Hydrogen content of plasma deposited a-Si:H

Amorphous hydrogenated Si is deposited using a remote Ar/H plasma. The plasma is generated in a d.c. thermal arc and expands into a low pressure chamber (20 Pa). Pure silane is injected into the plasma jet immediately after the arc source in a typical flow mixt. of Ar:H2:SiH4 = 55:10:6 scc/s. At the low Te in the jet (0.3 eV), silane radicals are produced mainly by H abstraction. In-situ ellipsometry yields refractive indexes of 3.6-4.2 at 632.8 nm and growth rates of 10-20 nm/s. FTIR anal. yields a H content of 9-25 at.% and refractive indexes of 2.7-3.3 in the IR. The SiH d. decreases with increasing H content, whereas the SiH2 d. increases, indicating a deterioration of the microstructure. The optical bandgap remains const. at .apprx.1.72 eV. The photocond. is of the order 10-6 (Wcm)-1 and the photoresponse 106. [on SciFinder (R)

An expanding thermal plasma for deposition of a-Si:H

A remote argon/hydrogen plasma is used to deposit amorphous hydrogenated silicon. The plasma is generated in a DC thermal arc (typical operating conditions 0.5 bar, 5 kW) and expands into a low pressure chamber (20 Pa) thus creating a plasma jet with a typical flow velocity of 103 m/s. Pure silane is injected into the jet immediately after the nozzle, in a typical flow mixture of Ar:H2:SiH4=55:10:6 scc/s. The electron temperature in the jet is low (typ. 0.3 eV): silane radicals are thought to be produced mainly by hydrogen abstraction, but also by a sequence of dissociative charge exchange and consecutive dissociative recombination. In-situ ellipsometry yields refractive indices of 3.6-4.2 at 632.8 nm and growth rates of 10-20 nm/s. FTIR analysis yields a hydrogen content of 9-25 at.% and refractive indices of 2.7-3.3 in the infrared. The SiH density decreases with increasing hydrogen content, whereas the SiH2 density increases. Above 11 at.%, the majority of hydrogen is bonded in the SiH2 configuration. The optical bandgap remains constant at approximately 1.72 eV. The photoconductivity is of the order 10-6 (Ωcm)-1 and the photoresponse 106.</p

An expanding thermal plasma for deposition of a-Si:H

A remote argon/hydrogen plasma is used to deposit amorphous hydrogenated silicon. The plasma is generated in a DC thermal arc (typical operating conditions 0.5 bar, 5 kW) and expands into a low pressure chamber (20 Pa) thus creating a plasma jet with a typical flow velocity of 103 m/s. Pure silane is injected into the jet immediately after the nozzle, in a typical flow mixture of Ar:H2:SiH4=55:10:6 scc/s. The electron temperature in the jet is low (typ. 0.3 eV): silane radicals are thought to be produced mainly by hydrogen abstraction, but also by a sequence of dissociative charge exchange and consecutive dissociative recombination. In-situ ellipsometry yields refractive indices of 3.6-4.2 at 632.8 nm and growth rates of 10-20 nm/s. FTIR analysis yields a hydrogen content of 9-25 at.% and refractive indices of 2.7-3.3 in the infrared. The SiH density decreases with increasing hydrogen content, whereas the SiH2 density increases. Above 11 at.%, the majority of hydrogen is bonded in the SiH2 configuration. The optical bandgap remains constant at approximately 1.72 eV. The photoconductivity is of the order 10-6 (Ωcm)-1 and the photoresponse 106.</p

Methyl substituents at the 11 or 12 position of retinal profoundly and differentially affect photochemistry and signalling activity of rhodopsin.

Contains fulltext : 50556.pdf (publisher's version ) (Closed access)The C-11=C-12 double bond of the retinylidene chromophore of rhodopsin holds a central position in its light-induced photoisomerization and hence the photosensory function of this visual pigment. To probe the local environment of the HC-11=C-12H element we have prepared the 11-methyl and 12-methyl derivatives of 11-Z retinal and incorporated these into opsin to generate the rhodopsin analogs 11-methyl and 12-methyl rhodopsin. These analog pigments form with much slower kinetics and lower efficiency than the native pigment. The initial photochemistry and the signaling activity of the analog pigments were investigated by UV-vis and FTIR spectroscopy, and by a G protein activation assay. Our data indicate that the ultrafast formation of the first photointermediate is strongly perturbed by the presence of an 11-methyl substituent, but much less by a 12-methyl substituent. These results support the current concept of the mechanism of the primary photoisomerization event in rhodopsin. An important stronghold of this concept is an out-of-plane movement of the C-12H element, which is facilitated by torsion as well as extended positive charge delocalization into the C-10-C-13 segment of the chromophore. We argue that this mechanism is maintained principally with a methyl substituent at C-12. In addition, we show that both an 11-methyl and a 12-methyl substitutent perturb the photointermediate cascade and finally yield a low-activity state of the receptor. The 11-methyl pigment retains about 30% of the G protein activation rate of native rhodopsin, while the 12-methyl chromophore behaves like an inverse agonist up to at least 20 degrees C, trapping the protein in a perturbed Meta-I-like conformation. We conclude that the isomerization region of the chromophore and the spatial structure of the binding site are finely tuned, in order to achieve a high photosensory potential with an efficient pathway to a high-activity state

Ultra-high-field MAS NMR assay of a multispin labeled ligand bound to its G-protein receptor target in the natural membrane environment: electronic structure of the retinylidene chromophore in rhodopsin.

