bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Chain‐end Functionalized Polyolefins and Polyolefin Diblock Copolymers via the Combination of Metallocene Catalysts and Reactive Chain Transfer Agents
Authors: Chung T.C. (Mike) 
Published: April 2004

AbstractThis paper discusses a facile route to prepare chain‐end functionalized polyolefins containing a terminal functional group (OH, COOH, NH2, etc.), and polyolefin diblock copolymers containing a polyolefin block and a functional polymer block. The chemistry is centered at an in situ chain transfer reaction during metallocene‐mediated α‐olefin polymerization using two reactive chain transfer (CT) agents, including dialkylborane (R2B‐H) and styrenic molecule/H2, to form polyolefin containing a reactive alkylborane and styrenic terminal group, respectively. With the appropriate choice of metallocene catalyst, the polymer formed shows narrow molecular weight distribution (Mw/Mn∼2), and the polymer molecular weight is inversely proportional to the molar ratio of [CT agent]/[α‐olefin]. In turn, the terminal borane group is very versatile in interconversion to various polar groups. More importantly, it can be quantitatively transformed to a living radical initiator for chain extension reaction with functional monomers. On the other hand, the terminal styrenic group was then selectively metallated and transformed to a stable polymeric anion for living anionic polymerization. The overall diblock co‐polymer process resembles a transformation reaction from metallocene‐mediated α‐olefin polymerization to a living free radical or a living anionic polymerization of functional monomers.
Mutations of phenylalanine‐193 in the putative substrate access channel alter the substrate specificity of cytochrome P450cam
Authors: Stevenson Julie‐Anne , Jones Jonathan P. , Wong Luet‐Lok 
Published: April 2004

AbstractThe Phe‐193 residue on the surface of cytochrome P450cam is part of a cluster of residues proposed to undergo dynamic fluctuations to permit the entry of substrates into the active site pocket. The role of this residue in the activity of P450cam has been investigated. The F193A, F193V, F193I, and F193L mutations were introduced into the Y96F mutant, which had been shown to oxidize a wider range of molecules at faster rates than the wild‐type enzyme. The F193L mutation had very little effect, while the F193A and F193I mutations reduced the camphor oxidation rate and almost abolished the styrene and naphthalene oxidation activity of the Y96F mutant. In contrast, the high activity of the Y96F mutant for the oxidation of adamantane, hexane, and 3‐methylpentane was largely retained, although the product distributions were significantly altered. This dramatic difference between the F193L and F193I mutations warrants further investigation. The turnover rates of the Y96F–F193I with all the substrates showed the same dependence on the Pd:P450cam concentration ratio as for the Y96F mutant, clearly indicating that if the F193 mutations had affected substrate access, substrate entry was still fast compared to the first electron transfer, which remained the rate‐limiting step for the overall reaction. We concluded that the F193A and F193I mutations shifted the substrate specificity of P450cam by causing structural changes that were relayed from their surface position down to the vicinity of the heme. The altered substrate binding resulted in differential electron transfer kinetics between classes of compounds.
A mechanistic study: Nucleophile dependence in glucosylations with glucosyl bromides
Authors: Bowden Tim , Garegg Per J. , Maloisel Jean‐Luc , Konradsson Peter 
Published: April 2004

AbstractGlycosylations using glucosyl bromides and various promoters (Et4NBr, HgBr2, or AgOTf) were investigated, competitively and kinetically. The reactions were found to be dependent in both glucosyl bromide and nucleophilic concentration, indicating a SN2‐type rate, determining step. For the AgOTf promoted reaction an ion pair mechanism involving glucosyl triflates is suggested.
High field conduction in poly(p‐phenylene vinylene)
Authors: Conwell Esther M. , Rakhmanova Svetlana V. 
Published: April 2004

AbstractWe have shown that in polyacetylene, for electric fields above 106 V/cm polarons are dissociated because the electron or hole can move much faster than the lattice distortion. Similar results should hold for poly(p‐phenylene vinylene), PPV. To determine whether the free carriers thus created can be heated by the field sufficiently to allow impact ionization, we investigated free‐carrier scattering in PPV. The important scatterers are longitudinal acoustic modes, molecular vibrations, and librational torsional modes. The coupling constants and important frequencies are known approximately for the first two of these processes in PPV. Using these values, some reasonable values for librons, and the calculated band structure of PPV, we conclude that at least some of the carriers could be heated to 2 eV at a field of ∼106 V/cm, and that they could acquire energy required for impact ionization at not much higher fields.
Nanoparticles of CdCl2 with closed cage structures
Authors: Tenne Reshef , Popovitz‐Biro Ronit , Twersky Anton , Rosenfeld Hacohen Yaron 
Published: April 2004

