bluuebunny/crossref_metadata_2025 huggingface dataset:
Late Devensian and Holocene relative sealevel changes at Loch nan Eala, near Arisaig, northwest Scotland
Authors: Shennan Ian , Innes James B. , Long Antony J. , Zong Yongqiang
Published: February 2007

Pollen, diatom, radiocarbon and lithostratigraphical data from isolation basins in northwest Scotland are used to quantify the reference water (tide) level, indicative range and age of differenty types of isolation and connection contacts. Tendencies of sea‐level movement and relative sea‐level changes from the mid‐Lateglacial Interstadial (11.8 ka BP) to the late Holocene are constructed from these data.

Relative sea‐level fell continuously from + 17.8 m OD at 11.8 ka BP to ca. + 5.2 m OD at 10.1 ka BP. From an unkown minimum between 10 ka and 9 ka BP relative sea‐level then rose to +6.3 m OD at 8.3 ka BP. The maximum Holocene sea‐level occurred within the range +6.6 m OD to +9.3 m OD between 6.6 ka BP and 4.0 ka BP before falling to present. Isobase, age‐altitude and quantitative rebound models for northwest Scotland are tested using these sealevel data, but none of the published models shows close agreement with the new results.
Late Devensian and Holocene palaeoecology and palaeoenvironments of the Morrone Birkwoods, Aberdeenshire, Scotland
Authors: Huntley Brian
Published: February 2007

Results are presented from analyses of pollen, vascular plant macrofossils and bryophyte remains at the Morrone Birkwoods, a site in the eastern Highlands of Scotland. The sedimentary record spans the past ca. 12 500 yr and is dated by a series of radiocarbon determinations.

Quantitative palaeoclimate reconstructions are made using pollen‐climate response surfaces, with the selection of analogues constrained using evidence from the macrofossil stratigraphy. The results generally are in remarkably close agreement with those reconstructed from beetle remains by Atkinson et al. The only significant discrepancy is with respect to the extent of the warming at ca. 12500 yr BP.

The palaeoclimate record indicates a marked cooling that coincides in age with the ‘Older Dryas’ event and which interrupts an overall cooling trend throughout the duration of the late‐glacial interstadial that culminates in the ‘Younger Dryas’. There is also evidence of a climate fluctuation during the first 500 yr of the Holocene. The mid‐ and late Holocene record of palaeoclimate is, in contrast, remarkably invariant until the last ca. 1500 yr, during which there is evidence of a period of warming followed by a subsequent cooling; it is speculated that these may correspond to the ‘Medieval Warm Period’ and to the ‘Little Ice Age’ respectively.

The Morrone Birkwoods are noted today for their sub‐Arctic vegetation and their rich flora, with the Arctic—Alpine and northern montane biogeographical elements especially well represented. The macrofossil record indicates that the flora has long had this general character, whilst both this and the pollen record indicate that the sub‐Arctic character of the vegetation has most likely persisted since earliest Holocene times.
Strandflat development and Quaternary shorelines on Tiree and Coll, Scottish Hebrides
Authors: Dawson Alastair G.
Published: February 2007

The islands of Tiree and Coll in the Scottish Inner Hebrides are dominated by staircases of glaciated rock‐platform surfaces in Lewisian gneiss that are interpreted here as areas of strandflat. The rock platform surfaces exhibit differential glacio‐isostatic uplift from east to west and are considered to indicate at least four separate periods of strandflat formation during prolonged intervals of Quaternary cold climate. It is suggested that many of the well‐known areas of high rock platform located farther east in the Scottish Inner Hebrides represent eroded remnants of the strandflat surfaces described here. The existence of the Tiree and Coll strandflat surfaces in conjunction with their formation during periods of Quaternary glaciation implies that they were produced during periods when mainland Scotland was ice‐covered yet when the western margin of the ice sheet was normally located east of these islands. A prominent Late‐glacial raised shoreline also occurs on both islands and declines in altitude to the west, from 22 m in northeastern Coll to 9 m in western Tiree. It is believed that this shoreline, whose regional gradient is 0.39 m km−1, may represent part of the Main Wester Ross Shoreline that was formed in the Northwest Highlands of Scotland during a period of glacial advance that interrupted the decay of the last (Late Devensian) ice sheet. The general similarity in altitude between the Late‐glacial shoreline features and rock platform surfaces implies that during each period of Quaternary strandflat formation, relative sea‐level returned to the same approximate position. This would appear to indicate that the glacio‐isostatic and glacio‐eustatic components affecting the positions of relative sea level in Scotland have remained in approximate equilibrium throughout the duration of the Quaternary.
Late middle pleistocene interglacial deposits at upper strensham, worcestershire, england
Authors: de Rouffignac C. , Bowen D. Q. , Coope G. R. , Keen D. H. , Lister A. M. , Maddy D. , Robinson J. E. , Sykes G. A. , Walker M. J. C.
Published: February 2007

Pleistocene deposits containing the disarticulated skeleton of a mammoth, and associated faunal and floral remains, were discovered in July 1990 at Upper Strensham, Worcestershire. The environmental evidence from the fauna and flora together with limited geological evidence, indicates that the deposits accumulated within a low energy fluvial environment with a surrounding marsh and restricted tree cover on, or close to, the floodplain. The patchy occurrence of trees in a species‐rich grassland is discussed, and the climatic significance of the fauna and flora is considered.

