bluuebunny/crossref_metadata_2025 huggingface dataset:
HLA typing and immunological characterization of young‐onset diabetes mellitus in a Hong Kong Chinese population
Authors: Kelly M. A. , Chan J. C. N. , Heward J. , Mijovic C. H. , Zimmet P. Z. , Yeung V. T. F. , Cockram C. , Barnett A. H.
Published: July 2002

SUMMARY

Aims  A study of the Hong Kong Chinese showed that the majority of subjects with young‐onset diabetes (age of diagnosis < 35 years) present with a phenotype suggestive of Type 2 diabetes mellitus, although up to 50% subsequently need insulin treatment. The aim of this study was to use a combination of clinical, genetic and immunological markers to characterize the disease phenotype further in such individuals and to determine whether the requirement for insulin is the result of autoimmune disease.

Methods  One hundred and thirty‐seven Hong Kong Chinese with young‐onset diabetes were studied, irrespective of their mode of presentation. The subjects were typed for alleles of the HLA‐DR and ‐DQ genes and investigated for the presence of autoantibodies to glutamic acid decarboxylase (GAD). Plasma C‐peptide concentration and requirement for insulin were also determined.

Results  One hundred and three subjects presented with a syndrome resembling Type 2 diabetes, while 34 presented with Type 1 diabetes. Of the former group, 35 patients (34.0%) were insulin‐deficient, 16 (15.5%) were insulin‐treated and seven (6.9%) were positive for GAD autoantibodies. Among the GAD‐positive subjects presenting with Type 2 diabetes, the HLA‐DRB1*03 allele may be a marker of early progression to insulin therapy.

Conclusions  Seven subjects with Type 2 diabetes at presentation had autoantibodies to GAD. Causes other than GAD autoimmunity, however, must be sought to explain the high prevalence of insulin deficiency observed in the Chinese patients. This study highlights the heterogeneity of the pathogenic processes leading to the diabetic phenotype.
Doppler ultrasound imaging: a new technique to detect lung hypoplasia before birth?
Authors: Laudy J. A. M. , Gaillard J. L. J. , Anker J. N. V. D. , Tibboel D. , Wladimiroff J. W.
Published: July 2002

Combined color‐coded Doppler and pulsed Doppler ultrasonography allows visualization 0f the fetal pulmonary circulation and study of pulmonary blood flow velocity waveforms. Systolic and diastolic changes were observed in fetal pulmonary artery flow velocity waveforms in a case of fetal pulmonary hypoplasia at 34 weeks of gestation. This observation supports our hypothesis that Doppler velocimetry can detect lung hypoplasia based on post‐ mortem examination of decreased total size of the pulmonary vascular bed, decreased number of pulmonary vessels per unit lung tissue and increased pulmonary vascular muscularization. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Patterns of Predation Risk and Survival of Bird Nests in a Chilean Agricultural Landscape
Authors: Willson Mary F. , Morrison Joan L. , Sieving Kathryn E. , De Santo Toni L. , Santisteban Leonard , Díaz Iván
Published: July 2002

Abstract: We used experimental nests baited with California Quail ( Callipepla californica) eggs or clay eggs to examine relative risks of nest predation in an agricultural landscape and in two large forest preserves in a south‐temperate rainforest in Chile. The most common predators, as identified by marks on clay eggs, were a caracara (  Milvago chimango), a blackbird (Curaeus curaeus), and rodents. Nest losses from predation were similar in large and small forest patches and lower in patches than in extensive forest. In general, predation risk was higher (and nest survival therefore lower) on forest edges than in forest interior, in short‐grass pasture than in tall‐grass pasture, in narrow corridors than in wide corridors, and on visible nests than on concealed nests. High predation risks in pasture habitat tended to increase the risk of nest predation in adjacent forest edges. For open‐cup nesters, the risk of nest predation was relatively high in the present agricultural landscape, indicating that much of the available wooded habitat (  forest edges, narrow corridors) offers poor nesting habitat, although it may be suitable for foraging and traveling. The numerous bird‐plant mutualisms in this landscape may be at risk if nesting success of the principal mutualists is consistently low.
Effects of Vigabatrin on Brain GABA+/CR Signals in Patients with Epilepsy Monitored by 1H‐NMR‐Spectroscopy: Responder Characteristics
Authors: Mueller S. G. , Weber O. M. , Duc C. O. , Weber B. , Meier D. , Russ W. , Boesiger P. , Wieser H. G.
Published: July 2002

Summary:  Purpose: Vigabatrin (VGB) is a new antiepileptic drug that increases the human brain γ‐aminobutyric acid (GABA) level by irreversibly inhibiting GABA transaminase. Although some patients respond to VGB with a significant seizure reduction, others do not. The aim of this study was to identify possible responders before or in an early phase of VGB treatment by measuring the GABA and homocarnosine contaminated with macromolecules/creatine and phosphocreatine ratio (GABA+/Cr) signal by means of proton‐nuclear magnetic resonance (1H NMR) spectroscopy.

Methods: Measurements were performed immediately before and after a titration period of 1 month (2 g/day during the past 2 weeks). A third measurement followed a maintenance period of 3 months (2 or 3 g/day). In 14 patients with drug‐resistant temporal lobe epilepsy and 3 patients with occipital lobe epilepsy, GABA+/Cr was measured in the ipsilateral (i.e., epileptogenic) hemisphere and contralateral (i.e., nonepileptogenic) hemisphere in a volume of 8 cm3.

