Measuring the variability of local characteristics in complex networks: Empirical and analytical analysis

We examine the dynamics for the average degree of a node's neighbors in complex networks. It is a Markov stochastic process, and at each moment of time, this quantity takes on its values in accordance with some probability distribution. We are interested in some characteristics of this distribution: its expectation and its variance, as well as its coefficient of variation. First, we look at several real communities to understand how these values change over time in social networks. The empirical analysis of the behavior of these quantities for real networks shows that the coefficient of variation remains at high level as the network grows. This means that the standard deviation and the mean degree of the neighbors are comparable. Then, we examine the evolution of these three quantities over time for networks obtained as simulations of one of the well-known varieties of the Barabási-Albert model, the growth model with nonlinear preferential attachment (NPA) and a fixed number of attached links at each iteration. We analytically show that the coefficient of variation for the average degree of a node's neighbors tends to zero in such networks (albeit very slowly). Thus, we establish that the behavior of the average degree of neighbors in Barabási-Albert networks differs from its behavior in real networks. In this regard, we propose a model based on the NPA mechanism with the rule of random number of edges added at each iteration in which the dynamics of the average degree of neighbors is comparable to its dynamics in real networks.

Theory of Magnetic Domain Phases in Ferromagnetic Superconductors

Recently discovered superconducting P-doped EuFe_{2}As_{2} compounds reveal the situation when the superconducting critical temperature substantially exceeds the ferromagnetic transition temperature. The main mechanism of the interplay between magnetism and superconductivity occurs to be an electromagnetic one, and a short-period magnetic domain structure was observed just below Curie temperature [V. S. Stolyarov et al., Sci. Adv. 4, eaat1061 (2018)SACDAF2375-254810.1126/sciadv.aat1061]. We elaborate a theory of such a transition and demonstrate how the initial sinusoidal magnetic structure gradually transforms into a solitonlike domain one. Further cooling may trigger a first-order transition from the short-period domain Meissner phase to the self-induced ferromagnetic vortex state, and we calculate the parameters of this transition. The size of the domains in the vortex state is basically the same as in the normal ferromagnet, but with the domain walls which should generate the set of vortices perpendicular to the vortices in the domains.

Towards wormhole beyond Horndeski

We address the issue of whether a no-go theorem for static, spherically symmetric wormholes, proven in Horndeski theories, can be circumvented by going beyond Horndeski. We show that the ghost instabilities which are at the heart of the no-go theorem, can indeed be avoided. The wormhole solutions with the latter property are, however, strongly fine tuned, and hence it is likely that they are unstable. Furthermore, it remains unclear whether these solutions have other pathologies, like gradient instabilities along angular and radial directions.

Cosmological bounce in Horndeski theory and beyond

We discuss the stability of the classical bouncing solutions in the general Horndeski theory and beyond Horndeski theory. We restate the no-go theorem, showing that in the general Horndeski theory there are no spatially flat non-singular cosmological solutions which are stable during entire evolution. We show the way to evade the no-go in beyond Horndeski theory and give two specific examples of bouncing solutions, whose asymptotic past and future or both are described by General Relativity (GR) with a conventional massless scalar field. Both solutions are free of any pathologies at all times.

From a reversible code to the quantum one: R-matrix

This research has been carried out in collaboration with D.Melnikov, A.Mironov, A.Morozov and An.Morozov. We study the relation between quantum programming and knot theory. The general idea is that knot theory provides a special basis for unitary matrices. We suggest to use R-matrices of knot theory as universal gates in quantum code. We also examine basic operations in reversible programming.

Spontaneous Currents in Superconducting Systems with Strong Spin-Orbit Coupling

We show that Rashba spin-orbit coupling at the interface between a superconductor and a ferromagnet should produce a spontaneous current in the atomic thickness region near the interface. This current is counterbalanced by the superconducting screening current flowing in the region of the width of the London penetration depth near the interface. Such a current-carrying state creates a magnetic field near the superconductor surface, generates a stray magnetic field outside the sample edges, changes the slope of the temperature dependence of the critical field H_{c3}, and may generate the spontaneous Abrikosov vortices near the interface.

Ventricular remodelling in rabbits with sustained high-fat diet

AIM

Excess weight gain and obesity are one of the most serious health problems in the western societies. These conditions enhance risk of cardiac disease and have been linked with increased prevalence for cardiac arrhythmias and sudden death. Our goal was to study the ventricular remodelling occurring in rabbits fed with high-fat diet (HFD) and its potential arrhythmogenic mechanisms.

METHODS

We used 15 NZW rabbits that were randomly assigned to a control (n = 7) or HFD group (n = 8) for 18 weeks. In vivo studies included blood glucose, electrocardiographic, and echocardiographic measurements. Optical mapping was performed in Langendorff-perfused isolated hearts.

