bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct evidence for radar reflector originating from changes in crystal-orientation fabric
Authors: Eisen O. , Hamann I. , Kipfstuhl S. , Steinhage D. , Wilhelms F.
Published: April 2010

Abstract. The origin of a strong continuous radar reflector observed with airborne radio-echo sounding (RES) at the EPICA deep-drilling site in Dronning Maud Land, Antarctica, is identified as a transition in crystal fabric orientation from a vertical girdle- to increased single-pole orientation seen along the ice core. The reflector is observed with a 60 ns and 600 ns long pulse at a frequency of 150 MHz, spans one pulse length, is continuous over 5 km, and occurs at a depth of about 2020–2030 m at the drill site. Changes in conductivity as reflector origin are excluded by investigating the ice-core profile and synthetic RES data. Our observations allow to extrapolate the crystal orientation feature along the reflector in space, with implications for ice-sheet dynamics. As the conductivity profile of the EPICA shows no distinctive peak at this depths, we exclude changes in conductivity as the reflector origin. This is supported by application of numerical forward modelling of electromagnetic wave propagation, based on the conductivity profile, which is able to reproduce nearby reflections, but fails to reproduce this one. Because of background noise, the permittivity profile based on dielectric does not show prominent signals at these depths. We therefore interpret the observed reflector to originate from this change in crystal fabric.
High-resolution simulations of the surface mass balance of Greenland at the end of this century
Authors: Krinner G. , Julien N.
Published: April 2010

Abstract. We present atmospheric general circulation model simulations of the present (1981–2005) and future (2081–2100) climate according to the SRES A1B greenhouse gas scenario. Focusing on Greenland, we use a stretched grid in the global model, thereby reaching a horizontal grid spacing of 60 km in the region of interest. This allows to capture reasonably the escarpment zone of the ice sheet. For the end of this century, the model suggests a precipitation increase in the central region of Greenland, which is overcompensated for by a strong increase of meltwater production in the lower areas. We calculate the changes of water fluxes into the adjacent seas according the simulated surface mass balances changes. The calculated freshwater flux at the end of the 21st century appears too weak to induce a significant reduction of the meridional overturning circulation in the North Atlantic. The resulting surface mass balance decrease between the last decades of the 20th and 21st centuries is equivalent to a positive contribution of 0.8 mm yr−1 to global eustatic sea-level rise.
Changes of Wilkins Ice Shelf over the past 15 years and inferences on its stability
Authors: Braun M. , Humbert A. , Moll A.
Published: April 2010

Abstract. The Wilkins Ice Shelf is situated along the Antarctic Peninsula, a region where seven ice shelves disintegrated between 1995 and 2002. This study combines various remote sensing data sets over Wilkins Ice Shelf, with the aim to detect its present and near-past dynamics as well as recent changes. The survey includes structural mapping, ERS-1/2 SAR interferometry and analysis of ICESat GLAS ice surface elevation data. Ice front retreat rates from 1986 to 2008 showed distinct break-up events, including a recent event in February 2008, where 40% of a bonding of the ice shelf to two islands broke off. Surface elevations have been used to study tidal effects, crack formation and to estimate the ice thickness over the floating area. The interferometric velocities cover the south-eastern part of the ice shelf as well as major tributaries and reveal maximum inflow speeds of up to 330 ma−1. We show that drainage of melt ponds into crevasses were of no relevance for the break-up at Wilkins Ice Shelf. Buoyancy forces caused the rift formation before the break-up of February 2008. Additionally, the evolution of failure zones of the order of tenths of kilometres in length in pre-conditioned locations at ice rises could be shown. Analysis of satellite image time series revealed that evolution and coalescence of failure zones coincides with major break-up events and is assumed to be triggered by them. Investigation of the current (April 2008) situation shows that about 38% at the northern Wilkins Ice Shelf is directly endangered, however, there is no visible signature that the remaining 8000 km2 are at risk.
Lessons from the short history of ice sheet model intercomparison
Authors: Bueler E.
Published: April 2010

Abstract. Intercomparison should include measurement of differences, between model results and observations, among the model results themselves, or between model results and exact solutions. The processes of measuring differences and critically analyzing those differences are vital. Without such measurement as a component of intercomparison, the only expected benefits of an intercomparison project are participation, possibly the discovery of communal confusion, and the establishment of public, non-proprietary data sets.
High resolution modelling of snow transport in complex terrain using simulated wind fields
Authors: Bernhardt M. , Strasser U. , Liston G. E. , Mauser W.
Published: April 2010

Abstract. Snow transport is one of the most dominant processes influencing the snow cover accumulation and ablation in high alpine mountain environments. Hence, the spatial and temporal variability of the snow cover is significantly modified with respective consequences on the total amount of water in the snow pack, on the temporal dynamics of the runoff and on the energy balance of the surface. For the presented study we used the snow transport model SnowTran-3D in combination with MM5 (Penn State University – National Center for Atmospheric Research MM5 model) generated wind fields. In a first step the MM5 wind fields were downscaled by using a semi-empirical approach which accounts for the elevation difference of model and real topography, as well as aspect, inclination and vegetation. The target resolution of 30 m corresponds to the resolution of the best available DEM and land cover map. For the numerical modelling, data of six automatic meteorological stations were used, comprising the winter season (September–August) of 2003/04 and 2004/05. In addition we had automatic snow depth measurements and periodic manual measurements of snow courses available for the validation of the results. In this paper we describe the downscaling of the wind fields and discuss the results of the snow transport simulations with respect to the measurements and remotely sensed data.
Partitioning of melt energy and meltwater fluxes in the ablation zone of the west Greenland ice sheet
Authors: Van den Broeke M. , Smeets P. , Ettema J. , Van der Veen C. , Van de Wal R. , Oerlemans J.
Published: April 2010

