Pregnancy rates of Holstein cows after postinsemination treatment with a progesterone-releasing intravaginal device.

Our objective was to determine whether pregnancy rates following first services would be improved by supplementing lactating dairy cows with exogenous progesterone via a progesterone-releasing intravaginal device. Estrus was induced in cows with PGF2 alpha (3-wk clusters of cows ranging from 42 to 63 d postpartum) following a positive milk test for high progesterone. Cows were inseminated at estrus (d 0), and progesterone was administered via the device from d 5 to 13 or d 13 to 21 following estrus; untreated inseminated cows served as controls. Blood was collected from each cow on d 5, 13, and 21 to determine concentrations of progesterone in blood serum. A fourth group of inseminated cows not receiving PGF2 alpha served as an additional untreated, and nonbled, control group. Pregnancy rates at first services, which were followed by insertion of the device, were unaffected by treatments. Concentrations of progesterone in serum were higher in pregnant than nonpregnant cows on d 13 but similar in cows regardless of postinsemination treatment. By d 21, when concentrations of progesterone remained consistently higher as a result of pregnancy, cows given progesterone from d 13 to 21 had higher progesterone in their blood serum, regardless of pregnancy status, than cows receiving progesterone from d 5 to 13. Only serum progesterone in nonpregnant controls on d 21 was less than that of nonpregnant cows given progesterone on d 13 to 21. Pregnancy rates of cows returning to estrus 21 to 27 d after their first service tended to be higher (60 versus 39%) in those cows previously treated with exogenous progesterone than in controls. Furthermore, the proportion returning to estrus 17 to 27 d after first service was reduced in cows previously supplemented with exogenous progesterone (27 versus 49%). Days from calving to conception were 19 d fewer in cows previously treated with progesterone than controls, because average intervals to first service were decreased by 13 d relative to controls. We conclude that supplementing cows with progesterone after insemination initially failed to improve pregnancy rates but appeared to increase pregnancy rate at the subsequent service.     

An Objective Illustration of the Inadequacy of the Official EC “Ewers” Method for the Determination of Starch

The Ewers method for starch determination is currently the Official EEC method for measurement of starch purity. In this communication we demonstrate that the use of trifluroacetic acid for solubilisation of starch prior to polarimetric measurements is preferred over the use of mineral acids since the degree of hydrolytic degradation observed with this reagent was minimal compared to mineral acids, thereby giving improved starch purity values. Of particular concern we demonstrate that the Ewers method is non-specific in that the addition of an epichlorohydrin cross-linked dextran as an adulterant enhances the value of starch purity obtained. The Ewers method however was able to detect agarose and carboxymethyl cellulose added to starch as adulterants. It is concluded that the Ewers method is not an acceptably satisfactory method for starch purity measurement on which to base quality control or eligibility for rebate and refund schemes.     

Improved epoxy-amine matrices for composites

The physical and mechanical properties of epoxy-amine matrices can be improved by the use of additives known as epoxy fortifiers. The tensile strength of a typical aminecured epoxy increased from 82 MPa to 123 MPa, the tensile modulus form 2.5 GPa to 4.1 GPa, and the tensile test specimens also failed in a ductile fashion. The improvements in matrix properties translated into improved performance for filament-wound and cloth-reinforced composites. For example, the transverse moduli and compression strengths of carbon fiber/epoxy filament-wound tubes and plates increased at least 20 percent with the addition of fortifiers, while the compression strength of glass cloth/epoxy laminates increased by up to 41 percent.     

A comparison of bond strengths of complete crowns using two types of cements and three cleaning agents

In the past, biomechanical investigations on the dorsal pelvic ring have generally been performed on a small number of cadaveric pelves in various non-standardized procedures. Significant differences in stability between different internal fixation methods of unstable pelvic ring fractures were not found. The experimental design presented here was based as closely as possible on the physiological loading of the pelvis in one-leg stance. This method made it possible to carry out standardized, reproducible tests on different osteosytheses of the sacroiliac joint. Furthermore, the suitability of artificial bones for such investigations can be assessed on the basis of a larger number of similar experiments on artificial and human pelves and the number of human pelves required for such studies could be reduced.     

