bluuebunny/crossref_metadata_2025 huggingface dataset:
Automotive FMCW Radar-Enhanced Range Estimation via a Local Resampling Fourier Transform
Authors: Wang Cailing , Liu Huajun , Han Guang , Jing Xiaoyuan
Published: February 2016

In complex traffic scenarios, more accurate measurement and discrimination for an automotive frequency-modulated continuous-wave (FMCW) radar is required for intelligent robots, driverless cars and driver-assistant systems. A more accurate range estimation method based on a local resampling Fourier transform (LRFT) for a FMCW radar is developed in this paper. Radar signal correlation in the phase space sees a higher signal-noise-ratio (SNR) to achieve more accurate ranging, and the LRFT - which acts on a local neighbour as a refinement step - can achieve a more accurate target range. The rough range is estimated through conditional pulse compression (PC) and then, around the initial rough estimation, a refined estimation through the LRFT in the local region achieves greater precision. Furthermore, the LRFT algorithm is tested in numerous simulations and physical system experiments, which show that the LRFT algorithm achieves a more precise range estimation than traditional FFT-based algorithms, especially for lower bandwidth signals.
Carrier Attitude Adjustment Strategy of a Space Robot for On-Orbit Detection
Authors: Wu Jianwei , Zhang Yin , Cui Jiwen , Tan Jiubin
Published: February 2016

A strategy for attitude adjustment of a free-floating space robot is proposed to reduce fuel consumption and time required to operate a space manipulator and its carrier before and after the detection of an on-orbit spacecraft. This strategy can be used in such a way that the carrier attitude and space manipulator joint angle reach their expected values at the same time. In order to obtain an advanced effect of carrier attitude adjustment, a novel parameterization method of joint trajectory is proposed, which extends the search scope of the joint trajectory by the fusion of the 4-3-4 and 3-5-3 planning methods. An objective function is defined according to the difference of the expected and initial carrier attitudes. A genetic algorithm is used to search for an optimal solution of the parameters. The effectiveness of the proposed strategy is verified through simulations for a six-degree-of-freedom (6-DOF) space robot system.
Too Much Testing, Too Little Control, Transparency Needed
Authors: Reys Robert
Published: February 2016

The continuous movement toward increased testing has a winner and many losers.
Illustrating the Central Limit Theorem
Authors: Corcoran Mimi
Published: February 2016

Sampling experiments with different types of beads give students a memorable hands-on experience.
Multiplication Principle Problems and Permutation Problems
Authors: Caddle Mary C. , Brizuela Bárbara M.
Published: February 2016

Distinguishing multiplication principle problems and permutation problems in the classroom helps us examine common student errors.
Math Rocks!
Authors: McConnell Marcella , Caniglia Joanne
Published: February 2016

The Rock and Roll Hall of Fame and Museum in Cleveland, Ohio, is a 150,000-square-foot building that serves as the permanent home of rock and roll's most memorable experiences. Designed by internationally renowned architect Ieoh Ming Pei, the building rises above the shores of Lake Erie. “In designing this building,” Pei explained, “it was my intention to echo the energy of rock and roll. I have consciously used an architectural vocabulary that is bold and new, and I hope the building will become a dramatic landmark for the city of Cleveland and for fans of rock and roll around the world.”
Birthday Party Patterns
Authors: Switzer J. Matt
Published: February 2016

Students are presented with a growing geometric pattern for table configurations at a birthday party. They must verbally describe how to extend the pattern and use their verbal description to generate an expression for the number of tables for different configurations. Each month, elementary school teachers receive a problem along with suggested instructional notes and are asked to use the problem in their own classrooms and report solutions, strategies, reflections, and misconceptions to the journal audience.
A Simple Photogrammetry Rig for the Reliable Creation of 3D Artifact Models in the Field
Authors: Porter Samantha Thi , Roussel Morgan , Soressi Marie
Published: February 2016

Three-dimensional (3D) artifact modeling is becoming an increasingly utilized tool in archaeology. In comparison with other methods of 3D scanning, photogrammetry has the benefits of being relatively inexpensive, mobile, and more adaptable for use in field conditions. As part of a larger project to document variability in lithic production systems across the Middle to Upper Paleolithic Transition in Western Europe, we developed a photography rig for the express purpose of systematically capturing images for the creation of 3D photogrammetric models. This low-cost rig greatly streamlines both the photo-taking and post-processing stages of model creation. Additional tips relating to the coating of difficult-to-capture objects with a mineral spray are also provided. Three-dimensional models of lithic cores from the Châtelperronian, Protoaurignacian, and Early Aurignacian levels of the site of Les Cottés (France) are presented as examples of the quality of model that can be produced using this system.
Immunologic response in treatment‐naïve HIV‐2‐infected patients: the IeDEA West Africa cohort
Authors: Balestre Eric , Ekouevi Didier Koumavi , Tchounga Boris , Eholie Serge Paul , Messou Eugène , Sawadogo Adrien , Thiébaut Rodolphe , May Margaret T , Sterne Jonathan Ac , Dabis François ,   the International Epidemiological Database to Evaluate AIDS (IeDEA) West Africa Collaboration
Published: February 2016

Introduction

Response to antiretroviral therapy (ART) among individuals infected with HIV‐2 is poorly described. We compared the immunological response among patients treated with three nucleoside reverse‐transcriptase inhibitors (NRTIs) to boosted protease inhibitor (PI) and unboosted PI‐based regimens in West Africa.

Methods

This prospective cohort study enrolled treatment‐naïve HIV‐2‐infected patients within the International Epidemiological Databases to Evaluate AIDS collaboration in West Africa. We used mixed models to compare the CD4 count response to treatment over 12 months between regimens.

