ResumenEn las últimas décadas, la ecografía veterinaria ha vivido un gran avance tecnológico y técni-co. Los médicos veterinarios no solo la utilizan para las valoraciones comunes de abdomen, o incluso corazón, sino que han descrito técnicas para exploraciones más especiales, como para el sistema musculoesquelético, el vascular, el ocular, entre otros. La literatura sobre el tema ha reseñado el desarrollo y aplicación de la ecografía ocular modo A, específica para la valoración oftalmológica por parte veterinarios especializados en esta área. Actualmente, un gran número de clínicas veterinarias cuenta con ecógrafos con modo B tiempo real, que permiten una excelente valoración descriptiva de la anatomía ocular para orientar posibles diagnósticos. Este artículo de revisión presenta de forma concisa las principales indicaciones de la ecografía ocular modo B y la técnica de realización, y describe cualitativamente las imágenes normales de la exploración de este órgano de los sentidos.Palabras clave: ecografía ocular, modo B, perros. Basic ocular ultrasound examination in dogs (real-time B-mode) AbstractIn recent decades, veterinary ultrasound has experienced a great technological and technical progress. Veterinary doctors not only use it for common evaluation of abdomen, or even heart, but techniques have been described for more special examinations, such as for the musculoskeletal, vascular, and ocular systems, among others. Literature on the subject has reviewed the development and application of A-mode ocular ultrasound, specific for ophthalmologic evaluation by veterinarians specialized in this area. Currently, a large number of veterinary clinics has real-time B-mode ultrasound scanners, which allow an excellent descriptive evaluation of the ocular anatomy to guide possible diagnoses. This review article concisely presents the main indications and realization technique for B-mode ocular ultrasound, as well as qualitatively describes normal scan images of this sense organ.

This paper addresses the performance of the bidirectional Dual Active Bridge (DAB) converter. One of the advantages of the DAB is the possibility to achieve Zero Voltage Switching (ZVS) operation in all the switches of this converter. However, the ZVS operation range can be lost for light loads, especially if high voltage is required in at least one of the DAB ports and the phase-shift control is used to regulate the power processed by the converter. Theoretically simple averaged and small-signal models are presented for the DAB converter. Using the study presented in this paper, the boundaries of ZVS operation can be easily evaluated. The proposed models and analysis of the ZVS boundaries allow the proposal and evaluation of two different design strategies with different purposes: on the one hand, increasing the ZVS operation range and, on the other, improving efficiency at full load. Moreover, some techniques are presented for increasing the ZVS operation range and improving the efficiency of the DAB at full load (both using phase-shift control) employing the aforementioned analysis to obtain certain design criteria and conclusions. Finally, the proposed models, design strategies and techniques to improve the performance of the DAB are experimentally tested using a 1kW prototype with input and output voltages of 48V and 400V, respectively. I.

This paper analyzes two modular power converter concepts, based on Cascaded H-Bridges (CHB) and Modular Multilevel Converter (MMC) topologies respectively, with special attention to the second design. Both have common characteristics and can provide the required functionalities for Power Electronic Transformers (PETs). Criteria for their analysis will include aspects like number of required cells, characteristics of the power devices, functionalities and potential uses. Conventional Line-Frequency Transformers (LFTs) are key elements in transmission and distribution systems to interface the different voltage levels in the grid. LFTs are a well established technology, they are relatively cheap, efficient and reliable. However, they have several limitations, including: voltage drop under load; sensitivity to harmonics, load imbalances and DC offsets; no overload protection and low efficiency when operate with low load levels or no load [1]. PETs, also called Solid State Transformers (SSTs), are envisioned as a semiconductor based alternative to LFTs. PETs are able to provide advanced functionalities such as power flow control, reactive power, harmonics and imbalances compensation, availability of low voltage DC (LVDC) link and smart protection. High switching frequencies of the semiconductors also enable a significant reduction of the volume and weight of the core material [1]-[4]. Generally speaking, PETs are expected to beat the LFTs in terms of power density and much superior functionalities, but would be inferior in terms of cost, efficiency (full load) and reliability. Based on this, there is a number of applications in which the use of PETs can be advantageous compared to standard LFTs. Smart-grid applications require an efficient integration of distributed generation and storage resources, flexible routing mechanisms, active filtering and protection mechanism. While power density might not be a key aspect for onshore applications, it can be of paramount importance for offshore applications [5]. Traction and subsea systems are also examples of space-critical applications in which the improved performances and power density of PETs compared to LFTs can be determinant [6], [7].

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In 1997, the Centers for Disease Control and Prevention, the Mexican Secretariat of Health, and border health officials began the development of the Border Infectious Disease Surveillance (BIDS) project, a surveillance system for infectious diseases along the U.S.-Mexico border. During a 3-year period, a binational team implemented an active, sentinel surveillance system for hepatitis and febrile exanthems at 13 clinical sites. The network developed surveillance protocols, trained nine surveillance coordinators, established serologic testing at four Mexican border laboratories, and created agreements for data sharing and notification of selected diseases and outbreaks. BIDS facilitated investigations of dengue fever in Texas-Tamaulipas and measles in California–Baja California. BIDS demonstrates that a binational effort with local, state, and federal participation can create a regional surveillance system that crosses an international border. Reducing administrative, infrastructure, and political barriers to cross-border public health collaboration will enhance the effectiveness of disease prevention projects such as BIDS.