276 research outputs found
Fibrin D-dimer, markers of coagulation activation and the risk of major ischaemic heart disease in the Caerphilly Study
We have previously reported that plasma fibrin D-dimer (a marker of turnover of cross-linked Fibrin) showed a strong and independent association with incident ischaemic heart disease (IHD) in the Caerphilly Study cohort of 1,998 men a-ed 49-65. To establish the specificity of this finding, we assayed plasma samples from this cohort with a more specific assay for fibrin D-dimer: this showed an association with incident IHD which was at least as strong and independent as that for the original assay (odds ratio, OR for top fifth compared to bottom fifth 3.79; 95% CI 1.77-8.10; p lt 0.0001). To establish potential causes of the increased fibrin turnover. we also assayed several potential markers of coagulation activation or thrombotic tendency (prothrombin fragment F1+2, thrombin- antithrombin complexes, factor VIIc, activated partial thromboplastin time [APTT] and activated protein C resistance): none of these variables were associated with incident IHD in this cohort. We suggest that further studies are required to establish the causes of increased cross-linked fibrin turnover, which is associated with incident IHD in the general population when measured by a specific assay
Parametric amplification via superconducting contacts in a Ka band niobium pillbox cavity
Superconducting parametric amplifiers are commonly fabricated using planar
transmission lines with a non-linear inductance provided by either Josephson
junctions or the intrinsic kinetic inductance of the thin film. However, Banys
et al. [1] reported non-linear behaviour in a niobium pillbox cavity,
hypothesising that below Tc, the pair iris-bulk resonator would act as a
superconducting contact surface exploiting a Josephson-like non-linearity. This
work investigates this effect further by applying Keysight Technologies'
Advanced Design System (ADS) to simulate the cavity using an equivalent circuit
model that includes a user defined Josephson inductance component. The
simulations show that for a resonance centred at nu0 = 30.649 GHz, when two
tones (pump and signal) are injected into the cavity, mixing and parametric
gain occur. The maximum achievable gain is explored when the resonator is taken
to its bifurcation energy. These results are compared to cryogenic measurements
where the pump and signal are provided by a Vector Network Analyzer
The Impact of Surface Passivation on Kapitza Resistance at the Interface between a Semiconductor and Liquid Nitrogen
Cooling electronic devices to cryogenic temperatures (< 77 K) is crucial in
various scientific and engineering domains. Efficient cooling involves the
removal of heat generated from these devices through thermal contact with
either a liquid cryogen or a dry cryostat cold stage. However, as these devices
cool, thermal boundary resistance, also known as Kapitza resistance, hinders
the heat flow across thermal interfaces, resulting in elevated device
temperatures. In transistors, the presence of passivation layers like Silicon
Nitride (SiN) introduces additional interfaces that further impede heat
dissipation. This paper investigates the impact of passivation layer thickness
on Kapitza resistance at the interface between a solid device and liquid
nitrogen. The Kapitza resistance is measured using a capacitance thermometer
that has been passivated with SiN layers ranging from 0 to 240 nm. We observe
that Kapitza resistance increases with increasing passivation thickness.Comment: 6 pages, 5 Figure
Parametric amplification via superconducting contacts in a Ka band niobium pillbox cavity
Superconducting parametric amplifiers are commonly fabricated using planar
transmission lines with a non-linear inductance provided by either Josephson
junctions or the intrinsic kinetic inductance of the thin film. However, Banys
et al. [1] reported non-linear behaviour in a niobium pillbox cavity,
hypothesising that below Tc, the pair iris-bulk resonator would act as a
superconducting contact surface exploiting a Josephson-like non-linearity. This
work investigates this effect further by applying Keysight Technologies'
Advanced Design System (ADS) to simulate the cavity using an equivalent circuit
model that includes a user defined Josephson inductance component. The
simulations show that for a resonance centred at nu0 = 30.649 GHz, when two
tones (pump and signal) are injected into the cavity, mixing and parametric
gain occur. The maximum achievable gain is explored when the resonator is taken
to its bifurcation energy. These results are compared to cryogenic measurements
where the pump and signal are provided by a Vector Network Analyzer
Measuring the Kapitza Resistance between a Passivated Semiconductor and Liquid Helium
In this paper, we describe an experimental investigation into the effect of
passivation layer thickness on heat dissipation between a quartz substrate and
liquid helium. We have observed that by depositing SiN from 0 to 240 nm, the
Kapitza resistance increases by 0.0365 m^2.K/W per nanometer more than for an
unpassivated semiconductor. We hypothesize that this increase in Kapitza
resistance represents an additional barrier to the cooling of semiconductor
devices in liquid helium.Comment: 7 page
Fibrinogen, viscosity, and white blood cell count are major risk factors for ischemic heart disease. The Caerphilly and Speedwell collaborative heart disease studies.
BACKGROUND Recent studies have suggested that hemostatic factors and white blood cell count are predictive of ischemic heart disease (IHD). The relations of fibrinogen, viscosity, and white blood cell count to the incidence of IHD in the Caerphilly and Speedwell prospective studies are described.
METHODS AND RESULTS The two studies have a common core protocol and are based on a combined cohort of 4,860 middle-aged men from the general population. The first follow-up was at a nearly constant interval of 5.1 years in Caerphilly and 3.2 years in Speedwell; 251 major IHD events had occurred. Age-adjusted relative odds of IHD for men in the top 20% of the distribution compared with the bottom 20% were 4.1 (95% confidence interval, 2.6-6.5) for fibrinogen, 4.5 (95% confidence interval, 2.8-7.4) for viscosity, and 3.2 (95% confidence interval, 2.0-4.9) for white blood cell count. Associations with IHD were similar in men who had never smoked, exsmokers, and current smokers, and the results suggest that at least part of the effect of smoking on IHD is mediated through fibrinogen, viscosity, and white blood cell count. Multivariate analysis shows that white blood cell count is an independent risk factor for IHD as is either fibrinogen or viscosity, or possibly both. Jointly, these three variables significantly improve the fit of a logistic regression model containing all the main conventional risk factors. Further, a model including age, smoking habits, fibrinogen, viscosity, and white blood cell count predicts IHD as well as one in which the three hemostatic/rheological variables are replaced by total cholesterol, diastolic pressure, and body mass index.
CONCLUSION Jointly, fibrinogen, viscosity, and white blood cell count are important risk factors for IHD
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