bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coseismic velocity change associated with the 2011 Van earthquake (M7.1): Crustal response to a major event
Authors: Acarel Diğdem , Bulut Fatih , Bohnhoff Marco , Kartal Recai 
Published: June 2014

AbstractMonitoring coseismic velocity changes is a major challenge, since the Earth crust has to be uniformly sampled at preseismic, coseismic, and postseismic stages using repeating active or natural sources. Here we investigate the crustal response to the 2011 Van/Turkey earthquake using ambient noise, which provides the best possible temporal resolution. Combined recordings from the nearest five broadband stations are analyzed for a time period of 6 months framing the main shock. We observe a coseismic velocity decrease of up to 0.76% in the vicinity of the main shock in the frequency range of 0.05–0.3 Hz. The velocity drop is largest at close proximity to the earthquake hypocenter and decreases systematically with distance. We also find a correlation between coseismic velocity decrease and the amount of coseismic slip on the rupture plane. The observed velocity drop shows the drastic response of the brittle crust in response to a major earthquake.
A physical mechanism of the precipitation dipole in the western United States based on PDO‐storm track relationship
Authors: Sung Mi‐Kyung , An Soon‐Il , Kim Baek‐Min , Woo Sung‐Ho 
Published: June 2014

AbstractIt is known that the western United States (US) precipitation displays a north‐south contrast, i.e., the so‐called “precipitation dipole,” during El Niño and La Niña winters. Furthermore, the Pacific Decadal Oscillation (PDO) has been known to modulate this precipitation dipole. However, the underlying physical mechanism regulating this modulation is not well understood. This study revisits previous studies and suggests a physical mechanism of precipitation dipole modulation based on the PDO‐storm track relationship. We found that both jet stream and storm track tend to move northward (southward) over the North Pacific during negative (positive) PDO winters, contributing to the increase of precipitation over the northwestern (southwestern) US, respectively. This relationship is robust regardless of El Niño‐Southern Oscillation (ENSO), possibly facilitating modulation of the precipitation dipole. Moreover, changes in oceanic baroclinicity associated with the PDO phase are suggested to be responsible for anchorage of storm tracks over the North Pacific.
Model of blue jet formation and propagation in the nonuniform atmosphere
Authors: Milikh G. M. , Shneider M. N. , Mokrov M. S. 
Published: June 2014

AbstractAbout two decades ago, researchers discovered upward propagating flashes of light originating above thunderstorms. Due to their distinctive, principally blue color, they were named “blue jets” (BJ). The broadly accepted production mechanism of a BJ is through a lightning leader which rises through the nonuniform atmosphere. Specifically, the formation of the initial lightning leader is thought to be governed by the contraction of the current of a streamer flash into a small radius channel. This paper presents results of simulations of the current contraction in the air as a function of both the pressure and convective heat removal time. We have shown that transitions to the contracted state occur in a hysteresis mode that allows both contracted and diffusive states to coexist. We have obtained the critical current for this phase transition and studied the formation and propagation of BJs in the atmosphere through a combination of quantitative models and existing observations of BJs that combine optical images with the data of the electric current carried by the jets.
Solid‐Phase Microextraction and its Application to Natural Products
Authors: Mottaleb M. Abdul , Meziani Mohammed J. , Islam M. Rafiq 
Published: June 2014

AbstractSolid‐phase microextraction (SPME) is a simple, fast, and efficient sample preparation technique that eliminates the need for solvents and integrates sampling, isolation, and enrichment in one step. Fibers or capillary tubes coated with an appropriate stationary phase are key players in the process. By controlling the polarity and thickness of the coating on fibers or tubes, sampling time, and other extraction parameters, an analyst can achieve very reliable, accurate, and highly quantifiable robust results at subfemtogram level, for gaseous to macromolecular target solutes, with a shorter analysis time compared to conventional extraction methods. This solvent‐free technique requires small samples, saves sample preparation time as well as solvent purchase and disposal costs. Moreover, it is environmental friendly and poses low health hazard risk to the laboratory associates. Today,SPMEhas been integrated to gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), high performance liquid chromatography (HPLC or LC), LC–MS, or capillary electrophoresis (CE) for analysis of complex mixtures of samples that include environmental, chemical, biochemical, biological, pharmaceuticals, clinical, biomedical, natural products, food abstracts, plant extracts, and organic compounds in media containing nanoparticles.
High Pressure Liquid Chromatography and Ultra‐high Pressure Liquid Chromatography of Plants: Basic Concepts
Authors: Meyer Veronika R. 
Published: June 2014

