bluuebunny/crossref_metadata_2025 huggingface dataset:
A high potential Tesla coil impulse generator for lecture demonstrations and science exhibitions
Authors: Skeldon Kenneth D. , Grant Alastair I. , Scott Slan A.
Published: March 2005

Demonstrations of high voltage phenomena are among the most spectacular and visually beautiful illustrations of physics. Here, we describe a high potential generator (several hundred thousand volts) which is based on a resonant transformer, derived from a standard Tesla coil arrangement with high Q secondary coil. Control electronics have been implemented that allow the user to command single shot discharges, should they be required for a particular demonstration. We review the behavior of a coupled resonant system with relevance to the spark-gap excited Tesla circuit implemented in our generator. The importance of the Q factor in the secondary coil design is emphasized, but only with due regard to other design factors including the coupling coefficient and primary spark-gap, which in certain configurations can outweigh the benefits of achieving very high Q.
Undergraduate experiment designed to show the proportionality between the phase difference and the thickness of a uniaxial crystal
Authors: Blanco M. A. , Yuste M. , Carreras C.
Published: March 2005

We propose a simple, inexpensive laboratory experiment, designed to show the proportionality between the phase difference produced by a uniaxial birefringent crystal and the thickness of the crystal.
Is it possible to detect permanent electric dipole moments using fluorescence measurements?
Authors: Ejnisman Renato , Bigelow Nicholas P.
Published: March 2005

We investigate the interaction of two-level atoms possessing finite permanent electric dipole moments with electromagnetic radiation. After framing the problem in a historical perspective, we solve it in the interaction picture and examine the possibility of extracting information on atomic permanent dipole moments from fluorescence measurements.
Decomposition of electromagnetic fields into radiation and bound components
Authors: Comay E.
Published: March 2005

The decomposition of electromagnetic fields for a system of elementary classical point charges into velocity fields and acceleration fields is suggested by the appropriate terms in the Lienard–Wiechert formulas. This paper introduces “bound” fields and “radiation” fields which are related but not identical to velocity and acceleration fields, respectively. It is shown how this approach can be used in the construction of an energy–momentum tensor that is free of infinite quantities and settles the 4/3 problem in the Lorentz transformation of momentum.
Energy and momentum for the electromagnetic field described by three outstanding electrodynamics
Authors: Accioly Antonio
Published: March 2005

A prescription for computing the symmetric energy–momentum tensor from the field equations is presented. The method is then used to obtain the total energy and momentum for the electromagnetic field described by Maxwell electrodynamics, Born–Infeld nonlinear electrodynamics, and Podolsky generalized electrodynamics, respectively.
Scattering by a Coulomb field in two dimensions
Authors: Lin Qiong-gui
Published: March 2005

The scattering cross section in a Coulomb field in two dimensions is obtained by solving the Schrödinger equation in parabolic coordinates. In contrast with the three-dimensional case, the result is different from the corresponding classical one and does not coincide with the Born approximation in general. The quantum-mechanical cross section depends on ℏ and reduces to the classical one in the limit ℏ→0.
Measurements on a rotating frame in relativity, and the Wilson and Wilson experiment
Authors: Weber T. A.
Published: March 2005

Pellegrini and Swift have recently suggested that the use of special relativity in the calculation of the electric dipole moment of a moving magnetic dipole cannot be applied to the classic experiment of Wilson and Wilson, which used rotational motion. This paper contests that view. The disagreement arises in the choice of coordinates used to represent physical quantities measured in the rotating frame. The arguments of this paper are based on Einstein’s discussion of the validity of arbitrary coordinates and the difficulty in their interpretation. Because of the lack of synchronization of clocks, caution must be used in assigning values to physical quantities in the usual coordinates that describe a rotating frame. This paper gives the detailed transformations to an inertial rest frame, where the interpretation of measurements is assured. Other aspects of the rotating frame are also discussed.
The personal and professional interactions of J. J. Thomson and Arthur Schuster
Authors: Mulligan Joseph F.
Published: March 2005

This paper reviews the relationships, both personal and professional, between J. J. Thomson and Arthur Schuster, the first physicist to attempt quantitative measurements on cathode rays in the years 1884–1890. Their relationships were unusually close, since they both attended the same college (Owens in Manchester), worked in the same research field (discharge of electricity through gases), and served many terms together in executive positions in the Royal Society of London. There were occasional misunderstandings and priority disputes between them about cathode rays, but after Thomson received his Nobel Prize in 1906 harmony again prevailed. In 1897, Thomson had available the important experimental results of Hertz, Lenard, Perrin, Wiechert, and Kaufmann on cathode rays, whereas in 1890, Schuster could benefit from none of this work. But the main reason that Thomson, and not Schuster, “discovered the electron” was that he was a better experimental physicist than Schuster.
The physics of tennis. III. The ball–racket interaction
Authors: Brody H.
Published: March 2005

A simple, one-dimensional, rigid-body model of a tennis racket interacting with a tennis ball agrees well with data taken when balls are fired at a stationary, free racket. The results are then transformed into the tennis court frame of reference, where the racket is moving. Data obtained on the rotational aspects of a tennis swing are then included in the model. For ground strokes, the results are used to predict strategies that will reduce unforced errors by players. The serve is then analyzed with respect to the current problem of the speed of the game. This paper is the third of a series of papers on tennis by this author. The two previous papers were “Physics of the Tennis Racket” [Am. J. Phys. 47, 482 (1979)] and “Physics of the Tennis Racket. II. The Sweet Spot” [Am. J. Phys. 49, 816 (1981)].
Finding the surface temperature of the Sun using a parked car
Authors: Lee Wei , Gilley Heidi L. , Caris Joshua B.
Published: March 2005

