266 research outputs found
Avaliação de sêmen congelado de bovinos. Provas lenta e rápida de termo-resistência: efeitos sobre a fertilidade.
O objetivo do presente trabalho foi avaliar a eficiência de sêmen congelado, submetido as provas rápida e lenta de termo-resistência, sobre a fertilidade de fêmeas da espécie bovina
Biometria testicular de touros Nelore (Bos taurus indicus) e touros cruzados Nelore-europeu (Bos taurus indicus x Bos taurus taurus) aos 20 e 24 mês de idade.
O objetivo deste trabalho foi estudar os efeitos da idade, do grupo genético e da interação entre idade e grupo genético, sobre as biometrias testiculares (circunferência escrotal e consistência testicular) Foram avaliados, aos 20 e 24 meses de idade, 190 touros Nelore e 447 touros cruzados Nelore-europeu. Aos 24 meses os exames foram repetidos. A circunferência escrotal e a consistência testicular foram influenciadas pelo grupo genético, idade e interação grupo genético x idade. Foram encontradas maiores médias de circunferência escrotal e menores de consistência testicular em cruzados que em Nelore, tanto aos 20 quanto aos 24 meses. Correlações entre circunferência escrotal As correlações entre circunferência escrotal e idade, observadas no presente experimento, foram baixas para os touros Nelore aos 20 meses e aos 24 meses assim como para os cruzados aos 20 meses e aos 24 meses, entretanto, as correlações entre circunferência escrotal e peso corporal foram maiores. As correlações entre consistência testicular e idade e entre consistência testicular e peso corporal foram baixas para a maioria dos cruzados, para os cruzados em conjunto e para os Nelores
Landau Theory of the Phase Transitions in Half Doped Manganites: Interplay of Magnetic, Charge and Structural Orders
The order parameters of the magnetic, charge and structural orders at
half-doped manganites are identified. A corresponding Landau theory of the
phase transitions is formulated. Many structural and thermodynamical behaviors
are accounted for and clarified within the framework. In particular, the theory
provides a unified picture for the scenario of the phase transitions and their
nature with respect to the variation of the tolerance factor of the manganites.
It also accounts for the origin of the incommensurate nature of the orbital
order and its subsequently accompanying antiferromagnetic order.Comment: 4 pages, 3 eps figures, Revtex, Phys. Rev. B61, 200
Simulation of Special Bubble Detectors for PICASSO
The PICASSO project is a cold dark matter (CDM) search experiment relying on
the superheated droplet technique. The detectors use superheated freon liquid
droplets (active material) dispersed and trapped in a polymerized gel. This
detection technique is based on the phase transition of superheated droplets at
about room temperature and ambient pressure. The phase transition is induced by
nuclear recoils when an atomic nucleus in the droplets interacts with incoming
subatomic particles. This includes CDM particles candidate as the neutralino (a
yet-to-discover particle predicted in extensions of the Standard Model of
particle physics). Simulations performed to understand the detector response to
neutrons and alpha particles are presented along with corresponding data
obtained at the Montreal Laboratory.Comment: 13 pages, 4 figures. To appear in the Proceedings of the 14th
International Conference on Solid State Dosimetry, June 27 - July 2 2004,
Yale University, New Haven, CT, US
Sperm cryodamage occurs after rapid freezing phase: flow cytometry approach and antioxidant enzymes activity at different stages of cryopreservation
Abstract\ud
\ud
Background\ud
In order to improve the efficiency of bovine sperm cryopreservation process, it is important to understand how spermatozoa respond to differences in temperature as well as the ability to recover its own metabolism. The combination between flow cytometry approach and antioxidant enzymes activity allows a more sensible evaluation of sperm cell during cryopreservation. The aim of this study was to evaluate sperm attributes and antioxidant enzymes activity during different stages of cryopreservation process. Semen samples from Holstein bulls (n = 4) were separated in 3 treatments: fresh (37 °C); cooled (5 °C); and thawed. Evaluation occurred at 0 h and 2 h after incubation. Membrane integrity, mitochondrial membrane potential (MMP) and DNA damages were evaluated by flow cytometry; activities of antioxidant enzymes such as catalase, superoxide dismutase and gluthatione peroxidase were measured by spectrofotometry.\ud
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\ud
Results\ud
