Mode conversion in rectangular-core optical fibers

Mode conversion from the fundamental to a higher-order mode in a rectangular-core optical fiber is accomplished by applying pressure with the edge of a flat plate. Modal analysis of the near and far field images of the fiber's transmitted beam determines the purity of the converted mode. Mode conversion reaching 75% of the targeted higher-order mode is achieved using this technique. Conversion from a higher-order mode back to the fundamental mode is also demonstrated with comparable efficiency. Propagation of a higher-order mode in a rectangular-core fiber allows for better thermal management and bend-loss immunity than conventional circular-core fibers, extending the power-handling capabilities of optical fibers.     

An experimental study on flow patterns and heat transfer characteristics during cryogenic chilldown in a vertical pipe

In the present paper, the experimental results of a cryogenic chilldown process are reported. The physical phenomena involve unsteady two-phase vapor–liquid flow and intense boiling heat transfer of the cryogenic fluid that is coupled with the transient heat conduction inside pipe walls. The objective for the present study is to compare the chilldown rates and flow patterns between the upward flow and downward flow in a vertical pipe. Liquid nitrogen is employed as the working fluid and the test section is a vertical straight segment of a Pyrex glass pipe with an inner diameter of 8 mm. The effects of mass flow rate on the flow patterns, heat transfer characteristics and interface movement were determined through experiments performed under several different mass flow rates. Through flow visualization, measurement and analysis on the flow patterns and temperature variations, a physical explanation of the vertical chilldown is given. By observing the process and analyzing the results, it is concluded that pipe chilldown in a vertical flow is similar to that in microgravity to some extent.     

Sawdust: A green and economical sorbent for thallium removal

Removal/preconcentration of thallium(I) ions from aqueous solution by sawdust; a waste material derived from the commercial processing of Cedrus Deodar wood for furniture production was investigated. A simple and low-cost modification results in increasing the sorption capacity of raw sawdust from 2.71 to 13.18 mg g⁻¹. Sorption was found to be rapid (98% within 8 min). The binding of metal ions was found to be pH dependent, optimal sorption accruing at around pH 6–9. Potentiometeric titrations of sawdust revealed two distinct pK_a values, the first having the value similar to carboxylic groups (3.3–4.8) and second comparable with that of amines (8.53–10.2) with the surface site densities of 1.99 × 10⁻⁴ and 7.94 × 10⁻⁵ mol g⁻¹, respectively. Retained Tl(I) ions were eluted with 5 ml 0.1 mol l⁻¹ HCl. Detection limit of 0.0125 μg ml⁻¹ was achieved with an enrichment factor of 160. Recovery was quantitative using sample volume of 800 ml. The Langmuir, Freundlich and D–R isotherm equations were used to describe partitioning behavior for the system at different temperatures. Kinetic and thermodynamic behavior of sawdust for Tl(I) ions removal was also studied.     

Simplified speciation and atmospheric volatile organic compound emission rates from non-aerosol personal care products

Volatile organic compounds (VOCs) emitted from personal care products (PCPs) can affect indoor air quality and outdoor air quality when ventilated. In this paper, we determine a set of simplified VOC species profiles and emission rates for a range of non-aerosol PCPs. These have been constructed from individual vapor analysis from 36 products available in the UK, using equilibrium headspace analysis with selected-ion flow-tube mass spectrometry (SIFT-MS). A simplified speciation profile is created based on the observations, comprising four alcohols, two cyclic volatile siloxanes, and monoterpenes (grouped as limonene). Estimates are made for individual unit-of-activity VOC emissions for dose-usage of shampoos, shower gel, conditioner, liquid foundation, and moisturizer. We use these values as inputs to the INdoor air Detailed Chemical Model (INDCM) and compare results against real-world case-study experimental data. Activity-based emissions are then scaled based on plausible usage patterns to estimate the potential scale of annual per-person emissions for each product type (eg, 2 g limonene person⁻¹ yr⁻¹ from shower gels). Annual emissions from non-aerosol PCPs for the UK are then calculated (decamethylcyclopentasiloxane 0.25 ktonne yr⁻¹ and limonene 0.15 ktonne yr⁻¹) and these compared with the UK National Atmospheric Emissions Inventory estimates for non-aerosol cosmetics and toiletries.     

Screening and treatment of distress.

The screening and treatment of psychological distress is an increasingly important aspect of providing comprehensive care to medical patients. The importance of this within oncology was illustrated most recently by the publication of the National Comprehensive Cancer Network's Distress Guidelines (Holland, 1997). Given that measures of general distress assess for symptoms across diagnostic categories, it is not unusual to have a combination of symptoms indicating distress without meeting diagnostic criteria (Derogatis, Morrow, & Petting, 1983). We would suggest that general measures of distress and psychiatric diagnoses not assessed by Coyne et al. (e.g., somatoform or adjustment disorders) may reflect better the distress (health anxiety and somatic preoccupation) of women at increased risk for cancer and be more informative than assessing selectively for mood disorders, anxiety disorders, and alcohol abuse. The authors additionally concluded that if there is not psychiatric disorder, then there is no impairment. We believe it premature at best to reify the DSM in a nonpsychiatric population. Distress exists on a continuum. To wait until patients meet psychiatric criteria before they are seen is not in the spirit of comprehensive medical care. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial and temporal variation in indicator microbe sampling is influential in beach management decisions

