bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal dependence of localized, high‐latitude dayside aurora (HiLDA)
Authors: Frey H. U. , Østgaard N. , Immel T. J. , Korth H. , Mende S. B.
Published: April 2004

The FUV instrument on the IMAGE spacecraft frequently observes intense ultraviolet (UV) emissions from a localized High Latitude Dayside Aurora (HiLDA) poleward of the general auroral oval location [Frey et al., 2003a]. It has been shown that this aurora is entirely created by high‐energy precipitating electrons, which have probably been accelerated in a quasi‐static field‐aligned electric potential. Here we extend the previous case study to an investigation of the HiLDA occurrence in the Northern Hemisphere over more than 2 years and compare it with the averaged solar wind plasma and interplanetary magnetic field (IMF) properties. HiLDA occurrence is strongly biased toward low solar wind density and IMF with positive Bz, strong positive By (clock angles around 70°), and negative Bx components. Such IMF conditions are favorable for lobe reconnection in the Northern Hemisphere, and the creation of a dominating dusk convection cell with an upward field‐aligned current in its center. Additionally, we investigate the seasonal occurrence of this phenomenon, which shows a maximum in the Northern Hemisphere during sunlit summer months and an almost complete absence in the dark winter. In contrast to the daylight‐suppressed aurora in the auroral oval, the HiLDA cannot be the result of ionospheric feedback due to the stronger ionospheric conductance in sunlight. Instead, in agreement with ionospheric convection models, it is caused by the asymmetry of field‐aligned currents in different seasons, which result from the different dipole tilt angles in summer and winter. We further discuss two scenarios for how the low solar wind density can enhance the field‐aligned parallel potential over the dusk convection cell.
Response of the benthic nepheloid layer to near‐inertial internal waves in southern Lake Michigan
Authors: Hawley Nathan
Published: April 2004

Time series measurements of water transparency, water temperature, and current velocity were made at a station located in 58 m of water in southern Lake Michigan during the summer of 1995. Currents generated by near‐inertial internal waves are correlated with variations in the thickness and in the vertical distribution of suspended sediment in the benthic nepheloid layer. Although a direct causal link between internal wave action and changes in the nepheloid layer could not be established, the data suggest that local resuspension by shoaling internal waves maintains the layer during the stratified period. The origin and maintenance of the benthic nepheloid layer is most likely the result of local resuspension due to a combination of internal wave action and longer‐term processes.
Accuracy of plagioclase compositions from laboratory and Mars spacecraft thermal emission spectra
Authors: Milam Keith A. , McSween Harry Y. , Hamilton Victoria E. , Moersch Jeffrey M. , Christensen Philip R.
Published: April 2004

Plagioclase, the most abundant mineral in many terrestrial and Martian igneous rocks, exhibits a range of compositions that reflects changing conditions during crystallization. Thermal emission spectrometers (TES, THEMIS, and Mini‐TES) on board Mars spacecraft provide a means of determining average plagioclase compositions directly. We demonstrate that spectrally modeled average plagioclase compositions in terrestrial basalts, andesites, and dacites correspond to measured values to within +10/−6 An (molar [Ca/(Ca + Na)] × 100) of weighted average values and +13/−14 An of normative compositions. Analyses of spectra from two‐component plagioclase mixtures (varied by volume and composition) provide additional insight into potential effects of plagioclase zoning. Considering the variability in types of observed plagioclase zoning patterns in terrestrial volcanic rocks, normal zoning (calcic cores and sodic rims) cannot be assumed and thus cannot account for an apparent “sodic bias” seen in previous spectrally modeled compositions. This bias is better explained by higher abundances of sodic groundmass plagioclase relative to calcic phenocrysts. Deconvolution modeling of laboratory spectra of physical mixtures (convolved to various instrument resolutions) predicts that TES, THEMIS, and Mini‐TES spectra may be used to extract plagioclase compositions to within +9/−12 An, +11/−12 An, and +8/12 An (respectively) of measured values in coarse sand plagioclase mixtures, with 1σ standard deviations of ±4 An for laboratory, TES, and Mini‐TES resolutions and ±6 An for THEMIS resolution.
Size, shape, orientation, speed, and duration of GPS equatorial anomaly scintillations
Authors: Kintner P. M. , Ledvina B. M. , de Paula E. R. , Kantor I. J.
Published: April 2004

GPS L1 C/A signal scintillation data were collected at the equatorial anomaly over a period of three months using five receivers spaced on magnetic east‐west and north‐south axes to examine the speed, orientation, shape, width, and duration of GPS scintillation fade patterns. The nighttime speeds were primarily eastward in the range of 100–200 m/s with a significant spread to both larger values and negative (westward) values as expected, given the known behavior of ionospheric drifts and GPS signal path movement. The characteristic velocity was found to be small so that the true velocity was equal to the apparent velocity to a very good approximation. The orientation of the scintillation fade patterns was organized by a simple projection model of the magnetic field along the GPS signal path onto the horizontal plane when the signal paths were aligned no closer than 60° from the magnetic field. The shape of the scintillation fade pattern was greatly elongated in the magnetic north‐south direction, and no change could be detected over a distance of 1 km. The east‐west widths of the scintillation fade patterns were variable, but after normalizing to the elevation angle, accounting for the fade orientation, and eliminating signal paths within 60° of the magnetic field, an organized scale length of about 450 m was determined. The duration of the scintillation fade patterns was examined using the optimal cross‐correlation amplitude as a measure of change. For a 5 s duration, 49% of the optimal cross‐correlation amplitudes exceed a value of 0.8.
Immediate skin reactivity to histamine and to allergens in cohorts of 9‐year‐old schoolchildren studied 16 years apart
Authors: Ronchetti R. , Villa M. P. , Pagani J. , Martella S. , Guglielmi F. , Paggi B. , Bohmerova Z. , Falasca C. , Barreto M.
Published: April 2004

Background
Differing or increasing prevalence of positive allergen skin‐prick tests observed in Europe could at least in part be explained by population changes in histamine skin reactivity. These changes would also alter the relationship between positive allergen skin‐prick tests and serum IgE.

