bluuebunny/crossref_metadata_2025 huggingface dataset:
Satellite observations of the impact of weak volcanic activity on marine clouds
Authors: Gassó Santiago
Published: March 2008

Because emissions from weak volcanic eruptions tend to remain in the low troposphere, they may have a significant radiative impact through the indirect effect on clouds. However, this type of volcanic activity is underreported and its global impact has been assessed only by model simulations constrained with very limited observations. First observations of the impact of high‐latitude active volcanoes on marine boundary layer clouds are reported here. These observations were made using a combination of standard derived products and visible images from the MODIS, AMSR‐E and GOES detectors. Two distinctive effects are identified. When there is an existing boundary layer cloud deck, an increase in cloud brightness and a decrease in both cloud effective radius and liquid water content were observed immediately downwind of the volcanoes. The visible appearance of these “volcano tracks” resembles the effect of man‐made ship tracks. When synoptic conditions favor low cloudiness, the volcano plume (or volcano cloud) increases significantly the cloud cover downwind. The volcano cloud can extend for hundreds of kilometers until mixing with background clouds. Unlike violent eruptions, the volcano clouds reported here (the Aleutian Islands in the North Pacific and the South Sandwich Islands in the South Atlantic) have retrieved microphysical properties similar to those observed in ship tracks. However, when comparing the volcano clouds from these two regions, liquid water content can decrease, increase or remain unchanged with respect to nearby unperturbed clouds. These differences suggest that composition at the source, type of eruption and meteorological conditions influence the evolution of the cloud.
Comparison of adjoint and analytical Bayesian inversion methods for constraining Asian sources of carbon monoxide using satellite (MOPITT) measurements of CO columns
Authors: Kopacz Monika , Jacob Daniel J. , Henze Daven K. , Heald Colette L. , Streets David G. , Zhang Qiang
Published: March 2008

We apply the adjoint of an atmospheric chemical transport model (GEOS‐Chem CTM) to constrain Asian sources of carbon monoxide (CO) with 2° × 2.5° spatial resolution using Measurement of Pollution in the Troposphere (MOPITT) satellite observations of CO columns in February–April 2001. Results are compared to the more common analytical method for solving the same Bayesian inverse problem and applied to the same data set. The analytical method is more exact but because of computational limitations it can only constrain emissions over coarse regions. We find that the correction factors to the a priori CO emission inventory from the adjoint inversion are generally consistent with those of the analytical inversion when averaged over the large regions of the latter. The adjoint solution reveals fine‐scale variability (cities, political boundaries) that the analytical inversion cannot resolve, for example, in the Indian subcontinent or between Korea and Japan, and some of that variability is of opposite sign which points to large aggregation errors in the analytical solution. Upward correction factors to Chinese emissions from the prior inventory are largest in central and eastern China, consistent with a recent bottom‐up revision of that inventory, although the revised inventory also sees the need for upward corrections in southern China where the adjoint and analytical inversions call for downward correction. Correction factors for biomass burning emissions derived from the adjoint and analytical inversions are consistent with a recent bottom‐up inventory on the basis of MODIS satellite fire data.
Significance of transient luminous events to neutral chemistry: Experimental measurements
Authors: Rodger Craig J. , Seppälä Annika , Clilverd Mark A.
Published: March 2008

For many years it has been suggested that transient luminous events (TLE) occurring over thunderstorms may produce significant modifications to neutral atmospheric chemistry. Some have speculated that large ionisation increases from red sprites, one type of TLE, could result in enhancements of odd nitrogen. In this study we make use of nighttime NO2 observations by the GOMOS instrument to test whether TLE are producing significant NOx enhancements in the middle atmosphere on a regional scale. Comparing regional variations of NO2 with 2–3 order of magnitude variations in lightning activity, we show that there is no significant impact of red sprites, giant jets or blue jets upon NOx levels in the stratosphere and mesosphere (20–70 km), within the detection levels of the instrument. While individual TLE may cause a local variation in NOx, these do not appear to be significant on regional scales (or beyond).
Modulation of sensory neuron potassium conductances by anandamide indicates roles for metabolites
Authors: Evans R M , Wease K N , MacDonald C J , Khairy H A , Ross R A , Scott R H
Published: March 2008

Background and purpose: The endogenous cannabinoid anandamide (AEA) acts at cannabinoid (CB1) and vanilloid (TRPV1) receptors. AEA also shows antinociceptive properties; although the underlying mechanism for this is not fully understood, both CB1 and TRPV1 may be involved. Voltage‐activated Ca2+ channels in rat‐cultured dorsal root ganglion (DRG) neurons are modulated by AEA. However, AEA in different populations of neurons enhanced or attenuated KCl‐evoked Ca2+ influx; these effects were linked with soma size. The aim of this study was to determine how AEA or its metabolites might produce these variable responses.

Experimental approach: The whole cell patch‐clamp technique and fura‐2 Ca2+ imaging were used to characterize the actions of AEA on action potential firing and voltage‐activated K+ currents and to determine whether AEA metabolism plays any role in its effects on cultured DRG neurons.

Key results: AEA attenuated multiple action potential firing evoked by 300 ms depolarizing current commands in a subpopulation of DRG neurons. Application of 1 μM AEA attenuated voltage‐activated K+ currents and the recovery of KCl‐evoked Ca2+ transients. The insensitivity of these responses to the CB1 receptor antagonist rimonabant (100 nM) and preincubation of DRG neurons with pertussis toxin suggested that these actions are not CB1 receptor‐mediated. Preincubating DRG neurons with the fatty acid amide hydrolase (FAAH) inhibitor phenylmethylsulphonyl fluoride (PMSF) attenuated the inhibitory actions of AEA on K+ currents and Ca2+ influx.

