6,994 research outputs found
Supersonic through-flow fan engine and aircraft mission performance
A study was made to evaluate potential improvement to a commercial supersonic transport by powering it with supersonic through-flow fan turbofan engines. A Mach 3.2 mission was considered. The three supersonic fan engines considered were designed to operate at bypass ratios of 0.25, 0.5, and 0.75 at supersonic cruise. For comparison a turbine bypass turbojet was included in the study. The engines were evaluated on the basis of aircraft takeoff gross weight with a payload of 250 passengers for a fixed range of 5000 N.MI. The installed specific fuel consumption of the supersonic fan engines was 7 to 8 percent lower than that of the turbine bypass engine. The aircraft powered by the supersonic fan engines had takeoff gross weights 9 to 13 percent lower than aircraft powered by turbine bypass engines
Embedding of global attractors and their dynamics
Using shape theory and the concept of cellularity, we show that if is the
global attractor associated with a dissipative partial differential equation in
a real Hilbert space and the set has finite Assouad dimension ,
then there is an ordinary differential equation in , with , that has unique solutions and reproduces the dynamics on . Moreover,
the dynamical system generated by this new ordinary differential equation has a
global attractor arbitrarily close to , where is a homeomorphism
from into
Heat Capacity Measurements in Pulsed Magnetic Fields
The new NHMFL 60T quasi-continuous magnet produces a flat-top field for a
period of 100 ms at 60 Tesla, and for longer time at lower fields, e.g. 0.5 sec
at 35 Tesla. We have developed for the first time the capability to measure
heat capacity at very high magnetic fields in the NHMFL 60 T quasi-continuous
magnet at LANL, using a probe built out of various plastic materials. The field
plateau allows us to utilize a heat-pulse method to obtain heat capacity data.
Proof-of-principle heat capacity experiments were performed on a variety of
correlated electron systems. Both magnet performance characteristics and
physical properties of various materials studied hold out a promise of wide
application of this new tool.Comment: 6 pages, 3 figures, World Scientific Pub. Co., to be publishe
Exploring the evolutionary paths of the most massive galaxies since z~2
We use Spitzer MIPS data from the FIDEL Legacy Project in the Extended Groth
Strip to analyze the stellar mass assembly of massive (M>10^11 M_sun) galaxies
at z<2 as a function of structural parameters. We find 24 micron emission for
more than 85% of the massive galaxies morphologically classified as disks, and
for more than 57% of the massive systems morphologically classified as
spheroids at any redshift, with about 8% of sources harboring a bright X-ray
and/or infrared emitting AGN. More noticeably, 60% of all compact massive
galaxies at z=1-2 are detected at 24 micron, even when rest-frame optical
colors reveal that they are dead and evolving passively. For spheroid-like
galaxies at a given stellar mass, the sizes of MIPS non-detections are smaller
by a factor of 1.2 in comparison with IR-bright sources. We find that disk-like
massive galaxies present specific SFRs ranging from 0.04 to 0.2 Gyr^-1 at z<1
(SFRs ranging from 1 to 10 M_sun/yr), typically a factor of 3-6 higher than
massive spheroid-like objects in the same redshift range. At z>1, and more
pronouncedly at z>1.3, the median specific SFRs of the disks and spheroids
detected by MIPS are very similar, ranging from 0.1 to 1 Gyr^-1 (SFR=10-200
M_sun/yr). We estimate that massive spheroid-like galaxies may have doubled (at
the most) their stellar mass from star-forming events at z<2: less than 20%
mass increase at 1.7<z<2.0, up to 40% more at 1.1<z<1.7, and less than 20%
additional increase at z<1. Disk-like galaxies may have tripled (at the most)
their stellar mass at z<2 from star formation alone: up to 40% mass increase at
1.7<z<2.0, and less than 180% additional increase below z=1.7 occurred at a
steady rate.Comment: Accepted for publication in ApJ; 10 pages, 5 figures, 1 tabl
Quantum critical 5f-electrons avoid singularities in U(Ru,Rh)2Si2
We present specific heat measurements of 4% Rh-doped U(Ru,Rh)2Si2 at magnetic
fields above the proposed metamagnetic transition field Hm~34 T, revealing
striking similarities to the isotructural Ce analog CeRu2Si2, suggesting that
strongly renormalized hybridized band models apply equally well to both
systems. The vanishing bandwidths as H --> Hm are consistent with a putative
quantum critical point close to Hm. The existence of a phase transition into an
ordered phase in the vicinity of Hm for 4% Rh-doped U(Ru,Rh)2Si2, but not for
CeRu2Si2, is consistent with a stronger super-exchange in the case of the U 5-f
system, with irreversible processes at the transition revealing a strong
coupling of the 5f orbitals to the lattice, most suggestive of orbital or
electric quadrupolar order.Comment: 4 pages, 4 figure
Estudio serológico de la infección por Salmonella spp. en cerdos de engorde del Noreste de España y factores de riesgo asociados
