bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyhydroxyalkanoates: Structure, Properties and Sources
Authors: Berezina Nathalie , Maria Martelli Silvia
Published: November 2014

Economic and environmental concerns have driven the development of biobased polymers and materials in recent years. The PHAs family was not the main focus of studies for decades, however, this class of polymers has been gaining scientific and industrial interest. The variety of polymers that make up the PHA family—more than 150—is due to different producers and carbon sources. The most studied producers of short-chain length PHAs (PHASCL) are the microorganisms of the Cupriavidus genus, however, recent developments in the field of mixed cultures have also produced interesting results. An important point is that whatever the carbon source, the PHASCL producing organism will produce these biopolymers; this has allowed an extensive study of noble and waste carbon sources, usage of limiting factors and of nutrient-sufficient media. On the other hand, the structure of medium-chain length PHAs (PHAMCL) is intimately related to the carbon source used for the growth of the producing organism and the biopolymer accumulation. Also the properties of this family are very wide, ranging from brittle thermoplastic PHASCL to elastomeric PHAMCL. These properties can be triggered by post-fermentation modifications such as grafting, surface treatment etc., to reach the necessary thermo-chemical constraints. Finally, the biocompatibility of PHAs, influenced by their structure, makes them extremely interesting candidates for biomedical applications. This new market has specific constraints, which can influence the choice of the initial carbon source. The relationships between sources, structure and properties of different types of PHAs are discussed in this chapter.
Recovery and Extraction of Polyhydroxyalkanoates (PHAs)
Authors: Mohammadi Mitra , Ghaffari-Moghaddam Mansour
Published: November 2014

Polyhydroxyalkanoates (PHAs) are biopolymers synthesized by various bacteria from renewable sources and have drawn much interest from academic and industrial communities for their unique properties of biodegradability and biocompatibility. Nevertheless, PHA production is restricted due to their high cost compared to petrochemical-based plastics, which is mainly affected by downstream processing. Therefore, the development of PHA extraction methods is required to make the overall process much simpler and cheaper. This chapter reviews a useful classification of different recovery methods that are available to extract PHAs from cells. It has been found that some of the most successful laboratory cell disruption techniques have no possibility of commercialization. Thus, a commercial recovery system with a simple, efficient and economical procedure will probably focus on a non-solvent extraction-based recovery amongst a variety of PHA recovery methods. It is seen that the halogen-free methods could be considered as green alternative technologies for PHA recovery which are able to eliminate the usage of harsh organic solvents and their negative impact on the environment.
Nanocomposites of Polyhydroxyalkanoates (PHAs)
Authors: Gumel A. M. , Annuar M. S. M.
Published: November 2014

A strong research interest in developing biodegradable nanocomposites and innovative process technologies is crucial to the development of sustainable materials for niche applications. Polyhydroxyalkanoate (PHA) nanocomposites are considered to be the next generation of smart biomaterials with diverse industrial applications, due to their biodegradability and compatibility. Intercalating PHAs with nanofillers results in materials with a higher aspect ratio and extendable surface area, which enhances their strength and stiffness without compromising toughness, leads to improved gas barrier properties, low thermal expansion coefficients etc. These altered properties expand their applications, surpassing those of neat PHA and its conventional microcomposites.
Modification of Polyhydroxyalkanoates (PHAs)
Authors: Gumel A. M. , Aris M. H. , Annuar M. S. M.
Published: November 2014

The excellent biodegradability, compatibility and versatile structural composition of polyhydroxyalkanotes (PHAs) have secured their significance for industrial applications. More importantly, these polymers can also play a critical role in biomedical applications such as a 3D scaffold for tissue engineering, bio-adhesive, surgical sutures, implants and anticoagulant films. Unfortunately, their hydrophobicity, crystallinity and lack of surface ligand groups potentially limit their applications in this area. Hence, the future of these biodegradable polymers as biomedical device components is strongly dependent on successful modifications to tailor their properties and characteristics. Chemical, physical and enzymatic approaches have been explored for polymer modifications, resulting in a uniquely transformed PHA endowed with functionalized reactive groups and/or enhanced properties such as thermal stability, elasticity, improved hydrophilicity and degradability. While chemical modification processes provide a large degree of freedom in controlling and designing modified PHAs in bulk quantities to suit a particular function, most often they have to contend with the drawback of toxic impurities that require difficult downstream processing. Physical or enzymatic modifications are therefore considered to be alternative methods that involve no toxic compounds. A number of modified PHAs are easily prepared by physical methods and have been successfully applied in diverse applications where neat PHAs may have easily failed. However, the current concern over environmental degradation and deterioration coupled with elevated health hazards discourage the use of high energy radiation and co-initiator chemicals in physical methods, pushing the emerging environmentally friendly enzyme catalyzed process to the center stage of the modification arena. In this chapter, the chemical, physical and enzymatic processes typically employed for polymer modification and functionalization are discussed.
Polyhydroxyalkanoates as Packaging Materials: Current Applications and Future Prospects
Authors: Hartley Yee Lachlan , Ray Foster Leslie John
Published: November 2014

