bluuebunny/crossref_metadata_2025 huggingface dataset:
A theoretical model study on the cyclic reaction of 4-hydroxybutanal catalyzed by Brønsted acid
Authors: Meng Qingyong , Zhang Chenggen , Huang Ming-Bao
Published: October 2009

For a theoretical model study on the cyclic reaction of 4-hydroxybutanal (4-OH-BL), we have examined five assumed reaction pathways (I–V) by performing the B3LYP calculations in the gas phase and self-consistent isodensity polarized continuum model (SCIPCM)-B3LYP calculations in aqueous solution. Pathways II (4-OH-BL + H+), III (4-OH-BL + H3O+), and IV (4-OH-BL + H3O+ + H2O) represent three models for the cyclic reaction catalyzed by Brønsted acids. The present study leads to the following conclusions concerning the five pathways (mainly on the basis of the calculation results in the solution). The high barrier along pathway I (with no catalyst) implies that the reaction does not occur without a catalyst, and the extremely large stabilization energy of the intermediate implies that pathway II is not a realistic model for the reaction catalyzed by Brønsted acid. Along pathway III, there are two intermediates and a transition state in between, and they are 10–16 kcal/mol lower in energy than the reactants (4-OH-BL + H3O+). Along pathway IV, there is only one intermediate, and it is 20.6 kcal/mol lower in energy than the reactants (4-OH-BL + H3O+ + H2O). Pathways III and IV are predicted to be feasible. Energetically, pathway IV is more favourable than pathway III and it is considered as a rational model for the cyclic reaction of 4-OH-BL catalyzed by Brønsted acid. Our calculations for pathway V (catalyzed by H2O) indicate that the water molecule may also serve as a catalyst for the cyclic reaction. The transition state along pathway V is 20.0 kcal/mol higher in energy than the reactants (4-OH-BL + H2O), and one can clearly see the “proton wire” in its structure. Our calculations show strong solvent effects on energetics of the charged intermediates along pathways II, III, and IV.
Emitting-state properties of square-planar dithiocarbamate complexes of palladium(II) and platinum(II) probed by pressure-dependent luminescence spectroscopy
Authors: Genre Caroline , Levasseur-Thériault Geneviève , Reber Christian
Published: October 2009

Temperature- and pressure-dependent Raman and luminescence spectra of four crystalline complexes of palladium(II) and platinum(II) with chelating diethyldithiocarbamate (EDTC) and pyrrolidine-N-dithiocarbamate (PDTC) ligands are reported. The crystal structure of [Pd(PDTC)2] was resolved at 120 K. Luminescence band maxima are observed at approximately 14 500 cm–1and 16 000 cm–1for the palladium(II) and platinum(II) complexes, respectively. Pressure leads to blue shifts of the band maxima by +9 and +13 cm–1/kbar for [Pd(EDTC)2] and [Pd(PDTC)2], and +15 cm–1/kbar for [Pt(EDTC)2]. These spin-forbidden d–d luminescence transitions have lifetimes of approximately 600 µs at temperatures below 20 K. Luminescence intensities at room temperature are low, but they increase significantly with external pressure. The experimental results show that strong increases of luminescence intensities caused by pressure are not limited to complexes with monodentate ligands, a result providing insight on the coordinates with emitting-state distortions responsible for this effect.
Root induction in hybrid poplar by Agrobacterium genetic transformation
Authors: Charest P. J. , Stewart D. , Budicky P. L.
Published: October 2009

Three Agrobacteriumrhizogenes strains (A4, 8196, and ATC39207) and two Agrobacteriumtumefaciens mutant strains (A208 (pTiT37•14a/a) and C58 (pGV3297)) were evaluated for their genetic transformation frequency invitro on cuttings of Populusdeltoides × nigra line DN106 and Populusnigra × maximowiczii lines NM1 and NM6. The aim of this work was to increase biomass production by genetically modifying hybrid poplar root systems. Inoculation of the cut end of invitro grown stems with the A. rhizogenes strain ATC39207 gave the highest frequency of typical hairy root formation with line DN106. The other combinations of Agrobacterium strains and poplar lines yielded very low frequencies of hairy root induction or induction of tumours instead of hairy roots. Similar attempts with greenhouse-grown plants gave negative results. The modified root system resulting from the invitro inoculation of line DN106 cuttings yielded an increase in root and aerial biomass production after 175 days of growth invitro. Preliminary data confirm this observation in the greenhouse. Genetic transformation of the tissues was proven by phenotype (hairy root or tumour), hormone autotrophy, and opine production in the resulting tissues. Because of the host range restriction and inefficiency of this approach, it is not practical at this time for use in the transformation of hybrid poplar.
Isozyme variation in eastern hemlock
Authors: Zabinski Catherine
Published: October 2009

Tsugacanadensis (L.) Carr., commonly known as eastern hemlock, is a coniferous tree native to eastern North America. The western and southern edges of its geographic distribution are characterized by disjunct populations 50–100 km or more from the continuous distribution. Genetic variation was measured using starch gel electrophoresis of needle tissue enzymes from 17 populations throughout the species' distribution. Six enzyme systems including 10 putative loci were assayed, with only 1 of the 10 loci being polymorphic. The polymorphic locus, cytochrome oxidase, consisted of two alleles present in all but two populations. Allele frequencies averaged 0.69 and 0.31. The low level of genetic variation in eastern hemlock was an unexpected result, given that most coniferous species are highly variable.
Sulfate adsorption and microbial immobilization in northern hardwood forests along an atmospheric deposition gradient
Authors: Randlett Diana L. , Zak Donald R. , MacDonald Neil W.
Published: October 2009

