bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid up‐regulation of P2Y messengers during granulocytic differentiation of HL‐60 cells
Authors: Communi Didier , Janssens Rodolphe , Robaye Bernard , Zeelis Natacha , Boeynaems Jean-Marie
Published: July 2002

HL‐60 cells are human promyelocytic cells expressing two ATP receptors: the P2Y2 and P2Y11 subtypes. Our Northern blotting experiments have shown that P2Y2 and P2Y11 messengers were up‐regulated in these cells, rapidly and independently of protein synthesis, following treatment with granulocytic differentiating agents such as retinoic acid, dimethylsulfoxide, granulocyte‐colony stimulating factor, dibutyryl cyclic AMP and ATP. AR‐C67085 and adenosine 5′‐O‐(3‐thiotriphosphate), two potent agonists of the recombinant P2Y11 receptor, increased intracellular cAMP concentration in HL‐60 cells more potently than ATP itself. These observations support the conclusion that the effect of ATP on HL‐60 cell differentiation is mediated by the P2Y11 receptor.
Cytoplasmic vacuolation, adaptation and cell death: A view on new perspectives and features
Authors: Henics Tamás , Wheatley Denys N
Published: July 2002

Summry— This review focuses on a widely‐observed morphological phenomenon, a unique class of cytoplasmic vacuolation, found in cultured (mammalian) cells. This vacuolation is quite distinct from autophagosomal and heterophagosomal, ie excessive lysosomal vacuolation, and occurs in most cell types spontaneously or via a wide range of inductive stimuli. Apart from vacuolation arising artefactually (usually due to poor fixation), spontaneous vacuolation occurs in individual or small clusters of cultured cells without apparent change in their local environment, while neighbouring cells remain completely unaffected. Since spontaneous vacuolation is unpredictable, the process of vacuolation — or ‘vacuolisation’ — (‘Vacuolation’ is the state of being with vacuoles; ‘vacuolisation’ therefore implies the process of becoming vacuolated. However, only the quicker term vacuolation will be used throughout this review to refer to the process of vacuole development.) induced experimentally, and hence relatively reproducibly by a range of substances and disturbances, offers an experimental approach which should give further insight into its physiology and pathophysiology. Unfortunately, our knowledge here remains woefully inadequate compared with the purely morphological aspects of the phenomenon. Vacuolation following disturbances could have an underlying common mechanism; however, a review of the literature suggests that this is not the case, and that it occurs via several different pathways, involving many different cell organelles and structures. All cells appear to retain the capacity to vacuolate for some physiological purpose, and it can be a permanent feature in many cell types, particularly ‘lower’ organisms and plants. Vacuolation in cells is generally seen as an adaptive physiological response, presumably for ‘damage limitation’, but very little is known about the intracellular homeostatic mechanisms which operate to restore the status quo. Where damage limitation fails, cells usually die quickly, but no clear evidence has been found that this is in any way ‘programmed’. It is argued that the demise which occurs via the vacuolation route may, in fact, be a distinct form of cell death which is difficult to fit into the conventional lytic and apoptotic modes.
Ingredient and labeling issues associated with allergenic foods
Authors: Taylor Steve L. , Hefle Susan L.
Published: July 2002

Foods contain a wide range of food ingredients that serve numerous technical functions. Per capita consumer exposure to most of these food ingredients is rather low with a few notable exceptions such as sugar and starch. Some food ingredients including edible oils, hydrolyzed proteins, lecithin, starch, lactose, flavors and gelatin may, at least in some products, be derived from sources commonly involved in IgE‐mediated food allergies. These ingredients should be avoided by consumers with allergies to the source material if the ingredient contains detectable protein residues. Other food ingredients, including starch, malt, alcohol and vinegar, may be derived in some cases from wheat, rye or barley, the grains that are implicated in the causation of celiac disease. If these ingredients contain gluten residues, then they should be avoided by celiac sufferers. A few food ingredients are capable of eliciting allergic sensitization, although these ingredients would be classified as rarely allergenic. These ingredients include carmine, cochineal extract, annatto, tragacanth gum and papain. Food manufacturers should declare the presence of allergenic food ingredients in the ingredient listings on product labels so that allergic consumers can know to avoid these potentially hazardous products.
Mechanisms balancing skeletal matrix synthesis and degradation
Authors: BLAIR Harry C. , ZAIDI Mone , SCHLESINGER Paul H.
Published: July 2002

Bone is regulated by evolutionarily conserved signals that balance continuous differentiation of bone matrix-producing cells against apoptosis and matrix removal. This is continued from embryogenesis, where the skeleton differentiates as a solid mass and is shaped into separate bones by cell death and proteolysis. The two major tissues of the skeleton are avascular cartilage, with an extracellular matrix based on type II collagen and hydrophilic proteoglycans, and bone, a stronger and lighter material based on oriented type I collagen and hydroxyapatite. Both differentiate from the same mesenchymal stem cells. This differentiation is regulated by a family of related signals centred on bone morphogenic proteins. Fibroblast growth factors, Indian hedgehog and parathyroid hormone-related protein are important in determining the type of matrix and the relation of skeletal and non-skeletal structures. Removal of mineralized matrix involves apoptosis of matrix cells and differentiation of acid-secreting cells (osteoclasts) from macrophage precursors. Key regulators of matrix removal are signals in the tumour-necrosis-factor family. Osteoclasts dissolve bone by isolating a region of the matrix and secreting HCl and proteinases at that site. Successive cycles of removal and replacement allow growth, repair and remodelling. The signals for bone turnover are predominantly cell-membrane-associated, allowing very specific spatial regulation. In addition to its support function, bone is a reservoir of Ca2+, PO3-4 and OH−. Secondary modulation of mineral secretion and bone degradation are mediated by humoral signals, including parathyroid hormone and vitamin D, as well as the cytokines that also regulate the underlying cell differentiation.
Population structure and establishment of the threatened long‐lived perennial Scorzonera humilis in relation to environment
Authors: Colling Guy , Matthies Diethart , Reckinger Claude
Published: July 2002

