Cylindrical determinations compared using Jackson Cross Cylinder technique and modified Lebensohn\u27s Arrowhead chart

The purpose of this study is to make a comparison between the Jackson Cross Cylinder technique for determining the axis and power of the far cylinder correction and with the axis and power determination obtained by a subjectively rotated Lebensohn\u27s Arrow-head Figure type astigmatic chart. The question to be resolved is whether the Lebensohn\u27s Arrow-head Figure type chart could be substituted for the Jackson Cross Cylinder test for the determination of both astigmatic cylindrical power and axis

Empirical potentials for rovibrational energy transfer of hydrogen fluoride in collisions with argon

Rovibrational energy transfer of hydrogen fluoride in collisions with argon was investigated by using the coupled-states approximation to the quantum scattering problem. Empirically determined 3-D ab initio potential energy surfaces (PES) for the interaction between hydrogen fluoride and argon are presented. Second-order Møller-Plesset perturbation theory (MP2) was used to provide an initial approximate PES for the complex. The MP2 PES was subsequently modified to compensate for the underestimated dispersion interaction and adjusted until the desired agreement between calculated and observed spectroscopic quantities was achieved. Calculated rotational cross sections are in good agreement with experimental results as well as those obtained with a highly accurate vibrationally averaged empirical PES [J. M. Hutson, J. Chem. Phys. 96, 6752 (1992)]. The rate constants for the collision induced relaxation of the first vibrational state of hydrogen fluoride are presented as functions of temperature. The rate constants show structure at low temperature corresponding to cross-section resonances. The calculated rate constants are in good agreement with available high temperature experimental results. The calculations provide lower temperature rate constants and a wealth of detailed state-to-state information that are not available from experiment. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71344/2/JCPSA6-115-10-4573-1.pd

Sunlight Induced Movement of Planktonic Organisms and Their Relationships to Water Movements

Previous studies have shown the planktonic organisms of various natural water bodies to be quite sensitive to the levels of solar ultraviolet radiation incident at the water surface in summer. It has been assumed that the majority of the phytoplankton are simply carried about in the mass of the water which they inhabit with little control of their position or sunlight exposure. Photosynthetic microorganisms must strike a delicate balance with regard to solar radiation; they must obtain enough visible light for adequate photosynthesis while avoiding an excessive exposure to the injurious solar UV-B radiation. It is proposed that the circulation in natural waters is such that organisms can ride the current to obtain radiation exposures approximating the average radiation level of the euphotic zone. If exposure tends to become excessive, the plankton drops out of the circulation into the relatively immobile thermocline region until conditions are :favorable for a return to the highly illuminated surface waters. Observations with two species of aquatic plants generally confirm the proposed model. A radiation regime where the entire population receives essentially the same exposure to sunlight could be substantially more efficient in using the available light for photosynthesis than the static model where it is assumed that part of the population is overly exposed and another segment continuously dwells deep in the water in very dim light. The uniform dosage raises the potential problem that, should the average UV-B dose exceed the tolerance of the individual, virtually the entire population would be wiped out in a very short time. Perhaps such a species might gradually recover its prominence from the limited survivors or return the next season after being supplanted in its niche by other more resistant organisms

Photospheric acne at the bottom of the main-sequence: Doppler images of M4.5 - M9V stars

Starspots are an important manifestation of stellar activity and yet their distribution patterns on the lowest mass stars is not well known. Time series spectra of fully convective M dwarfs taken in the red-optical with UVES reveal numerous line profile distortions which are interpreted as starspots. New Doppler images of HU Del (GJ 791.2A; M4.5V), BL Ceti (GJ 65A; M5.5V) and UV Ceti (GJ 65B; M6V) at two epochs separated by three nights are presented. We find that contrast ratios corresponding to photosphere-spot temperature differences of only 100-400 K are sufficient to model the time series spectra of M4.5V - M9V stars. Starspots are reconstructed at a range of phases and latitudes with mean spot filling factors of only a few per cent. The distribution and low-contrast of the spots/spot-groups that we recover are likely to be responsible for the low amplitude photometric variability seen in late-M dwarfs. The stability of the spot patterns in the two sets of timeseries observations enables us to measure the latitude dependent differential rotation, which we find to be consistent with zer

