bluuebunny/crossref_metadata_2025 huggingface dataset:
An audit of nutritional supplement distribution and consumption on a care of the elderly ward
Authors: Ross F.
Published: July 2002

Background: Malnutrition in hospital is often an unrecognized problem which can affect recovery from illness or injury and highlights the need for comprehensive training on clinical nutrition. One group at high risk of malnutrition are the elderly and several studies have described how dietary supplementation with oral sip feeds can improve the outcome in this group of patients.

Aim: The aim of this audit was to establish how much of the prescribed volume of oral sip feed was offered to and consumed by the patients on an acute 35‐bed care of the elderly ward over a 12‐day period including one weekend.

Methods: A standard pro‐forma was used to record what supplements had been prescribed, what had been offered to the patient and what volume had been consumed.

Results: Not all patients received the supplements prescribed and 39% of patients who did receive a supplement consumed none or hardly any of it. Forty‐three per cent consumed nearly all of the supplement provided, similar to the results from other studies.

Conclusions: The study highlighted the need for training of ward staff about the preparation and distribution of supplements.
Detection of movement at the erythrocyte's edge by scanning phase contrast microscopy
Authors: Bitler A. , Barbul A. , Korenstein R.
Published: July 2002

A time‐dependent set of line scans across an erythrocyte was recorded by a phase contrast laser scanning microscope. A method for edge detection, based on a two‐stage fitting procedure of the theoretical intensity distribution in a line scan of phase contrast image to the experimental one, is suggested. Time‐resolved fluctuations of the human erythrocyte's edge were obtained, employing this method. The same procedure was carried out for a metallic strip yielding a test for the background noise level. The suggested method was applied in examining the effect of chemical crosslinking and thiol reduction on cell membrane fluctuations of human erythrocytes.
SEARCH international case–control study of childhood brain tumours: role of index pregnancy and birth, and mother’s reproductive history
Authors: McCredie  , Little  , Cotton  , Mueller  , Peris‐Bonet  , Choi  , Cordier  , Filippini  , Holly  , Modan  , Arslan  , Preston‐Martin
Published: July 2002

A series of co‐ordinated population‐based case–control studies of childhood brain tumours (CBT) was undertaken under the auspices of the Surveillance of Environmental Aspects Related to Cancer in Humans (SEARCH) programme of the International Agency for Research on Cancer (IARC) to evaluate, inter alia, the risk in relation to characteristics of the index pregnancy and birth, and maternal reproductive history. Subjects comprised 1218 cases aged 0–19 years and 2223 controls. Risk estimates were calculated by unconditional logistic regression, adjusted for age, sex, centre and mother’s years of schooling, for all types of CBT combined as well as for four groups defined by histopathology (astroglial tumours, primitive neuroectodermal tumours of the brain, ‘other glial’ tumours and ‘other histological types’) and for five age groups (0–1, 0–4, 5–9, 10–14, 15–19 years). Use of anaesthetic ‘gas’ was associated with an increased risk of CBT (OR = 1.5, 95% CI [1.1, 2.0]), apparent in children aged 0–4 years (OR = 2.4, 95% CI [1.4, 4.1]) and for astroglial tumours (OR = 1.6, 95% CI [1.1, 2.2]) with non‐significantly increased relative risks for each of the other histological groups. However, not all centre‐specific relative risks were elevated. No other aspect of the index pregnancy, delivery and early neonatal period or of the mother’s previous reproductive history was associated with risk for CBT.
Peripheral Blood T‐Cell Receptor β‐Chain V‐Repertoire in Atopic Dermatitis Patients After In Vitro Exposure to Pityrosporum orbiculare Extract
Authors: JOHANSSON C. , JEDDI‐TEHRANI M. , GRUNEWALD J. , TENGVALL LINDER M. , BENGTSSON Å. , HALLDÉN G. , SCHEYNIUS A.
Published: July 2002

The yeast Pityrosporum orbiculare belongs to the normal cutaneous flora but is also considered to be one of the factors that may contribute to atopic dermatitis (AD). In the present study we investigated the possibility that P. orbiculare can act with superantigen activity in AD. P. orbiculare‐reactive T‐cell lines (TCLs) were obtained after stimulation of peripheral blood mononuclear cells (PBMC) with P. orbiculare extract. T‐cell receptor β‐chain V‐segment (TCRBV) usage was investigated using monoclonal antibodies and flow cytometry. We could not find any difference in TCRBV usage between AD patients (n = 10) and healthy controls (n = 5), either in fresh PBMC or in P. orbiculare‐reactive TCLs. Compared with their original PBMCs the P. orbiculare‐reactive TCLs showed a decreased usage of several TCRBVs, although increased usage of certain TCRBVs could be seen in some of the individuals. Further analysis of the CDR3‐length polymorphism exhibited a shift in CDR3‐length distribution, indicating oligoclonal expansion of T cells specific to different antigens in the P. orbiculare extract. In conclusion we have not found any evidence for superantigen activity in P. orbiculare extract, but our data support the importance of classical major histocompatibility complex (MHC)‐restricted allergens in P. orbiculare.
High Peptide Affinity for MHC Class I does not Correlate with Immunodominance
Authors: Müllbacher A. , Lobigs M. , Yewdell J. W. , Bennink J. R. , Tha Hla R. , Blanden R. V.
Published: July 2002