The intensification of agriculture has resulted in the decline of many plant species of nutrient‐poor wet grasslands. At some sites local populations of long‐lived characteristic species have persisted and might benefit from recent extensification schemes. However, little is known about the population biology of these plants, and the prospects for the populations are uncertain.

We studied the population structure and establishment of the long‐lived Scorzonera humilis in 23 populations in Luxembourg and neighbouring Belgium. Two types of populations could be distinguished according to their population structure: regenerating populations, with a high proportion of plants with only one or a few rosettes, and aged populations, with a low proportion of small, young plants but a high proportion of individuals with many rosettes. The total density of Scorzonera individuals was higher in regenerating than in aged populations.

Within sites, S. humilis was restricted to more open and nutrient‐poor patches. The composition of the vegetation in plots where S. humilis was present was significantly different from that of plots without the species, indicating that S. humilis is restricted to particular microhabitats.

In multiple regression analyses, environmental variables explained a large part of the variation in the total density of genets, the density of genets of different size and the density of rosettes. The main variables of influence were site productivity and soil moisture. With increasing productivity and decreasing soil moisture the proportion of small genets decreased and that of large genets increased. Increased productivity had contrasting effects at the genet and ramet (rosette) levels. While genet density decreased, ramet density increased, indicating that if a site is fertilized, recruitment of new genets and survival of genets is reduced, but growth of surviving genets is increased.

The results of a sowing experiment indicated that an aged population structure was due to a lack of recruitment. The number of seeds that germinated and the proportion of seedlings that survived until the next summer were positively correlated with soil moisture and negatively with productivity. Germination rate and establishment success were significantly higher in Molinion grassland than in the Calthion grasslands.

The results suggest that for long‐lived species the size and number of populations may not be good indicators of the status of a species. In S. humilis large populations (> 1000 genets) still exist, but all are of the aged type. In order to preserve existing populations of S. humilis, management should aim to reduce productivity and increase soil moisture.
Collection of peripheral blood stem cells with granulocyte‐colony‐stimulating factor alone in testicular cancer patients
Authors: HANAZAWA KISABURO , TANAKA MICHIO , WATANABE RYOTA , FUJIME MAKOTO
Published: July 2002

Background
: High‐dose chemotherapy with the transplantation of peripheral blood stem cells (PBSC) has been performed for the treatment of advanced testicular cancer patients. Recently, it has been reported that, in healthy donors, a large quantity of stem cells can be transferred to peripheral blood using granulocyte‐colony‐stimulating factor (G‐CSF) alone. Therefore, it was decided to try to harvest PBSC from three patients having testicular cancers with G‐CSF alone.

Methods
: The three patients with testicular cancer were 26, 56 and 62‐years‐old. They had undergone five, two and three cycles of chemotherapy, respectively, but no radiation therapy. Granulocyte colony‐stimulating factor was subcutaneously injected (250 μg) into each patient twice per day for 6 days. Peripheral blood stem cells were harvested for 3 days (days 4–6) and mononuclear cells (MNC), CD34‐positive cells and colony‐forming units of granulocyte‐macrophage (CFU‐GM) in PBSC collected by apheresis were measured.

Results
: Apheresis showed that the total MNC count was 20.2 × 108/kg (range, 10.6–25.9 × 108/kg), the CD34‐positive cell count was 0.98 × 106/kg (range, 0.75–1.4 × 106/kg) and the total CFU‐GM count was 1.36 × 105/kg (range, 0.25–3.0 × 105/kg).

Conclusion
: After mobilization of peripheral blood stem cells with G‐CSF alone, sufficient amounts of MNC were obtained from testicular cancer patients who had undergone chemotherapy several times. However, sufficient amounts of CD34‐positive cells and CFU‐GM could not be obtained. These results suggested that the G‐CSF dose was not adequate for harvesting sufficient amounts of CD34‐positive cells and CFU‐GM.
Reliability and correlation of measurements during and after bladder neck surgery
Authors: Bump  , Hurt  , Addison  , Fantl  , Mcclish  ,   THE CONTINENCE PROGRAM FOR WOMEN RESEARCH GROUP (SEE APPENDIX)
Published: July 2002

Objectives

 To assess the reliability of seven intra‐operative measurements of the effects of bladder neck suspension and correlate these measurements with postoperative dynamic urethral obstruction, quantified as the cough‐pressure transmission ratio.

Patients and methods

 Sixty women undergoing surgery for bladder neck hypermobility had seven measurements performed in duplicate: (i) the endoscopic appearance of the bladder neck: (ii) the bladder neck‐retropubic surface distance (BN‐RP distance); (iii) urethral axis; (iv) slow urethral pressure profilometry (UPP); (v) fast UPP; (vi) straining UPP; and (vii) dynamic UPP. Reliabilities were assessed by computing the intraclass correlation coefficient (R) for continuous data or Kappa statistic (K) for ordinal data. Pearson correlation coefficients were used to assess the relationships between the intra‐operative measures and postoperative pressure transmission.

