Control of radiative processes using tunable plasmonic nanopatch antennas.

The radiative processes associated with fluorophores and other radiating systems can be profoundly modified by their interaction with nanoplasmonic structures. Extreme electromagnetic environments can be created in plasmonic nanostructures or nanocavities, such as within the nanoscale gap region between two plasmonic nanoparticles, where the illuminating optical fields and the density of radiating modes are dramatically enhanced relative to vacuum. Unraveling the various mechanisms present in such coupled systems, and their impact on spontaneous emission and other radiative phenomena, however, requires a suitably reliable and precise means of tuning the plasmon resonance of the nanostructure while simultaneously preserving the electromagnetic characteristics of the enhancement region. Here, we achieve this control using a plasmonic platform consisting of colloidally synthesized nanocubes electromagnetically coupled to a metallic film. Each nanocube resembles a nanoscale patch antenna (or nanopatch) whose plasmon resonance can be changed independent of its local field enhancement. By varying the size of the nanopatch, we tune the plasmonic resonance by ∼ 200 nm, encompassing the excitation, absorption, and emission spectra corresponding to Cy5 fluorophores embedded within the gap region between nanopatch and film. By sweeping the plasmon resonance but keeping the field enhancements roughly fixed, we demonstrate fluorescence enhancements exceeding a factor of 30,000 with detector-limited enhancements of the spontaneous emission rate by a factor of 74. The experiments are supported by finite-element simulations that reveal design rules for optimized fluorescence enhancement or large Purcell factors

Probing Local Variations of Superconductivity on the Surface of Ba(Fe1-xCox)2As2 Single Crystals

The spatially resolved electrical transport properties have been studied on the surface of optimally-doped superconducting Ba(Fe1-xCox)2As2 single crystal by using a four-probe scanning tunneling microscopy. While some non-uniform contrast appears near the edge of the cleaved crystal, the scanning electron microscopy (SEM) reveals mostly uniform contrast. For the regions that showed uniform SEM contrast, a sharp superconducting transition at TC = 22.1 K has been observed with a transition width (delta)Tc = 0.2 K. In the non-uniform contrast region, TC is found to vary between 19.6 and 22.2 K with (delta)Tc from 0.3 to 3.2 K. The wavelength dispersive x-ray spectroscopy reveals that Co concentration remains 7.72% in the uniform region, but changes between 7.38% and 7.62% in the non-uniform region. Thus the variations of superconductivity are associated with local compositional change.Comment: 18 pages, 5 figure

Primary ovarian cancer chemotherapy: current standards of care

Chemotherapy has been regarded as standard therapy for the majority of women with advanced epithelial ovarian cancer for several decades, with this role filled largely by the alkylating agents — used as monotherapy — until the mid-1980s. The activity of cisplatin in this disorder was established during the 1970s, and combinations of cisplatin and an alkylating agent were widely used during the late 1980s. However, further research prompted by continuing concerns over poor survival and tolerability led to the adoption of paclitaxel in combination with either cisplatin or carboplatin as first-line therapy in ovarian cancer during the 1990s. Most recent research has focused on further optimisation of these regimens to maximise clinical benefit while minimising toxicity, and investigations into alternative taxanes (e.g. docetaxel), other novel agents and new treatment schedules are ongoing

Statistical modeling of ground motion relations for seismic hazard analysis

We introduce a new approach for ground motion relations (GMR) in the probabilistic seismic hazard analysis (PSHA), being influenced by the extreme value theory of mathematical statistics. Therein, we understand a GMR as a random function. We derive mathematically the principle of area-equivalence; wherein two alternative GMRs have an equivalent influence on the hazard if these GMRs have equivalent area functions. This includes local biases. An interpretation of the difference between these GMRs (an actual and a modeled one) as a random component leads to a general overestimation of residual variance and hazard. Beside this, we discuss important aspects of classical approaches and discover discrepancies with the state of the art of stochastics and statistics (model selection and significance, test of distribution assumptions, extreme value statistics). We criticize especially the assumption of logarithmic normally distributed residuals of maxima like the peak ground acceleration (PGA). The natural distribution of its individual random component (equivalent to exp(epsilon_0) of Joyner and Boore 1993) is the generalized extreme value. We show by numerical researches that the actual distribution can be hidden and a wrong distribution assumption can influence the PSHA negatively as the negligence of area equivalence does. Finally, we suggest an estimation concept for GMRs of PSHA with a regression-free variance estimation of the individual random component. We demonstrate the advantages of event-specific GMRs by analyzing data sets from the PEER strong motion database and estimate event-specific GMRs. Therein, the majority of the best models base on an anisotropic point source approach. The residual variance of logarithmized PGA is significantly smaller than in previous models. We validate the estimations for the event with the largest sample by empirical area functions. etc

How heel oxygenation changes under pressure

The mechanism of heel pressure ulcers after hip surgery is not entirely understood. The purpose of this one-group, prospective, repeated-measures design study was to examine how the external pressure of the bed surface affects heel skin oxygen tension in adults on the first 3 days after hip surgery. Transcutaneous oxygen sensors were placed on the plantar surface of each foot, close to the heels. Measures were taken on room air and with an oxygen challenge with the heels (1) suspended above the bed surface (preload), (2) on the bed surface for 15 minutes (loading), and (3) again suspended above the bed surface for 15 minutes (unloading). Eighteen hip surgery patients (mean age 58.3±16.1 years) from two hospitals participated. When compared with preload on room air, both loading and unloading on all 3 days resulted in a reduction in heel oxygen tension bilaterally (p\u3c0.001). Heel oxygenation decreased without the anticipated hyperemic response, raising the question of whether this is a sign of increased pressure ulcer risk. Further work is needed to understand why this short period of external pressure results in decreased oxygenation and why oxygen tension does not return to baseline when pressure is removed

