bluuebunny/crossref_metadata_2025 huggingface dataset:
First hyperpolarizabilities of triazine derivatives. Ab initio studies and Hammett correlation
Authors: Park Gyoosoon , Cho Bong Rae
Published: February 2004

First hyperpolarizabilities (β) of triazine derivatives were studied by the ab initio method (HF/6–31G). The β values of these molecules increase with a stronger donor and as the conjugation length increases, probably because the electronic charge becomes more delocalized and the HOMO–LUMO energy gap (ΔE) and the bond length alternation (BLA) decrease with variation of the chromophore structure. Also, the susceptibility of β to the donor strength is found to be larger for a more elongated substrate. Noteworthy is the excellent linear relationship between β and BLA and also the gas‐phase substituent constants (σ+gas). This result may serve as a useful guideline for the design of two‐dimensional octupoles with large first hyperpolarizabilities. Copyright © 2004 John Wiley & Sons, Ltd.
Regio‐ and stereochemistry of Michael addition of methanol to Thiele's ester
Authors: Minter David E. , Smith William B. , Marchand Alan P. , Etukala Jagan Reddy , Sivappa Rasapalli
Published: February 2004

Acid‐promoted esterification of Thiele's acid with methanol was found to afford three products. In addition to the expected major product (i.e. the corresponding dimethyl ester, 2a), two minor products are obtained, one of which, 3, results from subsequent Michael addition of methanol to the norbornene CC double bond in 2a. Analysis of its one‐ and two‐dimensional NMR spectra indicates that this minor product possesses structure 3a in which the (C‐5)—OCH3 and (C‐6)—CO2CH3 bonds are exo and endo, respectively. This conclusion is reinforced by the results of thermodynamics calculations and associated chemical shift calculations. In addition, theoretical analysis of competing transition states for Michael addition of methanol to 2a suggests that exo approach of methanol towards the (C‐5)(C‐6) double bond in the substrate is preferred kinetically over the corresponding endo reaction pathway. Copyright © 2004 John Wiley & Sons, Ltd.
Specific acid catalysis and Lewis acid catalysis of Diels–Alder reactions in aqueous media
Authors: Mubofu Egid B. , Engberts Jan B. F. N.
Published: February 2004

A comparative study of specific acid catalysis and Lewis acid catalysis of Diels–Alder reactions between dienophiles (1, 4 and 6) and cyclopentadiene (2) in water and mixed aqueous media is reported. The reactions were performed in water with copper(II) nitrate as the Lewis acid catalyst whereas hydrochloric acid was employed for specific acid catalysis. At equimolar amounts of copper(II) nitrate and hydrochloric acid (0.01 M, for example) and under the same reaction conditions, the reaction rate for 1a with 2 is about 40 times faster with copper catalysis than with specific acid catalysis. Moreover, at 32°C and 0.01 M HCl, the reaction of 1b with 2 is about 21 times faster than the same uncatalyzed reaction in pure water under the same reaction conditions. The inverse solvent kinetic isotope effect shows that these Diels–Alder reactions undergo specific acid catalysis. Copyright © 2004 John Wiley & Sons, Ltd.
Characterization of solvatochromic probes: simulation of merocyanine 540 absorption spectra in binary solvent mixtures and pure solvent systems
Authors: Bae S. Y. , Arnold B. R.
Published: February 2004

An empirical extension of the continuum model was used to reproduce the absorption spectrum of the optical probe merocyanine 540 in numerous solvents based on 27 probe‐specific parameters in conjunction with the dielectric constant and refractive index of the solvent. The calibrated absorption spectrum of this dye allowed the accurate determination of the dielectric constant and refractive index of the bulk solvent. This study incorporates several binary solvent mixtures in addition to several pure solvents of differing functionality, including protic and aprotic solvents. A single, generally applicable, set of probe‐specific parameters is presented. The accuracy of the determined solvent properties using this general set of probe parameters suggests that the influence of specific solvent–solute interactions on the absorption spectrum of this dye must be constant if not insignificant in the range of solvents studied, with the notable exception of water. Copyright © 2004 John Wiley & Sons, Ltd.
Radiation‐induced oxidation of substituted benzaldehydes: a pulse radiolysis study
Authors: Geeta S. , Rao B. S. M. , Mohan H. , Mittal J. P.
Published: February 2004

The reactions of the oxidizing radicals hydroxyl radical (.OH), azidyl radical $({\rm N}_3^\cdot)$ and sulfate radical anion $({\rm SO}_4^{-\cdot})$ with hydroxy‐, methoxy‐, chloro‐ and nitro‐substituted benzaldehydes were studied by pulse radiolysis. The rate constants for the .OH reaction [k ≈ (2.6–12.0) × 109 l mol−1 s−1] with these compounds are higher than those for the ${\rm N}_3^\cdot$ or ${\rm SO}_4^{-\cdot}$ reactions [k ≈ (0.01–4.2) × 109 l mol−1 s−1]. The .OH reaction shows a significant substituent effect which is reflected in the rate constants (k ≈ 12.0 × 109 dm3 mol−1 s−1 with hydroxybenzaldehyde and k ≈ 3.0 × 109 dm3 mol−1 s−1 with nitrobenzaldehyde). The transient species produced by the reaction of .OH with the m‐substituted benzaldehydes shows an absorption maximum at 370–400 nm, whereas the p‐substituted isomers exhibit two absorption peaks centred around 325 and 410 nm, except in the case of p‐nitrobenzaldehyde, which shows only a single peak at 330 nm. These spectra are identical with the spectra obtained for the $({\rm N}_3^\cdot)$ or ${\rm SO}_4^{-\cdot}$ reactions with substituted benzaldehydes. .OH adduct formation and subsequent decomposition to the corresponding phenoxyl radicals is the main reaction channel for the .OH‐induced oxidation of substituted benzaldehydes. One‐electron oxidation by $({\rm N}_3^\cdot)$ or ${\rm SO}_4^{-\cdot}$ of substituted benzaldehydes proceeds via an electron transfer process producing the corresponding radical cations. Copyright © 2004 John Wiley & Sons, Ltd.
Photophysics of Poly{2,2′‐bipyridine‐5,5′‐diylethynylene [2,5‐di(2‐ethylhexyl)oxy‐1,4‐phenylene[ethynylene}: a comparison with monomer and dimer model compounds
Authors: Grummt U.‐W. , Pautzsch Th. , Birckner E. , Utterodt A. , Neugebauer U. , Klemm E.
Published: February 2004

