bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the BioClog model for landfill leachate clogging of gravel-packed columns
Authors: Cooke A J , Rowe R K , VanGulck J , Rittmann B E
Published: January 2006

A numerical, multiple-species, reactive chemical transport model (BioClog) developed to predict clogging in landfill leachate collection systems is used to interpret results from experiments conducted with gravel-packed columns permeated with landfill leachate. The model predicts changes to the microbial community and leachate chemistry, including the concentrations of volatile fatty acids, suspended biomass, dissolved calcium, and suspended inorganic solids. The calculated quantity and composition of the clog matter (biomass and mineral), along with the associated decrease in porosity, are compared to the measured values. The modelled clogging is in reasonable agreement with that observed in the gravel column experiments. By identifying and quantitatively linking many microbiological, chemical, and transport mechanisms, the model helps elucidate the phenomena controlling the rate and extent of clogging.Key words: clogging, landfills, leachate collection systems, biofilms, mineral precipitation.
Numerical analysis and monitoring of Pappadai dam
Authors: Lollino Piernicola , Cotecchia Federica , Zdravkovic Lidija , Potts David M
Published: January 2006

This paper presents a case history for the construction of the Pappadai dam in Italy. The dam is constructed from rockfill, with an upstream bituminous membrane, and is built on stiff clay foundations. The instrumentation of the dam and of the foundation soil provides detailed insight into the deformation patterns and pore-water pressure changes during dam construction and for the subsequent 7 years. Two-dimensional plane-strain finite element analyses, using fairly simple constitutive models for soil and rockfill behaviour, were performed to reproduce the soilstructure interaction so that the effects of reservoir impoundment, which has yet to be carried out, could be investigated. The paper shows that a careful choice of parameters and an understanding of the mechanical behaviour of the in situ soils can result in satisfactory predictions of the overall soilstructure interaction.Key words: rockfill, stiff clay, dam, field data, numerical analysis.
Using complex permittivity and artificial neural networks to identify and classify copper, zinc, and lead contamination in soil
Authors: Amegashie F , Shang J Q , Yanful E K , Ding W , Al-Martini S
Published: January 2006

Complex permittivity measurements combined with artificial neural networks (ANNs) are investigated as a method for assessing and identifying heavy metal contamination in soil. The measurements are carried out with a custom-built device on 164 compacted samples of a natural clayey soil, artificially contaminated with various simple salts including heavy metals (Cu, Zn, and Pb). The soil samples are prepared by mixing solutions of the various salts with the soil at various concentrations and water contents. A database has been set up consisting of complex per mittivity measurements made between the frequencies of 200 and 500 MHz and measured physical and chemical properties of the soil samples. Using this database as input, two ANN models are designed, the first to detect the presence or absence of heavy metals in the soil samples and the second to determine whether the heavy metal, if present in a given sample, is Cu, Zn, or Pb. Both ANN models perform reasonably well. Overall, the first model is able to detect the presence of heavy metals in 92.7% of cases, and the second is successful in distinguishing the particular type of heavy metal in 76.4% of all the samples containing heavy metals. These encouraging results underscore the potential of complex permittivity and ANNs as promising tools for nondestructive subsurface contamination assessment.Key words: heavy metals, subsurface contamination, complex permittivity, artificial neural networks, contaminant detection.
Acceleration of the methanolysis of phosphate diesters promoted by La(OTf)3  The analysis of non-integer pH/rate profiles resulting from changes in metal ion speciation
Authors: Gibson Graham TT , Neverov Alexei A , Teng Allen Chun-Tien , Brown R S
Published: January 2006

In a previous publication (A.A. Neverov and R.S. Brown. Inorg. Chem. 40, 3588 (2001)) we reported very effective catalysis of the methanolysis of some phosphate diesters (methyl p-nitrophenyl phosphate (1), bis(p-nitrophenyl) phosphate (2), and diphenyl phosphate (3)) promoted by La3+, and noted a general observation that the plots of logkcat vs. [Formula: see text]pH had non-integer gradients. In this report the origins of that behaviour are studied and analyzed through determination of the speciation of La3+(OCH3)n, (La3+)2(OCH3)m, (La3+)2:phosphate:(OCH3)y forms in solution as a function of [Formula: see text]pH. Potentiometric titrations of solutions of La(OTf)3 in methanol at low (<1 × 104 mol/L) and high (>1 × 103 mol/L) concentration were analyzed through fits of the data to various models to provide speciation diagrams of the various La3+ forms in the absence of phosphate. Titrations of La3+ in the presence of diphenyl phosphate were also analyzed to provide speciation diagrams for phosphate bound forms. The kinetic data for the La3+ catalyzed methanolysis of 1 were analyzed through fitting the kinetic data at low and high [La3+] as a function of [Formula: see text]pH to a linear combination of the individual kinetic contributions of each species. Overall the data are best analyzed in the low [La3+] domain as resulting from methoxide attack on a transient complex of phosphate bound to La3+(OCH3)0,1. In the high [La3+] domain the data fit two kinetically equivalent processes involving either a spontaneous decomposition of (La3+)2:1:(OCH3)2,3,4,5 or external methoxide attack on (La3+)2:1:(OCH3)1,2,3,4. Key words: lanthanides, phosphate diester, methanolysis, kinetics, speciation, metal ion catalysis of methanolysis, DNA model methanolysis.
The structure, photochemical reactivity, and photophysical properties of adamantyl X-substituted aryl ethers and a comparison with the alkyl groups, methyl, tert-butyl, and allyl
Authors: Pincock A L , Pincock J A
Published: January 2006

