4,487 research outputs found
The Changing Face of Milk Production, Milk Quality and Milking Technology in Brazil
This introductory paper gives an overview of milk production in Brazil and discusses a series of recent regulations implemented to improve milk quality with the purpose of asserting the Brazilian dairy industry as a competitor on the international market. It also points out the economic advantage of setting design guidelines for milking machines that would be best suited to Brazilian crossbred cows.Brazilian Milk Quality, Brazil Dairy Industry, Brazilian Milk Production, Brazilian Milk Prices, Agribusiness, Farm Management, Food Consumption/Nutrition/Food Safety, Industrial Organization, International Development, Political Economy,
On the normal subgroups of SL(2, A)
AbstractLet A be a commutative ring having 2 in the stable range. Let N be a subgroup of SL(2, A) having level ideal J. It is shown that if either A is von Neumann regular or 2 is invertible in A, then N is normal in SL(2, A) if and only if N contains the commutator group H(J) = [E(2, A), L(2, A, J)]. Structure theorems for normal subgroups of SL(2, A) are deduced from this result
Itinerant Nature of Atom-Magnetization Excitation by Tunneling Electrons
We have performed single-atom magnetization curve (SAMC) measurements and
inelastic scanning tunneling spectroscopy (ISTS) on individual Fe atoms on a
Cu(111) surface. The SAMCs show a broad distribution of magnetic moments with
\unit[3.5]{\mu_{\rm B}} being the mean value. ISTS reveals a magnetization
excitation with a lifetime of \unit[200]{fsec} which decreases by a factor of
two upon application of a magnetic field of \unit[12]{T}. The experimental
observations are quantitatively explained by the decay of the magnetization
excitation into Stoner modes of the itinerant electron system as shown by newly
developed theoretical modeling.Comment: 3 Figures, Supplement not included, updated version after revisio
Non-therapeutic administration of a model antimicrobial growth promoter modulates intestinal immune responses
<p>Abstract</p> <p>Background</p> <p>The development of efficacious alternatives to antimicrobial growth promoters (AGP) in livestock production is an urgent issue, but is hampered by a lack of knowledge regarding the mode of action of AGP. The belief that AGP modulate the intestinal microbiota has become prominent in the literature; however, there is a lack of experimental evidence to support this hypothesis. Using a chlortetracycline-murine-<it>Citrobacter rodentium </it>model, the ability of AGP to modulate the intestinal immune system in mammals was investigated.</p> <p>Results</p> <p><it>C. rodentium </it>was transformed with the tetracycline resistance gene, <it>tet</it>O, and continuous oral administration of a non-therapeutic dose of chlortetracycline to mice did not affect densities of <it>C. rodentium </it>CFU in feces throughout the experiment or associated with mucosal surfaces in the colon (i.e. at peak and late infection). However, chlortetracycline regulated transcription levels of Th1 and Th17 inflammatory cytokines in a temporal manner in <it>C. rodentium</it>-inoculated mice, and ameliorated weight loss associated with infection. In mice inoculated with <it>C. rodentium</it>, those that received chlortetracycline had less pathologic changes in the distal colon than mice not administered CTC (i.e. relative to untreated mice). Furthermore, chlortetracycline administration at a non-therapeutic dose did not impart either prominent or consistent effects on the colonic microbiota.</p> <p>Conclusion</p> <p>Data support the hypothesis that AGP function by modulating the intestinal immune system in mammals. This finding may facilitate the development of biorationale-based and efficacious alternatives to AGP.</p
Replication-deficient Adenoviral Vector for Gene Transfer Potentiates Airway Neurogenic Inflammation
Human trials for the treatment of cystic fibrosis lung disease with adenoviral vectors have been complicated
by acute inflammatory reactions of unknown etiology. Because replicating respiratory viruses can
potentiate tachykinin-mediated neurogenic inflammatory responses in airways, we studied whether the
endotracheal administration of a replication-deficient adenoviral vector potentiated this response. The vector
Ad5CMVLacZ was administered endotracheally to rats and the leakage of Evans blue dye was used
to measure the capsaicin-induced neurogenic albumin extravasation. These studies show that neurogenic
albumin extravasation is significantly potentiated in the airways of rats after administration of Ad5CMVLacZ.
