bluuebunny/crossref_metadata_2025 huggingface dataset:
Unconventional Magnetic and Resistive Hysteresis in an Iodine‐Bonded Molecular Conductor
Authors: Kawaguchi Genta , Maesato Mitsuhiko , Komatsu Tokutaro , Kitagawa Hiroshi , Imakubo Tatsuro , Kiswandhi Andhika , Graf David , Brooks James S.
Published: July 2015

Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine‐bonded molecular conductor (DIETSe)2FeBr2Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin‐flop transition. Utilizing a mixed‐anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties.
Enantioselective Synthesis of Quaternary Carbon Stereocenters: Addition of 3‐Substituted Oxindoles to Vinyl Sulfone Catalyzed by Pentanidiums
Authors: Zong Lili , Du Shubo , Chin Kek Foo , Wang Chao , Tan Choon‐Hong
Published: July 2015

A pentanidium‐catalyzed highly enantioselective conjugate addition of 3‐alkyloxindoles to phenyl vinyl sulfone has been demonstrated. This approach allows the construction of 3,3‐dialkyl‐substituted oxindole frameworks with high yield and excellent enantioselectivity (up to 99 %) under simple phase‐transfer conditions. A variety of oxindoles bearing all‐carbon quaternary stereogenic centers were obtained in the presence of 0.25 mol % pentanidium. Meanwhile, practicality was illustrated by a gram‐scale asymmetric synthesis of two 3,3‐dialkyl‐substituted oxindoles. The resulting adduct can be smoothly transformed to the natural product analogue in a short synthetic route.
A Catalytic SEAr Approach to Dibenzosiloles Functionalized at Both Benzene Cores
Authors: Omann Lukas , Oestreich Martin
Published: July 2015

A general procedure for the catalytic preparation of dibenzosiloles functionalized at one or both benzene rings starting from readily available ortho‐silylated biphenyls is reported. This method provides rapid access to silole building blocks substituted with chlorine atoms at both phenylene groups, thereby allowing catalytic access to directly polymerizable dibenzosiloles. Moreover, it is shown that, despite the involvement of highly electrophilic intermediates, a considerable range of Lewis‐basic, for example, oxygen‐ and nitrogen‐containing, functional groups is tolerated. The mechanism of this intramolecular electrophilic aromatic substitution (SEAr) proceeds through a sulfur‐stabilized silicon cation, generated catalytically from the hydrosilane precursor.
Electrophilic Fluorophosphonium Cations in Frustrated Lewis Pair Hydrogen Activation and Catalytic Hydrogenation of Olefins
Authors: vom Stein Thorsten , Peréz Manuel , Dobrovetsky Roman , Winkelhaus Daniel , Caputo Christopher B. , Stephan Douglas W.
Published: July 2015

The combination of phosphorus(V)‐based Lewis acids with diaryl amines and diaryl silylamines promotes reversible activation of dihydrogen and can be further exploited in metal‐free catalytic olefin hydrogenation. Combined experimental and density functional theory (DFT) studies suggest a frustrated Lewis pair type activation mechanism.
A Kinetic Model for Exfoliation Kinetics of Layered Materials
Authors: Texter John
Published: July 2015

Exfoliation of two‐dimensional materials is key to obtaining high‐performance properties. We present a simple kinetic model for exfoliation that is readily solved analytically. Random and irreversible sheet separation is postulated in the presence of highly effective stabilizers. This model appears to quantitatively fit graphene exfoliation data, and it illuminates mechanistic aspects of exfoliation. Thicker sheets exfoliate much faster than trilayer and bilayer sheets. Exfoliation follows highly activated diffusion‐controlled intercalation of stabilizer into inter‐sheet galleries. Application to the most concentrated graphene exfoliation data available supports these assumptions and provides insight for practical treatment regimens.
Aging of polyamide 11. Part 2: General multiscale model of the hydrolytic degradation applied to predict the morphology evolution
Authors: Mazan Tobiasz , Jørgensen Jens Kjær , Echtermeyer Andreas
Published: July 2015

Accelerated aging tests are the conventional way to evaluate long‐term degradation of polymers, in particular for offshore flexible risers. In this article, a multiscale model has been developed combining diffusion, chemical kinetic reactions, structure–property relationships, and composite models to provide faster and less labor extensive property predictions. A general methodology is presented and applied to predict the density and crystallinity evolution. Results are compared with experimental ageing of polyamide 11 in deoxygenated water at 120 °C. For both density and degree of crystallinity the modeled trend is close to the experimental test results. Accurate prediction of the morphological parameters during degradation allows extension of the multiscale model for the prediction of mechanical properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42630.
Thermoplastic polyurethane synthesis with modified montmorillonite prepared by torque rheometry: Investigation of morphological, thermal, chemical, and physical properties
Authors: Ornaghi Felipe Gustavo , Pistor Vinicios , de Oliveira Ricardo Vinícius Boff
Published: July 2015

In this study, samples of thermoplastic polyurethane (TPU) were synthesized by reactive processing in an instrumented batch mixer with 0, 1, 2, 5, and 10 wt % of organophilic montmorillonite (OMMT) clay. Fourier transform infrared spectroscopy confirmed the obtainment of TPU. Transmission electron microscopy showed several types of clay dispersion. Analysis by X‐ray diffraction revealed modifications in the TPU microstructure, a reduction in the degree of crystallinity, and an increase in the crystal size. Dynamic mechanical properties showed that the incorporation of OMMT has a strong influence on the storage and loss moduli obtained for the TPU matrix. The incorporation of OMMT also altered the crystallization and thermal stability of the TPU. With the use of the Flynn–Wall–Ozawa method it was observed that the nanoclay had a higher apparent activation energy. The results obtained applying the Criado method indicated that the solid state reaction is essentially controlled by geometric contraction, random nucleation with one nucleus for each individual particle and diffusion. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42640.
Design and Comparison Base Analysis of Adaptive Estimator for Completely Unknown Linear Systems in the Presence of OE Noise and Constant Input Time Delay
Authors: Tutsoy Onder
Published: July 2015