Results: Depending on the therapeutic efficacy of VGB, we defined three groups: (a) full responders (n = 7), (b) nonresponders (n = 7), and (c) partial responders (n = 3). The nonresponders had no significant change in the GABA+/Cr signal during the treatment compared with baseline. The full responders had a significant increase of the GABA+/Cr signal during the whole treatment phase and a lower ipsilateral level at baseline. The partial responders had also a lowered ipsilateral GABA+/Cr signal at baseline and an increase during treatment but a decrease when the seizures started again.

Conclusions: Responders to VGB could be identified by a lower ipsilateral baseline GABA+/Cr signal and a steeper increase during VGB treatment. However, it was not possible to predict the duration of the response (full versus partial responder) with these criteria.
The Validation of a Mailed Health Survey for Screening of Dementia of the Alzheimer's Type
Authors: Ball Linda J. , Ogden Allison , Mandi Deepak , Birge Stanley J.
Published: July 2002

OBJECTIVE: To test the efficacy of a mailed health survey, which included the Clock Completion Test (CCT), to screen previously undiagnosed older adults for dementia of the Alzheimer's type (DAT) in a community‐dwelling population, and to determine whether the addition of selected risk factors for Alzheimer's disease (AD) would enhance the screening instrument's operating characteristics.

DESIGN: Comparison of the results of a self‐administered screen for DAT with the diagnosis of DAT by clinician evaluation or telephone interviews.

SETTING: A geriatric assessment clinic.

PARTICIPANTS: Three hundred and five women age 65 and older from St. Louis, Missouri.

MEASUREMENTS: The sensitivity and specificity of the CCT and the CCT plus risk factors for AD were evaluated using two standards: The Short Blessed Test (SBT) and the physician diagnosis of probable AD using National Institute of Neurological and Communicative Disorders and Stroke—Alzheimer's Disease and Related Disorders Association criteria.

RESULTS: Sensitivity and specificity for the CCT by SBT criteria were 63% and 79%, respectively. Using the physician's assessment as a criterion, the CCT had better sensitivity (67%) but poorer specificity (69%). Adding two or more risk factors for AD improved sensitivity and specificity to 71% and 89% and, in the physician assessment subgroup, to 75% and 87%, primarily by halving the false‐positive rate.

CONCLUSION: The combination of the simple, self‐administered CCT and two or more AD risk factors is a more effective screening instrument for DAT and potentially preclinical DAT than the CCT alone. However, the instrument may be better suited for use in an office setting because of a poor response rate by subjects with dementia.
RAPD Analysis Reveals Geographic Differentiations within Allium schoenoprasum L. (Alliaceae)
Authors: Friesen N. , Blattner F. R.
Published: July 2002

Abstract: Random amplified polymorphic DNA (RAPD) analysis was used to study the phylogenetic relationships between species in Allium section Schoenoprasum and for the investigation of the intraspecific differentiation of A. schoenoprasum. RAPD analysis of 39 samples representing eight species of sect. Schoenoprasum and one sample of A. atrosanguineum (sect. Annuloprasum) resulted in 233 interpretable RAPD bands. The analysis clearly distinguishes the species of section Schoenoprasum. The arrangement of the accessions of A. schoenoprasum in all dendrograms mirrors the geographical distribution, with a clear differentiation between an Asian and European subgroup. Within the European group, Scandinavian material is clearly distinct from S and E European material. Informally described morphological types of A. schoenoprasum could not be confirmed by RAPD analysis but represent recurrent ecological adaptations. A combination of phenetic (UPGMA, neighbour‐joining analysis), cladistic (parsimony analysis), and statistical (PCA) methods of data analysis resulted in clearer phylogenetic interpretations than each of the methods facilitates when used separately.
The Growth Response of Ecotypes of Holcus lanatus L. from Different Soil Types in Northwestern Europe to Phenolic Acids
Authors: Kidd P. S. , Proctor J.
Published: July 2002

Abstract: Phenolics are often discussed in relation to either allelopathy or to herbivory. This work, however, was undertaken to determine if phenolic acids benefit the growth of plants in very acid soils. We here report racial differences in the phenolic acid concentrations of the important plant species found in five sites within Central Scotland which covered a wide range in soil acidity from very acid (organic peats) to mildly acid (calcareous), and describe the racial differences in the growth response of Holcus lanatus L. to phenolic acids with increasing acidity. The total concentrations of phenolic acids in the ecotypes of important species were correlated with the total concentrations found in their respective soils. In general, the most phenolic‐rich ecotypes of the five came from the organic acid soils (Flanders Moss [FM] and Sheriffmuir [SMB]). However, with the exception of ferulic acid which was a major component of both acid soils and their associated vegetation, individual simple phenolic acids extracted from either plants or soils were not consistently correlated. The addition of dry plant material collected from the five sites (0.5 g plant material 100 g‐1 soil) to the acid‐organic Flanders Moss (FM) soil stimulated the growth of two ecotypes of Holcus (acid‐mineral Sheriffmuir [SMM], calcareous Kinloch Rannoch [KR]) but the same litter addition in non‐organic, less acidic or calcareous soil inhibited growth of these ecotypes. In hydroponic solutions, growth response of Flanders Moss (FM) and Kinloch Rannoch (KR) to pH and phenolic acid mixtures was interdependent: in acid solutions (pH 4.0) but not at pH 6.5 root elongation rates (RER) of both ecotypes, and shoot elongation rates (SER) of Flanders Moss (FM), increased after treatment with a mixture of seven commonly occurring phenolic acids.
Homology Assessment of the Boundary Tissue in Fruiting Bodies of the Lichen Family Sphaerophoraceae (Lecanorales, Ascomycota)
Authors: Döring H. , Wedin M.
Published: July 2002