Conclusion and implications: These data suggest that the products of AEA metabolism by FAAH contribute to the attenuation of K+ conductances and altered excitability of cultured sensory neurons.

British Journal of Pharmacology (2008) 154, 480–492; doi:10.1038/bjp.2008.93; published online 31 March 2008
Neuropeptide S is a stimulatory anxiolytic agent: a behavioural study in mice
Authors: Rizzi A , Vergura R , Marzola G , Ruzza C , Guerrini R , Salvadori S , Regoli D , Calo G
Published: March 2008

Background and purpose:

Neuropeptide S (NPS) was recently identified as the endogenous ligand of an orphan receptor, now referred to as the NPS receptor. In vivo, NPS produces a unique behavioural profile by increasing wakefulness and exerting anxiolytic‐like effects. In the present study, we further evaluated the effects of in vivo supraspinal NPS in mice.

Experimental approach:

Effects of NPS, injected intracerebroventricularly (i.c.v.), on locomotor activity (LA), righting reflex (RR) recovery and on anxiety states (measured with the elevated plus maze (EPM) and stress‐induced hyperthermia (SIH) tests) were assessed in Swiss mice.

Key results:

NPS (0.01–1 nmol per mouse) caused a significant increase in LA in naive mice, in mice habituated to the test cages and in animals sedated with diazepam (5 mg kg−1). In the RR assay, NPS dose dependently reduced the proportion of animals losing the RR in response to diazepam (15 mg kg−1) and their sleeping time. In the EPM and SIH test, NPS dose dependently evoked anxiolytic‐like effects by increasing the time spent by animals in the open arms and reducing the SIH response, respectively.

Conclusions and implications:

We provide further evidence that NPS acts as a novel modulator of arousal and anxiety‐related behaviours by promoting a unique pattern of effects: stimulation associated with anxiolysis. Therefore, NPS receptor ligands may represent innovative drugs for the treatment of sleep and anxiety disorders.

British Journal of Pharmacology (2008) 154, 471–479; doi:10.1038/bjp.2008.96; published online 31 March 2008
Upregulation of Adipose 11‐β‐Hydroxysteroid Dehydrogenase Type 1 Expression in Ovariectomized Rats Is due to Obesity Rather Than Lack of Estrogen
Authors: Paulsen Søren K. , Nielsen Maria P. , Richelsen Bjørn , Bruun Jens M. , Flyvbjerg Allan , Pedersen Steen B.
Published: March 2008

Objective: Increased tissue activity of cortisol induced by the activation of inert cortisone to active cortisol through 11‐β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1) may play a role in the metabolic syndrome. We recently found that 11β‐HSD1 in subcutaneous adipose tissue (AT) was lower in lean women compared with lean men. Estrogen suppresses hepatic and renal 11β‐HSD1 in rats; hence we investigated the in vitro effect of estrogen on human and rat AT, and the in vivo effects on rat AT 11β‐HSD1 expression.

Methods and Procedures: Wistar rats were divided into four groups of eight animals. One group was sham‐operated (controls) and others were ovariectomized (OVX). One OVX group was left untreated (OVX−E), another (OVX+E) received estrogen treatment, and one received a hypo‐caloric diet (OVX−E+D), matching the weight gain of the control group. AT from women undergoing liposuction or surgery and from killed male and female rats were incubated with estrogen alone or in the presence of IL‐1β. Gene expressions were determined by real‐time reverse transcriptase PCR.

Results: Ovariectomy resulted in a 280% increase in adipose 11β‐HSD1 expression P < 0.05). 11β‐HSD1 expression in the (OVX+E)‐group was significantly reduced compared with the nonsubstituted group (P < 0.05). 11β‐HSD1 expression in the (OVX−E+D)‐group was reduced significantly (P < 0.05) when compared with the level of the estrogen‐substituted group. No significant differences between the control group, the (OVX+E)‐group, and the (OVX−E+D)–group were found. In the in vitro studies, no direct effect of estrogen on adipose 11β‐HSD1 was found.

Discussion: The upregulation of 11β‐HSD1 in ovariectomized rats was most likely due to changes in body composition rather than lack of estrogen.
Negative Peer Perceptions of Obese Children in the Classroom Environment
Authors: Zeller Meg H. , Reiter‐Purtill Jennifer , Ramey Christina
Published: March 2008

Objective: It is asserted that the more immediate and observable consequences of pediatric obesity are psychosocial in nature. This study examines the peer relations of clinically referred obese youth compared to demographically comparable nonoverweight peers within the classroom environment.

Methods and Procedures: Peer‐, teacher‐, and self‐reports of behavioral reputation (Revised Class Play (RCP)), and peer reports of social acceptance, nonsocial attributes (attractiveness, athleticism, academic competence), and health interference (school absence, illness, fatigue) were obtained regarding 90 obese youth (BMI > 95th percentile; 8–16 years, 57% girls, 50% African American) and 76 nonoverweight demographically similar comparison classmates.

Results: Relative to comparison peers, obese children were nominated significantly less often as a best friend and rated lower in peer acceptance, although the two groups did not differ in the number of reciprocated friendships. Obese youth were described by peer, teacher, and self‐report as more socially withdrawn and by peers as displaying less leadership and greater aggressive‐disruptive behavior. Peers also described obese youth as less physically attractive, less athletic, more sick, tired, and absent from school. Being seen as less attractive and less athletic by peers helped to explain differences in obese and nonoverweight youth's levels of peer acceptance.