While a number of studies have investigated adsorption and microbial immobilization as sulfate (SO42−) retention mechanisms, few have investigated these processes under field-like conditions on a regional, ecosystem basis. Adsorption and microbial immobilization of SO42− were studied in four northern hardwood stands that span an atmospheric deposition gradient in the Lake States region (5 to 10 kg S•ha−1•year−1). Soil cores collected in spring, summer, and autumn were labeled with 35SO42− to trace the flux of S between physical and biological sinks, and to investigate seasonal variation in sink strength. Intact soil cores were injected with Na235SO4 and incubated for 8 d in the laboratory at field temperature to study rates of adsorption and microbial immobilization. The amount of 35S recovered within these pools was significantly different between surface and subsurface soil horizons. Microbial immobilization was the dominant S sink in the A + E horizon, whereas adsorption was the most important S sink in the B horizon. During the 8-d incubation, the proportion of 35S that was immobilized in the A horizon (49% of applied 35S) was equivalent to the proportion of 35S adsorbed in the B horizon (47% of applied 35S). Microbial immobilization sequestered an additional 25% of the applied 35S in the B horizon. Adsorption and microbial immobilization were not significantly different among sampling dates. Sulfur retention in forested ecosystems should be viewed as a combination of geochemical and microbially mediated processes. However, given current levels of S deposition at these sites, neither process seems to represent a significant mechanism for long-term S retention.
Modeling survival of loblolly pine trees in thinned and unthinned plantations
Authors: Avila Olga B. , Burkhart Harold E.
Published: October 2009

The probability of survival for an individual tree was modeled. A variable screening algorithm, screen, was used to find the best set of predictor variables. Stepwise procedures in SAS and BMDP were also used, and results were compared with those obtained from the SCREEN algorithm. The logistic model, with independent variables that were found to be significant through the SCREEN algorithm, was fitted to the data. The fitted models were validated by splitting the data and applying equations fitted to the estimation set to the data in the testing set. Two methods of data splitting were applied: (i) according to time period and (ii) at random. Validation statistics were similar for both cases. The final distance-dependent logistic model for the unthinned plots included the following independent variables: crown ratio (CR), total height/average height of dominant and codominant trees (HH), and competition index (CI). The logistic model with CR, HH, and quadratic mean diameter/DBH (DD) was used as the distance-independent model of survival for the unthinned plots. The final distance-dependent logistic model for the thinned plots included as predictor variables HH, CI, and CR1.5. For the thinned plots the final distance-independent model used DD, CI, and CR1.5 as independent variables. The logistic models of survival obtained in this study were compared with survival models developed previously for distance-dependent and distance-independent stand simulators. Only slight improvement is shown by the logistic models.
Influence of sampling date and substrate on nitrogen mineralization: comparison of laboratory-incubation and buried-bag methods for two Massachusetts forest soils
Authors: Boone Richard D.
Published: October 2009

Nitrogen (N) mineralization potential and net N mineralization insitu were measured monthly over 7 months for the forest floor horizons (Oi, Oe, Oa) and mineral soil (0–15 cm) of a pine stand and the mineral soil (0–15 cm) of a maple stand in Massachusetts, United States. In all cases, N mineralization potential per unit organic matter (anaerobic laboratory incubation) varied significantly by sampling month but was unrelated to the seasonal pattern for net N mineralization (buried-bag method). The organic horizons in the pine stand exhibited the most variable N mineralization potential, with the Oe horizon having more than a fourfold seasonal range. For the pine stand the Oe horizon also had the highest N mineralization potential (per unit organic matter) and the highest net N mineralization insitu (per unit area). In general, temporal and depth-wise variability should be considered when sites are assessed with respect to the pool of mineralizable N.
Production physiology and morphology of Populus species and their hybrids grown under short rotation. I. Clonal comparisons of 4-year growth and phenology
Authors: Ceulemans R. , Scarascia-Mugnozza G. , Wiard B. M. , Braatne J. H. , Hinckley T. M. , Stettler R. F. , Isebrands J. G. , Heilman P. E.
Published: October 2009

Height and diameter growth, stem volume production, leaf phenology and leaf number, and number of branches of Populustrichocarpa Torr. & Gray, Populusdeltoides Bartr., and their F1 hybrids (P. trichocarpa × P. deltoides) were studied for 4 years in a research plantation in western Washington, United States. Twelve clones (three of each species and six of the hybrids) grew under a short-rotation silviculture regime in monoclonal plots at spacings of 1 × 1 m (10 000 stems/ha). Clones represented a north-south gradient within the geographic distribution of both the two North American poplar species and the parentage of the hybrid material. The results support earlier work by contributing additional evidence for the superiority of the hybrids. However, the relative hybrid superiority in these monoclonal plots was less pronounced than that found earlier in field trials with single-tree plots because of heightened intraclonal competition. After 4 years, mean estimated stem volume of the hybrids was 1.5 times that of P. trichocarpa and 2.3 times that of P. deltoides. Total tree height of the hybrids was 1.1 times that off. trichocarpa and 1.3 times that off. deltoides. Clonal variation was the dominant theme in height and diameter growth, stem volume productivity, time of bud break and bud set, tree mortality, and number of branches. Populustrichocarpa had the highest number of sylleptic branches, P. deltoides had the lowest, and hybrids were intermediate. Significant clone by replicate interactions were observed in height, diameter, and volume growth. Phenological traits, such as the dates of bud break and bud set, and the length of growing period only partly explained the observed differences in growth between the P. trichocarpa × P. deltoides hybrids and the parental species.
Seasonal changes of frost hardiness in Piceaabies and Pinussylvestris in Finland
Authors: Repo T.
Published: October 2009