Abstract: The ascoma ontogeny of the family Sphaerophoraceae is reviewed. The development of the boundary tissue in Leifidium tenerum is described and compared with similar structures in some other mazaediate representatives of the family (Sphaerophorus globosus, Bunodophoron dodgei and B. diplotypum), and with the non‐mazaedia‐producing genera Austropeltum and Neophyllis. The dominant structure in the base of mature ascomata in all genera is a boundary tissue forming the border between ascomatal (“generative”) and thalline (“vegetative”) tissue. In the mazaedia‐forming genera, the boundary tissue is composed of two layers. The upper layer is a zone of ascogenous hyphae, homologous to similar zones in Neophyllis and Austropeltum. The lower layer is a pseudoparenchymatic and often strongly pigmented zone formed by generative tissue, homologous to a zone of generative tissue present in Neophyllis but lacking in Austropeltum.
Evaluation of Morphological Variation in the Lichen Diploschistes ocellatus (Ascomycota, Ostropales): Evidence from Nuclear rDNA ITS Sequence Data
Authors: Martín M. P. , Winka K. , Llimona X. , Lumbsch H. T.
Published: July 2002

Abstract: A morphologically distinct population (var. almeriensis) of the lichen species Diploschistes ocellatus from southern Spain is examined using morphological and molecular methods. While the morphological examination revealed some unique features of var. almeriensis, the ITS sequence data did not support a distinction from D. ocellatus s. str. The Kishino‐Hasegawa test did not rule out trees distinguishing between the two morphotypes, although spectral analytical data support an inclusion of var. almeriensis in D. ocellatus. The influence of potentially erronously aligned ambiguous sites is evaluated by analysis of different alignments. However, all alignments agree in placing all specimens of D. ocellatus together and, consequently, in the consensus tree D. ocellatus s. lat. forms a monophyletic clade with high bootstrap support.
Compartmentation of Assimilate Fluxes in Leaves
Authors: Gamalei Y. V. , Pakhomova Marina V. , Syutkina Anna V. , Voitsekhovskaja Olga V.
Published: July 2002

Abstract: Leaf cell structures were studied in relation to assimilate export and storage in plant species with numerous plasmodesmata at the mesophyll/phloem interface (Coleus blumei, Cucurbita pepo) and in plants with a much reduced frequency of plasmodesmata (Pisum sativum, Helianthus annuus). Cold girdling of petioles and darkening of plants was used to induce changes in the levels of assimilates in the symplast and the apoplast of leaves. The volume of the endoplasmic reticulum in intermediary cells and of the vacuole in transfer cells showed changes corresponding to the experimental changes of photosynthate export. When export was blocked, the endoplasmic reticulum of intermediary cells collapsed in Coleus and Cucurbita, and the vacuoles of transfer cells enlarged in Pisum and Helianthus. These changes were accompanied by starch accumulation in the mesophyll cells of all species studied. Condensation of the cytosol in the transfer cells reminiscent of plasmolysis was observed under export blockage. Condensation of organellar matrixes in the intermediary cells was a usual (probably osmotic) response to cold girdling in the case of symplastic species. The data presented are discussed in relation to two basic pathways of assimilate flux in leaves of different groups of plants.
The Impact of Herbivory and Competition on Flowering and Survival during Saltmarsh Succession
Authors: Dormann C. F. , Bakker J. P.
Published: July 2002

Abstract: For succession, the establishment and turnover of plants, in terms of generative spreading and renewal, is of crucial importance. Especially the success of seedling establishment into the existing vegetation might be of prime importance for the further development of plant species composition. Flowering, on the other hand, is the necessary first step towards generative output and later seed set. In a chronosequential gradient of a saltmarsh succession, we investigated the performance of transplants of three common species under different conditions: Artemisia maritima, Atriplex portulacoides and Plantago maritima were transplanted as seedlings and mature plants into plots in early‐, mid‐, and late‐successional stages (15, 30 and 40 years) on the Dutch island of Schiermonnikoog. Natural herbivory (by hares and geese) and neighbourhood competition were excluded in a factorial design. Flowering and survival rates of the three species were generally greatly reduced under natural conditions, compared to competition‐ and herbivory‐free plots. The survival rates of Artemisia maritima and Plantago maritima reflect their position as early‐successional species: early in succession, both show their highest survival and abundance. For late‐dominant Atriplex portulacoides a different explanation has to be invoked for the medium‐high survival and low abundance: probably winter grazing by hares and the importance of a high nitrogen supply rate, rather than flowering and survival, determine its low abundance in the early and mid‐phase of this saltmarsh succession. Some long‐term impacts of herbivores affecting flowering and survival are discussed.
The Ultrastructure and Development of the Light Line in the Geraniaceae Seed Coat
Authors: Meisert A. , Schulz D. , Lehmann H.
Published: July 2002

Abstract: In 32 Geraniaceae species, we investigated the so‐called light line in the palisade layer of the seed coat. The light line is an incrustation of electron‐dense substances in the secondary cell wall. The existence of different gaps in the line and its complete absence near the chalazal area suggest that this cell wall structure is not responsible for hardseededness in the Geraniaceae seed coat. The multiple light line pattern within idioblasts of the palisade layer is characteristic of this cell type, named multiple light line (mll) cells. The palisade cells and their light line in Geraniaceae differ structurally from those in the Fabaceae.
Deposition of Cytokinesis‐Related Callose in Riella helicophylla and Arabidopsis thaliana. Effects of Photolytically Altered Nifedipine1
Authors: Scherp P. , Grotha R. , Kutschera U.
Published: July 2002

