bluuebunny/crossref_metadata_2025 huggingface dataset:
Conformation study of poly(p‐dioxanone) fibers by polarized Raman spectroscopy, X‐ray diffraction, and conformation analysis
Authors: Jaidann Mounir , Brisson Josée
Published: December 2007

The molecular orientation distribution of poly(p‐dioxanone) (PPDX) uniaxially oriented commercial fibers was determined by polarized Raman spectroscopy and X‐ray diffraction. The order parameters 〈P200〉 and 〈P400〉 of the orientation distribution function were determined by polarized Raman spectroscopy. For the CO stretching band, the values of 〈P200〉 and 〈P400〉 obtained are equal to −0.40 ± 0.04 and 0.28 ± 0.04, respectively. These results clearly indicate that the carbonyl groups are highly oriented perpendicular to the fiber axis. X‐ray diffraction led to a fiber repeat value of 0.628 nm for these samples, and to 〈P200〉 and 〈P400〉 values of 0.93 and 0.82, respectively, for the c‐axis orientation, indicating a high orientation in the draw direction of the fibers. A Monte‐Carlo conformational search led to 20 low‐energy conformations, but only one of these was found compatible with both the fiber repeat and the angle between the CO bond and the fiber axis. This conformation, a 21 helix with a tg−ttg− succession of torsion angles, is proposed as the existing conformation in the crystalline state. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 406–417, 2008
The glass transition in athermal poly(α‐methyl styrene)/oligomer blends
Authors: Zheng Wei , Simon Sindee L.
Published: December 2007

The glass transition behavior in athermal blends of poly(α‐methyl styrene) (PaMS) and its hexamer is investigated using differential scanning calorimetry (DSC). The results, along with previous data on similar blends of PaMS/pentamer, are analyzed in the context of the Lodge–McLeish self‐concentration model. A methodology is described to partition the calorimetric transition to obtain effective Tgs for each component of the blend. The dependences of these effective Tgs on overall blend composition are described by the Lodge–McLeish model, although the self‐concentration effect is less than expected based on the Kuhn length. The length scales of the cooperatively rearranging regions for the two components in the blends are also calculated adapting Donth's fluctuation model to the partitioned DSC transitions and are found to be similar for the two components and show a slight decrease at intermediate concentrations. The kinetics associated with the glass temperature, Tg, is examined by studying the cooling rate dependence of Tg for the pure components and the blends, as well as by examining the enthalpy overshoots in the heating DSC scans. It is observed that the cooling rate dependence of Tg in PaMS/hexamer blends at intermediate concentrations is similar to that of the hexamer, indicating that the kinetics of the glass transition for blends is dominated by the high mobility oligomeric component. Moreover, compared to the pure materials, the PaMS/hexamer blends exhibit a considerably depressed enthalpy overshoot, presumably resulting from their broader relaxation time distribution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 418–430, 2008
Plasma Deposition of Silver Nanoparticles onto Stainless Steel for the Prevention of Fungal Biofilms: A Case Study on Saccharomyces cerevisiae
Authors: Guillemot Gaëlle , Despax Bernard , Raynaud Patrice , Zanna Sandrine , Marcus Philippe , Schmitz Philippe , Mercier‐Bonin Muriel
Published: December 2007

A silver nanoparticle composite film was deposited onto stainless steel to reduce the adhesion strength of the model yeast S. cerevisiae. Deposition was carried out under cold‐plasma conditions, combining RF glow discharge and silver sputtering. Shear‐flow‐induced detachment experiments demonstrated the film's anti‐adhesive properties. However, the surface tended to undergo some chemical changes after use, such an increase in hydrophilicity. XPS analysis confirmed the presence of metallic silver for the native plasma‐modified surface and revealed silver oxidation after use. The silver content was also lowered, due to the progressive release of ionic silver from the composite into the medium.

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Interpretation of Light Scattering Spectra of Dispersions – A Hybrid Approach to Account for Interparticle Interactions
Authors: Thennadil Suresh N. , Garcia‐Rubio Luis H.
Published: December 2007

The problem of extracting quantitative information on individual particle properties from spectroscopic measurements conducted at concentrations where particle interactions become significant is of great industrial and theoretical importance. For dispersions of charged particles, this can happen at fairly low concentrations. The effect of the fluid (slurry) structure has to be taken into account to interpret the light scattering spectra of such dispersions. In this paper, a hybrid method that addresses the effect of the fluid structure is proposed. The hybrid approach describes the fluid structure by relating the “effective” Percus‐Yevick hard‐sphere parameters to the system parameters using empirical models. The feasibility of this approach is examined through a theoretical study with data generated by Monte Carlo simulations of a monodisperse dispersion of charged spherical particles using realistic interaction potentials under single scattering conditions.
Particle Size of Pneumatically Conveyed Powders Measured Using Impact Duration
Authors: Coghill Peter J.
Published: December 2007

