333 research outputs found
Lipopolysaccharides and outer membrane proteins as main structures involved in complement evasion strategies of non-typhoidal Salmonella strains
Non-typhoidal Salmonella (NTS) infections pose a serious public health problem. In addition to the typical course of salmonellosis, an infection with Salmonella bacteria can often lead to parenteral infections and sepsis, which are particularly dangerous for children, the elderly and immunocompromised. Bacterial resistance to serum is a key virulence factor for the development of systemic infections. Salmonella, as an enterobacterial pathogen, has developed several mechanisms to escape and block the antibacterial effects of the complement system. In this review, we discuss the relevance of outer membrane polysaccharides to the complement evasion mechanisms of NTS strains. These include the influence of the overall length and density of the lipopolysaccharide molecules, modifications of the O-antigen lipopolysaccharide composition and the role of capsular polysaccharides in opsonization and protection of the outer membrane from the lytic action of complement. Additionally, we discuss specific outer membrane protein complement evasion mechanisms, such as recruitment of complement regula-tory proteins, blocking assembly of late complement components to form the membrane attack complex and the proteolytic cleavage of complement proteins.Peer reviewe
A caricature of a singular curvature flow in the plane
We study a singular parabolic equation of the total variation type in one
dimension. The problem is a simplification of the singular curvature flow. We
show existence and uniqueness of weak solutions. We also prove existence of
weak solutions to the semi-discretization of the problem as well as convergence
of the approximating sequences. The semi-discretization shows that facets must
form. For a class of initial data we are able to study in details the facet
formation and interactions and their asymptotic behavior. We notice that our
qualitative results may be interpreted with the help of a special composition
of multivalued operators
Kinematics of Tycho-2 Red Giant Clump Stars
Based on the Ogorodnikov-Milne model, we analyze the proper motions of 95 633
red giant clump (RGC) stars from the Tycho-2 Catalogue. The following Oort
constants have been found: A = 15.9+-0.2 km/s/kpc and B = -12.0+-0.2 km/s/kpc.
Using 3632 RGC stars with known proper motions, radial velocities, and
photometric distances, we show that, apart from the star centroid velocity
components relative to the Sun, only the model parameters that describe the
stellar motions in the XY plane differ significantly from zero. We have studied
the contraction (a negative K-effect) of the system of RGC stars as a function
of their heliocentric distance and elevation above the Galactic plane. For a
sample of distant (500--1000 pc) RGC stars located near the Galactic plane
(|Z|<200 pc) with an average distance of d=0.7 kpc, the contraction velocity is
shown to be Kd= -3.5+-0.9 km/s; a noticeable vertex deviation, lxy = 9.1+-0.5
degrees, is also observed for them. For stars located well above the Galactic
plane (|Z|>=200 pc), these effects are less pronounced, Kd = -1.7+-0.5 km/s and
lxy = 4.9+-0.6 degrees. Using RGC stars, we have found a rotation around the
Galactic X axis directed toward the Galactic center with an angular velocity of
-2.5+-0.3 km/s/kpc, which we associate with the warp of the Galactic
stellar-gaseous disk.Comment: 23 pages, 7 figures, 4 table
Desenvolvimento e aceitação de barra de cereal sabor umbu (Spondias tuberosa).