Results

Of 422 HIV‐2‐infected patients, 285 (67.5%) were treated with a boosted PI‐based regimen, 104 (24.6%) with an unboosted PI‐based regimen and 33 (7.8%) with three NRTIs. Treatment groups were comparable with regard to gender (54.5% female) and median age at ART initiation (45.3 years; interquartile range 38.3 to 51.8). Treatment groups differed by clinical stage (21.2%, 16.8% and 17.3% at CDC Stage C or World Health Organization Stage IV for the triple NRTI, boosted PI and unboosted PI groups, respectively, p=0.02), median length of follow‐up (12.9, 17.7 and 44.0 months for the triple NRTI, the boosted PI and the unboosted PI groups, respectively, p<0.001) and baseline median CD4 count (192, 173 and 129 cells/µl in the triple NRTI, the boosted PI and the unboosted PI‐based regimen groups, respectively, p=0.003). CD4 count recovery at 12 months was higher for patients treated with boosted PI‐based regimens than those treated with three NRTIs or with unboosted PI‐based regimens (191 cells/µl, 95% CI 142 to 241; 110 cells/µl, 95% CI 29 to 192; 133 cells/µl, 95% CI 80 to 186, respectively, p=0.004).

Conclusions

In this observational study using African data, boosted PI‐containing regimens had better immunological response compared to triple NRTI combinations and unboosted PI‐based regimens at 12 months. A randomized clinical trial is still required to determine the best initial regimen for treating HIV‐2 infected patients.
Loss of the transcription factor Meis1 prevents sympathetic neurons target-field innervation and increases susceptibility to sudden cardiac death
Authors: Bouilloux Fabrice , Thireau Jérôme , Ventéo Stéphanie , Farah Charlotte , Karam Sarah , Dauvilliers Yves , Valmier Jean , Copeland Neal G , Jenkins Nancy A , Richard Sylvain , Marmigère Frédéric
Published: February 2016

Although cardio-vascular incidents and sudden cardiac death (SCD) are among the leading causes of premature death in the general population, the origins remain unidentified in many cases. Genome-wide association studies have identified Meis1 as a risk factor for SCD. We report that Meis1 inactivation in the mouse neural crest leads to an altered sympatho-vagal regulation of cardiac rhythmicity in adults characterized by a chronotropic incompetence and cardiac conduction defects, thus increasing the susceptibility to SCD. We demonstrated that Meis1 is a major regulator of sympathetic target-field innervation and that Meis1 deficient sympathetic neurons die by apoptosis from early embryonic stages to perinatal stages. In addition, we showed that Meis1 regulates the transcription of key molecules necessary for the endosomal machinery. Accordingly, the traffic of Rab5+ endosomes is severely altered in Meis1-inactivated sympathetic neurons. These results suggest that Meis1 interacts with various trophic factors signaling pathways during postmitotic neurons differentiation.
Preservation of three-dimensional anatomy in phosphatized fossil arthropods enriches evolutionary inference
Authors: Schwermann Achim H , dos Santos Rolo Tomy , Caterino Michael S , Bechly Günter , Schmied Heiko , Baumbach Tilo , van de Kamp Thomas
Published: February 2016

External and internal morphological characters of extant and fossil organisms are crucial to establishing their systematic position, ecological role and evolutionary trends. The lack of internal characters and soft-tissue preservation in many arthropod fossils, however, impedes comprehensive phylogenetic analyses and species descriptions according to taxonomic standards for Recent organisms. We found well-preserved three-dimensional anatomy in mineralized arthropods from Paleogene fissure fillings and demonstrate the value of these fossils by utilizing digitally reconstructed anatomical structure of a hister beetle. The new anatomical data facilitate a refinement of the species diagnosis and allowed us to reject a previous hypothesis of close phylogenetic relationship to an extant congeneric species. Our findings suggest that mineralized fossils, even those of macroscopically poor preservation, constitute a rich but yet largely unexploited source of anatomical data for fossil arthropods.
PhyloPythiaS+: a self-training method for the rapid reconstruction of low-ranking taxonomic bins from metagenomes
Authors: Gregor Ivan , Dröge Johannes , Schirmer Melanie , Quince Christopher , McHardy Alice C.
Published: February 2016

Background.Metagenomics is an approach for characterizing environmental microbial communitiesin situ, it allows their functional and taxonomic characterization and to recover sequences from uncultured taxa. This is often achieved by a combination of sequence assembly and binning, where sequences are grouped into ‘bins’ representing taxa of the underlying microbial community. Assignment to low-ranking taxonomic bins is an important challenge for binning methods as is scalability to Gb-sized datasets generated with deep sequencing techniques. One of the best available methods for species bins recovery from deep-branching phyla is the expert-trainedPhyloPythiaSpackage, where a human expert decides on the taxa to incorporate in the model and identifies ‘training’ sequences based on marker genes directly from the sample. Due to the manual effort involved, this approach does not scale to multiple metagenome samples and requires substantial expertise, which researchers who are new to the area do not have.

Results.We have developedPhyloPythiaS+, a successor to ourPhyloPythia(S)software. The new (+) component performs the work previously done by the human expert.PhyloPythiaS+also includes a newk-mer counting algorithm, which accelerated the simultaneous counting of 4–6-mers used for taxonomic binning 100-fold and reduced the overall execution time of the software by a factor of three. Our software allows to analyze Gb-sized metagenomes with inexpensive hardware, and to recover species or genera-level bins with low error rates in a fully automated fashion.PhyloPythiaS+was compared toMEGAN,taxator-tk,Krakenand the genericPhyloPythiaSmodel. The results showed thatPhyloPythiaS+performs especially well for samples originating from novel environments in comparison to the other methods.

