bluuebunny/crossref_metadata_2025 huggingface dataset:
A mathematical formulation and an NSGA-II algorithm for minimizing the makespan and energy cost under time-of-use electricity price in an unrelated parallel machine scheduling
Authors: Rego Marcelo F. , Pinto Júlio Cesar E.M. , Cota Luciano P. , Souza Marcone J.F.
Published: February 2022

In many countries, there is an energy pricing policy that varies according to the time-of-use. In this context, it is financially advantageous for the industries to plan their production considering this policy. This article introduces a new bi-objective unrelated parallel machine scheduling problem with sequence-dependent setup times, in which the objectives are to minimize the makespan and the total energy cost. We propose a mixed-integer linear programming formulation based on the weighted sum method to obtain the Pareto front. We also developed an NSGA-II method to address large instances of the problem since the formulation cannot solve it in an acceptable computational time for decision-making. The results showed that the proposed NSGA-II is able to find a good approximation for the Pareto front when compared with the weighted sum method in small instances. Besides, in large instances, NSGA-II outperforms, with 95% confidence level, the MOGA and NSGA-I multi-objective techniques concerning the hypervolume and hierarchical cluster counting metrics. Thus, the proposed algorithm finds non-dominated solutions with good convergence, diversity, uniformity, and amplitude.
Syntax and prejudice: ethically-charged biases of a syntax-based hate speech recognizer unveiled
Authors: Mastromattei Michele , Ranaldi Leonardo , Fallucchi Francesca , Zanzotto Fabio Massimo
Published: February 2022

Hate speech recognizers (HSRs) can be the panacea for containing hate in social media or can result in the biggest form of prejudice-based censorship hindering people to express their true selves. In this paper, we hypothesized how massive use of syntax can reduce the prejudice effect in HSRs. To explore this hypothesis, we propose Unintended-bias Visualizer based on Kermit modeling (KERM-HATE): a syntax-based HSR, which is endowed with syntax heat parse trees used as a post-hoc explanation of classifications. KERM-HATE significantly outperforms BERT-based, RoBERTa-based and XLNet-based HSR on standard datasets. Surprisingly this result is not sufficient. In fact, the post-hoc analysis on novel datasets on recent divisive topics shows that even KERM-HATE carries the prejudice distilled from the initial corpus. Therefore, although tests on standard datasets may show higher performance, syntax alone cannot drive the “attention” of HSRs to ethically-unbiased features.
Identification and expression profiles of the YABBY transcription factors in wheat
Authors: Hao Lidong , Zhang Jinshan , Shi Shubing , Li Peng , Li Dandan , Zhang Tianjiao , Guo Haibin
Published: February 2022

Background

YABBY is a plant-specific transcription factor (TF) that belongs to the zinc finger protein superfamily and is composed of a C2–C2 domain at the N-terminus and a YABBY domain at the C-terminus. It plays a role in plant development and growth.

Methods

In this study, 20 YABBY TFs were identified in the wheat genome. Phylogenetic relationships, collinearity relationships, gene structures, conserved motifs, and expression patterns were analyzed.

Results

Twenty TaYABBY TFs were distributed unevenly on 15 chromosomes. Collinearity analysis showed that these genes have a close relationship with monocot plants. The phylogenetic tree of wheat YABBYs classified these TaYABBYs into FIL, YAB2, INO, and CRC clades. Gene structure and conserved motif analyses showed that they share similar components in the same clades. Expression profile analysis showed that many TaYABBY genes have high expression levels in leaf tissues and are regulated by abiotic stresses, especially salt stress. Our results provide a basis for further functional characterization of the YABBY gene family.
Первая находка эпибионтов на раковинах уральских атрипид, "Природа"
Authors: Комаров В.Н. , Павлова Ю.Э. , Бушманова Ю.Д.
Published: February 2022

Приведены данные о первых находках эпибионтов на раковинах атрипид Carinatina arimaspa из карпинского горизонта эмсского яруса и Karpinskia conjugula из пражского яруса (оба яруса принадлежат девонской системе) восточного склона Северного Урала. Единственный экземпляр Palaeconchus обнаружен на спинной створке раковины Carinatina arimaspa вблизи боковой комиссуры. На двух раковинах C.arimaspa и на двух раковинах K.conjugula вблизи комиссуры встречены следы сверлений. На долю найденных поселенцев приходится лишь около 1.5% от общего числа изученных атрипид, что свидетельствует либо о крайней редкости самих эпибионтов, либо о малом использовании ими раковин атрипид в качестве субстрата. Решение вопроса о прикреплении эпибионта к раковине брахиоподы при ее жизни или уже после ее гибели зависит от определения систематической принадлежности сверлящих организмов. Если сверления оставили водоросли, то можно предполагать посмертное прикрепление. Если же следы принадлежат губкам, следует говорить о прижизненном поселении.
ИСТОРИЯ АКАДЕМИИ НАУК ВАЖНА НЕ ТОЛЬКО ДЛЯ УЧЁНЫХ, НО И ДЛЯ ВЛАСТЬ ИМУЩИХ, "Энергия: экономика, техника, экология"
Authors: Фандо Р.А.
Published: February 2022

О перспективах развития научно-исторического знания в России рассказывает директор Института истории естествознания и техники им. С.И. Вавилова РАН, кандидат биологических наук, доктор исторических наук РОМАН ФАНДО
ОСВОЕНИЕ АРКТИКИ, ДАЛЬНЕГО ВОСТОКА И СИБИРИ КАК ЭКОНОМИЧЕСКАЯ СТРАТЕГИЯ РФ, "Энергия: экономика, техника, экология"
Authors: Ранцев-Картинов В.А.
Published: February 2022

