bluuebunny/crossref_metadata_2025 huggingface dataset:
Some new aspects of the transient ionization layer of comet Siding Spring origin in the Martian upper atmosphere
Authors: Venkateswara Rao N. , ManasaMohana P. , Jayaraman A. , Rao S. V. B.
Published: April 2016

The close encounter of comet Siding Spring with Mars resulted in the formation of a dense transient ionization layer in the Martian upper atmosphere at altitudes between 80 and 120 km. Instruments on three spacecraft orbiting Mars detected the presence of this layer, as reported in previous publications. In this study, we reanalyzed the ionograms of the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument on Mars Express to get further insight about the recurrence of the layer. For this purpose, data from three periapsis passes of MARSIS that took place 5 h, 12 h, and 19 h after peak dust deposition are used. We found that the transient ionization layer was sustained at least for 19 h on the nightside and 12 h on the dayside. While the peak density of the layer on the nightside gradually decreases from orbit to orbit, it does not change much on the dayside. Some ionograms in all three orbits show two transient ionization layers that are separated by ~60 km in apparent altitude. These double layers occur preferentially in regions of strong vertical magnetic fields. The bottom layer of the double structure is probably an oblique echo due to reflections from ionization bulges (formed in regions of vertical magnetic fields) at altitudes of the transient ionization layer. Horizontal bifurcation of the original layer is considered as another plausible mechanism for explaining the double‐layer structure.
Troposphere‐stratosphere dynamical coupling in the southern high latitudes and its linkage to the Amundsen Sea
Authors: England Mark R. , Shaw Tiffany A. , Polvani Lorenzo M.
Published: April 2016

Extremes in the distribution of Southern Hemisphere stratospheric heat flux are connected simultaneously to anomalous high‐latitude tropospheric weather patterns in reanalysis, consistent with results from the Northern Hemisphere. The dynamical links are revealed using a metric based on extreme stratospheric planetary‐scale wave heat flux events, defined as the 10th and 90th percentiles of the daily high‐latitude wave 1 heat flux distribution at 50 hPa. We show extreme negative (positive) heat flux events are linked to a westward (eastward) shift in the Amundsen Sea Low and anomalous warming (cooling) over the Amundsen Bellingshausen Seas in reanalysis data. Since coupling to the stratosphere via planetary waves has significant impacts on the tropospheric circulation of both hemispheres, it is important to understand which coupled climate models can reproduce this phenomenon. The heat flux metric is used to evaluate troposphere‐stratosphere coupling in models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and compare their performance across hemispheres. The results show that models with a degraded representation of stratospheric extremes exhibit robust biases in tropospheric sea level pressure variability over the Antarctic Peninsula. Models which fail to capture the extremes in stratospheric heat flux, significantly underestimate the variance of the distribution of mean sea level pressure anomalies over Western Antarctica.
A seismologically consistent expression for the total area and volume of earthquake‐triggered landsliding
Authors: Marc Odin , Hovius Niels , Meunier Patrick , Gorum Tolga , Uchida Taro
Published: April 2016

We present a new, seismologically consistent expression for the total area and volume of populations of earthquake‐triggered landslides. This model builds on a set of scaling relationships between key parameters, such as landslide spatial density, seismic ground acceleration, fault length, earthquake source depth, and seismic moment. To assess the model we have assembled and normalized a catalog of landslide inventories for 40 shallow, continental earthquakes. Low landscape steepness causes systematic overprediction of the total area and volume of landslides. When this effect is accounted for, the model predicts the total landslide volume of 63% of 40 cases to within a factor 2 of the volume estimated from observations (R2=0.76). The prediction of total landslide area is also sensitive to the landscape steepness, but less so than the total volume, and it appears to be sensitive to controls on the landslide size‐frequency distribution, and possibly the shaking duration. Some outliers are likely associated with exceptionally strong rock mass in the epicentral area, while others may be related to seismic source complexities ignored by the model. However, the close match between prediction and estimate for about two thirds of cases in our database suggests that rock mass strength is similar in many cases and that our simple seismic model is often adequate, despite the variety of lithologies and tectonic settings covered. This makes our expression suitable for integration into landscape evolution models and application to the anticipation or rapid assessment of secondary hazards associated with earthquakes.
The effect of temperature and moisture on trace gas emissions from deciduous and coniferous leaf litter
Authors: Gritsch Christine , Egger Florian , Zehetner Franz , Zechmeister‐Boltenstern Sophie
Published: April 2016

The forest litter layer lies at the boundary between soil and atmosphere and is a major factor in biogeochemical cycles. While there are several studies on how the litter layer controls soil trace gas emissions, litter emissions itself are less well understood, and it is still unclear how important gases respond to changing temperature and moisture. In order to assess leaf litter gas exchange, we conducted laboratory incubation experiments in which the full set of climate relevant gases, i.e., carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and nitric oxide (NO) coming from deciduous and coniferous leaf litter were measured at five temperatures and seven moisture contents. In addition, we compared litter and soil from different origin in terms of temperature/moisture responses of gas fluxes and investigated possible interactions between the two climate factors. Deciduous litter emitted more CO2 (up to 335 mg CO2‐C kg−1 h−1) than coniferous litter, whereas coniferous litter released maximum amounts of NO (207 µg NO‐N kg−1 h−1). N2O was only emitted from litter under very moist and warm conditions (>70% wet weight, >10°C). CH4 emissions were close to zero. Temperature sensitivities of litter emissions were generally lower than for soil emissions. Nevertheless, wet and warm conditions always enhanced litter emissions, suggesting a strong feedback effect of the litter layer to predicted future climate change.
Statistical analysis of turbulent super‐streamwise vortices based on observations of streaky structures near the free surface in the smooth open channel flow
Authors: Zhong Qiang , Chen Qigang , Wang Hao , Li Danxun , Wang Xingkui
Published: April 2016

