bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of α‐Galactosyl Epitopes via Combined Use of Two Recombinant Whole Cells Harboring UDP‐Galactose 4‐Epimerase and α‐1,3‐Galactosyltransferase
Authors: Chen Xi , Zhang Wei , Wang Jianqiang , Fang Jianwen , Wang Peng George
Published: July 2002

α‐Galactosyl epitopes (or α‐Gal, oligosaccharides with a terminal Galα1,3Gal sequence) are a class of biologically important oligosaccharides in great demand in bulk quantities for basic and clinical studies on preventing hyperacute rejection in pig‐to‐primate organ xenotransplantaion. A truncated bovine α‐1,3‐galactosyltransferase, the key enzyme responsible for the biosynthesis of the terminal structure of α‐Gal, was cloned and overexpressed previously. The acceptor specificity was further studied in the present paper, and lactose and galactose derivatives were found to be good acceptors. To develop a more proficient reaction process, we report herein an example of an efficient enzymatic synthesis of α‐Gal oligosaccharides catalyzed by the combination of two recombinant Escherichia coli whole cells harboring the genes of a UDP‐galactose 4‐epimerase and the α‐1,3‐galactosyltransferase, respectively. Using lactosyl azide (LacN3) as the acceptor for the glycosyltransferase, the combined use of the two recombinant cells efficiently produced α‐Gal epitope Galα1,3LacN3 in 60−68% yield.
Patients with de novo acute myeloid leukaemia and complex karyotype aberrations show a poor prognosis despite intensive treatment: a study of 90 patients
Authors: Schoch Claudia , Haferlach Torsten , Haase Detlef , Fonatsch Christa , Löffler Helmut , Schlegelberger Brigitte , Staib Peter , Sauerland Maria Cristina , Heinecke Achim , Büchner Thomas , Hiddemann Wolfgang ,   for the German AML Cooperative Study Group
Published: July 2002

The clinical significance of complex chromosome aberrations for adults with acute myeloid leukaemia (AML) was assessed in 920 patients with de novo AML who were karyotyped and treated within the German AML Cooperative Group (AMLCG) trials. Complex chromosome aberrations were defined as three or more numerical and/or structural chromosome aberrations excluding translocations t(8;21)(q22;q22), t(15;17)(q22;q11–q12) and inv(16)(p13q22). Complex chromosome anomalies were detected in 10% of all cases with a significantly higher incidence in patients  60 years of age (17·8% vs. 7·8%, P < 0·0001). Clinical follow‐up data were available for 90 patients. Forty‐five patients were < 60 years of age and were randomly assigned to double induction therapy with either TAD‐TAD [thioguanine, daunorubicin, cytosine arabinoside (AraC)] or TAD‐HAM (high‐dose AraC, mitoxantrone). Twenty‐one patients achieved complete remission (CR) (47%), 20 patients (44%) were non‐responders and 9% of patients died during aplasia (early death). The median overall survival (OS) was 7 months and the OS rate at 3 years was 12%. Patients receiving TAD‐HAM showed a significantly higher CR rate than patients receiving TAD‐TAD (56% vs. 23%, P = 0·04). Median event‐free survival was less than 1 month in the TAD‐TAD group and 2 months in the TAD‐HAM group, respectively (P = 0·04), with a median OS of 4·5 months vs. 7·6 months (P = 0·13) and an OS after 3 years of 7·6% vs. 19·6%. Forty‐five patients were  60 years of age: 28 of these patient were treated for induction using one or two TAD courses and 17 cases received TAD‐HAM with an age‐adjusted reduction of the AraC dose. The CR rate was 44%, 38% were non‐responders and 18% experienced early death. The median OS was 8 months and the OS rate at 3 years was 6%. In conclusion, complex chromosome aberrations in de novo AML predicted a dismal outcome, even when patients were treated with intensive chemotherapy. Patients under the age of 60 years with complex aberrant karyotypes may benefit from HAM treatment during induction. However, long‐term survival rates are low and alternative treatment strategies for remission induction and consolidation are urgently needed.
A comparison of the naloxone test with the insulin stress test in patients following transsphenoidal surgery
Authors: McAllister  , McCance  , Hadden  , Bell  , Leslie  , Sheridan  , Atkinson
Published: July 2002

OBJECTIVE

To study the reliability of the naloxone test in assessing the hypothalamic‐pituitary‐adrenal (HPA) axis in patients following transsphenoidal pituitary surgery, by comparison with the insulin stress test (IST). Also, to establish a normal range for the response to naloxone in healthy controls.

DESIGN

All patients had the IST performed, soluble insulin 0.1–0.3 U/kg (usually 0.15 U/kg) being administered intravenously, followed by venous sampling for plasma glucose and serum cortisol at 0, 15, 30, 45, 60, 75 and 90 minutes. Naloxone (125 μg/kg body weight) was similarly administered to all patients 6 days later, with sampling at −15, 0, 15, 30, 45, 60, 90 and 120 minutes for plasma glucose, serum cortisol and plasma ACTH. The naloxone test was also performed on control subjects using an identical protocol.

SUBJECTS

Twenty patients (11F/9M) aged 48.8 ± 2.8 years (mean ± SE) 4–6 weeks following transsphenoidal pituitary surgery. Twelve normal healthy control subjects (6F/6M) aged 31.5 ± 3.0 years.

