bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring the Association of Socio-Economic Factors with Knowledge of Eco-Friendly Farming Practices among Vegetable Growers in Madhya Pradesh, India
Authors: Yadav Shailu , Rai DP , Singh YK , Misra Abhishek
Published: February 2025

Eco-friendly terms used to describe products and services that have minimal or no negative impact on the environment. Eco-friendly farming focuses on natural food production, avoiding the use of synthetic chemicals and genetically modified organisms. The goal of eco-friendly farming is to ensure zero environmental impact. This study was conducted in the Satna district of Madhya Pradesh, covering three blocks and twelve villages. A total of 240 vegetable farmers were selected for the study. The findings show that the majority of respondents (67.08%) had moderate knowledge of eco-friendly vegetable cultivation practices. The knowledge of various crop management practices was ranked based on their mean scores. Cultural pest management practices had the highest mean score (6.36), indicating strong effectiveness or preference, while seed treatment had the lowest score of 1.87, suggesting it was less favoured or effective compared to the other practices. The study also found that various factors, including age, education, farming experience, and extension participation, were significantly associated with farmers' knowledge of eco-friendly practices.
Analysis of Submersible Pump Performance in a Waterlogged Environment
Authors: Odion Joshua , Ukpong Inimfon Ndueso , Etuk Aniebiet Friday , Okpo Ekom, Enefiok
Published: February 2025

This study investigates the performance of a submersible pump in a waterlogged environment, focusing on the relationship between pressure, flow rate and angular velocity. The system, consisting of a centrifugal pump, hydraulic pipeline, and local resistances, was simulated using MATLAB/Simulink for a duration of 44 seconds. Pressure measurements was conducted using a hydraulic pressure sensor connected to both the pump and pipeline to capture data at varying angular velocities ranging from 100 rad/s to 550 rad/s. The results showed a linear increase in both pump and pipeline flow rates with increasing angular velocity. The pump pressure ranged from 6.4209e+04 Pa to 1.9228e+06 Pa, while the pipeline pressure varied from 6.4159e+04 Pa to 1.9078e+06 Pa over the same range. Flow rate measurements was also conducted using a hydraulic flow rate sensor connected to both the pump and pipeline to capture data at varying angular velocities ranging from 100 rad/s to 550 rad/s as well. The results showed a linear increase in both pump and pipeline flow rates with increasing angular velocity. The pump flow rate ranged from 0.0021 m³/s to 0.0115 m³/s, while the pipeline flow rate varied from 0.0007 m³/s to 0.0042 m³/s over the same range. The difference in both the pressure and flow rates was attributed to frictional losses and minor flow restrictions within the pipeline. These findings provide insights into the operational efficiency of submersible pumps in waterlogged environments and offer a basis for optimizing pump performance in similar hydraulic systems.
Prüfungsausschuss – Quo vadis?
Authors: Arnold Michael , Reinhardt Maximilian
Published: February 2025

Der Prüfungsausschuss erfüllt seit seiner Einführung ins deutsche Aktienrecht wichtige Aufgaben innerhalb der Governance großer Aktiengesellschaften. Doch die Tätigkeit im Prüfungsausschuss ist im Wandel: Hohe Regulierungsdynamik, „Trendthemen“ wie ESG- und Cyber-Governance sowie steigende Qualifikationsanforderungen beeinflussen die Arbeit der Prüfungsausschüsse und ihre Mitglieder. Die Autoren analysieren die gewachsenen Erwartungen an Prüfungsausschüsse, nehmen eine wertende Bestandsaufnahme vor und zeigen Anpassungsbedarf für Gesetzgeber und Praxis auf.
Fusionskontrolle 2023/24
Authors: Emmerich Volker
Published: February 2025

Im Anschluss an den letzten Bericht über die Entwicklung der Fusionskontrolle aus dem Jahr 2022/23 (Emmerich, AG 2023, 610) gibt der Beitrag einen Überblick über die Entwicklung der deutschen und der europäischen Fusionskontrolle bis zum Spätherbst 2024. Der Schwerpunkt des Berichts liegt wie üblich auf der deutschen Praxis.
Die Identifizierbarkeit i.S.d. Art. 4 Nr. 1 DSGVO insbesondere durch Informationen aus dem Internet — (Endlich) alles klar durch die Rechtsprechungslinie des EuGH zum Personenbezug?
Authors: Hubert Tom
Published: February 2025

Die Identifizierbarkeit i.S.d. Art. 4 Nr. 1 der Datenschutz- Grundverordnung (DSGVO) ist ein zentrales, jedoch umstrittenes Thema im Datenschutzrecht. Insbesondere die Frage, welche Mittel zur Identifizierung einer natürlichen Person verhältnismäßig und zumutbar heranzuziehen sind, ist in der Praxis von großer Bedeutung. Die Rechtsprechung des Gerichtshofs der Europäischen Union (EuGH) hat hierzu wesentliche Streitpunkte geklärt, lässt jedoch auch Spielräume für Interpretationen. Diese Unsicherheiten betreffen sowohl die Perspektive, aus der die Verhältnismäßigkeit des Aufwands zur Identifizierung ermittelt werden soll, als auch die konkreten Maßstäbe, die dieser Prüfung anzulegen sind. Der Beitrag widmet sich einer eingehenden Analyse der relevanten EuGH-Rechtsprechung und beleuchtet, wie der Aufwand zur Identifizierbarkeit zu bemessen ist und welche Rolle externe Informationsquellen - wie insbesondere das Internet - dabei spielen.
Datenschutzrechtliche Erlaubnistatbestände für den Einsatz von predictive analytics im Beschäftigungsverhältnis — Bewerbungsaussortierung und Malmail-Identifizierung auf dem Prüfstand
Authors: Hofmann Moritz
Published: February 2025