We present an activity, involving a parked car, for estimating the surface temperature of the Sun. The activity entails both outdoor quantitative observations and theoretical analysis, and yields a result for the surface temperature of the Sun within 12% of the accepted value. It can be used as an independent study project to spark students’ interest and facilitate learning.
Accidental degeneracy in a simple quantum system: A new symmetry group for a particle in an impenetrable square-well potential
Authors: Leyvraz F. , Frank A. , Lemus R. , Andrés M. V.
Published: March 2005

The two-dimensional square-well potential is one of the simplest quantum-mechanical systems that exhibits accidental degeneracy. We show that the double degeneracy present is a consequence of a dynamical symmetry and derive a new symmetry group associated with the system.
Average value of position for the anharmonic oscillator: Classical versus quantum results
Authors: Robinett Richard W.
Published: March 2005

The evaluation of the average value of the position coordinate, 〈x〉, of a particle moving in a harmonic oscillator potential (V(x)=kx2/2) with a small anharmonic piece (V(x)=−λkx3) is a standard calculation in classical Newtonian mechanics and statistical mechanics where the problem has relevance to thermal expansion. In each case, the calculation is most easily done using a perturbative expansion. In this note, we perform the same computation of 〈x〉 in quantum mechanics using time-independent perturbation theory and the ladder operator formalism to show how similar results are obtained. We also indicate how a semiclassical calculation using a classical probability distribution can also be used to obtain the same result.
WKB energy quantization and first-order perturbation theory
Authors: Robinett Richard W.
Published: March 2005

The WKB quantization condition can be used to estimate the quantized bound state energies, En, in a potential V(x). If a small perturbation of the form λV(x) is added to this potential, we show that the resulting shift in the quantized energy eigenvalues is given by a form which is quite similar to standard first-order perturbation theory. Several examples are presented in which the large n form of the lowest-order energy shift is more easily evaluated using WKB-perturbation techniques than by using standard first-order perturbation methods.
Visualizing classical periodic orbits from the quantum energy spectrum via the Fourier transform: Simple infinite well examples
Authors: Robinett Richard W.
Published: March 2005

The Fourier transform of the density of quantized energy levels for a quantum mechanical particle in a two-dimensional (2-D) infinite well (or billiard geometry) is known to exhibit δ-function-like spikes at distance values (L) corresponding to the lengths of periodic orbits or closed trajectories. We show how these Fourier transforms can be rather easily calculated numerically for simple infinite well geometries including the square and rectangular well in 2 D, the cubical well in three dimensions, as well as the circular infinite well (and variations) in two dimensions. Such calculations provide a novel, well-motivated, and relatively straightforward example of numerical Fourier transform techniques and make interesting connections between quantum energy levels and classical trajectories in a way which is seldom stressed in the undergraduate curriculum.
Dynamic modeling of speed skiing
Authors: Catalfamo R. S.
Published: March 2005

The equations of motion that describe a skier descending a speed-skiing hill are solved both analytically and numerically. The model is shown to agree well with actual official results but only when the hill profile is considered. A sensitivity analysis reveals which parameters most affect the skier’s exit speed. Other factors, such as scaling effects and wind gusts, are included to determine whether these need to be considered in official results. One surprising result is that, under certain conditions and hill profiles, maximum skier speed is attained prior to entry into the timing zone—thus bringing into question the optimum placement of the timing gates.
The fields outside a long solenoid with a time-dependent current
Authors: McDonald Kirk T.
Published: March 2005

An instructive version of this well-known problem is the case of a current that is zero to t<0 and varies as αt for t>0. A generally excellent discussion of this case by Abbott and Griffiths features, however, a singularity in the fields at any point at the moment they first become nonzero. This singularity can be avoided by careful approximation, derived here using expressions for time-dependent fields rather than potentials. The result is that while the fields assume a quasistatic character for long times after the current has started to flow, they include a small amount of radiation at short times. Such an effect was observed in a simple experiment involving a kitchen appliance.
A curvature-based derivation of the Schwarzschild metric
Authors: Santander Mariano , Nieto Luis M. , Cordero Nicolás A.
Published: March 2005

We give a derivation of Schwarzschild and other spherically symmetric solutions in general relativity which starts by computing the curvatures directly from Einstein’s equations and Bianchi identities, and then derives the metric. This transforms the “plausibility” argument for the Schwarzschild metric given by Berry in his book Principles of Cosmology and Gravitation into a complete derivation, which puts the stress from the beginning on the curvatures, the quantities which actually correspond to the gravitational field.
Simulations of nonlinear pivot-driven pendula
Authors: Grandy W. T. , Schöck Matthias
Published: March 2005

The inverted plane pendulum is re-examined for the cases of horizontal or vertical driving of the pivot by a harmonic force, with principal interest in the computer simulation of the ensuing motions. While the regions of parameter values for which the vertically driven inverted motion is stable are well understood, and numerical simulation itself is quite stable, the situation is not as clear for the case of horizontal driving. We investigate the origins of these differences from the vertically driven case and resolve them. In doing so, some little-known modes of the horizontally driven hanging pendulum are uncovered and some of their properties are discussed.
Resource Letter ITP-1: Information Theory in Physics
Authors: Grandy W. T.
Published: March 2005

