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1.
Rev Sci Instrum ; 93(5): 055104, 2022 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-35649811

RESUMEN

Superconducting Radio Frequency (SRF) cavities used in particle accelerators are typically formed from or coated with superconducting materials. Currently, high purity niobium is the material of choice for SRF cavities that have been optimized to operate near their theoretical field limits. This brings about the need for significant R & D efforts to develop next generation superconducting materials that could outperform Nb and keep up with the demands of new accelerator facilities. To achieve high quality factors and accelerating gradients, the cavity material should be able to remain in the superconducting Meissner state under a high RF magnetic field without penetration of quantized magnetic vortices through the cavity wall. Therefore, the magnetic field at which vortices penetrate a superconductor is one of the key parameters of merit of SRF cavities. Techniques to measure the onset of magnetic field penetration on thin film samples need to be developed to mitigate the issues with the conventional magnetometry measurements that are strongly influenced by the film orientation and shape and edge effects. In this work, we report the development of an experimental setup to measure the field of full flux penetration through films and multi-layered superconductors. Our system combines a small superconducting solenoid that can generate a magnetic field of up to 500 mT at the sample surface and three Hall probes to detect the full flux penetration through the superconductor. This setup can be used to study alternative materials that could potentially outperform niobium, as well as superconductor-insulator-superconductor (SIS) multilayer coatings on niobium.

2.
Khirurgiia (Mosk) ; (10): 44-51, 2017.
Artículo en Ruso | MEDLINE | ID: mdl-29076481

RESUMEN

MATERIAL AND METHODS: For the period 2013-2016 four patients were treated at the Filatov Children's City Clinical Hospital #13. There were 2 children aged 14 years and 2 children aged 17 years. All patients have been diagnosed via anamnesis, complaints, pulse-wave doppler sonography, contrast-enhanced MDCT and angiography. After comprehensive examination 3 patients underwent laparoscopic decompression of celiac trunk. In all cases celiac trunk compression was predominantly caused by median arcuate ligament of the diaphragm combined with neurofibrotic tissue of celiac plexus. RESULTS: All patients were discharged after laparoscopic decompression of celiac trunk. Intra- and postoperative complications, as well as cases of conversion were absent. Mean time of surgery was 65 minutes. In all cases postoperative period was smooth (4 days on the average). Two patients underwent follow-up examination in long-term postoperative period: pulse-wave doppler sonography, contrast-enhanced MDCT and angiography. In both cases reduced severity, incidence and duration of pain syndrome were observed. CONCLUSION: Clinical examples show some problems in diagnosis and treatment of compressive stenosis of celiac trunk due to rarity of pathology especially in childhood. Nevertheless, combination of abdominal ischemia and celiac trunk stenosis confirmed by instrumental diagnosis is indication for surgical treatment.


Asunto(s)
Arteria Celíaca , Descompresión Quirúrgica/métodos , Laparoscopía/métodos , Síndrome del Ligamento Arcuato Medio , Adolescente , Cuidados Posteriores/métodos , Cuidados Posteriores/estadística & datos numéricos , Angiografía/métodos , Arteria Celíaca/diagnóstico por imagen , Arteria Celíaca/patología , Arteria Celíaca/cirugía , Femenino , Humanos , Efectos Adversos a Largo Plazo , Masculino , Síndrome del Ligamento Arcuato Medio/diagnóstico , Síndrome del Ligamento Arcuato Medio/cirugía , Evaluación de Procesos y Resultados en Atención de Salud , Federación de Rusia , Tomografía Computarizada por Rayos X/métodos , Ultrasonografía Doppler/métodos
3.
Nat Commun ; 8(1): 85, 2017 07 20.
Artículo en Inglés | MEDLINE | ID: mdl-28729642