CSIRO Minerals has developed a technique for measuring particle size in pneumatically conveyed powders [1] by measurement of the acoustic waves produced by particle impacts upon a specially designed transducer. Previous work has focused on using the peak acoustic wave amplitude to determine particle size. This produces a spectrum that is hard to determine the particle size from, as the peak amplitude is a non‐linear function of particle diameter, and is strongly affected by angle of incidence and velocity of the impacting particle. In this paper impact duration measurements are used to overcome these difficulties while retaining the advantages of being able to measure in high solids loadings of up to at least 0.5 kg/m3 of powder. In laboratory tests the impact size monitor's (ISM) results have been correlated with optical diffraction measurements of the mean (by number) powder size with a correlation coefficient of 0.985 and a relative error of 5.5 %. The ISM operated successfully in the laboratory at a loading of 0.5 kg/m3 of powder and measured particles down to 50 microns in size.
Computing Particle Surface Areas and Contact Areas from Three‐Dimensional Tomography Data of Particulate Materials
Authors: Thompson Karsten E.
Published: December 2007

Microtomography is an emerging technique for particle and particulate‐materials characterization. To use this technology effectively, robust and accurate computational algorithms are needed to compute relevant particle properties, including particle surface area and particle‐particle contact area. However, the most accurate algorithms that have been developed for computing the exposed (void/solid) surface area in a microtomography image cannot be used directly for computing surface areas or particle‐particle contact areas for individual particles in a dense packing. This paper presents an algorithm for extracting particle contact areas from a digitized, segmented image of a packed granular material, which in turn can be used to find individual particle surface areas (even if the complete surfaces are not exposed because of contacts in the packing). Results show that small errors in the binary surface‐area computations are magnified in the course of determining particle contact areas; the total error in the computation depends mainly on the size of the contact area in voxel units.
Continuous Size Classification of Nanoparticles Utilizing Brownian Motion in Microchannel Size Exclusion Chromatography
Authors: Yamaguchi Tetsuji , Okuyama Kikuo
Published: December 2007

This study presents a new method for classifying the sizes of colloidal nanoparticles of below 100 nm in diameter in liquid dispersion using a microchannel size exclusion chromatography (SEC) chip. This chip can classify polydisperse colloidal nanoparticles containing a mix of two monodisperse nanoparticles into several monodisperse particle populations. The particles classified by the SEC chip are then sequentially analyzed by a photon correlation spectroscopy (PCS) method in combination with a flow cell. Two different pillar patterns of such SEC chips were used in experiments to investigate the effects of these patterns on the nanoparticle classification performance. The results obtained were compared with those from a numerical simulation. Standard polystyrene latex particles with diameters of 20 nm and 100 nm were used in this study. The usefulness of this methodology was verified since the simulation and measurement results were in good agreement with each other.
A Simple Approximate Formula for the Aspect Ratio of Oblate Particles
Authors: Pabst Willi , Berthold Christoph
Published: December 2007

A simple approximative formula is derived, which can be used to quantify the shape of oblate particles or an average shape of the corresponding particle system, when the results of sedimentation analysis (Stokes equivalent diameters) are known and results from either microscopic image analysis (assuming stable orientation, i.e., with the plane perpendicular to the direction of observation) or laser diffraction (assuming random orientation) are available for the same sample. In the latter case Cauchy's stereological theorem is applied to account for random orientation. Furthermore, it is shown that for sufficiently large aspect ratios, this formula is very close to the well‐known Jennings‐Parslow relation and can replace this more complicated expression in many practical cases, e.g., in the routine characterization of ceramic raw materials (kaolins and oxide or non‐oxide platelet powders).
Finasteride, prostate cancer, and weight gain: Evidence for genetic or environmental factors that affect cancer outcomes during finasteride treatment
Authors: Song YoonJu , Tangen Catherine , Goodman Phyllis , Parnes Howard L. , Lucia M. Scott , Thompson Ian M. , Kristal Alan R.
Published: December 2007

OBJECTIVE

Finasteride affects both prostate cancer risk and body weight. We examined whether, during 7 years of finasteride treatment, the magnitude of weight change was associated with the diagnosis of no, low‐, or high‐grade cancer.

METHODS

Data are from 10,057 participants in Prostate Cancer Prevention Trial (PCPT), a randomized trial of finasteride for primary prevention of prostate cancer. Mixed linear models were used to calculate percentage change in weight per year, controlling for demographic and health‐related covariates.

RESULTS

Weight gain was modestly lower in the finasteride compared to placebo arms (0.14 vs. 0.16% per year, P < 0.025). On the placebo arm, there was no association of weight gain with cancer outcomes. In the finasteride arm, annual weight gain among men without cancer was 0.14%, and among men with cancer ranged from 0.01% for those diagnosed with high‐grade cancer following a clinical indication for biopsy (P = 0.03 vs. no cancer) to 0.25% among men diagnosed with low‐grade cancer at the end of the trial with no indication for biopsy (P = 0.002 vs. no cancer).

CONCLUSIONS

In finasteride‐treated men, there are significant associations between prostate cancer outcomes and weight gain, which suggest that there are common or closely related individual‐level factors that affect both treatment responses. This supports the hypothesis that there are genetic characteristics and/or environmental exposures that affect finasteride outcomes which, when identified, could be used to target men most likely to benefit from finasteride treatment. Prostate 68: 281–286, 2008. © 2007 Wiley‐Liss, Inc.
A molecular analysis of prokaryotic and viral DNA sequences in prostate tissue from patients with prostate cancer indicates the presence of multiple and diverse microorganisms
Authors: Sfanos Karen S. , Sauvageot Jurga , Fedor Helen L. , Dick James D. , De Marzo Angelo M. , Isaacs William B.
Published: December 2007

BACKGROUND

Inflammation, both acute and chronic, is a common feature of prostate histology. While inflammation has been proposed to play an important role in both benign and malignant growth of the prostate, the stimuli for this inflammation remain poorly characterized. Infectious pathogens are potential stimuli for prostatic inflammation.

