Critical Role of Methylammonium Librational Motion in Methylammonium Lead Iodide (CH3NH3PbI3) Perovskite Photochemistry.

Raman and photoluminescence (PL) spectroscopy are used to investigate dynamic structure-function relationships in methylammonium lead iodide (MAPbI3) perovskite. The intensity of the 150 cm-1 methylammonium (MA) librational Raman mode is found to be correlated with PL intensities in microstructures of MAPbI3. Because of the strong hydrogen bond between hydrogens in MA and iodine in the PbI6 perovskite octahedra, the Raman activity of MA is very sensitive to structural distortions of the inorganic framework. The structural distortions directly influence PL intensities, which in turn have been correlated with microstructure quality. Our measurements, supported with first-principles calculations, indicate how excited-state MA librational displacements mechanistically control PL efficiency and lifetime in MAPbI3-material parameters that are likely important for efficient photovoltaic devices

Importance of electronic self-consistency in the TDDFT based treatment of nonadiabatic molecular dynamics

A mixed quantum-classical approach to simulate the coupled dynamics of electrons and nuclei in nanoscale molecular systems is presented. The method relies on a second order expansion of the Lagrangian in time-dependent density functional theory (TDDFT) around a suitable reference density. We show that the inclusion of the second order term renders the method a self-consistent scheme and improves the calculated optical spectra of molecules by a proper treatment of the coupled response. In the application to ion-fullerene collisions, the inclusion of self-consistency is found to be crucial for a correct description of the charge transfer between projectile and target. For a model of the photoreceptor in retinal proteins, nonadiabatic molecular dynamics simulations are performed and reveal problems of TDDFT in the prediction of intra-molecular charge transfer excitations.Comment: 9 pages, 8 figures. Minor changes in content wrt older versio

Infrared spectroscopy of phytochrome and model pigments

Fourier-transform infrared difference spectra between the red-absorbing and far-red-absorbing forms of oat phytochrome have been measured in H2O and 2H2O. The difference spectra are compared with infrared spectra of model compounds, i.e. the (5Z,10Z,15Z)- and (5Z,10Z,15E)-isomers of 2,3,7,8,12,13,17,18-octaethyl-bilindion (Et8-bilindion), 2,3-dihydro-2,3,7,8,12,13,17,18-octaethyl-bilindion (H2Et8-bilindion), and protonated H2Et8-bilindion in various solvents. The spectra of the model compounds show that only for the protonated forms can clear differences between the two isomers be detected. Since considerable differences are present between the spectra of Et8-bilindion and H2Et8-bilindion, it is concluded that only the latter compound can serve as a model system of phytochrome. The 2H2O effect on the difference spectrum of phytochrome supports the view that the chromophore in red-absorbing phytochrome is protonated and suggests, in addition, that it is also protonated in far-red-absorbing phytochrome. The spectra show that protonated carboxyl groups are influenced. The small amplitudes in the difference spectra exclude major changes of protein secondary structure

Continued Value Creation in Crowdsourcing from Creative Process Engagement

Purpose Crowdsourcing delivers creative ideas for the issuing firm, but participants’ engagement in the creative process also creates additional benefits to firms and participating customers. To investigate if these spill-over values endure over time, this study uses data from two time points, i.e. at submission and after announcement of the contest winners, to investigate the relationship between the degree of a participant’s creative process engagement (CPE) and value creation from a crowdsourcing contest, and how these perceptions of value change over time. Design/methodology/approach Data was collected from 154 participants in a crowdsourcing contest at two time points with an online survey: at submission, and after receiving feedback (in term of rankings, rewards, and comments) from the community. Partial Least Square (PLS) path modelling was used to estimate both main and moderating effects. Findings CPE increases the perceived value of customers (social and epistemic value) and firms alike (knowledge-sharing intention and customer loyalty), though all but epistemic value decrease over time. Disconfirmation of expectations and need for recognition moderate these effects. Originality/value This paper is the first longitudinal study that helps understanding the effect of CPE on value creation from crowdsourcing across time. It also uses the theoretical lens of the honeymoon hangover effect to explain how perceived value changes. The resulting insights into the role of customer engagement in crowdsourcing contests and subsequent value creation will be beneficial to the growing research stream on consumer value co-creation and user innovation

Colloidal pathways of amorphous calcium carbonate formation lead to distinct water environments and conductivity

CaCO3 is the most abundant biomineral and a major constituent of incrustations arising from water hardness. Polycarboxylates play key roles in controlling mineralization. Herein, we present an analytical and spectroscopic study of polycarboxylate-stabilized amorphous CaCO3 (ACC) and its formation via a dense liquid precursor phase (DLP). Polycarboxylates facilitate pronounced, kinetic bicarbonate entrapment in the DLP. Since bicarbonate is destabilized in the solid state, DLP dehydration towards solid ACC necessitates the formation of locally calcium deficient sites, thereby inhibiting nucleation. Magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy of poly-aspartate-stabilized ACC reveals the presence of two distinct environments. The first contains immobile calcium and carbonate ions and structural water molecules, undergoing restricted, anisotropic motion. In the second environment, water molecules undergo slow, but isotropic motion. Indeed, conductive atomic force microscopy (C-AFM) reveals that ACC conducts electrical current, strongly suggesting that the mobile environment pervades the bulk of ACC, with dissolved hydroxide ions constituting the charge carriers. We propose that the distinct environments arise from colloidally stabilized interfaces of DLP nanodroplets, consistent with the pre-nucleation cluster (PNC) pathway

