bluuebunny/crossref_metadata_2025 huggingface dataset:
Note: A simple dual polarity dual nanoelectrospray ionization source for ion/ion reactions
Authors: Myer Matthew J. , Danell Ryan M. , Danell Allison S.
Published: June 2010

A continuously operated dual polarity dual nanoelectrospray ionization source has been constructed and tested. A commercial quadrupole ion trap mass spectrometer was modified to accumulate and trap ions of opposite charge. All changes to the commercial three-dimensional quadrupole ion trap have been made external to the instrument outside of the vacuum system. Few hardware modifications were required because the two emitters send ion beams through the same transmission guides. Computer controlled source voltage polarities are switched quickly and efficiently to transmit one of two continuously generated ion beams. With customized software, this design has proved simple to implement and to operate.
Structure and dielectric relaxation of double-perovskite La2CuTiO6 ceramics
Authors: Yang W. Z. , Mao M. M. , Liu X. Q. , Chen X. M.
Published: June 2010

Dielectric properties of La2CuTiO6 ceramics were investigated in a broad frequency and temperature range. There is only one dielectric relaxation in the curve of temperature dependence of dielectric properties for La2CuTiO6 ceramics. This dielectric relaxation is a thermal activated process. The bulk and grain boundary resistances can be obtained from results of the least-mean-square fitting on impedance spectra. The conduction mechanism of the present ceramics is also a thermal activated process. The activation energy of dielectric relaxation is almost same as that of electrical conductivity and this indicates the closely correlation between the dielectric relaxation and electrical conductivity. The dielectric relaxation in the present ceramics should be attributed to the mixed-valent structure (Cu+/Cu2+ and Ti3+/Ti4+), which is induced from the oxygen vacancy.
Dynamic tensile response of Zr-based bulk amorphous alloys: Fracture morphologies and mechanisms
Authors: Escobedo J. P. , Gupta Y. M.
Published: June 2010

Plate impact experiments were conducted to examine the dynamic tensile response of Zr-based bulk amorphous alloys (BAAs) having a nominal composition of Zr56.7Cu15.3Ni12.5Nb5.0Al10.0Y0.5. The experimental configuration used in our work permitted soft recovery of the samples to allow a careful examination of the fractured samples along with real-time measurements of the sample free-surface velocity (FSV) histories. Tensile loading was preceded by elastic compressive loading to peak stresses in the 3.6 to 6.0 GPa range. Tensile damage in the recovered samples was examined using optical and electron microscopy. The microscopy results showed that the BAA samples exhibit a brittle behavior (as a glass) at the macroscopic level and a ductile behavior (as a metal) at the microscopic level; in addition, corrugations and bumps are observed at the nanoscale. The observed fracture morphologies are related to three key features present in our spall experiments: preceding compressive stress (3.6–6.0 GPa), high tensile loading rate (∼106/s), high mean tensile stress (∼2.3 GPa); and are intrinsically related to the amorphous glassy structure of the BAAs (free volume content). We propose that the compressive stress depletes the free volume content. With increasing compressive stress, the available free volume decreases causing a suppression of shear stresses during tension. Thus, the mean tensile component becomes more dominant at higher stresses. Consequently, the observed surface morphology results from brittle cleavage, causing an increased damage localization in the recovered samples spalled at higher stresses. These observations support the inferences made from measurements of FSV histories. The high tensile loading rate is proposed to be responsible for cracking by multiple shear band propagation and interception, rendering the observed serrated surface morphology. Finally, we proposed that the corrugations are created due to a succession of arrest and propagation of mode I cracks. A subsequent dilatation, due to the effect of the tensile mean stress, caused the corrugations to evolve to bump-type features with sizes in the range of 10–100 nm. Our proposed mechanisms, although qualitative, constitute a systematic attempt to provide an explanation for the fracture morphologies observed in spalled BAA samples.
Relative pressure, temperature, and gas composition sensitivity of damping-based resonant sensors
Authors: Martin Michael J. , Houston Brian H.
Published: June 2010

Measurement of the damping in resonant microsystems and nanosystems has been proposed for measurement of pressure, temperature, and gas composition. Because the damping will be a function of all three of these variables, estimating the sensitivity of these transducers requires modeling the effect each of these variables will have on the damping of the system. Using viscous flow theory, the relative sensitivity of damping to pressure, temperature, relative humidity, and the concentration of selected contaminants is computed. These results show that these sensors are accurate as pressure sensors across a range of conditions. Resonators are accurate as temperature sensors only if the relative humidity is known. Resonators are not accurate as humidity sensors, and are accurate as gas composition sensors only under limited conditions.
Field assisted sintering of nickel nanoparticles during in situ transmission electron microscopy
Authors: Holland Troy B. , Thron Andrew M. , Bonifacio Cecile S. , Mukherjee Amiya K. , van Benthem Klaus
Published: June 2010

This study reports the in situ transmission electron microscopy (TEM) observation of pressure-less field-assisted sintering of agglomerated nanometric nickel particles. Scanning tunneling microscopy inside the TEM was used to apply an electrical current directly to the powder particles. Electrical testing during the experiment reveals that consolidation occurs in the absence of an external heat source. Neck formation between adjacent particles and attendant increase in local Joule heating causes rapid densification. The results represent a first stepping stone towards achieving a fundamental mechanistic understanding of the atomic-scale processes that enable field-enhanced sintering of conductive nanogranular materials.
Carbon nanotube network electrodes enabling efficient organic solar cells without a hole transport layer
Authors: Barnes Teresa M. , Bergeson Jeremy D. , Tenent Robert C. , Larsen Brian A. , Teeter Glenn , Jones Kim M. , Blackburn Jeffrey L. , van de Lagemaat Jao
Published: June 2010