The title compound (P) was synthesized via Pd‐ and Cu‐catalyzed coupling reactions (Sonogashira reaction). Two model compounds prepared by similar synthetic routes, 1,4‐bis(2,2′‐bipyridin‐5′‐ylethynyl)‐2,5‐di(2‐ethylhexyl)oxybenzene (M), and 5,5′‐[1‐ethynyl‐4‐(2,2′‐bipyridin‐5′‐ylethynyl)‐2,5‐di(2‐ethylhexyl)oxybenzene]‐2,2′‐bipyridine (D), were included in the spectroscopic investigations for comparison. As a result of steady‐state and time‐resolved absorption and fluorescence investigations in solution and in solid films, we conclude that the π‐conjugation is restricted by torsional motions of the aromatic chain segments at ordinary temperature. It comprises about 2–3 repetition units in the S1 state as concluded from a comparison of the experimental radiative rate constant with that calculated from the Strickler–Berg relation. It is even less in the ground state. The theoretical limit obtained from DFT calculations is about twice as large for the ideal coplanar conformation. Whereas the π–π stacking interaction in pure polymer films is very weak in the ground state, it is significantly stronger in the S1 state, giving rise to excimer fluorescence. Energy migration along the polymer backbone is inefficient. Intermolecular energy migration and transfer to embedded acceptors becomes efficient in solid films. Copyright © 2004 John Wiley & Sons, Ltd.
Photochemistry of 9‐fluorenone oxime phenylglyoxylate: a combined TRIR, TREPR and ab initio study
Authors: Kolano Christoph , Bucher Götz , Wenk Hans Henning , Jäger Martin , Schade Olaf , Sander Wolfram
Published: February 2004

The photochemistry of 9‐fluorenone oxime phenylglyoxylate (1) in tetrachloromethane was investigated by a variety of time‐resolved methods [STEP‐SCAN TRIR and time‐resolved EPR (TREPR)]. Photolysis of 1 yields the benzoyl radical, carbon dioxide and the fluorene‐9‐iminyl radical on pulsed irradiation (λ = 355 nm). All radicals have a lifetime in the range of microseconds and can be detected within the rise time of our time‐resolved equipment before undergoing recombination or reactions with the solvent. The benzoyl radical shows a strong absorption ($(\tilde \nu$C=O = 1824 cm−) in the IR spectrum. Upon purging the solution with oxygen, the benzoyl radical is quenched to yield the benzoylperoxy radical ($(\tilde \nu$C=O = 1814 cm−), which has a lifetime that is several microseconds longer than that of the benzoyl radical. Owing to the lack of a good IR chromophore, the fluorene‐9‐iminyl radical is not detected by IR spectroscopy. It can, however, be detected by TREPR spectroscopy, which allows the detection of a 1 : 1 : 1 triplet of the fluorene‐9‐iminyl radical at 3456 G and a 1 : 2 : 1 triplet of the benzoyl radical at 3460 G. Copyright © 2004 John Wiley & Sons, Ltd.
Diethyl ketone triperoxide: thermal decomposition reaction in chlorobenzene solution and its application as initiator of polymerization
Authors: Cañizo Adriana I. , Eyler Gladys N. , Morales Graciela , Cerna Jorge R.
Published: February 2004

The kinetics of the thermal decomposition reaction of diethyl ketone triperoxide (3,3,6,6,9,9‐hexaethyl‐1,2,4,5,7,8‐hexaoxacyclononane, DEKT) in chlorobenzene solution were studied in the temperature range 99.0–148.0°C and at initial concentrations of (1.65–4.97) × 10−2 M. The thermolysis of DEKT follows a first‐order kinetic law up to at least ca 80% triperoxide conversion. The activation parameter values for the initial O—O bond rupture in chlorobenzene (ΔH‡=134.6±1.7 kJ mol−1; ΔS‡ = 4.2 ± 3.8 J mol−1 K−1) and the reaction products observed support a stepwise reaction mechanism which includes as a first step the unimolecular homolytic cleavage of one peroxidic bond of the DEKT molecule giving rise to a biradical as intermediate. Additionally, the results obtained were compared with those obtained in toluene, toluene–styrene (50%, v/v) and chlorobenzene–styrene (50%, v/v) solution, showing that the decomposition reaction is strongly solvent dependant. Further, the biradical intermediate obtained in all cases was used to initiate styrene polymerization. It was demonstrated that DEKT can effectively act as initiator in styrene polymerization and its performance is similar to that presented by a multifunctional initiator giving rise to high molecular weight polystyrene at a high reaction rate. Copyright © 2004 John Wiley & Sons, Ltd.
Effect of pressure on sterically hindered reactions with late transition states
Authors: Gacem Badra , Jenner Gérard
Published: February 2004

