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1.
Phys Rev Lett ; 120(2): 020505, 2018 Jan 12.
Artículo en Inglés | MEDLINE | ID: mdl-29376684

RESUMEN

The quantum Zeno effect is the suppression of Hamiltonian evolution by repeated observation, which pins the system to an eigenstate of the measurement observable. Using measurement alone, control of the state can be achieved if the observable is slowly varied, so that the state tracks the now time-dependent eigenstate. We demonstrate this using a circuit-QED readout technique that couples to a dynamically controllable observable of a qubit. Continuous monitoring of the measurement record allows us to detect an escape from the eigenstate, thus serving as a built-in form of error detection. We show this by postselecting on realizations with high fidelity with respect to the target state. Our dynamical measurement operator technique offers a new tool for numerous forms of quantum feedback protocols, including adaptive measurements and rapid state purification.

2.
Epidemiol Infect ; 143(5): 975-85, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25274140

RESUMEN

SUMMARY Environmental samples are a cost-saving and easy-to-use approach to diagnose paratuberculosis at the herd level. Detailed knowledge concerning its uncertainties in herds with a low prevalence of Mycobacterium avium spp. paratuberculosis (MAP) is required to design sampling strategies in control programmes. This study aimed to calculate a threshold level of the apparent within-herd prevalence (WHPapp) as determined by individual mycobacterial cultivation (faecal culture; FC) of all cows thus allowing the detection of a herd as MAP-positive at a certain probability level (P d). Out of 200 environmental samples taken twice from five predefined locations in a barn, 25 were positive by FC and 60 were positive by a quantitative real-time PCR method (qPCR). A logistic regression model was used to calculate the WHPapp threshold of detection. For 50% P d, a WHPapp threshold of 2.9% was calculated for the combination of three samples (milking area, main cow alleyways, holding pen) tested simultaneously both by FC and qPCR. The threshold increased to 6.2% for 90% P d. Repeated environmental sampling did not reduce the WHPapp threshold. Depending on the particular needs for prevalence estimation or in control programmes (single or repeated sampling) the provided WHPapp thresholds at different P d will enable decisions to be made about various sampling strategies.


Asunto(s)
Enfermedades de los Bovinos/epidemiología , ADN Bacteriano/análisis , Heces/microbiología , Mycobacterium avium subsp. paratuberculosis/genética , Paratuberculosis/epidemiología , Reacción en Cadena en Tiempo Real de la Polimerasa/veterinaria , Animales , Técnicas Bacteriológicas/veterinaria , Bovinos , Enfermedades de los Bovinos/diagnóstico , Femenino , Modelos Logísticos , Mycobacterium avium subsp. paratuberculosis/aislamiento & purificación , Paratuberculosis/diagnóstico , Prevalencia , Análisis de Secuencia de ADN/veterinaria
3.
Nature ; 511(7511): 570-3, 2014 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-25079554

RESUMEN

A central feature of quantum mechanics is that a measurement result is intrinsically probabilistic. Consequently, continuously monitoring a quantum system will randomly perturb its natural unitary evolution. The ability to control a quantum system in the presence of these fluctuations is of increasing importance in quantum information processing and finds application in fields ranging from nuclear magnetic resonance to chemical synthesis. A detailed understanding of this stochastic evolution is essential for the development of optimized control methods. Here we reconstruct the individual quantum trajectories of a superconducting circuit that evolves under the competing influences of continuous weak measurement and Rabi drive. By tracking individual trajectories that evolve between any chosen initial and final states, we can deduce the most probable path through quantum state space. These pre- and post-selected quantum trajectories also reveal the optimal detector signal in the form of a smooth, time-continuous function that connects the desired boundary conditions. Our investigation reveals the rich interplay between measurement dynamics, typically associated with wavefunction collapse, and unitary evolution of the quantum state as described by the Schrödinger equation. These results and the underlying theory, based on a principle of least action, reveal the optimal route from initial to final states, and may inform new quantum control methods for state steering and information processing.

4.
Phys Rev Lett ; 106(4): 040402, 2011 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-21405309

RESUMEN

We generalize the derivation of Leggett-Garg inequalities to systematically treat a larger class of experimental situations by allowing multiparticle correlations, invasive detection, and ambiguous detector results. Furthermore, we show how many such inequalities may be tested simultaneously with a single setup. As a proof of principle, we violate several such two-particle inequalities with data obtained from a polarization-entangled biphoton state and a semiweak polarization measurement based on Fresnel reflection. We also point out a nontrivial connection between specific two-party Leggett-Garg inequality violations and convex sums of strange weak values.

