Agroforestry systems in Romania

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Parallel algorithm with spectral convergence for nonlinear integro-differential equations

We discuss a numerical algorithm for solving nonlinear integro-differential equations, and illustrate our findings for the particular case of Volterra type equations. The algorithm combines a perturbation approach meant to render a linearized version of the problem and a spectral method where unknown functions are expanded in terms of Chebyshev polynomials (El-gendi's method). This approach is shown to be suitable for the calculation of two-point Green functions required in next to leading order studies of time-dependent quantum field theory.Comment: 15 pages, 9 figure

Gauge Coupling Beta Functions in the Standard Model to Three Loops

In this paper we compute the three-loop corrections to the beta functions of the three gauge couplings in the Standard Model of particle physics using the minimal subtraction scheme and taking into account Yukawa and Higgs self couplings.Comment: 4 pages, 1 figure, v2: minor changes, references adde

Continuum coupled cluster expansion

We review the basics of the coupled-cluster expansion formalism for numerical solutions of the many-body problem, and we outline the principles of an approach directed towards an adequate inclusion of continuum effects in the associated single-energy spectrum. We illustrate our findings by considering the simple case of a single-particle quantum mechanics problem.Comment: 16 pages, 1 figur

Renormalization constants and beta functions for the gauge couplings of the Standard Model to three-loop order

We compute the beta functions for the three gauge couplings of the Standard Model in the minimal subtraction scheme to three loops. We take into account contributions from all sectors of the Standard Model. The calculation is performed using both Lorenz gauge in the unbroken phase of the Standard Model and background field gauge in the spontaneously broken phase. Furthermore, we describe in detail the treatment of $\gamma_5$ and present the automated setup which we use for the calculation of the Feynman diagrams. It starts with the generation of the Feynman rules and leads to the bare result for the Green's function of a given process.Comment: 44 pages, 9 figures; v2: sign in eq.(29) corrected; final result unchange

Ground state correlations and mean-field in 16^{16}O: Part II

We continue the investigations of the $^{16}$O ground state using the coupled-cluster expansion [$\exp({\bf S})$] method with realistic nuclear interaction. In this stage of the project, we take into account the three nucleon interaction, and examine in some detail the definition of the internal Hamiltonian, thus trying to correct for the center-of-mass motion. We show that this may result in a better separation of the internal and center-of-mass degrees of freedom in the many-body nuclear wave function. The resulting ground state wave function is used to calculate the "theoretical" charge form factor and charge density. Using the "theoretical" charge density, we generate the charge form factor in the DWBA picture, which is then compared with the available experimental data. The longitudinal response function in inclusive electron scattering for $^{16}$O is also computed.Comment: 9 pages, 7 figure

A quantitative study of spin noise spectroscopy in a classical gas of 41^{41}K atoms

We present a general derivation of the electron spin noise power spectrum in alkali gases as measured by optical Faraday rotation, which applies to both classical gases at high temperatures as well as ultracold quantum gases. We show that the spin-noise power spectrum is determined by an electron spin-spin correlation function, and we find that measurements of the spin-noise power spectra for a classical gas of $^{41}$K atoms are in good agreement with the predicted values. Experimental and theoretical spin noise spectra are directly and quantitatively compared in both longitudinal and transverse magnetic fields up to the high magnetic field regime (where Zeeman energies exceed the intrinsic hyperfine energy splitting of the $^{41}$K ground state)

Numerical Approximations Using Chebyshev Polynomial Expansions

We present numerical solutions for differential equations by expanding the unknown function in terms of Chebyshev polynomials and solving a system of linear equations directly for the values of the function at the extrema (or zeros) of the Chebyshev polynomial of order N (El-gendi's method). The solutions are exact at these points, apart from round-off computer errors and the convergence of other numerical methods used in connection to solving the linear system of equations. Applications to initial value problems in time-dependent quantum field theory, and second order boundary value problems in fluid dynamics are presented.Comment: minor wording changes, some typos have been eliminate

Minimally invasive approach to colorectal tumors - 3 years of experience in a private hospital

