bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression Analysis of Four Peroxiredoxin Genes from Tamarix hispida in Response to Different Abiotic Stresses and Exogenous Abscisic Acid (ABA)
Authors: Gao Caiqiu , Zhang Kaimin , Yang Guiyan , Wang Yucheng
Published: March 2012

Peroxiredoxins (Prxs) are a recently discovered family of antioxidant enzymes that catalyze the reduction of peroxides and alkyl peroxides. In this study, four Prx genes (named as ThPrxII, ThPrxIIE, ThPrxIIF, and Th2CysPrx) were cloned from Tamarix hispida. Their expression profiles in response to stimulus of NaCl, NaHCO3, PEG, CdCl2 and abscisic acid (ABA) in roots, stems and leaves of T. hispida were investigated using real-time RT-PCR. The results showed that the four ThPrxs were all expressed in roots, stems and leaves. Furthermore, the transcript levels of ThPrxIIE and ThPrxII were the lowest and the highest, respectively, in all tissue types. All the ThPrx genes were induced by both NaCl and NaHCO3 and reached their highest expression levels at the onset of stress in roots. Under PEG and CdCl2 stress, the expression patterns of these ThPrxs showed temporal and spatial specificity. The expressions of the ThPrxs were all differentially regulated by ABA, indicating that they are all involved in the ABA signaling pathway. These findings reveal a complex regulation of Prxs that is dependent on the type of Prx, tissue, and the signaling molecule. The divergence of the stress-dependent transcriptional regulation of the ThPrx gene family in T. hispida may provide an essential basis for the elucidation of Prx function in future work.
Recent Advances of Flowering Locus T Gene in Higher Plants
Authors: Xu Feng , Rong Xiaofeng , Huang Xiaohua , Cheng Shuiyuan
Published: March 2012

Flowering Locus T (FT) can promote flowering in the plant photoperiod pathway and also facilitates vernalization flowering pathways and other ways to promote flowering. The expression of products of the FT gene is recognized as important parts of the flowering hormone and can induce flowering by long-distance transportation. In the present study, many FT-like genes were isolated, and the transgenic results show that FT gene can promote flowering in plants. This paper reviews the progress of the FT gene and its expression products to provide meaningful information for further studies of the functions of FT genes.
Inroads to Predict in Vivo Toxicology—An Introduction to the eTOX Project
Authors: Briggs Katharine , Cases Montserrat , Heard David J. , Pastor Manuel , Pognan François , Sanz Ferran , Schwab Christof H. , Steger-Hartmann Thomas , Sutter Andreas , Watson David K. , Wichard Jörg D.
Published: March 2012

There is a widespread awareness that the wealth of preclinical toxicity data that the pharmaceutical industry has generated in recent decades is not exploited as efficiently as it could be. Enhanced data availability for compound comparison (“read-across”), or for data mining to build predictive tools, should lead to a more efficient drug development process and contribute to the reduction of animal use (3Rs principle). In order to achieve these goals, a consortium approach, grouping numbers of relevant partners, is required. The eTOX (“electronic toxicity”) consortium represents such a project and is a public-private partnership within the framework of the European Innovative Medicines Initiative (IMI). The project aims at the development of in silico prediction systems for organ and in vivo toxicity. The backbone of the project will be a database consisting of preclinical toxicity data for drug compounds or candidates extracted from previously unpublished, legacy reports from thirteen European and European operation-based pharmaceutical companies. The database will be enhanced by incorporation of publically available, high quality toxicology data. Seven academic institutes and five small-to-medium size enterprises (SMEs) contribute with their expertise in data gathering, database curation, data mining, chemoinformatics and predictive systems development. The outcome of the project will be a predictive system contributing to early potential hazard identification and risk assessment during the drug development process. The concept and strategy of the eTOX project is described here, together with current achievements and future deliverables.
Vitamin D and Its Role During Pregnancy in Attaining Optimal Health of Mother and Fetus
Authors: Wagner Carol L. , Taylor Sarah N. , Dawodu Adekunle , Johnson Donna D. , Hollis Bruce W.
Published: March 2012

Despite its discovery a hundred years ago, vitamin D has emerged as one of the most controversial nutrients and prohormones of the 21st century. Its role in calcium metabolism and bone health is undisputed but its role in immune function and long-term health is debated. There are clear indicators from in vitro and animal in vivo studies that point to vitamin D’s indisputable role in both innate and adaptive immunity; however, the translation of these findings to clinical practice, including the care of the pregnant woman, has not occurred. Until recently, there has been a paucity of data from randomized controlled trials to establish clear cut beneficial effects of vitamin D supplementation during pregnancy. An overview of vitamin metabolism, states of deficiency, and the results of recent clinical trials conducted in the U.S. are presented with an emphasis on what is known and what questions remain to be answered.
Forming nanoparticles of water-soluble ionic molecules and embedding them into polymer and glass substrates
Authors: Kiel Stella , Grinberg Olga , Perkas Nina , Charmet Jerome , Kepner Herbert , Gedanken Aharon
Published: March 2012

