bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of milling on the burning rates of red lead‐ferrosilicon‐antimony(III) sulfide delay compositions
Authors: Nakamura Hidetsugu , Taniguchi Hiroyuki , Hara Yasutake
Published: May 2005

In order to clarify the effect of surface properties on the burning characteristics of a delay powder, the burning rates of the red lead‐ferrosilicon‐antimony(III) sulfide delay compositions have been measured when the ingredient was pulverized using a vibro‐mill. It was found that the burning rates increased with the mixing time when the ferrosilicon ingredient alone was pulverized before preparation of the delay powder. On the other hand, the burning rate decreased if the red lead or the antimony(III) sulfide were pulverized. The reason for this is ascribed to the chemical reaction in the combustion wave.
Studies on Thermal Decomposition Kinetics of Polyvinyl Nitrate
Authors: Mishra S. C. , Pant Jyotsna , Pant G. C. , Dutta P. K. , Durgapal U. C.
Published: May 2005

Non‐isothermal TG curves for four samples of polyvinyl nitrate (PVN), having 15.71%, 14.95%, 13.34% and 11.76% nitrogen contents, were obtained at 5°C/min heating rate. The weight loss of PVN samples depends directly on their % N and occurs in three or more temperature zones. For PVN with 15.71% N (max 15.73% N in theory), the main decomposition step results in more rapid and complete weight loss than for PVN with lower % N, probably due to higher oxygen balance of the former. The TG data were subjected to kinetic analysis using a computer programme. For each decomposition step, the kinetic parameters (E and A) and the regression coefficient (r) were calculated on the basis of several kinetic models and equations consistent with the Arrhenius relationship. It was concluded that the thermal decomposition kinetics of all four PVN sample are best expressed by the Random nucleation model (Mampel unimolecular law) first‐order reaction. For the initial and slowest decomposition step, E ranged between 188 kJ/mol − 217 kJ/mol and In A between 46.88 s−1 ‐ 60.13 s−1. The In A versus E plots for all PVN samples exhibited a linear relationship, probably due to the kinetic compensation effect.
Pressure Oscillations in Regenerative Liquid Propellant Guns
Authors: Wren G. P. , Coffee T. P. , DeSpirito J. , Knapton J. D. , Klingenberg G.
Published: May 2005

The present paper deals with pressure oscillations in regenerative liquid propellant guns (RLPG) presenting the state‐of‐the‐art research into sources and control of these combustion instabilities. Pressure oscillations with amplitudes up to 50 % of mean pressure and frequencies up to 60 kHz or more are present in experimental data of RLPGs, especially at medium and large calibers. Amplitudes increase with the volumetric energy density of the liquid propellant and the mass flow rate during injection. Frequency analyses reveal that both acoustic modes and combustion noise are components of the recorded oscillations. Acoustic modes, in particular, have the potential to couple to resonant modes in near‐field mechanical structures. A multi‐phase, multi‐dimensional model investigation at ARL indicates that pressure waves reflected from internal boundaries are amplified as they pass the combustion zone of the highly pressure‐sensitive liquid propellant in a localized region near the injector. Experimental data lead to a similar understanding of the amplification of pressure oscillations in RLPGs. Experiments in the United States and in Germany confirm that the pressure oscillations can be mitigated by altering the combustion characteristics of the liquid propellant. Also, techniques that more effectively disperse the liquid propellant jet and thereby decrease the local accumulation of liquid propellant, may reduce pressure oscillations as shown in 30‐mm RLPG experiments. Further, energy‐absorb‐ing chamber walls or liners can serve as broad‐band filters and have been shown experimentally to be effective in reducing the amplitude of all frequencies. In addition, physical methods such as cavities and baffles reduce significantly specific acoustic frequencies of the oscillations.
X‐ray diffraction spectroscopic and thermal studies on 1,3,5‐trinitro‐hexahydropyrimidine (TNP)
Authors: Prabhakaran K. V. , Naidu S. R. , Kurian E. M.
Published: May 2005

TNP, a heterocyclic nitramine containing a CNO2 functionality, has been studied as regards the kinetics and mechanism of thermal decomposition, morphology and the gaseous products evolved therof, using thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR), differential scanning calorimetry (DSC), X‐ray diffraction (XRD) and hot stage microscopy. The elementary cell parameters obtained form the XRD pattern are: a = 18.818 ± 0.005 Å, b = 18.818 ± 0.005 Å and c = 4.867 ± 0.005 Å. The crystal belongs to the hexagonal system with c/a ratio = 0.259. IR spectra of TNP have also been recorded and the bands assigned. Kinetics of thermolysis has been followed both by isothermal TG and IR. The best linearity with a correlation coefficient of 0.986 was obtained for the three‐dimensional diffusion controlled Jander‐equation. Kinetic parameters were evaluated from the induction period as well as from isothermal TG. Activation energy was found to be 202.05 kJ/mol and log A(in s‐1) 22.78 from TG and 181.133 kJ/mol and log A (in s1) 20.97 from IR, respectively. The corresponding values were 171.17 kJ/mol and log A (in s‐1) 21.20 from the induction period data. The effect of a series of additives incorporated to the extent of 5 %, on the initial thermolysis of TNP, has also been studied. Evolved gas analysis by IR showed that CO2, NO2, NO and N2O are produced in larger amounts than CO and HCN. The cleavage of the NN bond appears to be the primary step in the thermolysis of TNP.
The Simplified Model for Predicting Shaped Charge Jet Parameters
Authors: Gui‐Xi Liu
Published: May 2005

