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71.
We consider the family of fibres of a polynomial function f on a smooth noncompact algebraic real surface and we characterise the regular fibres of f which are atypical due to their asymptotic behaviour at infinity. We compare to the similar problem in the complex case.
Received: 5 May 1998 / Revised version: 20 March 1999 相似文献
72.
If H is a Hopf algebra with bijective antipode and α, β ∈ Aut
Hopf
(H), we introduce a category
, generalizing both Yetter-Drinfeld modules and anti-Yetter-Drinfeld modules. We construct a braided T-category
having all the categories
as components, which, if H is finite dimensional, coincides with the representations of a certain quasitriangular T-coalgebra DT(H) that we construct. We also prove that if (α, β) admits a so-called pair in involution, then
is isomorphic to the category of usual Yetter-Drinfeld modules
.
Research partially supported by the programme CERES of the Romanian Ministry of Education and Research, contract no. 4-147/2004. 相似文献
73.
tefan Ciornei Dan Drugociu Liliana Margareta Ciornei Mihai Mare Petru Roca 《Molecules (Basel, Switzerland)》2021,26(20)
The aim of the study was to establish the complete microbiological profile of boar semen (Sus scrofa domesticus) and to choose the most effective antiseptic measures in order to control and optimize AI reproduction in pig farms. One hundred and one semen samples were collected and analyzed from several pig farms. The microbiological profile of ejaculates was determined by evaluating the degree of contamination of fresh semen and after dilution with specific extenders. The bacterial and fungal load of fresh boar semen recorded an average value of 82.41/0.149 × 103 CFU/mL, while after diluting the ejaculates the contamination value was 0.354/0.140 × 103 CFU/mL. Twenty-four germs (15 bacterial and 9 fungal species) were isolated, the most common being Candida parapsilosis/sake (92%) and Escherichia coli (81.2%). Modification of the sperm collection protocol (HPBC) reduced contamination in raw sperm by 49.85% in bacteria (significant (p < 0.00001) and by 9.67% in fungi (non-significant (p < 0.111491). The load in bacteria and filamentous fungi can be controllable, but not in levuras fungi. Some fluconazole-added extenders (12.5 mg%), ensure fungal aseptization, and even an increase in sperm progressivity (8.39%) for at least a 12 h shelf life after dilution. Validation of sperm aseptization was done by maintaining sow fecundity unchanged after AI (insignificant p > 0.05). 相似文献
74.
Percec V Aqad E Peterca M Rudick JG Lemon L Ronda JC De BB Heiney PA Meijer EW 《Journal of the American Chemical Society》2006,128(50):16365-16372
Structural and retrostructural analysis of helical dendronized polyacetylenes (i.e., self-organizable polyacetylenes containing first generation dendrons or minidendrons as side groups) synthesized by the polymerization of minidendritic acetylenes with [Rh(nbd)Cl]2 (nbd = 2,5-norbornadiene) reveals an approximately 10% change in the average column stratum thickness (l) of the cylindrical macromolecules with a chiral periphery, through which a strong preference for a single-handed screw-sense is communicated. The cylindrical macromolecules reversibly interconvert between a three-dimensional (3D) centered rectangular lattice (Phi r-c,k) exhibiting long-range intracolumnar helical order at lower temperatures and a two-dimensional (2D) hexagonal columnar lattice (Phi h) with short-range helical order at higher temperatures. A polymer containing chiral, nonracemic peripheral alkyl tails is found to have a larger l as compared to the achiral polymers. In methyl cyclohexane solution, the same polymer exhibits an intense signal in circular dichroism (CD) spectra, whose intensity decreases upon heating. The observed change in l indicates that the chiral tails alter the polymer conformation from that of the corresponding polymer with achiral side chains. This change in conformation results in a relatively large free energy difference (DeltaGh) favoring one helix-sense over the other (per monomer residue). The capacity to distort the polymer conformation and corresponding free energy is related to the population of branches in the chiral tails and their distance from the polymer backbone by comparison to recently reported first and second generation dendronized polyphenylacetylenes. 相似文献
75.
Polyelectrolyte complex (PEC) dispersions were prepared by controlled mixing of three random copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) with either t-butyl acrylamide (TBA) [P(AMPS54-co-TBA46) and P(AMPS37-co-TBA63)] or methyl methacrylate (MM) [P(AMPS52-co-MM48)] with an ionene-type polycation, containing 95 mol % N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units (PCA5), with their structural characteristics being deeply investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM). Shape, size, and polydispersity of the PEC dispersions were directly observed by AFM as a function of polyanion structure, the ratio between charges, n-/n+, and the titrant addition rate (TAR). The particle sizes increased and the colloidal stability decreased with the increase of the nonionic comonomer content and with the decrease of TAR. It was demonstrated that the medium particle sizes of the complex nanoparticles adsorbed on silicon wafers measured by AFM, in the dry state, were close but always lower than those measured by DLS, both before and after the complex stoichiometry. 相似文献
76.