Данная статья представляет только некоторые энергетические аспекты большого общенационального проекта по освоению Арктики, Дальнего Востока и Сибири. В 2019 г. после обращения в правительство РФ о рассмотрении предложений по проекту получен ответ из Министерства РФ по развитию Дальнего Востока и Арктики: “…предложения будут учитываться при подготовке новой редакции стратегии развития Арктической зоны РФ”. Предварительные оценки автора показали, что претворение в жизнь этого проекта на федеральном уровне может дать дополнительный вклад в доходную часть бюджета страны, вплоть до её удвоения. Это обусловлено применением разра- ботанных и запатентованных новых высокоэффективных нанотехнологий в различных областях промышленного производства.
Model complexes suggest certain S‐state changes of the photosynthetic water‐oxidation enzyme may involve an Mn(II)–Mn(III) transition
Authors: Vincent John B. , Christou George
Published: July 2002

The ultraviolet‐visible absorbance differences spectra of Mn(II,III) and Mn(III,III) oxo‐bridged carboxylate complexes are reported. The difference spectra are remarkably similar to those of the photosynthetic water‐oxidation enzyme complex reported by Dekker et al. [(1984) Biochim. Biophys. Acta 764, 301–309] which were interpreted as being due exclusively to Mn(II→IV) transitions. This result indicates that certain S‐state changes of the enzyme complex may instead involve Mn(II→III) transitions, and that difference spectra alone cannot be used with confidence to assign the Mn oxidation state changes during water oxidation.
15‐cis‐β‐Carotene found in the reaction center of spinach photosystem II
Authors: Bialek-Bylk Grazyna E. , Tomo Tatsuya , Satoh Kimiyuki , Koyama Yasushi
Published: July 2002

Solvent extraction at ∼4°C in complete darkness, and subsequent analysis by high‐pressure liquid chromatography (at ∼4°C) using an apparatus equipped with a two‐dimensional diodearray detector, spectroscopically identified 15‐cis‐β‐carotene in the reaction center (RC) of spinach photosystem 11 (PS 11). The result revises a previous conclusion that /3‐carotene bound to the PS 11 RC takes the all‐trans configuration [Fujiwara, H., Hayashi, H., Tasumi, M., Kanaji, M., Koyama, Y. and Satoh, K. (1987) Chem. Lett. 2005–2008], and generalizes the concept established for purple photosynthetic bacteria that 15‐cis‐carotenoid is naturally selected by the photosynthetic reaction centers.
14‐3‐3 proteins interact with a 13‐lipoxygenase, but not with a 9‐lipoxygenase
Authors: Holtman Wessel L. , Roberts Michael R. , Oppedijk Berry J. , Testerink Christa , van Zeijl Mieke J. , Wang Mei
Published: July 2002

Associations between lipoxygenases (Lox) and 14‐3‐3 proteins were demonstrated by two different methods. First, immunoprecipitation experiments, using isoenzyme‐specific monoclonal Lox antibodies, showed that 14‐3‐3 proteins co‐precipitate with 13‐Lox, but not with the 9‐Lox from barley. Second, interactions between 13‐Lox and 14‐3‐3 were established by surface plasmon resonance studies, showing that 13‐Lox binds with 14‐3‐3 proteins in a concentration‐dependent manner. The interactions between 14‐3‐3 proteins and 13‐Lox may reveal their role during plant development.
Update of recent clinical trials in heart failure and myocardial infarction
Authors: Richardson Mark , Cockburn Neil , Cleland John G.F.
Published: July 2002

Background:

There are currently many on‐going clinical trials assessing therapies for the treatment of patients with heart failure.

Aims:

The purpose of this series of papers is to present concise summaries of current randomised trials in the field of heart failure and myocardial infarction (MI).

Methods:

Data from large double‐blind, placebo‐controlled trials, which are on‐going or have only recently been published, are given in a format allowing easy comparison. Where appropriate, data from smaller studies are included.

Results:

Major studies which are examined in this issue include CIBIS II, MERIT‐HF, RESOLVD, SPICE, VEST, MACH‐1, ATLAS, RALES, CIDS and CASH. These trials assess the efficacy and safety of beta‐blocker, angiotensin‐II‐receptor blocker, positive inotropic agent, calcium antagonist, angiotensin‐converting enzyme (ACE) inhibitor, aldosterone receptor blocker, and antiarrhythmic interventions in the treatment of heart failure.

Conclusions:

The presentation of data from these on‐going trials should allow an up‐to‐date assessment, by physicians, of the most appropriate and effective treatment for patients with heart failure. It is evident that some therapies may play no further role in the treatment of heart failure, due to the increased risk of mortality associated with their administration, whilst others may convey significant benefits.
Influence of Aeration on Cytoplasmic pH of Yeast in an NMR Airlift Bioreactor
Authors: Melvin Brenda K. , Shanks Jacqueline V.
Published: July 2002

