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Sample records for ad libitum hf

  1. Soda consumption during ad libitum food intake predicts weight change.

    PubMed

    Bundrick, Sarah C; Thearle, Marie S; Venti, Colleen A; Krakoff, Jonathan; Votruba, Susanne B

    2014-03-01

    Soda consumption may contribute to weight gain over time. Objective data were used to determine whether soda consumption predicts weight gain or changes in glucose regulation over time. Subjects without diabetes (128 men, 75 women; mean age 34.3±8.9 years; mean body mass index 32.5±7.4; mean percentage body fat 31.6%±8.6%) self-selected their food from an ad libitum vending machine system for 3 days. Mean daily energy intake was calculated from food weight. Energy consumed from soda was recorded as were food choices that were low in fat (<20% of calories from fat) or high in simple sugars (>30%). Food choices were expressed as percentage of daily energy intake. A subset of 85 subjects had measurement of follow-up weights and oral glucose tolerance (57 men, 28 women; mean follow-up time=2.5±2.1 years, range 6 months to 9.9 years). Energy consumed from soda was negatively related to age (r=-0.27, P=0.0001) and choosing low-fat foods (r=-0.35, P<0.0001), but positively associated with choosing solid foods high in simple sugars (r=0.45, P<0.0001) and overall average daily energy intake (r=0.46, P<0.0001). Energy intake from food alone did not differ between individuals who did and did not consume beverage calories (P=0.11). Total daily energy intake had no relationship with change in weight (P=0.29) or change in glucose regulation (P=0.38) over time. However, energy consumed from soda correlated with change in weight (r=0.21, P=0.04). This relationship was unchanged after adjusting for follow-up time and initial weight. Soda consumption is a marker for excess energy consumption and is associated with weight gain.

  2. Oral fluid cannabinoids in chronic frequent cannabis smokers during ad libitum cannabis smoking.

    PubMed

    Lee, Dayong; Vandrey, Ryan; Mendu, Damodara R; Murray, Jeannie A; Barnes, Allan J; Huestis, Marilyn A

    2015-06-01

    Oral fluid (OF) offers a simple, non-invasive, directly observable sample collection for clinical and forensic drug testing. Given that chronic cannabis smokers often engage in drug administration multiple times daily, evaluating OF cannabinoid pharmacokinetics during ad libitum smoking is important for practical development of analytical methods and informed interpretation of test results. Eleven cannabis smokers resided in a closed research unit for 51 days, and underwent four, 5-day oral delta-9-tetrahydrocannabinol (THC) treatments. Each medication period was separated by 9 days of ad libitum cannabis smoking from 12:00 to 23:00 h daily. Ten OF samples were collected from 9:00-22:00 h on each of the last ad libitum smoking days (Study Days 4, 18, 32, and 46). As the number of cannabis cigarettes smoked increased over the study days, OF THC, cannabinol (CBN), and 11-nor-9-carboxy-THC (THCCOOH) also increased with a significant effect of time since last smoking (Δtime; range, 0.0-17.4 h) and ≥88% detection rates; concentrations on Day 4 were significantly lower than those on Days 32 and 46 but not Day 18. Within 30 min of smoking, median THC, CBN, and THCCOOH concentrations were 689 µg/L, 116 µg/L, and 147 ng/L, respectively, decreasing to 19.4 µg/L, 2.4 µg/L, and 87.6 ng/L after 10 h. Cannabidiol and 11-hydroxy-THC showed overall lower detection rates of 29 and 8.6%, respectively. Cannabinoid disposition in OF was highly influenced by Δtime and composition of smoked cannabis. Furthermore, cannabinoid OF concentrations increased over ad libitum smoking days, in parallel with increased cannabis self-administration, possibly reflecting development of increased cannabis tolerance. PMID:25220020

  3. Oral fluid cannabinoids in chronic frequent cannabis smokers during ad libitum cannabis smoking.

    PubMed

    Lee, Dayong; Vandrey, Ryan; Mendu, Damodara R; Murray, Jeannie A; Barnes, Allan J; Huestis, Marilyn A

    2015-06-01

    Oral fluid (OF) offers a simple, non-invasive, directly observable sample collection for clinical and forensic drug testing. Given that chronic cannabis smokers often engage in drug administration multiple times daily, evaluating OF cannabinoid pharmacokinetics during ad libitum smoking is important for practical development of analytical methods and informed interpretation of test results. Eleven cannabis smokers resided in a closed research unit for 51 days, and underwent four, 5-day oral delta-9-tetrahydrocannabinol (THC) treatments. Each medication period was separated by 9 days of ad libitum cannabis smoking from 12:00 to 23:00 h daily. Ten OF samples were collected from 9:00-22:00 h on each of the last ad libitum smoking days (Study Days 4, 18, 32, and 46). As the number of cannabis cigarettes smoked increased over the study days, OF THC, cannabinol (CBN), and 11-nor-9-carboxy-THC (THCCOOH) also increased with a significant effect of time since last smoking (Δtime; range, 0.0-17.4 h) and ≥88% detection rates; concentrations on Day 4 were significantly lower than those on Days 32 and 46 but not Day 18. Within 30 min of smoking, median THC, CBN, and THCCOOH concentrations were 689 µg/L, 116 µg/L, and 147 ng/L, respectively, decreasing to 19.4 µg/L, 2.4 µg/L, and 87.6 ng/L after 10 h. Cannabidiol and 11-hydroxy-THC showed overall lower detection rates of 29 and 8.6%, respectively. Cannabinoid disposition in OF was highly influenced by Δtime and composition of smoked cannabis. Furthermore, cannabinoid OF concentrations increased over ad libitum smoking days, in parallel with increased cannabis self-administration, possibly reflecting development of increased cannabis tolerance.

  4. Brisk walking reduces ad libitum snacking in regular chocolate eaters during a workplace simulation.

    PubMed

    Oh, Hwajung; Taylor, Adrian H

    2012-02-01

    Workplace snacking can contribute to obesity. Exercise reduces chocolate cravings but effects on chocolate consumption are unknown. This study investigated the effect of brief exercise on ad libitum consumption during breaks in a computerised task. Seventy-eight regular chocolate eaters, age: 24.90±8.15 years, BMI: 23.56±3.78 kg/m(2) abstained for 2 days. They were randomly assigned to one of four conditions, in a 2 × 2 factorial design, involving either a 15 min brisk walk or quiet rest, and then computerised Stroop tasks with low or high demanding conditions, in three 180 s blocks with a 90 s interval. Throughout, a pre-weighed bowl of chocolates was available for ad libitum eating. A two-way ANOVA revealed no interaction effect of exercise and stress on total chocolate consumption, or main effect of stress, but a main effect of exercise [F(1, 74)=7.12, p<.01]. Mean (SD) chocolate consumption was less (t(73.5)=2.69, 95% CI for difference 3.4-22.9, ES=0.61) for the exercise (15.6 g) than control (28.8 g) group. Exercise also increased affective activation, but there was no mediating effect of change in affect on chocolate consumption. A brief walk may help to reduce ad libitum snacking in regular chocolate eaters. PMID:22100187

  5. Walking reduces cue-elicited cigarette cravings and withdrawal symptoms, and delays ad libitum smoking.

    PubMed

    Taylor, Adrian; Katomeri, Magdalena

    2007-11-01

    Stress and exposure to smoking cues influence smoking cravings and behavior. Exercise appears to reduce cigarette cravings and withdrawal symptoms, but no study has investigated the effects of exercise on cue-elicited cravings and withdrawal symptoms, or ad libitum smoking behavior. In this study, 60 regular smokers, invited by public advertisements, were assessed at baseline following 2 hr of abstinence, and randomized to a 15-min brisk walk or passive condition. Both groups then completed three tasks (Stroop color-word interference task, speech task, and handling a lit cigarette). Cravings were assessed with two single items, and withdrawal symptoms were assessed using the seven-item Mood and Physical Symptoms Scale. After the laboratory session, ad libitum smoking was determined from the subject's cell phone text message. Exercise (mean heart rate reserve = 24%) attenuated increases in strength of desire to smoke, tension, poor concentration, and stress, in response to a lit cigarette, but had minimal effects on increases in cravings and withdrawal symptoms in response to the stressors. Absolute levels of cravings and withdrawal symptoms were reduced during and following exercise. Exercisers engaged in ad libitum smoking a net 57 min (CI = 31-83) later than those in the passive condition. A 15-min brisk walk not only reduced cigarette cravings and withdrawal symptoms but also could attenuate increases in cue-elicited cravings and withdrawal symptoms, and increase the time between cigarettes smoked.

  6. Caloric beverages consumed freely at meal-time add calories to an ad libitum meal.

    PubMed

    Panahi, Shirin; El Khoury, Dalia; Luhovyy, Bohdan L; Goff, H Douglas; Anderson, G Harvey

    2013-06-01

    The objective was to compare the effects of ad libitum consumption of commonly consumed meal-time beverages on energy and fluid intakes and post-meal average subjective appetite and blood glucose in healthy adults. In a randomized controlled design, 29 males and females consumed to satiation an ad libitum pizza meal with one of five beverages in unlimited amount including water (0 kcal), 1% milk (44 kcal/100 ml), regular cola (44 kcal/100 ml), orange juice (44 kcal/100 ml) and diet cola (0 kcal). Food and fluid intakes were measured at the meal. Average subjective appetite and blood glucose were measured before and for 2h after the meal. Although energy intake from pizza was similar among all beverage treatments, the amount of fluid consumed (g) varied among the beverages with intake of orange juice higher than regular and diet cola, but not different from water or milk. Meal-time ingestion of caloric beverages, milk, orange juice and regular cola, led to higher total meal-time energy intakes compared to either water or diet cola. Post-meal blood glucose area under the curve (AUC) was lower after milk than after meals with water, orange juice and regular cola and post-meal average subjective appetite AUC was lower after milk than after meals with water. Meal intakes of nutrients including protein, calcium, phosphorus, zinc, vitamins B12, A and D were higher at the meal with milk compared to the other beverages. Thus, caloric beverages consumed ad libitum during a meal add to total meal-time energy intake, but 1% milk favors a lower post-meal blood glucose and average subjective appetite score and adds to nutrient intake.

  7. Effect of exercise on cigarette cravings and ad libitum smoking following concurrent stressors.

    PubMed

    Fong, Angela J; De Jesus, Stefanie; Bray, Steven R; Prapavessis, Harry

    2014-10-01

    The health consequences of smoking are well documented, yet quit rates are modest. While exercise has supported decreased cravings and withdrawal symptoms in temporarily abstinent smokers, it has yet to be applied when smokers are experiencing concurrent stressors. This study examined the effect of an acute bout of moderate intensity exercise on cravings (primary outcome) and ad libitum smoking (secondary outcome) following concurrent stressors (i.e., temporary abstinence and environmental manipulation-Stroop cognitive task+cue-elicited smoking stimuli). Twenty-five smokers (>10cig/day; Mean age=37.4years) were randomized into either exercise (n=12) or passive sitting conditions. A repeated measure (RM) ANOVA showed that psychological withdrawal symptoms (a measure of distress) were significantly exacerbated after temporary abstinence and then again after the environmental manipulation for all participants (p<.0001, η(2)=.50). Furthermore, a treatment by time RM ANOVA revealed decreases in psychological withdrawal symptoms for only the exercise condition (p<.001, η(2)=.42). A treatment by time RM ANOVA also revealed craving reductions for only the exercise condition (p<.0001, η(2)=.82). Exercise had no effect on ad libitum smoking. This is the first study to use a lab-based scenario with high ecological validity to show that an acute bout of exercise can reduce cravings following concurrent stressors. Future work is now needed where momentary assessment is used in people's natural environment to examine changes in cigarette cravings following acute bouts of exercise. PMID:24971700

  8. Effect of exercise on cigarette cravings and ad libitum smoking following concurrent stressors.

    PubMed

    Fong, Angela J; De Jesus, Stefanie; Bray, Steven R; Prapavessis, Harry

    2014-10-01

    The health consequences of smoking are well documented, yet quit rates are modest. While exercise has supported decreased cravings and withdrawal symptoms in temporarily abstinent smokers, it has yet to be applied when smokers are experiencing concurrent stressors. This study examined the effect of an acute bout of moderate intensity exercise on cravings (primary outcome) and ad libitum smoking (secondary outcome) following concurrent stressors (i.e., temporary abstinence and environmental manipulation-Stroop cognitive task+cue-elicited smoking stimuli). Twenty-five smokers (>10cig/day; Mean age=37.4years) were randomized into either exercise (n=12) or passive sitting conditions. A repeated measure (RM) ANOVA showed that psychological withdrawal symptoms (a measure of distress) were significantly exacerbated after temporary abstinence and then again after the environmental manipulation for all participants (p<.0001, η(2)=.50). Furthermore, a treatment by time RM ANOVA revealed decreases in psychological withdrawal symptoms for only the exercise condition (p<.001, η(2)=.42). A treatment by time RM ANOVA also revealed craving reductions for only the exercise condition (p<.0001, η(2)=.82). Exercise had no effect on ad libitum smoking. This is the first study to use a lab-based scenario with high ecological validity to show that an acute bout of exercise can reduce cravings following concurrent stressors. Future work is now needed where momentary assessment is used in people's natural environment to examine changes in cigarette cravings following acute bouts of exercise.

  9. Plasma Cannabinoid Pharmacokinetics After Controlled Smoking and Ad libitum Cannabis Smoking in Chronic Frequent Users.

    PubMed

    Lee, Dayong; Bergamaschi, Mateus M; Milman, Garry; Barnes, Allan J; Queiroz, Regina H C; Vandrey, Ryan; Huestis, Marilyn A

    2015-10-01

    More Americans are dependent on cannabis than any other illicit drug. The main analytes for cannabis testing include the primary psychoactive constituent, Δ(9)-tetrahydrocannabinol (THC), equipotent 11-hydroxy-THC (11-OH-THC) and inactive 11-nor-9-carboxy-THC (THCCOOH). Eleven adult chronic frequent cannabis smokers resided on a closed research unit with unlimited access to 5.9% THC cannabis cigarettes from 12:00 to 23:00 during two ad libitum smoking phases, followed by a 5-day abstinence period in seven participants. A single cigarette was smoked under controlled topography on the last day of the smoking and abstinence phases. Plasma cannabinoids were quantified by two-dimensional gas chromatography-mass spectrometry. Median plasma maximum concentrations (Cmax) were 28.3 (THC), 3.9 (11-OH-THC) and 47.0 μg/L (THCCOOH) 0.5 h after controlled single cannabis smoking. Median Cmax 0.2-0.5 h after ad libitum smoking was higher for all analytes: 83.5 (THC), 14.2 (11-OH-THC) and 155 μg/L (THCCOOH). All 11 participants' plasma samples were THC and THCCOOH-positive, 58.3% had THC ≥5 μg/L and 79.2% were 11-OH-THC-positive 8.1-14 h after last cannabis smoking. Cannabinoid detection rates in seven participants 106-112 h (4-5 days) after last smoking were 92.9 (THC), 35.7 (11-OH-THC) and 100% (THCCOOH), with limits of quantification of 0.5 μg/L for THC and THCCOOH, and 1.0 μg/L for 11-OH-THC. These data greatly expand prior research findings on cannabinoid excretion profiles in chronic frequent cannabis smokers during ad libitum smoking. Smoking multiple cannabis cigarettes led to higher Cmax and AUC compared with smoking a single cigarette. The chronic frequent cannabis smokers exhibited extended detection windows for plasma cannabinoids, reflecting a large cannabinoid body burden. PMID:26378131

  10. Plasma Cannabinoid Pharmacokinetics After Controlled Smoking and Ad libitum Cannabis Smoking in Chronic Frequent Users

    PubMed Central

    Lee, Dayong; Bergamaschi, Mateus M.; Milman, Garry; Barnes, Allan J.; Queiroz, Regina H.C.; Vandrey, Ryan; Huestis, Marilyn A.

    2015-01-01

    More Americans are dependent on cannabis than any other illicit drug. The main analytes for cannabis testing include the primary psychoactive constituent, Δ9-tetrahydrocannabinol (THC), equipotent 11-hydroxy-THC (11-OH-THC) and inactive 11-nor-9-carboxy-THC (THCCOOH). Eleven adult chronic frequent cannabis smokers resided on a closed research unit with unlimited access to 5.9% THC cannabis cigarettes from 12:00 to 23:00 during two ad libitum smoking phases, followed by a 5-day abstinence period in seven participants. A single cigarette was smoked under controlled topography on the last day of the smoking and abstinence phases. Plasma cannabinoids were quantified by two-dimensional gas chromatography–mass spectrometry. Median plasma maximum concentrations (Cmax) were 28.3 (THC), 3.9 (11-OH-THC) and 47.0 μg/L (THCCOOH) 0.5 h after controlled single cannabis smoking. Median Cmax 0.2–0.5 h after ad libitum smoking was higher for all analytes: 83.5 (THC), 14.2 (11-OH-THC) and 155 μg/L (THCCOOH). All 11 participants' plasma samples were THC and THCCOOH-positive, 58.3% had THC ≥5 μg/L and 79.2% were 11-OH-THC-positive 8.1–14 h after last cannabis smoking. Cannabinoid detection rates in seven participants 106–112 h (4–5 days) after last smoking were 92.9 (THC), 35.7 (11-OH-THC) and 100% (THCCOOH), with limits of quantification of 0.5 μg/L for THC and THCCOOH, and 1.0 μg/L for 11-OH-THC. These data greatly expand prior research findings on cannabinoid excretion profiles in chronic frequent cannabis smokers during ad libitum smoking. Smoking multiple cannabis cigarettes led to higher Cmax and AUC compared with smoking a single cigarette. The chronic frequent cannabis smokers exhibited extended detection windows for plasma cannabinoids, reflecting a large cannabinoid body burden. PMID:26378131

  11. Plasma Cannabinoid Pharmacokinetics After Controlled Smoking and Ad libitum Cannabis Smoking in Chronic Frequent Users.

    PubMed

    Lee, Dayong; Bergamaschi, Mateus M; Milman, Garry; Barnes, Allan J; Queiroz, Regina H C; Vandrey, Ryan; Huestis, Marilyn A

    2015-10-01

    More Americans are dependent on cannabis than any other illicit drug. The main analytes for cannabis testing include the primary psychoactive constituent, Δ(9)-tetrahydrocannabinol (THC), equipotent 11-hydroxy-THC (11-OH-THC) and inactive 11-nor-9-carboxy-THC (THCCOOH). Eleven adult chronic frequent cannabis smokers resided on a closed research unit with unlimited access to 5.9% THC cannabis cigarettes from 12:00 to 23:00 during two ad libitum smoking phases, followed by a 5-day abstinence period in seven participants. A single cigarette was smoked under controlled topography on the last day of the smoking and abstinence phases. Plasma cannabinoids were quantified by two-dimensional gas chromatography-mass spectrometry. Median plasma maximum concentrations (Cmax) were 28.3 (THC), 3.9 (11-OH-THC) and 47.0 μg/L (THCCOOH) 0.5 h after controlled single cannabis smoking. Median Cmax 0.2-0.5 h after ad libitum smoking was higher for all analytes: 83.5 (THC), 14.2 (11-OH-THC) and 155 μg/L (THCCOOH). All 11 participants' plasma samples were THC and THCCOOH-positive, 58.3% had THC ≥5 μg/L and 79.2% were 11-OH-THC-positive 8.1-14 h after last cannabis smoking. Cannabinoid detection rates in seven participants 106-112 h (4-5 days) after last smoking were 92.9 (THC), 35.7 (11-OH-THC) and 100% (THCCOOH), with limits of quantification of 0.5 μg/L for THC and THCCOOH, and 1.0 μg/L for 11-OH-THC. These data greatly expand prior research findings on cannabinoid excretion profiles in chronic frequent cannabis smokers during ad libitum smoking. Smoking multiple cannabis cigarettes led to higher Cmax and AUC compared with smoking a single cigarette. The chronic frequent cannabis smokers exhibited extended detection windows for plasma cannabinoids, reflecting a large cannabinoid body burden.

  12. Spending one's time: the hedonic principle in ad libitum viewing of pictures.

    PubMed

    Kron, Assaf; Pilkiw, Maryna; Goldstein, Ariel; Lee, Daniel H; Gardhouse, Katherine; Anderson, Adam K

    2014-12-01

    The hedonic principle maintains that humans strive to maximize pleasant feelings and avoid unpleasant feelings. Surprisingly, and contrary to hedonic logic, previous experiments have demonstrated a relationship between picture viewing time and arousal (activation) but not with valence (pleasure vs. displeasure), suggesting that arousal rather than the hedonic principle accounts for how individuals choose to spend their time. In 2 experiments we investigated the arousal and hedonic principles underlying viewing time behavior while controlling for familiarity with stimuli, picture complexity, and demand characteristics. Under ad libitum conditions of picture viewing, we found strong relationships between viewing time, valence, and facial corrugator electomyographic (EMG) activity with familiar but not novel pictures. Viewing time of novel stimuli was largely associated with arousal and visual complexity. We conclude that only after initial information about the stimulus is gathered, where we choose to spend our time is guided by the hedonic principle.

  13. Ad-libitum drinking and performance during a 40-km cycling time trial in the heat.

    PubMed

    Berkulo, Meriam A R; Bol, Susan; Levels, Koen; Lamberts, Robert P; Daanen, Hein A M; Noakes, Timothy D

    2016-01-01

    The aim of this study was to investigate if drinking ad-libitum can counteract potential negative effects of a hypohydrated start caused by fluid restriction during a 40-km time trial (TT) in the heat. Twelve trained males performed one 40-km cycling TT euhydrated (EU: no water during the TT) and two 40-km cycling TTs hypohydrated. During one hypohydrated trial no fluid was ingested (HYPO), during the other trial ad-libitum water ingestion was allowed (FLUID). Ambient temperature was 35.2 ± 0.2 °C, relative humidity 51 ± 3% and airflow 7 m·s(-1). Body mass (BM) was determined at the start of the test, and before and after the TT. During the TT, power output, heart rate (HR), gastrointestinal temperature, mean skin temperature, rating of perceived exertion (RPE), thermal sensation, thermal comfort and thirst sensation were measured. Prior to the start of the TT, BM was 1.2% lower in HYPO and FLUID compared to EU. During the TT, BM loss in FLUID was lower compared to EU and HYPO (1.0 ± 0.8%, 2.7 ± 0.2% and 2.6 ± 0.3%, respectively). Hydration status had no effect on power output (EU: 223 ± 32 W, HYPO: 217 ± 39 W, FLUID: 224 ± 35 W), HR, gastrointestinal temperature, mean skin temperature, RPE, thermal sensation and thermal comfort. Thirst sensation was higher in HYPO than in EU and FLUID. It was concluded that hypohydration did not adversely affect performance during a 40-km cycling TT in the heat. Therefore, whether or not participants consumed fluid during exercise did not influence their TT performance.

  14. Comparison of behaviour, performance and mortality in restricted and ad libitum-fed growing rabbits.

    PubMed

    Dalmau, A; Abdel-Khalek, A M; Ramon, J; Piles, M; Sanchez, J P; Velarde, A; Rafel, O

    2015-07-01

    The objective of this study was to determine whether rabbits fed in a restricted regimen (75%) showed increased competition for feeding, drinking and use of specific areas of the cages as compared with those provided feed ad libitum. This evaluation was carried out by measuring their space utilisation in the cage, the incidence of agonistic behaviour and rates of mortality. In total, 504 rabbits between 31 and 66 days of age were used in this study. A total of 200 heavy-weight rabbits and 56 light-weight rabbits were randomly housed in 32 cages, each cage containing eight rabbits: 25 cages housing heavy rabbits and seven cages housing the light-weight ones. They were all fed ad libitum (AD). In addition, a total of 208 heavy-weight rabbits and 40 light-weight rabbits were randomly housed in 31 cages, each of them containing eight rabbits: 26 cages housing heavy weight rabbits and five cages housing light-weight ones. They were all fed a restricted diet (R) regimen. The restriction was calculated to be 75% of the feed consumed by the AD group. The total space available in the cage was 3252 cm(2), with a stocking density of 24.6 animals/m(2). Animals between 32 and 60 days of age from 20 different cages were observed nine times per week (morning or afternoon) by means of scan and focal sampling by one observer. During each period, cages were assessed for 5 min, registering every minute the position of all the animals in relation to Area A (feeder), Area B (central part) or Area C (back and drinker area). The incidence of agonistic behaviour such as displacement, biting and jumping on each other was also assessed. Performance variables such as daily gain and feed conversion ratio, in addition to general health status and mortality rates, were recorded for all rabbits. When the rabbits were under restricted feeding, the competition for feed and drink increased with clear signs of agonistic behaviour such as biting, displacement and animals jumping on top of each other

  15. Comparison of behaviour, performance and mortality in restricted and ad libitum-fed growing rabbits.

    PubMed

    Dalmau, A; Abdel-Khalek, A M; Ramon, J; Piles, M; Sanchez, J P; Velarde, A; Rafel, O

    2015-07-01

    The objective of this study was to determine whether rabbits fed in a restricted regimen (75%) showed increased competition for feeding, drinking and use of specific areas of the cages as compared with those provided feed ad libitum. This evaluation was carried out by measuring their space utilisation in the cage, the incidence of agonistic behaviour and rates of mortality. In total, 504 rabbits between 31 and 66 days of age were used in this study. A total of 200 heavy-weight rabbits and 56 light-weight rabbits were randomly housed in 32 cages, each cage containing eight rabbits: 25 cages housing heavy rabbits and seven cages housing the light-weight ones. They were all fed ad libitum (AD). In addition, a total of 208 heavy-weight rabbits and 40 light-weight rabbits were randomly housed in 31 cages, each of them containing eight rabbits: 26 cages housing heavy weight rabbits and five cages housing light-weight ones. They were all fed a restricted diet (R) regimen. The restriction was calculated to be 75% of the feed consumed by the AD group. The total space available in the cage was 3252 cm(2), with a stocking density of 24.6 animals/m(2). Animals between 32 and 60 days of age from 20 different cages were observed nine times per week (morning or afternoon) by means of scan and focal sampling by one observer. During each period, cages were assessed for 5 min, registering every minute the position of all the animals in relation to Area A (feeder), Area B (central part) or Area C (back and drinker area). The incidence of agonistic behaviour such as displacement, biting and jumping on each other was also assessed. Performance variables such as daily gain and feed conversion ratio, in addition to general health status and mortality rates, were recorded for all rabbits. When the rabbits were under restricted feeding, the competition for feed and drink increased with clear signs of agonistic behaviour such as biting, displacement and animals jumping on top of each other

  16. Evidence for hepatic involvement in control of ad libitum food intake in rats.

    PubMed

    Friedman, M I; Sawchenko, P E

    1984-07-01

    Sectioning the hepatic branch of the anterior abdominal vagal trunk attenuated but did not abolish the normal nocturnal bias in the day-night distribution of food intake in female rats. Neither total daily food intake nor body weight was affected by hepatic vagotomy. This effect appeared to be specific to the hepatic branch of the nerve because sectioning the remaining (gastric and celiac) abdominal vagal branches did not influence daily feeding rhythms and appeared to be specific to feeding behavior, because the day-night rhythms of drinking behavior and wheel-running activity were not affected by hepatic vagotomy. In male rats, hepatic vagotomy also produced an increase in daytime food consumption but without commensurate reduction in nighttime eating. As a result, male rats with hepatic vagotomy displayed a modest chronic hyperphagia and body weight gain, which was associated primarily with increased linear growth. The effect of nerve section on daytime food intake was expressed quite rapidly. Daytime food intake increased within 8 h after hepatic vagotomy, which was produced at light onset by pulling on a previously implanted suture. Collectively, these results demonstrate that hepatic vagotomy changes daily feeding rhythms and suggest that the liver and perhaps its vagal innervation are involved in the control of ad libitum eating behavior.

  17. Predicting ad libitum dry matter intake and yields of Jersey cows.

    PubMed

    Holter, J B; West, J W; McGilliard, M L; Pell, A N

    1996-05-01

    Two data files were used that contained weekly mean values for ad libitum DMI of lactating Jersey cows along with appropriate cow, ration, and environmental traits for predicting DMI. One data file (n = 666) was used to develop prediction equations for DMI because that file represented a number of separate experiments and contained more diversity in potential predictors, especially those related to ration, such as forage type. The other data file (n = 1613) was used primarily to verify these equations. Milk protein yield displaced 4% FCM output as a prediction variable and improved the R2 by several units but was not used in the final equations, however, for the sake of simplicity. All equations contained adjustments for the effects of heat stress, parity (1 vs. > 1), DIM > 15, BW, use of recombinant bST, and other significant independent variables. Equations were developed to predict DMI of cows fed individually or in groups and to predict daily yields of 4% FCM and milk protein; equations accounted for 0.69, 0.74, 0.81, and 0.76 of the variation in the dependent variables with standard deviations of 1.7, 1.6, 2.7, and 0.084 kg/ d, respectively. These equations should be applied to the development of software for computerized dairy ration balancing.

  18. Food intake and blood glucose in normal and diabetic cats fed ad libitum.

    PubMed

    Martin, G J; Rand, J S

    1999-12-01

    Ten diabetic cats were studied at intervals for up to 12 months with twice-daily insulin injections. Ten clinically healthy cats were also studied. Diets fed were based on the individual cat's performance, using mainly commercial dry or canned cat foods and fresh meat. In most cases more than one food was offered. Food was given fresh twice daily, and the cats allowed to eat ad libitum. The food intake and blood glucose were measured every 2 h in diabetic cats after insulin injection and in diabetic and normal cats without insulin injections. Food was quantified by the energy consumed (kJ ME), crude protein (g), crude fat (g), and carbohydrate (g). The blood glucose in 10 diabetic cats was measured for 2 h following a 20-min meal. Both diabetic cats and normal cats showed similar patterns of eating, with a higher food intake in the 2 h after fresh food was placed. Both groups of cats ate multiple small meals spread through the day and night. There was little or no correlation between the blood glucose and the amount of food consumed over the previous 2-h period, in insulin- or non-insulin-treated diabetic cats, or in normal cats. An overnight fast did not significantly alter morning blood glucose in diabetic cats. No demonstrable appetite stimulation occurred following an occurrence of low blood glucose; however, recorded incidences were few. No post-prandial hyperglycaemia was seen in the 10 diabetic cats during a 2-h period following the ingestion of typical cat foods.

  19. Effects of acute exercise on appetite hormones and ad libitum energy intake in men and women.

    PubMed

    Hagobian, Todd Alan; Yamashiro, Megan; Hinkel-Lipsker, Jake; Streder, Katherine; Evero, Nero; Hackney, Terry

    2013-01-01

    Acute exercise suppresses relative energy intake; however, it remains unclear whether this occurs in both men and women exposed to the same relative exercise treatment. Eleven healthy men (22 ± 2 years; 16% ± 6% body fat (BF); 26 ± 4 body mass index (BMI); 42.9 ± 6.5 mL·kg(-1)·min(-1) peak oxygen consumption ([Formula: see text]O(2peak))) and 10 healthy women (21 ± 2 years; 24 ± 2 BMI; 23% ± 3% BF; 39.9 ± 5.5 mL·kg(-1)·min(-1) [Formula: see text]O(2peak)) rested for 60 min or exercised on a cycle ergometer at 70% [Formula: see text]O(2peak) until 30% of total daily energy expenditure was expended (men, expenditure = 975 ± 195 kcal in 82 ± 13 min; women, expenditure = 713 ± 86 kcal in 84 ± 17 min) in a counterbalanced, crossover fashion. Appetite hormones and appetite ratings were assessed in response to each condition. Forty minutes after both conditions, ad libitum total and relative energy intake (energy intake minus energy cost of exercise) were assessed at a buffet meal. There was no significant sex or condition effect in appetite hormones (PYY(3-36), acylated ghrelin, insulin) and appetite ratings (hunger, satisfaction, fullness). Total energy intake in men was significantly higher (P < 0.05) in exercise and rest conditions (1648 ± 950, 1216 ± 633 kcal, respectively) compared with women (591 ± 183, 590 ± 231 kcal, respectively). Relative energy intake was significantly lower (P < 0.05) after exercise compared with rest in men (672 ± 827, 1133 ± 619 kcal, respectively) and women (-121 ± 243, 530 ± 233 kcal, respectively). These data highlight the effectiveness of acute exercise to suppress relative energy intake regardless of sex.

