bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical field‐assisted solid‐phase extraction coupled on‐line to capillary electrophoresis‐mass spectrometry
Authors: Morales‐Cid Gabriel , Simonet Bartolomé M. , Cárdenas Soledad , Valcárcel Miguel
Published: April 2008

A substantial demand currently exists for analytical methods affording the determination of very low concentrations of analytes in complex matrices, such as those of environmental and biological samples, as simply as possible. However, the pretreatment of complex samples, which is unavoidable prior to CE‐MS analysis, is usually complicated and time‐consuming. In this work, we used voltage‐assisted SPE for the first time as an alternative to conventional treatments for preconcentrating and purifying analytes. To this end, we used a simple flow system coupled on‐line to CE‐MS equipment. The system is quite robust and provides reproducible peak areas (the precision ranges from 2.5 to 3.8%). Also, it provides increased sensitivity affording the determination of trace amounts (nanogram per liter levels) of analytes in only a few milliliters of sample. The proposed system was applied to the determination of members of two compound families (viz. tetracyclines and amines).
Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling‐micellar electrokinetic chromatography‐mass spectrometry with reversal of electroosmotic flow
Authors: Ge Liya , Yong Jean Wan Hong , Tan Swee Ngin , Hua Lin , Ong Eng Shi
Published: April 2008

In this paper, we present the results of simultaneous screening of eight gibberellins (GAs) in coconut (Cocos nucifera L.) water by MEKC directly coupled to ESI‐MS detection. During the development of MEKC‐MS, partial filling (PF) was used to prevent the micelles from reaching the mass spectrometer as this is detrimental to the MS signal, and a cationic surfactant, cetyltrimethylammonium hydroxide, was added to the electrolyte to reverse the EOF. On the basis of the resolution of the neighboring peaks, different parameters (i.e., the pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF‐MEKC separation of eight GA standards. Under optimum conditions, a baseline separation of GA standards, including GA1, GA3, GA5, GA6, GA7, GA9, GA12, and GA13, was accomplished within 25 min. Satisfactory results were obtained in terms of precision (RSD of migration time below 0.9%), sensitivity (LODs in the range of 0.8–1.9 μM) and linearity (R2 between 0.981 and 0.997). MS/MS with multiple reaction monitoring (MRM) detection was carried out to obtain sufficient selectivity. PF‐MEKC‐MS/MS allowed the direct identification and confirmation of the GAs presented in coconut water (CW) sample after SPE, while, the quantitative analysis of GAs was performed by PF‐MEKC‐MS approach. GA1 and GA3 were successfully detected and quantified in CW. It is anticipated that the current PF‐MEKC‐MS method can be applicable to analyze GAs in a wide range of biological samples.
Constant pressure‐assisted electrokinetic injection for on‐line enhanced detection of monophthalates in capillary electrophoresis‐mass spectrometry with application to human urine
Authors: Feng Yong‐Lai , Zhu Jiping
Published: April 2008

Electrophoresis characteristics of several monophthalates in the sample zone and EOF variation in a fused‐silica capillary column during a constant pressure‐assisted electrokinetic injection (PAEKI) in an on‐line CE‐MS were studied in an effort to reconcile the mobility theory and field amplification with the enhancement achieved in present work. Influences of capillary length on the amount injected using PAEKI were investigated in detail and except for the injection time, the amount injected was found to increase linearly with capillary column length. A longer capillary provides a longer linear increase time range with PAEKI injection. The results show that smaller m/z analytes generate a large enhancement power using PAEKI, which is in agreement with the mobility theory. ACN was used as an example to investigate influences of organic additives on the amount injected and was found to decrease the amount injected with PAEKI injection, which is in agreement with an increase of resistivity in running buffer by organic additives. The peak width obtained with PAEKI injection proved to be independent of the amount injected. The band size of the sample zone was estimated by comparison with conventional hydrodynamic injection. A 240 s PAEKI injection achieved the same size of sample zone as a 2 s of hydrodynamic injection. Existance of two ion layers around the boundary of the buffer and sample solutions in sample zone was hypothesized to contribute the narrow sample zone with a long time of PAEKI injection. With a 240 s on‐line PAEKI injection in CZE‐MS, five monophthalates were enriched several hundred times without compromise in their separation efficiency and peak shape. With appropriate sample cleanup, PAEKI was applied to the analysis of monophthalates in urine samples, achieving detection limits ranging between 0.53 and 1.3 ng/mL.
Biodegradation of Methyl Ethyl Ketone and Methyl Isopropyl Ketone in a Composite Bead Biofilter
Authors: Chan W.‐C. , Peng K.‐H.
Published: April 2008

Biodegradation of methyl ethyl ketone (MEK) and methyl isopropyl ketone (MIPK) in a composite bead biofilter was investigated. The composite bead represents a spherical PVA/peat/KNO3/GAC one. Both the microbial growth rate μ and the biochemical reaction rate coefficient kd could be affected with increasing inlet concentration. For the microbial growth process, an inhibitory effect of almost the same sensitivity for the two ketone compounds and the μ value of MEK was more pronounced than that of MIPK in the inlet concentration range of 100 to 300 ppm. The half‐saturation constant Ks values of MEK and MIPK were 21.56 and 22.96 ppm, respectively. The maximum reaction rate Vm values of MEK and MIPK were 9.06 and 7.55 g C/h kg of packed material, respectively. Zero‐order kinetics with diffusion limitation could be regarded as the most adequate biochemical reaction model. For the biochemical process, the inhibitory effect for MEK was more notable than that for MIPK in the inlet concentration range of 100 to 150 ppm whereas it was the reverse in the inlet concentration range of 150 to 300 ppm. The kd value of MEK was greater than that of MIPK in the inlet concentration range of 100 to 300 ppm. The maximum elimination capacities of MEK and MIPK were found to be 44.2 and 35.2 g C/h m3 of bed volume. MEK, in particular the compound with a lower number of carbons or no side groups in the main chain, was easier biodegraded by the microorganisms than MIPK.
Applications of PAT‐Process Analytical Technology in Recombinant Protein Processes with Escherichia coli
Authors: Kaiser C. , Pototzki T. , Ellert A. , Luttmann R.
Published: April 2008