Long streamwise‐elongated high‐ and low‐speed streaks are repeatedly observed near the free surface in open channel flows in natural rivers and lab experiments. Super‐streamwise vortex model has been proposed to explain this widespread phenomenon for quite some time. However, statistical evidence of the existence of the super‐streamwise vortices as one type of coherent structures is still insufficient. Correlation and proper orthogonal decomposition (POD) analysis based on PIV experimental data in the streamwise‐spanwise plane near the free surface in a smooth open channel flow are employed to investigate this topic. Correlation analysis revealed that the streaky structures appear frequently near the free surface and their occurrence probability at any spanwise position is equal. The spanwise velocity fluctuation usually flows from low‐speed streaks toward high‐speed streaks. The average spanwise width and spacing between neighboring low (or high) speed streaks are approximately h and 2h respectively. POD analysis reveals that there are streaks with different spanwise width in the instantaneous flow fields. Typical streamwise rotational movement can be sketched out directly based on the results from statistical analyses. Point‐by‐point analysis indicates that this pattern is consistent everywhere in the measurement window and is without any inhomogeneity in the spanwise direction, which reveals the essential difference between coherent structures and secondary flow cells. The pattern found by statistical analysis is consistent with the notion that the super‐streamwise vortices exist universally as one type of coherent structure in open channel flows.
The overlooked tropical oceanic CO2 sink
Authors: Ibánhez J. Severino P. , Araujo Moacyr , Lefèvre Nathalie
Published: April 2016

The intense rainfall in the tropical Atlantic spatially overlaps with the spread of the Amazon plume. Based on remote‐sensed sea surface salinity and rainfall, we removed the contribution of rainfall to the apparent Amazon plume area, thus refining the quantification of its extension (0.84 ± 0.06 × 106 km2 to 0.89 ± 0.06 × 106 km2). Despite the previous overestimation of the Amazon plume area due to the influence of rainfall (>16%), our calculated annual CO2 flux based on rainfall‐corrected sea surface CO2 fugacity confirms that the Amazon River plume is an atmospheric CO2 sink of global importance (−7.61 ± 1.01 to −7.85 ± 1.02 Tg C yr−1). Yet we show that current sea‐air CO2 flux assessments for the tropical Atlantic could be overestimated in about 10% by neglecting the CO2 sink associated to the Amazon plume. Thus, including the Amazon plume, the sea‐air CO2 exchange for the tropical Atlantic is estimated to be 81.1 ± 1.1 to 81.5 ± 1.1 Tg C yr−1.
The necessity of cloud feedback for a basin‐scale Atlantic Multidecadal Oscillation
Authors: Brown Patrick T. , Lozier M. Susan , Zhang Rong , Li Wenhong
Published: April 2016

The Atlantic Multidecadal Oscillation (AMO), characterized by basin‐scale multidecadal variability in North Atlantic sea surface temperatures (SSTs), has traditionally been interpreted as the surface signature of variability in oceanic heat convergence (OHC) associated with the Atlantic Meridional Overturning Circulation (AMOC). This view has been challenged by recent studies that show that AMOC variability is not simultaneously meridionally coherent over the North Atlantic and that AMOC‐induced low‐frequency variability of OHC is weak in the tropical North Atlantic. Here we present modeling evidence that the AMO‐related SST variability over the extratropical North Atlantic results directly from anomalous OHC associated with the AMOC but that the emergence of the coherent multidecadal SST variability over the tropical North Atlantic requires cloud feedback. Our study identifies atmospheric processes as a necessary component for the existence of a basin‐scale AMO, thus amending the canonical view that the AMOC‐AMO connection is solely attributable to oceanic processes.
Subseasonal changes observed in subglacial channel pressure, size, and sediment transport
Authors: Gimbert Florent , Tsai Victor C. , Amundson Jason M. , Bartholomaus Timothy C. , Walter Jacob I.
Published: April 2016

Water that pressurizes the base of glaciers and ice sheets enhances glacier velocities and modulates glacial erosion. Predicting ice flow and erosion therefore requires knowledge of subglacial channel evolution, which remains observationally limited. Here we demonstrate that detailed analysis of seismic ground motion caused by subglacial water flow at Mendenhall Glacier (Alaska) allows for continuous measurement of daily to subseasonal changes in basal water pressure gradient, channel size, and sediment transport. We observe intermittent subglacial water pressure gradient changes during the melt season, at odds with common assumptions of slowly varying, low‐pressure channels. These observations indicate that changes in channel size do not keep pace with changes in discharge. This behavior strongly affects glacier dynamics and subglacial channel erosion at Mendenhall Glacier, where episodic periods of high water pressure gradients enhance glacier surface velocity and channel sediment transport by up to 30% and 50%, respectively. We expect the application of this framework to future seismic observations acquired at glaciers worldwide to improve our understanding of subglacial processes.
Kinematically consistent models of viscoelastic stress evolution
Authors: DeVries Phoebe M. R. , Meade Brendan J.
Published: April 2016

