Anti-phase locking in a two-dimensional Josephson junction array

We consider theoretically phase locking in a simple two-dimensional Josephson junction array consisting of two loops coupled via a joint line transverse to the bias current. Ring inductances are supposed to be small, and special emphasis is taken on the influence of external flux. Is is shown, that in the stable oscillation regime both cells oscillate with a phase shift equal to $\pi$ (i.e. anti-phase). This result may explain the low radiation output obtained so far in two-dimensional Josephson junction arrays experimentally.Comment: 11 pages, REVTeX, 1 Postscript figure, Subm. to Appl. Phys. Let

Sleep Diplomacy: an Approach to Boosting global brain health

Sleep diplomacy highlights the urgent need to address the widespread issue of sleep deprivation and its detrimental effects on overall health, particularly brain health and healthy ageing. By providing practical advice on sleep hygiene, healthy schedules, and light exposure, sleep diplomacy aims to promote a comprehensive approach to well-being. Despite the well-established importance of sleep for optimal cognitive function, emotional regulation, and physical abilities, it is often neglected in public and medical recommendations. Our proposed concept of sleep diplomacy also offers practical recommendations to address sleep issues in various settings and populations

Perioperative fluid overload increases anastomosis thrombosis in the free TRAM flap used for breast reconstruction

To increase perfusion pressure with vasoactive drugs may be in conflict with the opinion of the reconstructive surgeon who maintains that the systemic administration of vasoactive agents causes vasoconstriction of the pedicle artery and the microvasculature. In free flap surgery, deliberate fluid therapy is used with a minimum of vasoactive drugs. This retrospective study was performed to analyse the perioperative fluid therapy, its effect on hemodynamic parameters and on the outcome of free flap surgery. One hundred and four patients were included in this retrospective study. The muscle sparing free transverse rectus abdominis myocutaneous flap was used for breast reconstruction. Perioperative hemodynamic data was used for this study. Twenty-seven patients had one or two complications requiring return to the operating room (OR). Two cases returned to the OR because of postoperative bleeding; in 11 patients, the anastomosis was revised. The reason for surgery in the latter group was venous stasis, due to thrombus formation at the venous anastomosis. The volume of fluid therapy was significantly higher in patients who returned to the OR due to thrombus formation at the anastomosis. Based on the results of this study, restricted intravenous fluid therapy or guided fluid therapy is recommended. Invasive monitoring such as central venous pressure and invasive arterial monitoring is recommended. Fluid loss should be replaced, and fluid overload should be avoided when the breast is reconstructed using free-tissue transfers

27. New echocardiogram index alternatives to MAPSE and TAPSE z-scores in children

BackgroundMitral annular plane systolic excursion (MAPSE), and tricuspid annular plane systolic excursion (TAPSE) are relatively load independent longitudinal left ventricle (LV) and right ventricle (RV) measurement in both adults and children. Normal paediatric values of MAPSE and TAPSE unlike adults are based on inconvenient z-scores. We hypothesize novel indexes of (LSI) LV longitudinal systolic index and (RSI) RV longitudinal systolic index are BSA, age, gender independent and nullifies the need for MAPSE and TAPSE z-scores.MethodsNormal echocardiograms were retrospectively reviewed from 2009 to 2011. Ejection fraction, LV dimensions, MAPSE, and TAPSE were determined. LSI and RSI were calculated using MAPSE and TAPSE divided by LV length. Echocardiogram indices were correlated. Regression analysis was done for BSA, age, and gender.ResultsTwo hundred and one patients had normal ejection fractions (67.3;±5.1%). Mean MAPSE 10.4;±3.3mm, z-score −0.07;±1.2, and LSI 0.20;±0.03; Mean TAPSE 17.4;±5.4mm, z-score 0.74;±1.7, and RSI 0.34;±0.06. LSI and MAPSE z-scores correlated, r=0.73, p<0.001. Age, gender, and BSA did not correlate with LSI. RSI and TAPSE z-scores correlated with r=0.76, p<0.001. Age influences RSI, R2=0.58, p value <0.001, BSA and gender does not. RSI, with age stratification, is significantly decreased less than 2months.ConclusionLSI obviates need for-MAPSE z scores. RSI offers an additional non TAPSE z-score method to evaluate RV function, but does not nullify age effect. RSI, especially in the first two months is decreased

Theory of phase-locking in generalized hybrid Josephson junction arrays

A recently proposed scheme for the analytical treatment of the dynamics of two-dimensional hybrid Josephson junction arrays is extended to a class of generalized hybrid arrays with ''horizontal'' shunts involving a capacitive as well as an inductive component. This class of arrays is of special interest, because the internal cell coupling has been shown numerically to favor in-phase synchronization for certain parameter values. As a result, we derive limits on the circuit design parameters for realizing this state. In addition, we obtain formulas for the flux-dependent frequency including flux-induced switching processes between the in-phase and anti-phase oscillation regime. The treatment covers unloaded arrays as well as arrays shunted via an external load.Comment: 24 pages, REVTeX, 5 Postscript figures, Subm. to Phys. Rev.

