1,845 research outputs found
Parton distribution functions and quark orbital motion
Covariant version of the quark-parton model is studied. Dependence of the
structure functions and parton distributions on the 3D quark intrinsic motion
is discussed. The important role of the quark orbital momentum, which is a
particular case of intrinsic motion, appears as a direct consequence of the
covariant description. Effect of orbital motion is substantial especially for
polarized structure functions. At the same time, the procedure for obtaining
the quark momentum distributions of polarized quarks from the combination of
polarized and unpolarized structure functions is suggested.Comment: 17 pages, 2 figures, 1 table. Paper is accepted for publication in
Eur.Phys.J.
Magnetic and axial vector form factors as probes of orbital angular momentum in the proton
We have recently examined the static properties of the baryon octet (magnetic
moments and axial vector coupling constants) in a generalized quark model in
which the angular momentum of a polarized nucleon is partly spin and partly orbital . The orbital momentum was
represented by the rotation of a flux-tube connecting the three constituent
quarks. The best fit is obtained with ,
. We now consider the consequences of this
idea for the -dependence of the magnetic and axial vector form factors. It
is found that the isovector magnetic form factor
differs in shape from the axial form factor by an amount that
depends on the spatial distribution of orbital angular momentum. The model of a
rigidly rotating flux-tube leads to a relation between the magnetic, axial
vector and matter radii, , where , . The shape of is found to be close to a dipole
with GeV.Comment: 18 pages, 5 ps-figures, uses RevTe
Physicochemical Studies of La(III), Ce(III), Pr(III), Nd(III), Sm(III) & Gd(III) Chelates of o-(2-Pyrrolideneimino)benzoic Acid & 3-(2-pyrrolideneimino)propionic Acid
1104-110
Optimization of influential parameters for extracellular keratinase production of Bacillus subtilis (MTCC9102) in solid state fermentation using horn meal - a biowaste management
A Bacillus subtilis (MTCC9102) isolate was shown to produce significant amount of keratinase under optimized conditions in solid-state fermentation using Horn meal as a substrate. Optimized value for moisture, inoculum, and aeration were found to be 100% (v/w), 50% (v/w), and 150% (w/w), respectively, and the optimum nitrogen source was peptone and carbon source was dextrose. Maximum keratinolytic activity was observed at 48 h after incubation, and the optimum age (24 h) of inoculum was significant. The influence of cultivation temperature and initial pH of the medium on keratinase production revealed the optimum values for the temperature and pH as 37°C and 7, respectively. Maximum keratinase activity of the crude extract was 15,972 U/mg/ml. These results indicate that this bacterial strain shows a high biotechnological potential for keratinase production in solid-state fermentation, and use of the horn meal as the substrate can be implemented for keratinous solid wastes management
Sagnac Interferometer Enhanced Particle Tracking in Optical Tweezers
A setup is proposed to enhance tracking of very small particles, by using
optical tweezers embedded within a Sagnac interferometer. The achievable
signal-to-noise ratio is shown to be enhanced over that for a standard optical
tweezers setup. The enhancement factor increases asymptotically as the
interferometer visibility approaches 100%, but is capped at a maximum given by
the ratio of the trapping field intensity to the detector saturation threshold.