This work describes a general method for the preparation of salt nanoparticles (NPs) made from an aqueous solution of ionic compounds (NaCl, CuSO4 and KI). These nanoparticles were created by the application of ultrasonic waves to the aqueous solutions of these salts. When the sonication was carried out in the presence of a glass microscope slide, a parylene-coated glass slide, or a silicon wafer the ionic NPs were embedded in these substrates by a one-step, ultrasound-assisted procedure. Optimization of the coating process resulted in homogeneous distributions of nanocrystals, 30 nm in size, on the surfaces of the substrates. The morphology and structure of each of the coatings were characterized by physical and chemical methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). After 24 h of leaching into water the nanoparticles of the inorganic salts were still present on the slides, and complete leaching of nanoparticles occurred only after 96 h. A mechanism of the ultrasound-assisted coating is proposed.
Adaptive Network Based Fuzzy Interference System (ANFIS) Modeling of an Anaerobic Wastewater Treatment Process
Authors: Mullai P. , Rene Eldon R. , Park Hung Suck , Sabarathinam P. L.
Published: March 2012

The successful operation of a high-rate anaerobic reactor, up flow anaerobic sludge blanket (UASB) reactor depends on the prevailing physico-chemical and biological conditions during its operation. The wastewater characteristics and composition, the hydrodynamics of the process, and microbial activity are critical for achieving long term, optimal reactor performance. Modeling UASBs can be beneficial for design, prediction, and control purposes. This chapter provides sufficient background information on the different biochemical stages of anaerobic treatment, viz., hydrolysis of biodegradable solids, acetogenesis and methanogenesis, the working of a UASB reactor, and some insight into mechanistic modeling of UASBs. The application of neural networks, and a conceptual neural fuzzy model, i.e., adaptive network based fuzzy inference system (ANFIS), to model the performance of UASB is systematically outlined in this chapter.
Feasible Automatic Reconfigurations of Real-Time OS Tasks
Authors: Gharsellaoui Hamza , Gharbi Atef , Khalgui Mohamed , Ben Ahmed Samir
Published: March 2012

This research deals with reconfigurable uniprocessor embedded real-time systems to be implemented by different OS tasks that should be independent, synchronous, and periodic, and that should meet functional and temporal properties described in user requirements. The authors define two forms of automatic reconfigurations assumed to be applied at run-time: addition-removal of tasks or just modifications of their temporal parameters; WCET and/or periods. The authors define a new semantic of reconfigurations where a crucial criterion to consider is the automatic improvement of the system’s feasibility at run-time.
SoftPLC-Based Control
Authors: Scanzio Stefano
Published: March 2012

Nowadays, most control systems are based on programmable logic controllers (PLCs) and on commercial programs, but the use of conventional PCs is becoming an increasing by popularity and competitive alternative. After an introduction that underlines the positive and negative aspects of both solutions, EtherCAT, a hard real-time industrial Ethernet protocol that allows the use of both conventional PCs and open-source software, is analyzed. Two different EtherCAT master implementations are compared, which are based on a commercial and on a open-source software, respectively. In order to highlight differences and provide a short reference, a simple example was implemented in the two environments.
E-Government in Syria
Authors: Farzali Elias , Kanaan Ghassan , Kanaan Raed Kareem , Atieh Kamal
Published: March 2012

The information technology revolution has forced many governments to create new mechanisms for delivering services in order to reduce costs, increase the ease of administration, and overcome some of the economic and social problems. E-Government uses the methods of new technology to simplify administrative procedures and assist decision-makers in their operations. Using the survey method and interviews, this chapter investigates e-Government activities in Syria in order to explore the main barriers of e-Government. It focuses on how to utilize the necessary frameworks in policy, economics, administrative procedures, society, and technology, with the aim of showing the benefits of Enterprise Integration in e-Government. The chapter extensively reviews the literature on barriers to e-Government and Enterprise Integration technologies. Based on the investigation of barriers to current e-Government activities in Syria, the chapter proposes an e-Government Interoperability Framework that is designed to address effective implementation of e-Government in developing countries.
The e-Government Concept and e-Government Applications
Authors: Sisman Aziz
Published: March 2012

Since the end of the last century, computers have become a widespread phenomenon in most developed and developing countries. In the last decade, all around the world, governments and private organizations have attempted to explore new searches, opportunities, and investments for making their services vibrant, independent from space and/or time, comfortable, and contemporary. These initiatives have also been done with a view to increase their services’ quality by employing the opportunities offered by the Internet technology. The electronic government (e-government) concept has developed as a result of these efforts. E-government offers the opportunities that offer citizens and the government to execute their mutual duties and obligations via electronic communication and process. E-government has several aspects, including social, technical, economic, political, and public administrative. However, most dominating concepts of e-government arise from the technical perspective and a combination of the socio-economic and public administrative perspectives. In this study; concept, structure, and frame of e-government were defined. The Networked Readiness Index was investigated, and featured topics for e-government applications were determined. Necessity of e-government in both developed and developing countries were investigated, and digital divide, which negatively affects e-government formation in developing countries, was investigated.
Listening to the Ground
Authors: Bagui Laban , Bytheway Andrew
Published: March 2012

