bluuebunny/crossref_metadata_2025 huggingface dataset:
A new composite sorbent for water and dye uptake: Highly swollen acrylamide/2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid/clay hydrogels crosslinked by 1,4‐butanediol dimethacrylate
Authors: Kundakci Semiha , Üzüm Ömer Barış , Karadağ Erdener
Published: April 2008

A novel type of highly swollen hydrogels based on acrylamide (AAm) with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) and clay such as bentonite (Bent) crosslinked by 1,4‐butanediol dimethacrylate (BDMA) was prepared by free radical solution polymerization in aqueous media. Water uptake and dye sorption properties of polyelectrolyte AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels were investigated as a function of composition to find materials with swelling and sorption properties. FTIR analyses were made. Swelling experiments were performed in water and dye solution at 25°C, gravimetrically. Highly swollen AAm/AMPS and AAm/AMPS/Bent hydrogels were used in experiments on sorption of water‐soluble monovalent cationic dye such as Lauths violet “LV, (Thionin).” Swelling of AAm/AMPS hydrogels was increased up to 1,920–9,222% in water and 867–4,644% in LV solutions, while AAm hydrogels swelled 905% in water and swelling of AAm/AMPS/Bent hydrogels was increased up to 2,756–10,422% in water and 1,200–3,332% in LV solutions, while AAm/Bent hydrogels swelled 849% in water. Some swelling kinetic and diffusional parameters were found. Water and LV diffusion into hydrogels was found to be non‐Fickian in character. For sorption of cationic dye, LV into AAm/AMPS and AAm/AMPS/Bent hydrogel was studied by batch sorption technique at 25°C. The amount of the dye sorbed per unit mass removal effiency and partition coefficient of the hydrogels was investigated. The influence of AMPS content in the hydrogels to sorption was examined. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Morphologies and applied properties of PSI/PA composite particles synthesized at low temperature
Authors: Wu Yumin , Ge Chengyue , Xu Jun , Bi Jianmei , Chen Qingfen
Published: April 2008

Latex with a poly(dimethyl‐siloxane) core and a poly(methylmethacrylate‐ butylacrylate‐ 2‐hydroxypropyl acrylate) shell have been prepared at low temperature with potassium‐persulphate (KPS), sodium formaldehyde sulfoxylate (SFS) and 2,2′‐azobis [2‐(2‐imidazolin‐ 2‐yl)propane] dihydrochloride (VA‐044) as composite initiators by staged emulsion polymerization. Reactive surfactants were used to significantly improve the applied properties such as water adsorption ratio and thermo‐properties. Transmission electron microscopy (TEM) results indicated that increasing the amount of 2‐hydroxypropyl acrylate (HPA) and butylacrylate (BA) was favorable to form the core/shell particles. Particle size distribution results showed with increasing the dosages of surfactants, initiators, and seed‐latex, particle size decreased. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA) results indicated the high temperature‐reserved of copolymer was improved in the presence of polysiloxane. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Studies on mechanical properties of sisal fiber/phenol formaldehyde resin in‐situ composites
Authors: Mu Qiuhong , Wei Chun , Feng Shengyu
Published: April 2008

Phenol formaldehyde resin (PF) reinforced with short sisal fibers (SF) were obtained by two methods, direct‐mixing and polymerization filling. Impact and bending properties of resulting composites were compared. Under the same compression molding conditions, polymerization filled composites showed better mechanical properties than those of direct‐mixed composites. The influences of fiber modifications on the mechanical properties of SF/PF in‐situ (polymerization filled) composites have been investigated. Treated‐SF‐reinforced composites have better mechanical properties than those of untreated‐SF‐reinforced composites. The effects of SF on water absorption tendencies of SF/PF composites have also been studied. In addition, sisal/glass (SF/GF) hybrid PF composites of alkali‐treated SF were prepared. Scanning electron microscopic studies were carried out to study the fiber‐matrix adhesion. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Three‐dimensional fiber orientation in vibration welded joints of glass fiber reinforced polyamide‐6
Authors: Kamal Musa R. , Chung Young‐Mi , Gomez Rodolfo
Published: April 2008

A technique was developed to obtain the three‐dimensional distribution of fiber orientation in vibration‐welded joints of polyamide‐6 (PA‐6) reinforced with 30 wt% glass fibers. The heat‐affected zone (HAZ) of fiber‐reinforced PA‐6 was successfully revealed by polishing and etching the vibration welded joints. Examination with the polarized light microscope in the reflection mode showed detailed microstructure domains, including the bulk crystalline zone and the HAZ. Experimental elliptical fiber cross‐section images were used to obtain second order orientation tensors, thus providing a quantitative description of the three‐dimensional fiber orientation distribution. The fibers in the HAZ were reoriented towards the squeeze flow direction, when compared with the bulk phase. Low welding pressure does not necessarily produce a more favorable fiber orientation in the tensile direction than high welding pressure. High welding pressure and low amplitude promote fiber reorientation in both the squeeze flow and tensile (weld thickness) directions. Overall, it was found that, at 30% fiber content, vibration‐welded joints of injection molded fiber‐reinforced PA‐6 are weaker than vibration‐welded joints in unreinforced injection molded samples. The fibers in the former do not undergo sufficient reorientation to influence weld strength in the tensile direction. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Crystal morphology, melting behaviors and isothermal crystallization kinetics of SCF/PTT composites
Authors: Run Mingtao , Song Hongzan , Wang Sujuan , Bai Libin , Jia Yinghua
Published: April 2008

