bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small‐scale environmental heterogeneity and the analysis of species distributions along gradients
Authors: Palmer Michael W. , Dixon Philip M. 
Published: April 2006

Abstract. The observed distribution of a species along an environmental gradient is strongly affected by environmental variability within a quadrat. Because a quadrat does not represent a point along an environmental gradient, but rather a range of conditions, it is likely to contain species not typically associated with the mean conditions in the quadrat. Systematic relationships exist between a species' true distribution, the observed distribution as a function of mean quadrat environment, and the frequency distribution of the environment within that quadrat. The observed species habitat breadth increases and the observed maximum abundance decreases as within‐quadrat environmental heterogeneity increases.If species distributions or beta diversities are to be compared among species or coenoclines, they should be correctedforintra‐quadratheterogeneity.Wederive simple corrections for environmental heterogeneity. The distributions of hardwood forest understory species along a soil acidity gradient in the North Carolina piedmont are presented as an example.
Politics as a Vocation—Praxis and Political Engagement
Authors: Kaufman Robert M. 
Published: April 2006

Were one to ask the typical, sophisticated American voter what it is that political scientists do, he or she might respond, “Why, they study politics!” Were one to ask the same of the somewhat more sophisticated congressional or campaign staffer, a likely response would be, “they study politics in the abstract,” accompanied by a faintly condescending smile. Lastly, were one to pose the question to the rather more sophisticated subject of this inquiry, the political science practitioner, among the range of amorphous, if not conflicting, responses one might expect would be the following: “We study the how and why of politics, the exercise of power, the underlying patterns and contexts of political and governmental behavior.” Truth, like beauty, lies in the eye of the beholder.The following contributions, from significant scholar/practitioners, are characterized by an abiding realism as to the hazards of crossing the line, of venturing beyond the tower, towards the enchanted forest of politics. They are marked by an awareness of the distinctiveness of the two life worlds, of knowledge and power, heirs to a reflective tradition traceable to the Platonic Epistles, Hume, Weber (above all), the Frankfurt School, and Foucault. They stand in a line of intellectual activism, from Plato's tutelage of Dionysius to the examples of Sartre, Camus, Malraux, or of Vargas Llosa and Havel in our day.
Synthesis of Substituted Benzylamino‐ and Heterocyclylmethylamino Carbodithioate Derivatives of 4‐(3H)‐Quinazolinone and their Cytotoxic Activity
Authors: Cao Sheng‐Li , Feng Yu‐Ping , Zheng Xiao‐Lin , Jiang Yu‐Yang , Zhang Mei , Wang Yue , Xu Meng 
Published: April 2006

AbstractA new series of substituted benzylamino‐ and heterocyclylmethylamino carbodithioate derivatives of 4‐(3H)‐quinazolinone were synthesized via four steps starting from 2‐amino‐5‐methylbenzoic acid and initially screened against A‐549 (human non‐small cell lung cancer), HCT‐8 (human colon cancer), and Bel‐7402 (human liver cancer) cell lines at the single concentration of 5 μg/mL using the colorimetric MTT assay. The IC50 values were determined for the compounds reaching ⪈70% inhibition in primary screening by serial dilution. Among the newly synthesized compounds, 9n exhibited potent in vitro cytotoxicity against A‐549, HCT‐8, and Bel‐7402 cell lines with the IC50 values of 1.65, 0.93, and 1.43 μM, respectively.
Occupational magnetic field exposure and melatonin: Interaction with light‐at‐night
Authors: Juutilainen Jukka , Kumlin Timo 
Published: April 2006