The effect of high pressure is examined in two types of sterically congested reactions presenting late transition states: isopolar Diels–Alder cycloadditions of isoprene and quinones of various steric environment and conjugate additions of tert‐butylamine and acrylic compounds. In the Diels–Alder cycloadditions, pressure has no enhanced kinetic sensitivity in sterically demanding reactions compared with unhindered ones. This is due to the structural closeness of the transition state and product. At variance, in the conjugate addition of amines, the effect of pressure is magnified with increasing steric congestion at the reaction centres. This is ascribed to enhanced electrostriction with removal of steric hindrance to ionization. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis, x‐ray structure and spectroscopic and electronic properties of two new synthesized flavones
Authors: Cotelle Nicole , Vrielynck Laurence , Nowogrocki Guy , Cotelle Philippe , Vezin Hervé
Published: February 2004

Two new flavones (1 and 2) in which one or two di‐tert‐butylhydroxyphenyl groups replace the B‐ring of flavonoids, respectively, were synthesized according to the Baker–Vankataraman method. Their crystal structures were determined by x‐ray diffraction methods and compared with those obtained by theoretical calculations using join Monte Carlo conformational search analysis and geometry optimization ab initio formalism. NMR NOE data, ESR spectra and electronic properties were obtained in order to understand their implication in the enhancement of low‐density lipoprotein (LDL) resistance to oxidation. The oxidative modification of LDL has been alleged to play an important role in the development of human atherosclerosis and neurodegenerative diseases. Copyright © 2004 John Wiley & Sons, Ltd.
Comparative study of the catalytic behaviour of Ru(III) and Ru(VI) on the oxidation of alcohols by hexacyanoferrate(III)
Authors: Mucientes A. E. , Gabaldón R. E. , Poblete F. J. , Villarreal S.
Published: February 2004

The oxidation reactions of 2‐methyl‐2,4‐pentanediol upon treatment with alkaline hexacyanoferrate(III) using Ru(III) or Ru(VI) as catalysts are governed by two quasi‐identical experimental rate equations, which show that both catalysts are equally effective for the oxidation of alcohols by ${\rm Fe(CN)}_6^{3-}$. The reaction mechanism proposed involves the oxidation of 2‐methyl‐2,4‐pentanediol by the catalyst, a process that occurs through the formation of a substrate–catalyst complex. The decomposition of this complex yields Ru(IV) and a protonated ketone (owing to a hydride transfer from the α‐C—H bond of the alcohol to the oxoligand of ruthenium) in the case of Ru(VI), but a ketyl radical and Ru(II) (hydrogen transfer) for Ru(III). The role of the co‐oxidant, ${\rm Fe(CN)}_6^{3-}$, is to regenerate the catalyst. For both oxidation reactions, the rate constants of complex decomposition and catalyst regeneration have been determined. Copyright © 2004 John Wiley & Sons, Ltd.
The gas‐phase reactivity of epichlorohydrin with hydroxide
Authors: Merrill G. N.
Published: February 2004

The reaction of hydroxide with epichlorohydrin in the gas phase was investigated with ab initio calculations. Three mechanisms were examined, each corresponding to nucleophilic attack at a different carbon atom of the substrate. It was determined that through attack at the ring methylene position was favored, whereas attacks at the alkyl methylene or ring methine positions were found to have larger activation energies. These results are consistent with experimental results found in the literature. Copyright © 2004 John Wiley & Sons, Ltd.
Mechanism of Ir(III)‐catalysed and Hg(II)‐co‐catalysed oxidation of reducing sugars by N‐bromoacetamide in acidic medium
Authors: Singh Ashok Kumar , Rahmani Shahla , Singh Bharat , Singh Ramesh Kumar , Singh Manju
Published: February 2004

The kinetics of Ir(III)‐catalysed and Hg(II)‐co‐catalysed oxidation of D‐glucose (Glu) and D‐fructose (Fru) by N‐bromoacetamide (NBA) were studied in acidic medium. The reactions follow identical kinetics, being zero order in each sugar concentration. The experimental results show a first‐order dependence on NBA and Ir(III) at low concentrations, but tending towards zeroth order at higher concentrations. A negative effect of variation of [H+], [Cl−] and [NHA] was observed whereas the ionic strength (I) of the medium has no influence on oxidation rate. The important feature of the reaction is that it follows a second‐order dependence on mercury(II) ion concentration at low concentrations, but it tends towards first order at higher concentrations. Various activation parameters were calculated and recorded. The corresponding acids were identified as the main oxidation products of the reaction. On the basis of the experimental findings, a suitable mechanism consistent with the observed kinetics was proposed. A comparative study was also made between the kinetic results of the present investigation and those of Ru(III)‐ and Pd(II)‐catalysed oxidations of reducing sugars. Copyright © 2004 John Wiley & Sons, Ltd.
NMR spectroscopic and molecular modelling study of the solution structure and the complexational behavior of maleonitrile tetrathia crown ethers with silver(I)
Authors: Holzberger Anja , Holdt Hans‐Jürgen , Kleinpeter Erich
Published: February 2004