Abstract: The cytokinesis‐related callose deposition in cell plates and juvenile cross walls of meristematic cells was investigated in the liverwort Riella helicophylla and seedlings of Arabidopsis thaliana. The β‐1,3‐glucan callose was detected by its specific staining properties with sirofluor and aniline blue by fluorescence microscopy. The photo‐labile calcium antagonist nifedipine (NIF) exerted a specific promotive effect when the substance was exposed to light. The nitroso derivative of photolysed NIF was found to be the active compound which was responsible for the enhancement in callose deposition. The nitroso derivative was isolated after photolysis of NIF by UV light (365 nm) and its structure was verified with 1H‐nuclear magnetic resonance and infrared spectroscopy. The characteristic absorption maximum at 770 nm in dimethyl sulfoxide was employed to determine the concentration of the nitrosopyridine in solutions by use of the molar absorption coefficient of the isolated substance. In addition, the nitro derivative of nifedipine was prepared. This nitropyridine was ineffective with respect to the stimulation of callose deposition in dividing cells. The possible mechanism of this cytotoxic effect and its implications for symplastic growth in meristems is discussed.
Growth and Photosynthetic Carbon Metabolism in Tobacco Plants under an Oscillating CO2 Concentration in the Atmosphere
Authors: Chaves M. M. , Pantschitz E. , Schulze E.‐D.
Published: July 2002

Abstract: The hypothesis for the present work was that photosynthetic acclimation to increased atmospheric CO2 in Nicotiana tabacum could be prevented by an oscillating supply of CO2. This was tested by growing half of the plants (for the 20 day period after sowing) at 700 μmol mol‐1 CO2 (S+ plants) and half at 350 μmol mol‐1 CO2 (S‐ plants) and thereafter switching them every 48 h from high to low CO2 and vice versa. These plants were compared with plants continuously kept (from sowing onwards) at 350 μmol mol‐1 CO2 (C‐ plants) and 700 μmol mol‐1 CO2 (C+ plants). Switching plants from high to low CO2 and vice versa (S+ and S‐) did not improve plant growth efficiency, as hypothesized. The extra carbon fixed by the leaves under increased CO2 in the atmosphere, supplied either continuously or intermittently, was mostly stored as starch and not used to build additional structural biomass. The differences in final plant biomass, observed between S+ and S‐ plants, are explained by the CO2 concentration in the atmosphere during the first 20 days after sowing, the oscillation in CO2 supply thereafter is playing a smaller role in this response. Switching plants from high to low CO2 and vice versa, also did not prevent down‐regulation of photosynthesis, despite lower leaf sugar concentrations than in C+ plants. Nitrate concentration decreased dramatically in C+, S+ and S‐ plants. The leaf C/N ratio was highest in C+ plants (ranging from 8 to 13), intermediate in S+ and S‐ plants (from 7 to 11) and lowest in C‐ plants (from 6 to 8). This supports the view that the balance between carbohydrates and nitrogen may have a triggering role in plant response under elevated CO2. Carbon export rates by the leaves seem to be independent of total carbon assimilation, suggesting a sink limiting effect on tobacco growth and phototsynthesis under elevated CO2.
The Arabidopsis ISR1 Locus is Required for Rhizobacteria‐Mediated Induced Systemic Resistance Against Different Pathogens
Authors: Ton J. , van Pelt J. A. , van Loon L. C. , Pieterse C. M. J.
Published: July 2002

Abstract: In Arabidopsis thaliana, non‐pathogenic, root‐colonizing Pseudomonas fluorescens WCS417r bacteria trigger an induced systemic resistance (ISR) that is phenotypically similar to pathogen‐induced systemic acquired resistance (SAR). In contrast to SAR, WCS417r‐mediated ISR is controlled by a salicylic acid (SA)‐independent signalling pathway that requires an intact response to the plant hormones jasmonic acid (JA) and ethylene (ET). Arabidopsis accessions RLD1 and Ws‐0 fail to express ISR against Pseudomonas syringae pv. tomato and show enhanced disease susceptibility to this pathogen. Genetic analysis of progeny from crosses between WCS417r‐responsive and non‐responsive accessions demonstrated that ISR inducibility and basal resistance against P. syringae pv. tomato are controlled by a single dominant locus (ISR1) on chromosome III (Ton et al., 1999[294]). Here, we investigated the role of the ISR1 locus in ISR, SAR and basal resistance against three additional pathogens: Xanthomonas campestris pv. armoraciae, Peronospora parasitica and turnip crinkle virus (TCV), using accessions Col‐0 (ISR1), RLD1 (isr1) and Ws‐0 (isr1) as host plants.
Kinetics of solid phase epitaxy in thick amorphous Si layers formed by MeV ion implantation
Authors: Roth J. A. , Olson G. L. , Jacobson D. C. , Poate J. M.
Published: July 2002

