Precision mapping

The nondestructive determination of plant total dry matter (TDM) in the field is greatly preferable to the harvest of entire plots in areas such as the Sahel where small differences in soil properties may cause large differences in crop growth within short distances. Existing equipment to nondestructively determine TDM is either expensive or unreliable. Therefore, two radiometers for measuring reflected red and near-infrared light were designed, mounted on a single wheeled hand cart and attached to a differential Global Positioning System (GPS) to measure georeferenced variations in normalized difference vegetation index (NDVI) in pearl millet fields [Pennisetum glaucum (L.) R. Br.]. The NDVI measurements were then used to determine the distribution of crop TDM. The two versions of the radiometer could (i) send single NDVI measurements to the GPS data logger at distance intervals of 0.03 to 8.53 m set by the user, and (ii) collect NDVI values averaged across 0.5, 1, or 2 m. The average correlation between TDM of pearl millet plants in planting hills and their NDVI values was high (r^2 = 0.850) but varied slightly depending on solar irradiance when the instrument was calibrated. There also was a good correlation between NDVI, fractional vegetation cover derived from aerial photographs and millet TDM at harvest. Both versions of the rugged instrument appear to provide a rapid and reliable way of mapping plant growth at the field scale with a high spatial resolution and should therefore be widely tested with different crops and soil types.

Molecular mechanisms controlling the precision of chemokine guided cell migration

By the end of the first day of embryonic development, zebrafish primordial germ cells (PGCs) arrive at the site where the gonad develops. In our study we investigated the mechanisms controlling the precision of primordial germ cell arrival at their target. We found that in contrast with our expectations which were based on findings in Drosophila and mouse, the endoderm does not constitute a preferred migration substrate for the PGCs. Rather, endoderm derivatives are important for later stages of organogenesis keeping the PGC clusters separated. It would be interesting to investigate the precise mechanism by which endoderm controls germ cell position in the gonad. In their migration towards the gonad, zebrafish germ cells follow the gradient of chemokine SDF-1a, which they detect using the receptor CXCR4b that is expressed on their membrane. Here we show that the C-terminal region of CXCR4b is responsible for down-regulation of receptor activity as well as for receptor internalization. We demonstrate that receptor molecules unable to internalize are less potent in guiding germ cells to the site where the gonad develops, thereby implicating chemokine receptor internalization in facilitating precision of migration during chemotaxis in vivo. We demonstrate that while CXCR4b activity positively regulates the duration of the active migration phases, the down-regulation of CXCR4b signalling by internalization limits the duration of this phase. This way, receptor signalling contributes to the persistence of germ cell migration, whereas receptor down-regulation enables the cells to stop and correct their migration path close to the target where germ cells encounter the highest chemokine signal. Chemokine receptors are involved in directing cell migration in different processes such as lymphocyte trafficking, cancer and in the development of the vascular system. The C-terminal domain of many chemokine receptors was shown to be essential for controlling receptor signalling and internalization. It would therefore be important to determine whether the role for receptor internalization in vivo as described here (allowing periodical corrections to the migration route) and the mechanisms involved (reducing the level of signalling) apply for those other events, too.

Precision laser spectroscopy of the ground state hyperfine splitting of hydrogenlike ^209 Bi^82+

The first direct observation of a hyperfine splitting in the optical regime is reported. The wavelength of the M1 transition between the F = 4 and F = 5 hyperfine levels of the ground state of hydrogenlike ^209 Bi^82+ was measured to be \lamda_0 = 243.87(4) nm by detection of laser induced fluorescence at the heavy-ion storage ring ESR at GSI. In addition, the lifetime of the laser excited F = 5 sublevel was determined to be \tau_0 = 0.351(16) ms. The method can be applied to a number of other nuclei and should allow a novel test of QED corrections in the previously unexplored combination of strong magnetic and electric fields in highly charged ions.

Performance Evaluation of the Scheme 86 and HP Precision Architecture

The Scheme86 and the HP Precision Architectures represent different trends in computer processor design. The former uses wide micro-instructions, parallel hardware, and a low latency memory interface. The latter encourages pipelined implementation and visible interlocks. To compare the merits of these approaches, algorithms frequently encountered in numerical and symbolic computation were hand-coded for each architecture. Timings were done in simulators and the results were evaluated to determine the speed of each design. Based on these measurements, conclusions were drawn as to which aspects of each architecture are suitable for a high- performance computer.

Assessing the Precision of Compositional Data in a Stratified Double Stage Cluster Sample: Application to the Swiss Earnings Structure Survey

Precision of released figures is not only an important quality feature of official statistics, it is also essential for a good understanding of the data. In this paper we show a case study of how precision could be conveyed if the multivariate nature of data has to be taken into account. In the official release of the Swiss earnings structure survey, the total salary is broken down into several wage components. We follow Aitchison's approach for the analysis of compositional data, which is based on logratios of components. We first present diferent multivariate analyses of the compositional data whereby the wage components are broken down by economic activity classes. Then we propose a number of ways to assess precision

Peer Tutors in the School of Medicine

Since 2003 the School of Medicine at the Universidad del Rosario in Bogotá, Colombia, offers to the students a program named Peer Tutors. The program’s objectives are: to generate a social interaction mechanism that favors knowledge construction side by side with advanced peers; to promote the development of ethical, moral and coexistence oriented values through an academic experience, and to generate a space to explore specific academic interests and teacher´s potential. This article presents the theoretic frame that supports the importance of social interaction in knowledge construction, as well as some indicators that allow a first appraisal of the program. Several achievements that account for the synergic value of an experience that not only fulfills the function of initiating a process of teaching formation and academic support, but that also builds a proactive attitude before learning, are highlighted.

Some Topics in Relation to José Celestino Mutis and Medicine

José Celestino Mutis showed different interest areas of study and worked in multiple knowledge fields: mathematics, mineralogy, astronomy, zoology and botanic, the one in which is best known. However, he was a medical doctor, whit profound an up to date knowledge. He studied at Sevilla University, and in the Royal College of Cadiz. He arrived to the “Nuevo Reino de Granada” as personal medical doctor of the the viceroy Pedro Messía de la Cerda and during 47 years, period of time he lived there, he always exercised his profession. We showed a special interest in the study of cinchona and the only work he published was El Arcano de la quina. He advised in public health many viceroys and he contributed in different fields but particularly in the prevention of smallpox by inoculation. He played a decisive role in the reopening of the medical school of the Colegio Mayor de Nuestra Señora del Rosario. Some of his achievements justifies the appellative “Father of the Medicine in Colombia”.

Auditory difference limen for duration in deaf and hearing listeners

This paper reviews a study to determine if deaf children can discriminate fine durational changes in acoustic signals or whether the impairment of the peripheral auditory system interferes with the temporal precision necessary for such tasks.