bluuebunny/crossref_metadata_2025 huggingface dataset:
Repeated Reading with Performance-Feedback to Improve Oral Reading Fluency in Saudi Arabian Students with Autism Spectrum Disorders
Authors: Naji Ahmed Al , Green Bridget M. , Mathieu-Sher Reva , McCallum Elizabeth
Published: August 2024

The prevalence of students with autism spectrum disorders (ASD) is increasing in the Kingdom of Saudi Arabia (KSA) and around the world. In school, students with ASD face academic challenges, specifically in reading. Targeted evidence-based practices (EBPs) are needed to support reading development for students with ASD. To date, limited research has examined the efficacy of EBPs on improving reading skills of learners with ASD, specifically in the area of oral reading fluency (ORF). This study examined the effectiveness of Repeated Reading (RR) coupled with a performance-feedback component for three students with ASD in Saudi Arabia using a single-subject, multiple-baseline across participants design. The results of this study demonstrated improved increased correct words per minute (CWPM) and decreased errors per minute for all students. Limitations and directions for future research are discussed.
Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations
Authors: Paulot F. , Jacob D. J. , Johnson M. T. , Bell T. G. , Baker A. R. , Keene W. C. , Lima I. D. , Doney S. C. , Stock C. A.
Published: July 2015

Current global inventories of ammonia emissions identify the ocean as the largest natural source. This source depends on seawater pH, temperature, and the concentration of total seawater ammonia (NHx(sw)), which reflects a balance between remineralization of organic matter, uptake by plankton, and nitrification. Here we compare [NHx(sw)] from two global ocean biogeochemical models (BEC and COBALT) against extensive ocean observations. Simulated [NHx(sw)] are generally biased high. Improved simulation can be achieved in COBALT by increasing the plankton affinity for NHx within observed ranges. The resulting global ocean emissions is 2.5 TgN a−1, much lower than current literature values (7–23 TgN a−1), including the widely used Global Emissions InitiAtive (GEIA) inventory (8 TgN a−1). Such a weak ocean source implies that continental sources contribute more than half of atmospheric NHx over most of the ocean in the Northern Hemisphere. Ammonia emitted from oceanic sources is insufficient to neutralize sulfate aerosol acidity, consistent with observations. There is evidence over the Equatorial Pacific for a missing source of atmospheric ammonia that could be due to photolysis of marine organic nitrogen at the ocean surface or in the atmosphere. Accommodating this possible missing source yields a global ocean emission of ammonia in the range 2–5 TgN a−1, comparable in magnitude to other natural sources from open fires and soils.
Changes in the relationship in the SST variability between the tropical Pacific and the North Pacific across the 1998/1999 regime shift
Authors: Jo Hyun‐Su , Yeh Sang‐Wook , Lee Sang‐Ki
Published: July 2015

This study shows that sea surface temperature (SST) variability in the central to eastern tropical Pacific has a strong negative correlation with that of the central to eastern North Pacific in the boreal winter after the 1998/1999 regime shift. This phenomenon is in contrast to before the 1998/1999 regime shift. The anomalous Aleutian low pressure associated with the tropical SST forcing became stronger, and its center shifted to the south and to the west after 1998/1999. Such a modulation caused the change in the North Pacific SST response. This also resulted in a close relationship between the tropical Pacific and North Pacific SST variability. The modulation of the Aleutian low pressure is primarily due to the westward shift in the location of the tropical convective heating around the dateline, which occurred during 1998/1999. The results of simple atmospheric model experiments support this hypothesis that the shift in the tropical convective heating to the west is responsible for the modulation of the Aleutian low pressure and the associated change in the relationship of the SST variability between the tropical Pacific and North Pacific. These results imply that the seasonal predictability of the North Pacific SST has increased since 1998/1999 due to its increased correlation with the tropical Pacific SST variability.
The effect of diamagnetic drift on motion of the dayside magnetopause reconnection line
Authors: Trenchi L. , Marcucci M. F. , Fear R. C.
Published: July 2015

Magnetic reconnection at the magnetopause occurs with a large density asymmetry and for a large range of magnetic shears. In these conditions, a motion of the X line has been predicted in the direction of the electron diamagnetic drift. When this motion is super Alfvenic, reconnection should be suppressed. We analysed a large data set of Double Star TC‐1 dayside magnetopause crossings, which includes reconnection and nonreconnection events. Moreover, it also includes several events during which TC‐1 is near the X line. With these close events, we verified the diamagnetic suppression condition with local observations near the X line. Moreover, with the same close events, we also studied the motion of the X line along the magnetopause. It is found that, when reconnection is not suppressed, the X line moves northward or southward according to the orientation of the guide field, which is related to the interplanetary magnetic field BY component, in agreement with the diamagnetic drift.
Time‐lapse imaging of a localized weak change with multiply scattered waves using numerical‐based sensitivity kernel
Authors: Kanu Chinaemerem , Snieder Roel
Published: July 2015