  20. Sleep duration modifies effects of free ad libitum school meals on adiposity and blood pressure.

    PubMed

    Hjorth, Mads F; Sjödin, Anders; Dalskov, Stine-Mathilde; Damsgaard, Camilla Trab; Michaelsen, Kim F; Biltoft-Jensen, Anja; Andersen, Rikke; Ritz, Christian; Chaput, Jean-Philippe; Astrup, Arne

    2016-01-01

    Insufficient sleep can potentially affect both energy intake and energy expenditure, resulting in obesity and reduced cardiometabolic health. The objective of the study was to investigate if habitual sleep duration of 8- to 11-year-olds modifies the effect of free ad libitum school meals on cardiometabolic markers, body composition, dietary intake, and physical activity. For 2 consecutive 3-month periods, this cluster-randomized, controlled, cross-over trial provided 530 children with school meals or usual lunch brought from home. Dietary intake, activity, and sleep were measured simultaneously for 7 consecutive days using dietary records and accelerometers. Short- and long-sleeping children were defined as lower and upper tertile of sleep duration. Body composition, blood pressure, blood lipids, and homeostatic model assessment of insulin resistance (HOMAIR) were measured/calculated. Overall, school meals compared with lunch from home had positive effects on physical activity and blood pressure in long-sleeping children and negative effects on body fat in short-sleeping children. Short-sleeping children increased fat mass compared with long-sleeping children by 0.21 (95% confidence interval 0.03-0.38) kg, android fat mass by 0.02 (0.001-0.04) kg, waist circumference by 0.73 (0.23-1.24) cm, blood pressure by 1.5 (0.4-2.6) mm Hg, fat intake by 1.1 (0.2-2.0) percentage of energy, and decreased total physical activity by 7.2 (1.6-12.7) % (all P ≤ 0.04), while HOMAIR and blood lipids were not modified by sleep duration (all P ≥ 0.32). In conclusion, the susceptibility to increase abdominal adiposity and blood pressure when exposed to dietary changes can potentially be explained by too little sleep, which results in increased caloric intake and reduced physical activity. PMID:26647154

  1. A return to ad libitum feeding following caloric restriction promotes hepatic steatosis in hyperphagic OLETF rats.

    PubMed

    Linden, Melissa A; Fletcher, Justin A; Meers, Grace M; Thyfault, John P; Laughlin, M Harold; Rector, R Scott

    2016-09-01

    Hyperphagic Otsuka Long-Evans Tokushima fatty (OLETF) rats develop obesity, insulin resistance, and nonalcoholic fatty liver disease (NAFLD), but lifestyle modifications, such as caloric restriction (CR), can prevent these conditions. We sought to determine if prior CR had protective effects on metabolic health and NAFLD development following a 4-wk return to ad libitum (AL) feeding. Four-week-old male OLETF rats (n = 8-10/group) were fed AL for 16 wk (O-AL), CR for 16 wk (O-CR; ∼70% kcal of O-AL), or CR for 12 wk followed by 4 wk of AL feeding (O-AL4wk). CR-induced benefit in prevention of NAFLD, including reduced hepatic steatosis, inflammation, and markers of Kupffer cell activation/number, was largely lost in AL4wk rats. These findings occurred in conjunction with a partial loss of CR-induced beneficial effects on obesity and serum triglycerides in O-AL4wk rats, but in the absence of changes in serum glucose or insulin. CR-induced increases in hepatic mitochondrial respiration remained significantly elevated (P < 0.01) in O-AL4wk compared with O-AL rats, while mitochondrial [1-(14)C]palmitate oxidation, citrate synthase activity, and β-hydroxyacyl-CoA dehydrogenase activity did not differ among OLETF groups. NAFLD development in O-AL4wk rats was accompanied by increases in the protein content of the de novo lipogenesis markers fatty acid synthase and stearoyl-CoA desaturase-1 and decreases in phosphorylated acetyl-CoA carboxylase (pACC)/ACC compared with O-CR rats (P < 0.05 for each). The beneficial effects of chronic CR on NAFLD development were largely lost with 4 wk of AL feeding in the hyperphagic OLETF rat, highlighting the importance of maintaining energy balance in the prevention of NAFLD. PMID:27445343

  2. Sleep duration modifies effects of free ad libitum school meals on adiposity and blood pressure.

    PubMed

    Hjorth, Mads F; Sjödin, Anders; Dalskov, Stine-Mathilde; Damsgaard, Camilla Trab; Michaelsen, Kim F; Biltoft-Jensen, Anja; Andersen, Rikke; Ritz, Christian; Chaput, Jean-Philippe; Astrup, Arne

    2016-01-01

    Insufficient sleep can potentially affect both energy intake and energy expenditure, resulting in obesity and reduced cardiometabolic health. The objective of the study was to investigate if habitual sleep duration of 8- to 11-year-olds modifies the effect of free ad libitum school meals on cardiometabolic markers, body composition, dietary intake, and physical activity. For 2 consecutive 3-month periods, this cluster-randomized, controlled, cross-over trial provided 530 children with school meals or usual lunch brought from home. Dietary intake, activity, and sleep were measured simultaneously for 7 consecutive days using dietary records and accelerometers. Short- and long-sleeping children were defined as lower and upper tertile of sleep duration. Body composition, blood pressure, blood lipids, and homeostatic model assessment of insulin resistance (HOMAIR) were measured/calculated. Overall, school meals compared with lunch from home had positive effects on physical activity and blood pressure in long-sleeping children and negative effects on body fat in short-sleeping children. Short-sleeping children increased fat mass compared with long-sleeping children by 0.21 (95% confidence interval 0.03-0.38) kg, android fat mass by 0.02 (0.001-0.04) kg, waist circumference by 0.73 (0.23-1.24) cm, blood pressure by 1.5 (0.4-2.6) mm Hg, fat intake by 1.1 (0.2-2.0) percentage of energy, and decreased total physical activity by 7.2 (1.6-12.7) % (all P ≤ 0.04), while HOMAIR and blood lipids were not modified by sleep duration (all P ≥ 0.32). In conclusion, the susceptibility to increase abdominal adiposity and blood pressure when exposed to dietary changes can potentially be explained by too little sleep, which results in increased caloric intake and reduced physical activity.

  3. The interdependence of glycolytic and pentose cycle intermediates in ad libitum fed rats.

    PubMed

    Casazza, J P; Veech, R L

    1986-01-15

    .0008. These data indicate the interdependence of the liver content of glycolytic intermediates and pentose cycle intermediates in ad libitum fed rats.

  4. Biomedical responses of rats to chronic exposure to dietary cadmium fed in ad libitum and equalized regimes.

    PubMed

    Cousins, R J; Squibb, K S; Feldman, S L; de Bari, A; Silbon, B L

    1977-03-01

    Forty 100 g male rats were fed, in groups of eight, either 0, 5, or 25 ppm cadmium in a purified diet for 14 wk. Three groups were fed each of the levels of cadmium on an ad libitum basis. Two other groups were fed either 0 or 5 ppm cadmium in amounts that were equalized to that consumed by the 25 ppm group fed ad libitum. Cadmium ingestion decreased daily diet consumption, weight gain, and terminal body weight. These parameters were not significantly different in rats whose diet consumption was equalized. Packed cell volume and serum iron as well as serum zinc were decreased in the rats fed 25 ppm cadmium. These effects were not related to diet intake. No major differences were observed in serum ceruloplasmin, glucose, protein, leucine aminopeptidase activity, or copper in any of the groups. Blood urea nitrogen and renal leucine aminopeptidase activity were decreased by cadmium ingestion in the rats fed ad libitum only. In contrast, serum alkaline phosphatase activity was elevated by cadmium in the equalized-intake groups only. Cadmium and zinc concentrations were elevated and the iron concentration was decreased in the kidney, liver, and intestinal mucosa of the cadmium-fed rats irrespective of level of diet consumption. The increased uptake of cadmium in these tissues was coincident with the increased content of the cadmium-binding protein, metallothionein, in the cytosol fraction. The results indicate that some parameters of chronic cadmium toxicity are associated with diet consumption whereas others are not.

  5. On-demand antimicrobial release from a temperature-sensitive polymer - comparison with ad libitum release from central venous catheters.

    PubMed

    Sjollema, Jelmer; Dijkstra, Rene J B; Abeln, Caroline; van der Mei, Henny C; van Asseldonk, Dirk; Busscher, Henk J

    2014-08-28

    Antimicrobial releasing biomaterial coatings have found application for instance in the fixation of orthopedic joint prostheses and central venous catheters. Most frequently, the release kinetics is such that antimicrobially-effective concentrations are only reached within the first days to weeks after implantation, leaving no local antimicrobial release available when a biomaterial-associated infection occurs later. Here we compare the ad libitum release of chlorhexidine and silver-sulfadiazine from a central venous catheter with their release from a new, on-demand release coating consisting of a temperature-sensitive copolymer of styrene and n-butyl (meth)acrylate. The copolymer can be loaded with an antimicrobial, which is released when the temperature is raised above its glass transition temperature. Ad libitum release of chlorhexidine and silver-sulfadiazine from a commercially-purchased catheter and associated antimicrobial efficacy against Staphylococcus aureus was limited to 16days. Consecutive temperature-triggers of our on-demand coating yielded little or no antimicrobial efficacy of silver-acetate release, but antimicrobially-effective chlorhexidine concentrations were observed over a time period of 60-80days. This attests to the clear advantage of on-demand coatings above ad libitum releasing coatings, that may have released their antimicrobial content before it is actually needed. Importantly, glass transition temperature of chlorhexidine loaded copolymers was lower (48°C) than of silver loaded ones (61°C), facilitating their clinical use. PMID:24950430

  6. Comparison of the Pharmacokinetics of Nicotine Following Single and Ad Libitum Use of a Tobacco Heating System or Combustible Cigarettes

    PubMed Central

    Picavet, Patrick; Haziza, Christelle; Lama, Nicola; Weitkunat, Rolf

    2016-01-01

    Introduction: We aimed to compare the pharmacokinetics of nicotine between the heat-not-burn Tobacco Heating System 2.1 (THS 2.1) and combustible cigarettes (CCs). We also examined whether the subjective urge to smoke was associated with the pharmacokinetics of nicotine. Methods: This open-label, randomized, two-period, two-sequence crossover study conducted in 28 healthy smokers assessed the pharmacokinetics of nicotine after single and ad libitum use of the THS 2.1 or CCs. During the 7-day confinement period, blood samples were drawn for pharmacokinetic analysis. Subjective effects related to THS 2.1 or CC use were assessed using the Questionnaire of Smoking Urges (QSU-Brief). Results: The nicotine delivery rate was similar with the THS 2.1 and CCs after single and ad libitum use. The time to the maximum nicotine concentration was 8 minutes after single use of the THS 2.1 and CCs. The time to the peak concentration following ad libitum use was similar between the THS 2.1 and CCs. The maximum plasma nicotine concentration after single use of the THS 2.1 was 8.4ng/mL, 70.3% of that obtained with CCs. A transient reduction from baseline in the urge to smoke of 40% was observed 15 minutes after the single use of both the THS 2.1 and CCs. The mean QSU-Brief total scores following single and ad libitum use were similar for the THS 2.1 and CCs. Conclusions: These results suggest that the THS 2.1 effectively delivers nicotine and achieves similar pharmacokinetic profiles to CCs. The THS 2.1 also reduced the urge to smoke similarly to CCs. Implications: Reducing exposure to toxicants and safer delivery of nicotine are among the strategies that may reduce the harm of smoking-related diseases. In the present study, we investigated the pharmacokinetics of nicotine and their effects on the urge to smoke using the THS 2.1. It was developed to replicate the ritual of smoking as closely as possible by providing nicotine in a way that mimics CC smoking, but limits pyrolysis and

  7. Fattening Holstein heifers by feeding high-moisture corn (whole or ground) ad libitum separately from concentrate and straw.

    PubMed

    Devant, M; Quintana, B; Aris, A; Bach, A

    2015-10-01

    The objectives of this study were to evaluate the effects of high-moisture corn (HMC), either whole or ground, fed separately from concentrate and straw on feeding behavior, rumen fermentation, whole tract digestibility, and nitrogen balance. Twenty-four Holstein heifers (199 ± 5.5 kg BW and 157 ± 6.9 d age) housed in individual pens were assigned to 3 treatments: 1) whole (unprocessed) HMC fed along with concentrate and barley straw, all fed separately and ad libitum (WHMC); 2) HMC ground through a 0.4-cm screen before ensiling and fed along with concentrate and barley straw, all fed separately and ad libitum (GHMC); and 3) a concentrate composed of mainly corn meal, ground through a roller mill with screen openings of 6 mm, and barley straw, both fed separately and ad libitum (Control). Concentrate, HMC, and straw were offered separately ad libitum in a free-choice situation and consumption was recorded daily and BW was recorded weekly. Apparent nutrient digestibility and N balance were determined at the beginning, middle, and end of the study. At the same time points, rumen fluid was collected through rumenocentesis to determine rumen pH and VFA concentrations. Feeding behavior was monitored throughout the study. Animals were harvested after 134 d and HCW, rumen and cecum wall lesions, and liver abscesses were recorded. Treatment did not affect total DMI, feed efficiency, ADG, final BW, and carcass weight or classification. Concentrate consumption (6.6 ± 0.35 kg/d) of Control heifers was greater ( < 0.001) than that of GHMC (4.1 ± 0.35 kg/d) and WHMC heifers (2.8 ± 0.35 kg/d), and GHMC heifers consumed less ( < 0.001) HMC than WHMC heifers (2.3 ± 0.31 and 4.2 ± 0.31 kg/d, respectively). Dietary treatments did not affect rumination, self-grooming, nonnutritive oral behaviors, and rumen pH. However, rumen acetate to propionate ratio decreased when heifers received HMC (1.77 ± 0.276) compared with when heifers received the Control (2.82 ± 0.276). Total

  8. The Ratio of Macronutrients, Not Caloric Intake, Dictates Cardiometabolic Health, Aging, and Longevity in Ad Libitum-Fed Mice

    PubMed Central

    Solon-Biet, Samantha M.; McMahon, Aisling C.; Ballard, J. William O.; Ruohonen, Kari; Wu, Lindsay E.; Cogger, Victoria C.; Warren, Alessandra; Huang, Xin; Pichaud, Nicolas; Melvin, Richard G.; Gokarn, Rahul; Khalil, Mamdouh; Turner, Nigel; Cooney, Gregory J.; Sinclair, David A.; Raubenheimer, David; Le Couteur, David G.; Simpson, Stephen J.

    2016-01-01

    Summary The fundamental questions of what represents a macronutritionally balanced diet and how this maintains health and longevity remain unanswered. Here, the Geometric Framework, a state-space nutritional modeling method, was used to measure interactive effects of dietary energy, protein, fat, and carbohydrate on food intake, cardiometabolic phenotype, and longevity in mice fed one of 25 diets ad libitum. Food intake was regulated primarily by protein and carbohydrate content. Longevity and health were optimized when protein was replaced with carbohydrate to limit compensatory feeding for protein and suppress protein intake. These consequences are associated with hepatic mammalian target of rapamycin (mTOR) activation and mitochondrial function and, in turn, related to circulating branched-chain amino acids and glucose. Calorie restriction achieved by high-protein diets or dietary dilution had no beneficial effects on lifespan. The results suggest that longevity can be extended in ad libitum-fed animals by manipulating the ratio of macronutrients to inhibit mTOR activation. PMID:24606899

  9. Quantifying hepatic glycogen synthesis by direct and indirect pathways in rats under normal ad libitum feeding conditions.

    PubMed

    Soares, Ana F; Viega, Francisco J; Carvalho, Rui A; Jones, John G

    2009-01-01

    Hepatic glycogen synthesis from intact hexose (direct pathway) relative to that from gluconeogenic precursors (indirect pathway) was quantified in ad libitum-fed rats. Following (2)H(2)O administration and overnight feeding, the livers were removed and glycogen (2)H-enrichment was measured by (2)H NMR. Six controls and six rats rendered hyperglycemic by streptozotocin (STZ; fasting blood glucose = 385 +/- 31 mg/dl) were studied. The indirect pathway contribution, estimated as glycogen hydrogen 5 relative to hydrogen 2 enrichment, was 54% +/- 4% for control rats-similar to values from healthy, meal-fed humans. In STZ-treated rats, the indirect pathway contribution was significantly higher (68% +/- 4%, P < 0.05 vs. controls), similar to that of Type 1 diabetic (T1D) patients. In conclusion, sources of hepatic glycogen synthesis in rats during ad libitum nocturnal feeding were quantified by analysis of glycogen enrichment from (2)H(2)O. STZ caused alterations resembling the pathophysiology of hepatic glycogen synthesis in T1D patients.

  10. Effect of extended morning fasting upon ad libitum lunch intake and associated metabolic and hormonal responses in obese adults

    PubMed Central

    Chowdhury, E A; Richardson, J D; Tsintzas, K; Thompson, D; Betts, J A

    2016-01-01

    Background/Objectives: Breakfast omission is positively associated with obesity and increased risk of disease. However, little is known about the acute effects of extended morning fasting upon subsequent energy intake and associated metabolic/regulatory factors in obese adults. Subjects/Methods: In a randomised cross-over design, 24 obese men (n=8) and women (n=16) extended their overnight fast by omitting breakfast consumption or ingesting a typical carbohydrate-rich breakfast of 2183±393 kJ (521±94 kcal), before an ad libitum pasta lunch 3 h later. Blood samples were obtained throughout the day until 3 h post lunch and analysed for hormones implicated in appetite regulation, along with metabolic outcomes and subjective appetite measures. Results: Lunch intake was unaffected by extended morning fasting (difference=218 kJ, 95% confidence interval −54 kJ, 490 kJ; P=0.1) resulting in lower total intake in the fasting trial (difference=−1964 kJ, 95% confidence interval −1645 kJ, −2281 kJ; P<0.01). Systemic concentrations of peptide tyrosine–tyrosine and leptin were lower during the afternoon following morning fasting (P⩽0.06). Plasma-acylated ghrelin concentrations were also lower following the ad libitum lunch in the fasting trial (P<0.05) but this effect was not apparent for total ghrelin (P⩾0.1). Serum insulin concentrations were greater throughout the afternoon in the fasting trial (P=0.05), with plasma glucose also greater 1 h after lunch (P<0.01). Extended morning fasting did not result in greater appetite ratings after lunch, with some tendency for lower appetite 3 h post lunch (P=0.09). Conclusions: We demonstrate for the first time that, in obese adults, extended morning fasting does not cause compensatory intake during an ad libitum lunch nor does it increase appetite during the afternoon. Morning fasting reduced satiety hormone responses to a subsequent lunch meal but counterintuitively also reduced concentrations of

  11. Higher Daily Energy Expenditure and Respiratory Quotient, Rather Than Fat-Free Mass, Independently Determine Greater ad Libitum Overeating

    PubMed Central

    Thearle, Marie S.; Krakoff, Jonathan; Votruba, Susanne B.

    2015-01-01

    Context: Body fat-free mass (FFM), energy expenditure (EE), and respiratory quotient (RQ) are known predictors of daily food intake. Because FFM largely determines EE, it is unclear whether body composition per se or the underlying metabolism drives dietary intake. Objective: The objective of the study was to test whether 24-hour measures of EE and RQ and their components influence ad libitum food intake independently of FFM. Design and Participants: One hundred seven healthy individuals (62 males/45 females, 84 Native Americans/23 whites; age 33 ± 8 y; body mass index 33 ± 8 kg/m2; body fat 31% ± 8%) had 24-hour measures of EE in a whole-room indirect calorimeter during energy balance, followed by 3 days of ad libitum food intake using computerized vending machine systems. Body composition was estimated by dual-energy x-ray absorptiometry. Main Outcome Measures: FFM, 24-hour EE, RQ, spontaneous physical activity, sleeping EE (sleeping metabolic rate), awake and fed thermogenesis, and ad libitum food intake (INTAKE) were measured. Results: Higher 24-hour RQ (P < .001, partial R2 = 16%) and EE (P = .01, partial R2 = 7%), but not FFM (P = .65), were independent predictors of INTAKE. Mediation analysis demonstrated that 24-hour EE is responsible for 80% of the FFM effect on INTAKE (44.5 ± 16.9 kcal ingested per kilogram of FFM, P= .01), whereas the unique effect due to solely FFM was negligible (10.6 ± 23.2, P = .65). Spontaneous physical activity (r = 0.33, P = .001), but not sleeping metabolic rate (P = .71), positively predicted INTAKE, whereas higher awake and fed thermogenesis determined greater INTAKE only in subjects with a body mass index of 29 kg/m2 or less (r = 0.44, P = .01). Conclusions: EE and RQ, rather than FFM, independently determine INTAKE, suggesting that competitive energy-sensing mechanisms driven by the preferential macronutrient oxidation and total energy demands may regulate food intake. PMID:26086330

  12. Influence of a high-protein diet on energy balance in obese cats allowed ad libitum access to food.

    PubMed

    Wei, A; Fascetti, A J; Liu, K J; Villaverde, C; Green, A S; Manzanilla, E G; Havel, P J; Ramsey, J J

    2011-06-01

    The influence of a high-protein [HP, 47% of metabolizable energy (ME)] diet on energy balance was evaluated in obese cats allowed ad libitum access to food. Energy intake, body weight, body composition, energy expenditure, and concentrations of hormones and metabolites associated with carbohydrate and lipid metabolism (glucose, insulin, free fatty acids, triglycerides and leptin) were measured in cats after consuming either a moderate protein (MP, 27% of ME) or HP diet for 4 months. Indirect respiration calorimetry showed that resting and total energy expenditure (kJ/day) adjusted for either body weight or lean body mass was increased in cats consuming the HP in relation to MP diets. However, voluntary energy intake also was increased in the HP treatment and, thus, there was no difference in body weight between animals consuming the two diets. Body composition measurements using deuterium oxide dilution showed that dietary protein content did not alter amounts of either lean body mass or fat mass. No significant differences (p > 0.05) were observed between the two treatment groups for blood glucose, free fatty acid or leptin concentrations, although there was a trend (p = 0.054) towards an increase of serum insulin concentrations in the cats eating the HP diet. This study showed that short-term ad libitum feeding of an HP diet did not reduce food intake or promote weight loss in obese cats. However, energy expenditure was increased in the HP diet group and it is possible that this effect of HP might help promote weight loss when energy intake is restricted. PMID:21039925

  13. Snack food intake in ad libitum fed rats is triggered by the combination of fat and carbohydrates

    PubMed Central

    Hoch, Tobias; Pischetsrieder, Monika; Hess, Andreas

    2014-01-01

    Snack food like potato chips substantially contributes to energy intake in humans. In contrast to basic food, snacks are consumed additionally to other meals and may thereby lead to non-homeostatic energy intake. Snack food is also frequently associated with hedonic hyperphagia, a food intake independent from hunger. Analysis of brain activity patterns by manganese-enhanced MRI has previously revealed that the intake of potato chips in ad libitum fed rats strongly activates the reward system of the rat brain, which may lead to hedonic hyperphagia. The purpose of the present study was to develop a two-choice preference test to identify molecular determinants of snack food triggering extra food intake in ad libitum fed rats. Different kinds of test food were presented three times a day for 10 min each time. To minimize the influence of organoleptic properties, each test food was applied in a homogenous mixture with standard chow. Food intake as well as food intake-related locomotor activity were analyzed to evaluate the effects induced by the test foods in the two-choice preference test. In summary, fat (F), carbohydrates (CH), and a mixture of fat and carbohydrates (FCH) led to a higher food intake compared to standard chow. Notably, potato chip test food (PC) was highly significantly preferred over standard chow (STD) and also over their single main macronutrients F and CH. Only FCH induced an intake comparable to PC. Despite its low energy density, fat-free potato chip test food (ffPC) was also significantly preferred over STD and CH, but not over F, FCH, and PC. Thus, it can be concluded that the combination of fat and carbohydrates is a major molecular determinant of potato chips triggering hedonic hyperphagia. The applied two-choice preference test will facilitate future studies on stimulating and suppressive effects of other food components on non-homeostatic food intake. PMID:24744741

  14. Snack food intake in ad libitum fed rats is triggered by the combination of fat and carbohydrates.

    PubMed

    Hoch, Tobias; Pischetsrieder, Monika; Hess, Andreas

    2014-01-01

    Snack food like potato chips substantially contributes to energy intake in humans. In contrast to basic food, snacks are consumed additionally to other meals and may thereby lead to non-homeostatic energy intake. Snack food is also frequently associated with hedonic hyperphagia, a food intake independent from hunger. Analysis of brain activity patterns by manganese-enhanced MRI has previously revealed that the intake of potato chips in ad libitum fed rats strongly activates the reward system of the rat brain, which may lead to hedonic hyperphagia. The purpose of the present study was to develop a two-choice preference test to identify molecular determinants of snack food triggering extra food intake in ad libitum fed rats. Different kinds of test food were presented three times a day for 10 min each time. To minimize the influence of organoleptic properties, each test food was applied in a homogenous mixture with standard chow. Food intake as well as food intake-related locomotor activity were analyzed to evaluate the effects induced by the test foods in the two-choice preference test. In summary, fat (F), carbohydrates (CH), and a mixture of fat and carbohydrates (FCH) led to a higher food intake compared to standard chow. Notably, potato chip test food (PC) was highly significantly preferred over standard chow (STD) and also over their single main macronutrients F and CH. Only FCH induced an intake comparable to PC. Despite its low energy density, fat-free potato chip test food (ffPC) was also significantly preferred over STD and CH, but not over F, FCH, and PC. Thus, it can be concluded that the combination of fat and carbohydrates is a major molecular determinant of potato chips triggering hedonic hyperphagia. The applied two-choice preference test will facilitate future studies on stimulating and suppressive effects of other food components on non-homeostatic food intake.

  15. Snack food intake in ad libitum fed rats is triggered by the combination of fat and carbohydrates.

    PubMed

    Hoch, Tobias; Pischetsrieder, Monika; Hess, Andreas

    2014-01-01

    Snack food like potato chips substantially contributes to energy intake in humans. In contrast to basic food, snacks are consumed additionally to other meals and may thereby lead to non-homeostatic energy intake. Snack food is also frequently associated with hedonic hyperphagia, a food intake independent from hunger. Analysis of brain activity patterns by manganese-enhanced MRI has previously revealed that the intake of potato chips in ad libitum fed rats strongly activates the reward system of the rat brain, which may lead to hedonic hyperphagia. The purpose of the present study was to develop a two-choice preference test to identify molecular determinants of snack food triggering extra food intake in ad libitum fed rats. Different kinds of test food were presented three times a day for 10 min each time. To minimize the influence of organoleptic properties, each test food was applied in a homogenous mixture with standard chow. Food intake as well as food intake-related locomotor activity were analyzed to evaluate the effects induced by the test foods in the two-choice preference test. In summary, fat (F), carbohydrates (CH), and a mixture of fat and carbohydrates (FCH) led to a higher food intake compared to standard chow. Notably, potato chip test food (PC) was highly significantly preferred over standard chow (STD) and also over their single main macronutrients F and CH. Only FCH induced an intake comparable to PC. Despite its low energy density, fat-free potato chip test food (ffPC) was also significantly preferred over STD and CH, but not over F, FCH, and PC. Thus, it can be concluded that the combination of fat and carbohydrates is a major molecular determinant of potato chips triggering hedonic hyperphagia. The applied two-choice preference test will facilitate future studies on stimulating and suppressive effects of other food components on non-homeostatic food intake. PMID:24744741

  16. Feed intake and competition in ewes on ad libitum or semi-restricted feeding of grass silage and hay.

    PubMed

    Bøe, K E; Ottosen, A M; Andersen, I L

    2012-11-01

    The aim of the present experiment was to investigate the effect of feeding level and type of roughage on feed intake, feeding behavior and competition of ewes. A 2 × 2 factorial experiment was conducted with amount of roughage available (ad libitum or semi restricted) and type of roughage (grass silage or hay) as main factors. Forty-eight ewes were randomly assigned to 8 groups of 6 ewes. All groups were subjected to all 4 treatments, each treatment period lasted 7 d, and the order of treatments was rotated systematically. The ewes were video recorded for the 2 last days of each treatment period and feeding and general activity were scored every 10 min. All aggressive interactions and displacement at the feed barrier were scored continuously the first 3 h after feeding. Daily feed intake (P < 0.0001) and DMI (P < 0.0001) were both greater in the silage than in the hay treatment. Ewes in the semi-restricted treatment spent less time feeding (P < 0.0001), had a greater individual variation in feeding time (P < 0.05) and spent more time queuing for feed (standing maximum 1.5 m from the feeding barrier with the head towards the feed; P < 0.0001). Individual data showed that 5 ewes fed hay and 3 ewes fed silage reduced their time spent feeding more than 50% when the feeding level was reduced. When fed hay, the level of feeding did not affect number of aggressive interactions or displacements, but when fed silage the number of aggressive interactions (P < 0.01) and the number of displacements (P < 0.05) were much greater in the semi-restricted than in the ad libitum treatment. We conclude that even a minor restriction in the level of feeding will decrease time spent feeding and increase queuing and number of aggressive interactions when feeding space is also restricted, and that the increase in aggressive interactions is mainly for ewes fed grass silage.

  17. Data on the phospholipid fatty acyl composition of retroperitoneal white adipose tissue in ad libitum fed and fasted mice

    PubMed Central

    Marks, Kristin A.; Marvyn, Phillip M.; Henao, Juan J. Aristizabal; Bradley, Ryan M.; Stark, Ken D.; Duncan, Robin E.

    2016-01-01

    Data are presented on the fatty acyl composition of phospholipid from retroperitoneal white adipose tissue of female mice that were either given ad libitum access to food or fasted for 16 h overnight prior to sacrifice. Our data show that total adipose phospholipid concentrations were more than 2-fold higher in the fasted animals compared with the fed animals (33.48±7.40 versus 16.57±4.43 μg phospholipid fatty acids/100 mg tissue). Concentrations of several individual phospholipid fatty acyl species, including palmitic acid (16:0), vaccenic acid (18:1n-7), linoleic acid (18:2n-6), dihomo-gamma-linolenic acid (20:3n-6), arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3), as well as total phospholipid saturated fatty acids, n-6 polyunsaturated fatty acids and n-3 polyunsaturated fatty acids, were significantly higher in adipose tissue from the fasted animals compared with the fed animals. However, when the relative abundance of phospholipid fatty acyl species was analyzed, only 20:4n-6 was specifically enriched (by ~2.5-fold) in adipose phospholipid with fasting. PMID:27014729

  18. Adipose tissue partitioning of limit-fed beef cattle and beef cattle with ad libitum access to feed differing in adaptation to heat.

    PubMed

    Sprinkle, J E; Ferrell, C L; Holloway, J W; Warrington, B G; Greene, L W; Wu, G; Stuth, J W

    1998-03-01

    We compared fat distribution and lipoprotein lipase (LPL) activity in steers differing in adaptability to the subtropics. Steers were fed a grain diet (3.13 Mcal ME/kg DM) at limited (150 kcal ME x kg[-.75] x d[-1]; .23 kg ADG) or ad libitum levels for 140 d, then slaughtered. Sixteen British- (8 Angus, 8 Hereford; S), 16 Boran- (R), 16 Brahman- (B), and 16 Tuli- (T) cross steers from MARC III composite cows were used. Adipose tissue samples from perirenal, omental, and subcutaneous depots were analyzed for LPL activity. Carcass measurements including omental, external, and seam fat trim from 1/ 2 of the carcass were measured. Subcutaneous fat had greater (P < .05) LPL activity than fat from the other depots. Generally, there were no differences (P > .05) in fat distribution for steers fed at limited levels. Means for ADG, slaughter weights, carcass weights, yield grades, and carcass lipid weights for S and B fed for ad libitum intake were greater (P < .05) than those for T and R. Marbling was greatest (P < .05) for S and did not differ (P > .05) for the other breeds with ad libitum intake. Factor analysis of fat depots for animals with ad libitum intake indicated that Bos taurus cattle differing in adaptation to heat deposited fat differently; S deposited greater (P < .05) proportions of carcass fat and T deposited greater (P < .05) proportions of internal fat. It seems that accumulation of internal fat is detrimental for ADG for Bos taurus cattle. PMID:9535321

  19. Sensory-specific satiety for a food is unaffected by the ad libitum intake of other foods during a meal. Is SSS subject to dishabituation?

