bluuebunny/crossref_metadata_2025 huggingface dataset:
Homogeneous longitudinal profiles and synchronous fluctuations of mitochondrial transmembrane potential
Authors: Diaz Giacomo , Falchi Angela Maria , Gremo Fulvia , Isola Raffaella , Diana Andrea
Published: July 2002

This study reports for the first time (a) the longitudinal profile of the transmembrane potential (mΔψ) of single mitochondria using a Nernstian fluorescent probe and (b) the distribution of mΔψ fluctuations of mitochondria undergoing permanent depolarization. Our findings show that (1) mitochondria in different energetic conditions coexist in the same cell, (2) mΔψ is rather homogeneous along the entire length of single mitochondria, (3) mΔψ is not influenced by the surrounding cytoplasmic environment and (4) mΔψ fluctuations occur simultaneously in groups of mitochondria connected in a network. Taken together, these findings provide further evidence for a functional relationship between mitochondrial arrangement and energetic condition.
The importance of the conserved Arg191–Asp227 salt bridge of triosephosphate isomerase for folding, stability, and catalysis
Authors: Kursula Inari , Partanen Sanna , Lambeir Anne-Marie , Wierenga Rik K.
Published: July 2002

Triosephosphate isomerase (TIM) has a conserved salt bridge 20 Å away from both the active site and the dimer interface. In this study, four salt bridge mutants of Trypanosoma brucei brucei TIM were characterized. The folding and stability of the mutants are impaired compared to the wild‐type enzyme. This salt bridge is part of a hydrogen bonding network which tethers the C‐terminal β7α7β8α8 unit to the bulk of the protein. In the variants D227N, D227A, and R191S, this network is preserved, as can be deduced from the structure of the R191S variant. In the R191A variant, the side chain at position 191 cannot contribute to this network. Also the catalytic power of this variant is most affected.
Rac1 prevents cisplatin‐induced apoptosis through down‐regulation of p38 activation in NIH3T3 cells
Authors: Jeong Hye-Gwang , Cho Hyun-Ju , Chang In-Youb , Yoon Sang-Pil , Jeon Young-Jin , Chung Myung-Hee , You Ho Jin
Published: July 2002

In this study, the role of V12‐Rac1 in the cisplatin‐induced apoptosis was investigated. Cisplatin‐induced apoptosis is associated with cytochrome c release, which can be inhibited by V12‐Rac1 expression. The analysis of mitogen‐activated protein kinase activity indicated that V12‐Rac1 expression led to a decrease in p38 activity after exposure to cisplatin but not c‐jun N‐terminal kinase and extracellular signal‐regulated kinase. Using pharmacological inhibitors, it was found that only p38 is a critical mediator in the cisplatin‐induced apoptosis of NIH3T3 cells. This suggests that V12‐Rac1 can stimulate the anti‐apoptotic signaling pathway in response to cisplatin, and that decreased p38 activity caused by V12‐Rac1 expression in cisplatin‐treated NIH3T3 cells is crucial for V12‐Rac1‐dependent cell survival.
Degradation of human Aurora‐A protein kinase is mediated by hCdh1
Authors: Taguchi Sei-ichi , Honda Kei , Sugiura Kazumitsu , Yamaguchi Akio , Furukawa Koichi , Urano Takeshi
Published: July 2002

Human Aurora‐A is related to a protein kinase originally identified by its close homology to Ipl1p from Saccharomyces cerevisiae and aurora from Drosophila melanogaster, which are key regulators of the structure and function of the mitotic spindle. We previously showed that human Aurora‐A is turned over through the anaphase promoting complex/cyclosome (APC/C)–ubiquitin–proteasome pathway. The association of two distinct WD40 repeat proteins known as Cdc20 and Cdh1, respectively, sequentially activates the APC/C. The present study shows that Aurora‐A degradation is dependent on hCdh1 in vivo, not on hCdc20, and that Aurora‐A is targeted for proteolysis through distinct structural features of the destruction box, the KEN box motifs and its kinase activity.
Extracellular superoxide dismutase and glomerular mesangial cells: its production and regulation
Authors: Yamada Harutaka , Adachi Tetsuo , Fukatsu Atsushi , Misao Sachiko , Yamada Yasukazu , Aoki Takanari , Miura Naoto , Sakuma Masato , Nishikawa Kazuhiro , Futenma Arao , Kakumu Shinichi
Published: July 2002

Extracellular superoxide dismutase (EC‐SOD) is synthesized in mesenchymally derived cells and prevents the oxygen radical‐induced injury. We studied whether kidney mesangial cells (MCs) produce EC‐SOD and how its production is associated with chemokine secretion. Under unstimulated condition, MCs produced EC‐SOD, and its production was correlated positively with cyclic adenosine monophosphate (cAMP), but negatively with interleukin (IL)‐6 or IL‐8 production. By prednisolone or phorbol myristate acetate treatment, EC‐SOD levels were correlated negatively with levels of IL‐6 and IL‐8. The presence of adenylate cyclase inhibitor 2′,3′‐dideoxyadenosine lost the prednisolone effect. The stimulation of EC‐SOD production might be one of the important effects of prednisolone via cAMP pathway in MCs.
N‐terminal methylation of the core light‐harvesting complex in purple photosynthetic bacteria
Authors: Wang Zheng-Yu , Shimonaga Masahiro , Kobayashi Masayuki , Nozawa Tsunenori
Published: July 2002

