Plasmapheresis can correct refractoriness of insulin on triglyceride metabolism - A case report of hypertriglyceridemia-induced acute pancreatitis.

Hypertriglyceridemia associated acute pancreatitis is a medical emergency and it causes significant morbidity and mortality. Here we report a case of 47 years old male with hypertriglyceridemia associated acute pancreatitis. The diagnosis was confirmed by elevated serum triglyceride levels and elevated lipase levels. Initially, Insulin infusion started with fibrates and statins but due to worsening hypertriglyceridemia and he underwent one session of plasmapheresis, following which triglyceride levels improved. Triglyceride assessment in removed plasma in plasmapheresis showed that the amount of triglyceride level reduction was 4 times the amount removed in plasmapheresis. The study showed that plasmapheresis improves insulin-related triglyceride metabolism besides removal.

Relationship between nonlinearities and thermalization in classical open systems: The role of the interaction range.

We discuss results on the dynamics of thermalization for a model with Gaussian interactions between two classical many-body systems trapped in external harmonic potentials. Previous work showed an approximate power-law scaling of the interaction energy with the number of particles, with particular focus on the dependence of the anomalous exponent on the interaction strength. Here we explore the role of the interaction range in determining anomalous exponents, showing that it is a more relevant parameter to differentiate distinct regimes of responses of the system. More specifically, on varying the interaction range from its largest values while keeping the interaction strength constant, we observe a crossover from an integrable system, approximating the Caldeira-Leggett interaction term in the long-range limit, to an intermediate interaction range in which the system manifests anomalous scaling, and finally to a regime of local interactions in which anomalous scaling disappears. A Fourier analysis of the interaction energy shows that nonlinearities give rise to an effective bath with a broad band of frequencies, even when starting with only two distinct trapping frequencies, yielding efficient thermalization in the intermediate regime of interaction range. We provide qualitative arguments, based on an analogous Fourier analysis of the standard map, supporting the view that anomalous scaling and features of the Fourier spectrum may be used as proxies to identify the role of chaotic dynamics. Our work, that encompasses models developed in different contexts and unifies them in a common framework, may be relevant to the general understanding of the role of nonlinearities in a variety of many-body classical systems, ranging from plasmas to trapped atoms and ions.

Stochastic modeling of phenotypic switching and chemoresistance in cancer cell populations.

Phenotypic heterogeneity in cancer cells is widely observed and is often linked to drug resistance. In several cases, such heterogeneity in drug sensitivity of tumors is driven by stochastic and reversible acquisition of a drug tolerant phenotype by individual cells even in an isogenic population. Accumulating evidence further suggests that cell-fate transitions such as the epithelial to mesenchymal transition (EMT) are associated with drug resistance. In this study, we analyze stochastic models of phenotypic switching to provide a framework for analyzing cell-fate transitions such as EMT as a source of phenotypic variability in drug sensitivity. Motivated by our cell-culture based experimental observations connecting phenotypic switching in EMT and drug resistance, we analyze a coarse-grained model of phenotypic switching between two states in the presence of cytotoxic stress from chemotherapy. We derive analytical results for time-dependent probability distributions that provide insights into the rates of phenotypic switching and characterize initial phenotypic heterogeneity of cancer cells. The results obtained can also shed light on fundamental questions relating to adaptation and selection scenarios in tumor response to cytotoxic therapy.

Scaling laws for harmonically trapped two-species mixtures at thermal equilibrium.

We discuss the scaling of the interaction energy with particle numbers for a harmonically trapped two-species mixture at thermal equilibrium experiencing interactions of arbitrary strength and range. In the limit of long-range interactions and weak coupling, we recover known results for the integrable Caldeira-Leggett model in the classical limit. In the case of short-range interactions and for a balanced mixture, numerical simulations show scaling laws with exponents that depend on the interaction strength, its attractive or repulsive nature, and the dimensionality of the system. Simple analytic considerations based on equilibrium statistical mechanics and small interspecies coupling quantitatively recover the numerical results. The dependence of the scaling on interaction strength helps to identify a threshold between two distinct regimes. Our thermalization model covers both local and extended interactions, allowing for interpolation between different systems such as fully ionized gases and neutral atoms, as well as parameters describing integrable and chaotic dynamics.

