266 research outputs found
Cost Analysis of Cattle Feedlot Designs
A cost analysis of fixed and non-fixed costs of gain was conducted on 3 cattle feedlot designs. The three facility designs compared were conventional open pens (OPN), open pens with shelter over the feeding area (OS), and a monoslope confinement barn (MON). The OPN design was the least expensive facility to build and operate. However, because of poorer cattle performance (P \u3c 0.05), it was not the most cost effective. The MON design had significantly higher operating costs when compared to the OPN or OS designs, especially for the tractor/spreader (P \u3c 0.05), skid loader (P \u3c 0.10), labor (P \u3c 0.05), and straw (P \u3c 0.05). The operating and fixed costs, combined, made the MON design the most expensive cost of gain design (P \u3c 0.05). The OS design was the most expensive facility to build but with current feed prices and the cattle performance, it was the most cost effective cattle feeding design
The Influence of Growth Stage on Carcass Compositionand Factors Associated with Marbling Development in Beef Cattle
There are many cellular regulatory factors that ultimately determine the intramuscular fat, or marbling content and quality of beef carcasses. Identifying factors which play a critical role in the development of intramuscular fat throughout the feeding period and determining how cattle feeders can manipulate these factors will be crucial to continue improving beef quality. Ideally, marbling must increase without excess accumulation of adipose in depots that are undesirable and economically detrimental (subcutaneous and visceral). The results of this study are novel as they show not only what cellular factors play a role in marbling development, but also how their expression and presence change as an animal grows in an American‐style production system. The increase in both expression and presence of peroxisome proliferator‐activated receptor γ (PPARγ) at the end of the feeding phase suggest the proliferation and differentiation of additional cells to adipocytes is required in order to increase intramuscular fat content. This does not mean that adipocyte filling (lipogenesis) does not play a key role as well. However marbling content will reach a plateau without the recruitment of additional adipocytes. While it has been previously established that intramuscular adipocytes have a pattern of metabolism unique to other adipocytes, further research into how the metabolism of intramuscular fat differs from other fat depots and how this metabolism changes throughout the feeding phase will enhance the ability to produce high quality carcasses while limiting undesirable carcass fat
Cooling a low noise amplifier with a micromachined cryogenic cooler
The sensitivity of antenna systems increases with increasing active area, but decreases at higher noise figure of the low-noise amplifier (LNA). Cooling the LNA locally results in significant improvement in the gain and in lowering the noise figure of the LNA. Micromachined Joule-Thomson (JT) coolers can provide a cryogenic environment to the LNA. They are attractive because they have no cold moving parts and can be scaled down to match the size and the power consumption of LNAs. The performance of a LNA mounted on a JT microcooler with dimensions of 60.0 × 9.5 × 0.72 mm3 is reported in this paper. The microcooler is operated with nitrogen gas and the cold-end temperature is controlled at 115 K. The measured net cooling power of the microcooler is about 43 mW when the LNA is not operating. The power dissipation of the LNA is 26 mW, with a supply voltage of 2 V. At room temperature the noise figure of the LNA is 0.83 dB and the gain lies between 17.9 and 13.1 dB, in the frequency range of 0.65 and 1.05 GHz. Upon cooling to 115 K, the noise figure drops to 0.50 dB and the increase in gain varies in the range of 0.6–1.5 d
A theoretical analysis of how plant growth is limited by carbon allocation strategies and respiration
Improving crop yield is essential to meet increasing global food demands. Boosting crop yield requires the coordination of carbon acquisition by leaves and carbon utilization by roots and seeds. Simple modelling approaches may be used to explain how this coordination is achieved within plant growth. Here, the limits to allocation strategies and the influence of maintenance costs are explored by analysing the sensitivity of a simple root–shoot carbon allocation model for vegetative and reproductive growth. The model is formulated based on fundamental constraints on plant growth and therefore can be applied to all plants. This general but quantitative approach shows that the relative costs of root and leaf respiration alter the relationship between carbon allocation and final plant size, enabling a range of allocation strategies to produce a similar total amount of plant material during vegetative growth. This plasticity is enhanced by increasing assimilation rate within the model. Results show that high leaf allocation during vegetative growth promotes early reproduction with respect to yield. Having higher respiration in leaves than roots delays the optimal age to reproduce for plants with high leaf allocation during vegetative growth and increases the restrictions on flowering time for plants with high root allocation during vegetative growth. It is shown that, when leaf respiration is higher than root respiration, reallocating carbon towards the roots can increase the total amount of plant material. This analysis indicates that crop improvement strategies should consider the effects of maintenance costs on growth, a previously under-appreciated mechanism for yield enhancement