METHODS

Universal eubacterial PCR was used to test 170 prostate tissue core samples from 30 cancer patients for 16S rDNA gene sequences. Positive PCR products (n = 64, 37%) were cloned and sequenced. For comparison, tissue samples from 30 patients were cultured using standard clinical microbiological techniques. DNA samples from 200 additional patients were tested by organism‐specific PCR for the presence of Chlamydia trachomatis, Propionibacterium acnes, Trichomonas vaginalis, BK virus, Epstein–Barr virus, human cytomegalovirus, human papillomavirus, and xenotropic murine leukemia‐related virus.

RESULTS

16S sequencing results indicated the presence of 83 distinct microorganisms. Microbiological culture isolated markedly fewer species. In general, organism‐specific PCR failed to detect multiple organisms previously reported as common in the prostate. There was no significant association between the presence of particular species of bacteria and histologic evidence of acute or chronic inflammation.

CONCLUSIONS

Most prostates from men undergoing prostatectomy (87%) contain bacterial DNA from one or more species. However, the majority of individual tissue core samples were negative, suggesting regional heterogeneity in the presence of bacteria and a lack of a generalized or ubiquitous prostatic flora. Culture results suggest either the “unculturable” nature of species present in the prostate or that 16S rDNA sequences were derived from non‐viable bacteria. Prostate 68: 306–320, 2008. © 2007 Wiley‐Liss, Inc.
The Glu228Ala polymorphism in the ligand binding domain of death receptor 4 is associated with increased risk for prostate cancer metastases
Authors: Langsenlehner Tanja , Langsenlehner Uwe , Renner Wilfried , Kapp Karin S. , Krippl Peter , Hofmann Günter , Clar Heimo , Pummer Karl , Mayer Ramona
Published: December 2007

Background

Death receptor 4, encoded by the TNFRSF10A gene, is an important mediator of apoptosis and its dysfunction may be related to cancer development and distant tumor spread. A single nucleotide polymorphism in TNFRSF10A (Glu228Ala, rs20576) within a conserved region of the extracellular cysteine‐rich domain of death receptor 4 has been associated with an increased risk for a variety of tumor entities. Aim of the present study was to evaluate the role of the TNFRSF10A polymorphism in metastatic progression of prostate cancer after radiation therapy.

Methods

We carried out a prospective study including 702 prostate cancer patients from the Austrian PROCAGENE (Prostate Cancer Genetics) study. Development of metastases was examined in regular follow‐up investigations. TNFRSF10A genotypes were determined by a 5′‐nuclease assay (TaqMan).

Results

Within a median follow‐up time of 10 months (range 0–60 months), 24 (3.4%) patients developed metastases. In a Cox regression model including age at diagnosis and risk group as potential confounders, carriage of an 228Ala allele was associated with a relative risk of 2.47 (95% CI 1.10–5.54; P = 0.028) for metastases. TNFRSF10A genotypes were not associated with tumor stage, grade, risk group or age at diagnosis.

Conclusion

We conclude that the TNFRSF10A Glu228Ala polymorphism may be a novel independent risk factor for prostate cancer metastases after radiation therapy. Prostate 68: 264–268, 2008. © Wiley‐Liss, Inc.
TGF‐β signaling and androgen receptor status determine apoptotic cross‐talk in human prostate cancer cells
Authors: Zhu Meng‐Lei , Partin James V. , Bruckheimer Elizabeth M. , Strup Stephen E. , Kyprianou Natasha
Published: December 2007

BACKGROUND

A signaling interaction between transforming growth factor‐β (TGF‐β) and androgens promotes apoptosis in human prostate cancer cells LNCaP‐TβRII (androgen‐sensitive and TGF‐β responsive). This study investigated the contribution of androgen receptor (AR) in the combined effect of TGF‐β and dihydrotestosterone (DHT), on regulation of apoptosis and AR‐ and TGF‐β mediated transcriptional activity in human prostate cancer cells.

METHODS

Transcriptional activation in response to TGF‐β (5 ng/ml) and DHT (1 nM) was evaluated using transient transfections and luciferase assays in human prostate cancer cells, LNCaP‐TβRII and PC‐3, overexpressing the wild type AR. The apoptotic response to DHT/TGFβ treatment was correlated with AR cellular distribution and the AR interaction with TGF‐β intracellular effector Smad4.

RESULTS

The results revealed that TGF‐β signaling induced AR‐mediated transcriptional activation in two androgen‐responsive promoters [probasin and prostate specific antigen (PSA)]. TGF‐β1 induced transcriptional activity enhanced by DHT in both cell lines (LNCaP‐TβRII and PC‐3‐AR) via AR‐Smad4 interaction. This interaction however does not exclusively drive TGF‐β mediated apoptosis as DHT failed to enhance such an effect in PC‐3 AR (wt) cells.