Results

 The intra‐operative reliabilities for maximum pressure, length and area from the three UPP techniques were high (R=0.88–0.98) as were those for urethral axis measurements (R=0.98). In contrast, reliabilities were poor for pressure transmission ratios (R=0.15–0.33), BN‐RP distance (R=0.55), and endoscopic appearance (K=0.10). There were significant correlations of the pressures from the UPPs and intra‐operative pressure transmission ratios with postoperative pressure transmission ratios; however, the poor intra‐operative reliability of intra‐operative pressure transmission limits their usefulness. None of the other measures correlated significantly with postoperative pressure transmission ratios.

Conclusions

 Of the measures studied, only intra‐operative UPPs had both high reliability and good postoperative correlations.
Visceral obesity and metabolic syndrome
Authors: Bosello O. , Zamboni M.
Published: July 2002

There is increasing evidence for the existence of a condition consisting of a cluster of metabolic disorders which include insulin resistance, alterations in glucose and lipid metabolism, increased blood pressure and visceral obesity. The metabolic syndrome is now the favoured definition of the cluster. Each single component of the cluster increases the cardiovascular risk, but the combination of factors is much more important. Insulin resistance is the most frequently associated factor to the singular components of the syndrome: most authors believe that it may be the common aetiological factor. However, visceral obesity seems to be the main driving factor by means of the increased production of free fatty acids whose activity, in turn, might interfere with the action of insulin. Some questions exist about the syndrome because of the frequent lack in the cluster of one of the factors. This does not mean that the missing factor does not belong to the syndrome, but only that it is not yet clinically evident. Weight gain has been shown to be a strong predictor of the metabolic syndrome. This aspect gives strength to treatment and prevention because it means that losing weight or stopping weight increase might reduce the risk of a future appearance of a factor that is still not evident. Interventions to treat visceral obesity by means of losing weight seem to be the most efficacious way to treat the metabolic syndrome thus improving the most widespread cardiovascular risk factor in western countries.
Survival after fetal aortic balloon valvoplasty
Authors: Allan L. D. , Maxwell D. J. , Carminat M. , Tynan M. J.
Published: July 2002

The pre‐ and postnatal course of a child surviving after successful intrauterine balloon aortic valvoplasty for critical aortic stenosis is described. She is now well at 4 years of age. A clearer understanding of the hemodynamics in such cases and improved catheter technology are necessary before this is advocated as a generally applicable technique. However, the outcome in this case is promising for the future of fetal interventional procedures. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology
Successful pregnancy after bilateral internal iliac artery ligation monitored by color Doppler imaging
Authors: Papp Z. , Sztanyik L. , Szabó I. , Inovay J.
Published: July 2002

Ligation of the internal iliac (hypogastric) arteries can be a life‐saving procedure in cases of severe hemorrhage from pelvic viscera. In young women it is the only way to preserve fertility when conservative methods have failed to control the bleeding.

We present the case of a 21‐year‐old woman whose first pregnancy was terminated, after which profuse vaginal bleeding occurred and could not be controlled by conservative methods. An urgent laparotomy was performed and both internal iliac arteries were ligated. Two years after surgery, the patient conceived and after an uneventful pregnancy delivered a healthy infant. Uterine and fetal circulations were monitored with color Doppler imaging and were normal throughout pregnancy. A normal 3550‐g male infant was delivered vaginally at 39 weeks' gestation. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Both coloured overlays and coloured lenses can improve reading fluency, but their optimal chromaticities differ
Authors: Lightstone Anita , Lightstone Tamsin , Wilkins Arnold
Published: July 2002

Some individuals read more fluently when the text is coloured: i.e., when coloured sheets of plastic (overlays) are placed upon the page, or when coloured lenses are worn. Overlays provide a surface colour whereas lenses mimic a change in the colour of a light source. The neural mechanisms that underlie colour constancy ensure that the chromaticity of overlays and lenses is processed differently by the visual system. We investigated (1) the relationship between the optimal colours of overlays and lenses, and (2) how reading rate is affected by a particular colour in overlays and lenses. In 100 patients we noted (1) the overlay(s) chosen from among the 29 combinations of the 10 IOO Intuitive Overlays® which sample chromaticity systematically and (2) the chromaticity co‐ordinates of the lenses subsequently chosen using the Intuitive Colorimeter®, a device providing a light source that can be adjusted in hue, saturation and luminance independently. The relationship between the chromaticities of the overlays and the lenses showed considerable variation. In a second study, patients attending the Specific Learning Difficulties clinic at the Institute of Optometry, London, were given overlays to use for two months. Seventeen who derived benefit were examined using the Intuitive Colorimeter. Patients were asked to read aloud randomly ordered common words (Wilkins Rate of Reading Test): (1) with no colour, (2) with the chosen overlay, (3) with lenses matching the chosen overlay and (4) with lenses matching the Colorimeter setting. The aids increased reading rate significantly only in conditions (2) and (4). There was no significant improvement when lenses matching the overlay colour were used, and under this condition the reading rate was significantly poorer than in conditions (2) and (4). The colour of a lens will improve reading only if it is selected under conditions that mimic a change in the colour of a light source: coloured overlays give no clinically reliable guide to optimal lens colour.
COST‐BENEFIT RATIO OF INTRAVENOUS IMMUNOGLOBULIN TREATMENT IN CHRONIC INFLAMMATORY DEMYELINATING POLYRADICULONEUROPATHY
Authors: Gragnani F. , Ceschin V. , Morino S. , Clemenzi A. , Soscia F. , Gozzer M. , Rusignuolo A. , Antonini G.
Published: July 2002

