On the ambipolar diffusion formulation for ion-neutral drifts in the non-negligible drift velocity limit.

The ambipolar diffusion approximation is used to model partially ionized plasma dynamics in a single-fluid setting. To correctly apply the commonly used version of ambipolar diffusion, a set of criteria should be satisfied including the requirement that the difference in velocity between charges and neutral species (known as drift velocity) is much smaller than the thermal velocity, otherwise the drift velocity will drive a non-negligible level of further collisions between the two species. In this paper, we explore the consequences of relaxing this assumption. We show that a new induction equation can be formulated without this assumption. This formulation reduces to the ambipolar induction equation in the case the drift velocity is small. In the large drift velocity limit, the feedback of the drift velocity on the collision frequency results in decreased diffusion of the magnetic field compared with the standard ambipolar diffusion approximation for the same parameters. This has a natural consequence of reducing the frictional heating that can occur. Applying this to results from flux emergence simulations where the expansion of the magnetic field leads to strong adiabatic cooling of the partially ionized chromosphere resulted in a noticeable reduction in the magnitude of the predicted drift velocities. This article is part of the theme issue 'Partially ionized plasma of the solar atmosphere: recent advances and future pathways'.

Kelvin-Helmholtz-induced mixing in multi-fluid partially ionized plasmas.

Turbulence is a fundamental process that drives mixing and energy redistribution across a wide range of astrophysical systems. For warm ([Formula: see text]) plasma, the material is partially ionized, consisting of both ionized and neutral species. The interactions between ionized and neutral species are thought to play a key role in heating (or cooling) of partially ionized plasmas. Here, mixing is studied in a two-fluid partially ionized plasma undergoing the shear-driven Kelvin-Helmholtz instability to evaluate the thermal processes within the mixing layer. Two-dimensional numerical simulations are performed using the open-source (PIP) code that solves for a two-fluid plasma consisting of a charge-neutral plasma and multiple excited states of neutral hydrogen. Both collisional and radiative ionization and recombination are included. In the mixing layer, a complex array of ionization and recombination processes occur as the cooler layer joins the hotter layer, and vice versa. In localized areas of the mixing layer, the temperature exceeds the initial temperatures of either layer with heating dominated by collisional recombinations over turbulent dissipation. The mixing layer is in approximate ionization-recombination equilibrium, however the obtained equilibrium is different to the Saha-Boltzmann local thermal equilibrium. The dynamic mixing processes may be important in determining the ionization states, and with that intensities of spectral lines, of observed mixing layers. This article is part of the theme issue 'Partially ionized plasma of the solar atmosphere: recent advances and future pathways'.

Assessment of owner perceptions of caregiver burden, veterinarian-client relationship and satisfaction with the provider in canine pruritus: An experimental vignette study.

BACKGROUND: Complicated treatments for skin disease are linked to owner-caregiver burden and poorer perception of the veterinarian-client relationship, regardless of disease severity. HYPOTHESES/OBJECTIVES: Using experimental vignettes, we explored the impact on owner perception of the interaction of treatment complexity and skin disease outcomes. We hypothesised that: (i) vignette conditions involving injection therapy would result in lower burden, better veterinary-client relationship and greater satisfaction relative to multimodal therapy conditions; (ii) the vignette condition of injection therapy with a completely effective outcome would be superior to all other conditions; (iii) ineffective vignette conditions would be inferior to all other conditions; and (iv) the vignette condition injection with a mostly effective outcome would be similar or superior to the multimodal therapy with a completely effective outcome condition. PARTICIPANTS: Three hundred and nine owners of pruritic dogs recruited from a general veterinary practice, pet-related podcast, or social media dog allergy group. MATERIALS AND METHODS: Participants were presented with six counterbalanced online vignettes representing three levels of treatment effectiveness (Completely Effective, Mostly Effective, Ineffective) and two treatment regimens (Multimodal, Injection). Measurements of participant perceptions of caregiver burden, veterinarian-client relationship and satisfaction were recorded. RESULTS: Injection with perfect outcome was superior to other conditions (p < 0.001). Conditions with poor effectiveness were inferior (p < 0.001). Comparison of Injection with a mostly effective outcome to Multimodal treatment with perfect outcome yielded small-to-medium effects of preference for the latter in veterinarian-client relationship and satisfaction (p < 0.01); no difference was observed for caregiver burden. When good effectiveness was assured, injection was preferred (p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Owners preferred a Completely Effective outcome and were prepared to select the Injection regimen or Multimodal therapy to achieve this; Injection was preferred when effectiveness was assured.