The kinetics of solid phase epitaxy (SPE) have been measured in MeV ion-implanted amorphous Si layers up to 5 μm thick. Epitaxial crystallization in these layers occurs at a constant rate throughout the entire film, without loss of interface planarity or competition from random nucleation or twin formation. The activation energy for SPE in thick layers is found to be 2.70 eV, in excellent agreement with the value determined previously in much thinner films. The SPE kinetics are shown not to depend on the implant dose for doses up to 1000 times the threshold for amorphization. The presence of water vapor in the annealing ambient during SPE results in the indiffusion of hydrogen and a concomitant reduction of the SPE growth rate at distances as great as 2 μm from the surface. This effect may have important implications for the development of a microscopic model of the SPE process in silicon.
Sidewall damage in a silicon substrate caused by trench etching
Authors: Hamamoto Takeshi
Published: July 2002

The sidewall damage in a silicon substrate caused by trench etching has been investigated using deep level transient spectroscopy. In order to detect surface and near-surface modifications resulting from trench etching, a special device structure consisting of an n+/p junction array is used. It is found that three kinds of deep level are introduced onto the sidewall. The energy levels of these traps are Ec − 0.30 eV, Ev + 0.60 eV, and Ev + 0.66 eV, respectively. The deep level at Ev + 0.60 eV acts as a G-R center. The reverse current characteristics of the same device have three modes with activation energies of 0.59, 0.64, and 0.13 eV, respectively. These modes also result from the sidewall damage. It is found that a transformation of the sidewall damage occurs at 1000 °C. The G-R center and two of the reverse current modes disappear, but the damage is not completely annealed out because the others still remain.
InGaAs/InP long wavelength quantum well infrared photodetectors
Authors: Gunapala S. D. , Levine B. F. , Ritter D. , Hamm R. , Panish M. B.
Published: July 2002

We demonstrate the first long-wavelength quantum well infrared detector using the lattice-matched In0.53Ga0.47As/InP materials system. The responsivity has been found to be larger than that for similar GaAs/AlxGa1−xAs detectors.
A temporally resolved position sensing device for autofocusing
Authors: Shie Jin-Shown , Chang Gow-Dawn
Published: July 2002

A position-sensing method for autofocus purpose is demonstrated, based on the triangular ranging principle applied to a photoconductive Haynes–Shockley device. This method provides a linear variation of the minority-carrier transit time in the sensor with respect to the inverse of the object distance, or to the image distance to be adjusted from the focal point. Hence it can provide a convenient autofocusing control with a fully digital signal processing circuit. The principle of the autofocus triangular ranging is justified, and its resolution is analyzed with a p-type silicon photoconductor. The result shows that our method indeed can provide a high resolution and practically low cost autofocusing device for the camera industry.
An easy to build, high intensity monochromator for helium II radiation applied to inner valence photoelectron studies of small molecules
Authors: Baltzer P. , Göthe M. Carlsson , Wannberg B. , Karlsson L.
Published: July 2002

An easy to build, high intensity monochromator for helium II radiation is presented. The design includes a double focusing, nonblazed, toroidal grating with a groove density of 800 ℓ/mm. The adjustment and focusing properties of the design have been studied using an optical simulation program. It is found that all necessary adjustments of the grating may be performed by using only two degrees of freedom; rotation and sidewise shifting. Inner and outer valence photoelectron spectra of N2 and CO have been recorded using monochromatized HeIIα radiation. The study reveals extensive vibrational structures in the inner valence region of both molecules. A new state has been identified in the CO molecule.
Ultraviolet micro-Raman spectrograph for the detection of small numbers of bacterial cells
Authors: Chadha S. , Nelson W. H. , Sperry J. F.
Published: July 2002

The construction of a practical UV micro-Raman spectrograph capable of selective excitation of bacterial cells and other microscopic samples has been described. A reflective objective is used to focus cw laser light on a sample and at the same time collect the scattered light at 180°. With the aid of a quartz lens the image produced is focused on the slits of a spectrograph equipped with a single 2400 grooves/mm grating optimized for 250 nm. Spectra were detected by means of a blue-intensified diode array detector. Resonance Raman spectra of Bacillus subtilis and Flavobacterium capsulatum excited by the 257.2 nm output of a cw laser were recorded in the 900–1800 cm−1 region. Bacterial cells were immobilized on a quartz plate by means of polylysine and were counted visually. Cooling was required to retard sample degradation. Sample sizes ranged from 1 to 50 cells with excitation times varying from 15 to 180 s. Excellent spectra have been obtained from 20 cells in 15 s using a spectrograph having only 3% throughput.
A combined scanning tunneling, scanning force, frictional force, and attractive force microscope
Authors: Eng L. M. , Jandt K. D. , Descouts D.
Published: July 2002

We report on the adaptation of a commercially available scanning force microscope (SFM) for the simultaneous measurement of electrical and mechanical surface properties combining the scanning tunneling microscope, the SFM, and the friction force microscope. Furthermore, the microscope may be operated in the noncontact or attractive mode (AC-SFM) which is specially suited for the nondestructive investigation of soft sample surfaces.
Enhanced-efficiency spray extractor for sampling volatile organic compounds in aqueous systems
Authors: Nölke Birgit , Baykut Gökhan
Published: July 2002

The spray extractor for sampling volatile organic compounds in water, reported in Rev. Sci. Instrum. 63, 3196 (1992), has been modified and optimized for high extraction efficiencies. A low-flow spray nozzle is placed in the spray chamber, which produces very small droplets at water flow rates around 80 ml/min. Compounds extracted during a 2 min sampling period are trapped in a sorbent tube and analyzed by gas chromatography/mass spectrometry. With carrier gas (nitrogen) flow rates around 250 ml/min, spray-and-trap efficiencies up to 62% (tetrachloroethene) were achieved for various volatile organic compounds.
A high-brightness duoplasmatron ion source for microprobe secondary-ion mass spectrometry
Authors: Coath C. D. , Long J. V. P.
Published: July 2002

