Microphotonic parabolic light directors fabricated by two-photon lithography

We have fabricated microphotonic parabolic light directors using two-photon lithography, thin-film processing, and aperture formation by focused ion beam lithography. Optical transmission measurements through upright parabolic directors 22 μm high and 10 μm in diameter exhibit strong beam directivity with a beam divergence of 5.6°, in reasonable agreement with ray-tracing and full-field electromagnetic simulations. The results indicate the suitability of microphotonic parabolic light directors for producing collimated beams for applications in advanced solar cell and light-emitting diode designs

Brain activation during anticipation of sound sequences

Music consists of sound sequences that require integration over time. As we become familiar with music, associations between notes, melodies, and entire symphonic movements become stronger and more complex. These associations can become so tight that, for example, hearing the end of one album track can elicit a robust image of the upcoming track while anticipating it in total silence. Here, we study this predictive “anticipatory imagery” at various stages throughout learning and investigate activity changes in corresponding neural structures using functional magnetic resonance imaging. Anticipatory imagery (in silence) for highly familiar naturalistic music was accompanied by pronounced activity in rostral prefrontal cortex (PFC) and premotor areas. Examining changes in the neural bases of anticipatory imagery during two stages of learning conditional associations between simple melodies, however, demonstrates the importance of fronto-striatal connections, consistent with a role of the basal ganglia in “training” frontal cortex (Pasupathy and Miller, 2005). Another striking change in neural resources during learning was a shift between caudal PFC earlier to rostral PFC later in learning. Our findings regarding musical anticipation and sound sequence learning are highly compatible with studies of motor sequence learning, suggesting common predictive mechanisms in both domains

A basic population balance model for fluid bed spray granulation

Abstract A basic population balance approach is developed for a granulation process in a fluid bed spray granulator. The particle size distribution predicted by the model is confirmed by plant data. Hence this model is considered to be useful to describe and optimize an industrial process. The model depends on a limited number of parameters (most of these factors can be measured or are known): the spray volume flux, the nucleation fraction (the fraction of the spray volume flux which leads to new particles formed), the nucleation particle diameter, the product withdrawal threshold diameter, and the product withdrawal rate. Analysis of the model reveals a steady state constraint; a steady state does not exist if the nucleation fraction is too large. For cases where the steady state does exist, the steady state particle size distribution is solved analytically. A numerical implementation of the model is used to illustrate the transient evolution of the process. The steady state solution appears to be stable for a constant nucleation fraction. However, if the nucleation fraction depends on the bed height the steady state can be unstable. Such a situation may occur if the spray inlet is near the height of the bed surface. Instead of convergence towards a steady state, the transient solution displays ongoing oscillatory behavior with an oscillation period of a number of hours. A linear stability analysis is performed to confirm the findings on the stability of the steady state

Microphotonic parabolic light directors fabricated by two-photon lithography

We have fabricated microphotonic parabolic light directors using two-photon lithography, thin-film processing, and aperture formation by focused ion beam lithography. Optical transmission measurements through upright parabolic directors 22 m high and 10 m in diameter exhibit strong beam directivity with a beam divergence of 5.6, in reasonable agreement with ray-tracing and full-field electromagnetic simulations. The results indicate the suitability of microphotonic parabolic light directors for producing collimated beams for applications in advanced solar cell and light-emitting diode designs. © 2011 American Institute of Physics.Peer Reviewe

Plasmonic light trapping in thin-film Si solar cells

Plasmonic nanostructures have been recently investigated as a possible way to improve absorption of light in solar cells. The strong interaction of small metal nanostructures with light allows control over the propagation of light at the nanoscale and thus the design of ultrathin solar cells in which light is trapped in the active layer and efficiently absorbed. In this paper we review some of our recent work in the field of plasmonics for improved solar cells. We have investigated two possible ways of integrating metal nanoparticles in a solar cell. First, a layer of Ag nanoparticles that improves the standard antireflection coating used for crystalline and amorphous silicon solar cells has been designed and fabricated. Second, regular and random arrays of metal nanostructures have been designed to couple light in waveguide modes of thin semiconductor layers. Using a large-scale, relative inexpensive nano-imprint technique, we have designed a back-contact light trapping surface for a-Si:H solar cells which show enhanced efficiency over standard randomly textured cells