The frost hardiness of 15- to 25-year-old Scots pine (Pinussylvestris L.) and Norway spruce (Piceaabies (L.) Karst.) growing under central Finnish conditions was followed during 1985–1987. Shoots were subjected to artificial frost in the laboratory. Frost hardiness was assessed by the impedance method and by visual scoring. Frost hardiness varied during the years from −3.5 °C to lower than −40 °C. The rate of dehardening increased after about mid-April in both tree species when the daily mean temperature increased by several degrees above 0 °C. The maximum rate of dehardening varied slightly from year to year. In both species the frost hardiness of the previous year's shoot decreased during shoot elongation. This phenomenon was more prominent in pine than in spruce. Shoots were most susceptible to frost damage at the time when shoot elongation was ceasing. The onset and development of hardiness in autumn varied from year to year, especially in spruce. Some difference in hardening was found between the current and the previous year's shoots. The rate of hardening increased typically around mid-September in both species, when the mean daily temperatures decreased to within the range of 5–10 °C.
Field performance of black spruce and jack pine inoculated with selected species of ectomycorrhizal fungi
Authors: Browning Mark H.R. , Whitney Roy D.
Published: October 2009

Seedlings of black spruce (Piceamariana (Mill.) B.S.P.) and jack pine (Pinusbanksiana Lamb.) were inoculated with fragmented hyphae of one of five species of ectomycorrhizal fungi and outplanted on reforestation sites after 14 weeks of growth in the nursery. Black spruce were planted on a peatland site and a stony loam site; jack pine were planted on the same stony loam site and on a sandy site. Inoculation of both species with Laccariaproximo (Boud.) Maire resulted in significantly better shoot growth compared with uninoculated seedlings over a 2-year period on all sites. Hebelomacylindrosporum Romagn. improved the height growth of black spruce on the peatland site and of jack pine on the stony loam site after 2 years. Laccariabicolor (Maire) Orton also improved the height growth of jack pine on the stony loam after 2 years. Black spruce inoculated with L. bicolor were significantly smaller than uninoculated seedlings. Size differences present in black spruce at outplanting persisted for two growing seasons, whereas initial size did not predict the field performance of jack pine. Inoculation of black spruce with L. proxima resulted in higher foliar concentrations of K and Zn compared with uninoculated seedlings on the peatland site. Foliar concentrations of N, P, K, and Zn in jack pine inoculated with L. proxima were significantly higher than those of uninoculated seedlings at the stony loam site. All inoculated fungi (except Pisolithustinctorius (Pers.) Coker & Couch, which did not form mycorrhizae) remained on the root systems for two growing seasons, but their presence declined sharply in the 2nd year. Laccariabicolor was the most persistent mycobiont on root systems of both tree species. Colonization of black spruce by indigenous ectomycorrhizal fungi was faster on the stony loam site than on the peatland site. The diversity of wild ectomycorrhizae on the planted seedlings was higher on both the peatland and sand sites than on the stony loam site.
Constrained empirical Bayes estimates for cell values in a two-way table
Authors: Green Edwin J. , Kohl Michael , Strawderman William E.
Published: October 2009

It is common to summarize the results of a forest inventory in two-way tables. Unfortunately, while the overall sample size may be large, the sample size for an individual cell in the table may be quite small. Thus the estimate may have a large standard error. We propose a simultaneous estimation method to reduce the variance and (or) mean squared error of individual cell estimates while retaining table additivity, i.e., preserving the observed row and column sums of the table.
Sapwood thickness in Pinuscontorta var. latifolia
Authors: Yang K.C. , Murchison H.G.
Published: October 2009

The vertical variation in the number of sapwood growth rings and sapwood thickness in Pinuscontorta Dougl. var. latifolia Engelm. was studied in relation to aspect, tree age, bole diameter, sapwood radial growth rate, and whole-xylem radial growth rate. Samples from 19 trees growing on the western slope of the Rocky Mountains near Kamloops, British Columbia, Canada, formed the data base. Sapwood width for individual trees ranged from 20 to 26 mm for both the east and west aspects, and was constant at various heights of the tree bole. Sapwood width for this species was found to be independent of age, diameter, sapwood radial growth rate, and whole-xylem radial growth rate. Sapwood consisted of 25 to 50 growth rings and decreased from the ground level upward to the tree crown. The number of sapwood growth rings was strongly correlated with age, diameter, and radial growth rates for both sapwood and the whole tree. No significant correlation existed between sapwood width and sapwood growth-ring counts.
Litter quality of native herbaceous legumes in a burned pine forest of the Georgia Piedmont
Authors: Hendricks Joseph J. , Boring Lindsay R.
Published: October 2009

The objectives of this study were to compare the nitrogen retranslocation efficiency and the litter substrate quality of eight native and one naturalized herbaceous legume species growing in a periodically burned pine forest of the Georgia Piedmont. A survey of the nine species revealed a wide range of nitrogen retranslocation (8.3–51.9%) from senescent leaf tissue, as well as differences in nitrogen concentrations (0.9–2.5%), C:N ratios (17.7–51.2), and initial lignin contents (8.6–20.1%) of senescent leaves. Intraspecific differences in Desmodiumviridiflorum L., Lespedezahirta L., and Lespedezaprocumbens Michx. were found in the leaf, stem, coarse- and fine-root tissue C:N ratio and in the lignin concentrations. Overall, the litter of these nitrogen-fixing herbaceous legumes is predicted to decompose at moderate rates and may have a significant effect upon the long-term soil organic matter and soil nitrogen accumulations of frequently burned forest sites.
Light rings and the age of jack pine trees
Authors: Volney W.J.A. , Mallett K.I.
Published: October 2009

