Biochemical sensors: The state of the art

The basic components of a (bio)chemical sensor and the main concepts involved in the (bio)chemical sensor methodology are considered in order to depict the state of the art of the development of research in this field, paying special attention to the evolution of the published scientific literature in analytical chemistry.     

Biomass gasification technology: The state of the art overview

In the last decades the interest in the biomass gasification process has increased due to the growing attention to the use of sustainable energy. Biomass is a renewable energy source and represents a valid alternative to fossil fuels. Gasification is the thermochemical conversion of an organic material into a valuable gaseous product, called syngas, and a solid product, called char. The biomass gasification represents an efficient process for the production of power and heat and the production of hydrogen and second-generation biofuels.This paper deals with the state of the art biomass gasification technologies, evaluating advantages and disadvantages, the potential use of the syngas and the application of the biomass gasification. Syngas cleaning though fundamental to evaluate any gasification technology is not included in this paper since; in the authors' opinion, a dedicated review is necessary.     

Fenton-type treatment: state of the art

The different currently used Fenton-type treatments, either chemically or electrochemically generated, are reviewed. A particular attention is devoted to the traditional Fe++/H2O2 chemical process and to the indirect electrochemical oxidation which uses in situ generated hydrogen peroxide. Mechanisms and experimental conditions employed for the optimisation of each technology are reported; moreover advantages and main limitations are discussed.     

The discovery of metallocene catalysts and their present state of the art

Metallocene and other transition metal complexes activated by methylaluminoxane are highly active catalysts for the polymerization of olefins, diolefins, and styrene, which was discovered at the University of Hamburg about 25 years ago. These catalysts allow the synthesis of polymers with a highly defined microstructure, tacticity, and stereoregularity, as well as new copolymers with superior properties such as film clarity, tensile strength, and lower extractables. A better understanding of the mechanism of olefin polymerization leads to findings of other new single site catalysts. The development of the metallocene/MAO‐catalysts from their discovery to their present state of the art is presented. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3911–3921, 2004     

Niosomes from 80s to present: The state of the art

Efficient and safe drug delivery has always been a challenge in medicine. The use of nanotechnology, such as the development of nanocarriers for drug delivery, has received great attention owing to the potential that nanocarriers can theoretically act as “magic bullets” and selectively target affected organs and cells while sparing normal tissues. During the last decades the formulation of surfactant vesicles, as a tool to improve drug delivery, brought an ever increasing interest among the scientists working in the area of drug delivery systems. Niosomes are self assembled vesicular nanocarriers obtained by hydration of synthetic surfactants and appropriate amounts of cholesterol or other amphiphilic molecules. Just like liposomes, niosomes can be unilamellar or multilamellar, are suitable as carriers of both hydrophilic and lipophilic drugs and are able to deliver drugs to the target site. Furthermore, niosomal vesicles, that are usually non-toxic, require less production costs and are stable over a longer period of time in different conditions, so overcoming some drawbacks of liposomes.     

The state of the art in the rheology of polymers: Achievements and challenges

The state of the art in the rheology of polymer fluids (polymer solutions and melts) and filled composites is reviewed. This review includes two parts: analysis of the basic principles for the construction of rheological constitutive equations in terms of the continuum mechanics and finding correlations between the rheological characteristics and molecular structure of polymers on the basis of molecular models. Possible approaches to the formulation of constitutive equations are discussed. Special attention is focused on the correct selection of the form of the elastic potential for rubbery deformations induced under the flow of polymer fluids. The use of a power-law potential leads to the best results. To gain unequivocal results and minimize the number of free constants, viscoelastic characteristics of polymer fluids should be described in terms of a continuous relaxation spectrum as a power-law function limited by the maximum relaxation time. To solve the boundary problems by the selected constitutive equation, analysis of the dynamic stability is required, because the combination of viscosity and elasticity controls the limits of flow upon shear and tensile. Deformation can also lead to changes in the phase state of a polymer system. Furthermore, correct formulation of the boundary conditions is necessary because, in many cases, polymer fluids and, in particular, filled materials tend to efficient slip along walls. The existing molecular models adequately describe the characteristics of monodisperse polymers; however, on passing to polydisperse polymers, the additional use of semiempirical approaches is required. The modern level of experimental studies allows test measurements over a wide range of deformation rates, frequencies, and temperatures. However, in this field, the mainstream tendency in experimental studies is concerned with hybrid methods, which combine direct rheological measurements with optical observations of local structure and its evolution in the material. In this case, various physical principles of measurements are applied. In recent years, much interest has been focused on studying polymer compositions containing nanosized fillers, which are able to produce their structures in melt.     