    PubMed

    Meillon, S; Thomas, A; Havermans, R; Pénicaud, L; Brondel, L

    2013-04-01

    Sensory-specific satiety (SSS) is defined as a decrease in the pleasantness of a specific food that has just been eaten to satiation, while other non-eaten foods remain pleasant. The objectives of this study were the following: (1) to investigate whether SSS for a food is affected by the ad libitum intake of other foods presented sequentially during a meal, (2) to compare the development of SSS when foods are presented simultaneously or sequentially during a meal, and (3) to examine whether SSS is modified when foods are presented in an unusual order within a meal. Twelve participants participated in three tasting sessions. In session A, SSS for protein-, fat- and carbohydrate-rich sandwiches was measured after the ad libitum consumption of single type of each of these foods. In session B, SSS was measured for the same three foods consumed ad libitum but presented simultaneously. Session C was identical to session A, except that the presentation order of the three foods was reversed. The results indicate that once SSS for a given food is reached, the ad libitum consumption of other foods with different sensory characteristics does not decrease SSS, regardless of the order in which the foods are presented. Once reached, SSS is thus not subject to dishabituation during a meal.

  20. Adipose tissue partitioning of limit-fed beef cattle and beef cattle with ad libitum access to feed differing in adaptation to heat.

    PubMed

    Sprinkle, J E; Ferrell, C L; Holloway, J W; Warrington, B G; Greene, L W; Wu, G; Stuth, J W

    1998-03-01

    We compared fat distribution and lipoprotein lipase (LPL) activity in steers differing in adaptability to the subtropics. Steers were fed a grain diet (3.13 Mcal ME/kg DM) at limited (150 kcal ME x kg[-.75] x d[-1]; .23 kg ADG) or ad libitum levels for 140 d, then slaughtered. Sixteen British- (8 Angus, 8 Hereford; S), 16 Boran- (R), 16 Brahman- (B), and 16 Tuli- (T) cross steers from MARC III composite cows were used. Adipose tissue samples from perirenal, omental, and subcutaneous depots were analyzed for LPL activity. Carcass measurements including omental, external, and seam fat trim from 1/ 2 of the carcass were measured. Subcutaneous fat had greater (P < .05) LPL activity than fat from the other depots. Generally, there were no differences (P > .05) in fat distribution for steers fed at limited levels. Means for ADG, slaughter weights, carcass weights, yield grades, and carcass lipid weights for S and B fed for ad libitum intake were greater (P < .05) than those for T and R. Marbling was greatest (P < .05) for S and did not differ (P > .05) for the other breeds with ad libitum intake. Factor analysis of fat depots for animals with ad libitum intake indicated that Bos taurus cattle differing in adaptation to heat deposited fat differently; S deposited greater (P < .05) proportions of carcass fat and T deposited greater (P < .05) proportions of internal fat. It seems that accumulation of internal fat is detrimental for ADG for Bos taurus cattle.

  1. Effects of feeding wheat straw or orchardgrass at ad libitum or restricted intake during the dry period on postpartum performance and lipid metabolism.

    PubMed

    Litherland, N B; Weich, W D; Hansen, W P; Linn, J G

    2012-12-01

    The objectives of this study were to investigate the effects of forage source [wheat straw (WS) or orchardgrass hay (OG)] and total amount of diet dry matter fed [ad libitum or restricted to 70% of predicted dry matter intake (DMI)] prepartum on postpartum performance. The study design was a 2×2 factorial design with 10 cows per treatment. Treatments were WS total mixed ration (TMR) ad libitum, OG TMR ad libitum, WS TMR restricted, and OG TMR restricted. The WS TMR (dry matter basis) contained 30% WS, 20.7% corn silage, 10.0% alfalfa hay, 18.2% ground corn, 16.8% soybean meal, and 4.3% molasses mineral mix (14.7% CP, 1.5 Mcal/kg of net energy for lactation, 37.0% neutral detergent fiber). The OG TMR contained 30% OG, 46.2% corn silage, 10.0% alfalfa hay, 9.5% soybean meal, and 4.3% molasses (14.2% CP, 1.5 Mcal/kg of net energy for lactation, 41.0% neutral detergent fiber). Cows received 1 lactation diet after calving (17.7% CP, 1.6 Mcal/kg of net energy for lactation, 27.3% neutral detergent fiber). Total diet DMI prepartum was higher for ad libitum than for restricted as designed, but forage source had no effect on DMI. Total tract apparent digestibilities of DM and NDF were greater for OG than for WS. Postpartum DMI expressed as a percentage of body weight for the first week of lactation was higher for ad libitum than for restricted diets. Postpartum DMI during the first 30 d of lactation was higher for OG than for WS, but no effect was observed for the amount fed prepartum. Milk yield during the first week of lactation was higher for OG than for WS; however, during the first 30 d, 3.5% fat-corrected milk yield and yield of milk fat were highest for OG TMR restricted and WS TMR ad libitum. Prepartum treatments had a limited effect on pre- and postpartum lipid metabolism; however, cows fed WS TMR ad libitum had the highest postpartum β-hydroxybutyrate. Eating behavior was observed by 10-min video scans of 24-h video surveillance for 5d pre- and postpartum

  2. Reappraise the Situation but Express Your Emotions: Impact of Emotion Regulation Strategies on ad libitum Food Intake.

    PubMed

    Taut, Diana; Renner, Britta; Baban, Adriana

    2012-01-01

    Research investigating the role of maladaptive emotion regulation (ER) on food intake has exclusively focused on food intake in a forced consumption situation. In contrast, the present study examined the effect of negative emotions (fear, negative affect) and ER strategies (suppression, reappraisal) on food intake in a non-forced, free eating setting where participants (N = 165) could choose whether and how much they ate. This free (ad libitum) eating approach enabled, for the first time, the testing of (1) whether eating (yes/no) is used as a secondary ER strategy and (2) whether the amount of food intake differed, depending on the ER strategy. In order to produce a more ecologically valid design, ER strategy manipulation was realized while exposing participants to emotion induction procedures. To induce an initial negative emotional state, a movie clip was presented without ER instruction. The instructions to regulate emotions (suppression, reappraisal, no ER instruction) then preceded a second clip. The results show that whereas about two-thirds of the control (no ER instruction) and suppression groups began to eat, only one-third of the reappraisal group did. However, when reappraisers began to eat, they ate as much as participants in the suppression and control groups. Accordingly, the results suggest that when people are confronted with a negative event, eating is used as a secondary coping strategy when the enacted ER is ineffective. Conversely, an adaptive ER such as reappraisal decreases the likelihood of eating in the first place, even when ER is employed during rather than before the unfolding of the negative event. Consequently, the way we deal with negative emotions might be more relevant for explaining emotional eating than the distress itself.

  3. Ad libitum fluid intake leads to no leg swelling in male Ironman triathletes – an observational field study

    PubMed Central

    2012-01-01

    Background An association between fluid intake and limb swelling has been described for 100-km ultra-marathoners. We investigated a potential development of peripheral oedemata in Ironman triathletes competing over 3.8 km swimming, 180 km cycling and 42.2 km running. Methods In 15 male Ironman triathletes, fluid intake, changes in body mass, fat mass, skeletal muscle mass, limb volumes and skinfold thickness were measured. Changes in renal function, parameters of skeletal muscle damage, hematologic parameters and osmolality in both serum and urine were determined. Skinfold thicknesses at hands and feet were measured using LIPOMETER® and changes of limb volumes were measured using plethysmography. Results The athletes consumed a total of 8.6 ± 4.4 L of fluids, equal to 0.79 ± 0.43 L/h. Body mass, skeletal muscle mass and the volume of the lower leg decreased (p <0.05), fat mass, skinfold thicknesses and the volume of the arm remained unchanged (p >0.05). The decrease in skeletal muscle mass was associated with the decrease in body mass (p <0.05). The decrease in the lower leg volume was unrelated to fluid intake (p >0.05). Haemoglobin, haematocrit and serum sodium remained unchanged (p >0.05). Osmolality in serum and urine increased (p <0.05). The change in body mass was related to post-race serum sodium concentration ([Na+]) (r = −0.52, p <0.05) and post-race serum osmolality (r = −0.60, p <0.05). Conclusions In these Ironman triathletes, ad libitum fluid intake maintained plasma [Na+] and plasma osmolality and led to no peripheral oedemata. The volume of the lower leg decreased and the decrease was unrelated to fluid intake. Future studies may investigate ultra-triathletes competing in a Triple Iron triathlon over 11.4 km swimming, 540 km cycling and 126.6 km running to find an association between fluid intake and the development of peripheral oedemata. PMID:22937792

  4. Circadian variation in heart rate, blood pressure, body temperature and EEG of immature broiler breeder chickens in restricted-fed and ad libitum-fed states.

    PubMed

    Savory, C J; Kostal, L; Nevison, I M

    2006-10-01

    1. Heart rate, intra-aortic blood pressure, deep body temperature and telencephalic EEG were monitored by radiotelemetry in 6 freely moving immature broiler breeders (three in each of two years), during routine food restriction and then ad libitum feeding, over two 24-h periods in each feeding state.2. Heart rate, blood pressure and body temperature were all higher during ad libitum than restricted feeding, and heart rate and body temperature were higher by day (12 h) than at night (12 h). The decreases in heart rate and body temperature at night were greater during restricted than ad libitum feeding. Blood pressure tended to be higher at night, except in year 2 during restricted feeding. Body temperature and ambient temperature were higher in year 2 than year 1.3. During restricted feeding, marked peaks in heart rate, blood pressure and body temperature in the 15 min after provision of the daily food ration at 09:00 h, when birds were eating, were equivalent to corresponding values seen during ad libitum feeding.4. Relative powers in delta (1 to 4 Hz) and theta (4 to 8 Hz) frequency bands of the EEG power spectrum were higher at night in year 2 only, while power in the alpha (8 to 12 Hz) band was higher at night in both years.5. It is concluded that most of the variation in heart rate, blood pressure and body temperature between feeding states and times of day/night can be accounted for in terms of variation in food intake and energy expenditure. The greater slow wave (delta, theta) EEG activity seen after lights-off in year 2 may reflect non-paradoxical sleep at that time.

  5. Wholegrain vs. refined wheat bread and pasta. Effect on postprandial glycemia, appetite, and subsequent ad libitum energy intake in young healthy adults.

    PubMed

    Kristensen, Mette; Jensen, Morten G; Riboldi, Giancarlo; Petronio, Michela; Bügel, Susanne; Toubro, Søren; Tetens, Inge; Astrup, Arne

    2010-02-01

    Wholegrain foods have received much attention in recent years, and have been proposed to play a role in energy regulation through lowering of postprandial glycemia and appetite. This randomized crossover single meal study in 16 young adults was conducted to test the effect of iso-caloric meals based on wholemeal wheat breads and pasta in comparison to similar refined wheat products on postprandial glycemia, appetite and ad libitum energy intake (EI). Test meals (50 g carbohydrates; 2MJ) consisted of refined wheat bread (RWB), wholegrain wheat bread (WWB), refined wheat pasta (RWP) and wholegrain wheat pasta (WWP) and were served after an overnight fast. Appetite ratings and blood glucose were assessed for 180 min after which an ad libitum lunch meal was served and EI measured. The 180 min glucose responses were similar for wholemeal and refined products, but pasta meals gave significantly lower glucose responses. Only RWP had a lower glycemic index compared to RWB. WWB, but not WWP, resulted in increased satiety and reduced hunger compared to RWB. Ad libitum EI did not differ. In conclusion, the results show that wholemeal breads increased satiety measures compared to their refined counterparts; however no significant effect on subsequent EI was observed.

  6. Ad libitum Pasture Feeding in Late Pregnancy Does Not Improve the Performance of Twin-bearing Ewes and Their Lambs.

    PubMed

    Corner-Thomas, R A; Back, P J; Kenyon, P R; Hickson, R E; Ridler, A L; Stafford, K J; Morris, S T

    2015-03-01

    The present study evaluated the effect of controlled ryegrass-white clover herbage availability from day 128 until day 142 of pregnancy in comparison to unrestricted availability, on the performance of twin-bearing ewes of varying body condition score (BCS; 2.0, 2.5, or 3.0) and their lambs. It was hypothesised that under conditions of controlled herbage availability, the performance of lambs born to ewes with a greater BCS would be greater than those born to ewes with a lower BCS. During the period that the nutritional regimens were imposed, the pre- and post-grazing herbage masses of the Control regimen (1,070±69 and 801±30 kg dry matter [DM]/ha) were lower than the ad libitum regimen (1,784±69 and 1,333±33 kg DM/ha; p<0.05). The average herbage masses during lactation were 1,410±31 kg DM/ha. Nutritional regimen had no effect on ewe live weight, BCS and back fat depth or on lamb live weight, indices of colostrum uptake, maximal heat production, total litter weight weaned or survival to weaning (p>0.05). The difference in ewe BCSs and back fats observed among body condition groups was maintained throughout pregnancy (p<0.05). At weaning, ewes from the BCS2.0 group had lower BCS and live weight (2.4±0.2, 74.3±2.6 kg) than both the BCS2.5 (2.6±0.2, 78.6±2.4 kg) and BCS3.0 ewes (2.7±0.2, 79.0±2.6 kg; p<0.05), which did not differ (p>0.05). Ewe BCS group had no effect on lamb live weight at birth or weaning or on maximal heat production (p>0.05). Serum gamma glutamyl transferase concentrations of lambs born to BCS3.0 ewes were higher within 36 hours of birth than lambs born to BCS2.0 ewes and BCS2.5 ewes (51.8±1.9 vs 46.5±1.9 and 45.6±1.9 IU/mL, respectively [p<0.05]). There was, however, no effect of ewe body condition on lamb plasma glucose concentration (p>0.05). Lamb survival was the only lamb parameter that showed an interaction between ewe nutritional regimen and ewe BCS whereby survival of lambs born to BCS2.5 and BCS3.0 ewes differed but only

  7. Ad libitum food intake on a "cafeteria diet" in Native American women: relations with body composition and 24-h energy expenditure.

    PubMed

    Larson, D E; Tataranni, P A; Ferraro, R T; Ravussin, E

    1995-11-01

    Epidemiologic studies consistently report associations between obesity and dietary fat but not total energy intake. We measured ad libitum food intake in a laboratory setting and evaluated its relation to body weight and composition, energy expenditure, and macronutrient utilization in 28 women of Pima-Papago heritage (aged 27 +/- 7 y, 85.3 +/- 19.0 kg, 44 +/- 6% body fat; means +/- SD). All women were studied during the follicular phase of the menstrual cycle. After a 4-d weight-maintenance period, the volunteers selected their food for 5 d from computerized vending machines offering a variety of familiar and preferred foods, ie, a "cafeteria diet". Twenty-four-hour energy expenditure and substrate oxidation were measured in a respiratory chamber on the 4th d o weight maintenance and the 5th d of ad libitum intake. Average ad libitum intake was 13,732 +/- 4238 kJ/d (11 +/- 1% protein, 40 +/- 1% fat, 49 +/- 4% carbohydrate), ie, moderate overeating by 27 +/- 37% above weight maintenance requirements (range: -27% to 124%). Percent body fat correlated with daily energy intake (r = 0.53, P < 0.01), the degree of overeating (r = 0.41, P < 0.05), and the selection of a diet higher in fat and lower in carbohydrate (r = 0.70 and r = -0.63, respectively, P < 0.001). Excess carbohydrate intake caused an increase in carbohydrate oxidation (r = 0.51, P < 0.01), whereas excess fat intake resulted in a decrease in fat oxidation (r = -0.53, P < 0.01) and thus a positive fat balance of 85 +/- 65 g/d. The positive relations among degrees of obesity, dietary fat intake and overeating, and the fact that dietary fat does not induce fat oxidation, support the hypothesis that dietary fat promotes obesity in women. PMID:7572735

  8. Carbohydrate-rich breakfast attenuates glycaemic, insulinaemic and ghrelin response to ad libitum lunch relative to morning fasting in lean adults.

    PubMed

    Chowdhury, Enhad A; Richardson, Judith D; Tsintzas, Kostas; Thompson, Dylan; Betts, James A

    2015-07-14

    Breakfast omission is associated with obesity and CVD/diabetes, but the acute effects of extended morning fasting upon subsequent energy intake and metabolic/hormonal responses have received less attention. In a randomised cross-over design, thirty-five lean men (n 14) and women (n 21) extended their overnight fast or ingested a typical carbohydrate-rich breakfast in quantities relative to RMR (i.e. 1963 (sd 238) kJ), before an ad libitum lunch 3 h later. Blood samples were obtained hourly throughout the day until 3 h post-lunch, with subjective appetite measures assessed. Lunch intake was greater following extended fasting (640 (sd 1042) kJ, P< 0.01) but incompletely compensated for the omitted breakfast, with total intake lower than the breakfast trial (3887 (sd 1326) v. 5213 (sd 1590) kJ, P< 0.001). Systemic concentrations of peptide tyrosine-tyrosine and leptin were greater during the afternoon following breakfast (both P< 0.05) but neither acylated/total ghrelin concentrations were suppressed by the ad libitum lunch in the breakfast trial, remaining greater than the morning fasting trial throughout the afternoon (all P< 0.05). Insulin concentrations were greater during the afternoon in the morning fasting trial (all P< 0.01). There were no differences between trials in subjective appetite during the afternoon. In conclusion, morning fasting caused incomplete energy compensation at an ad libitum lunch. Breakfast increased some anorectic hormones during the afternoon but paradoxically abolished ghrelin suppression by the second meal. Extending morning fasting until lunch altered subsequent metabolic and hormonal responses but without greater appetite during the afternoon. The present study clarifies the impact of acute breakfast omission and adds novel insights into second-meal metabolism. PMID:26004166

  9. Carbohydrate-rich breakfast attenuates glycaemic, insulinaemic and ghrelin response to ad libitum lunch relative to morning fasting in lean adults.

    PubMed

    Chowdhury, Enhad A; Richardson, Judith D; Tsintzas, Kostas; Thompson, Dylan; Betts, James A

    2015-07-14

    Breakfast omission is associated with obesity and CVD/diabetes, but the acute effects of extended morning fasting upon subsequent energy intake and metabolic/hormonal responses have received less attention. In a randomised cross-over design, thirty-five lean men (n 14) and women (n 21) extended their overnight fast or ingested a typical carbohydrate-rich breakfast in quantities relative to RMR (i.e. 1963 (sd 238) kJ), before an ad libitum lunch 3 h later. Blood samples were obtained hourly throughout the day until 3 h post-lunch, with subjective appetite measures assessed. Lunch intake was greater following extended fasting (640 (sd 1042) kJ, P< 0.01) but incompletely compensated for the omitted breakfast, with total intake lower than the breakfast trial (3887 (sd 1326) v. 5213 (sd 1590) kJ, P< 0.001). Systemic concentrations of peptide tyrosine-tyrosine and leptin were greater during the afternoon following breakfast (both P< 0.05) but neither acylated/total ghrelin concentrations were suppressed by the ad libitum lunch in the breakfast trial, remaining greater than the morning fasting trial throughout the afternoon (all P< 0.05). Insulin concentrations were greater during the afternoon in the morning fasting trial (all P< 0.01). There were no differences between trials in subjective appetite during the afternoon. In conclusion, morning fasting caused incomplete energy compensation at an ad libitum lunch. Breakfast increased some anorectic hormones during the afternoon but paradoxically abolished ghrelin suppression by the second meal. Extending morning fasting until lunch altered subsequent metabolic and hormonal responses but without greater appetite during the afternoon. The present study clarifies the impact of acute breakfast omission and adds novel insights into second-meal metabolism.

  10. Acute effects of protein composition and fibre enrichment of yogurt consumed as snacks on appetite sensations and subsequent ad libitum energy intake in healthy men.

    PubMed

    Doyon, Caroline Y; Tremblay, Angelo; Rioux, Laurie-Eve; Rhéaume, Caroline; Cianflone, Katherine; Poursharifi, Pegah; Turgeon, Sylvie L

    2015-10-01

    The objective of the study was to assess the impact of protein composition and/or fibre enrichment of yogurt on appetite sensations and subsequent energy intake. In this double-blind crossover study, 20 healthy men (aged 32.4 ± 9.1 years) were submitted to 5 randomized testing sessions, during which they had to consume 5 isocaloric and isonproteinemic yogurt snacks (120-g servings, ∼230 kJ, ∼4.5 g protein) differing by their casein-to-whey protein ratio (C:W) or dietary fibre content: (i) control C:W = 2.8:1; (ii) high whey (HW) C:W = 1.5:1, and fibre-enriched formulations using control; (iii) 2.4 g of inulin; (iv) 1.9 g of inulin and 0.5 g of β-glucan (+IN-βG); and (v) 0.5 g of β-glucan. Appetite sensations were assessed using 150-mm visual analog scales. Plasma variables (glucose, insulin, ghrelin) were measured at 30-min intervals post-yogurt consumption for 2 h. Finally, energy intakes during ad libitum lunches offered 2 h after yogurt snacks were recorded. None of the yogurts impacted appetite sensations. Ad libitum energy intake was significantly different only between HW and control yogurts (-812 kJ; p = 0.03). Regarding post-yogurt plasma variables, a significant difference was found only between ghrelin area under the curve of the +IN-βG and the HW yogurts (-15 510 pmol/L per 120 min, p = 0.04). In conclusion, although appetite sensations were not influenced by variations in yogurts' protein compositions, a reduced energy intake was observed during the ad libitum lunch after the HW yogurt that may be attributable to its lower C:W. Surprisingly, the fibre enrichments studied did not exert effect on appetite sensations and energy intake.

  11. Acute effects of protein composition and fibre enrichment of yogurt consumed as snacks on appetite sensations and subsequent ad libitum energy intake in healthy men.

    PubMed

    Doyon, Caroline Y; Tremblay, Angelo; Rioux, Laurie-Eve; Rhéaume, Caroline; Cianflone, Katherine; Poursharifi, Pegah; Turgeon, Sylvie L

    2015-10-01

    The objective of the study was to assess the impact of protein composition and/or fibre enrichment of yogurt on appetite sensations and subsequent energy intake. In this double-blind crossover study, 20 healthy men (aged 32.4 ± 9.1 years) were submitted to 5 randomized testing sessions, during which they had to consume 5 isocaloric and isonproteinemic yogurt snacks (120-g servings, ∼230 kJ, ∼4.5 g protein) differing by their casein-to-whey protein ratio (C:W) or dietary fibre content: (i) control C:W = 2.8:1; (ii) high whey (HW) C:W = 1.5:1, and fibre-enriched formulations using control; (iii) 2.4 g of inulin; (iv) 1.9 g of inulin and 0.5 g of β-glucan (+IN-βG); and (v) 0.5 g of β-glucan. Appetite sensations were assessed using 150-mm visual analog scales. Plasma variables (glucose, insulin, ghrelin) were measured at 30-min intervals post-yogurt consumption for 2 h. Finally, energy intakes during ad libitum lunches offered 2 h after yogurt snacks were recorded. None of the yogurts impacted appetite sensations. Ad libitum energy intake was significantly different only between HW and control yogurts (-812 kJ; p = 0.03). Regarding post-yogurt plasma variables, a significant difference was found only between ghrelin area under the curve of the +IN-βG and the HW yogurts (-15 510 pmol/L per 120 min, p = 0.04). In conclusion, although appetite sensations were not influenced by variations in yogurts' protein compositions, a reduced energy intake was observed during the ad libitum lunch after the HW yogurt that may be attributable to its lower C:W. Surprisingly, the fibre enrichments studied did not exert effect on appetite sensations and energy intake. PMID:26394259

  12. Validating growth and development of a seabird as an indicator of food availability: captive-reared Caspian Tern chicks fed ad libitum and restricted diets

    USGS Publications Warehouse

    Lyons, Donald E.; Roby, Daniel D.

    2011-01-01

    For seabirds raising young under conditions of limited food availability, reducing chick provisioning and chick growth rates are the primary means available to avoid abandonment of a breeding effort. For most seabirds, however, baseline data characterizing chick growth and development under known feeding conditions are unavailable, so it is difficult to evaluate chick nutritional status as it relates to foraging conditions near breeding colonies. To address this need, we examined the growth and development of young Caspian Terns (Hydroprogne caspia), a cosmopolitan, generalist piscivore, reared in captivity and fed ad libitum and restricted (ca. one-third lower caloric intake) diets. Ad libitum-fed chicks grew at similar rates and achieved a similar size at fledging as previously documented for chicks in the wild and had energetic demands that closely matched allometric predictions. We identified three general characteristics of food-restricted Caspian Tern chicks compared to ad libitum chicks: (1) lower age-specific body mass, (2) lower age-specific skeletal and feather size, such as wing chord length, and (3) heightened levels of corticosterone in blood, both for baseline levels and in response to acute stress. Effects of diet restriction on feather growth (10-11% slower growth in diet-restricted chicks) were less pronounced than effects on structural growth (37-52% slower growth) and body mass (24% lower at fledging age), apparently due to preferential allocation of food resources to maintain plumage growth. Our results suggest that measurements of chick body mass and feather development (e.g., wing chord or primary length) or measurement of corticosterone levels in the blood would allow useful evaluation of the nutritional status of chicks reared in the wild and of food availability in the foraging range of adults. Such evaluations could also inform demography studies (e.g., predict future recruitment) and assist in evaluating designated piscivorous waterbird

  13. Impact of fluid restriction and ad libitum water intake or an 8% carbohydrate-electrolyte beverage on skill performance of elite adolescent basketball players.

    PubMed

    Carvalho, Pedro; Oliveira, Bruno; Barros, Renata; Padrão, Patricia; Moreira, Pedro; Teixeira, Vitor Hugo

    2011-06-01

    Twelve adolescent athletes underwent, in a crossover-design study, 3 separate 90-min training sessions in the following conditions: no fluid ingestion allowed (NF), ad libitum ingestion of water (W), and ad libitum ingestion of a commercial 8% carbohydrate-electrolyte sports beverage (CSB). After each session athletes performed a set of basketball drills (2-point, 3-point, and free-throw shootout, suicide sprints, and defensive zigzags). Body weight (before and after sessions), rating of perceived exertion (RPE), urine color, and beverage acceptability were determined in each session. Athletes also completed a survey about their knowledge and behaviors regarding hydration and fluid replacement. The percentage of weight loss was significantly higher in NF (2.46% ± 0.87%) than in the other 2 conditions (W, 1.08% ± 0.67%, p = .006; CSB, 0.65% ± 0.62%, p = .001) but also higher in W than CSB (p = .012). RPE was higher in NF (16.8 ± 1.96) than in the W (14.2 ± 1.99, p = .004) and CSB (13.3 ± 2.06, p = .002) trials. Athletes' fluid intake was positively correlated with proper self-reported behaviors (r = .75, p = .005) and knowledge (r = .76, p = .004) about fluid and hydration. In conclusion, fluid restriction during exercise was associated with a greater level of dehydration and increased perceived exertion but had no impact on basketball performance compared with ad libitum drinking of water or a CSB. Athletes with more knowledge about hydration and better self-reported hydration behaviors ingested more fluids during training sessions.

  14. Exercise Does Not Protect against Peripheral and Central Effects of a High Cholesterol Diet Given Ad libitum in Old ApoE−/− Mice

    PubMed Central

    Di Cataldo, Vanessa; Géloën, Alain; Langlois, Jean-Baptiste; Chauveau, Fabien; Thézé, Benoît; Hubert, Violaine; Wiart, Marlène; Chirico, Erica N.; Rieusset, Jennifer; Vidal, Hubert; Pialoux, Vincent; Canet-Soulas, Emmanuelle

    2016-01-01

    Aim: Advanced atherosclerosis increases inflammation and stroke risk in the cerebral vasculature. Exercise is known to improve cardio-metabolic profiles when associated with a caloric restriction, but it remains debated whether it is still beneficial without the dietary control. The aim of this study was to determine both the peripheral and central effects of exercise training combined with a cholesterol-rich diet given ad libitum in old ApoE−/− mice. Methods: Forty-five-weeks old obese ApoE−/− mice fed with a high cholesterol diet ad libitum were divided into Exercise-trained (EX; running wheel free access) and Sedentary (SED) groups. Insulin tolerance and brain imaging were performed before and after the twelve-weeks training. Tissue insulin resistance, oxidative stress, and inflammation markers in plasma, aorta, and brain were then assessed. Results: In EX ApoE−/− mice, no beneficial effect of exercise was observed on weight, abdominal fat, metabolic parameters, oxidative stress, or inflammation compared to SED. Despite the regular exercise training in ApoE−/− EX mice (mean of 12.5 km/week during 12 weeks), brain inflammation imaging score was significantly associated with increased blood brain barrier (BBB) leakage evaluated by imaging follow-up (r2 = 0.87; p = 0.049) with a faster evolution compared to SED ApoE−/−mice. Conclusion: We conclude that in a context of high cardio-metabolic risk, exercise does not provide any protective effect in old ApoE−/− animals under high cholesterol diet given ad libitum. Peripheral (insulin sensitivity and oxidative/inflammatory status) but also central features (BBB preservation and protection against inflammation) did not show any benefits of exercise. Indeed, there was a fast induction of irreversible brain damage that was more pronounced in exercise-trained ApoE−/− mice. PMID:27766082

  15. Maintained total body water content and serum sodium concentrations despite body mass loss in female ultra-runners drinking ad libitum during a 100 km race.

    PubMed

    Knechtle, Beat; Senn, Oliver; Imoberdorf, Reinhard; Joleska, Irena; Wirth, Andrea; Knechtle, Patrizia; Rosemann, Thomas

    2010-01-01

    We investigated in 11 female ultra-runners during a 100 km ultra-run, the association between fluid intake and prevalence of exercise-associated hyponatremia in a cross-sectional study. Athletes drank ad libitum and recorded their fluid intake. They competed at 8.0 (1.0) km/h and finished within 762 (91) min. Fluid intake was 4.1 (1.3) L during the race, equal to 0.3 (0.1) L/h. Body mass decreased by 1.5 kg (p< 0.01); pre race body mass was related to speed in the race (r = -0.78, p< 0.05); and change (Delta) in body mass was not associated with speed in the race. Change in body mass was positively (r = 0.70; p< 0.05), and Delta urinary specific gravity negatively (r = -0.67; p< 0.05), correlated to Delta percent total body water. Changes in body mass were not related to fluid intake during the race. Fluid intake was not correlated to running speed and showed no association with either Delta percent total body water nor Delta [Na] in plasma. Fluid intake showed no relationship with both Delta haematocrit and Delta plasma volume. No exercise-associated hyponatremia occurred. Female ultra- runners consuming fluids ad libitum during the race experienced no fluid overload, and ad libitum drinking protects against exercise-associated hyponatremia. The reported higher incidence of exercise-associated hyponatremia in women is not really a gender effect but due to women being more prone to overdrink. PMID:20199991

  16. Repeated consumption of a large volume of liquid and semi-solid foods increases ad libitum intake, but does not change expected satiety.

