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991.
992.
In this paper, we report, for the first time, the effect of the lowered freezing point in a 50% water/50% anti-freeze coolant (PAC) or 50% water/50% ethylene glycol (EG) solution by the addition of carbon nanotubes and other particles. The experimental results indicated that the nano materials are much more efficient (hundreds fold) in lowering the freezing point than the regular ionic materials (e.g., NaCl). The possible explanation for this interesting phenomenon is the colligative property of fluid and relative small size of nano material. It is quite certain that the carbon nanotubes and metal oxide nano particles could be a wonderful candidate for the nano coolant application because they could not only increase the thermal conductivity, but also efficiently lower the freezing point of traditional coolants. 相似文献
993.
Buxboim A Bar-Dagan M Frydman V Zbaida D Morpurgo M Bar-Ziv R 《Small (Weinheim an der Bergstrasse, Germany)》2007,3(3):500-510
We have developed a biochip platform technology suitable for controlled cell-free gene expression at the micrometer scale. A new hybrid molecule, "Daisy", was designed and synthesized to form in a single step a biocompatible lithographic interface on silicon dioxide. A protocol is described for the immobilization of linear DNA molecules thousands of base pairs long on Daisy-coated surfaces with submicrometer spatial resolution and up to high densities. On-chip protein synthesis can be obtained with a dynamic range of up to four orders of magnitude and minimal nonspecific activity. En route to on-chip artificial gene circuits, a simple two-stage gene cascade was built, in which the protein synthesized at the first location diffuses to regulate the synthesis of another protein at a second location. We demonstrate the capture of proteins from crude extract onto micrometer-scale designated traps, an important step for the formation of miniaturized self-assembled protein chips. Our biochip platform can be combined with elastomeric microfluidic devices, thereby opening possibilities for isolated and confined reaction chambers and artificial cells in which the transport of products and reagents is done by diffusion and flow. The Daisy molecule and described approach enables groups not proficient in surface chemistry to construct active biochips based on cell-free gene expression. 相似文献
994.
995.
Hydrogen embrittlement has been recognized as a serious prob-lem in the application of metallic structural materials,where hy-drogen degrades the mechanical pro... 相似文献
996.
We report here the first demonstration of the cleavage of an mRNA in trans by delta ribozyme derived from the antigenomic version of the human hepatitis delta virus (HDV). We characterized potential delta ribozyme cleavage sites within HDV mRNA sequence (i.e. C/UGN6), using oligonucleotide binding shift assays and ribonuclease H hydrolysis. Ribozymes were synthesized based on the structural data and then tested for their ability to cleave the mRNA. Of the nine ribozymes examined, three specifically cleaved a derivative HDV mRNA. All three active ribozymes gave consistent indications that they cleaved single-stranded regions. Kinetic characterization of the ability of ribozymes to cleave both the full-length mRNA and either wild-type or mutant small model substrate suggests: (i) delta ribozyme has turnovers, that is to say, several mRNA molecules can be successively cleaved by one ribozyme molecule; and (ii) the substrate specificity of delta ribozyme cleavage is not restricted to C/UGN6. Specifically, substrates with a higher guanosine residue content upstream of the cleavage site (i.e. positions -4 to -2) were always cleaved more efficiently than wild-type substrate. This work shows that delta ribozyme constitutes a potential catalytic RNA for further gene-inactivation therapy. 相似文献
997.
G. D. Sharma Dhiraj Saxena M. S. Roy 《Journal of Materials Science: Materials in Electronics》1999,10(7):539-544
The electrical and photovoltaic properties of a newly designed two-layered photocell having the configuration ITO/ZnPc/CHR/In p-n junction were investigated. The rectification effect observed in the device is due to an energy barrier formed between the CHR and ZnPc layer. The depletion layer characteristics of the device were investigated by measuring the temperature variation of capacitance. These measurements indicate that a depletion layer of width 190 nm as well as potential barrier height of about 0.78 eV, decreases with temperature. The current–voltage characteristics of the device yield a barrier height of about 0.74 eV formed between ZnPc and CHR. The device showed a response to light over the whole visible region extending from 400 nm to 800 nm. The comparison of photoaction spectra with the absorption spectra also indicates the formation of an energy barrier between CHR and ZnPc. The dissociation of excitons induced by the built-in field potential existing between the CHR and ZnPc layers is responsible for photogeneration of the carriers. Various photovoltaic parameters were calculated and are discussed in detail. 相似文献
998.
999.
Manish Roy 《Bulletin of Materials Science》1999,22(6):1009-1012
The primary objective of this work was to evaluate the influence of various reinforcements and matrix materials on the dynamic
hardness of polymer matrix materials (PMC). Therefore, the impact of a WC ball, using a gravity drop system, was studied on
PMCs. The two parameters, coefficient of restitution and dynamic hardness, of PMCs were determined. The mechanical properties
of the PMCs were evaluated, and the correlation of the two parameters with the mechanical properties of PMCs was attempted. 相似文献
1000.
V. A. Sadykov Svetlana N. Pavlova Galina V. Zabolotnaya Raisa I. Maximovskaya Sergei V. Tsybulya Elena B. Burgina Vladimir I. Zaikovskii Galina S. Litvak Marina V. Chaikina Valerii V. Lunin Natalya N. Kuznetsova Rustum Roy Dinesh K. Agrawal 《Materials Research Innovations》1999,2(6):328-337
High-power ball mill activation of the mixture of hydrated zirconium and lanthanum salts (oxonitrates, oxochlorides) with
ammonium phosphate followed by hydrothermal treatment at temperatures not exceeding 200°C and a nearly neutral pH was found
to yield crystalline dispersed phase of a cubic NH4Zr2(PO4)3 type along with admixtures of disordered orthorhombic compounds of a zirconium orthophosphate type. In the same conditions
and at the same Zr/P ratio, hydrothermal treatment of gels obtained by reacting mixed zirconium and lanthanum nitrates solutions
with ammonium phosphates yields no crystalline products, and only treatment in acid media generates a phase of the α-ZrPO4(OH) type coexisting with the NH4Zr2(PO4)3 phase if polyethylene oxide is present. X-ray powder diffraction, transmission electron microscopy, 31MAS-NMR, FTIRS and thermal analysis were applied to elucidate factors affecting crystallization of complex zirconium phosphates
in the hydrothermal conditions. The most essential factor appears to be generation of some nuclei of zirconium phosphates
under high pressures developed in the course of mixed solids mechanical activation. These nuclei are embedded into matrix
of such well-crystallized solid products as ammonium nitrate or chloride. Hence, metastable cubic or orthorhombic structure
of the phases obtained via mechanical activation route can be assigned to the nuclei-matrix orientation relationship. Due
to easily scaled-up synthesis procedure, these results appear to be very promising for manufacturing of dispersed framework
zirconium phosphates as acid catalysts or fast proton conductors.
Received: 18 November 1998 / Reviewed and accepted: 2 December 1998 相似文献