Packaging serves a number of essential functions and conventional thermoplastics derived from fossil fuels are dominant in the packaging industry. However, there are serious issues with their environmental persistence and the leaching of their various additives. In contrast, the use of natural, biodegradable bioplastics supports sustainable development. The family of polyhydroxyalkanoates (PHAs) offers versatility in the properties required for plastic packaging. While their biodegradation ensures the continued development of PHAs for sustainable packaging, researchers are also using this property for the controlled release of agricultural agents such as herbicides and pesticides. Similarly, the biocompatibility and FDA approval have supported the investigation of PHAs in the packaging and delivery of pharmaceutical agents and cells for medical applications. Thus, PHAs have been used to produce value-added packaging with properties beyond current plastics while promoting an environmentally friendly alternative for a sustainable future. This chapter summarises the requirements for sustainable packaging and how the properties of PHAs support their continued development in their environmentally-friendly medical packaging applications.
Packaging Applications of Polyhydroxyalkanoates (PHAs)
Authors: Matta Fakhouri Farayde , Carvalho Marcelo , Manique Barreto Pedro Luis , Cardoso de Jesus Rodolfo , Maria Martelli Silvia
Published: November 2014

Packaging is an important processes to maintain the quality of food products during storage, transportation and consumption. Also, packaging is a powerful marketing tool, inspiring consumers and bringing to the consumer of the brand all the information needed to make a choice. Over the last fifty years, synthetic polymers have replaced conventional materials (metals, ceramics, paper) in packaging applications due to their functionality, light weight, ease of processing, and low cost. However, the use of synthetic polymers manufactured from fossil fuels, which are non-renewable, have a strong impact on the environment. In this way, the use of renewable biodegradable polymers such as polyhydroxyalkanoates (PHAs) can fill a niche market, significantly reducing packaging waste, contributing to sustainable development and, if properly managed, reducing their environmental impact upon disposal. This chapter discusses the use of PHA in food packaging considering its intrinsic characteristics.
Synthesis of Well-defined Solid Catalysts by Surface Organometallic Chemistry
Authors: Lefebvre Frédéric
Published: November 2014

The chapter describes the synthesis and use in catalysis of supported complexes prepared by using the surface organometallic strategy. After a short description of the grafting sites of the support the rules governing their reactivity with organometallic complexes are given. The reactivity of these supported complexes is also explained and finally some examples of the use of these systems are listen, in the case of alkanes (hydrogenolysis, metathesis), olefins (metathesis, dimerization, trimerization, asymmetric epoxidation) and nitrogen.
Bimetallic Supported Catalysts from Single-source Precursors
Authors: Hermans Sophie
Published: November 2014

In order to obtain synergistic effects, two (or more) metals need to be associated intimately within supported nanoparticles. However, it is very difficult to ensure homogeneity of composition using conventional preparation procedures starting from commercial metal precursors. In this chapter, we will show how mixed-metal molecular complexes as well-defined single-source precursors allow the preparation of supported metal nanoparticles with controlled compositions. Special emphasis will be placed on metal clusters.
Atomically Precise Gold Catalysis
Authors: Krishna Katla Sai , Liu Jing , Tarakeshwar Pilarisetty , Mujica Vladimiro , Spivey James J. , Kumar Challa S. S. R.
Published: November 2014

Atomically precise nanoclusters, with sizes ranging from about ten to a few hundred atoms, are a new class of nanocatalysts that have been gaining prominence in the past decade as seen by increasing number of publications including review articles. This is especially true in the case of atomically precise gold nanocatalysts. In this chapter, we review this field starting with an introduction followed by highlighting synthesis and catalytic applications of the atomically precise gold clusters, an overview of their electronic and magnetic structure, and opportunities for correlation of the electronic and magnetic structure of the clusters with their catalytic activity. Especially new insights into the magnetic properties of these atomically precise catalysts are presented paving the way toward potentially chemically turn-on and tune-in their magnetism and thereby providing an opportunity not only to tailor-make atomically precise nanomagnetic clusters but also to investigate magnetic structure dependent catalysis. In general, we believe that correlation of the atomic structure of these atomically precise nanoclusters with their catalytic properties will provide significant guidelines for the future design of catalysts, with atomic precision, for any specific chemical reaction.
Atomically Precise Gold Nanoclusters: Synthesis and Catalytic Application
Authors: Li Gao , Jin Rongchao
Published: November 2014

Atomically precise gold nanoclusters protected by thiolate ligands, Aun(SR)m, have emerged as a new class of nanomaterial in recent years. Many different sizes of Aun(SR)m nanoclusters have been synthesized and some have been crystallographically characterized. These atomically precise Aun(SR)m nanoclusters exhibit strong electron-energy quantization effects due to their ultra-small size (1–2 nm diameter), in contrast with the continuous electronic conduction band in metallic gold nanoparticles. These unique nanoclusters have also been demonstrated to be promising catalysts for a wide range of reactions, such as selective oxidation and hydrogenation, and carbon–carbon coupling reactions. These atomically precise Aun(SR)m nanoclusters (especially Au25(SCH2CH2Ph)18) can serve as new model catalysts and provide an opportunity to correlate the catalytic properties with the intrinsic structure of gold nanoclusters, and such structure–property correlation offers exciting insights into the mechanistic aspects of gold nanocluster-catalyzed reaction processes.
Atomic Layer Deposition in Nanoporous Catalyst Materials
Authors: Dendooven Jolien
Published: November 2014

