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Notes: Conduction and low-frequency noise are analyzed in the channel of hydrogenated amorphous silicon (a-Si:H) thin-film transistors. 1/f noise expressions are proposed starting from a simple conduction model describing drain current in the ohmic range. Carrier fluctuations (ΔN model) and mobility fluctuations (Δμ model) are investigated. For long-channel transistors the conduction is quite similar to crystalline metal–oxide–semiconductor field-effect transistors but involving low mobility values. The 1/f noise behavior is analyzed by mobility fluctuations as predicted by Hooge's theory. For small channel transistors a crowding effect appears and access series resistances affect the conduction. The excess noise is then mainly controlled by these resistances when large gate voltages VGS are applied. © 1996 American Institute of Physics.

Notes: A parametric study of single-crystal silicon roughness induced by an SF6 plasma has been carried out by means of atomic force microscopy. An helicon source (also called resonant inductive plasma etcher) has been used to study the relation between plasma parameters and subsequent surface damage. The surface damage has been examined in terms of height roughness analysis and in terms of spatial (lateral) extent of the surface roughness. The central result is that roughness scales with the ratio of the ion flux over the reactive neutral flux (J+/JF), showing the combined role of both ionic and neutral species. At low ion flux, the neutrals smooth the surface, while at higher ion flux, they propagate the ion-induced defects, allowing the roughness to be enhanced. Influences of other parameters such as exposure duration, ion energy, or substrate temperature have also been quantified. It is shown that the roughness growth is well described by an empirical law: rms∝(1/(square root of)E)(J+/JF)ηtβ, with η≈0.45 and β≈1 (rms is the root mean square of the roughness). In other respects, we analyze the data with a Fourier transform analysis. The main advantage is to minimize noise and to separate the magnitude of the roughness, the lateral correlation length on which the roughness is growing, and the behavior of short and long range roughness. The results are identical to the rms analysis, especially, the above scaling law. The time evolution of the lateral correlation length follows a scaling law (which is not accessible by means of the rms) leading to a fractal dimension of 2.67. Also is observed a variation of the short range roughness as a function of the substrate bias voltage. Consequence for further scaling down of integrated circuits is called to mind.

Notes: Human skin sections were studied using synchrotron-powered infrared microscopy. The superior lateral resolution achieved with this technique (diffraction-limited spot sizes) allows the detailed analysis of the biocomposition of the skin layers. It is shown that highly organized lipids are present in the stratum corneum, as evidenced by a slight frequency difference in the symmetric stretch mode of the methylene groups. Biochemical images were generated showing the precise location of the lipids, proteins and collagen across the skin section. More enhanced images were generated using a statistical approach (fuzzy C-means clustering). Penetration of two external agents (cyanophenol and a cosmetic compound, ethylhexyl methoxycinnamate) was studied. The penetration pathway across the stratum corneum is favored at locations of lower lipid concentration. Both compounds penetrated into the epidermis, but neither of them induced a change in the protein secondary structure. It was shown that hair follicle is a favored penetration pathway for these agents.

Notes: The authors report the results of a retrospective controlled study on the incidence of migraine in centro-temporal epilepsy compared to absence epilepsy, partial epilepsy and a group of patients with cranial trauma without epilepsy. The following observations from this series of 129 patients were made. Migraine was present in 63% of the patients with centro-temporal epilepsy (rolandic epilepsy), in 33% with absence epilepsy, in 7% with partial epilepsy and in 9% of the cranial trauma group. These results suggest that the association of centro-temporal epilepsy and migraine is non-fortuitous and also to a lesser degree in absence epilepsy. The role of neurotransmitters in this association is discussed. No decrease in cerebral blood flow was observed in 12 patients with rolandic epilepsy on a Hm-PAO SPECT study.