The Strensham site lies within the valley of the River Avon, which is known to contain at least five altitudinally distinct river terraces. The deposits at Strensham lie beneath a terraced surface that cannot be accommodated within the existing framework of terrace development in the valley, and evidence is presented which may suggest that these deposits form a previously unrecognised fluvial unit, the Strensham Member of the Avon Valley Formation. Amino‐acid age estimates from shells taken from the fossiliferous sediments of the Strensham Member suggest a correlation with Oxygen Isotope Stage 7. This correlation suggests that the temperate deposits at this site should be correlated with the temperate phase recorded at Marsworth, Buckinghamshire and Stoke Goldington in the valley of the Great Ouse.
A Late‐glacial colluvial sequence at Watcombe Bottom, Ventnor, Isle of Wight, England
Authors: Preece R. C. , Kemp R. A. , Hutchinson J. N.
Published: February 2007

In a dry valley near Ventnor, Isle of Wight, thick subaerial slope deposits of Devensian Late‐glacial age overlie the Chalk. The deposits are crudely stratified chalk muds and rubble produced by frost‐shattering, and moved downslope by the release of water from melting snow‐fields and frozen ground. A laterally extensive humic horizon of a rendzina soil occurs within the sequence, clearly reflecting a period of relative slope stability. In places this horizon divides and its upper surface appears to have been disturbed, possibly by cryoturbation. Micromorphological and other analyses confirm the pedogenic origin of this humic horizon, but also demonstrate the occurrence of pedological features both above and below it. The humic horizon therefore is not a ‘buried’ soil in the strictest sense, but is part of a vertical sequence representing a single complex soil with transported, accretionary and welded components.

Molluscan analyses reveal that the sequence can be divided into four local mollusc zones, showing a progressive increase in faunal diversity throughout the profile. This succession is broadly similar to other Late‐glacial sequences described from south‐east England. Minute fragments of charcoal from the lower part of the humic horizon have yielded an AMS date of 11690 ± 120 vr BP, demonstrating formation during the ‘Allerød phase’ of the Late‐glacial Interstadial. This humic horizon is correlated provisionally with the ‘Pitstone Soil’, even though existing dates from its type‐site in Buckinghamshire are somewhat younger.
Rapid late‐glacial atmospheric CO2 changes reconstructed from the stomatal density record of fossil leaves
Authors: Beerling David J. , Birks Hilary H. , Woodward F. Ian
Published: February 2007

The Younger Dryas stadial (11 000‐10 000 yr BP) was an abrupt return to a glacial climate during the termination of the last glaciation. We have reconstructed atmospheric CO2 concentrations from a high‐resolution sequence of fossil Salix herbacea leaves through this climatic oscillation from Kråkenes, western Norway, using the relationship between leaf stomatal density and atmospheric CO2 concentration. High Allerød CO2 values (median 273 ppmv) decreased rapidly during 130–200 14C‐years of the late Allerød to ca. 210 ppmv at the start of the Younger Dryas. They then increased steadily through the Younger Dryas, reaching typical interglacial values once more (ca. 275 ppmv) in the Holocene. The rapid late Allerød decrease in CO2 concentration preceded the Younger Dryas temperature drop, possibly by several decades. This striking pattern of changes has not so far been recorded unambiguously in temporally coarse measurements of atmospheric CO2 from ice cores. Our observed late‐glacial CO2 changes have implications for global modelling of the ocean‐atmosphere‐biosphere over the last glacial‐interglacial transition.
Optimisation of production and storage stability of the starter bacteria Streptococcus thermophilus and Lactobacillus plantarum
Authors: Selma Maria V , MacNaughtan William , Mitchell John , Waites William
Published: February 2007

The growth of Lactobacillus plantarum and Streptococcus thermophilus was modelled by fitting isothermal calorimetric traces to arbitrary mathematical functions. There was a correlation between certain features on the thermal trace and parameters derived from a Baranyi fit to viable count data. In the presence of 75 g L−1 lactose, S. thermophilus showed a slower rate of growth than in the presence of 5 g L−1 lactose when measured by both viable count and heat flow. A simple equation described the variation in glass transition temperature with water activity for all preparations. A master curve fit for all mortality data for S. thermophilus showed the importance of a transition temperature for the survival of freeze‐dried preparations of bacteria. The temperature at which survival began to be impaired was 15–20 °C below the glass transition temperature determined by differential scanning calorimetry. Copyright © 2007 Society of Chemical Industry
Effect of salts on the solubility of phenolic compounds: experimental measurements and modelling
Authors: Noubigh Adel , Mgaidi Arbi , Abderrabba Manef , Provost Elise , Fürst Walter
Published: February 2007

Phenolic compounds can be found in industrial or agricultural waste, such as waste water from olive mills. Because of the environmental problem caused by this residue from olive oil production, the aim of this work was to model the effect of salts on the solubility of four phenolic compounds. For this purpose, the solubilities of gallic acid, protocatechuic acid, vanillic acid and vanillin have been measured in various chloride solutions at constant temperature. The Clegg–Simonson–Pitzer activity coefficient, together with the dissociation constant obtained from the literature, has been used to represent the equilibrium solid‐liquid data. Good agreement (3.4%) between the experimental and calculated values for solubility was obtained. Copyright © 2007 Society of Chemical Industry
Synthesis and Characterization of N‐Propargyl Cinnamamide Polymers and Copolymers
Authors: Deng Jianping , Wang Jianmin , Zhao Weiguo , Zhang Zhigang , Yang Wantai
Published: February 2007