CONCLUSIONS

These results demonstrate that the AR status determines the sensitivity of prostate cancer cells to the apoptotic effects of TGF‐β1, thus providing a new insight into the mechanism via which TGF‐β cross‐sections the AR axis toward the functional convergence of the two pathways in the development of androgen‐independent prostate cancer. This study is potentially significant in defining the contribution of AR status to the emergence of androgen‐independent prostate tumors. Prostate 68: 287–295, 2008. © 2007 Wiley‐Liss, Inc.
Galiellalactone is a novel therapeutic candidate against hormone‐refractory prostate cancer expressing activated Stat3
Authors: Hellsten Rebecka , Johansson Martin , Dahlman Anna , Dizeyi Nishtman , Sterner Olov , Bjartell Anders
Published: December 2007

BACKGROUND

Signal transducer and activator of transcription 3 (Stat3) is constitutively active (phosphorylated) in several forms of cancer, including prostate cancer (PCa). Stat3 signaling may be an interesting target for cancer therapy since inhibition of this pathway mediates growth inhibition and apoptosis of these cells. In this study we investigated the in vitro and in vivo effects of the fungal metabolite galiellalactone, a direct inhibitor of Stat3, on PCa cells.

METHODS

The human PCa cell lines DU145, PC‐3, and LNCaP were used. Nude mice with subcutaneous PCa cell xenografts were subjected to daily intraperitoneal injections of galiellalactone for 3 weeks. The effect of galiellalactone on the induction of apoptosis of cultured PCa cells was investigated by Western blot analysis, immunocytochemistry, and annexin V staining. Effects of galiellalactone on Stat3 signaling were investigated by a luciferase reporter gene assay. Expression of Stat3 associated proteins and mRNA was investigated by Western blot and real‐time quantitative PCR analysis.

RESULTS

Galiellalactone induced apoptosis of p‐Stat3 positive PCa cells (androgen‐insensitive DU145 and PC‐3) but not in cells lacking p‐Stat3 (androgen‐sensitive LNCaP). Galiellalactone inhibited Stat3‐mediated luciferase activity (IC50 ∼ 5 µM) and reduced the expression of Bcl‐2, Bcl‐xL, c‐myc, and cyclin D1. Furthermore, galiellalactone significantly suppressed DU145 xenograft growth in vivo (42% growth reduction; P < 0.002) and reduced the relative mRNA expression of Bcl‐xL and Mcl‐1.

CONCLUSIONS

Galiellalactone induced growth inhibition and apoptosis in androgen‐insensitive PCa cells expressing p‐Stat3. We suggest that galiellalactone is a potential anti‐tumor lead against hormone‐refractory PCa with constitutively active Stat3. Prostate 68: 269–280, 2008. © 2007 Wiley‐Liss, Inc.
Expression of BNIP3 correlates with hypoxia‐inducible factor (HIF)‐1α, HIF‐2α and the androgen receptor in prostate cancer and is regulated directly by hypoxia but not androgens in cell lines
Authors: Shaida Nadeem , Launchbury Rosalind , Boddy Jane L. , Jones Catherine , Campo Leticia , Turley Helen , Kanga Suresh , Banham Alison H. , Malone Peter R. , Harris Adrian L. , Fox Stephen B.
Published: December 2007

Background

BNIP3 is a hypoxia‐induced protein involved in cell death and survival but its role in human tumors is unclear. This study investigated the role of BNIP3 in prostate cancer.

Methods

The expression of BNIP3, the androgen receptor (AR), hypoxia inducible factor (HIF)‐1α, HIF‐2α and the hypoxia regulated gene GLUT1 were assessed in tissue microarrays constructed from 149 radical prostatectomy specimens. Statistics compared expression of these factors between each other, conventional clinicopathological parameters and PSA recurrence. Since an association between BNIP3 and AR and the HIFs was observed, the influence of hypoxia, dihydrotestosterone and the AR blocker, Casodex, was also investigated in prostate cell lines.

Results

BNIP3 was expressed in the nucleus and cytoplasm. Eight of 149 (5.5%) tumors showed no expression, 44/149 (29.5%) cases showed exclusively cytoplasmic expression, 17/149 (11.5%) cases showed exclusively nuclear expression and 80/149 (53.5%) cases showed both cytoplasmic and nuclear expression. There was a significant correlation between cytoplasmic BNIP3 expression and Gleason score (P = 0.005), age (P = 0.02), AR (P = 0.001), and GLUT1 (P = 0.006). There was a significant correlation between nuclear BNIP3 expression and HIF‐1α expression (P = 0.006) and HIF‐2α expression (P = 0.013) but no correlation between BNIP3 and pre‐operative PSA, tumor volume, margin positivity or capsular invasion (all P > 0.05). There was an increase in BNIP3 expression under conditions of hypoxia (0.1% 02) but not with dihydrotestosterone stimulation or with Casodex treatment.

Conclusions

These findings suggest that BNIP3 is directly regulated by hypoxia but that there may be a hormonal independent mechanism coordinating the expression of BNIP3 in prostate tumors. Prostate 68: 336–343, 2008. © Wiley‐Liss, Inc.
Diagnosis and treatment of anaemia in primary care
Authors: Smith Alastair , Wechalekar Ashu
Published: December 2007

The management of anaemia requires a systematic approach to diagnosis and treatment. Our Drug review considers the various causes of anaemia and the treatments available, followed by an analysis of prescription data, sources of further information and the Datafile. Copyright © 2007 Wiley Interface Ltd
Abatacept: first T cell co‐stimulation modulator for severe active RA
Authors: Chaplin Steve , Ostor Andrew
Published: December 2007