Isothermal crystallization kinetics, subsequent melting behavior, and the crystal morphology of short carbon fiber and poly(trimethylene terephthalate) composites (SCF/PTT) were investigated by using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The crystal morphology of the composites isothermally crystallized at Tc = 205°C is predominantly banded spherulites observed under polarizing micrographs, while the pattern of banded spherulites changed from ring to serration as the SCF content added into the PTT. Moreover, nonbanded spherulites formed at Tc = 180°C. The commonly used Avrami equation was used to fit the primary stage of the isothermal crystallization. The Avrami exponents n are evaluated to be 1.6–2.0 for the neat PTT and 2.7–3.0 for SCF/PTT composites, and the SCF acting as nucleation agents in composites accelerates the crystallization rate with decreasing the half‐time of crystallization and the sample with SCF component of 2% has the fastest crystallization rate. The crystallization activation energy calculated from the Arrhenius formula suggests that the adding SCF component improved the crystallization ability of the PTT matrix greatly, and the sample with of 2% SCF component has the most crystallization ability. Subsequent melting scans of the isothermally crystallized composites all exhibited triple melting endotherms, in which the more the component of SCF, the lower temperature of the melting peak, indicating the less perfect crystallites formed in those composites. Furthermore, the melting peaks of the same sample are shifted to higher temperature with increasing Tc, suggesting the more perfect crystallites formed at higher Tc. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Interfacial interactions and performance of polyamide 6/modified attapulgite clay nanocomposites
Authors: Pan Bingli , Ren Junfang , Yue Qunfeng , Liu Bin , Zhang Junyan , Yang Shengrong
Published: April 2008

Attapulgite (AT) clay was firstly treated with sodium polyacrylate (PAS), then polyamide 6 (PA6)/AT nanocomposites were prepared by simple melt compounding. Transmission electron microscope (TEM) and Fourier transform infrared spectrometry (FT‐IR) of treated AT confirm the success of purifying and surface modification of the original AT by PAS. X‐ray diffraction spectra for the nanocomposites show that the microstructure of AT in PA6 matrix is almost unchanged. It indicates that a strong interfacial adhesion exists between AT and PA6 matrix through analyzing fracture surfaces of the nanocomposites, the variation of glass transition temperature (Tg) obtained by dynamic mechanical analysis, and interfacial interaction factors; field emission scanning electron microscopy on the fracture surfaces of the nanocomposites shows that a uniform dispersion of AT is obtained. The above two aspects conform to the improvement of mechanical and thermal properties of the nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Structure and flammability properties of NR‐organoclay nanocomposites
Authors: Liu Lan , Jia Demin , Luo Yuanfang , Li Bo
Published: April 2008

The nanocomposites of natural rubber (NR) and organoclay modified by tributyl phosphate (TMMT) were prepared by the mixing intercalation method and the structure and the flammability properties of them were studied. The structure of the NR‐TMMT nanocomposites were characterized by X‐ray diffraction, transmission electron microscopy, fourier transform infrared spectroscopy and the results show that the d‐spacing of TMMT increase substantially with tributyl phosphate addition and the layers of TMMT disperse in rubber matrix on a nanometer scale. The flammability properties of them were demonstrated by cone calorimeter and indicate that the NR‐TMMT nanocomposites have significantly decreased in heat release rate, mass loss rate, and smoke produce rate. The NR‐TMMT nanocomposites appears very good the flame retardant properties. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Influence of wood flour loading on tribological behavior of epoxy composites
Authors: Dwivedi U.K. , Chand Navin
Published: April 2008

A series of wood flour (WF) filled epoxy composites consisting of five samples were prepared by varying the concentration of WF in step of 10 wt%. These samples were characterized for its wear behavior in abrasive and sliding wear modes to study the influence of WF. It was observed that specific wear rate (k0) of all the composites decreased with increasing load in sliding wear mode. Specific wear rate was of the order of 10−10 m3/Nm in abrasive wear mode and ∼10−14 m3/Nm in sliding wear mode. Composite containing 40 wt% WF exhibited the lowest specific wear rate in abrasive wear mode. While composite containing 20 wt% WF exhibited lowest specific wear rate in sliding wear mode. This was attributed to the fact that in abrasive wear mode, the wear debris consisting of mainly WF particles was maximum for 10 wt% composite and minimum for 40 wt% composite. In sliding wear mode, the exposed WF particles caused maximum roughening of steel counterface in the case of composite containing higher concentration of WF particles. Hence, they exhibited a higher value of specific wear rate. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Effect of surface‐modification on the dynamic behaviors of fly ash cenospheres filled epoxy composites
Authors: Gu Jian , Wu Gaohui , Zhao Xiao
Published: April 2008

An inexpensive fly ash (FA), which is from a waste production, has been used as the filler to prepare the epoxy composites. With the purpose of characterizing the effect of surface‐modification on the dynamic behaviors of FA cenospheres/epoxy composites, Fourier transform infrared spectral analysis (FTIR), microstructure observation as well as dynamic mechanical analysis (DMA) were systematically investigated, respectively. At the same time, the impact toughness was also evaluated by impact property testing. With FTIR analysis, it can be found that the functionalized groups exist on the surface of FA cenospheres. The SEM photographs show that the FA cenosphere particulates with surface‐modification are distributed homogeneously and have a good interface bonding with the matrix, and the ruptures occur not in the two phases interface, but in the middle parts of FA cenospheres after impact. In addition, DMA indicates that the composite filled with surface‐modified FA cenospheres has a wider glass transition temperature region and a higher loss factor, and its relatively higher impact toughness can also be revealed through impact property test. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Exercise‐induced changes in respiratory impedance in young wheezy children and nonatopic controls
Authors: Malmberg L. Pekka , Mäkelä Mika J. , Mattila Petri S. , Hammarén‐Malmi Sari , Pelkonen Anna S.
Published: April 2008

