392 research outputs found
The mouse median nerve experimental model in regenerative research
Sciatic nerve crush injury in rat animal model is one of the most common experimental models used in regenerative research. However, the availability of transgenic mouse for nerve regeneration studies is constantly increasing and, therefore, the shift from rat model to mouse model is, in some cases, necessary. Moreover, since most of the human nerve lesions occur in the upper limb, it is also advantageous to shift from sciatic nerve to median nerve. In this study we described an experimental model which involves lesions of the median nerve in the mouse. Data showed that the finger flexor muscle contraction strength, assessed to evaluate the motor function recovery, and reached values not different from the control already 20 days after injury. The degree of nerve regeneration evaluated with stereological methods in light microscopy showed that, 25 days after injury, the number of regenerated myelinated fibers was comparable to the control, but they were smaller with a thinner myelin thickness. Stereological analysis made in electron microscopy confirmed these results, although the total number of fibers quantified was significantly higher compared to light microscopy analysis, due to the very small size of some fibers that can be detected only in electron microscopy
Enhancing the Theory of Planned Behaviour by Incorporating Social Marketing Behavioural Enhancers: A First VS Second Order Confirmatory Factor Analysis Approach
This study investigated the need to extend the TPB model to SMBE variables as suggested by Ayikwa and De Jager (2017) in the quest to better understand sexual behavioural patterns using the Confirmatory Factor Analysis (CFA) approach. The main research question to be answered: "how the TPB and SMBE variables should be structured into a validated CFA model?" Data were carefully collected in South Africa’s Gauteng Province using a disproportionate multi-stage stratified random sampling method to retain 607 respondents. The survey questionnaires distributed consisted of revisited pre-existing instruments. The data were then analysed by CFA model that followed Exploratory Factor Analysis (EFA) to determine the suitability of the sample size. Assessment of the second order extended TPB model confirmed that it is worthwhile to integrate SMBE variables while extending the TPB model in the context of HIV/AIDS related behaviours
The Effects of Thermonuclear Reaction-Rate Variations on 26Al Production in Massive Stars: a Sensitivity Study
We investigate the effects of thermonuclear reaction rate variations on 26Al
production in massive stars. The dominant production sites in such events were
recently investigated by using stellar model calculations: explosive
neon-carbon burning, convective shell carbon burning, and convective core
hydrogen burning. Post-processing nucleosynthesis calculations are performed
for each of these sites by adopting temperature-density-time profiles from
recent stellar evolution models. For each profile, we individually multiplied
the rates of all relevant reactions by factors of 10, 2, 0.5 and 0.1, and
analyzed the resulting abundance changes of 26Al. Our simulations are based on
a next-generation nuclear physics library, called STARLIB, which contains a
recent evaluation of Monte Carlo reaction rates. Particular attention is paid
to quantifying the rate uncertainties of those reactions that most sensitively
influence 26Al production. For stellar modelers our results indicate to what
degree predictions of 26Al nucleosynthesis depend on currently uncertain
nuclear physics input, while for nuclear experimentalists our results represent
a guide for future measurements. We tabulate the results of our reaction rate
sensitivity study for each of the three distinct massive star sites referred to
above. It is found that several current reaction rate uncertainties influence
the production of 26Al. Particularly important reactions are 26Al(n,p)26Mg,
25Mg(alpha,n)28Si, 24Mg(n,gamma)25Mg and 23Na(alpha,p)26Mg. These reactions
should be prime targets for future measurements. Overall, we estimate that the
nuclear physics uncertainty of the 26Al yield predicted by the massive star
models explored here amounts to about a factor of 3.Comment: 44 pages, 16 figure
The Mouse Median Nerve Experimental Model in Regenerative Research
Sciatic nerve crush injury in rat animal model is one of the most common experimental models used in regenerative research. However, the availability of transgenic mouse for nerve regeneration studies is constantly increasing and, therefore, the shift from rat model to mouse model is, in some cases, necessary. Moreover, since most of the human nerve lesions occur in the upper limb, it is also advantageous to shift from sciatic nerve to median nerve. In this study we described an experimental model which involves lesions of the median nerve in the mouse. Data showed that the finger flexor muscle contraction strength, assessed to evaluate the motor function recovery, and reached values not different from the control already 20 days after injury. The degree of nerve regeneration evaluated with stereological methods in light microscopy showed that, 25 days after injury, the number of regenerated myelinated fibers was comparable to the control, but they were smaller with a thinner myelin thickness. Stereological analysis made in electron microscopy confirmed these results, although the total number of fibers quantified was significantly higher compared to light microscopy analysis, due to the very small size of some fibers that can be detected only in electron microscopy
Two populations of X-ray pulsars produced by two types of supernovae