Discussion: Clinically referred obese youth are characterized by peer relations that differ from those of nonoverweight youth. The peer environment provides a rich context to understand the social consequences of pediatric obesity as well as factors that could be targeted in intervention to promote more positive health and psychosocial outcomes.
Obesity and C‐reactive Protein Levels Among White, Black, and Hispanic US Adults
Authors: Wee Christina C. , Mukamal Kenneth J. , Huang Annong , Davis Roger B. , McCarthy Ellen P. , Mittleman Murray A.
Published: March 2008

Objective: Studies suggest that obesity's adverse impact on cardiovascular mortality may be reduced in African Americans relative to white Americans. We examined whether obesity's association with novel cardiovascular risk factors such as C‐reactive protein (CRP) also varies by race and ethnicity.

Methods and Procedures: We analyzed data from 10,492 white, African‐American, and Hispanic‐American participants of the 1999–2004 National Health and Nutrition Examination Survey, who were aged 20 years and older, with a BMI ≥18.5 kg/m2 and CRP ≤10 mg/l. We fit sex‐specific multivariable models of the association of BMI or waist circumference with log CRP levels and tested for interactions of BMI or waist circumference with race/ethnicity.

Results: Higher BMI was significantly associated with higher CRP in all racial/ethnic groups for both men and women (P > 0.05 for BMI–race/ethnicity interaction) before and after adjustment for age, education, and health behaviors. Larger waist circumference was also associated with higher CRP levels in all racial/ethnic groups before and after adjustment; among women, the relationship was strongest for Mexican Hispanics (P < 0.01 for waist circumference–race/ethnicity interaction). Results were similar after additional adjustment for medications that might affect CRP levels.

Discussion: The association between obesity and CRP is at least as strong in African Americans and Hispanic Americans as in white Americans. Racial differences in the relationship between obesity and cardiovascular mortality are unlikely to be due to racial differences in obesity's impact on CRP.
The effects of conformational heterogeneity on the binding of the Notch intracellular domain to effector proteins: a case of biologically tuned disorder
Authors: Bertagna Angela , Toptygin Dima , Brand Ludwig , Barrick Doug
Published: March 2008

Cell-fate decisions in metazoans are frequently guided by the Notch signalling pathway. Notch signalling is orchestrated by a type-1 transmembrane protein, which, upon interacting with extracellular ligands, is proteolytically cleaved to liberate a large intracellular domain [NICD (Notch intracellular domain)]. NICD enters the nucleus where it binds the transcription factor CSL (CBF1/suppressor of Hairless/Lag-1) and activates transcription of Notch-responsive genes. In the present paper, the interaction between the Drosophila NICD and CSL will be examined. This interaction involves two separate binding regions on NICD: the N-terminal tip of NICD {the RAM [RBP-Jκ (recombination signal-binding protein 1 for Jκ)-associated molecule] region} and an ankyrin domain ∼100 residues away. CD studies show that the RAM region of NICD lacks α-helical and β-sheet secondary structure, and also lacks rigid tertiary structure. Fluorescence studies show that the tryptophan residues in RAM are highly solvated and are quenched by solvent. To assess the impact of this apparent disorder on the bivalent binding of NICD to CSL, we modelled the region between the RAM and ANK (ankyrin repeat)-binding regions using polymer statistics. A WLC (wormlike chain) model shows that the most probable sequence separation between the two binding regions is ∼50 Å (1 Å=0.1 nm), matching the separation between these two sites in the complex. The WLC model predicts a substantial enhancement of ANK occupancy via effective concentration, and suggests that the linker length between the two binding regions is optimal for bivalent interaction.
Receptor protein tyrosine phosphatase μ: measuring where to stick
Authors: Aricescu A. Radu , Siebold Christian , Jones E. Yvonne
Published: March 2008

We review here recent results on the structure and function of a receptor protein tyrosine phosphatase, RPTPμ. In addition to their intercellular catalytic domains which bear the phosphatase activity, the RPTPs are cell-surface-receptor-type molecules and in many cases have large extracellular regions. What role can these extracellular regions play in function? For RPTPμ, the extracellular region is known to mediate homophilic adhesion. Sequence analysis indicates that it comprises six domains: an N-terminal MAM (meprin/A5/μ), one immunoglobulin-like domain and four fibronectin type III (FN) repeats. We have determined the crystal structure of the entire extracellular region for RPTPμ in the form of a functional adhesion dimer. The physical characteristics and dimensions of the adhesion dimer suggest a mechanism by which the location of this phosphatase can be influenced by cell–cell spacings.
Cryoelectron tomography of isolated desmosomes
Authors: Owen Gethin Rh. , Acehan Devrim , Derr K.D. , Rice William J. , Stokes David L.
Published: March 2008