AbstractNanoparticles of various layered compounds having a closed cage or nanotubular structure, designated also inorganic fullerene‐like (IF) materials, have been reported in the past. In this work IF‐CdCl2 nanoparticles were synthesized by two methods. In one technique, a high temperature evaporation and subsequent condensation of dried cadmium chloride powder was used. In the other method, electron beam irradiation of the source powder led to its recrystallization into closed nanoparticles with a nonhollow core. The two methods are shown to produce nanoparticles of different topologies. While mostly spherical nested structures are obtained from the high temperature process, polyhedra with hexagonal or elongated rectangular characters are obtained by the electron beam induced process. The analysis also shows that, while the source (dried) powder is orthorhombic cadmium chloride monohydrate, the crystallized IF cage consists of the anhydrous 3R polytype which is not stable as bulk material in ambient atmosphere. Consistent with previous observations, this study shows that the seamless structure of the IF materials can stabilize phases, which are otherwise unstable in ambient conditions.
The relationship between electron transfer rate and molecular conduction 2. The sequential hopping case
Authors: Nitzan Abraham 
Published: April 2004

AbstractThis note discusses the relationship between a given bridge‐assisted electron transfer rate and the corresponding zero‐bias molecular conduction of the same molecular species, in the limit where both processes occur by sequential hopping. It follows a previous publication (A. Nitzan,J. Phys. Chem. A2001,105, 2677‐2679) in which the same issue was discussed for coherent tunneling transfer.
Prevalence of Pretreatment Testing Recommended for Patients With Chronic Inflammatory Skin Diseases
Authors: Schneeweiss Maria C. , Shay Denys , Ly Sophia , Wyss Richard , Schneeweiss Sebastian , Glynn Robert J. , Mostaghimi Arash 
Published: January 2024

ImportanceLaboratory testing for the presence of tuberculosis, hepatitis, and other conditions before starting most systemic immunomodulatory agents is recommended in patients with chronic inflammatory skin diseases (CISD) but current testing patterns in the US are unclear.ObjectiveTo determine the prevalence of pretreatment testing that is recommended for patients with CISD (psoriasis, hidradenitis suppurativa, or atopic dermatitis).Design, Setting, and ParticipantsThis descriptive analysis of US commercial insurance claims databases from December 31, 2002, to December 31, 2020, included adult patients with CISD (psoriasis, hidradenitis suppurativa, or atopic dermatitis) who started an immunomodulatory agent, including methotrexate, tumor necrosis factor α inhibitors, interleukin (IL)–17Ai, ustekinumab, IL-23i, dupilumab, or apremilast.Main Outcomes and MeasuresThe proportion of patients who underwent the screening tests as suggested by professional societies—including for tuberculosis, hepatitis, and liver function; complete blood cell counts; and lipid panels—were determined within 6 months before and during 2 years after treatment start.ResultsA total of 122 308 patients with CISDs (median [IQR] age, 49 [38-58] years; 63 663 [52.1%] male) starting systemic immunomodulatory treatment in the US were included. Treatment for patients with CISDs comprised methotrexate (28 684), tumor necrosis factor α inhibitors (40 965), ustekinumab (12 841), IL-23i (6116), IL-17Ai (9799), dupilumab (7787), or apremilast (16 116). Complete blood cell count was the most common test, performed in 41% (3161/7787) to 69% (19 659/28 684) of individuals before initiation across treatments. Between 11% (889/7787) and 59% (3613/6116) of patients had tuberculosis screening within 6 months before treatment, and 3% (149/4577) to 26% (1559/6097) had updated tests 1 year later. Between 13% (1006/7787) and 41% (16 728/40 965) had hepatitis panels before treatment. Low pretreatment testing levels before apremilast (15% [2331/16 116] to 45% [7253/16 116]) persisted a year into treatment (9% [816/8496] to 36% [2999/8496]) and were similar to dupilumab (11% [850/7787] to 41% [3161/7787] vs 3% [149/4577] to 25% [1160/4577]).Conclusions and RelevanceIn this descriptive analysis of patients with CISDs starting systemic immunomodulatory treatment in the US, less than 60% received the recommended pretreatment testing. Additional research is required to understand whether variations in testing affect patient outcomes.
Utilizing Gradient Oxidized Alloys to Establish a Highly Stable Interfacial Chemical Environment for Aqueous Zinc‐ion Batteries
Authors: Wang Tiantian , Wang Yu Ao , Wang Xiaomei , Chang Mengwei , Zhang Yue , You Junhua , Hu Fang , Zhu Kai 
Published: January 2024

