Effect of the dose of exogenous fibrolytic enzyme preparations on preingestive fiber hydrolysis, ruminal fermentation, and in vitro digestibility of bermudagrass haylage.

PubMed

Romero, J J; Zarate, M A; Adesogan, A T

2015-01-01

Our objectives were to evaluate the effects of the dose rates of 5 Trichoderma reesei and Aspergillus oryzae exogenous fibrolytic enzymes (EFE; 1A, 2A, 11C, 13D, and 15D) on in vitro digestibility, fermentation characteristics, and preingestive hydrolysis of bermudagrass haylage and to identify the optimal dose of each EFE for subsequent in vitro and in vivo studies. In experiment 1, EFE were diluted in citrate-phosphate buffer (pH 6) and applied in quadruplicate in each of 2 runs at 0× (control), 0.5×, 1×, 2×, and 3×; where 1× was the respective manufacturer-recommended dose (2.25, 2.25, 10, 15, and 15g of EFE/kg of dry matter). The suspension was incubated for 24h at 25°C and for a further 24h at 39°C after the addition of ruminal fluid. In experiment 2, a similar approach to that in experiment 1 was used to evaluate simulated preingestive effects, except that sodium azide (0.02% wt/vol) was added to the EFE solution. The suspension was incubated for 24h at 25°C and then 15mL of water was added before filtration to extract water-soluble compounds. For both experiments, data for each enzyme were analyzed separately as a completely randomized block design with a model that included effects of EFE dose, run, and their interaction. In experiment 1, increasing the EFE dose rate nonlinearly increased the DM digestibility of 1A, 2A, 11C, and 13D and the neutral detergent fiber digestibility (NDFD) of 1A, 2A, 11C, and 13D. Optimal doses of 1A, 2A, 11C, 13D, and 15D, as indicated by the greatest increases in NDFD at the lowest dose tested, were 2×, 2×, 1×, 0.5×, and 0.5×, respectively. Increasing the dose rate of 2A, 11C, and 13D nonlinearly increased concentrations of total volatile fatty acids and propionate (mM), decreased their acetate-to-propionate ratios and linearly decreased those of samples treated with 1A and 15D. In experiment 2, increasing the dose rate of each EFE nonlinearly decreased concentrations of netural detergent fiber; also, increasing the dose rate of 1A, 2A, 11C, and 1D nonlinearly increased concentrations of water-soluble carbohydrates and free ferulic acid (μg/g). Application of increasing doses of the EFE increased NDF hydrolysis, NDFD, and ruminal fluid fermentation of bermudagrass haylage, but the optimal dose varied with the EFE. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Evidence of Rapid Modulation by Social Information of Subjective, Physiological, and Neural Responses to Emotional Expressions

PubMed Central

Mermillod, Martial; Grynberg, Delphine; Pio-Lopez, Léo; Rychlowska, Magdalena; Beffara, Brice; Harquel, Sylvain; Vermeulen, Nicolas; Niedenthal, Paula M.; Dutheil, Frédéric; Droit-Volet, Sylvie

2018-01-01

Recent research suggests that conceptual or emotional factors could influence the perceptual processing of stimuli. In this article, we aimed to evaluate the effect of social information (positive, negative, or no information related to the character of the target) on subjective (perceived and felt valence and arousal), physiological (facial mimicry) as well as on neural (P100 and N170) responses to dynamic emotional facial expressions (EFE) that varied from neutral to one of the six basic emotions. Across three studies, the results showed reduced ratings of valence and arousal of EFE associated with incongruent social information (Study 1), increased electromyographical responses (Study 2), and significant modulation of P100 and N170 components (Study 3) when EFE were associated with social (positive and negative) information (vs. no information). These studies revealed that positive or negative social information reduces subjective responses to incongruent EFE and produces a similar neural and physiological boost of the early perceptual processing of EFE irrespective of their congruency. In conclusion, the article suggests that the presence of positive or negative social context modulates early physiological and neural activity preceding subsequent behavior. PMID:29375330

Factors associated with survival of epiploic foramen entrapment colic: a multicentre, international study.

PubMed

Archer, D C; Pinchbeck, G L; Proudman, C J

2011-08-01

Epiploic foramen entrapment (EFE) has been associated with reduced post operative survival compared to other types of colic but specific factors associated with reduced long-term survival of these cases have not been evaluated in a large number of horses using survival analysis. To describe post operative survival of EFE cases and to identify factors associated with long-term survival. A prospective, multicentre, international study was conducted using clinical data and long-term follow-up information for 126 horses diagnosed with EFE during exploratory laparotomy at 15 clinics in the UK, Ireland and USA. Descriptive data were generated and survival analysis performed to identify factors associated with reduced post operative survival. For the EFE cohort that recovered following anaesthesia, survival to hospital discharge was 78.5%. Survival to 1 and 2 years post operatively was 50.6 and 34.3%, respectively. The median survival time of EFE cases undergoing surgery was 397 days. Increased packed cell volume (PCV) and increased length of small intestine (SI) resected were significantly associated with increased likelihood of mortality when multivariable analysis of pre- and intraoperative variables were analysed. When all pre-, intra- and post operative variables were analysed separately, only horses that developed post operative ileus (POI) were shown to be at increased likelihood of mortality. Increased PCV, increased length of SI resected and POI are all associated with increased likelihood of mortality of EFE cases. This emphasises the importance of early diagnosis and treatment and the need for improved strategies in the management of POI in order to reduce post operative mortality in these cases. The present study provides evidence-based information to clinicians and owners of horses undergoing surgery for EFE about long-term survival. These results are applicable to university and large private clinics over a wide geographical area. © 2011 EVJ Ltd.

In vitro gas production of foliage from three browse tree species treated with different dose levels of exogenous fibrolytic enzymes.

PubMed

López, D; Vázquez-Armijo, J F; López-Villalobos, N; Lee-Rangel, H A; Salem, A Z M; Borquez-Gastelum, J L; Domínguez-Vara, I A; Rojo-Rubio, R

2016-10-01

The aim of this study was to evaluate the effect of different dose levels of exogenous fibrolytic enzymes (EFE) on in vitro ruminal fermentation kinetics and energy utilization of foliages from three browse trees (Pithecellobium dulce, Heliocarpus velutinus and Guazuma ulmifolia). Mixture of EFE product was added to the leaves of the three browse tree species at three dose levels: 0 (control), 3.5 and 7.0 mg/g of DM. Chemical composition of the foliages, including plant secondary metabolites such as total phenolics (TP), saponins (SAP) and aqueous fraction (AF), was determined. In addition, in vitro assaying of ruminal gas production kinetics was determined for the three browse three foliages treated with EFE. P. dulce had the highest crude protein content (p < 0.05), whereas G. ulmifolia had the highest content of neutral detergent fibre and SAP (p < 0.05) and H. velutinus had the lowest content of TP (p < 0.05). The interaction between tree species and dose level of EFE was significant (p < 0.05) for gas production (GP) at 24 h of incubation, parameters b and c of the accumulated GP curve, short-chain fatty acids (SCFA) and metabolizable energy (ME). The lowest (p < 0.01) extent of accumulated GP as well as the b and c values occurred in G. ulmifolia at 0 mg EFE/g DM. P. dulce had the highest (p < 0.05) values for ME and SCFA at the highest dose of EFE. Tree species and dose level had significant (p < 0.05) effects on all parameters describing in vitro ruminal fermentation kinetics and energy utilization. Addition of EFE improved the fermentation kinetics of the browse species considered in this study. Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.

Differential patterns of implicit emotional processing in Alzheimer's disease and healthy aging.

PubMed

García-Rodríguez, Beatriz; Fusari, Anna; Rodríguez, Beatriz; Hernández, José Martín Zurdo; Ellgring, Heiner

2009-01-01

Implicit memory for emotional facial expressions (EFEs) was investigated in young adults, healthy old adults, and mild Alzheimer's disease (AD) patients. Implicit memory is revealed by the effect of experience on performance by studying previously encoded versus novel stimuli, a phenomenon referred to as perceptual priming. The aim was to assess the changes in the patterns of priming as a function of aging and dementia. Participants identified EFEs taken from the Facial Action Coding System and the stimuli used represented the emotions of happiness, sadness, surprise, fear, anger, and disgust. In the study phase, participants rated the pleasantness of 36 faces using a Likert-type scale. Subsequently, the response to the 36 previously studied and 36 novel EFEs was tested when they were randomly presented in a cued naming task. The results showed that implicit memory for EFEs is preserved in AD and aging, and no specific age-related effects on implicit memory for EFEs were observed. However, different priming patterns were evident in AD patients that may reflect pathological brain damage and the effect of stimulus complexity. These findings provide evidence of how progressive neuropathological changes in the temporal and frontal areas may affect emotional processing in more advanced stages of the disease.

A meta-analysis on the effect of dietary application of exogenous fibrolytic enzymes on the performance of dairy cows.

PubMed

Arriola, Kathy G; Oliveira, Andre S; Ma, Zhengxin X; Lean, Ian J; Giurcanu, Mihai C; Adesogan, Adegbola T

2017-06-01

The aim of this study was to use meta-analytical methods to estimate effects of adding exogenous fibrolytic enzymes (EFE) to dairy cow diets on their performance and to determine which factors affect the response. Fifteen studies with 17 experiments and 36 observations met the study selection criteria for inclusion in the meta-analysis. The effects were compared by using random-effect models to examine the raw mean difference (RMD) and standardized mean difference between EFE and control treatments after both were weighted with the inverse of the study variances. Heterogeneity sources evaluated by meta-regression included experimental duration, EFE type and application rate, form (liquid or solid), and method (application to the forage, concentrate, or total mixed ration). Only the cellulase-xylanase (C-X) enzymes had a substantial number of observations (n = 13 studies). Application of EFE, overall, did not affect dry matter intake, feed efficiency but tended to increase total-tract dry matter digestibility and neutral detergent fiber digestibility (NDFD) by relatively small amounts (1.36 and 2.30%, respectively, or <0.31 standard deviation units). Application of EFE increased yields of milk (0.83 kg/d), 3.5% fat-corrected milk (0.55 kg/d), milk protein (0.03 kg/d), and milk lactose (0.05 kg/d) by moderate to small amounts (<0.30 standard deviation units). Low heterogeneity (I  2 statistic <25%) was present for yields and concentrations of milk fat and protein and lactose yield. Moderate heterogeneity (I  2 = 25 to 50%) was detected for dry matter intake, milk yield, 3.5% fat-corrected milk, and feed efficiency (kg of milk/kg of dry matter intake), whereas high heterogeneity (I  2 > 50%) was detected for total-tract dry matter digestibility and NDFD. Milk production responses were higher for the C-X enzymes (RMD = 1.04 kg/d; 95% confidence interval: 0.33 to 1.74), but were still only moderate, about 0.35 standardized mean difference. A 24% numerical increase in the RMD resulting from examining only C-X enzymes instead of all enzymes (RMD = 1.04 vs. 0.83 kg/d) suggests that had more studies met the inclusion criteria, the C-X enzymes would have statistically increased the milk response relative to that for all enzymes. Increasing the EFE application rate had no effect on performance measures. Application of EFE to the total mixed ration improved only milk protein concentration, and application to the forage or concentrate had no effect. Applying EFE tended to increase dry matter digestibility and NDFD and increased milk yield by relatively small amounts, reflecting the variable response among EFE types. The Authors. Published by the Federation of Animal Science Societies and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

The varying cosmological constant: a new approximation to the Friedmann equations and universe model

NASA Astrophysics Data System (ADS)

Öztaş, Ahmet M.; Dil, Emre; Smith, Michael L.

2018-05-01

We investigate the time-dependent nature of the cosmological constant, Λ, of the Einstein Field Equation (EFE). Beginning with the Einstein-Hilbert action as our fundamental principle we develop a modified version of the EFE allowing the value of Λ to vary as a function of time, Λ(t), indirectly, for an expanding universe. We follow the evolving Λ presuming four-dimensional space-time and a flat universe geometry and present derivations of Λ(t) as functions of the Hubble constant, matter density, and volume changes which can be traced back to the radiation epoch. The models are more detailed descriptions of the Λ dependence on cosmological factors than previous, allowing calculations of the important parameters, Ωm and Ωr, to deep lookback times. Since we derive these without the need for extra dimensions or other special conditions our derivations are useful for model evaluation with astronomical data. This should aid resolution of several difficult problems of astronomy such as the best value for the Hubble constant at present and at recombination.

Supporting Learning to Teach in Early Field Experiences: The UTE Model

ERIC Educational Resources Information Center

Bieda, Kristen N.; Dillman, Brittany; Gundlach, Michael; Voogt, Kevin

2017-01-01

Most teacher preparation programs require prospective teachers (PTs) to engage in early field experiences (EFEs) prior to completing required coursework. These EFEs, however, may lack meaningful connections to course content and provide limited opportunities to experience the demands of classroom teaching. In this paper, we share evidence from the…

Effect of ethanolic flax (Linum usitatissimum L.) extracts on lipid oxidation and changes in nutritive value of frozen-stored meat products.

PubMed

Waszkowiak, Katarzyna; Szymandera-Buszka, Krystyna; Hęś, Marzanna

2014-01-01

Flaxseed (Linum usitatissimum L.) is an important source of phenolic compounds, mainly lignans. Antioxidant capacities of flaxseed extracts that contain the compounds have been reported earlier. However, there is a lack of accessible information about their activity against lipid oxidation in meat products. Therefore, the effect of ethanolic flaxseed extracts (EFEs) on lipid stability and changes in nutritive value of frozen-stored meat products (pork meatballs and burgers) was determined. EFEs from three Polish flax varieties (Szafir, Oliwin, Jantarol) were applied in the study. During 150-day storage of meat products, the lipid oxidation (peroxide and TBARS value) and thiamine retention were periodically monitored, alongside with methionine and lysine availability and protein digestibility. The addition of EFEs significantly limited lipid oxidation in stored meatballs and burgers. EFE from brown seeds of Szafir var. was superior to the others from golden seeds of Jantarol and Oliwin. Moreover, the extracts reduced changes in thiamine and available lysine content, as well as protein digestibility, during storage time. The effect of EFE addition on available methionine retention was limited. The ethanolic flaxseed extracts exhibit antioxidant activity during frozen storage of meat products. They can be utilized to prolong shelf-life of the products by protecting them against lipid oxidation and deterioration of their nutritional quality. However, antioxidant efficiency of the extracts seems to depend on chemical composition of raw material (flax variety). Further investigations should be carried on to explain the issue.

Progress toward Implementation of the Education for Employment Policy. 1987-88. ICoVE Survey Report. Report 20.

ERIC Educational Resources Information Center

Piland, Joseph; And Others

During the annual convention of the Illinois Vocational Association, a survey was conducted to determine perceptions about progress being made toward implementation of the Education for Employment (EFE) policy. Questions focused on four perceptions held by the EFE community about the needed changes: knowledge and awareness of expected changes;…

Seeing What They See--A Photovoice Analysis of Exploratory Early Field Experiences

ERIC Educational Resources Information Center

Baker, Marshall A.; Culbertson, Avery L.; Robinson, J. Shane; Ramsey, Jon W.

2017-01-01

The purpose of this photovoice study was to investigate what and how pre-service teachers conceive and make meaning of exploration observations of early field experiences (EFEs). EFEs are vital components of the teacher preparation program and include all activities that occur in pre-service teacher education prior to student teaching, including…

Visuo-spatial interference affects the identification of emotional facial expressions in unmedicated Parkinson's patients.

PubMed

García-Rodríguez, Beatriz; Guillén, Carmen Casares; Barba, Rosa Jurado; io Valladolid, Gabriel Rub; Arjona, José Antonio Molina; Ellgring, Heiner

2012-02-15

There is evidence that visuo-spatial capacity can become overloaded when processing a secondary visual task (Dual Task, DT), as occurs in daily life. Hence, we investigated the influence of the visuo-spatial interference in the identification of emotional facial expressions (EFEs) in early stages of Parkinson's disease (PD). We compared the identification of 24 emotional faces that illustrate six basic emotions in, unmedicated recently diagnosed PD patients (16) and healthy adults (20), under two different conditions: a) simple EFE identification, and b) identification with a concurrent visuo-spatial task (Corsi Blocks). EFE identification by PD patients was significantly worse than that of healthy adults when combined with another visual stimulus. Published by Elsevier B.V.

Asymptotic normalization coefficients of resonant and bound states from the phase shifts for α α and α 12C scattering

NASA Astrophysics Data System (ADS)

Orlov, Yu. V.; Irgaziev, B. F.; Nikitina, L. I.

2016-01-01

Recently we have published a paper [Irgaziev, Phys. Rev. C 91, 024002 (2015), 10.1103/PhysRevC.91.024002] where the S -matrix pole method (SMP), which is only valid for resonances, has been developed to derive an explicit expression for the asymptotic normalization coefficient (ANC) and is applied to the low-energy resonant states of nucleon +α and α +12C systems. The SMP results are compared with the effective-range expansion method (EFE) results. In the present paper the SMP and EFE plus the Padé approximation are applied to study the excited 2+ resonant states of 9Be. A contradiction is found between descriptions of the experimental phase shift data for α α scattering and of the 9Be resonant energy for 2+ state. Using the EFE method, we also calculate the ANC for the 9Be ground 0+ state with a very small width. This ANC agrees well with the value calculated using the known analytical expression for narrow resonances. In addition, for the α +12C states 1- and 3- the SMP results are compared with the Padé approximation results. We find that the Padé approximation improves a resonance width description compared with the EFE results. The EFE method is also used to calculate the ANCs for the bound 0mml:mprescripts>O ground 0+ state and for the excited 1- and 2+ levels, which are situated near the threshold of α +12C channel.

Effects of Repeated Concussions and Sex on Early Processing of Emotional Facial Expressions as Revealed by Electrophysiology.

PubMed

Carrier-Toutant, Frédérike; Guay, Samuel; Beaulieu, Christelle; Léveillé, Édith; Turcotte-Giroux, Alexandre; Papineau, Samaël D; Brisson, Benoit; D'Hondt, Fabien; De Beaumont, Louis

2018-05-06

Concussions affect the processing of emotional stimuli. This study aimed to investigate how sex interacts with concussion effects on early event-related brain potentials (ERP) measures (P1, N1) of emotional facial expressions (EFE) processing in asymptomatic, multi-concussion athletes during an EFE identification task. Forty control athletes (20 females and 20 males) and 43 multi-concussed athletes (22 females and 21 males), recruited more than 3 months after their last concussion, were tested. Participants completed the Beck Depression Inventory II, the Beck Anxiety Inventory, the Post-Concussion Symptom Scale, and an Emotional Facial Expression Identification Task. Pictures of male and female faces expressing neutral, angry, and happy emotions were randomly presented and the emotion depicted had to be identified as fast as possible during EEG acquisition. Relative to controls, concussed athletes of both sex exhibited a significant suppression of P1 amplitude recorded from the dominant right hemisphere while performing the emotional face expression identification task. The present study also highlighted a sex-specific suppression of the N1 component amplitude after concussion which affected male athletes. These findings suggest that repeated concussions alter the typical pattern of right-hemisphere response dominance to EFE in early stages of EFE processing and that the neurophysiological mechanisms underlying the processing of emotional stimuli are distinctively affected across sex. (JINS, 2018, 24, 1-11).

Ethylene-producing bacteria that ripen fruit.

PubMed

Digiacomo, Fabio; Girelli, Gabriele; Aor, Bruno; Marchioretti, Caterina; Pedrotti, Michele; Perli, Thomas; Tonon, Emil; Valentini, Viola; Avi, Damiano; Ferrentino, Giovanna; Dorigato, Andrea; Torre, Paola; Jousson, Olivier; Mansy, Sheref S; Del Bianco, Cristina

2014-12-19

Ethylene is a plant hormone widely used to ripen fruit. However, the synthesis, handling, and storage of ethylene are environmentally harmful and dangerous. We engineered E. coli to produce ethylene through the activity of the ethylene-forming enzyme (EFE) from Pseudomonas syringae. EFE converts a citric acid cycle intermediate, 2-oxoglutarate, to ethylene in a single step. The production of ethylene was placed under the control of arabinose and blue light responsive regulatory systems. The resulting bacteria were capable of accelerating the ripening of tomatoes, kiwifruit, and apples.

Overcoming substrate limitations for improved production of ethylene in E. coli

DOE PAGES

Lynch, Sean; Eckert, Carrie; Yu, Jianping; ...

2016-01-04

Ethylene is an important industrial compound for the production of a wide variety of plastics and chemicals. At present, ethylene production involves steam cracking of a fossil-based feedstock, representing the highest CO 2-emitting process in the chemical industry. Biological ethylene production can be achieved via expression of a single protein, the ethylene-forming enzyme (EFE), found in some bacteria and fungi; it has the potential to provide a sustainable alternative to steam cracking, provided that significant increases in productivity can be achieved. A key barrier is determining factors that influence the availability of substrates for the EFE reaction in potential microbialmore » hosts. In the presence of O 2, EFE catalyzes ethylene formation from the substrates α-ketoglutarate (AKG) and arginine. The concentrations of AKG, a key TCA cycle intermediate, and arginine are tightly controlled by an intricate regulatory system that coordinates carbon and nitrogen metabolism. Thus, reliably predicting which genetic changes will ultimately lead to increased AKG and arginine availability is challenging.« less

Overcoming substrate limitations for improved production of ethylene in E. coli.

PubMed

Lynch, Sean; Eckert, Carrie; Yu, Jianping; Gill, Ryan; Maness, Pin-Ching

2016-01-01

Ethylene is an important industrial compound for the production of a wide variety of plastics and chemicals. At present, ethylene production involves steam cracking of a fossil-based feedstock, representing the highest CO2-emitting process in the chemical industry. Biological ethylene production can be achieved via expression of a single protein, the ethylene-forming enzyme (EFE), found in some bacteria and fungi; it has the potential to provide a sustainable alternative to steam cracking, provided that significant increases in productivity can be achieved. A key barrier is determining factors that influence the availability of substrates for the EFE reaction in potential microbial hosts. In the presence of O2, EFE catalyzes ethylene formation from the substrates α-ketoglutarate (AKG) and arginine. The concentrations of AKG, a key TCA cycle intermediate, and arginine are tightly controlled by an intricate regulatory system that coordinates carbon and nitrogen metabolism. Therefore, reliably predicting which genetic changes will ultimately lead to increased AKG and arginine availability is challenging. We systematically explored the effects of media composition (rich versus defined), gene copy number, and the addition of exogenous substrates and other metabolites on the formation of ethylene in Escherichia coli expressing EFE. Guided by these results, we tested a number of genetic modifications predicted to improve substrate supply and ethylene production, including knockout of competing pathways and overexpression of key enzymes. Several such modifications led to higher AKG levels and higher ethylene productivity, with the best performing strain more than doubling ethylene productivity (from 81 ± 3 to 188 ± 13 nmol/OD600/mL). Both EFE activity and substrate supply can be limiting factors in ethylene production. Targeted modifications in central carbon metabolism, such as overexpression of isocitrate dehydrogenase, and deletion of glutamate synthase or the transcription regulator ArgR, can effectively enhance substrate supply and ethylene productivity. These results not only provide insight into the intricate regulatory network of the TCA cycle, but also guide future pathway and genome-scale engineering efforts to further boost ethylene productivity.

A Genetic Toolbox for Modulating the Expression of Heterologous Genes in the Cyanobacterium Synechocystis sp. PCC 6803

DOE PAGES

Wang, Bo; Eckert, Carrie; Maness, Pin -Ching; ...

2017-12-12

Cyanobacteria, genetic models for photosynthesis research for decades, have recently become attractive hosts for producing renewable fuels and chemicals, owing to their genetic tractability, relatively fast growth, and their ability to utilize sunlight, fix carbon dioxide, and in some cases, fix nitrogen. Despite significant advances, there is still an urgent demand for synthetic biology tools in order to effectively manipulate genetic circuits in cyanobacteria. In this study, we have compared a total of 17 natural and chimeric promoters, focusing on expression of the ethylene-forming enzyme (EFE) in the cyanobacterium Synechocystis sp. PCC 6803. We report the finding that the E.more » coli σ 70 promoter Ptrc is superior compared to the previously reported strong promoters, such as PcpcB and PpsbA, for the expression of EFE. In addition, we found that the EFE expression level was very sensitive to the 5'-untranslated region upstream of the open reading frame. A library of ribosome binding sites (RBSs) was rationally designed and was built and systematically characterized. We demonstrate a strategy complementary to the RBS prediction software to facilitate the rational design of an RBS library to optimize the gene expression in cyanobacteria. Our results show that the EFE expression level is dramatically enhanced through these synthetic biology tools and is no longer the rate-limiting step for cyanobacterial ethylene production. Furthermore, these systematically characterized promoters and the RBS design strategy can serve as useful tools to tune gene expression levels and to identify and mitigate metabolic bottlenecks in cyanobacteria.« less

A Genetic Toolbox for Modulating the Expression of Heterologous Genes in the Cyanobacterium Synechocystis sp. PCC 6803

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Bo; Eckert, Carrie; Maness, Pin -Ching

Cyanobacteria, genetic models for photosynthesis research for decades, have recently become attractive hosts for producing renewable fuels and chemicals, owing to their genetic tractability, relatively fast growth, and their ability to utilize sunlight, fix carbon dioxide, and in some cases, fix nitrogen. Despite significant advances, there is still an urgent demand for synthetic biology tools in order to effectively manipulate genetic circuits in cyanobacteria. In this study, we have compared a total of 17 natural and chimeric promoters, focusing on expression of the ethylene-forming enzyme (EFE) in the cyanobacterium Synechocystis sp. PCC 6803. We report the finding that the E.more » coli σ 70 promoter Ptrc is superior compared to the previously reported strong promoters, such as PcpcB and PpsbA, for the expression of EFE. In addition, we found that the EFE expression level was very sensitive to the 5'-untranslated region upstream of the open reading frame. A library of ribosome binding sites (RBSs) was rationally designed and was built and systematically characterized. We demonstrate a strategy complementary to the RBS prediction software to facilitate the rational design of an RBS library to optimize the gene expression in cyanobacteria. Our results show that the EFE expression level is dramatically enhanced through these synthetic biology tools and is no longer the rate-limiting step for cyanobacterial ethylene production. Furthermore, these systematically characterized promoters and the RBS design strategy can serve as useful tools to tune gene expression levels and to identify and mitigate metabolic bottlenecks in cyanobacteria.« less

Jumping-droplet electronics hot-spot cooling

NASA Astrophysics Data System (ADS)

Oh, Junho; Birbarah, Patrick; Foulkes, Thomas; Yin, Sabrina L.; Rentauskas, Michelle; Neely, Jason; Pilawa-Podgurski, Robert C. N.; Miljkovic, Nenad

2017-03-01

Demand for enhanced cooling technologies within various commercial and consumer applications has increased in recent decades due to electronic devices becoming more energy dense. This study demonstrates jumping-droplet based electric-field-enhanced (EFE) condensation as a potential method to achieve active hot spot cooling in electronic devices. To test the viability of EFE condensation, we developed an experimental setup to remove heat via droplet evaporation from single and multiple high power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm × 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and the transistor. Heat transfer measurements were performed in ambient air (22-25 °C air temperature, 20%-45% relative humidity) to determine the effect of gap spacing (2-4 mm), electric field (50-250 V/cm) and applied heat flux (demonstrated to 13 W/cm2). EFE condensation was shown to enhance the heat transfer from the local hot spot by ≈200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases promises hot spot heat dissipation rates approaching 120 W/cm2. This work provides a framework for the development of active jumping droplet based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.

Jumping-droplet electronics hot-spot cooling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oh, Junho; Birbarah, Patrick; Foulkes, Thomas

Demand for enhanced cooling technologies within various commercial and consumer applications has increased in recent decades due to electronic devices becoming more energy dense. This study demonstrates jumping-droplet based electric-field-enhanced (EFE) condensation as a potential method to achieve active hot spot cooling in electronic devices. To test the viability of EFE condensation, we developed an experimental setup to remove heat via droplet evaporation from single and multiple high power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobicmore » surface to the transistor hot spots by applying electric fields between the condensing surface and the transistor. Heat transfer measurements were performed in ambient air (22-25°C air temperature, 20-45% relative humidity) to determine the effect of gap spacing (2-4 mm), electric field (50-250 V/cm), and heat flux (demonstrated to 13 W/cm 2). EFE condensation was shown to enhance the heat transfer from the local hot spot by ≈ 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases promises hot spot heat dissipation rates approaching 120 W/cm 2. Finally, this work provides a framework for the development of active jumping droplet based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.« less

Jumping-droplet electronics hot-spot cooling

DOE PAGES

Oh, Junho; Birbarah, Patrick; Foulkes, Thomas; ...

2017-03-20

Demand for enhanced cooling technologies within various commercial and consumer applications has increased in recent decades due to electronic devices becoming more energy dense. This study demonstrates jumping-droplet based electric-field-enhanced (EFE) condensation as a potential method to achieve active hot spot cooling in electronic devices. To test the viability of EFE condensation, we developed an experimental setup to remove heat via droplet evaporation from single and multiple high power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobicmore » surface to the transistor hot spots by applying electric fields between the condensing surface and the transistor. Heat transfer measurements were performed in ambient air (22-25°C air temperature, 20-45% relative humidity) to determine the effect of gap spacing (2-4 mm), electric field (50-250 V/cm), and heat flux (demonstrated to 13 W/cm 2). EFE condensation was shown to enhance the heat transfer from the local hot spot by ≈ 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases promises hot spot heat dissipation rates approaching 120 W/cm 2. Finally, this work provides a framework for the development of active jumping droplet based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.« less

Effect of additional vitamin E and zinc supplementation on immunological changes in peripartum Sahiwal cows.

PubMed

Chandra, G; Aggarwal, A; Kumar, M; Singh, A K; Sharma, V K; Upadhyay, R C

2014-12-01

This study was conducted to exploit ameliorative effect of additional vitamin E and/or zinc supplementation on immune response of peripartum Sahiwal cows. Thirty-two pregnant dry Sahiwal cows were blocked into four treatment groups (n = 8), namely control, zinc (Zn), vitamin E (Vit E) and zinc + vitamin E (Zn + Vit E). Feeding regimen was same in all the groups except that the Sahiwal cows in the zinc-, vitamin E- and zinc + vitamin E-fed groups were additionally supplemented with 60 mg Zn/kg DM, 1000 IU vitamin E and 60 mg/kg + 1000 IU Zn + vitamin E, respectively, from day 60 pre-partum to day 90 post-partum. Blood samples were collected on days -60, -45, -30, -15, -7, -3, 0, 3, 7, 15, 30, 45, 60, 90 and 120 with respect to day of parturition and analysed for total immunoglobulin (TIG), immunoglobulin G (IgG), interleukin-2 (IL-2), vitamin E (Vit E) and zinc (Zn) status. Before calving, cows showed a decrease in plasma TIG, IgG, IL-2, Vit E and Zn levels. However, increased levels of plasma TIG, IgG, IL-2, Vit E and Zn were observed after calving. After calving, Sahiwal cows supplemented with Zn + Vit E had higher plasma TIG, IgG and IL-2 in comparison with cows of control and Zn + Vit E-fed groups. In the present study, plasma vitamin E level was higher in Vit E-fed and Zn + Vit E-fed cows; however, zinc level was higher in Zn- and Zn + Vit E-supplemented cows. In conclusion, a reduced immune response during peripartum period in Sahiwal cows was ameliorated by dietary vitamin E and zinc supplementation. Journal of Animal Physiology and Animal Nutrition © 2014 Blackwell Verlag GmbH.

Brain response during the M170 time interval is sensitive to socially relevant information.

PubMed

Arviv, Oshrit; Goldstein, Abraham; Weeting, Janine C; Becker, Eni S; Lange, Wolf-Gero; Gilboa-Schechtman, Eva

2015-11-01

Deciphering the social meaning of facial displays is a highly complex neurological process. The M170, an event related field component of MEG recording, like its EEG counterpart N170, was repeatedly shown to be associated with structural encoding of faces. However, the scope of information encoded during the M170 time window is still being debated. We investigated the neuronal origin of facial processing of integrated social rank cues (SRCs) and emotional facial expressions (EFEs) during the M170 time interval. Participants viewed integrated facial displays of emotion (happy, angry, neutral) and SRCs (indicated by upward, downward, or straight head tilts). We found that the activity during the M170 time window is sensitive to both EFEs and SRCs. Specifically, highly prominent activation was observed in response to SRC connoting dominance as compared to submissive or egalitarian head cues. Interestingly, the processing of EFEs and SRCs appeared to rely on different circuitry. Our findings suggest that vertical head tilts are processed not only for their sheer structural variance, but as social information. Exploring the temporal unfolding and brain localization of non-verbal cues processing may assist in understanding the functioning of the social rank biobehavioral system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Face processing in chronic alcoholism: a specific deficit for emotional features.

PubMed

Maurage, P; Campanella, S; Philippot, P; Martin, S; de Timary, P

2008-04-01

It is well established that chronic alcoholism is associated with a deficit in the decoding of emotional facial expression (EFE). Nevertheless, it is still unclear whether this deficit is specifically for emotions or due to a more general impairment in visual or facial processing. This study was designed to clarify this issue using multiple control tasks and the subtraction method. Eighteen patients suffering from chronic alcoholism and 18 matched healthy control subjects were asked to perform several tasks evaluating (1) Basic visuo-spatial and facial identity processing; (2) Simple reaction times; (3) Complex facial features identification (namely age, emotion, gender, and race). Accuracy and reaction times were recorded. Alcoholic patients had a preserved performance for visuo-spatial and facial identity processing, but their performance was impaired for visuo-motor abilities and for the detection of complex facial aspects. More importantly, the subtraction method showed that alcoholism is associated with a specific EFE decoding deficit, still present when visuo-motor slowing down is controlled for. These results offer a post hoc confirmation of earlier data showing an EFE decoding deficit in alcoholism by strongly suggesting a specificity of this deficit for emotions. This may have implications for clinical situations, where emotional impairments are frequently observed among alcoholic subjects.

The combined effect of subthalamic nuclei deep brain stimulation and L-dopa increases emotion recognition in Parkinson's disease.

PubMed

Mondillon, Laurie; Mermillod, Martial; Musca, Serban C; Rieu, Isabelle; Vidal, Tiphaine; Chambres, Patrick; Auxiette, Catherine; Dalens, Hélène; Marie Coulangeon, Louise; Jalenques, Isabelle; Lemaire, Jean-Jacques; Ulla, Miguel; Derost, Philippe; Marques, Ana; Durif, Franck

2012-10-01

Deep brain stimulation of the subthalamic nucleus (DBS) is a widely used surgical technique to suppress motor symptoms in Parkinson's disease (PD), and as such improves patients' quality of life. However, DBS may produce emotional disorders such as a reduced ability to recognize emotional facial expressions (EFE). Previous studies have not considered the fact that DBS and l-dopa medication can have differential, common, or complementary consequences on EFE processing. A thorough way of investigating the effect of DBS and l-dopa medication in greater detail is to compare patients' performances after surgery, with the two therapies either being administered ('on') or not administered ('off'). We therefore used a four-condition (l-dopa 'on'/DBS 'on', l-dopa 'on'/DBS 'off', l-dopa 'off'/DBS 'on', and l-dopa 'off'/DBS 'off') EFE recognition paradigm and compared implanted PD patients to healthy controls. The results confirmed those of previous studies, yielding a significant impairment in the detection of some facial expressions relative to controls. Disgust recognition was impaired when patients were 'off' l-dopa and 'on' DBS, and fear recognition impaired when 'off' of both therapies. More interestingly, the combined effect of both DBS and l-dopa administration seems much more beneficial for EFE recognition than the separate administration of each individual therapy. We discuss the implications of these findings in the light of the inverted U curve function that describes the differential effects of dopamine level on the right orbitofrontal cortex (OFC). We propose that, while l-dopa could "overdose" in dopamine the ventral stream of the OFC, DBS would compensate for this over-activation by decreasing OFC activity, thereby restoring the necessary OFC-amygdala interaction. Another finding is that, when collapsing over all treatment conditions, PD patients recognized more neutral faces than the matched controls, a result that concurs with embodiment theories. Copyright © 2012 Elsevier Ltd. All rights reserved.

Ethylene production with engineered Synechocystis sp PCC 6803 strains.

PubMed

Veetil, Vinod Puthan; Angermayr, S Andreas; Hellingwerf, Klaas J

2017-02-23

Metabolic engineering and synthetic biology of cyanobacteria offer a promising sustainable alternative approach for fossil-based ethylene production, by using sunlight via oxygenic photosynthesis, to convert carbon dioxide directly into ethylene. Towards this, both well-studied cyanobacteria, i.e., Synechocystis sp PCC 6803 and Synechococcus elongatus PCC 7942, have been engineered to produce ethylene by introducing the ethylene-forming enzyme (Efe) from Pseudomonas syringae pv. phaseolicola PK2 (the Kudzu strain), which catalyzes the conversion of the ubiquitous tricarboxylic acid cycle intermediate 2-oxoglutarate into ethylene. This study focuses on Synechocystis sp PCC 6803 and shows stable ethylene production through the integration of a codon-optimized version of the efe gene under control of the Ptrc promoter and the core Shine-Dalgarno sequence (5'-AGGAGG-3') as the ribosome-binding site (RBS), at the slr0168 neutral site. We have increased ethylene production twofold by RBS screening and further investigated improving ethylene production from a single gene copy of efe, using multiple tandem promoters and by putting our best construct on an RSF1010-based broad-host-self-replicating plasmid, which has a higher copy number than the genome. Moreover, to raise the intracellular amounts of the key Efe substrate, 2-oxoglutarate, from which ethylene is formed, we constructed a glycogen-synthesis knockout mutant (ΔglgC) and introduced the ethylene biosynthetic pathway in it. Under nitrogen limiting conditions, the glycogen knockout strain has increased intracellular 2-oxoglutarate levels; however, surprisingly, ethylene production was lower in this strain than in the wild-type background. Making use of different RBS sequences, production of ethylene ranging over a 20-fold difference has been achieved. However, a further increase of production through multiple tandem promoters and a broad-host plasmid was not achieved speculating that the transcription strength and the gene copy number are not the limiting factors in our system.

Geochemistry of Israeli oil shales: a review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirav, M.; Ginzburg, D.

1983-01-01

The oil shales of Israel are widely distributed throughout the country and have current reserves of about 3500 million tons located in the following deposits: Zin, Oron, Ef'e, Hartuv, and Nabi-Musa. The geochemistry and chemical analysis of these shales are discussed, along with the calorific value, oil yield, and trace elements. The main components influencing the quality of the oil shales are organic matter, carbonate, clay minerals, and apatite. Compositional variations within the organic matter are responsible for changes in the relative calorific value and retorted oil yield while fluidized bed combustion is affected by the inorganic components. (JMT)

Rapid Presentation of Emotional Expressions Reveals New Emotional Impairments in Tourette’s Syndrome

PubMed Central

Mermillod, Martial; Devaux, Damien; Derost, Philippe; Rieu, Isabelle; Chambres, Patrick; Auxiette, Catherine; Legrand, Guillaume; Galland, Fabienne; Dalens, Hélène; Coulangeon, Louise Marie; Broussolle, Emmanuel; Durif, Franck; Jalenques, Isabelle

2013-01-01

Objective: Based on a variety of empirical evidence obtained within the theoretical framework of embodiment theory, we considered it likely that motor disorders in Tourette’s syndrome (TS) would have emotional consequences for TS patients. However, previous research using emotional facial categorization tasks suggests that these consequences are limited to TS patients with obsessive-compulsive behaviors (OCB). Method: These studies used long stimulus presentations which allowed the participants to categorize the different emotional facial expressions (EFEs) on the basis of a perceptual analysis that might potentially hide a lack of emotional feeling for certain emotions. In order to reduce this perceptual bias, we used a rapid visual presentation procedure. Results: Using this new experimental method, we revealed different and surprising impairments on several EFEs in TS patients compared to matched healthy control participants. Moreover, a spatial frequency analysis of the visual signal processed by the patients suggests that these impairments may be located at a cortical level. Conclusion: The current study indicates that the rapid visual presentation paradigm makes it possible to identify various potential emotional disorders that were not revealed by the standard visual presentation procedures previously reported in the literature. Moreover, the spatial frequency analysis performed in our study suggests that emotional deficit in TS might lie at the level of temporal cortical areas dedicated to the processing of HSF visual information. PMID:23630481

Analysis of IFE, EFE and QSPM matrix on business development strategy

NASA Astrophysics Data System (ADS)

Zulkarnain, A.; Wahyuningtias, D.; Putranto, T. S.

2018-03-01

IFE matrix, EFE matrix, and QSPM matrix are business strategy tools that can be used to identify the threat, opportunity, weakness, strength as internal, external business factors. The goal of Danti’s Deli Bakery is to provide pastry product and distribute to other food and beverage outlet all around Jakarta. Thus, Danti’s Deli Bakery requires development strategy in order to win the tight competition. Applied descriptive research and data collected from focus group discussion, questionnaire, interview, observation and literature review. The objectives of this paper are (1) to identify and evaluate internal and external factors, (2) to formulate alternative strategy toward business development program, and (3) to give effective recommendation. The result shows that Danti’s Deli Bakery should apply product differentiation strategy. Implementation of this study is providing the recommendation for pastry and bakery industry to establish a successful business.

Low temperature synthesis of diamond-based nano-carbon composite materials with high electron field emission properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saravanan, A.; Huang, B. R.; Yeh, C. J.

2015-06-08

A diamond-based nano-carbon composite (d/NCC) material, which contains needle-like diamond grains encased with the nano-graphite layers, was synthesized at low substrate temperature via a bias enhanced growth process using CH{sub 4}/N{sub 2} plasma. Such a unique granular structure renders the d/NCC material very conductive (σ = 714.8 S/cm), along with superior electron field emission (EFE) properties (E{sub 0} = 4.06 V/μm and J{sub e} = 3.18 mA/cm{sup 2}) and long lifetime (τ = 842 min at 2.41 mA/cm{sup 2}). Moreover, the electrical conductivity and EFE behavior of d/NCC material can be tuned in a wide range that is especially useful for different kind of applications.

Synthesis of ultra-nano-carbon composite materials with extremely high conductivity by plasma post-treatment process of ultrananocrystalline diamond films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yeh, Chien-Jui; Leou, Keh-Chyang; Manoharan, Divinah

2015-08-24

Needle-like diamond grains encased in nano-graphitic layers are an ideal granular structure of diamond films to achieve high conductivity and superior electron field emission (EFE) properties. This paper describes the plasma post-treatment (ppt) of ultrananocrystalline diamond (UNCD) films at low substrate temperature to achieve such a unique granular structure. The CH{sub 4}/N{sub 2} plasma ppt-processed films exhibit high conductivity of σ = 1099 S/cm as well as excellent EFE properties with turn-on field of E{sub 0} = 2.48 V/μm (J{sub e} = 1.0 mA/cm{sup 2} at 6.5 V/μm). The ppt of UNCD film is simple and robust process that is especially useful for device applications.

Development of a new laparoscopic Foramen Epiploicum Mesh Closure (FEMC) technique in 6 horses.

PubMed

van Bergen, T; Wiemer, P; Bosseler, L; Ugahary, F; Martens, A

2016-05-01

Epiploic foramen entrapment (EFE) is, based on the number of reports in the literature, a relatively important life-threatening cause of colic in horses that could be prevented by closing the epiploic foramen (EF) in horses at risk of developing EFE. To describe the laparoscopic foramen epiploicum mesh closure (FEMC) technique and its outcome. Descriptive experimental study. The EF of 6 horses was closed with the FEMC technique. A diabolo-shaped constructed mesh was introduced into the omental vestibule through the EF under laparoscopic visualisation in the standing sedated horse. Clinical and laboratory parameters were recorded during the post operative period. Four weeks after the intervention, repeat laparoscopy was performed in all horses. Three horses were subjected to euthanasia one, 2 and 3 months after the intervention, and were examined on necropsy and histopathology. The remaining 3 horses were followed clinically for 6 months. The 6 FEMC procedures were performed successfully in a median surgery time of 22 min (range 18-27 min). One horse was treated for large colon impaction in the immediate post operative period. On repeat laparoscopy at 4 weeks all 6 EFs were closed and no undesired adhesions were identified. This was confirmed on gross and histopathological examination of the 3 horses that were subjected to euthanasia. The 3 remaining horses were clinically normal in the 6-month post operative observation period. This FEMC technique provides a fast, simple, reliable and safe procedure to obliterate the EF and may be useful in horses at risk for EFE. © 2015 EVJ Ltd.

Additional Guidance for Evaluating and Calculating Degradation Kinetics in Environmental Media

EPA Pesticide Factsheets

EFED compiled examples where the PestDF (version 0.8.4), the tool used most commonly by USEPA to conduct kinetic analysis following the NAFTA guidance, results required additional interpretation. Here are some of these examples.

Facile synthesis of pyrite (FeS2/C) nanoparticles as an electrode material for non-aqueous hybrid electrochemical capacitors.

PubMed

Pham, Duong Tung; Baboo, Joseph Paul; Song, Jinju; Kim, Sungjin; Jo, Jeonggeun; Mathew, Vinod; Alfaruqi, Muhammad Hilmy; Sambandam, Balaji; Kim, Jaekook

2018-03-29

Pyrite (FeS2) is a promising electrode material for lithium ion batteries (LIBs) because of its high natural availability, low toxicity, cost-effectiveness, high theoretical capacity (894 mA h g-1) and high theoretical specific energy density (1270 W h kg-1, 4e-/FeS2). Nevertheless, the use of FeS2 in electrochemical capacitors was restricted due to fast capacity fading as a result of polysulfide (S/Sn2-) formation during the initial electrochemical cycling. In order to avoid the formation of polysulfides, we employed the strategy of utilizing an ether based electrolyte (1.0 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/diglyme (DGM)). Herein, we introduce FeS2/C as the Faradaic electrode for a non-aqueous hybrid electrochemical capacitor (NHEC) in combination with activated carbon (AC) as a non-Faradaic electrode, and 1.0 M LiTFSI/DGM as a non-aqueous electrolyte. Specifically, FeS2/C nanoparticles have been prepared via the sulfidation of a room temperature synthesized Fe-based MOF (metal organic framework) precursor. The fabricated FeS2/C∥AC NHEC, operating within the chosen voltage window of 0-3.2 V, delivered energy densities in the range of 63-9 W h kg-1 at power densities of 152-3240 W kg-1. Remarkable cycling stability with stable energy density retention for 2500 cycles at high power densities (729, 1186 and 3240 W kg-1) was observed.

A census of the expected properties of classical Milky Way dwarfs in Milgromian dynamics

NASA Astrophysics Data System (ADS)

Lüghausen, F.; Famaey, B.; Kroupa, P.

2014-07-01

Prompted by the recent successful predictions of the internal dynamics of Andromeda's satellite galaxies, we revisit the classical Milky Way dwarf spheroidal satellites Draco, Sculptor, Sextans, Carina and Fornax in the framework of Milgromian dynamics (MOND). We use for the first time a Poisson solver with adaptive mesh refinement (AMR) in order to account simultaneously for the gravitational influence of the Milky Way and its satellites. This allows us to rigorously model the important external field effect (EFE) of Milgromian dynamics, which can reduce the effective acceleration significantly. We make predictions on the dynamical mass-to-light ratio (Mdyn/L) expected to be measured by an observer who assumes Newtonian dynamics to be valid. We show that Milgromian dynamics predicts typical Mdyn/L ≈ 10-50 M⊙/L⊙. The results for the most luminous ones, Fornax and Sculptor, agree well with available velocity dispersion data. Moreover, the central power-law slopes of the dynamical masses agree exceedingly well with values inferred observationally from velocity dispersion measurements. The results for Sextans, Carina and Draco are low compared to usually quoted observational estimates, as already pointed out by Angus. For Milgromian dynamics to survive further observational tests in these objects, one would thus need that either (a) previous observational findings based on velocity dispersion measurements have overestimated the dynamical mass due to, e.g. binaries and contaminant outliers, (b) the satellites are not in virial equilibrium due to the Milky Way tidal field, or (c) the specific theory used here does not describe the EFE correctly (e.g. the EFE could be practically negligible in some other theories), or a combination of (a)-(c).

USER MANUAL FOR EXPRESS, THE EXAMS-PRZM EXPOSURE SIMULATION SHELL

EPA Science Inventory

The Environmental Fate and Effects Division (EFED) of EPA's Office of Pesticide Programs(OPP) uses a suite of ORD simulation models for the exposure analysis portion of regulatory risk assessments. These models (PRZM, EXAMS, AgDisp) are complex, process-based simulation codes tha...

Microstructural Evolution of Nanocrystalline Diamond Films Due to CH4/Ar/H2 Plasma Post-Treatment Process.

PubMed

Lin, Sheng-Chang; Yeh, Chien-Jui; Manoharan, Divinah; Leou, Keh-Chyang; Lin, I-Nan

2015-10-07

Plasma post-treatment process was observed to markedly enhance the electron field emission (EFE) properties of ultrananocrystalline diamond (UNCD) films. TEM examinations reveal that the prime factor which improves the EFE properties of these films is the coalescence of ultrasmall diamond grains (∼5 nm) forming large diamond grains about hundreds of nanometers accompanied by the formation of nanographitic clusters along the grain boundaries due to the plasma post-treatment process. OES studies reveal the presence of large proportion of atomic hydrogen and C2 (or CH) species, which are the main ingredients that altered the granular structure of the UNCD films. In the post-treatment process, the plasma interacts with the diamond films by a diffusion process. The recrystallization of diamond grains started at the surface region of the material, and the interaction zone increased with the post-treatment period. The entire diamond film can be converted into a nanocrystalline granular structure when post-treated for a sufficient length of time.

PREFACE: Many-body correlations from dilute to dense nuclear systems

NASA Astrophysics Data System (ADS)

Otsuka, Takaharu; Urban, Michael; Yamada, Taiichi

2011-09-01

The International EFES-IN2P3 conference on "Many body correlations from dilute to dense nuclear systems" was held at the Institut Henri Poincaré (IHP), Paris, France, from 15-18 February 2011, on the occasion of the retirement of our colleague Peter Schuck. Correlations play a decisive role in various many-body systems such as nuclear systems, condensed matter and quantum gases. Important examples include: pairing correlations (Cooper pairs) which give rise to nuclear superfluidity (analogous to superconductivity in condensed matter); particle-hole (RPA) correlations in the description of the ground state beyond mean-field theory; clusters; and α-particle correlations in certain nuclei. Also, the nucleons themselves can be viewed as clusters of three quarks. During the past few years, researchers have started to study how the character of these correlations changes with the variation of the density. For instance, the Cooper pairs in dense matter can transform into a Bose-Einstein condensate (BEC) of true bound states at low density (this is the BCS-BEC crossover studied in ultracold Fermi gases). Similar effects play a role in neutron matter at low density, e.g., in the "neutron skin" of exotic nuclei. The α-cluster correlation becomes particularly important at lower density, such as in the excited states of some nuclei (e.g., the α-condensate-like structure in the Hoyle state of 12C) or in the formation of compact stars. In addition to nuclear physics, topics from astrophysics (neutron stars), condensed matter, and quantum gases were discussed in 48 talks and 19 posters, allowing the almost 90 participants from different communities to exchange their ideas, experiences and methods. The conference dinner took place at the Musée d'Orsay, and all the participants enjoyed the very pleasant atmosphere. One session of the conference was dedicated to the celebration of Peter's retirement. We would like to take this opportunity to wish Peter all the best and we hope that he will continue his scientific work full of creative and original ideas. We would like to thank all those who helped to make the conference a success: Nguyen van Giai, S Fujii, J Margueron, K Hagino, and Y Kanada-En'yo for their help with the organization; the advisory committee for suggesting invited speakers; V Frois for her administrative help; L Petizon for the website; and the director of IPN Orsay, F Azaiez, for his support. We are indebted to IHP for providing the lecture hall free of charge, and we acknowledge the financial support from JSPS through its EFES core-to-core program, from CNRS (IN2P3 and INP), and from LIA France-Japon. Last but not least, we are grateful to all of the participants for making the conference exciting and successful. Takaharu Otsuka, Michael Urban, Taiichi YamadaEditors of the proceedings

CTC Sentinel. Volume 6, Issue 9. September 2013

DTIC Science & Technology

2013-09-01

Yemeni government officials trumpeted the “ liberation ” of Abyan from Ansar al- Shari`a fighters.4 Yet the year that has followed has made such...Pacifico Sur en el estado de Morelos,” EFE, February 11, 2013. 7 “Cronologia narcotraficantes caidos en los ultimos anos,” El Universal, July 15

Overexpression of bacterial ethylene-forming enzyme gene in Trichoderma reesei enhanced the production of ethylene

PubMed Central

Chen, Xi; Liang, Yong; Hua, Jing; Tao, Li; Qin, Wensheng; Chen, Sanfeng

2010-01-01

In order to efficiently utilize natural cellulose materials to produce ethylene, three expression vectors containing the ethylene-forming enzyme (efe) gene from Pseudomonas syringae pv. glycinea were constructed. The target gene was respectively controlled by different promoters: cbh I promoter from Trichoderma reesei cellobiohydrolases I gene, gpd promoter from Aspergillus nidulans glyceraldehyde-3-phosphate dehydrogenase gene and pgk I promoter from T. reesei 3-phosphoglycerate kinase I gene. After transforming into T. reesei QM9414, 43 stable transformants were obtained by PCR amplification and ethylene determination. Southern blot analysis of 14 transformants demonstrated that the efe gene was integrated into chromosomal DNA with copy numbers from 1 to 4. Reverse transcription polymerase chain reaction (RT-PCR) analysis of 6 transformants showed that the heterologous gene was transcribed. By using wheat straw as a carbon source, the ethylene production rates of aforementioned 14 transformants were measured. Transformant C30-3 with pgk I promoter had the highest ethylene production (4,012 nl h-1 l-1). This indicates that agricultural wastes could be used to produce ethylene in recombinant filamentous fungus T. reesei. PMID:20150979

Sedna and the cloud of comets surrounding the solar system in Milgromian dynamics

NASA Astrophysics Data System (ADS)

Paučo, R.; Klačka, J.

2016-05-01

We reconsider the hypothesis of a vast cometary reservoir surrounding the solar system - the Oort cloud of comets - within the framework of Milgromian dynamics (MD or MOND). For this purpose we built a numerical model of the cloud, assuming the theory of modified gravity, QUMOND. In modified gravity versions of MD, the internal dynamics of a system is influenced by the external gravitational field in which the system is embedded, even when this external field is constant and uniform, a phenomenon dubbed the external field effect (EFE). Adopting the popular pair ν(x) = [1-exp(-x1 / 2)] -1 for the MD interpolating function and a0 = 1.2 × 10-10 m s-2 for the MD acceleration scale, we found that the observationally inferred Milgromian cloud of comets is much more radially compact than its Newtonian counterpart. The comets of the Milgromian cloud stay away from the zone where the Galactic tide can torque their orbits significantly. However, this does not need to be an obstacle for the injection of the comets into the inner solar system as the EFE can induce significant change in perihelion distance during one revolution of a comet around the Sun. Adopting constraints on different interpolating function families and a revised value of a0 (provided recently by the Cassini spacecraft), the aforementioned qualitative results no longer hold, and, in conclusion, the Milgromian cloud is very similar to the Newtonian in its overall size, binding energies of comets and hence the operation of the Jupiter-Saturn barrier. However, EFE torquing of perihelia still play a significant role in the inner parts of the cloud. Consequently Sedna-like orbits and orbits of large semi-major axis Centaurs are easily comprehensible in MD. In MD, they both belong to the same population, just in different modes of their evolution.

Developing a Capacity to Make "English for Everyone" Worthwhile: Reconsidering Outcomes and How to Start Achieving Them

ERIC Educational Resources Information Center

Wedell, Martin

2008-01-01

Past decades have seen a growing assumption worldwide that national governments should provide "English for Everyone" (EFE) as a core component of their school curricula. Personal and national benefits expected from such English provision are generally expressed in terms of developing learners' abilities to communicate in English. Despite enormous…

Preservice Teachers' Use of Production and Reproduction Teaching Styles within Multi-Activity and Sport Education Units

ERIC Educational Resources Information Center

Parker, Mitchum; Curtner-Smith, Mathew

2012-01-01

The purpose of this study was to examine the influence of one component of physical education teacher education on preservice teachers' (PTs) use of Mosston's (1981) spectrum of teaching styles within an early field experience (EFE). Participants were two PTs who were trained to use the spectrum within a methods course and team/turn-taught…

JPRS Report, Environmental Issues

DTIC Science & Technology

1991-06-26

been coordinated by the National Environ- mental Policy Commission [Comision Nacional de Politica Ambiental ]. The first step was the creation of a...May 91 [Text] Santiago, 30 May (EFE)—The Permanent South Pacific Commission (CPPS), which comprises Colombia, Chile, Ecuador , and Peru, has lodged a...decisions. We are adopting measures that will create the State Secretariat for the Environment [Secretaria de Estado del Medio Ambiente ], which will be

The characteristics of RF modulated plasma boundary sheaths: An analysis of the standard sheath model

NASA Astrophysics Data System (ADS)

Naggary, Schabnam; Brinkmann, Ralf Peter

2015-09-01

The characteristics of radio frequency (RF) modulated plasma boundary sheaths are studied on the basis of the so-called ``standard sheath model.'' This model assumes that the applied radio frequency ωRF is larger than the plasma frequency of the ions but smaller than that of the electrons. It comprises a phase-averaged ion model - consisting of an equation of continuity (with ionization neglected) and an equation of motion (with collisional ion-neutral interaction taken into account) - a phase-resolved electron model - consisting of an equation of continuity and the assumption of Boltzmann equilibrium -, and Poisson's equation for the electrical field. Previous investigations have studied the standard sheath model under additional approximations, most notably the assumption of a step-like electron front. This contribution presents an investigation and parameter study of the standard sheath model which avoids any further assumptions. The resulting density profiles and overall charge-voltage characteristics are compared with those of the step-model based theories. The authors gratefully acknowledge Efe Kemaneci for helpful comments and fruitful discussions.

Personality Characteristics of Effective Organizational Effectiveness Consultants in the U.S. Navy

DTIC Science & Technology

1984-12-01

Testing, ~ 20. ABSTRACT (Continue on ,eo~efe side It necesaryt aid Identify bI. block number) This study examines the relationship between personality...Science Kneale T. Marh•’l.k, D-=-n o* In ormation!n P_• -’ Sciences 3 3 . ....-. ADSTRACT This study examines the relationship betweern personality...between the client and the consultant; without that relationship the OD effort will never be effective. According to Bennis (1969) the competence of the

Discrimination and categorization of emotional facial expressions and faces in Parkinson's disease.

PubMed

Alonso-Recio, Laura; Martín, Pilar; Rubio, Sandra; Serrano, Juan M

2014-09-01

Our objective was to compare the ability to discriminate and categorize emotional facial expressions (EFEs) and facial identity characteristics (age and/or gender) in a group of 53 individuals with Parkinson's disease (PD) and another group of 53 healthy subjects. On the one hand, by means of discrimination and identification tasks, we compared two stages in the visual recognition process that could be selectively affected in individuals with PD. On the other hand, facial expression versus gender and age comparison permits us to contrast whether the emotional or non-emotional content influences the configural perception of faces. In Experiment I, we did not find differences between groups, either with facial expression or age, in discrimination tasks. Conversely, in Experiment II, we found differences between the groups, but only in the EFE identification task. Taken together, our results indicate that configural perception of faces does not seem to be globally impaired in PD. However, this ability is selectively altered when the categorization of emotional faces is required. A deeper assessment of the PD group indicated that decline in facial expression categorization is more evident in a subgroup of patients with higher global impairment (motor and cognitive). Taken together, these results suggest that the problems found in facial expression recognition may be associated with the progressive neuronal loss in frontostriatal and mesolimbic circuits, which characterizes PD. © 2013 The British Psychological Society.

Facial decoding in schizophrenia is underpinned by basic visual processing impairments.

PubMed

Belge, Jan-Baptist; Maurage, Pierre; Mangelinckx, Camille; Leleux, Dominique; Delatte, Benoît; Constant, Eric

2017-09-01

Schizophrenia is associated with a strong deficit in the decoding of emotional facial expression (EFE). Nevertheless, it is still unclear whether this deficit is specific for emotions or due to a more general impairment for any type of facial processing. This study was designed to clarify this issue. Thirty patients suffering from schizophrenia and 30 matched healthy controls performed several tasks evaluating the recognition of both changeable (i.e. eyes orientation and emotions) and stable (i.e. gender, age) facial characteristics. Accuracy and reaction times were recorded. Schizophrenic patients presented a performance deficit (accuracy and reaction times) in the perception of both changeable and stable aspects of faces, without any specific deficit for emotional decoding. Our results demonstrate a generalized face recognition deficit in schizophrenic patients, probably caused by a perceptual deficit in basic visual processing. It seems that the deficit in the decoding of emotional facial expression (EFE) is not a specific deficit of emotion processing, but is at least partly related to a generalized perceptual deficit in lower-level perceptual processing, occurring before the stage of emotion processing, and underlying more complex cognitive dysfunctions. These findings should encourage future investigations to explore the neurophysiologic background of these generalized perceptual deficits, and stimulate a clinical approach focusing on more basic visual processing. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Large Eddy Simulation of Bubbly Ship Wakes

DTIC Science & Technology

2005-08-01

as, [Cm +BI(p)+ DE (u)+D,(u,)] (2.28) aRm, =-[E,+FE )(p) (229O•., L pe•,z+_tpjj.( F.(]-](2.29) where Ci and EP represent the convective terms, Bi is the...discrete operator for the pressure gradient term, DE and D, (FE and FI) are discrete operators for the explicitly treated off diagonal terms and the...Bashforth scheme is employed for all the other terms. The off diagonal viscous terms ( DE ) are treated explicitly in order to simplify the LHS matrix of the

Military Review, September 1994. Volume 74, Number 9

DTIC Science & Technology

1994-09-01

next year, MR must also visibly share in the reduc- tion of resources. In January 1995 , MR will stop its monthly production for the first time since...Comim Special Close Air Amphibious - Delon"H MWolle Intel Forces Support Force& rEor -cRedc Atak ire Finghtner Airlfiedt REtC Atac Rescuerft efe Caaa...l) EF ) thr-ough thc CJCS aiid, oftenl conicurr-ently, thle supporting (INC low conitrols at lar1ger arrfay to USACOM. The SECDEFE thr’ough thle CICS

Coal Conversion at Picatinny Arsenal and Forts Campbell, Bragg, and Gordon: A Feasibility Study

DTIC Science & Technology

1993-12-01

David M. Joncich is Chief, USACERL-FE, and Dr. Michael J. O’Connor is Chief, USACERL-FL. The USACERL technical editor was William J. Wolfe, Information...PanFr apel B4. S.. .......................................... U ,20 .. .... . .... ........ .. ’.... . ... .. i"....... 20 .......... .......... 1...i ~ ~ Chng In X Fgr14 Efe oEsatio Rat onte LC of a iolFrdSoe lnFr apel * S S i S e• B * S S e S e S SS* e e o * S S

Gravity with free initial conditions: A solution to the cosmological constant problem testable by CMB B -mode polarization

NASA Astrophysics Data System (ADS)

Totani, Tomonori

2017-10-01

In standard general relativity the universe cannot be started with arbitrary initial conditions, because four of the ten components of the Einstein's field equations (EFE) are constraints on initial conditions. In the previous work it was proposed to extend the gravity theory to allow free initial conditions, with a motivation to solve the cosmological constant problem. This was done by setting four constraints on metric variations in the action principle, which is reasonable because the gravity's physical degrees of freedom are at most six. However, there are two problems about this theory; the three constraints in addition to the unimodular condition were introduced without clear physical meanings, and the flat Minkowski spacetime is unstable against perturbations. Here a new set of gravitational field equations is derived by replacing the three constraints with new ones requiring that geodesic paths remain geodesic against metric variations. The instability problem is then naturally solved. Implications for the cosmological constant Λ are unchanged; the theory converges into EFE with nonzero Λ by inflation, but Λ varies on scales much larger than the present Hubble horizon. Then galaxies are formed only in small Λ regions, and the cosmological constant problem is solved by the anthropic argument. Because of the increased degrees of freedom in metric dynamics, the theory predicts new non-oscillatory modes of metric anisotropy generated by quantum fluctuation during inflation, and CMB B -mode polarization would be observed differently from the standard predictions by general relativity.

Anatomy of the vestibule of the omental bursa and epiploic foramen in the horse.

PubMed

Freeman, D E; Pearn, A R

2015-01-01

Epiploic foramen entrapment (EFE) is a common cause of colic in horses and available anatomical descriptions of this foramen and the associated vestibule of the omental bursa tend to be inconsistent, contradictory and inaccurate. To describe the anatomy of the vestibule of the omental bursa and epiploic foramen. Dissection of 21 fresh equine cadavers shortly after euthanasia. The anatomy of the vestibule of the omental bursa, epiploic foramen and related structures in the cranial abdomen were examined in situ and after removal from the abdomen. Photographs were taken and illustrations rendered to bring the relationship of the different folds, ligaments and organs involved into a 3D concept. The entrance into the vestibule and the passageway through it to the epiploic foramen is bounded by the gastropancreatic fold dorsally, caudally and ventrally. This fold constitutes the caudoventral boundary of the epiploic foramen along with the portal vein cranially and ventrally. The craniodorsal boundary of the epiploic foramen is formed by the caudate lobe of the liver. The gastropancreatic fold plays a more important role in the anatomy of the vestibule of the omental bursa and the epiploic foramen than has been documented in the most widely used anatomy textbooks written in English. Because of the importance of EFE in horses, information from this study about the relevant anatomy could provide a first step towards improved methods for treatment and laparoscopic prevention of these diseases. © 2014 EVJ Ltd.

Monitoring N2O Production Using a cNOR Modeled Active Site

NASA Astrophysics Data System (ADS)

Griffiths, Z. G.; Hegg, E. L.; Finders, C.; Haslun, J. A.