The structure, photophysical properties, and photochemistry of the adamantyl aryl ethers 1 in both methanol and cyclohexane have been examined. UV absorption spectra, 13C NMR chemical shifts, X-ray structures, and Gaussian calculations (B3LYP/6-31G(d)) indicate that these ethers adopt a 90° conformer in the ground state. In contrast, fluorescence spectra, excited singlet state lifetimes, and calculations (TDDFT) indicated a 0° conformer is preferred in the first excited singlet state S1. Irradiation in either solvent results in the formation of adamantane and the corresponding phenol as the major products, both derived from radical intermediates generated by homolytic cleavage of the ether bond. The 4-cyano substituted ether 1j was the only one to form the ion-derived product, 1-methoxyadamantane (16% yield), on irradiation in methanol. Rate constants of bond cleavage for these ethers from S1 were estimated by two different methods by comparison with the unreactive anisoles 2, but the effect of substituents was too small to determine structurereactivity correlations. The temperature dependence of the quantum yields of the fluorescence of the unsub stituted, 4-methoxy and 4-cyano derivatives of 1 and 2 were also determined. These results indicated that the activated process for 1 was mainly bond cleavage for the 4-cyano substrate whereas for 2, it was internal conversion and intersystem crossing. Key words: aryl ether photochemistry, fluorescence, excited-state rate constants, excited-state temperature effects.
The art of discovery in biophysical organic chemistry
Authors: Kosower Edward M
Published: January 2006

Observations made in the course of experiments on pyridinium salts led to important discoveries in physical organic chemistry. The way in which the discoveries were made is likened to art rather than goal-directed "cold logic". We can describe the art of discovery as an effort enhanced by practice and intuition to recognize novelty in a finding and provide productive insight into its nature. We shall present some examples, and describe what happened after finding an unexpected light absorption band, a surprising solvent effect on spectra, and an unexpectedly stable and beautiful small organic radical.Key words: art of discovery, solvent polarity parameter, charge-transfer complex, stable free radical, solvent effect on spectra.
Bicyclo[3.2.0]hepta-1,3,6-triene  UV photoelectron spectroscopic and computational studies
Authors: Bajorek T , Werstiuk N H
Published: January 2006

Pyrolysis of N,N-dimethylbicyclo[3.2.0]hepta-3,6-dien-1-amine oxide (5) at 120 °C in the source chamber of the UV photoelectron (PE) spectrometer yielded bicyclo[3.2.0]hepta-1,3,6-triene (6). The triene dimerizes to yield a mixture of two dimers in equal amounts. A PE spectrum of an authentic mixture of dimers was also recorded for the purpose of spectral subtraction. Pyrolysis of 5 also generates dimethylhydroxylamine (7), a spectrum of which was also recorded from an authentic sample. Spectral subtraction allowed the first two ionization potentials of triene 6 at 7.2 and 9.8 eV to be identified. The resultant PE spectrum was compared very favorably with a simulated spectrum obtained from DFT calculations. A QTAIM analysis and calculation of delocalization indexes showed that while homoconjugation between C4 and C6 is negligible there is a weak through-space interaction between the bridgehead carbon atom C1 and C6 of the four-membered ring.Key words: bicyclo[3.2.0]hepta-1,3,6-triene, UV photoelectron spectroscopy, DFT calculations, QTAIM, delocalization indexes.
Competitive endo- and exo-cyclic CN fission in the hydrolysis of N-aroyl β-lactams
Authors: Tsang Wing Y , Ahmed Naveed , Hemming Karl , Page Michael I
Published: January 2006

The balance between endo- and exo-cyclic CN fission in the hydrolysis of N-aroyl β-lactams shows that the difference in reactivity between strained β-lactams and their acyclic analogues is minimal. Attack of hydroxide ion occurs preferentially at the exocyclic acyl centre rather than that of the β-lactam during the hydrolysis of N-p-nitrobenzoyl β-lactam. In general, both endo- and exo-cyclic CN bond fission occurs in the alkaline hydrolysis of N-aroyl β-lactams, the ratio of which varies with the aryl substituent. Hence, the Brønsted β-values differ for the two processes: 0.55 for the ring-opening reaction and 1.54 for the exocyclic CN bond fission reaction. For the pH-independent and acid-catalysed hydrolysis of N-benzoyl β-lactam, less than 3% of products are derived from exocyclic CN bond fission. Key words: β-lactams, hydrolysis, linear free energy relationships, strain.
Pople, Schneider, and Bernstein  A truly seminal treatise of NMR
Authors: Roberts John D
Published: January 2006

The appearance of the authoritative and comprehensive book, High-Resolution Nuclear Resonance Spectroscopy, by John A. Pople, William G. Schneider, and Harold J. Bernstein in 1959 came at just the right time for chemists and other scientists to develop a clear vision of the wide breadth of applications of this critical emerging field and, in addition, to have the opportunity to learn the underlying basic theory in substantial detail.Key words: Pople, Schneider, Bernstein, NMR theory, NMR applications.
Effect of modification of the electrophilic center on the α effect
Authors: Um Ik-Hwan , Lee Ji-Youn , Bae Sun-Young , Buncel Erwin
Published: January 2006

