bluuebunny/crossref_metadata_2025 huggingface dataset:
DABCOnium: Ein effizienter und Hochspannungs‐stabiler Singulett‐Sauerstoff‐Löscher für Metall‐O2‐Zellen
Authors: Petit Yann K. , Leypold Christian , Mahne Nika , Mourad Eléonore , Schafzahl Lukas , Slugovc Christian , Borisov Sergey M. , Freunberger Stefan A.
Published: March 2019

Singulett‐Sauerstoff (1O2) verursacht einen Großteil der parasitären Chemie während des Zellbetriebs von nichtwässrigen Alkalimetall‐O2‐Batterien und trägt auch zur Grenzflächenreaktivität von Übergangsmetalloxid‐Einlagerungsverbindungen bei. Wir führen DABCOnium, die monoalkylierte Form von 1,4‐Diazabicyclo[2.2.2]octan (DABCO), als effizienten 1O2‐Löscher mit ungewöhnlich hoher Oxidationsstabilität von ≈4.2 V vs. Li/Li+ ein. Bisher bekannte Löscher sind stark Lewis‐basische Amine mit zu geringer Oxidationsstabilität. DABCOnium ist eine ionische Flüssigkeit, nicht flüchtig, im Elektrolyten hochlöslich, stabil gegen Superoxid und Peroxid, und kompatibel mit Lithiummetall. Die elektrochemische Stabilität deckt den erforderlichen Bereich für Metall‐O2‐Batterien ab und reduziert die 1O2‐bedingte parasitäre Chemie erheblich, wie für die Li‐O2‐Zelle gezeigt wird.
Strain Release of Fused Pentagons in Fullerene Cages by Chemical Functionalization
Authors: Guan Runnan , Chen Muqing , Jin Fei , Yang Shangfeng
Published: March 2019

According to the isolated pentagon rule (IPR), for stable fullerenes, the 12 pentagons should be isolated from one another by hexagons, otherwise the fused pentagons will result in an increase in the local steric strain of the fullerene cage. However, the successful isolation of more than 100 endohedral and exohedral fullerenes containing fused pentagons over the past 20 years has shown that strain release of fused pentagons in fullerene cages is feasible. Herein, we present a general overview on fused‐pentagon‐containing (i.e. non‐IPR) fullerenes through an exhaustive review of all the types of fused‐pentagon‐containing fullerenes reported to date. We clarify how the strain of fused pentagons can be released in different manners, and provide an in‐depth understanding of the role of fused pentagons in the stability, electronic properties, and chemical reactivity of fullerene cages.
DABCOnium: An Efficient and High‐Voltage Stable Singlet Oxygen Quencher for Metal–O2 Cells
Authors: Petit Yann K. , Leypold Christian , Mahne Nika , Mourad Eléonore , Schafzahl Lukas , Slugovc Christian , Borisov Sergey M. , Freunberger Stefan A.
Published: March 2019

Singlet oxygen (1O2) causes a major fraction of the parasitic chemistry during the cycling of non‐aqueous alkali metal‐O2 batteries and also contributes to interfacial reactivity of transition‐metal oxide intercalation compounds. We introduce DABCOnium, the mono alkylated form of 1,4‐diazabicyclo[2.2.2]octane (DABCO), as an efficient 1O2 quencher with an unusually high oxidative stability of ca. 4.2 V vs. Li/Li+. Previous quenchers are strongly Lewis basic amines with too low oxidative stability. DABCOnium is an ionic liquid, non‐volatile, highly soluble in the electrolyte, stable against superoxide and peroxide, and compatible with lithium metal. The electrochemical stability covers the required range for metal–O2 batteries and greatly reduces 1O2 related parasitic chemistry as demonstrated for the Li–O2 cell.
Wound dressings: Current advances and future directions
Authors: Rezvani Ghomi Erfan , Khalili Shahla , Nouri Khorasani Saied , Esmaeely Neisiany Rasoul , Ramakrishna Seeram
Published: March 2019

Wound healing is a complicated and continuous process affected by several factors, which needs an appropriate surrounding to achieve accelerated healing. Wound healing process recruits three different phases: inflammation, proliferation, and maturation. Due to the different types of wounds, as well as the advancement in medical technology, various products have been developed to repair different skin lesions. Our objective is to investigate the advancement in wound dressings from traditional to the current methods of treatment. The article presents the characteristics of an ideal wound dressing, the requirements for the appropriate selection of different types of wounds, and a detailed classification of wound dressings. Animal origin, herbal origin, and synthetic dressings are firstly introduced and reviewed. Then, nonmedicated dressings including alginate, hydrogel, and hydrocolloid dressings, as well as medicated dressings are discussed. Finally, the developmental prospectives of the new generations of wound dressings for future researches are presented. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47738.
Testing Hopkins’ Bioclimatic Law with PhenoCam data
Authors: Richardson Andrew D. , Hufkens Koen , Li Xiaolu , Ault Toby R.
Published: March 2019

Premise of the Study

We investigated the spatial and temporal patterns of vegetation phenology with phenometrics derived from PhenoCam imagery. Specifically, we evaluated the Bioclimatic Law proposed by Hopkins, which relates phenological transitions to latitude, longitude, and elevation.

Methods

“Green‐up” and “green‐down” dates—representing the start and end of the annual cycles of vegetation activity—were estimated from measures of canopy greenness calculated from digital repeat photography. We used data from 65 deciduous broadleaf (DB) forest sites, 18 evergreen needleleaf (EN) forest sites, and 21 grassland (GR) sites.