2017-12-01

Nitrous oxide (N2O) is a potent greenhouse gas with a 100-year global warming potential 265-296 times greater than carbon dioxide (CO2). It is the leading contributor to ozone depletion and can persist in the stratosphere for approximately 114 years. Hence, understanding the sources of atmospheric N2O emissions is critical to remediating the effects of climate change. Agricultural activities are the largest contributor to N2O emissions in the U.S. with microbial nitrification and denitrification as the dominating soil processes. The enzyme cytochrome c nitric oxide reductase (cNOR) is involved in bacterial denitrification. It is often difficult to study the enzymes involved in biotic N2O production, hence, model enzymes are a useful tool. The enzyme I107EFeBMb, a sperm whale myoglobin derivative, models the active site of cNOR and was used to simulate the anaerobic reduction of NO to N2O by cNOR. Dithionite was used to induce the catalytic activity of I107EFeBMb by reducing the enzyme. However, dithionite is a strong reductant that is capable of reducing NO to N2O directly. Therefore, the dithionite-enzyme mixture was passed through a size-exclusion column to isolate the reduced enzyme. This reduced and purified enzyme was then utilized to investigate N2O production from NO. This project will provide both an enzymatic and abiotic model to study N2O production.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ray, Sekhar C., E-mail: raysc@unisa.ac.za; Mishra, D. K.; Department of Physics, Institute of Technical Research and Education, Siksha ‘O’ Anusandhan University, Khandagiri Square, Bhubaneswar 751030, Odisha

The electronic structures and magnetic properties of graphene nanoflakes (GNFs) exposed to an organo-silane precursor [tetra-methyl-silane, Si(CH{sub 3}){sub 4}] were studied using atomic force microscopy, electron field emission (EFE), x-ray photoelectron spectroscopy (XPS), and magnetization. The result of XPS indicates that silyl radical based strong covalent bonds were formed in GNFs, which induced local structural relaxations and enhanced sp{sup 3} hybridization. The EFE measurements show an increase in the turn-on electric field from 9.8 V/μm for pure GNFs to 26.3 V/μm for GNFs:Si having highest Si/(Si + C) ratio ( ≅ 0.35) that also suggests an enhancement of the non-metallic sp{sup 3} bonding in the GNFsmore » matrix. Magnetic studies show that the saturation magnetization (Ms) is decreased from 172.53 × 10{sup −6} emu/g for pure GNFs to 13.00 × 10{sup −6} emu/g for GNFs:Si with the highest Si/(Si + C) ratio 0.35, but on the other side, the coercivity (Hc) increases from 66 to 149 Oe due to conversion of sp{sup 2} → sp{sup 3}-hybridization along with the formation of SiC and Si-O bonding in GNFs. The decrease in saturation magnetization and increase in coercivity (Hc) in GNFs on Si-functionalization are another routes to tailor the magnetic properties of graphene materials for magnetic device applications.« less

Locating Direction Finders in a Generalized Search and Rescue Network

DTIC Science & Technology

1991-03-01

David A . Drake and Alfred B. Marsb. Conv-ersation at NationalI Security Agenc, 29 September 1990. 7. Daskin , Mark S. " A M-admum Fpeced Co-:efing...91 7 19 134 .flT/GORjEnSj9I-M LOCATING DIRECTION FIND’RS IN A GENERALIZED SEARCH AND RESCUE NETWORK THESIS Jean M. Steppe Captain, USAF AFIT/GOR/EN S...91-Mk-7 APPROVED FOR PUBLIC RELI ASE: DISTRIBUTION UNLIMITED. 1191-05734 .. 91.. .7 19 134 i i . nMIGOR4M.S/91-MI LOCATING DIRECTION FINDERS IW A

Committees and supporting organizations

NASA Astrophysics Data System (ADS)

2011-09-01

Advisory Committee:Organizing Committee: Marcello Baldo (Catania)Takaharu Otsuka (Tokyo), co-chair George Bertsch (Seattle)Michael Urban (Orsay), co-chair Jean-Paul Blaizot (Saclay)Taiichi Yamada (Yokohama) Michel Girod (Bruyères-le-Châtel)Nguyen van Giai (Orsay) Hisashi Horiuchi (Osaka)Shinichiro Fujii (Tokyo) Umberto Lombardo (Catania)Jérôme Margueron (Orsay) Gerd Röpke (Rostock)Kouichi Hagino (Sendai) Hiroyuki Sagawa (Aizu)Yoshiko Kanada-En'yo (Kyoto) Piet Van Isacker (Caen) Enrico Vigezzi (Milano) IPN logo　　　　EFES logo　　　　CNRS logo　　　　ihp logo

[Changes of heart-type fatty acid-binding protein in children with chronic heart failure and its significance].

PubMed

Sun, Yu-Ping; Wang, Wen-Di; Ma, Shao-Chun; Wang, Li-Yan; Qiao, Ling-Yan; Zhang, Li-Ping

2013-02-01

To study serum levels of heart-type fatty acid-binding protein (h-FABP) in children with chronic heart failure (CHF), and the correlation between heart function and the level of h-FABP, with the aim of studying the significance of h-FABP in CHF. Thirty-six children with CHF, including 16 cases of endocardial fibroelastosis (EFE) and 20 cases of dilated cardiomyopathy (DCM) were enrolled in the study. Thirty healthy children sevred as the control group. Serum levels of h-FABP were determined using ELISA, and left ventricular ejection fraction (LVEF), cardiac index (CI) and fractional shortening of the left ventricle (LVSF) were measured by two-dimensional echocardiography in the CHF group. Mean levels of h-FABP in the CHF group were significantly higher than in the control group (21.7±4.3 ng/mL vs 6.2±1.7 ng/mL; P<0.01). The worse the heart function, the higher the h-FABP levels (P<0.01). Mean levels of h-FABP in both the EFE and DCM groups were significantly higher than in the control group (P<0.01). Serum h-FABP concentrations were negatively correlated with LVEF, CI and LVSF (r=-0.65, -0.64 and -0.71 respectively; P<0.01) in the CHF group. Serum h-FABP levels increase in children with CHF and are closely related to the severity of the condition. Serum h-FABP levels can be used as a biomarker for the diagnosis of heart failure and the evaluation of its severity.

Ethnic Affirmation versus Social Desirability as a Determinant of Discrepancies in the Responses of Hispanic Bilinguals to Spanish and English Versions of a Questionnaire.

DTIC Science & Technology

1982-08-01

and/or Dist Special Unclassified SEUIYCLASSIFPICATION OF THIS PAGE (When Data Nat efeQ REPORT DOCUMENTATION PAGE uu"o CO CMINOF 1. REPORT NUMINER...1) versus expected (7) 5.3 5.8 -2.99 .004 You feel that is undesirable (1) versus desirable (7) 5.1 5.7 -2.13 .038 You are talking with your co ...McPherson, GA 30330 Dr. Brian Usilaner GAO Army Research Institute Washington, DC 20548 Field Unit - Leavenworth P.O. Box 3122 Nat’l Institute of

Skin Wound-Enhanced Survival and Myelocytopoiesis in Mice after Whole- Body Irradiation

DTIC Science & Technology

1980-09-16

I. Sprotects both conventional (SMITH at coil. I 58 HAil .- 1. M: The efOets of whole body irrldiation 0onpN Rt H bt coi nd efe i neln colony...Department Diroctor Research was conducted according to the principles enunciated in the "Guide for the Care and Use of Laboratory Animals," prepared by the ...r Skin womIiding at 24 hi be fore whole-body, 60(’o irraxdiation of mice raise’d the LN13 from 8.09 to 9.71 Gy, resulting In a dose reduction factor

Numerical modeling of interaction of the aircraft engine with concrete protective structures

NASA Astrophysics Data System (ADS)

Radchenko, P. A.; Batuev, S. P.; Radchenko, A. V.; Plevkov, V. S.

2018-01-01

The paper presents numerical modeling results considering interaction of Boeing 747 aircraft engine with nuclear power station protective shell. Protective shell has been given as a reinforced concrete structure with complex scheme of reinforcement. The engine has been simulated by cylinder projectile made from titanium alloy. The interaction velocity has comprised 180 m/s. The simulation is three-dimensional solved by finite element method using the author’s own software package EFES. Fracture and fragmentation of materials have been considered in calculations. Program software has been assessed to be used in calculation of multiple-contact objectives.

RECOVERY, A Mathematical Model to Predict the Temporal Response of Surface Water to Contaminated Sediments.

DTIC Science & Technology

1994-11-01

NewEngl d U.S. Art RAYo WAERAYaEPRIENCSATO Incudebilio grapicr•efe "M ( p prgam) 3dCOeTt L -E nv i Eroa BORpR of E. Nw Y ri.ARm E er Wter...constant = 8.206 x 10.5 atm m3/(gmole-kelvins) T = absolute temperature, kelvins. A temperature of 298K (25 °C) is assumed in the model. The parameter...bottom sediment material are shown in Table 3. Table 2 Concentrations of DDE and Lindane In Water Column Sampling Day DDE, ppt, X ± SD Undane, ppt, X

Enhanced iron and zinc accumulation in genetically engineered pineapple plants using soybean ferritin gene.

PubMed

Mhatre, Minal; Srinivas, Lingam; Ganapathi, Thumballi R

2011-12-01

Pineapple (Ananas comosus L. Merr., cv. "Queen") leaf bases were transformed with Agrobacterium tumefaciens strain EHA 105 harboring the pSF and pEFESF plasmids with soybean ferritin cDNA. Four to eight percent of the co-cultivated leaf bases produced multiple shoots 6 weeks after transfer to Murashige and Skoog's medium supplemented with α-naphthalene acetic acid 1.8 mg/l, indole-3-butyric acid 2.0 mg/l, kinetin 2.0 mg/l, cefotaxime 400 mg/l, and kanamycin 50 mg/l. Putatively transformed shoots (1-2 cm) were selected and multiplied on medium of the same composition and elongated shoots (5 cm) were rooted on liquid rooting medium supplemented with cefotaxime 400 mg/l and kanamycin 100 mg/l. The rooted plants were analyzed through PCR, genomic Southern analysis, and reverse transcription PCR. The results clearly confirmed the integration and expression of soybean ferritin gene in the transformed plants. Atomic absorption spectroscopic analysis carried out with six independently transformed lines of pSF and pEFE-SF revealed a maximum of 5.03-fold increase in iron and 2.44-fold increase in zinc accumulation in the leaves of pSF-transformed plants. In pEFE-SF-transformed plants, a 3.65-fold increase in iron and 2.05-fold increase in zinc levels was observed. Few of the transgenic plants were hardened in the greenhouse and are being grown to maturity to determine the enhanced iron and zinc accumulation in the fruits. To the best of our knowledge this is the first report on the transformation of pineapple with soybean ferritin for enhanced accumulation of iron and zinc content in the transgenic plants.

Age-Related Changes in the Processing of Emotional Faces in a Dual-Task Paradigm.

PubMed

Casares-Guillén, Carmen; García-Rodríguez, Beatriz; Delgado, Marisa; Ellgring, Heiner

2016-01-01

Background/ Study Context: Age-related changes appear to affect the ability to identify emotional facial expressions in dual-task conditions (i.e., while simultaneously performing a second visual task). The level of interference generated by the secondary task depends on the phase of emotional processing affected by the interference and the nature of the secondary task. The aim of the present study was to investigate the effect of these variables on age-related changes in the processing of emotional faces. The identification of emotional facial expressions (EFEs) was assessed in a dual-task paradigm using the following variables: (a) the phase during which interference was applied (encoding vs. retrieval phase); and (b) the nature of the interfering stimulus (visuospatial vs. verbal). The sample population consisted of 24 healthy aged adults (mean age = 75.38) and 40 younger adults (mean age = 26.90). The accuracy of EFE identification was calculated for all experimental conditions. Consistent with our hypothesis, the performance of the older group was poorer than that of the younger group in all experimental conditions. Dual-task performance was poorer when the interference occurred during the encoding phase of emotional face processing and when both tasks were of the same nature (i.e., when the experimental condition was more demanding in terms of attention). These results provide empirical evidence of age-related deficits in the identification of emotional facial expressions, which may be partially explained by the impairment of cognitive resources specific to this task. These findings may account for the difficulties experienced by the elderly during social interactions that require the concomitant processing of emotional and environmental information.

Geochemistry of Israeli oil shales - A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirav, M.; Ginzbury, D.

1983-02-01

The oil shales in Israel are widely distributed throughout the country. Outcrops are rare and the information is based on boreholes data. The oil shale sequence is of UpperCampanian - Maastrichtian age and belongs to the Chareb Formation. In places, part of the phosphorite layer below the oil shales is also rich in kerogen. The host rocks are biomicritic limestones and marls, in which the organic matter is generally homogeneously and finely dispersed. The occurrence of authigenic feldspar and the preservation of the organic matter (up to 26% of the total rock) indicate euxinic hypersaline conditions which prevailed in themore » relative closed basins of deposition during the Maastrichtian. Current reserves of oil shales in Israel are about 3,500 million tons, located in the following deposits: Zin, Oron, Ef'e, Hartuv and Nabi-Musa. The 'En Bokek deposit, although thoroughly investigated, is of limited reserves and is not considered for future exploitation. Other potential areas, in the Northern Negev and along the Coastal Plain are under investigation. Future successful utilization of the Israeli oil shales, either by fluidizid-bed combustion or by retorting will contribute to the state's energy balance.« less

Ethylene and Wound-Induced Gene Expression in the Preclimacteric Phase of Ripening Avocado Fruit and Mesocarp Discs.

PubMed Central

Starrett, D. A.; Laties, G. G.

1993-01-01

Whereas intact postharvest avocado (Persea americana Mill.) fruit may take 1 or more weeks to ripen, ripening is hastened by pulsing fruit for 24 h with ethylene or propylene and is initiated promptly by cutting slices, or discs, of mesocarp tissue. Because the preclimacteric lag period constitutes the extended and variable component of the ripening syndrome, we postulated that selective gene expression during the lag period leads to the triggering of the climacteric. Accordingly, we sought to identify genes that are expressed gradually in the course of the lag period in intact fruit, are turned on sooner in response to a pulse, and are induced promptly in response to wounding (i.e. slicing). To this end, a mixed cDNA library was constructed from mRNA from untreated fruit, pulsed fruit, and aged slices, and the library was screened for genes induced by wounding or by pulsing and/or wounding. The time course of induction of genes encoding selected clones was established by probing northern blots of mRNA from tissues variously treated over a period of time. Four previously identified ripening-associated genes encoding cellulase, polygalacturonase (PG), cytochrome P-450 oxidase (P-450), and ethylene-forming enzyme (EFE, or 1-aminocyclopropane-1-carboxylic acid synthase), respectively, were studied in the same way. Whereas cellulase, PG, and EFE were ruled out as having a role in the initiation of the climacteric, the time course of P-450 induction, as well as the response of same to pulsing and wounding met the criteria[mdash]together with several clones from the mixed library[mdash]for a gene potentially involved in preclimacteric events leading to the onset of the climacteric. Further, it was established that the continuous presence of ethylene is required for persisting induction, and it is suggested that in selected cases wounding may exert a synergistic effect on ethylene action. PMID:12231929

Crystal structure of bacterial cell-surface alginate-binding protein with an M75 peptidase motif

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maruyama, Yukie; Ochiai, Akihito; Mikami, Bunzo

Research highlights: {yields} Bacterial alginate-binding Algp7 is similar to component EfeO of Fe{sup 2+} transporter. {yields} We determined the crystal structure of Algp7 with a metal-binding motif. {yields} Algp7 consists of two helical bundles formed through duplication of a single bundle. {yields} A deep cleft involved in alginate binding locates around the metal-binding site. {yields} Algp7 may function as a Fe{sup 2+}-chelated alginate-binding protein. -- Abstract: A gram-negative Sphingomonas sp. A1 directly incorporates alginate polysaccharide into the cytoplasm via the cell-surface pit and ABC transporter. A cell-surface alginate-binding protein, Algp7, functions as a concentrator of the polysaccharide in the pit.more » Based on the primary structure and genetic organization in the bacterial genome, Algp7 was found to be homologous to an M75 peptidase motif-containing EfeO, a component of a ferrous ion transporter. Despite the presence of an M75 peptidase motif with high similarity, the Algp7 protein purified from recombinant Escherichia coli cells was inert on insulin B chain and N-benzoyl-Phe-Val-Arg-p-nitroanilide, both of which are substrates for a typical M75 peptidase, imelysin, from Pseudomonas aeruginosa. The X-ray crystallographic structure of Algp7 was determined at 2.10 A resolution by single-wavelength anomalous diffraction. Although a metal-binding motif, HxxE, conserved in zinc ion-dependent M75 peptidases is also found in Algp7, the crystal structure of Algp7 contains no metal even at the motif. The protein consists of two structurally similar up-and-down helical bundles as the basic scaffold. A deep cleft between the bundles is sufficiently large to accommodate macromolecules such as alginate polysaccharide. This is the first structural report on a bacterial cell-surface alginate-binding protein with an M75 peptidase motif.« less

Use of natural gas, methanol, and ethanol fuel emulsions as environmentally friendly energy carriers for mobile heat power plants

NASA Astrophysics Data System (ADS)

Likhanov, V. A.; Lopatin, O. P.

2017-12-01

The need for using environmentally friendly energy carriers for mobile heat power plants (HPPs) is grounded. Ecologically friendly sources of energy, such as natural gas as well as renewable methyl and ethyl alcohols, are investigated. In order to develop, determine, and optimize the composition of environmentally friendly energy carriers for an HPP, the latter has been tested when working on diesel fuel (DF), compressed natural gas (CNG), and methanol and ethanol fuel emulsions (MFE, EFE). It has been experimentally established that, for the application of environmentally friendly energy carriers for a 4Ch 11.0/12.5 diesel engine of a mobile fuel and power plant, it is necessary to maintain the following ratio of components when working on CNG: 80% gas and 20% DF primer portion. When working on an alcohol mixture, emulsions of the following composition were used: 25% alcohol (methanol or ethanol), 0.5% detergent-dispersant additive succinimide C-5A, 7% water, and 67.5% DF. When this diesel passed from oil DF to environmentally friendly energy sources, it allowed for the reduction of the content of exhaust gases (EG) (1) when working on CNG with recirculation of exhaust gases (EGR) (recirculation was used to eliminate the increased amount of nitric oxides by using CNG): carbon black by 5.8 times, carbon dioxide by 45.9%, and carbon monoxide by 23.8%; (2) when working on MFE: carbon black by 6.4 times, nitrogen oxides by 29.6%, carbon dioxide by 10.1%, and carbon oxide by 47.6%; (3) when working on EFE: carbon black by 4.8 times; nitrogen oxides by 40.3%, carbon dioxide by 26.6%, and carbon monoxide by 28.6%. The prospects of use of environmentally friendly energy carriers in diesels of mobile HPPs, such as natural gas, ethanol, and methanol, has been determined.

Chlorite dismutases, DyPs, and EfeB: 3 microbial heme enzyme families comprise the CDE structural superfamily

PubMed Central

Goblirsch, Brandon; Kurker, Richard C.; Streit, Bennett R.; Wilmot, Carrie M.; DuBois, Jennifer L.

2011-01-01

Heme proteins are extremely diverse, widespread, and versatile biocatalysts, sensors, and molecular transporters. The chlorite dismutase family of hemoproteins received its name due to the ability of the first-isolated members to detoxify anthropogenic ClO2−, a function believed to have evolved only in the last few decades. Family members have since been found in fifteen bacterial and archaeal genera, suggesting ancient roots. A structure- and sequence-based examination of the family is presented, in which key sequence and structural motifs are identified and possible functions for family proteins are proposed. Newly identified structural homologies moreover demonstrate clear connections to two other large, ancient, and functionally mysterious protein families. We propose calling them collectively the CDE superfamily of heme proteins. PMID:21354424

Spectral fitting of SDSS passive galaxies with α-enhanced single stellar populations

NASA Astrophysics Data System (ADS)

Gomes, Jean Michel; Coelho, Paula

2012-08-01

The power of population synthesis as a mean to estimate the star-formation and chemical histories of galaxies has been well established in the last decade. The major developments were due to a huge avalanche of methods, codes and high-quality galaxy data sets, such as the 2dF, 6dF and SDSS surveys. Semi-empirical spectral synthesis allows for the decomposition of a galaxy spectrum in terms of linear combinations of base elements, i.e. Single Stellar Populations (SSPs) of different ages and metallicities, which are computed from evolutionary synthesis codes (BPASS, GALEV, GALAXEV, MILES, PÉGASE, etc. . .), containing distinct ingredients like: stellar library, evolutionary tracks, metallicities and Initial Mass Function. In general, they have solar-scaled relative abundances, but this is about to change with the unfolding of new α-enhanced SSP models (Coelho et al. 2007). However, passive galaxies have some spectral features corresponding to ``enhanced-ratios'' ([E/Fe]), like O, Ne, Si, S, Mg, Na, C and N over Fe that are not well modeled using solar-scaled SSPs (Trager et al. 2000), leading to residuals between observed and modeled spectra, which also correlate with the velocity dispersion (σ*) and stellar mass (M *): Massive galaxies exhibit a larger [E/Fe] discrepancy than less massive ones. This result can be interpreted as a signature of distinct previous star-formation efficiencies in passive galaxies, leading to distinctive ratios of type Ia and II SNe. We have applied the starlight spectral synthesis code (Cid Fernandes et al. 2005) to a sample of ~ 1000 passive galaxies from the SDSS DR7 with a S/N at the continuum >= 20 to investigate possible enhancements in the derived [E/Fe] ratios. Three sets of SSPs based on Coelho et al. (2007) theoretical models and Walcher et al. (2009) prescriptions were computed for [α/Fe]=0.0, [α/Fe]=0.2 and [α/Fe]=0.4. Our aim is to determine: (1) the quality of the fits, (2) the mean stellar age and metallicity distributions, and (3) the star-formation history of passive galaxies. Using [α/Fe]=0.0 SSPs, we have identified the strongest residuals in the CN (4142.125-4177.125 Å), Na D (5876.875-5909.375 Å) and Mg (5069.125-5196.625 Å) bands. On the other hand, [α/Fe]=0.2 and [α/Fe]=0.4 SSP models tend to reproduce better the Mg band, as compared to solar-scaled SSPs ([α/Fe]=0.0). The residuals are decreased by 1.77 Å ([α/Fe]=0.2) and 2.92 Å ([α/Fe]=0.4). However, as expected, these α-enhanced models lead to worse fits for the CN and Na D bands. These residuals may even reach up to 2.08 Å (CN) and 4.20 Å (Na D), using [α/Fe]=0.2 SSPs and 2.28 Å (CN) and 7.94 Å (Na D), using [α/Fe]=0.4 SSPs. In terms of mean stellar ages and metallicities, we obtain non-negligible biases in both quantities when we compare the solar-scaled SSPs with α-enhanced ones, which tend to have mean stellar ages by 0.12 dex ([α/Fe]=0.2) and 0.14 dex ([α/Fe]=0.4) higher and mean stellar metallicities by 0.1 dex ([α/Fe]=0.2) and 0.2 dex ([α/Fe]=0.4) lower.

Techno-economic analysis of a conceptual biofuel production process from bioethylene produced by photosynthetic recombinant cyanobacteria

DOE PAGES

Markham, Jennifer N.; Tao, Ling; Davis, Ryan; ...

2016-08-25

Ethylene is a petrochemical produced in large volumes worldwide. It serves as a building block for a wide variety of plastics, textiles, and chemicals, and can be converted into liquid transportation fuels. There is great interest in the development of technologies that produce ethylene from renewable resources, such as biologically derived CO 2 and biomass. One of the metabolic pathways used by microbes to produce ethylene is via an ethylene-forming enzyme (EFE). By expressing a bacterial EFE gene in a cyanobacterium, ethylene has been produced through photosynthetic carbon fixation. Here, we present a conceptual design and techno-economic analysis of amore » process of biofuel production based on the upgradation of ethylene generated by the recombinant cyanobacterium. This analysis focuses on potential near-term to long-term cost projections for the integrated process of renewable fuels derived from ethylene. The cost projections are important in showing the potential of this technology and determining research thrusts needed to reach target goals. The base case for this analysis is a midterm projection using tubular photobioreactors for cyanobacterial growth and ethylene production, cryogenic distillation for ethylene separation and purification, a two-step Ziegler oligomerization process with subsequent hydrotreatment and upgradation for fuel production, and a wastewater treatment process that utilizes anaerobic digestion of cyanobacterial biomass. The minimum fuel selling price (MFSP) for the midterm projection is 15.07 per gallon gasoline equivalent (GGE). Near-term and long-term projections are 28.66 per GGE and 5.36 per GGE, respectively. Single- and multi-point sensitivity analyses are conducted to determine the relative effect that chosen variables could have on the overall costs. This analysis identifies several key variables for improving the overall process economics and outlines strategies to guide future research directions. Finally, the productivity of ethylene has the largest effect on cost and is calculated based on a number of variables that are incorporated into this cost model (i.e., quantum requirement, photon transmission efficiency, and the percent of energy going to either ethylene or cyanobacterial biomass production).« less

Techno-economic analysis of a conceptual biofuel production process from bioethylene produced by photosynthetic recombinant cyanobacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markham, Jennifer N.; Tao, Ling; Davis, Ryan

Ethylene is a petrochemical produced in large volumes worldwide. It serves as a building block for a wide variety of plastics, textiles, and chemicals, and can be converted into liquid transportation fuels. There is great interest in the development of technologies that produce ethylene from renewable resources, such as biologically derived CO 2 and biomass. One of the metabolic pathways used by microbes to produce ethylene is via an ethylene-forming enzyme (EFE). By expressing a bacterial EFE gene in a cyanobacterium, ethylene has been produced through photosynthetic carbon fixation. Here, we present a conceptual design and techno-economic analysis of amore » process of biofuel production based on the upgradation of ethylene generated by the recombinant cyanobacterium. This analysis focuses on potential near-term to long-term cost projections for the integrated process of renewable fuels derived from ethylene. The cost projections are important in showing the potential of this technology and determining research thrusts needed to reach target goals. The base case for this analysis is a midterm projection using tubular photobioreactors for cyanobacterial growth and ethylene production, cryogenic distillation for ethylene separation and purification, a two-step Ziegler oligomerization process with subsequent hydrotreatment and upgradation for fuel production, and a wastewater treatment process that utilizes anaerobic digestion of cyanobacterial biomass. The minimum fuel selling price (MFSP) for the midterm projection is 15.07 per gallon gasoline equivalent (GGE). Near-term and long-term projections are 28.66 per GGE and 5.36 per GGE, respectively. Single- and multi-point sensitivity analyses are conducted to determine the relative effect that chosen variables could have on the overall costs. This analysis identifies several key variables for improving the overall process economics and outlines strategies to guide future research directions. Finally, the productivity of ethylene has the largest effect on cost and is calculated based on a number of variables that are incorporated into this cost model (i.e., quantum requirement, photon transmission efficiency, and the percent of energy going to either ethylene or cyanobacterial biomass production).« less

Comparison of Percutaneous Cementoplasty with and Without Interventional Internal Fixation for Impending Malignant Pathological Fracture of the Proximal Femur

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Qing-Hua, E-mail: ddqinghua-tian@163.com; He, Cheng-Jian, E-mail: tianhechengjian@163.com; Wu, Chun-Gen, E-mail: 649514608@qq.com

PurposeTo compare the efficacy of percutaneous cementoplasty (PCP) with and without interventional internal fixation (IIF) on malignant impending pathological fracture of proximal femur.MethodsA total of 40 patients with malignant impending pathological fracture of proximal femur were selected for PCP and IIF (n = 19, group A) or PCP alone (n = 21, group B) in this non-randomized prospective study. Bone puncture needles were inserted into the proximal femur, followed by sequential installation of the modified trocar inner needles through the puncture needle sheath. Then, 15–45 ml cement was injected into the femur lesion.ResultsThe overall excellent and good pain relief rate during follow-ups were significantly highermore » in group A than that in group B (89 vs. 57 %, P = 0.034). The average change of VAS, ODI, KPS, and EFES in group A were significantly higher than those in group B at 1-, 3-, 6-month, 1-year (P < 0.05). Meanwhile, The stability of the treated femur was significantly higher in group A than that in group B (P < 0.05).ConclusionPCP and IIF were not only a safe and effective procedure, but resulted in greater pain relief, bone consolidation, and also reduced the risk of fracture than the currently recommended approach of PCP done on malignant proximal femoral tumor.« less

The ecology of birth seasonality among agriculturalists in central Africa.

PubMed

Bailey, R C; Jenike, M R; Ellison, P T; Bentley, G R; Harrigan, A M; Peacock, N R

1992-07-01

The Lese are subsistence farmers living in the Ituri Forest of north-east Zaïre. They exhibit significant birth seasonality, with lowest frequencies of conception when food production is least, nutritional status is low and ovarian function, as measured by salivary steroid hormone levels, is reduced. Efe pygmy foragers, who live in the same geographical area but are less dependent on cultivated foods and have a more flexible life style, do not exhibit frequent fluctuations in nutritional status nor significant birth seasonality. These findings support a model of birth seasonality relating climatic variables to variation in fertility through a causal chain linking rainfall to food production to energy balance to ovarian function to fertility. The model, which emphasises an ecological approach to the study of human reproduction, should have broad applicability since seasonality of food production and energy balance is widespread geographically and across a wide variety of economies and cultures.

Anode current density distribution in a cusped field thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Huan, E-mail: wuhuan58@qq.com; Liu, Hui, E-mail: hlying@gmail.com; Meng, Yingchao

2015-12-15

The cusped field thruster is a new electric propulsion device that is expected to have a non-uniform radial current density at the anode. To further study the anode current density distribution, a multi-annulus anode is designed to directly measure the anode current density for the first time. The anode current density decreases sharply at larger radii; the magnitude of collected current density at the center is far higher compared with the outer annuli. The anode current density non-uniformity does not demonstrate a significant change with varying working conditions.

PM10 emissions from aggregate fractions of an Entic Haplustoll under two contrasting tillage systems

NASA Astrophysics Data System (ADS)

Mendez, Mariano J.; Aimar, Silvia B.; Buschiazzo, Daniel E.

2015-12-01

Tillage systems affect physical and chemical properties of soils modifying its aggregation. How changes of the aggregate size distribution affect the capacity of the soil to emit fine particulate matter (PM10) to the atmosphere during wind erosion processes, is a less investigated issue. In order to answer this question, PM10 emissions from an Entic Haplustoll submitted to 25 years of continuous conventional tillage (LC) and no-till (NT) were analyzed. Soil samples were sieved with a rotary sieve in order to determine the aggregate size distribution (fractions : <0.42 mm, 0.42-0.84 mm, 0.84-2 mm, 2-6.4 mm, 6.4-19.2 mm, and >19.2 mm), the dry aggregate stability (DAS) and the erodible fraction (EF). The organic matter contents (OM), the particle size composition and the PM10 emission of each aggregate fraction were also measured. Results showed that NT promoted OM accumulations in all aggregate fractions which favored DAS and soil aggregation. The <0.42 mm sized aggregates (27%) predominated in CT and the >19.2 mm (41.7%) in NT, while the proportion of the other aggregate fractions was similar in both tillage systems. As a consequence of the smaller proportion of the <0.42 mm aggregates, the erodible fraction was lower in NT (EF: 17.3%) than in CT (30.8%). PM10 emissions of each aggregate fraction (AE) decreased exponentially with increasing size of the fractions in both tillage systems, mainly as a consequence of the smaller size and higher specific surface. AE was higher in CT than in NT for all aggregate fractions, but the higher differences were found in the <0.42 mm aggregates (18 μg g-1 in CT vs 8 μg g-1 in NT). The PM10 emission of the whole soil was three times higher in CT than in NT, while the emission of the erodible fraction (EFE) was in CT four times higher than in NT. PM10 emissions of the <0.42 mm aggregates represented over 50% of SE and 90% of EFE. We concluded that NT reduced the capacity of soils of the semiarid Pampas to emit PM10 because it produced a better aggregation that reduced the proportion and emission of the <0.42 mm aggregates. These aggregates had, by far, the highest emission potential.

Globally optimal superconducting magnets part I: minimum stored energy (MSE) current density map.

PubMed

Tieng, Quang M; Vegh, Viktor; Brereton, Ian M

2009-01-01

An optimal current density map is crucial in magnet design to provide the initial values within search spaces in an optimization process for determining the final coil arrangement of the magnet. A strategy for obtaining globally optimal current density maps for the purpose of designing magnets with coaxial cylindrical coils in which the stored energy is minimized within a constrained domain is outlined. The current density maps obtained utilising the proposed method suggests that peak current densities occur around the perimeter of the magnet domain, where the adjacent peaks have alternating current directions for the most compact designs. As the dimensions of the domain are increased, the current density maps yield traditional magnet designs of positive current alone. These unique current density maps are obtained by minimizing the stored magnetic energy cost function and therefore suggest magnet coil designs of minimal system energy. Current density maps are provided for a number of different domain arrangements to illustrate the flexibility of the method and the quality of the achievable designs.

Two-dimensional relativistic space charge limited current flow in the drift space

NASA Astrophysics Data System (ADS)

Liu, Y. L.; Chen, S. H.; Koh, W. S.; Ang, L. K.

2014-04-01

Relativistic two-dimensional (2D) electrostatic (ES) formulations have been derived for studying the steady-state space charge limited (SCL) current flow of a finite width W in a drift space with a gap distance D. The theoretical analyses show that the 2D SCL current density in terms of the 1D SCL current density monotonically increases with D/W, and the theory recovers the 1D classical Child-Langmuir law in the drift space under the approximation of uniform charge density in the transverse direction. A 2D static model has also been constructed to study the dynamical behaviors of the current flow with current density exceeding the SCL current density, and the static theory for evaluating the transmitted current fraction and minimum potential position have been verified by using 2D ES particle-in-cell simulation. The results show the 2D SCL current density is mainly determined by the geometrical effects, but the dynamical behaviors of the current flow are mainly determined by the relativistic effect at the current density exceeding the SCL current density.

Current density tensors

NASA Astrophysics Data System (ADS)

Lazzeretti, Paolo

2018-04-01

It is shown that nonsymmetric second-rank current density tensors, related to the current densities induced by magnetic fields and nuclear magnetic dipole moments, are fundamental properties of a molecule. Together with magnetizability, nuclear magnetic shielding, and nuclear spin-spin coupling, they completely characterize its response to magnetic perturbations. Gauge invariance, resolution into isotropic, deviatoric, and antisymmetric parts, and contributions of current density tensors to magnetic properties are discussed. The components of the second-rank tensor properties are rationalized via relationships explicitly connecting them to the direction of the induced current density vectors and to the components of the current density tensors. The contribution of the deviatoric part to the average value of magnetizability, nuclear shielding, and nuclear spin-spin coupling, uniquely determined by the antisymmetric part of current density tensors, vanishes identically. The physical meaning of isotropic and anisotropic invariants of current density tensors has been investigated, and the connection between anisotropy magnitude and electron delocalization has been discussed.

Numerical investigation of split flows by gravity currents into two-layered stratified water bodies

NASA Astrophysics Data System (ADS)

Cortés, A.; Wells, M. G.; Fringer, O. B.; Arthur, R. S.; Rueda, F. J.

2015-07-01

The behavior of a two-dimensional (2-D) gravity current impinging upon a density step in a two-layered stratified basin is analyzed using a high-resolution Reynolds-Averaged Navier-Stokes model. The gravity current splits at the density step, and the portion of the buoyancy flux becoming an interflow is largely controlled by the vertical distribution of velocity and density within the gravity current and the magnitude of the density step between the two ambient layers. This is in agreement with recent laboratory observations. The strongest changes in the ambient density profiles occur as a result of the impingement of supercritical currents with strong density contrasts, for which a large portion of the gravity current detaches from the bottom and becomes an interflow. We characterize the current partition process in the simulated experiments using the densimetric Froude number of the current (Fr) across the density step (upstream and downstream). When underflows are formed, more supercritical currents are observed downstream of the density step compared to upstream (Fru < Frd), and thus, stronger mixing of the current with the ambient water downstream. However, when split flows and interflows are formed, smaller Fr values are identified after the current crosses the density step (Fru > Frd), which indicates lower mixing between the current and ambient water after the impingement due to the significant stripping of interfacial material at the density step.

THEMIS two‐point measurements of the cross‐tail current density: A thick bifurcated current sheet in the near‐Earth plasma sheet

PubMed Central

2015-01-01

Abstract The basic properties of the near‐Earth current sheet from 8 RE to 12 RE were determined based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from 2007 to 2013. Ampere's law was used to estimate the current density when the locations of two spacecraft were suitable for the calculation. A total of 3838 current density observations were obtained to study the vertical profile. For typical solar wind conditions, the current density near (off) the central plane of the current sheet ranged from 1 to 2 nA/m2 (1 to 8 nA/m2). All the high current densities appeared off the central plane of the current sheet, indicating the formation of a bifurcated current sheet structure when the current density increased above 2 nA/m2. The median profile also showed a bifurcated structure, in which the half thickness was about 3 RE. The distance between the peak of the current density and the central plane of the current sheet was 0.5 to 1 RE. High current densities above 4 nA/m2 were observed in some cases that occurred preferentially during substorms, but they also occurred in quiet times. In contrast to the commonly accepted picture, these high current densities can form without a high solar wind dynamic pressure. In addition, these high current densities can appear in two magnetic configurations: tail‐like and dipolar structures. At least two mechanisms, magnetic flux depletion and new current system formation during the expansion phase, other than plasma sheet compression are responsible for the formation of the bifurcated current sheets. PMID:27722039

Magneto-acousto-electrical tomography: a potential method for imaging current density and electrical impedance.

PubMed

Haider, S; Hrbek, A; Xu, Y

2008-06-01

Primarily this report outlines our investigation on utilizing magneto-acousto-electrical-tomography (MAET) to image the lead field current density in volume conductors. A lead field current density distribution is obtained when a current/voltage source is applied to a sample via a pair of electrodes. This is the first time a high-spatial-resolution image of current density is presented using MAET. We also compare an experimental image of current density in a sample with its corresponding numerical simulation. To image the lead field current density, rather than applying a current/voltage source directly to the sample, we place the sample in a static magnetic field and focus an ultrasonic pulse on the sample to simulate a point-like current dipole source at the focal point. Then by using electrodes we measure the voltage/current signal which, based on the reciprocity theorem, is proportional to a component of the lead field current density. In the theory section, we derive the equation relating the measured voltage to the lead field current density and the displacement velocity caused by ultrasound. The experimental data include the MAET signal and an image of the lead field current density for a thin sample. In addition, we discuss the potential improvements for MAET especially to overcome the limitation created by the observation that no signal was detected from the interior of a region having a uniform conductivity. As an auxiliary we offer a mathematical formula whereby the lead field current density may be utilized to reconstruct the distribution of the electrical impedance in a piecewise smooth object.

High current density cathode for electrorefining in molten electrolyte

DOEpatents

Li, Shelly X.

2010-06-29

A high current density cathode for electrorefining in a molten electrolyte for the continuous production and collection of loose dendritic or powdery deposits. The high current density cathode eliminates the requirement for mechanical scraping and electrochemical stripping of the deposits from the cathode in an anode/cathode module. The high current density cathode comprises a perforated electrical insulated material coating such that the current density is up to 3 A/cm.sup.2.

Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

NASA Technical Reports Server (NTRS)

Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

1976-01-01

Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

Analysis of recoverable current from one component of magnetic flux density in MREIT and MRCDI.

PubMed

Park, Chunjae; Lee, Byung Il; Kwon, Oh In

2007-06-07

Magnetic resonance current density imaging (MRCDI) provides a current density image by measuring the induced magnetic flux density within the subject with a magnetic resonance imaging (MRI) scanner. Magnetic resonance electrical impedance tomography (MREIT) has been focused on extracting some useful information of the current density and conductivity distribution in the subject Omega using measured B(z), one component of the magnetic flux density B. In this paper, we analyze the map Tau from current density vector field J to one component of magnetic flux density B(z) without any assumption on the conductivity. The map Tau provides an orthogonal decomposition J = J(P) + J(N) of the current J where J(N) belongs to the null space of the map Tau. We explicitly describe the projected current density J(P) from measured B(z). Based on the decomposition, we prove that B(z) data due to one injection current guarantee a unique determination of the isotropic conductivity under assumptions that the current is two-dimensional and the conductivity value on the surface is known. For a two-dimensional dominating current case, the projected current density J(P) provides a good approximation of the true current J without accumulating noise effects. Numerical simulations show that J(P) from measured B(z) is quite similar to the target J. Biological tissue phantom experiments compare J(P) with the reconstructed J via the reconstructed isotropic conductivity using the harmonic B(z) algorithm.

In vivo mapping of current density distribution in brain tissues during deep brain stimulation (DBS)

NASA Astrophysics Data System (ADS)

Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2017-01-01

New methods for in vivo mapping of brain responses during deep brain stimulation (DBS) are indispensable to secure clinical applications. Assessment of current density distribution, induced by internally injected currents, may provide an alternative method for understanding the therapeutic effects of electrical stimulation. The current flow and pathway are affected by internal conductivity, and can be imaged using magnetic resonance-based conductivity imaging methods. Magnetic resonance electrical impedance tomography (MREIT) is an imaging method that can enable highly resolved mapping of electromagnetic tissue properties such as current density and conductivity of living tissues. In the current study, we experimentally imaged current density distribution of in vivo canine brains by applying MREIT to electrical stimulation. The current density maps of three canine brains were calculated from the measured magnetic flux density data. The absolute current density values of brain tissues, including gray matter, white matter, and cerebrospinal fluid were compared to assess the active regions during DBS. The resulting current density in different tissue types may provide useful information about current pathways and volume activation for adjusting surgical planning and understanding the therapeutic effects of DBS.

Current-voltage characteristics influenced by the nanochannel diameter and surface charge density in a fluidic field-effect-transistor.

PubMed

Singh, Kunwar Pal; Guo, Chunlei

2017-06-21

The nanochannel diameter and surface charge density have a significant impact on current-voltage characteristics in a nanofluidic transistor. We have simulated the effect of the channel diameter and surface charge density on current-voltage characteristics of a fluidic nanochannel with positive surface charge on its walls and a gate electrode on its surface. Anion depletion/enrichment leads to a decrease/increase in ion current with gate potential. The ion current tends to increase linearly with gate potential for narrow channels at high surface charge densities and narrow channels are more effective to control the ion current at high surface charge densities. The current-voltage characteristics are highly nonlinear for wide channels at low surface charge densities and they show different regions of current change with gate potential. The ion current decreases with gate potential after attaining a peak value for wide channels at low values of surface charge densities. At low surface charge densities, the ion current can be controlled by a narrow range of gate potentials for wide channels. The current change with source drain voltage shows ohmic, limiting and overlimiting regions.

Surface currents associated with external kink modes in tokamak plasmas during a major disruption

NASA Astrophysics Data System (ADS)

Ng, C. S.; Bhattacharjee, A.

2017-10-01

The surface current on the plasma-vacuum interface during a disruption event involving kink instability can play an important role in driving current into the vacuum vessel. However, there have been disagreements over the nature or even the sign of the surface current in recent theoretical calculations based on idealized step-function background plasma profiles. We revisit such calculations by replacing step-function profiles with more realistic profiles characterized by a strong but finite gradient along the radial direction. It is shown that the resulting surface current is no longer a delta-function current density, but a finite and smooth current density profile with an internal structure, concentrated within the region with a strong plasma pressure gradient. Moreover, this current density profile has peaks of both signs, unlike the delta-function case with a sign opposite to, or the same as the plasma current. We show analytically and numerically that such current density can be separated into two parts, with one of them, called the convective current density, describing the transport of the background plasma density by the displacement, and the other part that remains, called the residual current density. It is argued that consideration of both types of current density is important and can resolve past controversies.

(Project 13-5292) Correlating thermal and mechanical coupling based multiphysics behavior of nuclear materials through in-situ measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomar, Vikas

Irradiations and post characterization experiments were performed first on Zr samples. This step will help understand the effect of the 2.5% alloying elements on the behavior of Zircaloy-4 (PWR cladding material) when compared to pure Zr. Irradiation flux measurements and sample temperature calibrations were performed at different energies prior to the irradiation experiments. Irradiations were performed with two different energy regimes1: non-displacment energies and displacement energies. Time was also dedicated to optimize transmission electron microscopy (TEM) sample preparation conditions via electropolishing technique. This step is crucial to prepare TEM samples for the in-situ TEM/irradiation experiments (Year 2). In addition, Zircaloy-4more » samples are being prepared for irradiation, and a setup is built by one of our collaborators (Dr. Mert Efe) to prepare ultrafine (UF) and nanocrystalline (NC) Zircaloy-4 samples for comparison with the commercial Zircaloy-4 samples.« less

An exploratory study on emotion recognition in patients with a clinically isolated syndrome and multiple sclerosis.

PubMed

Jehna, Margit; Neuper, Christa; Petrovic, Katja; Wallner-Blazek, Mirja; Schmidt, Reinhold; Fuchs, Siegrid; Fazekas, Franz; Enzinger, Christian

2010-07-01

Multiple sclerosis (MS) is a chronic multifocal CNS disorder which can affect higher order cognitive processes. Whereas cognitive disturbances in MS are increasingly better characterised, emotional facial expression (EFE) has rarely been tested, despite its importance for adequate social behaviour. We tested 20 patients with a clinically isolated syndrome suggestive of MS (CIS) or MS and 23 healthy controls (HC) for the ability to differ between emotional facial stimuli, controlling for the influence of depressive mood (ADS-L). We screened for cognitive dysfunction using The Faces Symbol Test (FST). The patients demonstrated significant decreased reaction-times regarding emotion recognition tests compared to HC. However, the results also suggested worse cognitive abilities in the patients. Emotional and cognitive test results were correlated. This exploratory pilot study suggests that emotion recognition deficits might be prevalent in MS. However, future studies will be needed to overcome the limitations of this study. Copyright 2010 Elsevier B.V. All rights reserved.

Variation of magnetoimpedance of electrodeposited NiFe/Cu with deposition current density

NASA Astrophysics Data System (ADS)

Mishra, A. C.; Jha, A. K.

2017-12-01

An investigation about influence of deposition current density on electrodeposited magnetic film is reported in this paper. Ferromagnetic NiFe thin films were electrodeposited on copper wires of 100 μm diameter for various electrdepostion current densities ranging from 10 to 60 mA/cm2 maintaining equal thickness in all films. The composition of deposited film varied with deposition current density and in particular, a composition of Ni79Fe21 was achieved for a current density of 20 mA/cm2. The surface microstructure of the film deposited at the current density of 20 mA/cm2 was found to have excellent smoothness. The coercivity of the film was lowest and highest value of magnetoimpedance was measured for this film. The influence of current density on film composition and hence magnetic properties was attributed to the change of deposition mechanism.

Near-surface Density Currents Observed in the Southeast Pacific Stratocumulus-topped Marine Boundary Layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilbanks, Matt C.; Yuter, S. E.; de Szoeke, S.

2015-09-01

Density currents (i.e. cold pools or outflows) beneath marine stratocumulus clouds are characterized using a 30-d data set of ship-based observations obtained during the 2008 Variability of American Monsoon Systems (VAMOS) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in the southeast Pacific. An objective method identifies 71 density current fronts using an air density criterion and isolates each density current’s core (peak density) and tail (dissipating) zone. Compared to front and core zones, most density current tails exhibited weaker density gradients and wind anomalies elongated about the axis of the mean wind. The mean cloud-level advection relative to the surface layer windmore » (1.9 m s-1) nearly matches the mean density current propagation speed (1.8 m s-1). The similarity in speeds allows drizzle cells to deposit tails in their wakes. Based on high-resolution scanning Doppler lidar data, prefrontal updrafts had a mean intensity of 0.91 m s-1, reached an average altitude of 800 m, and were often surmounted by low-lying shelf clouds not connected to the overlying stratocumulus cloud. Nearly 90% of density currents were identified when C-band radar estimated 30-km diameter areal average rain rates exceeded 1 mm d-1. Rather than peaking when rain rates are highest overnight, density current occurrence peaks between 0600 and 0800 local solar time when enhanced local drizzle co-occurs with shallow subcloud dry and stable layers. The dry layers may contribute to density current formation by enhancing subcloud evaporation of drizzle. Density currents preferentially occur in regions of open cells but also occur in regions of closed cells.« less

Particle Image Velocimetry Study of Density Current Fronts

ERIC Educational Resources Information Center

Martin, Juan Ezequiel

2009-01-01

Gravity currents are flows that occur when a horizontal density difference causes fluid to move under the action of gravity; density currents are a particular case, for which the scalar causing the density difference is conserved. Flows with a strong effect of the horizontal density difference, even if only partially driven by it--such as the…

Correcting magnetic probe perturbations on current density measurements of current carrying plasmas.

PubMed

Knoblauch, P; Raspa, V; Di Lorenzo, F; Lazarte, A; Clausse, A; Moreno, C

2010-09-01

A method to infer the current density distribution in the current sheath of a plasma focus discharge from a magnetic probe is formulated and then applied to experimental data obtained in a 1.1 kJ device. Distortions on the magnetic probe signal caused by current redistribution and by a time-dependent total discharge current are considered simultaneously, leading to an integral equation for the current density. Two distinct, easy to implement, numerical procedures are given to solve such equation. Experimental results show the coexistence of at least two maxima in the current density structure of a nitrogen sheath.

Equity in adherence to and effect of prenatal food and micronutrient supplementation on child mortality: results from the MINIMat randomized trial, Bangladesh

PubMed Central

2014-01-01

Background Evidence is often missing on social differentials in effects of nutrition interventions. We evaluated the adherence to and effect of prenatal food and micronutrient supplementations on mortality before the age of five years in different social groups as defined by maternal schooling. Methods Data came from the MINIMat study (Maternal and Infant Nutrition Interventions, Matlab), a randomized trial of prenatal food supplementation (invitation early, about 9 weeks [E], or at usual time, about 20 weeks [U] of pregnancy) and 30 mg or 60 mg iron with 400 μgm folic acid, or multiple micronutrients (Fe30F, Fe60F, MMS) resulting in six randomization groups, EFe30F, UFe30F, EFe60F, UFe60F, EMMS, and UMMS (n = 4436). Included in analysis after omissions (fetal loss and out-migration) were 3625 women and 3659 live births of which 3591 had information on maternal schooling. The study site was rural Matlab, Bangladesh. The main stratifying variable was maternal schooling dichotomized as <6 years and ≥6 years. We used Cox proportional hazard model for survival analyses. Results Overall, women having <6 years of schooling adhered more to food (81 vs. 69 packets, P=0.0001) but a little less to micronutrient (104 vs. 120 capsules, P = 0.0001) supplementation compared to women having more schooling, adjusted for maternal age (years), parity and body mass index (BMI, kg/m2) at week 8 pregnancy. Children of mothers with ≥6 years of schooling had lower under-five mortality, but the EMMS supplementation reduced the social difference in mortality risk (using standard program and schooling <6 years as reference; standard program and schooling ≥6 years HR 0.54, 95% CI 0.27-1.11; EMMS and schooling ≥6 years HR 0.28, 95% CI 0.12-0.70; EMMS and schooling <6 years HR 0.26, 95% CI 0.11-0.63), adjusted for maternal age (years), parity and body mass index (kg/m2) at week 8 pregnancy. Conclusions The combination of an early invitation to prenatal food supplementation and multiple micronutrient supplementation lowered mortality in children before the age of five years and reduced the gap in child survival chances between social groups. The pattern of adherence to the supplementations was complex; women with less education adhered more to food supplementation while those with more education had higher adherence to micronutrients. Trial registration ISRCTN16581394. PMID:24393610

Impact of Te and ne on edge current density profiles in ELM mitigated regimes on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Dunne, M. G.; Rathgeber, S.; Burckhart, A.; Fischer, R.; Giannone, L.; McCarthy, P. J.; Schneider, P. A.; Wolfrum, E.; the ASDEX Upgrade Team

2015-01-01

ELM resolved edge current density profiles are reconstructed using the CLISTE equilibrium code. As input, highly spatially and temporally resolved edge electron temperature and density profiles are used in addition to data from the extensive set of external poloidal field measurements available at ASDEX Upgrade, flux loop difference measurements, and current measurements in the scrape-off layer. Both the local and flux surface averaged current density profiles are analysed for several ELM mitigation regimes. The focus throughout is on the impact of altered temperature and density profiles on the current density. In particular, many ELM mitigation regimes rely on operation at high density. Two reference plasmas with type-I ELMs are analysed, one with a deuterium gas puff and one without, in order to provide a reference for the behaviour in type-II ELMy regimes and high density ELM mitigation with external magnetic perturbations at ASDEX Upgrade. For type-II ELMs it is found that while a similar pedestal top pressure is sustained at the higher density, the temperature gradient decreases in the pedestal. This results in lower local and flux surface averaged current densities in these phases, which reduces the drive for the peeling mode. No significant differences between the current density measured in the type-I phase and ELM mitigated phase is seen when external perturbations are applied, though the pedestal top density was increased. Finally, ELMs during the nitrogen seeded phase of a high performance discharge are analysed and compared to ELMs in the reference phase. An increased pedestal pressure gradient, which is the source of confinement improvement in impurity seeded discharges, causes a local current density increase. However, the increased Zeff in the pedestal acts to reduce the flux surface averaged current density. This dichotomy, which is not observed in other mitigation regimes, could act to stabilize both the ballooning mode and the peeling mode at the same time.

Silicon-Based Lithium-Ion Capacitor for High Energy and High Power Application

NASA Technical Reports Server (NTRS)

Wu, James J.; Demattia, Brianne; Loyselle, Patricia; Reid, Concha; Kohout, Lisa

2017-01-01

Si-based Li-ion capacitor has been developed and demonstrated. The results show it is feasible to improve both power density and energy density in this configuration. The applied current density impacts the power and energy density: low current favors energy density while high current favors power density. Active carbon has a better rate capability than Si. Next StepsFuture Directions. Si electrode needs to be further studied and improved. Further optimization of SiAC ratio and evaluation of its impact on energy density and power density.

Fourier transform magnetic resonance current density imaging (FT-MRCDI) from one component of magnetic flux density.

PubMed

Ider, Yusuf Ziya; Birgul, Ozlem; Oran, Omer Faruk; Arikan, Orhan; Hamamura, Mark J; Muftuler, L Tugan

2010-06-07

Fourier transform (FT)-based algorithms for magnetic resonance current density imaging (MRCDI) from one component of magnetic flux density have been developed for 2D and 3D problems. For 2D problems, where current is confined to the xy-plane and z-component of the magnetic flux density is measured also on the xy-plane inside the object, an iterative FT-MRCDI algorithm is developed by which both the current distribution inside the object and the z-component of the magnetic flux density on the xy-plane outside the object are reconstructed. The method is applied to simulated as well as actual data from phantoms. The effect of measurement error on the spatial resolution of the current density reconstruction is also investigated. For 3D objects an iterative FT-based algorithm is developed whereby the projected current is reconstructed on any slice using as data the Laplacian of the z-component of magnetic flux density measured for that slice. In an injected current MRCDI scenario, the current is not divergence free on the boundary of the object. The method developed in this study also handles this situation.

In-vivo measurement of relationship between applied current amplitude and current density magnitude from 10 mA to 110 mA.

PubMed

DeMonte, Tim P; Wang, Dinghui; Ma, Weijing; Gao, Jia-Hong; Joy, Michael L G

2009-01-01

Current density imaging (CDI) is a magnetic resonance imaging (MRI) technique used to quantitatively measure current density vectors throughout the volume of an object/subject placed in the MRI system. Electrical current pulses are applied externally to the object/subject and are synchronized with the MRI sequence. In this work, CDI is used to measure average current density magnitude in the torso region of an in-vivo piglet for applied current pulse amplitudes ranging from 10 mA to 110 mA. The relationship between applied current amplitude and current density magnitude is linear in simple electronic elements such as wires and resistors; however, this relationship may not be linear in living tissue. An understanding of this relationship is useful for research in defibrillation, human electro-muscular incapacitation (e.g. TASER(R)) and other bioelectric stimulation devices. This work will show that the current amplitude to current density magnitude relationship is slightly nonlinear in living tissue in the range of 10 mA to 110 mA.

Space-charge-limited currents for cathodes with electric field enhanced geometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Dingguo, E-mail: laidingguo@nint.ac.cn; Qiu, Mengtong; Xu, Qifu

This paper presents the approximate analytic solutions of current density for annulus and circle cathodes. The current densities of annulus and circle cathodes are derived approximately from first principles, which are in agreement with simulation results. The large scaling laws can predict current densities of high current vacuum diodes including annulus and circle cathodes in practical applications. In order to discuss the relationship between current density and electric field on cathode surface, the existing analytical solutions of currents for concentric cylinder and sphere diodes are fitted from existing solutions relating with electric field enhancement factors. It is found that themore » space-charge-limited current density for the cathode with electric-field enhanced geometry can be written in a general form of J = g(β{sub E}){sup 2}J{sub 0}, where J{sub 0} is the classical (1D) Child-Langmuir current density, β{sub E} is the electric field enhancement factor, and g is the geometrical correction factor depending on the cathode geometry.« less

Current density imaging sequence for monitoring current distribution during delivery of electric pulses in irreversible electroporation.

PubMed

Serša, Igor; Kranjc, Matej; Miklavčič, Damijan

2015-01-01

Electroporation is gaining its importance in everyday clinical practice of cancer treatment. For its success it is extremely important that coverage of the target tissue, i.e. treated tumor, with electric field is within the specified range. Therefore, an efficient tool for the electric field monitoring in the tumor during delivery of electroporation pulses is needed. The electric field can be reconstructed by the magnetic resonance electric impedance tomography method from current density distribution data. In this study, the use of current density imaging with MRI for monitoring current density distribution during delivery of irreversible electroporation pulses was demonstrated. Using a modified single-shot RARE sequence, where four 3000 V and 100 μs long pulses were included at the start, current distribution between a pair of electrodes inserted in a liver tissue sample was imaged. Two repetitions of the sequence with phases of refocusing radiofrequency pulses 90° apart were needed to acquire one current density image. For each sample in total 45 current density images were acquired to follow a standard protocol for irreversible electroporation where 90 electric pulses are delivered at 1 Hz. Acquired current density images showed that the current density in the middle of the sample increased from first to last electric pulses by 60%, i.e. from 8 kA/m2 to 13 kA/m2 and that direction of the current path did not change with repeated electric pulses significantly. The presented single-shot RARE-based current density imaging sequence was used successfully to image current distribution during delivery of short high-voltage electric pulses. The method has a potential to enable monitoring of tumor coverage by electric field during irreversible electroporation tissue ablation.

Modeling of Optical Waveguide Poling and Thermally Stimulated Discharge (TSD) Charge and Current Densities for Guest/Host Electro Optic Polymers

NASA Technical Reports Server (NTRS)

Watson, Michael D.; Ashley, Paul R.; Abushagur, Mustafa

2004-01-01

A charge density and current density model of a waveguide system has been developed to explore the effects of electric field electrode poling. An optical waveguide may be modeled during poling by considering the dielectric charge distribution, polarization charge distribution, and conduction charge generated by the poling field. These charge distributions are the source of poling current densities. The model shows that boundary charge current density and polarization current density are the major source of currents measured during poling and thermally stimulated discharge These charge distributions provide insight into the poling mechanisms and are directly related to E(sub A), and, alpha(sub r). Initial comparisons with experimental data show excellent correlation to the model results.

Safety parameter considerations of anodal transcranial Direct Current Stimulation in rats.

PubMed

Jackson, Mark P; Truong, Dennis; Brownlow, Milene L; Wagner, Jessica A; McKinley, R Andy; Bikson, Marom; Jankord, Ryan

2017-08-01

A commonly referenced transcranial Direct Current Stimulation (tDCS) safety threshold derives from tDCS lesion studies in the rat and relies on electrode current density (and related electrode charge density) to support clinical guidelines. Concerns about the role of polarity (e.g. anodal tDCS), sub-lesion threshold injury (e.g. neuroinflammatory processes), and role of electrode montage across rodent and human studies support further investigation into animal models of tDCS safety. Thirty-two anesthetized rats received anodal tDCS between 0 and 5mA for 60min through one of three epicranial electrode montages. Tissue damage was evaluated using hemotoxylin and eosin (H&E) staining, Iba-1 immunohistochemistry, and computational brain current density modeling. Brain lesion occurred after anodal tDCS at and above 0.5mA using a 25.0mm 2 electrode (electrode current density: 20.0A/m 2 ). Lesion initially occurred using smaller 10.6mm 2 or 5.3mm 2 electrodes at 0.25mA (23.5A/m 2 ) and 0.5mA (94.2A/m 2 ), respectively. Histological damage was correlated with computational brain current density predictions. Changes in microglial phenotype occurred in higher stimulation groups. Lesions were observed using anodal tDCS at an electrode current density of 20.0A/m 2 , which is below the previously reported safety threshold of 142.9A/m 2 using cathodal tDCS. The lesion area is not simply predicted by electrode current density (and so not by charge density as duration was fixed); rather computational modeling suggests average brain current density as a better predictor for anodal tDCS. Nonetheless, under the assumption that rodent epicranial stimulation is a hypersensitive model, an electrode current density of 20.0A/m 2 represents a conservative threshold for clinical tDCS, which typically uses an electrode current density of 2A/m 2 when electrodes are placed on the skin (resulting in a lower brain current density). Copyright © 2017 Elsevier Inc. All rights reserved.

Breaking the current density threshold in spin-orbit-torque magnetic random access memory

NASA Astrophysics Data System (ADS)

Zhang, Yin; Yuan, H. Y.; Wang, X. S.; Wang, X. R.

2018-04-01

Spin-orbit-torque magnetic random access memory (SOT-MRAM) is a promising technology for the next generation of data storage devices. The main bottleneck of this technology is the high reversal current density threshold. This outstanding problem is now solved by a new strategy in which the magnitude of the driven current density is fixed while the current direction varies with time. The theoretical limit of minimal reversal current density is only a fraction (the Gilbert damping coefficient) of the threshold current density of the conventional strategy. The Euler-Lagrange equation for the fastest magnetization reversal path and the optimal current pulse is derived for an arbitrary magnetic cell and arbitrary spin-orbit torque. The theoretical limit of minimal reversal current density and current density for a GHz switching rate of the new reversal strategy for CoFeB/Ta SOT-MRAMs are, respectively, of the order of 105 A/cm 2 and 106 A/cm 2 far below 107 A/cm 2 and 108 A/cm 2 in the conventional strategy. Furthermore, no external magnetic field is needed for a deterministic reversal in the new strategy.

Optimal geometry toward uniform current density electrodes

NASA Astrophysics Data System (ADS)

Song, Yizhuang; Lee, Eunjung; Woo, Eung Je; Seo, Jin Keun

2011-07-01

Electrodes are commonly used to inject current into the human body in various biomedical applications such as functional electrical stimulation, defibrillation, electrosurgery, RF ablation, impedance imaging, and so on. When a highly conducting electrode makes direct contact with biological tissues, the induced current density has strong singularity along the periphery of the electrode, which may cause painful sensation or burn. Especially in impedance imaging methods such as the magnetic resonance electrical impedance tomography, we should avoid such singularity since more uniform current density underneath a current-injection electrode is desirable. In this paper, we study an optimal geometry of a recessed electrode to produce a well-distributed current density on the contact area under the electrode. We investigate the geometry of the electrode surface to minimize the edge singularity and produce nearly uniform current density on the contact area. We propose a mathematical framework for the uniform current density electrode and its optimal geometry. The theoretical results are supported by numerical simulations.

MgB2 wire diameter reduction by hot isostatic pressing—a route for enhanced critical current density

NASA Astrophysics Data System (ADS)

Morawski, A.; Cetner, T.; Gajda, D.; Zaleski, A. J.; Häßler, W.; Nenkov, K.; Rindfleisch, M. A.; Tomsic, M.; Przysłupski, P.

2018-07-01

The effect of wire diameter reduction on the critical current density of pristine MgB2 wire was studied. Wires were treated by a hot isostatic pressing method at 570 °C and at pressures of up to 1.1 GPa. It was found that the wire diameter reduction induces an increase of up to 70% in the mass density of the superconducting cores. This feature leads to increases in critical current, critical current density, and pinning force density. The magnitude and field dependence of the critical current density are related to both grain connectivity and structural defects, which act as effective pinning centers. High field transport properties were obtained without doping of the MgB2 phase. A critical current density jc of 3500 A mm‑2 was reached at 4 K, 6 T for the best sample, which was a five-fold increase compared to MgB2 samples synthesized at ambient pressure.

Correlation of ion and beam current densities in Kaufman thrusters.

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1973-01-01

In the absence of direct impingement erosion, electrostatic thruster accelerator grid lifetime is defined by the charge exchange erosion that occurs at peak values of the ion beam current density. In order to maximize the thrust from an engine with a specified grid lifetime, the ion beam current density profile should therefore be as flat as possible. Knauer (1970) has suggested this can be achieved by establishing a radial plasma uniformity within the thruster discharge chamber; his tests with the radial field thruster provide an example of uniform plasma properties within the chamber and a flat ion beam profile occurring together. It is shown that, in particular, the ion density profile within the chamber determines the beam current density profile, and that a uniform ion density profile at the screen grid end of the discharge chamber should lead to a flat beam current density profile.

Impact of crystal orientation on the modulation bandwidth of InGaN/GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Monavarian, M.; Rashidi, A.; Aragon, A. A.; Oh, S. H.; Rishinaramangalam, A. K.; DenBaars, S. P.; Feezell, D.

2018-01-01

High-speed InGaN/GaN blue light-emitting diodes (LEDs) are needed for future gigabit-per-second visible-light communication systems. Large LED modulation bandwidths are typically achieved at high current densities, with reports close to 1 GHz bandwidth at current densities ranging from 5 to 10 kA/cm2. However, the internal quantum efficiency (IQE) of InGaN/GaN LEDs is quite low at high current densities due to the well-known efficiency droop phenomenon. Here, we show experimentally that nonpolar and semipolar orientations of GaN enable higher modulation bandwidths at low current densities where the IQE is expected to be higher and power dissipation is lower. We experimentally compare the modulation bandwidth vs. current density for LEDs on nonpolar (10 1 ¯ 0 ), semipolar (20 2 ¯ 1 ¯) , and polar (" separators="|0001 ) orientations. In agreement with wavefunction overlap considerations, the experimental results indicate a higher modulation bandwidth for the nonpolar and semipolar LEDs, especially at relatively low current densities. At 500 A/cm2, the nonpolar LED has a 3 dB bandwidth of ˜1 GHz, while the semipolar and polar LEDs exhibit bandwidths of 260 MHz and 75 MHz, respectively. A lower carrier density for a given current density is extracted from the RF measurements for the nonpolar and semipolar LEDs, consistent with the higher wavefunction overlaps in these orientations. At large current densities, the bandwidth of the polar LED approaches that of the nonpolar and semipolar LEDs due to coulomb screening of the polarization field. The results support using nonpolar and semipolar orientations to achieve high-speed LEDs at low current densities.

