bluuebunny/crossref_metadata_2025 huggingface dataset:
Eccrine poroma: When dermoscopy is useful for diagnosis
Authors: El Jazouly Madiha , Salih Alj Maha Salih , Chahboun FatimZahra , Al Bouzidi Abderahman , Chiheb Soumya
Published: October 2022

Eccrine Poroma is a rare benign adnexal tumor. It presents the problem of differential diagnosis with several entities. Dermoscopic features are suggestive and may guide the diagnosis. We report a new observation. A 44-year-old woman, presented with an asymptomatic lesion on the dorsal side of the left foot for 2 years. Clinically the nodule was brownish, well delimited with superficial erosions, and firm on palpation. Dermoscopy showed linear and irregular vessels with perivascular white halos. Based on the clinical and dermoscopic features a diagnosis of eccrine poroma was made and confirmed by histological findings.
Marketing Challenges Faced by Seaweed Farmers in Zanzibar, Tanzania
Authors: Burra Nina Joan , Devi K. N. Usha
Published: October 2022

Aim/Purpose: This study was conducted to identify the marketing challenges faced by Zanzibar’s seaweed producers and to recommend suitable strategies.

Methodology: A case study approach was adopted. The study combined semi-structured questionnaires and informal group discussions with the farmers as tools for primary data collection. A total of 592 seaweed farmers from both Unguja and Pemba participated in the study. The farmers were selected through multistage sampling. Analysis of challenges was done through the Garrett ranking method.

Results: It was found that the leading marketing challenges for seaweed farmers are the absence of minimum selling price (MSP), limited buyers and the inability to set prices. The absence of MSP was linked to the absence of the industry’s supporting policies. At the same time, limited buyers emanated from the lack of the industry’s business strategy, limited linkage to the domestic market and lack of export differentiation. Farmers’ inability to set prices was found to be a result of exporters’ setting buying prices. Similarly, the study found that the farmers face intense competition due to limited production variety and being large in number. Farmers also were found to have limited marketing and promotional skills and lacked business strategies.

Conclusion: Several interventions are required to support the seaweed farmers in Zanzibar. First, the creation of guiding industry’s business and marketing/product strategies. Further creation of the industry’s guiding and supporting policies is crucial. Second, establishing domestic demand and linking the industry to its potential users at individual and industrial levels is critical for the survival of Zanzibar’s seaweed industry. Third, the establishment of carrageenan extraction industries to establish export product differentiation. Capacity-building training is vital for farmers in agri-business and financial management areas. Government procurement and provision of storage facilities to minimise the offloading challenge are also needed to lessen the effect of same-time offloading, which exposes farmers to low prices. Lastly, financial assistance should also be provided to promote and upscale seaweed value-addition activities on the island.

Originality/Value:  Examination of marketing challenges faced by seaweed farmers in Zanzibar was conducted using the Garrett ranking technique, and suitable recommendations were proposed.
The Effect of Inquiry-based Learning on Senior High School Students’ Achievement in Plane Geometry: Pre-test-Post-test Randomized Experimental Design
Authors: Assuah Charles Kojo , Osei Louis , Mantey Gershon Kwame
Published: October 2022

Using inquiry-based learning, this study investigates high school students' achievement in plane geometry. It employed the pre-test-post-test randomized experimental design, often known as the control group design. The participants (students) were randomly assigned to one of two classes/groups and were given either an intervention (the treatment group) or no intervention (the control group). One hundred and twenty (120) third-year high school students of similar mathematical aptitude (a control group = 60 students; an experimental group = 60 students) were chosen from a high school in Ghana's central region. Shapiro-Wilk had a p-value greater than.05 (p >.05) for each statistic, indicating that both the pre-test and post-test scores were normally distributed, before and after the test. The findings of the independent samples t-test showed that there was no statistically significant difference between the experimental and control pre-test scores (t = -.48, p >.05, C. I = [-1.78, 1.08]). The one-way ANOVA after inquiry-based learning showed a significant effect on student scores, F (1, 118) = 363.41, p < .05). Furthermore, independent samples t-test findings for the post-test showed statistically significant differences between the experimental and control post-test scores (t = -22.68, p < .05, C. I = [-24.29, 20.40]). The study's implications are that students can make their own connections with the content they learn. They may also comprehend the themes rather than simply recalling rules and formulas. The study concludes that inquiry-based learning improves senior high school students’ achievement in plane geometry.
Identification and in vitro Evaluation of Environmental Stress Resilient Plant Growth Promoting Rhizobacterial Consortia for Rice (Oryza sativa L.)
Authors: Srija A. , Latha P. C. , Tejashree M. , Reddy K. Pavan Chandra , Triveni S. , Bandeppa S. , Phule Amol S. , Venkatanna B.
Published: October 2022