For an achievable visibility of 99%, the signal-to-noise ratio is enhanced by a
factor of 200, and the minimum trackable particle size is 2.4 times smaller
than without the interferometer
Tau Polarization in and
We discuss the longitudinal and transverse -polarization in inclusive
decays of hadrons containing -quarks. The calculation is performed by means
of an OPE in HQET. Some mathematical difficulties in calculating transverse
polarizations are explained. Numerical results are presented for longitudinal
and for transverse polarizations, both in and perpendicular to the decay plane.Comment: LATEX, 20 pages, 5 Postscript figure
Effects on pregnancy in mice of passive immunization against ovine LH and human chorionic gonadotrophin
Mice given daily i.p. injections of immunoglobulins against ovine LH on Days 3-7 of pregnancy were devoid of implantation sites on Day 8 whereas mice treated with antibodies to hCG had embryos of normal number and appearance on Day 8. These antibody treatments reduced the mean ± s.d. serum progesterone concentrations from 65.4 ± 15.3 ng/ml (control globulins) to 8.6 ± 4.9 ng/ml (anti-LH) and 9.2 ± 3.1 ng/ml (anti-hCG) on Day 8 and had no differential effect on serum oestrogen levels on Day 4. However, the mice treated with anti-hCG did not litter; resorption of the embryos took place between Days 10 and 14 of pregnancy. Indirect immunofluorescence and quantitative immunoenzymic assays showed the presence of anti-ovine LH and anti-hCG reacting antigens in the mouse feto-placental unit. On Day 6, the values of reacting antigens (mean ± s.d. absorbance units/10 µm section of embryo) were 0.050 ± 0.002 with control globulins, 0.059 ± 0.002 with anti-hCG-Ig and 0.196 ± 0.018 with anti-LH-Ig; the corresponding values on Day 12 were 0.075 ± 0.009, 0.402 ± 0.02 and 0.416 ± 0.015. The quantitative disposition of the reacting antigens to the two types of anti-gonadotrophins seems to bear a temporal relationship to their respective antifertility action. The pregnancy terminating action of immunoglobulins to ovine LH (Days 6, 7 & 8) and hCG (Days 8, 9 & 10) was counteracted by administration of 2 mg medroxyprogesterone acetate on Days 6, 9 and 12, indicating the importance of progesterone in the maintenance of pregnancy in the mouse
Quark Orbital-Angular-Momentum Distribution in the Nucleon
We introduce gauge-invariant quark and gluon angular momentum distributions
after making a generalization of the angular momentum density operators. From
the quark angular momentum distribution, we define the gauge-invariant and
leading-twist quark {\it orbital} angular momentum distribution . The
latter can be extracted from data on the polarized and unpolarized quark
distributions and the off-forward distribution in the forward limit. We
comment upon the evolution equations obeyed by this as well as other orbital
distributions considered in the literature.Comment: 8 pages, latex, no figures, minor corrections mad
Rare Decays
The rare decays of the meson have had a long tradition as a laboratory
for testing the symmetry properties of the weak interactions, and the manner in
which these symmetries are broken by higher order effects. Present--day
interest is focussed on decays that are suppressed by --symmetry or GIM
symmetry. Such decays, in the standard theory, are sensitive to effects of the
virtual top quark, and could also reveal new interactions transcending the
standard model. In addition, the radiative decays of the meson have become
a useful testing--ground for effective Lagrangians describing the low energy
interactions of pions, kaons and photons.Comment: Invited Talk at the Third Workshop on High Energy Particle Physics
(WHEPP 3) Madras, 1994, LaTex, 14 pages, 3 figures available upon reques
Deletion of STAT5a/b in vascular smooth muscle abrogates the male bias in hypoxic pulmonary hypertension in mice: implications in the human disease
Chronic hypoxia typically elicits pulmonary hypertension (PH) in mice with a male-dominant phenotype. There is an opposite sex-bias in human PH with higher prevalence in women, but greater survival (the estrogen paradox ). We investigated the involvement of STAT5a/b species, previously established to mediate sexual dimorphism in other contexts, in the sex-bias in PH. Mice with heterozygous or homozygous deletions of the STAT5a/b locus in vascular smooth muscle cells (SMC) were generated in crosses between STAT5a/bfl/fl and transgelin (SM22alpha)-Cre+/+ parents. Wild-type (wt) males subjected to chronic hypoxia showed significant PH and pulmonary arterial remodeling, with wt females showing minimal changes (a male-dominant phenotype). However, in conditional STAT5+/- or -/- mice, hypoxic females showed the severest manifestations of PH (a female-dominant phenotype). Immunofluorescence studies on human lung sections showed that obliterative pulmonary arterial lesions in patients with idiopathic or hereditary pulmonary arterial hypertension (IPAH or HPAH), both male and female, overall, had reduced STAT5a/b, reduced PY-STAT5 and reduced endoplasmic reticulum (ER) GTPase atlastin-3 (ATL3). Studies of SMC and endothelial cell (EC) lines derived from vessels isolated from lungs of male and female IPAH patients and controls, revealed instances of coordinate reductions in STAT5a, STAT5b and ATL3 in IPAH-derived cells, including in SMCs and ECs from the same patient. Taken together, these data provide the first definitive evidence for a contribution of STAT5a/b to the sex-bias in PH in the hypoxic mouse, and implicate reduced STAT5 in the pathogenesis of the human disease
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