This inflammatory response can be blocked by selective antagonists of the substance Preceptor
or by glucocorticoids. Therefore, (1) the acute airway inflammation observed in patients after exposure
to adenoviral vectors may exhibit a neurogenic component, which can be blocked pharmacologically, and
(2) preclinical adenoviral vector safety studies of other organs innervated by the tachykinin system, e.g.,
coronary arteries and gastrointestinal tract, should include assessment of neurogenic inflammation
Evaluation of two ultrasonic systems for analysis of porosity in ceramic
The Ultrasound Laboratory of the Nuclear Engineering Institute (LABUS / IEN) has developed an ultrasonic
technique to measure porosity in nuclear fuel pellets (UO2). By difficulties related to the handling of UO2
pellets, Alumina (Al2O3) pellets have been used in preliminary tests, until a methodology for tests with pellets
of UO2 could be defined. In a previous work, in which a contact ultrasonic technique was used, good results
were obtained to measure the porosity of Alumina pellets. In the current studies, it was found that the frequency
spectrum of an ultrasonic pulse is very sensitive to the porosity of the medium in which it propagates. In order
to define the most appropriate experimental apparatus for using immersion technique in future tests, two
ultrasonic systems, available in LABUS, which permit to work with the ultrasonic pulse in the frequency
domain were evaluated . One system was the Explorer II (Matec INSTRUMENTS) and the other the ultrasonic
pulse generator Epoch 4 Plus (Panametrics) coupled with an oscilloscope TDS 3032B (Tektronix). For this
evaluation, several frequency spectra were obtained with the two equipment, by the passage of the ultrasonic
wave in the same pellet of Alumina. This procedure was performed on four different days, on each day 12
ultrasonic signals were acquired, one signal every 10 minutes, with each apparatus. The results were compared and analyzed as regard the repeatability of the frequency spectra obtained
Analysis of ultrasonic techniques for the characterization of microfiltration polymeric membranes
The use of polymeric membranes is extremely important in several industries such as nuclear, biotechnology,
chemical and pharmaceutical. In the nuclear area, for instance, systems based on membrane separation
technologies are currently being used in the treatment of radioactive liquid effluent, and new technologies using
membranes are being developed at a great rate. The knowledge of the physical characteristics of these
membranes, such as, pore size and the pore size distribution, is very important to the membranes separation
processes. Only after these characteristics are known is it possible to determine the type and to choose a
particular membrane for a specific application. In this work, two ultrasonic non destructive techniques were
used to determine the porosity of membranes: pulse echo and transmission. A 25 MHz immersion transducer
was used. Ultrasonic signals were acquired, for both techniques, after the ultrasonic waves passed through a
microfiltration polymeric membrane of pore size of 0.45 μm and thickness of 180 μm. After the emitted
ultrasonic signal crossed the membrane, the received signal brought several information on the influence of the
membrane porosity in the standard signal of the ultrasonic wave. The ultrasonic signals were acquired in the
time domain and changed to the frequency domain by application of the Fourier Fast Transform (FFT), thus
generating the material frequency spectrum. For the pulse echo technique, the ultrasonic spectrum frequency
changed after the ultrasonic wave crossed the membrane. With the transmission technique there was only a
displacement of the ultrasonic signal at the time domain
A New Spin on Galactic Dust
We present a new puzzle involving Galactic microwave emission and attempt to
resolve it. On one hand, a cross-correlation analysis of the WHAM H-alpha map
with the Tenerife 10 and 15 GHz maps shows that the well-known DIRBE correlated
microwave emission cannot be dominated by free-free emission. On the other
hand, recent high resolution observations in the 8-10 GHz range with the Green
Bank 140 ft telescope by Finkbeiner et al. failed to find the corresponding 8
sigma signal that would be expected in the simplest spinning dust models. So
what physical mechanism is causing this ubiquitous dust-correlated emission? We
argue for a model predicting that spinning dust is the culprit after all, but
that the corresponding small grains are well correlated with the larger grains
seen at 100 micron only on large angular scales. In support of this grain
segregation model, we find the best spinning dust template to involve higher
frequency maps in the range 12-60 micron, where emission from transiently
heated small grains is important. Upcoming CMB experiments such as ground-based
interferometers, MAP and Planck LFI with high resolution at low frequencies
should allow a definitive test of this model.Comment: Minor revisions to match accepted ApJ version. 6 pages, 4 figs. Color
figures and more foreground information at
http://www.hep.upenn.edu/~angelica/foreground.html#spin or from
[email protected]
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