Experimental study on magnetically insulated transmission line electrode surface evolution process under MA/cm current density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, PengFei; Qiu, Aici; State Key Laboratory of Intense Pulse Radiation of Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024

The design of high-current density magnetically insulated transmission line (MITL) is a difficult problem of current large-scale Z-pinch device. In particular, a thorough understanding of the MITL electrode surface evolution process under high current density is lacking. On the “QiangGuang-I” accelerator, the load area possesses a low inductance short-circuit structure with a diameter of 2.85 mm at the cathode, and three reflux columns with a diameter of 3 mm and uniformly distributed circumference at the anode. The length of the high density MITL area is 20 mm. A laser interferometer is used to assess and analyze the state of the MITL cathode andmore » anode gap, and their evolution process under high current density. Experimental results indicate that evident current loss is not observed in the current density area at pulse leading edge, and peak when the surface current density reaches MA/cm. Analysis on electrode surface working conditions indicates that when the current leading edge is at 71.5% of the peak, the total evaporation of MITL cathode structure can be realized by energy deposition caused by ohmic heating. The electrode state changes, and diffusion conditions are reflected in the laser interferometer image. The MITL cathode area mainly exists in metal vapor form. The metal vapor density in the cathode central region is higher than the upper limit of laser penetration density (∼4 × 10{sup 21}/cm{sup 3}), with an expansion velocity of ∼0.96 km/s. The metal vapor density in the electrode outer area may lead to evident distortion of fringes, and its expansion velocity is faster than that in the center area (1.53 km/s).« less

Influence of the current density on the electrochemical treatment of concentrated 1-butyl-3-methylimidazolium chloride solutions on diamond electrodes.

PubMed

Marcionilio, Suzana M L de Oliveira; Alves, Gisele M; E Silva, Rachel B Góes; Marques, Pablo J Lima; Maia, Poliana D; Neto, Brenno A D; Linares, José J

2016-10-01

This paper focuses on the influence of the current density treatment of a concentrated 1-butyl-3-methylimidazolium chloride (BMImCl) solution on an electrochemical reactor with a boron-doped diamond (BDD) anode. The decrease in the total organic carbon (TOC) and the BMImCl concentration demonstrate the capability of BDD in oxidizing ionic liquids (ILs) and further mineralizing (to CO2 and NO3 (-)) more rapidly at higher current densities in spite of the reduced current efficiency of the process. Moreover, the presence of Cl(-) led to the formation of oxychlorinated anions (mostly ClO3 (-) and ClO4 (-)) and, in combination with the ammonia generated in the cathode from the nitrate reduction, chloramines, more intensely at higher current density. Finally, the analysis of the intermediates formed revealed no apparent influence of the current density on the BMImCl degradation mechanism. The current density presents therefore a complex influence on the IL treatment process that is discussed throughout this paper.

Individual differences in transcranial electrical stimulation current density

PubMed Central

Russell, Michael J; Goodman, Theodore; Pierson, Ronald; Shepherd, Shane; Wang, Qiang; Groshong, Bennett; Wiley, David F

2013-01-01

Transcranial electrical stimulation (TCES) is effective in treating many conditions, but it has not been possible to accurately forecast current density within the complex anatomy of a given subject's head. We sought to predict and verify TCES current densities and determine the variability of these current distributions in patient-specific models based on magnetic resonance imaging (MRI) data. Two experiments were performed. The first experiment estimated conductivity from MRIs and compared the current density results against actual measurements from the scalp surface of 3 subjects. In the second experiment, virtual electrodes were placed on the scalps of 18 subjects to model simulated current densities with 2 mA of virtually applied stimulation. This procedure was repeated for 4 electrode locations. Current densities were then calculated for 75 brain regions. Comparison of modeled and measured external current in experiment 1 yielded a correlation of r = .93. In experiment 2, modeled individual differences were greatest near the electrodes (ten-fold differences were common), but simulated current was found in all regions of the brain. Sites that were distant from the electrodes (e.g. hypothalamus) typically showed two-fold individual differences. MRI-based modeling can effectively predict current densities in individual brains. Significant variation occurs between subjects with the same applied electrode configuration. Individualized MRI-based modeling should be considered in place of the 10-20 system when accurate TCES is needed. PMID:24285948

Characterizing a December 2005 density current event in the Chicago River, Chicago, Illinois

USGS Publications Warehouse

Garcia, C.M.; Jackson, P.R.; Oberg, K.A.; Johnson, K.K.; Garcia, M.H.

2007-01-01

During the winter months, the Chicago River in Chicago, Illinois is subject to bi-directional flows, and density currents are thought to be responsible for these flow variations. This paper presents detailed field measurements using three acoustic Doppler current profiler instruments and simultaneous water-quality measurements made during December 2005. Observations indicate that the formation of density currents within the Chicago River and density differences are mostly due to salinity differences between the North Branch and the main stem of the Chicago River, whereas temperature difference does not appreciably affect the creation of density currents. Sources of higher water temperature, conductivity, and salinity values should be addressed in future studies. ?? 2007 ASCE.

Method for determining transport critical current densities and flux penetration depth in bulk superconductors

NASA Technical Reports Server (NTRS)

Israelsson, Ulf E. (Inventor); Strayer, Donald M. (Inventor)

1992-01-01

A contact-less method for determining transport critical current density and flux penetration depth in bulk superconductor material. A compressor having a hollow interior and a plunger for selectively reducing the free space area for distribution of the magnetic flux therein are formed of superconductor material. Analytical relationships, based upon the critical state model, Maxwell's equations and geometrical relationships define transport critical current density and flux penetration depth in terms of the initial trapped magnetic flux density and the ratio between initial and final magnetic flux densities whereby data may be reliably determined by means of the simple test apparatus for evaluating the current density and flux penetration depth.

Effect of electrode sub-micron surface feature size on current generation of Shewanella oneidensis in microbial fuel cells

NASA Astrophysics Data System (ADS)

Ye, Zhou; Ellis, Michael W.; Nain, Amrinder S.; Behkam, Bahareh

2017-04-01

Microbial fuel cells (MFCs) are envisioned to serve as compact and sustainable sources of energy; however, low current and power density have hindered their widespread use. Introduction of 3D micro/nanostructures on the MFC anode is known to improve its performance by increasing the surface area available for bacteria attachment; however, the role of the feature size remains poorly understood. To delineate the role of feature size from the ensuing surface area increase, nanostructures with feature heights of 115 nm and 300 nm, both at a height to width aspect ratio of 0.3, are fabricated in a grid pattern on glassy carbon electrodes (GCEs). Areal current densities and bacteria attachment densities of the patterned and unpatterned GCEs are compared using Shewanella oneidensis Δbfe in a three-electrode bioreactor. The 115 nm features elicit a remarkable 40% increase in current density and a 78% increase in bacterial attachment density, whereas the GCE with 300 nm pattern does not exhibit significant change in current density or bacterial attachment density. The current density dependency on feature size is maintained over the entire 160 h experiment. Thus, optimally sized surface features have a substantial effect on current production that is independent of their effect on surface area.

Theoretical model and experimental investigation of current density boundary condition for welding arc study

NASA Astrophysics Data System (ADS)

Boutaghane, A.; Bouhadef, K.; Valensi, F.; Pellerin, S.; Benkedda, Y.

2011-04-01

This paper presents results of theoretical and experimental investigation of the welding arc in Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) processes. A theoretical model consisting in simultaneous resolution of the set of conservation equations for mass, momentum, energy and current, Ohm's law and Maxwell equation is used to predict temperatures and current density distribution in argon welding arcs. A current density profile had to be assumed over the surface of the cathode as a boundary condition in order to make the theoretical calculations possible. In stationary GTAW process, this assumption leads to fair agreement with experimental results reported in literature with maximum arc temperatures of ~21 000 K. In contrast to the GTAW process, in GMAW process, the electrode is consumable and non-thermionic, and a realistic boundary condition of the current density is lacking. For establishing this crucial boundary condition which is the current density in the anode melting electrode, an original method is setup to enable the current density to be determined experimentally. High-speed camera (3000 images/s) is used to get geometrical dimensions of the welding wire used as anode. The total area of the melting anode covered by the arc plasma being determined, the current density at the anode surface can be calculated. For a 330 A arc, the current density at the melting anode surface is found to be of 5 × 107 A m-2 for a 1.2 mm diameter welding electrode.

Definition of current density in the presence of a non-local potential.

PubMed

Li, Changsheng; Wan, Langhui; Wei, Yadong; Wang, Jian

2008-04-16

In the presence of a non-local potential arising from electron-electron interaction, the conventional definition of current density J(c) = (e/2m)([(p-eA)ψ](*)ψ-ψ(*)[(p-eA)ψ]) cannot satisfy the condition of current conservation, i.e., [Formula: see text] in the steady state. In order to solve this problem, we give a new definition of current density including the contribution due to the non-local potential. We show that the current calculated based on the new definition of current density conserves the current and is the same as that obtained from the Landauer-Büttiker formula. Examples are given to demonstrate our results.

Cathode-constriction and column-constriction in high current vacuum arcs subjected to an axial magnetic field

NASA Astrophysics Data System (ADS)

Zhang, Zaiqin; Ma, Hui; Liu, Zhiyuan; Geng, Yingsan; Wang, Jianhua

2018-04-01

The influence of the applied axial magnetic field on the current density distribution in the arc column and electrodes is intensively studied. However, the previous results only provide a qualitative explanation, which cannot quantitatively explain a recent experimental data on anode current density. The objective of this paper is to quantitatively determine the current constriction subjected to an axial magnetic field in high-current vacuum arcs according to the recent experimental data. A magnetohydrodynamic model is adopted to describe the high current vacuum arcs. The vacuum arc is in a diffuse arc mode with an arc current ranged from 6 kArms to 14 kArms and an axial magnetic field ranged from 20 mT to 110 mT. By a comparison of the recent experimental work of current density distribution on the anode, the modelling results show that there are two types of current constriction. On one hand, the current on the cathode shows a constriction, and this constriction is termed as the cathode-constriction. On the other hand, the current constricts in the arc column region, and this constriction is termed as the column-constriction. The cathode boundary is of vital importance in a quantitative model. An improved cathode constriction boundary is proposed. Under the improved boundary, the simulation results are in good agreement with the recent experimental data on the anode current density distribution. It is demonstrated that the current density distribution at the anode is sensitive to that at the cathode, so that measurements of the anode current density can be used, in combination with the vacuum arc model, to infer the cathode current density distribution.

Measurement of neoclassically predicted edge current density at ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Dunne, M. G.; McCarthy, P. J.; Wolfrum, E.; Fischer, R.; Giannone, L.; Burckhart, A.; the ASDEX Upgrade Team

2012-12-01

Experimental confirmation of neoclassically predicted edge current density in an ELMy H-mode plasma is presented. Current density analysis using the CLISTE equilibrium code is outlined and the rationale for accuracy of the reconstructions is explained. Sample profiles and time traces from analysis of data at ASDEX Upgrade are presented. A high time resolution is possible due to the use of an ELM-synchronization technique. Additionally, the flux-surface-averaged current density is calculated using a neoclassical approach. Results from these two separate methods are then compared and are found to validate the theoretical formula. Finally, several discharges are compared as part of a fuelling study, showing that the size and width of the edge current density peak at the low-field side can be explained by the electron density and temperature drives and their respective collisionality modifications.

A novel model for through-silicon via (TSV) filling process simulation considering three additives and current density effect

NASA Astrophysics Data System (ADS)

Wang, Fuliang; Zhao, Zhipeng; Wang, Feng; Wang, Yan; Nie, Nantian

2017-12-01

Through-silicon via (TSV) filling by electrochemical deposition is still a challenge for 3D IC packaging, and three-component additive systems (accelerator, suppressor, and leveler) were commonly used in the industry to achieve void-free filling. However, models considering three additive systems and the current density effect have not been fully studied. In this paper, a novel three-component model was developed to study the TSV filling mechanism and process, where the interaction behavior of the three additives (accelerator, suppressor, and leveler) were considered, and the adsorption, desorption, and consumption coefficient of the three additives were changed with the current density. Based on this new model, the three filling types (seam void, ‘V’ shape, and key hole) were simulated under different current density conditions, and the filling results were verified by experiments. The effect of the current density on the copper ion concentration, additives surface coverage, and local current density distribution during the TSV filling process were obtained. Based on the simulation and experimental results, the diffusion-adsorption-desorption-consumption competition behavior between the suppressor, the accelerator, and the leveler were discussed. The filling mechanisms under different current densities were also analyzed.

3-D time-domain induced polarization tomography: a new approach based on a source current density formulation

NASA Astrophysics Data System (ADS)

Soueid Ahmed, A.; Revil, A.

2018-04-01

Induced polarization (IP) of porous rocks can be associated with a secondary source current density, which is proportional to both the intrinsic chargeability and the primary (applied) current density. This gives the possibility of reformulating the time domain induced polarization (TDIP) problem as a time-dependent self-potential-type problem. This new approach implies a change of strategy regarding data acquisition and inversion, allowing major time savings for both. For inverting TDIP data, we first retrieve the electrical resistivity distribution. Then, we use this electrical resistivity distribution to reconstruct the primary current density during the injection/retrieval of the (primary) current between the current electrodes A and B. The time-lapse secondary source current density distribution is determined given the primary source current density and a distribution of chargeability (forward modelling step). The inverse problem is linear between the secondary voltages (measured at all the electrodes) and the computed secondary source current density. A kernel matrix relating the secondary observed voltages data to the source current density model is computed once (using the electrical conductivity distribution), and then used throughout the inversion process. This recovered source current density model is in turn used to estimate the time-dependent chargeability (normalized voltages) in each cell of the domain of interest. Assuming a Cole-Cole model for simplicity, we can reconstruct the 3-D distributions of the relaxation time τ and the Cole-Cole exponent c by fitting the intrinsic chargeability decay curve to a Cole-Cole relaxation model for each cell. Two simple cases are studied in details to explain this new approach. In the first case, we estimate the Cole-Cole parameters as well as the source current density field from a synthetic TDIP data set. Our approach is successfully able to reveal the presence of the anomaly and to invert its Cole-Cole parameters. In the second case, we perform a laboratory sandbox experiment in which we mix a volume of burning coal and sand. The algorithm is able to localize the burning coal both in terms of electrical conductivity and chargeability.

Statistical parametric mapping of LORETA using high density EEG and individual MRI: application to mismatch negativities in schizophrenia.

PubMed

Park, Hae-Jeong; Kwon, Jun Soo; Youn, Tak; Pae, Ji Soo; Kim, Jae-Jin; Kim, Myung-Sun; Ha, Kyoo-Seob

2002-11-01

We describe a method for the statistical parametric mapping of low resolution electromagnetic tomography (LORETA) using high-density electroencephalography (EEG) and individual magnetic resonance images (MRI) to investigate the characteristics of the mismatch negativity (MMN) generators in schizophrenia. LORETA, using a realistic head model of the boundary element method derived from the individual anatomy, estimated the current density maps from the scalp topography of the 128-channel EEG. From the current density maps that covered the whole cortical gray matter (up to 20,000 points), volumetric current density images were reconstructed. Intensity normalization of the smoothed current density images was used to reduce the confounding effect of subject specific global activity. After transforming each image into a standard stereotaxic space, we carried out statistical parametric mapping of the normalized current density images. We applied this method to the source localization of MMN in schizophrenia. The MMN generators, produced by a deviant tone of 1,200 Hz (5% of 1,600 trials) under the standard tone of 1,000 Hz, 80 dB binaural stimuli with 300 msec of inter-stimulus interval, were measured in 14 right-handed schizophrenic subjects and 14 age-, gender-, and handedness-matched controls. We found that the schizophrenic group exhibited significant current density reductions of MMN in the left superior temporal gyrus and the left inferior parietal gyrus (P < 0. 0005). This study is the first voxel-by-voxel statistical mapping of current density using individual MRI and high-density EEG. Copyright 2002 Wiley-Liss, Inc.

Dependences of contraction/expansion of stacking faults on temperature and current density in 4H-SiC p–i–n diodes

NASA Astrophysics Data System (ADS)

Okada, Aoi; Nishio, Johji; Iijima, Ryosuke; Ota, Chiharu; Goryu, Akihiro; Miyazato, Masaki; Ryo, Mina; Shinohe, Takashi; Miyajima, Masaaki; Kato, Tomohisa; Yonezawa, Yoshiyuki; Okumura, Hajime

2018-06-01

To investigate the mechanism of contraction/expansion behavior of Shockley stacking faults (SSFs) in 4H-SiC p–i–n diodes, the dependences of the SSF behavior on temperature and injection current density were investigated by electroluminescence image observation. We investigated the dependences of both triangle- and bar-shaped SSFs on the injection current density at four temperature levels. All SSFs in this study show similar temperature and injection current density dependences. We found that the expansion of SSFs at a high current density was converted to contraction at a certain value as the current decreased and that the value is temperature-dependent. It has been confirmed that SSF behavior, which was considered complex or peculiar, might be explained mainly by the energy change caused by SSFs.

Study of the time-resolved, 3-dimensional current density distribution in solid metallic liners at 1 MA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bott-Suzuki, S. C.; Cordaro, S. W.; Caballero Bendixsen, L. S.

We present a study of the time varying current density distribution in solid metallic liner experiments at the 1MA level. Measurements are taken using an array of magnetic field probes which provide 2D triangulation of the average centroid of the drive current in the load at 3 discrete axial positions. These data are correlated with gated optical self-emission imaging which directly images the breakdown and plasma formation region. Results show that the current density is azimuthally non-uniform, and changes significantly throughout the 100ns experimental timescale. Magnetic field probes show clearly motion of the current density around the liner azimuth overmore » 10ns timescales. If breakdown is initiated at one azimuthal location, the current density remains non-uniform even over large spatial extents throughout the current drive. The evolution timescales are suggestive of a resistive diffusion process or uneven current distributions among simultaneously formed but discrete plasma conduction paths.« less

Study of the time-resolved, 3-dimensional current density distribution in solid metallic liners at 1 MA

DOE PAGES

Bott-Suzuki, S. C.; Cordaro, S. W.; Caballero Bendixsen, L. S.; ...

2016-09-01

We present a study of the time varying current density distribution in solid metallic liner experiments at the 1MA level. Measurements are taken using an array of magnetic field probes which provide 2D triangulation of the average centroid of the drive current in the load at 3 discrete axial positions. These data are correlated with gated optical self-emission imaging which directly images the breakdown and plasma formation region. Results show that the current density is azimuthally non-uniform, and changes significantly throughout the 100ns experimental timescale. Magnetic field probes show clearly motion of the current density around the liner azimuth overmore » 10ns timescales. If breakdown is initiated at one azimuthal location, the current density remains non-uniform even over large spatial extents throughout the current drive. The evolution timescales are suggestive of a resistive diffusion process or uneven current distributions among simultaneously formed but discrete plasma conduction paths.« less

Zinc electrodeposition from flowing alkaline zincate solutions: Role of hydrogen evolution reaction

NASA Astrophysics Data System (ADS)

Dundálek, Jan; Šnajdr, Ivo; Libánský, Ondřej; Vrána, Jiří; Pocedič, Jaromír; Mazúr, Petr; Kosek, Juraj

2017-12-01

The hydrogen evolution reaction is known as a parasitic reaction during the zinc electrodeposition from alkaline zincate solutions and is thus responsible for current efficiency losses during the electrolysis. Besides that, the rising hydrogen bubbles may cause an extra convection within a diffusion layer, which leads to an enhanced mass transport of zincate ions to an electrode surface. In this work, the mentioned phenomena were studied experimentally in a flow through electrolyzer and the obtained data were subsequently evaluated by mathematical models. The results prove the indisputable influence of the rising hydrogen bubbles on the additional mixing of the diffusion layer, which partially compensates the drop of the current efficiency of the zinc deposition at higher current flows. Moreover, the results show that the current density ratio (i.e., the ratio of an overall current density to a zinc limiting current density) is not suitable for the description of the zinc deposition, because the hydrogen evolution current density is always involved in the overall current density.

Abnormalities of P300 cortical current density in unmedicated depressed patients revealed by LORETA analysis of event-related potentials.

PubMed

Kawasaki, Toshihiko; Tanaka, Shin; Wang, Jijun; Hokama, Hiroto; Hiramatsu, Kenichi

2004-02-01

The purpose of the present study was to investigate the neural substrates underlying event-related potential (ERP) abnormalities, with respect to the generators of the ERP components in depressed patients. Using an oddball paradigm, ERP from auditory stimuli were recorded from 22 unmedicated patients with current depressive episodes and compared with those from 22 age- and gender-matched normal controls. Cortical current densities of the N100 and P300 components were analyzed using low-resolution electromagnetic tomography (LORETA). Group differences in cortical current density were mapped on a 3-D cortex model. The results revealed that N100 cortical current densities did not differ between the two groups, while P300 cortical current densities were significantly lower in depressed patients over the bilateral temporal lobes, the left frontal region, and the right temporal-parietal area. Furthermore, the cortical area in which the group difference in P300 current density had been identified was remarkably larger over the right than the left hemisphere, thus supporting the hypothesis of right hemisphere dysfunction in depression.

High performance direct methanol fuel cell with thin electrolyte membrane

NASA Astrophysics Data System (ADS)

Wan, Nianfang

2017-06-01

A high performance direct methanol fuel cell is achieved with thin electrolyte membrane. 320 mW cm-2 of peak power density and over 260 mW cm-2 at 0.4 V are obtained when working at 90 °C with normal pressure air supply. It is revealed that the increased anode half-cell performance with temperature contributes primarily to the enhanced performance at elevated temperature. From the comparison of iR-compensated cathode potential of methanol/air with that of H2/air fuel cell, the impact of methanol crossover on cathode performance decreases with current density and becomes negligible at high current density. Current density is found to influence fuel efficiency and methanol crossover significantly from the measurement of fuel efficiency at different current density. At high current density, high fuel efficiency can be achieved even at high temperature, indicating decreased methanol crossover.

Modelling of the reactive sputtering process with non-uniform discharge current density and different temperature conditions

NASA Astrophysics Data System (ADS)

Vašina, P; Hytková, T; Eliáš, M

2009-05-01

The majority of current models of the reactive magnetron sputtering assume a uniform shape of the discharge current density and the same temperature near the target and the substrate. However, in the real experimental set-up, the presence of the magnetic field causes high density plasma to form in front of the cathode in the shape of a toroid. Consequently, the discharge current density is laterally non-uniform. In addition to this, the heating of the background gas by sputtered particles, which is usually referred to as the gas rarefaction, plays an important role. This paper presents an extended model of the reactive magnetron sputtering that assumes the non-uniform discharge current density and which accommodates the gas rarefaction effect. It is devoted mainly to the study of the behaviour of the reactive sputtering rather that to the prediction of the coating properties. Outputs of this model are compared with those that assume uniform discharge current density and uniform temperature profile in the deposition chamber. Particular attention is paid to the modelling of the radial variation of the target composition near transitions from the metallic to the compound mode and vice versa. A study of the target utilization in the metallic and compound mode is performed for two different discharge current density profiles corresponding to typical two pole and multipole magnetics available on the market now. Different shapes of the discharge current density were tested. Finally, hysteresis curves are plotted for various temperature conditions in the reactor.

A finite element analysis of the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in tDCS

NASA Astrophysics Data System (ADS)

Faria, Paula; Hallett, Mark; Cavaleiro Miranda, Pedro

2011-12-01

We investigated the effect of electrode area and inter-electrode distance on the spatial distribution of the current density in transcranial direct current stimulation (tDCS). For this purpose, we used the finite element method to compute the distribution of the current density in a four-layered spherical head model using various electrode montages, corresponding to a range of electrode sizes and inter-electrode distances. We found that smaller electrodes required slightly less current to achieve a constant value of the current density at a reference point on the brain surface located directly under the electrode center. Under these conditions, smaller electrodes also produced a more focal current density distribution in the brain, i.e. the magnitude of the current density fell more rapidly with distance from the reference point. The combination of two electrodes with different areas produced an asymmetric current distribution that could lead to more effective and localized neural modulation under the smaller electrode than under the larger one. Focality improved rapidly with decreasing electrode size when the larger electrode sizes were considered but the improvement was less marked for the smaller electrode sizes. Also, focality was not affected significantly by inter-electrode distance unless two large electrodes were placed close together. Increasing the inter-electrode distance resulted in decreased shunting of the current through the scalp and the cerebrospinal fluid, and decreasing electrode area resulted in increased current density on the scalp under the edges of the electrode. Our calculations suggest that when working with conventional electrodes (25-35 cm2), one of the electrodes should be placed just 'behind' the target relative to the other electrode, for maximum current density on the target. Also electrodes with areas in the range 3.5-12 cm2 may provide a better compromise between focality and current density in the scalp than the traditional electrodes. Finally, the use of multiple small return electrodes may be more efficient than the use of a single large return electrode.

Current density and catalyst-coated membrane resistance distribution of hydro-formed metallic bipolar plate fuel cell short stack with 250 cm2 active area

NASA Astrophysics Data System (ADS)

Haase, S.; Moser, M.; Hirschfeld, J. A.; Jozwiak, K.

2016-01-01

An automotive fuel cell with an active area of 250 cm2 is investigated in a 4-cell short stack with a current and temperature distribution device next to the bipolar plate with 560 current and 140 temperature segments. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this current scan shunt module. The applied fuel cell consists of bipolar plates constructed of 75-μm-thick, welded stainless-steel foils and a graphitic coating. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this module with a 6% deviation in in-plane conductivity. The current density distribution is evaluated up to 2.4 A cm-2. The entire cell's investigated volumetric power density is 4.7 kW l-1, and its gravimetric power density is 4.3 kW kg-1 at an average cell voltage of 0.5 V. The current density distribution is determined without influencing the operating cell. In addition, the current density distribution in the catalyst-coated membrane and its effective resistivity distribution with a finite volume discretisation of Ohm's law are evaluated. The deviation between the current density distributions in the catalyst-coated membrane and the bipolar plate is determined.

Time and space resolved current density mapping in three dimensions using magnetic field probe array in a high voltage coaxial gap

NASA Astrophysics Data System (ADS)

Cordaro, S. W.; Bott-Suzuki, S. C.

2017-12-01

We present an experimental analysis of the symmetry of current density in a coaxial geometry, diagnosed using a magnetic field probe array and calculations of the Fowler-Nordheim enhancement factor. Data were collected on the coaxial gap breakdown device (240 A, 25 kV, 150 ns, ˜0.1 Hz), and data from experiments using 2 different gap sizes and different penetration depths are compared over runs comprising 50 shots for each case. The magnetic field probe array quantifies the distribution of current density at three axial locations, on either sides of a vacuum breakdown, and tracks the evolution with time and space. The results show asymmetries in current density, which can be influenced by changes in the gap size and the penetration depth (of the center electrode into the outer electrode). For smaller gap sizes (400 μm), symmetric current profiles were not observed, and the change in the penetration depth changes both the symmetric behavior of the current density and the enhancement factor. For larger gaps (900 μm), current densities were typically more uniform and less influenced by the penetration depth, which is reflected in the enhancement factor values. It is possible that the change in inductance caused by the localization of current densities plays a role in the observed behavior.

Growth and characterization of high current density, high-speed InAs/AlSb resonant tunneling diodes

NASA Technical Reports Server (NTRS)

Soderstrom, J. R.; Brown, E. R.; Parker, C. D.; Mahoney, L. J.; Yao, J. Y.

1991-01-01

InAs/AlSb double-barrier resonant tunneling diodes with peak current densities up to 370,000 A/sq cm and high peak-to-valley current ratios of 3.2 at room temperature have been fabricated. The peak current density is well-explained by a stationary-state transport model with the two-band envelope function approximation. The valley current density predicted by this model is less than the experimental value by a factor that is typical of the discrepancy found in other double-barrier structures. It is concluded that threading dislocations are largely inactive in the resonant tunneling process.

Software Toolbox for Low-Frequency Conductivity and Current Density Imaging Using MRI.

PubMed

Sajib, Saurav Z K; Katoch, Nitish; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2017-11-01

Low-frequency conductivity and current density imaging using MRI includes magnetic resonance electrical impedance tomography (MREIT), diffusion tensor MREIT (DT-MREIT), conductivity tensor imaging (CTI), and magnetic resonance current density imaging (MRCDI). MRCDI and MREIT provide current density and isotropic conductivity images, respectively, using current-injection phase MRI techniques. DT-MREIT produces anisotropic conductivity tensor images by incorporating diffusion weighted MRI into MREIT. These current-injection techniques are finding clinical applications in diagnostic imaging and also in transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and electroporation where treatment currents can function as imaging currents. To avoid adverse effects of nerve and muscle stimulations due to injected currents, conductivity tensor imaging (CTI) utilizes B1 mapping and multi-b diffusion weighted MRI to produce low-frequency anisotropic conductivity tensor images without injecting current. This paper describes numerical implementations of several key mathematical functions for conductivity and current density image reconstructions in MRCDI, MREIT, DT-MREIT, and CTI. To facilitate experimental studies of clinical applications, we developed a software toolbox for these low-frequency conductivity and current density imaging methods. This MR-based conductivity imaging (MRCI) toolbox includes 11 toolbox functions which can be used in the MATLAB environment. The MRCI toolbox is available at http://iirc.khu.ac.kr/software.html . Its functions were tested by using several experimental datasets, which are provided together with the toolbox. Users of the toolbox can focus on experimental designs and interpretations of reconstructed images instead of developing their own image reconstruction softwares. We expect more toolbox functions to be added from future research outcomes. Low-frequency conductivity and current density imaging using MRI includes magnetic resonance electrical impedance tomography (MREIT), diffusion tensor MREIT (DT-MREIT), conductivity tensor imaging (CTI), and magnetic resonance current density imaging (MRCDI). MRCDI and MREIT provide current density and isotropic conductivity images, respectively, using current-injection phase MRI techniques. DT-MREIT produces anisotropic conductivity tensor images by incorporating diffusion weighted MRI into MREIT. These current-injection techniques are finding clinical applications in diagnostic imaging and also in transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and electroporation where treatment currents can function as imaging currents. To avoid adverse effects of nerve and muscle stimulations due to injected currents, conductivity tensor imaging (CTI) utilizes B1 mapping and multi-b diffusion weighted MRI to produce low-frequency anisotropic conductivity tensor images without injecting current. This paper describes numerical implementations of several key mathematical functions for conductivity and current density image reconstructions in MRCDI, MREIT, DT-MREIT, and CTI. To facilitate experimental studies of clinical applications, we developed a software toolbox for these low-frequency conductivity and current density imaging methods. This MR-based conductivity imaging (MRCI) toolbox includes 11 toolbox functions which can be used in the MATLAB environment. The MRCI toolbox is available at http://iirc.khu.ac.kr/software.html . Its functions were tested by using several experimental datasets, which are provided together with the toolbox. Users of the toolbox can focus on experimental designs and interpretations of reconstructed images instead of developing their own image reconstruction softwares. We expect more toolbox functions to be added from future research outcomes.

Reineke’s stand density index: a quantitative and non-unitless measure of stand density

Treesearch

Curtis L. VanderSchaaf

2013-01-01

When used as a measure of relative density, Reineke’s stand density index (SDI) can be made unitless by relating the current SDI to a standard density but when used as a quantitative measure of stand density SDI is not unitless. Reineke’s SDI relates the current stand density to an equivalent number of trees per unit area in a stand with a quadratic mean diameter (Dq)...

Defect Related Dark Currents in III-V MWIR nBn Detectors

DTIC Science & Technology

2014-01-01

theory indicates a thermal activation energy of half the bandgap, and a direct proportionality between dark current density and defect density. 2.2...density due to defects maintains a full bandgap thermal activation energy , and is proportional to the square root of the defect density. Although neutral...photodiodes, and cooling is more efficient in reducing nBn’s dark current due to the full bandgap activation energy . Downloaded From: http

Enhancing critical current density of cuprate superconductors

DOEpatents

Chaudhari, Praveen

2015-06-16

The present invention concerns the enhancement of critical current densities in cuprate superconductors. Such enhancement of critical current densities include using wave function symmetry and restricting movement of Abrikosov (A) vortices, Josephson (J) vortices, or Abrikosov-Josephson (A-J) vortices by using the half integer vortices associated with d-wave symmetry present in the grain boundary.

Charge and Spin Currents in Open-Shell Molecules:  A Unified Description of NMR and EPR Observables.

PubMed

Soncini, Alessandro

2007-11-01

The theory of EPR hyperfine coupling tensors and NMR nuclear magnetic shielding tensors of open-shell molecules in the limit of vanishing spin-orbit coupling (e.g., for organic radicals) is analyzed in terms of spin and charge current density vector fields. The ab initio calculation of the spin and charge current density response has been implemented at the Restricted Open-Shell Hartree-Fock, Unrestricted Hartree-Fock, and unrestricted GGA-DFT level of theory. On the basis of this formalism, we introduce the definition of nuclear hyperfine coupling density, a scalar function of position providing a partition of the EPR observable over the molecular domain. Ab initio maps of spin and charge current density and hyperfine coupling density for small radicals are presented and discussed in order to illustrate the interpretative advantages of the newly introduced approach. Recent NMR experiments providing evidence for the existence of diatropic ring currents in the open-shell singlet pancake-bonded dimer of the neutral phenalenyl radical are directly assessed via the visualization of the induced current density.

Linear calculations of edge current driven kink modes with BOUT++ code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, G. Q., E-mail: ligq@ipp.ac.cn; Xia, T. Y.; Lawrence Livermore National Laboratory, Livermore, California 94550

This work extends previous BOUT++ work to systematically study the impact of edge current density on edge localized modes, and to benchmark with the GATO and ELITE codes. Using the CORSICA code, a set of equilibria was generated with different edge current densities by keeping total current and pressure profile fixed. Based on these equilibria, the effects of the edge current density on the MHD instabilities were studied with the 3-field BOUT++ code. For the linear calculations, with increasing edge current density, the dominant modes are changed from intermediate-n and high-n ballooning modes to low-n kink modes, and the linearmore » growth rate becomes smaller. The edge current provides stabilizing effects on ballooning modes due to the increase of local shear at the outer mid-plane with the edge current. For edge kink modes, however, the edge current does not always provide a destabilizing effect; with increasing edge current, the linear growth rate first increases, and then decreases. In benchmark calculations for BOUT++ against the linear results with the GATO and ELITE codes, the vacuum model has important effects on the edge kink mode calculations. By setting a realistic density profile and Spitzer resistivity profile in the vacuum region, the resistivity was found to have a destabilizing effect on both the kink mode and on the ballooning mode. With diamagnetic effects included, the intermediate-n and high-n ballooning modes can be totally stabilized for finite edge current density.« less

Multi-species genetic connectivity in a terrestrial habitat network.

PubMed

Marrotte, Robby R; Bowman, Jeff; Brown, Michael G C; Cordes, Chad; Morris, Kimberley Y; Prentice, Melanie B; Wilson, Paul J

2017-01-01

Habitat fragmentation reduces genetic connectivity for multiple species, yet conservation efforts tend to rely heavily on single-species connectivity estimates to inform land-use planning. Such conservation activities may benefit from multi-species connectivity estimates, which provide a simple and practical means to mitigate the effects of habitat fragmentation for a larger number of species. To test the validity of a multi-species connectivity model, we used neutral microsatellite genetic datasets of Canada lynx ( Lynx canadensis ), American marten ( Martes americana ), fisher ( Pekania pennanti ), and southern flying squirrel ( Glaucomys volans ) to evaluate multi-species genetic connectivity across Ontario, Canada. We used linear models to compare node-based estimates of genetic connectivity for each species to point-based estimates of landscape connectivity (current density) derived from circuit theory. To our knowledge, we are the first to evaluate current density as a measure of genetic connectivity. Our results depended on landscape context: habitat amount was more important than current density in explaining multi-species genetic connectivity in the northern part of our study area, where habitat was abundant and fragmentation was low. In the south however, where fragmentation was prevalent, genetic connectivity was correlated with current density. Contrary to our expectations however, locations with a high probability of movement as reflected by high current density were negatively associated with gene flow. Subsequent analyses of circuit theory outputs showed that high current density was also associated with high effective resistance, underscoring that the presence of pinch points is not necessarily indicative of gene flow. Overall, our study appears to provide support for the hypothesis that landscape pattern is important when habitat amount is low. We also conclude that while current density is proportional to the probability of movement per unit area, this does not imply increased gene flow, since high current density tends to be a result of neighbouring pixels with high cost of movement (e.g., low habitat amount). In other words, pinch points with high current density appear to constrict gene flow.

Ultra-High Intensity Magnetic Field Generation in Dense Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisch, Nathaniel J.

2014-01-08

The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereas the efficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new formsmore » of current drive in regimes appropriate for new fusion concepts.« less

Influence of γ-phase on corrosion resistance of Zn–Ni alloy electrodeposition from acetate electrolytic bath

NASA Astrophysics Data System (ADS)

Selvaraju, V.; Thangaraj, V.

2018-05-01

The electrodeposition of Zn–Ni alloy containing 10% to 15% nickel was deposited from acetate electrolytic bath. The effect of current density, pH, temperature, cathodic current efficiency on the deposition of Zn–Ni alloy and the throwing power ability of the solution was investigated. The composition of the deposits and the morphology were strongly influenced by the temperature and applied current density. Corrosion resistance of a Zn–Ni alloy deposit was increases with the increase of current density. Zn–Ni alloy deposits shows higher corrosion resistance at optimum current density of 3.0 A dm‑2. X-Ray diffraction measurement confirms the presence of γ –phase Zn–Ni alloy deposition. The XRD reflection of Zn–Ni (831) was found to be increased with increase in current density. SEM studies reveal that the nanovial structure of Zn–Ni alloy deposited at 3.0 A dm‑2 gives high protection against corrosion.

Numerical simulation of inductive method for determining spatial distribution of critical current density

NASA Astrophysics Data System (ADS)

Kamitani, A.; Takayama, T.; Tanaka, A.; Ikuno, S.

2010-11-01

The inductive method for measuring the critical current density jC in a high-temperature superconducting (HTS) thin film has been investigated numerically. In order to simulate the method, a non-axisymmetric numerical code has been developed for analyzing the time evolution of the shielding current density. In the code, the governing equation of the shielding current density is spatially discretized with the finite element method and the resulting first-order ordinary differential system is solved by using the 5th-order Runge-Kutta method with an adaptive step-size control algorithm. By using the code, the threshold current IT is evaluated for various positions of a coil. The results of computations show that, near a film edge, the accuracy of the estimating formula for jC is remarkably degraded. Moreover, even the proportional relationship between jC and IT will be lost there. Hence, the critical current density near a film edge cannot be estimated by using the inductive method.

Effects of Current Density on Microstructure and Corrosion Property of Coating on AZ31 Mg Alloy Processed via Plasma Electrolytic Oxidation

NASA Astrophysics Data System (ADS)

Lee, Kang Min; Einkhah, Feryar; Sani, Mohammad Ali Faghihi; Ko, Young Gun; Shin, Dong Hyuk

The effects of the current density on the micro structure and the corrosion property of the coating on AZ31 Mg alloy processed by the plasma electrolytic oxidation (PEO) were investigated. The present coatings were produced in an acid electrolyte containing K2ZrF6 with three different current densities, i.e., 100, 150, and 200 mA/cm2. From the microstructural observations, as the applied current density was increased, the diameter of micro-pores formed by the plasma discharges with high temperature increased. The coatings on AZ31 Mg alloy were mainly composed of MgO, ZrO2, MgF2, and Mg2Zr5O12 phases. The results of potentiodynamic polarization clearly showed that the PEO-treated AZ31 Mg alloy applied at 100 mA/cm2 of current density exhibited better corrosion properties than the others.

Properties of micro-arc oxidation coatings on aluminum alloy at different negative peak current densities

NASA Astrophysics Data System (ADS)

Gu, Xin; Jiang, Bailing; Li, Hongtao; Liu, Cancan; Shao, Lianlian

2018-05-01

Micro-arc oxidation coatings were fabricated on 6061 aluminum alloy using whereby bipolar pulse mode in the case of different negative peak current densities. The phase composition, microstructures and wear properties were studied using x-ray diffraction, scanning electron microscopy and ball-on-disk wear tester, respectively. As results indicate, by virtue of negative peak current density, the oxygen can be expelled by produced hydrogen on anode in the case of negative pulse width and via the opened discharge channel. The results of x-ray diffraction, surface and cross-sectional morphology indicated that the coating was structured compactly taking on less small-diameter micro-pores and defects with negative peak current density of 75 A dm‑2. Additionally, as the results of wear tracks and weight loss bespeak, by virtue of appropriate negative peak current density, coatings resisted the abrasive wear and showed excellent wear resistance.

Anodic Oxidation of Carbon Steel at High Current Densities and Investigation of Its Corrosion Behavior

NASA Astrophysics Data System (ADS)

Fattah-Alhosseini, Arash; Khan, Hamid Yazdani

2017-06-01

This work aims at studying the influence of high current densities on the anodization of carbon steel. Anodic protective coatings were prepared on carbon steel at current densities of 100, 125, and 150 A/dm2 followed by a final heat treatment. Coatings microstructures and morphologies were analyzed using X-ray diffraction (XRD) and scanning electron microscope (SEM). The corrosion resistance of the uncoated carbon steel substrate and the anodic coatings were evaluated in 3.5 wt pct NaCl solution through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results showed that the anodic oxide coatings which were prepared at higher current densities had thicker coatings as a result of a higher anodic forming voltage. Therefore, the anodized coatings showed better anti-corrosion properties compared to those obtained at lower current densities and the base metal.

Synthesis of thoria nano-particles at low temperature through base electrogeneration on steel 316L surface: Effect of current density

NASA Astrophysics Data System (ADS)

Yousefi, Taher; Torab-Mostaedi, Meisam; Mobtaker, Hossein Ghasemi; Keshtkar, Ali Reza

2016-10-01

The strategy developed in this study, offers significant advantages (simplicity and cleanness of method and also a product purity and new morphology of the product) over the conventional routes for the synthesis of ThO2 nanostructure. The effect of current density on morphology was studied. The synthesized powder was characterized by means of Powder X-ray Diffraction (PXRD), Transmission Electron Microscopy (TEM, Phillips EM 2085) Brunauer-Emmett-Teller (BET) and Fourier Transform Infrared (FT-IR) spectroscopy. The results show that the current density has a great effect on the morphology of the samples. The average size of the particles decreases as the applied current density increases and the average size of the samples decreases from 50 to 15 nm when the current density increases from 2 to 5 mA cm-2.

Electron density profile measurements at a self-focusing ion beam with high current density and low energy extracted through concave electrodes.

PubMed

Fujiwara, Y; Hirano, Y; Kiyama, S; Nakamiya, A; Koguchi, H; Sakakita, H

2014-02-01

The self-focusing phenomenon has been observed in a high current density and low energy ion beam. In order to study the mechanism of this phenomenon, a special designed double probe to measure the electron density and temperature is installed into the chamber where the high current density ion beam is injected. Electron density profile is successfully measured without the influence of the ion beam components. Estimated electron temperature and density are ∼0.9 eV and ∼8 × 10(8) cm(-3) at the center of ion beam cross section, respectively. It was found that a large amount of electrons are spontaneously accumulated in the ion beam line in the case of self-forcing state.

Electron dynamics inside a vacuum tube diode through linear differential equations

NASA Astrophysics Data System (ADS)

González, Gabriel; Orozco, Fco. Javier González; Orozco

2014-04-01

In this paper we analyze the motion of charged particles in a vacuum tube diode by solving linear differential equations. Our analysis is based on expressing the volume charge density as a function of the current density and coordinates only, i.e. ρ=ρ(J,z), while in the usual scheme the volume charge density is expressed as a function of the current density and electrostatic potential, i.e. ρ=ρ(J,V). We show that, in the case of slow varying charge density, the space-charge-limited current is reduced up to 50%. Our approach gives the well-known behavior of the classical current density proportional to the three-halves power of the bias potential and inversely proportional to the square of the gap distance between electrodes, and does not require the solution of the nonlinear differential equation normally associated with the Child-Langmuir formulation.

Azimuthal swirl in liquid metal electrodes and batteries

NASA Astrophysics Data System (ADS)

Ashour, Rakan; Kelley, Douglas

2016-11-01

Liquid metal batteries consist of two molten metals with different electronegativity separated by molten salt. In these batteries, critical performance related factors such as the limiting current density are governed by fluid mixing in the positive electrode. In this work we present experimental results of a swirling flow in a layer of molten lead-bismuth alloy driven by electrical current. Using in-situ ultrasound velocimetery, we show that poloidal circulation appears at low current density, whereas azimuthal swirl becomes dominant at higher current density. The presence of thermal gradients produces buoyant forces, which are found to compete with those produced by current injection. Taking the ratio of the characteristic electromagnetic to buoyant flow velocity, we are able to predict the current density at which the flow becomes electromagnetically driven. Scaling arguments are also used to show that swirl is generated through self-interaction between the electrical current in the electrode with its own magnetic field.

Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawakami, S.; Ohno, N.; Shibata, Y.

2013-11-15

According to an early work [Y. Shibata et al., Nucl. Fusion 50, 025015 (2010)] on the behavior of the plasma current decay in the JT-60U disruptive discharges caused by the radiative collapse with a massive neon-gas-puff, the increase of the internal inductance mainly determined the current decay time of plasma current during the initial phase of current quench. To investigate what determines the increase of the internal inductance, we focus attention on the relationship between the electron temperature (or the resistivity) profile and the time evolution of the current density profile and carry out numerical calculations. As a result, wemore » find the reason of the increase of the internal inductance: The current density profile at the start of the current quench is broader than an expected current density profile in the steady state, which is determined by the temperature (or resistivity) profile. The current density profile evolves into peaked one and the internal inductance is increasing.« less

Synthesis of zinc oxide nanostructures on graphene/glass substrate by electrochemical deposition: effects of current density and temperature.

PubMed

Hambali, Nur Ashikyn; Yahaya, Hafizal; Mahmood, Mohamad Rusop; Terasako, Tomoaki; Hashim, Abdul Manaf

2014-01-01

The electrochemical growth of zinc oxide (ZnO) nanostructures on graphene on glass using zinc nitrate hexahydrate was studied. The effects of current densities and temperatures on the morphological, structural, and optical properties of the ZnO structures were studied. Vertically aligned nanorods were obtained at a low temperature of 75°C, and the diameters increased with current density. Growth temperature seems to have a strong effect in generating well-defined hexagonal-shape nanorods with a smooth top edge surface. A film-like structure was observed for high current densities above -1.0 mA/cm(2) and temperatures above 80°C due to the coalescence between the neighboring nanorods with large diameter. The nanorods grown at a temperature of 75°C with a low current density of -0.1 mA/cm(2) exhibited the highest density of 1.45 × 10(9) cm(-2). X-ray diffraction measurements revealed that the grown ZnO crystallites were highly oriented along the c-axis. The intensity ratio of the ultraviolet (UV) region emission to the visible region emission, I UV/I VIS, showed a decrement with the current densities for all grown samples. The samples grown at the current density below -0.5 mA/cm(2) showed high I UV/I VIS values closer to or higher than 1.0, suggesting their fewer structural defects. For all the ZnO/graphene structures, the high transmittance up to 65% was obtained at the light wavelength of 550 nm. Structural and optical properties of the grown ZnO structures seem to be effectively controlled by the current density rather than the growth temperature. ZnO nanorod/graphene hybrid structure on glass is expected to be a promising structure for solar cell which is a conceivable candidate to address the global need for an inexpensive alternative energy source.

Evaluation of a Magnetically-Filtered Faraday Probe for Measuring the ion Current Density Profile of a Hall Thruster

DTIC Science & Technology

2004-07-01

The ability of a magnetically-filtered Faraday probe (MFFP) to obtain the ion current density profile of a Hall thruster is investigated. The MFFP is...MFFP, boxed Faraday probe (BFP), and nude Faraday probe are used to measure the ion current density profile of a 5 kW Hall thruster operated over the

LORETA current source density for duration mismatch negativity and neuropsychological assessment in early schizophrenia.

PubMed

Miyanishi, Tomohiro; Sumiyoshi, Tomiki; Higuchi, Yuko; Seo, Tomonori; Suzuki, Michio

2013-01-01

Patients with schizophrenia elicit cognitive decline from the early phase of the illness. Mismatch negativity (MMN) has been shown to be associated with cognitive function. We investigated the current source density of duration mismatch negativity (dMMN), by using low-resolution brain electromagnetic tomography (LORETA), and neuropsychological performance in subjects with early schizophrenia. Data were obtained from 20 patients meeting DSM-IV criteria for schizophrenia or schizophreniform disorder, and 20 healthy control (HC) subjects. An auditory odd-ball paradigm was used to measure dMMN. Neuropsychological performance was evaluated by the brief assessment of cognition in schizophrenia Japanese version (BACS-J). Patients showed smaller dMMN amplitudes than those in the HC subjects. LORETA current density for dMMN was significantly lower in patients compared to HC subjects, especially in the temporal lobes. dMMN current density in the frontal lobe was positively correlated with working memory performance in patients. This is the first study to identify brain regions showing smaller dMMN current density in early schizophrenia. Further, poor working memory was associated with decreased dMMN current density in patients. These results are likely to help understand the neural basis for cognitive impairment of schizophrenia.

Fully non-inductive plasma start-up with lower-hybrid waves using the outboard-launch and top-launch antennas on the TST-2 spherical tokamak

NASA Astrophysics Data System (ADS)

Tsujii, Naoto; Takase, Yuichi; Ejiri, Akira; Shinya, Takahiro; Yajima, Satoru; Yamazaki, Hibiki; Togashi, Hiro; Moeller, Charles P.; Roidl, Benedikt; Takahashi, Wataru; Toida, Kazuya; Yoshida, Yusuke

2017-10-01

Removal of the central solenoid is essential to realize an economical spherical tokamak fusion reactor, but non-inductive plasma start-up is a challenge. On the TST-2 spherical tokamak, non-inductive plasma start-up using lower-hybrid (LH) waves has been investigated. Using the capacitively-coupled combline (CCC) antenna installed at the outboard midplane, fully non-inductive plasma current ramp-up up to a quarter of that of the typical Ohmic discharges has been achieved. Although it was desirable to keep the density low during the plasma current ramp-up to avoid the LH density limit, it was recognized that there was a maximum current density that could be carried by a given electron density. Since the density needed to increase as the plasma current was ramped-up, the achievable plasma current was limited by the maximum operational toroidal field of TST-2. The top-launch CCC antenna was installed to access higher density with up-shift of the parallel index of refraction. Numerical analysis of LH current drive with the outboard-launch and top-launch antennas was performed and the results were qualitatively consistent with the experimental observations.

Shot-to-shot reproducibility of a self-magnetically insulated ion diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pushkarev, A. I.; Isakova, Yu. I.; Khailov, I. P.

In this paper we present the analysis of shot to shot reproducibility of the ion beam which is formed by a self-magnetically insulated ion diode with an explosive emission graphite cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: the first pulse is of negative polarity (300-500 ns, 100-150 kV), and this is followed by a second pulse of positive polarity (150 ns, 250-300 kV). The ion current density was 10-70 A/cm{sup 2} depending on the diode geometry. The beam was composed from carbon ions (80%-85%) and protons. It was found that shot to shotmore » variation in the ion current density was about 35%-40%, whilst the diode voltage and current were comparatively stable with the variation limited to no more than 10%. It was shown that focusing of the ion beam can improve the stability of the ion current generation and reduces the variation to 18%-20%. In order to find out the reason for the shot-to-shot variation in ion current density we examined the statistical correlation between the current density of the accelerated beam and other measured characteristics of the diode, such as the accelerating voltage, total current, and first pulse duration. The correlation between the ion current density measured simultaneously at different positions within the cross-section of the beam was also investigated. It was shown that the shot-to-shot variation in ion current density is mainly attributed to the variation in the density of electrons diffusing from the drift region into the A-K gap.« less

Shot-to-shot reproducibility of a self-magnetically insulated ion diode.

PubMed

Pushkarev, A I; Isakova, Yu I; Khailov, I P

2012-07-01

In this paper we present the analysis of shot to shot reproducibility of the ion beam which is formed by a self-magnetically insulated ion diode with an explosive emission graphite cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: the first pulse is of negative polarity (300-500 ns, 100-150 kV), and this is followed by a second pulse of positive polarity (150 ns, 250-300 kV). The ion current density was 10-70 A/cm(2) depending on the diode geometry. The beam was composed from carbon ions (80%-85%) and protons. It was found that shot to shot variation in the ion current density was about 35%-40%, whilst the diode voltage and current were comparatively stable with the variation limited to no more than 10%. It was shown that focusing of the ion beam can improve the stability of the ion current generation and reduces the variation to 18%-20%. In order to find out the reason for the shot-to-shot variation in ion current density we examined the statistical correlation between the current density of the accelerated beam and other measured characteristics of the diode, such as the accelerating voltage, total current, and first pulse duration. The correlation between the ion current density measured simultaneously at different positions within the cross-section of the beam was also investigated. It was shown that the shot-to-shot variation in ion current density is mainly attributed to the variation in the density of electrons diffusing from the drift region into the A-K gap.

Cortical inhibition and excitation by bilateral transcranial alternating current stimulation.

PubMed

Cancelli, Andrea; Cottone, Carlo; Zito, Giancarlo; Di Giorgio, Marina; Pasqualetti, Patrizio; Tecchio, Franca

2015-01-01

Transcranial electric stimulations (tES) with amplitude-modulated currents are promising tools to enhance neuromodulation effects. It is essential to select the correct cortical targets and inhibitory/excitatory protocols to reverse changes in specific networks. We aimed at assessing the dependence of cortical excitability changes on the current amplitude of 20 Hz transcranial alternating current stimulation (tACS) over the bilateral primary motor cortex. We chose two amplitude ranges of the stimulations, around 25 μA/cm2 and 63 μA/cm2 from peak to peak, with three values (at steps of about 2.5%) around each, to generate, respectively, inhibitory and excitatory effects of the primary motor cortex. We checked such changes online through transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs). Cortical excitability changes depended upon current density (p = 0.001). Low current densities decreased MEP amplitudes (inhibition) while high current densities increased them (excitation). tACS targeting bilateral homologous cortical areas can induce online inhibition or excitation as a function of the current density.

Electrophysiological heterogeneity of pacemaker cells in the rabbit intercaval region, including the SA node: insights from recording multiple ion currents in each cell.

PubMed

Monfredi, Oliver; Tsutsui, Kenta; Ziman, Bruce; Stern, Michael D; Lakatta, Edward G; Maltsev, Victor A

2018-03-01

Cardiac pacemaker cells, including cells of the sinoatrial node, are heterogeneous in size, morphology, and electrophysiological characteristics. The exact extent to which these cells differ electrophysiologically is unclear yet is critical to understanding their functioning. We examined major ionic currents in individual intercaval pacemaker cells (IPCs) sampled from the paracristal, intercaval region (including the sinoatrial node) that were spontaneously beating after enzymatic isolation from rabbit hearts. The beating rate was measured at baseline and after inhibition of the Ca 2+ pump with cyclopiazonic acid. Thereafter, in each cell, we consecutively measured the density of funny current ( I f ), delayed rectifier K + current ( I K ) (a surrogate of repolarization capacity), and L-type Ca 2+ current ( I Ca,L ) using whole cell patch clamp . The ionic current densities varied to a greater extent than previously appreciated, with some IPCs demonstrating very small or zero I f . The density of none of the currents was correlated with cell size, while I Ca,L and I f densities were related to baseline beating rates. I f density was correlated with I K density but not with that of I Ca,L . Inhibition of Ca 2+ cycling had a greater beating rate slowing effect in IPCs with lower I f densities. Our numerical model simulation indicated that 1) IPCs with small (or zero) I f or small I Ca,L can operate via a major contribution of Ca 2+ clock, 2) I f -Ca 2+ -clock interplay could be important for robust pacemaking function, and 3) coupled I f - I K function could regulate maximum diastolic potential. Thus, we have demonstrated marked electrophysiological heterogeneity of IPCs. This heterogeneity is manifested in basal beating rate and response to interference of Ca 2+ cycling, which is linked to I f . NEW & NOTEWORTHY In the present study, a hitherto unrecognized range of heterogeneity of ion currents in pacemaker cells from the intercaval region is demonstrated. Relationships between basal beating rate and L-type Ca 2+ current and funny current ( I f ) density are uncovered, along with a positive relationship between I f and delayed rectifier K + current. Links are shown between the response to Ca 2+ cycling blockade and I f density.

Solvent effects on polysulfide redox kinetics and ionic conductivity in lithium-sulfur batteries

DOE PAGES

Fan, Frank Y.; Pan, Menghsuan Sam; Lau, Kah Chun; ...

2016-11-25

Lithium-sulfur (Li-S) batteries have high theoretical energy density and low raw materials cost compared to present lithium-ion batteries and are thus promising for use in electric transportation and other applications. A major obstacle for Li-S batteries is low rate capability, especially at the low electrolyte/sulfur (E/S) ratios required for high energy density. Herein, we investigate several potentially rate-limiting factors for Li-S batteries. We study the ionic conductivity of lithium polysulfide solutions of varying concentration and in different ether-based solvents and their exchange current density on glassy carbon working electrodes. We believe this is the first such investigation of exchange currentmore » density for lithium polysulfide in solution. Exchange current densities are measured using both electrochemical impedance spectroscopy and steady-state galvanostatic polarization. In the range of interest (1-8 M [S]), the ionic conductivity monotonically decreases with increasing sulfur concentration while exchange current density shows a more complicated relationship to sulfur concentration. The electrolyte solvent dramatically affects ionic conductivity and exchange current density. Finally, the measured ionic conductivities and exchange current densities are also used to interpret the overpotential and rate capability of polysulfide-nanocarbon suspensions; this analysis demonstrates that ionic conductivity is the rate-limiting property in the solution regime (i.e. between Li 2S 8 and Li 2S 4).« less

A Critical Evaluation of the Influence of the Dark Exchange Current on the Performance of Dye-Sensitized Solar Cells

PubMed Central

García-Rodríguez, Rodrigo; Villanueva-Cab, Julio; Anta, Juan A.; Oskam, Gerko

2016-01-01

The influence of the thickness of the nanostructured, mesoporous TiO2 film on several parameters determining the performance of a dye-sensitized solar cell is investigated both experimentally and theoretically. We pay special attention to the effect of the exchange current density in the dark, and we compare the values obtained by steady state measurements with values extracted from small perturbation techniques. We also evaluate the influence of exchange current density, the solar cell ideality factor, and the effective absorption coefficient of the cell on the optimal film thickness. The results show that the exchange current density in the dark is proportional to the TiO2 film thickness, however, the effective absorption coefficient is the parameter that ultimately defines the ideal thickness. We illustrate the importance of the exchange current density in the dark on the determination of the current–voltage characteristics and we show how an important improvement of the cell performance can be achieved by decreasing values of the total series resistance and the exchange current density in the dark. PMID:28787833

Current-driven orbital order-disorder transition in LaMnO3

NASA Astrophysics Data System (ADS)

Mondal, Parthasarathi; Bhattacharya, Dipten; Mandal, P.

2011-08-01

We report a significant influence of electric current on the orbital order-disorder transition in LaMnO3. The transition temperature TOO, thermal hysteresis in the resistivity ρ versus temperature T plot around TOO, and latent heat L associated with the transition decrease with an increase in current density. Eventually, at a critical current density, L reaches zero. The transition zone, on the other hand, broadens with an increase in current density. The states at ordered, disordered, and transition zones are all found to be stable within the time window from ˜10-3 to ˜104 s.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fertig, Fabian, E-mail: fabian.fertig@ise.fraunhofer.de; Greulich, Johannes; Rein, Stefan

We present a spatially resolved method to determine the short-circuit current density of crystalline silicon solar cells by means of lock-in thermography. The method utilizes the property of crystalline silicon solar cells that the short-circuit current does not differ significantly from the illuminated current under moderate reverse bias. Since lock-in thermography images locally dissipated power density, this information is exploited to extract values of spatially resolved current density under short-circuit conditions. In order to obtain an accurate result, one or two illuminated lock-in thermography images and one dark lock-in thermography image need to be recorded. The method can be simplifiedmore » in a way that only one image is required to generate a meaningful short-circuit current density map. The proposed method is theoretically motivated, and experimentally validated for monochromatic illumination in comparison to the reference method of light-beam induced current.« less

Non-axisymmetric equilibrium reconstruction and suppression of density limit disruptions in a current-carrying stellarator

NASA Astrophysics Data System (ADS)

Ma, Xinxing; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Knowlton, S. F.; Maurer, D. A.

2017-10-01

Non-axisymmetric equilibrium reconstructions have been routinely performed with the V3FIT code in the Compact Toroidal Hybrid (CTH), a stellarator/tokamak hybrid. In addition to 50 external magnetic measurements, 160 SXR emissivity measurements are incorporated into V3FIT to reconstruct the magnetic flux surface geometry and infer the current distribution within the plasma. Improved reconstructions of current and q profiles provide insight into understanding the physics of density limit disruptions observed in current-carrying discharges in CTH. It is confirmed that the final scenario of the density limit of CTH plasmas is consistent with classic observations in tokamaks: current profile shrinkage leads to growing MHD instabilities (tearing modes) followed by a loss of MHD equilibrium. It is also observed that the density limit at a given current linearly increases with increasing amounts of 3D shaping fields. Consequently, plasmas with densities up to two times the Greenwald limit are attained. Equilibrium reconstructions show that addition of 3D fields effectively moves resonance surfaces towards the edge of the plasma where the current profile gradient is less, providing a stabilizing effect. This work is supported by US Department of Energy Grant No. DE-FG02-00ER54610.

Electromigration Mechanism of Failure in Flip-Chip Solder Joints Based on Discrete Void Formation.

PubMed

Chang, Yuan-Wei; Cheng, Yin; Helfen, Lukas; Xu, Feng; Tian, Tian; Scheel, Mario; Di Michiel, Marco; Chen, Chih; Tu, King-Ning; Baumbach, Tilo

2017-12-20

In this investigation, SnAgCu and SN100C solders were electromigration (EM) tested, and the 3D laminography imaging technique was employed for in-situ observation of the microstructure evolution during testing. We found that discrete voids nucleate, grow and coalesce along the intermetallic compound/solder interface during EM testing. A systematic analysis yields quantitative information on the number, volume, and growth rate of voids, and the EM parameter of DZ*. We observe that fast intrinsic diffusion in SnAgCu solder causes void growth and coalescence, while in the SN100C solder this coalescence was not significant. To deduce the current density distribution, finite-element models were constructed on the basis of the laminography images. The discrete voids do not change the global current density distribution, but they induce the local current crowding around the voids: this local current crowding enhances the lateral void growth and coalescence. The correlation between the current density and the probability of void formation indicates that a threshold current density exists for the activation of void formation. There is a significant increase in the probability of void formation when the current density exceeds half of the maximum value.

Incorporation of Ca and P on anodized titanium surface: Effect of high current density.

PubMed

Laurindo, Carlos A H; Torres, Ricardo D; Mali, Sachin A; Gilbert, Jeremy L; Soares, Paulo

2014-04-01

This study systematically evaluated the surface and corrosion characteristics of commercially pure titanium (grade 2) modified by plasma electrolytic oxidation (PEO) with high current density. The anodization process was carried out galvanostatically (constant current density) using a solution containing calcium glycerophosphate (0.02mol/L) and calcium acetate (0.15mol/L). The current densities applied were 400, 700, 1000 and 1200mA/cm(2) for a period of 15s. Composition, crystalline structure, morphology, roughness, wettability and "in-vitro" bioactivity test in SBF of the anodized layer were evaluated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, profilometry and contact angle measurements. Corrosion properties were evaluated by open circuit potential, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the TiO2 oxide layers present an increase of thickness, porosity, roughness, wettability, Ca/P ratio, and bioactivity, with the applied current density up to 1000mA/cm(2). Corrosion resistance also increases with applied current density. It is observed that for 1200mA/cm(2), there is a degradation of the oxide layer. In general, the results suggest that the anodized TiO2 layer with better properties is formed with an applied current of 1000mA/cm(2). Copyright © 2014 Elsevier B.V. All rights reserved.

Application of hybrid supercapacitor using granule Li4Ti5O12/activated carbon with variation of current density

NASA Astrophysics Data System (ADS)

Lee, Byung-Gwan; Lee, Seung-Hwan

2017-03-01

We report the electrochemical performance of asymmetric hybrid supercapacitors composed of granule Li4Ti5O12 as an anode and activated carbon as a cathode with different current densities. It is demonstrated that the hybrid supercapacitors show good initial discharge capacities were ranged from 39.8 to 46.4 F g-1 in the current densities range of 0.3-1 A g-1. The performance degradation is proportional to the current density due to quick gassing, resulting from H2O and HF formation. In particular, the hybrid supercapacitors show the pretty good cycling stability of 97.4%, even at the high current density of 0.8 A g-1, which are among most important performance in the real application for energy storage devices. Therefore, we believe that hybrid supercapacitors using granule Li4Ti5O12/activated carbon are eligible for the promising next generation energy devices.

Investigating the polar ionosphere during the development of neutral density enhancements on 24-25 September 2000

NASA Astrophysics Data System (ADS)

Horvath, Ildiko; Lovell, Brian C.