This Resource Letter provides a guide to the literature on the role of information theory in physics. Journal articles and books are cited for the following topics: early history, physical and mathematical connections, and a broad range of physical applications.
Millikan Lecture 1997: Is there a text in this class?
Authors: Griffiths David J.
Published: March 2005

I’ll propose a physicist’s answer to Stanley Fish’s impudent question, and offer some thoughts about the role of text(book)s in the teaching and learning process. Also—with a view to offending as many listeners as possible—I will indulge in some gratuitous curmudgeonly remarks about the reform movement in physics education.
Translational Operator of mRNA on the Ribosome: How Repressor Proteins Exclude Ribosome Binding
Authors: Jenner Lasse , Romby Pascale , Rees Bernard , Schulze-Briese Clemens , Springer Mathias , Ehresmann Chantal , Ehresmann Bernard , Moras Dino , Yusupova Gulnara , Yusupov Marat
Published: March 2005

The ribosome of
Thermus thermophilus
was cocrystallized with initiator transfer RNA (tRNA) and a structured messenger RNA (mRNA) carrying a translational operator. The path of the mRNA was defined at 5.5 angstroms resolution by comparing it with either the crystal structure of the same ribosomal complex lacking mRNA or with an unstructured mRNA. A precise ribosomal environment positions the operator stem-loop structure perpendicular to the surface of the ribosome on the platform of the 30
S
subunit. The binding of the operator and of the initiator tRNA occurs on the ribosome with an unoccupied tRNA exit site, which is expected for an initiation complex. The positioning of the regulatory domain of the operator relative to the ribosome elucidates the molecular mechanism by which the bound repressor switches off translation. Our data suggest a general way in which mRNA control elements must be placed on the ribosome to perform their regulatory task.
Mortality and Greenhouse Gas Impacts of Biomass and Petroleum Energy Futures in Africa
Authors: Bailis Robert , Ezzati Majid , Kammen Daniel M.
Published: March 2005

We analyzed the mortality impacts and greenhouse gas (GHG) emissions produced by household energy use in Africa. Under a business-as-usual (BAU) scenario, household indoor air pollution will cause an estimated 9.8 million premature deaths by the year 2030. Gradual and rapid transitions to charcoal would delay 1.0 million and 2.8 million deaths, respectively; similar transitions to petroleum fuels would delay 1.3 million and 3.7 million deaths. Cumulative BAU GHG emissions will be 6.7 billion tons of carbon by 2050, which is 5.6% of Africa's total emissions. Large shifts to the use of fossil fuels would reduce GHG emissions by 1 to 10%. Charcoal-intensive future scenarios using current practices increase emissions by 140 to 190%; the increase can be reduced to 5 to 36% using currently available technologies for sustainable production or potentially reduced even more with investment in technological innovation.
Neuronal Coherence as a Mechanism of Effective Corticospinal Interaction
Authors: Schoffelen Jan-Mathijs , Oostenveld Robert , Fries Pascal
Published: March 2005

Neuronal groups can interact with each other even if they are widely separated. One group might modulate its firing rate or its internal oscillatory synchronization to influence another group. We propose that coherence between two neuronal groups is a mechanism of efficient interaction, because it renders mutual input optimally timed and thereby maximally effective. Modulations of subjects' readiness to respond in a simple reaction-time task were closely correlated with the strength of gamma-band (40 to 70 hertz) coherence between motor cortex and spinal cord neurons. This coherence may contribute to an effective corticospinal interaction and shortened reaction times.
Cell Senescence in the Dock
Authors: Austad Steven N.
Published: March 2005

Cells, Aging, and Human Disease
.
By Michael B. Fossel
. Oxford University Press, New York, 2004. 503 pp. $69.95, £43. ISBN 0-19-514035-4.

Approaching aging from the perspective of senescence at the levels of cells and organs, the author discusses aging diseases in the context of the tissues that they impact.
Of Bubbles, Landscapes, and Vines
Authors: West Stuart
Published: March 2005

Uncorked:
The Science of Champagne.
By Gérard Liger-Belair
. Princeton University Press, Princeton, NJ, 2004. 158 pp. $19.95, £12.95. ISBN 0-691-11919-8.

Great Wine Terroirs
.
By Jacques Fanet, translated by Florence Brutton
. University of California Press, Berkeley, CA, 2004. 240 pp. $39.95, £26.95. ISBN 0-520-23858-3.

Paying particular attention to the physics of bubbles, Liger-Belair explores the history, preparation, and future prospects of champagne. Fanet's tour of celebrated wine-growing regions examines the links between the vines and their environments.
Interaction of dietary sodium chloride and waterborne copper in rainbow trout (Oncorhynchus mykiss): copper toxicity and sodium and chloride homeostasis
Authors: Kamunde Collins N , Niyogi Soumya , Wood Chris M
Published: March 2005