This paper deals with synthesis and characterization of a novel poly(N‐propargylamide) containing cinnamamide groups (poly(1)) in its side chains. Monomer 1, CHCCH2NHCOCHCH(C6H5), was synthesized and polymerized with a rhodium catalyst, (nbd)Rh+B−(C6H5)4 (nbd = 2,5‐norbornadiene). Effects of some factors on polymerization of monomer 1 such as solvent, temperature, and the ratio of monomer/catalyst were investigated in detail; polymers with moderate number‐average molecular weights ($\overline M _{\rm n}$) and low index of polydispersity ($\overline M _{\rm w} /\overline M _{\rm n}$) were obtained. To improve the polymers' solubility and to elucidate whether poly(1) could form helical conformation, another N‐propargylamide monomer 2, CHCCH2NHCOCH(CH2CH3)2, was employed to accomplish copolymerization with monomer 1. Copolymerization with monomer 2 improved obviously the solubility of the (co)polymers; the copolymers with certain monomer ratios could form helices under the examined conditions according to the related UV‐vis spectra.

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Second‐trimester uterine artery Doppler pulsatility index and maternal serum PP13 as markers of pre‐eclampsia
Authors: Spencer Kevin , Cowans Nicholas J. , Chefetz Ilana , Tal Joseph , Kuhnreich Ido , Meiri Hamutal
Published: February 2007

Objective

To evaluate whether measurement of maternal serum PP13 at 22 to 24 weeks of gestation, alone or in combination with second‐trimester biochemical markers or uterine artery pulsatility measured by Doppler velocimetry, is useful in predicting those women at risk of developing pre‐eclampsia.

Study Design

A nested case‐control study of pre‐eclampsia cases with controls matched for gestational age and storage time for the maternal serum. PP13 was tested by an ELISA, with the samples blinded to pregnancy outcome. All patients also underwent uterine artery Doppler flow velocimetry at 22–24 weeks to measure the mean pulsatility index (PI). Results for Inhibin, Activin, PAPP‐A and Free β‐hCG were available from previous studies.

Results

There were 73 controls and five cases with early pre‐eclampsia in which delivery was induced prior to 35 weeks. In addition, there were a further seven cases with pre‐eclampsia in which delivery was not induced before term. Median PP13 levels for controls and all cases were 295.9 and 212.6 pg/ml, and 171.2 pg/ml amongst the early pre‐eclampsia cases, with the MoMs 1.00, 0.94 and 0.63, respectively (p < 0.001). Receiver operator characteristic (ROC) curve analysis for either all cases or early cases versus controls yielded areas under the curve of 0.588 (95% CI: 0.42–0.76; p = 0.1526) and 0.693 (0.47–0.92; p = 0.0441) for PP13. At a specificity set to 0.80, the sensitivity for PP13 in the early cases was 0.40 and that in all cases was 0.25. Combining PP13 bivariately with any of the markers (PI, PAPP‐A, Activin, Inhibin or Free β‐hCG) tested in the 22–24 week period did not improve the detection of early, late or all cases of pre‐eclampsia compared with either marker alone.

Conclusion

Late second‐trimester PP13 alone is unlikely to be useful in predicting pre‐eclampsia and early pre‐eclampsia, and its prediction does not increase when coupled with second‐trimester Doppler PI or other potential biochemical markers. Measuring between‐trimester temporal changes may be worthy of further investigation. Copyright © 2007 John Wiley & Sons, Ltd.
Toughening of polypropylene combined with nanosized CaCO3 and styrene–butadiene–styrene
Authors: Yu Jianghua , Wang Guoquan , Chen Jianfeng , Zeng Xiaofei , Wang Wenyi
Published: February 2007

Nanocomposites of nanosized CaCO3/SBS/PP were prepared by using twin‐screw and single‐screw extruder. By adding nanosized CaCO3 particles into SBS/PP blend, the notched impact strength, flexural modulus, and tensile strength of the composites can be improved, whereas, by adding microsized CaCO3 particles into SBS/PP blend, the notched impact strength of the composite is decreased markedly. At nanosized CaCO3 content of 16 phr (parts per hundred PP resin by weight), the impact strength of nanosized CaCO3/SBS/PP composite reaches 56.55 KJ/m2, which is 1.27 times that of SBS/PP blend. At nanosized CaCO3 content of 4 phr, the tensile strength of the composites reaches 31.3 MPa, which is 1.23 times that of SBS/PP blend. The maximum and balanced torque of the composites improves significantly by the addition of CaCO3 nanoparticles. The increased shear force during compounding continuously breaks down SBS particles, resulting in the reduction of the SBS particles size, and improving the dispersion of SBS particles in PP matrix. Thus the toughening effect of SBS on matrix was improved. Simultaneously, the existence of SBS provides the matrix with a good intrinsic toughness, satisfying the condition that nanosized inorganic particle of CaCO3 efficiently toughens polymer matrix. The synergistic toughening function of nanosized CaCO3 and SBS on PP matrix was exhibited. POLYM. ENG. SCI. 47:201–206, 2007. © 2007 Society of Plastics Engineers
Preparation, surface chemistry, and electrical conductivity of novel silicon carbide/polypyrrole composites containing an anionic surfactant
Authors: Mičušík Matej , Omastová Mária , Boukerma Kada , Albouy Aurélie , Chehimi Mohamed M. , Trchová Miroslava , Fedorko Pavol
Published: February 2007

