Photonic bandgap narrowing in conical hollow core Bragg fibers

Cataloged from PDF version of article.We report the photonic bandgap engineering of Bragg fibers by controlling the thickness profile of the fiber during the thermal drawing. Conical hollow core Bragg fibers were produced by thermal drawing under a rapidly alternating load, which was applied by introducing steep changes to the fiber drawing speed. In conventional cylindrical Bragg fibers, light is guided by omnidirectional reflections from interior dielectric mirrors with a single quarter wave stack period. In conical fibers, the diameter reduction introduced a gradient of the quarter wave stack period along the length of the fiber. Therefore, the light guided within the fiber encountered slightly smaller dielectric layer thicknesses at each reflection, resulting in a progressive blueshift of the reflectance spectrum. As the reflectance spectrum shifts, longer wavelengths of the initial bandgap cease to be omnidirectionally reflected and exit through the cladding, which narrows the photonic bandgap. A narrow transmission bandwidth is particularly desirable in hollow waveguide mid-infrared sensing schemes, where broadband light is coupled to the fiber and the analyte vapor is introduced into the hollow core to measure infrared absorption. We carried out sensing simulations using the absorption spectrum of isopropyl alcohol vapor to demonstrate the importance of narrow bandgap fibers in chemical sensing applications. © 2014 AIP Publishing LLC

Surface Textured Polymer Fibers for Microfluidics

Cataloged from PDF version of article.This article introduces surface textured polymer fibers as a new platform for the fabrication of affordable microfluidic devices. Fibers are produced tens of meters-long at a time and comprise 20 continuous and ordered channels (equilateral triangle grooves with side lengths as small as 30 micrometers) on their surfaces. Extreme anisotropic spreading behavior due to capillary action along the grooves of fibers is observed after surface modification with polydopamine (PDA). These flexible fibers can be fixed on any surface - independent of its material and shape - to form three-dimensional arrays, which spontaneously spread liquid on predefined paths without the need for external pumps or actuators. Surface textured fibers offer high-throughput fabrication of complex open microfluidic channel geometries, which is challenging to achieve using current photolithography-based techniques. Several microfluidic systems are designed and prepared on either planar or 3D surfaces to demonstrate outstanding capability of the fiber arrays in control of fluid flow in both vertical and lateral directions. Surface textured fibers are well suited to the fabrication of flexible, robust, lightweight, and affordable microfluidic devices, which expand the role of microfluidics in a scope of fields including drug discovery, medical diagnostics, and monitoring food and water quality. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Analysis of Mars Analogue Soil Samples Using Solid-Phase Microextraction, Organic Solvent Extraction and Gas Chromatography/Mass Spectrometry

Polycyclic aromatic hydrocarbons (PAHs) are robust and abundant molecules in extraterrestrial environments. They are found ubiquitously in the interstellar medium and have been identified in extracts of meteorites collected on Earth. PAHs are important target molecules for planetary exploration missions that investigate the organic inventory of planets, moons and small bodies. This study is part of an interdisciplinary preparation phase to search for organic molecules and life on Mars. We have investigated PAH compounds in desert soils to determine their composition, distribution and stability. Soil samples (Mars analogue soils) were collected at desert areas of Utah in the vicinity of the Mars Desert Research Station (MDRS), in the Arequipa region in Peru and from the Jutland region of Denmark. The aim of this study was to optimize the solid-phase microextraction (SPME) method for fast screening and determination of PAHs in soil samples. This method minimizes sample handling and preserves the chemical integrity of the sample. Complementary liquid extraction was used to obtain information on five- and six-ring PAH compounds. The measured concentrations of PAHs are, in general, very low, ranging from 1 to 60 ng g(sup -1). The texture of soils is mostly sandy loam with few samples being 100% silt. Collected soils are moderately basic with pH values of 8-9 except for the Salten Skov soil, which is slightly acidic. Although the diverse and variable microbial populations of the samples at the sample sites might have affected the levels and variety of PAHs detected, SPME appears to be a rapid, viable field sampling technique with implications for use on planetary missions

Macroscopic assembly of indefinitely long and parallel nanowires into large area photodetection circuitry