The model is based on the more recent work of Hirsch and the original analytical work of Pugh, Eichelberger and Rostoker. Namely, the simplified Gurney formula for imploding cylinders derived by Hirsch is combined with the PER theory forming one‐dimensional computer code, and then it is used for predicting the 80‐mm diameter shaped charge jet parameters. Good agreement has been found with the experimental results.
Improving the Safety of a Pyrotechnic Igniter through a controlled experiment
Authors: Milman Benjamin , Sirota Issachar , Steinberg David M.
Published: May 2005

One of the important goals of quality management in today's competitive marketplace is to build quality into products and processes at the development stage. The use of statistically controlled experiments, in which several parameters are studied simultaneously, can help accomplish this goal efficiently. This paper describes a case study that illustrates the utility of controlled experiments in product development. The customer required improvements in the safety of a pyrotechnic igniter used in one of the products they purchased. The safety improvements could be met by replacing the “match‐head” initiator by a type IA/IW no fire initiator. However, there was concern that changing the initiator might degrade other important product performance characteristics. A controlled experiment was designed to compare three different initiators, the booster charge and the main charge. The experiment quickly and efficiently pointed to a superior initiator and the optimal charges to maintain high performance with enhanced product safety.
Surfactant coatings for the stabilization of barium peroxide and lead dioxide in pyrotechnic compositions
Authors: Brent G. F. , Harding M. D.
Published: May 2005

BaO2 and PbO2 are widely used oxidizers which have been observed to suffer degradation after storage in unsealed systems. It is evident that reaction occurs with atmospheric water and carbon dioxide forming carbonates. The inhibition of these reactions by the application of protective coatings is considered, Such techniques appear to be gaining importance in pyrotechnic applications, and criteria for suitable coatants are discussed. Various surfactants were applied to BaO2 and evaluated in an accelerated aging test. Selected anionic and non‐ionic surfactants conferred improved aging resistance, with stearic acid giving the greatest advantage. A very high degree of protection was also afforded to PbO2. Low energy fuses based on a BaO2/Si composition were evaluated and a high resistance to aging was realized using the coated BaO2. There were no adverse effects on other properties, thus satisfying the criteria established for coatants.
Combustion of Ti and Zr Particles with KNO3
Authors: Miyata Kohsei , Kubota Naminosuke
Published: May 2005

This paper describes the thermochemical properties and combustion characteristics of pyrolants consisting of Ti/KNO3 and Zr/KNO3 mixtures. Differential thermal analysis (DTA) and thermogravimetry (TG) were conducted in order to elucidate the reaction processes of these pyrolants. The results of the experiments suggest that Ti particles react exothermically at 970 K with the decomposed gases of KNO3, and Zr particles react also exothermically at 700 K with liquified product of KNO3. Burning rates of the pyrolants were measured with a chimney type strand burner which was pressurized with argon gas. The burning rate of Ti/KNO3 is more sensitive to pressure than that of Zr/KNO3. The results indicate that a major exothermic reaction on the combustion wave of Zr/KNO3 pyrolants is in the condensed phase. The burning rates of both pyrolants are dependent on the oxidizer/fuel ratio and initial temperature of the pyrolants.
A Study of Some Charge‐Transfer Complexes of 2‐methyl‐1,3,6,8‐tetranitronaphthalene
Authors: Cuming S. , Wells C. H. J.
Published: May 2005

Charge‐transfer complexes have been prepared with 2‐methyl‐1,3,6,8‐tetranitronaphthalene (I) as electron acceptor and various 9‐substituted anthracenes as electron donor. The electron affinity of (I) has been determined as 1.12 ± 0.07 eV, and the energy of activation for conduction in the complexes studied lie in the range 0.27 eV–0.74 eV.
Strain Rate Insensitivity of Damage‐Induced Surface Area in M30 and JA2 gun propellants
Authors: Gazonas George A. , Juhasz Arpad A. , Ford James C.
Published: May 2005

Uniaxial compression tests are conducted on single‐grain seven‐perforated specimens of M30 and JA2 gun propellant using the U.S. Army's high rate servohydraulic test apparatus in order to investigate the effects of strain rate, temperature, and percent axial strain on the combustion characteristics (apparent burn rate and pressurization rate) of the propellants. At room temperature M30 primarily deforms by macroscopic fracture and JA2 deforms by macroscopic flow. The total number of tests (sixteen) is minimized by designing the experimental program according to a 24 statistical design strategy. The single grains of deformed propellant are then burned in a newly designed 7.8‐cm3 mini closed‐bomb and plots of pressure, pressurization rate and surface area ratio versus time, and apparent burning rate versus pressure are compared with baseline results for the undeformed propellant specimens. The apparent burn rates of damaged M30 propellant vary considerably and the degree of damage induced surface area approaches six times that of the undeformed baseline M30 specimens. The apparent burn rates of JA2 are relatively unaffected by the induced deformation. Results indicate that the apparent burn rate of JA2 at 20 MPa is primarily dependent on the deformation temperature, yet the apparent burn rate of M30 at 20 MPa is dependent primarily on percent axial specimen strain. The apparent burn rates for these propellants are relatively insensitive to the deformation strain rate over the range 10−2 to 100 sec−1.
Synthesis of Trinitrophenyl C60 Derivative
Authors: Wang Naixing , Li Jisheng , Ji Gaijiao
Published: May 2005

Trinitrophenyl C60 derivative was synthesized by allowing C60 to react with trinitrochlorobenzene and sodium azide. This fullerene derivative would first provide a brillant prospect in the energetic materials. The product structure was identified by FD‐MS, UV‐VIS, IR and 13C‐NMR.
Agglomeration of magnesium particles in magnesium‐sodium nitrate combustion
Authors: Bhaskara Rao R. , Srinivasa Rao P. , Singh Harihar
Published: May 2005

Agglomeration phenomenon of magnesium particles during combustion of MgNaNO3 propellant has been studied. High speed photographs of combustion zones and the burning surface temperature data indicate that the metal particles form agglomerates on the burning surface in varying degree depending on the mass fraction of NaNO3. It is found that the increase of oxidizer content increases the metal agglomeration and the agglomerate size depends on the initial particle size of the ingredients.

