From Top-Down to Bottom-Up to Hybrid Nanotechnologies: Road to Nanodevices

The current development and future prospects of nanotechnology are discussed with special emphasis on the pros and cons of the “bottom-up” and “top-down” approaches to nanotechnology, and the eventual merging of the two, at the scale of about 30 nm in feature size, to form a new “hybrid” technology. At the scale of about 3 nm in feature size, this “hybrid” technology will be challenged by the emerging “supramolecular” and “molecular” technologies epitomized by large-scale integration of single-molecule devices. Ultimately the “supramolecular” and “molecular” technologies will yield to “atomic” or “nuclear” technologies at the dimension of below 0.3 nm whereby single-atom, single-electron, single-spin, single-photon devices become realities.     

Synthetic routes to cyclopropylidenecarbinols and to cyclopropylidienes

Functionalized alkylidine cyclopropanes have beeen prepared from 1-seleno 1-vinyl cyclopropanes using [2,3] sigmatropic rearrangement of their corresponding selenonium ylides. A comparison with sulphur analogues is presented.     

How to Use Visual Basic to Interface Scientific Instruments to a Personal Computer

Computer-controlled instruments are expensive and for this reason are not widely used in student laboratories. In this paper we describe how to interface a data-acquisition board using Microsoft Visual Basic. Visual Basic can be used to quickly develop an application in the Microsoft Windows environment. A single computer system can serve as several different measuring systems by simple adaptation of the software.     

Application of Biomarkers to Assessment of Risk to Human Health from Exposure to Mycotoxins

Mycotoxins, the toxic compounds produced by mold secondary metabolism, represent a relevant source of danger to humans through alimentary channels. Efforts have been made by researchers and by national authorities to assess mycotoxin incidence in food, but often results are to be considered approximate or inaccurate due to the huge difficulties posed by sampling procedures. More recently the evaluation of mycotoxins in biological fluids have been given increasing attention since the results may offer valuable indications, although general on the overall status of mycotoxin contamination in food and feed. The assessment of the degree of exposure to these contaminants in the population or in specific groups can also be pursued. Researches on mycotoxins in biological fluids greatly contribute to clarify the mechanism of health impairment attributable to these toxic compounds and to elucidate the dose–response relationship. Despite the considerable efforts devoted to mycotoxin research in the past few decades, improvements in methodology has to be achieved mainly in sampling procedures and in quality assurance of the laboratories involved in mycotoxin analysis, as well as in the selection of appropriate biomarkers.     

Hair analysis as a new tool to monitor adherence to long-term therapy to statins

Statins are cholesterol-lowering medications which are widely prescribed as first-line treatment for hyperlipidemia, against high blood cholesterol aimed at reducing the risk of atherosclerotic diseases. Notwithstanding their undoubted efficacy, the needed long-term treatment with these drugs is characterized by a high percentage of dropout. Consequently, an effective tool to verify the patients’ compliance to statin therapy is needed. In this context, the analysis for drugs and drug metabolites in the hair may represent an almost ideal tool because, according to a sound body of forensic toxicological literature, concentrations in the hair matrix reflect the chronic intake of drugs and pharmaceuticals. In this light, in the present study, a novel, specific and sensitive ultra-performance liquid chromatography–tandem mass spectrometry method has been developed to determine six statins and their metabolites (namely atorvastatin, (p)α-OH-atorvastatin-lactone, (o)α-OH-atorvastatin-lactone, rosuvastatin, N-desmethyl rosuvastatin and pravastatin) in human hair. After optimization, the method was successfully validated in terms of selectivity, linearity, sensitivity, precision, accuracy, stability and matrix effect. Moreover, the practical applicability of this method for verifying adherence to statin therapy was assessed by testing samples of hair collected from subjects under long-term therapy with statins.     