Cytotoxic T (Tc)‐cell responses against influenza virus infection in BALB/c (H‐2d) mice are dominated by Tc clones reactive to the viral nucleoprotein (NP). Here, we report investigations using recombinant vaccinia viruses (VV) encoding major histocompatibility complex (MHC) class I H‐2Kd molecules differing by a single amino acid from glutamine (wild‐type, Kdw) to histidine (mutant, Kdm) at position 114 located in the floor of the peptide‐binding groove. Influenza‐infected target cells expressing Kdw were strongly lysed by Kd‐restricted Tc cells against A/WSN influenza virus or the immunodominant peptide of viral NP (NPP147–155), whereas infected Kdm‐expressing targets gave little or no lysis, respectively, thus showing the immunodominance of NPP147–155. Kdm‐expressing target cells saturated with synthetic NPP147–155 (10−5 m) were lysed similarly to Kdw‐expressing targets by NPP147–155‐specific Tc cells. Thus the defect in influenza‐infected Kdm‐expressing targets was quantitative; insufficient Kdm–peptide complexes were expressed. Tc‐cell responses against four other viruses or alloantigens showed no effect of Kdm. When peptide transport‐defective cells were infected with VV‐Kdw or VV‐Kdm and co‐infected with a recombinant VV encoding an endoplasmic reticulum‐targeted viral peptide, two influenza haemaglutinin peptides caused higher expression of Kdw than NPP147–155 indicating their higher affinity for Kdw. These results are inconsistent with the hypothesis that immunodominance in the anti‐influenza response reflects high affinity of the immunodominant peptide, but are consistent with skewing of the Tc‐cell receptor repertoire.
Contrast‐enhanced Doppler ultrasound for renal artery stenosis
Authors: Bourke Rj Dowling, Mk House, Pm King, Jl , Gibson RN
Published: July 2002

The use of renal artery Doppler ultrasound for the diagnosis of renal artery stenosis is a well‐established technique in selected populations, but the technical failure rate of the examination leading to incomplete studies is a major drawback. The results of ultrasound contrast‐enhanced renal artery Doppler for renal artery stenosis, using the echo‐enhancing agent, Levovist, are reported here. Sixteen patients (22 arteries) were examined with Levovist. The technical success rate of these examinations was 91%, and all four renal artery stenoses were correctly identified. It is concluded that the use of ultrasound contrast (Levovist) increases the technical success rate of renal artery Doppler ultrasound in this setting, with similar accuracy to unenhanced Doppler examinations.
Molecular genetics of diabetes mellitus in Chinese subjects: identification of mutations in glucokinase and hepatocyte nuclear factor‐1α genes in patients with early‐onset Type 2 diabetes mellitus/MODY
Authors: Ng M. C. Y. , Cockburn B. N. , Lindner T. H. , Yeung V. T. F. , Chow C. ‐C. , So W. ‐Y. , Li J. K. Y. , Lo Y. M. D. , Lee Z. S. K. , Cockram C. S. , Critchley J. A. J. H. , Bell G. I. , Chan J. C. N.
Published: July 2002

Aims To examine the prevalence of identified MODY‐related genes in Chinese subjects with early onset Type 2 diabetes mellitus and a positive family history of diabetes and to look for possible associations between the gene mutations and the development of diabetes.

Methods Ninety‐two unrelated Chinese subjects with diabetes diagnosed before the age of 40 years who had a positive family history of diabetes were screened for mutations in hepatocyte nuclear factors (HNF‐1α and HNF‐4α) and glucokinase genes by direct sequencing. The family members of patients with mutations and 100 healthy controls were also examined.

Results Mutations in the HNF‐1α and the glucokinase genes were found in 5% and 3% of the diabetic subjects, respectively but no mutations were found in the coding region of the HNF‐4α gene. Three mutations found in the glucokinase gene were novel missense mutations (I110T, A119D and G385V). The mutations in the HNF‐1α gene were also new and included four missense mutations (G20R, R203H, S432C, I618M) and one splice acceptor site mutation (IVS2nt‐1G→A). Patients with mutations in these genes were clinically heterogeneous with respect to phenotype and basal pancreatic beta cell function.

Conclusions Genetic factors such as mutations in the HNF‐1α and glucokinase genes may be important in the development of diabetes in Chinese people, especially when the disease is of early onset.
Fetal akinesia deformation sequence: behavioral development in a case of congenital myopathy
Authors: Mulder E. J. H. , Nikkels P. G. J. , Visser G. H. A.
Published: July 2002

Objective

To monitor behavioral development in a fetus affected by the Pena—Shokeir phenotype due to fetal akinesia deformation sequence of myogenic origin.

Methods

Fetal behavioral development was studied sonographically in a fetus suspected of having fetal akinesia deformation sequence, between 15 and 35 weeks of gestation at 1–4‐week intervals.

Results

Fetal body movements were quantitatively and qualitatively abnormal from 28 weeks onwards. Behavioral deterioration coincided with the observation of structural anomalies such as club feet. Fetal heart rate and its variation remained within normal limits and showed normal ultradian cyclicity, but the temporal linkage between body movements and heart rate pattern worsened with advancing gestation. Breathing movements, although present until the end of pregnancy, became increasingly shallow.

