Microarray screening of Guillain-Barré syndrome sera for antibodies to glycolipid complexes

Objective: To characterize the patterns of autoantibodies to glycolipid complexes in a large cohort of Guillain-Barré syndrome (GBS) and control samples collected in Bangladesh using a newly developed microarray technique. Methods: Twelve commonly studied glycolipids and lipids, plus their 66 possible heteromeric complexes, totaling 78 antigens, were applied to polyvinylidene fluoride–coated slides using a microarray printer. Arrays were probed with 266 GBS and 579 control sera (2 μL per serum, diluted 1/50) and bound immunoglobulin G detected with secondary antibody. Scanned arrays were subjected to statistical analyses. Results: Measuring antibodies to single targets was 9% less sensitive than to heteromeric complex targets (49.2% vs 58.3%) without significantly affecting specificity (83.9%–85.0%). The optimal screening protocol for GBS sera comprised a panel of 10 glycolipids (4 single glycolipids GM1, GA1, GD1a, GQ1b, and their 6 heteromeric complexes), resulting in an overall assay sensitivity of 64.3% and specificity of 77.1%. Notable heteromeric targets were GM1:GD1a, GM1:GQ1b, and GA1:GD1a, in which exclusive binding to the complex was observed. Conclusions: Rationalizing the screening protocol to capture the enormous diversity of glycolipid complexes can be achieved by miniaturizing the screening platform to a microarray platform, and applying simple bioinformatics to determine optimal sensitivity and specificity of the targets. Glycolipid complexes are an important category of glycolipid antigens in autoimmune neuropathy cases that require specific analytical and bioinformatics methods for optimal detection

Improved efficiency of graphene/Si Schottky junction solar cell based on back contact structure and DUV treatment

© 2017 Elsevier Ltd A graphene/Si Schottky junction solar cell is commonly fabricated by using the top-window structure. However, reported devices have many drawbacks such as a small active area of 0.11 cm 2 , s-shape in the J-V curves, recombination process of charge carriers at the graphene/textured Si interface, high cost and a complex fabrication process. Here, we report a novel graphene/Si Schottky junction solar cell with a back contact-structure, which has benefits of a simpler fabrication process, lower fabrication cost, and larger active area in comparison with a device fabricated with the previous structure. Additionally, we found that the PMMA residue left on graphene surfaces is the key to eliminate the s-shape in the J-V curves. Thus, the deep UV treatment of the CVD graphene is applied within the wet transfer process to effectively remove the PMMA residue, suppress the behavior of s-shaped kink in J-V curves and enhance the solar cell efficiency. As a result, the recorded power conversion efficiency of 10% is achieved for graphene/textured Si devices without chemical doping and anti-reflection coating, and this value is improved to 14.1% after applying chemical doping. Doped devices also show great stability and retain 84% of the efficiency after 9 days storage in air

Magnetotransport properties of a magnetically modulated two-dimensional electron gas with the spin-orbit interaction

We study the electrical transport properties of a two-dimensional electron gas with the Rashba spin-orbit interaction in presence of a constant perpendicular magnetic field $(B_0 \hat z)$ which is weakly modulated by ${\bf B_1} = B_1 \cos (q x) \hat z$, where $B_1 \ll B_0$ and $q = 2 \pi/a$ with $a$ is the modulation period. We obtain the analytical expressions of the diffusive conductivities for spin-up and spin-down electrons. The conductivities for spin-up and spin-down electrons oscillate with different frequencies and produce beating patterns in the amplitude of the Weiss and Shubnikov-de Haas oscillations. We show that the Rashba strength can be determined by analyzing the beating pattern in the Weiss oscillation. We find a simple equation which determines the Rashba spin-orbit interaction strength if the number of Weiss oscillations between any two successive nodes is known from the experiment. We compare our results with the electrically modulated 2DEG with the Rashba interaction. For completeness, we also study the beating pattern formation in the collisional and the Hall conductivities.Comment: 11 pages, 5 figures, re-written with new result

Low temperature structural phase transition and incommensurate lattice modulation in the spin gap compound BaCuSi2O6

Results of high resolution x-ray diffraction experiments are presented for single crystals of the spin gap compound BaCuSi$_2$O$_6$ in the temperature range from 16 to 300 K. The data show clear evidence of a transition from the room temperature tetragonal phase into an incommensurately modulated orthorhombic structure below $\sim$100 K. This lattice modulation is characterized by a resolution limited wave vector {\bf q}$_{IC}$=(0,$\sim$0.13,0) and its 2$^{nd}$ and 3$^{rd}$ harmonics. The phase transition is first order and exhibits considerable hysteresis. This observation implies that the spin Hamiltonian representing the system is more complex than originally thought.Comment: 4 pages, 4 figure

Effective chemical treatment for high efficiency graphene/Si Schottky junction solar cells with a graphene back-contact structure

We demonstrate a high-efficiency graphene/Si Schottky junction solar cell with an easy to fabricate graphene back-contact structure and effective chemical treatments. This device effectively overcame the current challenges associated with reported graphene/Si Schottky solar cell structures. The short-circuit current density for such a device is increased by around 20% due to the increase of the active area of this device, compared to previous graphene/Si Schottky junction solar cell devices. The undesirable s-shaped kink in J-V curves, as found in previous works, have been eliminated by using Formamide treatment for 30 min prior to an annealing process in the forming gas. The fill factor of this device is improved by 40% after this treatment, due to the effective removal of the unwanted PMMA residue. Moreover, volatile oxidant vapour and anti-reflection coating are applied within the fabrication process for this device to further improve solar cell performance. An efficiency of 9.5% has successfully been achieved for the fabricated device using the fabrication techniques developed in this work. Our device presents a viable and achievable approach to preparing low-cost and high-performance graphene/Si Schottky junction solar cells

Asymmetric Thermal Lineshape Broadening in a Gapped 3-Dimensional Antiferromagnet - Evidence for Strong Correlations at Finite Temperature

It is widely believed that magnetic excitations become increasingly incoherent as temperature is raised due to random collisions which limit their lifetime. This picture is based on spin-wave calculations for gapless magnets in 2 and 3 dimensions and is observed experimentally as a symmetric Lorentzian broadening in energy. Here, we investigate a three-dimensional dimer antiferromagnet and find unexpectedly that the broadening is asymmetric - indicating that far from thermal decoherence, the excitations behave collectively like a strongly correlated gas. This result suggests that a temperature activated coherent state of quasi-particles is not confined to special cases like the highly dimerized spin-1/2 chain but is found generally in dimerized antiferromagnets of all dimensionalities and perhaps gapped magnets in general