双相角结构不变量与Harker作图法在柯卡因卤化物结构相角计算中的联合应用

结合Hauptman的概率式与Harker作图法计算了不同条件下柯卡因卤化物的结构相角,分析了模拟的实验误差对相角精度的影响,为使用真实实验数据进行计算提供了参考依据。     

Suppression of ringing oscillations from high speed rubber compression curves through a detailed modal characterization of servo-hydraulic machines

System ringing is one of the most important factors affecting the quality of data obtained in high speed dynamic material tests using servo-hydraulic machines. This phenomenon is characterized by vibrations originated by the excitation of predominant modes of the machine during tests, producing distinctive waves in material curves that severely distort the required results. In the specialized literature, the quantitative study of these vibrations has mainly been carried out considering the testing machine as a single degree of freedom system, which has led to a general understanding of the variables involved in the process. However, discrepancies between analytical predictions and experimental observations have been detected using the single degree of freedom approach, so the need for further detailed study of machine dynamic characteristics has been reported. The work presented in this paper addresses this requirement by means of a detailed characterization of the dynamic behavior of a MTS 819.10 high rate testing system. Natural frequencies, mode shapes and damping factors have been obtained from an experimental modal analysis performed on the machine and a mathematical model of the process has been developed from these modal parameters. This model has been used to detect the modes that have the greatest influence in system ringing when testing rubber at high strain rates, and to predict quantitatively the amplitudes of vibrations produced in the process. Material curves have been corrected by subtracting the predicted undulations from the original measurements, obtaining smooth curves that adequately reflect the real material behavior at high strain rates and, thus, demonstrating the effectiveness of the proposed procedure. Although the research conducted in this work has been focused on rubber, the procedure can be extended equally to characterize other materials, thus constituting a valuable tool to correct experimental measurements contaminated by ringing.     

Advanced high-performance liquid chromatography method for highly polar nitroaromatic compounds in ground water samples from ammunition waste sites

An advanced HPLC-photodiode array detection method for the determination of 12 selected highly polar nitroaromatic compounds in ground water samples of ammunition waste sites has been developed and validated. After solid-phase extraction the limits of detection were in the range 0.1–0.5 μg/l. To prove the applicability of the method to other polar nitroaromatic compounds the retention time of another 32 polar compounds under the specified chromatographic conditions were determined and their UV spectra recorded. To review the method, interlaboratory comparisons were performed with a spiked and a real ground water sample.     

Diagramme polythermique du systeme ternaire H2O—Al(NO3)3—Mg(NO3)2

The solid—liquid equilibria of the ternary system H₂O—Al(NO₃)₃—Mg(NO₃)₂ were studied at –30, –20, –10 and 0°C by using a synthetic method which allows to detemine all the characteristic points of isothermal sections. The stable solid phases which appear are respectively: ice, Al(NO₃)₃·9H₂O, Mg(NO₃)₂·9H₂O and Mg(NO₃)₂·6H₂O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied. Polytherm diagram layout show two invariant transformations correspond with an eutectic point and a peritectic point.This revised version was published online in November 2005 with corrections to the Cover Date.     

Hydrogen bonding cooperativity of water to nucleotide recognition: structure of octadecahydrated inosine 5′-monophosphate, 2(C10H12N4O8P)·18H2O at atomic resolution

The crystal structure of an octadecahydrated complex between two inosine 5-monophosphate (IMP) has been determined at atomic resolution, which reveals the hydrogen bonding and the coordination cooperativity of water molecules to nucleotide recognition. The crystal belongs to monoclinic space group P2₁ with cell dimensions a = 8.65(1), b = 21.90(1), c = 12.37(1)Å, and = 110.38(9)°. The ribose hydroxyls, purine N7, keto(O6) bonded water molecules W1, W2, W5, W6, W8 and the phosphate bridge forming water oxygens of W4, W7, W11 appear to play an invariant role in their hydrogen bonding interactions with the IMPs. The synergistic role of the water molecules W5, W6, W8 in the purine staking domain N27W5=2.583,O16W8=2.759,O2627W6=2.723 Åhave been clearly observed for the first time. The complexation of the water molecules through variable hydrogen bonding coordination indicate their functional involvement through extensive cooperative donor-acceptor network mechanism. The occurrence of hydrogen-bonded water spines, water bridges and their interplay in the structural association of IMPs could indicate the possible viability of those aquatic centers in the biological situation.     

High temperature corrosion behaviour of M(Co,Ni)CrAIY-coatings on high temperature materials-microanalytical investigations

In our former investigations, the phenomenon high temperature corrosion (HTC) was described exemplarily on selected materialcoating combinations for blades of stationary gas turbines, mainly in the temperature region of up to 750° C. To answer the question, in which manner higher gas inlet and/or higher material surface temperature would influence the HTC behaviour, a special analytical technique—the integral layer profile analysis—was introduced to ameliorate concentration profile methods. By examining IN 738 LC specimens with CoCrAlY plasma spray coating, stressed by hot gas at 900° C, the limits of this system are shown by explaining the corrosion mechanism; the method is also used for other systems, e.g. U 520 with NiCrAlY coating at 750° C.     

Cathode catalysts degradation mechanism from liquid electrolyte to membrane electrode assembly

Single-cell and half-cell degradation test procedures were evaluated for carbon-supported Pt/C, PtCo/C and PtNi/C catalysts. Half-cell analyses were employed to understand the effect of the number of cycles and of the scan rate over the cathode catalysts degradation under potential cycling from 0.6 to 1.2 V. The data suggested a time-dependent degradation for all three catalytic systems. Single-cell measurements were used to evaluate the impact of catalyst degradation on fuel cell performance. The measurements in both setups showed similar ECSA and ORR mass activity losses. Specific degradation mechanisms related to Pt dissolution, Pt agglomeration, and transitional metal leaching were quantified and correlated with performance losses.     

Almost Complex Structures Which Are Compatible with Kähler or Symplectic Structures

In this note we prove that half of all homotopy classes of almost complex structures on M is not compatible with any symplectic structure for a certain class of oriented compact 4-manifolds M. In particular, half of all homotopy classes of almost complex structures on an oriented 4-manifold is not compatible to any Kähler structure.