Objective
To assess changes in histamine reactivity, allergen skin‐prick tests and serum IgE in our geographical setting.

Methods
We compared the outcome of two epidemiological surveys conducted 16 years apart in unselected 9‐year‐old schoolchildren (170 in 1983 and 176 in 1999) from a semi‐rural region in central Italy. Outcome measures were skin‐prick tests with two histamine concentrations (10 and 1 mg/mL) and 11 locally relevant allergens; serum total and specific IgE for positive allergens.

Results
The two histamine concentrations induced significantly larger mean weal diameters in 1999 than in 1983 (10 mg/mL: 5.28±0.82 mm vs. 3.25±0.97 mm; P<0.001). Whereas the prevalence of subjects with at least one positive allergen‐induced weal reaction (≥3 mm) increased over the 16 years (from 15.3% in 1983 to 25.6% in 1999), the prevalence of positive skin‐prick tests, expressed as the allergen/ histamine weal ratio, remained almost unchanged. A given allergen weal diameter yielded less total (P<0.05 by Student's t‐test for cumulative weals <8 mm) and specific (P<0.01 by Student's t‐test for weals <3 mm, P<0.05 by Kruskal–Wallis test) serum IgE in 1999 than in 1983.

Conclusions
Although the causes and mechanisms remain unclear, the increased histamine skin reactivity over time is associated with an increase in positive allergen skin‐prick tests. In the presence of increased tissue and organ susceptibility to histamine, minute amounts of specific IgE could have important biological consequences.
Role of mitogen‐activated protein kinases in influenza virus induction of prostaglandin E2 from arachidonic acid in bronchial epithelial cells
Authors: Mizumura K. , Hashimoto S. , Maruoka S. , Gon Y. , Kitamura N. , Matsumoto K. , Hayashi S. , Shimizu K. , Horie T.
Published: April 2004

Background
Influenza virus (IV) infection causes airway inflammation; however, it has not been determined whether IV infection could catabolize arachidonic acid cascade in airway epithelial cells. In addition, the responsible intracellular signalling molecules that catabolize arachidonic acid cascade have not been determined.

Objective
In the present study, to clarify these issues, we examined the cyclooxygenase (COX) expression, cytosolic phospholipase A2 (cPLA2) phosphorylation and prostaglandin E2 (PGE2) release in human bronchial epithelial cells (BEC) upon IV infection, and the role of mitogen‐activated protein kinase (MAPK) including extracellular signal‐regulated kinase (ERK), p38 MAPK and c‐Jun‐NH2‐terminal kinase (JNK) in catabolizing arachidonic acid cascade in BEC.

Methods
COX‐2 expression, phosphorylation of cPLA2 and phosphorylation of ERK, JNK and p38 MAPK were determined by Western blot. The concentrations of PGE2 were determined by ELISA. PD 98059 as a specific inhibitor of MAPK kinase‐1 (MEK‐1), an up‐stream kinase of ERK, SB 203580 as a specific inhibitor of p38 MAPK and CEP‐11004 as a specific inhibitor of JNK cascade were used to investigate the role of ERK, p38 MAPK and JNK in catabolizing arachidonic acid cascade in BEC.

Results
The results showed that (1) IV infection increases COX‐2 expression, cPLA2 phosphorylation and PGE2 release, (2) ERK, p38 MAPK and JNK were phosphorylated, (3) CEP‐11004 and PD 98059 predominantly attenuated COX‐2 expression and cPLA2 phosphorylation, respectively, (4) SB 203580 did not remarkably affect COX‐2 expression and cPLA2 phosphorylation, and (5) each inhibitor dose‐dependently attenuated PGE2 release by various extents.

Conclusion
These results indicate that IV infection activates three distinct MAPKs, ERK, p38 MAPK and JNK, to participate to various extents in the induction of PGE2 synthesis from arachidonic acid in BEC.
Endotoxin contamination contributes to the pulmonary inflammatory and functional response toAspergillus fumigatusextract inhalation in heaves horses
Authors: Pirie R. S. , Dixon P. M. , McGorum B. C.
Published: April 2004

BackgroundMould extract inhalation challenges have been used extensively in the investigation of heaves. Such challenges have induced pulmonary neutrophilic inflammation and dysfunction, consistent with, but less severe than the natural disease. However, the method of mould extract production is likely to result in endotoxin contamination.

ObjectiveTo investigate whether insufficient dose delivery was responsible for the shortfall in response to inhaled extract compared with natural disease, and whether endotoxin contamination of mould extract contributed to the pulmonary inflammation and dysfunction.

MethodsWe measured the response of six heaves horses following inhalation of saline (placebo) and three doses ofAspergillus fumigatusextract. We then compared the response of six heaves horses toA. fumigatusextract inhalation before and after lipopolysaccharide (LPS) depletion.