Following large earthquakes, coseismic stresses at the base of the seismogenic zone may induce rapid viscoelastic deformation in the lower crust and upper mantle. As stresses diffuse away from the primary slip surface in these lower layers, the magnitudes of stress at distant locations (>1 fault length away) may slowly increase. This stress relaxation process has been used to explain delayed earthquake triggering sequences like the 1992 Mw = 7.3 Landers and 1999 Mw = 7.1 Hector Mine earthquakes in California. However, a conceptual difficulty associated with these models is that the magnitudes of stresses asymptote to constant values over long time scales. This effect introduces persistent perturbations to the total stress field over many earthquake cycles. Here we present a kinematically consistent viscoelastic stress transfer model where the total perturbation to the stress field at the end of the earthquake cycle is zero everywhere. With kinematically consistent models, hypotheses about the potential likelihood of viscoelastically triggered earthquakes may be based on the timing of stress maxima, rather than on any arbitrary or empirically constrained stress thresholds. Based on these models, we infer that earthquakes triggered by viscoelastic earthquake cycle effects may be most likely to occur during the first 50% of the earthquake cycle regardless of the assumed long‐term and transient viscosities.
Reduced spatial extent of extreme storms at higher temperatures
Authors: Wasko Conrad , Sharma Ashish , Westra Seth
Published: April 2016

Extreme precipitation intensity is expected to increase in proportion to the water‐holding capacity of the atmosphere. However, increases beyond this expectation have been observed, implying that changes in storm dynamics may be occurring alongside changes in moisture availability. Such changes imply shifts in the spatial organization of storms, and we test this by analyzing present‐day sensitivities between storm spatial organization and near‐surface atmospheric temperature. We show that both the total precipitation depth and the peak precipitation intensity increases with temperature, while the storm's spatial extent decreases. This suggests that storm cells intensify at warmer temperatures, with a greater total amount of moisture in the storm, as well as a redistribution of moisture toward the storm center. The results have significant implications for the severity of flooding, as precipitation may become both more intense and spatially concentrated in a warming climate.
Toward an integrated view of ionospheric plasma instabilities: Altitudinal transitions and strong gradient case
Authors: Makarevich Roman A.
Published: April 2016

A general dispersion relation is derived that integrates the Farley‐Buneman, gradient‐drift, and current‐convective plasma instabilities (FBI, GDI, and CCI) within the same formalism for an arbitrary altitude, wave propagation vector, and background density gradient. The limiting cases of the FBI/GDI in the E region for nearly field‐aligned irregularities, GDI/CCI in the main F region at long wavelengths, and GDI at high altitudes are successfully recovered using analytic analysis. Numerical solutions are found for more general representative cases spanning the entire ionosphere. It is demonstrated that the results are consistent with those obtained using a general FBI/GDI/CCI theory developed previously at and near E region altitudes under most conditions. The most significant differences are obtained for strong gradients (scale lengths of 100 m) at high altitudes such as those that may occur during highly structured soft particle precipitation events. It is shown that the strong gradient case is dominated by inertial effects and, for some scales, surprisingly strong additional damping due to higher‐order gradient terms. The growth rate behavior is examined with a particular focus on the range of wave propagations with positive growth (instability cone) and its transitions between altitudinal regions. It is shown that these transitions are largely controlled by the plasma density gradients even when FBI is operational.
Response time of mean square slope to wind forcing: An empirical investigation
Authors: Chen David D. , Ruf Christopher S. , Gleason Scott T.
Published: April 2016

We present an empirical study of the response time of surface wave mean square slope to local wind forcing using data collected over 11 years by 46 discus buoys moored at a wide variety of locations. The response time is defined as the time lag at which the time dependence of the waves exhibits the highest correlation with that of the local wind speed. The response time at each location is found to be fairly stable, with the time varying between 0.4 and 1.8 h depending on the location. Examination of long‐term statistics reveals response time dependencies on wind speed magnitude, fetch, atmospheric stability, and wavelength. With the increasing reliance on satellite microwave remote sensing as a source of wind data, these results provide useful insights and bounds for their use.
Gregarious convection and radiative feedbacks in idealized worlds
Authors: Mapes B. E.
Published: April 2016

What role does convection play in cloud feedbacks? What role does convective aggregation play in climate? A flurry of recent studies explores “self‐aggregation” of moist convection in diverse simulations using explicit convection and interactive radiation. The implications involve upper level dry areas acting as infrared windows—the climate system's “radiator fins.” A positive feedback maintains these: dry columns undergo radiative cooling which drives descent and further drying. If the resulting clumpiness of vapor and cloud fields depends systematically on global temperature, then convective organization could be a climate system feedback. How reconcilable and how relevant are these interesting but idealized studies?
FGT‐1‐mediated glucose uptake is defective in insulin/IGF‐like signaling mutants in Caenorhabditis elegans
Authors: Kitaoka Shun , Morielli Anthony D. , Zhao Feng‐Qi
Published: April 2016

