bluuebunny/crossref_metadata_2025 huggingface dataset:
Designing Catalysts for Chirality‐Selective Synthesis of Single‐Walled Carbon Nanotubes: Past Success and Future Opportunity
Authors: He Maoshuai , Zhang Shuchen , Wu Qianru , Xue Han , Xin Benwu , Wang Dan , Zhang Jin
Published: August 2018

A major obstacle for the applications of single‐walled carbon nanotubes (SWNTs) in electronic devices is their structural diversity, ending in SWNTs with diverse electrical properties. Catalytic chemical vapor deposition has shown great promise in directly synthesizing high‐quality SWNTs with a high selectivity to specific chirality (n, m). During the growth process, the tube–catalyst interface plays crucial roles in regulating the SWNT nucleation thermodynamics and growth kinetics, ultimately governing the SWNT chirality distribution. Starting with the introduction of SWNT growth modes, this review seeks to extend the knowledge about chirality‐selective synthesis by clarifying the energetically favored SWNT cap nucleation and the threshold step for SWNT growth, which describes how the tube–catalyst interface affects both the nucleus energy and the new carbon atom incorporation. Such understandings are subsequently applied to interpret the (n, m) specific growth achieved on a variety of templates, such as SWNT segments or predefined molecular seeds, transition metal (Fe, Co and Ni)‐containing catalysts at low reaction temperatures, W‐based alloy catalysts, and metal carbides at relatively high reaction temperatures. The up to date achievements on chirality‐controlled synthesis of SWNTs is summarized and the remaining major challenges existing in the SWNT synthesis field are discussed.
Electron Tomography: A Unique Tool Solving Intricate Hollow Nanostructures
Authors: Song Hao , Yang Yannan , Geng Jing , Gu Zhengying , Zou Jin , Yu Chengzhong
Published: August 2018

Innovations in nanofabrication have expedited advances in hollow‐structured nanomaterials with increasing complexity, which, at the same time, set challenges for the precise determination of their intriguing and complicated 3D configurations. Conventional transmission electron microscopy (TEM) analysis typically yields 2D projections of 3D objects, which in some cases is insufficient to reflect the genuine architectures of these 3D nano‐objects, providing misleading information. Advanced analytical approaches such as focused ion beam (FIB) and ultramicrotomy enable the real slicing of nanomaterials, realizing the direct observation of inner structures but with limited spatial discrimination. Electron tomography (ET) is a technique that retrieves spatial information from a series of 2D electron projections at different tilt angles. As a unique and powerful tool kit, this technique has experienced great advances in its application in materials science, resolving the intricate 3D nanostructures. Here, the exceptional capability of the ET technique in the structural, chemical, and quantitative analysis of hollow‐structured nanomaterials is discussed in detail. The distinct information derived from ET analysis is highlighted and compared with conventional analysis methods. Along with the advances in microscopy technologies, the state‐of‐the‐art ET technique offers great opportunities and promise in the development of hollow nanomaterials.
Additive Manufacturing and Performance of Architectured Cement‐Based Materials
Authors: Moini Mohamadreza , Olek Jan , Youngblood Jeffrey P. , Magee Bryan , Zavattieri Pablo D.
Published: August 2018

There is an increasing interest in hierarchical design and additive manufacturing (AM) of cement‐based materials. However, the brittle behavior of these materials and the presence of interfaces from the AM process currently present a major challenge. Contrary to the commonly adopted approach in AM of cement‐based materials to eliminate the interfaces in 3D‐printed hardened cement paste (hcp) elements, this work focuses on harnessing the heterogeneous interfaces by employing novel architectures (based on bioinspired Bouligand structures). These architectures are found to generate unique damage mechanisms, which allow inherently brittle hcp materials to attain flaw‐tolerant properties and novel performance characteristics. It is hypothesized that combining heterogeneous interfaces with carefully designed architectures promotes such damage mechanisms as, among others, interfacial microcracking and crack twisting. This, in turn, leads to damage delocalization in brittle 3D‐printed architectured hcp and therefore results in quasi‐brittle behavior, enhanced fracture and damage tolerance, and unique load‐displacement response, all without sacrificing strength. It is further found that in addition to delocalization of the cracks, the Bouligand architectures can also enhance work of failure and inelastic deflection of the architectured hcp elements by over 50% when compared to traditionally cast elements from the same materials.
Biological Tissues as Active Nematic Liquid Crystals
Authors: Saw Thuan Beng , Xi Wang , Ladoux Benoit , Lim Chwee Teck
Published: August 2018

Live tissues can self‐organize and be described as active materials composed of cells that generate active stresses through continuous injection of energy. In vitro reconstituted molecular networks, as well as single‐cell cytoskeletons show that their filamentous structures can portray nematic liquid crystalline properties and can promote nonequilibrium processes induced by active processes at the microscale. The appearance of collective patterns, the formation of topological singularities, and spontaneous phase transition within the cell cytoskeleton are emergent properties that drive cellular functions. More integrated systems such as tissues have cells that can be seen as coarse‐grained active nematic particles and their interaction can dictate many important tissue processes such as epithelial cell extrusion and migration as observed in vitro and in vivo. Here, a brief introduction to the concept of active nematics is provided, and the main focus is on the use of this framework in the systematic study of predominantly 2D tissue architectures and dynamics in vitro. In addition how the nematic state is important in tissue behavior, such as epithelial expansion, tissue homeostasis, and the atherosclerosis disease state, is discussed. Finally, how the nematic organization of cells can be controlled in vitro for tissue engineering purposes is briefly discussed.
Large Intercalation Pseudocapacitance in 2D VO2 (B): Breaking through the Kinetic Barrier
Authors: Xia Chuan , Lin Zifeng , Zhou Yungang , Zhao Chao , Liang Hanfeng , Rozier Patrick , Wang Zhiguo , Alshareef Husam N.
Published: August 2018