An attempt has been made to predict the size of the agglomerates based on the consideration that the agglomerate size depends on the thickness of the molten oxidizer layer enveloping the metal particles in the condensed phase and surface heat flux providing local temperature environment to agglomerate the metal particles and to eject from the burning surface for the vapour phase combustion. The results were compared with the experimental data. The prediction describes fairly well the observed effects of the concentration and particle size.
LOVA Propellant Aging: Effect of Residual Solvent
Authors: Pesce‐Rodriguez Rose A. , Fifer Robert A.
Published: May 2005

An investigation of LOVA propellant aging was performed to identify the cause of stabilization periods in certain propellant lots. Two important observations were made: (1) the level of residual solvent in propellant grains slowly decrease while in storage, and (2) during the drying process and while the grains are in storage, plasticizer “co‐migrates” with solvent, resulting in plasticizer accumulation at grain surfaces. It was also observed that while in storage, residual solvent may be oxidized to generate organic acids. Based on these results, it is proposed that stabilization periods result from processes related to migration, evaporation, and oxidation of residual solvent.
Thermal decomposition mechanisms of bis(2‐fluoro‐2,2‐dinitroethyl) formal (FEFO) and bis(2‐fluoro‐2,2‐dinitroethyl) difluoroformal (DFF) from simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) measurements
Authors: Minier Leanna M. G. , Behrens Richard
Published: May 2005

The simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) technique has been applied to measure the vapor pressures and evaluate the thermal decomposition chemistry of two energetic liquids, bis(2‐fluoro‐2,2‐dinitroethyl)formal (FEFO) and bis(2‐fluoro‐2,2‐dinitroethyl)difluoroformal (DFF). The resulting heat of vaporization (ΔHvap) and vapor pressure at 25°C are 20.3 ± 0.2 kcal/mol and 0.4 ± 0.1 millitorr for FEFO, and 17.3 ± 0.2 kcal/mol and 5.1 ± 1.1 millitorr for DFF. The thermal decomposition of FEFO indicates there are six major pyrolysis pathways. The results suggest that FEFO initially decomposes at 150°C by rearrangement of the nitro group (NO2) to the nitrite group (ONO), followed by loss of NO. Some NO2 is also formed at 170°C. Between 200°C–300°C, further pyrolysis occurs. In one pathway, the FEFO backbone remains intact and a high molecular‐weight product is formed. The other three pathways involve scission of the FEFO backbone; one yielding CO2 (possibly N2O), one yielding CH2O and CO, and one yielding C3H2NOF. Differences in the thermal decomposition behaviors in the liquid and gas phases are observed. In the thermal decomposition of DFF, the formal fluorine atoms stabilize the backbone structure. Numerous minor thermal decomposition products are also reported.
Cast PBX B2238 for Small‐Calibre High Performance Insensitive Munitions
Authors: Kent Ralph
Published: May 2005

Generally speaking, today's small‐calibre munitions, filled with conventional melt‐cast or pressed high explosives, are classified in the 1.1 or 1.2 Hazard Divisions because they explode when exposed to various threats, such as fuel fire and sympathetic detonation. The RDX‐based B2238 composition is a low‐cost and less sensitive cast PBX originally developed by SNPE for the initiation of cast PBX main charges. While it is easily initiated with conventional detonators, B2238 offers the same degree of insensitivity as other cast PBXs used for main charges (HEXABU 88A or OCTORANE 86B for example) and does not explode when exposed to fire and/or bullet impact. Feasibility tests carried out on several types of small‐calibre munitions have shown B2238 explosive filling to be an excellent solution in the design of small calibre insensitive munitions with a high performance (in terms of fragments and shaped charge jet) comparable to that of the most energetic conventional high explosives such as 98RDX/2wax. As a result, the new IM standards, currently being defined, should allow in the future to reclassify the small‐calibre munitions filled with B2238 in Hazard Divisions other than 1.1 and 1.2.
Study on the Nitrolysis of Hexamethylenetetramine by NMR spectrometry II. Some new evidences of the intermediate of HOCH2NHNO2 as a possible precursor to RDX
Authors: Fang Zhijie , Chen Li , Wang Shaofang , Chen Ju , Li Fuping
Published: May 2005

In this research, the RDX yield from nitrolysing hexamethylenetetramine (hexamine, HA) together with methylenedinitramine (MDNA) in 90% nitric acid was more than 100%. It was found that MDNA decomposed completely in 90% nitric acid, forming O(CH2ONO2)2, while in HNO3NH4NO3 system the decomposed fragments of MDNA condensed into RDX. On the basis of the comparison of the experimental results to the 1H‐NMR spectra obtained by following the decomposition reaction of MDNA with nitric acid, the intermediate, HOCH2NHNO2, was postulated as one of the possible precursors to RDX both in Hale and in K process.
BAMO/NMMO Copolymer with Polyester Initiation
Authors: Kawasaki Hidetoshi , Anan Toshiyuki , Kimura Eishu , Oyumi Yoshio
Published: May 2005