Perception and usage of short-term prednisone and prednisolone in dogs.

BACKGROUND: Corticosteroids are widely used with low rates of reported side effects and a broad level of comfort in the hands of most veterinarians. With a low side effect reporting level of < 5% and high level of comfort there may be complacency and underestimation of the impact side effects of corticosteroids may have on a pet and pet owner. OBJECTIVE: The objective of this clinical study was to describe the experience and perception of an owner who administered anti-inflammatory doses of oral prednisolone and prednisone to their dog for up to 14 days. We hypothesized dogs receiving anti-inflammatory doses of prednisone and prednisolone would experience much greater rates of side effects by day 14 then reported in current literature. ANIMALS: There were 45 dogs initially enrolled in the study. RESULTS: At each study point, 31 owners provided results. On day 5, 74% (23/31) reported at least 1 change in their dog's behavior including polyuria, polydipsia, polyphagia, polypnea and/or increased vocalization, with 11 individuals (35%) reporting these changes greatly increased. On day 14, 90% of owners (28/31) reported at least 1 change in their dog's behavior including polyuria, polydipsia, polyphagia, and/or polypnea as the most common changes noted. Overall, 61% (19/31) of owners reported an increase in filling of the water bowl over baseline and one-third (11/31) of pet owners reported cleaning up urinary accidents for pets who had been continent prior to the start of the study. Pet owner steroid satisfaction remained high through day 14 at 4.5/5 (1 = very unsatisfied, 5 = very satisfied). CONCLUSION: This study highlights the impact short term anti-inflammatory doses of prednisone or prednisolone have on dog behaviour and confirms our hypothesis that by day 14, 90% of dogs experienced one or more behaviour changes, with polyuria and polydipsia most commonly reported. Adverse events were noted regardless of starting dosage or regimen. Although most pet owners expressed satisfaction with steroid treatment due to its high efficacy, 70% would select a more costly treatment if that treatment had fewer side effects.

Single-Walled Carbon Nanotube Probes for the Characterization of Biofilm-Degrading Enzymes Demonstrated against Pseudomonas aeruginosa Extracellular Matrices.

Hydrolase co-therapies that degrade biofilm extracellular polymeric substances (EPS) allow for a better diffusion of antibiotics and more effective treatment; current methods for quantitatively measuring the enzymatic degradation of EPS are not amendable to high-throughput screening. Herein, we present biofilm EPS-functionalized single-walled carbon nanotube (SWCNT) probes for rapid screening of hydrolytic enzyme selectivity and activity on EPS. The extent of biofilm EPS degradation is quantified by monitoring the quenching of the SWCNT fluorescence. We used this platform to screen 16 hydrolases with varying bond breaking selectivity against a panel of wild-type Pseudomonas aeruginosa and mutants deficient or altered in one or more EPS. Next, we performed concentration-dependent studies of six enzymes on two common strains found in cystic fibrosis (CF) environments and, for each enzyme, extracted three first-order rate constants and their relative contributions by fitting a parallel, multi-site degradation model, with a good model fit (R2 from 0.65 to 0.97). Reaction rates (turnover rates) are dependent on the enzyme concentration and range from 6.67 × 10-11 to 2.80 × 10-3 *s-1 per mg/mL of enzymes. Lastly, we confirmed findings from this new assay using an established crystal-violet staining assay for a subset of hydrolase panels. In summary, our work shows that this modular sensor is amendable to the high-throughput screening of EPS degradation, thereby improving the rate of discovery and development of novel hydrolases.