Multiply scattered seismic waves, due to their long path length within a finite volume, provide information that can be used to detect and image weak time‐lapse changes within a medium. Such weak changes are usually not resolved with singly scattered waves. Previous use of multiply scattered waves for time‐lapse monitoring assume statistical homogeneity of the scattering property of the scattering medium. This homogeneity is usually characterized by either a constant mean free path or a diffusion coefficient. In a realistic medium, however, this assumption of homogeneity likely breaks down. We demonstrate the capability of resolving a localized time‐lapse velocity change within a three‐layer 2‐D scattering model using multiply scattered waves. The layers within the model have different scattering properties. The imaging algorithm requires numerically generating the sensitivity kernel that correctly represents the statistical heterogeneity of the scattering model. We localize the weak velocity change, but the resolution of the imaged change degrades with increasing coda traveltime. A comparison of the imaged changes from the numerical kernel and the kernel that assumes statistical homogenous model suggests that the numerical kernel provides a stronger constraint on the shape of the imaged velocity change.
Pore pressure sensitivities to dynamic strains: Observations in active tectonic regions
Authors: Barbour Andrew J.
Published: July 2015

Triggered seismicity arising from dynamic stresses is often explained by the Mohr‐Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid‐saturated rock. The seismic response of a fluid‐rock system naturally depends on its hydromechanical properties, but accurately assessing how pore fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 to 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas Fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends nonlinearly on the inverse fault‐perpendicular distance, with the response decreasing toward the fault; the SJB cluster is at the northern transition from creeping‐to‐locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto Fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength of the pore pressure response in fluid‐saturated rock near active faults is controlled by shear strain accumulation associated with tectonic loading, which implies a strong feedback between fault strength and permeability: dynamic triggering susceptibilities may vary in space and also in time.
The eddy, wave, and interface structure of turbulent shear layers below/above stably stratified regions
Authors: Hunt Julian C. R. , Moustaoui Mohamed , Mahalov Alex
Published: July 2015

High resolution three‐dimensional simulations are presented of the interactions between turbulent shear flows moving with mean relative velocity ΔU below a stably stratified region with buoyancy frequency (N+). An artificial forcing in the simulation, with a similar effect as a small negative eddy viscosity, leads to a steady state flow which models thin interfaces. Characteristic eddies of the turbulence have length scale L. If the bulk Richardson number Rib=(LN+/ΔU)2 lies between lower and upper critical values denoted as Ri∗(<1/5) and
, a “detached” layer is formed in the stable region with thickness L+ greater than L, in which rotational fluctuations and inhomogeneous turbulence are induced above an interface with large gradients of density/temperature. Comparisons are made with shear turbulent interfaces with no stratification. When
, vertical propagating waves are generated, with shear stresses carrying significant momentum flux and progressively less as Rib increases. Simulations for a jet and a turbulent mixing layer show similar results. A perturbation analysis, using inhomogeneous Rapid Distortion Theory, models the transition zone between shear eddies below the interface and the fluctuations in the stratified region, consistent with the simulations. It demonstrates how the wave‐momentum‐flux has a maximum when Rib∼2 and then decreases as Rib increases. This coupling mechanism between eddies and waves, which is neglected in eddy viscosity models for shear layers, can drive flows in the stratosphere and the deeper ocean, with significant consequences for short‐ and long‐term flow phenomena. The “detached layer” is a mechanism that contributes to the formation of stratus clouds and polluted layers above the atmospheric boundary layer.
An analysis of long‐term relationships among count statistics and metrics of synthetic tropical cyclones downscaled from CMIP5 models
Authors: Reed Andra J. , Mann Michael E. , Emanuel Kerry A. , Titley David W.
Published: July 2015

In a changing climate, the impact of tropical cyclones on the United States Atlantic and Gulf Coasts will be affected both by how intense and how frequent these storms become. The observational record of tropical cyclones in the Atlantic Basin is too short (A.D. 1851 to present) to allow for accurate assessment of low‐frequency variability in storm activity. In order to overcome the limitations of the short observational record, we downscale four Coupled Model Intercomparison Project Phase 5 models to generate synthetic tropical cyclone data sets for the Atlantic Basin that span the interval of A.D. 850–2005. Using these long‐term synthetic tropical cyclone data sets, we investigate the relationship between power dissipation and ocean temperature metrics, as well as the relationship between basin‐wide and landfalling tropical cyclone count statistics over the past millennium. Contrary to previous studies, we find only a very weak relationship between power dissipation and main development region sea surface temperature in the Atlantic Basin. Consistent with previous studies, we find that basin‐wide and landfalling tropical cyclone counts are significantly correlated with one another, lending further support for the use of paleohurricane landfall records to infer long‐term basin‐wide tropical cyclone trends.
Assessing the accuracy of 1‐D analytical heat tracing for estimating near‐surface sediment thermal diffusivity and water flux under transient conditions
Authors: Rau Gabriel C. , Cuthbert Mark O. , McCallum Andrew M. , Halloran Landon J. S. , Andersen Martin S.
Published: July 2015

Amplitude decay and phase delay of oscillating temperature records measured at two vertical locations in near‐surface sediments can be used to infer water fluxes, thermal diffusivity, and sediment scour/deposition. While methods that rely on the harmonics‐based analytical heat transport solution assume a steady state water flux, many applications have reported transient fluxes but ignored the possible violation of this assumption in the method. Here we use natural heat tracing as an example to investigate the extent to which changes in the water flux, and associated temperature signal nonstationarity, can be separated from other influences. We systematically scrutinize the assumption of steady state flow in analytical heat tracing and test the capabilities of the method to detect the timing and magnitude of flux transients. A numerical model was used to synthesize the temperature response to different step and ramp changes in advective thermal velocity magnitude and direction for both a single‐frequency and multifrequency temperature boundary. Time‐variable temperature amplitude and phase information were extracted from the model output with different signal‐processing methods. We show that a worst‐case transient flux induces a temperature nonstationarity, the duration of which is less than 1 cycle for realistic sediment thermal diffusivities between 0.02 and 0.13 m2/d. However, common signal‐processing methods introduce erroneous temporal spreading of advective thermal velocities and significant anomalies in thermal diffusivities or sensor spacing, which is used as an analogue for streambed scour/deposition. The most time‐variant spectral filter can introduce errors of up to 57% in velocity and 33% in thermal diffusivity values with artifacts spanning ±2 days around the occurrence of rapid changes in flux. Further, our results show that analytical heat tracing is unable to accurately resolve highly time‐variant fluxes and thermal diffusivities and does not allow for the inference of scour/depositional processes due to the limitations of signal processing in disentangling flux‐related signal nonstationarities from those stemming from other sources. To prevent erroneous interpretations, hydrometric data should always be acquired in combination with temperature records.
Snow bedforms: A review, new data, and a formation model
Authors: Filhol Simon , Sturm Matthew
Published: July 2015