2017-04-01

We focus on the well-known northern daytime neutral density spikes detected by CHAMP on 25 September 2000 and related coupled magnetospheric-ionospheric-thermospheric processes. We investigate the underlying magnetic events and resultant thermospheric variations plus the state of the ionospheric polar region by employing multi-instrument CHAMP and DMSP data. Results show the unfolding of a weak (SYM-HMin ≈ -27 nT; 0345 UT) magnetic storm during which these northern density spikes occurred. Some smaller southern daytime density spikes were also detected prior to this storm on the previous day. All these density spikes were detected in or near polar convection flow channels (FCs). Each FC was characterized by strong antisunward zonal ion drifts that excited the zonal and meridional neutral winds leaving the signature of FC in the CHAMP neutral wind measurements and thus providing direct observational evidence of FC underlying the density spike. Additional to the small-scale field-aligned current (SS-FAC) filaments, the sudden intensifications of ionospheric closure current in the FC fueled the thermosphere and contributed to the development of upwelling and density spike. Some smaller density increases occurred due to the weak intensification of ionospheric closure currents. Equatorward (poleward) directed meridional neutral winds strengthened (weakened) the density spike by moving the neutral density up and along (down and against) the upwelling fueled by the ionospheric closure current and SS-FAC filaments.

Two-dimensional electron density characterisation of arc interruption phenomenon in current-zero phase

NASA Astrophysics Data System (ADS)

Inada, Yuki; Kamiya, Tomoki; Matsuoka, Shigeyasu; Kumada, Akiko; Ikeda, Hisatoshi; Hidaka, Kunihiko

2018-01-01

Two-dimensional electron density imaging over free burning SF6 arcs and SF6 gas-blast arcs was conducted at current zero using highly sensitive Shack-Hartmann type laser wavefront sensors in order to experimentally characterise electron density distributions for the success and failure of arc interruption in the thermal reignition phase. The experimental results under an interruption probability of 50% showed that free burning SF6 arcs with axially asymmetric electron density profiles were interrupted with a success rate of 88%. On the other hand, the current interruption of SF6 gas-blast arcs was reproducibly achieved under locally reduced electron densities and the interruption success rate was 100%.

Ionization and current growth in N/sub 2/ at very high electric field to gas density ratios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gylys, V.T.; Jelenkovic, B.M.; Phelps, A.V.

1989-05-01

Measurements and analyses have been made of electron impact ionization and of current growth in pulsed, low-current, prebreakdown discharges in parallel-plane geometry in N/sub 2/ at very high electric field to gas density ratios E/n and low products of the gas density n and electrode separation d. The E/n range and nd ranges were 1

Differences observed in the surface morphology and microstructure of Ni-Fe-Cu ternary thin films electrochemically deposited at low and high applied current densities

NASA Astrophysics Data System (ADS)

Sarac, U.; Kaya, M.; Baykul, M. C.

2016-10-01

In this research, nanocrystalline Ni-Fe-Cu ternary thin films using electrochemical deposition technique were produced at low and high applied current densities onto Indium Tin Oxide (ITO) coated conducting glass substrates. Change of surface morphology and microstructural properties of the films were investigated. Energy dispersive X-ray spectroscopy (EDX) measurements showed that the Ni-Fe-Cu ternary thin films exhibit anomalous codeposition behaviour during the electrochemical deposition process. From the X-ray diffraction (XRD) analyses, it was revealed that there are two segregated phases such as Cu- rich and Ni-rich within the films. The crystallographic structure of the films was face-centered cubic (FCC). It was also observed that the film has lower lattice micro-strain and higher texture degree at high applied current density. Scanning electron microscopy (SEM) studies revealed that the films have rounded shape particles on the base part and cauliflower-like structures on the upper part. The film electrodeposited at high current density had considerably smaller rounded shape particles and cauliflower-like structures. From the atomic force microscopy (AFM) analyses, it was shown that the film deposited at high current density has smaller particle size and surface roughness than the film grown at low current density.

LORETA Current Source Density for Duration Mismatch Negativity and Neuropsychological Assessment in Early Schizophrenia

PubMed Central

Miyanishi, Tomohiro; Sumiyoshi, Tomiki; Higuchi, Yuko; Seo, Tomonori; Suzuki, Michio

2013-01-01

Introduction Patients with schizophrenia elicit cognitive decline from the early phase of the illness. Mismatch negativity (MMN) has been shown to be associated with cognitive function. We investigated the current source density of duration mismatch negativity (dMMN), by using low-resolution brain electromagnetic tomography (LORETA), and neuropsychological performance in subjects with early schizophrenia. Methods Data were obtained from 20 patients meeting DSM-IV criteria for schizophrenia or schizophreniform disorder, and 20 healthy control (HC) subjects. An auditory odd-ball paradigm was used to measure dMMN. Neuropsychological performance was evaluated by the brief assessment of cognition in schizophrenia Japanese version (BACS-J). Results Patients showed smaller dMMN amplitudes than those in the HC subjects. LORETA current density for dMMN was significantly lower in patients compared to HC subjects, especially in the temporal lobes. dMMN current density in the frontal lobe was positively correlated with working memory performance in patients. Conclusions This is the first study to identify brain regions showing smaller dMMN current density in early schizophrenia. Further, poor working memory was associated with decreased dMMN current density in patients. These results are likely to help understand the neural basis for cognitive impairment of schizophrenia. PMID:23577204

Rostral Anterior Cingulate Cortex Theta Current Density and Response to Antidepressants and Placebo in Major Depression

PubMed Central

Korb, Alexander S.; Hunter, Aimee M.; Cook, Ian A.; Leuchter, Andrew F.

2009-01-01

Objective To assess whether pretreatment theta current density in the rostral anterior cingulate (rACC) and medial orbitofrontal cortex (mOFC) differentiates responders from non-responders to antidepressant medication or placebo in a double-blinded study. Methods Pretreatment EEGs were collected from 72 subjects with Major Depressive Disorder (MDD) who participated in one of three placebo-controlled trials. Subjects were randomized to receive treatment with fluoxetine, venlafaxine, or placebo. Low-resolution brain electromagnetic tomography (LORETA) was used to assess theta current density in the rACC and mOFC. Results Medication responders showed elevated rACC and mOFC theta current density compared to medication non-responders (rACC: p=0.042; mOFC: p=0.039). There was no significant difference in either brain region between placebo responders and placebo non-responders. Conclusions Theta current density in the rACC and mOFC may be useful as a biomarker for prediction of response to antidepressant medication. Significance This is the first double-blinded treatment study to examine pretreatment rACC and mOFC theta current density in relation to antidepressant response and placebo response. Results support the potential clinical utility of this approach for predicting clinical outcome to antidepressant treatments in MDD. PMID:19539524

Analysis of current density and specific absorption rate in biological tissue surrounding an air-core type of transcutaneous transformer for an artificial heart.

PubMed

Shiba, Kenji; Nukaya, Masayuki; Tsuji, Toshio; Koshiji, Kohji

2006-01-01

This paper reports on the specific absorption rate (SAR) and the current density analysis of biological tissue surrounding an air-core type of transcutaneous transformer for an artificial heart. The electromagnetic field in the biological tissue surrounding the transformer was analyzed by the transmission-line modeling method, and the SAR and current density as a function of frequency (200k-1 MHz) for a transcutaneous transmission of 20 W were calculated. The model's biological tissue has three layers including the skin, fat and muscle. As a result, the SAR in the vicinity of the transformer is sufficiently small and the normalized SAR value, which is divided by the ICNIRP's basic restriction, is 7 x 10(-3) or less. On the contrary, the current density is slightly in excess of the ICNIRP's basic restrictions as the frequency falls and the output voltage rises. Normalized current density is from 0.2 to 1.2. In addition, the layer in which the current's density is maximized depends on the frequency, the muscle in the low frequency (<700 kHz) and the skin in the high frequency (>700 kHz). The result shows that precision analysis taking into account the biological properties is very important for developing the transcutaneous transformer for TAH.

Line length dependence of threshold current density and driving force in eutectic SnPb and SnAgCu solder electromigration

NASA Astrophysics Data System (ADS)

Yoon, Min-Seung; Ko, Min-Ku; Kim, Bit-Na; Kim, Byung-Joon; Park, Yong-Bae; Joo, Young-Chang

2008-04-01

The relationship between the threshold current density and the critical line length in eutectic SnPb and SnAgCu electromigrations were examined using solder lines with the various lengths ranging from 100to1000μm. When the electron wind-force was balanced by the back-stress gradient force, the net flux of electromigration is zero, at which the current density and line length are defined as the threshold current density and the critical length, respectively. It was found that in SnAgCu electromigration, the 1/L dependence on the threshold current density showed good agreement, whereas the threshold current densities of the eutectic SnPb deviated from the 1/L dependence. The balance between the electron wind-force and the back-stress gradient force was the main factor determining the threshold product of SnAgCu electromigration. On the other hand, in the case of eutectic SnPb, the chemical driving force is contributed as a back-flux force in addition to the back-stress gradient force. The existence of the chemical driving force was caused by the nonequilibrium Pb concentration inside the Pb-rich phases between the cathode and anode during the electromigration procedure.

Current density reversibly alters metabolic spatial structure of exoelectrogenic anode biofilms

NASA Astrophysics Data System (ADS)

Sun, Dan; Cheng, Shaoan; Zhang, Fang; Logan, Bruce E.

2017-07-01

Understanding how current densities affect electrogenic biofilm activity is important for wastewater treatment as current densities can substantially decrease at COD concentrations greater than those suitable for discharge to the environment. We examined the biofilm's response, in terms of viability and enzymatic activity, to different current densities using microbial electrolysis cells with a lower (0.7 V) or higher (0.9 V) added voltage to alter current production. Viability was assessed using florescent dyes, with dead cells identified on the basis of dye penetration due to a compromised cell outer-membrane (red), and live cells (intact membrane) fluorescing green. Biofilms operated with 0.7 V produced 2.4 ± 0.2 A m-2, and had an inactive layer near the electrode and a viable layer at the biofilm-solution interface. The lack of cell activity near the electrode surface was confirmed by using an additional dye that fluoresces only with enzymatic activity. Adding 0.9 V increased the current by 61%, and resulted in a single, more homogeneous and active biofilm layer. Switching biofilms between these two voltages produced outcomes associated with the new current rather than the previous biofilm conditions. These findings suggest that maintaining higher current densities will be needed to ensure long-term viability electrogenic biofilms.

UCB current detector experiment on Swedish auroral payloads. [ionospheric current and plasma flow measurements

NASA Technical Reports Server (NTRS)

Mozer, F.

1974-01-01

A split Langmuir probe has been developed to make in situ measurements of ionospheric current density and plasma bulk flow. The probe consists of two conducting elements that are separated by a thin insulator that shield each other over a 2 pi solid angle, and that are simultaneously swept from negative to positive with respect to the plasma. By measuring the current to each plate and the difference current between plates, information is obtained on the plasma's current density, bulk flow, electron temperature, and density. The instrument was successfully flown twice on sounding rockets into auroral events. Measurement data indicate that the total auroral current configuration is composed of several alternating east and west electrojets associated with several alternating up and down Birkeland currents.

Influence of field dependent critical current density on flux profiles in high Tc superconductors

NASA Technical Reports Server (NTRS)

Takacs, S.

1990-01-01

The field distribution for superconducting cylinders and slabs with field dependent critical current densities in combined DC and AC magnetic fields and the corresponding magnetic fluxes are calculated. It is shown that all features of experimental magnetic-field profile measurements can be explained in the framework of field dependent critical current density. Even the quantitative agreement between the experimental and theoretical results using Kim's model is very good.

Characterization of thunderstorm induced Maxwell current densities in the middle atmosphere

NASA Technical Reports Server (NTRS)

Baginski, Michael Edward

1989-01-01

Middle atmospheric transient Maxwell current densities generated by lightning induced charge perturbations are investigated via a simulation of Maxwell's equations. A time domain finite element analysis is employed for the simulations. The atmosphere is modeled as a region contained within a right circular cylinder with a height of 110 km and radius of 80 km. A composite conductivity profile based on measured data is used when charge perturbations are centered about the vertical axis at altitudes of 6 and 10 km. The simulations indicate that the temporal structure of the Maxwell current density is relatively insensitive to altitude variation within the region considered. It is also shown that the electric field and Maxwell current density are not generally aligned.

Progress on a high current density low cost Niobium3Tin conductor scaleable to modern niobium titanium production

NASA Astrophysics Data System (ADS)

Zeitlin, Bruce A.; Pyon, Taeyoung; Gregory, Eric; Scanlan, R. M.

2002-05-01

A number of configurations of a mono element internal tin conductor (MEIT) were fabricated designed to explore the effect of local ratio, niobium content, and tin content on the overall current density. Critical current densities on four configurations were measured, two to 17T. Current density as a function of filament size was also measured with filaments sizes ranging from 1.8 to 7.1 microns. A Nb60wt%Ta barrier was also explored as a means to reduce the high cost of the Tantalum barrier. The effectiveness of radial copper channels in high Nb conductors is also evaluated. Results are used to suggest designs for more optimized conductors.

Current densities in a pregnant woman model induced by simultaneous ELF electric and magnetic field exposure

NASA Astrophysics Data System (ADS)

Cech, R.; Leitgeb, N.; Pediaditis, M.

2008-01-01

The pregnant woman model SILVY was studied to ascertain to what extent the electric current densities induced by 50 Hz homogeneous electric and magnetic fields increase in the case of simultaneous exposure. By vectorial addition of the electric current densities, it could be shown that under worst case conditions the basic restrictions recommended by ICNIRP (International Commission on Non-Ionizing Radiation Protection) guidelines are exceeded within the central nervous system (CNS) of the mother, whereas in sole field exposure they are not. However, within the foetus the induced current densities do not comply with basic restrictions, either from single reference-level electric fields or from simultaneous exposure to electric and magnetic fields. Basic limits were considerably exceeded.

Density-functional theory for internal magnetic fields

NASA Astrophysics Data System (ADS)

Tellgren, Erik I.

2018-01-01

A density-functional theory is developed based on the Maxwell-Schrödinger equation with an internal magnetic field in addition to the external electromagnetic potentials. The basic variables of this theory are the electron density and the total magnetic field, which can equivalently be represented as a physical current density. Hence, the theory can be regarded as a physical current density-functional theory and an alternative to the paramagnetic current density-functional theory due to Vignale and Rasolt. The energy functional has strong enough convexity properties to allow a formulation that generalizes Lieb's convex analysis formulation of standard density-functional theory. Several variational principles as well as a Hohenberg-Kohn-like mapping between potentials and ground-state densities follow from the underlying convex structure. Moreover, the energy functional can be regarded as the result of a standard approximation technique (Moreau-Yosida regularization) applied to the conventional Schrödinger ground-state energy, which imposes limits on the maximum curvature of the energy (with respect to the magnetic field) and enables construction of a (Fréchet) differentiable universal density functional.

First evidence of ethylene production by Fusarium mangiferae associated with mango malformation

PubMed Central

Ansari, Mohammad Wahid; Shukla, Alok; Pant, Ramesh Chandra; Tuteja, Narendra

2013-01-01

Malformation is arguably the most crucial disease of mango (Mangifera indica L.) at present. It is receiving great attention not only because of its widespread and destructive nature but also because of its etiology and control is not absolutely understood. Recently, Fusarium mangiferae is found to be associated with mango malformation disease. There are indications that stress ethylene production could be involved in the disease. Here we have shown the first direct evidence of production of ethylene in pure culture of F. mangiferae obtained from mango. The study also revealed that all the isolates dissected from mango acquire morphological features of F. mangiferae showing most similarity to the features of species with accepted standard features. The isolates of F. mangiferae from mango were observed to produce ethylene in significant amounts, ranging from 9.28–13.66 n mol/g dry wt/day. The findings presented here suggest that F. mangiferae could contribute to the malformation of mango by producing ethylene and probably stimulating stress ethylene production in malformed tissue of mango. Ethylene might be produced through 2-oxoglutarate-dependent oxygenase-type ethylene-forming-enzyme (EFE) pathway in Fusarium sp, which needs to be investigated. PMID:23221756

Ethylene production in relation to nitrogen metabolism in Saccharomyces cerevisiae.

PubMed

Johansson, Nina; Persson, Karl O; Quehl, Paul; Norbeck, Joakim; Larsson, Christer

2014-11-01

We have previously shown that ethylene production in Saccharomyces cerevisiae expressing the ethylene-forming enzyme (EFE) from Pseudomonas syringae is strongly influenced by variations in the mode of cultivation as well as the choice of nitrogen source. Here, we have studied the influence of nitrogen metabolism on the production of ethylene further. Using ammonium, glutamate, glutamate/arginine, and arginine as nitrogen sources, it was found that glutamate (with or without arginine) correlates with a high ethylene production, most likely linked to an observed increase in 2-oxoglutarate levels. Arginine as a sole nitrogen source caused a reduced ethylene production. A reduction of arginine levels, accomplished using an arginine auxotrophic ARG4-deletion strain in the presence of limiting amounts of arginine or through CAR1 overexpression, did however not correlate with an increased ethylene production. As expected, arginine was necessary for ethylene production as ethylene production in the ARG4-deletion strain ceased at the time when arginine was depleted. In conclusion, our data suggest that high levels of 2-oxoglutarate and a limited amount of arginine are required for successful ethylene production in yeast. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

First evidence of ethylene production by Fusarium mangiferae associated with mango malformation.

PubMed

Ansari, Mohammad Wahid; Shukla, Alok; Pant, Ramesh Chandra; Tuteja, Narendra

2013-01-01

Malformation is arguably the most crucial disease of mango (Mangifera indica L.) at present. It is receiving great attention not only because of its widespread and destructive nature but also because of its etiology and control is not absolutely understood. Recently, Fusarium mangiferae is found to be associated with mango malformation disease. There are indications that stress ethylene production could be involved in the disease. Here we have shown the first direct evidence of production of ethylene in pure culture of F. mangiferae obtained from mango. The study also revealed that all the isolates dissected from mango acquire morphological features of F. mangiferae showing most similarity to the features of species with accepted standard features. The isolates of F. mangiferae from mango were observed to produce ethylene in significant amounts, ranging from 9.28-13.66 n mol/g dry wt/day. The findings presented here suggest that F. mangiferae could contribute to the malformation of mango by producing ethylene and probably stimulating stress ethylene production in malformed tissue of mango. Ethylene might be produced through 2-oxoglutarate-dependent oxygenase-type ethylene-forming-enzyme (EFE) pathway in Fusarium sp, which needs to be investigated.

Overexpression of NtPR-Q Up-Regulates Multiple Defense-Related Genes in Nicotiana tabacum and Enhances Plant Resistance to Ralstonia solanacearum.

PubMed

Tang, Yuanman; Liu, Qiuping; Liu, Ying; Zhang, Linli; Ding, Wei

2017-01-01

Various classes of plant pathogenesis-related proteins have been identified in the past several decades. PR-Q, a member of the PR3 family encoding chitinases, has played an important role in regulating plant resistance and preventing pathogen infection. In this paper, we functionally characterized NtPR-Q in tobacco plants and found that the overexpression of NtPR-Q in tobacco Yunyan87 resulted in higher resistance to Ralstonia solanacearum inoculation. Surprisingly, overexpression of NtPR-Q led to the activation of many defense-related genes, such as salicylic acid (SA)-responsive genes NtPR1a/c , NtPR2 and NtCHN50 , JA-responsive gene NtPR1b and ET production-associated genes NtACC Oxidase and NtEFE26 . Consistent with the role of NtPR-Q in multiple stress responses, NtPR-Q transcripts were induced by the exogenous hormones SA, ethylene and methyl jasmonate, which could enhance the resistance of tobacco to R. solanacearum . Collectively, our results suggested that NtPR-Q overexpression led to the up-regulation of defense-related genes and enhanced plant resistance to R. solanacearum infection.

3D Magnetic Field Analysis of a Turbine Generator Stator Core-end Region

NASA Astrophysics Data System (ADS)

Wakui, Shinichi; Takahashi, Kazuhiko; Ide, Kazumasa; Takahashi, Miyoshi; Watanabe, Takashi

In this paper we calculated magnetic flux density and eddy current distributions of a 71MVA turbine generator stator core-end using three-dimensional numerical magnetic field analysis. Subsequently, the magnetic flux densities and eddy current densities in the stator core-end region on the no-load and three-phase short circuit conditions obtained by the analysis have good agreements with the measurements. Furthermore, the differences of eddy current and eddy current loss in the stator core-end region for various load conditions are shown numerically. As a result, the facing had an effect that decrease the eddy current loss of the end plate about 84%.

On simulation of local fluxes in molecular junctions

NASA Astrophysics Data System (ADS)

Cabra, Gabriel; Jensen, Anders; Galperin, Michael

2018-05-01

We present a pedagogical review of the current density simulation in molecular junction models indicating its advantages and deficiencies in analysis of local junction transport characteristics. In particular, we argue that current density is a universal tool which provides more information than traditionally simulated bond currents, especially when discussing inelastic processes. However, current density simulations are sensitive to the choice of basis and electronic structure method. We note that while discussing the local current conservation in junctions, one has to account for the source term caused by the open character of the system and intra-molecular interactions. Our considerations are illustrated with numerical simulations of a benzenedithiol molecular junction.

Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa2Cu3O7 thin films

NASA Technical Reports Server (NTRS)

Xing, W.; Heinrich, B.; Zhou, HU; Fife, A. A.; Cragg, A. R.; Grant, P. D.

1995-01-01

Mapping of the magnetic flux density B(sub z) (perpendicular to the film plane) for a YBa2Cu3O7 thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B(sub z) distributions. From the known sheet magnetization, the tangential (B(sub x,y)) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B(sub x,y)/d, where d is the film thickness. The evolution of flux penetration as a function of applied field will be shown.

Calculation of induced current densities for humans by magnetic fields from electronic article surveillance devices

NASA Astrophysics Data System (ADS)

Gandhi, Om P.; Kang, Gang

2001-11-01

This paper illustrates the use of the impedance method to calculate the electric fields and current densities induced in millimetre resolution anatomic models of the human body, namely an adult and 10- and 5-year-old children, for exposure to nonuniform magnetic fields typical of two assumed but representative electronic article surveillance (EAS) devices at 1 and 30 kHz, respectively. The devices assumed for the calculations are a solenoid type magnetic deactivator used at store checkouts and a pass-by panel-type EAS system consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to obtain induced current densities averaged over a cross section of 1 cm2 perpendicular to the direction of induced currents. This is done to compare the peak current densities with the limits or the basic restrictions given in the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm2 area-averaged current densities for the CNS tissues such as the brain and the spinal cord are increasingly larger for smaller models and are the highest for the model of the 5-year-old child. For both the EAS devices, the maximum 1 cm2 area-averaged current densities for the brain of the model of the adult are lower than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10- and 5-year-old children if sufficiently strong magnetic fields are used.

Calculation of induced current densities for humans by magnetic fields from electronic article surveillance devices.

PubMed

Gandhi, O P; Kang, G

2001-11-01

This paper illustrates the use of the impedance method to calculate the electric fields and current densities induced in millimetre resolution anatomic models of the human body, namely an adult and 10- and 5-year-old children, for exposure to nonuniform magnetic fields typical of two assumed but representative electronic article surveillance (EAS) devices at 1 and 30 kHz, respectively. The devices assumed for the calculations are a solenoid type magnetic deactivator used at store checkouts and a pass-by panel-type EAS system consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to obtain induced current densities averaged over a cross section of 1 cm2 perpendicular to the direction of induced currents. This is done to compare the peak current densities with the limits or the basic restrictions given in the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm2 area-averaged current densities for the CNS tissues such as the brain and the spinal cord are increasingly larger for smaller models and are the highest for the model of the 5-year-old child. For both the EAS devices, the maximum 1 cm2 area-averaged current densities for the brain of the model of the adult are lower than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10- and 5-year-old children if sufficiently strong magnetic fields are used.

Correlations between critical current density, j(sub c), critical temperature, T(sub c),and structural quality of Y1B2Cu3O(7-x) thin superconducting films

NASA Technical Reports Server (NTRS)

Chrzanowski, J.; Xing, W. B.; Atlan, D.; Irwin, J. C.; Heinrich, B.; Cragg, R. A.; Zhou, H.; Angus, V.; Habib, F.; Fife, A. A.

1995-01-01

Correlations between critical current density (j(sub c)) critical temperature (T(sub c)) and the density of edge dislocations and nonuniform strain have been observed in YBCO thin films deposited by pulsed laser ablation on (001) LaAlO3 single crystals. Distinct maxima in j(sub c) as a function of the linewidths of the (00 l) Bragg reflections and as a function of the mosaic spread have been found in the epitaxial films. These maxima in j(sub c) indicate that the magnetic flux lines, in films of structural quality approachingthat of single crystals, are insufficiently pinned which results in a decreased critical current density. T(sub c) increased monotonically with improving crystalline quality and approached a value characteristic of a pure single crystal. A strong correlation between j(sub c) and the density of edge dislocations ND was found. At the maximum of the critical current density the density of edge dislocations was estimated to be N(sub D) approximately 1-2 x 10(exp 9)/sq cm.

Time evolving bed shear stress due the passage of gravity currents estimated with ADVP velocity measurements

NASA Astrophysics Data System (ADS)

Zordan, Jessica; Schleiss, Anton J.; Franca, Mário J.

2016-04-01

Density or gravity currents are geophysical flows driven by density gradients between two contacting fluids. The physical trigger mechanism of these phenomena lays in the density differences which may be caused by differences in the temperature, dissolved substances or concentration of suspended sediments. Saline density currents are capable to entrain bed sediments inducing signatures in the bottom of sedimentary basins. Herein, saline density currents are reproduced in laboratory over a movable bed. The experimental channel is of the lock-exchange type, it is 7.5 m long and 0.3 m wide, divided into two sections of comparable volumes by a sliding gate. An upstream reach serves as a head tank for the dense mixture; the current propagates through a downstream reach where the main measurements are made. Downstream of the channel a tank exist to absorb the reflection of the current and thus artifacts due to the limited length of the channel. High performance thermoplastic polyurethane simulating fine sediments forms the movable bed. Measures of 3D instantaneous velocities will be made with the use of the non-intrusive technique of the ADV (Acoustic Doppler Current Profiler). With the velocity measurements, the evolution in time of the channel-bed shear stress due the passage of gravity currents is estimated. This is in turn related to the observed erosion and to such parameters determinant for the dynamics of the current as initial density difference, lock length and channel slope. This work was funded by the ITN-Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7-PEOPLE-2013-ITN under REA grant agreement n_607394-SEDITRANS.

Growth mechanism of surface roughed platinum nanowires through electrodeposition current control and their electrochemical applications

NASA Astrophysics Data System (ADS)

Ruan, Dajiang

The aim of this work is to investigate the effect of current density on the grain size and surface morphology of electrodeposited platinum nanowires and their applications. Platinum (Pt) nanowires were fabricated by a galvanostatic electrodeposition method in a porous anodic alumina oxide (AAO) template with different current densities. Both direct current and pulse current electrodeposition were used to synthesize the Pt nanowires. The grain size and surface morphology of the Pt nanowires were studied by field emission scanning electron microscopy (FE-SEM), transmission electron microcopy (TEM) and X-ray diffraction (XRD). The experimental results showed that the current density was the key factor to control the surface roughness. The surface of the Pt nanowires became rougher and the grain sizes were increased by increasing the current densities. From the experimental results, a growth mechanism of Pt nanowires based on progressive nucleation and crystallization was proposed in order to find out the relationship between the surface morphology and current density. The electrochemical properties and catalytic activities of these surface roughed Pt nanowires were investigated in the detection of H20 2 and for the methanol oxidation. Cyclic voltammograms of Pt nanowire modified electrodes were obtained using a potentiostat, which showed that rougher Pt nanowires have higher response and better activity than that of smooth nanowires. For H202 detection, the effect of scan rate and H202 concentration were studied and it was found that the peak current for hydrogen peroxide reduction became larger with the increasing of either scan rate or H202 concentration. It can be inferred that the process of electrocatalytic hydrogen peroxide reduction may be controlled by diffusion of hydrogen peroxide and the Pt nanowire modified glassy carbon electrode (GCE) is well suited for the detection of H202. From the relationship between the peak current and square root of scan rates for methanol oxidation, it can be inferred that the process of electrocatalytic methanol oxidation was controlled by diffusion of methanol. To understand the effect of the morphological feature on the electrocatalytic activity of the Pt nanowire catalysts, the electrochemically active surface area (ECSA) as a function of deposited current density was investigated, which suggests that Pt nanowire catalysts deposited at highest current density had the most ECSA surface morphology of the Pt nanowires. The chronoamperometric curves and electrochemical impedance spectroscopy (EIS) results confirmed that the Pt nanowire catalyst synthesized at higher current density possessed longer durability and gave more efficient electrochemical performance.

Energy transmission transformer for a wireless capsule endoscope: analysis of specific absorption rate and current density in biological tissue.

PubMed

Shiba, Kenji; Nagato, Tomohiro; Tsuji, Toshio; Koshiji, Kohji

2008-07-01

This paper reports on the electromagnetic influences on the analysis of biological tissue surrounding a prototype energy transmission system for a wireless capsule endoscope. Specific absorption rate (SAR) and current density were analyzed by electromagnetic simulator in a model consisting of primary coil and a human trunk including the skin, fat, muscle, small intestine, backbone, and blood. First, electric and magnetic strength in the same conditions as the analytical model were measured and compared to the analytical values to confirm the validity of the analysis. Then, SAR and current density as a function of frequency and output power were analyzed. The validity of the analysis was confirmed by comparing the analytical values with the measured ones. The SAR was below the basic restrictions of the International Commission on Nonionizing Radiation Protection (ICNIRP). At the same time, the results for current density show that the influence on biological tissue was lowest in the 300-400 kHz range, indicating that it was possible to transmit energy safely up to 160 mW. In addition, we confirmed that the current density has decreased by reducing the primary coil's current.

Banning tobacco sales and advertisements near educational institutions may reduce students' tobacco use risk: evidence from Mumbai, India.

PubMed

Mistry, Ritesh; Pednekar, Mangesh; Pimple, Sharmila; Gupta, Prakash C; McCarthy, William J; Raute, Lalit J; Patel, Minal; Shastri, Surendra S

2015-03-01

India's Cigarettes and Other Tobacco Products Act bans tobacco sales and advertisements within 100 yards of educational institutions. In school-adjacent neighbourhoods in Mumbai, we assessed adherence to these policies and whether tobacco vendor and advertisement densities were associated with students' tobacco use. High school students' tobacco use was measured using a multistage cluster sampling survey (n=1533). Field geographic information systems data were obtained for all tobacco vendors and advertisements within 500 m of schools (n=26). Random-effects multilevel logistic regression was used to estimate associations of tobacco vendor and advertisement densities with ever tobacco use, current smokeless tobacco use and current tobacco use. There were 1741 tobacco vendors and 424 advertisements within 500 m of schools, with 221 vendors (13%) and 42 advertisements (10%) located within 100 m. School-adjacent tobacco vendor density within 100 m was not associated with the tobacco use outcomes, but tobacco advertisement density within 100 m was associated with all outcomes when comparing highest to lowest density tertiles: ever use (OR: 2.01; 95% CI 1.00 to 4.07), current use (2.23; 1.16, 4.28) and current smokeless tobacco use (2.01; 1.02, 3.98). Tobacco vendor density within 200, 300, 400 and 500 m of schools was associated with current tobacco use and current smokeless tobacco use, but not ever use. The tobacco sales ban near educational institutions could be expanded beyond 100 m. Greater enforcement is needed regarding the current bans, particularly because advertisement density within 100 m of schools was associated with all students' tobacco use outcomes. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Evaluation of double-layer density modulated Si thin films as Li-ion battery anodes

NASA Astrophysics Data System (ADS)

Taha Demirkan, Muhammed; Yurukcu, Mesut; Dursun, Burcu; Demir-Cakan, Rezan; Karabacak, Tansel

2017-10-01

Double-layer density modulated silicon thin films which contain alternating low and high density Si film layers were fabricated by magnetron sputtering. Two different samples consisting of alternating layers of high-density/low-density and low-density/high-density Si thin film layers were investigated as anode electrodes in Li-ion batteries. Si thin film in which the terminating layer at the top is low density Si layer-quoted as low-density/high-density film (LD/HD)- exhibits better performance than Si thin film that has high density layer at the top, -quoted as high-density/low-density (HD/LD). A highly stabilized cycling performance with the specific charge capacities of 2000 mAh g-1 at the 150th cycle at C/2 current density, and 1200 mAh g-1 at the 240th cycle at 10 C current density were observed for the LD/HD Si anode in the presence of fluoroethylene carbonate (FEC) electrolyte additive.

Maximum current density and beam brightness achievable by laser-driven electron sources

NASA Astrophysics Data System (ADS)

Filippetto, D.; Musumeci, P.; Zolotorev, M.; Stupakov, G.

2014-02-01

This paper discusses the extension to different electron beam aspect ratio of the Child-Langmuir law for the maximum achievable current density in electron guns. Using a simple model, we derive quantitative formulas in good agreement with simulation codes. The new scaling laws for the peak current density of temporally long and transversely narrow initial beam distributions can be used to estimate the maximum beam brightness and suggest new paths for injector optimization.

Intelligence and EEG current density using low-resolution electromagnetic tomography (LORETA).

PubMed

Thatcher, R W; North, D; Biver, C

2007-02-01

The purpose of this study was to compare EEG current source densities in high IQ subjects vs. low IQ subjects. Resting eyes closed EEG was recorded from 19 scalp locations with a linked ears reference from 442 subjects ages 5 to 52 years. The Wechsler Intelligence Test was administered and subjects were divided into low IQ (< or =90), middle IQ (>90 to <120) and high IQ (> or =120) groups. Low-resolution electromagnetic tomographic current densities (LORETA) from 2,394 cortical gray matter voxels were computed from 1-30 Hz based on each subject's EEG. Differences in current densities using t tests, multivariate analyses of covariance, and regression analyses were used to evaluate the relationships between IQ and current density in Brodmann area groupings of cortical gray matter voxels. Frontal, temporal, parietal, and occipital regions of interest (ROIs) consistently exhibited a direct relationship between LORETA current density and IQ. Maximal t test differences were present at 4 Hz, 9 Hz, 13 Hz, 18 Hz, and 30 Hz with different anatomical regions showing different maxima. Linear regression fits from low to high IQ groups were statistically significant (P < 0.0001). Intelligence is directly related to a general level of arousal and to the synchrony of neural populations driven by thalamo-cortical resonances. A traveling frame model of sequential microstates is hypothesized to explain the results.

Electromagnetic effects on the biological tissue surrounding a transcutaneous transformer for an artificial anal sphincter system*

PubMed Central

Zan, Peng; Yang, Bang-hua; Shao, Yong; Yan, Guo-zheng; Liu, Hua

2010-01-01

This paper reports on the electromagnetic effects on the biological tissue surrounding a transcutaneous transformer for an artificial anal sphincter. The coupling coils and human tissues, including the skin, fat, muscle, liver, and blood, were considered. Specific absorption rate (SAR) and current density were analyzed by a finite-length solenoid model. First, SAR and current density as a function of frequency (10–107 Hz) for an emission current of 1.5 A were calculated under different tissue thickness. Then relations between SAR, current density, and five types of tissues under each frequency were deduced. As a result, both the SAR and current density were below the basic restrictions of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The results show that the analysis of these data is very important for developing the artificial anal sphincter system. PMID:21121071

Electromagnetic effects on the biological tissue surrounding a transcutaneous transformer for an artificial anal sphincter system.

PubMed

Zan, Peng; Yang, Bang-hua; Shao, Yong; Yan, Guo-zheng; Liu, Hua

2010-12-01

This paper reports on the electromagnetic effects on the biological tissue surrounding a transcutaneous transformer for an artificial anal sphincter. The coupling coils and human tissues, including the skin, fat, muscle, liver, and blood, were considered. Specific absorption rate (SAR) and current density were analyzed by a finite-length solenoid model. First, SAR and current density as a function of frequency (10-10(7) Hz) for an emission current of 1.5 A were calculated under different tissue thickness. Then relations between SAR, current density, and five types of tissues under each frequency were deduced. As a result, both the SAR and current density were below the basic restrictions of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The results show that the analysis of these data is very important for developing the artificial anal sphincter system.

Nanoscale cross-point diode array accessing embedded high density PCM

NASA Astrophysics Data System (ADS)

Wang, Heng; Liu, Yan; Liu, Bo; Gao, Dan; Xu, Zhen; Zhan, Yipeng; Song, Zhitang; Feng, Songlin

2017-08-01

The main bottlenecks in the development of current embedded phase change memory (PCM) technology are the current density and data storage density. In this paper, we present a PCM with 4F2 cross-point diode selector and blade-type bottom electrode contact (BEC). A blade TiN BEC with a cross-sectional area of 630 nm2 (10 nm × 63 nm) reduces the reset current down to about 750 μA. The optimized diode array could supply this 750 μA reset current at about 1.7 V and low off-current 1 × 10-4 μA at about -5.05 V. The on-off ratio of this device is 7.5 × 106. The proposed nanoscale PCM device simultaneously exhibits an operation voltage as low as 3 V and a high density drive current with an ultra small cell size of 4F2 (108 nm × 108 nm). Over 106 cycling endurance properties guarantee that it can work effectively on the embedded memory.

Interaction of pyroclastic density currents with human settlements: Evidence from ancient Pompeii

NASA Astrophysics Data System (ADS)

Gurioli, Lucia; Pareschi, M. Teresa; Zanella, Elena; Lanza, Roberto; Deluca, Enrico; Bisson, Marina

2005-06-01

Integrating field observations and rock-magnetic measurements, we report how a turbulent pyroclastic density current interacted with and moved through an urban area. The data are from the most energetic, turbulent pyroclastic density current of the A.D. 79 eruption of Vesuvius, Italy, which partially destroyed the Roman city of Pompeii. Our results show that the urban fabric was able to divide the lower portion of the current into several streams that followed the city walls and the intracity roads. Vortices, revealed by upstream particle orientations and decreases in deposit temperature, formed downflow of obstacles or inside cavities. Although these perturbations affected only the lower part of the current and were localized, they could represent, in certain cases, cooler zones within which chances of human survival are increased. Our integrated field data for pyroclastic density current temperature and flow direction, collected for the first time across an urban environment, enable verification of coupled thermodynamic numerical models and their hazard simulation abilities.

Electromigration and morphological changes in Ag nanostructures

NASA Astrophysics Data System (ADS)

Chatterjee, A.; Bai, T.; Edler, F.; Tegenkamp, C.; Weide-Zaage, K.; Pfnür, H.

2018-02-01

Electromigration (EM) as a structuring tool was investigated in Ag nanowires (width 300 nm, thickness 25 nm) and partly in notched and bow-tie Ag structures on a Si(1 0 0) substrate in ultra-high vacuum using a four-tip scanning tunneling microscope in combination with a scanning electron microscope. From simulations of Ag nanowires we got estimates of temperature profiles, current density profiles, EM and thermal migration (TM) mass flux distributions within the nanowire induced by critical current densities of 108 A cm-2. At room temperature, the electron wind force at these current densities by far dominates over thermal diffusion, and is responsible for formation of voids at the cathode and hillocks at the anode side. For current densities that exceed the critical current densities necessary for EM, a new type of wire-like structure formation was found both at room temperature and at 100 K for notched and bow-tie structures. This suggests that the simultaneous action of EM and TM is structure forming, but with a very small influence of TM at low temperature.

Resource Assessment of Tidal Current Energy in Hangzhou Bay Based on Long Term Measurement

NASA Astrophysics Data System (ADS)

Zhang, Feng; Dai, Chun-Ni; Xu, Xue-Feng; Wang, Chuan-Kun; Ye, Qin

2017-05-01

Compared with other marine renewable energy, tidal current energy benefits a lot in high energy density and good predictability. Based on the measured tidal current data in Hangzhou Bay from Nov 2012 to Oct 2012, this paper analysed temporal and spatial changes of tidal current energy in the site. It is the first time measured data of such long time been taken in tidal current energy analysis. Occurrence frequency and duration of the current of different speed are given out in the paper. According to the analysis results, monthly average power density changed a lot in different month, and installation orientation of tidal current turbine significantly affected energy acquisition. Finally, the annual average power density of tidal current energy with coefficient Cp in the site was calculated, and final output of a tidal current plant was also estimated.

Current induced perpendicular-magnetic-anisotropy racetrack memory with magnetic field assistance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Y.; Klein, J.-O.; Chappert, C.

2014-01-20

High current density is indispensable to shift domain walls (DWs) in magnetic nanowires, which limits the using of racetrack memory (RM) for low power and high density purposes. In this paper, we present perpendicular-magnetic-anisotropy (PMA) Co/Ni RM with global magnetic field assistance, which lowers the current density for DW motion. By using a compact model of PMA RM and 40 nm design kit, we perform mixed simulation to validate the functionality of this structure and analyze its density potential. Stochastic DW motion behavior has been taken into account and statistical Monte-Carlo simulations are carried out to evaluate its reliability performance.

In-plane structuring of proton exchange membrane fuel cell cathodes: Effect of ionomer equivalent weight structuring on performance and current density distribution

NASA Astrophysics Data System (ADS)

Herden, Susanne; Riewald, Felix; Hirschfeld, Julian A.; Perchthaler, Markus

2017-07-01

Within the active area of a fuel cell inhomogeneous operating conditions occur, however, state of the art electrodes are homogenous over the complete active area. This study uses current density distribution measurements to analyze which ionomer equivalent weight (EW) shows locally the highest current densities. With this information a segmented cathode electrode is manufactured by decal transfer. The segmented electrode shows better performance especially at high current densities compared to homogenous electrodes. Furthermore this segmented catalyst coated membrane (CCM) performs optimal in wet as well as dry conditions, both operating conditions arise in automotive fuel cell applications. Thus, cathode electrodes with an optimized ionomer EW distribution might have a significant impact on future automotive fuel cell development.

Photovoltaic and thermophotovoltaic devices with quantum barriers

DOEpatents

Wernsman, Bernard R [Jefferson Hills, PA

2007-04-10

A photovoltaic or thermophotovoltaic device includes a diode formed by p-type material and n-type material joined at a p-n junction and including a depletion region adjacent to said p-n junction, and a quantum barrier disposed near or in the depletion region of the p-n junction so as to decrease device reverse saturation current density while maintaining device short circuit current density. In one embodiment, the quantum barrier is disposed on the n-type material side of the p-n junction and decreases the reverse saturation current density due to electrons while in another, the barrier is disposed on the p-type material side of the p-n junction and decreases the reverse saturation current density due to holes. In another embodiment, both types of quantum barriers are used.

Decreased voltage-gated potassium currents in rat dorsal root ganglion neurons after chronic constriction injury.

PubMed

Xiao, Yun; Wu, Yang; Zhao, Bo; Xia, Zhongyuan

2016-01-20

Voltage-gated potassium channels (KV) regulate pain transmission by controlling neuronal excitability. Changes in KV expression patterns may thus contribute toward hyperalgesia following nerve injury. The aim of this study was to characterize KV current density in dorsal root ganglion (DRG) neurons following chronic constriction injury (CCI) of the right sciatic nerve, a robust model of post-traumatic neuropathic pain. The study examined changes in small-diameter potassium ion currents (<30 µm) in neurons in the L4-L6 DRG following CCI by whole-cell patch-clamping and the association with post-CCI mechanical and thermal nociceptive thresholds. Compared with the control group, 7 days after CCI, the mechanical force and temperature required to elicit ipsilateral foot withdrawal decreased significantly, indicating tactile allodynia and thermal hyperalgesia. Post-CCI neurons had a significantly lower rheobase current and depolarized resting membrane potential than controls, suggesting KV current downregulation. Some ipsilateral DRG neurons also had spontaneous action potentials and repetitive firing. There was a 55% reduction in the total KV current density caused by a 55% decrease in the sustained delayed rectifier potassium ion current (IK) density and a 17% decrease in the transient A-type potassium ion current (IA) density. These results indicated that changes in DRG neuron IK and IA current density and concomitant afferent hyperexcitability may contribute toward neuropathic pain following injury. The rat CCI model may prove valuable for examining pathogenic mechanisms and potential therapies, such as KV channel modulators.

Large Eddy Simulations of Compositional Density Currents Flowing Over a Mobile Bed

NASA Astrophysics Data System (ADS)

Kyrousi, Foteini; Zordan, Jessica; Leonardi, Alessandro; Juez, Carmelo; Zanello, Francesca; Armenio, Vincenzo; Franca, Mário J.

2017-04-01

Density currents are a ubiquitous phenomenon caused by natural events or anthropogenic activities, and play an important role in the global sediment cycle; they are agents of long distance sediment transport in lakes, seas and oceans. Density gradients induced by salinity, temperature differences, or by the presence of suspended material are all possible triggers of a current. Such flows can travel long distances while eroding or depositing bed materials. This can provoke rapid topological changes, which makes the estimation of their transport capacity of prime interest for environmental engineering. Despite their relevance, field data regarding their dynamics is limited due to density currents scattered and unpredictable occurrence in nature. For this reason, laboratory experiments and numerical simulations have been a preferred way to investigate sediment transport processes associated to density currents. The study of entrainment and deposition processes requires detailed data of velocities spatial and temporal distributions in the boundary layer and bed shear stress, which are troublesome to obtain in laboratory. Motivated by this, we present 3D wall-resolved Large Eddy Simulations (LES) of density currents generated by lock-exchange. The currents travel over a smooth flat bed, which includes a section composed by erodible fine sediment susceptible of eroding. Several sediment sizes and initial density gradients are considered. The grid is set to resolve the velocity field within the boundary layer of the current (a tiny fraction of the total height), which in turn allows to obtain predictions of the bed shear stress. The numerical outcomes are compared with experimental data obtained with an analogous laboratory setting. In laboratory experiments salinity was chosen for generating the initial density gradient in order to facilitate the identification of entrained particles, since salt does not hinder the possibility to track suspended particles. Under these circumstances, it is possible to focus alone on the effect of the dynamics of the current on the particles entrainment. To achieve this, LES-filtered Navier-Stokes equations are coupled with two scalar transport equations: one for salinity and one for sediment concentration. We discuss the use of different sediment pick-up and settling formulations, which are key factors in reproducing the correct erosion and sedimentation mechanisms. The simulations show the emergence of longitudinal bed forms, and highlight the role of turbulent structures in the entrainment pattern for different regions within the current.

Charge Trapping in Interface Doped MNOS Structures.

DTIC Science & Technology

1981-07-01

Current density 55 0 JN Current density in nitride at gate 55 k Boltzmann’s constant: 1.38 x 10-23 joule /0K 85 m Effective mass of carrier 89 xi MIS...Trap Barrier Lowering by Applied Field: Poole-Frenkel Effect 90 vi Figure 3- 2: Thermally Stimulated Current System 92 Figure 3- 3: TSC Curves from a...Tungsten Atomic Concentration vs Effective Thickness 175 ix List of Tables Table 1-1: Trap Energy Levels and Spatial Densities 31 Table 2-1: Device

Possibilities for Estimating Horizontal Electrical Currents in Active Regions on the Sun

NASA Astrophysics Data System (ADS)

Fursyak, Yu. A.; Abramenko, V. I.

2017-12-01

Part of the "free" magnetic energy associated with electrical current systems in the active region (AR) is released during solar flares. This proposition is widely accepted and it has stimulated interest in detecting electrical currents in active regions. The vertical component of an electric current in the photosphere can be found by observing the transverse magnetic field. At present, however, there are no direct methods for calculating transverse electric currents based on these observations. These calculations require information on the field vector measured simultaneously at several levels in the photosphere, which has not yet been done with solar instrumentation. In this paper we examine an approach to calculating the structure of the square of the density of a transverse electrical current based on a magnetogram of the vertical component of the magnetic field in the AR. Data obtained with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO) for the AR of NOAA AR 11283 are used. It is shown that (1) the observed variations in the magnetic field of a sunspot and the proposed estimate of the density of an annular horizontal current around the spot are consistent with Faraday's law and (2) the resulting estimates of the magnitude of the square of the density of the horizontal current {j}_{\\perp}^2 = (0.002- 0.004) A2/m4 are consistent with previously obtained values of the density of a vertical current in the photosphere. Thus, the proposed estimate is physically significant and this method can be used to estimate the density and structure of transverse electrical currents in the photosphere.

Improving the aluminum-air battery system for use in electrical vehicles

NASA Astrophysics Data System (ADS)

Yang, Shaohua

The objectives of this study include improvement of the efficiency of the aluminum/air battery system and demonstration of its ability for vehicle applications. The aluminum/air battery system can generate enough energy and power for driving ranges and acceleration similar to that of gasoline powered cars. Therefore has the potential to be a power source for electrical vehicles. Aluminum/air battery vehicle life cycle analysis was conducted and compared to that of lead/acid and nickel-metal hydride vehicles. Only the aluminum/air vehicles can be projected to have a travel range comparable to that of internal combustion engine vehicles (ICE). From this analysis, an aluminum/air vehicle is a promising candidate compared to ICE vehicles in terms of travel range, purchase price, fuel cost, and life cycle cost. We have chosen two grades of Al alloys (Al alloy 1350, 99.5% and Al alloy 1199, 99.99%) in our study. Only Al 1199 was studied extensively using Na 2SnO3 as an electrolyte additive. We then varied concentration and temperature, and determined the effects on the parasitic (corrosion) current density and open circuit potential. We also determined cell performance and selectivity curves. To optimize the performance of the cell based on our experiments, the recommended operating conditions are: 3--4 N NaOH, about 55°C, and a current density of 150--300 mA/cm2. We have modeled the cell performance using the equations we developed. The model prediction of cell performance shows good agreement with experimental data. For better cell performance, our model studies suggest use of higher electrolyte flow rate, smaller cell gap, higher conductivity and lower parasitic current density. We have analyzed the secondary current density distributions in a two plane, parallel Al/air cell and a wedge-type Al/air cell. The activity of the cathode has a large effect on the local current density. With increases in the cell gap, the local current density increases, but the increase is not as significant as the increase in the current density away from the entrance. By extending the cathode below the anode, the high local current density can be reduced.

Noise distribution and denoising of current density images

PubMed Central

Beheshti, Mohammadali; Foomany, Farbod H.; Magtibay, Karl; Jaffray, David A.; Krishnan, Sridhar; Nanthakumar, Kumaraswamy; Umapathy, Karthikeyan

2015-01-01

Abstract. Current density imaging (CDI) is a magnetic resonance (MR) imaging technique that could be used to study current pathways inside the tissue. The current distribution is measured indirectly as phase changes. The inherent noise in the MR imaging technique degrades the accuracy of phase measurements leading to imprecise current variations. The outcome can be affected significantly, especially at a low signal-to-noise ratio (SNR). We have shown the residual noise distribution of the phase to be Gaussian-like and the noise in CDI images approximated as a Gaussian. This finding matches experimental results. We further investigated this finding by performing comparative analysis with denoising techniques, using two CDI datasets with two different currents (20 and 45 mA). We found that the block-matching and three-dimensional (BM3D) technique outperforms other techniques when applied on current density (J). The minimum gain in noise power by BM3D applied to J compared with the next best technique in the analysis was found to be around 2 dB per pixel. We characterize the noise profile in CDI images and provide insights on the performance of different denoising techniques when applied at two different stages of current density reconstruction. PMID:26158100

Reduction of I(Ca,L) and I(to1) density in hypertrophied right ventricular cells by simulated high altitude in adult rats.

PubMed

Chouabe, C; Espinosa, L; Megas, P; Chakir, A; Rougier, O; Freminet, A; Bonvallet, R

1997-01-01

The present paper describes the effect of a simulated hypobaric condition (at the altitude of 4500 m) on morphological characteristics and on some ionic currents in ventricular cells of adult rats. According to current data, chronic high-altitude exposure led to mild right ventricular hypertrophy. Increase in right ventricular weight appeared to be due wholly or partly to an enlargement of myocytes. The whole-cell patch-clamp technique was used and this confirmed, by cell capacitance measurement, that chronic high-altitude exposure induced an increase in the size of the right ventricular cells. Hypertrophied cells showed prolongation of action potential (AP). Four ionic currents, playing a role along with many others in the precise balance of inward and outward currents that control the duration of cardiac AP, were investigated. We report a significant decrease in the transient outward (I(to1)) and in the L-type calcium current (I(Ca,L)) densities while there was no significant difference in the delayed rectifier current (I(K)) or in the inward rectifier current (I(K1)) densities in hypertrophied right ventricular cells compared to control cells. At a given potential the decrease in I(to 1) density was relatively more important than the decrease in I(Ca,L) density. In both cell types, all the currents displayed the same voltage dependence. The inactivation kinetics of I(to 1) and I(Ca,L) or the steady-state activation and inactivation relationships were not significantly modified by chronic high-altitude exposure. We conclude that chronic high-altitude exposure induced true right ventricular myocyte hypertrophy and that the decrease in I(to 1) density might account for the lengthened action potential, or have a partial effect.

Detection of an electron beam in a high density plasma via an electrostatic probe

NASA Astrophysics Data System (ADS)

Majeski, Stephen; Yoo, Jongsoo; Zweben, Stewart; Yamada, Masaaki

2018-07-01

An electron beam is detected by a 1D floating potential probe array in a relatively high density (1012–1013 cm‑3) and low temperature (∼5 eV) plasma of the Magnetic Reconnection Experiment. Clear perturbations in the floating potential profile by the electron beam are observed. Based on the floating potential profile and a current balance equation to the probe array tips, the effective width of the electron beam is determined, from which we determine the radial and toroidal beam current density profiles. After the profile of the electron beam is specified from the measured beam current, we demonstrate the consistency of the current balance equation and the location of the perturbation is also in agreement with field line mapping. No significant broadening of the electron beam is observed after the beam propagates for tens of centimeters through the high density plasma. These results prove that the field line mapping is, in principle, possible in high density plasmas.

Detection of an electron beam in a high density plasma via an electrostatic probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majeski, Stephen; Yoo, Jongsoo; Zweben, Stewart

Here, an electron beam is detected by a 1D floating potential probe array in a relatively high density (10 12–10 13 cm -3) and low temperature (~5 eV) plasma of the Magnetic Reconnection Experiment. Clear perturbations in the floating potential profile by the electron beam are observed. Based on the floating potential profile and a current balance equation to the probe array tips, the effective width of the electron beam is determined, from which we determine the radial and toroidal beam current density profiles. After the profile of the electron beam is specified from the measured beam current, we demonstratemore » the consistency of the current balance equation and the location of the perturbation is also in agreement with field line mapping. No significant broadening of the electron beam is observed after the beam propagates for tens of centimeters through the high density plasma. These results prove that the field line mapping is, in principle, possible in high density plasmas.« less

Detection of an electron beam in a high density plasma via an electrostatic probe

DOE PAGES

Majeski, Stephen; Yoo, Jongsoo; Zweben, Stewart; ...

2018-05-08

Here, an electron beam is detected by a 1D floating potential probe array in a relatively high density (10 12–10 13 cm -3) and low temperature (~5 eV) plasma of the Magnetic Reconnection Experiment. Clear perturbations in the floating potential profile by the electron beam are observed. Based on the floating potential profile and a current balance equation to the probe array tips, the effective width of the electron beam is determined, from which we determine the radial and toroidal beam current density profiles. After the profile of the electron beam is specified from the measured beam current, we demonstratemore » the consistency of the current balance equation and the location of the perturbation is also in agreement with field line mapping. No significant broadening of the electron beam is observed after the beam propagates for tens of centimeters through the high density plasma. These results prove that the field line mapping is, in principle, possible in high density plasmas.« less

Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

DOEpatents

Coppi, B.; Montgomery, D.B.

1973-12-11

A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

The most intense electric currents in turbulent high speed solar wind

NASA Astrophysics Data System (ADS)

Podesta, J. J.

2017-12-01

Theory and simulations suggest that dissipation of turbulent energy in collisionless astrophysical plasmas occurs most rapidly in spatial regions where the current density is most intense. To advance understanding of plasma heating by turbulent dissipation in the solar corona and solar wind, it is of interest to characterize the properties of plasma regions where the current density takes exceptionally large values and to identify the operative dissipation processes. In the solar wind, the curl of the magnetic field cannot be measured using data from a single spacecraft, however, a suitable proxy for this quantity can be constructed from the spatial derivative of the magnetic field along the flow direction of the plasma. This new approach is used to study the properties of the most intense current carrying structures in a high speed solar wind stream near 1 AU. In this study, based on 11 Hz magnetometer data from the WIND spacecraft, the spatial resolution of the proxy technique is approximately equal to the proton inertial length. Intense current sheets or current carrying structures were identified as events where the magnitude of the current density exceeds μ+5σ, where μ and σ are the mean and standard deviation of the magnitude of the current density (or its proxy), respectively. Statistical studies show (1) the average size of these 5σ events is close to the smallest resolvable scale in the data set, the proton inertial length; (2) the linear distance between neighboring events follows a power law distribution; and (3) the average peak current density of 5σ events is around 1 pA/cm2. The analysis techniques used in these studies have been validated using simulated spacecraft data from three dimensional hybrid simulations which show that results based on the analysis of the proxy are qualitatively and quantitatively similar to results based on the analysis of the true current density.

DE 1 observations of type 1 counterstreaming electrons and field-aligned currents

NASA Technical Reports Server (NTRS)

Lin, C. S.; Burch, J. L.; Barfield, J. N.; Sugiura, M.; Nielsen, E.

1984-01-01

Dynamics Explorer 1 satellite observations of plasma and magnetic fields during type one counterstreaming electron events are presented. Counterstreaming electrons are observed at high altitudes in the region of field-aligned current. The total current density computed from the plasma data in the 18-10,000 eV energy range is generally about 1-2 micro-A/sq m. For the downward current, low-energy electrons contribute more than 40 percent of the total plasma current density integrated above 18 eV. For the upward current, such electrons contribute less than 50 percent of that current density. Electron beams in the field-aligned direction are occasionally detected. The pitch angle distributions of counterstreaming electrons are generally enhanced at both small and large pitch angles. STARE simultaneous observations for one DE 1 pass indicated that the field-aligned current was closed through Pedersen currents in the ionosphere. The directions of the ionospheric current systems are consistent with the DE 1 observations at high altitudes.

Three-dimensional forward solver and its performance analysis for magnetic resonance electrical impedance tomography (MREIT) using recessed electrodes.

PubMed

Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyoung; Kwon, Ohin; Seo, Jin Keun; Lee, June-Yub; Baek, Woon Sik

2003-07-07

In magnetic resonance electrical impedance tomography (MREIT), we try to reconstruct a cross-sectional resistivity (or conductivity) image of a subject. When we inject a current through surface electrodes, it generates a magnetic field. Using a magnetic resonance imaging (MRI) scanner, we can obtain the induced magnetic flux density from MR phase images of the subject. We use recessed electrodes to avoid undesirable artefacts near electrodes in measuring magnetic flux densities. An MREIT image reconstruction algorithm produces cross-sectional resistivity images utilizing the measured internal magnetic flux density in addition to boundary voltage data. In order to develop such an image reconstruction algorithm, we need a three-dimensional forward solver. Given injection currents as boundary conditions, the forward solver described in this paper computes voltage and current density distributions using the finite element method (FEM). Then, it calculates the magnetic flux density within the subject using the Biot-Savart law and FEM. The performance of the forward solver is analysed and found to be enough for use in MREIT for resistivity image reconstructions and also experimental designs and validations. The forward solver may find other applications where one needs to compute voltage, current density and magnetic flux density distributions all within a volume conductor.

Resistive switching near electrode interfaces: Estimations by a current model

NASA Astrophysics Data System (ADS)

Schroeder, Herbert; Zurhelle, Alexander; Stemmer, Stefanie; Marchewka, Astrid; Waser, Rainer

2013-02-01

The growing resistive switching database is accompanied by many detailed mechanisms which often are pure hypotheses. Some of these suggested models can be verified by checking their predictions with the benchmarks of future memory cells. The valence change memory model assumes that the different resistances in ON and OFF states are made by changing the defect density profiles in a sheet near one working electrode during switching. The resulting different READ current densities in ON and OFF states were calculated by using an appropriate simulation model with variation of several important defect and material parameters of the metal/insulator (oxide)/metal thin film stack such as defect density and its profile change in density and thickness, height of the interface barrier, dielectric permittivity, applied voltage. The results were compared to the benchmarks and some memory windows of the varied parameters can be defined: The required ON state READ current density of 105 A/cm2 can only be achieved for barriers smaller than 0.7 eV and defect densities larger than 3 × 1020 cm-3. The required current ratio between ON and OFF states of at least 10 requests defect density reduction of approximately an order of magnitude in a sheet of several nanometers near the working electrode.

Influence of Electrolyte Modulus on the Local Current Density at a Dendrite Tip on a Lithium Metal Electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harry, Katherine J.; Higa, Kenneth; Srinivasan, Venkat

Understanding and controlling the electrochemical deposition of lithium is imperative for the safe use of rechargeable batteries with a lithium metal anode. Solid block copolymer electrolyte membranes are known to enhance the stability of lithium metal anodes by mechanically suppressing the formation of lithium protrusions during battery charging. Time-resolved hard X-ray microtomography was used to monitor the internal structure of a symmetric lithium-polymer cell during galvanostatic polarization. The microtomography images were used to determine the local rate of lithium deposition, i.e. local current density, in the vicinity of a lithium globule growing through the electrolyte. Measurements of electrolyte displacement enabledmore » estimation of local stresses in the electrolyte. At early times, the current density was maximized at the globule tip, as expected from simple current distribution arguments. At later times, the current density was maximized at the globule perimeter. We show that this phenomenon is related to the local stress fields that arise as the electrolyte is deformed. The local current density, normalized for the radius of curvature, decreases with increasing compressive stresses at the lithium-polymer interface. To our knowledge, our study provides the first direct measurement showing the influence of local mechanical stresses on the deposition kinetics at lithium metal electrodes.« less

On the threshold conditions for electron beam damage of asbestos amosite fibers in the transmission electron microscope (TEM).

PubMed

Martin, Joannie; Beauparlant, Martin; Sauvé, Sébastien; L'Espérance, Gilles

2016-12-01

Asbestos amosite fibers were investigated to evaluate the damage caused by a transmission electron microscope (TEM) electron beam. Since elemental x-ray intensity ratios obtained by energy dispersive x-ray spectroscopy (EDS) are commonly used for asbestos identification, the impact of beam damage on these ratios was evaluated. It was determined that the magnesium/silicon ratio best represented the damage caused to the fiber. Various tests showed that most fibers have a current density threshold above which the chemical composition of the fiber is modified. The value of this threshold current density varied depending on the fiber, regardless of fiber diameter, and in some cases could not be determined. The existence of a threshold electron dose was also demonstrated. This value was dependent on the current density used and can be increased by providing a recovery period between exposures to the electron beam. This study also established that the electron beam current is directly related to the damage rate above a current density of 165 A/cm 2 . The large number of different results obtained suggest, that in order to ensure that the amosite fibers are not damaged, analysis should be conducted below a current density of 100 A/cm 2 .

Influence of Electrolyte Modulus on the Local Current Density at a Dendrite Tip on a Lithium Metal Electrode

DOE PAGES

Harry, Katherine J.; Higa, Kenneth; Srinivasan, Venkat; ...

2016-08-10

Understanding and controlling the electrochemical deposition of lithium is imperative for the safe use of rechargeable batteries with a lithium metal anode. Solid block copolymer electrolyte membranes are known to enhance the stability of lithium metal anodes by mechanically suppressing the formation of lithium protrusions during battery charging. Time-resolved hard X-ray microtomography was used to monitor the internal structure of a symmetric lithium-polymer cell during galvanostatic polarization. The microtomography images were used to determine the local rate of lithium deposition, i.e. local current density, in the vicinity of a lithium globule growing through the electrolyte. Measurements of electrolyte displacement enabledmore » estimation of local stresses in the electrolyte. At early times, the current density was maximized at the globule tip, as expected from simple current distribution arguments. At later times, the current density was maximized at the globule perimeter. We show that this phenomenon is related to the local stress fields that arise as the electrolyte is deformed. The local current density, normalized for the radius of curvature, decreases with increasing compressive stresses at the lithium-polymer interface. To our knowledge, our study provides the first direct measurement showing the influence of local mechanical stresses on the deposition kinetics at lithium metal electrodes.« less

Rule of formation of aluminum electroplating layer on Q235 steel.

PubMed

Ding, Zhimin; Feng, Qiuyuan; Shen, Changbin; Gao, Hong

2011-06-01

Aluminum electroplating layer on Q235 steel in AlCl3-NaCl-KCl molten salt was obtained, and the rule of its nucleation and growth were investigated. The results showed that aluminum electroplating layer formed through nucleating and growing of aluminum particles, and thickened by delaminating growth pattern. At low current density, the morphology of aluminum particles took on flake-like, while at high current density they changed to spherical. The thickness of plating layer increases with increasing current density and electroplating time. The relationship between the plating thickness (δ) and electroplating time (t) or current density (i) can be expressed as δ = 0.28f(137), and δ = 1.1i(1-39). Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Towards the definition of AMS facies in the deposits of pyroclastic density currents

USGS Publications Warehouse

Ort, M.H.; Newkirk, T.T.; Vilas, J.F.; Vazquez, J.A.; Ort, M.H.; Porreca, Massimiliano; Geissman, J.W.

2014-01-01

Anisotropy of magnetic susceptibility (AMS) provides a statistically robust technique to characterize the fabrics of deposits of pyroclastic density currents (PDCs). AMS fabrics in two types of pyroclastic deposits (small-volume phreatomagmatic currents in the Hopi Buttes volcanic field, Arizona, USA, and large-volume caldera-forming currents, Caviahue Caldera, Neuquén, Argentina) show similar patterns. Near the vent and in areas of high topographical roughness, AMS depositional fabrics are poorly grouped, with weak lineations and foliations. In a densely welded proximal ignimbrite, this fabric is overprinted by a foliation formed as the rock compacted and deformed. Medial deposits have moderate–strong AMS lineations and foliations. The most distal deposits have strong foliations but weak lineations. Based on these facies and existing models for pyroclastic density currents, deposition in the medial areas occurs from the strongly sheared, high-particle-concentration base of a density-stratified current. In proximal areas and where topography mixes this denser base upwards into the current, deposition occurs rapidly from a current with little uniformity to the shear, in which particles fall and collide in a chaotic fashion. Distal deposits are emplaced by a slowing or stalled current so that the dominant particle motion is vertical, leading to weak lineation and strong foliation.

