1,203 research outputs found
Magnetic and the magnetocaloric properties of Ce1-xRxFe2 and Ce(Fe1-xMx)2 compounds
We have studied selected rare earth doped and transition metal doped CeFe2
compounds by examining their structural, magnetic and magneto-thermal
properties. With substitution of Ce by 5 and 10% Gd and 10% Ho, the Curie
temperature can be tuned to the range of 267-318 K. Localization of Ce 4f
electronic state with rare earth substitutions is attributed for the
enhancement of Curie temperature. On the other hand, with Ga and Al
substitution at the Fe site, system undergoes paramagnetic to ferromagnetic
transition and then to an antiferromagnetic phase on cooling. The
magnetocaloric effect across the transitions has been studied from both
magnetization isotherms and heat capacity data. It is shown that by choosing
the appropriate dopant and its concentration, the magnetocaloric effect around
room temperature can be tuned.Comment: 13 pages, 6 figures, 2 table
The C-terminal portion of the cleaved HT motif is necessary and sufficient to mediate export of proteins from the malaria parasite into its host cell
The malaria parasite exports proteins across its plasma membrane and a surrounding parasitophorous vacuole membrane, into its host erythrocyte. Most exported proteins contain a Host Targeting motif (HT motif) that targets them for export. In the parasite secretory pathway, the HT motif is cleaved by the protease plasmepsin V, but the role of the newly generated N-terminal sequence in protein export is unclear. Using a model protein that is cleaved by an exogenous viral protease, we show that the new N-terminal sequence, normally generated by plasmepsin V cleavage, is sufficient to target a protein for export, and that cleavage by plasmepsin V is not coupled directly to the transfer of a protein to the next component in the export pathway. Mutation of the fourth and fifth positions of the HT motif, as well as amino acids further downstream, block or affect the efficiency of protein export indicating that this region is necessary for efficient export. We also show that the fifth position of the HT motif is important for plasmepsin V cleavage. Our results indicate that plasmepsin V cleavage is required to generate a new N-terminal sequence that is necessary and sufficient to mediate protein export by the malaria parasite
Observation of re-entrant spin glass behavior in (Ce1-xErx)Fe2 compounds
Clear experimental evidence of re-entrant spin glass state has been revealed
in Er doped CeFe2 compounds. The zero field cooled - field cooled bifurcation
in dc magnetization, frequency dependence of freezing temperature, relaxation
in zero field cooled magnetization and presence of large remanence confirm the
spin glass state in these compounds. Frequency dependence is found to follow
the critical slowing down mechanism. The random substitution of Er and the
change in the valence state of Ce along with an enhancement of the
ferromagnetic component in the Fe sublattice seem to be responsible for the
spin glass state. Using detailed experimental protocols, we also prove that the
low temperature state in these compounds is not a magnetic glass. The absence
of exchange bias gives an indication that there is no coexistence of
ferromagnetism and spin glass state in these compounds. The RSG state is found
to be associated with the randomly magnetized clusters instead of atomic level
randomness.Comment: 19 pages, 9 figure
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The impact of adjusting for baseline in pharmacogenomic genome-wide association studies of quantitative change.
In pharmacogenomic studies of quantitative change, any association between genetic variants and the pretreatment (baseline) measurement can bias the estimate of effect between those variants and drug response. A putative solution is to adjust for baseline. We conducted a series of genome-wide association studies (GWASs) for low-density lipoprotein cholesterol (LDL-C) response to statin therapy in 34,874 participants of the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort as a case study to investigate the impact of baseline adjustment on results generated from pharmacogenomic studies of quantitative change. Across phenotypes of statin-induced LDL-C change, baseline adjustment identified variants from six loci meeting genome-wide significance (SORT/CELSR2/PSRC1, LPA, SLCO1B1, APOE, APOB, and SMARCA4/LDLR). In contrast, baseline-unadjusted analyses yielded variants from three loci meeting the criteria for genome-wide significance (LPA, APOE, and SLCO1B1). A genome-wide heterogeneity test of baseline versus statin on-treatment LDL-C levels was performed as the definitive test for the true effect of genetic variants on statin-induced LDL-C change. These findings were generally consistent with the models not adjusting for baseline signifying that genome-wide significant hits generated only from baseline-adjusted analyses (SORT/CELSR2/PSRC1, APOB, SMARCA4/LDLR) were likely biased. We then comprehensively reviewed published GWASs of drug-induced quantitative change and discovered that more than half (59%) inappropriately adjusted for baseline. Altogether, we demonstrate that (1) baseline adjustment introduces bias in pharmacogenomic studies of quantitative change and (2) this erroneous methodology is highly prevalent. We conclude that it is critical to avoid this common statistical approach in future pharmacogenomic studies of quantitative change
A Plasmodium falciparum Host-Targeting Motif Functions in Export during Blood Stage Infection of the Rodent Malarial Parasite Plasmodium berghei
Plasmodium falciparum (P. falciparum) secretes hundreds of proteins—including major virulence proteins—into the host erythrocyte. In order to reach the host cytoplasm, most P. falciparum proteins contain an N terminal host-targeting (HT) motif composed of 11 amino acids. In silico analyses have suggested that the HT motif is conserved throughout the Plasmodium species but experimental evidence only exists for P. falciparum. Here, we show that in the rodent malaria parasite Plasmodium berghei (P. berghei) a reporter-like green fluorescent protein expressed by the parasite can be exported to the erythrocyte cytoplasm in a HT-specific manner. This provides the first experimental proof that the HT motif can function as a signal for protein delivery to the erythrocyte across Plasmodium species. Further, it suggests that P. berghei may serve as a model for validation of P. falciparum secretome proteins. We also show that tubovesicular membranes extend from the vacuolar parasite into the erythrocyte cytoplasm and speculate that these structures may facilitate protein export to the erythrocyte
A novel, high-sensitivity, bacteriophage-based assay identifies low level Mycobacterium tuberculosis bacteraemia in immunocompetent patients with active and incipient tuberculosis
Haematogenous dissemination of M. tuberculosis (Mtb) is critical to pathogenesis of progressive tuberculous infection in animal models. Using a novel phage-based blood assay, we report the first concordant evidence in well-characterised immunocompetent human cohorts, demonstrating associations of Mtb bacteraemia with progressive phenotypes of latent infection and active pulmonary TB respectively
Spectral fluctuation and noise in the energy level statistics of interacting trapped bosons
It has been recently shown numerically that the transition from integrability
to chaos in quantum systems and the corresponding spectral fluctuations are
characterized by noise with . The
system of interacting trapped bosons is inhomogeneous and a complex system. The
presence of external harmonic trap makes it more interesting as in the atomic
trap the bosons occupy partly degenerate single-particle states. Earlier
theoretical and experimental results show that at zero temperature the
low-lying levels are of collective nature and high-lying excitations are of
single particle nature. We observe that for few bosons, distribution
shows the Shnirelman peak which exhibits a large number of quasi-degenerate
states. For large number of bosons the low-lying levels are strongly affected
by the interatomic interaction and the corresponding level fluctuation shows a
transition to Wigner with increase in particle number. It does not follow GOE
(Gaussian Orthogonal Ensemble) Random Matrix predictions. For high-lying levels
we observe the uncorrelated Poisson distribution. Thus it may be a very
realistic system to prove that noise is ubiquitous in
nature
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