Juvenile rainbow trout (Oncorhynchus mykiss) maintained on either low sodium chloride (LS (control), 1.4% NaCl) or high sodium chloride (HS, 11% NaCl) diet were exposed to 55 µg·L1waterborne copper (Cu) for 28 days. Cu-exposed fish maintained on the LS diet exhibited 26% mortality, more than double (11%) that in fish maintained on the HS diet. Waterborne Cu exposure inhibited growth by 56% in fish maintained on the LS diet and by 35% in those maintained on the HS diet. Whole-body and tissue Na+levels, measured 6 h after feeding, were increased by exposure to HS diet and reduced by waterborne Cu exposure. Exposure to elevated waterborne Cu increased whole-body and tissue Cu levels, whereas exposure to HS diet decreased these levels. Moreover, whole-body and tissue Cu concentrations were consistently lower in Cu-exposed fish maintained on HS diet relative to those maintained on LS diet. Plasma Na+and Cllevels were elevated by HS diet exposure and reduced by waterborne Cu exposure, whereas plasma Cu levels were decreased and increased by exposure to HS diet and waterborne Cu, respectively. These results demonstrate that elevated dietary NaCl modulates Na+and Clhomeostasis and reduces accumulation and toxicity of waterborne Cu.
Nonlethal estimation of proximate composition in fish
Authors: Cox M Keith , Hartman Kyle J
Published: March 2005

The need to precisely measure growth is a common denominator in many fisheries studies, but growth measures other than total masses or lengths are nearly nonexistent because more precise measurements such as body composition analysis are often too difficult and time consuming. Here, we present a means of estimating body composition in fish quickly, and after validation, without the need to sacrifice the animal. Models built with brook trout (Salvelinus fontinalis) were linear with strong validation group relationships (R2 > 0.96) for composition parameters including water, protein, fat, fat-free, and dry masses. Subject responses to bioelectrical impedance analysis were minimal, with only slight bruising (p < 0.001) with no effect on swimming, color, bleeding, or feeding. The model was also tested on the water and dry masses of 10 warmwater fish species and found to have strong correlations (R2 > 0.86), suggesting that more general relationships may exist. Nonlethal estimation of body composition using bioelectrical impedance analysis will permit increased precision in bioenergetics energy flow and compositional studies as well as permit study of community energetics and condition on spatial and temporal scales not previously possible.
Exploration of riffle-scale interactions between abiotic variables and microbial assemblages in the hyporheic zone
Authors: Sliva Lucie , Williams D Dudley
Published: March 2005

Molecular methods were applied to explore the composition of hyporheic bacterial assemblages and their possible interaction with interstitial physicochemical variables. Hyporheic flows on a riffle were manipulated (a downwelling zone was converted to an upwelling zone and vice versa) in order to examine the influence of vertical flow patterns on microbial assemblages. Bacterial assemblages were heterogeneously distributed throughout the riffle, the greatest similarity among them occurring at similar depths rather than in areas of similar flow regimes (upwelling versus downwelling). There was no correlation between the measured physicochemical variables and the microbial assemblages, with the exception of depth and sediment particle size. The flow manipulation in the original downwelling zone appeared to have had an effect on the microbial assemblages, although this influence may have been primarily due to a change in temperature in the manipulated region rather than an alteration of the vertical-flow direction per se.
Linkages between weather, dissolved organic carbon, and cold-water habitat in a Boreal Shield lake recovering from acidification
Authors: Keller W. (Bill) , Heneberry Jocelyne , Leduc Julie
Published: March 2005

To investigate potential effects of climate change on lake thermal structure, we examined relationships between the amount of cold-water habitat in late summer (defined as the 10 °C depth), summer weather, and dissolved organic carbon (DOC) concentration over a two-decade period (19812002) in a small Boreal Shield lake recovering from acidification. DOC concentration, wind-days (the product of mean daily wind speed and the number of days between ice-out and late-summer stratification), and mean daily temperature were significant predictors of the 10 °C depth in a multiple-regression model. A similar model using simply the number of ice-free days instead of wind-days was almost as effective. The models were quite successful in explaining interannual variations in the 10 °C depth when tested on a chemically and morphometrically similar nearby lake. While factors related to summer weather were important in explaining interannual variations in the amount of late-summer cold-water habitat, increased DOC concentration over the study period largely explained observed long-term decreases in the 10 °C depth (increases in cold-water habitat). DOC concentration was positively correlated with pH. In acidified regions, increases in DOC that accompany the recovery of acidified lakes will need to be considered in assessments of potential climate-change effects on lake thermal structure.
Spatial dynamics of female snow crab (Chionoecetes opilio) in the eastern Bering Sea
Authors: Ernst Billy , Orensanz JM (Lobo) , Armstrong David A
Published: March 2005

Snow crab (Chionoecetes opilio) migrations in the eastern Bering Sea have long been ignored. Based on preliminary information, we hypothesized that females undergo an extensive ontogenetic migration, tracking down environmental gradients. We analyzed a 25-year time series of survey data and defined ontogenetic stages in terms of a "shell condition index" calibrated with radiochemical methods. "Pseudo-cohorts" of mature females (groups of females that undergo puberty molt in a given year) "recruit" to the mature female pool in the Middle Domain (50100 m) of the intermediate shelf. Females undergo puberty molt and primiparous mating in winter. Over the next year, they migrate an average net distance of 73.5 nautical miles towards the shelf edge following a predominantly northeastsouthwest direction. Maximum post-terminal molt life span is 67 years. Results support the hypothesis that the variable tracked is near-bottom temperature. Although near-bottom temperature fields vary from year to year, the corresponding vector field is a conservative template, which explains the consistency observed in the pattern of migration. Elucidation of the life history schedule of mature female snow crabs in the eastern Bering Sea revealed that it is very similar to that reported for eastern Canada, although patterns of migration may differ substantially between the two systems.
Comparison of virtual population analysis and statistical kill-at-age analysis for a recreational, kill-dominated fishery
Authors: Radomski Paul , Bence James R , Quinn II Terrance J
Published: March 2005