Integration of nanowires into functional devices with high yields and good reliability turned out to be a lot more challenging and proved to be a critical issue obstructing the wide application of nanowire-based devices and exploitation of their technical promises. Here we demonstrate a relatively easy macrofabrication of a nanowire-based imaging circuitry using a recently developed nanofabrication technique. Extremely long and polymer encapsulated semiconducting nanowire arrays, mass-produced using the iterative thermal drawing, facilitate the integration process; we manually aligned the fibers containing selenium nanowires over a lithographically defined circuitry. Controlled etching of the encapsulating polymer revealed a monolayer of nanowires aligned over an area of 1 cm 2 containing a 10 × 10 pixel array. Each light-sensitive pixel is formed by the contacting hundreds of parallel photoconductive nanowires between two electrodes. Using the pixel array, alphabetic characters were identified by the circuitry to demonstrate its imaging capacity. This new approach makes it possible to devise extremely large nanowire devices on planar, flexible, or curved substrates with diverse functionalities such as thermal sensors, phase change memory, and artificial skin. © 2012 American Chemical Society

Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range

Network Meta-Analysis of Tofacitinib, Biologic Disease-Modifying Antirheumatic Drugs, and Apremilast for the Treatment of Psoriatic Arthritis

Background: Tofacitinib and other new treatments approved for use in psoriatic arthritis have only recently been included in psoriatic arthritis treatment guidelines, and studies evaluating the relative efficacy of available therapies are important to inform treatment decisions by healthcare professionals. Objective: To perform a network meta-analysis to evaluate the efficacy and safety profiles of tofacitinib, biologic disease-modifying antirheumatic drugs (bDMARDs), and apremilast in patients with psoriatic arthritis naive to tumor necrosis factor inhibitor therapy (TNFi-naive) or with an inadequate response (TNFi-IR). Methods: A systematic literature review used searches of MEDLINE, Embase, and The Cochrane Library on October 9, 2017. Randomized controlled trials including adult patients with psoriatic arthritis receiving treatment administered as monotherapy or with conventional synthetic DMARDs were selected. Efficacy outcomes included American College of Rheumatology 20 response, change from baseline in Health Assessment Questionnaire-Disability Index, >/=75% improvement in Psoriasis Area and Severity Index, and change from baseline in Dactylitis Severity Score and Leeds Enthesitis Index. Treatment effects were evaluated during placebo-controlled phases, using a binomial logit model for binary outcomes and a normal identify link model for other outcomes. Discontinuations due to adverse events and serious infection events were assessed as safety outcomes. Results: The network meta-analysis included 24 published randomized controlled trials, of which 13 enrolled TNFi-naive patients only, 3 enrolled TNFi-IR patients only, and 8 enrolled both TNFi-naive and TNFi-IR patients. Placebo-controlled treatment durations ranged from 12 to 24 weeks. Indirect comparisons showed tofacitinib 5 and 10 mg BID to have similar efficacy compared with most bDMARDs and apremilast in improving joint symptoms (based on American College of Rheumatology 20 response), and with some bDMARDs in improving skin symptoms (based on Psoriasis Area and Severity Index) (tofacitinib 10 mg BID only in TNFi-IR) in patients with psoriatic arthritis who were TNFi-naive or TNFi-IR. Results also showed that, compared with placebo, the improvement in physical functioning (based on Health Assessment Questionnaire-Disability Index) with tofacitinib 5 and 10 mg BID was similar to that observed with most bDMARDs and apremilast in TNFi-naive patients, and similar to that observed with all bDMARDs with available data in the TNFi-IR population. Improvements in Dactylitis Severity Score and Leeds Enthesitis Index scores were comparable between treatments. Tofacitinib 5 and 10 mg BID were median-ranked 8 and 15, respectively, for discontinuation due to any adverse events, and 5 and 16, respectively, for a serious infection event out of a total of 20 treatments in the network (lower numbers are more favorable). Conclusions: Tofacitinib provides an additional treatment option for patients with psoriatic arthritis, both in patients naive to TNFi and in those with TNFi-IR. (Curr Ther Res Clin Exp. 2020; 81:XXX-XXX)

