Propagation of cosmic rays through interstellar space

The propagation of cosmic rays through interstellar space has been investigated with the view of determining what particles can traverse astronomical distances without serious loss of energy. The principal method of loss of energy of high energy particles is by interaction with radiation. It is found that high energy (10¹³-10¹⁸ev) electrons drop to one-tenth their energy in 10⁸ light years in the radiation density in the galaxy and that protons are not significantly affected in this distance. The origin of the cosmic rays is not known so that various hypotheses as to their origin are examined. If the source is near a star it is found that the interaction of electrons and photons with the stellar radiation field and the interaction of electrons with the stellar magnetic field limit the amount of energy which these particles can carry away from the star. However, the interaction is not strong enough to affect the energy of protons or light nuclei appreciably. The chief uncertainty in the results is due to the possible existence of general galactic magnetic field. The main conclusion reached is that if there is a general galactic magnetic field, then the primary spectrum has very few photons, only low energy (˂ 10¹³ ev) electrons and the higher energy particles are primarily protons regardless of the source mechanism, and if there is no general galactic magnetic field, then the source of cosmic rays accelerates mainly protons and the present rate of production is much less than that in the past.

Catch trends from Lake Victoria - Tanzanian waters

Catch trends from Fisheries Department reports from the last eleven years (1985-1995) were analyzed. These showed a shift in the fishery from a cichlid-based system to one dominated by Nile perch and tilapias. In recent years, catches have declined from a peak in the early 1990s. Catch per unit effort appears to have remained stable except for a drop in 1995, however, this is considered dubious because the effort showed a doubling in that year. Limitations of the fisheries data collection system for the Tanzanian sector of Lake Victoria are highlighted and discussed.

Observation and interpretation of tectonic strain release mechanisms

In four chapters various aspects of earthquake source are studied.

Chapter I

Surface displacements that followed the Parkfield, 1966, earthquakes were measured for two years with six small-scale geodetic networks straddling the fault trace. The logarithmic rate and the periodic nature of the creep displacement recorded on a strain meter made it possible to predict creep episodes on the San Andreas fault. Some individual earthquakes were related directly to surface displacement, while in general, slow creep and aftershock activity were found to occur independently. The Parkfield earthquake is interpreted as a buried dislocation.

Chapter II

The source parameters of earthquakes between magnitude 1 and 6 were studied using field observations, fault plane solutions, and surface wave and S-wave spectral analysis. The seismic moment, M_O, was found to be related to local magnitude, M_L, by log M_O = 1.7 M_L + 15.1. The source length vs magnitude relation for the San Andreas system found to be: M_L = 1.9 log L - 6.7. The surface wave envelope parameter AR gives the moment according to log M_O = log AR₃₀₀ + 30.1, and the stress drop, τ, was found to be related to the magnitude by τ = 0.54 M - 2.58. The relation between surface wave magnitude M_S and M_L is proposed to be M_S = 1.7 M_L - 4.1. It is proposed to estimate the relative stress level (and possibly the strength) of a source-region by the amplitude ratio of high-frequency to low-frequency waves. An apparent stress map for Southern California is presented.

Chapter III

Seismic triggering and seismic shaking are proposed as two closely related mechanisms of strain release which explain observations of the character of the P wave generated by the Alaskan earthquake of 1964, and distant fault slippage observed after the Borrego Mountain, California earthquake of 1968. The Alaska, 1964, earthquake is shown to be adequately described as a series of individual rupture events. The first of these events had a body wave magnitude of 6.6 and is considered to have initiated or triggered the whole sequence. The propagation velocity of the disturbance is estimated to be 3.5 km/sec. On the basis of circumstantial evidence it is proposed that the Borrego Mountain, 1968, earthquake caused release of tectonic strain along three active faults at distances of 45 to 75 km from the epicenter. It is suggested that this mechanism of strain release is best described as "seismic shaking."

Chapter IV

The changes of apparent stress with depth are studied in the South American deep seismic zone. For shallow earthquakes the apparent stress is 20 bars on the average, the same as for earthquakes in the Aleutians and on Oceanic Ridges. At depths between 50 and 150 km the apparent stresses are relatively high, approximately 380 bars, and around 600 km depth they are again near 20 bars. The seismic efficiency is estimated to be 0.1. This suggests that the true stress is obtained by multiplying the apparent stress by ten. The variation of apparent stress with depth is explained in terms of the hypothesis of ocean floor consumption.

