830 research outputs found
Inversion of perturbation series
We investigate the inversion of perturbation series and its resummation, and
prove that it is related to a recently developed parametric perturbation
theory. Results for some illustrative examples show that in some cases series
reversion may improve the accuracy of the results
Variational collocation for systems of coupled anharmonic oscillators
We have applied a collocation approach to obtain the numerical solution to
the stationary Schr\"odinger equation for systems of coupled oscillators. The
dependence of the discretized Hamiltonian on scale and angle parameters is
exploited to obtain optimal convergence to the exact results. A careful
comparison with results taken from the literature is performed, showing the
advantages of the present approach.Comment: 14 pages, 10 table
Variational collocation on finite intervals
In this paper we study a new family of sinc--like functions, defined on an
interval of finite width. These functions, which we call ``little sinc'', are
orthogonal and share many of the properties of the sinc functions. We show that
the little sinc functions supplemented with a variational approach enable one
to obtain accurate results for a variety of problems. We apply them to the
interpolation of functions on finite domain and to the solution of the
Schr\"odinger equation, and compare the performance of present approach with
others.Comment: 12 pages, 8 figures, 1 tabl
The confined hydrogen atom with a moving nucleus
We study the hydrogen atom confined to a spherical box with impenetrable
walls but, unlike earlier pedagogical articles on the subject, we assume that
the nucleus also moves. We obtain the ground-state energy approximately by
means of first--order perturbation theory and by a more accurate variational
approach. We show that it is greater than the one for the case in which the
nucleus is clamped at the center of the box. Present approach resembles the
well-known treatment of the helium atom with clamped nucleus
Solution to the Equations of the Moment Expansions
We develop a formula for matching a Taylor series about the origin and an
asymptotic exponential expansion for large values of the coordinate. We test it
on the expansion of the generating functions for the moments and connected
moments of the Hamiltonian operator. In the former case the formula produces
the energies and overlaps for the Rayleigh-Ritz method in the Krylov space. We
choose the harmonic oscillator and a strongly anharmonic oscillator as
illustrative examples for numerical test. Our results reveal some features of
the connected-moments expansion that were overlooked in earlier studies and
applications of the approach
Colour superconductivity in finite systems
In this paper we study the effect of finite size on the two-flavour colour
superconducting state. As well as restricting the quarks to a box, we project
onto states of good baryon number and onto colour singlets, these being
necessary restrictions on any observable ``quark nuggets''. We find that
whereas finite size alone has a significant effect for very small boxes, with
the superconducting state often being destroyed, the effect of projection is to
restore it again. The infinite-volume limit is a good approximation even for
quite small systems.Comment: 14 pages RevTeX4, 12 eps figure
Presence of Candida zemplinina in Sicilian Musts and Selection of a Strain for Wine Mixed Fermentations
The purpose of this work was to investigate the presence of C. zemplinina yeasts in Sicilian musts andgrapes and to identify strains of oenological interest. We report on the taxonomical reclassificationof Candida yeast isolates from Sicilian musts and on the selection of one strain of oenological interest(Cz3), based on mixed micro-fermentation experiments in sterile Nero d’Avola musts. Our results showthat Candida zemplinina is abundant in Sicilian grapes and musts, and that the Cz3 strain is suitablefor Candida zemplinina/Saccharomyces cerevisiae mixed fermentations. The higher glycerol content andthe lower ethanol level stood out as the most promising features of the wines obtained upon sequentialinoculation of the Cz3 and (S. cerevisiae) NDA21 yeast starters. We therefore have isolated a Sicilian Czstrain endowed with very promising features for the future development of mixed fermentation protocols
Chiral quark-soliton model in the Wigner-Seitz approximation
In this paper we study the modification of the properties of the nucleon in
the nucleus within the quark-soliton model. This is a covariant, dynamical
model, which provides a non-linear representation of the spontaneously broken
SU(2)_L X SU(2)_R symmetry of QCD. The effects of the nuclear medium are
accounted for by using the Wigner-Seitz approximation and therefore reducing
the complex many-body problem to a simpler single-particle problem. We find a
minimum in the binding energy at finite density, a change in the isoscalar
nucleon radius and a reduction of the in-medium pion decay constant. The latter
is consistent with a partial restoration of chiral symmetry at finite density,
which is predicted by other models.Comment: 30 pages, 13 figures; uses REVTeX and epsfi
The efficacy of buprenorphine in major depression, treatment-resistant depression and suicidal behavior. A systematic review
Although several pharmacological options to treat depression are currently available, approximately one third of patients who receive antidepressant medications do not respond adequately or achieve a complete remission. Thus, novel strategies are needed to successfully address those who did not respond, or partially respond, to available antidepressant pharmacotherapy. Research findings revealed that the opioid system is significantly involved in the regulation of mood and incentives salience and may be an appropriate target for novel therapeutic agents. The present study aimed to systematically review the current literature about the use of buprenorphine (BUP) for major depression, treatment-resistant depression (TRD), non-suicidal self-injury (NSSI) behavior, and suicidal behavior. We investigated Pubmed and Scopus databases using the following keywords: “buprenorphine AND depression”, “buprenorphine AND treatment resistant depression”, “buprenorphine AND suicid*”, “buprenorphine AND refractory depression”. Several evidence demonstrate that, at low doses, BUP is an efficacious, well-tolerated, and safe option in reducing depressive symptoms, serious suicidal ideation, and NSSI, even in patients with TRD. However, more studies are needed to evaluate the long-term effects, and relative efficacy of specific combinations (e.g., BUP + samidorphan (BUP/SAM), BUP + naloxone (BUP/NAL), BUP + naltrexone) over BUP monotherapy or adjunctive BUP treatment with standard antidepressants, as well as to obtain more uniform guidance about the optimal BUP dosing interval
Deep venous thrombosis and abortion: an unusual clinical manifestation of severe form of pectus excavatum
Pectus excavatum is a chest wall malformation with a strong psychological and aesthetic impact. Rarely, pectus excavatum patients can show respiratory or cardiac symptoms occurring mainly during physical exertion. We report a case of a 34-year-old pregnant woman with a severe degree of pectus excavatum who developed serious cardiovascular disease resulting in spontaneous twin abortion at the twenty-first week of gestation. Cardiovascular disease was resolved after open surgical correction of pectus excavatum. This case shows how a tardive diagnosis and a delayed surgical approach for pectus excavatum can lead to severe consequences
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