We report on the effects of replacing both In2O3:Sn (ITO) and the hole transport layer (HTL) in organic photovoltaic (OPV) cells with single-walled carbon nanotube (SWNT) network transparent electrodes. We have produced an OPV device without an HTL exhibiting an NREL-certified efficiency of 2.65% and a short-circuit current density of 11.2 mA/cm2. Our results demonstrate that SWNT networks can be used to replace both ITO and the HTL in efficient OPV devices and that the HTL serves distinctly different roles in ITO- and SWNT-based devices.
Tube-based geometries for organic photovoltaics
Authors: Li Yuan , Peterson Eric D. , Huang Huihui , Wang Mingjun , Xue Dan , Nie Wanyi , Zhou Wei , Carroll David L.
Published: June 2010

We demonstrate a waveguiding tube-based optical geometry that provides a general approach to improving organic photovoltaic performance. By fabricating bulk-heterojunction photovoltaics onto thin tubular light pipes, the optical energy can be effectively captured within the absorbing layer without associated reflective losses at the front and rear surfaces of the devices as is typical in planar structures. We have used a common absorber system: poly-3-hexyl-thiophene:phenyl-C61-butyric-acid-methyl-ester to demonstrate these tubular optical geometries result in very little overall radiative loss. Surprisingly, this also leads to an overall broadening of the absorption window for the device as indicated by the external quantum efficiency.
Scaling down of amorphous indium gallium zinc oxide thin film transistors on the polyethersulfone substrate employing the protection layer of parylene-C for the large-scale integration
Authors: Chang Seongpil , Dong Ki-Young , Park Jung-Ho , Oh Tae-Yeon , Kim Jong-Woo , Lee Sang Yeol , Ju Byeong-Kwon
Published: June 2010

We have investigated the parylene-groups for the device scaling-down as the protection layer of polyethersulfone (PES) substrate. In general, photolithography process on the PES substrate could not be allowed due to its poor chemical resistance. In this work, parylene-C is used as the protection layer. However, adhesion problem is observed caused by the hydrophobic property of parylene-groups. Thereby we additionally used SiO2 as the adhesion layer. Finally, we demonstrated the scaling-down of amorphous indium gallium zinc oxide thin film transistor on a plastic substrate by using lithography technique. Field-effect mobility, threshold voltage, current on-to-off ratio are measured to be 0.84 cm2/V s, 19.7 V, and 7.62×104, respectively.
Self-organized phase segregation between inorganic nanocrystals and PC61BM for hybrid high-efficiency bulk heterojunction photovoltaic cells
Authors: Tsang Sai-Wing , Fu Huiying , Ouyang Jianying , Zhang Yanguang , Yu Kui , Lu Jianping , Tao Ye
Published: June 2010

We demonstrate a simple approach to generate phase segregation between colloidal PbS nanocrystals (NCs) and organic [6,6]-phenyl C61 butyric acid methyl ester (PC61BM). Continuous vertical phase segregation is observed in cross-linked composite films of NCs and PC61BM. Hybrid bulk heterojunction photovoltaic cells fabricated with the phase segreated composite layer have achieved the state-of-art power conversion efficiency of 3.7% under one sun of simulated Air Mass 1.5 Global solar irradiation. The presented method can be generally applied in other NC/organic systems for the development of hybrid heterojunction photovoltaic cells.
Domain wall contributions in Pb(Zr,Ti)O3 ceramics at morphotropic phase boundary: A study of dielectric dispersion
Authors: Jin Li , Porokhonskyy Viktor , Damjanovic Dragan
Published: June 2010

The dielectric properties of undoped, Nb-, and Fe-doped Pb(Zr,Ti)O3 ceramics with composition near morphotropic phase boundary were investigated in the frequency range from 1 MHz to 20.2 GHz at room temperature. Temperature dependences of dielectric permittivity ε′ and loss ε″ are measured at 100 kHz from 50 to 300 K and around 13.4 GHz from 100 to 300 K. These measurements permit estimation of the upper limit of the intrinsic permittivity and lower limit of the extrinsic contributions to the permittivity as a function of temperature. The extrinsic contributions account for more than 50% of the quasistatic dielectric permittivity in studied samples.
Metal nanoparticle plasmonics inside reflecting metal films
Authors: Earp A. A. , Smith G. B.
Published: June 2010

Oxide coated metal nanoparticles buried within a thin metal layer support a surface plasmon resonance. A local dip occurs in spectral reflectance along with a switching off of the film’s plasmonic response. Models are introduced in which these resonances are tunable by altering the ratio of oxide thickness to core particle radius. The optical response of two experimental examples is presented and modeled using effective medium theory. Beyond the resonance zone the doped layer switches back to the plasmonic response of a nanoporous version of the host metal whose effective plasma frequency arises only from the percolating component.
Helping with Homework? Homework as a Site of Tension for Parents and Teenagers
Authors: Solomon Yvette , Warin Jo , Lewis Charlie
Published: June 2010