Results

DB green‐up dates were well correlated with mean annual temperature and varied along spatial gradients consistent with the Bioclimatic Law. Interannual variation in DB phenology was most strongly associated with temperature anomalies during a relatively narrow window of time. EN phenology was not well correlated with either climatic factors or spatial gradients, but similar to DB phenology, interannual variation was most closely associated with temperature anomalies. For GR sites, mean annual precipitation explained most of the spatial variation in the duration of vegetation activity, whereas both temperature and precipitation anomalies explained interannual variation in phenology.

Discussion

PhenoCam data provide an objective and consistent means by which spatial and temporal patterns in vegetation phenology can be investigated.
The Preparation of Enantiopure [6]‐ and [7]Helicenes from Binaphthanol
Authors: Chen Shaojin , Ge Zhaohai , Jia Qiang , Wang Kun‐Peng , Gan Li‐Hua , Hu Zhi‐Qiang
Published: March 2019

A general and efficient synthetic methodology for the preparation of enantio‐ and diastereopure [6]‐, and [7]helicenes is developed. Commercially available chiral binaphthanols are utilized to generate the arylene‐vinylene precursors, which undergo helical folding via photocyclization to give enantio‐ and diastereopure [6]‐, and [7]helicenes. These optically pure helicenes could be easily obtained via silica gel column chromatography without the use of expensive HPLC or chiral resolution reagents. The configurations and structures of these helicenes are confirmed by CD spectra and X‐ray crystallographic analysis. This work provides a new method for preparation of enantiopure helicenes.
Semiparametric spatio‐temporal analysis of regional GDP growth with respect to renewable energy consumption levels
Authors: Formánek Tomáš
Published: March 2019

This article evaluates the impact of renewable energy consumption levels on GDP growth. Renewable energy sources may be significantly more costly as compared to classical (fossil) sources. Hence, high relative proportion of renewable energy has the potential of obstructing economic growth. On the other hand, in developed countries, renewable energy adoption processes are often subject to prominent state‐level incentives, administrative ingerence, and fiscal subsidies. For stratified and unbiased evaluation of the overall effect of renewables on GDP, this article applies a spatio‐temporal analysis of GDP growth at the regional NUTS2 level in a conveniently selected group of 11 spatially adjacent yet heterogeneous EU member states. As macroeconomic covariates are controlled for, along with spatial and temporal interdependencies, there is no sign of negative impact of renewable energy consumption on GDP growth. While the estimated overall effect is positive and statistically significant, its economic significance is small. Yet, given the data and economies considered, we may conclude that renewable energy consumption does not exert negative influence on economic growth rates.
Effectiveness of point‐of‐use/point‐of‐entry systems to remove per‐ and polyfluoroalkyl substances from drinking water
Authors: Patterson Craig , Burkhardt Jonathan , Schupp Donald , Krishnan E. Radha , Dyment Stephen , Merritt Steven , Zintek Lawrence , Kleinmaier Danielle
Published: March 2019

The contamination of groundwater sources with per‐ and polyfluoroalkyl substances (PFAS) in the United States is a widespread problem for the drinking water industry. Well water supplies in the municipalities of Fountain, Security, and Widefield, Colorado, contain perfluorooctanoic acid and perfluorooctane sulfonate levels greater than the U.S. Environmental Protection Agency (USEPA) health advisory level of 70 ng/L. The source of PFAS has been associated with aqueous film‐forming foam at Peterson Air Force Base. To assist property owners and limit the exposure of PFAS to residential drinking water systems, treatability studies were conducted by the USEPA on the PFAS removal effectiveness of commercially available point‐of‐use/point‐of‐entry units using reverse osmosis treatment and granular activated carbon adsorbents. Household water systems were tested with a test water containing the water quality characteristics and six PFAS contaminants found in Widefield aquifer region groundwater samples. This study also documents the installation, startup, and continuous/intermittent operation of the treatment systems.
Motivated by guilt and low felt trust: The impact of negotiators' anger expressions on the implementation of negotiated agreements
Authors: Campagna Rachel L. , Mislin Alexandra A. , Bottom William P.
Published: March 2019

Prior research has identified benefits from certain emotion tactics in negotiation, particularly expressing anger to achieve short‐term gains. We demonstrate that such tactics can be strategically problematic due to their impact on an actor's emotions and felt trust. Through five studies, we find that negotiators' use of anger tactics during a negotiation increased their feelings of guilt and reduced the extent to which they felt trusted by their counterpart following the negotiation. We found this guilt to be the result of their aggressive tone and how they treated their counterpart. The guilt and diminished felt trust in turn motivated negotiators to engage in greater cooperative behaviors during the deal implementation process that benefited their counterpart, even if doing so was costly to the negotiator. Our results demonstrate that negotiator guilt and felt trust resulting from anger tactics influence the dynamic relationship between negotiators and their counterparts. This in turn has strategic implications for negotiators, who attempt to mitigate these negative feelings during the crucial implementation phase of a negotiated agreement.
Assessment of dynamic functional connectivity in resting‐state fMRI using the sliding window technique
Authors: Savva Antonis D. , Mitsis Georgios D. , Matsopoulos George K.
Published: March 2019

Introduction

Recent studies related to assessing functional connectivity (FC) in resting‐state functional magnetic resonance imaging have revealed that the resulting connectivity patterns exhibit considerable fluctuations (dynamic FC [dFC]). A widely applied method for quantifying dFC is the sliding window technique. According to this method, the data are divided into segments with the same length (window size) and a correlation metric is employed to assess the connectivity within these segments, whereby the window size is often empirically chosen.