Exercise‐induced bronchoconstriction (EIB) is a specific sign of active asthma, but its assessment in young children may be difficult with lung function techniques requiring active cooperation. The aim of the study was to assess the normal pattern of exercise‐induced responses of respiratory impedance by using impulse oscillometry (IOS), and to investigate how these responses discriminate wheezy children from control subjects. IOS measurements were performed in a consecutive sample of wheezy children aged 3–7 years (n = 130) and in an aged matched control group of nonatopic children without respiratory symptoms (n = 79) before and after a free running test. After exercise, wheezy children showed significantly larger responses in respiratory resistance (Rrs5), reactance (Xrs5), and the resonance frequency (Fr) than the control subjects. In the control group, the upper 95% confidence limit of the maximal change was 32.5% for Rrs5, 85.7% for Xrs5, and 53.1% for Fr. By using analysis of receiver operating characteristics, the change in Rrs5 distinguished the wheezy children from the control subjects more effectively than change in Xrs5 or Fr. In wheezy children, the response was significantly effected by the outdoor temperature and exercise intensity in terms of maximum heart rate. In conclusion, an increase of 35% in Rrs5 after a free running test can be regarded as an abnormal response. Wheezy children show an enhanced airway response, which is clearly distinguishable from the control subjects. IOS is a feasible method to detect EIB in young children. Pediatr Pulmonol. 2008; 43:538–544. © 2008 Wiley‐Liss, Inc.
A randomized, controlled trial of smoking cessation counseling provided during child hospitalization for respiratory illness
Authors: Ralston Shawn , Roohi Mahshid
Published: April 2008

The impact of parental smoking on children is enormous. Injury and illness related to parental smoking result in 6,200 excess pediatric deaths per year, which places smoking as the leading preventable cause of death in US children. Parental smoking doubles the risk of child hospitalization for respiratory illness therefore pediatricians have frequent contact with smoking parents. A single study has previously investigated the effect of child hospitalization on parental smoking cessation.

Smoking caregivers of children hospitalized for respiratory illness at the University of New Mexico were offered a smoking cessation intervention during the child's hospitalization. Participants were randomized to receive either a brief anti‐smoking message or more extensive counseling based on current clinical practice guidelines.

Forty‐two parents enrolled in the study. Fourteen percent of participants in the counseling group and 5% in the brief message group were self‐reported quitters at 6 months.

A significant percentage of smoking parents of children hospitalized for respiratory illness are willing to receive smoking cessation counseling while their child is in the hospital. Abstinence rates appear similar to other pediatric office‐based interventions. Child hospitalization should be considered an important opportunity to provide parents with smoking cessation services, particularly since many smoking parents will not have access to these services elsewhere. Pediatr Pulmonol. 2008; 43:561–566. © 2008 Wiley‐Liss, Inc.
Structural and functional characterization of a novel phosphatase from the Arabidopsis thaliana gene locus At1g05000
Authors: Aceti David J. , Bitto Eduard , Yakunin Alexander F. , Proudfoot Michael , Bingman Craig A. , Frederick Ronnie O. , Sreenath Hassan K. , Vojtik Frank C. , Wrobel Russell L. , Fox Brian G. , Markley John L. , Phillips George N.
Published: April 2008

The crystal structure of the protein product of the gene locus At1g05000, a hypothetical protein from A. thaliana, was determined by the multiple‐wavelength anomalous diffraction method and was refined to an R factor of 20.4% (Rfree = 24.9%) at 3.3 Å. The protein adopts the α/β fold found in cysteine phosphatases, a superfamily of phosphatases that possess a catalytic cysteine and form a covalent thiol‐phosphate intermediate during the catalytic cycle. In At1g05000, the analogous cysteine (Cys150) is located at the bottom of a positively‐charged pocket formed by residues that include the conserved arginine (Arg156) of the signature active site motif, HCxxGxxRT. Of 74 model phosphatase substrates tested, purified recombinant At1g05000 showed highest activity toward polyphosphate (poly‐P12‐13) and deoxyribo‐ and ribonucleoside triphosphates, and less activity toward phosphoenolpyruvate, phosphotyrosine, phosphotyrosine‐containing peptides, and phosphatidyl inositols. Divalent metal cations were not required for activity and had little effect on the reaction. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Single and multiple input modules in regulatory networks
Authors: Konagurthu Arun S. , Lesk Arthur M.
Published: April 2008