E-Government can be seen as governing through the use of information technology, and a key component of e-Government is e-Participation, the use of information and communications technologies to engage citizens more closely in government processes. Public participation is achieved by a range of means, any or all of which might benefit from the use of technology in order to reduce costs and improve effectiveness. In South Africa, the public has a generally poor opinion of government services, even though Web and mobile technologies are being used. That sentiment sometimes ensues in social tensions. In this chapter, a review of literature, opinions of informed experts, and a scenario analysis develop indications and a model for e-Participation maturing with e-readiness improving.
Reducing co-administration of clopidogrel and proton pump inhibitors in acute coronary syndromes
Authors: Vassiliou V , Silva A , Kavvoura F , Schofield R , Rowlands DB
Published: March 2012

Background: Recent concerns about clopidogrel and proton pump inhibitor (PPI) co-administration in patients following an acute coronary syndrome (ACS) led us to investigate our practice. Guidance recommends that omeprazole and esomeprazole should not be co-administered with clopidogrel as they can decrease its efficacy. Pantoprazole and lansoprazole are safer for use in these cases.

Methods: Patients discharged between August 2008 and July 2009 with a diagnosis of ACS, on both clopidogrel and any PPI, were identified using the pharmacy database. Their notes were retrospectively reviewed, the indication for a PPI was checked and whether an appropriate one had been prescribed was assessed. As a result of our findings a simple algorithm was introduced to set out guidance on appropriate use and junior doctors were informed of the new procedure. We then performed another audit of patients discharged between August 2009 and February 2010 to ensure that the guidelines were being followed.

Results: During the first phase of the audit 43 out of 91 patients (47.5%) received a PPI with clopidogrel. Following our intervention, re-auditing confirmed that clopidogrel and PPI co-administration had decreased significantly to 27 out of 101 patients (26.7%) (p = 0.018).

Conclusions: Through a simple intervention with an algorithm and education of junior doctors we have shown that significant improvement and adherence to guidance can be achieved.
Aircraft-based observations and high-resolution simulations of an Icelandic dust storm
Authors: Blechschmidt A.-M. , Kristjánsson J. E. , Ólafsson H. , Burkhart J. F. , Hodnebrog Ø.
Published: March 2012

Abstract. The first aircraft-based observations of an Icelandic dust storm are presented. The measurements were carried out over the ocean near Iceland's south coast in February 2007. This dust event occurred in conjunction with an easterly barrier jet of more than 30 m s−1. The aircraft measurements show high particle mass mixing ratios in an area of low wind speeds in the wake of Iceland near the coast, decreasing abruptly towards the jet. Simulations from the Weather Research and Forecasting Model coupled with Chemistry (WRF/Chem) indicate that the measured high mass mixing ratios and observed low visibility inside the wake are due to dust transported from Icelandic sand fields towards the ocean. This is confirmed by meteorological station data. Primary dust sources are glacial outwash terrains located near the Mýrdalsjökull glacier. Sea salt aerosols produced by the impact of strong winds on the ocean surface started to dominate as the aircraft flew away from Iceland into the jet. The present results support recent studies which suggest that Icelandic deserts should be considered as important dust sources in global and regional climate models.
The carbon emissions of Chinese cities
Authors: Wang H. , Bi J. , Zhang R. , Liu M.
Published: March 2012

Abstract. As increasing urbanization has become a national policy priority for economic growth in China, cities have become important players in efforts to reduce carbon emissions. However, their efforts have been hampered by the lack of specific and comparable carbon emission inventories. Comprehensive carbon emission inventories, which present both a relatively current snapshot and also show how emissions have changed over the past several years, of twelve Chinese cities were developed using bottom-up approach. Carbon emissions in most of Chinese cities rose along with economic growth from 2004 to 2008. Yet per capita carbon emissions varied between the highest and lowest emitting cities by a factor of nearly 7. Average per capita carbon emissions varied across sectors, including industrial energy consumption (64.3%), industrial processes (10.2%), transportation (10.6%), household energy consumption (8.0%), commercial energy consumption (4.3%) and waste processing (2.5%). The levels of per capita carbon emissions in China's cities were higher than we anticipated before comparing them with the average of global cities. This is mainly due to the major contribution of industry sector encompassing industrial energy consumption and industrial processes to the total carbon emissions of Chinese cities.
The CORA dataset: validation and diagnostics of ocean temperature and salinity in situ measurements
Authors: Cabanes C. , Grouazel A. , von Schuckmann K. , Hamon M. , Turpin V. , Coatanoan C. , Guinehut S. , Boone C. , Ferry N. , Reverdin G. , Pouliquen S. , Le Traon P.-Y.
Published: March 2012