Suitably functionalized tetrahydropyridines (methyl pipecolates) have been used as conformationally biased templates for radical cyclizations to access benzoisoquinuclidines and linearly fused indenopiperidines. Variation of skeletal types is determined by location of a radical-initiating element. 相似文献
77.
Percec V Peterca M Yurchenko ME Rudick JG Heiney PA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(3):909-918
Twin-dendritic organogelators have been prepared through selective functionalization of N-(3-aminopropyl)-1,3-propanediamine (APPDA) with self-assembling dendrons by using 1,1'-carbonyldiimidazole (CDI). Subsequent modification of the APPDA linker provided an additional degree of structural diversity by which to tailor the gelator self-assembly in bulk or in the gel state. These compounds are able to gel cyclohexane, toluene, n-butyl acetate, ethyl acetate, dichloromethane, and tetrahydrofuran. 3,4-Disubstituted apical branching units provided the most efficient organogelators and show a propensity to form thixotropic gels, wherein the gel recovers its elasticity after being subjected to shear. Structural and retrostructural analysis of the twin-dendritic organogelators reveals the bulk structural characteristics to be indicative of the subsequent gel properties. Diverse self-organized arrays were identified in bulk and all are able to form gels, thus indicating the role of quasiequivalence in mediating self-assembly in the gel state. Furthermore, we have found that porous columnar mesophases provide a strategy by which to prepare thixotropic gels. We demonstrate the importance of weak lateral hydrogen bonding within a column stratum versus hydrogen bonding along the length of the column for forming porous columnar mesophases and, by extension, thixotropic gels. 相似文献
78.
Rapid identification of common hexapyranose monosaccharide units by a simple TOCSY matching approach
Gheysen K Mihai C Conrath K Martins JC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(29):8869-8878
Solution NMR spectroscopy is a well established technique for non-destructive characterization of the structures and conformations of complex oligo- and polysaccharides. One of the key experiments involves the use of 2D TOCSY to collect the 1H spins into groups that can be associated with the individual saccharide units that are present in the molecule under study. It is well known that the magnetization transfer rate through the 1H spin system during the TOCSY spin lock period is sensitive to the intervening 3J(H,H) scalar couplings, and therefore also to the saccharide stereochemistry. Here, we have investigated the potential to extract information on the stereochemistry of hexapyranose monosaccharide units directly from TOCSY spectra. Through a systematic experimental investigation of the magnetization transfer initiated from the anomeric 1H resonance in D-glucose, D-galactose and D-mannose it is shown that a 100 ms spin lock time provides optimal spectroscopic discrimination between these three commonly occurring building blocks. A simple matching scheme is proposed as a new tool for rapid attribution of the TOCSY traces originating from the anomeric 1H resonances towards the underlying monosaccharide type. The scheme appears robust with regard to structural variations and fairly tolerant to incidental overlap. Its application provides useful guidance during the subsequent NMR assignment process, as demonstrated with the PS7F polysaccharide from Streptococcus pneumonia. In addition, we show that our scheme affords a clear-cut distinction between the alpha- and beta-epimers of D-mannose-type units, which can be difficult to discriminate by NMR analysis. Application to the N-glycan 100.2 demonstrates the potential and wide applicability of this new discrimination approach. 相似文献
79.
Katsuhide Murata Mihai Brebu Yusaku Sakata 《Journal of Analytical and Applied Pyrolysis》2009,86(1):33-38
A continuous flow reactor was operated at atmospheric pressure and feed rate of 0–1.5 kg h−1 for degradation of PE, PP and PS in presence of 1–2 wt% PVC. The degradation temperatures were between 360 and 440 °C depending on the feeding material. The influence of PVC, temperature and silica-alumina catalysts on degradation behavior and on the properties of the products was studied and discussed. Different effects were observed for binary PE/PVC, PP/PVC, PS/PVC and complex PE/PP/PS/PVC mixtures due to specific interactions between PVC and each hydrocarbon polyolefin. Silica-alumina catalysts decreased the Cl concentration in oils but it seems to generate high amounts of Cl-containing organic compounds in gases. 相似文献
80.
Multiple zeta values (MZVs) are generalizations of Riemann zeta values at positive integers to multiple variable setting. These values can be further generalized to level N multiple polylog values by evaluating multiple polylogs at Nth roots of unity. In this paper, we consider another level N generalization by restricting the indices in the iterated sums defining MZVs to congruence classes modulo N, which we call the MZVs at level N. The goals of this paper are twofold. First, we shall lay down the theoretical foundations of these values such as their regularizations and double shuffle relations. Second, we will generalize the bracket functions related to multiple divisor sums defined by Bachmann and Kühn to arbitrary level N and study their relations to MZVs at level N. The brackets are all q-series and similar to MZVs, they have both weight and depth filtrations. But unlike that of MZVs, the product of brackets usually has mixed weights; however, after projecting to the highest weight we can obtain an algebra homomorphism from brackets to MZVs. Moreover, the image of the derivation \({\mathfrak{D}=q\frac{d}{dq}}\) on brackets vanishes on the MZV side, which gives rise to many nontrivial \({\mathbb{Q}}\)-linear relations. 相似文献