AbstractThe evidence of magnetic field (MF) effects on melatonin production in humans is limited and inconsistent. Part of the inconsistencies might be explained by findings suggesting interaction with light in pineal responses to MFs. To test this hypothesis, we reanalyzed data from a previously published study on 6‐hydroxy melatonin sulfate (6‐OHMS) excretion in women occupationally exposed to extremely low‐frequency MFs. Based on questionnaire data on exposure to light‐at‐night (LAN), and measurement‐based MF data, the 60 women were classified to four groups: no MF, no LAN; MF, no LAN; no MF, LAN; MF, LAN. The lowest excretion of 6‐OHMS was observed in the group of women who were exposed to both MF and LAN, and the differences between the four groups were significant (P < .0001). The result is based on low numbers, but supports the hypothesis that daytime occupational exposure to MF enhances the effects of nighttime light exposure on melatonin production. Bioelectromagnetics 27:423–426, 2006. © 2006 Wiley‐Liss, Inc.
Analysis of Longitudinal Multinomial Outcome Data
Authors: Li Yen‐Peng , Chan Wenyaw 
Published: April 2006

AbstractAnalysis of categorical outcomes in a longitudinal study has been an important statistical issue. Continuous outcome in a similar study design is commonly handled by the mixed effects model. The longitudinal binary or Poisson‐like outcome analysis is often handled by the generalized estimation equation (GEE) method. Neither method is appropriate for analyzing a multinomial outcome in a longitudinal study, although the cross‐sectional multinomial outcome is often analyzed by generalized linear models. One reason that these methods are not used is that the correlation structure of two multinomial variables can not be easily specified. In addition, methods that rely upon GEE or mixed effects models are unsuitable in instances when the focus of a longitudinal study is on the rate of moving from one category to another. In this research, a longitudinal model that has three categories in the outcome variable will be examined. A continuous‐time Markov chain model will be used to examine the transition from one category to another. This model permits an unbalanced number of measurements collected on individuals and an uneven duration between pairs of consecutive measurements. In this study, the explicit expression for the transition probability is derived that provides an algebraic form of the likelihood function and hence allows the implementation of the maximum likelihood method. Using this approach, the instantaneous transition rate that is assumed to be a function of the linear combination of independent variables can be estimated. For a comparison between two groups, the odds ratios of occurrence at a particular category and their confidence intervals can be calculated. Empirical studies will be performed to compare the goodness of fit of the proposed method with other available methods. An example will also be used to demonstrate the application of this method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Copper(II) Complexes of the Tetraazamacrocyclic Tertiary Amide Ligand Alanyl‐Cyclam
Authors: Schickaneder Christian , Heinemann Frank W. , Alsfasser Ralf 
Published: April 2006

AbstractHydrogen bonding to the electrically neutral tertiary carboxamide nitrogen atom of peptidyl‐prolyl groups is known to facilitate the C–N bond rotation during peptide and protein folding. Since metal complexes with nitrogen‐coordinated tertiary amide ligands are formally analogous, they may be used to model this so‐called electrophilic activation. In this paper we report on the synthesis of a monoacylated cyclam complex, [(Boc‐Ala‐cyclam)Cu](CF3SO3)2 (8; Boc: tert‐butyloxycarbonyl, Ala: alanine, cyclam: 1,4,8,11‐tetraazacyclotetradecane). It contains a fully sp3‐hybridized metal‐bound amide nitrogen atom. The resonance is completely cancelled and the observed C–N distance of 147 pm is consistent with a single bond. These features are exceptional among Werner‐type complexes and define the maximal possible electrophilic distortion of an amide bond.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
The Relationship Between Aromaticity and Charge‐Transfer Transitions: A Combined Study of Square‐Planar Metal Complexes Based on DFT, NMR and Nucleus‐Independent Chemical Shifts
Authors: Makedonas Christodoulos , Mitsopoulou Christiana A. 
Published: April 2006

AbstractThe aromaticity of square‐planar metal complexes, in this case mixed diiminodithiolate complexes of group VIII metals, has been investigated by 1H and 1H‐15N NMR spectroscopy, both experimentally and theoretically, as well as NICS indices. The electron‐donating/‐attracting ability of the substituent group and the metal ion interact with each other and control the aromaticity of the chelated rings and, as a consequence, the extent of the delocalization in the molecular plane. Evolution of the nucleus‐independent chemical shift (NICS) of the ligands upon complexation is consistent with the change in their electron distribution. At the same time, and in analogy with the EMF in closed circuits, a positive difference of the NICS value (ΔNICS) between two points (where HOMO and LUMO are located) can be envisioned as the driving force for charge‐transfer transitions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
New Reagent for Convenient Access to the α,β‐UnsaturatedN‐Methoxy‐N‐methyl‐amide Functionality by a Synthesis Based on the Julia Olefination Protocol
Authors: Narayana Manjunath Beedimane , Sane Neeraj P. , Singh Aidhen Indrapal 
Published: April 2006