Nuclear magnetic resonance spectroscopy has been increasingly pursued as a tool for noninvasive, real‐time studies of metabolic processes of cell suspensions in bioreactors. One acute challenge in NMR bioreactor design has been supplying enough oxygen for cell respiration in a suspension that contains sufficient cells for NMR signal detection. The use of cytoplasmic pH as an intracellular marker of adequate oxygenation was evaluated from 31P NMR spectra of the yeast Saccharomyces cerevisiae at several cell densities, ranging from low (0.9% (v/v)) to very high (45% (v/v)) cell densities, in an airlift bioreactor. 31P NMR spectra were obtained for derepressed yeast cells prior to, and during, glycolysis under nongrowth conditions. During endogenous respiration, pHcyt can be used as an intracellular marker for aeration for cell densities up to 18% (v/v) based on two criteria: a value of pHcyt at least 0.2 pH units higher under aerobic than anaerobic conditions and an absolute pHcyt value of 7.1−7.2. These results were more conservative than values of the maximum cell density obtained from calculations using kLa and respiration rate estimates and highlight the utility of intracellular measurements in conjunction with engineering design calculations. During glycolysis, pHcyt values were similar under aerobic and anaerobic conditions and hence pHcyt cannot be used as a marker under these conditions. Carbon dioxide in the influent gas was observed to aid cells in maintaining physiological pHcyt at high cell densities.
Polyclonal anti‐T‐cell globulin as part of the preparative regimen for pediatric allogeneic stem‐cell transplantation
Authors: Remberger Mats , Mattsson Jonas , Ringdén Olle
Published: July 2002

Abstract:To prevent graft rejection and graft‐versus‐host disease (GvHD) after allogeneic stem‐cell transplantation (ASCT), 56 children were given polyclonal anti‐T‐cell globulin (ATG) as part of the conditioning regimen. Of the 56 children in the cohort, 27 had a non‐malignant disease and 29 had different hematological malignancies. Eight were in first remission of leukemia and the remainder in later stages. Donors were in 16 cases a human leucocyte antigen (HLA)‐identical sibling and in 40 a matched unrelated donor (MUD). The control group comprised 16 patients with an HLA‐identical donor; the children in this group were not treated with ATG. Side‐effects related to the ATG treatment occured in 63% of the patients and included fever, chills, headache, dyspnoea, nausea/vomiting, body pain, fall in blood pressure, and transient respiratory arrest. Engraftment occured in 55 (98%) of the ATG‐treated patients at a median of 17 (11–27) days after ASCT. One rejection occured at 23 days post‐SCT. The probabilities of acute graft‐versus‐host disease (GvHD) of grades II–IV were 6% for patients with an HLA‐identical donor, 12% for controls, and 26% for the MUD group. Chronic GvHD occured in 20%, 50%, and 50% of patients in the three groups, respectively. Transplant‐related mortality rates at 100 days were 6%, 6%, and 7%, respectively. The 5‐yr survival rate was 94% and 81% using sibling donors, with and without ATG respectively, and 53% using unrelated donors (p = 0.002). Disregarding donor type, among the ATG‐treated patients 5‐yr survival rates were 46% in patients with a malignant disease and 77% in non‐malignant disorders. Relapse and relapse‐free survival rates were 42% and 46%, respectively. Five out of 12 patients who showed an early full donor chimerism in the T‐cell lineage developed acute GvHD of grades II–IV, compared to none out of 13 patients being mixed chimeras (p = 0.01). Hence, the use of polyclonal ATG as part of conditioning prior to ASCT in children is safe and the survival rate encouraging.
Nasogastric feeding enhances nutritional status in paediatric liver disease but does not alter circulating levels of IGF‐I and IGF binding proteins
Authors: Holt Richard , Miell John , Jones Jennifer , Mieli‐Vergani Giorgina , Baker Alastair
Published: July 2002

OBJECTIVE

Complications of childhood cirrhosis include abnormal growth and malnutrition, associated with abnormalities in circulating IGFs and IGFBPs. Controlled studies suggest that intensive enteral feeding enhances nutritional status. The aim was to ascertain whether nasogastric feeding improves nutritional status in clinical practice and to assess the effect of feeding on serum IGF‐I and IGFBPs.

PATIENTS

Thirty‐three children (median age 0.6 years) with biliary atresia and failure to thrive who were treated with nasogastric feeding.

MEASUREMENTS

Height, weight and triceps skin fold thickness were measured prior to feeding and regularly for 1 year or until feeding was stopped. Serum IGF‐I and IGFBPs were measured by immunoassay at the same intervals.

RESULTS

The median duration of feeding was 3.7 months. Twenty‐two stopped feeding after liver transplantation, while 10 stopped electively and 1 boy died. Before feeding, the children were losing weight and height centile. Triceps skin fold thickness, weight and height sd scores improved with feeding. Baseline serum IGF‐I and IGFBP‐3 were low, while IGFBP‐1 and IGFBP‐2 were raised. IGF‐I and IGFBP‐1 did not change with feeding. IGFBP‐2 fell and reached a nadir by 3 months, while IGFBP‐3 rose temporarily for 4–6 weeks.

CONCLUSIONS

Nasogastric feeding improves body composition in paediatric liver disease but circulating IGF‐I and IGFBPs remain abnormal and do not play a major role in mediating these changes. This does not exclude a paracrine or autocrine effect of IGF‐I.
Infant care practices in a metropolitan Aboriginal population
Authors: Eades SJ , Read AW , Team the Bibbulung Gnarneep
Published: July 2002

Objective:To describe sleeping position, room and bed‐sharing, tobacco smoke exposure and infant feeding for a sample of Australian Aboriginal infants from a metropolitan area.

Methods:Interviews with Aboriginal mothers who resided in the Perth metropolitan area and had given birth during a continuous15‐month study period. The interviews took place when the infants were approximately 6–12 weeks old and efforts were made to contact all eligible mothers. Results are presented as proportions with 95% confidence intervals.

Results:Of all the eligible mothers (n= 515), 87% were contacted and 53% (n= 273) completed the interview. Of all the infants, 11% slept prone, 96% shared a room and 68% shared a bed; 65% of mothers smoked during pregnancy and 65% were smokers at the time of interview; 66% of the partners were smokers and 80% of the infants were regularly exposed to tobacco smoke; 89% of mothers initiated breast‐feeding and 70% were breast‐feeding at time of interview.

