bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt‐Catalyzed Hydroformylation
Authors: MacNeil Connor S. , Mendelsohn Lauren N. , Zhong Hongyu , Pabst Tyler P. , Chirik Paul J. 
Published: March 2020

AbstractIntermediates relevant to cobalt‐catalyzed alkene hydroformylation have been isolated and evaluated in fundamental organometallic transformations relevant to aldehyde formation. The 18‐electron (R,R)‐(iPrDuPhos)Co(CO)2H has been structurally characterized, and it promotes exclusive hydrogenation of styrene in the presence of 50 bar of H2/CO gas (1:1) at 100 °C. Deuterium‐labeling studies established reversible 2,1‐insertion of styrene into the Co−D bond of (R,R)‐(iPrDuPhos)Co(CO)2D. Whereas rapid β‐hydrogen elimination from cobalt alkyls occurred under an N2 atmosphere, alkylation of (R,R)‐(iPrDuPhos)Co(CO)2Cl in the presence of CO enabled the interception of (R,R)‐(iPrDuPhos)Co(CO)2C(O)CH2CH2Ph, which upon hydrogenolysis under 4 atm H2 produced the corresponding aldehyde and cobalt hydride, demonstrating the feasibility of elementary steps in hydroformylation. Both the hydride and chloride derivatives, (X=H−, Cl−), underwent exchange with free 13CO. Under reduced pressure, (R,R)‐(iPrDuPhos)Co(CO)2Cl underwent CO dissociation to form (R,R)‐(iPrDuPhos)Co(CO)Cl.
Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using ‘Ene’‐Reductases with Photoredox Catalysts
Authors: Nakano Yuji , Black Michael J. , Meichan Andrew J. , Sandoval Braddock A. , Chung Megan M. , Biegasiewicz Kyle F. , Zhu Tianyu , Hyster Todd K. 
Published: March 2020

AbstractFlavin‐dependent ‘ene’‐reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long‐lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic models.
An Aqueous Conducting Redox‐Polymer‐Based Proton Battery that Can Withstand Rapid Constant‐Voltage Charging and Sub‐Zero Temperatures
Authors: Strietzel Christian , Sterby Mia , Huang Hao , Strømme Maria , Emanuelsson Rikard , Sjödin Martin 
Published: March 2020

AbstractElectrodes based on organic matter operating in aqueous electrolytes enable new approaches and technologies for assembling and utilizing batteries that are difficult to achieve with traditional electrode materials. Here, we report how thiophene‐based trimeric structures with naphthoquinone or hydroquinone redox‐active pendent groups can be processed in solution, deposited, dried and subsequently polymerized in solid state to form conductive (redox) polymer layers without any additives. Such post‐deposition polymerization offers efficient use of material, high mass loading (up to 10 mg cm−2) and good flexibility in the choice of substrate and coating method. By employing these materials as anode and cathode in an acidic aqueous electrolyte a rocking‐chair proton battery is built. The battery shows good cycling stability (85 % after 500 cycles), withstands rapid charging, with full capacity (60 mAh g−1) reached within 100 seconds, allows for direct integration with photovoltaics, and retains its favorable characteristics even at −24 °C.
On the Crucial Role of Isolated Electronic States in the Thermal Reaction of ReC+ with Dihydrogen
Authors: Li Jilai , Geng Caiyun , Weiske Thomas , Schwarz Helmut 
Published: March 2020

AbstractPresented here is that isolated, long‐lived electronic states of ReC+ serve as the root cause for distinctly different reactivities of this diatomic ion in the thermal activation of dihydrogen. Detailed high‐level quantum chemical calculations support the experimental findings obtained in the highly diluted gas phase using FT‐ICR mass spectrometry. The origin for the existence of these long‐lived excited electronic states and the resulting implications for the varying mechanisms of dihydrogen splitting are addressed.
Edge detection for the buried archaeological structures with the geophysical image processing method in the Alabanda Ancient Cistern in Turkey
Authors: Karaaslan Hasan 
Published: March 2020

