Characterization of Erythritol Tetranitrate Physical Properties

The article describes the molecular structure and fundamental physical properties of erythritol tetranitrate (ETN). Although ETN is simple nitrate ester this explosive is described in the literature relatively briefly. The molecular structure of ETN was characterized by single‐crystal X‐ray diffraction. The structure of the ETN molecule is composed of the central carbohydrate chain and two pairs of facing coplanar ONO₂ groups. The crystal density of ETN is 1.827 g cm⁻³. It is a non‐hygroscopic compound. Solubility in water was determined in a temperature range from 5 °C to 80 °C. ETN is slightly soluble in water; solubility at 20 °C is on the same level as that of PETN.     

Explosive Performance Properties of Erythritol Tetranitrate (ETN)

Erythritol tetranitrate (ETN) is a melt‐castable explosive with impressive performance, similar to the well‐known related nitrate ester, pentaerythritol tetranitrate (PETN). Though ETN has been known since 1849, its properties have not been thoroughly investigated. We report here the first 1/2′′ copper cylinder tests of ETN, compared with PETN. We discuss detonation and wall expansion velocity, along with diameter effect information in unconfined rate stick tests. The detonation velocity of ETN is 99 % that of PETN in the same test setup, showing that performance properties are very similar for the two nitrate esters.     

Characterization and Analysis of Tetranitrate Esters

Thermal behaviors, vapor pressures, densities, and drop weight impact results, as well as analytical protocols, are reported for three tetranitrate esters: erythritol tetranitrate (ETN), 1,4‐dinitrato‐2,3‐dinitro‐2,3bis(nitratomethylene) butane (DNTN), and pentaerythritol tetranitrate (PETN). ETN and DNTN both melt below 100 °C and have ambient vapor pressures comparable to TNT. While LC/MS was shown to be a viable technique for analysis of all three tetranitrate esters, only ETN was successfully analyzed by GC/MS. Performance of these nitrate esters as evaluated in lab using the small‐scale explosivity device (SSED) suggested RDX≫DNTN>PETN>ETN. Detonation velocities were calculated using Cheetah 6.0. Since the starting material is now widely available, it is likely that law enforcement will find ETN in future improvised explosive devices. This paper with its analytical schemes should prove useful in identification of this homemade explosive.     

Synthesis and Thermal Energy Storage Properties of Erythritol Tetrastearate and Erythritol Tetrapalmitate

Erythritol tetrapalmitate (ETP) and erythritol tetrastearate (ETS) were synthesized as novel solid‐liquid phase change materials (PCM) by means of the direct esterification reaction of the erythritol with palmitic and stearic acids. The ETP and ETS esters were characterized chemically using FT‐IR and ¹H NMR techniques. The energy storage properties of the esters were determined by DSC analysis. The results indicated that the ETP and ETS esters synthesized as novel solid‐liquid PCMs are promising materials for thermal energy storage applications at large scale such as solar energy storage, building heating or cooling, indoor temperature controlling, and production of smart textile and insulation clothing.     

The Effects of Yield Stress and Casing Thickness on Blast Impulse and Fragment Velocity

A previous paper by the author [1] showed how his equation [2], based on the model first proposed by Gurney [3] for the blast impulse from cased munitions, can be modified to allow for the yield stress of the casing metal. This paper [1] also provided validation for this further equation from available experimental data. Further issues regarding the many smaller but significant interactions between the fracturing casing and the expanding gases need to be investigated before it can be said that a complete theory of blast impulse and fragment initial velocity is in place. In this paper, an approximate evaluation will be made of the potential effect and significance of kinetic energy losses, due to dissipation by means of casing strain energy dissipation. As expected, these losses are found to be most significant for thick, low density, high yield stress casings. The effect of finite casing thickness, also not previously considered, has been found to be small.     