Use of Freely-Available Weebly in Creating Quick and Easy Web Pages: poster presentation

Weebly is a freely-available software for creating Web pages without having to know HTML. It is easy to use, with its drag and drop editor, and offers the ability to add documents, Web links, videos, slideshows, audio, forms, polls, etc. It is hosted by Weebly and has no limits on storage space. Many templates are available for Web page design. One can publish and update almost immediately. Combined with usage of the freely-available Google Analytics, for example, it is possible to gather usage statistics. The site can be password protected, if need be. Weebly for Education is a special version for teachers and schools.

偏振光飞秒双脉冲微加工

利用具有纳焦能量、高重复频率的偏振光飞秒双脉冲对金属铬膜样品进行微加工,样品表面都会产生微突起状结构,它们的宽度在0～400 ps的双脉冲时延范围内没有明显的变化,但高度却都在1～10 ps的双脉冲时延范围内呈现明显的下降,在此时延范围之外并没有明显的变化。通过加工样品的扫描电子显微镜(SEM)图片发现,对于偏振光,利用双脉冲方法,可以获得更好的加工质量。并且线偏振光得到的微突起状结构比较细长,在入射光束的偏振方向上有所伸长;圆偏振光得到的微突起状结构比较接近圆形。即在低脉冲能量、高重复频率情况下,具体的微加工特征形貌与入射光束的偏振状态有关。

Ultrafast double pulses ablation of Cr film on glass

Ultrafast lasers ablation of Cr film was investigated by using double-pulse method. Experimental results show that there exists a temporal ablation window effect with each of the double pulses adjusted just smaller than the threshold. When the delay between the double pulses is within the order of 400 ps, the ablation of Cr film could happen. When the delay between the double pulses is beyond the order of 400 ps, the ablation of Cr film would not happen, and the reflectivity from the surface of the Cr film shows a sharp rise at the same time. The two-temperature model was developed into the form of double pulses to explain the experimental phenomena. Furthermore, microbump structures were formed on the surface of Cr film after ablation by ultrafast double pulses. Their heights exhibit an obvious drop between 1 and 10 ps double pulses delay, which is involved with the electron-phonon coupling process according to the numerical simulation. These results should be helpful for understanding the dynamic processes during ultrafast lasers ablation of metal films. (C) 2008 Elsevier B.V. All rights reserved.

利用晶体串接实现高效宽带三倍频

从耦合波方程出发,分别在小信号、高功率(1.5 GW/cm2)条件下研究KDP晶体串接三次谐波转换。当两块混频晶体的长度选择为8 mm和6 mm,晶体分别偏离原混频匹配角0.35 mrad和-0.25 mrad时可以有0.3 nm的谐波转换带宽,同时系统的三次谐波转换效率与两块混频晶体之间的距离有密切关系,当两块晶体之间的距离使从第一块混频晶体出射的光波之间的相位差改变π时,会使第一块混频晶体产生的三次谐波大部分回流到基频和倍频光,从而使转换效率大幅度下降,最合适的距离应当使光波之间的相位差改变为2π。

一种制作掺Yb相移光纤光栅激光器的实验方案

采用遮挡法引入相移制作了掺Yb相移光纤光栅(PS-FBG)。在制作光栅的过程中,将其作为激光器的谐振腔,通过监测激光器的输出功率来确定相移大小。当激光器的输出功率开始下降时,停止曝光,此时引入的相移为π/2。为了使光栅的特性尽快稳定下来需要对光栅进行退火,这将导致引入的相移小于π/2。为了弥补退火过程中引起的相移降低,需要对退火后的光栅进行二次曝光,以使光栅的相移恢复π/2。利用该方法制作了一只光纤光栅激光器。当抽运功率为100 mW时,获得了25 mW的输出功率,信噪比(SNR)为60 dB。在1 h内

Estudo da Comunidade de anfíbios anuros ao longo de um gradiente altitudinal na Ilha Grande, Angra dos Reis, RJ. Rio de Janeiro 2010

