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1.
Phys Rev Lett ; 126(8): 080603, 2021 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-33709732

RESUMO

We introduce and realize demons that follow a customary gambling strategy to stop a nonequilibrium process at stochastic times. We derive second-law-like inequalities for the average work done in the presence of gambling, and universal stopping-time fluctuation relations for classical and quantum nonstationary stochastic processes. We test experimentally our results in a single-electron box, where an electrostatic potential drives the dynamics of individual electrons tunneling into a metallic island. We also discuss the role of coherence in gambling demons measuring quantum jump trajectories.

2.
Phys Rev E ; 102(3-1): 030102, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33075879

RESUMO

Heat flow management at the nanoscale is of great importance for emergent quantum technologies. For instance, a thermal sink that can be activated on-demand is a highly desirable tool that may accommodate the need to evacuate excess heat at chosen times, e.g., to maintain cryogenic temperatures or reset a quantum system to ground, and the possibility of controlled unitary evolution otherwise. Here we propose a design of such heat switch based on a single coherently driven qubit. We show that the heat flow provided by a hot source to the qubit can be switched on and off by varying external parameters, the frequency and the intensity of the driving. The complete suppression of the heat flow is a quantum effect occurring for specific driving parameters that we express and we analyze the role of the coherences in the free-qubit energy eigenbasis. We finally study the feasibility of this quantum heat switch in a circuit QED setup involving a charge qubit coupled to thermal resistances. We demonstrate robustness to experimental imperfections such as additional decoherence, paving the road towards experimental verification of this effect.

3.
Nat Commun ; 11(1): 4326, 2020 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-32859939

RESUMO

Heat is detrimental for the operation of quantum systems, yet it fundamentally behaves according to quantum mechanics, being phase coherent and universally quantum-limited regardless of its carriers. Due to their robustness, superconducting circuits integrating dissipative elements are ideal candidates to emulate many-body phenomena in quantum heat transport, hitherto scarcely explored experimentally. However, their ability to tackle the underlying full physical richness is severely hindered by the exclusive use of a magnetic flux as a control parameter and requires complementary approaches. Here, we introduce a dual, magnetic field-free circuit where charge quantization in a superconducting island enables thorough electric field control. We thus tune the thermal conductance, close to its quantum limit, of a single photonic channel between two mesoscopic reservoirs. We observe heat flow oscillations originating from the competition between Cooper-pair tunnelling and Coulomb repulsion in the island, well captured by a simple model. Our results highlight the consequences of charge-phase conjugation on heat transport, with promising applications in thermal management of quantum devices and design of microbolometers.

4.
Phys Rev Lett ; 122(15): 150604, 2019 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-31050528

RESUMO

We experimentally realize protocols that allow us to extract work beyond the free energy difference from a single-electron transistor at the single thermodynamic trajectory level. With two carefully designed out-of-equilibrium driving cycles featuring kicks of the control parameter, we demonstrate work extraction up to large fractions of k_{B}T or with probabilities substantially greater than 1/2, despite the zero free energy difference over the cycle. Our results are explained in the framework of nonequilibrium fluctuation relations. We thus show that irreversibility can be used as a resource for optimal work extraction even in the absence of feedback from an external operator.

5.
ACS Nano ; 12(6): 5753-5760, 2018 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-29733575

RESUMO

Advances in nanomechanics within recent years have demonstrated an always expanding range of devices, from top-down structures to appealing bottom-up MoS2 and graphene membranes, used for both sensing and component-oriented applications. One of the main concerns in all of these devices is frequency noise, which ultimately limits their applicability. This issue has attracted a lot of attention recently, and the origin of this noise remains elusive to date. In this article we present a very simple technique to measure frequency noise in nonlinear mechanical devices, based on the presence of bistability. It is illustrated on silicon-nitride high-stress doubly clamped beams, in a cryogenic environment. We report on the same T/ f dependence of the frequency noise power spectra as reported in the literature. But we also find unexpected damping fluctuations, amplified in the vicinity of the bifurcation points; this effect is clearly distinct from already reported nonlinear dephasing and poses a fundamental limit on the measurement of bifurcation frequencies. The technique is further applied to the measurement of frequency noise as a function of mode number, within the same device. The relative frequency noise for the fundamental flexure δ f/ f0 lies in the range 0.5-0.01 ppm (consistent with the literature for cryogenic MHz devices) and decreases with mode number in the range studied. The technique can be applied to any type of nanomechanical structure, enabling progress toward the understanding of intrinsic sources of noise in these devices.

