Mass spectrometry of laser-initiated carbene reactions for protein topographic analysis

We report a protein labeling method using nonselective carbene reactions of sufficiently high efficiency to permit detection by mass spectrometric methods. The approach uses a diazirine-modified amino acid (l-2-amino-4,4'-azipentanoic acid, "photoleucine") as a label source, which is converted to a highly reactive carbene by pulsed laser photolysis at 355 nm. Labeling of standard proteins and peptides (CaM, Mb, M13) was achieved with yields up to 390-fold higher than previous studies using methylene. Carbene labeling is sensitive to changes in protein topography brought about by conformational change and ligand binding. The modification of apo-CaM was 45 ± 7% higher than that of holo-CaM. Modification of the CaM-M13 complex reflected a 39 ± 1% reduction in labeling for bound holo-CaM relative to free holo-CaM. Labeling yield is independent of protein concentration over approximately 2 orders of magnitude but is weakly dependent on the presence of other chromophores in a photon-limited apparatus. The current configuration required 2 min of irradiation for full reagent conversion; however, it is shown that comparable yields can be achieved with a single high-energy laser pulse (>100 mJ/pulse, <10 ns), offering a labeling method with high temporal resolution. We suggest a mechanism of labeling governed by limited carbene diffusion and the protein surface activity of the diazirine precursor. This surface activity is speculated to return a measure of selectivity relative to methylene labeling, which ultimately may be tunable.     

Laser initiation of PETN containing light-scattering additives

We suggest to improve the efficiency of the laser initiation of pentaerythritol tetranitrate (PETN) by increasing the photon trajectory length in the initiated material due to multiple scattering. The proposed method has been experimentally verified. The introduction of a light-scattering additive (0.5 wt % MgO) into PETN decreases the initiation threshold by a factor of ∼3.5 for the first harmonic radiation of a neodymium laser (1060 nm).     

Electron beam induced explosive luminescence of PETN

We have studied the spectrum and kinetics of optical emission in the wavelength range from 550 to 1000 nm accompanying explosive decomposition of pentaerythritol tetranitrate (PETN) single crystals initiated by a nanosecond electron beam. The explosive luminescence kinetics reveals two components with a continuous spectrum, identified as luminescence accompanying the explosive decomposition, and a component with a linear spectrum due to molecular nitrogen formed as a result of explosion.     

PETN detonation initiated by a high-power electron beam

We have studied for the first time the physicochemical processes developed in pentaerythritol tetranitrate (PETN) under the action of a pulsed electron beam in a broad range of the beam power densities. Data on the pulsed cathodoluminescence spectrum and kinetics, explosive optical emission kinetics, and thresholds of the mechanical fracture and explosive decomposition of PETN are presented.     

2,4-MDNI/PETN低共熔物的制备与性能表征

为降低高能炸药季戊四醇四硝酸酯（PETN）的感度,使用钝感高能炸药1-甲基-2,4-二硝基咪唑（2,4-MDNI）与PETN制备了2,4-MDNI/PETN二元混合体系。通过差示扫描量热法（DSC）研究了不同组分比例的2,4-MDNI/PETN的熔融液化过程,建立了2,4-MDNI/PETN二元混合体系的T-x相图,并得到低共熔物组成。研究了不同升温速率下2,4-MDNI/PETN低共熔物的分解过程,并计算了其热分解反应动力学参数。通过体积收缩率、凝固表面微观形貌等研究了2,4-MDNI/PETN低共熔物的凝固性能。测试了2,4-MDNI、PETN及2,4-MDNI/PETN低共熔物的机械感度,并计算了2,4-MDNI/PETN低共熔物的爆轰参数。结果表明:2,4-MDNI/PETN低共熔物中2,4-MDNI与PETN的摩尔比为71∶29,平均熔融温度116.9 ℃,平均热分解反应温度207.5 ℃,热分解反应活化能167.05 kJ/mol,体积收缩率14.4%,撞击感度32%,摩擦感度0,生成焓－37.1 kJ/mol,理论密度1.732 g/cm³,计算爆速8 031 m/s,爆压27.89 GPa。表明2,4-MDNI的加入可以显著降低PETN的感度,同时保持其较高的能量水平。     

Fracture surface energies of high explosives PETN and RDX

Journal of Materials Science -     

Real time low temperature decomposition of explosives - PETN

Chemiluminescence NO/NO_x analyzers have been used to make real-time measurements of PETN decomposition products near storage temperatures. Over the     