We used simulations to compare the distributions of estimation errors for virtual population analysis using forward calculation (FVPA) and three variants of statistical kill-at-age analysis (KAA). The KAA variants assumed constant, time-blocked, and nonadditive selectivity. Simulations were based on a recreational walleye (Sander vitreus) fishery in Lake Mille Lacs, Minnesota. The focus of our experiments was on how model mis-specification (incorrect assumptions about selectivity for KAA or that kill had no error for FVPA) interacted with the magnitude of measurement errors and fishing mortality. We found that KAA models outperformed FVPA when they assumed the correct selectivity pattern, even when kill was measured without error. Of particular concern was a strong tendency by FVPA to overestimate stock size when kill was measured with substantial error. When KAA was based on an incorrect assumption regarding fishery selectivity and kill was measured with little error, wide distributions of errors and substantial biases sometimes resulted. KAA models that allowed fishery selectivity to change over time performed about as well as a constant-selectivity KAA model when selectivity was constant, and they performed much better when selectivity changed over time. Careful consideration of alternative fishery selectivity models should be a fundamental part of any age-structured assessment.
Influence of moderate phosphate addition on nitrogen retention in an acidic boreal lake
Authors: Kaste Øyvind , Lyche-Solheim Anne
Published: March 2005

Inorganic phosphorus (P) fertilizer was added to a small, acidic lake in southernmost Norway to test the potential of this technique to increase the retention of total inorganic nitrogen (TIN) and thereby mitigate the effects of elevated leaching of atmospherically derived N. The experiment was conducted over 4 years (1 pretreatment year followed by 3 years with weekly P additions during the growing season). To avoid any undesirable eutrophication effects, the total P concentration was increased from 45 µg P·L1 to a moderate level of 1012 µg P·L1. Compared with the pretreatment year, the P additions increased the average TIN retention in the experimental lake by nearly 70% (from 53 to 88 mmol·m2·year1) during three growing seasons. However, when considering that the reference lake experienced a 55% decrease in TIN retention during the same period, the increase might have been even larger. This underlines the role of P (both natural and anthropogenic) as an important regulator of N retention in upland lake districts that in large parts of southernmost Norway contribute significantly to the N loading on coastal marine areas.
Pelagic response of a humic lake to three years of phosphorus addition
Authors: Donali Espen , Brettum Pål , Kaste Øyvind , Løvik Jarl Eivind , Lyche-Solheim Anne , Andersen Tom
Published: March 2005

Three years of whole-lake phosphorus (P) fertilization, conducted in a 12-ha boreal forest lake, revealed significant changes in epilimnion nutrients, biomasses, and primary production. As a time average for all three treatment years, primary production increased 257% relative to the reference basin value of 16.5 mg·m3·day1, whereas the carbon masses of both nanoalgae (>2 µm) and zooplankton increased roughly 130% from their initial values of 15 mg·m3and 17 mg·m3, respectively. Calculated from a difference, the absolute increase in the sum of ciliates and picoplankton (heterotrophic bacteria and picoalgae) was more than six times as large as for algae larger than 2 µm, indicating that most added P ended in this compartment. Moreover, fertilization did not change the species inventory among nanoalgae and zooplankton, although the biomass composition changed somewhat. Only the former dominant species, the chrysophytes Dinobryon crenulatum, D. sociale v. americanum, Mallomonas allorgei, and Ochromonas sp. and the calanoid copepod Eudiaptomus gracilis increased substantially in biomass owing to the added P. Surprisingly, we observed a substantial delay in the food web response to fertilization, where most variables increased monotonously in size from year to year during the fertilization period. The underlying mechanisms for these delayed increases remains to be explained.
Introduction pathways and establishment rates of invasive aquatic species in Europe
Authors: García-Berthou E , Alcaraz C , Pou-Rovira Q , Zamora L , Coenders G , Feo C
Published: March 2005

Species invasion is one of the leading mechanisms of global environmental change, particularly in freshwater ecosystems. We used the Food and Agriculture Organization's Database of Invasive Aquatic Species to study invasion rates and to analyze invasion pathways within Europe. Of the 123 aquatic species introduced into six contrasting European countries, the average percentage established is 63%, well above the 5%20% suggested by Williamson's "tens" rule. The introduction and establishment transitions are independent of each other, and species that became widely established did so because their introduction was attempted in many countries, not because of a better establishment capability. The most frequently introduced aquatic species in Europe are freshwater fishes. We describe clear introduction pathways of aquatic species into Europe and three types of country are observed: "recipient and donor" (large, midlatitude European countries, such as France, the United Kingdom, and Germany, that give and receive the most introductions), "recipient" (most countries, but particularly southern countries, which give few species but receive many), and "neither recipient nor donor" (only two countries). A path analysis showed that the numbers of species given and received are mediated by the size (area) of the country and population density, but not gross domestic product per capita.
Hydroacoustic fish stock assessment in the presence of dense aggregations of Chaoborus larvae
Authors: Malinen Tommi , Tuomaala Antti , Peltonen Heikki
Published: March 2005