6.
BJU Int ; 119(6): 942-947, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28083998

RESUMO

OBJECTIVES: To evaluate the outcomes of hypospadias surgery according to age and to determine if some complications are age-related. PATIENTS AND METHODS: This retrospective study was based on 722 boys with hypospadias undergoing primary repair. A total of 501 boys underwent urethroplasty and were included in the study. Complications requiring an additional procedure (stenosis, fistula, dehiscence, relapse of curvature, urethrocele) were included in the analysis, as well as healing problems, infections, haematomas and detrusor-sphincter dyssynergy. Logistic regression analysis was performed. RESULTS: Hypospadias was anterior in 63.1%, mid-penile in 20.5%, posterior in 8.4% and scrotal in 7.9% of the boys. The median (range) age was 4 (1-16) years. The overall rates of re-intervention and complications were 22.8% and 36.2%, respectively. Age >2 years was a significant predictor of complications (P = 0.002, odds ratio 1.98 [95% confidence interval 1.26-3.13]). Some periods of time appeared to be associated with a specific complication: dyssynergy was more common between the ages of 24 and 36 months (12.5 vs 3.6%; P = 0.01) and healing problems were more common in boys aged >13 years (1.5 vs 28.5%; P = 0.06). CONCLUSION: Delayed surgery may be detrimental for patients. Factors related to age may influence the rate of complications. After the age of 2 years, urethral surgery may interfere with the normal toilet-training process. During puberty, endogenous testosterone may alter healing. Even if no specific data exist for severe hypospadias, it may be prudent to continue to advocate early surgery in patients with disorders of sex development.


Assuntos
Hipospadia/cirurgia , Adolescente , Fatores Etários , Criança , Pré-Escolar , Humanos , Lactente , Masculino , Complicações Pós-Operatórias/epidemiologia , Estudos Retrospectivos , Medição de Risco , Resultado do Tratamento , Uretra/cirurgia , Procedimentos Cirúrgicos Urológicos Masculinos/métodos
7.
J Cutan Pathol ; 43(8): 697-701, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27080330

RESUMO

Eccrine nevi are rare hamartomas characterized by an increase in the number or size of eccrine glands. A polypoid form located in the coccygeal area has been described in a few cases and termed coccygeal polypoid eccrine nevus (CPEN). No association with internal malformations was reported in any of these cases. We describe herein a case of CPEN associated with imperforate anus and unilateral multicystic kidney dysplasia. We review the clinical and pathological characteristics of CPENs and discuss the differential diagnoses.


Assuntos
Anormalidades Múltiplas/patologia , Anus Imperfurado/complicações , Glândulas Écrinas/patologia , Hamartoma/patologia , Rim Displásico Multicístico/complicações , Feminino , Hamartoma/complicações , Humanos , Lactente , Região Sacrococcígea
8.
J Pediatr Surg ; 49(9): 1419-23, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25148751