Desmosomes are a complex assembly of protein molecules that form at the cell surface and mediate cell–cell adhesion. Much is known about the composition of desmosomes and there is an established consensus for the location of and interactions between constituent proteins within the assembly. Furthermore, X-ray crystallography has determined atomic structures of isolated domains from several constituent proteins. Nevertheless, there is a lack of understanding about the architecture of the intact assembly and the physical principles behind the adhesive strength of desmosomes therefore remain vague. We have used electron tomography to address this problem. In previous work, we investigated the in situ structure of desmosomes from newborn mouse skin preserved by freeze-substitution and imaged in resin-embedded thin sections. In our present work, we have isolated desmosomes from cow snout and imaged them in the frozen unstained state. Although not definitive, the resulting images provide support for the irregular groupings of cadherin molecules seen previously in mouse skin.
Structure of artificial and natural VE-cadherinbased adherens junctions
Authors: Taveau Jean-Christophe , Dubois Mathilde , Le Bihan Olivier , Trépout Sylvain , Almagro Sébastien , Hewat Elizabeth , Durmort Claire , Heyraud Stéphanie , Gulino-Debrac Danielle , Lambert Olivier
Published: March 2008

In vascular endothelium, adherens junctions between endothelial cells are composed of VE-cadherin (vascular endothelial cadherin), an adhesive receptor that is crucial for the proper assembly of vascular structures and the maintenance of vascular integrity. As a classical cadherin, VE-cadherin links endothelial cells together by homophilic interactions mediated by its extracellular part and associates intracellularly with the actin cytoskeleton via catenins. Although, from structural crystallographic data, a dimeric structure arranged in a trans orientation has emerged as a potential mechanism of cell–cell adhesion, the cadherin organization within adherens junctions remains controversial. Concerning VE-cadherin, its extracellular part possesses the capacity to self-associate in solution as hexamers consisting of three antiparallel cadherin dimers. VE-cadherin-based adherens junctions were reconstituted in vitro by assembly of a VE-cadherin EC (extracellular repeat) 1–EC4 hexamer at the surfaces of liposomes. The artificial adherens junctions revealed by cryoelectron microscopy appear as a two-dimensional self-assembly of hexameric structures. This cadherin organization is reminiscent of that found in native desmosomal junctions. Further structural studies performed on native VE-cadherin junctions would provide a better understanding of the cadherin organization within adherens junctions. Homophilic interactions between cadherins are strengthened intracellularly by connection to the actin cytoskeleton. Recently, we have discovered that annexin 2, an actin-binding protein connects the VE-cadherin–catenin complex to the actin cytoskeleton. This novel link is labile and promotes the endothelial cell switch from a quiescent to an angiogenic state.
Hyper-adhesion: a new concept in cell–cell adhesion
Authors: Garrod David , Kimura Tomomi E.
Published: March 2008

We have developed a new concept of cell–cell adhesion termed ‘hyper-adhesion’, the very strong adhesion adopted by desmosomes. This uniquely desmosomal property accounts for their ability to provide the intercellular links in the desmosome–intermediate filament complex. These links are targeted by diseases, resulting in disruption of the complex with severe consequences. Hyper-adhesion is characteristic of desmosomes in tissues and is believed to result from a highly ordered arrangement of the extracellular domains of the desmosomal cadherins that locks their binding interaction so that it is highly resistant to disruption. This ordered arrangement may be reflected by and dependent upon a similarly ordered molecular structure of the desmosomal plaque. Hyper-adhesion can be down-regulated to a more weakly adhesive state by cell signalling involving protein kinase C, which translocates to the desmosomal plaque. Down-regulation takes place in wound edge epithelium and appears to be accompanied by loss of the ordered arrangement causing desmosomes to adopt the type of weaker adhesion characteristic of adherens junctions. We review the evidence for hyper-adhesion and speculate on the molecular basis of its mechanism.
Beyond structure: mechanism and dynamics of intercellular adhesion
Authors: Leckband Deborah
Published: March 2008

This review summarizes findings from multiple complementary quantitative investigations of adhesion by classical cadherins. The systems investigated range from single molecules to cells, and the approaches used quantify the kinetics, energetics and mechanical strengths of cadherin bonds. The cumulative results demonstrate that cadherins adhere via a multistage binding mechanism that involves multiple extracellular domains. In kinetic measurements of cell adhesion, cell pairs first form a low-probability-binding state with fast kinetics. This is followed by a lag and a slow transition to a second, high-probability, binding state. This two-stage process is independent of the cytoplasmic domain. Studies with domain-deletion mutants demonstrate that the N-terminal domains are required for the first, fast, weak binding. However, the full-ectodomain and EC3 (extracellular repeat 3), in particular, are required to form the second, high-probability, binding state, which is characterized by slow dissociation kinetics and much stronger adhesive bonds. Together, these different studies reveal a more complex multistage binding mechanism than was predicted by structural models.
Host response to cytoadherence inPlasmodium falciparum
Authors: Chakravorty Srabasti J. , Hughes Katie R. , Craig Alister G.
Published: March 2008

Cytoadherence of PRBCs (Plasmodium falciparum-infected red blood cells) to host endothelium has been associated with pathology in severe malaria, but, despite extensive information on the primary processes involved in the adhesive interactions, the mechanisms underlying the disease are poorly understood. Endothelial cells have the ability to mobilize immune and pro-adhesive responses when exposed to both PRBCs and TNF (tumour necrosis factor). In addition, there is also an up-regulation by PRBCs and TNF and a concurrent down-regulation of a range of genes involved in inflammation and cell death, by PRBCs and TNF. We propose that the balance between positive and negative regulation will contribute to endothelial pathology during malarial infection. Apposition of PRBCs has been shown by a number of groups to activate signalling pathways. This is dependent, at least in part, on the cytoadherence characteristics of the invading isolate, such that the avidity of the PRBC for the receptor on host endothelium is proportional to the level of activation of the signalling pathways. An understanding of the post-adhesive processes produced by cytoadherence may help us to understand the variable pathology seen in malaria and to design appropriate therapies to alleviate severe disease.
Integrin activation
Authors: Banno Asoka , Ginsberg Mark H.
Published: March 2008