Abstract. We present four years of surface mass balance data from the ablation zone of the west Greenland ice sheet along the 67° N latitude circle. Sonic height rangers and automatic weather stations continuously measured accumulation/ablation and near-surface climate at distances of 6, 38 and 88 km from the ice sheet margin at elevations of 490, 1020 and 1520 m a.s.l. Using a melt model and reasonable assumptions about snow density and percolation characteristics, these data are used to quantify the partitioning of energy and mass fluxes during melt episodes. The lowest site receives very little winter accumulation, and ice melting is nearly continuous in June, July and August. Due to the lack of snow accumulation, little refreezing occurs and virtually all melt energy is invested in runoff. Higher up the ice sheet, the ice sheet surface freezes up during the night, making summer melting intermittent. At the intermediate site, refreezing in snow consumes about 10% of the melt energy, increasing to 40% at the highest site. The sum of these effects is that total melt and runoff increase exponentially towards the ice sheet margin, each time doubling between the stations. At the two lower sites, we estimate that radiation penetration causes 20–30% of the ice melt to occur below the surface.
The role of radiation penetration in the energy budget of the snowpack at Summit, Greenland
Authors: Kuipers Munneke P. , van den Broeke M. R. , Reijmer C. H. , Helsen M. M. , Boot W. , Schneebeli M. , Steffen K.
Published: April 2010

Abstract. Measurements of the summer surface energy balance at Summit, Greenland, are presented (8 June–20 July 2007). These measurements serve as input to an energy balance model that searches for a surface temperature for which closure of all energy terms is achieved. A good agreement between observed and modeled surface temperatures was found, with an average difference of 0.45°C and an RMSE of 0.85°C. It turns out that penetration of shortwave radiation into the snowpack plays a small but important role in correctly simulating snow temperatures. After 42 days, snow temperatures in the first meter are 3.6–4.0°C higher compared to a model simulation without radiation penetration. Sensitivity experiments show that these results cannot be reproduced by tuning the heat conduction process alone, by varying snow density or snow diffusivity. We compared the two-stream radiation penetration calculations with a sophisticated radiative transfer model and discuss the differences. The average diurnal cycle shows that net shortwave radiation is the largest energy source (+61 W m−2 on average), net longwave radiation the largest energy sink (−42 W m−2). On average, subsurface heat flux, sensible and latent heat fluxes are the remaining, small heat sinks (−5, −5 and −7 W m−2, respectively), although these are more important on a subdaily timescale.
Layer disturbances and the radio-echo free zone in ice sheets
Authors: Drews R. , Eisen O. , Hamann I. , Kipfstuhl S. , Lambrecht A. , Steinhage D. , Wilhelms F. , Miller H.
Published: April 2010

Abstract. Radio-echo sounding of the Antarctic and Greenlandic ice sheets often reveals a layer in the lowest hundreds of meters above bedrock more or less free of radio echoes, known as the echo-free zone (EFZ). The cause of this feature is unclear, so far lacking direct evidence for its origin. We compare echoes around the EPICA drill site in Dronning Maud Land, Antarctica, with the microstructural and dielectrical properties of the EPICA-DML ice core. We find that echoes disappear in the depth range, where the coherency of the layers is lost due to disturbances caused by the ice flow. At the drill site, the EFZ onset at ~2100 m marks a boundary, below which the ice core may have experienced flow induced disturbances on various scales. The dating of the climate record becomes increasingly difficult below 1900 m, until correlation with the Dome C record is lost below 2417 m depth. The onset also indicates changing rheology which needs to be accounted for in the modeling of ice sheet dynamics.
Multi-temporal airborne LIDAR-DEMs for glacier and permafrost mapping and monitoring
Authors: Abermann J. , Fischer A. , Lambrecht A. , Geist T.
Published: April 2010

Abstract. The proposed method presents a simple and robust way to derive glacier extent by using multi-temporal high-resolution DEMs (digital elevation models) as a main data source. For glaciers that are not debris covered, we perform the glacier boundary delineation by analysing roughness differences between ice and its surroundings. A promising way to distinguish dead ice, debris-covered ice or permafrost from its rocky surroundings is shown by taking elevation changes from DEMs of different dates into consideration. In case data has a high spatial and temporal resolution a good representation of the extent of debris cover and thus the overall ice covered area can be given. We use examples to show how potentially ambiguous areas can be treated decisively by the additional qualitative analysis of aerial photographs. Problems and limitations are discussed in comparison with selected other remote sensing techniques and accuracies are quantified. For glaciers larger than 1 km2 an accuracy of ±1% of the glacier area could be assessed. The errors of smaller glaciers do not exceed ±5% of the glacier area.
A comparison of different methods of evaluating glacier response characteristics: application to glacier AX010, Nepal Himalaya
Authors: Adhikari S. , Marshall S. J. , Huybrechts P.
Published: April 2010