AbstractA new reagent for the synthesis of the α,β‐unsaturatedN‐methoxy‐N‐methyl‐amide structural unit has been developed. 2‐(Benzo[d]thiazol‐2‐ylsulfonyl)‐N‐methoxy‐N‐methylacetamide, a crystalline solid with an indefinite shelf life that can be easily prepared in two convenient steps from 2‐chloro‐N‐methoxy‐N‐methylacetamide, reacted with a variety of aldehydes under Julia conditions to furnish the α,β‐unsaturatedN‐methoxy‐N‐methyl‐amide functionality. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Analysis of jitter due to call‐level fluctuations
Authors: Mandjes Michel 
Published: April 2006

AbstractIn communication networks used by constant bit rate applications, call‐level dynamics (i.e. entering and leaving calls) lead to fluctuations in the load, and therefore also fluctuations in the delay (‘jitter’). By intentionally delaying the packets at the destination, one can transform the ‘perturbed’ packet stream back into the original periodic stream; in other words: there is a trade off between jitter and delay, in that jitter can be removed at the expense of delay. As a consequence, for streaming applications for which the packet delay should remain below some predefined threshold, it is desirable that the jitter remains small.This paper presents a set of procedures to compute the jitter due to call‐level variations. We consider a network resource shared by a fluctuating set of constant bit rate applications (modelled as periodic sources). As a first step, we study the call‐level dynamics: supposing that a tagged call seesn0calls when entering the system, then we compute the probability that at the end of its duration (consisting of, say,ipackets)nicalls are present, of whichn0,istem from the originaln0calls. As a second step, we show how to compute the jitter, for givenn0,ni, andn0,i; in this analysis generalised Ballot‐problems have to be solved. We find an iterative exact solution to these, and explicit approximations and bounds. Then, as a final step, the (packet‐level) results of the second step are weighed with the (call‐level) probabilities of the first step, thus resulting in the probability distribution of the jitter experienced within the call duration. An explicit Gaussian approximation is proposed. Extensive numerical experiments validate the accuracy of the approximations and bounds. Copyright © 2006 AEIT
Performance indicator for DMT systems with non perfect channel estimation
Authors: Bueche D. , Corlay P. , Gazalet M. G. , Coudoux F. X. , Slachciak M. 
Published: April 2006

AbstractIn this letter, we analyse the bit error rate (BER) of a discrete multitone modulation system considering the channel estimation error for the frequency equalisation. After having established an approximate relation for the BER, we propose a simple performance indicator, which accounts for the channel estimation error, the power emitted and the noise level. In order to check the validity of the indicator, simulation has been performed. The results prove that it is more adapted to discrete multi‐tone modulation (DMT) systems than the classical mean squared channel estimation error (MSE), above all when the channel additive noise is coloured. Copyright © 2006 AEIT
A new MAP‐based channel estimation technique for multiple input multiple output diversity schemes
Authors: Hoteit Wajih , Shayan Yousef R. , Elhakeem Ahmed K. 
Published: April 2006

AbstractThis paper presents a channel estimation technique amenable to space‐time coding (STC). An array of transmission antennas operates in band‐limited channels with intersymbol interference. The effectiveness of STC schemes requires the development of practical and high‐performance algorithms for channel estimation. The channel parameters, to be estimated at the reception antennas, are the attenuations and delays incurred by the signals transversal along the different propagation paths. The estimation technique is based on an iterative procedure derived through the maximuma posterioriprobability (MAP) approach. Unlike classic estimation techniques, we iterate on the different probabilities of different coefficients rather than the coefficient values themselves. Two practical approaches are proposed, which are simplified versions of the general approach to implement the derived expressions required to estimate the actual channel coefficients. The performance of the two proposed algorithms has been assessed by simulation. Combined analysis/simulation results are presented and compared against those of conventional channel estimation techniques. Simulation results show that the required performance can be achieved with fewer number of iterations compared to conventional techniques. Copyright © 2006 AEIT
Inversion of heterogeneous parabolic‐type equations using the pilot points method
Authors: Alcolea Andrés , Carrera Jesús , Medina Agustín 
Published: April 2006