Agonist stimulation of integrin receptors, composed of transmembrane α and β subunits, leads cells to regulate integrin affinity (‘activation’), a process that controls cell adhesion and migration, and extracellular matrix assembly. A final step in integrin activation is the binding of talin to integrin β cytoplasmic domains. We used forward, reverse and synthetic genetics to engineer and order integrin activation pathways of a prototypic integrin, platelet αIIbβ3. PMA activated αIIbβ3 only after expression of both PKCα (protein kinase Cα) and talin at levels approximating those in platelets. Inhibition of Rap1 GTPase reduced αIIbβ3 activation, whereas expression of constitutively active Rap1A(G12V) bypassed the requirement for PKCα. Overexpression of a Rap effector, RIAM (Rap1-GTP-interacting adaptor molecule), activated αIIbβ3 and bypassed the requirement for PKCα and Rap1. In addition, shRNA (short hairpin RNA)-mediated knockdown of RIAM blocked talin interaction with and activation of integrin αIIbβ3. Rap1 activation caused the formation of an ‘activation complex’ containing talin and RIAM that redistributed to the plasma membrane and activated αIIbβ3. The central finding was that this Rap1-induced formation of an ‘integrin activation complex’ leads to the unmasking of the integrin-binding site on talin, resulting in integrin activation.
Structural insight into Slit–Robo signalling
Authors: Hohenester Erhard
Published: March 2008

Drosophila Slit and its vertebrate orthologues Slit1–Slit3 are secreted glycoproteins that play important roles in the development of the nervous system and other organs. Human Slits are also involved in a number of pathological situations, such as cancer and inflammation. Slits exert their effects by activating receptors of the Robo (Roundabout) family, which resemble cell adhesion molecules in their ectodomains and have large, mainly unstructured cytosolic domains. HS (heparan sulfate) is required for Slit–Robo signalling. The hallmark of Slit proteins is a tandem of four LRR (leucine-rich repeat) domains, which mediate binding to the IG (immunoglobulin-like) domains of Robos. A major question is how Slit binding is translated into the recruitment of effector molecules to the cytosolic domain of Robo. Detailed structure–function studies have shown that the second LRR domain of Slit (D2) binds to the first two IG domains of Robo, and that HS serves to stabilize the Slit–Robo interaction and is required for biological activity of Slit D2. Very recently, the crystal structure of a minimal Slit–Robo complex revealed that the IG1 domain of Robo is bound by the concave face of Slit D2, confirming earlier mutagenesis data. To define the mechanism of Robo transmembrane signalling, these structural insights will have to be complemented by new cell biology and microscopy approaches.
Studies of focal adhesion assembly
Authors: Campbell Iain D.
Published: March 2008

Recent studies of some proteins involved in the formation of focal adhesions are described. These include fibronectin, integrins, talin, Dok1 and filamin. Emphasis is placed on features that facilitate regulated assembly of complexes; these include a modular construction and flexible regions that provide interaction sites whose affinity can be adjusted by conformational masking and phosphorylation.
Fabrication of magnetic porous hollow silica drug carriers using CaCO3∕Fe3O4 composite nanoparticles and cationic surfactant double templates
Authors: Ma H. , Zhou J. , Caruntu D. , Yu M. H. , Chen J. F. , O’Connor C. J. , Zhou W. L.
Published: March 2008

Magnetic porous hollow silica nanosphere is a new class of structured nanomaterials for drug delivery. In this paper, we report a synthesis of magnetic porous hollow silica nanospheres (MPHSNs) using CaCO3∕Fe3O4 composite nanoparticles and cationic surfactant double templates. Fe3O4 nanoparticles were first mixed into CaCO3 using rotating packed bed forming CaCO3∕Fe3O4 composite nanoparticles. Tetraethoxysilane was then added as precursor to form silica layer on the surface of CaCO3∕Fe3O4 composite nanoparticles, while hexadecyltrimethylammonium bromide was used as a second template to direct the formation of porous silica shells. After the calcination of the surfactants and etching away CaCO3, MPHSNs were formed with the magnetite nanoparticles remaining in the cores. Transmission electron microscopy was applied for the nanostructure determination. The pore size can be measured by micromeritics analyzer. Magnetic properties of MPHSNs were measured by a superconducting quantum interface device. Zero-field-cooled and field-cooled magnetization data in the temperature range of 5–300K show that the MPHSNs are superparamagnetism above the blocking temperature and ferromagnetism below the blocking temperature after the calcination. The MPHSNs can be used as potential nanocarriers for targeted delivery and controlled releasing.
The temperature dependence of hysteretic processes in Co nanowires arrays
Authors: Astefanoaei I. , Dumitru I. , Diaconu A. , Spinu L. , Stancu A.
Published: March 2008

In this paper, the temperature dependence of the hysteretic processes of Co nanowires, squarelly ordered in an array prepared by electrodeposition in nanopores of alumina membranes was analyzed. Both the magnetostatic interactions induced in the nanowires arrays and the thermal stresses (radial, azimuthal and axial stresses), which appear during the cooling of the system (nanowire and alumina template) from room temperature to 3K was evaluated. The analysis of thermal induced stresses provides useful informations concerning the magnetic anisotropy in the Co nanowires. The temperature dependence of the remanent magnetization and coercitive field as an effect of the induced thermal stresses and magnetostatic interactions between nanowires was studied.
Dynamic range evaluation of linear permanent magnet machine through design parameters estimation and continuous motion
Authors: You Dae-Joon , Lee Sung-Ho , Jang Seok-Myeong
Published: March 2008