The setting of homework is strongly encouraged by the Department for Education and Employment on the assumption that support from parents, once gained, is unproblematic and useful. However, a number of researchers have observed the possibility of a negative impact of homework on families. This article presents interview data from families with teenagers, in which homework was described as a significant site of parent‐teenager tensions. For many parents, homework was invested with the opportunity for reparation for their own scholastic failures or lost opportunities. Others felt that they lacked the competence to help and were disenfranchised by homework demands. Parents' concerns about their children's futures create a climate of pressure to succeed as they support a homework agenda that is not necessarily their own and which they have little power to influence.
YIG magnonics
Authors: Serga A A , Chumak A V , Hillebrands B
Published: June 2010

Early experiments in magnonics were made using ferrite samples, largely due to the intrinsically low magnetic (spin-wave) damping in these materials. Historically, magnonic phenomena were studied on micrometre to millimetre length scales. Today, the principal challenge in applied magnonics is to create sub-micrometre devices using modern polycrystalline magnetic alloys. However, until certain technical obstacles are overcome in these materials, ferrites—in particular yttrium iron garnet (YIG)—remain a valuable source of insight. At a time when interest in magnonic systems is particularly strong, it is both useful and timely to review the main scientific results of YIG magnonics of the last two decades, and to discuss the transferability of the concepts and ideas learned in ferrite materials to modern nano-scale systems.
Magnonic logic circuits
Authors: Khitun Alexander , Bao Mingqiang , Wang Kang L
Published: June 2010

We describe and analyse possible approaches to magnonic logic circuits and basic elements required for circuit construction. A distinctive feature of the magnonic circuitry is that information is transmitted by spin waves propagating in the magnetic waveguides without the use of electric current. The latter makes it possible to exploit spin wave phenomena for more efficient data transfer and enhanced logic functionality. We describe possible schemes for general computing and special task data processing. The functional throughput of the magnonic logic gates is estimated and compared with the conventional transistor-based approach. Magnonic logic circuits allow scaling down to the deep submicrometre range and THz frequency operation. The scaling is in favour of the magnonic circuits offering a significant functional advantage over the traditional approach. The disadvantages and problems of the spin wave devices are also discussed.
Blistering Skin Conditions
Authors: Young Peter
Published: June 2010

Blisters are fluid-filled eruptions on the skin or mucous membranes. They are commonly seen in general practice in patients with herpes infection, insect bites, burns and friction trauma. Primary blistering disorders, for example bullous pemphigoid (BP) and pemphigus vulgaris (PV) are rare in comparison. These are immune or inherited disorders of proteins that bind the skin together. Blistering conditions may present alone or in association with other diseases, for example dermatitis herpetiformis and gluten-sensitive enteropathy. Blistering may be trivial or life threatening and therefore requires a logical approach to assessment, management and referral in the primary care setting.
Management of Gastrointestinal Symptoms in Palliative Care
Authors: Shah Vishal , Shah Sachil
Published: June 2010

The population in the UK is ageing, with increasing proportions living beyond 65 years of age. The epidemiology of diseases is shifting to more people dying of chronic as opposed to acute illnesses. It has been predicted that the number of people dying each year in the UK will rise by 17% in the next 20 years. Thus, there will be a rapidly increasing demand for provision of palliative care in the future. Much of this care will continue to be provided by the GP. This article specifically discusses the management of gastrointestinal symptoms in palliative care.
Management of Respiratory Symptoms in Palliative Care
Authors: Potter Andrew , Dietsch Ben
Published: June 2010

Respiratory symptoms are extremely common in palliative care patients. They can have significant and profound effects on the quality of life of the patient and those around them so their control is essential. Assessment and management of respiratory symptoms in palliative care patients broadly follow that of the general population and are within the abilities of all clinicians. However, this patient group does pose particular management problems that the GP should be familiar with. The aim of this review is to familiarize the GP with the main respiratory symptoms encountered in palliative care along with the main causes, their assessment and management.
Helicobacter pylori and Iron‐deficiency Anemia in Adolescents in Brazil
Authors: Araf Litza Neves , Pereira Carlos Alberto de Bragança , Machado Rodrigo Strehl , Raguza Daniele , Kawakami Elisabete
Published: June 2010

Aim:

The aim of the study was to evaluate the association between Helicobacter pylori infection and iron deficiency (ID) in adolescents attending a public school.

Patients and Methods:

From March to June 2001, a cross‐sectional study was conducted among adolescents (10–16 years) enrolled in a single public school in São Paulo, Brazil. Of 400 eligible students, 195 agreed to participate, but 1 was excluded due to sickle cell disease. A blood sample was collected from each subject to measure hemoglobin and ferritin. H pylori status was investigated with the 13C‐urea breath test. All of the subjects with either anemia or ID were given iron therapy.

Results:

H pylori prevalence was 40.7% (79/194), being higher in male subjects (45/90 vs 34/104, P = 0.014). There was no relation between infection and nutritional status. Abnormally low serum ferritin was observed in 12 subjects, half of whom were positive for H pylori (odds ratio [OR] 1.49, 95% confidence interval [CI] 0.38–5.81). The median serum ferritin was 33.6 ng/mL (interquartile range 23.9–50.9) in infected subjects and 35.1 ng/mL (interquartile range 23.7–53.9) in uninfected subjects. Anemia was detected in 2% (4/194) of the students, half of whom were infected (OR 1.47, 95% CI 0.1–20.6). The mean hemoglobin value in infected subjects was 13.83 g/dL ± 1.02 versus 14 g/dL ± 1.06 in uninfected subjects.