Abstract. The French program Coriolis as part of the French oceanographic operational system produces the COriolis dataset for Re-Analysis (CORA) on a yearly basis which is based on temperature and salinity measurements on observed levels from different data types. The latest release of CORA covers the period 1990 to 2010. To qualify this dataset, several tests have been developed to improve in a homogeneous way the quality of the raw dataset and to fit the level required by the physical ocean re-analysis activities (assimilation and validation). These include some simple tests, climatological tests and a model background check based on a global ocean reanalysis. Visual quality control (QC) is performed on all suspicious temperature (T) and salinity (S) profiles identified by the tests and quality flags are modified in the dataset if necessary. In addition, improved diagnostic tools were developed – including global ocean indicators – which give information on the potential and quality of the CORA dataset for all applications. This Coriolis product is available on request through the MyOcean Service Desk (http://www.myocean.eu/).
Managing Vulnerabilities of Tactical Wireless RF Network Systems: A Case Study
Authors: Chan Philip , Nowicki David , Man Hong , Mansouri Mo
Published: March 2012

Organisations and individuals benefit when wireless networks are protected. After assessing the risks associated with wireless technologies, organisations can reduce the risks by applying countermeasures to address specific threats and vulnerabilities. These countermeasures include management, operational and technical controls. While these countermeasures will not prevent all penetrations and adverse events, they can be effective in reducing many of the common risks associated with wireless RF networks. Among engineers dealing with different scaled and interconnected engineering systems, such as tactical wireless RF communication systems, there is a growing need for a means of analysing complex adaptive systems. We propose a methodology based on the systematic resolution of complex issues to manage the vulnerabilities of tactical wireless RF systems. There are is a need to assemble and balance the results of any successful measure, showing how well each solution meets the system's objectives. The uncertain arguments used and other test results are combined using a form of mathematical theory for their analysis. Systems engineering thinking supports design decisions and enables decision-makers to manage and assess the support for each solution. In these circumstances, complexity management arises from the many interacting and conflicting requirements of an increasing range of possible parameters. There may not be a single ‘right’ solution, only a satisfactory set of resolutions which this system helps to facilitate. Smart and innovative performance matrixes are introduced using a mathematical Bayesian network to manage, model, calculate and analyse all the potential vulnerability paths in wireless RF networks.
A Real Time Quality Monitoring System for the Lighting Industry: A Practical and Rapid Approach Using Computer Vision and Image Processing (CVIP) Tools
Authors: Ng C.K. , Wu C.H. , Ip W.H. , Chan C.Y. , Ho G.T.S.
Published: March 2012

In China, the manufacturing of lighting products is very labour intensive. The approach used to check quality and control production relies on operators who test using various types of fixtures. In order to increase the competitiveness of the manufacturer and the efficiency of production, the authors propose an integrated system. This system has two major elements: a computer vision system (CVS) and a real-time monitoring system (RTMS). This model focuses not only on the rapid and practical application of modern technology to a traditional industry, but also represents a process innovation in the lighting industry. This paper describes the design and development of the prototyped lighting inspection system based on a practical and fast approach using computer vision and imaging processing (CVIP) tools. LabVIEW with IMAQ Vision Builder is the chosen tool for building the CVS. Experimental results show that this system produces a lower error rate than humans produce in the quality checking process. The whole integrated manufacturing strategy, aimed at achieving a better performance, is most suitable for a China and other labour intensive environments such as India.
The Study on Using Passive RFID Tags for Indoor Positioning
Authors: Ting S.L. , Kwok S.K. , Tsang Albert H.C. , Ho George T.S.
Published: March 2012

Radio frequency identification (RFID) is the technology that put an RFID tag on objects or people, so that they can be identified, tracked, and managed automatically. With its wide application in the automobile assembly industry, warehouse management and the supply chain network, RFID has been recognized as the next promising technology in serving the positioning purpose. Existing positioning technologies such as GPS are not available indoors as the terminal cannot get the signal from satellites. To enhance the availability of the positioning systems for indoors, the development of RFID positioning system for locating objects or people have became a hot topic in recent research. Compared with conventional active and high-cost solutions, this paper studied the feasibility of using passive RFID tags for indoor positioning and object location detection to provide real time information for tracking movement. Results of experiment show that readability of the passive RFID positioning system is satisfactory, and it is a more cost effective solution when compared with other positioning technologies.
Application Service Providers (ASP) Adoption in Core and Non-Core Functions
Authors: Chan Aman Y.M. , Cho Vincent
Published: March 2012

With the further improvement in internet bandwidth, connection stability and data transmission security, a new wave of Application Service Providers (ASP) is on his way. The recent booming on some models such as Software Application as Service (SaaS) and On-Demand in 2008, has led to emergence of ASP model in core business functions. The traditional IS outsourcing covers the non-core business functions that are not critical to business performance and competitive advantages. Comparing with traditional IS outsourcing, ASP is a new phenomenon that can be considered as an emerging innovation as it covers both core and non-core business functions. Most of the executives do not comprehend the difference and similarity between traditional IS outsourcing and ASP mode. Hence, we propose to conduct a research so as to identify the determinants (cost benefit, gap in IS capability complementing the company's strategic goal, and trust to ASP's service and security level) and moderating factors (management's attitude in ownership & control, and company aggressiveness) of ASP adoption decision in both core and non-core business functions.
Fuzzy Multiple Regression Model for Estimating Software Development Time
Authors: Marza Venus , Seyyedi Mir Ali
Published: March 2012

