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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: 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: We present true color maps of a metal surface imaged by scanning tunneling microscopy (STM). Light emission spectra were acquired at each imaging pixel, and converted into a real color map. A rough gold film was shown to exhibit minimal color changes across the sample, so spectra are dependent on material and not sample geometry, due to a small radius tip. A larger tip was still able to distinguish between Ag and Cu clusters with ∼10 nm resolution, despite the onset of geometric effects. We conclude that color mapping represents an ideal way of identifying metals in STM on the nanometer scale. © 2002 American Institute of Physics.

Notes: We have investigated the scanning-tunneling-microscopy-induced light emission originating from a single GaAs quantum well. The 5-nm-thick quantum well was confined between a 30-nm-thick AlAs barrier (grown onto a GaAs substrate) and the vacuum tunneling gap. Low currents ensured a nonintrusive investigation of the surface. Optical spectroscopy of the light emitted while injecting electrons from the tip revealed two peaks associated with the band-to-band recombination in the bulk GaAs (at 1.43 eV), and with the electronic transition in the surface quantum well (at 1.52 eV). The surface sensitivity of the technique is evidenced and the quantum efficiencies of both processes are estimated. © 2000 American Institute of Physics.

Notes: Light emission with a blackbody-like spectrum was observed during current flow through atomic-size metallic contacts formed in the scanning tunneling microscope. Within the contact, the electron temperature rises above the lattice temperature as electron–phonon energy transfer vanishes. Electron temperatures of up to 9000 K were deduced from optical spectroscopy of stable contacts. An important consequence of greatly reduced electron energy losses is that these atomic-size metal contacts have maximum current densities of ∼1015 A m−2, several orders of magnitude greater than for macroscopic wires. © 2002 American Institute of Physics.

Notes: The fabrication of microcavities by a sol–gel process and their optical properties are described. The cavities are constituted of an Eu3+-doped SiO2 active layer inserted between two Bragg mirrors, fabricated by stacking alternatiely undoped TiO2 and SiO2 sol–gel thin films. Eu3+ luminescence modification due to the cavity effect, intensity enhancement and modification of the line shape has been observed, and shows a cavity quality factor of 1200. The reflectivity factor of the associated Bragg mirrors reaches 99.8% for seven alternate SiO2/TiO2 layers. © 2001 American Institute of Physics.

Notes: Necrotic insults such as seizure are excitotoxic. Logically, membrane hyperpolarization by increasing outwardly conducting potassium channel currents should attenuate hyperexcitation and enhance neuron survival. Therefore, we overexpressed a small-conductance calcium-activated (SK2) or voltage-gated (Kv1.1) channel via viral vectors in cultured hippocampal neurons. We found that SK2 or Kv1.1 protected not only against kainate or glutamate excitotoxicity but also increased survival after sodium cyanide or staurosporine. In vivo overexpression of either channel in dentate gyrus reduced kainate-induced CA3 lesions. In hippocampal slices, the kainate-induced increase in granule cell excitability was reduced by overexpression of either channel, suggesting that these channels exert their protective effects during hyperexcitation. It is also important to understand any functional disturbances created by transgene overexpression alone. In the absence of insult, overexpression of Kv1.1, but not SK2, reduced baseline excitability in dentate gyrus granule cells. Furthermore, while no behavioral disturbances during spatial acquisition in the Morris water maze were observed with overexpression of either channel, animals overexpressing SK2, but not Kv1.1, exhibited a memory deficit post-training. This difference raises the possibility that the means by which these channel subtypes protect may differ. With further development, potassium channel vectors may be an effective pre-emptive strategy against necrotic insults.

Notes: Tyrosine hydroxylase (TH) gene promoter activity is increased in PC12 cells that are treated with the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA). Mutagenesis of either the cAMP responsive element (CRE) or the activator protein-1 element (AP1) within the TH gene proximal promoter leads to a dramatic inhibition of the TPA response. The TH CRE and TH AP1 sites are also independently responsive to TPA in minimal promoter constructs. TPA treatment results in phosphorylation of cAMP responsive element binding protein (CREB) and activation of cAMP-dependent protein kinase (PKA) in PC12 cells; hence, we tested whether CREB and/or PKA are essential for the TPA response. In CREB-deficient cells, the response of the full TH gene proximal promoter or the independent response of the TH CRE by itself to TPA is inhibited. The TPA-inducibility of TH mRNA is also blocked in CREB-deficient cells. Expression of the PKA inhibitor protein, PKI, also inhibits the independent response of the TH CRE to TPA. Our results support the hypothesis that TPA stimulates the TH gene promoter via signaling pathways that activate either the TH AP1 or TH CRE sites. Both signaling pathways are dependent on CREB and the TH CRE-mediated pathway is dependent on PKA.