Outcome of ATP-based tumor chemosensitivity assay directed chemotherapy in heavily pre-treated recurrent ovarian carcinoma

BACKGROUND: We wished to evaluate the clinical response following ATP-Tumor Chemosensitivity Assay (ATP-TCA) directed salvage chemotherapy in a series of UK patients with advanced ovarian cancer. The results are compared with that of a similar assay used in a different country in terms of evaluability and clinical endpoints. METHODS: From November 1998 to November 2001, 46 patients with pre-treated, advanced ovarian cancer were given a total of 56 courses of chemotherapy based on in-vitro ATP-TCA responses obtained from fresh tumor samples or ascites. Forty-four patients were evaluable for results. Of these, 18 patients had clinically platinum resistant disease (relapse < 6 months after first course of chemotherapy). There was evidence of cisplatin resistance in 31 patients from their first ATP-TCA. Response to treatment was assessed by radiology, clinical assessment and tumor marker level (CA 125). RESULTS: The overall response rate was 59% (33/56) per course of chemotherapy, including 12 complete responses, 21 partial responses, 6 with stable disease, and 15 with progressive disease. Two patients were not evaluable for response having received just one cycle of chemotherapy: if these were excluded the response rate is 61%. Fifteen patients are still alive. Median progression free survival (PFS) was 6.6 months per course of chemotherapy; median overall survival (OAS) for each patient following the start of TCA-directed therapy was 10.4 months (95% confidence interval 7.9-12.8 months). CONCLUSION: The results show similar response rates to previous studies using ATP-TCA directed therapy in recurrent ovarian cancer. The assay shows high evaluability and this study adds weight to the reproducibility of results from different centre

Limited contribution of permafrost carbon to methane release from thawing peatlands

Models predict that thaw of permafrost soils at northern high-latitudes will release tens of billions of tonnes of carbon (C) to the atmosphere by 21001-3. The effect on the Earth's climate depends strongly on the proportion of this C which is released as the more powerful greenhouse gas methane (CH4), rather than carbon dioxide (CO2)1,4; even if CH4 emissions represent just 2% of the C release, they would contribute approximately one quarter of the climate forcing5. In northern peatlands, thaw of ice-rich permafrost causes surface subsidence (thermokarst) and water-logging6, exposing substantial stores (10s of kg C m-2, ref. 7) of previously-frozen organic matter to anaerobic conditions, and generating ideal conditions for permafrost-derived CH4 release. Here we show that, contrary to expectations, although substantial CH4 fluxes (>20 g CH4 m 2 yr-1) were recorded from thawing peatlands in northern Canada, only a small amount was derived from previously-frozen C (<2 g CH4 m-2 yr-1). Instead, fluxes were driven by anaerobic decomposition of recent C inputs. We conclude that thaw-induced changes in surface wetness and wetland area, rather than the anaerobic decomposition of previously-frozen C, may determine the effect of permafrost thaw on CH4 emissions from northern peatlands

IRS-2 Deficiency Impairs NMDA Receptor-Dependent Long-term Potentiation

The beneficial effects of insulin and insulin-like growth factor I on cognition have been documented in humans and animal models. Conversely, obesity, hyperinsulinemia, and diabetes increase the risk for neurodegenerative disorders including Alzheimer's disease (AD). However, the mechanisms by which insulin regulates synaptic plasticity are not well understood. Here, we report that complete disruption of insulin receptor substrate 2 (Irs2) in mice impairs long-term potentiation (LTP) of synaptic transmission in the hippocampus. Basal synaptic transmission and paired-pulse facilitation were similar between the 2 groups of mice. Induction of LTP by high-frequency conditioning tetanus did not activate postsynaptic N-methyl-D-aspartate (NMDA) receptors in hippocampus slices from Irs2−/− mice, although the expression of NR2A, NR2B, and PSD95 was equivalent to wild-type controls. Activation of Fyn, AKT, and MAPK in response to tetanus stimulation was defective in Irs2−/− mice. Interestingly, IRS2 was phosphorylated during induction of LTP in control mice, revealing a potential new component of the signaling machinery which modulates synaptic plasticity. Given that IRS2 expression is diminished in Type 2 diabetics as well as in AD patients, these data may reveal an explanation for the prevalence of cognitive decline in humans with metabolic disorders by providing a mechanistic link between insulin resistance and impaired synaptic transmission

High-Throughput Top-Down Fabrication of Uniform Magnetic Particles

Ion Beam Aperture Array Lithography was applied to top-down fabrication of large dense (108–109 particles/cm2) arrays of uniform micron-scale particles at rates hundreds of times faster than electron beam lithography. In this process, a large array of helium ion beamlets is formed when a stencil mask containing an array of circular openings is illuminated by a broad beam of energetic (5–8 keV) ions, and is used to write arrays of specific repetitive patterns. A commercial 5-micrometer metal mesh was used as a stencil mask; the mesh size was adjusted by shrinking the stencil openings using conformal sputter-deposition of copper. Thermal evaporation from multiple sources was utilized to form magnetic particles of varied size and thickness, including alternating layers of gold and permalloy. Evaporation of permalloy layers in the presence of a magnetic field allowed creation of particles with uniform magnetic properties and pre-determined magnetization direction. The magnetic properties of the resulting particles were characterized by Vibrating Sample Magnetometry. Since the orientation of the particles on the substrate before release into suspension is known, the orientation-dependent magnetic properties of the particles could be determined