A new method for eliminating reverberation due to Chaoborus larvae from hydroacoustic recordings is presented based on an assumption of a constant dependence between the area backscattering strength (sa) with a high-volume backscattering threshold (sv) and sa with a low sv threshold for fish. The idea was to analyze data with a threshold high enough to eliminate reverberation and then convert the estimate to coincide with the result that would have been achieved with a low threshold containing all backscattering from fish. The approach was validated with a secondary dataset, and the magnitude of overestimation of fish density by reverberation was evaluated using data from four surveys conducted in a clay-turbid lake, where small planktivorous fish, smelt (Osmerus eperlanus), and larvae of Chaoborus flavicans coexist in the water column. With the presented method, estimation of smelt density was possible even when Chaoborus density was >200 individuals·m3. The analyses revealed that the overestimation of fish density could be as high as 50% if the reverberation is not taken into account. The presented method might also be applicable for eliminating reverberation due to other unwanted targets, because it is based on the acoustic properties of fish rather than those of unwanted targets.
2004 Alcan Award LectureFrom dinuclear to triakontahexanuclear complexes  Adventures in supramolecular coordination chemistry
Authors: Thompson Laurence K
Published: March 2005

Polynuclear coordination complexes result from the interplay between the arrangement of the binding sites of a ligand, and their donor content, and the coordination preferences of the metal ion involved. Rational control of the ligand properties, such as denticity, geometry, and size, can lead to large, and sometimes predictable, polynuclear assemblies. This Alcan Award Lecture highlights our "adventures" with polynucleating ligands over the last 25 years, with examples ranging from simple dinucleating to more exotic high-denticity ligands. Complexes with nuclearities ranging from 2 to 36 have been produced, many of which have novel magnetic, electrochemical, and spectroscopic properties. Self-assembly strategies using relatively simple "polytopic" ligands have been very successful in producing high-nuclearity clusters in high yield. For example, linear "tritopic" ligands produce M9 (M = Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II)) [3 × 3], flat grid-like molecules, which have quantum dot-like arrays of nine closely spaced metal centers in electronic communication. Some of these grids are discussed in terms of their novel magnetic and electrochemical properties, and also as multistable nanometer-scale platforms for potential molecular device behaviour. Bigger ligands with extended arrays of coordination pockets, and the capacity to self-assemble into much larger grids, are highlighted to illustrate our current and longer term goals of generating polymetallic molecular two-dimensional layers on surfaces.Key words: Alcan Award Lecture, transition metal, polynuclear, structure, magnetism, electrochemistry, surface studies, molecular device.
Stereoselective synthesis of multiply substituted [1,2]oxazinan-3-ones via ring-closing metathesis
Authors: Shustov Gennady V , Chandler Melanie K , Wolfe Saul
Published: March 2005

The title compounds are α-amino acids whose nitrogen atoms are enclosed within 4,5-disubstituted, six-membered cyclic hydroxamates and they are of interest as potential β-lactam surrogates. The compounds have been synthesized in the present work by functionalization of the double bonds of N-substituted 6H-[1,2]oxazin-3-ones, which are obtained upon successive reaction of the triflates of S-α-hydroxy esters with O-allylhydroxylamine and acryloyl chloride, followed by cyclization of the resulting R-α-N-acryloyl-N-allyloxyamino esters in the presence of the ring-closing metathesis (RCM) catalyst bis(tricyclohexylphosphine)benzylideneruthenium dichloride. The olefins are also accessible, but less efficiently so, by a Wittig sequence that employs bromoacetyl bromide in place of acryloyl chloride, followed successively by triphenylphosphine, silver triflate, ozonolysis, and cyclization. Asymmetric dihydroxylation of these chiral olefins affords a single diastereomer in high yield having either the αR,4S,5S- or the αR,4R,5R configuration, depending on the auxiliary. The configuration of the αR,4R,5R isomer has been confirmed by its conversion to (αR,4S,5R)-2-(α-carboxyethyl)-4-phenylacetylamino-5-hydroxy-1,2-oxazinan-3-one, whose αR,4R,5S diastereomer was previously prepared from L-ascorbic acid. With N-bromosuccinimide in aqueous dimethylformamide, a 6H-[1,2]oxazin-3-one afforded a separable 1:1 mixture of bromohydrins, which could be cyclized to epoxides or hydrogenolyzed to 5-hydroxy-1,2-oxazinan-3-ones. Key words: penicillin surrogates, asymmetric dihydroxylation, bis(tricyclohexylphosphine)benzylideneruthenium dichloride, cyclic sulfite, epoxides, azidohydrin, bromohydrin.
2002 W.A.E. McBryde Award Lecture  Affinity recognition, capillary electrophoresis, and laser-induced fluorescence polarization for ultrasensitive bioanalysis
Authors: Le X Chris , Pavski Victor , Wang Hailin
Published: March 2005

The combination of affinity recognition, capillary electrophoresis (CE), laser-induced fluorescence (LIF), and fluorescence polarization for the ultrasensitive determination of compounds of biological interest is described. Competitive immunoassays using CELIF eliminate the need for fluorescently labeling trace analytes of interest and are particularly useful for determination of small molecules, such as cyclosporine, gentamicin, vancomycin, and digoxin. Fluorescence polarization allows for differentiation of the antibody-bound from the unbound small molecules. Noncompetitive affinity CELIF assays are shown to be highly effective in the determination of biomarkers for DNA damage and HIV-1 infection. An antibody (or aptamer) is used as a fluorescent probe to bind with a target DNA adduct (or the reverse transcriptase of the HIV-1 virus), with the fluorescent reaction products being separated by CE and detected by LIF. Aptamers are attractive affinity probes for protein analysis because of high affinity, high specificity, and the potential for a wide range of target proteins. Fluorescence polarization provides unique information for studying molecular interactions. Innovative integrations of these technologies will have broad applications ranging from cancer research, to biomedical diagnosis, to pharmaceutical and environmental analyses.Key words: capillary electrophoresis, laser-induced fluorescence, fluorescence polarization, immunoassay, affinity probes, antibodies, aptamers, DNA damage, toxins, therapeutic drugs.
1H NMR studies on the solution conformation of the [L-Ser10] and [D-Ser10] analogues of contulakin-G
Authors: Kindahl Lill , Kenne Lennart , Sandström Corine
Published: March 2005