Emergence of local synchronization in neuronal networks with adaptive couplings.

Local synchronization, both prolonged and transient, of oscillatory neuronal behavior in cortical networks plays a fundamental role in many aspects of perception and cognition. Here we study networks of Hindmarsh-Rose neurons with a new type of adaptive coupling, and show that these networks naturally produce both permanent and transient synchronization of local clusters of neurons. These deterministic systems exhibit complex dynamics with 1/fη power spectra, which appears to be a consequence of a novel form of self-organized criticality.

Ehrenfest approach to open double-well dynamics.

We consider an Ehrenfest approximation for a particle in a double-well potential in the presence of an external environment schematized as a finite resource heat bath. This allows us to explore how the limitations in the applicability of Ehrenfest dynamics to nonlinear systems are modified in an open system setting. Within this framework, we have identified an environment-induced spontaneous symmetry breaking mechanism, and we argue that the Ehrenfest approximation becomes increasingly valid in the limit of strong coupling to the external reservoir, either in the form of an increasing number of oscillators or increasing temperature. The analysis also suggests a rather intuitive picture for the general phenomenon of quantum tunneling and its interplay with classical thermal activation processes, which may be of relevance in physical chemistry, ultracold atom physics, and fast-switching dynamics such as in superconducting digital electronics.

Attack robustness and centrality of complex networks.

Many complex systems can be described by networks, in which the constituent components are represented by vertices and the connections between the components are represented by edges between the corresponding vertices. A fundamental issue concerning complex networked systems is the robustness of the overall system to the failure of its constituent parts. Since the degree to which a networked system continues to function, as its component parts are degraded, typically depends on the integrity of the underlying network, the question of system robustness can be addressed by analyzing how the network structure changes as vertices are removed. Previous work has considered how the structure of complex networks change as vertices are removed uniformly at random, in decreasing order of their degree, or in decreasing order of their betweenness centrality. Here we extend these studies by investigating the effect on network structure of targeting vertices for removal based on a wider range of non-local measures of potential importance than simply degree or betweenness. We consider the effect of such targeted vertex removal on model networks with different degree distributions, clustering coefficients and assortativity coefficients, and for a variety of empirical networks.

Competitively coupled maps and spatial pattern formation.

Spatial pattern formation is a key feature of many natural systems in physics, chemistry, and biology. The essential theoretical issue in understanding pattern formation is to explain how a spatially homogeneous initial state can undergo spontaneous symmetry breaking leading to a stable spatial pattern. This problem is most commonly studied using partial differential equations to model a reaction-diffusion system of the type introduced by Turing. We report here on a much simpler and more robust model of spatial pattern formation, which is formulated as a novel type of coupled map lattice. In our model, the local site dynamics are coupled through a competitive, rather than diffusive, interaction. Depending only on the strength of the interaction, this competitive coupling results in spontaneous symmetry breaking of a homogeneous initial configuration and the formation of stable spatial patterns. This mechanism is very robust and produces stable pattern formation for a wide variety of spatial geometries, even when the local site dynamics is trivial.

Persistent patterns and multifractality in fluid mixing.

Persistent patterns in periodically driven dynamics have been reported in a wide variety of contexts ranging from table-top and ocean-scale fluid mixing systems to the weak quantum-classical transition in open Hamiltonian systems. We illustrate a common framework for the emergence of these patterns by considering a simple measure of structure maintenance provided by the average radius of the scalar distribution in transform space. Within this framework, scaling laws related to both the formation and persistence of patterns in phase space are presented. Further, preliminary results linking the scaling exponents associated with the persistent patterns to the multifractal nature of the advective phase-space geometry are shown.

Robotic-assisted laparoscopic ureteral reimplantation with psoas hitch: a multi-institutional, multinational evaluation.