Snow bedforms, like sand bedforms, consist of various shapes that form under the action of wind on mobile particles. Throughout a year, they can cover up to 11% of the Earth surface, concentrated toward the poles. These forms impact the local surface energy balance and the distribution of precipitation. Only a few studies have concentrated on their genesis. Their size ranges from 2 cm (ripple marks) to 2.5 m tall (whaleback dunes). We counted a total of seven forms that are widely recognized. Among them sastrugi, an erosional shape, is the most widespread. From laser scans, we compared scaling of snow versus sand barchan morphology. We found that both have proportionally the same footprint, but snow barchans are flatter. The key difference is that snow can sinter, immobilizing the bedform and creating an erodible material. Using a model, we investigated the effect of sintering on snow dune dynamics. We found that sintering limits their size because it progressively hardens the snow and requires an ever‐increasing wind speed to maintain snow transport. From the literature and results from this model, we have reclassified snow bedforms based on two parameters: wind speed and snow surface conditions. The new data show that snow dune behavior mirrors that of sand dunes, with merging, calving, and collision. However, isolated snow barchans are rare, with most of the snow surfaces encountered in the field consisting of several superimposed bedforms formed sequentially during multiple weather events. Spatially variable snow properties and geometry can explain qualitatively these widespread compound snow surfaces.
Interactive effects of wildfire and climate on permafrost degradation in Alaskan lowland forests
Authors: Brown Dana R. N. , Jorgenson M. Torre , Douglas Thomas A. , Romanovsky Vladimir E. , Kielland Knut , Hiemstra Christopher , Euskirchen Eugenie S. , Ruess Roger W.
Published: July 2015

We examined the effects of fire disturbance on permafrost degradation and thaw settlement across a series of wildfires (from ~1930 to 2010) in the forested areas of collapse‐scar bog complexes in the Tanana Flats lowland of interior Alaska. Field measurements were combined with numerical modeling of soil thermal dynamics to assess the roles of fire severity and climate history in postfire permafrost dynamics. Field‐based calculations of potential thaw settlement following the loss of remaining ice‐rich permafrost averaged 0.6 m. This subsidence would cause the surface elevations of forests to drop on average 0.1 m below the surface water level of adjacent collapse‐scar features. Up to 0.5 m of thaw settlement was documented after recent fires, causing water impoundment and further thawing along forest margins. Substantial heterogeneity in soil properties (organic layer thickness, texture, moisture, and ice content) was attributed to differing site histories, which resulted in distinct soil thermal regimes by soil type. Model simulations showed increasing vulnerability of permafrost to deep thawing and thaw settlement with increased fire severity (i.e., reduced organic layer thickness). However, the thresholds of fire severity that triggered permafrost destabilization varied temporally in response to climate. Simulated permafrost dynamics underscore the importance of multiyear to multidecadal fluctuations in air temperature and snow depth in mediating the effects of fire on permafrost. Our results suggest that permafrost is becoming increasingly vulnerable to substantial thaw and collapse after moderate to high‐severity fire, and the ability of permafrost to recover is diminishing as the climate continues to warm.
Optical coherence tomography reflects brain atrophy in multiple sclerosis: A four‐year study
Authors: Saidha Shiv , Al‐Louzi Omar , Ratchford John N. , Bhargava Pavan , Oh Jiwon , Newsome Scott D. , Prince Jerry L. , Pham Dzung , Roy Snehashis , van Zijl Peter , Balcer Laura J. , Frohman Elliot M. , Reich Daniel S. , Crainiceanu Ciprian , Calabresi Peter A.
Published: July 2015

Objective

The aim of this work was to determine whether atrophy of specific retinal layers and brain substructures are associated over time, in order to further validate the utility of optical coherence tomography (OCT) as an indicator of neuronal tissue damage in patients with multiple sclerosis (MS).

Methods

Cirrus high‐definition OCT (including automated macular segmentation) was performed in 107 MS patients biannually (median follow‐up: 46 months). Three‐Tesla magnetic resonance imaging brain scans (including brain‐substructure volumetrics) were performed annually. Individual‐specific rates of change in retinal and brain measures (estimated with linear regression) were correlated, adjusting for age, sex, disease duration, and optic neuritis (ON) history.