Novel silicon carbide/polypyrrole (SiC/PPy) conducting composites were prepared using silicon carbide as inorganic substrate in the presence or absence of an anionic surfactant, dodecylbenzenesulfonic acid (DBSA). The surface modification of SiC particles was performed in aqueous solution containing the anionic surfactant by oxidative polymerization of pyrrole using ferric chloride as oxidant. Ash content analysis was used to determine the mass loading of organic fraction in the SiC/PPy composites. Scanning electron microscopy showed the surface modification of SiC by PPy. The presence of PPy in the composites was confirmed by infrared spectroscopy. The small gradual red shift of the band of the stretching vibrations of SiCO and SiOSi bonds and more intensive of PPy spectrum were observed when DBSA was used for composite preparation. The presence of both polypyrrole and surfactant was also detected by their respective N1s and S2p core level peaks recorded by X‐ray photoelectron spectroscopy. The electrical conductivity of SiC‐DBSA/PPy composites depends on PPy content at the surface and on pyrrole/DBSA molar ratio. The DBSA‐containing composites have a conductivity about 2 orders of magnitude higher than in the case of the composites prepared without DBSA when PPy loading was lower than 15 wt%. Above this PPy loading the difference in conductivity almost diminished due to a increased amount of PPy polymerized on the surface of the SiC substrate. SiC‐DBSA/PPy composites containing 15 wt% PPy prepared using a molar ratio pyrrole/DBSA = 5, exhibited a very hydrophobic behavior compared to the corresponding DBSA‐free composites, as they floated on water and did not sediment even after a prolonged period of time. POLYM. ENG. SCI., 47:1198–1206, 2007. © 2007 Society of Plastics Engineers
Effect of P‐induced gettering on extended defects in n‐type multicrystalline silicon
Authors: Acciarri M. , Binetti S. , Le Donne A. , Marchionna S. , Vimercati M. , Libal J. , Kopecek R. , Wambach K.
Published: February 2007

The electrical properties and the minority charge carrier recombination behaviour of grain boundaries (GBs) and intragrain dislocations in different n‐type multicrystalline silicon (mc‐Si) ingots were systematically studied through microwave‐detected PhotoConductance Decay (µW‐PCD), Electron Beam Induced Current (EBIC) and PhotoLuminescence (PL) spectroscopy on as‐grown samples and on samples submitted to P‐diffusion step. It was confirmed that the overall quality of n‐type mc‐Si is high, indicating that n‐type‐Si is a valid source for photovoltaic applications. As expected, the average lifetime increases after the P‐diffusion process, which induces impurity gettering effects at the external surfaces, like in the case of p‐type samples, but an evident local increase of electrical activity of some GBs after that process was also observed using the EBIC mapping technique. Apparently, a redistribution of impurities occurs at the processing temperature and impurities are captured at the deepest sinks. In fact, while all GBs act as heterogeneous segregation/precipitation sites, some of them will compete with the external surfaces sinks, partly vanishing the effect of P‐gettering. Last but not least, it was experimentally demonstrated that the average lifetime values measured with the µW‐PCD technique well correlate with the recombination activity of GBs measured with the EBIC technique, showing the extreme importance of GBs on the effective lifetime of this material. Copyright © 2007 John Wiley & Sons, Ltd.
Rule of five cyclizations in 5‐hexenyl radicals and photocycloadditions of 1,5‐hexadienes: effect of 4‐oxa substitution
Authors: Matlin Albert R. , Brinton Karen Feit , Nivaggioli Belinda Tsao
Published: February 2007

The effect of 4‐oxa substitution on the regiochemistry and rate of 5‐hexenyl radical cyclizations was investigated, as a potential model for [2 + 2] photocycloadditions of 2‐acyl‐4‐oxa‐1,5‐hexadienes. Increasing the electron density in the alkene decreases the rate of cyclization in the 4‐oxa‐hexenyl radicals, relative to the all carbon analogs, but has little effect on the regioselectivity of the cyclization. The radical model does not reproduce the high degree of 1,6 closure, observed in the [2 + 2] photocycloadditions for 4‐oxa‐1,5‐hexadiene 1a. However, the radical model does reinforce the interpretation that ground state conformational effects, engendered by substitution remote from the reacting centers have important rate consequences for cyclization reactions. Copyright © 2007 John Wiley & Sons, Ltd.
Transesterification of an RNA model in buffer solutions in H2O and D2O
Authors: Virtanen Noora , Nevalainen Ville , Lehtinen Taru , Mikkola Satu
Published: February 2007