The present study screened bacteria isolated from rice rhizosphere for various beneficial traits related to three categories of plant growth promotion, abiotic stress tolerance, and compatibility with multiple agrichemicals to identify a microbial consortium that performs better than individual isolates in improving rice growth under normal and stressful environmental conditions. Among thirty-two isolates screened, 29, 9, 20 isolates were able to solublilize insoluble minerals of nutrients like phosphorous, potassium and zinc respectively. About 29, 31, 23, 17 isolates were found to possess the traits of IAA, ammonia, siderophore and HCN production respectively. Abiotic stress related traits of salinity, drought and high temperature tolerance were displayed by 8, 2 and 10 isolates respectively when examined for their growth in NaCl (4%, 6% 8%), in PEG (64 g/l equivalent to -0.73Mpa) and at 45℃ temperature. Agrichemical tolerant isolates were identified by screening for compatibility with fertilizers and commonly used rice pesticides. Based on the scores assigned during screening tests, 9 best isolates, three from each category, were selected for development of consortia. Our aim in this initial study was to identify three consortia (C-1, 2 and 3) consisting of three compatible bacteria, and to evaluate their effect on rice seed germination and seedling  growth under normal in vitro conditions. C1 enhanced the growth of rice when compared with individual strains, C2 and C3 with highest vigour index I, II values of 1616 ± 18 and 5.47 ± 0.68 respectively. The 16S rRNA sequence analysis identified the bacterial isolates in C1 as Achromobacter sp, Stenotrophomonas sp and Pseudomonas stutzeri. Therefore, this study has identified a unique consortium that can be used for rice growth promotion while simultaneously demonstrating the advantage of bacterial consortia over single isolate inoculants under non stressed conditions.
Performance of Pigeonpea (Cajanus cajan L.) Varieties Sown on Ridge under Front Line Demonstration at Farmer’s Field in Deoria District of Uttar Pradesh, India
Authors: Meena Kamlesh , Srivastva Rajneesh , Singh Shamsher , Tiwari Ajay
Published: October 2022

Aims: The production of pigeon pea is lower than the other pulse crops due to non-adoption of recommended high-yielding varieties and advanced technologies by the farming community in the eastern plains of Uttar Pradesh. To replace this anomalous, we conducted 152 front-line demonstrations (FLDs) at farmers' fields in various adopted villages by Krishi Vigyan Kendra, Deoria.

Place and Duration of Study: The study was carried out by the Krishi Vigyan Kendra,                Malhana, Deoria, under the Indian Institute of Vegetable Research, Varanasi, UP. A total of 90, 12 and 50 FLDs were conducted sown on ridge method with three varieties of pigeon pea                  (Narendra Arhar 1, Pusa Bahar and Narendra Arhar 2) from 2014-15 to 2018-19                    respectively.

Methodology: Conducted 152 front-line demonstrations (FLDs) at farmers' fields in various adopted villages by Krishi Vigyan Kendra, Deoria. Cultivation practices comprised under FLD viz. improved varieties, sowing methods, irrigation, date of sowing, seed treatment, spacing, balance use of fertilizers, intercultural operations, and plant protection measures etc.

Results: Showed an increase in yield of pigeon pea varieties sown on ridge from 4.76–39.20% over traditional cultivation practices. As presented in Fig. 3, the technology gap was highest in Narendra Arhar 1 (1680 kg/ha) during 2016-17 and lowest in Narendra Arhar 2 (340 kg/ha) during 2018-19. The analysis of data for extension gap showed that Narendra Arhar 2 had the highest gap (540 kg/ha) during 2017-18 and Narendra Arhar 1 had the lowest gap (60 kg/ha) during 2016-17. The technology index was highest (56%) in Narendra Arhar 1 in 2016-17 and lowest (15%) in Narendra Arhar 2 in 2018-19.

Conclusion: The lower the value of the technology index, the more feasible the technology is in the eastern plains of UP.
Time Series Prediction Using Hybrid ARIMA-ANN Models for Sugarcane
Authors: Sanjeev . , Bhardwaj Nitin
Published: October 2022

Recently Hybrid model approach has led to a tremendous surge in many domains of science and engineering. In this study, we present the advantage of ANN to improve time series forecasting precision. The Autoregressive Integrated Moving Average (ARIMA) and Artificial Neural Network (ANN) models are used to separately recognize the linear and nonlinear components in the data set respectively. In this manner, the proposed approach tactically utilizes the unique strengths ARIMA and ANN to improve the forecasting accuracy. Our hybrid method is tested on two Yamunanagar and Panipat sugarcane time series of Haryana. Results clearly indicate that Hybrid ARIMA-ANN model was better perform than ARIMA models with smaller values of RMSE and MAPE for both districts.
The Prevalence of Malaria Parasites and the Dynamics of Malaria Vectors in Adenta-Barrier in Ghana
Authors: Agyapong Genevive Afia Amoakoa , Nikoi Cindy Naadei , Waqas Fahad Bin , Akanlu Servacious A. , Bunkunmi Shittu D. , Mohammed Abdul Rahim , Osisiogu Emmanuel Udochukwu
Published: October 2022

Background: Malaria burden is generally lower in urban settings. Urban malaria is likely to surge due to rapid and unplanned urbanization. Hence, this study sought to determine the prevalence of malaria parasite and malaria vectors in Adenta-barrier, a suburb of Adentan Municipality.

Methods: The study followed a cross sectional study design pattern. Mosquitoes were collected from 40 houses in the study site using the pyrethrum spray catches (PSC) method, and malaria parasite screening was carried out on 90 participants. A well-structured form was used to record data on the use of insecticide-treated nets, insecticide spray, and mosquito coil in the community. The mosquitoes collected were morphologically identified.

Results: The malaria parasite prevalence at the study site was 1.1%, and the use of insecticide-treated nets, insecticide spray, and mosquito coil were 13.4%, 7.5%, and 11.9% respectively. As far as vector abundance were concerned, habitat, resting and feeding behavior were taken into consideration. The majority of the mosquitoes collected during the study were Culex 95.7% (22), and the rest was Aedes 4.3% (1). Both Culex and Aedes mosquitoes were found in resting states. Study participants reported majority (80%) of the bites they sustained to have occurred during the early hours of the day. The study area also possessed several easily identifiable breeding sites for mosquitoes.