Conversion-type fluoride cathodes: Current state of the art

Conversion-type transition metal fluoride cathodes offer a 200%–300% higher theoretical energy density limit than state-of-the-art intercalation cathodes. Recent publications have reshaped our understanding of the reaction mechanism in these materials. Herein, we review recent reports highlighting how active material dissolution, particle fusing, electrolyte consumption, and the resultant capacity fade can be mitigated by rational electrolyte design. Recent work has established the possibility of high discharge rate in transition metal fluorides at significant active material mass fraction; we examine the relationship between rate capability and active material fraction. Tuning transition metal fluoride chemistry via cation and anion substitution has demonstrated the potential to improve its electrochemical properties. A brief technoeconomic analysis is presented to highlight the practical advantages of different transition metal chemistries.     

The state of the art in thin-layer chromatography-mass spectrometry: a critical appraisal.

Thin-layer chromatography-mass spectrometry (TLC-MS) is a readily implemented technique that, in its simplest form, puts few demands on either chromatography or spectrometry. Nevertheless, compared to the situation with high performance liquid chromatography, it is much less highly developed. Currently, the bulk of the practical applications of TLC-MS are directed towards the use of fast atom, or ion bombardment. Recent developments, however, include the use of matrix assisted laser desorption ionisation (MALDI), surface assisted laser desorption (SALDI) and the development of a TLC-electrospray interface. Here, the state of the art of TLC-MS is described and future trends identified.     

Review of the state of the art of preparative thin-layer chromatography

The state of the art of preparative thin-layer chromatography (PTLC) based on the literature published from 2007 through 2016 is reviewed. Classical capillary flow PTLC, forced flow PTLC, precoated and laboratory prepared plates, instruments, and micropreparative TLC are all covered, including techniques, instruments, and applications. Prospects for future applications and advances in PTLC are suggested.     

Parallel computer architectures: state of the art and trends

Summary An increasing number of parallel architectures is becoming available for numerically intensive applications. Many chemical problems need intensive calculations due to the complexity of the underlying physical models. Very often these applications show an intrinsic parallelism and therefore can be easily adapted to parallel machines. In the future, in addition to the classical numerically intensive applications, the use of these machines will be extended to a more general purpose use (e.g. data base machines, advanced graphics, AI and expert systems applications, etc.). The principal aim of this paper is to show the state of the art of the commercially available parallel architectures and related trends. A comparison of the main features of shared and distributed memory systems will be presented. The characteristics of coarse and fine grained architectures will be discussed. The analysis will include not only the large-scale machines (usually called supercomputers), but also smaller machines (e.g. minisuper and multicomputers) having a very favourable price/performance ratio.     

Photodynamic therapy for periodontal diseases: state of the art

BACKGROUND: Photodynamic killing of periodontopathogenic bacteria may be an alternative to the systemic application of antibacterial drugs used in the treatment of periodontal diseases. Even though the method is still in the experimental stage, increasing bacterial resistance problems may promote the introduction of photodynamic therapy (PDT) into periodontal practice. AIM: In this review a literature survey is given of PDT as seen from a periodontal perspective. METHODS: In this review, the present knowledge and experience of PDT is summarized. Literature data are presented on drawbacks of conventional antibiotics, the mechanism of PDT, bactericidal effects of PDT as well as results of clinical efforts. The future prospects of the method are discussed. RESULTS: The application of photosensitizing dyes and their excitation by visible light enables effective killing of periodontopathogens. Encouraging studies using PDT in periodontitis and in peri-implantitis are known. CONCLUSION: Even though PDT is still in experimental stages of development and testing, the method may be an adjunct to conventional antibacterial measures in periodontology. Clinical follow-up studies are needed to confirm the efficacy of the procedure.     

Electrochemical fluorination: state of the art and future tendences

A brief survey of the ECF process for the preparation of perfluorinated organo-compounds is given. The yield of perfluorinated products depends on the experimental conditions and on the nature of the starting material. Some useful rules are reported in order to optimise the ECF process. An improved operational technique allowed to obtain high yield of perfluorodimorpholinepropane (PFDMP) by simultaneous fluorination of dimorpholinepropane and N-methylmorpholine.     

Fourier transform ion cyclotron resonance: state of the art

This short review summarizes recent and projected advances in Fourier transform ion cyclotron resonance mass spectrometry instrumentation and applications, ranging from petroleomics to proteomics. More details are available from the cited primary literature and topical reviews.     

The state of the art in asymmetric induction: the aldol reaction as a case study

This review highlights the achievements in asymmetric induction in the context of the aldol reaction during the years 2003–2007. While chiral auxiliary-mediated methods are the best understood and developed, catalytic methods based on chiral metal–ligand complexes and more recently organocatalysts promise to improve the efficacy and economics of asymmetric induction. This review provides a brief summary of work prior to 2003 on chiral auxiliaries, metal catalysts and organocatalysts, and then delineates the state of the art in each process. It appears that no one method of achieving asymmetric induction in the aldol reaction is universally superior.