VO2 (B) features two lithiation/delithiation processes, one of which is kinetically facile and has been commonly observed at 2.5 V versus Li/Li+ in various VO2 (B) structures. In contrast, the other process, which occurs at 2.1 V versus Li/Li+, has only been observed at elevated temperatures due to large interaction energy barrier and extremely sluggish kinetics. Here, it is demonstrated that a rational design of atomically thin, 2D nanostructures of VO2 (B) greatly lowers the interaction energy and Li+‐diffusion barrier. Consequently, the kinetically sluggish step is successfully enabled to proceed at room temperature for the first time ever. The atomically thin 2D VO2 (B) exhibits fast charge storage kinetics and enables fully reversible uptake and removal of Li ions from VO2 (B) lattice without a phase change, resulting in exceptionally high performance. This work presents an effective strategy to speed up intrinsically sluggish processes in non‐van der Waals layered materials.
A Metamaterial Analog of the Ising Model
Authors: Cong Longqing , Savinov Vassili , Srivastava Yogesh Kumar , Han Song , Singh Ranjan
Published: August 2018

The interaction between microscopic particles is always a fascinating and intriguing area of science. Direct interrogation of such interactions is often difficult. Structured electromagnetic systems offer a rich toolkit for mimicking and reproducing the key dynamics that govern the microscopic interactions, and thus provides an avenue to explore and interpret the microscopic phenomena. In particular, metamaterials offer the freedom to artificially tailor light–matter coupling and to control the interaction between unit cells in the metamaterial array. Here, a terahertz metamaterial that mimics spin‐related interactions of microscopic particles in a 2D lattice via complex electromagnetic multipoles scattered within the metamaterial array is demonstrated. Fano resonances featured by distinct mode properties due to strong nearest‐neighbor interactions are discussed, which draw parallels with the 2D Ising model. Interestingly, a phase transition from single Fano resonance to hyperfine splitting of the Fano spectrum is observed by manipulating the 2D interactions without applying external magnetic or electric fields, which provides a potential multispectral platform for applications in super‐resolution imaging, biosensing, and selective thermal emission. The dynamic approach to reproduce static interaction between microscopic particles will enable more profound significance in exploring the unknown physical world by the macroscopic analogs.
Resonant Silicon Nanoparticles for Enhanced Light Harvesting in Halide Perovskite Solar Cells
Authors: Furasova Aleksandra , Calabró Emanuele , Lamanna Enrico , Tiguntseva Ekaterina , Ushakova Elena , Ubyivovk Eugene , Mikhailovskii Vladimir , Zakhidov Anvar , Makarov Sergey , Di Carlo Aldo
Published: August 2018

Implementation of resonant nanoparticles (NPs) for improving performance of organometal halide perovskites solar cells is highly prospective approach, because it is compatible with the solution processing techniques used for any organic materials. Previously, resonant metallic NPs have been incorporated into perovskite solar cells for better light absorption and charge separation. However, high inherent optical losses and high reactivity of noble metals with halides in perovskites are main limiting factors for this approach. Incidentally, low‐loss and chemically inert resonant silicon NPs allow for light trapping and enhancement at nanoscale, being suitable for thin film photovoltaics. Here photocurrent and fill‐factor (FF) enhancements in meso‐superstructured perovskite solar cells, incorporating resonant silicon NPs between mesoporous TiO2 transport and active layers, are demonstrated. This results in a boost of device efficiency up to 18.8% and FF up to 79%, being a record among the previously reported values on NPs incorporation into CH3NH3PbI3 perovskite‐based solar cells. Theoretical modeling and optical characterization reveal the significant role of Si NPs for increased light absorption in the active layer rather than for better charge separation. The proposed strategy is universal and can be applied in perovskite solar cells with various compositions, as well as in other optoelectronic devices.
Refractory Metamaterial Microwave Absorber with Strong Absorption Insensitive to Temperature
Authors: Li Yukun , Li Wei , Wang Yi , Cao Jie , Guan Jianguo
Published: August 2018

The so far developed microwave absorbers all exhibit dramatically changing absorption with temperature, hindering them from working in a broad temperature range. Here, a refractory metamaterial microwave absorber (rfMMA) with the absorption insensitive to temperature by using refractory ceramics of conductive titanium diboride (TiB2) as unit cells and dielectric alumina (Al2O3) as a spacer is designed and experimentally demonstrated. The as‐proposed rfMMA shows strong microwave absorption in a wide temperature range. A definite physical equivalent circuit model that tightly links the structural and constitutive parameters of the rfMMA to its absorption properties is established. It reveals that with a stable configuration of the as‐proposed rfMMA, the little temperature effect on the permittivity of Al2O3 spacer and the big enough conductivity of TiB2 unit cells ensure an almost constant absorption in a wide temperature range, avoiding the temperature‐sensitive problem of traditional refractory absorbers. Moreover, the excellent chemical stability of TiB2 and Al2O3 at high temperature further ensures the long‐term service of the as‐fabricated rfMMA, as confirmed by experiments. This work provides a route to achieve refractory microwave absorbers with strong absorption at a wide temperature range, and illustrates a bright prospect of the all‐ceramic metamaterial absorbers in high temperature applications.
Knee pain in nursing home workers after implementation of a safe resident handling program
Authors: Gold Judith E. , Kurowski Alicia , Gore Rebecca J. ,   ProCare Research Team, Punnett Laura
Published: August 2018

Purpose

Approximately 25‐30% of nursing personnel experience knee pain (KP). We sought to identify physical and psychosocial work exposures, and personal factors related to prevalent, incident, and persistent KP 5‐8 years after safe resident handing program (SRHP) implementation in nursing homes.