Fecal indicator microbes, such as enterococci, are often used to assess potential health risks caused by pathogens at recreational beaches. Microbe levels often vary based on collection time and sampling location. The primary goal of this study was to assess how spatial and temporal variations in sample collection, which are driven by environmental parameters, impact enterococci measurements and beach management decisions. A secondary goal was to assess whether enterococci levels can be predictive of the presence of Staphylococcus aureus, a skin pathogen. Over a ten-day period, hydrometeorologic data, hydrodynamic data, bather densities, enterococci levels, and S. aureus levels including methicillin-resistant S. aureus (MRSA) were measured in both water and sand. Samples were collected hourly for both water and sediment at knee-depth, and every 6 h for water at waist-depth, supratidal sand, intertidal sand, and waterline sand. Results showed that solar radiation, tides, and rainfall events were major environmental factors that impacted enterococci levels. S. aureus levels were associated with bathing load, but did not correlate with enterococci levels or any other measured parameters. The results imply that frequencies of advisories depend heavily upon sample collection policies due to spatial and temporal variation of enterococci levels in response to environmental parameters. Thus, sampling at different times of the day and at different depths can significantly impact beach management decisions. Additionally, the lack of correlation between S. aureus and enterococci suggests that use of fecal indicators may not accurately assess risk for some pathogens.     

Estimating person-to-person variability in VOC emissions from personal care products used during showering

An increasing fraction of volatile organic compounds (VOC) emissions come from the domestic use of solvents, contained within myriad commonplace consumer products. Emission rates are often poorly characterized and depend significantly on individual behavior and specific product formulation and usage. Time-concentration profiles of volatile organic compounds (VOCs) arising from the use of a representative selection of personal care products (PCPs) during showering are generated, and person-to-person variability in emissions calculated. A panel of 18 participants used a standardized set of products, dosages, and application times during showering in a controlled indoor bathroom setting. Proton transfer mass spectrometry was used to measure the in-room VOC evolution of limonene (representing the sum of monoterpenes), benzyl alcohol, and ethanol. The release of VOCs had reproducible patterns between users, but noticeable variations in absolute peak concentrations, despite identical amounts of material being used. The amounts of VOC emitted to air for one showering activity were as follows: limonene (1.77 mg ± 42%), benzyl alcohol (1.07 mg ± 41%), and ethanol (0.33 mg ± 78%). Real-world emissions to air were between 1.3 and 11 times lower than bottom-up estimates based on dynamic headspace measurements of product emissions rates, likely a result of PCPs being washed away before VOC evaporation could occur.     

Histidine Ligated Iron-Sulfur Peptides

Iron-sulfur clusters are thought to be ancient cofactors that could have played a role in early protometabolic systems. Thus far, redox active, prebiotically plausible iron-sulfur clusters have always contained cysteine ligands to the cluster. However, extant iron-sulfur proteins can be found to exploit other modes of binding, including ligation by histidine residues, as seen with [2Fe-2S] Rieske and MitoNEET proteins. Here, we investigated the ability of cysteine- and histidine-containing peptides to coordinate a mononuclear Fe²⁺ center and a [2Fe-2S] cluster and compare their properties with purified iron-sulfur proteins. The iron-sulfur peptides were characterized by UV-vis, circular dichroism, and paramagnetic NMR spectroscopies and cyclic voltammetry. Small (≤6 amino acids) peptides can coordinate [2Fe-2S] clusters through a combination of cysteine and histidine residues with similar reduction potentials as their corresponding proteins. Such complexes may have been important for early cell-like systems.     

As the number falls,alternatives to the Hagberg–Perten falling number method: A review

This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging.     

A simple molecular assay differentiates two burrowing mayfly species, Hexagenia limbata and H. rigida (Ephemeroptera: Ephemeridae), in western Lake Erie

Burrowing mayflies (Hexagenia spp.) are important indicators of mesotrophic water conditions, and have been studied for several decades in conjunction with the changing trophic status of western Lake Erie. However, most studies on the biology of burrowing mayflies have failed to differentiate between immature H. limbata and H. rigida, the life stages that are most commonly collected. We developed a simple molecular assay to facilitate species-level identification of the two mayflies as an easier alternative to sequencing the COI gene. We analyzed a total of 152 cytochrome c oxidase, subunit I barcoding sequences from the Barcode of Life Data System (BOLD) for these mayfly species and developed a diagnostic primer set. We tested our primers on 46 random burrowing Lake Erie mayfly nymphs using both conventional PCR and qPCR. Results of the two methods were consistent and unambiguous. Sequencing of the COI barcoding region in the mayflies confirmed that the PCR assays correctly identified mayflies in all cases. Our assay is simple and effective, and will facilitate species-level identification of burrowing mayflies in future studies on their biology where the two species co-occur.