Abatacept (Orencia) is licensed for the treatment of severe RA in combination with methotrexate when at least one anti‐TNF agent has failed. Here, Steve Chaplin presents the clinical data relating to its efficacy and adverse effects, and Dr Andrew Ostor comments on its place in RA therapy. Copyright © 2007 Wiley Interface Ltd
Grape seed extract treatment reduces hepatic ischemia‐reperfusion injury in rats
Authors: Şehirli Özer , Ozel Yahya , Dulundu Ender , Topaloglu Umit , Ercan Feriha , Şener Goksel
Published: December 2007

This study was designed to determine the possible protective effect of grape seed extract (GSE), a widely used antioxidant dietary supplement, on hepatic ischemia/reperfusion (I/R) injury. Wistar albino rats were subjected to 45 min of hepatic ischemia, followed by a 60 min reperfusion period. GSE was administered in a dose of 50 mg/kg/day orally for 15 days before I/R injury and repeated before the reperfusion period. Liver samples were taken for histological examination or determination of hepatic malondialdehyde (MDA), glutathione (GSH) and myeloperoxidase (MPO) activity. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were determined to assess liver functions. Lactate dehydrogenase (LDH) and cytokines (TNF‐α and IL‐1β) were also assayed in serum samples for the evaluation of generalized tissue damage. Ischemia/reperfusion caused a significant decrease in hepatic GSH, and significant increases in MDA level, and MPO activity. Serum AST and ALT levels, as well as LDH activity and plasma TNF‐α and IL‐1β levels were also elevated in the I/R group. Treatment with GSE reversed all these biochemical parameters as well as histological alterations induced by I/R. In conclusion, GSE reduced I/R‐induced organ injury through its ability to balance the oxidant–antioxidant status, to inhibit neutrophil infiltration and to regulate the release of inflammatory mediators. Copyright © 2007 John Wiley & Sons, Ltd.
Relationships between hydrology, spatial heterogeneity, and fish recruitment dynamics in a temperate floodplain river
Authors: Zeug S. C. , Winemiller K. O.
Published: December 2007

Fish populations in the Brazos River, Texas, were surveyed monthly for 2 years to determine the relative influence of hydrology and habitat characteristics on the recruitment dynamics of seven species representing three divergent life history strategies. Surveys were conducted in two oxbow lakes with different flood recurrence intervals and the main river channel. The first year was relatively dry with few oxbow‐river connections, whereas year 2 was relatively wet and connections between the main channel and floodplain habitats were common. Oxbow lakes supported greater juvenile abundances of most species relative to the main channel and were particularly important for nest building species with parental care. The river channel supported small species with extended reproductive periods and large, long‐lived species that are able to store reproductive potential during sub‐optimal periods. Hydrologic isolation was associated with greater rotifer densities in oxbows, and species with the greatest fecundity produced strong year classes during this period. Hydrologic connectivity did not increase juvenile production for most species, suggesting that recruitment dynamics in the Brazos River are similar to predictions of the low flow recruitment hypothesis (LFR). These results suggest that both hydrology and habitat heterogeneity interact with fish life history strategy to determine optimal conditions for recruitment and all three factors must be considered in restoration strategies for floodplain rivers. Copyright © 2007 John Wiley & Sons, Ltd.
Fast Projection‐Based Methods for the Least Squares Nonnegative Matrix Approximation Problem
Authors: Kim Dongmin , Sra Suvrit , Dhillon Inderjit S.
Published: December 2007

Nonnegative matrix approximation (NNMA) is a popular matrix decomposition technique that has proven to be useful across a diverse variety of fields with applications ranging from document analysis and image processing to bioinformatics and signal processing. Over the years, several algorithms for NNMA have been proposed, e.g. Lee and Seung's multiplicative updates, alternating least squares (ALS), and gradient descent‐based procedures. However, most of these procedures suffer from either slow convergence, numerical instability, or at worst, serious theoretical drawbacks. In this paper, we develop a new and improved algorithmic framework for the least‐squares NNMA problem, which is not only theoretically well‐founded, but also overcomes many deficiencies of other methods. Our framework readily admits powerful optimization techniques and as concrete realizations we present implementations based on the Newton, BFGS and conjugate gradient methods. Our algorithms provide numerical results superior to both Lee and Seung's method as well as to the alternating least squares heuristic, which was reported to work well in some situations but has no theoretical guarantees1. Our approach extends naturally to include regularization and box‐constraints without sacrificing convergence guarantees. We present experimental results on both synthetic and real‐world datasets that demonstrate the superiority of our methods, both in terms of better approximations as well as computational efficiency. Copyright © 2007 Wiley Periodicals, Inc., A Wiley Company Statistical Analy Data Mining 1: 000‐000, 2007
Cytotoxicity of Nanoparticles
Authors: Lewinski Nastassja , Colvin Vicki , Drezek Rebekah
Published: December 2007

Human exposure to nanoparticles is inevitable as nanoparticles become more widely used and, as a result, nanotoxicology research is now gaining attention. However, while the number of nanoparticle types and applications continues to increase, studies to characterize their effects after exposure and to address their potential toxicity are few in comparison. In the medical field in particular, nanoparticles are being utilized in diagnostic and therapeutic tools to better understand, detect, and treat human diseases. Exposure to nanoparticles for medical purposes involves intentional contact or administration; therefore, understanding the properties of nanoparticles and their effect on the body is crucial before clinical use can occur. This Review presents a summary of the in vitro cytotoxicity data currently available on three classes of nanoparticles. With each of these nanoparticles, different data has been published about their cytotoxicity due to varying experimental conditions as well as differing nanoparticle physiochemical properties. For nanoparticles to move into the clinical arena, it is important that nanotoxicology research uncovers and understands how these multiple factors influence the toxicity of nanoparticles so that their undesirable properties can be avoided.
Reducing Measurement Error in Student Achievement Estimation
Authors: Battauz Michela , Bellio Ruggero , Gori Enrico
Published: December 2007