Results

Rates of ganglion cell + inner plexiform layer (GCIP) and whole‐brain (r = 0.45; p < 0.001), gray matter (GM; r = 0.37; p < 0.001), white matter (WM; r = 0.28; p = 0.007), and thalamic (r = 0.38; p < 0.001) atrophy were associated. GCIP and whole‐brain (as well as GM and WM) atrophy rates were more strongly associated in progressive MS (r = 0.67; p < 0.001) than relapsing‐remitting MS (RRMS; r = 0.33; p = 0.007). However, correlation between rates of GCIP and whole‐brain (and additionally GM and WM) atrophy in RRMS increased incrementally with step‐wise refinement to exclude ON effects; excluding eyes and then patients (to account for a phenotype effect), the correlation increased to 0.45 and 0.60, respectively, consistent with effect modification. In RRMS, lesion accumulation rate was associated with GCIP (r = −0.30; p = 0.02) and inner nuclear layer (r = −0.25; p = 0.04) atrophy rates.

Interpretation

Over time GCIP atrophy appears to mirror whole‐brain, and particularly GM, atrophy, especially in progressive MS, thereby reflecting underlying disease progression. Our findings support OCT for clinical monitoring and as an outcome in investigative trials. Ann Neurol 2015;78:Ann Neurol 2015;78:679–696
Zum Charakter der chemischen Bindung von Argonatomen mit gemischten Gold/Silber‐Trimeren
Authors: Shayeghi Armin , Johnston Roy L. , Rayner David M. , Schäfer Rolf , Fielicke André
Published: July 2015

Die vorliegende Arbeit beschäftigt sich mit der kontrovers diskutierten Natur der chemischen Bindung von Edelmetallen mit Edelgasen. Experimentelle Untersuchungen verweisen auf besonders starke Au‐Ar‐Bindungen in Argon‐Komplexen gemischter Au/Ag‐Trimere. Infrarotspektren zeigen einen enormen Einfluss des Edelgases auf die Schwingungsmoden, insbesondere in Au‐reichen Trimeren, in denen die Ar‐Atome aufgrund einer relativistisch erhöhten Kovalenz der Au‐Ar‐Bindung stark involviert sind. In Ag‐reichen Trimeren dominieren die Schwingungsmoden des Metallgerüstes, was auf einen stärkeren elektrostatischen Charakter der Ag‐Ar‐Bindung hinweist. Die Experimente werden durch Dichtefunktionaltheorie‐Rechnungen gestützt, die zeigen, wie die relativistischen Unterschiede zwischen Au und Ag zu stärkeren Au‐Ar‐Bindungen führen. Durch die Möglichkeit, die Zusammensetzung und somit die Ladungsverteilung zu variieren, erweisen sich die Trimere als ideales Modellsystem, um die chemische Natur der Wechselwirkung von Edelgasen mit geschlossenschaligen Goldverbindungen zu studieren.
Copper(I)/Copper(II)‐Assisted Tandem Catalysis: The Case Study of Ullmann/Chan–Evans–Lam N1,N3‐Diarylation of 3‐Aminopyrazole
Authors: Beyer Astrid , Castanheiro Thomas , Busca Patricia , Prestat Guillaume
Published: July 2015

Unprecedented CuI/CuII‐assisted tandem catalysis allowing an Ullmann/Chan–Evans–Lam sequence was achieved. This three‐component, one‐pot reaction triggered by a change in the oxidation state of the metal leads to the selective N1,N3‐diarylation of 3‐aminopyrazole. This new method should be a valuable tool for small‐molecule drug discovery that requires suitable regio‐ and/or chemoselective strategies for the N‐arylation of nitrogen‐containing heterocycles.
Poisoning of Highly Porous Platinum Electrodes by Amino Acids and Tissue Fluid Constituents
Authors: Köhler Christian , Bleck Lena , Frei Maxi , Zengerle Roland , Kerzenmacher Sven
Published: July 2015

The first comprehensive study of the poisoning behavior of physiological amino acids and important tissue fluid constituents on porous platinum electrodes was performed. On the basis of chronoamperometry under physiological conditions, the results are highly relevant for the development of enzyme‐free implantable glucose fuel cells and possibly also glucose sensors. The strongest poisoning was exhibited by positively charged alkaline amino acids and by some of the neutral amino acids, as well as by uric acid and creatinine. In contrast to previous work, sulfur‐containing amino acids showed no poisoning effect. This was explained by the use of highly porous platinum electrodes in the current study and experimental methods that were more relevant for practical applications. Furthermore, comprehensive analysis regarding the degree of recovery in the absence of poisoning species and the extent of electrode regeneration by cyclic voltammetry was performed for each of the amino acids and physiological substances.
Rhodium‐Mediated Oxygenation of Nitriles with Dioxygen: Isolation of Rhodium Derivatives of Peroxyimidic Acids
Authors: Bittner Annemarie , Braun Thomas , Herrmann Roy , Mebs Stefan
Published: July 2015

Dioxygen is used as the oxygenation agent in the rhodium‐mediated conversion of nitriles into amides. The characterization of intermediate species and model compounds as well as isotope‐labeling studies provided an insight into the reaction mechanism. The conversions of rhodium hydroperoxido or methylperoxido complexes with nitriles into metallacyclic rhodium‐ κ2‐(N,O)‐peroxyimidate compounds represent essential key steps. The former are accessible from a rhodium(III) peroxido complex and the latter represent rhodium derivatives of Payne’s reagent (peroxyimidic acids).
Über Rosmarin und Rosmarinsäure
Authors: Gao Ying Ying , Siehl Hans‐Ullrich , Petzold Heike , Sicker Dieter , Zeller Klaus‐Peter , Berger Stefan
Published: July 2015

