917 research outputs found
Behavioral and electroencephalographic analysis of seizures induced by intrahippocampal injection of granulitoxin, a neurotoxic peptide from the sea anemone Bunodosoma granulifera
In this study, the behavioral and electroencephalographic (EEG) analysis of seizures induced by the intrahippocampal injection in rats of granulitoxin, a neurotoxic peptide from the sea anemone Bunodosoma granulifera, was determined. The first alterations occurred during microinjection of granulitoxin (8 µg) into the dorsal hippocampus and consisted of seizure activity that began in the hippocampus and spread rapidly to the occipital cortex. This activity lasted 20-30 s, and during this period the rats presented immobility. During the first 40-50 min after its administration, three to four other similar short EEG seizure periods occurred and the rats presented the following behavioral alterations: akinesia, facial automatisms, head tremor, salivation, rearing, jumping, barrel-rolling, wet dog shakes and forelimb clonic movements. Within 40-50 min, the status epilepticus was established and lasted 8-12 h. These results are similar to those observed in the acute phase of the pilocarpine model of temporal lobe epilepsy and suggest that granulitoxin may be a useful tool not only to study the sodium channels, but also to develop a new experimental model of status epilepticus.Universidade Estadual do Ceará Departamento de Ciências Fisiológicas Laboratório de NeurofarmacologiaUniversidade Federal de São Paulo (UNIFESP) Departamento de Neurologia e Neurocirurgia Laboratório de Neurologia ExperimentalUniversidade de Brasília Departamento de Biologia Celular Centro Brasileiro de Serviços e Pesquisas em ProteínasUNIFESP, Depto. de Neurologia e Neurocirurgia Laboratório de Neurologia ExperimentalSciEL
The radial BAO scale and Cosmic Shear, a new observable for Inhomogeneous Cosmologies
As an alternative explanation of the dimming of distant supernovae it has
recently been advocated that we live in a special place in the Universe near
the centre of a large spherical void described by a Lemaitre-Tolman-Bondi (LTB)
metric. In this scenario, the Universe is no longer homogeneous and isotropic,
and the apparent late time acceleration is actually a consequence of spatial
gradients. We propose in this paper a new observable, the normalized cosmic
shear, written in terms of directly observable quantities, and calculable in
arbitrary inhomogeneous cosmologies. This will allow future surveys to
determine whether we live in a homogeneous universe or not. In this paper we
also update our previous observational constraints from geometrical measures of
the background cosmology. We include the Union Supernovae data set of 307 Type
Ia supernovae, the CMB acoustic scale and the first measurement of the radial
baryon acoustic oscillation scale. Even though the new data sets are
significantly more constraining, LTB models -- albeit with slightly larger
voids -- are still in excellent agreement with observations, at chi^2/d.o.f. =
307.7/(310-4)=1.005. Together with the paper we also publish the updated
easyLTB code used for calculating the models and for comparing them to the
observations.Comment: 18 pages, 8 figures, the code can be downloaded at
http://www.phys.au.dk/~haugboel/software.shtm
Evaluation of biofertilizers in irrigated rice: effects on grain yield at different fertilizer rates
Biofertilizers are becoming increasingly popular in many countries and for many crops, but very few studies on their effect on grain yield have been conducted in rice. Therefore, we evaluated three different biofertilizers (based on Azospirillum, Trichoderma, or unidentified rhizobacteria) in the Philippines during four cropping seasons between 2009 and 2011, using four different fertilizer rates (100% of the recommended rate [RR], 50% RR, 25% RR, and no fertilizer as Control). The experiments were conducted under fully irrigated conditions in a typical lowland rice environment. Significant yield increases due to biofertilizer use were observed in all experimental seasons with the exception of the 2008/09 DS. However, the effect on rice grain yield varied between biofertilizers, seasons, and fertilizer treatments. In relative terms, the seasonal yield increase across fertilizer treatments was between 5% and 18% for the best biofertilizer (Azospirillum-based), but went up to 24% in individual treatments. Absolute grain yield increases due to biofertilizer were usually below 0.5 t·ha−1, corresponding to an estimated additional N uptake of less than 7.5 kg N ha−1. The biofertilizer effect on yield did not significantly interact with the inorganic fertilizer rate used but the best effects on grain yield were achieved at low to medium fertilizer rates. Nevertheless, positive effects of the biofertilizers even occurred at grain yields up to 5 t·ha−1. However, the trends in our results seem to indicate that biofertilizers might be most helpful in rainfed environments with limited inorganic fertilizer input. However, for use in these target environments, biofertilizers need to be evaluated under conditions with abiotic stresses typical of such systems such as drought, soil acidity, or low soil fertility.Niño Paul Meynard Banayo, Pompe C. Sta. Cruz, Edna A. Aguila, Rodrigo B. Badayos and Stephan M. Haefel
The Stress-Energy Tensor in Soluble Models of Spherically Symmetric Charged Black Hole Evaporation
We study the decay of a near-extremal black hole in AdS, related to the
near-horizon region of 3+1-dimensional Reissner-Nordstr\"om spacetime,
following Fabbri, Navarro, and Navarro-Salas. Back-reaction is included in a
semiclassical approximation. Calculations of the stress-energy tensor of matter
coupled to the physical spacetime for an affine null observer demonstrate that
the black hole evaporation proceeds smoothly and the near-extremal black hole
evolves back to an extremal ground state, until this approximation breaks down.Comment: 19 pages, 14 figure
Expanding and Collapsing Scalar Field Thin Shell
This paper deals with the dynamics of scalar field thin shell in the