    PubMed

    Hogenkamp, P S; Mars, M; Stafleu, A; de Graaf, C

    2012-10-01

    Food intake and a food's expected satiating effect initially rely on sensory attributes. People will learn about the food's satiating capacity by exposure. We investigated whether repeated consumption changed the expected satiety effects and intake of iso-energetic liquid and semi-solid foods. In a randomised cross-over study, participants (n=53; age: 21±2.9 y; BMI: 21.8±2.0 kg/m²) consumed one of two iso-energetic dairy foods (liquid or semi-solid) for breakfast in each 5-day test condition. Expectations regarding satiety were measured on days 1, 2, and 5. Foods were offered ad libitum on days 1 and 5 and in a fixed volume on days 2-4. Appetite sensations were rated up to 180 min after the start of the session on fixed time points. Expected satiety effects of the semi-solid food were higher than of the liquid food on all days (p<0.0001). Ad libitum intake of the liquid food was higher than of the semi-solid food on day 1 (liquid: 391±177 g, semi-solid: 277±98 g; p<0.0001) and day 5 (liquid: 477±161 g, semi-solid: 375±148 g; p<0.0001). On day 2, hunger was rated lower and fullness rated higher after the semi-solid compared with the liquid food; on day 4, no differences were observed (significant product∗ exposure interaction AUC). Changes in hunger and fullness indicated that the fixed volumes of liquid and solid food were perceived to be equally satiating after repeated consumption, but this did not result in the anticipated changes: expected satiety effects remained lower, and ad libitum intake higher for the liquid compared with the semi-solid food. The effect of texture on a food's expected satiety effects and its ad libitum intake appears to be large, also after repeated consumption. Expectations based on sensory cues are not easily changed.

  17. Acute effects of active gaming on ad libitum energy intake and appetite sensations of 8-11-year-old boys.

    PubMed

    Allsop, Susan; Dodd-Reynolds, Caroline J; Green, Benjamin P; Debuse, Dorothée; Rumbold, Penny L S

    2015-12-28

    The present study examined the acute effects of active gaming on energy intake (EI) and appetite responses in 8-11-year-old boys in a school-based setting. Using a randomised cross-over design, twenty-one boys completed four individual 90-min gaming bouts, each separated by 1 week. The gaming bouts were (1) seated gaming, no food or drink; (2) active gaming, no food or drink; (3) seated gaming with food and drink offered ad libitum; and (4) active gaming with food and drink offered ad libitum. In the two gaming bouts during which foods and drinks were offered, EI was measured. Appetite sensations - hunger, prospective food consumption and fullness - were recorded using visual analogue scales during all gaming bouts at 30-min intervals and at two 15-min intervals post gaming. In the two bouts with food and drink, no significant differences were found in acute EI (MJ) (P=0·238). Significant differences were detected in appetite sensations for hunger, prospective food consumption and fullness between the four gaming bouts at various time points. The relative EI calculated for the two gaming bouts with food and drink (active gaming 1·42 (sem 0·28) MJ; seated gaming 2·12 (sem 0·25) MJ) was not statistically different. Acute EI in response to active gaming was no different from seated gaming, and appetite sensations were influenced by whether food was made available during the 90-min gaming bouts. PMID:26435259

  18. Acute effects of active gaming on ad libitum energy intake and appetite sensations of 8-11-year-old boys.

    PubMed

    Allsop, Susan; Dodd-Reynolds, Caroline J; Green, Benjamin P; Debuse, Dorothée; Rumbold, Penny L S

    2015-12-28

    The present study examined the acute effects of active gaming on energy intake (EI) and appetite responses in 8-11-year-old boys in a school-based setting. Using a randomised cross-over design, twenty-one boys completed four individual 90-min gaming bouts, each separated by 1 week. The gaming bouts were (1) seated gaming, no food or drink; (2) active gaming, no food or drink; (3) seated gaming with food and drink offered ad libitum; and (4) active gaming with food and drink offered ad libitum. In the two gaming bouts during which foods and drinks were offered, EI was measured. Appetite sensations - hunger, prospective food consumption and fullness - were recorded using visual analogue scales during all gaming bouts at 30-min intervals and at two 15-min intervals post gaming. In the two bouts with food and drink, no significant differences were found in acute EI (MJ) (P=0·238). Significant differences were detected in appetite sensations for hunger, prospective food consumption and fullness between the four gaming bouts at various time points. The relative EI calculated for the two gaming bouts with food and drink (active gaming 1·42 (sem 0·28) MJ; seated gaming 2·12 (sem 0·25) MJ) was not statistically different. Acute EI in response to active gaming was no different from seated gaming, and appetite sensations were influenced by whether food was made available during the 90-min gaming bouts.

  19. Total Body Water, Electrolyte, and Thermoregulatory Responses to Ad Libitum Water Replacement Using Two Different Water Delivery Systems During a 19-km Route March.

    PubMed

    Nolte, Heinrich W; Nolte, Kim; van der Meulen, Julia

    2015-11-01

    Hands-free hydration systems are often advocated for improved hydration and performance in military populations. The aim was to assess whether such systems indeed result in improved hydration in exercising soldiers. Subjects were required to complete a route march while consuming water ad libitum from either a hydration bladder (BG) or traditional canteen (CG). Water intakes of 538 ml·h⁻¹ (BG) and 533 ml·h⁻¹ (CG) resulted in no differences for changes in body mass, serum [Na], plasma osmolality, total body water, or time required to complete the march. There were no differences between peak exercise core temperature of the BG (38.9° C) and CG (38.7° C) groups. There were no differences between the groups for fluid balance, thermoregulation, or performance. This is a not a surprising finding because the amount of fluid consumed ad libitum is determined by changes in serum osmolality and not the fluid delivery system as often proposed. PMID:26506205

  20. Voluntary feed intake and leptin sensitivity in ad libitum fed obese ponies following a period of restricted feeding: a pilot study.

    PubMed

    Van Weyenberg, S; Buyse, J; Kalmar, I D; Swennen, Q; Janssens, G P J

    2013-08-01

    The relation between plasma leptin and daily ad libitum roughage intake was evaluated during a 14-day period in eight obese Shetland ponies. When the feeding strategy was changed from maintenance feeding to ad libitum feeding, feed intake increased the first day, decreased the second day and increased again during the following days to reach a constant level after 8 days. Plasma leptin concentration increased during the first 2 days, but remained constant afterwards. Although the same pattern was found in all ponies, the magnitude of the increase in leptin on day 1 and the resulting decrease in feed intake on day 2 differed between ponies. A lower anorectic effect was seen in ponies with higher initial leptin concentration, suggesting the presence of different degrees in leptin sensitivity in obese ponies. High leptin production in a attempt to compensate for the decrease in leptin sensitivity might explain large variations in plasma leptin among obese ponies with similar body condition score. Further research is necessary to clarify whether the reduced leptin sensitivity precedes obesity in equines or vice versa.

  1. Effects of feed consumption rate of beef cattle offered a diet supplemented with nitrate ad libitum or restrictively on potential toxicity of nitrate.

    PubMed

    Lee, C; Araujo, R C; Koenig, K M; Beauchemin, K A

    2015-10-01

    The objective of the study was to investigate the effects of feed consumption rate on potential toxicity, rumen fermentation, and eating behavior when beef heifers were fed a diet supplemented with nitrate (NI). Twelve ruminally cannulated heifers (827 ± 65.5 kg BW) were used in a randomized complete block design. The experiment consisted of 10-d adaptation, 8-d urea-feeding, and 3-d nitrate-feeding periods. All heifers were fed a diet supplemented with urea (UR) during the adaptation and urea-feeding periods, whereas the NI diet (1.09% NO in dietary DM) was fed during the nitrate-feeding period. After adaptation, heifers were randomly assigned to ad libitum or restrictive feeding (about 80% of ad libitum intake) for the urea- and nitrate-feeding periods. Ad libitum DMI decreased (14.1 vs. 15.1 kg/d; < 0.01) when heifers were fed the NI diet compared with the UR diet. The amount of feed consumed increased ( < 0.01) at 0 to 3 h and decreased ( ≤ 0.03) at 3 to 24 h for restrictive vs. ad libitum feeding of both the UR and NI diets. Compared to the UR diet, the NI diet decreased ( < 0.01) feed consumption at 0 to 3 h and increased ( < 0.02) feed consumption at 3 to 24 h (except feed consumption at 9 to 12 h; = 0.90), indicating nitrate feeding changed the consumption pattern (a more even distribution of feed intake over the day). The increased feed consumption from 0 to 3 h after feeding the NI diet restrictively vs. ad libitum numerically decreased ( = 0.11) rumen pH and numerically or significantly increased ( = 0.01 to 0.28) rumen ammonia, NO, and NO; blood methemoglobin; and plasma NO and NO at 3 h. Regression analysis indicated that increased feed consumption (0 to 3 h) exponentially elevated ( < 0.01; = 0.75) blood methemoglobin, and plasma NO + NO among other rumen and blood variables had the greatest correlation (sigmoid response; < 0.01, = 0.47) with feed consumption (0 to 3 h). Particle size distribution of orts was partially altered ( = 0.02 to 0

  2. The Effect of Ad Libitum Consumption of a Milk-Based Liquid Meal Supplement vs. a Traditional Sports Drink on Fluid Balance After Exercise.

    PubMed

    Baguley, Brenton; Zilujko, Jessica; Leveritt, Michael D; Desbrow, Ben; Irwin, Christopher

    2016-08-01

    The aim of this study was to compare the effect of ad libitum intake of a milk-based liquid meal supplement against a carbohydrate-electrolyte sports drink following exercise induced fluid loss. Seven male participants (age 22.3 ± 3.4 years, height 179.3 ± 7.9 cm, body mass 74.3 ± 7.3 kg; mean ± SD) completed 4 separate trials and lost 1.89 ± 0.44% body mass through moderate intensity exercise in the laboratory. After exercise, participants consumed ad libitum over 2 h a milk-based liquid meal supplement (Sustagen Sport) on two of the trials (S1, S2) or a carbohydrate-electrolyte sports drink (Powerade) on two of the trials (P1, P2), with an additional 1 hr observational period. Measures of body mass, urine output, gastrointestinal tolerance and palatability were collected throughout the recovery period. Participants consumed significantly more Powerade than Sustagen Sport over the 2 h rehydration period (P1 = 2225 ± 888 ml, P2 = 2602 ± 1119 mL, S1 = 1375 ± 711 mL, S2 = 1447 ± 857 ml). Total urine output on both Sustagen trails was significantly lower than the second Powerade trial (P2 = 1447 ± 656 ml, S1 = 153 ± 62 ml, S2 = 182 ± 118 mL; p < .05) and trended toward being lower compared with the first Powerade trial (P1 = 1057 ± 699 ml vs. S1, p = .067 and vs. S2, p = .061). No significant differences in net fluid balance were observed between any of the drinks at the conclusion of each trial (P1 = -0.50 ±0. 46 kg, P2 = -0.40 ± 0.35 kg, S1 = -0.61 ± 0.74 kg, S2 = -0.45 ± 0.58 kg). Gastrointestinal tolerance and beverage palatability measures indicated Powerade to be preferred as a rehydration beverage. Ad libitum milk-based liquid meal supplement results in similar net fluid balance as a carbohydrate-electrolyte sports drink after exercise induced fluid loss.

  3. The Effect of Ad Libitum Consumption of a Milk-Based Liquid Meal Supplement vs. a Traditional Sports Drink on Fluid Balance After Exercise.

    PubMed

    Baguley, Brenton; Zilujko, Jessica; Leveritt, Michael D; Desbrow, Ben; Irwin, Christopher

    2016-08-01

    The aim of this study was to compare the effect of ad libitum intake of a milk-based liquid meal supplement against a carbohydrate-electrolyte sports drink following exercise induced fluid loss. Seven male participants (age 22.3 ± 3.4 years, height 179.3 ± 7.9 cm, body mass 74.3 ± 7.3 kg; mean ± SD) completed 4 separate trials and lost 1.89 ± 0.44% body mass through moderate intensity exercise in the laboratory. After exercise, participants consumed ad libitum over 2 h a milk-based liquid meal supplement (Sustagen Sport) on two of the trials (S1, S2) or a carbohydrate-electrolyte sports drink (Powerade) on two of the trials (P1, P2), with an additional 1 hr observational period. Measures of body mass, urine output, gastrointestinal tolerance and palatability were collected throughout the recovery period. Participants consumed significantly more Powerade than Sustagen Sport over the 2 h rehydration period (P1 = 2225 ± 888 ml, P2 = 2602 ± 1119 mL, S1 = 1375 ± 711 mL, S2 = 1447 ± 857 ml). Total urine output on both Sustagen trails was significantly lower than the second Powerade trial (P2 = 1447 ± 656 ml, S1 = 153 ± 62 ml, S2 = 182 ± 118 mL; p < .05) and trended toward being lower compared with the first Powerade trial (P1 = 1057 ± 699 ml vs. S1, p = .067 and vs. S2, p = .061). No significant differences in net fluid balance were observed between any of the drinks at the conclusion of each trial (P1 = -0.50 ±0. 46 kg, P2 = -0.40 ± 0.35 kg, S1 = -0.61 ± 0.74 kg, S2 = -0.45 ± 0.58 kg). Gastrointestinal tolerance and beverage palatability measures indicated Powerade to be preferred as a rehydration beverage. Ad libitum milk-based liquid meal supplement results in similar net fluid balance as a carbohydrate-electrolyte sports drink after exercise induced fluid loss. PMID:26693643

  4. Direct and correlated responses to selection in two lines of rabbits selected for feed efficiency under ad libitum and restricted feeding: I. Production traits and gut microbiota characteristics.

    PubMed

    Drouilhet, L; Achard, C S; Zemb, O; Molette, C; Gidenne, T; Larzul, C; Ruesche, J; Tircazes, A; Segura, M; Bouchez, T; Theau-Clément, M; Joly, T; Balmisse, E; Garreau, H; Gilbert, H

    2016-01-01

    To get insights into selection criteria for feed efficiency, 2 rabbit lines have been created: the ConsoResidual line was selected for residual feed intake (RFI) with ad libitum feeding and the ADGrestrict line was selected for ADG under restricted feeding (-20% of voluntary intake). The first objective of this study was to evaluate, after 9 generations of selection, the direct and correlated responses to selection on production traits in the 2 lines for traits recorded during growth. Second, applying the 2 feeding conditions used for selection to both selected lines plus the control unselected line (generation 0, G0) in a 2 × 3 factorial trial, the line performances were compared and the gut microbiota of the lines was characterized. The correlated responses in feed conversion ratio (FCR) were remarkably equivalent in both selected lines (-2.74 genetic σ) but correlated responses in other traits were notably different. In the ConsoResidual line, selection for decreased RFI resulted in a small negative correlated response in BW at 63 d old (BW63) and in a null response in ADG. In the ADGrestrict line, on the contrary, the correlated response in BW63 was substantial (+1.59 σ). The 2 selected lines had a FCR reduced by 0.2 point compared with the G0 line, and the same difference was found in both feeding regimens ( < 0.001). Indeed, selection on ADG would lead to heavier animals with no significant reduction of feed costs, whereas selection on RFI leads to lower feed costs and no increase of animal BW under ad libitum feeding. Altogether, our results do not suggest any genotype × environment interaction in the response to feeding regimens. The intestinal microbial communities from efficient rabbits differed from their unselected counterparts in terms of fermentation end products and microbial phylotypes, suggesting a central role of these microbes in the better feed efficiency of the rabbits.

  5. Postprandial appetite ratings are reproducible and moderately related to total day energy intakes, but not ad libitum lunch energy intakes, in healthy young women.

    PubMed

    Tucker, Amy J; Heap, Sarah; Ingram, Jessica; Law, Marron; Wright, Amanda J

    2016-04-01

    Reproducibility and validity testing of appetite ratings and energy intakes are needed in experimental and natural settings. Eighteen healthy young women ate a standardized breakfast for 8 days. Days 1 and 8, they rated their appetite (Hunger, Fullness, Desire to Eat, Prospective Food Consumption (PFC)) over a 3.5 h period using visual analogue scales, consumed an ad libitum lunch, left the research center and recorded food intake for the remainder of the day. Days 2-7, participants rated their at-home Hunger at 0 and 30 min post-breakfast and recorded food intake for the day. Total area under the curve (AUC) over the 180 min period before lunch, and energy intakes were calculated. Reproducibility of satiety measures between days was evaluated using coefficients of repeatability (CR), coefficients of variation (CV) and intra-class coefficients (ri). Correlation analysis was used to examine validity between satiety measures. AUCs for Hunger, Desire to Eat and PFC (ri = 0.73-0.78), ad libitum energy intakes (ri = 0.81) and total day energy intakes (ri​ = 0.48) were reproducible; fasted ratings were not. Average AUCs for Hunger, Desire to Eat and PFC, Desire to Eat at nadir and PFC at fasting, nadir and 180 min were correlated to total day energy intakes (r = 0.50-0.77, P < 0.05), but no ratings were correlated to lunch consumption. At-home Hunger ratings were weakly reproducible but not correlated to reported total energy intakes. Satiety ratings did not concur with next meal intake but PFC ratings may be useful predictors of intake. Overall, this study adds to the limited satiety research on women and challenges the accepted measures of satiety in an experimental setting. PMID:26763471

  6. Acute effects of mustard, horseradish, black pepper and ginger on energy expenditure, appetite, ad libitum energy intake and energy balance in human subjects.

    PubMed

    Gregersen, N T; Belza, A; Jensen, M G; Ritz, C; Bitz, C; Hels, O; Frandsen, E; Mela, D J; Astrup, A

    2013-02-14

    Chilli peppers have been shown to enhance diet-induced thermogenesis (DIT) and reduce energy intake (EI) in some studies, but there are few data on other pungent spices. The primary aim of the present study was to test the acute effects of black pepper (pepper), ginger, horseradish and mustard in a meal on 4 h postprandial DIT. The secondary aim was to examine the effects on subjective appetite measures, ad libitum EI and energy balance. In a five-way placebo-controlled, single-blind, cross-over trial, twenty-two young (age 24·9 (SD 4·6) years), normal-weight (BMI 21·8 (SD 2·1) kg/m²) males were randomly assigned to receive a brunch meal with either pepper (1·3 g), ginger (20 g), horseradish (8·3 g), mustard (21 g) or no spices (placebo). The amounts of spices were chosen from pre-testing to make the meal spicy but palatable. No significant treatment effects were observed on DIT, but mustard produced DIT, which tended to be larger than that of placebo (14 %, 59 (SE 3) v. 52 (SE 2) kJ/h, respectively, P=0·08). No other spice induced thermogenic effects approaching statistical significance. Subjective measures of appetite (P>0·85), ad libitum EI (P=0·63) and energy balance (P=0·67) also did not differ between the treatments. Finally, horseradish decreased heart rate (P=0·048) and increased diastolic blood pressure (P= 0·049) compared with placebo. In conclusion, no reliable treatment effects on appetite, EI or energy balance were observed, although mustard tended to be thermogenic at this dose. Further studies should explore the possible strength and mechanisms of the potential thermogenic effect of mustard actives, and potential enhancement by, for example, combinations with other food components.

  7. CH4 and N2O emissions from China's beef feedlots with ad libitum and restricted feeding in fall and spring seasons.

    PubMed

    Lin, Zhi; Liao, Wenhua; Yang, Yuanyuan; Gao, Zhiling; Ma, Wenqi; Wang, Dianwu; Cao, Yufeng; Li, Jianguo; Cai, Zhenjiang

    2015-04-01

    Accurately quantifying methane (CH4) and nitrous oxide (N2O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N2O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH4 from the beef feedlot with an ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N2O emissions between two feeding strategies was observed. The two-season average CH4 emission rates of the two intensive feedlots were 230 and 198gCH4animal(-1)d(-1) and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH4 conversion factor at the feedlot level. However, the average N2O emission rates (21.2g N2Oanimal(-1)d(-1)) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N2O emission rate and conversion factor of 9.2g N2Oanimal(-1)d(-1) and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N2O emissions from beef feedlots. In addition, comparison indicated that China's beef and dairy cattle in feedlots appeared to have similar CH4 conversion factors.

  8. Effects of dietary vanadium on growth and lipid storage in a larval anuran: results from studies employing ad libitum and rationed feeding.

    PubMed

    Rowe, Christopher L; Heyes, Andrew; Hopkins, William

    2009-01-31

    Vanadium (V) exerts a variety of effects related to metabolic function in vertebrates, including modifying glycolytic pathways and lipid metabolism. However, little is known about toxicity of V to wildlife in natural systems. We conducted parallel, independent studies to evaluate the effect of dietary exposure to vanadium on survival, metabolism, growth, and lipid storage of larval leopard frogs (Rana sphenocephala). In one study ("Ad lib") larvae were fed unlimited food and in the other ("Ration") larvae were fed a restricted diet. Experimental diets contained 10 ppm dw V(total) (Control, "C"), 109 ppm (Low, "L"), and 363 ppm (High, "H"). In neither study did V affect metabolic rate or survival to forelimb emergence. However, in the Ration study, 31% of individuals in H that had initiated metamorphosis died prior to completion of metamorphosis, compared with 22% in M and 9% in C, however the difference was not significant at alpha=0.05. Mortality during metamorphosis in the Ad lib study was more variable, yet followed a similar trend (26, 14, and 12% mortality in H, L, and C). In both studies, individuals that died during the metamorphic period were smaller at the time of forelimb emergence than those that survived. In the Ration study, individuals in H also had significantly lower growth rates, delayed metamorphosis, and reduced lipid content at metamorphosis compared to C and L. Growth was not affected by V in the Ad lib study. Our results suggest that habitat contamination by V may present risks to amphibians during the metamorphic period attributable to energetic responses influencing size at the initiation of metamorphosis and body lipid stores. Furthermore, while we cannot make formal comparisons between the studies, our results imply that protocols that employ ad libitum feeding regimes could fail to capture the effects of contaminants as they may be expressed in natural situations in which resources are typically more limited.

  9. CH{sub 4} and N{sub 2}O emissions from China’s beef feedlots with ad libitum and restricted feeding in fall and spring seasons

    SciTech Connect

    Lin, Zhi; Liao, Wenhua; Yang, Yuanyuan; Gao, Zhiling; Ma, Wenqi; Wang, Dianwu; Cao, Yufeng; Li, Jianguo; Cai, Zhenjiang

    2015-04-15

    Accurately quantifying methane (CH{sub 4}) and nitrous oxide (N{sub 2}O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N{sub 2}O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH{sub 4} from the beef feedlot with an ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N{sub 2}O emissions between two feeding strategies was observed. The two-season average CH{sub 4} emission rates of the two intensive feedlots were 230 and 198 g CH{sub 4} animal{sup −1} d{sup −1} and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH{sub 4} conversion factor at the feedlot level. However, the average N{sub 2}O emission rates (21.2 g N{sub 2}O animal{sup −1} d{sup −1}) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N{sub 2}O emission rate and conversion factor of 9.2 g N{sub 2}O animal{sup −1} d{sup −1} and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N{sub 2}O emissions from beef feedlots. In addition, comparison indicated that China’s beef and dairy cattle in feedlots appeared to have similar CH{sub 4} conversion factors. - Highlights: • CH{sub 4} and N{sub 2}O emissions from China’s beef feedlots were

  10. Effect of prepartal ad libitum feeding of grass silage on transcriptional adaptations of the liver and subcutaneous adipose tissue in dairy cows during the periparturient period.

    PubMed

    Selim, S; Kokkonen, T; Taponen, J; Vanhatalo, A; Elo, K

    2015-08-01

    Prepartal energy overfeeding may predispose cows to a state of increased insulin resistance with greater lipolysis after parturition. The aim of the study was to evaluate the effects of prepartal overfeeding in terms of abundant grass silage ration on the liver and subcutaneous adipose tissue (SAT) gene expression around parturition. Sixteen multiparous Finnish Ayrshire dairy cows were fed ad libitum either grass silage [high energy, HE; 144 MJ/d of metabolizable energy (ME) intake, n=8] or a mixture of grass silage, wheat straw, and rapeseed meal [55:40:5 (CON), 109 MJ/d of ME, n=8] during the dry period (58.2±4.89 d, mean ± standard deviation). Tissue biopsies and blood samples were collected at -14 (±4.98), 1, and 7 d relative to the actual parturition date. The HE cows had greater total dry matter intake, ME intake, and ME balance during the dry period than the CON cows. Compared with CON, the increases in body weight and body condition score were greater in HE during the dry period. Milk yield during the first 2 wk of lactation was not different between the groups. Plasma glucose, nonesterified fatty acids, insulin, glucagon, and β-hydroxybutyrate did not differ between the groups during the transition period. Dietary treatment did not affect hepatic triglyceride content; however, a delayed increase in hepatic total lipid content was observed in the HE cows at d 1 postpartum. Hepatic cytosolic phosphoenolpyruvate carboxykinase 1 mRNA expression was lower in HE than in CON at d 1 and 7 postpartum. Adiponectin receptor 1 and 2 mRNA abundance tended to be lower in SAT of HE than CON. Lower lipoprotein lipase, leptin, and stearoyl-coenzyme A desaturase mRNA abundances were observed at d 7 postpartum in SAT of the HE cows compared with the CON cows. We concluded that prepartal ad libitum feeding of grass silage may decrease insulin sensitivity and lipogenesis in SAT during peripartal period and may attenuate the increase of hepatic gluconeogenic capacity from

  11. Direct and correlated responses to selection in two lines of rabbits selected for feed efficiency under ad libitum and restricted feeding: II. Carcass and meat quality.

    PubMed

    Molette, C; Gilbert, H; Larzul, C; Balmisse, E; Ruesche, J; Manse, H; Tircazes, A; Theau-Clément, M; Joly, T; Gidenne, T; Garreau, H; Drouilhet, L

    2016-01-01

    To get insights into selection criteria for feed efficiency, 2 rabbit lines have been created: the ConsoResidual line was selected for residual feed intake (RFI) with ad libitum feeding and the ADGrestrict line was selected for ADG under restricted feeding. The aim of the present study was to evaluate the impact on carcass and meat quality of the genetic selections. This comparison was performed using 2 different feeding strategies corresponding to the selection design. Carcass and meat quality traits were recorded for the 3 lines (ConsoResidual, ADGrestrict, and an unselected control [generation 0 {G0}]) in the 2 feeding systems (ad libitum and restricted) for 163 animals. Concerning the line effect, the BW at 63 d old was higher for the ADGrestrict line compared with the G0 and ConsoResidual lines ( < 0.0001). There was no line effect on the gastrointestinal tract. The rabbits did not exhibit a different carcass yield but showed different carcass traits. Indeed, the ConsoResidual rabbits had a higher hind leg yield ( < 0.0001) but no difference in the meat-to-bone ratio of the hind leg. On the contrary, the ADGrestrict line had a higher proportion of forelegs plus thoracic cage ( = 0.03). We also found lower perirenal ( < 0.0001) and scapular fat yields ( < 0.0001) in ConsoResidual rabbits. The ADGrestrict line had an intermediate perirenal fat yield compared with the other 2 lines. The G0 line always exhibited higher fat yields. Concerning meat quality, the ConsoResidual rabbits showed a lower ultimate pH ( < 0.0001) and higher water loss (drip and cooking loss; < 0.002) compared with the G0 and ADGrestrict rabbits. The feeding level had a strong effect on the gastrointestinal tract ( = 0.0004) and the carcass yield ( = 0.001). The latter was decreased in restricted rabbits. The effects of feeding strategy on meat quality were detrimental in the case of restricted feeding. Even if the ultimate pH was slightly higher in restricted rabbits ( = 0.0002), the carcass

  12. Effect of prepartal ad libitum feeding of grass silage on transcriptional adaptations of the liver and subcutaneous adipose tissue in dairy cows during the periparturient period.

    PubMed

    Selim, S; Kokkonen, T; Taponen, J; Vanhatalo, A; Elo, K

    2015-08-01

    Prepartal energy overfeeding may predispose cows to a state of increased insulin resistance with greater lipolysis after parturition. The aim of the study was to evaluate the effects of prepartal overfeeding in terms of abundant grass silage ration on the liver and subcutaneous adipose tissue (SAT) gene expression around parturition. Sixteen multiparous Finnish Ayrshire dairy cows were fed ad libitum either grass silage [high energy, HE; 144 MJ/d of metabolizable energy (ME) intake, n=8] or a mixture of grass silage, wheat straw, and rapeseed meal [55:40:5 (CON), 109 MJ/d of ME, n=8] during the dry period (58.2±4.89 d, mean ± standard deviation). Tissue biopsies and blood samples were collected at -14 (±4.98), 1, and 7 d relative to the actual parturition date. The HE cows had greater total dry matter intake, ME intake, and ME balance during the dry period than the CON cows. Compared with CON, the increases in body weight and body condition score were greater in HE during the dry period. Milk yield during the first 2 wk of lactation was not different between the groups. Plasma glucose, nonesterified fatty acids, insulin, glucagon, and β-hydroxybutyrate did not differ between the groups during the transition period. Dietary treatment did not affect hepatic triglyceride content; however, a delayed increase in hepatic total lipid content was observed in the HE cows at d 1 postpartum. Hepatic cytosolic phosphoenolpyruvate carboxykinase 1 mRNA expression was lower in HE than in CON at d 1 and 7 postpartum. Adiponectin receptor 1 and 2 mRNA abundance tended to be lower in SAT of HE than CON. Lower lipoprotein lipase, leptin, and stearoyl-coenzyme A desaturase mRNA abundances were observed at d 7 postpartum in SAT of the HE cows compared with the CON cows. We concluded that prepartal ad libitum feeding of grass silage may decrease insulin sensitivity and lipogenesis in SAT during peripartal period and may attenuate the increase of hepatic gluconeogenic capacity from

  13. Effects of Dietary Protein and Fiber at Breakfast on Appetite, ad Libitum Energy Intake at Lunch, and Neural Responses to Visual Food Stimuli in Overweight Adults

    PubMed Central

    Sayer, R. Drew; Amankwaah, Akua F.; Tamer, Gregory G.; Chen, Ningning; Wright, Amy J.; Tregellas, Jason R.; Cornier, Marc-Andre; Kareken, David A.; Talavage, Thomas M.; McCrory, Megan A.; Campbell, Wayne W.

    2016-01-01

    Increasing either protein or fiber at mealtimes has relatively modest effects on ingestive behavior. Whether protein and fiber have additive or interactive effects on ingestive behavior is not known. Fifteen overweight adults (5 female, 10 male; BMI: 27.1 ± 0.2 kg/m2; aged 26 ± 1 year) consumed four breakfast meals in a randomized crossover manner (normal protein (12 g) + normal fiber (2 g), normal protein (12 g) + high fiber (8 g), high protein (25 g) + normal fiber (2 g), high protein (25 g) + high fiber (8 g)). The amount of protein and fiber consumed at breakfast did not influence postprandial appetite or ad libitum energy intake at lunch. In the fasting-state, visual food stimuli elicited significant responses in the bilateral insula and amygdala and left orbitofrontal cortex. Contrary to our hypotheses, postprandial right insula responses were lower after consuming normal protein vs. high protein breakfasts. Postprandial responses in other a priori brain regions were not significantly influenced by protein or fiber intake at breakfast. In conclusion, these data do not support increasing dietary protein and fiber at breakfast as effective strategies for modulating neural reward processing and acute ingestive behavior in overweight adults. PMID:26742068

  14. Effects of Dietary Protein and Fiber at Breakfast on Appetite, ad Libitum Energy Intake at Lunch, and Neural Responses to Visual Food Stimuli in Overweight Adults.

    PubMed

    Sayer, R Drew; Amankwaah, Akua F; Tamer, Gregory G; Chen, Ningning; Wright, Amy J; Tregellas, Jason R; Cornier, Marc-Andre; Kareken, David A; Talavage, Thomas M; McCrory, Megan A; Campbell, Wayne W

    2016-01-01

    Increasing either protein or fiber at mealtimes has relatively modest effects on ingestive behavior. Whether protein and fiber have additive or interactive effects on ingestive behavior is not known. Fifteen overweight adults (5 female, 10 male; BMI: 27.1 ± 0.2 kg/m²; aged 26 ± 1 year) consumed four breakfast meals in a randomized crossover manner (normal protein (12 g) + normal fiber (2 g), normal protein (12 g) + high fiber (8 g), high protein (25 g) + normal fiber (2 g), high protein (25 g) + high fiber (8 g)). The amount of protein and fiber consumed at breakfast did not influence postprandial appetite or ad libitum energy intake at lunch. In the fasting-state, visual food stimuli elicited significant responses in the bilateral insula and amygdala and left orbitofrontal cortex. Contrary to our hypotheses, postprandial right insula responses were lower after consuming normal protein vs. high protein breakfasts. Postprandial responses in other a priori brain regions were not significantly influenced by protein or fiber intake at breakfast. In conclusion, these data do not support increasing dietary protein and fiber at breakfast as effective strategies for modulating neural reward processing and acute ingestive behavior in overweight adults.