We report on a nucleophilic study of esters R-C(=X)-Y-Ar in which the electrophilic center has been modified by replacing O by S in the leaving group or carbonyl center: 4-nitrophenyl acetate (1), S-4-nitrophenyl thioacetate (2), 4-nitrophenyl benzoate (3), and O-4-nitrophenyl thionobenzoate (4). The studies include O and S nucleophiles as well as α nucleophiles in H2O at 25.0 ± 0.1 °C. The sulfur nucleophile (4-chlorothiophenoxide, 4-ClPhS) exhibits significant enhanced reactivity for the reactions with thiol and thione esters 2 and 4 compared with their oxygen analogues 1 and 3. On the contrary, the common nucleophile OH is much less reactive towards 2 and 4 compared with 1 and 3. The effect of changing both the electrophilic center and the nucleofugic center on the reactivity of the other oxygen nucleophiles is not so significant: 4-chlorophenoxide (4-ClPhO) is four to six times more reactive in the reactions with thiol and thione esters 2 and 4 compared with their oxygen analogues 1 and 3. The α effects exhibited by butan-2,3-dione monoximate (Ox) and HOO are strongly dependent on the nature of the electrophilic center of the substrates, indicating that the difference in the ground-state solvation energy cannot be fully responsible for the α effect. Our results clearly emphasize the strong dependence of the α effect on the substrate structure, notably, the nature of the electrophilic center. The impact of change in the nucleofuge (1→2) and the electrophilic center (3→4) on reactivity indicates that α nucleophiles will need to be “purpose built” for decontamination and nucleophilic degradation of specific biocides.Key words: α effect, nucleophilicity, nucleofuge effect, electrophilicity, polarizability.
The addition of alkynes to a tetrasilyldisilene  Evidence for a biradical intermediate
Authors: Gottschling Stephen E , Jennings Michael C , Baines Kim M
Published: January 2006

The addition of two newly developed mechanistic probes, (trans,trans-2-methoxy-3-phenylcyclopropyl)ethyne (1) and (trans,trans-2-methoxy-1-methyl-3-phenylcyclopropyl)ethyne (2), to tetrakis(tert-butyldimethylsilyl)disilene (3) has been investigated. The addition of 1 to 3 gave 1-[2-(cis-2-methoxy-3-phenylcyclopropylidene)vinyl]-1,1,2,2-tetrakis(tert-butyldimethylsilyl)disilane (5) as the major product; whereas addition of alkyne 2 to the disilene gave three stereoisomers of 1,1,2,2-tetrakis(tert-butyldimethylsilyl)-6-methoxy-5-methyl-7-phenyl-1,2-disilacyclohepta-3,4-diene (79) and 1,1,2,2- tetrakis(tert-butyldimethylsilyl)-3-(trans,trans-2-methoxy-1-methyl-3-phenylcyclopropyl)-1,2-disilacy-clobut-3-ene (10) as the major products. The formation of cycloheptaallenes 79 provides convincing evidence that the addition of alkynes to tetrasilyldisilenes involves the formation of a biradical intermediate. Key words: disilene, alkyne, cycloaddition, reaction mechanism, mechanistic probe.
Comparison of the nucleophilicities of alcohols and alkoxides
Authors: Phan Thanh Binh , Mayr Herbert
Published: January 2006

The kinetics of the reactions of benzhydrylium ions with some alcohols and alkoxides dissolved in the corresponding alcohols were photometrically investigated. Using the correlation equation log k (20 °C) = s(E + N), the N and s parameters of methoxide, ethoxide, n-propoxide, and isopropoxide in alcoholacetonitrile (91:9, v/v) were determined. The cosolvent acetonitrile has only a little influence on the rate constants of the reactions of alcohols and alkoxides. The order of N values (OH << MeO < EtO < n-PrO < i-PrO) shows that alkoxides differ only moderately in reactivity but are considerably more nucleophilic than hydroxide. As a consequence, the nucleophilic reactivity of a 0.5 mmol/L aqueous hydroxide solution increases by a factor of 13 when 10% (v/v) methanol is added. In 110 mmol/L alkoxide solutions in alcohols, weak electrophiles react considerably faster with alkoxides than with the corresponding alcohols. With increasing electrophilicity, the preference for alkoxides decreases, and electrophiles of 3 < E < 3 react with alkoxides (110 mmol/L) and alcohols with comparable rates. Stronger electrophiles will react with alcohols exclusively when alkoxides are present in concentrations ≤10 mmol/L. Key words: kinetics, alcohol, alkoxide, linear free energy relationship, nucleophilicity.<
A multinuclear solid-state magnetic resonance study of silver nitrate triphenylphosphine
Authors: Oh Se-Woung , Bernard Guy M , Wasylishen Roderick E , McDonald Robert , Ferguson Michael J
Published: January 2006