Methods

In this study, we rigorously investigate the assessment of dFC using the sliding window approach. Specifically, we perform a detailed comparison between different correlation metrics, including Pearson, Spearman and Kendall correlation, Pearson and Spearman partial correlation, Mutual Information (MI), Variation of Information (VI), Kullback–Leibler divergence, Multiplication of Temporal Derivatives and Inverse Covariance.

Results

Using test–retest datasets, we show that MI and VI yielded the most consistent results by achieving high reliability with respect to dFC estimates for different window sizes. Subsequent hypothesis testing, based on multivariate phase randomization surrogate data generation, allowed the identification of dynamic connections between the posterior cingulate cortex and regions in the frontal lobe and inferior parietal lobes, which were overall in agreement with previous studies.

Conclusions

In the case of MI and VI, a window size of at least 120 s was found to be necessary for detecting dFC for some of the previously identified dynamically connected regions.
RETRACTED: CUL4B promotes aggressive phenotypes of HNSCC via the activation of the Wnt/β‐catenin signaling pathway
Authors: Wang Yuanyuan , Yue Dan
Published: March 2019

Previous studies have revealed that CUL4B is overexpressed in various types of cancer and that its overexpression is related to the progression and metastasis of tumors. However, the biological functions of CUL4B in the progression of head and neck squamous cell carcinoma (HNSCC) are still not well understood. In the current study, we aimed to determine the changes in biological functions and molecular events that are related to CUL4B overexpression. Interestingly, our results showed that CUL4B is upregulated in HNSCC and that its upregulation is associated with poor survival and worse histological grade. Overexpression of CUL4B promoted cancer cell growth, invasion, and migration, as well as epithelial‐mesenchymal transition, whereas the loss of CUL4B abrogated these malignant phenotypes. Moreover, our mechanistic investigations suggest that the Wnt/β‐catenin signaling pathway was activated by CUL4B overexpression. Treatment with a Wnt/β‐catenin inhibitor decreased CUL4B‐induced migration and invasion, establishing a key role of Wnt/β‐catenin signaling in mediating the effects of CUL4B expression. Together, these results demonstrate a key contribution of CUL4B overexpression in the malignant behavior of HNSCC cells, at least in part through the stimulation of angiogenesis and the activation of the Wnt/β‐catenin signaling pathway.
SNP mutation‐related genes in breast cancer for monitoring and prognosis of patients: A study based on the TCGA database
Authors: Gao Chundi , Zhuang Jing , Zhou Chao , Li Huayao , Liu Cun , Liu Lijuan , Feng Fubin , Liu Ruijuan , Sun Changgang
Published: March 2019

Advances in cancer biology have allowed early diagnosis and more comprehensive treatment of breast cancer (BC). However, it remains the most common cause of cancer death in women worldwide because of its strong invasiveness and metastasis. In‐depth study of the molecular pathogenesis of BC and of relevant prognostic markers would improve the quality of life and prognosis of patients. In this study, bioinformatics analysis of SNP‐related data from BC patients provided in the TCGA database revealed that six mutant genes (NCOR1, GATA3, CDH1, ATM, AKT1, and PTEN) were significantly associated with the corresponding expression levels of the proteins. The proteins were involved in multiple pathways related to the development of cancer, including the PI3K‐Akt signaling pathway, pertinent microRNAs, and the MAPK signaling pathway. In addition, overall survival and recurrence‐free survival analysis revealed the close associations of the expression of GATA3, NCOR1, CDH1, and ATM with survival of BC patients. Therefore, detecting these gene mutations and exploring their corresponding expression could be valuable in predicting the prognosis of patients. The results of the high‐throughput data mining provide important fundamental bioinformatics information and a relevant theoretical basis for further exploring the molecular pathogenesis of BC and assessing the prognosis of patients.
Lin28a expression protects against streptozotocin‐induced β‐cell destruction and prevents diabetes in mice
Authors: Sung Yonghun , Jeong Jain , Kang Ri jin , Choi Minjee , Park Song , Kwon Wookbong , Lee Jinhee , Jang Soyoung , Park Si Jun , Kim Sung‐Hyun , Yi Junkoo , Choi Seong‐Kyoon , Lee Mee‐Hyun , Liu Kangdong , Dong Zigang , Ryoo Zae Young , Kim Myoung Ok
Published: March 2019

Lin28, which is highly expressed during embryogenesis, has been shown to play an important role in cell growth and embryonic development. Meanwhile, Lin28 represses let‐7 miRNA biogenesis and block pre‐let‐7 processing in the cytoplasm. The let‐7 family of miRNAs is known to repress oncogenesis and cell cycle progression by targeting oncogenic genes and signalling pathways. Consequently, Lin28 acts as an oncogene by upregulating let‐7 targets through the repression of let‐7 biogenesis. A recent genome‐wide association study (GWAS) showed that many genes related to Type 2 diabetes (T2D) are also oncogenes or cell cycle regulators. The role of Lin28 in mouse growth and glucose metabolism in metabolic‐related tissues has also been studied. In these studies, whole‐body Lin28 overexpression was found to promote glucose utilization and prevent weight gain by inhibiting let‐7 biogenesis. Furthermore, Lin28 has been found to directly stimulate skeletal myogenesis and cell growth. Therefore, we determined whether similar effects mediated by Lin28a, which is essential for cell growth and proliferation, may also apply to pancreatic ß‐cells. We found that overexpression of Lin28a protects pancreatic β‐cells from streptozotocin (STZ)‐induced β‐cell destruction in vitro and in vivo. Furthermore, Lin28a‐overexpressing transgenic (Tg) mice had higher insulin secretion in the presence of glucose than in control mice. Our findings suggest that the Lin28/let‐7 axis is an important regulator of pancreatic β‐cell functions and that precise modulation of this axis may be helpful in treating metabolic diseases such as diabetes.