Interactions between transcription factors and target genes form regulatory networks that control target gene expression. Regulatory networks contain canonical motifs, including the feed forward loop (FFL), single input module (SIM), and multiple input module (MIM) (Fig. 1). A challenge for network analysis is to identify and enumerate the motifs, required to illuminate their biological significance. Although there is consensus about the definition of the FFL, published definitions of the SIM and MIM are unclear and often used inconsistently. Here, we provide, for the first time, a complete and consistent definition of SIM and MIM, and algorithms for enumerating SIMs and MIMs in any network. From the algorithmic point of view, enumeration of SIMs and MIMs is substantially harder than enumerating FFLs. We compare the distributions of motifs in the Yeast regulatory network under different physiological conditions, reported earlier by the landmark paper of Luscombe et al. (Nature 2004, 431: 308–312). Our reanalysis shows major differences in the number of motifs compared with the results of those authors, requiring significant revision of some of their conclusions. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Crystal structure of DFA0005 complexed with α‐ketoglutarate: A novel member of the ICL/PEPM superfamily from alkali‐tolerant Deinococcus ficus
Authors: Liao Cheng‐Jen , Chin Ko‐Hsin , Lin Chao‐Hsiung , Tsai Peter Shi‐Fong , Lyu Ping‐Chiang , Young Chiu‐Chung , Wang Andrew H.‐J. , Chou Shan‐Ho
Published: April 2008

The crystal structure of the DFA0005 protein complexed with α‐ketoglutarate (AKG) from an alkali‐tolerant bacterium Deinococcus ficus has been determined to a resolution of 1.62 Å. The monomer forms an incomplete α7/β8 barrel with a protruding α8 helix that interacts extensively with another subunit to form a stable dimer of two complete α8/β8 barrels. The dimer is further stabilized by four glycerol molecules situated at the interface. One unique AKG ligand binding pocket per subunit is detected. Fold match using the DALI and SSE servers identifies DFA0005 as belonging to the isocitrate lyase/phosphoenolpyruvate mutase (ICL/PEPM) superfamily. However, further detailed structural and sequence comparison with other members in this superfamily and with other families containing AKG ligand indicate that DFA0005 protein exhibits considerable distinguishing features of its own and can be considered a novel member in this ICL/PEPM superfamily. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Pulsed layer growth of AlInGaN nanostructures
Authors: Jetter Michael , Michler Peter
Published: April 2008

A pulsed layer growth mode in the metal‐organic vapor phase epitaxy (MOVPE) was used to fabricate excellent quality AlInGaN nanostructures. The amount of material was varied, resulting in AlInGaN layer thicknesses between nominally 1.5 nm and 6 nm, respectively. We have analyzed the material properties by X‐ray diffraction (XRD) as well as photoluminescence (PL) spectroscopy. The observed XRD‐spectra and the PL intensity show the high quality of the deposited material.

By analyzing the PL spectra we have found an energetic shift of the resonance lines from 2.65 eV to 3.33 eV with decreasing well thickness. We attribute this shift mainly to the presence of internal electric fields at the AlIn‐GaN/GaN interface. Power‐dependent and time resolved PL experiments confirm this observation. Comparing the luminescence at elevated temperatures, the pulsed layer epitaxy structures reveal a much higher intensity as the conventional grown samples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Power AlGaN/GaN HFETs with excellent Vb/Ron for high speed switching
Authors: Ikeda Nariaki , Kato Kazuo , Li Jiang , Kaya Syusuke , Nomura Takehiko , Masuda Mitsuru , Yoshida Seikoh
Published: April 2008

AlGaN/GaN HFETs with a large current and a high breakdown voltage were fabricated. We examined the switching characteristics and capacitance parameters such as an input capacitance (Ciss), a reverse transfer capacitance (Crss), a gate to a source charge (Qgs) and a gate to a drain charge (Qgd) using the GaN HFET devices. In order to confirm the advantage for the high‐frequency switching operation of the GaN HFETs compared with Si devices, capacitance parameters and the figure of merit (FOM) Vb/(Ron) for a switching capability were examined. As a result, a low Ciss, Crss, and Qg were obtained and the FOMs of GaN HFETs have one order of magnitude larger than those of Si power devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of fluorine‐plasma‐induced deep centers in AlGaN/GaN heterostructure by persistent photoconductivity
Authors: Li B. K. , Chen K. J. , Lau K. M. , Ge W. K. , Wang J. N.
Published: April 2008

Fluorine plasma treatment technique can effectively incorporate negatively‐charged fluorine ions in the AlGaN barrier and deplete the two‐dimensional electron gas in the channel of AlGaN/GaN high electron mobility transistors (HEMTs). In applications, this technique can be used to convert the device from depletion‐mode to enhancement‐mode. To reveal the underlying physical mechanisms, the properties of F‐related deep centers in an AlGaN/GaN heterostructure are studied using temperature‐dependent persistent photoconductivity (PPC) and Hall measurements. Weakly temperature‐independent 2DEG mobility and much more pronounced PPC effect are observed in the F‐treated sample. Energy barrier for electron‐recapture by the F‐related centers has also been extracted from the PPC decay behaviour. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical conduction in cubic GaN films grown on GaAs(001) by RF‐MBE
Authors: Kohno M. , Nakamura T. , Kataoka T. , Katayama R. , Onabe K.
Published: April 2008

The electrical conduction property of c‐GaN films grown on GaAs(001) by RF‐MBE has been studied in relation with the amount of the hexagonal phase inclusion, or cubic phase purity. In a high‐phase‐purity (93%) film, the electron concentration and mobility at 300 K are typically 8×1017 cm–3 and 110 cm2/V‐s, respectively. It is known that a parallel conduction is occurring in which the high mobility region somewhat away from the hetero‐interface dominates the conduction at higher currents. In a lower‐phase‐purity (75%) film, it is indicated that the low mobility region extends over the larger region of the film. Above the cubic phase purity of about 90%, the electron concentration rapidly decreases and the mobility rapidly increases by one or two orders of magnitudes, suggesting that the stacking faults are the major source of the carrier electrons and causing the scattering centers responsible for the low mobility region. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN ultraviolet avalanche photodiodes fabricated on free‐standing bulk GaN substrates
Authors: Zhang Yun , Yoo Dongwon , Limb Jae‐Boum , Ryou Jae‐Hyun , Dupuis Russell D. , Shen Shyh‐Chiang
Published: April 2008