In a routine determination of jack pine (Pinusbanksiana Lamb.) tree ages, several rings were overlooked or were difficult to count. Sections of the wood, when examined at higher magnification, revealed an unusually high proportion of "light rings." Light rings are characterized by having a small number of latewood cells whose walls are not as thick as those of latewood cells found in normal rings. Under low magnification, bands of these light rings may be interpreted as a single annual ring. Light rings may thus be a source of error in determining tree ages for forest productivity studies, particularly in older stands that have been affected by defoliators and root disease.
MULTI-SOLITON SOLUTIONS AND THEIR INTERACTIONS FOR THE (2+1)-DIMENSIONAL SAWADA-KOTERA MODEL WITH TRUNCATED PAINLEVÉ EXPANSION, HIROTA BILINEAR METHOD AND SYMBOLIC COMPUTATION
Authors: LÜ XING , GENG TAO , ZHANG CHENG , ZHU HONG-WU , MENG XIANG-HUA , TIAN BO
Published: October 2009

In this paper, the (2+1)-dimensional Sawada-Kotera equation is studied by the truncated Painlevé expansion and Hirota bilinear method. Firstly, based on the truncation of the Painlevé series we obtain two distinct transformations which can transform the (2+1)-dimensional Sawada-Kotera equation into two bilinear equations of different forms (which are shown to be equivalent). Then employing Hirota bilinear method, we derive the analytic one-, two- and three-soliton solutions for the bilinear equations via symbolic computation. A formula which denotes the N-soliton solution is given simultaneously. At last, the evolutions and interactions of the multi-soliton solutions are graphically discussed as well. It is worthy to be noted that the truncated Painlevé expansion provides a useful dependent variable transformation which transforms a partial differential equation into its bilinear form and by means of the bilinear form, further study of the original partial differential equation can be conducted.
DIGITAL STREAM CIPHER BASED ON SCS-PRBG
Authors: WANG XINGYUAN , LIU WEI , GU NINI , ZHANG HUAGUANG
Published: October 2009

Limitations caused by degeneration of dynamics characteristics may exist in the traditional single chaotic system. The authors propose a method i.e., switch controller chaos and pseudo random bit generator (it is called SCS-PRBG for short), which is based on multiple chaotic systems and switch control. By the theoretic analysis of random key stream and performance of SCS-PRBG, we can see that its digital stream cipher has better randomicity and security. And if using hardware parallel computation, the speed of encryption can be improved sharply. The results of the experiments also present better security of this arithmetic.
DELOCALIZATION IN ONE-DIMENSIONAL TOPOLOGICALLY DISORDERED SYSTEMS
Authors: BREZINI A. , FULDE P. , DAIRI M. , ZANOUN A.
Published: October 2009

A Kronig–Penney model with short-range correlated impurities is used to investigate the electronic transport properties of one-dimensional disordered systems simulating both superlattices, protein chains, and polymers. Physical magnitudes characterizing the electronic charge transfer are analytically the transmission coefficient and the localization length. It is shown that a set of delocalized states occurs at particular well-defined energies. The divergence of the localization length is investigated and a critical exponent 1 is found for the barrier case which differs with the results of literature. These results support the idea that the nature of the extended states depend on the typical nature of the correlation in disorder. On this basis, the conductance of disordered superlattices is investigated as well as the relative fluctuations of the transmission coefficient.
Latest Danian carbon isotope anomaly and associated environmental change in the southern Tethys (Nile Basin, Egypt)
Authors: Bornemann André , Schulte Peter , Sprong Jorinde , Steurbaut Etienne , Youssef Mohamed , Speijer Robert P.
Published: October 2009

During the Palaeocene and Eocene Epochs (65.5–33.9 Ma) the Earth experienced the warmest conditions of the Cenozoic. This Palaeogene greenhouse episode is characterized by several short-lived negative carbon isotope (δ
13
C) excursions, which are usually interpreted as transient warming events (‘hyperthermals') as indicated by rising temperatures of surface and bottom waters, and accompanied carbonate dissolution in deep-sea settings. Among these events, the Palaeocene–Eocene Thermal Maximum (PETM,
c
. 55.5 Ma) is globally the best documented and most prominent. Further negative δ
13
C anomalies have recently been identified in the Eocene, but the early to middle Palaeocene has mostly been neglected. Here, benthic foraminiferal δ
13
C records are presented from four upper Danian–lower Selandian sections in the Nile Basin (eastern Egypt). All records show a negative δ
13
C shift with an amplitude of up to 2‰ at the base of planktonic foraminiferal subzone P3b (
c
. 61 Ma). The supra-regional nature of this event is emphasized by correlation with a well-dated, similar δ
13
C record from Zumaia (Spain). Lithological changes, the δ
13
C signature and biotic responses strongly resemble those of the PETM in Egypt, which leads to the hypothesis that this ‘Latest Danian Event' (LDE) may represent another early Palaeocene hyperthermal.
Petrology, Sr–Nd–Hf isotopic geochemistry and zircon chronology of the Late Palaeozoic volcanic rocks in the southwestern Tianshan Mountains, Xinjiang, NW China
Authors: ZHU YONGFENG , GUO XUAN , SONG BIAO , ZHANG LIFEI , GU LIBING
Published: October 2009