A cold-cathode duoplasmatron ion source for producing beams of Ar+ or O− has been designed for the Cambridge P7-Concept microprobe secondary-ion mass spectrometer. An experimental investigation of the performance of the ion source as a function of arc current, extraction potential, magnetic field, anode to extraction-electrode spacing and, in the case of O−, intermediate electrode bore diameter and lateral offset, is presented. The conditions giving maximum source brightness have been determined. Brightness measurements give 1700 and 96 A cm−2 sr−1 for Ar+ and O−, respectively. Focused probes 4.2 μm in diameter have been produced carrying current densities of 0.1 and 0.007 A cm−2 for Ar+ and O−, respectively.
Dielectric-insensitive capacitive differential pressure gauge for use at low temperature
Authors: Talbot Tokeem , Brisson J. G.
Published: July 2002

A capacitive differential pressure gauge for use at temperatures below 4 K is described. Fluid is admitted to two sample chambers with flexible walls to which a sensing capacitor is mechanically connected. Differential pressures between the chambers flex these walls and change the capacitance of the gauge. Because the capacitor is located outside these chambers, the gauge is insensitive to the dielectric variations of the fluid. Typical differential pressures of 105 Pa were measured with a common mode rejection ratio in excess of 50.
Angle-resolving electron-electron coincidence setup
Authors: Wehlitz R. , Pibida L. S. , Levin J. C. , Sellin I. A.
Published: July 2002

We introduce a novel angle-resolving electron-spectrometer system for coincidence studies of gas-phase targets using the timing structure of synchrotron radiation. The experimental setup, mainly consisting of a cylindrical mirror analyzer with a position sensitive detector and an electron time-of-flight spectrometer is particularly useful in cases where low-kinetic-energy electrons are measured in coincidence with high-kinetic-energy electrons. The experimental method and corresponding electronics are discussed. As an example, we present argon LMM Auger electron spectra taken in coincidence with KL2,3L2,3 and KL1L2,3 Auger electrons after resonant 1s→4p photoexcitation.
Materials selection for the in situ mirrors of laser diagnostics in fusion devices
Authors: Voitsenya Vladimir S. , Konovalov Vladimir G. , Becker Michael F. , Motojima Osamu , Narihara Kazumichi , Schunke Beatrix
Published: July 2002

When mirrors for the laser scattering diagnostic for large fusion devices need to be inside the vacuum chamber, they are subjected to irradiation by multiple high-energy laser pulses and bombardment by charge exchange atoms. Both of these assaults are known to degrade and eventually damage metal laser mirrors given sufficient time and flux. Our aim in this article is to use current data on these damage mechanisms to make design selections of metal mirror materials for application in fusion device diagnostics. We identify tradeoffs between low sputtering rates and multipulse laser damage resistance in candidate metals. The data for multipulse laser damage are incomplete and extend to a maximum of only 104 shots for a few metals. However, there is a clear trend of decreasing laser-damage threshold with increasing number of shots, and damage threshold fluences can fall to 10% of the single-pulse damaging laser fluence. Further experiments up to 106 or 108 laser shots need to be conducted on the likely mirror candidate metals for use in new plasma devices. We define a figure-of-merit based on current laser damage data and employ it in our analysis. Recent data on the sputtering yield and reflectance degradation of metal mirrors give a different priority ranking of candidate metals. Overall, the preferred material selection depends on the number of laser shots and the number of plasma pulses that the mirror must endure before replacement is allowed. For example, we find that for conditions typical of the LHD (10 s plasma pulses with a 10 Hz laser PRF), Au, Ag, and Cu are candidate materials if mirrors are replaced after 103 plasma pulses; Au and Rh are candidates if the replacement interval is 104 pulses; and if the replacement interval is further increased to 105 plasma pulses, then Mo is the candidate material. Other materials might also be candidates but the data on them are still insufficient.
A new data acquisition system for measuring the movement of atmospheric speckle patterns
Authors: Li Ruiming , Takabe Masao , Aruga Tadashi
Published: July 2002

To measure the movement of atmospheric speckle patterns, we establish a new data acquisition system that consists of a 50 cm telescope, an intensified charge-coupled device (ICCD) camera, a photomultiplier with a pinhole, and two personal computers (PCs) including data acquisition hardware. This system is easy to establish and allows the capture of a high-resolution image. A simple positioning method of the pinhole in front of the photomultiplier is introduced. With 1500 pairs of the measurement data samples, a clear correlation peak can be found by processing them according to the general definition of correlation. Some measurement and analysis results are given.
Phase locked 270–440 GHz local oscillator based on flux flow in long Josephson tunnel junctions
Authors: Koshelets Valery P. , Shitov Sergey V. , Filippenko Lyudmila V. , Vaks Vladimir L. , Mygind Jesper , Baryshev Andrey M. , Luinge Willem , Whyborn Nick
Published: July 2002

The combination of narrow linewidth and wide band tunability makes the Josephson flux flow oscillator (FFO) a perfect on-chip local oscillator for integrated sub-mm wave receivers for, e.g., spectral radio astronomy. The feasibility of phase locking the FFO to an external reference oscillator is demonstrated experimentally. A FFO linewidth as low as 1 Hz (determined by the resolution bandwidth of the spectrum analyzer) has been measured in the frequency range 270–440 GHz relative to a reference oscillator. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. The results of residual FFO phase noise measurements are also presented. Finally, we propose a single-chip fully superconductive receiver with two superconductor–insulator–superconductor mixers and an integrated phase-locked loop.
Al
x
Ga
1−x
N
(0⩽x⩽1) ultraviolet photodetectors grown on sapphire by metal-organic chemical-vapor deposition
Authors: Walker D. , Zhang X. , Saxler A. , Kung P. , Xu J. , Razeghi M.
Published: July 2002