The synthesis of the O-glycosylated serine-10 analogue of contulakin-G yielded both the [L-] and the [D-Ser10] analogues. The1H NMR study indicated that the sugars of the two Ser10-glycosylated peptides lacked the hydrogen bond to the peptide backbone that exists in contulakin-G. NOEs showed that the glycan part of the [D-Ser10] analogue had a different orientation to the peptide backbone than that of the [L-Ser10] analogue. The peptide backbones in the two compounds were found to exist mainly in random coil conformations, with transient turns at the site of glycosylation. A transient turn was also found at the C-terminus of the [D-Ser10] glycopeptide. The NMR data indicated that the average conformation of the [D-Ser10] analogue resembles the conformation of contulakin-G more than the [L-Ser] does. Since biological data showed that the [D-Ser10] glycopeptide was as active as contulakin-G, while the [L-Ser10] glycopeptide was only slightly active at more than 100 times the dose, it is possible that it is the orientation of the glycan relative to the peptide chain that is actually recognized by the proteolytic enzyme.Key words: conformation, contulakin-G analogues, NMR, O-linked glycopeptide.
An intriguing effect of lithium perchlorate dispersed on silica gel in the bromination of aromatic compounds by N-bromosuccinimide
Authors: Bagheri Mojtaba , Azizi Najmedin , Saidi Mohammad R
Published: March 2005

A convenient and efficient procedure for electrophilic aromatic bromination has been developed by mixing of N-bromosuccinimide and an aromatic compound at room temperature on the surface of silica gel mixed with solid anhydrous LiClO4. All of the substrates examined underwent clean electrophilic aromatic bromination in reaction times of a few minutes to afford the corresponding bromoarenes under neutral conditions in excellent yield. In the case of thiophenol, no substitution reaction occurred, and the corresponding disulfide was obtained in excellent yield.Key words: LP-SiO2, NBS, arenes, electrophilic bromination, regioselectivity.
Synthesis, characterization, and biological activity of a new palladium(II) complex with deoxyalliin
Authors: Corbi Pedro P , Massabni Antonio C , Moreira Andréia G , Medrano Francisco J , Jasiulionis Miriam G , Costa-Neto Claudio M
Published: March 2005

Synthesis, characterization, and biological activity of a new water-soluble Pd(II)deoxyalliin (S-allyl-L-cysteine) complex are described in this article. Elemental and thermal analysis for the complex are consistent with the formula [Pd(C6H10NO2S)2].13C NMR,1H NMR, and IR spectroscopy show coordination of the ligand to Pd(II) through S and N atoms in a square planar geometry. Final residue of the thermal treatment was identified as a mixture of PdO and metallic Pd. Antiproliferative assays using aqueous solutions of the complex against HeLa and TM5 tumor cells showed a pronounced activity of the complex even at low concentrations. After incubation for 24 h, the complex induced cytotoxic effect over HeLa cells when used at concentrations higher than 0.40 mmol/L. At lower concentrations, the complex was nontoxic, indicating its action is probably due to cell cycle arrest, rather than cell death. In agreement with these results, the flow cytometric analysis indicated that after incubation for 24 h at low concentrations of the complex cells are arrested in G0/G1.Key words: palladium(II), deoxyalliin, S-allyl-L-cysteine, tumor cells, cancer.
Synthesis, characterization, and coordination chemistry of phosphines with ethylenedioxythiophene substituents
Authors: Chahma M'hamed , Myles Daniel JT , Hicks Robin G
Published: March 2005

The preparation of several new phosphines bearing one or more 3,4-ethylenedioxythiophene (EDOT) units as substituents linked at the 2-thienyl position is described. The phosphines were prepared by reaction of lithiated EDOT intermediates with appropriate chlorophosphines to afford (3,4-ethylenedioxy-2-thienyl)diphenylphosphine (1), (bis(3,4-ethylenedioxy-2-thienyl)phenylphosphine (2), tris(3,4-ethylenedioxy-2-thienyl)phosphine (3), 2,5-bis(diphenylphosphino)-3,4-ethylenedioxythiophene (4), and 2-diphenylphosphino-5-mesitylthio-3,4-ethylenedioxythiophene (5). Molybdenum carbonyl complexes of compounds 13 were prepared by reaction of the phosphine ligands with cis-Mo(CO)4(pip)2. In all cases, spectroscopic evidence is fully consistent with the phosphines acting as monodentate, P-bound ligands. Electrochemical studies on the phosphines as well as their metal complexes indicate that the normal electrochemical redox robustness of the EDOT group is dramatically decreased by the presence of phosphine substituents: all compounds exhibited irreversible oxidation processes and no evidence of electropolymerization was observed for the phosphines bearing two or three EDOT groups. Key words: phosphines, thiophene, 3,4-ethylenedioxythiophene, EDOT, electrochemistry, coordination complexes.
Échelles pKHBet enthalpique du pouvoir accepteur de liaison hydrogène de thioéthers, thiols et disulfures
Authors: Laurence Christian , Berthelot Michel , Evain Karine , Illien Bertrand
Published: March 2005