As software becomes more complex and its scope dramatically increase, the importance of research on developing methods for estimating software development time has perpetually increased, so accurate estimation is the main goal of software managers for reducing risks of projects. The purpose of this article is to introduce a new Fuzzy Multiple Regression approach, which has the higher accurate than other methods for estimating. Furthermore, we compare Fuzzy Multiple Regression model with Fuzzy Logic model & Multiple Regression model based on their accuracy.
Power Industry Reliability Coordination in Asia in a Market Environment
Authors: Hammons Thomas J. , Voropai Nikolai I.
Published: March 2012

This paper addresses the problems of power supply reliability in a market environment. The specific features of economic interrelations between the power supply organization and consumers in terms of reliability assurance are examined and the principles of providing power supply reliability are formulated. The economic mechanisms of coordinating the interests of power supply organization and consumers to provide power supply reliability are discussed. Reliability of restructuring China's power industry is introduced. Some reliability data is provided. The data shows that the reliability level has increased significantly in the past two decades. More and more measures are being applied to guarantee reliability of the restructured power systems. The reliability issues and challenges that are facing the Chinese power industry are considered The paper, then examines the evolution of power grids in India, the establishment of a regulatory framework, and operational philosophy in reliability aspects of long-, mid- as well as short-term (operational / outage) planning. Grid security, restoration, and mock trial for black start, etc. from the reliability angle are considered. Related issues for islanding operation to improve service reliability for Thailand's Electric Power System are then analyzed.
Using Integer Programming for Airport Service Planning in Staff Scheduling
Authors: Ip W.H. , Chung Nick , Ho George
Published: March 2012

Reliability and safety in flight is extremely necessary and that depend on the adoption of proper maintenance system. Therefore, it is essential for aircraft maintenance companies to perform the manpower scheduling efficiently. One of the objectives of this paper is to provide an Integer Programming approach to determine the optimal solutions to aircraft maintenance planning and scheduling and hence the planning and scheduling processes can become more efficient and effective. Another objective is to develop a set of computational schedules for maintenance manpower to cover all scheduled flights. In this paper, a sequential methodology consisting of 3 stages is proposed. They are initial maintenance demand schedule, the maintenance pairing and the maintenance group(s) assignment. Since scheduling would split up into different stages, different mathematical techniques have been adopted to cater for their own problem characteristics. Microsoft Excel would be used. Results from the first stage and second stage would be inputted into integer programming model using Microsoft Excel Solver to find the optimal solution. Also, Microsoft Excel VBA is used for devising a scheduling system in order to reduce the manual process and provide a user friendly interface. For the results, all can be obtained optimal solution and the computation time is reasonable and acceptable. Besides, the comparison of the peak time and non-peak time is discussed.
Analysis of Radicals byEPR
Authors: Walton John C.
Published: March 2012

This article explains why electron paramagnetic resonance (EPR) spectroscopy is one of the most versatile and useful techniques for investigating free radicals. Easy to use EPR tools are expounded for organic chemists to exploit in researching the structures and reactivities of radicals and as a resource for synthetic planning. The article provides key references and introduces the literature on the EPR spectra of a wide range of organic radicals in solution. How EPR spectra result from molecules containing one unpaired electron (UPE) is explained and basic theory is presented for isotropic conditions. A correlation chart enablesg‐factors, which are key spectral parameters, to be used in determining which element is the principal site of the UPE. Methods of analysing complex EPR spectra and obtaining hyperfine splittings (hfs) are described. How geometries around the central atoms of radicals, and conformations about neighboring bonds, can be deduced from EPR data is explained. Modernab initiomethods of computing EPR parameters are briefly sketched. Features of the EPR spectra of model radicals centered on elements from groups 13, 14, 15, and 16 of the periodic table are surveyed. EPR methods for concentration measurements and for studying radical kinetics in time‐resolved and steady‐state modes are set out. Derivations from EPR spectral data of thermodynamic parameters such as radical enthalpies of formation and bond dissociation enthalpies are also explained.
Radical Stability—Thermochemical Aspects
Authors: Hioe Johnny , Zipse Hendrik
Published: March 2012

Reaction enthalpies for hydrogen transfer reactions provide a quantitative basis for the definition of the stability of C‐, S‐, O‐, N‐, and B‐centered radicals. The radical stabilization energies (RSEs) obtained in this way reflect the influence of the substitution pattern on the unpaired spin as well as ground state effects in the respective closed shell parent systems. The combination of theoretically calculated RSEs with experimentally measured bond dissociation energy (BDE) data allows for the construction of global stability scales for radicals of different type and thus the opportunity to predict reaction energies for a wide range of hydrogen transfer reactions.
Radical Cation/Anion and Neutral Radicals: A Comparison
Authors: Hancock Amber N. , Tanko J. M.
Published: March 2012