Rosmarinsäure, ein Labiatengerbstoff, kommt in Rosmarin aber auch in anderen Pflanzen wie Thymian, Buntnessel, Bohnenkraut, Salbei, Oregano oder Zitronenmelisse vor, aus der sie hier isoliert wurde. Sie ist als Ester der Kaffeesäure ein chiraler, aromatischer Naturstoff. Rosmarinsäure schmeckt bitter, was bei Rosmarin als Gewürz reizvoll sein kann. Wegen ihrer Brenzkatechin‐Substruktur ist sie ein Antioxidans. Anwendungen als Heilmittel sind aufgrund der vielfältigen physiologischen Wirkungen möglich und werden weiter untersucht. Die an der Buntnessel komplett aufgeklärte Biosynthese hat zu Versuchen geführt, Rosmarinsäure in pflanzlichen Zellkulturen biotechnologisch in hoher Ausbeute herzustellen. Die Darstellung einer spektroskopisch reinen Probe ist anspruchsvoll. Alle analytischen Spektren werden vollständig entweder im Hauptteil oder in der supporting information wiedergegeben und interpretiert.
Self‐Assembly of PEG‐Coated Ceria Nanoparticles Shows Dependence on PEG Molecular Weight and Ageing
Authors: Neal Craig J. , Das Soumen , Saraf Shashank , Tetard Laurene , Seal Sudipta
Published: July 2015

Cerium oxide (ceria) nanoparticles (CNPs) were synthesized in poly(ethylene glycol)s (PEGs) of different molecular weights (MWs; 300, 600, 1500, 3000, 4000, and 6000 Da) with water as a cosolvent, and changes in physicochemical properties, especially morphology and size, were monitored as a function of time. High‐resolution transmission electron microscopy (HRTEM) was performed for all solutions and revealed octahedral, star morphologies for CNPs coated with 1500 MW PEG. Raman and FTIR spectroscopy, HRTEM images, conductivity, and electrophoretic mobility imply the self‐assembly of small spherical particles to octahedral, star‐shaped particles by means of a fractal assembly method. Dynamic light scattering measures were used to create an empirical growth model of the observed octahedral self‐assembly. It was also determined that PEG polymer chain lengths and age‐dependent redox activities of CNPs limit or allow this assembly owing to molecular‐weight‐dependent physicochemical properties. This study highlights the significance of ageing on solution‐based nanoparticles and its implications in the use of nanoparticles over long periods of time. As PEG‐ylated nanoparticles have found extensive use in biomedical applications, we have tested the aged particles in vitro for toxicity.
Selective Oxidation of Sulfides Catalyzed by the Nanocluster Polyoxomolybdate (NH4)12[Mo36(NO)4O108(H2O)16]
Authors: Amini Mojtaba , Naslhajian Hadi , Farnia S. Morteza F. , Hołyńska Małgorzata
Published: July 2015

The (NH4)12[Mo36(NO)4O108(H2O)16]·30.84H2O ({Mo36}) catalyst has been synthesized and successfully employed in the selective oxidation of various sulfides to sulfoxides with urea hydrogen peroxide as oxidant under mild reaction conditions with 84–99 % conversion and 58–99 % selectivity, with active functional groups such as the hydroxy group and C=C bonds tolerated in the oxidation. The {Mo36} catalyst showed high catalytic activity for a high substrate/catalyst ratio (up to 30000:1) and is recyclable.
π‐Excess σ2P=C–N–Heterocycles: Catalytic P‐Arylation and Alkylation of N‐Alkyl‐1,3‐benzazaphospholes and Isolation of P,N‐Disubstituted Dihydrobenzaza­phosphole P‐Oxides
Authors: Niaz Basit , Aluri Bhaskar R. , Jones Peter G. , Heinicke Joachim W.
Published: July 2015

2‐Unsubstituted N‐alkyl‐1,3‐benzazaphospholes, diagonally P–C related to 2,3‐unsubstituted indoles, were successfully arylated by aryl iodides and bromides or alkylated by neopentyl iodide by heating in DMF in the presence of a catalytic amount of PdCl2 or H2PtCl6 and a suitable base. In contrast to the known 2‐arylations of indoles under these conditions, the reactions led to arylation in the 3‐position and proceeded via highly moisture‐sensitive intermediates to P‐substituted 1,3‐benzazaphosphole P‐oxides. Thus, we present a novel route for the direct P‐substitution of aromatic σ2P‐heterocycles with electrophilic aryl/alkyl halides. Characteristic NMR spectroscopic data of the intermediates are consistent with –P(aryl)–C(Br/Cl)–N– species formed by metal‐mediated addition of the aryl halides at the P=C bond rather than by oxidative addition to ylidic intermediates. Benzazaphospholium salts, accessible by using triethyloxonium tetrafluoroborate at room temperature and also very sensitive to hydrolysis, display distinct NMR spectroscopic data. The structures of the products were elucidated by conclusive NMR spectroscopy and HRMS data and crystal‐structure analysis. Minor amounts of a bis(arylation) product could likewise be identified by crystal‐structure analysis.
Mechanisms and Factors Controlling Photoisomerization Equilibria, Ligand Exchange, and Water Oxidation Catalysis Capabilities of Mononuclear Ruthen­ium(II) Complexes
Authors: Hirahara Masanari , Hakamata Tomoya , League Aaron B. , Ertem Mehmed Z. , Takahashi Kosuke , Nagai Sho , Inaba Keisuke , Yamazaki Hirosato , Saito Kenji , Yui Tatsuto , Cramer Christopher J. , Yagi Masayuki
Published: July 2015