Monitoring of bioprocesses and thus observation and identification of such processes is one of the main aims of bioprocess engineering. It is of vital importance in bioprocess development to improve the overall productivity by avoiding unintentional limitations to ensure not only optimal process conditions but also the observation of established production processes. Furthermore, reproducibility needs to be improved and final product quality and quantity be guaranteed. Therefore, an advanced monitoring and control system has been developed, which is based on different in‐line, on‐line and at‐line measurements for substrates and products. Observation of cell viability applying in‐line radio frequency impedance measurement and on‐line determination of intracellular recombinant target protein using the reporter protein T‐Sapphire GFP based on in‐line fluorescence measurement show the ability for the detection of critical process states. In this way, the possibility for the on‐line recognition of optimal harvest times arises and disturbances in the scheduled process route can be perceived.
Maximum kurtosis estimation of the optimal filter and convergence step size parameter in blind adaptive TEQ for multicarrier systems
Authors: Bellahsene H. , Rouvaen J. M. , Djeddi M.
Published: April 2008

The effective channel channel shortening equalisers (CSE) using blind adaptive algorithms have run into great interest. These are very important for orthogonal sub‐carrier maintained for multicarrier modulation (MCM) and reduce consequently the complexity of multi‐users detection algorithms. We review in this paper the evolution from classical equalisation to the channel shortening equalisation. We utilise the calculus of maximum kurtosis for determining the optimal time domain equaliser (TEQ) and synchronisation delay for the maximum shortening signal to noise ratio (MSSNR) algorithm. We compare the optimal filters obtained by other methods and the proposed method based on maximum kurtosis. Copyright © 2008 John Wiley & Sons, Ltd.
Chemical variability of the leaf oil of 113 hybrids from Citrus clementina (Commun) × Citrus deliciosa (Willow Leaf)
Authors: Tomi Félix , Barzalona Marina , Casanova Joseph , Luro François
Published: April 2008

Essential oils of 113 Citrus clementina (Commun) × Citrus deliciosa (Willow Leaf) hybrids were obtained from leaves collected on trees located in the same orchard. Their chemical composition was investigated by capillary GC, GC–MS and 13C‐NMR and the results were submitted to statistical analysis. Three chemical compositions were characterized. The crossing between clementine and mandarin produces mainly leaf oils characterized by a composition similar to those of the parents (sabinene/linalool or methyl N‐methylanthranylate). However, several samples exhibited an original composition (γ‐terpinene/linalool). Copyright © 2008 John Wiley & Sons, Ltd.
New chitinozoans from the historical type area of the Hirnantian Stage and additional key sections in the Wye Valley, Wales, UK
Authors: Vandenbroucke Thijs R. A. , Hennissen Jan , Zalasiewicz Jan A. , Verniers Jacques
Published: April 2008

The type locality for several core elements of the Hirnantia brachiopod fauna is a small disused quarry on the western slopes of Cwm Hirnant. There, the Hirnant Limestone Member of the Foel‐y‐Ddinas Mudstone Formation yields a new, well‐preserved chitinozoan assemblage, attributed to the Spinachitina taugourdeaui Biozone. This allows tight correlation with the Hirnantian of Baltica and Laurentia and neatly ties the chitinozoan zonation with the classical brachiopod fauna. Nearby, the chitinozoan assemblage from the Caradoc Cymerig Limestone Member at Gelli‐grîn belongs to the Spinachitina cervicornis Biozone?, and is identical to that recovered from the Burrellian in the Onny Valley, Welsh Borderland. A Silurian assemblage higher up section, discovered in the Cwm‐yr‐Aethnen Formation, is attributed to the globally recognized Eisenackitina dolioliformis Biozone. Attempts to integrate the chitinozoan and graptolite biozonation, in the central Welsh Rhayader area, were less successful. Copyright © 2008 John Wiley & Sons, Ltd.
The role of institutional assessment in assessing student learning outcomes
Authors: Bers Trudy H.
Published: April 2008

Institutional Research has the potential to play an important role in assessment of student learning outcomes by lending leadership and assistance to departmental and institutional efforts.
Estrogen‐mediated downregulation of CD24 in breast cancer cells
Authors: Kaipparettu Benny Abraham , Malik Simeen , Konduri Santhi D. , Liu Wensheng , Rokavec Matjaž , van der Kuip Heiko , Hoppe Reiner , Hammerich‐Hille Stephanie , Fritz Peter , Schroth Werner , Abele Ina , Das Gokul M. , Oesterreich Steffi , Brauch Hiltrud
Published: April 2008