Conclusion

Our results provide sound evidence that the trajectory of behavioral development with fetal akinesia deformation sequence, which has been hypothesized to occur in man exclusively on the basis of retrospective analyses and animal experiments, does indeed take place. Copyright © 2001 International Society of Ultrasound in Obstetrics and Gynecology
Prenatal ultrasound diagnosis of Leroy I cell disease
Authors: Lees C. , Homfray T. , Nicolaides K. H.
Published: July 2002

Leroy I cell disease is a rare autosomal recessive disorder which progressively leads to death within the first decade of life. Invasive prenatal diagnosis is possible but is only undertaken in families who have previously had an affected child. We describe the antenatal ultrasound diagnosis of the disease in a case referred at 30 weeks' gestation for suspected polyhydramnios. Copyright © 2001 International Society of Ultrasound in Obstetrics and Gynecology
Clonal Diversity in Differently‐Aged Populations of the Pseudo‐Annual Clonal Plant Circaea lutetiana L.
Authors: Verburg R. , Maas J. , During H. J.
Published: July 2002

Abstract: In many clonal plant species seedling recruitment is restricted to short colonization episodes early in the development of the population, and clonal diversity (i.e., genet diversity) in the population is expected to decrease with increasing population age. In established populations of the pseudo‐annual Circaea lutetiana seedling recruitment has previously not been observed. Therefore, we expected established populations to have low clonal diversities. We analysed number and frequency of genets and spatial distribution of genets in six differently‐aged C. lutetiana populations with the use of four informative RAPD primers. We found relatively low clonal diversities in young populations but very high clonal diversities in established populations. Therefore, the hypothesis was rejected that seedling recruitment does not occur in established populations. Moreover, we did not find large genet size asymmetries in established populations. Genet size differences can be caused by stochastic processes or by fitness related traits, such as differences in vegetative reproduction. Because vegetative propagation of ramets is dependent on ramet size, and the number of ramets and the size of each ramet determine genet size, we expected that large genets produced, on average, large ramets. However, this was not the case, suggesting that stochastic processes caused genet size differences. Genet size may also be bounded if spatial distribution of genets is affected by micro‐habitat differences. For this we expected to find a clumped spatial distribution of ramets of the same genet. However, ramets of large genets were always found intermingled with ramets belonging to other genets.
Offspring Performance in Oxalis acetosella, a Cleistogamous Perennial Herb
Authors: Berg H. , Redbo‐Torstensson P.
Published: July 2002

Abstract: Seed weight, seed germination, seedling survival, and juvenile/adult fitness in chasmogamously (CH) and cleistogamously (CL) derived offspring of Oxalis acetosella were compared during three growing seasons, to test hypotheses of fitness differences between the offspring types accounting for the maintenance of cleistogamy. In plots at three field sites, CH and CL seeds originating from all sites were sown to compare the performance of offspring growing in their habitat of origin and offspring growing in new habitats. Seeds were also sown in pots in a common garden, to test for effects of sibling competition. CL seeds had significantly lower germination than CH seeds in the field, possibly because of lower mean seed weight due to later flowering. Since the outcrossing rate in the CH flowers of O. acetosella is not known, it is uncertain whether the lower CL germination is a consequence of inbreeding depression. CH seeds had higher germination if sown at their home sites than at new sites, while for CL seeds this made no difference; this contradicts the local adaptation hypothesis for cleistogamy. No other fitness differences were found between the offspring types, and the findings did not support the sibling competition or local adaptation hypotheses. We suggest that the maintenance of the dimorphic reproductive system in O. acetosella is not explained by offspring characteristics, but rather by the two flowering phases complementing each other in maximizing annual seed production in the face of environmental variability. It is, therefore, important to include temporal and spatial variation in studies of reproductive strategies.
Juvenile Development of the Cyanolichen Lobaria scrobiculata and the Green Algal Lichens Platismatia glauca and Platismatia norvegica in a Boreal Picea abies Forest
Authors: Hilmo O. , Ott S.
Published: July 2002

Abstract: Juvenile development from sown vegetative diaspores of the cyanobacterial lichen Lobaria scrobiculata and the green algal lichens Platismatia glauca and P. norvegica was studied through a four‐year field experiment in a boreal spruce forest. All three species developed juvenile thalli within the period of observation. The largest lobules of L. scrobiculata and Platismatia were 0.4 mm and 1.3 mm, respectively, four years after sowing the diaspores. The first very tiny lobule (0.1 mm) of L. scrobiculata was observed 29 months after sowing the soredia. This period of juvenile development is the longest period so far reported for lichens. A long phase of dormancy, after the diaspores were attached to the substrate, was characteristic for the investigated species. Apical growth of the isidia of Platismatia glauca and P. norvegica was not observed until 21 months after sowing. Low light levels, low temperatures and snow covering the diaspores during winter, causes a short growth season in boreal spruce forests. These factors might explain the long period for juvenile development. The results indicate a slow rate of colonization of a new habitat for the investigated species since they need several years to grow to visible thalli.
Analysis of thermal stress-induced grain boundary cavitation and notching in narrow Al-Si metallizations
Authors: Li Che-Yu , Black Ronald D. , LaFontaine William R.
Published: July 2002

Grain boundary voiding and notching have been found to produce failures in narrow metallizations during thermal aging. The nucleation and growth of grain boundary voids are considered to occur as a result of grain boundary sliding and the subsequent stress-induced mass transport. A proposed model yields the linewidth and temperature dependence of the observed failure rate.
Resonant tunneling diodes for switching applications
Authors: Diamond S. K. , Özbay E. , Rodwell M. J. W. , Bloom D. M. , Pao Y. C. , Harris J. S.
Published: July 2002