  15. Effects of Dietary Protein and Fiber at Breakfast on Appetite, ad Libitum Energy Intake at Lunch, and Neural Responses to Visual Food Stimuli in Overweight Adults.

    PubMed

    Sayer, R Drew; Amankwaah, Akua F; Tamer, Gregory G; Chen, Ningning; Wright, Amy J; Tregellas, Jason R; Cornier, Marc-Andre; Kareken, David A; Talavage, Thomas M; McCrory, Megan A; Campbell, Wayne W

    2016-01-01

    Increasing either protein or fiber at mealtimes has relatively modest effects on ingestive behavior. Whether protein and fiber have additive or interactive effects on ingestive behavior is not known. Fifteen overweight adults (5 female, 10 male; BMI: 27.1 ± 0.2 kg/m²; aged 26 ± 1 year) consumed four breakfast meals in a randomized crossover manner (normal protein (12 g) + normal fiber (2 g), normal protein (12 g) + high fiber (8 g), high protein (25 g) + normal fiber (2 g), high protein (25 g) + high fiber (8 g)). The amount of protein and fiber consumed at breakfast did not influence postprandial appetite or ad libitum energy intake at lunch. In the fasting-state, visual food stimuli elicited significant responses in the bilateral insula and amygdala and left orbitofrontal cortex. Contrary to our hypotheses, postprandial right insula responses were lower after consuming normal protein vs. high protein breakfasts. Postprandial responses in other a priori brain regions were not significantly influenced by protein or fiber intake at breakfast. In conclusion, these data do not support increasing dietary protein and fiber at breakfast as effective strategies for modulating neural reward processing and acute ingestive behavior in overweight adults. PMID:26742068

  16. Exercise and food ad libitum reduce the impact of early in life nutritional inbalances on nitrergic activity of hippocampus and striatum.

    PubMed

    Viana, Lane Coelho; Torres, João Bento; Farias, José Augusto; Kawhage, Rafael; Lins, Nara; Passos, Aline; Quintairos, Amanda; Trévia, Nonata; Guedes, Rubem Carlos Araújo; Diniz, Cristovam Wanderley Picanço

    2007-01-01

    Nutritional imbalances were produced by varying litter size pups per dam: 3 (small), 6 (medium), and 12 (large). On the 21st day, 4 subjects of each litter, were sacrificed and the remaining were grouped, 2 per cage, with or without running wheels, with food and water ad libitum. Adult subjects were tested in water maze, their brains processed for NADPH-diaphorase histochemistry and quantified by densitometry. No differences were detected in water maze. At 21st day, S and L compared with M presented reduced NADPH-d in the stratum molecular of dentate gyrus (DG), stratum lacunosum of CA1 and in all CA3 layers but not in the striatum. On the 58th day, actvity remained low in S and L in CA3 and striatum and L in CA1 and DG. Voluntary exercise increased NADPH-d in DG, CA1, CA3, and striatum in S, and in the stratum lacunosum of CA1 and CA3 in L.

  17. Increased restrictive feeding practices are associated with reduced energy density in 4–6-year-old, multi-ethnic children at ad libitum laboratory test-meals✩

    PubMed Central

    Sud, Shama; Tamayo, Nina Carmela; Faith, Myles S.; Keller, Kathleen L.

    2016-01-01

    Increased reports of restrictive feeding have shown positive relationships to child obesity, however, the mechanism between the two has not been elucidated. This study examined the relationship between reported use of restrictive feeding practices and 4–6-year-old children’s self-selected energy density (ED) and total energy intake from an ad libitum, laboratory dinner including macaroni and cheese, string beans, grapes, baby carrots, cheese sticks, pudding, milks, and a variety of sweetened beverages. A second objective explored the relationship between ED and child body mass index (BMI) z-score. Seventy (n = 70) healthy children from primarily non-Caucasian and lower socioeconomic status families participated. Mothers completed the Child Feeding Questionnaire (CFQ) to assess restrictive feeding practices. Energy density (kcal/g) values for both foods and drinks (EDfood+drink) and ED for foods only (EDfoods) were calculated by dividing the average number of calories consumed by the average weight eaten across 4 meals. Higher maternal restriction was associated with lower EDfood+drink. In overweight and obese children only, higher maternal restriction was associated with lower EDfood. There was a non-significant trend for both ED measures to be negatively associated with child BMI z-score. Overall, restrictive feeding practices were not associated with child BMI z-score. However, when analyzing separate aspects of restriction, parents reported higher use of restricting access to palatable foods but lower use of using palatable foods as rewards with heavier children. Previous reports of positive associations between child obesity and restrictive feeding practices may not apply in predominantly non-Caucasian, lower socioeconomic status cohorts of children. PMID:20594990

  18. Manganese-enhanced magnetic resonance imaging for mapping of whole brain activity patterns associated with the intake of snack food in ad libitum fed rats.

    PubMed

    Hoch, Tobias; Kreitz, Silke; Gaffling, Simone; Pischetsrieder, Monika; Hess, Andreas

    2013-01-01

    Non-homeostatic hyperphagia, which is a major contributor to obesity-related hyperalimentation, is associated with the diet's molecular composition influencing, for example, the energy content. Thus, specific food items such as snack food may induce food intake independent from the state of satiety. To elucidate mechanisms how snack food may induce non-homeostatic food intake, it was tested if manganese-enhanced magnetic resonance imaging (MEMRI) was suitable for mapping the whole brain activity related to standard and snack food intake under normal behavioral situation. Application of the MnCl2 solution by osmotic pumps ensured that food intake was not significantly affected by the treatment. After z-score normalization and a non-affine three-dimensional registration to a rat brain atlas, significantly different grey values of 80 predefined brain structures were recorded in ad libitum fed rats after the intake of potato chips compared to standard chow at the group level. Ten of these areas had previously been connected to food intake, in particular to hyperphagia (e.g., dorsomedial hypothalamus or the anterior paraventricular thalamic nucleus) or to the satiety system (e.g., arcuate hypothalamic nucleus or solitary tract); 27 areas were related to reward/addiction including the core and shell of the nucleus accumbens, the ventral pallidum and the ventral striatum (caudate and putamen). Eleven areas associated to sleep displayed significantly reduced Mn2+ -accumulation and six areas related to locomotor activity showed significantly increased Mn2+ -accumulation after the intake of potato chips. The latter changes were associated with an observed significantly higher locomotor activity. Osmotic pump-assisted MEMRI proved to be a promising technique for functional mapping of whole brain activity patterns associated to nutritional intake under normal behavior. PMID:23408973

  19. The effect of an incremental increase in exercise on appetite, eating behaviour and energy balance in lean men and women feeding ad libitum.

    PubMed

    Whybrow, Stephen; Hughes, Darren A; Ritz, Patrick; Johnstone, Alexandra M; Horgan, Graham W; King, Neil; Blundell, John E; Stubbs, R James

    2008-11-01

    The effects of incremental exercise on appetite, energy intake (EI), expenditure (EE) and balance (EB) in lean men and women were examined. Six men (age 29.7 (SD 5.9) years, weight 75.2 (SD 15.3) kg, height 1.75 (SD 0.11) m) and six women (age 24.7 (SD 5.9) years, weight 66.7 (SD 9.10) kg, height 1.70 (SD 0.09) m) were each studied three times during a 16 d protocol, corresponding to no additional exercise (Nex), moderate-intensity exercise (Mex; 1.5-2.0 MJ/d) and high-intensity exercise (Hex; 3.0-4.0 MJ/d) regimens. Subjects were fed to EB during days 1-2, and during days 3-16 they fed ad libitum from a medium-fat diet of constant composition. Daily EE, assessed using the doubly labelled water method, was 9.2, 11.6 and 13.7 MJ/d (P < 0.001; SED 0.45) for the women and 12.2, 14.0 and 16.7 MJ/d (P = 0.007; SED 1.11) for the men on the Nex, Mex and Hex treatments, respectively. EI was 8.3, 8.6 and 9.9 MJ/d (P = 0.118; SED 0.72) for the women and 10.6, 11.6 and 12.0 MJ/d (P = 0.031; SED 0.47) for the men, respectively. On average, subjects compensated for about 30 % of the exercise-induced energy deficit. However, the degree of compensation varied considerably among individuals. The present study captured the initial compensation in EI for exercise-induced energy deficits. Total compensation would take a matter of weeks.

  20. Episodic sucrose intake during food restriction increases synaptic abundance of AMPA receptors in nucleus accumbens and augments intake of sucrose following restoration of ad libitum feeding.

    PubMed

    Peng, X-X; Lister, A; Rabinowitsch, A; Kolaric, R; Cabeza de Vaca, S; Ziff, E B; Carr, K D

    2015-06-01

    Weight-loss dieting often leads to loss of control, rebound weight gain, and is a risk factor for binge pathology. Based on findings that food restriction (FR) upregulates sucrose-induced trafficking of glutamatergic AMPA receptors to the nucleus accumbens (NAc) postsynaptic density (PSD), this study was an initial test of the hypothesis that episodic "breakthrough" intake of forbidden food during dieting interacts with upregulated mechanisms of synaptic plasticity to increase reward-driven feeding. Ad libitum (AL) fed and FR subjects consumed a limited amount of 10% sucrose, or had access to water, every other day for 10 occasions. Beginning three weeks after return of FR rats to AL feeding, when 24-h chow intake and rate of body weight gain had normalized, subjects with a history of sucrose intake during FR consumed more sucrose during a four week intermittent access protocol than the two AL groups and the group that had access to water during FR. In an experiment that substituted noncontingent administration of d-amphetamine for sucrose, FR subjects displayed an enhanced locomotor response during active FR but a blunted response, relative to AL subjects, during recovery from FR. This result suggests that the enduring increase in sucrose consumption is unlikely to be explained by residual enhancing effects of FR on dopamine signaling. In a biochemical experiment which paralleled the sucrose behavioral experiment, rats with a history of sucrose intake during FR displayed increased abundance of pSer845-GluA1, GluA2, and GluA3 in the NAc PSD relative to rats with a history of FR without sucrose access and rats that had been AL throughout, whether they had a history of episodic sucrose intake or not. A history of FR, with or without a history of sucrose intake, was associated with increased abundance of GluA1. A terminal 15-min bout of sucrose intake produced a further increase in pSer845-GluA1 and GluA2 in subjects with a history of sucrose intake during FR

  1. Episodic sucrose intake during food restriction increases synaptic abundance of AMPA receptors in nucleus accumbens and augments intake of sucrose following restoration of ad libitum feeding.

    PubMed

    Peng, X-X; Lister, A; Rabinowitsch, A; Kolaric, R; Cabeza de Vaca, S; Ziff, E B; Carr, K D

    2015-06-01

    Weight-loss dieting often leads to loss of control, rebound weight gain, and is a risk factor for binge pathology. Based on findings that food restriction (FR) upregulates sucrose-induced trafficking of glutamatergic AMPA receptors to the nucleus accumbens (NAc) postsynaptic density (PSD), this study was an initial test of the hypothesis that episodic "breakthrough" intake of forbidden food during dieting interacts with upregulated mechanisms of synaptic plasticity to increase reward-driven feeding. Ad libitum (AL) fed and FR subjects consumed a limited amount of 10% sucrose, or had access to water, every other day for 10 occasions. Beginning three weeks after return of FR rats to AL feeding, when 24-h chow intake and rate of body weight gain had normalized, subjects with a history of sucrose intake during FR consumed more sucrose during a four week intermittent access protocol than the two AL groups and the group that had access to water during FR. In an experiment that substituted noncontingent administration of d-amphetamine for sucrose, FR subjects displayed an enhanced locomotor response during active FR but a blunted response, relative to AL subjects, during recovery from FR. This result suggests that the enduring increase in sucrose consumption is unlikely to be explained by residual enhancing effects of FR on dopamine signaling. In a biochemical experiment which paralleled the sucrose behavioral experiment, rats with a history of sucrose intake during FR displayed increased abundance of pSer845-GluA1, GluA2, and GluA3 in the NAc PSD relative to rats with a history of FR without sucrose access and rats that had been AL throughout, whether they had a history of episodic sucrose intake or not. A history of FR, with or without a history of sucrose intake, was associated with increased abundance of GluA1. A terminal 15-min bout of sucrose intake produced a further increase in pSer845-GluA1 and GluA2 in subjects with a history of sucrose intake during FR

  2. Does Increased Exercise or Physical Activity Alter Ad-Libitum Daily Energy Intake or Macronutrient Composition in Healthy Adults? A Systematic Review

    PubMed Central

    Donnelly, Joseph E.; Herrmann, Stephen D.; Lambourne, Kate; Szabo, Amanda N.; Honas, Jeffery J.; Washburn, Richard A.

    2014-01-01

    Background The magnitude of the negative energy balance induced by exercise may be reduced due to compensatory increases in energy intake. Objective To address the question: Does increased exercise or physical activity alter ad-libitum daily energy intake or macronutrient composition in healthy adults? Data Sources PubMed and Embase were searched (January 1990–January 2013) for studies that presented data on energy and/or macronutrient intake by level of exercise, physical activity or change in response to exercise. Ninety-nine articles (103 studies) were included. Study Eligibility Criteria Primary source articles published in English in peer-reviewed journals. Articles that presented data on energy and/or macronutrient intake by level of exercise or physical activity or changes in energy or macronutrient intake in response to acute exercise or exercise training in healthy (non-athlete) adults (mean age 18–64 years). Study Appraisal and Synthesis Methods Articles were grouped by study design: cross-sectional, acute/short term, non-randomized, and randomized trials. Considerable heterogeneity existed within study groups for several important study parameters, therefore a meta-analysis was considered inappropriate. Results were synthesized and presented by study design. Results No effect of physical activity, exercise or exercise training on energy intake was shown in 59% of cross-sectional studies (n = 17), 69% of acute (n = 40), 50% of short-term (n = 10), 92% of non-randomized (n = 12) and 75% of randomized trials (n = 24). Ninety-four percent of acute, 57% of short-term, 100% of non-randomized and 74% of randomized trials found no effect of exercise on macronutrient intake. Forty-six percent of cross-sectional trials found lower fat intake with increased physical activity. Limitations The literature is limited by the lack of adequately powered trials of sufficient duration, which have prescribed and measured exercise energy expenditure

  3. Effekt einer ad libitum verzehrten fettreduzierten Kost, reich an Obst, Gemüse und Milchprodukten auf den Blutdruck bei Borderline-Hypertonikern

    NASA Astrophysics Data System (ADS)

    Möseneder, Jutta M.

    2002-01-01

    In der randomisierten, multizentrischen DASH-Studie (Dietary Approaches to Stop Hy-pertension), die unter kontrollierten Bedingungen stattfand, führte eine fettreduzierte Mischkost, reich an Obst, Gemüse und Milchprodukten, bei Borderline-Hypertonikern zu einer signifikanten Blutdrucksenkung. Während der Studienphase wurden Körpermasse, Natrium-Aufnahme sowie Alkoholzufuhr aufgrund der bekannten Einflussnahme auf den Blutdruck konstant gehalten. In der eigenen Pilot-Studie sollte untersucht werden, ob das Ergebnis der DASH-Studie (i) mit deutschen Hypertonikern und (ii) unter habituellen Ernährungs- und Lebensbedingungen mit regelmäßig durchgeführter Ernährungsberatung und ad libitum Verzehr anstelle des streng kontrollierten Studienansatzes bestätigt werden kann. Eine Konstanz der Körpermasse, der Natrium-Urinausscheidung (unter diesem Studienansatz valider als die Aufnahme) und des Alkoholkonsums wurde vorausgesetzt. Die Studienpopulation setzte sich aus 53 übergewichtigen Probanden mit einer nicht medikamentös therapierten Borderline-Hypertonie und ohne Stoffwechselerkrankungen zusammen. Die Studienteilnehmer wurden randomisiert entweder der Idealgruppe mit einer fettarmen Kost reich an Milchprodukten, Obst und Gemüse (ähnlich der DASH-Idealgruppe) oder der Kontrollgruppe mit habitueller Ernährungsweise zugeteilt. Über einen Zeitraum von fünf Wochen wurde den Probanden etwa 50% ihres täglichen Lebensmittelbedarfes entsprechend ihrer Gruppenzugehörigkeit kostenfrei zur Verfügung gestellt. Gelegenheitsblutdruckmessungen und 24h-Blutdruckmessungen, Ernährungs- und Aktivitätsprotokolle, Blut- und Urinproben sowie anthropometrische Messungen wurden vor, während und fünf Wochen nach der Interventionsphase durchgeführt. Die Ergebnisse zeigen, dass in der Idealgruppe keine signifikante Blutdrucksenkung beobachtet werden konnte. Dies lässt sich durch die Tatsache erklären, dass die Lebens-mittel- und Nährstoffaufnahme der deutschen

  4. Effekt einer ad libitum verzehrten fettreduzierten Kost, reich an Obst, Gemüse und Milchprodukten auf den Blutdruck bei Borderline-Hypertonikern

    NASA Astrophysics Data System (ADS)

    Möseneder, Jutta M.

    2002-01-01

    In der randomisierten, multizentrischen DASH-Studie (Dietary Approaches to Stop Hy-pertension), die unter kontrollierten Bedingungen stattfand, führte eine fettreduzierte Mischkost, reich an Obst, Gemüse und Milchprodukten, bei Borderline-Hypertonikern zu einer signifikanten Blutdrucksenkung. Während der Studienphase wurden Körpermasse, Natrium-Aufnahme sowie Alkoholzufuhr aufgrund der bekannten Einflussnahme auf den Blutdruck konstant gehalten. In der eigenen Pilot-Studie sollte untersucht werden, ob das Ergebnis der DASH-Studie (i) mit deutschen Hypertonikern und (ii) unter habituellen Ernährungs- und Lebensbedingungen mit regelmäßig durchgeführter Ernährungsberatung und ad libitum Verzehr anstelle des streng kontrollierten Studienansatzes bestätigt werden kann. Eine Konstanz der Körpermasse, der Natrium-Urinausscheidung (unter diesem Studienansatz valider als die Aufnahme) und des Alkoholkonsums wurde vorausgesetzt. Die Studienpopulation setzte sich aus 53 übergewichtigen Probanden mit einer nicht medikamentös therapierten Borderline-Hypertonie und ohne Stoffwechselerkrankungen zusammen. Die Studienteilnehmer wurden randomisiert entweder der Idealgruppe mit einer fettarmen Kost reich an Milchprodukten, Obst und Gemüse (ähnlich der DASH-Idealgruppe) oder der Kontrollgruppe mit habitueller Ernährungsweise zugeteilt. Über einen Zeitraum von fünf Wochen wurde den Probanden etwa 50% ihres täglichen Lebensmittelbedarfes entsprechend ihrer Gruppenzugehörigkeit kostenfrei zur Verfügung gestellt. Gelegenheitsblutdruckmessungen und 24h-Blutdruckmessungen, Ernährungs- und Aktivitätsprotokolle, Blut- und Urinproben sowie anthropometrische Messungen wurden vor, während und fünf Wochen nach der Interventionsphase durchgeführt. Die Ergebnisse zeigen, dass in der Idealgruppe keine signifikante Blutdrucksenkung beobachtet werden konnte. Dies lässt sich durch die Tatsache erklären, dass die Lebens-mittel- und Nährstoffaufnahme der deutschen

  5. Integrating spot short-term measurements of carbon emissions and backward dietary energy partition calculations to estimate intake in lactating dairy cows fed ad libitum or restricted.

    PubMed

    Pereira, A B D; Utsumi, S A; Dorich, C D; Brito, A F

    2015-12-01

    The objective of this study was to use spot short-term measurements of CH4 (QCH4) and CO2 (QCO2) integrated with backward dietary energy partition calculations to estimate dry matter intake (DMI) in lactating dairy cows. Twelve multiparous cows averaging 173±37d in milk and 4 primiparous cows averaging 179±27d in milk were blocked by days in milk, parity, and DMI (as a percentage of body weight) and, within each block, randomly assigned to 1 of 2 treatments: ad libitum intake (AL) or restricted intake (RI=90% DMI) according to a crossover design. Each experimental period lasted 22d with 14d for treatments adaptation and 8d for data and sample collection. Diets contained (dry matter basis): 40% corn silage, 12% grass-legume haylage, and 48% concentrate. Spot short-term gas measurements were taken in 5-min sampling periods from 15 cows (1 cow refused sampling) using a portable, automated, open-circuit gas quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) with intervals of 12h between the 2daily samples. Sampling points were advanced 2h from a day to the next to yield 16 gas samples per cow over 8d to account for diurnal variation in QCH4 and QCO2. The following equations were used sequentially to estimate DMI: (1) heat production (MJ/d)=(4.96 + 16.07 ÷ respiratory quotient) × QCO2; respiratory quotient=0.95; (2) metabolizable energy intake (MJ/d)=(heat production + milk energy) ± tissue energy balance; (3) digestible energy (DE) intake (MJ/d)=metabolizable energy + CH4 energy + urinary energy; (4) gross energy (GE) intake (MJ/d)=DE + [(DE ÷ in vitro true dry matter digestibility) - DE]; and (5) DMI (kg/d)=GE intake estimated ÷ diet GE concentration. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) and Fit Model procedure in JMP (α=0.05; SAS Institute Inc.). Cows significantly differed in DMI measured (23.8 vs. 22.4kg/d for AL and RI, respectively). Dry matter intake estimated using QCH4 and QCO2 coupled with

  6. Effect of CSN1S1 genotype and its interaction with diet energy level on milk production and quality in Girgentana goats fed ad libitum.

    PubMed

    Pagano, Renato Italo; Pennisi, Pietro; Valenti, Bernardo; Lanza, Massimiliano; Di Trana, Adriana; Di Gregorio, Paola; De Angelis, Anna; Avondo, Marcella

    2010-05-01

    A study was carried out to evaluate how the energy level of the diet can affect milk production and quality in Girgentana lactating goats in relation to polymorphism at the alphas1-casein (CSN1S1) genotype locus. Twenty-seven goats, homogeneous for milk production (1.5+/-0.3 kg/d), days of lactation (90+/-10 d) and body weight (35.8+/-5.5 kg) were selected on the basis of their CSN1S1 genotype, as follows: nine goats homozygous for strong (AA) alleles, nine goats homozygous for weak alleles (FF) and nine goats heterozygous (AF). The goats were used in a 3x3 factorial arrangement of treatments, with three genotypes (AA, FF, AF) and three diets at different energy levels (100%, 65% and 30% of hay inclusion). The experiment consisted of three simultaneous 3x3 Latin squares for the three genotypes, with one square for each level of hay inclusion in the diet. All the animals were housed in individual pens. Each experimental period lasted 23 d and consisted of 15 d for adaptation and 8 d for data and sample collection, during which the goats received the scheduled diet ad libitum. The animals were fed three different diets designed to have the same crude protein content (about 15%) but different energy levels: a pelleted alfalfa hay (H100) and two feeds including 65% (H65) and 30% (H30) of alfalfa hay (respectively 1099, 1386 and 1590 kcal NE for lactation/kg DM). All the diets were ground and pelleted (6 mm diameter). AA goats were more productive than AF and FF goats (respectively: 1419 v. 1145 and 1014 g/d; P=0.002). Indeed the interaction energy levelxgenotype was significant (P=0.018): in fact AA goats showed their milk increase only when fed with concentrates. Differences in protein and in casein levels between the three genotypes were in line with results expected from the different allele contribution to alphas1-casein synthesis. Milk urea levels were significantly lower in AA goats compared with AF and FF genotypes (respectively 32.7 v. 40.4 and 40.4 mg/dl; P=0

  7. Integrating spot short-term measurements of carbon emissions and backward dietary energy partition calculations to estimate intake in lactating dairy cows fed ad libitum or restricted.

    PubMed

    Pereira, A B D; Utsumi, S A; Dorich, C D; Brito, A F

    2015-12-01

    The objective of this study was to use spot short-term measurements of CH4 (QCH4) and CO2 (QCO2) integrated with backward dietary energy partition calculations to estimate dry matter intake (DMI) in lactating dairy cows. Twelve multiparous cows averaging 173±37d in milk and 4 primiparous cows averaging 179±27d in milk were blocked by days in milk, parity, and DMI (as a percentage of body weight) and, within each block, randomly assigned to 1 of 2 treatments: ad libitum intake (AL) or restricted intake (RI=90% DMI) according to a crossover design. Each experimental period lasted 22d with 14d for treatments adaptation and 8d for data and sample collection. Diets contained (dry matter basis): 40% corn silage, 12% grass-legume haylage, and 48% concentrate. Spot short-term gas measurements were taken in 5-min sampling periods from 15 cows (1 cow refused sampling) using a portable, automated, open-circuit gas quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) with intervals of 12h between the 2daily samples. Sampling points were advanced 2h from a day to the next to yield 16 gas samples per cow over 8d to account for diurnal variation in QCH4 and QCO2. The following equations were used sequentially to estimate DMI: (1) heat production (MJ/d)=(4.96 + 16.07 ÷ respiratory quotient) × QCO2; respiratory quotient=0.95; (2) metabolizable energy intake (MJ/d)=(heat production + milk energy) ± tissue energy balance; (3) digestible energy (DE) intake (MJ/d)=metabolizable energy + CH4 energy + urinary energy; (4) gross energy (GE) intake (MJ/d)=DE + [(DE ÷ in vitro true dry matter digestibility) - DE]; and (5) DMI (kg/d)=GE intake estimated ÷ diet GE concentration. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) and Fit Model procedure in JMP (α=0.05; SAS Institute Inc.). Cows significantly differed in DMI measured (23.8 vs. 22.4kg/d for AL and RI, respectively). Dry matter intake estimated using QCH4 and QCO2 coupled with

  8. Long-term effects of ad libitum whole milk prior to weaning and prepubertal protein supplementation on skeletal growth rate and first-lactation milk production.

    PubMed

    Moallem, U; Werner, D; Lehrer, H; Zachut, M; Livshitz, L; Yakoby, S; Shamay, A

    2010-06-01

    Our objectives were to determine the effects of rapid growth rate during the preweaning period and prepubertal protein supplementation on long-term growth pattern and milk production during the first lactation. Forty-six Israeli Holstein heifer calves were fed either milk replacer (MR) or whole milk (WM) from 4 to 60 d age. Calves had free access to WM or MR for 30 min twice daily and free-choice water and starter mix for the entire day. From weaning until 150 d of age, all heifers were fed the same ration. At 150 d of age the heifers were divided into 2 subgroups, with one subgroup supplemented with an additional 2% protein until 320 d of age. Thereafter, all heifers were housed and fed together until calving. Another cluster of 20 heifers was raised on MR and WM treatments and 3 animals from each nursery treatment were slaughtered at 60 d and 10 mo age to determine effects of nursery treatment on organ and adipose tissue mass. Prior to weaning, the MR heifers consumed 0.12 kg/d more DM than the WM heifers, but metabolizable energy intake was not different. Body weight at weaning and average daily gain during the preweaning period were 3.1 kg and 0.074 kg/d higher, respectively, in the WM treatment than in the MR treatment, with no differences in other measurements. Nursery feeding treatment and added protein had no effect on growth rate in the prepubertal period, but the postweaning difference in BW between the WM and MR heifers remained throughout the entire rearing period. The age at first insemination was 23 d earlier and age at pregnancy and first calving was numerically lower for the WM heifers than for the MR heifers. Adipose tissue weights at weaning were doubled in the WM calves. First-lactation milk production and 4% fat-corrected milk were 10.3 and 7.1% higher, respectively, for WM heifers than for MR heifers, whereas prepubertal added protein tended to increase milk yield. In conclusion, preweaning WM at high feeding rates appears to have long

  9. Short communication: Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted.

    PubMed

    Dorich, C D; Varner, R K; Pereira, A B D; Martineau, R; Soder, K J; Brito, A F

    2015-04-01

    The objective of this study was to measure enteric CH4 emissions using a new portable automated open-circuit gas quantification system (GQS) and the sulfur hexafluoride tracer technique (SF6) in midlactation Holstein cows housed in a tiestall barn. Sixteen cows averaging 176 ± 34 d in milk, 40.7 ± 6.1 kg of milk yield, and 685 ± 49 kg of body weight were randomly assigned to 1 out of 2 treatments according to a crossover design. Treatments were (1) ad libitum (adjusted daily to yield 10% orts) and (2) restricted feed intake [set to restrict feed by 10% of baseline dry matter intake (DMI)]. Each experimental period lasted 22d, with 14 d for treatment adaptation and 8d for data and sample collection. A common diet was fed to the cows as a total mixed ration and contained 40.4% corn silage, 11.2% grass-legume haylage, and 48.4% concentrate on a dry matter basis. Spot 5-min measurements using the GQS were taken twice daily with a 12-h interval between sampling and sampling times advanced 2h daily to account for diurnal variation in CH4 emissions. Canisters for the SF6 method were sampled twice daily before milking with 4 local background gas canisters inside the barn analyzed for background gas concentrations. Enteric CH4 emissions were not affected by treatments and averaged 472 and 458 g/d (standard error of the mean = 18 g/d) for ad libitum and restricted intake treatments, respectively (data not shown). The GQS appears to be a reliable method because of the relatively low coefficients of variation (ranging from 14.1 to 22.4%) for CH4 emissions and a moderate relationship (coefficient of determination = 0.42) between CH4 emissions and DMI. The SF6 resulted in large coefficients of variation (ranging from 16.0 to 111%) for CH4 emissions and a poor relationship (coefficient of determination = 0.17) between CH4 emissions and DMI, likely because of limited barn ventilation and high background gas concentration. Research with improved barn ventilation systems or

  10. Short communication: Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted.

    PubMed

    Dorich, C D; Varner, R K; Pereira, A B D; Martineau, R; Soder, K J; Brito, A F

    2015-04-01

    The objective of this study was to measure enteric CH4 emissions using a new portable automated open-circuit gas quantification system (GQS) and the sulfur hexafluoride tracer technique (SF6) in midlactation Holstein cows housed in a tiestall barn. Sixteen cows averaging 176 ± 34 d in milk, 40.7 ± 6.1 kg of milk yield, and 685 ± 49 kg of body weight were randomly assigned to 1 out of 2 treatments according to a crossover design. Treatments were (1) ad libitum (adjusted daily to yield 10% orts) and (2) restricted feed intake [set to restrict feed by 10% of baseline dry matter intake (DMI)]. Each experimental period lasted 22d, with 14 d for treatment adaptation and 8d for data and sample collection. A common diet was fed to the cows as a total mixed ration and contained 40.4% corn silage, 11.2% grass-legume haylage, and 48.4% concentrate on a dry matter basis. Spot 5-min measurements using the GQS were taken twice daily with a 12-h interval between sampling and sampling times advanced 2h daily to account for diurnal variation in CH4 emissions. Canisters for the SF6 method were sampled twice daily before milking with 4 local background gas canisters inside the barn analyzed for background gas concentrations. Enteric CH4 emissions were not affected by treatments and averaged 472 and 458 g/d (standard error of the mean = 18 g/d) for ad libitum and restricted intake treatments, respectively (data not shown). The GQS appears to be a reliable method because of the relatively low coefficients of variation (ranging from 14.1 to 22.4%) for CH4 emissions and a moderate relationship (coefficient of determination = 0.42) between CH4 emissions and DMI. The SF6 resulted in large coefficients of variation (ranging from 16.0 to 111%) for CH4 emissions and a poor relationship (coefficient of determination = 0.17) between CH4 emissions and DMI, likely because of limited barn ventilation and high background gas concentration. Research with improved barn ventilation systems or

  11. Metabolic determinants of body weight after cats were fed a low-carbohydrate high-protein diet or a high-carbohydrate low-protein diet ad libitum for 8 wk.