Transesterification of a phosphodiester bond of RNA models has been studied in various buffer solutions, under neutral and slightly alkaline conditions in H2O and D2O. The results show that imidazole is the only buffer system where a clear buffer catalysis on the cleavage of a phosphodiester bond is observed. The rate enhancement in sulphonic acid buffers is smaller, and a sulphonate base, particularly, is inactive as a catalyst. The rate‐enhancing effect of imidazole is, however, catalytic, and the catalytic inactivity of sulphonate buffers can be attributed to their structure and/or charge. The catalysis by imidazole is a complex system which, in addition to first‐order reactions, involves a process that shows a second‐order dependence in imidazole concentration. The latter reaction becomes significant in acidic imidazole buffers (pH < pKa), as the buffer concentration increases. The kinetic solvent deuterium isotope effect kH/kD, referring to first‐order catalysis by imidazole base, is 2.3 ± 0.3. That referring to second‐order catalysis is most probably much larger, but an accurate value could not be obtained. Copyright © 2007 John Wiley & Sons, Ltd.
Effects of ortho‐substituents in SE1 protonolysis of phenylmercuric chloride
Authors: Wang Yulan , Zhang Jinli , Wu Yangjie
Published: February 2007

The kinetics of the reactions of o‐substituted phenylmercuric chlorides, o‐RC6H4HgCl (R = CH3, H, C2H5O, CH3O, C6H5, F, COOC2H5, Cl, Br, CF3, NO2), with hydrochloric acid in 80% aqueous dioxane in the presence of NaI were studied. The reactions are of the first order. The rate constant at 40°C decreases in the order of R: CH3 > H > C2H5O > CH3O > C6H5 > F > COOC2H5 > Cl > Br > CF3 > NO2. The analysis of effects of those o‐substitutes is carried out through multiple regression of log k/kH with the corresponding inductive substituent constants σI and the various resonance substituent constants σ, σR(BA), σ, σ and σx, and the corresponding Swain–Lupton field effect constant $\Im $ and resonance effect constant $\Re $. The results showed that o‐substituent intramolecular coordination with the neighbor mercury (field effect) is the main effect in effects of o‐substituents on rate of the SE1 protonolysis. Copyright © 2007 John Wiley & Sons, Ltd.
Cryoelectrochemical reduction of a phenyl sulfide in tetrahydrofuran: mediated reduction gives different products compared to direct reduction
Authors: Burasov Alexander V. , Paddon Christopher A. , Bhatti Farrah L. , Donohoe Timothy J. , Compton Richard G.
Published: February 2007

An electrocatalytic reduction of [(3‐{[trans‐4‐(methoxymethoxy)cyclohexyl]oxy}propyl)thio]benzene (RSPh) in the presence of naphthalene as a mediator is investigated, using steady‐state voltammetry at various sized platinum microelectrodes and at low temperature (201 K) in tetrahydrofuran (THF). This mediated process has been found to involve the transfer of one electron, in contrast to the direct electrochemical reduction which involves two electrons. In addition, the mediated reduction proceeds at a potential, some 500 mV less negative than the direct electrochemical reduction. The evidence for the proposed mechanism has been obtained from theoretical simulations, using DIGISIM which shows satisfactory fitting to experimental results and allowed the determination of the rate constant for the homogeneous step. In contrast to direct reduction of RSPh where only one product, trans‐1‐ (methoxymethoxy)‐4‐propoxycyclohexane (RH), has been obtained, the isolation of two products, RH and the dimer, diphenyl disulfide, PhSSPh, following mediated preparative electrolysis of RSPh, in presence of naphthalene shows that this one‐electron process may be carried out at the reduction potential of naphthalene at low temperature and has also validated deductions made from voltammetric results. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis, dynamic light scattering, and luminescence properties of copolymers containing iridium(III) bisterpyridine in the side chain
Authors: Aamer Khaled A. , Tew Gregory N.
Published: February 2007

Supramolecular block‐random copolymers containing [Ir(terpy)2]3+ in the side chain were synthesized via postfunctionalization of a P(S‐b‐ACterpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐ACterpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007
Temperature‐induced spontaneous sol–gel transitions of poly(D,L‐lactic acid‐co‐glycolic acid)‐b‐poly(ethylene glycol)‐b‐poly(D,L‐lactic acid‐co‐glycolic acid) triblock copolymers and their end‐capped derivatives in water
Authors: Yu Lin , Chang Guangtao , Zhang Huan , Ding Jiandong
Published: February 2007

The spontaneous hydrogel formation of a sort of biocompatible and biodegradable amphiphilic block copolymer in water was observed, and the underlying gelling mechanism was assumed. A series of ABA‐type triblock copolymers [poly(D,L‐lactic acid‐co‐glycolic acid)‐b‐poly(ethylene glycol)‐b‐poly(D,L‐lactic acid‐co‐glycolic acid)] and different derivatives end‐capped by small alkyl groups were synthesized, and the aqueous phase behaviors of these samples were studied. The virgin triblock copolymers and most of the derivatives exhibited a temperature‐dependent reversible sol–gel transition in water. Both the poly(D,L‐lactic acid‐co‐glycolic acid) length and end group were found to significantly tune the gel windows in the phase diagrams, but with different behaviors. The critical micelle concentrations were much lower than the associated critical gel concentrations, and an intact micellar structure remained after gelation. A combination of various measurement techniques confirmed that the sol–gel transition with an increase in the temperature was induced not simply via the self‐assembly of amphiphilic polymer chains but also via the further hydrophobic aggregation of micelles resulting in a micelle network due to a large‐scale self‐assembly. The coarsening of the micelle network was further suggested to account for the transition from a transparent gel to an opaque gel. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1122–1133, 2007
Mechanical weathering rates on Signy Island, maritime antarctic
Authors: Hall Kevin
Published: February 2007