Asymmetric Reduction of Activated Alkenes by Pentaerythritol Tetranitrate Reductase: Specificity and Control of Stereochemical Outcome by Reaction Optimisation

We show that pentaerythritol tetranitrate reductase (PETNR), a member of the ‘ene’ reductase old yellow enzyme family, catalyses the asymmetric reduction of a variety of industrially relevant activated α,β‐unsaturated alkenes including enones, enals, maleimides and nitroalkenes. We have rationalised the broad substrate specificity and stereochemical outcome of these reductions by reference to molecular models of enzyme‐substrate complexes based on the crystal complex of the PETNR with 2‐cyclohexenone 4a . The optical purity of products is variable (49–99% ee), depending on the substrate type and nature of substituents. Generally, high enantioselectivity was observed for reaction products with stereogenic centres at Cβ (>99% ee). However, for the substrates existing in two isomeric forms (e.g., citral 11a or nitroalkenes 18 – 19a ), an enantiodivergent course of the reduction of E/Z‐forms may lead to lower enantiopurities of the products. We also demonstrate that the poor optical purity obtained for products with stereogenic centres at Cα is due to non‐enzymatic racemisation. In reactions with ketoisophorone 3a we show that product racemisation is prevented through reaction optimisation, specifically by shortening reaction time and through control of solution pH. We suggest this as a general strategy for improved recovery of optically pure products with other biocatalytic conversions where there is potential for product racemisation.     

Simultaneous Determination of Pentaerythritol Tetranitrate and 2,4,6‐Trinitrotoluene by High Performance Thin Layer Chromatography and Partial Least Squares Regression (PLSR) Method

High performance thin layer chromatography (HPTLC) has been used for the simultaneous determination of pentaerythritol tetranitrate (PETN) and 2,4,6‐trinitrotoluene (TNT). With this aim, the spots were developed on silica gel 60 F₂₅₄ layers with petroleum ether–acetone (2 : 1 v/v). Both PETN and TNT compounds were separated from other constituent materials, and were developed at the same speed, by this solvent system. Then ultraviolet (UV) spectra of these materials were recorded with TLC‐scanner3 of CAMAG Company, and partial least squares regression‐2 (PLSR‐2) method was applied for the calibration and quantitative determination of these materials. The figure of merit (FOM) of this method was determined, and the method was applied for the analysis of an artificial sample.     

Replacing the Equations of Fano and Fisher for Cased Charge Blast Equivalence – I Ductile Casings

The initial velocity of casing fragments from bombs, shells etc. was first calculated by R. W. Gurney in 1943 [1]. Subsequent to this derivation by Gurney, which was based on a reasonable simplification of the case and gas dynamics, his wartime co‐worker, U. Fano [2], claimed to have calculated the proportion of kinetic energy remaining with the explosive gases following energy partition with the casing. This paper shows that both Fano’s equation for cased charge blast equivalence and a further derivation by Fisher in 1953 [3], based on Fano’s, are in fact inconsistent with Gurney’s reasonable physical model. Neither of these two reports has ever been the subject of independent peer‐review, despite having been extensively cited. This paper identifies the error made by Fano and copied by Fisher and draws attention to an alternate equation recently published by the author which gives similar predictions to that of Fisher, while being consistent with Gurney’s original derivation. Also, this paper establishes for the first time that the use of such equations for cased charge blast impulse equivalence is valid.     

Replacing the Equations of Fano and Fisher for Cased Charge Blast Impulse – III – Yield Stress Method

Previous papers by the author [1–3] pointed to a discovery by Fisher [4] that an equation by Fano [5], when used to predict blast impulse from cased munitions, did not fit the available data. These previous papers showed that an alternative equation for casing‐modified blast impulse could be derived directly from an equation by Gurney [6] for the kinetic energy balance between the mass of casing metal and the mass of explosive gases. However, this equation was derived for very ductile casings that are accelerated to their ideal Gurney velocity before they fracture. A previous paper [3] showed how the finite fracture strain of real casing metal can be taken into account in determining the relative blast impulse from a cased charge. This paper shows how, based on previous work by Taylor [7], the equation in [2] can instead be modified to allow for the yield stress of the casing metal and provides validation for this further equation from available experimental data.     