5.
Phys Rev Lett ; 104(24): 240401, 2010 Jun 18.
Artículo en Inglés | MEDLINE | ID: mdl-20867281

RESUMEN

We introduce contextual values as a generalization of the eigenvalues of an observable that takes into account both the system observable and a general measurement procedure. This technique leads to a natural definition of a general conditioned average that converges uniquely to the quantum weak value in the minimal disturbance limit. As such, we address the controversy in the literature regarding the theoretical consistency of the quantum weak value by providing a more general theoretical framework and giving several examples of how that framework relates to existing experimental and theoretical results.

6.
Arzneimittelforschung ; 47(9): 1016-23, 1997 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-9342414

RESUMEN

These studies were designed to investigate the protective effects of the new angiotensin II receptors antagonist BAY 10-6734 (6-n-butyl-4-methoxycarbonyl-2-oxo-1[(2'-(1H-tetrazol-5-yl) -3-fluorobiphenyl-4-yl)methyl] 1,2-dihydropyridine, CAS 156001-18-2) on haemodynamic, hormonal, renal, and structural parameters in renin transgenic rats (TGR(mRen2)27), salt-loaded Dahl S and R rats, and salt-loaded stroke-prone spontaneously hypertensive rats (SHR-SP) in long-term trials. Study 1: In SHR-SP the development of blood pressure, cardiac hypertrophy, and the deleterious effects of salt loading on kidney structure and kidney function was prevented by BAY 10-6734. Study 2: In salt-loaded Dahl S rats with a suppressed plasma renin activity treatment with BAY 10-6734 did not delay the increase in blood pressure but prevented cardiac hypertrophy and the increase in plasma ANP (Atrial natriuretic peptide). Study 3: TGR develop malignant hypertension associated with cardiac hypertrophy, elevated left-ventricular end-diastolic pressure and increased plasma ANP. After 6 weeks of treatment with BAY 10-6734 (30 mg/kg p.o. bid) cardiac pump function was improved and cardiac hypertrophy was reversed in this angiotension dependent form of hypertension. The beneficial effects of BAY 10-6734 in these different animal hypertension models are also emphasized by a reduction in mortality.


Asunto(s)
Angiotensina II/metabolismo , Antagonistas de Receptores de Angiotensina , Antihipertensivos/farmacología , Trastornos Cerebrovasculares/fisiopatología , Dihidropiridinas/farmacología , Hipertensión/prevención & control , Renina/genética , Tetrazoles/farmacología , Aldosterona/sangre , Animales , Animales Modificados Genéticamente , Factor Natriurético Atrial/sangre , Peso Corporal/efectos de los fármacos , Trastornos Cerebrovasculares/genética , GMP Cíclico/sangre , Hemodinámica/efectos de los fármacos , Hormonas/sangre , Hipertensión/inducido químicamente , Hipertensión/genética , Riñón/patología , Riñón/fisiopatología , Ratas , Ratas Endogámicas SHR
7.
Hypertens Res ; 19(3): 151-9, 1996 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-8891743

RESUMEN

The cardiovascular consequences of mixed angiotensin converting enzyme and neutral endopeptidase (ACE/NEP) inhibition with alatriopril/alatrioprilat were compared with the consequences of endopeptidase (NEP) inhibition alone with (S)-thiorphan/ecadotril by determining the acute effects of the compounds on hemodynamic, hormonal, and renal parameters in hypertensive transgenic rats harboring an additional mouse renin gene (TGR(mRen2)27). Infusion of alatrioprilat and (S)-thiorphan in anesthetized TGR decreased blood pressure in a dose-dependent manner, but heart rate remained unchanged. The renal excretion of water, sodium, and cGMP also increased dose-dependently, with nearly the same maximal effects after infusion of (S)-thiorphan and alatrioprilat. At the end of infusion, plasma ANP and cGMP were elevated both after (S)-thiorphan and after alatrioprilat, whereas plasma renin activity increased only after alatrioprilat. The ACE inhibition effect was studied in ganglion-blocked rats receiving a continous infusion of angiotensin I. Alatrioprilat decreased the mean blood pressure dose-dependently, but about 30 times higher concentrations were needed to produce the same effects as the ACE inhibitor captopril. At a dose of 30 mg/kg p.o., ecadotril, the orally active prodrug of (S)-thiorphan, decreased the systolic blood pressure in conscious TGR by 22 mmHg for 6 h, whereas alatriopril (100 mg/kg p.o.) also reduced the systolic pressure in these rats with a maximal reduction of 22 mmHg. In addition, ecadotril and alatriopril significantly increased the urinary excretion of sodium. In contrast, ACE inhibition with captopril decreased the excretion of sodium dose-dependently in conscious TGR. In conclusion, combined ACE/NEP inhibition produced a comparable lowering of blood pressure and improvement in renal function as those with NEP inhibition in TGR. Dual ACE/NEP inhibition may therefore be useful in cardiovascular conditions such as hypertension or heart failure.