In this paper, an adaptive estimator (AE) is introduced to learn the approximate Q‐function and control policy by only using the noisy states and control signals of the unknown linear, discrete time systems having constant input time delay. The system measurements are uncertain owing to output error (OE)‐type noise acting randomly on the system measurements. Therefore, this research differs from the designed AE in the literature since previous research ignores the role of the external random disturbances on AE‐based learning. In order to compare the AE‐based learning results with traditional system identification (SI) approaches, a modified version of the OE model structure for unstable systems is reviewed and parameters of a second‐order unstable system with constant input time delay are identified. The simulation results demonstrate that the designed AE efficiently minimizes the stochastic cost function and the temporal difference error by learning the approximate solution for the Hamilton‐Jacobi‐Bellman (HJB) equation. It is noted that the error in the Q‐function obtained with the AE is slightly larger than the Q‐function attained with the identified OE parameters. However, as the noise standard deviation increases, the error in the AE‐based learning results reduces whereas the error in the OE‐based learning increases. This indicates that even though the added random noise deteriorates the performance of the OE predictor, it improves the learning efficiency of the AE since it acts like exploration noise.
A novel approach to safety stock management in a coordinated supply chain with controllable lead time using present value
Authors: Braglia Marcello , Castellano Davide , Frosolini Marco
Published: July 2015

This paper considers the management of safety stock in a coordinated single‐vendor single‐buyer supply chain under continuous review and Gaussian lead‐time demand. The lead time is supposed controllable, and shortages are not allowed. We follow the present value criterion by considering both inflation and time value of money. Our aim is to present a novel approach to optimizing the safety stock in such system. Under the conditions considered, the safety stock is typically determined according to the value assigned to the safety factor, which is thus treated as a parameter of the model, and not as a decision variable. In this paper, we take a different perspective by putting the order quantity and the safety factor in functional dependence through the adoption of a specific parameter. More precisely, we express the service level as a function of the number of admissible stockouts per time unit and the order quantity. This allows optimizing the safety stock taking into account the constraint on the number of admissible stockouts per time unit. We present both exact and approximated minimization algorithms. Numerical examples are finally shown to illustrate the effectiveness of the approximation algorithm, and to investigate the sensitivity of the model with respect to variations in some fundamental parameters. Copyright © 2015 John Wiley & Sons, Ltd.
Heme oxygenase‐1 promoter polymorphisms and risk of spina bifida
Authors: Fujioka Kazumichi , Yang Wei , Wallenstein Matthew B. , Zhao Hui , Wong Ronald J. , Stevenson David K. , Shaw Gary M.
Published: July 2015

Background

Spina bifida is the most common form of neural tube defects (NTDs). Etiologies of NTDs are multifactorial, and oxidative stress is believed to play a key role in NTD development. Heme oxygenase (HO), the rate‐limiting enzyme in heme degradation, has multiple protective properties including mediating antioxidant processes, making it an ideal candidate for study. The inducible HO isoform (HO‐1) has two functional genetic polymorphisms: (GT)n dinucleotide repeats and A(‐413)T SNP (rs2071746), both of which can affect its promoter activity. However, no study has investigated a possible association between HO‐1 genetic polymorphisms and risk of NTDs. Methods: This case‐control study included 152 spina bifida cases (all myelomeningoceles) and 148 nonmalformed controls obtained from the California Birth Defects Monitoring Program reflecting births during 1990 to 1999. Genetic polymorphisms were determined by polymerase chain reaction and amplified fragment length polymorphisms/restriction fragment length polymorphisms using genomic DNA extracted from archived newborn blood spots. Genotype and haplotype frequencies of two HO‐1 promoter polymorphisms between cases and controls were compared. Results: For (GT)n dinucleotide repeat lengths and the A(‐413)T SNP, no significant differences in allele frequencies or genotypes were found. Linkage disequilibrium was observed between the HO‐1 polymorphisms (D′: 0.833); however, haplotype analyses did not show increased risk of spina bifida overall or by race/ethnicity. Conclusion: Although, an association was not found between HO‐1 polymorphisms and risk of spina bifida, we speculate that the combined effect of low HO‐1 expression and exposures to known environmental oxidative stressors (low folate status or diabetes), may overwhelm antioxidant defenses and increase risk of NTDs and warrants further study. Birth Defects Research (Part A) 103:741–746, 2015. © 2015 Wiley Periodicals, Inc.
Interior decoration: Adapting multiwell plates for high throughput mechanobiology
Authors: Gilbert Hamish T. J. , Swift Joe
Published: July 2015

In this issue of Biotechnology Journal, Harkness et al. [1] demonstrate a technology that combines patterned substrates, for the purpose of controlling cell geometry, with multi‐well plate layouts to allow a high‐throughput analysis of the inputs that affect cell behavior.
Rapid metabolic analysis of Rhodococcus opacus PD630 via parallel 13C‐metabolite fingerprinting
Authors: Hollinshead Whitney D. , Henson William R. , Abernathy Mary , Moon Tae Seok , Tang Yinjie J.
Published: July 2015