RESUMEN

Quantized magnetic vortices driven by electric current determine key electromagnetic properties of superconductors. While the dynamic behavior of slow vortices has been thoroughly investigated, the physics of ultrafast vortices under strong currents remains largely unexplored. Here, we use a nanoscale scanning superconducting quantum interference device to image vortices penetrating into a superconducting Pb film at rates of tens of GHz and moving with velocities of up to tens of km/s, which are not only much larger than the speed of sound but also exceed the pair-breaking speed limit of superconducting condensate. These experiments reveal formation of mesoscopic vortex channels which undergo cascades of bifurcations as the current and magnetic field increase. Our numerical simulations predict metamorphosis of fast Abrikosov vortices into mixed Abrikosov-Josephson vortices at even higher velocities. This work offers an insight into the fundamental physics of dynamic vortex states of superconductors at high current densities, crucial for many applications.Ultrafast vortex dynamics driven by strong currents define eletromagnetic properties of superconductors, but it remains unexplored. Here, Embon et al. use a unique scanning microscopy technique to image steady-state penetration of super-fast vortices into a superconducting Pb film at rates of tens of GHz and velocities up to tens of km/s.

5.
Sci Rep ; 5: 7598, 2015 Jan 07.
Artículo en Inglés | MEDLINE | ID: mdl-25564043

RESUMEN

The dynamics of quantized magnetic vortices and their pinning by materials defects determine electromagnetic properties of superconductors, particularly their ability to carry non-dissipative currents. Despite recent advances in the understanding of the complex physics of vortex matter, the behavior of vortices driven by current through a multi-scale potential of the actual materials defects is still not well understood, mostly due to the scarcity of appropriate experimental tools capable of tracing vortex trajectories on nanometer scales. Using a novel scanning superconducting quantum interference microscope we report here an investigation of controlled dynamics of vortices in lead films with sub-Angstrom spatial resolution and unprecedented sensitivity. We measured, for the first time, the fundamental dependence of the elementary pinning force of multiple defects on the vortex displacement, revealing a far more complex behavior than has previously been recognized, including striking spring softening and broken-spring depinning, as well as spontaneous hysteretic switching between cellular vortex trajectories. Our results indicate the importance of thermal fluctuations even at 4.2 K and of the vital role of ripples in the pinning potential, giving new insights into the mechanisms of magnetic relaxation and electromagnetic response of superconductors.

6.
Urologiia ; (6): 93-97, 2015 Dec.
Artículo en Ruso | MEDLINE | ID: mdl-28247687

RESUMEN

Disorders of pelvic organs' evacuation function, manifested by difficulty in urination and constipation, in conjunction with incontinence, and childhood stool smearing is an urgent medical and social problem. The study presents results of treatment of 36 children (mean age 7,2 +/- 2,3 years) with non-neurogenic variants of pelvic organ dysfunction. The choice of treatment was based on an attempt to form managed urination. Indications to treatment were defined both by traditional methods, and by transperineal ultrasonography - the method developed by the authors. Increased rear urethrovesical angle at rest and during functional tests with retention and straining, the deviation of the bladder neck and urethra to sacrum, shortening of urethra and bladder neck, lack of bladder neck and urethra movement, or the inability to perform volitional exercises were seen as signs of pelvic floor paradoxical movements. Analysis of the results of clinical trials showed, that the method is a reliable, non-invasive and does not require expert class ultrasound equipment. The treatment consisted of biofeedback therapy sessions performed in outpatient settings. 25 children were found to have positive changes, 7 of them fully recovered from voiding dysfunction.


Asunto(s)
Biorretroalimentación Psicológica , Diafragma Pélvico , Trastornos Urinarios , Niño , Preescolar , Incontinencia Fecal/terapia , Humanos , Ultrasonografía , Enfermedades de la Vejiga Urinaria/terapia , Incontinencia Urinaria/terapia , Trastornos Urinarios/terapia
7.
Phys Rev Lett ; 113(8): 087001, 2014 Aug 22.
Artículo en Inglés | MEDLINE | ID: mdl-25192119

RESUMEN

A theory of dissipative nonlinear conductivity, σ(1)(ω,H), of s-wave superconductors under strong electromagnetic fields at low temperatures is proposed. Closed-form expressions for σ(1)(H) and the surface resistance R(s)(ω,H) are obtained in the nonequilibrium dirty limit for which σ(1)(H) has a significant minimum as a function of a low-frequency (hω ≪ k(B)T) magnetic field H. The calculated microwave suppression of R(s)(H) is in good agreement with recent experiments on alloyed Nb resonator cavities. It is shown that superimposed dc and ac fields, H = H(0) + H(a)cosωt, can be used to reduce ac dissipation in thin film nanostructures by tuning σ(1)(H(0)) with the dc field.