Availability.PhyloPythiaS+in a virtual machine is available for installation under Windows, Unix systems or OS X on:https://github.com/algbioi/ppsp/wiki.
The personality trait of behavioral inhibition modulates perceptions of moral character and performance during the trust game: behavioral results and computational modeling
Authors: Radell Milen L. , Sanchez Rosanna , Weinflash Noah , Myers Catherine E.
Published: February 2016

Decisions based on trust are critical for human social interaction. We judge the trustworthiness of partners in social interactions based on a number of partner characteristics as well as experiences with those partners. These decisions are also influenced by personality. The current study examined how the personality trait of behavioral inhibition, which involves the tendency to avoid or withdraw from novelty in both social and non-social situations, is related to explicit ratings of trustworthiness as well as decisions made in the trust game. In the game, healthy young adults interacted with three fictional partners who were portrayed as trustworthy, untrustworthy or neutral through biographical information. Participants could choose to keep $1 or send $3 of virtual money to a partner. The partner could then choose to send $1.5 back to the participant or to keep the entire amount. On any trial in which the participant chose to send, the partner always reciprocated with 50% probability, irrespective of how that partner was portrayed in the biography. Behavioral inhibition was assessed through a self-report questionnaire. Finally, a reinforcement learning computational model was fit to the behavior of each participant. Self-reported ratings of trust confirmed that all participants, irrespective of behavioral inhibition, perceived differences in the moral character of the three partners (trustworthiness of good > neutral > bad partner). Decisions made in the game showed that inhibited participants tended to trust the neutral partner less than uninhibited participants. In contrast, this was not reflected in the ratings of the neutral partner (either pre- or post-game), indicating a dissociation between ratings of trustworthiness and decisions made by inhibited participants. Computational modeling showed that this was due to lower initial trust of the neutral partner rather than a higher learning rate associated with loss, suggesting an implicit bias against the neutral partner. Overall, the results suggest inhibited individuals may be predisposed to interpret neutral or ambiguous information more negatively which could, at least in part, account for the tendency to avoid unfamiliar people characteristic of behaviorally inhibited temperament, as well as its relationship to anxiety disorders.
Activation of autophagy through calcium‐dependent AMPK/mTOR and PKCθ pathway causes activation of rat hepatic stellate cells under hypoxic stress
Authors: Jin Yuepeng , Bai Yongyu , Ni Haizhen , Qiang Li , Ye Lechi , Shan Yunfeng , Zhou Mengtao
Published: February 2016

The activation of hepatic stellate cells (HSCs) is a prominent event in liver fibrogenesis. However, how HSCs are activated in the hypoxic microenvironment remains unclear. Here, we found that hypoxia increased autophagy in rat HSCs. Moreover, hypoxia induced an elevation of the intracellular calcium concentration ([Ca2+]i), which was abolished by the cytosolic Ca2+ chelator or the phospholipase C (PLC)‐specific inhibitor. Furthermore, hypoxia‐induced autophagy involved the calcium‐dependent activation of the 5ʹ‐adenosine monophosphate‐activated protein kinase (AMPK)–mammalian target of rapamycin (mTOR) and protein kinase C‐theta (PKCθ) pathways. In addition, hypoxia‐mediated activation of HSCs depended on autophagy. Our results suggest that autophagy induction via the calcium‐dependent AMPK–mTOR and PKCθ pathways might lead to the activation of HSCs during hypoxic stress.
Remagnetization of lower Silurian black shale and insights into shale gas in the Sichuan Basin, south China
Authors: Zhang Yong , Jia Dong , Yin Hongwei , Liu Mancang , Xie Wuren , Wei Guoqi , Li Yongxiang
Published: February 2016

The organic‐rich lower Silurian shale of the Longmaxi Formation in the Sichuan Basin is the most important target for shale‐gas exploration in China. Most Paleozoic rocks of the Sichuan Basin have experienced extraordinarily pervasive remagnetizations. To test a hypothesized connection between hydrocarbon generation and remagnetization and contribute to shale‐gas exploration in the region, we undertook an integrated magnetic, geochemical, and petrographic study of 160 specimens from the shale. The results suggest that the shale contains a reliable remanent magnetization (Dec = 41.4°, Inc = 40.8°, and α95 = 6.8°). The magnetization predates tilting, and the paleopole plots close to the Late Triassic segment of the south China apparent polar wander path. The rock magnetic data and scanning electron microscope (SEM) observations confirm that framboidal magnetites carry the bulk of the magnetization, which suggest a Late Triassic chemical remanent magnetization in the shale. 87Sr/86Sr and magnetic analyses indicate that the amount of magnetite was unaffected by fluid alterations around the veins but is strongly covariant with the amount of total organic matter. Moreover, SEM observations reveal possible evidence of the replacement of pyrite framboids by magnetite, probably in the presence of organic acids. These analyses, therefore, suggest that the remagnetization was caused by organic maturation rather than orogenic fluids and that the maturation occurred in the Late Triassic. This timing of organic maturation has been validated by independent modeling studies and provides important constraints on the complex thermal history of the Longmaxi Shale as well as contributing to shale‐gas exploration efforts.
A two‐dimensional analytical model of petroleum vapor intrusion
Authors: Yao Yijun , Verginelli Iason , Suuberg Eric M.
Published: February 2016