In order to improve of mechanical properties at low temperature region, 3,3‐bis(azidomethyl)oxetan (BAMO), 3‐nitratomethyl‐3‐methyloxetane (NMMO) and polyester (PE) copolymer were synthesized by using polyester initiator with boron trifluoride etherate. The molar ratio of each units in the BAMO/NMMO/PE copolymer was 7.4/2.6/0.39 according to the 1H‐NMR spectrum analysis and was almost exactly the same composition as the monomer fed (7/3/0.33). The relative composition of triad microstructures was same as theoretical value and they were randomly arranged. The PE, which was a replacement of 1,4‐butanediol, acted as an excellent soft segment in the copolymer, and the glass transition point of the elastomer was 4.8 degrees lowered by the replacement. This effect was also verified in the mechanical properties of the composite propellant and the tensile elongation was increased from 15% to 40%percnt; at −40 °C.
Burning Behaviour of Nitramine Model Formulations
Authors: Eckl Wilhelm , Weiser Volker , Langer Gesa , Eisenreich Norbert
Published: May 2005

Model formulations of RDX and a hydrocarbon binder were studied by various methods to investigate the effect of additional fuel on the burning mechanism. The fuel reduces the burning rate at higher pressures and the pressure exponent. Extinguished burning surfaces show that the RDX is depleted at the surface. Emission spectra in the UV/VIS are dominated by the OH, NH and CN similar to the case of pure RDX. However, the OH decreases at higher distances from the surface obviously consumed by decomposition products of the fuel. At high pressures (> 2 MPa) soot emits strong continuous radiation. The temperatures obtained from the OH bands at 306 nm range from 2800 K to 3000 K which is close to the adiabatic flame temperature. The temperatures evaluated from the continuous radiation are considerably lower indicating radiation cooling.
Suitability of Modified Supercritical Carbon Dioxide as Solvent for polar substances
Authors: Niehaus Michael , Teipel Ulrich , Bunte Gudrun , Krause Horst H.
Published: May 2005

As solvent supercritical carbon dioxide offers unique possibilities, like non‐toxicity and therefore reduction of environmental pollution or access of low‐temperature processing resulting in additional process safety. Therefore, knowledge to the influence of modifiers due to better solubility of polar substances is important for evaluating novel manufacturing techniques like the RESS‐ or GAS‐process. Dynamic supercritical fluid extraction of PETN, nitroguanidine (NIGU) and RDX, respectively, with pure as well as with modified carbon dioxide indicated that all explosives except nitroguanidine were extracted though for RDX and 3‐nitro‐1,2,4‐triazole the use of modifiers proved to be necessary. The results show the high capacity of modified supercritical carbon dioxide as a solvent in RESS‐ and GAS‐processes.
Spectroscopic Investigation of Nitromethane Flames
Authors: Eckl Wilhelm , Weiser Volker , Weindel Martin , Eisenreich Norbert
Published: May 2005

Nitromethane (CH3NO2) Pool Fire Flames have been investigated analysing both, the radiation emitted from intermediate combustion radicals (diatomic molecules) in the ultraviolet (UV) and visible (VIS) spectral range, and the near infrared spectra dominated by broad water bands. Comparing the UV/VIS spectra to calculated band profiles, rotational and vibrational temperatures (Trot, Tvib) of OH, NH and CN have been determined. At local thermal equilibrium Trot and Tvib must be equal. The determined temperatures show that the OH and NH emissions originate from pure thermal excitation (Trot = Tvib = 2300 K–2380 K) but the CN emissions show additionally a chemical excitation indicated by different vibrational and rotational temperatures in the Boltzman factor (Trot = 2100 K, Tvib = 4300 K). For a more detailed study of the flame, the emission of OH radicals has been investigated more extensively by monitoring a two‐dimensional rotational temperature and emissivity profile. In cooler flame regions, the observed spectra are dominated by the near infrared radiation emitted from stable combustion products like water and carbon dioxide. Therefore, NIR spectra (1000 nm to 2500 nm) have been compared to broad band profiles calculated with a self‐developed code basing on the data of the ‘Handbook of Infrared Radiation of Combustion Gases’. The flame temperatures obtained by this method range from 1800 K to 1900 K. The results are correlated to flames of methane and nitrogen oxide which emit similar spectra indicating similar reaction mechanisms in the gaseous phase.
CL‐20 performance exceeds that of HMX and its sensitivity is moderate
Authors: Simpson R. L. , Urtiew P. A. , Ornellas D. L. , Moody G. L. , Scribner K. J. , Hoffman D. M.
Published: May 2005

The explosive performance of ϵ‐CL‐20 was found to be approximately 14% greater than HMX as determined by cylinder expansion and tantalum plate acceleration experiments. This makes it the most powerful explosive ever tested at small volume expansions of the detonation products. In general CL‐20 is more sensitive than HMX. However, the sensitivity of CL‐20 to one‐dimensional shock loading was found to be similar to HMX.
Relationships Between Electron Structures of Substitutive Ureas and their reactivity in Mannich reaction
Authors: Zhang Yuejun , Yu Mahong , Li Weimin
Published: May 2005