Conclusions:

The study was not able to find a relation between H pylori infection and ID or anemia.
Abdominal Pain in Dutch Schoolchildren: Relations With Physical and Psychological Comorbid Complaints in Children and Their Parents
Authors: van der Veek Shelley MC , Derkx HHF , de Haan Else , Benninga Marc A , Boer Frits
Published: June 2010

Objectives:

Children with functional abdominal pain (FAP) frequently report comorbid complaints such as anxiety and activity limitations. Their parents often experience heightened levels of anxiety, depression, and somatization. The aim of the present study was to investigate whether these comorbid complaints in children and their parents are specific for FAP or can also be found in a community sample.

Patients and Methods:

Six hundred sixty‐five schoolchildren (ages 7–18 years) filled out questionnaires concerning AP, activity limitations, somatic complaints, quality of life, and symptoms of anxiety and depression. A total of 391 of their parents filled out questionnaires concerning parental anxiety, depression, and somatization. Pearson correlations and multiple regression analyses were performed.

Results:

A total of 56.5% of the children reported AP at least once in a 2‐week period. Univariate relations with AP were found for activity limitations (r = 0.392), somatic complaints (r = 0.408), 3 of 5 domains of quality of life (r ranging from −0.120 to −0.209), and symptoms of anxiety and depression (r, respectively, 0.329 and 0.361). Multivariate analyses showed only significant relations for female sex (β = 0.230), younger age (β = −0.077), activity limitations (β = 0.247), somatic complaints (β = 0.170), and depressive symptoms (β = 0.093).

Conclusions:

Activity limitations, somatic complaints, and depressive symptoms are related to AP in the general population, whereas a reduced quality of life, anxiety, and parental internalizing problems seem specific comorbid complaints for FAP. Future research on parental internalizing problems, quality of life, and anxiety as risk factors for FAP is warranted.
Utility of Fecal Lactoferrin in Identifying Crohn Disease Activity in Children
Authors: Pfefferkorn Marian D , Boone James H , Nguyen James T , Juliar Beth E , Davis Miriam A , Parker Kelly K
Published: June 2010

Objectives:

Fecal lactoferrin (FL) is a noninvasive biomarker that is elevated in Crohn disease (CD) compared to irritable bowel syndrome. The purpose of this study was to evaluate FL in identifying children with active versus inactive CD.

Patients and Methods:

Fresh stool samples were collected from children with CD scheduled for endoscopy or a clinic visit, and from new outpatients who were scheduled for colonoscopy. FL was determined using a polyclonal antibody‐based enzyme‐linked immunosorbent assay. Physical global assessment, endoscopic findings, erythrocyte sedimentation rate (ESR), and the Pediatric CD Activity Index (PCDAI) were recorded for patients with CD. The PCDAI scores symptoms, laboratory parameters, physical examination, and extraintestinal manifestations. A score of ≤10 is inactive disease, 11 to 30 is mild active, and ≤31 is moderate to severe active.

Results:

Of 101 study patients (4‐ to 20‐year‐old, 66 boys), 31 had active CD, 23 had inactive CD, and 37 had noninflammatory bowel disease (non‐IBD) conditions. Four patients with ulcerative colitis and 6 patients with polyposis were excluded from analysis. FL was significantly elevated in CD versus non‐IBD (P < 0.001) and in active versus inactive CD (P < 0.001). The PCDAI and ESR were higher in active CD than in inactive CD (both P < 0.001). Using an FL cutoff of 7.25 μg/g, FL has 100% sensitivity and 100% negative predictive value in detecting active CD. Using an FL cutoff level of 60 μg/g, FL had 84% sensitivity, 74% specificity, 81% positive predictive value, and 77% negative predictive value for detecting active CD.

Conclusions:

FL is a promising biomarker of active CD and may be more practical to use when it is not feasible to obtain all of the necessary clinical information for the PCDAI.
Liver Fat Change in Obese Children After a 1‐year Nutrition‐behavior Intervention
Authors: Pozzato Carlo , Verduci Elvira , Scaglioni Silvia , Radaelli Giovanni , Salvioni Michela , Rovere Antonio , Cornalba Gianpaolo , Riva Enrica , Giovannini Marcello
Published: June 2010

Objectives:

To evaluate whether a 1‐year nutrition‐behavior intervention based on normocaloric balanced diet and physical exercise may reduce liver fat in obese children.

Patients and Methods:

Twenty‐six obese children (11 boys and 15 girls), aged 6 to 14 years, underwent anthropometric, nutritional, metabolic, and liver magnetic resonance imaging (MRI) examinations at baseline and after a 1‐year nutrition‐behavior intervention. Anthropometry included weight, height, waist and hip circumference, and total upper arm area. Body mass indexzscores were calculated. Biochemistry included serum aminotransferases, lipid profile, glucose, and insulin. Liver steatosis was judged as hepatic fat fraction (FF) by MRI and was ≥9%.