For rapid analysis of microbial metabolisms,13C‐fingerprinting employs a set of tracers to generate unique labeling patterns in key amino acids that can highlight active pathways. In contrast to rigorous 13C‐metabolic flux analysis (13C‐MFA), this method aims to provide metabolic insights without expensive flux measurements. Using13C‐fingerprinting, we investigated the metabolic pathways in Rhodococcus opacus PD630, a promising biocatalyst for the conversion of lignocellulosic feedstocks into value‐added chemicals. Specifically, seven metabolic insights were gathered as follows: (1) glucose metabolism mainly via the Entner–Doudoroff (ED) pathway; (2) lack of glucose catabolite repression during phenol co‐utilization; (3) simultaneous operation of gluconeogenesis and the ED pathway for the co‐metabolism of glucose and phenol; (4) an active glyoxylate shunt in acetate‐fed culture; (5) high flux through anaplerotic pathways (e.g., malic enzyme and phosphoenolpyruvate carboxylase); (6) presence of alternative glycine synthesis pathway via glycine dehydrogenase; and (7) utilization of preferred exogenous amino acids (e.g., phenylalanine). Additionally, a13C‐fingerprinting kit was developed for studying the central metabolism of non‐model microbial species. This low‐cost kit can be used to characterize microbial metabolisms and facilitate the design‐build‐test‐learn cycle during the development of microbial cell factories. Biotechnol. Bioeng. 2016;113: 91–100. © 2015 Wiley Periodicals, Inc.
Engineering the iron‐oxidizing chemolithoautotroph Acidithiobacillus ferrooxidans for biochemical production
Authors: Kernan Timothy , Majumdar Sudipta , Li Xiaozheng , Guan Jingyang , West Alan C. , Banta Scott
Published: July 2015

There is growing interest in developing non‐photosynthetic routes for the conversion of CO2 to fuels and chemicals. One underexplored approach is the transfer of energy to the metabolism of genetically modified chemolithoautotrophic bacteria. Acidithiobacillus ferrooxidans is an obligate chemolithoautotroph that derives its metabolic energy from the oxidation of iron or sulfur at low pH. Two heterologous biosynthetic pathways have been expressed in A. ferrooxidans to produce either isobutyric acid or heptadecane from CO2 and the oxidation of Fe2+. A sevenfold improvement in productivity of isobutyric acid was obtained through improved media formulations in batch cultures. Steady‐state efficiencies were lower in continuous cultures, likely due to ferric inhibition. If coupled to solar panels, the photon‐to‐fuel efficiency of this proof‐of‐principle process approaches estimates for agriculture‐derived biofuels. These efforts lay the foundation for the utilization of this organism in the exploitation of electrical energy for biochemical synthesis. Biotechnol. Bioeng. 2016;113: 189–197. © 2015 Wiley Periodicals, Inc.
Nature of foulants and fouling mechanism in the Protein A MabSelect resin cycled in a monoclonal antibody purification process
Authors: Zhang Shaojie , Daniels William , Salm Jeffrey , Glynn Judy , Martin Joseph , Gallo Christopher , Godavarti Ranga , Carta Giorgio
Published: July 2015

The composition and origin of foulants and their spatial distribution within the particles of the Protein A MabSelect resin cycled in a mAb purification process are determined using electron and confocal microscopy techniques with gold and fluorescently labeled protein probes that associate with the foulants. The results show that the foulants are primarily related to the mAb product, are heterogeneously dispersed both on the outer surface and in the interior of the resin beads, and accumulate only when loading the conditioned CHO cell culture supernatant. Insignificant accumulation is seen if the process is run with purified mAb or with the null cell culture supernatant. When bound to the Protein A ligand, the mAb responsible for the observed fouling behavior is shown to associate with BSA and α‐lactalbumin. This property is exploited using labeled versions of these lipophilic proteins to assess the effectiveness of improved resin cleaning processes and to elucidate the fouling mechanism. Resin fouling for this mAb appears to be consistent with the occurrence of conformational changes that occur upon binding, which, in turn, facilitate association of lipophilic proteins with the mAb. Upon desorption at low pH, these destabilized mAb complexes are deposited on and within the resin growing with each cycle and eventually leading to significant degradation of process performance. Biotechnol. Bioeng. 2016;113: 141–149. © 2015 Wiley Periodicals, Inc.
Preventive brain radio‐chemotherapy alters plasticity associated metabolite profile in the hippocampus but seems to not affect spatial memory in young leukemia patients
Authors: Brandt Moritz D. , Brandt Kalina , Werner Annett , Schönfeld Robby , Loewenbrück Kai , Donix Markus , Schaich Markus , Bornhäuser Martin , von Kummer Rüdiger , Leplow Bernd , Storch Alexander
Published: July 2015

Background

Neuronal plasticity leading to evolving reorganization of the neuronal network during entire lifespan plays an important role for brain function especially memory performance. Adult neurogenesis occurring in the dentate gyrus of the hippocampus represents the maximal way of network reorganization. Brain radio‐chemotherapy strongly inhibits adult hippocampal neurogenesis in mice leading to impaired spatial memory.

Methods

To elucidate the effects of CNS radio‐chemotherapy on hippocampal plasticity and function in humans, we performed a longitudinal pilot study using 3T proton magnetic resonance spectroscopy (1H‐MRS) and virtual water‐maze‐tests in 10 de‐novo patients with acute lymphoblastic leukemia undergoing preventive whole brain radio‐chemotherapy. Patients were examined before, during and after treatment.

Results

CNS radio‐chemotherapy did neither affect recall performance in probe trails nor flexible (reversal) relearning of a new target position over a time frame of 10 weeks measured by longitudinal virtual water‐maze‐testing, but provoked hippocampus‐specific decrease in choline as a metabolite associated with cellular plasticity in 1H‐MRS.