Advantages and Limitations of Direct PCR Amplification of Bacterial 16S-rDNA from Resected Heart Tissue or Swabs Followed by Direct Sequencing for Diagnosing Infective Endocarditis: A Retrospective Analysis in the Routine Clinical Setting

Infective endocarditis (IE) is a life-threatening disease that is associated with high morbidity and mortality. Its long-term prognosis strongly depends on a timely and optimized antibiotic treatment. Therefore, identification of the causative pathogen is crucial and currently based on blood cultures followed by characterization and susceptibility testing of the isolate. However, antibiotic treatment starting prior to blood sampling or IE caused by fastidious or intracellular microorganisms may cause negative culture results. Here we investigate the additional diagnostic value of broad-range PCR in combination with direct sequencing on resected heart tissue or swabs in patients with tissue or swab culture-negative IE in a routine clinical setting. Sensitivity, specificity, and positive and negative predictive values of broad-range PCR from diagnostic material in our patients were 33.3%, 76.9%, 90.9%, and 14.3%, respectively. We identified a total of 20 patients (21.5%) with tissue or culture-negative IE who profited by the additional application of broad-range PCR. We conclude that broad-range PCR on resected heart tissue or swabs is an important complementary diagnostic approach. It should be seen as an indispensable new tool for both the therapeutic and diagnostic management of culture-negative IE and we thus propose its possible inclusion in Duke’s diagnostic classification scheme

"Freezing" the Tumor in a Known Position During Radiation Therapy In Regard to Boda-Heggemann et al

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Xenobiotic metabolism: the effect of acute kidney injury on non-renal drug clearance and hepatic drug metabolism.

Acute kidney injury (AKI) is a common complication of critical illness, and evidence is emerging that suggests AKI disrupts the function of other organs. It is a recognized phenomenon that patients with chronic kidney disease (CKD) have reduced hepatic metabolism of drugs, via the cytochrome P450 (CYP) enzyme group, and drug dosing guidelines in AKI are often extrapolated from data obtained from patients with CKD. This approach, however, is flawed because several confounding factors exist in AKI. The data from animal studies investigating the effects of AKI on CYP activity are conflicting, although the results of the majority do suggest that AKI impairs hepatic CYP activity. More recently, human study data have also demonstrated decreased CYP activity associated with AKI, in particular the CYP3A subtypes. Furthermore, preliminary data suggest that patients expressing the functional allele variant CYP3A5*1 may be protected from the deleterious effects of AKI when compared with patients homozygous for the variant CYP3A5*3, which codes for a non-functional protein. In conclusion, there is a need to individualize drug prescribing, particularly for the more sick and vulnerable patients, but this needs to be explored in greater depth

Silver Catalysts Supported on High Surface Area α-Alumina: Effect of Carbohydrate Template Size and Heat Treatment on Phase Purity

α-Alumina is a non-porous metal oxide with applications in ceramics and catalysis. Introducing pores into this material to create catalytically relevant surface area is challenging due to phase transitions over a wide temperature range. Current synthesis strategies involve hard templates such as synthetic polymers, e. g. polymethylmethacrylate (PMMA). Here, we compare cellulose and carbonized glucose as low-cost and natural alternative templates for high surface area α-alumina with a two-step heating method. Quantitative XRD was used to methodically investigate alumina phase purity. Increasing the template size in the range of 220–1000 nm improved α-alumina purity from 75 to 98 %, while maintaining high surface areas (21–29 m2 g−1). Phase purity increases substantially by prolonging the calcination time. The synthesized high surface area α-alumina was studied as support for silver catalysts in the epoxidation of ethylene and allowed high silver loadings. Ethylene oxide selectivity increased with enhanced α-alumina phase purity. Our 30 wt % silver catalyst on pure high surface area α-alumina did not show loss in selectivity compared to a 15 wt % silver catalyst on commercial non-porous α-alumina. This shows the potential of carbohydrate templates, the importance of templating parameters and the benefits of pure high surface area α-alumina as support for silver catalysts