Abstract. Himalayan glaciers are considered to be amongst the most sensitive glaciers to climate change. However, the response behaviour of these glaciers is not well understood. Here we use several approaches to estimate characteristic timescales of glacier AX010, a small valley glacier in the Nepal Himalaya, as a measure of glacier sensitivity. Assuming that temperature solely defines the mass budget, glacier AX010 waits for about 8 yr (reaction time) to exhibit its initial terminus response to changing climate. On the other hand, it takes between 29–56 yr (volume response time) and 37–70 yr (length response time) to adjust its volume and length following the changes in mass balance conditions, respectively. A numerical ice-flow model, the only method that yields both length and volume response time, confirms that a glacier takes longer to adjust its length than its volume.
The Gregoriev Ice Cap evolution according to the 2-D ice flowline model for various climatic scenarios in the future
Authors: Konovalov Y. V. , Nagornov O. V.
Published: April 2010

Abstract. Different flowline thickness distributions and flowline length changes of the Gregoriev Ice Cap were obtained for some surface mass balance histories which can be considered as possible surface mass balances in the future. The ice cap modeling was performed by solving full Stokes equations in the form of one mechanical equilibrium equation in terms of stress deviator components in couple with continuity equation for incompressible substance. The numerical solution was obtained by the finite-difference method. The problem of diagnostic equations stability was overcome by a~compound approximation of the ice surface boundary condition based on the extending of the mechanical equilibrium equation to ice surface points. The problem of stability in the prognostic equation can arise at relatively small grid size in horizontal direction in the case of steep velocity decreasing closely to the ice front and was overcome by introducing the artificial viscosity into the prognostic equation. The basal sliding can arise in the glacier tongue at certain climatic conditions and was introduced through the linear friction law. The correlations between glacier length changes and annual air temperature histories were investigated within the simplified equation in the form of linear dependence of annual air temperature versus the glacier length and time derivation of the length.
Multi-channel ground-penetrating radar to explore spatial variations in thaw depth and moisture content in the active layer of a permafrost site
Authors: Wollschläger U. , Gerhards H. , Yu Q. , Roth K.
Published: April 2010

Abstract. Multi-channel ground-penetrating radar was applied at a permafrost site on the Tibetan Plateau to investigate the influence of surface properties and soil texture on the late-summer thaw depth and average soil moisture content of the active layer. Measurements were conducted on an approximately 85×60 m2 sized area with surface and soil textural properties that ranged from medium to coarse textured bare soil to finer textured, vegetated areas covered with fine, wind blown sand, and it included the bed of a gravel road. The survey allowed a clear differentiation of the various units. It showed (i) a shallow thaw depth and low average soil moisture content below the sand-covered, vegetated area, (ii) an intermediate thaw depth and high average soil moisture content along the gravel road, and (iii) an intermediate to deep thaw depth and low to intermediate average soil moisture content in the bare soil terrain. From our measurements, we found plausible hypotheses for the permafrost processes at this site leading to the observed late-summer thaw depth and soil moisture conditions. The study clearly indicates the complicated interactions between surface and subsurface state variables and processes in this environment. In addition, the survey demonstrates the potential of multi-channel ground-penetrating radar to efficiently map thaw depth and soil moisture content of the active layer with high spatial resolution at scales from a few meters to a few kilometers.
Monitoring of active layer dynamics at a permafrost site on Svalbard using multi-channel ground-penetrating radar
Authors: Westermann S. , Wollschläger U. , Boike J.
Published: April 2010

Abstract. Multi-channel ground-penetrating radar is used to investigate the late-summer evolution of the thaw depth and the average soil water content of the thawed active layer at a high-arctic continuous permafrost site on Svalbard, Norway. Between mid of August and mid of September 2008, five surveys have been conducted over transect lengths of 130 and 175 m each. The maximum thaw depths range from 1.6 m to 2.0 m, so that they are among the deepest thaw depths recorded for Svalbard so far. The thaw depths increase by approximately 0.2 m between mid of August and beginning of September and subsequently remain constant until mid of September. The thaw rates are approximately constant over the entire length of the transects within the measurement accuracy of about 5 to 10 cm. The average volumetric soil water content of the thawed soil varies between 0.18 and 0.27 along the investigated transects. While the measurements do not show significant changes in soil water content over the first four weeks of the study, strong precipitation causes an increase in average soil water content of up to 0.04 during the last week. These values are in good agreement with evapotranspiration and precipitation rates measured in the vicinity of the the study site. While we cannot provide conclusive reasons for the detected spatial variability of the thaw depth at the study site, our measurements show that thaw depth and average soil water content are not directly correlated. The study demonstrates the potential of multi-channel ground-penetrating radar for mapping thaw depth in permafrost areas. The novel non-invasive technique is particularly useful when the thaw depth exceeds 1.5 m, so that it is hardly accessible by manual probing. In addition, multi-channel ground-penetrating radar holds potential for mapping the latent heat content of the active layer and for estimating weekly to monthly averages of the ground heat flux during the thaw period.
Local scaling characteristics of Antarctic surface layer turbulence
Authors: Basu S. , Ruiz-Columbié A. , Phillipson J. A. , Harshan S.
Published: April 2010

Abstract. Over the past years, several studies have validated Nieuwstadt's local scaling hypothesis by utilizing turbulence observations from the mid-latitude, nocturnal stable boundary layers. In this work, we probe into the local scaling characteristics of polar, long-lived stable boundary layers by analyzing turbulence data from the South Pole region of the Antarctic Plateau.
Climate of the Greenland ice sheet using a high-resolution climate model – Part 1: Evaluation
Authors: Ettema J. , van den Broeke M. R. , van Meijgaard E. , van de Berg W. J. , Box J. E. , Steffen K.
Published: April 2010