Significance of the study

We demonstrate that Lin28a prevents pancreatic β‐cell death against streptozotocin (STZ)‐induced β‐cell destruction in vitro and in vivo. Furthermore, Lin28a promotes cell survival and proliferation by activating the PI3K‐Akt signalling pathway, which may be dependent on let‐7 regulation. Taken together, our results imply that the Lin28a/let‐7 axis is an important regulator of pancreatic β‐cell functions and that precise modulation of this axis may be helpful in treating metabolic diseases such as diabetes.
Highly Efficient Rh‐catalysts Immobilised by π‐π Stacking for the Asymmetric Hydroformylation of Norbornene under Continuous Flow Conditions
Authors: Cunillera Anton , Blanco Carolina , Gual Aitor , Marinkovic Jakob Maximilian , Garcia‐Suarez Eduardo J. , Riisager Anders , Claver Carmen , Ruiz Aurora , Godard Cyril
Published: March 2019

The application of C1‐symmetrical diphosphite ligands containing furanose backbone in the Rh‐catalysed asymmetric hydroformylation of norbornene is described. The catalysts were highly active and produced exclusively exo‐norbornanecarboxaldehyde with enantioselectivities (ee) up to 71 %. Considering these promising results, the ligands were modified with a pyrene moiety to accomplish their immobilisation onto carbon materials. The corresponding Rh complexes bearing the novel pyrene‐tagged ligands were synthesised and immobilised onto multiwalled carbon nanotubes (MWCNT), reduced graphene oxide (rGO) and carbon beads (CBs). The novel catalytic systems were tested in the asymmetric hydroformylation of norbornene providing similar performance in terms of both activity and selectivity compared to the non‐immobilised systems. The recyclability of the new heterogenised catalysts was studied in the target reaction in batch mode. Nevertheless, the recycling was unsuccessful due to catalyst leaching. When used under continuous flow mode, these catalysts revealed robust and provided even higher ee than the corresponding homogeneous systems.
Unexpected Selective Methyl Group Abstractions from SiMe3 Moieties of CH2SiMe3 Ligands To Give New Cationic Titanium Complexes
Authors: Fischer Malte , Barbul Daniel , Schmidtmann Marc , Beckhaus Ruediger
Published: March 2019

The synthesis of the alkylated pentafulvene titanium complex Cp*Ti(CH2SiMe3)(π‐η5:σ‐η1‐C5H4=CR2) (CR2=adamantylidene) is described. The coordination mode of the pentafulvene ligand in this complex allowed for the subsequent synthesis of a series of nitrile‐insertion products. By reacting these neutral compounds with the strong Lewis acid B(C6F5)3, unprecedented selective methyl‐group abstractions from the SiMe3 moieties under formation of novel cationic titanium complexes with the corresponding MeB(C6F5)3− anion are demonstrated. The proposed silylium ion intermediates of these reactions are directly stabilized by either the exocyclic carbon atom of the pentafulvene ligand or by the lone pairs of the nitrogen atoms of the chelating Cp,N‐ligands. In addition, a titanium enamine complex and its reaction with B(C6F5)3 is reported, which results in the formation of a betaine.
Furanosyl Oxocarbenium Ion Conformational Energy Landscape Maps as a Tool to Study the Glycosylation Stereoselectivity of 2‐Azidofuranoses, 2‐Fluorofuranoses and Methyl Furanosyl Uronates
Authors: van der Vorm Stefan , Hansen Thomas , van Rijssel Erwin R. , Dekkers Rolf , Madern Jerre M. , Overkleeft Herman S. , Filippov Dmitri V. , van der Marel Gijsbert A. , Codée Jeroen D. C.
Published: March 2019

The 3D shape of glycosyl oxocarbenium ions determines their stability and reactivity and the stereochemical course of SN1 reactions taking place on these reactive intermediates is dictated by the conformation of these species. The nature and configuration of functional groups on the carbohydrate ring affect the stability of glycosyl oxocarbenium ions and control the overall shape of the cations. We herein map the stereoelectronic substituent effects of the C2‐azide, C2‐fluoride and C4‐carboxylic acid ester on the stability and reactivity of the complete suite of diastereoisomeric furanoses by using a combined computational and experimental approach. Surprisingly, all furanosyl donors studied react in a highly stereoselective manner to provide the 1,2‐cis products, except for the reactions in the xylose series. The 1,2‐cis selectivity for the ribo‐, arabino‐ and lyxo‐configured furanosides can be traced back to the lowest‐energy 3E or E3 conformers of the intermediate oxocarbenium ions. The lack of selectivity for the xylosyl donors is related to the occurrence of oxocarbenium ions adopting other conformations.
Excited‐State Dynamics of Thienoguanosine, an Isomorphic Highly Fluorescent Analogue of Guanosine
Authors: Martinez‐Fernandez Lara , Gavvala Krishna , Sharma Rajans , Didier Pascal , Richert Ludovic , Segarra Martì Javier , Mori Mattia , Mely Yves , Improta Roberto
Published: March 2019