OBJECTIVES: To report the collective experience of three multinational institutions with the use of robotics to evaluate and treat complex distal ureteral obstruction. METHODS: A total of 12 patients from The Ohio State University, Columbus, Ohio; Onze-Lieve-Vrouw Ziekenhuis, Aalst, Belgium; and Hospital Sultanah Aminah, Kuala Lumpur, Malaysia underwent robotic-assisted laparoscopic ureteral reimplantation between August 2004 and July 2006. The indications for ureteral reimplantation included ureteral stricture (n = 10) and ureterovaginal fistula (n = 2). Nine patients had pathology on the left side and 4 patients had right-sided disease. Surgery was performed by three experienced laparoscopic robotic surgeons with the daVinci Surgical System. RESULTS: The mean patient age (range) was 41.3 years (19 to 67 years). The mean operative time was 208 minutes (80 to 360 minutes). The mean robot time was 173 minutes (75 to 300 minutes). The mean estimated blood loss was 48 mL (45 to 100 minutes). The mean length of hospitalization was 4.3 days (2 to 8 days). All the procedures were completed successfully robotically without open conversion. There were no intraoperative or postoperative complications. Postoperative intravenous urography and Mercapto Acetyl TriGlycine 3 showed normal findings in 10 patients and a mild residual hydronephrosis in 2 patients. After a mean follow-up of 15.5 months, all patients were asymptomatic of their initial disease state. CONCLUSIONS: This multi-institutional, multinational experience illustrates that ureteral reimplantation with psoas hitch can be performed safely and effectively to treat lower tract ureteral obstruction.

Field-induced phases of an orientable charged particle in a dilute background of point charges.

We report numerical simulations of a two-dimensional dynamical model comprised of a rodlike particle surrounded by a cloud of smaller particles of the same charge, in the presence of an alternating electric field inside a box. We show that this system displays a remarkable dynamical effect; at low forcing frequencies the rod tends to align perpendicularly to the external field, whereas for higher field frequencies the standard orientation (parallel to the field) prevails. Interestingly, the transition between orientations is abrupt enough to resemble a phase transition. The fact that the "anomalous" orientation (perpendicular to the field) takes place is also interesting in the light of some recent laboratory experiments on colloidal solutions, where anomalous orientation at low frequencies was observed. Our toy model suggests that future physically realistic simulations of these systems should explore whether the anomalous orientation may be due to the collective dynamics of the colloidal particles, without necessarily involving more sophisticated electro-osmotic effects.

Semiclassics of the chaotic quantum-classical transition.

We elucidate the basic physical mechanisms responsible for the quantum-classical transition in one-dimensional, bounded chaotic systems subject to unconditioned environmental interactions. We show that such a transition occurs due to the dual role of noise in regularizing the semiclassical Wigner function and averaging over fine structures in classical phase space. The results are interpreted in the context of applying recent advances in the theory of measurement and open systems to the semiclassical quantum regime. We use these methods to show how a local semiclassical picture is stabilized and can then be approximated by a classical distribution at later times. The general results are demonstrated explicitly via high-resolution numerical simulations of the quantum master equation for a chaotic Duffing oscillator.

Conditions for the quantum-to-classical transition: trajectories versus phase-space distributions.

We contrast two sets of conditions that govern the transition in which classical dynamics emerges from the evolution of a quantum system. The first was derived by considering the trajectories seen by an observer (dubbed the "strong" transition) [Bhattacharya et al., Phys. Rev. Lett. 85, 4852 (2000)], and the second by considering phase-space densities (the "weak" transition) [Greenbaum et al., Chaos 15, 033302 (2005)]. On the face of it these conditions appear rather different. We show, however, that in the semiclassical regime, in which the action of the system is large compared to h, and the measurement noise is small, they both offer an essentially equivalent local picture. Within this regime, the weak conditions dominate while in the opposite regime where the action is not much larger than h, the strong conditions dominate.

Robotic repair of vesicovaginal fistula: case series of five patients.

