Structure of penetrable-rod fluids: Exact properties and comparison between Monte Carlo simulations and two analytic theories

Bounded potentials are good models to represent the effective two-body interaction in some colloidal systems, such as dilute solutions of polymer chains in good solvents. The simplest bounded potential is that of penetrable spheres, which takes a positive finite value if the two spheres are overlapped, being 0 otherwise. Even in the one-dimensional case, the penetrable-rod model is far from trivial, since interactions are not restricted to nearest neighbors and so its exact solution is not known. In this paper we first derive the exact correlation functions of penetrable-rod fluids to second order in density at any temperature, as well as in the high-temperature and zero-temperature limits at any density. Next, two simple analytic theories are constructed: a high-temperature approximation based on the exact asymptotic behavior in the limit $T\to\infty$ and a low-temperature approximation inspired by the exact result in the opposite limit $T\to 0$. Finally, we perform Monte Carlo simulations for a wide range of temperatures and densities to assess the validity of both theories. It is found that they complement each other quite well, exhibiting a good agreement with the simulation data within their respective domains of applicability and becoming practically equivalent on the borderline of those domains. A perspective on the extension of both approaches to the more realistic three-dimensional case is provided.Comment: 19 pages, 11 figures, 4 tables: v2: minor changes; published final versio

Thermodynamic Field Theory with the Iso-Entropic Formalism

A new formulation of the thermodynamic field theory (TFT) is presented. In this new version, one of the basic restriction in the old theory, namely a closed-form solution for the thermodynamic field strength, has been removed. In addition, the general covariance principle is replaced by Prigogine's thermodynamic covariance principle (TCP). The introduction of TCP required the application of an appropriate mathematical formalism, which has been referred to as the iso-entropic formalism. The validity of the Glansdorff-Prigogine Universal Criterion of Evolution, via geometrical arguments, is proven. A new set of thermodynamic field equations, able to determine the nonlinear corrections to the linear ("Onsager") transport coefficients, is also derived. The geometry of the thermodynamic space is non-Riemannian tending to be Riemannian for hight values of the entropy production. In this limit, we obtain again the same thermodynamic field equations found by the old theory. Applications of the theory, such as transport in magnetically confined plasmas, materials submitted to temperature and electric potential gradients or to unimolecular triangular chemical reactions can be found at references cited herein.Comment: 35 page

Total pelvic exenteration for recurrence of uterine leiomyosarcoma (case report)

Universitatea de Medicină şi Farmacie “Carol Davila”, Spitalul “Ponderas”, Bucureşti, România, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Leiomiosarcoamele uterine sunt tumori rare cu o capacitate importantă de a produce atât recidive locale căt și la distanță. Odată ce diagnosticul de recidivă este pus, aceasta este tratată cel mai eficient prin re-rezecție. Caz clinic: Prezentăm cazul unei paciente de 44 ani, diagnosticată cu leiomiosarcom uterin în urmă cu 2 ani când s-a practicat histerectomie totală radicală cu anexectomie bilaterală, limfodisecție pelvină și paraaortică urmată de radioterapie adjuvantă. Doi ani mai târziu pacienta a fost diagnosticată cu recidivă pelvină cu invazia vezicii urinare și a rectului pentru care s-a practicat exenterație pelvină totală.Introduction: Uterine leyomiosarcomas are rare malignancies with a high capacity of giving birth to local or distant recurrent tumors. Once the diagnosis is established, the most efficient way to treat recurrent disease is re-resection. Clinical case: We present the case of a 44 year old patient diagnosed with an uterine leiomyosarcoma two years ago when a total hysterectomy with bilateral adnexectomy, pelvic and para-aortic lymph node dissection were performed followed by adjuvant radiotherapy. Two years later the patient was diagnosed with a pelvic recurrence invading the rectum and the urinary bladder, so a total pelvic exenteration was performed

Neutrino magnetohydrodynamics

A new neutrino magnetohydrodynamics (NMHD) model is formulated, where the effects of the charged weak current on the electron-ion magnetohydrodynamic fluid are taken into account. The model incorporates in a systematic way the role of the Fermi neutrino weak force in magnetized plasmas. A fast neutrino-driven short wavelengths instability associated with the magnetosonic wave is derived. Such an instability should play a central role in strongly magnetized plasma as occurs in supernovae, where dense neutrino beams also exist. In addition, in the case of nonlinear or high frequency waves, the neutrino coupling is shown to be responsible for breaking the frozen-in magnetic field lines condition even in infinite conductivity plasmas. Simplified and ideal NMHD assumptions were adopted and analyzed in detail

Transition Probability to Turbulent Transport Regime

Transition phenomena between thermal noise state and turbulent state observed in a submarginal turbulent plasma are analyzed with statistical theory. Time-development of turbulent fluctuation is obtained by numerical simulations of Langevin equation which contains hysteresis characteristics. Transition rates between two states are analyzed. Transition from turbulent state to thermal noise state occurs in entire region between subcritical bifurcation point and linear stability boundary.Comment: 9 pages, 6 figures, to be published in Plasma Phys. Control. Fusio

Dispersion and damping of potential surface waves in a degenerate plasma

Potential (electrostatic) surface waves in plasma half-space with degenerate electrons are studied using the quasi-classical mean-field kinetic model. The wave spectrum and the collisionless damping rate are obtained numerically for a wide range of wavelengths. In the limit of long wavelengths, the wave frequency $\omega$ approaches the cold-plasma limit $\omega=\omega_p/\sqrt{2}$ with $\omega_p$ being the plasma frequency, while at short wavelengths, the wave spectrum asymptotically approaches the spectrum of zero-sound mode propagating along the boundary. It is shown that the surface waves in this system remain weakly damped at all wavelengths (in contrast to strongly damped surface waves in Maxwellian electron plasmas), and the damping rate nonmonotonically depends on the wavelength, with the maximum (yet small) damping occuring for surface waves with wavelength of $\approx5\pi\lambda_{F}$, where $\lambda_{F}$ is the Thomas-Fermi length.Comment: 22 pages, 6 figure