Conclusion:Prevalences of non‐prone sleeping and breast‐feeding are similar to the overall Western Australian population, whilst tobacco smoke exposure of the infants is markedly higher. Programs of community and family education and support are required urgently to decrease this exposure.
Incidence and risk factors of severe hypertriglyceridaemia in the era of highly active antiretroviral therapy: the Aquitaine Cohort, France, 1996–99
Authors: Thiébaut R , Dequae‐Merchadou L , Ekouevi DK , Mercié P , Malvy D , Neau D , Dabis F , The Groupe d'Epidémiologie Cliniquedu Sida en Aquitaine (gec
Published: July 2002

1
Unité INSERM 330, Institut de Santé Publique, d'Epidémiologie et de Développement (ISPED), Université Victor Segalen Bordeaux 2, Bordeaux and

2
Centre d'Information et de Soins de l'Immunodéficience Humaine, Centre Hospitalier Universitaire de Bordeaux, France

Objective  To estimate the incidence of serum hypertriglyceridaemia > 6 mm/L (HTG) and identify associated factors in the era of highly active antiretroviral therapy (HAART).

Methods  A prospective cohort, multirisk, both genders, of HIV‐infected patients was treated with several patterns of antiretrovirals. Cox's model was used to estimate the effect of explanatory variables documented at the first normal triglyceride measurement (< 2 mm/L) on the subsequent occurrence of HTG.

Results  Among 925 patients (27% treated with a protease inhibitor (PI) containing regimen and 48% treated with other HAART combinations) followed 25 months in median with a median triglyceridaemia of 1.1 mm/L at baseline, 70 experienced an HTG, 4.2 cases per 100 person years[95% confidence interval (CI)=2,2,3,3–5]. Univariate analysis retained the following as risk factors of HTG: male gender, homosexual transmission group, greater age, higher body weight, AIDS stage, ≥ 2 antiretrovirals including PI, higher triglyceride level and lower CD4+ cell count at baseline. In multivariate analysis, the risk of HTG remained associated with being male homosexual [hazard ratio (HR) = 1.68, P = 0.04], at the AIDS stage (HR = 1.84, P = 0.03), with increased triglyceride level (HR = 2.82 for 1 mm/L higher at baseline, P < 10−3), impaired CD4+ cell count (HR = 1.2 for 100 cells/μL lower, P = 0.02) and increased body weight (HR = 1.3 for 10 kg higher, P = 0.02).

Conclusions  Baseline triglyceride level and being overweight are risk factors of HTG, together with advanced HIV disease, but the contribution of HAART is not demonstrated.
Manipulation of Si nucleation on artificial sites of SiNx (x<4/3) over SiO2
Authors: Sato N. , Yonehara T.
Published: July 2002

A matrix of Si crystals can be formed on amorphous substrates by manipulating nucleation sites. We have investigated various SiNx by x-ray photon spectroscopy in order to search for suitable artificial nucleation sites and measured the density of Si nuclei deposited on the SiNx. It is found that the Si/N compositional ratio of the Si+ ion implanted SiNx surface is much higher than the theoretically estimated value. Si nucleus density on these surfaces increases with the Si/N compositional ratio. Si crystals were well manipulated on the portions of the Si-enriched SiNx dotted over SiO2 due to improved selectivity.
Femtosecond optical absorption studies of nonequilibrium electronic processes in high T
c superconductors
Authors: Chwalek J. M. , Uher C. , Whitaker J. F. , Mourou G. A. , Agostinelli J. , Lelental M.
Published: July 2002

We report the results of femtosecond optical transient absorption experiments performed on the superconducting compounds YBa2Cu3O7−x(x ∼ 0) and Bi2Sr2Ca2Cu3O10+δ(δ ∼ 0) and nonsuperconducting YBa2Cu3O6+y(y<0.4) for sample temperatures ranging from ∼7 K to room temperature. Nonequilibrium heating was found to occur on a subpicosecond time scale. A distinct, dramatic increase in the relaxation time was observed for the superconducting samples as the sample temperature was lowered below the critical temperatures of the respective films. Accompanying the increase in relaxation time was an increase in the peak fractional transmissivity change. No such changes were observed for the nonsuperconducting YBCO sample. We believe the above described behavior is electronic in origin and intimately related to the superconductivity of the compounds.
Simultaneous sum-frequency and second-harmonic generation from a proton-exchanged MgO-doped LiNbO3 waveguide
Authors: Yamamoto Kazuhisa , Yamamoto Hiroaki , Taniuchi Tetsuo
Published: July 2002

Frequency conversion of two laser diodes in a proton-exchanged MgO-doped LiNbO3 waveguide is reported. Simultaneous generation of blue (0.43 μm), green (0.52 μm), and red (0.65 μm) coherent radiation by sum-frequency and second-harmonic generation of laser diodes at wavelengths of 0.86 and 1.3 μm has been observed for the first time. This is made possible by the wide phase-matching bandwidth of the Cherenkov radiation scheme.
1/ f noise reduction of metal-oxide-semiconductor transistors by cycling from inversion to accumulation
Authors: Bloom I. , Nemirovsky Y.
Published: July 2002

A new experimental setup for the study of 1/ f noise of metal-oxide-semiconductor transistor under nonsteady state conditions is presented. The noise measurements demonstrate for the first time that, by interposing periods of negative bias corresponding to accumulation between the monitored periods of positive bias corresponding to inversion, the low-frequency noise sampled in the positive bias intervals is reduced.
Single quantum well GaAs/AlGaAs separate confinement heterostructure lasers with n-type modulation doped cores
Authors: Shank S. M. , Varriano J. A. , Wicks G. W.
Published: July 2002