Spitalul Privat ”Sanador”, București, România, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: Abordul minim invaziv al tumorilor colo-rectale reprezintă o preocupare a colectivului Spitalului privat Sanador, în pofida adresabilității crescute a cancerelor în stadii avansate, procentul acestora din totalul intervențiilor chirurgicale pentru această patologie rămânând constant, printr-o atentă selecție a pacienților, care sa beneficieze de avantajele laparoscopiei. Material și metode: Studiul prezent analizează intervențiile chirurgicale pentru tumori colo-rectale efectuate între anii 2016-2018 în Spitalul Sanador București. Din totalul de 214 intervenții chirurgicale pentru patologia colo-rectală, 41 au fost prin abord minim invaziv, reprezentând procentual 20% din totalul intervențiilor pentru această patologie, procentul fiind constant în fiecare din acești ani: 2016 – 13 intervenții prin abord minim invaziv din totalul de 68 (19.11%); 2017 – 17 intervenții prin abord minim invaziv din totalul de 79 (21.5%); 2018 – 11 intervenții chirurgicale prin abord minim invaziv dintr-un total de 57 (19.3%). Rezultate: Cele mai frecvente localizări ale tumorilor pentru care indicația a fost de abord minim invaziv, au fost cele recto-sigmoidiene (28). Selecția pacienților s-a facut după stadializarea preoperatorie, admitându-se ca și abord laparoscopic tumori T1, T2, T3, în rare cazuri T4. În cazul tumorilor avansate, substadializate preoperator, s-a tentat efectuarea a cât mai multor timpi din cadrul rezecției, prin abord minim invaziv, iar cazurile in care anastomozele au fost efectuate extracorporeal nu au fost interpretate ca și conversie. Concluzii: Rezultatele bune se înscriu în rândul celor ale centrelor cu volum și experiența mari în abordarea minim invazivă a tumorilor colo-rectale și constituie premize pentru creșterea procentului de astfel de intervenții în clinica noastră.Introduction: The minimally invasive approach of colorectal tumors is a concern of the Sanador private hospital team, despite the increased addressability of cancers in advanced stages, their percentage of total surgical interventions for this pathology remaining constantly through a careful selection of patients who benefit from the advantages of laparoscopy. Material and methods: The present study examines surgical interventions for colorectal tumors performed between 2016-2018 at Sanador Hospital Bucharest. Of the total of 214 surgical procedures for rectal pathology, 41 were by minimally invasive approach, accounting for 20% of all interventions for this pathology, the percentage being constant in each of these years: 2016-13 interventions through the minimally invasive approach of the total of 68 (19.11%); 2017 - 17 interventions through minimally invasive approach from the total of 79 (21.5%); 2018 - 11 minimally invasive surgical interventions from a total of 57 (19.3%). Results: The most common tumor localizations for which the indication was minimally invasive were the recto-sigmoid (28). Selection of patients was made after preoperative staging, admitting as a laparoscopic approach T1, T2, T3 tumors, in rare cases T4. In the case of advanced tumors, pre-operative substations, it was tempting to perform as many times as possible in the resection through a minimally invasive approach, and the cases in which the anastomoses were performed extracorporeally were not interpreted as conversion. Conclusions: Good results are among those with large volume centers and great experience in the minimally invasive approach of colorectal tumors and are prerequisites for increasing the percentage of such interventions in our clinic

Band structure of SnTe studied by Photoemission Spectroscopy

We present an angle-resolved photoemission spectroscopy study of the electronic structure of SnTe, and compare the experimental results to ab initio band structure calculations as well as a simplified tight-binding model of the p-bands. Our study reveals the conjectured complex Fermi surface structure near the L-points showing topological changes in the bands from disconnected pockets, to open tubes, and then to cuboids as the binding energy increases, resolving lingering issues about the electronic structure. The chemical potential at the crystal surface is found to be 0.5eV below the gap, corresponding to a carrier density of p =1.14x10^{21} cm^{-3} or 7.2x10^{-2} holes per unit cell. At a temperature below the cubic-rhombohedral structural transition a small shift in spectral energy of the valance band is found, in agreement with model predictions.Comment: 4 figure