Conclusion: The prevalence of malaria in the study area was low and no Anopheles mosquitoes was found. The majority of mosquito species present in the locality was Culex with a few Aedes.
Prevalence and Risk Factors Associated with Preterm Birth at Irene-Neto Lubango Provincial Maternity- Huila /Angola
Authors: Francisco Ketha , Ussanje Belo , Chitungu Joana , Luggatti Lorenzo
Published: October 2022

According to WHO (2018), almost 15 million babies are born every year before 37 weeks of pregnancy, the majority taking place in Sub Saharan Africa and in south Asia. Preterm birth is a common complication of pregnancy and usually bore heavy short- and long-term medical, socio-economic and financial burden to the affected children, the family, the heath system and the community as all. Angola with one of the highest fertility rates in the world, 6.2 according to the DHS 2015-2016, coupled with the fact that preterm birth is regarded as a traumatic social even for the parent and a quite expensive condition to the health system will need to stablish the main risk factors for preterm birth in order to inform strategies to prevent its occurrence.

We conducted an hospital based cross sectional study to determine the prevalence and the risk factors of preterm birth at Irene Neto Maternity Hospital- Lubango-Angola.

Three trained research assistants were recruited from the post labour wards and the new born unit and trained to collect data. Gestational age was calculated using a standard obstetric wheel based on menstrual dates or first trimester ultrasound (when available).  A Newborn clinical assessment using the Finnstrom Score aided by a printed pictorial scoring chart was then conducted within 24 hours of birth, by a trained medical Doctor for confirmation.

17.7% of women giving birth at Lubango maternity hospital had a preterm new-born.

Among the socio- demographics factors, only maternal age (p :0.021), family income(p:0.032), use of alcohol (p: 0.013) and lack ANC (p: <0.001) were associated with premature birth. Clinical factors found to increase the risk of premature birth included Antecedent of hypertension (p: 0.021), Preeclampsia (p: 0.026), Malaria (p:0.001) and multiple gestation (p: 0.01).

Only antecedent of premature birth (p:0.0049), lack of antenatal care (p<0.001), malaria (p:0.009) and multiple gestation (p: 0.001) remained significant after controlling for confounders.

Premature birth is still a public health problem in Angola, principally among pregnant women who do not attend ANC clinic and those with multiple gestation. Malaria infection during pregnancy as well as preeclampsia are also serious predictors of premature birth.

With a prevalence of 17.7%, premature birth is a still a serious problem at lubangopediatric hospital and deserve a multisectoral well-coordinated action.

ANC clinic should be actively promoted, improved and expended.

Pregnant women with antecedent of premature birth should be closely monitored

Preeclampsia and malaria should be prevented, searched and serious treated when present during pregnancy.

We the recommend a Multicentre and large sample size, longitudinal observational analytic study for better understanding of the principal predictors at a country level.
Cell cycle regulation of the primitive dinoflagellate Crypthecodinium cohnii Biecheler: Evidence for the presence of an homolog of cyclin B
Authors: Barbier Michèle , Albert Marie , Géraud Marie‐Line , Bhaud Yvonne , Picard André , Soyer‐Gobillard Marie‐Odile
Published: July 2002

Summry— Despite their early emergence in evolution, the protist dinoflagellates present similarities in cell cycle regulation with higher eukaryotes and yeasts. Using antibody directed against the p56edc13 of the fission yeast, we present evidence for the presence of a cyclin B homolog in the dinoflagellate Crypthecodinium cohnii. Biochemistry, immunofluorescence and electron microscopy show the continuous presence of the cyclin B homolog during the C cohnii cell cycle progression. Cyclin B, which appears to be exclusively cytoplasmic, is associated with a specific H1 kinase activity more active in M phase.
Metabolic Control Analysis of Monoclonal Antibody Synthesis
Authors: Gonzalez Ramon , Asenjo Juan A. , Andrews Barbara A.
Published: July 2002

A general route for protein synthesis in eukaryotic cells has been proposed and applied to monoclonal antibody (MAb) synthesis. It takes into account transcription of the gene, binding of ribosomes to mRNA, and polypeptide elongation including binding to SRP (signal recognition particles) and SRP‐receptor, competing translocation, folding and glycosylation, assembly of the heavy and light chains in a tetrameric protein and Golgi processing and secretion. A comprehensive model was built on the basis of the proposed pathway. The model takes into account the mechanism of each step. Metabolic control analysis (MCA) principles were applied to the general pathway using the proposed model, and control coefficients were calculated. The results show a shared flux control (of both pathway flux and flux ratio at the branch) among different steps, i.e., transcription, folding, glycosylation, translocation and building blocks synthesis. The steps sharing the control depend on the concentration of building blocks, pathway flux and levels of OST (oligosacharyl transferase), BiP (heavy chain binding protein) and PDI (protein disulfide isomerase). Model predictions compare well with experimental data for MAb synthesis, explaining the control structure of the route and the heterogeneity of the product and also addressing future targets for improvement of the production rate of MAbs.
Permeabilization of Metabolites from Biologically Viable Soybeans (Glycine max)
Authors: Wang Henry Y. , Komolpis Kittinan , Kaufman Peter B. , Malakul Pomthong , Shotipruk Artiwan
Published: July 2002

