Back somersault is a basic element of gymnastics; its performance is strongly influenced by the take-off phase. The present work aimed to study how hip extension in the take-off of the tucked back somersault influences the velocity of rotation and the height of t h e somersault. To this end, we recorded a total of 60 somersaults by 4 gymnasts (i.e., 15 somersaults each). There were three groups of somersaults based on the instructions that were given to the gymnasts: no specific instruction, somersault as high as possible and rotate as fast as possible. The records were then analyzed in order to quantify the following variables: maximal height of the mass center and maximal body angular velocity during somersault, the hip angle and the knee angle at the take-off. Gymnasts seemed to be inclined to bend their knees rather than extend their hips in order to carry out the instruction.

Trans-resveratrol, total antioxidant capacity (TAC), and total phenolic compounds were assessed in Bolivian grape cultivars collected at high altitude valleys. The TAC of the grapes ranged from 0.8 to 22 μmol Trolox equivalents/g dry matter determined by 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid), and from 0.6 to 10 determined by the ferric reduction antioxidant power. In the present study, we observed that under certain conditions trans-resveratrol levels in Bolivian grapes are 10-fold higher than the reported data from the literature. Additionally, the temporal evolution in three different solar ultraviolet-B radiation levels was carried out to understand their effect on the oxidative processes.

Analysis of existing potential precursors in Bolivia, and processes for obtaining semiconductor metal sulfides (In 2S3, SnS 2 and CuInS 2) were made, key materials in the energy field, photovoltaic panels, photocatalytic processes, systems Lithium ion accumulation and others were done. Two methods of synthesis (chemical bath deposition and solvothermal) were developed, evaluating the role of precursors, complexing agents, and sulfur source, characterizing the crystallinity, morphology, and semiconducting properties of the products obtained. ‡ Original Spanish title : Perspectivas en el desarrollo de sulfuros metalicos semiconductores de interes tecnologico en bolivia

We optimized the purity in lithium manganese oxide (Spinel or LiMn 2O4) cathode material, using the response surface methodology (MSR), in function of the variables (temperature and time) in solid state reactions. The obtained product has been optimized at 782 ° C and 12.8 hours of reaction in air atmosphere, this product have a purity of 99.4 ± 0.4%, with a particle diameter in order of 6 ± 1 �m, and a surface area 1.015 m 2 /g, the conductance is 1.57 × 10 -3 S /m, with a specific capacity of 116 mA - hr/g, these parameters are comparable with commercial LiMn 2O4 cathode materials for LIB. The kinetic study of the reaction has an expression of velocity

The existing aspects about synthesis, characterization and electrochemical properties of different electrodes for lithium ion batteries are analyzed. Identification and synthesis of precursors are included and also the processes of these materials obtaining in Bolivia. The commercial properties for these materials offered by different companies are mentioned. Finally local synthesis of two cathode electrodes (LiMn 2O4) and (LiFePO 4) from potential precursors present in Bolivia are reported.

In the present paper, synthetic methods of lithium titanate (Li4Ti5O12) have been investigated by atraneroute reaction.The crystal structure of the sample wa...

La jatata (Geonoma deversa) es una palmera tropical con un larga historia de aprovechamiento tradicional para la elaboraci´on de pa ˜nos utilizados para techados de adorno, que son elaborados principalmente por el grupo ´etnico T’simane. Estos pa ˜nos han sido introducidos y comercializados en el ´area urbana de las tres capitales principales de Bolivia, sufriendo un deterioro en la estructura misma de la hoja, principalmente en la ciudad de La Paz, lo que provoca una dram´atica disminuci´on en su tiempo de vida, siendo las causas posibles de este da ˜no las condiciones clim´aticas a las que fueron expuestas. En este trabajo se realiz´o un estudio de la fragilidad de las hojas de jatata bajo cambios t´ermicos, h´idricos, y exposiciones a radiaci´on UV. Se encontr´o que los ciclos diarios de humedad de La Paz (saturaci ´on a seco) causan los mayores da ˜nos a las hojas de jatata

In the present work, aqueous cyanide has been eliminated by addition of H2O2 as oxidant agent, and by heterogeneousphotocatalysis with titanium oxide activat...