The Late Palaeozoic volcanic rocks, mainly consisting of basalt, trachyte, trachy-andesite, andesite and rhyolite, widely distributed in the southwestern Tianshan Mountains, have been proven to be formed during Late Devonian to Late Carboniferous time (>361–313 Ma) based on zircon sensitive high-resolution ion microprobe dating. The geochemistry demonstrates that the studied volcanic rocks represent a continental arc formed during the subduction of the Palaeo-southern Tianshan Ocean. The ε
Hf(T)
values of zircons in these volcanic rocks vary from +1.4 to +15.6 with weighted average values of +9.5 (Late Devonian), +8.9 (Early Carboniferous) and +10.3 (Late Carboniferous), suggesting a depleted mantle origin. However, the Late Devonian basaltic samples have negative ε
Nd(T)
values (from −5.16 to −3.07) and high initial
87
Sr/
86
Sr ratios (0.7073–0.7098), whereas the Early Carboniferous volcanic rocks mostly have positive ε
Nd(T)
values (from −0.18 to +3.07) with low initial
87
Sr/
86
Sr ratios (0.7044–0.7067), and the Late Carboniferous volcanic rocks are characterized by high ε
Nd(T)
values (+2.79 to +5.89) and low initial
87
Sr/
86
Sr ratios (0.7032–0.7054). The assimilation–fractional crystallization (AFC) model is used to explain the isotope characteristics of the Late Devonian volcanic rocks in the southwestern Tianshan Mountains. Calculation shows that the Late Devonian samples could be formed by the AFC process between depleted mantle and continental crust. The Carboniferous basaltic rocks originated by partial melting of the mantle wedge.

Supplementary material:

Data are available at
http://www.geolsoc.org.uk/SUP18378
.
Eclogite–high-pressure granulite metamorphism records early collision in West Gondwana: new data from the Southern Brasília Belt, Brazil
Authors: RENO BARRY L. , BROWN MICHAEL , KOBAYASHI KATSURA , NAKAMURA EIZO , PICCOLI PHILIP M. , TROUW RUDOLPH A.J.
Published: October 2009

Nappes in the southern sector of the Southern Brasília Belt record suturing of the Paranapanema Block and Socorro–Guaxupé Arc with a subducted passive margin on the western side of the São Francisco Craton. We report secondary ion mass spectrometry U–Pb zircon ages that for the first time constrain the age of: (1) retrograded eclogite from a block along the tectonic contact beneath the uppermost nappe in a stack of passive margin-derived nappes; (2) high-pressure granulite-facies metamorphism in the uppermost passive margin-derived nappe; (3) high-pressure granulite-facies metamorphism in the overlying arc-derived nappe. Rare zircons from a retrograded eclogite yield a
206
Pb/
238
U age of 678 ± 29 Ma, which we interpret as most likely to date close-to-peak-
P
metamorphism and to provide a minimum age for detachment of the overlying passive margin-derived nappe from the subducting plate. Zircon associated with ilmenite in samples from two structural levels in the passive margin-derived high-pressure granulite nappe yields
206
Pb/
238
U ages of 648 ± 12 and 647 ± 11 Ma, and Ti-in-zircon crystallization temperatures from
c
. 860 °C down to
c
. 785 °C, but skewed toward the lower part of the range. These data indicate zircon formation during cooling from around peak
T
to the solidus, consistent with the high-
T
retrograde
P
–
T
path deduced from microstructures linked to phase assemblage fields in isochemical phase diagrams. Rb–Sr multi-mineral–whole-rock isochrons from two samples from close to the bottom of this nappe date formation of a retrograde sillimanite-bearing penetrative fabric to
c
. 590 Ma at temperatures of
c
. 750 °C (based on Ti-in-quartz thermometry). Rare zircons from leucosome in high-pressure granulite from the overlying arc-derived nappe yield a
206
Pb/
238
U age of 622 ± 28 Ma and Ti-in-zircon crystallization temperatures from
c
. 970 °C down to
c
. 820 °C, which we interpret to record formation of zircon during cooling from peak high-pressure granulite-facies conditions. These ages indicate that the first stage of craton amalgamation in West Gondwana may have occurred earlier than previously inferred.

Supplementary material:

Geochemical and geochronological data are available at
http://www.geolsoc.org.uk/SUP18377
.
Mechanical stratigraphy and folding style of the Lurestan region in the Zagros Fold–Thrust Belt, Iran
Authors: Farzipour-Saein A. , Yassaghi A. , Sherkati S. , Koyi H.
Published: October 2009