Notes: The extent of changes with aging depends largely on how much the skin is exposed to sunlight and also on the genetic disposition of the individual. There are thus two main processes, extrinsic aging because of environmental stress, and intrinsic genetically programmed aging [1]. Hence, the processes of aging depends on a person's ethnic origin and the part of the world in which they live.〈section xml:id="abs1-1"〉〈title type="main"〉MethodsThe present study investigates the influence of age and exposure to sunlight on the facial skin of 31 healthy Japanese women, aged 20–78 years old, living in Osaka city. Skin samples were obtained during plastic surgery from the face, from areas exposed to varying intensities of sunlight (forehead, cheek, nose, upper eyelid). Samples were fixed in formalin and embedded in paraffin. Sections (5–7 μm) were cut and stained with hematoxylin–phloxyn–safran, orcein or Masson's trichrome. Others were immunostained for p63, β1-integrin, type IV collagen CD1a and AQP3. Statistical analysis of quantitative and qualitative parameters were performed by analysis of variance (anova) with linear regressions, and the chi-squared test.〈section xml:id="abs1-2"〉〈title type="main"〉Results and discussion〈section xml:id="abs1-3"〉〈title type="main"〉Epidermis and dermal-epidermal junction: histological organizationWe confirmed that the whole living epidermis becomes thinner with increasing age, with an average decrease of about 5 μm per decade. This thinning is mainly because of a significant reduction in the number of keratinocyte layers. The thinning of the epidermis and the reduction of the keratinocytes layers in Japanese skin do not seem to be reflected in the thickness of the stratum corneum, which appears to remain constant whatever the age in the sample studied.The epidermal papillary structures also became flatter with age, associated with an increase in the thickness of the dermal–epidermal junction (DEJ). Thus, in addition to the loss of epidermal cells, the epidermis and dermis become less overlapped, so reducing the surface area for exchange between the two compartments. The DEJ also become thicker as Japanese ages and the expression of type IV collagen, the main constituent of the lamina densa and anchoring plaques is reduced in the most photoexposed skin areas. This accounts for the major changes in the function and molecular structure of DEJ components, as in aged Caucasian skin [2].〈section xml:id="abs1-4"〉〈title type="main"〉Keratinocyte growth and differentiation –β1-integrin and p63There is no doubt that the rate of cell turnover decreases in the flat aged epidermis, as indicated by the smaller number of proliferative cells [3, 4]. This study focused on two key regulatory proteins. One was p63, that is involved in maintaining the proliferative potential of basal keratinocytes and blocking their calcium-induced differentiation [5]. The other was β1-integrin, an adhesion protein present in basal keratinocytes and linked to their clonogenic potential [6].We found p63-positive cells in the basal layer of the epidermis and in the suprabasal layers (〈link href="#f1-7"〉Fig. 1a), in agreement with others [7]. The used pan anti-p63 antibody suggest that other isoforms of the protein in addition to the major ΔNp63α mainly expressed in the basal cells, could take part to other functions like differentiation in the suprabasal layers [5]. The great interindividual variation in the staining intensity for p63 in the samples studied made it impossible to detect significant changes in the number of p63-positive cells with age. Only an increase of p63 was observed in photoexposed areas compared to others within this case, a possible relation to the epidermal thickening.〈figure xml:id="f1-7"〉1〈mediaResource alt="image" href="urn:x-wiley:01425463:ICS254_7_7:ICS_254_f1-7"/〉Immunostaining of Japanese facial skin showing AQP3 expression at the plasma membrane of keratinocytes throughout the living epidermis (a) and the age-related change in AQP3 (b).β1-integrin was detected only in the basal keratinocytes, and the staining intensity varied from one segment of the basal layer to another. We evaluated the length of immune-labeled epidermis and the intensity of labeling in each fragment, using an arbitrary colorimetric scale (0–5). We observed a significant decrease in the intermediate intensities (equal to 2 only) with age in the zone least exposed to sunlight. This is consistent with the loss of adhesive properties of freshly isolated epidermal cells in aged skin [2] and the existence of different pools of basal keratinocytes [6]. It suggests that the effect of aging could affect particularly on the transit amplifying cells containing intermediate quantities of β1-integrin.〈section xml:id="abs1-5"〉〈title type="main"〉Osmotic and water homeostasis – aquaporin-3In addition to the stratum corneum (SC) that limits transepidermal water loss, the osmotic equilibrium inside the epidermis and hydration is controlled by the aquaglyceroporins 3 (AQP3) [8, 9]. Immunostaining for AQP-3 confirmed the presence of the protein in the plasma membranes of keratinocytes throughout the epidermis, together with AQP-3 cytoplasmic expression of the basal layer cells (〈link href="#f1-7"〉Fig. 1a). There was no immunostaining in the SC (〈link href="#f1-7"〉Fig. 1a) to retain water in the epidermis via the tight junction proteins [10], so maintaining the water-lipid barrier within the SC. The immunostaining for AQP3 decreased significantly with the skin age (〈link href="#f1-7"〉Fig. 1b), but there was no significant difference between areas exposed to sunlight and those not exposed. This suggests that there is an overall reduction in the natural hydration potential as Japanese facial epidermis ages.〈section xml:id="abs1-6"〉〈title type="main"〉The immune system – epidermal CD1a-positive cellsEpidermal dendritic cells, mainly Langerhans cells, control the skin immune system. These cells are CD1a positive (CD1a+). Immunostaining showed a major population of highly dendritic cells throughout the epidermis of all the Japanese skin samples. It also showed that the areas most exposed to sunlight (cheeks, forehead and nose) had significantly more CD1a+ cells than less exposed areas (upper eyelid) (〈link href="#f2-7"〉Fig. 2a). This confirms previous findings on the wrinkling of area of Caucasian facial skin after chronic exposure to UV light [11]. The number of CD1a+ cells in less exposed areas of skin increased significantly with donor age (〈link href="#f2-7"〉Fig. 2b). This shows that chronological aging and exposure to sunlight give rise to an epidermis which cellular immune homeostasis is perturbed.〈figure xml:id="f2-7"〉2〈mediaResource alt="image" href="urn:x-wiley:01425463:ICS254_7_7:ICS_254_f2-7"/〉Immunostaining for CD1a in Japanese facial skin: numbers of CD1a-positive (CD1a+) epidermal cells per mm of dermal–epidermal junction (DEJ) in skin exposed to sunlight and skin from protected areas (a), and sun-protected area of facial skin from subjects of different ages (b).〈section xml:id="abs1-7"〉〈title type="main"〉The pigmentation system – melanocytes and melanin depositsPigmentation is part of the protective system developed by the skin epidermis, but unwanted pigmentation is one of the first signs of aging and has a major social impact. The pigmentation of the facial skin of Japanese women increases with age, and spots develop, particularly on the cheeks [12]. We found a significantly greater density of melanocytes in the epidermis of older donors in both sun-exposed and protected areas. But there were significantly fewer melanocytes in the areas exposed to sunlight than in protected areas. As expected, there were greater deposits of melanin in keratinocytes in the regions exposed to sunlight. This suggests that older donors had a pool of highly active melanocytes in areas of skin exposed to sunlight, with a high rate of melanin transfer to keratinocytes and/or reduced keratinoc