MEASUREMENTS

Serum cortisol was measured by radioimmunoassay and plasma ACTH by immunoradiometric assay.

RESULTS

Adequate hypoglycaemia (≤2.0 mmol/l) was achieved in all patients. Peak cortisol was >550 nmol/l in 17 subjects (range 572–867 nmol/l) and a subnormal response observed in 3 (peak cortisol 163–498 nmol/l). In the 17 patients with a normal cortisol response to hypoglycaemia the response to naloxone was extremely variable, with serum cortisol falling in 4 and an increment of ≤100 nmol/l in 6 others. In the 3 patients who failed the IST, two responded to naloxone and one did not. In normal controls, 3 of the 12 had little or no response to naloxone.

CONCLUSIONS

As the naloxone test fails to produce a response in all normal subjects it is impossible to define a ‘normal’ response. The numerous discrepancies with the IST in patients are further evidence of the test's lack of reliability in assessing the HPA‐axis and it is consequently not a viable alternative to traditional dynamic methods such as the IST.
Food availability and the nocturnal vs. diurnal foraging trade‐off in juvenile salmon
Authors: Metcalfe Neil B. , Fraser Neil H. C. , Burns Martin D.
Published: July 2002

1.Much attention has been devoted to explaining the spatial distribution of foraging animals, but rather little to their temporal distribution (i.e. whether they are diurnal, nocturnal or crepuscular). Many animals face predictable diel cycles of food availability or predation risk, and so the approach of measuring the relative ratio of mortality risk to food gained (the ‘minimize μ/f’ rule) can be applied equally as well to different time periods of the day as to alternative food patches or habitats.

2.This method is used here to investigate the diel activity patterns of juvenile Atlantic salmon, which have previously been shown to become increasingly biased towards nocturnal activity in winter, hiding for much of the day in streambed refuges. Calculations based on published data show that nocturnal foraging in winter is far safer per unit of food obtained than is diurnal, despite greatly reduced food capture efficiency at night‐time light levels.

3.Using an automated activity monitoring system based on passive integrated transponder (PIT) tags, this study shows that winter diel activity patterns in salmon are dependent on food availability. A change in food density led to a parallel change in time spent in the refuge, but (as predicted by the μ/frule) the effect was greatest at the time of day with the least favourable ratio of predation cost to feeding benefit. Thus an experimental increase in food availability led to a 16% reduction in time spent in nocturnal foraging but a 98% reduction in time spent foraging by day, with fish spending only 0·6% of the daylight hours out of the refuge at the highest food density.

4.However, brief daytime foraging bouts had a major impact on growth rates (presumably because feeding efficiency was much greater in daylight), especially when food was scarce. Daytime feeding was thus profitable in terms of rapid food acquisition but normally suboptimal in terms of risk of predation.

5.Daily activity patterns are therefore suggested to be the result of a complex trade‐off between growth and survival, which takes account of diel fluctuations in food availability, food capture efficiency and predation risk; individual variation in the extent of diurnal feeding in salmon may result from state‐dependent differences in the benefits of rapid feeding and growth.
Early enhanced enteral nutrition in burned patients is associated with fewer infective complications and shorter hospital stay
Authors: Taylor S. J.
Published: July 2002

Background: Major burn injury causes a catabolic state associated with depressed immunocompetence and a high incidence of morbidity and mortality. Previous studies have shown that provision of patients’ energy and nitrogen requirements early in the postburn period reduces net catabolism and supports the immune response.

Methods: This observational study determined the effect of providing at least 50% of a patient's estimated requirement of energy and nitrogen (‘enhanced enteral nutrition, EN’) in 106 burned patients requiring intravenous fluid resuscitation. Multiple regression was used to determine associations between the delay to enhanced EN and the incidence of death, infection and total complications, and hospital stay.

Results: Delay to enhanced EN was associated with infective complications (P=0.01) when adjusted for potential confounding factors. The risk of infection increases from 29% at 24 h to 66% at 48 h (number needed to treat, NNT: 3, and 1.5, respectively). In addition, the delay to enhanced EN was associated with hospital stay (P=0.001, 95% CI 1.5–5.5). A delay of 24 h was associated with an increase in hospital stay of 3.5 days. The associations held in survivors as well as the total group and therefore were not the result of early death causing a reduction in infections and hospital stay. No associations were found with death or total complications.

Conclusion: Earlier commencement of EN which meets 50% of estimated energy and nitrogen requirements may reduce the incidence of infection and hospital stay. The potential clinical benefits and cost savings must be confirmed in prospective randomized controlled trials.
Postregistration training and education: the NAGE experience
Authors: Copeman J. , Hyland K. , Oldfield G.
Published: July 2002

Background: This paper reviews the NAGE postregistration course and describes how it has responded to the changing demands of the major stakeholders in the health and social care sectors. It demonstrates how the course team have fulfilled the stated aims and objectives and sought to provide a rich experience for the course participants while being aware of the changing needs of the National Health Service (NHS) and expectations of dietitians, other health professionals and the wider community, particularly with the formation of Primary Care Groups (PCGs). Evidence to inform this review is drawn from a range of sources including dietetic managers, dietitians working with older people, past participants and course evaluations.

Aims: The overall purpose of the course has been to enhance the ability of the participants, i.e. dietitians working with older people, to reflect on their professional practice and become more effective in their membership of the multidisiciplinary team, with the ultimate goal of improving the provision of health care for older people and enhancing their quality of life. This ultimate goal is in line with the government Quality Agenda as reflected in the First Class Service and clinical effectiveness and the future National Service Framework for Older People.

