2,045 research outputs found
Spin-phonon coupling in Gd(Co1/2Mn1/2)O3 perovskite
We have investigated the temperature-dependent Raman-active phonons and the
magnetic properties of Gd(Co1/2Mn1/2)O3 perovskite ceramics in the temperature
range from 40 K to 300 K. The samples crystallized in an orthorhombic distorted
simple perovskite, whose symmetry belongs to the Pnma space group. The data
reveals spin-phonon coupling near the ferromagnetic transition occurring at
around 120 K. The correlation of the Raman and magnetization data suggests that
the structural order influences the magnitude of the spin-phonon coupling.Comment: 3 Figures, suplementary materia
Mechanisms underlying gas exchange alterations in an experimental model of pulmonary embolism
The aim of the present study was to determine the ventilation/perfusion ratio that contributes to hypoxemia in pulmonary embolism by analyzing blood gases and volumetric capnography in a model of experimental acute pulmonary embolism. Pulmonary embolization with autologous blood clots was induced in seven pigs weighing 24.00 ± 0.6 kg, anesthetized and mechanically ventilated. Significant changes occurred from baseline to 20 min after embolization, such as reduction in oxygen partial pressures in arterial blood (from 87.71 ± 8.64 to 39.14 ± 6.77 mmHg) and alveolar air (from 92.97 ± 2.14 to 63.91 ± 8.27 mmHg). The effective alveolar ventilation exhibited a significant reduction (from 199.62 ± 42.01 to 84.34 ± 44.13) consistent with the fall in alveolar gas volume that effectively participated in gas exchange. The relation between the alveolar ventilation that effectively participated in gas exchange and cardiac output (V Aeff/Q ratio) also presented a significant reduction after embolization (from 0.96 ± 0.34 to 0.33 ± 0.17 fraction). The carbon dioxide partial pressure increased significantly in arterial blood (from 37.51 ± 1.71 to 60.76 ± 6.62 mmHg), but decreased significantly in exhaled air at the end of the respiratory cycle (from 35.57 ± 1.22 to 23.15 ± 8.24 mmHg). Exhaled air at the end of the respiratory cycle returned to baseline values 40 min after embolism. The arterial to alveolar carbon dioxide gradient increased significantly (from 1.94 ± 1.36 to 37.61 ± 12.79 mmHg), as also did the calculated alveolar (from 56.38 ± 22.47 to 178.09 ± 37.46 mL) and physiological (from 0.37 ± 0.05 to 0.75 ± 0.10 fraction) dead spaces. Based on our data, we conclude that the severe arterial hypoxemia observed in this experimental model may be attributed to the reduction of the V Aeff/Q ratio. We were also able to demonstrate that V Aeff/Q progressively improves after embolization, a fact attributed to the alveolar ventilation redistribution induced by hypocapnic bronchoconstriction.1197120
Reduced order models for control of fluids using the Eigensystem Realization Algorithm
In feedback flow control, one of the challenges is to develop mathematical
models that describe the fluid physics relevant to the task at hand, while
neglecting irrelevant details of the flow in order to remain computationally
tractable. A number of techniques are presently used to develop such
reduced-order models, such as proper orthogonal decomposition (POD), and
approximate snapshot-based balanced truncation, also known as balanced POD.
Each method has its strengths and weaknesses: for instance, POD models can
behave unpredictably and perform poorly, but they can be computed directly from
experimental data; approximate balanced truncation often produces vastly
superior models to POD, but requires data from adjoint simulations, and thus
cannot be applied to experimental data.
In this paper, we show that using the Eigensystem Realization Algorithm (ERA)
\citep{JuPa-85}, one can theoretically obtain exactly the same reduced order
models as by balanced POD. Moreover, the models can be obtained directly from
experimental data, without the use of adjoint information. The algorithm can
also substantially improve computational efficiency when forming reduced-order
models from simulation data. If adjoint information is available, then balanced
POD has some advantages over ERA: for instance, it produces modes that are
useful for multiple purposes, and the method has been generalized to unstable
systems. We also present a modified ERA procedure that produces modes without
adjoint information, but for this procedure, the resulting models are not
balanced, and do not perform as well in examples. We present a detailed
comparison of the methods, and illustrate them on an example of the flow past
an inclined flat plate at a low Reynolds number.Comment: 22 pages, 7 figure
Determination of protein content in cooked foods consumed by toddlers aged 1-2 years in Sri Lanka
In early life, protein deficiency as well as heavy protein intake cause adverse conditions. Therefore, the present study aimed to assess the protein adequacy of diets in 1-2-year-old toddlers in the Alawwa Medical Officer of Health (MOH) area, Kurunegala, Sri Lanka. Data on food consumption was obtained by 24-hour dietary recall method from selected caregivers (n=60) andcommonly consumed foods (n=30) were cooked using household preparation protocols practiced in the area. They were homogenized and analyzed for protein. The majority of toddlers among the selected population consumed rice-based meals (73%) as the main meal (cooked rice with vegetable accompaniments), while 27% preferred mixed diets (a mixture of vegetables, pulses, leafy vegetables and fish along with rice). A serving of commercial cereal products provided the highest estimateddaily intake (EDI) of protein (10.70 ± 0.40 g). The average EDI of protein of all categories of foods per portion (rice, vegetables, pulses, green leaves, fish, eggs, rice mixtures and cereal products) was 31.55 ± 0.88 g, contributing to the recommended dietary allowance (RDA) of 242.64% and 150.17% for 1-2 year toddlers as defined by the Department of Agriculture, United States (USDA) and Sri Lankan RDA defined by Medical Research Institute (MRI), respectively. In conclusion, the cooked foods prepared according to local recipes fulfilled the dietary requirements of protein for toddlers aged 1-2 years in the Alawwa MOH area following USDA and Sri Lankan nutrition guidelines.