Methods

Health and exposure information was obtained from worker surveys 5‐6 years (“F5”) and 7‐8 years (“F6”) post‐SRHP implementation. Prevalent KP correlates were examined at F5; persistent and incident KP predictors were analyzed at F6, utilizing robust Poisson multivariable regression.

Results

F5 KP prevalence (19.7%) was associated with combined physical exposures, and with either high job strain or low social support, in separate models. Two‐year persistent KP was similarly associated with these psychosocial exposures. Being overweight was associated with KP in all analyses.

Conclusions

The SRHP program did not eliminate knee physical loading, which should be reduced to prevent nursing home worker KP. Workplace psychosocial exposures (high job strain, low social support) also appeared germane.
Variation in levels of AMH among Maya and non‐Maya women in Campeche, Mexico
Authors: Kyweluk Moira A. , Sievert Lynnette Leidy , Huicochea‐Gómez Laura , Cahuich‐Campos Diana , McDade Thomas , Brown Daniel E.
Published: August 2018

Objectives

The purpose of this study was to examine anti‐Müllerian hormone (AMH) levels among women of Maya and non‐Maya ancestry in the city of Campeche, Mexico. Levels of AMH can potentially predict age at menopause. Previous studies have indicated an early mean age at menopause among the Maya.

Materials and methods

Women aged 40‐60 (n = 97) participated in semistructured interviews, anthropometric measures, and blood samples. Maya/non‐Maya ethnicity was determined by the last names, languages spoken, and birthplace of the woman, her parents, and her grandparents. AMH values were categorized as detectable (0.05‐4.19 ng/mL) and undetectable (<0.05 ng/mL). Logistic regressions calculated odds ratios (OR) for undetectable AMH.

Results

Women were categorized as Maya (n = 44), not Maya (n = 39), or not able to be clearly defined (n = 14). In bivariate comparisons, women with detectable levels of AMH were younger, more likely to be pre‐menopausal, and not Maya. Age, menopausal status, and ethnicity remained significant in a logistic regression models after controlling for age at menarche. Maya women were more than five times as likely to have nondetectable AMH levels as non‐Maya women.

Discussion

Increasing age and progression through the menopausal transition were both associated with declining levels of AMH. The association between Maya ethnicity and a lower likelihood of detecting AMH is consistent with the early ages at menopause reported in previous studies. We considered a rapid life history model as an explanatory framework, and suggest, from an ecological perspective, that future research should consider measures of developmental stress that may compromise ovarian reserves.
Ecological and cultural shifts of hunter‐gatherers of the Jomon period paralleled with environmental changes
Authors: Kusaka Soichiro , Yamada Yasuhiro , Yoneda Minoru
Published: August 2018

Objectives

Holocene hunter‐gatherers adapted to climatic and environmental changes over time. Carbon and nitrogen stable isotope analysis of human skeletal remains from the Inariyama shell mound of the Final Jomon period have revealed large dietary variations in the population. This study analyzed radiocarbon dates of these individuals to test temporal changes in diet and its relationship with tooth ablation.

Materials and Methods

Twenty‐nine human skeletal remains from Inariyama were included in this study. Extracted bone collagen samples were purified to graphite. Then, radiocarbon dating of these samples was performed using the accelerator mass spectrometer.

Results

The radiocarbon ages of Inariyama ranged about, 3,230–2,140 cal BP and showed three peaks of occupation. In the early and late phases, terrestrial resource consumption and incisor extraction were observed, while marine resource consumption and canine extraction were observed in the middle phase.

Discussion

These temporal changes of diet and tooth ablation types occurred in parallel with climatic cooling and environmental change and help reveal how Holocene hunter‐gatherers adapted to the changing environments.
Female status, food security, and stature sexual dimorphism: Testing mate choice as a mechanism in human self‐domestication
Authors: Gleeson Ben Thomas , Kushnick Geoff
Published: August 2018

Objectives

Humans exhibit multiple anatomical and behavioral signatures of domestication syndrome, leading evolutionary‐minded scholars to suggest Homo sapiens is a “self‐domesticated” species. We examined one of three mechanisms proposed to explain human self‐domestication—that is, intersexual selection against reactive aggression. We hypothesized that this process has been, at least in part, caused by context‐dependent female preferences for less‐aggressive males. We predicted that societies where women have higher social status will show relatively elevated signs of self‐domestication—as indicated by lower stature sexual dimorphism (SSD)—and that this relationship should be mediated by food security.

Materials and methods

To test our prediction, we used male and female stature data for 28 societies from the Standard Cross‐Cultural Sample. We applied multivariate regression to examine our hypothesis while controlling for theoretically important confounders.

Results

We found convincing support for the prediction that the relationship between SSD and female status is mediated by food security. As predicted, higher female status was associated with less sexual dimorphism and the effect is stronger when food resources are secure.