Este estudo investigou a variação altitudinal da comunidade de anfíbios anuros em uma montanha de floresta Atlântica da Ilha Grande, avaliando a ocorrência, distribuição, organização e riqueza de anuros nas diferentes altitudes. Estabelecemos seis faixas de altitude para realização do estudo: 150, 300, 450, 600, 750 e 900 metros acima do nível do mar. Utilizamos duas metodologias de amostragem: o método de parcelas grandes (5 x 5 metros) e o método de transecção, entre janeiro de 2008 e março de 2009. Os dados indicaram que na região de Mata Atlântica do Pico do Papagaio ocorre uma considerável riqueza de espécies de anuros, a qual varia dependendo da faixa de altitude ao longo do gradiente altitudinal do morro. Houve em geral uma tendência a um decréscimo da riqueza com aumento da altitude, com exceção da altitude de 900 metros, onde a riqueza teve um aumento quando comparado à faixa altitudinal imediatamente abaixo. Nossos dados mostram ainda que ao longo de todo o gradiente altitudinal do morro, as maiores riquezas de anuros em geral ocorrem nas faixas de altitudes de 150 e 300 metros. Nossos dados indicaram para a região estudada uma considerável densidade de anuros, que além de variar significativamente entre as estações seca e chuvosa, foi influenciada negativamente pela altitude: na medida em que houve um aumento da altitude ocorreu uma correspondente diminuição na densidade geral de anuros da comunidade componente. A anurofauna da região do Pico do Papagaio apresentou uma queda abrupta na abundância a partir dos 450 metros de altitude, com grande dominância, em termos numéricos, de três espécies com desenvolvimento direto. Nossos dados mostraram haver uma variação sazonal na abundância e, nas densidades de anuros na região do Pico do Papagaio. Concluímos que a região de Mata Atlântica do Pico do Papagaio possui uma elevada riqueza de espécies de anuros, a qual varia ao longo do gradiente altitudinal com os maiores valores de riqueza e abundâncias encontradas entre as faixas de 150 e 300 metros, o que pode ser favorecido pela menor inclinação do terreno, pela maior ocorrência de cursos dágua e pela elevada pluviosidade que ocorre nestas faixas altitudinais na Ilha Grande. A considerável similaridade na comunidade componente de anuros entre as altitudes de 150 e 300 pode resultar da similaridade estrutural da vegetação entre estas faixas de altitudes. A região em geral teve uma alta densidade de anuros, que além de variar sazonalmente, foi negativamente influenciada pela altitude. A observada redução na abundância dos anuros a partir dos 450 metros de altitude pareceu favorecer espécies com desenvolvimento direto.

Structural change of laser-irradiated Ge2Sb2Te5 films studied by electrical property measurement

Sheet resistance of laser-irradiated Ge2Sb2Te5 thin films prepared by magnetron sputtering was measured by the four-point probe method. With increasing laser power the sheet resistance undergoes an abrupt drop from 10(7) to 10(3) Omega/square at about 580 mW. The abrupt drop in resistance is due to the structural change from amorphous to crystalline state as revealed by X-ray diffraction (XRD) study of the samples around the abrupt change point. Crystallized dots were also formed in the amorphous Ge2Sb2Te5 films by focused short pulse laser-irradiated, the resistivities at the crystallized dots and the non-crystallized area are 3.375 x 10(-3) and 2.725 Omega m, sheet resistance is 3.37 x 10(4) and 2.725 x 10(7) Omega/square respectively, deduced from the I-V Curves that is obtained by conductive atomic force microscope (C-AFM). (C) 2008 Elsevier B.V. All rights reserved.

