120 research outputs found
Bifurcations of equilibria in DNA elasticity
No full textDNA molecules in the familiar double helical B form are treated here as though they have rod-like structures obtained by stacking the
nearly planar base pairs comprising them one on top of another with each rotated by approximately one-tenth of a full turn with respect
to its immediate predecessor in the stack. As each base in a base pair is attached to the sugar-phosphate backbone chain of one of the
two DNA strands that have come together to form the Watson-Crick structure, and each phosphate group in a backbone chain bears one electronic charge, two such charges are associated with each base pair. Thus, each base pair is subject to not only the elastic forces and moments exerted on it by its neighboring base pairs but also to remote electrostatic forces that, because they are only partially screened out by positively charged counter ions, can render the molecule's equilibrium configurations sensitive to changes in the concentration c of salt in the medium.
The observation that the step from one base pair to the next can be one of several distinct types, each having its own mechanical properties that depend on the nucleotide composition of the step, and the assumption that a base pair is rigid, led to the development of a theory of sequence dependent DNA elasticity [Coleman, Olson, and Swigon, J. Chem. Phys. 118 ,7127-7140, (2003)]. The theory of DNA molecules in aqueous solution developed here is based on but goes beyond that theory. It takes into account the intramolecular electrostatic interactions of the negatively charged phosphate groups in the molecule and the impenetrability of the DNA molecule for cases in which the
electrostatic repulsive forces do not suffice to avoid self penetration. The theory permits one to calculate equilibrium configurations, to determine their stability, and to study the dependence of them on salt concentration and on all kinds of end conditions.
When the intramolecular electrostatic forces are taken into account, the equations of mechanical equilibrium for a DNA molecule with N+1 base pairs are a system of mu*N non-linear equations, where mu, the number of kinematical variables describing the relative displacement and orientation of adjacent base pairs is in general 6; it reduces to 3 when base-pair steps are assumed to be inextensible and non-shearable. An efficient numerically stable computational scheme is here presented for
solving those equations and determining the mechanical stability of the calculated equilibrium configurations. That scheme is employed to compute and analyze bifurcation diagrams in which c is the bifurcation parameter and to show that, for an intrinsically curved molecule, small changes in c can have a strong effect on stable
equilibrium configurations. Cases are presented in which self-contact must be taken into account even though the intramolecular electrostatic forces of repulsion are strong.Ph.D.Includes bibliographical references (p. 106-110)
Informed Consent in Child Psychiatry -- a Theoretical Review
No full textIn this theoretical review we examine the issue of informed consent in child psychiatry. We describe the development of the concept of informed consent in the history of medicine and review the limited research on its application in child psychiatry. We analyze special features of informed consent unique to our field, such as the capacity of the child to give consent, the status of the "mature minor", the special situation of the child within the family, the place of informed consent in psychotherapy, and the ability of child psychiatrists to give full information prior to consent. We conclude that children, even under the legal age, should be part of the process of giving consent to treatment. On the other hand the complex process of obtaining consent should be aimed at achieving real involvement of patients and families and not merely adhering to formal requirements
Association of the type 2 diabetes mellitus susceptibility gene, TCF7L2, with schizophrenia in an Arab-Israeli family sample.
No full textMany reports in different populations have demonstrated linkage of the 10q24-q26 region to schizophrenia, thus encouraging further analysis of this locus for detection of specific schizophrenia genes. Our group previously reported linkage of the 10q24-q26 region to schizophrenia in a unique, homogeneous sample of Arab-Israeli families with multiple schizophrenia-affected individuals, under a dominant model of inheritance. To further explore this candidate region and identify specific susceptibility variants within it, we performed re-analysis of the 10q24-26 genotype data, taken from our previous genome-wide association study (GWAS) (Alkelai et al, 2011). We analyzed 2089 SNPs in an extended sample of 57 Arab Israeli families (189 genotyped individuals), under the dominant model of inheritance, which best fits this locus according to previously performed MOD score analysis. We found significant association with schizophrenia of the TCF7L2 gene intronic SNP, rs12573128, (p = 7.01×10⁻⁶) and of the nearby intergenic SNP, rs1033772, (p = 6.59×10⁻⁶) which is positioned between TCF7L2 and HABP2. TCF7L2 is one of the best confirmed susceptibility genes for type 2 diabetes (T2D) among different ethnic groups, has a role in pancreatic beta cell function and may contribute to the comorbidity of schizophrenia and T2D. These preliminary results independently support previous findings regarding a possible role of TCF7L2 in susceptibility to schizophrenia, and strengthen the importance of integrating linkage analysis models of inheritance while performing association analyses in regions of interest. Further validation studies in additional populations are required
A policy model for Tunisia with real and financial flows
No full textThis model was developed to provide a moacroeconomic framework for Tunisia's structural adjustment program and a flexible tool for further country economic analysis. As currently specified, it is designed to analyze fiscal, debt, and incomes policies, while deriving implications for the exchange rate and for the availability of credit to the private sector. Several policy experiments are carried out to illustrate this focus, and suggestions are offered for variations in model closure and detail.Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Economic Stabilization,Financial Intermediation
Credit rationing, tenancy, productivity, and the dynamics of inequality
No full textWhy, when given the same resources, might productivity be lower on farms operated through sharecropping than on owner-run farms? The reason is that sharecropping, much less wage contracts, cannot overcome the divergence of interests between those who till the land and those who own it. Only land redistribution can do that. This paper presents notes toward a general equilibrium theory of land tenancy that suggest how changes in technology and publicly provided infrastructure can affect the equilibrium distribution of land in countries where credit is rationed. When credit to famers is rationed, changes in technology can increase the inequality in landholdings - with a long term increase in share tenancy. This is turn might reduce productivity, at least partially offsetting the initial improvements. The paper suggests that the development of effective rural financial institutions would reduce the likelihood of these negative effects on equality and productivity. It further cautions though that past attempts in creating such institutions have failed because of a lack of accountability and of enforcement procedures.Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,Economic Growth,Municipal Financial Management
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Arab Jews, Mizrahi studies and Shimon Ballas' Outcast
No full texttextThis report examines the novel Outcast by Israeli author Shimon Ballas and its themes in respect to the prominent debates in the field of Mizrahi studies. It discusses the prominent scholars who deal with the history of Arab Jews in Israel and Mizrahi studies in general. It examines these issues both in the scholarship and literature and posits that each adds to and complicates the debate. The discussion also includes the treatments of Arab Jews in modern Zionist discourse and the history of Mizrahi political and scholarly activity in Israel.Middle Eastern Studie
Review of the Change 2010-2017
No full textReview of changes made by journals to their author instructions in light of the replication crisis, between 2010 and 201
Review of the Change 2010-2017
No full textReview of changes made by journals to their author instructions in light of the replication crisis, between 2010 and 201
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