Thienoguanosine (thG) is an isomorphic analogue of guanosine with promising potentialities as fluorescent DNA label. As a free probe in protic solvents, thG exists in two tautomeric forms, identified as the H1, being the only one observed in nonprotic solvents, and H3 keto–amino tautomers. We herein investigate the photophysics of thG in solvents of different polarity, from water to dioxane, by combining time‐resolved fluorescence with PCM/TD‐DFT and CASSCF calculations. Fluorescence lifetimes of 14.5–20.5 and 7–13 ns were observed for the H1 and H3 tautomers, respectively, in the tested solvents. In methanol and ethanol, an additional fluorescent decay lifetime (≈3 ns) at the blue emission side (λ≈430 nm) as well as a 0.5 ns component with negative amplitude at the red edge of the spectrum, typical of an excited‐state reaction, were observed. Our computational analysis explains the solvent effects observed on the tautomeric equilibrium. The main radiative and nonradiative deactivation routes have been mapped by PCM/TD‐DFT calculations in solution and CASSCF in the gas phase. The most easily accessible conical intersection, involving an out‐of plane motion of the sulfur atom in the five‐membered ring of thG, is separated by a sizeable energy barrier (≥0.4 eV) from the minimum of the spectroscopic state, which explains the large experimental fluorescence quantum yield.
Metal‐Assisted Opening of Intact P4 Tetrahedra
Authors: Modl Moritz , Heinl Sebastian , Balázs Gabor , Delgado Calvo Fuencisla , Caporali Maria , Manca Gabriele , Keilwerth Martin , Meyer Karsten , Peruzzini Maurizio , Scheer Manfred
Published: March 2019

The reactivity of ruthenium and manganese complexes bearing intact white phosphorus in the coordination sphere was investigated towards the low‐valent transition‐metal species [Cp′′′Co] (Cp′′′=η5‐C5H2‐1,2,4‐tBu3) and [L0M] (L0=CH[CHN(2,6‐Me2C6H3)]2; M=Fe, Co). Remarkably, and irrespective of the metal species, the reaction proceeds by the selective cleavage of two P–P edges and the formation of a square‐planar cyclo‐P4 ligand. The reaction products [{CpRu(PPh3)2}{CoCp′′′}(μ,η1:4‐P4)][CF3SO3] (5), [{CpBIGMn(CO)2}2{CoCp′′′}(μ,η1:1:4‐P4)] (6) and [{CpBIGMn(CO)2}2{ML0}(μ,η1:1:4‐P4)] (CpBIG=C5(C6H4nBu)5; L0=CH[CHN(2,6‐Me2C6H3)]2; M=Fe (7 a), Co (7 b)), respectively, were fully characterized by single‐crystal X‐ray diffraction and spectroscopic methods. The electronic structure of the cyclo‐P4 ligand in the complexes 5–7 is best described as a π‐delocalized P42− system, which is further stabilized by two and three metal moieties, respectively. DFT calculations envisaged a potential intermediate in the reaction to form 5, in which a quasi‐butterfly‐shaped P4 moiety bridges the two metals and behaves as an η3‐coordinated ligand towards the cobalt center.
Total Synthesis, Stereochemical Revision, and Biological Assessment of Iriomoteolide‐2a
Authors: Sakamoto Keita , Hakamata Akihiro , Iwasaki Arihiro , Suenaga Kiyotake , Tsuda Masashi , Fuwa Haruhiko
Published: March 2019

Iriomoteolide‐2a is a marine macrolide metabolite isolated from a cultured broth of the benthic dinoflagellate Amphidinium sp. HYA024 strain. This naturally occurring substance was reported to show remarkable cytotoxic activity against human cancer cell lines HeLa and DG‐75 and in vivo antitumor activity against murine leukemia P388 cell line. Herein, the total synthesis, stereochemical revision, and biological assessment of iriomoteolide‐2a are reported in detail. Total synthesis of the proposed structure 1 of iriomoteolide‐2a featured a late‐stage convergent assembly of three components by a Suzuki–Miyaura coupling, an esterification, and a ring‐closing metathesis. However, the NMR data of synthetic 1 were not identical to those of the natural product. Careful analysis of the NMR data of the authentic material and synthesis/NMR analysis of appropriately designed model compounds led to consideration of four possible stereoisomers 2–5 as candidates for the correct structure. Accordingly, total syntheses of 2–5 were achieved by taking advantage of the convergent strategy, and comparison of the NMR spectra of synthetic 2–5 with those of the natural product led to the conclusion that 5 shows the correct relative configuration of iriomoteolide‐2a. The absolute configuration of this natural product was finally established through chiral HPLC analysis of synthetic 5/ent‐5 with the authentic sample. The antiproliferative activity of the synthetic compounds was assessed against HeLa and A549 cells to show that, in contrast to expectation, synthetic 5 and ent‐5 were only marginally active in these cell lines. This work clearly underscores the vital role of total synthesis in the establishment of the structure and biological activity of natural products.
Ring Expansions of Nonpolar Polyphosphorus Rings
Authors: Piesch Martin , Seidl Michael , Stubenhofer Markus , Scheer Manfred
Published: March 2019