Validade e confiabilidade do Questionário de Qualidade de Vida para Pacientes Orto-cirúrgicos (B-OQLQ)

O Orthognathic Quality of Life Questionnaire (OQLQ) foi desenvolvido em 2000 e validado em 2002, com o objetivo de analisar os impactos e benefícios do tratamento orto-cirúrgico na qualidade de vida dos pacientes. O objetivo deste trabalho foi avaliar a validade de construto e confiabilidade da versão brasileira deste instrumento, B-OQLQ, para verificar se, no processo de adaptação transcultural, as propriedades psicométricas do questionário original foram mantidas. Para tal, foi realizado um estudo seccional com uma amostra composta por cento e um pacientes com necessidade de tratamento ortodôntico-cirúrgico no Hospital Universitário Pedro Ernesto (HUPE) e na Faculdade de Odontologia da Universidade do Estado do Rio de Janeiro (UERJ), utilizando o B-OQLQ na forma de autopreenchimento. A média de idade dos pacientes foi de 26,51 (dp= 9,25), sendo a maioria do sexo feminino (58,42%; n=59) e maior que 21 anos (n=68, 67,33%). Quanto ao tipo de cirurgia, 42,57% (n=43) da amostra necessitavam fazer procedimento cirúrgico que envolveria as duas bases ósseas, 16,83% (n=17) necessitavam operar apenas uma das bases ósseas e para 40,59% (n=41) dos pacientes ainda não era possível definir qual o tipo de cirurgia seria necessária. Uma ortodontista treinada examinou os dentes dos pacientes para registrar o Índice de Dentes Cariados, Perdidos e Obturados (CPOD). A validade de construto foi acessada através do teste de correlação de Spearman entre as pontuações do B-OQLQ e do questionário Oral Health Impact Profile (OHIP-14) e das pontuações do B-OQLQ com as pontuações obtidas através de indicadores subjetivos e objetivos de saúde. A confiabilidade foi acessada em termos de consistência interna e estabilidade (teste-reteste), utilizando-se o alfa de Cronbach e o Coeficiente de Correlação Intraclasse (CCI), respectivamente. Os escores do B-OQLQ se correlacionaram significativamente com: o escore total do OHIP-14 (rs=0,70, p<0,001), a saúde bucal percebida (rs=-0,24, p=0,02), a qualidade de vida medida por um item único de avaliação (rs=-0,29, p=0,03), a satisfação com a aparência física (rs=-0,40, p<0,001) e a satisfação com a aparência facial (rs=-0,39, p=0,0001). Foi encontrada uma associação entre a faixa etária e o escore total do B-OQLQ (p=0,0012), sendo que pacientes maiores de 21 anos obtiveram escores mais elevados que pacientes mais novos. A associação entre o escore total do B-OQLQ e o tipo de cirurgia não foi estatisticamente significativa. O alfa de Cronbach e o CCI foram 0,95 e 0,90, respectivamente. Os domínios do B-OQLQ que mais causaram impacto na qualidade de vida foram aspectos sociais da deformidade (13,0; dp= 10,54) e estética facial (11,81; dp= 6,23). A versão brasileira do questionário OQLQ se mostrou um instrumento válido e confiável, com boas propriedades psicométricas podendo, portanto, ser considerada um instrumento apropriado para acessar o impacto da deformidade dentofacial na qualidade de vida de pacientes portadores desta condição.

Improved Mechanical Properties of Compatibilized Polypropylene/Polyamide-12 Blends

Compatibilized blends of polypropylene (PP) and polyamide-12 (PA12) as a second component were obtained by direct injection molding having first added 20% maleic anhydride-modified copolymer (PP-g-MA) to the PP, which produced partially grafted PP (gPP). A nucleating effect of the PA12 took place on the cooling crystallization of the gPP, and a second crystallization peak of the gPP appeared in the PA12-rich blends, indicating changes in the crystalline morphology. There was a slight drop in the PA12 crystallinity of the compatible blends, whereas the crystallinity of the gPP increased significantly in the PA12-rich blends. The overall reduction in the dispersed phase particle size together with the clear increase in ductility when gPP was used instead of PP proved that compatibilization occurred. Young's modulus of the blends showed synergistic behavior. This is proposed to be both due to a change in the crystalline morphology of the blends on the one hand and, on the other, in the PA12-rich blends, to the clear increase in the crystallinity of the gPP phase, which may, in turn, have been responsible for the increase in its continuity and its contribution to the modulus.

Propiedades básicas de materiales soporte y parámetros de control en biofiltración.

