6,386 research outputs found
Revised Results for Non-thermal Recombination Flare Hard X-Ray Emission
Brown and Mallik (BM) recently showed that, for hot sources, recombination of
non-thermal electrons (NTR) onto highly ionised heavy ions is not negligible
compared to non-thermal bremsstrahlung (NTB) as a source of flare hard X-rays
(HXRs) and so should be included in modelling non-thermal HXR flare emission.
In view of major discrepancies between BM results for the THERMAL continua and
those of the Chianti code and of RHESSI solar data, we critically re-examine
and correct the BM analysis and modify the conclusions concerning the
importance of NTR. Although the analytic Kramers expression used by BM is
correct for the purely hydrogenic recombination cross section, the heuristic
expressions used by BM to extend the Kramers expression beyond the `bare
nucleus' case to which it applies had serious errors. BM results have therefore
been recalculated using corrected expressions, which have been validated
against the results of detailed calculations. At T ~ 10-30 MK the dominant ions
are Fe 22+, 23+, 24+ for which BM erroneously overestimated NTR emission by
around an order of magnitude. Contrary to the BM claim, NTR in hot flare
plasmas does NOT dominate over NTB, although in some cases it can be comparable
and so still very important in inversions of photon spectra to derive electron
spectra, especially as NTR includes sharp edge features. The BM claim of
dominance of NTR over NTB in deka-keV emission is incorrect due to a serious
error in their analysis. However, the NTR contribution can still be large
enough to demand inclusion in spectral fitting, the spectral edges having
potentially serious effects on inversion of HXR spectra to infer fast electron
spectra.Comment: 6 pages, 8 figures, 1 tabl
Magnetic behaviour of Eu_2CuSi_3: Large negative magnetoresistance above Curie temperature
We report here the results of magnetic susceptibility,
electrical-resistivity, magnetoresistance (MR), heat-capacity and ^{151}Eu
Mossbauer effect measurements on the compound, Eu_2CuSi_3, crystallizing in an
AlB_2-derived hexagonal structure. The results establish that Eu ions are
divalent, undergoing long-range ferromagnetic-ordering below (T_C=) 37 K. An
interesting observation is that the sign of MR is negative even at temperatures
close to 3T_C, with increasing magnitude with decreasing temperature exhibiting
a peak at T_C. This observation, being made for a Cu containing magnetic
rare-earth compound for the first time, is of relevance to the field of
collosal magnetoresistance.Comment: To appear in PRB, RevTex, 4 pages text + 6 psFigs. Related to our
earlier work on Gd systems (see cond-mat/9811382, cond-mat/9811387,
cond-mat/9812069, cond-mat/9812365
Experimental investigation of the response of a harmonically excited hard Duffing oscillator
A single degree-of-freedom torsional vibratory system, which constitutes a third-order dissipative dynamical system, has been fabricated as a mechanical analogue of hard Duffing equation with strong nonlinearity. The forced response of the system reveals complicated and chaotic motion at low frequency regime. Besides usual jump phenomenon, unpredictable jump phenomenon with two and three coexisting periodic attractors is also observed
Correlation of cancer treatment related fatigue with biochemical & hormonal profile a prospective study
Background: Cancer treatment using chemotherapy or radiotherapy results in
considerable cancer treatment related fatigue. Fatigue can induce significant stress
causing hormonal alteration through hypothalamic pituitary axis leading to change in the
internal milieu. We evaluated hormonal and biochemical profile to find out a putative
corr~lation. Materials & Method: Fifty two histopathology documented cases of cancer
patients were subjected to Pipers Fatigue Score (PFS) and blood test for hormone and
other biochemical parameters before and after radiotherapy and chemotherapy
treatment. Human growth hormone, adenocorticotrophic hormone, thyroid stimulating
hormone and serum free cortisol level were evaluated along with routine biochemical
analysis before and after anticancer treatment. The individual fatigue score were
compared with individual hormone levels and other biochemical parameters. Results:
Fifty two cancer patients planned for anticancer therapy completed initial pretreatment
evaluation however post treatment assessment was not possible in 8 cases as they died
during therapy. There were 20 males and 32 females in the study with a median age of
50 years (range15-78 years). The stage distribution was as stage-1 (12°k), stage-11
(17°.4>), stage-Ill (44%) and stage-IV (26°/o).The primary cancer were in breast (19°/o),
sarcomas (9°/o), head and neck (19°k), gynecological (19°/o) and miscellaneous sites
(14o/o). The individual fatigue score were behavioral severity (26.6°.4>), affective meaning
(28°/o), sensory (22.2%), cognitive mood (8.8%) and total score (22.2°.4>) respectively.