OBJECTIVES: To describe a technique of robotic repair of vesicovaginal fistula (VVF) and present our experience with 5 such patients. METHODS: A total of 5 patients were diagnosed with posthysterectomy (n = 4) or postmyomectomy (n = 1) VVF. All patients were first treated conservatively with continuous drainage using a Foley catheter without any success. After 12 weeks, these patients underwent robotic repair of the VVF. The steps of the technique of robotic repair are (a) vaginoscopy, (b) cystoscopy, (c) bilateral ureteral catheterization, (d) placement of ports for robotic repair, (e) peritoneoscopy, (f) lysis of adhesions, (g) incision of the bladder and cystotomy in reverse tennis racquet fashion encircling the fistula, (h) excision and freshening of the fistulous margins after complete separation of the bladder from the vagina, (i) closure of the vaginal opening horizontally and bladder opening vertically with interrupted Vicryl sutures, and, finally, (j) interposition of the omentum between these suture lines. RESULTS: Fistula repair was successful in all cases, with a mean operative time (from cystoscopy to the end of the procedure) of 233 minutes (range 150 to 330) and estimated blood loss of less than 70 mL. The length of hospital stay was a mean of 5 days (range 4 to 7). The Foley catheter was removed on the 10th postoperative day after voiding cystourethrography. At 6 months of follow-up, these patients continued to void normally without any recurrence of VVF. CONCLUSIONS: These data suggest that robot-assisted VVF repair is feasible and results in lower morbidity, a shorter hospital stay, and a quicker recovery. The minimally invasive approach of robot-assisted VVF repair may be a more attractive option for patients with VVF.

Acoustical dead zones and the spatial aggregation of whale strandings.

Cetacean strandings display a marked geographical clustering. We propose a simple, two-dimensional ray-dynamics model of cetacean echolocation to examine the role played by coastline topography in influencing the location and clustering of stranding sites. We find that a number of coastlines known to attract cetacean strandings produce acoustical "Dead Zones" where echolocation signals are severely distorted by purely geometric effects. Using available cetacean stranding data bases from four disparate areas, we show that the geographical clusters in the observations correlate strongly with the regions of distorted echolocation signals as predicted by the model.

The semiclassical regime of the chaotic quantum-classical transition.

An analysis of the semiclassical regime of the quantum-classical transition is given for open, bounded, one-dimensional chaotic dynamical systems. Environmental fluctuations-characteristic of all realistic dynamical systems-suppress the development of a fine structure in classical phase space and damp nonlocal contributions to the semiclassical Wigner function, which would otherwise invalidate the approximation. This dual regularization of the singular nature of the semiclassical limit is demonstrated by a numerical investigation of the chaotic Duffing oscillator.

Relativistic kicked rotor.

Transport properties in the relativistic analog of the periodically kicked rotor are contrasted under classically and quantum mechanical dynamics. The quantum rotor is treated by solving the Dirac equation in the presence of the time-periodic delta-function potential resulting in a relativistic quantum mapping describing the evolution of the wave function. The transition from the quantum suppression behavior seen in the nonrelativistic limit to agreement between quantum and classical analyses in the relativistic regime is discussed. The absence of quantum resonances in the relativistic case is also addressed.

Chaos and quantum mechanics.

The relationship between chaos and quantum mechanics has been somewhat uneasy--even stormy, in the minds of some people. However, much of the confusion may stem from inappropriate comparisons using formal analyses. In contrast, our starting point here is that a complete dynamical description requires a full understanding of the evolution of measured systems, necessary to explain actual experimental results. This is of course true, both classically and quantum mechanically. Because the evolution of the physical state is now conditioned on measurement results, the dynamics of such systems is intrinsically nonlinear even at the level of distribution functions. Due to this feature, the physically more complete treatment reveals the existence of dynamical regimes--such as chaos--that have no direct counterpart in the linear (unobserved) case. Moreover, this treatment allows for understanding how an effective classical behavior can result from the dynamics of an observed quantum system, both at the level of trajectories as well as distribution functions. Finally, we have the striking prediction that time-series from measured quantum systems can be chaotic far from the classical regime, with Lyapunov exponents differing from their classical values. These predictions can be tested in next-generation experiments.

Parameter scaling in the decoherent quantum-classical transition for chaotic systems.

The quantum to classical transition for a system depends on many parameters, including a scale length for its action, variant Planck's over 2 pi, a measure of its coupling to the environment, D, and, for chaotic systems, the classical Lyapunov exponent, lambda. We propose measuring the proximity of quantum and classical evolutions as a multivariate function of (Planck's over 2 pi,lambda,D) and searching for transformations that collapse this hypersurface into a function of a composite parameter zeta= Planck's over 2 pi alpha)lambda beta D gamma. We report results for the quantum Cat Map and Duffing oscillator, showing accurate scaling behavior over a wide parameter range, indicating that this may be used to construct universality classes for this transition.