The electron structures of urea, substitutive ureas and N‐methylolamine with special structure and its imine cation were studied by SCF‐MO AM1 computation. The influence of different electronegative substituents on the reactivity of substitutive ureas acting as acid components to react with Mannich reaction intermediates and on the requirement of their reaction conditions were discussed according to the charge density of reaction‐centre atoms. The reactivity of imine cations was also discussed on the basis of Frontier Orbital Theory and Bonding Principle. These results showed that the electronegativity of substituents make effects not only obviously on the nucleophilicity of acid components but also on the requirement of media acidity. As the electron‐withdrawing ability of substituents increases, the nucleophilicity of nitrogen atom which acts as a reaction‐centre in substitutive ureas increases so that they can exist stably in strong acidic media and can condense further with the Mannich intermediate imine cation. These conclusions were confirmed by experimental facts.
Determination of traces of water in liquid dinitrogen tetroxide‐nitric oxide propellant mixtures by Fourier transform proton magnetic resonance spectrometry
Authors: Dove Michael F. A. , Logan Norman , Wood Simon A.
Published: May 2005

Liquid dinitrogen tetroxide, N2O4, and mixed oxides of nitrogen as used as rocket propellant oxidizers, contain the products of the reaction of N2O4 with adventitious water. The determination of the total concentration of water and water‐derived species, called the water equivalent content, is essential in view of the effect of the hydrolysis products upon the rate of corrosion of containment metals and the physical state of the corrosion products. High field Fourier transform proton magnetic resonance spectrometry has now been validated for the direct measurement of water equivalent for MON blends up to MON‐3, without prior oxidation. Oxidation does, however, give slightly better precision. The technique is shown to be a reliable, absolute method for the determination of water equivalent contents as low as 0.003 wt% and up to at least 0.2 wt%. The precision of the method in this range is within 5%: it is estimated that the water equivalent content could be determined at levels as low as 0.0001 wt%. Samples of N2O4 prepared for NMR analysis are stable in sealed glass tubes for more than 1 year.
Effects of the polymer matrix density on the shock, bullet impact and high strain‐rate ignition sensitivity of polymer bonded explosives
Authors: Dagley Ian J. , Ho Sook‐Ying , Nanut Victor
Published: May 2005

Four HMX/polymer cast‐cured explosive compositions containing a constant volume percentage (24%) of acrylate polymers ranging in density from 0.93 Mg/m3–1.65 Mg/m3 were evaluated in shock sensitivity, bullet impact sensitivity and high strain‐rate impact ignition tests. It was observed that shock sensitivity and bullet impact sensitivity, measured for flat‐ended projectiles impacting the bare face of elsewhere confined charges, increased with the density of the polymer matrix in the compositions. This correlation between the tests occurs because the detonations observed in the bullet impact test are initiated by shock, with shock initiation presumably occurring more readily when there is less impedance mismatch (i.e. a smaller density difference) at the polymer matrix/HMX crystal interface. In the Hopkinson Bar test a poorer correlation of ignition sensitivity with polymer density was observed because at these lower impact energies other initiation mechanisms such as macroscopic shear and plastic heating, viscous flow, etc. also play an important role.
Studies on 2,4,6‐trinitrophenyl substituted naphthalenes. Part III: Synthesis of nitro‐ and polynitro‐1‐methyl‐4‐(2,4,6‐trinitrophenyl)naphthalenes
Authors: Bergman John S. , Duffin Henry C. , Wells Clifford H. J.
Published: May 2005

The nitration of 1‐methyl‐4‐(2,4,6‐trinitrophenyl)naphthalene (1) and of mono‐ and dinitro‐derivatives of (1) has been studied with a view to obtaining precursors of high energy compounds possessing thermal stability. A number of nitro‐, dinitro‐ and trinitro‐derivatives of (1) have been synthesized. Some of these derivatives have also been synthesized from 4‐bromo‐1‐methylnaphthalene by a combination of nitration and Ullmann reactions.
Study on the Nitrolysis of Hexamethylenetetramine by NMR Spectrometry. Part III: The NMR spectral data of some products and intermediates from the nitrolysis of HA
Authors: Fang Zhijie , Chen Ju , Li Fuping
Published: May 2005

The 1H and 13C chemical shifts of methylene groups in nitric acid are reported for seven products and intermediates involved in the formation of 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX) from the nitrolysis of hexamethylenetetramine (HA). Based on the results, the 1H and 13C chemical shift ranges of the methylene groups in different kinds of methylenenitramines from the nitrolysis liquors of HA were discussed.
Energetics of the structure and chain tilting of antiparallel β‐barrels in proteins
Authors: Chou Kuo‐Chen , Heckel Armin , Némethy George , Rumsey Shirley , Carlacci Louis , Scheraga Harold A.
Published: May 2005

The preferred structural pattern of antiparallel β‐barrels in proteins, described as the right‐handed tilting of the peptide strands with respect to the axis of the barrel, is accounted for in terms of intra‐ and interchain interaction energies. It is related to the preference of β‐sheets for right‐handed twisting. Conformational energy computations have been carried out on three eight‐stranded antiparallel β‐barrels composed of six‐residue strands, in which L‐Val and Gly alternate, and having a right‐handed, a left‐handed, or no tilt. After energy minimization, the relative energies of these structures were 0.0, 8.6, and 46.1 kcal/mol, respectively; i.e., the right‐tilted β‐barrel is favored energetically, in agreement with anti‐parallel β‐barrels observed in proteins. Tilting of the barrel is favored, relative to the nontilted structure, by both intra‐ and interstrand interactions, because tilting allows better packing of the bulky side chains. On the other hand, the energy difference between the left‐ and right‐tilted barrels arises essentially from intrachain interactions. This is a consequence of the preference of β‐sheets for a right‐handed twist. Space limitations inside the barrel are satisfied if there is an alternation of bulky residues and residues with small or no side chain (preferably Gly) in neighboring positions on adjacent strands. Such a pattern is seen frequently in antiparallel β‐barrels of globular proteins. The computations indicate that a structure with Val…Gly pairs can be accommodated in a β‐barrel with no distortion.
Prediction of homologous protein structures based on conformational searches and energetics
Authors: Schiffer Celia A. , Caldwell James W. , Kollman Peter A. , Stroud Robert M.
Published: May 2005

