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AbstractPoor cardiac pumping efficiency has shown to lead to cognitive impairments in patients with cardiovascular disease (CVD). The current study examined the relationship between left ventricular ejection fraction and sustained attention and inhibitory processes measured by the Adaptive Rate Continuous Performance Task and the Go/No-go test. Participants were 67 older outpatients (age 68.5 ? 7.4) with a range of CVD. Associations between cognition and ejection fraction were examined vialinear regression analysis. Results were consistent with the hypothesis that lower ejection fraction is significantly associated with decrements in sustained attention and vigilance. Overall, the results provide support for the hypothesis that a change in cardiac pumping leads to decrements in some aspects of attention; however, inhibitory processes are relatively spared. (JINS, 2009, 15, 137?141.) [ABSTRACT FROM AUTHOR]

In the present study we examined cognitive function, radiographic features, and functional ability in individuals with vascular dementia (VaD). Subjects were subdivided into individuals with only white matter involvement (WM) and individuals with evidence of a cortical infarction in addition to white matter ischemic change (C+WM). Results revealed that both groups of subjects were impaired across cognitive functions. Cognitive performance was more severely impaired among the C+WM group, but the general pattern of deficits did not differ between the two groups. Hachinski scores were significantly higher and instrumental activities of daily living were more severely affected in the C+WM group compared to the WM group. No significant differences were evident between the two groups on overall dementia severity or the extent of white matter involvement. These findings indicate that cognitive function in VaD may be globally impaired, and that cortical infarction in addition to white matter ischemia results in greater impairment, but the differences are largely quantitative rather than qualitative. [ABSTRACT FROM AUTHOR]

X-ray absorption spectra of aqueous 4 and 6 M potassium hydroxide solutions have been measured near the oxygen K edge. Upon addition of KOH to water, a new spectral feature (532.5 eV) emerges at energies well below the liquid water pre-edge feature (535 eV) and is attributed to OH-ions. In addition to spectral changes explicitly due to absorption by solvated OH-ions, calculated XA spectra indicate that first-solvation-shell water molecules exhibit an absorption spectrum that is unique from that of bulk liquid water. It is suggested that this spectral change results primarily from direct electronic perturbation of the unoccupied molecular orbitals of first-shell water molecules and only secondarily from geometric distortion of the local hydrogen bond network within the first hydration shell. Both the experimental and the calculated XA spectra indicate that the nature of the interaction between the OH-ion and the solvating water molecules is fundamentally different than the corresponding interactions of aqueous halide anions with respect to this direct orbital distortion. Analysis of the Mulliken charge populations suggests that the origin of this difference is a disparity in the charge asymmetry between the hydrogen atoms of the solvating water molecules. The charge asymmetry is induced both by electric field effects due to the presence of the anion and by charge transfer from the respective ions. The computational results also indicate that the OH-ion exists with a predominately “hyper-coordinated” solvation shell and that the OH-ion does not readily donate hydrogen bonds to the surrounding water molecules. [ABSTRACT FROM AUTHOR]

It was recently suggested that liquid water primarily comprises hydrogen-bonded rings and chains, as opposed to the traditionally accepted locally tetrahedral structure (Wernet et al. Science2004, 304, 995). This controversial conclusion was primarily based on comparison between experimental and calculated X-ray absorption spectra (XAS) using computer-generated ice-like 11-molecule clusters. Here we present calculations which conclusively show that when hydrogen-bonding configurations are chosen randomly, the calculated XAS does not reproduce the experimental XAS regardless of the bonding model employed (i.e., rings and chains vs tetrahedral). Furthermore, we also present an analysis of a recently introduced asymmetric water potential (Soper, A. K. J. Phys.:  Condens. Matter2005, 17, S3273), which is representative of the rings and chains structure, and make comparisons with the standard SPC/E potential, which represents the locally tetrahedral structure. We find that the calculated XAS from both potentials is inconsistent with the experimental XAS. However, we also show the calculated electric field distribution from the rings and chains structure is strongly bimodal and highly inconsistent with the experimental Raman spectrum, thus casting serious doubt on the validity of the rings and chains model for liquid water. [ABSTRACT FROM AUTHOR]

Oxygen K-edge X-ray absorption spectra (XAS) of aqueous chloride solutions have been measured for Li+, Na+, K+, NH4+, C(NH2)3+, Mg2+, and Ca2+ at 2 and 4 M cation concentrations. Marked changes in the liquid water XAS are observed upon addition of the various monovalent cation chlorides that are nearly independent of the identity of the cation. This indicates that interactions with the dissolved monovalent cations do not significantly perturb the unoccupied molecular orbitals of water molecules in the vicinity of the cations and that water−chloride interactions are primarily responsible for the observed spectral changes. In contrast, the addition of the divalent cations engenders changes unique from the case of the monovalent cations, as well as from each other. Density functional theory calculations suggest that the ion-specific spectral variations arise primarily from direct electronic perturbation of the unoccupied orbitals due to the presence of the ions, probably as a result of differences in charge transfer from the water molecules onto the divalent cations. [ABSTRACT FROM AUTHOR]

