Vineyard microclimate and yield under different plastic covers.

The use of plastic cover in vineyards minimizes effects of adverse weather conditions. The northwest of São Paulo State is one of the largest grape producing regions in Brazil; however, few studies investigate the effects of different plastic covers on vineyards in this region. This study compared the effect of black shading screen (BSS) and braided polypropylene film (BPF) on BRS Morena vineyard microclimate, grown on an overhead trellis system in the northwestern São Paulo. The experiments were carried out during three growing seasons (2012 ? 2014). BSS allowed superior incoming solar radiation (SR) transmissivity, resulting in higher net radiation (Rn), and higher ratio between photosynthetically active (PAR) and SR. No differences were observed between the average air temperatures (T) and relative humidity (RH) of covered environments (BPF and BSS) and outside condition (automatic weather station ? AWS), due to high air circulation, despite wind speed (WS) reduction caused by plastic covers. BPF provided better conditions for vineyard growth with higher fruit yield than vineyard under BSS regarding the number of shoots with bunches per plant, bunch and stem weights, longitudinal diameter of berries, quantity of fertile buds per shoot, and yield per shoot and per plant. BPF covers also influenced leaf size and growth speed of plants in vineyards. Keywords Black shading screen . Braided polypropylene film . BRS Morena . Leaf wetness duration . Yiel

Identification and Classification of Conserved RNA Secondary Structures in the Human Genome

The discoveries of microRNAs and riboswitches, among others, have shown functional RNAs to be biologically more important and genomically more prevalent than previously anticipated. We have developed a general comparative genomics method based on phylogenetic stochastic context-free grammars for identifying functional RNAs encoded in the human genome and used it to survey an eight-way genome-wide alignment of the human, chimpanzee, mouse, rat, dog, chicken, zebra-fish, and puffer-fish genomes for deeply conserved functional RNAs. At a loose threshold for acceptance, this search resulted in a set of 48,479 candidate RNA structures. This screen finds a large number of known functional RNAs, including 195 miRNAs, 62 histone 3′UTR stem loops, and various types of known genetic recoding elements. Among the highest-scoring new predictions are 169 new miRNA candidates, as well as new candidate selenocysteine insertion sites, RNA editing hairpins, RNAs involved in transcript auto regulation, and many folds that form singletons or small functional RNA families of completely unknown function. While the rate of false positives in the overall set is difficult to estimate and is likely to be substantial, the results nevertheless provide evidence for many new human functional RNAs and present specific predictions to facilitate their further characterization

Photochemical upconversion: The primacy of kinetics

Incoherent photochemical upconversion is a process by which low-energy light can be converted into a higher-energy form with promising applications in solar energy conversion and storage, photocatalysis, biological imaging, and photochemical drug activation. Despite intensive research in recent years, there remains an underappreciation of the chemical kinetics that controls the efficiency of the upconversion process. Here, we provide a brief overview of research into photochemical upconversion and provide a tutorial to guide the design of efficient upconversion compositions. We further provide our perspective on where this area of research is heading and how very efficient systems will be developed. (Graph Presented)

Near-field optical addressing of luminescent photoswitchable supramolecular systems embedded in inert polymer matrices

Optical recording and luminescence readout of novel covalently linked photochrome/luminophore supramolecular complexes has been demonstrated by near-field scanning optical microscopy (NSOM). Localized UV irradiation of these complexes dispersed in polymeric matrices resulted in photoinduced state switching and a concomitant increase in emission intensity. Subsequent luminescence imaging showed well-resolved luminescent data bit arrays with good signal-to-noise ratios. Spatially resolved emission spectra of the luminescent data bits confirmed the switching mechanism

Catalytic proton reduction with transition metal complexes of the redox-active ligand bpy2PYMe

A new pentadentate, redox-active ligand bpy2PYMe has been synthesized and its corresponding transition metal complexes of Fe2+ (1), Co 2+ (2), Ni2+ (3), Cu2+ (4), and Zn2+ (5) have been investigated for electro- and photo-catalytic proton reduction in acetonitrile and water, respectively. Under weak acid conditions, the Co complex displays catalytic onset at potentials similar to those of the ligand centered reductions in the absence of acid. Related Co complexes devoid of ligand redox activity catalyze H2 evolution under similar conditions at significantly higher overpotentials, showcasing the beneficial effect of combining ligand-centered redox activity with a redox-active Co center. Furthermore, turnover numbers as high as 1630 could be obtained under aqueous photocatalytic conditions using [Ru(bpy)3]2+ as a photosensitizer. Under those conditions catalytic hydrogen production was solely limited by photosensitizer stability. Introduction of an electron withdrawing CF3 group into the pyridine moiety of the ligand as in bpy2PYMe-CF3 renders its corresponding Co complex 6 less active for proton reduction in electro- and photocatalytic experiments. This surprising effect of ligand substitution was investigated by means of density functional theory calculations which suggest the importance of electronic communication between Co1+ and the redox-active ligand. Taken together, the results provide a path forward in the design of robust molecular catalysts in aqueous media with minimized overpotential by exploiting the synergy between redox-active metal and ligand components. © 2013 The Royal Society of Chemistry

Towards a comprehensive understanding of visible-light photogeneration of hydrogen from water using cobalt(ii) polypyridyl catalysts

