Controlled core removal from a D-shaped optical fiber

The partial removal of a section of the core from a continuous D-shaped optical fiber is presented. In the core removal process, selective chemical etching is used with hydrofluoric (HF) acid. A 25% HF acid solution removes the cladding material above the core, and a 5% HF acid solution removes the core. A red laser with a wavelength of 670 nm is transmitted through the optical fiber during the etching. The power transmitted through the optical fiber is correlated to the etch depth by scanning electron microscope imaging. The developed process provides a repeatable method to produce an optical fiber with a specific etch depth.     

High flux ultrafiltration membranes based on electrospun nanofibrous PAN scaffolds and chitosan coating

Conventional ultrafiltration (UF) or nanofiltration (NF) filters for water treatments are based on porous membranes, typically manufactured by the phase immersion method. The torturous porosity in these membranes usually results in a relatively low flux rate. In this study, we demonstrated a new type of high flux UF/NF medium based on an electrospun nanofibrous scaffold (e.g. polyacrylonitrile, PAN) coupled with a thin top layer of hydrophilic, water-resistant, but water-permeable coating (e.g. chitosan). Such nanofibrous composite membranes can replace the conventional porous membranes and exhibit a much higher flux rate for water filtration. The interconnected porosity of the non-woven nanofibrous scaffold can be controlled partially by varying the fiber diameter (from about 100 nm to a few micrometers) through the electrospinning processing. The example membrane, containing an electrospun PAN scaffold with an average diameter from 124 to 720 nm and a porosity of about 70%, together with a chitosan top layer having a thickness of about 1 μm, although not yet fully optimized, exhibited a flux rate that is an order magnitude higher than commercial NF membranes in 24 h of operation, while maintaining the same rejection efficiency (>99.9%) for oily waste-water filtration.     

New thermodynamic-transport theory for systems with continuous component density distributions

Transport theories, equilibrium, and non-equilibrium thermodynamics become useless when applied to materials, such as multicomponent mixtures of dissociating or reacting gases, industrial fuels or polymers, which must be characterized by very large numbers of equations and composition parameters (e.g., component diffusivities, specific heats, chemical affinities, chemical potentials, heats of reactions). This work deals with a new theory in which the numerous equations and parameters required in current thermodynamic and transport theories for such materials are replaced by a smaller number of proper moments of the distribution function.Introducing new conservation laws (expressed in terms of moments) together with new definitions for chemical potentials, specific heats, heat and mass fluxes, diffusivities, affinities and entropy-production rates, a new theory is presented for continuous systems. A few thermodynamic functions and rules are also re-examined.The advantage of the proposed theory lies mainly in the practical possibility to approximate the behavior of many multicomponent gaseous mixtures as well as many industrial fuels and polymers by a much smaller number of moments than the number of distinct chemical components present.     

Organizational citizenship behavior and performance evaluations: Exploring the impact of task interdependence.

The influence of task interdependence on the importance attributed to organizational citizenship behavior (OCB) in evaluations of employee performance was investigated in 3 studies. In Study 1,238 undergraduates were exposed to a task interdependence manipulation and a unit-level performance manipulation and provided citizenship ratings. In Study 2,148 master of business administration students were exposed to a task interdependence manipulation and then rated the importance of OCB in their evaluations of employee performance. In Study 3,130 managers rated the task interdependence in their unit of principal responsibility and the importance of OCB in their overall evaluations of employee performance. The results suggest task interdependence may affect the importance attributed to OCB by evaluators. Implications of these results are explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactions of the flavonoid hesperetin with chlorine: a spectroscopic study of the reaction pathways

The flavonoid hesperetin (Hsp) contains aromatic rings substituted with hydroxyl and methoxyl groups, which activate it toward electrophilic attack and hence make it a potential surrogate for natural organic matter with respect to reactions with chlorine. This paper describes the chlorination pathway of Hsp, based on a combination of electrospray tandem mass spectrometry (MS/MS) and absorbance spectroscopy. When a solution containing Hsp is dosed with NaOCl at pH 7, chlorine substitution into Hsp occurs exclusively into the meta-dihydroxy substituted ring. The first two Cl atoms to enter the ring do so at the highly activated carbons that are each ortho to two oxygenated carbon atoms. These substitutions make the molecule more acidic, but do not change its primary structure or aromaticity. The third Cl atom that substitutes into the molecule does so at one of the previously chlorinated sites, destroying the aromaticity of the ring and altering the molecular properties more dramatically than do the first two. The absorbance spectra of Hsp and mono- and di-chlorinated Hsp are all very similar and are very distinct from that of trichlorinated Hsp. In particular, the latter is the only one of those species that absorbs visible light (in a characteristic band centered at approximately 422nm). Di- and trichloroHsp form even at low molar Cl/Hsp ratios, and can coexist with Hsp and monochloroHsp in neutral, aqueous solutions for at least 24 h in the absence of free chlorine. If free chlorine is present, the less-chlorinated species continue to acquire Cl, and trichloroHsp undergoes further reaction, until either the free chlorine or the trichloroHsp is fully depleted. The appearance of di- and trichloroHsp while substantial amounts of Hsp remain unreacted indicates that substitution of one or two Cl atoms into the ring facilitates the incorporation of yet more Cl into the ring. This autoacceleration of the chlorination process is hypothesized to be induced by the increase in acidity that accompanies Cl incorporation. Specifically, the increase in the acidity of the phenolic groups shifts the equilibrium toward the enolate anion, which is considered to be much more amenable to electrophilic attack than the enol.     