    PubMed

    Coradini, M; Rand, J S; Morton, J M; Rawlings, J M

    2014-10-01

    Overweight and obese conditions are common in cats and are associated with the development of a number of diseases. Knowledge of metabolic determinants and predictors of weight gain may enable better preventative strategies for obesity in cats. Lean, healthy cats were fed either a low-carbohydrate high-protein diet (n 16) or a high-carbohydrate low-protein (n 16) diet ad libitum for 8 wk. Potential determinants and predictors of final body weight assessed were body fat and lean masses, energy required for maintenance, energy requirements above maintenance for each kilogram of weight gain, insulin sensitivity index, fasting, mean 24-h and peak plasma glucose, insulin, and leptin concentrations, and fasting and mean 24-h serum adiponectin concentrations. In cats fed the low-carbohydrate high-protein diet, after adjusting for initial body weight, those with higher energy requirements for weight gain and higher fasting glucose concentration had higher final body weights (P ≤ 0.01). Predicted final body weights using initial body weight, fasting glucose and mean 24-h insulin concentrations (partial R(2) 37.3%) were imprecise. An equation using just initial body weight and fasting glucose concentration would be of more practical value, but was marginally less precise. In cats fed the high-carbohydrate low-protein diet, those with lower fasting leptin concentration initially had higher final body weights (P = 0.01). Predicted final body weights using initial body weight, energy requirements for maintenance, total body fat percentage and fasting leptin concentration (partial R(2) 39.2%) were reasonably precise. Further studies are warranted to confirm these findings and to improve the precision of predicted final body weights. PMID:25084314

  12. Metabolic determinants of body weight after cats were fed a low-carbohydrate high-protein diet or a high-carbohydrate low-protein diet ad libitum for 8 wk.

    PubMed

    Coradini, M; Rand, J S; Morton, J M; Rawlings, J M

    2014-10-01

    Overweight and obese conditions are common in cats and are associated with the development of a number of diseases. Knowledge of metabolic determinants and predictors of weight gain may enable better preventative strategies for obesity in cats. Lean, healthy cats were fed either a low-carbohydrate high-protein diet (n 16) or a high-carbohydrate low-protein (n 16) diet ad libitum for 8 wk. Potential determinants and predictors of final body weight assessed were body fat and lean masses, energy required for maintenance, energy requirements above maintenance for each kilogram of weight gain, insulin sensitivity index, fasting, mean 24-h and peak plasma glucose, insulin, and leptin concentrations, and fasting and mean 24-h serum adiponectin concentrations. In cats fed the low-carbohydrate high-protein diet, after adjusting for initial body weight, those with higher energy requirements for weight gain and higher fasting glucose concentration had higher final body weights (P ≤ 0.01). Predicted final body weights using initial body weight, fasting glucose and mean 24-h insulin concentrations (partial R(2) 37.3%) were imprecise. An equation using just initial body weight and fasting glucose concentration would be of more practical value, but was marginally less precise. In cats fed the high-carbohydrate low-protein diet, those with lower fasting leptin concentration initially had higher final body weights (P = 0.01). Predicted final body weights using initial body weight, energy requirements for maintenance, total body fat percentage and fasting leptin concentration (partial R(2) 39.2%) were reasonably precise. Further studies are warranted to confirm these findings and to improve the precision of predicted final body weights.

  13. Differential effects of methamphetamine on expression of neuropeptide Y mRNA in hypothalamus and on serum leptin and ghrelin concentrations in ad libitum-fed and schedule-fed rats.

    PubMed

    Crowley, W R; Ramoz, G; Keefe, K A; Torto, R; Kalra, S P; Hanson, G R

    2005-01-01

    Relatively little is known concerning the interaction of psychostimulants with hypothalamic neuropeptide systems or metabolic hormones implicated in regulation of energy balance. The present studies tested whether methamphetamine alters the expression of neuropeptide Y (NPY) and agouti-related peptide (AgRP), two important orexigenic neuropeptides, or proopiomelanocortin (POMC), the precursor for the anorexigenic peptide alpha-melanocyte-stimulating hormone, or the secretion of leptin, insulin and ghrelin, concomitant with inhibition of food intake. Female rats were either fed ad libitum (AL) or placed on a scheduled feeding (SF) regimen, with access to food limited to 4 h/day. Administration of (+/-)-methamphetamine (7.5 mg/kg, i.p.) 2 h prior to food presentation significantly inhibited food intake in SF animals, but did not affect intake in AL animals. In a separate study, AL and SF animals were killed just prior to expected food presentation, and expression of NPY, AgRP and POMC mRNAs in hypothalamus was determined using in situ hybridisation; concentrations of leptin, insulin and ghrelin in serum were determined with radioimmunoassays. In saline-treated, SF controls, NPY and AgRP mRNA expression in arcuate nucleus and serum ghrelin were significantly elevated, and serum leptin and insulin were significantly reduced. Methamphetamine reversed the up-regulation of NPY mRNA expression observed in the SF condition, without affecting AgRP mRNA or the serum concentrations of metabolic hormones. However, in AL animals, NPY mRNA expression in arcuate and dorsomedial nuclei was significantly increased by methamphetamine, which also reduced serum leptin and insulin and increased serum ghrelin concentrations. These findings suggest that the inhibition of NPY expression in SF animals may be a mechanism underlying the anorexigenic effect of methamphetamine seen in this condition. The increase in NPY expression produced by methamphetamine in AL animals may be mediated by the

  14. Effects of adding HfO2 on the microstructure and dielectric properties of giant dielectric constant ceramic CaCu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Yuan, W. X.; Hark, S. K.

    2010-03-01

    CaCu3Ti4O12 (CCTO), an unusual perovskite-like ceramic, is known for its extraordinarily high (˜10^4) and relatively frequency independent dielectric constant. It has drawn a lot of attention recently because of its potential applications in microelectronics and microwave devices. In this investigation, HfO2 powder was added to a pre-reacted CCTO powder, which was synthesized by a conventional solid-state reaction, at different concentrations from 1 to 70 wt% and the mixture was sintered into disc-shaped ceramic samples. The effects of adding HfO2 on the microstructure and dielectric properties of CCTO ceramics were investigated. In general, we found that the dielectric constant tends to increase with HfO2 addition up to 8 wt% and then decrease with further addition. Moreover, the dielectric loss was also influenced by the addition of HfO2, and a low loss tangent of ˜0.035 was obtained. The ac conductivity, impedance, complex dielectric permittivity and electric modulus graphs were used to analyze the data. These observations were explained on the basis of the internal-barrier-layer capacitor model with Maxwell-Wagner relaxations.

  15. Moderate caloric restriction in lactating rats programs their offspring for a better response to HF diet feeding in a sex-dependent manner.

    PubMed

    Palou, Mariona; Torrens, Juana María; Priego, Teresa; Sánchez, Juana; Palou, Andreu; Picó, Catalina

    2011-06-01

    We aimed to assess the lasting effects of moderate caloric restriction in lactating rats on the expression of key genes involved in energy balance of their adult offspring (CR) and their adaptations under high-fat (HF) diet. Dams were fed with either ad libitum normal-fat (NF) diet or a 30% caloric restricted diet throughout lactation. After weaning, the offspring were fed with NF diet until the age of 15 weeks and then with an NF or a HF diet until the age of 28 weeks, when they were sacrificed. Body weight and food intake were followed. Blood parameters and the expression of selected genes in hypothalamus and white adipose tissue (WAT) were analysed. CR ate fewer calories and showed lower body weight gain under HF diet than their controls. CR males were also resistant to the increase of insulin and leptin occurring in their controls under HF diet, and HF diet exposed CR females showed lower circulating fasting triglyceride levels than controls. In the hypothalamus, CR males had higher ObRb mRNA levels than controls, and CR females displayed greater InsR mRNA levels than controls and decreased neuropeptide Y mRNA levels when exposed to HF diet. CR males maintained WAT capacity of fat uptake and storage and of fatty-acid oxidation under HF diet, whereas these capacities were impaired in controls; female CR showed higher WAT ObRb mRNA levels than controls. These results suggest that 30% caloric restriction in lactating dams ameliorates diet-induced obesity in their offspring by enhancing their sensitivity to insulin and leptin signaling, but in a gender-dependent manner.

  16. Improved single pellet grasping using automated ad libitum full-time training robot.

    PubMed

    Fenrich, Keith K; May, Zacnicte; Hurd, Caitlin; Boychuk, Carolyn E; Kowalczewski, Jan; Bennett, David J; Whishaw, Ian Q; Fouad, Karim

    2015-03-15

    The single pellet grasping (SPG) task is a skilled forelimb motor task commonly used to evaluate reaching and grasp kinematics and recovery of forelimb function in rodent models of CNS injuries and diseases. To train rats in the SPG task, the animals are usually food restricted then placed in an SPG task enclosure and presented food pellets on a platform located beyond a slit located at the front of the task enclosure for 10-30 min, normally every weekday for several weeks. When the SPG task is applied in studies involving various experimental groups, training quickly becomes labor intensive, and can yield results with significant day-to-day variability. Furthermore, training is frequently done during the animals' light-cycle, which for nocturnal rodents such as mice and rats could affect performance. Here we describe an automated pellet presentation (APP) robotic system to train and test rats in the SPG task that reduces some of the procedural weaknesses of manual training. We found that APP trained rats performed significantly more trials per 24 h period, and had higher success rates with less daily and weekly variability than manually trained rats. Moreover, the results show that success rates are positively correlated with the number of dark-cycle trials, suggesting that dark-cycle training has a positive effect on success rates. These results demonstrate that automated training is an effective method for evaluating and training skilled reaching performance of rats, opening up the possibility for new approaches to investigating the role of motor systems in enabling skilled forelimb use and new approaches to investigating rehabilitation following CNS injury. PMID:25523027

  17. Improved single pellet grasping using automated ad libitum full-time training robot.

    PubMed

    Fenrich, Keith K; May, Zacnicte; Hurd, Caitlin; Boychuk, Carolyn E; Kowalczewski, Jan; Bennett, David J; Whishaw, Ian Q; Fouad, Karim

    2015-03-15

    The single pellet grasping (SPG) task is a skilled forelimb motor task commonly used to evaluate reaching and grasp kinematics and recovery of forelimb function in rodent models of CNS injuries and diseases. To train rats in the SPG task, the animals are usually food restricted then placed in an SPG task enclosure and presented food pellets on a platform located beyond a slit located at the front of the task enclosure for 10-30 min, normally every weekday for several weeks. When the SPG task is applied in studies involving various experimental groups, training quickly becomes labor intensive, and can yield results with significant day-to-day variability. Furthermore, training is frequently done during the animals' light-cycle, which for nocturnal rodents such as mice and rats could affect performance. Here we describe an automated pellet presentation (APP) robotic system to train and test rats in the SPG task that reduces some of the procedural weaknesses of manual training. We found that APP trained rats performed significantly more trials per 24 h period, and had higher success rates with less daily and weekly variability than manually trained rats. Moreover, the results show that success rates are positively correlated with the number of dark-cycle trials, suggesting that dark-cycle training has a positive effect on success rates. These results demonstrate that automated training is an effective method for evaluating and training skilled reaching performance of rats, opening up the possibility for new approaches to investigating the role of motor systems in enabling skilled forelimb use and new approaches to investigating rehabilitation following CNS injury.

  18. Enhancement in the transport critical current density Jc in YBa2Cu3O7-δ added with an insulating nano crystalline YBa2HfO5.5 perovskite

    NASA Astrophysics Data System (ADS)

    Rejith, P. P.; Vidya, S.; Solomon, Sam; Thomas, J. K.

    2014-01-01

    When a magnetic field is applied to type II superconductors, such as YBa2Cu307-δ (YBCO), the flux quanta penetrate the material as a regular array of vortices. However when transport currents are applied, they act to move these vortices, thus lowers the critical current density (Jc) as well as destroying superconductivity. The development of microstructures made of YBCO materials has enabled engineers to increase the critical current density, within Type II materials by introducing flux pinning centres into the material. The microstructure and flux pinning properties of YBa2Cu3O7-δ system with varying levels (0-5 wt. %) of a nano perovskite ceramic insulator; YBa2HfO5.5 addition was studied in detail. Orthorhombic YBa2Cu3O7-δ powder was prepared through conventional solid state route and a modified combustion method was used for synthesizing nanocrystalline YBa2HfO5.5. The structure and microstructure of the samples examined by X-ray diffraction and scanning electron microscopy showed that YBa2HfO5.5 and YBCO remained unreacted even at higher processing temperature without deteriorating the superconducting properties. The scanning electron microscope image shows that YBa2HfO5.5 forms an electrical-network between grains. These observations suggest that the YBa2HfO5.5 addition to the Y-123-compounds improve the electrical connection between superconducting grains and substantial improvements in the relative electrical transport properties of the composites. The variation of sintering temperature, density, critical transition temperature (Tc) and magnetic field dependence of critical current density (Jc) of YBa2Cu3O7-δ having different proportions of YBa2HfO5.5 in the matrix were also studied in detail. It is found that the addition of these elements considerably enhances the flux pinning strength of the system, and there is also an increase of critical temperature (Tc) and critical current density (Jc) up to an optimum value of 8.76 × 104 A/cm2 for a

  19. Food branding influences ad libitum intake differently in children depending on weight status. Results of a pilot study.

    PubMed

    Forman, Jamie; Halford, Jason C G; Summe, Heather; MacDougall, Megan; Keller, Kathleen L

    2009-08-01

    Environmental changes have facilitated the rapid increase in childhood obesity. One such change is increased presence of food marketing which promotes intake of high-fat, energy-dense foods. This study tested the hypotheses that overweight (OW) children are more sensitive to the intake-enhancing effects of food branding than non-OW children, and that the relationship between weight status and intake of branded foods is mediated by level of food brand awareness. Forty-three non-OW (n = 23) and OW (n = 20) children from diverse ethnic backgrounds participated in four dinnertime visits to test their intake of meals where food brands were present ("branded") or absent ("unbranded"). Food brand awareness was assessed by testing children's abilities to match food brand logos with correct foods and name specific brands from recall. Weight and height were measured on the first visit to determine BMI z-score and weight status. OW children consumed significantly more energy per meal than non-OW. Child age and brand awareness were positively associated. OW children consumed an additional 40 kcal in branded vs. unbranded meals whereas non-OW children consumed 45 kcal less in branded meals. Overweight children showed greater responsiveness to food branding, and they may be at risk in environments that are highly inundated with messages about food.

  20. Demonstration of tank effect on growth indices of juvenile rainbow trout (Oncorhynchus mykiss) during an ad libitum feeding trial.

    PubMed

    Speare, D J; MacNair, N; Hammell, K L

    1995-10-01

    Growth indices were examined in 24 identically managed tanks, each containing 120 diploid juvenile rainbow trout (initial mean body weight, 9.3 g) during a 12-week study to examine tank effects associated with tank location in a multi user research facility. Growth indices included mean body weight, feed intake, feed conversion index, and specific growth rate. The null hypothesis that tank effect had no effect on growth over the 12-week period was rejected (P = 0.038), and mean weight in individual tanks differed by as much as 18.7%). During the study it was determined that the proximity of tanks to common-use walkways in the facility could affect growth indices. This was indicated by significant differences in the mean fish weights among blocks of tanks served by different header tanks after 4 (P = 0.001) and 8 (P = 0.024) week. The block containing tanks of fish with the highest them weight was nearest to the 2 common-use walkways in the facility. Fish in this block of tanks, compared with those in other blocks, had significantly greater feed intake but no significant differences in conversion efficiency. Compensatory growth, a well known growth attribute in fishes, diminished the difference in mean weight be tween these blocks of tanks by the end of the study. Comparison of paired ranks within header tank blocks indicated that fish in those located nearest to walkways had higher feeding rates over the 12-week period (P = 0.048), but less efficient feed conversion (P = 0.040) than did fish in matched tanks located farthest from walkways. However, there were no differences in mean weight of fish. Results of this trial document the risks involved in identifying fish in a tank as the experimental unit when treatments are administered to the tank of fish, the latter being the true experimental unit.

  1. Chocolate versions of the Food Cravings Questionnaires. Associations with chocolate exposure-induced salivary flow and ad libitum chocolate consumption.

    PubMed

    Meule, Adrian; Hormes, Julia M

    2015-08-01

    The Food Cravings Questionnaires are the most commonly used instruments for the assessment of trait and state food craving. Chocolate is the most frequently craved food in Western societies. In the current studies, the Food Cravings Questionnaire-Trait-reduced (FCQ-T-r) and the Food Cravings Questionnaire-State (FCQ-S) were adapted to capture strong urges for chocolate. In study 1, students (n = 492; 81.3% female) completed chocolate versions of the FCQ-T-r and FCQ-S among other measures online. The FCQ-T-r (α = .94) comprised two subscales representing lack of control (α = .91) and thoughts about chocolate (α = .91). The FCQ-S (α = .87) comprised two subscales representing chocolate craving (α = .90) and hunger (α = .85). FCQ-T-r scores were significantly and positively correlated with self-reported frequency of consuming chocolate and with scores on the Attitudes to Chocolate Questionnaire, indicating good convergent validity. In study 2, students (n = 76; 73.7% female) underwent a chocolate exposure in the laboratory. FCQ-S scores increased during chocolate exposure and increases in momentary chocolate craving were significantly positively correlated with increases in salivary flow. Higher momentary chocolate craving was positively correlated with higher laboratory chocolate consumption. Exploratory analyses revealed that increases in salivary flow were only associated with increased chocolate consumption in participants scoring high, but not low on trait chocolate craving. The chocolate versions of the FCQ-T-r and FCQ-S represent reliable and valid self-report measures for the assessment of trait and state chocolate craving.

  2. Food branding influences ad libitum intake differently in children depending on weight status. Results of a pilot study.

    PubMed

    Forman, Jamie; Halford, Jason C G; Summe, Heather; MacDougall, Megan; Keller, Kathleen L

    2009-08-01

    Environmental changes have facilitated the rapid increase in childhood obesity. One such change is increased presence of food marketing which promotes intake of high-fat, energy-dense foods. This study tested the hypotheses that overweight (OW) children are more sensitive to the intake-enhancing effects of food branding than non-OW children, and that the relationship between weight status and intake of branded foods is mediated by level of food brand awareness. Forty-three non-OW (n = 23) and OW (n = 20) children from diverse ethnic backgrounds participated in four dinnertime visits to test their intake of meals where food brands were present ("branded") or absent ("unbranded"). Food brand awareness was assessed by testing children's abilities to match food brand logos with correct foods and name specific brands from recall. Weight and height were measured on the first visit to determine BMI z-score and weight status. OW children consumed significantly more energy per meal than non-OW. Child age and brand awareness were positively associated. OW children consumed an additional 40 kcal in branded vs. unbranded meals whereas non-OW children consumed 45 kcal less in branded meals. Overweight children showed greater responsiveness to food branding, and they may be at risk in environments that are highly inundated with messages about food. PMID:19481125

  3. Hairy AdS solitons

    NASA Astrophysics Data System (ADS)

    Anabalón, Andrés; Astefanesei, Dumitru; Choque, David

    2016-11-01

    We construct exact hairy AdS soliton solutions in Einstein-dilaton gravity theory. We examine their thermodynamic properties and discuss the role of these solutions for the existence of first order phase transitions for hairy black holes. The negative energy density associated to hairy AdS solitons can be interpreted as the Casimir energy that is generated in the dual filed theory when the fermions are antiperiodic on the compact coordinate.

  4. Advanced HF anti-jam network architecture

    NASA Astrophysics Data System (ADS)

    Jackson, E. M.; Horner, Robert W.; Cai, Khiem V.

    The Hughes HF2000 system was developed using a flexible architecture which utilizes a wideband RF front-end and extensive digital signal processing. The HF2000 antijamming (AJ) mode was field tested via an HF skywave path between Fullerton, CA and Carlsbad, CA (about 100 miles), and it was shown that reliable fast frequency-hopping data transmission is feasible at 2400 b/s without adaptive equalization. The necessary requirements of an HF communication network are discussed, and how the HF2000 AJ mode can be used to support those requirements is shown. The Hughes HF2000 AJ mode system architecture is presented.

  5. Value Added?

    ERIC Educational Resources Information Center

    UCLA IDEA, 2012

    2012-01-01

    Value added measures (VAM) uses changes in student test scores to determine how much "value" an individual teacher has "added" to student growth during the school year. Some policymakers, school districts, and educational advocates have applauded VAM as a straightforward measure of teacher effectiveness: the better a teacher, the better students…

  6. Enhancement in the transport critical current density J{sub c} in YBa{sub 2}Cu{sub 3}O{sub 7−δ} added with an insulating nano crystalline YBa{sub 2}HfO{sub 5.5} perovskite

    SciTech Connect

    Rejith, P. P.; Vidya, S.; Thomas, J. K.; Solomon, Sam

    2014-01-28

    When a magnetic field is applied to type II superconductors, such as YBa{sub 2}Cu{sub 3}0{sub 7−δ} (YBCO), the flux quanta penetrate the material as a regular array of vortices. However when transport currents are applied, they act to move these vortices, thus lowers the critical current density (J{sub c}) as well as destroying superconductivity. The development of microstructures made of YBCO materials has enabled engineers to increase the critical current density, within Type II materials by introducing flux pinning centres into the material. The microstructure and flux pinning properties of YBa{sub 2}Cu{sub 3}O{sub 7−δ} system with varying levels (0-5 wt. %) of a nano perovskite ceramic insulator; YBa{sub 2}HfO{sub 5.5} addition was studied in detail. Orthorhombic YBa{sub 2}Cu{sub 3}O{sub 7−δ} powder was prepared through conventional solid state route and a modified combustion method was used for synthesizing nanocrystalline YBa{sub 2}HfO{sub 5.5}. The structure and microstructure of the samples examined by X-ray diffraction and scanning electron microscopy showed that YBa{sub 2}HfO{sub 5.5} and YBCO remained unreacted even at higher processing temperature without deteriorating the superconducting properties. The scanning electron microscope image shows that YBa{sub 2}HfO{sub 5.5} forms an electrical-network between grains. These observations suggest that the YBa{sub 2}HfO{sub 5.5} addition to the Y-123-compounds improve the electrical connection between superconducting grains and substantial improvements in the relative electrical transport properties of the composites. The variation of sintering temperature, density, critical transition temperature (T{sub c}) and magnetic field dependence of critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}O{sub 7−δ} having different proportions of YBa{sub 2}HfO{sub 5.5} in the matrix were also studied in detail. It is found that the addition of these elements considerably enhances the flux pinning

  7. The dipolar endofullerene HF@C60.

    PubMed

    Krachmalnicoff, Andrea; Bounds, Richard; Mamone, Salvatore; Alom, Shamim; Concistrè, Maria; Meier, Benno; Kouřil, Karel; Light, Mark E; Johnson, Mark R; Rols, Stéphane; Horsewill, Anthony J; Shugai, Anna; Nagel, Urmas; Rõõm, Toomas; Carravetta, Marina; Levitt, Malcolm H; Whitby, Richard J

    2016-10-01

    The cavity inside fullerenes provides a unique environment for the study of isolated atoms and molecules. We report the encapsulation of hydrogen fluoride inside C60 using molecular surgery to give the endohedral fullerene HF@C60. The key synthetic step is the closure of the open fullerene cage with the escape of HF minimized. The encapsulated HF molecule moves freely inside the cage and exhibits quantization of its translational and rotational degrees of freedom, as revealed by inelastic neutron scattering and infrared spectroscopy. The rotational and vibrational constants of the encapsulated HF molecules were found to be redshifted relative to free HF. The NMR spectra display a large (1)H-(19)F J coupling typical of an isolated species. The dipole moment of HF@C60 was estimated from the temperature dependence of the dielectric constant at cryogenic temperatures and showed that the cage shields around 75% of the HF dipole. PMID:27657872

  8. The dipolar endofullerene HF@C60

    NASA Astrophysics Data System (ADS)

    Krachmalnicoff, Andrea; Bounds, Richard; Mamone, Salvatore; Alom, Shamim; Concistrè, Maria; Meier, Benno; Kouřil, Karel; Light, Mark E.; Johnson, Mark R.; Rols, Stéphane; Horsewill, Anthony J.; Shugai, Anna; Nagel, Urmas; Rõõm, Toomas; Carravetta, Marina; Levitt, Malcolm H.; Whitby, Richard J.

    2016-10-01

    The cavity inside fullerenes provides a unique environment for the study of isolated atoms and molecules. We report the encapsulation of hydrogen fluoride inside C60 using molecular surgery to give the endohedral fullerene HF@C60. The key synthetic step is the closure of the open fullerene cage with the escape of HF minimized. The encapsulated HF molecule moves freely inside the cage and exhibits quantization of its translational and rotational degrees of freedom, as revealed by inelastic neutron scattering and infrared spectroscopy. The rotational and vibrational constants of the encapsulated HF molecules were found to be redshifted relative to free HF. The NMR spectra display a large 1H-19F J coupling typical of an isolated species. The dipole moment of HF@C60 was estimated from the temperature dependence of the dielectric constant at cryogenic temperatures and showed that the cage shields around 75% of the HF dipole.

  9. Environmentally friendly HF (DF) lasers

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.

    2016-08-01

    Dedicated to the 100th anniversary of the birth of Academician A M Prokhorov, this paper reviews the physics of self-sustained volume discharge without preionization—self-initiated volume discharge (SIVD)—in the working mixtures of non-chain hydrofluoride HF (deuterofluoride (DF)) lasers. The dynamics of SIVD in discharge gaps with different geometries is thoroughly described. The mechanisms for the restriction of current density in a diffuse channel in electric discharges in SF6 and SF6 based mixtures (which determines whether SIVD is possible) are proposed and analyzed using simple models. The most probable mechanisms are the electron impact dissociation of SF6 and other mixture components, electron–ion recombination and electron attachment to vibrationally excited SF6 molecules. Starting from a comparative analysis of the rate coefficients of these processes, it is shown that electron–ion recombination is capable of compensating for electron detachment from negative ions via electron impact. It is also established that SIVD is not only observed in SF6, but also in other strongly electronegative gases. The factors that determine the uniformity of the active medium in non-chain HF (DF) lasers are analyzed. Some special features of non-chain HF (DF) lasers with different apertures operating are carefully examined. Consideration is given to the problem of increasing the aperture and discharge volume of non-chain HF (DF) lasers. Based on our experimental results, the possibility of increasing the energy of such lasers to ~1 kJ and above is shown.

  10. Environmentally friendly HF (DF) lasers

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.

    2016-08-01

    Dedicated to the 100th anniversary of the birth of Academician A M Prokhorov, this paper reviews the physics of self-sustained volume discharge without preionization—self-initiated volume discharge (SIVD)—in the working mixtures of non-chain hydrofluoride HF (deuterofluoride (DF)) lasers. The dynamics of SIVD in discharge gaps with different geometries is thoroughly described. The mechanisms for the restriction of current density in a diffuse channel in electric discharges in SF6 and SF6 based mixtures (which determines whether SIVD is possible) are proposed and analyzed using simple models. The most probable mechanisms are the electron impact dissociation of SF6 and other mixture components, electron-ion recombination and electron attachment to vibrationally excited SF6 molecules. Starting from a comparative analysis of the rate coefficients of these processes, it is shown that electron-ion recombination is capable of compensating for electron detachment from negative ions via electron impact. It is also established that SIVD is not only observed in SF6, but also in other strongly electronegative gases. The factors that determine the uniformity of the active medium in non-chain HF (DF) lasers are analyzed. Some special features of non-chain HF (DF) lasers with different apertures operating are carefully examined. Consideration is given to the problem of increasing the aperture and discharge volume of non-chain HF (DF) lasers. Based on our experimental results, the possibility of increasing the energy of such lasers to ~1 kJ and above is shown.

  11. Crystal growth of HfS 2 by chemical vapour transport with halogen (Cl, Br, I)

    NASA Astrophysics Data System (ADS)

    Fiechter, S.; Eckert, K.

    1988-05-01

    Single crystals of HfS 2 have been prepared by chemical vapour transport (CVT) with halogen. Depending on the transporting agent added, exergonic or endergonic transport was observed. Employing 0.5 mg/cm 3 chlorine or bromine in evacuated and sealed quartz ampoules, exergonic transport occurs. In a temperature gradient from 850 to 870 K transparent reddish-orange crystal platelets of pseudohexagonal shape (10×10×0.05 mm3) were obtained. Endergonic transport, found with iodine as transporting agent, first starts at higher temperatures (1270-1220 K). A thermochemical study of the vapour phase composition revealed that gaseous HfHal 4 and HfHal 3 ( Hal = Cl, Br) are responsible for the exergonic transport observed. Because of the higher stability of HfS 2 against iodine, CVT first starts at elevated temperatures. In the vapour phase Hfl and Hfl 2 dominate and effect a reversal of the transport direction.

  12. DIS in AdS

    SciTech Connect

    Albacete, Javier L.; Kovchegov, Yuri V.; Taliotis, Anastasios

    2009-03-23

    We calculate the total cross section for the scattering of a quark-anti-quark dipole on a large nucleus at high energy for a strongly coupled N = 4 super Yang-Mills theory using AdS/CFT correspondence. We model the nucleus by a metric of a shock wave in AdS{sub 5}. We then calculate the expectation value of the Wilson loop (the dipole) by finding the extrema of the Nambu-Goto action for an open string attached to the quark and antiquark lines of the loop in the background of an AdS{sub 5} shock wave. We find two physically meaningful extremal string configurations. For both solutions we obtain the forward scattering amplitude N for the quark dipole-nucleus scattering. We study the onset of unitarity with increasing center-of-mass energy and transverse size of the dipole: we observe that for both solutions the saturation scale Q{sub s} is independent of energy/Bjorken-x and depends on the atomic number of the nucleus as Q{sub s}{approx}A{sup 1/3}. Finally we observe that while one of the solutions we found corresponds to the pomeron intercept of {alpha}{sub P} = 2 found earlier in the literature, when extended to higher energy or larger dipole sizes it violates the black disk limit. The other solution we found respects the black disk limit and yields the pomeron intercept of {alpha}{sub P} = 1.5. We thus conjecture that the right pomeron intercept in gauge theories at strong coupling may be {alpha}{sub P} = 1.5.

  13. Surface-tension-tailored aqueous ink for low-temperature deposition of high-k HfO2 thin film

    NASA Astrophysics Data System (ADS)

    Han, Sun Woong; Lee, Keun Ho; Yoo, Young Bum; Park, Jee Ho; Song, Kie Moon; Baik, Hong Koo

    2016-08-01

    In this paper, solution-based deposition of HfO2 thin film at low temperature was demonstrated. By using aqueous HfCl4 solution, the precursor was effectively decomposed with low annealing temperature of 150 °C. Thus it is preferable to use this solution for dielectric coating on flexible substrates. To achieve conformal coating on substrate, formic acid as a cosolvent was added to aqueous ink solution to reduce surface tension of the solution. Due to improved coating quality of HfO2 thin film, the fabricated HfO2 gate dielectric shows reliable breakdown characteristics and low leakage current.

  14. Can HF heating generate ESF bubbles?

    NASA Astrophysics Data System (ADS)

    Zawdie, K. A.; Huba, J. D.

    2014-12-01

    The injection of powerful HF waves into the ionosphere can lead to strong electron heating followed by a pressure perturbation which can locally reduce the plasma density. In the postsunset equatorial ionosphere, density perturbations can provide the seed to generate equatorial spread F (ESF) bubbles. In this paper, a modified version of the SAMI3/ESF ionosphere code is used to model the density depletions created by HF heating and to determine if ESF bubbles can be artificially generated. It is found that HF heating primarily redistributes plasma along the geomagnetic field and does not significantly perturb the flux tube integrated conductivities. Thus, HF heating does not appear to be a viable method to seed or generate ESF bubbles.

  15. Cardiovascular, Metabolic Effects and Dietary Composition of Ad-Libitum Paleolithic vs. Australian Guide to Healthy Eating Diets: A 4-Week Randomised Trial.