[ES]En la problemática medioambiental generada por la contaminación atmosférica hay tres aspectos que marcan las directrices de actuación institucional: la presión social, la legislación vigente y la tecnología disponible. En cuanto a este último aspecto, la biofiltración es una tecnología eficaz, asequible y sostenible basada en la actividad biodegradadora de microorganismos específicos adheridos a la superficie de un material soporte que constituye el lecho del biofiltro. La elección de un material soporte adecuado es de especial importancia para asegurar el correcto funcionamiento de los biofiltros. Esta decisión está basada en las propiedades intrínsecas del material que deben ser analizadas previamente a su uso. En este proyecto se ha seleccionado cuales son estas propiedades básicas a partir de una revisión bibliográfica, destacando la capacidad de retención de humedad, superficie específica, porosidad, y estabilidad física y química del material. En este trabajo, también se han fijado los parámetros de control que deben ser medidos de forma rutinaria en un biofiltro para asegurar la eficacia del tratamiento de descontaminación. En base a la información bibliográfica recopilada, se ha concluido que los parámetros básicos son pH, temperatura, contenido de humedad del lecho y pérdidas de carga. A nivel experimental, se han medido las pérdidas de carga generadas en biofiltros empacados con tres materiales soportes que son de especial interés para una investigación posterior a desarrollar por el grupo Biofiltración de la Universidad del País Vasco (UPV/EHU). Durante el período de arranque inicial de los tres biofiltros, las pérdidas de carga medidas fueron muy bajas en los tres casos, aunque algo superiores cuando la alimentación era en sentido ascendente frente al flujo descendente. Sin embargo, cuando se midieron las pérdidas de carga bajo condiciones de encharcamiento del lecho, que es una de las situaciones más problemáticas en un biofiltro, todos los soportes presentaron un aumento puntual de la pérdida de carga aunque la tendencia en los días posteriores fue claramente descendente, recuperando valores de operación habituales. La comparativa del comportamiento frente a las pérdidas de carga permitió seleccionar el soporte más idóneo de los tres analizados, aunque los otros dos podrían ser alternativas viables en caso de sustitución.

Hypoxic and low pH water in the nearshore marine environments of Monterey Bay, California: characterizing a decade of oxygen and pH, and drivers of variability.

A decade-long time series recorded in southern Monterey Bay, California demonstrates that the shallow, near-shore environment (17 m depth) is regularly inundated with pulses of cold, hypoxic and low pH water. During these episodes, oxygen can drop to biologically threatening levels, and pH levels were lower than expected. Weekly water chemistry monitoring revealed that the saturation state of aragonite (the more soluble form of calcium carbonate) was often below saturation and had a moderate positive relationship with pH, however, analytical and human error could be high. Pulses of hypoxia and low pH water with the greatest intensity arise at the onset of the spring upwelling season, and fluctuations are strongly semidurnal (tidal) and diurnal. Arrival of cold, hypoxic water on the inner shelf typically occurs 3 days after the arrival of a strong upwelling event and appears to be driven by upwelling modulated by internal tidal fluctuations. I found no relationship between the timing of low-oxygen events and the diel solar cycle nor with terrestrial nutrient input. These observations are consistent with advection of hypoxic water from the deep, offshore environment where water masses experience a general decline of temperature, oxygen and pH with depth, and inconsistent with biochemical forcing. Comparisons with concurrent temperature and oxygen time series taken ~20 km away at the head of the Monterey Canyon show similar patterns but even more intense hypoxic events due to stronger semidiurnal forcing there. Analysis of the durations of exposure to low oxygen levels establishes a framework for assessing the ecological relevance of these events. Increasing oceanic hypoxia and acidification of both surface and deep waters may increase the number, intensity, duration and spatial extent of future intrusions along the Pacific coast. Evaluation of the resiliency of nearshore ecosystems such as kelp forests, rocky reefs and sandy habitats, will require consideration of these events.

Dimensionamiento geométrico y resistente de manipulador paralelo XY.

[ES]Se trata de diseñar, programar, fabricar y montar un manipulador paralelo de 5 pares de revolución, que sirva para el atrape y posterior desplazamiento de objetos pequeños en un área de trabajo determinado. Este proyecto se centra exclusivamente en el análisis cinemático, resistente y posterior optimización del diseño del mecanismo de barras del manipulador.