Effect of Pb Volatilization on Dielectric Properties of 0.77PbMg1/3(Nb0.9Ta0.1)2/3O3-0.23PbTiO3

Lead magnesium niobate-lead titanate (PMN-PT) is an intriguing candidate for applications in many electronic devices such as multi-layer capacitors, electro-mechanical transducers etc. because of its high dielectric constant, low dielectric loss and high strain near the Curie temperature. As an extension of our previous work on Ta-doped PMNT-PT aimed at optimizing the performance and reducing the cost, this paper focuses on the effect of Pb volatilization on the dielectric properties of 0.77Pb(Mg1/3(Nb0.9Ta0.1)2/3)O3-0.23PbTiO3. The dielectric constant and loss of the samples are measured at different frequencies and different temperatures. The phase purity of this compound is determined by X-ray diffraction pattern. It is found that the volatilization during sintering does influence the phase formation and dielectric properties. The best condition is sintering with 0.5 g extra PbO around a 4 g PMNT-PT sample.

El desarrollo profesional de los trabajadores como ventaja competitiva de las empresas

[ES] En este trabajo se hace una revisión de la literatura sobre el concepto de profesión y a continuación se propone un modelo de desarrollo profesional en el que se destacan los retos profesionales de los trabajadores y la posibilidad de las empresas de ayudarles a afrontarlos. También se analizan los sistemas de desarrollo profesional y los roles que en ellos juegan empleados, directores y empresas. Para finalizar, se exponen varias cuestiones de actualidad relativas al desarrollo profesional: incorporación y orientación, estabilización, obsolescencia de las habilidades, doble trayectoria profesional, conflictos trabajo-familia, pérdida del puesto de trabajo y jubilación.

Informational report: Bycatch reduction devices used in the Pink Shrimp trawl fishery

The California Fish and Game Commission (Commission) has the authority to require one or any combination of Bycatch Reduction Device (BRD) types in the trawl fishery within California waters for Pacific ocean shrimp (Pandalus jordani), most commonly referred to as pink shrimp. The purpose of this report is to provide the Commission with the best available information about the BRDs used in the pink shrimp trawl fishery. The mandatory requirement for BRDs occurred in California in 2002, and in Oregon and Washington in 2003, resulting from an effort to minimize bycatch of overfished and quota managed groundfish species. Three types of BRDs currently satisfy the requirement for this device in the California fishery: 1) the Nordmøre grate (rigid-grate excluder); 2) soft-panel excluder; and 3) fisheye excluder; however, the design, specifications, and efficacy differ by BRD type. Although no data has been collected on BRDs directly from the California pink shrimp fishery, extensive research on the efficacy and differences among BRD types has been conducted by the Oregon Department of Fish and Wildlife (ODFW) since the mid-1990s. Rigid-grate excluders are widely considered to be the most effective of the three BRD types at reducing groundfish bycatch. Over 90 percent of the Oregon pink shrimp fleet use rigid-grate excluders. The majority of the current California pink shrimp fleet also uses rigid-grate excluders, according to a telephone survey conducted by the California Department of Fish and Game (Department) in 2007-2008 of pink shrimp fishermen who have been active in the California fishery in recent years. Hinged rigid-grate excluders have been developed in recent years to reduce the bending of the BRD on vessels that employ net reels to stow and deploy their trawl nets, and they have been used successfully on both single- and double-rig vessels in Oregon. Soft-panel excluders have been demonstrated to be effective at reducing groundfish bycatch, although excessive shrimp loss and other problems have also been associated with this design. Fisheye excluders have been used in the California fishery in the past, but they were disapproved in Oregon and Washington in 2003 because they were found to be less effective at reducing groundfish bycatch than other designs. The reputation of the United States west coast pink shrimp fishery as one of the cleanest shrimp fisheries in the world is largely attributed to the effectiveness of BRDs at reducing groundfish bycatch. Nevertheless, BRD research and development is still a relatively new field and additional modifications and methods may further reduce bycatch rates in the pink shrimp fishery.(PDF contains 12 pages.)