The reaction of the phosphinidene complex [Cp*P{W(CO)5}2] (1 a) (Cp*=C5Me5) with the anionic cyclo‐Pn ligand complex [(η3‐P3)Nb(ODipp)3]− (2, Dipp=2,6‐diisopropylphenyl) resulted in the formation of [{W(CO)5}2{μ3,η3:1:1‐P4Cp*}Nb(ODipp)3]− (3), which represents an unprecedented example of a ring expansion of a polyphosphorus‐ligand complex initiated by a phosphinidene complex. Furthermore, the reaction of the pnictinidene complexes [Cp*E{W(CO)5}2] (E=P: 1 a, As: 1 b) with the neutral complex [Cp′′′Co(η4‐P4)] (Cp′′′=1,2,4‐tBu3C5H2) led to a cyclo‐P4E ring (E=P, As) through the insertion of the pentel atom into the cyclo‐P4 ligand. Starting from 1 a, the two isomers [Cp′′′Co(μ3,η4:1:1‐P5Cp*){W(CO)5}2] (5 a,b), and from 1 b, the three isomers [Cp′′′Co(μ3,η4:1:1‐AsP4Cp*){W(CO)5}2] (6 a–c) with unprecedented cyclo‐P4E ligands (E=P, As) were isolated. The complexes 6 a–c represent unique examples of ring expansions which lead to new mixed five‐membered cyclo‐P4As ligands. The possible reaction pathways for the formation of 5 a,b and 6 a–c were investigated by a combination of temperature‐dependent 31P{1H} NMR studies and DFT calculations.
Production of Viral Constructs for Neuroanatomy, Calcium Imaging, and Optogenetics
Authors: Chen Shih‐Heng , Haam Juhee , Walker Mitzie , Scappini Erica , Naughton John , Martin Negin P.
Published: March 2019

Advances in design and use of light‐sensitive and light‐emitting sensors have facilitated observation, measurement, and control of neuronal activities. Viruses are effective vectors for delivery of these valuable research tools to mammalian brains. Recombinant viruses are optimized to mediate regulatable, long‐term, and cell‐specific gene expression. Here, we describe production methods for three of the most commonly used types of recombinant viruses in neurobiology research: adeno‐associated virus (AAV), retrovirus/lentivirus, and glycoprotein‐deleted rabies virus. These viral constructs are frequently used for calcium imaging or to deliver neural tracers and optogenetic tools. Popular constructs are readily obtained commercially; however, customized virus production through commercial sources is time consuming and costly. This article aims to provide readers with detailed technical information for rapid production and validation of high‐quality viral particles in a laboratory setting while highlighting advantages and limitations of each viral type. © 2019 by John Wiley & Sons, Inc.
Bias through selective inclusion and attrition: Representativeness when comparing provider performance with routine outcome monitoring data
Authors: de Beurs Edwin , Warmerdam Lisanne , Twisk Jos
Published: March 2019

Background

Observational research based on routine outcome monitoring is prone to missing data, and outcomes can be biased due to selective inclusion at baseline or selective attrition at posttest. As patients with complete data may not be representative of all patients of a provider, missing data may bias results, especially when missingness is not random but systematic.

Methods

The present study establishes clinical and demographic patient variables relevant for representativeness of the outcome information. It applies strategies to estimate sample selection bias (weighting by inclusion propensity) and selective attrition bias (multiple imputation based on multilevel regression analysis) and estimates the extent of their impact on an index of provider performance. The association between estimated bias and response rate is also investigated.

Results

Provider‐based analyses showed that in current practice, the effect of selective inclusion was minimal, but attrition had a more substantial effect, biasing results in both directions: overstating and understating performance. For 22% of the providers, attrition bias was estimated to be in excess of 0.05 ES. Bias was associated with overall response rate (r = .50). When selective inclusion and attrition bring providers' response below 50%, it is more likely that selection bias increased beyond a critical level, and conclusions on the comparative performance of such providers may be misleading.

Conclusions

Estimates of provider performance were biased by selection, especially by missing data at posttest. Results on the extent and direction of bias and minimal requirements for response rates to arrive at unbiased performance indicators are discussed.
A Facile and Versatile “Click” Approach Toward Multifunctional Ionic Metal–organic Frameworks for Efficient Conversion of CO2
Authors: Zhou Li‐Jiao , Sun Wei , Yang Ning‐Ning , Li Peng , Gong Teng , Sun Weng‐Jie , Sui Qi , Gao En‐Qing
Published: March 2019

Ionic metal–organic frameworks (IMOFs) that integrate synergistic Lewis‐acid sites (intrinsic metal centers of the frameworks) and nucleophilic anions (halides encapsulated within pores) are intriguing platforms for the design of fully heterogeneous catalytic systems for cycloaddition of CO2 to epoxides. A new, facile and versatile synthetic approach has been used to fabricate triazolium‐based IMOFs for the first time. The approach makes use of azide–alkyne click chemistry and subsequent N‐alkylation to post‐synthetically create a cationic triazolium ring and introduce exchangeable counteranions at the same time. The IMOFs are efficient and recyclable heterogeneous catalysts for CO2 conversion under mild and cocatalyst‐free conditions. In particular, the click‐accessible triazolium ring provides a handle to incorporate further functionality. The MIL‐101‐tzmOH‐Br catalyst, which integrates hydrogen‐bonding hydroxy groups besides metal centers and bromide anions, shows superior catalytic performance under mild conditions.
From P‐Functional Thiazol‐2‐thione Derivatives to Phosphaalkenes
Authors: Begum Imtiaz , Schnakenburg Gregor , Han Zeyu , Franconetti Antonio , Frontera Antonio , Gates Derek P. , Streubel Rainer
Published: March 2019