Replacing the Equations of Fano and Fisher for Cased Charge Blast Impulse‐II‐Fracture Strain Method

Previous papers by the author [1, 2] pointed to a discovery by Fisher [3] that an equation by Fano [4], when used to predict blast impulse from cased munitions, did not fit the available data. These previous papers showed that an alternative equation for casing‐modified blast impulse could be derived directly from an equation by Gurney [5] for the kinetic energy balance between the mass of casing metal and the mass of explosive gases. However, this equation was derived for very ductile casings that are accelerated to their ideal Gurney velocity before they fracture. Many real casings, even under high dynamic strain rates, fracture before they can receive the full drive available from the explosive gases. This paper shows how the equation in reference [2] can be modified to allow for casing fracture at finite dynamic strain and provides validation for this modified equation from previously unpublished AWE archive experimental data.     

A Simple Fragment of Cyclic Acyldepsipeptides Is Necessary and Sufficient for ClpP Activation and Antibacterial Activity

The development of new antibacterial agents, particularly those with unique biological targets, is essential to keep pace with the inevitable emergence of drug resistance in pathogenic bacteria. We identified the minimal structural component of the cyclic acyldepsipeptide (ADEP) antibiotics that exhibits antibacterial activity. We found that N‐acyldifluorophenylalanine fragments function via the same mechanism of action as ADEPs, as evidenced by the requirement of ClpP for the fragments' antibacterial activity, the ability of fragments to activate Bacillus subtilis ClpP in vitro, and the capacity of an N‐acyldifluorophenylalanine affinity matrix to capture ClpP from B. subtilis cell lysates. N‐acyldifluorophenylalanine fragments are much simpler in structure than the full ADEPs and are also highly amenable to structural diversification. Thus, the stage has been set for the development of non‐peptide activators of ClpP that can be used as antibacterial agents.     

天然气储罐泄漏后燃烧爆轰性分析

针对某市天然气利用工程中一个储量为10000 m3的天然气储罐泄漏的危险性进行了分析,求出了泄漏总时间和最大的泄漏质量。对天然气-空气预混云团的火灾危害进行了评估,对其形成火球的参数进行了计算,结果表明一旦发生燃烧能形成半径达73.89 m的巨大火球,对324.1 m范围内的人员可造成三度烧伤。如果天然气-空气预混云团产生爆轰,其等效TNT质量为12206.67 kg,76.9 m的范围内大部分人员死亡。     

空气及半硬质聚氨酯泡沫塑料中爆炸波传播特性的研究

对半硬质聚氨脂泡沫(SRPUF)塑料中雷管爆炸场的反射压力分布进行了测试,并利用理想气体状态方程将空气中雷管爆炸后所测的入射压力分布转化成反射压力分布.对这两种介质(空气、SRPUF材料)中反射压力分布进行了对比和分析,定性地讨论了两种介质中爆炸波的传播特性,并对SRPUF材料隔爆缓冲性能进行了分析说明.     

Inhibitors of Human Divalent Metal Transporters DMT1 (SLC11A2) and ZIP8 (SLC39A8) from a GDB-17 Fragment Library

Solute carrier proteins (SLCs) are membrane proteins controlling fluxes across biological membranes and represent an emerging class of drug targets. Here we searched for inhibitors of divalent metal transporters in a library of 1,676 commercially available 3D-shaped fragment-like molecules from the generated database GDB-17, which lists all possible organic molecules up to 17 atoms of C, N, O, S and halogen following simple criteria for chemical stability and synthetic feasibility. While screening against DMT1 (SLC11A2), an iron transporter associated with hemochromatosis and for which only very few inhibitors are known, only yielded two weak inhibitors, our approach led to the discovery of the first inhibitor of ZIP8 (SLC39A8), a zinc transporter associated with manganese homeostasis and osteoarthritis but with no previously reported pharmacology, demonstrating that this target is druggable.     