Insulin signaling plays a central role in the regulation of facilitative glucose transporters (GLUTs) in humans. To establish Caenorhabditis elegans (C. elegans) as a model to study the mechanism underlying insulin regulation of GLUT, we identified that FGT‐1 is most likely the only functional GLUT homolog in C. elegans and is ubiquitously expressed. The FGT‐1‐mediated glucose uptake was almost completely defective in insulin/IGF‐like signaling (IIS) mutants daf‐2 and age‐1, and this defect mainly resulted from the down‐regulated FGT‐1 protein expression. However, glycosylation may also be involved because OGA‐1, an O‐GlcNAcase, was essential for the function of FGT‐1. Thus, our study showed that C. elegans can be a new powerful model system to study insulin regulation of GLUT.
Transparent InP Quantum Dot Light‐Emitting Diodes with ZrO2 Electron Transport Layer and Indium Zinc Oxide Top Electrode
Authors: Kim Hee Yeon , Park Yu Jin , Kim Jiwan , Han Chul Jong , Lee Jeongno , Kim Yohan , Greco Tonino , Ippen Christian , Wedel Armin , Ju Byeong‐Kwon , Oh Min Suk
Published: April 2016

Because of outstanding optical properties and non‐vacuum solution processability of colloidal quantum dot (QD) semiconductors, many researchers have developed various light emitting diodes (LEDs) using QD materials. Until now, the Cd‐based QD‐LEDs have shown excellent properties, but the eco‐friendly QD semiconductors have attracted many attentions due to the environmental regulation. And, since there are many issues about the reliability of conventional QD‐LEDs with organic charge transport layers, a stable charge transport layer in various conditions must be developed for this reason. This study proposes the organic/inorganic hybrid QD‐LEDs with Cd‐free InP QDs as light emitting layer and inorganic ZrO2 nanoparticles as electron transport layer. The QD‐LED with bottom emission structure shows the luminescence of 530 cd m−2 and the current efficiency of 1 cd/A. To realize the transparent QD‐LED display, the two‐step sputtering process of indium zinc oxide (IZO) top electrode is applied to the devices and this study could fabricate the transparent QD‐LED device with the transmittance of more than 74% for whole device array. And when the IZO top electrode with high work‐function is applied to top transparent anode, the device could maintain the current efficiency within the driving voltage range without well‐known roll‐off phenomenon in QD‐LED devices.
Atom Probe Tomography on Semiconductor Devices
Authors: Khan Mansoor Ali , Ringer Simon P. , Zheng Rongkun
Published: April 2016

In this paper, state‐of‐the‐art Atom Probe Tomography (APT) on industrial semiconductor products is reviewed to explore their device physics and to develop an understanding of atomic‐scale interfaces in them. Different semiconductor devices, such as Light Emitting Diodes (LEDs), High‐Electron‐Mobility Transistors (HEMTs), Field‐Effect Transistors (FETs), Metal‐Oxide‐Semiconductor Field‐Effect Transistors (MOSFETs), Static or Dynamic Random Access Memory (SRAM or DRAM) and solar cells, have been reviewed in light of their surface morphologies, chemical compositions, dopant distributions, grain boundaries and interface characteristics. The APT approach allows for the further optimization of device techniques, which are suggested for better performance.
Ferroelectric Polarization Switching Dynamics and Domain Growth of Triglycine Sulfate and Imidazolium Perchlorate
Authors: Ma He , Gao Wenxiu , Wang Junling , Wu Tom , Yuan Guoliang , Liu Junming , Liu Zhiguo
Published: April 2016

The weak bond energy and large anisotropic domain wall energy induce many special characteristics of the domain nucleation, growth, and polarization switch in triglycine sulfate (TGS) and imidazolium perchlorate (IM), two typical molecular ferroelectrics. Their domain nucleation and polarization switch are rather slower than those of conventional oxide ferroelectrics, which may be due to the weaker bond energy of hydrogen bond or van der Waals bond than that of ionic bond. These chemical bonds dominate the elastic energy, with the latter being an important component of domain wall energy and playing an important role in domain nucleation and domain growth. The ratio of anisotropic domain wall energy to Gibbs free energy is large in TGS and IM, which allows a favorable domain shape and a special domain evolution under a certain electric field. Therefore, this study not only sheds light on the physical nature but also indicates the application direction for molecular ferroelectrics.
Al‐Doped ZnO Transistors Processed from Solution at 120 °C
Authors: Lin Yen‐Hung , Thomas Stuart R. , Faber Hendrik , Li Ruipeng , McLachlan Martyn A. , Patsalas Panos A. , Anthopoulos Thomas D.
Published: April 2016

A simple Al‐doping method that is used to significantly enhance the operating characteristics of ZnO thin‐film transistors processed from solution at temperatures down to 120 °C is reported. The two‐step doping process relies on the dissolution of zinc oxide hydrate in ammonia hydroxide to form an aqueous Zn‐ammine complex solution and the subsequent immersion of Al pellets into it at room temperature. The pellets are then removed, and the doped precursor solution is spin‐coated onto the substrate followed by thermal annealing in air to form the n‐doped ZnO:Al layers. By controlling the immersion time of the Al pellets in the precursor solution, the free electron concentration in ZnO can be tuned. The resulting ZnO:Al layers are shown to be polycrystalline with tuneable electrical properties. ZnO:Al‐based transistors processed at 180 °C exhibit enhanced electron mobility when compared to intrinsic ZnO devices with the maximum values exceeding 5 cm2 V−1 s−1. Even when the process temperature is reduced to 120 °C, the ZnO:Al transistors retain their excellent operating characteristics with a maximum electron mobility of 3 cm2 V−1 s−1. This is amongst the highest values reported to date for soluton‐deposited ZnO transistors processed at 120 °C in air.
Remarkably High Conversion Efficiency of Inverted Bulk Heterojunction Solar Cells: From Ultrafast Laser Spectroscopy and Electron Microscopy to Device Fabrication and Optimization
Authors: Alsulami Qana A. , Murali Banavoth , Alsinan Yara , Parida Manas R. , Aly Shawkat M. , Mohammed Omar F.
Published: April 2016