AbstractHigh‐performance liquid chromatography (HPLC) is an essential method in plant analysis. Although it is primarily a separation method, it offers also the possibility of on‐line quantitative analysis during the separation. It can be used for both, the investigation of classes of compounds as well as of individual substances. HPLC is an instrumental method of great flexibility with regard to the separation conditions and to the detection principle. In any case, high pressure is needed; conventional HPLC acts up to about 350 bar. As the available pressure limits the speed of analysis and its separation power, the more recent technology of ultra high‐performance liquid chromatography (UHPLC) works at pressures up to 1000 bar. It allows very fast analyses or high peak capacity (i.e., the number of resolved compounds) or a combination of both demands. The separation environment can be aqueous, for example, in reversed‐phase or ion‐exchange HPLC, or nonpolar with organic solvents in adsorption chromatography, thus allowing a great choice of investigative principles.
Liquid Chromatography and Liquid Chromatograpy‐Mass Spectrometry of Plants: Techniques and Applications
Authors: Arens Nadja , Doell Stefanie , Mock Hans‐Peter 
Published: June 2014

Abstract
Technical advances in LC–MS hardware instrumentation and in data analysis software tools have enabled the routine implementation of comprehensive metabolite studies in many biological laboratories. In this chapter, we describe the current types of MS instruments and corresponding applications. LC–MS systems can be coupled to UV or fluorescence detectors and even spatial resolution of metabolic distribution (MALDI‐imaging) is feasible to gain valuable additional information.
LC–MS applications usually divide into targeted or untargeted approaches, whereby the general aims are either to quantify a known substance or to analyze and compare metabolite profiles of two conditions to identify potential biomarkers. For tentative annotation of unknown compounds, LC–MS/MS analysis are conducted.
An incessantly growing number of software tools have been developed to handle the challenge of extracting biologically valuable information from LC–MS analysis, which generates enormous amounts of data. Furthermore, various databases have been set up to facilitate annotation of compounds of interest.
Strategies for the Analysis of Plant Lipids
Authors: Guschina Irina A. , Harwood John L. 
Published: June 2014

AbstractPlant lipids are characterized by a number of features unexpected by scientists who study animal or bacterial systems. Photosynthetic tissues contain high amounts of glycosylglycerides while the surfaces are covered in cutin and suberin. The acyl composition is highly unsaturated. Lipid extraction of plants needs special precautions as does general handling of the extracts. In general, complex lipids are best analyzed by a combination of thin‐layer and gas–liquid chromatography. Surface layers need particular methods. For identification, combinations of techniques are required. Recent advances in mass spectrometry allow detailed examination of complex lipid mixtures, lipidomics, and tissue localization of individual classes. Other physical techniques (such as infrared spectroscopy and nuclear magnetic resonance) have particular applications.This chapter describes the most useful methods currently in use including the use of isotopes to study metabolism. Precautions for nonexperts are mentioned as well as prospects for useful future developments.
Plant Steroids: Occurrence, Biological Significance and their Analysis
Authors: B. Gunaherath G. M. Kamal , Gunatilaka A. A. Leslie 
Published: June 2014

Abstract

Plant steroids constitute a diverse group of natural products. Biosynthetically, they are derived from
S
‐squalene‐2,3‐epoxide via acetate‐mevalonate pathway. Among the plant steroids, phytosterols are ubiquitous in the plant kingdom. It is significant that some phytosterols have been reported to possess hypocholesterolemic activity. Withanolides are a large group of steroidal lactones with various biological activities. Brassinosteroids are a small group of plant steroids exhibiting plant growth hormonal activity. Phytoecdysteroids are polyhydroxylated plant steroids, many of which are known to exhibit anabolic effects with no undesirable side effects. Steroidal alkaloids are nitrogen‐containing plant steroids with an array of biological activities. It is noteworthy that trace amounts of cholesterol and mammalian steroidal hormones including progesterone have been detected in some plants. Analyses of plant steroids mainly utilize chromatographic methods such as thin‐layer chromatography (
TLC
), high performance liquid chromatography (
HPLC
), ultra high performance liquid chromatography (
UHPLC
), and gas liquid chromatography (
GLC
), while photodiode array (
PDA
), evaporative light scattering (
ELS
), and fluorescence (
FL
) detectors and mass spectrometry (
MS
) are commonly used for their detection, quantification, and identification. Some less common techniques employed for the analyses of plant steroids are immunoassays and biological assays.
Plant Proteomics
Authors: Yang Liming , Xu Haibin , Chen Shilin 
Published: June 2014

