Search

(Figure Presented) Controlling the morphology of soluble small molecule organic semiconductors is crucial for the application of such materials in electronic devices. Using a simple dip-coating process we systematically vary the film drying speed to produce a range of morphologies, including oriented needle-like crystals. Structural characterization as well as electrical transistor measurements show that intermediate drying velocities produce the most uniformly aligned films. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.

Senile graying of human hair has been the subject of intense research since ancient times. Reactive oxygen species have been implicated in hair follicle melanocyte apoptosis and DNA damage. Here we show for the first time by FT-Raman spectroscopy in vivo that human gray/white scalp hair shafts accumulate hydrogen peroxide (H(2)O(2)) in millimolar concentrations. Moreover, we demonstrate almost absent catalase and methionine sulfoxide reductase A and B protein expression via immunofluorescence and Western blot in association with a functional loss of methionine sulfoxide (Met-S=O) repair in the entire gray hair follicle. Accordingly, Met-S=O formation of Met residues, including Met 374 in the active site of tyrosinase, the key enzyme in melanogenesis, limits enzyme functionality, as evidenced by FT-Raman spectroscopy, computer simulation, and enzyme kinetics, which leads to gradual loss of hair color. Notably, under in vitro conditions, Met oxidation can be prevented by L-methionine. In summary, our data feed the long-voiced, but insufficiently proven, concept of H(2)O(2)-induced oxidative damage in the entire human hair follicle, inclusive of the hair shaft, as a key element in senile hair graying, which does not exclusively affect follicle melanocytes. This new insight could open new strategies for intervention and reversal of the hair graying process.

Estrogen plays an important role in skin homeostasis, as demonstrated by the changes seen in the skin of post-menopausal women, changes reversed by HRT. Estrogen also has a role in wound healing, since estrogen deficiency as occurs post-menopausally and in ovariectomised animals, is associated with a reduced rate of wound healing. Estrogen appears to modulate all phases of wound healing with effects on inflammatory cells, epithelialization, angiogenesis, extracellular matrix deposition and tissue remodelling. This study was designed to investigate the effects of 17beta-estradiol on cultured human dermal fibroblasts using an in vitro wound-healing assay. The end points investigated were cell migration, proliferation, total collagen secretion and active TGF-beta1 secretion. 17beta-estradiol significantly increased the migration and proliferation of cultured dermal fibroblasts following mechanical wounding, although the secretion of total soluble collagen was not altered. An increase in TGF-beta1 was demonstrated by unwounded confluent dermal fibroblast monolayers in response to 17beta-estradiol, but paradoxically, a decrease in the secretion of TGF-beta1 was demonstrated in the mechanically wounded dermal fibroblasts. These results identify human dermal fibroblasts as estrogen target cells and provide further evidence for a role by which estrogen regulates this particular cell type as part of the wound-healing process. However, the paradoxical nature of the effect of estrogen on TGF-beta1 secretion following mechanical wounding suggests that the cellular mechanism of action is complex. A greater understanding of the cell-specific action of estrogen may help to develop therapies that will improve cutaneous wound healing in the future.