Rape and respectability: ideas about sexual violence and social class
Women on low incomes are disproportionately represented among sexual violence survivors, yet feminist research on this topic has paid very little attention to social class. This article blends recent research on class, gender and sexuality with what we know about sexual violence. It is argued that there is a need to engage with classed distinctions between women in terms of contexts for and experiences of sexual violence, and to look at interactions between pejorative constructions of working-class sexualities and how complainants and defendants are perceived and treated. The classed division between the sexual and the feminine, drawn via the notion of respectability, is applied to these issues. This piece is intended to catalyse further research and debate, and raises a number of questions for future work on sexual violence and social class
Properties of a Dilute Bose Gas near a Feshbach Resonance
In this paper, properties of a homogeneous Bose gas with a Feshbach resonance
are studied in the dilute region at zero temperature. The stationary state
contains condensations of atoms and molecules. The ratio of the molecule
density to the atom density is . There are two types of excitations,
molecular excitations and atomic excitations. Atomic excitations are gapless,
consistent with the traditional theory of a dilute Bose gas. The molecular
excitation energy is finite in the long wavelength limit as observed in recent
experiments on Rb. In addition, the decay process of the condensate is
studied. The coefficient of the three-body recombination rate is about 140
times larger than that of a Bose gas without a Feshbach resonance, in
reasonably good agreement with the experiment on Na.Comment: 11 pages, 1 figure, comparison between the calculated three-body
recombination rate and the experimental data for Na system has been adde
Quantum correlated twin atomic beams via photo-dissociation of a molecular Bose-Einstein condensate
We study the process of photo-dissociation of a molecular Bose-Einstein
condensate as a potential source of strongly correlated twin atomic beams. We
show that the two beams can possess nearly perfect quantum squeezing in their
relative numbers.Comment: Corrected LaTeX file layou
Thermopower of a 2D electron gas in suspended AlGaAs/GaAs heterostructures
We present thermopower measurements on a high electron mobility
two-dimensional electron gas (2DEG) in a thin suspended membrane.We show that
the small dimension of the membrane substantially reduces the thermal
conductivity compared to bulk material so that it is possible to establish a
strong thermal gradient along the 2DEG even at a distance of few micrometers.
We find that the zero-field thermopower is significantly affected by the micro
patterning. In contrast to 2DEGs incorporated in a bulk material, the diffusion
contribution to the thermopower stays dominant up to a temperature of 7 K until
the phonon-drag becomes strong and governs the run of the thermopower. We also
find that the coupling between electrons and phonons in the phonon-drag regime
is due to screened deformation potentials, in contrast to piezoelectric
coupling found with bulk phonons.Comment: 7 page
Noncommutative quantum mechanics and Bohm's ontological interpretation
We carry out an investigation into the possibility of developing a Bohmian
interpretation based on the continuous motion of point particles for
noncommutative quantum mechanics. The conditions for such an interpretation to
be consistent are determined, and the implications of its adoption for
noncommutativity are discussed. A Bohmian analysis of the noncommutative
harmonic oscillator is carried out in detail. By studying the particle motion
in the oscillator orbits, we show that small-scale physics can have influence
at large scales, something similar to the IR-UV mixing
A Classification of Hyper-heuristic Approaches
The current state of the art in hyper-heuristic research comprises a set of approaches that share the common goal of automating the design and adaptation of heuristic methods to solve hard computational search problems. The main goal is to produce more generally applicable search methodologies. In this chapter we present and overview of previous categorisations of hyper-heuristics and provide a unified classification and definition which captures the work that is being undertaken in this field. We distinguish between two main hyper-heuristic categories: heuristic selection and heuristic generation. Some representative examples of each category are discussed in detail. Our goal is to both clarify the main features of existing techniques and to suggest new directions for hyper-heuristic research
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