Variable-temperature solid-state31P,15N, and2H NMR spectroscopy, X-ray diffraction, and differential scanning calorimetry studies of the 1:1 adduct of silver nitrate and triphenylphosphine (AgNO3·PPh3) reveal a solidsolid phase transition at 300 K. The principal components of the phosphorus and nitrogen chemical shift tensors for both phases are determined from NMR spectra of MAS and stationary samples. In addition, the indirect spin-spin coupling between phosphorus and the naturally occurring isotopes of silver (107Ag and109Ag) are resolved. Experimental2H NMR line shapes for silver nitrate perdeuterated triphenylphosphine are those characteristic of rigid phenyl groups at temperatures above and below the phase-transition temperature. Powder and single-crystal X-ray diffraction data for AgNO3·PPh3obtained at 193, 295, and 313 K are reported; data obtained at 193 and 295 K are almost identical, but are significantly different from those obtained at 313 K and from an earlier single-crystal X-ray diffraction investigation performed at 298 K. All X-ray studies found that AgNO3·PPh3crystallizes in the monoclinic form, space group P21/c.Key words: 1:1 silver nitrate triphenylphosphine adduct, solid-state NMR, X-ray diffraction, phase transition.
SN2 and SN2′ reaction dynamics of cyclopropenyl chloride with halide ion  A direct ab initio molecular dynamics (MD) study
Authors: Tachikawa Hiroto
Published: January 2006

Direct ab initio molecular dynamics (MD) calculations have been carried out for the reaction of cyclopropenyl chloride with halide ion (F) (F+ (CH)3Cl → F(CH)3+ Cl) in gas phase. Both SN2 and SN2′ channels were found as product channels. These channels are strongly dependent on the collision angle of Fto the target (CH)3Cl molecule. The collision at one of the carbon atoms of the C=C double bond leads to the SN2′ reaction channel; whereas the collision at the methylene carbon atom leads to the SN2 reaction channel. The reactions proceed via a direct mechanism without long-lived complexes. The reaction mechanism is discussed on the basis of the theoretical results.Key words: SN2 reaction, direct ab initio molecular dynamics, halogen exchange, reaction mechanism.
Thermodynamics of organic mixtures containing amines. IV. Systems with aniline
Authors: González Juan Antonio , Mozo Ismael , García de la Fuente Isaías , Cobos José Carlos
Published: January 2006

Binary mixtures of aniline with benzene, toluene, alkane, alkanol, or N,N-dialkylamide have been investigated in the framework of the DISQUAC model. The reported interaction parameters change regularly with the molecular structure of the mixture components. The model consistently describes a set of thermodynamic properties including liquidliquid equilibria, vaporliquid equilibria, and molar excess enthalpies. The two latter properties for ternary systems are well-represented by DISQUAC using binary parameters only (i.e., neglecting ternary interactions). A comparison of DISQUAC results and those obtained from the UNIFAC (Dortmund version) and ERAS models is also shown. The experimental molar excess enthalpies for binary and ternary mixtures are better described by DISQUAC than by UNIFAC. ERAS fails when representing molar excess enthalpies of those binary systems including methanol or ethanol. This may be due to the existence of strong dipolar interactions among aniline molecules as well as to effects related to the equation of state term, evaluated comparing molar excess enthalpies, and molar excess internal energies at constant volume. The study of the aniline systems in terms of the concentrationconcentration structure factor also underlines the importance of dipolar interactions in solutions with alkanes or alcohols, which may be due to the high polarizability of the aniline molecule.Key words: thermodynamics, mixtures, aniline, dipolar interactions, structural effects.
Dynamics of the transient species generated upon photolysis of diarylmethanes within zeolites  Deprotonation and oxidation reactions
Authors: Shea Suzanne , Schepp Norman P , Keirstead Amy E , Cozens Frances L
Published: January 2006

The oxidation of diarylmethanes is a multistep process involving initial formation of a radical cation, deprotonation of the radical cation to the radical, and oxidation of the radical to the carbocation. The dynamics and efficiency of the last two steps in this process, namely deprotonation and oxidation, in acidic zeolites and non-acid zeolites are examined in the present work as a function of the acidity of the diarylmethane radical cations and the oxidation potential of the diarylmethyl radicals. Our results indicate that rate constants for deprotonation strongly depend on the acidity of the radical cations, but not on the composition of the zeolites. In addition, oxidation of the radicals to the diarylmethyl cations is strongly dependent on both the oxidation potential of the radicals and the oxidizing ability of the zeolite. This dependence allows oxidation potentials of the zeolites to be estimated.Key words: radical cations, carbocations, zeolites, laser flash photolysis.
Synthesis of novel sulfonyl-stabilized phosphorus ylides, and the kinetics and mechanism of their conventional and flash vacuum pyrolysis reactions
Authors: Al-Bashir Rasha F , Al-Awadi Nouria A , El-Dusouqui Osman ME
Published: January 2006

Nine substituted sulfonyl-stabilized phosphorus ylides were prepared by treating their intermediate ylide analogues with phenylmethanesulfonyl fluoride. The stoichiometric ratio of the reactants for each preparation needed to be adjusted according to the basicity of each ylide intermediate. The nine ylide compounds were then subjected to conventional (sealed-tube) gas-phase pyrolysis at 470545 K. The pyrolytic reactions were homogeneous and obeyed a first-order rate equation. The values of the Arrhenius log A (s1) and Ea (kJ mol1) obtained for these reactions averaged 11.12 ± 2.00 and 131.8 ± 24.4, respectively. Analysis of the pyrolysates from conventional pyrolysis and from flash vacuum pyrolysis at 600 K showed the products to be complex mixtures of triphenylphosphine, triphenylphosphine oxide, triphenylphosphine sulfide, and symmetric and unsymmetric alkenes. Conventional pyrolysis also gave novel mixed sulfones and, for the p-methoxyaryl substituent, p-anisaldehyde. The products of the reactions under study are explained on the basis of a mechanism involving a sulfonyl carbene intermediate, and the reaction mechanism is used to rationalize the kinetic results and molecular reactivities.Key words: ylides, synthesis, pyrolysis, kinetics, mechanism.
Infection of radiata and bishop pine by Mycosphaerella pini in California
Authors: Muir John A , Cobb, Jr. Fields W
Published: January 2006