AbstractWith the increase in the completion of the genome sequence of plant organisms, more attention has been focused on understanding the functions of genes on a genome‐wide scale, not only the exact time and location of gene expression, but also which proteins and under what conditions they express in certain cells, tissues, or organs. While the transcriptomic analysis can only provide us the spatial and temporal specificities or regulatory network relationships of gene expressions, proteome analysis can illustrate the post‐translational modifications of proteins, subcellular localizations, protein–protein interactions, and protein conformations. This chapter focuses on the background and concept of proteomics and the principal research techniques of plant proteomics. These techniques are primarily divided into (i) gel‐based proteomics, (ii) mass spectrometry‐based proteomics, and (iii) chip‐based proteomics. Two‐dimensional electrophoresis (2‐DE) and isobaric tags for relative and absolute quantitation (iTRAQ), which are the two most commonly used methods with the highest resolution in high throughput plant proteomics, are described in details. Finally, opportunities and current challenges to the development of plant proteomic research techniques are discussed.
Gold‐Catalyzed Addition ofHXto Alkynes
Authors: Genin Emilie , Michelet Veronique 
Published: June 2014

AbstractAmong the myriad of organic transformations that have been developed in the area of gold catalysis, the addition of HX to alkynes has been a field of intense investigation. This chapter presents the main and recent contributions in the field of gold‐catalyzed nucleophilic addition of HX to alkynes. The presentation includes the addition ofO‐nucleophiles (including water, alcohols and carboxylic acids), ofN‐nucleophiles and other heteroatom nucleophiles (including thiols and halogens) to alkynes. The historical background for inter‐ and intramolecular additions, the domino processes and the applications to natural products synthesis are highlighted.
[18O]‐Peroxides: Synthesis and Biological Applications
Authors: Mascio Paolo Di , Miyamoto Sayuri , Medeiros Marisa H. G. , Martinez Glaucia R. , Cadet Jean 
Published: June 2014

AbstractThe peroxidation reactions of the main cellular targets including nucleic acids, proteins and unsaturated lipids have received major attention during the last two decades. This was particularly the case for the hydroperoxides generated by1O2, one of the main reactive oxygen species that usually oxidizes biomolecules in a more specific way than either •OH or one‐electron oxidants. Most of the endoperoxides and hydroperoxides produced by 1O2 have been shown to be unstable and therefore their identification is often difficult. The use of [18O]‐labeled1O2released from thermolabile endoperoxides in association with HPLC‐ESI‐MS/MS analysis provides a highly suitable way to gain relevant mechanistic insights into the formation and the decomposition pathways of initially generated peroxidic compounds. The possibility of cell penetration afforded by suitable naphthalene endoperoxides has also been exploited for investigating the reaction of1O2with DNA for accrediting the mechanism of oxidation of guanine in the nucleus and providing an elegant approach for assessing the validity of DNA isolation methods used in the measurement of 8‐oxo‐7,8‐dihydroguanine, an ubiquitous oxidation product. Further developments are expected both in mechanistic studies and applications in cells using [18O]‐labeled1O2generators.
The First Allylation of Esters by an Allylsilane: One‐Pot Domino Synthesis of Triallylmethane Derivatives
Authors: Bandi Chenna Kesava Reddy , Belostotskii Anatoly , Hassner Alfred 
Published: June 2014

AbstractWe report the first successful allylation of aromatic esters by allyltrimethylsilane. The reaction is mediated by 0.3–1.0 equiv. of titanium tetrachloride (TiCl4) at room temperature and leads in a multi‐step, one‐pot reaction to quaternary triallylmethane derivatives 5. The most efficient ester possessed two ortho‐methoxy substituents on the phenol ring. Molecular modelling revealed the ability of this compound to form a bidentate titanium complex, thus improving the steric accessibility of the ester carbonyl to nucleophilic attack.magnified image
Trifluormethylierung von Alkenen unter gleichzeitiger Einführung weiterer funktioneller Gruppen
Authors: Egami Hiromichi , Sodeoka Mikiko 
Published: June 2014

