523 research outputs found
Silício No Desenvolvimento In Vitro Da Orquídea Cattleya Forbesii
Addition of Silicon (Si) to culture media has been shown to improve the development of seedlings grown in vitro, and to reduce losses during the acclimatization phase. The objective of this study was to evaluate the in vitro growth of Cattleya forbesii (Orchidaceae) in MS medium containing five different concentrations of SiO2 (0.0, 0.5, 1.0, 1.5, and 2.0 g·L−1). At day 200, the following variables were measured: number of roots, average length of the root system, leaf area, number of leaves and shoots, shoot height, fresh and dry masses of roots and shoots, water content of roots and shoots, and pH of the culture medium. Most variables decreased as the concentration of Si increased, reducing the in vitro vegetative growth of C. forbesii. Accumulation of Si in leaf tissues was detected by scanning electron microscopy, confirming uptake by plants. The Si source and concentrations tested showed no beneficial effect on in vitro growth of C. forbesii. © 2016, Universidade Federal Rural do Semi-Arid. All rights reserved.291182
Comparison of airflow homogeneity in Compost Dairy Barns with different ventilation systems using the CFD model
In the pursuit of high milk productivity, producers are using confinement systems in
order to improve performance and animal welfare. Among the housing systems, the Compost
bedded-pack barns (CBP) stand out. In these barns a bedding area is provided inside, where cows
move freely. Generally this area is covered with carbon source material (such as sawdust or fine
dry wood shavings) which together with manure, thanks a regular mechanically stirring, ensures
the aerobic composting process. The ventilation in these facilities has the function of
dehumidifying the air, improving the air quality, drying the bedding, improving the thermal
comfort conditions of the confined animals. This work aimed at validating a computational model
using Computational Fluid Dynamics (CFD) to determine the best homogeneity of airflows
generated by different forced ventilation systems used in CBP barns. Two CBP barns were
compared with different ventilation systems: high volume low speed (HVLS) and low volume
high-speed (LVHS) fans. The results showed that the proposed model was satisfactory to predict
the flows generated by both types of fans. It was concluded that the use of HVLS fans produced
a more homogeneous airflow when compared to LVHS fans. The use of mechanical ventilation
in tropical conditions is necessary for the proper functioning of the system. In this study, the
systems used promoted the increase in air speed to levels close to adequate
Estimate of manure present in compost dairy barn systems for sizing of manure storage
Milk production is increasingly modernized as a result of the growing demand for food
around the world. Improvements in livestock facilities are observed, with a large increase in the
use of feedlot systems such as the Compost Dairy Barn. Increasing milk production in
confinement systems has also raised concerns such as the management of wastes (water, faeces
and urine) from the system, which has become one of the most important issues in the intensive
dairy farms. The aim of this work was to estimate the amount of manure present in compost dairy
barn systems in order to size the manure storage. The study was conducted at four compost dairy
barns in southern Minas Gerais, Brazil. These compost barns had different bedding materials and
dimensions. In each farm, data on milk yield and quality (daily production, fat and protein
content), animal weight and amount of feed ingested by the animals were collected. Total-day
manure delivered by the cows in the feeding alley and milking parlour was piled up together and
weighed. Based on the results, it was observed that, in the compost dairy barns, only part of the
total manure produced per day was delivered in the milking parlour (1.6 and 2.0%) and in the
feed alley (27.6 to 49.3%). These results are very important for designers for the proper manure
management system design of the dairy farms
Analysis of environmental conditions in two different Compost Bedded Pack Barn systems for dairy cattle
Received: February 1st, 2023 ; Accepted: April 27th, 2023 ; Published: May 10th, 2023 ; Correspondence: [email protected], [email protected] objective of this study was to analyse and compare the thermal environment of