Several core light‐harvesting complexes from both sulfur and non‐sulfur purple photosynthetic bacteria have been identified to be methylated at the N‐terminal α‐amino group of β‐polypeptides by using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and nuclear magnetic resonance. Monomethylation has been confirmed for the N‐terminal alanine residues of the β‐polypeptides from Rhodospirillum rubrum, Thermochromatium tepidum and Chromatium vinosum, but not for the β‐polypeptide from Rhodobacter sphaeroides. The modification appears to be related with the amino acid sequence and charge distribution in the N‐terminal end. Some common features and possible functions are discussed.
Classification of female urinary incontinence by the scored incontinence questionnaire
Authors: Ishiko O. , Sumi T. , Hirai K. , Ogita S.
Published: July 2002

Objectives: Our purpose was to investigate whether urinary incontinence (UI) severity could be graded by UI scores. Methods: The study included 168 UI patients diagnosed by conventional procedures as stress incontinence (SI, n=108) or urge incontinence (URI, n=60). A questionnaire containing 15 items scored for stress‐score (s‐s) and urge‐score (u‐s) was administered to patients to assess the correlation between pad test values (PTVs) and s‐s in SI and u‐s in URI. Results: Significant correlations were found between log[PTVs] and both s‐s and u‐s: log[PTVSI]=0.051s‐s−0.207 (r=0.830, P<0.0001) and log[PTVURI]=0.064u‐s−0.459 (r=0.827, P<0.0001). Based on theoretical PTVs obtained using these equations, s‐s of 26–24, 23–18, and 17–10 in SI were equivalent to severe, moderate, and mild, respectively, and u‐s of 22–19 and 18–12 in URI were equivalent to moderate and mild, respectively, according to the classification of the International Continence Society. Conclusion: The UI score should be a simple and useful procedure for use by general gynecologists to grade UI severity clinically.
Exposure to human immunodeficiency virus among healthcare workers in South Africa
Authors: Gounden Y.P. , Moodley J.
Published: July 2002

There have been no reports in the literature on occupational hazards of HIV in developing countries. The aim of this study was to evaluate occupational exposure to HIV in healthcare workers in Durban, South Africa. Individuals with occupational exposure to HIV were interviewed. Thirteen percent of the staff reported injuries with HIV positive patients. Registrars in training were the highest risk group (60%). Of the injuries, 94% were percutaneous and 65% occurred during emergency surgery. The commonest place of injury was the operating theater (46%) and the commonest procedure associated with accidental exposure was cesarean section (57%). Fifty‐one percent were not wearing eye protection during procedures and although 83% initiated post‐exposure prophylaxis (PEP), 48% discontinued treatment due to side effects of the drugs. Occupational exposure to HIV is common in the developing world. Rectifiable factors identified in this study that contributes to the milieu of occupational acquisition of HIV include less than proper adherence to universal precaution; inadequate documentation procedures and failure of a large percentage of respondents to complete post‐exposure prophylaxis.
Socio‐economic correlates of traumatic injuries to the permanent incisors in schoolchildren aged 12 years in Blumenau, Brazil
Authors: Marcenes W , Zabot N. E. , Traebert J.
Published: July 2002

Abstract – This study aimed to assess the prevalence of injuries to the permanent incisors in Blumenau, Brazil. In addition, the relationship between dental injuries and socio‐economic indicators was examined. A cross‐sectional survey was carried out. It included a random sample of 652 children aged 12 years, from both sexes, attending public and private primary schools in Blumenau, Brazil. Multi‐stage sampling technique and proportional representation were adopted. A trained and calibrated dentist collected the data through clinical examinations and interviews. Clinical examination included type of damage, treatment provided and needed, size of incisal overjet and type of lip coverage. The response rate was 82.5%. The prevalence of dental injuries was 58.6%. Boys experienced more injuries than girls, 67.2% and 50.2% (P=0.001), respectively. Children from mothers with higher schooling experienced more dental injuries than those from of mothers with lower schooling, 68.2% and 56.6% (P=0.03). Father’s level of education, parents’ employment status and family income were not statistically significantly associated with dental injuries (P>0.05). There was a tendency for children with incisal overjet greater than 5 mm (P=0.2) and inadequate lip coverage (P=0.1) to have more dental injuries, but differences were not statistically significant. Nearly all (97.3%) children who had dental injuries needed treatment. In conclusion, the prevalence of dental injuries in Blumenau, Brazil, was very high, treatment of dental injuries was severely neglected, and boys and children from mothers with high schooling were more likely to have experienced dental injuries.
Marked decrease in the Epstein‐Barr virus positivity rate in nodular sclerosis subtype Hodgkin's disease in Tokyo: trend between 1955 and 1999
Authors: Takeuchi Kengo , Morishita Yasuyuki , Fukayama Masashi , Mori Shigeo
Published: July 2002

We studied the trends of the Epstein‐Barr virus (EBV) positivity rate in Hodgkin's disease (HD) between 1955 and 1999. The overall positivity rate gradually decreased over time [12 out of 23 (52%) in 1955–69; 18 out of 39 (46%) in 1970–84; 13 out of 44 (35%) in 1985–99; P = 0·135]. Interestingly, a marked decrease in the rate was noted in the nodular sclerosis (NS) subtype [5 out of 11 (45%); 4 out of 19 (21%); 1 out of 24 (4%); P < 0·01] but not in other classic HD [7 out of 11 (63%); 14 out of 18 (78%); 12 out of 18 (67%); P = 0·775]. Our results indicate that the EBV positivity rate in HD has decreased over time and that this trend reflected the increasing incidence of EBV‐negative NS.
Long‐term effect of radioactive iodine on thyroid function and size in patients with solitary autonomously functioning toxic thyroid nodules
Authors: Nygaard Birte , Hegedüs Laszlo , Gerhard Nielsen Kamilla , Ulriksen Peter , Hansen Jens Mølholm
Published: July 2002

OBJECTIVE

To investigate the long‐term effects of radioiodine (131I) on thyroid function and size in patients with a solitary toxic thyroid nodule.