Infection of radiata pine (Pinus radiata D. Don) and bishop pine (Pinus muricata D. Don) by Myco sphaerella pini Rostr. in Munk was determined on needles of infected forest trees in central to northern coastal California. Conidia from infected trees were used to inoculate radiata pine seedlings maintained in constant and (or) fluctuating moisture and temperature regimes. On needles of radiata pine but not bishop pine plantation trees, most conidial germ tubes grew directly towards and entered the nearest epistomatal opening. On inoculated radiata pine seedlings in infection chambers, germ tubes grew haphazardly and few entered openings. Germ tubes entered epistomatal openings more often on abaxial than adaxial needle surfaces of both plantation trees and inoculated seedlings, and more lesions developed on the abaxial surface. Simple hyphae penetrated through epistomatal chambers, between guard cells, and into substomatal chambers. On radiata pine plantation trees, germ tubes that penetrated below guard cells occasionally formed substomatal vesicles. On needles of northern race bishop pine that had few disease lesions per needle, substomatal vesicles were common and frequently partially disintegrated. On seedlings, "water-soaked" spots formed 5 days after hyphae of the fungus penetrated slightly below guard cells. Development of typical lesions was delayed when seedlings were initially exposed to up to 16 days of continuous mist spray and then kept dry for 8 weeks. Penetration on inoculated seedlings was significantly greater in a variable than in a constant air temperature regime on abaxial needle surfaces, and greater in 24 h/day than in a 16 h/day exposure of seedlings to mist spray. In both temperature regimes more needles were infected on seedlings exposed to 24 h/day mist spray and fewest were infected in the variable temperature, 16 h/day moisture regime.
Effects of a recent wildfire and clearcuts on ground-dwelling boreal forest spider assemblages
Authors: Larrivée Maxim , Fahrig Lenore , Drapeau Pierre
Published: January 2006

Ground-dwelling spider (Araneae) assemblages were compared between recent clearcuts and burned black spruce (Picea mariana (Mill.) BSP) forests. Spiders were sampled using pitfall traps placed in 6 recently burned sites, 6 recently clear-cut sites, and 6 undisturbed sites in eastern Quebec, Canada. A total of 2935 individuals from 95 spider species were identified. Catch rates for hunting spiders were significantly higher in the clear-cut stands than in the burned stands, but between-stand species turnover of hunting spiders was twice as high in the burned stands as in the clear-cut stands. Web-building spiders had similar catch rates in the three stand types, but had the highest species turnover and gamma diversity in the undisturbed sites. Correspondence analysis showed that the composition of the spider assemblages varied among the three types of stands. Spider assemblages found in clearcuts were associated with environmental variables reflecting dry, open, disturbed forest floor, while assemblages found in burned stands were correlated with high percentages of shrub cover and dried mosslichen substrate and deeper litter. We conclude that ground-living spider assemblages in boreal forest respond very differently to clearcuts and fires and we suggest modifications to present forestry practices to create disturbances that are more similar to wildfires.
The effects of patch harvesting and site preparation on ground beetles (Coleoptera, Carabidae) in yellow birch dominated forests of southeastern Quebec
Authors: Klimaszewski Jan , Langor David W , Work Timothy T , Pelletier Georges , Hammond HE James , Germain Carole
Published: January 2006

We studied the impacts of increasing size and number of gapcuts and the effects of site preparation by scarification on the species richness and community composition of ground beetles (Coleoptera: Carabidae), using pitfall traps in early-successional yellow birch dominated forests in eastern Canada. Catches of all carabids, forest specialists, and generalists were generally higher in uncut controls than in treatments. The catch of open-habitat specialists was generally lower in controls than in treatments. Although not significant, there was a common trend for scarification to decrease the catches of forest specialists and generalists. BrayCurtis similarity measures and nonmetric multidimensional scaling ordination indicated that the composition of the carabid assemblage was more affected by harvesting treatment than by scarification. Carabid species composition varied consistently with increasing gap size and corresponded to the a priori generalized habitat-preference designations. Forest-specialist species were confined to uncut sites, while generalist species were widely distributed across all sites. Open-habitat species were found predominantly in clear-cut and two-gap sites. Hygrophilous species were consistently associated with two-gap, four-gap, and clear-cut sites. Small-gap harvesting is more favorable to the maintenance of the structure of natural arthropod assemblages than are traditional, larger clearcuts.
Modeling trade-offs between fire threat reduction and late-seral forest structure
Authors: Calkin David E , Hummel Susan Stevens , Agee James K
Published: January 2006

Evaluating the effects of managing for one forest resource in terms of associated impacts on other resources is not easy. Yet methods to identify potential trade-offs among forest resources are necessary to inform people about the implications of management options on public land. This paper uses a case study from a forest reserve in the northwestern United States to quantify trade-offs between fire threat (FT) and late-seral forest (LSF) structure at stand and landscape levels. Simulation of forest dynamics was done with and without silvicultural treatments. A landscape optimization algorithm maximized FT reduction subject to constraints on amount of LSF structure and total area treated. Results suggest that compatibility between the two objectives is possible at the landscape level when LSF structure is about 45% or less of the total reserve area. Conflict can exist between them at the stand level and when more area is required to be in LSF structure in the reserve landscape.
Biases in LI-COR Plant Canopy Analyzer estimates of seasonal light interception by black spruce and trembling aspen canopies
Authors: Groot Arthur
Published: January 2006