Celiac disease in the Mediterranean area

Background: The World Gastroenterology Organization recommends developing national guidelines for the diagnosis of Celiac Disease (CD): hence a profile of the diagnosis of CD in each country is required. We aim to describe a cross-sectional picture of the clinical features and diagnostic facilities in 16 countries of the Mediterranean basin. Since a new ESPGHAN diagnostic protocol was recently published, our secondary aim is to estimate how many cases in the same area could be identified without a small intestinal biopsy. Methods: By a stratified cross-sectional retrospective study design, we examined clinical, histological and laboratory data from 749 consecutive unselected CD children diagnosed by national referral centers. Results: The vast majority of cases were diagnosed before the age of 10 (median: 5 years), affected by diarrhea, weight loss and food refusal, as expected. Only 59 cases (7.8%) did not suffer of major complaints. Tissue transglutaminase (tTG) assay was available, but one-third of centers reported financial constraints in the regular purchase of the assay kits. 252 cases (33.6%) showed tTG values over 10 times the local normal limit. Endomysial antibodies and HLA typing were routinely available in only half of the centers. CD was mainly diagnosed from small intestinal biopsy, available in all centers. Based on these data, only 154/749 cases (20.5%) would have qualified for a diagnosis of CD without a small intestinal biopsy, according to the new ESPGHAN protocol. Conclusions: This cross-sectional study of CD in the Mediterranean referral centers offers a puzzling picture of the capacities to deal with the emerging epidemic of CD in the area, giving a substantive support to the World Gastroenterology Organization guidelines.

The long road of climate negotiations: From Kyoto to Paris stopping over in Doha

4 p.

Warsaw Conference: “Small steps forward while awaiting major decisions at the 2015 Paris Conference”

6 p.

La Cumbre de Varsovia: “Pequeños avances en espera de decisiones de envergadura en la Cumbre de Paris 2015”

6 p.

A fundamental approach to phase noise reduction in hybrid Si/III-V lasers

Spontaneous emission into the lasing mode fundamentally limits laser linewidths. Reducing cavity losses provides two benefits to linewidth: (1) fewer excited carriers are needed to reach threshold, resulting in less phase-corrupting spontaneous emission into the laser mode, and (2) more photons are stored in the laser cavity, such that each individual spontaneous emission event disturbs the phase of the field less. Strong optical absorption in III-V materials causes high losses, preventing currently-available semiconductor lasers from achieving ultra-narrow linewidths. This absorption is a natural consequence of the compromise between efficient electrical and efficient optical performance in a semiconductor laser. Some of the III-V layers must be heavily doped in order to funnel excited carriers into the active region, which has the side effect of making the material strongly absorbing.

This thesis presents a new technique, called modal engineering, to remove modal energy from the lossy region and store it in an adjacent low-loss material, thereby reducing overall optical absorption. A quantum mechanical analysis of modal engineering shows that modal gain and spontaneous emission rate into the laser mode are both proportional to the normalized intensity of that mode at the active region. If optical absorption near the active region dominates the total losses of the laser cavity, shifting modal energy from the lossy region to the low-loss region will reduce modal gain, total loss, and the spontaneous emission rate into the mode by the same factor, so that linewidth decreases while the threshold inversion remains constant. The total spontaneous emission rate into all other modes is unchanged.

Modal engineering is demonstrated using the Si/III-V platform, in which light is generated in the III-V material and stored in the low-loss silicon material. The silicon is patterned as a high-Q resonator to minimize all sources of loss. Fabricated lasers employing modal engineering to concentrate light in silicon demonstrate linewidths at least 5 times smaller than lasers without modal engineering at the same pump level above threshold, while maintaining the same thresholds.

光纤光栅滤波的瓦斯传感系统的研究

差分吸收法是进行瓦斯远距离监测的重要方法，根据瓦斯在近红外波段的吸收特性，报道了一种新型的远距离光纤瓦斯传感系统。采用1．3μm超辐射发光二极管为光源，利用光纤布拉格光栅(FBG)优良的窄带滤波特性实现了对瓦斯的差分吸收测量。和传统的干涉滤光片相比，光纤光栅滤波器插入损耗低、制备简单。系统具有全光纤化、结构简单、工作距离远、稳定性好的特点。工作距离10km，测量灵敏度为0．1％，是瓦斯爆炸极限的2％。

Avaliação in vivo da densidade óssea ao redor de implantes osteointegráveis com diferentes plataformas