In this study we present an analytical solution of a two‐dimensional petroleum vapor intrusion model, which incorporates a steady‐state diffusion‐dominated vapor transport in a homogeneous soil and piecewise first‐order aerobic biodegradation limited by oxygen availability. This new model can help practitioners to easily generate two‐dimensional soil gas concentration profiles for both hydrocarbons and oxygen and estimate hydrocarbon indoor air concentrations as a function of site‐specific conditions such as source strength and depth, reaction rate constant, soil characteristics and building features. The soil gas concentration profiles generated by this new model are shown in good agreement with three‐dimensional numerical simulations and two‐dimensional measured soil gas data from a field study. This implies that for cases involving diffusion dominated soil gas transport, steady state conditions and homogenous source and soil, this analytical model can be used as a fast and easy‐to‐use risk screening tool by replicating the results of 3‐D numerical simulations but with much less computational effort.
Dressed to kill? Visible markers of coalitional affiliation enhance conceptualized formidability
Authors: Fessler Daniel M. T. , Holbrook Colin , Dashoff David
Published: February 2016

Displaying markers of coalitional affiliation is a common feature of contemporary life. In situations in which interaction with members of rival coalitions is likely, signaling coalitional affiliation may simultaneously constitute an implicit challenge to opponents and an objective commitment device, binding signalers to their coalitions. Individuals who invite conflict, and who cannot readily back out of conflict, constitute a greater threat than those who avoid conflict and preserve the option of feigning neutrality. As a consequence, the former should be viewed as more formidable than the latter. Recent research indicates that relative formidability is summarized using the envisioned physical size and strength of a potential antagonist. Thus, individuals who display markers of coalitional affiliation should be conceptualized as more physically imposing than those who do not. We tested this prediction in two experiments. In Study 1, conducted with U.S. university students, participants inspected images of sports fans' faces. In Study 2, conducted with U.S. Mechanical Turk workers, participants read vignettes depicting political partisans. In both studies, participants estimated the physical formidability of the target individuals and reported their own ability to defend themselves; in Study 2, participants estimated the target's aggressiveness. Consonant with predictions, targets depicted as signaling coalitional affiliation in situations of potential conflict were envisioned to be more physically formidable and more aggressive than were those not depicted as signaling thusly. Underscoring that the calculations at issue concern the possibility of violent conflict, participants' estimates of the protagonist's features were inversely correlated with their ability to defend themselves. Aggr. Behav. 42:299–309, 2016. © 2016 Wiley Periodicals, Inc.
Architecture of Conjugated Donor–Acceptor (D–A)‐Type Polymer Films with Cross‐Linked Structures
Authors: Huang Jin , Peng Bangan , Wang Weina , Ji Hanxu , Li Linling , Xi Kai , Lai Wenyong , Zhang Xinwen , Jia Xudong
Published: February 2016

A series of new donor–acceptor (D–A)‐type semiconducting conjugated polymers (SCPs), which can form cross‐linked structural and supramolecular assembly films by hydrogen‐bonding, is successfully synthesized. The microstructures of supramolecular assembly films are further investigated by X‐ray diffraction (XRD), high‐ resolution transmission electron microscopy (HRTEM), and variable‐temperature Fourier transform infrared (FT‐IR) absorption spectra. As electronic transmission (ET) materials, the SCPs demonstrate superior properties by means of fabricating electron‐only devices with the configuration of ITO/ET (SCPs)/Ca/Al. According to space‐charge‐limited current (SCLC) measurements, fluorine‐containing SCPs exhibit much smaller threshold voltages and much higher electron mobilities than Alq3. Meanwhile, a significant enhancement for their luminescence properties is verified by the photoluminescence (PL) and electroluminescent (EL) spectra of cross‐linked‐type SCPs, compared to non‐cross‐linked‐type SCPs. The fabricated polymer light‐emitting diodes (PLEDs) with the configuration of ITO/PEDOT:PSS/EML (SCPs)/BCP/LiF/Al are able to emit the color from green to red with moderately low turn‐on voltages. These results suggested that cross‐linked D–A‐type SCP can become a potential candidate as a kind of multifunctional materials applied in the field of optoelectronic devices.
Fine Tuned Nanolayered Metal/Metal Oxide Electrode for Semitransparent Colloidal Quantum Dot Solar Cells
Authors: Zhang Xiaoliang , Hägglund Carl , Johansson Malin B. , Sveinbjörnsson Kári , Johansson Erik M. J.
Published: February 2016

Semitransparent photovoltaics have great potential, for example, in building‐integration or in portable electronics. However, the front and back contact electrodes significantly affect the light transmission and photovoltaic performance of the complete device. Herein, the use of a semitransparent nanolayered metal/metal oxide electrode for a semitransparent PbS colloidal quantum dot solar cell to increase the light transmission and power conversion efficiency is reported. The effect of the nanolayered electrode on the optical properties within the solar cells is studied and compared to a theoretically model to identify the origin of optical losses that lower the device transmission. The results show that the light transmission in the visible region and the photovoltaic performance are significantly enhanced with the nanolayered electrode. The solar cell shows an efficiency of 5.4% and average visible transmittance of 24.1%, which is an increase by 28.6% and 59.6%, respectively, compared to the device with a standard Au film as the electrode. These results demonstrate that the optical and electrical modification of transparent electrode is possible and essential for reducing the light reflection and absorption of the electrode in semitransparent photovoltaics, and, meanwhile the demonstrated nanolayered materials may provide an avenue for enhancing the device transparency and efficiency.
Engineering of Spin Injection and Spin Transport in Organic Spin Valves Using π‐Conjugated Polymer Brushes
Authors: Geng Rugang , Roy Anandi , Zhao Wenbo , Subedi Ram Chandra , Li Xiaoguang , Locklin Jason , Nguyen Tho Duc
Published: February 2016