In the case of the manufactured linear permanent magnet synchronous machines (PMLSMs), dynamic range evaluation for system efficiency and performance limits is difficult to accomplish because of the moving length restriction with mover and the absence of interface between the design field and control field. To solve this problem, this paper presents a dynamic analysis based on design parameters by magnetic field analysis of the linear PM machine. And then, maximum operating range of the system is estimated considering the control method of a fixed dc-link voltage of the inverter. This analysis is verified from the dynamic experiments through continuous progressive motion of the manufactured disk-type PMLSM by current control.
Large-scale chemical synthesis of shape and size controlled BaFe12−xScxO19 platelets for in-plane oriented thick screen printed films
Authors: Sakai T. , Chinnasamy C. N. , Yoon S. D. , Geiler A. , Vittoria C. , Harris V. G.
Published: March 2008

Scandium (Sc) doped, single phase BaFe12−xScxO19 (x=0.3 and 0.8) were prepared at large scale (10g) by a modified chemical coprecipitation technique. The scanning electron micrograph analysis shows the formation of nearly uniform hexagonal platelets with an average size of <1μm. The sizes of the platelets were controlled by sintering temperature. The screen printed, in-plane oriented films were annealed at different temperatures to produce a dense and thick ferrite film. The hysteresis loops for x=0.3 show a squareness ratio of 0.9 and the saturation magnetic moment of 3700G and the coercivity of 250Oe. The saturation magnetic moment was decreased with increase of Sc substitution. Ferromagnetic resonance measurements exhibited a peak-to-peak derivative linewidth (ΔH) of ∼800Oe at 34GHz for x=0.3 and at 37GHz for the x=0.8 film. The Lande spectroscopic splitting factor (g) value for the screen printed films was found to be 1.92 for x=0.3 and 2.01 for x=0.8.
Choice of electrode geometry for accurate measurement of organic photovoltaic cell performance
Authors: Kim Myung-Su , Kang Myung-Gyu , Guo L. Jay. , Kim Jinsang
Published: March 2008

The relationship between the performance and the electrode geometry of organic photovoltaic devices was investigated to establish the proper electrode geometry for reproducible and accurate performance measurement. Photovoltaic cells (ITO∕PEDOT:PSS∕P3HT+PCBM∕LiF∕Al) having crossbar-type and island-type electrode geometries were fabricated. The crossbar-type cells varied greatly in performance depending on the illuminated light beam size relative to the overlap area of the crossbar-type electrodes due to excess photocurrent generated from the cell region outside the overlapped electrode area, where PEDOT:PSS serves as anode. We systematically investigated the relationship between the conductivity of the PEDOT:PSS, the illumination area, and the amount of excess photocurrent generated.
Buckling behavior of metal film/substrate structure under pure bending
Authors: Li Ying , Wang Xi-Shu , Meng Xiang-Kang
Published: March 2008

Many studies on the thin film/substrate structure and its failure mechanism were reported in recent years. The direct experimental results of thin film/substrate structure by scanning electron microscopy presents an intriguing problem: there exists a buckling failure mechanism at the lateral edge of metal film under pure bending. The qualitative theoretical analysis has been done on such buckling failure of thin film/substrate structure. The experimental results and theoretical analysis are helpful to understand the extrinsic stresses or deformations that are induced by external physical effects.
Simultaneous excitation of fast and slow surface plasmon polaritons in a high dielectric contrast system
Authors: Webb-Wood Grady , Kik Pieter G.
Published: March 2008

Surface plasmon polaritons propagating in a high dielectric contrast system are investigated numerically. Using frequency domain simulations, we show that a three layer system consisting of air–silicon (7nm)–silver supports two different modes at the Ag–Si interface: a fast mode, which exhibits normal dispersion, and a slow mode, which exhibits anomalous dispersion. Near the Ag–Si surface plasmon polariton resonance frequency, surface waves with a wavelength of 25nm are observed at a vacuum wavelength of 595nm, equivalent to λf∕24. The results show the possibility of exciting surface waves with extreme ultraviolet wavelengths using visible frequencies.
Spectrally smoothed supercontinuum generation by using unstably mode-locked laser pulses
Authors: Shi Kebin , Liu Zhiwen
Published: March 2008

We report on a simple approach to obtain spectrally smoothed supercontinuum (SC) by using unstably mode-locked femtosecond laser pulses. The spectrum smoothing effect is due to the averaging of the supercontinua generated in a nonlinear photonic crystal fiber by modulated pulses. Theoretical analysis based upon solving the generalized nonlinear Schrödinger equation is presented, which qualitatively agrees well with the experimental observation. Finally, the application of the smoothed SC to broadband coherent anti-Stokes Raman scattering spectroscopy is demonstrated, which can result in a relatively smooth nonresonant background and suppress spurious peaks.
Two-port vectorial terahertz electro-optic sampling system
Authors: Meignien L. , Mangeney J. , Crozat P. , Duvillaret L. , Hanna M.
Published: March 2008