DESIGN

Prospective study of patients treated for a solitary autonomous toxic nodule, followed by evaluation of thyroid volume and function.

PATIENTS

Sixty‐two consecutive patients followed for a minimum of 12 months (range 12–168, median 60). Seventeen patients received antithyroid drug treatment before 131I.

MEASUREMENTS

Standard thyroid function variables and ultrasonically determined thyroid volume before as well as 0.75, 1.5, 3, 6 and 12 months after treatment, and then once a year were investigated.

RESULTS

131I treatment (3.7 MBq/g thyroid tissue corrected to a 100% 24‐h 131I uptake) was given as a single dose in 53 patients; six needed two doses and another three were given 3–5 131I treatments. The median initial dose was 310 MBq (140–666) and the median total dose was 332 MBq (148–1576). In patients receiving one 131I treatment (n = 53) the total thyroid volume decreased significantly from a median of 40 ml (range 19–77) to 24 ml (8–50) within 3 months. This represented a median reduction of 35%. A further significant decrease was seen after 24 months to a total reduction of 45%. In patients given more than one dose the thyroid volume was reduced from a median of 45 ml (19–104) before treatment to 30 ml (14–50) after a follow‐up of 60 months (9–132) after the last 131I treatment. Patients without antithyroid pretreatment, receiving one 131I treatment (n = 39) became euthyroid after a median of 1.5 months (0.75–9) after treatment. Seventy‐five per cent were euthyroid within 3 months. In patients pretreated with antithyroid drugs and treated with one dose of 131I (n = 14) euthyroidism was achieved after a median of 12 months (0.75–24) after 131I treatment. Hypothyroidism developed in five patients (8%) after a median of 36 months (6–60) after 131I treatment.

CONCLUSION

A cure‐rate of 75% within 3 months is seen when treating autonomous solitary toxic thyroid nodules with 131I. The thyroid volume is reduced by 35% within 3 months and 45% after 2 years. Side‐effects are few and consist of hypothyroidism in less than 10% with a median follow‐up of 5 years. This treatment should be regarded as the standard treatment for this condition until prospective comparisons with surgery and ethanol injection therapy have been performed.
Reproducibility of the cortisol response to stimulation with the low dose (1 μg) of ACTH
Authors: Park Y. J. , Park K. S. , Kim J. H. , Shin C. S. , Kim S. Y. , Lee H. K.
Published: July 2002

OBJECTIVE

Previous studies have shown that the rapid ACTH stimulation test using a low dose of 1 μg is more sensitive than that using 250 μg ACTH for detecting subtle cases of adrenal insufficiency. However, there are controversies for the reproducibility of the 1 μg‐test. To evaluate the reproducibility of the 1 μg‐test, we assessed both day‐to‐day and diurnal variations of cortisol responses to 1 μg ACTH injection. In addition, optimum sampling time for the 1 μg‐test was also determined.

SUBJECTS

AND DESIGN Eight healthy volunteers and five patients with secondary adrenal insufficiency were recruited. Healthy subjects were given 1 μg ACTH 3 times in the morning (0800 h) and 2 times in the afternoon (1600 h). Patients with adrenal insufficiency had 2‐tests in the morning and 2 in the afternoon. Serum cortisol levels were measured every 10 minutes for 1 h after the injection.

RESULTS

In healthy subjects, basal and peak serum cortisol levels were significantly higher in the morning (P < 0.05), whereas maximum cortisol increments were higher in the afternoon (P < 0.001). In patients with adrenal insufficiency, basal and peak serum cortisol levels in the morning were not different from corresponding values in the afternoon. Intra‐individual coefficient of variation (CV) of peak serum cortisol response to 1 μg ACTH ranged from 3.0 to 16.4% in healthy subjects and 10.0–34.4% in patients. Also, there was a significant correlation between peak morning or afternoon cortisol levels after 1 μg ACTH injection given in different days in both healthy subjects and patients. Twenty‐six of the 40 studies in healthy subjects showed peak response at 20 minutes, while nine showed it at 30 minutes Using the data acquired at 20 and 30 minutes, all 40 studies in healthy subjects showed normal results while none of 20 studies in patients was normal.

CONCLUSIONS

We conclude that the cortisol response to 1 μg ACTH stimulation was reproducible in both healthy subjects and patients with secondary adrenal insufficiency. In order to assess adrenal function more accurately with the 1 μg ACTH stimulation test, serum cortisol should be measured before and 20 and 30 minutes after ACTH injection.
Assessing the suitability of central European landscapes for the reintroduction of Eurasian lynx
Authors: Schadt Stephanie , Revilla Eloy , Wiegand Thorsten , Knauer Felix , Kaczensky Petra , Breitenmoser Urs , Bufka Luděk , Červený Jaroslav , Koubek Petr , Huber Thomas , Staniša Cvetko , Trepl Ludwig
Published: July 2002

After an absence of almost 100 years, the Eurasian lynx Lynx lynx is slowly recovering in Germany along the German–Czech border. Additionally, many reintroduction schemes have been discussed, albeit controversially, for various locations. We present a habitat suitability model for lynx in Germany as a basis for further management and conservation efforts aimed at recolonization and population development.

We developed a statistical habitat model using logistic regression to quantify the factors that describe lynx home ranges in a fragmented landscape. As no data were available for lynx distribution in Germany, we used data from the Swiss Jura Mountains for model development and validated the habitat model with telemetry data from the Czech Republic and Slovenia. We derived several variables describing land use and fragmentation, also introducing variables that described the connectivity of forested and non‐forested semi‐natural areas on a larger scale than the map resolution.