Conclusion

Albeit this pilot study needs to be followed up to definitely resolve the question about the functional role of adult human neurogenesis, the presented data suggest that 1H‐MRS allows the detection of neurogenesis‐associated plasticity in the human brain.
Knockdown of NF‐κB p65 subunit expression suppresses growth of nude mouse lung tumour cell xenografts by inhibition of Bcl‐2 apoptotic pathway
Authors: Qu Yun , Qu Bo , Wang Xiaofang , Wu Rong , Zhang Xiaoye
Published: July 2015

Nuclear factor‐kappaB (NF‐κB) is an important transcriptional factor and regulates a variety of pathophysiologic process involved in cell survival and death. This study aimed to assess the effects of NF‐κB p65 subunit knockdown in suppression of nude mouse lung tumour cell xenografts and understands the underlying molecular events. A nude mouse Lewis lung carcinoma cell xenograft model was established, and the mice were intraperitoneally injected with NF‐κB p65 small interfering RNA (siRNA) and sacrificed after 2weeks of tumour cell injection. Tumour xenografts were harvested for terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, Western blot and quantitative reverse transcription‐polymerase chain reaction analyses. Results found that compared to the phosphate‐buffered saline (PBS)‐treated or the negative control (NC) siRNA‐treated mice tumour xenograft weight and volume were significantly decreased in the NF‐κB p65 siRNA‐treated mice. The TUNEL positive (apoptosis) cells in xenograft sections were 45 ± 5 in PBS and 38 ± 3 in NC siRNA but increased to 271 ± 11 in p65 siRNA‐treated mice. Compared to the PBS or the NC mice, levels of Bcl‐2 mRNA and protein in tumour xenografts were significantly downregulated in p65 siRNA‐treated mice. Knockdown of NF‐κB p65 subunit expression can significantly inhibit the growth of nude mouse Lewis tumour cell xenografts by inducing tumour cell apoptosis and downregulating pro‐apoptotic protein Bcl‐2 expression. Targeting NF‐κB p65 subunit expression as a potential therapeutic strategy needs further evaluation in treating human lung cancer. Copyright © 2015 John Wiley & Sons, Ltd.
Inhibition of bleomycin‐induced pulmonary fibrosis by bone marrow‐derived mesenchymal stem cells might be mediated by decreasing MMP9, TIMP‐1, INF‐γ and TGF‐β
Authors: Yu Shi‐huan , Liu Li‐jie , Lv Bin , Che Chun‐li , Fan Da‐ping , Wang Li‐feng , Zhang Yi‐mei
Published: July 2015

The study was aimed to investigate the mechanism and administration timing of bone marrow‐derived mesenchymal stem cells (BMSCs) in bleomycin (BLM)‐induced pulmonary fibrosis mice. Thirty‐six mice were divided into six groups: control group (saline), model group (intratracheal administration of BLM), day 1, day 3 and day 6 BMSCs treatment groups and hormone group (hydrocortisone after BLM treatment). BMSCs treatment groups received BMSCs at day 1, 3 or 6 following BLM treatment, respectively. Haematoxylin and eosin and Masson staining were conducted to measure lung injury and fibrosis, respectively. Matrix metalloproteinase (MMP9), tissue inhibitor of metalloproteinase‐1 (TIMP‐1), γ‐interferon (INF‐γ) and transforming growth factor β1 (TGF‐β) were detected in both lung tissue and serum. Histologically, the model group had pronounced lung injury, increased inflammatory cells and collagenous fibres and up‐regulated MMP9, TIMP‐1, INF‐γ and TGF‐β compared with control group. The histological appearance of lung inflammation and fibrosis and elevation of these parameters were inhibited in BMSCs treatment groups, among which, day 3 and day 6 treatment groups had less inflammatory cells and collagenous fibres than day 1 treatment group. BMSCs might suppress lung fibrosis and inflammation through down‐regulating MMP9, TIMP‐1, INF‐γ and TGF‐β. Delayed BMSCs treatment might exhibit a better therapeutic effect. Copyright © 2015 John Wiley & Sons, Ltd.

Highlights are as follows:

BMSCs repair lung injury induced by BLM.

BMSCs attenuate pulmonary fibrosis induced by BLM.

BMSCs transplantation down‐regulates MMP9 and TIMP‐1.

BMSCs transplantation down‐regulates INF‐γ and TGF‐β.

Delayed transplantation timing of BMSCs might exhibit a better effect against BLM.
Proinflammatory interleukins' production by adipose tissue‐derived mesenchymal stromal cells: the impact of cell culture conditions and cell‐to‐cell interaction
Authors: Andreeva Elena , Andrianova Irina , Rylova Julia , Gornostaeva Aleksandra , Bobyleva Polina , Buravkova Ludmila
Published: July 2015

The impact of culture conditions and interaction with activated peripheral blood mononuclear cells on the interleukin (IL) gene expression profile and proinflammatory IL‐6 and IL‐8 production by adipose‐derived stromal cells (ASCs) was investigated. A microarray analysis revealed a wide range of IL genes either under standard (20%) or hypoxic (5%) O2 concentrations, some highly up‐regulated at hypoxia. IL‐6 and IL‐8 production was inversely dependent on cell culture density. In early (first–third) passages, IL‐6 and IL‐8 concentration was higher at 20% O2 and in late (8th‐12th) passages under 5% O2. Interaction between ASCs and mononuclear cells in indirect setting was accompanied with a significant decrease of IL‐6 and did not result in the elevation of IL‐8 concentration.

Thereby, the production of proinflammatory interleukins (IL‐6 and IL‐8) may be affected by the ASC intrinsic features (density in culture, and duration of expansion), as well as by microenvironmental factors, such as hypoxia and the presence of blood‐borne cells. These data are important for elucidating ASC paracrine activity regulation in vitro. They would also be on demand for optimisation of the cell therapy protocols, based on the application of ASC biologically active substances. Copyright © 2015 John Wiley & Sons, Ltd.