    PubMed

    Genoni, Angela; Lyons-Wall, Philippa; Lo, Johnny; Devine, Amanda

    2016-01-01

    (1) BACKGROUND: The Paleolithic diet is popular in Australia, however, limited literature surrounds the dietary pattern. Our primary aim was to compare the Paleolithic diet with the Australian Guide to Healthy Eating (AGHE) in terms of anthropometric, metabolic and cardiovascular risk factors, with a secondary aim to examine the macro and micronutrient composition of both dietary patterns; (2) METHODS: 39 healthy women (mean ± SD age 47 ± 13 years, BMI 27 ± 4 kg/m²) were randomised to either the Paleolithic (n = 22) or AGHE diet (n = 17) for four weeks. Three-day weighed food records, body composition and biochemistry data were collected pre and post intervention; (3) RESULTS: Significantly greater weight loss occurred in the Paleolithic group (-1.99 kg, 95% CI -2.9, -1.0), p < 0.001). There were no differences in cardiovascular and metabolic markers between groups. The Paleolithic group had lower intakes of carbohydrate (-14.63% of energy (E), 95% CI -19.5, -9.7), sodium (-1055 mg/day, 95% CI -1593, -518), calcium (-292 mg/day 95% CI -486.0, -99.0) and iodine (-47.9 μg/day, 95% CI -79.2, -16.5) and higher intakes of fat (9.39% of E, 95% CI 3.7, 15.1) and β-carotene (6777 μg/day 95% CI 2144, 11410) (all p < 0.01); (4) CONCLUSIONS: The Paleolithic diet induced greater changes in body composition over the short-term intervention, however, larger studies are recommended to assess the impact of the Paleolithic vs. AGHE diets on metabolic and cardiovascular risk factors in healthy populations. PMID:27223304

  16. The clinical effect of dentifrices containing stabilized stannous fluoride on plaque formation and gingivitis--a six-month study with ad libitum brushing.

    PubMed

    Beiswanger, B B; Doyle, P M; Jackson, R D; Mallatt, M E; Mau, M s; Bollmer, B W; Crisanti, M M; Guay, C B; Lanzalaco, A C; Lukacovic, M F

    1995-01-01

    The effects of stabilized 0.454% stannous fluoride dentifrices on supragingival plaque, gingival inflammation and gingival bleeding were studied in 549 adult male and female subjects who completed a six-month, double blind clinical study. Following an oral prophylaxis, subjects were randomly assigned to brush with one of the following dentifrices: 1) 0.454% SnF2 stabilized with 2.08% sodium gluconate, 2) 0.454% SnF2 stabilized with 4.16% sodium gluconate, 3) an experimental dentifrice, or 4) 0.243% NaF control dentifrice. Follow-up examinations were conducted at 3 and 6 months. Compared to the control dentifrice at 6 months, stannous fluoride dentifrices stabilized with 2.08% or 4.16% sodium gluconate significantly reduced gingivitis by 18.8% and 18.0%, respectively. There were no statistically significant differences between the two stabilized SnF2 groups with respect to their beneficial effects on gingival health. Gingival bleeding was also reduced, relative to the control dentifrice, for both stabilized SnF2 dentifrices. However, these differences were not statistically significant at p=0.05. The stabilized SnF2 dentifrices were not significantly different from the control dentifrice in their effects on supragingival plaque. No significant differences in adverse oral soft tissue effects were observed between the test and control groups. As expected, accumulation of extrinsic tooth stain increased in the stabilized SnF2 groups. However, the difficulty in removing accumulated dental stain was similar between the control and stabilized SnF2 dentifrices. Since use of SnF2 dentifrices has been reported to produce tooth stain, gingivitis examinations were done with and without custom-made tooth covers to evaluate the potential for examiner bias. Comparable gingivitis and gingival bleeding benefits were observed when the evaluations were conducted with or without the tooth covers. Results from this study support that 0.454% stabilized stannous fluoride dentifrices can provide an important adjunct to the prevention and control of gingivitis when used in combination with regular personal oral hygiene procedures and professional care.

  17. Dietary protein level and source differentially affect bone metabolism, strength, and intestinal calcium transporter expression during ad libitum and food-restricted conditions in male rats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High protein diets may attenuate bone loss during energy restriction (ER). The objective of the current study was to determine whether high protein diets suppress bone turnover and improve bone quality in rats during ER and whether dietary protein source affects this relationship. Eighty 12-week o...

  18. Cardiovascular, Metabolic Effects and Dietary Composition of Ad-Libitum Paleolithic vs. Australian Guide to Healthy Eating Diets: A 4-Week Randomised Trial

    PubMed Central

    Genoni, Angela; Lyons-Wall, Philippa; Lo, Johnny; Devine, Amanda

    2016-01-01

    (1) Background: The Paleolithic diet is popular in Australia, however, limited literature surrounds the dietary pattern. Our primary aim was to compare the Paleolithic diet with the Australian Guide to Healthy Eating (AGHE) in terms of anthropometric, metabolic and cardiovascular risk factors, with a secondary aim to examine the macro and micronutrient composition of both dietary patterns; (2) Methods: 39 healthy women (mean ± SD age 47 ± 13 years, BMI 27 ± 4 kg/m2) were randomised to either the Paleolithic (n = 22) or AGHE diet (n = 17) for four weeks. Three-day weighed food records, body composition and biochemistry data were collected pre and post intervention; (3) Results: Significantly greater weight loss occurred in the Paleolithic group (−1.99 kg, 95% CI −2.9, −1.0), p < 0.001). There were no differences in cardiovascular and metabolic markers between groups. The Paleolithic group had lower intakes of carbohydrate (−14.63% of energy (E), 95% CI −19.5, −9.7), sodium (−1055 mg/day, 95% CI −1593, −518), calcium (−292 mg/day 95% CI −486.0, −99.0) and iodine (−47.9 μg/day, 95% CI −79.2, −16.5) and higher intakes of fat (9.39% of E, 95% CI 3.7, 15.1) and β-carotene (6777 μg/day 95% CI 2144, 11410) (all p < 0.01); (4) Conclusions: The Paleolithic diet induced greater changes in body composition over the short-term intervention, however, larger studies are recommended to assess the impact of the Paleolithic vs. AGHE diets on metabolic and cardiovascular risk factors in healthy populations. PMID:27223304

  19. Comparison of time-restricted and ad libitum self-feeding on the growth, feeding behavior and daily digestive enzyme profiles of Atlantic salmon

    NASA Astrophysics Data System (ADS)

    Shi, Ce; Liu, Ying; Yi, Mengmeng; Zheng, Jimeng; Tian, Huiqin; Du, Yishuai; Li, Xian; Sun, Guoxiang

    2016-07-01

    Although it has been hypothesized that a predictable feeding regime in animals allows physiological variables to be adjusted to maximize nutrient utilization and, hence, better growth performance, the assumption has rarely been tested. This study compares the Effects of time-restricted versus free access self-feeding on the growth, feeding behavior and daily digestive enzyme rhythms of Atlantic salmon (Salmo salar). In an experiment that lasted 6 weeks, fish (109.9 g) were divided into two groups: group 1 had free access to a self-feeder (FA); group 2 received three meals per day (2 h per meal) at dawn, midday and dusk via a time-restricted self-feeder (TR). At the end of the experiment, the fish were sampled every 3 h over a 24-h period. The results showed that the TR fish quickly synchronized their feeding behavior to the feeding window and their blood glucose showed a significant postprandial increase, while FA fish displayed no statistically significant rhythms (P<0.05). Pepsin activity of TR fish also showed a significant daily rhythm (P<0.05) with the acrophase at the second feed and a decrease over the next 12 h. Average daily trypsin, lipase and amylase levels of FA fish were significantly lower than those of TR fish (P<0.01); however, the growth performance of both groups was similar (P>0.05). In conclusion, the study failed to confirm a link between the entrainment of daily digestive enzyme profiles and growth performance, with the TR group showing comparatively poor blood glucose regulation.

  20. Drinking guidelines for exercise: what evidence is there that athletes should drink "as much as tolerable", "to replace the weight lost during exercise" or "ad libitum"?

    PubMed

    Noakes, T D

    2007-05-01

    The most recent (1996) drinking guidelines of the American College of Sports Medicine (ACSM) propose that athletes should drink "as much as tolerable" during exercise. Since some individuals can tolerate rates of free water ingestion that exceed their rates of free water loss during exercise, this advice has caused some to overdrink leading to water retention, weight gain and, in a few, death from exercise-associated hyponatraemic encephalopathy. The new drinking guidelines of the International Olympic Committee (IOC), recently re-published in this Journal, continue to argue that athletes must drink enough to replace all their weight lost during exercise and to ingest sodium chloride since sodium is "the electrolyte most critical to performance and health". In this rebuttal to that Consensus Document, I argue that these new guidelines, like their predecessors, lack an adequate, scientifically proven evidence base. Nor have they been properly evaluated in appropriately controlled, randomized, prospective clinical trials. In particular, these new guidelines provide erroneous recommendations on five topics. If novel universal guidelines for fluid ingestion during exercise are to be promulgated by important international bodies including the IOC, they should first be properly evaluated in appropriately controlled, randomized, prospective clinical trials conducted under environmental and other conditions that match those found in "out-of-doors" exercise. This, and the potential influence of commercial interests on scientific independence and objectivity, are the two most important lessons to be learned from the premature adoption of those 1996 ACSM drinking guidelines that are not evidence-based. These concerns need to be addressed before the novel IOC guidelines are accepted uncritically. Otherwise the predictable consequences of the premature adoption of the 1996 ACSM guidelines will be repeated.

  1. HF Accelerated Electron Fluxes, Spectra, and Ionization

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert C.; Jensen, Joseph B.

    2015-10-01

    Wave particle interactions, an essential aspect of laboratory, terrestrial, and astrophysical plasmas, have been studied for decades by transmitting high power HF radio waves into Earth's weakly ionized space plasma, to use it as a laboratory without walls. Application to HF electron acceleration remains an active area of research (Gurevich in Usp Fizicheskikh Nauk 177(11):1145-1177, 2007) today. HF electron acceleration studies began when plasma line observations proved (Carlson et al. in J Atmos Terr Phys 44:1089-1100, 1982) that high power HF radio wave-excited processes accelerated electrons not to ~eV, but instead to -100 times thermal energy (10 s of eV), as a consequence of inelastic collision effects on electron transport. Gurevich et al (J Atmos Terr Phys 47:1057-1070, 1985) quantified the theory of this transport effect. Merging experiment with theory in plasma physics and aeronomy, enabled prediction (Carlson in Adv Space Res 13:1015-1024, 1993) of creating artificial ionospheres once ~GW HF effective radiated power could be achieved. Eventual confirmation of this prediction (Pedersen et al. in Geophys Res Lett 36:L18107, 2009; Pedersen et al. in Geophys Res Lett 37:L02106, 2010; Blagoveshchenskaya et al. in Ann Geophys 27:131-145, 2009) sparked renewed interest in optical inversion to estimate electron spectra in terrestrial (Hysell et al. in J Geophys Res Space Phys 119:2038-2045, 2014) and planetary (Simon et al. in Ann Geophys 29:187-195, 2011) atmospheres. Here we present our unpublished optical data, which combined with our modeling, lead to conclusions that should meaningfully improve future estimates of the spectrum of HF accelerated electron fluxes. Photometric imaging data can significantly improve detection of emissions near ionization threshold, and confirm depth of penetration of accelerated electrons many km below the excitation altitude. Comparing observed to modeled emission altitude shows future experiments need electron density profiles

  2. Tailoring the Electrical Properties of HfO2 MOS-Devices by Aluminum Doping.

    PubMed

    Paskaleva, Albena; Rommel, Mathias; Hutzler, Andreas; Spassov, Dencho; Bauer, Anton J

    2015-08-12

    In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enhanced atomic layer deposition in dependence on the thickness and the added Al amount in the films have been investigated. Special attention is dedicated to C-V and I-V hysteresis analysis as a measure for trapping phenomena in the films. A detailed study of conduction mechanisms in dependence on the composition of the layers has also been performed. The densities and spatial and energy positions of traps have been examined. It is found that only a small amount of Al-doping decreases the trapping which is assigned to a reduction of oxygen vacancy-related traps in HfO2. On the contrary, higher amounts of Al introduced in HfO2 films increase the trapping ability of the stacks which is due to the introduction of deeper Al2O3-related traps. The results imply that by adding a proper amount of Al into HfO2 it is possible to tailor dielectric and electrical properties of high-k layers toward meeting the criteria for particular applications. PMID:26196163

  3. Lu-Hf constraints on the evolution of lunar basalts

    SciTech Connect

    Fujimaki, H.; Tatsumoto, M.

    1984-02-15

    Very low Ti basalts andd green glass samples from the moon show high Lu/Hf ratios and low Hf concentrations. Low-Ti lunar basalts show high and variable Lu/Hf ratios and higher Hf concentrations, whereas high-Ti lunar basalts show low Lu/Hf ratios and high Hf concentrations. KREEP basalts have constant Lu/Hf ratios and high but variable Hf concentrations. Using the Lu-Hf behavior as a constraint, we propose a model for the mare basalts evolution. This constraint requires extensive crystallization of the primary lunar magma ocean prior to formation of the lunar mare basalt sources and the KREEP basalts. Mare basalts are produced by the melting of the cumulate rocks, and KREEP basalts represent the residual liquid of the magma ocean.

  4. Comparison of HfCl4, HfI4, TEMA-Hf, and TDMA-Hf as precursors in early growing stages of HfO2 films deposited by ALD: A DFT study

    NASA Astrophysics Data System (ADS)

    Cortez-Valadez, M.; Fierro, C.; Farias-Mancilla, J. R.; Vargas-Ortiz, A.; Flores-Acosta, M.; Ramírez-Bon, R.; Enriquez-Carrejo, J. L.; Soubervielle-Montalvo, C.; Mani-Gonzalez, P. G.

    2016-06-01

    The final structure of HfO2 films grown by atomic layer deposition (ALD) after reaction with OH- ions has been analyzed by DFT (density functional theory). The interaction of the precursors: HfCl4 (hafnium tetrachloride), HfI4 (hafnium tetraiodide), TEMA-Hf (tetrakis-ethylmethylamino hafnium), and TDMA-Hf (tetrakis-dimethylamino hafnium) with HO-H was studied employing the B3LYP (Becke 3-parameter, Lee-Yang-Parr) hybrid functional and the PBE (Perdew-Burke-Ernzerhof) generalized gradient functional. The structural evolution at the Si(100) surface has been analyzed by LDA (local density approximation). The structural parameters: bond length and bond angle, and the vibrational parameters for the optimized structures are also reported. The presence of hafnium silicate at the interface was detected. The infrared spectra and structural parameters obtained in this work agree with previously reported experimental results.

  5. HF Radio Wave Production of Artificial Ionospheres

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert

    In 1993 it was predicted that artificial ionospheres would be produced by high power HF radio waves, once HF transmitters approached a GWatt ERP. When that threshold was very recently achieved, such production was indeed detected and published at two high latitude high power HF facilities. Here we review: the first-principles logic behind that prediction, which aspects of such production are critically dependent on magnetic latitude, and which aspects of such production depend only on physical parameters independent of latitude. These distinctions follow directly from decomposition of the problem of ionization production into its components of: radio-wave propagation, wave-particle interactions, electron transport, and quantitative elastic/inelastic cross-sections. We outline this analysis to show that, within the context of early observations, the production of ionization is inevitable, and only a question of competing instability thresholds, and scale of ionization production. This illustrates complimentary aeronomy and plasma physics to advance understanding of both.

  6. HF emissions in manufacturing traditional ceramics

    SciTech Connect

    Brosnan, D.A.

    1997-01-01

    Hydrogen fluoride (HF) evolves in kiln drafts during the preheating of clay-based ceramics. The fluorine source is clay dehydroxylation, i.e., the decomposition of clay crystals. Fluorine evolution can continue in the kiln soak zone as fluorine compounds formed during the initial fluorine-evolution period eventually decompose. Because North America clays exhibit a wide range of fluorine content--typically 200--1,200 ppm--the quantity of HF emitted varies considerably from one manufacturing site to another. Variables in firing--such as preheat rate, soak temperature and exit gas temperature--also affect the emission quantity. Because HF is classified as a hazardous air pollutant under the US Clean Air Act, it is subject to federal regulation, and individual states can impose more stringent regulations than the federal standards. Several states already have imposed such regulations.

  7. Segmented strings in AdS 3

    NASA Astrophysics Data System (ADS)

    Callebaut, Nele; Gubser, Steven S.; Samberg, Andreas; Toldo, Chiara

    2015-11-01

    We study segmented strings in flat space and in AdS 3. In flat space, these well known classical motions describe strings which at any instant of time are piecewise linear. In AdS 3, the worldsheet is composed of faces each of which is a region bounded by null geodesics in an AdS 2 subspace of AdS 3. The time evolution can be described by specifying the null geodesic motion of kinks in the string at which two segments are joined. The outcome of collisions of kinks on the worldsheet can be worked out essentially using considerations of causality. We study several examples of closed segmented strings in AdS 3 and find an unexpected quasi-periodic behavior. We also work out a WKB analysis of quantum states of yo-yo strings in AdS 5 and find a logarithmic term reminiscent of the logarithmic twist of string states on the leading Regge trajectory.

  8. Polarised black holes in AdS

    NASA Astrophysics Data System (ADS)

    Costa, Miguel S.; Greenspan, Lauren; Oliveira, Miguel; Penedones, João; Santos, Jorge E.

    2016-06-01

    We consider solutions in Einstein-Maxwell theory with a negative cosmological constant that asymptote to global AdS 4 with conformal boundary {S}2× {{{R}}}t. At the sphere at infinity we turn on a space-dependent electrostatic potential, which does not destroy the asymptotic AdS behaviour. For simplicity we focus on the case of a dipolar electrostatic potential. We find two new geometries: (i) an AdS soliton that includes the full backreaction of the electric field on the AdS geometry; (ii) a polarised neutral black hole that is deformed by the electric field, accumulating opposite charges in each hemisphere. For both geometries we study boundary data such as the charge density and the stress tensor. For the black hole we also study the horizon charge density and area, and further verify a Smarr formula. Then we consider this system at finite temperature and compute the Gibbs free energy for both AdS soliton and black hole phases. The corresponding phase diagram generalizes the Hawking-Page phase transition. The AdS soliton dominates the low temperature phase and the black hole the high temperature phase, with a critical temperature that decreases as the external electric field increases. Finally, we consider the simple case of a free charged scalar field on {S}2× {{{R}}}t with conformal coupling. For a field in the SU(N ) adjoint representation we compare the phase diagram with the above gravitational system.

  9. Removal of uranium from aqueous HF solutions

    DOEpatents

    Pulley, Howard; Seltzer, Steven F.

    1980-01-01

    This invention is a simple and effective method for removing uranium from aqueous HF solutions containing trace quantities of the same. The method comprises contacting the solution with particulate calcium fluoride to form uranium-bearing particulates, permitting the particulates to settle, and separting the solution from the settled particulates. The CaF.sub.2 is selected to have a nitrogen surface area in a selected range and is employed in an amount providing a calcium fluoride/uranium weight ratio in a selected range. As applied to dilute HF solutions containing 120 ppm uranium, the method removes at least 92% of the uranium, without introducing contaminants to the product solution.

  10. Low Temperature Silicon Surface Cleaning by HF Etching/Ultraviolet Ozone Cleaning (HF/UVOC) Method (I)—Optimization of the HF Treatment—

    NASA Astrophysics Data System (ADS)

    Suemitsu, Maki; Kaneko, Tetsuya; Miyamoto, Nobuo

    1989-12-01

    Several variations of fluoric acid (HF) treatments of silicon substrates were examined for their adaptability as a pretreatment method for a silicon epitaxy process. Treatments with and without distilled, deionized (DI) water rinse, of different HF concentrations, and of different methods of HF supply were tested and their residual carbonic impurity contents were measured using RHEED. As a result, HF treatments by themselves were found to be insufficient in passivating the surface dangling bonds irrespective of the method of HF supply: dipping into the solution or exposure to the vapor. The optimum procedure of HF treatment thus proposed is a succession of (a) HF dipping, (b) DI-water rinsing, (c) nitrogen-gas blowing, and (d) UV-ozone cleaning.

  11. Oxygen vacancy defect engineering using atomic layer deposited HfAlOx in multi-layered gate stack

    NASA Astrophysics Data System (ADS)

    Bhuyian, M. N.; Sengupta, R.; Vurikiti, P.; Misra, D.

    2016-05-01

    This work evaluates the defects in high quality atomic layer deposited (ALD) HfAlOx with extremely low Al (<3% Al/(Al + Hf)) incorporation in the Hf based high-k dielectrics. The defect activation energy estimated by the high temperature current voltage measurement shows that the charged oxygen vacancies, V+/V2+, are the primary source of defects in these dielectrics. When Al is added in HfO2, the V+ type defects with a defect activation energy of Ea ˜ 0.2 eV modify to V2+ type to Ea ˜ 0.1 eV with reference to the Si conduction band. When devices were stressed in the gate injection mode for 1000 s, more V+ type defects are generated and Ea reverts back to ˜0.2 eV. Since Al has a less number of valence electrons than do Hf, the change in the co-ordination number due to Al incorporation seems to contribute to the defect level modifications. Additionally, the stress induced leakage current behavior observed at 20 °C and at 125 °C demonstrates that the addition of Al in HfO2 contributed to suppressed trap generation process. This further supports the defect engineering model as reduced flat-band voltage shifts were observed at 20 °C and at 125 °C.

  12. SEMICONDUCTOR TECHNOLOGY: Wet etching characteristics of a HfSiON high-k dielectric in HF-based solutions

    NASA Astrophysics Data System (ADS)

    Yongliang, Li; Qiuxia, Xu

    2010-03-01

    The wet etching properties of a HfSiON high-k dielectric in HF-based solutions are investigated. HF-based solutions are the most promising wet chemistries for the removal of HfSiON, and etch selectivity of HF-based solutions can be improved by the addition of an acid and/or an alcohol to the HF solution. Due to densification during annealing, the etch rate of HfSiON annealed at 900 °C for 30 s is significantly reduced compared with as-deposited HfSiON in HF-based solutions. After the HfSiON film has been completely removed by HF-based solutions, it is not possible to etch the interfacial layer and the etched surface does not have a hydrophobic nature, since N diffuses to the interface layer or Si substrate formation of Si-N bonds that dissolves very slowly in HF-based solutions. Existing Si-N bonds at the interface between the new high-k dielectric deposit and the Si substrate may degrade the carrier mobility due to Coulomb scattering. In addition, we show that N2 plasma treatment before wet etching is not very effective in increasing the wet etch rate for a thin HfSiON film in our case.

  13. Origin of Excess 176Hf in Meteorites

    NASA Astrophysics Data System (ADS)

    Thrane, Kristine; Connelly, James N.; Bizzarro, Martin; Meyer, Bradley S.; The, Lih-Sin

    2010-07-01

    After considerable controversy regarding the 176Lu decay constant (λ176Lu), there is now widespread agreement that (1.867 ± 0.008) × 10-11 yr-1 as confirmed by various terrestrial objects and a 4557 Myr meteorite is correct. This leaves the 176Hf excesses that are correlated with Lu/Hf elemental ratios in meteorites older than ~4.56 Ga meteorites unresolved. We attribute 176Hf excess in older meteorites to an accelerated decay of 176Lu caused by excitation of the long-lived 176Lu ground state to a short-lived 176m Lu isomer. The energy needed to cause this transition is ascribed to a post-crystallization spray of cosmic rays accelerated by nearby supernova(e) that occurred after 4564.5 Ma. The majority of these cosmic rays are estimated to penetrate accreted material down to 10-20 m, whereas a small fraction penetrate as deep as 100-200 m, predicting decreased excesses of 176Hf with depth of burial at the time of the irradiation event.

  14. Characteristics of HfO2/Hf-based bipolar resistive memories

    NASA Astrophysics Data System (ADS)

    Jinshun, Bi; Zhengsheng, Han

    2015-06-01

    Nano-scale Hf/HfO2-based resistive random-access-memory (RRAM) devices were fabricated. The cross-over between top and bottom electrodes of RRAM forms the metal-insulator-metal sandwich structure. The electrical responses of RRAM are studied in detail, including forming process, SET process and RESET process. The correlations between SET voltage and RESET voltage, high resistance state and low resistance state are discussed. The electrical characteristics of RRAM are in a strong relationship with the compliance current in the SET process. The conduction mechanism of nano-scale Hf/HfO2-based RRAM can be explained by the quantum point contact model. Project supported by the National Natural Science Foundation of China (Nos. 11179003, 61176095).

  15. Simultaneous observation of HF-enhanced plasma waves and HF-wave self-focusing

    SciTech Connect

    Frey, A.; Duncan, L.M.

    1984-07-01

    Intense HF-radiowaves of the ordinary mode transmitted from the ground enhance plasma waves near the reflection height. These have been extensively studied in the past by the use of Incohernt-Scatter-Radars. Intense HF-radiowaves propagating in the ionosphere also produce electron density irregularities with scale sizes much larger than the HF wavelength of approx.60 m. These have been observed by radio star intensity scintillations. For the past 2 years a new method was used at Arecibo, P.R. which allows radar- and scintillation-measurements at 430 MHz to be performed simultaneously along the same line of sight. The scale sizes deduced from the scintillation measurements are shorter than the scale sizes observed with the radar and are inconsistent with the HF-power density thresholds predicted by existing theories.

  16. Effect of Hf Additions to Pt Aluminide Bond Coats on EB-PVD TBC Life

    NASA Technical Reports Server (NTRS)

    Nesbitt, James; Nagaraj, Ben; Williams, Jeffrey

    2000-01-01

    Small Hf additions were incorporated into a Pt aluminide coating during chemical vapor deposition (CVD) on single crystal RENE N5 substrates. Standard yttria-stabilized zirconia top coats were subsequently deposited onto the coated substrates by electron beam-physical vapor deposition (EB-PVD). The coated substrates underwent accelerated thermal cycle testing in a furnace at a temperature in excess of 1121 C (2050 F) (45 minute hot exposure, 15 minute cool to approximately 121 C (250 F)) until the thermal barrier coating (TBC) failed by spallation. Incorporating Hf in the bond coat increased the TBC life by slightly more than three times that of a baseline coating without added Hf. Scanning electron microscopy of the spalled surfaces indicated that the presence of the Hf increased the adherence of the thermally grown alumina to the Pt aluminide bond coat. The presence of oxide pegs growing into the coating from the thermally grown alumina may also partially account for the improved TBC life by creating a near-surface layer with a graded coefficient of thermal expansion.

  17. AdS duals of matrix strings

    NASA Astrophysics Data System (ADS)

    Morales, Jose F.; Samtleben, Henning

    2003-06-01

    We review recent work on the holographic duals of type II and heterotic matrix string theories described by warped AdS3 supergravities. In particular, we compute the spectra of Kaluza-Klein primaries for type I, II supergravities on warped AdS3 × S7 and match them with the primary operators in the dual two-dimensional gauge theories. The presence of non-trivial warp factors and dilaton profiles requires a modification of the familiar dictionary between masses and 'scaling' dimensions of fields and operators. We present these modifications for the general case of domain wall/QFT correspondences between supergravities on warped AdSd+1 × Sq geometries and super Yang-Mills theories with 16 supercharges.

  18. K = 6+ Isomers in Hf, yb and W Nuclei

    NASA Astrophysics Data System (ADS)

    Rath, Aswini Kumar; Walker, P. M.; Praharaj, C. R.; Xu, F. R.

    Using deformed Hartree-Fock and angular momentum projection (PHF) technique we try to understand the intrinsic structure and the systematics in the life times of K = 6+ isomers in the Hf isotopes (in 172-178Hf nuclei) and N = 104 Yb, Hf and W isotones. The band structure in 172Hf is reasonably well reproduced. The variation in the B(E2;2+ → 0+) values in the Hf isotopes as well as N = 104 isotones are well reproduced. The calculated K-forbidden E2 transition probabilities from the isomer bandheads to the 4+ yrast states qualitatively explain the variation of the lifetimes with N and Z.

  19. Soft X-ray photoemission studies of Hf oxidation

    SciTech Connect

    Suzer, S.; Sayan, S.; Banaszak Holl, M.M.; Garfunkel, E.; Hussain, Z.; Hamdan, N.M.

    2002-02-01

    Soft X-Ray Photoemission Spectroscopy using surface sensitive Synchrotron Radiation has been applied to accurately determine the binding energy shifts and the valence band offset of the HfO2 grown on Hf metal. Charging of oxide films under x-rays (or other irradiation) is circumvented by controlled and sequential in-situ oxidation. Photoemission results show the presence of metallic Hf (from the substrate) with the 4f7/2 binding energy of 14.22 eV, fully oxidized Hf (from HfO2) with the 4f7/2 binding energy of 18.16 eV, and at least one clear suboxide peak. The position of the valence band of HfO2 with respect to the Hf(m) Fermi level is determined as 4.05 eV.

  20. The WISP/HF system for Spacelab

    NASA Technical Reports Server (NTRS)

    James, H. G.

    1980-01-01

    The high frequency part of the waves in space plasmas system, WISP/HF, is a flexible shuttle Spacelab instrument for transmitting, receiving, and processing signals in the 0.3 to 30 MHz range. It permits a wide range of plasma wave experiments in the ionosphere including studies of the transmitting antenna, fundamentals of electromagnetic (EM) and electrostatic (ES) waves in magnetoplasmas, instabilities and nonlinearities, and remote sounding of ionospheric structure. Collaborative investigations involving other WISP equipment (e.g., antenna and propagation studies with the WISP/VLF system) or other Spacelab facilities (e.g., beam plasma interactions using charged particle guns) are envisaged. A few specific examples illustrate the relevance of WISP/HF to current scientific interest. The overall goal is to help build a comprehensive understanding of plasmaspheric wave physics through group studies.

  1. Studies of dispersion energy in hydrogen-bonded systems. H2O-HOH, H2O-HF, H3N-HF, HF-HF

    NASA Astrophysics Data System (ADS)

    Szcześniak, M. M.; Scheiner, Steve

    1984-02-01

    Dispersion energy is calculated in the systems H2O-HOH, H2O-HF, H3N-HF, and HF-HF as a function of the intermolecular separation using a variety of methods. M≂ller-Plesset perturbation theory to second and third orders is applied in conjunction with polarized basis sets of 6-311G** type and with an extended basis set including a second set of polarization functions (DZ+2P). These results are compared to a multipole expansion of the dispersion energy, based on the Unsöld approximation, carried out to the inverse tenth power of the intermolecular distance. Pairwise evaluation is also carried out using both atom-atom and bond-bond formulations. The MP3/6-311G** results are in generally excellent accord with the leading R-6 term of the multipole expansion. This expansion, if carried out to the R-10 term, reproduces extremely well previously reported dispersion energies calculated via variation-perturbation theory. Little damping of the expansion is required for intermolecular distances equal to or greater than the equilibrium separation. Although the asymptotic behavior of the MP2 dispersion energy is somewhat different than that of the other methods, augmentation of the basis set by a second diffuse set of d functions leads to quite good agreement in the vicinity of the minima. Both the atom-atom and bond-bond parametrization schemes are in good qualitative agreement with the other methods tested. All approaches produce similar dependence of the dispersion energy upon the angular orientation between the two molecules involved in the H bond.

  2. SERVE-HF: More Questions Than Answers.

    PubMed

    Javaheri, Shahrokh; Brown, Lee K; Randerath, Winfried; Khayat, Rami

    2016-04-01

    The recent online publication of the SERVE-HF trial that evaluated the effect of treating central sleep apnea (CSA) with an adaptive servoventilation (ASV) device in patients with heart failure and reduced ejection fraction (HFrEF) has raised serious concerns about the safety of ASV in these patients. Not only was ASV ineffective but post hoc analysis found excess cardiovascular mortality in treated patients. The authors cited as one explanation an unfounded notion that CSA is a compensatory mechanism with a protective effect in HFrEF patients. We believe that there are several possible considerations that are more likely to explain the results of SERVE-HF. In this commentary, we consider methodological issues including the use of a previous-generation ASV device that constrained therapeutic settings to choices that are no longer in wide clinical use. Patient selection, data collection, and treatment adherence as well as group crossovers were not discussed in the trial as potential confounding factors. We have developed alternative reasons that could potentially explain the results and that can be explored by post hoc analysis of the SERVE-HF data. We believe that our analysis is of critical value to the field and of particular importance to clinicians treating these patients. PMID:26836904

  3. Room temperature formation of Hf-silicate layer by pulsed laser deposition with Hf-Si-O ternary reaction control

    NASA Astrophysics Data System (ADS)

    Hotta, Yasushi; Ueoka, Satoshi; Yoshida, Haruhiko; Arafune, Koji; Ogura, Atsushi; Satoh, Shin-ichi

    2016-10-01

    We investigated the room temperature growth of HfO2 layers on Si substrates by pulsed laser deposition under ultra-high vacuum conditions. The laser fluence (LF) during HfO2 layer growth was varied as a growth parameter in the experiments. X-ray photoemission spectroscopy (XPS) was used to observe the interface chemical states of the HfO2/Si samples produced by various LFs. The XPS results indicated that an interface Hf-silicate layer formed, even at room temperature, and that the thickness of this layer increased with increasing pulsed LF. Additionally, Hf-Si bonds were increasingly formed at the interface when the LF was more than 2 J/cm2. This bond formation process was related to decomposition of HfO2 to its atomic states of Hf and O by multiphoton photochemical processes for bandgap excitation of the HfO2 polycrystalline target. However, the Hf-Si bond content of the interface Hf-silicate layer is controllable under high LF conditions. The results presented here represent a practical contribution to the development of room temperature processing of Hf-compound based devices.