The skin locally synthesizes significant amounts of sexual hormones with intracrine or paracrine actions. The local level of each sexual steroid depends upon the expression of each of the androgen- and estrogen-synthesizing enzymes in each cell type, with sebaceous glands and sweat glands being the major contributors. Sebocytes express very little of the key enzyme, cytochrome P450c17, necessary for synthesis of the androgenic prohormones dehydroepiandrosterone and androstenedione, however, these prohormones can be converted by sebocytes and sweat glands, and probably also by dermal papilla cells, into more potent androgens like testosterone and dihydrotestosterone. Five major enzymes are involved in the activation and deactivation of androgens in skin. Androgens affect several functions of human skin, such as sebaceous gland growth and differentiation, hair growth, epidermal barrier homeostasis and wound healing. Their effects are mediated by binding to the nuclear androgen receptor. Changes of isoenzyme and/or androgen receptor levels may have important implications in the development of hyperandrogenism and the associated skin diseases such as acne, seborrhoea, hirsutism and androgenetic alopecia. On the other hand, estrogens have been implicated in skin aging, pigmentation, hair growth, sebum production and skin cancer. Estrogens exert their actions through intracellular receptors or via cell surface receptors, which activate specific second messenger signaling pathways. Recent studies suggest specific site-related distribution of ERalpha and ERbeta in human skin. In contrast, progestins play no role in the pathogenesis of skin disorders. However, they play a major role in the treatment of hirsutism and acne vulgaris, where they are prescribed as components of estrogen-progestin combination pills and as anti-androgens. These combinations enhance gonadotropin suppression of ovarian androgen production. Estrogen-progestin treatment can reduce the need for shaving by half and arrest progression of hirsutism of various etiologies, but do not necessarily reverse it. However, they reliably reduce acne. Cyproterone acetate and spironolactone are similarly effective as anti-androgens in reducing hirsutism, although there is wide variability in individual responses.

The aim of our study was to evaluate a three-dimensional gadolinium-enhanced breath-hold MR angiography sequence using standard MR gradients in detecting renal artery stenosis.Forty-two patients referred for angiography for suspected renal artery stenosis underwent both conventional digital subtraction angiography (DSA) and MR angiography. MR angiography was performed on a 1.5-T scanner with standard gradients. A fast multiplanar spoiled gradient-echo sequence was used with the following parameters: TR/TE, 10.3/1.9; flip angle, 45 degrees; field of view, 36 x 32 cm; matrix size, 256 x 128; one excitation; volume thickness, 70 mm; and partitions, 28. Gadolinium was administered IV as a dynamic bolus of 30-40 ml. Conventional and MR angiographic images were interpreted by two radiologists in consensus.DSA revealed 87 renal arteries, of which 79 were in 35 patients with native kidneys and eight arteries were in seven patients with transplanted kidneys. Gadolinium-enhanced MR angiography showed 85 (98%) of 87 renal arteries. Seventeen patients had 20 significant (50% stenosis) renal artery stenoses and five patients had five occluded renal arteries revealed by DSA. MR angiography revealed 85 renal arteries (98%), 20 stenoses (100%), and five occlusions (100%). Gadolinium-enhanced MR angiography led to one false-positive interpretation for renal artery stenosis and no false-negative interpretations. Thus, the sensitivity, specificity, and accuracy of MR angiography for renal artery stenosis were 100%, 98%, and 99%, respectively.The MR angiography pulse sequence we used was an effective and reliable technique for the diagnosis of renal artery stenosis. The sequence can be performed on widely available MR equipment that does not require fast gradient hardware.

Studies of the spin diffusion and magnetoresistance of multiwall carbon nanotubes contacted to by both cobalt and gold electrodes in magnetic fields of up to 4T are reported. The measured room temperature contact resistance of the Au and Co electrodes ranged from 10^3 to 10^[email protected] The magnetoresistance of tubes contacted to by Au electrodes and measured up to 4T at 4.2 and 2.2K was observed to be negative. The maximum negative magnetoresistance for the nanotubes contacted to by Co electrodes was 25%. As the temperature was increased the magnetoresistance decreased and disappeared above 25K. The spin diffusion length was calculated to be 650nm.

The anomalous properties of the Kondo lattice are compared with the well behaved Kondo system, CePd. The low-temperature thermal expansion of CePd is in agreement with previous heat capacity data, showing a ferromagnetic transition at and a second transition at 3.5 K probably due to reorientation of the magnetic moments. The Gruneisen factor, calculated from thermal-expansion and heat capacity is , the same as the Gruneisen factor calculated from the pressure dependence and comparable to a previous measurement of . Thermal expansion measurements (in fields of up to 8 T) and ac susceptibility measurements (under pressures of up to 7.33 kbar) have been made on in the temperature range 1.6-40 K. The zero-pressure ac susceptibility measurements confirm that there is an antiferromagnetic transition at , as previously reported. The magnetic contribution to the linear thermal-expansion coefficient of polycrystalline in zero magnetic field has a maximum value near 17 K and becomes small by 29 K. There is no peak in at the Neel temperature. The Neel temperature is found to decrease under pressure at the rate of , which indicates that is a magnetic Kondo lattice (with ) on the right-hand side of the Doniach diagram.