We report high‐performance MOCVD‐grown GaN ultraviolet (UV) p‐i‐n avalanche photodiodes (APD) on bulk GaN substrates. The fabricated APD achieved avalanche gain of > 3 × 104 and low leakage current density (<10–7 A/cm2) at voltages below 50% of the device avalanche breakdown voltage. To the best of our knowledge, this is the highest linear gain reported to date among III‐N‐based UV APDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlxGa1–xN‐based avalanche photodiodes with high reproducible avalanche gain
Authors: Tut Turgut , Gokkavas Mutlu , Ozbay Ekmel
Published: April 2008

We report high performance solar‐blind photodetectors with reproducible avalanche gain as high as 1570 under ultraviolet illumination. The solar‐blind photodetectors have a sharp cut‐off around 276 nm. The dark currents of the 40 μm diameter devices are measured to be lower than 8 femto‐amperes for bias voltages up to 20 V. The responsivity of the photodetectors is 0.13 A/W at 272 nm under 20 V reverse bias. The thermally limited detectivity is calculated as D* = 1.4 × 1014 cm Hz1/2 W–1 for a 40 µm diameter device. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
2.3 nm barrier AlN/GaN HEMTs with insulated gates
Authors: Deen David , Zimmermann Tom , Cao Yu , Jena Debdeep , Xing Huili Grace
Published: April 2008

Ultra‐shallow channel AlN/GaN high electron mobility transistor (HEMT) structures with a 2.3 nm AlN barrier were grown by plasma‐assisted molecular beam epitaxy (PAMBE) on sapphire substrates. They exhibit 2‐D electron gas densities of ∼ 1.4 x 1013 cm–2 and electron hall mobilities of ∼ 1600 cm2/Vs. Insulated‐gate stacks of SiNx/Al2O3/Ni/Au were used to suppress the gate leakage current, which is found to largely stem from dislocation‐assisted leakage paths. AlN/GaN HEMTs with 250 nm gate length showed DC output current densities of up to 1.6 A/mm, transconductances of ∼ 300 mS/mm, and extrinsic ft/fmax of 24/52 GHz. These performance metrics demonstrate that these ultra‐shallow channel AlN/GaN heterostructures hold a lot of promises for high‐power high‐frequency device applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and catalytic activity of hybrid metal/silicon nanocomposites
Authors: Polisski Sergej , Goller Bernhard , Lapkin Alexei , Fairclough Simon , Kovalev Dmitry
Published: April 2008

In this Letter we demonstrate that hydrogen‐terminated porous silicon (PSi) layers and powders can serve as highly efficient reductive templates for noble metal salts. The reduction results in metal nanoparticle (NP) formation in the pores of PSi. Gold NP formation has been monitored in‐situ by measuring the plasmon resonance response. Pt NPs, formed in the PSi matrix, were investigated by transmission electron microscopy and energy‐dispersive X‐ray analysis. Furthermore, hybrid Pt/PSi nanocomposites exhibit a high catalytic activity for CO oxidation.

magnified image

HRTEM image of a Pt nanoparticle reduced inside the PSi matrix. Platinum lattice fringes d〈111〉 = 2.27 Å can be seen.

(© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Small fetal abdominal circumference in the second trimester and subsequent low maternal plasma glucose after a glucose challenge test is associated with the delivery of a small‐for‐gestational age neonate
Authors: Bienstock J. L. , Holcroft C. J. , Althaus J.
Published: April 2008

Objectives

To evaluate the predictive value of a combination of the 1 h 50‐g glucose challenge test (GCT) and second‐trimester ultrasound measurement of fetal abdominal circumference (AC) in identifying patients who will go on to deliver small‐for‐gestational age (SGA) neonates. The individual predictive power of these tests has been indicated by previous studies, but this study examines the combined use of these indicators in predicting SGA.

Methods

This retrospective cohort study included 576 consecutive patients with singleton gestations examined over a 3‐year period. Patients' electronic medical records were abstracted to obtain the result of the GCT, the fetal AC measured by ultrasound examination between 18 and 22 weeks' gestation, and the birth weight. SGA and small AC were defined as birth weight or AC < 10th percentile for gestational age, according to published nomograms. A low GCT was defined as < 100 mg/dL. P < 0.05 was considered significant.

Results

The prevalence of SGA in the study population was 8.7% (50/576). The frequency of SGA neonates was significantly higher in patients with a low GCT (27/207) in the second trimester than in those with a normal GCT (23/369) (13% vs. 6.2%, P = 0.005). Similarly, the frequency of SGA neonates was higher among patients with fetal AC < 10th percentile than among those with a normal fetal AC on second‐trimester ultrasound examination (17% vs. 8%, P = 0.08), although this difference did not reach statistical significance. Of interest, among patients with both a small fetal AC and a low GCT the incidence of SGA neonates was 32% (6/19), but there were no SGA neonates among those with a small AC and normal GCT (0/17) (P = 0.014). Among patients with a small fetal AC the sensitivity of using low GCT to predict subsequent delivery of a SGA neonate was 100%, with a specificity of 57%, positive predictive value 32% and negative predictive value 100%.

