Aging of HTPB/Al/AP Rocket Propellant Formulations Investigated by DMA Measurements

Three HTPB‐based rocket propellant formulations containing ammonium perchlorate and aluminum particles, with different aluminum content and particle size, have been manufactured. The study has focused on the change of mechanical properties with aging time by using dynamic mechanical analysis (DMA). Therefore, propellant formulations underwent an accelerated aging program, in air (RH<10 %), between 60 °C and 90 °C with aging time adjusted to a thermal equivalent load of 15 to 20 years at 25 °C. DMA investigations revealed distinct changes in the shape of the loss factor curve. These curves were modeled with three exponentially modified Gaussian (EMG) functions in order to get the molecular interpretation of the involved aging phenomena by separating the binder fractions with different mobility. Aging of propellant formulations can be followed by considering only two parameters: the areas of the second and third loss factor transition peaks (A₂, A₃), and the corresponding maximum temperature values of the assigned Gauss peaks (Tc₂, Tc₃).     

Sulfur–Iodine plant for large scale hydrogen production by nuclear power

The Sulfur–Iodine (S_I) cycle, driven by nuclear power, seems to be one of the main candidates to produce hydrogen on a large scale. A new S_I process flowsheet is proposed, set up at CEA and simulated by ProSim code and, based on that, data and results on the coupling of the thermochemical plant with a Very High Temperature Nuclear Reactor (VHTR) are presented. The scale up to industrial level, the conceptual design and cost estimation of the plant are then presented and discussed. In order to support a high temperature aggressive environment, well established chemical engineering methods as well as non traditional materials, devices and technologies have been selected. The influence of the adopted technology on the H₂ cost has also been investigated and is widely discussed, comparing two different cases. An economic sensitivity analysis carried out by varying the hydrogen production level is presented, showing that an optimum H₂ production exists and, due to relevant heat recovery processes, the minimum cost is not achieved for the maximum allowable H₂ production rate. Finally an optimized layout for the minimum cost plant, set up adopting the pinch technique, is presented leading to a further reduction of H₂ production costs.     

Measurement of magnetic fields radiated from ESD using fieldsensors

The goal of this paper is to show that commercial sensors, whose frequency response is not specifically designed, can be effectively used to measure very fast transient fields applying a proper reconstructing procedure based on the knowledge of the sensor transfer function. To do this, it is necessary to characterize a structure supporting a transverse electromagnetic (TEM) field, that will be used to set up a calibration procedure for elementary magnetic field sensors. The approach is completely analytical and allows us to know rigorously the field inside the structure. From the knowledge of this field, the transfer function of the sensor, in amplitude and phase, is evaluated up to 2 GHz. The complete characterization of the sensor allows us to reconstruct the sensed field from its output voltage waveform. The calibration procedure is carried out in time domain and therefore the fast Fourier transform (FFT) algorithm is used to achieve the sensor transfer function, as well as an inverse FFT (IFFT) is necessary to retrieve the transient impinging field. An experimental validation of the procedure shows the consistency of the approach     

Capillary electrophoresis, nuclear magnetic resonance and mass spectrometry studies of opposite chiral recognition of chlorpheniramine enantiomers with various cyclodextrins

Markedly different chiral separation abilities were observed for native beta-cyclodextrin (beta-CD), carboxymethyl-beta-CD (CM-beta-CD) and heptakis (2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD) towards the enantiomers of (+/-)-chlorpheniramine ((+/-)-CHL) in capillary electrophoresis (CE). Native beta-CD afforded almost baseline enantioseparation at a concentration of 18 mg/mL, whereas only 1 mg/mL solution of CM-beta-CD was required for adequate enantioseparation. TM-beta-CD allowed the nearly baseline enantioseparation only at a concentration as high as 80 mg/mL. Moreover, the migration order of (+/-)-CHL in the presence of TM-beta-CD was opposite to that with beta-CD and CM-beta-CD. 1H and 13C-NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) have been used in order to obtain preliminary information about the stoichiometry and the binding constants in the intermolecular diastereomeric complexes of (+/-)-CHL with these CDs.     

