Electron temperature measurements in a copper chloride laser utilizing a microwave radiometer

The electron temperature as a function of laser tube temperature of a copper vapor laser utilizing copper chloride as a lasant has been obtained by measuring the microwave incoherent radiation from the plasma in the laser tube. An unexpected increase of electron temperature at higher laser tube temperature may be due mainly to Penning ionization of the Cu atom by the metastable state of He or Ne buffer gases. The results obtained in this work provide part of the basis for understanding the behavior of the laser output as a function of tube temperature

A 10 GHz Quasi-Optical Grid Amplifier Using Integrated HBT Differential Pairs

We report the fabrication and testing of a 10 GHz grid amplifier utilizing sixteen GaAs chips each containing an HBT differential pair plus integral bias/feedback resistors. The overall amplifier consists of a 4x4 array of unit cells on an RT Duroid™ board having a relative permittivity of 2.2. Each unit cell consists of an emitter-coupled differential pair at the center, an input antenna which extends horizontally in both directions from the two base leads, an output antenna which extends vertically in both directions from the two collector leads, and high inductance bias lines. In operation, the active grid array is placed between a pair of crossed polarizers. The horizontally polarized input wave passes through the input polarizer and couples to the input leads. An amplified current then flows on the vertical leads, which radiate a vertically polarized amplified signal through the output polarizer. The polarizers serve dual functions, providing both input-output isolation as well as independent impedance matching for the input and output ports. The grid thus functions essentially as a free-space beam amplifier. Calculations indicate that output powers of several watts per square centimeter of grid area should be attainable with optimized structures

Historical and Typological Characterization of Churches in the Historical Centre of Cusco, Peru

UNESCO declared Cusco a historical site due to the importance of its constructions and traditions. However, Cusco lies on an active tectonic area with several plate faults and thus, is prone to endure seismic activity. The 1650 and 1950 earthquakes had devastating consequences on churches, with collapses of bell towers, roofs and vertical walls. After these earthquakes, the churches became more complex because of reinforcement and diverse structural changes introduced. Therefore, it is necessary to understand their current static and dynamic behaviour. In addition, it is fundamental to establish control measures to preserve churches and to guarantee safety of the hosted people, as well as to protect the artistic, architectural and cultural treasures they contain. The first step, however, is to survey the churches and to fully identify their structural features. This article presents a description of the architectural and structural typologies of the churches in the historic centre of Cusco and its relation to the most common failure mechanisms experienced by churches during earthquakes. To this end, this research carefully recreates typologies, geometry, materials and interventions carried on over centuries on these churches. It contributes to the seismic vulnerability knowledge of the studied churches and gives conclusions for decision-makers in future resilience plans

Avian Influenza in Wild Birds, Central Coast of Peru

To determine genotypes of avian influenza virus circulating among wild birds in South America, we collected and tested environmental fecal samples from birds along the coast of Peru, June 2006–December 2007. The 9 isolates recovered represented 4 low-pathogenicity avian influenza strains: subtypes H3N8, H4N5, H10N9, and H13N2

Circulating Strains of Human Respiratory Syncytial Virus in Central and South America

Human respiratory syncytial virus (HRSV) is a major cause of viral lower respiratory tract infections among infants and young children. HRSV strains vary genetically and antigenically and have been classified into two broad subgroups, A and B (HRSV-A and HRSV-B, respectively). To date, little is known about the circulating strains of HRSV in Latin America. We have evaluated the genetic diversity of 96 HRSV strains by sequencing a variable region of the G protein gene of isolates collected from 2007 to 2009 in Central and South America. Our results show the presence of the two antigenic subgroups of HRSV during this period with the majority belonging to the genotype HRSV-A2

Historical and Typological Characterization of Churches in the Historical Centre of Cusco, Peru

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