Structure: The review is divided into three broad sections: detailed reflection of the courses held; nutrition and dietetic managers views; changes in the external environment that directly and indirectly influence the course.
Implications of weed composition and thrips species for the epidemiology of tomato spotted wilt in chrysanthemum (Dendranthema grandiflora)
Authors: Martinez D. L. Ochoa , Zavaleta‐Mejía E. , Mora‐Aguilera G. , Johansen N. R. M.
Published: July 2002

The effects of 21 weeds acting as hosts of tomato spotted wilt virus (TSWV), temperature, thrips population and diversity on disease progress in chrysanthemum cv. Polaris were studied. Under greenhouse conditions, only Taraxacum officinale, Bidens sp., Resedaluteola and Mirabilis jalapa were hosts for TSWV. Of 38 weeds species in the area surrounding a chrysanthemum field, Tithonia tubaeformis and R. luteola had the highest populations of adult and immature thrips. These weeds, as well as M. jalapa, had an extensive seasonal distribution and may play a key role in the disease progress. Seventeen thrips species belonging to the genera Bravothrips, Thrips and Frankliniella were identified on weed flowers, with Frankliniella occidentalis (FOC) representing 9.5% of all thrips identified. Of 123 thrips collected from chrysanthemum inflorescences, 9.75% were FOC, and only 2.5% of them transmitted TSWV. Of all the thrips species collected from chrysanthemum flowers in the field, only FOC was capable of transmitting TSWV. On 120 experimental plots established at two sites, with three transplanting dates (June, July and August), it was estimated that 1.25% of the chrysanthemum cuttings were already infected with TSWV when transplanted. Secondary spread, vectored by FOC, occurred only for the earliest transplanting date and resulted in a further 2.36% disease incidence.
Management of diabetic retinopathy by Australian optometrists
Authors: Mph Cathy A McCarty PhD , Mph Rob McKay Mbbs , PhD Jill E Keeffe , Distribution The Working Group on Evaluation of Nhmrc Retinopathy Guideli
Published: July 2002

Purpose: To describe current practices related to the management of diabetic retinopathy by Australian optometrists.

Setting and Methods: A two‐page self‐administered questionnaire was mailed to a random sample of 504 Australian optometrists. The survey included questions about the practice (such as size and location); current practice with regard to management of patients with diabetic retinopathy; barriers to use of dilating drops; and a number of patient scenarios related to screening, follow‐up and treatment of diabetic retinopathy.

Results: Completed questionnaires were returned by 407 of the 473 eligible optometrists (86%). They had been practising optometry between 1 and 50 years (median 14). Of the 243 optometrists who provided details about the location of their practices, 145 (37%) had at least one of their practices in a rural area. The estimated percentage of patients with diagnosed diabetes ranged from 0.5 to 40% (median = 5.0%). Three‐hundred and twenty‐two optometrists (79%) reported that they would often or almost always ask new patients over the age of 40 whether they have diabetes. The majority of optometrists (n = 387, 95%) would often or almost always ask their new patients with diabetes about their control of blood glucose levels and the majority of optometrists (n = 330, 81%) would often or almost always tell their patients with diabetes about the importance of strict glucose control in delaying retinopathy. The most common barrier to dilated ophthalmoscopy was patients not wanting to be dilated, with 38.1% of optometrists reporting this to be a moderate or major barrier. The next most common barrier was fear of precipitating angle closure glaucoma; 17.1% of optometrists reported this to be a moderate or major barrier.

Conclusion: The National Health and Medical Research Council (NHMRC) guidelines for the management of diabetic retinopathy are timely in relation to the expressed desire of Australian optometrists to learn more about management of diabetic retinopathy. These data will be used prospectively to assess changes in management of patients with diabetic retinopathy as a result of the release of the NHMRC guidelines.
Preretinal haemorrhages: an unusual manifestation of intravitreal amikacin toxicity
Authors: Md Atul Kumar , Md Tanuj Dada
Published: July 2002

Purpose: To report a case with multiple preretinal haemorrhages after intravitreal amikacin.

Method: A 58‐year‐old patient developed postoperative endophthalmitis following a routine extracapsular cataract extraction in his left eye. He received two intravitreal injections of cephazoline (2.25 mg) and amikacin (0.4 mg), given 48 h apart.

Results: The patient presented to us with large preretinal haemorrhages at the posterior pole. Multiple large areas of blocked fluorescence were seen on fundus fluorescein angiography.

Conclusion: Widespread posterior pole preretinal haemorrhages may be an unusual manifestation of intravitreal amikacin toxicity.
Paediatric ureteric calculi: efficacy of primary in situ extracorporeal shock wave lithotripsy
Authors: AL Busaidy  , Prem  , Medhat  , Giriraj  , Gopakumar  , Bhat
Published: July 2002

Objective

 To evaluate the efficacy of primary in situ extracorporeal shockwave lithotripsy (ESWL) for the treatment of ureteric calculi in children.

Patients and methods

 The Wolf 2500 Piezolith was used to treat 63 children (aged 4 months to 12 years) with 76 ureteric calculi, including 10 children with impacted calculi. The calculi were located in 14 upper, 13 mid and 44 lower ureters, and the stone burden varied from 4 to 17.8 mm (mean 12.6). All children aged ≤10 years were treated under general anaesthesia; lithotripsy was attempted under intravenous sedation in the older children.