Atomic layer deposition (ALD) is a self-limited growth method which relies on sequential reactions of gas phase precursor molecules with a solid surface to deposit oxides, metals and other materials in an atomic layer-by-layer fashion. The unique surface-controlled chemistry of ALD enables the conformal coating of high surface area nanoporous materials and provides atomic-level control over the coating thickness. These key advantages offer ALD the ability to precisely tune the pore size and chemical surface composition of nanoporous materials, and therefore render ALD an enabling technology for the controlled atomic-scale design of supported catalysts. Following a short introduction to the basic principles of the ALD technique, experimental studies are presented that demonstrate the ability of ALD for conformal deposition in nanometer-sized mesopores and in the bulk of high surface area powder particles. Selected examples are then discussed, illustrating the versatility of ALD for tailoring nanoporous supports and engineering the presence of catalytic sites or nanoparticles on the pore walls. A specific case study shows the potential of ALD for generating acid sites in ordered mesoporous silica materials. A second case study highlights an ALD-based approach for the synthesis of uniformly dispersed anatase nanoparticles in mesoporous silica thin films, resulting in photocatalytic activity.
Controllable Synthesis of Metal Nanoparticles for Electrocatalytic Activity Enhancement
Authors: Li Qing , Zhu Wenlei , Sun Shouheng
Published: November 2014

Electrochemical systems, such as fuel cells, batteries, and water-splitting devices, represent the most efficient and environmentally friendly technologies for energy conversion and storage to date. Typical electrochemical reactions for energy use such as the oxygen reduction reaction (ORR) require efficient catalysts to reduce reaction over-potentials. Advances in chemical syntheses have led to the formation of various types of nanoparticles (NPs) with more rational control of size, shape, composition, structure and catalysis. This chapter will review our recent efforts in the development of Pt and non-Pt based NPs as advanced catalysts for electrochemical reactions including ORR, formic acid oxidation (FAOR), and selective CO2 reduction. Various alloy and core–shell NPs with controlled electronic (alloying) and strain (geometric) effects for tuning electrocatalytic activity are systematically discussed. Guidance to rational design and synthesis of advanced electrocatalysts with much improved activity and performance durability for electrochemical energy applications is also addressed.
Investigating Nano-structured Catalysts at the Atomic scale by Field Ion Microscopy and Atom Probe Tomography
Authors: Barroo Cédric , Bagot Paul A. J. , Smith George D. W. , Visart de Bocarmé Thierry
Published: November 2014

Recent synthesis developments have refined the use of catalyst alloys, creating structures consisting of an active shell surrounding an inert core. These have been remarkably successful in reducing the total metal costs while also enhancing the surface activity of the shell. To reach an atomic-scale understanding of their structure and chemistry, Field ion/field electron microscopy (FIM/FEM) and atom probe tomography (APT) are uniquely suited to this task. This chapter will review the highlights of the research aiming at characterizing the surface reactivity, the three-dimensional structure and the composition of nano-engineered solid catalysts, as well as discussing ongoing experimental developments to improve the specimen forms and to construct in situ reaction cells, both designed to allow experiments to mimic the structures and operating conditions of industrial catalysts as closely as possible.
Instrumental Isotopic Fractionation
Authors: Irrgeher Johanna , Prohaska Thomas
Published: November 2014

In mass spectrometry, the term ‘instrumental isotopic fractionation’ is recommended to describe the sum of the effects in a mass spectrometer occurring during sample introduction, ion formation, ion extraction, ion separation and ion detection leading to a difference of the measured isotope ratio from the true isotope ratio in a sample. Instrumental isotopic fractionation (IIF) describes the instrumental fractionation between nuclides of the same element resulting in erroneous results of isotope ratios. The major aspects of IIF for the different techniques (i.e. (LA)-ICP-MS, GDMS, TIMS, SIMS and IRMS) based on magnetic sector field analysers are presented. A special focus is set on the description of the major causes of IIF, the areas of occurrence in the respective instrumentations as well as the impact of IIF on the final measurement result and the related measurement uncertainty. The described techniques differ strongly in the extent of IIF, mainly due to the different ionization sources as well as vacuum conditions.
Interferences
Authors: Prohaska Thomas
Published: November 2014

An interference in spectroscopy can be defined as anything that alters, modifies, or disrupts a measurement signal. Therefore, interferences are usually grouped in spectral interferences (also termed spectroscopic interferences) and nonspectral interferences. The latter refer mainly to matrix effects (also termed matrix interferences) and are specific for the different ionisation sources or sample introduction systems. A third source of interferences would result from the system electronics or stray electrons in the system or the detection unit. Within this section, the major focus is set on the occurrence of spectral interferences. A large number of interferences can be resolved by applying higher mass resolution as a key feature of a sector field mass spectrometers. Different approaches have been discussed in the literature and selected examples will be covered briefly in this chapter (e.g. mathematical correction procedures, sample preparation and introduction systems as well as modified instrumental parameters).
Glow Discharge Mass Spectrometry
Authors: Venzago Cornel , Pisonero Jorge
Published: November 2014