Produto bastante consumido nos dias atuais, a barra de cereal é uma alternativa saudável e prática. Este trabalho teve como objetivo formular barra de cereais contendo umbu, de preparo simples e baixo custo, e avaliar a aceitação do produto pelos consumidores, afim de propor a possÃvel elaboração por pequenas agroindústrias. Foram desenvolvidas três formulações contendo ingredientes em diferentes proporções. A amostra 1 foi composta por xarope de polpa de umbu com sacarose, aveia prensada, coco ralado, castanha de caju, flocos de arroz, uva passa e doce de umbu em corte. A amostra 2 continha xarope de polpa de umbu com glicose, aveia prensada, coco ralado, castanha de caju, flocos de arroz e uva passa; e a amostra 3 foi composta por xarope caramelizado de polpa de umbu com sacarose, aveia prensada, coco ralado, castanha de caju, flocos de arroz e uva passa. Foi realizado teste de aceitação das barrinhas com 50 consumidores que avaliaram o quanto gostaram do produto utilizando escala hedônica de nove pontos (1=desgostei x extremamente; 9=gostei extremamente), além do grau de intenção de compra (1=certamente não compraria; 5=certamente compraria). Para aceitação da aparência, cor e textura as três formulações obtiveram notas sem diferença estatÃstica (p < 0.05) entre si, e acima de 7, equivalente a ?gostei moderadamente? na escala. Para aroma, sabor e impressão global, as amostras 1 e 3 destacaram -se da amostra 2, sendo que a amostra 3 obteve as maiores médias de aceitação. Com relação ao sabor, a amostra 3 obteve média 8, equivalente a ?gostei muito? na escala. Segundo o teste de intenção de compra, 60% dos consumidores responderam que ?certamente comprariam? a amostra 3 caso estivesse a venda. Através desse trabalho pode-se concluir que as formulações testadas apresentaram bons resultados de aceitação, e que a formulação com xarope caramelizado foi a preferida pelos consumidores
Design and performance of the ADMX SQUID-based microwave receiver
The Axion Dark Matter eXperiment (ADMX) was designed to detect ultra-weakly
interacting relic axion particles by searching for their conversion to
microwave photons in a resonant cavity positioned in a strong magnetic field.
Given the extremely low expected axion-photon conversion power we have
designed, built and operated a microwave receiver based on a Superconducting
QUantum Interference Device (SQUID). We describe the ADMX receiver in detail as
well as the analysis of narrow band microwave signals. We demonstrate the
sustained use of a SQUID amplifier operating between 812 and 860 MHz with a
noise temperature of 1 K. The receiver has a noise equivalent power of
1.1x10^-24 W/sqrt(Hz) in the band of operation for an integration time of
1.8x10^3 s.Comment: 8 pages, 12 figures, Submitted to Nuclear Inst. and Methods in
Physics Research,
Experimental evaluation of sub-sampling IQ detection for low-level RF control in particle accelerator systems
The low-level radio frequency (LLRF) control system is one of the fundamental parts of a particle accelerator, ensuring the stability of the electro-magnetic (EM) field inside the resonant cavities. It leverages on the precise measurement of the field by in-phase/quadrature (IQ) detection of an RF probe signal from the cavities, usually performed using analogue downconversion. This approach requires a local oscillator (LO) and is subject to hardware non-idealities like mixer nonlinearity and long-term temperature drifts. In this work, we experimentally evaluate IQ detection by direct sampling for the LLRF system of the Polish free electron laser (PolFEL) now under development at the National Centre for Nuclear Research (NCBJ) in Poland. We study the impact of the sampling scheme and of the clock phase noise for a 1.3-GHz input sub-sampled by a 400-MSa/s analogue-to-digital converter (ADC), estimating amplitude and phase stability below 0.01% and nearly 0.01â—¦, respectively. The results are in line with state-of-the-art implementations, and demonstrate the feasibility of direct sampling for GHz-range LLRF systems
A Search for Scalar Chameleons with ADMX
Scalar fields with a "chameleon" property, in which the effective particle
mass is a function of its local environment, are common to many theories beyond
the standard model and could be responsible for dark energy. If these fields
couple weakly to the photon, they could be detectable through the "afterglow"
effect of photon-chameleon-photon transitions. The ADMX experiment was used in
the first chameleon search with a microwave cavity to set a new limit on scalar
chameleon-photon coupling excluding values between 2*10^9 and 5*10^14 for
effective chameleon masses between 1.9510 and 1.9525 micro-eV.Comment: 4 pages, 3 figure
A SQUID-based microwave cavity search for dark-matter axions
Axions in the micro eV mass range are a plausible cold dark matter candidate
and may be detected by their conversion into microwave photons in a resonant
cavity immersed in a static magnetic field. The first result from such an axion
search using a superconducting first-stage amplifier (SQUID) is reported. The
SQUID amplifier, replacing a conventional GaAs field-effect transistor
amplifier, successfully reached axion-photon coupling sensitivity in the band
set by present axion models and sets the stage for a definitive axion search
utilizing near quantum-limited SQUID amplifiers.Comment: 4 pages, 5 figures, submitted to PR
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