The photoisomerization equilibrium between distal‐ and proximal‐[Ru(tpy)(pyqu)OH2]2+ [d‐ and p‐RuH2O, tpy = 2,2′;6′,2″‐terpyridine, pyqu = 2‐(2′‐pyridyl)quinoline] is characterized. The kinetic analysis of the pD‐dependent photoisomerization reactions (monitored by 1H NMR) of d‐RuH2O and p‐RuH2O shows (1) that both hydroxo isomers, distal‐ and proximal‐[Ru(tpy)(pyqu)OH]+, are inert to photoisomerization, and (2) that the back reaction (distal to proximal) is 3.0 times faster than the forward reaction (proximal to distal). Isolation of distal‐ and proximal‐[Ru(tpy)(pyqu)Cl]+ (d‐ and p‐RuCl) as well as d‐ and p‐RuH2O isomers enabled comprehensive studies on geometric structures, ligand exchange and redox reactions, and water oxidation catalysis for these isomers. The observed aquation rate constant (9.2 × 10–2 s–1 at 40 μM) of p‐RuCl to form p‐RuH2O is 1700 times higher than that (5.4 × 10–5 s–1 at 63 μM) of d‐RuCl at 298 K owing to the steric repulsion between a chloro ligand and the 8‐proton of the quinoline moiety. The turnover frequency (TOF = 1.7 × 10–3 s–1) of p‐RuH2O for catalytic water oxidation is 1.7 times greater than that (1.0 × 10–3 s–1) for d‐RuH2O, in contrast to the [Ru(tpy)(pynp)OH2]2+ isomer system, in which the TOF of the distal isomer is higher than that of the proximal one by one order of magnitude. The mechanisms and factors controlling the photoisomerization equilibria and water oxidation catalysis of the d‐ and p‐RuH2O isomers are discussed on the basis of experimental and theoretical investigations.
Tertiary Amine Promoted Asymmetric ­Aldol Reaction of Aldehydes
Authors: Gut Bartosz , Mlynarski Jacek
Published: July 2015

The direct asymmetric self‐aldol reactions of various α‐oxyaldehydes catalyzed by tertiary amines have been demonstrated. By using 10 mol‐% of quinine catalyst, dimerization products have been prepared in high yields, with good anti‐diastereocontrol, and up to 80 % ee. The presented enolate‐mediated synthesis of protected tetrose sugars has never been accomplished before by chiral tertiary amine organocatalysts.
A Non‐Aldol Preparation of Enantiopure Propionate‐Derived Motifs with the Assistance of Chiral Sulfoxides: Application to a Convergent Synthesis of the Lactone Core of Octalactins
Authors: Bauder Claude
Published: July 2015

Propionate‐derived fragments were prepared by a non‐aldol method using chiral sulfoxide chemistry. A methacrylate ester, assisted by a chiral sulfoxide as an auxiliary agent, was easily transformed into an optically pure allylic alcohol, which was then subjected to diastereoselective hydroboration with the bulky dialkylborane 9‐BBN. The diastereofacial selectivity was governed by a preferred spatial arrangement of a staggered conformation model, as suggested by Houk, taking into account of the various A(1,2) allylic strains. Thus, the the two adjacent stereocentres in the enantiopure allylic alcohol were installed with an anti configuration. As an application of this work, we have described an enantioselective synthesis of the unusual eight‐membered lactone ring of the octalactins. Two propionate‐derived fragments were coupled to give precursor 18, which was subjected to Yamaguchi's macrolactonisation to give the required lactone ring.
Undecorated Cu(OAc)2‐Catalyzed C(sp3)–C(sp3) Bond Formation through para‐Hydroxy Group Triggered Remote Benzylic C(sp3)–H Bond Functionalization
Authors: Huang Jian‐Gang , Guo Ying , Li Yu‐Dan , Liu Hong‐Wei , Liao Dao‐Hua , Ji Ya‐Fei
Published: July 2015

The undecorated Cu(OAc)2‐catalyzed para‐hydroxy group triggered oxidative coupling of 2,6‐disubstituted 4‐cresols with fluorinated β‐keto esters or malonates leading to benzylic C(sp3)–C(sp3) bond formation was investigated. This formal double C(sp3)–H coupling method features mild conditions, atom economy, ligand‐ and additive‐free catalysis, and ambient air as the terminal oxidant. This ecofriendly method allows rapid access to highly functionalized 3‐phenylpropanoate derivatives containing fluorinated quaternary carbon‐like centers. On the basis of active p‐benzoquinone methide intermediates, a plausible mechanism was proposed.
The role of starvation in biomass harvesting and lipid accumulation: Co‐culture of microalgae–bacteria in synthetic wastewater
Authors: Xu Yanjia , Wang Yao , Yang Yang , Zhou Dandan
Published: July 2015