Originally, glow discharge (GD) plasmas were used as ion sources in the early days of mass spectrometry, in particular at the beginning of the 20th century on the pioneering studies carried out by J. J. Thomson, A. J. Dempster, and F. W. Aston. Today, glow discharge ion sources coupled to sector field mass spectrometers (GDSFMS) are mostly applied to direct solid sample multi-element and ultra trace analysis of high purity materials, mainly for electronics and photovoltaics industry. Limited matrix effects are shown in GDSFMS due to temporally and spatially separation of atomization and ionization processes. Most elements of the periodic table, except noble gases, can be measured and quantified to certain extents. Quantification is usually based on the ion beam ratio (IBR) between analyte and matrix ion signals. The range of quantification reaches from semi-quantitative to fully quantitative analysis. A concise overview of the technical background of GD ionisation as well as the numerous applications of this technique is given here.
Gas Source Isotope Ratio Mass Spectrometry (IRMS)
Authors: Brand Willi A. , Douthitt Charles B. , Fourel Francois , Maia Rodrigo , Rodrigues Carla , Maguas Cristina , Prohaska Thomas
Published: November 2014

Gas source isotope ratio mass spectrometry is usually referred to as isotope ratio mass spectrometry (IRMS) or stable-isotope ratio mass spectrometry (SIRMS). IRMS is a conventional method for measuring isotope ratios and has benefited from more than 65 years of research and development. Modern mass spectrometers are all based on gas source isotope ratio mass spectrometry field mass separators. More recently, the development of high-resolution sector field devices has added a new dimension to IRMS. Modern instruments achieve a high sample throughput, which is a prerequisite, e.g., for ecosystem studies where usually a large number of samples needs to be analysed and high precision is required. IRMS is used specifically for the measurement of stable-isotope ratios of a limited number of elements (C, H, N, O and S) after transfer into a gaseous species. Si, Cl, Br and Se can be added to the list even though their applications are limited compared to the other isotope systems. A concise overview of the technical background is given here as well as numerous applications of this technique in earth and geosciences, paleoclimate research, cosmochemistry, environmental sciences and life sciences.
Gas Source Isotope Ratio Mass Spectrometry for the Analysis of Noble Gases
Authors: Assonov Sergey , Prohaska Thomas
Published: November 2014

Geological processes result in redistribution of noble gases on Earth, with some isotopes being accumulated due to radioactive decay and cosmic irradiation. Therefore noble gas isotope and concentration ratios can be used as tracers of geological processes and geologic age. Analytical techniques for measuring noble gases are complex and differ substantially from the techniques used for stable isotopes. This chapter describes the historical development of noble gas isotope ratio mass spectrometry, sampling requirements, noble gas extraction techniques and sample gas purification and also gives the overview of modern commercially available instruments. Next the referencing strategy and calibration approaches are considered. The only international reference for noble gas isotope ratios is the Earth atmosphere reservoir – an artifact-based scale. In contrast to stable isotopes, noble gas applications require not only relative determinations vs. the international scale but mostly numerical values of isotope and elemental ratios. Up to date many publications refer to the noble gas isotope ratios determined in 1940s. Since then several re-determinations have been reported, being mostly based on commercially available noble gases. Unsolved discrepancies in the isotope ratios, e.g. for atmospheric Ar imply not well-identified uncertainty component for noble gas data which needs more attention. Finally an overview of applications is given.
Outlook
Authors: Prohaska Thomas , Irrgeher Johanna , Zitek Andreas
Published: November 2014

Thrilling developments of analytical capabilities and technological novelties of the 20th century have also fostered the field of elemental and isotopic mass spectrometry. Computer control catapulted the method into modern times and – still – the tremendously increasing amount of data is almost impossible to handle with basic modern computer technology. After the first generation of mass spectrometers had been dedicated to pure science, the instruments have faced a steady development and can nowadays not only be found in almost every scientific laboratory but have also entered many fields of routine analysis. Continued enhancements in performance allow for the investigation of areas that have even not been considered before. Smaller sample sizes, increased measurement precision, detection limits heading towards the detection of single atoms, combination of simultaneous measurements of sample properties – to name a few – and the race is not over, yet. Even though it is illusory and impossible to predict the future – which is by the way the intrinsic beauty of the future – we allow a glimpse into the crystal ball – or better to say, we summarise the rainbow wishes and lilac dreams of analytical scientists for the future.
A fluorescent probe for sensing ferric ions in bean sprouts based onl-histidine-stabilized gold nanoclusters
Authors: Su Yuan , Qi Li , Mu Xiaoyu , Wang Minglin
Published: November 2014

Fluorescentl-histidine-stabilized Au NCs were successfully synthesized by a green one-pot process sincel-histidine played dual roles as both a stabilizer and a reducing agent. Moreover, the prepared Au NCs were used as a novel fluorescent probe for selective sensing of ferric ions in bean sprouts.
Successive detection of glucose and bio-copper in human serum based on a multiplex biosensor of gold nanorods
Authors: Chen Shenna , Zhao Qian , Zhang Lingyang , Xia Xiaodong , Huang Haowen
Published: December 2014

A promising combined assay for the successive detection of blood glucose and sera copper levels based on etching of gold nanorods (GNRs) was developed.
Zn10(Im)20·4DBF: an unprecedented 10-nodal zeolitic topology with a 10-MR channel and 10 crystallographically independent Zn atoms
Authors: Shi Qi , Kang Xiaozhen , Shi Fa-Nian , Dong Jinxiang
Published: November 2014

Zn10(Im)20·4DBF has an unprecedented zeolitic topology and features 10 crystallographically independent Zn atoms and an unusual 4-connected 10-nodal net.
Non-universal tracer diffusion in crowded media of non-inert obstacles
Authors: Ghosh Surya K. , Cherstvy Andrey G. , Metzler Ralf
Published: November 2014