Reissner-Nordstrm geometry. The Israel junction conditions between
Reissner-Nordstrm spacetimes are derived, which lead to the equation
of motion of scalar field shell and Klien-Gordon equation. These equations are
solved numerically by taking scalar field model with the quadratic scalar
potential. It is found that solution represents the expanding and collapsing
scalar field shell. For the better understanding of this problem, we
investigate the case of massless scalar field (by taking the scalar field
potential zero). Also, we evaluate the scalar field potential when is an
explicit function of . We conclude that both massless as well as massive
scalar field shell can expand to infinity at constant rate or collapse to zero
size forming a curvature singularity or bounce under suitable conditions.Comment: 15 pages, 11 figure
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EXPLORING IN718 ALLOY PRODUCTION WITH BI-DIRECTIONAL RASTER AND STOCHASTIC SPOT MELTING TECHNIQUES USING AN OPEN-SOURCE ELECTRON MELTING SYSTEM
This study compares the fabrication of IN718 alloy using bi-directional raster and stochastic spot melting
techniques with the open-source FreemeltOne Electron Beam Melting (EBM) system. The research aimed to
produce dense parts using both scanning strategies, employing custom Python code for raster melt beam path
generation and PixelMelt software for stochastic spot melting path generation. After optimizing process
parameters, 10mm height builds for each scanning strategy were fabricated, and their microstructure, hardness,
and density were analyzed using optical microscopy and SEM, Vickers microhardness scale, and a pycnometer.
The findings reveal valuable insights into the effects of scanning strategies on the microstructure, hardness, and
density of IN718 alloy components, advancing additive manufacturing knowledge.Mechanical Engineerin
Quantum dilaton gravity as a linear dilaton conformal field theory
A model of matter-coupled gravity in two dimensions is quantized. The crucial
requirement for performing the quantization is the vanishing of the conformal
anomaly, which is achieved by tuning a parameter in the interaction potential.
The spectrum of the theory is determined by mapping the model first onto a
field theory with a Liouville interaction, then onto a linear dilaton conformal
field theory. In absence of matter fields a pure gauge theory with massless
ground state is found; otherwise it is possible to minimally couple up to 11
matter scalar fields: in this case the ground state is tachyonic and the matter
sector decouples, like the transverse oscillators in the critical bosonic
string.Comment: 7 pages, RevTeX4 file. v2: some comments and one reference adde
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Fatigue Endurance Investigation of Post-processed Surfaces of LPBF Ti-6Al-4V under Flexural Stress
Numerous research works can be found focusing on fatigue properties of AM components,
however most of this literature is focused on uniaxial testing. Because the very few actual
components under uniaxial loading conditions found in any application, it is also important to
investigate fatigue performance under loads that produce combined stresses, such as bending. This
project investigates the fatigue endurance of LPBF Ti-6Al-4V specimens subjected to four
different surface finishing prost-processes (milled, ground, polished and abrasive media). The test
consisted of a force-controlled cyclic load applied on the specimen in a 4-point bending setup until
fracture. The study incorporated mechanical and optical techniques to measure and quantify the
characteristic surface roughness of the post-processes. Additionally, failure mechanisms are
discussed on fractographs. The data analyses suggested that internal defects commonly present in
additively manufactured parts had a more significant impact on the fatigue life than surface
roughness of post-processed parts.Mechanical Engineerin
Effective genome editing in Leishmania (Viannia) braziliensis stably expressing Cas9 and T7 RNA polymerase
Until 2015, loss-of-function studies to elucidate protein function in Leishmania relied on gene disruption through homologous recombination. Then, the CRISPR/Cas9 revolution reached these protozoan parasites allowing efficient genome editing with one round of transfection. In addition, the development of LeishGEdit, a PCR-based toolkit for generating knockouts and tagged lines using CRISPR/Cas9, allowed a more straightforward and effective genome editing. In this system, the plasmid pTB007 is delivered to Leishmania for episomal expression or integration in the β-tubulin locus and for the stable expression of T7 RNA polymerase and Cas9. In South America, and especially in Brazil, Leishmania (Viannia) braziliensis is the most frequent etiological agent of tegumentary leishmaniasis. The L. braziliensis β-tubulin locus presents significant sequence divergence in comparison with Leishmania major, which precludes the efficient integration of pTB007 and the stable expression of Cas9. To overcome this limitation, the L. major β-tubulin sequences, present in the pTB007, were replaced by a Leishmania (Viannia) β-tubulin conserved sequence generating the pTB007_Viannia plasmid. This modification allowed the successful integration of the pTB007_Viannia cassette in the L. braziliensis M2903 genome, and in silico predictions suggest that this can also be achieved in other Viannia species. The activity of Cas9 was evaluated by knocking out the flagellar protein PF16, which caused a phenotype of immobility in these transfectants. Endogenous PF16 was also successfully tagged with mNeonGreen, and an in-locus complementation strategy was employed to return a C-terminally tagged copy of the PF16 gene to the original locus, which resulted in the recovery of swimming capacity. The modified plasmid pTB007_Viannia allowed the integration and stable expression of both T7 RNA polymerase and Cas9 in L. braziliensis and provided an important tool for the study of the biology of this parasite
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