76,429 research outputs found
Association of antihypertensive monotherapy with serum sodium and potassium levels in Chinese patients
<b>Background</b> International guidelines on management of hypertension recommend any major classes of antihypertensive drugs. However, the low prescribing rate of thiazides has been attributed to concerns about electrolyte disturbances and studies between antihypertensive drug classes and hyponatremia/hypokalemia among Chinese patients were scarce. <p></p>
<b>Methods</b> From clinical databases we included 2,759 patients who received their first-ever antihypertensive monotherapy from January 2004 to June 2007 in a large territory of Hong Kong. We studied the plasma sodium and potassium levels 8 weeks after prescriptions and factors associated with hyponatremia and hypokalemia by multivariable regression analyses. <p></p>
<b>Results</b> Among major antihypertensive drug classes, thiazide users had the lowest sodium level (139.6 mEq/l, 95% confidence interval (CI) 139.3, 140.0, P < 0.001) and patients-prescribed calcium channel blockers (CCBs; 3.92 mEq/l, 95% CI 3.89, 3.95) or thiazide diuretics (3.99 mEq/l, 95% CI 3.93, 4.04) had the lowest potassium levels (P < 0.001). Multivariate analysis reported that advanced age (>/=70 years, odds ratio (OR) 7.49, 95% CI 2.84, 19.8, P < 0.001), male gender (OR 2.38, 95% CI 1.45, 3.91, P < 0.001), and thiazide users (OR 2.42, 95% CI 1.29, 4.56, P = 0.006) were significantly associated with hyponatremia, while renin-angiotensin system (RAS) (OR 0.31, 95% CI 0.13, 0.73, P = 0.008) and beta-blockers (BBs) (OR 0.35, 95% CI 0.23, 0.54, P < 0.001) users were less likely to present with hypokalemia. However, the proportions having normonatremic (95.1%) and normokalemic (89.4%) levels were high. <p></p>
<b>Conclusions</b> In view of the low prevalence of hyponatremia and hypokalemia associated with thiazides, physicians should not be deterred from prescribing thiazide diuretics as first-line antihypertensive agents as recommended by most international guidelines
Improved turbine disk design to increase reliability of aircraft jet engines
An analytical study was conducted on a bore entry cooled turbine disk for the first stage of the JT8D-17 high pressure turbine which had the potential to improve disk life over existing design. The disk analysis included the consideration of transient and steady state temperature, blade loading, creep, low cycle fatigue, fracture mechanics and manufacturing flaws. The improvement in life of the bore entry cooled turbine disk was determined by comparing it with the existing disk made of both conventional and advanced (Astroloy) disk materials. The improvement in crack initiation life of the Astroloy bore entry cooled disk is 87% and 67% over the existing disk made of Waspaloy and Astroloy, respectively. Improvement in crack propagation life is 124% over the Waspaloy and 465% over the Astroloy disks. The available kinetic energies of disk fragments calculated for the three disks indicate a lower fragment energy level for the bore entry cooled turbine disk
Delay Measurements and Self Characterisation on FPGAs
This thesis examines new timing measurement methods for self delay characterisation of Field-Programmable Gate Arrays (FPGAs) components and delay measurement of complex circuits
on FPGAs. Two novel measurement techniques based on analysis of a circuit's output failure
rate and transition probability is proposed for accurate, precise and efficient measurement of
propagation delays. The transition probability based method is especially attractive, since
it requires no modifications in the circuit-under-test and requires little hardware resources,
making it an ideal method for physical delay analysis of FPGA circuits.
The relentless advancements in process technology has led to smaller and denser transistors
in integrated circuits. While FPGA users benefit from this in terms of increased hardware
resources for more complex designs, the actual productivity with FPGA in terms of timing
performance (operating frequency, latency and throughput) has lagged behind the potential
improvements from the improved technology due to delay variability in FPGA components
and the inaccuracy of timing models used in FPGA timing analysis. The ability to measure
delay of any arbitrary circuit on FPGA offers many opportunities for on-chip characterisation
and physical timing analysis, allowing delay variability to be accurately tracked and variation-aware optimisations to be developed, reducing the productivity gap observed in today's FPGA
designs.
The measurement techniques are developed into complete self measurement and characterisation platforms in this thesis, demonstrating their practical uses in actual FPGA hardware for
cross-chip delay characterisation and accurate delay measurement of both complex combinatorial and sequential circuits, further reinforcing their positions in solving the delay variability
problem in FPGAs
Bounds on Cubic Lorentz-Violating Terms in the Fermionic Dispersion Relation
We study the recently proposed Lorentz-violating dispersion relation for
fermions and show that it leads to two distinct cubic operators in the
momentum. We compute the leading order terms that modify the non-relativistic
equations of motion and use experimental results for the hyperfine transition
in the ground state of the ion to bound the values of the
Lorentz-violating parameters and for neutrons. The resulting
bounds depend on the value of the Lorenz-violating background four-vector in
the laboratory frame.Comment: Revtex 4, four pages. Version to match the one to appear in Physical
Review
The effects of shock waves on meteorites Final report
Shock wave effects on iron and iron-nickel alloys in meteorites analyzed by phase diagrams and residual effects due to shock loadin
Direct observation of voids in the vacancy excess region of ion bombarded silicon
The results reported in this letter indicate that the spatial separation of the vacancy and interstitial excesses which result from ion bombardment gives rise to stable voids upon annealing at 850 °C even for implants where the projected ion range is only of the order of a few thousand Ångstrom. Such voids have been observed directly by transmission electron microscopy. Furthermore, in cases where both voids and interstitial-based defects are present at different depths, it is found that Au has a strong preference for decorating void surfaces and hence Au can, indeed, be used as a selective detector of open volume defects in Si.One of the authors ~J.W.-L.!
acknowledges the Australian Research Council for financial
support
Anomalous Soft Photons in Hadron Production
Anomalous soft photons in excess of what is expected from electromagnetic
bremsstrahlung have been observed in association with the production of
hadrons, mostly mesons, in high-energy (K+)p, (pi+)p, (pi-)p, pp, and (e+)(e-)
collisions. We propose a model for the simultaneous production of anomalous
soft photons and mesons in quantum field theory, in which the meson production
arises from the oscillation of color charge densities of the quarks of the
underlying vacuum in the flux tube. As a quark carries both a color charge and
an electric charge, the oscillation of the color charge densities will be
accompanied by the oscillation of electric charge densities, which will in turn
lead to the simultaneous production of soft photons during the meson production
process. How the production of these soft photons may explain the anomalous
soft photon data will be discussed. Further experimental measurements to test
the model will be proposed.Comment: 19 pages, 2 figures, to be published in Physical Review
A Study of Non-Neutral Networks with Usage-based Prices
Hahn and Wallsten wrote that network neutrality "usually means that broadband
service providers charge consumers only once for Internet access, do not favor
one content provider over another, and do not charge content providers for
sending information over broadband lines to end users." In this paper we study
the implications of non-neutral behaviors under a simple model of linear
demand-response to usage-based prices. We take into account advertising
revenues and consider both cooperative and non-cooperative scenarios. In
particular, we model the impact of side-payments between service and content
providers. We also consider the effect of service discrimination by access
providers, as well as an extension of our model to non-monopolistic content
providers
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