Results

 At the 3‐month follow‐up, there was an overall successful outcome in 55 children (87%), which included 12 of 13, eight of nine (89%) and 35 of 41 (85%) of the children with upper, mid and lower ureteric calculi, respectively, and nine of the 10 with impacted calculi. Re‐treatment was required in 20 (36%) patients, while auxiliary procedures after ESWL were required in three (6%). The major complications encountered were ureteric obstruction with sepsis in two children, bacteraemia in another and urinary retention due to a urethral stone fragment in a fourth child.

Conclusions

 In situ ESWL was an effective treatment modality for ureteric calculi at all levels in children, even when impacted. In the short term, complications were minimal, but the long‐term effects need further assessment.
Severe diabetic ketoacidosis: the need for large doses of insulin
Authors: Fisken R. A.
Published: July 2002

A 21‐year‐old female with Type 1 diabetes mellitus (DM) presented in ketoacidosis. She received intravenous normal saline and insulin at 6 U/h and 1.26 % sodium bicarbonate solution. After the blood glucose had fallen to 9.5 mmol/l, the saline infusion was changed to 5 % glucose solution and the insulin infusion rate to 2 to 3 U/h. The next day the patient became more drowsy (Glasgow coma scale 13/15, later falling to 4/15). Computed tomography (CT) scan suggested cerebral oedema and the patient was treated with dexamethasone and mannitol. She remained critically ill for 48 h, eventually making a full recovery. Insulin was given at rates of 8 to 14 U/h, with 10 % or 20 % glucose infusion to maintain the blood glucose above 5 mmol/l; despite this it was not until the fifth day that her serum bicarbonate became normal. Textbooks usually advise starting insulin at 6 U/h and reducing the infusion rate to 1–4 U/h when the blood glucose falls below a certain level. In this case, even with high rates of insulin infusion, it took 5 days before the patient’s serum bicarbonate returned to normal. Thus, in severe diabetic ketoacidosis (DKA), protocols should advise that the insulin infusion be continued at high dose (4 to 6 U/h or more), with appropriate glucose infusion to prevent hypoglycaemia, until the serum bicarbonate is normal or nearly so.

Diabet. Med. 16, 347–351 (1999)
Universal vs. risk factor‐based screening for gestational diabetes mellitus: detection rates, gestation at diagnosis and outcome
Authors: Griffin M. E. , Coffey M. , Johnson H. , Scanlon P. , Foley M. , Stronge J. , O’Meara N. M. , Firth R. G.
Published: July 2002

Aims Gestational diabetes mellitus (GDM) is associated with adverse maternal and fetal outcome. Screening for GDM is therefore recommended but the best screening method remains controversial. This prospective, randomized study compared a risk factor‐based screening programme with a universally based one.

Methods Subjects were randomized at booking to one of two groups: the risk factor group had a 3‐h 100‐g oral glucose tolerance test (OGTT) at 32 weeks if any risk factor for GDM was present; the universal group had a 50‐g glucose challenge test performed and if their plasma glucose at 1 h was ≥ 7.8 mmol/l, a formal 3‐h 100‐g OGTT was then performed.

Results Universal screening detected a prevalence of GDM of 2.7%, significantly more than the 1.45% detected in the risk factor screened group (P < 0.03). Universal screening facilitated earlier diagnosis than risk factor screening – mean gestation 30 ± 2.6 weeks vs. 33 ± 3.7 weeks (P < 0.05). A higher rate of spontaneous vaginal delivery at term, and lower rates of macrosomia, Caesarean section, prematurity, pre‐eclampsia and admission to neonatal intensive care unit were observed in the universally screened, early diagnosis group.

Conclusions Universal screening for GDM is superior to risk factor based screening – detecting more cases, facilitating early diagnosis and is associated with improved pregnancy outcome.
Ultrasonic features of intra‐amniotic ‘unidentified debris’ at 14–16 weeks' gestation
Authors: Zimmer E. Z. , Bronshtein M.
Published: July 2002

The objective of the study was to define the sonographic features of various echogenic materials which have been observed in the amniotic cavity of pregnancies in the early second trimester. The study population consisted of women who underwent a transvaginal ultrasound scan of pregnancy at 14–16 weeks' gestation. Our experience in 6500 examinations performed in both low‐ and high‐risk pregnancies is reported; 249 cases of intra‐amniotic debris were identified in this population. Five different types of echogenic material were observed in the amniotic fluid: small floating particles, round structures, cystic structures, solid and semi‐solid masses and highly echogenic material which looked like calcification. We conclude that intra‐amniotic echogenic material may be observed during early pregnancy. Its origin and clinical significance need further evaluation. Copyright © 1996 International Society of Ultrasound in Obstetrics and Gynecology
Fourier analysis of video‐keratographic data. A tool for separation of spherical, regular astigmatic and irregular astigmatic corneal power components
Authors: Hjortdal Jesper Ø. , Erdmann Lotte , Bek Toke
Published: July 2002