Caregiver burden, treatment complexity, and the veterinarian-client relationship in owners of dog with skin disease.

BACKGROUND: Increasing complexity of treatment plans is associated with higher levels of caregiver burden in owners of dogs with skin disease. It is possible that elevated caregiver burden resulting from treatment complexity could, in turn, affect the veterinarian-client relationship. HYPOTHESES/OBJECTIVES: We expected that treatment complexity, caregiver burden, and the client's perception of the veterinarian-client relationship would be related to each other. We also expected an indirect effect of caregiver burden on the cross-sectional association between treatment complexity and the veterinarian-client relationship, and that this effect would be robust to adjustment for the dog's skin disease course and severity. PARTICIPANTS: Participants were 349 owners of dogs with skin disease recruited through online consumer panels. MATERIALS AND METHODS: Cross-sectional online assessments were completed for caregiver burden, treatment plan complexity, veterinarian-client relationship, and skin disease course and severity. Demographic information also was collected. RESULTS: The indirect effect of caregiver burden on the relationship between treatment complexity and veterinarian-client relationship was statistically significant, accounting for 42.76% of the variance in the model. After controlling for disease severity and course, that effect remained statistically significant, accounting for 37.76% of the variance. CONCLUSIONS AND CLINICAL IMPORTANCE: Findings support the notion that greater treatment complexity is related to the owner's perception of the veterinarian-client relationship via caregiver burden. Efforts to reduce caregiver burden by using the simplest effective treatment may benefit the veterinarian-client relationship.

Contexte - La complexité croissante des plans de traitement est associée à des niveaux plus élevés de fardeau pour les soignants propriétaires de chiens atteints de maladies de peau. Il est possible que le fardeau élevé des soignants résultant de la complexité du traitement pourrait, à son tour, affecter la relation vétérinaire-client. Hypothèses/Objectifs - Nous nous attendions à ce que la complexité du traitement, le fardeau des soignants et la perception du client de la relation vétérinaire-client seraient liés les uns aux autres. Nous nous attendions également à un effet indirect de le fardeau du soignant sur l'association transversale entre la complexité du traitement et le vétérinaire-client relation, et que cet effet serait robuste à l'ajustement de l'évolution et de la gravité de la maladie de peau du chien. Participants - Les participants étaient 349 propriétaires de chiens atteints de maladies de la peau recrutés par le biais de consommateurs en ligne panneaux. Matériels et méthodes - Des évaluations transversales en ligne ont été réalisées pour le fardeau des soignants, le traitement la complexité du plan, la relation vétérinaire-client et l'évolution et la gravité des maladies de la peau. Informations démographiques a également été collecté. Résultats - L'effet indirect du fardeau des soignants sur la relation entre la complexité du traitement et le vétérinaire-la relation client était statistiquement significative, représentant 42,76 % de la variance du modèle. Après contrôle pour la gravité et l'évolution de la maladie, cet effet est resté statistiquement significatif, représentant 37,76 % des la variance. Conclusions et importance clinique - Les résultats appuient l'idée qu'une plus grande complexité du traitement est liée à la perception du propriétaire de la relation vétérinaire-client via le fardeau des soignants. Efforts pour réduire le soignant fardeau en utilisant le traitement efficace le plus simple peut être bénéfique pour la relation vétérinaire-client.