We present a fiber-based two-port terahertz electro-optic (EO) sampling system at 1.55μm wavelength, including an ultrafast In0.53Ga0.47As photoconductive switch and a freely positionable prismatic EO probe. Frequency components are extended up to 2THz and the dynamic range is larger than 40dB, regardless of the direction of the electromagnetic wave propagating in the waveguide, thanks to the two-port system. The symmetrical two-port pigtailed EO probe allows to determine the direction of propagation of the guided picosecond electromagnetic pulses.
Effect of superconductivity on the electronic transport and capacitance of La1.85Sr0.15CuO4∕Nb doped SrTiO3 heterojunction
Authors: Shi J. P. , Zhao Y. G. , Zhang H. J. , Zhang X. P.
Published: March 2008

The authors report the effect of superconductivity on the electronic transport and capacitance of La1.85Sr0.15CuO4∕Nb doped SrTiO3 heterojunction. This heterojunction shows good rectifying property. With the occurrence of superconductivity, the capacitance, junction resistance, and diffusion voltage of the heterojunction show jumps, which correlate with the resistance change of La1.85Sr0.15CuO4. Analysis shows that the current-voltage behavior of the heterojunction is consistent with that of the inhomogeneous Schottky contacts. The results were discussed by considering the effect of superconductivity on the inhomogeneous heterojunction. This work is helpful for the understanding of superconductor based heterojunctions and inhomogeneous Schottky contacts.
Electrostatic force microscopy study about the hole trap in thin nitride/oxide/semiconductor structure
Authors: Kim Jong-Hun , Noh Hyunho , Khim Z. G. , Jeon Kwang Sun , Park Young June , Yoo Hyunseung , Choi Eunseok , Om Jaechul
Published: March 2008

The stoichiometric nitride (SiN1.33) and Si-rich nitride (SiN1.1) are characterized by the conductive atomic force microscopy (c-AFM) and electrostatic force microscopy (EFM). Only in SiN1.1, EFM is capable of resolving the domains of positive charges with ∼10nm radius. However, the phase dependence on the bias elsewhere is similar to that of SiN1.33, supporting electron tunneling. The following c-AFM image also exhibits that the local leakage is found exclusively on SiN1.1. We suggest that the hole injection which breaks the SiSi bond occur in the structure with the voltage, increasing the overall conductance.
High efficiency diffractive grating couplers for interfacing a single mode optical fiber with a nanophotonic silicon-on-insulator waveguide circuit
Authors: Roelkens G. , Vermeulen D. , Van Thourhout D. , Baets R. , Brision S. , Lyan P. , Gautier P. , Fédéli J.-M.
Published: March 2008

High efficiency diffractive grating structures to interface a single mode optical fiber and a nanophotonic integrated circuit fabricated on silicon-on-insulator are presented. The diffractive grating structures are designed to be inherently very directional by adding a silicon overlay before grating definition. 55% coupling efficiency at a wavelength of 1.53μm is experimentally demonstrated on devices fabricated using standard complementary metal-oxide semiconductor technology. By optimizing the grating parameters, we theoretically show that 80% grating coupling efficiency can be obtained for a uniform grating structure.
Features of formation and propagation of 60° and 90° misfit dislocations in GexSi1−x∕Si (x∼0.4–0.5) films caused by Si substrate misorientation from (001)
Authors: Bolkhovityanov Yu. B. , Deryabin A. S. , Gutakovskii A. K. , Sokolov L. V.
Published: March 2008

We have studied the dislocation structure at the initial stage of relaxation of GexSi1−x films (x∼0.4–0.5) grown on Si substrates tilted 6° about the ⟨011⟩ axis. It is demonstrated that edge misfit dislocations (MDs) in the miscut direction arise in the form of short segments on intersections of 60° MDs. Substrate misorientation from the singular plane made it possible to discover the MD configurations consisting of a short segment of an edge MD and only two 60° MDs diverging from this segment in the miscut direction.
Temperature dependence of the phase-coherence length in InN nanowires
Authors: Blömers Ch. , Schäpers Th. , Richter T. , Calarco R. , Lüth H. , Marso M.
Published: March 2008

We report on low-temperature magnetotransport measurements on InN nanowires, grown by plasma-assisted molecular beam epitaxy. The characteristic fluctuation pattern observed in the conductance was employed to obtain information on phase-coherent transport. By analyzing the root mean square and the correlation field of the conductance fluctuations at various temperatures, the phase-coherence length was determined.
What goes through an examiner's mind? Using verbal protocols to gain insights into the GCSE marking process
Authors: Suto W. M. Irenka , Greatorex Jackie
Published: March 2008

The process of examination marking is complex, requiring examiners to engage in a variety of cognitive operations. While consideration has been given to marking practices in a few specific contexts, those of General Certificate of Secondary Education (GCSE) examiners have yet to receive serious attention. This study's aims, therefore, were: first, to investigate the cognitive strategies used when marking GCSEs; and second, to interpret them within the context of psychological theories of human judgement. Two contrasting GCSE examination papers were considered: Mathematics used a ‘points‐based’ marking scheme, while Business Studies relied on a ‘levels‐based’ scheme. Small groups of experienced examiners marked script samples, and using a concurrent ‘think aloud’ method, verbal protocols were obtained. Using a semi‐structured interview schedule, the examiners were then questioned retrospectively. Qualitative data analysis supported a model of five distinct cognitive marking strategies, which can be interpreted within dual‐processing theories of judgement. The implications for GCSE marking are discussed.
The Representation of Geometric Cues in Infancy
Authors: Lourenco Stella F. , Huttenlocher Janellen
Published: March 2008