Separate confinement heterostructure single quantum well GaAs/AlGaAs lasers with n-type modulation doped active regions are studied. Quantum well absorption is significantly modified by n-type modulation doping. The effects of modulation doping on transparency current density and threshold current density are determined. Modulation doping is shown to reduce transparency current density, thereby also reducing threshold current density. Threshold current densities are reduced by 30%, to values of less than 150 A/cm2 for long cavities. The effects on distributed loss and differential gain are also reported. No degradation of laser performance is observed due to the location of the electrical junction away from the active region or due to free carrier absorption loss. Heavily modulation doped structures lase on the second quantized state.
Coherent detection with a GaAs/AlGaAs multiple quantum well structure
Authors: Brown E. R. , McIntosh K. A. , Smith F. W. , Manfra M. J.
Published: July 2002

A GaAs/AlGaAs multiple quantum well (MQW) structure has been investigated as a coherent detector using a CO2-laser local oscillator (LO). At an operating temperature of 77 K, an LO power of 10 mW, an LO wavelength of 10.2 μm, and a bias voltage of 2.0 V, a 150-μm-diam detector displayed an external quantum efficiency η0 of 11% and a 3-dB electrical bandwidth BIF of 1.5 GHz. Under the same conditions the noise-equivalent power density (NEPHET/Δf) at an intermediate frequency of 1.5 GHz was 5.5×10−19 W/Hz, which is within 50% of the photon-noise limit for this detector. A 75-μm-diam detector with a lower-capacitance bond wire was found to have a BIF of 8 GHz and an NEPHET/Δf of 4.1×10−19 W/Hz with only 2.5 mW of LO power. The photoelectron lifetime in the MQW structure at 77 K was estimated to be 2.5 ps corresponding to an intrinsic detector bandwidth of 64 GHz.
Thermodynamic and kinetic processes involved in the growth of epitaxial GaN thin films
Authors: Newman N. , Ross J. , Rubin M.
Published: July 2002

Our experimental results using reactive magnetron sputtering, combined with earlier literature, are used to understand the thermodynamic and kinetic processes involved in GaN film growth and the limiting factors involved in the incorporation of nitrogen during the growth process. We show that GaN films fabricated with low pressure growth techniques (<0.1 Torr) such as sputtering and molecular beam epitaxy are formed under metastable conditions with a nonequilibrium kinetically limited reaction. For these methods, the growth process is controlled by a competition between the forward reaction, which depends on the arrival of activated nitrogen species at the growing surface, and the reverse reaction whose rate is limited by the unusually large kinetic barrier of decomposition of GaN. In practice, the thermally activated rate of decomposition sets an upper bound to the growth temperature.
Model for the vaporization of mixed organometallic compounds in the metalorganic chemical vapor deposition of high temperature superconducting films
Authors: Meng Guangyao , Zhou Gang , Schneider Roger L. , Sarma Bimal K. , Levy Moises
Published: July 2002

A model of the vaporization and mass transport of mixed organometallics from a single source for thin film metalorganic chemical vapor deposition is presented. A stoichiometric gas phase can be obtained from a mixture of the organometallics in the desired mole ratios, in spite of differences in the volatilities of the individual compounds. Proper film composition and growth rates are obtained by controlling the velocity of a carriage containing the organometallics through the heating zone of a vaporizer.
Selective poling of nonlinear optical polymer films by means of a monoenergetic electron beam
Authors: Yang G.-M. , Bauer-Gogonea S. , Sessler G. M. , Bauer S. , Ren W. , Wirges W. , Gerhard-Multhaupt R.
Published: July 2002

Electron beams with an energy of 10 keV were employed for selectively poling only the lower part of a typical nonlinear optical guest/host polymer at a temperature of 90 °C. The resulting dipole orientation was examined by means of electro-optical measurements and thermally stimulated depolarization, while the nonuniform charge and polarization profiles were probed with laser-induced pressure pulses and thermal waves. The concept of nonlinear optical frequency conversion with simultaneous mode conversion is described as an example for the advantages of such a selective poling process.
Voltage tunable acoustoelectric interaction in GaAs/AlGaAs heterojunctions
Authors: Rocke C. , Manus S. , Wixforth A. , Sundaram M. , English J. H. , Gossard A. C.
Published: July 2002

The interaction between surface acoustic waves and high mobility quasi-two-dimensional electron systems (2DES) in GaAs/AlGaAs heterojunctions with variable carrier density is investigated experimentally. In specially designed samples the strength of this acoustoelectric interaction can be controlled via the field-effect induced variation of the carrier density of the 2DES. Since the sensitivity of surface acoustic wave experiments is particularly high at very low conductivities, the proposed technique will be an especially valuable tool for the investigation of 2DES with extremely low sheet carrier densities. We demonstrate that the proper use of a metallic gate electrode does not conflict with the piezoelectric interaction between the mobile carriers confined in the heterostructure and the surface acoustic wave propagating on the piezoelectric substrate.
InAs island-induced-strain driven adatom migration during GaAs overlayer growth
Authors: Xie Qianghua , Chen P. , Madhukar A.
Published: July 2002