The flexibility and complex formation of two maleonitrile tetrathia crown ethers were studied in solution using 1H and 13C NMR spectroscopy and molecular modelling. Both the stoichiometry and the stability of the complexes that these crown ethers form with Ag(I) were determined by NMR titration measurements. Spin–lattice relaxation time measurements provided information concerning the donor atoms involved in complex formation and also the intramolecular mobility of the free and complexed ligands. Molecular modelling was also used to gain further insight into the conformational space of the free ligands and their silver(I) complexes. Copyright © 2004 John Wiley & Sons, Ltd.
Receptor‐mediated transcytosis of follicle‐stimulating hormone through the rat testicular microvasculature
Authors: Vu Hai Mai Thu , Lescop Pierre , Loosfelt Hugues , Ghinea Nicolae
Published: February 2004

Abstract Accumulated data suggest that endothelial cells express specific receptors for several peptide and (glyco)protein hormones that may transport hormones across the cell to be delivered to the interstitial fluid and tissue target cells. Surprisingly, very little information is available on the actual endothelial organelles involved in this cellular process. In the present study the transfer of follicle‐stimulating hormone (FSH) through the endothelial barrier of rat testes was examined by analysing the binding and transport of gold‐tagged recombinant human (rh)FSH under various conditions using electron microscopy. At 4°C the probe bound specifically to the luminal surface of the endothelial cells without internalization. The use of 125I‐rhFSH, which allows precise quantitation of the binding, confirmed the specificity of hormone interaction with the testicular microvasculature. At 37°C the hormone was internalized via coated pits and vesicles into an extensive subluminal tubulo‐vesicular compartment and was transported across the endothelium via a system of tubules and vesicles. Moreover, monoclonal antibodies against the FSH receptor ectodomain coupled to colloidal gold followed the same route. In contrast, a non specific, fluid‐phase uptake via caveolae was observed for a major plasma protein — rat serum albumin and a fluid‐phase tracer — peroxidase. These results suggest that FSH transcytosis across the testicular endothelial barrier is receptor‐mediated and involves luminal uptake via coated pits/vesicles, sorting at the level of luminal early endosomes, and transcellular transport through transcytotic tubulo‐vesicular organelles. Similar receptor‐mediated pathways are likely to be involved in the physiological functioning of a number of other protein and peptide hormones that must translocate specifically from blood to the target cells.
Simultaneous Sv and TS measurements on Young-of-the-Year (YOY) freshwater fish using three frequencies
Authors: Guillard J , Lebourges-Dhaussy A , Brehmer P
Published: February 2004

In autumn, the fish population above the thermocline in Lake Annecy mainly comprises young perch (Perca fluviatilis) of the year. The fish are distributed in schools during the day and as scattered individual fish targets at night. Measurements of volume-backscattering strength and target strengths (TS) were carried out in a synchronous way using three echosounders operating at three frequencies (70, 120, and 129 kHz), with different characteristics (split beam, dual beam, beam shape, pulse length, etc.). Target-strength values show variability from one elementary sampling unit to another and from one device to another, but the mean global TS values are similar, independently of the frequency. The volume-backscattering strengths measured on precise schools by the three acoustic devices give significantly similar results. Acoustic measurements on YOY perch are completely independent of the frequency and the characteristics of the echosounders.
Fitting growth models to length frequency data
Authors: Laslett Geoff M. , Eveson J. Paige , Polacheck Tom
Published: February 2004

A novel two-stage procedure for fitting growth curves to length frequency data collected from commercial fisheries is described. The method is suitable for species in which cohorts are spawned over a limited time period, and samples of length frequency data are collected regularly (e.g. in weekly, fortnightly, or monthly time intervals) over an extended time period. In the first stage of analysis, Gaussian mixtures are fitted separately to the data for each time interval, and summary statistics (component means and standard errors) are extracted. In the second stage, parametric growth models, such as the von Bertalanffy seasonal growth curve, are fitted to the summary data. The error structure in this second stage of analysis incorporates random between-year effects, random within-year age-group effects, random within-year time-interval effects, random within-year age-group and time-interval interactions, and sampling errors. This complex error structure incorporating unbalanced crossed and nested random effects acknowledges that commercial fishing is not an exercise in random sampling, and allows for the inevitable additional sources of random variation in such an enterprise. The method is applied to South Australian southern bluefin tuna length frequency data collected from 1964 to 1989, and leads to the conclusion that juvenile tuna grew faster in the 1980s than in the 1960s, with the 1970s being a decade of highly variable growth.
The Russian Realist school of international relations
Authors: Shakleyina Tatyana A. , Bogaturov Aleksei D.
Published: February 2004

This article analyses realist school in the Russian international relations scholarshipand discusses the debates among Russian realists. It focuses on the characteristics of the newly emerging world order and the development of an adequate strategy for Russia to pursue in its international behavior. The authors argue that over the 1990s, realism has made considerable intellectual progress and has gained the status of a leading intellectual movement in Russia. It assisted Russian intellectual and political community in defining the country’s interests and priorities in the emerging international relations, and it provided a necessary analysis of the world order’s structure and polarity.
Radiocarbon calibration beyond 20,000 14C yr B.P. by means of planktonic foraminifera of the Iberian Margin
Authors: Bard Edouard , Rostek Frauke , Ménot-Combes Guillemette
Published: February 2004