SIGNIFICANCE PARAGRAPH

Ex vivo expansion is widely used for increasing the number of adipose‐derived stromal cells (ASCs) and improving of their quality. The present study was designed to elucidate the particular factors influencing the interleukin production in ASCs. The presented data specified the parameters (i.e. cell density, duration of cultivation, hypoxia, etc.) that should be taken in mind when ASCs are intended to be used in protocols implying their paracrine activity. These data would be of considerable interest for researchers and clinicians working in the biomedical science.
Operando Tracking of Electrochemical Activity in Solid Oxide Electrochemical Cells by using Near‐Infrared Imaging
Authors: Geller Aaron , Pomfret Michael , Steinhurst Daniel A. , Yu Yi , Liu Zhi , Owrutsky Jeffrey C. , Eichhorn Bryan W.
Published: July 2015

Near‐infrared (NIR) imaging is used in conjunction with near ambient pressure X‐ray photoelectron spectroscopy (APXPS) to study chemical and electrochemical redox processes on a ceria‐based solid oxide electrochemical cell (SOC). Electrochemical water electrolysis tests conducted in ambient operating conditions on standard SOCs show that NIR imaging can be used to spatially resolve the electrochemically active regions associated with an accumulation of Ce3+. These effective emissivity changes are attributed to changes in optical properties (e.g. the index of refraction) of ceria that occur upon reduction. These data correlate strongly with APXPS measurements, simultaneously supporting the model (near ambient conditions and single‐sided cell setup required by APXPS experiments) and the ability to elucidate mechanistic details on an operating SOC using an inexpensive, convenient NIR imaging technique.
Manifold preprocessing for laser‐induced breakdown spectroscopy under Mars conditions
Authors: Boucher Thomas , Carey CJ , Dyar Melinda Darby , Mahadevan Sridhar , Clegg Samuel , Wiens Roger
Published: July 2015

Laser‐induced breakdown spectroscopy (LIBS) is currently being used onboard the Mars Science Laboratory rover Curiosity to predict elemental abundances in dust, rocks, and soils using a partial least squares regression model developed by the ChemCam team. Accuracy of that model is constrained by the number of samples needed in the calibration, which grows exponentially with the dimensionality of the data, a phenomenon known as the curse of dimensionality. LIBS data are very high dimensional, and the number of ground‐truth samples (i.e., standards) recorded with the ChemCam before departing for Mars was small compared with the dimensionality, so strategies to optimize prediction accuracy are needed. In this study, we first use an existing machine learning algorithm, locally linear embedding (LLE), to combat the curse of dimensionality by embedding the data into a low‐dimensional manifold subspace before regressing. LLE constructs its embedding by maintaining local neighborhood distances and discarding large global geodesic distances between samples, in an attempt to preserve the underlying geometric structure of the data. We also introduce a novel supervised version, LLE for regression (LLER), which takes into account the known chemical composition of the training data when embedding. LLER is shown to outperform traditional LLE when predicting most major elements. We show the effectiveness of both algorithms using three different LIBS datasets recorded under Mars‐like conditions. Copyright © 2015 John Wiley & Sons, Ltd.
Selective Single‐Step Separation of a Mixture of Three Metal Ions by a Triphasic Ionic‐Liquid–Water–Ionic‐Liquid Solvent Extraction System
Authors: Vander Hoogerstraete Tom , Blockx Jonas , De Coster Hendrik , Binnemans Koen
Published: July 2015

In a conventional solvent extraction system, metal ions are distributed between two immiscible phases, typically an aqueous and an organic phase. In this paper, the proof‐of‐principle is given for the distribution of metal ions between three immiscible phases, two ionic liquid phases with an aqueous phase in between them. Three‐liquid‐phase solvent extraction allows separation of a mixture of three metal ions in a single step, whereas at least two steps are required to separate three metals in the case of two‐liquid‐phase solvent extraction. In the triphasic system, the lower organic phase is comprised of the ionic liquid betainium‐ or choline bis(trifluoromethylsulfonyl)imide, whereas the upper organic phase is comprised of the ionic liquid trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide. The triphasic system was used for the separation of a mixture of tin(II), yttrium(III), and scandium(III) ions.
Supramolecular Ionic‐Liquid Gels with High Ionic Conductivity
Authors: Maršavelski Aleksandra , Smrečki Vilko , Vianello Robert , Žinić Mladen , Moguš‐Milanković Andrea , Šantić Ana
Published: July 2015

Supramolecular ionogels were prepared by the gelation of room‐temperature ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF4]) with (S,S)‐bis(leucinol)oxalamide. Remarkably, the ionic conductivity of solutions and ionogels with low gelator concentrations is higher than that of neat [BMIm][BF4]. On the basis of molecular dynamics simulations and quantum mechanical calculations, the origin of this phenomenon is attributed to the higher affinity of gelator molecules towards [BF4]− ions, which reduces the electrostatic attraction between [BMIm]+ and [BF4]− and thus increases their mobility. With increasing gelator concentration, the ionic conductivity decreases due to the formation of a denser gelator matrix, which hinders the pathways for ionic transport. However, even for very dense ionogels, this decrease is less than one order of magnitude relative to neat [BMIm][BF4], and thus they can be classified as highly conductive materials with strong potential for application as functional electrolytes.
A Unified Strategy to 6–5–6–5–6‐Membered Epipolythiodiketopiperazines: Studies towards the Total Synthesis of Scabrosin Diacetate and Haematocin
Authors: Zipfel Hannes F. , Carreira Erick M.
Published: July 2015

