Study Objective. To investigate the occurrence of tramadol‐associated seizures.
Design. Retrospective cohort and case‐control studies.
Setting. UnitedHealth Group‐affiliated independent practice ...model health plans, from different regions of the United States, contracting with large networks of physicians.
Intervention. Analysis of administrative data from a large U.S. managed care population.
Patients. A cohort of 9218 adult tramadol users and 37,232 concurrent nonusers.
Measurements and Main Results. Fewer than 1% of users (80) had a presumed incident seizure claim after the first tramadol prescription. Risk of seizure claim was increased 2‐ to 6‐fold among users adjusted for selected comorbidities and concomitant drugs. Risk was highest among those aged 25–54 years, those with more than four tramadol prescriptions, and those with history of alcohol abuse, stroke, or head injury. A case‐control study among users was conducted to validate incident seizure outcomes from medical records. Only eight cases were confirmed, and all had cofactors associated with increased seizure risk.
Conclusion. In a general population, risk of seizure may be associated with long‐term therapy with tramadol or the presence of cofactors, or confined to a small sensitive population subset.
The gas of magnetic monopoles in spin ice is governed by one key parameter: the monopole chemical potential. A significant variation of this parameter could access hitherto undiscovered magnetic ...phenomena arising from monopole correlations, as observed in the analogous electrical Coulomb gas, like monopole dimerization, critical phase separation, or charge ordering. However, all known spin ices have values of chemical potential imposed by their structure and chemistry that place them deeply within the weakly correlated regime, where none of these interesting phenomena occur. Here we use high-pressure synthesis to create a new monopole host, Dy(2)Ge(2)O(7), with a radically altered chemical potential that stabilizes a large fraction of monopole dimers. The system is found to be ideally described by the classic Debye-Huckel-Bjerrum theory of charge correlations. We thus show how to tune the monopole chemical potential in spin ice and how to access the diverse collective properties of magnetic monopoles.
Background The pre- and pen-natal drug exposures reported by women participating in a case-control study of children in Colorado were examined for association withinfant craniosynostosis. Methods ...Mothers of case and control children underwent a standardized telephone interview and obstetric and newborn medical record review. The interview included questions on the use of prescription and non-prescription drugs, nutritional supplements, recreational and drugs of abuse. The mother's obstetric record was abstracted for information about pharmacologic agents taken before and during the antepartum period. Results There were no statistically significant risk ratios associating craniosynostosis with prenatal exposure to hydantoin, vaiproic acid, or cocaine. Mothers of four case children and one control child reported specific exposure to retinoic acid. There were no statisicafly significant increases in the odds ratio (OR) for any suture type among children exposed to hypoxigenic agents, sympathomimetic or parasympatholytic agents, or metal-containing agents. The OR was 1.87 (lower bound of the two-sided 95% test-based confidence interval (CI) : 1.08) among children with sagittal/lambdoid suture synostosis who were exposed to nitro satable drugs chiorpheniramine, chlordiazepoxide, and nitrofurantoin compared to controls. Conclusions Certain nitrosatable drugs may be associated with increased risk of infant sagittal/lambdoid craniosynostosis. A possible mechanism related to ischaernia/ reperfusion injury is suggested.
The geometrically frustrated antiferromagnet Gd2Ti2O7 exhibits magnetic behaviour of such complexity that it poses a challenge to both experiment and theory. Magnetic ordering commences at TN = 1.1 K ...and there is a further magnetic phase transition at T' = 0.7 K. Here we use neutron diffraction to definitively establish the nature of the phase transition at T' and the magnetic structure adopted below this temperature. Between T' and TN the structure is partly ordered, as previously reported. Below T' the remaining spins order, but only weakly. The magnetic structure in this temperature range is shown to be a 4-k structure, closely related to the 1-k structure previously suggested. The 4-k and 1-k variants of the structure are distinguished by analysis of the diffuse scattering, which we believe represents a new method of solving the 'multi-k' problem of magnetic structure determination.
In this paper we report the resistivity and neutron scattering experiments on Nd3Co4Sn13. These results indicate that Nd3Co4Sn13 undergoes a structural distortion from a high-temperature primitive ...cubic unit cell to an I-centered superstructure and a concomitant doubling of the lattice constant. The P m -3 n structure of Yb3Rh4Sn13 describes well the neutron powder diffraction pattern collected at room temperature, but failed to fit the low–temperature profiles due to the presence of (h/2 k/2 l)-type diffraction peaks. Single crystal elastic neutron scattering performed in the h h l scattering plane shows the lattice distortion with mean field character at 124 (2) K as the temperature is lowered. Besides, three I-centered space groups are excluded by the single crystal diffraction work, including I -4 3 d symmetry which is observed in other R3T4Sn13 compounds.
Liquids are expected to crystallize at low temperature. The only exception is helium, which can remain liquid at 0 K, owing to quantum fluctuations. Similarly, the atomic magnetic moments (spins) in ...a magnet are expected to order at a temperature scale set by the Curie-Weiss temperature CW (ref. 3). Geometrically frustrated magnets represent an exception. In these systems, the pairwise spin interactions cannot be simultaneously minimized because of the lattice symmetry. This can stabilize a liquid-like state of short-range-ordered fluctuating moments well below CW (refs 5-7). Here we use neutron scattering to observe the spin liquid state in a geometrically frustrated system, Tb2Ti2O7, under conditions of high pressure (∼9 GPa) and low temperature (∼1 K). This compound is a three-dimensional magnet with CW = -19 K, where the negative value indicates antiferromagnetic interactions. At ambient pressure Tb2Ti2O7 remains in a spin liquid state down to at least 70 mK (ref. 8). But we find that, under high pressure, the spins start to order or 'crystallize' below 2.1 K, with antiferromagnetic order coexisting with liquid-like fluctuations. These results indicate that a spin liquid/solid mixture can be induced by pressure in geometrically frustrated systems.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The pyrochlore material Ho2Ti2O7 has been suggested to show "spin ice" behavior. We present neutron scattering and specific heat results that establish unambiguously that Ho2Ti2O7 exhibits spin ice ...correlations at low temperature. Diffuse magnetic neutron scattering is quite well described by a nearest neighbor spin ice model and very accurately described by a dipolar spin ice model. The heat capacity is well accounted for by the sum of a dipolar spin ice contribution and an expected nuclear spin contribution, known to exist in other Ho3+ salts. These results settle the question of the nature of the low temperature spin correlations in Ho2Ti2O7 for which contradictory claims have been made.
This report describes the preparation of a series of new cellulose-based polymer inclusion membranes (PIMs) and compares their properties to those made with cellulose triacetate (CTA). The cellulose ...derivatives considered in this study include cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) containing both high and low butyryl content, and cellulose tributyrate (CTB). PIMs were prepared containing bis-
tert-butylcyclohexano-18-crown-6 as a metal cation carrier. Differences in ion permeability based on polymer type were investigated by monitoring K
+ flux. Flux of K
+ diminished with increasing size of the polymer side chains. The resistance of varying PIMs to hydrolysis under acidic and alkaline conditions was determined. It was found that the length of polymer alkyl chain is proportional to PIM durability under pH conditions favoring hydrolytic cleavage of the polymer β-glucosidic linkages.
PDF