Conclusions

Small AC on routine second‐trimester anomaly sonogram should trigger a closer evaluation of maternal GCT. If the GCT is also low, more intensive surveillance for the possible development of a SGA infant is warranted. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Prenatal imaging findings in rapidly involuting congenital hemangioma of the skull
Authors: Elia D. , Garel C. , Enjolras O. , Vermouneix L. , Soupre V. , Oury J.‐F. , Guibaud L.
Published: April 2008

We report two cases of rapidly involuting congenital hemangioma (RICH) of the skull diagnosed in the third trimester of gestation, and also present a brief review of the literature. In both of our cases ultrasound examination showed a soft tissue vascular mass of the skull with a specific sonographic finding: a thin hyperechogenic line over the lesion and continuous with the calvaria, suggesting a subperiosteal origin and possibly accounting for a mass effect on the underlying skull. This was slight in one case and marked in the other (and associated with involvement of the calvaria). On prenatal T2‐weighted magnetic resonance imaging, the signal of each of the lesions was less marked than the hypersignal encountered in the postnatal period. Postnatal clinical and radiological follow‐up over the first few months after delivery confirmed the diagnosis of RICH in each case by demonstrating a significant decrease in the size of the tumor and regression of the vascular component, with complete involution of the lesion within a year. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Effects of additives on fusion parameters of rigid PVC formulations
Authors: Moghri M. , Garmabi H. , Akbarian M.
Published: April 2008

The effects of varying amounts of tribasic lead sulfate (TBLS), dibasic lead stearate (DBLS), neutral lead stearate (NLS), calcium stearate (Ca.St.), stearic acid (St.Ac.), and paraffin wax (PW) on the fusion properties of a rigid PVC formulation were investigated. The materials showed varying effects on fusion. Thus, fusion time was lowered and fusion factor increased by TBLS, DBLS, and Ca.St., while the reverse was true with NLS, St.Ac., and PW. The behavior of the materials is discussed in terms of their effects on the transformation of PVC grains. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.
Centromeres: Old tales and new tools
Authors: Vagnarelli P. , Ribeiro S.A. , Earnshaw W.C.
Published: April 2008

In this review, we will analyse how centromeres are organised with respect to chromatin types and arrangements.
Differential hTERT mRNA processing between young and older glioma patients
Authors: Shervington A. , Patel R.
Published: April 2008

The amplification of hTERT was detected in glioma tissues, although telomerase activity was not always found within these specimens. The aim of this study was to correlate the level of hTERT transcription with telomerase activity in two glioma age groups. hTERT was significantly transcribed at similar copy numbers in both age groups. However, these mRNAs translated to telomerase in 100% of the young compared to only 25% of the older patients. While hTERT transcription correlated directly to telomerase protein level and activity, as well as longer telomeres in the young group, such correlations were missing in the older group.
Vitamin D deficiency and low bone status in adult female garment factory workers in Bangladesh
Authors: Islam Md Zahirul , Shamim Abu Ahmed , Kemi Virpi , Nevanlinna Antti , Akhtaruzzaman Mohammad , Laaksonen Marika , Jehan Atia H. , Jahan Khurshid , Khan Habib Ullah , Lamberg-Allardt Christel
Published: April 2008

The manufacture of garments is the main industry in Bangladesh and employs 1·6 million female workers. Due to the indoor lifestyle and low dietary intake of calcium, we hypothesised that they are at risk of low vitamin D and bone mineral status. Two hundred female garment workers (aged 18–36 years) were randomly selected. Serum 25-hydroxyvitamin D (S-25OHD), serum intact parathyroid hormone (S-iPTH), serum calcium (S-Ca), serum phosphate (S-P) concentration and serum alkaline phosphatase activity (S-ALP) were measured from fasting samples. Bone indexes of hip and spine were measured by dual-energy X-ray absorptiometry. The mean S-25OHD (36·7 nmol/l) was low compared to that recommended for vitamin D sufficiency. About 16 % of the subjects were found to be vitamin D-deficient (S-25OHD < 25 nmol/l). We observed a high prevalence (88·5 %) of vitamin D insufficiency (S-25OHD < 50 nmol/l) as well as a significant inverse relationship between S-25OHD and S-iPTH (r − 0·25, P ≤ 0·001). A decrease in S-25OHD ( < 38 nmol/l) and an increase in S-iPTH (>21 ng/l) was associated with progressive reduction in bone mineral density at the femoral neck and lumbar spine. According to the WHO criteria, the mean T-score of the femoral neck and lumbar spine of the subjects were within osteopenic range. We observed that subjects with a bone mineral density T-score < − 2·5 had a trend of lower values of BMI, waist–hip circumference, mid-upper-arm circumference, S-25OHD and higher S-iPTH and S-ALP. The high prevalence of hypovitaminosis D and low bone mineral density among these subjects are indicative of higher risk for osteomalacia or osteoporosis and fracture.
THE CONSTANT DEMAND OF THE FRENCH: THE MASCARENE SLAVE TRADE AND THE WORLDS OF THE INDIAN OCEAN AND ATLANTIC DURING THE EIGHTEENTH AND NINETEENTH CENTURIES
Authors: ALLEN RICHARD B.
Published: April 2008

