891 research outputs found
Surface acoustic waves for acousto-optic modulation in buried silicon nitride waveguides
We theoretically investigate the use of Rayleigh surface acoustic waves
(SAWs) for refractive index modulation in optical waveguides consisting of
amorphous dielectrics. Considering low-loss SiN waveguides with a
standard core cross section of 4.40.03 m size, buried 8 m
deep in a SiO cladding we compare surface acoustic wave generation in
various different geometries via a piezo-active, lead zirconate titanate film
placed on top of the surface and driven via an interdigitized transducer (IDT).
Using numerical solutions of the acoustic and optical wave equations, we
determine the strain distribution of the SAW under resonant excitation. From
the overlap of the acoustic strain field with the optical mode field we
calculate and maximize the attainable amplitude of index modulation in the
waveguide. For the example of a near-infrared wavelength of 840 nm, a maximum
shift in relative effective refractive index of 0.7x10 was obtained for
TE polarized light, using an IDT period of 30 - 35 m, a film thickness of
2.5 - 3.5 m, and an IDT voltage of 10 V. For these parameters, the
resonant frequency is in the range 70 - 85 MHz. The maximum shift increases to
1.2x10, with a corresponding resonant frequency of 87 MHz, when the
height of the cladding above the core is reduced to 3 m. The relative
index change is about 300-times higher than in previous work based on
non-resonant proximity piezo-actuation, and the modulation frequency is about
200-times higher. Exploiting the maximum relative index change of
1.210 in a low-loss balanced Mach-Zehnder modulator should allow
full-contrast modulation in devices as short as 120 m (half-wave voltage
length product = 0.24 Vcm).Comment: 19 pages, 8 figure
Bacterial Infection Elicits Heat Shock Protein 72 Release from Pleural Mesothelial Cells
Heat shock protein 70 (HSP70) has been implicated in infection-related processes and has been found in body fluids during infection. This study aimed to determine whether pleural mesothelial cells release HSP70 in response to bacterial infection in vitro and in mouse models of serosal infection. In addition, the in vitro cytokine effects of the HSP70 isoform, Hsp72, on mesothelial cells were examined. Further, Hsp72 was measured in human pleural effusions and levels compared between non-infectious and infectious patients to determine the diagnostic accuracy of pleural fluid Hsp72 compared to traditional pleural fluid parameters. We showed that mesothelial release of Hsp72 was significantly raised when cells were treated with live and heat-killed Streptococcus pneumoniae. In mice, intraperitoneal injection of S. pneumoniae stimulated a 2-fold increase in Hsp72 levels in peritoneal lavage (p<0.01). Extracellular Hsp72 did not induce or inhibit mediator release from cultured mesothelial cells. Hsp72 levels were significantly higher in effusions of infectious origin compared to non-infectious effusions (p<0.05). The data establish that pleural mesothelial cells can release Hsp72 in response to bacterial infection and levels are raised in infectious pleural effusions. The biological role of HSP70 in pleural infection warrants exploration
Surface acoustic waves for acousto-optic modulation in buried silicon nitride waveguides
We theoretically investigate the use of Rayleigh surface acoustic waves (SAWs) for refractive index modulation in optical waveguides consisting of amorphous dielectrics. Considering low-loss Si 3 N 4 waveguides with a standard core cross section of 4.4× 0.03 μ m 2 size, buried 8 μ m deep in a SiO 2 cladding we compare surface acoustic wave generation in various different geometries via a piezo-active, lead zirconate titanate film placed on top of the surface and driven via an interdigitized transducer (IDT). Using numerical solutions of the acoustic and optical wave equations, we determine the strain distribution of the SAW under resonant excitation. From the overlap of the acoustic strain field with the optical mode field we calculate and maximize the attainable amplitude of index modulation in the waveguide. For the example of a near-infrared wavelength of 840 nm, a maximum shift in relative effective refractive index of 0.7x10 −3 was obtained for TE polarized light, using an IDT period of 30 - 35 μ m, a film thickness of 2.5 - 3.5 μ m, and an IDT voltage of 10 V. For these parameters, the resonant frequency is in the range 70 - 85 MHz. The maximum shift increases to 1.2x10 −3 , with a corresponding resonant frequency of 87 MHz, when the height of the cladding above the core is reduced to 3 μ m. The relative index change is about 300-times higher than in previous work based on non-resonant proximity piezo-actuation, and the modulation frequency is about 200-times higher. Exploiting the maximum relative index change of 1.2× 10 −3 in a low-loss balanced Mach-Zehnder modulator should allow full-contrast modulation in devices as short as 120 μ m (half-wave voltage length product = 0.24 Vcm)
Eficacia de la suplementación con β-hydroxy-β-methylbutyrate (HMB) en el deporte: actualización e implicación práctica
Introduction: although β-hydroxy-β-methylbutyrate
(HMB) is generally marketed as a supplement for increasing
muscle mass and strength, it is still not fully understood
how and in which particular sports and conditions
HMB can be more effective.