8.
Phys Rev Lett ; 111(16): 165001, 2013 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-24182272

RESUMEN

The results of simultaneous radio and gamma emission measurements during thunderstorms are presented. A gamma detector situated at the height 3840 m and two radio detectors of Tien-Shan Mountain Scientific Station (altitude 3340 m) registered intensive gamma flashes and radio pulses during the time of lightning initiation. The radio-gamma correlation grows abruptly at the initial moment (a few hundred microseconds), and the correlation coefficient reaches 0.9-0.95. The gamma-energy spectrum measured during lightning initiation is close to the characteristic spectrum of runaway breakdown. Radio pulses observed at the same time have highest amplitudes. Combined observation of gamma and radio emissions confirm the conception of lightning initiation due to multiple simultaneous electric discharges at hydrometeors stimulated and synchronized by low-energy electrons generated in the runaway breakdown process.

10.
Phys Rev Lett ; 110(18): 185005, 2013 May 03.
Artículo en Inglés | MEDLINE | ID: mdl-23683210

RESUMEN

The particular electric pulse discharges are observed in thunderclouds during the initiation stage of negative cloud-to-ground lightning. The discharges are quite different from conventional streamers or leaders. A detailed analysis reveals that the shape of the pulses is determined by the runaway breakdown of air in the thundercloud electric field initiated by extensive atmospheric showers (RB-EAS). The high amplitude of the pulse electric current is due to the multiple microdischarges at hydrometeors stimulated and synchronized by the low-energy electrons generated in the RB-EAS process. The series of specific pulse discharges leads to charge reset from hydrometeors to the free ions and creates numerous stretched ion clusters, both positive and negative. As a result, a wide region in the thundercloud with a sufficiently high fractal ion conductivity is formed. The charge transport by ions plays a decisive role in the lightning leader preconditioning.

11.
Phys Rev Lett ; 109(8): 085002, 2012 Aug 24.
Artículo en Inglés | MEDLINE | ID: mdl-23002751

RESUMEN

The generation of an avalanche of runaway electrons is demonstrated for the first time in a laboratory experiment. Two flows of runaway electrons are formed sequentially in an extended air discharge gap at the stage of delay of a pulsed breakdown. The first, picosecond, runaway electron flow is emitted in the cathode region where the field is enhanced. Being accelerated in the gap, this beam generates electrons due to impact ionization. These secondary electrons form a delayed avalanche of runaway electrons if the field is strong enough. The properties of the avalanche correspond to the existing notions about the runaway breakdown in air. The measured current of the avalanche exceeds up to an order the current of the initiating electron beam.

12.
J Nutr Health Aging ; 16(6): 557-61, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-22659997

RESUMEN

Atypical antipsychotics seem to be preferable than conventional agents in treating psychological symptoms of dementia (BPSD), because they have substantially lower risks of extrapyramidal neurological effects with lower reported rates of parkinsonism and tardive dyskinesia. However, in the course of time, with the increase in their use, more and more side effects have been reported. The benefits and risks of antipsychotic treatment should be carefully evaluated according to the co-morbidity and the severity of the psychological and behavioral symptoms and their impact on the individual elderly patient. It is recommended to keep those medications in the lower range of therapeutic doses. Due to the complexity of the individual patient, no guidelines have been yet established. Therefore, clinical judgment should be used in applying the dose and the type of those drugs.