Charge transport in amorphous organic semiconductors is governed by carriers hopping between localized states with small spin diffusion length. Furthermore, the interfacial resistance of organic spin valves (OSVs) is poorly controlled resulting in controversial reports of the magnetoresistance (MR) response. Here, surface‐initiated Kumada transfer polycondensation is used to covalently graft π‐conjugated poly(3‐methylthiophene) brushes from the La0.67Sr0.33MnO3 (LSMO) bottom electrode. The covalent attachment along with the brush morphology allows control over the LSMO/brush interfacial resistance and large spacer mobility. Remarkably, with 15 nm brush spacer layer, an optimum MR effect of 70% at cryogenic temperatures and a MR of 2.7% at 280 K are observed. The temperature dependence of the MR is nearly an order of magnitude weaker than that found in control OSVs made from spin‐coated poly(3‐hexylthiophene). Using a variety of different brush layer thicknesses, the thickness‐dependent MR at 20 K is investigated. A spin diffusion length of 17 nm at −5 mV junction voltage rapidly increased to 48.4 nm at −260 mV.
Smart Ferrofluid with Quick Gel Transformation in Tumors for MRI‐Guided Local Magnetic Thermochemotherapy
Authors: Hayashi Koichiro , Sakamoto Wataru , Yogo Toshinobu
Published: February 2016

Improved techniques for local administration of anticancer drugs are needed to reduce the side effects of chemotherapy owing to leakage of anticancer drugs from tumors and to enhance therapeutic efficacy. This study presents the development of smart ferrofluid that transforms immediately into a gel in tumors and generates heat in response to an alternating magnetic field (AMF), simultaneously releasing the anticancer drug. The smart ferrofluid, which is synthesized using less toxic magnetic materials (Fe3O4 nanoparticles), natural polysaccharides (alginate), and amino acids (cysteine), can also act as a contrast agent for magnetic resonance imaging (MRI). The ferrofluid also incorporates an anticancer drug (i.e., doxorubicin, DOX) via hydrogen bonds. AMF causes heating of gels prepared from the DOX‐containing ferrofluid, resulting in gel shrinkage and DOX release. In vivo experiments demonstrated that the ferrofluid transforms into a gel in the tumor, with the gel remaining in the tumor. Furthermore, magnetic thermochemotherapy using this ferrofluid inhibited tumor growth, while magnetic hyperthermia alone had only a marginal effect. Thus, the combination of magnetic hyperthermia and chemotherapy may be important for suppressing tumor growth. In summary, the ferrofluid presented here has the potential to facilitate MRI‐guided magnetic thermochemotherapy through a combination of endoscopic technologies in the future.
High Responsivity Phototransistors Based on Few‐Layer ReS2 for Weak Signal Detection
Authors: Liu Erfu , Long Mingsheng , Zeng Junwen , Luo Wei , Wang Yaojia , Pan Yiming , Zhou Wei , Wang Baigeng , Hu Weida , Ni Zhenhua , You Yumeng , Zhang Xueao , Qin Shiqiao , Shi Yi , Watanabe Kenji , Taniguchi Takashi , Yuan Hongtao , Hwang Harold Y. , Cui Yi , Miao Feng , Xing Dingyu
Published: February 2016

2D transition metal dichalcogenides are emerging with tremendous potential in many optoelectronic applications due to their strong light–matter interactions. To fully explore their potential in photoconductive detectors, high responsivity is required. Here, high responsivity phototransistors based on few‐layer rhenium disulfide (ReS2) are presented. Depending on the back gate voltage, source drain bias and incident optical light intensity, the maximum attainable photoresponsivity can reach as high as 88 600 A W−1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS2. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement due to the existence of trap states in the few‐layer ReS2 flakes. It further enables the detection of weak signals, as successfully demonstrated with weak light sources including a lighter and limited fluorescent lighting. Our studies underscore ReS2 as a promising material for future sensitive optoelectronic applications.
Chloride and Indium‐Chloride‐Complex Inorganic Ligands for Efficient Stabilization of Nanocrystals in Solution and Doping of Nanocrystal Solids
Authors: Sayevich Vladimir , Guhrenz Chris , Sin Maria , Dzhagan Volodymyr M. , Weiz Alexander , Kasemann Daniel , Brunner Eike , Ruck Michael , Zahn Dietrich R. T. , Leo Karl , Gaponik Nikolai , Eychmüller Alexander
Published: February 2016

Here, the surface functionalization of CdSe and CdSe/CdS core/shell nanocrystals (NCs) with compact chloride and indium‐chloride‐complex ligands is reported. The ligands provide not only short interparticle distances but additionally control doping and passivation of surface trap states, leading to enhanced electronic coupling in NC‐based arrays. The solids based on these NCs show an excellent electronic transport behavior after heat treatment at the relatively low temperature of 190 °C. Indeed, the indium‐chlorido‐capped 4.5 nm CdSe NC based thin‐film field‐effect transistor reaches a saturation mobility of μ = 4.1 cm2 (V s)−1 accompanied by a low hysteresis, while retaining the typical features of strongly quantum confined semiconductor NCs. The capping with chloride ions preserves the high photoluminescence quantum yield (≈66%) of CdSe/CdS core/shell NCs even when the CdS shell is relatively thin (six monolayers). The simplicity of the chemical incorporation of chlorine and indium species via solution ligand exchange, the efficient electronic passivation of the NC surface, as well as their high stability as dispersions make these materials especially attractive for wide‐area solution‐processable fabrication of NC‐based devices.
Beyond Creation of Mesoporosity: The Advantages of Polymer‐Based Dual‐Function Templates for Fabricating Hierarchical Zeolites
Authors: Tian Qiwei , Liu Zhaohui , Zhu Yihan , Dong Xinglong , Saih Youssef , Basset Jean‐Marie , Sun Miao , Xu Wei , Zhu Liangkui , Zhang Daliang , Huang Jianfeng , Meng Xiangju , Xiao Feng‐Shou , Han Yu
Published: February 2016