dairy cattle facilities in an open compost bedded pack barn (CBP) with natural ventilation and
closed CBP (without thermal insulation) and climate control system. The research was conducted
in a property located in Zona da Mata, Minas Gerais, Brazil. During the summer and for different
periods of the day, the following average environmental variables observed inside the facilities
were measured: dry bulb temperature, relative humidity and Temperature and Humidity Index
(THI). The results were submitted to an analysis of variance to determine the significance of the
variables in the different treatments. It was found that the closed and climate control system CBP
promoted greater control of the facility's internal microclimate, registering smaller thermal
amplitudes and a greater reduction in the animals' exposure time to stressful thermal conditions,
compared to the CBP with natural ventilation. However, during summer afternoons, comfort
indices indicated moderate stress. It is concluded that the closed CBP, regarding the analysed
variables, indicated potential use, provided that a careful study of the climate of the region is
carried out before implementation, the factors related to the ambient conditioning and better
insulation of the construction are adjusted. The climatic variables inside the open CBP indicated
a high stress condition for the animals, suggesting the placement of positive pressure fans and
sprinklers properly distributed in the feed alley, to guarantee benefits to the entire area of the
animal housing
Spatial distribution of bed variables, animal welfare indicators, and milk production in a closed compost-bedded pack barn with a negative tunnel ventilation system
This research aimed to characterize, evaluate and compare the spatial distribution of the leading bed variables,
animal welfare indicators, and milk production in a closed compost-bedded pack barn (CBP) with a negative
tunnel ventilation system, for summer and winter periods. The study was carried out in a CBP located in the Zona
da Mata region, Minas Gerais, Brazil. The geostatistical modeling technique evaluated the variables of temper ature, moisture content, and pH (on the surface and depth of 0.20m) across the length of the bed. Bed samples
were characterized for carbon (C), nitrogen (N), and C:N ratio. Cows housed in the CBP were assessed for
locomotion and hygiene scores and average milk production. To evaluate the thermoregulation of the cows, the
respiratory rate (RR) and surface temperature (ST) were measured. Geostatistical analysis showed spatial
dependence and the non-uniformity of the spatial distribution of bed variables. The worst levels of bed tem perature and moisture were found in the regions close to the evaporative cooling plate, surrounding the feeding
alley, and in the region with the highest cow stocking. The C:N ratio, obtained in both climatic seasons of the
year, remained outside the recommended range for ideal composting. During the summer and winter, the bed
variables’ values suggest that the material was below levels for optimal composting; however, the aerated inner
layer was biologically active. The high animal density significantly impacted the worsening of the bed moisture
content and internal temperature. In general, dairy cows showed adequate hygiene (score of 1 and 2) and
locomotion (score of 0 and 1) scores for the two climatic seasons evaluated, indicating good welfare conditions.
In relation to RR and ST, the summer period presented less favorable environmental conditions. During winter,
the average milk production was 28.1 ± 7.2 kg day-1, and during summer, it was 26.9 ± 6.7 kg day-1
Acoustic Black Holes from Abelian Higgs Model with Lorentz Symmetry Breaking
In this paper we derive acoustic black hole metrics in the (3+1) and
(2+1)-dimensional Abelian Higgs model with Lorentz symmetry breaking. In this
set up the sound waves lose the Lorentz boost invariance and suffer a
'birefringence' effect. We have found acoustic black holes and respective
Hawking temperatures depending on the Lorentz violating parameter. Furthermore,
we obtain an acoustic Kerr-like black hole metric with the Lorentz violating
term affecting its rate of loss of mass. We also have shown that for suitable
values of the Lorentz violating parameter a wider spectrum of particle wave
function can be scattered with increased amplitude by the acoustic black hole.Comment: 12 pages, Latex, no figures, version accepted to Phys. Lett.