The impact of the strain fields associated with partially strain relaxed InAs islands on GaAs (100) on the evolution of the growth front profile during subsequent GaAs capping layer growth as a function of the growth temperature is examined via placement of very thin AlGaAs marker layers. Transmission electron microscope studies reveal the presence of strain dominated atom migration away from the islands over dynamically evolving length scales of ∼100–400 Å at higher growth temperature whereas at lower growth temperature such an effect is minimal. Anisotropy in the length scale of impact between the [011] and [011̄] directions is observed. Estimates based upon a suitably adapted formulation of the classical theory of grain growth shows the mass transport to be dominantly strain rather than surface curvature driven.
Raman scattering by folded longitudinal acoustic phonons in InAs/GaSb superlattices: Resonant enhancement and effect of interfacial bonding
Authors: Wagner J. , Schmitz J. , Herres N. , Ralston J. D. , Koidl P.
Published: July 2002

We have studied backfolded longitudinal acoustic (LA) phonons in InAs/GaSb superlattices (SLs) intentionally grown with either InSb-like or GaAs-like interfaces (IFs). Raman scattering by folded LA phonons was found to be resonantly enhanced for incident photon energies slightly below the 2.0 eV electronic SL interband transition, observed previously by spectroscopic ellipsometry and by resonant Raman scattering from longitudinal optical SL phonons. Under resonant excitation, InAs/GaSb SLs with InSb-like IFs showed scattering by folded LA phonons up to the 7th order. For SLs with GaAs-like IFs, the folded LA phonon modes occurred at systematically higher frequencies than for SLs with the same nominal period and InSb-like IFs. The difference in frequency increased with decreasing SL period.
Photoconductive ultraviolet sensor using Mg-doped GaN on Si(111)
Authors: Stevens K. S. , Kinniburgh M. , Beresford R.
Published: July 2002

This work characterizes a GaN:Mg on silicon ultraviolet photodetector with a cutoff at 3.3 eV and a responsivity of 12 A/W at 4 V bias for optical intensities on the order of 1 W/m2 and below. A weak photovoltaic response is also reported. The photocurrent is nearly linear versus optical intensity for up to 10 W/m2. The responsivity increases nearly linearly with applied voltage up to 8 V, then the increase slows toward saturation. To explain this high responsivity in a direct gap semiconductor, it is hypothesized that holes are captured at either compensated Mg deep acceptor sites or Mg-related trap/recombination centers, resulting in a greatly prolonged electron free-carrier lifetime.
Large-area, single-transverse-mode semiconductor laser with diffraction-limited super-Gaussian output
Authors: Mowry Greg , Leger James R.
Published: July 2002

An external cavity semiconductor laser that incorporates a large-area amplifier has been successfully stabilized into a single transverse mode over the 600 μm width of the amplifier. Single-transverse-mode operation is achieved by using the combination of a diffractive mode-selecting mirror and an aperture. 2.8 W of stable diffraction-limited output power is achieved.
Simple pipe gun for hydrogen pellet injection
Authors: Combs S. K. , Milora S. L. , Foust C. R.
Published: July 2002

A new single-shot hydrogen pellet injector based on a simple ‘‘pipe gun’’ design is described. In the cryogenic gun block, the 4-mm-diam (nominal) pellet is frozen in situ directly from the gaseous hydrogen isotope and then accelerated in the gun barrel with a burst of high-pressure (≤130-bar) hydrogen gas to speeds of up to 1680 m/s.
Pendulously suspended magnetometer sensors
Authors: Trigg D. F. , Olson D. G.
Published: July 2002

Variations in three orthogonal components of the earth’s magnetic field are measured and recorded continuously at Canadian magnetic observatories. The sensors (defined as X, Y, and Z) are oriented such that the X sensor axis is aligned with geographic north, the Y sensor axis with geographic east, and the Z sensor axis is aligned vertical. Improved magnetometer stability has made the seasonal tilting of the marble or cement piers on which the sensors are mounted to appear as a remaining contaminant in the magnetic observatory data. One approach to removing tilt errors is to suspend the sensors in a pendulum-type mount. Such a suspension, which will be used at Canadian magnetic observatories, is described here. This suspension is shown to be insensitive to dimensional changes in its critical parts; to be capable of attenuating tilts by factors in excess of 10 000; to be insensitive to magnetic torque experienced by the sensors, and with suitable damping, to be insensitive to teleseismic ground motions expected from distant large earthquakes.
New method for thermal desorption spectroscopy using field electron emission microscopy
Authors: Choi D. S. , Han J. H. , Park N. G. , Kim K. S. , Whang C. N.
Published: July 2002

We have developed a new method for thermal desorption spectroscopy using field electron emission microscopy. To investigate the validity of our method, we have performed hydrogen adsorption experiments on the well known W(100) and W(110) surfaces and also on W(310). The thermal desorption spectra of these systems show that this method permits the study of adsorption on various single crystal plans of a metal with one sample. This method also gives information about the dipole direction of the adsorbates directly from the thermal desorption spectrum without additional measurement of the work function change induced by adsorbates.
Spot welder for making small electrical contacts
Authors: Walker I. R. , Moss C. J.
Published: July 2002

A capacitive-discharge spot welder is described which is primarily intended for making electrical connections between small (<25–150 μm diameter) wires and samples of metallic materials, although it can be used in many applications where miniature welds must be made. It has been particularly useful in allowing low resistance (several mΩ) contacts to be created on samples of rare earth and actinide intermetallic compounds which are highly resistant to soldering. The device has a minimum time constant of about 25 μs and can deliver a maximum of between 700 μJ and 400 mJ of energy to the weld region, depending on the resistance of the latter. A suitable electrode holder is also described, and considerations for choosing the electrode materials, selecting the contact wires, preparing the sample, and creating a weld are discussed.
Energy-dispersive x-ray diffraction equipment for fluids at extreme conditions of high temperatures and high pressures
Authors: Tamura Kozaburo , Inui Masanori , Hosokawa Shinya
Published: July 2002