Influence of High-Current-Density Impulses on the Compression Behavior: Experiments with Iron and a Nickel-Based Alloy

NASA Astrophysics Data System (ADS)

Demler, E.; Gerstein, G.; Dalinger, A.; Epishin, A.; Rodman, D.; Nürnberger, F.

2017-01-01

Difficulties of processing of high strength and/or brittle materials by plastic deformation, e.g., by forging, require to develop new industrial technologies. In particular, the feasible deformation rates are limited for low-ductile metallic materials. For this reason, processes were investigated to improve the deformability in which electrical impulses are to be applied to lower the yield strength. However, owing to the impulse duration and low current densities, concomitant effects always occur, e.g., as a result of Joule heating. Current developments in power electronics allow now to transmit high currents as short pulses. By reducing the impulse duration and increasing the current density, the plasticity of metallic materials can be correspondingly increased. Using the examples of polycrystalline iron and a single-crystal, nickel-based alloy (PWA 1480), current advances in the development of methods for forming materials by means of high-current-density impulses are demonstrated. For this purpose, appropriate specimens were loaded in compression and, using novel testing equipment, subjected to a current strength of 10 kA with an impulse duration of 2 ms. For a pre-defined strain, the test results show a significant decrease in the compressive stress during the compression test and a significant change in the dislocation distribution following the current impulse treatment.

First principle study of transport properties of a graphene nano structure

NASA Astrophysics Data System (ADS)

Kumar, Naveen; Sharma, Munish; Sharma, Jyoti Dhar; Ahluwalia, P. K.

2013-06-01

The first principle quantum transport calculations have been performed for graphene using Tran SIESTA which calculates transport properties using nonequilibrium Green's function method in conjunction with density-functional theory. Transmission functions, electron density of states and current-voltage characteristic have been calculated for a graphene nano structure using graphene electrodes. Transmission function, density of states and projected density of states show a discrete band structure which varies with applied voltage. The value of current is very low for applied voltage between 0.0 V to 5.0 V and lies in the range of pico ampere. In the V-I characteristic current shows non-linear fluctuating pattern with increase in voltage.

Burnout current density of bismuth nanowires

NASA Astrophysics Data System (ADS)

Cornelius, T. W.; Picht, O.; Müller, S.; Neumann, R.; Völklein, F.; Karim, S.; Duan, J. L.

2008-05-01

Single bismuth nanowires with diameters ranging from 100nmto1μm were electrochemically deposited in ion track-etched single-pore polycarbonate membranes. The maximum current density the wires are able to carry was investigated by ramping up the current until failure occurred. It increases by three to four orders of magnitude for nanowires embedded in the template compared to bulk bismuth and rises with diminishing diameter. Simulations show that the wires are heated up electrically to the melting temperature. Since the surface-to-volume ratio rises with diminishing diameter, thinner wires dissipate the heat more efficiently to the surrounding polymer matrix and, thus, can tolerate larger current densities.

Boiling-over dense pyroclastic density currents during the formation of the 100 km3 Huichapan ignimbrite in Central Mexico: Stratigraphic and lithofacies analysis

NASA Astrophysics Data System (ADS)

Pacheco-Hoyos, Jaime G.; Aguirre-Díaz, Gerardo J.; Dávila-Harris, Pablo

2018-01-01

A lithofacies analysis of the Huichapan ignimbrite has been undertaken to evaluate its depositional history from large pyroclastic density currents. The Huichapan ignimbrite is a massive ignimbrite sheet with a maximum runout of at least 55 km and thickness variations between 6 and 80 m. The lower portion of the Huichapan ignimbrite consists of a large plateau [ 100 km3; 69 km3 as dense-rock equivalent (DRE)] of massive ignimbrites with welding variations from densely welded to partly welded, devitrification, and high-temperature vapor-phase alteration. The lower part grades laterally to moderately welded and non-devitrified ignimbrites. These variations are interpreted as the sedimentation of density-stratified pyroclastic density currents erupted as boiling-over pulses from the Huichapan-Donguinyó caldera complex at a continuous rate, supporting deposition by quasi-steady progressive aggradation of sustained and hot currents. To the north of the caldera, the lower portion of the ignimbrite consists of a small plateau (< 10 km3) in which the densely welded and devitrified lithofacies are absent. Our interpretation is that the pyroclastic density currents flowed late to the north of the caldera and formed a smaller ignimbrite plateau with respect to the western one. This northern ignimbrite plateau cooled faster than the western ignimbrite plateau. Deposition-induced topographic modifications suggest that topographic obstacles, such as remnants of older volcanoes, may have promoted the deviation of the density currents to the north. The upper portion of the ignimbrite is composed of extensive, massive, coarse clast-rich, non-devitrified, and non-welded ignimbrites with abundant fines-poor pipes. This upper part was deposited from largely sustained and rapidly aggrading high-concentration currents in a near end-member, fluid escape-dominated flow boundary zone. The absence of welding in the upper portion may record pyroclastic density currents cooling during the formation of a relatively high pyroclastic fountain at the vent. We have established a depositional model for the Huichapan ignimbrite that explains the differences between the western and northern plateaus. The Huichapan ignimbrite was formed during a large caldera-forming eruption with concentrated pyroclastic fountains. High mass-flow rate was maintained for long periods, promoting the mobility of the pyroclastic density currents.

3-D capacitance density imaging system

DOEpatents

Fasching, G.E.

1988-03-18

A three-dimensional capacitance density imaging of a gasified bed or the like in a containment vessel is achieved using a plurality of electrodes provided circumferentially about the bed in levels and along the bed in channels. The electrodes are individually and selectively excited electrically at each level to produce a plurality of current flux field patterns generated in the bed at each level. The current flux field patterns are suitably sensed and a density pattern of the bed at each level determined. By combining the determined density patterns at each level, a three-dimensional density image of the bed is achieved. 7 figs.

3-D capacitance density imaging of fluidized bed

DOEpatents

Fasching, George E.

1990-01-01

A three-dimensional capacitance density imaging of a gasified bed or the like in a containment vessel is achieved using a plurality of electrodes provided circumferentially about the bed in levels and along the bed in channels. The electrodes are individually and selectively excited electrically at each level to produce a plurality of current flux field patterns generated in the bed at each level. The current flux field patterns are suitably sensed and a density pattern of the bed at each level determined. By combining the determined density patterns at each level, a three-dimensional density image of the bed is achieved.

Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa{sub 2}Cu{sub 3}O{sub 7}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, W.; Heinrich, B.; Zhou, H.

1994-12-31

Mapping of the magnetic flux density B{sub z} (perpendicular to the film plane) for a YBa{sub 2}Cu{sub 3}O{sub 7} thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B{sub z} distributions. From the known sheet magnetization, the tangential (B{sub x,y}) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B{sub x,y}/d, where d is the film thickness. The evolution of flux penetration as a function of applied field willmore » be shown.« less

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis bumpy torus plasma

NASA Technical Reports Server (NTRS)

Roth, J. R.

1976-01-01

Parametric variation of independent variables which may affect the characteristics of bumpy torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied included the type of gas, the polarity of the midplane electrode rings, the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

High-current fast electron beam propagation in a dielectric target.

PubMed

Klimo, Ondrej; Tikhonchuk, V T; Debayle, A

2007-01-01

Recent experiments demonstrate an efficient transformation of high intensity laser pulse into a relativistic electron beam with a very high current density exceeding 10(12) A cm(-2). The propagation of such a beam inside the target is possible if its current is neutralized. This phenomenon is not well understood, especially in dielectric targets. In this paper, we study the propagation of high current density electron beam in a plastic target using a particle-in-cell simulation code. The code includes both ionization of the plastic and collisions of newborn electrons. The numerical results are compared with a relatively simple analytical model and a reasonable agreement is found. The temporal evolution of the beam velocity distribution, the spatial density profile, and the propagation velocity of the ionization front are analyzed and their dependencies on the beam density and energy are discussed. The beam energy losses are mainly due to the target ionization induced by the self-generated electric field and the return current. For the highest beam density, a two-stream instability is observed to develop in the plasma behind the ionization front and it contributes to the beam energy losses.

Steady state and transient simulation of anion exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Dekel, Dario R.; Rasin, Igal G.; Page, Miles; Brandon, Simon

2018-01-01

We present a new model for anion exchange membrane fuel cells. Validation against experimental polarization curve data is obtained for current densities ranging from zero to above 2 A cm-2. Experimental transient data is also successfully reproduced. The model is very flexible and can be used to explore the system's sensitivity to a wide range of material properties, cell design specifications, and operating parameters. We demonstrate the impact of gas inlet relative humidity (RH), operating current density, ionomer loading and ionomer ion exchange capacity (IEC) values on cell performance. In agreement with the literature, high air RH levels are shown to improve cell performance. At high current densities (>1 A cm-2) this effect is observed to be especially significant. Simulated hydration number distributions across the cell reveal the related critical dependence of cathode hydration on air RH and current density values. When exploring catalyst layer design, optimal intermediate ionomer loading values are demonstrated. The benefits of asymmetric (cathode versus anode) electrode design are revealed, showing enhanced performance using higher cathode IEC levels. Finally, electrochemical reaction profiles across the electrodes uncover inhomogeneous catalyst utilization. Specifically, at high current densities the cathodic reaction is confined to a narrow region near the membrane.

Impact of electro-stimulation on denitrifying bacterial growth and analysis of bacterial growth kinetics using a modified Gompertz model in a bio-electrochemical denitrification reactor.

PubMed

Liu, Hengyuan; Chen, Nan; Feng, Chuanping; Tong, Shuang; Li, Rui

2017-05-01

This study aimed to investigate the effect of electro-stimulation on denitrifying bacterial growth in a bio-electrochemical reactor, and the growth were modeled using modified Gompertz model under different current densities at three C/Ns. It was found that the similar optimum current density of 250mA/m 2 was obtained at C/N=0.75, 1.00 and 1.25, correspondingly the maximum nitrate removal efficiencies were 98.0%, 99.2% and 99.9%. Moreover, ATP content and cell membrane permeability of denitrifying bacteria were significantly increased at optimum current density. Furthermore, modified Gompertz model fitted well with the microbial growth curves, and the highest maximum growth rates (µ max ) and shorter lag time were obtained at the optimum current density for all C/Ns. This study demonstrated that the modified Gompertz model could be used for describing microbial growth under different current densities and C/Ns in a bio-electrochemical denitrification reactor, and it provided an alternative for improving the performance of denitrification process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Apparent isotropic electrical property for electrical brain stimulation (EBS) using magnetic resonance diffusion weighted imaging (MR-DWI)

NASA Astrophysics Data System (ADS)

Lee, Mun Bae; Kwon, Oh-In

2018-04-01

Electrical brain stimulation (EBS) is an invasive electrotherapy and technique used in brain neurological disorders through direct or indirect stimulation using a small electric current. EBS has relied on computational modeling to achieve optimal stimulation effects and investigate the internal activations. Magnetic resonance diffusion weighted imaging (DWI) is commonly useful for diagnosis and investigation of tissue functions in various organs. The apparent diffusion coefficient (ADC) measures the intensity of water diffusion within biological tissues using DWI. By measuring trace ADC and magnetic flux density induced by the EBS, we propose a method to extract electrical properties including the effective extracellular ion-concentration (EEIC) and the apparent isotropic conductivity without any auxiliary additional current injection. First, the internal current density due to EBS is recovered using the measured one component of magnetic flux density. We update the EEIC by introducing a repetitive scheme called the diffusion weighting J-substitution algorithm using the recovered current density and the trace ADC. To verify the proposed method, we study an anesthetized canine brain to visualize electrical properties including electrical current density, effective extracellular ion-concentration, and effective isotropic conductivity by applying electrical stimulation of the brain.

Numerical modeling of lower hybrid current drive in fully non-inductive plasma start-up experiments on TST-2

NASA Astrophysics Data System (ADS)

Tsujii, N.; Takase, Y.; Ejiri, A.; Shinya, T.; Togashi, H.; Yajima, S.; Yamazaki, H.; Moeller, C. P.; Roidl, B.; Sonehara, M.; Takahashi, W.; Toida, K.; Yoshida, Y.

2017-12-01

Non-inductive plasma start-up is a critical issue for spherical tokamaks since there is not enough room to provide neutron shielding for the center solenoid. Start-up using lower hybrid (LH) waves has been studied on the TST-2 spherical tokamak. Because of the low magnetic field of a spherical tokamak, the plasma density needs to be kept at a very low value during the plasma current ramp-up so that the plasma core remains accessible to the LH waves. However, we have found that higher density was required to sustain larger plasma current. The achievable plasma current was limited by the maximum operational toroidal field of TST-2. The existence of an optimum density for LH current drive and its toroidal field dependence is explained through a numerical simulation based on a ray tracing code and a Fokker-Planck solver. In order to access higher density at the same magnetic field, a top-launch antenna was recently installed in addition to the existing outboard-launch antenna. Increase in the density limit was observed when the power was launched from the top antenna, consistently with the numerical predictions.

Effect of cathodic current density on performance of tungsten coatings on molybdenum prepared by electrodeposition in molten salt

NASA Astrophysics Data System (ADS)

Jiang, Fan

2016-02-01

Smooth tungsten coatings were prepared at current density below 70 mA cm-2 by electrodeposition on molybdenum substrate from Na2WO4-WO3 -melt at 1173 K in air atmosphere. As the current density reached up to 90 mA cm-2, many significant nodules were observed on the surface of the coating. Surface characterization, microstructure and mechanical properties were performed on the tungsten coatings. As the increasing of current density, the preferred orientation of the coatings changed to (2 0 0). All coatings exhibited columnar-grained-crystalline. There was about a 2 μm thick diffusion layer between tungsten coating and molybdenum substrate. The bending test revealed the tungsten coating had -good bonding strength with the molybdenum substrate. There is a down trend of the grain size of the coating on molybdenum as the current density increased from 30 mA cm-2 to 50 mA cm-2. The coating obtained at 50 mA cm-2 had a minimum grain size of 4.57 μm, while the microhardness of this coating reached to a maximum value of 495 HV.

Influence of propellant choice on MPD arcjet cathode surface current density distribution

NASA Astrophysics Data System (ADS)

Sheshadri, T. S.

1989-10-01

The radial current density on an MPD arcjet cathode surface is theoretically investigated for five propellants. It is found that excessive current concentration at the upstream end of the cathode occurs in the case of hydrogen. This undesirable effect is traced to the higher electrical conductivity of hydrogen plasma.

Current-induced depairing in the Bi2Te3/FeTe interfacial superconductor

NASA Astrophysics Data System (ADS)

Kunchur, M. N.; Dean, C. L.; Moghadam, N. Shayesteh; Knight, J. M.; He, Q. L.; Liu, H.; Wang, J.; Lortz, R.; Sou, I. K.; Gurevich, A.

2015-09-01

We investigated current induced depairing in the Bi2Te3 /FeTe topological insulator-chalcogenide interface superconductor. The measured depairing current density provides information on the magnetic penetration depth and superfluid density, which in turn shed light on the nature of the normal state that underlies the interfacial superconductivity.

Laser-induced electron source in a vacuum diode

NASA Astrophysics Data System (ADS)

Ghera, U.; Boxman, R. L.; Kleinman, H.; Ruschin, S.

1989-11-01

Experiments were conducted in which a high-power CO2 TEA laser interacted with metallic cathode in a high-vacuum (10 to the -8th Torr) diode. For power densities lower than 5 x 10 to the 7th W/sq cm, no current was detected. For power densities in the range of 5 x 10 to the 7th to 5 x 10 to the 8th W/sq cm, the Cu cathode emitted a maximum current of 40 mA. At a higher power density level, a circuit-limited current of 8 A was detected. The jump of a few orders of magnitude in the current is attributed to breakdown of the diode gap. The experimental results are similar to those of a triggered vacuum gap, and a thorough comparison is presented in this paper. The influence of the pressure in the vacuum chamber on the current magnitude shows the active role that adsorbed gas molecules have in the initial breakdown. When the cathode material was changed from metal to metal oxide, much lower laser power densities were required to reach the breakdown current region.

Generation of high-density biskyrmions by electric current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Licong; Zhang, Ying; He, Min

Much interest has been focused on the manipulation of magnetic skyrmions, including the generation, annihilation, and motion behaviors, for potential applications in spintronics. We experimentally demonstrate that a high-density Bloch-type biskyrmion lattice in MnNiGa can be generated by applying electric current. It is revealed that the density of biskyrmions can be remarkably increased by increasing the electric current, in contrast to the scattered biskyrmions induced by a magnetic field alone. Furthermore, the transition from the ferromagnetic state to the stripe domain structure can be terminated by the electric current, leading to the biskyrmions dominated residual domain pattern. These biskyrmions inmore » such residual domain structure are extremely stable at zero magnetic and electric fields and can further evolve into the high-density biskyrmion lattice over a temperature range from 100 to 330 K. Finally, our experimental findings open up a new pathway for the generation of skyrmion lattice by electric current manipulation.« less

Direct mapping of local redox current density on a monolith electrode by laser scanning.

PubMed

Lee, Seung-Woo; Lopez, Jeffrey; Saraf, Ravi F

2013-09-15

An optical method of mapping local redox reaction over a monolith electrode using simple laser scanning is described. As the optical signal is linearly proportional to the maximum redox current that is measured concomitantly by voltammetry, the optical signal quantitatively maps the local redox current density distribution. The method is demonstrated on two types of reactions: (1) a reversible reaction where the redox moieties are ionic, and (2) an irreversible reaction on two different types of enzymes immobilized on the electrode where the reaction moieties are nonionic. To demonstrate the scanning capability, the local redox behavior on a "V-shaped" electrode is studied where the local length scale and, hence, the local current density, is nonuniform. The ability to measure the current density distribution by this method will pave the way for multianalyte analysis on a monolith electrode using a standard three-electrode configuration. The method is called Scanning Electrometer for Electrical Double-layer (SEED). Copyright © 2013 Elsevier B.V. All rights reserved.

Generation of high-density biskyrmions by electric current

DOE PAGES

Peng, Licong; Zhang, Ying; He, Min; ...

2017-06-16

Much interest has been focused on the manipulation of magnetic skyrmions, including the generation, annihilation, and motion behaviors, for potential applications in spintronics. We experimentally demonstrate that a high-density Bloch-type biskyrmion lattice in MnNiGa can be generated by applying electric current. It is revealed that the density of biskyrmions can be remarkably increased by increasing the electric current, in contrast to the scattered biskyrmions induced by a magnetic field alone. Furthermore, the transition from the ferromagnetic state to the stripe domain structure can be terminated by the electric current, leading to the biskyrmions dominated residual domain pattern. These biskyrmions inmore » such residual domain structure are extremely stable at zero magnetic and electric fields and can further evolve into the high-density biskyrmion lattice over a temperature range from 100 to 330 K. Finally, our experimental findings open up a new pathway for the generation of skyrmion lattice by electric current manipulation.« less

Fast and efficient STT switching in MTJ using additional transient pulse current

NASA Astrophysics Data System (ADS)

Pathak, Sachin; Cha, Jongin; Jo, Kangwook; Yoon, Hongil; Hong, Jongill

2017-06-01

We propose a profile of write pulse current-density to switch magnetization in a perpendicular magnetic tunnel junction to reduce switching time and write energy as well. Our simulated results show that an overshoot transient pulse current-density (current spike) imposed to conventional rectangular-shaped pulse current-density (main pulse) significantly improves switching speed that yields the reduction in write energy accordingly. For example, we could dramatically reduce the switching time by 80% and thereby reduce the write energy over 9% in comparison to the switching without current spike. The current spike affects the spin dynamics of the free layer and reduces the switching time mainly due to spin torque induced. On the other hand, the large Oersted field induced causes changes in spin texture. We believe our proposed write scheme can make a breakthrough in magnetic random access memory technology seeking both high speed operation and low energy consumption.

High current densities enable exoelectrogens to outcompete aerobic heterotrophs for substrate.

PubMed

Ren, Lijiao; Zhang, Xiaoyuan; He, Weihua; Logan, Bruce E

2014-11-01

In mixed-culture microbial fuel cells (MFCs), exoelectrogens and other microorganisms compete for substrate. It has previously been assumed that substrate losses to other terminal electron acceptors over a fed-batch cycle, such as dissolved oxygen, are constant. However, a constant rate of substrate loss would only explain small increases in coulombic efficiencies (CEs, the fraction of substrate recovered as electrical current) with shorter cycle times, but not the large increases in CE that are usually observed with higher current densities and reduced cycle times. To better understand changes in CEs, COD concentrations were measured over time in fed-batch, single-chamber, air-cathode MFCs at different current densities (external resistances). COD degradation rates were all found to be first-order with respect to COD concentration, even under open circuit conditions with no current generation (first-order rate constant of 0.14 ± 0.01 h(-1) ). The rate of COD removal increased when there was current generation, with the highest rate constant (0.33 ± 0.02 h(-1) ) obtained at the lowest external resistance (100 Ω). Therefore, as the substrate concentration was reduced more quickly due to current generation, the rate of loss of substrate to non-exoelectrogens decreased due to this first-order substrate-concentration dependence. As a result, coulombic efficiencies rapidly increased due to decreased, and not constant, removal rates of substrate by non-exoelectrogens. These results show that higher current densities (lower resistances) redirect a greater percentage of substrate into current generation, enabling large increase in CEs with increased current densities. Biotechnol. Bioeng. 2014;111: 2163-2169. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

Measurement of the densities of Cu and Ag vapours in a low-voltage switch using the hook method

NASA Astrophysics Data System (ADS)

Lins, Günter

2012-05-01

In a research model of a low-voltage circuit breaker with fixed contacts and windows for optical access, arcs powered by either a high-current transformer or a capacitor bank were initiated by the explosion of tungsten wires. Air at atmospheric pressure was the switching medium. The number densities of neutral silver and copper vapours from contacts and arc runners were measured simultaneously by the hook method using a Mach-Zehnder interferometer combined with a 1 m spectrograph and a gated intensified CCD camera. When an arc current was flowing, a substantial fraction of the metal vapour was ionized, and thus not amenable to a density measurement with the technique chosen. To nevertheless obtain approximate density values, the arc current was forced to zero within 8 to 10 µs at a preset time and measurements were carried out 100 µs after extinction of the arc. At that time the metal vapour was expected to have recombined to a large extent but not yet diffused to the walls in significant amounts. Depending on the current amplitude reached within the arc duration the arc remained anchored to the silver contacts or commutated to the copper arc runners. At a maximum current amplitude of 650 A Ag vapour densities of the order of 1022 m-3 were observed near the anode outweighing the Cu vapour density by a factor of 20. When at 1600 A the arc commutated to the arc runners a Cu vapour density of 8 × 1021 m-3 was reached while the Ag density remained limited to 2 × 1021 m-3.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Injection lasers based on the AlGaAsSb system emitting at 1.6 μm

NASA Astrophysics Data System (ADS)

Virro, A. L.; Eliseev, P. G.; Lyuk, P. A.; Fridental, Ya K.; Khaller, Yu E.

1988-11-01

An experimental dependence of the threshold current density jth on the thickness of the active region was used to find the reduced threshold current density for AlGaAsSb (λ = 1.59μm, T = 295K) lasers: this density was 8 kA·cm-2·μm-1. The minimum threshold current was jth = 1.8 kA/cm2. Wide-contact lasers exhibited cw operation down to 175 K.

MHD Equilibrium with Reversed Current Density and Magnetic Islands Revisited: the Vacuum Vector Potential Calculus

NASA Astrophysics Data System (ADS)

L. Braga, F.

2013-10-01

The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic (MHD) equilibrium with reversed current density (RCD) profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.

Comparative study of methods to measure the density of Cementious powders

PubMed Central

Helsel, Michelle A.; Bentz, Dale

2016-01-01

The accurate measurement of the density of hydraulic cement has an essential role in the determination of concrete mixture proportions. As more supplementary cementitious materials (SCM), such as fly ash, and slag, or cement replacements materials such as limestone and calcium carbonate are used in blended cements, knowledge of the density of each powder or of the blended cement would allow a more accurate calculation of the proportions of a concrete mixture by volume instead of by mass. The current ASTM standard for measuring cement density is the “Test Method for Density of Hydraulic Cements” (ASTM C188-14), which utilizes a liquid displacement method to measure the volume of the cement. This paper will examine advantageous modifications of the current ASTM test, by alcohol substitutions for kerosene. In addition, a gas (helium) pycnometry method is evaluated as a possible alternative to the current standard. The described techniques will be compared to determine the most precise and reproducible method for measuring the density of hydraulic cements and other powders. PMID:27099404

Comparative study of methods to measure the density of Cementious powders.

PubMed

Helsel, Michelle A; Ferraris, Chiara F; Bentz, Dale

2016-11-01

The accurate measurement of the density of hydraulic cement has an essential role in the determination of concrete mixture proportions. As more supplementary cementitious materials (SCM), such as fly ash, and slag, or cement replacements materials such as limestone and calcium carbonate are used in blended cements, knowledge of the density of each powder or of the blended cement would allow a more accurate calculation of the proportions of a concrete mixture by volume instead of by mass. The current ASTM standard for measuring cement density is the "Test Method for Density of Hydraulic Cements" (ASTM C188-14), which utilizes a liquid displacement method to measure the volume of the cement. This paper will examine advantageous modifications of the current ASTM test, by alcohol substitutions for kerosene. In addition, a gas (helium) pycnometry method is evaluated as a possible alternative to the current standard. The described techniques will be compared to determine the most precise and reproducible method for measuring the density of hydraulic cements and other powders.

Magnetic Configurations of the Tilted Current Sheets and Dynamics of Their Flapping in Magnetotail

NASA Astrophysics Data System (ADS)

Shen, C.; Rong, Z. J.; Li, X.; Dunlop, M.; Liu, Z. X.; Malova, H. V.; Lucek, E.; Carr, C.

2009-04-01

Based on multiple spacecraft measurements, the geometrical structures of tilted current sheet and tail flapping waves have been analyzed and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1) The magnetic field lines (MFLs) are generally plane curves and the osculating planes in which the MFLs lie are about vertical to the magnetic equatorial plane, while the tilted current sheet may lean severely to the dawn or dusk side. (2) The tilted current sheet may become very thin, its half thickness is generally much less than the minimum radius of the curvature of the MFLs. (3) In the neutral sheet, the field-aligned current density becomes very large and has a maximum value at the center of the current sheet. (4) In some cases, the current density is a bifurcated one, and the two humps of the current density often superpose two peaks in the gradient of magnetic strength, indicating that the magnetic gradient drift current is possibly responsible for the formation of the two humps of the current density in some tilted current sheets. Tilted current sheets often appear along with tail thick current sheet flapping waves. It is found that, in the tail flapping current sheets, the minimum curvature radius of the MFLs in the current sheet is rather large with values around 1RE, while the neutral sheet may be very thin, with its half thickness being several tenths ofRE. During the flapping waves, the current sheet is tilted substantially, and the maximum tilt angle is generally larger than 45

Fermionic currents in AdS spacetime with compact dimensions

NASA Astrophysics Data System (ADS)

Bellucci, S.; Saharian, A. A.; Vardanyan, V.

2017-09-01

We derive a closed expression for the vacuum expectation value (VEV) of the fermionic current density in a (D +1 )-dimensional locally AdS spacetime with an arbitrary number of toroidally compactified Poincaré spatial dimensions and in the presence of a constant gauge field. The latter can be formally interpreted in terms of a magnetic flux treading the compact dimensions. In the compact subspace, the field operator obeys quasiperiodicity conditions with arbitrary phases. The VEV of the charge density is zero and the current density has nonzero components along the compact dimensions only. They are periodic functions of the magnetic flux with the period equal to the flux quantum and tend to zero on the AdS boundary. Near the horizon, the effect of the background gravitational field is small and the leading term in the corresponding asymptotic expansion coincides with the VEV for a massless field in the locally Minkowski bulk. Unlike the Minkowskian case, in the system consisting of an equal number of fermionic and scalar degrees of freedom, with same masses, charges and phases in the periodicity conditions, the total current density does not vanish. In these systems, the leading divergences in the scalar and fermionic contributions on the horizon are canceled and, as a consequence of that, the charge flux, integrated over the coordinate perpendicular to the AdS boundary, becomes finite. We show that in odd spacetime dimensions the fermionic fields realizing two inequivalent representations of the Clifford algebra and having equal phases in the periodicity conditions give the same contribution to the VEV of the current density. Combining the contributions from these fields, the current density in odd-dimensional C -,P - and T -symmetric models are obtained. As an application, we consider the ground state current density in curved carbon nanotubes described in terms of a (2 +1 )-dimensional effective Dirac model.

Current density distributions, field distributions and impedance analysis of segmented deep brain stimulation electrodes

NASA Astrophysics Data System (ADS)

Wei, Xuefeng F.; Grill, Warren M.

2005-12-01

Deep brain stimulation (DBS) electrodes are designed to stimulate specific areas of the brain. The most widely used DBS electrode has a linear array of 4 cylindrical contacts that can be selectively turned on depending on the placement of the electrode and the specific area of the brain to be stimulated. The efficacy of DBS therapy can be improved by localizing the current delivery into specific populations of neurons and by increasing the power efficiency through a suitable choice of electrode geometrical characteristics. We investigated segmented electrode designs created by sectioning each cylindrical contact into multiple rings. Prototypes of these designs, made with different materials and larger dimensions than those of clinical DBS electrodes, were evaluated in vitro and in simulation. A finite element model was developed to study the effects of varying the electrode characteristics on the current density and field distributions in an idealized electrolytic medium and in vitro experiments were conducted to measure the electrode impedance. The current density over the electrode surface increased towards the edges of the electrode, and multiple edges increased the non-uniformity of the current density profile. The edge effects were more pronounced over the end segments than over the central segments. Segmented electrodes generated larger magnitudes of the second spatial difference of the extracellular potentials, and thus required lower stimulation intensities to achieve the same level of neuronal activation as solid electrodes. For a fixed electrode conductive area, increasing the number of segments (edges) decreased the impedance compared to a single solid electrode, because the average current density over the segments increased. Edge effects played a critical role in determining the current density distributions, neuronal excitation patterns, and impedance of cylindrical electrodes, and segmented electrodes provide a means to increase the efficiency of DBS.

Over 15 MA/cm2 of critical current density in 4.8 µm thick, Zr-doped (Gd,Y)Ba2Cu3Ox superconductor at 30 K, 3T.

PubMed

Majkic, Goran; Pratap, Rudra; Xu, Aixia; Galstyan, Eduard; Selvamanickam, Venkat

2018-05-03

An Advanced MOCVD (A-MOCVD) reactor was used to deposit 4.8 µm thick (Gd,Y)BaCuO tapes with 15 mol% Zr addition in a single pass. A record-high critical current density (J c ) of 15.11 MA/cm 2 has been measured over a bridge at 30 K, 3T, corresponding to an equivalent (I c ) value of 8705 A/12 mm width. This corresponds to a lift factor in critical current of ~11 which is the highest ever reported to the best of author's knowledge. The measured critical current densities at 3T (B||c) and 30, 40 and 50 K, respectively, are 15.11, 9.70 and 6.26 MA/cm 2 , corresponding to equivalent Ic values of 8705, 5586 and 3606 A/12 mm and engineering current densities (J e ) of 7068, 4535 and 2928 A/mm 2 . The engineering current density (J e ) at 40 K, 3T is 7 times higher than that of the commercial HTS tapes available with 7.5 mol% Zr addition. Such record-high performance in thick films (>1 µm) is a clear demonstration that growing thick REBCO films with high critical current density (J c ) is possible, contrary to the usual findings of strong J c degradation with film thickness. This achievement was possible due to a combination of strong temperature control and uniform laminar flow achieved in the A-MOCVD system, coupled with optimization of BaZrO 3 nanorod growth parameters.

An Electrochemical Capacitor with Applicable Energy Density of 7.4 Wh/kg at Average Power Density of 3000 W/kg.

PubMed

Zhai, Teng; Lu, Xihong; Wang, Hanyu; Wang, Gongming; Mathis, Tyler; Liu, Tianyu; Li, Cheng; Tong, Yexiang; Li, Yat

2015-05-13

Electrochemical capacitors represent a new class of charge storage devices that can simultaneously achieve high energy density and high power density. Previous reports have been primarily focused on the development of high performance capacitor electrodes. Although these electrodes have achieved excellent specific capacitance based on per unit mass of active materials, the gravimetric energy densities calculated based on the weight of entire capacitor device were fairly small. This is mainly due to the large mass ratio between current collector and active material. We aimed to address this issue by a 2-fold approach of minimizing the mass of current collector and increasing the electrode performance. Here we report an electrochemical capacitor using 3D graphene hollow structure as current collector, vanadium sulfide and manganese oxide as anode and cathode materials, respectively. 3D graphene hollow structure provides a lightweight and highly conductive scaffold for deposition of pseudocapacitive materials. The device achieves an excellent active material ratio of 24%. Significantly, it delivers a remarkable energy density of 7.4 Wh/kg (based on the weight of entire device) at the average power density of 3000 W/kg. This is the highest gravimetric energy density reported for asymmetric electrochemical capacitors at such a high power density.

Structural and phase transformations in zinc and brass wires under heating with high-density current pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pervikov, A. V.

The work is focused on revealing the mechanism of structure and phase transformations in the metal wires under heating with a high-density current pulse (the electric explosion of wires, EEWs). It has been demonstrated on the example of brass and zinc wires that the transition of a current pulse with the density of j ≈ 3.3 × 10{sup 7} A/cm{sup 2} results in homogeneous heating of the crystalline structure of the metal/alloy. It has been determined that under heating with a pulse of high-density current pulse, the electric resistance of the liquid phases of zinc and brass decreases as the temperature increases. The results obtainedmore » allow for a conclusion that the presence of the particles of the condensed phase in the expanding products of EEW is the result of overheating instabilities in the liquid metal.« less

InAs-based interband-cascade-lasers emitting around 7 μm with threshold current densities below 1 kA/cm{sup 2} at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dallner, Matthias; Hau, Florian; Kamp, Martin

2015-01-26

Interband cascade lasers (ICLs) grown on InAs substrates with threshold current densities below 1 kA/cm{sup 2} are presented. Two cascade designs with different lengths of the electron injector were investigated. Using a cascade design with 3 InAs quantum wells (QWs) in the electron injector, a device incorporating 22 stages in the active region exhibited a threshold current density of 940 A/cm{sup 2} at a record wavelength of 7 μm for ICLs operating in pulsed mode at room temperature. By investigating the influence of the number of stages on the device performance for a cascade design with 2 QWs in the electron injector, amore » further reduction of the threshold current density to 800 A/cm{sup 2} was achieved for a 30 stage device.« less

Current drive at plasma densities required for thermonuclear reactors.

PubMed

Cesario, R; Amicucci, L; Cardinali, A; Castaldo, C; Marinucci, M; Panaccione, L; Santini, F; Tudisco, O; Apicella, M L; Calabrò, G; Cianfarani, C; Frigione, D; Galli, A; Mazzitelli, G; Mazzotta, C; Pericoli, V; Schettini, G; Tuccillo, A A

2010-08-10

Progress in thermonuclear fusion energy research based on deuterium plasmas magnetically confined in toroidal tokamak devices requires the development of efficient current drive methods. Previous experiments have shown that plasma current can be driven effectively by externally launched radio frequency power coupled to lower hybrid plasma waves. However, at the high plasma densities required for fusion power plants, the coupled radio frequency power does not penetrate into the plasma core, possibly because of strong wave interactions with the plasma edge. Here we show experiments performed on FTU (Frascati Tokamak Upgrade) based on theoretical predictions that nonlinear interactions diminish when the peripheral plasma electron temperature is high, allowing significant wave penetration at high density. The results show that the coupled radio frequency power can penetrate into high-density plasmas due to weaker plasma edge effects, thus extending the effective range of lower hybrid current drive towards the domain relevant for fusion reactors.

Linear increases in carbon nanotube density through multiple transfer technique.

PubMed

Shulaker, Max M; Wei, Hai; Patil, Nishant; Provine, J; Chen, Hong-Yu; Wong, H-S P; Mitra, Subhasish

2011-05-11

We present a technique to increase carbon nanotube (CNT) density beyond the as-grown CNT density. We perform multiple transfers, whereby we transfer CNTs from several growth wafers onto the same target surface, thereby linearly increasing CNT density on the target substrate. This process, called transfer of nanotubes through multiple sacrificial layers, is highly scalable, and we demonstrate linear CNT density scaling up to 5 transfers. We also demonstrate that this linear CNT density increase results in an ideal linear increase in drain-source currents of carbon nanotube field effect transistors (CNFETs). Experimental results demonstrate that CNT density can be improved from 2 to 8 CNTs/μm, accompanied by an increase in drain-source CNFET current from 4.3 to 17.4 μA/μm.

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis Bumpy Torus plasma

NASA Technical Reports Server (NTRS)

Roth, J. R.

1976-01-01

Parametric variation of independent variables which may affect the characteristics of the NASA Lewis Bumpy Torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power-law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of the potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied include the type of gas, the polarity of the midplane electrode rings (and hence the direction of the radial electric field), the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

LORETA imaging of P300 in schizophrenia with individual MRI and 128-channel EEG.

PubMed

Pae, Ji Soo; Kwon, Jun Soo; Youn, Tak; Park, Hae-Jeong; Kim, Myung Sun; Lee, Boreom; Park, Kwang Suk

2003-11-01

We investigated the characteristics of P300 generators in schizophrenics by using voxel-based statistical parametric mapping of current density images. P300 generators, produced by a rare target tone of 1500 Hz (15%) under a frequent nontarget tone of 1000 Hz (85%), were measured in 20 right-handed schizophrenics and 21 controls. Low-resolution electromagnetic tomography (LORETA), using a realistic head model of the boundary element method based on individual MRI, was applied to the 128-channel EEG. Three-dimensional current density images were reconstructed from the LORETA intensity maps that covered the whole cortical gray matter. Spatial normalization and intensity normalization of the smoothed current density images were used to reduce anatomical variance and subject-specific global activity and statistical parametric mapping (SPM) was applied for the statistical analysis. We found that the sources of P300 were consistently localized at the left superior parietal area in normal subjects, while those of schizophrenics were diversely distributed. Upon statistical comparison, schizophrenics, with globally reduced current densities, showed a significant P300 current density reduction in the left medial temporal area and in the left inferior parietal area, while both left prefrontal and right orbitofrontal areas were relatively activated. The left parietotemporal area was found to correlate negatively with Positive and Negative Syndrome Scale total scores of schizophrenic patients. In conclusion, the reduced and increased areas of current density in schizophrenic patients suggest that the medial temporal and frontal areas contribute to the pathophysiology of schizophrenia, the frontotemporal circuitry abnormality.

RAPID COMMUNICATION: Effect of strain, magnetic field and field angle on the critical current density of Y Ba2Cu3O7-δ coated conductors

NASA Astrophysics Data System (ADS)

van der Laan, D. C.; Ekin, J. W.; Douglas, J. F.; Clickner, C. C.; Stauffer, T. C.; Goodrich, L. F.

2010-07-01

A large, magnetic-field-dependent, reversible reduction in critical current density with axial strain in Y Ba2Cu3O7-δ coated conductors at 75.9 K has been measured. This effect may have important implications for the performance of Y Ba2Cu3O7-δ coated conductors in applications where the conductor experiences large stresses in the presence of a magnetic field. Previous studies have been performed only under tensile strain and could provide only a limited understanding of the in-field strain effect. We now have constructed a device for measuring the critical current density as a function of axial compressive and tensile strain and applied magnetic field as well as magnetic field angle, in order to determine the magnitude of this effect and to create a better understanding of its origin. The reversible reduction in critical current density with strain becomes larger with increasing magnetic field at all field angles. At 76 K the critical current density is reduced by about 30% at - 0.5% strain when a magnetic field of 5 T is applied parallel to the c-axis of the conductor or 8 T is applied in the ab-plane, compared to a reduction of only 13% in self-field. Differences in the strain response of the critical current density at various magnetic field angles indicate that the pinning mechanisms in Y Ba2Cu3O7-δ coated conductors are uniquely affected by strain. Contribution of NIST, not subject to US copyright.

Reformulated space-charge-limited current model and its application to disordered organic systems

NASA Astrophysics Data System (ADS)

Woellner, Cristiano F.; Freire, José A.

2011-02-01

We have reformulated a traditional model used to describe the current-voltage dependence of low mobility materials sandwiched between planar electrodes by using the quasi-electrochemical potential as the fundamental variable instead of the local electric field or the local charge carrier density. This allows the material density-of-states to enter explicitly in the equations and dispenses with the need to assume a particular type of contact. The diffusion current is included and as a consequence the current-voltage dependence obtained covers, with increasing bias, the diffusion limited current, the space-charge limited current, and the injection limited current regimes. The generalized Einstein relation and the field and density dependent mobility are naturally incorporated into the formalism; these two points being of particular relevance for disordered organic semiconductors. The reformulated model can be applied to any material where the carrier density and the mobility may be written as a function of the quasi-electrochemical potential. We applied it to the textbook example of a nondegenerate, constant mobility material and showed how a single dimensionless parameter determines the form of the I(V) curve. We obtained integral expressions for the carrier density and for the mobility as a function of the quasi-electrochemical potential for a Gaussianly disordered organic material and found the general form of the I(V) curve for such materials over the full range of bias, showing how the energetic disorder alone can give rise, in the space-charge limited current regime, to an I∝Vn dependence with an exponent n larger than 2.

Diamagnetic currents

NASA Astrophysics Data System (ADS)

Macris, N.; Martin, Ph. A.; Pulé, J. V.

1988-06-01

We study the diamagnetic surface currents of particles in thermal equilibrium submitted to a constant magnetic field. The current density of independent electrons with Boltzmann (respectively Fermi) statistics has a gaussian (respectively exponential) bound for its fall off into the bulk. For a system of interacting particles at low activity with Boltzmann statistics, the current density is localized near to the boundary and integrable when the two-body potential decays as |x|-α, α >4, α>4, in three dimensions. In all cases, the integral of the current density is independent of the nature of the confining wall and correctly related to the bulk magnetisation. The results hold for hard and soft walls and all field strength. The analysis relies on the Feynman-Kac-Ito representation of the Gibbs state and on specific properties of the Brownian bridge process.

Isotopic effect in experiments on lower hybrid current drive in the FT-2 tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lashkul, S. I., E-mail: Serguey.lashkul@mail.ioffe.ru; Altukhov, A. B.; Gurchenko, A. D., E-mail: aleksey.gurchenko@mail.ioffe.ru

To analyze factors influencing the limiting value of the plasma density at which lower hybrid (LH) current drive terminates, the isotopic factor (the difference in the LH resonance densities in hydrogen and deuterium plasmas) was used for the first time in experiments carried out at the FT-2 tokamak. It is experimentally found that the efficiency of LH current drive in deuterium plasma is appreciably higher than that in hydrogen plasma. The significant role of the parametric decay of the LH pumping wave, which hampers the use of the LH range of RF waves for current drive at high plasma densities,more » is confirmed. It is demonstrated that the parameters characterizing LH current drive agree well with the earlier results obtained at large tokamaks.« less

Electric currents and coronal heating in NOAA active region 6952

NASA Technical Reports Server (NTRS)

Metcalf, T. R.; Canfield, R. C.; Hudson, H. S.; Mickey, D. L.; Wulser, J. -P.; Martens, P. C. H.; Tsuneta, S.

1994-01-01

We examine the spatial and temporal relationship between coronal structures observed with the soft X-ray telescope (SXT) on board the Yohkoh spacecraft and the vertical electric current density derived from photospheric vector magnetograms obtained using the Stokes Polarimeter at the Mees Solar Observatory. We focus on a single active region: AR 6952 which we observed on 7 days during 1991 December. For 11 independent maps of the vertical electric current density co-aligned with non-flaring X-ray images, we search for a morphological relationship between sites of high vertical current density in the photosphere and enhanced X-ray emission in the overlying corona. We find no compelling spatial or temporal correlation between the sites of vertical current and the bright X-ray structures in this active region.

The most intense current sheets in the high-speed solar wind near 1 AU

NASA Astrophysics Data System (ADS)

Podesta, John J.

2017-03-01

Electric currents in the solar wind plasma are investigated using 92 ms fluxgate magnetometer data acquired in a high-speed stream near 1 AU. The minimum resolvable scale is roughly 0.18 s in the spacecraft frame or, using Taylor's "frozen turbulence" approximation, one proton inertial length di in the plasma frame. A new way of identifying current sheets is developed that utilizes a proxy for the current density J obtained from the derivatives of the three orthogonal components of the observed magnetic field B. The most intense currents are identified as 5σ events, where σ is the standard deviation of the current density. The observed 5σ events are characterized by an average scale size of approximately 3di along the flow direction of the solar wind, a median separation of around 50di or 100di along the flow direction of the solar wind, and a peak current density on the order of 0.5 pA/cm2. The associated current-carrying structures are consistent with current sheets; however, the planar geometry of these structures cannot be confirmed using single-point, single-spacecraft measurements. If Taylor's hypothesis continues to hold for the energetically dominant fluctuations at kinetic scales 1

Current Density Measurements of an Annular-Geometry Ion Engine

NASA Technical Reports Server (NTRS)

Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.

2012-01-01

The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential nonuniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to 10% of the average current density in the discharge and 5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.

Current Density Measurements of an Annular-Geometry Ion Engine

NASA Technical Reports Server (NTRS)

Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.

2012-01-01

The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential non-uniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to +/-10% of the average current density in the discharge and +/-5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 - 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.

Experiments with planar inductive ion source meant for creation of H+ beams.

PubMed

Vainionpaa, J H; Kalvas, T; Hahto, S K; Reijonen, J

2007-06-01

In this article the effects of different engineering parameters of rf-driven ion sources with an external spiral antenna and a quartz rf window are studied. This article consists of three main topics: the effect of source geometry on the operation gas pressure, the effect of source materials and magnetic confinement on extracted current density and ion species, and the effect of different antenna geometries on the extracted current density. The effect of source geometry was studied using three cylindrical plasma chambers with different inner diameters. The chamber materials were studied using two materials, aluminum (Al) and alumina (Al(2)O(3)). The removable 14 magnet multicusp confinement arrangement enabled us to compare the effects of the two wall materials with and without the magnetic confinement. The highest measured proton fractions were measured using Al(2)O(3) plasma chamber and no multicusp confinement. For the compared ion sources the source with multicusp confinement and Al(2)O(3) plasma chamber yields the highest current densities. Multicusp confinement increased the maximum extracted current by up to a factor of 2. Plasma production with different antenna geometries were also studied. The highest current density was achieved using 4.5 loop solenoid antenna with 6.0 cm diameter. A slightly lower current density with lower pressure was achieved using a tightly wound 3 loop spiral antenna with 3.3 cm inner diameter and 6 cm outer diameter.

On the estimation of the current density in space plasmas: Multi- versus single-point techniques

NASA Astrophysics Data System (ADS)

Perri, Silvia; Valentini, Francesco; Sorriso-Valvo, Luca; Reda, Antonio; Malara, Francesco

2017-06-01

Thanks to multi-spacecraft mission, it has recently been possible to directly estimate the current density in space plasmas, by using magnetic field time series from four satellites flying in a quasi perfect tetrahedron configuration. The technique developed, commonly called ;curlometer; permits a good estimation of the current density when the magnetic field time series vary linearly in space. This approximation is generally valid for small spacecraft separation. The recent space missions Cluster and Magnetospheric Multiscale (MMS) have provided high resolution measurements with inter-spacecraft separation up to 100 km and 10 km, respectively. The former scale corresponds to the proton gyroradius/ion skin depth in ;typical; solar wind conditions, while the latter to sub-proton scale. However, some works have highlighted an underestimation of the current density via the curlometer technique with respect to the current computed directly from the velocity distribution functions, measured at sub-proton scales resolution with MMS. In this paper we explore the limit of the curlometer technique studying synthetic data sets associated to a cluster of four artificial satellites allowed to fly in a static turbulent field, spanning a wide range of relative separation. This study tries to address the relative importance of measuring plasma moments at very high resolution from a single spacecraft with respect to the multi-spacecraft missions in the current density evaluation.

Ultrahigh-Density Nanowire Arrays Grown in Self-Assembled Diblock Copolymer Templates

NASA Astrophysics Data System (ADS)

Thurn-Albrecht, T.; Schotter, J.; Kästle, G. A.; Emley, N.; Shibauchi, T.; Krusin-Elbaum, L.; Guarini, K.; Black, C. T.; Tuominen, M. T.; Russell, T. P.

2000-12-01

We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 × 1011 wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.

Computational analysis of thresholds for magnetophosphenes

NASA Astrophysics Data System (ADS)

Laakso, Ilkka; Hirata, Akimasa

2012-10-01

In international guidelines, basic restriction limits on the exposure of humans to low-frequency magnetic and electric fields are set with the objective of preventing the generation of phosphenes, visual sensations of flashing light not caused by light. Measured data on magnetophosphenes, i.e. phosphenes caused by a magnetically induced electric field on the retina, are available from volunteer studies. However, there is no simple way for determining the retinal threshold electric field or current density from the measured threshold magnetic flux density. In this study, the experimental field configuration of a previous study, in which phosphenes were generated in volunteers by exposing their heads to a magnetic field between the poles of an electromagnet, is computationally reproduced. The finite-element method is used for determining the induced electric field and current in five different MRI-based anatomical models of the head. The direction of the induced current density on the retina is dominantly radial to the eyeball, and the maximum induced current density is observed at the superior and inferior sides of the retina, which agrees with literature data on the location of magnetophosphenes at the periphery of the visual field. On the basis of computed data, the macroscopic retinal threshold current density for phosphenes at 20 Hz can be estimated as 10 mA m-2 (-20% to  + 30%, depending on the anatomical model); this current density corresponds to an induced eddy current of 14 μA (-20% to  + 10%), and about 20% of this eddy current flows through each eye. The ICNIRP basic restriction limit for the induced electric field in the case of occupational exposure is not exceeded until the magnetic flux density is about two to three times the measured threshold for magnetophosphenes, so the basic restriction limit does not seem to be conservative. However, the reasons for the non-conservativeness are purely technical: removal of the highest 1% of electric field values by taking the 99th percentile as recommended by the ICNIRP leads to the underestimation of the induced electric field, and there are difficulties in applying the basic restriction limit for the retinal electric field.

Superconducting current injection transistor with very high critical-current-density edge-junctions

NASA Astrophysics Data System (ADS)

van Zeghbroeck, B. J.

1985-03-01

A Superconducting Current Injection Transistor (Super-CIT) was fabricated with very high critical current-density edge-junctions. The junctions have a niobium base electrode and a lead-alloy counter electrode. The length of the junctions is 30 microns and the critical-current density is 190KA/sq cm. The Super-CIT has a current gain of 2, a large signal transresistance of 100 mV/A, and the turn-on delay, inferred from the junction resonance, is 7ps. The power dissipation is 3.5 microwatts and the power-delay product is 24.5aJ. Gap reduction due to heating was observed, limiting the maximum power dissipation per unit length to 1.1 microwatt/micron. Compared to lead-alloy Super-CITs, the device is five times smaller, three times faster, and has a three times larger output voltage. The damping resistor and the contact junction could also be eliminated.

Topological analysis of the current density field in molecules

NASA Astrophysics Data System (ADS)

Gomes, J. A. N. F.

A global qualitative theory of the current density has been very recently introduced by the author. These topological studies are reviewed and special attention is given to the shape of the separatrices which encase both toroidal and axial vortices.

Small Barriers Trigger Liftoff of Unconfined Dilute Heated Laboratory Density Currents

NASA Astrophysics Data System (ADS)

Fauria, K.; Andrews, B. J.; Manga, M.

2015-12-01

Dilute pyroclastic density currents (PDCs) are hot, turbulent, particle-laden flows that propagate because they are denser than air. PDCs can traverse tens to hundreds of kilometers and surmount ridges 100s of m tall, yet the effects of complex topography on PDC liftoff and runout distance are uncertain. Here we used scaled laboratory experiments to explore how barriers affect dilute density current dynamics and the occurrence of liftoff. We created dilute density currents by heating and suspending 20 μm diameter talc in air in an 8.5 x 6.1 x 2.6 m tank. We scaled the currents with respect to Froude, densimetric and thermal Richardson, particle Stokes and Settling numbers such that they were dynamically similar to natural PDCs. While currents were fully turbulent, their Reynolds numbers were not as high as those for natural PDCs. We performed the first set of experiments in a laterally unconfined volume, used laser sheets to illuminate the currents, measured bulk sedimentation rates down the current centerlines, and positioned four to twenty-four cm tall ridge-like barriers in the path of the currents. We found that relatively small barriers (~ half the current height) caused PDC liftoff. By comparison, conservation of kinetic and potential energy predicts that incompressible density currents are able to surmount barriers twice their height. Furthermore, we observed increased sedimentation immediately upstream of barriers and conclude that small barriers initiated buoyancy reversal through a combination of increased air entrainment and sedimentation. We conducted a second set of experiments with the same thermal scaling and mass flux rates but where the currents were laterally confined within a 0.6 m wide channel. We found that small barriers also triggered liftoff of confined currents, but that the body of these currents reattached after liftoff. Those results suggest that lateral confinement inhibits buoyancy reversal by limiting the surface area of the current-air interface and air entrainment. Real dilute PDCs that originate in confined valleys may therefore have different fates and longer runout distances than those on unconfined planes.

Use of a spread sheet to calculate the current-density distribution produced in human and rat models by low-frequency electric fields.

PubMed

Hart, F X

1990-01-01

The current-density distribution produced inside irregularly shaped, homogeneous human and rat models by low-frequency electric fields is obtained by a two-stage finite-difference procedure. In the first stage the model is assumed to be equipotential. Laplace's equation is solved by iteration in the external region to obtain the capacitive-current densities at the model's surface elements. These values then provide the boundary conditions for the second-stage relaxation solution, which yields the internal current-density distribution. Calculations were performed with the Excel spread-sheet program on a Macintosh-II microcomputer. A spread sheet is a two-dimensional array of cells. Each cell of the sheet can represent a square element of space. Equations relating the values of the cells can represent the relationships between the potentials in the corresponding spatial elements. Extension to three dimensions is readily made. Good agreement was obtained with current densities measured on human models with both, one, or no legs grounded and on rat models in four different grounding configurations. The results also compared well with predictions of more sophisticated numerical analyses. Spread sheets can provide an inexpensive and relatively simple means to perform good, approximate dosimetric calculations on irregularly shaped objects.

Impedance of an intense plasma-cathode electron source for tokamak startup

NASA Astrophysics Data System (ADS)

Hinson, E. T.; Barr, J. L.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Perry, J. M.

2016-05-01

An impedance model is formulated and tested for the ˜1 kV , 1 kA/cm2 , arc-plasma cathode electron source used for local helicity injection tokamak startup. A double layer sheath is established between the high-density arc plasma ( narc≈1021 m-3 ) within the electron source, and the less dense external tokamak edge plasma ( nedge≈1018 m-3 ) into which current is injected at the applied injector voltage, Vinj . Experiments on the Pegasus spherical tokamak show that the injected current, Iinj , increases with Vinj according to the standard double layer scaling Iinj˜Vinj3 /2 at low current and transitions to Iinj˜Vinj1 /2 at high currents. In this high current regime, sheath expansion and/or space charge neutralization impose limits on the beam density nb˜Iinj/Vinj1 /2 . For low tokamak edge density nedge and high Iinj , the inferred beam density nb is consistent with the requirement nb≤nedge imposed by space-charge neutralization of the beam in the tokamak edge plasma. At sufficient edge density, nb˜narc is observed, consistent with a limit to nb imposed by expansion of the double layer sheath. These results suggest that narc is a viable control actuator for the source impedance.

Analysis of current density and specific absorption rate in biological tissue surrounding transcutaneous transformer for an artificial heart.

PubMed

Shiba, Kenji; Nukaya, Masayuki; Tsuji, Toshio; Koshiji, Kohji

2008-01-01

This paper reports on the current density and specific absorption rate (SAR) analysis of biological tissue surrounding an air-core transcutaneous transformer for an artificial heart. The electromagnetic field in the biological tissue is analyzed by the transmission line modeling method, and the current density and SAR as a function of frequency, output voltage, output power, and coil dimension are calculated. The biological tissue of the model has three layers including the skin, fat, and muscle. The results of simulation analysis show SARs to be very small at any given transmission conditions, about 2-14 mW/kg, compared to the basic restrictions of the International Commission on nonionizing radiation protection (ICNIRP; 2 W/kg), while the current density divided by the ICNIRP's basic restrictions gets smaller as the frequency rises and the output voltage falls. It is possible to transfer energy below the ICNIRP's basic restrictions when the frequency is over 250 kHz and the output voltage is under 24 V. Also, the parts of the biological tissue that maximized the current density differ by frequencies; in the low frequency is muscle and in the high frequency is skin. The boundary is in the vicinity of the frequency 600-1000 kHz.

Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

NASA Astrophysics Data System (ADS)

Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2015-03-01

Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as Bz. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple Bz data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured Bz data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

Determination of plasma density from data on the ion current to cylindrical and planar probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voloshin, D. G., E-mail: dvoloshin@mics.msu.su; Vasil’eva, A. N.; Kovalev, A. S.

2016-12-15

To improve probe methods of plasma diagnostics, special probe measurements were performed and numerical models describing ion transport to a probe with allowance for collisions were developed. The current–voltage characteristics of cylindrical and planar probes were measured in an RF capacitive discharge in argon at a frequency of 81 MHz and plasma densities of 10{sup 10}–10{sup 11} cm{sup –3}, typical of modern RF reactors. 1D and 2D numerical models based on the particle-in-cell method with Monte Carlo collisions for simulating ion motion and the Boltzmann equilibrium for electrons are developed to describe current collection by a probe. The models weremore » used to find the plasma density from the ion part of the current–voltage characteristic, study the effect of ion collisions, and verify simplified approaches to determining the plasma density. A 1D hydrodynamic model of the ion current to a cylindrical probe with allowance for ion collisions is proposed. For a planar probe, a method to determine the plasma density from the averaged numerical results is developed. A comparative analysis of different approaches to calculating the plasma density from the ion current to a probe is performed.« less

Influence of lifestyle factors on mammographic density in postmenopausal women.

PubMed

Brand, Judith S; Czene, Kamila; Eriksson, Louise; Trinh, Thang; Bhoo-Pathy, Nirmala; Hall, Per; Celebioglu, Fuat

2013-01-01

Mammographic density is a strong risk factor for breast cancer. Apart from hormone replacement therapy (HRT), little is known about lifestyle factors that influence breast density. We examined the effect of smoking, alcohol and physical activity on mammographic density in a population-based sample of postmenopausal women without breast cancer. Lifestyle factors were assessed by a questionnaire and percentage and area measures of mammographic density were measured using computer-assisted software. General linear models were used to assess the association between lifestyle factors and mammographic density and effect modification by body mass index (BMI) and HRT was studied. Overall, alcohol intake was positively associated with percent mammographic density (P trend  = 0.07). This association was modified by HRT use (P interaction  = 0.06): increasing alcohol intake was associated with increasing percent density in current HRT users (P trend  = 0.01) but not in non-current users (P trend  = 0.82). A similar interaction between alcohol and HRT was found for the absolute dense area, with a positive association being present in current HRT users only (P interaction  = 0.04). No differences in mammographic density were observed across categories of smoking and physical activity, neither overall nor in stratified analyses by BMI and HRT use. Increasing alcohol intake is associated with an increase in mammography density, whereas smoking and physical activity do not seem to influence density. The observed interaction between alcohol and HRT may pose an opportunity for HRT users to lower their mammographic density and breast cancer risk.

Influence of Lifestyle Factors on Mammographic Density in Postmenopausal Women

PubMed Central

Brand, Judith S.; Czene, Kamila; Eriksson, Louise; Trinh, Thang; Bhoo-Pathy, Nirmala; Hall, Per; Celebioglu, Fuat

2013-01-01

Background Mammographic density is a strong risk factor for breast cancer. Apart from hormone replacement therapy (HRT), little is known about lifestyle factors that influence breast density. Methods We examined the effect of smoking, alcohol and physical activity on mammographic density in a population-based sample of postmenopausal women without breast cancer. Lifestyle factors were assessed by a questionnaire and percentage and area measures of mammographic density were measured using computer-assisted software. General linear models were used to assess the association between lifestyle factors and mammographic density and effect modification by body mass index (BMI) and HRT was studied. Results Overall, alcohol intake was positively associated with percent mammographic density (P trend  = 0.07). This association was modified by HRT use (P interaction  = 0.06): increasing alcohol intake was associated with increasing percent density in current HRT users (P trend  = 0.01) but not in non-current users (P trend  = 0.82). A similar interaction between alcohol and HRT was found for the absolute dense area, with a positive association being present in current HRT users only (P interaction  = 0.04). No differences in mammographic density were observed across categories of smoking and physical activity, neither overall nor in stratified analyses by BMI and HRT use. Conclusions Increasing alcohol intake is associated with an increase in mammography density, whereas smoking and physical activity do not seem to influence density. The observed interaction between alcohol and HRT may pose an opportunity for HRT users to lower their mammographic density and breast cancer risk. PMID:24349146

Net field-aligned currents observed by Triad

NASA Technical Reports Server (NTRS)

Sugiura, M.; Potemra, T. A.

1975-01-01

From the Triad magnetometer observation of a step-like level shift in the east-west component of the magnetic field at 800 km altitude, the existence of a net current flowing into or away from the ionosphere in a current layer was inferred. The current direction is toward the ionosphere on the morning side and away from it on the afternoon side. The field aligned currents observed by Triad are considered as being an important element in the electro-dynamical coupling between the distant magnetosphere and the ionosphere. The current density integrated over the thickness of the layer increases with increasing magnetic activity, but the relation between the current density and Kp in individual cases is not a simple linear relation. An extrapolation of the statistical relation to Kp = 0 indicates existence of a sheet current of order 0.1 amp/m even at extremely quiet times. During periods of higher magnetic activity an integrated current of approximately 1 amp/m and average current density of order 0.000001 amp/sq m are observed. The location and the latitudinal width of the field aligned current layer carrying the net current very roughly agree with those of the region of high electron intensities in the trapping boundary.

Performance of conversion efficiency of a crystalline silicon solar cell with base doping density

NASA Astrophysics Data System (ADS)

Sahin, Gokhan; Kerimli, Genber; Barro, Fabe Idrissa; Sane, Moustapha; Alma, Mehmet Hakkı

In this study, we investigate theoretically the electrical parameters of a crystalline silicon solar cell in steady state. Based on a one-dimensional modeling of the cell, the short circuit current density, the open circuit voltage, the shunt and series resistances and the conversion efficiency are calculated, taking into account the base doping density. Either the I-V characteristic, series resistance, shunt resistance and conversion efficiency are determined and studied versus base doping density. The effects applied of base doping density on these parameters have been studied. The aim of this work is to show how short circuit current density, open circuit voltage and parasitic resistances are related to the base doping density and to exhibit the role played by those parasitic resistances on the conversion efficiency of the crystalline silicon solar.

A novel photoactive and three-dimensional stainless steel anode dramatically enhances the current density of bioelectrochemical systems.

PubMed

Feng, Huajun; Tang, Chenyi; Wang, Qing; Liang, Yuxiang; Shen, Dongsheng; Guo, Kun; He, Qiaoqiao; Jayaprada, Thilini; Zhou, Yuyang; Chen, Ting; Ying, Xianbin; Wang, Meizhen

2018-04-01

This study reports a high-performance 3D stainless-steel photoanode (3D SS photoanode) for bioelectrochemical systems (BESs). The 3D SS photoanode consists of 3D carbon-coated SS felt bioactive side and a flat α-Fe 2 O 3 -coated SS plate photoactive side. Without light illumination, the electrode reached a current density of 26.2 ± 1.9 A m -2 , which was already one of the highest current densities reported thus far. Under illumination, the current density of the electrode was further increased to 46.5 ± 2.9 A m -2 . The mechanism of the photo-enhanced current production can be attributed to the reduced charge-transfer resistance between electrode surface and the biofilm with illumination. It was also found that long-term light illumination can enhance the biofilm formation on the 3D SS photoanode. These findings demonstrate that using the synergistic effect of photocatalysis and microbial electrocatalysis is an efficient way to boost the current production of the existing high-performance 3D anodes for BESs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Theory of flux cutting and flux transport at the critical current of a type-II superconducting cylindrical wire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clem, John R

2011-02-17

I introduce a critical-state theory incorporating both flux cutting and flux transport to calculate the magnetic-field and current-density distributions inside a type-II superconducting cylinder at its critical current in a longitudinal applied magnetic field. The theory is an extension of the elliptic critical-state model introduced by Romero-Salazar and Pérez-Rodríguez. The vortex dynamics depend in detail on two nonlinear effective resistivities for flux cutting (ρ{sub ∥}) and flux flow (ρ{sub ⊥}), and their ratio r=ρ{sub ∥}/ρ{sub ⊥}. When r<1, the low relative efficiency of flux cutting in reducing the magnitude of the internal magnetic-flux density leads to a paramagnetic longitudinal magneticmore » moment. As a model for understanding the experimentally observed interrelationship between the critical currents for flux cutting and depinning, I calculate the forces on a helical vortex arc stretched between two pinning centers when the vortex is subjected to a current density of arbitrary angle Φ. Simultaneous initiation of flux cutting and flux transport occurs at the critical current density J{sub c}(Φ) that makes the vortex arc unstable.« less

Theory of flux cutting and flux transport at the critical current of a type-II superconducting cylindrical wire

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clem, John R.

2011-02-17

I introduce a critical-state theory incorporating both flux cutting and flux transport to calculate the magnetic-field and current-density distributions inside a type-II superconducting cylinder at its critical current in a longitudinal applied magnetic field. The theory is an extension of the elliptic critical-state model introduced by Romero-Salazar and Perez-Rodriguez. The vortex dynamics depend in detail on two nonlinear effective resistivities for flux cutting ({rho}{parallel}) and flux flow ({rho}{perpendicular}), and their ratio r = {rho}{parallel}/{rho}{perpendicular}. When r < 1, the low relative efficiency of flux cutting in reducing the magnitude of the internal magnetic-flux density leads to a paramagnetic longitudinal magneticmore » moment. As a model for understanding the experimentally observed interrelationship between the critical currents for flux cutting and depinning, I calculate the forces on a helical vortex arc stretched between two pinning centers when the vortex is subjected to a current density of arbitrary angle {phi}. Simultaneous initiation of flux cutting and flux transport occurs at the critical current density J{sub c}({phi}) that makes the vortex arc unstable.« less

Theory of flux cutting and flux transport at the critical current of a type-II superconducting cylindrical wire

NASA Astrophysics Data System (ADS)

Clem, John R.