This article examines four sources of bias in the estimation of seasonal light interception by black spruce (Picea mariana (Mill.) BSP) and trembling aspen (Populus tremuloides Michx.) canopies using the LI-COR LAI-2000 Plant Canopy Analyzer: (i) geometric averaging of gap fractions, (ii) unrepresentative elevation angle intervals for radiation detectors, (iii) assumption of isotropic radiance distribution, and (iv) inclusion of light intercepted by stems in the estimate of canopy light interception. Bias source i caused overestimates of canopy light interception, source ii caused underestimates, source iii caused little bias, and source iv caused overestimates. The magnitude of bias from sources i, ii, and iv increased as fractional light interception by canopies decreased. The average bias in seasonal light interception for all sources combined was 5% for black spruce canopies and 17% for trembling aspen canopies. It is recommended that canopy light interception and understorey light level estimates be calculated in a way to reduce bias from sources i and ii. For estimates of canopy interception alone, bias from source iv should also be reduced.
Seed and bud legacies interact with varying fire regimes to drive long-term dynamics of boreal forest communities
Authors: McIntire Eliot JB , Duchesneau Robin , Kimmins JP (Hamish)
Published: January 2006

Sustainable forest management that employs the emulation of natural disturbance paradigm develops plans based on disturbance-driven forest succession. However, most research on forest succession has focused primarily on postdisturbance species change, often ignoring predisturbance legacies. We used the FORECAST ecosystem management model and a newly created natural regeneration submodel to examine the interaction of fire severity, fire frequency, and natural regeneration to produce multicycle dynamics of white spruce (Picea glauca (Moench) Voss), lodgepole pine (Pinus contorta Dougl. ex Loud.), and trembling aspen (Populus tremuloides Michx.) in a western Canadian boreal forest. We simulated 19 different scenarios in a factorial disturbance experiment of three severities and six frequencies and a no-disturbance scenario. Our simulations resulted in a wide diversity of boreal forest community types, including trembling aspen dominated mixedwoods with high-frequency (75 year), high-severity (100% mortality) fires, and nearly pure lodgepole pine stands at midfrequency (100125 year) and high-severity fires. With the unvarying disturbance regimes we used, a variety of different but recurring temporal patterns emerged. We show that the loss of seed source legacies reinforces the disturbance-driven species dominance, demonstrating community inertia. This study provides a long-term perspective to boreal forest management that demonstrates the role of disturbance and legacies in long-term dynamics.
Fine-scale variability in growthclimate relationships of Douglas-fir, North Cascade Range, Washington
Authors: Case Michael J , Peterson David L
Published: January 2006

Information about the sensitivity to climate of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is valuable because it will allow forest managers to maximize growth, better understand how carbon sequestration may change over time, and better model and predict future ecosystem responses to climatic change. We examined the effects of climatic variability on the growth of Douglas-fir along an elevational gradient in the North Cascade Range, Washington (USA), at annual timescales during the 20th century. Multivariate analysis and correlation analysis were used to identify climate-growth relationships. Mid-elevation chronologies were negatively correlated with growing season maximum temperature and positively correlated with growing season precipitation. In contrast, high-elevation chronologies were positively correlated with annual temperatures and negatively correlated with previous-year winter Pacific Decadal Oscillation index. Projected increases in summer temperatures will likely cause greater soil moisture stress in many forested ecosystems. The potential of extended summer drought periods over decades may significantly alter spatial patterns of productivity, thus impacting carbon storage. It is likely that the productivity of Douglas-fir in the Cascade Range will decrease at sites with shallow, excessively drained soils, south- and west-facing aspects, and steep slopes and will increase at high-elevation sites.
An application of Markov models to the dynamics of Minnesota's forests
Authors: Pastor John , Sharp Angela , Wolter Peter
Published: January 2006

Markov models are matrices of transition probabilities between states and are used to project a vector of state distribution forward in time. Traditionally, Markov models of landscapes assume that the transition probabilities are independent of age for all pixels in a given cover type. But harvesting practices vary the probability of harvesting within cover types by stand age, and so the transition probabilities between older age-classes or into other cover types depend not only on the cover type but also on the age-class within a cover type or successional stage. We used satellite imagery and stand inventory data for northern Minnesota to parameterize and set initial conditions for both age-class independent and age-class dependent Markov models. The assumptions of an age-class independent Markov model are not satisfied by current landscape dynamics in northern Minnesota. Making the probability of harvest depend on age within a cover type results in different landscape dynamics than making the harvest independent of age. Decreasing the nominal rotation age and increasing the spread of harvest ages around the nominal rotation age results in greater abundance of land in regeneration stages, even if the amount of land harvested annually is held constant. Forest landscape models should consider age-dependent as well as cover type-dependent transitions.
Effects of different forest management systems on plant species diversity in aFagus crenataforested landscape of central Japan
Authors: Nagaike Takuo , Kamitani Tomohiko , Nakashizuka Tohru
Published: January 2006

