Condensed phase reactions in solid propellants

The paper investigates the cause for the difference between differential scanning calorimetric results and mass spectrometric studies on polystyrene (PS) ammonium perchlorate (AP) propellants as related to the method of preparation of the propellant and the difference in experimental conditions by the use of mass spectrometry. Sufficient time is given for the product sublimates to interact with each other and attain equilibrium. It is shown that the propellant decomposition is a nonadditive phenomenon and that even a physical mixture of AP and PS does not yield additive decomposition products of its components. Results on the identification of a yellow compound containing chlorine in the bulk of the propellant suggest a condensed phase reaction. The occurrence of the reaction in the porous condensed phase of the propellant may explain the larger exothermicity of the propellant compared to the additive heats of decomposition of its components.

ESR study of copper diethyldithiophosphate

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from 63Cu, 65Cu, and 31P nuclei. At much higher gain, hyperfine interaction from 33S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g = 2.085, g =2.025, A63Cu = 149.6 × 10−4 cm−1, A65Cu = 160.8 × 10−4 cm−1, BCu = 32.5 × 10−4 cm−1 and QCu 5.5 × 10−4cm−1. The 31P interaction is isotropic with a coupling constant AP = 9.6 × 10−4 cm−1. Angular variation of the 33S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu S bonds. The experimentally determined hyperfine constants are A =34.9×10−4 cm−1, B =26.1×10−4 cm−1, A =60.4×10−4 cm−1, B =55.5×10−4 cm−1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the bond, the bonds are also strongly covalent. ©1973 The American Institute of Physics

A simple non-linear D/A converter

A simple generalized technique for realizing a non-linear digital to analogue converter (N-DAC), based on the principles of ' segment of equal digital interval ' is described. The simplicity of the proposed technique is demonstrated by realizing an N-DAC having a square law transfer function.

Ternary function and circuit design using ternary multiplexers

The recent trend towards minimizing the interconnections in large scale integration (LSI) circuits has led to intensive investigation in the development of ternary circuits and the improvement of their design. The ternary multiplexer is a convenient and useful logic module which can be used as a basic building block in the design of a ternary system. This paper discusses a systematic procedure for the simplification and realization of ternary functions using ternary multiplexers as building blocks. Both single level and multilevel multiplexing techniques are considered. The importance of the design procedure is highlighted by considering two specific applications, namely, the development of ternary adder/subtractor and TCD to ternary converter.

Analyticity of the charge-monopole scattering amplitude

We study the analyticity in cosθ of the exact quantum-mechanical electric-charge-magnetic-monopole scattering amplitude by ascribing meaning to its formally divergent partial-wave expansion as the boundary value of an analytic function. This permits us to find an integral representation for the amplitude which displays its analytic structure. On the physical sheet we find only a branch-point singularity in the forward direction, while on each of the infinitely many unphysical sheets we find a logarithmic branch-point singularity in the backward direction as well as the same forward structure.

Storage stability of solid rocket fuel. 1. Effect of temperature

Ageing behaviour of polystyrene (PS)/ammonium perchlorate (AP) propellent leading to ballistic changes has been studied. It follows a zero-order kinetic law. Ageing behaviour leading to change in burning rate ( ) in the temperature range of 60–200 ° C was found to remain the same. The dependence of the change of the average thermal decomposition (TD) rate at 230 and 260°C on the change in burning rate for the propellant aged at 100 ° C in air suggests that the slow TD of the propellant is the cause of ageing. The safe-life (for a pre-assigned burning-rate change limit) at 25 ° C in air has been calculated as a function of the rate of change.

Effect of pretreatment on the sublimation of ammonium perchlorate

The effects of pretreatments on the sublimation of pure ammonium perchlorate (AP) were studied by differential thermal analysis. The addition of inorganic salts (doping), or preheating, lead to desensitisation of the sublimation process, whereas it was sensitised by precompression. Sublimation increased with decrease in the particle size of the AP from 500 to 200 microns, but decreased with a further decrease in size from 200 to 100 microns. The results are interpreted in terms of gross imperfections and strain in the AP crystals.