Homogeneous aqueous solutions of photocatalytic ensembles, consisting of [Ru(bpy)3]2+ as a photosensitizer, ascorbic acid/ascorbate as the electron source, and 10 distinct Co2+-based molecular catalysts, were evaluated for visible-light induced hydrogen evolution using high-throughput screening. The combined results demonstrate that Co2+ complexes bearing tetradentate ligands yield more active photocatalytic compositions than their congeners with pentadentate ligands while operating with high catalyst stability. Additionally, molecular Co2+ catalysts with cis open coordination sites appear to be significantly more active for hydrogen evolution than those with trans open sites. As evidenced by mass spectrometric analysis of the reactor headspace and associated deuteration experiments, the H2 gas generated in all instances was derived from aqueous protons. One of the most promising cis-disposed Co2+ species, [Co(bpyPY2Me)(CH3CN)(CF3SO3)](CF 3SO3) (1), engages in highly efficient hydrogen evolving photocatalysis, achieving a turnover number of 4200 (H2/Co) and a turnover frequency of 3200 (H2/Co per h) at pH 4 under simulated sunlight (AM 1.5G, 100 mW cm-2) at room temperature. At equimolar concentrations of photosensitizer and 1, the total hydrogen produced appears to be exclusively limited by the photostability of [Ru(bpy)3] 2+, which was observed to decompose into an Ru(bpy) 2-ascorbate adduct, as evidenced by HPLC and ESI-MS experiments. Lowering the operating temperature from 27 to 5 °C significantly attenuates bpy dissociation from the sensitizer, resulting in a net ∼two-fold increase in hydrogen production from this composition. The primary electron transfer steps of this photocatalytic ensemble were investigated by nanosecond transient absorption spectroscopy. Photoexcited [Ru(bpy)3]2+ undergoes reductive quenching by ascorbic acid/ascorbate (kq = 2.6 × 107 M-1 s-1), releasing [Ru(bpy) 3]+ from the encounter solvent cage with an efficiency of 55 ± 5%. In the presence of catalyst 1, [Ru(bpy)3]+ generated in the initial flash-quench experiment transfers an electron (k et = 2 × 109 M-1 s-1) at an efficiency of 85 ± 10% to the catalyst, which is believed to enter the hydrogen evolution cycle subsequently. Using a combinatorial approach, all ten Co2+ catalysts were evaluated for their potential to operate under neutral pH 7.0 conditions. Catalyst 7, [Co(PY4MeH2)(CH 3CN)(CF3SO3)](CF3SO3), was revealed to be most promising, as its performance metrics were only marginally affected by pH and turnover numbers greater than 1000 were easily obtained in photocatalytic hydrogen generation. These comprehensive findings provide guidelines for the development of molecular compositions capable of evolving hydrogen from purely aqueous media. This journal is © the Partner Organisations 2014

Luminescent charge transfer platinum(II) metallacycle

The photophysical and electrochemical properties of a platinum(II) diimine complex bearing the bidentate diacetylide ligand tolan-2,2\u27-diacetylide (tda), Pt(dbbpy)(tda) [dbbpy = 4,4\u27-di-tert-butyl-2,2\u27-bipyridine] (1), are compared with two reference compounds, Pt(dbbpy)(C CPh)(2) (2) and Pt(dppp)tda [dppp = 1,3-bis(diphenylphosphino)propane] (3), respectively, The X-ray crystal structure of 1 is reported, which illustrates the nearly perfect square planarity exhibited by this metallacycle. Chromophore 2 possesses low-lying charge-transfer excited states analogous to 1, whereas structure 3 lacks such excited states but features a low-lying platinum-perturbed tda intraligand triplet manifold. In CH2Cl2, 1 exhibits a broad emission centered at 562 nm at ambient temperature, similar to 2, but with a higher photoluminescence quantum yield and longer excited-state lifetime. In both instances, the photoluminescence is consistent with triplet-charge-transfer excited-state parentage. The rigidity imposed by the cyclic diacetylide ligand in 1 leads to a reduction in nonradiative decay, which enhances its room-temperature photophysical properties. By comparison, 3 radiates highly structured tda-localized triplet-state phosphorescence at room temperature. The 77 K emission spectrum of 1 in 4:1 EtOH/MeOH becomes structured and is quantitatively similar to that measured for 3 under the same conditions. Because the 77 K spectra are nearly identical, the emissions are assigned as (3)tda in nature, implying that the charge-transfer states are raised in energy, relative to the (3)tda levels in 1 in the low-temperature glass. Nanosecond transient absorption spectrometry and ultrafast difference spectra were determined for 1-3 in CH2Cl2 and DMF at ambient temperature. In 1 and 2, the major absorption transients are consistent with the one-electron reduced complexes, corroborated by reductive spectroelectrochemical measurements performed at room temperature. As 3 does not possess any charge-transfer character, excitation into the pi pi* transitions of the tda ligand generated transient absorptions in the relaxed excited state assigned to the ligand-localized triplet state. In all three cases, the excited-state lifetimes measured by transient absorption are similar to those measured by time-resolved photoluminescence, suggesting that the same excited states giving rise to the photoluminescence are responsible for the absorption transients. ESR spectroscopy of the anions 1(-) and 2(-) and reductive spectroelectrochemistry of 1 and 2 revealed a LUMO based largely on the pi* orbital of the dbbpy ligand. Time-dependent density functional theory calculations performed on 1-3 both in vacuum and in a CH2Cl2 continuum revealed the molecular orbitals, energies, dipole moments, and oscillator strengths for the various electronic transitions in these molecules. A Delta SCF-method-derived shift applied to the calculated transition energies in the solvent continuum yielded good agreement between theory and experiment for each molecule in this study