Two types of supernova are thought to produce the overwhelming majority of neutron stars in the Universe. The first type, iron-core collapse supernovae, occurs when a high-mass star develops a degenerate iron core that exceeds the Chandrasekhar limit. The second type, electron-capture supernovae, is associated with the collapse of a lower-mass oxygen-neon-magnesium core as it loses pressure support owing to the sudden capture of electrons by neon and/or magnesium nuclei. It has hitherto been impossible to identify the two distinct families of neutron stars produced in these formation channels. Here we report that a large, well-known class of neutron-star-hosting X-ray pulsars is actually composed of two distinct sub-populations with different characteristic spin periods, orbital periods and orbital eccentricities. This class, the Be/X-ray binaries, contains neutron stars that accrete material from a more massive companion star. The two sub-populations are most probably associated with the two distinct types of neutron-star-forming supernovae, with electron-capture supernovae preferentially producing system with short spin period, short orbital periods and low eccentricity. Intriguingly, the split between the two sub-populations is clearest in the distribution of the logarithm of spin period, a result that had not been predicted and which still remains to be explaine
Guideline attainment and morbidity/mortality rates in a large cohort of European hemodialysis patients (EURODOPPS)
International audienceBackground. Haemodialysis patients experience a wide variety of intermediate complications, such as anaemia, hypertension and mineral bone disease (MBD). We aimed to assess the risk of death and hospital admissions as a function of the simultaneous attainment of different guideline targets (for hypertension, anaemia andMBD) in a large European cohort of dialysis patients. Methods. EURODOPPS is part of the Dialysis Outcomes and Practice Patterns Study (DOPPS) international, prospective cohort study of adult, in-centre haemodialysis patients for whom clinical data are extracted from medical records. In the present analysis, 6317 patients from seven European countries were included between 2009 and 2011. The percentages of patients treated according to the international guidelines on anaemia, hypertension and MBD were determined. The overall degree of guideline attainment was considered to be high if four or all five of the evaluated targets were attained, moderate if two or three targets were attained, and low if fewer than two targets were attained. Fully adjusted multivariate Cox models were used to investigate the relationship of target attainment with mortality and first hospital admission. Results. At baseline, the degree of target attainment was low in 1751 patients (28%), moderate in 3803 (60%) and high in 763 (12%). In the fully adjusted model using time-dependent covariates, low attainment was associated with higher all-cause mortality [hazard ratio (95% confidence interval) = 1.19 (1.05-1.34)] and high attainment was associated with lower all-cause mortality [0.82 (0.68-0.99)]. In a similarmodel that additionally accounted for death as a competing risk, low and high attainments were not associated with hospital admission. Conclusion. In a large international cohort of dialysis patients, we have shown that more stringent application of guidelines is associated with lower mortality
Black Hole Formation in Failing Core-Collapse Supernovae
We present results of a systematic study of failing core-collapse supernovae
and the formation of stellar-mass black holes (BHs). Using our open-source
general-relativistic 1.5D code GR1D equipped with a three-species neutrino
leakage/heating scheme and over 100 presupernova models, we study the effects
of the choice of nuclear equation of state (EOS), zero-age main sequence (ZAMS)
mass and metallicity, rotation, and mass-loss prescription on BH formation. We
find that the outcome, for a given EOS, can be estimated, to first order, by a
single parameter, the compactness of the stellar core at bounce. By comparing
protoneutron star (PNS) structure at the onset of gravitational instability
with solutions of the Tolman-Oppenheimer-Volkof equations, we find that thermal
pressure support in the outer PNS core is responsible for raising the maximum
PNS mass by up to 25% above the cold NS value. By artificially increasing
neutrino heating, we find the critical neutrino heating efficiency required for
exploding a given progenitor structure and connect these findings with ZAMS
conditions, establishing, albeit approximately, for the first time based on
actual collapse simulations, the mapping between ZAMS parameters and the
outcome of core collapse. We also study the effect of progenitor rotation and
find that the dimensionless spin of nascent BHs may be robustly limited below
a^* = Jc/GM^2 = 1 by the appearance of nonaxisymmetric rotational
instabilities.Comment: 20 emulateapj pages, 13 figures, published in the Astrophysical
Journal, minor revision
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Multicolored Stain-Free Histopathology with Coherent Raman Imaging
Conventional histopathology with hematoxylin & eosin (H&E) has been the gold standard for histopathological diagnosis of a wide range of diseases. However, it is not performed in vivo and requires thin tissue sections obtained after tissue biopsy, which carries risk, particularly in the central nervous system. Here we describe the development of an alternative, multicolored way to visualize tissue in real-time through the use of coherent Raman imaging (CRI), without the use of dyes. CRI relies on intrinsic chemical contrast based on vibrational properties of molecules and intrinsic optical sectioning by nonlinear excitation. We demonstrate that multicolor images originating from and vibrations of lipids and protein, as well as two-photon absorption of hemoglobin, can be obtained with subcellular resolution from fresh tissue. These stain-free histopathological images show resolutions similar to those obtained by conventional techniques, but do not require tissue fixation, sectioning or staining of the tissue analyzed.Chemistry and Chemical Biolog
A four-hours long burst from Serpens X-1
During a serendipitous observation of the BeppoSAX Wide Field Cameras, a very
long Type I X-ray burst was observed from the low mass X-ray binary Serpens
X-1. The burst lasted for approximately 4 hours and had an exponential decay
time of 69+/-2 min (2-28 keV). The bolometric peak-luminosity is
(1.6+/-0.2)x10^38 erg/s and the fluence (7.3+/-1.4)x10^41 erg. The first
'normal' Type I burst was observed 34 days after the superburst. This is in
rough agreement with recent predictions for unstable carbon burning in a heavy
element ocean.Comment: 4 pages, 2 figures, accepted for publication by A&
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