16 resultados para 35-324

em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast


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The results of PVT measurements of the liquid phase within the temperature range of (298 to 393) K and up to 35 MPa are presented for some aliphatic esters. Measurements were made by means of a vibrating-tube densimeter, model DMA 512P from Anton Parr. The calibration of the densimeter was performed with water and n-heptane as reference fluids. The experimental PVT data have been correlated by a Tait equation. This equation gives excellent results when used to predict the density of the esters using the method proposed by Thomson et al. (AIChE J. 1982, 28, 671-676). Isothermal compressibilities, isobaric expansivities, thermal pressure coefficients, and changes in the isobaric heat capacity have been calculated from the volumetric data.

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The aggregation of beta-amyloid to plaques in the brain is one of the hallmarks of Alzheimer disease (AD). Numerous studies have tried to elucidate to what degree amyloid peptides play a role in the neurodegenerative developments seen in AD. While most studies report an effect of amyloid on neural activity and cognitive abilities of rodents, there have been many inconsistencies in the results. This study investigated to what degree the different genetic backgrounds affect the outcome of beta-amyloid fragment (25-35) on synaptic plasticity in vivo in the rat hippocampus. Two strains, Wistar and Lister hooded rats, were tested. In addition, the effects of a strong (600 stimuli) and a weak stimulation protocol (100 stimuli) on impairments of LTP were analysed. Furthermore, since the state of amyloid aggregation appears to play a role in the induction of toxic processes, it was tested by dual polarisation interferometry to what degree and at what speed beta-amyloid (25-35) can aggregate in vitro. It was found that 100 nmol beta-amyloid (25-35) injected icv did impair LTP in Wistar rats when using the weak but not the strong stimulation protocol (P <0.001). One-hundred nano mole of the reverse sequence amyloid (35-25) had no effect. LTP in Lister Hooded rats was not impaired by amyloid at any stimulation protocol. The aggregation studies showed that amyloid (25-35) aggregated within hours, while amyloid (35-25) did not. These results show that the genetic background and the stimulation protocol are important variables that greatly influence the experimental outcome. The fact that amyloid (25-35) aggregated quickly and showed neurophysiological effects, while amyloid (35-25) did not aggregate and did not show any effects indicates that the state of aggregation plays an important role in the physiological effects.

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Objective

To examine whether students’ school engagement, relationships with teachers, educational aspirations and involvement in fights at school are associated with various measures of subsequent substance use.
Methods

Data were drawn from the Belfast Youth Development Study (n = 2968). Multivariate logistic models examined associations between school-related factors (age 13/14) and substance use (age 15/16).
Results

The two factors which were consistently and independently associated with regular substance use among both males and females were student–teacher relationships and fighting at school: positive teacher-relationships reduced the risk of daily smoking by 48%, weekly drunkenness by 25%, and weekly cannabis use by 52%; being in a fight increased the risk of daily smoking by 54%, weekly drunkenness by 31%, and weekly cannabis use by 43%. School disengagement increased the likelihood of smoking and cannabis use among females only.
Conclusion

Further research should focus on public health interventions promoting positive relationships and safety at school.

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Objective of the study: To determine the extent and nature of unlicensed/off-label prescribing patterns in hospitalised children in Palestine. Setting: Four paediatric wards in two public health system hospitals in Palestine [Caritas children’s hospital (Medical and neonatal intensive care units) and Rafidia general hospital (Medical and surgical units)]. Method: A prospective survey of drugs administered to infants and children <18 years old was carried out over a five-week period in the four paediatric wards. Main outcome measure: Drug-licensing status of all prescriptions was determined according to the Palestinian Registered Product List and the Physician’s Desk Reference. Results: Overall, 917 drug prescriptions were administered to 387 children. Of all drug prescriptions, 528 (57.5%) were licensed for use in children; 65 (7.1%) were unlicensed; and 324 (35.3%) were used off-label. Of all children, 49.6% received off-label prescriptions, 10.1% received unlicensed medications and 8.2% received both. Seventy-two percent of off-label drugs and 66% of unlicensed drugs were prescribed for children <2 years. Multivariate analysis showed that patients who were admitted to the neonatal intensive care unit and infants aged 0–1 years were most likely to receive a greater number of off-label or unlicensed medications (OR 1.80; 95% CI 1.03–3.59 and OR 1.99; 95% CI 0.88–3.73, respectively). Conclusion: The present findings confirmed the elevated prevalence of unlicensed and off-label paediatric drugs use in Palestine and strongly support the need to perform well designed clinical studies in children.

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Very collimated bunches of high energy electrons have been produced by focusing super-intense femtosecond laser pulses in submillimeter under-dense plasmas. The density of the plasma, preformed with the laser exploding-foil technique, was mapped using Nomarski interferometry. The electron beam was fully characterized: up to 10(9) electrons per shot were accelerated, most of which in a beam of aperture below 10(-3) sterad, with energies up to 40 MeV. These measurements, which are well modeled by three-dimensional numerical simulations, validate a reliable method to generate ultrashort and ultracollimated electron bunches. (C) 2002 American Institute of Physics.

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This paper presents an ultrafast wideband low-loss single-pole double-throw (SPDT) differential switch in 0.35 µ m SiGe bipolar technology. The proposed topology adopting current-steering technique results in a total measured switching time of 75 ps , which suggests a maximum switching rate of 13 Gb/s, the fastest ever reported at V-band. In addition, the switch exhibits an insertion loss lower than 1.25 dB and an isolation higher than 18 dB from 42 GHz to 70 GHz. © 2006 IEEE.

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This paper presents the design and characterization of ultrafast wideband low-loss single-pole single-throw (SPST) and single-pole double-throw (SPDT) differential switches. The SPDT switch exhibits insertion loss of lower than 1.25 dB from 42 to 70 GHz and isolation of better than 20 dB from 40 to 65 GHz. Similar low-loss and broadband characteristics are also observed from the measured SPST switch. The proposed switch topologies adopting current-steering technique and implemented in 0.35 µm SiGe bipolar technology result in a switching time of only 75 ps. This suggests a maximum switching speed of 13 Gbps, the fastest ever reported at V-band.