By means of re‐evaluating a number of properties of rock tablets left in the field for varying time periods, an estimation of rock breakdown rates is attained. From data obtained during the last five years, it would appear that rates are very slow, only of the order of 2% mass loss per 100 years. These rates refer to omnidirectionally frozen, relatively wet samples and, on the basis of laboratory simulation results, are over 50 times greater than for unidirectionally frozen bedrock. It is suggested that mechanical weathering rates in the maritime Antarctic are very slow.
A note on biological weathering on nunataks of the juneau icefield, Alaska
Authors: Hall Kevin , Otte Wulf
Published: February 2007

Observations on a number of nunataks of the Juneau Icefield indicate that chasmolithic algae play a major role in the breakdown of granitic rock. Expansion and contraction of the algal mucilage, caused by wetting and drying episodes, results in the surface flaking of the rock. Available data suggest that the average mass of material lost per year from 1 m2 of rock could be as high as 562 g. It is suggested that biological weathering may be a major destructive mechanism of the granitic lithologies.
Relict periglacial features east of waterton‐glacier parks, alberta and montana, and their palaeoclimatic significance
Authors: Karlstrom Eric T.
Published: February 2007

Stratigraphy and inferred genesis of relict periglacial features east of Waterton‐Glacier Parks provide information on the magnitude of Quaternary climate changes. Periglacial wedges, involutions, patterned ground and soil wedges are locally preserved in pre‐Wisconsinan outwash/ alluvium and till on a series of erosion surfaces east of the Lewis Range mountain front and in Wisconsinan outwash near Cutbank, Montana. Formation of periglacial wedges required development of perennially frozen ground and mean annual temperatures at least about 10°C below those of today. All the observed relict periglacial features occur within about 20 km of Wisconsinan glacier margins. Strongly weathered, 2+ m thick, pre‐Illinoian palaeosols, also preserved locally on the erosion surfaces, are truncated and/or completely stripped in the areas most affected by cryoturbation. Hence, most of the periglacial features postdate the palaeosols. Stratigraphic and geomorphic relations suggest that the periglacial features formed during at least three glacial/periglacial episodes, probably including the Wisconsinan, Illinoian and a pre‐Illinoian glaciation.
Sedimentology and genesis of slope deposits at sonskyn, Eastern Cape Drakensberg, South Africa
Authors: Hanvey Patricia M. , Lewis Colin A.
Published: February 2007

The morphology and sedimentology of slope deposits exposed in a road cutting at Sonskyn are examined. The deposits have a lobate morphology and extend outwards from the lower reaches of a basin hollow at an altitude of approximately 2000 m a.s.l. The general stratigraphy shows an upward sequence from shattered bedrock and isolated pockets of colluvium, through stratified angular sediments which in turn are truncated by a series of channelized bouldery deposits.

The concentration of colluvium towards the base of the sequence, together with the subjacent shattered bedrock, suggest cold‐climatic conditions, a scarcity of vegetation cover and slopewash processes. The transition up‐sequence to more clastic stratified sediments is indicative of freeze‐thaw cycles accompanied by slopewash during the melting phases. This has been attributed to the seasonal ablation of a snow patch. The overlying channelized bouldery deposits are attributed to solifluction processes related to the final dissolution of the snow patch.

Palaeolithic artefacts found within the stratified sediments were used in southern Africa between 140000 and 40000 years BP. This indicates that the slope deposits at Sonskyn were laid down within the last 140000 years.
Pentes, Granulométrie et Mobilité des Matériaux le long d'un Talus d'Eboulis en Milieu Alpin
Authors: Francou Bernard
Published: February 2007

On a sélectionné dans les Alpes deux talus d'éboulis présentant un matériel de faible cohésion sur le profil desquels on a fait des mesures de pente et de granulométrie selon un pas régulier. Sur l'un d'eux, on a relevé et localisé les apports reçus de la corniche pendant 10 ans et mesuré le déplacement des fragments pendant 2 ans. Le traitement statistique de ces données et les résultats obtenus convergent vers un modèle biphasé de ce type d'accumulation: le segment proximal fonctionne en accumulation‐transit, le segment distal en accumulation pure. Le passage d'une phase à l'autre se réalise par un point de rupture dynamique bien repérable sur le profil. Ce modèle remet en question les précédents, notamment ceux qui ont été conçus à partir de talus artificiels.
Localisation, Genèse et Fonte de Quelques Naleds du Nord du Yukon (Canada)
Authors: Lauriol B. , Clark J. Cinq Mars Et I. D.
Published: February 2007

Les naleds sont fréquents dans le nord du Yukon, surtout dans le lit des rivières qui entaillent les monts British et Richardson. Presque tous se situent dans le voisinage de massifs calcaires et de failles. Leur épaisseur atteint plusieurs mètres et leur surface peut couvrir des kilomètres carrés. Le plus grand, celui de la rivière Firth, atteint 28 km2. Les eaux et les dépéts de calcite de quatre naleds, ceux de Timber Creek, Fish Hole Creek, Babbage River et Salmon Fork River ont fait l'objet d'analyses isotopiques é18O, é13C et é2H. Les résultats indiquent que l'origine des eaux est locale et que leur gel par la base est un processus assez lent, ce qui permet à la calcite de pr°Cipiter en équilibre á une température proche de 0 °C. Une comparaison entre la superficie du naled de la rivière Firth au cours de l'été et les valeurs de rayonnement solaire enregistrées à Inuvik, montre une bonne corrélation.
Changes in microstructure of fine‐grained soils due to freezing
Authors: Grechishchev S. E. , Pavlov A. V. , Ponomarev V. V.
Published: February 2007