Chemical permeabilization has been widely studied for the release useful metabolites from many types of plant cells and tissues. In this study, the effect of 0−30% (v/v) of aqueous methanol solutions were used to permeabilize soybeans for the release of two isoflavonoids: daidzein and genistein. The release of these metabolites increases with increasing methanol concentrations. The amounts of daidzein and genistein released can increase up to 40‐ and 86‐fold, respectively, when incubated in a 30% (v/v) methanol solution for 24 h compared with those incubated with water only. The effect of methanol on the release rates is primarily due to an increase in solubility of the stored daidzein and genistein (14‐ to 18‐fold) inside the seeds, thus maximizing the concentration gradients for metabolite release. However, the viability of the seeds dropped with increase in methanol concentrations and the incubation time. The viability of soybeans (indicated by their ability to germinate) after permeabilization treatment with 0−20% (v/v) methanol solutions was maintained above 80% throughout the 24 h, whereas no seeds were found to be viable when 30% (v/v) methanol solution was used. The permeability coefficients (P) of daidzein and genistein were found to increase as the methanol concentration used was increased. These P values were estimated to range from 1.1 × 10−9 to 1.9 × 10−8 m/s and 1.0 × 10−9 to 1.7 × 10−8 m/s, respectively. The increase in Pcan be attributed primarily to an increase in the partition coefficient of the metabolites in the soybean seedcoats. An empirical correlation is proposed in which the log Pvalues are described as a function of the metabolite molecular weights and the partition coefficients of the metabolites between octanol and water, Koct/water, which was modified to include the effect of methanol present. Knowledge obtained from this study will help provide useful selection criteria for chemical permeabilization of plant tissues, such as seeds, with minimal loss in their viability.
Influence of Agitation and Sparging on the Growth Rate and Infection of Insect Cells in Bioreactors and a Comparison with Hybridoma Culture
Authors: Kioukia N. , Nienow A. W. , Al‐Rubeai M. , Emery A. N.
Published: July 2002

Sf9 insect cells have been cultivated in paired agitated 1.4 L bioreactors with and without Pluronic F‐68 and with and without sparging. The results are reported and, as appropriate, compared to those of hybridoma culture. Without sparging, the cells grew well at agitator speeds from 100 to 400 rpm (equivalent to a realistic range of specific energy dissipation rates). At the higher speeds, a small reduction in growth rate and maximum viable cell concentration was observed. This reduction was shown not to be dependent on the energy dissipation rate but to be due to bubble entrainment. These results are rather similar to those found with hybridoma cells. However, unlike hybridoma cells which grow like unsparged controls when sparged at 0.007 vvm, these insect cells at such a sparge rate show a significant reduction in growth rate and in maximum cell number. This reduction due to the presence of bubbles, whether from head space entrainment or from sparging, could be eliminated by the presence of Pluronic F‐68. These insect cells have then also been infected with recombinant or wild type AcNPV. Agitation had no effect on the rate of infection, but higher levels of MOI enhanced it. Both findings support a diffusion mechanism as previously. The presence of Pluronic F‐68 did not have any impact on the rate of infection and was able to prevent cell damage while agitating and sparging infected cells.
Absence of Na+/K+/2Cl− cotransporter activity in corneal endothelial cell plasma membrane vesicles
Authors: Lane Jason R. , Wigham Chris G. , Hodson Stuart A.
Published: July 2002

There are various models to describe coupling between transmembrane Na− flux and transendothelial net HCO−3 flux in the cornea, including a direct coupling via a Na+/HCO−3 cotransporter or an indirect coupling utilizing a Na+/K+/2Cl− cotransporter further coupled to a Cl−/HCO−3 exchanger. In this study we investigate the presence of Na+/K+/2Cl− cotransporter activity by using corneal endothelial cell plasma membrane vesicles. By controlling the external and internal compartments of the vesicles we were able to monitor Na+ movement across the membranes.

If the Na+/K+/2Cl− cotransporter is present in the corneal endothelial cell membrane vesicles then the presence of K+ should lead to a significant increase in uptake of 22Na+. The rate of accumulation of 22Na+ in the presence of K+ was 25.7 ± 2.8 nmoles Na+ mg−1 protein 15 s−1 which was not significantly different from that in the absence of K+ (23.8 ± 2.0 nmoles Na+ mg−1 protein 15 s−1) indicating that Na+ uptake into the vesicles was not dependent on K+.

The present work provides no evidence for Na+/K+/2Cl− cotransport in corneal endothelial cell plasma membrane vesicles. The nature of the coupling mechanism between HCO−3 and Na+ is still unresolved.
cAMP stimulates corneal endothelial HCO−3 transport
Authors: Ogbuehi K. , Wigham C. G. , Hodson S. A.
Published: July 2002

A previous study has demonstrated that corneal endothelial HCO−3 transport is stimulated by the non‐specific phosphodiesterase (PDE) inhibitor IBMX. The objective of this study was to use more specific inhibitors of PDE isoenzymes to resolve which cyclic nucleotide is responsible for the observed effect of IBMX.

Rolipram, an inhibitor of cAMP hydrolysing PDE, and Zaprinast, an inhibitor of cGMP hydrolysing PDE, were added to de‐epithelialized corneas mounted in vitro in modified Ussing‐type chambers. Trans‐endothelial potential difference (Pde), resistance (Re) and short circuit current (SCC) were measured. To determine if Rolipram and Zaprinast increased cyclic nucleotide concentrations the intracellar concentrations of cAMP and cGMP were also determined.