In this study, the microalgae–bacterial culture, composed of Chlorella vulgaris and activated sludge, was cultivated under starvation condition by controlling synthetic wastewater concentrations. After 8‐day culturing, nutrients such as organic carbon, ammonium nitrogen and phosphate were basically removed. The dynamic formation phases of the microalgae–bacterial consortium were identified to microalgae adsorbed by sludge flocs, new bacteria adhesion on microalgae and bacteria uniformly distributed and attachment and detachment of biomass in balance. The consortiums had much better settle‐ability than pure microalgae, and this phenomenon was particularly obvious in starvation term. Lipid accumulation of microalgae was also critically influenced by starvation cultivation, lipid content and lipid productivity of bioreactor with 5% initial wastewater (IW) were 17.1% and 0.045 g (L day−1)−1. This study gave a new insight into formation processes of microalgae–bacterial consortium, and confirmed that starvation term was an effective strategy to enhance the consortium settle‐ability and lipid accumulation capability. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 103–109, 2016
Particulate flow at the mouth of the Soummam watershed (Algeria)
Authors: Allili‐Ailane Chafika , Laignel Benoît , Adjeroud Nawel , Bir Hassiba , Madani Khodir
Published: July 2015

In Algeria, the particulate flow in rivers is poorly quantified in the wadi due to the absence and the non‐standardization of the acquisition of measurement data. Most studies on particulate flows are quantified from time series of hydrometric stations. The present study is based on weekly sampling of water at the mouth of the Soummam watershed for the hydrological year 2011/2012. The sediment flux is analyzed from measurements of suspended solids (SS). The determination coefficients between the annual and seasonal “ liquid flow–solid flow‐” relationships vary from 75% to 82%, respectively. During this period, the watershed of 9125 km2 has provided a solid input estimated to 4.9 × 106 t yr−1, hence a specific flow of 538 t km−2 yr−1. In general, autumn floods were characterized by high concentrations of SS, which varies from 820 to 1275 mg L−1. The most important sediment transport volumes were observed during the period of December to February, this period is characterized by strong turbulence, due to extreme flows, favoring the largest volumes of solid transport. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 204–211, 2016
Effect of NaOH on delignification of Saccharum spontaneum
Authors: Ashgar Umar , Nadeem Muhammad , Irfan Muhammad , Syed Quratulain , Nelofer Rubina , Iram Mehvish
Published: July 2015

Saccharum spontaneum abundantly available in Pakistan has great potential for production of bioethanol due to high cellulosic contents. In the present study, S. spontaneum grass was impregnated in various concentrations of NaOH (0.5%–3% wt/vol) for different soaking periods (1 h, 2 h, 4 h, 6 h, 12 h, 24 h, and 48 h). The results showed that relative cellulose contents and delignification increased with the increase in concentration of alkali and soaking time. However, maximum cellulose content and delignification (52.5% and 47.6%) was observed with 2.5% wt/vol NaOH after 24 h of soaking period. In physiochemical pretreatment, the substrate was soaked in alkaline solution for 2 h followed by steaming at 121°C for various intervals (15–60 min). Maximum relative cellulose content (81.2%) was achieved after 60 min while delignification was found 74%. These findings indicated that proper concentration of alkali as well as steaming period at specific temperature play a major role in exposure of maximum cellulosic contents of S. spontaneum to exploit it as a potential substrate for bio‐fuel production. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 284–288, 2016
Modeling river dune development and dune transition to upper stage plane bed
Authors: Naqshband Suleyman , van Duin Olav , Ribberink Jan , Hulscher Suzanne
Published: July 2015

Large asymmetric bedforms known as dunes commonly dominate the bed of sand rivers. Due to the turbulence generation over their stoss and lee sides, dunes are of central importance in predicting hydraulic roughness and water levels. During floods in steep alluvial rivers, dunes are observed to grow rapidly as flow strength increases, undergoing an unstable transition regime, after which they are washed out in what is called upper stage plane bed. This transition of dunes to upper stage plane bed is associated with high transport of bed sediment in suspension and large decrease in bedform roughness. In the present study, we aim to improve the prediction of dune development and dune transition to upper stage plane bed by introducing the transport of suspended sediment in an existing dune evolution model. In addition, flume experiments are carried out to investigate dune development under bed load and suspended load dominated transport regimes, and to get insight in the time scales related to the transition of dunes to upper stage plane bed. Simulations with the extended model including the transport of suspended sediment show significant improvement in the prediction of equilibrium dune parameters (e.g. dune height, dune length, dune steepness, dune migration rate, dune lee side slope) both under bed load dominant and suspended load dominant transport regimes. The chosen modeling approach also allows us to model the transition of dunes to upper stage plane bed which was not possible with the original dune evolution model. The extended model predicts change in the dune shapes as was observed in the flume experiments with decreasing dune heights and dune lee slopes. Furthermore, the time scale of dune transition to upper stage plane bed was quite well predicted by the extended model. Copyright © 2015 John Wiley & Sons, Ltd.
The stingless bee species, Scaptotrigona aff. depilis, as a potential indicator of environmental pesticide contamination
Authors: de Souza Rosa Annelise , I'Anson Price Robbie , Ferreira Caliman Maria Juliana , Pereira Queiroz Elisa , Blochtein Betina , Sílvia Soares Pires Carmen , Imperatriz-Fonseca Vera Lucia
Published: July 2015

Neonicotinoids have the potential to enter the diet of pollinators that collect resources from contaminated plants. The species Scaptotrigona aff. depilis (Moure, 1942) can be a useful indicator of the prevalence of these chemicals in the environment. Using high-performance liquid chromatography–mass spectrometry, the authors devised a protocol for neonicotinoid residue extraction and detected the presence of neonicotinoids in the bee bodies. Thus, the authors consider this species to be a potential indicator of environmental contamination. Environ Toxicol Chem 2015;34:1851–1853. © 2015 SETAC
Biopesticide-induced behavioral and morphological alterations in the stingless bee Melipona quadrifasciata
Authors: Barbosa Wagner F. , Tomé Hudson Vaner V. , Bernardes Rodrigo C. , Siqueira Maria Augusta L. , Smagghe Guy , Guedes Raul Narciso C.
Published: July 2015