The structural style of the folds from the central part of the Lurestan salient located in the NW portion of the Zagros Fold–Thrust Belt has been studied by constructing a regional balanced cross-section from field data, existing geological maps, seismic profiles, stratigraphic surface sections and well data. The regional balanced structural cross-section that is constructed from the High Zagros Fault to the Mountain Front Fault highlights the difference in the folding style across the area. The vertical and lateral changes in the style of the folding indicate the influence of mechano-stratigraphic contrast between the sedimentary units. Three main décollement levels (the basal Lower Palaeozoic, the intermediate Triassic, and the upper Upper Cretaceous–Lower Palaeocene) have been interpreted. Folds developed during the Zagros Fold–Thrust Belt evolution above and below these décollement horizons are decoupled from each other and are different in both geometry and size. Similarly, thickness and facies changes of some formations across the region cause lateral variation in folding pattern from the north to the south. Polyharmonic folds exist in the south, where the different structural levels are relatively strongly coupled. To the north, however, strongly disharmonic folding occurs where a combination of increased décollement thickness and decreased mechanical competence has led to decoupling at different structural levels. This change in folding style has a direct impact on hydrocarbon exploration in the area. To reduce structural risk in exploration, the incorporation of high-resolution deep seismic data with the surface geology is recommended for future hydrocarbon exploration activities within the Lurestan region.
Late Jurassic palaeoclimatic change from clay mineralogy and gamma-ray spectrometry of the Kimmeridge Clay, Dorset, UK
Authors: HESSELBO STEPHEN P. , DECONINCK JEAN-FRANÇOIS , HUGGETT JENNIFER M. , MORGANS-BELL HELEN S.
Published: October 2009

The Late Jurassic was a time of increasing aridity in NW Europe. Here, a new clay mineral dataset is presented from a 600 m thick composite core through the Kimmeridge Clay Formation, southern England. Clay mineral assemblages comprise mainly illite and kaolinite, with minor randomly interstratified illite–smectite mixed-layer clays. SEM observations indicate that clay minerals are mainly detrital, except in silty strata of late Tithonian age, which contain abundant pore-filling kaolinite aggregates. Th/K ratios determined from gamma-ray spectrometry mirror palaeoclimatically significant variations in kaolinite/illite ratios, with notable exception where diagenetic kaolinite occurs. Comparison with age-equivalent strata identifies regional cyclic variations in clay minerals at the 100–300 m scale. Small-scale (10–20 m) variations in clay minerals and Th/K also occur. It is proposed that the region experienced progressively intense humidity through the Kimmeridgian, followed by a return to more arid conditions during the early Tithonian. Following a mid-Tithonian peak in aridity (the ‘Hudlestoni Event'), more humid climatic conditions returned prior to the development of latest Tithonian intense aridity. Late Jurassic climate was apparently subject to synchronously cyclic changes across a broad area of the Laurasian continent. Such changes could not have resulted from mountain building or continental rotations.

Supplementary material:

Clay data are available at
http://www.geolsoc.org.uk/SUP18376
.
Smothering of microbial mats by macrobiota: implications for the Ediacara biota
Authors: McILROY DUNCAN , BRASIER MARTIN D. , LANG ANDREW S.
Published: October 2009

Recent advances in understanding the preservation of the soft-bodied Neoproterozoic Ediacara biota have centred upon the role of microbes in casting the morphologies of static or dead macrobiota on the Precambrian sea floor. This experimental study explores the preservational effects brought about by the passive movement of dead macro-organisms upon a pre-established marine microbial mat under laboratory conditions. This demonstrates the potential for making multiple impressions of body tissues on the surface of microbial mats by means of passive transport alone. This throws doubt on the evidence for active feeding in Ediacaran fossils such as
Dickinsonia
and
Yorgia
.

Supplementary material:

Methods are available at
http://www.geolsoc.org.uk/SUP18375
.
Infracambrian petroleum play elements of the NE Taoudenni Basin (Algeria)
Authors: Rahmani A. , Goucem A. , Boukhallat S. , Saadallah N.
Published: October 2009

The Taoudenni Basin, North Africa's largest sedimentary basin, is located in western Mauritania, northern Mali and southwestern Algeria. Of the four petroleum wildcat wells drilled to date, the Abolag-1 well, Mauritania, yielded gas shows in Infracambrian (Neoproterozoic) stromatolitic carbonates. We present details of the different plays of the basin from the Chenachène region in Algeria. The Infracambrian is generally composed of three sedimentary packages: a basal sandstone (a unit of the Douik Group), overlain by carbonates (the Hank Group), sandstones and shales (the Dar Echeikh Group). The play is sourced by Infracambrian organic-rich black shales. In neighbouring Mauritania these were penetrated by water wells and shallow boreholes, containing in places >20% TOC. In the Hank Group the best reservoirs are associated with fractured intervals. The Dar Echeikh Group includes several potential reservoir units with porosities of up to 26%. Potential petroleum trap types in the Algerian part of the Taoudenni Basin are associated with folds, the basal Palaeozoic unconformity, and Infracambrian and Triassic–Jurassic half-graben.
Neoproterozoic timescales and stratigraphy
Authors: Smith Alan G.
Published: October 2009

The Infracambrian is a term for mostly Neoproterozoic successions in North Africa and areas to the east. Its base lies within the middle Neoproterozoic period, or Cryogenian, includes the youngest Neoproterozoic period, or Ediacaran, and continues into the early Cambrian to the level at which trilobites first appear. The Cryogenian lacks any biostratigraphic zonation; and no global biostratigraphic schemes exist for the Ediacaran. The formal classification of the Neoproterozoic is currently under review.

The Cryogenian–Ediacaran (CE) interval includes at least three prominent diamictite horizons that are clearly linked to penecontemporaneous glaciations. The oldest is ‘Sturtian’, next oldest is ‘Marinoan’ (probably the most extensive), both names are Australian in origin but are used internationally. The Gaskiers glaciation is the youngest and probably the least extensive. There are important unresolved problems of the precise number, age, extent and nomenclature of the Neoproterozic glaciations in Australia.

Several palaeomagnetic poles in the age range 600–550 Ma place glacial deposits of that age range in Australia in tropical latitudes. These data, together with older poles from Laurentia, gave rise to the notion of the Snowball Earth, in which the Earth froze over completely, but the profound refrigeration required appears to have had very little effect on biological evolution.