Abstract. A simulation of 51 years (1957–2008) has been performed over Greenland using the regional atmospheric climate model RACMO2 at a horizontal grid spacing of 11 km forced by ECMWF analysis products. To better represent processes affecting ice sheet surface mass balance, such as melt water refreezing and penetration, an additional snow/ice surface module has been developed and implemented into the surface parameterisation of RACMO2v1. The temporal evolution and climatology of the model is evaluated with in situ coastal and ice sheet atmospheric measurements of near-surface variables and surface energy balance components. The bias for the near-surface air temperature (0.9 °C), specific humidity (0.1 g kg−1), wind speed (0.3 m s−1) as well as for radiative (2.5 W m−2 for net radiation) and turbulent heat fluxes shows that the model is in good accordance with available observations. The modeled surface energy budget underestimates the downward longwave radiation and overestimates the sensible heat flux. Due to their compensating effect, the averaged 2 m temperature bias is less than −0.9°C. The katabatic wind circulation is well captured by the model.
Rubidium and Rubidium Compounds
Authors: Lenk Winfried , Prinz Horst , Steinmetz Anja
Published: April 2010

The article contains sections titled:1.Introduction2.Properties3.Raw Materials and Production4.Rubidium Compounds5.Quality Specifications and Analysis6.Storage and Transportation7.Uses and Economic Aspects8.Toxicology and Occupational Health
Rheometry
Authors: Strivens Trevor A. , Schoff Clifford K.
Published: April 2010

The article contains sections titled:1.The Science of Rheology1.1.Introduction1.2.Terminology1.2.1.Rheological Measurement Terms1.2.2.Rheological Classification of Materials1.2.3.Classification of Rheological Experiments and Measuring Systems1.3.Examples of Rheological Behavior1.3.1.Newtonian Liquids1.3.2.Elastic Solids1.3.3.Simple Viscoelastic Liquids1.3.4.Complex Viscoelastic Liquids1.3.5.Thixotropic Liquids2.Rheological Measurements2.1.Basic Deformation Modes for Measurement2.1.1.Shear Deformation2.1.2.Extensional Deformation2.2.Torsional Shear Deformation2.2.1.Rheometer Types2.2.2.Measurement Geometries2.2.2.1.Parallel Plates2.2.2.2.Cone and Plate2.2.2.3.Concentric Cylinder (Cup and Bob, Couette)2.2.2.4.Other Geometries2.3.Capillary (Poiseuille) Shear Flow2.4.Extensional Flow2.5.Measurement Procedures2.5.1.Steady‐State Measurements2.5.2.Dynamic (Oscillatory) Measurements2.5.3.Transient Methods2.5.4.Combined Methods2.5.5.Normal Stress Measurements3.Results of Rheological Measurements3.1.Steady‐State Measurements3.2.Dynamic (Oscillatory) Measurements3.3.Transient Measurements
Graphene Oxide: Surface Activity and Two‐Dimensional Assembly
Authors: Kim Franklin , Cote Laura J. , Huang Jiaxing
Published: April 2010

Graphene oxide (GO) is a promising precursor for preparing graphene‐based composites and electronics applications. Like graphene, GO is essentially one‐atom thick but can be as wide as tens of micrometers, resulting in a unique type of material building block, characterized by two very different length scales. Due to this highly anisotropic structure, the collective material properties are highly dependent on how these sheets are assembled. Therefore, understanding and controlling the assembly behavior of GO has become an important subject of research. In this Research News article the surface activity of GO and how it can be employed to create two‐dimensional assemblies over large areas is discussed.
Lrp4: A novel modulator of extracellular signaling in craniofacial organogenesis
Authors: Ohazama Atsushi , Porntaveetus Thantrira , Ota Masato S. , Herz Joachim , Sharpe Paul T.
Published: April 2010

The low‐density lipoprotein (LDL) receptor family is a large evolutionarily conserved group of transmembrane proteins. It has been shown that LDL receptor family members can also function as direct signal transducers or modulators for a broad range of cellular signaling pathways. We have identified a novel mode of signaling pathway integration/coordination that occurs outside cells during development that involves an LDL receptor family member. Physical interaction between an extracellular protein (Wise) that binds BMP ligands and an Lrp receptor (Lrp4) that modulates Wnt signaling, acts to link these two pathways. Mutations in either Wise or Lrp4 in mice produce multiple, but identical abnormalities in tooth development that are linked to alterations in BMP and Wnt signaling. Teeth, in common with many other organs, develop by a series of epithelial–mesenchymal interactions, orchestrated by multiple cell signaling pathways. In tooth development, Lrp4 is expressed exclusively in epithelial cells and Wise mainly in mesenchymal cells. Our hypothesis, based on the mutant phenotypes, cell signaling activity changes and biochemical interactions between Wise and Lrp4 proteins, is that Wise and Lrp4 together act as an extracellular mechanism of coordinating BMP and Wnt signaling activities in epithelial–mesenchymal cell communication during development. © 2010 Wiley‐Liss, Inc.
Identical but not the same: The value of discordant monozygotic twins in genetic research
Authors: Zwijnenburg Petra J.G. , Meijers‐Heijboer Hanne , Boomsma Dorret I.
Published: April 2010

