A theoretical study on calculation of absolute hydration enthalpies for some univalent ions

Using the total radius of alkaline fluorides and sodium halides and their experimental total enthalpy values, absolute hydration enthalpies of sodium and fluoride ions ( and ) were previously calculated. Also, by the help of data of sodium and fluoride ions for all alkaline metal ions and halides absolute hydration enthalpies were determined.

ΔThe effect of co-doping on the yttrium local environment and ionic conductivity of yttria-stabilised zirconia

The effect of co-doping yttria-stabilised zirconia with calcia and scandia has been investigated. Changes in the yttrium ion local environment have been monitored using solid-state magic angle sample spinning ⁸⁹Y nuclear magnetic resonance. The effect on the low-temperature (below 320 °C) bulk ionic conductivity has been observed using AC impedance spectroscopy. It was found that the number of oxygen vacancies in the nearest-neighbour sites to yttrium ions decreased on co-doping with scandia, correlating with an increase in conductivity, but increased on co-doping with calcia, correlating with a decrease in conductivity. This behaviour can be explained by proposing the trapping of oxygen vacancies in the nearest-neighbour yttrium ion sites so that they no longer contribute to the conduction mechanism.

Editorial

An overview of the special issue of the Journal of Nanoparticle Research on Occupational and Environmental Health of nanotechnology is presented. Papers published in this special issue show considerable progress in understanding nanoparticle toxicity, monitoring, generation, dustiness, filtration, and applications of nanoparticles. More research is needed to ensure safe handling of nanomaterials as nanotechnology continues to develop at an incredible pace.

Republication of: The cosmological constant and the theory of elementary particles (By Ya. B. Zeldovich)

The seminal paper by Ya. B. Zeldovich (Soviet Physics Uspekhi 11, 381–393, 1968) is reprinted here, together with an editorial comment on its lasting scientific relevance, and a biography of the author.

Public perception of nanotechnology

While several studies on the public opinion of nanotechnology have pointed to a rather enthusiastic U.S. public, the public uptake of nanotechnology in Europe is more contained. The results of the Swiss publifocus on nanotechnology reveal a pragmatic attitude of citizens toward the emerging technologies, thus confirming what has been identified as a “balanced approach” in the NanoJury UK.

General methods for flash chromatography using disposable columns

As technology has evolved available guidelines for normal-phase flash chromatography have become less relevant. Years of experience performing chromatography with disposable columns have been condensed into simple guidelines useful for translating TLC results into either isocratic- or gradient-flash chromatography. The described studies should provide researchers with a means of selecting adequate columns and guidelines to reduce the waste of solvents, silica, time, and money. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

General model for the functional dependence of defect concentration on oxygen potential in mixed conducting oxides

To understand and engineer applications for mixed conducting oxides, it is desirable to have explicit, analytical expressions for the functional dependence of defect concentration and transport properties on the partial pressure of the external gas phase. To fulfill this need, general expressions are derived for the functional dependence of defect concentration on the oxygen partial pressure () for the mixed ionic electronic conductors. The model presented in this paper differs from expressions obtained using the popular Brouwer approach because they are continuous across multiple Brouwer regions.

Developing nanotechnology in Latin America

This article investigates the development of nanotechnology in Latin America with a particular focus on Argentina, Brazil, Chile, and Uruguay. Based on data for nanotechnology research publications and patents and suggesting a framework for analyzing the development of R&D networks, we identify three potential strategies of nanotechnology research collaboration. Then, we seek to identify the balance of emphasis upon each of the three strategies by mapping the current research profile of those four countries. In general, we find that they are implementing policies and programs to develop nanotechnologies but differ in their collaboration strategies, institutional involvement, and level of development. On the other hand, we find that they coincide in having a modest industry participation in research and a low level of commercialization of nanotechnologies.