ResultsInhalation challenge with 0.5, 1.6 and 5 mg ofA. fumigatusextract resulted in a significant increase in bronchoalveolar lavage fluid (BALF) neutrophil ratio when compared with saline inhalation. Only 1.6 and 5 mg extract inhalation resulted in significant lung dysfunction compared with saline. There was no significant difference between 1.6 and 5 mg extract inhalation with respect to airway neutrophil numbers or lung function, suggesting a plateau in both measured responses. LPS depletion of 1.6 mgA. fumigatusextract resulted in a significant reduction in airway neutrophil numbers and increase in arterial oxygen tension. There was no significant difference between saline and the LPS‐depletedA. fumigatusextract challenges with respect to neutrophil count and lung function. The reduction in airway neutrophil numbers was greater than would be predicted by extrapolation from previously reported soluble LPS dose–response inhalation experiments.

ConclusionThis study supports a role for other inhalants, in addition to soluble components ofA. fumigatus, in the aetiopathogenesis of heaves. Also the amplification in response to LPS when inhaled withA. fumigatusextract, suggests that the role of inhaled endotoxin in the pulmonary inflammation and dysfunction in naturally occurring heaves may currently be underestimated.
Stringent environmental control in pregnancy and early life: the long‐term effects on mite, cat and dog allergen
Authors: Simpson A. , Simpson B. , Custovic A. , Craven M. , Woodcock A.
Published: April 2004

Background As part of a primary prevention of asthma study, we measured the effect of environmental control measures on Der p 1, Fel d 1 and Can f 1 over a 3.5‐year period.

Methods High‐risk infants (both parents atopic) without pets, were randomized to the Active group (n = 142, vinyl flooring in child's room, allergen‐impermeable cot mattress, hot‐washable toy, mite allergen‐impermeable encasings to parental bed and to child's bed when older, high filtration vacuum cleaner, hot‐washing of bedding) or the Control group (n = 136, no intervention), in early pregnancy. Dust samples from the parental mattress, living room floor, child's mattress and floor at baseline (pregnancy), birth and at 3 years were analysed for Der p 1, Fel d 1 and Can f 1.

Results A total of 278 families completed the baseline visit, 259 the birth visit and 239 the 3‐year visit. In the Active group at 3 years, 58% remained compliant with all measures likely to reduce the child's exposure to allergen and 77% of parents still used encasings on their bed. Levels of Der p 1, Fel d 1 and Can f 1 were significantly lower in the Active group in the child's floor and the child's mattress at 3 years compared to the Control group (P < 0.001). For the parental mattress, the levels of Der p 1 and Fel d 1 were lower in the Active group (P < 0.001) and there was a strong trend towards a lower level for Can f 1. There was no difference in the levels of any of the allergens between the groups in the living room floor. Childrens' bedrooms with no detectable mite, cat or dog allergen were significantly more common in the Active than the Control group (25 vs. 2, P < 0.001).

Conclusions Environmental control measures are effective in substantially reducing levels of Der p 1, Fel d 1 and Can f 1 in homes without pets in the long term and are acceptable to families. The effect of this environmental manipulation on the development of sensitization and allergic disease remains to be seen.
Effect of pollinator on haploid production in durum wheat crossed with maize and pearl millet
Authors: GARCIA‐LLAMAS C. , RAMIREZ M. C. , BALLESTEROS J.
Published: April 2004

The aim of this work was to analyse the influence of the male parent on the production of embryos and haploid plants in durum wheat crossed with maize and pearl millet, to find a proper trait to identify the most efficient pollinators and to evaluate the mixtures of pollen. Two genotypes of durum wheat, low and high responding, were crossed with eight pollen samples: (i) three maize hybrids, (ii) three pearl millet inbred lines, (iii) a mixture of maize pollen and (iv) another mixture of pearl millet pollen. No significant differences on embryos and haploid plant production were observed among the four samples of maize pollen, but there were clear genotypic differences for the production of haploids between genotypes of pearl millet. The best pearl millet genotype produced significantly more haploid plants than the other two and the mixture of pollen. There was no correlation between the production of embryos and haploid plants. Therefore, the production of haploid plants must be the criterion to identify superior pollinators. In addition, a mixture of pollen is inappropriate except when using genotypes previously identified as good pollinators.
Pyramiding of insect‐ and disease‐resistance genes into an elite indica, cytoplasm male sterile restorer line of rice,‘Minghui 63′
Authors: Jiang G. H. , Xu C. G. , Tu J. M. , Li X. H. , He Y. Q. , Zhang Q. F.
Published: April 2004

The wild‐rice‐derived dominant gene Xa21 conferring multi‐race resistance to bacterial blight and a fused Bt gene cry1Ab/cry1Ac conferring resistance to lepidopteran insects were individually introduced into the same genetic background of an elite indica cytoplasm male sterile (CMS) restorer line ‘Minghui 63′. The line showed the desirable insect‐ and disease‐resistant phenotypes. To maximize the effect, the two genes were also pyramided into the same recipient plant of ‘Minghui 63’ by marker‐assisted selection. After being subjected to natural infestation of leaf‐folders and yellow stem borers and inoculation of Xoo strain mixtures, the pyramiding line and its derived hybrids showed high levels of resistance against both insect damage and disease. Furthermore, data from field trials demonstrated that the hybrids made by crossing this pyramiding line with the CMS lines ‘Zhenshan 97A’ and ‘Maxie A’ retained a similar level of yield under conditions without chemical spray, indicating that the pyramiding genes have a yield‐stabilizing effect on the recipient line and its hybrids.
Interspecific hybrids of sunflower as a source of Sclerotinia resistance
Authors: Rönicke S. , Hahn V. , Horn R. , Grone I. , Brahm L. , Schnabl H. , Friedt W.
Published: April 2004