Notes: Synchrotron-based infrared microscopic measurements have been performed on various hair transverse sections, sampled either from the heads of Caucasian or Afro-American subjects. Lipid content of various virgin hair transverse sections was established, with an unprecedented resolution. The variations in shape and intensity of the CH2, CH3, amide I and amide II bands, before and after lipid removal by solvent extraction, were profiled, showing clearly that Caucasian hair often contains lipids localized inside the medulla and to a lesser extent inside the cuticle. This statement does not hold for the Afro-American hair analysed. For this, the FT-IR spectra do not change within the hair section and are insensitive to solvent extraction. The importance of the origin of hair on its physical and chemical properties has to be taken into account in future investigations.

Notes: To determine the effect of subject self-selection on the alpha-hypnotizability correlation, the correlations between volunteer and invited subject groups were compared. For 8 volunteers the correlation between baseline eyes-closed occipital alpha and the Harvard Group Scale of Hypnotic Susceptibility score was r=.72; for 12 invited subjects, that correlation was r=-.02. The significant difference in these correlations gives support to a previously published paper which hypothesized, on the basis of a literature review, that sampling modifications generated by subject self-selection were responsible for the occurrence of significant alpha-hypnotizability correlations.

Notes: Experimental investigations of the relationships between EEG alpha indices and hypnotic susceptibility are reviewed. The literature is characterized as indicating that the simple alpha-hypnotizability correlation does not exist in the general population. When such correlations are found, they are usually due to complex patterns which result in non-representative subject pools when subjects are non-naive volunteers. When subjects are invited to participate in experiments, significant correlations are not found.The implications of these conclusions are threefold: 1) The research on the relationship between EEG alpha and hypnotizability can now center on describing the mechanisms by which volunteer samples yield such correlations. 2) Researchers should be aware that subject selection methods can be the primary determinants of significant results. 3) Experiments based on the assumption that there is no alpha-hypnotizability correlation in the population can yield information on the differences in cognitive ability between high and low hypnotizables.