Monozygotic (MZ) twins show remarkable resemblance in many aspects of behavior, health, and disease. Until recently, MZ twins were usually called “genetically identical”; however, evidence for genetic and epigenetic differences within rare MZ twin pairs has accumulated. Here, we summarize the literature on MZ twins discordant for Mendelian inherited disorders and chromosomal abnormalities. A systematic literature search for English articles on discordant MZ twin pairs was performed in Web of Science and PubMed. A total number of 2,016 publications were retrieved and reviewed and 439 reports were retained. Discordant MZ twin pairs are informative in respect to variability of phenotypic expression, pathogenetic mechanisms, epigenetics, and post‐zygotic mutagenesis and may serve as a model for research on genetic defects. The analysis of single discordant MZ twin pairs may represent an elegant approach to identify genes in inherited disorders. © 2010 Wiley‐Liss, Inc.
Ileal disease is associated with surgery for perianal disease in a population-based Crohn's disease cohort
Authors: Eglinton T , Reilly M , Chang C , Barclay M , Frizelle F , Gearry R
Published: April 2010

Background

The aim of this study was describe the frequency and characteristics of perianal surgical intervention (PSI) for Crohn's disease in a population-based cohort of patients with inflammatory bowel disease (IBD).

Methods

A total of 1421 patients with IBD were recruited, representing approximately 91 per cent of people with IBD in Canterbury, New Zealand. The clinical notes were screened to confirm the diagnosis and extract clinical data, including details of PSIs.

Results

Some 649 patients with Crohn's disease were included in the analysis, of whom 119 (18·3 per cent) had at least one PSI. Of these, 61 (51·3 per cent) required further procedures. Operations for perianal abscess and fistula accounted for 72·4 per cent of interventions. PSI rates did not differ between the sexes (P = 0·218). Age less than 17 years (adjusted odds ratio (OR) 1·89 (95 per cent confidence interval 1·08 to 3·28)) and ileal disease (OR 1·76 (1·06 to 2·92)) were identified as predictors of PSI. As disease duration increased, so did the proportion of patients with complicated intestinal disease among those who had undergone PSI. The median time to first PSI from diagnosis of Crohn's disease was 28 (interquartile range 7–82) months. Sex, age at diagnosis and disease location did not influence the time to first PSI.

Conclusion

PSIs are frequent in patients with Crohn's disease, particularly those with ileal disease and those diagnosed at a young age.
Clinicoradiological score for predicting the risk of strangulated small bowel obstruction
Authors: Schwenter F , Poletti P A , Platon A , Perneger T , Morel P , Gervaz P
Published: April 2010

Background

Intestinal ischaemia as a result of small bowel obstruction (SBO) requires prompt recognition and early intervention. A clinicoradiological score was sought to predict the risk of ischaemia in patients with SBO.

Methods

A clinico-radiological protocol for the assessment of patients presenting with SBO was used. A logistic regression model was applied to identify determinant variables and construct a clinical score that would predict ischaemia requiring resection.

Results

Of 233 consecutive patients with SBO, 138 required laparotomy of whom 45 underwent intestinal resection. In multivariable analysis, six variables correlated with small bowel resection and were given one point each towards the clinical score: history of pain lasting 4 days or more, guarding, C-reactive protein level at least 75 mg/l, leucocyte count 10 × 109/l or greater, free intraperitoneal fluid volume at least 500 ml on computed tomography (CT) and reduction of CT small bowel wall contrast enhancement. The risk of intestinal ischaemia was 6 per cent in patients with a score of 1 or less, whereas 21 of 29 patients with a score of 3 or more underwent small bowel resection. A positive score of 3 or more had a sensitivity of 67·7 per cent and specificity 90·8 per cent; the area under the receiver operating characteristic curve was 0·87 (95 per cent confidence interval 0·79 to 0·95).

Conclusion

By combining clinical, laboratory and radiological parameters, the clinical score allowed early identification of strangulated SBO.
The effects of organic solvents on the efficiency and regioselectivity of N‐acetyl‐lactosamine synthesis, using the β‐galactosidase from Bacillus circulans in hydro‐organic media
Authors: Bridiau Nicolas , Issaoui Neyssène , Maugard Thierry
Published: April 2010

The enzymatic synthesis of N‐acetyl‐lactosamine (LacNAc) by the transgalactosylation of N‐acetyl‐D‐glucosamine (GlcNAc), catalyzed by the β‐galactosidase from Bacillus circulans (BcβGal), was studied in hydro‐organic media, starting from o‐nitrophenyl‐β‐D‐galactopyranoside (oNPG) as a galactosyl donor. Thermal stability and synthesis activity of BcβGal were shown to depend on the organic solvent polarity, characterized by its Log P value. BcβGal was thus most stable in 10% (v/v) t‐BuOH, an organic solvent found to have a stabilizing and/or weakly denaturing property, which was confirmed for high t‐BuOH concentrations. In the same manner, the optimal synthesis yield increased as the Log P value of the organic solvent increased. The best results were obtained for reactions carried out in 10% (v/v) pyridine or 2‐methyl‐2‐butanol, which gave 47% GlcNAc transgalactosylation yield based on starting oNPG, of which 23% (11 mM; 4.3 g/L) consisted in LacNAc synthesis. Furthermore, it was also established that both the GlcNAc transgalactosylation yield and the enzyme regioselectivity depended on the percentage of organic solvent used, the optimal percentage varying from 10 to 40% (v/v), depending on the solvent. This phenomenon was found to correlate mainly with the thermodynamic activity of water (aw) in the aqueous organic solvent mixture, which was found to be optimal when close to 0.96, whatever the organic solvent used. Finally, this study highlighted the fact that the regioselectivity of BcβGal for 1‐4 linkage formation could be advantageously managed by controlling the aw parameter. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010
Estimation of Reliable Parameters for Solid‐Liquid Equilibrium Description of Chiral Systems
Authors: Haida H. , Kaemmerer H. , Lorenz H. , Seidel‐Morgenstern A.
Published: April 2010