Rise times for simple pulse-forming circuits are presented. Switching times for present best devices are in the range of 5–15 ps. An equivalent circuit model for resonant tunneling diodes inclusive of space-charge effects and transit time effects in the depletion region is presented. From these models it is shown that switching times are limited by the device RC time constants and are relatively unaffected by the resonant state lifetime or depletion layer transit times. Appropriate figures of merit for switching applications are the device capacitance and peak current density. Less emphasis should be placed on improving the peak-to-valley ratio. Optimally designed devices which maximize the current density should be capable of switching in under 5 ps.
Large magnetization induced in single crystalline iron films by high-dose nitrogen implantation
Authors: Nakajima Kensuke , Okamoto Shoichi
Published: July 2002

Nitrogen ions were implanted in 200-nm-thick single crystalline iron films for a stoichiometric concentration of Fe16 N2 (11.1 at. %) by way of a multiple implantation. X-ray diffraction revealed that the as-implanted films were composed of 70% nitrogen martensite and 30% residual α-Fe. A slight amount of α″-martensite, that is, Fe16 N2, was detected but the principal constituent of the nitrogen martensite was α′-martensite. The saturation magnetic moment increased by 13.4 % with the implantation. Annealing the implanted films at 150 °C for 2 h in vacuum resulted in an increase in a constituent of the α″ phase, but affected the magnetic moment only slightly. It was deduced that the saturation magnetization of the nitrogen martensite is ∼257 emu/g at room temperature. It was also found that the implantation induced a perpendicular magnetic anisotropy due to the characteristics of the nitrogen martensite.
Film thickness dependence of dislocation density reduction in GaAs-on-Si substrates
Authors: Tachikawa Masami , Yamaguchi Masafumi
Published: July 2002

Low dislocation density (4×105 cm−2) GaAs films on Si substrates have been obtained with a GaAs film thickness of 180 μm using vapor mixing epitaxy based on GaCl-AsH3 (hydride) vapor phase epitaxy for the first time. Dislocation density decreases as the GaAs film thickness increases. Dislocation density is inversely proportional to film thickness in the film thickness region of <10 μm. However, in the film thickness region >50 μm (and/or of dislocation density <107 cm−2), dislocation density is exponentially proportional to the film thickness. Assuming that this dependence results from a dislocation reaction during GaAs growth, it can be interpreted that the dislocation-dislocation coalescence reaction mainly occurs with high dislocation density crystals, and additionally, a dislocation annihilation reaction, deflection, occurs with low dislocation density crystals.
Two-photon absorption in In1−x−yGaxAlyAs/InP waveguides at communications wavelengths
Authors: Villeneuve A. , Sundheimer M. , Finlayson N. , Stegeman G. I. , Morasca S. , Rigo C. , Calvani R. , De Bernardi C.
Published: July 2002

We have observed and measured two-photon absorption in In1−x−yGaxAlyAs/InP waveguides grown by molecular beam epitaxy over the wavelength range of 1.5–1.65 μm. The values of β2, the two-photon absorption coefficient, were 63 and 20 cm/GW for waveguides of compositions x=0.32, y=0.17 and x=0.15, y=0.31, respectively. These values are comparable with those predicted by scaling laws. We estimate the associated nonlinear refractive index coefficient n2 and discuss the implications for all-optical switching.
Effects of beam parameters on excimer laser deposition of YBa2Cu3O7−δ
Authors: Muenchausen R. E. , Hubbard K. M. , Foltyn S. , Estler R. C. , Nogar N. S. , Jenkins C.
Published: July 2002

Broad angular distributions have been observed for XeCl laser ablation plumes used in the deposition of YBa2Cu3O7−δ thin films. Distributions (inferred from film thickness) and film stoichiometry were measured as a function of laser fluence, beam shape, and oxygen pressure. Parallel to the long axis of the laser spot, plumes exhibited a cos3.5(θ) spread and composition varied with angle; in the perpendicular direction, more diffuse [cos1.5(θ)] plume distributions were associated with stoichiometric deposition. The observed phenomena are consistent with formation of a Knudsen layer near the target surface.
Ultrafast time resolution in scanned probe microscopies
Authors: Hamers R. J. , Cahill David G.
Published: July 2002

The speed limitations conventionally encountered in scanning tunneling microscopy, scanning capacitance microscopy, and atomic force microscopy result from the external electronics and are not inherent to the techniques themselves. Ultrafast time resolution faster than the bandwidth of the measuring electronics can be achieved by combining these techniques with picosecond optical excitation and utilizing inherent nonlinearities in the physical system. We demonstrate this idea by directly measuring carrier relaxation times at the Si(111)-(7×7) surface on the nanosecond time scale via scanning capacitance microscopy measurements of the surface photovoltage.
Surface acoustic wave response to changes in viscoelastic film properties
Authors: Martin S. J. , Frye G. C.
Published: July 2002

Changes in polymer viscoelastic properties have been monitored using polymer-coated surface acoustic wave (SAW) devices. Glass transitions induced by temperature changes and absorption of gas phase species have been observed. The changes in wave propagation velocity and attenuation which accompany these transitions are explained using a Maxwell model to describe the viscoelastic properties of the film.
Preparation of ultrathin Bi-Sr-Ca-Cu-O superconducting films by metalorganic chemical vapor deposition
Authors: Sugimoto Tsunemi , Yoshida Masaji , Sugawara Kazushi , Shiohara Yuh , Tanaka Shoji
Published: July 2002