Predictive analytics Anwendungen bergen aufgrund ihrer Zukunftsgerichtetheit sowohl großes Potential als auch Gefahren für diejenigen, welche deren datenintensiven Verarbeitungen unterliegen. Für die Anwender ist es daher unerlässlich, sich mit den Voraussetzungen für einen rechtmäßigen Einsatz zu befassen. Unter Bezugnahme auf die technische Funktionsweise von predictive analytics zeigt der Beitrag deshalb zwei typische Anwendungsszenarien beispielhaft auf und untersucht in diesen die Belastbarkeit der relevanten Rechtfertigungsgründe für die Datenverarbeitung.
Gesetzesentwurf zur Umsetzung der e-Evidence-Richtlinie: Diensteanbieter im Pflichtenlabyrinth des EBewMG
Authors: Rexin Lewin
Published: February 2025

Der Beitrag analysiert den Referentenentwurf des Elektronische- Beweismittel-Umsetzungs- und Durchführungsgesetzes (EBewMG-E), das die Vorgaben der e-Evidence-VO und -RL in deutsches Recht überführen soll (I.). Er erläutert die im EBewMG-E umgesetzten organisatorischen Pflichten für Diensteanbieter, insbesondere die Benennung/Bestellung von Adressaten und die diesbezügliche Mitteilung (II.), sowie das Verhältnis zwischen Diensteanbietern und Adressaten (III.). Dabei wird deutlich, dass der Gesetzgeber Nachbesserungen vornehmen muss, um Rechtsunsicherheiten und Widersprüche zu beseitigen. Zudem sind - derzeit vom Gesetzgeber nicht beabsichtigte - Anpassungen des TDDDG und der StPO erforderlich (IV.).
Transforming growth factor α protects against Fas‐mediated liver apoptosis in mice
Authors: Kanda Daisuke , Takagi Hitoshi , Toyoda Mitsuo , Horiguchi Norio , Nakajima Hiroaki , Otsuka Toshiyuki , Mori Masatomo
Published: July 2002

The Fas/Fas ligand interaction plays a crucial role in various liver diseases, and administration of agonistic anti‐Fas antibody to mice causes massive hepatic apoptosis and fulminant hepatic failure. Several growth factors have recently been found to function in preventing apoptosis. In this study, we demonstrated that overexpression of transforming growth factor α (TGFα) has a dramatic protective effect on Fas‐mediated hepatic apoptosis at the biochemical and histological levels. Moreover, 85.7% (six out of seven) of TGFα transgenic mice survived the lethal liver damage, whereas all wild‐type mice died. Expression of Bcl‐xL, an anti‐apoptotic protein, was greatly increased in the transgenic mice. Taken together, our findings suggest that TGFα protects against Fas‐mediated liver apoptosis in vivo and up‐regulation of Bcl‐xL may participate in protective effect of TGFα.
Electron tomographic reconstruction of plastic‐embedded organelles involved in the chitin secretion process
Authors: Shillito Bruce , Koster Abraham J. , Walz Jochen , Baumeister Wolfgang
Published: July 2002

Summry— Structural investigations on the chitin secretion system of a deep‐sea hydrothermal vent tubeworm, Riftia pachyptila, are presented. In this organism, 300‐nm cup‐shaped organelles are responsible for the formation of large (50 nm) crystalline chitin microfibrils of the rare β form. Electron tomographic reconstructions of plastic‐embedded cup‐shaped organelles were carried out, using 93 projections distributed over a ± 70° angular range with a 0.63‐nm pixel size. In addition, the shrinkage profile of the plastic sections was measured to determine the required imaging conditions. The entire data collection was done automatically and carried out under cryo‐conditions. Automation resulted in an efficient use of irradiation dose; 96% of the total dose is required for the data itself, only 4% is used for the required compensation of focus change and image shift. The results are presented as 3‐nm thick slices through the 3‐D reconstruction, (parallel to the original thin section, ie the x‐y plane). The 3‐nm slices allow to visualize separate structures that are overlapping in a conventional 2‐D projection of the initial thin section. Also, these thin slices through the 3‐D reconstruction show the fine contours of the nascent microfibril tip, which appears to be cone‐shaped.
Cross‐reactivity betweenPlatanuspollen and vegetables
Authors: Miralles J. C. , Caravaca F. , Guillén F. , Lombardero M. , Negro J. M.
Published: July 2002

Background: Several associations have been described between tree and plant pollens and certain foods. The objective of this study is to verify whether there is cross‐reactivity betweenPlatanuspollen and vegetable origin foods.

Methods: We selected 56 patients allergic to vegetable foods and subjected them to cutaneous tests with aeroallergens and vegetable foods. A statistical analysis was performed to evaluate the association ofPlatanuspollen with foods and with other aeroallergens. Later, a specific IgE determination was performed as well as a RAST (radioallergosorbent) inhibition experiment, to verify the existence of cross‐reactivity in vitro.

Results: In the cutaneous tests we found a positive correlation betweenPlatanuspollen and hazelnut, peanut, banana and celery. The results of the RAST inhibition experiment indicate an important cross‐reactivity between the pollen ofPlatanus acerifoliaand hazelnut and banana fruit, and an intermediate cross‐reactivity with celery and peanut.