In organic donor–acceptor systems, ultrafast interfacial charge transfer (CT), charge separation (CS), and charge recombination (CR) are key determinants of the overall performance of photovoltaic devices. However, a profound understanding of these photophysical processes at device interfaces remains superficial, creating a major bottleneck that circumvents advancements and the optimization of these solar cells. Here, results from time‐resolved laser spectroscopy and high‐resolution electron microscopy are examined to provide the fundamental information necessary to fabricate and optimize organic solar cell devices. In real time, CT and CS are monitored at the interface between three fullerene acceptors (FAs) (PC71BM, PC61BM, and IC60BA) and the PTB7‐Th donor polymer. Femtosecond transient absorption (fs‐TA) data demonstrates that photoinduced electron transfer from the PTB7‐Th polymer to each FA occurs on the sub‐picosecond time scale, leading to the formation of long‐lived radical ions. It is also found that the power conversion efficiency improves from 2% in IC60BA‐based solar cells to >9% in PC71BM‐based devices, in support of our time‐resolved results. The insights reported in this manuscript provide a clear understanding of the key variables involved at the device interface, paving the way for the exploitation of efficient CS and subsequently improving the photoconversion efficiency.
Healthcare utilization in chromosome 22q11.2 deletion patients with cardiac disease and low T cell counts
Authors: Sullivan Kathleen E. , Burrows Evanette , McDonald McGinn Donna M.
Published: April 2016

Chromosome 22q11.2 deletion manifests a highly variable phenotype. Healthcare institutions are often not optimally designed for children with multispecialty needs and a siloed approach may make it hard to understand the full healthcare utilization by these patients. This study was undertaken to understand the healthcare utilization by these patients. Records on 932 patients from a single institution were examined, anchoring on diagnosis codes and extracting costs and types of visits. Healthcare costs were high for patients and increased costs were associated with low T cells and the presence of a cardiac anomaly. The lifetime costs per individual ranged from negligible to over 20 million dollars. The greater healthcare utilization crossed nearly all types of visits. Healthcare costs are one metric of the great burden complex medical care places on patients and families. Identification of two high utilization subgroups will help to optimize care for these patients. © 2016 Wiley Periodicals, Inc.
Safety and efficacy of rivastigmine in children with Down syndrome: A double blind placebo controlled trial
Authors: Spiridigliozzi Gail A. , Hart Sarah J. , Heller James H. , Schneider Heather E. , Baker Jane Ann , Weadon Cathleen , Capone George T. , Kishnani Priya S.
Published: April 2016

Individuals with Down syndrome (DS) have decreased cholinergic function and an uneven profile of cognitive abilities, with more pronounced deficits in learning, memory, and expressive language. Cholinesterase inhibitors may improve cognitive function in adults and adolescents with DS, but studies in children with DS have been limited. This study aimed to: (i) investigate the safety and efficacy of rivastigmine treatment; (ii) build upon our open‐label studies in children with DS in a double‐blind, placebo‐controlled clinical trial; and (iii) investigate specific cognitive domains that may respond to rivastigmine treatment. We conducted a 20‐week double‐blind, placebo‐controlled trial to investigate the safety and efficacy of rivastigmine in 22 children and adolescents with DS aged 10–17 years. Safety measures included reports of adverse events, laboratory parameters, and electrocardiograms. Efficacy measures included parental assessments of adaptive behavior and executive function, and direct measures of language and memory. No group differences were found on safety measures and 22 of 24 participants that passed study screening completed the study. The results did not demonstrate evidence for significant improvement in aspects of cognition, language, or overall function in the children receiving rivastigmine. Our results suggest that rivastigmine is safe and well‐tolerated for children and adolescents with DS, but may not be effective for improving performance on the selected measures in this study. However, larger samples and/or alternate measures could possibly reveal improvements in cognitive function with rivastigmine treatment. Further research is needed to define a battery of cognitive measures that is sensitive to treatment effects in DS. © 2016 Wiley Periodicals, Inc.
Mobility during the neolithic and bronze age in northern ireland explored using strontium isotope analysis of cremated human bone
Authors: Snoeck Christophe , Pouncett John , Ramsey Greer , Meighan Ian G. , Mattielli Nadine , Goderis Steven , Lee‐Thorp Julia A. , Schulting Rick J.
Published: April 2016

Objectives

As many individuals were cremated in Neolithic and Bronze Age Ireland, they have not featured in investigations of individual mobility using strontium isotope analysis. Here, we build on recent experiments demonstrating excellent preservation of biogenic 87Sr/86Sr in calcined bone to explore mobility in prehistoric Northern Ireland.

Materials and Methods

A novel method of strontium isotope analysis is applied to calcined bone alongside measurements on tooth enamel to human remains from five Neolithic and Bronze Age sites in Northern Ireland. We systematically sampled modern vegetation around each site to characterize biologically available strontium, and from this calculated expected values for humans consuming foods taken from within 1, 5, 10 and 20 Km catchments. This provides a more nuanced way of assessing human use of the landscape and mobility than the ‘local’ vs. ‘non‐local’ dichotomy that is often employed.

Results

The results of this study 1) provide further support for the reliability of strontium isotope analysis on calcined bone, and 2) demonstrate that it is possible to identify isotopic differences between individuals buried at the same site, with some consuming food grown locally (within 1‐5 Km) while others clearly consumed food from up to 50 Km away from their burial place.