AbstractEdge detection techniques are some of the most useful techniques to determine the lineaments of buried structures from magnetic data. In this context, many techniques have been designed by using the magnetic gradient tensor (MGT). In this work, eigenvalue analysis of the full MGT and a new normalized approach [normalized edge detector (NK)], which balances strong and weak amplitude anomalies simultaneously, was utilized to outline lineaments of the buried archaeological structures. Satisfactory results were obtained from noisy and noise free synthetic data which were generated from prism models. The techniques were implemented on the archaeological magnetic data acquired from a buried ancient cistern. In addition, three‐dimensional (3D) electrical resistivity tomography (ERT) inversion sections and two‐dimensional (2D) magnetic inversion section and tilt angle methods were used to compare them against the results of edge detection analysis. The results of the normalized eigenvalue analysis agreed closely with all techniques in detecting the lineaments of the buried archaeological structure. NK detected the lineaments of the buried structure more clearly than the tilt angle and had better resolution. All of the results have shown that eigenvalue analysis of the full MGT and especially the newly introduced approach NK can provide important information for archaeological studies.
Wilcoxon‐type rank‐sum statistics for selecting the best population: Some advances
Authors: Koutras Markos V. , Triantafyllou Ioannis S. 
Published: March 2020

AbstractIn this article, we introduce three new nonparametric procedures for testing the equality of two lifetime distributions. The proposed testing processes are based on appropriately modified Wilcoxon‐type rank‐sum statistics. The exact null distribution of these statistics is studied and closed formulae for the corresponding exact probability of correct selection of the best population are derived for the class of Lehmann alternatives. A detailed numerical study is carried out to elucidate the performance of the proposed testing schemes. For illustration purposes, a real data application is presented in some detail.
Metallocenyl 7‐ACA Conjugates: Antibacterial Activity Studies and Atomic‐Resolution X‐ray Crystal Structure with CTX‐M β‐Lactamase
Authors: Lewandowski Eric M. , Szczupak Łukasz , Kowalczyk Aleksandra , Mendoza Gracia , Arruebo Manuel , Jacobs Lian M. C. , Stączek Paweł , Chen Yu , Kowalski Konrad 
Published: March 2020

AbstractThe conjugation of organometallic groups to current β‐lactam antibiotics is a field of increasing study due to the ability of certain organometallic groups to enhance the antibiotic potency of these drugs. Herein, we report the antibacterial properties of two metallocenyl (ferrocenyl and ruthenocenyl) 7‐aminocephalosporanic acid (7‐ACA) antibiotic conjugates. Continuing a trend we found in our previous studies, the ruthenocenyl conjugate showed greater antibacterial activity than its ferrocenyl counterpart. Compared with the previously published 7‐aminodesacetoxycephalosporanic acid (7‐ADCA) conjugates, the 3‐acetyloxymethyl group significantly improved the compounds’ activity. Furthermore, the Rc‐7‐ACA compound was more active against clinical Staphylococcus aureus isolates than the ampicillin reference. Noticeably, neither of the two new compounds showed an undesirable toxic effect in HeLa and L929 cells at the concentrations at which they displayed strong antibacterial effects. The antibacterial activity of the two metallocenyl 7‐ACA derivatives was further confirmed by scanning electron microscopy (SEM). SEM micrographs showed that bacteria treated with metallocenyl 7‐ACA derivatives feature cell wall damage and morphology changes. Using a CTX‐M‐14 β‐lactamase competition assay based on nitrocefin hydrolysis, we showed that the Rc‐7‐ACA bound more favorably to CTX‐M‐14 than its ferrocenyl counterpart, again confirming the superiority of the ruthenocenyl moiety over the ferrocenyl one in interacting with proteins. We also report a 1.47 Å resolution crystal structure of Rc‐7‐ACA in complex with the CTX‐M‐14 E166A mutant, an enzyme sharing a similar active site configuration with penicillin‐binding proteins, the molecular target of β‐lactam antibiotics. These results strengthen the case for the antibacterial utility of the Rc and Fc groups.
Surface Display of Complex Enzymes by in Situ SpyCatcher‐SpyTag Interaction
Authors: Gallus Sabrina , Peschke Theo , Paulsen Malte , Burgahn Teresa , Niemeyer Christof M. , Rabe Kersten S. 
Published: March 2020