Discussion

Context‐dependent female mate choices significantly contribute to lower SSD, suggesting female mate choice is likely to have played an influential role in human self‐domestication. Future research on this theme will benefit by including more of the expected symptoms of human self‐domestication and examining other potential drivers of this process.
Variation in obstetric dimensions of the human bony pelvis in relation to age‐at‐death and latitude
Authors: Auerbach Benjamin M. , King Kathyrn A. , Campbell Ryan M. , Campbell Meadow L. , Sylvester Adam D.
Published: August 2018

Objectives

Previous studies associate females who died in young adulthood with narrower obstetric pelvic dimensions, presumably in association with obstetric insufficiency (though this causal relationship is unresolved). In this study, we examine whether females within groups living at higher latitudes present this pattern, as high‐latitude groups have larger pelvic dimensions than groups previously examined. These patterns are compared with males. We assess whether there is evidence for younger ages‐at‐death in females to have been in response to natural selection against narrower true pelvis dimensions.

Methods

We measured 14 pelvic dimensions in 327 adults (188 females, 139 males), representing archaeological sites from mid‐latitude and high‐latitude North America. Individuals were placed into a “young” or “not young” age‐at‐death category. Latitude, sex, and age‐at‐death groups were compared using ANOVAs and scaled variance, and evidence for selection was examined with F‐tests.

Results

Pelvic dimensions were larger in high‐latitude females and males. Females but not males who died at younger ages had smaller pelvic canals than older individuals, especially in the mediolateral inlet and anteroposterior outlet dimensions. Variance in all pelvic dimensions is equal between the two female age‐at‐death groups.

Conclusions

We found narrower obstetrical dimensions in the female pelvis among individuals who died at younger ages. However, statistically equivalent variances in the two female age‐at‐death groups does not support natural selection on pelvic dimensions as leading to younger ages at death. We instead argue that this difference is result of continued growth due to remodeling in the pelvis occurring in females, but not males, after early adulthood.
Event‐related deep brain stimulation of the subthalamic nucleus affects conflict processing
Authors: Ghahremani Ayda , Aron Adam R. , Udupa Kaviraja , Saha Utpal , Reddy Duemani , Hutchison William D. , Kalia Suneil K. , Hodaie Mojgan , Lozano Andres M. , Chen Robert
Published: August 2018

Objective

Many lines of evidence suggest that response conflict recruits brain regions in the cortical–basal ganglia system. Within the basal ganglia, deep brain recordings from the subthalamic nucleus (STN) have shown that conflict triggers a transient increase in low‐frequency oscillations (LFOs; 2–8Hz). Here, we deployed a new method of delivering short trains of event‐related deep brain stimulation (DBS) to the STN to test the causal role of the STN and its associated circuits in conflict‐related processing.

Methods

In a double‐blind design, we stimulated the STN in patients with Parkinson disease by locking brief trains of DBS to specific periods of the trial within a Stroop task.

Results

Stimulation had a specific effect on conflict compared to nonconflict trials by relatively speeding responses on conflict trials (ie, reducing the Stroop effect, defined as the difference in reaction time between conflict and nonconflict trials) when it was delivered in the preresponse period in the preparation phase. Stimulation also increased errors when it was delivered early in the response window. This latter result corresponded to the timing of the conflict‐induced increase in LFOs observed in the absence of stimulation but was not directly related to the reduction in the Stroop effect.

Interpretation

These results support the theory that the time of LFO increase recorded from the STN corresponds to a conflict‐processing function. They also provide one of the first demonstrations of event‐related DBS of the STN in humans during a cognitive control paradigm. Ann Neurol 2018;84:515–526
Cerebrospinal fluid vasopressin and symptom severity in children with autism
Authors: Oztan Ozge , Garner Joseph P. , Partap Sonia , Sherr Elliott H. , Hardan Antonio Y. , Farmer Cristan , Thurm Audrey , Swedo Susan E. , Parker Karen J.
Published: August 2018

Autism is a brain disorder characterized by social impairments. Progress in understanding autism has been hindered by difficulty in obtaining brain‐relevant tissues (eg, cerebrospinal fluid [CSF]) by which to identify markers of disease and targets for treatment. Here, we overcome this barrier by providing evidence that mean CSF concentration of the “social” neuropeptide arginine vasopressin (AVP) is lower in children with autism versus controls. CSF AVP concentration also significantly differentiates individual cases from controls and is associated with greater social symptom severity in children with autism. These findings indicate that AVP may be a promising CSF marker of autism's social deficits. Ann Neurol 2018;84:611–615
Synthese und Charakterisierung von Cs4Ga6Q11 (Q=S, Se) – Chalkogenogallate mit außergewöhnlichen polymeren Anionen
Authors: Friedrich Daniel , Greim Dominik , Schlosser Marc , Siegel Renée , Senker Jürgen , Pfitzner Arno
Published: August 2018