Item does not contain fulltext11-Z-[8,9,10,11,12,13,14,15,19,20-(13)C10]Retinal prepared by total synthesis is reconstituted with opsin to form rhodopsin in the natural lipid membrane environment. The 13C shifts are assigned with magic angle spinning NMR dipolar correlation spectroscopy in a single experiment and compared with data of singly labeled retinylidene ligands in detergent-solubilized rhodopsin. The use of multispin labeling in combination with 2-D correlation spectroscopy improves the relative accuracy of the shift measurements. We have used the chemical shift data to analyze the electronic structure of the retinylidene ligand at three levels of understanding: (i) by specifying interactions between the 13C-labeled ligand and the G-protein-coupled receptor target, (ii) by making a charge assessment of the protonation of the Schiff base in rhodopsin, and (iii) by evaluating the total charge on the carbons of the retinylidene chromophore. In this way it is shown that a conjugation defect is the predominant ground-state property governing the molecular electronics of the retinylidene chromophore in rhodopsin. The cumulative chemical shifts at the odd-numbered carbons (Delta(sigma)odd) of 11-Z-protonated Schiff base models relative to the unprotonated Schiff base can be used to measure the extent of delocalization of positive charge into the polyene. For a series of 11-Z-protonated Schiff base models and rhodopsin, Delta(sigma)odd appears to correlate linearly with the frequency of maximum visible absorption. Since rhodopsin has the largest value of Delta(sigma)odd, the data contribute to existing and converging spectroscopic evidence for a complex counterion stabilizing the protonated Schiff base in the binding pocket

An expanding thermal plasma for deposition of a-Si:H

A remote argon/hydrogen plasma is used to deposit amorphous hydrogenated silicon. The plasma is generated in a DC thermal arc (typical operating conditions 0.5 bar, 5 kW) and expands into a low pressure chamber (20 Pa) thus creating a plasma jet with a typical flow velocity of 103 m/s. Pure silane is injected into the jet immediately after the nozzle, in a typical flow mixture of Ar:H2:SiH4=55:10:6 scc/s. The electron temperature in the jet is low (typ. 0.3 eV): silane radicals are thought to be produced mainly by hydrogen abstraction, but also by a sequence of dissociative charge exchange and consecutive dissociative recombination. In-situ ellipsometry yields refractive indices of 3.6-4.2 at 632.8 nm and growth rates of 10-20 nm/s. FTIR analysis yields a hydrogen content of 9-25 at.% and refractive indices of 2.7-3.3 in the infrared. The SiH density decreases with increasing hydrogen content, whereas the SiH2 density increases. Above 11 at.%, the majority of hydrogen is bonded in the SiH2 configuration. The optical bandgap remains constant at approximately 1.72 eV. The photoconductivity is of the order 10-6 (Ωcm)-1 and the photoresponse 106

Prevalence of physical symptoms of itch, pain and fatigue in patients with skin diseases in general practice.

BACKGROUND: Physical symptoms of skin diseases have been shown to negatively affect patients' wellbeing. Although insight into physical symptoms accompanying skin diseases is relevant for the management and treatment of skin diseases, the prevalence of physical symptoms among patients with skin diseases is a rather unexplored territory. OBJECTIVES: The goal of the present study was to examine the prevalence of physical symptoms of itch, pain and fatigue in patients with skin diseases. METHODS: On the basis of a systematic morbidity registration system in primary care, questionnaires were sent to 826 patients with skin diseases. Eventually, questionnaires from 492 patients were suitable for our analyses. RESULTS: Results indicated that patients with skin diseases particularly experience symptoms of itch and fatigue. Approximately 50% of all patients report experiencing these symptoms and about 25% experience these symptoms as relatively severe. Pain was relatively less frequently reported by 23% of all patients, and was on average somewhat less intense. The physical symptoms showed relatively strong correlations with disease-related quality of life and self-reported disease severity. In contrast, only moderate correlations were found with comorbidity and demographic variables, which suggests that the physical symptoms of itch, pain and fatigue are consequences of the skin diseases. CONCLUSIONS: Itch and fatigue and, to a somewhat lesser extent, pain have a high prevalence among patients with skin diseases. Clinicians should be encouraged to carefully assess itch, pain and fatigue in patients with skin diseases, and where appropriate focus treatment to these symptoms