Improved mechanical properties of poly(ethylene terephthalate) nanocomposite fibers

Improvements in Young's modulus and strength (tenacity) of poly(ethylene terephthalate) (PET) fibers were obtained by drawing unoriented nanocomposite filaments containing low concentrations (<3 wt%) of various organically modified montmorillonites (MMTs) in a second step at temperatures above the glass transition. Prior to melt spinning, solid‐state polymerization was used to rebuild lost molecular weight, due to MMT‐induced degradation, to a level suitable for producing high strength fibers. Greater improvements in mechanical properties occurred when the MMT stacks were intercalated with PET. A nominal 1 wt% loading of dimethyl‐dehydrogenated tallow quaternary ammonium surface modified MMT in drawn PET fiber showed a 28% and 63% increase in Young's modulus and strength, respectively. Relative to an unfilled PET fiber, these results surpassed the upper bound of the rule of mixtures estimate and suggested that both the type of surface modification and concentration of MMT affect the degree of PET orientation and crystallinity. Furthermore, drawability above T_g and elongation at break increased upon the addition of organically modified MMT to unoriented PET fibers, which was a key distinction of this work from others examining similar systems. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Axial mixing in a 15 cm diameter reciprocating plate bubble column

Axial dispersion coefficients (E) in the liquid phase have been measured by unsteady tracer response methods in a 15 cm internal diameter reciprocating plate bubble column, using air and water in countercurrent and cocurrent flow. The operating variables studied were amplitude (0.6–1.27 cm) and frequency (0–5 Hz) of reciprocation, and the superficial velocities of the liquid and gas phases and the spacing between plates. Three types of plate were studied; conventional Karr-type plates with perforation diameters 1.43 cm, plates with smaller (0.635 cm) perforations, and single-perforation (doughnut) plates with internal diameter 7 cm. Measured values of E ranged from about 1 cm²/s to a maximum of 116 cm²/s. In general, the plates with 0.635 cm perforations gave the smallest values of E while the largest values of E were obtained with the doughnut plates, due to vortex ring shedding. The single liquid phase data for the three types of plate were approximately consistent with the correlation of Stevens and Baird (1990). The gas-liquid flow results were interpreted in terms of several different hydrodynamic effects.     

Responses of Human Cells to PAH-Induced DNA Damage

Benzo[ a ]pyrene (B[ a ]P) and dibenzo[ a,l ]pyrene (DB[ a,l ]P) induce cytochrome P450 (CYP) CYP1A1 and CYP1B1, which metabolize these polycyclic aromatic hydrocarbons (PAHs) into DNA-binding species. In order to detail roles of CYP1A1 and CYP1B1 in activation of DB[ a,l ]P to the diol epoxide, we here report the inhibition of CYP1A1 in human MCF-7 cells with phosphorodiamidate morpholino antisense oligomers (morpholinos). PAH-DNA adduct formation was also determined after treatment with morpholinos and B[ a ]P or DB[ a,l ]P. p53 is involved in DNA repair, cell cycle arrest, and apoptosis. Cells with normal p53 protein arrest in the G1 phase of the cell cycle on exposure to DNA-damaging agents (presumably allowing the cell sufficient time to repair damaged DNA prior to replication). Previous studies in human MCF-7 cells indicate that cells with PAH-DNA adducts escape cell cycle arrest and accumulate in the S phase. In the present study the effect of PAH-DNA adducts on the cell cycle were observed in human diploid fibroblasts (HDF). We found that treatment of HDF with the diol epoxide of DB[ a,l ]P causes cell cycle arrest in G 1 . An increase in DNA adduct formation with increase in concentration of dibenzo[ a,l ]pyrene diol epoxide {( m )- anti -DB[ a,l ]PDE} was also observed.     

Neural networks applied for the identification and fault diagnosis of process valves and actuators

This paper is concerned with the instrumentation and technology of fault detection and isolation (FDI) in process valves and actuators. A classification of faults in process valves and actuators is followed by a brief review of EDI techniques. Artificial neural networks (ANNs) are classified and introduced as an effective way of modelling valves and actuators, which are severely nonlinear components. Experimental results obtained from tests conducted on a double acting, twin piston rack-and-pinion actuator, are presented.     