A facile synthetic methodology is reported that permits access to the backbone (Et2N)2P‐substituted thiazol‐2‐thione 2 [(Et2N)2P‐THSMe; THSMe = 3‐methylthiazol‐2‐thione‐5‐yl]. Starting from 2, Et2N(Cl)P‐substituted thiazol‐2‐thione 3 [Et2N(Cl)P‐THSMe] was formed using chloride scrambling with PCl3. Subsequently, nucleophilic substitution using Ph2CHLi afforded [Et2N(Ph2CH)P‐THSMe] (4) which, via reaction with PCl3, afforded [Ph2CHP(Cl)THSMe] (5). Conversion of 4 into phosphaalkene [Ph2C=P‐THSMe] (6) was achieved, but its thermal instability precluded isolation. Complex [κP‐W(CO)5{Ph2CH(Cl)P}‐THSMe] (7) was then synthesized and used to access end‐on complex [W(CO)5(Ph2C=P‐THSMe)] (8); the 1,2‐addition product of 8 with H2O, complex [Ph2CH(OH)P‐THSMe] (10), was confirmed by X‐ray crystallography. The head‐to‐tail dimers of 8, the diastereomeric dinuclear 1,3‐diphosphetane complex 9 were assigned based on NMR results. In contrast, DFT calculations of all regio‐ and stereochemical isomers of 9 revealed a slight energetic preference for the head‐to‐head dimer. However, since transition states could not be localized, a detailed computational rationale for these experimental findings remains open.
Hydrazine‐Free Facile Synthesis of Palladium‐Tetrakis(Triphenylphosphine)
Authors: Carrasco Sergio , Martín‐Matute Belén
Published: March 2019

We present an easy and very efficient procedure for the synthesis of Pd(PPh3)4 using nontoxic reducing agents. The complex is obtained in a remarkable 83 % yield, and the method can be scaled up. A very detailed spectroscopic and spectrometric characterization is reported.
In situ Generation of Hypervalent Iodine Reagents for the Electrophilic Chlorination of Arenes
Authors: Granados Albert , Jia Zhiyu , del Olmo Marc , Vallribera Adelina
Published: March 2019

Efficient metal‐free methods for the electrophilic chlorination of arenes using PIFA and simple chlorine sources are reported. The in situ formation of PhI(Cl)OCOCF3 from PIFA and KCl is proposed, which resulted in a chlorinating species for moderately activated arenes. Moreover, the in situ formation of PhICl2 from PIFA and TMSCl resulted in an excellent approach for the chlorination of a great variety of arenes (20 examples) in high yields, even when working on a multigram scale.
Lignin valorization meets synthetic biology
Authors: Zhang Renkuan , Zhao Chen‐Hui , Chang Han‐Chen , Chai Meng‐Zhe , Li Bing‐Zhi , Yuan Ying‐Jin
Published: March 2019

Lignin, an abundant renewable resource in nature, is a highly heterogeneous biopolymer consisting of phenylpropanoid units. It is essential for sustainable utilization of biomass to convert lignin to value‐added products. However, there are technical obstacles for lignin valorization due to intrinsic heterogeneity. The emerging of synthetic biology technologies brings new opportunities for lignin breakdown and utilization. In this review, we discussed the applications of synthetic biology on lignin conversion, especially the production of value‐added products, such as aromatic chemicals, ring‐cleaved chemicals from lignin‐derived aromatics and bio‐active substances. Synthetic biology will offer new potential strategies for lignin valorization by optimizing lignin degradation enzymes, building novel artificial converting pathways, and improving the chassis of model microorganisms.
Induction and genetic identification of a callus‐like growth developed in the brown alga Fucus vesiculosus
Authors: Zayed Ahmed , Kovacheva Mariya , Muffler Kai , Breiner Hans‐Werner , Stoeck Thorsten , Ulber Roland
Published: March 2019

Induction of an axenic filamentous‐like callus growth from the brown algae Fucus vesiculosus is described. Different treatments were investigated in various combinations to develop axenic cultures based on identification of surface symbionts via 18S ribosomal RNA. Moreover, viability was confirmed after such processes by 2,3,5‐triphenyl tetrazolium chloride assay that demonstrated an average viability of 29%, relative to nonsterilized explants. After six weeks of a phototrophic cultivation on artificial sea water‐12‐nitrilotriacetic acid (0.5% w/v agar), a filamentous‐like callus growth was observed, which was identified genetically through its mitochondrial DNA after subculturing. Achievement of confirmed marine callus cultures might enrich old previously established blue biotechnology techniques and open new chances for cultivation of brown algae for production of good manufacturing practice‐compliant bioproducts.
Optimal placement and sizing of photovoltaics and battery storage in distribution networks
Authors: Chedid Riad , Sawwas Ahmad
Published: March 2019

A two‐step optimization approach is proposed to study the effects of adding a battery energy storage system (BESS) to a distribution network incorporating renewable energy sources. In this article, the first step finds the optimal size and placement of the photovoltaic (PV) arrays that lead to the lowest possible losses, cost and voltage deviation from the reference bus, while the second step starts by performing another optimization in order to find the optimal size and placement of the BESS that lead to a further reduction in the same objectives. The optimized Grid‐PV and Grid‐PV‐BESS configurations are subjected to a time domain power flow so that the annual energy losses and voltage profile of each bus can be observed. The article provides a novel formulation that treats the problem as a multi‐objective optimization and uses the Genetic Algorithm technique to reach optimal configuration in both steps. An Institute of Electrical and Electronic Engineers 13‐Bus test feeder is used to demonstrate the usefulness of the proposed technique.
Better thermal management options with heat storage systems for various applications: An Evaluation
Authors: Acar Canan , Dincer Ibrahim
Published: March 2019