Extended Thromboprophylaxis with Betrixaban in Acutely Ill Medical Patients

Background Patients with acute medical illnesses are at prolonged risk for venous thrombosis. However, the appropriate duration of thromboprophylaxis remains unknown. Methods Patients who were hospitalized for acute medical illnesses were randomly assigned to receive subcutaneous enoxaparin (at a dose of 40 mg once daily) for 10±4 days plus oral betrixaban placebo for 35 to 42 days or subcutaneous enoxaparin placebo for 10±4 days plus oral betrixaban (at a dose of 80 mg once daily) for 35 to 42 days. We performed sequential analyses in three prespecified, progressively inclusive cohorts: patients with an elevated d-dimer level (cohort 1), patients with an elevated d-dimer level or an age of at least 75 years (cohort 2), and all the enrolled patients (overall population cohort). The statistical analysis plan specified that if the between-group difference in any analysis in this sequence was not significant, the other analyses would be considered exploratory. The primary efficacy outcome was a composite of asymptomatic proximal deep-vein thrombosis and symptomatic venous thromboembolism. The principal safety outcome was major bleeding. Results A total of 7513 patients underwent randomization. In cohort 1, the primary efficacy outcome occurred in 6.9% of patients receiving betrixaban and 8.5% receiving enoxaparin (relative risk in the betrixaban group, 0.81; 95% confidence interval [CI], 0.65 to 1.00; P=0.054). The rates were 5.6% and 7.1%, respectively (relative risk, 0.80; 95% CI, 0.66 to 0.98; P=0.03) in cohort 2 and 5.3% and 7.0% (relative risk, 0.76; 95% CI, 0.63 to 0.92; P=0.006) in the overall population. (The last two analyses were considered to be exploratory owing to the result in cohort 1.) In the overall population, major bleeding occurred in 0.7% of the betrixaban group and 0.6% of the enoxaparin group (relative risk, 1.19; 95% CI, 0.67 to 2.12; P=0.55). Conclusions Among acutely ill medical patients with an elevated d-dimer level, there was no significant difference between extended-duration betrixaban and a standard regimen of enoxaparin in the prespecified primary efficacy outcome. However, prespecified exploratory analyses provided evidence suggesting a benefit for betrixaban in the two larger cohorts. (Funded by Portola Pharmaceuticals; APEX ClinicalTrials.gov number, NCT01583218. opens in new tab.

The Cognitive Perception of a Multi-room Music System with Spatial Interaction

Abstract. In recent years we have seen a growing interest in exploring spatial interaction as a means of interacting with computer systems through what has been labelled “proxemic interaction”. In order to explore the potentials and challenges of spatial interaction spanning across separate physical locations, we have developed a multi-room music system and performed a field evaluation of use. The system extends Apple AirPlay to allow spatial interaction with one’s music player, for example, adapting an App interface to the current location of the user, and allowing music to follow the user around the house. The prototype was deployed in two households over a three-week period, where data was col-lected through logging, user-written diaries and interviews. The field evaluation revealed a number of findings related to the cognitive perception of the spaces it was used in, such as importance of a simple interaction, the importance of providing local interaction, the challenge of foreground and background inter-actions, and challenges in designing interaction with music in discrete zones

Perovskite Silicon Tandem Solar Cells Above 30 Conversion Efficiency on Submicron Sized Textured Czochralski Silicon Bottom Cells with Improved Hole Transport Layers

In perovskite silicon tandem solar cells, the utilization of silicon heterojunction SHJ solar cells as bottom cells is one of the most promising concepts. Here, we present optimization strategies for the top cell processing and their integration into SHJ bottom cells based on industrial Czochralski Cz Si wafers of 140 amp; 956;m thickness. We show that combining the self assembled monolayer [4 3,6 dimethyl 9H carbazol 9 yl butyl]phosphonic acid Me 4PACz with an additional phosphonic acid PA with different functional groups, can improve film formation when used as a hole transport layer improving wettability, minimizing shunt fraction and reducing nonradiative losses at the buried interface. Transient surface photovoltage and transient photoluminescence measurements confirm that the combined Me 4PACz PA layer has similar charge transport properties to Me 4PACz alone. Moreover, this work demonstrates the potential for thin, double side submicron sized textured industry relevant silicon bottom cells yielding a high accumulated short circuit current density of 40.2 mA cm2 and reaching a stabilized power conversion efficiency of gt;30 . This work paves the way toward industry compatible, highly efficient tandem cells based on a production compatible SHJ bottom cel