2011-06-01

I introduce a critical-state theory incorporating both flux cutting and flux transport to calculate the magnetic-field and current-density distributions inside a type-II superconducting cylinder at its critical current in a longitudinal applied magnetic field. The theory is an extension of the elliptic critical-state model introduced by Romero-Salazar and Pérez-Rodríguez. The vortex dynamics depend in detail on two nonlinear effective resistivities for flux cutting (ρ∥) and flux flow (ρ⊥), and their ratio r=ρ∥/ρ⊥. When r<1, the low relative efficiency of flux cutting in reducing the magnitude of the internal magnetic-flux density leads to a paramagnetic longitudinal magnetic moment. As a model for understanding the experimentally observed interrelationship between the critical currents for flux cutting and depinning, I calculate the forces on a helical vortex arc stretched between two pinning centers when the vortex is subjected to a current density of arbitrary angle ϕ. Simultaneous initiation of flux cutting and flux transport occurs at the critical current density Jc(ϕ) that makes the vortex arc unstable.

Tobacco retail outlet density and risk of youth smoking in New Zealand.

PubMed

Marsh, Louise; Ajmal, Ali; McGee, Rob; Robertson, Lindsay; Cameron, Claire; Doscher, Crile

2016-12-01

Evidence suggests inconsistent findings on the relationship between density of tobacco outlets around schools and risk of smoking among students. This study examines the density of tobacco outlets around secondary schools in New Zealand (NZ) and current smoking, experimental smoking, susceptibility to smoking, and attempted and successful tobacco purchasing. Smoking data came from the 2012 ASH Year 10 survey, a national survey of youth smoking in NZ. Geographic Information Systems were used to map tobacco retail outlets; a layer of secondary school locations was obtained from Koordinates.com. Logistic regression examined the relationship between density of outlets around schools and smoking behaviours, adjusting for individual-level and school-level confounders. Of the 27 238 students surveyed, 3.5% (952) were current smokers, 4.1% (n=1 128) were experimental smokers, and 39.8% (10 454) of nonsmokers were susceptible to smoking. An inverse relationship was found between the density of tobacco retail outlets and current smoking. Current smokers were significantly more likely to attempt to purchase tobacco if the density of tobacco retail outlets around their school was high. Non-smoking students were more likely to be susceptible to smoking if the density of tobacco outlets around their school was high. There was no statistically significant association between density of tobacco outlets and successful purchasing, nor experimental smoking. Restricting the permitted density of tobacco retail outlets around schools should be part of comprehensive tobacco control. In this regard, both smokers and non-smokers support the introduction of increased regulation of the tobacco retail environment to achieve our national smoke-free 2025 goal. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

A novel feedback algorithm for simulating controlled dynamics and confinement in the advanced reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahlin, J.-E.; Scheffel, J.

2005-06-15

In the advanced reversed-field pinch (RFP), the current density profile is externally controlled to diminish tearing instabilities. Thus the scaling of energy confinement time with plasma current and density is improved substantially as compared to the conventional RFP. This may be numerically simulated by introducing an ad hoc electric field, adjusted to generate a tearing mode stable parallel current density profile. In the present work a current profile control algorithm, based on feedback of the fluctuating electric field in Ohm's law, is introduced into the resistive magnetohydrodynamic code DEBSP [D. D. Schnack and D. C. Baxter, J. Comput. Phys. 55,more » 485 (1984); D. D. Schnack, D. C. Barnes, Z. Mikic, D. S. Marneal, E. J. Caramana, and R. A. Nebel, Comput. Phys. Commun. 43, 17 (1986)]. The resulting radial magnetic field is decreased considerably, causing an increase in energy confinement time and poloidal {beta}. It is found that the parallel current density profile spontaneously becomes hollow, and that a formation, being related to persisting resistive g modes, appears close to the reversal surface.« less

Analysis of the processes occurring in a submicrosecond discharge with a linear current density of up to 3 MA/cm through a thick-wall stainless-steel electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branitsky, A. V.; Grabovski, E. V.; Dzhangobegov, V. V.

The state of conductors carrying a megampere current from the generator to the load is studied experimentally. It is found that the plasma produced from cylindrical stainless-steel tubes during the passage of a submicrosecond current pulse with a linear density of 3 MA/cm expands with a velocity of 5.5 km/s. Numerical results on the diffusion of the magnetic field induced by a current with a linear density of 1–3MA/cm into metal electrodes agree with the experimental data on the penetration time of the magnetic field. For a linear current density of 3.1 MA/cm, the experimentally determined electric field strength onmore » the inner surface of the tube is 4 kV/cm. The calculated electric field strength on the inner surface of the tube turns out to be two times higher, which can be explained by plasma production on the outer and inner surfaces of the electrode.« less

High Current Plasma Electrolytic Oxidation Coating Processes for Wear and Corrosion Prevention of Al 2024

NASA Astrophysics Data System (ADS)

Wang, Rui

Plasma electrolytic oxidation (PEO) treatments have been used in the aerospace and automotive industries because the coating formed on light metals or alloys has great hardness, high wear, corrosion, and oxidation resistance, and a low friction coefficient that improves lifetime length and provide a higher surface quality. However, the PEO treatments that are presently used for industrial applications require a long period of time to confirm the quality of the coating. For this reason, the present study seeks to increase the current density of PEO treatments to improve their efficiency and explore the performance of the obtained coatings. It was found that for high current density (0.18A/cm2) PEO treatments, smaller ratio, such as 50% and 70%, is beneficial to obtaining a better performance coating. When compared with the coating of a "normal" (current density: 0.09A/cm2) PEO treatment, it had better wear resistance; however, for corrosion resistance, it had a lower performance than the coatings obtained by the "normal" current density PEO treatment which was attributed to the negative influence of porosity increase.

Evaluation of Delamination of X80 Pipeline Steel Coating Under Alternating Stray Current Via Scanning Electrochemical Microscopy

NASA Astrophysics Data System (ADS)

Wang, Xinhua; Liu, Qiang; Chun, Yingchun; Li, Yingchao; Wang, Zuquan

2018-04-01

The delamination of epoxy coating on X80 pipeline steel was evaluated under various stray alternating current (AC) interferences (0-300 A/m2). Qualitative and quantitative analyses were carried out using scanning electrochemical microscopy (SECM), electrochemical impedance spectroscopy (EIS), and three-dimensional digital microscopy. The results show that the SECM current is directly proportional to the soaking time and applied current density. The variation in SECM current curve shape indicates the delamination distance of epoxy coatings at the defect area. The depths of corrosion pits at 50, 100, and 300 A/m2 stray currents were 140, 160, and 240 μm, respectively. The corrosion pits also became wider with increasing current densities. With increasing stray AC densities, both the coating delamination and pit depth became more severe at the same soaking time. The EIS results show that the change in impedance was not significant without stray current, whereas the impedance first decreased and then increased when stray current was applied. These results are consistent with the SECM measurements.

Comparison of current distributions in electroconvulsive therapy and transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Sekino, Masaki; Ueno, Shoogo

2002-05-01

We compared current density distributions in electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS) by numerical calculations. The model consisted of an air region and three types of tissues with different conductivities representing the brain, the skull, and the scalp. In the ECT model, electric currents were applied through electrodes with a voltage of 100 V. In the TMS model, a figure-eight coil (6 cm diameter per coil) was placed on the vertex of the head model. An alternating current with a peak intensity of 3.0 kA and a frequency of 4.2 kHz was applied to the coil. The maximum current densities inside the brain in ECT (bilateral electrode position) and TMS were 234 and 322 A/m2, respectively. The results indicate that magnetic stimulators can generate comparable current densities to ECT. While the skull significantly affected current distributions in ECT, TMS efficiently induced eddy currents in the brain. In addition, TMS is more beneficial than ECT because the localized current distribution reduces the risk of adverse side effects.

Correlations between critical current density, j{sub c}, critical temperature, T{sub c}, and structural quality of Y{sub 1}B{sub 2}Cu{sub 3}O{sub 7-x} thin superconducting films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chrzanowski, J.; Xing, W.B.; Atlan, D.

1994-12-31

Correlations between critical current density (j{sub c}) critical temperature (T{sub c}) and the density of edge dislocations and nonuniform strain have been observed in YBCO thin films deposited by pulsed laser ablation on (001) LaAlO{sub 3} single crystals. Distinct maxima in j{sub c} as a function of the linewidths of the (00{ell}) Bragg reflections and as a function of the mosaic spread have been found in the epitaxial films. These maxima in j{sub c} indicate that the magnetic flux lines, in films of structural quality approaching that of single crystals, are insufficiently pinned which results in a decreased critical currentmore » density. T{sub c} increased monotonically with improving crystalline quality and approached a value characteristic of a pure single crystal. A strong correlation between j{sub c} and the density of edge dislocations N{sub D} was found. At the maximum of the critical current density the density of edge dislocations was estimated to be N{sub D}{approximately}1-2 x 10{sup 9}/cm{sup 2}.« less

Calculation of nuclear spin-spin coupling constants using frozen density embedding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Götz, Andreas W., E-mail: agoetz@sdsc.edu; Autschbach, Jochen; Visscher, Lucas, E-mail: visscher@chem.vu.nl

2014-03-14

We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects inmore » the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between {sup 199}Hg and {sup 13}C upon coordination of dimethylsulfoxide solvent molecules.« less

Investigation of the silicon ion density during molecular beam epitaxy growth

NASA Astrophysics Data System (ADS)

Eifler, G.; Kasper, E.; Ashurov, Kh.; Morozov, S.

2002-05-01

Ions impinging on a surface during molecular beam epitaxy influence the growth and the properties of the growing layer, for example, suppression of dopant segregation and the generation of crystal defects. The silicon electron gun in the molecular beam epitaxy (MBE) equipment is used as a source for silicon ions. To use the effect of ion bombardment the mechanism of generation and distribution of ions was investigated. A monitoring system was developed and attached at the substrate position in the MBE growth chamber to measure the ion and electron densities towards the substrate. A negative voltage was applied to the substrate to modify the ion energy and density. Furthermore the current caused by charge carriers impinging on the substrate was measured and compared with the results of the monitoring system. The electron and ion densities were measured by varying the emission current of the e-gun achieving silicon growth rates between 0.07 and 0.45 nm/s and by changing the voltage applied to the substrate between 0 to -1000 V. The dependencies of ion and electron densities were shown and discussed within the framework of a simple model. The charged carrier densities measured with the monitoring system enable to separate the ion part of the substrate current and show its correlation to the generation rate. Comparing the ion density on the whole substrate and in the center gives a hint to the ion beam focusing effect. The maximum ion and electron current densities obtained were 0.40 and 0.61 μA/cm2, respectively.

Impaired emotional facial expression decoding in alcoholism is also present for emotional prosody and body postures.

PubMed

Maurage, Pierre; Campanella, Salvatore; Philippot, Pierre; Charest, Ian; Martin, Sophie; de Timary, Philippe

2009-01-01

Emotional facial expression (EFE) decoding impairment has been repeatedly reported in alcoholism (e.g. Philippot et al., 1999). Nevertheless, several questions are still under debate concerning this alteration, notably its generalization to other emotional stimuli and its variation according to the emotional valence of stimuli. Eighteen recently detoxified alcoholic subjects and 18 matched controls performed a decoding test consisting in emotional intensity ratings on various stimuli (faces, voices, body postures and written scenarios) depicting different emotions (anger, fear, happiness, neutral, sadness). Perceived threat and difficulty were also assessed for each stimulus. Alcoholic individuals had a preserved decoding performance for happiness stimuli, but alcoholism was associated with an underestimation of sadness and fear, and with a general overestimation of anger. More importantly, these decoding impairments were observed for faces, voices and postures but not for written scenarios. We observed for the first time a generalized emotional decoding impairment in alcoholism, as this impairment is present not only for faces but also for other visual (i.e. body postures) and auditory stimuli. Moreover, we report that this alteration (1) is mainly indexed by an overestimation of anger and (2) cannot be explained by an 'affect labelling' impairment, as the semantic comprehension of written emotional scenarios is preserved. Fundamental and clinical implications are discussed.

Supernova-driven outflows and chemical evolution of dwarf spheroidal galaxies

PubMed Central

Qian, Yong-Zhong; Wasserburg, G. J.

2012-01-01

We present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the intergalactic medium and are fossilized systems with their stars undergoing slow internal evolution. For a wide variety of infall histories of unprocessed baryonic matter to feed star formation, most of the observed MDs can be well described by our model. The key requirement is that the fraction of the gas mass lost by supernova-driven outflows is close to unity. This model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their dark matter halos. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. We show that, for infall rates far below the net rate of gas loss to star formation and outflows, the MD in our model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. This result suggests that globular clusters may be end members of the same family as dSphs. PMID:22411827

Supernova-driven outflows and chemical evolution of dwarf spheroidal galaxies.

PubMed

Qian, Yong-Zhong; Wasserburg, G J

2012-03-27

We present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the intergalactic medium and are fossilized systems with their stars undergoing slow internal evolution. For a wide variety of infall histories of unprocessed baryonic matter to feed star formation, most of the observed MDs can be well described by our model. The key requirement is that the fraction of the gas mass lost by supernova-driven outflows is close to unity. This model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their dark matter halos. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. We show that, for infall rates far below the net rate of gas loss to star formation and outflows, the MD in our model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. This result suggests that globular clusters may be end members of the same family as dSphs.

High-current discharge channel contraction in high density gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutberg, Ph. G.; Bogomaz, A. A.; Pinchuk, M. E.

Research results for discharges at current amplitudes of 0.5-1.6 MA and current rise rate of {approx}10{sup 10} A/s are presented. The discharge is performed in the hydrogen environment at the initial pressure of 5-35 MPa. Initiation is implemented by a wire explosion. The time length of the first half-period of the discharge current is 70-150 {mu}s. Under such conditions, discharge channel contraction is observed; the contraction is followed by soft x-ray radiation. The phenomena are discussed, which are determined by high density of the gas surrounding the discharge channel. These phenomena are increase of the current critical value, where themore » channel contraction begins and growth of temperature in the axis region of the channel, where the initial density of the gas increases.« less

High field superconductors for superconducting machines

NASA Astrophysics Data System (ADS)

Rupp, G.; Wilhelm, M.; Wohlleben, K.; Ziegler, G.; Springer, E.

1980-11-01

High current capacity Nb3Sn multifilament conductors were fabricated. A solid state diffusion process was used. The number of conductor filaments approaches 70,000 with filament diameters being approximately 1.5 microns. Effective current densities reach 86,000 A/sq cm at a magnetic flux density of 10 T and operating temperature of 4.2 K. Calibrated flattened cables of twisted strands were fabricated for higher currents (up to 1000 A at 10 T). Generally, quantitative relations can be given for the rise in the critical current of Nb3Sn multifilament conductors, observed under the influence of mechanical stresses. Long lengths (km) of these conductors were used to manufacture superconducting solenoids two different ways. These rise to the short sample current, usually without conditioning, and deliver magnetic flux densities up to 14 T with an 8.5 T NbTi background field.

Investigation of electrodes under flow of a submicrosecond current pulse with linear density up to 3 MA/cm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Branitskii, A. V.; Grabovskii, E. V.; Dzhangobegov, V. V.

The states of current-carrying elements at the transmission of megaampere current into load are studied. It is determined that the expansion velocity of plasma generated at the outer surface of cylindrical tubes produced of stainless steel, at flowing through them of submicrosecond current pulses with linear density of 3 MA/cm is 5.5 km/s. The evolution of various modes of instability is analyzed.

Reduction, analysis, and properties of electric current systems in solar active regions

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Demoulin, Pascal

1995-01-01

The specific attraction and, in large part, the significance of solar magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 deg ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 deg ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local `preferred' direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar (beta) (gamma) (delta)-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA/sq m and have a linear decreasing distribution to a diameter of 30 Mn.

Reduction, Analysis, and Properties of Electric Current Systems in Solar Active Regions

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Demoulin, Pascal

1995-01-01

The specific attraction and, in large part, the significance of solar vector magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 degree ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 degree ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local "preferred" direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar beta gamma delta-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA per square meter and have a linear decreasing distribution to a diameter of 30 Mm.

Supercapacitors based on self-assembled graphene organogel.

PubMed

Sun, Yiqing; Wu, Qiong; Shi, Gaoquan

2011-10-14

Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability.

Bioelectricity generation in microbial fuel cell using natural microflora and isolated pure culture bacteria from anaerobic palm oil mill effluent sludge.

PubMed

Nor, Muhamad Hanif Md; Mubarak, Mohd Fahmi Muhammad; Elmi, Hassan Sh Abdirahman; Ibrahim, Norahim; Wahab, Mohd Firdaus Abdul; Ibrahim, Zaharah

2015-08-01

A double-chambered membrane microbial fuel cell (MFC) was constructed to investigate the potential use of natural microflora anaerobic palm oil mill effluent (POME) sludge and pure culture bacteria isolated from anaerobic POME sludge as inoculum for electricity generation. Sterilized final discharge POME was used as the substrate with no addition of nutrients. MFC operation using natural microflora anaerobic POME sludge showed a maximum power density and current density of 85.11mW/m(2) and 91.12mA/m(2) respectively. Bacterial identification using 16S rRNA analysis of the pure culture isolated from the biofilm on the anode MFC was identified as Pseudomonas aeruginosa strain ZH1. The electricity generated in MFC using P. aeruginosa strain ZH1 showed maximum power density and current density of 451.26mW/m(2) and 654.90mA/m(2) respectively which were five times higher in power density and seven times higher in current density compared to that of MFC using anaerobic POME sludge. Copyright © 2015 Elsevier Ltd. All rights reserved.

Properties of the electrostatically driven helical plasma state

NASA Astrophysics Data System (ADS)

Akçay, Cihan; Finn, John M.; Nebel, Richard A.; Barnes, Daniel C.; Martin, Neal

2018-02-01

A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a (m =1 ,n =1 ) (helical) symmetry where m and n represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius r

Effects of electrolysis by low-amperage electric current on the chlorophyll fluorescence characteristics of Microcystis aeruginosa.

PubMed

Lin, Li; Feng, Cong; Li, Qingyun; Wu, Min; Zhao, Liangyuan

2015-10-01

Effects of electrolysis by low-amperage electric current on the chlorophyll fluorescence characteristics of Microcystis aeruginosa were investigated in order to reveal the mechanisms of electrolytic inhibition of algae. Threshold of current density was found under a certain initial no. of algae cell. When current density was equal to or higher than the threshold (fixed electrolysis time), growth of algae was inhibited completely and the algae lost the ability to survive. Effect of algal solution volume on algal inhibition was insignificant. Thresholds of current density were 8, 10, 14, 20, and 22 mA cm(-2) at 2.5 × 10(7), 5 × 10(7), 1 × 10(8), 2.5 × 10(8), and 5 × 10(8) cells mL(-1) initial no. of algae cell, respectively. Correlativity between threshold of current and initial no. of algae cells was established for scale-up and determining operating conditions. Changes of chlorophyll fluorescence parameters demonstrated that photosystem (PS) II of algae was damaged by electrolysis but still maintained relatively high activity when algal solution was treated by current densities lower than the threshold. The activity of algae recovered completely after 6 days of cultivation. On the contrary, when current density was higher than the threshold, connection of phycobilisome (PBS) and PS II core complexes was destroyed, PS II system of algae was damaged irreversibly, and algae could not survive thoroughly. The inactivation of M. aeruginosa by electrolysis can be attributed to irreversible separation of PBS from PS II core complexes and the damage of PS II of M. aeruginosa.

Faraday-effect polarimeter-interferometer system for current density measurement on EAST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H. Q.; Jie, Y. X., E-mail: yx-jie@ipp.ac.cn; Zou, Z. Y.

2014-11-15

A multichannel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique is under development for current density and electron density profile measurements in the EAST tokamak. Novel molybdenum retro-reflectors are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which will provide real-time Faraday rotation angle and density phase shift output, have been developed for use on the POINT system. Initial calibration indicates the electron line-integrated density resolution is less than 5 × 10{sup 16} m{sup −2} (∼2°), and the Faraday rotation angle rms phase noise is <0.1°.

Ultrahigh-density nanowire arrays grown in self-assembled diblock copolymer templates.

PubMed

Thurn-Albrecht, T; Schotter, J; Kästle, G A; Emley, N; Shibauchi, T; Krusin-Elbaum, L; Guarini, K; Black, C T; Tuominen, M T; Russell, T P

2000-12-15

We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 x 10(11) wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.

High performance all-solid-state symmetric supercapacitor based on porous carbon made from a metal-organic framework compound

NASA Astrophysics Data System (ADS)

Yu, Feng; Wang, Teng; Wen, Zubiao; Wang, Hongxia

2017-10-01

In this work, we demonstrate the synthesis of porous carbon material with high specific surface area by using metal-organic framework (MOF) as precursor. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have confirmed that the material was amorphous and consisted of nanoparticles (5-6 nm) and hierarchical distribution of pores. The characterization of the material by N2 adsorption/desorption isotherm measurement have shown that the material had a high specific surface area reaching to 2618.7 m2 g-1 and abundant porosity with pore size less than 10 nm. The investigation of the electrochemical properties of the material has shown the porous carbon electrode possessed excellent rate performance with high specific capacitances of 150.8 F g-1 at a current density of 5 A g-1, and 133.6 F g-1 at a current density of 50 A g-1, respectively. An all-solid-state symmetric supercapacitor assembled using the as-prepared porous carbon as electrodes and Na2SO4/PVA gel as an electrolyte delivered a high power density of 13 516.4 W kg-1 with an energy density of 8.26 Wh kg-1. A high energy density of 17.37 Wh kg-1 was obtained at discharge current density of 1 A g-1. In addition, the device exhibited superior cycling performance with 94.8% retention rate after 10 000 cycles at a current density of 10 A g-1.

Particle-in-cell simulations of electron beam control using an inductive current divider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanekamp, S. B.; Angus, J. R.; Cooperstein, G.

2015-11-15

Kinetic, time-dependent, electromagnetic, particle-in-cell simulations of the inductive current divider are presented. The inductive current divider is a passive method for controlling the trajectory of an intense, hollow electron beam using a vacuum structure that inductively splits the beam's return current. The current divider concept was proposed and studied theoretically in a previous publication [Swanekamp et al., Phys. Plasmas 22, 023107 (2015)]. A central post carries a portion of the return current (I{sub 1}), while the outer conductor carries the remainder (I{sub 2}) with the injected beam current given by I{sub b} = I{sub 1} + I{sub 2}. The simulations are in agreement withmore » the theory which predicts that the total force on the beam trajectory is proportional to (I{sub 2}−I{sub 1}) and the force on the beam envelope is proportional to I{sub b}. Independent control over both the current density and the beam angle at the target is possible by choosing the appropriate current-divider geometry. The root-mean-square (RMS) beam emittance (ε{sub RMS}) varies as the beam propagates through the current divider to the target. For applications where control of the beam trajectory is desired and the current density at the target is similar to the current density at the entrance foil, there is a modest 20% increase in ε{sub RMS} at the target. For other applications where the beam is pinched to a current density ∼5 times larger at the target, ε{sub RMS} is 2–3 times larger at the target.« less

An analysis of the gradient-induced electric fields and current densities in human models when situated in a hybrid MRI-LINAC system

NASA Astrophysics Data System (ADS)

Liu, Limei; Trakic, Adnan; Sanchez-Lopez, Hector; Liu, Feng; Crozier, Stuart

2014-01-01

MRI-LINAC is a new image-guided radiotherapy treatment system that combines magnetic resonance imaging (MRI) with a linear accelerator (LINAC) in a single unit. One drawback is that the pulsing of the split gradient coils of the system induces an electric field and currents in the patient which need to be predicted and evaluated for patient safety. In this novel numerical study the in situ electric fields and associated current densities were evaluated inside tissue-accurate male and female human voxel models when a number of different split-geometry gradient coils were operated. The body models were located in the MRI-LINAC system along the axial and radial directions in three different body positions. Each model had a region of interest (ROI) suitable for image-guided radiotherapy. The simulation results show that the amplitudes and distributions of the field and current density induced by different split x-gradient coils were similar with one another in the ROI of the body model, but varied outside of the region. The fields and current densities induced by a split classic coil with the surface unconnected showed the largest deviation from those given by the conventional non-split coils. Another finding indicated that the distributions of the peak current densities varied when the body position, orientation or gender changed, while the peak electric fields mainly occurred in the skin and fat tissues.

Effect of mass and charge transport speed and direction in porous anodes on microbial electrolysis cell performance.

PubMed

Sleutels, Tom H J A; Hamelers, Hubertus V M; Buisman, Cees J N

2011-01-01

The use of porous electrodes like graphite felt as anode material has the potential of achieving high volumetric current densities. High volumetric current densities, however, may also lead to mass transport limitations within these porous materials. Therefore, in this study we investigated the mass and charge transport limitations by increasing the speed of the forced flow and changing the flow direction through the porous anode. Increase of the flow speed led to a decrease in current density when the flow was directed towards the membrane caused by an increase in anode resistance. Current density increased at higher flow speed when the flow was directed away from the membrane. This was caused by a decrease in transport resistance of ions through the membrane which increased the buffering effect of the system. Furthermore, the increase in flow speed led to an increase of the coulombic efficiency by 306%. Copyright © 2010 Elsevier Ltd. All rights reserved.

Unsteady density-current equations for highly curved terrain

NASA Technical Reports Server (NTRS)

Sivakumaran, N. S.; Dressler, R. F.

1989-01-01

New nonlinear partial differential equations containing terrain curvature and its rate of change are derived that describe the flow of an atmospheric density current. Unlike the classical hydraulic-type equations for density currents, the new equations are valid for two-dimensional, gradually varied flow over highly curved terrain, hence suitable for computing unsteady (or steady) flows over arbitrary mountain/valley profiles. The model assumes the atmosphere above the density current exerts a known arbitrary variable pressure upon the unknown interface. Later this is specialized to the varying hydrostatic pressure of the atmosphere above. The new equations yield the variable velocity distribution, the interface position, and the pressure distribution that contains a centrifugal component, often significantly larger than its hydrostatic component. These partial differential equations are hyperbolic, and the characteristic equations and characteristic directions are derived. Using these to form a characteristic mesh, a hypothetical unsteady curved-flow problem is calculated, not based upon observed data, merely as an example to illustrate the simplicity of their application to unsteady flows over mountains.

Microstructure and properties of ceramic coatings prepared by micro-arc oxidation on 7075 aluminum alloy

NASA Astrophysics Data System (ADS)

Cao, G. P.; Song, R. G.

2018-02-01

Micro-arc oxidation (MAO) ceramic coatings were prepared in silicate-based electrolyte on 7075 aluminum alloy. The effects of current density on microstructure and properties of the MAO coatings were studied by scanning electron microscopy (SEM), stereoscopic microscopy, x-ray diffraction (XRD), electrochemical tests as well as tribological and wear tests. The results showed that the current density plays an important role in affecting the quality of the MAO coatings. XRD results showed that the α-Al2O3 phase first increased then decreased with increasing the current density, which matched well with the micro-hardness test and the wearing test results. On the other hand, the coalescent strength measurements revealed that the coating prepared at the current density of 12 A dm-2 is of the highest adhesion force. The potentiodynamic polarization test proved that the coating obtained under 10 A dm-2 exhibits the best corrosion resistance, which is directly related to the morphology of coating.

On the Maximum and Characteristic Curvature of Current Density of High tc Superconductor Ybco in Flux Relaxation

NASA Astrophysics Data System (ADS)

Ye, Jiping; Sun, Lei; Dai, Xianxi; Dai, Jixin

The flux relaxation is one of important topics in the studies of high Tc superconductivity, because it is related to the energy loss in practical applications. There are many mechanisms, theories and relaxation laws suggested in the literatures. It is very interesting to test them according to the characters and compare them with the experiments. Some people think that the characters of the famous theories are their negative curvature. According our inversion solution, the relaxation ArcG law and experimental data analysis, the relaxation law has both positive and negative signs. This prediction is hopeful to be checked by experiments in future. The current densities of many high Tc superconductors decrease very rapidly in the early time in the relaxation. People do not know what their maximums are. In this work, a theory to determine these maximums of the current densities is presented. The theory is concretely realized by inversion for some real data of the YBCO and their maximum current densities are obtained.

A comparison between block and smooth modeling in finite element simulations of tDCS*

PubMed Central

Indahlastari, Aprinda; Sadleir, Rosalind J.

2018-01-01

Current density distributions in five selected structures, namely, anterior superior temporal gyrus (ASTG), hippocampus (HIP), inferior frontal gyrus (IFG), occipital lobe (OCC) and pre-central gyrus (PRC) were investigated as part of a comparison between electrostatic finite element models constructed directly from MRI-resolution data (block models), and smoothed tetrahedral finite element models (smooth models). Three electrode configurations were applied, mimicking different tDCS therapies. Smooth model simulations were found to require three times longer to complete. The percentage differences between mean and median current densities of each model type in arbitrarily chosen brain structures ranged from −33.33–48.08%. No clear relationship was found between structure volumes and current density differences between the two model types. Tissue regions nearby the electrodes demonstrated the least percentage differences between block and smooth models. Therefore, block models may be adequate to predict current density values in cortical regions presumed targeted by tDCS. PMID:26737023

Obtaining source current density related to irregularly structured electromagnetic target field inside human body using hybrid inverse/FDTD method.

PubMed

Han, Jijun; Yang, Deqiang; Sun, Houjun; Xin, Sherman Xuegang

2017-01-01

Inverse method is inherently suitable for calculating the distribution of source current density related with an irregularly structured electromagnetic target field. However, the present form of inverse method cannot calculate complex field-tissue interactions. A novel hybrid inverse/finite-difference time domain (FDTD) method that can calculate the complex field-tissue interactions for the inverse design of source current density related with an irregularly structured electromagnetic target field is proposed. A Huygens' equivalent surface is established as a bridge to combine the inverse and FDTD method. Distribution of the radiofrequency (RF) magnetic field on the Huygens' equivalent surface is obtained using the FDTD method by considering the complex field-tissue interactions within the human body model. The obtained magnetic field distributed on the Huygens' equivalent surface is regarded as the next target. The current density on the designated source surface is derived using the inverse method. The homogeneity of target magnetic field and specific energy absorption rate are calculated to verify the proposed method.

Study of the origin and structure of a nocturnal atmospheric density current from observations and numerical simulations

NASA Astrophysics Data System (ADS)

Ander Arrillaga, Jon; Yagüe, Carlos; Román-Cascón, Carlos; Sastre, Mariano

2016-04-01

Density currents are flows generated when a dense fluid passes through a less dense surrounding, under the influence of gravity. They usually appear as a consequence of sea-breeze circulations, thunderstorm outflows or katabatic flows. Density currents acquire a particular relevance during nocturnal stable situations, as their onset causes a significant turbulence increase (both from buoyancy and shear) and they occasionally produce turbulence intermittency through the formation of gravity waves. In this work, the arrival of a density current on 23 September 2015 is analysed in the CIBA site (Spain), which is located in the Spanish Northern Plateau, approximately 200 km away from the sea and 100 km away from the closest mountain ranges. Previous studies at this location associated similar nocturnal events with daytime sea breeze in the eastern Cantabrian coast [1]. Micrometeorological measurements from sonic anemometers and different sensors at multiple levels up to 100 m agl provide a solid database. In this specific case, the outbreak of the density current occurs 2 hours after sunset, causing an abrupt increase of the wind speed and a significant weakening of the surface-based thermal inversion. Besides, turbulent parameters and fluxes such as the friction velocity, the sensible heat flux and the Turbulent Kinetic Energy (TKE) are sharply altered with its arrival. The latter, indeed, increases by two orders of magnitude and the Multi Resolution Flux Decomposition (MRFD) of this and other turbulent variables gives the approximate size of the contributing eddies. Furthermore, simulations with the WRF model, which is tested for different Planetary Boundary Layer (PBL) schemes and the topo_wind option for complex topography [2], give meaningful information about the vertical structure and origin of this density current. [1] Udina, M., Soler, M.R., Viana, S. & Yagüe, C. (2013). Model simulation of gravity waves triggered by a density current. Q J R Meteorol Soc, 139, 701-714. [2] Jiménez, P.A., Dudhia, J., González-Rouco, J.F., Navarro, J., Montávez, J.P., García-Bustamante, E. (2012). A revised scheme for the wrf surface layer formulation. Mon Weather Rev, 140, 898-918.

Compatibility of separatrix density scaling for divertor detachment with H-mode pedestal operation in DIII-D

NASA Astrophysics Data System (ADS)

Leonard, A. W.; McLean, A. G.; Makowski, M. A.; Stangeby, P. C.

2017-08-01

The midplane separatrix density is characterized in response to variations in upstream parallel heat flux density and central density through deuterium gas injection. The midplane density is determined from a high spatial resolution Thomson scattering diagnostic at the midplane with power balance analysis to determine the separatrix location. The heat flux density is varied by scans of three parameters, auxiliary heating, toroidal field with fixed plasma current, and plasma current with fixed safety factor, q 95. The separatrix density just before divertor detachment onset is found to scale consistent with the two-point model when radiative dissipation is taken into account. The ratio of separatrix to pedestal density, n e,sep/n e,ped varies from  ⩽30% to  ⩾60% over the dataset, helping to resolve the conflicting scaling of core plasma density limit and divertor detachment onset. The scaling of the separatrix density at detachment onset is combined with H-mode power threshold scaling to obtain a scaling ratio of minimum n e,sep/n e,ped expected in future devices.

The Fixed-Bias Langmuir Probe on the Communication-Navigation Outage Forecast System Satellite: Calibration and Validation

NASA Technical Reports Server (NTRS)

Klenzing, J.; Rowland, D.

2012-01-01

A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication Navigation Outage Forecast System (CNOFS) satellite.CNOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H+ and O+. The ion current collected by the probe surface per unit plasma density is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the CNOFS satellite. The application of the calibration is discussed with respect to future fixed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on CNOFS.

Flute type micropores activated carbon from cotton stalk for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Tian, Xun; Ma, Hongru; Li, Zhe; Yan, Shaocun; Ma, Lei; Yu, Feng; Wang, Gang; Guo, Xuhong; Ma, Yanqing; Wong, Chingping

2017-08-01

Flute type micropores activated carbon (FTMAC) has been successfully obtained from cotton stalk via KOH-chemical activation method. The synthesized carbon material exhibits an ordered pore structure with high specific surface area of 1964.46 m2 g-1 and pore volume of 1.03 m3 g-1. The assembled FTMAC-based electrode delivers a high specific capacitance of 254 F g-1 at a current density of 0.2 A g-1 in 1 M H2SO4 aqueous electrolyte. It still can maintain 221 F g-1at a current density of 10 A g-1, demonstrating a good rate capacity (87% retention), as well as long cyclic stability of 96% capacitance retention after 10000 charging and discharging cycles at current density of 1 A g-1. Moreover, the symmetric supercapacitor can deliver a high energy density of 18.14 W h kg-1 and a power density of 450.37 W kg-1 which is operated in the voltage range of 0-1.8 V.

Huge critical current density and tailored superconducting anisotropy in SmFeAsO₀.₈F₀.₁₅ by low-density columnar-defect incorporation.

PubMed

Fang, L; Jia, Y; Mishra, V; Chaparro, C; Vlasko-Vlasov, V K; Koshelev, A E; Welp, U; Crabtree, G W; Zhu, S; Zhigadlo, N D; Katrych, S; Karpinski, J; Kwok, W K

2013-01-01

Iron-based superconductors could be useful for electricity distribution and superconducting magnet applications because of their relatively high critical current densities and upper critical fields. SmFeAsO₀.₈F₀.₁₅ is of particular interest as it has the highest transition temperature among these materials. Here we show that by introducing a low density of correlated nano-scale defects into this material by heavy-ion irradiation, we can increase its critical current density to up to 2 × 10⁷ A cm⁻² at 5 K--the highest ever reported for an iron-based superconductor--without reducing its critical temperature of 50 K. We also observe a notable reduction in the thermodynamic superconducting anisotropy, from 8 to 4 upon irradiation. We develop a model based on anisotropic electron scattering that predicts that the superconducting anisotropy can be tailored via correlated defects in semimetallic, fully gapped type II superconductors.

Fast electrochemical deposition of Ni(OH)2 precursor involving water electrolysis for fabrication of NiO thin films

NASA Astrophysics Data System (ADS)

Koyama, Miki; Ichimura, Masaya

2018-05-01

Ni(OH)2 precursor films were deposited by galvanostatic electrochemical deposition (ECD), and NiO thin films were fabricated by annealing in air. The effects of the deposition current densities were studied in a range that included current densities high enough to electrolyze water and generate hydrogen bubbles. The films fabricated by ECD involving water electrolysis had higher transparency and smoother surface morphology than those deposited with lower current densities. In addition, the annealed NiO films clearly had preferred (111) orientation when the deposition was accompanied by water electrolysis. p-type conduction was confirmed for the annealed films.

Shielding and flux trapping properties of high temperature superconductors in the shape of hollow cylinders

NASA Technical Reports Server (NTRS)

Israelsson, U. E.; Strayer, D. M.

1991-01-01

Allowing for a field-dependent critical current density, the authors calculate the magnetic field that can be supported by hollow cylinders of varying wall thickness. An adiabatically stable field of 1.0 T can be shielded by or trapped in a cylinder with a wall thickness of 0.4 cm if the critical current density varies linearly with magnetic field and has a value of 104 A/sq cm at a field of 1.0 T. Such a current density appears to be within reach of present state-of-the-art melt-processed YBa2Cu3O7 (123) materials.

Optimization of magnetic flux density measurement using multiple RF receiver coils and multi-echo in MREIT.

PubMed

Jeong, Woo Chul; Chauhan, Munish; Sajib, Saurav Z K; Kim, Hyung Joong; Serša, Igor; Kwon, Oh In; Woo, Eung Je

2014-09-07

Magnetic Resonance Electrical Impedance Tomography (MREIT) is an MRI method that enables mapping of internal conductivity and/or current density via measurements of magnetic flux density signals. The MREIT measures only the z-component of the induced magnetic flux density B = (Bx, By, Bz) by external current injection. The measured noise of Bz complicates recovery of magnetic flux density maps, resulting in lower quality conductivity and current-density maps. We present a new method for more accurate measurement of the spatial gradient of the magnetic flux density gradient (∇ Bz). The method relies on the use of multiple radio-frequency receiver coils and an interleaved multi-echo pulse sequence that acquires multiple sampling points within each repetition time. The noise level of the measured magnetic flux density Bz depends on the decay rate of the signal magnitude, the injection current duration, and the coil sensitivity map. The proposed method uses three key steps. The first step is to determine a representative magnetic flux density gradient from multiple receiver coils by using a weighted combination and by denoising the measured noisy data. The second step is to optimize the magnetic flux density gradient by using multi-echo magnetic flux densities at each pixel in order to reduce the noise level of ∇ Bz and the third step is to remove a random noise component from the recovered ∇ Bz by solving an elliptic partial differential equation in a region of interest. Numerical simulation experiments using a cylindrical phantom model with included regions of low MRI signal to noise ('defects') verified the proposed method. Experimental results using a real phantom experiment, that included three different kinds of anomalies, demonstrated that the proposed method reduced the noise level of the measured magnetic flux density. The quality of the recovered conductivity maps using denoised ∇ Bz data showed that the proposed method reduced the conductivity noise level up to 3-4 times at each anomaly region in comparison to the conventional method.

Large-scale forcing of the European Slope Current and associated inflows to the North Sea

NASA Astrophysics Data System (ADS)

Marsh, Robert; Haigh, Ivan; Cunningham, Stuart; Inall, Mark; Porter, Marie; Moat, Ben

2017-04-01

Drifters drogued at 50 m in the European Slope Current at the Hebridean shelf break follow a wide range of pathways, indicating highly variable Atlantic inflow to the North Sea. Slope Current pathways, timescales and transports over 1988-2007 are further quantified in an eddy-resolving ocean model hindcast. Particle trajectories calculated with model currents indicate that Slope Current water is largely "recruited" from the eastern subpolar North Atlantic. Observations of absolute dynamic topography and climatological density support theoretical expectations that Slope Current transport is to first order associated with meridional density gradients in the eastern subpolar gyre, which support a geostrophic inflow towards the slope. In the model hindcast, Slope Current transport variability is dominated by abrupt 25-50% reductions of these density gradients over 1996-1998. Concurrent changes in wind forcing, expressed in terms of density gradients, act in the same sense to reduce Slope Current transport. This indicates that coordinated regional changes of buoyancy and wind forcing acted together to reduce Slope Current transport during the 1990s. Particle trajectories further show that 10-40% of Slope Current water is destined for the northern North Sea within 6 months of passing to the west of Scotland, with a clear decline in this Atlantic inflow over 1988-2007. The influence of variable Slope Current transport on the northern North Sea is also expressed in salinity variations. A proxy for Atlantic inflow may be found in sea level records. Variability of Slope Current transport is implicit in mean sea level differences between Lerwick (Shetland) and Torshavn (Faeroes), in both tide gauge records and a longer model hindcast spanning 1958-2013. Potential impacts of this variability on North Sea biogeochemistry and ecosystems, via associated changes in temperature and seasonal stratification, are discussed.

Magnetic storm of September 4, 1984 - A synthesis of ring current spectra and energy densities measured with AMPTE/CCE

NASA Technical Reports Server (NTRS)

Krimigis, S. M.; Mcentire, R. W.; Potemra, T. A.; Gloeckler, G.; Scarf, F. L.; Shelley, E. G.

1985-01-01

Compositional studies of the equatorial distributions of ring current ions during the September 4, 1984 magnetic storm have been made possible by comprehensive energy, charge state, and mass coverage data from the Charge Composition Explorer satellite. An examination of ion spectra at an L value of about 4 on September 5, in the local evening sector, shows that energy density was dominated by protons, with O ions contributing about 27 percent at the peak of about 150 keV, while He ions contributed less than about 2 percent. September 6 ion spectra, taken during the recovery phase of the storm, indicate that ion densities at more than 20 keV had decreased markedly, and that the ring current energy density was primarily provided by protons.

Kinetic simulations of the stability of a plasma confined by the magnetic field of a current rod

NASA Astrophysics Data System (ADS)

Tonge, J.; Leboeuf, J. N.; Huang, C.; Dawson, J. M.

2003-09-01

The kinetic stability of a plasma in the magnetic field of a current rod is investigated for various temperature and density profiles using three-dimensional particle-in-cell simulations. Such a plasma obeys similar physics to a plasma in a dipole magnetic field, while it is easier to perform computer simulations, and do theoretical analysis, of a plasma in the field of a current rod. Simple energy principle calculations and simulations with a variety of temperature and density profiles show that the plasma is stable to interchange for pressure profiles proportional to r-10/3. As predicted by theory the simulations also show that the density profile will be stationary as long as density is proportional to r-2 even though the temperature profile may not be stable.

Electrode kinetics of a water vapor electrolysis cell

NASA Technical Reports Server (NTRS)

Jacobs, G.

1974-01-01

The anodic electrochemical behavior of the water vapor electrolysis cell was investigated. A theoretical review of various aspects of cell overvoltage is presented with special emphasis on concentration overvoltage and activation overvoltage. Other sources of overvoltage are described. The experimental apparatus controlled and measured anode potential and cell current. Potentials between 1.10 and 2.60 V (vs NHE) and currents between 0.1 and 3000 mA were investigated. Different behavior was observed between the standard cell and the free electrolyte cell. The free electrolyte cell followed typical Tafel behavior (i.e. activation overvoltage) with Tafel slopes of about 0.15, and the exchange current densities of 10 to the minus 9th power A/sq cm, both in good agreement with literature values. The standard cell exhibitied this same Tafel behavior at lower current densities but deviated toward lower than expected current densities at higher potentials. This behavior and other results were examined to determine their origin.

Spatiotemporal and spectral characteristics of X-ray radiation emitted by the Z-pinch during the current implosion of quasispherical multiwire arrays

NASA Astrophysics Data System (ADS)

Gritsuk, A. N.

2017-12-01

For the first time, a quasi-spherical current implosion has been experimentally realized on a multimegaampere facility with the peak current of up to 4 MA and a soft X-ray source has been created with high radiation power density on its surface of up to 3 TW/cm2. An increase in the energy density at the centre of the source of soft X-ray radiation (SXR) was experimentally observed upon compression of quasi-spherical arrays with the linear-mass profiling. In this case, the average power density on the surface of the SXR source is three times higher than for implosions of cylindrical arrays of the same mass and close values of the discharge current. Obtained experimental data are compared with the results of modelling the current implosion of multi-wire arrays performed with the help of a three-dimensional radiation-magneto-hydrodynamic code.

Investigating the origin of efficiency droop by profiling the temperature across the multi-quantum well of an operating light-emitting diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Euihan; Hwang, Gwangseok; Chung, Jaehun

2015-01-26

Performance degradation resulting from efficiency droop during high-power operation is a critical problem in the development of high-efficiency light-emitting diodes (LEDs). In order to resolve the efficiency droop and increase the external quantum efficiency of LEDs, the droop's origin should be identified first. To experimentally investigate the cause of efficiency droop, we used null-point scanning thermal microscopy to quantitatively profile the temperature distribution on the cross section of the epi-layers of an operating GaN-based vertical LED with nanoscale spatial resolution at four different current densities. The movement of temperature peak towards the p-GaN side as the current density increases suggestsmore » that more heat is generated by leakage current than by Auger recombination. We therefore suspect that at higher current densities, current leakage becomes the dominant cause of the droop problem.« less

Ultralow-current-density and bias-field-free spin-transfer nano-oscillator

PubMed Central

Zeng, Zhongming; Finocchio, Giovanni; Zhang, Baoshun; Amiri, Pedram Khalili; Katine, Jordan A.; Krivorotov, Ilya N.; Huai, Yiming; Langer, Juergen; Azzerboni, Bruno; Wang, Kang L.; Jiang, Hongwen

2013-01-01

The spin-transfer nano-oscillator (STNO) offers the possibility of using the transfer of spin angular momentum via spin-polarized currents to generate microwave signals. However, at present STNO microwave emission mainly relies on both large drive currents and external magnetic fields. These issues hinder the implementation of STNOs for practical applications in terms of power dissipation and size. Here, we report microwave measurements on STNOs built with MgO-based magnetic tunnel junctions having a planar polarizer and a perpendicular free layer, where microwave emission with large output power, excited at ultralow current densities, and in the absence of any bias magnetic fields is observed. The measured critical current density is over one order of magnitude smaller than previously reported. These results suggest the possibility of improved integration of STNOs with complementary metal-oxide-semiconductor technology, and could represent a new route for the development of the next-generation of on-chip oscillators. PMID:23478390

Ultralow-current-density and bias-field-free spin-transfer nano-oscillator.

PubMed

Zeng, Zhongming; Finocchio, Giovanni; Zhang, Baoshun; Khalili Amiri, Pedram; Katine, Jordan A; Krivorotov, Ilya N; Huai, Yiming; Langer, Juergen; Azzerboni, Bruno; Wang, Kang L; Jiang, Hongwen

2013-01-01

The spin-transfer nano-oscillator (STNO) offers the possibility of using the transfer of spin angular momentum via spin-polarized currents to generate microwave signals. However, at present STNO microwave emission mainly relies on both large drive currents and external magnetic fields. These issues hinder the implementation of STNOs for practical applications in terms of power dissipation and size. Here, we report microwave measurements on STNOs built with MgO-based magnetic tunnel junctions having a planar polarizer and a perpendicular free layer, where microwave emission with large output power, excited at ultralow current densities, and in the absence of any bias magnetic fields is observed. The measured critical current density is over one order of magnitude smaller than previously reported. These results suggest the possibility of improved integration of STNOs with complementary metal-oxide-semiconductor technology, and could represent a new route for the development of the next-generation of on-chip oscillators.

Electric fields and current densities under small Florida thunderstorms

NASA Technical Reports Server (NTRS)

Deaver, Lance E.; Krider, E. P.

1991-01-01

Results are presented of measurements of the electric field E and Maxwell current density that were performed simultaneously under and near small Florida thunderstorms. It is shown that the amplitude of JM is of the order of 1 nA/sq cm or less in the absence of precipitation and that there are regular time variations in JM during the intervals between lightning discharges that tend to have the same shapes after different discharges in different storms. It is argued that the major causes of time variations in JM between lightning discharges are currents that flow in the finitely conducting atmosphere in response to the field changes rather than rapid time variations in the strength of cloud current sources. The displacement current densities that are computed from the E records dominate JM except when there is precipitation, when E is large and steady, or when E is unusually noisy.

Measuring Joule heating and strain induced by electrical current with Moire interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Bicheng; Basaran, Cemal

2011-04-01

This study proposes a new method to locate and measure the temperature of the hot spots caused by Joule Heating by measuring the free thermal expansion in-plane strain. It is demonstrated that the hotspot caused by the Joule heating in a thin metal film/plate structure can be measured by Phase shifting Moire interferometry with continuous wavelet transform (PSMI/CWT) at the microscopic scale. A demonstration on a copper film is conducted to verify the theory under different current densities. A correlation between the current density and strain in two orthogonal directions (one in the direction of the current flow) is proposed.more » The method can also be used for the measurement of the Joule heating in the microscopic solid structures in the electronic packaging devices. It is shown that a linear relationship exists between current density squared and normal strains.« less

The current-density distribution in a pulsed dc magnetron deposition discharge

NASA Astrophysics Data System (ADS)

Vetushka, Alena; Bradley, James W.

2007-04-01

Using a carefully constructed magnetic probe (a B-dot probe) the spatial and temporal evolution of the perturbation in the magnetic field ΔB in an unbalanced pulsed dc magnetron has been determined. The plasma was run in argon at a pressure of 0.74 Pa and the plasma ions sputtered a pure graphite target. The pulse frequency and duty were set at 100 kHz and 55%, respectively. From the ΔB measurements (measured with magnitudes up to about 0.01 mT) the axial, azimuthal and radial components of the total current density j in the plasma bulk were determined. In the plasma 'on' phase, the axial current density jz has a maximum value of approximately 200 A m-2 above the racetrack region, while high values in the azimuthal current density jΦ are distributed in a region from 1 to 3 cm into the bulk plasma with jΦ exceeding 350 A m-2. In the 'off' phase of the plasma, jz decays almost instantaneously (at least within the 100 ns time-resolution of the ΔB measurements) as the electric field collapses; however, jΦ decays with a characteristic time constant of about 1 µs. This slow decay can be attributed to the presence of decaying Grad-B and curvature drifts, with their rates controlled by the decay in the plasma density. A comparison between axial and azimuthal current densities in the plasma 'on' time, when the plasma is being driven, strongly indicates that classical transport does not operate in the magnetron discharge.

Influences of the current density on the performances of the chrome-plated layer in deterministic electroplating repair

NASA Astrophysics Data System (ADS)

Xia, H.; Shen, X. M.; Yang, X. C.; Xiong, Y.; Jiang, G. L.

2018-01-01

Deterministic electroplating repair is a novel method for rapidly repairing the attrited parts. By the qualitative contrast and quantitative comparison, influences of the current density on performances of the chrome-plated layer were concluded in this study. The chrome-plated layers were fabricated under different current densities when the other parameters were kept constant. Hardnesses, thicknesses and components, surface morphologies and roughnesses, and wearability of the chrome-plated layers were detected by the Vickers hardness tester, scanning electron microscope / energy dispersive X-ray detector, digital microscope in the 3D imaging mode, and the ball-milling instrument with profilograph, respectively. In order to scientifically evaluate each factor, the experimental data was normalized. A comprehensive evaluation model was founded to quantitative analyse influence of the current density based on analytic hierarchy process method and the weighted evaluation method. The calculated comprehensive evaluation indexes corresponding to current density of 40A/dm2, 45A/dm2, 50A/dm2, 55A/dm2, 60A/dm2, and 65A/dm2 were 0.2246, 0.4850, 0.4799, 0.4922, 0.8672, and 0.1381, respectively. Experimental results indicate that final optimal option was 60A/dm2, and the priority orders were 60A/dm2, 55A/dm2, 45A/dm2, 50A/dm2, 40A/dm2, and 65A/dm2.

Carbon deposition thresholds on nickel-based solid oxide fuel cell anodes II. Steam:carbon ratio and current density

NASA Astrophysics Data System (ADS)

Kuhn, J.; Kesler, O.

2015-03-01

For the second part of a two part publication, coking thresholds with respect to molar steam:carbon ratio (SC) and current density in nickel-based solid oxide fuel cells were determined. Anode-supported button cell samples were exposed to 2-component and 5-component gas mixtures with 1 ≤ SC ≤ 2 and zero fuel utilization for 10 h, followed by measurement of the resulting carbon mass. The effect of current density was explored by measuring carbon mass under conditions known to be prone to coking while increasing the current density until the cell was carbon-free. The SC coking thresholds were measured to be ∼1.04 and ∼1.18 at 600 and 700 °C, respectively. Current density experiments validated the thresholds measured with respect to fuel utilization and steam:carbon ratio. Coking thresholds at 600 °C could be predicted with thermodynamic equilibrium calculations when the Gibbs free energy of carbon was appropriately modified. Here, the Gibbs free energy of carbon on nickel-based anode support cermets was measured to be -6.91 ± 0.08 kJ mol-1. The results of this two part publication show that thermodynamic equilibrium calculations with appropriate modification to the Gibbs free energy of solid-phase carbon can be used to predict coking thresholds on nickel-based anodes at 600-700 °C.

Room Temperature Electroluminescence from Tensile-Strained Si0.13Ge0.87/Ge Multiple Quantum Wells on a Ge Virtual Substrate

PubMed Central

Lin, Guangyang; Chen, Ningli; Zhang, Lu; Huang, Zhiwei; Huang, Wei; Wang, Jianyuan; Xu, Jianfang; Chen, Songyan; Li, Cheng

2016-01-01

Direct band electroluminescence (EL) from tensile-strained Si0.13Ge0.87/Ge multiple quantum wells (MQWs) on a Ge virtual substrate (VS) at room temperature is reported herein. Due to the competitive result of quantum confinement Stark effect and bandgap narrowing induced by tensile strain in Ge wells, electroluminescence from Γ1-HH1 transition in 12-nm Ge wells was observed at around 1550 nm. As injection current density increases, additional emission shoulders from Γ2-HH2 transition in Ge wells and Ge VS appeared at around 1300–1400 nm and 1600–1700 nm, respectively. The peak energy of EL shifted to the lower energy side superquadratically with an increase of injection current density as a result of the Joule heating effect. During the elevation of environmental temperature, EL intensity increased due to a reduction of energy between L and Γ valleys of Ge. Empirical fitting of the relationship between the integrated intensity of EL (L) and injection current density (J) with L~Jm shows that the m factor increased with injection current density, suggesting higher light emitting efficiency of the diode at larger injection current densities, which can be attributed to larger carrier occupations in the Γ valley and the heavy hole (HH) valance band at higher temperatures. PMID:28773923

Room Temperature Electroluminescence from Tensile-Strained Si0.13Ge0.87/Ge Multiple Quantum Wells on a Ge Virtual Substrate.

PubMed

Lin, Guangyang; Chen, Ningli; Zhang, Lu; Huang, Zhiwei; Huang, Wei; Wang, Jianyuan; Xu, Jianfang; Chen, Songyan; Li, Cheng

2016-09-27

Direct band electroluminescence (EL) from tensile-strained Si 0.13 Ge 0.87 /Ge multiple quantum wells (MQWs) on a Ge virtual substrate (VS) at room temperature is reported herein. Due to the competitive result of quantum confinement Stark effect and bandgap narrowing induced by tensile strain in Ge wells, electroluminescence from Γ1-HH1 transition in 12-nm Ge wells was observed at around 1550 nm. As injection current density increases, additional emission shoulders from Γ2-HH2 transition in Ge wells and Ge VS appeared at around 1300-1400 nm and 1600-1700 nm, respectively. The peak energy of EL shifted to the lower energy side superquadratically with an increase of injection current density as a result of the Joule heating effect. During the elevation of environmental temperature, EL intensity increased due to a reduction of energy between L and Γ valleys of Ge. Empirical fitting of the relationship between the integrated intensity of EL ( L ) and injection current density ( J ) with L ~ J m shows that the m factor increased with injection current density, suggesting higher light emitting efficiency of the diode at larger injection current densities, which can be attributed to larger carrier occupations in the Γ valley and the heavy hole (HH) valance band at higher temperatures.

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation.

PubMed

Yilmaz, A Erdem; Boncukcuoğlu, Recep; Kocakerim, M Muhtar

2007-06-01

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0 mA/cm(2), initial boron concentration 100mg/L and solution temperature 293 K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following; [formula in text]. Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.

Dosimetry of typical transcranial magnetic stimulation devices

NASA Astrophysics Data System (ADS)

Lu, Mai; Ueno, Shoogo

2010-05-01

The therapeutic staff using transcranial magnetic stimulation (TMS) devices could be exposed to magnetic pulses. In this paper, dependence of induced currents in real human man model on different coil shapes, distance between the coil and man model as well as the rotation of the coil in space have been investigated by employing impedance method. It was found that the figure-of-eight coil has less leakage magnetic field and low current density induced in the body compared with the round coil. The TMS power supply cables play an important role in the induced current density in human body. The induced current density in TMS operator decreased as the coil rotates from parallel position to perpendicular position. Our present study shows that TMS operator should stand at least 110 cm apart from the coil.

Engineered cost-effective growth of Co-based nanoflakes as a sustainable water oxidation electrocatalyst

NASA Astrophysics Data System (ADS)

Pourreza, M.; Naseri, N.

2017-11-01

Developing low-cost, scalable and reproducible synthesis methods for water oxidation reaction (WOR) catalysts is highly desirable and also challenging in energy, environmental and industrial applications. In this context, electrochemical deposition is known as an easy and cost-effective technique in nanomaterial growth. Herein, cobalt-based nanoflakes were grown on a flexible and commercially available steel mesh substrate by electrodeposition approach with a crystalline structure as a mixture of oxide, hydroxide and oxyhydroxide phases. For the first time, the correlation between electrodeposition parameters, time and current density, and morphological characteristics of the grown nanoflakes (density and aspect ratio based on SEM results) has been derived. According to a comprehensive study of the flakes’ electrocatalytic performance in WOR, the optimized sample fabricated with a moderate electrodeposition current density (7 mA cm-2) and duration time (2000 s) revealed the highest density (7.6  ×  108 cm-2) and aspect ratio (7.1) as well as the lowest values for overpotential (OP  =  324 mV) and charge transfer resistance (14 Ω). This designed array of Co-based nanoflakes also showed the lowest value of overpotential for bare cobalt-based WOR electrocatalysts reported yet. High and low values for deposition current density and/or deposition time had a negative effect on the sample surface, leaving some areas without any flakes or with incomplete and inefficient formation of nanoflakes with low densities and aspect ratios. A similar effect was observed for annealed samples in the range of 200-400 °C. Based on recorded overpotentials and extracted surface morphological parameters, a linear and logarithmic behavior in overpotential-flake density dependency was proposed for current density and time controlled systems, respectively.

Advances in Electrical Current Collection

DTIC Science & Technology

1982-01-01

goal for advanced land or sea pro- wpulsion machiniery. Even higher current densities (18 MA mj 2) and speods (300 in s-1) are required for the...subsecoiid operation of inertial storage pulsed pow-er souirces. Speeds and current densities more than an order of magnitude higher , although for milliseond...ONR-Westinghouse . program has shown that solid or moaolitbic brushes made from relatively conventional materials can be operated up to much higher

Emission current from a single micropoint of explosive emission cathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ping; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024; Sun, Jun

Explosive emission cathodes (EECs) are widely used due to their large current. There has been much research on the explosive electron emission mechanism demonstrating that a current density of 10{sup 8}–10{sup 9 }A/cm{sup 2} is necessary for a micropoint to explode in several nanoseconds and the micropoint size is in micron-scale according to the observation of the cathode surface. This paper, however, makes an effort to research the current density and the micropoint size in another way which considers the space charge screening effect. Our model demonstrates that the relativistic effect is insignificant for the micropoint emission due to the smallmore » size of the micropoint and uncovers that the micron-scale size is an intrinsic demand for the micropoint to reach a space charge limited current density of 10{sup 8}–10{sup 9 }A/cm{sup 2}. Meanwhile, our analysis shows that as the voltage increases, the micropoint emission will turn from a field limited state to a space charge limited state, which makes the steady-state micropoint current density independent of the cathode work function and much less dependent on the electric field and the field enhancement factor than that predicted by the Fowler-Nordheim formula.« less

The development of the time dependence of the nuclear EMP electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eng, C

The nuclear electromagnetic pulse (EMP) electric field calculated with the legacy code CHAP is compared with the field given by an integral solution of Maxwell's equations, also known as the Jefimenko equation, to aid our current understanding on the factors that affect the time dependence of the EMP. For a fair comparison the CHAP current density is used as a source in the Jefimenko equation. At first, the comparison is simplified by neglecting the conduction current and replacing the standard atmosphere with a constant density air slab. The simplicity of the resultant current density aids in determining the factors thatmore » affect the rise, peak and tail of the EMP electric field versus time. The three dimensional nature of the radiating source, i.e. sources off the line-of-sight, and the time dependence of the derivative of the current density with respect to time are found to play significant roles in shaping the EMP electric field time dependence. These results are found to hold even when the conduction current and the standard atmosphere are properly accounted for. Comparison of the CHAP electric field with the Jefimenko electric field offers a direct validation of the high-frequency/outgoing wave approximation.« less

Space plasma contactor research, 1987

NASA Technical Reports Server (NTRS)

Wilbur, Paul J.

1988-01-01

A simple model describing the process of electron collection from a low pressure ambient plasma in the absence of magnetic field and contactor velocity effects is presented. Experimental measurments of the plasma surrounding the contactor are used to demonstrate that a double-sheath generally develops and separates the ambient plasma from a higher density, anode plasma located adjacent to the contactor. Agreement between the predictions of the model and experimental measurements obtained at the electron collection current levels ranging to 1 A suggests the surface area at the ambient plasma boundary of the double-sheath is equal to the electron current being collected divided by the ambient plasma random electron current density; the surface area of the higher density anode plasma boundary of the double-sheath is equal to the ion current being emitted across this boundary divided by the ion current density required to sustain a stable sheath; and the voltage drop across the sheath is determined by the requirement that the ion and electron currents counterflowing across the boundaries be at space-charge limited levels. The efficiency of contactor operation is shown to improve when significant ionization and excitation is induced by electrons that stream from the ambient plasma through the double-sheath and collide with neutral atoms being supplied through the hollow cathode.

High-current-density electrodeposition using pulsed and constant currents to produce thick CoPt magnetic films on silicon substrates

NASA Astrophysics Data System (ADS)

Ewing, Jacob; Wang, Yuzheng; Arnold, David P.

2018-05-01

This paper investigates methods for electroplating thick (>20 μm), high-coercivity CoPt films using high current densities (up to 1 A/cm2) and elevated bath temperatures (70 °C). Correlations are made tying current-density and temperature process parameters with plating rate, elemental ratio and magnetic properties of the deposited CoPt films. It also investigates how pulsed currents can increase the plating rate and film to substrate adhesion. Using 500 mA/cm2 and constant current, high-quality, dense CoPt films were successfully electroplated up to 20 μm thick in 1 hr on silicon substrates (0.35 μm/min plating rate). After standard thermal treatment (675°C, 30 min) to achieve the ordered L10 crystalline phase, strong magnetic properties were measured: coercivities up 850 kA/m, remanences >0.5 T, and maximum energy products up to 46 kJ/m3.

Current profile redistribution driven by neutral beam injection in a reversed-field pinch

NASA Astrophysics Data System (ADS)

Parke, E.; Anderson, J. K.; Brower, D. L.; Den Hartog, D. J.; Ding, W. X.; Johnson, C. A.; Lin, L.

2016-05-01

Neutral beam injection in reversed-field pinch (RFP) plasmas on the Madison Symmetric Torus [Dexter et al., Fusion Sci. Technol. 19, 131 (1991)] drives current redistribution with increased on-axis current density but negligible net current drive. Internal fluctuations correlated with tearing modes are observed on multiple diagnostics; the behavior of tearing mode correlated structures is consistent with flattening of the safety factor profile. The first application of a parametrized model for island flattening to temperature fluctuations in an RFP allows inferrence of rational surface locations for multiple tearing modes. The m = 1, n = 6 mode is observed to shift inward by 1.1 ± 0.6 cm with neutral beam injection. Tearing mode rational surface measurements provide a strong constraint for equilibrium reconstruction, with an estimated reduction of q0 by 5% and an increase in on-axis current density of 8% ± 5%. The inferred on-axis current drive is consistent with estimates of fast ion density using TRANSP [Goldston et al., J. Comput. Phys. 43, 61 (1981)].

Influence of basal-plane dislocation structures on expansion of single Shockley-type stacking faults in forward-current degradation of 4H-SiC p-i-n diodes

NASA Astrophysics Data System (ADS)

Hayashi, Shohei; Yamashita, Tamotsu; Senzaki, Junji; Miyazato, Masaki; Ryo, Mina; Miyajima, Masaaki; Kato, Tomohisa; Yonezawa, Yoshiyuki; Kojima, Kazutoshi; Okumura, Hajime

2018-04-01

The origin of expanded single Shockley-type stacking faults in forward-current degradation of 4H-SiC p-i-n diodes was investigated by the stress-current test. At a stress-current density lower than 25 A cm-2, triangular stacking faults were formed from basal-plane dislocations in the epitaxial layer. At a stress-current density higher than 350 A cm-2, both triangular and long-zone-shaped stacking faults were formed from basal-plane dislocations that converted into threading edge dislocations near the interface between the epitaxial layer and the substrate. In addition, the conversion depth of basal-plane dislocations that expanded into the stacking fault was inside the substrate deeper than the interface. These results indicate that the conversion depth of basal-plane dislocations strongly affects the threshold stress-current density at which the expansion of stacking faults occurs.