Intravenous immunoglobulin (IVIG) is considered an efficacious but expensive treatment in dysimmune polyneuropathies. Nevertheless, to date, no studies have been conducted on the cost of this therapy. We retrospectively studied 21 patients affected by chronic inflammatory demyelinating polyradiculoneuropathy (idiopathic‐CIDP and CIDP‐MGUS), comparing the clinical response and costs of IVIG therapy with those of plasma exchange (PE). Patients were treated either with IVIG (400 mg/Kg/die for five days) or PE (6 exchanges in 3 weeks). Responders continued the same therapy, which was progressively tapered down to one IVIG infusion or one PE monthly. IVIG nonresponders received PE and vice versa. Patients were followed for a period ranging from 3 to 67 months (median: 29 months). The modified Rankin disability scale was used to determine functional impairment at baseline and during treatment.

Eleven of 21 patients (52%) improved with the first choice of treatment. Of the remaining 10 patients, 3 benefited from the alternative treatment; 2 patients who did not respond to the alternative treatment were again treated with the first choice therapy and subsequently improved; 2 patients on IVIG abandoned the therapy. One nonresponder to IVIG is currently receiving PE. The overall response rate to the two therapies was similar. The mean cost per patient was 1,128,000 lire/session for PE therapy (excluding equipment and medical staff costs) and 1,204,000 lire/dose for IVIG therapy. However, the responders to PE required a longer treatment than responders to IVIG.
UNILATERAL SCIATIC NEUROPATHY OF THE TERMINAL BRANCHES, WITH ABNORMAL MRI OF THE NERVE AT THE THIGH
Authors: Lori S. , Briccoli M. , Zanfranceschi G. , Fusi I.
Published: July 2002

A 52‐year‐old woman had a subarachnoid haemorrhage in 1996. No cause of bleeding was detected. After a hospital stay of 2 months, the patient fully recovered, except for a persistent distal paralysis of her right lower limb. The patient is currently undergoing a reevaluation.

The knee jerks are slightly asymmetric dx > sn, whereas the right Achilles tendon reflex is lost. Atrophic hypotonic paralysis of the muscles of the right leg is a prominent feature, with sparing of the thigh. Sensory loss is distributed in leg's sciatic area. Some tenderness is consistently appreciated with deep palpation of the posterior aspect of the thigh. EMG shows severe denervation of TA and calf muscles on right, whereas ischio‐crural muscles are bilaterally normal. The latencies of MAPs from TA and gastrocnemius, evoked by nerve stimulation at the knee, are prolonged (>20 msec). Sural nerve antidromic SAP is undetectable.

An MRI comparative study of the thighs has been performed (1.5 TESLA, SPIR suppression of fat tissue technique, and MIP reconstructions for the nerve). The sciatic nerve imaging is sharply asymmetric. The left nerve is barely visible, as expected. On the right, one can see normal fascicular structure and no evidence of either extrinsic compression or hypertrophy. The unusual ease of imaging is ascribed to increased water content, suggesting persistent edema and/or inflammation.

The hypothesis of ongoing activity of disease is consistent with the neurographic findings, but the cause and mechanism of nerve damage are not clear. The hypothesis of a compartment syndrome may be suggested by the history of coma, but the selective distal damage is not easily explained on this basis.
SENSORY‐MOTOR NEUROPATHY, MENTAL RETARDATION, SEIZURES AND KERATOCONUS: A NEW GENETIC SYNDROME?
Authors: Manganelli F. , Bruno R. , Del Giudice E. , Criscuolo C. , Santoro L.
Published: July 2002

We describe two siblings, V.A. 30 years old and V.U. 26 years old, affected by an atypical genetic syndrome. Paternal grandfather and grandmother were first cousins. Clinical history revealed, since the first infancy, generalized and partial seizures, drug resistance, and a mental retardation more severe in V.U. Neurological examination showed in V.A. congenital bilateral twisted feet, absence of tendon reflexes, reduction of vibration sense, calf enlargement and fasciculations in lower limbs. Mild ataxia, mild distal wasting more marked in the lower limbs with foot drop, absence of tendon reflexes, reduction of vibration sense and pes cavus were observed in V.U. Cutaneous hyperkeratosis was also present. Electrophysiological study showed in both, axonal sensory‐motor neuropathy, confirmed by sural nerve biopsy, performed in V.A. In the same patient the muscle biopsy excluded a mitochondrial dysfunction. Ophthalmologic evaluation demonstrated normal fundus oculi and the presence of keratoconus, monolaterally in V.U. and bilaterally in V.A. Laboratory investigations disclosed mild increase of CK. Furthermore, brain magnetic resonance, brainstem and somatosensory evoked potentials, urinary oligosaccharides, fragile X syndrome analysis, Arylsulfatase‐A and lactate levels were normal. Conclusion: The two patients are affected by sensory‐motor neuropathy, mental retardation, seizures and keratoconus. This symptom association is not present in medical literature.
Seasonal Changes in the Photosynthetic Efficiency of Thuja occidentalis (L.) and Chamaecyparis lawsonia (A. Murray bis.)
Authors: Wiese C. , Heber U.
Published: July 2002