We obtained a model with only one significant variable that described the connectivity of forested and non‐forested semi‐natural areas on a scale of about 80 km2. This result is biologically meaningful, reflecting the absence of intensive human land use on the scale of an average female lynx home range. Model testing at a cut‐off level of P > 0·5 correctly classified more than 80% of the Czech and Slovenian telemetry location data of resident lynx. Application of the model to Germany showed that the most suitable habitats for lynx were large‐forested low mountain ranges and the large forests in east Germany.

Our approach illustrates how information on habitat fragmentation on a large scale can be linked with local data to the potential benefit of lynx conservation in central Europe. Spatially explicit models like ours can form the basis for further assessing the population viability of species of conservation concern in suitable patches.
Maternal cigarette smoking and pregnancy outcome
Authors: Tuthill  , Stewart  , Coles  , Andrews  , Cartlidge
Published: July 2002

Maternal smoking rates in pregnancy have declined, particularly in the non‐manual social classes, and perinatal mortality rates have fallen over the last 20 years. We have therefore re‐evaluated the relationship between maternal cigarette smoking and pregnancy outcome against this background. A total of 608 stillbirths and 634 infant deaths were identified using the All Wales Perinatal Survey. The cause of death was classified using the clinicopathological system. Maternal smoking rates and social class groupings were compared with those in a cohort of 16047 survivors born to women resident in South Glamorgan. The smoking rate was 37.8% in mothers of babies who died compared with 27.2% in mothers of survivors, an odds ratio (OR) of 1.63 [95% CI 1.44, 1.84]. The OR for unexplained stillbirth was 1.72 [95% CI 1.38, 2.13], placental abruption 2.07 [95% CI 1.29, 3.31], infection 3.70 [95% CI 2.23, 6.13] and sudden infant death syndrome 4.84 [95% CI 3.05, 7.69]. Maternal smoking was not associated with death due to prematurity or a congenital anomaly. Despite changes in smoking habits and the causes of perinatal death, smoking during pregnancy continues to be strongly associated with fetal and infant mortality. It is important that health promotion activities are effective in reducing smoking during pregnancy.
DUPLICATED POPLITEAL AND SUPERFICIAL FEMORAL VEINS: INCIDENCE AND POTENTIAL SIGNIFICANCE
Authors: Dona E. , Fletcher J. P. , Hughes T. M. D. , Saker K. , Batiste P. , Ramanathan I.
Published: July 2002

Background: Duplication of the popliteal and superficial femoral veins (PV, SFV) is a normal variant previously reported in up to 25% of limbs. Little clinical significance, however, has been attributed to this apparently common anomaly. The present study was designed to determine the incidence of duplications in individuals presenting for venous incompetence studies, and whether their presence could, in theory, act as a predisposing factor to deep venous thrombosis (DVT) formation.

Methods: Duplex ultrasound examinations were performed in which venous duplications were actively searched for and recorded. The diameters of both limbs of any duplicated system and the single vessel immediately distal to it were recorded. Using these measurements, the changes in total cross‐sectional area (CSA) associated with these anomalies were calculated. In addition, with the knowledge that the volume flow rate must remain constant, the velocity changes associated with such systems were calculated.

Results: A total of 248 limbs from 177 patients was scanned. Duplications were found in 39 (15.7%) of these limbs. Of these, 30 limbs (77%) involved only the SFV, seven (18%) involved both the SFV and PV, and two (5%) involved only the PV. Short‐segment SFV duplications were used to calculate the percentage change in total CSA and therefore blood flow velocities. Of the 13 (33%) suitable for such calculations, and calculating for each individual duplicated system, a mean increase in the vessel’s total CSA of 42%, which corresponded to a theoretical decrease in blood flow velocity of 36%, was found.

Conclusion: The present study confirms the significantly high incidence of duplications of the PV and SFV and raises the possibility of the potential for DVT formation secondary to changes in flow velocities.
Urinary incontinence among community‐dwelling people aged 40 years or older in Japan: Prevalence, risk factors, knowledge and self‐perception
Authors: UEDA TOMOHIRO , TAMAKI MASAHIRO , KAGEYAMA SUSUMU , YOSHIMURA NAOKI , YOSHIDA OSAMU
Published: July 2002

Background
: Urinary incontinence (UI) is a common problem in adults, especially among the elderly. We examined the prevalence and risk factors of UI and potential factors hindering individuals from seeking treatment for UI among a community‐dwelling population aged over 40 years.

Methods
: Data were collected by mailing a 23‐item urinary incontinence questionnaire to a random sample of community‐dwelling individuals aged 40–75 years (n = 3500) in seven towns of Shiga Prefecture, Japan. Collected data were then used to estimate the prevalence of UI and to provide information regarding subtypes of UI, knowledge and self‐perception about UI.

Results
: The overall response rate was 52.5%. Prevalence of UI for male and female respondents were 10.5% and 53.7%, respectively. The incidence of urge incontinence increased as age increased in the male group. In women, stress incontinence was prevalent at all ages and the incidence of urge incontinence increased over 70 years of age. Urinary incontinence was more likely as activities of daily living limitations and cystitis increased. Women with a history of hysterectomy or diabetes mellitus and men who had stroke were at increased risk for UI. Of those who reported UI, only 3% had ever consulted doctors or other health care professionals concern‐ ing it, 25% recognized their condition as a disease and 38% considered it curable by appropriate treatments. In addition, 63% regarded UI as an unavoidable consequence of aging, 63% con‐ sidered their condition was embarrassing and 54% were reluctant to seek treatment from a health professional.

