In-situ high temperature Raman spectroscopic (HTRS) technique in combination with density functional theory (DFT) analysis has been adopted to investigate the micro-structure of solid and molten ...A2W2O7 (A=Li, Na, K). The WO6 octahedra were found to be connected to each other by corner and edge sharing in the crystalline Li2W2O7 and K2W2O7 compounds. In the crystal lattice of Na2W2O7, on the other hand, the WO4 tetrahedra and WO6 octahedra were found to coexist and paired by corner sharing. Although the structural diversity has clearly led to distinct Raman spectra of the crystalline A2W2O7 compounds, the spectra of their melts tended to be analogous, showing the typical vibration modes of (W2O7)2− dimer. A mechanism was then proposed to explain the structure evolution occurring during the melting process of A2W2O7. The effect of A+ cation on the Raman bands of (W2O7)2− dimer in molten A2W2O7 has also been investigated. Both the wavenumber and full width at half-height (FWHH) of the characteristic band assigned to the symmetrical stretching vibration mode of WOnb (non-bridging oxygen) in (W2O7)2− were found to decrease in the sequence of Li+, Na+ and K+, indicating the cation effect on the mean bond length and its distribution range of WOnb. In addition, the relative intensity of this band was also influenced by the cation and it was increased in the order of Li2W2O7, Na2W2O7 and K2W2O7, which has been explained by the charge transfer process and confirmed by Mulliken overlap population analysis.
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•Distinct Raman spectra of A2W2O7 crystals due to structure diversity are discussed.•A mechanism to explain the structure evolution of A2W2O7 during melting is proposed.•A+ cation has dramatic effect on Raman scattering activity of the (W2O7)2− dimer.
In recent years there has been an increasing focus on the relation between cerebrovascular health, physical exercise and Alzheimer's disease. The aim of the current study was to determine the effect ...of moderate-to-high-intensity aerobic exercise on cerebral blood flow in patients with mild to moderate Alzheimer's disease. Fifty-one patients were randomized to either usual care or moderate-to-high intensity aerobic exercise for 16 weeks. Exercise had no consistent effect on whole brain or regional cerebral blood flow. Sixteen weeks of exercise are, therefore, not sufficient to produce a consistent increase in cerebral blood flow in a relatively small sample of Alzheimer's patients.
•An effect of aerobic exercise in people with Alzheimer's disease is hypothesized.•In a clinical trial, the effect of exercise on cerebral blood flow was assessed.•16 weeks of aerobic exercise is insufficient for detectable changes in CBF.•Future studies should consider a longer intervention or patients with milder AD.
Abstract
Here we report a successful one-step synthesis of vanadium-doped anatase mesocrystals by reactive annealing of NH
4
TiOF
3
/PEG2000 mesocrystal precursors with NH
4
VO
3
. The formation ...solid solution Ti
1−
x
V
x
O
2
with vanadium content up to
x
= 25 at% inheriting the structure of mesocrystals is observed for the first time. The doping mechanism via vapor phase transport of vanadium is proposed. The Ti
1−
x
V
x
O
2
mesocrystals exhibit improved specific capacity of 175 mAh g
−1
(compared to 150 mAh g
−1
for pure anatase phase) and decreased potential gap between charge and discharge processes.
The article deals with the processes associated with obtaining and drying hydrogen under steam-carbon dioxide conversion of methane. A fuzzy Sugeno model has been created, and with the help of the ...training this model, a sample of process parameters has been obtained, some of which values worsen the process, and some, on the contrary, are optimal for its flow.
Objective: This study concerns the question of whether obese subjects in a community sample experience depression in a different way from the nonobese, especially whether they overeat to the point of ...gaining weight during periods of depression. Design: A representative sample of adults was interviewed regarding depression and obesity. Subjects: The sample consisted of 1396 subjects whose interviews were studied regarding relationships between obesity and depression and among whom 114 had experienced a major depressive episode at some point in their lives and provided information about the symptoms experienced during the worst or only episode of major depression. Measurements: The Diagnostic Interview Schedule (DIS) was used to identify major depressive episodes. Information was also derived from the section on Depression and Anxiety (DPAX) of the Stirling Study Schedule. Obesity was calculated as a body mass index >30. Logistic regressions were employed to assess relationships, controlling for age and gender, by means of odds ratios and 95% confidence intervals. Results: In the sample as a whole, obesity was not related to depression although it was associated with the symptom of hopelessness. Among those who had ever experienced a major depressive episode, obese persons were 5 times more likely than the nonobese to overeat leading to weight gain during a period of depression (P<0.002). These obese subjects, compared to the nonobese, also experienced longer episodes of depression, a larger number of episodes, and were more preoccupied with death during such episodes. Conclusions: Depression among obese subjects in a community sample tends to be more severe than among the nonobese. Gaining weight while depressed is an important marker of that severity. Further research is needed to understand and possibly prevent the associations, sequences and outcomes among depression, obesity, weight gain and other adversities.
Detailed studies of the polarized Raman spectra of lutetium pyrosilicate single crystals have been performed in a wide temperature range from 20 to 1500 K. This has made it possible for the first ...time to identify the entire set and symmetry of the internal vibrations of the Si
2
O
7
6−
anion and the lattice vibrations of this compound. The Raman spectra of the lutetium pyrosilicate have been investigated in the temperature ranges preceding the melting, the molten state, and the overheated melt of the compound up to 2173 K. The Raman spectra of lutetium pyrosilicate single-crystal microregions have been studied in order to elucidate the nature of defect inclusions in their bulk.
—
The structure and typical behavior of boron–oxygen groups in Li
2
O–B
2
O
3
melts and glasses have been studied by high-temperature Raman spectroscopy. Under conditions similar to those of lithium ...triborate crystal growth, we have detected the formation of BO
2
monomers, which influence the growth process. The results have been compared to those for structural groups of pure boron oxide.
Objective: Building on a report about the prevalence of depression over time, this paper examines historical trends regarding anxiety in terms of its prevalence, its distribution by age and gender, ...and its comorbidity with depression. Methods for conducting such time trend analysis are reviewed.
Method: Representative samples of adults were selected and interviewed in 1952, 1970, and 1992. Logistic regressions were used for statistical analysis.
Results: Although twice as common as depression, the prevalence of anxiety was equally stable. Anxiety was consistently and significantly more characteristic of women than men. A re‐distribution of rates in 1992 indicated that depression but not anxiety had significantly increased among younger women (P = 0.03). Throughout the study, approximately half of the cases of anxiety also suffered depression.
Conclusion: The relationships between anxiety and depression remained similar over time with the exception that depression came to resemble anxiety as a disorder to which women were significantly more vulnerable than men. Social and historical factors should be investigated to assess their relevance to this change.
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