We present a new set of 14C ages obtained by accelerator mass spectrometry (AMS) on planktonic foraminifera from a deep-sea core collected off the Iberian Margin (MD952042). This site, at 37°N, is distant from the high-latitude zones where 14C reservoir age is large and variable. Many independent proxies — alkenones, magnetic susceptibility, ice-rafted debris, foraminifera stable isotopes, abundances of foraminifera, pollen, and dinoflagellates — show abrupt changes correlative with Dansgaard-Oeschger and Heinrich events of the last glacial period. The good stratigraphic agreement of all proxies — from the fine to the coarse-size fractions — indicates that the foraminifera 14C ages are representative of the different sediment fractions. To obtain reliable 14C ages of foraminifera beyond 20,000 14C yr B.P. we leached the shells prior to carbonate hydrolysis and subsequent analysis. For a calendar age scale, we matched the Iberian Margin profile with that of Greenland Summit δ18O. Both are proxies for temperature, which in models varies synchronously in the two areas. The match creates no spurious jumps in sedimentation rate and requires only a limited number of tie points. Except for ages older than 40,000 14C yr B.P. Greenland's GISP2 and GRIP records yield similar calendars. The 14C and imported calendar ages of the Iberian Margin record are then compared to data — from lacustrine annual varves and from corals and speleothems dated by U–Th — previously used to extend the calibration beyond 20,000 14C yr B.P. The new record follows a smooth pattern between 23,000 and 50,000 cal yr B.P. We find good agreement with the previous data sets between 23,000 and 31,000 cal yr B.P. In the interval between 33,000 and 41,000 cal yr B.P. for which previous records disagree by up to 5000 cal yr, the Iberian Margin record closely follows the polynomial curve that was previously defined by an interpolation of the coral ages and runs between the Lake Suigetsu and the Bahamian speleothem data sets.
Hydrological changes in the European midlatitudes associated with freshwater outbursts from Lake Agassiz during the Younger Dryas event and the early Holocene
Authors: Magny Michel , Bégeot Carole
Published: February 2004

Recent studies of lake-level fluctuations during the last deglaciation in eastern France (Jura Mountains and Pre-Alps) and on the Swiss Plateau show distinct phases of higher water level developing at the beginning and during the latter part of Greenland Stade 1 (i.e. Younger Dryas event) and punctuating the early Holocene period at 11,250–11,050, 10,300–10,000, 9550–9150, 8300–8050, and 7550–7250 cal yr B.P. The phases at 11,250–11,050 and 8300–8050 cal yr B.P. appear to be related to the cool Preboreal Oscillation and the 8200 yr event assumed to be associated with deglaciation events. A comparison of this mid-European lake-level record with the outbursts from proglacial Lake Agassiz in North America suggests that, between 13,000 and 8000 cal yr B.P. phases of positive water balance were the response in west-central Europe to climate cooling episodes, which were induced by perturbation of the thermohaline circulation due to sudden freshwater releases to oceans. This probably was in response to a southward migration of the Atlantic Westerly Jet and its associated cyclonic track. Moreover, it is hypothesized that, during the early Holocene, varying solar activity could have been a crucial factor by amplifying or reducing the possible effects of Lake Agassiz outbursts on the climate.
Gene fusions with β‐lactamase show that subunit I of the cytochrome bd quinol oxidase from E. coli has nine transmembrane helices with the O2 reactive site near the periplasmic surface
Authors: Zhang Jie , Barquera Blanca , Gennis Robert B
Published: February 2004

The cytochrome bd quinol oxidase is a component of the respiratory chain of many prokaryotes. The enzyme contains two subunits, CydA and CydB, which were initially predicted based on the sequence of the Escherichia coli oxidase to have seven and eight transmembrane spans, respectively. More recently, the topological model of CydA was revised to predict nine transmembrane helices, based on additional sequence information from other organisms. In the current work, the topology of the E. coli oxidase was experimentally examined using β‐lactamase gene fusions. The results confirm the revised topology, which places the oxygen reactive site near the periplasmic surface.
Class III nucleotide cyclases in bacteria and archaebacteria: lineage‐specific expansion of adenylyl cyclases and a dearth of guanylyl cyclases
Authors: Shenoy Avinash R. , Visweswariah Sandhya S.
Published: February 2004

The Class III nucleotide cyclases are found in bacteria, eukaryotes and archaebacteria. Our survey of the bacterial and archaebacterial genome and plasmid sequences identified 193 Class III cyclase genes in only 29 species, of which we predict the majority to be adenylyl cyclases. Interestingly, several putative cyclase genes were found to have non‐conserved substrate specifying residues. Ancestors of the eukaryotic C1‐C2 domain containing soluble adenylyl cyclases as well as the protist guanylyl cyclases were found in bacteria. Diverse domains were fused to the cyclase domain and phylogenetic analysis indicated that most proteins within a single cluster have similar domain compositions, emphasising the ancient evolutionary origin and versatility of the cyclase domain.
Where are the major gaps in the reserve network for Africa's
mammals?
Authors: Fjeldså Jon , Burgess Neil D. , Blyth Simon , de Klerk Helen M.
Published: February 2004