Contexto - O aumento da complexidade dos planos de tratamento está associado a altos níveis de sobrecarga do cuidador de cães com doenças de pele. É possível que a sobrecarga do cuidador elevada resultante da complexidade da terapia possa, desta forma, afetar a relação veterinário-cliente. Hipótese/Objetivos - Nós imaginamos que a complexidade do tratamento, a sobrecarga do cuidador, e a percepção do cliente da relação veterinário-cliente estariam relacionadas. Nós também imaginamos que poderia uma mediação da sobrecarga do cuidador na associação transversal entre a complexidade do tratamento e a relação veterinário-cliente, e que este efeito seria robusto para ajustar o curso e a gravidade da doença de pele do cão. Participantes - Os participantes foram 349 tutores de cães com doença de pele recrutados através de formulários online. Materiais e métodos - Avaliações transversais online foram preenchidas para sobrecarga do cuidador, complexidade do plano de tratamento, relação veterinário-cliente, e curso da doença de pele e gravidade. Dados demográficos também foram coletados. Resultados - O efeito indireto da sobrecarga do cuidador na relação entre a complexidade do tratamento e a relação veterinário-cliente foi significativamente significativa, sendo responsável por 42,76% da variância no modelo. Após controlar para gravidade da doença e curso, esse efeito permaneceu estatisticamente significativo, respondendo por 37,76% da variância. Conclusões e importância clínica - Os achados corroboram com a ideia de que a complexidade do tratamento está relacionada à percepção do tutor sobre a relação veterinário-cliente pela sobrecarga do cuidador. Esforços para reduzir a sobrecarga do cuidador utilizando planos terapêuticos mais simples podem beneficiar a relação veterinário-cliente.

Introducción- el aumento de la complejidad de los planes de tratamiento se asocia a mayores niveles de responsabilidad de los propietarios de perros con enfermedades de la piel. Es posible que esta mayor carga para el propietario resultante de la complejidad del tratamiento pueda, a su vez, afectar a la relación veterinario-cliente. Hipótesis/Objetivos- esperábamos que la complejidad del tratamiento, la mayor responsabilidad para cuidadores y la percepción de los propietarios de la relación veterinario-cliente estuvieran relacionadas entre sí. También esperábamos un efecto de mediación de la mayor carga del cuidador en la asociación transversal entre la complejidad del tratamiento y la relación veterinario-cliente, y que este efecto sería sólido para el ajuste del curso y la gravedad de la enfermedad de la piel del perro. Participantes- los participantes fueron 349 propietarios de perros con enfermedades de la piel reclutados a través de paneles de consumidores vía telemática. Materiales y métodos- se completaron evaluaciones transversales en línea sobre la carga del cuidador, la complejidad del plan de tratamiento, la relación veterinario-cliente y el curso y la gravedad de la enfermedad de la piel. También se recopiló información demográfica. Resultados - El efecto indirecto de la carga del cuidador sobre la relación entre la complejidad del tratamiento y la relación veterinario-cliente fue estadísticamente significativo, explicando el 42,76% de la varianza del modelo. Después de controlar la gravedad y el curso de la enfermedad, ese efecto siguió siendo estadísticamente significativo y representó el 37,76 % de la varianza. Conclusiones e importancia clínica- los hallazgos respaldan la noción de que una mayor complejidad del tratamiento está relacionada con la percepción del propietario de la relación veterinario-cliente mediante una mayor carga del cuidador. Esfuerzos para reducir la carga del cuidador mediante el uso de tratamientos efectivos más simples pueden beneficiar a la relación veterinario-cliente.

Treatment complexity and caregiver burden are linked in owners of dogs with allergic/atopic dermatitis.

BACKGROUND: Skin disease severity and treatment plan complexity are both related to owner experience of caregiver burden; however, to date they have not been examined simultaneously in owners of dogs with atopic or other chronic allergic dermatitis. HYPOTHESES/OBJECTIVES: We expected to replicate and extend previous work by showing that caregiver burden is linked to treatment complexity and disease severity in this population. Moreover, we hypothesized that a relationship between burden and treatment complexity would be present in both subjective (owner report of experience) and objective (number of weekly treatments) measures, and that these relationships would exist independent of skin disease severity. PARTICIPANTS: Eighty-six owners of dogs with atopic or other chronic allergic dermatitis recruited through social media dog allergy groups. METHODS AND MATERIALS: Cross-sectional online assessments were completed for caregiver burden, treatment plan complexity and skin disease severity. RESULTS: Caregiver burden was correlated with skin disease severity (r = 0.40) and both subjective (r = 0.37) and objective (r =0.30) measures of treatment complexity (P < 0.01 for all). Relationships between caregiver burden and treatment complexity remained significant after accounting for skin disease severity. CONCLUSIONS AND CLINICAL IMPORTANCE: Greater treatment plan complexity is associated with higher caregiver burden in owners of dogs with atopic or other chronic allergic dermatitis. The independence of this relationship highlights the importance of simplicity in effective treatment planning.