Sclerotinia sclerotiorum is considered the most devastating pathogen of sunflower grown in humid environments. In this study, progenies of partial hybrids between Helianthus maximiliani, a wild species that has been shown to be resistant to S. sclerotiorum, and H. annuus were characterized by amplified fragment length polymorphism (AFLP) analysis to identify whether there are introgressions from H. maximiliani into the cultivated sunflower at the molecular level. Wild species‐specific fragments as well as fragments not found in either parent were detected. Progenies tended to cluster together according to the original partial hybrids in the dendrogram by the use of bootstrap procedures. The progenies were studied for their reaction to S. sclerotiorum using artificial inoculation of sunflower heads. Some of the progenies showed a higher level of resistance compared with resistant inbred lines. It was possible to identify two AFLP‐fragments which seem to be linked to Sclerotinia resistance.
Breeding for high yield and fibre quality in coloured cotton
Authors: Dutt Y. , Wang X. D. , Zhu Y. G. , Li Y. Y.
Published: April 2004

In the present study, three types of coloured fibre cottons, i.e. white, brown and green, were compared for their fibre quality and yield. The comparison of fibre quality suggested that coloured fibre cotton was inferior as compared with white fibre cotton. To understand the effect of cellulose, mineral elements [nitrogen (N), phosphorus (P) and potassium (K)] and pH of fibre cells on the quality of fibre, these components were studied at different fibre cell developed stages in all three fibre cotton types. The cellulose content is closely associated with the quality of fibre. The higher fibre quality of white fibre cotton might be the result of the high cellulose content in it compared with coloured fibre cotton. A rapid and slow decrease in pH in white and coloured cottons, respectively, might have some effects on fibre elongation. Among the mineral contents, potassium is positively correlated with the fibre quality traits. The pigment development patterns in brown and green fibre cottons are not similar. In green fibre cotton it takes more time to deepen in colour as compared with brown fibre cotton. Possible strategies for the improvement in quality of coloured fibre cotton are discussed. The results of heterosis studies in coloured fibre cotton suggest that heterosis could improve yield and quality of coloured fibre cotton. In the present study, the hybrids between ZJU12A x ZJU05R and ZJU18A x ZJU01R, having an acceptable lint colour types plus better fibre quality and high yield performance, may be exploited further for their heterotic advantages.
Identification of resistance gene analogue markers closely linked to wheat powdery mildew resistance gene Pm31
Authors: XIE C. , SUN Q. , NI Z. , YANG T. , NEVO E. , FAHIMA T.
Published: April 2004

Specific oligonucleotide primers, designed for the sequences of known plant disease resistance genes, were used to amplify resistance gene analogues (RGAs) from wheat genomic DNA. This method was applied in a bulked segregant analysis to screen for the RGA markers linked to the powdery mildew resistance gene Pm31, introgressed into common wheat from wild emmer. Two RGA markers (RGA200 and RGA390) were found to be closely linked to Pm31 and completely co‐segregating with the marker allele of Xpsp3029 linked to Pm31, with a genetic distance of 0.6 cM. These two RGA markers were then integrated into the formerly established microsatellite map of Pm31 region. The result showed the effectiveness of the RGA approach for developing molecular markers linked to disease resistance genes and demonstrated the efficiency of denaturing polyacrylamide‐gel electrophoresis for detecting polymerase chain reaction polymorphism.
Effect of PI‐HAART on the prevalence of oral lesions in HIV‐1 infected patients. A Greek study
Authors: Nicolatou‐Galitis O , Velegraki A , Paikos S , Economopoulou P , Stefaniotis T , Papanikolaou IS , Kordossis T
Published: April 2004

Objective:  To investigate the association between the prevalence of oral lesions and highly active antiretroviral therapy (HAART) including a protease inhibitor (PI).

Design:  Prospective study.

Patients and methods:  Ninety‐five consecutive patients, attending an AIDS Unit, in Greece entered the study. Fourty‐four patients were receiving PI‐ HAART, 14 patients were on double antiretroviral therapy, and 37 patients were not receiving antiretroviral therapy at the time of oral examination.

Oral lesions were diagnosed by established presumptive clinical criteria.

Main outcome measures:  Oral lesions were scored. CD4 counts and viral load were determined and related to the prevalence of oral lesions.

Results:  Oral lesions, and specifically oral candidiasis, were significantly reduced (P < 0.001) in patients receiving PI‐HAART. Oral lesions were significantly increased in patients with CD4 counts <200 cells μl−1 and viral load >20 000 copies ml−1 (P < 0.001). The percentage of patients, with lesions on PI‐HAART, and with CD4 < 200 and viral load >20 000 was 1.5 times lower (37.5%vs 58.8%, P < 0.001) than that of patients not receiving antiretroviral therapy, but with similar immune and viremic status.

Conclusions:  Oral lesions were significantly reduced in patients on PI‐HAART. A direct anticandidal effect of PI was suggestive and seemed to have accounted, beyond the HAART‐related immune reconstitution, for the reduction of candidiasis and all other oral lesions.
Is the incidence of oral and pharyngeal cancer increasing in Finland? An epidemiological study of 17 383 cases in 1953–1999
Authors: Tarvainen L , Suuronen R , Lindqvist C , Malila N
Published: April 2004

Objective:  The aim of this study was to describe the occurrence of oral and pharyngeal cancer in Finland over the last half century.

Materials and methods:  The study included all lip, oral and pharyngeal cancer cases diagnosed in Finland and reported to the nation‐wide Finnish Cancer Registry between 1953 and 1999.

Results:  The study comprised 17 383 new cancer cases: 11 666 in males and 5717 in females. Of these, 83% were squamous cell carcinomas. By the end of the study, 1999, the mean age at diagnosis had increased to 63 years for males and 67 for females. The age‐adjusted incidence of oral and pharyngeal cancer decreased in males from 12.5 per 105 to 8.4 per 105 while it increased in females from 3.0 per 105 to 3.9 per 105. This was because of a decrease in lip cancer incidence in males, while the incidence of tongue, mouth and salivary gland cancers increased in both genders. The annual number of new oral cancer cases increased, however, in both genders.