Preimplantation hormonal differences between the conception and non-conception menstrual cycles of 32 normal women

We compared daily urinary concentrations of oestrogen and progesterone metabolites in paired menstrual cycles (conception and non-conception) from 32 women. Volunteers with no known fertility problems were enrolled in the study at the time they began trying to become pregnant. They collected first-morning urine specimens and kept daily records of menstrual bleeding and sexual intercourse for 6 months or until they became clinically pregnant. Intercourse in non-conception cycles was close to the time of ovulation so that failure to conceive was caused by factors other than poorly timed intercourse. Compared with non-conception cycles, conception cycles had a steeper early luteal rise in progesterone and higher mid-luteal oestrogen and progesterone concentrations. These hormonal characteristics may be markers of better quality cycles, but because all these differences were in the luteal phase, we cannot rule out the possibility that the preimplantation embryo had stimulated early increases in steroid production. We propose an analysis strategy that could help support or refute the importance of preimplantation embryonic signalling, but our small sample size limits our own conclusions about this mechanism.     

NUMERICAL SIMULATION OF THE TRANSPORT OF VORTEX RINGS IN AN INITIALLY STRATIFIED FLUID

A numerical study of the formation and transport of vortex rings in a cylindrical tank initially occupied by a thermally stratified fluid is presented. A control-volume based finite-difference technique (Patankar's SIMPLER method) is used. The formation of a vortex ring was simulated by injecting a quantity of a fluid through a tube centrally located near the free surface. Initially, the fluid in the tank was stably thermally stratified, with a low density in the upper half and higher density in the lower half. Buoyancy effects were considered. Modelling aspects are discussed and the formation and transport of a vortex ring in the stratified fluid as well as the resulting mixing characteristics are presented.     

Steady state hydrodynamics and mass transfer characteristics of a karr extraction column

The steady state hydrodynamics of the holdup in a 15 cm column agree quite well with mechanistic predictions at conditions approaching flooding. In the presence of mass transfer (acetic acid from the dispersed kerosene phase to the continuous water phase), the holdup data below flooding are not well predicted by the model due to enhanced droplet coalescence. The prediction of holdup at flooding is a function of the ratio of the flow rates but is independent of the physicochemical properties of the extraction system, and therefore can be used to estimate the flooding holdup regardless of the occurrence of mass transfer. In the second part of the paper, steady state mass transfer characteristics of the column were also simulated using a mechanistic model. Despite the difficulty of estimating parameters such as the mass transfer coefficient, the model curves could be arbitrarily adjusted to fit observed exit concentrations. These steady state results provide useful insights on the non-linearity of the system from a control viewpoint.     

Failure of stationary but not of flying honeybees (Apis mellifera) to respond to magnetic field stimuli.

Trained individual honeybees (Apis mellifera) to feed to repletion from a well of sucrose solution so constructed that shock could be delivered when the proboscis was in contact with the solution. If shock was signaled by vibration of the substrate or by an airstream, the animals learned readily to avoid it by breaking contact briefly, but there was no response to change (either constant or time-varying) in the ambient magnetic field. When, however, a magnetic field anomaly in the region of the food well signaled to flying animals that contact would be punished with shock, hesitation to settle was greater in presence than absence of the anomaly. Parallel results were obtained with light, to which flying Ss clearly responded but to which stationary Ss hardly responded at all. We conclude that stationary bees detect magnetic field stimuli but do not process them successfully in the training situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Managed Care and the Independent Practice of Psychology.

How has managed care impacted the independent practice of psychology? The present article reports on data from 2 national surveys (from 1996 and 2001) that address this question. Both surveys indicated that managed care was a source of stress, with external constraints, paperwork, and managed care reimbursement being the most highly rated stresses. These stresses had not increased in the 5 years between surveys, and the most recent survey suggested that, overall, psychologists did not report high levels of burnout. However, in contrast to respondents with low managed care involvement, respondents with high managed care caseloads worked longer hours, had more client contact, received less supervision, reported more negative client behaviors, experienced more stress, were less satisfied with their incomes, and scored higher on emotional exhaustion. Implications for burnout are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)