Abstract: Seasonal changes in the efficiency of charge separation in PSII were studied in Thuja occidentalis (L.) and Chamaecyparis lawsonia (A. Murray bis.). Maximum light‐dependent charge separation decreased with decreasing temperatures in early winter in both species, but this was less drastic in Chamaecyparis than in Thuja. No positive relationship was seen between photoinhibition and irradiance. Rather, photoinhibition increased as photon flux densities decreased towards midwinter, and it decreased as photon flux densities increased towards spring. However, the decrease in maximum light‐dependent charge separation was much stronger on the light‐exposed upper surface of the twigs, where in Thuja visible browning occurred, than on the underside of the twigs. During spring, recovery of the photosynthetic efficiency and regreening were observed as both mean temperatures and irradiance increased. Transfer in midwinter of strongly photo‐inhibited twigs of Thuja to temperatures close to 20 °C resulted in considerable recovery of PSII activity within several days when low light was also present. Recovery did not occur at temperatures close to freezing or at room temperature in darkness. An analysis of fluorescence quenching suggested photoprotective dissipation of excess radiation not only in the light harvesting antennae of PSII but also in the reaction centres. Reaction centre quenching appeared to be stronger in Thuja than in Chamaecyparis. PSI was fully active in twigs whether or not PSII was photoinhibited. The antioxidant ascorbate was almost fully reduced even in midwinter.
Many but not all Genes in Chlamydomonas reinhardtii are Regulated by the Circadian Clock
Authors: Jacobshagen S. , Whetstine J. R. , Boling J. M.
Published: July 2002

Abstract: Total RNA from autotrophic Chlamydomonas reinhardtii cultures grown in constant dim light and 17 °C constant temperature was subjected to Northern blot analyses. The mRNAs for cytochrome c, β‐tubulin, HSP70B (a chloroplastic heat shock protein of the 70 kD family), chloroplastic fructose‐bisphosphate aldolase, and GAS3 (a “gamete‐specific” protein of unknown function with high expression in gametes but low expression in vegetative cells) each exhibit a clear circadian rhythm in abundance. The rhythms differ significantly in phase and amplitude. The findings show that the genes for cytochrome c and β‐tubulin indeed are regulated by the circadian clock, as previously suggested. Experiments with cultures grown at 27 °C instead of 17 °C further revealed that the rhythms in mRNA abundance for HSP70B, chloroplastic aldolase, and GAS3 also occur with a similar period at the higher temperature. Thus, the rhythms conform to the criterion of temperature compensation for the period and therefore represent true circadian rhythms. In contrast, the combined amount of mRNA for ubiquitin 52 amino acid fusion protein and ubiquitin 78 to 81 amino acid fusion protein stays constant under both temperature conditions. Because the combined amount of mRNA for the ubiquitin fusion proteins was previously shown to cycle under diurnal conditions when cell division activity is high, our data suggest a regulation of these genes by the cell division cycle and not the circadian clock. In summary, our data, together with several other reports, suggest that the circadian clock regulates many but not all genes in Chlamydomonas reinhardtii.
Evolution of the band gap and the dominant radiative recombination center versus the composition for ZnSe1−xTex alloys grown by molecular beam epitaxy
Authors: Brasil M. J. S. P. , Nahory R. E. , Turco-Sandroff F. S. , Gilchrist H. L. , Martin R. J.
Published: July 2002

We report a systematic study of the optoelectronic properties of ZnSe1−xTex alloys grown by molecular beam epitaxy over the entire range of compositions. The band-gap energy as a function of the composition presents a minimum at x≂0.65. The main luminescence emission observed at 5 K becomes narrower and closer to the band-gap energy as we increase the Te content. The linewidth and the difference between the emission peak and band-gap energy decrease significantly with increasing x and present a break in the slope at x≂0.65.
Crack formation in epitaxial [110] thin films of YBa2Cu3O7−δ and PrBa2Cu3O7−x on [110]SrTiO3 substrates
Authors: Olsson E. , Gupta A. , Thouless M. D. , Segmüller A. , Clarke D. R.
Published: July 2002

A characteristic feature of epitaxial [110] thin films of YBa2Cu3O7−δ and PrBa2Cu3O7−x on [110]SrTiO3 substrates is that the films have a tendency to crack along the (001) planes. We have studied the crack spacing as a function of deposition temperature and film thickness. The experimental data have been found to be in excellent agreement with a theoretical analysis of the crack spacings in brittle films. The study has allowed us to determine the critical thickness below which no cracks are expected to form as a function of temperature for [110] films of YBa2Cu3O7−δ, PrBa2Cu3O7−x, and YBa2Cu3O7−δ/ PrBa2Cu3O7−x bilayers.
Microtransport induced by ultrasonic Lamb waves
Authors: Moroney R. M. , White R. M. , Howe R. T.
Published: July 2002