Conclusion:  The incidence of lip cancer decreased in males, probably because of a decrease in smoking and in outdoor work. The incidence of intra‐oral cancers increased in both genders, possibly because of increased alcohol consumption.
Isolation and characterization of subgingival staphylococci from periodontitis patients and controls
Authors: Murdoch FE , Sammons RL , Chapple ILC
Published: April 2004

Objectives:  To isolate and characterize subgingival staphylococci from patients with periodontal disease and from periodontally healthy controls, to evaluate the periodontal environment as a potential source for systemic staphylococcal infections.

Methods:  PeriopaperTM strips were used to isolate subgingival staphylococci from 28 patients with chronic periodontitis and 28 periodontally healthy age and sex‐matched controls. Staphylococci were identified by microbiological methods and antibiotic resistance profiles determined.

Results:  Staphylococci were isolated from 54% diseased subgingival and 43% healthy subgingival sites in over 50% periodontitis patients and from 29% healthy subgingival sites in 54% controls. No significant differences in the frequency of isolation or numbers of staphylococci isolated from diseased and healthy sites were noted. Staphylococcus epidermidis was the predominant oral species. Seventy per cent (115 of 165) of all isolates were penicillin‐resistant.

Conclusions:  Subgingival staphylococci are present in both periodontitis patients and controls. In periodontitis there is an increased risk of bacteraemia because of the increased dentogingival surface area. The dental and periodontal health of patients at risk from haematogenous infections should therefore be maintained at a high level. Antibiotic resistance profiles of the oral staphylococcal isolates suggest that amoxicillin may no longer be a suitable antibiotic for prophylaxis against systemic infections such as prosthetic valve endocarditis.
African countries propose a regional oral health strategy: The Dakar Report from 1998
Authors: Myburgh NG , Hobdell MH , Lalloo R
Published: April 2004

It is clear that the African region faces a number of serious oral diseases, either because of their high prevalence or because of the severe tissue damage or death that can occur. Previous approaches to oral health in Africa have failed to recognise the epidemiological priorities of the region or to identify reliable and appropriate strategies to assess them. Efforts have consisted of an unplanned, ad hoc and spasmodic evolution of curative oral health services. This document focuses on the most severe oral problems that people have to live with like noma, oral cancer and the oral consequences of HIV/AIDS infection. It proposes a strategy for assisting member states and partners to identify priorities and interventions at various levels of the health system, particularly at the district level. The strategy aims at strengthening the capacity of countries to improve community oral health by effectively using proven interventions to address specific oral health needs. The strategy identifies five main ‘programmatic areas’, including (i) the development of national oral health strategies and implementation plans, (ii) integration of oral health in other programmes, (iii) delivery of effective and safe oral health services, (iv) regional approach to education and training for oral health, and (v) development of effective oral health management information systems. Many of the programmatic areas share similar characteristics described as a ‘strategic orientation’. These strategic orientations give effect to the concepts of advocacy, equity, quality, partnership, operational research, communication and capacity building. The WHO Regional Committee for Africa (RC) is invited to review the proposed oral health strategy for the African region for the period 1999–2008 and provide an orientation for the improvement of oral health in member states in the region.
Corn-shape carbon nanofibers with dense graphite synthesized by microwave plasma-enhanced chemical vapor deposition
Authors: Hayashi Y. , Tokunaga T. , Soga T. , Jimbo T. , Yogata Y. , Toh S. , Kaneko K.
Published: April 2004

Corn-shape carbon nanofibers (CCNFs) with metal-free tips have been synthesized by a microwave plasma-enhanced chemical-vapor deposition method using CH4 and H2 gasses. The CCNFs were grown on Ni/SiO2/Si and Ni/Mo mesh substrates using a bias-enhanced growth method, and they were analyzed by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The cones are composed of cylindrical pure graphite sheets, and have nanometer-sized tips and roots. The tips’ apex angles of CCNFs have cone angles of 20°, 39°, and 60° depending on the growth conditions such as substrate temperature.
Target charging effects on proton acceleration during high-intensity short-pulse laser-solid interactions
Authors: Beg F. N. , Wei M. S. , Dangor A. E. , Gopal A. , Tatarakis M. , Krushelnick K. , Gibbon P. , Clark E. L. , Evans R. G. , Lancaster K. L. , Norreys P. A. , Ledingham K. W. D. , McKenna P. , Zepf M.
Published: April 2004

We report results from experiments performed at the Rutherford Appleton Laboratory using the VULCAN laser facility (I>5×1019 W cm−2). Single wire targets were used, and on some shots additional objects were placed near the target. These were positioned so that they were not irradiated by the laser. Proton emission from single wire targets was observed as radially symmetric structures (“stripes”) in both the forward and backward directions, and was due to plasma sheath acceleration around the wire. The presence of objects in the vicinity of the interaction had a significant effect on the angular emission pattern of protons from the primary target. Importantly, the secondary object was also observed to be a source of energetic proton emission.
Anisotropic spectroscopy of nitrogen K-edge in group-III nitrides
Authors: Gao Shang-Peng , Zhang Aihua , Zhu Jing , Yuan Jun
Published: April 2004