A miniature, monolithic radiofrequency sensor operating with MESFET circuitry in the GHz range is able to detect a wide variety of magnetic, metallic and dielectric materials via the losses induced in the sensitive volume around a coil. Application of the sensor to detect plastic and metal gearwheels and falling liquid drops is illustrated; the signal-to-noise ratio falls off as the inverse distance from the coil to the liquid drop. (C) 2001 Elsevier Science B.V. All rights reserved.

We present an analysis of spin injection efficiency that is of general application and relevant to a wide range of spin-electronic devices. By applying simple band structure ideas to a single interface between a metallic ferromagnet and a three-dimensional semiconductor, two conflicting figures of merit are identified - spin accumulation and polarization of injected current - and their validity to the analysis of different device types is discussed. The injected spin accumulation is smaller than the all-metal injection case by a factor (m*/me)3/2(kT/EF)1/2e^eD/kT. Moreover, the injected spin current at the interface is reduced by the factor (m*/me)3/2(kT/EF)(γS/γF) e^eD/kT, where γ for a particular material is the square root of its momentum scattering to spin-flip scattering ratio, m* and me are the effective and free masses, respectively, and eD is the donor binding energy. These results are consequent on the boundary condition that the spin channel electrochemical potentials are continuous at the interface. By inserting an insulating tunnel barrier between the ferromagnet and the semiconductor, not only is this boundary condition removed and the spin polarization of the injected current restored to the all-metal magnitude, but also the spin accumulations in the metal and the semiconductor even have opposite signs. This implies that thin or discontinuous tunnel barriers have the worst spin injection efficiency of any configuration. We finally note that for injected spin current into metals with polarization approaching 100%, the Fermi surface is polarized to a depth which exceeds the equilibrium carrier depth by a factor lSD/λ, hence >>1.

The positronium (Ps) formation cross-section, Q(Ps), for positron-argon interactions has been measured for incident positron energies from threshold to 60 eV, in an attempt to resolve the apparent discrepancy between earlier experimental results. Q(Ps) was found to vary smoothly with positron energy between 15 and 30 eV, in qualitative agreement with earlier results using methods involving the measurement of positron neutralization (as in the current experiment) and in disagreement with the double-peak energy dependence reported by Laricchia et al (2002 J. Phys. B: At. Mol. Opt. Phys. 35 2525-40), who used a positron-ion coincidence detection method. Possible reasons for this discrepancy, including Ps fragmentation and excited-state Ps formation, are discussed.

Results are given for the analysis of particle size distribution of a sample of finely ground phenothiazine by four different methods. Each method is reproducible and is in use for the size analysis of phenothiazine in different laboratories, but the results differ considerably. The advantages and disadvantages of each method are discussed briefly, and a means of comparing the results with those obtained by surface area measurements is shown.

Some surface-active agents enhance the absorption of griseofulvin from suspensions administered to rats and man. The method of incorporating the agent into the suspension is important. No similar effect is observed with tablets of griseofulvin in man. The effect of particle size on the absorption of griseofulvin when administered as a suspension and as tablets has been studied in a statistically designed experiment in man. The results show that doses of 0.5 g. griseofulvin of surface area 0.35 m.2/g. or 0.25 g. of material with a surface area of 1.5 m.2/g. give similar concentrations of griseofulvin in the blood.

A method of programming an electronic computer has been developed which fits the results of size analyses obtained by means of a Coulter counter to a logarithmic normal curve from which a specific surface area figure is derived. Applications of the method to suspensions of phenothiazine are discussed.