787 research outputs found
Analyzing the Longevity of Sperm Within the Female Japanese Quail by Assessing Sperm Penetration of the Perivitelline Layer Under Optimal and Suboptimal Conditions.
After mating, birds have the ability to store semen within the female reproductive tract. The sperm storage tubules will store and subsequently release semen to travel up the oviduct. Sperm cells that make the trek up the oviduct have a chance to fertilize the ovum. These sperm cells will bind to the perivitelline layer of the ovum and hydrolyze a hole in the perivitelline layer, where it has the possibility to fertilize the female sex cell. Analyzing the number of penetration points on the perivitelline layer is an effective way to analyze reproductive efficiency. Many environmental factor has its effect on reproductive efficiency, however, only a few research trials have been done that analyze how environmental variables affect sperm penetration in itself. A population of 120 twelve week old random bred Japanese coturnix quail was separated into breeding ratios of three hens per cock making 30 pens with four birds in each. Treatments of optimal nutrition, suboptimal nutrition, and mild heat stress 75-80°F were utilized. These treatments were compared to a control group, where the males were not removed from the pen after 14 days. Males were left in the breeding pens for 14 days and then taken out, except for the control group where the males resided for the entire duration of the study. Sperm penetration assays were taken and analyzed every other day until no fertile eggs were laid. On every other consecutive day, eggs were collected and set to incubate until hatch. After hatch, percent hatchability was calculated. It was observed according to
Davis’ Correlation coefficients that day of the trial has a substantial negative correlation on sperm penetration and percent hatch by (-0.65871) and (-0.5058) respectfully. Sperm penetration and percent hatch show a very strong positive correlation of (0.76404). This population of quail was observed to store semen in sufficient quantities to maintain at »30 sperm penetration points (SPP) for 3 days before dropping significantly in SPP (p \u3c 0.0001). Where this same population could lay hatchable eggs for 8 days before dropping in hatching percentage, (P \u3c 0.0024). Additionally, it was observed that proper nutrition had a more significantly greater effect by increasing SPP and slightly increasing percent hatch than the effects of heat stress. Overall, it appears that similar trials that observe the longevity of fertility could be used to model the environmental effects on SPP, transversely affecting hatchability
Prospects for probing the gluon density in protons using heavy quarkonium hadroproduction
We examine carefully bottomonia hadroproduction in proton colliders,
especially focusing on the LHC, as a way of probing the gluon density in
protons. To this end we develop some previous work, getting quantitative
predictions and concluding that our proposal can be useful to perform
consistency checks of the parameterization sets of different parton
distribution functions.Comment: LaTeX, 14 pages, 6 EPS figure
Locus coeruleus to basolateral amygdala noradrenergic projections promote anxiety-like behavior
Increased tonic activity of locus coeruleus noradrenergic (LC-NE) neurons induces anxiety-like and aversive behavior. While some information is known about the afferent circuitry that endogenously drives this neural activity and behavior, the downstream receptors and anatomical projections that mediate these acute risk aversive behavioral states via the LC-NE system remain unresolved. Here we use a combination of retrograde tracing, fast-scan cyclic voltammetry, electrophysiology, and in vivo optogenetics with localized pharmacology to identify neural substrates downstream of increased tonic LC-NE activity in mice. We demonstrate that photostimulation of LC-NE fibers in the BLA evokes norepinephrine release in the basolateral amygdala (BLA), alters BLA neuronal activity, conditions aversion, and increases anxiety-like behavior. Additionally, we report that β-adrenergic receptors mediate the anxiety-like phenotype of increased NE release in the BLA. These studies begin to illustrate how the complex efferent system of the LC-NE system selectively mediates behavior through distinct receptor and projection-selective mechanisms
Hole dynamics and photoemission in a t-J model for SrCu_2(BO_3)_2
The motion of a single hole in a t-J model for the two-dimensional spin-gap
compound SrCu_2(BO_3)_2 is investigated. The undoped Heisenberg model for this
system has an exact dimer eigenstate and shows a phase transition between a
dimerized and a Neel phase at a certain ratio of the magnetic couplings. We
calculate the photoemission spectrum in the disordered phase using a
generalized spin-polaron picture. By varying the inter-dimer hopping parameters
we find a cross-over between a narrow quasiparticle band regime known from
other strongly correlated systems and free-fermion behavior. The hole motion in
the Neel-ordered phase is also briefly considered.Comment: 4 pages, 3 fig
Detection of a CMB decrement towards a cluster of mJy radiosources
We present the results of radio, optical and near-infrared observations of
the field of TOC J0233.3+3021, a cluster of milliJansky radiosources from the
TexOx Cluster survey. In an observation of this field with the Ryle Telescope
(RT) at 15 GHz, we measure a decrement in the cosmic microwave background (CMB)
of Jy on the RT's 0.65 k baseline. Using
optical and infrared imaging with the McDonald 2.7-m Smith Reflector, Calar
Alto 3.5-m telescope and UKIRT, we identify the host galaxies of five of the
radiosources and measure magnitudes of , , .