空气中PETN爆炸产物初始参数的计算研究

为了研究PETN爆炸产物的初始参数,以爆炸理论为依据,利用计算机数值模拟PETN装药密度与爆速的关系。采用软件编程的方法实现其爆炸产物初始参数的计算,并拟合得出爆炸产物初始参数与PETN装药密度的关系曲线和方程。用密度分别为1.56、1.65、1.69、1.74 g/cm3的PETN爆炸产物初始参数验证拟合方程的准确度。结果表明拟合方程具有较好的准确度。     

Electric breakdown and explosive decomposition of PETN monocrystals initiated by electron beam

The glowing, fracture, and explosive decomposition of pentaerythritol tetranitrate (PETN) monocrystals initiated by a nanosecond pulsed high-current electron beam (HEB) have been experimentally studied. It is established that crystallographically oriented electric (strimer) discharges are formed within the electron-beam action range in the crystal in a broad range of energy densities (0.1?C75.0 J/cm²). Threshold energy density for the electric breakdown, fracture, and explosive decomposition of PETN monocrystals under HEB action have been determined. In contrast to pressed PETN samples, monocrystals exhibit incomplete explosion with expansion of the majority of unreacted substance.     

表面活性剂在处理太安表面静电中的应用

通过实验检验表面活性剂对太安表面静电积累的降解效果,测定表面活性剂对太安基本性质的影响,分析比较对表面活性剂的优化选择。     

硼系高能点火药对太安燃烧转爆轰的影响

文章研究了硼系高能点火药对PETN燃烧转爆轰的影响.试验证明高能点火药剂BKF1在有外界加强约束的条件下,能够使装药压力小于13.8 MPa的PETN完全燃烧转爆轰;对改性后的BKF2进行PETN燃烧转爆轰试验,在相同条件下,BKF2使PETN燃烧转爆轰的概率远远大于BKF1 .     

Test duration in choice of helicopter maintenance policy

In the course of a review of the maintenance policy for a certain type of helicopter, it was found necessary to determine whether the frequency of one of the scheduled tests could be reduced without a shorter mean time between failures (MTBF). A sequential-testing procedure was worked out for an experiment in which hypotheses on the ratio of the respective MTBFs under the new and present maintenance policies are to be verified. In it, two groups of helicopters, subjected to the respective maintenance systems, are observed (Manipulation of two groups in parallel neutralizes the effect of uncontrolled factors, such as variation of the helicopters' operational load and the maintenance-quality level). It is assumed that the failure rates are constant. A decision-making algorithm, and a program, were constructed. The program yielded the decision parameters, densities and mean test duration up to the positive/negative decision in dependence on the actual MTBF ratio, the permissible level of the latter, and the given error probability levels. Prediction of the test duration, together with the operating characteristic, permits more rational planning of the experiment, hence of the maintenance policy.     

Fatigue crack growth from stage I to stage II in a corrosive environment

How a corrosive environment such as a 3.5% NaCl aqueous solution would affect the transition of fatigue crack initiation mode from stage I (shear mode) cracking to stage II (normal mode) cracking was investigated, using notched specimens of HT80 and SNCM439 steels (corresponding to AISI 4340 steel).The experimental result that the transition of fatigue crack growth from stage I to stage II was accelerated in a hydrogen-related environment was discussed in terms of hydrogen induced dislocation multiplication near a crack tip. The microstructures immune to environmental damage were examined, using a precipitate-hardened steel.     

SPC scheme to monitor surgery duration

A unified statistical process control (SPC) scheme is developed to monitor work-process duration of repetitive processes (constant work content), semi-repetitive (work content somewhat varies between cycles) and memoryless (no typical work content). As a basic paradigm to develop the new scheme, we monitor surgery duration (SD), known to represent durations of all three types of work processes. Recently, a new bi-variate model for SD was developed and empirically validated. Based on the new model, we derive an approximation to the distribution of SD sample average and use it to construct a two-stage SPC scheme (for a medically specified subcategory of surgeries). In the first stage, SD distributional shape, as reflected in third and fourth moments, is monitored to determine that no shape-changing assignable causes are active (e.g., work-content variation is stable); in the second stage, location and scale parameters are separately monitored via a traditional Shewhart scheme. Using an existent database of surgery times, application of the new scheme is demonstrated, and average-run-length properties explored. Extensions (like incorporating co-variates) and generalizations are addressed.