Synthetic Approaches to Triarylboranes from 1885 to 2020

In recent years, research in the fields of optoelectronics, anion sensors and bioimaging agents have been greatly influenced by novel compounds containing triarylborane motifs. Such compounds possess an empty p-orbital at boron which results in useful optical and electronic properties. Such a diversity of applications was not expected when the first triarylborane was reported in 1885. Synthetic approaches to triarylboranes underwent various changes over the following century, some of which are still used in the present day, such as the generally applicable routes developed by Krause et al. in 1922, or by Grisdale et al. in 1972 at Eastman Kodak. Some other developments were not pursued further after their initial reports, such as the synthesis of two triarylboranes bearing three different aromatic groups by Mikhailov et al. in 1958. This review summarizes the development of synthetic approaches to triarylboranes from their first report nearly 135 years ago to the present.     

Direct catalytic oxidation of n-butane to to tetrahydrofuran

The feasibility of partially oxidizing n-butane to tetrahydrofuran in the presence of promoted V-P-O catalyst was demonstrated. Tetrahydrofuran formation was identified by means of chromatography and mass spectrometry. From the relationship between its concentration and reaction temperature tetrahydrofuran could be proposed as a possible intermediate in the transformation of n-butane into maleic anhydride.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 2, pp. 159–162, March–April, 1992.     

A new approach to counterpoise correction to BSSE

In the present work the intermolecular BSSE, associated to the A-B interaction, is obtained by subtracting the intramolecular BSSE of the fragments from the intramolecular BSSE of the supermolecule, and considering every atom as a fragment in the calculation of each intramolecular BSSE. This atom by atom scheme (CP(aa)) is based on the consideration that the proximity of the fragments may affect the intramolecular BSSE of every involved species, and artificially influences the value of the BSSE associated to the supermolecule formation. It drastically decreases the reported counterpoise overcorrection of the A-B interaction, even though it does not deal with all the overcorrection because it includes all the orbitals, and not only the unoccupied ones. This new approach has been tested on the water dimer, some hydrogen fluoride weakly bonded complexes, the conformational analysis of 1,2-dichloroethane, and the reaction profile of formaldehyde + OH reaction.     

Utilization of thermodesorption coupled to GC-MS to study stability of different wood species to thermodegradation

Thermodesorption coupled to gas chromatography coupled to mass spectroscopy (TD-GC-MS) has been investigated to identify volatile degradation products generated during wood heat treatment by mild pyrolysis. For this purpose, wood samples of different softwood and hardwood species have been heat treated under nitrogen for different temperatures comprised between 180 and 230 °C during 15 min in the glass thermal desorption tube of the thermodesorber and the volatile wood degradation products trapped. The trapped products were then thermodesorbed and analysed by GC-MS. Chromatograms of the different samples indicated the formation of different products resulting from degradation of lignin and hemicelluloses. Hardwoods were shown to be more sensitive to thermodegradation than softwoods, for which degradation products appear at slightly higher temperature. The important formation of acetic acid is concomitant with the formation of most of degradation products and at the origin of the difference of reactivity observed between softwoods and hardwoods.     

Adhesion to mineralized tissue: Bonding to human dentin

We consider the conditions and demonstrable reactions which promote chemical bonding to human dentin. The desirability of developing durable adhesion to dentin is used as background for a discussion of feasible reactions to the dentin components, for possible use in new formulations. This is followed by a discussion of the demonstrable reactions found in the literature, as well as our own surface-sensitive IR work on the reaction between dentin protein and 2-hydroxyethyl methacrylate, an ingredient found in proprietary tissue replacement formulations.     

A General Introduction to SCTA and to Rate-Controlled SCTA

Journal of Thermal Analysis and Calorimetry -     

How to Persuade Undergraduates to Use Chemical Graph Theory

New techniques are presented that permit the use of chemical graph theory to obtain secular equations for small molecules. The new techniques significantly accelerate manual calculations. A previously unrecognized relationship between the characteristic polynomial for a Hückel annulene and the secular equation for the corresponding Mobius annulene is deduced. The power of the graph-theoretical approach to illuminate chemically useful generalizations at the Hückel level is exemplified.