AbstractThe research on rechargeable aqueous Zinc(Zn)‐ion batteries has expanded exponentially. However, the performance of Zn anodes during cycling and their commercial application is restricted by severe corrosion and dendritic formation. In this study, a facile approach is presented to address these challenges by introducing minute quantities of Zr(NO3)4 into the 3 m ZnSO4 electrolyte. The Zr(NO3)4 additive facilitates the creation of a protective layer comprising spatial gradient oxidation alloy (GOA) particles. The insulating zirconium‐based materials provide the necessary potential gradient to induce the Zn plate under the covering film. As a proof of concept, the in situ GOA coating anode exhibits exceptional cycling stability for 8000 cycles and an ultralow hysteresis voltage of 41 mV at current density of 5 mA cm−2. Furthermore, Density Functional Theory analyses reveal that the GOA coating anode homogenizes the electric field surrounding the Zn anode surface providing abundant zincophilic sites for Zn nucleation compared to bare Zn plates. This ensures uniform Zn deposition, preventing dendritic growth. In addition, the in situ characterization and computation of Gibbs free energy (ΔGH*) reveal that the GOA coating anode may effectively suppress the hydrogen evolution reaction.
High‐performance Photoelectrochemical Hydrogen Production Using Asymmetric Quantum Dots
Authors: Wang Kanghong , Wang Chao , Tao Yi , Tang Zikun , Benetti Daniele , Vidal François , Liu Yu , Rummeli Mark H. , Zhao Haiguang , Rosei Federico , Sun Xuhui 
Published: January 2024

AbstractSolar‐driven photoelectrochemical (PEC) reactions using colloidal quantum dots (QDs) as photoabsorbers have shown great potential for the production of clean fuels. However, the low H2 evolution rate, consistent with low values of photocurrent density, and their limited operational stability are still the main obstacles. To address these challenges, the heterostructure engineering of asymmetric capsule‐shaped CdSe/CdxZn1‐xSe QDs with broad absorption and efficient charge extraction compared to pure‐shell QDs is reported. By engineering the shell composition from pure ZnSe shells into CdxZn1‐xSe gradient shells, the electron transfer rate increased from 4.0 × 107 s−1 to 32.7 × 107 s−1. Moreover, the capsule‐shaped architecture enables more efficient spatial carrier separation, yielding a saturated current density of average of 25.4 mA cm−2 under AM 1.5 G one sun illumination. This value is the highest ever observed for QDs‐based devices and comparable to the best‐known Si‐based devices, perovskite‐based devices, and metal oxide‐based devices. Furthermore, PEC devices based on heterostructured QDs maintained 96% of the initial current density after 2 h and 82% after 10 h under continuous illumination, respectively. The results represent a breakthrough in hydrogen production using heterostructured asymmetric QDs.
Hepatic Stellate Cell‐Targeting Micelle Nanomedicine for Early Diagnosis and Treatment of Liver Fibrosis
Authors: Wang Lei , Zhou Jieying , Wang Jian , Wang Xiaotang , Dong Haijuan , Zhao Lingzhi , Wu Junchen , Peng Juanjuan 
Published: January 2024

AbstractDiagnosing and treating liver fibrosis is a challenging yet crucial endeavor due to its complex pathogenesis and risk of deteriorating into cirrhosis, liver failure, and even hepatic cancer. Herein, a silica cross‐linked micelles (SCLMs) based nano‐system is developed for both diagnosing and treating liver fibrosis. The SCLMs are first modified with peptide CTCE9908 (CT‐SCLMs) and can actively target CXCR4, which is overexpressed in activated hepatic stellate cells (HSCs). To enable diagnosis, an ONOO−‐responded near‐infrared fluorescent probe NOF2 is loaded into the CT‐SCLMs. This nano‐system can target the aHSCs and diagnose the liver fibrosis particularly in CCl4‐induced liver damage, by monitoring the reactive nitrogen species. Furthermore, a step is taken toward treatment by co‐encapsulating two anti‐fibrosis drugs, silibinin and sorafenib, within the CT‐SCLMs. This combined approach results in a significant alleviation of liver injury. Symptoms associated with liver fibrosis, such as deposition of collagen, expression of hydroxyproline, and raised serological indicators show notable improvement. In summary, the CXCR4‐targeted nano‐system can serve as a promising theragnostic system of early warning and diagnosis for liver fibrosis, offering hope against progression of this serious liver condition.
Autoantigen‐Dexamethasone Conjugate‐Loaded Liposomes Halt Arthritis Development in Mice
Authors: Benne Naomi , ter Braake Daniëlle , Porenta Deja , Lau Chun Yin Jerry , Mastrobattista Enrico , Broere Femke 
Published: January 2024