AbstractDie Trifluormethylgruppe ist Bestandteil vieler synthetischer bioaktiver Verbindungen, und die Difunktionalisierung von CC‐Bindung wurde als wirksame Strategie zum Aufbau von Verbindungen mit verschiedenen Funktionalitäten intensiv erforscht. Folgerichtig ist die difunktionalisierende Trifluormethylierung von Alkenen auf wachsendes Interesse gestoßen, da die Produkte potenzielle Bausteine für bioaktive Moleküle darstellen. Dieser Aufsatz stellt neueste Fortschritte bei der Trifluormethylierung von Alkenen unter gleichzeitiger Einführung weiterer funktioneller Gruppen vor.
Strategien für die Synthese funktioneller Naphthalindiimide
Authors: Suraru Sabin‐Lucian , Würthner Frank 
Published: June 2014

AbstractNaphthalindiimide, die lange im Schatten ihrer größeren homologen Perylendiimide standen, gehören gegenwärtig zu einer der am meisten untersuchten organischen Substanzklassen. Zu verdanken ist dies vornehmlich den präparativen Vorarbeiten zur Kernfunktionalisierung zu Beginn des letzten Jahrzehnts, welche die vielfältigen strukturellen Modifizierungen des Naphthalindiimid‐Grundkörpers ermöglichten. Mit relativ geringem Syntheseaufwand sind Verbindungen mit stark veränderten optischen und elektrochemischen Eigenschaften zugänglich, die je nach Funktionalisierung leicht und effektiv eingestellt werden können. Dies hat verschiedene interessante Anwendungen zur Folge. So macht der elektronenarme Charakter der Verbindungen sie besonders auf dem Gebiet der organischen Elektronik als luftstabile n‐Halbleiter höchst bedeutsam, während die durch Kernsubstituenten über den gesamten sichtbaren Spektralbereich einstellbaren Absorptionsbanden interessante Photosysteme und Photovoltaikanwendungen möglich gemacht haben. Dieser Aufsatz gibt einen Überblick über die verschiedenen Möglichkeiten zur Kernfunktionalisierung und die vornehmlich in den letzten fünf Jahren entwickelten Synthesestrategien zur Kernexpansion des Naphthalindiimids.
Elektrochemisch erzeugte Gradienten
Authors: Krabbenborg Sven O. , Huskens Jurriaan 
Published: June 2014

AbstractGegenstand dieses Aufsatz ist die aktuellen Entwicklung auf dem Gebiet von elektrochemisch erzeugten Gradienten. Eine graduelle Änderung von Merkmalen, die das Charakteristikum von Gradienten ist, hat für Technologie und Biologie eine große Bedeutung, wie das “directional wetting” bzw. die Chemotaxis zeigen. Elektrochemische Techniken bieten viele Vorteile, darunter die Erzeugung von dynamischen Lösungs‐ und Oberflächengradienten, die Integration von elektronischen Bauteilen und die Automatisierung. Hier werden neue Methoden vorgestellt, von rein elektrochemischen Techniken bis hin zur Kombination von Elektrochemie mit anderen Verfahren. Elektrochemisch erzeugte Gradienten werden in biologischem und technologischem Kontext eingesetzt. Beispiele sind Hochdurchsatzscreening und ‐galvanisierung sowie elektronische Bauelemente. Besonders vielversprechend sind Entwicklungen, die sich mit der Untersuchung und gezielten Beeinflussung von dynamischen Phänomenen befassen, etwa mit der gerichteten Bewegung von Molekülen, Tröpfchen und Zellen.
Organokatalytische asymmetrische Hydrolyse von Epoxiden
Authors: Monaco Mattia Riccardo , Prévost Sébastien , List Benjamin 
Published: June 2014

AbstractDie hydrolytische Ringöffnung von Epoxiden ist eine wichtige biosynthetische Umwandlung und wird auch industriell eingesetzt. Wir berichten von der ersten organokatalytischen Variante dieser Reaktion. Hierbei nutzen wir unsere kürzlich entdeckte Aktivierung von Carbonsäuren mit chiralen Phosphorsäuren über Heterodimerbildung. Die Methode ahmt den enzymatischen Mechanismus nach, der ein enzymgebundenes Carboxylatnukleophil aufweist. Eine neu entwickelte Phosphorsäure zeigt hohe Stereokontrolle in der Desymmetrisierung von meso‐Epoxiden. Die Methode ist breit anwendbar auf cyclische, acyclische, aromatische und aliphatische Substrate. Des Weiteren nutzen wir unsere Methode in der ersten hochenantioselektiven anti‐Dihydroxylierung von einfachen Olefinen.
Self‐Assembly of DNA–Oligo(p‐phenylene‐ethynylene) Hybrid Amphiphiles into Surface‐Engineered Vesicles with Enhanced Emission
Authors: Albert Shine K. , Thelu Hari Veera Prasad , Golla Murali , Krishnan Nithiyanandan , Chaudhary Soma , Varghese Reji 
Published: June 2014