Conclusions
: Although UI is common among community‐dwelling individuals over 40 years of age, the majority of affected individuals remained untreated due to lack of knowledge and/or a negative perception of UI. Thus, community education on UI may be needed to increase the number of UI patients who receive treatment.
Are the meiofaunal polychaetes Hesionides arenaria and Stygocapitella subterranea true cosmopolitan species? — results of RAPD‐PCR investigations
Authors: Schmidt Hartmut , Westheide Wilfried
Published: July 2002

The interstitial meiofauna of sand beaches includes many species that are regarded as cosmopolites, on the basis of records from various sites throughout the world. There is a long‐standing debate about the causes of such a distribution, but for most of these species it is still questionable whether they are in fact true species or ‘merely’ complexes of cryptic species. Here genetic differentiation is examined within and between two species considered typically cosmopolitan, Hesionides arenaria arenaria (Hesionidae) and Stygocapitella subterranea (Parergodrilidae), by RAPD‐PCR analyses of specimens from diverse marine regions on two continents. For S. subterranea at three sites, on the North Sea coast (Sylt) and the US Atlantic (Massachusetts) and Pacific (Washington) coasts, with 14 primers 335 different DNA fragments were found: 20 diagnostic ones for the European animals, 17 for the animals from the American East Coast and 14 for those from the American West Coast. Five cluster procedures were used, all of which significantly distinguished the three populations as separate genetic clades; it is recommended that each be given species status. In contrast, the individual specimens of H. a. arenaria from eight European sites, between Skagerrak and the eastern Mediterranean (including the Canary Islands), and the North American Pacific coast, for which 468 different DNA fragments were amplified with 12 primers, do not form separate genetic clades. For no single population was it possible to demonstrate even one diagnostic character. Therefore the cosmopolitan nature of H. a. arenaria has been confirmed at the DNA level.
Growth of cubic (zinc blende) CdSe by molecular beam epitaxy
Authors: Samarth N. , Luo H. , Furdyna J. K. , Qadri S. B. , Lee Y. R. , Ramdas A. K. , Otsuka N.
Published: July 2002

We report the growth of cubic (zinc blende) CdSe epilayers on [100] GaAs substrates by molecular beam epitaxy. The lattice constant of the CdSe epilayers is 6.077 Å, and the energy gap is 1.75, 1.74, and 1.67 at 10, 80, and 300 K, respectively.
Electric field induced solidification
Authors: Tao R. , Woestman J. T. , Jaggi N. K.
Published: July 2002

We present a description of electrorheological fluids in terms of an electric field induced phase transition at a critical electric field Ec. Theoretically, we find that as the applied field exceeds Ec, the osmotic pressure becomes negative and the liquid experiences a phase transition to a solid phase. Ec is experimentally determined as a function of concentration in one system. Our theoretically predicted phase diagram is in reasonable agreement with our experimental data.
Heteroepitaxial growth of Y2O3 films on silicon
Authors: Fukumoto Hirofumi , Imura Takeshi , Osaka Yukio
Published: July 2002

Yttria (Y2 O3 ) films have been grown on Si (100) and Si (111) substrates heated at 800 °C by vacuum evaporation. X-ray diffraction and reflection high-energy electron diffraction observations reveal the heteroepitaxial growth of Y2 O3 films on Si (100) and Si (111) substrates. The (111) oriented Y2 O3 films are grown directly on Si (111) substrates. The (100) oriented Y2 O3 films are grown on the thin (Y2 O3 )0.09 (ZrO2 )0.91 layer predeposited on Si (100) substrates instead of direct growth on Si (100) substrates.
Damage-induced uphill diffusion of implanted Mg and Be in GaAs
Authors: Robinson Heyward G. , Deal Michael D. , Stevenson David A.
Published: July 2002

The redistribution of Be and Mg implants upon post-implant annealing is studied in order to evaluate the influence of implant damage on the diffusion process. Rapid uphill diffusion is observed in the peak of Mg implants in GaAs, whereas Be implants show only uniform, concentration-dependent diffusion. This behavior is explained by the substitutional-interstitial-diffusion mechanism and computer simulations of damage-produced point defects. In the region of uphill diffusion, the dopants diffuse from areas of excess interstitials toward areas of excess vacancies. A critical concentration of point defects is necessary to initiate uphill diffusion. Uphill diffusion can be induced in Be implants by co-implanting with a heavier element such as Ar.
Voltage-dependent scanning tunneling microscopy images of liquid crystals on graphite
Authors: Mizutani W. , Shigeno M. , Ono M. , Kajimura K.
Published: July 2002

Voltage-dependent images of liquid crystals on graphite were observed in air by scanning tunneling microscopy (STM). Molecular rows of liquid crystals and the atomic pattern of the graphite substrate were imaged with high (above 1 V) and low (below 0.1 V) bias voltages, respectively. Patterns of molecules, grain boundaries, and distinguishable defects of the liquid crystal arrangement were reproduced even after imaging the substrate in the same area. This indicates that the graphite lattice can be seen by STM without touching or disturbing the adsorbed molecules on it. A resonant tunneling model is proposed to explain the phenomenon.
Correlation length of interface roughness and its enhancement in molecular beam epitaxy grown GaAs/AlAs quantum wells studied by mobility measurement
Authors: Noda T. , Tanaka M. , Sakaki H.
Published: July 2002