Keywords: Estimated Daily Intake, Protein, Recommended Dietary Allowance, Toddler
A Programmable look-up table-based interpolator with nonuniform sampling scheme
Interpolation is a useful technique for storage of complex functions on limited memory space: some few sampling values are stored on a memory bank, and the function values in between are calculated by interpolation. This paper presents a programmable Look-Up Table-based interpolator, which uses a reconfigurable nonuniform sampling scheme: the sampled points are not uniformly spaced. Their distribution can also be reconfigured to minimize the approximation error on specific portions of the interpolated function's domain. Switching from one set of configuration parameters to another set, selected on the fly from a variety of precomputed parameters, and using different sampling schemes allow for the interpolation of a plethora of functions, achieving memory saving and minimum approximation error. As a study case, the proposed interpolator was used as the core of a programmable noise generatoroutput signals drawn from different Probability Density Functions were produced for testing FPGA implementations of chaotic encryption algorithms. As a result of the proposed method, the interpolation of a specific transformation function on a Gaussian noise generator reduced the memory usage to 2.71% when compared to the traditional uniform sampling scheme method, while keeping the approximation error below a threshold equal to 0.000030518
Walking training improves systemic and local pathophysiological processes in intermittent claudication
Objective: This study examined the impact of submaximal walking training (WT) on local and systemic nitric oxide (NO) bioavailability, inflammation, and oxidative stress in patients with intermittent claudication (IC). Methods: The study employed a randomised, controlled, parallel group design and was performed in a single centre. Thirty-two men with IC were randomly allocated to two groups: WT (n = 16, two sessions/week, 15 cycles of two minutes walking at an intensity corresponding to the heart rate obtained at the pain threshold interspersed by two minutes of upright rest) and control (CO, n = 16, two sessions/week, 30 minutes of stretching). NO bioavailability (blood NO and muscle nitric oxide synthase [eNOS]), redox homeostasis (catalase [CAT], superoxide dismutase [SOD], lipid peroxidation [LPO] measured in blood and muscle), and inflammation (interleukin-6 [IL-6], C-reactive protein [CRP], tumour necrosis factor α [TNF-α], intercellular adhesion molecules [ICAM], vascular adhesion molecules [VCAM] measured in blood and muscle) were assessed at baseline and after 12 weeks. Results: WT statistically significantly increased blood NO, muscle eNOS, blood SOD and CAT, and muscle SOD and abolished the increase in circulating and muscle LPO observed in the CO group. WT decreased blood CRP, ICAM, and VCAM and muscle IL-6 and CRP and eliminated the increase in blood TNF-α and muscle TNF-α, ICAM and VCAM observed in the CO group. Conclusion: WT at an intensity of pain threshold improved NO bioavailability and decreased systemic and local oxidative stress and inflammation in patients with IC. The proposed WT protocol provides physiological adaptations that may contribute to cardiovascular health in these patients
COMPORTAMENTO HIDROLÓGICO DE ENCOSTA EM SUBSTRATO ROCHOSO GRANÍTICO SOB INFLUÊNCIA DE DESLIZAMENTO RASO - NOVA FRIBURGO, RIO DE JANEIRO
Tendo a água como principal agente deflagrador dos deslizamentos em regiões tropicais, este trabalho objetivou o estudo hidrológico de uma encosta com um cicatriz de deslizamento do tipo translacional raso, no evento extremo de chuva de Janeiro de 2011, Nova Friburgo-RJ. Para o entendimento da influência da água subterrânea na deflagração dos movimentos de massa, a área foi sondada e instrumenta, visando a caracterização física da encosta
On the thickness of a mildly relativistic collisional shock wave
We consider an imperfect relativistic fluid which develops a shock wave and
discuss its structure and thickness, taking into account the effects of
viscosity and heat conduction in the form of sound absorption. The junction
conditions and the non linear equations describing the evolution of the shock
are derived with the corresponding Newtonian limit discussed in detail. As
happens in the non relativistic regime, the thickness is inversely proportional
to the discontinuity in the pressure, but new terms of purely relativistic
origin are present. Particularizing for a polytropic gas, it is found that the
pure viscous relativistic shock is thicker than its nonrelativistic
counterpart, while the opposite holds for pure heat conduction.Comment: 11 pages, no figures, title changed, improved introduction and
discussion. New author adde
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