Nonequilibrium Dephasing in an Electronic Mach-Zehnder Interferometer

We study nonequilibrium dephasing in an electronic Mach-Zehnder interferometer. We demonstrate that the shot noise at the beam splitter of the interferometer generates an ensemble of nonequilibrium electron density configurations and that electron interactions induce configuration-specific phase shifts of an interfering electron. The resulting dephasing exhibits two characteristic features, a lobe pattern in the visibility and phase jumps of $\pi$, in good agreement with experimental data.Comment: 4 pages, 3 figures; some typos are corrected; published versio

Microvascular oxygen delivery-to-utilization mismatch at the onset of heavy-intensity exercise in optimally treated patients with CHF

Sperandio PA, Borghi-Silva A, Barroco A, Nery LE, Almeida DR, Neder JA. Microvascular oxygen delivery-to-utilization mismatch at the onset of heavy-intensity exercise in optimally treated patients with CHF. Am J Physiol Heart Circ Physiol 297: H1720-H1728, 2009. First published September 4, 2009; doi:10.1152/ajpheart.00596.2009.-Impaired muscle blood flow at the onset of heavy-intensity exercise may transiently reduce microvascular O(2) pressure and decrease the rate of O(2) transfer from capillary to mitochondria in chronic heart failure (CHF). However, advances in the pharmacological treatment of CHF (e. g., angiotensin-converting enzyme inhibitors and third-generation beta-blockers) may have improved microvascular O(2) delivery to an extent that intramyocyte metabolic inertia might become the main locus of limitation of O(2) uptake ((V)over dot(O2)) kinetics. We assessed the rate of change of pulmonary (V)over dot(O2) ((V)over dot(O2p)), (estimated) fractional O(2) extraction in the vastus lateralis (similar to Delta[deoxy-Hb + Mb] by near-infrared spectroscopy), and cardiac output ((Q)over dot(T)) during high-intensity exercise performed to the limit of tolerance (Tlim) in 10 optimally treated sedentary patients (ejection fraction = 29 +/- 8%) and 11 controls. Sluggish (V)over dot(O2p) and (Q)over dot(T) kinetics in patients were significantly related to lower Tlim values (P < 0.05). the dynamics of Delta[deoxy-Hb + Mb], however, were faster in patients than controls [mean response time (MRT) = 15.9 +/- 2.0 s vs. 19.0 +/- 2.9 s; P < 0.05] with a subsequent response overshoot being found only in patients (7/10). Moreover, tau(V)over dot(O2)/MRT-[deoxy-Hb + Mb] ratio was greater in patients (4.69 +/- 1.42 s vs. 2.25 +/- 0.77 s; P < 0.05) and related to (Q)over dot(T) kinetics and Tlim (R = 0.89 and -0.78, respectively; P < 0.01). We conclude that despite the advances in the pharmacological treatment of CHF, disturbances in central and peripheral circulatory adjustments still play a prominent role in limiting (V)over dot(O2p) kinetics and tolerance to heavy-intensity exercise in nontrained patients.Fed Univ São Paulo UNIFESP, Dept Med, Div Resp Med, Pulm Funct & Clin Exercise Physiol Unit SEFICE, São Paulo, BrazilFed Univ São Paulo UNIFESP, Dept Med, Div Cardiol, São Paulo, BrazilFed Univ Sao Carlos UFSCar, Nucleus Res Phys Exercise, Cardiopulm Lab, Sao Carlos, SP, BrazilFed Univ São Paulo UNIFESP, Dept Med, Div Resp Med, Pulm Funct & Clin Exercise Physiol Unit SEFICE, São Paulo, BrazilFed Univ São Paulo UNIFESP, Dept Med, Div Cardiol, São Paulo, BrazilWeb of Scienc

Expression of methylthioadenosine phosphorylase (MTAP) in pilocytic astrocytomas

BACKGROUND/OBJECTIVES Pilocytic astrocytomas (PAs) are the most frequent astrocytomas in children and adolescents. Methilthioadenosine phosphorylase(MTAP) is a tumor-suppressor gene, the loss of expression of which is associated with a poor prognosis and better response to specific chemotherapy in leukemia and non-small-cell lung cancer. The expression of MTAP in brain tumors remains largely unknown and its biological role in PA is still unexplored. Our aims were to describe the immunohistochemical MTAP expression in a series of PAs and relate it to the clinicopathological features of the patients. METHODS We assessed MTAP expression on immunohistochemistry in 69 pediatric and adult patients with PA in a tissue microarray platform. RESULTS Retained expression of MTAP was seen in >85% of the tumors compared to in the nonneoplastic adjacent tissue. Only 3 supratentorial tumors showed a complete loss of MTAP expression. No significant association with clinicopathological features or overall survival of the patients was found. CONCLUSIONS MTAP expression is retained in PAs and is not an outcome predictor for these tumors. Nevertheless, a subset of patients with PAs exhibiting a loss of MTAP could potentially benefit from treatment with specific chemotherapy, especially when lesions are recurrent or surgical resection is not recommended.This study was partially supported by the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (2012/19590-0) and an HCB program of financial support (Programa de Apoio e Incentivo a Pesquisa)