AbstractSurface‐addressable nanostructures of linearly π‐conjugated molecules play a crucial role in the emerging field of nanoelectronics. Herein, by using DNA as the hydrophilic segment, we demonstrate a solid‐phase “click” chemistry approach for the synthesis of a series of DNA–chromophore hybrid amphiphiles and report their reversible self‐assembly into surface‐engineered vesicles with enhanced emission. DNA‐directed surface addressability of the vesicles was demonstrated through the integration of gold nanoparticles onto the surface of the vesicles by sequence‐specific DNA hybridization. This system could be converted to a supramolecular light‐harvesting antenna by integrating suitable FRET acceptors onto the surface of the nanostructures. The general nature of the synthesis, surface addressability, and biocompatibility of the resulting nanostructures offer great promises for nanoelectronics, energy, and biomedical applications.
Die Totalsynthese von (−)‐Nitidasin
Authors: Hog Daniel T. , Huber Florian M. E. , Mayer Peter , Trauner Dirk 
Published: June 2014

AbstractNitidasin, ein komplexes Sesterterpenoid mit einem seltenen 5‐8‐6‐5‐Kohlenstoffgerüst, wurde aus dem peruanischen Naturheilmittel “Hercampuri” isoliert und ist ein Vertreter einer kleinen Gruppe von polycyclischen Sesterterpenoiden, die eine trans‐Hydrindaneinheit mit einem Isopropylsubstituenten aufweisen. Als erstes Ergebnis unseres allgemeinen Ansatzes zur Synthese solcher Naturstoffe stellen wir die Totalsynthese der Titelverbindung vor. Die Schlüsselsequenz unserer stereoselektiven und konvergenten Route besteht aus der Addition einer komplexen Alkenyllithiumverbindung an ein trans‐Hydrindanon, einer chemoselektiven Epoxidierung und einer Ringschlussmetathese.
A Supercharged Fluorescent Protein as a Versatile Probe for Homogeneous DNA Detection and Methylation Analysis
Authors: Lei Chunyang , Huang Yan , Nie Zhou , Hu Jun , Li Lijun , Lu Guoyan , Han Yitao , Yao Shouzhuo 
Published: June 2014

AbstractSupercharged proteins are a new class of functional proteins with exceptional stability and potent ability to deliver bio‐macromolecules into cells. As a proof‐of‐principle, a novel application of supercharged proteins as a versatile biosensing platform for nucleic acid detection and epigenetics analysis is presented. Taking supercharged green fluorescent protein (ScGFP) as the signal reporter, a simple turn‐on homogenous method for DNA detection has been developed based on the polyionic nanoscale complex of ScGFP/DNA and toehold strand displacement. This assay shows high sensitivity and potent ability to detect single‐base mismatch. Furthermore, combined with bisulfite conversion, this ScGFP‐based assay was further applied to analyze site‐specific DNA methylation status of genomic DNA extracted from real human colon carcinoma tissue sample with ultrahigh sensitivity (4 amol methylated DNA).
Bent Molecules with a 60° Central Core Angle that Form B7 and B2 Phases
Authors: Lee Eun‐Woo , Takimoto Koji , Tokita Masatoshi , Watanabe Junji , Kang Sungmin 
Published: June 2014

AbstractSmall‐angle bent‐core liquid‐crystalline (LC) molecules based on a 1,2‐bis(phenylethynyl)benzene central core have been synthesized that form banana smectic phases with a ferroelectric B7–antiferroelectric B2 phase sequence upon cooling. The formation of polar, switchable ferro‐/antiferroelectric banana phases indicates that, despite the low core bend angle of approximately 60°, banana smectic phases are still formed with the bend direction parallel to the layer. This study offers significant evidence that shows bent‐core molecules with a 60° bend angle can form the well‐known B2 and B7 banana phases. Consequently, it may lead to the preparation of a wide variety of novel bent molecules with low bend angles that spontaneously form an LC phase with both polarization and chirality.