Results:

Prevalence of steatosis was 34.6% at baseline and declined to 7.7% after intervention (P< 0.0001). Mean (95% CI) reduction of liver FF was 8.0% (4.0%–12.0%). In 77.8% of children with liver steatosis at baseline, the FF declined lower than 9% at the end of intervention, going from a mean (SD) of 18.7% (9.1) to 1.3% (4.1), (P< 0.0001). At the end of the intervention, children showed a mean reduction in body mass indexzscore of 0.26 (0.11–0.41) and waist circumference of 1.46 (0.34–2.60) cm. Triglycerides, total cholesterol, apolipoprotein A1, apolipoprotein B, ApoA1/ApoB ratio, and gamma‐glutamyltransferase plasma values in plasma decreased at the end of intervention (P< 0.05).

Conclusions:

The results suggest that in obese children nutritional‐behavior interventions may reduce the liver fat.
Isolation of Legionella rubrilucens from a pneumonia patient co-infected with Legionella pneumophila
Authors: Matsui Mikio , Fujii Shin-ichiro , Shiroiwa Rieko , Amemura-Maekawa Junko , Chang Bin , Kura Fumiaki , Yamauchi Kohei
Published: June 2010

We report what we believe to be the first clinical isolation of Legionella rubrilucens from a pneumonia patient co-infected with Legionella pneumophila. L. rubrilucens strains were found in both a patient's sputum and the water of a hot spring in which the patient bathed, and DNA analysis by PFGE showed that they were indistinguishable.
Analysis of Yersinia enterocolitica invasin expression in vitro and in vivo using a novel luxCDABE reporter system
Authors: Trček Janja , Fuchs Thilo M. , Trülzsch Konrad
Published: June 2010

A novelluxCDABEplasmid for the analysis of promoter elements by site-specific integration into the genome ofYersinia enterocoliticawas constructed. The versatility of this reporter system was demonstrated by comparing the activity of theinvpromoter in theY. enterocoliticahigh-pathogenic serotype O : 8 (strain WA-314) with that of the low pathogenic serotype O : 9 (strain Y127). The luciferase activity of a transcriptional fusion between theinvpromoter of serotype O : 8 andluxCDABEwas about fourfold lower than the activity of the respective O : 9 promoter. This correlated with lower invasin production byY. enterocoliticaserotype O : 8 compared with serotypes O : 9, O : 3 and O : 5,27. However,Y. enterocoliticaof serotype O : 8 revealed higher invasiveness than serotype O : 9. When both invasins were expressedin transat similar levels in theY. enterocoliticaO : 8 Δinvbackground strain, cell invasion assays showed a slightly higher invasiveness of the strain producing Inv(O : 8) than the strain producing Inv(O : 9). We provide experimental evidence that this might be due to a higher binding capacity of Inv(O : 8) for cells expressingβ1 integrins compared with Inv(O:9). TheY. enterocoliticaO : 8 strain harbouring the Pinv(O : 8) : : luxCDABEfusion was then successfully used to followinvexpression in a mouse infection model. These experiments showed for the first time that theinvpromoter is active in infected living mice, especially in Peyer's patches of the ileum, the caecal lymph follicle, and the lymph nodes, liver and spleen. The production of invasin in the spleen was demonstrated by Western blot analysis. In conclusion, the presented reporter system enables stable genomic integration of theluxCDABEoperon into the chromosome ofYersinia, facilitatesin vitroquantification of promoter activities under different bacterial growth conditions, and enables detection of promoter activities in a mouse model.
Coupling metabolism and chemotaxis-dependent behaviours by energy taxis receptors
Authors: Alexandre Gladys
Published: June 2010

Bacteria have evolved the ability to monitor changes in various physico-chemical parameters and to adapt their physiology and metabolism by implementing appropriate cellular responses to these changes. Energy taxis is a metabolism-dependent form of taxis and is the directed movement of motile bacteria in gradients of physico-chemical parameters that affect metabolism. Energy taxis has been described in diverse bacterial species and several dedicated energy sensors have been identified. The molecular mechanism of energy taxis has not been studied in as much detail as chemotaxis, but experimental evidence indicates that this behaviour differs from metabolism-independent taxis only by the presence of dedicated energy taxis receptors. Energy taxis receptors perceive changes in energy-related parameters, including signals related to the redox and/or intracellular energy status of the cell. The best-characterized energy taxis receptors are those that sense the redox state of the electron transport chain via non-covalently bound FAD cofactors. Other receptors shown to mediate energy taxis lack any recognizable redox cofactor or conserved energy-sensing motif, and some have been suggested to monitor changes in the proton motive force. The exact energy-sensing mechanism(s) involved are yet to be elucidated for most of these energy sensors. By monitoring changes in energy-related parameters, energy taxis receptors allow cells to couple motility behaviour with metabolism under diverse environmental conditions. Energy taxis receptors thus provide fruitful models to decipher how cells integrate sensory behaviours with metabolic activities.
Diamond plates on dome-like particles: preparation, characterization and field emission properties
Authors: Tiwari Rajanish N. , Chen Wei-Chun , Tiwari Jitendra N. , Wang Wei-Lin , Chang Li
Published: June 2010

