18,872 research outputs found
Progress and problems in vaccination against necrotic enteritis in broiler chickens
Necrotic enteritis in broilers is caused by Clostridium perfringens type A strains that produce the NetB toxin. Necrotic enteritis is one of the gastrointestinal diseases in poultry that has gained worldwide importance during the last decade due to efforts to improve broiler performance. Prevention strategies include avoiding predisposing factors, such as coccidiosis, and in-feed supplementation with a variety of feed additives. However, vaccination with modified toxin or other secreted immunogenic proteins seems a logical preventive tool for protection against a toxin-producing bacterium. Formalin-inactivated crude supernatant has been used initially for vaccination. Several studies have been carried out recently to identify the most important immunogenic and protective proteins that can be used for vaccination. These include the NetB toxin, as well as a number of other proteins. There is evidence that immunization with single proteins is not protective against severe challenge and that combinations of different antigens are needed. Most published studies have used multiple dosage vaccination regimens that are not relevant for practical use in the broiler industry. Single vaccination regimens for 1-day-old chicks appear to be non-protective. This review describes the history of vaccination strategies against necrotic enteritis in broilers and gives an update on future vaccination strategies that are applicable in the field. These may include breeder hen vaccination, in ovo vaccination and live attenuated vectors to be used in feed or in drinking water
Variable protection against experimental broiler necrotic enteritis after immunisation with the C-terminal fragment of Clostridium perfringens alpha-toxin and a non-toxic NetB variant
Necrotic enteritis toxin B (NetB) is a pore-forming toxin produced by Clostridium perfringens and has been shown to play a key role in avian necrotic enteritis (NE), a disease causing significant costs to the poultry production industry worldwide. The aim of this work was to determine whether immunisation with a non-toxic variant of NetB (NetB W262A) and the C-terminal fragment of C. perfringens alpha-toxin (CPA247â370) would provide protection against experimental NE. Immunised animals with either antigen or a combination of antigens developed serum antibody levels against NetB and CPA. When CPA247â370 and NetB W262A were used in combination as immunogens, an increased protection was observed after oral challenge by individual dosing, but not after in-feed challenge
Resistive switching in ZrO2 films: physical mechanism for filament formation and dissolution
Resistive switching devices, also called memristors, have attracted much attention
due to their potential memory, logic and even neuromorphic applications. Multiple physical
mechanisms underpin the non-volatile switching process and are ultimately believed to give
rise to the formation and dissolution of a discrete conductive filament within the active layer.
However, a detailed nanoscopic analysis that fully explains all the contributory events remains
to be presented. Here, we present aspects of the switching events that are correlated back to
tunable details of the device fabrication process. Transmission electron microscopy and
atomically resolved electron energy loss spectroscopy (EELS) studies of electrically stressed
devices will then be presented, with a view to understanding the driving forces behind filament
formation and dissolution
Bounds on Correlation Functions of Quantum Rotators
We derive a McBryan-Spencer bound to the correlation function of a
one-dimensional array of quantum rotators in the Villain approximation of the
cosine interaction. We obtain the partition function of the system in the gas
representation and establish a lower bound on the external charge correlation
function. We also discuss the possible existence of a Kosterlitz-Thouless phase
for the quantum rotator in the Villain approximation.Comment: Latex 7 page
Growth in Public Interest and Scientific Research on Kinesiology Taping
Kinesiology taping has grown in popularity, though there are a number of unsubstantiated claims made by some kinesiology taping advocates. An investigation was conducted into trends in general and scientific interest in kinesiology taping. Data in the public domain (Google Trends and Google Scholar data) indicated significant growth of interest both in terms of public search queries and scientific publications relevant to kinesiology taping. Cyclical trends in interest relevant to kinesiology taping were identified. Segmented regression indicated some of the growth in interest in kinesiology taping may be attributed to exposure of spectators of the Olympic Games to kinesiology taping in athletes. Despite substantial growth in research on kinesiology taping there remain unsubstantiated claims
The impact of shifting cultivation in the forestry ecosystems of timor-leste
Every year thousands of hectares of forest are destructed as a result of the practice of swidden agriculture, shifting cultivation or "slush and burn" causing changes in forest ecosystems. In Timor- Leste shifting cultivation is still practiced nowadays as a form of subsistence agriculture.
Swidden agriculture is characterized by slash and burn clearing, by a rotation of fields rather than of
crops, and by short periods of cropping (1-3 years) alternating with long fallow periods.
Based on the characterization of shifting cultivation in two Sucos of Bobonaro district, a reflection is
made on the impact of this practice in the sustainable development of forest ecosystems of Timor-
Leste.
Primary data collection was performed using a questionnaire survey of farmers practicing shifting cultivation. The questionnaire characterized shifting cultivation, and asked farmersâ opinion on slash and burning of forest areas and on the importance of forests.
According to the results obtained, in most situations the existing vegetation before the slash was composed of dense forest, the slash is made by the family group, the majority of farmers have been doing the âslush and burnâ for more than ten years and the size of the plots where slash is made is less than 2 hectares. The materials resulting from the slash are used for firewood, building materials and fencing. The burning of vegetable residues is done before planting and soil preparation and sowing is done with a lever. Land and forest, despite having an individual use, have a tenure regime of ownership and access in which its nature of common pool good prevails. Every year thousands of hectares of forest are destructed as a result of the practice of swidden agriculture, shifting cultivation or "slush and burn" causing changes in forest ecosystems. In Timor-Leste shifting cultivation is still practiced nowadays as a form of subsistence agriculture
Spin Waves in Antiferromagnetic Spin Chains with Long Range Interactions
We study antiferromagnetic spin chains with unfrustrated long-range
interactions that decays as a power law with exponent , using the spin
wave approximation. We find for sufficiently large spin , the Neel order is
stable at T=0 for , and survive up to a finite Neel temperature for
, validating the spin-wave approach in these regimes. We estimate
the critical values of and for the Neel order to be stable. The spin
wave spectra are found to be gapless but have non-linear momentum dependence at
long wave length, which is responsible for the suppression of quantum and
thermal fluctuations and stabilizing the Neel state. We also show that for
and for a large but finite-size system size , the excitation
gap of the system approaches zero slower than , a behavior that is in
contrast to the Lieb-Schulz-Mattis theorem
A Cluster Expansion for Dipole Gases
We give a new proof of the well-known upper bound on the correlation function
of a gas of non-overlapping dipoles of fixed length and discrete orientation
working directly in the charge representation, instead of the more usual
sine-Gordon representation.Comment: 8 pages, Late
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