Rolipram (0.1 mM) significantly increased SCC in a transient manner. The maximum stimulated value for SCC was 16 ± 3% above control (mean ± SEM, n = 4). Rolipram also increased [cAMP]i from782 ± 29 to 2167 ± 111 pM mg−1 protein (mean ± SEM, n = 36). Zaprinast (0.5 mM) reversibly reduced SCC by 9 ± 3% (mean ± SEM, n = 3) and did not change [cGMP]i which measured 370 ± 15 pM mg−1 protein (mean ± SEM, n = 36). Neither drug affected Re. These results demonstrate that PDE induced elevation of [cAMP]i can increase corneal endothelial HCO−3 transport and that cGMP is apparently unchanged and without effect.
Effects of induced transverse chromatic aberration from an afocal prismatic lens on spatio–temporal sensitivity1
Authors: Faubert J. , Simonet P. , Gresset J.
Published: July 2002

The goal of this study was to evaluate the effect of ophthalmic lens‐induced transverse chromatic aberrations (TCA) in natural viewing conditions on spatio–temporal thresholds. Three psychophysical experiments were performed; the first isolating the spatial component, the second isolating the temporal component and the third assessing spatio–temporal combinations. Taken together, the results show that TCA has profound effects on medium to high spatial frequencies (above 1 cpd) consistent with previous studies, and that the ratio of deficit TCA/blur can be higher than 2:1 for equivalent dioptric strengths. Furthermore, the results of Experiment 1 and 3 taken together show that the relative sensitivity loss caused by TCA can differ significantly between individuals and that a possible factor for this differential loss is the overall baseline spatio–temporal sensitivity profile of the individual.
Assessment of oxygen in gallium arsenide by infrared local vibrational mode spectroscopy
Authors: Schneider J. , Dischler B. , Seelewind H. , Mooney P. M. , Lagowski J. , Matsui M. , Beard D. R. , Newman R. C.
Published: July 2002

Two infrared local vibrational mode (LVM) absorption lines occurring at 715 and 845 cm−1 shift to 679 and 802 cm−1 in gallium arsenide doped with 18O, proving that the lines arise from the vibrations of oxygen impurities. The 715 cm−1 line exhibits a triplet 69,71Ga isotope fine structure consistent with that expected from a quasi-substitional VAs-O center. The 845 cm−1 line appears as a closely spaced doublet expected for a bonded interstitial oxygen atom.
Growth studies of pseudomorphic GaAs/InGaAs/AlGaAs modulation-doped field-effect transistor structures
Authors: Chan K. T. , Lightner M. J. , Patterson G. A. , Yu K. M.
Published: July 2002

Strained GaAs/InGaAs/AlGaAs quantum well structures have been grown by molecular beam epitaxy at substrate temperatures from 375 to 510 °C. The well layer thickness and In composition are analyzed by ion channeling and particle-induced x-ray emission as a function of growth temperature. Test structures for modulation-doped field-effect transistors grown at 375 and 510 °C under two different As4 overpressures were also characterized by Van der Pauw measurements and low-temperature photoluminescence. The observed differences in film quality can be explained by the influence of substrate temperature and As4 flux on the cation surface mobility during growth of the InGaAs layer.
Microwave response of YBaCuO thin-film Dayem bridges
Authors: Gijs M. A. M. , Jansen R. J. E.
Published: July 2002

1-μm-wide Dayem bridges were patterned with a pulsed Xe laser in c-axis-oriented YBaCuO films prepared according to the BaF2 method. The microbridges have a critical current density of 2×106 A/cm2 at 77 K, which is typical for an epitaxial film without grain boundaries. When microwave radiation in the centimeter wavelength range is applied, we observe current steps in the current-voltage characteristic up to 72 K. The dependence of these steps on microwave power is compared with the model of Golovashkin and Lykov {Zh. Eksp. Teor. Fiz. 74, 214 (1978) [Sov. Phys. JETP 47, 110 (1978)]}; we find that the step amplitude is smaller than predicted.
p-type delta-doped layers in silicon: Structural and electronic properties
Authors: Mattey N. L. , Dowsett M. G. , Parker E. H. C. , Whall T. E. , Taylor S. , Zhang J. F.
Published: July 2002

We report on the properties of p-type delta-doped layers prepared in molecular beam epitaxy-Si by growth interruption and evaporation of elemental B. Secondary-ion mass spectrometry measurements at several primary ion energies have been used to show that the full width at half maximum is ∼2 nm. Hall measurements confirm that the layers are completely activated at 300 K with a mobility of 30±5 cm2/V s for a carrier density of (9±2)×1012 cm−2. At temperatures below 70 K nonmetallic behavior is observed which we have attributed to conduction between impurity states. It is concluded that the critical acceptor separation for the Mott metal-insulator transition in this system is significantly less than the value found in uniformly doped Si:B.
Sidelobe suppression in an acousto-optic filter with a raised-cosine interaction strength
Authors: Smith D. A. , Johnson J. J.
Published: July 2002

We have demonstrated a 10-dB reduction in the intensity sidelobes of an apodized-interaction-strength guided-wave acousto-optic filter with a center passband of 1530 nm. Acoustic-intensity weighting was achieved by launching a surface acoustic wave (SAW) beam in a straight acoustic waveguide, and gradually transferring this SAW intensity to the active device, and back out, by evanescent-wave coupling across a 20 μm barrier over a 19-mm interaction length. The intensity sidelobe was −5 dB for an unapodized filter with abrupt onset and cutoff of the interaction, but sidelobes were reduced to at most −15 dB for a SAW intensity with raised-cosine weighting. A conversion efficiency of 97% was achieved with 80 mW input power for the 2.0-nm-wide apodized filter.
Strong room-temperature photoluminescence of hydrogenated amorphous silicon oxide and its correlation to porous silicon
Authors: Lin Chi-Huei , Lee Si-Chen , Chen Yang-Fang
Published: July 2002