AbstractThe inverse problem (also referred to as parameter estimation) consists of evaluating the medium properties ruling the behaviour of a given equation from direct measurements of those properties and of the dependent state variables. The problem becomes ill‐posed when the properties vary spatially in an unknown manner, which is often the case when modelling natural processes. A possibility to fight this problem consists of performing stochastic conditional simulations. That is, instead of seeking a single solution (conditional estimation), one obtains an ensemble of fields, all of which honour the small scale variability (high frequency fluctuations) and direct measurements. The high frequency component of the field is different from one simulation to another, but a fixed component for all of them. Measurements of the dependent state variables are honoured by framing simulation as an inverse problem, where both model fit and parameter plausibility are maximized with respect to the coefficients of the basis functions (pilot point values). These coefficients (model parameters) are used for parameterizing the large scale variability patterns. The pilot points method, which is often used in hydrogeology, uses the kriging weights as basis functions. The performance of the method (both its variants of conditional estimation/simulation) is tested on a synthetic example using a parabolic‐type equation. Results show that including the plausibility term improves the identification of the spatial variability of the unknown field function and that the weight assigned to the plausibility term does lead to optimal results both for conditional estimation and for stochastic simulations. Copyright © 2006 John Wiley & Sons, Ltd.
Electromagnetic scattering simulation using an H(curl) conforming hp finite element method in three dimensions
Authors: Ledger P. D. , Morgan K. , Hassan O. 
Published: April 2006

AbstractThis work describes an approach to solving electromagnetic scattering problems in three dimensions using arbitrary order tetrahedral H(curl) conforming finite elements. We use geometric refinement of the grid to isolate the effect of singularities and use non‐uniform polynomial degree to reduce the number of unknowns. Initial distributions of the polynomial degree are generated automatically through the use of a dispersion relationship. The large complex linear system is solved efficiently by using a parallel linear equation solver. Both bistatic and monostatic scattering examples are presented to demonstrate the capabilities of the approach. Copyright © 2006 John Wiley & Sons, Ltd.
Properties and Performance of SOFCs Produced on a Pre‐Pilot Plant Scale
Authors: Hagen A. , Menon M. , Barfod R. , Hendriksen P. V. , Ramousse S. , Larsen P. H. 
Published: April 2006

AbstractIn the present paper, anode supported solid oxide fuel cells (SOFCs), produced on a pre‐pilot plant scale in ten batches of ∼100 cells, are characterised with respect to performance. The main purpose was to evaluate the reproducibility of the scaled‐up process. Based on 20 tests, the average area specific cell resistance at 850 °C was found to be 0.24 Ω cm2 with a standard deviation of 0.05 Ω cm2. The variation in performance between the cells can be largely attributed to variations in the cathode performance. Experimental evidence will be presented on full 4 × 4 cm2 cells, symmetric cells with two cathodes on a YSZ strip, and a special cell with a divided cathode.
How do changes in monetary policy affect bank lending? An analysis of Austrian bank data
Authors: Frühwirth‐Schnatter Sylvia , Kaufmann Sylvia 
Published: April 2006

AbstractUsing a panel of Austrian bank data we show that the lending decisions of the smallest banks are more sensitive to interest rate changes, and that for all banks, sensitivity changes over time. We propose to estimate the groups of banks that display similar lending reactions by means of a group indicator which, after estimation, indicates each bank's classification. Additionally, we estimate a state indicator that indicates the periods during which the lending reaction differs from what we normally observe. Bayesian methods are used for estimation; a sensitivity analysis and a forecast evaluation confirm our model choice. Copyright © 2006 John Wiley & Sons, Ltd.
Normal mixture GARCH(1,1): applications to exchange rate modelling
Authors: Alexander Carol , Lazar Emese 
Published: April 2006