The hydrogen bond acceptor (HBA) strength of 31 tetrahedral sulfur bases (thioethers, thiols, disulfides) has been measured by IR spectrometry from: (i) their 1:1 complexation constants with 4-fluorophenol in CCl4at 25 °C (the pKHBscale); (ii) their HB enthalpies; and (iii) the frequency shifts, Δν(OH), of the ν(OH) band of 4-fluorophenol hydrogen bonded to sulfur. The comparison of the pKHB, ΔH°, and Δν(OH) scales points to their distinctive features. The HBA strength depends on: (i) the nature of the atomic site: oxygen bases are always stronger than sulfur bases, in agreement with the hard and soft acids and bases principle; (ii) the functionality of this atom (for sulfur bases: phosphine sulfur > thioamide > thioketone > thioether > thiol > isothiocyanate ~ disulfide); and (iii) the substituent effects on the function. The main substituent effects are: (i) the polarizability effect of alkyl groups; (ii) the field-inductive effect; (iii) the resonance effect; and (iv) the cyclization effect, which changes the percentage of the s character of sulfur lone pairs. In addition to the attachment to the sulfur atom, IR spectra show the attachment of 4-fluorophenol to the chlorine of MeSCH2Cl and MeSCH2CH2Cl, and the interaction to the π cloud of PhSMe, Ph2S, PhCH2SMe, and EtSCH=CH2. Key words: hydrogen bond, thioethers, thiols, disulfides, pKHBscale.
Stereoselective synthesis and stereochemistry of r-2-alkoxycarbonyl-c-3-o-substituted phenyl-1,4-thiazane 1,1-dioxides
Authors: Bhavani N , Perumal S , Banureka R
Published: March 2005

r-2-Alkoxycarbonyl-c-3-aryl-1,4-thiazane 1,1-dioxides were obtained as the stereoselective product, when the aldehyde used was o-substituted benzaldehyde while the p-substituted benzaldehydes gave a trans product. The relative configuration of the adjacent alkoxycarbonyl and aryl groups was assigned from the vicinal coupling constant, 3J = 10.6 Hz in the trans isomer and 3.2 Hz in the cis isomer, and from the multiplicity pattern, i.e., a doublet for the H-2 proton of the trans isomer and a triplet for the H-2 proton of the cis isomer. The unusual, large long-range coupling (4J = 2.8 Hz) because of the "W" arrangement between H-2e and H-6e across the ring type was very useful for confirming the cis configuration and chair conformation of the isomer. The various 1H and 13C NMR assignments were made with the help of 1H1H COSY, 1H13C COSY, HMBC, and NOESY spectral analyses.Key words: 1H and 13C NMR, 1H1H COSY, 1H13C COSY, HMBC, NOESY, stereoselectivity, 1,4-thiazane.
Oxidation of 1-(4′-substituted phenyl)-2-(4-methylphenyl)diazene  Benzylic substitution vs. Cazo bond breaking
Authors: Razus Alexandru C , Nitu Carmen , Pavel Claudia , Ciuculescu Crinu-Anghel , Cimpeanu Valentin , Stanciu Corneliu , Power Philip P
Published: March 2005

The low oxidation potential of 1-phenyl-2-(4-methylphenyl)diazene 4′-substituted with a dimethylamino or methoxy group (10 and 11) allows the easy single electron transfer with radical cation generation in the presence of FeCl3. At the same time, the stabilizing effect of the positive charge exerted by 4-dimethylaminophenyl > 4-methoxy groups on the intermediate carbocation favors the hydrogen atom elimination in comparison with proton loss. Whereas benzylic substitution towards di- and triarylmethane derivatives takes place starting from diazene 11, the oxidation of diazene 10 leads mainly to products of Cazo breaking. This difference is well-supported by the idea that the electron, in the first step of oxidation, is extracted from the azo and (or) from the amino nitrogen atom.Key words: diazenes, oxidation, single electron transfer, benzylic substitution, Cazo bond breaking.
Synthesis of some heterocyclic systems of anticipated biological activities via 6-aryl-4-pyrazol-1-yl-pyridazin-3-one
Authors: Youssef A SA , Marzouk M I , Madkour H MF , El-Soll A MA , El-Hashash M A
Published: March 2005

6-Aryl-4-pyrazol-1-yl-pyridazin-3-one (1) reacted with a PCl5POCl3 mixture to give the 3-chloropyridazine derivative 3. Reaction of 3 with 2-hydroxybenzoylhydrazide and semicarbazide hydrochloride afforded 4 and 5. Reaction of 1 with ethyl chloroacetate gave 8. Reaction of 8 with hydrazine hydrate yielded the hydrazide 9. The hydrazide 9 condensed with the acetylenic ketones and esters 10a10d and acetylacetone to give the adducts 11a, 11b, 12, 13, and 14. Reacting 1 with formaldehyde and piperidine, morpholine, or piperazine, 3-bromopropanoic acid, acetic anhydride, p-toluenesulphonyl chloride, succinyl chloride, oxalyl chloride, ethanolamine, or ethyl chloroacetate gave the adducts 1522. The structures of all newly synthesized compounds were evidenced from their spectral and microanalytical data. Key words: 6-aryl-4-pyrazol-1-yl-pyridazinone derivative, 6-aryl-3-chloropyridazine derivative, 3,6-diaryl-1,2,4-triazino[4,3-b]pyridazine derivative, 6-aryl-3-ethoxycarbonylmethoxypyridazine derivative, 6-aryl-3-(ω-benzoylacetophenone)hydrazinocarbonylmethoxypyridazine.