The spin resonance and high frequency optical properties of the cuprates

We argue that recently observed superconductivity-induced blue shift of the plasma frequency $\delta \omega_{pl}$ in $Bi_2Sr_2CaCu_2O_{8+\delta}$ is related to the change in the integrated dynamical structure factor associated with the development of the spin resonance below $T_c$. We show that the magnitude of $\delta \omega_{pl}$ is consistent with the small integrated spectral weight of the resonance, and its temperature dependences closely follow that of the spin resonance peak.Comment: 5 pages, 3 figure

Virtual geological outcrops - fieldwork and analysis made less exhaustive?

For geologists studying outcrops in the field, there is an ever‐increasing need for the acquisition of accurate and comprehensive data, whatever their purpose. Fortunately, this need is mirrored by an expanding range of digital data capturing technologies that provide the possibility of examining geological outcrops in minute detail from the desktop. Although difficult technologically, there is also a need to combine differing datasets into a single, accurate, digital model that will allow field geologists to place their data in a wider context. This paper examines the techniques available, and highlights new Light Detection and Ranging (LIDAR) technology which should prove to be a unifying technique, being able to combine images and local coordinates on‐site

DHCR7 mutations linked to higher vitamin D status allowed early human migration to Northern latitudes

PMCID: PMC3708787This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Dispersion Anomalies in Cuprate Superconductors

We argue that the shape of the dispersion along the nodal and antinodal directions in the cuprates can be understood as a consequence of the interaction of the electrons with collective spin excitations. In the normal state, the dispersion displays a crossover at an energy where the decay into spin fluctuations becomes relevant. In the superconducting state, the antinodal dispersion is strongly affected by the spin resonance and displays an S-shape whose magnitude scales with the resonance intensity. For nodal fermions, relevant spin excitations do not have resonance behavior, rather they are better characterized as a gapped continuum. As a consequence, the S-shape becomes a kink, and superconductivity does not affect the dispersion as strongly. Finally, we note that optical phonons typically lead to a temperature independent S-shape, in disagreement with the observed dispersion.Comment: 12 pages, 7 eps figure

Inflammatory Activity on Natalizumab Predicts Short-term but not Long-term Disability in Multiple Sclerosis

BACKGROUND: In people with multiple sclerosis treated with interferon-beta or glatiramer acetate, new MRI lesions and relapses during the first year of treatment predict a poor prognosis. OBJECTIVE: To study this association in those receiving natalizumab. METHODS: Data were collected on relapses, new MRI activity, and Modified Rio Score after initiation of natalizumab in an observational cohort of 161 patients with high baseline disability. These were correlated with Expanded Disability Status Scale (EDSS) progression at years 1, 2, 3, and 3-7 after treatment initiation, versus pre-treatment baseline. RESULTS: 46/161 patients had a relapse in the first year and 44/161 had EDSS progression by year 2. Relapses and Modified Rio Score in the first year of treatment predicted EDSS progression at year 1 and 2 after treatment initiation. However, this effect disappeared with longer follow-up. Paradoxically, there was a trend towards inflammatory activity on treatment (first year Modified Rio Score, relapses, and MRI activity) predicting a lower risk of EDSS progression by years 3-7, although this did not reach statistical significance. Those with and without EDSS progression did not differ in baseline age, EDSS, or pre-treatment relapse rate. Relapses in year 0-1 predicted further relapses in years 1-3. CONCLUSIONS: Breakthrough inflammatory activity after natalizumab treatment is predictive of short-term outcome measures of relapses or EDSS progression, but does not predict longer term EDSS progression, in this cohort with high baseline disability