A set of hydrogenated amorphous silicon oxide (a-SiOx:H) films have been fabricated by plasma enhanced chemical vapor deposition. Some of the films exhibit strong room-temperature photoluminescence and others do so only after annealing at high temperature. The variation of photoluminescence after different annealing treatments for these films is found to be similar to that of porous silicon. Assisted by infrared spectra it is concluded that the photoluminescence from a-SiOx:H is originated from the small a-Si clusters or microcrystalline silicon embedded in the amorphous SiOx network. This argument may support a similar model proposed to explain the visible photoluminescence of porous silicon.
Tokamak ion temperature determination via cw far-infrared laser scattering
Authors: Park H. , Lee P. S. , Peebles W. A. , Luhmann N. C.
Published: July 2002

A successful proof-of-principle experimental determination of ion temperature in a tokamak plasma via cw far-infrared (FIR) collective laser scattering from ion Bernstein waves is reported. The Bernstein waves are excited via mode conversion of an externally launched fast Alfven wave at the second-harmonic cyclotron layer. A fit of the experimentally determined ion Bernstein wave dispersion to the temperature-dependent theoretical dispersion yields the local ion temperature. Partial ion temperature profiles (chord averaged) have been obtained with temperature values consistent with charge exchange measurements. Single-shot measurements should be available in the near future with the use of the multichannel scattering systems and high-power laser sources developed at UCLA.
Furnace for rapid change of temperature for neutron diffraction
Authors: Katano S. , Motohashi H. , Iizumi M.
Published: July 2002

A new furnace for neutron diffraction experiments is capable of heating and cooling a sample very rapidly. The rapid heating is done by two circular infrared lamps placed over and under a sample, whose radiation is roughly focused on the sample by a reflector. The rapid cooling is done by high-pressure gas blows against the sample from two circular nozzles which are also placed over and under the sample. This system enables us to obtain the heating rate of over 1000°C/min and cooling rate of −500°C/min for an alloy of 10 mm diameter and 30 mm length. The performance is sufficient to carry out some kinetics measurements in real-time neutron diffraction by the use of a position-sensitive detector. This kind of experiment is demonstrated by the observation of the relaxation process of order–disorder transitions in CuZn and Ni3Mn alloys.
An optical technique for measurement of semiconductor surface electric fields
Authors: Sardesai Harshad P. , Nunnally William C. , Williams P. F.
Published: July 2002

We present an optical technique for the measurement of semiconductor surface electric fields. The measurement technique uses the Kerr electro-optic effect in nitrobenzene, a phase sensitive interferometer, and associated data acquisition units to measure the surface electric fields between the contacts of a planar semiconductor device. This technique was used to measure the surface fields on silicon devices used in pulsed power applications, but has the potential for use as an electric field probe for any device having high surface electric fields, both pulsed and dc. The measurement technique showed a temporal resolution of 100 ns, which can be easily reduced to a few nanoseconds using superior data acquisition and detection systems. The spatial resolution was about 50 μm for devices that had a typical contact separation of about 500 μm (power devices). This technique can be applied to measure the surface fields on devices commonly used in microelectronic applications. In this paper we discuss in detail the measurement technique and present the results obtained for silicon photoconductive power switches.
Electron temperature estimation in the Saha Institute of Nuclear Physics tokamak from the soft x-ray imaging system
Authors: Paul R. K. , Banik D. , Iyengar A. N. S. , Hui A. K.
Published: July 2002

A soft x-ray imaging diagnostics has been developed for the study of magnetohydrodynamics activities in the Saha Institute of Nuclear Physics tokamak plasma and also to estimate the plasma electron temperature. The main feature of this diagnostics is the use of p–i–n photodiodes, and in this article we present the results of the estimated plasma electron temperature Te(eV) by the absorber foil method. These values agree very closely with the estimated values from Spitzer resistivity. We feel that this technique of using a soft x-ray array for temperature measurement has a good potential for providing very economical Te(r,t) measurements with good time and spatial resolution especially for low budget small tokamaks.
Infrared spectroscopy of hydrides on the 6H-SiC surface
Authors: Tsuchida H. , Kamata I. , Izumi K.
Published: July 2002

Hydrides on the 6H-SiC(0001̄) and (0001) surfaces before and after hydrogen annealing were investigated by infrared attenuated total reflection spectroscopy. The absorption bands of CH2 and CH3 were observed from the 6H-SiC(0001̄) and (0001) surfaces before hydrogen annealing. After hydrogen annealing, a sharp C–H stretching vibration attributable to a monohydride appeared on the 6H-SiC(0001̄) surface, in contrast to a sharp Si–H stretching vibration which can be observed on the 6H-SiC(0001) surface.
Low temperature scanning-tip microwave near-field microscopy of YBa2Cu3O7−x films
Authors: Takeuchi I. , Wei T. , Duewer Fred , Yoo Y. K. , Xiang X.-D. , Talyansky V. , Pai S. P. , Chen G. J. , Venkatesan T.
Published: July 2002

