Hydroclimatology: Perspectives and Applications,by Marlyn L. Shelton

The interstellar space of the spiral arms of our galaxy contains dust clouds in which some 20 kinds of molecule are now known to exist. Many of the molecules are polyatomic. Only five years ago the general opinion was that such molecules could not survive the ultraviolet radiation thought to be present. At that time the diatomic CH, CH + and CN were known from the optical work of the 1930's, and the OH line had been studied for five years by radio-telescopes. But in 1968 observation showed that the climate of interstellar space was not hostile to even fairly complex molecules. They are there within rolatively cool dense clouds of molecular hydrogen that contains the dust particles whose surface may facilitate formation of the molecules, and whose presence certainly protects them from the ultraviolet radiation of stars.

This review tells how the emission and absorption of spectral lines, revealing the presence of molecules, can also furnish estimates of their numbers, densities and isotopic abundances. Departures from thermal equilibrium, including maser and reverse maser action are mentioned. The radio-telescopes and their spectrometers are described.     

Lift‐off protocols for thin films for use in EXAFS experiments

Lift‐off protocols for thin films for improved extended X‐ray absorption fine structure (EXAFS) measurements are presented. Using wet chemical etching of the substrate or the interlayer between the thin film and the substrate, stand‐alone high‐quality micrometer‐thin films are obtained. Protocols for the single‐crystalline semiconductors GeSi, InGaAs, InGaP, InP and GaAs, the amorphous semiconductors GaAs, GeSi and InP and the dielectric materials SiO₂ and Si₃N₄ are presented. The removal of the substrate and the ability to stack the thin films yield benefits for EXAFS experiments in transmission as well as in fluorescence mode. Several cases are presented where this improved sample preparation procedure results in higher‐quality EXAFS data compared with conventional sample preparation methods. This lift‐off procedure can also be advantageous for other experimental techniques (e.g. small‐angle X‐ray scattering) that benefit from removing undesired contributions from the substrate.     

When does management matter in a dog-eat-dog world: An “Interaction Value Analysis” model of organizational climate

Interaction Value Interaction Value Analysis (I.V.A.) models a network of rational actors who generate value by interacting with each other. This model can be used to understand human organizations. Since people form organizations to facilitate interactions between productive individuals, the value added by interaction is the contribution of the organization. This paper examines the result of varying the queuing discipline used in selecting among back-logged interaction requests. Previously developed I.V.A. models assumed a First-in-first-out (FIFO) discipline, but using other disciplines can better represent the “Climate” of an organization. I.V.A. identifies circumstances under which organizations that control members’ interaction choices outperform organizations where individuals choose their own interaction partners. Management can be said to “matter” when individual choices converge to a point where interactions generate a lower than optimal value. In previous I.V.A. models, relinquishing central control of interaction choices reduced the aggregate value by anything from 0% to 12%, depending on circumstances. This paper finds the difference between the two modes of organization to go as high as 47% if actors display preferences between interaction partners instead of treating all equally. A politically divided, dog-eat-dog, “Capitalist” climate follows one queuing discipline, which is found to generally increase the value that a strong control structure can add. A chummy, in-bred “Fraternal” climate gains from control in some circumstances (low interdependence or low differentiation), but not in others (high or medium interdependence and differentiation under low diversity, for example). These are compared to the previous version of I.V.A., in which the queuing discipline was FIFO and the climate deemed “Disciplined”. Previously published findings on Organizational Climate are duplicated and extended with a higher level of detail. Priority queuing in an I.V.A. model is thus a useful proxy for Organizational Climate, open to future validation because its detailed predictions can be confirmed or falsified by observation. Walid Nasrallah is currently Assistant Professor in the Engineering Management program at the American University of Beirut (AUB). He received his Ph.D. from the Construction Engineering and Management program at Stanford University in 2000 and his Master’s degree at MIT in 1989. Between the two, he occupied several positions in the construction and software engineering fields. His research interests today include simulation, decision theory, and the evolution of organizations in response to new technologies.     

Weak complexes of sulphur and selenium: a thermodynamic view on solvent effects in mixed solvents

The effect of mixed solvent on complex stability is discussed from a thermodynamic standpoint. The variation in the free energy of formation for a complex species in different solvent mixtures is an indication of solvent-solute and solvent-solvent interactions. The complexity of the systems in mixed solvents makes entropy data difficult to interpret. Evidence is given on solvent-solvent interactions.     

Fast Neutron Albedo Calculations for a Concrete Shield with Different Curvatures

The O5R Monte Carlo neutron transport Code had been used to calculate the neutron albedo for neutrons reflected from plane and curved concrete shields. The present calculations were performed to investigate the fast-neutron albedo in case of ordinary concrete shield, in order to perform comparative studies with the case of neutron reflection against a flat wall. The calculations were performed for three different neutron source energies of 1 MeV, 5 MeV and 15 MeV and at neutron incident angles of 5°, 30°, 45°, 60° and 90° and for surfaces with different curvatures (flat, 100, 50, 20 and 5 cm). The results obtained reveal that there will be an appreciable error on using the flat wall albedo value in the case of duct penetration calculations. The error was assumed to be due to the neglection of the curvature effect as well as to the improper choice of the neutron incident angle.     

New Converging Collimator for Cold Neutrons Time-Of-Flight Measurements

An idea to design a new converging collimator for cold neutron time-of-flight measurements is presented. Using this new facility in combination with a neutron time-of-flight spectrometer, we may have neutron intensity gain factors about three times that obtained using the conventional straight slit collimators. Expressions for calculating the collimators dimensions as well as the intensity gain and the time resolution broading were presented.     

Blood flow evaluation in high-frequency, 40 MHz imaging: A comparative study of four vector velocity estimation methods

Ultrasonic imaging is often used to estimate blood flow velocity. Currently, estimates are carried out using Doppler-based techniques. However, there are a number of shortcomings such as the limited spatial resolution and the inability to estimate longitudinal flows. Thus, alternative methods have been proposed to overcome them. Difficulties are notably encountered with high-frequency imaging systems that use swept-scan techniques. In this article, we propose to compare four vector velocity estimation methods that are complementary to Doppler, focusing on 40 MHz, high-frequency imaging. The goal of this study is to evaluate which method could circumvent the limitations of Doppler methods for evaluation of microcirculation, in the vessels having diameter on the order of 1 mm. We used two region-based approaches, one decorrelation-based approach and one spatiotemporal approach. Each method has been applied to seven flow sequences with various orientations and mean velocities. Four sequences were simulated with a system approach based on a 3D set of moving scatterers. Three experimental sequences were carried out by injecting blood-mimicking fluid within a gelatin phantom and then acquiring images with Visualsonics, Vevo 660 system. From velocity estimates, several performance criteria such as the normalized mean error or the normalized mean standard deviation were defined to compare the performance of the four estimators. The results show that region-based methods are the most accurate exhibiting mean errors less than 10% and mean standard deviation less than 13%. However, region-based approaches are those that require the highest calculative cost compared to the decorrelation-based method, which is the fastest. Finally, the spatiotemporal approach appeared to be a trade-off in terms of computational complexity and accuracy of estimates. It provides estimates with errors less than 10% for mean velocity and the CPU time is approximately 17 s for a ROI of size 40 * 80 pixels.