Electron diffraction studies of hot molecules. IV. Asymmetries of nonbonded distribution functions of SF6, SiF4, and CF4

Highly significant improvements in the agreement between observed and calculated intensities of electrons diffracted by hot molecules were obtained by optimizing the skew parameter â for the nonbonded distributions. Derived â values (±2σ) were 2.75(11), 0.72(13), and 2.0(4) Å−1 for SF6, SiF4, and CF4, respectively. These measured skew parameters are approximately 2 Å−1 higher in each case than values previously proposed on the basis of Morse asymmetry factors and the nonlinear transformation between curvilinear and normal coordinates of molecules. The principal factor responsible for the increase is the previously unknown intrinsic anharmonicity in bending deformations. Silicon tetrafluoride has a lower â value than the other molecules studied primarily because its bending force constant is lower, relative to stretching. Practical as well as theoretical implications of present findings are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70475/2/JCPSA6-81-9-3792-1.pd

Sources of Oklahoma Agricultural History

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Pseudopotential SCF–MO studies of hypervalent compounds. I. XeF2 and XeF4

The (ab initio) effective potential theory developed by Ewig et al. has been applied to a series of hypervalent compounds with a view to elucidating the anomalous properties of several of the higher fluorides of xenon and iodine. In this initial paper the development of a minimal basis set substantially better than an STO‐4G atom‐optimized set is described. Calculations carried out on XeF2 and XeF4 give valence orbital energies in fair agreement with those obtained with the more flexible, all‐electron SCF–MO calculations by Basch et al. Equilibrium structures of XeF2 and XeF4 provided by the effective potential calculations possess the correct symmetries. Bond lengths, although too long by 0.09 Å, correctly reproduce the contraction observed experimentally upon fluorination of XeF2. Calculated bending and stretch–stretch interaction force constants are in pleasing agreement with experiment, as is the stretching anharmonicity. Stretching frequencies evaluated at the experimental bond length, however, are 25% high. Overall, the ability of the present treatment to give a reasonable account of the structures and force fields of XeF2 and XeF4 justifies its application to the higher fluorides where interpretations of observations are more speculative.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70823/2/JCPSA6-73-1-367-1.pd

Pseudopotential SCF–MO studies of hypervalent compounds. II. XeF+5 and XeF6

New evidence bearing upon the anomalous properties of xenon hexafluoride has been obtained via the ab initio molecular orbital approach applied successfully to the di‐ and tetrafluorides in paper I. Structures of both XeF+5 and XeF6 are governed by a stereochemically active lone pair. In the case of the square–pyramidal cation the Fax–Xe–Feq angle calculated for the bare ion is within 2° of the value observed in the crystalline complex. For the hexafluoride, however, the calculated deformation from Oh symmetry is appreciably greater than that deduced from electron diffraction intensities. Nevertheless, the results of calculations are in sufficient conformity with the Bartell–Gavin, Pitzer–Bernstein interpretation and at variance with the ’’electronic‐isomers’’ interpretation to leave little doubt about the answer. With increasing fluorination in the XeFn series the HOMO–LUMO energy difference decreases and the second‐order Jahn–Teller effect is enhanced. Increasing fluorination (and increased positive charge on Xe) also shortens bond lengths; calculated shortenings parallel observed shortenings. The deformation of XeF6 from Oh is along t1u bend and stretch coordinates to a C3v structure with long bonds adjacent to the lone pair, as expected according to the valence‐shell–electron‐pair‐repulsion model. Pure t2g deformations are destabilizing but anharmonic t1u–t2g coupling significantly stabilizes the deformation. Steric aspects of the structure and force field are diagnosed and found to be minor. Values for the force constants f44, f55, f̄4444, f̄444′4′, and f̄445 are derived and found to be of the magnitude forecast in the Bartell–Gavin and Pitzer–Bernstein treatments except that the calculations do not reproduce the delicate balances believed to lead to almost free pseudorotation in XeF6.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69894/2/JCPSA6-73-1-375-1.pd

