Spatial distribution of the gain and temperature across the flow in a slit-nozzle supersonic chemical oxygen-iodine laser with transonic and supersonic schemes of iodine injection

Spatial distributions of the gain and temperature across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit-nozzle supersonic chemical oxygen-iodine laser as a function of the iodine and secondary nitrogen flow rate, jet penetration parameter, and gas pumping rate. The mixing efficiency for supersonic injection of iodine (/spl sim/0.85) is much larger than for transonic injection (/spl sim/0.5), the maximum values of the gain being /spl sim/0.65%/cm for both injection schemes. Measurements of the gain distribution as a function of the iodine molar flow rate nI/sub 2/ were carried out. For transonic injection, the optimal value of nI/sub 2/ at the now centerline is smaller than that at off axis locations. The temperature is distributed homogeneously across the flow, increasing only in the narrow boundary layers near the walls. Opening a leak downstream of the cavity in order to decrease the Mach number results in a much larger mixing efficiency (/spl sim/0.8) than for a closed leak.     

Filtering of quaternion signals

Filtering of quaternion signals that specify group point objects and images in the form of polyhedrons in a 3D space is considered. It is shown that the main difference between a quaternion filter and filters for real and complex-valued signals is that, in a quaternion filter, each mth harmonic of the input signal is split into two harmonics: the reference harmonic with frequency m and the image harmonic with the frequency s-m. This behavior of the filter results from the noncommutativity of the multiplication operation for quaternions, a circumstance that necessitates the calculation of two scalar products with nonzero values at frequencies m and s-m, respectively, rather than one scalar product.     

The role of nitrites in carcinogenesis

Data from literature as well as the results of the author's investigations on the genotoxic and carcinogenic effects of sodium nitrite (SN) are presented. Carcinogenicity of SN detected in animal experiments proved to be connected with the formation of nitroso compounds from endogenous nitrosable precursors. Sodium nitrite possessed the transforming and promoting effects in the cell cultures as well as the mutagenic effects in the bacterial systems where predominant effect of SN as compared with N-nitrosodimethylamine (NDMA) was registered. The prolonged pretreatment with SN amplified the liver DNA damage in rats in case of NDMA endogenous synthesis.     

Twenty-month outcome in ventilator-dependent, very low birth weight infants born during the early years of dexamethasone therapy

We sought to examine the effect of the introduction of dexamethasone therapy on health, growth, and neurodevelopmental outcome in very low birth weight (VLBW) infants at 20 months of age. We compared outcomes in all 86 VLBW infants (mean birth weight 871 gm, mean gestational age 26.4 weeks) who were ventilator dependent on day 21 of life during the 2 years preceding October 1988 (period 1), when dexamethasone therapy became accepted clinical practice in our unit, with outcomes in all 124 infants (mean birth weight 891 gm, mean gestational age 26.9 weeks) with similar ventilator status during the subsequent 2 years (period 2). In addition, we compared outcomes in infants who received dexamethasone during period 2 with those in a concurrent cohort of less ill infants who were not given dexamethasone. There were no significant differences between periods 1 and 2 in mortality rates after 21 days (17% vs 21%), need for home oxygen (23% vs 25%), oxygen dependence at 20 months of corrected age (11% vs 10%), rate of neurosensory impairment (24% vs 25%), and mean Bayley Mental scores (81.5 vs 77.2) or Psychomotor Development Index (81.6 vs 71.1). Infants who received dexamethasone during period 2 had significantly more severe lung disease and poorer respiratory, growth, and developmental outcomes. We conclude that VLBW infants with ventilator-dependent chronic lung disease have very poor outcomes, even when treated with dexamethasone. More information is needed from prospective, randomized trials before dexamethasone can be accepted as routine therapy for chronic lung disease.     

Nuclear polarization and entanglement in spin systems

We investigated relationships between entanglement measures and the order parameter (nuclear polarization) in nuclear spin systems controlled by the nuclear magnetic resonance (NMR) technique. Since spin polarization can be easily manipulated by the NMR technique, experimentalists are presented with an opportunity to study the dynamic properties of entanglement, i.e., the creation and evolution of entangled states. Our approach may constitute the basis for researching the relations between the entanglement measures and measurable parameters of order in other quantum systems. An erratum to this article can be found at     

Polyethylene-co-methacrylic acid healing agents for mendable epoxy resins

A new thermoplastic healing agent and associated healing agent delivery mechanism have been investigated. Polyethylene-co-methacrylic acid (EMAA) particles were mixed into an epoxy resin, resulting in an increase in the fracture strength of the resin. Damaged single edge notched bars and tapered double cantilever beams were healed at 150 °C for 30 min to achieve up to an 85% recovery in critical stress intensity and over 100% recovery in sustainable peak load. Optical and scanning electron microscopy revealed that strength recovery in the damaged resin was achieved via EMAA particle healing as well as the formation of an adhesive EMAA layer between adjacent epoxy fracture surfaces. Microscopy also showed that small bubbles in the EMAA particles act as a new healing agent delivery mechanism wherein expansion during heating forced larger volumes of healing agent into the damaged region of the resin.     

Inhibition of a ventricular synchronous pacemaker

Noncompetitive ventricular synchronous pacemakers (VVT) have been available since 1965. Most presently available and earlier models have a single, fixed pulse-to-pulse interval divided into a total refractory period of 350 to 400 msec., followed by a sensitive period. During the refractory period the pacemaker will not respond to QSR complexes or electrical signals, but a pacer stimulus will be produced during the sensitive period. The generator cannot be inhibited under any circumstances. The Cordis Omni-Sctocor has a refractory period and two sensitive periods, during one of which the generator is inhibited. Unlike other ventricular synchronous pacers, the Omni-Ectocor is capable of inhibition by single or multiple ventricular or other signals, of slowing or increase of the stimulus formation rate which depends on the timing of the premature ventricular contractions, and of inhibition by a run of ventricular tachycardia or by electromagnetic interference. The rate of interference producing these effects is a function of the automatic rate to which the generator is programmed. All of these factors must be considered for proper interpretation of the ECG.     

Photocatalytic reaction intensification using monolithic supports designed by stereolithography

An original photocatalytic reactor for the treatment of polluted air is designed. The titanium dioxide is supported on various supports that consist in photopolymers and are built using the stereolithography technique and placed in a glass tube illuminated from the outside, while the air containing the pollutant to be removed flows through the glass tube and the photocatalyst support. It is shown that the gas–solid mass transfer plays a role only at the very smallest gas velocities investigated. The global depollution kinetics are then determined for the different geometrical forms of the photocatalyst support and the efficiency of the forms compared.