We have studied the correlation length (Λ) of interface roughness in GaAs/AlAs quantum wells (QWs) prepared by molecular beam epitaxy (MBE). It is found that the mobility of two-dimensional electrons in very thin selectively doped GaAs/AlAs QW structures is substantially enhanced when the bottom AlAs barrier layer is prepared by alternate beam MBE and/or by the use of superlattice buffer layer below the QW. By measuring the electron concentration dependence of mobility and comparing with the theory of interface roughness scattering, we have found that Λ of the bottom (GaAs-on-AlAs) interface of the QW gets as large as 200–300 Å, when prepared by the modified growth technique, which is about three times as large as that (∼70 Å) by conventional MBE.
Atom probe analysis of Fe73.5Si13.5B9Nb3Cu1 nanocrystalline soft magnetic material
Authors: Hono K. , Inoue A. , Sakurai T.
Published: July 2002

The microstructure of Fe73.5Si13.5B9Nb3Cu1 soft magnetic material with a nanocrystalline structure has been investigated by atom probe field ion microscopy. In the as-quenched amorphous sample, all the alloying elements were found to distribute homogeneously as an amorphous solid solution. In the annealed sample with the optimum soft magnetic properties, we found that two phases were present. One was Fe-Si solid solution and the other was the B- and Nb-enriched region with less Si content. Although some uncertainty remains regarding Cu, the present result is consistent with an early speculation based on the lattice parameter measurement.
Synthesis of high quality diamond films in a turbulent flame
Authors: Snail Keith A. , Craigie Cameron J.
Published: July 2002

High quality polycrystalline diamond films have been synthesized in a premixed, turbulent oxygen-acetylene flame, using a commercial brazing torch. The quality of the films was measured by Raman spectroscopy, electron microscopy, and hemispherical transmittance measurements in the ultraviolet, visible, and infrared. Turbulence was achieved by operating the torch with a sufficiently high Reynolds number. The presence of turbulence was confirmed by observations of changes in the flame shape, the characteristic sound of the flame, and calculation of the Reynold’s number.
Van der Waals bonding of GaAs on Pd leads to a permanent, solid-phase-topotaxial, metallurgical bond
Authors: Yablonovitch E. , Sands T. , Hwang D. M. , Schnitzer I. , Gmitter T. J. , Shastry S. K. , Hill D. S. , Fan J. C. C.
Published: July 2002

Various forms of wafer bonding have now emerged as a serious competitor to heteroepitaxy for optoelectronic integration of dissimilar semiconductor materials. Among the types of wafer bonding, perhaps the most flexible is that which employs free-standing III–V films as created by epitaxial liftoff. For some purposes, weak Van der Waals forces provide an adequate bond between the native oxides of the III–V film and its new substrate. If the substrate is coated by palladium however, a low temperature solid-phase-topotaxial reaction occurs, producing oriented Pd4GaAs under the GaAs film. In effect, the topotaxy comes about through mechanical contact alone. The resulting metallurgical bond is an ohmic contact, a thermal contact and a robust, permanent, adherent contact.
Thermal boundary resistance for YBa2Cu3O7−δ films
Authors: Nahum M. , Verghese S. , Richards P. L. , Char K.
Published: July 2002

We have made direct measurements of the thermal boundary resistance, Rbd, between high quality epitaxial films of YBa2Cu3O7−δ and a variety of substrates with and without buffer layers. The boundary resistance was deduced from measurements of the electrical resistance changes in three parallel strips of YBa2Cu3O7−δ when one was electrically heated. Our measurements indicate that Rbd is weakly dependent on temperature and, for all the measured samples, has a value of 0.8–1.4×10−3 K cm2/W between 90 and 200 K, which is a factor of ≊80 larger than the prediction of the acoustic mismatch model at 100 K. The thermal response time of ≊1 ns which results from the heat capacity of the film and Rbd is observed in many experiments with pulsed laser sources.
Exchange anisotropy in coupled films of Ni81Fe19 with NiO and CoxNi1−xO
Authors: Carey M. J. , Berkowitz A. E.
Published: July 2002

Shifted hysteresis loops were used to investigate exchange anisotropy in 500 Å CoxNi1−xO/300 Å Ni81Fe19 polycrystalline bilayer couples. Bilayers of Ni81Fe19 with NiO have a room-temperature exchange field, He, of 30 Oe in the as-deposited state. A maximum in the exchange field at room temperature was observed near x=0.4, indicating an optimal alloying of the properties of the high anisotropy CoO and the high Néel temperature NiO. The blocking temperatures of the exchange couples vary linearly with x, suggesting a linear dependence of the oxide Néel temperature with x.
Impact ionization and positive charge formation in silicon dioxide films on silicon
Authors: DiMaria D. J. , Arnold D. , Cartier E.
Published: July 2002

Positive charge formation and its possible relationship to impact ionization in silicon dioxide have been controversial issues for many years. In this study, band-gap ionization due to the development of a high-energy tail in the hot-electron energy distribution is shown to occur in films thicker than 20.0 nm at fields higher than 7 MV/cm. This process is demonstrated to ‘‘directly’’ account for hole currents in the substrate circuit of n-channel field-effect transistors and for the observation of positively trapped charges accumulating at the substrate-silicon/silicon-dioxide interface at low injected-carrier fluences (less than 0.001 C/cm2) before the onset of trap creation.
Characterization of diamondlike carbon by infrared spectroscopy?
Authors: Grill A. , Patel V.
Published: July 2002

Comparison of Fourier transform infrared (FTIR) absorption spectroscopy, high resolution 13C nuclear magnetic resonance spectroscopy, and hydrogen evaluation by forward recoil elastic scattering (FRES) measurements shows that FTIR cannot be used to determine the carbon hybridization or total hydrogen content of diamondlike carbon films (DLC). FTIR absorption reflects only the optically active hydrogen in the DLC and, using it together with FRES, it can provide an estimate of the unbound hydrogen contained in the films. The fraction of unbound hydrogen can reach values of up to ∼50%.
Epitaxial growth of MgO on GaAs(001) for growing epitaxial BaTiO3 thin films by pulsed laser deposition
Authors: Nashimoto Keiichi , Fork David K. , Geballe Theodore H.
Published: July 2002