Incomplete equilibrium in long-range interacting systems

We use a Hamiltonian dynamics to discuss the statistical mechanics of long-lasting quasi-stationary states particularly relevant for long-range interacting systems. Despite the presence of an anomalous single-particle velocity distribution, we find that the Central Limit Theorem implies the Boltzmann expression in Gibbs' $\Gamma$-space. We identify the nonequilibrium sub-manifold of $\Gamma$-space characterizing the anomalous behavior and show that by restricting the Boltzmann-Gibbs approach to this sub-manifold we obtain the statistical mechanics of the quasi-stationary states.Comment: Title changed, throughout revision of the tex

Kinetic properties of particle-in-cell simulations compromised by Monte Carlo collisions

he particle-in-cell method with Monte Carlo collisions is frequently used when a detailed kinetic simulation of a weakly collisional plasma is required. In such cases, one usually desires, inter alia, an accurate calculation of the particle distribution functions in velocity space. However, velocity space diffusion affects most, perhaps all, kinetic simulations to some degree, leading to numerical thermalization (i.e., relaxation of the velocity distribution toward a Maxwellian), and consequently distortion of the true velocity distribution functions, among other undesirable effects. The rate of such thermalization can be considered a figure of merit for kinetic simulations. This article shows that, contrary to previous assumption, the addition of Monte Carlo collisions to a one-dimensional particle-in-cell simulation seriously degrades certain properties of the simulation. In particular, the thermalization time can be reduced by as much as three orders of magnitude. This effect makes obtaining strictly converged simulation results difficult in many cases of practical interest

Exact Markovian kinetic equation for a quantum Brownian oscillator

We derive an exact Markovian kinetic equation for an oscillator linearly coupled to a heat bath, describing quantum Brownian motion. Our work is based on the subdynamics formulation developed by Prigogine and collaborators. The space of distribution functions is decomposed into independent subspaces that remain invariant under Liouville dynamics. For integrable systems in Poincar\'e's sense the invariant subspaces follow the dynamics of uncoupled, renormalized particles. In contrast for non-integrable systems, the invariant subspaces follow a dynamics with broken-time symmetry, involving generalized functions. This result indicates that irreversibility and stochasticity are exact properties of dynamics in generalized function spaces. We comment on the relation between our Markovian kinetic equation and the Hu-Paz-Zhang equation.Comment: A few typos in the published version are correcte

Hepatobiliopancreatic resections as part of primary cytoreduction in advanced stage ovarian cancer

Universitatea de Medicină şi Farmacie “Carol Davila”, Spitalul “Ponderas”, Departamentul de Chirurgie Generală şi Transplant Hepatic “Dan Setlacec”, Institutul Clinic Fundeni, Bucureşti, România, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Neoplasmul ovarian este unul din cele mai agresive neoplazii ginecologice diagnosticat de obicei în stadii tardive, când sunt deja prezente diseminări la distanţă. Scop: De a studia siguranţa şi eficienţa includerii gesturilor de chirurgie hepato-bilio-pancreatică în citoreducţia primară pentru neoplasm ovarian avansat Material şi metodă: În perioada 2002-2014, 338 pacienţi au fost submişi la citoreducţie primară în Departamentul de Chirurgie Generală şi Transplant Hepatic “Dan Setlacec”, Institutul Clinic Fundeni, Bucureşti, România. Printre aceştia rezecţii hepatobilio- pancreatice au fost efectuate în 38 cazuri. Rezultate: Principalele proceduri efectuate au fost: rezecţiile hepatice în 7 cazuri, pancretectomie distală într-un caz precum şi colecistectomie în 30 cazuri. În toate cazurile invazia neoplazică a fost dovedită histopatologic. Postoperator s-a înregistrat o singură complicaţie legată de gesturile hepato-bilio-pancreatice – o fistulă biliară ce a necesitat reintervenţie. Concluzii: Gesturile de chirurgie hepatobiliopancreatică se pot adăuga cu succes citoreducţiei pentru neoplasm ovarian avansat cu scopul de a creşte rata rezecţiilor R0.Introduction: Ovarian cancer is one of the most aggressive gynaecological malignancies which is usually diagnosed in an advanced stage of the disease when distant disseminations are already present. Aim: To study the safety and effectiveness of hepatobiliopancraetic surgery in primary cytoreduction for advanced stage epithelial ovarian cancer. Material and methods: Between 2002-2014, 338 patients were submitted to primary cytoreductive surgery in “Dan Setlacec” Department of General Surgery and Liver Transplantation, Fundeni Clinical Institute, Bucharest, Romania. Among these patients, hepatobiliopancreatic surgical procedures were associated in 38 cases. Results: The main surgical procedures were: liver resections in 7 cases, distal pancreatectomy in one case and cholecystectomy in 30 cases. In all cases tumoral invasion was demonstrated by the histopathological studies. Postoperatively hepatobiliopancreatic surgery associated complications occurred in a single case – a biliary fistula which necessitated reoperation. Conclusions: Hepatobiliopancreatic surgical procedures can be safely associated for advanced stage ovarian cancer in order to increase the rate of R0 resections