Ultrathin Bi-Sr-Ca-Cu-O films close to a single unit cell [c=3.1 nm for Bi2Sr2CaCu2Ox (2212) phase] were grown on a (100)MgO substrate by metalorganic chemical vapor deposition. The ultrathin film, having an average thickness of 3.5 nm, exhibited a zero-resistance superconducting transition, Tc,0=64 K, comparable with the Tc,0 of much thicker films, whereas the superconducting property of thinner films than 3.5 nm was drastically deteriorated. The x-ray diffraction (XRD) measurement of the ultrathin films showed that the reflection peaks from 00l contributed to a 2212 phase were observed even in the 2.2-nm-thick film, and that its c-axis lattice constant was consistent with that of a bulk 2212 phase. On the other hand, the thicker films than 5.5 nm mainly consisted of the Bi2Sr2Ca2Cu3Ox (2223) phase with a trace amount of the 2212 phase from the XRD patterns.
Electromigration in a single crystalline submicron width aluminum interconnection
Authors: Shingubara Shoso , Nakasaki Yasushi , Kaneko Hisashi
Published: July 2002

Electromigration properties in a single crystalline submicron width aluminum interconnection formed on Si(111) have been examined by resistance change measurements and in situ observations using scanning electron microscopy. It was observed that single crystalline aluminum has an extremely high resistance to electromigration-induced open circuit failures, when compared to polycrystalline copper and aluminum. The mechanism for the high resistance is considered to be a large activation energy, resulting from lattice diffusion. A tendency for void formation to become parallel to the longitudinal direction of the interconnection assisted the life time prolongation.
Epitaxial growth of Al on Si(001) by sputtering
Authors: Niwa H. , Kato Masaharu
Published: July 2002

Epitaxy of Al deposited by sputtering on Si(001) substrates was investigated in detail by transmission electron microscopy studies. Heat treatment during or after deposition and growth to greater thickness enlarged the Al grains in the film and made the epitaxial relationship more distinct. It is confirmed that the Al epitaxy formed by the sputtering method is as perfect as that by other techniques.
Beam profile reflectometry: A new technique for dielectric film measurements
Authors: Rosencwaig Allan , Opsal Jon , Willenborg D. L. , Kelso S. M. , Fanton J. T.
Published: July 2002

We describe a new technique for measuring the thickness and optical constants of dielectric, semiconducting, and thin metal films. Beam profile reflectometry provides excellent precision for films as thin as 30 Å and as thick as 20 000 Å. The technique is also capable of simultaneous 2 and 3 parameter measurements and it performs all measurements with a submicron spot size.
Epitaxial growth of (011) Al on (100) Si by vapor deposition
Authors: Thangaraj N. , Westmacott K. H. , Dahmen U.
Published: July 2002

The morphology, orientation relationship and interface structure of Al vapor deposited on (100) Si single-crystal substrates were investigated by x-ray diffraction and transmission electron microscopy. It was shown that vapor growth at room-temperature results in a random (111) texture whereas growth at 280 °C leads to films with high-quality (011) epitaxy and a high degree of grain boundary faceting. Due to alignment of close-packed directions in the plane of the interface there are two orientation variants with a morphology characterized by an oriented 90° 〈011〉 mazed bicrystal structure.
Influence of ion-implanted titanium on the performance of edge-defined, film-fed grown silicon solar cells
Authors: Borenstein J. T. , Hanoka J. I. , Bathey B. R. , Kalejs J. P. , Mil’shtein S.
Published: July 2002

The electrical properties of edge-defined, film-fed grown and Czochralski silicon solar cells ion implanted with titanium have been investigated using deep level transient spectroscopy. In both types of solar cell materials, the observed degradation in cell performance is associated with the Ti deep level reported in earlier studies. During the cell fabrication sequence, Ti in-diffuses into the bulk of the sample, creating a low-lifetime zone extending beneath the junction. Solar cell modeling, based on the extent of the titanium-diffused layer and the properties of the Ti center, is in excellent agreement with observed cell performance.
Ion beam synthesis of cubic FeSi2
Authors: Desimoni J. , Bernas H. , Behar M. , Lin X. W. , Washburn J. , Liliental-Weber Z.
Published: July 2002

Cubic FeSi2 precipitates were synthesized in Si (100) by room-temperature Fe ion implantation followed by Si 500 keV ion beam induced epitaxial crystallization at 320 °C. High resolution electron microscopy and Rutherford backscattering/channeling techniques show that the cubic precipitates occur in both aligned (A) and twinned (B) types with a lattice parameter very similar to that of the Si (100) matrix.
Influence of the vertical structure on the mirror facet temperatures of visible GaInP quantum well lasers
Authors: Epperlein P. W. , Bona G. L.
Published: July 2002

Reflectance modulation measurements on red-emitting GaInP quantum well ridge lasers show a sensitive dependence of the laser mirror temperatures on the number of quantum wells, the type of cladding layers, the configuration of a heat spreader layer covering the ridge waveguide, and on how the laser is mounted on a heat sink. The temperature versus injection current curves also demonstrate the contribution of laser radiation heating even in single quantum well lasers. The temperatures decay rapidly from the mirror into the cavity within about 6 μm (1/e-point) as found from spatially resolved electroluminescence spectra detected along the laser cavity.
Simulations for the high-speed response of GaN metal-semiconductor-metal photodetectors
Authors: Joshi R. P. , Dharamsi A. N. , McAdoo J.
Published: July 2002

Results of our Monte Carlo computations for the dynamic response of GaN photodetectors are reported. Electron and hole transport, circuit loading, electric field effects, and the intensity dependence are all comprehensively included. The impulse transient compares favorably with a 0.25 μm GaAs metal-semiconductor-metal device. The performance is better at lower photoexcitation intensities, and improvements for higher intensities are possible by increasing the applied voltage and operating in the ballistic regime at electric fields around 150 kV/cm.
Microcavity effects in organic semiconductors
Authors: Dodabalapur A. , Rothberg L. J. , Miller T. M. , Kwock E. W.
Published: July 2002