Resonant-Cavity-Induced Phase Locking and Voltage Steps in a Josephson Array

We describe a simple dynamical model for an underdamped Josephson junction array coupled to a resonant cavity. From numerical solutions of the model in one dimension, we find that (i) current-voltage characteristics of the array have self-induced resonant steps (SIRS), (ii) at fixed disorder and coupling strength, the array locks into a coherent, periodic state above a critical number of active Josephson junctions, and (iii) when $N_a$ active junctions are synchronized on an SIRS, the energy emitted into the resonant cavity is quadratic with $N_a$. All three features are in agreement with a recent experiment [Barbara {\it et al}, Phys. Rev. Lett. {\bf 82}, 1963 (1999)]}.Comment: 4 pages, 3 eps figures included. Submitted to PRB Rapid Com

THEORY OF PHASE-LOCKING IN SMALL JOSEPHSON JUNCTION CELLS

Within the RSJ model, we performed a theoretical analysis of phase-locking in elementary strongly coupled Josephson junction cells. For this purpose, we developed a systematic method allowing the investigation of phase-locking in cells with small but non-vanishing loop inductance.The voltages across the junctions are found to be locked with very small phase difference for almost all values of external flux. However, the general behavior of phase-locking is found to be just contrary to that according to weak coupling. In case of strong coupling there is nearly no influence of external magnetic flux on the phases, but the locking-frequency becomes flux-dependent. The influence of parameter splitting is considered as well as the effect of small capacitive shunting of the junctions. Strongly coupled cells show synchronization even for large parameter splitting. Finally, a study of the behavior under external microwave radiation shows that the frequency locking-range becomes strongly flux-dependent, whereas the locking frequency itself turns out to be flux-independent.Comment: 26 pages, REVTEX, 9 PS figures appended in uuencoded form at the end, submitted to Phys. Rev. B

Sleep diplomacy alone will widen sleep disparities - Authors' reply.

Timothy Daly argues that preexisting sleep disparities according to socioeconomic status will make behavioural approaches and lifestyle advice widen sleep disparities. Although we fully agree that strong public policy measures must be implemented to reduce socioeconomic status inequalities in brain health,1 and in particular those that might impact sleep problems, there is good evidence reporting the success of behavioural interventions to improve sleep conditions in different populations.2 Specific interventions have been proposed in lowsocioeconomic status populations, which should also be included in our sleep diplomacy3 category.Fil: Golombek, Diego Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de San Andrés; ArgentinaFil: Booi, Laura. Trinity College; Irlanda. Leeds Beckett University; Reino UnidoFil: Campbell, Dominic. Trinity College; IrlandaFil: Dawson, Walter D.. Trinity College; Irlanda. University of California; Estados Unidos. Global Brain Health Institute; Estados Unidos. Oregon Health and Science University; Estados Unidos. Portland State University; Estados UnidosFil: Eyre, Harris. University of California; Estados Unidos. Rice University; Estados UnidosFil: Lawlor, Brian. Trinity College; IrlandaFil: Ibañez, Agustin Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de San Andrés; Argentina. Trinity College; Irlanda. University of California; Estados Unidos. Global Brain Health Institute; Estados Unidos. Universidad Adolfo Ibañez; Chil

Dynamics of a Josephson Array in a Resonant Cavity

We derive dynamical equations for a Josephson array coupled to a resonant cavity by applying the Heisenberg equations of motion to a model Hamiltonian described by us earlier [Phys. Rev. B {\bf 63}, 144522 (2001); Phys. Rev. B {\bf 64}, 179902 (E)]. By means of a canonical transformation, we also show that, in the absence of an applied current and dissipation, our model reduces to one described by Shnirman {\it et al} [Phys. Rev. Lett. {\bf 79}, 2371 (1997)] for coupled qubits, and that it corresponds to a capacitive coupling between the array and the cavity mode. From extensive numerical solutions of the model in one dimension, we find that the array locks into a coherent, periodic state above a critical number of active junctions, that the current-voltage characteristics of the array have self-induced resonant steps (SIRS's), that when $N_a$ active junctions are synchronized on a SIRS, the energy emitted into the resonant cavity is quadratic in $N_a$, and that when a fixed number of junctions is biased on a SIRS, the energy is linear in the input power. All these results are in agreement with recent experiments. By choosing the initial conditions carefully, we can drive the array into any of a variety of different integer SIRS's. We tentatively identify terms in the equations of motion which give rise to both the SIRS's and the coherence threshold. We also find higher-order integer SIRS's and fractional SIRS's in some simulations. We conclude that a resonant cavity can produce threshold behavior and SIRS's even in a one-dimensional array with appropriate experimental parameters, and that the experimental data, including the coherent emission, can be understood from classical equations of motion.Comment: 15 pages, 10 eps figures, submitted to Phys. Rev.

Full capacitance-matrix effects in driven Josephson-junction arrays

We study the dynamic response to external currents of periodic arrays of Josephson junctions, in a resistively capacitively shunted junction (RCSJ) model, including full capacitance-matrix effects}. We define and study three different models of the capacitance matrix $C_{\vec{r},\vec{r}'}$: Model A includes only mutual capacitances; Model B includes mutual and self capacitances, leading to exponential screening of the electrostatic fields; Model C includes a dense matrix $C_{\vec{r},\vec{r}'}$ that is constructed approximately from superposition of an exact analytic solution for the capacitance between two disks of finite radius and thickness. In the latter case the electrostatic fields decay algebraically. For comparison, we have also evaluated the full capacitance matrix using the MIT fastcap algorithm, good for small lattices, as well as a corresponding continuum effective-medium analytic evaluation of a finite voltage disk inside a zero-potential plane. In all cases the effective $C_{\vec{r},\vec{r}'}$ decays algebraically with distance, with different powers. We have then calculated current voltage characteristics for DC+AC currents for all models. We find that there are novel giant capacitive fractional steps in the I-V's for Models B and C, strongly dependent on the amount of screening involved. We find that these fractional steps are quantized in units inversely proportional to the lattice sizes and depend on the properties of $C_{\vec{r},\vec{r}'}$. We also show that the capacitive steps are not related to vortex oscillations but to localized screened phase-locking of a few rows in the lattice. The possible experimental relevance of these results is also discussed.Comment: 12 pages 18 Postscript figures, REVTEX style. Paper to appear in July 1, Vol. 58, Phys. Rev. B 1998 All PS figures include