Asunto(s)
Envejecimiento , Antipsicóticos/efectos adversos , Síntomas Conductuales/tratamiento farmacológico , Demencia/tratamiento farmacológico , Anciano , Anciano de 80 o más Años , Acatisia Inducida por Medicamentos/prevención & control , Antipsicóticos/administración & dosificación , Antipsicóticos/uso terapéutico , Demencia/psicología , Monitoreo de Drogas , Tractos Extrapiramidales/efectos de los fármacos , Femenino , Humanos , Masculino , Neuronas/efectos de los fármacos , Enfermedad de Parkinson Secundaria/inducido químicamente , Enfermedad de Parkinson Secundaria/prevención & control
13.
Phys Rev Lett ; 108(12): 125001, 2012 Mar 23.
Artículo en Inglés | MEDLINE | ID: mdl-22540588

RESUMEN

We report here for the first time about the registration of an extraordinary high flux of low-energy neutrons generated during thunderstorms. The measured neutron count rate enhancements are directly connected with thunderstorm discharges. The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm: the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed.

14.
Nanotechnology ; 22(36): 365707, 2011 Sep 07.
Artículo en Inglés | MEDLINE | ID: mdl-21844640

RESUMEN

The existence of intrinsic carrier interface states in heterostructures with no common atom at the interface (such as ZnSe/BeTe) is shown experimentally by ellipsometry and photoluminescence spectroscopy. These states are located on interfaces and lie inside the effective bandgap of the structure; they are characterized by a high density and a long lifetime. A tight binding model confirms theoretically the existence of these states in ZnSe/BeTe heterostructures for a ZnTe-type interface, in contrast to the case of the BeSe-type interface for which they do not exist.

15.
Arkh Patol ; 73(2): 14-7, 2011.
Artículo en Ruso | MEDLINE | ID: mdl-21695982

RESUMEN

The data of renal ultrasonographic and Doppler studies were comparatively assessed in children with congenital hydronephrosis. The degree of renal B-mode ultrasound hemodynamic parameters was used as the basis for grouping of the children. The resistance index (RI) of all branches of renal arteries receives attention. Morphological studies were carried out on renal biopsy specimens from 29 children from different groups and on 12 removed kidneys; the expression of TGF beta1 and alphaSMA was revealed using the streptavidin-biotin-peroxidase method. Morphological changes as hypoplasia or dysplasia became more pronounced from Group 1 to Group 3, RI increasing to peak in Group 3. Vascular changes were confined to compensatory processes following the pattern of remodeling that was manifested by vascular wall thickening and a gradual increase in RI. Failing compensatory processes resulted in the development of renal functional and hormonal decompensation and in the elevation of RI. There was a coupling between the magnitude of morphological changes and RI increases. A set of the findings emphasizes the undoubtedly important role of renal ultrasound study that makes it possible to judge the state of the vascular bed and to suggest renal structural problems in congenital hydronephrosis.


Asunto(s)
Hemodinámica , Hidronefrosis/patología , Hidronefrosis/fisiopatología , Riñón/patología , Riñón/fisiopatología , Niño , Preescolar , Humanos , Hidronefrosis/diagnóstico por imagen , Lactante , Riñón/diagnóstico por imagen , Arteria Renal/diagnóstico por imagen , Arteria Renal/patología , Ultrasonografía Doppler Dúplex
16.
Phys Rev Lett ; 104(8): 087002, 2010 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-20366959

RESUMEN

We report the effect of alpha-particle irradiation on the reduction of the critical temperature T{c} of a NdFeAs(OF) single crystal. Our data indicate that irradiation defects cause both nonmagnetic and magnetic scattering, resulting in the Kondo-like excess resistance Delta rho(T) proportional to lnT over 2 decades in temperatures above T{c}. The critical density of magnetic irradiation defects which suppresses T{c} is found to be much higher than those for cuprates and multiband BCS superconductors. We suggest that such anomalously weak pair breaking by irradiation defects indicates that magnetic scattering in pnictides is coupled with pairing interactions mediated by spin fluctuations.