Topographic analysis of the cornea and computation of changes in corneal topography is difficult because of the lack of a standardized concept for analysing topographic information. We have used Fourier series harmonic analysis to decompose the often very complex information given in topographic images (TMS‐1 video‐keratograph). The polar data values arising from each mire were separated into spherical (average power), regular astigmatic (2′ harmonic) and non‐regular astigmatic components. The non‐regular astigmatic components were further divided into a decentration component (1′ harmonic) and a higher order irregular refractive component (root mean square (r.m.s.) of the residual between original data and the sum of spherical, 1′ and 2′ order components). Algorithms for utilizing the Fourier analysis technique on subjective refractive and on keratometric changes in regular astigmatism were also derived. Averages of the separate refractive components were calculated for groups of normal (right and left eye of 25 patients), keratoconic (13 eyes), and transplanted eyes (20 eyes), and average topographic maps were reconstructed and imaged. Changes in the separate topographic refractive components were compared with subjective refractive changes in eyes that had undergone combined myopic‐astigmatic excimer laser ablation (8 eyes). Fourier series analysis was found superior to conventional keratometry in predicting spherical and regular astigmatic changes in subjective refraction. Fourier series analysis seems to be a powerful tool to decompose the information of complex topographic corneal images into rational optical components.
Actin‐Based Domains of the “Cell Periphery Complex” and their Associations with Polarized “Cell Bodies” in Higher Plants
Authors: Baluška F. , Volkmann D. , Barlow P. W.
Published: July 2002

Abstract: Nascent cellulosic cell wall microfibrils and transverse (with respect of cell growth axis) arrays of cortical microtubules (MTs) beneath the plasma membrane (PM) are two well established features of the periphery of higher plant cells. Together with transmembrane synthase complexes, they represent the most characteristic form of a “cell periphery complex” of higher plant cells which determines the orientation of the diffuse (intercalary) type of their cell growth. However, there are some plant cell types having distinct cell cortex domains which are depleted of cortical MTs. These particular cell cortex domains are, instead, typically enriched with components of the actin‐based cytoskeleton. In higher plants, this feature is prominent at extending apices of two cell types displaying tip growth ‐ pollen tubes and root hairs. In the latter cell type, highly dynamic F‐actin meshworks accumulate at extending tips, and they appear to be critical for the apparently motile character of these subcellular domains. Importantly, tip growth of both root hairs and pollen tubes is immediately stopped when the most dynamic F‐actin population is depolymerized with low levels of anti‐F‐actin drugs. Intriguingly, MTs of tip‐growing plant cells are organized in the form of longitudinal arrays, throughout the cytoplasm, which interconnect the extending tips with the subapical nuclei. This suggests that actin‐rich cell cortex domains polarize plant “cell bodies” represented by nucleus‐MTs complexes. A similar polarization of “cell bodies” is typical of mitotic and cytokinetic plant cells. A further type of MT‐depleted and actomyosin‐enriched plant cell cortex domain comprises the plasmodesmata. Primary plasmodesmata are formed during cytokinesis as part of the myosin VIII‐enriched callosic cell plates, representing “juvenile” forms of the plant “cell periphery complex”. In phylogenetic terms the association between F‐actin and the PM may be considered for a more “primitive” form of cellular organization than does the association of cortical MTs with the PM. We hypothesize that the actin cytoskeleton is a natural partner of the PM in all eukaryotic cells. In most plant cells, however, it was replaced by a tubulin‐based “cell periphery apparatus” which regulates, via still unknown mechanisms, the spatial deposition of nascent cellulosic microfibrils synthesized by PM‐associated synthase complexes.
Palynological Features as a Systematic Marker in Artemisia L. and Related Genera (Asteraceae, Anthemideae)
Authors: Martín J. , Torrell M. , Vallès J.
Published: July 2002

Abstract: Using optical and scanning electron microscopy, we carried out a palynological study of some plant species with a systematic position that has been controversial. One of the taxa belongs to the genus Artemisia (Asteraceae, Anthemideae), but has been described in another genus (Artemisia incana/Tanacetum incanum). The remaining taxa have been named or combined in Artemisia but are now considered members of small genera mostly segregated from Artemisia (Ajania, Hippolytia, Kaschgaria, Lepidolopsis, Mausolea, Turaniphytum), or belong to very close genera (Brachanthemum, Sphaeromeria). We confirm the existence of two pollen morphological patterns ‐ concerning ornamentation ‐ in the tribe Anthemideae: one with long spines (Anthemis type) and the other with short spinules (Artemisia type). Artemisia and its related genera can also be divided into two groups according to this feature, which is a good taxonomic marker, well correlated with other morphological and molecular characters.
Granular Fe in a metallic matrix
Authors: Childress J. R. , Chien C. L. , Nathan M.
Published: July 2002

Ultrafine Fe particles with coercivities in excess of 500 Oe have been obtained by rapid annealing of sputtered metastable FexCu1−x alloys. The enhanced magnetic properties of these phase-separated materials are typical of single-domain Fe grains, and can be controlled by the annealing temperature. The Cu matrix, however, is highly conducting, unlike conventional granular materials where the matrix is generally insulating. The evolution of the magnetic properties and microstructure during annealing are described.
Anomalous silicon and tin doping behavior in indium phosphide grown by chemical beam epitaxy
Authors: Skevington P. J. , Andrews D. A. , Davies G. J.
Published: July 2002