The knowledge of accurate solid‐liquid phase equilibria serves in general as a strong basis for the design of any crystallization process. The available database is often limited and the experimental determination of necessary and reliable thermodynamic data is a tedious and time‐consuming task. In this study, the predictive power of a multi‐component gE model fed with limited experimental data was evaluated. Hereby, the impact of uncertainties in the underlying experimental data and the obtained model parameters was of particular interest. Statistical methods were used in order to extend the knowledge about the reliability of the model correlation and to evaluate its predictive characteristics. Therefore, binary and ternary phase equilibria for the system methionine/water were taken from the literature, and analyzed.
Outlier detection and ambiguity detection for microarray data in probabilistic discriminant partial least squares regression
Authors: Botella C. , Ferré J. , Boqué R.
Published: April 2010

The reject option plays an important role in the classification of microarray data. In this work, a reject option is implemented in the probabilistic discriminant partial least squares (p‐DPLS) method in order to reject to classify both outliers and ambiguous samples. Microarray data are highly susceptible to present outliers because of the many steps involved in the experimental process. During the development of the classifier, outliers in the training data may strongly influence the model and degrade its performance. Some future samples to be classified may also be outliers that will most probably be misclassified. Ambiguous samples are samples that cannot be clearly assigned to any of the classes with a high confidence. In this work, outlier detection and ambiguity detection are implemented taking into account the x‐residuals, the leverage and the predicted ŷ. The method was applied to oligonucleotide microarray data and cDNA microarray data. For the first dataset (prostate cancer data set), the outlier detection criteria allowed us to remove nine samples from the training set. The model without those samples had better classification ability, with a decrease in the classification cost per sample from 0.10 to 0.07. The method was also used in a second dataset (small round blue cell tumours of childhood dataset) to detect prediction outliers so that most of the outliers were rejected to classify and misclassifications were reduced from 100 to 5%. Copyright © 2010 John Wiley & Sons, Ltd.
A concise summary of experimental facts about the Soai reaction
Authors: Gehring Timo , Busch Mark , Schlageter Martin , Weingand Daniel
Published: April 2010

The Soai reaction amplifies small enantiomeric excesses in a spectacular manner. Being known for 20 years, it has drawn the attention of many scientists in different fields as it is to date the only chemical reaction offering the chance to study the phenomenon of asymmetric autocatalysis in conjunction with high amplification of enantiomeric excess (ee). This mini‐review comprises an introduction to the discovery of asymmetric autocatalysis with amplification of ee and a concise summary of published experimental results showing which starting materials and reaction parameters play an important role in this reaction and which influences are understood. It is addressed especially to scientists entering the field of the Soai reaction to get a quick overview of important aspects. Chirality 2010. © 2010 Wiley‐Liss, Inc.
Enhanced cell migration and invasion of CD133+ pancreatic cancer cells cocultured with pancreatic stromal cells
Authors: Moriyama Taiki , Ohuchida Kenoki , Mizumoto Kazuhiro , Cui Lin , Ikenaga Naoki , Sato Norihiro , Tanaka Masao
Published: April 2010

BACKGROUND:

Recently, cancer stem cells have been reported as a new therapeutic target in pancreatic cancer as well as other cancers, but the specific role of these cells is unknown.

METHODS:

The authors investigated the functional roles of CD133+ cells, 1 of the putative cancer stem cell candidates in pancreatic cancer. CD133 expression was assessed in human pancreatic cancer and cancer cell lines by quantitative real‐time reverse transcriptase polymerase chain reaction and flow cytometry. Next, they compared the ability of CD133+ and CD133− cells to proliferate, migrate, and invade using 2 pancreatic cancer cell lines. In particular, they evaluated the relationship between CD133+ cells and primary pancreatic stromal cells.

RESULTS:

CD133 was expressed in primary human pancreatic cancer tissues and some cancer cell lines, whereas there was little expression in primary normal pancreatic epithelial cells and primary pancreatic stromal cells. CD133+ cells, isolated by flow cytometry, showed increased cell proliferation under anchorage‐independent conditions (P < .01), and enhanced migration and invasion, particularly when cocultured with primary pancreatic stromal cells (P < .001). Chemokine‐related receptor‐4 (CXCR4), markedly overexpressed in CD133+ cells, may be responsible for the increased invasive ability of the cells cocultured with pancreatic stromal cells, which express stromal derived factor‐1, the ligand to CXCR4.