Microcavity structures containing hydroxyquinoline aluminum and diamine layers commonly used in electroluminescent devices are described. We show that it is possible to obtain emission at red, green, and blue wavelengths by changing the thickness of a polyimide filler layer in the cavity. The angular dependence of the emission wavelength and linewidth are reported and the implications for organic electroluminescent color displays are discussed.
Growth of highly oriented Bi4Ti3O12(104) thin films on Al2O3(0001) substrates using pulsed laser deposition
Authors: Jo W. , Noh T. W.
Published: July 2002

Using pulsed laser deposition, Bi4Ti3O12 thin films were grown on Al2O3(0001) substrates. Laser fluence, substrate temperature, and oxygen pressure during deposition were varied in wide ranges, and their effects on Bi4Ti3O12 growth behaviors were investigated. It is possible to grow a Bi4Ti3O12 film whose (104) planes are normal to the Al2O3 c axis. However, the Bi4Ti3O12 film is not grown epitaxially. Instead, it is composed of grains with their c axes along six crystallographic orientations. This growth behavior of preferential orientations is explained in terms of atomic arrangements in the Bi4Ti3O12(104) and the Al2O3(0001) planes.
Quasi-two-dimensional exciton in ZnSe/ZnMgSSe single quantum well
Authors: Miyajima T. , Logue F. P. , Donegan J. F. , Hegarty J. , Okuyama H. , Ishibashi A. , Mori Y.
Published: July 2002

We have studied the quasi-two-dimensional exciton in ZnSe/ZnxMg1−xSySe1−y (x=0.85, y=0.21) single quantum wells (SQWs) by photoluminescence and photoluminescence excitation spectroscopy. Self-consistent calculations of the peak energies for a series of SQWs give the conduction band discontinuity ΔEc=0.40ΔEg and the binding energy of the n=1 heavy-hole exciton Eb(hh1)=22.1 meV for an 8 nm well width. We believe that the binding energy of the n=1 heavy-hole exciton is smaller than the LO phonon energy our samples resulting in a very large exciton-phonon interaction strength observed through the broadening of the exciton resonance with temperature.
Fabrication of metallic nanowires with a scanning tunneling microscope
Authors: Kramer N. , Birk H. , Jorritsma J. , Schönenberger C.
Published: July 2002

A procedure to pattern thin metal films on a nanometer scale with a scanning tunneling microscope (STM) operating in air is reported. A 30 nm film of hydrogenated amorphous silicon (a-Si:H) is deposited on a 10 nm film of TaIr. Applying a negative voltage between the STM tip and the a-Si:H film causes the local oxidation of a-Si:H. The oxide which is formed is used as a mask to wet etch the not-oxidized a-Si:H and subsequently, the remaining pattern is transferred into the metal film by Ar ion milling. Metal wires as narrow as 40 nm have been fabricated. Since a-Si:H can be deposited in very thin layers on almost any substrate, the presented procedure can be applied to structure all kind of thin films on a nanometer scale.
Solute segregation to grain boundaries in MgO-doped alumina
Authors: Soni K. K. , Thompson A. M. , Harmer M. P. , Williams D. B. , Chabala J. M. , Levi-Setti R.
Published: July 2002

The spatial distribution of Mg solute in polycrystalline, single-phase Al2O3 has been obtained, using a secondary ion imaging technique. Segregation of Mg to the Al2O3 grain boundaries is clearly observed—strong evidence that the principal role of MgO is to reduce the grain boundary mobility via a solute-drag mechanism. In addition, Mg (dopant) and Ca (impurity) are shown to cosegregate, shedding further light on magnesium’s ability to stabilize microstructural evolution in Al2O3.
Mechanism of bias-enhanced nucleation of diamond on Si
Authors: Robertson J. , Gerber J. , Sattel S. , Weiler M. , Jung K. , Ehrhardt H.
Published: July 2002

The nucleation of diamond on Si is enhanced for negative substrate bias of 200–250 V. We show that the ion flux is the critical factor causing the enhanced nucleation. The ion energy distribution has a maximum at about 80 eV, the optimum to subplant C ions into a-C. We propose that subplantation causes deposition of nanocrystalline graphitic C, and that diamond nucleates where the graphitic planes are locally oriented perpendicular to the surface. An atomic model is proposed that allows a matching of the diamond, graphite, and Si lattice.
New microcalorimeter for the measurement of differential heats of adsorption of gases on high surface area solids
Authors: Orsquo;Neil Matthew , Lovrien Rex , Phillips Jonathan
Published: July 2002

A new calorimeter of the heat-flow type designed to measure the differential heats of adsorption of gases on high surface area solids (e.g., catalysts) is described. Heat flow is measured using conventional thermopiles; the signals from which are amplified, digitized, and then sent to a laboratory computer for ease of data handling and analysis. The instrument allows conventional isotherm and heat data to be collected concomitantly. Other useful information obtained includes qualitative data regarding the rate at which processes take place, the total amount of gas chemisorbed, and the integrated value of the heat of adsorption. The instrument is capable of operating at temperatures from 273 to 373 K. One major advance over previous designs is that the dosing gas is allowed to thermally equilibrate before entering the sample chamber. The results of a simple study of the differential heats of adsorption of oxygen on a high surface area carbon material are presented. This study demonstrates the reliability and utility of the instrument.
Bandpass photon detector with high efficiency for inverse photoemission spectroscopy
Authors: Schäfer I. , Drube W. , Schlüter M. , Plagemann G. , Skibowski M.
Published: July 2002