We have observed pumping of water induced by 4.7 MHz ultrasonic Lamb waves traveling in a 4-μm-thick composite membrane of silicon nitride and piezoelectric zinc oxide. The observed pumping speed is proportional to the square of the wave amplitude; the speed was 100 μm/s for a rf drive voltage of 8 V and a 6.5 nm wave amplitude. A nonlinear model based on acoustic streaming theory predicts velocities in good agreement with experiment.
Surface segregation of In atoms during molecular beam epitaxy and its influence on the energy levels in InGaAs/GaAs quantum wells
Authors: Muraki K. , Fukatsu S. , Shiraki Y. , Ito R.
Published: July 2002

Surface segregation of In atoms during molecular beam epitaxy (MBE) and its influence on the energy levels in InGaAs/GaAs quantum wells (QWs) were systematically studied using secondary-ion mass spectroscopy (SIMS) and photoluminescence (PL). Strong dependence of In surface segregation on the growth conditions was found; when the growth temperature was raised from 370 to 520 °C, the segregation length was observed to increase from 0.8 up to 2.9 nm, accompanied by an appreciable peak energy shift in the PL spectra of the InGaAs/GaAs QWs. The correlation between In surface segregation and the energy levels in InGaAs/GaAs QWs was clarified for the first time.
Influence of capillary condensation of water on nanotribology studied by force microscopy
Authors: Binggeli M. , Mate C. M.
Published: July 2002

The influence of capillary condensation and humidity to friction and adhesion properties on a nanometer scale has been studied using a bidirectional force microscope. On a hydrophilic silicon oxide surface strong capillary formation could be observed at high humidities, whereas, on less hydrophilic amorphous carbon films and lubricated silicon oxide surfaces, capillary formation is suppressed. The hydrophilicity of the surface is also found to promote the lubricative effects of adsorbed water.
Indium seals for low-temperature and moderate-pressure applications
Authors: Lim C. C.
Published: July 2002

Some ideas as to what the important factors are that will produce a reliable indium O-ring seal are discussed. Four novel indium seal designs which are based on these ideas are presented. Three of these seals have been incorporated in a Brillouin cell. They include a simple sapphire window seal, a filling line union, and a flange seal. All of them have withstood low temperatures down to 77 K and moderate pressures up to 177 bar. The fourth seal described is a Pyrex tube seal for a Raman cell.
Soft x-ray emission spectroscopy using monochromatized synchrotron radiation (invited)
Authors: Nordgren J. , Bray G. , Cramm S. , Nyholm R. , Rubensson J.-E. , Wassdahl N.
Published: July 2002

Soft x-ray emission spectroscopy is a common tool for the study of the electronic structure of molecules and solids. However, the interpretation of spectra is sometimes made difficult by overlaying lines due to satellite transitions or close-lying core holes. Also, irrelevant inner core transitions may accidentally fall in the wavelength region under study. These problems, which often arise for spectra excited with electrons or broadband photon sources can be removed by using monochromatized synchrotron radiation. In addition, one achieves other advantages as well, such as the ability to study resonant behavior. Another important aspect is the softness of this excitation agent, which allows chemically fragile compounds to be investigated. In this work we demonstrate the feasibility of using monochromatized synchrotron radiation to excite soft x-ray spectra. We also show new results which have been accomplished as a result of the selectivity of the excitation. The work has been carried out using the Flipper I wiggler beamline at HASYLAB in Hamburg using a new grazing incidence instrument designed specifically for this experiment. The photon flux at the Flipper I station (typically 5×1012 photons per second on the sample with a 1% bandpass) is enough to allow soft x-ray fluorescence spectra to be recorded at relatively high resolution and within reasonable accumulation times (typically, the spectra presented in this work were recorded in 30 min).

The spectrometer is based on a new concept which allows the instrument to be quite small, still covering a large wavelength range (10–250 Å). The basic idea involves the use of several fixed mounted gratings and a large two-dimensional detector. The grating arrangement provides simple mounting within a limited space and, in particular, large spectral range. The detector can be moved in a three-axis coordinate system in order to cover the different Rowland curves defined by the different gratings. The arrangement permits the use of gratings with different radii, which further facilitate the achievement of optimum performance over a large range. Two-dimensional detection is used to allow a large solid angle, without suffering from loss of resolution due to imaging errors. The detector is based on five 2-in. MCPs with resistive anode read out. The sensitivity of the detector, which is normally very low for soft x rays, especially at grazing angles, is enhanced by CsI coating and by using an entrance electrode.
Two-dimensional hard x-ray imaging diagnostic for lower hybrid current drive experiments in PBX-M
Authors: Kaita R. , von Goeler S. , Sesnic S. , Bernabei S. , Fredrickson E. , McGuire K. , Stodiek W.
Published: July 2002

The efficiency of plasma current drive with lower hybrid waves is reflected in the distribution of suprathermal electrons formed during this process. Past measurements of the bremsstrahlung radiation from these electrons depended on arrays of hard x-ray detectors at different toroidal and poloidal locations around tokamaks [Nucl. Fusion 25, 1515 (1985)]. To avoid the space requirements and the complex correlation and inversion procedures associated with such systems, a single 23-cm-diam hard x-ray image intensifier tube is being installed for two-dimensional imaging on PBX-M. It will be optically coupled to an image processor already in place for a soft x-ray pinhole camera [Rev. Sci. Instrum. 59, 1831 (1988)], and analysis algorithms similar to those already developed for this diagnostic will be used.
An improved coaxial coupler for measurement of the microwave Hall effect
Authors: Al Zoubi A. Y. , Cross T. E. , Mohamed Isa D. A.
Published: July 2002