The results of a serological survey carried out in northeastern Spain to estimate the seroprevalence to Salmonella spp. and to determine potential risk factors are presented. Sera were obtained from farms submitting serum samples to the Regional Diagnostic Laboratory (RDL) for the diagnosis of other infectious diseases included within official eradication/surveillance programs, and farm data collected through a questionnaire. Out of 6,182 pig sera (217 farms) analyzed 1,219 (19.7%) were positive (optical density, OD ≥ 40%). More than 70% of the herds presented ≥ 1 seropositive animal indicating that salmonellosis was widespread. In a multivariable logistic mixed regression model seroprevalence was associated with farms where birds were visible inside the fattening units (OR = 2.1; 95% CI: 1.3-3.2) or that shared workers with other pig farms (OR = 2.5; 95% CI: 1.4-4.7). Seropositivity also increased when farmers used footwear exclusive for the farm (OR = 3.1; 95% CI: 1.3-7.3) or pigs were fed mostly with pellets (OR = 1.7; 95% CI: 1.1-2.6). It was also higher during the fall and winter months. The presence of a changing room and shower in the farm was negatively associated with it (OR = 0.5; 95% CI: 0.3-0.8). Most risk factors could be mitigated through strict hygiene and biosecurity measures, but the high (> 40%) within-herd seroprevalence observed in many herds may challenge the capacity of intervention of animal health authorities.Se presentan los resultados de un estudio serológico realizado en explotaciones porcinas del Noreste de España para estimar la seroprevalencia frente a Salmonella spp. y determinar posibles factores de riesgo asociados. Los sueros se obtuvieron a partir de aquellos enviados por las explotaciones al Laboratorio Regional de Diagnóstico para el diagnóstico de otras enfermedades infecciosas sometidas a erradicación/vigilancia oficial, y los datos sobre las explotaciones se recogieron mediante un cuestionario. De un total de 6.182 sueros de cerdo (217 granjas) analizados 1.219 (19,7%) resultaron positivos (densidad óptica, DO ≥ 40%). Más del 70% de los rebaños presentaron al menos un animal positivo, indicando que la salmonelosis está ampliamente distribuida en la región. Según un modelo multivariable mixto de regresión logística, la seroprevalencia se asoció con granjas en las cuales se veían aves en el interior de las naves (OR = 2,1; IC 95%: 1,3-3,2) y también con granjas que compartían trabajadores (OR = 2,5; IC 95%: 1,4-4,7). Se observó que la seropositividad se incrementaba cuando los trabajadores usaban botas exclusivas en la explotación (OR = 3,1; IC 95%: 1,3-7,3) o al alimentar a los cerdos principalmente con alimento granulado (OR = 1,7; IC 95%: 1,1-2,6). La seroprevalencia también fue superior durante los meses de otoño e invierno. La existencia en las granjas de vestuarios y duchas para el personal se asoció negativamente con la seroprevalencia (OR = 0,5; IC 95%: 0,3-0,8). La mayoría de los factores de riesgo podrían controlarse a través de estrictas medidas de higiene y bioseguridad, pero el gran número de rebaños que presentaron alta seroprevalencia (> 40%) puede poner a prueba la capacidad de intervención de las autoridades sanitarias oficiales
Hall-Effect Sign Anomaly and Small-Polaronic Conduction in (La_{1-x}Gd_x)_{0.67}Ca_{0.33}MnO_3
The Hall coefficient of Gd-doped La_{2/3}Ca_{1/3}MnO_3 exhibits Arrhenius
behavior over a temperature range from 2T_c to 4T_c, with an activation energy
very close to 2/3 that of the electrical conductivity. Although both the doping
level and thermoelectric coefficient indicate hole-like conduction, the Hall
coefficient is electron-like. This unusual result provides strong evidence in
favor of small-polaronic conduction in the paramagnetic regime of the
manganites.Comment: 11 pages, 4 figures, uses revtex.st
Salmonellosis in wild birds and its relationship with the infection in finishing pigs
The potential relationship between Salmonella infection in wild birds and pigs was investigated. Feces from pigs, wild birds, and bird droppings or other environmental samples from 25 finishing farms were cultured for Salmonella isolation. In 17 (68%) farms Salmonella was isolated. Out of 57 Salmonella isolates found, 32 (56.1%) were Typhimurium. In 6 (24%) farms the same Salmonella serotype was isolated from samples from different origins and similar AR and PFGE patterns were found, which would support the existence of a transmission cycle of Salmonella infection between birds and pigs in this area. Preventing bird access to farm premises is highly recommended
Serological characterization of Salmonella spp. infection in finishing pigs from NE Spain
The seroprevalence of salmonella spp. In finishing pigs in Aragón (NE of Spain) and the potential factors associated with it were assessed. Serum samples were collected directly from the Regional Diagnostic Laboratory (RDL). Only farms submitting a minimum of 30 serum samples to the RDL were included, i.e. exporting and farrow-to-finish farms, and those in the last stages of the Aujezsky\u27s disease eradication program
- …