For tracer motion in an array of attractive obstacles we observe transient, non-ergodic anomalous diffusion depending on the obstacle density.
Aggregation induced emission enhancement of 4,4′-bis(diethylamino)benzophenone with an exceptionally large blue shift and its potential use as glucose sensor
Authors: Mazumdar Prativa , Das Debasish , Sahoo Gobinda Prasad , Salgado-Morán Guillermo , Misra Ajay
Published: November 2014

Aggregation induced emission enhancement of 4,4′-bis(diethylamino)benzophenone with exceptionally blue shift is observed and it is used for potential glucose sensor.
The effect of an elastic functional group in a rigid binder framework of silicon–graphite composites on their electrochemical performance
Authors: Yim Taeeun , Choi Soo Jung , Park Jeong-Han , Cho Woosuk , Jo Yong Nam , Kim Tae-Hyun , Kim Young-Jun
Published: November 2014

A binder which is modified by embedding an additional elastic functional group into a rigid binder framework is investigated to enhance the electrochemical performance of Si–graphite composites.
A functionalised nickel cyclam catalyst for CO2 reduction: electrocatalysis, semiconductor surface immobilisation and light-driven electron transfer
Authors: Neri Gaia , Walsh James J. , Wilson Calum , Reynal Anna , Lim Jason Y. C. , Li Xiaoe , White Andrew J. P. , Long Nicholas J. , Durrant James R. , Cowan Alexander J.
Published: November 2014

Covalent immobilisation of a low cost electrocatalyst leads to an enhanced rate of photoelectron transfer from a light absorbing semiconductor.
Efficient hydrosilylation of imines using catalysts based on iridium(iii) metallacycles
Authors: Corre Y. , Iali W. , Hamdaoui M. , Trivelli X. , Djukic J.-P. , Agbossou-Niedercorn F. , Michon C.
Published: November 2014

Ir(iii) metallacycles were applied as catalysts for the hydrosilylation of ketimines and aldimines by using sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate, NaBArF24, as an additive. By using a slight excess of the organosilane reagent, the reactions proceeded rapidly and efficiently, at low catalyst loadings and at room temperature.
Structure and water exchange dynamics of hydrated oxo halo ions in aqueous solution using QMCF MD simulation, large angle X-ray scattering and EXAFS
Authors: Eklund Lars , Hofer Tomas S. , Persson Ingmar
Published: November 2014

The structure and water exchange dynamics of the hydrated oxo halo ions in aqueous solution, studied by QMCF MD simulation and experimental X-ray methods, show that they are all structure breakers, thus the hydrogen bonding between the ion and surrounding water molecules is weaker than between water molecules in pure water.
Click chemistry mediated synthesis of bio-inspired phosphonyl-functionalized ionic liquids
Authors: Braun Richard A. , Bradfield Joseph L. , Henderson Codey B. , Mobarrez Niloufar , Sheng Yinghong , O'Brien Richard A. , Stenson Alexandra C. , Davis James H. , Mirjafari Arsalan
Published: November 2014

The key objective of this work is to develop bio-inspired ionic liquids that are highly lipophilic via “click” chemistry.
Electrochemical characterization of hydroquinone derivatives with different substituents in acetonitrile
Authors: Salazar Ricardo , Vidal Jorge , Martínez-Cifuentes Maximiliano , Araya-Maturana Ramiro , Ramírez-Rodríguez Oney
Published: November 2014

The effect of carbonyl groups in the ortho position with respect to a hydroxyl group on the electrochemical oxidation of hydroquinones in acetonitrile is studied.
Manganese triacetate as an efficient catalyst for bisperoxidation of styrenes
Authors: Terent'ev Alexander O. , Sharipov Mikhail Yu. , Krylov Igor B. , Gaidarenko Darya V. , Nikishin Gennady I.
Published: November 2014

Bisperoxidation of styrenes with tert-butyl hydroperoxide in the presence of a catalytic amount of Mn(OAc)3.
Enzyme-triggered delivery of chlorambucil from conjugates based on the cell-penetrating peptide BP16
Authors: Soler Marta , González-Bártulos Marta , Figueras Eduard , Ribas Xavi , Costas Miquel , Massaguer Anna , Planas Marta , Feliu Lidia
Published: November 2014

The combination of the cell-penetrating peptide BP16 with the enzymatic cleavable sequence Gly-Phe-Leu-Gly constitutes a drug delivery system for the effective uptake and release of chlorambucil in cancer cells.
Investigation of end processing and degradation of premature tRNAs and their application to stabilization of in vitro transcripts in wheat germ extract
Authors: Ogawa Atsushi , Doi Yasunori
Published: November 2014

We investigated the end processing and degradation of premature tRNAs in wheat germ extract (left), which led to the findings of end protectors for efficiently stabilizing an in vitro transcript (purple, right).
Magnetic clusters based on octacyanidometallates
Authors: Pinkowicz Dawid , Podgajny Robert , Nowicka Beata , Chorazy Szymon , Reczyński Mateusz , Sieklucka Barbara
Published: November 2014