To clarify how different forest management systems affect the diversity of understory vascular plant species at the plot level and the forest-type level, we examined a forested landscape originally occupied by primary Japanese beech, Fagus crenata Blume, in central Japan. The landscape is currently composed of four types of forest: primary F. crenata forest, shelterwood logged F. crenata forest, abandoned coppice forest, and coniferous plantation. Species richness per plot (α diversity) and in each forest type (γ diversity) and species turnover among plots in each forest type (β diversity) reached their highest values in plantation forests. While the difference in species composition between primary and shelterwood logged forests was not significant, the other pairs of forest types showed significant differences. Ordination analysis revealed that variation in species composition within the plantations seemed to be related to the dominance of naturally regenerated tree species, which reflected the intensity of tending. Although the species composition of less intensively tended plantations was similar to that of abandoned coppice forests that had been repeatedly cut in the past, their species composition differed from that of the primary forests. This suggests that most of the plantation and coppice forests, which were clear-cut at least once, do not revert to primary forest conditions after management is abandoned.
Characterizing flow regimes for floodplain forest conservation: an assessment of factors affecting sapling growth and survivorship on three cold desert rivers
Authors: Andersen Douglas C
Published: January 2006

I analyzed annual height growth and survivorship of Fremont cottonwood (Populus fremontii S. Watson) saplings on three floodplains in Colorado and Utah to assess responses to interannual variation in flow regime and summer precipitation. Mammal exclosures, supplemented with an insecticide treatment at one site, were used to assess flow regime  herbivore interactions. Multiple regression analyses on data collected over 711 years indicated that growth of continuously injury-free saplings was positively related to either peak discharge or the maximum 30-day discharge but was not related to interannual decline in the late-summer river stage (ΔWMIN) or precipitation. Growth was fastest where ΔWMIN was smallest and depth to the late-summer water table moderate (≤1.5 m). Survivorship increased with ΔWMIN where the water table was at shallow depths. Herbivory reduced long-term height growth and survivorship by up to 60% and 50%, respectively. The results support the concept that flow history and environmental context determine whether a particular flow will have a net positive or negative influence on growth and survivorship and suggest that the flow regime that best promotes sapling growth and survival along managed rivers features a short spring flood pulse and constant base flow, with no interannual variation in the hydrograph. Because environmental contexts vary, interannual variation may be necessary for best overall stand performance.
Evaluating desiccation sensitivity of Quercus rubra acorns using X-ray image analysis
Authors: Goodman Rosa C , Jacobs Douglass F , Karrfalt Robert P
Published: January 2006

Desiccation of northern red oak (Quercus rubra L.) acorns can impact seed viability. We examined use of X-ray image analysis of cotyledon damage in dried acorns to predict germination capacity and seedling vigor. Acorns collected from five half-sib sources were X-rayed before and after drying to one of four moisture content (MC) levels (30%, 25%, 20%, or 15%) or maintained as nondesiccated controls (35%38% MC). X-ray images were scored qualitatively according to degree of cotyledoncotyledon and cotyledon-pericarp separation. Following sowing, acorns were evaluated for number of days to reach each of three developmental stages (emergence of radicle, epicotyl, and first leaf flush) and growth for 80 d. Both MC and family significantly affected all variables. The percentage of acorns to reach each developmental stage, as well as final height and root-collar diameter declined with decreasing MC and dropped most notably between 20% and 15% MC. X-ray separation scores more effectively predicted the percentage of acorns to reach each of the first three developmental stages than MC level (R2 = 0.490.63 vs. 0.400.59). Our results confirm the recalcitrant nature of northern red oak acorns and demonstrate the potential of X-ray image analysis to provide a rapid and nondestructive means to successful predict acorn viability.
Temporal development of decaying log habitats in wet sprucefir stands in east-central British Columbia
Authors: DeLong S Craig , Daniels Lori D , Heemskerk Ben , Storaunet Ken Olaf
Published: January 2006

Time since death and time since fall were estimated for hybrid spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) logs to quantify temporal changes in log decay and habitat quality in east-central British Columbia. We sampled 136 logs (72 spruce and 64 fir) for species, size, and morphological attributes and used dendroecological techniques to estimate year of death (n = 97) and fall (n =  22). Time since death and time since fall of spruce and fir were similar in decay classes 1 and 2; fir was older than spruce in more advanced stages of decay. Discriminant analysis based on time since fall correctly classified logs into four decay classes for 67% and 80% of spruce and fir, respectively. Function as wildlife habitat changed significantly as logs decayed. Logs served as elevated runways for approximately 15 years and then increased in value as habitat for invertebrates and insectivores as wood softened and vegetation established. Concealed spaces increased as the wood decomposed but decreased when logs collapsed. We conclude that decay classes represent biologically and statistically significant stages of log decomposition that are relevant to wildlife habitat and therefore provide a useful construct for model development and field interpretation..
WHAT IS A MATTER PARTICLE?
Authors: CHAN TSAN UNG
Published: January 2006