Conclusion: We have described an association between the pollen of thePlatanustree and some vegetable foods such as hazelnut, banana, peanut and celery. This association could be explained by thein vitroIgE cross‐reactivity detected.
Cytoplasmic free Ca2+dynamics in single tomato (Lycopersicon esculentum) protoplasts subjected to chilling temperatures
Authors: Sebastiani Luca , Lindberg Sylvia , Vitagliano Claudio
Published: July 2002

Protoplasts were isolated from leaves of tomato seedlings (Lycopersicon esculentumMill., cv. Marmande) at the 2nd to 4th true leaf stage and were loaded with the calcium binding tetra[acetoxymethyl+] ester of the fluorescent stilbene chromophore, Fura 2. Although the loading efficiency of the dye in these protoplasts was low, many protoplasts loaded only in the cytosol were always obtained. Changes in the cytosolic calcium concentration ([Ca2+]cyt) were determined in single protoplasts in a temperature‐controlled perfusion chamber by use of fluorescence photometry microscopy after excitation at 340 and 380 nm. When the protoplasts were subjected to chilling temperatures (10–15°C) by a circulating solution, the [Ca2+]cytincreased in 64% of the analysed protoplasts. Depending on the initial resting level of [Ca2+]cyt, three main types of kinetics were obtained in these protoplasts: (1) In 21% of the protoplasts, [Ca2+]cytincreased to a maximum within 10–20 s from the start of temperature decrease, followed by a fast decrease; (2) in 11% of the protoplasts, the [Ca2+]cytboth increased and decreased somewhat slower; and (3) in 32% a constant increase of [Ca2+]cytwas obtained 1 min after the start of temperature decrease.
New oligo-α-pyridylamino ligands and their metal complexes
Authors: Yang Ming-hwa , Lin Tzu-Wei , Chou Chin-Cheng , Lee Hsiao-Ching , Chang Hsiao-Chi , Lee Gene-Hsiang , Leung Man-kit , Peng Shie-Ming
Published: July 2002

Three novel oligo-α-pyridylamino ligands, tripyridyldi-amine (H2tpda), tetrapyridyltriamine (H3teptra), pentapyridyltetramine (H4peptea) are synthesized; the crystal structures of their metal complexes with the all-anti configuration of the chelating ligands are reported.
Differential role of glycolipid-enriched membrane domains in glycoprotein VI- and integrin-mediated phospholipase Cγ2 regulation in platelets
Authors: WONEROW Peter , OBERGFELL Achim , WILDE Jonathan I. , BOBE Régis , ASAZUMA Naoki , BRDIČKA Tomáš , LEO Albrecht , SCHRAVEN Burkhart , HOŘEJŠÍ Václav , SHATTIL Sanford J. , WATSON Steve P.
Published: July 2002

The platelet collagen receptor glycoprotein VI (GPVI) and the fibrinogen receptor integrin αIIbβ3 trigger intracellular signalling cascades involving the tyrosine kinase Syk, the adapter SLP-76 and phospholipase Cγ2 (PLCγ2). Similar pathways are activated downstream of immune receptors in lymphocytes, where they have been localized in part to glycolipid-enriched membrane domains (GEMs). Here we provide several lines of evidence that GPVI-mediated tyrosine phosphorylation of PLCγ2 in platelets is dependent on GEM-organized signalling and utilizes the GEM resident adapter protein LAT (linker for activation of T cells). In sharp contrast, although fibrinogen binding to platelets stimulates αIIbβ3-dependent activation of Syk and tyrosine phosphorylation of SLP-76 and PLCγ2, it does not utilize GEMs to promote these responses or to support platelet aggregation. These results establish that GPVI and αIIbβ3 trigger distinct patterns of receptor signalling in platelets, leading to tyrosine phosphorylation of PLCγ2, and they highlight the role of GEMs in compartmentalizing signalling reactions involved in haemostasis.
Tissue factor activity in human monocytes is regulated by plasma: implications for the high and low responder phenomenon
Authors: Nijziel Marten , Van Oerle René , Van Cornelis , T Veer ‘ , Van Pampus Elisabeth , Lindhout Theo , Hamulyák Karly
Published: July 2002

The ‘high and low responder phenomenon’ of monocyte tissue factor (MTF) activity has been attributed to effects on monocytes by granulocytes, platelets and lipopolysaccharide (LPS). To study the possible contribution of plasma to the high and low responder phenomenon, we measured the MTF activity in isolated cryopreserved human monocytes from two donors (monocytes A and monocytes B) after incubation in a plasma environment depleted of granulocytes, platelets and LPS. In buffer only, MTF activity was 643 and 679 fM (fM = final concentration of tissue factor), in normal pooled plasma, it was 1478 and 1615 fM (P = 0·001), respectively, in monocytes A and in monocytes B. Incubation with individual plasma samples from healthy controls (n = 43) gave a median MTF of 1355 fM (range 1044–1976 fM) and 1329 fM (range 858–1951 fM) respectively. A plasma consistently induced a higher or lower level of MTF activity in both monocytes: r = 0·82 (P < 0·00001). Coumarin use did not influence the high and low responder phenomenon. In the absence of granulocytes, platelets and LPS, plasma determines the high and low responder phenomenon. This phenomenon is not influenced by coumarin treatment.
Non‐incarcerated psychopaths: why we need to know more about the psychopaths who live amongst us
Authors: Kirkman C. A.
Published: July 2002