Thin diamond microplates have been grown on dome-like/hemispherical carbon particles on titanium carbide by a microwave plasma chemical vapour deposition (MPCVD) method using a gas mixture of methane and hydrogen. The diamond microplates have a thickness of about 200 nm. A thin (300 nm) film of titanium carbide was formed during carburization of sputtered titanium on an Si(100) substrate in MPCVD. The hemispherical carbon particles were covered with diamond microplates. The diamond microplates are isolated electron-emitting spherules and exhibit a low threshold (50 V µm−1) and high current density (0.92 mA cm−2) in their field emission properties. A possible mechanism for the formation of the diamond microplates and hemispherical carbon particles is presented.
Quantitative analysis of diffuse X-ray scattering in partially transformed 3C-SiC single crystals
Authors: Boulle A. , Dompoint D. , Galben-Sandulache I. , Chaussende D.
Published: June 2010

The X-ray scattering of partially transformed 3C-SiC single crystals is considered in detail. Extended diffuse scattering streaks, originating from stacking faults (SFs) lying in the {111} planes, are clearly observed in the wide-range reciprocal-space maps. The intensity distribution along the diffuse streaks is simulated with a model including the contributions of the diffuse scattering originating from the SFs [based on the pioneering theoretical description given by Kabra, Pandey & Lele (1986).J. Mater. Sci.21, 1654–1666], the coherent scattering emanating from untransformed areas of the crystals and all θ-dependent terms that affect the scattered intensity (the layer structure factor, the irradiated volume and the polarization of the beam). The quantitative simulation of the diffuse streaks reveals that the transformation occurs through the glide of partial dislocations and allows one to derive the transformation level. It is shown that the 3C polytype is indeed unstable at high temperature. However, it is further shown that defect-free 3C-SiC single crystals remain stable at temperatures where 3C-SiC is known to be usually unstable (2173 K). The origin of this apparent stability is very likely of kinetic nature,i.e.the lack of crystalline defects inhibits the transformation.
In-house characterization of protein powder
Authors: Hartmann Christian Grundahl , Nielsen Ole Faurskov , Ståhl Kenny , Harris Pernille
Published: June 2010

X-ray powder diffraction patterns of lysozyme and insulin were recorded on a standard in-house powder diffractometer. The experimental powder diffraction patterns were compared with patterns calculated from Protein Data Bank coordinate data. Good agreement was obtained by including straightforward corrections for background, unit-cell parameters, disordered bulk solvent and geometric factors. In particular the solvent correction was found crucial for a good agreement. A revised Lorentz factor was derived, which gave a minor, but significant, improvement to the fit in the low-angle region. An attempt to include calculated H-atom positions did not improve the overall fit and was abandoned. The method devised was shown to be a quick and convenient tool for distinguishing precipitates and polymorphs of proteins.
Features of the secondary structure of a protein molecule from powder diffraction data
Authors: Basso Sebastian , Besnard Céline , Wright Jonathan P. , Margiolaki Irene , Fitch Andrew , Pattison Philip , Schiltz Marc
Published: June 2010

Protein powder diffraction is shown to be suitable for obtainingde novosolutions to the phase problem at low resolutionviaphasing methods such as the isomorphous replacement method. Two heavy-atom derivatives (a gadolinium derivative and a holmium derivative) of the tetragonal form of hen egg-white lysozyme were crystallized at room temperature. Using synchrotron radiation, high-quality powder patterns were collected in which pH-induced anisotropic lattice-parameter changes were exploited in order to reduce the challenging and powder-specific problem of overlapping reflections. The phasing power of two heavy-atom derivatives in a multiple isomorphous replacement analysis enabled molecular structural information to be obtained up to approximately 5.3 Å resolution. At such a resolution, features of the secondary structure of the lysozyme molecule can be accurately located using programs dedicated to that effect. In addition, the quoted resolution is sufficient to determine the correct hand of the heavy-atom substructure which leads to an electron-density map representing the protein molecule of proper chirality.
X-ray structure of the metcyano form of dehaloperoxidase fromAmphitrite ornata: evidence for photoreductive dissociation of the iron–cyanide bond
Authors: de Serrano V. S. , Davis M. F. , Gaff J. F. , Zhang Qi , Chen Z. , D'Antonio E. L. , Bowden E. F. , Rose R. , Franzen S.
Published: June 2010

X-ray crystal structures of the metcyano form of dehaloperoxidase-hemoglobin (DHP A) fromAmphitrite ornata(DHPCN) and the C73S mutant of DHP A (C73SCN) were determined using synchrotron radiation in order to further investigate the geometry of diatomic ligands coordinated to the heme iron. The DHPCN structure was also determined using a rotating-anode source. The structures show evidence of photoreduction of the iron accompanied by dissociation of bound cyanide ion (CN−) that depend on the intensity of the X-ray radiation and the exposure time. The electron density is consistent with diatomic molecules located in two sites in the distal pocket of DHPCN. However, the identities of the diatomic ligands at these two sites are not uniquely determined by the electron-density map. Consequently, density functional theory calculations were conducted in order to determine whether the bond lengths, angles and dissociation energies are consistent with bound CN−or O2in the iron-bound site. In addition, molecular-dynamics simulations were carried out in order to determine whether the dynamics are consistent with trapped CN−or O2in the second site of the distal pocket. Based on these calculations and comparison with a previously determined X-ray crystal structure of the C73S–O2form of DHP [de Serranoet al.(2007),Acta Cryst.D63, 1094–1101], it is concluded that CN−is gradually replaced by O2as crystalline DHP is photoreduced at 100 K. The ease of photoreduction of DHP A is consistent with the reduction potential, but suggests an alternative activation mechanism for DHP A compared with other peroxidases, which typically have reduction potentials that are 0.5 V more negative. The lability of CN−at 100 K suggests that the distal pocket of DHP A has greater flexibility than most other hemoglobins.
Structure of theEscherichia coliRNA polymerase α subunit C-terminal domain
Authors: Lara-González Samuel , Birktoft Jens J. , Lawson Catherine L.
Published: June 2010