Because of their natural origin, biopesticides are assumed to be less harmful to beneficial insects, including bees, and therefore their use has been widely encouraged for crop protection. There is little evidence, however, to support this ingrained notion of biopesticide safety to pollinators. Because larval exposure is still largely unexplored in ecotoxicology and risk assessment on bees, an investigation was performed on the lethal and sublethal effects of a diet treated with 2 bioinsecticides, azadirachtin and spinosad, on the stingless bee, Melipona quadrifasciata, which is one of the most important pollinators in the Neotropics. Survival of stingless bee larvae was significantly compromised at doses above 210 ng a.i./bee for azadirachtin and 114 ng a.i./bee for spinosad. No sublethal effect was observed on larvae developmental time, but doses of both compounds negatively affected pupal body mass. Azadirachtin produced deformed pupae and adults as a result of its insect growth regulator properties, but spinosad was more harmful and produced greater numbers of deformed individuals. Only spinosad compromised walking activity of the adult workers at doses as low as 2.29 ng a.i./bee, which is 1/5000 of the maximum field recommended rate. In conclusion, the results demonstrated that bioinsecticides can pose significant risks to native pollinators with lethal and sublethal effects; future investigations are needed on the likelihood of such effects under field conditions. Environ Toxicol Chem 2015;34:2149–2158. © 2015 SETAC
Linking drugs of abuse in wastewater to contamination of surface and drinking water
Authors: Rodayan Angela , Afana Shadi , Segura Pedro A. , Sultana Tamanna , Metcalfe Chris D. , Yargeau Viviane
Published: July 2015

The concentrations of 17 drugs of abuse, including cocaine, several amphetamines, opioid drugs, and 2 metabolites—benzoylecgonine, a metabolite of cocaine, and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrolidine, a metabolite of methadone—were investigated in an urban watershed that is heavily impacted by discharges of municipal wastewater. The artificial sweetener sucralose was also monitored as a persistent tracer of contamination from municipal wastewater. Monitoring was conducted in a municipal wastewater treatment plant (WWTP) and at sites upstream and downstream of the WWTP discharge, as well as in a drinking water treatment plant (DWTP) located 19 km downstream of the WWTP discharge that withdraws raw water from the river. Drug concentrations were monitored with polar organic chemical integrative samplers deployed for 2 wk in the river and in the WWTP and DWTP. Several of the investigated compounds exhibited a decrease in concentration with distance downstream from the wastewater discharge into the river, but there was little attenuation of sucralose, cocaine, benzoylecgonine, morphine, acetylmorphine, acetylcodeine, and oxycodone. Heroin and methadone were not detected at any sample locations. Amphetamine, methamphetamine, 3,4-methylenedioxy-methamphetamine, and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrolidine were not detected in the samples collected at the drinking water intake. Many of the drugs of abuse were not removed effectively in the DWTP, including cocaine, benzoylecgonine, methylenedioxyamphetamine, ephedrine, and several prescription opioids, most probably because the DWTP was operating at or above its rated treatment capacity. These data indicate that there can be transport of drugs of abuse from wastewater sources into drinking water in urban watersheds. Environ Toxicol Chem 2016;35:843–849. © 2015 SETAC
Selenite supplementation reduces arsenate uptake greater than phosphate but compromises the phosphate level and physiological performance in hydroponically grown Oryza sativa L.
Authors: Kumar Navin , Dubey Arvind Kumar , Jaiswal Praveen Kumar , Sahu Nayan , Behera Soumit Kumar , Tripathi Rudra Deo , Mallick Shekhar
Published: July 2015

The present study evaluates the reduction of arsenate (As[V]) uptake in rice seedlings through individual and combined supplementation of phosphate (PO43–) and selenite (Se[IV]) in a hydroponic condition. The toxic response in seedlings receiving As(V) manifested as inhibition in physiological parameters such as water use efficiency, stomatal conductance, photosynthetic assimilation rate, transpiration rate, photochemical quenching, and electron transport rate, along with growth. Arsenic accumulation significantly decreased with Se(IV) treatment (0.5 μg mL−1, 1 μg mL−1, and 2 μg mL−1) in a dose-dependent manner (20%, 35%, and 53%, respectively); however, it compromised the PO43– level and physiological performance. The lower level of Se(IV), (0.5 μg mL−1), was relatively beneficial in terms of reduction in As accumulation than the higher level of Se(IV), (2 μg mL−1), which was rather toxic. Further, decrease in As uptake, replenished the level of PO43– and physiological performance in seedlings treated with As+Se+P compared with those treated with As+Se. However, supplementation with only PO43– (10 μg mL−1 and 20 μg mL−1) along with As(V) was less effective in reducing As accumulation compared with As+Se. Seedlings receiving As+Se+P also exhibited lower thiobarbituric acid–reactive substances (TBARS) and electrical conductivity levels compared with both As+Se and As+P. Among all the treatments, the activity of antioxidant enzymes was highest in plants treated with As+Se+P. Hence, the higher antioxidant enzyme activity in As+Se+P along with lower levels of TBARS, H2O2, and As accumulation are attributed to the competitive reduction in As uptake in the presence of Se(IV) and PO43–. Environ Toxicol Chem 2016;35:163–172. © 2015 SETAC