Structural effects of multiple-bonds on aggregating tendencies of long-chain esters

The kinetics of the hydrolysis of p-nitrophenyl esters of three types of single-chain carboxylic acids, namely, saturated, olefinic and acetylenic, was investigated in two aquiorgano binary solvent systems, DMSO-H₂O and dioxane (DX)-H₂O. The ester probes used are: octanoic (C8), dodecanoic (C12) , stearic (C18) , oleic (C18-ol) , elaidic (C18-el ) and stearolic (C18-st). The order of measured CAgC values is: C18-ol>C18-el>C18>C18-st, whereas the order of decreasing magnitude of the observed hydrolytic rate constants of the monomeric species (k_m) is: C18>C18-el>C18-ol> C18-st. These rather unanticipated results are discussed.     

Hochschild cohomology and “smoothness” in monoidal categories

We introduce and investigate the properties of Hochschild cohomology of algebras in an abelian monoidal category M. We show that the second Hochschild cohomology group of an algebra in M classifies extensions of A up to an equivalence. We characterize algebras of Hochschild dimension 0 (separable algebras), and of Hochschild dimension ≤1 (formally smooth algebras). Several particular cases and applications are included in the last section of the paper.     

一个非协调膜元的高精度分析

本文讨论一个四自由度三角形非协调膜元的整体超收敛性，外推和亏量校正。     

硫酰胺的快速分析（Ⅱ） 

硫酰胺生产过程中副产的大量氯化铵要干扰硫酰胺的测定，采用四苯硼钠将全部氯化铵呈沉淀析出，再用次溴酸钠把滤液中的硫酰胺分解成氮气，测其体积，计算出硫酰胺的含量。对样品进行测定的结果表明，该法重现性好、准确度高、分析周期在３５ｍｉｎ内，相对误差在±１％以内。     

BIFURCATION DIAGRAMS OF SYSTEM =-y δx lx~2 ny~2,=x ax~2

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Simulated cosmic strings in a “big bang” in superfluid3He at 100 μK

During studies of the impact of single neutrons on superfluid³He at around 100μK we have measured the thermal energy released in the superfluid following the nuclear reaction, n+³He→p+³H+764keV. However, we find that the measured energy deposited in the quasiparticle system shortly after this reaction is substantially less than what we expect. We believe that this energy deficit represents that energy which has gone into the creation of vortices, in analogy to the creation of cosmic strings in the early universe via the Kibble mechanism. Furthermore, from the magnitude of the deficit, we can infer the vortex density which compares favorably with that predicted in Zurek’s scenairo.     

Intramolecular hemiacetals. The acid-base-catalyzed ring-chain interconversion of 2-substituted 2-hydroxy-4,4-dimethylmorpholinium cations in aqueous solution.

The ring-chain tautomerism in aqueous solution of some aryl-substituted morpholinium salts (bromides), has been studied and equilibrium constants are reported. In the crystals the substrates exist entirely in their cyclic forms as hemiacetals, but in aqueous solution NMR measurements reveal that an equilibrium is established between the cyclic (hemiacetal) and the noncyclic (ketone) form, the degree of ring-opening being more pronounced with electron-donating aryl substituents at the carbonyl carbon. The kinetics of the ring-chain interconversion in water has been investigated spectrophotometrically by a 'pH jump' stopped-flow technique. General base catalysis is observed with a Br?nsted beta value apparently independent of substituent and equal to 0.60. The Hammett rho values for various base catalysts are close to those for very similar intermolecular reactions involving hemiacetal breakdown, leading to the suggestion of a 'normal' class n mechanism for base catalysis. For acid catalysis, however, a quite different situation is encountered, since no general acid but only (weak) catalysis by the hydronium ion can be detected. We believe this deviation from 'normal' general acid catalysis is caused by an electrostatic interaction, and we suggest that it might result from a change in the usual class e mechanism for general acid catalysis by a situation in which rate-limiting concerted proton transfer is replaced by rate-limiting preprotonation. This is supported by the observed drastic change in Hammett rho value for catalysis by the hydronium ion, compared with the 'normal' case. An interesting case is encountered for the 4-aminophenyl-substituted substrate, in which the amino group becomes protonated in acid solution, thus representing a new substituent. Despite this complication, the various equilibrium and rate constants may also be evaluated experimentally for this substrate.     

Monitoring genomic alterations with a panel of oligonucleotide probes specific for various simple repeat motifs

Germline and somatic instability of the human genome was studied, using synthetic oligonucleotides specific for simple repeat motifs. The following probes were used: (GTG)5, (GACA)4, (GATA)4, (CT)8, (TTAGGG)3, (GT)8, (GAA)6 and (GGAT)4. Each of them is unique with respect to the target regions recognized in the genome. Thus compilation of the various fingerprint data provides a complex map of the genome (and its deviations). While the fingerprints of differentiated somatic tissues never showed any alterations, in tumor tissues (namely gliomas) many changes could be detected. Most of the latter reflect secondary karyological aberrations. In nearly one third of the gliomas, drastically amplified and apparently monomorphic DNA fragments were identified. This marker should make it possible to deal with causal pathogenetic mechanisms as well as novel diagnostic strategies.