An experimental study of the interaction of highly charged, energetic ions (52 MeV (58)Ni(13+) and 15.7 MeV (16)O(5+)) with mixed H(2)O : C(18)O(2) astrophysical ice analogs at two different temperatures is presented. This analysis aims to simulate the chemical and the physicochemical interactions induced by cosmic rays inside dense, cold astrophysical environments, such as molecular clouds or protostellar clouds as well at the surface of outer solar system bodies. The measurements were performed at the heavy ion accelerator GANIL (Grand Accelerateur National d'Ions Lourds) in Caen, France. The gas samples were deposited onto a CsI substrate at 13 K and 80 K. In situ analysis was performed by a Fourier transform infrared (FTIR) spectrometer at different fluences. Radiolysis yields of the produced species were quantified. The dissociation cross section at 13 K of both H(2)O and CO(2) is about 3-4 times smaller when O ions are employed. The ice temperature seems to affect differently each species when the same projectile was employed. The formation cross section at 13 K of molecules such as C(18)O, CO (with oxygen from water), and H(2)O(2) increases when Ni ions are employed. The formation of organic compounds seems to be enhanced by the oxygen projectiles and at lower temperatures. In addition, because the organic production at 13 K is at least 4 times higher than the value at 80 K, we also expect that interstellar ices are more organic-rich than the surfaces of outer solar system bodies. 相似文献
We have observed a new mechanism for compression of a non-neutral plasma, where antiprotons embedded in an electron plasma are compressed by a rotating wall drive at a frequency close to the sum of the axial bounce and rotation frequencies. The radius of the antiproton cloud is reduced by up to a factor of 20 and the smallest radius measured is ~ 0.2 mm. When the rotating wall drive is applied to either a pure electron or pure antiproton plasma, no compression is observed in the frequency range of interest. The frequency range over which compression is evident is compared to the sum of the antiproton bounce frequency and the system’s rotation frequency. It is suggested that bounce resonant transport is a likely explanation for the compression of antiproton clouds in this regime. 相似文献
The influence of nanofiller, plasticizer and hydroxyvalerate (HV) contents on the properties of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/clay nano-biocomposites is studied.Analyses by wide-angle X-ray diffraction and differential scanning calorimetry showed that both the organo-modified montmorillonite clay and acetyl tributyl citrate plasticizer facilitate the crystallization process of PHBV. Despite its nucleating effect, the nanoclay hampers the spherulite growth and leads to a reduction in the copolymer crystallinity, while the addition of plasticizer induces the formation of thicker spherulites.For all studied systems, it was shown that the variation of mechanical properties of these nano-biocomposites is strongly influenced by their changes in crystallinity. 相似文献
A sensitive, specific and rapid high-performance liquid chromatography method was developed in an effort to quantify extremely low curcuminoid levels for the future transdermal experiments where the curcuminoids are incorporated with excipients such as microemulsion, liposomes, and micelles. The chromatographic separation was performed using a Symmetry® C18, 250 × 4.6 mm, 5-μm column, with a mobile phase composed of 5 mM acetonitrile:phosphoric acid (45:55, v/v) at a flow rate of 1.0 mL min?1, it was sensitive with a low limit of quantitation for curcuminoids (0.626 ng mL?1 for curcumin) and good linearity (r2 ≥ 0.999) over the range 1–100 ng mL?1. All the validation data, such as accuracy and precision, were within the required limits from the ICH guideline. The assay method was successfully applied during forced degradation of curcuminoid solutions. The method retained its accuracy and precision when the standard addition technique was applied. 相似文献
A sensitive, specific and rapid high-performance liquid chromatography method was developed in an effort to quantify extremely low curcuminoid levels for the future transdermal experiments where the curcuminoids are incorporated with excipients such as microemulsion, liposomes, and micelles. The chromatographic separation was performed using a Symmetry® C18, 250 × 4.6 mm, 5-μm column, with a mobile phase composed of 5 mM acetonitrile:phosphoric acid (45:55, v/v) at a flow rate of 1.0 mL min−1, it was sensitive with a low limit of quantitation for curcuminoids (0.626 ng mL−1 for curcumin) and good linearity (r2 ≥ 0.999) over the range 1–100 ng mL−1. All the validation data, such as accuracy and precision, were within the required limits from the ICH guideline. The assay method was successfully applied during forced degradation of curcuminoid solutions. The method retained its accuracy and precision when the standard addition technique was applied.
Herein, we present a new method based on separation by ion-pair chromatography with pulsed amperometric detection for evaluating various diuretics, including hydrochlorothiazide, chlorthalidone, furosemide, and amiloride, which are adulterants in herbal-based pharmaceutical formulations. The amperometric detection cycle (time?=?2 s) was performed at a gold electrode by applying a detection potential (E1) of +800 mV for 0.4 s and an oxidation potential (E2) of +1,000 mV for 0.40 s, followed by a reduction potential (E3) of ?200 mV for 1.20 s. The mobile phase for separating the diuretics was composed of 5 mmol L?1 phosphate buffer and 0.3 mmol L?1 sodium dodecyl sulfate in 50 % (v/v) methanol (pH 4.5). This method enabled the quantification of the drugs at low concentrations (i.e., 0.08 mg/capsule for hydrochlorothiazide, 0.01 mg/capsule for chlorthalidone, and 0.007 mg/capsule for furosemide). Twenty-six herbal formulations were analyzed, and eight samples (30.8 %) were found to contain diuretics that were added to the final composition (declared or not). 相似文献
The bacterium E. coli maneuvers itself to regions with high chemoattractant concentrations by performing two stereotypical moves: "runs," in which it moves in near-straight lines, and "tumbles," in which it does not advance but changes direction randomly. The duration of each move is stochastic and depends upon the chemoattractant concentration experienced in the recent past. We relate this stochastic behavior to the steady-state density of a bacterium population, and we derive the latter as a function of chemoattractant concentration. In contrast to earlier treatments, here we account for the effects of temporal correlations and variable tumbling durations. A range of behaviors is obtained that depends subtly upon several aspects of the system -- memory, correlation, and tumbling stochasticity, in particular. 相似文献
Candida species are the main fungal agents causing infectious conditions in hospital patients. The development of new drugs with antifungal potential, increased efficacy, and reduced toxicity is essential to face the challenge of fungal resistance to standard treatments. The aim of this study is to evaluate the in vitro antifungal effects of two crude extracts of Crinum americanum L., a rich alkaloid fraction and lycorine alkaloid, on the Candida species. As such, we used a disk diffusion susceptibility test, determined the minimum inhibitory concentration (MIC), and characterized the components of the extracts using Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI FT-ICR MS). The extracts were found to have antifungal activity against various Candida species. The chemical characterization of the extracts indicated the presence of alkaloids such as lycorine and crinine. The Amaryllidaceae family has a promising antifungal potential. Furthermore, it was found that the alkaloid lycorine directly contributes to the effects that were observed for the extracts and fraction of C. americanum. 相似文献
This work reports a comparative study of the catalytic behaviour for a series of metallocenes derived from Ti, Zr, Hf and Nb, which after activation with methylaluminoxane can polymerize ethylene. Results show that the Zr metallocene with a (CH3)2Si Bridge presents the highest activity, and the metallocenes based on Hf and Nb do not show any significant activity under the tested conditions. 相似文献