Design and Generation of Highly Diverse Fluorinated Fragment Libraries and their Efficient Screening with Improved 19F NMR Methodology

Fragment screening performed with ¹⁹F NMR spectroscopy is becoming increasingly popular in drug discovery projects. With this approach, libraries of fluorinated fragments are first screened using the direct‐mode format of the assay. The choice of fluorinated motifs present in the library is fundamental in order to ensure a large coverage of chemical space and local environment of fluorine (LEF). Mono‐ and poly‐fluorinated fragments to be included in the libraries for screening are selected from both in‐house and commercial collections, and those that are ad hoc designed and synthesized. Additional fluorinated motifs to be included in the libraries derive from the fragmentation of compounds in development and launched on the market, and compounds contained in other databases (such as Integrity, PDB and ChEMBL). Complex mixtures of highly diverse fluorine motifs can be rapidly screened and deconvoluted in the same NMR tube with a novel on the fly combined procedure for the identification of the active molecule(s). Issues and problems encountered in the design, generation and screening of diverse fragment libraries of fluorinated compounds with ¹⁹F NMR spectroscopy are analyzed and technical solutions are provided to overcome them. The versatile screening methodology described here can be efficiently applied in laboratories with limited NMR setup and could potentially lead to the increasing role of ¹⁹F NMR in the hit identification and lead optimization phases of drug discovery projects.     

Hydrogels with Acid Groups for Removal of Copper(II) and Lead(II) Ions

Acrylamide-maleic acid (AAM-MA) hydrogels having high acid group content prepared with different maleic acid ratios were used for the removal of Cu(II) and Pb(II) ions from aqueous solutions in competitive and noncompetitive conditions. The effects of pH, time, and initial metal ion concentration on the metal ion adsorption capacity were investigated. The adsorption isotherm models were applied on experimental data and it is shown that the Freundlich equation was the best model for Cu(II) ion while the Langmuir isotherm model was the best one for Pb(II) ion. The stability constants of acrylamide-maleic acid hydrogel-Cu(II) and Pb(II) complexes were also determined by van den Berg/Ruzic transformation, and K values obtained were 1.60 × 10³ and 1.81 × 10³ for Cu(II) and Pb(II) ions, respectively. The experiments under competitive conditions showed that the hydrogels prefered Pb(II) ion and this preference increased with increasing of carboxylic acid group content (AGC) of polymers. It is stated that these hydrogels can be regenerated efficiently (>95%) and used repeatedly.     

Experimental Studies of the Effect of the Ground Atmospheric Layer and the Underlying Surface on the Amplitude of Weak Air Blast Waves from Ground Chemical Explosions

This paper reports results from experiments of the effect of the underlying surface, temperature stratification, and wind speed in the ground atmospheric layer on the amplitude of a weak air blast wave at large distances.     

Charge transfer and SEIRAS studies of 1,4-benzoquinone functionalized mixed monothiol/dithiol self-assembled monolayers

Although substantial information can be obtained from electrochemical measurements, much greater detail concerning molecular structure can be obtained by coupling such measurements with molecular spectroscopy. To this end, electrochemical and in situ surface enhanced infrared spectroscopy (SEIRAS) was performed to analyze 1,4-benzoquinone (BQ) terminated self-assembled monolayers. Monolayers were derived via the Michael addition of BQ to a pre-formed mixed monolayer composed of methyl and thiol terminated functionalities. This approach resulted in relatively robust but non-ideal redox-active monolayers. Spectroscopic and electrochemical measurements have allowed us to determine the pH dependence of both the apparent formal potential and the heterogeneous standard rate constant for proton coupled electron transfer (PCET) for this 2e⁻/2H⁺ redox system. While the former is in excellent agreement with predictions of step-wise PCET, the latter deviates from the expected kinetic response.