The achievement level is a variable measured with error, that can be estimated by means of the Rasch model. Teacher grades also measure the achievement level but they are expressed on a different scale. This paper proposes a method for combining these two scores to obtain a synthetic measure of the achievement level based on the theory developed for regression with covariate measurement error. In particular, the focus is on ordinal scaled grades, using the SIMEX method for measurement error correction. The result is a measure comparable across subjects with smaller measurement error variance. An empirical application illustrates the method.
Kinesin‐driven transport in cell‐free environment
Authors: Böhm Konrad J.
Published: December 2007

Conventional kinesin is an ATPase‐active motor protein that is involved in the microtubule‐dependent transport of cytoplasmic cargoes. The present paper provides a condensed overview on kinesin‐1 and its motility generation outside a living cell. Moreover, it demonstrates that the neuron‐specific kinesin KIF5A enables the formation of microtubules under conditions where pure tubulin does not assemble.
Nonclassical secretion of human catalase on the surface of CHO cells is more efficient than classical secretion
Authors: He Zuyong , Sun Xiuzhu , Mei Gui , Yu Shengli , Li Ning
Published: December 2007

There is a great demand for improved production of therapeutic proteins using mammalian cell expression systems and transgenic animals. There have been intensive endeavors to optimize production at the transcriptional and translational levels, but comparatively little attention has been paid to the secretory level, especially to nonclassical secretion. To compare the efficiencies of classical and nonclassical secretion, we expressed GFP‐tagged human catalase conjugated with a classical signal peptide and with several short peptides derived from mouse Engrailed 2 (mEN2) homeoprotein for nonclassical secretion and internalization in CHO cells. Surprisingly, the results showed that the secretory efficiency was significantly greater (up to 2.3 fold) than classical secretion when the fusion protein was driven by the secretory sequence (SS) of mEN2, and up to 1.9 fold when the classical secretion process was modified by incorporating the internalization sequence (IS) of mEN2. The effect of these short peptides on nonclassical secretion and internalization may indicate potential applications in the improved production of complex therapeutic proteins in mammalian cell expression systems and transgenic animals.
Age‐associated alterations of lipofuscin, membrane‐bound ATPases and intracellular calcium in cortex, striatum and hippocampus of rat brain: protective role of glutathione monoester
Authors: Murali Ganesan , Panneerselvam Kavin S. , Panneerselvam Chinnakkannu
Published: December 2007

Brain aging has become an area of intense research and a subject of much speculation fueled largely from the widely recognized fact that age is the biggest risk factor in most neurodegenerative diseases and age‐related increase of reactive oxygen species is particularly detrimental to postmitotic tissues. In the present study, we have evaluated the possible role of glutathione monoester (GME), when administered intraperitoneally (12 mg/kg body weight) for 20 days on age‐associated changes in the levels of lipofuscin, Na+K+, Mg2+, Ca2+ ATPase activities and intracellular calcium levels in discrete brain regions of young and aged male albino Wistar rats. An age‐associated increase in lipofuscin, intracellular calcium in cortex, striatum and hippocampus was observed and contradictorily, a decrease in the activities of membrane‐bound enzyme activities was also observed. Supplementation of GME brought these changes to near normalcy. Thus, GME improves neuronal antioxidant status, thereby effectively attenuating any putative increase in oxidative stress with age.
An optical model for heat and salt budget estimation for shallow seas
Authors: Warrior Hari , Carder Kendall
Published: December 2007

The effects of the underwater light field on heat‐budget calculations for shallow waters are developed and applied for the region of Bahamas. Most of the general circulation models use a simplified heat budget scheme based on Jerlov water types, and do not account for optical bottom effects. By optical bottom effect, we mean the bottom absorption and reflection of the short‐wave radiation, which in turn affects the thermal stratification and heat exchange with the atmosphere. In this paper, this optical bottom effect is added to a 3D turbulence model (a 1D model called GOTM is coupled to a 3D model called POM) and the evolution of the temperature structure studied. We call the coupled model 3DGOTM. This optical bottom effect is found to be important in the areas with clear water, shallow depths and small solar zenith angle. On the basis of the coastal meteorological measurements from Andros Island, we have used this three‐dimensional turbulence closure model (3DGOTM) to show the influence of bottom reflection and absorption on the sea surface temperature field. The final temperature of the developed water column depends on water depth and bottom albedo. Effects of varying the bottom albedo were studied by comparing results for coral sand and sea grass bottoms. This has an appreciable contribution to the heat budget and salt budget of the shallow waters in these coastal regions. The salinities of the shallow regions near Andros Island have been found to reach as high as 46 psu by summer. In addition to the thermohaline plumes generated by these bottom effects, this warming process has an impact on the moisture feedbacks into the atmosphere due to evaporation.
Density‐dependent variations of the along‐isobath flow in the East Greenland Current from Fram Strait to Denmark Strait
Authors: Schlichtholz Pawel
Published: December 2007

