Molded composite pyrogen igniter for rocket motors

A lightweight pyrogen igniter assembly including an elongated molded plastic tube adapted to contain a pyrogen charge was designed for insertion into a rocket motor casing for ignition of the rocket motor charge. A molded plastic closure cap provided for the elongated tube includes an ignition charge for igniting the pyrogen charge and an electrically actuated ignition squib for igniting the ignition charge. The ignition charge is contained within a portion of the closure cap, and it is retained therein by a noncorrosive ignition pellet retainer or screen which is adapted to rest on a shoulder of the elongated tube when the closure cap and tube are assembled together. A circumferentially disposed metal ring is provided along the external circumference of the closure cap and is molded or captured within the plastic cap in the molding process to provide, along with O-ring seals, a leakproof rotary joint

From arteries to boreholes: Steady-state response of a poroelastic cylinder to fluid injection

The radially outward flow of fluid into a porous medium occurs in many practical problems, from transport across vascular walls to the pressurisation of boreholes. As the driving pressure becomes non-negligible relative to the stiffness of the solid structure, the poromechanical coupling between the fluid and the solid has an increasingly strong impact on the flow. For very large pressures or very soft materials, as is the case for hydraulic fracturing and arterial flows, this coupling can lead to large deformations and, hence, to strong deviations from a classical, linear-poroelastic response. Here, we study this problem by analysing the steady-state response of a poroelastic cylinder to fluid injection. We consider the qualitative and quantitative impacts of kinematic and constitutive nonlinearity, highlighting the strong impact of deformation-dependent permeability. We show that the wall thickness (thick vs. thin) and the outer boundary condition (free vs. constrained) play a central role in controlling the mechanics

Dynamics of multi-kinks in the presence of wells and barriers

Sine-Gordon kinks are a much studied integrable system that possesses multi-soliton solutions. Recent studies on sine-Gordon kinks with space-dependent square-well-type potentials have revealed interesting dynamics of a single kink interacting with wells and barriers. In this paper, we study a class of smooth space-dependent potentials and discuss the dynamics of one kink in the presence of different wells. We also present values for the critical velocity for different types of barriers. Furthermore, we study two kinks interacting with various wells and describe interesting trajectories such as double-trapping, kink knock-out and double-escape.Comment: 17 pages, 7 figure

What are the indications for treatment with angiotensin-converting enzyme (ACE) inhibitors in patients with diabetes?

Tight control of hypertension treatment is key in preventing the vascular complications of diabetes. ACE inhibitors appear to have a protective effect that is independent of their antihypertensive effect. Unless there is a contraindication, all patients with diabetes who have hypertension should be treated with ACE inhibitors. Patients with diabetes who have microalbuminuria should be treated with ACE inhibitors, even if normotensive, as should those with overt nephropathy. (Grade of recommendation: A, based on randomized controlled trials.

Experimental and Computational Studies of Environmentally Persistent Free Radicals (EPFRs) Formation

The first part of the thesis investigates the use of theoretical quantum calculations for the study of EPFRs as the initial and fundamental step in the formation of polychlorinated dibenzo-p-dioxin and dibenzofuran. The computational model comprised of density functionals (B3LYP, PBE1PBE, and M06) and two types of basis set namely: LANL2DZ for all atoms and GEN (LANL2DZ for metals and aug-cc-pVDZ for non-metals). Full mechanisms of EPFRs formation over (CuO)1-8, and aluminum oxide clusters were studied. The most stable intermediates and products have been determined and compared to available experimental data. In case of (CuO)1-8 clusters, the small clusters are more exoergic and thus more reactive than larger clusters. However, Al4O6 cluster is more exoergic than Al2O3 cluster. Bader charge analysis was used to examine the degree of electron transfer from phenolic species to metal cluster. A low degree of electron transfer was observed for small clusters (CuO - Cu5O5). There was essentially no electron transfer for the large clusters studied (Cu6O6 - Cu8O8), and this suggests that the catalytic sites are likely to be small “islands of metal oxide clusters. These studies serve to refine proposed mechanisms for EPFRs formation in Prof. Dellinger laboratory. In the second part of the thesis, the dependency of EPFRs yield and their persistency on different CuO content on silica is reported. The EPFRs were generated through exposure of particles to adsorbate vapors of phenol, 2-chlorophenol, and 1,2-dichlorobenzene at 230 0C using a custom-made vacuum chamber. Adsorption resulted in the formation of surface-bound phenoxyl- and semiquinoine–type radicals with characteristic EPR spectra displaying a g-value ranging from ~2.0037 - 2.006. The highest EPFRs yield was observed for CuO concentrations between 1-3% in relation for 2-chlorophenol and phenol adsorption. The two longest lifetimes, 25 h and 23 h, were observed for phenoxyl-type radicals on 0.5% CuO and chlorophenoxyl-type radicals on 0.75% CuO, respectively. The EPFR-containing particle generated twice as much DMPO-OH compared to non-EPFR containing radical. On average, the ratio of OH radical concentration to the number of EPFRs was estimated to be 10:1 signaling a cyclic process

Mothers’ knowledge on essential newborn care at Juba Teaching Hospital, South Sudan

Introduction: Globally neonatal mortality remains high and in South Sudan is estimated at 52/1000 live births.Objective: To identify the gaps in the knowledge and practices of essential newborn care among postnatal mothers at Juba Teaching Hospital and to determine the socio-demographic factors that influenced these.Methodology: A hospital-based cross-sectional study among 384 postnatal mothers using consecutive sampling, a pretested questionnaire to assess knowledge and a three point Likert scale to find out to which practices mothers did, or did not, agree.Results: 45% of mothers were aged between 25-34 years; 23.9% had some secondary school education; 70% were multiparous and 82% had attended an antenatal care clinic. 90% knew about breastfeeding on demand and 74% about exclusive breastfeeding. Only 18.2% of mothers knew the cord should be cared for while uncovered; 90% used warm clothing and 33% kangaroo care for thermoregulation. Only 20.8% identified BCG and OPV as birth vaccines; 3.4% believed vaccines were harmful. Hypothermia was the danger sign least frequently identified by the mothers (41.4%).Conclusion: Adequate knowledge was found regarding breastfeeding with knowledge gaps existing in cord care, immunization, eye care and thermoregulation. Positive practice was found concerning breastfeeding, cord care, eye care and immunization. Socio-demographic factors were not found to be associated with maternal knowledge on newborn care.Key Words: Essential newborn care, Immunization, South Suda

Garnet–monazite rare earth element relationships in sub-solidus metapelites: a case study from Bhutan

A key aim of modern metamorphic geochronology is to constrain precise and accurate rates and timescales of tectonic processes. One promising approach in amphibolite and granulite-facies rocks links the geochronological information recorded in zoned accessory phases such as monazite to the pressure–temperature information recorded in zoned major rock-forming minerals such as garnet. Both phases incorporate rare earth elements (REE) as they crystallize and their equilibrium partitioning behaviour potentially provides a useful way of linking time to temperature. We report REE data from sub-solidus amphibolite-facies metapelites from Bhutan, where overlapping ages, inclusion relationships and Gd/Lu ratios suggest that garnet and monazite co-crystallized. The garnet–monazite REE relationships in these samples show a steeper pattern across the heavy (H)REE than previously reported. The difference between our dataset and the previously reported data may be due to a temperature-dependence on the partition coefficients, disequilibrium in either dataset, differences in monazite chemistry or the presence or absence of a third phase that competed for the available REE during growth. We urge caution against using empirically-derived partition coefficients from natural samples as evidence for, or against, equilibrium of REE-bearing phases until monazite–garnet partitioning behaviour is better constrained