A “knowledge‐based” method of predicting the unknown structure of a protein from a homologous known structure using energetics to determine a sidechain conformation is proposed. The method consists of exchangin the residues in the known structure for the sequence of the unknown protein. Then a conformational search with molecular mechanics energy minimization is done on the exchanged residues. The lowest energy conformer is the one picked to be the predicted structure. In the structure of bovine trypsin, the importance of including a solvation energy term in the search is demonstrated for solvent accessible residues, while molecular mechanics alone is enough to correctly predict the conformation of internal residues. The correctness of the model is assessed by a volume error overlap of the predicted structure compared to the crystal structure. Finally, the structure of rat trypsin is predicted from the crystal structure of bovine trypsin. The sequences of these two proteins are 74% identical and all of the significant changes between them are on external residues. Thus, the inclusion of solvation energy in the conformational search is necessary to accurately predict the structure of the exchanged residues.
Conformational flexibility of a scorpion toxin active on mammals and insects: A circular dichroism study
Authors: Loret Erwann P. , Sampieri François , Roussel Alain , Granier Claude , Rochat Hervé
Published: May 2005

Three scorpion toxins have been analyzed by circular dichroism in water and in 2,2,2‐trifluoroethanol (TFE) solutions. These toxins were chosen because they are representative of three kinds of pharmacological activities: (1) toxin AaH IT2, an antiinsect toxin purified from the venom of Androctonus australis Hector, which is able to bind to insect nervous system preparation, (2) toxin Css II, from the venom of Centruroides suffusus suffusus, which is a β‐type antimammal toxin capable of binding to mammal nervous system preparation, and (3) the toxin Ts VII from the venom of Tityus serrulatus, which is able to bind to both types of nervous systems. In order to minimize bias, CD data were analyzed by a predictive algorithm to assess secondary structure content. Among the three molecules, Ts VII presented the most unordered secondary structure in water, but it gained in ordered forms when solubilized in TFE. These results indicated that the Ts VII backbone is the most flexible, which might result in a more pronounced tendency for this toxin molecule to undergo conformational changes. This is consistent with the fact that it competes with both antiinsect and β‐type antimammal toxins for the binding to the sodium channel.
Substrate‐enzyme interactions and catalytic mechanism in phospholipase C: A molecular modeling study using the GRID program
Authors: Byberg Jette R. , Jørgensen Flemming S. , Hansen Sissel , Hough Edward
Published: May 2005

Based on the high‐resolution X‐ray crystallographic structure of phospholipase C from Bacillus cereus, the orientation of the phosphatidylcholine substrate in the active site of the enzyme is proposed. The proposal is based on extensive calculations using the GRID program and molecular mechanics geometry relaxations. The substrate model has been constructed by successively placing phosphate, choline and diacylglycerol moieties in the positions indicated from GRID calculations. On the basis of the resulting orientation of a complete phosphatidylcholine molecule, we propose a mechanism for the hydrolysis of the substrate.
Molecular dynamics simulation of hydration in myoglobin
Authors: Gu Wei , Schoenborn Benno P.
Published: May 2005

This study was carried out to evaluate the stability of the 89 bound water molecules that were observed in the neutron diffraction study of CO myoglobin. The myoglobin structure derived from the neutron analysis was used as the starting point in the molecular dynamics simulation using the software package CHARMM. After solvation of the protein, energy minimization and equilibration of the system, 50 ps of Newtonian dynamics was performed. This data showed that only 4 water molecules are continously bound during the length of this simulation while the other solvent molecules exhibit considerable mobility and are breaking and reforming hydrogen bonds with the protein. At any instant during the simulation, 73 of the hydration sites observed in the neutron structure are occupied by water. © 1995 Wiley‐Liss, Inc.
Crystallization and preliminary diffraction studies of thioesterase II from rat mammary gland
Authors: Buchbinder Jenny L. , Witkowski Andrzej , Smith Stuart , Fletterick Robert J.
Published: May 2005

Thioesterase II from rat mammary gland has been crystallized in the presence of decanoic acid by the vapor diffusion method. The crystals belong to the orthorhombic space group P212121, and have cell dimensions, a = 52.7 Å, b = 78.0 Å, and c = 133.6 Å. The asymmetric unit likely consists of two protein monomers based on predictions from its calculated Matthews coefficient. Crystals typically diffract to at least 2.5 Å resolution and are suitable for X‐ray crystallographic analysis. © 1995 Wiley‐Liss, Inc.
The mass spectrum of mercury/cesium complex clusters (Hg)n Cs+ ranging up to m/z = 118 000
Authors: Sakurai T. , Ito H. , Matsuo T. , Katakuse I. , Costello C. E.
Published: May 2005

The mass spectrum of mercury/cesium complex clusters (Hg)nCs+ is observed up to m/z=118 000 (n = 590). Singly charged clusters are produced by Cs+ ion bombardment. The presence of an alkali metal in the ionization process yields cluster ions of the form (Hg)nX+. The clusters are analysed using the grand‐scale mass spectrometer, GEMMY, at Osaka University. The mass resolution of the instrument is high enough to resolve each cluster up to m/z=70 000. From the pattern of cluster distribution, the structrues of the large clusters can be studied. The number of Hg groups in metastable decay increases with the cluster size n. The ion intensities of the mercury/cesium clusters are much stronger than that from CsI (used for mass calibration). The mass spectrum of the clusters can therefore easily be utilized for direct mass calibration up to m/z=70 000.
Determination of the glycosidic linkage in peracetylated disaccharides comprised of d‐glucopyranose units by use ofr desorption electron‐ionization mass spectrometry
Authors: Peltier John M. , MacLean David B. , Szarek Walter A.
Published: May 2005