17.
Phys Rev Lett ; 100(22): 227007, 2008 Jun 06.
Artículo en Inglés | MEDLINE | ID: mdl-18643452

RESUMEN

We show that the size effects radically affect the electric-field-current (E-I) relation of superconducting films. We calculate E(J) due to thermally activated hopping of single vortices driven by a current I across the film in a magnetic field H, taking into account the interaction of free vortices with their antivortex images and peaks in the Meissner currents at the film edges. The unbinding of the virtual vortex-antivortex pairs not only mimics the transport uniform Berezinskii-Kosterlitz-Thouless behavior, it can also dominate the observed E(J) and result in the field-dependent Ohmic resistance at small I. We show that E(I) can be tuned by changing the film geometry and propose experimental tests of this theory.

18.
Phys Rev Lett ; 100(17): 174504, 2008 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-18518297

RESUMEN

The Lagrangian velocity structure functions in the inertial range of fully developed fluid turbulence are for the first time derived based on the Navier-Stokes equation. For time tau much smaller than the correlation time, the structure functions are shown to obey the scaling relations K_{n}(tau) proportional, varianttau;{zeta_{n}}. The scaling exponents zeta_{n} are calculated analytically without any fitting parameters. The obtained values are in amazing agreement with the experimental results of the Bodenschatz group. A new relation connecting the Lagrangian structure functions of different orders analogously to the extended self-similarity ansatz is found.

19.
Nature ; 453(7197): 903-5, 2008 Jun 12.
Artículo en Inglés | MEDLINE | ID: mdl-18509332

RESUMEN

The recent synthesis of the superconductor LaFeAsO(0.89)F(0.11) with transition temperature T(c) approximately 26 K (refs 1-4) has been quickly followed by reports of even higher transition temperatures in related compounds: 41 K in CeFeAsO(0.84)F(0.16) (ref. 5), 43 K in SmFeAsO(0.9)F(0.1) (ref. 6), and 52 K in NdFeAsO(0.89)F(0.11) and PrFeAsO(0.89)F(0.11) (refs 7, 8). These discoveries have generated much interest in the mechanisms and manifestations of unconventional superconductivity in the family of doped quaternary layered oxypnictides LnOTMPn (Ln: La, Pr, Ce, Sm; TM: Mn, Fe, Co, Ni; Pn: P, As), because many features of these materials set them apart from other known superconductors. Here we report resistance measurements of LaFeAsO(0.89)F(0.11) at high magnetic fields, up to 45 T, that show a remarkable enhancement of the upper critical field B(c2) compared to values expected from the slopes dB(c2)/dT approximately 2 T K(-1) near T(c), particularly at low temperatures where the deduced B(c2)(0) approximately 63-65 T exceeds the paramagnetic limit. We argue that oxypnictides represent a new class of high-field superconductors with B(c2) values surpassing those of Nb(3)Sn, MgB(2) and the Chevrel phases, and perhaps exceeding the 100 T magnetic field benchmark of the high-T(c) copper oxides.

20.
Bioorg Khim ; 33(2): 245-50, 2007.
Artículo en Ruso | MEDLINE | ID: mdl-17476985

RESUMEN

An artificial gene encoding oxyntomodulin was obtained using chemical and enzymatic methods and cloned into Escherichia coli. A recombinant plasmid was constructed containing a hybrid oxyntomodulin gene and Ssp dnaB intein from Synechocystis sp. The expression of the resulting hybrid gene in E. coli, its properties, and the conditions of its autocatalytic cleavage to oxyntomodulin were studied.


Asunto(s)
Oxintomodulina/biosíntesis , Proteínas Recombinantes/biosíntesis , Secuencia de Aminoácidos , Catálisis , AdnB Helicasas/biosíntesis , AdnB Helicasas/genética , Escherichia coli/genética , Inteínas/genética , Datos de Secuencia Molecular , Mutación , Oxintomodulina/genética , Oxintomodulina/aislamiento & purificación , Plásmidos/química , Plásmidos/genética , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/aislamiento & purificación , Proteínas Recombinantes/genética , Proteínas Recombinantes/aislamiento & purificación , Synechocystis/enzimología , Synechocystis/genética
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