We have previously reported on the relevance of the prevalence of CD44+/CD24−/low cells in primary breast tumors. To study regulation of CD24, we queried a number of publicly available expression array studies in breast cancer cells and found that CD24 was downregulated upon estrogen treatment. We confirmed this estrogen‐mediated repression of CD24 mRNA by quantitative real‐time PCR in MCF7, T47D and ZR75‐1 cells. Repression was also seen at the protein level as measured by flow cytometry. CD24 was not downregulated in the ERα negative MDA‐MB‐231 cells suggesting that ERα was necessary. This was further confirmed by ERα silencing in MCF7 cells resulting in increased CD24 levels and by reintroduction of ERα into C4‐12 cells resulting in decreased CD24 levels. Estrogen treatment did not alter half‐life of CD24 mRNA and new protein synthesis was not essential for repression, suggesting a primary transcriptional effect. Histone deacetylase inhibition by Trichostatin A completely abolished the repression, but decrease of the ERα corepressors NCoR, LCoR, RIP140, silencing mediator of retinoid and thyroid hormone receptors, SAFB1 and SAFB2 by siRNA or overexpression of SAFB2, NCoR and silencing mediator of retinoid and thyroid hormone receptors had no effect. In silico promoter analyses led to the identification of two estrogen responsive elements in the CD24 promoter, one of which was able to bind ERα as shown by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. Together, our results show that CD24 is repressed by estrogen and that this repression is a direct transcriptional effect depending on ERα and histone deacetylases. © 2008 Wiley‐Liss, Inc.
Supramolecular hydrogels based on self‐assembly between PEO‐PPO‐PEO triblock copolymers and α‐cyclodextrin
Authors: Ni Xiping , Cheng Alan , Li Jun
Published: April 2008

This article reports a detailed study on the hydrogel formation of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO‐PPO‐PEO) triblock copolymers with α‐cyclodextrin (α‐CD) in aqueous solutions. The gelation kinetics and the gel rheological properties were studied using viscometry. The sol–gel phase transitions were studied using phase diagrams, while the gelation mechanism was studied using differential scanning calorimetric analysis. It was concluded that the gelation was induced by the complex formation between the PEO segments of the PEO‐PPO‐PEO triblock copolymer and α‐CD, and the further self‐assembly of the partially formed inclusion complexes. The addition of α‐CD largely reduced the concentration of the copolymer needed for gel formation. The gels were thixotropic and reversible, and potentially suitable for use as an injectable drug‐delivery system. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Poly(ethylene imine)‐g‐chitosan using EX‐810 as a spacer for nonviral gene delivery vectors
Authors: Lou Yu‐Lun , Peng Yu‐Shiang , Chen Bing‐Hung , Wang Li‐Fang , Leong Kam W.
Published: April 2008

Polyelectrolyte complexes have been widely studied as gene carriers in recent years. In this study, poly (ethylene imine) was grafted onto chitosan (PEI‐g‐CHI) as a nonviral gene carrier in order to improve the water solubility as well as the inherent transfection efficiency of chitosan. We present a novel method to conjugate the amine or hydroxyl groups of chitosan (CHI) and the amine groups of PEI through opening the epoxide rings of ethylene glycol diglycidyl ether (EX‐810), which also brings the merits as mentioned in PEGylation chemistry. The degree of substitution of PEI onto CHI was characterized by NMR. The preliminarily cellular mechanisms, from the cellular entry to the endosomal release, were investigated by the correlations among the physicochemical properties of the DNA‐polymer complexes, the buffering capacity of the modified polymer, the cytotoxicity, and the efficiency of the transgene expression. The cytotoxicity assayed by MTT shows that cell viability of PEI‐g‐CHI is higher than CHI especially noticeable at high concentrations using human kidney 293T cells. The efficiency of transgene expression and the amount of intracellular plasmid were monitored using green fluorescent protein (GFP) and visualized by fluorescence microscopy. The transfection efficiency of PEI‐g‐CHI/DNA polyplex is significantly better than CHI/DNA polyplex when using the weight ratios higher than 2.5. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Physicochemical properties, surface active species and formation of reverse micelles in the Cyanex 923‐n‐heptane/cerium(IV)‐H2SO4 extraction system
Authors: Wang Weiwei , Wang Xianglan , Wang Yanliang , Li Deqian , Liao Wuping
Published: April 2008

BACKGROUND: The Cyanex® 923 (trialkylphosphine oxides, TRPO)‐n‐heptane/cerium(IV)‐H2SO4 extraction system has been investigated focusing on the physicochemical properties, surface active species and interfacial phenomena. The effects of H2SO4 and Ce(IV) extraction on them were considered.

RESULTS: Results showed that the density and refractive index reflect the mass transfer by H2SO4 and Ce(IV) extraction and the change of refractive index was more sensitive than density. The interfacial tension decreased on extraction of H2SO4 but increased on extraction of Ce(IV). The viscosity of the equilibrium organic phase increased abruptly when the extracted H2SO4 concentration in the organic phase reached certain high values. The formation of reversed micelles, with mean diameter of about 10 nm, at high H2SO4 concentrations in the organic phase, is suggested by various measurements such as viscosity, interfacial tension and dynamic light‐scattering (DLS).