This article examines similarities between radical and radical ion reactions. Radicals and radical ions have worked there way into almost every facet of mainstream chemistry over the past 60 years. The importance as well as usefulness now associated with the reactions of radicals is in stark contrast to their prior role as poorly understood scapegoat molecules often blamed for failed reactions. The processes discussed herein demonstrate two critically important concepts to the radical chemist: (i) kinetic studies are an excellent and versatility applicable tool to determine mechanistic data for chemical reactions and (ii) published mechanistic data for more thoroughly studied radical processes have provided and continue to provide key insight into the factors governing reactivity and mechanism of their charge bearing counterparts.
Atmospheric Radical Chemistry
Authors: Wine Paul H. , Nicovich J. Michael
Published: March 2012

The atmosphere is a complex photochemical reactor where a vast majority of the chemical transformations involve reactions of reactive free radicals that are generated by solar photolysis of stable precursors. This article focuses on radical chemistry in the lowest 50 km of the atmosphere, an altitude regime that contains about 99.9% of the atmospheric mass. The altitude regime of interest is divided into two layers, the lower altitude troposphere that contains about 85% of the atmospheric mass, and the higher altitude stratosphere. The stratosphere contains 90% of all atmospheric ozone, and this ozone protects the earth's biosphere from the harmful effects of ultraviolet radiation. Hence, our discussion of stratospheric chemistry focuses on radical‐catalyzed pathways for ozone destruction. Tropospheric radical chemistry is extremely complex, owing largely to the presence in the troposphere of a multitude of organic compounds that are too short‐lived to be transported to the stratosphere. Our discussion of tropospheric radical chemistry focuses on the complex chain reactions involving ozone, hydroxyl radicals, nitrogen oxide radicals, and organics that maintain the oxidizing power of the troposphere, that is, the ability of the troposphere to cleanse itself of pollutants.
Basic Concepts on Radical Chain Reactions
Authors: Sherburn Michael S.
Published: March 2012

This article serves as an introduction to basic concepts in radical chemistry and is written in the form of a tutorial review. The intention is to provide the reader with the necessary fundamental information on structure, reactions, and mechanism to permit a basic understanding of the radical chemistry in the articles that follow. The content is based upon undergraduate and postgraduate courses in synthetic free radical chemistry taught over the past 15 years by the author. The material is presented into two sections. The first serves as a primer on radical structure and reactivity, on discrete processes involving radicals, and on how these radicals and discrete processes are sequenced into chain reactions. The second section extends the concepts of the first and introduces the major classes of radical chain reactions.
Radical Cascade Reactions
Authors: Baralle Alexandre , Baroudi Abdulkader , Daniel Marion , Fensterbank Louis , Goddard Jean‐Philippe , Lacôte Emmanuel , Larraufie Marie‐Hélène , Maestri Giovanni , Malacria Max , Ollivier Cyril
Published: March 2012

This article deals with the recent developments in radical cascade reactions with a special emphasis on their applications in natural product synthesis. Particular attention has been paid to the mechanisms of the cascade sequences and the involvement of original elementary steps. Section 2 is dedicated to cascades occurring via a purely radical chain mechanism, describing first intramolecular processes, then processes involving both inter‐ and intramolecular steps. Section 3 is devoted to cascade reactions combining radical and ionic steps. The reactions are classified according to the type of metal reagent used, such as, samarium, titane, manganese, cerium, iron, zinc, silver, and copper. In addition, newer developments in radical cascades triggered by visible light photoredox catalysis are discussed.
The S
RN
1 Reaction
Authors: Bardagí Javier I. , Vaillard Victoria A. , Rossi Roberto A.
Published: March 2012

Since its discovery, the radical nucleophilic substitution, or S
RN
1 reaction, has been widely used to achieve new CC or C‐heteroatom bonds. The mechanism involves a chain propagation cycle with radicals and radical anions as intermediates. The initiation step is an electron transfer to a substrate to form its radical anion, which fragments to afford a radical and the anion of the leaving group. The radical thus formed couples with a nucleophile to give a new radical anion which, in the next propagation step, transfers its extra electron to the substrate, closing the cycle.

Here we discuss S
RN
1 reactions of aromatic substrates with carbanions and heteroaromatic nucleophiles as well as ring‐closure reactions to obtain heterocycles by different approaches.

S
RN
1 reactions of vinylic halides with nucleophiles and the competing mechanisms are also examined. Reactions of aliphatic substrates that do not react or are poorly reactive toward polar nucleophilic substitutions (cycloalkyl, bridgehead, neopentyl, and perfluoroalkyl halides) are discussed in terms of mechanistic requirements to follow an S
RN
1 process. In addition, the reactions of alkyl substrates with electron‐withdrawing groups also are presented.