The establishment of protected areas for wildlife conservation in Africa
was motivated by a number of different reasons (including hunting,
recreation and wildlife conservation). The current reserve network provides
good coverage of the distributions of the 194 species of larger mammals
(>3 kg) and 51 species of threatened larger mammals. However, it is less
effective in covering the distribution of all 197 of Africa's threatened
mammal species, which includes >140 smaller bodied species (<3 kg)
often restricted to habitat patches. A fully comprehensive network of areas
for the conservation of African mammals, especially those facing extinction,
is not yet in place, and further reserves may be needed in the Horn of
Africa (Somalia in particular), the Cameroon Highlands, parts of the eastern
African coastal forests and Eastern Arc Mountains, and parts of the
Albertine Rift Mountains. More and larger reserve areas are also required to
adequately cover all the species of South Africa. Parts of these gaps are
already covered by government forest reserves, and the importance of this
reserve category for the conservation of African mammals, especially
threatened species, needs to be better recognized. As many of the gaps in
reserve coverage are in areas of high human population and good agricultural
potential, conservation goals may be difficult to achieve unless we
supplement traditional reserves with novel approaches to maintain natural
habitats and wildlife outside reserves.
Inventory of free-ranging lions Panthera leo in Africa
Authors: Bauer H. , Van Der Merwe S.
Published: February 2004

The number of free ranging African lions Panthera
leo has never been comprehensively assessed. We present an
inventory of available information, covering most protected areas and
ranging in quality from educated guesses to individually known populations.
This gives a conservative estimate of 16,500–30,000 free ranging lions in
Africa. The inventory shows that populations are small and fragmented in
West and Central Africa, whereas the species still occurs widely in East and
Southern Africa. The results concur with the current IUCN Red List
categorization of the lion as Vulnerable.
Dramatic decline of wild South China tigers Panthera tigris
amoyensis: field survey of priority tiger reserves
Authors: Tilson Ronald , Defu Hu , Muntifering Jeff , Nyhus Philip J.
Published: February 2004

This paper describes results of a Sino-American field survey seeking
evidence of South China tigers Panthera tigris
amoyensis in the wild. In 2001 and 2002 field surveys were
conducted in eight reserves in five provinces identified by government
authorities as habitat most likely to contain tigers. The surveys evaluated
and documented evidence for the presence of tigers, tiger prey and habitat
disturbance. Approximately 290 km of mountain trails were evaluated.
Infrared remote cameras set up in two reserves captured 400 trap days of
data. Thirty formal and numerous informal interviews were conducted with
villagers to document wildlife knowledge, livestock management practices,
and local land and resource use. We found no evidence of wild South China
tigers, few prey species, and no livestock depredation by tigers reported in
the last 10 years. Forest areas designated as tiger reserves, averaging
about 100 km2 in size, are too small to support even a
few tigers because commercial tree farms and other habitat conversion is
common, and people and their livestock dominate these fragments. While our
survey may not have been exhaustive, and there may be a single tiger or a
few isolated tigers still remaining at sites we missed, our results strongly
indicate that no remaining viable populations of South China tigers occur
within its historical range. We conclude that continued field efforts are
needed to ascertain whether any wild tigers may yet persist, concurrent with
the need to consider options for the eventual recovery and restoration of
wild tiger populations from existing captive populations.
Evidence for a decline of François' langur Trachypithecus
francoisi in Fusui Nature Reserve, south-west Guangxi, China
Authors: Hu Gang , Dong Xin , Wei Yi , Zhu Ying , Duan Xihuan
Published: February 2004

Between July 2000 and June 2001 we undertook a survey of François'
langur Trachypithecus francoisi and its habitat
in the Fusui Nature Reserve in south-west Guangxi, China, where 86
individual langurs were recorded in 1995. In our first survey period we
located 45 individuals in 10 groups, but c. 12
months later, despite expending more effort, we were only able to locate
three of the 10 groups, totalling 23 individuals. In all, in three separate
surveys, we recorded densities that were 26–52% of the 1995 figures. Within
the Reserve almost all of the valley bottoms and most flat areas in the
hills have been cultivated and there is steady encroachment into the hills
and forests. The majority of local families depend on the forest for
firewood. It appears that habitat loss and illegal hunting are responsible
for the decline of François' langur. We recommend that alternative income
generating activities and energy sources should be explored to reduce human
pressure on these langurs and their habitat. More funding should also be
made available to the Reserve to enable staff to adequately tackle issues of
hunting and habitat destruction.
Distribution and conservation status of the endemic Chinese mountain cat
Felis bieti
Authors: He Li , García-Perea Rosa , Li Ming , Wei Fuwen
Published: February 2004

Records of the Vulnerable Chinese mountain cat Felis
bieti are known from the eastern border of the Tibetan
Plateau, mostly from Qinghai province, but also from other areas further
north, east and north-west. Disagreement regarding the reliability of some
records has led to uncertainty about the species' distribution. In order to
obtain information about its current distribution and status we conducted
surveys in various Chinese provinces and evaluated former records and
specimens. Forty-five specimens and living individuals were examined, and
189 records were gathered from local sources. Our data confirm that this cat
is endemic to China, and occurs in montane forest edge, alpine shrubland and
meadow habitats. At present it is confined to the provinces of eastern
Qinghai and northern Sichuan. Its wild populations are facing a number of
threats and environmental pressures such as poaching, use of chemical
rodenticides, and environmental changes. We recommend moving this species to
Category I of Chinese law, enforcement of its protection in reserves, and
the establishment of new reserves, specifically for this species, in areas
in which it is currently unprotected.
Monitoring of Asian houbara bustard Chlamydotis macqueenii
populations in Kazakhstan reveals dramatic decline
Authors: Tourenq Christophe , Combreau Olivier , Pole Sergey B. , Lawrence Mark , Ageyev Vladimir S. , Karpov Alekzey A. , Launay Frédéric
Published: February 2004