An oxonium ion at m/z 317 is present in the desorption electron ionization and ammonia desorption chemical ionization mass spectra of peracetylated disaccharides, comprised of glucopyranose units linked (1 → 2), (1 → 3), (1 → 4) and (1 → 6), but is absent in the spectra of the (1 → 1)‐linked isomer. The ion aat m/z 317, which is derived from the reducing moiety, has an O‐formyl group at the position of linkage to the non‐reducing moiety, and O‐acetyl groups at each of the remaining positions. The iosmeric monoformyl, triacetyl oxonium ions (at m/z 317), derived from the (1 → 2)‐, (1 → 3)‐, (1 → 4)‐ and (1 → 6)‐linked disaccharides, give distinctly different mass‐analysed ion kinetic energy spectra, thereby enabling the linkage position to be assigned unambiguously.
Simple physical models for coulomb‐induced frequency shifts and coulomb‐induced inhomogenous broadening for like and unlike ions in fourier transform ion cyclotron resonance mass spectrometry
Authors: Chen Shu‐Ping , Comisarow Melvin B.
Published: May 2005

Two simple models which Correspond more closely to physical reality than some prior models are proposed to account for the Coulomb‐induced frequency shifts to lower frequency, Which have been observed in Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry. The first model consists of two different‐mass point charges which undergo cyclotron orbits with the same orbit centers at their respective cyclotron frequencies. The model predicts that each excited cyclotron motion should induce a negative frequency shift in the other's cyclotron motion. The model predicts a zero frequency shift for ions of the same mass. The physical basis for the Coulomb‐induced shift is most easily seen in a coordinate frame which rotates at the cyclotron motion of the ion whose frequency is shifted. It is noted that a prior model for Coulomb‐induced frequency shifts is more appropriate for scanning ICR than FT‐ICR and the reason is described for the correctness of the predictions of this less appropriate model. A second model, the line model, is created by extension of the point model. The line model gives rise to a position‐dependent frequency shift which is synonymous with inhomogeneous Coulomb broadening. When a non‐quadrupolar electrostatic trapping field is included in the model, ‘like’ ions become ‘unlike’ and Coulomb‐shifting and Coulomb‐broadening apply, as for ‘like’ ions. The analysis predicts that ICR cells which are designed to have negligible trapping fields over most of their volume will be less sensitive to Coulomb shifting/broadening than ordinary ICR cells.
Electron‐pair ion coincidence (EPIC) techniques for spectrometry and state‐selective chemistry of doubly charged ions
Authors: Eland J. H. D. , Mathur D. , Brenton A. G.
Published: May 2005

Multiple‐coincidence techniques involving detection of two near‐threshold electrons in coincidence with each other and with product ions are proposed to measure spectra of doubly charged ions and the decay of their energy‐selected states. The new techniques are demonstrated by laboratory experiments on double photoionization of CO2 and SO2.
Isotopic evidence for the existence of the diatomic sulphur molecule with three positive charges
Authors: Morvay L. , Cornides I.
Published: May 2005

The existence of the diatomic S ion has been established by accurate mass measurements using normal and isotopically enriched sulphur.
Electron ionization mass spectra of the diterpenoid isomers atractyligenine, atractyliretine, 2‐ß‐hydroxy‐15‐oxo‐atractylan‐4‐carboxylic acid and of some related nor‐kaurane derivatives
Authors: Camarda Lorenzo , Ceraulo Leopoldo , Ferrugia Mirella , Sprio Vincenzo
Published: May 2005

The 75eV electron ionization mass spectra of eight nor‐kaurane compounds related to atractyligenine were investigated. The different fragmentation pathways and ion intensities from isomeric compounds are indicated.
Electron ionization mass spectra of some substituted stereoisomeric 1,6,7,11b‐tetrahydro‐2h,4H[1,3]oxazino[4,3‐a]‐isoquinolines and 1,6,7,11b‐tetrahydro‐2H[1,3]oxazino [4,3‐a]‐isoquinolin‐4‐ones1
Authors: Joutsiniemi Karoliina , Vainiotalo Pirjo , Lázár László , Fülöp Ferenc , Bernáth Gábor
Published: May 2005

The mass spectra often substituted oxazino[4,3‐a]isoquinolines, two isoquino[2,1‐c][1,3]benzoxazines and seven substituted oxazino[4,3‐a]isoquinolin‐4‐ones were recorded under electron impact ionization. Fragmentations were examined by metastable ion analysis, collision induced dissociation and exact mass measurement. The oxazinoisoquinolines and oxazinoisoquinolin‐4‐ones behaved similarly, although there were a few differences in the fragmentation and especially in the peak intensities. The most important fragmentation began with the opening of the oxazole ring. The substituents affected the fragmentation of the isomeric compounds, whereas the spectra of the stereoisomeric compounds were identical. The two isoquinobenzoxazines differed noticeably from the other compounds in their fragmentation behaviour; the additional phenyl ring prompted entirely new fragmentations unique to this structure.
Tryptic mapping of human chorionic gonadotropin by matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Laidler Paul , Hider Robert C. , Cowan David A. , Kicman Andrew T. , Keane Anita
Published: May 2005

