1,946 research outputs found

    Integrals of motion and the shape of the attractor for the Lorenz model

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    In this paper, we consider three-dimensional dynamical systems, as for example the Lorenz model. For these systems, we introduce a method for obtaining families of two-dimensional surfaces such that trajectories cross each surface of the family in the same direction. For obtaining these surfaces, we are guided by the integrals of motion that exist for particular values of the parameters of the system. Nonetheless families of surfaces are obtained for arbitrary values of these parameters. Only a bounded region of the phase space is not filled by these surfaces. The global attractor of the system must be contained in this region. In this way, we obtain information on the shape and location of the global attractor. These results are more restrictive than similar bounds that have been recently found by the method of Lyapunov functions.Comment: 17 pages,12 figures. PACS numbers : 05.45.+b / 02.30.Hq Accepted for publication in Physics Letters A. e-mails : [email protected] & [email protected]

    Water Quality in Rainwater Tanks in Rural and Metropolitan Areas of New South Wales, Australia

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    This paper compares the water quality of rainwater tanks throughout the Sydney metropolitan area to that in rural New South Wales, Australia. The water quality is compared against the Australian Guidelines for Water Recycling (AGWR) to determine if the untreated rainwater from both areas can be considered suitable for non-potable water supply without filtration. Additionally this paper reports on a set of experiments where rainwater collected from a typical domestic roof in Sydney, New South Wales, Australia was treated by a pre-treatment of granular activated carbon (GAC) adsorption filter followed by micro-filtration. The GAC column removed the pollutants through an adsorption mechanism. GAC is a macroporous solid with a very large surface area providing many sites for adsorption and it is this property that makes it an efficient adsorbent. The parameters analysed were ammonia, anions and cations, heavy metals, nitrate and nitrite, pH, total hardness, total organic carbon, total suspended solids and turbidity. The results indicate that before treatment, the rainwater already complied to many of the parameters specified in the AGWR, certain pollutants have the potential at times to exceed the AGWR. The water quality was within the AGWR limits after the treatment. The micro- filtration flux values demonstrate that rainwater was able to be filtered through the membranes under low gravitational heads that are typically available in a rainwater tank while still producing sufficient membrane flux and pollutant removal rates

    Nonlinear Field Dependence of the Mobility of a Charge Subjected to a Superposition of Dichotomous Stochastic Potentials

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    A general prescription is presented to address a large variety of forms of the nonlinear dependence of the static charge mobility on the applied electric field. The system consists of a classical charge subjected to an arbitrarily strong steady state electric field and to a stochastic potential consisting of a linear superposition of an unlimited number of dichotomous potentials in one-dimensional space. It is shown that the nonlinear mobility can be calculated for arbitrary forms of the density function of the individual dichotomous components of the stochastic potential. Specific cases of physical interest are analyzed. One of them provides a curious possibility for an explanation of the universally observed square root field dependence of the logarithm of the mobility of photoinjected charge carriers in molecularly doped polymers

    Nonlinear Response Theory: Transport Coefficients for Driving Fields of Arbitrary Magnitude

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    A theory of nonlinear response is developed for driving fields of arbitrary magnitude. Exact and usable expressions are provided for electrical and thermal mobility, and related transport coefficients, in terms of correlation functions of the system. A generalization into the nonlinear domain is provided of the Wiedemann-Franz law connecting electrical and thermal response and of the Einstein relation relating the diffusion constant and the mobility

    Renyi-Wehrl entropies as measures of localization in phase space

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    We generalize the concept of the Wehrl entropy of quantum states which gives a basis-independent measure of their localization in phase space. We discuss the minimal values and the typical values of these R{enyi-Wehrl entropies for pure states for spin systems. According to Lieb's conjecture the minimal values are provided by the spin coherent states. Though Lieb's conjecture remains unproven, we give new proofs of partial results that may be generalized for other systems. We also investigate random pure states and calculate the mean Renyi-Wehrl entropies averaged over the natural measure in the space of pure quantum states.Comment: 18 pages, no figures, some improved versions of main proofs, added J.referenc

    Spin-Boson Hamiltonian and Optical Absorption of Molecular Dimers

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    An analysis of the eigenstates of a symmetry-broken spin-boson Hamiltonian is performed by computing Bloch and Husimi projections. The eigenstate analysis is combined with the calculation of absorption bands of asymmetric dimer configurations constituted by monomers with nonidentical excitation energies and optical transition matrix elements. Absorption bands with regular and irregular fine structures are obtained and related to the transition from the coexistence to a mixing of adiabatic branches in the spectrum. It is shown that correlations between spin states allow for an interpolation between absorption bands for different optical asymmetries.Comment: 15 pages, revTeX, 8 figures, accepted for publication in Phys. Rev.

    Noncandidal vaginitis: a comprehensive approach to diagnosis and management

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    Vaginitis is one of the most common causes of patient visits to gynecologists, primary care providers, and urgent care centers. However, many women leave without a clear diagnosis or experience recurrent symptoms despite treatment. The 3 most common etiologies of vaginitis are trichomonas, bacterial vaginosis, and vulvovaginal candidiasis, which account for an estimated 70% of cases. The remaining 30% may be related to other causes of vaginitis, including atrophic vaginitis, desquamative inflammatory vaginitis, and vaginal erosive disease. The purpose of this review is to describe the noncandidal causes of acute and recurrent vaginitis, with the goal of improving the likelihood of accurate diagnosis as well as efficient and effective therapy. We excluded candidal vaginitis from our review because there was a recently published review on this topic in the Journal. The clinical presentation and evaluation of patients with symptoms of vaginitis can be triaged into 1 of 2 diagnostic pathways: noninflammatory and inflammatory vaginitis. The most common noninflammatory cause is bacterial vaginosis. Features such as irritation, purulent discharge, and the presence of polymorphonuclear neutrophils are more suggestive of an inflammatory process. Trichomoniasis is the most common cause of inflammatory vaginitis. Other well-described forms of inflammatory vaginitis include atrophic vaginitis, desquamative inflammatory vaginitis, and erosive disease. We present a review of the pathogenesis, symptoms, examination findings, diagnostic testing, and treatment for each of these causes of noncandidal vaginitis

    Non-Hodgkin Lymphoma Secondary to Cancer Chemotherapy in a Patient with Small Cell Carcinoma of the Pancreas

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    Increased survival seen in patients with solid cancers achieved through aggressive treatment has transformed the prognosis and the complications of the therapy. The carcinogenic effect of the therapeutical agents has given leads to an increased incidence of second malignancies. This case report describes the rare metachronous association of two malignancies and to discuss the etiological links. A 51-year-old man presented with enlargement of right axilla and mesentery lymph nodes. The patient had a history of small cell carcinoma at the head of the pancreas and was treated with chemotherapy cisplatin and gemcitabine for 12 cycles two years prior. Biopsies were then performed. Diagnosis of Non-Hodgkin Lymphoma (NHL) follicular (nodular) type was decided from microscopic and immunohistochemistry results. We discussed that secondary NHL due to chemotherapy for solid cancer is rare. Testicular cancer, ovarian cancer, and breast cancer are the common primary tumors. The primary tumor from a small cell carcinoma of the pancreas (SCCP) is sporadic. The risk ofsecondary lymphoma increases after the first five years of completion of chemotherapy or radiotherapy and persists for more than three decades. In conclusion, this case reinforces the need for long-term follow-up of all patients exposed to chemotherapy for the treatment of pancreatic cancer. Keywords: Secondary NHL, chemotherapy, small cell carcinoma of the pancrea
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