Os implantes osteointegráveis assumiram condição prioritária na reabilitação da perda dentária unitária ou múltipla em função das elevadas taxas de sucesso e previsibilidade no tratamento e vêm sendo cada vez mais utilizados por especialistas e clínicos. Atualmente existe a preocupação com a manutenção dos tecidos moles periimplantares, principalmente em áreas estéticas. De modo geral, um ano após a instalação dos implantes osteointegráveis ocorre uma perda óssea proximal de 1,5 mm e em média 0,1 mm durante os anos subsequentes. Nos últimos anos, achados clínicos evidenciaram menor perda óssea inicial associada a intermediários de diâmetro reduzido em relação à plataforma dos implantes. Com o objetivo de comparar, por meio de imagens radiográficas o comportamento ósseo proximal ao redor de implantes osteointegráveis com plataformas convencionais e plataformas de diâmetro intermediário reduzido, foi estabelecido o seguinte desenho de estudo clínico prospectivo: em 08 pacientes totalmente edentados, foram instalados 40 implantes, 5 implantes mandibulares por paciente. Cada paciente recebeu 3 implantes com plataforma convencional e 2 com plataforma associada aos intermediários de diâmetro reduzido (cone morse). Foram confeccionadas próteses em resina acrílica e fixadas precocemente aos implantes por intermédio de parafusos, seguindo o modelo protocolo Bränemark. Foram feitas radiografias periapicais padronizadas em intervalos de 21 dias, 3, 6 e 12 meses, após a instalação dos implantes. As imagens radiográficas foram digitalizadas e realizada a subtração radiográfica digital pelo programa emago, sendo comparadas com a radiografia inicial. Os resultados obtidos neste estudo mostraram uma regularidade no remodelamento ósseo ao longo do tempo para todos os implantes, não tendo sido encontradas diferenças significativas entre os diferentes implantes analisados.

MEMS for Diabetic Retinopathy

As the worldwide prevalence of diabetes mellitus continues to increase, diabetic retinopathy remains the leading cause of visual impairment and blindness in many developed countries. Between 32 to 40 percent of about 246 million people with diabetes develop diabetic retinopathy. Approximately 4.1 million American adults 40 years and older are affected by diabetic retinopathy. This glucose-induced microvascular disease progressively damages the tiny blood vessels that nourish the retina, the light-sensitive tissue at the back of the eye, leading to retinal ischemia (i.e., inadequate blood flow), retinal hypoxia (i.e., oxygen deprivation), and retinal nerve cell degeneration or death. It is a most serious sight-threatening complication of diabetes, resulting in significant irreversible vision loss, and even total blindness.

Unfortunately, although current treatments of diabetic retinopathy (i.e., laser therapy, vitrectomy surgery and anti-VEGF therapy) can reduce vision loss, they only slow down but cannot stop the degradation of the retina. Patients require repeated treatment to protect their sight. The current treatments also have significant drawbacks. Laser therapy is focused on preserving the macula, the area of the retina that is responsible for sharp, clear, central vision, by sacrificing the peripheral retina since there is only limited oxygen supply. Therefore, laser therapy results in a constricted peripheral visual field, reduced color vision, delayed dark adaptation, and weakened night vision. Vitrectomy surgery increases the risk of neovascular glaucoma, another devastating ocular disease, characterized by the proliferation of fibrovascular tissue in the anterior chamber angle. Anti-VEGF agents have potential adverse effects, and currently there is insufficient evidence to recommend their routine use.

In this work, for the first time, a paradigm shift in the treatment of diabetic retinopathy is proposed: providing localized, supplemental oxygen to the ischemic tissue via an implantable MEMS device. The retinal architecture (e.g., thickness, cell densities, layered structure, etc.) of the rabbit eye exposed to ischemic hypoxic injuries was well preserved after targeted oxygen delivery to the hypoxic tissue, showing that the use of an external source of oxygen could improve the retinal oxygenation and prevent the progression of the ischemic cascade.

The proposed MEMS device transports oxygen from an oxygen-rich space to the oxygen-deficient vitreous, the gel-like fluid that fills the inside of the eye, and then to the ischemic retina. This oxygen transport process is purely passive and completely driven by the gradient of oxygen partial pressure (pO₂). Two types of devices were designed. For the first type, the oxygen-rich space is underneath the conjunctiva, a membrane covering the sclera (white part of the eye), beneath the eyelids and highly permeable to oxygen in the atmosphere when the eye is open. Therefore, sub-conjunctival pO₂ is very high during the daytime. For the second type, the oxygen-rich space is inside the device since pure oxygen is needle-injected into the device on a regular basis.