Coupled low-energy - ring current plasma diffusion in the Jovian magnetosphere

NASA Technical Reports Server (NTRS)

Summers, D.; Siscoe, G. L.

1985-01-01

The outwardly diffusing Iogenic plasma and the simultaneously inwardly diffusing ring current plasma in the Jovian magnetosphere are described using a coupled diffusion model which incorporates the effects of the pressure gradient of the ring current into the cross-L diffusion coefficient. The coupled diffusion coefficient is derived by calculating the total energy available to drive the diffusion process. The condition is imposed that the diffusion coefficient takes on a local minimum value at some point in the region L = 7-8, at which point the gradient of the Io plasma density is specified as ramp value given by Siscoe et al. (1981). The hypothesis that the pressure gradient of the ring current causes the diminution of radial plasma transport is tested, and solution profiles for the Iogenic and ring current plasma densities are obtained which imply that the Io plasma ramp is caused by a high-density, low-energy component of the ring current hitherto unobserved directly.

Current-driven dynamics of skyrmions stabilized in MnSi nanowires revealed by topological Hall effect

PubMed Central

Liang, Dong; DeGrave, John P.; Stolt, Matthew J.; Tokura, Yoshinori; Jin, Song

2015-01-01

Skyrmions hold promise for next-generation magnetic storage as their nanoscale dimensions may enable high information storage density and their low threshold for current-driven motion may enable ultra-low energy consumption. Skyrmion-hosting nanowires not only serve as a natural platform for magnetic racetrack memory devices but also stabilize skyrmions. Here we use the topological Hall effect (THE) to study phase stability and current-driven dynamics of skyrmions in MnSi nanowires. THE is observed in an extended magnetic field-temperature window (15–30 K), suggesting stabilization of skyrmions in nanowires compared with the bulk. Furthermore, we show in nanowires that under the high current density of 108–109 A m−2, the THE decreases with increasing current densities, which demonstrates the current-driven motion of skyrmions generating the emergent electric field in the extended skyrmion phase region. These results open up the exploration of skyrmions in nanowires for fundamental physics and magnetic storage technologies. PMID:26400204

Site of maxima of conductivity, temperatures, density of the current and specific capacity of the thermal emission in the HFI-discharge

NASA Astrophysics Data System (ADS)

Gerasimov, A.; Kirpichnikov, A.; Sabirova, F.; Gainullin, R.

2017-11-01

On the basis of theoretical analysis of distributions of the conductivity, current density and specific power of heat release in the high-frequency induction discharge, a law of crowding of maxima of these values has been established.

Quasi-steady-state high confinement at high density by lower hybrid waves in the HT-6M tokamak

NASA Astrophysics Data System (ADS)

Li, Jiangang; Luo, Jiarong; Wan, Baonian; Wan, Yuanxi; Liu, Yuexiu; Yin, Finxian; Gong, Xianzu; Li, Duochuan; Liu, Shen; Jie, Yinxian; Gao, Xiang; Luo, Nancang; Jiang, Jiaguang; Han, Yuqing; Wu, Mingjun; Wang, Guangxin; Liang, Yunfeng; Yao, Ailing; Wu, Zhenwei; Zhang, Shouyin; Mao, Jiansan; Cui, Lingzhuo; Xu, Yuhong; Meng, Yuedong; Zhao, Junyu; Ding, Bolong; Li, Guiming; Xu, Xiangdong; Lin, Bili; Wei, Meishen; Yie, Weiwei

2000-03-01

The quasi-steady-state (tH > 10 τEoh) H mode with high plasma density (ELMy and ELM free) was routinely obtained by the injection of lower hybrid wave heating and lower hybrid current drive with a power threshold of 50 kW. The antenna spectrum was scanned over a wide range and τE was about 1.5-2.0 times that of the L mode scaling. The density increases by almost a factor of 3 during the H phase by gas puffing and the particle confinement time increases by more than this factor even with a line averaged density of 3 × 1013cm-3, which is about 60% of the Greenwald density limit. A hollow Te profile was achieved in the high density case. The experimental results reproducibly show a good agreement with the theoretical prediction for the LH off-axis power deposition profile. When a certain fraction of the plasma current is non-inductively sustained by the LH waves, a hollow current density profile is formed and the magnetic shear is reversed. This off-axis hollow profile and enhanced confinement improvement are attributed to a strong reduction of the electron thermal diffusivity in the reversed shear region.

An asymmetric supercapacitor with ultrahigh energy density based on nickle cobalt sulfide nanocluster anchoring multi-wall carbon nanotubes hybrid

NASA Astrophysics Data System (ADS)

Wen, Ping; Fan, Mingjin; Yang, Desuo; Wang, Yan; Cheng, Hualei; Wang, Jinqing

2016-07-01

The development of novel electrode materials with high energy density and long cycling life is critical to realize electrochemical capacitive energy storage for practical applications. In this paper, the hybrids of nickle cobalt sulfide/multi-wall carbon nanotubes (NiCo2S4/MWCNTs) with different contents of MWCNTs are prepared using a facile one-pot solvothermal reaction. As novel active materials for supercapacitors, the electrochemistry tests show that the hybrid of NiCo2S4/MWCNTs-5 is able to deliver a high specific capacitance of 2080 F g-1 at the current density of 1 A g-1, even superior rate capability of 61% capacitance retention after a 20-fold increase in current densities, when the content of MWCNTs is up to 5%. More importantly, an asymmetric supercapacitor assembled by NiCo2S4/MWCNTs-5 as positive electrode and reduced graphene oxide (rGO) as negative electrode delivers a high energy density of 51.8 Wh Kg-1 at a power density of 865 W kg-1, and 85.7% of its initial capacitance is retained at the current density of 4 A g-1 after 5000 charge-discharge cycles, exhibiting potential prospect for practical applications.

GaAsP/InGaP HBTs grown epitaxially on Si substrates: Effect of dislocation density on DC current gain

NASA Astrophysics Data System (ADS)

Heidelberger, Christopher; Fitzgerald, Eugene A.

2018-04-01

Heterojunction bipolar transistors (HBTs) with GaAs0.825P0.175 bases and collectors and In0.40Ga0.60P emitters were integrated monolithically onto Si substrates. The HBT structures were grown epitaxially on Si via metalorganic chemical vapor deposition, using SiGe compositionally graded buffers to accommodate the lattice mismatch while maintaining threading dislocation density at an acceptable level (˜3 × 106 cm-2). GaAs0.825P0.175 is used as an active material instead of GaAs because of its higher bandgap (increased breakdown voltage) and closer lattice constant to Si. Misfit dislocation density in the active device layers, measured by electron-beam-induced current, was reduced by making iterative changes to the epitaxial structure. This optimized process culminated in a GaAs0.825P0.175/In0.40Ga0.60P HBT grown on Si with a DC current gain of 156. By considering the various GaAsP/InGaP HBTs grown on Si substrates alongside several control devices grown on GaAs substrates, a wide range of threading dislocation densities and misfit dislocation densities in the active layers could be correlated with HBT current gain. The effect of threading dislocations on current gain was moderated by the reduction in minority carrier lifetime in the base region, in agreement with existing models for GaAs light-emitting diodes and photovoltaic cells. Current gain was shown to be extremely sensitive to misfit dislocations in the active layers of the HBT—much more sensitive than to threading dislocations. We develop a model for this relationship where increased base current is mediated by Fermi level pinning near misfit dislocations.

Reliability and Characteristics of Wafer-Level Chip-Scale Packages under Current Stress

NASA Astrophysics Data System (ADS)

Chen, Po-Ying; Kung, Heng-Yu; Lai, Yi-Shao; Hsiung Tsai, Ming; Yeh, Wen-Kuan

2008-02-01

In this work, we present a novel approach and method for elucidating the characteristics of wafer-level chip-scale packages (WLCSPs) for electromigration (EM) tests. The die in WLCSP was directly attached to the substrate via a soldered interconnect. The shrinking of the area of the die that is available for power, and the solder bump also shrinks the volume and increases the density of electrons for interconnect efficiency. The bump current density now approaches to 106 A/cm2, at which point the EM becomes a significant reliability issue. As known, the EM failure depends on numerous factors, including the working temperature and the under bump metallization (UBM) thickness. A new interconnection geometry is adopted extensively with moderate success in overcoming larger mismatches between the displacements of components during current and temperature changes. Both environments and testing parameters for WLCSP are increasingly demanded. Although failure mechanisms are considered to have been eliminated or at least made manageable, new package technologies are again challenging its process, integrity and reliability. WLCSP technology was developed to eliminate the need for encapsulation to ensure compatibility with smart-mount technology (SMT). The package has good handing properties but is now facing serious reliability problems. In this work, we investigated the reliability of a WLCSP subjected to different accelerated current stressing conditions at a fixed ambient temperature of 125 °C. A very strong correlation exists between the mean time to failure (MTTF) of the WLCSP test vehicle and the mean current density that is carried by a solder joint. A series of current densities were applied to the WLCSP architecture; Black's power law was employed in a failure mode simulation. Additionally, scanning electron microscopy (SEM) was adopted to determine the differences existing between high- and low-current-density failure modes.

Non-invasive Hall current distribution measurement in a Hall effect thruster

NASA Astrophysics Data System (ADS)

Mullins, Carl R.; Farnell, Casey C.; Farnell, Cody C.; Martinez, Rafael A.; Liu, David; Branam, Richard D.; Williams, John D.

2017-01-01

A means is presented to determine the Hall current density distribution in a closed drift thruster by remotely measuring the magnetic field and solving the inverse problem for the current density. The magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned just outside the thruster channel on a 1.5 kW Hall thruster equipped with a center-mounted hollow cathode. In the sensor array location, the static magnetic field is approximately 30 G, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is approximately tens of milligauss, which is within the sensitivity range of the TMR sensors. Because of the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field does provide the current density distributions. These distributions are shown as a function of time in contour plots. The measured ratios between the average Hall current and the average discharge current ranged from 6.1 to 7.3 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 1.5 kW exhibited a breathing mode frequency of 24 kHz, which was in agreement with temporal measurements of the discharge current.

Non-invasive Hall current distribution measurement in a Hall effect thruster.

PubMed

Mullins, Carl R; Farnell, Casey C; Farnell, Cody C; Martinez, Rafael A; Liu, David; Branam, Richard D; Williams, John D

2017-01-01

A means is presented to determine the Hall current density distribution in a closed drift thruster by remotely measuring the magnetic field and solving the inverse problem for the current density. The magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned just outside the thruster channel on a 1.5 kW Hall thruster equipped with a center-mounted hollow cathode. In the sensor array location, the static magnetic field is approximately 30 G, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is approximately tens of milligauss, which is within the sensitivity range of the TMR sensors. Because of the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field does provide the current density distributions. These distributions are shown as a function of time in contour plots. The measured ratios between the average Hall current and the average discharge current ranged from 6.1 to 7.3 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 1.5 kW exhibited a breathing mode frequency of 24 kHz, which was in agreement with temporal measurements of the discharge current.

Comparison of entrainment in constant volume and constant flux dense currents over sloping bottoms

NASA Astrophysics Data System (ADS)

Bhaganagar, K.; Nayamatullah, M.; Cenedese, C.

2014-12-01

Three dimensional high resolution large eddy simulations (LES) are employed to simulate lock-exchange and constant flux dense flows over inclined surface with the aim of investigating, visualizing and describing the turbulent structure and the evolution of bottom-propagating compositional density current at the channel bottom. The understanding of dynamics of density current is largely determined by the amount of interfacial mixing or entrainment between the ambient and dense fluids. No previous experimental or numerical studies have been done to estimate entrainment in classical lock-exchange system. The differences in entrainment between the lock-exchange and constant flux are explored. Comparing the results of flat bed with inclined surface results, flow exhibits significant differences near the leading edge or nose of the front of the density currents due to inclination of surface. Further, the instabilities are remarkably enhanced resulting Kelvin-Helmholtz and lobe-cleft type of instabilities arises much earlier in time. In this study, a brief analysis of entrainment on lock-exchange density current is presented using different bed slopes and a set of reduced gravity values (g'). We relate the entrainment value with different flow parameters such as Froude number (Fr) and Reynolds number (Re).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Qing; Gerhardt, Michael R.; Aziz, Michael J.

We measure the polarization characteristics of a quinone-bromide redox flow battery with interdigitated flow fields, using electrochemical impedance spectroscopy and voltammetry of a full cell and of a half cell against a reference electrode. We find linear polarization behavior at 50% state of charge all the way to the short-circuit current density of 2.5 A/cm 2. We uniquely identify the polarization area-specific resistance (ASR) of each electrode, the membrane ASR to ionic current, and the electronic contact ASR. We use voltage probes to deduce the electronic current density through each sheet of carbon paper in the quinone-bearing electrode. By alsomore » interpreting the results using the Newman 1-D porous electrode model, we deduce the volumetric exchange current density of the porous electrode. We uniquely evaluate the power dissipation and identify a correspondence to the contributions to the electrode ASR from the faradaic, electronic, and ionic transport processes. We find that, within the electrode, more power is dissipated in the faradaic process than in the electronic and ionic conduction processes combined, despite the observed linear polarization behavior. We examine the sensitivity of the ASR to the values of the model parameters. The greatest performance improvement is anticipated from increasing the volumetric exchange current density.« less

Impact of operating conditions on the acetylene contamination in the cathode of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Zhai, Yunfeng; St-Pierre, Jean

2017-12-01

Realistically, proton exchange membrane fuel cells (PEMFCs) are operated under varying operating conditions that potentially impact the acetylene contamination reactions. In this paper, the effects of the cell operating conditions on the acetylene contamination in PEMFCs are investigated under different current densities and temperatures with different acetylene concentrations in the cathode. Electrochemical impedance spectroscopy is applied during the constant-current operation to analyze the impacts of the operating conditions on the acetylene electrochemical reactions. The experimental results indicate that higher acetylene concentrations, higher current densities and lower cell temperatures decrease the cell performance more. In particular, cathode poisoning becomes more severe at medium cell current densities. The cell cathode potentials at such current densities are not sufficient to completely oxidize the intermediate or sufficiently low to completely reduce the adsorbed acetylene. Based on these investigations, the possible condition-dependent limitations of the acetylene concentration and cell operating voltage are proposed for insight into the acetylene contamination mitigation stratagem. Regarding the barrier conditions, the acetylene reactions change abruptly, and adjusting the cell operation parameters to change the acetylene adsorbate and intermediate accumulation conditions to induce complete oxidation or reduction conditions may mitigate the severe acetylene contamination effects on PEMFCs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fertig, Fabian, E-mail: fabian.fertig@ise.fraunhofer.de; Greulich, Johannes; Rein, Stefan

Spatially resolved determination of solar cell parameters is beneficial for loss analysis and optimization of conversion efficiency. One key parameter that has been challenging to access by an imaging technique on solar cell level is short-circuit current density. This work discusses the robustness of a recently suggested approach to determine short-circuit current density spatially resolved based on a series of lock-in thermography images and options for a simplified image acquisition procedure. For an accurate result, one or two emissivity-corrected illuminated lock-in thermography images and one dark lock-in thermography image have to be recorded. The dark lock-in thermography image can bemore » omitted if local shunts are negligible. Furthermore, it is shown that omitting the correction of lock-in thermography images for local emissivity variations only leads to minor distortions for standard silicon solar cells. Hence, adequate acquisition of one image only is sufficient to generate a meaningful map of short-circuit current density. Beyond that, this work illustrates the underlying physics of the recently proposed method and demonstrates its robustness concerning varying excitation conditions and locally increased series resistance. Experimentally gained short-circuit current density images are validated for monochromatic illumination in comparison to the reference method of light-beam induced current.« less

Generation of coronal electric currents due to convective motions on the photosphere

NASA Astrophysics Data System (ADS)

Sakurai, T.; Levine, R. H.

1981-09-01

Generation of electric currents in a magnetized plasma overlying a dense convective layer is studied, assuming that the magnetic field perturbation is small and satisfies the force-free equation. Currents are produced by rotational motions on the boundary in the case of a uniform equilibrium field. In a simple two-dimensional bipolar configuration, however, both irrotational and incompressible motions give rise to currents, and the current density has a peak at the magnetic neutral line. Scaling laws for the current density as well as for the stored magnetic energy are derived, and the possibility of heating the solar corona through the dissipation of coronal currents generated in this way is discussed.

Generation of coronal electric currents due to convective motions on the photosphere

NASA Technical Reports Server (NTRS)

Sakurai, T.; Levine, R. H.

1981-01-01

Generation of electric currents in a magnetized plasma overlying a dense convective layer is studied, assuming that the magnetic field perturbation is small and satisfies the force-free equation. Currents are produced by rotational motions on the boundary in the case of a uniform equilibrium field. In a simple two-dimensional bipolar configuration, however, both irrotational and incompressible motions give rise to currents, and the current density has a peak at the magnetic neutral line. Scaling laws for the current density as well as for the stored magnetic energy are derived, and the possibility of heating the solar corona through the dissipation of coronal currents generated in this way is discussed.

Critical current and electric transport properties of superconducting epitaxial Nb(Ti)N submicron structures

NASA Astrophysics Data System (ADS)

Klimov, A.; Słysz, W.; Guziewicz, M.; Kolkovsky, V.; Wegrzecki, M.; Bar, J.; Marchewka, M.; Seredyński, B.

2016-12-01

Critical current and current-voltage characteristics of epitaxial Nb(Ti)N submicron ultrathin structures were measured as function of temperature. For 700-nm-wide bridge we found current-driven vortex de-pinning at low temperatures and thermally activated flux flow closer to the transition temperature, as the limiting factors for the critical current density. For 100-nm-wide meander we observed combination of phase-slip activation and vortex-anti-vortex pair (VAP) thermal excitation. Our Nb(Ti)N meander structure demonstrates high de-pairing critical current densities 107 A/cm2 at low temperatures, but the critical currents are much smaller due to presence of the local constrictions.

Influence of the initial parameters of the magnetic field and plasma on the spatial structure of the electric current and electron density in current sheets formed in helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ostrovskaya, G. V., E-mail: galya-ostr@mail.ru; Markov, V. S.; Frank, A. G., E-mail: annfrank@fpl.gpi.ru

The influence of the initial parameters of the magnetic field and plasma on the spatial structure of the electric current and electron density in current sheets formed in helium plasma in 2D and 3D magnetic configurations with X-type singular lines is studied by the methods of holographic interferometry and magnetic measurements. Significant differences in the structures of plasma and current sheets formed at close parameters of the initial plasma and similar configurations of the initial magnetic fields are revealed.

Spectral broadening measurement of the lower hybrid waves during long pulse operation in Tore Supra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger-By, G.; Decampy, J.; Goniche, M.

2014-02-12

On many tokamaks (C-Mod, EAST, FTU, JET, HT-7, TS), a decrease in current drive efficiency of the Lower Hybrid (LH) waves is observed in high electron density plasmas. The cause of this behaviour is believed to be: Parametric Instabilities (PI) and Scattering from Density Fluctuations (SDF). For the ITER LH system, our knowledge must be improved to avoid such effects and to maintain the LH current drive efficiency at high density. The ITPA IOS group coordinates this effort [1] and all experimental data are essential to validate the numerical codes in progress. Usually the broadening of the LH wave frequencymore » spectrum is measured by a probe located in the plasma edge. For this study, the frequency spectrum of a reflected power signal from the LH antenna was used. In addition, the spectrum measurements are compared with the density fluctuations observed on RF probes located at the antenna mouth. Several plasma currents (0.6 to 1.4 MA) and densities up to 5.2 × 10{sup 19} m−3 have been realised on Tore Supra (TS) long pulses and with high injected RF power, up to 5.4 MW-30s. This allowed using a spectrum analyser to make several measurements during the plasma pulse. The side lobe amplitude, shifted by 20-30MHz with respect to the main peak, grows with increasing density. Furthermore, for an increase of plasma current at the same density, the spectra broaden and become asymmetric. Some parametric dependencies are shown in this paper.« less

Spectral broadening measurement of the lower hybrid waves during long pulse operation in Tore Supra

NASA Astrophysics Data System (ADS)

Berger-By, G.; Decampy, J.; Antar, G. Y.; Goniche, M.; Ekedahl, A.; Delpech, L.; Leroux, F.; Tore Supra Team

2014-02-01

On many tokamaks (C-Mod, EAST, FTU, JET, HT-7, TS), a decrease in current drive efficiency of the Lower Hybrid (LH) waves is observed in high electron density plasmas. The cause of this behaviour is believed to be: Parametric Instabilities (PI) and Scattering from Density Fluctuations (SDF). For the ITER LH system, our knowledge must be improved to avoid such effects and to maintain the LH current drive efficiency at high density. The ITPA IOS group coordinates this effort [1] and all experimental data are essential to validate the numerical codes in progress. Usually the broadening of the LH wave frequency spectrum is measured by a probe located in the plasma edge. For this study, the frequency spectrum of a reflected power signal from the LH antenna was used. In addition, the spectrum measurements are compared with the density fluctuations observed on RF probes located at the antenna mouth. Several plasma currents (0.6 to 1.4 MA) and densities up to 5.2 × 1019 m-3 have been realised on Tore Supra (TS) long pulses and with high injected RF power, up to 5.4 MW-30s. This allowed using a spectrum analyser to make several measurements during the plasma pulse. The side lobe amplitude, shifted by 20-30MHz with respect to the main peak, grows with increasing density. Furthermore, for an increase of plasma current at the same density, the spectra broaden and become asymmetric. Some parametric dependencies are shown in this paper.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Addy, Susan Amrose

Arsenic in drinking water is a major public health problem threatening the lives of over 140 million people worldwide. In Bangladesh alone, up to 57 million people drink arsenic-laden water from shallow wells. ElectroChemical Arsenic Remediation(ECAR) overcomes many of the obstacles that plague current technologies and can be used affordably and on a small-scale, allowing for rapid dissemination into Bangladesh to address this arsenic crisis. In this work, ECAR was shown to effectively reduce 550 - 580 μg=L arsenic (including both As[III]and As[V]in a 1:1 ratio) to below the WHO recommended maximum limit of 10 μg=L in synthetic Bangladesh groundwatermore » containing relevant concentrations of competitive ions such as phosphate, silicate, and bicarbonate. Arsenic removal capacity was found to be approximately constant within certain ranges of current density, but was found to change substantially between ranges. In order of decreasing arsenic removal capacity, the pattern was: 0.02 mA=cm 2> 0.07 mA=cm 2> 0.30 - 1.1 mA=cm 2> 5.0 - 100 mA=cm 2. Current processing time was found to effect arsenic removal capacity independent of either charge density or current density. Electrode polarization studies showed no passivation of the electrode in the tested range (up to current density 10 mA=cm 2) and ruled out oxygen evolution as the cause of decreasing removal capacity with current density. Simple settling and decantation required approximately 3 days to achieve arsenic removal comparable to filtration with a 0.1 mu m membrane. X-ray Absorption Spectroscopy (XAS) showed that (1) there is no significant difference in the arsenic removal mechanism of ECAR during operation at different current densities and (2) the arsenic removal mechanism in ECAR is consistent with arsenate adsorption onto a homogenous Fe(III)oxyhydroxide similar in structure to 2-line ferrihydrite. ECAR effectively reduced high arsenic concentrations (100 - 500 mu g=L) in real Bangladesh tube well water collected from three regions to below the WHO limit of 10 mu g=L. Prototype fabrication and field testing are currently underway.« less

High-Current-Density Vertical-Tunneling Transistors from Graphene/Highly Doped Silicon Heterostructures.

PubMed

Liu, Yuan; Sheng, Jiming; Wu, Hao; He, Qiyuan; Cheng, Hung-Chieh; Shakir, Muhammad Imran; Huang, Yu; Duan, Xiangfeng

2016-06-01

Scalable fabrication of vertical-tunneling transistors is presented based on heterostructures formed between graphene, highly doped silicon, and its native oxide. Benefiting from the large density of states of highly doped silicon, the tunneling transistors can deliver a current density over 20 A cm(-2) . This study demonstrates that the interfacial native oxide plays a crucial role in governing the carrier transport in graphene-silicon heterostructures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Pt/TiO(2)/Ti Schottky-type selection diode for alleviating the sneak current in resistance switching memory arrays.

PubMed

Park, Woo Young; Kim, Gun Hwan; Seok, Jun Yeong; Kim, Kyung Min; Song, Seul Ji; Lee, Min Hwan; Hwang, Cheol Seong

2010-05-14

This study examined the properties of Schottky-type diodes composed of Pt/TiO(2)/Ti, where the Pt/TiO(2) and TiO(2)/Ti junctions correspond to the blocking and ohmic contacts, respectively, as the selection device for a resistive switching cross-bar array. An extremely high forward-to-reverse current ratio of approximately 10(9) was achieved at 1 V when the TiO(2) film thickness was 19 nm. TiO(2) film was grown by atomic layer deposition at a substrate temperature of 250 degrees C. Conductive atomic force microscopy revealed that the forward current flew locally, which limits the maximum forward current density to < 10 A cm(-2) for a large electrode (an area of approximately 60 000 microm(2)). However, the local current measurement showed a local forward current density as high as approximately 10(5) A cm(-2). Therefore, it is expected that this type of Schottky diode effectively suppresses the sneak current without adverse interference effects in a nano-scale resistive switching cross-bar array with high block density.

The effects of normal current density and the plasma spatial structuring in argon DBDs

NASA Astrophysics Data System (ADS)

Shkurenkov, I. A.; Mankelevich, Y. A.; Rakhimova, T. V.

2011-01-01

This paper presents the results of theoretical studies of high-pressure dielectric barrier discharges (DBD) in argon. Two different DBDs at the megahertz and the kilohertz power frequency range were simulated. The effect of normal current density was obtained in the numerical model for both types of the discharge. The discharge of megahertz range was uniform over the radius. The increase in the discharge current is accompanied by increase in the discharge area. The discharge of kilohertz range is not uniform over the radius. The concentric ring formation was observed during calculations. The increase in the discharge current occurs due to increase in the number of rings and as a result in the discharge area. The developed 2D model is able to describe only the first stage of the filament formation - the formation of concentric plasma rings. The filament formation starts at the edge of the current channel and spreads to its centre. Both the effect of normal current density and the filaments formation are caused by the nonstationarity at the current channel boundary.

Extended MHD modeling of tearing-driven magnetic relaxation

NASA Astrophysics Data System (ADS)

Sauppe, J. P.; Sovinec, C. R.

2017-05-01

Discrete relaxation events in reversed-field pinch relevant configurations are investigated numerically with nonlinear extended magnetohydrodynamic (MHD) modeling, including the Hall term in Ohm's law and first-order ion finite Larmor radius effects. Results show variability among relaxation events, where the Hall dynamo effect may help or impede the MHD dynamo effect in relaxing the parallel current density profile. The competitive behavior arises from multi-helicity conditions where the dominant magnetic fluctuation is relatively small. The resulting changes in parallel current density and parallel flow are aligned in the core, consistent with experimental observations. The analysis of simulation results also confirms that the force density from fluctuation-induced Reynolds stress arises subsequent to the drive from the fluctuation-induced Lorentz force density. Transport of the momentum density is found to be dominated by the fluctuation-induced Maxwell stress over most of the cross section with viscous and gyroviscous contributions being large in the edge region. The findings resolve a discrepancy with respect to the relative orientation of current density and flow relaxation, which had not been realized or investigated in King et al. [Phys. Plasmas 19, 055905 (2012)], where only the magnitude of flow relaxation is actually consistent with experimental results.

Degradation of (La(0.8)Sr(0.2))(0.98)MnO(3-δ)-Zr(0.84)Y(0.16)O(2-γ) composite electrodes during reversing current operation.

PubMed

Hughes, Gareth A; Railsback, Justin G; Yakal-Kremski, Kyle J; Butts, Danielle M; Barnett, Scott A

2015-01-01

Reversing-current operation of solid oxide cell (La(0.8)Sr(0.2))(0.98)MnO(3-δ)-Zr(0.84)Y(0.16)O(2-γ) (LSM-YSZ) oxygen electrodes is described. Degradation was characterized by impedance spectroscopy in symmetric cells tested at 800 °C in air with a symmetric current cycle with a period of 12 hours. No change in cell resistance could be detected, in 1000 h tests with a sensitivity of ∼1% per kh, at a current density of 0.5 A cm(-2) corresponding to an overpotential of 0.18 V. At a current density to 0.6 A cm(-2) (0.33 V overpotential) measurable resistance degradation at a rate of 3% per kh was observed, while higher current/overpotential values led to faster degradation. Degradation was observed mainly in the ohmic resistance for current densities of 0.6, 0.8 and 0.9 A cm(-2), with little change in the polarization resistance. Polarization degradation, mainly observed at higher current density, was present as an increase in an impedance response at ∼30 kHz, apparently associated with the resistance of YSZ grain boundaries within the electrode. Microstructural and chemical analysis showed significant changes in electrode structure after the current cycling, including an increase in LSM particle size and a reduction in the amount of YSZ and LSM at the electrode/electrolyte interface - the latter presumably a precursor to delamination.

Teaching of the subject "density difference caused by salinity", one of the reasons that plays role in the occurrence of currents in straits, seas and oceans by the use of a teaching material

NASA Astrophysics Data System (ADS)

Gumussoy, Verim

2015-04-01

Large masses of moving water in seas and oceans are called currents. Root causes of currents are steady winds that occur due to the global atmospheric system and the density differences caused by different heat and salinity levels of water masses. Different feeding and evaporation characteristics of seas and oceans result in salinity and density levels. As a result, subsurface currents occur in straits where seas with different salinity and density levels meet and in the nearby seas. The Bosporus in Istanbul where I live and the school I am working at is has these subsurface currents. In the Black Sea where the rivers the Danube, Dnieper, Don, Yesilirmak, Kizilirmak and Sakarya flow into and the evaporation level is less due to the latitude effect, salinity level is less compared to Marmara and Aegean Seas. As Marmara Sea has higher salt amount than Black Sea, there is a great density difference between these two seas. Marmara Sea has a higher concentration of salt and therefore a higher density than Black Sea. And this leads to occurrence of subsurface currents in the Bosporus. I get my students to carry out a small demonstration to help them understand the occurrence of ocean currents and currents in the seas and the Bosporus by the use of a material. We need very simple materials to carry out this demonstration. These are an aquarium, a bowl, water, salt, dye and a mixer. The demonstration is carried out as follows: we put water, salt and dye in the bowl and mix it well. The salt will increase the density of the water and the dye will help distinguish the salty water. Then we put tap water half way to the aquarium and pour the mixture in the bowl to the aquarium slowly. As a result, the colored salty water sinks down due to its higher density, setting an example of a subsurface current. Natural events occur in very long periods by great dynamic systems, making understanding of them difficult. It is important to use different kinds of materials that address to different senses in geography lessons to promote effective and fun learning. Thus, geography lessons should be based on teaching principles such as 'from concrete to abstract' and 'from near-to-far' principles. Also, teaching methods such as visualization, simulation and experiment should be applied during the lessons. The use of this material will help students comprehend how subsurface currents in the straits, seas and oceans occur. By this simple experiment, students will be able to see what kind of a movement takes place under the Bosporus on which they travel by ferry and they will have the opportunity to carry it out themselves, making the lesson more fun.

Coupled structural, thermal, phase-change and electromagnetic analysis for superconductors, volume 2

NASA Technical Reports Server (NTRS)

Felippa, Carlos A.; Farhat, Charbel; Park, K. C.; Militello, Carmelo; Schuler, James J.

1993-01-01

Two families of parametrized mixed variational principles for linear electromagnetodynamics are constructed. The first family is applicable when the current density distribution is known a priori. Its six independent fields are magnetic intensity and flux density, magnetic potential, electric intensity and flux density and electric potential. Through appropriate specialization of parameters the first principle reduces to more conventional principles proposed in the literature. The second family is appropriate when the current density distribution and a conjugate Lagrange multiplier field are adjoined, giving a total of eight independently varied fields. In this case it is shown that a conventional variational principle exists only in the time-independent (static) case. Several static functionals with reduced number of varied fields are presented. The application of one of these principles to construct finite elements with current prediction capabilities is illustrated with a numerical example.

The Fixed-bias Langmuir Probe on the Communication-navigation Outage Forecast System Satellite: Calibration and Validation

NASA Technical Reports Server (NTRS)

Klenzing, Jeffrey H.; Rowland, Douglas E.

2012-01-01

A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication Navigation Outage Forecast System (CNOFS) satellite.CNOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H+ and O+. The ion current collected by the probe surface per unit plasmadensity is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the CNOFS satellite. The application of the calibration is discussed with respect to future xed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on CNOFS.

Electroosmotic Flow Rectification in Membranes with Asymmetrically Shaped Pores: Effects of Current and Pore Density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, Gregory W.; Lopez, Marcos M.; Ramiah Rajasekaran, Pradeep

2015-07-09

We have recently demonstrated a new electrokinetic phenomenon—electroosmotic flow rectification in membranes with asymmetrically shaped pores. Flow rectification means that at constant driving force the flow rate in one direction through the membrane is faster than the flow rate in the opposite direction. EOF rectification could be of practical use in microfluidic devices incorporating porous membranes, but additional research is required. We explore here the effects of two key experimental variables—current density used to drive flow through the membrane and membrane pore density—on EOF rectification. We have found that the extent of EOF rectification, as quantified by the rectification ratio,more » increases with increasing current density. In contrast, the rectification ratio decreases with increasing membrane pore density. We propose explanations for these results based on simple EOF and membrane-transport theories.« less

Steady-State Density Functional Theory for Finite Bias Conductances.

PubMed

Stefanucci, G; Kurth, S

2015-12-09

In the framework of density functional theory, a formalism to describe electronic transport in the steady state is proposed which uses the density on the junction and the steady current as basic variables. We prove that, in a finite window around zero bias, there is a one-to-one map between the basic variables and both local potential on as well as bias across the junction. The resulting Kohn-Sham system features two exchange-correlation (xc) potentials, a local xc potential, and an xc contribution to the bias. For weakly coupled junctions the xc potentials exhibit steps in the density-current plane which are shown to be crucial to describe the Coulomb blockade diamonds. At small currents these steps emerge as the equilibrium xc discontinuity bifurcates. The formalism is applied to a model benzene junction, finding perfect agreement with the orthodox theory of Coulomb blockade.

Critical current density enhancement by phase decomposition of YBa 2Cu 4O 8 into YBa 2Cu 3O 7-σ and CuO

NASA Astrophysics Data System (ADS)

Krelaus, J.; Heinemann, K.; Ullmann, B.; Freyhardt, H. C.

1995-02-01

Bulk YBa 2Cu 4O 8 (Y-124) is prepared from YBa 2Cu 3O 7-σ (Y-123) and CuO by a powder-metallurgical method. The superconducting features of the Y-124, in particular critical current densities and activation energies, are measured resistively using a four-probe technique and magnetically using a Faraday magnetometer. In a second step the Y-124 is decomposed at high temperatures. The intragranular critical current density is measured at different annealing times, tA, in order to determine and discuss the characteristics of the jc( tA) curves.

Simulating the frontal instability of lock-exchange density currents with dissipative particle dynamics

NASA Astrophysics Data System (ADS)

Li, Yanggui; Geng, Xingguo; Wang, Heping; Zhuang, Xin; Ouyang, Jie

2016-06-01

The frontal instability of lock-exchange density currents is numerically investigated using dissipative particle dynamics (DPD) at the mesoscopic particle level. For modeling two-phase flow, the “color” repulsion model is adopted to describe binary fluids according to Rothman-Keller method. The present DPD simulation can reproduce the flow phenomena of lock-exchange density currents, including the lobe-and-cleft instability that appears at the head, as well as the formation of coherent billow structures at the interface behind the head due to the growth of Kelvin-Helmholtz instability. Furthermore, through the DPD simulation, some small-scale characteristics can be observed, which are difficult to be captured in macroscopic simulation and experiment.

Quantum mechanical probability current as electromagnetic 4-current from topological EM fields

NASA Astrophysics Data System (ADS)

van der Mark, Martin B.

2015-09-01

Starting from a complex 4-potential A = αdβ we show that the 4-current density in electromagnetism and the probability current density in relativistic quantum mechanics are of identical form. With the Dirac-Clifford algebra Cl1,3 as mathematical basis, the given 4-potential allows topological solutions of the fields, quite similar to Bateman's construction, but with a double field solution that was overlooked previously. A more general nullvector condition is found and wave-functions of charged and neutral particles appear as topological configurations of the electromagnetic fields.

Farfield Ion Current Density Measurements before and after the NASA HiVHAc EDU2 Vibration Test

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Kamhawi, Hani; Shastry, Rohit

2012-01-01

There is an increasing need to characterize the plasma plume of the NASA HiVHAc thruster in order to better understand the plasma physics and to obtain data for spacecraft interaction studies. To address this need, the HiVHAc research team is in the process of developing a number of plume diagnostic systems. This paper presents the initial results of the farfield current density probe diagnostic system. Farfield current density measurements were carried out before and after a vibration test of the HiVHAc engineering development unit 2 that simulate typical launch conditions. The main purposes of the current density measurements were to evaluate the thruster plume divergence and to investigate any changes in the plasma plume that may occur as a result of the vibration test. Radial sweeps, as opposed to the traditional polar sweeps, were performed during these tests. The charged-weighted divergence angles were found to vary from 16 to 28 degrees. Charge density profiles measured pre- and post-vibration-test were found to be in excellent agreement. This result, alongside thrust measurements reported in a companion paper, confirm that the operation of the HiVHAc engineering development unit 2 were not altered by full-level/random vibration testing.

Interaction of high voltage surfaces with the space plasma. [solar arrays

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.

1979-01-01

Tests were conducted using plasma densities of approximately 10 to the 5th power - 10 to the 6th power/cu cm. Insulating materials tested were polyimide (Dapton), mica and glass. Surface-area effects were found to be substantially reduced from those previously reported at lower plasma densities. The difference in typical plasma density was felt to be the major cause of this change, although a saturation effect may also be involved. At the 10 to the 5th power/cu cm plasma density range, surface effects on collection current appear limited to roughly 1 cm from the hole. A factor of several reduction of collected current was obtained with both surface scribing and a 2 x 2 cm conducting mesh. It appears possible that the effects of surface treatment might be more significant at lower plasma densities. Effects of repeated tests were also noted, with current collection decreasing with successive tests. Depending on the materials involved, the effect appeared due to either the smoothing of the inside of the insulator hole or the sputtering of insulator on the exposed conductor. A general conclusion was made from a variety of observations, that the generation of vapor is a major factor in the enhancement of collected current.

Mechanism of Carrier Transport in Hybrid GaN/AlN/Si Solar Cells

NASA Astrophysics Data System (ADS)

Ekinci, Huseyin; Kuryatkov, Vladimir V.; Gherasoiu, Iulian; Karpov, Sergey Y.; Nikishin, Sergey A.

2017-10-01

The particularities of the carrier transport in p- n-GaN/ n-AlN/ p- n-Si and n-GaN/ n-AlN /p- n-Si structures were investigated through temperature-dependent current density and forward voltage ( J- V) measurements, carrier distribution, and transport modeling. Despite the insulating properties of AlN, reasonably high current densities were achieved under forward bias. The experimental relationship between the current density and forward voltage was accurately approximated by an expression accounting for space-charge-limited current in the AlN layer and non-linear characteristics of the p- n junction formed in silicon. We suggest that extended defects throughout the AlN volume are responsible for the conduction, although the limited data available do not allow the accurate identification of the type of these defects.

Imaging of current density distributions with a Nb weak-link scanning nano-SQUID microscope

PubMed Central

Shibata, Yusuke; Nomura, Shintaro; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Ishiguro, Ryosuke; Takayanagi, Hideaki

2015-01-01

Superconducting quantum interference devices (SQUIDs) are accepted as one of the highest magnetic field sensitive probes. There are increasing demands to image local magnetic fields to explore spin properties and current density distributions in a two-dimensional layer of semiconductors or superconductors. Nano-SQUIDs have recently attracting much interest for high spatial resolution measurements in nanometer-scale samples. Whereas weak-link Dayem Josephson junction nano-SQUIDs are suitable to miniaturization, hysteresis in current-voltage (I-V) characteristics that is often observed in Dayem Josephson junction is not desirable for a scanning microscope. Here we report on our development of a weak-link nano-SQUIDs scanning microscope with small hysteresis in I-V curve and on reconstructions of two-dimensional current density vector in two-dimensional electron gas from measured magnetic field. PMID:26459874

Imaging of current density distributions with a Nb weak-link scanning nano-SQUID microscope

NASA Astrophysics Data System (ADS)

Shibata, Yusuke; Nomura, Shintaro; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Ishiguro, Ryosuke; Takayanagi, Hideaki

2015-10-01

Superconducting quantum interference devices (SQUIDs) are accepted as one of the highest magnetic field sensitive probes. There are increasing demands to image local magnetic fields to explore spin properties and current density distributions in a two-dimensional layer of semiconductors or superconductors. Nano-SQUIDs have recently attracting much interest for high spatial resolution measurements in nanometer-scale samples. Whereas weak-link Dayem Josephson junction nano-SQUIDs are suitable to miniaturization, hysteresis in current-voltage (I-V) characteristics that is often observed in Dayem Josephson junction is not desirable for a scanning microscope. Here we report on our development of a weak-link nano-SQUIDs scanning microscope with small hysteresis in I-V curve and on reconstructions of two-dimensional current density vector in two-dimensional electron gas from measured magnetic field.

The relative density of forests in the United States

Treesearch

Christopher W. Woodall; Charles H. Perry; Patrick D. Miles

2006-01-01

A relative stand density assessment technique, using the mean specific gravity of all trees in a stand to predict its maximum stand density index (SDI) and subsequently its relative stand density (current SDI divided by maximum SDI), was used to estimate the relative density of forests across the United States using a national-scale forest inventory. Live tree biomass...

Development and Application of a Wireless Sensor for Space Charge Density Measurement in an Ultra-High-Voltage, Direct-Current Environment

PubMed Central

Xin, Encheng; Ju, Yong; Yuan, Haiwen

2016-01-01

A space charge density wireless measurement system based on the idea of distributed measurement is proposed for collecting and monitoring the space charge density in an ultra-high-voltage direct-current (UHVDC) environment. The proposed system architecture is composed of a number of wireless nodes connected with space charge density sensors and a base station. The space charge density sensor based on atmospheric ion counter method is elaborated and developed, and the ARM microprocessor and Zigbee radio frequency module are applied. The wireless network communication quality and the relationship between energy consumption and transmission distance in the complicated electromagnetic environment is tested. Based on the experimental results, the proposed measurement system demonstrates that it can adapt to the complex electromagnetic environment under the UHVDC transmission lines and can accurately measure the space charge density. PMID:27775627

Development and Application of a Wireless Sensor for Space Charge Density Measurement in an Ultra-High-Voltage, Direct-Current Environment.

PubMed

Xin, Encheng; Ju, Yong; Yuan, Haiwen

2016-10-20

A space charge density wireless measurement system based on the idea of distributed measurement is proposed for collecting and monitoring the space charge density in an ultra-high-voltage direct-current (UHVDC) environment. The proposed system architecture is composed of a number of wireless nodes connected with space charge density sensors and a base station. The space charge density sensor based on atmospheric ion counter method is elaborated and developed, and the ARM microprocessor and Zigbee radio frequency module are applied. The wireless network communication quality and the relationship between energy consumption and transmission distance in the complicated electromagnetic environment is tested. Based on the experimental results, the proposed measurement system demonstrates that it can adapt to the complex electromagnetic environment under the UHVDC transmission lines and can accurately measure the space charge density.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael, Stephan; Chow, Weng; Schneider, Hans

In the framework of a microscopic model for intersubband gain from electrically pumped quantum-dot structures we investigate electrically pumped quantum-dots as active material for a mid-infrared quantum cascade laser. Our previous calculations have indicated that these structures could operate with reduced threshold current densities while also achieving a modal gain comparable to that of quantum well active materials. We study the influence of two important quantum-dot material parameters, here, namely inhomogeneous broadening and quantum-dot sheet density, on the performance of a proposed quantum cascade laser design. In terms of achieving a positive modal net gain, a high quantum-dot density canmore » compensate for moderately high inhomogeneous broadening, but at a cost of increased threshold current density. By minimizing quantum-dot density with presently achievable inhomogeneous broadening and total losses, significantly lower threshold densities than those reported in quantum-well quantum-cascade lasers are predicted by our theory.« less

Impact of the Hall effect on high-energy-density plasma jets.

PubMed

Gourdain, P-A; Seyler, C E

2013-01-04

Using a 1-MA, 100 ns-rise-time pulsed power generator, radial foil configurations can produce strongly collimated plasma jets. The resulting jets have electron densities on the order of 10(20) cm(-3), temperatures above 50 eV and plasma velocities on the order of 100 km/s, giving Reynolds numbers of the order of 10(3), magnetic Reynolds and Péclet numbers on the order of 1. While Hall physics does not dominate jet dynamics due to the large particle density and flow inside, it strongly impacts flows in the jet periphery where plasma density is low. As a result, Hall physics affects indirectly the geometrical shape of the jet and its density profile. The comparison between experiments and numerical simulations demonstrates that the Hall term enhances the jet density when the plasma current flows away from the jet compared to the case where the plasma current flows towards it.

First measurements of the temporal evolution of the plasma density in HiPIMS discharges using THz time domain spectroscopy

NASA Astrophysics Data System (ADS)

Meier, Steffen M.; Hecimovic, Ante; Tsankov, Tsanko V.; Luggenhölscher, Dirk; Czarnetzki, Uwe

2018-03-01

In this paper, the novel technique of THz time domain spectroscopy has been applied to obtain time-resolved measurements of the plasma density in the active zone of a HiPIMS discharge with a titanium target. The obtained peak values are in the range of 1012-1013 cm-3 for discharge current densities of 1-4 A cm-2 at 0.5 and 2 Pa argon pressure. The measured densities show good correlation with the discharge current and voltage and the intensity of various atomic and ionic lines. The well known phases of the discharge have been identified and related to the variation of the electron density. The measurement results show that the plasma density remains nearly constant during the runaway/self-sputtering phase. Based on that, it is conjectured that singly charged titanium ions are the dominant ion species during this phase.

Low-dark current 1024×1280 InGaAs PIN arrays

NASA Astrophysics Data System (ADS)

Yuan, Ping; Chang, James; Boisvert, Joseph C.; Karam, Nasser

2014-06-01

Photon counting imaging applications requires low noise from both detector and readout integrated circuit (ROIC) arrays. In order to retain the photon-counting-level sensitivity, a long integration time has to be employed and the dark current has to be minimized. It is well known that the PIN dark current is sensitive to temperature and a dark current density of 0.5 nA/cm2 was demonstrated at 7 °C previously. In order to restrain the size, weight, and power consumption (SWaP) of cameras for persistent large-area surveillance on small platforms, it is critical to develop large format PIN arrays with small pitch and low dark current density at higher operation temperatures. Recently Spectrolab has grown, fabricated and tested 1024x1280 InGaAs PIN arrays with 12.5 μm pitch and achieved 0.7 nA/cm2 dark current density at 15 °C. Based on our previous low-dark-current PIN designs, the improvements were focused on 1) the epitaxial material design and growth control; and 2) PIN device structure to minimize the perimeter leakage current and junction diffusion current. We will present characterization data and analyses that illustrate the contribution of various dark current mechanisms.

Effect of current density on electron beam induced charging in MgO

NASA Astrophysics Data System (ADS)

Boughariou, Aicha; Hachicha, Olfa; Kallel, Ali; Blaise, Guy

2005-11-01

It is well known that the presence of space charge in an insulator is correlated with an electric breakdown. Many studies have been carried out on the experimental characterization of space charges. In this paper, we outline the dependence on the current density of the charge-trapping phenomenon in magnesium oxide. Our study was performed with a dedicated scanning electron microscope (SEM) on the electrical property evolution of surface of magnesium oxide (1 0 0) (MgO) single crystal, during a 1.1, 5 and 30 keV electron irradiation. The types of charges trapped on the irradiated areas and the charging kinetics are determined by measuring the total secondary electron emission (SEE) σ during the injection process by means of two complementary detectors. At low energies 1.1 and 5 keV, two different kinds of self-regulated regime (σ = 1) were observed as a function of current density. At 30 keV energy, the electron emission appears to be stimulated by the current density, due to the Poole-Frenkel effect.

Visible-blind ultraviolet photodetectors on porous silicon carbide substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naderi, N.; Hashim, M.R., E-mail: roslan@usm.my

2013-06-01

Highlights: • Highly reliable UV detectors are fabricated on porous silicon carbide substrates. • The optical properties of samples are enhanced by increasing the current density. • The optimized sample exhibits enhanced sensitivity to the incident UV radiation. - Abstract: Highly reliable visible-blind ultraviolet (UV) photodetectors were successfully fabricated on porous silicon carbide (PSC) substrates. High responsivity and high photoconductive gain were observed in a metal–semiconductor–metal ultraviolet photodetector that was fabricated on an optimized PSC substrate. The PSC samples were prepared via the UV-assisted photo-electrochemical etching of an n-type hexagonal silicon carbide (6H-SiC) substrate using different etching current densities. Themore » optical results showed that the current density is an outstanding etching parameter that controls the porosity and uniformity of PSC substrates. A highly porous substrate was synthesized using a suitable etching current density to enhance its light absorption, thereby improving the sensitivity of UV detector with this substrate. The electrical characteristics of fabricated devices on optimized PSC substrates exhibited enhanced sensitivity and responsivity to the incident radiation.« less

Electrochemical disinfection of simulated ballast water on PbO2/graphite felt electrode.

PubMed

Chen, Shuiping; Hu, Weidong; Hong, Jianxun; Sandoe, Steve

2016-04-15

A novel PbO2/graphite felt electrode was constructed by electrochemical deposition of PbO2 on graphite felt and characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) analysis. The prepared electrode is a viable technology for inactivation of Escherichia coli, Enterococcus faecalis, and Artemia salina as indicator organisms in simulated ballast water treatment, which meets the International Maritime Organization (IMO) Regulation D-2. The effects of contact time and current density on inactivation were investigated. An increase in current density generally had a beneficial effect on the inactivation of the three species. E.faecalis and A.salina were more resistant to electrochemical disinfection than E. coli. The complete disinfection of E.coli was achieved in <8min at an applied current density of 253A/m(2). Complete inactivation of E. faecalis and A.salina was achieved at the same current density after 60 and 40min of contact time, respectively. A. salina inactivation follows first-order kinetics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Characterizing the plasma of the Rotating Wall Machine

NASA Astrophysics Data System (ADS)

Hannum, David A.

The Rotating Wall Machine (RoWM) is a line-tied linear screw pinch built to study current-driven external kink modes. The plasma column is formed by an array of seven electrostatic washer guns which can also be biased to drive plasma current. The array allows independent control over the electron density ne and current density Jz profiles of the column. Internal measurements of the plasma have been made with singletip Langmuir and magnetic induction ("B-dot") probes for a range of bias currents (Ib = 0, 300, 500 A/gun). Streams from the individual guns are seen to merge at a distance of z ≈ 36 cm from the guns; the exact distance depends on the value of Ib. The density of the column is directly proportional to the Ohmic dissipation power, but the temperature stays at a low, uniform value (Te ≈ 3.5 eV) for each bias level. Electron densities are on the order of ne ˜10 20 m-3. The electron density expands radially (across the Bz guide field) as the plasma moves along the column, though the current density Jz mainly stays parallel to the field lines. The singletip Langmuir probe diagnostic is difficult to analyze for Ib = 500 A/gun plasmas and fails as Ib is raised beyond this level. Spectrographic analysis of the Halpha line indicates that the hydrogen plasmas are nearly fully ionized at each bias level. Azimuthal E x B rotation is axially and radially sheared; rotation slows as the plasma reaches the anode. Perpendicular diffusivity is consistent with the classical value, D⊥ ≈ 5 m2/sec, while parallel resistivity is seen to be twice the classical Spitzer value, 2 x 10-4 O m.

Large-eddy-simulation approach in understanding flow structures of 2D turbulent density currents over sloping surfaces

NASA Astrophysics Data System (ADS)

Nayamatullah, M.; Rao Pillalamarri, Narasimha; Bhaganagar, Kiran

2018-04-01

A numerical investigation was performed to understand the flow dynamics of 2D density currents over sloping surfaces. Large eddy simulation was conducted for lock-exchange (L-E) release currents and overflows. 2D Navier-Stokes equations were solved using the Boussinesq approximation. The effects of the lock aspect-ratio (height/length of lock), slope, and Reynolds number on the flow structures and turbulence mixing have been analyzed. Results have confirmed buoyancy within the head of the two-dimensional currents is not conserved which contradicts the classical thermal theory. The lock aspect-ratio dictates the fraction of initial buoyancy which is carried by the head of the current at the beginning of the slumping (horizontal) and accelerating phase (over a slope), which has important implications on turbulence kinetic energy production, and hence mixing in the current. For L-E flows over a slope, increasing slope angle enhances the turbulence production. Increasing slope results in shear reversal within the density current resulting in shear-instabilities. Differences in turbulence production mechanisms and flow structures exist between the L-E and constant-flux release currents resulting in significant differences in the flow characteristics between different releases.

Child-Langmuir flow in a planar diode filled with charged dust impurities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang Xiaoyan; Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44870 Bochum; Shukla, Padma Kant

The Child-Langmuir (CL) flow in a planar diode in the presence of stationary charged dust particles is studied. The limiting electron current density and other diode properties, such as the electrostatic potential, the electron flow speed, and the electron number density, are calculated analytically. A comparison of the results with the case without dust impurities reveals that the diode parameters mentioned above decrease with the increase of the dust charge density. Furthermore, it is found that the classical scaling of D{sup -2} (the gap spacing D) for the CL current density remains exactly valid, while the scaling of V{sup 3/2}more » (the applied gap voltage V) can be a good approximation for low applied gap voltage and for low dust charge density.« less

Magnetic configurations of the tilted current sheets in magnetotail

NASA Astrophysics Data System (ADS)

Shen, C.; Rong, Z. J.; Li, X.; Dunlop, M.; Liu, Z. X.; Malova, H. V.; Lucek, E.; Carr, C.

2008-11-01

In this research, the geometrical structures of tilted current sheet and tail flapping waves have been analysed based on multiple spacecraft measurements and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1) The magnetic field lines (MFLs) in the tilted current sheet are generally plane curves and the osculating planes in which the MFLs lie are about vertical to the equatorial plane, while the normal of the tilted current sheet leans severely to the dawn or dusk side. (2) The tilted current sheet may become very thin, the half thickness of its neutral sheet is generally much less than the minimum radius of the curvature of the MFLs. (3) In the neutral sheet, the field-aligned current density becomes very large and has a maximum value at the center of the current sheet. (4) In some cases, the current density is a bifurcated one, and the two humps of the current density often superpose two peaks in the gradient of magnetic strength, indicating that the magnetic gradient drift current is possibly responsible for the formation of the two humps of the current density in some tilted current sheets. Tilted current sheets often appear along with tail current sheet flapping waves. It is found that, in the tail flapping current sheets, the minimum curvature radius of the MFLs in the current sheet is rather large with values around 1 RE, while the neutral sheet may be very thin, with its half thickness being several tenths of RE. During the flapping waves, the current sheet is tilted substantially, and the maximum tilt angle is generally larger than 45°. The phase velocities of these flapping waves are several tens km/s, while their periods and wavelengths are several tens of minutes, and several earth radii, respectively. These tail flapping events generally last several hours and occur during quiet periods or periods of weak magnetospheric activity.

Effect of a superconducting coil as a fault current limiter on current density distribution in BSCCO tape after an over-current pulse

NASA Astrophysics Data System (ADS)

Tallouli, M.; Shyshkin, O.; Yamaguchi, S.

2017-07-01

The development of power transmission lines based on long-length high temperature superconducting (HTS) tapes is complicated and technically challenging task. A serious problem for transmission line operation could become HTS power cable damage due to over-current pulse conditions. To avoid the cable damage in any urgent case the superconducting coil technology, i.e. superconductor fault current limiter (SFCL) is required. Comprehensive understanding of the current density characteristics of HTS tapes in both cases, either after pure over-current pulse or after over-current pulse limited by SFCL, is needed to restart or to continue the operation of the power transmission line. Moreover, current density distribution along and across the HTS tape provides us with the sufficient information about the quality of the tape performance in different current feeding regimes. In present paper we examine BSCCO HTS tape under two current feeding regimes. The first one is 100A feeding preceded by 900A over-current pulse. In this case none of tape protection was used. The second scenario is similar to the fist one but SFCL is used to limit an over-current value. For both scenarios after the pulse is gone and the current feeding is set up at 100A we scan magnetic field above the tape by means of Hall probe sensor. Then the feeding is turned of and the magnetic field scanning is repeated. Using the inverse problem numerical solver we calculate the corresponding direct and permanent current density distributions during the feeding and after switch off. It is demonstrated that in the absence of SFCL the current distribution is highly peaked at the tape center. At the same time the current distribution in the experiment with SFCL is similar to that observed under normal current feeding condition. The current peaking in the first case is explained by the effect of an opposite electric field induced at the tape edges during the overcurrent pulse decay, and by degradation of superconductivity at the edges due to penetration of magnetic field in superconducting core during the pulse.

Formation of Ion Beam from High Density Plasma of ECR Discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izotov, I.; Razin, S.; Sidorov, A.

2005-03-15

One of the most promising directions of ECR multicharged ion sources evolution is related with increase in frequency of microwave pumping. During last years microwave generators of millimeter wave range - gyrotrons have been used more frequently. Creation of plasma with density 1013 cm-3 with medium charged ions and ion flux density through a plug of a magnetic trap along magnetic field lines on level of a few A/cm2 is possible under pumping by powerful millimeter wave radiation and quasigasdynamic (collisional) regime of plasma confinement in the magnetic trap. Such plasma has great prospects for application in plasma based ionmore » implantation systems for processing of surfaces with complicated and petit relief. Use it for ion beam formation seams to be difficult because of too high ion current density. This paper continues investigations described elsewhere and shows possibility to arrange ion extraction in zone of plasma expansion from the magnetic trap along axis of system and magnetic field lines.Plasma was created at ECR gas discharge by means of millimeter wave radiation of a gyrotron with frequency 37.5 GHz, maximum power 100 kW, pulse duration 1.5 ms. Two and three electrode quasi-Pierce extraction systems were used for ion beam formation.It is demonstrated that there is no changes in ion charge state distribution along expansion routing of plasma under collisional confinement. Also ion flux density decreases with distance from plug of the trap, it allows to control extracting ion current density. Multicharged ion beam of Nitrogen with total current up to 2.5 mA at diameter of extracting hole 1 mm, that corresponds current density 320 mA/cm2, was obtained. Magnitude of total ion current was limited due to extracting voltage (60 kV). Under such conditions characteristic transversal dimension of plasma equaled 4 cm, magnetic field value in extracting zone was about 0.1 T at axisymmetrical configuration.« less

Reliability of quantitative EEG (qEEG) measures and LORETA current source density at 30 days.

PubMed

Cannon, Rex L; Baldwin, Debora R; Shaw, Tiffany L; Diloreto, Dominic J; Phillips, Sherman M; Scruggs, Annie M; Riehl, Timothy C

2012-06-14

There is a growing interest for using quantitative EEG and LORETA current source density in clinical and research settings. Importantly, if these indices are to be employed in clinical settings then the reliability of these measures is of great concern. Neuroguide (Applied Neurosciences) is sophisticated software developed for the analyses of power, and connectivity measures of the EEG as well as LORETA current source density. To date there are relatively few data evaluating topographical EEG reliability contrasts for all 19 channels and no studies have evaluated reliability for LORETA calculations. We obtained 4 min eyes-closed and eyes-opened EEG recordings at 30-day intervals. The EEG was analyzed in Neuroguide and FFT power, coherence and phase was computed for traditional frequency bands (delta, theta, alpha and beta) and LORETA current source density was calculated in 1 Hz increments and summed for total power in eight regions of interest (ROI). In order to obtain a robust measure of reliability we utilized a random effects model with an absolute agreement definition. The results show very good reproducibility for total absolute power and coherence. Phase shows lower reliability coefficients. LORETA current source density shows very good reliability with an average 0.81 for ECB and 0.82 for EOB. Similarly, the eight regions of interest show good to very good agreement across time. Implications for future directions and use of qEEG and LORETA in clinical populations are discussed. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Microstructure and corrosion behaviour in biological environments of the new forged low-Ni Co-Cr-Mo alloys.

PubMed

Hiromoto, Sachiko; Onodera, Emi; Chiba, Akihiko; Asami, Katsuhiko; Hanawa, Takao

2005-08-01

Corrosion behaviour and microstructure of developed low-Ni Co-29Cr-(6, 8)Mo (mass%) alloys and a conventional Co-29Cr-6Mo-1Ni alloy (ASTM F75-92) were investigated in saline solution (saline), Hanks' solution (Hanks), and cell culture medium (E-MEM + FBS). The forging ratios of the Co-29Cr-6Mo alloy were 50% and 88% and that of the Co-29Cr-8Mo alloy was 88%. Ni content in the air-formed surface oxide film of the low-Ni alloys was under the detection limit of XPS. The passive current densities of the low-Ni alloys were of the same order of magnitude as that of the ASTM alloy in all the solutions. The passive current densities of all the alloys did not significantly change with the inorganic ions and the biomolecules. The anodic current densities in the secondary passive region of the low-Ni alloys were lower than that of the ASTM alloy in the E-MEM + FBS. Consequently, the low-Ni alloys are expected to show as high corrosion resistance as the ASTM alloy. On the other hand, the passive current density of the Co-29Cr-6Mo alloy with a forging ratio of 50% was slightly lower than that with a forging ratio of 88% in the saline. The refining of grains by further forging causes the increase in the passive current density of the low-Ni alloy.

Impedance of an intense plasma-cathode electron source for tokamak startup

DOE PAGES

Hinson, Edward Thomas; Barr, Jayson L.; Bongard, Michael W.; ...

2016-05-31

In this study, an impedance model is formulated and tested for the ~1kV, ~1kA/cm 2, arc-plasma cathode electron source used for local helicity injection tokamak startup. A double layer sheath is established between the high-density arc plasma (n arc ≈ 10 21 m -3) within the electron source, and the less dense external tokamak edge plasma (n edge ≈ 10 18 m -3) into which current is injected at the applied injector voltage, V inj. Experiments on the Pegasus spherical tokamak show the injected current, I inj, increases with V inj according to the standard double layer scaling I injmore » ~ V inj 3/2 at low current and transitions to I inj ~ V inj 1/2 at high currents. In this high current regime, sheath expansion and/or space charge neutralization impose limits on the beam density n b ~ I inj/V inj 1/2. For low tokamak edge density n edge and high I inj, the inferred beam density n b is consistent with the requirement n b ≤ n edge imposed by space-charge neutralization of the beam in the tokamak edge plasma. At sufficient edge density, n b ~ n arc is observed, consistent with a limit to n b imposed by expansion of the double layer sheath. These results suggest that n arc is a viable control actuator for the source impedance.« less

Analytical results for the time-dependent current density distribution of expanding ultracold gases after a sudden change of the confining potential

NASA Astrophysics Data System (ADS)

Boumaza, R.; Bencheikh, K.

2017-12-01

Using the so-called operator product expansion to lowest order, we extend the work in Campbell et al (2015 Phys. Rev. Lett 114 125302) by deriving a simple analytical expression for the long-time asymptotic one-body reduced density matrix during free expansion for a one-dimensional system of bosons with large atom number interacting through a repulsive delta potential initially confined by a potential well. This density matrix allows direct access to the momentum distribution and also to the mass current density. For initially confining power-law potentials we give explicit expressions, in the limits of very weak and very strong interaction, for the current density distributions during the free expansion. In the second part of the work we consider the expansion of ultracold gas from a confining harmonic trap to another harmonic trap with a different frequency. For the case of a quantum impenetrable gas of bosons (a Tonks-Girardeau gas) with a given atom number, we present an exact analytical expression for the mass current distribution (mass transport) after release from one harmonic trap to another harmonic trap. It is shown that, for a harmonically quenched Tonks-Girardeau gas, the current distribution is a suitable collective observable and under the weak quench regime, it exhibits oscillations at the same frequencies as those recently predicted for the peak momentum distribution in the breathing mode. The analysis is extended to other possible quenched systems.

Transport studies in polymer electrolyte fuel cell with porous metallic flow field at ultra high current density

NASA Astrophysics Data System (ADS)

Srouji, Abdul-Kader

Achieving cost reduction for polymer electrolyte fuel cells (PEFC) requires a simultaneous effort in increasing power density while reducing precious metal loading. In PEFCs, the cathode performance is often limiting due to both the slow oxygen reduction reaction (ORR), and mass transport limitation caused by limited oxygen diffusion and liquid water flooding at high current density. This study is motivated by the achievement of ultra-high current density through the elimination of the channel/land (C/L) paradigm in PEFC flow field design. An open metallic element (OME) flow field capable of operating at unprecedented ultra-high current density (3 A/cm2) introduces new advantages and limitations for PEFC operation. The first part of this study compares the OME with a conventional C/L flow field, through performance and electrochemical diagnostic tools such as electrochemical impedance spectroscopy (EIS). The results indicate the uniqueness of the OME's mass transport improvement. No sign of operation limitation due to flooding is noted. The second part specifically examines water management at high current density using the OME flow field. A unique experimental setup is developed to measure steady-state and transient net water drag across the membrane, in order to characterize the fundamental aspects of water transport at high current density with the OME. Instead of flooding, the new limitation is identified to be anode side dry-out of the membrane, caused by electroosmotic drag. The OME improves water removal from the cathode, which immediately improves oxygen transport and performance. However, the low water content in the cathode reduces back diffusion of water to the membrane, and electroosmotic drag dominates at high current density, leading to dry-out. The third part employs the OME flow field as a tool that avoids C/L effects endemic to a typical flow field, in order to study oxygen transport resistance at the catalyst layer of a PEFC. In open literature, a resistance of unknown origin, was shown to directly or indirectly scale with Pt loading. A lack of understanding of the mechanism responsible for such resistance is noted, and several possible theories have been proposed. This lack of fundamental understanding of the origins of this resistance adds complexity to computational models which are designed to capture performance behavior with ultra-low loading electrodes. By employing the OME flow field as a tool to study this phenomena, the origins of the transport resistance appearing at ultra-low Platinum (Pt) loading is proposed to be an increase in oxygen dilution resistance through water film.