Massive Enhancement of Optical Transmission across a Thin Metal Film via Wave Vector Matching in Grating-Coupled Surface Plasmon Resonance.

We demonstrate how distinct surface plasmon resonance modes on opposite sides of a metal-coated grating can be coupled across the metal film. This coupling occurs by matching the resonance conditions on each side of the grating by tuning the refractive index directly adjacent to the metal film. In the first example, we deposited a high refractive index layer of tin oxide on top of the grating to red-shift the front side surface plasmon until it coupled with the backside surface plasmon across a semitransparent ∼45 nm thin silver grating. By shifting the resonance condition of the nearby surface plasmon, this high refractive index coating creates an effective matching of wave vectors across the metal film, allowing them to couple and enhance the optical response. A massive increase in the magnitude of enhanced transmission is observed, increasing from a 6-fold transmission enhancement through a bare silver grating to a near 100-fold enhancement after deposition of a tin oxide layer of appropriate thickness (∼310 nm). This optical transmission enhancement is then probed through computational modeling and by experiments with liquids of various refractive index values. The matched system shows an increased amplitude sensitivity with respect to refractive index changes and a waveguide like behavior within the tin oxide film. As an alternative configuration, we also demonstrate coupling the front and back-side plasmon modes by using a lower refractive index substrate in order to blue-shift the back-side surface plasmon. Coupling between the two plasmon modes is then demonstrated by introducing aqueous solutions of various refractive index values. Under the proper conditions, this matched system also shows a substantial enhancement in transmission. This technique of wave vector matching provides a route to substantially increasing the plasmon enhanced optical transmission through metal gratings, which has potential application in improved plasmonic sensing, spectroscopy, and plasmon-based optical devices.

A phase-change thin film-tuned photonic crystal device.

This paper reports a tunable photonic device that incorporates a thin layer of phase-change material, Ge2Sb2Te5 (GST), in a photonic crystal (PC) structure. The PC structure is based on a one-dimensional grating waveguide with a metal cladding. The metal-cladded PC structure supports a guided-mode resonance (GMR) that selectively absorbs light at a particular wavelength. Inserting the GST material into the gating waveguide makes it possible to control the GMR mode. Here, the GST-PC device was numerically designed and optimized to obtain significant tuning of the GMR mode around 1550 nm. The tuning phenomena were experimentally demonstrated by the heat-induced phase change between crystalline and amorphous phases of the GST thin film. A spectral shift of the resonant wavelength from 1440 to 1610 nm was achieved via the crystallization process. The phase tuning of GST exhibits good repeatability as demonstrated by switching between amorphous and crystalline phases of GST for multiple cycles. The GST-PC device represents a new approach for tuning optical resonances with potential applications including but not limited to integrated photonic circuits, optical communications, and high-performance optical filters.

Templating Colloidal Crystal Growth Using Chirped Surface Relief Gratings.

We report a method for controlling the lattice geometry of monodisperse colloidal crystals formed by confined convective self-assembly on a substrate patterned with a chirped surface relief grating. Chirped gratings were fabricated using laser interference lithography and a curved mirror reflector to create photoresist patterns with pitch values ranging from ∼500 to >10 000 nm spread over a planar surface. These surface nanostructures are shown to guide the formation of various lattice geometries not normally found via colloidal assembly on planar surfaces. It is shown that when the pitch of the grating is much larger than the diameter of the colloidal particles, the grating trenches serve as compartments for deposition and the particles form close-packed, linear chains. Various ordered structures are observed as the dimensions of the grating pitch decrease and approach the diameter of the particles. The grating nanostructures guide the formation of various lattice geometries due to specific particle-surface and particle-particle interactions. Observed crystal lattices include square, hexagonal, and rhombic structures. The formation of these structures is explained in terms of the geometrical constraints imposed by the surface pattern and the particle diameter. These crystal lattices can be translated into large area samples when using corresponding single-pitch grating substrates. The initial monolayer lattice can also serve as a template for the growth of unique, bilayer structures that include rectangular lattices, chains of particle pairs or triplets, and graphitelike structured lattices. In addition, when coated with a thin silver layer, these various lattice configurations are shown to produce optical reflection features that are precisely controlled by the underlying structure as it varies from widely spaced particle chains to close-packed lattice geometries.

