1,369 research outputs found
Effects of Chronic Hypoxemia on Chemosensitivity in Patients With Univentricular Heart
AbstractObjectives. We sought to compare the arterial blood gas chemosensitivity in relation to exercise ventilatory response in patients with univentricular heart and cyanosis and in patients with univentricular heart and Fontan-type circulation without cyanosis.Background. Patients with univentricular heart demonstrate excessive ventilation during exercise. Chronic hypoxemia may alter chemoreceptor function, affecting ventilation.Methods. Cardiopulmonary exercise testing was performed in 10 patients with rest or stress-induced cyanosis (cyanotic group: mean age ± SE 30.5 ± 2.3 years; 5 men), 8 patients without cyanosis with Fontan-type circulation (Fontan group: mean age 29.4 ± 1.5 years; 4 men) and 10 healthy control subjects (normal group: mean age 30.7 ± 1.9 years; 5 men). Hypoxic and hypercapnic chemosensitivity were assessed by using transient inhalations of pure nitrogen and the rebreathing of 7% CO2in 93% O2, respectively.Results. Peak O2consumption was comparable in both patient groups (21.7 ± 2.5 [cyanotic group] vs. 21.0 ± 1.9 ml/kg per min [Fontan group]) but was lower than that in the normal group (34.7 ± 1.9 ml/kg per min). The ventilatory response to exercise, characterized by the regression slope relating minute ventilation to CO2output, was higher in the cyanotic group (43.4 ± 4.0) than in the Fontan group (31.4 ± 3.0, p = 0.02) and the normal group (23.1 ± 1.1). Hypoxic chemosensitivity was blunted in the cyanotic group compared with that in the Fontan and normal groups (0.148 vs. 0.448 [p = 0.02] vs. 0.311 liter/min per percent arterial O2saturation, respectively) and did not correlate with the ventilatory response to exercise (r = −0.36, p = 0.29). In contrast, hypercapnic chemosensitivity represented by the slope of the hypercapnic-ventilatory response line was similar in the cyanotic, Fontan and normal groups (1.71 vs. 1.76 vs. 1.70 liter/min per mm Hg, respectively), but the response line had shifted to the left in the cyanotic group (x intercept = 31.9 vs. 39.9 mm Hg [p = 0.026]), compared with 45.2 mm Hg in normal subjects. These findings suggest that in the cyanotic group, ventilation is greater for a given level of arterial CO2tension and thus may partly explain the increased exercise ventilatory response in this group.Conclusions. Hypoxic chemosensitivity is blunted in patients with univentricular heart and cyanosis and does not determine the exercise ventilatory response. CO2elimination appears more important. The blunting of hypoxic chemosensitivity is reversible once chronic hypoxemia is relieved, as evident in the Fontan group
Hairpin DNA functionalized gold nanorods for mRNA detection in homogenous solution
We report a novel fluorescent probe for mRNA detection. It consists of a gold nanorod (GNR) functionalized with fluorophore labeled hairpin oligonucleotides (hpDNA) that are complementary to the mRNA of a target gene. This nanoprobe was found to be sensitive to a complementary oligonucleotide, as indicated by significant changes in both fluorescence intensity and lifetime. The influence of the surface density of hpDNA on the performance of this nanoprobe was investigated, suggesting that high hybridization efficiency could be achieved at a relatively low surface loading density of hpDNA. However, steady-state fluorescence spectroscopy revealed better overall performance, in terms of sensitivity and detection range, for nanoprobes with higher hairpin coverage. Time-resolved fluorescence lifetime spectroscopy revealed significant lifetime changes of the fluorophore upon hybridization of hpDNA with targets, providing further insight on the hybridization kinetics of the probe as well as the quenching efficiency of GNRs
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Multilevel converters for power system applications
Multilevel converters are emerging as a new breed of power converter options for power system applications. These converters are most suitable for high voltage high power applications because they connect devices in series without the need for component matching. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. To avoid voltage unbalance between different levels, several techniques have been proposed for different applications. Excluding magnetic-coupled converters, this paper introduces three multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded inverters with separate dc sources. The operation principle, features, constraints, and potential applications of these converters will be discussed
SB1 Comparison of Medical Care Consumption Between Duloxetine Initiators and Pregabalin Initiators Among Fibromyalgia Patients
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Power electronics and electric machinery challenges and opportunities in electric and hybrid vehicles
The development of power electronics and electric machinery presents significant challenges to the advancement of electric and hybrid vehicles. Electronic components and systems development for vehicle applications have progressed from the replacement of mechanical systems to the availability of features that can only be realized through interacting electronic controls and devices. Near-term applications of power electronics in vehicles will enable integrated powertrain controls, integrated chassis system controls, and navigation and communications systems. Future applications of optimized electric machinery will enable highly efficient and lightweight systems. This paper will explore the areas where research and development is required to ensure the continued development of power electronics and electric machines to meet the rigorous demands of automotive applications. Additionally, recent advances in automotive related power electronics and electric machinery at Oak Ridge National Laboratory will be explained. 3 refs., 5 figs
Coherent dynamics and decoherence in a superconducting weak link
We demonstrate coherent dynamics of quantized magnetic fluxes in a
superconducting loop with a weak link - a nanobridge patterned from the same
thin NbN film as the loop. The bridge is a short rounded shape constriction,
close to 10 nm long and 20 - 30 nm wide, having minimal width at its center.
Quantum state control and coherent oscillations in the driven time evolution of
the tunnel-junctionless system are achieved. Decoherence and energy relaxation
in the system are studied using a combination of microwave spectroscopy and
direct time-domain techniques. The effective flux noise behavior suggests
inductance fluctuations as a possible cause of the decoherence.Comment: 5 pages, 3 figure
Efficient quantum key distribution scheme with nonmaximally entangled states
We propose an efficient quantum key distribution scheme based on
entanglement. The sender chooses pairs of photons in one of the two equivalent
nonmaximally entangled states randomly, and sends a sequence of photons from
each pair to the receiver. They choose from the various bases independently but
with substantially different probabilities, thus reducing the fraction of
discarded data, and a significant gain in efficiency is achieved. We then show
that such a refined data analysis guarantees the security of our scheme against
a biased eavesdropping strategy.Comment: 5 Pages, No Figur
OL-085 A candidate genes study for the association of host single nucleotide polymorphisms with liver cirrhosis risk in Chinese hepatitis B patients
On the Design of Cognitive-Radio-Inspired Asymmetric Network Coding Transmissions in MIMO Systems
In this paper, a cognitive-radio-inspired asymmetric network coding (CR-AsNC) scheme is proposed for multiple-input-multiple-output (MIMO) cellular transmissions, where information exchange among users and base-station (BS) broadcasting can be accomplished simultaneously. The key idea is to apply the concept of cognitive radio (CR) in network coding transmissions, where the BS tries sending new information while helping users' transmissions as a relay. In particular, we design an asymmetric network coding method for information exchange between the BS and the users, although many existing works consider the design of network coding in symmetric scenarios. To approach the optimal performance, an iterative precoding design for CR-AsNC is first developed. Then, a channel-diagonalization-based precoding design with low complexity is proposed, to which power allocation can be optimized with a closed-form solution. The simulation results show that the proposed CR-AsNC scheme with precoding optimization can significantly improve system transmission performance
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