排序方式: 共有88条查询结果,搜索用时 15 毫秒
11.
We investigate the spatial dynamics of optical necklace beams in Kerr media. For powers corresponding to less than the critical power for self-focusing per bead, we experimentally confirm the confinement of these necklace beams as proposed in [Phys. Rev. Lett. 81, 4851 (1998)10.1103/PhysRevLett.81.4851]. At higher powers, we observe a transition from collective necklace behavior to one in which the beads of the necklace collapse independently. We observe that, below the transition power, the perturbed necklace still behaves in a collective manner with coupling between individual beads but that, at higher powers, it undergoes a similar transition to a decoupled state of the necklace. 相似文献
12.
Pham MH Vuong GT Vu AT Do TO 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):15261-15267
A new approach for the synthesis of uniform metal-organic framework (MOF) nanocrystals with controlled sizes and aspect ratios has been developed using simultaneously the non-ionic triblock co-polymer F127 and acetic acid as stabilizing and deprotonating agents, respectively. The alkylene oxide segments of the triblock co-polymer can coordinate with metal ions and stabilize MOF nuclei in the early stage of the formation of MOF nanocrystals. Acetic acid can control the deprotonation of carboxylic linkers during the synthesis and, thus, enables the control of the rate of nucleation, leading to the tailoring of the size and aspect ratio (length/width) of nanocrystals. Fe-MIL-88B-NH(2), as an iron-based MOF crystal, was selected as a typical example to illustrate our approach. The results reveal that this approach is used for not only the synthesis of uniform nanocrystals but also the control of the size and aspect ratio of the materials. The size and aspect ratio of nanocrystals increase with an increase in the concentration of acetic acid in the synthetic mixture. The non-ionic triblock co-polymer F127 and acetic acid can be easily removed from the Fe-MIL-88B-NH(2) nanocrystal products by washing with ethanol, and thus, their amine groups are available for practical applications. The approach is expected to synthesize various nanosized carboxylate-based MOF members, such as MIL-53, MIL-89, MIL-100, and MIL-101. 相似文献
13.
Jun-ichi Azuma Nam-Hun Kim Laurent Heux Roger Vuong Henri Chanzy 《Cellulose (London, England)》2000,7(1):3-19
The cellulose system of the viscous fibrous cellulosic polysaccharide (viscan) in the viscin tissue of the European mistletoe, Viscum album L., was analyzed by chemical and physicochemical techniques including sugar analysis, optical and transmission electron microscopy, X-ray and electron diffraction together with solid state CP/MAS 13C-NMR spectroscopy. The results confirmed that in the elongated thin viscin cells, the cellulose microfibrils (having a diameter of around 3 nm) were tightly coiled with their axes perpendicular to the long axis of the cell. Upon stretching these cells became deformed by more than a hundred fold. In such a deformation, the cellulose microfibrils became unwound to be perfectly aligned along the stretching direction. Based on solid-state CP/MAS 13C-NMR spectroscopic analysis of the viscin tissue, it was found that its cellulose consisted of I and I polymorphs in the ratio 1:1. 相似文献
14.
15.
We investigate the global exponential stability of equilibrium solutions of a projected dynamical system for variational inequalities. Under strong pseudomonotonicity and Lipschitz continuity assumptions, we prove that the dynamical system has a unique equilibrium solution. Moreover, this solution is globally exponentially stable. Some examples are given to analyze the effectiveness of the theoretical results. The numerical results confirm that the trajectory of the dynamical system globally exponentially converges to the unique solution of the considered variational inequality. The results established in this paper improve and extend some recent works. 相似文献
16.