A microstructural model of thermorheological processes during the freezing of fine‐grained soils is described. Using electron microscopy and X‐ray diffractometry, the changes due to freezing in the microstructures of kaolin, bentonite and askangel were experimentally studied. Curves of aggregate distribution and pore size for different freezing periods are presented. It is shown that there is good agreement between experimental results and theoretical hypotheses.
Prospecting and mapping of mountain permafrost and associated phenomena
Authors: King Lorenz , Gorbunov Aldar P. , Evin Michèle
Published: February 2007

Geomorphologists as well as engineering geologists are increasingly interested in the prediction and mapping of mountain permafrost and associated phenomena. Using several indirect geophysical and geomorphological methods, it is possible to detect and map permafrost that is usually invisible at the surface. This paper summarizes the merits of the most frequently used methods, their difficulties and limitations, and gives recommendations on how to use them. Brief recommendations for future research are also given.
Present‐day periglacial processes and landforms in mountain areas
Authors: Lautridou J. P. , Francou B. , Hall K.
Published: February 2007

This paper outlines recent advances in our understanding of periglacial processes and landforms in mountain areas, as reported in the literature over the last 8 years. Landforms investigated include rockwalls, screes, avalanche paths, bedded slope deposits and patterned ground phenomena. Processes subject to quantification include cliff recession, rock displacements on slopes, rock thermal and moisture regimes, frost creep, mass wasting and solution. Laboratory experimentation and modelling studies have also been undertaken.
Construction, environmental problems and natural hazards in periglacial mountain belts
Authors: Haeberli Wilfried
Published: February 2007

Experience with man‐induced permafrost problems in periglacial mountains has increased during recent years. Such problems can be local, as in the case of building foundations on ice‐bearing ground, or can affect larger areas, as in the case of ski‐run preparation on perennially and seasonally frozen ground. The most severe natural hazard concerns the destabilization, erosion and displacement by debris flows of loose, non‐frozen material or weak bedrock on steep slopes. Such flows often take place as a consequence of glacier retreat or permafrost degradation and relate to atmospheric warming, which may continue or even accelerate in the future.

The greatest drawback in man's behaviour with respect to these problems remains the ignorance of mountain permafrost. This probably originates from the fact that permafrost is not directly visible and, hence, is often not considered in the planning stage. The most important progress with respect to construction technology, environment protection and hazard mitigation in periglacial mountain belts can be achieved by improving communication and sharing of experience among scientists and technicians.
Borehole logging in alpine permafrost, upper Engadin, Swiss Alps
Authors: Mühll Daniel S. Vonder , Holub Petr
Published: February 2007

In two boreholes through Alpine permafrost, borehole geophysical measurements were performed. At the borehole through rock glacier Murtèl‐Corvatsch, where cores were taken, the main difficulty was to fill up the hole with water. Consequently, only some of the logging methods could be applied. Nevertheless, gamma‐gamma log (and qualitatively also gamma‐ray) made it possible to obtain density and to calculate ice content. At the Pontresina‐Schafberg drill site, a complete set of logs was run in a water‐filled hole. The bedrock was reached at a depth of approximately 16 m. No cores were obtained by the air‐lift percussion technique. Logging measurements were done to determine thickness of the perennially frozen debris layer above the bedrock and to investigate P‐wave velocity, resistivity and ice content of the whole permafrost body. The boreholes at both drill sites show a high ice content layer (80–95 % by volume), although temperature characteristics are quite different.
Automated mapping of mountain permafrost using the program PERMAKART within the geographical information system ARC/INFO
Authors: Keller Felix
Published: February 2007

The application PERMAKART of the glaciological information system KRYO on ARC/INFO plots supposed mountain permafrost distribution on any topographical map. Results of fieldwork since 1970 and surface analyses based on a digital terrain model (DTM) are used. In Switzerland PERMAKART could become a planning tool for decisions about possible occurrence of mountain permafrost because the DTM RIMINI is available for the entire country.
A model of potential direct solar radiation for investigating occurrences of mountain permafrost
Authors: Funk Martin , Hoelzle Martin
Published: February 2007

A model is described to compute the daily potential direct solar radiation on the basis of digital terrain models. This model is a useful tool for investigating distribution patterns of permafrost in mountain areas. An example of its application to a low‐altitude permafrost site in the Northern Prealps of Switzerland is presented.
Permafrost occurrence from BTS measurements and climatic parameters in the eastern Swiss Alps
Authors: Hoelzle Martin
Published: February 2007

Relations between climatic parameters such as temperature and potential direct solar radiation (PR) and measured bottom temperatures of the snow cover (BTS) as indicator of permafrost occurrence were investigated. No significant correlation exists between mean annual air temperature (MAAT) and BTS. The high correlation found between PR and BTS may help to develop a model for predicting permafrost distribution in mountain areas. This correlation and the low one between MAAT and BTS help to explain the existence of the low‐altitude permafrost in alpine regions.
Evidence of intrapermafrost groundwater flow beneath an active rock glacier in the Swiss Alps
Authors: Mühll Daniel S. Vonder
Published: February 2007