Discussion

Hints of patterning emerge in spite of small sample numbers. At Ballynahatty, for instance, those represented by unburnt remains appear to have consumed food growing locally, while those represented by cremated remains did not. Furthermore, it appears that some individuals from Ballynahatty, Annaghmare and Clontygora either moved in the last few years of their life or their cremated remains were brought to the site. These results offer new insights into the choice behind coterminous cremation and inhumation rites in the Neolithic. Am J Phys Anthropol 160:397–413, 2016. © 2016 Wiley Periodicals, Inc.
Photoelectrochemical H2 Evolution with a Hydrogenase Immobilized on a TiO2‐Protected Silicon Electrode
Authors: Lee Chong‐Yong , Park Hyun S. , Fontecilla‐Camps Juan C. , Reisner Erwin
Published: April 2016

The combination of enzymes with semiconductors enables the photoelectrochemical characterization of electron‐transfer processes at highly active and well‐defined catalytic sites on a light‐harvesting electrode surface. Herein, we report the integration of a hydrogenase on a TiO2‐coated p‐Si photocathode for the photo‐reduction of protons to H2. The immobilized hydrogenase exhibits activity on Si attributable to a bifunctional TiO2 layer, which protects the Si electrode from oxidation and acts as a biocompatible support layer for the productive adsorption of the enzyme. The p‐Si|TiO2|hydrogenase photocathode displays visible‐light driven production of H2 at an energy‐storing, positive electrochemical potential and an essentially quantitative faradaic efficiency. We have thus established a widely applicable platform to wire redox enzymes in an active configuration on a p‐type semiconductor photocathode through the engineering of the enzyme–materials interface.
The Benzyl Moiety in a Quinoxaline‐Based Scaffold Acts as a DNA Intercalation Switch
Authors: Mahata Tridib , Kanungo Ajay , Ganguly Sudakshina , Modugula Eswar Kalyan , Choudhury Susobhan , Pal Samir Kumar , Basu Gautam , Dutta Sanjay
Published: April 2016

Quinoxaline antibiotics intercalate dsDNA and exhibit antitumor properties. However, they are difficult to synthesize and their structural complexity impedes a clear mechanistic understanding of DNA binding. Therefore design and synthesis of minimal‐intercalators, using only part of the antibiotic scaffold so as to retain the key DNA‐binding property, is extremely important. Reported is a unique example of a monomeric quinoxaline derivative of a 6‐nitroquinoxaline‐2,3‐diamine scaffold which binds dsDNA by two different modes. While benzyl derivatives bound DNA in a sequential fashion, with intercalation as the second event, nonbenzyl derivatives showed only the first binding event. The benzyl intercalation switch provides important insights about molecular architecture which control specific DNA binding modes and would be useful in designing functionally important monomeric quinoxaline DNA binders and benchmarking molecular simulations.
Homolytic Cleavage of a B−B Bond by the Cooperative Catalysis of Two Lewis Bases: Computational Design and Experimental Verification
Authors: Wang Guoqiang , Zhang Honglin , Zhao Jiyang , Li Wei , Cao Jia , Zhu Chengjian , Li Shuhua
Published: April 2016

Density functional theory (DFT) investigations revealed that 4‐cyanopyridine was capable of homolytically cleaving the B−B σ bond of diborane via the cooperative coordination to the two boron atoms of the diborane to generate pyridine boryl radicals. Our experimental verification provides supportive evidence for this new B−B activation mode. With this novel activation strategy, we have experimentally realized the catalytic reduction of azo‐compounds to hydrazine derivatives, deoxygenation of sulfoxides to sulfides, and reduction of quinones with B2(pin)2 at mild conditions.
Hierarchical NiCo2O4 Hollow Microcuboids as Bifunctional Electrocatalysts for Overall Water‐Splitting
Authors: Gao Xuehui , Zhang Hongxiu , Li Quanguo , Yu Xuegong , Hong Zhanglian , Zhang Xingwang , Liang Chengdu , Lin Zhan
Published: April 2016

Bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte may improve the efficiency of overall water splitting. Nickel cobaltite (NiCo2O4) has been considered a promising electrode material for the OER. However, NiCo2O4 that can be used as an electrocatalyst in HER has not been studied yet. Herein, we report self‐assembled hierarchical NiCo2O4 hollow microcuboids for overall water splitting including both the HER and OER reactions. The NiCo2O4 electrode shows excellent activity toward overall water splitting, with 10 mA cm−2 water‐splitting current reached by applying just 1.65 V and 20 mA cm−2 by applying just 1.74 V across the two electrodes. The synthesis of NiCo2O4 microflowers confirms the importance of structural features for high‐performance overall water splitting.
Enzyme Shielding in an Enzyme‐thin and Soft Organosilica Layer
Authors: Correro M. Rita , Moridi Negar , Schützinger Hansjörg , Sykora Sabine , Ammann Erik M. , Peters E. Henrik , Dudal Yves , Corvini Philippe F.‐X. , Shahgaldian Patrick
Published: April 2016