Direct synthesis of hierarchical zeolites currently relies on the use of surfactant‐based templates to produce mesoporosity by the random stacking of 2D zeolite sheets or the agglomeration of tiny zeolite grains. The benefits of using nonsurfactant polymers as dual‐function templates in the fabrication of hierarchical zeolites are demonstrated. First, the minimal intermolecular interactions of nonsurfactant polymers impose little interference on the crystallization of zeolites, favoring the formation of 3D continuous zeolite frameworks with a long‐range order. Second, the mutual interpenetration of the polymer and the zeolite networks renders disordered but highly interconnected mesopores in zeolite crystals. These two factors allow for the synthesis of single‐crystalline, mesoporous zeolites of varied compositions and framework types. A representative example, hierarchial aluminosilicate (meso‐ZSM‐5), has been carefully characterized. It has a unique branched fibrous structure, and far outperforms bulk aluminosilicate (ZSM‐5) as a catalyst in two model reactions: conversion of methanol to aromatics and catalytic cracking of canola oil. Third, extra functional groups in the polymer template can be utilized to incorporate desired functionalities into hierarchical zeolites. Last and most importantly, polymer‐based templates permit heterogeneous nucleation and growth of mesoporous zeolites on existing surfaces, forming a continuous zeolitic layer. In a proof‐of‐concept experiment, unprecedented core–shell‐structured hierarchical zeolites are synthesized by coating mesoporous zeolites on the surfaces of bulk zeolites.
Graphene Doping Improved Device Performance of ZnMgO/PbS Colloidal Quantum Dot Photovoltaics
Authors: Hu Long , Li Deng‐Bing , Gao Liang , Tan Hua , Chen Chao , Li Kanghua , Li Min , Han Jun‐Bo , Song Haisheng , Liu Huan , Tang Jiang
Published: February 2016

Lead sulfide (PbS) colloidal quantum dots (CQDs) solar cells possess the advantages of absorption into the infrared, solution processing, and multiple exciton generation, making them very competitive as a low‐cost photovoltaic alternative. Employing an n‐i‐p ZnO/tetrabutylammonium (TBAI)–PbS/ethanedithiol (EDT)–PbS device configuration, the present study reports a 9.0% photovoltaic device through ZnMgO electrode engineering and graphene doping. Sol–gel‐derived Zn0.9Mg0.1O buffer layer shows better transparency and higher conduction band maximum than ZnO, and incorporation of graphene and chlorinated graphene oxide into the TBAI–PbS and EDT–PbS layer respectively boosts carrier collection, leading to device with significantly enhanced open circuit voltage and short‐circuit current density. It is believed that incorporation of graphene into PbS CQD film as proposed here, and more generally nanosheets of other materials, would potentially open a simple and powerful avenue to overcome the carrier transport bottleneck of CQD optoelectronic device, thus pushing device performance to a new level.
Morphological Engineering of CVD‐Grown Transition Metal Dichalcogenides for Efficient Electrochemical Hydrogen Evolution
Authors: Ji Qingqing , Zhang Yu , Shi Jianping , Sun Jingyu , Zhang Yanfeng , Liu Zhongfan
Published: February 2016

2D layered transition metal dichalcogenides (TMDCs) have emerged as new possibilites beyond conventional particulate catalysts in facilitating efficient electrochemical hydrogen evolution. This is mainly mediated by the ultrahigh surface‐to‐volume ratio and the effective coupling of all active sites with supporting electrodes. Especially, the facile chemical vapor deposition (CVD) method has enabled morphological engineering of monolayer TMDC catalysts toward development of abundant active edge sites within the 2D plane. Here, two pathways to achieve such purpose are highlighted, either by non‐equilibrium growth of MoS2 dendrites or throughout high‐density nucleation of MoS2 nanoflakes directly on the electrode materials. Furthermore, future research directions have also been proposed and discussed to further enhance the efficiency of such unique catalysts.
Functionalization of Two‐Dimensional Transition‐Metal Dichalcogenides
Authors: Chen Xin , McDonald Aidan R.
Published: February 2016

Two‐dimensional (2D) layered transition‐metal dichalcogenides (TMDs) are a fascinating class of nanomaterials that have the potential for application in catalysis, electronics, photonics, energy storage, and sensing. TMDs are rather inert, and thus pose problems for chemical derivatization. However, to further modify the properties of TMDs and fully harness their capabilities, routes towards their chemical functionalization must be identified. Herein, recent efforts toward the chemical (bond‐forming) functionalization of 2D TMDs are critically reviewed. Recent successes are highlighted, along with areas where further detailed analyses and experimentation are required. This burgeoning field is very much in its infancy but has already provided several important breakthroughs.
Black Phosphorus Schottky Diodes: Channel Length Scaling and Application as Photodetectors
Authors: Miao Jinshui , Zhang Suoming , Cai Le , Wang Chuan
Published: February 2016

Black phosphorus (BP) Schottky diodes with asymmetric metal contacts are demonstrated using gold and aluminum electrodes. The devices exhibit rectifying characteristics with current rectification ratio up to 1.5 × 103. The effect of channel length on the electrical characteristics of the BP Schottky diodes is also studied and the results reveal that the device loses its rectifying behavior (rectification ratio = 1.37) at ultrashort channel length of around 30 nm. The transition from rectifying to nonrectifying characteristics at extremely small channel length is attributed to the electric‐field‐induced barrier thinning, which results in significantly increased tunneling current under reverse bias. Using the BP Schottky diodes with relatively long channel length (≈1 μm), photodetectors with fast response time of less than 2 ms are demonstrated. This work demonstrates the potential of using BP‐based diode devices for optoelectronic applications.
Control and Optimization of the Electrochemical and Mechanical Properties of the Solid Electrolyte Interphase on Silicon Electrodes in Lithium Ion Batteries
Authors: Tokranov Anton , Kumar Ravi , Li Chunzeng , Minne Stephen , Xiao Xingcheng , Sheldon Brian W.
Published: February 2016