Anomalous doping behavior of the most commonly used n-type dopants, Si and Sn, has been observed in InP grown by chemical beam epitaxy from trimethylindium and cracked phosphine. In the case of Si, although incorporation is initially facile, the doping level decreases in successive runs. It is proposed that this decrease is due to the formation of SiC in the dopant cell. The behavior of Sn is more complex. In the range of Sn cell temperatures from 600 to 750 °C, incorporation is proportional to the elemental Sn vapor pressure. However, at low cell temperatures, 175–350 °C, anomalously large incorporations of Sn are observed. We attribute this behavior to the formation of a volatile metalorganic precursor within the Sn cell, its transport to the substrate, and subsequent decomposition and incorporation.
Growth of InGaAs/GaAs quantum wells with perfectly abrupt interfaces by molecular beam epitaxy
Authors: Gerard Jean-Michel , Le Roux Guy
Published: July 2002

The abruptness of InxGa1−xAs-on-GaAs as well as GaAs-on-InxGa1−xAs interfaces grown by molecular beam epitaxy is usually intrinsically limited by the surface segregation of indium atoms. The deposition of a one-monolayer-thick indium-rich prelayer of InGaAs (or of a submonolayer amount of InAs) prior to growth of InxGa1−xAs allows, however, the formation of a perfectly abrupt InxGa1−xAs-on-GaAs interface, as shown (for x=0.06 and x=0.11) by a detailed study of the surface composition at various stages of the growth of this heterostructure. A thermal annealing can also be performed at the GaAs-on-InGaAs interface so as to desorb surface indium atoms and suppress In incorporation in the GaAs overlayer. Both techniques preserve the optical quality of InxGa1−xAs/GaAs quantum wells.
Simultaneous molecular beam epitaxy growth and scanning tunneling microscopy imaging during Ge/Si epitaxy
Authors: Voigtländer Bert , Zinner André
Published: July 2002

A high temperature scanning tunneling microscope (STM) capable of simultaneous imaging and molecular beam epitaxy (MBE) growth at 600–900 K sample temperature is described. The formation of the two-dimensional Stranski–Krastanov layer and the evolution of three-dimensional islands during further growth of Ge on Si(111) was observed. An inversion of the aspect ratio of the islands with increasing coverage indicates a transition from coherent to dislocated 3D islands. This method (MBSTM) opens the possibility to follow MBE growth processes with STM in a real in situ way and gives access to the evolution of specific features during growth.
Optical parametric frequency conversion properties of KTiOAsO4
Authors: Bosenberg W. R. , Cheng L. K. , Bierlein J. D.
Published: July 2002

The new nonlinear optical crystal KTiOAsO4 (KTA) is characterized and evaluated for use in optical parametric oscillator devices (OPOs) capable of generating tunable radiation in the 3–5 μm region. Parametric tuning curves at the pump wavelength of 1.064 μm are measured and compared to predictions based on published Sellmeier equations. Oscillation thresholds and damage thresholds of KTA are measured relative to its well-known isomorph KTiOPO4 (KTP). A KTA OPO was constructed which obtained a maximum conversion efficiency of 20% when pumped 2.6 times above threshold. Our results demonstrate that KTA is a promising material for use in optical parametric devices.
Effects of monolayer coverage, flux ratio, and growth rate on the island density of InAs islands on GaAs
Authors: Solomon G. S. , Trezza J. A. , Harris J. S.
Published: July 2002

We have studied the effects of monolayer coverage, V/III flux ratio and growth rate on the density of three-dimensional growth induced isolated InAs islands grown on GaAs by molecular-beam epitaxy. Within the isolated island growth regime, increasing the monolayer coverage increases the InAs island density with only a small increase in island size. Decreasing the V/III flux ratio or decreasing the growth rate increases the island density without changing the average in-plane island diameter. We have observed island densities that are 80% of the ideal close-packed island density. We propose a model explaining the island density increase with monolayer coverage; local variations in accumulated strain in the wetting layer vary the point at which local islanding is initiated. As more material is deposited more islands are nucleated and the island density increases. The island density increases with decreasing V/III flux ratio or growth rate by increasing the adatom surface diffusion in the underlying wetting layer, leading to a more uniformly strain wetting layer and a more uniformly roughened growth front.
Negative photoconductivity in semiconductor heterostructures
Authors: Chaves A. S. , Chacham H.
Published: July 2002

Literature data on negative photoconductivity in GaAs/AlGaAs modulation doped heterojunctions and InAs/AlGaSb undoped quantum wells are explained in terms of electron–hole pair generation in the large gap layer, with subsequent charge separation and majority carrier annihilation in the well. This effect can be classified in two different limits, depending on the position of the quasi-Fermi level μ in the large gap layer. The limit with μ on the conduction band corresponds to the GaAs/AsGaAs heterostructures, and we are able to reproduce quantitatively the available experimental results. We also show that the limit with μ on the middle of the gap corresponds to the InAs/AlGaSb heterostructures.
Operation and cross calibration of the activation foil system on TFTR
Authors: Barnes Cris W. , Nieschmidt E. B. , Huibers A. G. A. , Ku L. P. , Motley R. W. , Saito T.
Published: July 2002