RESUMO

OBJECTIVE: Bilateral surgery has been largely advocated in premature boys with unilateral inguinal hernia owing to the high incidence of contralateral patent processus vaginalis. Recently, the potential morbidity of herniotomy in low birth-weight babies and the progress in pediatric anesthesia questioned this attitude. This study aims to evaluate the incidence of contralateral metachronous hernia in a large series of premature boys and to compare the morbidity of preventive versus elective surgery. METHODS: This retrospective multicenter analysis of 964 premature boys presenting with unilateral inguinal hernia operated from 1998 to 2012 included 557 infants who benefited from a unilateral herniotomy and 407 from a bilateral herniotomy (median follow-up 12months). RESULTS: Contralateral metachronous hernia after unilateral surgery occurred in 11% (n=60) without significant difference according to the initial symptomatic side (9.5% on right vs 13% on left, p>0.05). Postoperative morbidity on the contralateral side was higher after preventive surgery than elective surgery with metachronous hernia (2.45% versus 0.9%, p=0.05) especially for secondary cryptorchidism (1% vs 0%, p=0.03). Despite the risk of metachronous incarcerated hernia, elective surgery did not increase the rate of testicular hypotrophy on the opposite side (0.7%, vs 0.7%, p>0.05). CONCLUSION: Systematic bilateral herniotomy is unnecessary in almost 90% of patients and has a significant morbidity. Secondary surgery for metachronous hernia does not increase the risk of testicular lesion and even reduces the risk of secondary cryptorchidism. These results, along with the risk of hypofertility reported after bilateral surgery, may justify treating only the symptomatic side in premature boys.


Assuntos
Hérnia Inguinal/cirurgia , Herniorrafia/métodos , Seguimentos , Idade Gestacional , Hérnia Inguinal/embriologia , Hérnia Inguinal/patologia , Herniorrafia/efeitos adversos , Humanos , Lactente , Recém-Nascido de Baixo Peso , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Estudos Retrospectivos , Fatores de Risco
9.
J Pediatr Surg ; 47(8): e21-3, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22901938

RESUMO

Mesoblastic nephroma is by far the most frequent intrarenal fetal tumor. To the best of our knowledge, we report the first case of a newborn with an intrarenal neuroblastoma that was discovered prenatally. An intrarenal echogenic and homogenous mass was observed on routine prenatal ultrasonography, corroborated by magnetic resonance imaging, in a 30-week gestation fetus. A male weighing 3280 g was born with elevated blood pressure and cardiac failure. Postnatal ultrasound confirmed a left intrarenal tumor with microcalcifications and perirenal adenopathy. An open total left nephrectomy by laparotomy was performed. The pathologic study reported that the mass was an intrarenal neuroblastoma with local and regional invasion. Immediate postoperative urine analysis revealed a high level of vanillylmandelic acid, and blood samples showed high levels of normetanephrine. The purpose of this report is to demonstrate that prenatal intrarenal neuroblastoma can clinically and radiologically mimick a mesoblastic nephroma. High blood pressure, calcifications, and lymphadenopathy on ultrasound should raise the index of suspicion for a possible malignant process. Preoperative measurement of urinary vanillylmandelic acid (VMA) and metanephrines should be performed if the diagnosis is in doubt.


Assuntos
Erros de Diagnóstico , Neoplasias Renais/embriologia , Nefroma Mesoblástico/diagnóstico , Neuroblastoma/embriologia , Ultrassonografia Pré-Natal , Biomarcadores Tumorais/urina , Calcinose/congênito , Calcinose/etiologia , Cesárea , Insuficiência Cardíaca/congênito , Insuficiência Cardíaca/etiologia , Humanos , Hipertensão Renal/congênito , Hipertensão Renal/etiologia , Recém-Nascido , Neoplasias Renais/complicações , Neoplasias Renais/diagnóstico por imagem , Neoplasias Renais/patologia , Neoplasias Renais/cirurgia , Neoplasias Renais/urina , Neoplasias Hepáticas/secundário , Imageamento por Ressonância Magnética , Masculino , Nefrectomia , Neuroblastoma/complicações , Neuroblastoma/diagnóstico por imagem , Neuroblastoma/patologia , Neuroblastoma/secundário , Neuroblastoma/cirurgia , Neuroblastoma/urina , Normetanefrina/urina , Ácido Vanilmandélico/urina
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