Plasmonic light trapping in thin-film Si solar cells

Plasmonic nanostructures have been recently investigated as a possible way to improve absorption of light in solar cells. The strong interaction of small metal nanostructures with light allows control over the propagation of light at the nanoscale and thus the design of ultrathin solar cells in which light is trapped in the active layer and efficiently absorbed. In this paper we review some of our recent work in the field of plasmonics for improved solar cells. We have investigated two possible ways of integrating metal nanoparticles in a solar cell. First, a layer of Ag nanoparticles that improves the standard antireflection coating used for crystalline and amorphous silicon solar cells has been designed and fabricated. Second, regular and random arrays of metal nanostructures have been designed to couple light in waveguide modes of thin semiconductor layers. Using a large-scale, relative inexpensive nano-imprint technique, we have designed a back-contact light trapping surface for a-Si:H solar cells which show enhanced efficiency over standard randomly textured cells

Measures of adherence to HCV therapy in a specialty pharmacy setting and association with NON-SVR.

Background: Adherence to HCV antivirals is an important factor associated with SVR. Specialty pharmacies (SP) support adherence through benefits and prescription facilitation, and medication counseling for high cost or complex medication regimens. The goal of this study was to characterize the patient population with HCV managed by an institutional SP service and determine factors, including medication adherence, that are associated with NON‐SVR. METHODS: Retrospective cross‐sectional study with nested case‐control (1:3 matched) including adults receiving HCV therapy with a direct‐acting antiviral through SP Adherence was measured from electronic pharmacy data by two standard metrics: proportion of days covered (PDC) and medication possession ratio (MPR). MPR may be greater than 100% when accounting for early refill behavior. The outcome of interest was NON‐SVR. Additional data collected: patient, provider and disease characteristics. Variables associated with NON‐SVR were compared and included in a multivariable logistic regression model. RESULTS: 1,025 patients were included: 641 (63%) male, 407 (40%) black, median age 61, 882 (86%) HCV genotype 1. HCV treatment regimens were 99% sofosbuvir‐based: 746 (73%) ledipasvir‐sofosbuvir +/‐ ribavirin, 154 (15%) sofosbuvir with ribavirin, 11% other. 89 (9%) patients failed to achieve SVR. Among 344 pts in the case‐control study, PDC was not associated with SVR. A CART‐derived breakpoint of \u3c 102.1% MPR was associated NON‐SVR (unadjOR 2.0, 95%CI 1. 2‐3.4). Variables associated with NON‐SVR are listed in Table 1. CONCLUSIONS: MPR \u3e 102.1% was associated with improved SVR, and may reflect early refill behavior and fewer gaps in medication on hand. SP with HCV services should consider MPR and other modifiable factors to improve patient adherence and outcome

Measures of adherence to HCV therapy in a specialty pharmacy setting and association with NON-SVR.

Background: Adherence to HCV antivirals is an important factor associated with SVR. Specialty pharmacies (SP) support adherence through benefits and prescription facilitation, and medication counseling for high cost or complex medication regimens. The goal of this study was to characterize the patient population with HCV managed by an institutional SP service and determine factors, including medication adherence, that are associated with NON‐SVR. METHODS: Retrospective cross‐sectional study with nested case‐control (1:3 matched) including adults receiving HCV therapy with a direct‐acting antiviral through SP Adherence was measured from electronic pharmacy data by two standard metrics: proportion of days covered (PDC) and medication possession ratio (MPR). MPR may be greater than 100% when accounting for early refill behavior. The outcome of interest was NON‐SVR. Additional data collected: patient, provider and disease characteristics. Variables associated with NON‐SVR were compared and included in a multivariable logistic regression model. RESULTS: 1,025 patients were included: 641 (63%) male, 407 (40%) black, median age 61, 882 (86%) HCV genotype 1. HCV treatment regimens were 99% sofosbuvir‐based: 746 (73%) ledipasvir‐sofosbuvir +/‐ ribavirin, 154 (15%) sofosbuvir with ribavirin, 11% other. 89 (9%) patients failed to achieve SVR. Among 344 pts in the case‐control study, PDC was not associated with SVR. A CART‐derived breakpoint of \u3c 102.1% MPR was associated NON‐SVR (unadjOR 2.0, 95%CI 1. 2‐3.4). Variables associated with NON‐SVR are listed in Table 1. CONCLUSIONS: MPR \u3e 102.1% was associated with improved SVR, and may reflect early refill behavior and fewer gaps in medication on hand. SP with HCV services should consider MPR and other modifiable factors to improve patient adherence and outcome