There is evidence that, from an early age, humans are sensitive to spatial information such as simple landmarks and the size of objects. This study concerns the ability to represent a particular kind of spatial information, namely, the geometry of an enclosed layout—an ability present in older children, adults, and nonhuman animals (e.g., Cheng, 1986; Hermer & Spelke, 1996). Using a looking‐time procedure, 4.5‐ to 6.5‐month‐olds were tested on whether they could distinguish among the corners of an isosceles triangle. On each trial, the target corner was marked by a red dot. The stimulus (triangle with dot) appeared from different orientations across trials, ensuring that only cues related to the triangle itself could be used to differentiate the corners. When orientations were highly variable, infants discriminated the unique corner (i.e., the corner with the smaller angle and two equal‐length sides) from a nonunique corner; they could not discriminate between the two nonunique corners. With less variable orientations, however, infants did discriminate between the nonunique corners of the isosceles triangle. Implications for how infants represent geometric cues are discussed.
Fast Mapping but Poor Retention by 24‐Month‐Old Infants
Authors: Horst Jessica S. , Samuelson Larissa K.
Published: March 2008

Four experiments explored the processes that bridge between referent selection and word learning. Twenty‐four‐month‐old infants were presented with several novel names during a referent selection task that included both familiar and novel objects and tested for retention after a 5‐min delay. The 5‐min delay ensured that word learning was based on retrieval from long‐term memory. Moreover, the relative familiarity of objects used during the retention test was explicitly controlled. Across experiments, infants were excellent at referent selection, but very poor at retention. Although the highly controlled retention test was clearly challenging, infants were able to demonstrate retention of the first 4 novel names presented in the session when referent selection was augmented with ostensive naming. These results suggest that fast mapping is robust for reference selection but might be more transient than previously reported for lexical retention. The relations between reference selection and retention are discussed in terms of competitive processes on 2 timescales: competition among objects on individual referent selection trials and competition among multiple novel name–object mappings made across an experimental session.
Chloride Homeostasis in Saccharomyces cerevisiae: High Affinity Influx, V-ATPase-dependent Sequestration, and Identification of a Candidate Cl− Sensor
Authors: Jennings Michael L. , Cui Jian
Published: March 2008

Chloride homeostasis in Saccharomyces cerevisiae has been characterized with the goal of identifying new Cl− transport and regulatory pathways. Steady-state cellular Cl− contents (∼0.2 mEq/liter cell water) differ by less than threefold in yeast grown in media containing 0.003–5 mM Cl−. Therefore, yeast have a potent mechanism for maintaining constant cellular Cl− over a wide range of extracellular Cl−. The cell water:medium [Cl−] ratio is >20 in media containing 0.01 mM Cl− and results in part from sequestration of Cl− in organelles, as shown by the effect of deleting genes involved in vacuolar acidification. Organellar sequestration cannot account entirely for the Cl− accumulation, however, because the cell water:medium [Cl−] ratio in low Cl− medium is ∼10 at extracellular pH 4.0 even in vma1 yeast, which lack the vacuolar H+-ATPase. Cellular Cl− accumulation is ATP dependent in both wild type and vma1 strains. The initial 36Cl− influx is a saturable function of extracellular [36Cl−] with K1/2 of 0.02 mM at pH 4.0 and >0.2 mM at pH 7, indicating the presence of a high affinity Cl− transporter in the plasma membrane. The transporter can exchange 36Cl− for either Cl− or Br− far more rapidly than SO4=, phosphate, formate, HCO3−, or NO3−. High affinity Cl− influx is not affected by deletion of any of several genes for possible Cl− transporters. The high affinity Cl− transporter is activated over a period of ∼45 min after shifting cells from high-Cl− to low-Cl− media. Deletion of ORF YHL008c (formate-nitrite transporter family) strongly reduces the rate of activation of the flux. Therefore, Yhl008cp may be part of a Cl−-sensing mechanism that activates the high affinity transporter in a low Cl− medium. This is the first example of a biological system that can regulate cellular Cl− at concentrations far below 1 mM.
Differences in the expression of the ASIP gene are involved in the recessive black coat colour pattern in sheep: evidence from the rare Xalda sheep breed
Authors: Royo L. J. , Álvarez I. , Arranz J. J. , Fernández I. , Rodríguez A. , Pérez‐Pardal L. , Goyache F.
Published: March 2008

Here we have tested the hypothesis of association between different levels of agouti signalling peptide (ASIP) mRNA and the recessive black coat colour in the rare Xalda breed of sheep. To deal with this task, we first tested the possible action of both the dominant black extension allele (ED) and a 5‐bp deletion (X99692:c.100_104del; Adel) in the ovine ASIP coding sequence on the black coat colour pattern in 188 Xalda individuals. The ED allele was not present in the sample and only 11 individuals were homozygous for the AdelASIP allele. All Xalda individuals carrying the Adel/Adel genotype were phenotypically black. However, most black‐coated individuals (109 out of 120) were not homozygous for the 5‐bp deletion, thus rejecting the Adel/Adel genotype as the sole cause of recessive black coat colour in sheep. Differences in expression of ASIP mRNA were assessed via RT‐PCR in 14 black‐coated and 10 white‐coated Xalda individuals showing different ASIP genotypes (Awt/Awt, Awt/Adel and Adel/Adel). Levels of expression in black animals were significantly (P < 0.0001) lower than those assessed for white‐coated individuals. However, the ASIP genotype did not influence the ASIP mRNA level of expression. The consistency of these findings with those recently reported in humans is discussed, and the need to isolate the promoter region of ovine ASIP to obtain further evidence for a role of ASIP in recessive black ovine pigmentation is pointed out.