AbstractThere is no curative treatment for chronic auto‐inflammatory diseases including rheumatoid arthritis, and current treatments can induce off‐target side effects due to systemic immune suppression. This work has previously shown that dexamethasone‐pulsed tolerogenic dendritic cells loaded with the arthritis‐specific antigen human proteoglycan can suppress arthritis development in a proteoglycan‐induced arthritis mouse model. To circumvent ex vivo dendritic cell culture, and enhance antigen‐specific effects, drug delivery vehicles, such as liposomes, provide an interesting approach. Here, this work uses anionic 1,2‐distearoyl‐sn‐glycero‐3‐phosphoglycerol liposomes with enhanced loading of human proteoglycan‐dexamethasone conjugates by cationic lysine tetramer addition. Antigen‐pulsed tolerogenic dendritic cells induced by liposomal dexamethasone in vitro enhanced antigen‐specific regulatory T cells to a similar extent as dexamethasone‐induced tolerogenic dendritic cells. In an inflammatory adoptive transfer model, mice injected with antigen‐dexamethasone liposomes have significantly higher antigen‐specific type 1 regulatory T cells than mice injected with antigen only. The liposomes significantly inhibit the progression of arthritis compared to controls in preventative and therapeutic proteoglycan‐induced arthritis mouse models. This coincides with systemic tolerance induction and an increase in IL10 expression in the paws of mice. In conclusion, a single administration of autoantigen and dexamethasone‐loaded liposomes seems to be a promising antigen‐specific treatment strategy for arthritis in mice.
Diffusion‐Optimized Long Lifespan 4.6 V LiCoO2: Homogenizing Cycled Bulk‐To‐Surface Li Concentration with Reduced Structure Stress
Authors: Wu Kang , Ran Peilin , Wang Baotian , Wang Fangwei , Zhao Jinkui , Zhao Enyue 
Published: January 2024

AbstractIncreasing the charging cut‐off voltage (e.g., 4.6 V) to extract more Li ions are pushing the LiCoO2 (LCO) cathode to achieve a higher energy density. However, an inhomogeneous cycled bulk‐to‐surface Li distribution, which is closely associated with the enhanced extracted Li ions, is usually ignored, and severely restricts the design of long lifespan high voltage LCO. Here, a strategy by constructing an artificial solid–solid Li diffusion environment on LCO's surface is proposed to achieve a homogeneous bulk‐to‐surface Li distribution upon cycling. The diffusion optimized LCO not only shows a highly reversible capacity of 212 mA h g−1 but also an ultrahigh capacity retention of 80% over 600 cycles at 4.6 V. Combined in situ X‐ray diffraction measurements and stress‐evolution simulation analysis, it is revealed that the superior 4.6 V long‐cycled stability is ascribed to a reduced structure stress leaded by the homogeneous bulk‐to‐surface Li diffusion. This work broadens approaches for the design of highly stable layered oxide cathodes with low ion‐storage structure stress.
The high‐pressure response of trans‐cinnamic acid crystals studied by Raman spectroscopy
Authors: Marinopoulou Anna , Christopoulou Vasiliki , Karabinaki Olga , Christofilos Dimitris , Arvanitidis John 
Published: January 2024

AbstractThe pressure response of crystalline trans‐cinnamic acid is studied by means of Raman spectroscopy up to 6 GPa. Pressure application causes the reversible shift of all the observed Raman peaks to higher frequencies and changes in their relative intensities, with the intermolecular vibrational modes being by far more sensitive to pressurization compared to the intramolecular ones. The present high‐pressure Raman data indicate the structural stability of the trans‐cinnamic acid crystal and molecular conformation up to the highest pressure attained in the experiments, the importance of the hydrogen bonding, as well as the considerable strengthening of the intermolecular interactions at elevated pressures.
Pnictocatalysis
Authors: Garnes‐Portolés Francisco , Congost‐Escoin Pau , Abellán Gonzalo , Leyva‐Pérez. Antonio 
Published: January 2024