Adsorption of vapors by silica gels of different structures

1. 1. Isothermals were obtained at 25[deg]C. for the adsorption of the vapors of methyl alcohol, ethyl alcohol, n-propyl alcohol, benzene, carbon tetrachloride, hexane, and water by silica gels of different apparent densities. For certain of these systems additional isotherms at 40 or 45[deg]C. were obtained.2. 2. The specific surface area of each gel was determined by three independent methods as follows: (a) by application of the BET equation to the low temperature nitrogen adsorption isotherms, (b) by the method based upon the assumption of the existence of uniform circular capillaries (i.e., ), and (c) by treatment of the gravimetric data according to the free surface energy method of Fu and Bartell.3. 3. For each system the values of the adhesion tension, work of adhesion, and initial spreading coefficient were calculated from the adsorption data by means of the Gibbs equation which interrelates surface area, surface tension, surface excess and chemical potential.4. 4. It was found that the free surface energy changes which occurred when unit areas of the different porous solids were replaced by unit areas of given solid-liquid or solid-saturated vapor interfaces were independent of the apparent densities of the adsorbent, i.e., the adhesion tension values calculated for a given liquid against a series of silica gels which differed in average pore radius, pore volume, and specific surface area were practically the same.5. 5. Inasmuch as six different organic liquids, possessing widely different surface tensions as well as widely different interaction energies against silica gave for a given gel similar values for surface area, which values were in good agreement with values obtained with other accepted methods, it appears justifiable to conclude that the free surface energy method of Fu and Bartell is generally applicable.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32543/1/0000654.pd

Ipilimumab administration for advanced melanoma in patients with pre-existing Hepatitis B or C infection: a multicenter, retrospective case series

Ipilimumab is a fully human, monoclonal antibody directed against Cytotoxic T Lymphocyte Antigen-4 (CTLA-4) that has demonstrated a survival benefit and durable disease control in patients with advanced melanoma. Ipilimumab is associated with potentially serious immune-related adverse events, including autoimmune hepatitis. Because clinical trials of ipilimumab excluded patients with pre-existing hepatitis B or C infection, there is a paucity of data on the safety of ipilimumab administration to that patient population. Here, we report the largest case series to date of patients with hepatitis B or C who received ipilimumab for advanced melanoma. Two of the nine patients described in this case series experienced fluctuations in their liver function tests (LFTs) and were subsequently treated with corticosteroids. Although this is a small series, the rate of hepatotoxicity appears similar to what has been seen in the general population treated with ipilimumab, and the ability to administer ipilimumab did not appear to be affected by concomitant hepatitis B or C infection. The use of ipilimumab in patients with metastatic melanoma who have pre-existing hepatitis can be considered among other therapeutic options

A Highly Virulent Staphylococcus aureus: Rabbit Anterior Chamber Infection, Characterization, and Genetic Analysis

PURPOSE. To describe and characterize a Staphylococcus aureus strain with unique virulence that overcomes host defenses of the rabbit anterior chamber and mimics clinical cases of postcataract surgery endophthalmitis. METHODS. Nine isolates of S. aureus were tested to determine their viability in the rabbit anterior chamber. Growth of UMCR1 in the anterior chamber was established and expressed as log colony-forming units per milliliter of aqueous humor. Pathologic changes produced by UMCR1 were documented by photographs, slit lamp examination, histopathologic analysis, and quantification of neutrophils. UMCR1 was characterized by antibiotic susceptibility, biochemical tests, ribotyping, genome restriction mapping, and multilocus sequence typing (MLST). RESULTS. UMCR1 was the only S. aureus strain that grew within the anterior chamber, reaching log 6.97 Ϯ 0.18 CFU/mL by 16 hours after infection. Pathologic changes included conjunctival injection, chemosis, corneal edema, severe iritis, fibrin accumulation, and a 193-fold increase in neutrophils by 16 hours after infection. UMCR1 was only resistant to sulfamethoxazole and, like other S. aureus isolates, polymyxin B. UMCR1 also had biochemical reactions and a ribotype pattern typical of S. aureus. The genomic reconstruction analysis of UMCR1 was most similar to strains MW2 and MSSA476. MLST revealed a 1 in 3198 nucleotide difference between UMCR1 and strains MW2 and MSSA476. CONCLUSIONS. This study describes a unique S. aureus strain that overcomes host defenses and replicates in the anterior chamber. The survival and growth of this organism could be used for studies of S. aureus pathogenesis, host defenses, and effectiveness of antibiotics within the anterior chamber. (Invest Ophthalmol Vis Sci. 2010;51:5114 -5120