The East Greenland Current (EGC) dynamically connects the Arctic Ocean to the North Atlantic on the western side of the Nordic Seas. Observations show that the speed of the EGC considerably varies along the East Greenland Slope (EGS). Here it is shown, using current meter data reported in the literature and climatological hydrographic fields, that velocity and transport variations along the EGS are supported by the cross‐isobath component of the density‐dependent geostrophic flow relative to the bottom. The relative flow impinging on (leaving) the EGS in a northern (southern) limb of the cyclonic circulation in the Nordic Seas strengthens (weakens) the along‐isobath bottom geostrophic flow. Variations of the latter are clearly associated with along‐isobath bottom density gradients. Current observations indicate an increase of the along‐isobath bottom velocity from 79°N to 75°N equal to about 9 and 10 cm s−1 on the upper (1000 m isobath) and lower (2000 m isobath) EGS, respectively. Corresponding estimates based on bottom density distribution along the 1000 and 2000 m isobaths are grossly consistent with the observations given above though we obtain a higher increase (13 cm s−1) at 1000 m and lower increase (6 cm s−1) at 2000 m. Considering the variability of the system and the poor resolution of the observations we find this to be a very convincing result, demonstrating the power of the geostrophic approximation for such estimates.
Coordinated analyses of orbital and Spirit Rover data to characterize surface materials on the cratered plains of Gusev Crater, Mars
Authors: Lichtenberg Kimberly A. , Arvidson Raymond E. , Poulet Francois , Morris Richard V. , Knudson Amy , Bell James F. , Bellucci Giancarlo , Bibring Jean‐Pierre , Farrand William H. , Johnson Jeffrey R. , Ming Douglas W. , Pinet Patrick C. , Rogers A. Deanne , Squyres Steven W.
Published: December 2007

Comparison of the Mars Exploration Rover Spirit's Pancam (0.4 to 1.0 μm) and Mars Express Observatoire pour la Mineralogie l'Eau, les Glaces et l'Activité (OMEGA) (0.4 to 2.5 μm) spectral reflectance data over Spirit's traverses shows that Gusev cratered plains are dominated by nanophase ferric‐oxide‐rich dust covering weakly altered basaltic sands. This interpretation is also consistent with both observations from OMEGA data covering plains beyond the traverse region and interpretations of data from the other payload instruments on the Spirit Rover. OMEGA observations of relatively low albedo regions where dust has presumably been stripped by dust devils show negative spectral reflectance slopes from 1.5 to 2.5 μm and moderately masked spectral features which are indicative of olivine or pyroxene. High‐albedo regions north and south of the Spirit landing site have flat spectral reflectance slopes and few spectral features, although all spectra have a nanophase ferric‐oxide absorption edge between 0.4 and 0.75 μm. Comparison of THEMIS‐derived thermal inertia values with OMEGA‐derived spectral parameters shows that although the dust cover can be optically thick (0.4 to 2.5 μm wavelength region) in some areas, it is not thick enough (∼1 cm) to mask the thermal inertia of the underlying substrate for areas included in this study.
Life in the Atacama: A scoring system for habitability and the robotic exploration for life
Authors: Hock Andrew N. , Cabrol Nathalie A. , Dohm James M. , Piatek Jennifer , Warren‐Rhodes Kim , Weinstein Shmuel , Wettergreen David S. , Grin Edmond A. , Moersch Jeffrey , Cockell Charles S. , Coppin Peter , Ernst Lauren , Fisher Gregory , Hardgrove Craig , Marinangeli Lucia , Minkley Edwin , Ori Gian Gabriele , Waggoner Alan , Wyatt Mike , Smith Trey , Thompson David , Wagner Michael , Jonak Dominic , Stubbs Kristen , Thomas Geb , Pudenz Erin , Glasgow Justin
Published: December 2007

The science goals of the Life in the Atacama (LITA) robotic field experiment are to understand habitat and seek out life in the Atacama Desert, Chile, as an analog to future missions to Mars. To those ends, we present a new data analysis tool, the LITA Data Scoring System (DSS), which (1) integrates rover and orbital data relevant to environmental habitability and life detection, and (2) provides a standard metric, or “score” to evaluate (a) the potential habitability, and (b) the strength of evidence for life at all locales along the rover's traverse. Designed and tested during the 2005 field campaign, first results from the DSS indicate that the three selected sites in the Atacama Desert are generally inhospitable. The strength of evidence for life is positively correlated with potential habitability at two of the three sites. Using factor analysis, we find three factors explain 79.9% of the variance in biological observations and five factors explain 96.2% of the variance in potential habitability across all sites. These factors are used to focus a discussion of scoring variable definitions for future robotic missions in the Atacama and of instrument selection and strategy development for future robotic missions on Earth and Mars.
Recent Eurasian river discharge to the Arctic Ocean in the context of longer‐term dendrohydrological records
Authors: MacDonald G. M. , Kremenetski K. V. , Smith L. C. , Hidalgo H. G.
Published: December 2007