Creating metamaterial building blocks with directed photochemical metallization of silver onto DNA origami templates.

DNA origami can be used to create a variety of complex and geometrically unique nanostructures that can be further modified to produce building blocks for applications such as in optical metamaterials. We describe a method for creating metal-coated nanostructures using DNA origami templates and a photochemical metallization technique. Triangular DNA origami forms were fabricated and coated with a thin metal layer by photochemical silver reduction while in solution or supported on a surface. The DNA origami template serves as a localized photosensitizer to facilitate reduction of silver ions directly from solution onto the DNA surface. The metallizing process is shown to result in a conformal metal coating, which grows in height to a self-limiting value with increasing photoreduction steps. Although this coating process results in a slight decrease in the triangle dimensions, the overall template shape is retained. Notably, this coating method exhibits characteristics of self-limiting and defect-filling growth, which results in a metal nanostructure that maps the shape of the original DNA template with a continuous and uniform metal layer and stops growing once all available DNA sites are exhausted.

Magneto-thermal convection in solar prominences.

Coronal cavities are large low-density regions formed by hemispheric-scale magnetic flux ropes suspended in the Sun's outer atmosphere. They evolve over time, eventually erupting as the dark cores of coronal mass ejections. Although coronal mass ejections are common and can significantly affect planetary magnetospheres, the mechanisms by which cavities evolve to an eruptive state remain poorly understood. Recent optical observations of high-latitude 'polar crown' prominences within coronal cavities reveal dark, low-density 'bubbles' that undergo Rayleigh-Taylor instabilities to form dark plumes rising into overlying coronal cavities. These observations offered a possible mechanism for coronal cavity evolution, although the nature of the bubbles, particularly their buoyancy, was hitherto unclear. Here we report simultaneous optical and extreme-ultraviolet observations of polar crown prominences that show that these bubbles contain plasma at temperatures in the range (2.5-12) × 10(5) kelvin, which is 25-120 times hotter than the overlying prominence. This identifies a source of the buoyancy, and suggests that the coronal cavity-prominence system supports a novel form of magneto-thermal convection in the solar atmosphere, challenging current hydromagnetic concepts of prominences and their relation to coronal cavities.

A strain-tunable nanoimprint lithography for linear variable photonic crystal filters.

This paper presents the fabrication methodology of a linear variable photonic crystal (PC) filter with narrowband reflection that varies over a broad spectral range along the length of the filter. The key component of the linear variable PC filter is a polymer surface-relief grating whose period changes linearly as a function of its position on the filter. The grating is fabricated using a nanoreplica molding process with a wedge-shaped elastomer mold. The top surface of the mold carries the grating pattern and the wedge is formed by a shallow angle between the top and bottom surfaces of the mold. During the replica molding process, a uniaxial force is applied to stretch the mold, resulting in a nearly linearly varying grating period. The period of the grating is determined using the magnitude of the force and the local thickness of the mold. The grating period of the fabricated device spans a range of 421.8-463.3 nm over a distance of 20 mm. A high refractive index dielectric film is deposited on the graded-period grating to act as the waveguide layer of the PC device. The resonance reflection feature of the device varies linearly in a range of 680.2-737.0 nm over the length of the grating.

One-step sol-gel imprint lithography for guided-mode resonance structures.

