Polychromatic femtosecond fluorescence studies of metal–polypyridine complexes in solution

Femtosecond-resolved broadband fluorescence studies are reported for[M(bpy)3]2+ (M = Fe, Ru), RuN3 and RuN719 complexes in solution. We investigated the pump wavelength dependence of the fluorescence of aqueous [Fe(bpy)3]2+ and the solvent and ligand dependence of the fluorescence of Ru-complexes excited at 400 nm. For all complexes, the 1MLCT fluorescence appears at zero time delay with a mirror-like image with respect to the absorption. It decays in 630–45 fs due to intersystem crossing to the 3MLCT states, but a longer lived component of 190 fs additionally shows up in RuN719 and RuN3. No solvent effects are detected. The very early dynamics are characterized by internal conversion (IC) and intramolecular vibrational redistribution (IVR) processes on a time scale which we estimate to 610 fs using the 1MLCT lifetime as an internal clock

The violent youth of bright and massive cluster galaxies and their maturation over 7 billion years

In this study, we investigate the formation and evolution mechanisms of the brightest cluster galaxies (BCGs) over cosmic time. At high redshift (z ∼ 0.9), we selected BCGs and most massive cluster galaxies (MMCGs) from the Cl1604 supercluster and compared them to low-redshift (z ∼ 0.1) counterparts drawn from the MCXC meta-catalogue, supplemented by Sloan Digital Sky Survey imaging and spectroscopy. We observed striking differences in the morphological, colour, spectral, and stellar mass properties of the BCGs/MMCGs in the two samples. High-redshift BCGs/MMCGs were, in many cases, star-forming, late-type galaxies, with blue broad-band colours, properties largely absent amongst the low-redshift BCGs/MMCGs. The stellar mass of BCGs was found to increase by an average factor of 2.51 ± 0.71 from z ∼ 0.9 to z ∼ 0.1. Through this and other comparisons, we conclude that a combination of major merging (mainly wet or mixed) and in situ star formation are the main mechanisms which build stellar mass in BCGs/MMCGs. The stellar mass growth of the BCGs/MMCGs also appears to grow in lockstep with both the stellar baryonic and total mass of the cluster. Additionally, BCGs/MMCGs were found to grow in size, on average, a factor of ∼3, while their average Sérsic index increased by ∼0.45 from z ∼ 0.9 to z ∼ 0.1, also supporting a scenario involving major merging, though some adiabatic expansion is required. These observational results are compared to both models and simulations to further explore the implications on processes which shape and evolve BCGs/MMCGs over the past ∼7 Gyr

Improved morphology control using a modified two-step method for efficient perovskite solar cells

© 2014 American Chemical Society. A two-step wet chemical synthesis method for methylammonium lead(II) triiodide (CH3NH3PbI3) perovskite is further developed for the preparation of highly reproducible solar cells, with the following structure: fluorine-doped tin oxide (FTO)/TiO2 (compact)/TiO2 (mesoporous)/CH3NH3PbI3/spiro-OMeTAD/Ag. The morphology of the perovskite layer could be controlled by careful variation of the processing conditions. Specifically, by modifying the drying process and inclusion of a dichloromethane treatment, more uniform films could be prepared, with longer emission lifetime in the perovskite material and longer electron lifetime in solar cell devices, as well as faster electron transport and enhanced charge collection at the selective contacts. Solar cell efficiencies up to 13.5% were obtained

Human Hand Gesture Recognition

A Human Computer Interaction(HCI) between computers and human understands human language and improve a user friendly interface. Gestures a non-verbal form of communication supplies the HCI interface. The aim of gesture recognition is to make a system which can recognize specific-human gestures and employ them to convey information or for device control. Real-time visionbased hand gesture recognition is attempting to be more and more suitable for HCI with the assistance of the latest advances in the area of computer vision and pattern recognition. The gesture will able to reduce the use of most Prominent hardware devices which are used to control the activities of the computer. In this paper we introduces a mechanism for human computer interaction utilizing open source OpenCV. The proposed algorithm consists of preprocessing, segmentation and feature extraction.In segmentation we are used threshold BINARY-INV+threshold OTSU.Then make use of contours, convex hull and convexity defects to find the hand gesture.The hand gesture images are captured by a camera. That is used as the input to the algorithm. The proposed algorithm is able to recognize the number of fingers present in the hand gesture

Twisted Intramolecular Charge Transfer (TICT) Controlled by Dimerization : An Overlooked Piece of the TICT Puzzle

Organic dyes have shown high efficiencies in solar cells, which is mainly attributed to the push-pull strategy present in such dyes upon attaching to the semiconductor surfaces. We deeply studied the fundamental photophysical properties of cyanoacrylic dyes, mostly the L1 dye, and found unique emission properties that depend on many factors such as the solvent polarity and the concentration of the dye and could present a complete emission picture about this family of dyes. The L1 dye shows an intramolecular charge transfer (ICT) emission state at low concentrations (approximately nanomolar scale) and shows a twisted intramolecular charge transfer (TICT) emission state in specific solvents upon increasing the concentration to the micromolar scale. Moreover, the associated emission lifetimes of the ICT and TICT states of the L1 dye depend on solvent basicity, highlighting the role of hydrogen bond formation on controlling such states. Density functional theory calculations are performed to gain insight into the photophysical properties of the dye and revealed that H-bonding between the carboxylic groups triggers the dimerization at low concentrations. Using femtosecond transient absorption, we assigned the rate of TICT formation to be in the range (160-650 fs)(-1), depending on the size of the studied cyanoacrylic dye. Therefore, we add herein a new dimension for controlling the formation of the TICT state, in addition to the solvent polarity and acceptor strength parameters. These findings are not limited to the studied dyes, and we expect that numerous organic carboxylic acids dyes show similar properties

An Elliptical Boundary Skin Model For Hand Detection Based on HSV Color Space

Detection and tracking of human face and hands are curial for gesture recognition. In this paper, a skin segmentation framework is presented, where a robust elliptical model in HSV color space is developed, which promises not only to better model the skin color, but also to significantly lower the complexity of the hand detection process. In our approach, hand regions are identified and detected in Hue Saturation Value (HSV) color space that is proven to correspond closer to human perception of hand color than the traditional RGB color space. The obtained results show the potential of the method proposed and it yields good performance and has robustness with respect to illumination as well as with respect to image noise