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排序方式: 共有833条查询结果,搜索用时 15 毫秒
1.
Indermeet Kohli Taylor L. Braunberger Amanda F. Nahhas Fatima N. Mirza Mohsen Mokhtari Alexis B. Lyons Nikiforos Kollias Eduardo Ruvolo Henry W. Lim Iltefat H. Hamzavi 《Photochemistry and photobiology》2020,96(1):208-214
Human skin is exposed to visible light (VL; 400–700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range. 相似文献
2.
Muhammad Taher Abuelma'atti 《International Journal of Infrared and Millimeter Waves》1994,15(12):2077-2084
Analytical expressions are obtained for predicting the harmonic and intermodulation performance of subcarrier multiplexed systems owing to stimulated Brilloun scattering. These expressions are in terms of the ordinary Bessel functions with arguments depenedent on the modulation index. 相似文献
3.
Muhammad Taher Abuelma’atti 《Applied Acoustics》2007,68(10):1286-1296
A mathematical model for the open-circuit output voltage of a micromachined silicon inductive microphone is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the output components resulting from a multisinusoidal input acoustic pressure. The special case of an equal-amplitude two-tone acoustic pressure input is considered in detail. The results show that, the microphone generates both even and odd-order harmonic and intermodulation products. 相似文献
4.
Fatima Hassine Said Gmouh Mathieu Pucheault Michel Vaultier 《Monatshefte für Chemie / Chemical Monthly》2007,57(12):1167-1174
In this work was presented an application of the use of task specific onium salts (TSOSs) as soluble supports in Grieco’s multicomponent synthesis of tetrahydroquinolines. These soluble supports are of wide applicability and combine advantages
of solid phase synthesis without its limitations with those of solution phase chemistry. After a simple washing step, products
were cleaved from the supports and obtained in pure form and good yields. 相似文献
5.
Muhammad Taher Abuelma'atti 《International Journal of Infrared and Millimeter Waves》1991,12(8):911-918
An empirical model is presented for the current-voltage characteristics of resonanttunneling (RT) devices. By using this model an analytical study of millimeter-band electronic circuits employing RT devices can be performed. 相似文献
6.
Nickel was quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (Nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA Cl) onto benzophenone in the pH range 5.0-6.0 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of a nickel complex and benzophenone was dissolved with 5 ml of dimethylformamide (DMF) and the metal was determined by atomic absorption spectrometry (AAS). About 0.6 microg of nickel could be concentrated from 200 ml of an aqueous sample, where its concentration was as low as 3.0 ng/ml. Eight replicate determinations of 2.5 microg/ml of nickel in the final DMF solution gave a mean absorbance of 0.112 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 98 ng/ml. The interference of a number of anions and cations was studied and the developed optimized conditions were utilized for the trace determination of nickel in various alloys and biological samples. 相似文献
7.
Muhammad Taher Abuelma'atti 《International Journal of Infrared and Millimeter Waves》1995,16(2):391-400
A Fourier-series model describing the current-voltage characteristic of a quantum-well diode (QWD) is presented. Using this model, closed-form expressions are obtained for the harmonic and intermodulation performance of a QWD excited by a multisinusoidal voltage superimposed on a dc voltage. 相似文献
8.
Trituration and capillary solid-state spot-tests for 25 anions with a number of organic and inorganic reagents have been examined. A comparative study of the corresponding reactions in solution has also been made. Incorporation of a glass-wool plug in the capillary improves the selectivity. Schemes are presented for possible use of the technique. 相似文献
9.
Novel synthesis of (1H)‐pyridin‐2‐one, pyrazolo[1,5‐a]pyrimidine and isoxazole derivatives incorporating N‐methylphthalimide moiety are reported. Reaction of enaminone 2 with malononitrile affords 4. Condensation of 2 with cyanothioacetamide or benzoylacetonitrile affords compounds 6 and 7 respectively. Reaction of 2 with hydrazine hydrate afford 2,3‐dihydrophthalazine‐1,4‐dione ( 10 ). Condensation of 2 with hydroxylamine and 3‐aminopyrazole derivatives affords compounds 12 and 15a,b respectively. Antimicrobial and antifungal activity were determined for representative compounds and most of them showed moderate activity as antimicrobial agents, while compounds 2 and 7 show strong activity against Aspergillus niger. The structure of the newly synthesized compounds was elucidated by elemental analyses and 1H nmr spectra and some cases by 13C nmr investigation. 相似文献
10.
M. A. Taher 《Journal of Analytical Chemistry》2004,59(10):985-991
A highly selective, sensitive, rapid, and economical differential pulse polarographic method has been developed for the determination of trace amounts of lead in various standard alloys and biological samples after the adsorption of its 2-nitroso-l-naphthol-4-sulfonic acid (nitroso-S)—tetradecyldimethylbenzylammonium (TDBA) chloride on microcrystalline naphthalene in the pH range of 8.0–10.5. After filtration, the solid mass is shaken with 9.0 mL of 1 M hydrochloric acid, and lead is determined by differential pulse polarography (DPP). Lead can alternatively be quantitatively adsorbed on 2-nitroso-l-naphthol-4-sulfonic acid-tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. In this case, 1.0 g of lead can be concentrated in a column from 500 mL of an aqueous sample in which its concentration is as low as 2 ng/mL. Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters, such as the pH effect, volume of aqueous phase, HCl concentration, reagent concentration, naphthalene concentration, shaking time, and the interference of a number of metal ions on the determination of lead were studied in detail to optimize the conditions for determination in standard alloys and standard biological samples. 相似文献