Ab initio calculation of nitrogen K-edges for use in the core-level spectroscopy of industrially important group-III nitrides (AlN, GaN, InN) has been carried out systematically including the core-hole effect. The theoretical spectra for transition into final states with px,y and pz symmetries are in good agreement with the available anisotropic electron energy-loss measurements. Our spectra can be used as “fingerprints” to characterize the group-III nitrides, for example, not only to distinguish between different polymorphs of group-III nitrides, but also to identify the presence of surface oxidation. We have also presented our simulated results in terms of an orientation-average spectrum and a sample orientation-dependent dichroic spectrum for future reference.
Ultraviolet amplified spontaneous emission from thin films of 4,4′-bis(9-carbazolyl)-2,2′-biphenyl and the derivatives
Authors: Kawamura Yuichiro , Yamamoto Hidetoshi , Goushi Kenichi , Sasabe Hiroyuki , Adachi Chihaya , Yoshizaki Hiroki
Published: April 2004

We demonstrate 394 nm ultraviolet amplified spontaneous emission (ASE) with a low pumping power threshold of Eth=1.3±0.2 μJ/cm2, from a thin film of an organic semiconductor 4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) under the pulse excitation of a N2 gas laser (337 nm). 3-methyl and 3,6-dimethyl substituted CBP derivatives also exhibited pronounced ASE in the deep-blue region of 401 and 406 nm and ASE thresholds of less than Eth=2 μJ/cm2. We also examined the ASE characteristics of N,N′-di(m-tolyl)-N,N′-diphenylbenzidine (TPD), N,N,N′,N′-tetraphenylbenzidine (DPABP) and N,N′-di(α-naphtyl)-N,N′-diphenylbenzidine (α-NPD). While TPD and DPABP showed low ASE thresholds, α-NPD did not show any ASE. We show that the large radiative decay rate (kf) of DPABP and TPD, which is derived from their short fluorescence lifetime (τf) and large quantum efficiency (ηf), leads to a low ASE threshold. On the other hand, the lack of ASE from α-NPD is ascribable to the small kf of 0.8±0.1×108 s−1, which is due to the rather long τf of 3.5 ns and small ηf of 0.29±0.02. In addition, we observed that the ASE gain is closely correlated with kf. A larger kf resulted in a larger ASE gain.
Reflection/transmission confocal microscopy characterization of single-crystal diamond microlens arrays
Authors: Gu E. , Choi H. W. , Liu C. , Griffin C. , Girkin J. M. , Watson I. M. , Dawson M. D. , McConnell G. , Gurney A. M.
Published: April 2004

Using the method of photoresist reflow and inductively coupled plasma dry etching, we have fabricated microlens arrays in type-IIa natural single-crystal diamond, with diameters down to 10 μm. The surface profile of the microlenses was characterized by atomic force microscopy and was found to match well with a spherical shape, with a surface roughness of better than 1.2 nm. To characterize the optical properties of these diamond microlens arrays, a laser scanning reflection/transmission confocal microscopy technique has been developed. This technique enabled the surface profile of the microlenses to be measured simultaneously with optical parameters including focal length and spot size, opening up an application area for confocal microscopy.
Hall mobility of narrow Si0.2Ge0.8–Si quantum wells on Si0.5Ge0.5 relaxed buffer substrates
Authors: Tsujino S. , Falub C. V. , Müller E. , Scheinert M. , Diehl L. , Gennser U. , Fromherz T. , Borak A. , Sigg H. , Grützmacher D. , Campidelli Y. , Kermarrec O. , Bensahel D.
Published: April 2004

We studied in-plane transport of a two-dimensional hole gas in modulation-doped p-Si0.2Ge0.8 quantum wells (QWs) on Si0.5Ge0.5 relaxed buffer substrates with thicknesses L between 2.5 and 7 nm. We found that interface roughness scattering limits the low-temperature mobility μ of the samples with L between 2.5 and 4.5 nm. The interface roughness parameters were evaluated by fitting the experiment with the calculated μ limited by interface roughness scattering. We found that the obtained parameters were consistent with the values estimated from x-ray reflectivity and the transmission electron micrograph of the samples. When L is increased from 4.5 to 7 nm, μ increases only gradually and the highest μ of 0.44 m2/V s was observed for 7-nm-thick QWs. The scattering by defects, interface charge, and strain fluctuation are discussed as possible additional mobility-limiting mechanisms.
Current density mapping and pinhole imaging in magnetic tunnel junctions via scanning magnetic microscopy
Authors: Schrag B. D. , Liu Xiaoyong , Shen Weifeng , Xiao Gang
Published: April 2004

We have applied a magnetoresistive microscopy technique to the imaging of current densities and pinhole formation in magnetic tunnel junction devices. In this work, we demonstrate how the magnetic field distribution at the surface of the device can be used to understand the flow of current within the junction itself. By imaging the current-induced fields before and after pinhole formation in several different junctions, we find that many junctions exhibit an unexpectedly complicated current distribution after high-voltage-induced breakdown. Further, we have seen that pinhole locations can be correlated with current inhomogeneities observed before junction breakdown. Finally, we present the results of finite-element simulations which are in good agreement with experimental results.
Dual role of LiF as a hole-injection buffer in organic light-emitting diodes
Authors: Zhao J. M. , Zhang S. T. , Wang X. J. , Zhan Y. Q. , Wang X. Z. , Zhong G. Y. , Wang Z. J. , Ding X. M. , Huang W. , Hou X. Y.
Published: April 2004