AbstractThe display of complex proteins on the surface of cells is of great importance for protein engineering and other fields of biotechnology. Herein, we describe a modular approach, in which the membrane anchor protein Lpp‐OmpA and a protein of interest (passenger) are expressed independently as genetically fused SpyCatcher and SpyTag units and assembled in situ by post‐translational coupling. Using fluorescent proteins, we first demonstrate that this strategy allows the construct to be installed on the surface of E. coli cells. The scope of our approach was then demonstrated by using three different functional enzymes, the stereoselective ketoreductase Gre2p, the homotetrameric glucose 1‐dehydrogenase GDH, and the bulky heme‐ and diflavin‐containing cytochrome P450 BM3 (BM3). In all cases, the SpyCatcher‐SpyTag method enabled the generation of functional whole‐cell biocatalysts, even for the bulky BM3, which could not be displayed by conventional fusion with Lpp‐OmpA. Furthermore, by using a GDH variant carrying an internal SpyTag, the system could be used to display an enzyme with unmodified N‐ and C‐termini.
Electrochemistry of Tri‐substituted Porphyrins with β‐Appended Ethyl Acetoacetate and Acetylacetone in Neutral and Basic Nonaqueous Solvents
Authors: Fang Yuanyuan , Yadav Inderpal , Osterloh W. Ryan , Chaudhri Nivedita , Sankar Muniappan , Kadish Karl M. 
Published: March 2020

AbstractThe electrochemistry of β‐substituted tetraphenylporphyrins with a single ethyl acetoacetate (EAA), acetylacetone (acac), or ethyl acetate (EA) group and two antipodal H, Br or Ph groups was investigated in CH2Cl2 containing 0.1 M tetrabutylammonium perchlorate (TBAP) before and after addition of base to solution in the form of tetrabutylammonium hydroxide (TBAOH). The tri‐substituted porphyrins in their neutral form are represented as MTPP(EAA)X2, MTPP(acac)X2 and MTPP(EA)X2, where TPP is the dianion of tetraphenylporphyrin, M=H2, NiII, CuII or ZnII and X=H, Br or Ph. The singly reduced porphyrins are relatively stable on the cyclic voltammetry timescale, but this is not the case for the doubly reduced EAA and acac derivatives, which are highly reactive at room temperature, leading to a porphyrin product assigned as containing a deprotonated EAA− or acac− (enolate) substituent. Enolate‐appended porphyrins were also generated in‐situ by the addition of TBAOH, resulting in mono‐anionic porphyrins that are harder to reduce by 110–160 mV as compared to the neutral compounds with the same β‐substituents, suggesting a high degree of interaction between the deprotonated EAA− or acac− substituent and the porphyrin π‐ring system. The chemically or electrochemically generated enolate‐appended porphyrin could also be irreversibly oxidized by one electron at peak potentials between 0.10 and 0.30 V; the exact value depending upon solvent and type of β‐diketo substituent.
Synthesis and Photophysical Properties of T‐Shaped Coinage‐Metal Complexes
Authors: Kleinhans George , Chan Alan K.‐W. , Leung Ming‐Yi , Liles David C. , Fernandes Manuel A. , Yam Vivian W.‐W. , Fernández Israel , Bezuidenhout Daniela I. 
Published: March 2020

AbstractThe photophysical properties of a series of T‐shaped coinage d10 metal complexes, supported by a bis(mesoionic carbene)carbazolide (CNC) pincer ligand, are explored. The series includes a rare new example of a tridentate T‐shaped AgI complex. Post‐complexation modification of the AuI complex provides access to a linear cationic AuI complex following ligand alkylation, or the first example of a cationic square planar AuIII−F complex from electrophilic attack on the metal centre. Emissions ranging from blue (CuI) to orange (AgI) are obtained, with variable contributions of thermally‐dependent fluorescence and phosphorescence to the observed photoluminescence. Green emissions are observed for all three gold complexes (neutral T‐shaped AuI, cationic linear AuI and square planar cationic AuIII). The higher quantum yield and longer decay lifetime of the linear gold(I) complex are indicative of increased phosphorescence contribution.
Untersuchung von Polymerablagerungen während der Synthese in einem Wärmeübertrager
Authors: Hohlen Annika , Augustin Wolfgang , Scholl Stephan 
Published: March 2020