Arrays of indefinitely long uniform nanowires and nanotubes

Nanowires are arguably the most studied nanomaterial model to make functional devices and arrays. Although there is remarkable maturity in the chemical synthesis of complex nanowire structures, their integration and interfacing to macro systems with high yields and repeatability still require elaborate aligning, positioning and interfacing and post-synthesis techniques. Top-down fabrication methods for nanowire production, such as lithography and electrospinning, have not enjoyed comparable growth. Here we report a new thermal size-reduction process to produce well-ordered, globally oriented, indefinitely long nanowire and nanotube arrays with different materials. The new technique involves iterative co-drawing of hermetically sealed multimaterials in compatible polymer matrices similar to fibre drawing. Globally oriented, endlessly parallel, axially and radially uniform semiconducting and piezoelectric nanowire and nanotube arrays hundreds of metres long, with nanowire diameters less than 15ĝ€‰nm, are obtained. The resulting nanostructures are sealed inside a flexible substrate, facilitating the handling of and electrical contacting to the nanowires. Inexpensive, high-throughput, multimaterial nanowire arrays pave the way for applications including nanowire-based large-area flexible sensor platforms, phase-changememory, nanostructure-enhanced photovoltaics, semiconductor nanophotonics, dielectric metamaterials,linear and nonlinear photonics and nanowire-enabled high-performance composites. © 2011 Macmillan Publishers Limited. All rights reserved

Attomolar sensitivity microRNA detection using real-time digital microarrays.

MicroRNAs (miRNAs) are a family of noncoding, functional RNAs. With recent developments in molecular biology, miRNA detection has attracted significant interest, as hundreds of miRNAs and their expression levels have shown to be linked to various diseases such as infections, cardiovascular disorders and cancers. A powerful and high throughput tool for nucleic acid detection is the DNA microarray technology. However, conventional methods do not meet the demands in sensitivity and specificity, presenting significant challenges for the adaptation of miRNA detection for diagnostic applications. In this study, we developed a highly sensitive and multiplexed digital microarray using plasmonic gold nanorods as labels. For proof of concept studies, we conducted experiments with two miRNAs, miRNA-451a (miR-451) and miRNA-223-3p (miR-223). We demonstrated improvements in sensitivity in comparison to traditional end-point assays that employ capture on solid phase support, by implementing real-time tracking of the target molecules on the sensor surface. Particle tracking overcomes the sensitivity limitations for detection of low-abundance biomarkers in the presence of low-affinity but high-abundance background molecules, where endpoint assays fall short. The absolute lowest measured concentration was 100 aM. The measured detection limit being well above the blank samples, we performed theoretical calculations for an extrapolated limit of detection (LOD). The dynamic tracking improved the extrapolated LODs from femtomolar range to [Formula: see text] 10 attomolar (less than 1300 copies in 0.2 ml of sample) for both miRNAs and the total incubation time was decreased from 5 h to 35 min.K99 AI167063 - NIAID NIH HHSPublished versio

From Chemical Gardens to Fuel Cells: Generation of Electrical Potential and Current Across Self-Assembling Iron Mineral Membranes

We examine the electrochemical gradients that form across chemical garden membranes and investigate how self-assembling, out-of-equilibrium inorganic precipitates—mimicking in some ways those generated in far-from-equilibrium natural systems—can generate electrochemical energy. Measurements of electrical potential and current were made across membranes precipitated both by injection and solution interface methods in iron-sulfide and iron-hydroxide reaction systems. The battery-like nature of chemical gardens was demonstrated by linking multiple experiments in series which produced sufficient electrical energy to light an external light-emitting diode (LED). This work paves the way for determining relevant properties of geological precipitates that may have played a role in hydrothermal redox chemistry at the origin of life, and materials applications that utilize the electrochemical properties of self-organizing chemical systems

Altitude dependence of nightside Martian suprathermal electron depletions as revealed by MAVEN observations

The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft is providing new detailed observations of the Martian ionosphere thanks to its unique orbital coverage and instrument suite. During most periapsis passages on the nightside ionosphere suprathermal electron depletions were detected. A simple criterion was implemented to identify the 1742 depletions observed from 16 November 2014 to 28 February 2015. A statistical analysis reveals that the main ion and electron populations within the depletions are surprisingly constant in time and altitude. Absorption by CO2 is the main loss process for suprathermal electrons, and electrons that strongly peaked around 6 eV are resulting from this interaction. The observation of depletions appears however highly dependent on altitude. Depletions are mainly located above strong crustal magnetic sources above 170 km, whereas the depletions observed for the first time below 170 km are globally scattered onto the Martian surface with no particular dependence on crustal fields