CONCLUSION: It is suggested that TRPO‐H2SO4 complexes are more surface‐active than TRPO itself and tend to aggregate into reverse micelles by self‐assembling in the organic phase but the Ce(IV)‐TRPO complexes are neutral, less surface‐active than TRPO and not helpful for reverse micelle formation. Copyright © 2008 Society of Chemical Industry
Straight line embeddings of cubic planar graphs with integer edge lengths
Authors: Geelen Jim , Guo Anjie , McKinnon David
Published: April 2008

We prove that every simple cubic planar graph admits a planar embedding such that each edge is embedded as a straight line segment of integer length. © 2008 Wiley Periodicals, Inc. J Graph Theory 58:270‐274, 2008
From Vygotsky to Vygotskian psychology: Introduction to the history of the Kharkov School
Authors: Yasnitsky Anton , Ferrari Michel
Published: April 2008

Around the end of the 1920s, Vygotsky introduced his integrative framework for psycho‐logical research to the Soviet Union. This framework was not abandoned and forgotten until its rediscovery in Russia and America in the 1950s, as some claim. In fact, even after his untimely death in 1934, Vygotsky remained the spiritual leader of a group of his for‐mer students and collaborators, who became known as the Kharkov School. This paper reconstructs the early intellectual history of Vygotskian psychology, as it emerged, around the time of Vygotsky's death, in the research program of the Kharkov School.
Gadolinium‐enhanced echo‐planar T2‐weighted MRI of tumors in the extracranial head and neck: Feasibility study and preliminary results using a distributed‐parameter tracer kinetic analysis
Authors: Bisdas Sotirios , Baghi Mehran , Wagenblast Jens , Vogl Thomas J. , Thng Choon Hua , Koh Tong San
Published: April 2008

Purpose

To examine the feasibility of first‐pass dynamic contrast‐enhanced (DCE) T2‐weighted MRI of tumors in the extracranial head and neck by applying a distributed‐parameter (DP) tracer kinetic model to quantify the perfusion parameters.

Materials and Methods

A total of 16 patients with primary malignant and benign tumors in the head and neck underwent DCE‐MR studies. A spin‐echo (SE) echo‐planar‐imaging (EPI) MR‐sequence was applied for first‐pass DCE‐T2‐weighted imaging. The data were postprocessed applying a DP tracer kinetic model that accounts for capillary‐tissue exchange. Region‐of‐interest (ROI) analysis was performed in the tumor sites and the adjacent normal tissue. Blood flow (F), intravascular blood volume (v1), extravascular extracellular volume (v2), difference in bolus arrival time between arterial input and tissue (t0), intravascular mean transit time (t1), permeability (PS), and extraction ratio (E) maps were generated for each patient.

Results

All perfusion values in the tumor sites were significantly different (0.000 ≤ P ≤ 0.01) than those in the normal muscle tissue. The median perfusion values in the tumor tissue were: F = 150.5 mL/minute/100 g, v1 = 11.0 mL/100 g, v2 = 31.5 mL/100 g, t0 = 4.5 seconds, t1 = 8.0 seconds, PS = 96.0 mL/minute/100 g, and E = 32.5.

Conclusion

EPI‐T2‐weighted DCE‐MR in head and neck tumors as well as quantification of the perfusion values using DP model physiologic imaging was feasible and the promising initial results have encourages further validation studies in the future. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
In vivo knee loading characteristics during activities of daily living as measured by an instrumented total knee replacement
Authors: Mündermann Annegret , Dyrby Chris O. , D'Lima Darryl D. , Colwell Clifford W. , Andriacchi Thomas P.
Published: April 2008

We examined the relationship between activity, peak load, medial to lateral load distribution, and flexion angle at peak load for activities of daily living. An instrumented knee prosthesis was used to measure knee joint force simultaneously with motion capture during walking, chair sit to stand and stand to sit, stair ascending and descending, squatting from a standing position, and golf swings. The maximum total compressive load at the knee was highest during stair ascending and descending and lowest during rising from a chair. Maximum total compressive load occurred at substantially different flexion angles ranging from 8.5° during walking to 91.8° during squatting. For all activities, total compressive load exceeded 2 times body weight, and for most activities 2.5 times body weight. Most activities placed a greater load on the medial compartment than the lateral compartment. Activities were grouped into three categories: high cycle loading (walk), high load (stair ascent, descent, and golf), and high flexion angle (chair sit to stand/stand to sit, and squat). The results demonstrate that the forces and motion sustained by the knee are highly activity‐dependent and that the unique loading characteristics for specific activities should be considered for the design of functional and robust total knee replacements, as well as for rehabilitation programs for patients with knee osteoarthritis or following total knee arthroplasty. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1167–1172, 2008
Identification of epidermal L‐tryptophan and its oxidation products by in vivo FT‐Raman Spectroscopy further supports oxidative stress in patients with vitiligo
Authors: Rokos Hartmut , Wood John M. , Hasse Sybille , Schallreuter Karin U.
Published: April 2008

In the past, non‐invasive in vivo FT‐Raman spectroscopy has been used to detect H2O2‐mediated oxidation of methionine to methionine sulfoxide and methionine sulfone, as well as cysteine to cysteic acid, in the sequence of proteins in the epidermis of patients with vitiligo. L‐tryptophan (Trp) is another potential target for this oxidation. Owing to the presence of 10−3M epidermal albumin which contains one Trp residue, it was tempting to follow the oxidation of this amino acid. Using in vivo and in vitro FT‐Raman spectroscopy, we show for the first time that epidermal Trp is oxidised in patients with vitiligo, yielding 5‐OH‐Trp at 930 cm−1 and other oxidation products (i.e. N‐formyl kynurenine and kynurenine) from indole ring oxidation peaking at 1050 cm−1. On the basis of detailed in vitro results, we could conclude that 5‐OH‐Trp as well as formyl kynurenine and kynurenine are formed via H2O2‐mediated Fenton chemistry. These results once again bring out the strength of non‐invasive in vivo FT‐Raman Spectroscopy in dermatology to follow the effect of oxidative stress in the skin of patients with vitiligo. Copyright © 2008 John Wiley & Sons, Ltd.
A field test of group based exposure therapy with 102 veterans with war‐related posttraumatic stress disorder
Authors: Ready David J. , Thomas Kaprice R. , Worley Virginia , Backscheider Andrea G. , Harvey Leigh Anne C. , Baltzell David , Rothbaum Barbara Olasov
Published: April 2008