The α subunit C-terminal domain (αCTD) of RNA polymerase (RNAP) is a key element in transcription activation inEscherichia coli, possessing determinants responsible for the interaction of RNAP with DNA and with transcription factors. Here, the crystal structure ofE. coliαCTD (α subunit residues 245–329) determined to 2.0 Å resolution is reported. Crystals were obtained after reductive methylation of the recombinantly expressed domain. The crystals belonged to space groupP21and possessed both pseudo-translational symmetry and pseudo-merohedral twinning. The refined coordinate model (Rfactor = 0.193,Rfree= 0.236) has improved geometry compared with prior lower resolution determinations of the αCTD structure [Jeonet al.(1995),Science,270, 1495–1497; Benoffet al.(2002),Science,297, 1562–1566]. An extensive dimerization interface formed primarily by N- and C-terminal residues is also observed. The new coordinates will facilitate the improved modeling of αCTD-containing multi-component complexes visualized at lower resolution using X-ray crystallography and electron-microscopy reconstruction.
Structure of nondiscriminating glutamyl-tRNA synthetase fromThermotoga maritima
Authors: Ito Takuhiro , Kiyasu Noriko , Matsunaga Risa , Takahashi Seizo , Yokoyama Shigeyuki
Published: June 2010

Aminoacyl-tRNA synthetases produce aminoacyl-tRNAs from the substrate tRNA and its cognate amino acid with the aid of ATP. Two types of glutamyl-tRNA synthetase (GluRS) have been discovered: discriminating GluRS (D-GluRS) and nondiscriminating GluRS (ND-GluRS). D-GluRS glutamylates tRNAGluonly, while ND-GluRS glutamylates both tRNAGluand tRNAGln. ND-GluRS produces the intermediate Glu-tRNAGln, which is converted to Gln-tRNAGlnby Glu-tRNAGlnamidotransferase. Two GluRS homologues fromThermotoga maritima, TM1875 and TM1351, have been biochemically characterized and it has been clarified that only TM1875 functions as an ND-GluRS. Furthermore, the crystal structure of theT. maritimaND-GluRS, TM1875, was determined in complex with a Glu-AMP analogue at 2.0 Å resolution. TheT. maritimaND-GluRS contains a characteristic structure in the connective-peptide domain, which is inserted into the catalytic Rossmann-fold domain. The glutamylation ability of tRNAGlnby ND-GluRS was measured in the presence of the bacterial Glu-tRNAGlnamidotransferase GatCAB. Interestingly, the glutamylation efficiency was not affected even in the presence of excess GatCAB. Therefore, GluRS avoids competition with GatCAB and glutamylates tRNAGln.
Using a conformation-dependent stereochemical library improves crystallographic refinement of proteins
Authors: Tronrud Dale E. , Berkholz Donald S. , Karplus P. Andrew
Published: June 2010

The major macromolecular crystallographic refinement packages restrain models to ideal geometry targets defined as single values that are independent of molecular conformation. However, ultrahigh-resolution X-ray models of proteins are not consistent with this concept of ideality and have been used to develop a library of ideal main-chain bond lengths and angles that are parameterized by the φ/ψ angle of the residue [Berkholzet al.(2009),Structure,17, 1316–1325]. Here, it is first shown that the new conformation-dependent library does not suffer from poor agreement with ultrahigh-resolution structures, whereas current libraries have this problem. Using theTNTrefinement package, it is then shown that protein structure refinement using this conformation-dependent library results in models that have much better agreement with library values of bond angles with little change in theRvalues. These tests support the value of revising refinement software to account for this new paradigm.
Enhancing learning ecology on the Internet
Authors: Looi C.K.
Published: June 2010

AbstractRecent notions view learning as participation in a learning environment or community where learners work together and support each other as they use information resources and tools to pursue their learning goals and solve problems. A broader meaning is to extend the idea of the learning environment to the overall setting in which learning communities come into existence, evolve, fade away, regenerate or transform. The advent of the Internet has brought about a powerful medium for creating and supporting such a notion of the learning ecology. Through the image of biological ecologies with their diversity, complex dynamics, and opportunistic niches for growth, learning problems and solutions on the Internet are explored and ways to enhance the ecology are suggested.
Student responses to collaborating and learning in a web‐based environment
Authors: Oliver R. , Omari A.
Published: June 2010