Guided-mode resonance (GMR) structures consisting of sub-wavelength periodic gratings are capable of producing narrow-linewidth optical resonances. This paper describes a sol-gel-based imprint lithography method for the fabrication of submicron 1D and 2D GMR structures. This method utilizes a patterned polydimethylsiloxane (PDMS) mold to fabricate the grating coupler and waveguide for a GMR device using a sol-gel thin film in a single step. An organic-inorganic hybrid sol-gel film was selected as the imprint material because of its relatively high refractive index. The optical responses of several sol-gel GMR devices were characterized, and the experimental results were in good agreement with the results of electromagnetic simulations. The influence of processing parameters was investigated in order to determine how finely the spectral response and resonant wavelength of the GMR devices could be tuned. As an example potential application, refractometric sensing experiments were performed using a 1D sol-gel device. The results demonstrated a refractive index sensitivity of 50 nm/refractive index unit. This one-step fabrication process offers a simple, rapid, and low-cost means of fabricating GMR structures. We anticipate that this method can be valuable in the development of various GMR-based devices as it can readily enable the fabrication of complex shapes and allow the doping of optically active materials into sol-gel thin film.

Multipitched Diffraction Gratings for Surface Plasmon Resonance-Enhanced Infrared Reflection Absorption Spectroscopy.

We demonstrate the application of metal-coated diffraction gratings possessing multiple simultaneous pitch values for surface enhanced infrared absorption (SEIRA) spectroscopy. SEIRA increases the magnitude of vibrational signals in infrared measurements by one of several mechanisms, most frequently involving the enhanced electric field associated with surface plasmon resonance (SPR). While the majority of SEIRA applications to date have employed nanoparticle-based plasmonic systems, recent advances have shown how various metals and structures lead to similar signal enhancement. Recently, diffraction grating couplers have been demonstrated as a highly tunable platform for SEIRA. Indeed, gratings are an experimentally advantageous platform due to the inherently tunable nature of surface plasmon excitation at these surfaces since both the grating pitch and incident angle can be used to modify the spectral location of the plasmon resonance. In this work, we use laser interference lithography (LIL) to fabricate gratings possessing multiple pitch values by subjecting photoresist-coated glass slides to repetitive exposures at varying orientations. After metal coating, these gratings produced multiple, simultaneous plasmon peaks associated with the multipitched surface, as identified by infrared reflectance measurements. These plasmon peaks could then be coupled to vibrational modes in thin films to provide localized enhancement of infrared signals. We demonstrate the flexibility and tunability of this platform for signal enhancement. It is anticipated that, with further refinement, this approach might be used as a general platform for broadband enhancement of infrared spectroscopy.

Epitaxially grown collagen fibrils reveal diversity in contact guidance behavior among cancer cells.

Invasion of cancer cells into the surrounding tissue is an important step during cancer progression and is driven by cell migration. Cell migration can be random, but often it is directed by various cues such as aligned fibers composed of extracellular matrix (ECM), a process called contact guidance. During contact guidance, aligned fibers bias migration along the long axis of the fibers. These aligned fibers of ECM are commonly composed of type I collagen, an abundant structural protein around tumors. In this paper, we epitaxially grew several different patterns of organized type I collagen on mica and compared the morphology and contact guidance behavior of two invasive breast cancer cell lines (MDA-MB-231 and MTLn3 cells). Others have shown that these cells randomly migrate in qualitatively different ways. MDA-MB-231 cells exert large traction forces, tightly adhere to the ECM, and migrate with spindle-shaped morphology and thus adopt a mesenchymal mode of migration. MTLn3 cells exert small traction forces, loosely adhere to the ECM, and migrate with a more rounded morphology and thus adopt an amoeboid mode of migration. As the degree of alignment of type I collagen fibrils increases, cells become more elongated and engage in more directed contact guidance. MDA-MB-231 cells perceive the directional signal of highly aligned type I collagen fibrils with high fidelity, elongating to large extents and migrating directionally. Interestingly, behavior in MTLn3 cells differs. While highly aligned type I collagen fibril patterns facilitate spreading and random migration of MTLn3 cells, they do not support elongation or directed migration. Thus, different contact guidance cues bias cell migration differently and the fidelity of contact guidance is cell type dependent, suggesting that ECM alignment is a permissive cue for contact guidance, but requires a cell to have certain properties to interpret that cue.