Group‐based exposure therapy (GBET) was field‐tested with 102 veterans with war‐related posttraumatic stress disorder (PTSD). Nine to 11 patients attended 3 hours of group therapy per day twice weekly for 16–18 weeks. Stress management and a minimum of 60 hours of exposure was included (3 hours of within‐group war‐trauma presentations per patient, 30 hours of listening to recordings of patient's own war‐trauma presentations and 27 hours of hearing other patients' war‐trauma presentations). Analysis of assessments conducted by treating clinicians pre‐, post‐ and 6‐month posttreatment suggests that GBET produced clinically significant and lasting reductions in PTSD symptoms for most patients on both clinician symptoms ratings (6‐month posttreatment effect size δ = 1.22) and self‐report measures with only three dropouts.
Thermo‐Responsive Hydrogels with Nanodomains: Rapid Shrinking of a Nanogel‐Crosslinking Hydrogel of Poly(N‐isopropyl acrylamide)
Authors: Morimoto Nobuyuki , Ohki Takafumi , Kurita Kimio , Akiyoshi Kazunari
Published: April 2008

Rapidly shrinking poly(N‐isopropyl acrylamide) (PNIPAM) hydrogels are prepared by crosslinking with self‐assembled nanogels that consist of cholesteryl‐ and methacryloyl‐substituted pullulan (CHPMA). The CHPMA nanogel (Rh = 26.4 nm) was used as a crosslinker for a hydrophilic nanodomain. Transmission electron microscopy images of the nanogel‐crosslinked PNIPAM hydrogel reveal a well‐defined nanoporous structure. The nanogel‐crosslinked PNIPAM hydrogel shows rapid shrinking based on its structure. The shrinking half‐time was ≈2 min, which is about 3 400 times faster than that of a PNIPAM hydrogel crosslinked by methylene(bisacrylamide).

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Geminin is overexpressed in human pancreatic cancer and downregulated by the bioflavanoid apigenin in pancreatic cancer cell lines
Authors: Salabat Mohammad R. , Melstrom Laleh G. , Strouch Matthew J. , Ding Xian‐Zhong , Milam Benjamin M. , Ujiki Michael B. , Chen Catherine , Pelling Jill C. , Rao Sambasiva , Grippo Paul J. , McGarry Thomas J. , Bentrem David J.
Published: April 2008

Pancreatic adeniocarcinoma is among the deadliest of human cancers. Apigenin, an antitumor flavonoid, inhibits pancreatic cancer cell proliferation in vitro. Geminin is a recently identified novel protein that plays a critical role in preventing abnormal DNA replication by binding to and inhibiting the essential replication factor Cdt1. Microarray analysis identified geminin to be downregulated in pancreatic cancer cells treated with apigenin. Therefore, we investigated the effects of apigenin on geminin expression and other proteins involved in replication (Cdc6, Cdt1, and MCM7) in pancreatic cancer cell lines CD18 and S2013. Real time RT‐PCR and western blotting analysis showed that geminin expression is downregulated by apigenin at both mRNA and protein levels. Furthermore, treatment of cells with proteosome inhibitor MG132 reversed the downregulation of geminin by apigenin, supporting our hypothesis that the degradation pathway is another mechanism by which apigenin affects geminin expression. Apigenin treatment also resulted in downregulation of Cdc6 at both mRNA and protein levels. However, Cdt1 and MCM7 expression was not affected in apigenin‐treated cells. The effect of apigenin treatment on geminin promoter activity was measured by transient transfection of Hela cells with a reporter gene, demonstrating that apigenin inhibited geminin promoter activity. Geminin expression was also evaluated in human pancreatic tissue (n = 15) by immunohistochemistry and showed that geminin is overexpressed in human pancreatic cancer compared to normal adjacent pancreatic tissue. In conclusion, our studies demonstrated that geminin is overexpressed in human pancreatic cancer and downregulated by apigenin which may contribute to the antitumor effect of this natural flavonoid. © 2008 Wiley‐Liss, Inc.
A uniform optimal‐order estimate for an Eulerian‐Lagrangian discontinuous Galerkin method for transient advection–diffusion equations
Authors: Wang Kaixin
Published: April 2008

We prove an optimal‐order error estimate in a weighted energy norm for the Eulerian‐Lagrangian discontinuous Galerkin method for unsteady‐state advection–diffusion equations with general inflow and outflow boundary conditions. It is well‐known that these problems admit dynamic fronts with interior and boundary layers. The estimate holds uniformly with respect to the vanishing diffusion coefficient. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Adverse drug reactions reporting by physicians in Ibadan, Nigeria
Authors: Okezie Enwere O. , I. Fawole Olufunmilayo
Published: April 2008

Objective

To assess knowledge, extent of reporting and factors influencing reports of adverse drug reactions (ADRs) by resident doctors.

Study design and setting

Study site was the University College Hospital (UCH), Ibadan, an 850‐bed tertiary care hospital in western Nigeria. It was a cross‐sectional survey. Data were collected with a 46‐item self‐administered questionnaire from 192 clinical physicians.

Results

Older aged doctors, senior cadre and doctors in medical faculty were 1.5 times likely to be aware of ADR reporting guidelines. General knowledge on ADR was good while 58.3% of residents knew the burden of ADRs. Most (89.5%) had observed at least one ADR but only 32% had ever reported it. Residents in medical faculty were twice more likely to report ADRs than the surgeons [OR 2.1; 95%CI 1.1, 4.1]. The commonest factors that militate against ADR reporting were lack of knowledge that reporting forms were available (70.9%) and ignorance of reporting procedure (69%).