The formation of the solid electrolyte interphase (SEI) on Si is examined in detail using several in situ techniques. The results show that employing different conditions during the first lithiation cycle produces SEI films with substantially different properties. Longer time at higher potentials produces softer SEI, whereas inorganic phases produced at lower potentials have higher elastic moduli. The SEI thickness stabilizes during the first cycle; however, the SEI resistance decreases during the first 20 cycles (in sharp contrast to typical surface passivation processes, where resistance is expected to increase with time). This behavior is consistent with the slow growth of inorganic constituents at lower potentials, inside of a mesoporous soft SEI that initially forms at higher potentials. This interpretation is based on the premise that these inorganic phases have a lower resistivity than that associated with electrolyte transport through the mesoporous organic phase. Based on this set of observations, the multiphase structure that evolves during initial cycling determines critical electrochemical and mechanical properties of the SEI. A basic model of these tradeoffs is proposed to provide guidelines for creating more stable interfacial films.
Untersuchung der Tyrosinase‐Expression in nicht‐metastatischen und metastatischen Melanomgeweben durch elektrochemische Rastersondenmikroskopie
Authors: Lin Tzu‐En , Bondarenko Alexandra , Lesch Andreas , Pick Horst , Cortés‐Salazar Fernando , Girault Hubert H.
Published: February 2016

Trotz des enormen Fortschritts, der bei der Diagnose von Melanomen erzielt wurde, bleibt die zuverlässige Erkennung der verschiedenen Malignomstadien eine Herausforderung. Derzeitige Strategien setzen auf die optische Erfassung der Konzentration und räumlichen Verteilung spezifischer Biomarker. Neueste optische Methoden können allerdings durch Interferenzen mit Hintergrundfarben und durch Autofluoreszenz beeinflusst werden. Wir bewältigen diese Defizite hier unter Einsatz der elektrochemischen Rastersondenmikroskopie (SECM), um den prognostischen Indikator Tyrosinase (TyR) in nicht‐metastatischen und metastatischen Melanomgeweben mithilfe einer weichen Mikroelektrodensonde abzubilden. Das elektrochemische Auslesen der TyR‐Verteilung wurde durch das Adaptieren eines immunchemischen Verfahrens ermöglicht. Wir zeigen, dass die SECM die erwähnten Beschränkungen optischer Methoden übertreffen kann und bisher nicht gekannte Möglichkeiten für eine verbesserte Diagnose und das Verständnis der räumlichen Verteilung von TyR in verschiedenen Melanomstadien eröffnet.
A Unique Tryptophan C‐Prenyltransferase from the Kawaguchipeptin Biosynthetic Pathway
Authors: Parajuli Anirudra , Kwak Daniel H. , Dalponte Luca , Leikoski Niina , Galica Tomas , Umeobika Ugochukwu , Trembleau Laurent , Bent Andrew , Sivonen Kaarina , Wahlsten Matti , Wang Hao , Rizzi Ermanno , De Bellis Gianluca , Naismith James , Jaspars Marcel , Liu Xinyu , Houssen Wael , Fewer David Peter
Published: February 2016

Cyanobactins are a rapidly growing family of linear and cyclic peptides produced by cyanobacteria. Kawaguchipeptins A and B, two macrocyclic undecapeptides reported earlier from Microcystis aeruginosa NIES‐88, are shown to be products of the cyanobactin biosynthetic pathway. The 9 kb kawaguchipeptin (kgp) gene cluster was identified in a 5.26 Mb draft genome of Microcystis aeruginosa NIES‐88. We verified that this gene cluster is responsible for the production of the kawaguchipeptins through heterologous expression of the kgp gene cluster in Escherichia coli. The KgpF prenyltransferase was overexpressed and was shown to prenylate C‐3 of Trp residues in both linear and cyclic peptides in vitro. Our findings serve to further enhance the structural diversity of cyanobactins to include tryptophan‐prenylated cyclic peptides.
Quercetin‐2,4‐Dioxygenase aktiviert Sauerstoff in einem “side‐on” gebundenen O2‐Ni‐Komplex
Authors: Jeoung Jae‐Hun , Nianios Dimitrios , Fetzner Susanne , Dobbek Holger
Published: February 2016

Die Quercetin‐2,4‐Dioxygenase (Quercetinase) von Streptomyces nutzt Nickel als Kofaktor, um die oxidative Spaltung des Flavonols Quercetin zu katalysieren. Wie dieses ungewöhnliche Metall im aktiven Zentrum die Katalyse und Sauerstoffaktivierung unterstützt, ist unklar. Wir stellen Kristallstrukturen der Ni‐Quercetinase in drei verschiedenen Zuständen vor, die direkte Einblicke geben, wie Quercetin und O2 am Ni2+‐Ion aktiviert werden. Ni2+ wird in allen drei Zuständen durch drei Histidin‐Reste und einen Glutamat‐Rest (E76) koordiniert. Wenn Quercetin bindet, ersetzt es einen Wasserliganden am Nickel und wird durch eine kurze Wasserstoffbrücke zu E76 stabilisiert, dessen Carboxylat‐Gruppe sich um 90° dreht. Diese Konformationsänderung schwächt die Wechselwirkung zwischen Nickel und dem verbleibenden Wasserliganden und bereitet eine Koordinationsstelle am Nickel zur Bindung von O2 vor. O2 bindet “side‐on” an das Ni2+‐Ion und steht senkrecht zu den C2‐C3‐ und C3‐C4‐Bindungen des Quercetins, die in den folgenden Schritten gespalten werden.
Atompräzise organometallische Zinkcluster
Authors: Banh Hung , Dilchert Katharina , Schulz Christine , Gemel Christian , Seidel Rüdiger W. , Gautier Régis , Kahlal Samia , Saillard Jean‐Yves , Fischer Roland A.
Published: February 2016

