1,823 research outputs found
Infrared conductivity of a one-dimensional charge-ordered state: quantum lattice effects
The optical properties of the charge-ordering () phase of the
one-dimensional (1D) half-filled spinless Holstein model are derived at zero
temperature within a well-known variational approach improved including
second-order lattice fluctuations. Within the phase, the static lattice
distortions give rise to the optical interband gap, that broadens as the
strength of the electron-phonon () interaction increases. The lattice
fluctuation effects induce a long subgap tail in the infrared conductivity and
a wide band above the gap energy. The first term is due to the multi-phonon
emission by the charge carriers, the second to the interband transitions
accompanied by the multi-phonon scattering. The results show a good agreement
with experimental spectra.Comment: 5 figure
Overrepresentation of IL-17A and IL-22 Producing CD8 T Cells in Lesional Skin Suggests Their Involvement in the Pathogenesis of Psoriasis
Determination of irinotecan (CPT-11) and its active metabolite SN-38 in human plasma by reversed-phase high-performance liquid chromatography with fluorescence detection
Sensitive high-performance liquid chromatographic assays have been developed to determine the levels of the lactone and lactone plus carboxylate (total) forms of the antitumor agent irinotecan (CPT-11) and its active metabolite SN-38, in human plasma. The related compound camptothecin was used as the internal standard. The selective sample pretreatment for the lactone forms involved a single solvent extraction with acetonitrile-n-butyl chloride (1:4, v/v), whereas the sample clean-up for the total forms was a simple protein precipitation with aqueous perchloric acid-methanol (1:1, v/v), which results in the conversion of the carboxylate to the lactone forms. Chromatography was carried out on a Hypersil ODS column, with detection performed fluorimetrically. The methods have been validated, and stability tests under various conditions have been performed. The lower limits of quantitation are 0.5 and 2.0 ng/ml for the lactone and total forms, respectively. The assays have been used in a single pharmacokinetic experiment in a patient to investigate the applicability of the method in vivo
An ultrashort pulse ultra-violet radiation undulator source driven by a laser plasma wakefield accelerator
Narrow band undulator radiation tuneable over the wavelength range of 150–260 nm has been produced by short electron bunches from a 2 mm long laser plasma wakefield accelerator based on a 20 TW femtosecond laser system. The number of photons measured is up to 9 × 106 per shot for a 100 period undulator, with a mean peak brilliance of 1 × 1018 photons/s/mrad2/mm2/0.1% bandwidth. Simulations estimate that the driving electron bunch r.m.s. duration is as short as 3 fs when the electron beam has energy of 120–130 MeV with the radiation pulse duration in the range of 50–100 fs
Subwavelength-resolution near-field Raman spectroscopy
The resolution capabilities of near-field Raman spectroscopy based on a giant enhancement of the electric field near a nanosized metal probe are studied. As a test sample, bundles of single-walled carbon nanotubes deposited on glass substrates are used. It is shown that this method ensures a subwavelength spatial resolution of about 50 nm and demonstrates a Raman scattering enhancement of the order of 104. © 2007 Pleiades Publishing, Inc
Переходная зона между шельфом и континентальным склоном северной части Чёрного моря. Ландшафтный подход
На основе данных, полученных с применением обитаемых подводных
аппаратов, рассмотрена проблема положения бровки шельфа как важной
структурно фациальной границы морского бассейна. Описана ландшафтная фациальная зональность в диапазоне глубин 70–220 м в северной
части Черного моря. Выявлено, что смена фаций в переходной зоне между
шельфом и материковым склоном от бровки шельфа до глубины около 200 м
находится в тесной связи с усилением гипоксии до полной аноксии.На основі даних, отриманих із застосуванням підводних апаратів, розглянуто
проблему положення бровки шельфу як важливої структурно фаціальної межі морського басейну. Описано ландшафтну фаціальну зональність в діапазоні глибин 70–20 м
у північній частині Чорного моря. Виявлено, що зміна фацій у перехідній зоні між шельфом і материковим схилом від бровки шельфу до глибини близько 200 м тісно пов’язана із збільшенням гіпоксії до повної аноксії.The problem of continental shelf break position as an important structural – facial
marine basin boundary discussed on the basis of manned submersibles’ data. The range and
setting of Northern Black Sea facial zones in the depths interval 70 220m are described. It’s
found that the facial changes are related closely with hypoxia increasing to complete anoxia
from the shelf break to the depth of about 200 m
Structural identification and biological activity of 7-methyl-10,11-ethylenedioxy-20(S)-camptothecin, a photodegradant of lurtotecan
An additional chromatographic peak was observed in plasma samples of
patients receiving NX 211, a liposomal formulation of the topoisomerase I
inhibitor lurtotecan. We have isolated and purified this product by
sequential solid-phase extractions, and we report its structure and
cytotoxicity relative to lurtotecan and related agents. Nuclear magnetic
resonance data indicate that cleavage of the piperazino moiety occurred at
the N-C bond of the B-ring, yielding
7-methyl-10,11-ethylenedioxy-20(S)-camptothecin (MEC). Tests of the growth
inhibition potential of MEC in seven human tumor cell lines showed that
the compound was approximately 2-18-fold more cytotoxic than lurtotecan,
topotecan, and 7-ethyl-10-hydroxy-20(S)-camptothecin (SN-38).
Subsequently, we found that MEC was the product of rapid photolysis of
lurtotecan, with the rate of degradation inversely proportional to NX 211
concentrations, and greatly depends on light intensity. Furthermore, MEC
concentrations were found to increase significantly in plasma samples
exposed to laboratory light but not in blood. MEC was not produced from NX
211 in the presence of human liver microsomes, suggesting that it is not a
product of cytochrome P-450 metabolism. Using a validated analytical
method, trace levels of MEC were quantitated in blood samples of two
patients. These observations confirm that the precautions for protection
from light currently specified for preparation and administration of NX
211 dose solutions are critical. Procedures to minimize formation of MEC,
by the use of amber vials for NX 211 and by preparation of dilutions
immediately before clinical use in a fashion completely protected from
light, are now being routinely implemented
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