We have explored the low temperature capability of a scanning-tip microwave near-field microscope to study superconductors. The shift in the quality factor of the microscope resonator can be used to obtain the temperature dependence of the surface resistance of a local region under the tip. Patterned YBa2Cu3O7−x films were scanned at various temperatures and surface resistance mapping was performed with high spatial resolution at 1.2 GHz. Superconducting transitions at different positions on a film can be detected. Edge-region defects in wet-etched patterns were observed and were shown to be nonsuperconducting at microwave frequencies at 80 K.
Video rate near-field scanning optical microscopy
Authors: Bukofsky S. J. , Grober R. D.
Published: July 2002

The enhanced transmission efficiency of chemically etched near-field optical fiber probes makes it possible to greatly increase the scanning speed of near-field optical microscopes. This increase in system bandwidth allows sub-diffraction limit imaging of samples at video rates. We demonstrate image acquisition at 10 frames/s, rate-limited by mechanical resonances in our scanner. It is demonstrated that the optical signal to noise ratio is large enough for megahertz single pixel acquisition rates.
Growth of cubic GaN by phosphorus-mediated molecular beam epitaxy
Authors: Zhao Y. , Tu C. W. , Bae I.-T. , Seong T.-Y.
Published: July 2002

GaN epitaxial layers were grown on wurtzite GaN-on-sapphire substrates by phosphorus-mediated molecular beam epitaxy at different growth temperatures. The films were characterized by reflection high-energy electron diffraction, x-ray diffraction, energy-dispersive x-ray spectroscopy, and transmission electron microscopy. The growth temperature plays an important role in P incorporation as well as GaN crystallization. The introduction of the phosphorus flux during growth leads to a preferential growth of zinc-blende epilayers. The phase transition during growth is attributed to the modification of surface stoichiometry by the impinging phosphorus flux.
Optical properties of substituted phthalocyanine rare-earth metal complexes
Authors: Yoshino K. , Lee S. B. , Sonoda T. , Kawagishi H. , Hidayat R. , Nakayama K. , Ozaki M. , Ban K. , Nishizawa K. , Ohta K. , Shirai H.
Published: July 2002

Comparative study of optical properties of alkylthio-group-substituted phthalocyanine rare-earth metal sandwich complexes ([(CnS)8Pc]2M,M=Eu,Lu,Tb) is presented. Photoluminescence and photoconductivity of [(CnS)8Pc]2M complex is very weak. Two photoluminescence bands were observed at around 400–650 and 720–800 nm in chloroform solution corresponding to the Soret and Q bands in the absorption spectra, respectively. However, the emission from Eu3+ ion (as well as Tb3+) was not found compared with other Eu complexes because the 5d levels of the Eu3+ ion lie higher than the triplet level of the ligand. The significant enhancement of the photoconductivity of [(C16S)8Pc]2M after C60 doping is reported. The photoconductivity is positive at the low electric field in the ohmic regime while it becomes negative at the high electric field upon photoexcitation with strongly absorbed light. The negative photoconductivity is attributed to space-charge effects. The mechanism of photoluminescence and photoconductivity are discussed by taking the electronic energy schemes of phthalocyanine ligands and lanthanide ion and C60 into consideration.
Phase behavior of block copolymer melts with arbitrary architecture
Authors: Morozov A. N. , Fraaije J. G. E. M.
Published: July 2002

The Leibler theory [L. Leibler, Macromolecules 13, 1602 (1980)] for microphase separation in AB block copolymer melts is generalized for systems with arbitrary topology of molecules. A diagrammatic technique for calculation of the monomeric correlation functions is developed. The free energies of various mesophases are calculated within the second-harmonic approximation. Model highly branched tree-like structures are considered as an example and their phase diagrams are obtained. The topology of molecules is found to influence the spinodal temperature and asymmetry of the phase diagrams, but not the types of phases and their order. We suggest that all model AB block copolymer systems will exhibit the typical phase behavior.
Artificial modulation of magnetic structures on a monatomic layer scale in Co/Ru superlattices
Authors: Himi K. , Takanashi K. , Mitani S. , Yamaguchi M. , Ping D. H. , Hono K. , Fujimori H.
Published: July 2002

Artificial modulation of magnetic structure on a monatomic layer scale has been examined in Co/Ru superlattices. The samples alternating Co 1 ML and Ru x ML (x=1–4, ML: Monatomic Layer thickness) were prepared. Sharp fundamental and satellite peaks corresponding to superlattice structures are seen in the x-ray diffraction profiles for all the samples. For x=1, furthermore, high-resolution transmission electron microscopy observation indicates the formation of an ordered structure with hexagonal-close-packed stacking of alternate Co and Ru atomic planes. The magnetization measurements show that only 1 ML difference in the Ru thickness has significant influence on the magnetic structure. The results are consistent with the first-principles calculations.
Evidence for competing order parameters in the paramagnetic phase of layered manganites (invited)
Authors: Berger A. , Mitchell J. F. , Miller D. J. , Bader S. D.
Published: July 2002