Durch kontrollierte thermische Zersetzung von CsN3 in Gegenwart stöchiometrischer Mengen binärer Galliumchalkogenide und der elementaren Chalkogene wurden zwei neue ternäre Chalkogenogallate Cs4Ga6Q11 (Q=S, Se) gewonnen. Beide Verbindungen kristallisieren isotyp in der Raumgruppe P
(Nr. 2). Das auffälligste Strukturmerkmal dieser Chalkogenogallate sind die ungewöhnlichen strangförmigen anionischen Dreier‐Doppelketten
[Ga6Q11]4− aus sechs ecken‐ und kantenverknüpften GaQ4‐Tetraedern in der kleinsten Translationseinheit. 133Cs‐NMR‐spektroskopische Messungen und Rechnungen auf DFT‐Niveau zeigen einen ionischen Bindungscharakter der Caesiumteilstruktur. Die halbleitenden Verbindungen Cs4Ga6S11 (Eg=3.14 eV) und Cs4Ga6Se11 (Eg=2.41 eV) wurden weiterhin mittels UV/Vis‐Spektroskopie und ergänzenden DFT‐Rechnungen studiert. Die 133Cs‐MAS‐NMR‐Spektren sind charakteristisch für kationisches Caesium, und Schwingungsspektren zeigen zwei deutlich getrennte Bereiche, die jeweils den Ga‐Q‐Valenz‐ und Ga‐Q‐Deformationsschwingungen zugeordnet werden können.
Backbone‐Enabled Directional Peptide Macrocyclization through Late‐Stage Palladium‐Catalyzed δ‐C(sp2)−H Olefination
Authors: Bai Zengbing , Cai Chuangxu , Yu Zonglun , Wang Huan
Published: August 2018

C−H activation methods for peptide macrocyclization have the potential to provide peptidomimetics and cyclic peptides with expanded structural diversity. Now, a highly versatile peptide macrocyclization strategy via late‐stage palladium‐catalyzed δ‐C(sp2)−H olefination of phenylalanine residues has been developed. This method utilizes peptide backbone amides as internal directing groups and allows facile macrocyclization of peptides in the N‐to‐C direction. Combined with the previously developed β‐C(sp3)−H arylation method for peptide macrocyclization in the C‐to‐N direction, a pair of palladium‐catalyzed reactions were obtained that are directionally orthogonal, and the first example of one‐pot synthesis of bicyclic peptides via Pd‐catalyzed β‐C(sp3)−H and δ‐C(sp2)−H activation is demonstrated.
Barcoding mit Nukleinsäuren: Anwendung der DNA‐Sequenzierung als molekulares Zählwerk
Authors: Liszczak Glen , Muir Tom W.
Published: August 2018

Techniken der Hochdurchsatz‐DNA‐Sequenzierung haben eine Revolution in der Genomik ausgelöst, die in viele Bereiche der Lebens‐ und Naturwissenschaften eingedrungen ist. Die bemerkenswerten Eigenschaften der parallelen DNA‐Sequenzierung, wie hohe Sensitivität und Spezifität, hoher Durchsatz und Multiplexkapazität, führten zu Anwendungen als “molekulare Zählwerke” (molecular counter) für die Entdeckung niedermolekularer und peptidbasierter Inhibitoren, für die Hochdurchsatzbiochemie, die Protein‐ und Zelldetektion, die Diagnostik und sogar die Materialienwissenschaften. Ein wichtiger Aspekt bei der Extrapolation der DNA‐Sequenzierung auf “nichtklassische” Anwendungen besteht in der Anforderung, Nukleinsäure‐Barcodes an die interessierenden Entitäten anzuhängen. In diesem Aufsatz werden die chemischen und biochemischen Ansätze beschrieben, die ein einfaches Nukleinsäure‐Barcoding von proteinhaltigen und nichtproteinhaltigen Materialien ermöglicht haben. Wir zeigen Beispiele für die Verwendung von nachgelagerten Technologien, die durch DNA‐codierte Moleküle ermöglicht wurden. In Anbetracht der Tatsache, dass kommerziell erhältliche Hochdurchsatzsequenzer vor weniger als 15 Jahren eingeführt wurden, glauben wir, dass sich diesbezügliche Anwendungen auch in den kommenden Jahren zur Marktreife entwickeln werden.
Ultrafast Dynamics of a “Super” Photobase
Authors: Sheng Wei , Nairat Muath , Pawlaczyk Patrick D. , Mroczka Elizabeth , Farris Benjamin , Pines Ehud , Geiger James H. , Borhan Babak , Dantus Marcos
Published: August 2018

Molecular reactivity can change dramatically with the absorption of a photon due to the difference of the electronic configurations between the excited and ground states. Here we report on the discovery of a modular system (Schiff base formed from an aldehyde and an amine) that upon photoexcitation yields a more basic imine capable of intermolecular proton transfer from protic solvents. Ultrafast dynamics of the excited state conjugated Schiff base reveals the pathway for proton transfer, culminating in a 14‐unit increase in pKa to give the excited state pKa*>20 in ethanol.
Enhancing Selectivity and Kinetics in Oxidative Photocyclization by Supramolecular Control
Authors: Haldar Ritesh , Diring Stéphane , Samanta Pralok K. , Muth Marius , Clancy William , Mazel Antoine , Schlabach Sabine , Kirschhöfer Frank , Brenner‐Weiß Gerald , Pati Swapan K. , Odobel Fabrice , Wöll Christof
Published: August 2018

Photochemical reactions typically proceed via multiple reaction pathways, yielding a variety of isomers and products. Enhancing the selectivity is challenging. Now, the potential of supramolecular control for oxidative photocyclization of a tetraarylethylene, containing a stereogenic −C=C− bond, is demonstrated. In solution, this photochemical reaction produces three constitutional isomers (substituted phenanthrenes), with slow kinetics. When the reactant is assembled into a crystalline framework, only one product forms with accelerated kinetics. Key to this selectivity enhancement is the integration into a surface grown metal–organic framework (SURMOF); the dramatic gain in selectivity is ascribed to the hindrance of the rotational freedom of the −C=C− double bond. The structure of the MOF is key; the corresponding reaction in the solid does not result in such a high increase in selectivity. A striking change of luminescence properties after photocyclization is observed.
Enzymatic Cascade Reactions in Biosynthesis
Authors: Walsh Christopher T. , Moore Bradley S.
Published: August 2018