The design and construction of a low-losses coaxial double-slug tuner for impedance matching of a bimodal cavity resonator is described. Voltage-standing-wave-ratio values close to one were readily achieved and significant improvements in the cavity Q factor have been realized using this new coupler. Accurate microwave Hall mobility results have been obtained and 60% reduction in experimental time was possible. A decrease in resistive losses in the order of 2 dB enhanced the measurement sensitivity and the lower bound of the detectable mobility was also reduced to 2.5 cm2/V s.
Characterization and use of a novel optical position sensor for microposition control of a linear motor
Authors: Brenan Colin J. H. , Doukoglou Tilemachos D. , Hunter Ian W. , Lafontaine Serge
Published: July 2002

The performance of an optical reflective position sensor is evaluated as the position feedback element in the microposition control of a linear electromagnetic motor. The open loop position sensor characteristics are first measured to determine the analog controller design parameters. The performance of the controller, evaluated using an integrated Michelson interferometer, measures the control loop bidirectional accuracy, hysteresis, long-term stability, and position linearity. Compensation of the small nonlinearity measured required linearization of the input command signal and a practical application is demonstrated with a constant velocity scan of one of the interferometer mirrors. A final result is the submicron square wave modulation of the interferometer output with its scan mirror under closed-loop control using feedback from the reflective position sensor.
Automated null ellipsometer with rotating analyzer
Authors: Schrottke L. , Jungk G.
Published: July 2002

An automated version of a spectroscopic ac null ellipsometer is described. By simultaneous variation of the angle of incidence and the polarizer azimuth, circular polarization of the reflected radiation can be obtained for any sample configuration. This state of polarization is checked by a rotating analyzer detector system with lock-in technique, thus achieving the highest precision that is theoretically possible. The experimental details including the minimization routine (simplex method) are presented. First experiences gained with dielectric function spectra of InP show the high reproducibility and accuracy of the arrangement. From numerically calculated second derivatives the energy and type of critical interband points are determined.
Mg-doped p-type GaN grown by reactive molecular beam epitaxy
Authors: Kim Wook , Salvador A. , Botchkarev A. E. , Aktas O. , Mohammad S. N. , Morcoç H.
Published: July 2002

P-type conductivity in as-grown Mg-doped GaN films grown by reactive molecular beam epitaxy technique which employs ammonia as the nitrogen source is reported. Doping level and mobility of the films up to 4.5×1017 cm−3 and 6 cm2/V s, respectively, have been achieved without any post-growth treatments. The photoluminescence spectra show both band edge and Mg-related emission at room temperature. Neither annealing in nitrogen ambient furnace nor rapid thermal annealing was found to have any discernible influence on the electrical properties of the films. More than 6% of incorporated Mg was activated for the samples with relatively low Mg concentration. The measured activation energy of Mg acceptor was 160±5 meV.
Ferromagnetic Co–Fe–Zr–B amorphous alloys with glass transition and good high-frequency permeability
Authors: Inoue Akihisa , Koshiba Hisato , Itoi Takaomi , Makino Akihiro
Published: July 2002

A Co-based amorphous phase with glass transition and supercooled liquid region before crystallization was formed in Co70−xFexZr10B20 and Co72−xFexZr8B20 alloys containing more than 14 at % Fe. The crystallization temperature (Tx) is 899 K for the Co–Zr–B alloys and remains unchanged in the Fe concentration range up to 20%. The glass transition temperature (Tg) decreases with increasing Fe content, and the ΔTx(=Tx−Tg) increases from 25 K at 14% Fe to 34 K at 21% Fe. The amorphous alloys with glass transition crystallize with a single stage precipitation of bcc Fe(Co) and Co3ZrB2 phases. The Co-rich amorphous alloys exhibit good soft magnetic properties, i.e., saturation magnetization of 0.58–0.83 T, low coercivity of 4.7–8.3 A/m, and high permeability of 5500–18 300 in the frequency range of 1–103 kHz and low magnetostriction between −1.5×10−6 and +10×10−6 including zero. The success in synthesizing the soft magnetic amorphous alloys with high stability of supercooled liquid is promising for the future development of ferromagnetic Co-based bulk amorphous alloys.
Anisotropic apertures for polarization-stable laterally oxidized vertical-cavity lasers
Authors: Chua C. L. , Thornton R. L. , Treat D. W. , Donaldson R. M.
Published: July 2002

We disclose a method of eliminating the polarization instability in laterally oxidized vertical-cavity surface-emitting lasers. By employing an appropriately shaped device aperture, we are able to make the lasers operate in a single polarization direction through their entire L–I curve.
Hydrogen adsorption and cohesive energy of single-walled carbon nanotubes
Authors: Ye Y. , Ahn C. C. , Witham C. , Fultz B. , Liu J. , Rinzler A. G. , Colbert D. , Smith K. A. , Smalley R. E.
Published: July 2002

Hydrogen adsorption on crystalline ropes of carbon single-walled nanotubes (SWNT) was found to exceed 8 wt. %, which is the highest capacity of any carbon material. Hydrogen is first adsorbed on the outer surfaces of the crystalline ropes. At pressures higher than about 40 bar at 80 K, however, a phase transition occurs where there is a separation of the individual SWNTs, and hydrogen is physisorbed on their exposed surfaces. The pressure of this phase transition provides a tube-tube cohesive energy for much of the material of 5 meV/C atom. This small cohesive energy is affected strongly by the quality of crystalline order in the ropes.
Impact of GaAs buffer thickness on electronic quality of GaAs grown on graded Ge/GeSi/Si substrates
Authors: Carlin J. A. , Ringel S. A. , Fitzgerald E. A. , Bulsara M. , Keyes B. M.
Published: July 2002