Al x Ga 1−x N (0⩽x⩽1) ultraviolet photoconductors with cutoff wavelengths from 365 to 200 nm have been fabricated and characterized. The maximum detectivity reached 5.5×108 cmHz1/2/W at a modulating frequency of 14 Hz. The effective majority carrier lifetime in AlxGa1−xN materials, derived from frequency-dependent photoconductivity measurements, has been estimated to be from 6 to 35 ms. The frequency-dependent noise spectrum shows that it is dominated by Johnson noise at high frequencies for low-Al-composition samples.
Jumping mode scanning force microscopy
Authors: de Pablo P. J. , Colchero J. , Gómez-Herrero J. , Baró A. M.
Published: July 2002

In this letter, we present a new scanning probe microscopy mode, jumping mode, which allows the simultaneous measurement of the topography and of some other physical property of the sample. Essentially, at each image point first the topography of the sample is measured during a feedback phase of a cycle, and then the tip–sample interaction is evaluated in real time as the tip is moved away and towards the sample. Since the lateral motion is done out of contact the method is free, or nearly free, of shear forces. The general advantages of jumping mode are discussed. Finally, two different applications of this mode are presented. In addition to the topography, the first application measures the adhesion between the tip and the sample, while the second determines the corresponding electrostatic interaction.
Electro-optic modulation in crystal-ion-sliced z-cut LiNbO3 thin films
Authors: Ramadan Tarek A. , Levy M. , Osgood R. M.
Published: July 2002

Electro-optic modulation is demonstrated in 10-μm-thick single-crystal LiNbO3 films obtained by crystal ion slicing. This technique uses ion implantation of single-crystal bulk samples followed by selective etching. The measured electro-optic response of these films is comparable, within experimental error, to that of single-crystal bulk LiNbO3 and is superior to previously reported values for epitaxial polycrystalline thin films. The product of half-wave voltage and modulator length, VπL, is 8 V cm. Post lift-off annealing is shown to be of key importance in improving the modulator extinction ratio.
Binary condensation in a supersonic nozzle
Authors: Wyslouzil Barbara E. , Heath Christopher H. , Cheung Janice L. , Wilemski Gerald
Published: July 2002

We present data from the first systematic studies of binary condensation in supersonic nozzles. The apparatus used to conduct the experiments is described in detail, and the important issues of stability and reproducibility of the experiments are discussed. Experiments were conducted with water, ethanol, propanol, and binary mixtures of these compounds. Onset was determined in the temperature range of 190–215 K, and for each mixture composition the pressures of the condensible species at an onset temperature of 207 K were determined. For the ideal ethanol–propanol mixtures, the onset pressures at constant temperature vary almost linearly between those of the pure components. In contrast the isothermal onset pressures for the nonideal water–ethanol and water–propanol mixtures lie below the straight line joining the pure component values. This large reduction in the total pressure of condensible at onset for the aqueous alcohol mixtures is indicative of a strong mutual enhancement in the particle formation process.
Modeling of organic thin film transistors of different designs
Authors: Necliudov P. V. , Shur M. S. , Gundlach D. J. , Jackson T. N.
Published: July 2002

We report on modeling of direct current (DC) characteristics of organic pentacene thin film transistors of different designs. Our model incorporates a gate-voltage dependent mobility and highly nonlinear drain and source contact series resistances. The contact nonlinearities are especially pronounced in bottom source and drain contact thin film transistors. The model successfully reproduced both below- and above-threshold characteristics of top source and drain contact and bottom source and drain contact organic pentacene thin film transistors.
Self-assembled DNA networks and their electrical conductivity
Authors: Cai Lintao , Tabata Hitoshi , Kawai Tomoji
Published: July 2002

We report direct measurements of the intrinsic electrical characteristics of polynucleotides using a conducting-probe atomic-force microscope under vacuum. Poly(dA)⋅poly(dT) self-assemble a cross-interlaced network on mica, but poly(dG)⋅poly(dC) self-organize a uniform two-dimensional reticulated structure. Transport studies demonstrate that poly(dG)⋅poly(dC) can act as a semiconducting nanowire and show a better conductance than that in poly(dA)⋅poly(dT).
Local anisotropy in incompressible magnetohydrodynamic turbulence
Authors: Milano L. J. , Matthaeus W. H. , Dmitruk P. , Montgomery D. C.
Published: July 2002

It is a well known fact that in the presence of a dc applied magnetic field, magnetohydrodynamic (MHD) turbulence develops spectral anisotropy from isotropic initial conditions. Typically, the reduced spectrum is steeper in the direction of the magnetic field than it is in any transverse direction. One might expect that a dc field is not essential, and it is the local mean field that is responsible. To address this issue, three-dimensional MHD pseudo-spectral incompressible relaxation simulations are performed, and structure functions computed according to whether the separation is parallel to, or transverse to, the local mean magnetic field. Correlation lengths are longer in the locally averaged magnetic field direction than in any perpendicular direction, even when the global mean magnetic field is zero. Local anisotropy is observed to be stronger in regions of strong magnetic field. A general definition of anisotropy angles and a methodology to study local anisotropy are proposed.
High-resolution x-ray crystal spectrometer/polarimeter at torus experiment for technology oriented research-94
Authors: Weinheimer J. , Ahmad I. , Herzog O. , Kunze H.-J. , Bertschinger G. , Biel W. , Borchert G. , Bitter M.
Published: July 2002