On 1 November 2000, Robert Stewart, aged 20, was jailed for life for bludgeoning to death his Asian cellmate, Zahid Mubarek, aged 19 years because ‘he felt like it’. During the court hearing the term ‘psychopathic personality’ was used in relation to Stewart and, following this and other similar cases, the average man or woman could be forgiven for believing that psychopathy is inextricably linked with dangerousness and criminality. In the light of the Government consultation paper entitled Managing Dangerous People with Personality Disorder. Proposals for Policy Development and the Government White Paper Reforming the Mental Health Act – Part II: High‐risk patients, this article proposes that whilst studies conducted with incarcerated psychopaths will continue to increase our knowledge and understanding of criminality, non‐incarcerated psychopaths have an arguably equal potential to illuminate our understanding of the emotional difficulties, such as lack of empathy and lack of conscience, which underlie psychopathy and which lead to offending behaviour. Although a range of obstacles have hindered progress in this field of study, this paper proposes that developing an understanding of the nature of the emotional difficulties of the psychopath, unconfounded by criminality, has the potential to make a valuable contribution to the field of child psychiatry in ways which have implications for mental health nurses and society as a whole. It theorizes that if the psychological constructs which underlie psychopathy were better understood, children who display those emotional difficulties could be more accurately identified and strategies be generated which carry the ultimate aim of minimizing the risk of those children developing the offending behaviour associated with psychopathy.
I‐NjaI, a nuclear intron‐encoded homing endonuclease from Naegleria, generates a pentanucleotide 3′ cleavage‐overhang within a 19 base‐pair partially symmetric DNA recognition site
Authors: Elde Morten , Haugen Peik , Willassen Nils P. , Johansen Steinar
Published: July 2002

Different species of the amoebo‐flagellate Naegleria harbor optional group I introns in the nuclear ribosomal DNA that contain open reading frames. Intron proteins from Naegleria jamiesoni, Naegleria andersoni, and Naegleria italica (named I‐NjaI, I‐NanI and I‐NitI, respectively) were expressed in Escherichia coli and found to be isoschizomeric homing endonucleases that specifically recognize and cleave intron‐lacking homologous alleles of ribosomal DNA. The I‐NjaI endonuclease was affinity purified, characterized in more detail, and found to generate five‐nucleotide 3′ staggered ends at the intron insertion site which differs from the ends generated by all other known homing endonucleases. The recognition site was delimited and found to cover an ≈ 19 base‐pair partially symmetric sequence spanning both the cleavage site and the intron insertion site. The palindromic feature was supported by mutational analysis of the target DNA. All single‐site substitutions within the recognition sequence were cleaved by the purified I‐NjaI endonuclease, but at different efficiencies. The center of symmetry and cleavage was found to be completely degenerate in specificity, which resembles that of the subclass IIW bacterial restriction enzymes.
Anti‐viral strategies of cytotoxic T lymphocytes are manifested through a variety of granule‐bound pathways of apoptosis induction
Authors: Edwards Kirsten M , Davis Joanne E , Browne Kylie A , Sutton Vivien R , Trapani Joseph A
Published: July 2002

Cytotoxic T cells and natural killer cells together constitute a major defence against virus infection, through their ability to induce apoptotic death in infected cells. These cytolytic lymphocytes kill their targets through two principal mechanisms, and one of these, granule exocytosis, is essential for an effective in vivo immune response against many viruses. In recent years, the authors and other investigators have identified several distinct mechanisms that can induce death in a targeted cell. In the present article, it is postulated that the reason for this redundancy of lethal mechanisms is to deal with the array of anti‐apoptotic molecules elaborated by viruses to extend the life of infected cells. The fate of such a cell therefore reflects the balance of pro‐apoptotic (immune) and anti‐apoptotic (viral) strategies that have developed over eons of evolutionary time.
Decisional balance and stage of change in relation to weight loss, exercise and dietary fat reduction among Pacific Islands people
Authors: Fracp D Simmons , Mesui J
Published: July 2002

It has been postulated that changes in lifestyle follow five ‘stages of change’, which reflect a ‘decisional balance’ between the advantages and disadvantages of making such a change. We have assessed this model among Pacific Islands people in New Zealand. We questioned 105 Pacific Islands volunteers to identify their decisional balance for their reduction in dietary fat intake (DFI), weight control (WC) and the adoption of regular exercise habits (REH). Answers were used to develop a closed questionnaire, which was completed by a second group of 195 Pacific Islands volunteers. The major reported advantages were good health (45%) and increased physical attractiveness (41%) for WC; disease prevention (70%) for DFI; and increased fitness (71%) for REH. The major reported disadvantages were losing too much weight (40%) for WC; eating fatty foods was enjoyable (50%) for DFI; and the time required (47%) for REH. Major differences in responses were found by age, sex, Islands group and educational status. The derived decisional balance questions related to the stage of change with advantages outweighing disadvantages for those in the maintenance/action phases and the converse for those in the precontemplative phase. The use of this model will be helpful in evaluating long‐term programs aimed at the primary prevention of non‐insulin‐dependent diabetes through lifestyle change.
Epidemiology of dementia in Nigeria: results from the Indianapolis–Ibadan study
Authors: Ogunniyi A. , Baiyewu O. , Gureje O. , Hall K. S. , Unverzagt F. , Siu S. H. , Gao S. , Farlow M. , Oluwole O. S. A. , Komolafe O. , Hendrie H. C.
Published: July 2002

We determined the prevalence of dementia in a cohort of 2494 elderly Nigerians residents in Idikan Community, Ibadan, Nigeria. We utilized the Community Screening Instrument for Dementia to select subjects for clinical assessment in the second stage. The findings were compared with those of 2212 African Americans living in Indianapolis, studied simultaneously using similar methodology. The overall age‐adjusted prevalence rates of dementia and Alzheimer's disease in Ibadan were 2.29% and 1.41%, respectively. These rates were much lower than the respective values of 8.24% and 6.24% obtained for African Americans. In Ibadan, Alzheimer's disease accounted for 64.3% of the cases, with old age and female gender being the significant risk factors, whilst ‘living with others’ appeared to be protective (P < 0.05). Amongst African Americans, on the other hand, old age, rural living below the age of 19 years, low educational attainment and family history of dementia were the risk factors. There was a lack of association between Alzheimer's disease and possession of the apolipoprotein E ε4 allele in the Nigerian sample, unlike the finding in African Americans, where significant association was shown. In addition, the frequencies of the vascular risk factors investigated were lower in Nigerians.