Conclusion

Despite high observation and good knowledge of ADR among doctors, the rate of reporting was low. There is need for publicity of activities of the pharmacovigilance unit of the hospital. Copyright © 2008 John Wiley & Sons, Ltd.
Interfacial adsorption characteristics of ionic polymeric amphiphiles with comb‐like structures: Effect of dodecyl and poly(ethylene oxide) side chains
Authors: Chandrasekar K. , Baskar Geetha
Published: April 2008

Two sets of terpolymers, polymer A and polymer B consisting of almost same level of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) component at 0.635 ± 0.005 m and varying dodecyl methacrylate (DoDMAc) and monomethoxy poly(ethylene glycol) acrylate (PEGAc) components have been designed. Polymer A, consisting of less C12 component, has been shown to promote intermolecular aggregated structures wherein C12 domains exhibit compact packing characteristics. It is demonstrated that in polymer B, AMPS segments are predominantly present as ionic clusters contributing to a high pKa at about 9.50 for a low α of 0.20. From the results of interfacial adsorption estimations at air/solution and water/hexane interface, it is shown that open coil structures provided under high pH (>9.0) conditions promote efficiency of adsorption. This is shown from higher surface excess concentration (Γ) and lower interfacial area (a) estimated using Gibbs adsorption isotherm equation. For example, at water/hexane interface, polymer A exhibits Γ of 1.20 × 10−3 moles/1000 m2 at pH 3.2 and 1.97 × 10−3 moles/1000 m2 at pH 10.0. Significantly, in case of polymer B consisting of ionic clusters of AMPS, adsorption at the liquid/liquid interface is more efficient in comparison to polymer A at all pH. © 2008 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 3257–3271, 2008
Thermomechanical and optical characteristics of stretched polyvinylidene fluoride
Authors: Chang Wen‐Yang , Fang Te‐Hua , Lin Yu‐Cheng
Published: April 2008

The thermomechanical and optical characteristics of polyvinylidene fluoride (PVDF) are investigated using a thermomechanical, a nanoindentation, anda photometric analyzer for flexible electronic applications. Experimental results show that thermomechanical characteristics, thermal elongation, and expansion, are greatly influenced at stretching ratios of over four in the stretching direction. Consequently, shrinking occurs because of higher cohesion at the tie chains of the amorphous regions. Additionally, there are almost uniform hardness and Young's modulus of about 0.25 ± 0.01 and 3.44 ± 0.14 GPa when the penetration depth is about 1000 nm. Unstretched PVDF films have a higher absorbance in the ultraviolet light range than stretched films do. PVDF films stretched over three times their original length have transmittance of above 90% at near infrared light. In addition, PVDF films stretched at lower temperatures show a lower transmittance because the films easily whitened during α to β phase transformations. The results provide information to optimize PVDF films for applications in flexible designs. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 949–958, 2008
The interobserver variability of digital rectal examination in a large randomized trial for the screening of prostate cancer
Authors: Gosselaar C. , Kranse R. , Roobol M.J. , Roemeling S. , Schröder F.H.
Published: April 2008

BACKGROUND

To analyze to what extent the percentage of suspicious digital rectal examination (DRE) findings vary between examiners and to what extent the percentage of prostate cancers (PCs) detected in men with these suspicious findings varies between examiners.

METHODS

In the first screening round of the European Randomized study of Screening for PC (ERSPC) Rotterdam, 7,280 men underwent a PSA‐determination and DRE of whom 2,102 underwent prostate biopsy (biopsy indication PSA ≥ 4.0 ng/ml and/or suspicious DRE and/or TRUS). Descriptive statistics of DRE‐outcome per PSA‐range were used to determine the observer variability of six examiners. Because this analysis did not correct properly for other predictors of a suspicious DRE (PSA‐level, biopsy indication, TRUS‐outcome, prostate volume and age), a logistic regression analysis controlling for these explanatory variables was performed as well.

RESULTS

In 2,102 men biopsied, 443 PCs were detected (PPV = 21%). For all PSA levels the percentage suspicious DRE varied between examiners from 4% to 28% and percentage PC detected in men with a suspicious DRE varied from 18% to 36%. Logistic regression analysis showed that three of six examiners considered DRE significantly more often abnormal than others (ORs 3.48, 2.80, 2.47, P < 0.001). For all examiners the odds to have PC was statistically significantly higher in case of a suspicious DRE (ORs 2.21–5.96, P < 0.05). This increased chance to find PC was not significantly observer‐dependent.

CONCLUSIONS

Three of six examiners considered DRE significantly more often suspicious than the others. However, under equal circumstances a suspicious DRE executed by each examiner increased the chance of the presence of PC similarly. Prostate 68:985–993, 2008. © 2008 Wiley‐Liss, Inc.
Influence of dielectric surface modification on growth, structure and transport properties of perylene films
Authors: Effertz Christian , Beigmohamadi Maryam , Niyamakom Phenwisa , Schulz Philip , Wuttig Matthias
Published: April 2008