The CMB decrement is consistent with the Sunyaev-Zel'dovich (SZ) effect of a
massive cluster of galaxies, which if modelled as a spherical King profile of
core radius has a central temperature decrement
of K. The magnitudes and colours of the galaxies are consistent with
those of old ellipticals at . We therefore conclude that TOC
J0233.3+3021 is a massive, high redshift cluster. These observations add to the
growing evidence for a significant population of massive clusters at high
redshift, and demonstrate the effectiveness of combining searches for AGN
`signposts' to clusters with the redshift-independence of the SZ effect.Comment: Six pages; accepted for publication in MNRAS. Version with
full-resolution UV plot available from
http://www.mrao.cam.ac.uk/~garret/MB185.p
Lewis pair polymerization by classical and frustrated Lewis pairs: acid, base and monomer scope and polymerization mechanism
Classical and frustrated Lewis pairs (LPs) of the strong Lewis acid (LA) Al(C6F5)3 with several Lewis
base (LB) classes have been found to exhibit exceptional activity in the Lewis pair polymerization (LPP)
of conjugated polar alkenes such as methyl methacrylate (MMA) as well as renewable α-methylene-
γ-butyrolactone (MBL) and γ-methyl-α-methylene-γ-butyrolactone (γ-MMBL), leading to high molecular
weight polymers, often with narrow molecular weight distributions. This study has investigated a large
number of LPs, consisting of 11 LAs as well as 10 achiral and 4 chiral LBs, for LPP of 12 monomers of
several different types. Although some more common LAs can also be utilized for LPP, Al(C6F5)3-based
LPs are far more active and effective than other LA-based LPs. On the other hand, several classes of LBs,
when paired with Al(C6F5)3, can render highly active and effective LPP of MMA and γ-MMBL; such
LBs include phosphines (e.g., PtBu3), chiral chelating diphosphines, N-heterocyclic carbenes (NHCs),
and phosphazene superbases (e.g., P4-tBu). The P4-tBu/Al(C6F5)3 pair exhibits the highest activity of the
LP series, with a remarkably high turn-over frequency of 9.6 × 104 h−1 (0.125 mol% catalyst, 100%
MMA conversion in 30 s, Mn = 2.12 × 105 g mol−1, PDI = 1.34). The polymers produced by LPs at RT
are typically atactic (PγMMBL with ∼47% mr) or syndio-rich (PMMAwith ∼70–75% rr), but highly
syndiotactic PMMAwith rr ∼91% can be produced by chiral or achiral LPs at −78 °C. Mechanistic
studies have identified and structurally characterized zwitterionic phosphonium and imidazolium
enolaluminates as the active species of the current LPP system, which are formed by the reaction of the
monomer·Al(C6F5)3 adduct with PtBu3 and NHC bases, respectively. Kinetic studies have revealed that
the MMA polymerization by the tBu3P/Al(C6F5)3 pair is zero-order in monomer concentration after an
initial induction period, and the polymerization is significantly catalyzed by the LA, thus pointing to a
bimetallic, activated monomer propagation mechanism. Computational study on the active species
formation as well as the chain initiation and propagation events involved in the LPP of MMAwith some
of the most representative LPs has added our understanding of fundamental steps of LPP. The main
difference between NHC and PR3 bases is in the energetics of zwitterion formation, with the NHC-based
zwitterions being remarkably more stable than the PR3-based zwitterions. Comparison of the
monometallic and bimetallic mechanism
Various series expansions for a Heisenberg antiferromagnet model for SrCu(BO)
