University of North Carolina at Charlotte

About: University of North Carolina at Charlotte is a education organization based out in Charlotte, North Carolina, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 8772 authors who have published 22239 publications receiving 562529 citations. The organization is also known as: UNC Charlotte & UNCC.

Structure and redox and photophysical properties of a series of ruthenium heterocycles based on the ligand 2,3-bis(2-pyridyl)quinoxaline

Abstract: The synthesis, structure, and redox and photophysical properties of (Ru(bpy)/sub n/(BL)/sub 3-n/)/sup 2 +/, where n = 0-2, bpy is 2,2'-bipyridine, and BL is 2,3-bis(2-pyridyl)quinoxaline, are described. The (Ru(bpy)/sub 2/(BL))(PF/sub 6/)/sub 2/ complex crystallized in the monoclinic space group P2/sub 1//a and the cell parameters are repeated. All non-H atoms were refined anisotropically to an R value of 0.0672 for 5766 reflections with I > sigma(I). The ruthenium to nitrogen bond distances were Ru-N(pyridine) = 2.06 A (average) and Ru-N(pyrazine) = 2.096 (4) A. Absorption spectra contained bands (250-300 nm) in the ultraviolet region that were assignable to ligand ..pi.. ..-->.. ..pi..* transitions and visible bands (517-300 nm) that were assignable to d..pi.. ..-->.. ..pi..* MLCT transitions. Reduction potentials for the Ru/sup 3+/2+/ couples varied from about 1.40 to 1.70 V vs SSCE. Three reductions were observed and assigned to the one-electron reduction of each bidentate ligand. Weak luminescence was observed, and corrected emission energy maxima were located at 766 +/- 4 nm. Excited-state reduction potentials were estimated from the difference between emission energy maxima and ground-state reduction potentials. Excited-state lifetimes at room temperature in 4:1 EtOH-MeOH ranged from 167 to < 70 ns. Temperature-dependent-lifetime (90-298 K) data gave evidencemore » for ..delta..E' values of 1100 +/- 300 cm/sup -1/. The temperature dependence was attributed to either the third MLCT state according to the localized-orbital model or the presence of a fourth CT state for (Ru(BL)/sub 2/(bpy))/sup 2 +/, since little photochemistry was found for it, and to the third and/or the fourth CT state and the dd state for both (Ru(BL)/sub 2/(bpy))/sup 2 +/ and (Ru(BL)/sub 3/)/sup 2 +/. 54 references, 7 figures, 6 tables.« less

Physical weathering in arid landscapes due to diurnal variation in the direction of solar heating

Abstract: Despite the prominent role of physical weathering in arid and semi-arid landscapes, there has been little study of the specifi c processes responsible for the rapid breakdown of subaerially exposed rocks. For example, many boulders and cobbles in deserts exhibit fi ne near-vertical cracks. Although workers have hypothesized that these and other cracks are initiated by diurnal heating and cooling, no convincing specifi c mechanism for their formation has been proposed. We have characterized these cracks at eight sites on surfaces of different ages in the Mojave, Sonoran, and Chihuahuan Deserts, and the high desert of central New Mexico. Our data reveal four basic types of cracks: longitudinal, surfaceparallel, fabric-related, and meridional. The orientations of the fi rst three types are associated with clast shape and rock fabric. The azimuths of meridional cracks, however, are preferentially aligned north-south, typically with a nonrandom multimodal distribution. We propose that these cracks are caused by tensile stresses that arise in the interior of clasts due to strong radial gradients in temperature that evolve and rotate in alignment with the sun’s rays. We suggest that the multimodal nature of crack orientations may be in part attributable to the seasonally varying, latitude-dependent solar elevation angle. Over millennial time scales, we suggest that this thermal cracking is an effi cient weathering process that, together with cumulic soil epipedon development, creates the key attributes of most desert pavements. In addition to individual clasts exposed on desert surfaces, this mechanism of cracking is potentially signifi cant in other climates and on other planets, as well as for rock outcrops and for man-made structures.

Partially coherent beam propagation in atmospheric turbulence [invited].

Abstract: Partially coherent beams hold much promise in free-space optical communications for their resistance to the deleterious effects of atmospheric turbulence. We describe the basic theoretical and computational tools used to investigate these effects, and review the research to date.

Social Perception of the Victim's Causal Role in Rape: An Exploratory Examination of Four Factors

Abstract: An exploratory examination of the social perception of a rape victim was conducted. Sex of respondent, victim's history of rape, number of rapes in the area, and victim acquaintance with the rapist were investigated by having subjects respond to a standardized videotape of an interview with a presumed victim. Results revealed two consistent findings: Males viewed the victim as contributing to the rape to a greater degree than females. The victim was seen as provoking the episode to a greater degree when she had been raped before than when she had not been raped before. Several interactions were also obtained.

Locoregional Effects of Microbiota in a Preclinical Model of Colon Carcinogenesis.

Abstract: Inflammation and microbiota are critical components of intestinal tumorigenesis. To dissect how the microbiota contributes to tumor distribution, we generated germ-free (GF) ApcMin/+and ApcMin/+;Il10−/− mice and exposed them to specific-pathogen-free (SPF) or colorectal cancer-associated bacteria. We found that colon tumorigenesis significantly correlated with inflammation in SPF-housed ApcMin/+;Il10−/−, but not in ApcMin/+mice. In contrast, small intestinal neoplasia development significantly correlated with age in both ApcMin/+;Il10−/− and ApcMin/+ mice. GF ApcMin/+;Il10−/− mice conventionalized by an SPF microbiota had significantly more colon tumors compared with GF mice. Gnotobiotic studies revealed that while Fusobacterium nucleatum clinical isolates with FadA and Fap2 adhesins failed to induce inflammation and tumorigenesis, pks+Escherichia coli promoted tumorigenesis in the ApcMin/+;Il10−/− model in a colibactin-dependent manner, suggesting colibactin is a driver of carcinogenesis. Our results suggest a distinct etiology of cancers in different locations of the gut, where colon cancer is primarily driven by inflammation and the microbiome, while age is a driving force for small intestine cancer. Cancer Res; 77(10); 2620–32. ©2017 AACR.