ESR study of copper diethyldithiophosphate

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from 63Cu, 65Cu, and 31P nuclei. At much higher gain, hyperfine interaction from 33S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g|| = 2.085, g[perpendicular]=2.025, A63Cu = 149.6 × 10−4 cm−1, A65Cu = 160.8 × 10−4 cm−1, BCu = 32.5 × 10−4 cm−1 and QCu [infinity] 5.5 × 10−4cm−1. The 31P interaction is isotropic with a coupling constant AP = 9.6 × 10−4 cm−1. Angular variation of the 33S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu[Single Bond]S bonds. The experimentally determined hyperfine constants are A ₁^s=34.9×10−4 cm−1, B ₁^s=26.1×10−4 cm−1, A ₂^s=60.4×10−4 cm−1, B₂^s=55.5×10−4 cm−1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the sigma bond, the pi bonds are also strongly covalent. ©1973 The American Institute of Physics.

The role of lithium and magnesium perchlorate ammines in ammonium perchlorate decomposition

The preparation and thermal decomposition of lithium and magnesium perchlorate ammines have been investigated. The catalytic effect of these ammines on AP decomposition has been studied. The catalytic effect of lithium and magnesium salts on AP decomposition has been attributed to the formation of the metal perchlorate ammine intermediate. In the case of a magnesium salt: AP mixture, the melting of the magnesium perchlorate monoammine intermediate seems to play an important role in catalysing the decomposition.

Calculations of the free energy of interaction of the c-Fos−c-Jun coiled coil: Effects of the solvation model and the inclusion of polarization effects

The leucine zipper region of activator protein-1 (AP-1) comprises the c-Jun and c-Fos proteins and constitutes a well-known coiled coil protein−protein interaction motif. We have used molecular dynamics (MD) simulations in conjunction with the molecular mechanics/Poisson−Boltzmann generalized-Born surface area [MM/PB(GB)SA] methods to predict the free energy of interaction of these proteins. In particular, the influence of the choice of solvation model, protein force field, and water potential on the stability and dynamic properties of the c-Fos−c-Jun complex were investigated. Use of the AMBER polarizable force field ff02 in combination with the polarizable POL3 water potential was found to result in increased stability of the c-Fos−c-Jun complex. MM/PB(GB)SA calculations revealed that MD simulations using the POL3 water potential give the lowest predicted free energies of interaction compared to other nonpolarizable water potentials. In addition, the calculated absolute free energy of binding was predicted to be closest to the experimental value using the MM/GBSA method with independent MD simulation trajectories using the POL3 water potential and the polarizable ff02 force field, while all other binding affinities were overestimated.

Thermal Decomposition and Combustion Studies on Potassium Perchlorat e/Polystyrene Propellant Systems

STUDIES on potassium perchlorate/polystyrene (KP/PS) propellant systems have been carried out by using such techniques as thermogravimetry (TG), differential thermal analysis (DTA), and mass spectrometry (MS). It has been found that the thermal decomposition (TD) behavior of the KP/PS propellant is similar to that of the AP/PS propellant studied earlier.! It has also been observed that the TD of KP in the melt has a correlation with the burning rate (r) of KP/PS propellant at atmospheric pressure.

Qed On The Groenewold-Moyal Plane

We investigate a version of noncommutative QED where the interaction term, although natural, breaks the spin-statistics connection. We calculate e(-) + e(-) -> e(-) + e(-) and gamma + e(-) -> gamma + e(-) cross-sections in the tree approximation and explicitly display their dependence on theta(mu nu). Remarkably the zero of the elastic e(-) + e(-) -> e(-) + e(-) cross-section at 90 degrees in the center-of-mass system, which is due to Pauli principle, is shifted away as a function of theta(mu nu) and energy.

