov pulses by a wide-angle photomultiplier system was previously shown to have present in it a nonrandom component which seemed associated with the Right Ascension (RA) range approx. 20+or-04h. A recent examination of multi-muon events recorded by a photon-decay detector shows a similar time-dependent effect, closely matching the previous results, supporting the suggestion that the effect is of cosmic origin. However, even though Cyg. X-3 lies well inside the region of peak intensity, it does not seem possible to ascribe to it the whole effect, for the implied photon flux appears too large to be reconciled to various gamma-ray measurements of Cyg. X-3. The original data were subjected to a phase-histogram analysis and it as found that only 2.5% of overall recorded data are compatible with a phase-dependent emission from Cyg. X-3. Assuming these events to be gamma rays yields a detected flux of (2.6 + or - 0.3) x 10 to the minus 12th power gamma cm -2s-1 above 5 x 10 to the 14th power eV. Comparing this value with more recent ultra high energy (UHE) photon data from the same source, it is suggested that the available data generally favor a long-term reduction in the Cyg. X-3 inferred luminosity ( 10 to the 13th power eV) by a factor of (1.8 + or - 0.3) per year
Outcome of laparoscopic surgeries during pregnancy for non-obstetric emergencies
Background: This study was conducted to evaluate the surgical and obstetric outcome, safety and feasibility of various laparoscopic surgeries for non-obstetric indications in pregnancy.Methods: We did a retrospective analysis of 18 pregnant patients who underwent laparoscopic surgeries. Study period was from October 2013 till September 2015 conducted in Radhakrishna multispeciality hospital /IVF center Bangalore. Patients operated are 6 cases cholicystectomy, 6 cases appendicectomy, 5 adnexal mass removals, one salpingectomy for heterotopic pregnancy resulted from ART. All patients were between 11 to 32 weeks of gestation, with mean gestational age 21±6.5 weeks at the time of surgery and mean duration of surgery was 46±16.3 minutes.Results: All eighteen pregnant patients had uneventful hospital courses after laparoscopic procedures. Mean duration of hospital stay after surgery was 43±8.5 hours. One pregnancy was terminated at 11 weeks for suspected ovarian malignancy and 16 delivered full-term babies without complications, one patient delivered preterm at 35 weeks with NICU admission. The mean birth weight at the time of delivery was 2.8±550 gms. There was no maternal morbidity or mortality, or any identifiable neonatal birth defect. No conversion to laparotomy required in any case.Conclusions: Laparoscopic surgeries can be done in any trimester of pregnancy, but more safe and feasible during the second and early third trimester of pregnancy. Laparoscopic surgeries are as safe as laparotomy in the hands of experienced laparoscopic surgeon with no deleterious effects on either mother or fetus
On Observing Dynamic Prioritised Actions in SOC
We study the impact on observational semantics for SOC of priority mechanisms which combine dynamic priority with local pre-emption. We define manageable notions of strong and weak labelled bisimilarities for COWS, a process calculus for SOC, and provide alternative characterisations in terms of open barbed bisimilarities. These semantics show that COWS’s priority mechanisms partially recover the capability to observe receive actions (that could not be observed in a purely asynchronous setting) and that high priority primitives for termination impose specific conditions on the bisimilarities
Microscopic description of Gamow-Teller transitions in middle pf--shell nuclei by a realistic shell model calculation
GT transitions in nuclei are studied in terms of a large-scale
realistic shell-model calculation, by using Towner's microscopic parameters.
values to low-lying final states are reproduced with a reasonable
accuracy. Several gross properties with respect to the GT transitions are
investigated with this set of the wavefunctions and the operator. While the
calculated total GT strengths show no apparent disagreement with the
measured ones, the calculated total GT strengths are somewhat larger than
those obtained from charge-exchange experiments. Concerning the Ikeda sum-rule,
the proportionality of to persists to an excellent
approximation, with a quenching factor of 0.68. For the relative GT
strengths among possible isospin components, the lowest isospin component
gathers greater fraction than expected by the squared CG coefficients of the
isospin coupling. It turns out that these relative strengths are insensitive to
the size of model space. Systematics of the summed values are
discussed for each isospin component.Comment: IOP-LaTeX 23 pages, to appear in J. Phys. G., 5 Postscript figures
available upon reques
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