Abstract2D materials based on Group 15 elements (pnictogens) have appeared during the last ten years, with a rich surface chemistry characterized by a plethora of dangling electron pairs, ready to interact with outer molecules. These molecular interactions enable catalytic properties beyond any external electro‐ or photo‐stimulus. In analogy with carbocatalysis, defined as thermal catalytic processes over extended carbon surfaces (graphene, nanotubes, etc.), we propose here the term “pnictocatalysis”, defined as thermal catalytic processes over extended pnictogen surfaces (which include phospho‐, arsene‐, antimony‐ and bismuth‐catalysis). Pnictocatalysis consitutes a new field in catalysis, with unexplored latent reactions to be encountered. In this minireview, we show the few examples found to date (not more than ten), which mark the pathway to find new pnictocatalyzed reactions, not exclusive with two‐dimensional (2D) materials but also with other pnictogen nanostructures.
Porous Transport Photoelectrodes Fabricated on Felt Substrates and Applications to Polymer Electrolyte Photoelectrochemistry
Authors: Amano Fumiaki , Surya Rizki Marcony , Singh Surya Pratap 
Published: January 2024

AbstractPhotoelectrochemistry is used to develop solar energy technologies for fuel production and chemical transformations. Semiconductor materials such as TiO2, WO3, BiVO4, Fe2O3, and Cu2O are often investigated in devices designed to convert light energy into chemical energy, including for the production of hydrogen by photoelectrochemical (PEC) water splitting. The oxide electrodes are of significant interest due to their potential for efficient PEC reactions with high durability and their relatively low costs compared to other semiconductor materials. This review highlights the roles played by macroporous photoelectrodes in the development of highly efficient photoelectrodes and advanced PEC systems using polymer electrolytes. Three‐dimensional conductive fiber substrates, such as titanium felt and carbon paper, outperform their two‐dimensional counterparts owing to their larger interfacial areas that enhance PEC properties. The macroporous structures facilitate mass‐transport‐limited reactions when integrated with polymer electrolytes in membrane electrode assemblies. Such configurations are promising for PEC splitting of pure water, and for transforming gaseous molecules such as water vapor, volatile organic compounds, and methane. Optimizing the configuration, including electrode materials selection and ionomer‐coating treatment, can potentially improve the performance of polymer electrolyte membrane PEC cells. Porous transport photoelectrodes integrated with proton/anion‐exchange membranes offer significant opportunities for advanced PEC applications.
A high temperature resistance and hyper‐dispersed nanoparticle grafted by multi‐monomer via in‐situ polymerization: Preparation, characterization, and its imbibition performance
Authors: Yue Lei , Zhang Mian , Zuo Ting , Yang JiaHui , Zhou YiNing 
Published: January 2024

AbstractIn recent years, the excellent cleaning‐oil capacity of nanofluid has attracted extensive attention and it has been widely used in oilfields as an imbibition agent. To solve the poor dispersion stability of nanoparticles in high‐temperature and high‐salt reservoir, this paper has prepared a hyper‐dispersed nanoparticle, polymer grafted nanosilica (PNS) that is anti‐salt monomer and anti‐temperature monomer simultaneously grafting on the surface of nanosilica via in‐situ polymerization reaction. Its imbibition performance has been discussed. Results show that (1) The two monomers are all successfully grafted on the surface of nanosilica via optimization of in‐situ polymerization reaction conditions. This hyper‐dispersed nanoparticle has 14.5% final grafting rate, approximately 18 nm in particle size, and −41.2 mV of zeta potential; (2) PNS fluid has excellent dispersion stability and its grain size has no obvious change in 20 wt.% of NaCl or 4 wt.% of CaCl2 fluids at room temperature (25°C), as well as in 18 wt.% of NaCl or 4 wt.% of CaCl2 fluids at 130°C after 1 week; (3) Crude oil–water interface tension can be decreased and the hydrophilicity is significantly boosted by this PNS fluid. Meanwhile, the 10−3 mN/m of interface tension can be obtained and the contact angle of water phase is decreased to 12.8° by surfactant erucamide propyl hydroxysulfobetaine (EHSB) synergizing with PNS fluid; (4) Oil recovery efficiency replaced by PNS in surfactant fluid has reached 39.3%. That is mainly because the hyper‐dispersed nanoparticle provides a stronger spreading force to enhance the efficiency of cleaning oil.