To prevent too fast or too slow permeation of oxygen through the device that is made of parylene and silicone (two widely used biocompatible polymers in medical devices), the material properties of the hybrid parylene/silicone were investigated, including mechanical behaviors, permeation rates, and adhesive forces. Then the thicknesses of parylene and silicone became important design parameters that were fine-tuned to reach the optimal oxygen permeation rate.

The passive MEMS oxygen transporter devices were designed, built, and tested in both bench-top artificial eye models and in-vitro porcine cadaver eyes. The 3D unsteady saccade-induced laminar flow of water inside the eye model was modeled by computational fluid dynamics to study the convective transport of oxygen inside the eye induced by saccade (rapid eye movement). The saccade-enhanced transport effect was also demonstrated experimentally. Acute in-vivo animal experiments were performed in rabbits and dogs to verify the surgical procedure and the device functionality. Various hypotheses were confirmed both experimentally and computationally, suggesting that both the two types of devices are very promising to cure diabetic retinopathy. The chronic implantation of devices in ischemic dog eyes is still underway.

The proposed MEMS oxygen transporter devices can be also applied to treat other ocular and systemic diseases accompanied by retinal ischemia, such as central retinal artery occlusion, carotid artery disease, and some form of glaucoma.

Avaliação da corrosão microbiológica do aço carbono 1020 em água do mar sintética na presença de bactérias redutoras de sulfato

Bactérias redutoras de sulfato (BRS) possuem um papel importante na corrosão de ligas metálicas expostas em hábitats marinhos, óleos e solos úmidos. A redução do sulfato por estas bactérias resulta na produção de H2S, podendo influenciar os processos anódico e catódico na corrosão de materiais. Neste trabalho, o comportamento da corrosão microbiológica no aço carbono AISI 1020 foi avaliada em meio Postgate C, na presença e na ausência de BRS, as quais foram isoladas da camada de ferrugem presente numa tubulação submersa da Baía de Guanabara RJ. A taxa de corrosão e o comportamento eletroquímico do aço nas duas condições foram investigados através dos métodos de perda de massa e de polarização potenciodinâmica. A formação do biofilme e dos produtos de corrosão na superfície do aço foram observados por microscopia eletrônica de varredura (MEV) e por espectroscopia de energia dispersiva (EDS). Em complementação, foi realizada a quantificação das BRS (planctônicas e sésseis) pelo método do número mais provável (NMP). A presença de BRS no meio ocasionou o deslocamento do potencial de corrosão para valores mais negativos em todos os tempos de ensaio estudados, indicando um aumento no processo corrosivo. Nos ensaios de perda de massa, a taxa de corrosão do aço carbono foi maior na ausência de BRS, provavelmente devido à formação de um biofilme na superfície do metal nos ensaios com inóculo, e a uma menor tendência de haver corrosão generalizada neste tipo de meio. As micrografias de MEV revelaram a presença de agregado celular na superfície do aço carbono durante o experimento, e a presença de pites profundos após remoção do biofilme, mostrando prevalência deste tipo de corrosão. Com 35 dias de ensaio, a densidade de corrente de corrosão aumentou na presença de BRS

Experimental study of nonlinear switching characteristics of conventional 2×2 fused tapered couplers

The nonlinear switching characteristics of fused fiber directional couplers were studied experimentally. By using femtosecond laser pulses with pulse width of 100 fs and wavelength of about 1550 nm from a system of Ti:sapphire laser and optical parametric amplifier (OPA), the nonlinear switching properties of a null coupler and a 100% coupler were measured. The experimental results were coincident with the simulations based on nonlinear propagation equations in fiber by using super-mode theory. Nonlinear loss in fiber was also measured to get the injected power at the coupler. After deducting the nonlinear loss and input efficiency, the nonlinear switching critical peak powers for a 100% and a null fused couplers were calculated to be 9410 and 9440 W, respectively. The nonlinear loss parameter P_(N) in an expression of α_(NL)=αP/P_(N) was obtained to be P_(N)=0.23 W.