An energy-dispersive x-ray diffraction technique for fluid materials under high pressure, up to 2000 bar, and high temperature, up to 1650 °C, has been developed using an x-ray source with high energy up to 70 keV, a high-pressure vessel with Be windows pressurized with He gas, and a new sample cell made of single crystal sapphire. Using this technique one can overcome several difficulties intrinsic with x-ray diffraction measurements of fluids, such as high vapor pressure and high x-ray absorption constant of samples, x-ray scattering and absorption by sample cells, and x-ray absorption by high-pressure vessels. In order to show an excellent potential of the equipment, examples of the experiments for the liquid-vapor subcritical fluid Hg and Se are reported.
Interface inequivalence of the InP/InAlAs/InP staggered double heterostructure grown by metalorganic chemical vapor deposition
Authors: Böhrer J. , Krost A. , Heitz R. , Heinrichsdorff F. , Eckey L. , Bimberg D. , Cerva H.
Published: July 2002

The optical and structural properties of the normal InAlAs on InP and the inverted InP on the InAlAs staggered band lineup interface grown by metalorganic chemical vapor deposition (MOCVD) are compared by use of transmission electron microscopy (TEM), time integrated, and time resolved photoluminescence. TEM images show that both interfaces are dissimilar. The normal interface is very abrupt. The inverted interface shows an additional graded layer of about 2.5 nm in width of In1−xAlxAsyP1−y with x (0.48–0) and y (1.0–0.0). A large optical anisotropy exists because of the inequivalence of the two interfaces. The larger spatial separation of the carriers at the inverted interface is responsible for a smaller overlap of the electron and hole wave functions and for that reason a one order of magnitude longer e-h luminescence decay time of 45 ns is observed. The normal interface transition shifts approximately to the third root of excitation while the inverted interface transition shifts logarithmically.
Giant magnetoresistance of a two-dimensional ferromagnet La2−2xCa1+2xMn2O7
Authors: Asano H. , Hayakawa J. , Matsui M.
Published: July 2002

Bulk samples of La2−2xCa1+2xMn2O7 with the layered Sr3Ti2O7-type perovskite structure have been successfully synthesized and investigated with respect to their magnetic and electrical properties. It is found that La2−2xCa1+2xMn2O7 (x=0.25) is a metallic ferromagnet with a magnetic transition temperature Tc of 215 K. The large magnetoresistance (MR) effect with Δρ/ρ0 of ∼60% at 1.8 T was observed in a wide temperature range below a cusp temperature in resistivity of 96 K, which is well below the magnetic Tc. This behavior is quite different from that of the well-known double-exchange ferromagnets such as La1−xCaxMnO3, where large MR effects are restricted to a narrow temperature range around the ferromagnetic transition. The present result could be interpreted by using the double-exchange theory incorporating the anisotropy resulting from the two-dimensional Mn-O-Mn networks in La2−2xCa1+2xMn2O7.
Growth of highly textured LiNbO3 thin film on Si with MgO buffer layer through the sol-gel process
Authors: Yoon Jong-Gul , Kim Kun
Published: July 2002

Highly textured ferroelectric LiNbO3 thin films have been grown on MgO-buffered Si (100)/(111) through the sol-gel process under optimum conditions. These films show a high degree of c-axis orientation regardless of the orientation of the Si substrates. Structural properties of the films were strongly influenced by the thickness of the MgO buffer layer probably due to the strains induced by the lattice and the thermal mismatch. Optimum thickness of the MgO buffer layer was found to be about 50 nm for the growth of a highly textured LiNbO3 film. An epitaxial-like growth was observed by x-ray pole figure analysis for the film on MgO/Si(111) obtained under a rapid thermal process above 900 °C. The surface morphology investigated by atomic force microscopy showed a growth behavior of crystalline grains as the thermal process was varied.
A room-temperature silicon single-electron metal–oxide–semiconductor memory with nanoscale floating-gate and ultranarrow channel
Authors: Guo Lingjie , Leobandung Effendi , Chou Stephen Y.
Published: July 2002

We have demonstrated a room-temperature silicon single-electron transistor memory that consists of (i) a narrow channel metal-oxide–semiconductor field-effect transistor with a width (∼10 nm) smaller than the Debye screening length of single electron; and (ii) a nanoscale polysilicon dot (∼7×7 nm) as the floating gate embedded between the channel and the control gate. We have observed that storing one electron on the floating gate can significantly screen the channel from the potential on the control gate, leading to a discrete shift in the threshold voltage, a staircase relationship between the charging voltage and the threshold shift, and a self-limiting charging process.
Electron emission induced modifications in amorphous tetrahedral diamondlike carbon
Authors: Mercer T. W. , DiNardo N. J. , Rothman J. B. , Siegal M. P. , Friedmann T. A. , Martinez-Miranda L. J.
Published: July 2002

The cold-cathode electron emission properties of amorphous tetrahedral diamondlike carbon are promising for flat-panel display and vacuum microelectronics technologies. The onset of electron emission is, typically, preceded by “conditioning” where the material is stressed by an applied electric field. To simulate conditioning and assess its effect, we combined the spatially localized field and current of a scanning tunneling microscope tip with high-spatial-resolution characterization. Scanning force microscopy shows that conditioning alters surface morphology and electronic structure. Spatially resolved electron-energy-loss spectroscopy indicates that the predominant bonding configuration changes from predominantly fourfold to threefold coordination.
Bond-length strain in buried Ga1−xInxAs thin-alloy films grown coherently on InP(001)
Authors: Woicik J. C. , Gupta J. A. , Watkins S. P. , Crozier E. D.
Published: July 2002