A complete review of all known octacyanide-based clusters with an extensive discussion of their structures, magnetic properties and multifunctionality.
Preparation and enhanced supercapacitance performance of porous carbon spheres with a high degree of graphitization
Authors: Chang Binbin , Yang Baocheng , Guo Yanzhen , Wang Yiliang , Dong Xiaoping
Published: November 2014

This paper describes the preparation of graphitic porous carbon spheres (GPCS) from spherical resorcinol/formaldehyde resin by Fe-catalysis at 900 °C.
Thermodynamic, structural and functional properties of membrane protein inclusion bodies are analogous to purified counterparts: case study from bacteria and humans
Authors: Gupta Ankit , Iyer Bharat Ramasubramanian , Chaturvedi Deepti , Maurya Svetlana Rajkumar , Mahalakshmi Radhakrishnan
Published: November 2014

Purification-free transmembrane protein inclusion body preparations for rapid and cost-effective biophysical, functional and structural studies.
Carbon-coating functionalized La0.6Sr1.4MnO4+δ layered perovskite oxide: enhanced catalytic activity for the oxygen reduction reaction
Authors: Wang Yarong , Yang Zhibin , Lu Fanliang , Jin Chao , Wu Jiao , Shen Ming , Yang Ruizhi , Chen Fanglin
Published: November 2014

Efficient electrocatalysts for the oxygen reduction reaction (ORR) is a critical factor to influence the performance of lithium–oxygen batteries.
A biomass-involved strategy for the synthesis of N-arylated dibenzo[b,e][1,4]oxazepin-11(5H)-ones, acridones, 7,12-dihydrodibenzo[b,e][1,4]oxazocin-6H-ones and dibenzo[b,f]azepin-10(11H)-ones
Authors: Zhang Ensheng , Zhang Xuejing , Wei Wen , Wang Dejian , Cai Yuchen , Xu Tianlong , Yan Ming , Zou Yong
Published: December 2014

A chemo- and regio-selective method for the construction of benzo-fused six- to eight-membered N-heterocycles from renewable feedstock shikimic acid is described.
Oscillations in modulus in solutions of graphene oxide and reduced graphene oxide with grafted poly-N-isopropylamide
Authors: Hashmi Saud , GhavamiNejad Amin , Stadler Florian J. , Wu Dongmei
Published: November 2014

In a material consisting of graphene oxide or reduced graphene oxide and poly-N-isopropylamide (PNIPAM) in an aqueous solution, a new type of complex rheological behaviour is found, which is a new type of rheochaos.
Three-step sequential solution deposition of PbI2-free CH3NH3PbI3perovskite
Authors: Zhao Yixin , Zhu Kai
Published: November 2014

We demonstrate a facile approach for preparing PbI2-free CH3NH3PbI3perovskite filmsviaa three-step sequential solution process.
A photocatalytically inactive microporous titanate nanofiber as an excellent and versatile additive to enhance the TiO2 photocatalytic activity
Authors: Ide Y. , Komaguchi K.
Published: December 2014

When just mixed with a new and photocatalytically inactive material (microporous titanate nanofiber), TiO2 showed largely enhanced photocatalytic activities.
Acceptor defect-participating magnetic exchange in ZnO : Cu nanocrystalline film: defect structure evolution, Cu–N synergetic role and magnetic control
Authors: Hu Liang , Zhu Liping , He Haiping , Zhang Le , Ye Zhizhen
Published: November 2014

Acceptor defect: a more efficient ferromagnetic activation route than donor defect in Zn–Cu–O dilute magnetic semiconductor.
Metal toxicity and the p53 protein: an intimate relationship
Authors: Phatak Vinaya M. , Muller Patricia A. J.
Published: November 2014

The relationship between p53, ROS and transition metals.
Prismatic analyser concept for neutron spectrometers
Authors: Birk Jonas O. , Markó Márton , Freeman Paul G. , Jacobsen Johan , Hansen Rasmus L. , Christensen Niels B. , Niedermayer Christof , Månsson Martin , Rønnow Henrik M. , Lefmann Kim
Published: November 2014

Developments in modern neutron spectroscopy have led to typical sample sizes decreasing from few cm to several mm in diameter samples. We demonstrate how small samples together with the right choice of analyser and detector components makes distance collimation an important concept in crystal analyser spectrometers. We further show that this opens new possibilities where neutrons with different energies are reflected by the same analyser but counted in different detectors, thus improving both energy resolution and total count rate compared to conventional spectrometers. The technique can readily be combined with advanced focussing geometries and with multiplexing instrument designs. We present a combination of simulations and data showing three different energies simultaneously reflected from one analyser. Experiments were performed on a cold triple axis instrument and on a prototype inverse geometry Time-of-flight spectrometer installed at PSI, Switzerland, and shows excellent agreement with the predictions. Typical improvements will be 2.0 times finer resolution and a factor of 1.9 in flux gain compared to a focussing Rowland geometry, or of 3.3 times finer resolution and a factor of 2.4 in flux gain compared to a single flat analyser slab.
The principal indecomposable modules of the dilute Temperley-Lieb algebra
Authors: Belletête Jonathan , Saint-Aubin Yvan
Published: November 2014

