Dimensionality-driven spin-flop transition in quasi-one-dimensional PrBa2Cu4O8

In the quasi-one-dimensional cuprate PrBa$_2$Cu$_4$O$_8$, the Pr cations order antiferromagnetically at 17 K in zero field. Through a combination of magnetic susceptibility, torque magnetometry, specific heat and interchain transport measurements, the anisotropic temperature-magnetic field phase diagram associated with this ordering has been mapped out. A low-temperature spin-flop transition in the Pr sub-lattice is found to occur at the same magnetic field strength and orientation as a dimensional crossover in the ground state of the metallic CuO chains. This coincidence suggests that the spin reorientation is driven by a change in the anisotropic Rudermann-Kittel-Kasuya-Yosida (RKKY) interaction induced by a corresponding change in effective dimensionality of the conduction electrons.Comment: 8 pages, 8 figure

Irradiation-induced confinement in a quasi-one-dimensional metal

The anisotropic resistivity of PrBa$_2$Cu$_4$O$_8$ has been measured as a function of electron irradiation fluence. Localization effects are observed for extremely small amounts of disorder corresponding to electron mean-free-paths of order 100 unit cells. Estimates of the localization corrections suggest that this anomalous localization threshold heralds a crossover to a ground state with pronounced one-dimensional character in which conduction electrons become confined to a small cluster of chains.Comment: 4 pages, 4 figure

Possible co-existence of local itinerancy and global localization in a quasi-one-dimensional conductor

In the chain compound PrBa$_2$Cu$_4$O$_8$ localization appears simultaneously with a dimensional crossover in the electronic ground state when the scattering rate in the chains exceeds the hopping rate between the chains. Here we report the discovery of a large, transverse magnetoresistance in PrBa$_2$Cu$_4$O$_8$ in the localized regime. This result suggests a novel form of localization whereby electrons retain their metallic (quasi-one-dimensional) character over a microscopic length scale despite the fact that macroscopically, they exhibit localized (one-dimensional) behavior.Comment: 4 pages, 4 Figure

Fragile three-dimensionality in the quasi-one-dimensional cuprate PrBa_2Cu_4O_8

In this article we report on the experimental realization of dimensional crossover phenomena in the chain compound PrBa$_2$Cu$_4$O$_8$ using temperature, high magnetic fields and disorder as independent tuning parameters. In purer crystals of PrBa$_2$Cu$_4$O$_8$, a highly anisotropic three-dimensional Fermi-liquid state develops at low temperatures. This metallic state is extremely susceptible to disorder however and localization rapidly sets in. We show, through quantitative comparison of the relevant energy scales, that this metal/insulator crossover occurs precisely when the scattering rate within the chain exceeds the interchain hopping rate(s), i.e. once carriers become confined to a single conducting element.Comment: 12 pages, 5 figures, published at http://www.iop.org/EJ/article/1367-2630/8/9/172/njp6_9_172.htm

Anxiety as a consequence of modern dietary pattern in adults in Tehran-Iran

Food intake patterns in relation to mental health have already been revealed. To investigate the relationship between processed food consumption behavior and anxiety disorder, a cross sectional study was conducted. Overall, 1782 young adults aged 18-35 years were randomly selected using cluster sampling method from 22 districts of Tehran Iran in 2011. Diet assessment was done using a 24 hour recall questionnaire in two times with a week interval. Anxiety level was determined using the validated Speilburger test (Persian version). A proportional odds regression model was used to assess the effect of processed food consumption on anxiety variables. A significant statistical difference was found between men and women in terms of processed food consumption (p<0.001). Adjusting for age, total calorie intake, gender, body mass index, socioeconomic status, and history of sedative drug consumption as well as mental health disorders, the proportional odds regression model showed a significant relationship between increased consumption of processed foods and anxiety (OR = 4.73, 95 CI: 2.89-12.54 for state and OR = 4.91, 95 CI: 2.88-13.99 for trait). Identification, modification and adjusting incorrect food patterns in the community could be considered as valuable steps to turn down nutritional-based health difficulties. (C) 2012 Elsevier Ltd. All rights reserved

Influence of Ca²⁺ ions on the habit of KDP crystals

A few KDP (KH₂PO₄) and KDP:Ca²⁺ (CaCl₂) single crystals were grown based on the temperature reduction method. Investigations show that the presence of bivalent ions like Ca²⁺ could be a cause of retarded growth rate and induced crystalline lattice defects. Here the pure KDP crystals are compared with KDP:CaCl₂. Crystals of both types were also studied in aspect of other structural and optical properties

Type 1 diabetes genetic risk score discriminates between monogenic and Type 1 diabetes in children diagnosed at the age of < 5 years in the Iranian population

This is the final version. Available on open access from Wiley via the DOI in this recordAim To examine the extent to which discriminatory testing using antibodies and Type 1 diabetes genetic risk score, validated in European populations, is applicable in a non‐European population. Methods We recruited 127 unrelated children with diabetes diagnosed between 9 months and 5 years from two centres in Iran. All children underwent targeted next‐generation sequencing of 35 monogenic diabetes genes. We measured three islet autoantibodies (islet antigen 2, glutamic acid decarboxylase and zinc transporter 8) and generated a Type 1 diabetes genetic risk score in all children. Results We identified six children with monogenic diabetes, including four novel mutations: homozygous mutations in WFS1 (n=3), SLC19A2 and SLC29A3, and a heterozygous mutation in GCK. All clinical features were similar in children with monogenic diabetes (n=6) and in the rest of the cohort (n=121). The Type 1 diabetes genetic risk score discriminated children with monogenic from Type 1 diabetes [area under the receiver‐operating characteristic curve 0.90 (95% CI 0.83–0.97)]. All children with monogenic diabetes were autoantibody‐negative. In children with no mutation, 59 were positive to glutamic acid decarboxylase, 39 to islet antigen 2 and 31 to zinc transporter 8. Measuring zinc transporter 8 increased the number of autoantibody‐positive individuals by eight. Conclusions The present study provides the first evidence that Type 1 diabetes genetic risk score can be used to distinguish monogenic from Type 1 diabetes in an Iranian population with a large number of consanguineous unions. This test can be used to identify children with a higher probability of having monogenic diabetes who could then undergo genetic testing. Identification of these individuals would reduce the cost of treatment and improve the management of their clinical course.Wellcome TrustDiabetes U

Magnetized Kelvin-Helmholtz instability in the presence of a radiation field

The purpose of this study is to analyze the dynamical role of a radiation field on the growth rate of the unstable Kelvin - Helmholtz (KH) perturbations. As a first step toward this purpose, the analyze is done in a general way, irrespective of applying the model to a specific astronomical system. The transition zone between the two layers of the fluid is ignored. Then, we perform a linear analysis and by imposing suitable boundary conditions and considering a radiation field, we obtain appropriate dispersion relation. Unstable modes are studied by solving the dispersion equation numerically, and then growth rates of them are obtained. By analyzing our dispersion relation, we show that for a wide range of the input parameters, the radiation field has a destabilizing effect on KH instability. In eruptions of the galaxies or supermassive stars, the radiation field is dynamically important and because of the enhanced KH growth rates in the presence of the radiation; these eruptions can inject more momentum and energy into their environment and excite more turbulent motions.Comment: Accepted for publication in Astrophysics and Space Scienc