Laser collisional induced fluorescence electron density measurements as a function of ring bias and the onset of anode spot formation in a ring cusp magnetic field

NASA Astrophysics Data System (ADS)

Arthur, N. A.; Foster, J. E.; Barnat, E. V.

2018-05-01

Two-dimensional electron density measurements are made in a magnetic ring cusp discharge using laser collisional induced fluorescence. The magnet rings are isolated from the anode structure such that they can be biased independently in order to modulate electron flows through the magnetic cusps. Electron density images are captured as a function of bias voltage in order to assess the effects of current flow through the cusp on the spatial extent of the cusp. We anticipated that for a fixed current density being funneled through the magnetic cusp, the leak width would necessarily increase. Unexpectedly, the leak width, as measured by LCIF images, does not increase. This suggests that the current density is not constant, and that possibly either electrons are being heated or additional ionization events are occurring within the cusp. Spatially resolving electron temperature would be needed to determine if electrons are being heated within the cusp. We also observe breakdown of the anode magnetosheath and formation of anode spots at high bias voltage.

Dependence of SOL widths on plasma current and density in NSTX H-mode plasmas

NASA Astrophysics Data System (ADS)

Ahn, J.-W.; Maingi, R.; Boedo, J. A.; Soukhanovskii, V.; NSTX Team

2009-06-01

The dependence of various SOL widths on the line-averaged density ( n) and plasma current ( Ip) for the quiescent H-mode plasmas with Type-V ELMs in the National Spherical Torus Experiment (NSTX) was investigated. It is found that the heat flux SOL width ( λq), measured by the IR camera, is virtually insensitive to n and has a strong negative dependence on Ip. This insensitivity of λq to n¯e is consistent with the scaling law from JET H-mode plasmas that shows a very weak dependence on the upstream density. The electron temperature, ion saturation current density, electron density, and electron pressure decay lengths ( λTe, λjsat, λne, and λpe, respectively) measured by the probe showed that λTe and λjsat have strong negative dependence on Ip, whereas λne and λpe revealed only a little or no dependence. The dependence of λTe on Ip is consistent with the scaling law in the literature, while λne and λpe dependence shows a different trend.

Plasma stability analysis using Consistent Automatic Kinetic Equilibrium reconstruction (CAKE)

NASA Astrophysics Data System (ADS)

Roelofs, Matthijs; Kolemen, Egemen; Eldon, David; Glasser, Alex; Meneghini, Orso; Smith, Sterling P.

2017-10-01

Presented here is the Consistent Automatic Kinetic Equilibrium (CAKE) code. CAKE is being developed to perform real-time kinetic equilibrium reconstruction, aiming to do a reconstruction in less than 100ms. This is achieved by taking, next to real-time Motional Stark Effect (MSE) and magnetics data, real-time Thomson Scattering (TS) and real-time Charge Exchange Recombination (CER, still in development) data in to account. Electron densities and temperature are determined by TS, while ion density and pressures are determined using CER. These form, together with the temperature and density of neutrals, the additional pressure constraints. Extra current constraints are imposed in the core by the MSE diagnostics. The pedestal current density is estimated using Sauters equation for the bootstrap current density. By comparing the behaviour of the ideal MHD perturbed potential energy (δW) and the linear stability index (Δ') of CAKE to magnetics-only reconstruction, it can be seen that the use of diagnostics to reconstruct the pedestal have a large effect on stability. Supported by U.S. DOE DE-SC0015878 and DE-FC02-04ER54698.

Assessment of the magnetic field exposure due to the battery current of digital mobile phones.

PubMed

Jokela, Kari; Puranen, Lauri; Sihvonen, Ari-Pekka

2004-01-01

Hand-held digital mobile phones generate pulsed magnetic fields associated with the battery current. The peak value and the waveform of the battery current were measured for seven different models of digital mobile phones, and the results were applied to compute approximately the magnetic flux density and induced currents in the phone-user's head. A simple circular loop model was used for the magnetic field source and a homogeneous sphere consisting of average brain tissue equivalent material simulated the head. The broadband magnetic flux density and the maximal induced current density were compared with the guidelines of ICNIRP using two various approaches. In the first approach the relative exposure was determined separately at each frequency and the exposure ratios were summed to obtain the total exposure (multiple-frequency rule). In the second approach the waveform was weighted in the time domain with a simple low-pass RC filter and the peak value was divided by a peak limit, both derived from the guidelines (weighted peak approach). With the maximum transmitting power (2 W) the measured peak current varied from 1 to 2.7 A. The ICNIRP exposure ratio based on the current density varied from 0.04 to 0.14 for the weighted peak approach and from 0.08 to 0.27 for the multiple-frequency rule. The latter values are considerably greater than the corresponding exposure ratios 0.005 (min) to 0.013 (max) obtained by applying the evaluation based on frequency components presented by the new IEEE standard. Hence, the exposure does not seem to exceed the guidelines. The computed peak magnetic flux density exceeded substantially the derived peak reference level of ICNIRP, but it should be noted that in a near-field exposure the external field strengths are not valid indicators of exposure. Currently, no biological data exist to give a reason for concern about the health effects of magnetic field pulses from mobile phones.

Ubiquitin ligase Nedd4-2 modulates Kv1.3 current amplitude and ion channel protein targeting

PubMed Central

Velez, Patricio; Schwartz, Austin B.; Iyer, Subashini R.; Warrington, Anthony

2016-01-01

Voltage-dependent potassium channels (Kv) go beyond the stabilization of the resting potential and regulate biochemical pathways, regulate intracellular signaling, and detect energy homeostasis. Because targeted deletion and pharmacological block of the Kv1.3 channel protein produce marked changes in metabolism, resistance to diet-induced obesity, and changes in olfactory structure and function, this investigation explored Nedd4-2-mediated ubiquitination and degradation to regulate Kv1.3 channel density. Heterologous coexpression of Nedd4-2 ligase and Kv1.3 in HEK 293 cells reduced Kv1.3 current density without modulation of kinetic properties as measured by patch-clamp electrophysiology. Modulation of current density was dependent on ligase activity and was lost through point mutation of cysteine 938 in the catalytic site of the ligase (Nedd4-2CS). Incorporation of adaptor protein Grb10 relieved Nedd4-2-induced current suppression as did application of the proteasome inhibitor Mg-132. SDS-PAGE and immunoprecipitation strategies demonstrated a channel/adaptor/ligase signalplex. Pixel immunodensity was reduced for Kv1.3 in the presence of Nedd4-2, which was eliminated upon additional incorporation of Grb10. We confirmed Nedd4-2/Grb10 coimmunoprecipitation and observed an increased immunodensity for Nedd4-2 in the presence of Kv1.3 plus Grb10, regardless of whether the catalytic site was active. Kv1.3/Nedd4-2 were reciprocally coimmunoprecipated, whereby mutation of the COOH-terminal, SH3-recognition (493–498), or ubiquitination sites on Kv1.3 (lysines 467, 476, 498) retained coimmunoprecipitation, while the latter prevented the reduction in channel density. A model is presented for which an atypical interaction outside the canonical PY motif may permit channel/ligase interaction to lead to protein degradation and reduced current density, which can involve Nedd4-2/Grb10 interactions to disrupt Kv1.3 loss of current density. PMID:27146988

The use of segmented cathodes to determine the spoke current density distribution in high power impulse magnetron sputtering plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poolcharuansin, Phitsanu; The Technological Plasma Research Unit, Department of Physics, Mahasarakham University, Maha Sarakham 44150; Estrin, Francis Lockwood

2015-04-28

The localized target current density associated with quasi-periodic ionization zones (spokes) has been measured in a high power impulse magnetron sputtering (HiPIMS) discharge using an array of azimuthally separated and electrical isolated probes incorporated into a circular aluminum target. For a particular range of operating conditions (pulse energies up to 2.2 J and argon pressures from 0.2 to 1.9 Pa), strong oscillations in the probe current density are seen with amplitudes up to 52% above a base value. These perturbations, identified as spokes, travel around the discharge above the target in the E×B direction. Using phase information from the angularly separated probes,more » the spoke drift speeds, angular frequencies, and mode number have been determined. Generally, at low HiPIMS pulse energies E{sub p} < 0.8 J, spokes appear to be chaotic in nature (with random arrival times), however as E{sub p} increases, coherent spokes are observed with velocities between 6.5 and 10 km s{sup −1} and mode numbers m = 3 or above. At E{sub p} > 1.8 J, the plasma becomes spoke-free. The boundaries between chaotic, coherent, and no-spoke regions are weakly dependent on pressure. During each HiPIMS pulse, the spoke velocities increase by about 50%. Such an observation is explained by considering spoke velocities to be determined by the critical ionization velocity, which changes as the plasma composition changes during the pulse. From the shape of individual current density oscillations, it appears that the leading edge of the spoke is associated with a slow increase in local current density to the target and the rear with a more rapid decrease. The measurements show that the discharge current density associated with individual spokes is broadly spread over a wide region of the target.« less

ELF exposure from mobile and cordless phones for the epidemiological MOBI-Kids study.

PubMed

Calderón, Carolina; Ichikawa, Hiroki; Taki, Masao; Wake, Kanako; Addison, Darren; Mee, Terry; Maslanyj, Myron; Kromhout, Hans; Lee, Ae-Kyoung; Sim, Malcolm R; Wiart, Joe; Cardis, Elisabeth

2017-04-01

This paper describes measurements and computational modelling carried out in the MOBI-Kids case-control study to assess the extremely low frequency (ELF) exposure of the brain from use of mobile and cordless phones. Four different communication systems were investigated: Global System for Mobile (GSM), Universal Mobile Telecommunications System (UMTS), Digital Enhanced Cordless Telecommunications (DECT) and Wi-Fi Voice over Internet Protocol (VoIP). The magnetic fields produced by the phones during transmission were measured under controlled laboratory conditions, and an equivalent loop was fitted to the data to produce three-dimensional extrapolations of the field. Computational modelling was then used to calculate the induced current density and electric field strength in the brain resulting from exposure to these magnetic fields. Human voxel phantoms of four different ages were used: 8, 11, 14 and adult. The results indicate that the current densities induced in the brain during DECT calls are likely to be an order of magnitude lower than those generated during GSM calls but over twice that during UMTS calls. The average current density during Wi-Fi VoIP calls was found to be lower than for UMTS by 30%, but the variability across the samples investigated was high. Spectral contributions were important to consider in relation to current density, particularly for DECT phones. This study suggests that the spatial distribution of the ELF induced current densities in brain tissues is determined by the physical characteristics of the phone (in particular battery position) while the amplitude is mainly dependent on communication system, thus providing a feasible basis for assessing ELF exposure in the epidemiological study. The number of phantoms was not large enough to provide definitive evidence of an increase of induced current density with age, but the data that are available suggest that, if present, the effect is likely to be very small. Copyright © 2017 Elsevier Ltd. All rights reserved.

The September 14, 2015 phreatomagmatic eruption of Nakadake first crater, Aso Volcano, Japan: Eruption sequence inferred from ballistic, pyroclastic density current and fallout deposits

NASA Astrophysics Data System (ADS)

Miyabuchi, Yasuo; Iizuka, Yoshiyuki; Hara, Chihoko; Yokoo, Akihiko; Ohkura, Takahiro

2018-02-01

An explosive eruption occurred at Nakadake first crater, Aso Volcano in central Kyushu, southwestern Japan, on September 14, 2015. The sequence and causes of the eruption were reconstructed from the distribution, textures, grain-size, component and chemical characteristics of the related deposits, and video record. The eruptive deposits are divided into ballistics, pyroclastic density current and ash-fall deposits. A large number of ballistic clasts (mostly < 10 cm in diameter; maximum size 1.6 m) are scattered within about 500 m from the center of the crater. Almost half of the ballistics appear as fresh and unaltered basaltic andesite rocks interpreted to be derived from a fresh batch of magma, while the rest is weakly to highly altered clasts. A relatively thin ash derived from pyroclastic density currents covered an area of 2.3 km2 with the SE-trending main axis and two minor axes to the NE and NW. The pyroclastic density current deposit (maximum thickness < 10 cm even at the crater rim) is wholly fine grained, containing no block-sized clasts. Based on the isopach map, the mass of the pyroclastic density current deposit was estimated at ca. 5.2 × 104 tons. The ash-fall deposit is finer grained and clearly distributed to about 8 km west of the source crater. The mass of the ash-fall deposit was calculated at about 2.7 × 104 tons. Adding the mass of the pyroclastic density current deposit, the total discharged mass of the September 14, 2015 eruption was 7.9 × 104 tons. The September 14 pyroclastic density current and ash-fall deposits consist of glass shards (ca. 30%), crystals (20-30%) and lithic (40-50%) grains. Most glass shards are unaltered poorly crystallized pale brown glasses which probably resulted from quenching of juvenile magma. This suggests that the September 14, 2015 event at the Nakadake first crater was a phreatomagmatic eruption. Similar phreatomagmatic eruptions occurred at the same crater on September 6, 1979 and April 20, 1990 whose eruptive masses were one order larger than that of the September 14, 2015 eruption. These events highlight the potential hazard from phreatic or phreatomagmatic eruptions at Nakadake first crater, and provide useful information that will assist in preventing or mitigating future disasters at other similar volcanoes worldwide.

GALVANOTAXIS OF SLIME MOLD

PubMed Central

Anderson, John D.

1951-01-01

The plasmodium of Physarum polycephalum reacts to direct current by migration toward the cathode. Cathodal migration was obtained upon a variety of substrata such as baked clay, paper, cellophane, and agar with a current density in the substratum of 1.0 µa./mm.2 Injury was produced by current densities of 8.0 to 12.0 µa./mm.2 The negative galvanotactic response was not due to electrode products. Attempts to demonstrate that the response was due to gradients or orientation in the substratum, pH changes in the mold, cataphoresis, electroosmosis, or endosmosis were not successful. The addition of salts (CaCl2, LiCl, NaCl, Na2SO4, NaHCO3, KCl, MgSO4, sodium citrate, and sea water) to agar indicated that change of cations had more effect than anions upon galvanotaxis and that the effect was upon threshold values. K ion (0.01 M KCl) increased the lower threshold value to 8.0 µa./mm.2 and the upper threshold value to 32.0 µa./mm.2, whereas the Li ion (0.01 M LiCl) increased the lower threshold to only 4.0 µa./mm.2 and the upper threshold to only 16.0 µa./mm.2 The passage of electric current produced no increase in the rate of cathodal migration; neither was there a decrease until injurious current densities were reached. With increase of subthreshold current densities there was a progressive decrease in rate of migration toward the anode until complete anodal inhibition occurred. There was orientation at right angles to the electrodes in alternating current (60 cycle) with current density of 4.0 µa./mm.2 and in direct current of 5.0 µa./mm.2 when polarity of current was reversed every minute. It is concluded that the negative galvanotactic response of P. polycephalum is due to inhibition of migration on the anodal side of the plasmodium and that this inhibition results in the limitation of the normal migration of the mold to a cathodal direction. The mechanism of the anodal inhibition has not been elucidated. PMID:14873916

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawase, Kazumasa; Uehara, Yasushi; Teramoto, Akinobu

Silicon dioxide (SiO{sub 2}) films formed by chemical vapor deposition (CVD) were treated with oxygen radical oxidation using Ar/O{sub 2} plasma excited by microwave. The mass density depth profiles, carrier trap densities, and current-voltage characteristics of the radical-oxidized CVD-SiO{sub 2} films were investigated. The mass density depth profiles were estimated with x ray reflectivity measurement using synchrotron radiation of SPring-8. The carrier trap densities were estimated with x ray photoelectron spectroscopy time-dependent measurement. The mass densities of the radical-oxidized CVD-SiO{sub 2} films were increased near the SiO{sub 2} surface. The densities of the carrier trap centers in these films weremore » decreased. The leakage currents of the metal-oxide-semiconductor capacitors fabricated by using these films were reduced. It is probable that the insulation properties of the CVD-SiO{sub 2} film are improved by the increase in the mass density and the decrease in the carrier trap density caused by the restoration of the Si-O network with the radical oxidation.« less

Recent Results From Internal and Very-Near-Field Plasma Diagnostics of a High Specific Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Gallimore, Alec D.; Jacobson, David (Technical Monitor)

2003-01-01

Floating potential and ion current density measurements were taken on the laboratory model NASA-173Mv2 in order to improve understanding of the physical processes affecting Hall thruster performance at high specific impulse. Floating potential was measured on discharge chamber centerline over axial positions spanning 10 mm from the anode to 100 mm downstream of the exit plane. Ion current density was mapped radially up to 300 mm from thruster centerline over axial positions in the very-near-field (10 to 250 mm from the exit plane). All data were collected using a planar probe in conjunction with a high-speed translation stage to minimize probe-induced thruster perturbations. Measurements of floating potential at a xenon flow rate of 10 mg/s have shown that the acceleration layer moved upstream 3 1 mm when the voltage increased from 300 to 600 V. The length of the acceleration layer was 14 2 mm and was approximately constant with voltage and magnetic field. Ion current density measurements indicated the annular ion beam crossed the thruster centerline 163 mm downstream of the exit plane. Radial integration of the ion current density at the cathode plane provided an estimate of the ion current fraction. At 500 V and 5 mg/s, the ion current fraction was calculated as 0.77.

Orbital currents in a generalized Hubbard ladder

NASA Astrophysics Data System (ADS)

Fjaerestad, John O.

2004-03-01

We study a phase with orbital currents (d-density wave (DDW)/staggered flux phase) in a generalized Hubbard model on the two-leg ladder at zero temperature. Bosonization and perturbative renormalization-group calculations are used to identify a parameter region with long-range DDW order in the weakly interacting half-filled ladder. Finite-size density-matrix renormalization-group (DMRG) studies of ladders with up to 200 rungs, for rational hole dopings δ and intermediate-strength interactions, find that currents remain large in the doped DDW phase, with no evidence of decay.^1,2,3 Motivated by these results, we consider an effective bosonization description of the doped DDW phase in which quantum fluctuations in the total charge mode are neglected.^3 This leads to an analytically solvable Frenkel-Kontorova-like model which predicts that the staggered rung current and the rung electron density show periodic spatial oscillations with wavelengths 2/δ and 1/δ, respectively, with the density minima located at the zeros (domain walls) of the staggered rung current, in good agreement with the DMRG results. We comment on the question of the nature of the asymptotic current correlations in the doped DDW phase. ^1U. Schollwöck, S. Chakravarty, J. O. Fjaerestad, J. B. Marston, and M. Troyer, Phys. Rev. Lett. 90, 186401 (2003). ^2M. Troyer, invited talk at this meeting. ^3J. O. Fjaerestad, J. B. Marston, and U. Schollwöck, unpublished.

Long-Term Variability of Jupiter's Magnetodisk and Implications for the Aurora

NASA Astrophysics Data System (ADS)

Vogt, Marissa F.; Bunce, Emma J.; Nichols, Jonathan D.; Clarke, John T.; Kurth, William S.

2017-12-01

Observations of Jupiter's UV auroral emissions collected over several years show that the ionospheric positions of the main emission and the Ganymede footprint can vary by as much as 3° in latitude. One explanation for this shift is a change of Jupiter's current sheet current density, which would alter the amount of field line stretching and displace the ionospheric mapping of field lines from a given radial distance in the magnetosphere. In this study we measure the long-term variability of Jupiter's magnetodisk using Galileo magnetometer data collected from 1996 to 2003. Using the Connerney et al. (1981) current sheet model, we calculate the current sheet density parameter that gives the best fit to the data from each orbit and find that the current density parameter varies by about 15% of its average value during the Galileo era. We investigate possible relationships between the observed current sheet variability and quantities such as Io's plasma torus production rate inferred from volcanic activity and external solar wind conditions extrapolated from data at 1 AU but find only a weak correlation. Finally, we trace Khurana (1997) model field lines to show that the observed changes in Jupiter's current sheet are sufficient to shift the ionospheric footprint of Ganymede and main auroral emission by a few degrees of latitude, consistent with the magnitude of auroral variability observed by Hubble Space Telescope (HST). However, we find that the measured auroral shifts in HST images are not consistent with concurrent changes in the current density parameter measured by Galileo.

Revisiting the role of trap-assisted-tunneling process on current-voltage characteristics in tunnel field-effect transistors

NASA Astrophysics Data System (ADS)

Omura, Yasuhisa; Mori, Yoshiaki; Sato, Shingo; Mallik, Abhijit

2018-04-01

This paper discusses the role of trap-assisted-tunneling process in controlling the ON- and OFF-state current levels and its impacts on the current-voltage characteristics of a tunnel field-effect transistor. Significant impacts of high-density traps in the source region are observed that are discussed in detail. With regard to recent studies on isoelectronic traps, it has been discovered that deep level density must be minimized to suppress the OFF-state leakage current, as is well known, whereas shallow levels can be utilized to control the ON-state current level. A possible mechanism is discussed based on simulation results.

Four-dimensional ultrasound current source density imaging of a dipole field

NASA Astrophysics Data System (ADS)

Wang, Z. H.; Olafsson, R.; Ingram, P.; Li, Q.; Qin, Y.; Witte, R. S.

2011-09-01

Ultrasound current source density imaging (UCSDI) potentially transforms conventional electrical mapping of excitable organs, such as the brain and heart. For this study, we demonstrate volume imaging of a time-varying current field by scanning a focused ultrasound beam and detecting the acoustoelectric (AE) interaction signal. A pair of electrodes produced an alternating current distribution in a special imaging chamber filled with a 0.9% NaCl solution. A pulsed 1 MHz ultrasound beam was scanned near the source and sink, while the AE signal was detected on remote recording electrodes, resulting in time-lapsed volume movies of the alternating current distribution.

High power density from a miniature microbial fuel cell using Shewanella oneidensis DSP10.

PubMed

Ringeisen, Bradley R; Henderson, Emily; Wu, Peter K; Pietron, Jeremy; Ray, Ricky; Little, Brenda; Biffinger, Justin C; Jones-Meehan, Joanne M

2006-04-15

A miniature microbial fuel cell (mini-MFC) is described that demonstrates high output power per device cross-section (2.0 cm2) and volume (1.2 cm3). Shewanella oneidensis DSP10 in growth medium with lactate and buffered ferricyanide solutions were used as the anolyte and catholyte, respectively. Maximum power densities of 24 and 10 mW/m2 were measured using the true surface areas of reticulated vitreous carbon (RVC) and graphite felt (GF) electrodes without the addition of exogenous mediators in the anolyte. Current densities at maximum power were measured as 44 and 20 mA/m2 for RVC and GF, while short circuit current densities reached 32 mA/m2 for GF anodes and 100 mA/m2 for RVC. When the power density for GF was calculated using the cross sectional area of the device or the volume of the anode chamber, we found values (3 W/m2, 500 W/m3) similar to the maxima reported in the literature. The addition of electron mediators resulted in current and power increases of 30-100%. These power densities were surprisingly high considering a pure S. oneidensis culture was used. We found that the short diffusion lengths and high surface-area-to-chamber volume ratio utilized in the mini-MFC enhanced power density when compared to output from similar macroscopic MFCs.

Advanced electric propulsion research - 1990

NASA Technical Reports Server (NTRS)

Monheiser, Jeffery M.; Wilbur, Paul J.

1991-01-01

An experimental study of impingement current collection on the accelerator grid of an ion thruster is presented. The equipment, instruments, and procedures being used to conduct the study are discussed. The contribution to this current due to charge-exchange ions produced close to the grid is determined using a volume-integration procedure and measured ion beam current design, computed neutral atom density and measured beam plasma potential data. This current, which is expected to be almost equal to that measured directly, is found to be an order of magnitude less. The impingement current determined by integrating the current density of ambient ions in the beam plasma close to the grid is found to agree with the directly measured impingement current. Possible reasons for the disagreement between the directly measured and volume integrated impingement currents are discussed.

Electric field mill network products to improve detection of the lightning hazard

NASA Technical Reports Server (NTRS)

Maier, Launa M.

1987-01-01

An electric field mill network has been used at Kennedy Space Center for over 10 years as part of the thunderstorm detection system. Several algorithms are currently available to improve the informational output of the electric field mill data. The charge distributions of roughly 50 percent of all lightning can be modeled as if they reduced the charged cloud by a point charge or a point dipole. Using these models, the spatial differences in the lightning induced electric field changes, and a least squares algorithm to obtain an optimum solution, the three-dimensional locations of the lightning charge centers can be located. During the lifetime of a thunderstorm, dynamically induced charging, modeled as a current source, can be located spatially with measurements of Maxwell current density. The electric field mills can be used to calculate the Maxwell current density at times when it is equal to the displacement current density. These improvements will produce more accurate assessments of the potential electrical activity, identify active cells, and forecast thunderstorm termination.

Dark Current Characterization of SW HgCdTe IRFPAs Detectors on Si Substrate with Long Time Integration

NASA Astrophysics Data System (ADS)

Song, P. Y.; Ye, Z. H.; Huang, A. B.; Chen, H. L.; Hu, X. N.; Ding, R. J.; He, L.

2016-09-01

The dark currents of two short wave (SW) HgCdTe infrared focal plane arrays (IRFPA) detectors hybridized with direct injection (DI) readout and capacitance transimpedance amplifier (CTIA) with long time integration were investigated. The cutoff wavelength of the two SW IRFPAs is about 2.6 μm at 84 K. The dark current densities of DI and CTIA samples are approximately 8.0 × 10-12 A/cm2 and 7.2 × 10-10 A/cm2 at 110 K, respectively. The large divergence of the dark current density might arise from the injection efficiency difference of the two readouts. The low injection efficiency of the DI readout, compared with the high injection efficiency of the CTIA readout at low temperature, makes the dark current density of the DI sample much lower than that of the CTIA sample. The experimental value of injection efficiency of the DI sample was evaluated as 1.1% which is consistent with its theoretical value.

Crack problem in superconducting cylinder with exponential distribution of critical-current density

NASA Astrophysics Data System (ADS)

Zhao, Yufeng; Xu, Chi; Shi, Liang

2018-04-01

The general problem of a center crack in a long cylindrical superconductor with inhomogeneous critical-current distribution is studied based on the extended Bean model for zero-field cooling (ZFC) and field cooling (FC) magnetization processes, in which the inhomogeneous parameter η is introduced for characterizing the critical-current density distribution in inhomogeneous superconductor. The effect of the inhomogeneous parameter η on both the magnetic field distribution and the variations of the normalized stress intensity factors is also obtained based on the plane strain approach and J-integral theory. The numerical results indicate that the exponential distribution of critical-current density will lead a larger trapped field inside the inhomogeneous superconductor and cause the center of the cylinder to fracture more easily. In addition, it is worth pointing out that the nonlinear field distribution is unique to the Bean model by comparing the curve shapes of the magnetization loop with homogeneous and inhomogeneous critical-current distribution.

Predicting Grizzly Bear Density in Western North America

PubMed Central

Mowat, Garth; Heard, Douglas C.; Schwarz, Carl J.

2013-01-01

Conservation of grizzly bears (Ursus arctos) is often controversial and the disagreement often is focused on the estimates of density used to calculate allowable kill. Many recent estimates of grizzly bear density are now available but field-based estimates will never be available for more than a small portion of hunted populations. Current methods of predicting density in areas of management interest are subjective and untested. Objective methods have been proposed, but these statistical models are so dependent on results from individual study areas that the models do not generalize well. We built regression models to relate grizzly bear density to ultimate measures of ecosystem productivity and mortality for interior and coastal ecosystems in North America. We used 90 measures of grizzly bear density in interior ecosystems, of which 14 were currently known to be unoccupied by grizzly bears. In coastal areas, we used 17 measures of density including 2 unoccupied areas. Our best model for coastal areas included a negative relationship with tree cover and positive relationships with the proportion of salmon in the diet and topographic ruggedness, which was correlated with precipitation. Our best interior model included 3 variables that indexed terrestrial productivity, 1 describing vegetation cover, 2 indices of human use of the landscape and, an index of topographic ruggedness. We used our models to predict current population sizes across Canada and present these as alternatives to current population estimates. Our models predict fewer grizzly bears in British Columbia but more bears in Canada than in the latest status review. These predictions can be used to assess population status, set limits for total human-caused mortality, and for conservation planning, but because our predictions are static, they cannot be used to assess population trend. PMID:24367552

Predicting grizzly bear density in western North America.

PubMed

Mowat, Garth; Heard, Douglas C; Schwarz, Carl J

2013-01-01

Conservation of grizzly bears (Ursus arctos) is often controversial and the disagreement often is focused on the estimates of density used to calculate allowable kill. Many recent estimates of grizzly bear density are now available but field-based estimates will never be available for more than a small portion of hunted populations. Current methods of predicting density in areas of management interest are subjective and untested. Objective methods have been proposed, but these statistical models are so dependent on results from individual study areas that the models do not generalize well. We built regression models to relate grizzly bear density to ultimate measures of ecosystem productivity and mortality for interior and coastal ecosystems in North America. We used 90 measures of grizzly bear density in interior ecosystems, of which 14 were currently known to be unoccupied by grizzly bears. In coastal areas, we used 17 measures of density including 2 unoccupied areas. Our best model for coastal areas included a negative relationship with tree cover and positive relationships with the proportion of salmon in the diet and topographic ruggedness, which was correlated with precipitation. Our best interior model included 3 variables that indexed terrestrial productivity, 1 describing vegetation cover, 2 indices of human use of the landscape and, an index of topographic ruggedness. We used our models to predict current population sizes across Canada and present these as alternatives to current population estimates. Our models predict fewer grizzly bears in British Columbia but more bears in Canada than in the latest status review. These predictions can be used to assess population status, set limits for total human-caused mortality, and for conservation planning, but because our predictions are static, they cannot be used to assess population trend.

Effect of laser cavity parameters on saturation of light – current characteristics of high-power pulsed lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veselov, D A; Pikhtin, N A; Lyutetskiy, A V

2015-07-31

We report an experimental study of power characteristics of semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with a broadened waveguide as functions of cavity length, stripe contact width and mirror reflectivities. It is shown that at high current pump levels, the variation of the cavity parameters of a semiconductor laser (width, length and mirror reflectivities) influences the light – current (L – I) characteristic saturation and maximum optical power by affecting such laser characteristics, as the current density and the optical output loss. A model is elaborated and an optical power of semiconductor lasers is calculated by taking intomore » account the dependence of the internal optical loss on pump current density and concentration distribution of charge carriers and photons along the cavity axis of the cavity. It is found that only introduction of the dependence of the internal optical loss on pump current density to the calculation model provides a good agreement between experimental and calculated L – I characteristics for all scenarios of variations in the laser cavity parameters. (lasers)« less

Current profile redistribution driven by neutral beam injection in a reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parke, E.; Department of Physics, University of Wisconsin-Madison 1150 University Ave., Madison, Wisconsin 53706; Anderson, J. K.

2016-05-15

Neutral beam injection in reversed-field pinch (RFP) plasmas on the Madison Symmetric Torus [Dexter et al., Fusion Sci. Technol. 19, 131 (1991)] drives current redistribution with increased on-axis current density but negligible net current drive. Internal fluctuations correlated with tearing modes are observed on multiple diagnostics; the behavior of tearing mode correlated structures is consistent with flattening of the safety factor profile. The first application of a parametrized model for island flattening to temperature fluctuations in an RFP allows inferrence of rational surface locations for multiple tearing modes. The m = 1, n = 6 mode is observed to shift inward by 1.1 ± 0.6 cm withmore » neutral beam injection. Tearing mode rational surface measurements provide a strong constraint for equilibrium reconstruction, with an estimated reduction of q{sub 0} by 5% and an increase in on-axis current density of 8% ± 5%. The inferred on-axis current drive is consistent with estimates of fast ion density using TRANSP [Goldston et al., J. Comput. Phys. 43, 61 (1981)].« less

The auroral current circuit and field-aligned currents observed by FAST

NASA Astrophysics Data System (ADS)

Elphic, R. C.; Bonnell, J. W.; Strangeway, R. J.; Kepko, L.; Ergun, R. E.; McFadden, J. P.; Carlson, C. W.; Peria, W.; Cattell, C. A.; Klumpar, D.; Shelley, E.; Peterson, W.; Moebius, E.; Kistler, L.; Pfaff, R.

FAST observes signatures of small-scale downward-going current at the edges of the inverted-V regions where the primary (auroral) electrons are found. In the winter pre-midnight auroral zone these downward currents are carried by upward flowing low- and medium-energy (up to several keV) electron beams. FAST instrumentation shows agreement between the current densities inferred from both the electron distributions and gradients in the magnetic field. FAST data taken near apogee (˜4000-km altitude) commonly show downward current magnetic field deflections consistent with the observed upward flux of ˜109 electrons cm-2 s-1, or current densities of several µA m-2. The electron, field-aligned current and electric field signatures indicate the downward currents may be associated with “black aurora” and auroral ionospheric cavities. The field-aligned voltage-current relationship in the downward current region is nonlinear.

Particle Acceleration in Dissipative Pulsar Magnetospheres

NASA Technical Reports Server (NTRS)

Kazanas, Z.; Kalapotharakos, C.; Harding, A.; Contopoulos, I.

2012-01-01

Pulsar magnetospheres represent unipolar inductor-type electrical circuits at which an EM potential across the polar cap (due to the rotation of their magnetic field) drives currents that run in and out of the polar cap and close at infinity. An estimate ofthe magnitude of this current can be obtained by dividing the potential induced across the polar cap V approx = B(sub O) R(sub O)(Omega R(sub O)/c)(exp 2) by the impedance of free space Z approx eq 4 pi/c; the resulting polar cap current density is close to $n {GJ} c$ where $n_{GJ}$ is the Goldreich-Julian (GJ) charge density. This argument suggests that even at current densities close to the GJ one, pulsar magnetospheres have a significant component of electric field $E_{parallel}$, parallel to the magnetic field, a condition necessary for particle acceleration and the production of radiation. We present the magnetic and electric field structures as well as the currents, charge densities, spin down rates and potential drops along the magnetic field lines of pulsar magnetospheres which do not obey the ideal MHD condition $E cdot B = 0$. By relating the current density along the poloidal field lines to the parallel electric field via a kind of Ohm's law $J = sigma E_{parallel}$ we study the structure of these magnetospheres as a function of the conductivity $sigma$. We find that for $sigma gg OmegaS the solution tends to the (ideal) Force-Free one and to the Vacuum one for $sigma 11 OmegaS. Finally, we present dissipative magnetospheric solutions with spatially variable $sigma$ that supports various microphysical properties and are compatible with the observations.

Complete analytical solution of electromagnetic field problem of high-speed spinning ball

NASA Astrophysics Data System (ADS)

Reichert, T.; Nussbaumer, T.; Kolar, J. W.

2012-11-01

In this article, a small sphere spinning in a rotating magnetic field is analyzed in terms of the resulting magnetic flux density distribution and the current density distribution inside the ball. From these densities, the motor torque and the eddy current losses can be calculated. An analytical model is derived, and its results are compared to a 3D finite element analysis. The model gives insight into the torque and loss characteristics of a solid rotor induction machine setup, which aims at rotating the sphere beyond 25 Mrpm.

Kapton charging characteristics: Effects of material thickness and electron-energy distribution

NASA Technical Reports Server (NTRS)

Williamson, W. S.; Dulgeroff, C. R.; Hymann, J.; Viswanathan, R.

1985-01-01

Charging characteristics of polyimide (Kapton) of varying thicknesses under irradiation by a very-low-curent-density electron beam, with the back surface of the sample grounded are reported. These charging characteristics are in good agreement with a simple analytical model which predicts that in thin samples at low current density, sample surface potential is limited by conduction leakage through the bulk material. The charging of Kapton in a low-current-density electron beam in which the beam energy was modulated to simulate Maxwellian and biMaxwellian distribution functions is measured.

Phase slip process and charge density wave dynamics in a one dimensional conductor

NASA Astrophysics Data System (ADS)

Habiballah, N.; Zouadi, M.; Arbaoui, A.; Qjani, M.; Dumas, J.

In this paper, we study the phase slip effect on the charge density wave (CDW) dynamics in a one-dimensional conductor in the weak pinning limit. A considerable enhancement of JCDW is observed in the presence of phase slips. In addition, a spatial dependence of the CDW current density JCDW is also studied showing that a decrease of JCDW with distance from the current contact occurs. The results are discussed in terms the relationship between additional phase slips and the mobility of phase dislocations nucleated at electrical contacts.

Plasma monitoring of the RLVIP-process with a Langmuir probe

NASA Astrophysics Data System (ADS)

Huber, D.; Hallbauer, A.; Pulker, H. K.

2005-09-01

The aim of this investigation was to study the characteristics of a reactive-low-voltage-high-current-ion-plating plasma and to correlate the observed plasma data with the properties of films deposited under such conditions. A Langmuir probe system (Smart Probe - Scientific Systems) was inserted into a Balzers BAP 800 ion plating plant above the e-gun evaporation source close to the insulated substrate holder. In this position during RLVIP deposition, plasma potential, floating potential, self-bias voltage, electron temperature, ion current density, and particle number density were measured and calculated, respectively. All measurements were performed in dependence of arc current (20-80A) and oxygen partial pressure (1 - 36 x 10-4mbar). With rising arc current the number of charged particles, the self-bias voltage between plasma and substrates as well as the energy of the condensing and bombarding species were increased. These data explain the increase of density, refractive index and mechanical stress of RLVIP-metal-oxide-layers, like Ta2O5 and Nb2O5, deposited with higher arc currents. An increase of gas pressure decreased the energy of the particles and therefore reduced slightly film density and refractive index. However, it improved chemistry and eliminated unwanted residual optical absorption and also decreased compressive mechanical film stress.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes.

PubMed

Kumar, Niraj; Pal, Dharmendra Kumar; Jadon, Arvind Singh; Pal, Udit Narayan; Rahaman, Hasibur; Prakash, Ram

2016-03-01

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Niraj; Pal, Udit Narayan; Prakash, Ram

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electronmore » beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.« less

Dissection of the Voltage Losses of an Acidic Quinone Redox Flow Battery

DOE PAGES

Chen, Qing; Gerhardt, Michael R.; Aziz, Michael J.

2017-03-28

We measure the polarization characteristics of a quinone-bromide redox flow battery with interdigitated flow fields, using electrochemical impedance spectroscopy and voltammetry of a full cell and of a half cell against a reference electrode. We find linear polarization behavior at 50% state of charge all the way to the short-circuit current density of 2.5 A/cm 2. We uniquely identify the polarization area-specific resistance (ASR) of each electrode, the membrane ASR to ionic current, and the electronic contact ASR. We use voltage probes to deduce the electronic current density through each sheet of carbon paper in the quinone-bearing electrode. By alsomore » interpreting the results using the Newman 1-D porous electrode model, we deduce the volumetric exchange current density of the porous electrode. We uniquely evaluate the power dissipation and identify a correspondence to the contributions to the electrode ASR from the faradaic, electronic, and ionic transport processes. We find that, within the electrode, more power is dissipated in the faradaic process than in the electronic and ionic conduction processes combined, despite the observed linear polarization behavior. We examine the sensitivity of the ASR to the values of the model parameters. The greatest performance improvement is anticipated from increasing the volumetric exchange current density.« less

Electric current density imaging of tablet dissolution.

PubMed

Mikac, Ursa; Demsar, Alojz; Sersa, Igor; Demsar, Franci

2002-01-01

The Electric current density imaging technique (CDI) was used to monitor the dissolution of and ion migration from tablets of different acids in agar-agar gel. Conventional MRI cannot monitor these processes, since it can only show changes in the size of the tablet during the dissolving process. CDI traces the dissolved ions thanks to changes in conductivity.

Polarization curve measurements combined with potential probe sensing for determining current density distribution in vanadium redox-flow batteries

NASA Astrophysics Data System (ADS)

Becker, Maik; Bredemeyer, Niels; Tenhumberg, Nils; Turek, Thomas

2016-03-01

Potential probes are applied to vanadium redox-flow batteries for determination of effective felt resistance and current density distribution. During the measurement of polarization curves in 100 cm2 cells with different carbon felt compression rates, alternating potential steps at cell voltages between 0.6 V and 2.0 V are applied. Polarization curves are recorded at different flow rates and states of charge of the battery. Increasing compression rates lead to lower effective felt resistances and a more uniform resistance distribution. Low flow rates at high or low state of charge result in non-linear current density distribution with high gradients, while high flow rates give rise to a nearly linear behavior.

Reconstruction of F-Region Electric Current Densities from more than 2 Years of Swarm Satellite Magnetic data

NASA Astrophysics Data System (ADS)

Tozzi, R.; Pezzopane, M.; De Michelis, P.; Pignalberi, A.; Siciliano, F.

2016-12-01

The constellation geometry adopted by ESA for Swarm satellites has opened the way to new investigations based on magnetic data. An example is the curl-B technique that allows reconstructing F-region electric current density in terms of its radial, meridional, and zonal components based on data from two satellites of Swarm constellation (Swarm A and B) which fly at different altitudes. Here, we apply this technique to more than 2 years of Swarm magnetic vector data and investigate the average large scale behaviour of F-region current densities as a function of local time, season and different interplanetary conditions (different strength and direction of the three IMF components and/or geomagnetic activity levels).

The effects of chemical coagulants on the decolorization of dyes by electrocoagulation using response surface methodology (RSM)

NASA Astrophysics Data System (ADS)

Butler, Erick B.; Hung, Yung-Tse; Mulamba, Oliver

2017-09-01

This study assessed the efficiency of electrocoagulation (ECF) coupled with an addition of chemical coagulant to decolorize textile dye. Tests were conducted using Box Behnken methodology to vary six parameters: dye type, weight, coagulant type, dose, initial pH and current density. The combination of electrocoagulation and chemical coagulation was able to decolorize dye up to 99.42 % in 30 min of treatment time which is remarkably shorter in comparison with using conventional chemical coagulation. High color removal was found to be contingent upon the dye type and current density, along with the interactions between the current density and the coagulant dose. The addition of chemical coagulants did enhanced treatment efficiency.

Transtech PQI 301 pavement quality indicator device evaluation.

DOT National Transportation Integrated Search

2010-10-01

The PQI 301 Asphalt Density device, developed by Transtech Systems, Inc., was evaluated by MDOT to determine if it could be used in lieu of the currently required nuclear density gauge. Nuclear density gauges require MDOT personnel to have a license,...

High energy density electrochemical cell

NASA Technical Reports Server (NTRS)

Byrne, J. J.; Williams, D. L.

1970-01-01

Primary cell has an anode of lithium, a cathode containing dihaloisocyanuric acid, and a nonaqueous electrolyte comprised of a solution of lithium perchlorate in methyl formate. It produces an energy density of 213 watt hrs/lb and can achieve a high current density.

Modelling the effect of electrode displacement on transcranial direct current stimulation (tDCS)

NASA Astrophysics Data System (ADS)

Ramaraju, Sriharsha; Roula, Mohammed A.; McCarthy, Peter W.

2018-02-01

Objective. Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers a low-intensity, direct current to cortical areas with the purpose of modulating underlying brain activity. Recent studies have reported inconsistencies in tDCS outcomes. The underlying assumption of many tDCS studies has been that replication of electrode montage equates to replicating stimulation conditions. It is possible however that anatomical difference between subjects, as well as inherent inaccuracies in montage placement, could affect current flow to targeted areas. The hypothesis that stimulation of a defined brain region will be stable under small displacements was tested. Approach. Initially, we compared the total simulated current flowing through ten specific brain areas for four commonly used tDCS montages: F3-Fp2, C3-Fp2, Fp1-F4, and P3-P4 using the software tool COMETS. The effect of a slight (~1 cm in each of four directions) anode displacement on the simulated regional current density for each of the four tDCS montages was then determined. Current flow was calculated and compared through ten segmented brain areas to determine the effect of montage type and displacement. The regional currents, as well as the localised current densities, were compared with the original electrode location, for each of these new positions. Main results. Recommendations for montages that maximise stimulation current for the ten brain regions are considered. We noted that the extent to which stimulation is affected by electrode displacement varies depending on both area and montage type. The F3-Fp2 montage was found to be the least stable with up to 38% change in average current density in the left frontal lobe while the Fp1-F4 montage was found to the most stable exhibiting only 1% change when electrodes were displaced. Significance. These results indicate that even relatively small changes in stimulation electrode placement appear to result in surprisingly large changes in current densities and distribution.

Al embedded MgO barrier MTJ: A first principle study for application in fast and compact STT-MRAMs

NASA Astrophysics Data System (ADS)

Yadav, Manoj Kumar; Gupta, Santosh Kumar; Rai, Sanjeev; Pandey, Avinash C.

2017-03-01

The first principle comparative study of a novel single Al sheet embedded MgO and pure MgO barrier having Fe electrodes magnetic tunnel junction has been presented. Al embedded MgO is reported to provide enhanced spin polarised tunnelling current due to increase of spin-polarized density of states at Fermi energy in the barrier region. This novel MTJ provides a current density and resistance area (RA) product of 94.497 ×107 A / cm2 and 0.105  Ω - μm2 respectively. With such a low RA product; it allows higher deriving current due to which switching time of magnetization reversal reduces without inducing barrier related breakdowns in non-volatile magnetic random access memories. The low RA product and high current density of the proposed MTJ may have possible applications in integration with existing MOS circuits.

Microstructural and crystallographic imperfections of MgB2 superconducting wire and their correlation with the critical current density

NASA Astrophysics Data System (ADS)

Shahabuddin, Mohammed; Alzayed, Nasser S.; Oh, Sangjun; Choi, Seyong; Maeda, Minoru; Hata, Satoshi; Shimada, Yusuke; Hossain, Md Shahriar Al; Kim, Jung Ho

2014-01-01

A comprehensive study of the effects of structural imperfections in MgB2 superconducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB2 material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the π and σ bands of MgB2, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB2, however, even at low sintering temperature, and thus block current transport paths.

Violation of the continuity equation in the Krieger-Li-Iafrate approximation for current-density functional theory

NASA Astrophysics Data System (ADS)

Siegmund, Marc; Pankratov, Oleg

2011-01-01

We show that the exchange-correlation scalar and vector potentials obtained from the optimized effective potential (OEP) equations and from the Krieger-Li-Iafrate (KLI) approximation for the current-density functional theory (CDFT) change under a gauge transformation such that the energy functional remains invariant. This alone does not assure, however, the theory’s compliance with the continuity equation. Using the model of a quantum ring with a broken angular symmetry which is penetrated by a magnetic flux we demonstrate that the physical current density calculated with the exact-exchange CDFT in the KLI approximation violates the continuity condition. In contrast, the current found from a solution of the full OEP equations satisfies this condition. We argue that the continuity violation stems from the fact that the KLI potentials are not (in general) the exact functional derivatives of a gauge-invariant exchange-correlation functional.

In-depth porosity control of mesoporous silicon layers by an anodization current adjustment

NASA Astrophysics Data System (ADS)

Lascaud, J.; Defforge, T.; Certon, D.; Valente, D.; Gautier, G.

2017-12-01

The formation of thick mesoporous silicon layers in P+-type substrates leads to an increase in the porosity from the surface to the interface with silicon. The adjustment of the current density during the electrochemical etching of porous silicon is an intuitive way to control the layer in-depth porosity. The duration and the current density during the anodization were varied to empirically model porosity variations with layer thickness and build a database. Current density profiles were extracted from the model in order to etch layer with in-depth control porosity. As a proof of principle, an 80 μm-thick porous silicon multilayer was synthetized with decreasing porosities from 55% to 35%. The results show that the assessment of the in-depth porosity could be significantly enhanced by taking into account the pure chemical etching of the layer in the hydrofluoric acid-based electrolyte.

Low frequency noise in p-InAsSbP/n-InAs infrared photodiodes

NASA Astrophysics Data System (ADS)

Dyakonova, N.; Karandashev, S. A.; Levinshtein, M. E.; Matveev, B. A.; Remennyi, M. A.

2018-06-01

We report the first experimental study of low-frequency noise in p-InAsSbP/n-InAs infrared photodiodes. For forward bias, experiments have been carried out at 300 and 77 K, in the photovoltaic regime the measurements have been done at 300 K. At room temperature the current noise spectral density, SI , exhibits the ∼1/f frequency dependence. For low currents, I ≤ I 0 ∼ 4 × 10‑5 A, S I is proportional to I 2, at higher currents this dependence changes to S I ∼ I. At 77 K the noise spectral density is significantly higher than at 300 K, and Lorentzian contributions to noise are observed. The current dependences of spectral noise density can be approximately described as S I ∼ I 1.5 and show particularities suggesting the contribution of defects.

Field effect transistors based on phosphorene nanoribbon with selective edge-adsorption: A first-principles study

NASA Astrophysics Data System (ADS)

Hu, Mengli; Yang, Zhixiong; Zhou, Wenzhe; Li, Aolin; Pan, Jiangling; Ouyang, Fangping

2018-04-01

By using density functional theory (DFT) and nonequilibrium Green's function (NEGF), field effect transistor (FET) based on zigzag shaped phosphorene nanoribbons (ZPNR) are investigated. The FETs are constructed with bare-edged ZPNRs as electrodes and H, Cl or OH adsorbed ZPNRs as channel. It is found FETs with the three kinds of channel show similar transport properties. The FET is p-type with a maximum current on/off ratio of 104 and a minimum off-current of 1 nA. The working mode of FETs is dependent on the parity of channel length. It can be either enhancement mode or depletion mode and the off-state current shows an even-odd oscillation. The current oscillations are interpreted with density of states (DOS) analysis and methods of evolution operator and tight-binding Hamiltonian. Operating mechanism of the designed FETs is also presented with projected local density of states and band diagrams.

Plasmaspheric Erosion via Plasmasphere Coupling to Ring Current Plasmas: EUV Observations and Modeling

NASA Technical Reports Server (NTRS)

Adrian, M. L.; Gallagher, D. L.; Khazanov, G. V.; Chsang, S. W.; Liemohn, M. W.; Perez, J. D.; Green, J. L.; Sandel, B. R.; Mitchell, D. G.; Mende, S. B.;

The plasma environment, charge state, and currents of Saturn's C and D rings

NASA Technical Reports Server (NTRS)

Wilson, G. R.

1991-01-01

The charge state and associated currents of Saturn's C an D rings are studied by modeling the flow of ionospheric plasma from the mid- to low-latitude ionosphere to the vicinity of the rings. It is found that the plasma density near the C and D rings, at a given radial location, will experience a one to two order of magnitude diurnal variation. The surface charge density (SCD) of these rings can show significant radial and azimuthal variations due mainly to variation in the plasma density. The SCD also depends on structural features of the rings such as thickness and the nature of the particle size distribution. The associated azimuthal currents carried by these rings also show large diurnal variations resulting in field-aligned currents which close in the ionosphere. The resulting ionospheric electric field will probably not produce a significant amount of plasma convection in the topside ionosphere and inner plasmasphere.

431 kA/cm2 peak tunneling current density in GaN/AlN resonant tunneling diodes

NASA Astrophysics Data System (ADS)

Growden, Tyler A.; Zhang, Weidong; Brown, Elliott R.; Storm, David F.; Hansen, Katurah; Fakhimi, Parastou; Meyer, David J.; Berger, Paul R.

2018-01-01

We report on the design and fabrication of high current density GaN/AlN double barrier resonant tunneling diodes grown via plasma assisted molecular-beam epitaxy on bulk GaN substrates. A quantum-transport solver was used to model and optimize designs with high levels of doping and ultra-thin AlN barriers. The devices displayed repeatable room temperature negative differential resistance with peak-to-valley current ratios ranging from 1.20 to 1.60. A maximum peak tunneling current density (Jp) of 431 kA/cm2 was observed. Cross-gap near-UV (370-385 nm) electroluminescence (EL) was observed above +6 V when holes, generated from a polarization induced Zener tunneling effect, recombine with electrons in the emitter region. Analysis of temperature dependent measurements, thermal resistance, and the measured EL spectra revealed the presence of severe self-heating effects.

Response of the Equatorial Ionosphere to the Geomagnetic DP 2 Current System

NASA Technical Reports Server (NTRS)

Yizengaw, E.; Moldwin, M. B.; Zesta, E.; Magoun, M.; Pradipta, R.; Biouele, C. M.; Rabiu, A. B.; Obrou, O. K.; Bamba, Z.; Paula, E. R. De

2016-01-01

The response of equatorial ionosphere to the magnetospheric origin DP 2 current system fluctuations is examined using ground-based multiinstrument observations. The interaction between the solar wind and fluctuations of the interplanetary magnetic field (IMF) Bz, penetrates nearly instantaneously to the dayside equatorial region at all longitudes and modulates the electrodynamics that governs the equatorial density distributions. In this paper, using magnetometers at high and equatorial latitudes, we demonstrate that the quasiperiodic DP 2 current system penetrates to the equator and causes the dayside equatorial electrojet (EEJ) and the independently measured ionospheric drift velocity to fluctuate coherently with the high-latitude DP 2 current as well as with the IMF Bz component. At the same time, radar observations show that the ionospheric density layers move up and down, causing the density to fluctuate up and down coherently with the EEJ and IMF Bz.

Increasing the Life of a Xenon-Ion Spacecraft Thruster

NASA Technical Reports Server (NTRS)

Goebel, Dan; Polk, James; Sengupta, Anita; Wirz, Richard

2007-01-01

A short document summarizes the redesign of a xenon-ion spacecraft thruster to increase its operational lifetime beyond a limit heretofore imposed by nonuniform ion-impact erosion of an accelerator electrode grid. A peak in the ion current density on the centerline of the thruster causes increased erosion in the center of the grid. The ion-current density in the NSTAR thruster that was the subject of this investigation was characterized by peak-to-average ratio of 2:1 and a peak-to-edge ratio of greater than 10:1. The redesign was directed toward distributing the same beam current more evenly over the entire grid andinvolved several modifications of the magnetic- field topography in the thruster to obtain more nearly uniform ionization. The net result of the redesign was to reduce the peak ion current density by nearly a factor of two, thereby halving the peak erosion rate and doubling the life of the thruster.

Particle-bearing currents in uniform density and two-layer fluids

NASA Astrophysics Data System (ADS)

Sutherland, Bruce R.; Gingras, Murray K.; Knudson, Calla; Steverango, Luke; Surma, Christopher

2018-02-01

Lock-release gravity current experiments are performed to examine the evolution of a particle bearing flow that propagates either in a uniform-density fluid or in a two-layer fluid. In all cases, the current is composed of fresh water plus micrometer-scale particles, the ambient fluid is saline, and the current advances initially either over the surface as a hypopycnal current or at the interface of the two-layer fluid as a mesopycnal current. In most cases the tank is tilted so that the ambient fluid becomes deeper with distance from the lock. For hypopycnal currents advancing in a uniform density fluid, the current typically slows as particles rain out of the current. While the loss of particles alone from the current should increase the current's buoyancy and speed, in practice the current's speed decreases because the particles carry with them interstitial fluid from the current. Meanwhile, rather than settling on the sloping bottom of the tank, the particles form a hyperpycnal (turbidity) current that advances until enough particles rain out that the relatively less dense interstitial fluid returns to the surface, carrying some particles back upward. When a hypopycnal current runs over the surface of a two-layer fluid, the particles that rain out temporarily halt their descent as they reach the interface, eventually passing through it and again forming a hyperpycnal current. Dramatically, a mesopycnal current in a two-layer fluid first advances along the interface and then reverses direction as particles rain out below and fresh interstitial fluid rises above.

Simulation of Space Charge Dynamic in Polyethylene Under DC Continuous Electrical Stress

NASA Astrophysics Data System (ADS)

Boukhari, Hamed; Rogti, Fatiha

2016-10-01

The space charge dynamic plays a very important role in the aging and breakdown of polymeric insulation materials under high voltage. This is due to the intensification of the local electric field and the attendant chemical-mechanical effects in the vicinity around the trapped charge. In this paper, we have investigated the space charge dynamic in low-density polyethylene under high direct-current voltage, which is evaluated by experimental conditions. The evaluation is on the basis of simulation using a bipolar charge transport model consisting of charge injection, transports, trapping, detrapping, and recombination phenomena. The theoretical formulation of the physical problem is based on the Poisson, the continuity, and the transport equations. Numerical results provide temporal and local distributions of the electric field, the space charge density for the different kinds of charges (net charge density, mobile and trapped of electron density, mobile hole density), conduction and displacement current densities, and the external current. The result shows the appearance of the negative packet-like space charge with a large amount of the bulk under the dc electric field of 100 kV/mm, and the induced distortion of the electric field is largely near to the anode, about 39% higher than the initial electric field applied.

Alfven resonance mode conversion in the Phaedrus-T current drive experiments: Modelling and density fluctuations measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vukovic, M.; Harper, M.; Breun, R.

1995-12-31

Current drive experiments on the Phaedrus-T tokamak performed with a low field side two-strap fast wave antenna at frequencies below {omega}{sub cH} show loop volt drops of up to 30% with strap phasing (0, {pi}/2). RF induced density fluctuations in the plasma core have also been observed with a microwave reflectometer. It is believed that they are caused by kinetic Alfven waves generated by mode conversion of fast waves at the Alfven resonance. Correlation of the observed density fluctuations with the magnitude of the {Delta}V{sub loop} suggest that the {Delta}V{sub loop} is attributable to current drive/heating due to mode convertedmore » kinetic Alfven waves. The toroidal cold plasma wave code LION is used to model the Alfven resonance mode conversion surfaces in the experiments while the cylindrical hot plasma kinetic wave code ISMENE is used to model the behavior of kinetic Alfven waves at the Alfven resonance location. Initial results obtained from limited density, magnetic field, antenna phase, and impurity scans show good agreement between the RF induced density fluctuations and the predicted behavior of the kinetic Alfven waves. Detailed comparisons between the density fluctuations and the code predictions are presented.« less

Heating of the solar middle chromosphere by large-scale electric currents

NASA Technical Reports Server (NTRS)

Goodman, M. L.

1995-01-01

A global resistive, two-dimensional, time-dependent magnetohydrodynamic (MHD) model is used to introduce and support the hypothesis that the quiet solar middle chromosphere is heated by resistive dissipation of large-scale electric currents which fill most of its volume. The scale height and maximum magnitude of the current density are 400 km and 31.3 m/sq m, respectively. The associated magnetic field is almost horizontal, has the same scale height as the current density, and has a maximum magnitude of 153 G. The current is carried by electrons flowing across magnetic field lines at 1 m/s. The resistivity is the electron contribution to the Pedersen resitivity for a weakly ionized, strongly magnetized, hydrogen gas. The model does not include a driving mechanism. Most of the physical quantities in the model decrease exponentially with time on a resistive timescale of 41.3 minutes. However, the initial values and spatial; dependence of these quantities are expected to be essentially the same as they would be if the correct driving mechanism were included in a more general model. The heating rate per unit mass is found to be 4.5 x 10(exp 9) ergs/g/s, independent of height and latitude. The electron density scale height is found to be 800 km. The model predicts that 90% of the thermal energy required to heat the middle chromosphere is deposited in the height range 300-760 km above the temperature minimum. It is shown to be consistent to assume that the radiation rate per unit volume is proportional to the magnetic energy density, and then it follows that the heating rate per unit volume is also proportional to the energy from the photosphere into the overlying chromosphere are briefly discussed as possible driving mechanisms for establishing and maintaining the current system. The case in which part of or all of the current is carried by protons and metal ions, and the contribution of electron-proton scattering to the current are also considered, with the conclusion that these effects do not change the qualitative prediction of the model, but probably change the quantitative predictions slightly, mainly by increasing the maximum magntiude of the current density and magnetic field to at most approximately 100 mA/m and approximately 484 G, respectively. The heating rate per unit mass, current density scale height, magnetic field scale height, temperatures, and pressures are unchanged or are only slightly changed by including these additional effects due to protons and ions.

Generalization of the lightning electromagnetic equations of Uman, McLain, and Krider based on Jefimenko equations

DOE PAGES

Shao, Xuan-Min

2016-04-12

The fundamental electromagnetic equations used by lightning researchers were introduced in a seminal paper by Uman, McLain, and Krider in 1975. However, these equations were derived for an infinitely thin, one-dimensional source current, and not for a general three-dimensional current distribution. In this paper, we introduce a corresponding pair of generalized equations that are determined from a three-dimensional, time-dependent current density distribution based on Jefimenko's original electric and magnetic equations. To do this, we derive the Jefimenko electric field equation into a new form that depends only on the time-dependent current density similar to that of Uman, McLain, and Krider,more » rather than on both the charge and current densities in its original form. The original Jefimenko magnetic field equation depends only on current, so no further derivation is needed. We show that the equations of Uman, McLain, and Krider can be readily obtained from the generalized equations if a one-dimensional source current is considered. For the purpose of practical applications, we discuss computational implementation of the new equations and present electric field calculations for a three-dimensional, conical-shape discharge.« less

Numerical analysis of wet separation of particles by density differences

NASA Astrophysics Data System (ADS)

Markauskas, D.; Kruggel-Emden, H.

2017-07-01

Wet particle separation is widely used in mineral processing and plastic recycling to separate mixtures of particulate materials into further usable fractions due to density differences. This work presents efforts aiming to numerically analyze the wet separation of particles with different densities. In the current study the discrete element method (DEM) is used for the solid phase while the smoothed particle hydrodynamics (SPH) is used for modeling of the liquid phase. The two phases are coupled by the use of a volume averaging technique. In the current study, simulations of spherical particle separation were performed. In these simulations, a set of generated particles with two different densities is dropped into a rectangular container filled with liquid. The results of simulations with two different mixtures of particles demonstrated how separation depends on the densities of particles.

Measurements of copper ground-state and metastable level population densities in a copper-chloride laser

NASA Technical Reports Server (NTRS)

Nerheim, N. M.

1977-01-01

The population densities of both the ground and the 2D(5/2) metastable states of copper atoms in a double-pulsed copper-chloride laser are correlated with laser energy as a function of time after the dissociation current pulse. Time-resolved density variations of the ground and excited copper atoms were derived from measurements of optical absorption at 324.7 and 510.6 nm, respectively, over a wide range of operating conditions in laser tubes with diameters of 4 to 40 mm. The minimum delay between the two current pulses at which lasing was observed is shown to be a function of the initial density and subsequent decay of the metastable state. Similarly, the maximum delay is shown to be a function of the initial density and decay of the ground state.

Electrical and Mechanical Performance of Carbon Fiber-Reinforced Polymer Used as the Impressed Current Anode Material.

PubMed

Zhu, Ji-Hua; Zhu, Miaochang; Han, Ningxu; Liu, Wei; Xing, Feng

2014-07-24

An investigation was performed by using carbon fiber-reinforced polymer (CFRP) as the anode material in the impressed current cathodic protection (ICCP) system of steel reinforced concrete structures. The service life and performance of CFRP were investigated in simulated ICCP systems with various configurations. Constant current densities were maintained during the tests. No significant degradation in electrical and mechanical properties was found for CFRP subjected to anodic polarization with the selected applied current densities. The service life of the CFRP-based ICCP system was discussed based on the practical reinforced concrete structure layout.

Electric current in a unipolar sunspot with an untwisted field

NASA Technical Reports Server (NTRS)

Osherovich, V. A.; Garcia, H. A.

1990-01-01

The return flux (RF) sunspot model is applied to a round, unipolar sunspot observed by H. Kawakami (1983). Solving the magnetohydrostatic problem using the gas pressure deficit between the umbral and quiet-sun atmospheres as a source function, a distribution of electric current density in an untwisted, unipolar sunspot as a function of height and radial distance from the sunspot center is observed. Maximum electric current density is about 32 mA/sq m at the bottom of the sunspot.

Estimating historical snag density in dry forests east of the Cascade Range

Treesearch

Richy J. Harrod; William L. Gaines; William E. Hartl; Ann. Camp

1998-01-01

Estimating snag densities in pre-European settlement landscapes (i.e., historical conditions) provides land managers with baseline information for comparing current snag densities. We propose a method for determining historical snag densities in the dry forests east of the Cascade Range. Basal area increase was calculated from tree ring measurements of old ponderosa...

The Rocket Investigation of Current Closure in the Ionosphere (RICCI) mission: A novel application of CubeSats from a sounding rocket platform

NASA Astrophysics Data System (ADS)

Cohen, I. J.; Anderson, B. J.; Lessard, M.; Bonnell, J. W.; Bounds, S. R.; Lysak, R. L.; Erlandson, R. E.

2017-12-01

The transfer of energy and momentum between the terrestrial magnetosphere and ionosphere is substantially mediated by large-scale field-aligned currents (FACs), driven by magnetopause dynamics and magnetospheric pressures and closing through the ionosphere where the dissipation and drag are governed. While significant insight into ionospheric electrodynamics and the nature of magnetosphere-ionosphere (M-I) coupling have been gained by rocket and satellite measurements, in situ measurement of these ionospheric closure currents remains challenging. To date the best estimates of ionospheric current densities are inferred from ground-based radar observations combining electric fields calculated from drifts with conductivities derived from densities. RICCI aims to observe the structure of the ionospheric currents in situ to determine how the altitude structure of these currents is related to precipitation and density cavities, electromagnetic dynamics, and governs energy dissipation in the ionosphere. In situ measurement of the current density using multi-point measurements of the magnetic field requires precise attitude knowledge for which the only demonstrated technique is the use of star camera systems. The low vehicle rotation rates required for miniature commercial off-the-shelf (COTS) star cameras prohibit the use of available rocket sub-payload technologies at Wallops Flight Facility (WFF) which use high rates of spin to stabilize attitude. However, CubeSat attitude systems are already designed to achieve low vehicle rotation rates, so RICCI will use a set of three CubeSat sub-payloads deployed from a main low altitude payload with apogee of 160 km to provide precise current density measurement through the ionospheric closure altitude regime, together with a second rocket with apogee near 320 km to measure the incident input energy flux and convection electric field. The two rocket payloads and CubeSate sub-payloads are all instrumented with star cameras and science-grade magnetometers. We discuss the mission design, payload complement, and science closure of this sub-orbital mission to obtain the first direct measurement of ionospheric currents associated with an auroral arc.