Enzyme‐mediated cascade reactions are widespread in biosynthesis. To facilitate comparison with the mechanistic categorizations of cascade reactions by synthetic chemists and delineate the common underlying chemistry, we discuss four types of enzymatic cascade reactions: those involving nucleophilic, electrophilic, pericyclic, and radical reactions. Two subtypes of enzymes that generate radical cascades exist at opposite ends of the oxygen abundance spectrum. Iron‐based enzymes use O2 to generate high valent iron‐oxo species to homolyze unactivated C−H bonds in substrates to initiate skeletal rearrangements. At anaerobic end, enzymes reversibly cleave S‐adenosylmethionine (SAM) to generate the 5′‐deoxyadenosyl radical as a powerful oxidant to initiate C−H bond homolysis in bound substrates. The latter enzymes are termed radical SAM enzymes. We categorize the former as “thwarted oxygenases”.
Effects of addition mode on Zn–Co double metal cyanide catalyst for synthesis of oligo(propylene‐carbonate) diols
Authors: An Na , Li Qifeng , Yin Ning , Kang Maoqing , Wang Junwei
Published: August 2018

Zn–Co double metal cyanide (DMC) complexes are promising catalytic systems for copolymerization of epoxide and CO2. In the work reported, Zn–Co DMC catalysts were prepared by parallel‐flow dropping, forward dropping and reverse dropping methods, aiming to provide an insight into the effect of addition mode on catalyst structure and catalytic performance. Catalytic properties were evaluated using the copolymerization reaction of propylene oxide (PO) and CO2 in the presence of chain transfer agent. The results indicated that the factors that affect crystalline state are different for different modes. And excess zinc chloride is the prerequisite for organic ligands to be retained in the catalyst and affect the structure. In addition, a catalyst with flower‐like morphology was obtained with the parallel‐flow dropping method which provided larger surface area. An appropriate O/Zn value ensured abundant active PO which would suppress the backbiting process by forming consecutive PO units adjacent to CO2 units. Oligo(propylene‐carbonate) diols with average molecular weight of 1020 g mol−1, CO2 incorporation of 24.92% and WPC of 5.14 wt% were obtained at 80 °C and 2 MPa.
Effect of hydrophilic additive and PVC polymerization degree on morphology and electrochemical properties of PVC‐based heterogeneous cation‐exchange membrane
Authors: Khoiruddin Khoiruddin , Ariono Danu , Subagjo Subagjo , Wenten I Gede
Published: August 2018

Membrane solution composition is one of the important factors that determine properties of ion‐exchange membranes. In this study, PVC‐based heterogeneous cation‐exchange membranes were prepared by the solution casting method. Effects of a hydrophilic additive [poly(ethylene glycol), PEG400] and degree of polymerization of poly(vinyl chloride) (PVC) on the morphology and electrochemical properties of the cation‐exchange membranes were investigated. The results revealed that the hydrophilic additive can improve membrane properties, including water uptake (Wu), ion‐exchange capacity (IEC), conductivity, and permselectivity. The improvements might be associated with an increase in accessibility of functional sites in the membrane matrix due to a higher hydrophilicity, indicated by a reduction of water contact angle and the greater void fraction shown by scanning electron microscopy. However, the permselectivity slightly decreased when the additive concentration was increased further. Meanwhile, increasing the degree of polymerization and PVC concentration resulted in higher permselectivity and lower conductivity, which might be due to a better resin distribution and a lower void fraction. Overall, the prepared membranes had relatively good conductivities (up to ∼2.5 mS/cm) and permselectivities (up to ∼0.92). In general the conductivity increased with increasing Wu and IEC, while the permselectivity showed the opposite trends. This could be associated with the efficacy of Donnan exclusion indicated by the IEC/Wu ratio and the Donnan equilibrium constant of the cation (K+). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46690.
A phase separation method toward PPTA–polypropylene nanocomposite separator for safe lithium ion batteries
Authors: He Lianyuan , Qiu Teng , Xie Chunjie , Tuo Xinlin
Published: August 2018

The building of separators with high thermal stability and security is important for lithium ion batteries. A novel, simple and successive process, which aims at coating poly‐p‐phenylene terephthamide (PPTA) onto commercial polypropylene (PP) separators, has been demonstrated. Without any additional binder, the PPTA nanofiber coating layer sticks to the porous PP separators by physical anchoring, endowing the composite separators with modified wettability toward electrolytes and heat resistance. Meanwhile, migration routes for lithium ions are guaranteed by the porous structure controlled by the self‐assembly of the fibrillar units during the nonsolvent induced phase separation. The cells equipped with the composite separators show better cycling performances. Moreover, the system based on the composite separators shows a sharp drop in ion conductivity after heat treatment at 200 °C for a certain period, indicating the shutdown effect of the composite separators, which can contribute to additional safety of lithium ion batteries. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 134, 46697
Temperature, pH, and reduction triple‐stimuli‐responsive inner‐layer crosslinked micelles as nanocarriers for controlled release
Authors: Zhang Kehu , Liu Jiangtao , Ma Xiao , Lei Lei , Li Yan , Yang Hong , Lei Zhongli
Published: August 2018