CONCLUSIONS:

These data suggest that CD133+ cells exhibit more aggressive behavior, such as increased cell proliferation, migration, and invasion, especially in the presence of pancreatic stromal cells. The targeting therapy for the interaction between CD133+ cancer cells and stromal cells may be a new approach for the treatment of pancreatic cancer. Cancer 2010. © 2010 American Cancer Society.
Developmental instability of ano‐genital distance index: Implications for assessment of prenatal masculinization
Authors: Dušek Adam , Bartoš Luděk , Sedláček František
Published: April 2010

Prenatal androgens are generally assumed to permanently affect the morphology of external genitalia. In laboratory rodents, the ano‐genital distance index (AGDI) has become widely used as a marker of natural prenatal masculinization. A greater value should indicate a greater masculinization. The aim of this study was to assess the developmental stability of the AGDI in female mice during pre‐ (Days 1–21) and postweaning (Days 21–61) periods. Presuming that the AGDI reflects a permanent effect of prenatal masculinization, we hypothesized that the AGDI will be a developmentally stable morphometric measurement (interindividual differences in the AGDI measurement should persist over time). In contrast to our prediction, the AGDI showed poor repeatability both during pre‐ (.15) and postweaning (.22) periods, indicating developmental instability. (A value of 1 indicates perfect repeatability and a value of 0 indicates no repeatability.) The AGDI thus does not seem to be a reliable marker of prenatal female masculinization. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 52: 568–573, 2010.

This article was published online on 28 April 2010. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected 1 June 2010.
Do children with developmental dyslexia have impairments in implicit learning?
Authors: Pavlidou Elpis V. , Louise Kelly M. , Williams Joanne M.
Published: April 2010

We explored implicit learning in a group of typically developing and developmental dyslexic primary school children (9–12 y) using a modified artificial grammar learning task. Performance was calculated using two measures of performance: a perfect free recall (PFR) score and a grammaticality judgment score. Both groups of children required the same amount of exposure to memorize the items (i.e. PFR performance) (t(30)=1.620, p>0.05; p‐value reported two‐tailed). However, repeated measures ANOVA (Participant type × Grammaticality × Chunk strength) revealed a Participant type effect for grammaticality judgment scores (F(1,30)=4.521, p<0.05; p‐value reported two‐tailed). Typically developing children showed above chance performance in terms of both grammaticality and chunk strength of the stimuli. Children with developmental dyslexia on the other hand, failed to show implicit learning irrespective of the substring characteristics (i.e. grammaticality or chunk strength). We propose that children with developmental dyslexia may be impaired in their implicit rule abstraction mechanism, which can partially explain their persistent reading problems. Copyright © 2010 John Wiley & Sons, Ltd.
Catalyst Regeneration in Transition‐Metal‐Mediated Atom‐Transfer Radical Addition (ATRA) and Cyclization (ATRC) Reactions
Authors: Pintauer Tomislav
Published: April 2010

Transition‐metal‐catalyzed atom‐transfer radical addition (ATRA) and cyclization (ATRC) are considered fundamental reactions in organic chemistry for the formation of C–C bonds using free‐radical means. Until recently, both processes were plagued by the large amounts of catalysts needed to achieve high selectivity towards the desired target compound (as high as 30 mol‐%). The principal problem was the accumulation of the transition metal complex in the higher oxidation state as a result of unavoidable radical‐radical termination reactions. In this article, recent advanced in the area of catalyst regeneration in transition‐metal‐mediated ATRA and ATRC reactions in the presence of free‐radical diazo initiators or magnesium as reducing agents are reviewed. The role of the reducing agent in both systems is to continuously regenerate the activator (transition metal complex in the lower oxidation state) from the deactivator (transition metal complex in the higher oxidation state). As a result, ATRA and ATRC reactions can be conducted using very small concentrations of metal catalysts, making this methodology a “greener” alternative to currently available synthetic processes for such organic transformations.
Vapour‐Induced Amorphous–Crystalline Transformation of a Luminescent Platinum(II)–Diimine Complex
Authors: Kobayashi Atsushi , Yonemura Tsubasa , Kato Masako
Published: April 2010

A novel luminescent platinum(II)–diimine complex, Na2[Pt(CN)2(dcbpy)]·nH2O (H2dcbpy = 4,4′‐dicarboxy‐2,2′‐bipyridine, n = 2 or 5) was synthesized and investigated by using X‐ray diffraction measurements and spectroscopy. Complex Na2[Pt(CN)2(dcbpy)]·2H2O was first obtained as a red amorphous solid (1A) that exhibits bright luminescence at 623 nm. After recrystallization, two crystalline forms, the dihydrate form, 1C, and the pentahydrate form, Na2[Pt(CN)2(dcbpy)]·5H2O (2), were obtained and analyzed by the single‐crystal X‐ray diffraction method. Upon exposure of the amorphous form 1A to hydrophilic vapours such as those of MeOH and acetone, 1A irreversibly changed to a yellow crystalline solid 1C that showed luminescence at 608 nm with a shoulder at 568 nm. This vapour‐induced amorphous–crystalline transformation has never been observed either by exposing 1A to hydrophobic vapours nor by increasing the temperature up to 410 K. IR spectroscopy revealed that the amorphous–crystalline transformation did not involve the adsorption of the vapour. This phenomenon of irreversible structural transformation accompanied by change of luminescence is possibly applicable to vapour history sensors.
New Methodology for the Stereoselective Synthesis of α‐Furfurylamines from Sugars: Application to the Synthesis of Furyl Amino Acids and 3‐Furylisoserines
Authors: Molina Lidia , Moreno‐Clavijo Elena , Moreno‐Vargas Antonio J. , Carmona Ana T. , Robina Inmaculada
Published: April 2010