AbstractZur Untersuchung der unerwünschten Belagbildung von Polymeren auf wärmeübertragenden Oberflächen (Polymerisationsfouling) wird das Ablagerungsverhalten eines Vinylacetat/Vinylester‐Copolymers während der Emulsionspolymerisation untersucht. Hierbei sollen grundlegende Unterschiede zum Ablagerungsverhalten eines bereits reagierten Vinylacetat/Ethylen‐Copolymers identifiziert werden. Für einen qualitativen Vergleich wird die Ablagerungstopographie mithilfe eines Digitalmikroskops bestimmt. Für die quantitative Berechnung wird der Foulingwiderstand aus der Masse sowie der Schichthöhe des abgelagerten Materials berechnet. Der Polymerisationsgrad beeinflusst das Ablagerungsverhalten insb. die Topographie. Das bereits ausreagierte Stoffsystem weist eine größere Foulingmasse sowie eine deutlich ausgeprägtere, kraterförmige Ablagerungstopographie auf, wohingegen während des Polymerisationsfoulings eine optisch deutlich andere, tropfenförmige Topographie entsteht.
Nativity, ethnic enclave residence, and breast cancer survival among Latinas: Variations between California and Texas
Authors: Shariff‐Marco Salma , Gomez Scarlett Lin , Canchola Alison J. , Fullington Hannah , Hughes Amy E. , Zhu Hong , Pruitt Sandi L. 
Published: March 2020

BackgroundAmong Latinas with breast cancer, residence in an ethnic enclave may be associated with survival. However, findings from prior studies are inconsistent.MethodsThe authors conducted parallel analyses of California and Texas cancer registry data for adult (aged ≥18 years) Latinas who were diagnosed with invasive breast cancer from 1996 to 2005, with follow‐up through 2014. Existing indices applied to tract‐level 2000 US Census data were used to measure Latinx enclaves and neighborhood socioeconomic status (nSES). Multivariable Cox proportional hazard models were fit for all‐cause and breast cancer–specific survival adjusted for year of diagnosis, patient age, nativity (with multiple imputation), tumor stage, histology, grade, size, and clustering by census tract.ResultsAmong 38,858 Latinas, the majority (61.3% in California and 70.5% in Texas) lived in enclaves. In fully adjusted models for both states, foreign‐born women were found to be more likely to die of breast cancer and all causes when compared with US‐born women. Living in enclaves and in neighborhoods with higher SES were found to be independently associated with improved survival from both causes. When combined into a 4‐level variable, those in low nSES nonenclaves had worse survival for both causes compared with those living in low nSES enclaves and, in the all‐cause but not breast cancer–specific models, those in high nSES neighborhoods, regardless of enclave status, had improved survival from all causes.ConclusionsApplying the same methods across 2 states eliminated previously published inconsistent associations between enclave residence and breast cancer survival. Future studies should identify specific protective effects of enclave residence to inform interventions.
Fine‐needle aspiration cytology for the diagnosis of solid basaloid adenoid cystic carcinoma of the breast: Its role, limitation, and perspective
Authors: Noda Yuri , Nakanishi Yuko , Nishimae Ayaka , Takahashi Hiroyo , Oshiro Chiya , Inaji Hideo , Yamasaki Masaru 
Published: March 2020

AbstractSolid basaloid adenoid cystic carcinoma (SB‐AdCC) is a subtype of breast AdCC which shows more aggressive clinical behavior than other subtypes. Fine‐needle aspiration (FNA) cytology is a useful diagnostic tool for breast malignancies. However, most of the diagnostic cytological characteristics of AdCC are not present in SB‐AdCC and cytomorphological studies of this subtype are limited. Here, we evaluated the utility of FNA in the diagnosis of SB‐AdCC of the breast. A search of the pathology archives of our institutions for FNA specimens of histologically confirmed SB‐AdCC between 2012 and 2019 identified four patients with SB‐AdCC of the breast. All patients were female and the average age was 60 years. Cytologically, one case was classified as malignant, two as indeterminate, and one as unsatisfactory. Smears had low to moderate cellularity. All smears showed ribbon‐like material surrounding the clusters and a vertical nuclear arrangement toward the peripheral rim. Hyaline globules appeared only in one case. Cells in all cases showed an oval, angular, and spindle shape hyperchromatic nuclei with mild to severe atypia, and also dispersed naked nuclei similar to the cells of the clusters were detected in one case. In histological sections, these cytological findings were compatible with the histological findings and divergent histological differentiation was detected. Diagnosing of few cellular smears of SB‐AdCC is difficult whereas the features of peripheral rim of the clusters, naked nuclei, and the divergent differentiation may be important for diagnosing SB‐AdCC of the breast.
Generation of an Fsp1 (fibroblast‐specific protein 1)‐Flpo transgenic mouse strain
Authors: Cardot‐Ruffino Victoire , Chauvet Véronique , Caligaris Cassandre , Bertrand‐Chapel Adrien , Chuvin Nicolas , Pommier Roxane M. , Valcourt Ulrich , Vincent David , Martel Sylvie , Aires Sophie , Kaniewski Bastien , Dubus Pierre , Cassier Philippe , Sentis Stéphanie , Bartholin Laurent 
Published: March 2020