Reducing optical losses in organic solar cells using microlens arrays: theoretical and experimental investigation of microlens dimensions.

The performance of organic photovoltaic devices is improving steadily and efficiencies have now exceeded 10%. However, the incident solar spectrum still largely remains poorly absorbed. To reduce optical losses, we employed a microlens array (MLA) layer on the side of the glass substrate facing the incident light; this approach does not interfere with the processing of the active-layer. We observed up to 10% enhancement in the short circuit current of poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl}):(6,6)-phenyl C71-butyric acid methyl ester (PTB7:PC71BM) OPV cells. Theoretically and experimentally investigating several MLA dimensions, we found that photocurrent increases with the ratio of the height to the pitch size of MLA. Simulations reveal the enhancement mechanisms: MLA focuses light, and also increases the light path within the active-layer by diffraction. Photocurrent enhancements increase for a polymer system with thinner active-layers, as demonstrated in poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT):PC71BM OPVs with 17% improvement in short circuit current.

Angle-tunable enhanced infrared reflection absorption spectroscopy via grating-coupled surface plasmon resonance.

Surface enhanced infrared absorption (SEIRA) spectroscopy is an attractive method for increasing the prominence of vibrational modes in infrared spectroscopy. To date, the majority of reports associated with SEIRA utilize localized surface plasmon resonance from metal nanoparticles to enhance electromagnetic fields in the region of analytes. Limited work has been performed using propagating surface plasmons as a method for SEIRA excitation. In this report, we demonstrate angle-tunable enhancement of vibrational stretching modes associated with a thin poly(methyl methacrylate) (PMMA) film that is coupled to a silver-coated diffraction grating. Gratings are fabricated using laser interference lithography to achieve precise surface periodicities, which can be used to generate surface plasmons that overlap with specific vibrational modes in the polymer film. Infrared reflection absorption spectra are presented for both bare silver and PMMA-coated silver gratings at a range of angles and polarization states. In addition, spectra were obtained with the grating direction oriented perpendicular and parallel to the infrared source in order to isolate plasmon enhancement effects. Optical simulations using the rigorous coupled-wave analysis method were used to identify the origin of the plasmon-induced enhancement. Angle-dependent absorption measurements achieved signal enhancements of more than 10-times the signal in the absence of the plasmon.

Equine intradermal test threshold concentrations for house dust mite and storage mite allergens and identification of stable acari fauna.

BACKGROUND: House dust mite (HDM) and storage mite (SM) stable fauna and their associated equine intradermal test (IDT) threshold concentrations (TCs) for the midwestern region of the USA are unknown. HYPOTHESIS/OBJECTIVES: To determine IDT TCs and serum IgE concentrations for two HDM and three SM species in clinically normal horses over two seasons, and to identify the mite taxa and habitats in a stable. ANIMALS: Thirty-eight clinically normal horses. METHODS: Threshold concentrations for HDMs and SMs were determined using IDT subjective measurements and a statistical model. An enzyme-linked immunosorbent assay was used to quantify serum IgE concentrations for the same mite species. A modified flotation method was used to identify morphologically HDMs and SMs. RESULTS: Subjective IDT TCs were as follows: 1:80,000 w/v for Dermatophagoides farinae in both seasons; 1:80,000 w/v in spring and 1:160,000 w/v in late summer for Dermatophagoides pteronyssinus; 1:40,000 w/v in spring and 1:20,000 w/v in late summer for Acarus siro; 1:20,000 w/v for Lepidoglyphus destructor in both seasons; and 1:20,000 w/v in spring and 1:10,000 w/v in late summer for Tyrophagus putrescentiae. Statistically significant associations for increased serum IgE and a positive IDT reaction were evident for D. farinae in the spring and D. pteronyssinus in both seasons. One mite from all four genera specific to this study was identified; however,two HDM and A. siro species were not detected.Conclusions and clinical importance ­ This study established HDM and SM IDT dilution concentrations for the horses in this region. Exposure to diverse acaridae fauna may contribute to the pathogenesis of equine allergic disease.