Analysis of an inventory of 641 slaving voyages involving Mauritius and Réunion between 1768 and 1809 reveals that the Mascarene Islands were at the center of a substantial and dynamic regional slave trading network that also reached into the Americas in ways that raise questions about the relationship between the ‘worlds’ of the Indian Ocean and the Atlantic. The fact that colonial, as well as metropolitan, merchant capital underwrote Mascarene-based slave trading ventures raises additional questions about the role of locally generated and/or non-Western capital in financing the movement of slave, and ultimately ‘free’, labor throughout the eighteenth- and nineteenth-century colonial world.
Outbreaks of noroviral gastroenteritis in Florida, 2006–2007
Authors: DOYLE T. J. , STARK L. , HAMMOND R. , HOPKINS R. S.
Published: April 2008

Noroviruses are an important cause of sporadic cases and outbreaks of acute gastroenteritis. During 2006–2007, widespread increases in acute gastroenteritis outbreaks consistent with norovirus were observed in the United States. We conducted a statewide survey to characterize norovirus outbreak activity in Florida during a 1-year period. From July 2006 to June 2007, 257 outbreaks of norovirus gastroenteritis were identified in 39 of Florida's 67 counties. About 44% of outbreaks were laboratory confirmed as norovirus and 93% of these were due to genogroup GII. About 63% of outbreaks occurred in long-term care facilities and 10% of outbreaks were classified as foodborne. The median number of ill persons per outbreak was 24, with an estimated total of 7880 ill persons. During the study period, norovirus outbreak activity in Florida was widespread, persistent, and consistent with increased activity observed in other parts of the country.
Paleomagnetic and mineral magnetic investigation of the Baicaoyuan loess‐paleosol sequence of the western Chinese Loess Plateau over the last glacial‐interglacial cycle and its geological implications
Authors: Deng Chenglong
Published: April 2008

Closely spaced paleomagnetic and mineral magnetic studies were conducted on the Baicaoyuan (BCY) loess‐paleosol sequence since the last interglacial in the western Chinese Loess Plateau. The multiproxy records of mineral magnetic parameters clearly indicate loess‐paleosol alternations with the fine structure of pedostratigraphy over the last glacial‐interglacial cycle. However, the paleomagnetic results reveal the absence of any short‐lived geomagnetic excursions in the BCY section. This absence could be interpreted by two alternative mechanisms, such as magnetic overprinting and discontinuous sedimentation. The absence of the Mono Lake and Laschamp excursions in the loess unit L1 is probably due to the viscous overprinting of the remanence carried by coarse‐grained magnetite of eolian origin and/or to the episodic nature of loess accumulation during the last glacial period. However, discontinuous sediment accumulation may more probably lead to the absence of the Blake excursion in the last interglacial soil S1 as well as of the Mono Lake and Laschamp excursions in the last glacial loess L1 at the BCY section. Together with previously published paleomagnetic results from other sections over the Loess Plateau, the findings probably further indicate the discontinuous nature of loess accumulation in the western Loess Plateau, where sedimentation of the last interglacial soil may be episodic at the timescale equivalent to the duration of the Blake geomagnetic excursion (4–6 ka), much longer than the timescale for episodic loess sedimentation in the last glacial loess of both the western and eastern Loess Plateau due to the reduced sediment accumulation rate compared to that during the last glacial period. Thus, sediments with relatively high sedimentation rate in some parts of the western Loess Plateau do not consistently guarantee the faithful recording of high‐frequency geomagnetic variations.
Biophysical responses of the upper ocean to major Gulf of Mexico hurricanes in 2005
Authors: Gierach Michelle M. , Subrahmanyam Bulusu
Published: April 2008

The biophysical responses of the upper ocean to three major Gulf of Mexico (GoM) hurricanes in 2005 were analyzed using satellite observations. The degree and orientation of the responses exhibited by Hurricanes Katrina, Rita, and Wilma were greatly affected by the oceanic processes that occur within the GoM, as well as the translation speed of each hurricane. Maximum sea surface temperature change was 6–7°C, 4–5°C, and 5–6°C; whereas, chlorophyll‐a (chl‐a) enhancement was 3 mg m−3, 2 mg m−3, and 4 mg m−3, respectively. Areas of chl‐a enhancement (i.e., increases in phytoplankton biomass accumulation at the ocean's surface) were observed days after passage of each hurricane. Comparison of thermocline displacement estimates and depth approximations of the nitracline and deep chl‐a maximum suggests that the increases in surface phytoplankton biomass associated with Hurricanes Katrina and Rita were the result of new production from nutrient influx, as well as entrainment of phytoplankton from the deep chlorophyll maximum, while chl‐a enhancement linked with Hurricane Wilma appears to be attributable to the latter.
Evolution of ocean slicks under a rising wind
Authors: Marmorino George O. , Smith Geoffrey B. , Toporkov Jakov V. , Sletten Mark A. , Perkovic Dragana , Frasier Stephen J.
Published: April 2008