The oxygen K edge X-ray absorption spectra of aqueous HCl and NaCl solutions reveal distinct perturbations of the local water molecules by the respective solutes. While the addition of NaCl leads to large spectral changes, the effect of HCl on the observed X-ray absorption spectrum is surprisingly small. Density functional theory calculations suggest that this difference primarily reflects a strong blue shift of the hydrated proton (in either the Eigen (H9O4+) or Zundel (H2O5+) forms) spectrum relative to that of H2O, indicating the tighter binding of electrons in H3O+. This spectral shift counteracts the spectral changes that arise from direct electrostatic perturbation of water molecules in the first solvation shell of Cl-. Consequently, the observed spectral changes effected by HCl addition are minimal compared to those engendered by NaCl. Additionally, these results indicate that the effect of monovalent cations on the nature of the unoccupied orbitals of water molecules in the first solvation shell is negligible, in contrast to the large effects of monovalent anions. [ABSTRACT FROM AUTHOR]

The microscopic events engendering liquid water evaporation have received much attention over the last century, but remain incompletely understood. We present measurements of isotope fractionation occurring during free molecular evaporation from liquid microjets and show that the isotope ratios of evaporating molecules exhibit dramatic differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction, and a clear temperature dependence. These results indicate the existence of an energetic barrier to evaporation and that the evaporation coefficient of water is less than unity. These new insights into water evaporation promise to advance our understanding of the processes that control the formation and lifetime of clouds in the atmosphere. [ABSTRACT FROM AUTHOR]

Background and Purpose. Verbal working memory (VWM) deficits have been a well-replicated finding among patients with multiple sclerosis (MS). Functional magnetic resonance imaging (FMRI) studies have described a VWM system in healthy samples; however, functional neuroimaging of this system among MS patients is just beginning to appear. Methods. Fifteen MS patients and 15 sex-, age-, education-, and IQ-matched healthy control (HC) participants completed a 2-Back VWM task as whole-brain FMRI was conducted. Results. Each group exhibited increased brain activity compared to the 0-Back control task in regions associated with the 2-Back in previous neuroimaging studies. These included Broca's area, supplementary motor area (SMA), premotor cortices (PMC), and dorsolateral prefrontal cortices (DLPFC). MS patients exhibited greater cortical activity than did HC participants in left primary motor and somatosensory cortices, PMC, DLPFC, anterior cingulate, and bilateral SMA. MS patients exhibited relatively less activation in Broca's area, bilateral cerebellum, and other regions not typically associated with the 2-Back (eg, right fusiform gyrus, left lingual gyrus, right hippocampus). Performance accuracy and reaction time did not differ between groups. Conclusions. Normal performance of a challenging VWM task among high-functioning MS patients is associated with a shift toward greater activity in regions related to sensorimotor functions and anterior attentional/executive components of the VWM system. Posterior memory storage systems appeared unaffected, while portions of the visual processing and subvocal rehearsal systems were less active. Although a shift in neural activity was noted relative toHC participants, deviation from regions normally involved in VWM function was not observed in this patient sample. [ABSTRACT FROM AUTHOR]

Background and Purpose. Cerebral perfusion abnormalities and neuropsychological impairment are common sequelae of chronic cocaine abuse. While perfusion abnormalities have been shown to relate to cognitive deficits in this substance abuse population, the relationship between cognitive performance and the magnitude of perfusion abnormality has yet to be fully determined. Methods. Thirty-seven abstinent cocaine abusers and 13 normal controls were administered resting 99m-Tc-HMPAO single photon emission computed tomography (SPECT) scans followed by a neuropsychological assessment battery tapping executive skills, attention, memory, and motor performance. Statistical parametric mapping (SPM99) techniques were used to analyze the SPECT data to detect significant regional perfusion abnormalities in the cocaine group relative to normal controls, and resulting abnormal SPECT counts were employed for comparison with the assessment measures to examine the relationship between cocaineinduced perfusion abnormalities and cognitive performance. Results. SPECT data analysis revealed significant regional perfusion abnormalities in the cocaine abuse sample relative to controls and significant differences in neuropsychological functioning on measures of executive functioning, complex attention, memory, and manual dexterity. For chronic cocaine abusers, however, within-group comparisons of the magnitude of abnormal perfusion and neuropsychological performance were largely nonsignificant, with the exception of complex attention and motor speed. Conclusions. Perfusion abnormalities and neuropsychological impairments readily distinguished cocaine abusers from normal controls. However, when the magnitude of cocaine-induced perfusion abnormalities is examined in relation to cognitive performance, motor speed and complex attention appear to be the best behavioral indicants of the severity of perfusion dysfunction within this substance abuse population. [ABSTRACT FROM AUTHOR]