排序方式: 共有5条查询结果,搜索用时 0 毫秒
1
1.
G Fuchs K-H Müller J Freudenberger K Nenkov S-L Drechsler SV Shulga D Lipp A Gladun T Cichorek P Gegenwart 《Pramana》2002,58(5-6):791-797
The effect of substitutional disorder on the superconducting properties of YNi2B2C was studied by partially replacing yttrium and nickel by Lu and Pt, respectively. For the two series of (Y, Lu)Ni2B2C and Y(Ni, Pt)2B2C compounds, the upper critical field H
c2(T) and the specific heat c
p(T, H) in the superconducting mixed state have been investigated. Disorder is found to reduce several relevant quantities such
as T
c, the upper critical field H
c2(0) at T=0 and a characteristic positive curvature of H
c2(T) observed for these compounds near T
c. The H
c2(T) data point to the clean limit for (Y, Lu) substitutions and to a transition to the quasi-dirty limit for (Ni, Pt) substitutions.
The electronic specific heat contribution γ(H) exhibits significant deviations from the usual linear γ(H) law. These deviations reduce with growing substitutional disorder but remain even in the quasidirty limit which is reached
in the Y(Ni1−x
, Pt
x
)2B2C samples for x=0.1. 相似文献
2.
Non-resonant microwave absorption (NRMA) studies of superconducting MgB2 and a sample containing ∼10% by weight of MgO in MgB2 are reported. The NRMA results indicate near absence of intergranular weak links in the pure MgB2 sample. A linear temperature dependence of the lower critical field H
c1 is observed indicating a non-s wave superconductivity. However, the phase reversal of the NRMA signal which could suggest d wave symmetry is also not observed. In the MgB2 + MgO sample, much larger low field dependent absorption is observed indicating the presence of intergranular weak links.
The hysteretic behavior of NRMA is compared and contrasted in the two samples. In the pure MgB2 sample, a large hysteresis is observed between the forward and the reverse scans of the magnetic field indicating strong
pinning of flux lines. This hysteresis saturates a few degrees below T
c while in the MgB2 + MgO sample, a much slower increase of hysteresis with decreasing temperature is observed, a signature of weaker pinning. 相似文献
3.
Cerchiara T Straface SV Chidichimo G Belsito EL Liguori A Luppi B Bigucci F Zecchi V 《Natural product communications》2012,7(1):137-140
The purpose of this study was to analyse the chemical composition of Spartium junceum L. (also known as Spanish Broom) aromatic water and to evaluate its cytotoxic activity against a series of human cancer cell lines (melanoma: RPMI 7932; leukemia: K562; breast cancer cell: MCF7-Bart and MCF7-ICLC, colon adenocarcinoma: SW480). The results show that the aromatic water was cytotoxic toward the tumor cell lines analyzed (RPMI 7932, K562, MCF7-Bart, MCF7-ICLC, SW480), while it did not appreciably alter the viability of normal keratinocytes (NCTC 2544) suggesting its potential use as an antitumor agent for cancer treatment and/or prevention. 相似文献
4.
E Straface P U Giacomoni W Malorni 《Journal of photochemistry and photobiology. B, Biology》2001,63(1-3):52-60
In vivo, UV radiation induces a series of morphological and ultrastructural alterations in human epidermis. These and other changes eventually lead to well described pathological modifications including erythema and cancer. Morphological alterations are easier to detect in cultured cells, such as human keratinocytes or other epithelial cells. One can use different intensities of different radiation types (UV-A, -B and -C) and expose cell monolayers to different doses. In these experimental conditions it is possible to evaluate radiation risks and to provide additional information thanks to the reproducibility and the enormous amplification of the phenomena normally occurring in vivo. Alterations observed in structural studies can be summarized as the succession of the following events: (i) cell retraction with loss of cell-cell interactions; (ii) surface blebbing; and eventually (iii) cell death. Cytoskeletal components play a key role in this cascade. Morphogenesis of these changes can be ascribed to oxidative modifications due to reactive oxygen species formation following radiation that can modify both cell membrane and cytoskeleton. The use of in vitro systems can be of great relevance in the understanding of the pathogenetic mechanisms of UV radiation changes and to determine possible drugs capable of counteracting UV-mediated subcellular pathology. 相似文献
5.
Masella R Straface E Giovannini C Di Benedetto R Scazzocchio B Viora M Cantafora A Malorni W 《Photochemistry and photobiology》2000,71(1):97-102
Oxidized LDL (ox-LDL) have been involved in the pathogenesis of several human diseases including dermatological pathologies. Oxidative modification of low-density lipoproteins (LDL) is accompanied by both extensive degradation of its polyunsaturated fatty acids and production of lipoperoxides. These highly reactive products induce an intracellular oxidative stress with a variety of cytotoxic effects. In order to evaluate cellular damage induced by oxidative stress in epidermal cells, a human epidermoid carcinoma cell line in culture (A 431) was used as experimental model. Cell treatment with UV-oxidized LDL resulted in cytostatic and cytotoxic effects characterized by morphological and functional alterations: inhibition of cell proliferation, modifications of cytoskeleton network, microtubular derangement, loss of cell–cell and cell–substrate contacts, cell detachment and cell death by apoptosis. The ox-LDL-induced alterations were almost completely prevented by pre-incubating cells with α-tocopherol. The results presented here could be of relevance for a better comprehension of the pathogenic mechanisms of several human diseases, including dermatological pathologies, and could indicate that antioxidants such as α-tocopherol could represent an important therapeutic challenge in the maintenance of cell and tissue homeostasis in the long run. 相似文献
1