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排序方式: 共有93条查询结果,搜索用时 15 毫秒
1.
Micah I. Krichevsky 《Analytica chimica acta》1981,133(4):747-751
An interactive information system, MICRO-IS, is described. It comprises morphological, physiological, biochemical, and Chromatographic data describing microbial strains. A wide variety of retrieval, management, and editing functions can be invoked with easy-to-learn, user-oriented commands. 相似文献
2.
When a single DNA molecule is stretched beyond its normal contour length, a force-induced melting transition is observed. Ethidium binding increases the DNA contour length, decreases the elongation upon melting, and increases the DNA melting force in a manner that is consistent with the ethidium-induced changes in duplex DNA stability known from thermal melting studies. The DNA stretching curves map out a phase diagram and critical point in the force-extension-ethidium concentration space. Intercalation occurs between alternate base pairs at low forces and between every base pair at high forces. 相似文献
3.
We derive explicit, uniform, a priori interior Hessian and gradient estimates for special Lagrangian equations of all phases
in dimension two.
Y. Yuan is partially supported by an NSF grant. 相似文献
4.
The Linear Search Problem concerns a search for a point in the real line by continuous motion starting at 0. The optimal turning
points for such a search under the hypothesis that the location of the target is distributed normally about 0 have been approximated
by mechanical calculation, but no proof has been given that there is only a single minimizing strategy or that the numbers
calculated do indeed approximate that strategy. Plausible arguments have been made before, both by these authors and others.
In this paper, the plausible arguments are supplanted by mathematical proofs.
The research of the senior author has been supported by the Wisconsin Alumni Research Foundation.
The research of the junior author has been supported by Hewlett Packard, Inc. under a Faculty Development Fellowship at Cornell
University. 相似文献
5.
Micah T. Nelp Vahe Bandarian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(36):10773-10775
The biosynthesis of nitriles is known to occur through specialized pathways involving multiple enzymes; however, in bacterial and archeal biosynthesis of 7‐deazapurines, a single enzyme, ToyM, catalyzes the conversion of the carboxylic acid containing 7‐carboxy‐7‐deazaguanine (CDG) into its corresponding nitrile, 7‐cyano‐7‐deazaguanine (preQ0). The mechanism of this unusual direct transformation was shown to proceed via the adenylation of CDG, which activates it to form the newly discovered amide intermediate 7‐amido‐7‐deazaguanine (ADG). This is subsequently dehydrated to form the nitrile in a process that consumes a second equivalent of ATP. The authentic amide intermediate is shown to be chemically and kinetically competent. The ability of ToyM to activate two different substrates, an acid and an amide, accounts for this unprecedented one‐enzyme catalysis of nitrile synthesis, and the differential rates of these two half reactions suggest that this catalytic ability is derived from an amide synthetase that gained a new function. 相似文献
6.
Matthew Gursky Jeffrey Streets Micah Warren 《Calculus of Variations and Partial Differential Equations》2011,41(1-2):21-43
We show that on a compact Riemannian manifold with boundary there exists ${u \in C^{\infty}(M)}$ such that, u |?M ?? 0 and u solves the ?? k -Ricci problem. In the case k = n the metric has negative Ricci curvature. Furthermore, we show the existence of a complete conformally related metric on the interior solving the ?? k -Ricci problem. By adopting results of (Mazzeo and Pacard, Pacific J. Math. 212(1), 169?C185 (2003)), we show an interesting relationship between the complete metrics we construct and the existence of Poincaré?CEinstein metrics. Finally we give a brief discussion of the corresponding questions in the case of positive curvature. 相似文献
7.
Micah Stohlmann 《School science and mathematics》2019,119(5):287-296
Of the four subjects in an integrated science, technology, engineering, and mathematics (STEM) approach, mathematics has not received enough focus. This could be in part because mathematics teachers may be apprehensive or unsure about how to implement integrated STEM education in their classrooms. There are benefits to integrated STEM in a mathematics classroom though, including increased motivation, interest, and achievement for students. This article discusses three methods that middle school mathematics teachers can utilize to integrate STEM subjects. By focusing on open‐ended problems through engineering design challenges, mathematical modeling, and mathematics integrated with technology middle school students are more likely to see mathematics as relevant and valuable. Important considerations are discussed as well as recent research with these approaches. 相似文献
8.
Streed EW Mun J Boyd M Campbell GK Medley P Ketterle W Pritchard DE 《Physical review letters》2006,97(26):260402
Continuous and pulsed quantum Zeno effects were observed using a 87Rb Bose-Einstein condensate. Oscillations between two ground hyperfine states of a magnetically trapped condensate, externally driven at a transition rate omega(R), were suppressed by destructively measuring the population in one of the states with resonant light. The suppression of the transition rate in the two-level system was quantified for pulsed measurements with a time interval deltat between pulses and continuous measurements with a scattering rate gamma. We observe that the continuous measurements exhibit the same suppression in the transition rate as the pulsed measurements when gammadeltat=3.60(0.43), in agreement with the predicted value of 4. Increasing the measurement rate suppressed the transition rate down to 0.005 omega(R). 相似文献
9.
Campbell GK Mun J Boyd M Streed EW Ketterle W Pritchard DE 《Physical review letters》2006,96(2):020406
We have observed parametric generation and amplification of ultracold atom pairs. A 87Rb Bose-Einstein condensate was loaded into a one-dimensional optical lattice with quasimomentum k0 and spontaneously scattered into two final states with quasimomenta k1 and k2 . Furthermore, when a seed of atoms was first created with quasimomentum k1 we observed parametric amplification of scattered atoms pairs in states k1 and k2 when the phase-matching condition was fulfilled. This process is analogous to optical parametric generation and amplification of photons and could be used to efficiently create entangled pairs of atoms. Furthermore, these results explain the dynamic instability of condensates in moving lattices observed in recent experiments. 相似文献
10.
Coupled-cluster and density-functional methods have been used to determine specific rotations and electronic circular dichroism (ECD) rotational strengths for (S)-2-chloropropionitrile. Coupled-cluster specific rotations using both the length- and velocity-gauge representations of the electric-dipole operator, computed with basis sets of triple-zeta quality containing up to 326 functions, compare very well with recently reported gas-phase cavity-ring-down polarimetry data. ECD rotational strengths for the six lowest-lying excited states are found to vary in sign, and the second excited state, which has a larger rotational strength than the first by a factor of 4, was found to yield a much larger contribution (by a factor of 10) to the overall negative specific rotation observed both experimentally and theoretically. However, both valence and Rydberg states appear to make substantial contributions to the total rotation, often of opposite sign from the converged/linear-response result. Furthermore, the sum-over-states approach was found to be inadequate for reproducing the specific rotations derived from the linear-response approach, even when 100 excited states (well beyond the estimated ionization limit) were included in the summation. Density-functional specific rotations using the B3LYP functional with basis sets of quadruple-zeta quality containing up to 588 functions are found to be too large compared to experiment by approximately a factor of 2. This error appears to be related to both the underestimation of the electronic excitation energies, as well as concomitant overestimation of the corresponding ECD rotational strengths. Although earlier studies reported good agreement between density-functional specific rotations and experiment when electric-field-dependent functions were used in conjunction with a double-zeta-quality basis set, the results reported here, which are near the basis-set limit, suggest that this agreement may be fortuitous. 相似文献