Computationally Connecting Organic Photovoltaic Performance to Atomistic Arrangements and Bulk Morphology

Rationally designing roll-to-roll printed organic photovoltaics requires a fundamental understanding of active layer morphologies optimized for charge separation and transport, and which ingredients can be used to self-assemble those morphologies. In this review article we discuss advances in three areas of computational modeling that provide insight into active layer morphology and the charge transport properties that result. We explain the computational bottlenecks prohibiting atomistically-detailed simulations of device-scale active layers and the coarse-graining and hardware acceleration strategies for overcoming them. We review coarse-grained simulations of organic photovoltaic active layers and show that high throughput simulations of experimentally-relevant length scales are now accessible. We describe a new Python package diffractometer that permits grazing-incidence X-ray scattering patterns of simulated active layers to be compared against experiments. We explain the accurate calculation of charge-carrier mobilities from coarse-grained active layer morphologies by using atomistic backmapping, quantum chemical calculations, and kinetic Monte Carlo simulations. We employ these simulations to show that ordering of poly(3-hexylthiophene-2,5-diyl) explains a factor of 1000 improvement in charge mobility. In concert, we present a suite of computational tools enabling large-scale electronic properties of organic photovoltaics to be studied and screened for by molecular simulations

Popular Conceptions of Nationhood in Old and New European Member States: Partial Support for the Ethnic-Civic Framework

One of the most influential theories in the study of nationalism has been the ethnic-East/civic-West framework developed by Hans Kohn. Using the 2002 Eurobarometer survey on national identity and building on earlier survey studies, this article examines whether the Kohn framework is valid at the level of popular understandings of nationhood. It scrutinizes the framework both conceptually - do people define nationhood in civic or ethnic terms? - and regionally - is the East indeed more ethnic than the West and the West more civic than the East? It will show that identity markers cluster in a political, a cultural and an ethnic dimension. Respondents do not see these dimensions as competing sources of nationhood, however. The article further lends some support for the regional component of the framework. Lastly, it argues that it is the intensity of national identifications rather than their qualitative nature (ethnic-civic) that correlates with xenophobia. © 2006 Taylor & Francis

Silicon micromachined broad band light source

A micro electromechanical system (MEMS) broad band incandescent light source includes three layers: a top transmission window layer; a middle filament mount layer; and a bottom reflector layer. A tungsten filament with a spiral geometry is positioned over a hole in the middle layer. A portion of the broad band light from the heated filament is reflective off the bottom layer. Light from the filament and the reflected light of the filament are transmitted through the transmission window. The light source may operate at temperatures of 2500 K or above. The light source may be incorporated into an on board calibrator (OBC) for a spectrometer

Frontal Asymmetry Changes Following Passive Hypo-Hydration

INTRODUCTION: Universal fluid consumption prescriptions among both athletic and non-athletic populations continue to elicit both hypo- and hyper-hydration (hypo-natremia). Thus, the need to find novel, identifiable traits within individuals who may be at higher risk to experience hypo-hydration, as well as hypo-natremia, is warranted. Of interest here, behavior is encapsulated by two motivational systems, referred to as approach/reward (R) or avoidance/non-reward (NR), respectively, in response to a behavioral stimulus. Past literature has revealed individual differences in consumptive traits of various types of foods between these motivational systems. Therefore, the purpose of this study was to evaluate changes in R/NR via frontal asymmetry (FA) in response to water exposure during eu-hydrated and hypo-hydrated conditions. METHODS: Participants included 11 active college-aged males. Electroencephalogram (EEG) assessed motivational orientations to water exposure in both eu-hydrated and hypo-hydrated states. A 5-minute nature video was used to stabilize mood, followed by 2 minutes of resting EEG recordings. Then, FA was assessed with the presentation of a glass of ice water, with instructions to observe, but not consume for 3 minutes. FA was re-assessed in the same manner following a dehydration trial (~90 minutes). Dehydration trials were performed in a controlled hot water bath at a mean of 39°C. Participants remained in the bath until 2% body mass loss, with no fluids consumed during the trials. Urine voids were collected before and after trials to assess specific gravity and color. Body core temperature was monitored throughout the protocol, with \u3e38.7°C set as criteria for removal of the subject. Participants reported perceptual affective measures using Feeling Scale (FS) and Felt Arousal Scale (FAS) throughout the session to account for any unusual affective states. RESULTS: EEG recordings were applied to the Frontal Asymmetry Index (FAI) (log right alpha power minus log left alpha power). Higher scores on the FAI indicate higher relative left frontal lobe activity, corresponding with an affinity to the water (R). Where as a lower score indicates higher relative right frontal activity, thus less reward motivation (NR). Data revealed that FAI decreased by a mean of 0.055 ±0.193 from eu-hydrated to hypo-hydrated states, with eu-hydration and hypo-hydration FAI of 0.06 and 0.004 respectively. In total, 37.4% of participants showed an increased affinity(R) for water from eu-hydrated to hypo-hydrated states. Pre and post FS were 2.91 ±1.51 and .45 ±2.88, respectively. Pre and post FAS were 2.73 ±.91 and 2.73 ±1.49. DISCUSSION: Reward/non-reward motivational orientations (affinity to water) changes were less than anticipated following hypo-hydration trials. However, data revealed that 37.4% of participants exhibited an increased affinity for water according to the FAI scale, supporting the hypothesis. It is possible that 2% body mass loss is insufficient to create distinct motivational orientation changes within the present sample. Due to the small sample size of the current study, little can be concluded thus far. Additional research addressing the aforementioned methods, as well as larger sample sizes is warranted. If motivational orientation state variability can be established during eu-hydrated and hypo-hydrated states, it may be possible to identify the consumptive tendencies of fluids among individuals