It is demonstrated experimentally that the effect of a LiF buffer layer inserted at the ITO\N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′ biphenyl 4,4′-dimaine (NPB) interface on the hole injection is greatly dependent on the initial barrier height (IBH) existing at the interface. Only for a large IBH, will the introduction of the LiF show improvement effect. For small one, it will weaken the hole injection. These phenomena are explained in terms of tunneling model and calculations based on this model show a good agreement with the experimental results. This further confirms that the energy level realignment and the change in carrier tunneling probability are mainly responsible for the variation of current injection induced by the insulating buffers in organic light-emitting diodes.
Thermal hysteresis in the luminescence of Cr3+ ions in Sr0.6Ba0.4 (NbO3)2
Authors: Ramirez M. O. , Jaque D. , Montes M. , Garcı́a Solé J. , Bausá L. E. , Ivleva L.
Published: April 2004

The temperature dependence of the emission spectrum of Cr3+ ions in Sr0.6Ba0.4 (NbO3)2 has been systematically investigated around the ferroelectric phase transition of this crystal (≈370 K). In spite of the strong thermal quenching of the luminescence occurring at these temperatures, the emission spectrum is still clearly detectable and shows dramatic changes in both line shape and intensity when passing through the phase transition temperature. A redshift of about 6 nm occurs when the crystal is driven from the polar to the nonpolar phase. In addition, this shift displays a thermal hysteresis, then providing the possibility of realizing a bistable spectral system based on this material.
Strain hardening of an amorphous matrix composite due to deformation- induced nanocrystallization during quasistatic compression
Authors: Lee Jae-Chul , Kim Yu Chan , Ahn Jae-Pyoung , Lee Sunghak , Lee Byeong-Joo
Published: April 2004

Some amorphous matrix composites reinforced with micron-sized crystalline phases exhibited strengthening behaviors during quasistatic compression. Homogeneous precipitation of nanocrystallites from the amorphous matrix is believed to be responsible for the observed strengthening phenomenon. According to a molecular dynamics simulation, quasistatic deformation can indeed promote the homogeneous precipitation of nanocrystallites, which, in turn, can serve as a reinforcing phase. Based on findings in this study, a strengthening mechanism operative in the amorphous matrix composite is proposed.
Microcavity lasing behavior of oriented hexagonal ZnO nanowhiskers grown by hydrothermal oxidation
Authors: Qiu Zhiren , Wong K. S. , Wu Mingmei , Lin Wenjiao , Xu Huifang
Published: April 2004

The highly aligned ZnO whiskers, which are grown by hydrothermal oxidation of metallic zinc plate in the presence of ethylenediamine molecules, exhibit single and/or a few modes of supernarrow spectral emissions (∼0.7 nm) at near 378 nm and negligible deep level defects emissions. Time-integrated and time-resolved photoluminescence show that the supernarrow spectral peaks are due to the laser action with an excitation threshold about 70 μJ/cm2 and emission lifetime of <30 ps. The lasing emission is highly polarized along the excitation laser polarization direction. The low lasing threshold, stable and regular supernarrow longitudinal modes, and strong lasing polarization effects can be well explained by the model of microcavity laser where the two end facets of whisker form the microcavity.
Phosphorus ion implantation and POCl3 doping effects of n+-polycrystalline-silicon/high-k gate dielectric (HfO2 and Al2O3) films
Authors: Lee Chihoon , Choi Jihoon , Cho Moonju , Jeong Doo Seok , Hwang Cheol Seong , Kim Hyeong Joon
Published: April 2004

Phosphorus (P)-doped polycrystalline-silicon gate/HfO2 or HfO2–Al2O3/p-type Si (100) metal–oxide–semiconductor capacitors were fabricated using either a POCl3 diffusion or an ion implantation technique to investigate the relationship between P penetration and the electrical properties of the high-k gate dielectric stacks. The HfO2–Al2O3 bilayer showed higher P diffusion blocking properties as a result of the 4.1-nm-thick amorphous interface layer including Al2O3 (or Al-silicate). The P ion-implanted sample with the HfO2–Al2O3 bilayer sample had the smallest leakage current density of −8.8×10−10 A/cm2 at −1 V, which was due to the lower P penetration, and the higher trap depth of approximately 1.3±0.02 eV compared to 0.9±0.02 eV of the sample with only HfO2. However, the P doping by POCl3 diffusion was too excessive and only very leaky devices were produced.
Directed nanostructural evolution in Ti0.8Ce0.2N layers grown as a function of low-energy, high-flux ion irradiation
Authors: Lee T.-Y. , Kodambaka S. , Wen J. G. , Twesten R. D. , Greene J. E. , Petrov I.
Published: April 2004

We use a combination of alloying and low-energy ion irradiation during film growth to controllably manipulate the nanostructure of TiN-based layers. Ti0.8Ce0.2N films are grown on SiO2 at 350 °C using UHV reactive magnetron sputtering in N2. The N2+-to-metal ratio incident at the growing film is maintained constant at 15, while the ion energy EN2+ is varied from 14 to 45 eV. Films grown with EN2+=14 eV consist of equiaxed nanograins with an average size of 2.0 nm, while layers deposited with EN2+=45 eV exhibit a 2-nm-wide nanocolumnar structure. In both cases, the films are dense, atomically smooth, and have strong 002 texture with low stress. This is in dramatic contrast to TiN films deposited under the same conditions, which are underdense with extremely rough surfaces and consist of broad (≃ 30 nm) columns. We attribute the formation of controlled nanostructures to the interplay between ion-irradiation-induced effects and thermally driven Ce surface segregation, leading to continuous renucleation during film growth.
Electron blocking and hole injection: The role of N,N′-Bis(naphthalen-1-y)-N,N′-bis(phenyl)benzidine in organic light-emitting devices
Authors: Zhang S. T. , Wang Z. J. , Zhao J. M. , Zhan Y. Q. , Wu Y. , Zhou Y. C. , Ding X. M. , Hou X. Y.
Published: April 2004