With increasing worldwide population and rising standards of living, the global energy consumption is increasing at significant rates. Together with climate change concerns and negative impacts of fossil fuel use, the need for clean and smart energy systems is becoming more obvious. Clean and smart systems provide energy to all types of end‐use applications in an environmentally friendly, affordable, reliable, and efficient manner. Heat losses are recognized as some of the most significant causes of efficiency degradation in energy systems. Therefore, this study overviews and investigates current and future thermal management options for different end‐use purposes for a more sustainable future. In this study, a smart approach is taken when evaluating existing and emerging thermal management systems and smart targets are introduced for better thermal management systems. In addition, some novel thermal management systems for various applications such as electric/hybrid vehicles, power systems, and industrial processes are introduced as case studies and the energy and exergy efficiencies of these case studies are compared. In addition, some key future directions are provided in terms of better thermal management options for a sustainable future. The case study results of this study show that with better thermal management strategies, it is possible to reach energy and exergy efficiencies up to 60% and 50%, respectively in hybrid vehicles, industrial processes, and robotic applications.
Automated Essay Scoring at Scale: A Case Study in Switzerland and Germany
Authors: Rupp André A. , Casabianca Jodi M. , Krüger Maleika , Keller Stefan , Köller Olaf
Published: March 2019

In this research report, we describe the design and empirical findings for a large‐scale study of essay writing ability with approximately 2,500 high school students in Germany and Switzerland on the basis of 2 tasks with 2 associated prompts, each from a standardized writing assessment whose scoring involved both human and automated components. For the human scoring aspect, we describe the methodology for training and monitoring human raters as well as for collecting their ratings within a customized platform. For the automated scoring aspect, we describe the methodology for training, evaluating, and selecting appropriate automated scoring models as well as correlational patterns of resulting task scores with scores from secondary measures. Analyses show that the human ratings were highly reliable and that effective prompt‐specific automated scoring models could be built with state‐of‐the‐art features and machine learning methods, which resulted in correlational patterns with secondary measures that were in line with general expectations. In closing, we discuss the methodological implications for conducting this kind of work at scale in the future.
Using hydrogeochemical data to trace groundwater flow paths in a cold alpine catchment
Authors: Hu Yalu , Ma Rui , Wang Yanxin , Chang Qixin , Wang Shuo , Ge Mengyan , Bu Jianwei , Sun Ziyong
Published: March 2019

Significant uncertainty remains in understanding the groundwater flow pathways in the northeastern Qinghai–Tibet Plateau. Hydrogeochemical and isotopic data as well as hydrogeological data were combined to explore the groundwater flow path in a representative cold alpine catchment in the headwater region of the Heihe River. The results indicate that the suprapermafrost groundwater chemical components were mainly affected by calcite dissolution and evaporation, whereas the geochemistry of subpermafrost groundwater was controlled by dolomite and gypsum dissolution, calcite precipitation, and albite and halite dissolution. Distinct hydrogeochemical characteristics and controlling processes suggest a poor hydraulic connectivity between the suprapermafrost and subpermafrost groundwater. The hydraulic connectivity between permafrost groundwater and groundwater in the seasonally frozen area was confirmed by their similar hydrogeochemical features. In the seasonally frozen area, a silty clay layer with low permeability separates the aquifer into the deep (depth >20 m) and shallow (depth <20 m) flow paths. The deep groundwater was characterized by the enhanced dedolomitization and enhanced cation exchange processes compared with the shallow groundwater. Groundwater in the seasonally frozen area finally discharges as base flow into the stream. These results provide useful information about the groundwater flow systems in the unique alpine gorge catchments in Qinghai–Tibet Plateau. The above findings suggest that the permafrost distribution and the aquifer structures within the seasonally frozen area have significant impact on groundwater flow paths. Cross‐validation by drilling work and hydrograph data confirms that the hydrogeochemical and isotopic tracers combined with field investigations can be relatively low‐cost tools in interpreting the groundwater flow paths in similar alpine catchments.
Photochemically crosslinked cell‐laden methacrylated collagen hydrogels with high cell viability and functionality
Authors: Nguyen Thuy‐Uyen , Watkins Kori E. , Kishore Vipuil
Published: March 2019

Irgacure 2959 (I2959) is widely used as a photoinitiator for photochemical crosslinking of hydrogels. However, the free radicals generated from I2959 have been reported to be highly cytotoxic. In this study, methacrylated collagen (CMA) hydrogels were photochemically crosslinked using two different photoinitiators (i.e., I2959 and VA086) and the effect of photoinitiator type, photoinitiator concentration (i.e., 0.02 and 0.1%) and crosslinking time (1 and 10 min) on gel morphology, compressive modulus, and stability were investigated. In addition, Saos‐2 cells were encapsulated within the hydrogels and the effect of photochemical crosslinking conditions on cell viability, metabolic activity, and osteoblast functionality was assessed. Scanning electron microscopy imaging showed that photochemical crosslinking decreased the porosity of the hydrogels resulting in decrease in water retention ability compared to uncrosslinked hydrogels. On the other hand, photochemical crosslinking improved the stability of CMA hydrogels (p < 0.05). Uniaxial compression tests showed that increasing the photoinitiator concentration significantly improved the compressive modulus of CMA hydrogels (p < 0.05). Results from the live–dead assay showed that VA086 crosslinked hydrogels exhibited higher cell viability compared to I2959 (p < 0.05) crosslinked hydrogels indicating that VA086 is more cytocompatible compared to I2959. Furthermore, Alizarin Red S staining revealed a significantly more pronounced cell‐mediated mineralization on VA086 crosslinked hydrogels (p < 0.05) indicating that Saos‐2 cells retain their normal functionality in the presence of VA086. In summary, these results indicate that VA086 is a more biocompatible photoinitiator compared to I2959 for the generation of photochemically crosslinked CMA hydrogels for tissue engineering applications. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.