Superconducting properties of fractal Nb/Cu multilayers

Abstract

Multilayers of Nb and Cu with a fractal or periodic stacking sequence were prepared by electron-beam evaporation onto sapphire substrates. Their superconductivity was investigated by measurements of T c and the temperature and angular dependence of the upper critical field B c2 . For low temperatures TӶT c , all samples show the characteristic behavior of two-dimensional superconductivity independent of the stacking sequence, whereas for temperatures near T c the type of layering determines the effective dimensionality, resulting in a ''multicrossover'' behavior in fractal samples.

Magnetic penetration depth in Nb/Al and Nb/Cu superconducting proximity bilayers

“…Previous studies indicate that for the 10-nm thick Nb films, the change in T c,Nb can be as large as 0.3 K with a thickness change of 1 nm. 23,22 In our case, T c,Nb for a single, nominally 12-nm thick Nb film was 6.95 K. T c,Nb for the samples of Groups C, D, and E in Table II was chosen to be 6.95, 7.10, and 7.25 K, respectively, which led to the reasonable fits of both T c and data. T c,Al in these groups was 2.0 K, as determined from the downturn point in the (T) curves with largest R B .…”

Antibiotics inhibiting the biosynthesis of cholesterol (a review)

“…The same acid attached to a substituted tetrahydroindazole forms compound XII whose inhibition activity is 3 times that of lovastatin [50]. HO At present it is obvious that a decrease in the CS and atherogenic LP level in the blood under the action of statins is related to an increase in the amount of apo-B,E-receptors in the liver (known to enhance the trapping of atherogenic LP from the blood), rather than to a a suppression of the CS synthesis de novo [13,14,22,55,56]. A certain role also belongs to the ability of statins to activate the palmitoyl transferase activity and suppress the excretion of newly synthesized VLDLP species from liver into blood [57,58].…”

“…The regulatory activity of the liver, including a very important "elimination" function, can be increased by administration of various drugs [I0, 13,14,20]. One group of such drugs, efficiently reducing the atherogenic LP level in the blood by acting upon the liver function, is represented by the synthetic anion exchange resins cholestyramine and colestipol, sequestrants of the bile acids, which are administered perorally and are not absorbed in the gastrointestinal tract.…”

“…A pronounced decrease in the total level of CS and atherogenic LDLP and VLDLP, as well as some increase in the content of antiatherogenic HDLP, is observed upon the administration of a quite small drug dose (10-20 mg/day) that is advantageously lower compared to the doses of other hypolipidemic drugs [10,[12][13][14]17]. The use of the aforementioned statins was accompanied neither by accumulation of any potentially toxic products nor by depletion of substances synthesized according to the mevalonate pathway.…”

“…As a result, the CS content in liver cells decreases, an additional amount of apo-B,E-receptors appears on the plasm membranes, and a greater amount of LDLP species is trapped by hepatocyte receptors. This leads eventually to a marked decrease in the level ofatherogenic LP and CS in the bloodstream [10,[12][13][14][15]22].…”