The bond lengths in a series of strained, buried Ga1−xInxAs thin-alloy films grown coherently on InP(001) have been determined by high-resolution extended x-ray absorption fine-structure measurements. Comparison with a random-cluster calculation demonstrates that the external in-plane epitaxial strain imposed by pseudomorphic growth opposes the natural bond-length distortions due to alloying.
Green electroluminescence from Er-doped GaN Schottky barrier diodes
Authors: Steckl A. J. , Garter M. , Birkhahn R. , Scofield J.
Published: July 2002

Visible light electroluminescence (EL) has been obtained from Er-doped GaN Schottky barrier diodes. The GaN was grown by molecular beam epitaxy on Si substrates using solid sources (for Ga, and Er) and a plasma source for N2. Al was utilized for both the Schottky (small-area) and ground (large-area) electrodes. Strong green light emission was observed under reverse bias, with weaker emission present under forward bias. The emission spectrum consists of two narrow green lines at 537 and 558 nm and minor peaks at 413 and at 666/672 nm. The green emission lines have been identified as Er transitions from the H11/22 and S3/24 levels to the I15/24 ground state and the blue and red peaks as the H9/22 and F9/24 Er transitions to the same ground state. The reverse bias EL intensity was found to increase linearly with bias current.
Different fatigue behaviors of SrBi2Ta2O9 and Bi3TiTaO9 films: Role of perovskite layers
Authors: Kang B. S. , Park B. H. , Bu S. D. , Kang S. H. , Noh T. W.
Published: July 2002

To investigate the role of the perovskite layers on fatigue behaviors, SrBi2Ta2O9(SBT) and Bi3TiTaO9 (BTT) films were prepared by pulsed laser deposition using 15% Bi-excess bulk targets. The SBT and the BTT films grown at the similar deposition conditions showed similar growth behaviors, electrical properties, and retention characteristics. However, these films showed very different fatigue behaviors. The difference should come from the oxygen stability in the perovskite layer. Our work demonstrates that oxygen stability of the perovskite layers, as well as the self-regulating adjustment of the Bi2O2 layers, should be considered in the search for new candidate materials for nonvolatile ferroelectric memory devices.
Nanoscale icosahedral quasicrystalline phase formation in a rapidly solidified Zr80Pt20 binary alloy
Authors: Saida Junji , Matsushita Mitsuhide , Inoue Akihisa
Published: July 2002

It is found that an icosahedral quasicrystalline phase is directly formed in a Zr80Pt20 binary alloy during rapid solidification from the melt. The size of the icosahedral particles lies in the diameter range below 10 nm, and the particles are distributed homogeneously. The formation of the nanoscale icosahedral phase indicates that the icosahedral short-range order exists in the melted state of Zr–Pt binary alloy. The strong chemical affinity between Zr and Pt contributes to the restraint of the long-range rearrangement of constitutional elements to form a stable crystalline phase, which is the important factor of the stabilization of an icosahedral phase.
In situ observation of nucleation and subsequent growth of clusters in silane radio frequency discharges
Authors: Koga Kazunori , Matsuoka Yasuhiro , Tanaka Kenichi , Shiratani Masaharu , Watanabe Yukio
Published: July 2002

Growth processes of clusters in low-pressure and low-power silane radio frequency discharges are studied by using the newly developed double-pulse-discharge method which realizes in situ measurement of their size and density in a size range of 0.5–4 nm. The clusters begin to be composed of two size groups at about 10 ms after the discharge initiation: clusters in the small size group have an almost constant average size of about 0.5 nm through the discharge period, while those in the large one grow at about 4 nm/s in a monodisperse way. Time evolution of the measured average sizes and densities in the groups is transformed into that of size distributions assuming that the density of SinHx clusters for the small group decreases exponentially with the increase in the number of Si atoms, n, of them, and the size distribution for the large group is the lognormal one. The results show that a critical cluster size for nucleation is SinHx (n∼4).
A new potential surface and quasiclassical trajectory study of H+H2O→OH+H2
Authors: Wu Guo-sheng , Schatz George C. , Lendvay G. , Fang De-Cai , Harding L. B.
Published: July 2002

We present a method for developing potential-energy surfaces for abstraction reactions with four or more atoms which combines spline fits to high quality ab initio results for the three degrees of freedom that are most active in the reaction (two stretches and a bend) with simple empirical functions (Morse stretches, cosine bends, and torsions) for the spectator variables. The geometry and force constants associated with the spectator modes are allowed to vary along the reaction path so as to match stationary point properties from the ab initio calculations. In an application of this approach to the H+H2O reaction, we are able to generate a global surface for the H3O system that accurately matches ab initio properties, and is globally smooth and free of artifacts. Quasiclassical trajectory (QCT) calculations are used with this surface to study the H+H2O reaction dynamics for both the ground and local mode excited states. The resulting ground-state angular distributions, product state vibrational and rotational distributions, and rotational alignment factors are in excellent agreement with all known experiments. This represents an improvement over the results obtained using previous surfaces, but like the past surfaces, the calculated integral cross sections are below experiment by at least a factor of 2. For studies of the H+H2O reaction involving local mode excited states of water, the new surface is consistent with ab initio threshold behavior, with the (04)− local mode state having zero activation energy. However the reactive rate coefficients are substantially smaller than the observed total reactive plus inelastic rate coefficient. This indicates that recent experiments due to Barnes, Sharkey, Sims, and Smith are dominated by energy transfer rather than reaction.