The Effect of Electrochemical Potentials on the Durability of Rubber/Metal Bonds in Sea Water

A study of the role of electrochemical potentials on the durability of rubber/metal bonds in seawater is described. In electrochemically inert conditions, these adhesive bonds are shown to be extremely stable-even after more than 3 years immersion in seawater. However, some bond failure is shown to be possible within days-when the rubber is bonded to the more noble of a pair of metals in electrical and electrolytic contact. Resistance to bond failure increased as the cathodic potential was decreased. Mechanical strain in the elastomer layer was shown to have no effect on bond durability.     

包含负荷及系统动态的电力系统电压稳定仿真

本文提出一种对系统电压稳定进行详细仿真的方法，此方法考虑了系统及负荷动态的影响，诸如系统干扰、电动机力矩及滑差，变压器抽头的的换接、坚持Ｐ、Ｑ需要的负荷、抑制励磁以防止发电机过热，以及有电压偏移负反馈的ＳＶＣ等。由于是高阶次的非线性全模，作者采用一种既精确又快速的方法来进行积分，还应用了一种毋需经过亢介次矩阵求逆就可便捷地求解亢介次Ｊａｃｏｂｉ阵的方法。     

Knoop Microhardness Anisotropy and the Indentation Size Effect on the Basal Plane of Single-Crystal Alumina (Sapphire)

The Knoop microhardness anisotropy profile was determined for the basal plane of a Czochralski grown alumina single crystal for indentation test loads from 100 through 1000 g. Microhardness maxima occur at low indentation test loads for the long axis of the Knoop indenter parallel to the 〈2[Onemacr][Onemacr]0〉. Minima exist for the long axis parallel to the 〈10[Onemacr]0〉. This low indentation test load profile is attributed to slip on the primary slip system, the (0001)〈[Onemacr][Onemacr]20〉, as previously noted by Brookes and co-workers. The degree of the microhardness anisotropy decreases for higher indentation test loads. This results from the activation of multiple slip systems to accommodate the greater amounts of plastic flow required by the larger indentation sizes. The microhardness profile becomes more uniform with increasing indentation test load until the Knoop microhardness approaches a test-load-independent, orientation-independent microhardness of 1167 ± 34 kg/mm². The indentation size effect (ISE) was further investigated through lubricated indentation hardness measurements. Lubrication of the test specimen surface significantly reduces the ISE. Results indicate that friction between the test specimen surface and the indenter facets is a major portion of the ISE.     

Benefits of a high‐performance phosphite in the gamma irradiation of polyolefins

The highly active process stabilizer bis(2,4‐dicumylphenyl)pentaerythritol diphosphite (P1) was compared in a series of polyolefin formulations with tris(2,4‐di‐t‐butylphenyl) phosphite (P2). Because of its high activity, there was less polymer degradation during processing with P1 as compared to P2. As a result, improvements in color and other physical properties were observed for the polymers, not only during processing, but also after treatment with gamma radiation.     

Discovery of a Short‐Chain Dehydrogenase from Catharanthus roseus that Produces a New Monoterpene Indole Alkaloid

Plant monoterpene indole alkaloids, a large class of natural products, derive from the biosynthetic intermediate strictosidine aglycone. Strictosidine aglycone, which can exist as a variety of isomers, can be reduced to form numerous different structures. We have discovered a short‐chain alcohol dehydrogenase (SDR) from plant producers of monoterpene indole alkaloids (Catharanthus roseus and Rauvolfia serpentina) that reduce strictosidine aglycone and produce an alkaloid that does not correspond to any previously reported compound. Here we report the structural characterization of this product, which we have named vitrosamine, as well as the crystal structure of the SDR. This discovery highlights the structural versatility of the strictosidine aglycone biosynthetic intermediate and expands the range of enzymatic reactions that SDRs can catalyse. This discovery further highlights how a sequence‐based gene mining discovery approach in plants can reveal cryptic chemistry that would not be uncovered by classical natural product chemistry approaches.