Modeling finite buffer effects on TCP traffic over an IEEE 802.11 infrastructure WLAN

The network scenario is that of an infrastructure IEEE 802.11 WLAN with a single AP with which several stations (STAs) are associated. The AP has a finite size buffer for storing packets. In this scenario, we consider TCP-controlled upload and download file transfers between the STAs and a server on the wireline LAN (e.g., 100 Mbps Ethernet) to which the AP is connected. In such a situation, it is well known that because of packet losses due to finite buffers at the AP, upload file transfers obtain larger throughputs than download transfers. We provide an analytical model for estimating the upload and download throughputs as a function of the buffer size at the AP. We provide models for the undelayed and delayed ACK cases for a TCP that performs loss recovery only by timeout, and also for TCP Reno. The models are validated incomparison with NS2 simulations.

From neural stem cells to precursors : Molecular regulation of self-renewal and differentiation

Stem cells are responsible for tissue turnover throughout lifespan. Only highly controlled specific environment, the stem cell niche , can sustain undifferentiated stem cell-pool. The balance between maintenance and differentiation is crucial for individual s health: uncontrolled stem cell self-renewal or proliferation can lead to hyperplasia and mutations that further provoke malignant transformation of the cells. On the other hand, uninhibited differentiation may result in diminished stem cell population, which is unable to maintain tissue turnover. The mechanisms that control the switch from maintenance to differentiation in stem cells are not well known. The same mechanisms that direct the self-renewal and proliferation in normal stem cells are likely to be also involved in maintenance of cancer stem cell . Cancer stem cells exhibit stem cell like properties such as self-renewal- and differentiation capacity and they can also regenerate the tumor tissue. In this thesis, I have investigated the effect of classical oncogenes E6/E7 and c-Myc, tumor suppressors p53 and retinoblastoma (pRb) family, and vascular endothelial growth factor (VEGF) subfamily and glial cell line-derived neurothropic factor (GDNF) family ligands on behavior of embryonic neural stem cells (NSCs) and progenitors. The study includes also the characterization of cytoskeletal tumor suppressor neurofibromatosis 2 (NF2) protein merlin and ezrin-radixin-moesin (ERM) protein ezrin expression in neural progenitors cells and their progeny. This study reveals some potential mechanisms regarding to NSCs maintenance. In summary, the studied molecules are able to shift the balance either towards stem cell maintenance or differentiation; tumor suppressor p53 represses whereas E6/E7 oncogenes and c-Myc increase the proportion of self-renewing and proliferating NSCs or progenitors. The data suggests that active MEK-ERK signaling is critical for self-renewal of normal and oncogene expressing NSCs. In addition, the results indicate that expression of cytoskeletal tumor suppressor merlin and ERM protein ezrin in central nervous system (CNS) tissue and progenitors indicates their role in cell differentiation. Furthermore, the data suggests that VEGF-C a factor involved in lymphatic system development, angiogenesis, neovascularization and metastasis but also in maintenance of some neural populations in brain is a novel thropic factor for progenitors in early sympathetic nervous system (SNS). It seems that VEGF-C dose dependently through ERK-pathway supports the proliferation and survival of early sympathetic progenitor cells, and the effect is comparable to that of GDNF family ligands.

What the problem may be with family intervention . . . and with dissemination more generally: A commentary

While the two decades since the study by Kavanagh et al. (1993) has given additional insights into effective dissemination of family interventions, the accompanying papers show that progress remains limited. The effectiveness trial that triggered this series of papers offers a cautionary tale. Despite management support, 30–35 hr of workshop training and training of local supervisors who could act as champions, use of the full intervention was limited. In part, this seemed due to the demanding nature of the intervention and its incompatibility with practitioners’ roles, in part, to limitations in the training, among other factors. While the accompanying papers note these and other barriers to dissemination, they miss a more disturbing finding in the original paper: Practitioners said they were using several aspects in routine care, despite being unable to accurately describe what they were. This finding highlights the risks in taking practitioners’ reports of their practice in files or supervision sessions at face value and potentially has implications for reports of other clinical work. The fidelity of disseminated treatments can only be assured by audits of practice, accompanied by affirming but also corrective feedback.