The potential of matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI)(I‐TOF) mass spectrometry for use in the identification of human chorionic gonadotropin (hCG) seized by law enforcement agencies is investigated. Analysis of untreated hCG revealed signals corresponding to the molecular ions of the intact hCG heterodimer and both its non‐covalently linked subunits. Unfortunately, due to carbohydrate heterogeneity, the peaks are broad which makes accurate mass assignment, and consequently identification, difficult. Peptide mapping by MALDI‐TOF following‐tryptic digestion gave sequence coverage of 59% and 52% for the α and b̃‐subunits respectively. Nevertheless, the tryptic map was considered to provide unambiguous identification of hCG. This was confirmed by searching peptide‐mass databases with the experimentally determined masses. Our data suggest that peptide mapping by proteolytic digestion followed by MALDI‐TOF mass spectrometry is a suitable analytical technique for the identification of hCG seized by the legal authorities.
Ion exchange and purification of carbohydrates on a Nafion® membrane as a new sample pretreatment for matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Börnsen K. Olaf , Mohr Martin D. , Widmer H. Michael
Published: May 2005

A Nafion membrane was tested as a new tool for a fast and easy sample pretreatment for matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) measurements. This membrane material was used for ion exchange and carbohydrate purification with minimal quantities of sample solution. An ion exchange method for carbohydrates was developed and demonstrated on a Dextran sample. The cations of the original sample were replaced within minutes by potassium or cesium ions. Another feature of this membrane was the fact that proteins and peptides adsorb on the acid surface. This behavior was investigated as a purification step for carbohydrates with high peptide and protein impurity concentrations. It was found that oligosaccharide libraries from rat‐ and mouse IgG mass spectra can be obtained clearly in the presence of high peptide impurities.
Static SIMS for applied surface analysis
Authors: Brown A. , Vickerman J. C.
Published: May 2005

A review is presented of the use of static secondary ion mass spectrometry (SSIMS) and fast atom bombardment mass spectrometry (FABMS) in applied surface analysis. Some common criticisms of SIMS are discussed first, and then the experimental apparatus required is described briefly. Four main areas of application have been chosen: catalysts, polymers, glasses and metals, to illustrate the power of SSIMS/FABMS in characterising the chemical state of material surfaces. Finally the very new technique of SSIMS imaging has been described and some preliminary results presented, to indicate its potential in obtaining chemical state information at high spatial resolution.
Effects of elastic photoelectron collisions in quantitative XPS
Authors: Jablonski A. , Ebel H.
Published: May 2005

A fast Monte Carlo algorithm calculating the effects of elastic photoelectron collisions is presented. The algorithm is applicable to analyzer geometries with axial symmetry and with axis perpendicular to the surface (e.g. the CMA). The calculations were performed for four photoelectron lines: carbon 1s, aluminium 2s, cobalt 3p, and palladium 3d5/2. The following photoelectron characteristics were considered. (i) The angular distribution of photoelectrons leaving the surface. The distribution was found to follow the cosine distribution in practically all considered cases. Taking into account the elastic collisions did not change the shape of the distribution but decreased the photoelectron current leaving the surface, the difference increasing with atomic number of element. (ii) The distribution of emission depths of photoelectrons entering the analyzer. As a result of elastic collisions, more photoelectrons originate from the layer at the surface and less from the deeper layers. Thus, the actual depth of analysis is decreased. (iii) The total photoelectron current entering the analyzer. This current was also decreased by the elastic collisions. The difference reaches 1.6% for carbon 1s line, but increases to 16–19% for palladium 3d5/2 line. An elastic scattering correction in formalism of quantitative XPS is suggested. (iv) The average depth of analysis. This parameter was found to be most significantly affected by elastic scattering of photoelectrons. The depth of analysis was decreased by elastic collisions from 3–5% for carbon 1s line to 60–80% for palladium 3d5/2 line.
Effects of hydrogen on ISS analysis of dispersed metal catalysts
Authors: Diehl J. R. , Stencel J. M. , Spitler C. A. , Makovsky L. E.
Published: May 2005

The origin of inelastic scattering in ISS spectra at low energy ratios (E/E0 ≤ 0.3) is discussed, and a description of results from ISS and XPS experiments on well‐characterized Co/ZSM‐5 catalysts after calcination in air and reduction in H2, H2 + CO, or CO is given. These treatments show that the chemisorption of hydrogen on highly dispersed metallic Co and Fe causes shielding of the metal from ISS detection. Additionally, the presence of hydrogen, whether in a chemisorbed form or in other forms such as hydrocarbons or H2O, affects significantly the intensity of the inelastic scattering.
AES sputter profiling and angle resolved XPS of in situ grown very thin Tantalum‐oxide films
Authors: Mathieu H. J. , Landolt D.
Published: May 2005

Angle resolved Auger electron spectroscopy (AES) and x‐ray photo‐electron spectroscopy (XPS) are compared to AES sputter depth profiling of ultra thin (<2 nm) Ta2O5 films to study their relative ability to determine thickness. Films were grown in situ by oxygen exposure after sputter claning the Tantalum‐metal surface. This way films between 2 L and 1800 L (1 L = 10−6 Torr s) were obtained. Results show that for such thin films the 50% oxygen amplitude criterion used to determine thickness cannot be applied anymore, because no steady state is reached in the film. On the other hand, angle resolved AES and XPS measurements show systematically higher values than data obtained by sputtering. However, since the former are critically dependent on the precision of the electron mean free path, λ, reasonable agreement can be obtained if one assumes an intermediate λ value between bulk oxide and metal; this can be justified by the presence of suboxides.