From 1998 to 2002 we monitored changes in the relative abundance of
Asian houbara bustard Chlamydotis macqueenii
across the greater part of its range in Kazakhstan. The areas most
frequented by houbara bustard were the Kyzylkum region, with 35% of total
sightings, and the Betpak-Dala/Muyunkum region with 25%. For all survey
areas combined, mean relative abundance ranged from 0.004 to 0.017
individuals seen per km driven. Density estimates ranged from 0.025 to 0.086
houbara bustard per km2. Between 1999 and 2002 spring
relative abundance and density decreased by 65 and 51% respectively.
Likewise, autumn relative abundance decreased by 56% from 1998 to 2001 and
density decreased by 35% between 1999 and 2001. Kyzylkum had the greatest
declines in relative abundance during both spring (78%) and autumn (61%). It
is highly probable that this observed decline in houbara bustard populations
is linked to hunting and poaching pressure, both in Kazakhstan and on the
wintering grounds of these Central Asian breeding populations.
Characterizing human-tiger conflict in Sumatra, Indonesia: implications
for conservation
Authors: Nyhus Philip J. , Tilson Ronald
Published: February 2004

Human-tiger conflict occurs in Indonesia but there is little recent
information about the scope of the problem, and adequate policies are not in
place to address the conflict. Published and unpublished reports of conflict
between Sumatran tigers Panthera tigris sumatrae,
people and their livestock were collected and analysed to characterize the
extent, distribution and impact of human-tiger conflict on the island of
Sumatra, Indonesia. Reportedly, between 1978 and 1997, tigers killed 146
people and injured 30, and killed at least 870 livestock. Conflict was less
common in protected areas and more common in intermediate disturbance areas
such as multiple-use forests where tigers and people coexist. In Indonesia
there is a need to develop a definition of problem tigers, a database to
track conflicts, and a process to respond immediately to conflicts when they
occur. Without a better understanding of human-tiger conflict and a
concerted effort to proactively address the problem, future landscape-level
tiger conservation and management efforts may be jeopardized.
The use of degraded and shade cocoa forests by Endangered golden-headed
lion tamarins Leontopithecus chrysomelas
Authors: Raboy Becky E. , Christman Mary C. , Dietz James M.
Published: February 2004

Determining habitat requirements for threatened primates is critical to
implementing conservation strategies, and plans incorporating metapopulation
structure require understanding the potential of available habitats to serve
as corridors. We examined how three groups of golden-headed lion tamarins
Leontopithecus chrysomelas in Southern Bahia,
Brazil, used mature, swamp, secondary and shade cocoa
(cabruca) forests. Unlike callitrichids that
show affinities for degraded forest,
Leontopithecus species are presumed to depend
on primary or mature forests for sleeping sites in tree holes and epiphytic
bromeliads for animal prey. In this study we quantified resource
availability within each habitat, compared the proportion of time spent in
each habitat to that based on availability, investigated preferences for
sleeping site selection, and determined how golden-headed lion tamarins
allocated time to foraging behaviour in different habitats. Each group
preferred to range in certain habitats during the day, yet patterns were not
consistent across groups. In contrast, all groups preferred to sleep in
mature or cabruca forest. Golden-headed lion tamarins spent a greater
proportion of time foraging and eating fruits, flowers and nectar in cabruca
than in mature or secondary forests. Although the extent to which secondary
and cabruca forests can completely sustain breeding groups is unresolved, we
conclude that both habitats would make suitable corridors for the movement
of tamarins between forest fragments, and that the large trees remaining in
cabruca are important sources of food and sleeping sites. We suggest that
management plans for golden-headed lion tamarins should focus on protecting
areas that include access to tall forest, either as mature or cabruca, for
the long-term conservation of the species.
A review of the CITES listing of big-leaf mahogany
Authors: Blundell Arthur G.
Published: February 2004

Big-leaf mahogany Swietenia macrophylla King
(Meliaceae) is the premier timber species of Latin America. A lack of law
enforcement allows widespread illegal logging, and its unsustainable harvest
depletes local stocks, necessitating a shift in sources of supply. To better
control this exploitation, parties to the Convention on International Trade
in Endangered Species of Wild Fauna and Flora (CITES) recently elected to
list mahogany on Appendix II. This listing requires exporting countries to
verify that each shipment was legally acquired and its harvest was
non-detrimental to the survival of mahogany. The CITES listing poses
considerable challenges: 1) there is no precedent, as mahogany is the first
commonly traded timber species listed on Appendix II, and 2) given current,
unsustainable logging practices, CITES regulations will be difficult to
implement. This paper synthesizes information on the conservation and
management of mahogany that informed the listing decision, and provides
recommendations for implementation, including timber tracking to ensure
legality.
Identifying important endemic areas using ecoregions: birds and mammals
in the Indo-Pacific
Authors: Fa Julia E. , Burn Robert W. , Price Mark R. Stanley , Underwood Fiona M.
Published: February 2004