The current density-luminance-voltage characteristics of organic light-emitting devices (OLEDs) with N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl) benzidine (NPB) of various thicknesses as the hole transport layer have been investigated. It is found that for conventional structures of indium–tin–oxide/NPB/tris(8-hydroxyquinoline) aluminum (Alq3) (60 nm)/LiF (0.5 nm)/Al the optimal hole injection and luminescence efficiencies appear at NPB thicknesses of 5 and 20 nm, respectively. The large difference between the two optimal thicknesses suggests that the effective block of the NPB layer against electrons from across the Alq3/NPB interface is essential for high-efficiency operation of the OLEDs. The electron blocking effect of NPB is further confirmed by the electroluminescence (EL) behavior of devices with the structure of ITO/NPB(5 nm)/Alq3:4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) (30 nm)/NPB/Alq3(60 nm)/LiF(0.5 nm)/Al. The proportion of DCM EL to the whole EL decreases with increasing NPB thickness. This suggests that the NPB layer blocks electron transport to the Alq3:DCM layer. The Förster energy transfer from the 60 nm Alq3 layer to the DCM molecules is ruled out by the EL behavior observed after quenching excitons in the Alq3 layer. The origin of the difference in the optimal N,N′-Bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPD) thicknesses reported by other two different groups is also discussed.
Trilayer hybrid polymer-quantum dot light-emitting diodes
Authors: Chaudhary Sumit , Ozkan Mihrimah , Chan Warren C. W.
Published: April 2004

We report a trilayer hybrid polymer-quantum-dot light-emitting diode fabricated by sandwiching a CdSe-ZnS core–shell quantum-dot (QD) layer, a few monolayers thick, between films of polyvinylcarbazole (PVK) and an oxadiazole derivative (butyl-PBD). All the layers have been deposited by a controlled spin-coating technique. Stable aqueous dispersion of QDs has been prepared to make possible the spin coating of multiple layers without affecting the layer underneath. Our device shows 20 times the quantum efficiency (0.2%) and less than half the threshold voltage (5 V) of a single-layer device made from the PVK-QD-PBD blend. This is attributed to balanced carrier conduction, enhanced recombination, and reduced quenching of emission due to a better electro-optical device design.
Compression of Ti3Si0.5Ge0.5C2 to 53 GPa
Authors: Manoun Bouchaib , Liermann H. P. , Gulve R. P. , Saxena S. K. , Ganguly A. , Barsoum M. W. , Zha C. S.
Published: April 2004

Using a synchrotron radiation source and a diamond anvil cell, we measured the pressure dependence of the lattice parameters of a polycrystalline Ti3Si0.5Ge0.5C2 sample. Up to a pressure of 53 GPa, no phase transformations were observed. As for the isostructural hexagonal Ti3SiC2, the compressibility along the c axis was greater than along a. The bulk modulus is 183±4 GPa with a pressure derivative of 3.4±0.2. This work shows that the replacement of Si by Ge in Ti3SiC2 results in a systematic decrease in the bulk moduli.
Low-threshold amplified spontaneous emission and laser emission in a polyfluorene derivative
Authors: Liu X. , Py C. , Tao Y. , Li Y. , Ding J. , Day M.
Published: April 2004

The amplified spontaneous emission (ASE) and lasing properties of a fluorene copolymer PF3Cz film waveguide were investigated under optical pumping. Low ASE and lasing threshold were observed at 59 W/cm2/pulse and 1.7 KW/cm2/pulse, respectively. The stimulated emission cross section of the PF3Cz film was estimated to be approximately 1.6×10−16 cm2 at the ASE peak of 448 nm. The absorption cross section was estimated to be 2.8×10−16 cm2 at the absorption peak λ=370 nm. Gain and loss measurements at the ASE peak showed that the net gain coefficient reaches 26±1.7 cm−1 when pumped at 1.4 KW/cm2, and the loss coefficient of the waveguide was about 13±1.1 cm−1.
Vertically aligned conductive carbon nanotube junctions and arrays for device applications
Authors: Biswas Sujit K. , Vajtai Robert , Wei Bingqing , Meng Guowen , Schowalter Leo J. , Ajayan Pulickel M.
Published: April 2004

Electrical transport through high-density arrays of carbon nanotubes grown within vertical pores of anodized alumina was measured. Individual nanotubes were studied using conductive tip atomic force microscopy, with bias applied between the tip and platinum back electrode. Multiwalled nanotubes of diameter about 50 nm, with 5 nm thick walls were found to have a resistivity lower than 1.4×10−5 Ω m. A potential barrier was found to exist between the sensing tip and nanotube, resulting in nonlinear current–voltage characteristics. Low-resistance contact was formed by breaking down this barrier, once the circuit was stressed beyond 1.5 V.
Fast energy transfer in layer-by-layer assembled CdTe nanocrystal bilayers
Authors: Franzl T. , Koktysh D. S. , Klar T. A. , Rogach A. L. , Feldmann J. , Gaponik N.
Published: April 2004

We report on efficient resonant energy transfer in bilayers of water-soluble CdTe quantum dots. The bilayers of CdTe nanocrystals of two different sizes capped by short-chain thiols were formed by layer-by-layer assembly. Temporally and spectrally resolved fluorescence spectroscopy reveals spectral diffusion of the fluorescence signal for quantum dots within one layer as well as rapid (254 ps) energy transfer from layers of small dots to layers of larger dots, which is fast for nanocrystal pairs. Subspecies within the inhomogeneous distribution of donor nanocrystals even show energy transfer rates of (134 ps)−1 due to a large spectral overlap with acceptor nanocrystals.