Temperature measurements in borehole 2/1987 through rock glacier Murtèl Corvatsch revealed a very high mean heat flow of 150 mW/m2. Between 52 m and 56 m depth, seasonal variations are observed; above and underneath this zone temperatures have remained negative during the last 4 years. In addition, a zero curtain effect at the same depth hints at the existence of a water aquifer which is active mainly in summer. This phenomenon is interpreted as a talik at about 55 m depth. The permafrost may have a total thickness of approximately 100 m. The high heat flow is a result of the boundary conditions at the surface (mean annual temperature: −3 °C) and at the aquifer (at a depth of about 50 m), where the temperature is close to 0 °C.
Ground temperature measurements in mountain permafrost, Jotunheimen, southern Norway
Authors: Ødegård R. S. , Sollid J. L. , Liestøl O.
Published: February 2007

Ground temperatures have been measured over a 5 year period of between −1.8 °C and −2.3 °C at 10m depth on a mountain plateau, 1851 m a.s.l. in Jotunheimen, southern Norway (61°40′N, 8°20′E). On the basis of additional shallow ground temperature measurements at different altitudes, the change in ground temperature with altitude is estimated to be 0.57 °C/100 m. This estimate, combined with the measured mean annual ground temperature, indicates the lower limit of discontinuous permafrost in the area to be at 1450–1500 m a.s.l. The mean annual ground temperature above 2200 m a.s.l. is below −4 °C. These values are representative for flat or slightly convex areas. Owing to strong winds, there is little snow until late April at the ground temperature measurement site. Maximum snow depth in May is 0.5 m.
Cavity development in ice‐rich permafrost, Pangnirtung, Baffin Island, northwest territories
Authors: Hyatt James A.
Published: February 2007

Cavity development in ice‐rich permafrost at Pangnirtung followed a large rainstorm and runoff event in 1984. The cavities evolved along permeable zones in sediments containing segregated ice lenses. Cavities promoted subsurface flow and incremental collapse of the ground surface. Once formed, cavities remained relatively stable where they were free to drain, and where the enclosing ground remained frozen and rigid support was provided. Some cavities closed by infilling with sediment or freezing water, or by deformation of the surrounding frozen ground. Other cavities were enlarged by thermo‐erosional piping, a process involving both thermal and mechanical erosion of frozen ground together with sufficiently rapid throughflow to prevent refreezing.

A classification of cavities in permafrost permits qualitative appraisal of their stability with respect to the depth of zero annual temperature change and the degree of natural arching support. Assessment based on elastic plate theory indicates that seasonal temperature changes are important factors in destabilizing near‐surface cavities.
Weichselian upper pleniglacial aeolian and ice‐cored morphology in the southern Netherlands (Noord‐Brabant, groote peel)
Authors: Kasse K. , Bohncke S.
Published: February 2007

The morphology of the Weichselian Late Pleniglacial land surface in the Groote Peel nature reserve (southern Netherlands) is characterized by numerous circular to oval depressions. The depressions are up to 90 m wide and 3 m deep. Some are surrounded by low (50–100 cm) ridges. Two depressions were selected for detailed study. One, of aeolian origin, is shallow (less than 1 m), the underlying sedimentary units are undisturbed and the ridge surrounding it consists of horizontally bedded aeolian sand. The second, formed by the melting of an ice core, is deeper (3 m) and dissects older units. The ice lens probably formed during the Weichselian Late Pleniglacial. Ice segregation was favoured by a low topographic gradient, impermeable beds in the subsoil and poor drainage. After partial decay of the ice core, a remnant survived during the cold, arid conditions of the Beuningen deflation phase. Final melting of the ice core occurred after deposition of Late Pleniglacial aeolian coversand, at the onset of the Late Glacial climatic amelioration. Palynological analysis indicates that infilling of the ice‐core depression started in the Late Glacial Older Dryas and possibly even during Oldest Dryas.
Cryoturbations: A sediment structural analysis
Authors: Vandenberghe J.
Published: February 2007

Cryoturbations have always provoked discussions on their origin. However, the sedimentary structures which result from the deformations differ according to the mechanism involved. Diagnostic characterization by sedimentary structure is especially suited to distinguish between deformations caused by cryohydrostatic and cryostatic pressure on the one hand and by periglacial loading on the other.
Present‐day periglacial microforms in the Lesotho Highlands: Implications for present and past climatic conditions
Authors: Hanvey Patricia M. , Marker Margaret E
Published: February 2007

A variety of active periglacial microforms have been identified in the vicinity of Tlaeeng Pass (3275 m a.s.l.) in the Lesotho Highlands. These include thufa (both earth and stone‐cored varieties), terracettes, stone polygons and patterned ground. Ground ice within the saturated zone of soil profiles is clearly evident during the winter season, and pebbles perched on needle ice up to 5 cm in length are common. Although possible relict periglacial landforms (such as nivation hollows and protalus ramparts) have been recorded in the area, their identification and, hence, associated climatic inferences is problematic.

The presence of active features clearly indicates present‐day periglacial activity, with the variety of forms resulting from diurnal or seasonal freeze‐thaw cycles. Considering a widely accepted global decrease in temperature during the Quaternary, a severity of temperatures greater than what is experienced under present marginal periglacial conditions can be projected for the Lesotho Highlands. However, past moisture regimes are more difficult to project from present‐day features, and this problem is exacerbated by the general paucity of clearly defined diagnostic relict forms.