AbstractSome recent specifications for GARCH error processes explicitly assume a conditional variance that is generated by a mixture of normal components, albeit with some parameter restrictions. This paper analyses the general normal mixture GARCH(1,1) model which can capture time variation in both conditional skewness and kurtosis. A main focus of the paper is to provide evidence that, for modelling exchange rates, generalized two‐component normal mixture GARCH(1,1) models perform better than those with three or more components, and better than symmetric and skewed Student'st‐GARCH models. In addition to the extensive empirical results based on simulation and on historical data on three US dollar foreign exchange rates (British pound, euro and Japanese yen), we derive: expressions for the conditional and unconditional moments of all models; parameter conditions to ensure that the second and fourth conditional and unconditional moments are positive and finite; and analytic derivatives for the maximum likelihood estimation of the model parameters and standard errors of the estimates. Copyright © 2006 John Wiley & Sons, Ltd.
Cannabis, cocaine and jobs
Authors: van Ours Jan C. 
Published: April 2006

AbstractThis paper uses a dataset collected among inhabitants of Amsterdam, to study the employment effects of the use of cannabis and cocaine. For females no negative effects of drug use on the employment rate are found. For males there is a negative correlation between past cannabis and cocaine use and employment. However, after correcting for the effect of unobserved personal characteristics there is no negative effect of cannabis use or cocaine use on the employment status of males. Copyright © 2006 John Wiley & Sons, Ltd.
PAI‐1 transcriptional regulation during the G0 → G1 transition in human epidermal keratinocytes
Authors: Qi Li , Allen Rosalie R. , Lu Qi , Higgins Craig E. , Garone Rosemarie , Staiano‐Coico Lisa , Higgins Paul J. 
Published: April 2006

AbstractPlasminogen activator inhibitor type‐1 (PAI‐1) is the major negative regulator of the plasmin‐dependent pericellular proteolytic cascade. PAI‐1 gene expression is normally growth state regulated but frequently elevated in chronic fibroproliferative and neoplastic diseases affecting both stromal restructuring and cellular migratory activities. Kinetic modeling of cell cycle transit in synchronized human keratinocytes (HaCaT cells) indicated that PAI‐1 transcription occurred early after serum stimulation of quiescent (G0) cells and prior to entry into a cycling G1 condition. PAI‐1 repression (in G0) was associated with upstream stimulatory factor‐1 (USF‐1) occupancy of two consensus E box motifs (5′‐CACGTG‐3′) at the PE1 and PE2 domains in the PF1 region (nucleotides −794 to −532) of the PAI‐1 promoter. Chromatin immunoprecipitation (ChIP) analysis established that the PE1 and PE2 site E boxes were occupied by USF‐1 in quiescent cells and by USF‐2 in serum‐activated, PAI‐1‐expressing keratinocytes. This reciprocal and growth state‐dependent residence of USF family members (USF‐1 vs. USF‐2) at PE1/PE2 region chromatin characterized the G0 → G1 transition period and the transcriptional status of the PAI‐1 gene. A consensus E box motif was required for USF/E box interactions, as a CG → AT substitution at the two central nucleotides inhibited formation of USF/probe complexes. The 5′ flanking sites (AAT or AGAC) in the PE2 segment were not necessary for USF binding. USF recognition of the PE1/PE2 region E box sites required phosphorylation with several potential involved residues, including T153, maping to the USF‐specific region (USR). A T153A substitution in USF‐1 did not repress serum‐induced PAI‐1 expression whereas the T153D mutant was an effective suppressor. As anticipated from the ChIP results, transfection of wild‐type USF‐2 failed to inhibit PAI‐1 induction. Collectively, these data suggest that USF family members are important regulators of PAI‐1 gene control during serum‐stimulated recruitment of quiescent human epithelial cells into the growth cycle. J. Cell. Biochem. 99: 495–507, 2006. © 2006 Wiley‐Liss, Inc.