Our results showed lower prevalence of dementia and Alzheimer's disease in Nigerians, compared with African Americans. There was no association between Alzheimer's disease and apolipoprotein E (ε4 allele) in the former. The differences in the frequencies of vascular risk factors between Nigerian subjects and African Americans would suggest involvement of environmental factors in disease process.
Scratch resistance of rigid contact lens materials
Authors: Tranoudis Ioannis , Efron Nathan
Published: July 2002

Practitioners have long recognised the importance of determining the extent of scratching on the surface of rigid contact lenses when deciding on lens replacement. Despite this, little research has been undertaken to define this problem. The extent of scratching of rigid contact lens materials was evaluated and this property was related to material oxygen permeability and refractive index. One hundred and forty lenses made from 28 different rigid materials were evaluated in a masked and randomised manner. Scratches were created on the front surface of the lenses using an apparatus that was specifically designed and constructed for this experiment. The extent of scratching was quantitatively evaluated using a computer‐based scanning and image analysis system. The oxygen permeability of all materials was measured using the polarographic method. An Atago N3000 hand‐held refractometer was used to measure the refractive index of these materials. Three significant correlations were revealed: an inverse relationship (r = −0.813, P < 0.0001) between oxygen permeability and refractive index; a positive relationship (r = 0.511, P < 0.008) between oxygen permeability and the extent of scratching; and an inverse relationship (r = −0.539, P < 0.0058) between refractive index and the extent of scratching. The information generated in this study concerning scratch resistance of rigid contact lens materials may assist the contact lens industry and contact lens practitioners in developing and prescribing rigid lenses with optimal performance characteristics.
Depth profiles on ion implantation induced vacancy-type defects in GaAs and Si observed by slow positron
Authors: Lee Jong-Lam , Kim Jin Sup , Park Hyung Moo , Ma Dong Sung , Tanigawa S. , Uedono A.
Published: July 2002

Monoenergetic positrons with variable energies were used to study the depth distribution of implantation-induced vacancy-type defects in undoped GaAs and p-type Si. In the Si+-implanted GaAs, the concentration of vacancy-type defects decreased monotonically with increasing depth below the surface. In B+- and As+-implanted Si substrates, parabolic-type distributions of vacancy-type defects were observed. The present work demonstrates that the monoenergetic positron technique is a very powerful tool for the study of vacancy-type defects near surfaces in semiconductor processes.
Al0.3Ga0.7As/Al0.05Ga0.95As light-emitting diodes on GaAs-coated Si substrates grown by liquid phase epitaxy
Authors: Sakai Shiro , Chang Shi S. , Ramaswamy Ramu V. , Kim Jae-Hoon , Radhakrishnan Gouri , Liu John K. , Katz Joseph
Published: July 2002

Al0.3Ga0.7As/Al0.05Ga0.95As double-heterostructure light-emitting diodes (LED’s) were successfully grown for the first time by liquid phase epitaxy on a GaAs-coated Si substrate that was prepared by a sequential process of migration-enhanced epitaxy and molecular beam epitaxy. The edge-emitting LED’s had diode ideality factors of 1.54 at a forward-biased voltage higher than 0.9 V and external quantum efficiencies of 3.3×10−3 W/A per facet. This efficiency is 50 times higher than the previously reported value, and is on the same order as that of AlGaAs homojunction LED’s fabricated on the GaAs substrates by liquid phase epitaxy.
Stable single-mode operation of a 30 GHz free-electron laser
Authors: Harvey R. J. , Dolezal F. A.
Published: July 2002

Stable, single-mode, linearly polarized emission has been achieved with a free-electron laser (FEL) oscillator for pulses of up to 30 μs when gain differences are used to select between a limited number of cavity modes. The frequency- and phase-modulation noise spectra are monitored by heterodyning and homodyning techniques, and the measured linewidth is near 70 kHz at 31 GHz. The FEL oscillator mechanism is inherently frequency stable and step tunable over a practical range of control parameters determined primarily by the stability of the electron beam voltage.
Formation of low-temperature Al/n-Si Schottky contacts using a partially ionized beam deposition technique
Authors: Yapsir A. S. , Bai P. , Lu T.-M.
Published: July 2002

High quality Al/n-Si Schottky contacts have been fabricated using the partially ionized beam (PIB) deposition technique in a conventional vacuum condition without post heat treatment. The electrical characteristics of the diodes were extremely uniform across a 3 in. wafer and were stable with respect to a furnance annealing performed at 450 °C for 30 min. Scanning electron microscope examination revealed much shallower pit formation on the Si surface, as compared to that deposited by conventional means, following the heat treatment. A completely smooth Si surface was observed after a 10 s rapid thermal annealing at 450 °C. The observed behavior could be attributed to the creation of ‘‘contact openings’’ in the native oxide during deposition by ion bombardment, allowing Al to make an intimate contact to Si. This PIB deposition of metal-semiconductor contacts may be an important metallization scheme for the future low-temperature processing of shallow junctions for very high speed integrated circuits.
Growth and characterization of GaAs layers on Si substrates by migration-enhanced molecular beam epitaxy
Authors: Kim Jae-Hoon , Liu John K. , Radhakrishnan Gouri , Katz Joseph , Sakai Shiro , Chang Shi S. , El-Masry Nadia A.
Published: July 2002