Minority carrier lifetimes and interface recombination velocities for GaAs grown on a Si wafer using compositionally graded GeSi buffers have been investigated as a function of GaAs buffer thickness using monolayer-scale control of the GaAs/Ge interface nucleation during molecular beam epitaxy. The GaAs layers are free of antiphase domain disorder, with threading dislocation densities measured by etch pit density of 5×105–2×106 cm−2. Analysis indicates no degradation in either minority carrier lifetime or interface recombination velocity down to a GaAs buffer thickness of 0.1 μm. In fact, record high minority carrier lifetimes exceeding 10 ns have been obtained for GaAs on Si with a 0.1 μm GaAs buffer. Secondary ion mass spectroscopy reveals that cross diffusion of Ga, As, and Ge at the GaAs/Ge interface formed on the graded GeSi buffers are below detection limits in the interface region, indicating that polarity control of the GaAs/Ge interface formed on GeSi/Si substrates can be achieved.
Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz
Authors: Huber R. , Brodschelm A. , Tauser F. , Leitenstorfer A.
Published: July 2002

Bandwidth-limited infrared pulses as short as 50 fs are generated in thin GaSe crystals by phase-matched optical rectification of 10 fs laser pulses. The central frequency of the transients is continuously tunable over a wide interval extending from 41 THz (λ=7 μm) to the far-infrared. The electric field of the THz transients is directly monitored via ultrabroadband free-space electro-optic sampling. A simulation of the spectra based on a plane-wave model shows excellent agreement with the experiment.
Growth and characterization of thick oriented barium hexaferrite films on MgO (111) substrates
Authors: Oliver S. A. , Yoon S. D. , Kozulin I. , Chen M. L. , Vittoria C.
Published: July 2002

Highly oriented films of BaFe12O19 have been deposited onto MgO (111) substrates by pulsed laser ablation deposition. In contrast to epitaxial BaFe12O19 films grown on Al2O3 (001) substrates, these films experience an in-plane biaxial compressive stress, and do not crack or delaminate to thicknesses of at least 28 μm. X-ray diffraction, magnetometry, torque magnetometry, and ferrimagnetic resonance results all indicate excellent c-axis orientation normal to the film plane, and magnetic properties comparable to bulk values. The thickness and properties of these films approach those required for applications in low-loss self-biased nonreciprocal microwave devices.
Experimental demonstration of a leadless quantum-dot cellular automata cell
Authors: Amlani Islamshah , Orlov Alexei O. , Kummamuru Ravi K. , Bernstein Gary H. , Lent Craig S. , Snider Gregory L.
Published: July 2002

We present the experimental characterization of a leadless (floating) double-dot system and a leadless quantum-dot cellular automata cell, where aluminum metal islands are connected to the environment only by capacitors. Here, single electron charge transfer can be accomplished only by the exchange of an electron between the dots. The charge state of the dots is monitored using metal islands configured as electrometers. We show improvements in the cell performance relative to leaded dots, and discuss possible implications of our leadless design to the quantum-dot cellular automata logic implementation.
A theoretical study of stability, electronic, and optical properties of GeC and SnC
Authors: Pandey Ravindra , Rérat Michel , Darrigan Clovis , Causà Mauro
Published: July 2002

We present the results of a first principles study on the ordered Ge0.50C0.50 and Sn0.50C0.50 cubic alloys. A linear combination of atomic orbitals approach in the framework of density functional theory is employed for total energy calculations in the zincblende phase. A fitting of the energy surface to the equation of state yields the lattice constant of 4.61 and 5.17 Å and the bulk modulus of 181 and 119 GPa for GeC and SnC, respectively. Analysis of band structure suggests a crossover of the nature of the band gap from indirect to direct in going from SiC to GeC to SnC. Although both alloys predicted to be unstable with respect to their elemental components at zero pressure and temperature, GeC appears to become stable at higher pressure. It appears that both the lattice constant and bulk modulus of the ordered alloys do not follow Végard’s linear rule, though the calculated dielectric constant of the cubic alloys is approximately the average of the dielectric constant of their elemental components.
Quantum effects in hole-type Si/SiGe heterojunctions
Authors: Komnik Yu. F. , Andrievskiı̆ V. V. , Berkutov I. B. , Kryachko S. S. , Myronov M. , Whall T. E.
Published: July 2002

The temperature and magnetic-field dependences of the resistance of Si/SiGe heterojunctions with hole-type conductivity are investigated. It is shown that the features of these dependences are due to a manifestation of quantum interference effects — weak localization of the mobile charge carriers, and the hole–hole interaction in the two-dimensional electron system. On the basis of an analysis of the quantum interference effects, the temperature dependence of the dephasing time of the wave function of the charge carrier is determined: τφ=6.6×10−12T−1 s. This dependence τφ∝T−1 must be regarded as a manifestation of hole–hole scattering processes in the two-dimensional electron system. The contribution to the magnetoresistance from the hole–hole interaction in the Cooper channel is extracted, and the corresponding interaction constant λ0C≈0.5 is found.