612 research outputs found
Deflection hardening of sustainable fiber–cement composites
In the present study sisal fiber–cement composites reinforced with 4% and 6% of short fibers were
developed and their physical–mechanical behavior was characterized. To ensure the composite
sustainability and durability, the ordinary Portland cement matrix was modified by adding fly ash and
metakaolin, and the natural aggregate was substituted by 10% and 20% of recycled concrete
aggregate. Flat sheets were cast in a self-compacted cement matrix and bending tests were
performed to determine the first crack, postpeak strength and toughness of the composites. Cyclic
flexural tests were carried out to determine the stiffness variation of composite due to cracking
formation and propagation. It can be seen that the reinforcement provided by short sisal fibers for
recycled cement matrices guaranteed a composite with multiple cracking and an increase of strength
after the first crack. Reduction of stiffness and increase the damping capacity of composite are verified
with progressive cracking.CAPES (PVE Program: Project 047/2012) and CNPqBrazilian agency FAPESBBrazilian agency CAPES through the PVE Progra
Avaliação da resistência de plantas transgênicas resistentes a Begomovirus em relação à infecção por vírus de outros grupos.
Resumo 656-2
Phase Transition in Ferromagnetic Ising Models with Non-Uniform External Magnetic Fields
In this article we study the phase transition phenomenon for the Ising model
under the action of a non-uniform external magnetic field. We show that the
Ising model on the hypercubic lattice with a summable magnetic field has a
first-order phase transition and, for any positive (resp. negative) and bounded
magnetic field, the model does not present the phase transition phenomenon
whenever , where is the external
magnetic field.Comment: 11 pages. Published in Journal of Statistical Physics - 201
Resinose do coqueiro: como identificar essa doença.
bitstream/CPATC-2009-09/20372/1/f_15_2008.pd
On Bootstrap Percolation in Living Neural Networks
Recent experimental studies of living neural networks reveal that their
global activation induced by electrical stimulation can be explained using the
concept of bootstrap percolation on a directed random network. The experiment
consists in activating externally an initial random fraction of the neurons and
observe the process of firing until its equilibrium. The final portion of
neurons that are active depends in a non linear way on the initial fraction.
The main result of this paper is a theorem which enables us to find the
asymptotic of final proportion of the fired neurons in the case of random
directed graphs with given node degrees as the model for interacting network.
This gives a rigorous mathematical proof of a phenomena observed by physicists
in neural networks
Caffeine and Placebo Improved Maximal Exercise Performance Despite Unchanged Motor Cortex Activation and Greater Prefrontal Cortex Deoxygenation
Caffeine (CAF) is an ergogenic aid used to improve exercise performance. Independent studies have suggested that caffeine may have the ability to increase corticospinal excitability, thereby decreasing the motor cortex activation required to generate a similar motor output. However, CAF has also been suggested to induce a prefrontal cortex (PFC) deoxygenation. Others have suggested that placebo (PLA) may trigger comparable effects to CAF, as independent studies found PLA effects on motor performance, corticospinal excitability, and PFC oxygenation. Thus, we investigated if CAF and CAF-perceived PLA may improve motor performance, despite the likely unchanged MC activation and greater PFC deoxygenation. Nine participants (26.4 ± 4.8 years old, VO2MAX of 42.2 ± 4.6 mL kg-1 min-1) performed three maximal incremental tests (MITs) in control (no supplementation) and ∼60 min after CAF and PLA ingestion. PFC oxygenation (near-infrared spectroscopy at Fp1 position), MC activation (EEG at Cz position) and vastus lateralis and rectus femoris muscle activity (EMG) were measured throughout the tests. Compared to control, CAF and PLA increased rectus femoris muscle EMG (P = 0.030; F = 2.88; d = 0.84) at 100% of the MIT, and enhanced the peak power output (P = 0.006; F = 12.97; d = 1.8) and time to exhaustion (P = 0.007; F = 12.97; d = 1.8). In contrast, CAF and PLA did not change MC activation, but increased the PFC deoxygenation as indicated by the lower O2Hb (P = 0.001; F = 4.68; d = 1.08) and THb concentrations (P = 0.01; F = 1.96; d = 0.7) at 80 and 100% the MIT duration. These results showed that CAF and CAF-perceived PLA had the ability to improve motor performance, despite unchanged MC activation and greater PFC deoxygenation. The effectiveness of CAF as ergogenic aid to improve MIT performance was challenged
Valor nutritivo de grãos de sorgo com diferentes texturas do endosperma para leitões.
Utilizaram-se 20 leitões machos castrados, com 28kg de peso, em ensaio biológico baseado em coleta total de fezes e de urina para a determinação dos valores de digestibilidade aparente da matéria seca (DAMS), de digestibilidade aparente da proteína bruta (DAPB), de energia digestível aparente (EDA) e de energia metabolizável aparente (EMA) de grãos de sorgo com diferentes texturas do endosperma. Os genótipos avaliados foram BR 007B (textura macia), BR 304 (textura intermediária) e se 283 (textura du."a). As dietas-teste foram compostas por 70% de dieta referência, à base de milho e de farelo de soja, e por 30% de grãos de sorgo. O experimento foi montado em esquema inteiramente ao acaso, com quatro tratamentos e cinco repetições. Os valores de DAMS, de DAPB, de EDA e de EMA, expressos na matéria seca, dos grãos do genótipo BR 007B foram 97,1%, 89,7%, 3.840kcal/kg e 3.685kcal/kg; os do genótipo BR 304 foram 92,0%, 82,9%, 3.645kcal/kg e 3.544kcal/kg; e os do genótipo SC 283 foram 83,3%, 78,5%, 3.078kcal/kg e 3.021 kcal/kg, respectivamente. Todas as quatro variáveis analisadas apresentaram valores mais altos (P<0,05) para o genótipo BR 007B em relação ao genótipo se 283, demonstrando a influência negativa da textura do endosperma sobre o valor nutritivo dos grãos de sorgo para suínos
Reversal of Graft-Versus-Host Disease with Infusion of Stored Autologous Bone Marrow Cells Following Combined Liver-Bone Marrow Allotransplantation in Man.
Concordance between cytopathology and incisional biopsy in the diagnosis of oral squamous cell carcinoma
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