We first report on migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layer on Si substrates (GaAs/Si). Excellent surface morphology GaAs layers were successfully grown on (100)Si substrates misoriented 4° toward the [110] direction. The MEMBE growth method is described, and material properties are compared with those of normal two-step MBE-grown or in situ annealed layers. Micrographs of cross-section view transmission electron microscopy (TEM) and scanning surface electron microscopy (SEM) of MEMBE-grown GaAs/Si showed dislocation densities of 1×107 cm−2, over ten times lower than those of normal two-step MBE-grown or in situ annealed layers. AlGaAs/GaAs double heterostructures have been successfully grown on MEMBE GaAs/Si by both metalorganic chemical vapor deposition and liquid phase epitaxy.
Point defect enhanced grain growth in silicon thin films: The role of ion bombardment and dopants
Authors: Atwater Harry A. , Thompson Carl V.
Published: July 2002

We report the results of experiments which test the relationship between the enhanced grain growth rate in polycrystalline silicon films and the enhanced point defect concentration due to dopants and in situ ion bombardment. The experimental data indicate that the contributions to the grain growth rate from ion bombardment and doping are approximately additive, and they agree well with models which relate the grain growth rate to the vacancy concentration at grain boundaries. These results are consistent with the expectation that grain boundary mobilities can be altered through changes in the point defect concentration, regardless of how those changes are generated.
Nonlinear optical processes in a polymer waveguide: Grating coupler measurements of electronic and thermal nonlinearities
Authors: Burzynski R. , Singh B. P. , Prasad P. N. , Zanoni R. , Stegeman G. I.
Published: July 2002

We report here the first clear demonstration of intensity-dependent phase shift due to electronic nonlinearity in a nonlinear polymer waveguide in which propagation distances over 5 cm have been achieved with total attenuation of ∼1.2 cm−1 . Intensity-dependent coupling angle, intensity-dependent coupling efficiency, and limiter action behavior have been observed in the polyamic acid waveguide using grating excitation with 400 fs, 80 ps, and 10 ns pulses. A nonlinear grating coupler analysis identifies the subpicosecond and picosecond processes with electronic nonlinearity, but the dominant effect in the nanosecond experiment is due to thermal nonlinearity derived from weak absorptions. The magnitude and sign of n2 of electronic nonlinearity are measured.
Measurements of the polarization dependence of field-induced refractive index changes in GaAs/AlAs multiple quantum well structures
Authors: Shimizu J. , Hiroshima T. , Ajisawa A. , Sugimoto M. , Ohta Y.
Published: July 2002

The measurements of the polarization dependence of field-induced refractive index changes in GaAs/AlAs multiple quantum wells, which are directly measured by using the modulation spectroscopy method for the TE and TM modes, are described. Clear polarization dependences, such as differences in the spectra shape and the peak wavelength, were observed. The polarization dependences originate from the different excitonic transitions: the n=1 heavy-hole and light-hole exciton for the TE mode and the n=1 light-hole exciton for the TM mode. The experimental results show qualitatively good agreement with the theoretical calculation.
Growth and characterization of InP epilayers on ZnSehen;coated Si substrates by low-pressure metalorganic vapor phase epitaxy
Authors: Lee M. K. , Wuu D. S. , Tung H. H. , Chang J. H. , Lin Y. F.
Published: July 2002

Heteroepitaxial growth of InP on ZnSe-coated Si substrates by low-pressure metalorganic vapor phase epitaxy is reported for the first time. Single-crystal InP epilayers with specular surfaces can be obtained. The ZnSe buffer layer, which is evaporated onto the Si substrate in another furnace, is effective in reducing the magnitude of strain in the InP layer. The best room-temperature electron mobility of the undoped InP epilayer can reach 3100 cm2 /(V s) with a carrier concentration of 1.5×1015 cm−3 . It was found that the InP electron mobility is critically dependent on the ZnSe buffer-layer thickness. The efficient photoluminescence compared with that of InP homoepitaxy indicates that the InP heteroepilayer is of high optical quality.
Superconducting Tl-Ca-Ba-Cu-O thin films with zero resistance at temperatures of up to 120 K
Authors: Lee W. Y. , Lee V. Y. , Salem J. , Huang T. C. , Savoy R. , Bullock D. C. , Parkin S. S. P.
Published: July 2002

We have prepared superconducting Tl-Ca-Ba-Cu-O thin films on a variety of substrates with transition temperatures as high as ≂120 K, confirmed by sharp onsets of substantial Meissner and shielding signals at the same temperatures. The properties of the films are found to depend sensitively on the post-annealing conditions. Highly textured c-axis-oriented films comprised mostly of Tl2Ca1Ba2Cu2Ox, Tl1Ca2Ba2Cu3Ox, and Tl2Ca2Ba2Cu3Ox were synthesized by varying the annealing procedure with corresponding maximum superconducting transition temperatures of ≂100, 110, and 120 K, respectively.
Multilayer deposition of Tl-Ba-Ca-Cu-O films
Authors: Shih I. , Qiu C. X.
Published: July 2002

Thin films of Tl-Ba-Ca-Cu-O with different atomic ratios and a thickness of about 2 μm have been prepared by a sequential thermal evaporation method on alumina substrates followed by a heat treatment in an environment containing O2 and Tl. The results showed that films with a superconducting onset temperature of about 120 K and a zero resistance temperature of 85 K can be obtained with the following Tl:Ca:Ba:Cu ratios: 2:2:2:3 or 2:2:2:4. Films with a superconducting transition onset at 115 K and a zero resistance temperature of 74 K were also obtained by heating Tl-free multilayer films in the environment containing O2 and Tl. It was also found that this new material was more resistant to water.
Room-temperature exciton optical absorption peaks in InGaAsP/InP multiple quantum wells
Authors: Sugawara M. , Fujii T. , Yamazaki S. , Nakajima K.
Published: July 2002