We report on a significant improvement of a simple, but effective bandpass photon detector specially suited for inverse photoemission studies. It consists of a commercial open CuBe multiplier with a CaF2 entrance window. The latter acts as a low pass, the high pass and the quantum efficiency in the new version are determined by the photoyield of KBr evaporated onto the first dynode, resulting in a bandpass with maximum efficiency at ℏω=9.8 eV and ΔE=0.6 eV (FWHM). This detector is easy to operate and up to one order of magnitude more efficient than other systems currently used. Further improvement concerning combined efficiency and resolution seems possible by suitable variation of the cathode material and entrance window.
In situ reactive glow discharge cleaning of x-ray optical surfaces
Authors: Johnson E. D. , Hulbert S. L. , Garrett R. F. , Williams G. P. , Knotek M. L.
Published: July 2002

We report the first implementation of an in situ glow discharge cleaning procedure for the removal of carbon contamination from x-ray optical surfaces. In situ cleaning obviates the need for the time-consuming and costly process of element removal, cleaning or repolishing, remounting, and realignment usually necessary to restore x-ray optics to their original condition. The apparatus required is quite simple and can easily be fitted to most existing UHV (ultrahigh vacuum) mirror boxes or monochromators. Results with several monochromators at the Brookhaven National Labs National Synchrotron Light Source (NSLS) show that better than original performance can be obtained at the carbon K edge, since the elements are not exposed to atmosphere after in situ cleaning and do not accumulate the adventitious carbon layer associated with more traditional methods. Possible improvements and extensions of the technique are also described.
Fast scanning tunneling microscope for dynamic observation
Authors: Hosaka Sumio , Hasegawa Tsuyoshi , Hosoki Shigeyuki , Takata Keiji
Published: July 2002

A fast scanning tunneling microscope (FSTM) is developed using a new method of compensating for the probe tip servo error in constant current mode. The compensation value is derived from the ratio of tunnel current fluctuation to tunnel current (ΔI/I) in a differential tunnel current equation. Dynamic video images of Si(111) adatomic structures taken using the FSTM prove that this method is effective for fast scanning.
Design and characterization of a windowless resonant photoacoustic chamber equipped with resonance locking circuitry
Authors: Angeli György Z. , Bozóki Zoltán , Miklós András , Lörincz András , Thöny Andreas , Sigrist Markus W.
Published: July 2002

A novel design of a windowless resonant photoacoustic chamber with open acoustic filters and an electronic resonance locking circuitry is presented. The acoustic behavior of the cell and preliminary measurements on a certified gas mixture with a CO2 laser demonstrate the feasibility for trace gas monitoring.
An 8-T superconducting quantum interference device magnetometer
Authors: Genna J. C. , Biston S. , Cotillard J. C. , Lethuillier P. , Faurin C. , Hostachy P. , Rocca-Valero R. , Roullier J.
Published: July 2002

A variable-temperature (1.4–320 K) superconducting quantum interference device magnetometer, operating in magnetic fields up to 8 T, has been built. The sensitivity is 2×10−7 emu in low fields and 2×10−6 in high fields. The apparatus allows magnetization and anisotropy measurements to be performed and is entirely automated. It is of simple construction and has proved over a number of years to be very robust.
Influence of ionization cross sections on the gas mixing effect for the production of Ar9+ ions in a CAPRICE ECR source
Authors: Delaunay M.
Published: July 2002

The gas mixing effect in the electron cyclotron resonance (ECR) multicharged ion sources is analyzed while taking into account the ionization cross sections of different support gases such as H2, He, Ne, N2, and O2. The Ar9+ ion currents delivered by a CAPRICE ECR ion source are measured as a function of the support gas pressure. The efficiency of ionization of these different gases by electron impact may partially explain the improvement of the extracted Ar9+ ion current.
Permanent sextupole magnets for polarized Stern–Gerlach-type atomic beam sources
Authors: Schiemenz P. , Ross A. , Graw G.
Published: July 2002

Design and performance of high field permanent sextupole magnets, appropriate for the use in Stern–Gerlach-type atomic beam sources, is described. With neodymium–iron–boron alloys as permanent magnetic material, a usable pole tip field of 1.44 T has been obtained at a diameter of 24.5 mm.
Freeman ion source: An overview (invited)
Authors: Chivers D. J.
Published: July 2002

The Freeman ion source has now been in use for some 30 years. It is still the most versatile and most widely used ion source. Its ability to produce sharply focused milliampere beams of most elements over a wide range of energies continue to make it a popular choice of ion source. For use in semiconductor ion implanters its performance and relative ease of operation has led to it being extensively used for the production doping of silicon devices. Over the years the Freeman ion source has also been very successfully used in many other fields of ion implantation, including the routine production of multimilliampere beams of a wide range of metallic ions. The production of ion beams will be discussed in detail. Issues such as filament lifetime will also be covered. Recent developments and possible future innovations will be mentioned.
A variable temperature scanning tunneling microscope for use in ultrahigh vacuum
Authors: Wolkow Robert A.
Published: July 2002