MgO buffer layers were deposited on GaAs by pulsed laser deposition for epitaxial growth of BaTiO3. MgO was grown epitaxially on GaAs for the first time; the orientation is (001) on GaAs(001). The best crystallographic quality was obtained at 350 °C in 5×10−6 Torr O2. BaTiO3 films with (001) orientation grew epitaxially on MgO/GaAs. The in-plane epitaxial relationship was BaTiO3[100]∥ MgO[100]∥ GaAs[100] in spite of a large lattice mismatch (25.5%) between MgO and GaAs.
Effect of thermal annealing and surface coverage on porous silicon photoluminescence
Authors: Robinson M. B. , Dillon A. C. , Haynes D. R. , George S. M.
Published: July 2002

The effect of thermal annealing and surface coverage on porous silicon photoluminescence was studied in situ in an ultrahigh vacuum chamber. These investigations correlated simultaneously temperature, surface coverage, and photoluminescence intensity. The surface coverage was monitored using transmission Fourier transform infrared spectroscopy. The results demonstrated that the photoluminescence could not be defined only according to the presence of SiH2 surface species. Likewise, the disappearance of the photoluminescence versus thermal annealing did not scale directly with H2 desorption from SiH2 species. The loss of photoluminescence versus thermal annealing was attributed to surface structural changes or the production of surface states which provide pathways for nonradiative recombination.
Planar p-on-n HgCdTe heterostructure photovoltaic detectors
Authors: Arias J. M. , Pasko J. G. , Zandian M. , Shin S. H. , Williams G. M. , Bubulac L. O. , DeWames R. E. , Tennant W. E.
Published: July 2002

We report a process to fabricate planar Hg1−yCdyTe/Hg1−xCdxTe (x<y) heterostructure photodiodes with the p-on-n configuration. The material used for this demonstration was grown by molecular beam epitaxy. The p-on-n planar devices consist of an arsenic-doped p-type epilayer (y=0.28) on top of a long wavelength infrared n-type epilayer (x=0.225, λ=10 μm). The planar junctions were formed by selective pocket diffusion of arsenic deposited by ion implantation. The detailed analysis of the current-voltage characteristics of these diodes as a function of temperature show that they have high performance and that their dark currents are diffusion limited down to 52 K. The results also show that the R0A values for these devices are highly uniform at 77 K.
Si-SiO2 interface trap density in boron- and phosphorus-implanted silicon
Authors: Peterström S.
Published: July 2002

The Si-SiO2 interface trap density has been measured in boron- and phosphorus-implanted silicon. The implantations were made either prior to the oxidation process or through the gate oxide layer. In the boron implantation case the lowest number of interface traps for a specified substrate concentration was reached if the implantation was made through the gate oxide. In the phosphorus implantation case it is, however, favorable to make the implantation prior to the oxidation process.
Band gap bowing in GaP1−xNx alloys
Authors: Liu X. , Bishop S. G. , Baillargeon J. N. , Cheng K. Y.
Published: July 2002

The interband optical absorption edge of GaP1−xNx alloys grown by molecular beam epitaxy has been investigated by photoluminescence and photoluminescence excitation (PLE) spectroscopy. The results demonstrate the transition from nitrogen-bound exciton luminescence indicative of isoelectronic traps in lightly doped films of GaP:N to the formation of indirect band gap alloys in the heavily N-doped GaP films. A large red shift or reduction in band gap energy with increasing N concentration which is observed in PLE spectroscopy identifies the GaP1−xNx alloy system as one of the limited number of alloy systems whose intermediate compositions can have band gaps smaller than those of either of the constituent binary compounds.
Photoinduced hysteresis changes and charge trapping in BaTiO3 dielectrics
Authors: Warren W. L. , Dimos D.
Published: July 2002

We have been able to observe intrinsic photoinduced changes in the hysteresis response of BaTiO3 single crystals by the application of ultraviolet (UV) light in combination with an applied bias. The amount of switchable polarization can be suppressed by over 90% by this UV/bias treatment. The photoferroelectric effects are reproducible, reversible, and stable. Electron paramagnetic resonance measurements were also made to characterize the charge trapping associated with these electrical effects. We find that isolated Fe sites are trap centers in these ceramics and it appears that the Fe3+ density can be correlated to the amount of switchable polarization. These results also suggest that BaTiO3 ceramics can be used as a medium to store optical images.
Magnetic hardening of FeSiBCuNb ribbons and wires during the first stage of crystallization to a nanophase structure
Authors: Vázquez M. , Marin P. , Davies H. A. , Olofinjana A. O.
Published: July 2002

The structural and magnetic properties of Fe73.5Si13.5B9Cu1Nb3 alloy wire and ribbon have been studied after thermal treatments up to temperatures at which partial (75%) devitrification to a nanocrystalline structure occurs. Nanocrystals are detected by x-ray diffraction only after treatments around 500 °C, while differential scanning calorimetry studies suggest that substantial structural change is inititiated at a much lower temperature (about 400°). A clear magnetic hardening is observed in samples heated within the temperature range 400–480 °C. This phenomenon is also accompanied by an increase of the linear magnetostriction. These effects are discussed in terms of the local structural rearrangements produced during the first stages of the crystallization process. The study is also extended partly to FeSiB, FeSiBCu, and FeSiBNb alloys.
Ultralow-energy focused electron beam induced deposition
Authors: Hoyle P. C. , Cleaver J. R. A. , Ahmed H.
Published: July 2002