Aims: the primary purpose of this review is to update
and summarize the current knowledge about the usefulness
of HMB and to organize this information by different
sports with specific reference to sports with high
wear and tear phenomena as soccer, rugby or football.
Methods: a search was performed in PubMed database.
This review presents the results about HMB use in
sport.
Results: the articles identified in this review support
the notion that HMB could help to attenuate tissue catabolism
and initiate muscle anabolism particularly in untrained
individuals exposed to strenuous exercise or when
trained individual are exposed to periods of high physical
stress. HMB could therefore be applied in some specific
periods of athlete’s season where there are high-intensity
training periods, high density of competitions and little
recovery time between them, starting recovery phases
from an injury period and/or any other different situation
where performance or recovery could be affected by
a great catabolic environment.
Conclusion: this update contributes to clarify and define
possible mechanisms and/or effectiveness of HMB
supplementation related to endurance sports (i.e. cycling
and athletics), strength-power sports (i.e. resistance training,
football, rugby, soccer, judo, waterpolo and rowing)
and recreational activities.Introducción: aunque el β-hidroxi-β-metilbutirato
(HMB) se ha empleado generalmente como suplemento
para aumentar la masa muscular y la fuerza, es necesario
un mejor entendimiento de su función y averiguar en qué
deportes es más efectivo.
Objetivos: el objetivo principal de esta revisión es actualizar
y resumir el conocimiento existente en torno a la
utilización del HMB para clasificarla en función de cada
modalidad deportiva, con especial mención a aquellas
actividades con un alto grado de destrucción muscular,
como pueden ser el fútbol, el rugby o el fútbol americano.
Métodos: se utilizó la base de datos PubMed para la
búsqueda de artículos. Esta revisión presenta los resultados
sobre la utilización de HMB clasificados por deportes.
Resultados: la mayoría de los artículos seleccionados
sugieren que cuando una persona entrenada o no entrenada
se somete a un ejercicio intenso o diferente al habitual,
el HMB puede atenuar el catabolismo muscular
producido e iniciar los procesos anabólicos necesarios
para recuperar lo antes posible. De esta forma, el HMB
podría aplicarse en algunos momentos concretos de la
temporada deportiva en los que hubiera períodos con
entrenamientos de alta intensidad, o durante un periodo
con alta densidad competitiva y con poca recuperación
entre competiciones, o bien durante las primeras fases
de la readaptación física después de una lesión y/o durante
cualquier otra situación en la que el rendimiento o
la recuperación se pueden ver afectados por un entorno
altamente catabólico.
Conclusión: esta revisión pretende aclarar y definir
los posibles mecanismos por los que la suplementación
con HMB puede ser efectiva en deportes de resistencia
(ciclismo y carreras de fondo), en deportes de fuerza-potencia
(fútbol, yudo, waterpolo, remo, fútbol americano y
musculación) y en actividades deportivas recreacionales.This work was supported by the Andalusian Sports Medicine Centre (C.A.M.D.) through project no. EX-2005/07.
FBO is granted by the Ministry of Economy and
Competitiveness (RYC-2011-09011)
Farmers’ management of functional biodiversity goes beyond pest management in organic European apple orchards
Supporting functional biodiversity (FB), which provides natural pest regulation, is an environmentally sound and promising approach to reduce pesticide use in perennial cultures such as apple, especially in organic farming. However, little is known about farmers’ practices and motivations to implement techniques that favor FB, especially whether or not they really expect anything from FB in terms of pest regulation. In fact, FB-supporting techniques (FB-techniques) are massively questioned by practitioners due to inadequate information about their effectiveness. An interview survey was performed in eight European countries(i) to describe farmers’ practices and identify promising FB-techniques: (ii) to better understand their perceptions of and values associated with FB; and (iii) to identify potential drivers of (non-)adoption. Fifty-five advisors and 125 orchard managers with various degrees of experience and convictions about FB were interviewed and a total of 24 different FB-techniques which can be assigned to three different categories (ecological infrastructures, farming practices and redesign techniques) were described. Some were well-established measures (e.g., hedges and bird houses), while others were more marginal and more recent (e.g., animal introduction and compost). On average, farmers combined more than four techniques that had been implemented over a period of 13 years, especially during their establishment or conversion period. In general, it was difficult for farmers to evaluate the effectiveness of individual FB-techniques on pest regulation. They considered FB-techniques as a whole, targeting multiple species, and valued multiple ecosystem services in addition to pest regulation. The techniques implemented and their associated values differed among farmers who adopted various approaches towards FB. Three different approaches were defined: passive, active and integrated. Their appraisal of FB is even more complex because it may change with time and experience. These findings provide empirical evidence that the practical implementation of promising techniques remains a challenge, considering the diversity of situations and evaluation criteria. Increased cooperation between researchers, farmers and advisors should more effectively target research, advisory support and communication to meet farmers’ needs and perceptions
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