The fragile nature of most enzymes is a major hindrance to their use in industrial processes. Herein, we describe a synthetic chemical strategy to produce hybrid organic/inorganic nanobiocatalysts; it exploits the self‐assembly of silane building blocks at the surface of enzymes to grow an organosilica layer, of controlled thickness, that fully shields the enzyme. Remarkably, the enzyme triggers a rearrangement of this organosilica layer into a significantly soft structure. We demonstrate that this change in stiffness correlates with the biocatalytic turnover rate, and that the organosilica layer shields the enzyme in a soft environment with a markedly enhanced resistance to denaturing stresses.
N‐Heterocyclic Carbenes as Promotors for the Rearrangement of Phosphaketenes to Phosphaheteroallenes: A Case Study for OCP to OPC Constitutional Isomerism
Authors: Li Zhongshu , Chen Xiaodan , Benkő Zoltán , Liu Liu Leo , Ruiz David A. , Peltier Jesse L. , Bertrand Guy , Su Chen‐Yong , Grützmacher Hansjörg
Published: April 2016

The concept of isomerism is essential to chemistry and allows defining molecules with an identical composition but different connectivity (bonds) between their atoms (constitutional isomers) and/or a different arrangement in space (stereoisomers). The reaction of phosphanyl ketenes, (NHP)−P=C=O (NHP=N‐heterocyclic phosphenium) with N‐heterocyclic carbenes (NHCs) leads to phosphaheteroallenes (NHP)−O−P=C=NHC in which the PCO unit has been isomerized to OPC. Based on the isolation of several intermediates and DFT calculations, a mechanism for this fundamental isomerisation process is proposed.
Allosterische optische Steuerung eines Klasse‐B‐G‐Protein‐gekoppelten Rezeptors
Authors: Broichhagen Johannes , Johnston Natalie R. , von Ohlen Yorrick , Meyer‐Berg Helena , Jones Ben J. , Bloom Stephen R. , Rutter Guy A. , Trauner Dirk , Hodson David J.
Published: April 2016

Die allosterische Regulation von G‐Protein‐gekoppelten Rezeptoren (GPCRs) erhöht deren Arzneimittelspezifität und ermöglicht so neue therapeutische Ansätze. Dennoch ist die heutige Wirkstoffentwicklung gehemmt, da die allosterische Bindestelle nur unzureichend präzise kontrollierbar ist. Hier beschreiben wir Design, Synthese und Anwendung von PhotoETP, einem lichtabhängigen positiven allosterischen Regulator des Klasse‐B‐GPCR GLP‐1R (“glucagon‐like peptide‐1 receptor”), der an der Aufrechterhaltung der Glukose‐Homöostase beteiligt ist. PhotoETP ermöglicht die von GLP‐1 und dessen Metaboliten abhängige Potenzierung von Ca2+‐, cAMP‐ und Insulin‐Antworten nach Bestrahlung von Zellen und Pankreasgewebe mit blauem Licht. PhotoETP bietet somit eine Vorlage für die Entwicklung von niedermolekularen allosterischen Photoschaltern für Klasse‐B‐GPCRs, und es könnte nützlich dabei sein, die positive Kooperativität des GLP‐1R zu verstehen.
Computer‐Assisted Synthetic Planning: The End of the Beginning
Authors: Szymkuć Sara , Gajewska Ewa P. , Klucznik Tomasz , Molga Karol , Dittwald Piotr , Startek Michał , Bajczyk Michał , Grzybowski Bartosz A.
Published: April 2016

Exactly half a century has passed since the launch of the first documented research project (1965 Dendral) on computer‐assisted organic synthesis. Many more programs were created in the 1970s and 1980s but the enthusiasm of these pioneering days had largely dissipated by the 2000s, and the challenge of teaching the computer how to plan organic syntheses earned itself the reputation of a “mission impossible”. This is quite curious given that, in the meantime, computers have “learned” many other skills that had been considered exclusive domains of human intellect and creativity—for example, machines can nowadays play chess better than human world champions and they can compose classical music pleasant to the human ear. Although there have been no similar feats in organic synthesis, this Review argues that to concede defeat would be premature. Indeed, bringing together the combination of modern computational power and algorithms from graph/network theory, chemical rules (with full stereo‐ and regiochemistry) coded in appropriate formats, and the elements of quantum mechanics, the machine can finally be “taught” how to plan syntheses of non‐trivial organic molecules in a matter of seconds to minutes. The Review begins with an overview of some basic theoretical concepts essential for the big‐data analysis of chemical syntheses. It progresses to the problem of optimizing pathways involving known reactions. It culminates with discussion of algorithms that allow for a completely de novo and fully automated design of syntheses leading to relatively complex targets, including those that have not been made before. Of course, there are still things to be improved, but computers are finally becoming relevant and helpful to the practice of organic‐synthetic planning. Paraphrasing Churchill's famous words after the Allies’ first major victory over the Axis forces in Africa, it is not the end, it is not even the beginning of the end, but it is the end of the beginning for the computer‐assisted synthesis planning. The machine is here to stay.
Modular Bidentate Hybrid NHC‐Thioether Ligands for the Stabilization of Palladium Nanoparticles in Various Solvents
Authors: Rühling Andreas , Schaepe Kira , Rakers Lena , Vonhören Benjamin , Tegeder Patricia , Ravoo Bart Jan , Glorius Frank
Published: April 2016

The synthesis of four different bidentate hybrid NHC‐thioether ligands is presented. The corresponding palladium nanoparticles are stable in various solvents, depending on the ligand used, and show high chemoselectivity in the hydrogenation of olefins. The solubility of the nanoparticles can be switched multiple times depending on the pH value of the solvent. XPS analysis (which shows a subtle shift in the binding energy) was identified as a convenient tool to establish the binding mode of NHC ligands.
Specific Enzymatic Halogenation—From the Discovery of Halogenated Enzymes to Their Applications In Vitro and In Vivo
Authors: Weichold Veit , Milbredt Daniela , van Pée Karl‐Heinz
Published: April 2016