Rapid synthesis and size control of CuInS2 semi-conductor nanoparticles using microwave irradiation

The properties of CuInS₂ semi-conductor nanoparticles make them attractive materials for use in next-generation photovoltaics. We have prepared CuInS₂ nanoparticles from single source precursors via microwave irradiation. Microwave irradiation methods have allowed us to increase the efficiency of preparation of these materials by providing uniform heating and rapid reaction times. The synergistic effect of varying thiol capping ligand concentrations as well as reaction temperatures and times resulted in fine control of nanoparticle growth in the 3–5 nm size range. Investigation of the photophysical properties of the colloidal nanoparticles were performed using electronic absorption and luminescence emission spectroscopy. Qualitative nanoparticles sizes were determined from the photoluminescence (PLE) data and compared to HRTEM images.

Refining search terms for nanotechnology

The ability to delineate the boundaries of an emerging technology is central to obtaining an understanding of the technology’s research paths and commercialization prospects. Nowhere is this more relevant than in the case of nanotechnology (hereafter identified as “nano”) given its current rapid growth and multidisciplinary nature. (Under the rubric of nanotechnology, we also include nanoscience and nanoengineering.) Past efforts have utilized several strategies, including simple term search for the prefix nano, complex lexical and citation-based approaches, and bootstrapping techniques. This research introduces a modularized Boolean approach to defining nanotechnology which has been applied to several research and patenting databases. We explain our approach to downloading and cleaning data, and report initial results. Comparisons of this approach with other nanotechnology search formulations are presented. Implications for search strategy development and profiling of the nanotechnology field are discussed.

Nanotoxicology: characterizing the scientific literature, 2000–2007

Understanding the toxicity of nanomaterials and nano-enabled products is important for human and environmental health and safety as well as public acceptance. Assessing the state of knowledge about nanotoxicology is an important step in promoting comprehensive understanding of the health and environmental implications of these new materials. To this end, we employed bibliometric techniques to characterize the prevalence and distribution of the current scientific literature. We found that the nano-toxicological literature is dispersed across a range of disciplines and sub-fields; focused on in vitro testing; often does not specify an exposure pathway; and tends to emphasize acute toxicity and mortality rather than chronic exposure and morbidity. Finally, there is very little research on consumer products, particularly on their environmental fate, and most research is on the toxicity of basic nanomaterials. The implications for toxicologists, regulators and social scientists studying nanotechnology and society are discussed.

Expert opinion on nanotechnology: risks,benefits, and regulation

A survey of American (US) nanotechnology researchers (N = 177) suggests a diversity of views about what areas are most important to the burgeoning field, as well as perceptions about the overall benefits and risks of such research. On average, respondents saw a range of technologies as key and viewed public health and environmental issues as areas where both risks and the need for regulation are greatest. These areas were also where respondents said current regulations were least adequate. Factor analyses of the survey questions suggest that, when considering both risks and regulations, respondents make a distinction between health and environmental risks, and what might be termed “social risks” (e.g., invasion of privacy, use of nanotechnology in weapons, and economic impacts).

Pionic Kα X-ray energy and linewidth IN 20Ne and 22Ne

We have measured the energies and linewidths of the pionic K_α X-rays for ²⁰Ne and ²²Ne using a natural liquid-neon target. The results are

     

14.

On the Distribution of Free Path Lengths¶for the Periodic Lorentz Gas     

Jean Bourgain  François Golse  Bernt Wennberg 《Communications in Mathematical Physics》1998,190(3):491-508

Consider the domain

20Ne	22Ne
Neenergy (keV)	239.12±0.14	230.49±0.88
width (keV)	15.43±0.41	12.65±3.51

and let the free path length be defined as The distribution of values of is studied in the limit as for all . It is shown that the value is critical for this problem: in other words, the limiting behavior of depends only on whether γ is larger or smaller than . Received: 1 March 1996 / Accepted: 25 March 1997     

On the Distribution of Free Path Lengths¶for the Periodic Lorentz Gas

Consider the domain

A Simple Spectrofluorometric Assay to Measure Total Intracellular Magnesium by a Hydroxyquinoline Derivative