Asunto(s)
Alanina/análogos & derivados , Inhibidores de la Enzima Convertidora de Angiotensina/administración & dosificación , Dioxoles/farmacología , Hipertensión/genética , Neprilisina/antagonistas & inhibidores , Renina/genética , Alanina/farmacología , Animales , Animales Modificados Genéticamente , Presión Sanguínea/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Expresión Génica , Hipertensión/metabolismo , Hipertensión/fisiopatología , Ratas , Renina/metabolismo
8.
Clin Exp Hypertens ; 17(6): 861-76, 1995 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-7581258

RESUMEN

Inhibition of important degradative pathways of atrial natriuretic peptide (ANP) in vivo could be a valuable therapeutic tool for regulating endogenous levels of ANP. The aim was to investigate the in vivo effects of both blockade of atrial natriuretic peptide clearance receptor and inhibition of neutral endopeptidase 24.11, an enzyme shown to be involved in ANP breakdown. Therefore, we infused a specific neutral endopeptidase inhibitor ((S)-thiorphan) and an ANP-C receptor ligand (AP 811) alone or in combination into anaesthetized beagle dogs. Compared with vehicle controls, coadministration of (S)-thiorphan and AP 811 (100 micrograms/kg/min and 10 micrograms/kg/min, resp.) had greater effects on endocrine and renal parameters than administration of either substance alone. Coadministration of both compounds increased urinary excretion of volume and sodium, cGMP and ANP. We found also increased plasma cGMP, plasma ANP and decreased plasma renin activity. No effects were observed with respect to blood pressure, left ventricular pressure or heart rate during the infusion period of 2 h. We conclude from these investigations, that blocking both degrading pathways of ANP with the ANP-C receptor ligand AP 811 and the neutral endopeptidase inhibitor (S)-thiorphan is more effective than inhibition of either system alone. Such a combination might therefore be a useful therapeutic tool in cardiovascular diseases.


Asunto(s)
Neprilisina/antagonistas & inhibidores , Oligopéptidos/farmacología , Inhibidores de Proteasas/farmacología , Receptores del Factor Natriurético Atrial/efectos de los fármacos , Tiorfan/farmacología , Animales , Factor Natriurético Atrial/sangre , Factor Natriurético Atrial/metabolismo , Factor Natriurético Atrial/orina , Enfermedades Cardiovasculares/tratamiento farmacológico , GMP Cíclico/sangre , Diuresis/efectos de los fármacos , Perros , Interacciones Farmacológicas , Femenino , Riñón/efectos de los fármacos , Riñón/metabolismo , Ligandos , Natriuresis/efectos de los fármacos , Oligopéptidos/administración & dosificación , Inhibidores de Proteasas/administración & dosificación , Receptores del Factor Natriurético Atrial/metabolismo , Renina/sangre , Tiorfan/administración & dosificación
9.
J Am Chem Soc ; 108(3): 512-4, 1986 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-22175475
10.
Z Lebensm Unters Forsch ; 163(1): 11-3, 1977.
Artículo en Alemán | MEDLINE | ID: mdl-835339

RESUMEN

A method is described which enables low molecular nitrosamines to be determined in plant material and mineral soils. The principle of this method is based on the steam volatility of these nitrosamines by means of which they can be isolated. Their detection and quantiative determination is then carried out by gas chromatography. The limit of detection in this method is 4 to 8 ppb fresh plant material or soil, the possible sample weigth in each case being decisive. The various species of plants or soils have no influence.


Asunto(s)
Nitrosaminas/análisis , Plantas/análisis , Contaminantes del Suelo/análisis , Carcinógenos , Cromatografía de Gases
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