There was an increase in the percentage of sperm with DNA damage in the thawed group, compared to fresh and cooled, and for 2 hs of incubation when compared to 0 h. Considering MMP, there was an increase in the percentage of cells with medium potential in thawed group when compared to fresh and cooled groups. Opposingly, a decrease was observed in the thawed group considering high mitochondrial potential. Also in the thawed group, there was an increase on cells with damaged acrosome and membrane when compared to fresh and cooled groups. Significant correlations were found between antioxidant enzymes activity and membrane or mitochondrial parameters.\ud
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Conclusion\ud
Based on our results, we conclude that cryopreservation affects cellular and DNA integrity and that the critical moment is when sperm cells are exposed to freezing temperature. Also, our study indicates that intracellular antioxidant machinery (SOD and GPX enzymes) is not enough to control cryodamage.This study was supported by São Paulo Research Foundation (FAPESP),\ud
process number 2010/18978-9 and 2007/58487-1
The background in the neutrinoless double beta decay experiment GERDA
The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground
laboratory (LNGS) of INFN is searching for neutrinoless double beta decay of
76Ge. The signature of the signal is a monoenergetic peak at 2039 keV, the
Q-value of the decay, Q_bb. To avoid bias in the signal search, the present
analysis does not consider all those events, that fall in a 40 keV wide region
centered around Q_bb. The main parameters needed for the neutrinoless double
beta decay analysis are described. A background model was developed to describe
the observed energy spectrum. The model contains several contributions, that
are expected on the basis of material screening or that are established by the
observation of characteristic structures in the energy spectrum. The model
predicts a flat energy spectrum for the blinding window around Q_bb with a
background index ranging from 17.6 to 23.8*10^{-3} counts/(keV kg yr). A part
of the data not considered before has been used to test if the predictions of
the background model are consistent. The observed number of events in this
energy region is consistent with the background model. The background at Q-bb
is dominated by close sources, mainly due to 42K, 214Bi, 228Th, 60Co and alpha
emitting isotopes from the 226Ra decay chain. The individual fractions depend
on the assumed locations of the contaminants. It is shown, that after removal
of the known gamma peaks, the energy spectrum can be fitted in an energy range
of 200 kev around Q_bb with a constant background. This gives a background
index consistent with the full model and uncertainties of the same size
Strong Gravitational Lensing as a Probe of Gravity, Dark-Matter and Super-Massive Black Holes
Whereas considerable effort has been afforded in understanding the properties
of galaxies, a full physical picture, connecting their baryonic and dark-matter
content, super-massive black holes, and (metric) theories of gravity, is still
ill-defined. Strong gravitational lensing furnishes a powerful method to probe
gravity in the central regions of galaxies. It can (1) provide a unique
detection-channel of dark-matter substructure beyond the local galaxy group,
(2) constrain dark-matter physics, complementary to direct-detection
experiments, as well as metric theories of gravity, (3) probe central
super-massive black holes, and (4) provide crucial insight into galaxy
formation processes from the dark matter point of view, independently of the
nature and state of dark matter. To seriously address the above questions, a
considerable increase in the number of strong gravitational-lens systems is
required. In the timeframe 2010-2020, a staged approach with radio (e.g. EVLA,
e-MERLIN, LOFAR, SKA phase-I) and optical (e.g. LSST and JDEM) instruments can
provide 10^(2-4) new lenses, and up to 10^(4-6) new lens systems from
SKA/LSST/JDEM all-sky surveys around ~2020. Follow-up imaging of (radio) lenses
is necessary with moderate ground/space-based optical-IR telescopes and with
30-50m telescopes for spectroscopy (e.g. TMT, GMT, ELT). To answer these
fundamental questions through strong gravitational lensing, a strong investment
in large radio and optical-IR facilities is therefore critical in the coming
decade. In particular, only large-scale radio lens surveys (e.g. with SKA)
provide the large numbers of high-resolution and high-fidelity images of lenses
needed for SMBH and flux-ratio anomaly studies.Comment: White paper submitted to the 2010 Astronomy & Astrophysics Decadal
Surve
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