There were significant rise in the fatigue score followi~g chemotherapy and radiotherapy.
The serum human growth hormone and cortisol were positively correlated whereas
serum TSH level was negatively correlated with fatigue. Conclusions: Cancer treatment
related fatigue is a multidimensional event that affect stress hormonal ·milieu. The
human growth hormone and corticotrophins were affected among cancer patients
suffering from cancer treatment related fatigue. Probably this finding may help to
improve therapeutic intervention in the management fatigue in cance
Stochastic modeling of cargo transport by teams of molecular motors
Many different types of cellular cargos are transported bidirectionally along
microtubules by teams of molecular motors. The motion of this cargo-motors
system has been experimentally characterized in vivo as processive with rather
persistent directionality. Different theoretical approaches have been suggested
in order to explore the origin of this kind of motion. An effective theoretical
approach, introduced by M\"uller et al., describes the cargo dynamics as a
tug-of-war between different kinds of motors. An alternative approach has been
suggested recently by Kunwar et al., who considered the coupling between motor
and cargo in more detail. Based on this framework we introduce a model
considering single motor positions which we propagate in continuous time.
Furthermore, we analyze the possible influence of the discrete time update
schemes used in previous publications on the system's dynamic.Comment: Cenference proceedings - Traffic and Granular Flow 1
Isolation, genetic diversity and identification of a virulent pathogen of eriophyid mite, Aceria guerreronis (Acari: Eriophyidae) by DNA marker in Karnataka, India
Aceria guerreronis is a serious pest of coconut in India. Investigations were carried out to investigate fungal pathogens infecting the eriophyid mites for their utilisation as biocontrol agents in Karnataka, India. The fungal pathogens namely, Hirsutella thompsonii, Beauveria bassiana, Fusarium semitectum and few opportunistic pathogens namely, Fusarium moniliforme, Cladosporium tennuissimum, Aspergillus niger, Penicillium sp. and Mucor sp. were collected from eriophyid mite populations in different parts of Karnataka area. Of the total collected nuts, 3.54% were infected by H. thompsonii, 2.46 and 0.29% by B. bassiana and F. semitectum, respectively. A lower number of nuts (0.03 to 0.79%) were infected by opportunistic pathogens. The incidence of pathogen infected coconuts in areas with lower temperature and higher humidity were ranged from 4.37 to 19.52% whereas with higher temperature and lower humidity it was 0 to 4.54%. Occurrence of B. bassiana and F. semitectum on A. guerreronis are new records. Among isolates of H. thompsonii collected from different places, the isolate Bangalore was more virulent followed by Mysore, Mandya, Kanakapura, Arsikere and Hiriyur isolates, as it recorded maximum infection (HTCMBAN- 88.63%). The B. bassiana isolates caused mortality ranging from 72.87 to 86.97%. The virulent isolate H. thompsonii (HTCMBAN) was tested at different concentrations, with increase in the concentration mortality rate. The genetic diversity of isolates of H. thompsonii by random amplification of polymorphic DNA (RAPD) revealed that grouping of the isolates was in accordance with geographic location. DNA fragments of 850 and 950 bp (OPA-20) were specific to the virulent isolate HTCMBAN.Key words: Fungal pathogens, eriophyid mites, genetic diversity, DNA marker
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