The family of epipolythiodiketopiperazine (ETP) natural products consists of over 200 members possessing a wide diversity of structures and biological activity. Recently, the subgroup of 6–5–6–5–6‐membered ETPs has gained substantial attention, which has resulted in several total syntheses. Despite all the efforts that have been invested into accessing these complex structures, no synthesis of scabrosin diacetate (1 a) and its related esters has been reported. Herein, our attempts towards scabrosin diacetate (1 a) and haematocin (3) starting from diketopiperazine 12 a as a late‐stage intermediate are presented. Diketopiperazine 12 a can be conveniently accessed in multigram quantities from aldehyde 18 and diketopiperazine 21 and was envisioned to serve as a general platform for the synthesis of 6–5–6–5–6‐membered ETPs.
Hydrogels Triggered by Metal Ions as Precursors of Network CuS for DNA Detection
Authors: Wang Haiqiao , Song Shasha , Hao Jingcheng , Song Aixin
Published: July 2015

The gelation behavior of lithocholate (LC−) with different metal ions in water was investigated. The microstructures of hydrogels were determined to be three‐dimensional (3D) networks of fibrous aggregates. The formation of fibrils was speculated to be mainly driven by the coordination between carboxylate of LC− and metal ions, accompanied by the assistance of noncovalent interactions such as electrostatic and hydrophobic interactions. The hydrogels, which can maintain the mechanical strength at higher temperature, exhibit thermal stability. Their gelation capability was enhanced with the increase in acidity. The hydrogels of LC− and Cu2+ mixtures served as the precursors for producing network nanostructures of CuS nanoparticles. These new CuS networks exhibit high fluorescence quenching ability and can act as an effective fluorescent sensing platform for ssDNA detection.
Design of a Heterogeneous Catalyst Based on Cellulose Nanocrystals for Cyclopropanation: Synthesis and Solid‐State NMR Characterization
Authors: Liu Jiquan , Plog Andreas , Groszewicz Pedro , Zhao Li , Xu Yeping , Breitzke Hergen , Stark Annegret , Hoffmann Rudolf , Gutmann Torsten , Zhang Kai , Buntkowsky Gerd
Published: July 2015

Heterogeneous dirhodium(II) catalysts based on environmentally benign and biocompatible cellulose nanocrystals (CNC‐Rh2) as support material were obtained by ligand exchange between carboxyl groups on the CNC surface and Rh2(OOCCF3)4, as was confirmed by solid‐state 19F and 13C NMR spectroscopy. On average, two CF3COO− groups are replaced during ligand exchange, which is consistent with quantitative analysis by a combination of 19F NMR spectroscopy and thermogravimetry. CNC‐Rh2 catalysts performed well in a model cyclopropanation reaction, in spite of the low dirhodium(II) content on the CNC surface (0.23 mmol g−1). The immobilization through covalent bonding combined with the separate locations of binding positions and active sites of CNC‐Rh2 guarantees a high stability against leaching and allows the recovery and reuse of the catalyst during the cyclopropanation reaction.
Phenylboronic Acid Appended Pyrene‐Based Low‐Molecular‐Weight Injectable Hydrogel: Glucose‐Stimulated Insulin Release
Authors: Mandal Deep , Mandal Subhra Kanti , Ghosh Moumita , Das Prasanta Kumar
Published: July 2015

A pyrene‐containing phenylboronic acid (PBA) functionalized low‐molecular‐weight hydrogelator was synthesized with the aim to develop glucose‐sensitive insulin release. The gelator showed the solvent imbibing ability in aqueous buffer solutions of pH values, ranging from 8–12, whereas the sodium salt of the gelator formed a hydrogel at physiological pH 7.4 with a minimum gelation concentration (MGC) of 5 mg mL−1. The aggregation behavior of this thermoreversible hydrogel was studied by using microscopic and spectroscopic techniques, including transmission electron microscopy, FTIR, UV/Vis, luminescence, and CD spectroscopy. These investigations revealed that hydrogen bonding, π–π stacking, and van der Waals interactions are the key factors for the self‐assembled gelation. The diol‐sensitive PBA part and the pyrene unit in the gelator were judiciously used in fluorimetric sensing of minute amounts of glucose at physiological pH. The morphological change of the gel due to addition of glucose was investigated by scanning electron microscopy, which denoted the glucose‐responsive swelling of the hydrogel. A rheological study indicated the loss of the rigidity of the native gel in the presence of glucose. Hence, the glucose‐induced swelling of the hydrogel was exploited in the controlled release of insulin from the hydrogel. The insulin‐loaded hydrogel showed thixotropic self‐recovery property, which hoisted it as an injectable soft composite. Encouragingly, the gelator was found to be compatible with HeLa cells.
Color‐Controlled Ag Nanoparticles and Nanorods within Confined Mesopores: Microwave‐Assisted Rapid Synthesis and Application in Plasmonic Catalysis under Visible‐Light Irradiation
Authors: Mori Kohsuke , Verma Priyanka , Hayashi Ryunosuke , Fuku Kojirou , Yamashita Hiromi
Published: July 2015

Color‐controlled spherical Ag nanoparticles (NPs) and nanorods, with features that originate from their particle sizes and morphologies, can be synthesized within the mesoporous structure of SBA‐15 by the rapid and uniform microwave (MW)‐assisted alcohol reduction method in the absence or presence of surface‐modifying organic ligands. The obtained several Ag catalysts exhibit different catalytic activities in the H2 production from ammonia borane (NH3BH3, AB) under dark conditions, and higher catalytic activity is observed by smaller yellow Ag NPs in spherical form. The catalytic activities are specifically enhanced under the light irradiation for all Ag catalysts. In particular, under light irradiation, the blue Ag nanorod shows a maximum enhancement of more than twice that observed in the dark. It should be noted that the order of increasing catalytic performance is in close agreement with the order of absorption intensity owing to the Ag localized surface plasmon resonance (LSPR) at irradiation light wavelength. Upon consideration of infrared thermal effect, wavelength dependence on catalytic activity, and effect of radical scavengers, it can be concluded that the dehydrogenation of AB is promoted by change of charge density of the Ag NP surface derived from LSPR. The LSPR‐enhanced catalytic activity can be further realized in the tandem reaction consisting of dehydrogenation of AB and hydrogenation of 4‐nitrophenol, in which a similar tendency in the enhancement of catalytic activity is observed.
Bifunctional Behavior of Unsaturated Intramolecular Phosphane–Borane Frustrated Lewis Pairs Derived from Uncatalyzed 1,4‐Hydrophosphination of a Dienylborane
Authors: Chen Guo‐Qiang , Kehr Gerald , Daniliuc Constantin G. , Wibbeling Birgit , Erker Gerhard
Published: July 2015