Mapped correlations between annual discharges (AD 1938–1990) of the major Eurasian rivers entering the Arctic Ocean (Severnaya Dvina, Pechora, Ob', Yenisey, Lena, and Kolyma) demonstrate a positive relationship between discharge and the Palmer Drought Severity Index (PDSI) within the individual basins and more distant areas. The relationship between recent discharge and PDSI supports the application of dendrohydrological modeling to produce reconstructions of discharge extending back before the 20th century. The dendrohydrologic models explain from 41% (Yenisey) to 55% (Pechora) of the observed variability of flow in the individual basins and 39% of the total combined discharge. Discharge reconstructions for the period AD 1800–1990 indicate that there is no long‐term monotonic trend toward higher discharge over the past 200 years. Reconstructed annual discharge for the individual rivers and the total discharge from all the rivers experienced in the 20th century are within the bounds of natural variability experienced over the past 200 years. The S. Dvina, Pechora, Ob, and Kolyma reconstructions do display significant multidecadal variability in discharge similar to that observed in the North Atlantic, North Pacific, and Northern Hemisphere climatic parameters. Although the translation of such variability to the river discharges remains uncertain, the presence of multidecadal variability makes it more difficult to detect or ascribe annual discharge changes that may be attributable to global warming.
Angular momentum in the global atmospheric circulation
Authors: Egger Joseph , Weickmann Klaus , Hoinka Klaus‐Peter
Published: December 2007

Angular momentum is a variable of central importance to the dynamics of the atmosphere both regionally and globally. Moreover, the angular momentum equations yield a precise description of the dynamic interaction of the atmosphere with the oceans and the solid Earth via various torques as exerted by friction, pressure against the mountains and the nonspherical shape of the Earth, and by gravity. This review presents recent work with respect to observations and the theory of atmospheric angular momentum of large‐scale motions. It is mainly the recent availability of consistent global data sets spanning decades that sparked renewed interest in angular momentum. In particular, relatively reliable estimates of the torques are now available. In addition, a fairly wide range of theoretical aspects of the role of angular momentum in atmospheric large‐scale dynamics is covered.
On the relation between dynamic storage and runoff: A discussion on thresholds, efficiency, and function
Authors: Spence C.
Published: December 2007

Unit hydrograph theory as derived by Nash (1957), Dooge (1959), and Wooding (1965) provides a foundation for evaluating the function controlling catchment runoff. Past literature has often investigated this function converting catchment storage to runoff with probabilistic or statistical approaches. A geophysically based framework is missing. The objective of the research reported here is to evaluate this function explicitly, using empirical nested measurements of surface storage and runoff in a Canadian Prairie catchment during the 2006 spring snowmelt. Variation in the value of this function, K at the basin scale, or k at the sub‐basin scale, was found to embody the hydrological processes acting upon a catchment. It is the relative difference between the runoff rate and the change in storage that indicates the hydrological function of a sub‐basin, and k is indicative of the efficiency of this functioning. Field results show that previous assumptions of instantaneously responding reservoirs within catchments are not applicable in this landscape. Storage thresholds control the value of the transfer function by influencing when runoff production occurs. In doing so, storage thresholds play a crucial role in the efficiency with which a catchment can transfer water to its outlet. The transfer function and storage threshold, by dictating runoff, can be considered hydrological signatures. Applying these signatures within a geophysically based framework has proven to be successful in predicting the efficiency of runoff production in this particular catchment and is proposed as an approach to evaluate the interrelationships between catchment stores and runoff production. Furthermore, if hydrological processes or physioclimatic predictors can be related to these hydrological signatures in a dimensionally consistent framework, this framework could be tested as a bridging mechanism between hydrological processes at the sub‐basin scale and prediction of runoff at the basin scale.
Secondary current effects on cohesive river bank erosion
Authors: Papanicolaou Athanasios N. , Elhakeem Mohamed , Hilldale Robert
Published: December 2007

The emphasis of this research was placed on the development of a methodology that allows (1) an adequate representation of the distribution of the near‐bank shear stress τs when secondary currents are present and (2) estimation of the critical erosional strength τcr and other sediment erodibility parameters for fluvial erosion. These two factors combine to form the overarching objective of this investigation, which was carried out in Union Flat Creek, a stream with pronounced cross‐sectional irregularities located within the loess region of the Palouse basin of Washington State, United States. The study has shown that the presence of the secondary currents increases the magnitude of the depth‐averaged sidewall shear stress at least by a factor of 2.0. It was also found that the ratio of the maximum to the depth‐averaged sidewall shear stress is greater than 5. These findings suggest therefore that use of the may be a good approximation of the fluid shear stress magnitude for simple channel geometries but not for natural channels characterized by complex geometries. The measured critical erosional strength (τcr = 4.16 Pa) was comparable with the findings of other laboratory and field studies that also focused on Palouse sediments.
Could meltwater pulses have been sneaked unnoticed into the deep ocean during the last glacial?
Authors: Roche Didier M. , Renssen Hans , Weber Susanne L. , Goosse Hugues
Published: December 2007

The lack of climatic imprint left by the Meltwater Pulse‐1A (≃14.5 ka BP), equivalent to a sea‐level rise of 14 to 20 meters, is puzzling. Recent studies suggest the event might have occurred as a hyperpycnal flow in the Gulf of Mexico, preventing its detection in oceanic records throughout the North Atlantic. We present a suite of simulations with the LOVECLIM climate model, which mimic the effect of hyperpycnal flow under LGM conditions, in a first attempt to constrain its climatic effects. Analysing the ocean dynamics associated with the anomalous freshwater input, we show that the proposed mechanism is capable of sneaking a significant proportion of the MWP into the ocean (≃6 meters equivalent sea‐level rise using our model under LGM boundary conditions). We also demonstrate that, in our model, the meridional circulation is more sensitive to such inputs in the Arctic Ocean than in the Gulf of Mexico.