RESULTS

Body weight (3.69 ± 0.31 vs. 2.94 ± 0.18 kg, P < 0.001) and blood glucose levels (230 ± 61 vs. 141 ± 14 mg dL(-1) , P < 0.05) were higher in the HFD group vs. controls. The rate-corrected QT interval and its dispersion were increased in HFD rabbits vs. controls (169 ± 10 vs. 146 ± 13 ms and 37 ± 11 vs. 9 ± 2 ms, respectively; P < 0.05). Echocardiographic analysis showed morphological and functional alterations in HFD rabbits indicative of left ventricle (LV) hypertrophy. Isolated heart studies revealed no changes in repolarization and propagation properties under conditions of normal extracellular K(+) , suggesting that extrinsic factors could underlie those electrocardiographic modifications. There were no differences in the dynamics of ventricular fibrillation (frequency, wave breaks) in the presence of isoproterenol. However, HFD rabbits showed a small reduction in action potential duration and an increased incidence of arrhythmias during hyperkalaemia.

CONCLUSION

High-fat feeding during 18 weeks in rabbits induced a type II diabetes phenotype, LV hypertrophy, abnormalities in repolarization and susceptibility to arrhythmias during hyperkalaemia.

Vanishing Meissner effect as a hallmark of in-plane Fulde-Ferrell-Larkin-Ovchinnikov instability in superconductor-ferromagnet layered systems

We demonstrate that in a wide class of multilayered superconductor-ferromagnet structures (e.g., S/F, S/F/N, and S/F/F') the vanishing Meissner effect signals the appearance of the in-plane Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulated superconducting phase. In contrast to the bulk superconductors the FFLO instability in these systems can emerge at temperatures close to the critical one and is effectively controlled by the S layer thickness and the angle between magnetization vectors in the F/F' bilayers. The predicted FFLO state is revealed through the critical temperature oscillations vs the perpendicular magnetic field component.

The prognostic significance of supradiaphragmatic lymphadenopathy identified on preoperative computed tomography scan in patients undergoing primary cytoreduction for advanced stage epithelial ovarian cancer

e16512

Background: It has been hypothesized and shown in animal studies that the supradiaphragmatic lymph nodes serve as the principal nodes for lymphatic drainage of the entire peritoneal cavity. The purpose of this study was to determine the prognostic significance of enlarged supra-diaphragmatic nodes noted on preoperative computed tomography (CT) scan in patients with advanced epithelial ovarian cancer (EOC). Methods: We performed a retrospective chart review of all patients (pts) with FIGO stage III and IV EOC who had preoperative CT scans of the supradiaphragmatic region and primary cytoreductive surgery at our institution between 1997 and 2004. All scans were retrospectively reviewed by one board-certified radiologist (SM). To evaluate survival, Kaplan-Meier methods were used, with log rank Pvalues for comparisons. Results: A total of 212 eligible pts who underwent attempted primary cytoreduction followed by platinum-based systemic chemotherapy were identified for evaluation. With a median follow-up time of 52 mos, there were 135 deaths and a median overall survival of 48 mos (95% CI: 44–53). Of the 212 pts, 44 (21%) had supradiaphragmatic adenopathy with nodes >1 cm, while 168 (79%) did not have adenopathy in this distribution. None of the 44 pts with adenopathy had the enlarged nodes removed at primary cytoreduction. The median survival was 49 mos for pts with and 48 mos for patients without adenopathy (p = 0.46). In total, 155 (73%) patients underwent optimal cytoreduction (residual disease ≤ 1 cm). In the optimally cytoreduced pts, the median survival for the 125 pts without supradiaphragmatic adenopathy was 52 mos (95%CI: 45–59) compared to 51mos (95%CI: 41–58) for the 30 pts with supradiaphragmatic adenopathy (p = 0.33). Conclusions: Although a previous study has shown that supradiaphragmatic adenopathy was associated with poorer overall survival in EOC patients, our study did not confirm these findings. In our study, enlarged supradiaphragmatic nodes noted on preoperative CT scan did not have significant prognostic impact and therefore their clinical significance remains uncertain.

No significant financial relationships to disclose.

Superfluid-helium converter for accumulation and extraction of ultracold neutrons

We report the first successful extraction of accumulated ultracold neutrons (UCN) from a converter of superfluid helium, in which they were produced by downscattering neutrons of a cold beam from the Munich research reactor. Windowless UCN extraction is performed in vertical direction through a mechanical cold valve. This prototype of a versatile UCN source is comprised of a novel cryostat designed to keep the source portable and to allow for rapid cooldown. We measured time constants for UCN storage and extraction into a detector at room temperature, with the converter held at various temperatures between 0.7 and 1.3 K. The UCN production rate inferred from the count rate of extracted UCN is close to the theoretical expectation.