Biostratigraphic zonation with the precision attainable throughout the Phanerozoic does not appear possible for the CE interval. Thus, most correlations are based on about 40 U–Pb and Re–Os dates. These confirm the existence of at least three glacial sequences (sequence is used here as an informal term), but it is possible that the Sturtian and Marinoan were essentially one glacial unit. Deglaciation was accompanied by the unique ‘cap carbonates’.

The glacial sequences all show a characteristic δ
13
C pattern, but present knowledge is inadequate to use these patterns for detailed global correlation. The most reliable chemostratigraphic correlations are likely to be based on strontium isotope variations.

Black shale horizons commonly follow deglaciation. A few basins produce Neoproterozoic hydrocarbons; others are potential producers. As a whole, the Neoproterozoic represents both a scientific and an exploration frontier.
Late Proterozoic plate tectonics and palaeogeography: a tale of two supercontinents, Rodinia and Pannotia
Authors: Scotese Christopher R.
Published: October 2009

The plate tectonic and palaeogeographic history of the late Proterozoic is a tale of two supercontinents: Rodinia and Pannotia. Rodinia formed during the Grenville Event (
c
. 1100 Ma) and remained intact until its collision with the Congo continent (800–750 Ma). This collision closed the southern part of the Mozambique Seaway, and triggered the break-up of Rodinia. The Panthalassic Ocean opened as the supercontinent of Rodinia split into a northern half (East Gondwana, Cathyasia and Cimmeria) and a southern half (Laurentia, Amazonia–NW Africa, Baltica, and Siberia). Over the next 150 Ma, North Rodinia rotated counter-clockwise over the North Pole, while South Rodinia rotated clockwise across the South Pole. In the latest Precambrian (650–550 Ma), the three Neoproterozoic continents – North Rodinia, South Rodinia and the Congo continents – collided during the Pan-Africa Event forming the second Neoproterozoic supercontinent, Pannotia (Greater Gondwanaland). Pan-African mountain building and the fall in sea level associated with the assembly of Pannotia may have triggered the extreme Ice House conditions that characterize the middle and late Neoproterozoic. Although the palaeogeographic maps presented here do not prohibit a Snowball Earth, the mapped extent of Neoproterozoic ice sheets favour a bipolar Ice House World with a broad expanse of ocean at the equator. Soon after it was assembled (
c
. 560 Ma), Pannotia broke apart into the four principal Palaeozoic continents: Laurentia (North America), Baltica (northern Europe), Siberia and Gondwana. The amalgamation and subsequent break-up of Pannotia may have triggered the ‘Cambrian Explosion’. The first economically important accumulations of hydrocarbons are from Neoproterozoic sources. The two major source rocks of this age (Nepa of Siberia and Huqf of Oman) occur in association with massive Neoproterozoic evaporite deposits and in the warm equatorial–subtropical belt, within 30° of the equator.
187
Re-
187
Os geochronology of Precambrian organic-rich sedimentary rocks
Authors: Kendall Brian , Creaser Robert A. , Selby David
Published: October 2009

Global correlations of Precambrian stratigraphic successions can be hampered by the coarse resolution of biostratigraphic and chemostratigraphic records, and by the scarcity of reliable U–Pb zircon age constraints. The development of the
187
Re (rhenium)–
187
Os (osmium) radioisotope system as an accurate deposition-age geochronometer for organic-rich sedimentary rocks (e.g. black shales) holds great potential for an improved radiometric calibration of the Precambrian rock record. Here, we review Re–Os isotope data obtained for Precambrian black shales and revisit the discrepancy in Re–Os ages for the Neoproterozoic Aralka Formation (central Australia). In addition, we introduce new Re–Os isotope data for the Late Neoproterozoic Doushantuo Formation (South China) that highlights the necessity of a rigorous sampling protocol for depositional age determinations. Improvements in sampling and analytical methodologies have permitted the determination of precise ages (<1%, 2σ) from Late Neoproterozoic to Late Archaean shales. Whole-rock digestion using a Cr
VI
–H
2
SO
4
solution minimizes the release of detrital Re and Os from shale matrices, and selectively attacks organic matter that hosts hydrogenous Re and Os. The Re–Os system in organic-rich sedimentary rocks appears to be robust during hydrocarbon maturation and up to the onset of lowermost greenschist facies metamorphism, but post-depositional hydrothermal fluid flow can result in scattered Re–Os isotope data. The Re–Os black shale geochronometer should find utility for constraining the age of a diverse range of Precambrian geological phenomena. In addition, the initial
187
Os/
188
Os composition determined from Re–Os isochron regressions serves as a tracer for the Os isotope composition of Precambrian sea water.
Neoproterozoic-Early Cambrian (Infracambrian) hydrocarbon prospectivity of North Africa: a synthesis
Authors: Lottaroli Fabio , Craig Jonathan , Thusu Bindra
Published: October 2009

