Search results for "Ladder"

Population dynamics based on ladder bosonic operators

2021

Abstract We adopt an operatorial method, based on truncated bosons, to describe the dynamics of populations in a closed region with a non trivial topology. The main operator that includes the various mechanisms and interactions between the populations is the Hamiltonian, constructed with the density and transport operators. The whole evolution is derived from the Schrodinger equation, and the densities of the populations are retrieved from the normalized expected values of the density operators. We show that this approach is suitable for applications in very large domain, solving the computational issues that typically occur when using an Hamiltonian based on fermionic ladder operators.

Environmental Risk Factors in Superficial Bladder Cancer

2004

As a preliminary approach to define the object of larger case-control studies, the distribution of potential risk factors coming from environmental pollution among patients affected by superficial bladder cancer (TCCB) has been analyzed. Material e Methods. The analysis included only patients affected by medium risk superficial TCCB. Forty Italian urological centres joined the study. Detailed information about age, sex, residency, employment, active and passive cigarette smoking, water resource, hair-dye use were centralized. All patients underwent TUR and early intravesical chemotherapy. The distribution of the above mentioned environmental factors was related to tumor characteristics suc…

Sludge and stones in gallbladder after pregnancy

1987

Summary The prevalence of sludge and stones in the gallbladder of 298 women in the immediate post-partum period was ultrasonographically assessed. We have investigated some risk factors for the development of sludge or stones in these patients and followed up most of these patients by ultrasonography to detect the presence of sludge and/or stones in the year following their discovery. We found sludge in 80 (26.2%) and gallstones in 16 (5.2%) of these patients. Age, obesity and months of oral contraceptive use were risk factors only for the presence of gallstones. After 1 year of follow-up only 2 out of 45 patients with sludge but 13 out of 15 patients with gallstones still had abnormal ultr…

SonoAVC: a new tool in early diagnosis of patent urachus with bladder prolapse

2012

Calcitonin gene-related peptide partly protects cultured smooth muscle cells from apoptosis induced by an oxidative stress via activation of ERK1/2 M…

2003

Abstract Oxidative stress induced by a glucose/glucose oxidase (G/GO) generator system dose-dependently decreased the viability of cultured vascular smooth muscle cells (VSMC) as estimated by MTT assay. Cell death was induced in 40% of cells exposed to 0.2 IU/ml of the free radical generating mixture. Annexin-V labeling, Hoechst staining together with DNA laddering demonstrated that apoptosis was responsible for this cell loss. Pretreatment of the cells with 10−8 M calcitonin gene-related peptide (CGRP) significantly attenuated the damaging effect of the oxidative stress. Indeed, cell viability was estimated to be 80% in CGRP-treated group, instead of 60% in absence of CGRP treatment. This …

Factors predicting continence recovery 1 month after radical prostatectomy: Results of a multicenter survey

2011

Objectives: To assess the factors associated with continence recovery 1month after radical prostatectomy (RP) and to identify the correlation between these factors. Methods: In total, 2408 men treated with RP for prostate cancer (PCa) were enrolled in the present multicenter prospective study. Clinical (age, body mass index) and urological (catheterization or transurethral resection of the prostate) records, quality of life (QOL) scores determined using various instruments (including the International Index of Erectile Function [IIEF] and University of California Los Angeles, Prostate Cancer Index [UCLA-PCI]), PCa characteristics (clinical stage [cT], prostate-specific antigen, biopsy Gleas…

Finite-dimensional pseudo-bosons: a non-Hermitian version of the truncated harmonic oscillator

2018

We propose a deformed version of the commutation rule introduced in 1967 by Buchdahl to describe a particular model of the truncated harmonic oscillator. The rule we consider is defined on a $N$-dimensional Hilbert space $\Hil_N$, and produces two biorhogonal bases of $\Hil_N$ which are eigenstates of the Hamiltonians $h=\frac{1}{2}(q^2+p^2)$, and of its adjoint $h^\dagger$. Here $q$ and $p$ are non-Hermitian operators obeying $[q,p]=i(\1-Nk)$, where $k$ is a suitable orthogonal projection operator. These eigenstates are connected by ladder operators constructed out of $q$, $p$, $q^\dagger$ and $p^\dagger$. Some examples are discussed.

A no-go result for the quantum damped harmonic oscillator

2019

Abstract In this letter we show that it is not possible to set up a canonical quantization for the damped harmonic oscillator using the Bateman Lagrangian. In particular, we prove that no square integrable vacuum exists for the natural ladder operators of the system, and that the only vacua can be found as distributions. This implies that the procedure proposed by some authors is only formally correct, and requires a much deeper analysis to be made rigorous.

On the presence of families of pseudo-bosons in nilpotent Lie algebras of arbitrary corank

2019

We have recently shown that pseudo-bosonic operators realize concrete examples of finite dimensional nilpotent Lie algebras over the complex field. It has been the first time that such operators were analyzed in terms of nilpotent Lie algebras (under prescribed conditions of physical character). On the other hand, the general classification of a finite dimensional nilpotent Lie algebra $\mathfrak{l}$ may be given via the size of its Schur multiplier involving the so-called corank $t(\mathfrak{l})$ of $\mathfrak{l}$. We represent $\mathfrak{l}$ by pseudo-bosonic ladder operators for $t(\mathfrak{l}) \le 6$ and this allows us to represent $\mathfrak{l}$ when its dimension is $\le 5$.

A description of pseudo-bosons in terms of nilpotent Lie algebras

2017

We show how the one-mode pseudo-bosonic ladder operators provide concrete examples of nilpotent Lie algebras of dimension five. It is the first time that an algebraic-geometric structure of this kind is observed in the context of pseudo-bosonic operators. Indeed we don't find the well known Heisenberg algebras, which are involved in several quantum dynamical systems, but different Lie algebras which may be decomposed in the sum of two abelian Lie algebras in a prescribed way. We introduce the notion of semidirect sum (of Lie algebras) for this scope and find that it describes very well the behaviour of pseudo-bosonic operators in many quantum models.