We grew In1−xGaxAsyP1−y/InP quantum wells (QWs) by low-pressure metalorganic vapor phase epitaxy. The In1−xGaxAsyP1−y layer was closely lattice matched to InP with a composition of y=0.9 (x=0.47y). We investigated structural imperfections such as composition fluctuations, interface roughness, and nonperiodicity analyzing the low-temperature photoluminescence linewidth. We found that the InGaAsP layer composition fluctuated, causing about 5 meV inhomogeneity in the exciton energy level in QWs wider than about 3 nm. Since we obtained very smooth interfaces with less than one monolayer of fluctuation and excellent periodicity by lowering growth temperature to 570 °C, the inhomogeneity of the exciton energy level could be held at 6 meV for 20-period 10-nm multiple QWs. As a result, despite composition fluctuations, a clear room-temperature exciton optical absorption peak was observed at 1.5 μm for the first time to our knowledge.
Critical comparison of light-induced changes in sub-band-gap absorption and photoconductivity in hydrogenated amorphous silicon
Authors: Bhattacharya Enakshi , Mahan A. H. , Crandall Richard S. , Pankove J. I.
Published: July 2002

This work compares changes in the density of states due to light-induced degradation estimated by photoconductivity with those measured by photothermal deflection spectroscopy (PDS) on a series of hydrogenated amorphous silicon (a-Si:H) films having different valence bandtail widths (E0 ). We find that the photoconductivity measurements indicate orders of magnitude larger defect density changes than do the PDS measurements as the valence bandtail becomes broader. This conflict is resolved by showing that this difference is due to changes in the recombination rate coefficient K with valence bandtail width. The absolute change in K increases exponentially with E0. However, the change in K relative to the K of the annealed state decreases with E0, explaining why poor material shows a smaller light-induced effect.
Photocarrier generation and injection at the interface in double-layered organic photoconductors
Authors: Kanemitsu Yoshihiko , Imamura Shunji
Published: July 2002

Photocarrier generation and injection processes in double-layered organic photoconductors consisting of carrier generation layer (CGL) and carrier transport layer (CTL) were studied by means of photoacoustic and xerographic time-of-flight methods. In the photoacoustic method, the photocarrier generation efficiency in the CGL was derived by measuring the decrease in photoacoustic signal due to carrier recombination in the CGL. On the other hand, in the xerographic method, the ratio of the number of holes emitted into the CTL to that of absorbed photons in the CGL was obtained from the temporal change in surface voltage under light pulse irradiation. From comparing two experimental results, we evaluated the injection efficiency of holes at the CGL/CTL interface. The injection efficiency is determined by the trapping of holes at the CGL/CTL interface.
Photoluminescence studies of GaAs grown on InP substrates by molecular beam epitaxy
Authors: Huang D. , Agarwala S. , Morkoç H.
Published: July 2002

GaAs-based field-effect transistor structures have been grown on InP substrates with the InGaAs/GaAs strained-layer superlattices and 1.5 μm GaAs layer as the buffer. The low-temperature (4 K) photoluminescence (PL) from this GaAs buffer has been studied for the first time. Among five observable peaks, the excitonic transition at energy 1.513 eV and the impurity associated recombination at energy 1.483 eV have been identified with the aid of reflection, absorption, and temperature and excitation-intensity dependent PL measurements. The peak at 1.504 eV, most probably due to an exciton bound to a defect, is greatly enhanced compared with that of homoepitaxially grown GaAs. The optical results show that GaAs films of good quality can be grown on InP substrate, which is consistent with device results.
Redistribution of deep levels in semi-insulating GaAs wafer by rapid thermal processing
Authors: Usami Akira , Kitagawa Akio , Wada Takao
Published: July 2002

The distributions of deep levels in semi-insulating GaAs before and after rapid thermal processing (RTP) at 800 °C are obtained by the contactless measurement of the optically injected excess carrier signal height by reflectance microwave prober method. The deep levels in the liquid-encapsulated Czochralski-grown 2 in. GaAs wafer are redistributed by RTP, and its spatial variation shows a W-shaped pattern along the 〈100〉 radial direction. Furthermore, the distribution of deep levels in the RTP wafer corresponds to the crystallographic slip generation pattern, which is relief of the thermal stress during RTP, examined by x-ray topography. The redistribution of the deep levels is due to the production of the principal deep level EL2 by RTP.
Threshold voltage shift of amorphous silicon thin-film transistors by step doping
Authors: Matsumoto T. , Mishima Y. , Yanai K. , Oki K.
Published: July 2002

The threshold voltage (VT) shift of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) by boron doping has been investigated. In TFTs with a uniformly doped structure (SiN/B-doped a-Si:H), VT shifts to a positive voltage by boron doping, while the field-effect mobility decreases markedly. By using a step-doped structure (SiN/undoped a-Si:H/B-doped a-Si:H), the degradation of the field-effect mobility by boron doping becomes less than that of a uniformly doped TFT with the same VT shift, and a VT shift of 3.5 V was obtained without degradation of the field-effect mobility.
Minority-carrier lifetimes in undoped AlGaAs/GaAs multiple quantum wells
Authors: Hariz A. , Dapkus P. Daniel , Lee H. C. , Menu E. P. , DenBaars S. P.
Published: July 2002

The lifetime of minority carriers in AlGaAs-GaAs quantum well structures grown by metalorganic chemical vapor deposition has been studied at room temperature and carrier densities up to 3×1016 cm−3 using time-resolved photoluminescence. Decay times are observed to be strongly dependent upon the quality of the AlGaAs barrier regions, excitation, and well width. Strong saturation of the decay times is observed with excitation indicating the presence of nonradiative traps. Saturated lifetimes as long as 650 ns have been measured in quantum wells with 200 Å well widths.
Sequential nature of damage annealing and activation in implanted GaAs
Authors: Tandon J. L. , Madok J. H. , Leybovich I. S. , Bai G. , Nicolet M-A.
Published: July 2002

