733 research outputs found
Iron single crystal growth from a lithium-rich melt
\alpha-Fe single crystals of rhombic dodecahedral habit were grown from a
melt of LiNFe. Crystals of several millimeter along a
side form at temperatures around C. Upon further cooling
the growth competes with the formation of Fe-doped LiN. The b.c.c.
structure and good sample quality of \alpha-Fe single crystals were confirmed
by X-ray and electron diffraction as well as magnetization measurements and
chemical analysis. A nitrogen concentration of 90\,ppm was detected by means of
carrier gas hot extraction. Scanning electron microscopy did not reveal any
sign of iron nitride precipitates.Comment: 13 pages, 4 figure
CELL-TO-CELL INTERACTION IN THE IMMUNE RESPONSE : VII. REQUIREMENT FOR DIFFERENTIATION OF THYMUS-DERIVED CELLS
Experiments were designed to test the possibility that thymus-derived (T) cells cooperate with nonthymus derived (B) cells in antibody responses by acting as passive carriers of antigen. Thoracic duct lymphocytes (TDL) from fowl γG-tolerant mice were incubated in vitro with fowl anti-mouse lymphocyte globulin (FALG), which was shown not to be immunosuppressive in mice. On transfer into adult thymectomized, irradiated, and marrow protected (TxBM) hosts together with a control antigen, horse RBC, a response to horse RBC but not to fowl γG was obtained. By contrast, TxBM recipients of nontolerant, FALG-coated TDL responded to both antigens and the antibody-forming cells were shown to be derived from the host, not from the injected TDL. These findings suggested that, under the conditions of the experiment, triggering of unprimed B cells in the spleens of TxBM hosts was not achieved with antigen-coated tolerant lymphocytes. Another model utilized the ability of B cells to bind antibody-antigen complexes. Spleen cells from TxBM mice, incubated in vitro with anti-fowl γG-fowl γG·NIP, were injected with or without normal TDL (a source of T cells) into irradiated hosts. Only mice given both cell types could produce an anti-NIP antibody response. In a further experiment, spleen cells from HGG·NIP-primed mice were injected together with NIP-coated B cells (prepared as above) into irradiated hosts. A substantial anti-NIP antibody response occurred. If, however, the T cells in the spleens of HGG·NIP-primed mice were eliminated by treatment with anti-θ serum and complement, the NIP response was abolished. It was concluded that antigen-coated B cells could not substitute for T cells either in the primary or secondary response. Treatment of T cells from unprimed or primed mice with mitomycin C impaired their capacity to collaborate with B cells on transfer into irradiated hosts. Taken together these findings suggest that before collaboration can take place T cells must be activated by antigen to differentiate and in so doing may produce some factor essential for triggering of B cells
Pressure-Induced Dimerization and Collapse of Antiferromagnetism in the Kitaev Material α-Li2IrO3
We present magnetization measurements carried out on polycrystalline and single-crystalline samples of α-Li2IrO3 under hydrostatic pressures up to 2 GPa and establish the temperature-pressure phase diagram of this material. The Néel temperature (TN) of α-Li2IrO3 is slightly enhanced upon compression with dTN/dp = 1.5 K/GPa. Above 1.2 GPa, α-Li2IrO3 undergoes a first-order phase transition toward a nonmagnetic dimerized phase, with no traces of the magnetic phase observed above 1.8 GPa at low temperatures. The critical pressure of the structural dimerization is strongly temperature dependent. This temperature dependence is well reproduced on the ab initio level by taking into account lower phonon entropy in the nonmagnetic phase. We further show that the initial increase in TN of the magnetic phase is due to a weakening of the Kitaev interaction K along with the enhancement of the Heisenberg term J and off-diagonal anisotropy Γ. Our study reveals a common thread in the interplay of magnetism and dimerization in pressured Kitaev materials. © 2022 American Physical Society.This work was funded by the German Research Foundation (DFG) via Project No. 107745057 (TRR80) and via the Sino-German Cooperation Group on Emergent Correlated Matter. D.P. acknowledges financial support by the Russian Science Foundation, Grant No. 21-72-10136
Is telomere length socially patterned? Evidence from the West of Scotland Twenty-07 study
Lower socioeconomic status (SES) is strongly associated with an increased risk of morbidity and premature mortality, but it is not known if the same is true for telomere length, a marker often used to assess biological ageing. The West of Scotland Twenty-07 Study was used to investigate this and consists of three cohorts aged approximately 35 (N = 775), 55 (N = 866) and 75 years (N = 544) at the time of telomere length measurement. Four sets of measurements of SES were investigated: those collected contemporaneously with telomere length assessment, educational markers, SES in childhood and SES over the preceding twenty years. We found mixed evidence for an association between SES and telomere length. In 35-year-olds, many of the education and childhood SES measures were associated with telomere length, i.e. those in poorer circumstances had shorter telomeres, as was intergenerational social mobility, but not accumulated disadvantage. A crude estimate showed that, at the same chronological age, social renters, for example, were nine years (biologically) older than home owners. No consistent associations were apparent in those aged 55 or 75. There is evidence of an association between SES and telomere length, but only in younger adults and most strongly using education and childhood SES measures. These results may reflect that childhood is a sensitive period for telomere attrition. The cohort differences are possibly the result of survival bias suppressing the SES-telomere association; cohort effects with regard different experiences of SES; or telomere possibly being a less effective marker of biological ageing at older ages
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Study of cosolvent-induced α-chymotrypsin fibrillogenesis: Does protein surface hydrophobicity trigger early stages of aggregation reaction?
The misfolding of specific proteins is often associated with their assembly into fibrillar aggregates, commonly termed amyloid fibrils. Despite the many efforts expended to characterize amyloid formation in vitro, there is no deep knowledge about the environment (in which aggregation occurs) as well as mechanism of this type of protein aggregation. Alpha-chymotrypsin was recently driven toward amyloid aggregation by the addition of intermediate concentrations of trifluoroethanol. In the present study, approaches such as turbidimetric, thermodynamic, intrinsic fluorescence and quenching studies as well as chemical modification have been successfully used to elucidate the underlying role of hydrophobic interactions (involved in early stages of amyloid formation) in α-chymotrypsin-based experimental system. © 2009 Springer Science+Business Media, LLC
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
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