Impact of inherited polymorphisms in glutathione S-transferase M1, microsomal epoxide hydrolase, cytochrome P450 enzymes on DNA, and blood protein adducts of benzo(a)pyrene-diolepoxide

The benzo(a)pyrene (BaP) metabolite benzo(a)pyrenediolepoxide (BPDE) is strongly implicated as a causative agent of lung cancer. To assess the risk of exposure to BaP, we made a combined analysis of levels of BPDE adducts to hemoglobin (Hb), serum albumin (SA), and lymphocyte DNA in 44 patients with incident lung cancer, as a prototype of a population mainly exposed to tobacco-derived BaP. We also investigated whether genetic polymorphisms of cytochrome P450IA1 (CYPIA1), microsomal epoxide hydrolase (mEH), and glutathione S-transferase M1 (GSTM1), which are involved in BaP metabolism, can be determinants of adduct formation. BPDE-Hb, BPDE-SA, and BPDE-DNA adducts were quantified as BaP tetrols released from hydrolysis of macromolecules and measured by high-resolution gas chromatography-negative ion chemical ionization-mass spectrometry to achieve high specificity and sensitivity. Individuals with detectable Hb adducts were positive for SA adducts but not vice versa, suggesting that BPDE-Hb adducts are less informative indicators of BaP exposure. Using PCR methods on DNA, we characterized GSTM1 deletion, CYPIA1 MspI and exon 7 valine variants, and mEH polymorphisms at amino acid positions 113 (EH3) and 139 (EH4). Levels of BPDE adducts were no different among CYPIA1, mEH, and GSTM1 genotypes. However, individuals with measurable BPDE-SA adducts were CYPIA1 variant carriers more frequently (P = 0.03). There was a slightly higher percentage of DNA detectable adducts in subjects with CYPIA1 exon 7 valine polymorphism. When subjects were classified by both polymorphisms on the mEH gene, those with two slow alleles (EH3 homozygous mutated) and no fast alleles (EH4 homozygous wild type) had a lower frequency of BPDE-SA adducts and no DNA adducts (P = 0.06). These results are based on a small number of observations thus far, but this exploratory study suggests that CYPIA1 and mEH variants might have an impact on BPDE exposure markers such as BPDE-SA adducts. Chemical specificity in adduct measurements is important to identify the biomarkers that reflect BaP exposure more accurately.     

COPD,Pulmonary Fibrosis and ILAs in Aging Smokers: The Paradox of Striking Different Responses to the Major Risk Factors

Aging and smoking are associated with the progressive development of three main pulmonary diseases: chronic obstructive pulmonary disease (COPD), interstitial lung abnormalities (ILAs), and idiopathic pulmonary fibrosis (IPF). All three manifest mainly after the age of 60 years, but with different natural histories and prevalence: COPD prevalence increases with age to >40%, ILA prevalence is 8%, and IPF, a rare disease, is 0.0005–0.002%. While COPD and ILAs may be associated with gradual progression and mortality, the natural history of IPF remains obscure, with a worse prognosis and life expectancy of 2–5 years from diagnosis. Acute exacerbations are significant events in both COPD and IPF, with a much worse prognosis in IPF. This perspective discusses the paradox of the striking pathological and pathophysiologic responses on the background of the same main risk factors, aging and smoking, suggesting two distinct pathophysiologic processes for COPD and ILAs on one side and IPF on the other side. Pathologically, COPD is characterized by small airways fibrosis and remodeling, with the destruction of the lung parenchyma. By contrast, IPF almost exclusively affects the lung parenchyma and interstitium. ILAs are a heterogenous group of diseases, a minority of which present with the alveolar and interstitial abnormalities of interstitial lung disease.     

A rigorous model for radiated emission prediction in PCB circuits

The problem of the radiated emission from printed circuit boards, (PCBs) is theoretically and experimentally investigated. Differential mode and common mode currents are separately studied by means of a rigorous method based on proper Green's functions. The solution of the integral equations for the current distribution, derived from the problem formulation, is numerically achieved by the method of moments. Simulated results are in good agreement with measurements. The final products of this study are masks that establish the maximum allowable currents or voltage values as a function of frequency to comply with CISPR regulation     

Effect of heat treatments on mechanical properties and fracture behavior of a thixocast A356 aluminum alloy

The effect of different heat treatments (T5 and T6) on mechanical properties, fracture behavior and damage evolution of A356 Thixocast aluminum alloy have been examined in detail in the present work. Tensile tests of the material have been performed in the as cast and as treated conditions in order to observe the different fracture behavior in consequence of the heat treatments. Optical and scanning electron microscopy techniques have been used to characterize the microstructure and fracture surfaces of the specimens. Finally, the precipitation processes of the material have been analyzed by hardness and electrical conductivity measurements and EDS analysis has been used to characterize the different phases in the as-thixo and as-treated conditions.