The intracellular behaviour of diaza-18-crown-6 appended with two H-substituted hydroxyquinoline groups (DCHQ1) was investigated to explore its application as a new sensor for the evaluation of cell magnesium content and distribution. We used five cells lines characterised by different contents of magnesium and different intracellular membrane-defined compartments. The main result is the definition of the appropriate experimental conditions to quantitatively assess the total cell magnesium by fluorescence spectroscopy. We showed that disrupting cells by sonication, DCHQ1 was capable to assess total cell magnesium in all cell types examined, obtaining overlapping results with atomic absorption spectroscopy (AAS). This new analytical approach requires very small cell samples and a simple fluorimetric technique, and can be a valid alternative to AAS. The fluorescent properties of DCHQ1 in living cells are: (a) it consistently stains live cells, (b) it discriminates small variations of cell Mg contents, (c) cell staining is stable for at least 30 min. We also investigated the role of lipophilic environment on DCHQ1 fluorescence by mimicking cell membranes and described how the composition and structure of lipid vesicles affect Mg-DCHQ1 fluorescence. Thus, DCHQ1 may offer important information also on magnesium distribution in living cells, providing a novel strategy to map the intracellular compartmentalization of this cation.

The Millimeter Wave Radiation of a Traveling Wave Sinusoidal Wire Antenna

In this paper, investigation of radiation properties of the traveling-wave sinusoidal wire antennas is extended to the millimeter-wave frequencies (Ka-band) for the antennas whose geometrical dimensions vary in a wide range. Far-field patterns and S-parameters of composed three antenna sets were measured. A mathematical model was constructed for the structure and a MATLAB code based on this theoretical approach was written to calculate patterns, phase and attenuation constants of all investigated antennas. Frequency characteristics and the relation of antenna dimensions with wave parameters were investigated. Measured and calculated patterns were also compared with the constructed far-field patterns obtained by MoM (method of moments) and the MoM current distributions were used to explain the loss mechanisms of antennas. A directive, undistorted and smooth radiation can be achieved only choosing small undulated antennas whose peak-to-peak amplitude to period ratio κ is smaller than 0.4 (κ < 0.4). It is shown that wavelength of broadside radiation is not equal to antenna period for all antennas, except for very small undulated antennas (κ < 0.2). This antenna type can be used as a frequency-scan antenna for millimeter wave radars.

How interdisciplinary is nanotechnology?

Facilitating cross-disciplinary research has attracted much attention in recent years, with special concerns in nanoscience and nanotechnology. Although policy discourse has emphasized that nanotechnology is substantively integrative, some analysts have countered that it is really a loose amalgam of relatively traditional pockets of physics, chemistry, and other disciplines that interrelate only weakly. We are developing empirical measures to gauge and visualize the extent and nature of interdisciplinary interchange. Such results speak to research organization, funding, and mechanisms to bolster knowledge transfer. In this study, we address the nature of cross-disciplinary linkages using “science overlay maps” of articles, and their references, that have been categorized into subject categories. We find signs that the rate of increase in nano research is slowing, and that its composition is changing (for one, increasing chemistry-related activity). Our results suggest that nanotechnology research encompasses multiple disciplines that draw knowledge from disciplinarily diverse knowledge sources. Nano research is highly, and increasingly, integrative—but so is much of science these days. Tabulating and mapping nano research activity show a dominant core in materials sciences, broadly defined. Additional analyses and maps show that nano research draws extensively upon knowledge presented in other areas; it is not constricted within narrow silos.

Microwave spectrum,quadrupole hyperfine interaction,and electric dipole moment of the BrF molecule

The measurements of the microwave spectrum of BrF were carried out on the hyperfine components of J = 1 ← 0 and J = 2 ← 1 rotational transitions of ⁷⁹BrF and ⁸¹BrF. A direct diagonalization procedure of the energy matrix of the total Hamiltonian including Stark effect has been used. The following constants were derived:

     

19.