Inspiratory resistance decreases limb blood flow in COPD patients with heart failure

Hosp Clin Porto Alegre, Exercise Pathophysiol Res Lab, BR-90035007 Porto Alegre, RS, BrazilHosp Clin Porto Alegre, Div Cardiol, BR-90035007 Porto Alegre, RS, BrazilSerra Gaucha Coll, Phys Therapy Dept, Caxias Do Sul, RS, BrazilHosp Clin Porto Alegre, Pulmonary Div, Porto Alegre, RS, BrazilFed Univ Rio Grande, Fac Med, Dept Med, Porto Alegre, RS, BrazilUniversidade Federal de São Paulo, Dept Med, Div Resp Dis, Pulmonary Funct & Clin Exercise Physiol Unit, São Paulo, BrazilQueens Univ, Dept Med, Div Respirol, LACEP, Kingston, ON, CanadaKingston Gen Hosp, Kingston, ON K7L 2V7, CanadaUniversidade Federal de São Paulo, Dept Med, Div Resp Dis, Pulmonary Funct & Clin Exercise Physiol Unit, São Paulo, BrazilWeb of Scienc

Sildenafil improves microvascular O-2 delivery-to-utilization matching and accelerates exercise O-2 uptake kinetics in chronic heart failure

Sperandio PA, Oliveira MF, Rodrigues MK, Berton DC, Treptow E, Nery LE, Almeida DR, Neder JA. Sildenafil improves microvascular O-2 delivery-to-utilization matching and accelerates exercise O-2 uptake kinetics in chronic heart failure. Am J Physiol Heart Circ Physiol 303: H1474-H1480, 2012. First published September 28, 2012; doi:10.1152/ajpheart.00435.2012.-Nitric oxide (NO) can temporally and spatially match microvascular oxygen (O-2) delivery (QO(2mv)) to O-2 uptake (VO2) in the skeletal muscle, a crucial adjustment-to-exercise tolerance that is impaired in chronic heart failure (CHF). To investigate the effects of NO bioavailability induced by sildenafil intake on muscle QO(2mv)-to-O-2 utilization matching and VO2 kinetics, 10 males with CHF (ejection fraction = 27 +/- 6%) undertook constant work-rate exercise (70-80% peak). Breath-by-breath VO2, fractional O-2 extraction in the vastus lateralis {similar to deoxy-genated hemoglobin + myoglobin ([deoxy-Hb + Mb]) by near-infrared spectroscopy}, and cardiac output (CO) were evaluated after sildenafil (50 mg) or placebo. Sildenafil increased exercise tolerance compared with placebo by similar to 20%, an effect that was related to faster on-and off-exercise VO2 kinetics (P 0.05). On-exercise [deoxy-Hb + Mb] kinetics were slowed by sildenafil (similar to 25%), and a subsequent response overshoot (n = 8) was significantly lessened or even abolished. in contrast, [deoxy-Hb + Mb] recovery was faster with sildenafil (similar to 15%). Improvements in muscle oxygenation with sildenafil were related to faster on-exercise VO2 kinetics, blunted oscillations in ventilation (n = 9), and greater exercise capacity (P < 0.05). Sildenafil intake enhanced intramuscular QO(2mv)-to-VO2 matching with beneficial effects on VO2 kinetics and exercise tolerance in CHF. the lack of effect on CO suggests that improvement in blood flow to and within skeletal muscles underlies these effects.Universidade Federal de São Paulo, Dept Med, Div Resp Dis, Pulm Funct & Clin Exercise Physiol Unit, BR-04020050 São Paulo, BrazilQueens Univ, Dept Med, Div Resp & Crit Care Med, Kingston, ON K7L 3N6, CanadaUniversidade Federal de São Paulo, Dept Med, Div Cardiol, BR-04020050 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Med, Div Resp Dis, Pulm Funct & Clin Exercise Physiol Unit, BR-04020050 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Med, Div Cardiol, BR-04020050 São Paulo, BrazilWeb of Scienc

Single electron quantum tomography in quantum Hall edge channels

We propose a quantum tomography protocol to measure single electron coherence in quantum Hall edge channels and therefore access for the first time the wave function of single electron excitations propagating in ballistic quantum conductors. Its implementation would open the way to quantitative studies of single electron decoherence and would provide a quantitative tool for analyzing single to few electron sources. We show how this protocol could be implemented using ultrahigh sensitivity noise measurement schemes.Comment: Version 3: long version (7 figures): corrections performed and references have been added. Figures reprocessed for better readabilit