SummaryRecombination systems represent a major breakthrough in the field of genetic model engineering. The Flp recombinases (Flp, Flpe, and Flpo) bind and cleave DNA Frt sites. We created a transgenic mouse strain ([Fsp1‐Flpo]) expressing the Flpo recombinase in fibroblasts. This strain was obtained by random insertion inside mouse zygotes after pronuclear injection. Flpo expression was placed under the control of the promoter of Fsp1 (fibroblast‐specific protein 1) gene, whose expression starts after gastrulation at Day 8.5 in cells of mesenchymal origin. We verified the correct expression and function of the Flpo enzyme by several ex vivo and in vivo approaches. The [Fsp1‐Flpo] strain represents a genuine tool to further target the recombination of transgenes with Frt sites specifically in cells of mesenchymal origin or with a fibroblastic phenotype.
Liquid biopsy technologies based on membrane microfluidics: High‐yield purification and selective quantification of biomarkers in nanocarriers
Authors: Wang Ceming , Senapati Satyajyoti , Chang Hsueh‐Chia 
Published: March 2020

AbstractLiquid biopsy, screening cancer non‐invasively and frequently by detecting and quantifying molecular markers in physiological fluids, would significantly improve cancer survival rate but it remains a distant goal. The key obstacles presented by the highly heterogeneous samples are rapid/high‐yield purification and precise/selective marker capture by their antibody and oligo probes. As irregular expressions of these molecular biomarkers are the key signals, quantifying only those from the cancer cells would greatly enhance the performance of the screening tests. The recent discovery that the biomarkers are carried by nanocarriers, such as exosomes, with cell‐specific membrane proteins suggests that such selection may be possible, although a new suite of fractionation and quantification technologies would need to be developed. Although under‐appreciated, membrane microfluidics has made considerable contributions to resolving these issues. We review the progress made so far, based on ion‐selective, track‐etched, and gel membranes and advanced electrophoretic and nano‐filtration designs, in this perspective and suggest future directions.
Probabilistic analysis of security attacks in cloud environment using hidden Markov models
Authors: Al‐Karaki Jamal N. , Gawanmeh Amjad , Almalkawi Islam T. , Alfandi Omar 
Published: March 2020

SummaryThe rapidly growing cloud computing paradigm provides a cost‐effective platform for storing, sharing, and delivering data and computation through internet connectivity. However, one of the biggest barriers for massive cloud adoption is the growing cybersecurity threats/risks that influence its confidence and feasibility. Existing threat models for clouds may not be able to capture complex attacks. For example, an attacker may combine multiple security vulnerabilities into an intelligent, persistent, and sequence of attack behaviors that will continuously act to compromise the target on clouds. Hence, new models for detection of complex and diversified network attacks are needed. In this article, we introduce an effective threat modeling approach that has the ability to predict and detect the probability of occurrence of various security threats and attacks within the cloud environment using hidden Markov models (HMMs). The HMM is a powerful statistical analysis technique and is used to create a probability matrix based on the sensitivity of the data and possible system components that can be attacked. In addition, the HMM is used to provide supplemental information to discover a trend attack pattern from the implicit (or hidden) raw data. The proposed model is trained to identify anomalous sequences or threats so that accurate and up‐to‐date information on risk exposure of cloud‐hosted services are properly detected. The proposed model would act as an underlying framework and a guiding tool for cloud systems security experts and administrators to secure processes and services over the cloud. The performance evaluation shows the effectiveness of the proposed approach to find attack probability and the number of correctly detected attacks in the presence of multiple attack scenarios.