A high-resolution x-ray polarimeter has been installed at the torus experiment for technology oriented research (TEXTOR-94). The instrument consists of two spectrometers in Johann geometry, utilizing the dependence of Bragg reflection on the polarization. The dispersion plane of the so-called horizontal spectrometer coincides with the midplane of the tokamak, whereas the dispersion plane of the so-called vertical spectrometer lies perpendicular to the midplane of the tokamak. Both spectrometers operate with cylindrically bent quartz crystals of dimensions 153 mm×38 mm×0.7 mm with a 2d spacing of 4.9130 Å. The radii of curvature of the horizontal and vertical spectrometer crystals are 3820 mm and 4630 mm, respectively. The detectors are multiwire proportional counters having a large entrance window of 180 mm×90 mm, with a high count rate capability of up to 2.5×105 photons/s, and a spatial resolution of 0.4–0.65 mm, depending on the count rate. The unique data acquisition system makes it possible to record up to 8192 spectra per TEXTOR-94 discharge to study fast events and impurity transport. The instruments are sensitive to spurious amounts of argon in hydrogen or deuterium discharges and aim for x-ray polarization measurements and other core plasma diagnostics like electron temperature, ion temperature, plasma rotation, impurity transport, and relative abundance of Ar15+/Ar16+. The first measurements of toroidal rotation speed, ion and electron temperatures show a very good agreement with charge exchange recombination spectroscopy (XRS) and electron cyclotron emission (ECE) diagnostics available at TEXTOR-94. The measured values of the ratio Ar15+/Ar16+ are higher than that predicted from coronal equilibrium. The ratio depends strongly upon the electron density both for ohmic and neutral beam injection cases. This suggests that the charge state distribution is also dependent on diffusion and charge exchange processes in the plasmas.
Efficient argon K-shell radiation from a Z pinch at currents >15 MA
Authors: Sze H. , Coleman P. L. , Banister J. , Failor B. H. , Fisher A. , Levine J. S. , Song Y. , Waisman E. M. , Apruzese J. P. , Clark R. W. , Davis J. , Mosher D. , Thornhill J. W. , Velikovich A. L. , Weber B. V. , Coverdale C. A. , Deeney C. , Gilliland T. L. , McGurn J. , Spielman R. B. , Struve K. W. , Stygar W. A. , Bell D.
Published: July 2002

The first observations of gaseous load implosions with over 15 MA in >110 ns on the Z generator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] are reported. Starting from a diameter of over 8 cm, an argon double-shell Z pinch imploded to under 0.5 cm K-shell emission diameter. With a load mass of 0.8 mg/cm, K-shell x-ray output reached 274±24 kJ in a 15 TW peak power, 12 ns pulse. This record-high yield is consistent with the current-squared scaling predicted for the “efficient” emission regime.
Versatile beam calorimeter with a heat flux sensor
Authors: Kudomi N. , Itahashi T. , Takahisa K. , Yoshida S. , Komori M.
Published: July 2002

A versatile calorimeter has been developed to study astrophysical S factors for fusion reactions with gaseous targets. The number of incident projectiles are deduced from the deposited power. The principal technique employed here is based on the heat flux sensor output transferred linearly from the heat flow. Absolute values at various energies are obtained by calibration with current measurements by using a Faraday cup. This calorimeter is presently applied in measurement of the solar 3He+3He fusion reaction with an accuracy better than 2%.
Semiconductor 1/f noise from dynamic coupling of charge carriers and lattice
Authors: Pfeiffer Carl
Published: July 2002

A quantum mechanical model of an intrinsic semiconductor is used to derive the coupled dynamics of the lattice and charge carriers. It is shown that a source of noise current is proportional to vibration displacement of the lattice, and that ground state of this motion has the (1/frequency) power spectrum at frequencies below the lattice vibration frequency and a (1/frequency squared) form above that frequency. The voltage drop across a three-dimensional semiconductor sample is calculated by assuming that the random noise currents in the lattice sites are uncorrelated. The resulting power spectral density of the noise current in a sample has a form similar to the well-known Hooge formula. The scale factor is not a universal constant but instead depends upon the lattice vibration frequency, charge carrier mean-free-path and drift velocity, number of carriers per lattice site, and mass of a lattice atom. Calculated values with reasonable semiconductor parameters are consistent with those obtained from other theories of 1/f noise.
Sharp-line luminescence and absorption in ZnGeP2
Authors: Rablau C. I. , Giles N. C.
Published: July 2002

Photoluminescence and optical absorption spectroscopies have been used to study bulk ZnGeP2. Two sharp zero-phonon lines with opposite polarizations are resolved in emission at 1.7849 eV (at 70 K) and 1.7784 eV (at 5 K), respectively. Thermalization occurs between these two lines, suggesting a split excited state of the center. Considerable structural detail is resolved in the vibronic sidebands of these lines, revealing phonon energies of 6.3±0.1 meV and 43.7±0.1 meV. Similar phonon energies are resolved in low-temperature absorption spectra. These results for ZnGeP2 are explained by a model of radiative recombination of excitons bound to an isoelectronic defect center. The observed polarization behavior of the sharp-line spectra can be produced by the built-in tetragonal distortion along the c axis associated with the chalcopyrite structure.