The Temperley-Lieb algebra \documentclass[12pt]{minimal}\begin{document}$\mathsf {TL}_{n}(\beta )$\end{document}TLn(β) can be defined as the set of rectangular diagrams with n points on each of their vertical sides, with all points joined pairwise by non-intersecting strings. The multiplication is then the concatenation of diagrams. The dilute Temperley-Lieb algebra \documentclass[12pt]{minimal}\begin{document}$\mathsf {dTL}_{n}(\beta )$\end{document}dTLn(β) has a similar diagrammatic definition where, now, points on the sides may remain free of strings. Like \documentclass[12pt]{minimal}\begin{document}$\mathsf {TL}_{n}$\end{document}TLn, the dilute \documentclass[12pt]{minimal}\begin{document}$\mathsf {dTL}_{n}$\end{document}dTLn depends on a parameter \documentclass[12pt]{minimal}\begin{document}$\beta \in \mathbb {C}$\end{document}β∈C, often given as β = q + q−1 for some \documentclass[12pt]{minimal}\begin{document}$q\in \mathbb {C}^\times$\end{document}q∈C×. In statistical physics, the algebra plays a central role in the study of dilute loop models. The paper is devoted to the construction of its principal indecomposable modules. Basic definitions and properties are first given: the dimension of \documentclass[12pt]{minimal}\begin{document}$\mathsf {dTL}_{n}$\end{document}dTLn, its break up into even and odd subalgebras and its filtration through n + 1 ideals. The standard modules \documentclass[12pt]{minimal}\begin{document}$\mathsf {S}_{n,k}$\end{document}Sn,k are then introduced and their behaviour under restriction and induction is described. A bilinear form, the Gram product, is used to identify their (unique) maximal submodule \documentclass[12pt]{minimal}\begin{document}$\mathsf {R}_{n,k}$\end{document}Rn,k which is then shown to be irreducible or trivial. It is then noted that \documentclass[12pt]{minimal}\begin{document}$\mathsf {dTL}_{n}$\end{document}dTLn is a cellular algebra. This fact allows for the identification of complete sets of non-isomorphic irreducible modules and projective indecomposable ones. The structure of \documentclass[12pt]{minimal}\begin{document}$\mathsf {dTL}_{n}$\end{document}dTLn as a left module over itself is then given for all values of the parameter q, that is, for both q generic and a root of unity.
Positive feedback can lead to dynamic nanometer-scale clustering on cell membranes
Authors: Wehrens Martijn , ten Wolde Pieter Rein , Mugler Andrew
Published: November 2014

Clustering of molecules on biological membranes is a widely observed phenomenon. A key example is the clustering of the oncoprotein Ras, which is known to be important for signal transduction in mammalian cells. Yet, the mechanism by which Ras clusters form and are maintained remains unclear. Recently, it has been discovered that activated Ras promotes further Ras activation. Here we show using particle-based simulation that this positive feedback is sufficient to produce persistent clusters of active Ras molecules at the nanometer scale via a dynamic nucleation mechanism. Furthermore, we find that our cluster statistics are consistent with experimental observations of the Ras system. Interestingly, we show that our model does not support a Turing regime of macroscopic reaction-diffusion patterning, and therefore that the clustering we observe is a purely stochastic effect, arising from the coupling of positive feedback with the discrete nature of individual molecules. These results underscore the importance of stochastic and dynamic properties of reaction diffusion systems for biological behavior.
Low-energy photoelectron imaging of HS2 anion
Authors: Qin Zhengbo , Cong Ran , Liu Zhiling , Xie Hua , Tang Zichao
Published: November 2014

Low-energy photoelectron imaging of HS2− has been investigated, which provides the vibrational frequencies of the ground state as well as the first excited state of HS2. It allows us to determine more accurate electron affinity of HS2, 1.9080 ± 0.0018 eV. Combined with Frank-Condon simulation, the vibrational features have been unveiled related to S-S stretching and S-S-H bending modes for the ground state and S-S stretching, S-S-H bending, and S-H stretching modes for the first excited state. Photoelectron angular distributions are mainly characteristic of electron detachment from two different molecular orbitals (MOs) in HS2−. With the aid of accurate electron affinity value of HS2, corresponding thermochemical quantities can be accessed.
Electrically generated eddies at an eightfold stagnation point within a nanopore
Authors: Sherwood J. D. , Mao M. , Ghosal S.
Published: November 2014

Electrically generated flows around a thin dielectric plate pierced by a cylindrical hole are computed numerically. The geometry represents that of a single nanopore in a membrane. When the membrane is uncharged, flow is due solely to induced charge electroosmosis, and eddies are generated by the high fields at the corners of the nanopore. These eddies meet at stagnation points. If the geometry is chosen correctly, the stagnation points merge to form a single stagnation point at which four streamlines cross at a point and eight eddies meet.
Morphology and molecular bridging in comb- and star-shaped diblock copolymers
Authors: Hart Kyle E. , Abbott Lauren J. , Lísal Martin , Colina Coray M.
Published: November 2014

Block copolymers spontaneously self-assemble into nanostructured morphologies with industrially attractive properties; however, the relationships between polymer architecture and self-assembled morphology are difficult to tailor for copolymers with increased conformational restrictions. Using Dissipative Particle Dynamics, the self-assembled morphology of comb- and star-shaped diblock copolymers was simulated as a function of the number of arms, arm length, weight fraction, and A-B incompatibility. As the number of arms on the star, or grafting points for the comb, was increased from three to four to six, the ability to self-assemble into ordered morphologies was restricted. The molecular bridging between adjacent ordered domains was observed for both comb- and star-shaped copolymers, which was found to be enhanced with increasing number of arms. This study illustrates that comb- and star-shaped copolymers are viable alternatives for applications that would benefit from highly bridged nanostructural domains.
Singlet fission in linear chains of molecules
Authors: Ambrosio Francesco , Troisi Alessandro
Published: November 2014