Frequency Domain Fluorescence Lifetime Study of Crude Petroleum Oils     

Owens P  Ryder AG  Blamey NJ 《Journal of fluorescence》2008,18(5):997-1006

Frequency domain (FD) fluorescence lifetime data was collected for a series of 20 crude petroleum oils using a 405 nm excitation source and over a spectral range of ~426 to ~650 nm. Average fluorescence lifetimes were calculated using three different models: discrete multi-exponential, Gaussian distribution, and Lorentzian distribution. Fitting the data to extract accurate average lifetimes using the various models proved easier and less time consuming for the FD data than with Time Correlated Single Photon Counting (TCSPC) methods however the analysis of confidence intervals to the computed average lifetimes proved cumbersome for both methods. The uncertainty in the average lifetime was generally larger for the discrete lifetime multi-exponential model when compared to the distribution-based models. For the lifetime distributions, the data from the light crude oils with long lifetimes generally fit to a single decay term. Heavier oils with shorter lifetimes required multiple decay terms. The actual value for the average lifetime is more dependant on the specific fitting model employed than the data acquisition method used. Correlations between average fluorescence lifetimes and physical and chemical parameters of the crude oils were made with a view to developing a quantitative model for predicting the gross chemical composition of crude oils. It was found that there was no significant benefit gained by using FD over TCSPC other than more rapid data analysis in the FD case. For the FD data the Gaussian distribution model for fluorescence lifetime gave the best correlations with chemical composition allowing a qualitative correlation to some bulk oil parameters.

79BrF

81BrF

Be (MHz) 10 667.610 (60)

10 616.522 (70)

eq0Q (MHz) 1086.80 (30)

908.09 (20)

eq1Q (MHz) 1085.66 (60)

907.41

Alan G. RyderEmail:

     

Frequency Domain Fluorescence Lifetime Study of Crude Petroleum Oils

Frequency domain (FD) fluorescence lifetime data was collected for a series of 20 crude petroleum oils using a 405 nm excitation source and over a spectral range of ~426 to ~650 nm. Average fluorescence lifetimes were calculated using three different models: discrete multi-exponential, Gaussian distribution, and Lorentzian distribution. Fitting the data to extract accurate average lifetimes using the various models proved easier and less time consuming for the FD data than with Time Correlated Single Photon Counting (TCSPC) methods however the analysis of confidence intervals to the computed average lifetimes proved cumbersome for both methods. The uncertainty in the average lifetime was generally larger for the discrete lifetime multi-exponential model when compared to the distribution-based models. For the lifetime distributions, the data from the light crude oils with long lifetimes generally fit to a single decay term. Heavier oils with shorter lifetimes required multiple decay terms. The actual value for the average lifetime is more dependant on the specific fitting model employed than the data acquisition method used. Correlations between average fluorescence lifetimes and physical and chemical parameters of the crude oils were made with a view to developing a quantitative model for predicting the gross chemical composition of crude oils. It was found that there was no significant benefit gained by using FD over TCSPC other than more rapid data analysis in the FD case. For the FD data the Gaussian distribution model for fluorescence lifetime gave the best correlations with chemical composition allowing a qualitative correlation to some bulk oil parameters.

Exposure to nanoscale particles and fibers during machining of hybrid advanced composites containing carbon nanotubes

This study investigated airborne exposures to nanoscale particles and fibers generated during dry and wet abrasive machining of two three-phase advanced composite systems containing carbon nanotubes (CNTs), micron-diameter continuous fibers (carbon or alumina), and thermoset polymer matrices. Exposures were evaluated with a suite of complementary instruments, including real-time particle number concentration and size distribution (0.005–20 μm), electron microscopy, and integrated sampling for fibers and respirable particulate at the source and breathing zone of the operator. Wet cutting, the usual procedure for such composites, did not produce exposures significantly different than background whereas dry cutting, without any emissions controls, provided a worst-case exposure and this article focuses here. Overall particle release levels, peaks in the size distribution of the particles, and surface area of released particles (including size distribution) were not significantly different for composites with and without CNTs. The majority of released particle surface area originated from the respirable (1–10 μm) fraction, whereas the nano fraction contributed ~10% of the surface area. CNTs, either individual or in bundles, were not observed in extensive electron microscopy of collected samples. The mean number concentration of peaks for dry cutting was composite dependent and varied over an order of magnitude with highest values for thicker laminates at the source being >1 × 10⁶ particles cm⁻³. Concentration of respirable fibers for dry cutting at the source ranged from 2 to 4 fibers cm⁻³ depending on the composite type. Further investigation is required and underway to determine the effects of various exposure determinants, such as specimen and tool geometry, on particle release and effectiveness of controls.