Concentrations of large numbers of endemic species have been singled out
in prioritization exercises as significant areas for global biodiversity
conservation. This paper describes bird and mammal endemicity in
Indo-Pacific ecoregions. An ecoregion is a relatively large unit of land or
water that contains a distinct assemblage of natural communities. We
prioritize 133 ecoregions according to their levels of endemicity, and
explain how variables such as biome type, whether the ecoregion is on an
island or continental mass, montane or non-montane, correlate with the
proportion of the total species assemblage that are endemic. Following an
exploratory principal components analysis we classify all ecoregions
according to the relationship between numbers of endemics and overall
species richness. Endemicity is negatively correlated with species richness.
We show that plotting the logit transformation of the endemicity of birds
and mammals against log of species richness is a more effective and useful
way of identifying important ecoregions than simply ordering ecoregions by
the proportion of endemic species, or any other single measure. The plot,
divided into 16 regions corresponding to the quartiles of the two variables,
was used to identify ecoregions of high conservation value. These are the
ecoregions with the highest endemicity and lowest species richness. Further
analysis shows that island and montane ecoregions, regardless of their biome
type, are by far the most important for endemic species.
War and wildlife: a post-conflict assessment of Afghanistan's Wakhan
Corridor
Authors: Mishra Charudutt , Fitzherbert Anthony
Published: February 2004

Prior to the last two decades of conflict, Afghanistan's Wakhan Corridor
was considered an important area for conservation of the wildlife of high
altitudes. We conducted an assessment of the status of large mammals in
Wakhan after 22 years of conflict, and also made a preliminary assessment of
wildlife trade in the markets of Kabul, Faizabad and Ishkashem. The survey
confirmed the continued occurrence of at least eight species of large
mammals in Wakhan, of which the snow leopard Uncia
uncia and Marco Polo sheep Ovis
ammon are globally threatened. We found evidence of
human-wildlife conflict in Wakhan due to livestock depredation by snow
leopard and wolf Canis lupus. Large mammals are
hunted for meat, sport, fur, and in retaliation against livestock
depredation. The fur trade in Kabul is a threat to the snow leopard, wolf,
lynx Lynx lynx and common leopard
Panthera pardus.
Discovery of a relict breeding colony of northern bald ibis Geronticus
eremita in Syria
Authors: Serra Gianluca , Abdallah Mahmud , Assaed Adeeb , Abdallah Ahmed , Al Qaim Ghazy , Fayad Talal , Williamson Douglas
Published: February 2004

The eastern population of the northern bald ibis Geronticus
eremita had been presumed extinct following the loss of
the colony in Birecik, Turkey, in 1989. However, occasional sightings of
birds in Yemen, Eritrea, Saudi Arabia and Israel during the 1980s and 1990s
suggested that there was still a colony somewhere in the Middle East.
Intensive field surveys in spring 2002, based on the knowledge of Bedouin
nomads and local hunters, revealed that the species has never become
completely extinct on the Syrian desertic steppe. Following systematic
searches 15 old nesting sites were found, one of them still hosting an
active breeding colony of seven individuals. The species appears to have
been relatively common in the area until 20 years ago, when a combination of
overexploitation of rangelands and increasing hunting pressure initiated a
dramatic decline.
Abundance, seasonal haul-out patterns and conservation of spotted seals
Phoca largha along the coast of Bak-ryoung Island, South
Korea
Authors: Won Changman , Yoo Byoung-Ho
Published: February 2004

The spotted seal Phoca largha, which is found
in the Okhotsk, Bering, Chukchi, Beaufort and Yellow seas, is Critically
Endangered in the Yellow Sea of China and Korea because of habitat
destruction and human harassment in the region. Shipboard surveys were
conducted in the inshore waters of Bak-ryoung Island off western South Korea
from March 2000 to October 2002 to investigate the distribution, abundance
and seasonal haul-out patterns of spotted seals and thereby to lay a
foundation for developing conservation measures. Seals were seen on every
survey during the study period, hauled out on offshore rocks rather than on
beaches. The highest concentration of spotted seals occurred on Mul-Beum
Rock, probably because of the relatively lower exposure of this site to
waves and spray. There was a seasonal pattern in the total number of seals
hauled out, with the highest numbers seen from late spring to late summer.
Spotted seals arrived as early as 15 March and left the area by late
December. We suggest that spotted seals spend the spring, summer and autumn
feeding along the coast of Bak-ryoung Island and return to their breeding
grounds in Liaodong Bay, China, in October. Because the spotted seal
populations of China and South Korea are small and seasonally dispersed, the
establishment of an international protected areas network and research
cooperation between China and South Korea is urgently required.
From progressive to finite deformation and back
Authors: Provost Ariel , Buisson Cécile , Merle Olivier
Published: February 2004

It is widely accepted that any finite strain recorded in the field may be interpreted in terms of the simultaneous combination of a pure shear component with one or several simple shear components. To predict strain in geological structures, approximate solutions may be obtained by multiplying successive small increments of each elementary strain component. A more rigorous method consists in achieving the simultaneous combination in the velocity gradient tensor, but solutions already proposed in the literature are valid for some special cases only and cannot be used, e.g., for the general combination of a pure shear component and six elementary simple shear components. In this paper, we show that the combination of any strain components is very simple, both analytically and numerically. The finite deformation tensor is given by D = exp (LΔt), where LΔt is the time‐integrated velocity gradient tensor. This method makes it possible to predict finite strain for any combination of strain components. Reciprocally, LΔt = ln (D), which allows us to unravel the simplest deformation history that might have generated a given finite deformation. Given the strain ellipsoid only, it is still possible to constrain the range of compatible deformation tensors and thus the range of strain component combinations. Interestingly, certain deformation tensors, though geologically sensible, have no real logarithm and so cannot be explained by a deformation history implying strain rate components with a common time dependence. This implies significant changes of stress field or material rheology during deformation.