We use a variety of series expansion methods at both zero and finite
temperature to study an antiferromagnetic Heisenberg spin model proposed
recently by Miyahara and Ueda for the quasi two-dimensional material
SrCu(BO). We confirm that this model exhibits a first-order quantum
phase transition at T=0 between a gapped dimer phase and a gapless N\'eel phase
when the ratio of nearest and next-nearest neighbour interactions is
varied, and locate the transition at . Using longer series we are
able to give more accurate estimates of the model parameters by fitting to the
high temperature susceptibility data.Comment: RevTeX, 13 figure
Field dependent thermodynamics and Quantum Critical Phenomena in the dimerized spin system Cu2(C5H12N2)2Cl4
Experimental data for the uniform susceptibility, magnetization and specific
heat for the material Cu2(C5H12N2)2Cl4 (abbreviated CuHpCl) as a function of
temperature and external field are compared with those of three different
dimerized spin models: alternating spin-chains, spin-ladders and the bilayer
Heisenberg model. It is shown that because this material consists of weakly
coupled spin-dimers, much of the data is insensitive to how the dimers are
coupled together and what the effective dimensionality of the system is. When
such a system is tuned to the quantum critical point by application of a field,
the dimensionality shows up in the power-law dependences of thermodynamic
quantities on temperature. We discuss the temperature window for such a quantum
critical behavior in CuHpCl.Comment: Revtex, 5 pages, 4 figures (postscript
Naïve rat umbilical cord matrix stem cells significantly attenuate mammary tumor growth through modulation of endogenous immune responses
Background: Un-engineered human and rat umbilical cord matrix stem cells (rUCMSC) attenuate growth of several types of tumors in mice and rats. However, the mechanism by which UCMSC attenuate tumor growth has not been studied rigorously.
Methods- The possible mechanisms of tumor growth attenuation by rUCMSC were studied using orthotopic Mat B III rat mammary tumor grafts in female F344 rats. Tumor-infiltrating leukocytes were identified and quantified by immunohistochemical image analysis. Potential cytokines involved in lymphocyte infiltration in the tumors were determined by microarray and Western blot analysis. The Boyden chamber migration assay was performed for the functional analysis of identified cytokines.
Results: rUCMSC markedly attenuated the tumor growth; this attenuation was accompanied by considerable lymphocyte infiltration. Immunohistochemical analysis revealed that the majority of infiltrating lymphocytes in the rUCMSC-treated tumors were CD3+ T cells. In addition, treatment with rUCMSC significantly increased infiltration of CD 8+ and CD4+ T cells and NK cells throughout tumor tissue. CD68+ monocytes/macrophages and FoxP3+ regulatory T cells were scarcely observed, only in the tumors of the PBS control group. Microarray analysis of rUCMSC identified that monocyte chemotactic protein (MCP)-1 is involved in rUCMSCinduced lymphocyte infiltration in the tumor tissues.
Discussion: These results suggest that naïve rUCMSC attenuated mammary tumor growth at least in part by enhancing host anti-tumor immune responses. Thus, naïve UCMSC can be used as powerful therapeutic cells for breast cancer treatment, and MCP-1 may be a key molecule to enhance the effect of UCMSC at the tumor site
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