A compact spectroradiometer for solar simulator measurements

Compact spectral irradiance probe has been designed and built which uses wedge filter in conjunction with silicon cell and operational amplifier. Probe is used to monitor spectral energy distribution of solar simulators and other high intensity sources

A Predictive Model for Convective Flows Induced by Surface Reactivity Contrast

Concentration gradients in a fluid along a reactive surface due to contrast in surface reactivity generate convective flows. These flows result from contributions by electro and diffusio osmotic phenomena. In this study we have analyzed reactive patterns that release and consume protons, analogous to bimetallic catalytic conversion of peroxide. Here, we present a simple analytical model that accurately predicts the induced potentials and consequent velocities in such systems over a wide range of input parameters. Our model is tested against direct numerical solutions to the coupled Poisson, Nernst-Planck, and Navier-Stokes equations. Our analysis can be used to predict enhancement of mass transport and the resulting impact on overall catalytic conversion, and is also applicable to predicting the speed of catalytic nanomotors

Quantitative functional interrelations within the cis-regulatory system of the S. purpuratus Endo16 gene

Embryonic expression of the Endo16 gene of Strongylocentrotus purpuratus is controlled by interactions with at least 13 different DNA-binding factors. These interactions occur within a cis-regulatory domain that extends about 2300 bp upstream from the transcription start site. A recent functional characterization of this domain reveals six different subregions, or cis-regulatory modules, each of which displays a specific regulatory subfunction when linked with the basal promoter and in some cases various other modules (C.-H. Yuh and E. Davidson (1996) Development 122, 1069-1082). In the present work, we analyzed quantitative time-course measurements of the CAT enzyme output of embryos bearing expression constructs controlled by various Endo16 regulatory modules, either singly or in combination. Three of these modules function positively in that, in isolation, each is capable of promoting expression in vegetal plate and adjacent cell lineages, though with different temporal profiles of activity. Models for the mode of interaction of the three positive modules with one another were tested by assuming mathematical relations that would generate, from the measured single module time courses, the experimentally observed profiles of activity obtained when the relevant modules are physically linked in the same construct. The generated and observed time functions were compared, and the differences were minimized by least squares adjustment of a scale parameter. When the modules were tested in context of the endogenous promoter region, one of the positive modules (A) was found to increase the output of the others (B and G), by a constant factor. In contrast, a solution in which the time-course data of modules A and B are multiplied by one another was required for the interrelations of the positive modules when a minimal SV40 promoter was used. One interpretation is that, in this construct, each module independently stimulates the basal transcription complex. We used a similar approach to analyze the repressive activity of the three Endo16 cis-regulatory modules that act negatively in controlling spatial expression. The evidence obtained confirms that the repressive modules act only by affecting the output of module A (C.-H. Yuh and E. Davidson (1996) Development 122, 1069-1082). A new hierarchical model of the cis-regulatory system was formulated in which module A plays a central integrating role, and which also implies specific functions for certain DNA-binding sites within the basal promoter fragment of the gene. Additional kinetic experiments were then carried out, and key aspects of the model were confirmed

Unitary ambiguity in the extraction of the E2/M1 ratio for the γN↔Δ\gamma N\leftrightarrow\Delta transition

The resonant electric quadrupole amplitude in the transition $\gamma N\leftrightarrow\Delta(1232)$ is of great interest for the understanding of baryon structure. Various dynamical models have been developed to extract it from the corresponding photoproduction multipole of pions on nucleons. It is shown that once such a model is specified, a whole class of unitarily equivalent models can be constructed, all of them providing exactly the same fit to the experimental data. However, they may predict quite different resonant amplitudes. Therefore, the extraction of the E2/M1($\gamma N\leftrightarrow\Delta$) ratio (bare or dressed) which is based on a dynamical model using a largely phenomenological $\pi N$ interaction is not unique.Comment: 10 pages revtex including 4 postscript figure

SpMyb functions as an intramodular repressor to regulate spatial expression of CyIIIa in sea urchin embryos

The CyIIIa actin gene of Strongylocentrotus purpuratus is transcribed exclusively in the embryonic aboral ectoderm, under the control of 2.3 kb cis-regulatory domain that contains a proximal module that controls expression in early embryogenesis, and a middle module that controls expression in later embryogenesis. Previous studies demonstrated that the SpRunt-1 target site within the middle module is required for the sharp increase in CyIIIa transcription which accompanies differentiation of the aboral ectoderm, and that a negative regulatory region near the SpRunt-1 target site is required to prevent ectopic transcription in the oral ectoderm and skeletogenic mesenchyme. This negative regulatory region contains a consensus binding site for the myb family of transcription factors. In vitro DNA-binding experiments reveal that a protein in blastula-stage nuclei interacts specifically with the myb target site. Gene transfer experiments utilizing CyIIIa reporter constructs containing oligonucleotide substitutions indicate that this site is both necessary and sufficient to prevent ectopic expression of CyIIIa. Synthetic oligonucleotides containing the myb target site were used to purify a protein from sea urchin embryo nuclear extracts by affinity chromatography. This protein is immunoprecipitated by antibodies specific to the evolutionarily conserved myb domain, and amino acid sequences obtained from the purified protein were found to be identical to sequences within the myb domain. Sequence information was used to obtain cDNA clones of SpMyb, the S. purpuratus member of the myb family of transcription factors. Through interactions within the middle module, SpMyb functions to repress activation of CyIIIa in the oral ectoderm and skeletogenic mesenchyme