Despite the existence of proven Neoproterozoic–Early Cambrian (‘Infracambrian’) hydrocarbon plays in many parts of the world, the Neoproterozoic Eon, from 1000 Ma to the base of the Cambrian at 542 Ma, is relatively poorly known from a petroleum perspective. The so-called ‘Peri-Gondwanan Margin’ is one region of the Neoproterozoic world that is exciting particular interest in the search for ‘old’ hydrocarbon plays, mainly due to exploration success in time-equivalent sequences of Oman. The ‘Infracambrian’ succession in North Africa is widely accessible, and is already emerging as a hydrocarbon exploration target with considerable potential and with proven petroleum systems in different areas. The Taoudenni Basin (Mauritania, Mali, Algeria) in western North Africa is an underexplored basin, despite the Abolag-1 well (Texaco 1974) gas discovery. New palynological data have recently provided the first definitive Late Riphean age dates for the stromatolitic limestone reservoir sequence in Abolag-1. The widespread presence of stromatolitic carbonate units of potential reservoir facies in many parts of North Africa has been confirmed by new fieldwork in the Taoudenni Basin, in the Anti-Atlas region of Morocco and in the Al Kufrah Basin of Libya. Similar biostratigraphic age constraints have also been obtained from subsurface sequences of the Cyrenaica Platform bordering the East Sirte Basin of Libya, many of which have been traditionally assigned an ‘unconstrained’ Cambro-Ordovician age on the basis of lithological characteristics. Besides the proven, producing, weathered-granite reservoir in East Sirte Basin, the hydrocarbon potential of Neoproterozoic–Early Cambrian sequences developed in structural troughs bordering the south Cyrenaica Platform is still being evalutated. Neoproterozoic–Early Cambrian organic-rich strata with hydrocarbon source rock potential are widespread along the Peri-Gondwanan Margin. Some of the black shales encountered on the West African Craton may be as old as 1000 Ma and predate the Pan-African orogenic event. The Late Ordovician–Early Silurian systems in North Africa and the Middle East may form a good analogue for post-glacial source rock depositional systems in the Neoproterozoic, where black shale deposition may also have been triggered by post-glacial sea-level rise.
Infracambrian hydrocarbon source rock potential and petroleum prospectivity of NW Africa
Authors: Lüning S. , Kolonic S. , Geiger M. , Thusu B. , Bell J. S. , Craig J.
Published: October 2009

Proven Infracambrian hydrocarbon plays occur in various parts of the world, including Oman, the former Soviet Union, India, Pakistan and Australia. Organic-rich strata also occur in NW Africa, and gas shows originating from Infracambrian hydrocarbon source rocks are known from well Abolag-1 in the Mauritanian part of the Taoudenni Basin. The distribution of Infracambrian source rocks in North Africa is patchy and deposition commonly occurred in half-graben and pull-apart basins. In these intra-shelf basins, marine, organic-rich shales and limestones were deposited beneath the turbulent wave zone, away from the coarse siliciclastic Pan-African molasse detritus. On the West African Craton (including the Taoudenni Basin) organic-rich horizons were also deposited earlier, in pre- and syn-Pan-African times between 0.5 and 2 Ga (Ga is 10
9
years). The long-lasting sedimentation history in this area contrasts with that of the Pan-African regions, such as Oman, which lies in the Pan-African province of the East African Orogen, where preserved sediments are rarely older than 640 Ma. Infracambrian black phyllites in the Anti-Atlas region of Morocco were deposited on a continental slope of a short-lived ocean lying to the north of the West African Craton. Hydrocarbons generated during Infracambrian times from these deposits, however, have a low preservation potential.

Infracambrian organic-rich and/or black-pyritic deposits in North Africa are proven in the Taoudenni Basin, the Anti-Atlas and the Ahnet Basin. Thick carbonate successions exist in the Taoudenni Basin, indicating deposition in areas some distance from contaminating coarse siliciclastic hinterland influx. Infracambrian strata may also occur in the Tindouf Basin. However, their deep burial and consequent early maturation history may be unfavourable for the preservation of Infracambrian-sourced hydrocarbons in this area. Local development of Infracambrian source facies may also occur in the Reggane, Ahnet, Mouydir and Iullemeden basins, as indicated by black shales in wells MKRN-1 and MKRS-1 in the Ahnet Basin. Generally, however, these basins appear to be close to the active Pan-African orogenic belt and, consequently, probably received large quantities of coarse siliciclastic sediment, largely of continental facies, which may have diluted any significant hydrocarbon source potential.
Endocrine pulse identification using penalized methods and a minimum set of assumptions
Authors: Vis Daniel J. , Westerhuis Johan A. , Hoefsloot Huub C. J. , Pijl Hanno , Roelfsema Ferdinand , van der Greef Jan , Smilde Age K.
Published: October 2009

The detection of hormone secretion episodes is important for understanding normal and abnormal endocrine functioning, but pulse identification from hormones measured with short interval sampling is challenging. Furthermore, to obtain useable results, the model underlying hormone secretion and clearance must be augmented with restrictions based on biologically acceptable assumptions. Here, using the assumption that there are only a few time points at which a hormone is secreted, we used a modern penalized nonlinear least-squares setup to select the number of secretion events. We did not assume a particular shape or frequency distribution for the secretion pulses. Our pulse identfication method, VisPulse, worked well with luteinizing hormone (LH), cortisol, growth hormone, or testosterone. In particular, applying our modeling strategy to previous LH data revealed a good correlation between the modeled and measured LH hormone concentrations, the estimated secretion pattern was sparse, and the small and structureless residuals indicated a proper model with a good fit. We benchmarked our method to AutoDecon, a commonly used hormone secretion model, and performed releasing hormone infusion experiments. The results of these experiments confirmed that our method is accurate and outperforms AutoDecon, especially for detecting silent periods and small secretion events, suggesting a high-secretion event resolution. Method validation using (releasing hormone) infusion data revealed sensitivities and selectivities of 0.88 and 0.95 and of 0.69 and 0.91 for VisPulse and AutoDecon, respectively.