Three unsaturated C4‐bridged phospane/borane frustrated Lewis pairs (P/B FLPs) are prepared by uncatalyzed hydrophosphination of a dienylborane. The systems are bifunctional. Consequently, two examples undergo clean hydroboration reactions with HB(C6F5)2 to yield B/B/P systems. The 1,4‐P/B system (C6F5)2BCH2CHCMeCH2PMes2 reacts with benzaldehyde initially by allylborane addition, followed by internal P/B FLP addition to the pendant CC double bond, to yield a bicyclic product. The corresponding reaction of (C6F5)2BCH2CHCMeCH2PtBu2 stops at the allylborane/benzaldehyde addition product. The related system (C6F5)2BCH2CHCMeCH2PPh2 shows a similar bifunctional reaction pattern, whereby allylborane addition to benzaldehyde is combined with P/B addition to a second aldehyde equivalent to form the eight‐membered heterocyclic 1:2 addition product.
Structure Evolution and Associated Catalytic Properties of PtSn Bimetallic Nanoparticles
Authors: Rong Hongpan , Niu Zhiqiang , Zhao Yafan , Cheng Hao , Li Zhi , Ma Lei , Li Jun , Wei Shiqiang , Li Yadong
Published: July 2015

Bimetallic nanoparticles (NPs) often show new catalytic properties that are different from those of the parent metals. Carefully exploring the structures of bimetallic NPs is a prerequisite for understanding the structure‐associated properties. Herein, binary PtSn NPs with tunable composition are prepared in a controllable manner. X‐ray characterizations reveal that their structures evolve from SnO2−x‐patched PtSn alloys to SnO2−x‐patched Pt clusters when more tin is incorporated. An obvious composition‐dependent catalytic performance is observed for the hydrogenation of α,β‐unsaturated aldehydes: the selectivity to unsaturated alcohol increases substantially at high tin content, whereas the reaction rate follows a volcano shape. Furthermore, Pt sites are responsible for hydrogen dissociation, whereas oxygen vacancy (Ovac) sites, provided by SnO2−x, drastically enhance the adsorption of carbonyl group.
Hydroxymethylated Dioxobilins in Senescent Arabidopsis thaliana Leaves: Sign of a Puzzling Biosynthetic Intermezzo of Chlorophyll Breakdown
Authors: Süssenbacher Iris , Kreutz Christoph R. , Christ Bastien , Hörtensteiner Stefan , Kräutler Bernhard
Published: July 2015

1‐Formyl‐19‐oxobilin‐type tetrapyrroles are characteristic, abundant products of chlorophyll breakdown in senescent leaves. However, in some leaves, 1,19‐dioxobilin‐type chlorophyll catabolites (DCCs) lacking the formyl group accumulate instead. A P450 enzyme was identified in in vitro studies that removed the formyl group of a primary fluorescent chlorophyll catabolite (pFCC) and generated fluorescent DCCs. These DCCs are precursors of isomeric nonfluorescent DCCs (NDCCs). Here, we report a structural investigation of the NDCCs in senescent leaves of wild‐type Arabidopsis thaliana. Four new NDCCs were characterized, two of which carried a stereoselectively added hydroxymethyl group. Such formal DCC hydroxymethylations were previously found in DCCs in leaves of a mutant of A. thaliana. They are now indicated to be a feature of chlorophyll breakdown in A. thaliana, associated with the specific in vivo deformylation of pFCC en route to NDCCs.
Are Copper(I) Carbenes Capable Intermediates for Cyclopropanations? The Case for Ylide Intermediates
Authors: Aldajaei Jamal T. , Keeffe James R. , Swift Christopher A. , Gronert Scott
Published: July 2015

A novel approach is used to synthesize a stable, ligated copper(I) carbene in the gas phase that is capable of typical metal carbenoid chemistry. However, it is shown that copper(I) carbenes generally undergo rapid unimolecular rearrangements including insertions into copper‐ligand bonds and Wolff rearrangements. The results indicate that most copper(I) carbenes are inherently unstable and would not be viable intermediates in condensed‐phase applications; an alternative intermediate that is less prone to rearrangements is required. Computational data suggest that ylides formed by the complexation of the carbene with solvent or other weak nucleophiles are viable intermediates in the reactions of copper(I) carbenes.
Chemical Synthesis of a Glycopeptide Derived from Skp1 for Probing Protein Specific Glycosylation
Authors: Chinoy Zoeisha S. , Schafer Christopher M. , West Christopher M. , Boons Geert‐Jan
Published: July 2015