Elite handcycling: a qualitative analysis of recumbent handbike configuration for optimal sports performance

Our understanding of handbike configuration is limited, yet it can be a key determinant of performance in handcycling. This study explored how 14 handcycling experts (elite handcyclists, coaches, support staff, and manufacturers) perceived aspects of recumbent handbike configuration to impact upon endurance performance via semi-structured interviews. Optimising the handbike for comfort, stability, and power production was identified as key themes. Comfort and stability were identified to be the foundations of endurance performance and were primarily influenced by the seat, backrest, headrest, and their associated padding. Power production was determined by the relationship between the athletes’ shoulder and abdomen and the trajectories of the handgrips, which were determined by the crank axis position, crank arm length, and handgrip width. Future studies should focus on quantifying the configuration of recumbent handbikes before determining the effects that crank arm length, handgrip width, and crank position have on endurance performance.

Practitioner Summary: To gain a greater understanding of the impact of handbike configurations on endurance performance, the perceptions of expert handcyclists were explored qualitatively. Optimising the handbike for comfort and stability, primarily via backrest padding and power production, the position of the shoulders relative to handgrips and crank axis, were critical.     

Hyaluronic Acid–Based Activatable Nanomaterials for Stimuli‐Responsive Imaging and Therapeutics: Beyond CD44‐Mediated Drug Delivery

There is a rapidly increasing interest in developing stimuli‐responsive nanomaterials for treating a variety of diseases. By enabling the activation of function locally at the sites of interest, it is possible to increase therapeutic efficacy significantly while simultaneously reducing adverse side effects. While there are many sophisticated nanomaterials available, they are often highly complex and not easily transferrable to industrial scales and clinical settings. However, nanomaterials based on hyaluronic acid offer a compelling strategy for reducing their complexity while retaining several desirable benefits such as active targeting and stimuli‐responsive degradation. Herein, the basic properties of hyaluronic acid, its binding partners, and natural routes for degradation by hyaluronidases—hyaluronic‐acid‐degrading enzymes—and oxidative stresses are discussed. Recent advances in designing hyaluronic acid–based, actively targeted, hyaluronidase‐ or reactive‐oxygen‐species‐responsive nanomaterials for both diagnostic imaging and therapeutic delivery, which go beyond merely the classical targeting of CD44, are summarized.     

Automated mapping of rice fields using multi-year training sample normalization

Rice agriculture is of great ecological, environmental, and socioeconomic importance in the Lower Mississippi Alluvial Valley, as its distribution and size heavily impact food production and a number of ecosystem services. Long-term rice mapping is challenging as a result of insufficient training data – both in spatial amount and in temporal coverage, the high cost of powerful geospatial data processing platforms, and incomplete image coverage during the critical window to capture the unique rice signals. Here, we developed a simple yet effective method for rice field extraction without heavy reliance on the complete profiles of Landsat time series or repeated training data. The core is a multiple-year training sample normalization that extends the samples obtained in one year for classification in another year. Pseudo-invariant objects and a set of linear regressions were used to predict what the given vegetation index values of training samples would be if they had been acquired under the same conditions in a different mapping year. The generated pseudo training samples were further utilized to classify the mapping image. We experimented with four years’ Landsat Thematic Mapper and Operational Land Imager data and achieved comparable accuracies as the single-year classification. Because of its simplicity and low computational requirements, it can be efficiently implemented on cloud computing platforms, such as Google Earth Engine platform. This technique provides an affordable and effective solution to derive crop distribution information on a large-scale basis.     

Gain in single and paired parametric oscillators

ABSTRACT

The new concept of Quantum Amplification by Superradiant Emission of Radiation for generating high-frequency coherent light has produced several open questions, and one of the most important is how to determine the gain in two coupled oscillators with a parametric amplifier. In this article, we analytically derive the equation for the gain expression and state sufficient conditions to obtain gain. We also draw connections to single oscillator topics, including the Mathieu equation and the Kronig–Penney model.