Ein Bottom‐up‐Synthesekonzept zur Herstellung metallorganischer Zinkcluster wird vorgestellt. Das Kation {[Zn10](Cp*)6Me}+ (1) wird aus der Reaktion von [Zn2Cp*2] mit [FeCp2][BAr4F] in Gegenwart von ZnMe2 erhalten. Die hohe Reaktivität von 1 erlaubt durch Zugabe geeigneter Liganden die gezielte Entfernung einzelner Zinkatome, was den Zugang zu den niedriger nuklearen Clustern {[Zn9](Cp*)6} (2) und {[Zn8](Cp*)5(tBuNC)3}+ (3) ermöglicht. Nach DFT‐Rechnungen können 1 und 2 als “closed‐shell”‐Verbindungen mit Elektronenmangel in Bezug auf die Wade‐Mingos‐Regeln beschrieben werden, da den gerüstbildenden apikalen ZnCp*‐Einheiten nicht drei, sondern nur ein Grenzorbital für Clusterbindungen zur Verfügung steht. So verhält sich Zink bei der Bildung von Metall‐Metall‐Bindungen flexibel: Es kann entweder nur ein Grenzorbital zur Verfügung stellen (wie Gruppe‐11‐Metalle), oder auch drei Grenzorbitale (wie Gruppe‐13‐Elemente).
Framework Cationization by Preemptive Coordination of Open Metal Sites for Anion‐Exchange Encapsulation of Nucleotides and Coenzymes
Authors: Zhao Xiang , Mao Chengyu , Luong Karen Tu , Lin Qipu , Zhai Quan‐Guo , Feng Pingyun , Bu Xianhui
Published: February 2016

Cationic frameworks can selectively trap anions through ion exchange, and have applications in ion chromatography and drug delivery. However, cationic frameworks are much rarer than anionic or neutral ones. Herein, we propose a concept, preemptive coordination (PC), for targeting positively charged metal–organic frameworks (P‐MOFs). PC refers to proactive blocking of metal coordination sites to preclude their occupation by neutralizing ligands such as OH−. We use 20 MOFs to show that this PC concept is an effective approach for developing P‐MOFs whose high stability, porosity, and anion‐exchange capability allow immobilization of anionic nucleotides and coenzymes, in addition to charge‐ and size‐selective capture or separation of organic dyes. The CO2 and C2H2 uptake capacity of 117.9 cm3 g−1 and 148.5 cm3 g−1, respectively, at 273 K and 1 atm, is exceptionally high among cationic framework materials.
Capturing HBCy2: Using N,O‐Chelated Complexes of Rhodium(I) and Iridium(I) for Chemoselective Hydroboration
Authors: Drover Marcus W. , Schafer Laurel L. , Love Jennifer A.
Published: February 2016

1,3‐N,O‐chelated complexes of RhI and IrI cooperatively and reversibly stabilized the B−H bond of HBCy2 to afford six‐membered metallaheterocycles (M=Rh (7) or Ir (8)) having a δ‐[M]⋅⋅⋅H‐B agostic interaction. Treatment of these Shimoi‐type borane adducts 7 or 8 with both an aldehyde and an alkene resulted in chemoselective aldehyde hydroboration and reformation of the 1,3‐N,O‐chelated starting material. The observed chemoselectivity is inverted from that of free HBCy2, which is selective for alkene hydroboration.
A Telomerase‐Specific Doxorubicin‐Releasing Molecular Beacon for Cancer Theranostics
Authors: Ma Yi , Wang Zhaohui , Zhang Min , Han Zhihao , Chen Dan , Zhu Qiuyun , Gao Weidong , Qian Zhiyu , Gu Yueqing
Published: February 2016

A molecular beacon‐based drug delivery system was designed for both detection of telomerase activity in living cells and telomerase‐triggered drug release for precise cancer treatment. This system is composed of a gold nanoparticle core densely packed with FITC‐labeled hairpin DNA sequences hybridized with telomerase primers. Molecules of the anticancer drug doxorubicin were intercalated into the stem region of the DNA sequence. The presence of telomerase will elongate the primers, leading to inner chain substitution followed by the release of the FITC fluorescence and the trapped doxorubicin. This molecular beacon could specifically distinguish tumor cells and normal cells based on telomerase activity, precisely release doxorubicin in response to telomerase activity in the tumor cells, and prevent toxicity to normal organs.
Charge‐Induced Unzipping of Isolated Proteins to a Defined Secondary Structure
Authors: González Flórez Ana Isabel , Mucha Eike , Ahn Doo‐Sik , Gewinner Sandy , Schöllkopf Wieland , Pagel Kevin , von Helden Gert
Published: February 2016

Here we present a combined experimental and theoretical study on the secondary structure of isolated proteins as a function of charge state. In infrared spectra of the proteins ubiquitin and cytochrome c, amide I (C=O stretch) and amide II (N–H bend) bands can be found at positions that are typical for condensed‐phase proteins. For high charge states a new band appears, substantially red‐shifted from the amide II band observed at lower charge states. The observations are interpreted in terms of Coulomb‐driven transitions in secondary structures from mostly helical to extended C5‐type hydrogen‐bonded structures. Support for this interpretation comes from simple energy considerations as well as from quantum chemical calculations on model peptides. This transition in secondary structure is most likely universal for isolated proteins that occur in mass spectrometric experiments.