2,169 research outputs found
Analytical solution of generalized Burton--Cabrera--Frank equations for growth and post--growth equilibration on vicinal surfaces
We investigate growth on vicinal surfaces by molecular beam epitaxy making
use of a generalized Burton--Cabrera--Frank model. Our primary aim is to
propose and implement a novel analytical program based on a perturbative
solution of the non--linear equations describing the coupled adatom and dimer
kinetics. These equations are considered as originating from a fully
microscopic description that allows the step boundary conditions to be directly
formulated in terms of the sticking coefficients at each step. As an example,
we study the importance of diffusion barriers for adatoms hopping down
descending steps (Schwoebel effect) during growth and post-growth equilibration
of the surface.Comment: 16 pages, REVTeX 3.0, IC-DDV-94-00
Main technical differences in the processing of broilers: a comparison between slaughterhouses in Brazil and UK
Rapid technological advances in chicken processing in plants around the world have meant that different techniques are being employed regarding the slaughter’s flow process. This paper aimed to compare and contrast systems and practices in two large slaughterhouses—one in UK and the other in Brazil. Annotated observations were made during inspection visits to chicken slaughterhouses in the two countries between 2014 and 2016. Whilst there were similarities in the two systems, there are also clear differences. The Brazilian case is evidently adapted for a more tropical condition, rather than the temperate one in UK. The handling practices of birds used during transportation, waiting, stunning as well as pre-cooling differ in techniques employed and consequently likely their efficiencies. In UK, the practices are more geared towards water and energy saving. The difference in market conditions and the length of the respective supply chains also determine the type of primary packaging used in final products. Both countries adhere to similar rulings applied to slaughterhouses. However, in the Brazilian case, it tended to comply with mainly external market demands. In conclusion, managers in the Brazilian poultry system could consider looking into adopting some of the practices used in UK, such as cage/crate dimension which reduce bird’s lesions and bruises; the use of stunning by modified atmosphere and pre-cooling for resource efficiency reasons and improvement in animal welfare. Finally, when distances between sites of production and consumption are great such as in Brazil, the use of modified atmosphere technology could be also further explored to ensure better quality of the final product
Quality of refrigerated raw milk from buffalo cows (Bubalus bubalis bubalis) in different farms and seasons in Brazil
The present research aimed to examine the chemical and microbiological characteristics of refrigerated raw milk collected from buffalo-only dairy herds from different farms and seasons. Samples were collected from twelve farms producing buffalo milk, located in the Mideast region of São Paulo state, in Brazil, once a month throughout the dairy calendar year from 2011 to 2014. The analysis of fat, protein, lactose, dry extract, and total solids contents were carried out using Infrared Absorption. Residues for antimicrobial analysis were carried out using Delvo Test Kit technique, and both somatic cell count and standard plate count analysis were carried out using Flow Cytometry. The analysis of the chemical components as well as for the microbiological analysis of SPC proved to be statistically significant throughout the period. No antibiotic residues were found in the totality of the sample, hence indicating that the farmers complied with the current sanitary legislation in that country, as well as SCC; however, higher values were found for the SPC. Significant results for all parameters analyzed were found among the farms, indicating that price incentives paid for the quality of raw milk could be an alternative to dairy processing companies, favoring yield and quality of the final product
Determination of step--edge barriers to interlayer transport from surface morphology during the initial stages of homoepitaxial growth
We use analytic formulae obtained from a simple model of crystal growth by
molecular--beam epitaxy to determine step--edge barriers to interlayer
transport. The method is based on information about the surface morphology at
the onset of nucleation on top of first--layer islands in the submonolayer
coverage regime of homoepitaxial growth. The formulae are tested using kinetic
Monte Carlo simulations of a solid--on--solid model and applied to estimate
step--edge barriers from scanning--tunneling microscopy data on initial stages
of Fe(001), Pt(111), and Ag(111) homoepitaxy.Comment: 4 pages, a Postscript file, uuencoded and compressed. Physical Review
B, Rapid Communications, in press
Supernovae and Positron Annihilation
Radioactive nuclei, especially those created in SN explosion, have long been
suggested to be important contributors of galactic positrons. In this paper we
describe the findings of three independent OSSE/SMM/TGRS studies of positron
annihilation radiation, demonstrating that the three studies are largely in
agreement as to the distribution of galactic annihilation radiation. We then
assess the predicted yields and distributions of SN-synthesized radionuclei,
determining that they are marginally compatible with the findings of the
annihilation radiation studies.Comment: 7 pages, accepted for publication in New Astronomy Reviews (Astronomy
with Radioactivites III
Characterization of ENU-induced mutations in red blood cell structural proteins
Murine models with modified gene function as a result of N-ethyl-N-nitrosourea (ENU) mutagenesis have been used to study phenotypes resulting from genetic change. This study investigated genetic factors associated with red blood cell (RBC) physiology an
Pulsed Magnetic Field Measurements of the Composite Fermion Effective Mass
Magnetotransport measurements of Composite Fermions (CF) are reported in 50 T
pulsed magnetic fields. The CF effective mass is found to increase
approximately linearly with the effective field , in agreement with our
earlier work at lower fields. For a of 14 T it reaches , over 20
times the band edge electron mass. Data from all fractions are unified by the
single parameter for all the samples studied over a wide range of
electron densities. The energy gap is found to increase like at
high fields.Comment: Has final table, will LaTeX without error
Nonlinear optics via double dark resonances
Double dark resonances originate from a coherent perturbation of a system
displaying electromagnetically induced transparency. We experimentally show and
theoretically confirm that this leads to the possibility of extremely sharp
resonances prevailing even in the presence of considerable Doppler broadening.
A gas of 87Rb atoms is subjected to a strong drive laser and a weak probe laser
and a radio frequency field, where the magnetic coupling between the Zeeman
levels leads to nonlinear generation of a comb of sidebands.Comment: 6 pages, 9 figure
Reverse Monte Carlo modeling of amorphous silicon
An implementation of the Reverse Monte Carlo algorithm is presented for the
study of amorphous tetrahedral semiconductors. By taking into account a number
of constraints that describe the tetrahedral bonding geometry along with the
radial distribution function, we construct a model of amorphous silicon using
the reverse monte carlo technique. Starting from a completely random
configuration, we generate a model of amorphous silicon containing 500 atoms
closely reproducing the experimental static structure factor and bond angle
distribution and in improved agreement with electronic properties. Comparison
is made to existing Reverse Monte Carlo models, and the importance of suitable
constraints beside experimental data is stressed.Comment: 6 pages, 4 PostScript figure
Providing the Context for Intentional Learning
This article is written in response to Sharon Derry's article “Remediating Academic Difficulties Through Strategy Training: The Acquisition of Useful Knowledge.” The features of effective strategy instruction, to which Derry refers, are illustrated by examining the nature of the decisions the teacher confronts; specifically, determining the purposes of instruction, the context in which instruction occurs, and the roles of the teacher and students in instruction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69150/2/10.1177_074193259001100608.pd
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