Evidence for prelocalization of cytoplasmic factors affecting gene activation in early embryogenesis

Differentiation begins early in embryogenesis as different genes become active in different cells. Within the closed system of the early embryo, equal genomes thus direct the creation of diverse cell types. Though the nuclei of these cells contain complete copies of the same genome,(1,2) the nucleoplasmic and cytoplasmic environments of these genomes are not the same, as a result of the distribution of cleavage nuclei into diverse areas of egg cytoplasm early in the cleavage process. In some cases the fate of these nuclei, i.e., the type of differentiated cell to which they or their descendants give rise, has been seen to depend on the area of cytoplasm in which they come to lie

Impact reactivity of materials at very high oxygen pressure

The requirements for impact testing of materials in an oxygen atmosphere at pressures from 82.7 MPa (12,000 psi) to 172 MPa (25,000 psi) were evaluated. The impact tester system was evaluated for potential pressure increases from 69 MPa (10,000 psi) to 82.7 MPa (12,000 psi). The low pressure oxygen and nitrogen systems, the impact tower, the impact test cell, and the high pressure oxygen system were evaluated individually. Although the structural integrity of the impact test cell and the compressor were sufficient for operation at 82.7 MPa (12,000 psi), studies revealed possible material incompatibility at that pressure and above. It was recommended that if a component should be replaced for 82.7 MPa (12,000 psi) operation the replacement should meet the final objectives of 172 MPa (25,000 psi). Recommended changes in the system include; use of Monel 400 for pressures above 82.7 MPa (12,000 psi), use of bellows to replace the seal in the impact tester, use of a sapphire window attached to a fiber optic for event sensing, and use of a three diaphragm compressor

SpZ12-1, a negative regulator required for spatial control of the territory-specific CyIIIa gene in the sea urchin embryo

The CyIIIa cytoskeletal actin gene of the sea urchin Strongylocentrotus purpuratus is activated in late cleavage and expressed exclusively in the aboral ectoderm territory of the embryo. Previous gene transfer studies defined a 2.3 kb cis-regulatory region that is necessary and sufficient for correct temporal and spatial expression of a CyIIIa. CAT fusion gene. In this paper, a negative regulatory element within this region was identified that is required for repression of the CyIIIa gene in skeletogenic mesenchyme cells. The repression mediated by this regulatory element takes place after initial territorial specification. A cDNA clone encoding a DNA-binding protein with twelve Zn fingers (SpZ12-1) was isolated by probing an expression library with this cis-element. Deletion analysis of the SpZ12-1 protein confirmed that a DNA-binding domain is located within the Zn finger region. SpZ12-1 is the only DNA-binding protein in embryo nuclear extract that interacts with the specific cis-target sites required for repression of CyIIIa.CAT in skeletogenic mesenchyme and is likely to be the trans factor that mediates this repression

Range-Based Livestock Production in Turkmenistan

Turkmenistan retains a centralized system of livestock production in which many critical assets are owned by the state. Though technically in the temperate zone, the country\u27s climate is harsh and unstable. Groundwater resources are unevenly distributed, leaving many potential grazing areas seasonally inaccessible due to lack of drinking water for livestock. This paper summarizes the results of a three-year study of rangelands, livestock production, flock economics and land tenure at two study sites, one in central and the other in eastern Turkmenistan. The results of this study suggest that pastoral communities in Turkmenistan have coped remarkably well with the institutional changes that followed the demise of the Soviet Union, and with the country\u27s persistently unstable climate and scarce natural resources

Safety of Aggressive Lipid Management

Data from recent clinical trials of high- versus moderate-dose statin therapy support the recommendation to achieve a low-density lipoprotein (LDL) <100 mg/dl in high-risk patients and reveal that many patients will require a high-dose statin to achieve this goal. Overall, low rates of serious musculoskeletal (<0.6%) and hepatic (<1.3%) toxicity have been observed with high-dose statin therapy. In the long-term trials, atorvastatin 80 mg had higher rates of persistent transaminase elevations but rates of myopathy and rhabdomyolysis similar to lower doses of statins. The rate of myopathy and rhabdomyolysis for simvastatin 80 mg, although still low, was about 4× higher than for atorvastatin 80 mg and lower doses of statin. A similar margin of safety would be expected in properly selected patients with characteristics similar to those who participated in the clinical trials. High-dose statin therapy or combination therapy will be required for the large majority of very high-risk patients to achieve the optional LDL goal of <70 mg/dl. While the combination of ezetimibe, bile-acid sequestering agents, niacin, and fenofibrate with moderate dose statins appears to be reasonably safe, the long-term safety of combination with high-dose statins remains to be established. In order to optimize patient outcomes, clinicians should be aware of specific patient characteristics, such as advancing age, gender, body mass index, or glomerular filtration rate, which predict muscle and hepatic statin toxicity