A design is presented for a scanning tunneling microscope (STM) capable of operation over a temperature range of approximately 80–350 K in ultrahigh vacuum. An integral inchworm-like sample translation device avoids problems with unreliability and lock-up by using clamping elements which have an unusually large range of motion. The entire STM, including the sample and the tip, are held isothermal. Temperature drift is less than 0.1 Å/min. A set temperature may be maintained, within 2°, for over 10 h. Operation of the instrument is demonstrated with an image of the Si(001) surface recorded at 120 K.
Confinement in a cryogenic penning trap of highest charge state ions from EBIT
Authors: Schneider D. , Church D. A. , Weinberg G. , Steiger J. , Beck B. , McDonald J. , Magee E. , Knapp D.
Published: July 2002

The retrapping of highly charged Xe44+ and Th68+,72+ ions extracted from an ‘‘electron-beam ion trap’’ (EBIT) is demonstrated after injection of the ions into RETRAP, a cryogenic Penning trap (up to 6 T magnetic field) currently with an open cylinder design. Ion extraction in a short pulse (5–20 μs) from EBIT, essential for efficient retrapping, is employed. The ions are slowed down upon entering a deceleration tube mounted above the trap within the magnetic field. The potential is then rapidly (100 ns) decreased, enabling low-energy ions to enter the trap. Capture efficiencies up to 25% are observed via detection of the delayed ion release pulse with a detector below the trap. Signal voltages induced in a tuned circuit due to single and multiple ions have been observed by tuning the ion resonant axial oscillation frequencies for different ions. Results from transporting and retrapping of the ions, as well as their detection, are described and the trapping efficiency is discussed. The motivation for these studies is to cool the trapped very highly charged ions to low temperatures (<4 K) in order to perform ultrahigh-resolution precision spectroscopy, collision studies at ultralow energies, and to observe phase transitions in Coulomb clusters of highly charged ions.
Design studies for an advanced ECR ion source
Authors: Alton G. D. , Smithe D. N.
Published: July 2002

Magnet design codes, plasma dispersion solvers, and particle-in-cell (PIC) simulation codes have been used to arrive at the first step in the design of an advanced ion source based on electron cyclotron resonance (ECR) technology. The advanced concept design uses a minimum-B magnetic mirror geometry which consists of a multicusp magnetic field to assist in confining the plasma radially, a flat central field for tuning to the ECR resonant condition, and specially tailored mirror fields in the end zones to confine the plasma in the axial direction. The magnetic field is designed to achieve an axially symmetric plasma ‘‘volume’’ with constant mod-B, which extends over the length of the central field region. This design, which strongly contrasts with ‘‘surface’’ ECR zones characteristic of conventional ECR ion sources, results in dramatic increases in the absorption of rf power, thereby increasing the electron temperature and ‘‘hot’’ electron population within the ionization volume of the source. The creation of a volume rather than a surface ECR zone is, therefore, commensurate with the generation of higher beam intensities, higher charge states, and a higher degree of ionization. A summary of the results of these studies is presented in this report.
Conceptual design of SPring-8 contract beamline for structural biology
Authors: Yamamoto Masaki , Fujisawa Tetsuro , Nakasako Masayoshi , Tanaka Takashi , Uruga Tomoya , Kimura Hiroaki , Yamaoka Hitoshi , Inoue Yorinao , Iwasaki Hitoshi , Ishikawa Tetsuya , Kitamura Hideo , Ueki Tatzuo
Published: July 2002

At SPring-8, a contract beamline has been designed and developed for structural biology by the Institute of Physical and Chemical Research (RIKEN). In structural biology, three-dimensional knowledge of biological macromolecules is indispensable for understanding biological functions: x-ray crystallography, small-angle x-ray scattering (SAXS), and x-ray-absorption fine-structure are the typical techniques. The beamline contains two experimental stations, protein crystallography and SAXS. Both experiments can be carried out simultaneously, with dichromatic synchrotron radiation emitted from two undulators in serial arrangement. The branched beams are generated by a transparent diamond crystal. The beam for the protein crystallography station is provided by the ‘‘trichromator’’ to optimize for MAD (multiwavelength anomalous diffraction) experiments. The main feature of this concept is to minimize systematic errors in anomalous dispersion measurements for MAD experiments.
Air-bridge microcavities
Authors: Villeneuve Pierre R. , Fan Shanhui , Joannopoulos J. D. , Lim Kuo-Yi , Petrich G. S. , Kolodziejski L. A. , Reif Rafael
Published: July 2002

We introduce and analyze a new type of high-Q microcavity consisting of a channel waveguide and a one-dimensional photonic crystal. A band gap for the guided modes is opened and a sharp resonant state is created by adding a single defect in the periodic system. An analysis of the eigenstates shows that strong field confinement of the defect state can be achieved with a modal volume less than half of a cubic half-wavelength. We also present a feasibility study for the fabrication of suspended structures with micron-sized features using semiconductor materials.
On the nanostructure of pure amorphous silicon
Authors: Williamson D. L. , Roorda S. , Chicoine M. , Tabti R. , Stolk P. A. , Acco S. , Saris F. W.
Published: July 2002

New features of the nanoscale structure of amorphous (a)-Si produced by ion-implantation-induced amorphization of crystalline (c)-Si have been determined by the technique of small-angle x-ray scattering (SAXS). Si ion energies up to 17 MeV were used to generate a thick amorphous layer (8 μm) on a c-Si wafer to enable the SAXS measurements. As-implanted and thermally annealed (up to 540 °C) a-Si were studied. No nanovoids were detected within a sensitivity of 0.1 vol %, but the atomic-scale structure produced a measurable diffuse scattering signal that decreased with increasing anneal temperatures. These measurements show that the known density deficit of 1.8% in a-Si relative to c-Si cannot be due to voids and that a-Si is homogeneous on nm length scale.