Airborne synthetic aperture radar and high‐resolution infrared imagery are used to examine the evolution of natural ocean slicks during a period of freshening wind. Initially the slicks are of the order of 50 m in width and have radar and thermal contrasts of the order of 10 dB and several 0.1°C. While there can be over time a transient reorganization of surface film material by internal waves, the slicks are observed to disperse and are no longer detectible after 5 h. The dispersion occurs through the action of Langmuir circulation, which results in along‐wind streaks or “windrows”, as well as other effects. Prominent streaks occur preferentially along a slick's upwind side, the downwind side resembling more of a “leading edge”, at least early on. Over time, the leading edge develops a corrugated shape, and gaps begin to develop within the slicks. The formation of gaps is compared with a conceptual model by Dysthe (2006) for the tearing of a surface film in the region of positive surface straining. Eventually, the slicks break into elongated patches that co‐exist with windrows, which is consistent with the effects of advective dispersion.
Bromoform and dibromomethane measurements in the seacoast region of New Hampshire, 2002–2004
Authors: Zhou Yong , Mao Huiting , Russo Rachel S. , Blake Donald R. , Wingenter Oliver W. , Haase Karl B. , Ambrose Jesse , Varner Ruth K. , Talbot Robert , Sive Barkley C.
Published: April 2008

Atmospheric measurements of bromoform (CHBr3) and dibromomethane (CH2Br2) were conducted at two sites, Thompson Farm (TF) in Durham, New Hampshire (summer 2002–2004), and Appledore Island (AI), Maine (summer 2004). Elevated mixing ratios of CHBr3 were frequently observed at both sites, with maxima of 37.9 parts per trillion by volume (pptv) and 47.4 pptv for TF and AI, respectively. Average mixing ratios of CHBr3 and CH2Br2 at TF for all three summers ranged from 5.3–6.3 and 1.3–2.3 pptv, respectively. The average mixing ratios of both gases were higher at AI during 2004, consistent with AI's proximity to sources of these bromocarbons. Strong negative vertical gradients in the atmosphere corroborated local sources of these gases at the surface. At AI, CHBr3 and CH2Br2 mixing ratios increased with wind speed via sea‐to‐air transfer from supersaturated coastal waters. Large enhancements of CHBr3 and CH2Br2 were observed at both sites from 10 to 14 August 2004, coinciding with the passage of Tropical Storm Bonnie. During this period, fluxes of CHBr3 and CH2Br2 were 52.4 ± 21.0 and 9.1 ± 3.1 nmol m−2 h−1, respectively. The average fluxes of CHBr3 and CH2Br2 during nonevent periods were 18.9 ± 12.3 and 2.6 ± 1.9 nmol m−2 h−1, respectively. Additionally, CHBr3 and CH2Br2 were used as marine tracers in case studies to (1) evaluate the impact of tropical storms on emissions and distributions of marine‐derived gases in the coastal region and (2) characterize the transport of air masses during pollution episodes in the northeastern United States.
Obesity Indices and Self‐Reported Functional Health in Men and Women in the EPIC‐Norfolk
Authors: Myint Phyo K. , Welch Ailsa A. , Luben Robert N. , Wainwright Nicholas W.J. , Surtees Paul G. , Bingham Sheila A. , Wareham Nicholas J. , Smith Richard D. , Harvey Ian M. , Khaw Kay‐Tee
Published: April 2008

Objective: To investigate the association between two indices of obesity, BMI and waist‐to‐hip ratio (WHR), and self‐reported physical and mental functional health.

Research Methods and Procedures: We examined the relationship between obesity indices and self‐reported physical and mental functional health measured by the Anglicized version of the Short‐Form 36‐item questionnaire in a population‐based cross sectional study of 16, 806 men and women 40 to 79 years old living in the general community in Norfolk, United Kingdom.

Results: Higher BMI and WHR were both independently associated with poorer self‐reported physical functional health in men and women. The effect of BMI was greater in women compared with men, and the effect of WHR was greater in men compared with women, for poor physical functional health. Higher WHR but not BMI was associated with lower mental functional health in men and women.

Discussion: High BMI and WHR seem to be adversely related to self‐perceived functional health in both men and women, although their relative impacts seem to differ by sex. Our findings also highlight the importance of using WHR in addition to BMI in assessing the impact of obesity on health outcome.
Correlates of BMI Misreporting among Apparently Healthy Individuals: The ATTICA Study
Authors: Yannakoulia Mary , Panagiotakos Demosthenes B. , Pitsavos Christos , Stefanadis Christodoulos
Published: April 2008

Objective: The aim of this study was to investigate correlates of misreporting in BMI, based on self‐reported weight and height, in a randomly selected population sample of Greek adults and to evaluate the effect of obesity status misclassification on the associations between obesity and disease.

Research Methods and Procedures: During 2001 to 2002, we randomly enrolled 1514 men (18 to 87 years old) and 1528 women (18 to 89 years old) from the Attica area, Greece; the sampling was stratified by the age‐sex distribution of the region. Various sociodemographic, clinical, and psychological characteristics were self‐reported, and weight and height were measured and recorded in all participants.

Results: The proportions of true positives and true negatives for correct obesity status identification were 62% and 97%, respectively. Women were 9 times more likely to be under‐reporters than men, whereas men were 7.5 times more likely to be over‐reporters. A 10‐year increase in age was associated with a 48% higher likelihood of being an under‐reporter and 26% lower likelihood of being an over‐reporter, irrespective of sex and other characteristics of the participants. Clinical status, such as the presence of hypertension and diabetes, was associated with under‐reporting of body weight. Furthermore, the use of self‐reported data may substantially exaggerate associations between obesity and obesity‐related diseases, such as diabetes, hypercholesterolemia, and hypertension.

Discussion: The study indicates that, apart from age and sex, disease status may be another factor that influences misreporting of obesity status, with diabetic and hypertensive people to be more likely to under‐report their overweight. Use of self‐reported data may bias obesity—disease associations.