In this study the properties of organic thin film transistors (OTFTs) based on perylene films have been investigated. To tailor the film properties, the dielectric layer on which the perylene films were deposited on was modified by different chemical treatments. Both film properties and the device efficiency have been studied employing a range of techniques including atomic force microscopy, X‐ray diffraction and a drop shape analysis for the determination of the surface free energy. A clear correlation between the adhesion energy with the dielectric surface modification is found. The change in adhesion energy influences the thin‐film growth on the modified substrate and therefore the film morphology and structure. This in turn has a profound impact on the transistors performance as the charge carrier mobility and the on‐to‐off current ratio are effected. Hence by tailoring of the dielectric surface for the growth of perylene films, the thin‐film transistor performance can be optimized. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
m ‐plane GaN/InGaN/AlInN on LiAlO2 grown by MOVPE
Authors: Behmenburg H. , Wen T. C. , Dikme Y. , Mauder C. , Khoshroo L. Rahimzadeh , Chou M. M. C. , Rzheutskii M. V. , Lutsenko E. V. , Yablonskii G. P. , Woitok J. , Kalisch H. , Jansen R. H. , Heuken M.
Published: April 2008

We present a study of growth and properties of m ‐plane GaN/InGaN/AlInN structures on LiAlO2 substrates grown by metal organic vapour phase epitaxy (MOVPE). A buffer structure, including an m ‐plane AlInN interlayer prior to GaN growth, has been developed. Quantum well structures on top of this buffer showed absence of polarization‐induced electric fields verified by room temperature photoluminescence (RT PL) measurements with different excitation intensities. Different samples with peak emission wavelength between 433 nm and 495 nm exhibited stable peak position even for high excitation intensities of 500 kW/cm2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron irradiation and the equilibrium of open core dislocations in gallium nitride
Authors: Hawkridge M. , Cherns D. , Liliental‐Weber Z.
Published: April 2008

Under electron irradiation, nanopipes in GaN are found to evolve into the so‐called bamboo structure and eventually into a chain of voids [Pailloux et al., Appl. Phys. Lett. 86, 131908 (2005)]. Here, the driving mechanism for this morphological evolution is examined using transmission and scanning transmission electron microscopy studies of undoped GaN grown by hydride vapor phase epitaxy. Irradiation at varying beam energies shows that morphological evolution occurs below the threshold for direct knock‐on damage, and that voids migrate towards the beam. It is proposed that these observations can be explained by the stimulated diffusion of point defects. In areas relatively unexposed to electrons, a survey of core character, diameter and depth into the layer suggests that a similar process occurs by post‐growth annealing, i.e. due to point defects mobile at the growth temperature. The implications of these results for understanding dislocation core structures are assessed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rhodium‐based Schottky contacts on n‐doped gallium nitride
Authors: Tian F. , Chor E. F.
Published: April 2008

Electrical characteristics and thermal stability of Rhodium (Rh)‐based Schottky contacts on n‐GaN, including Rh/Au and Ni/Rh/Au, have been investigated and compared with those of the Ni/Au contact. Although the maximum Schottky barrier height (SBH) of the Rh/Au contact is slightly lower than that of Ni/Au, the inclusion of a thin Ni layer to yield the Ni/Rh/Au contact has led to a maximum SBH of 0.80 eV, surpassing that of Ni/Au by 0.07 eV and leading to a reduced reverse leakage current at ‐1 V by 1 order of magnitude com‐ pared to that of Ni/Au. The good performance of the Ni/Rh/Au contact can be attributed to the co‐existence of Rh and a thin layer of Ni, which leads to limited adverse reaction of Ni with the GaN substrate, and formation of NiO and reduced interfacial defects at the metal/GaN interface. In addition, thermal stability studies have shown that Rh‐based contacts exhibit better morphological stability than Ni/Au, and the Ni/Rh/Au contact has improved thermal stability over Rh/Au and Ni/Au contacts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sublimation growth of 2 inch diameter bulk AlN crystals
Authors: Chemekova T. Yu. , Avdeev O. V. , Barash I. S. , Mokhov E. N. , Nagalyuk S. S. , Roenkov A. D. , Segal A. S. , Makarov Yu. N. , Ramm M. G. , Davis S. , Huminic G. , Helava H.
Published: April 2008

The technology of sublimation growth of 15 mm diameter bulk single AlN crystals is scaled to grow similar 2‐inch diameter crystals. The best results are currently achieved with the two‐stage technique including 1) seeding and initial growth of 2‐3 mm thick single‐crystal AlN layers on 2‐inch diameter 6H‐SiC wafers in pre‐carbonized Ta crucibles in graphite equipment and 2) growth of bulk AlN crystals on the above AlN layers in tungsten crucibles and equipment. The initial AlN layers prove of good crystallographic quality but may contain up to 6 at.% of Si impurities. The eventual bulk AlN crystals consist of about 40 mm diameter round single‐crystal core and polycrystalline rim. No impurities in concentration higher than 0.01 at.% are found in the bulk crystals. The bulk AlN crystal may be separated from the initial AlN layer to use the latter repeatedly for growth of a new crystal. Such “secondary” crystals were found to be semi‐insulating. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nitride photocatalyst to generate hydrogen gas from water
Authors: Iwaki Yasuhiro , Ono Masato , Yamaguchi Kazuki , Kusakabe Kazuhide , Fujii Katsushi , Ohkawa Kazuhiro
Published: April 2008

We propose a new nitride photocatalyst of an n‐n+‐GaN structure to increase H2 gas generation. This structure consists of a thin lightly‐doped n‐type layer on a heavily‐doped n+‐type layer to realize an optimized depletion layer for optical absorption and highly conductive region, respectively. An optimized n‐n+‐GaN structure could generate much more H2 gas rather than a single n‐GaN layer structure by about 1.4 times. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and optical properties of nano‐structured semipolar InGaN/GaN quantum wells on c‐plane GaN template
Authors: Yu Hongbo , Jung Taeil , Ku P. C.
Published: April 2008