The magnetic field and temperature dependence of the magnetic susceptibility is studied for the ferromagnetic layered manganites SrO(La1−xSrxMnO3)2 in the composition range x=0.32–0.40. In the paramagnetic phase, the susceptibility exhibits an anomalous maximum at an intermediate magnetic field value. The size of this field-induced susceptibility enhancement increases dramatically with x from 10% for x=0.32 to 160% for x=0.40. The temperature dependence of the effect shows a maximum at T≈1.1 TC for all x. Quantitative analysis in terms of the Landau theory of phase transitions enables us to identify a distortion of the free energy F in the paramagnetic phase that is associated with the susceptibility anomaly. This free energy distortion corresponds to a magnetic system that approaches a first order magnetic phase transition as the temperature is lowered toward TC. Such a behavior is indicative of a second, competing order parameter, which is identified as the recently observed charge density wave. In the immediate vicinity of TC, the anomaly disappears and the system seems to undergo a more conventional second order paramagnetic–ferromagnetic phase transition.
Optical constants and critical-point parameters of GaAs from 0.73 to 6.60 eV
Authors: Zollner Stefan
Published: July 2002

The optical constants of GaAs from 0.73 to 6.60 eV at 300 K were determined using rotating-analyzer spectroscopic ellipsometry. The setup includes a computer-controlled MgF2 Berek wave plate compensator, which allows exact measurements of the ellipsometric angle Δ below the band gap. Therefore, these data are very accurate over a broad range. I also determined the interband critical-point parameters of the E0, E0+Δ0, E1, E1+Δ1, E0′, and E2 transitions (energies, broadenings, phase angles, and amplitudes).
Low-temperature resistance of individual single-walled carbon nanotubes: A theoretical estimation
Authors: Zhang Zhenhua , Peng Jingcui , Zhang Hua
Published: July 2002

The resistances of individual single-walled carbon nanotubes (SWNTs) are calculated based on Boltzmann transport equation, graphene approximation relation of electronic energy for SWNTs and weak localization (WL) theory. The theoretical results of resistance for SWNTs are compared with experimental measurements. It has been found that, for nearly metallic and semiconducting SWNTs the theoretical result is consistent with experimental data roughly, whereas for truly metallic SWNTs (armchair ones) the theoretical result is in good agreement with measurement.
Real time path integrals using the Herman–Kluk propagator
Authors: Burant John C. , Batista Victor S.
Published: July 2002

It is shown that the accuracy of quantum dynamics calculations obtained according to the Herman–Kluk (HK) semiclassical initial value representation (SC-IVR) is significantly improved when the time evolution operator is computed by concatenating finite time propagators. This approach results in an approximate calculation of a real-time path-integral in a discrete coherent-state representation, which becomes exact in the limit of sufficiently short time-slice intervals. The efficiency of the computational method is optimized by devising a compact coherent-state basis set that obviates the need for calculating the inverse overlap matrix. Quantitative agreement with full quantum mechanical results is verified in the description of tunneling between disjoint classically allowed regions in one- and two-dimensional systems, in the treatment of long-time dynamics, and in nonadiabatic dynamics in a model system with two coupled one-dimensional potential energy surfaces.
Quantum enveloping superalgebras and link invariants
Authors: Zhang R. B.
Published: July 2002

Corresponding to each finite dimensional simple basic classical Lie superalgebra, a new quantum enveloping superalgebra is introduced, which has the structure of a braided quasi-Hopf superalgebra. In the case of osp(1|2n), this quantum enveloping superalgebra is shown to be isomorphic to the standard Drinfeld–Jimbo quantum superalgebra Uq(osp(1|2n)) as braided quasi Hopf superalgebras. The new quantum enveloping superalgebras are applied to construct link invariants, from which Vassiliev invariants can be readily extracted. This, in particular, provides a useful construction for the Vassiliev invariants associated with Uq(osp(1|2n)).
Sustained rotational stabilization of DIII-D plasmas above the no-wall beta limit
Authors: Garofalo A. M. , Jensen T. H. , Johnson L. C. , La Haye R. J. , Navratil G. A. , Okabayashi M. , Scoville J. T. , Strait E. J. , Baker D. R. , Bialek J. , Chu M. S. , Ferron J. R. , Jayakumar J. , Lao L. L. , Makowski M. A. , Reimerdes H. , Taylor T. S. , Turnbull A. D. , Wade M. R. , Wong S. K.
Published: July 2002

Sustained stabilization of the n=1 kink mode by plasma rotation at beta approaching twice the stability limit calculated without a wall has been achieved in DIII-D by a combination of error field reduction and sufficient rotation drive. Previous experiments have transiently exceeded the no-wall beta limit. However, demonstration of sustained rotational stabilization has remained elusive because the rotation has been found to decay whenever the plasma is wall stabilized. Recent theory [Boozer, Phys. Rev. Lett. 86, 5059 (2001)] predicts a resonant response to error fields in a plasma approaching marginal stability to a low-n kink mode. Enhancement of magnetic nonaxisymmetry in the plasma leads to strong damping of the toroidal rotation, precisely in the high-beta regime where it is needed for stabilization. This resonant response, or “error field amplification” is demonstrated in DIII-D experiments: applied n=1 radial fields cause enhanced plasma response and strong rotation damping at beta above the no wall limit but have little effect at lower beta. The discovery of an error field amplification has led to sustained operation above the no-wall limit through improved magnetic field symmetrization using an external coil set. The required symmetrization is determined both by optimizing the external currents with respect to the plasma rotation and by use of feedback to detect and minimize the plasma response to nonaxisymmetric fields as beta increases. Ideal stability analysis and rotation braking experiments at different beta values show that beta is maintained 50% higher than the no wall stability limit for durations greater than 1 s, and approaches beta twice the no-wall limit in several cases, with steady-state rotation levels. The results suggest that improved magnetic-field symmetry could allow plasmas to be maintained well above no-wall beta limit for as long as sufficient torque is provided.