Rapid thermal processing of implanted GaAs reveals a definitive sequence in the damage annealing and the electrical activation of ions. Removal of implantation-induced damage and restoration of GaAs crystallinity occurs first. Irrespective of implanted species, at this stage the GaAs is n-type and highly resistive with almost ideal values of electron mobility. Electrical activation is achieved next when, in a narrow anneal temperature window, the material becomes n- or p-type, or remains semi-insulating, commensurate to the chemical nature of the implanted ion. Such a two-step sequence in the electrical doping of GaAs by ion implantation may be unique of GaAs and other compound semiconductors.
Low-temperature growth of 3C-SiC by the gas source molecular beam epitaxial method
Authors: Motoyama Shin-ichi , Kaneda Shigeo
Published: July 2002

Single crystalline 3C-SiC films were grown on a Si substrate by molecular beam epitaxy (MBE) using SiHCl3 and C2H4 gases. The optimal growth conditions were achieved at a growth temperature (Tsub ) of 1000 °C and a gas pressure ratio (PSiHCl3 /PC2H4 ) of 1/3 at PSiHCl3 =1×10−5 Torr. Prior to the essential growth of SiC, a carbonization process was performed with C2H4 gas only. A continuous observation by reflection high-energy electron diffraction (RHEED) was performed throughout the process of crystal growth. A series of RHEED patterns revealed that carbonization film could be grown at 750 °C and the lattice mismatch between Si and SiC crystals was satisfactorily relaxed. All processes of crystal growth were performed at a relatively low temperature.
All-optical spatial scanner
Authors: Varatharajah P. , Aceves A. B. , Moloney J. V.
Published: July 2002

The design of a simple all-optical spatial scanner, based on a propagating self-focused channel incident at an oblique angle to a nonlinear dielectric interface, is illustrated using the beam propagation method. The channel asymptotics are shown to be insensitive to the shape of the incident beam profile with the latter satisfying a simple area criterion.
Interferometric measurement of the pressure-enhanced crystallization rate of amorphous Si
Authors: Lu G. Q. , Nygren E. , Aziz M. J. , Turnbull D. , White C. W.
Published: July 2002

We have measured the pressure dependence of the solid phase epitaxial growth rate of self-implanted Si (100) by using the in situ time-resolved interferometric technique in a high-temperature and high-pressure diamond anvil cell. With fluid argon as the pressure transmission medium, a clean and perfectly hydrostatic pressure environment is achieved around the sample. The external heating geometry employed provides a uniform temperature across the sample. At temperatures in the range of 530–550 °C and pressures up to 3.2 GPa (32 kbar), the growth rate is enhanced by up to a factor of 5 over that at 1 atmosphere pressure. The results are characterized by a negative activation volume of approximately −3.3 cm3/mole (−28% of the atomic volume). These results show a significantly weaker pressure dependence than does the previous work of Nygren et al. [Appl. Phys. Lett. 47, 232 (1985)], who found an activation volume of −8.7 cm3/mole. The implication of this measurement for the nature of the defects responsible for crystal growth is discussed.
Anomalous dependence of threshold current on stripe width in gain-guided strained-layer InGaAs/GaAs quantum well lasers
Authors: Shieh C. , Mantz J. , Lee H. , Ackley D. , Engelmann R.
Published: July 2002

An anomalous dependence of the threshold current on the stripe width is observed for gain-guided strained-layer InGaAs/GaAs quantum well lasers. The threshold current increases strongly as the stripe width is reduced from relatively large values. This is attributed to the huge lateral loss caused by an unusually large index antiguide which manifests itself in the far-field behavior. This large loss also leads to a population of higher quantized energy levels in the InGaAs quantum well strongly reducing the lasing wavelength by as much as 61 nm.
Zn disordering of a Ga0.5In0.5P-(AlxGa1−x)0.5In0.5P quantum well heterostructure grown by metalorganic chemical vapor deposition
Authors: Meehan K. , Dabkowski F. P. , Gavrilovic P. , Williams J. E. , Stutius W. , Hsieh K. C. , Holonyak N.
Published: July 2002

It is well established by now that epitaxial layers of (AlxGa1−x)0.5In0.5P and Ga0.5In0.5P grown on (001) GaAs substrates by metalorganic chemical vapor deposition at temperatures below 700 °C show an ordered arrangement of the group III atoms on the column III sublattice, resulting in a shift of the band gap to lower energies by ≊90 meV. In this letter we show that an (AlxGa1−x)0.5In0.5P-Ga0.5In0.5P quantum well heterostructure containing the ordered phase can be converted to random alloy by a relatively short sealed-tube zinc diffusion at a temperature of 600 °C, without affecting the dimensional or compositional stability of the quantum well. Complete intermixing of the quantum well with the cladding layers occurs at diffusion times longer than that required to disorder the column III ordered structure.
Assessment of the ionized EL2 fraction in semi-insulating GaAs
Authors: Blakemore J. S. , Sargent L. , Tang R-S. , Swiggard E. M.
Published: July 2002

Both optical and electrical methods were used to provide separate evaluations of the fraction Pi of EL2 defect donors which have lost an electron. The semi-insulating GaAs which permitted these assessments had a large enough fraction of the EL2 compensated (by CAs acceptors) to make this a sensitive test. Room-temperature Hall effect data, analyzed with an ambipolar correction, indicated that Pi ≂0.34 in material from a vertical-zone grown crystal, while near-infrared optical absorption could be modeled on a superposition of EL2 photoionization and photoneutralization to yield Pi ≂0.35 in the same crystal. The presence of compensating CAs acceptors was verified by local mode vibrational absorption.