Skp1 is a cytoplasmic and nuclear protein, best known as an adaptor of the SCF family of E3‐ubiquitin ligases that label proteins for their degradation. Skp1 in Dictyostelium is posttranslationally modified on a specific hydroxyproline (Hyp) residue by a pentasaccharide, which consists of a Fucα1,2‐Galβ‐1,3‐GlcNAcα core, decorated with two α‐linked Gal residues. A glycopeptide derived form Skp1 was prepared to characterize the α‐galactosyltransferase (AgtA) that mediates the addition of the α‐Gal moieties, and to develop antibodies suitable for tracking the trisaccharide isoform of Skp1 in cells. A strategy was developed for the synthesis of the core trisaccharide‐Hyp based on the use of 2‐naphthylmethyl (Nap) ethers as permanent protecting groups to allow late stage installation of the Hyp moiety. Tuning of glycosyl donor and acceptor reactivities was critical for achieving high yields and anomeric selectivities of glycosylations. The trisaccharide‐Hyp moiety was employed for the preparation of the glycopeptide using microwave‐assisted solid phase peptide synthesis. Enzyme kinetic studies revealed that trisaccharide‐Hyp and trisaccharide‐peptide are poorly recognized by AgtA, indicating the importance of context provided by the native Skp1 protein for engagement with the active site. The trisaccharide‐peptide was a potent immunogen capable of generating a rabbit antiserum that was highly selective toward the trisaccharide isoform of full‐length Skp1.
Sequential Synthesis of 3 d–3 d, 3 d–4 d, and 3 d–5 d Hybrid Polyoxometalates and Application to the Electrocatalytic Oxygen Reduction Reactions
Authors: Rousseau Guillaume , Zhang Shuangshuang , Oms Olivier , Dolbecq Anne , Marrot Jérôme , Liu Rongji , Shang Xinke , Zhang Guangjin , Keita Bineta , Mialane Pierre
Published: July 2015

The Co7(AlePy)2 polyoxometalate, which encloses a {(PW9)2CoII7} core covalently bound to two free aminopyridine groups through bisphosphonate ligands (AlePy), has been isolated. It can be used as a precursor, allowing the synthesis of heterometallic hybrid compounds, as illustrated by the characterization of cobalt/zinc (Co7(AlePyZn)2), cobalt/palladium (Co7(AlePyPd)2), and cobalt/platinum (Co7(AlePyPt)2) species. A composite based on the water‐insoluble precious metal‐free Co7(AlePyZn)2 compound and the low‐cost carbon material Vulcan XC‐72 has been selected as a cathode material (Co7Zn/C) for oxygen reduction reaction studies. The electrocatalytic performances of the Co7Zn/C hybrids were assessed at neutral and basic pH, showing that Co7Zn/C exhibits high selectivity for the four‐electron reduction of O2. Moreover, its durability is superior to that of a commercial Pt/C catalyst with 20 % loading. Also, comparative studies performed in the presence of methanol have indicated that Co7Zn/C has a much better tolerance to the crossover effect than Pt/C. Altogether, these results indicate for the first time that, even in neutral media, polyoxometalate/carbon composites can represent low‐cost oxygen reduction catalysts that can function stably, for a long time, and with high performance.
Host–Guest‐Mediated DNA Templation of Polycationic Supramolecules for Hierarchical Nanocondensation and the Delivery of Gene Material
Authors: Gallego‐Yerga Laura , Blanco‐Fernández Laura , Urbiola Koldo , Carmona Thais , Marcelo Gema , Benito Juan M. , Mendicuti Francisco , Tros de Ilarduya Conchita , Ortiz Mellet Carmen , García Fernández José M.
Published: July 2015

Only a few examples of monodisperse molecular entities that can compact exogenous nucleic acids into nanocomplexes, protect the cargo from the biological environment, facilitate cell internalization, and promote safe transfection have been reported up to date. Although these species open new venues for fundamental studies on the structural requirements that govern the intervening processes and their application in nonviral gene‐vector design, the synthesis of these moieties generally requires a relatively sophisticated chemistry, which hampers further development in gene therapy. Herein, we report an original strategy for the reversible complexation and delivery of DNA based on the supramolecular preorganization of a β‐cyclodextrin‐scaffolded polycationic cluster facilitated by bisadamantane guests. The resulting gemini‐type, dual‐cluster supramolecules can then undergo DNA‐templated self‐assembly at neutral pH value by bridging parallel DNA oligonucleotide fragments. This hierarchical DNA condensation mechanism affords transfectious nanoparticles with buffering capabilities, thus facilitating endosomal escape following cell internalization. Protonation also destabilizes the supramolecular dimers and consequently the whole supramolecular edifice, thus assisting DNA release. Our advanced hypotheses are supported by isothermal titration calorimetry, NMR and circular dichroism spectroscopic analysis, gel electrophoresis, dynamic light scattering, TEM, molecular mechanics, molecular dynamics, and transfection studies conducted in vitro and in vivo.
Synthesis of New Phosphahelicene Scaffolds and Development of Gold(I)‐Catalyzed Enantioselective Allenene Cyclizations
Authors: Aillard Paul , Retailleau Pascal , Voituriez Arnaud , Marinetti Angela
Published: July 2015

This paper reports on the development of an efficient synthesis of enantiopure phospha[6]helicenes through a [2+2+2] alkyne cyclotrimerization reaction. The corresponding gold complexes proved to be highly efficient both in terms of catalytic activity and enantioselectivity in [2+2] and [4+2] cycloaddition reactions. Furthermore, in the presence of an external nucleophile, such as water or alcohols, the tandem cyclization/addition reactions take place in high yields and excellent diastereo‐ and enantioselectivities.
Metal‐Chelating N,N′‐Bis(4‐dimethylaminophenyl)acetamidinyl Radical: A New Chromophore for the Near‐Infrared Region
Authors: Ehret Fabian , Bubrin Martina , Záliš Stanislav , Kaim Wolfgang
Published: July 2015

A new non‐innocent ligand redox system, N,N′‐bis(4‐dimethylaminophenyl) substituted acetamidinato/acetamidinyl, has been designed and described by example of structurally and spectroscopically characterized ruthenium complexes. The hitherto unreported ligand is responsible for rather intense and narrow absorptions in the near‐infrared region of the one‐ and two‐electron oxidized forms. The spectroscopic, computational, and first structural characterization of an amidinyl radical complex adds to the list of established N‐based radical ligands.