Measurements and model calculations have been performed to study the effect of high surface albedo on erythemally effective UV irradiance. A central part of the investigation has been a one week measurement campaign at Salar de Uyuni in the Southern part of the Bolivian Altiplano. The Salar de Uyuni, the largest salt lake of the world, is characterized by largely homogeneous surface conditions during most of the year. Albedo measurements performed by an UV radiometer result in a reflectivity for erythemally effective radiation of 0.69 +/- 0.02. The measurements show hardly any dependency on solar elevation, indicating the homogeneity of the surface and nearly isotropic reflection properties of the Salar.The effects of the high albedo surface on the erythemally effective irradiance, i.e. the UV index (UVI), has been experimentally determined by simultaneous measurements of several UV radiometers located at different sites around and on the Salar. In this context a method for the minimization of systematic deviations between the individual detectors used for the investigation is presented. It ensures the intercomparability of the performed UV measurements within +/- 2% which is a distinct improvement compared to the typical absolute accuracy of UV irradiance measurements in the order of +/- 5%. For solar elevations around 50 degrees the UVI measured close to the center of the Salar is typically enhanced by 20% compared to the values determined outside. Towards lower solar elevations this increase becomes slightly weaker. The measurements agree well with both, own corresponding ID and previously published 3D radiative transfer calculations from literature. (c) 2006 Elsevier B.V. All rights reserved.

In July and August 2003 a field campaign was conducted to explore the diurnal circulation of the Bolivian Altiplano. Vertical soundings by remote-controlled aircraft yielded profiles of temperature, pressure, and humidity at six passes and in a valley. Pilot balloon observations provided wind profiles. Two permanent stations collected additional data. Typically, inflow toward the Altiplano commences a few hours after sunrise at about the time when the stable nocturnal layer near the ground is transformed by the solar heating into an almost neutrally stratified convective boundary layer. The depth of the inflow layer is comparable to but normally less than that of this boundary layer. There are indications of return flow aloft. The inflow continues at least until sunset. Moisture is imported at the passes leading to the Yungas in the east. Strong upvalley flows were found in the valley of the Rio de La Paz, which connects the wide canyon of La Paz with the tropical lowlands to the east. Inflow was absent at one of the passes despite favorable synoptic conditions. Cases of synoptically forced flows are presented as well where the diurnal signal is difficult to separate. A simple flow scheme is presented that fits the observations reasonably well.

Field measurements of reactive halogen and sulfur gas emissions were performed at the world's largest salt pan, the Salar de Uyuni, Southern Altiplano, Bolivia (19.8°–20.7°S, 67.0°–68.2°W), during the dry season in October/November 2002. Bromine monoxide (BrO) and sulfur dioxide (SO2) were studied by ground‐based scattered light Multi Axis Differential Optical Absorption Spectroscopy (MAX‐DOAS) at various locations upwind and inside the salar. Significant amounts of BrO were found at all locations with the lowest levels at the northern edge of the salar (upwind), while BrO slant column densities (differential with respect to zenith) of up to 3.7 × 1014 molec/cm2 were observed inside the salar. Using the MAX‐DOAS vertical profile information BrO mixing ratios of >20 ppt are calculated, which can have significant impact on tropospheric ozone chemistry both locally and regionally. SO2 slant column densities of >5 × 1016 molec/cm2 were found around the salar, suggesting emissions from volcanic activity.

We present main results of a 5 years ozonemeasurements program at La Paz, Bolivia, wherea Brewer spectrophotometer is in operation sinceJuly 1996. We also show interesting comparisonswith “overpassing” satellite data, taken by theTOMS (Total Ozone Mapping Spectrophotometer).Finally, results of an ozone sondecampaign, carried out in order to explore apossibly ozone anomaly over the AndeanHighland, are reported.