Temperature, pH, and reduction triple‐stimuli‐responsive inner‐layer crosslinked micelles as nanocarriers for drug delivery and release are designed. The well‐defined tetrablock copolymer poly(polyethylene glycol methacrylate)–poly[2‐(dimethylamino) ethyl methacrylate]–poly(N‐isopropylacrylamide)–poly(methylacrylic acid) (PPEGMA‐PDMAEMA‐PNIPAM‐PMAA) is synthesized via atom transfer radical polymerization, click chemistry, and esterolysis reaction. The tetrablock copolymer self‐assembles into noncrosslinked micelles in acidic aqueous solution. The core‐crosslinked micelles, shell‐crosslinked micelles, and shell–core dilayer‐crosslinked micelles are prepared via quaternization reaction or carbodiimide chemistry reaction. The crosslinked micelles are used as drug carriers to load doxorubicin (DOX), and the drug encapsulation efficiency with 20% feed ratio reached 59.2%, 73.1%, and 86.1%, respectively. The cumulative release rate of DOX is accelerated by single or combined stimulations. The MTT (3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay verifies that the inner‐layer crosslinked micelles show excellent cytocompatibility, and DOX‐loaded micelles exhibit significantly higher inhibition for HepG2 cell proliferation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46714.
Hybrid organosiloxane material/metal oxide composite as efficient anticorrosive coatings for mild steel in a saline medium
Authors: Suleiman Rami K. , Kumar A. Madhan , Sorour Ahmad A. , Al‐Badour Fadi A. , El Ali Bassam
Published: August 2018

Hybrid sol–gel materials have been found very promising anticorrosive coatings for metal substrates. In this article, the synthesis of novel hybrid organic‐inorganic sol–gel polymer; starting from tetraethyl orthosilicate, (3‐aminopropyl) trimethoxysilane, dimethoxy‐methyl‐octadecylsilane and polydimethylsiloxane, silanol terminated precursors, is reported. The hybrid polymer has been further loaded individually as well with five different metal oxides, then deposited on mild steel panels. All cured coating formulations have been characterized using thermogravimetric analysis, contact angle measurements, electrochemical impedance spectroscopy, vicker‐microhardness, surface roughness, and critical load analyses. Results have revealed that the parent coating exhibits excellent thermal stability and hydrophobic nature with minor observed changes on the two properties for the metal oxide‐loaded coatings. Electrochemical impedance and visual inspection results indicated excellent corrosion protection performance for all metal oxide composite coatings (except magnesium oxide) on steel when immersed in 3.5% NaCl solution for a prolonged time. Furthermore, the coating containing molybdenum oxide exhibited a maximum hardness, homogeneity, and adherence to the steel surface. The developed coating formulations in this study can be considered as a promising alternative to the currently‐used toxic chromate and phosphate coatings. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 134, 46718
Electrospun‐electrosprayed hydroxyapatite nanostructured composites for bone tissue regeneration
Authors: Gandhimathi Chinnasamy , Venugopal Jayarama Reddy , Ramakrishna Seeram , Srinivasan Dinesh Kumar
Published: August 2018

Electrospinning and electrospraying process provides a versatile approach for the fabrication of biocomposite nanofibrous scaffolds (NFS) with structural, mechanical, and biological properties is to mimick the native extracellular matrix. The present study was aimed to fabricate NFS of poly(l‐lactic acid)‐co‐poly(3‐caprolactone) (PLACL), silk fibroin (SF) and hydroxyapatite (HA) by blending (b) and spraying (s) methods. The biocomposite NFS were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy, water contact angle, tensile strength, fourier transform infrared spectroscopy (FTIR) analysis. The fabricated biocomposite NFS showed pore size around 1.5–7.8 μm and porosity of 68–93% with fiber diameter ranging from 213 ± 78 to 340 ± 52 nm. Furthermore, the mesenchymal stem cells (MSCs) were cultured on the biocomposite NFS and the cell interaction, proliferation, mineralization, and osteocalcin expression were analyzed by FESEM, MTS assay, alizarin Red S staining, and immunofluorescence analysis, respectively. The presence of bioactive SF/HA molecules supported biological functions namely cell attachment, proliferation, and differentiation of MSCs into osteoblasts. The observed results suggested that the biocomposite PLACL/SF/HA(s) NFS stimulated osteogenic differentiation of MSCs as evident from alkaline phosphatase activity, mineralization, and expression of osteocalcin for bone tissue engineering. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46756.
Simultaneous enhancement of proton conductivity and methanol resistance of sulfonated poly(phthalazinone ether sulfone ketone)/superacid sulfated zirconia composite membranes for direct methanol fuel cells
Authors: Zhen Dongxing , He Gaohong , Xu Xinlong , Yan Xiaoming , Du Naixu , Gong Xue , Li Tiantian , Dai Yan , Wu Xuemei
Published: August 2018

Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) is a kind of novel non‐fluorine polymer, whose high proton conductivity is dependent on high degree of sulfonation, which resulting in loss of dimensional stability. SPPESK/superacid sulfated zirconia (SZrO2) composite proton exchange membranes are fabricated first. The composite membrane shows good dimensional stability, ascribing to the restriction effect of hydrogen bonding force on the mobility and relaxation of polymer chains. Introducing SZrO2simultaneously enhances the conductivity and anti‐methanol permeation, owing to the connected ion domains, enlarged and aggregated ion clusters, excess proton conduction sites, and good blocking effect to methanol of SZrO2. For composite membrane containing 1.5 wt % SZrO2, the highest conductivity of 180 mS cm−1is obtained at 80 °C. Compared with pristine SPPESK and Nafion 115, the methanol permeability is reduced by 54 and 77%, and the maximum power density of direct methanol fuel cell is enhanced by 133 and 25%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2018,135, 46758.
Mechanical properties of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/wood flour composites: Effect of interface modifiers
Authors: Chan Clement Matthew , Vandi Luigi‐Jules , Pratt Steven , Halley Peter , Richardson Desmond , Werker Alan , Laycock Bronwyn
Published: August 2018

A fully biodegradable and biobased wood plastic composite based on a microbial biopolyester matrix, poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and a lignocellulosic filler, pine wood flour (WF), was manufactured using extrusion at industry‐standard level of wood content. The effects of three compatibilization techniques on the mechanical properties of the composites were investigated. Techniques include silicone fiber treatment using Sigmacote, maleic anhydride (MA) grafting of PHBV matrix, and the addition of polymethylene diphenyl‐diisocyanate (pMDI). Results showed that Sigmacote treatment resulted in a 20 ± 5% decrease in tensile strength of the composite. The use of MA‐grafted PHBV, independent of content, enhanced slightly the composites tensile strength (5 ± 3%) and impact strength (10 ± 4%). The addition of 2 wt % of pMDI improved the tensile strength of the composite by 25 ± 6%, but the strength level returned to the original state when 4 wt % was added. Processing conditions had a more significant effect on the composite properties giving a 40 ± 5% reduction in tensile strength and 45 ± 6% in impact strength when a higher shear extrusion configuration was used. The modeling of the mechanical data suggested that PHBV/WF composites have achieved better interfacial interactions without compatibilization when compared to other composite systems. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46828.
A sorbitol‐based phase‐selective organogelator for crude oil spills treatment
Authors: Zhuan Cailing , Li Yun , Yuan Xubo , Zhao Jin , Hou Xin
Published: August 2018

An efficient sorbitol‐based phase‐selective organogelator has been synthesized by an one‐step reaction between sorbitol and benzaldehyde with high yields up to 90%. The organogelator could gelate a wide range of oils with minimum gelation concentration ranging from 0.04 to 0.10 g/mL within 17 min. Besides, the self‐assembly mode of the organogelator in the oil phase was presented. The organogelator could self‐assemble in the oil phase through the hydrogen bonding and the π–π stacking interactions to form three‐dimensional networks. The organogelator showed better gelation properties when treated crude oil than other oils. Namely, a lower gelation concentration and a shorter gelling time were observed, while higher thermal stability and mechanical strength of the final crude oil gel were obtained. More importantly, the organogelator could be directly applied in a powder form to selectively gelate crude oil from oil–water mixtures within 10 min at ambient temperature without heating or adding carrier solvents. Inexpensive, simple‐synthesis, high‐yield and relatively simple operation performances of the organogelators indicate their potential and promising applications to remove oil spills in real life, especially for marine crude oil spills. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47052.
Equivalence analyses of dissolution profiles with the Mahalanobis distance
Authors: Hoffelder Thomas
Published: August 2018

For some postapproval changes, the manufacturer has to demonstrate that the dissolution profile of the drug product before the change is statistically equivalent to the dissolution profile after the change. Guidelines suggest the so‐called similarity factor f2 as standard approach for the equivalence analysis. f2 is a statistically questionable transformation of the Euclidean distance between both profile means and does not allow a control of the type I error rate. An alternative multivariate distance measure for quantifying the dissimilarity between both profile groups is the Mahalanobis distance. Current equivalence procedures based on the Mahalanobis distance implicate some practical problems in the dissolution context: either one chooses an exact method but the determination of a product independent equivalence margin will not be practically feasible or one chooses an approximate alternative that suffers from the bias of the Mahalanobis distance point estimate. This paper suggests the T2EQ approach for dissolution profile comparisons. T2EQ is a practically feasible equivalence procedure based on the Mahalanobis distance with an internal equivalence margin for comparing dissolution profiles. The equivalence margin is compliant with current dissolution guidelines. The operating characteristics (size, robustness, and power) are investigated via simulation: T2EQ meets the needs of both authorities and industry: not affected by the bias of the point estimate the type I error rate can be reliably controlled for various distribution assumptions and the power of T2EQ exceeds the power of methods recently discussed in the literature. These results were presented for the first time at CEN‐ISBS 2017.
Clinical evaluation of physical guidance procedures in the treatment of food selectivity
Authors: Silbaugh Bryant C. , Swinnea Samantha , Falcomata Terry S.
Published: August 2018

In some cases of pediatric feeding disorders, reinforcement‐based behavioral interventions are ineffective at increasing acceptance of target foods, and the child will not allow the feeder to deposit the bite in the mouth. A small body of research suggests that this barrier can be overcome using physical guidance procedures. The purpose of the current clinical evaluation was to extend and replicate prior research by evaluating and comparing the effects of physical guidance procedures in a home setting to treat feeding problems in a boy with autism and food selectivity, for whom previous attempts to improve feeding with a reinforcement‐based intervention were ineffective. Improvements in all dependent variables were observed, acceptance generalized to his mother, and decreased disordered feeding generalized to his mother and novel foods. Limitations and future lines of research are discussed.