Prospective trial of ifosfamide, paclitaxel, and cisplatin (ITP) in patients with advanced non-transitional cell (non-TCC) carcinomas of the urothelial tract

4542

Background: Non-TCC’s account for 5–10% of urothelial tract tumors and are each characterized by unique demographics, risk factors, and patterns of spread. A unifying feature of these malignancies is their aggressive course and poor outcomes with standard chemotherapeutic regimens. Given the rarity of these tumors, no prospective data are available to guide management. Methods: Patients with unresectable/metastatic adenocarcinoma, squamous cell, small cell, sarcomatoid, and poorly differentiated carcinomas of the urothelial tract were eligible. Treatment consisted of: Paclitaxel 200 mg/m2 IV on day 1, cisplatin 70 mg/m2 IV on day 1, ifosfamide 1500 mg/m2 IV on days 1–3 + mesna. GCSF was administered with each cycle. Treatment was recycled every 3 weeks for a maximum of 6 cycles. The primary endpoint was the response rate. Results: Twenty patients (pts) were enrolled with the following histologic types: adenocarcinoma 11/20, squamous cell carcinoma 8/20, small cell carcinoma 1/20. Pts received a median of 4 cycles (range, 1–6). The grade 3–4 toxicities included neutropenia (6/20), anemia (9/20), thrombocytopenia (4/20), confusion (1/20), seizure (1/20), neuropathy (1/20), renal insufficiency (2/20), fatigue (2/20), and hyponatremia (1/20). Thirteen of the 20 pts have died. The median survival for pts with adenocarcinoma is 24 months (95% CI 9.6–32.4) and with squamous cell carcinoma is 8.4 months (95% CI 5.3-NR). Five pts achieved durable disease-free survival (1+, 2+, 4+, 6+, and 8+ years) after ITP ± surgical consolidation. Conclusions: ITP is an active regimen in pts with advanced non-TCC’s of the urothelial tract. To our knowledge, this is the first prospective study of a chemotherapeutic regimen in this patient population.

[Table: see text]

[Table: see text]

Significance of non-calcified pulmonary nodules in patients with extrapulmonary cancers

BACKGROUND

This study sought to determine the rate and patterns of malignancy in patients with extrapulmonary cancers and non-calcified pulmonary nodules, and to develop a statistical model to guide clinicians regarding choice of patients for diagnostic biopsy.

METHOD

The medical records of 151 patients evaluated at the Memorial Sloan-Kettering Cancer Center between January 1999 and December 2001 for non-calcified pulmonary nodules were reviewed. Nodules were considered malignant based on the results of a diagnostic biopsy, and were considered benign if their appearance remained stable 2 years after the initial study, if they resolved, or if a biopsy showed a non-malignant condition.

RESULTS

Sixty four of 151 patients (42%) were diagnosed with malignant nodules; 32 had newly diagnosed lung cancers, 28 had metastatic spread of their primary cancers, and four had lesions that were either new cancers or of undetermined aetiology. On univariate analysis the likelihood of malignancy increased with nodule size, tobacco exposure, and the finding of a solitary nodule. On multivariable analysis only nodule size and tobacco exposure were predictive of malignancy. The model had good predictive accuracy (area under the curve 0.751) but had insufficient discrimination for use as a clinical tool to determine which patients should undergo diagnostic biopsy.

CONCLUSION

Nearly half the non-calcified pulmonary nodules identified in this series were malignant. Lung cancer was more common than metastatic disease. These findings support the need for close interval follow up and a low threshold for diagnostic biopsy in patients with extrapulmonary cancers and non-calcified pulmonary nodules. In smokers, such lesions should raise concern for lung cancer.

Control of spatial orientation and lifetime of scroll rings in excitable media

Excitable media, which range from autocatalytic chemical systems to biological cells and tissues, can maintain organized structures in the form of rotating spiral waves of excitation. The dynamics of spiral waves in two-dimensional systems have been shown to be susceptible to control by external fields (such as electric, thermal and optical). In three dimensions, the analogues of spiral waves are scroll waves. Here we show that an external field--a temperature gradient--can be used to control a particular class of scroll waves called scroll rings. The gradient allows scroll rings to be precisely oriented in space, and their spontaneous shrinkage to be accelerated, decelerated or even reversed (so that the ring expands). The temperature gradient also influences the lifetimes of the scroll rings. We suggest that these dynamics are likely to be generic to other types of field gradients and other excitable media.