The synthesis of two new furyl amino acids as rigid isosteres of the dipeptides (D)‐H‐Ser‐(D,L)‐Thr‐OH and (L)‐H‐Ser‐(D,L)‐Thr‐OH is presented. The developed synthetic methodology starts from D‐xylose and D‐arabinose and makes use of trihydroxypropylfurans as intermediates. The key step of the strategy is the introduction of an amino function at the α‐position of the adequate trihydroxypropylfuran derivative. This methodology was also applied to the synthesis of two new (2R,3R)‐3‐furylisoserines as analogues of the C‐13 Taxol/Taxotere side chain.
Axially Extended Perylene Dyes
Authors: Langhals Heinz , Pust Tim
Published: April 2010

Perylenecarboxylic anhydride imides were condensed with semicarbazide and thiosemicarbazide to form perylene dyes extended by triazoline rings and bathochromically shifted UV/Vis absorption and fluorescence. The thiocarbonyl derivative reacts with diazo compounds to cause a further extension with spiro‐arranged thiirane rings. Applications in analytics are discussed.
Highly Stereoselective Synthesis of syn‐1,3‐Diols through a Sequential Titanium‐Mediated Aldol Reaction and LiBH4 Reduction
Authors: Esteve Judit , Matas Sònia , Pellicena Miquel , Velasco Javier , Romea Pedro , Urpí Fèlix , Font‐Bardia Mercè
Published: April 2010

A sequential transformation based on a titanium‐mediated aldol reaction from chiral α‐tert‐butyldimethylsilyloxy ketones followed by reduction of the resultant aldolates with LiBH4 provides a straightforward access to syn‐1,3‐diols. These diols, containing up to three new stereocentres, can be easily isolated in high yields after a simple work‐up without any additional oxidative treatment, which confers to this procedure an appealing position to prepare stereoselectively such sort of structures.
The genotoxicity of particulate and soluble chromate in sperm whale (physeter macrocephalus) skin fibroblasts
Authors: Wise John Pierce , Wise Sandra S. , LaCerte Carolyne , Wise John Pierce , Aboueissa AbouEl‐Makarim
Published: April 2010

Hexavalent chromium is a marine pollutant of concern, both for the health of ocean ecosystems and for public health. Hexavalent chromium is known to induce genotoxicity in human and other terrestrial mammals. It is also known to be present in both water and air in the marine environment. However, currently there are limited data concerning both chromium levels and its toxicological effects in marine mammals. This study investigated the cytotoxic and genotoxic effects of soluble and particulate hexavalent chromium in sperm whale skin fibroblasts. Both forms of hexavalent chromium induced concentration‐dependent increases in cytotoxicity and genotoxicity indicating that these compounds can be a health risk if the whales are exposed to them. These data support a hypothesis that chromium is a concern in the marine environment in general and for the health of sperm whales in particular. Environ. Mol. Mutagen. 52:43–49, 2011. © 2010 Wiley‐Liss, Inc.
Genotoxicity of lavender oil, linalyl acetate, and linalool on human lymphocytes in vitro
Authors: Di Sotto Antonella , Mazzanti Gabriela , Carbone Fabio , Hrelia Patrizia , Maffei Francesca
Published: April 2010

The potential genotoxicity of lavender essential oil and its major components, linalool, and linalyl acetate, was evaluated in vitro by the micronucleus test on peripheral human lymphocytes. In the range of non‐toxic concentrations (0.5–100 μg/ml), linalyl acetate increased the frequency of micronuclei significantly and in concentration‐dependent manner; lavender oil did so only at the highest concentration tested, whereas linalool was devoid of genotoxicity. None of the tested substances led to an increase in nucleoplasmic bridges or nuclear buds frequency. These findings suggest that the mutagenic activity of lavender oil can be related to the presence of linalyl acetate, which seems to have a profile of an aneugenic agent. Environ. Mol. Mutagen. 52:69–71, 2011. © 2010 Wiley‐Liss, Inc.
Do different psychopathological pathways into eating disorder necessitate different therapeutic goals and/or approaches?
Authors: Vanderlinden Johan
Published: April 2010

This paper presenst a plea for a more flexible therapeutic approach which focuses not only on the underlying cognitions, behaviours and emotions related to the eating disorder, but an approach that adapts its focus depending also on the psychopathological pathway which has led to the development of the eating disorder.
An evaluation of the effectiveness and short‐term stability of an innovative Australian day patient programme for eating disorders
Authors: Willinge A. C. , Touyz S. W. , Thornton C.
Published: April 2010

There is a dearth of literature evaluating day patient treatment for eating disorders based upon the targeted goals of treatment, to conclude that day patient programmes are effective. This study aimed to explore the effectiveness of an innovative day patient programme by examining whether the seven key treatment goals improved across treatment and were maintained 3 months after discharge. Of the 58 participants who completed measures assessing BMI, eating disorder cognitions, behaviours, core beliefs, readiness to change, quality of life and perpetuating factors at admission, discharge and follow‐up, 44 completed the day programme with 14 non‐completers. The results demonstrated that all seven treatment goals improved across treatment and the improvements were maintained or further improved at 3 month follow‐up. The results are discussed in context of the published day patient programme literature with implications for future research to maximise optimal treatment outcomes from day patient treatment. Copyright © 2010 John Wiley & Sons, Ltd and Eating Disorders Association.