The ir absorption spectrum of hydrogenated amorphous silicon is discussed in the context of structural models for this material. It is shown that the integrated strength of the bond stretching bands in hydrogenated amorphous silicon cannot be used to determine the hydrogen concentration because the local effective charge for ir absorption is a function of hydrogen concentration and sample preparation. The effective charge for the wagging-rocking-rolling vibrations a t 640 cm-', however, is independent of hydrogen concentration and sample preparation. Hence the integrated strength of this band can be used to measure the hydrogen concentration provided the proportionality constant is determined empirically. Changes in the ir absorption bands as a function of isochronal annealing temperature show that two different types of bonds contribute t o the bond stretching band a t 2100 cm-l. The bond bending bands a t 890 and 840 cm-1 are associated with one of the bonds producing the 2100 cm-' stretching band. The relative strengths of the 890 and 840 cm-1 bands to the 2100 cm-l band depend strongly on the film preparation method: the glow discharge produced films show much stronger bending bands than those produced by r f sputtering. A structural model for hydrogenated amorphous silicon is presented in which a Maxwell-Garnetttype local field correction, which is dependent on the dipole location within a microvoid and the shape of the microvoid, is used to explain the data.Das IR-Absorptionsspektrum von hydrogenisiertem, amorphem Silizium wird im Zusammenhang mit Strukturmodellen fiir dieses Naterial untersucht. Es wird gezeigt, daB die integrale Starke der ,,bond-stretching"-Banden in hydrogenisiertem, amorphem Silizium nicht fur die Bestimmung der Wasserstoffkonzentration benutzt werden kann, weil die lokale effektive Ladung fur die IR-Absorption eine Funktion der Wasserstoffkonzentration und Probenpraparation ist. Die effektive Ladung fur die ,,wagging-rocking-rolling"-Schwingungen bei 640 cm-l ist jedoch unabhingig von der Wasserstoffkonzentration und Probenpraparation. Somit kann die integrale Starke dieser Bande benutzt werden, um die Wasserstoffkonzentrtion zu messen, vorausgesetzt, daB die Proportionalitatskonstante empirisch bestimmt wird. Anderungen in den IR-Absorptionsbanden in Abhangigkeit von der isochronen Temperungstemperatnr zeigen, daB zwei unterschiedliche Bindungsarten zur ,,bond-stretching"-Bande bei 2100 cm-1 beitragen. Die ,,bond-bending"-Banden bei 890 und 840 cm-l sind mit einer der Bindungen verknupft, die die 2100 cm-'-Stretching-Bande hervorrufen. Die relativen Starken der 890-und 840-cm-l-Banden zur 2100 cm-l-Bande hangen stark von der Schichtherstellungsmethode ab : die durch Glimmentladung hergestellten Schichten zeigen vie1 starkere Bindungsbanden als die durch HF-Sputtern hergestellten. Ein Strukturmodell fur hydrogenisiertes, amorphes Silizium wird angegeben, in dem eine lokale Feldkorrektur vom Maxwell-Garnett-Typ benutzt wird, die von der Dipollokalisierung im Innern eines Mikrohohlraume...

Elderly depression symptoms was the only factor significantly associating with poor sleep quality after adjustment. Higher level of physical activity was associated with better sleep quality in univariate analysis but not in multivariate analysis, which considered the factor of elderly depression symptoms in the elderly. The role of physical activity in late life potentially influence sleep quality but may have less significance compared with depression. Therefore, we suggest the need for more future research to investigate the relationship between elderly people's sleep and physical activity.

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It is worthwhile promoting a yoga and Pilates exercise programme for postpartum women in communities.

β-Sheets are one of the fundamental three-dimensional building blocks for protein structures. Oppositely charged amino acids are frequently observed directly across one another in antiparallel sheet structures, suggesting the importance of cross-strand ion pairing interactions. Despite the apparent electrostatic nature of ion pairing interactions, the charged amino acids Asp, Glu, Arg, Lys have different numbers of hydrophobic methylenes linking the charged functionality to the backbone. Accordingly, the effect of charged amino acid side chain length on cross-strand ion pairing interactions at lateral non-hydrogen bonded positions was investigated in a β-hairpin motif. The negatively charged residues with a carboxylate (Asp, Glu, Aad in increasing length) were incorporated at position 4, and the positively charged residues with an ammonium (Dap, Dab, Orn, Lys in increasing length) were incorporated at position 9. The fraction folded population and folding free energy were derived from the chemical shift deviation data. Double mutant cycle analysis was used to determine the interaction energy for the potential lateral ion pairs. Only the Asp/Glu-Dap interactions with shorter side chains and the Aad-Orn/Lys interactions with longer side chains exhibited stabilizing energetics, mostly relying on electrostatics and hydrophobics, respectively. This suggested the need for length matching of the interacting residues to stabilize the β-hairpin motif. A survey of a nonredundant protein structure database revealed that the statistical sheet pair propensity followed the trend Asp-Lys < Glu-Lys, also implying the need for length matching of the oppositely charged residues.

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β-Sheet is one of the major protein secondary structures. Oppositely charged residues are frequently observed across neighboring strands in antiparallel sheets, suggesting the importance of cross-strand ion pairing interactions. The charged amino acids Asp, Glu, Arg, and Lys have different numbers of hydrophobic methylenes linking the charged functionality to the backbone. To investigate the effect of side chain length of guanidinium- and carboxylate-containing residues on lateral cross-strand ion pairing interactions at non-hydrogen-bonded positions, β-hairpin peptides containing Zbb-Agx (Zbb = Asp, Glu, Aad in increasing length; Agx = Agh, Arg, Agb, Agp in decreasing length) sequence patterns were studied by NMR methods. The fraction folded population and folding energy were derived from the chemical shift deviation data. Peptides with high fraction folded populations involved charged residue side chain lengths that supported high strand propensity. Double mutant cycle analysis was used to determine the interaction energy for the potential lateral ion pairs. Minimal interaction was observed between residues with short side chains, most likely due to the diffused positive charge on the guanidinium group, which weakened cross-strand electrostatic interactions with the carboxylate side chain. Only the Aad-Arg/Agh interactions with long side chains clearly exhibited stabilizing energetics, possibly relying on hydrophobics. A survey of a non-redundant protein structure database revealed that the statistical sheet pair propensity followed the trend Asp-Arg < Glu-Arg, implying the need for matching long side chains. This suggested the need for long side chains on both guanidinium-bearing and carboxylate-bearing residues to stabilize the β-hairpin motif.