During the last 20 years, focus has shifted from haloperoxidases to flavin‐dependent and non‐heme‐iron halogenases because of their proven involvement in the biosynthesis of halogenated metabolites in different organisms and the regioselectivity of their reactions. During the first 10–12 years, the main research topics were the detection of halogenases as well as the elucidation of three‐dimensional structures and reaction mechanisms. This Review mainly deals with studies on halogenating enzymes published between 2010 and 2015. It focusses on the elucidation of the involvement of halogenating enzymes in halometabolite biosynthesis, application of halogenases in in vivo and in vitro systems, in vivo modification of biosynthetic pathways in bacteria and plants, improvement of enzyme stability, broadening of substrate specificity, and the combination of biocatalysis with chemical synthesis to produce new compounds.
Structure and Metabolic‐Flow Analysis of Molecular Complexity in a 13C‐Labeled Tree by 2D and 3D NMR
Authors: Komatsu Takanori , Ohishi Risa , Shino Amiu , Kikuchi Jun
Published: April 2016

Improved signal identification for biological small molecules (BSMs) in a mixture was demonstrated by using multidimensional NMR on samples from 13C‐enriched Rhododendron japonicum (59.5 atom%) cultivated in air containing 13C‐labeled carbon dioxide for 14 weeks. The resonance assignment of 386 carbon atoms and 380 hydrogen atoms in the mixture was achieved. 42 BSMs, including eight that were unlisted in the spectral databases, were identified. Comparisons between the experimental values and the 13C chemical shift values calculated by density functional theory supported the identifications of unlisted BSMs. Tracing the 13C/12C ratio by multidimensional NMR spectra revealed faster and slower turnover ratios of BSMs involved in central metabolism and those categorized as secondary metabolites, respectively. The identification of BSMs and subsequent flow analysis provided insight into the metabolic systems of the plant.
Activation of Methane Promoted by Adsorption of CO on Mo2C2− Cluster Anions
Authors: Liu Qing‐Yu , Ma Jia‐Bi , Li Zi‐Yu , Zhao Chongyang , Ning Chuan‐Gang , Chen Hui , He Sheng‐Gui
Published: April 2016

Atomic clusters are being actively studied for activation of methane, the most stable alkane molecule. While many cluster cations are very reactive with methane, the cluster anions are usually not very reactive, particularly for noble metal free anions. This study reports that the reactivity of molybdenum carbide cluster anions with methane can be much enhanced by adsorption of CO. The Mo2C2− is inert with CH4 while the CO addition product Mo2C3O− brings about dehydrogenation of CH4 under thermal collision conditions. The cluster structures and reactions are characterized by mass spectrometry, photoelectron spectroscopy, and quantum chemistry calculations, which demonstrate that the Mo2C3O− isomer with dissociated CO is reactive but the one with non‐dissociated CO is unreactive. The enhancement of cluster reactivity promoted by CO adsorption in this study is compared with those of reported systems of a few carbonyl complexes.
Controlled‐Potential Electromechanical Reshaping of Cartilage
Authors: Hunter Bryan M. , Kallick Jeremy , Kissel Jessica , Herzig Maya , Manuel Cyrus , Protsenko Dmitri , Wong Brian J. F. , Hill Michael G.
Published: April 2016

An alternative to conventional “cut‐and‐sew” cartilage surgery, electromechanical reshaping (EMR) is a molecular‐based modality in which an array of needle electrodes is inserted into cartilage held under mechanical deformation by a jig. Brief (ca. 2 min) application of an electrochemical potential at the water‐oxidation limit results in permanent reshaping of the specimen. Highly sulfated glycosaminoglycans within the cartilage matrix provide structural rigidity to the tissue through extensive ionic‐bonding networks; this matrix is highly permselective for cations. Our studies indicate that EMR results from electrochemical generation of localized, low‐pH gradients within the tissue: fixed negative charges in the proteoglycan matrix are protonated, resulting in chemically induced stress relaxation of the tissue. Re‐equilibration to physiological pH restores the fixed negative charges, and yields remodeled cartilage that retains a new shape approximated by the geometry of the reshaping jig.
Designer Micelles Accelerate Flux Through Engineered Metabolism in E. coli and Support Biocompatible Chemistry
Authors: Wallace Stephen , Balskus Emily P.
Published: April 2016

Synthetic biology has enabled the production of many value‐added chemicals via microbial fermentation. However, the problem of low product titers from recombinant pathways has limited the utility of this approach. Methods to increase metabolic flux are therefore critical to the success of metabolic engineering. Here we demonstrate that vitamin E‐derived designer micelles, originally developed for use in synthetic chemistry, are biocompatible and accelerate flux through a styrene production pathway in Escherichia coli. We show that these micelles associate non‐covalently with the bacterial outer‐membrane and that this interaction increases membrane permeability. In addition, these micelles also accommodate both heterogeneous and organic‐soluble transition metal catalysts and accelerate biocompatible cyclopropanation in vivo. Overall, this work demonstrates that these surfactants hold great promise for further application in the field of synthetic biotechnology, and for expanding the types of molecules that can be readily accessed from renewable resources via the combination of microbial fermentation and biocompatible chemistry.