Time-integrated neutron yields are measured with an activation foil system which pneumatically sends the foils to and from TFTR by remote control. The foils are then counted by high-purity germanium coaxial detectors which have an absolute efficiency calibration. Using different nuclear reactions in different foils with different energy thresholds allows measurements of both DD and DT neutron yields. Details of the system hardware, operation, and efficiency calibration are provided. The cross calibration of the system to other measurements of neutron source strength to provide an absolute measure of yield is described. Comparison of this cross calibration is made to previous absolute calibrations and to neutronics calculations of the response coefficients.
Construction of an in-vacuum type undulator for production of undulator x rays in the 5–25 keV region
Authors: Yamamoto Shigeru , Shioya Tatsuro , Hara Masanori , Kitamura Hideo , Zhang Xiao Wei , Mochizuki Tetsuro , Sugiyama Hiroshi , Ando Masami
Published: July 2002

A new 179-pole undulator with magnetic period of 4 cm for production of brilliant and quasimonochromatic hard x rays has been completed and installed in the TRISTAN Accumulation Ring (AR) in KEK, National Laboratory for High Energy Physics. The aperture of the undulator for the circulating electron can be flexibly changed to satisfy the operational requirements of AR, since the undulator magnets are encased in the vacuum chamber of the undulator. When it is operated at the magnet gap of 20 mm with 6.5-GeV operation of AR, intense 14.4-keV radiation for Mössbauer experiments is successfully obtained as the third harmonic of the undulator radiation.
Domain inversion in ferroelectric MgO:LiNbO3 by applying electric fields
Authors: Kuroda Atsuko , Kurimura Sunao , Uesu Yoshiaki
Published: July 2002

An antiparallel ferroelectric domain in LiNbO3 doped with 5 mol % MgO (MgO:LN) was inverted at room temperature by applying a step-like electric field. The lowest electric field was about one fifth of that for undoped LN, but a high field compared to that for BaTiO3 was found to be necessary from the analysis of the switching current. The long switching time (about 102 s under an electric field of 4.45 kV/mm) enabled us to observe the domain growth process in MgO:LN. The needle-shaped nuclei grew into larger domains by nucleation on the existing domain wall, and the wall of the coalesced domain moved forward slowly. The process was similar to the domain reversal model proposed for BaTiO3 under low electric fields.
Temperature-independent transport in high-mobility pentacene transistors
Authors: Nelson S. F. , Lin Y.-Y. , Gundlach D. J. , Jackson T. N.
Published: July 2002

The charge-carrier transport mechanism in the organic semiconductor pentacene is explored using thin-film transistor structures. The variation of the field-effect mobility with temperature differs from sample to sample, ranging from thermally activated to temperature-independent behavior. This result excludes thermally activated hopping as the fundamental transport mechanism in pentacene thin films, and suggests that traps and/or contact effects may strongly influence the observed characteristics. These results also indicate that field-effect transistors may not be appropriate vehicles for illuminating basic transport mechanisms in organic materials.
Optimization of hydrogenated amorphous silicon p–i–n solar cells with two-step i layers guided by real-time spectroscopic ellipsometry
Authors: Koh Joohyun , Lee Yeeheng , Fujiwara H. , Wronski C. R. , Collins R. W.
Published: July 2002

Hydrogenated amorphous silicon (a-Si:H) p–i–n solar cell performance has been optimized using a two-step i-layer growth process. This effort has been guided by real-time spectroscopic ellipsometry (RTSE) studies of the nucleation and growth of a-Si:H films by plasma-enhanced chemical vapor deposition at 200 °C using a variable H2-dilution gas flow ratio R=[H2]/[SiH4]. RTSE studies during film growth with R>15 reveal a transition from the amorphous to microcrystalline (a→μc) phase at a critical thickness that decreases with increasing R. From such results, the optimum two-step process was designed such that the initial stage of the i layer (∼200 Å) is deposited at much higher R than the bulk to ensure that the film remains within the amorphous side of the a→μc phase boundary, yet as close as possible to this boundary at low i-layer thicknesses.
Electro-optic characteristics and switching principle of a nematic liquid crystal cell controlled by fringe-field switching
Authors: Lee S. H. , Lee S. L. , Kim H. Y.
Published: July 2002

We have fabricated a nematic liquid crystal cell associated with a homogeneously aligned to twisted transition of a liquid crystal director. In the absence of an electric field, the liquid crystal molecule is homogeneously aligned under the crossed polarizers, and thus the cell appears to be black. When a fringe field induced by interdigital electrodes is applied, liquid crystal molecules rotate in plane even above electrodes and thus the cell transmits light. The device exhibits a high transmittance ratio as well as a wide viewing angle, which solves a long standing problem of low transmittance existing in the conventional in-plane switching mode. We show that the distance between electrodes smaller than the width of an electrode and cell gap is required for generating fringe field with applied voltage and rotating molecules above electrodes. We also investigate the mechanism of fringe-field switching and dependence of electro-optic effect on different cell conditions and dielectric anisotropy of liquid crystal.
Enhanced Mg doping efficiency in Al0.2Ga0.8N/GaN superlattices
Authors: Kozodoy Peter , Hansen Monica , DenBaars Steven P. , Mishra Umesh K.
Published: July 2002

High p-type conductivity of Mg-doped AlGaN/GaN superlattices is demonstrated. The measured hole concentration at room temperature is over 2.5×1018 cm−3, more than ten times that obtained in bulk AlGaN layers, and lateral resistivity as low as 0.2 Ω cm is realized. The temperature dependence of the resistivity is drastically reduced compared to bulk films, providing evidence of the formation of a confined hole gas. Valence band bending due primarily to piezoelectric and spontaneous polarization is identified as the origin of these effects.
Large magnetoresistance in tunnel junctions with an iron oxide electrode
Authors: Seneor P. , Fert A. , Maurice J.-L. , Montaigne F. , Petroff F. , Vaurès A.
Published: July 2002