Genotypic and phenotypic analyses of a Pseudomonas aeruginosa chronic bronchiectasis isolate reveal differences from cystic fibrosis and laboratory strains

Background Pseudomonas aeruginosa is an environmentally ubiquitous Gram-negative bacterium and important opportunistic human pathogen, causing severe chronic respiratory infections in patients with underlying conditions such as cystic fibrosis (CF) or bronchiectasis. In order to identify mechanisms responsible for adaptation during bronchiectasis infections, a bronchiectasis isolate, PAHM4, was phenotypically and genotypically characterized. Results This strain displays phenotypes that have been associated with chronic respiratory infections in CF including alginate over-production, rough lipopolysaccharide, quorum-sensing deficiency, loss of motility, decreased protease secretion, and hypermutation. Hypermutation is a key adaptation of this bacterium during the course of chronic respiratory infections and analysis indicates that PAHM4 encodes a mutated mutS gene responsible for a ~1,000-fold increase in mutation rate compared to wild-type laboratory strain P. aeruginosa PAO1. Antibiotic resistance profiles and sequence data indicate that this strain acquired numerous mutations associated with increased resistance levels to β-lactams, aminoglycosides, and fluoroquinolones when compared to PAO1. Sequencing of PAHM4 revealed a 6.38 Mbp genome, 5.9 % of which were unrecognized in previously reported P. aeruginosa genome sequences. Transcriptome analysis suggests a general down-regulation of virulence factors, while metabolism of amino acids and lipids is up-regulated when compared to PAO1 and metabolic modeling identified further potential differences between PAO1 and PAHM4. Conclusions This work provides insights into the potential differential adaptation of this bacterium to the lung of patients with bronchiectasis compared to other clinical settings such as cystic fibrosis, findings that should aid the development of disease-appropriate treatment strategies for P. aeruginosa infections

A Large Specific Deterrent Effect of Arrest for Patronizing a Prostitute

BACKGROUND: Prior research suggests that arrest, compared with no police detection, of some types of offenders does not decrease the chances they will reoffend. METHODOLOGY/PRINCIPAL FINDINGS: We assessed the specific deterrent effect of arrest for patronizing a street prostitute in Colorado Springs by comparing the incidence of arrest for clients of prostitutes first detected through public health surveillance with the incidence of rearrest for clients first detected by police arrest. Although these sets of clients were demographically and behaviorally similar, arrest reduced the likelihood of a subsequent arrest by approximately 70%. In other areas of the United States, arrest did not appear to displace a client's patronizing. CONCLUSIONS/SIGNIFICANCE: Our results suggest that apprehending clients decreases their patronizing behavior substantially

Attenuated Food Anticipatory Activity and Abnormal Circadian Locomotor Rhythms in Rgs16 Knockdown Mice

Regulators of G protein signaling (RGS) are a multi-functional protein family, which functions in part as GTPase-activating proteins (GAPs) of G protein α-subunits to terminate G protein signaling. Previous studies have demonstrated that the Rgs16 transcripts exhibit robust circadian rhythms both in the suprachiasmatic nucleus (SCN), the master circadian light-entrainable oscillator (LEO) of the hypothalamus, and in the liver. To investigate the role of RGS16 in the circadian clock in vivo, we generated two independent transgenic mouse lines using lentiviral vectors expressing short hairpin RNA (shRNA) targeting the Rgs16 mRNA. The knockdown mice demonstrated significantly shorter free-running period of locomotor activity rhythms and reduced total activity as compared to the wild-type siblings. In addition, when feeding was restricted during the daytime, food-entrainable oscillator (FEO)-driven elevated food-anticipatory activity (FAA) observed prior to the scheduled feeding time was significantly attenuated in the knockdown mice. Whereas the restricted feeding phase-advanced the rhythmic expression of the Per2 clock gene in liver and thalamus in the wild-type animals, the above phase shift was not observed in the knockdown mice. This is the first in vivo demonstration that a common regulator of G protein signaling is involved in the two separate, but interactive circadian timing systems, LEO and FEO. The present study also suggests that liver and/or thalamus regulate the food-entrained circadian behavior through G protein-mediated signal transduction pathway(s)