High density self‐assembled nanostructured semipolar (NSSP) GaN pyramids are fabricated based on c‐plane GaN template by in situ silane treatment followed by high temperature treatment. Semipolar InGaN/GaN multiple quantum wells (MQWs) were subsequently grown on the NSSP GaN. Optical properties of the MQWs were studied by temperature‐ dependent and excitation density varied photoluminescence. It was found that the internal electric field in the NSSP MQWs were remarkably reduced in comparison with planar c‐plane MQWs. The internal quantum efficiency of the NSSP MQWs was measured to be > 30% which showed potential applications in III‐nitride light emitters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical properties and optical absorption in InN:In structures
Authors: Komissarova T. A. , Plotnikov D. S. , Jmerik V. N. , Shubina T. V. , Mizerov A. M. , Semenov A. N. , Ivanov S. V. , Ryabova L. I. , Khokhlov D. R.
Published: April 2008

Electrophysical and optical absorption measurements have been performed for conventional InN epilayers and InN:In composite structures grown by plasma‐assisted molecular beam epitaxy. It is shown that intentional periodical introduction of In metallic inclusions into InN layers results in formation of inhomogeneous arrays of clusters. Their presence modifies the shape of absorption spectra. At the same time, significant amount of indium (up to 1/3 of a thickness) in these structures does not influence noticeably the carrier concentration and mobility. These parameters fall in the range of published data for the conventional InN layers. These finding can indicate that formation of In clusters in InN is a more frequent event than it is currently accepted. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degradation of III‐nitride laser diodes grown by molecular beam epitaxy
Authors: Xiu H. , Thrush E. J. , Kauer M. , Smeeton T. M. , Hooper S. E. , Heffernan J. , Humphreys C. J.
Published: April 2008

The defects found in electrically degraded GaN‐based lasers have been characterised by transmission electron microscopy. In a laser that had been operated until failure, defects containing contact metals were observed. Combined with data from the laser's current‐voltage characteristics, this suggests that the catastrophic failure may have been caused by local heating. In partially degraded lasers, four different types of defects were observed: cracks, stacking faults, inversion domains and dislocations. Cracks, stacking faults and inversion domains were present before and after the laser failure. The dislocation network, however, was only observed in the active region of a failed laser and may have resulted from recombination enhanced defect migration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of GaN‐based lateral polarity heterostructures
Authors: Lorenz P. , Lebedev V. , Niebelschütz F. , Hauguth S. , Ambacher O. , Schaefer J. A. , Krischok S.
Published: April 2008

GaN‐based lateral polarity heterostructures (LPH) were grown on sapphire substrates using molecular beam epitaxy. The LPH samples consist of periodical N‐face (000‐1) (grown directly on Al2O3) and Ga‐face (0001) (grown on a AlN bufferlayer) GaN stripes. The GaN‐based LPH have been characterized using surface sensitive techniques. The GaN‐based LPH consist of smooth Ga‐face (0.4 nm RMS) and N‐face regions of higher roughness (7 nm RMS) with small (<70 nm as measured by atomic force microscopy) and well‐defined inversion domain boundary regions (IDBR). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth mechanism of catalyst‐ and template‐free InN nanorods
Authors: Won Yong Sun , Kim Young Seok , Kryliouk Olga , Anderson Tim
Published: April 2008

A feasible mechanism for catalyst‐ and template‐free InN nanorod growth was proposed, consisting of the random nanoparticle nucleation from stable gas phase oligomers and the subsequent directional growth along the c‐axis. A combined study of equilibrium analysis and computational thermochemistry was used to determine the optimal growth conditions – growth temperature and Cl/In ratio – for InN nano‐rod growth based on the proposed mechanism, and the computationally determined values showed a good agreement with reported experimental results. The involvement of InCl3 as a key species in the proposed mechanism required the Cl/In ratio to be ∼ 3 by stoichiometry. The growth zone of InN nanorods by HVPE was demonstrated to lie in the vicinity of the growth‐etch transition. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of mass spectra of peptides in different matrices using matrix‐assisted laser desorption/ionization and a multi‐turn time‐of‐flight mass spectrometer, MULTUM‐IMG
Authors: Hazama Hisanao , Nagao Hirofumi , Suzuki Ren , Toyoda Michisato , Masuda Katsuyoshi , Naito Yasuhide , Awazu Kunio
Published: April 2008

The mass spectra of peptides obtained with different matrices were compared using a matrix‐assisted laser desorption/ionization (MALDI) ion source and a multi‐turn time‐of‐flight (TOF) mass spectrometer, MULTUM‐IMG, which has been developed at Osaka University. Two types of solid matrices, α‐cyano‐4‐hydroxycinnamic acid (CHCA) and 2,5‐dihydroxybenzoic acid (DHB), and a liquid matrix made from a mixture of 3‐aminoquinoline and CHCA were used. When measuring the peak signal intensity of human angiotensin II [M+H]+ from a fixed sample position, the liquid matrix produced a stable signal over 1000 laser shots, while the signal obtained with CHCA and DHB decayed after about 300 and 100 shots, respectively. Significant differences in the mass resolving power were not observed between the spectra obtained with the three matrices. Signal peak areas were measured as a function of the cycle number in a multi‐turn ion trajectory, i.e., the total flight time over a millisecond time scale. For both [M+H]+ of human angiotensin II and bovine insulin, the decay of the signal peak area was the most significant with CHCA, while that measured with DHB was the smallest. The results of the mean initial ion velocity measurements suggested that the extent of metastable decomposition of the analyte ions increased in order of DHB, the liquid matrix, and CHCA, which is consistent with the difference in the decay of the signal peak area as the total flight time increased. Copyright © 2008 John Wiley & Sons, Ltd.