Abstract This paper describes a study which explored students' responses and reactions to a web‐based environment supporting problem‐based learning. The study was undertaken among undergraduate students in an Australian university. The findings revealed that while the majority of the students saw value to be gained from learning in a student‐centred and collaborative setting, many expressed a preference for learning in the more conventional teacher‐directed forms. The study also sought to explore the potential of the environment to develop problem‐solving skills and to determine factors which impeded students' success and achievement. The results did not demonstrate any discernible development of problem‐solving skills despite students' extensive experience and participation in problem‐solving activities. The findings have suggested a number of important factors missing in the implemented setting including an organising strategy to aid students in the problem‐solving process and adequate feedback to ensure reflection among the learners on the quality of the solutions they were developing.
Guidelines for distance education: a case study in Taiwan
Authors: Liang C.C.
Published: June 2010

Abstract  Through a questionnaire survey and in‐depth interviews with the teachers, students and staff involved, this paper presents a case study which describes the current status of telecommunications distance education via real‐time interactive videoconferencing in Taiwan. Participants' views were analysed and showed that instructional development components, such as learner characteristics, instructional resources, support services and rehearsal, are quite different from the traditional mode especially with regard to neglected factors such as educational administration and policy. The paper summarises the findings as an itemised list of guidelines for operating instructional development for a telecommunications distance education. These guidelines can contribute not only to improving the quality of distance education, but also to faculty development, staff training, elaboration of theory and professional practice in the field.
Integrating computer‐mediated tools into the language curriculum
Authors: Yang S.C.
Published: June 2010

AbstractThe study reported in this paper investigated second‐year junior college students' attitudes and perceptions towards the web as an educational resource. The students in southern Taiwan were given an introduction to Internet use for research projects. Study data was collected using surveys and observation. Factor analysis was employed to identify six areas for furthert‐test analysis: cognitive disorientation, learning anxiety, perceived enhancement of language ability, perceived enhancement of cultural under‐standing, the web considered as a useful search tool and the overall perception of language learning on the web. The study showed that computer networks have the potential to empower students when they are implemented appropriately. Some pedagogical suggestions are made for the effective use of computer networking for second and foreign language learning.
Learning art with computers — a LISREL model
Authors: Mak B.
Published: June 2010

Abstract This paper surveys the attitudes on the use of computers for aesthetic communication. In spite of the proliferation of computer art software and the popularity of art galleries on the world‐wide web, many artists still find it difficult to accept computer art as a form of art. Many of them find only commercial values in computer art. To understand the latent attitudes constituting this rejection, a survey was conducted among high school students and the data was analysed with LISREL structural equation modelling techniques. Results indicate that aesthetic concerns, conservatism, and stereotypes are the major factors accounting for the negative attitude. Implications for system design to overcome the negative attitudes are discussed.
Technology‐supported learning:status, issues and trends
Authors: Vogel D. , Klassen J.
Published: June 2010

Abstract  Higher education is facing a broad range of challenges upon entering the new millennium with shifts in technology, paradigms and resources for learning. In response to these challenges, teachers are broadening their range of instructional methods. One area that is seeing increased attention is the provision of instructional support for ‘self‐accessed’ learning. This paper examines the status, issues and trends of multimedia instructional support. Examples associated with the development of CD‐ROMs and interactive web sites are presented to illustrate important considerations for such development. It is hoped that these considerations will result in greater educational support for individualised learning.
Designing CALL for learning Chinese characters
Authors: Lam H.C. , Ki W.W. , Law N. , Chung A.L.S. , Ko P.Y. , Ho A.H.S. , Pun S.W.
Published: June 2010

Abstract Despite the enormity of its quantity, printed or written forms of Chinese characters are composed from a limited number of common components. For example, the characters for pond(), lake(), stream(), river(), sea() and ocean() all contain a component in common, a three‐dot component representing water. When this clue is explicitly highlighted to students, the learning of Chinese characters can be greatly enhanced. Using a computer to help students to develop this kind of structural awareness about language learning has not yet been thoroughly examined. This paper reports on the design of CALL software based on a pedagogic method which helps students to develop the higher order skills to analyse and categorise Chinese characters by using components. The result of the classroom experiment has shown supportive evidence on the feasibility and the need of integrating the software with an affective and contextual way of teaching Chinese characters.
Current challenges facing the determination of product bioequivalence in veterinary medicine
Authors: MARTINEZ M. N. , HUNTER R. P.
Published: June 2010

Martinez, M.N., Hunter, R.P. Current challenges facing the determination of product bioequivalence in veterinary medicine.J. vet. Pharmacol. Therap.33, 418–433.

Despite the pharmacological and statistical advances that have occurred since the early days of bioequivalence assessments, there remain many unresolved issues associated with the bioequivalence evaluation of human and veterinary pharmaceuticals. While many of these issues are common to both human and veterinary medicine, there are also challenges specific to veterinary drug products. Examples of complex problems that remain to be resolved include the assessment of drugs associated with complex kinetics (e.g., sustained release formulations that produce multiple peaks), the evaluation of intramammary formulations, uncertainty associated with conditions under which specific enantiomers of metabolites need to be factored into the bioequivalence evaluation, the study design for products and active pharmaceutical ingredients that exhibit highly variable kinetics, equivalence of biomass products, methods for evaluating topical formulations or formulations with very long duration of release, the evaluation of products where destructive sampling is necessary (e.g., aquaculture products), and the evaluation of bioequivalence for Type A medicated articles. This manuscript highlights many of the unresolved challenges currently impacting the evaluation of product bioequivalence in veterinary medicine, and provides a summary of the associated scientific complexities with each of these issues.