231 research outputs found

    Similarity versus Coincidence Rotations of Lattices

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    The groups of similarity and coincidence rotations of an arbitrary lattice L in d-dimensional Euclidean space are considered. It is shown that the group of similarity rotations contains the coincidence rotations as a normal subgroup. Furthermore, the structure of the corresponding factor group is examined. If the dimension d is a prime number, this factor group is an elementary Abelian d-group. Moreover, if L is a rational lattice, the factor group is trivial (d odd) or an elementary Abelian 2-group (d even).Comment: 6 pages, paper presented at ICQ10 (Zurich, Switzerland

    Coincidence isometries of a shifted square lattice

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    We consider the coincidence problem for the square lattice that is translated by an arbitrary vector. General results are obtained about the set of coincidence isometries and the coincidence site lattices of a shifted square lattice by identifying the square lattice with the ring of Gaussian integers. To illustrate them, we calculate the set of coincidence isometries, as well as generating functions for the number of coincidence site lattices and coincidence isometries, for specific examples.Comment: 10 pages, 1 figure; paper presented at Aperiodic 2009 (Liverpool

    DC and high-frequency conductivity of the organic metals beta"-(BEDT-TTF)2SF5RSO3 (R = CH2CF2 and CHF)

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    The temperature dependences of the electric-transport properties of the two-dimensional organic conductors beta"-(BEDT-TTF)2SF5CH2CF2SO3, beta"-(d8-BEDT-TTF)2SF5CH2CF2SO3, and beta"-(BEDT-TTF)2SF5CHFSO3 are measured by dc methods in and perpendicular to the highly-conducting plane. Microwave measurements are performed at 24 and 33.5 GHz to probe the high-frequency behavior from room temperature down to 2 K. Superconductivity is observed in beta"-(BEDT-TTF)2SF5CH2CF2SO3 and its deuterated analogue. Although all the compounds remain metallic down to low-temperatures, they are close to a charge-order transition. This leads to deviations from a simple Drude behavior of the optical conductivity which become obvious already in the microwave range. In beta"-(BEDT-TTF)2SF5CH2CF2SO3, for instance, charge fluctuations cause an increase in microwave resistivity for T < 20 K which is not detected in dc measurements. beta"-(BEDT-TTF)2SF5CHFSO3 exhibits a simple metallic behavior at all frequencies. In the dc transport, however, we observe indications of localization in the perpendicular direction.Comment: 8 pages, 9 figure

    Training for interdisciplinary health research defining the required competencies

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    Although interdisciplinary research is becoming the dominant model for understanding complex health issues, little is known about the competencies required for successful interdisciplinary collaboration. Published research has discussed attitudes about interdisciplinary work and organizational resources but not the needed competencies. This report describes the method and results of the competency specification process for health research. Based on an established definition of interdisciplinary research, a preliminary set of competencies was developed from expert opinion of key informants and a review of the interdisciplinary research literature. A Delphi panel of interdisciplinary researchers then reached consensus on 17 competencies necessary for interdisciplinary research

    Referral of patients with depression to mental health care by Dutch general practitioners: an observational study

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    <p>Abstract</p> <p>Background</p> <p>Depression is a common illness, often treated in primary care. Guidelines provide recommendations for referral to mental health care. Several studies investigated determinants of referral, none investigated guideline criteria as possible determinants.</p> <p>We wanted to evaluate general practitioner's referral of depressed patients to mental health care and to what extent this is in agreement with (Dutch) guideline recommendations.</p> <p>Methods</p> <p>We used data of primary care respondents from the Netherlands Study of Depression and Anxiety with major depressive disorder in the past year (n = 478). We excluded respondents with missing data (n = 134). Referral data was collected from electronic patient files between 1 year before and after baseline and self report at baseline and 1-year follow-up. Logistic regression was used to describe association between guideline referral criteria (e.g. perceived need for psychotherapy, suicide risk, severe/chronic depression, antidepressant therapy failure) and referral.</p> <p>Results</p> <p>A high 58% of depressed patients were referred. Younger patients, those with suicidal tendency, chronic depression or perceived need for psychotherapy were referred more often. Patients who had used ≥2 antidepressants or with chronic depression were more often referred to secondary care. Referred respondents met on average more guideline criteria for referral. However, only 8-11% of variance was explained.</p> <p>Conclusion</p> <p>The majority of depressed patients were referred to mental health care. General practitioners take guideline criteria into account in decision making for referral of depressed patients to mental health care. However, other factors play a part, considering the small percentage of variance explained. Further research is necessary to investigate this.</p
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