Every year, new synthetic strategies and mechanistic studies involving S
RN
1 reactions are reported, which constitute a useful tool in the field of organic chemistry.
Radicals and Carbohydrates
Authors: Pérez‐Martín Inés , Suárez Ernesto
Published: March 2012

This article reviews the progress in the area of radicals in carbohydrate chemistry with special attention to new developments published during the past decade. No attempt has been made to present a comprehensive review of the literature but, rather, some specific examples are given to highlight the most synthetically valuable processes. The major focus is on inter‐ and intramolecular carbon–carbon bond‐forming radical reactions, with emphasis on the preparation of
C
‐glycosides,
C
‐ketosides,
C
‐disaccharides, and branched‐chain sugars, as well as on the synthesis of polyfunctionalized carbocycles by radical cyclization of acyclic carbohydrate derivatives. We also describe methods for the formation of carbon–hydrogen bonds, and synthesis in which a heteroatom‐centered radical plays a clear role in the carbon–heteroatom (C–N, C–P, C–O, C–S/Se, and C–Br) bond formation. Finally, a few selected examples of alkoxyl radical β‐fragmentation reactions, carried out under oxidative or reductive conditions, are included to illustrate their potential in the preparation of chiral synthons.
Electrochemically Initiated Radical Reactions
Authors: Bohn Martin A. , Paul Anna , Hilt Gerhard
Published: March 2012

This article reports on the applications of electrochemistry for the generation of radicals as neutral, cationic, and anionic intermediates and their use in preparative reactions for the formation of carbon–carbon and carbon–heteroatom bonds. The focus of this article is on electrochemical oxidation reactions of enol ethers, ketene acetals, and electron‐rich aromatic compounds. Furthermore, recent advances in the electrochemically induced synthesis of four‐membered ring systems and biaryl compounds are covered. The oxidative carbon–carbon bond formation by Kolbe electrolysis concludes the section dealing with oxidative transformations. The section describing reductive processes consists of indirect electrochemical reduction of alkylhalides and thioesters, as well as the reductive interconversion of functional groups described recently.
Radical Rearrangements: Ester‐Substituted Radicals and Hydrogen Atom Migrations
Authors: Sasaki Kaname , Cumpstey Ian , Crich David
Published: March 2012

This article covers radical rearrangements that do not involve the redistribution of the carbon skeleton of the substrate. The focus is on the rearrangement of ester‐substituted radicals and on hydrogen atom abstractions, and the emphasis is on the radical rearrangements themselves rather than on their application in synthesis, which is left to the imagination and creativity of the practitioner.
Manganese(III) Acetate,CAN, andFe(III) Salts in Oxidative Radical Chemistry
Authors: Burton Jonathan W.
Published: March 2012

This article provides a broad overview of oxidative radical methods for the formation of CC bonds using manganese(III) acetate, cerium(IV) ammonium nitrate, and various iron(III) salts. The article begins with a discussion of the various general mechanisms encountered in oxidative radical chemistry and then provides an overview of inter and intramolecular CC bond‐forming reactions. The oxidative radical chemistry of β‐dicarbonyl and related compounds forms a major part of the article. Comparison of the three metals is made whenever possible as well as highlighting reactions which are specific to, or higher yielding with, one particular metal. The discussed synthetic methodologies are illustrated with examples of complex molecule synthesis.
Oxidatively Formed Sugar Radicals in Nucleic Acids
Authors: Gimisis Thanasis , Chatgilialoglu Chryssostomos
Published: March 2012

This article focuses on the chemistry of sugar radicals in the context of oxidative damage in nucleic acids. The seven sp3‐hybridized CH bonds in 2‐deoxyribose (six in ribose) are attacked by reactive oxygen species, generated either by the cell's internal oxygen cycle or by environmental insults, by chemical nucleases including enediyne antibiotics and reactive metal complexes, to generate sugar nucleosidyl radicals. For each position on the 2‐deoxyribose or ribose moiety, the factors leading to the generation of the specific sugar radical, together with its fate under aerobic or anaerobic conditions in the nucleoside, nucleotide, single‐stranded oligonucleotide, or double helix DNA, are discussed. Furthermore, the model systems that have been constructed for the photochemical‐independent generation of each nucleosidyl radical or DNA lesion are described, together with the biochemical studies that have been performed in order to elucidate the stability, reparability, and mutagenic potential of each lesion. Other biologically important events involving modification of nearby nucleobases and the formation of DNA–DNA and DNA–protein cross‐links are also discussed.
Radical‐Based Damage of Sulfur‐Containing Amino Acid Residues
Authors: Schöneich Christian
Published: March 2012

The reactions of biologically relevant free radicals with S‐ and Se‐containing amino acids are reviewed with regard to amino acid reactivity, the nature of product radicals, and ensuing radical reactions. Emphasis is placed on the formation and reactions of thiyl and selenyl radicals as well as radical cations from sulfides and selenides. The reactions of thiols with carbon‐centered radicals, superoxide, nitrogen monoxide, nitrogen dioxide, and tyrosyl radicals are covered as well as the reactions of thiyl radicals with oxygen. Reversible
intra
‐ and
inter
molecular hydrogen transfer reactions of thiyl radicals are discussed in view of recent experimental and theoretical data. One‐electron oxidation reactions of sulfides are reviewed especially with regard to the stabilization of sulfide radical cations through heteroatom‐containing substituents, which are present in peptides and proteins. The relevance of these radical reactions for protein oxidation under conditions of oxidative stress is discussed.
Lipid Peroxidation
Authors: Niki Etsuo
Published: March 2012