Notes: Abstract.— The effect on growth and survival of the initial stocking density (50, 100, 150, and 200 larvae/ L) in larval rearing of spotted sand bass was evaluated over 30 d in a closed recirculating system. Larvae were fed with rotifers, copepods, nauplii and adult Artemia, and spotted sand bass yolk-sac larvae. Water quality was monitored daily. The notochordal or standard length of sampled larvae was measured by image analysis. Specific growth rates at each density were compared by covariance analysis. Survival was estimated from day 15 to the end of the experiment, when a resistance test was used to evaluate the juvenile quality among densities. At the end of the experiment, mean standard length of larvae at lower densities was significantly larger (P 〈 0.05) than at higher densities. Higher specific growth rates were found at lower densities. Significantly higher survival (P 〈 0.05) was recorded for the lowest density, but the highest number of harvested fish was obtained with the highest densities (150 and 200 larvae/L). The lowest density also showed the significantly (P 〈 0.05) higher survival after using a resistance test. We conclude the highest density can be used in larval rearing of spotted sand bass. However, better survival, growth, and seed quality are obtained at the lowest density. To recommend an optimal density for this specie, it is necessary to improve the water quality in the culture system and to make a cost-benefit study.

Notes: Net CO2 flux measurements conducted during the summer and winter of 1994–96 were scaled in space and time to provide estimates of net CO2 exchange during the 1995–96 (9 May 1995–8 May 1996) annual cycle for the Kuparuk River Basin, a 9200 km2 watershed located in NE Alaska. Net CO2 flux was measured using dynamic chambers and eddy covariance in moist-acidic, nonacidic, wet-sedge, and shrub tundra, which comprise 95% of the terrestrial landscape of the Kuparuk Basin. CO2 flux data were used as input to multivariate models that calculated instantaneous and daily rates of gross primary production (GPP) and whole-ecosystem respiration (R) as a function of meteorology and ecosystem development. Net CO2 flux was scaled up to the Kuparuk Basin using a geographical information system (GIS) consisting of a vegetation map, digital terrain map, dynamic temperature and radiation fields, and the models of GPP and R.Basin-wide estimates of net CO2 exchange for the summer growing season (9 May−5 September 1995) indicate that nonacidic tundra was a net sink of −31.7 ± 21.3 GgC (1 Gg = 109 g), while shrub tundra lost 32.5 ± 6.3 GgC to the atmosphere (negative values denote net ecosystem CO2 uptake). Acidic and wet sedge tundra were in balance, and when integrated for the entire Kuparuk River Basin (including aquatic surfaces), whole basin summer net CO2 exchange was estimated to be in balance (−0.9 ± 50.3 GgC). Autumn to winter (6 September 1995–8 May 1996) estimates of net CO2 flux indicate that acidic, nonacidic, and shrub tundra landforms were all large sources of CO2 to the atmosphere (75.5 ± 8.3, 96.4 ± 11.4, and 43.3 ± 4.7 GgC for acidic, nonacidic, and shrub tundra, respectively). CO2 loss from wet sedge surfaces was not substantially different from zero, but the large losses from the other terrestrial landforms resulted in a whole basin net CO2 loss of 217.2 ± 24.1 GgC during the 1995–96 cold season. When integrated for the 1995–96 annual cycle, acidic (66.4 + 25.25 GgC), nonacidic (64.7 ± 29.2 GgC), and shrub tundra (75.8 ± 8.4 GgC) were substantial net sources of CO2 to the atmosphere, while wet sedge tundra was in balance (0.4 + 0.8 GgC). The Kuparuk River Basin as a whole was estimated to be a net CO2 source of 218.1 ± 60.6 GgC over the 1995–96 annual cycle. Compared to direct measurements of regional net CO2 flux obtained from aircraft-based eddy covariance, the scaling procedure provided realistic estimates of CO2 exchange during the summer growing season. Although winter estimates could not be assessed directly using aircraft measurements of net CO2 exchange, the estimates reported here are comparable to measured values reported in the literature. Thus, we have high confidence in the summer estimates of net CO2 exchange and reasonable confidence in the winter net CO2 flux estimates for terrestrial landforms of the Kuparuk river basin. Although there is larger uncertainty in the aquatic estimates, the small surface area of aquatic surfaces in the Kuparuk river basin (≈ 5%) presumably reduces the potential for this uncertainty to result in large errors in basin-wide CO2 flux estimates.