Traveling waves in one-dimensional nonlinear models of strain-limiting viscoelasticity

In this article we investigate traveling wave solutions of a nonlinear differential equation describing the behaviour of one-dimensional viscoelastic medium with implicit constitutive relations. We focus on a subclass of such models known as the strain-limiting models introduced by Rajagopal. To describe the response of viscoelastic solids we assume a nonlinear relationship among the linearized strain, the strain rate and the Cauchy stress. We then concentrate on traveling wave solutions that correspond to the heteroclinic connections between the two constant states. We establish conditions for the existence of such solutions, and find those solutions, explicitly, implicitly or numerically, for various forms of the nonlinear constitutive relation

1H-magnetic resonance spectroscopy in first episode and chronic schizophrenia patients

Background/aim: The aim of this study was to compare metabolite levels of the dorsolateral prefrontal cortex (DLPFC), anterior cingulate gyrus (ACG), thalamus, and hippocampus in patients with chronic schizophrenia (CSPs) and first psychotic episode patients (FEPs) by the use of magnetic resonance spectroscopy (MRS). Materials and methods: Thirty CSPs, 20 FEPs, and 30 healthy subjects participated in this study. N-Acetylaspartate (NAA), creatine, choline (Cho), and myoinositol levels of the DLPFC, ACG, thalamus, and hippocampus were measured by 1H-MRS. Results: It was determined that the NAA/Cho ratio was lower in both the FEPs and CSPs than the healthy controls in the DLPFC. DLPFC Cho levels were also higher in CSPs than healthy controls. NAA levels in CSPs were significantly lower than in the control group in the hippocampus. There was no significant difference in neurometabolite levels and ratios in the ACG and thalamus between the groups. Conclusion: This study supports neuronal dysfunction or loss of neuronal integrity in the DLPFC and hippocampus in CSPs. FEPs showed less neuronal dysfunction in the DLPFC, but not in the hippocampus. Our results suggest that schizophrenic patients show brain metabolic changes with the onset of the disorder in the DLPFC; these changes could be more apparent in the hippocampus as the disease progresses to chronic stages. © TÜBİTAK

Factorizations of one dimensional classical systems

A class of one dimensional classical systems is characterized from an algebraic point of view. The Hamiltonians of these systems are factorized in terms of two functions that together with the Hamiltonian itself close a Poisson algebra. These two functions lead directly to two time-dependent integrals of motion from which the phase motions are derived algebraically. The systems so obtained constitute the classical analogues of the well known factorizable one dimensional quantum mechanical systems.Comment: 19 pages, 7 figure

Investigation of alexithymia and levels of anxiety and depression among patients with restless legs syndrome

Onur Yilmaz,1 Yildizhan Şengül,2 Hakan Serdar Şengül,3 Fatma Büşra Parlakkaya,1 Ahmet Öztürk1 1Bezmialem Foundation University Medical Faculty, Department of Psychiatry, Istanbul, Turkey; 2Bezmialem Foundation University Medical Faculty, Department of Neurology, IIstanbul, Turkey; 3Gaziosmanpasa Taksim Research and Training Hospital, Department of Psychiatry, Istanbul, Turkey Purpose: The purpose of this study was to examine alexithymia among restless legs syndrome (RLS) patients, compare with healthy controls, and argue the clinical inferences of this relationship. We searched for anxiety and depression and their clinical outcomes among patients and searched whether the results are similar to previous studies. Patients and methods: Eighty-seven RLS patients and 88 age, gender, and educationally matched healthy controls were assessed in Bezmialem Foundation University Hospital. RLS patients and healthy controls were assessed with the Sociodemographic Data Form constructed for the present study, 20-item Toronto Alexithymia Scale (TAS-20), Beck Depression Inventory (BDI), and Beck Anxiety Scale (BAS). The patient group was also assessed with the International Restless Legs Syndrome Study Group (IRLSSG) RLS Severity Scale. Results: RLS patients were found to have greater TAS-20, BDI, and BAS scores compared with the control group (P < 0.05). RLS severity score was positively correlated with the scores of anxiety and depression scales. However, no significant relationship was found between scores of IRLSSG RLS scale and TAS-20 total and subscale scores. Conclusion: RLS patients were found to be more alexithymic than healthy controls, whereas no significant relationship was found between RLS severity and levels of alexithymia. Still, alexithymia might be a predictor for early diagnosis and may be considered in the treatment and follow-up of RLS. RLS patients have higher depression and anxiety scores than healthy individuals. Thus, depression and anxiety should be taken into consideration throughout the RLS treatment. Keywords: restless legs syndrome, alexithymia, anxiety, depressio