We develop a model configuration interaction Hamiltonian to study the electronic structure of a chain of molecules undergoing singlet fission. We first consider models for dimer and trimer and then we use a matrix partitioning technique to build models of arbitrary size able to describe the relevant electronic structure for singlet fission in linear aggregates. We find that the multi-excitonic state (ME) is stabilized at short inter-monomer distance and the extent of this stabilization depends upon the size of orbital coupling between neighboring monomers. We also find that the coupling between ME states located on different molecules is extremely small leading to bandwidths in the order of ∼10 meV. This observation suggests that multi-exciton states are extremely localized by electron-phonon coupling and that singlet fission involves the transition between a relatively delocalized Frenkel exciton and a strongly localized multi-exciton state. We adopt the methodology commonly used to study non-radiative transitions to describe the singlet fission dynamics in these aggregates and we discuss the limit of validity of the approach. The results indicate that the phenomenology of singlet fission in molecular crystals is different in many important ways from what is observed in isolated dimers.
Entropic pressure in lattice models for polymers
Authors: Hammer Yosi , Kantor Yacov
Published: November 2014

In lattice models, local pressure on a surface is derived from the change in the free energy of the system due to the exclusion of a certain boundary site, while the total force on the surface can be obtained by a similar exclusion of all surface sites. In these definitions, while the total force on the surface of a lattice system matches the force measured in a continuous system, the local pressure does not. Moreover, in a lattice system, the sum of the local pressures is not equal to the total force as is required in a continuous system. The difference is caused by correlation between occupations of surface sites as well as finite displacement of surface elements used in the definition of the pressures and the force. This problem is particularly acute in the studies of entropic pressure of polymers represented by random or self-avoiding walks on a lattice. We propose a modified expression for the local pressure which satisfies the proper relation between the pressure and the total force, and show that for a single ideal polymer in the presence of scale-invariant boundaries it produces quantitatively correct values for continuous systems. The required correction to the pressure is non-local, i.e., it depends on long range correlations between contact points of the polymer and the surface.
Partition function zeros and finite size scaling for polymer adsorption
Authors: Taylor Mark P. , Luettmer-Strathmann Jutta
Published: November 2014

The zeros of the canonical partition functions for a flexible polymer chain tethered to an attractive flat surface are computed for chains up to length N = 1536. We use a bond-fluctuation model for the polymer and obtain the density of states for the tethered chain by Wang-Landau sampling. The partition function zeros in the complex eβ-plane are symmetric about the real axis and densest in a boundary region that has the shape of a nearly closed circle, centered at the origin, terminated by two flaring tails. This structure defines a root-free zone about the positive real axis and follows Yang-Lee theory. As the chain length increases, the base of each tail moves toward the real axis, converging on the phase-transition point in the thermodynamic limit. We apply finite-size scaling theory of partition-function zeros and show that the crossover exponent defined through the leading zero is identical to the standard polymer adsorption crossover exponent ϕ. Scaling analysis of the leading zeros locates the polymer adsorption transition in the thermodynamic (N → ∞) limit at reduced temperature \documentclass[12pt]{minimal}\begin{document}$T_c^*\break=1.027(3)$\end{document}Tc*=1.027(3) [\documentclass[12pt]{minimal}\begin{document}$\beta _c=1/T_c^*=0.974(3)$\end{document}βc=1/Tc*=0.974(3)] with crossover exponent ϕ = 0.515(25). Critical exponents for the order parameter and specific heat are determined to be \documentclass[12pt]{minimal}\begin{document}$\widetilde{\beta }=0.97(5)$\end{document}β̃=0.97(5) and α = 0.03(4), respectively. A universal scaling function for the average number of surface contacts is also constructed.
Dust ion acoustic solitary waves in a collisional dusty plasma with dust grains having Gaussian distribution
Authors: Maitra Sarit , Banerjee Gadadhar
Published: November 2014

The influence of dust size distribution on the dust ion acoustic solitary waves in a collisional dusty plasma is investigated. It is found that dust size distribution changes the amplitude and width of a solitary wave. A critical wave number is derived for the existence of purely damping mode. A deformed Korteweg-de Vries (dKdV) equation is obtained for the propagation of weakly nonlinear dust ion acoustic solitary waves and the effect of different plasma parameters on the solution of this equation is also presented.
Exponential approximation for one-component Yukawa plasma
Authors: Hlushak Stepan
Published: November 2014

A theory based on the exponential approximation of the liquid-state theory is applied to study properties of several models of one-component Yukawa plasma characterized by different values of the screening parameter z. The results of the new theory are compared to the results of a conventional theory, which is based on the first-order mean spherical approximation, and to the results of a Monte Carlo simulation. The new theory shows improvements in the predictions for the thermodynamic and structural properties of Yukawa plasmas with high and intermediate values of the screening parameter, z, and coupling parameter, Γ. For low values of z and Γ, the new theory is comparable in accuracy to the conventional theory, which in turn agrees well with the results of the Monte Carlo simulation.