Free and ester forms of fatty acids and cholesterol are physiologically important lipids. They are oxidized by free radicals to give diverse products. Above all, polyunsaturated fatty acids having more than two double bonds and their esters are quite susceptible to free radical attack and oxidized by chain mechanism. These lipids are oxidized also by nonradical oxidants such as ozone and singlet oxygen and by enzymes such as lipoxygenase, cyclooxygenase, and cytochromeP450 to produce specific products. The free‐radical‐mediated oxidation of lipids, often referred to aslipid peroxidation(LPO), proceeds bothin vitroandin vivo. LPO has been shown to induce disturbance of membrane organization and functional loss and modification of proteins and DNA bases, and LPO has been implicated in the pathogenesis of various diseases. Therefore, the role of antioxidants that inhibit LPO has received much attention. At the same time, LPO products have been shown to act as a redox signaling mediator. Although many LPO products exert cytotoxicity, sublethal concentrations of LPO products induce cellular adaptive response and enhance tolerance against subsequent oxidative stress through upregulation of antioxidant compounds and enzymes. Such opposite dual functions of LPO products imply that LPO may exert both deleterious and beneficial effectsin vivo. The levels of LPO products are assumed to be a biomarker of oxidative stressin vivo. The literatures show that the levels of LPO products in plasma of healthy human subjects are below 1 μM and that the molar ratios of LPO products to the respective parent lipids are below 1/1000, that is, below 0.1%. Numerous data show that the levels of LPO products in human fluids and tissues increase with a progress of various diseases.
Antioxidants in Chemistry and Biology
Authors: Valgimigli Luca , Pratt Derek A.
Published: March 2012

Antioxidants are omnipresent in nature and industry; they are used to slow down the autoxidative degradation of both organic tissues and petroleum‐derived products. Various mechanisms by which antioxidants can act are known, the most common of which are introduced here. Since autoxidation is a radical chain reaction, radical‐trapping antioxidants play a particularly important role; therefore, we will discuss these compounds in most detail. To introduce and develop central concepts relating to this topic, we present kinetic and thermodynamic data obtained for the reactions of phenols, the archetypical radical‐trapping antioxidants, with chain‐carrying peroxyl radicals, and describe the means to obtain these data. We then extend our discussion to other important classes of radical‐trapping antioxidants, beginning with the closely related polyphenols and newly developed pyridinol and pyrimidinol antioxidants, and then further to aromatic amines, organosulfur compounds, and their derivatives. We go on to touch upon the synergistic behavior in antioxidant combinations, and the effects of the medium on these interactions, and finally round things up with a few more important biological examples: ascorbate and β‐carotene. A few comments on the state of the field and areas requiring further research and development are included.
Nitroxide‐Mediated Polymerization and its Applications
Authors: Gigmes Didier , Marque Sylvain R. A.
Published: March 2012

In this survey, the fundamental aspects of nitroxide‐mediated polymerization (NMP) and the importance of each step/stage in its fate are discussed. The factors controlling the homolysis, reformation, and side‐reactions of alkoxyamines are presented. The various types of NMP—bulk, solution, aqueous, emulsion, miniemulsion, andin situ—are exemplified. The synthesis of advanced polymers by NMP is presented.
Photoinduced Reactions of Radical Ions via Charge Separation
Authors: Fukuzumi Shunichi , Ohkubo Kei
Published: March 2012

This article describes the recent development of photocatalytic reactions using a simple donor‐acceptor‐linked dyad, 9‐mesityl‐10‐methylacridinium ion (Acr+–Mes). The electron‐transfer state of Acr+–Mes (Acr·–Mes·+), produced on visible light irradiation, acts as an efficient oxidant and reductant. The use of Acr+–Mes, which has an extremely long‐lived charge‐separated state, enables the construction of highly efficient photocatalytic systems such as oxygenation, bromination, and carbon‐carbon bond formation of aromatic compounds.
Conducting Polymers: Applications in Electronics and Photovoltaics
Authors: Dong Huanli , Hu Wenping
Published: March 2012

The discovery of conducting polymers in 1970s shocked the world and then evoked increasing research interests from laboratory to technology because of their particular physical properties as well as the feasible solution‐processed superiority in potential low‐cost, large‐area optoelectronic devices. Following the report of first‐generation conducting polymer material, doped polyacetylene, remarkable progresses have been made in the development of novel conjugated polymers with reasonable functionality and demanding molecular architectures through molecular tailoring leading to various desired molecular electronic and optical applications. Among them, polymer‐based light‐emitting diodes (PLEDs), polymer‐based field‐effect transistors (PFETs), and polymer‐based solar cells (PSCs) are the most representative application fields and have undergone great progress, especially in the past decade. The aim of this article is to introduce briefly recent breakthrough improvement of conjugated polymers in these areas with an emphasis on some important and representative conjugated polymers in device applications as well as the principle of optimization approaches.