Klaudia Michalska Agnieszka Galanty Thanh Nguyen Le Janusz Malarz Nguyen Quoc Vuong Van Cuong Pham Anna Stojakowska 《Molecules (Basel, Switzerland)》2021,26(22)
Maesa membranacea A. DC. (Primulaceae) is a plant species that has been frequently used by practitioners of the traditional ethnobotany knowledge from northern and central Vietnam. However, the chemical constituents of the plant remained unknown until recently. Chromatographic separation of a chloroform-soluble fraction of extract from leaves of M. membranacea led to the isolation of two new polyesterified ursane triterpenes (1–2) and two known apocarotenoids: (+)-dehydrovomifoliol (3) and (+)-vomifoliol (4). The chemical structures of the undescribed triterpenoids were elucidated using 1D and 2D MNR and HRESIMS spectral data as 2α,6β,22α-triacetoxy-11α-(2-methylbutyryloxy)-urs-12-ene-3α,20β-diol (1) and 2α,6β,22α-triacetoxy-urs-12-ene-3α,11α,20β-triol (2). The newly isolated triterpenoids were tested for their cytotoxic activity in vitro against two melanoma cell lines (HTB140 and A375), normal skin keratinocytes (HaCaT), two colon cancer cell lines (HT29 and Caco-2), two prostate cancer cell lines (DU145 and PC3) and normal prostate epithelial cells (PNT-2). Doxorubicin was used as a reference cytostatic drug. The 2α,6β,22α-triacetoxy-11α-(2-methylbutyryloxy)-urs-12-ene-3α,20β-diol demonstrated cytotoxic activity against prostate cancer cell lines (Du145—IC50 = 35.8 µg/mL, PC3—IC50 = 41.6 µg/mL), and at a concentration of 100 µg/mL reduced viability of normal prostate epithelium (PNT-2) cells by 41%. 相似文献
17.
Isothermal Section at 1273 K in the System Ti? Si? O The isothermal section at 1273 K of the system Ti? Si? O has been investigated by means of phase analysis in quenched samples as well as by the investigation of the phase sequence in chemical vapour transport experiments. In equilibrium with SiO2 only TiSi2, TiSi, and Ti5Si3(O), respectively, can coexist as Si-containing compounds. Only Ti5Si3(O) can coexist with titanium oxides (Ti2O3 or TiO, respectively). Ti5Si4 is stable only if oxygen is absent. 相似文献
18.
Thai Thuan Quang Lien Vuong Lam Nguyen Van Dai 《Complex Analysis and Operator Theory》2013,7(1):237-259
The aim of this paper is to give some criterions for holomorphy of F-valued σ(F, W)-holomorphic functions which are bounded on bounded sets in a domain D of Fréchet spaces E (resp. ${\mathbb{C}^n}$ ) where ${W \subset F'}$ defines the topology of Fréchet space F. Base on these results we consider the problem on holomorphic extension of F-valued σ(F, W)-holomorphic functions from non-rare subsets of D and from subsets of D which determines uniform convergence in H(D). As an application of the above, some theorems of Vitali-type for a locally bounded sequence ${\{f_i\}_{i \in \mathbb{N}}}$ of Fréchet-valued holomorphic functions are also proved. 相似文献
19.
Nguyen Van Hung Cu Sy Thang Nguyen Ba Duc Dinh Quoc Vuong Tong Sy Tien 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(12):256
Thermodynamic properties, anharmonic effects and structural determination of fcc crystals have been studied based on the theoretical and experimental Debye–Waller factors presented in terms of cumulant expansion up to the third order, thermal expansion coefficient, X-ray absorption fine structure (XAFS) spectra and their Fourier transform magnitudes. The advances in these studies are performed by the further development of the anharmonic correlated Einstein model primary only for approximating three first XAFS cumulants into the method using that all the considered theoretical and experimental XAFS parameters have been provided based on only the calculated and measured second cumulants. The obtained cumulants describe the anharmonic effects in XAFS contributing to the accurate structural determination. Numerical results for Cu are found to be in good agreement with the experimental values extracted by using the present advanced method and with those obtained by the other measurements. 相似文献
20.
Musah RA Vuong AL Henck C Shepard JR 《Journal of the American Society for Mass Spectrometry》2012,23(5):996-999
The spermicide nonoxynol-9 is actually a complex mixture of dozens of closely related amphiphilic compounds, and the chemical
properties of this assortment significantly hamper its characterization by GC-MS. The inability to perform routine GC-MS testing
on nonoxynol-9 has limited its evidentiary value in forensic casework, which relies heavily on this technique for analysis.
A disturbing trend in sexual assault is the use of condoms by assailants, to avoid leaving behind DNA evidence that can connect
a perpetrator to a victim. This observation necessitates the development of alternative methods for the analysis of trace
evidence that can show causal links between a victim and a suspect. Detection of lubricants associated with sexual assault
is one such way to establish this connection. The development of GC-MS methods that permit facile detection of both nonoxynol-9
alone and nonoxynol-9 extracted from other complex matrices that have potential as trace evidence in sexual assault is reported.
A detection limit of 2.14 μg of nonoxynol-9 is demonstrated, and a detailed mass spectral profile that elaborates on what
is known of its structure is provided. 相似文献