We have studied focused electron beam induced deposition from W(CO)6 at beam primary energies between 20 and 0.06 keV. Submicrometer resolution with 4 nA beam current was maintained at very low primary energies using a retarding field configuration. Decomposition cross sections of W(CO)6 for primary energies below about 1 keV were found to be about a factor of 4 larger than those at 20 keV. Depending on the scan conditions, the resistivity of the deposits formed using low primary energies was found to be up to about a factor of 4 lower than at 20 keV implying a higher metallic content. These results form the basis of an improved method for repairing clear defects on x-ray masks and for making conducting tracks on semiconducting materials.
High-quality 4H-SiC homoepitaxial layers grown by step-controlled epitaxy
Authors: Itoh Akira , Akita Hironobu , Kimoto Tsunenobu , Matsunami Hiroyuki
Published: July 2002

4H-SiC bulk crystals were grown controllably by means of a modified Lely method. Homoepitaxial growth of 4H-SiC was carried out by vapor phase epitaxy utilizing step-controlled epitaxy on 4H-SiC substrates prepared by the modified Lely method. The physical properties (electrical and optical properties) of 4H-SiC epilayers were characterized by Hall effects and photoluminescence (PL) measurements. The electron mobilities as high as 720 cm2/V s at 292 K, and 11 000 cm2/V s at 77 K were obtained. In the PL measurement, the epilayers with a thickness more than 20 μm showed luminescence attributed to free exciton recombination, which indicates the improvement of crystal quality by step-controlled epitaxy.
Giant magnetoresistance in magnetic multilayered nanowires
Authors: Piraux L. , George J. M. , Despres J. F. , Leroy C. , Ferain E. , Legras R. , Ounadjela K. , Fert A.
Published: July 2002

Giant magnetoresistance (GMR) is observed in a new type of nanostructured material consisting of magnetic multilayered nanowires formed by electrodeposition into nanometer-sized pores of a template polymer membrane. The composition of these nanowires is modulated over nanometer length scales with distinct magnetic and nonmagnetic metallic layers. Magnetoresistance measurements with the current perpendicular to the layers were performed on the array of parallel nanowires. GMR of about 15% was observed at room temperature on Co/Cu multilayered nanowires.
Schottky effect at a metal-polymer interface
Authors: Rikken G. L. J. A. , Braun D. , Staring E. G. J. , Demandt R.
Published: July 2002

We report the observation of the Schottky effect at the interface between a metal and a semiconducting polymer by means of internal photoemission spectroscopy. The bias dependence of the barrier provides information on the electrical properties of the polymer.
High-sensitivity broadband microwave spectroscopy with small nonresonant coils
Authors: Mahdjour H. , Clark W. G. , Baberschke K.
Published: July 2002

The use of a small, nonresonant, coil of μm dimensions as the microwave magnetic field structure of a broadband electron-spin-resonance (ESR) spectrometer is described. The coil is driven by a broadband microwave generator which operates between 0.1 and 8.5 GHz. The samples may fill the coil to approximately 100%. It is shown that for small size samples this system offers higher sensitivity than a conventional cavity spectrometer. Because the system is broadband, either frequency scans or the conventional magnetic field scans can be used to traverse the resonance. Examples for DPPH and for the spin glass AgMn using this method are reported. Since the sample coil is small, it has many potential applications, such as insertion into the mixing chamber of a dilution refrigerator or high-pressure cell, efficient use of power in ENDOR and other double resonance experiments, and rapid recovery from transients in pulsed ESR experiments.
Neutron spectroscopy on TFTR
Authors: Strachan J. D. , Nishitani T. , Barnes Cris W.
Published: July 2002

A 3He ionization chamber was used to measure neutron spectra on TFTR during 1987. The ion temperature was deduced for one set of Ohmically heated plasmas and agreed within 20% with that measured by other diagnostics. The absolute efficiency was calibrated using a d–d neutron generator.
Atomic oxygen detection by a silver-coated quartz deposition monitor
Authors: Matijasevic V. , Garwin E. L. , Hammond R. H.
Published: July 2002

A method for measuring the flux of atomic oxygen utilizing a silver film on a quartz-crystal deposition rate monitor is described. Measuring the initial oxidation rate of the silver, which is proportional to the atomic oxygen flux, determines a lower limit on the atomic oxygen flux. This method is more direct than measuring the conductance of the silver film, has an intrinsic flux detection range of 1013–1017 atoms/cm2 s, and is reversible by exposing the sensor to an atomic hydrogen flux.
Microstrip resonators for electron-spin resonance
Authors: Wallace W. J. , Silsbee R. H.
Published: July 2002

Direct detection of thin-film and interfacial electron-spin resonance (ESR) pushes conventional techniques to the noise limit for those techniques and requires use of large-area samples. Several microstrip resonator structures are compared here to conventional techniques and experimental results reported. Aluminum microstrip resonators are shown to have from 3 to 10 times the sensitivity to two-dimensional systems as waveguide cavities, while needing only about 1/20th the sample area. A microstrip resonator metal-oxide-superconductor field-effect-transistor structure for study of inversion layer conduction electron-spin resonance is reported in which the resonator functions as the gate, and ohmic contact is made to the inversion layer. A ‘‘microstrip induction spectrometer’’ is described in which a bimodal microstrip resonator is used along with a cryogenically cooled amplifier for study of lines with very long relaxation times. The ultimate sensitivity to Curie law spins of this spectrometer is 1×108 spins in an area of 1 cm2 at 4.2 K for a 1-G linewidth at the onset of saturation. Superconducting microstrip resonators for ESR are reported and their use discussed.