Positive baryon numbers (A>0) and positive lepton numbers (L>0) characterize matter particles while negative baryon numbers and negative lepton numbers characterize antimatter particles. Matter particles and antimatter particles belong to two distinct classes of particles. Matter neutral particles are particles characterized by both zero baryon number and zero lepton number. This third class of particles includes mesons formed by a quark and an antiquark pair (a pair of matter particle and antimatter particle) and bosons which are messengers of known interactions (photons for electromagnetism, W and Z bosons for the weak interaction, gluons for the strong interaction). The antiparticle of a matter particle belongs to the class of antimatter particles, the antiparticle of an antimatter particle belongs to the class of matter particles. The antiparticle of a matter neutral particle belongs to the same class of matter neutral particles. A truly neutral particle is a particle identical with its antiparticle; it belongs necessarily to the class of matter neutral particles. All known interactions of the Standard Model conserve baryon number and lepton number; matter cannot be created or destroyed via a reaction governed by these interactions. Conservation of baryon and lepton number parallels conservation of atoms in chemistry; the number of atoms of a particular species in the reactants must equal the number of those atoms in the products. These laws of conservation valid for interaction involving matter particles are indeed valid for any particles (matter particles characterized by positive numbers, antimatter particles characterized by negative numbers, and matter neutral particles characterized by zero). Interactions within the framework of the Standard Model which conserve both matter and charge at the microscopic level cannot explain the observed asymmetry of our Universe. The strong interaction was introduced to explain the stability of nuclei: there must exist a powerful force to compensate the electromagnetic force which tends to cause protons to fly apart. The weak interaction with laws of conservation different from electromagnetism and the strong interaction was postulated to explain beta decay. Our observed material and neutral universe would signify the existence of another interaction that did conserve charge but did not conserve matter.
CHARACTERIZATION OF THE PLANCK SCALE
Authors: SIDHARTH B. G.
Published: January 2006

It is taken for granted in modern high energy approaches, that the Planck scale is the minimum scale. We investigate why this should be so, and provide a rationale for its numerical value.
NON-ADIABATIC COUPLED REARRANGEMENT CHANNEL CALCULATION OF ENERGY FOR MUONIC MOLECULE ttμ IN THE HYPER-SPHERICAL APPROACH
Authors: MAHDAVI M.
Published: January 2006

The hyper-spherical adiabatic expansion is a representation for the investigation of the muonic three-body bound states. In this research, we have used the method of hyper-spherical "surface" functions for the muonic molecule, tritium-tritium-muon. Through this approach, the binding energy of the ground state and the lowest eigenpotentials for the muonic molecular ions are calculated in the extreme adiabatic approximation. The results obtained are close to the calculation of other researchers.
FISSION OF METAL CLUSTERS
Authors: LYALIN A. , OBOLENSKY O. I. , SOLOV'YOV A. V. , GREINER W.
Published: January 2006

Advances achieved during recent years in model and ab initio descriptions of fission of metal clusters are reviewed. We focus on developments in ab initio treatment of the electronic subsystem within the jellium background model, as well as on applications of potential energy surface analysis to determining the characteristics of the fission process. We reiterate the main results obtained with the implementation of the Hartree–Fock and local density schemes for the two-center deformed jellium model. We overview the influences of the geometrical and statistical factors on the parameters of the fission process revealed recently. Also, we overview concisely the classical liquid drop model, the shell correction method, the asymmetric two-center-oscillator shell model, and the main approaches to the molecular dynamics simulations of the fission process.
SURPRISES FROM THE SEARCH FOR QUARK-GLUON PLASMA? WHEN WAS QUARK-GLUON PLASMA SEEN?
Authors: WEINER RICHARD M.
Published: January 2006

The historical context of the recent results from high energy heavy ion reactions devoted to the search of quark-gluon plasma (QGP) is reviewed, with emphasis on the surprises encountered. The evidence for QGP from heavy ion reactions is compared with that available from particle reactions.
cAMP signal transduction induces eNOS activation by promoting PKB phosphorylation
Authors: Zhang Xiao-Ping , Hintze Thomas H.
Published: January 2006

The objective of this study was to determine whether activation of protein kinase B (PKB) is involved in the production of nitric oxide (NO) induced by cAMP signal transduction. Mongrel dogs were used for this study. Coronary microvessels were isolated from the left ventricular free wall of these dog hearts. Forskolin (an activator of adenylyl cyclase that increases intracellular cAMP level) and 8-bromo-cAMP (a membrane-permeable cAMP analog) were used to stimulate NO release and activation of PKB and endothelial NO synthase (eNOS) in these blood vessels. We found that forskolin and 8-bromo-cAMP increased NO release (quantified by using the Griess reaction) from coronary microvessels by 80 ± 6 and 78 ± 11 pmol/mg (mean ± SE), respectively ( P < 0.05 vs. control). Western blot analysis showed that forskolin elicited a significant increase in eNOS phosphorylation (59 ± 11%) at serine-1177 (a positively regulatory phosphorylation site for eNOS) and a significant increase in dephosphorylation (28 ± 6%) at threonine-495 (a negatively regulatory phosphorylation site of eNOS) ( P < 0.05 vs. control). Interestingly, forskolin also increased the phosphorylation of PKB at serine-473 (by 49 ± 17%) and threonine-308 (by 53 ± 17%), respectively ( P < 0.05 vs. control; phosphorylation of both sites is required for a full activation of PKB). Nω-nitro-l-arginine methyl ester (an NOS inhibitor) blocked NO formation, Rp diastereomer of cAMP (a PKA inhibitor), and LY-294002 [a PI3-kinase (an activator of PKB) inhibitor] prevented the production of NO, phosphorylation of PKB, and eNOS induced by forskolin. Our data clearly show an involvement of PKB activation in cAMP signal-induced NO production. We are reporting for the first time that cAMP signal transduction stimulates eNOS activation through a PKB-mediated mechanism.