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Interesting Trends (interesting + trend)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

The Changing Nature of Presidential Policy Making on International Agreements

PRESIDENTIAL STUDIES QUARTERLY, Issue 3 2006
GLEN S. KRUTZ
Why are executive agreements (EAs), rather than treaties, increasingly used to formalize U.S. relations with other countries? We examine this question from two perspectives. In the first, known as the "evasion" hypothesis, presidents act strategically to evade the Senate when governing circumstances are difficult. This strategic view reflects the conventional wisdom. Second, we consider whether organizational efficiency drives presidential use of EAs. As the number of countries increases, requiring more international agreements, it becomes necessary to rely more on an efficient mechanism to "get things done." We test these rival hypotheses by analyzing EA use as a percentage of all international agreements, as well as a subset of important EAs, from 1949 to 1998. In contrast to the conventional wisdom, we find consistent support for the efficiency hypothesis and only mixed support for the evasion hypothesis. Within these mixed findings, an interesting trend emerges. As expected, presidents act more strategically on the subset of important agreements, but this behavior appears to be driven by the ideological makeup of the Senate rather than partisan cleavages. [source]

Off the Back or on the Side: Comparison of meso and 2-Substituted Donor-Acceptor Difluoroborondipyrromethene (Bodipy) Dyads

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2010
Andrew C. Benniston
Abstract The preparation of several difluoroborondipyrromethene (Bodipy) dyads is described incorporating covalently attached hydroquinone/quinone groups at the 2-position (BD-SHQ, BD-SQ, BD-SPHQ, BD-SPQ). The compounds, currently under investigation as chemical sensors for reactive oxygen species, show various levels of fluorescence depending on the oxidation state of the appended group. The 19F NMR spectrum for BD-SHQ in CDCl3 at room temperature reveals the two fluorines are inequivalent on the NMR timescale. In contrast, the 19F NMR spectrum for the counterpart quinone compound, BD-SQ, is consistent with two equivalent fluorine atoms. The two results are interpreted as the quinone is free to rotate around the connector bond, whereas this motion is restricted for the hydroquinone group and makes the fluorines chemically inequivalent. Cyclic voltammograms recorded for all derivatives in CH2Cl2 electrolyte solution are consistent with typical Bodipy-based redox chemistry; the potentials of which depend on factors such as presence of the phenylene spacer and oxidation state of the appended group. A comparison of the electrochemical behaviour with the counterpart meso derivatives reveals some interesting trends which are associated with the location of the HOMO/LUMOs. The absorption profiles for the compounds in CH3CN are again consistent with Bodipy-based derivatives, though there are some subtle differences in the band-shapes of the closely-coupled systems. In particular, the absorption spectra for the dyad, BD-SQ, in a wide range of solvents are appreciably broader than for BD-SHQ. Femtosecond transient absorption spectroscopy performed on the hydroquinone derivatives, BD-SHQ and its meso analogue is interpreted as electron transfer occurs from the hydroquinone unit to the first-excited singlet (S1) state of the Bodipy center, followed by ultrafast charge recombination to reinstate the ground state. The coupling of OH vibrations to the return electron transfer process is invoked to explain the lack of clear identification of the charge-separated state in the transient records. [source]

Fountain flow revisited: The effect of various fluid mechanics parameters

AICHE JOURNAL, Issue 5 2010
Evan Mitsoulis
Abstract Numerical simulations have been undertaken for the benchmark problem of fountain flow present in injection-mold filling. The finite element method (FEM) is used to provide numerical results for both cases of planar and axisymmetric domains under laminar, isothermal, steady-state conditions for Newtonian fluids. The effects of inertia, gravity, surface tension, compressibility, slip at the wall, and pressure dependence of the viscosity are all considered individually in parametric studies covering a wide range of the relevant parameters. These results extend previous ones regarding the shape of the front, and in particular the centerline front position, as a function of the dimensionless parameters. The pressures from the simulations have been used to compute the excess pressure losses in the system (front pressure correction or exit correction). Inertia leads to highly extended front positions relative to the inertialess Newtonian values, which are 0.895 for the planar case and 0.835 for the axisymmetric one. Gravity acting in the direction of flow shows the same effect, while gravity opposing the flow gives a reduced bulge of the fountain. Surface tension, slip at the wall, and compressibility, all decrease the shape of the front. Pressure-dependence of the viscosity leads to increased front position as a corresponding dimensionless parameter goes from zero (no effect) to higher values of the pressure-shift factor. The exit correction increases monotonically with inertia, compressibility, and gravity, while it decreases monotonically with slip and pressure-dependence of the viscosity. Contour plots of the primary variables (velocity-pressure) show interesting trends compared with the base case (zero values of the dimensionless parameters and of surface tension). © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Second-hand smoking and carboxyhemoglobin levels in children: a prospective observational study

PEDIATRIC ANESTHESIA, Issue 1 2010
BRANDEN E. YEE MD
Summary Aim:, To establish baseline noninvasive carboxyhemoglobin (COHb) levels in children and determine the influence of exposure to environmental sources of carbon monoxide (CO), especially environmental tobacco smoke, on such levels. Background:, Second-hand smoking may be a risk factor for adverse outcomes following anesthesia and surgery in children (1) and may potentially be preventable. Patients and Methods:, Parents and their children between the ages of 1,12 were enrolled on the day of elective surgery. The preoperative COHb levels of the children were assessed noninvasively using a CO-Oximeter (Radical-7 Rainbow SET Pulse CO-Oximeter; Masimo, Irvine, CA, USA). The parents were asked to complete an environmental air-quality questionnaire. The COHb levels were tabulated and correlated with responses to the survey in aggregate analysis. Statistical analyses were performed using the nonparametric Mann,Whitney and Kruskal,Wallis tests. P < 0.05 was statistically significant. Results:, Two hundred children with their parents were enrolled. Children exposed to parental smoking had higher COHb levels than the children of nonsmoking controls. Higher COHb values were seen in the youngest children, ages 1,2, exposed to parental cigarette smoke. However, these trends did not reach statistical significance, and confidence intervals were wide. Conclusions:, This study revealed interesting trends of COHb levels in children presenting for anesthesia and surgery. However, the COHb levels measured in our patients were close to the error margin of the device used in our study. An expected improvement in measurement technology may allow screening children for potential pulmonary perioperative risk factors in the future. [source]