We report on the fabrication and properties of (cobalt/alumina/iron oxide) tunnel junctions. We observe magnetoresistance (MR) effects reaching 43% at 4.2 K and 13% at room temperature. This large MR is ascribed to the presence of a Fe3−xO4 (close to half-metallic magnetite) phase identified by electron diffraction. At low temperature, the MR drops sharply when the bias voltage is smaller than 10 mV, which suggests that the magnetoresistance originates from the activation of tunneling channels through spin polarized states below and above the Fermi level in the iron oxide.
Enhanced ferroelectric properties and lowered processing temperatures of strontium bismuth niobates with vanadium doping
Authors: Wu Yun , Cao Guozhong
Published: July 2002

This letter reports on enhanced ferroelectric properties and lowered processing temperatures of a SrBi2(V, Nb)2O9 system with vanadium doping. The samples were prepared by reaction sintering of powder mixtures of constituent oxides. With partial substitution of niobium by vanadium cations (up to 10 at. %), the single-phase layered perovskite structure was preserved and the sintering temperature of the system was significantly lowered (∼ 200 °C). The incorporation of vanadium into the layered perovskite structure resulted in a shift of the Curie point to higher temperatures, from 435 to 457 °C with 10 at. % vanadium doping, and an increase in dielectric constant, from ∼700 to ∼1200 with 5 at. % vanadium doping, at their respective Curie points. Both enhanced Curie temperatures and dielectric constants at the Curie points indicate an increase in polarizability, which could be attributed to the increased “rattling space” due to the incorporation of much smaller vanadium cations. Further measurements also revealed that loss tangent of vanadium doped layered perovskites was the same as that without vanadium doping.
Exchange anisotropy of epitaxial Fe/MnPd bilayers
Authors: Tang Y. J. , Zhou X. , Chen X. , Liang B. Q. , Zhan W. S.
Published: July 2002

The anisotropy contributions in epitaxial Fe/MnPd bilayers were analyzed in this study. It was found that due to ferromagnetic–antiferromagnetic interfacial exchange coupling, large uniaxial and cubic anisotropy contributions are also induced, in addition to the unidirectional anisotropy. These contributions play an essential role in the magnetization reversal process of the system, in which unusual reversal processes were found upon some fields orientations.
Nonlinear time series analysis of normal and pathological human walking
Authors: Dingwell Jonathan B. , Cusumano Joseph P.
Published: July 2002

Characterizing locomotor dynamics is essential for understanding the neuromuscular control of locomotion. In particular, quantifying dynamic stability during walking is important for assessing people who have a greater risk of falling. However, traditional biomechanical methods of defining stability have not quantified the resistance of the neuromuscular system to perturbations, suggesting that more precise definitions are required. For the present study, average maximum finite-time Lyapunov exponents were estimated to quantify the local dynamic stability of human walking kinematics. Local scaling exponents, defined as the local slopes of the correlation sum curves, were also calculated to quantify the local scaling structure of each embedded time series. Comparisons were made between overground and motorized treadmill walking in young healthy subjects and between diabetic neuropathic (NP) patients and healthy controls (CO) during overground walking. A modification of the method of surrogate data was developed to examine the stochastic nature of the fluctuations overlying the nominally periodic patterns in these data sets. Results demonstrated that having subjects walk on a motorized treadmill artificially stabilized their natural locomotor kinematics by small but statistically significant amounts. Furthermore, a paradox previously present in the biomechanical literature that resulted from mistakenly equating variability with dynamic stability was resolved. By slowing their self-selected walking speeds, NP patients adopted more locally stable gait patterns, even though they simultaneously exhibited greater kinematic variability than CO subjects. Additionally, the loss of peripheral sensation in NP patients was associated with statistically significant differences in the local scaling structure of their walking kinematics at those length scales where it was anticipated that sensory feedback would play the greatest role. Lastly, stride-to-stride fluctuations in the walking patterns of all three subject groups were clearly distinguishable from linearly autocorrelated Gaussian noise. As a collateral benefit of the methodological approach taken in this study, some of the first steps at characterizing the underlying structure of human locomotor dynamics have been taken. Implications for understanding the neuromuscular control of locomotion are discussed.
Investigation of
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dependence of line shift, line broadening, and line narrowing coefficients in the ν1+3ν3 absorption band of acetylene
Authors: Valipour Hamid , Zimmermann Dieter
Published: July 2002

Line shift coefficients, line broadening coefficients, and line narrowing coefficients have been measured in the ν1+3ν3 band of acetylene using a diode laser system operating at 788 nm and a multipass Herriot absorption cell. Experimental data have been obtained for 20 lines of the P and R branches broadened by N2, O2, air, and the rare gases He, Ne, Ar, Kr, and Xe. The observed line shapes could successfully be reproduced by employing Galatry and Rautian functions which include the phenomenon of Dicke narrowing. Our results for the line broadening coefficients are in good agreement with the values reported previously for other vibrational bands. Thus, the present work confirms the vibrational independence of the broadening coefficients. On the other side, we observed a clear dependence of the narrowing coefficients on rotation in a vibrational transition of acetylene for the first time. In addition, the line center frequencies have been determined with improved accuracy.