Attempting to Acutely Manipulate Ground Contact Time Imbalances Impairs Running Economy

Running economy (RE) is a key performance determinant. Biomechanical markers have been linked to RE, including ground contact time (GCT), cadence, and vertical oscillation (VO). Recently, we showed a strong relationship between GCT imbalances and RE. Because these markers can be tracked real-time with consumer-wearable devices, runners now have access to instant feedback concerning their mechanics. PURPOSE: Determine if attempting to correct GCT imbalances real-time alters mechanics and RE. METHODS: 7 recreational runners (38 ± 15 years, 24.7 ± 2.8 kg/m2, 5 male) completed 2, 10-minute running trials (9.65 km/hr) on separate days. For both trials, subjects ran with a heart rate (HR) monitor/watch that measured GCT, GCT imbalances, cadence, and VO. For the control (CT) trial, subjects were not permitted to receive feedback from the watch. During the feedback (FB) trial, the watch was set to display GCT imbalances, and subjects were prompted every 20-30 seconds to monitor/attempt to correct any imbalances. Both trials were preceded by a dynamic warmup and 5-minute jog. For the FB trial warmup, subjects were acclimated to the watch and allowed to experiment with manipulating their GCT imbalances. VO2 was monitored continuously throughout each 10-minute trial, and average values from 6 to 9 minutes were determined for each trial. Average values for all running biomechanical variables were calculated from 0.5 minutes to 9.5 minutes. Comparisons between trials were made with a dependent sample t-test. RESULTS: The FB trial elicited a significantly higher (p = .011) working VO2 (35.5 ± 1.6 ml/kg/min) compared to the CT trial (33.4 ± 1.8 ml/kg/min). There were no other significant differences between trials for the other measured variables. Average values for each variable by trial were as follows: RER (CT: .91 ± .04; FB: .92 ± .05), HR (CT: 159 ± 26 bpm; FB: 163 ± 24 bpm), GCT % difference (CT: 1.69 ± .67%; FB: 1.70 ± 1.70%), GCT absolute difference (CT: 9 ± 3 ms; FB: 8 ± 7 ms), GCT (CT: 272 ± 26 ms; FB: 268 ± 31 ms), Cadence (CT: 165 ± 9 steps/min; FB: 167 ± 9 steps/min); VO (CT: 9.3 ± 2.0 cm; FB: 9.2 ± 1.9 cm), VO ratio (CT: 9.5 ± 1.6 cm/m; FB: 9.5 ± 1.6 cm/m). CONCLUSIONS: Acutely attempting to correct GCT imbalances did not result in improved mechanics and actually impaired RE. Altering mechanics based on real-time feedback from consumer-wearable devices may impair performance in the short term. Given that GCT imbalances have been linked to impaired RE, future research should determine how to better correct these imbalances rather than attempting to acutely manipulate them

Molecular Interactions of Polydimethylsiloxane and Ni-Mn-Ga

Tiny pumps that can deliver microliters of fluid against high back-pressures can be made from Ni-Mn-Ga alloys. The fluid is transported in a movable pocket made between the alloy and a surrounding seal material, enabled by the magnetic shape memory properties of the alloy. The interaction between the sealant and the alloy is therefore critical, in particular how hey adhere and delaminate during pumping. This simulation study aims to quantify the interactions between the sealant poly-dimethylsiloxane (PDMS) and the Ni-Mn-Ga alloy. To study these PDMS-alloy interfaces, molecular dynamics simulations are performed using HOOMD-Blue on graphics processing units. We develop atomistic models for the interface components and investigate how the adhesion of short PDMS chains on Ni-Mn-Ga depend on model parameters, and temperature. We measure simulation speed as a function of system size on different processors to determine limits to computational feasibility and we identify conditions that facilitate adhesion. These simulations provide a first step towards more detailed studies of such organic/alloy interfaces and may help to identify more optimal sealant chemistries in the future