Energetic analysis in compost dairy barn: a case study in southeastern Brazil
Received: February 2nd, 2023 ; Accepted: March 25th, 2023 ; Published: August 16th, 2023 ; Correspondence: [email protected], [email protected] efficiency aims to optimize the energy consumption of the processes, activities,
and machinery of the farm, ensuring the comfort, handling, and safety of the animals. The purpose
of the study was to identify the energy consumption demanded by the activities performed at the
Compost Dairy Barn facility, located in Itaguara, Minas Gerais, Brazil and to propose energysaving alternatives, applying the Energy Audit Methodology described by the Institute for Energy
Diversification and Saving (IDAE in Spanish) from Spain. The energy assessment at the facility
allowed us to recognize unnecessary energy expenses in machinery uses, variations in milk
production in relation to environmental conditions, waste disposal, and to propose improvement
alternatives to reduce energy consumption expenses. Waste production data of 1577.7 kg per year
was obtained, which corresponds to the bedding and feeding areas, and 175 kg of waste for the
feeding area. Data on the temperature and humidity of the bedding area were collected to
determine which of the five months of research is the most demanding in terms of energy. To
maintain the animal’s welfare, tracing the times of substantial use of machinery (e.g., fans,
tractors) at the facility and calculating Equivalent Temperature Index (ETI) was necessary. The
highest percentage consumption of energy was represented by tractors in bedding maintenance
and supply, by around 95.03%. The energy analysis of the farm showed a reduction in energy
consumption of 45.03%, compared to the initial consumption percentages of the overall livestock
activity
On the physico-mechanical, electrical and dielectric properties of mullite-glass composites
Mullite-glass composites were obtained by solid-state reactive sintering of kaolinite clay and kaolin waste mixtures with waste additions up to 100 wt%. The structural and microstructural analysis of starting powders and sintered samples were evaluated by X-ray diffractometry (XRD) and field-emission scanning electron microscopy (FESEM). The mechanical properties were evaluated by measuring the flexural strength of sintered bodies. Electrical properties of the composites were assessed by impedance spectroscopy (at 30 °C and from 400 to 700 °C) in air. A viscous flux mechanism resulting from the glassy phase filled up the open porosity and increased the mechanical strength. Electrical conductivity, dielectric constant and dielectric loss were strongly dependent on the microstructural features, namely glassy phase and porosity. The activation energies (0.89–0.99 eV) for electrical conduction were lower than typical literature values of mullite-based materials. The results indicated that the herein synthesized mullite-glass composites with up to 53.6 wt% mullite are promising low-cost materials for electronics-related applications.publishe
Scattering of particles by neutron stars: Time-evolutions for axial perturbations
The excitation of the axial quasi-normal modes of a relativistic star by
scattered particles is studied by evolving the time dependent perturbation
equations. This work is the first step towards the understanding of more
complicated perturbative processes, like the capture or the scattering of
particles by rotating stars. In addition, it may serve as a test for the
results of the full nonlinear evolution of binary systems.Comment: 7 pages, 5 figures, Phys. Rev. D in pres
Economic efficiency and productivity of life-cycle beef cattle production systems in the South of Bahia
Estudaram-se a produtividade e a eficiência econômica de quatro sistemas de bovinos de corte, por meio de simulação, que diferiram quanto à taxa de natalidade (TN). A pesquisa foi realizada em uma fazenda de ciclo completo (SCC) com TN de 87%, e mais três sistemas simulados: -4TN com TN de 83%; -2TN com TN de 85%; e +2TN com TN de 89%. O SCC foi baseado em dados de um sistema de cria, recria e engorda com média de 3.453 cabeças, localizado no sul da Bahia, no período de janeiro de 2000 a dezembro de 2002. As TN foram ajustadas à demanda energética dos animais em cada sistema e à evolução do rebanho durante três anos. A quantidade de carne vendida foi de 149, 146, 144, 141 kg/ha/ano para -4TN, -2TN, SCC e +2TN, respectivamente. O lucro total acumulado, na mesma ordem de citação, foi de R737.526,16; R703.907,58. O retorno do capital investido acumulado foi de 7,8; 7,4; 7,3 e 7,0% para -4 TN, -2TN, SCC e +2TN, respectivamente. A variação da TN na atividade de cria, recria e engorda de bovinos alterou a produtividade e a eficiência econômica dos sistemas simulados. As respostas em produtividade e eficiência econômica diminuíram com o aumento da taxa de natalidade.Economic efficiency and productivity of life-cycle cattle raising systems were studied by simulations that differed in calving rates (CR). The study was conducted on a life-cycle cattle production system (SCC) with 87% CR, and three simulated systems: -4CR with 83% CR, -2CR with 85% CR, and +2CR with 89% CR. The SCC was based on data from a life-cycle cattle system of 3,453 animals in the South of Bahia State, from January 2000 to December 2002. CR was adjusted according to energy requirement and herd composition in SCC during three years. Meat amount sold was 149, 146, 144, and 141kg/ha/year for -4CR, -2CR, SCC, and +2CR, respectively. Accumulated profit and return on invested capital were R 737,526.16 and 7.4%; R 703,907.58 and 7.0% for -4CR, -2CR, SCC, and +2CR, respectively. Calving rate variation modified the economic efficiency and productivity of simulated production systems. Economic efficiency and productivity results decreased as calving rate increased
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