  4. Theoretical influence of third molecule on reaction channels of weakly bound complex CO2? HF systems

    NASA Astrophysics Data System (ADS)

    Chen, Shyh-Jong; Chen, Cheng; Hong, Yaw-Shun

    In this investigation, reaction channels of weakly bound complexes CO2?HF, CO2?HF?NH3, CO2?HF?H2O and CO2?HF?CH3OH systems were established at the B3LYP/6-311++G(3df,2pd) level, using the Gaussian 98 program. The conformers of syn-fluoroformic acid or syn-fluoroformic acid plus a third molecule (NH3, H2O, or CH3OH) were found to be more stable than the conformers of the related anti-fluoroformic acid or anti-fluoroformic acid plus a third molecule (NH3, H2O, or CH3OH). However, the weakly bound complexes were found to be more stable than either the related syn- and anti-type fluoroformic acid or the acid plus third molecule (NH3, H2O, or CH3OH) conformers. They decomposed into CO2 + HF, CO2 + NH4F, CO2 + H3OF or CO2 + (CH3)OH2F combined molecular systems. The weakly bound complexes have four reaction channels, each of which includes weakly bound complexes and related systems. Moreover, each reaction channel includes two transition state structures. The transition state between the weakly bound complex and anti-fluoroformic acid type structure (T13) is significantly larger than that of internal rotation (T23) between the syn- and anti-FCO2H (or FCO2H?NH3, FCO2H?H2O, or FCO2H?CH3OH) structures. However, adding the third molecule NH3, H2O, or CH3OH can significantly reduce the activation energy of T13. The catalytic strengths of the third molecules are predicted to follow the order H2O < NH3 < CH3OH.

  5. LU-HF Age and Isotope Systematics of ALH84001

    NASA Technical Reports Server (NTRS)

    Righter, M.; Lapen, T. J.; Brandon, A. D.; Beard, B. L.; Shafer, J. T.; Peslier, A. H.

    2009-01-01

    Allan Hills (ALH) 84001 is an orthopyroxenite that is unique among the Martian meteorites in having the oldest inferred crystallization age (approx..4.5 to 4.0 Gyr) [e.g., 1-6 and references therein 7]. Its ancient origin makes this stone a critical constraint on early history of Mars, in particular the evolution of different planetary crust and mantle reservoirs. However, because there is significant variability in reported crystallization ages, determination of initial isotope compositions is imprecise making assessment of planetary reservoirs difficult. Here we report a new Lu-Hf mineral isochron age, initial Hf-176/Hf-177 isotope composition, and inferred Martian mantle source compositions for ALH84001 that place constraints on longlived source reservoirs for the enriched shergottite suite of Martian meteorites including Shergotty, Zagami, NWA4468, NWA856, RBT04262, LAR06319, and Los Angeles. Sm-Nd isotope analyses are under way for the same mineral aliquots analyzed for Lu-Hf. The Lu-Hf system was utilized because Lu and Hf are both lithophile and refractory and are not easily redistributed during short-lived thermal pulses associated with shock metamorphism. Moreover, chromite has relatively modest Hf concentrations with very low Lu/Hf ratios [9] yielding tight constraints on initial Hf-176/Hf-177 isotope compositions

  6. Agricultural Education: Value Adding.

    ERIC Educational Resources Information Center

    Riesenberg, Lou E.; And Others

    1989-01-01

    This issue develops the theme of "Agricultural Education--Value Adding." The concept value adding has been a staple in the world of agricultural business for describing adding value to a commodity that would profit the producer and the local community. Agricultural education should add value to individuals and society to justify agricultural…

  7. Influence of YBa2HfO5.5 - 'derived secondary phase' on the critical current density and flux-Pinning force of YBa2Cu3O7-δ thick films

    NASA Astrophysics Data System (ADS)

    Rejith, Pullanhiyodan Puthiyaveedu; Vidya, Sukumariamma; Thomas, Jijimon Kumbukkattu

    2015-12-01

    Enhancement in critical current density (Jc) and flux pinning force (Fp) in superconducting thick films of YBa2Cu3O7-δ (YBCO) added with small quantities of nanopowders of HfO2, BaHfO3 and YBa2HfO5.5, coated on YBa2ZrO5.5 substrate by dip-coating technique is reported. Critical current density measurements were done over an applied magnetic field using standard four probe technique and the results are compared with that of pure YBCO. High critical current density (Jc) of ∼4.84 MA/cm2 at 77 K in self-field was obtained for 2 wt% of YBa2HfO5.5 added YBCO. A systematic increase in Jc observed in YBCO films prepared by the addition of nano HfO2, BaHfO3 and YBa2HfO5.5, attributed to the formation of a non-reacting 'derived secondary phase' YBa2HfO5.5 (YBHO) in the YBCO matrix. YBCO-YBa2HfO5.5 composite thick films have showed eightfold increases in Jc (3.29 MA/cm2) at 77 K and 0.4 T compared to pure YBa2Cu3O7-δ film (0.37 MA/cm2), while maintaining a high transition temperature (Tc). The development of effective pinning centers in nano particle added YBCO thick film have enhanced the flux pinning force from 1.8 GN/m3 for pure YBCO to a maximum value of 13.15 GN/m3 for YBCO-YBa2HfO5.5. X-ray diffraction and energy dispersive spectroscopic analysis confirmed the presence of secondary phase, derived in the matrix.

  8. Laser cladding of Ni-Cr-Al-Hf on inconel 718 for improved high-temperature oxidation resistance

    SciTech Connect

    Singh, J.; Nagarathnam, K.; Mazumder, J.

    1987-08-03

    In-situ Ni-Cr-Al-Hf alloy was developed by laser surface cladding with a mixed-powder feed for improved high-temperature oxidation resistance. Oxidation-resistant materials for operation at elevated temperatures must satisfy two requirements: diffusion through the oxide scale must occur at the lowest possible rate, and the oxide scale must resist spallation. Formation of an Al/sub 2/O/sub 3/ protective scale fulfills the former requirement but its adherence is poor. A reactive metal such as Hf is added to improve adhesion. A 10-kW CO/sub 2/ laser was used for laser cladding. Optical, SEM and STEM microanalysis techniques were employed to characterize the different phases produced during the cladding process. Microstructural studies showed a high degree of grain refinement, increased solid solubility of Hf in the matrix and the formation of Hf-rich precipitates. A thermogravimetric analysis was carried out to determine the oxidation properties of these clad alloys with an extended solid solution of Hf. Considerable improvement over the base metal was observed. This paper discusses microstructural development in this laser-clad alloy and its effect on oxidation.

  9. Epitaxial Thin Films of Y doped HfO2

    NASA Astrophysics Data System (ADS)

    Serrao, Claudy; Khan, Asif; Ramamoorthy, Ramesh; Salahuddin, Sayeef

    Hafnium oxide (HfO2) is one of a few metal oxides that is thermodynamically stable on silicon and silicon oxide. There has been renewed interest in HfO2 due to the recent discovery of ferroelectricity and antiferroelectricity in doped HfO2. Typical ferroelectrics - such as strontium bismuth tantalate (SBT) and lead zirconium titanate (PZT) - contain elements that easily react with silicon and silicon oxide at elevated temperatures; therefore, such ferroelectrics are not suited for device applications. Meanwhile, ferroelectric HfO2 offers promise regarding integration with silicon. The stable phase of HfO2 at room temperature is monoclinic, but HfO2 can be stabilized in the tetragonal, orthorhombic or even cubic phase by suitable doping. We stabilized Y-doped HfO2 thin films using pulsed laser deposition. The strain state can be controlled using various perovskite substrates and controlled growth conditions. We report on Y-doped HfO2 domain structures from piezo-response force microscopy (PFM) and structural parameters via X-ray reciprocal space maps (RSM). We hope this work spurs further interest in strain-tuned ferroelectricity in doped HfO2.

  10. Synthesis and structural investigation of the compounds containing HF 2- anions: Ca(HF 2) 2, Ba 4F 4(HF 2)(PF 6) 3 and Pb 2F 2(HF 2)(PF 6)

    NASA Astrophysics Data System (ADS)

    Bunič, Tina; Tramšek, Melita; Goreshnik, Evgeny; Žemva, Boris

    2008-09-01

    Three new compounds Ca(HF 2) 2, Ba 4F 4(HF 2)(PF 6) 3 and Pb 2F 2(HF 2)(PF 6) were obtained in the system metal(II) fluoride and anhydrous HF (aHF) acidified with excessive PF 5. The obtained polymeric solids are slightly soluble in aHF and they crystallize out of their aHF solutions. Ca(HF 2) 2 was prepared by simply dissolving CaF 2 in a neutral aHF. It represents the second known compound with homoleptic HF environment of the central atom besides Ba(H 3F 4) 2. The compounds Ba 4F 4(HF 2)(PF 6) 3 and Pb 2F 2(HF 2)(PF 6) represent two additional examples of the formation of a polymeric zigzag ladder or ribbon composed of metal cation and fluoride anion (MF +) n besides PbF(AsF 6), the first isolated compound with such zigzag ladder. The obtained new compounds were characterized by X-ray single crystal diffraction method and partly by Raman spectroscopy. Ba 4F 4(HF 2)(PF 6) 3 crystallizes in a triclinic space group P1¯ with a=4.5870(2) Å, b=8.8327(3) Å, c=11.2489(3) Å, α=67.758(9)°, β=84.722(12), γ=78.283(12)°, V=413.00(3) Å 3 at 200 K, Z=1 and R=0.0588. Pb 2F 2(HF 2)(PF 6) at 200 K: space group P1¯, a=4.5722(19) Å, b=4.763(2) Å, c=8.818(4) Å, α=86.967(10)°, β=76.774(10)°, γ=83.230(12)°, V=185.55(14) Å 3, Z=1 and R=0.0937. Pb 2F 2(HF 2)(PF 6) at 293 K: space group P1¯, a=4.586(2) Å, b=4.781(3) Å, c=8.831(5) Å, α=87.106(13)°, β=76.830(13)°, γ=83.531(11)°, V=187.27(18) Å 3, Z=1 and R=0.072. Ca(HF 2) 2 crystallizes in an orthorhombic Fddd space group with a=5.5709(6) Å, b=10.1111(9) Å, c=10.5945(10) Å, V=596.77(10) Å 3 at 200 K, Z=8 and R=0.028.

  11. Adding flavor to AdS4/CFT3

    NASA Astrophysics Data System (ADS)

    Ammon, Martin; Erdmenger, Johanna; Meyer, René; O'Bannon, Andy; Wrase, Timm

    2009-11-01

    Aharony, Bergman, Jafferis, and Maldacena have proposed that the low-energy description of multiple M2-branes at a Bbb C4/Bbb Zk singularity is a (2+1)-dimensional Script N = 6 supersymmetric U(Nc) × U(Nc) Chern-Simons matter theory, the ABJM theory. In the large-Nc limit, its holographic dual is supergravity in AdS4 × S7/Bbb Zk. We study various ways to add fields that transform in the fundamental representation of the gauge groups, i.e. flavor fields, to the ABJM theory. We work in a probe limit and perform analyses in both the supergravity and field theory descriptions. In the supergravity description we find a large class of supersymmetric embeddings of probe flavor branes. In the field theory description, we present a general method to determine the couplings of the flavor fields to the fields of the ABJM theory. We then study four examples in detail: codimension-zero Script N = 3 supersymmetric flavor, described in supergravity by Kaluza-Klein monopoles or D6-branes; codimension-one Script N = (0,6) supersymmetric chiral flavor, described by D8-branes; codimension-one Script N = (3,3) supersymmetric non-chiral flavor, described by M5/D4-branes; codimension-two Script N = 4 supersymmetric flavor, described by M2/D2-branes. Finally we discuss special physical equivalences between brane embeddings in M-theory, and their interpretation in the field theory description.

  12. Hf-W chronometry of primitive achondrites

    NASA Astrophysics Data System (ADS)

    Schulz, T.; Münker, C.; Mezger, K.; Palme, H.

    2010-03-01

    Metal segregation and silicate melting on asteroids are the most incisive differentiation events in the early evolution of planetary bodies. The timing of these events can be constrained using the short-lived 182Hf- 182W radionuclide system. Here we present new 182Hf- 182W data for major types of primitive achondrites including acapulcoites, winonaites and one lodranite. These meteorites are of particular interest because they show only limited evidence for partial melting of silicates and are therefore intermediate between chondrites and achondrites. For acapulcoites we derived a 182Hf- 182W age of Δ tCAI = 4.1 +1.2/ -1.1 Ma. A model age for winonaite separates calculated from the intercept of the isochron defines an age of Δ tCAI = 4.8 +3.1/ -2.6 Ma (assuming a bulk Hf/W ratio of ˜1.2). Both ages most likely define primary magmatic events on the respective parent bodies, such as melting of metal, although metal stayed in place and did not segregate to form a core. A later thermal event is responsible for resetting of the winonaite isochron, yielding an age of Δ tCAI = 14.3 +2.7/ -2.2 Ma, significantly younger than the model age. Assuming a co-genetic relationship between winonaites and silicates present in IAB iron meteorites (based on oxygen isotope composition) and including data by Schulz et al. (2009), a common parent body chronology can be established. Magmatic activity occurred between ˜1.5 and 5 Ma after CAIs. More than 5 Ma later, intensive thermal metamorphism has redistributed Hf-W. Average cooling rates calculated for the winonaite/IAB parent asteroid range between ˜35 and ˜4 K/Ma, most likely reflecting different burial depths. Cooling rates obtained for acapulcoites were ˜40 K/Ma to ˜720 K and then ˜3 K/Ma to ˜550 K. Accretion and subsequent magmatism on the acapulcoite parent body occurred slightly later if compared to most achondrite parent bodies (e.g., angrites, ureilites and eucrites), in this case supporting the concept of an inverse

  13. Ferroelectricity of nondoped thin HfO2 films in TiN/HfO2/TiN stacks

    NASA Astrophysics Data System (ADS)

    Nishimura, Tomonori; Xu, Lun; Shibayama, Shigehisa; Yajima, Takeaki; Migita, Shinji; Toriumi, Akira

    2016-08-01

    We report on the impact of TiN interfaces on the ferroelectricity of nondoped HfO2. Ferroelectric properties of nondoped HfO2 in TiN/HfO2/TiN stacks are shown in capacitance–voltage and polarization–voltage characteristics. The Curie temperature is also estimated to be around 500 °C. The ferroelectricity of nondoped HfO2 clearly appears by thinning HfO2 film down to ∼35 nm. We directly revealed in thermal treatments that the ferroelectric HfO2 film on TiN was maintained by covering the top surface of HfO2 with TiN, while it was followed by a phase transition to the paraelectric phase in the case of the open surface of HfO2. Thus, it is concluded that the ferroelectricity in nondoped HfO2 in this study was mainly driven by both of top and bottom TiN interfaces.

  14. Twistor methods for AdS5

    NASA Astrophysics Data System (ADS)

    Adamo, Tim; Skinner, David; Williams, Jack

    2016-08-01

    We consider the application of twistor theory to five-dimensional anti-de Sitter space. The twistor space of AdS5 is the same as the ambitwistor space of the four-dimensional conformal boundary; the geometry of this correspondence is reviewed for both the bulk and boundary. A Penrose transform allows us to describe free bulk fields, with or without mass, in terms of data on twistor space. Explicit representatives for the bulk-to-boundary propagators of scalars and spinors are constructed, along with twistor action functionals for the free theories. Evaluating these twistor actions on bulk-to-boundary propagators is shown to produce the correct two-point functions.

  15. AdS3: the NHEK generation

    NASA Astrophysics Data System (ADS)

    Bena, Iosif; Heurtier, Lucien; Puhm, Andrea

    2016-05-01

    It was argued in [1] that the five-dimensional near-horizon extremal Kerr (NHEK) geometry can be embedded in String Theory as the infrared region of an infinite family of non-supersymmetric geometries that have D1, D5, momentum and KK monopole charges. We show that there exists a method to embed these geometries into asymptotically- {AdS}_3× {S}^3/{{Z}}_N solutions, and hence to obtain infinite families of flows whose infrared is NHEK. This indicates that the CFT dual to the NHEK geometry is the IR fixed point of a Renormalization Group flow from a known local UV CFT and opens the door to its explicit construction.

  16. Shadows, currents, and AdS fields

    SciTech Connect

    Metsaev, R. R.

    2008-11-15

    Conformal totally symmetric arbitrary spin currents and shadow fields in flat space-time of dimension greater than or equal to four are studied. A gauge invariant formulation for such currents and shadow fields is developed. Gauge symmetries are realized by involving the Stueckelberg fields. A realization of global conformal boost symmetries is obtained. Gauge invariant differential constraints for currents and shadow fields are obtained. AdS/CFT correspondence for currents and shadow fields and the respective normalizable and non-normalizable solutions of massless totally symmetric arbitrary spin AdS fields are studied. The bulk fields are considered in a modified de Donder gauge that leads to decoupled equations of motion. We demonstrate that leftover on shell gauge symmetries of bulk fields correspond to gauge symmetries of boundary currents and shadow fields, while the modified de Donder gauge conditions for bulk fields correspond to differential constraints for boundary conformal currents and shadow fields. Breaking conformal symmetries, we find interrelations between the gauge invariant formulation of the currents and shadow fields, and the gauge invariant formulation of massive fields.

  17. Parametric excitation of whistler waves by HF heater

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Lee, M. C.

    1989-01-01

    Possible generation of whistler waves by Tromso HF heater is investigated. It is shown that the HF heater wave can parametrically decay into a whistler wave and a Langmuir wave. Since whistler waves may have a broad range of frequency, the simultaneously excited Langmuir waves can have a much broader frequency bandwidth than those excited by the parametric decay instability.

  18. Fractionation of Zr and Hf in surface processes

    SciTech Connect

    Chyi, L.L.; Garg, A.N.

    1985-01-01

    Zircons from a pegmatite near Tuxedo, North Carolina were crushed and treated with different reagents under different conditions. The treated and untreated samples were determined for Zr and Hf with radiochemical neutron activation analysis. Zircons treated with 50% sulfuric acid were having lowered Zr content and Zr/Hf ratio. The conclusions are that a portion of Zr and Hf in zircons is sensitive to leaching, and Zr appears to be selectively leached over Hf. The conclusions of this work support the observations of small dissolutions of Zr in both acidic podzolic soils and in alkaline laterites, of lower Zr content in soils on glacial drift, and of lower Zr/Hf ratios in loess deposits from various parts of the world. The fractionation of Zr and Hf in surface processes appears to be due to selective leaching. Weakening of Zr-O over Hf-O bonds in zircon by fission projectiles is postulated to be the viable process. The observed fractionation from leaching experiments suggest that areas receiving leachates such as swamps, lakes, and oceans should have high to very high Zr/Hf ratios preserved in rocks. High ratios are found in the Springfield (No. 9) Coal, the Green River Shale, and various limestones. High ratio is also found in orchard leaves, which grow by absorbing leachate from soil.

  19. Theoretical study of reaction channels for the weakly bound complex systems created with HF, CO2, and various amines

    NASA Astrophysics Data System (ADS)

    Chen, Shyh-Jong; Chen, Cheng; Hong, Yaw-Shun

    This investigation conducted reaction channels of weakly bound complexes CO2...HF, CO2...HF...NH3, CO2...HF...NH2CH3, CO2...HF...NH(CH3)2, and CO2...HF...N(CH3)3 systems, using the Gaussian 98 package at the B3LYP/6-311++G(3df,2pd) level. The syn-fluoroformic acid or syn-fluoroformic acid plus NH3 or amine conformers are more stable than the related anti-fluoroformic acid or anti-fluoroformic acid plus NH3 or amine conformers. However, the above-mentioned weakly bound complexes are more stable than both the related syn- and anti-type fluoroformic acid or acid plus NH3 or amine conformers and their related decomposed into CO2 + HF or CO2 + NHR3F (RH, CH3) combined molecular systems. Five reaction channels of the weakly bound complexes exist. Each channel includes weakly bound complexes and their related above-mentioned systems. Moreover, each reaction channel contains two transition states. The transition state between the weakly bound complex and anti-fluoroformic acid type structure (T13) is significantly higher than that of internal rotation (T23) between syn- and anti-FCO2H (or FCO2H...NR3) structures. However, the above-mentioned T13 can significantly decrease its energy by adding the third molecule NH3 or NR3 (RH or CH3). The more CH3 that is substituted in NR3 of the reaction channel, the lower the activation energy of the transition state in the system is affected.

  20. Environmental Hf-Nd isotopic decoupling in World river clays

    NASA Astrophysics Data System (ADS)

    Bayon, Germain; Skonieczny, Charlotte; Delvigne, Camille; Toucanne, Samuel; Bermell, Sylvain; Ponzevera, Emmanuel; André, Luc

    2016-03-01

    The hafnium and neodymium radiogenic isotope systems behave differently during Earth surface processes, causing a wide dispersion of Hf and Nd isotopic compositions in sediments and other sedimentary rocks. The decoupling between Hf and Nd isotopes in sediments is generally attributed to a combination of preferential sorting of zircon during sediment transport and incongruent weathering processes on continents. In this study, we analysed size-fractions of sediment samples collected near the mouth of 53 rivers worldwide to better understand the factors controlling the distribution of Hf and Nd isotopes in sediments. Our results for rivers draining old cratonic areas and volcanic provinces demonstrate that both granite and basalt weathering can lead to significant grain-size dependent Hf isotopic variability. While silt-size fractions mainly plot along the Terrestrial Array, World river clays are systematically shifted towards more radiogenic Hf isotopic compositions, defining together with published data a new Clay Array (εHf = 0.78 ×εNd + 5.23). The Hf-Nd isotope decoupling observed in volcanogenic sediments is best explained by selective alteration of Lu-rich mineral phases (e.g. olivine) and preferential enrichment of resistant unradiogenic minerals, such as spinel and ilmenite, in silt fractions. We also show that the extent to which World river clays deviate from the Clay Array (ΔεHf clay) is not linked to the presence of zircons. Instead, it correlates positively with weathering indices and climatic parameters (temperature, rainfall) of the corresponding drainage basins. Overall, these findings demonstrate that the distribution of Hf-Nd isotopes in clay-size sediments is related to a large extent to weathering conditions on continents, although the precise mechanisms controlling this relationship remain unclear. We finally propose that the Hf-Nd isotope pair proxy could be used in palaeoenvironmental studies to provide semi-quantitative information on

  1. The (178m2)Hf Controversy

    SciTech Connect

    Becker, J A; Gemmell, D S; Schiffer, J P; Wilhelmy, J B

    2003-07-24

    Since its discovery in the 1960's the {sup 178m2}Hf isomer has garnered high attention from both the basic and applied communities in nuclear science. It's combination of high spin (16+), long half life (31 yrs), and high excitation energy (2.446 MeV) offer unique possibilities as an energy storage medium. Interest in the isomer was rekindled beginning in 1999 when a series of publications began to appear from a group (referred to here as the ''Texas collaboration'') primarily based at the University of Texas, Dallas [1]. They reported observations that some of the stored energy could be released (''triggered'') when the isomer was exposed to a fluence of photons in the energy range {approx}10 to {approx}60 keV. The implications of this observation are profound. Even though the claimed cross section for the process was {approx}7 orders of magnitude greater than would be predicted from the known systematics of photon absorption by nuclei in this mass range [2], such a highly efficient method for triggering the isomeric deexcitation immediately suggested applications utilizing the explosive or the controlled gradual energy release from a very compact source. The prospect of such applications has focused considerable interest on realizing the promise that is implicit in the reported observations. However, two experiments performed by a group from ANL/LANL/LLNL at the Advanced Photon Source at Argonne (the ''APS collaboration'') reported negative results for the observation of any photon-triggered deexcitation of the {sup 178m2}Hf isomer [3]. This has led to a continued controversy, where both sides have adamantly defended their observations. At this point an outsider has difficulty determining whether there is indeed a triggering effect that should be pursued energetically with substantial resources, or whether the phenomenon consists of overly optimistic interpretation of data.

  2. Ferroelectricity-modulated resistive switching in Pt/Si:HfO2/HfO2-x /Pt memory

    NASA Astrophysics Data System (ADS)

    Ran, Jiang; Xianghao, Du; Zuyin, Han

    2016-08-01

    It is investigated for the effect of a ferroelectric Si:HfO2 thin film on the resistive switching in a stacked Pt/Si:HfO2/highly-oxygen-deficient HfO2-x /Pt structure. Improved resistance performance was observed. It was concluded that the observed resistive switching behavior was related to the modulation of the width and height of a depletion barrier in the HfO2-x layer, which was caused by the Si:HfO2 ferroelectric polarization field effect. Reliable switching reproducibility and long data retention were observed in these memory cells, suggesting their great potential in non-volatile memories applications with full compatibility and simplicity. Project supported by the National Natural Science Foundation of China (No. 11374182), the Natural Science Foundation of Shandong Province (No. ZR2012FQ012), and the Jinan Independent Innovation Projects of Universities (No. 201303019).

  3. ADS pilot program Plan

    NASA Technical Reports Server (NTRS)

    Clauson, J.; Heuser, J.

    1981-01-01

    The Applications Data Service (ADS) is a system based on an electronic data communications network which will permit scientists to share the data stored in data bases at universities and at government and private installations. It is designed to allow users to readily locate and access high quality, timely data from multiple sources. The ADS Pilot program objectives and the current plans for accomplishing those objectives are described.

  4. Large Nd-Hf isotopic decoupling in Himalayan River Sediments

    NASA Astrophysics Data System (ADS)

    Garcon, M.; Chauvel, C.; France-Lanord, C.

    2011-12-01

    Nd isotopic compositions of river sediments are widely used to trace sediment provenance in the Himalayan mountain range. In contrast, Hf isotopic compositions are not used even though they are excellent proxies to record the history of continental areas (Hawkesworth and Kemp, Chem. Geol. 226, 2006). Here, we focus on the Hf isotopic message carried by Himalayan river sediments and combine it to the more classical Nd isotopes to better understand the behavior of the two systems during erosion. We report Nd-Hf isotopic compositions of bedloads and suspended loads sampled at different depths in the Narayani River in Nepal (upstream of the Ganga floodplain), in the Ganga River in Bangladesh (downstream of the Ganga floodplain) and in the Yamuna River, a major tributary of the Ganga in India. Nd-Hf isotopic compositions of bedloads span a small range of values (-18< ɛNd <-16 and -30< ɛHf <-23) and lie next to the terrestrial array in a ɛHf vs. ɛNd diagram. Nd isotopic compositions are similar to those of the main Himalayan sources. By contrast, suspended loads have much more variable ratios (-19< ɛNd <-10 and -25< ɛHf <-7) and plot well above the terrestrial array in a ɛHf vs. ɛNd diagram. Like oceanic sediments, they are characterized by high ɛHf compared to their ɛNd. We explain this Nd-Hf decoupling by mineralogical sorting, a process that enriches bottom sediments in coarse and dense minerals, such as unradiogenic zircons, while the surface sediments are enriched in fine material with radiogenic Hf signatures. Bedloads and suspended loads, collected at the same sampling site at different depths in the Narayani and Ganga Rivers, share similar ɛNd. However, differences of about 5 ɛNd and 15 ɛHf units are observed between bedload and surface samples in the Yamuna River. In this river, both Nd and Hf isotopic ratios decrease from surface to bottom. We believe that part of the Hf isotopic variability is due to mineralogical sorting but the rest of it

  5. Power-Stepped HF Cross Modulation Experiments at HAARP

    NASA Astrophysics Data System (ADS)

    Greene, S.; Moore, R. C.; Langston, J. S.

    2013-12-01

    High frequency (HF) cross modulation experiments are a well established means for probing the HF-modified characteristics of the D-region ionosphere. In this paper, we apply experimental observations of HF cross-modulation to the related problem of ELF/VLF wave generation. HF cross-modulation measurements are used to evaluate the efficiency of ionospheric conductivity modulation during power-stepped modulated HF heating experiments. The results are compared to previously published dependencies of ELF/VLF wave amplitude on HF peak power. The experiments were performed during the March 2013 campaign at the High Frequency Active Auroral Research Program (HAARP) Observatory. HAARP was operated in a dual-beam transmission format: the first beam heated the ionosphere using sinusoidal amplitude modulation while the second beam broadcast a series of low-power probe pulses. The peak power of the modulating beam was incremented in 1-dB steps. We compare the minimum and maximum cross-modulation effect and the amplitude of the resulting cross-modulation waveform to the expected power-law dependence of ELF/VLF wave amplitude on HF power.

  6. Microstructure and tensile properties of Fe-40 at. pct Al alloys with C, Zr, Hf, and B additions

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Draper, S. L.; Nathal, M. V.

    1989-01-01

    The influence of small additions of C, Zr, and Hf, alone or in combination with B, on the microstructure and tensile behavior of substoichiometric FeAl was investigated. Tensile properties were determined from 300 to 1100 K on powder which was consolidated by hot extrusion. All materials possessed some ductility at room temperature, although ternary additions generally reduced ductility compared to the binary alloy. Adding B to the C- and Zr-containing alloys changed the fracture mode from intergranular to transgranular and restored the ductility to approximately 5 percent elongation. Additions of Zr and Hf increased strength up to about 900 K. Fe6Al6Zr and Fe6Al6Hf precipitates, both with identical body-centered tetragonal structures, were identified as the principal second phase in these alloys. Strength decreased steadily as temperature increased above 700 K, as diffusion-assisted mechanisms became operative. Although all alloys had similar strengths at 1100 K, Hf additions significantly improved high-temperature ductility by suppressing cavitation.

  7. Critical Questions about PARADIGM-HF and the Future

    PubMed Central

    Chen, Chen-Huan

    2016-01-01

    Cardiovascular (CV) diseases in general and heart failure (HF) in particular are major contributors to death and morbidity and are also recognized as important drivers of health care expenditure. The PARADIGM-HF trial was a pivotal trial designed to compare the long-term effects of LCZ696 with enalapril in patients with symptomatic HF with reduced ejection fraction (HFrEF). This review article presents an in-depth view of the PARADIGM-HF trial and the implications of the results in the management of patients with HF and is based on peer reviewed manuscripts, editorials, perspectives and opinions written about the PARADIGM-HF trial. The article presents the key safety and efficacy results of the trial with specific emphasis on the clinical implications of these findings. The review highlights the highly statistically significant, 20% reduction in the primary composite endpoint of cardiovascular death or HF hospitalization, and a 16% reduction in the risk of death from any cause. It also provides an overview of the design, clinical findings, limitations and special areas of clinical interest. The review discusses the future of LCZ696 and additional trials that seek to answer questions in other sub-populations of patients with HF. The article reiterates what has been concluded by many experts in the field of HF- the introduction of LCZ696 into routine clinical care, while dependent on the regulatory approvals in various countries as well as acceptance by physicians, payers and patients, will change the treatment landscape for patients with HFrEF. PMID:27471351

  8. Stratospheric HF and HCl observations /15 June 1981/

    NASA Technical Reports Server (NTRS)

    Traub, W. A.; Chance, K. V.

    1981-01-01

    Balloon measurements of the stratospheric HF/HCl ratio are reported. Seven far-infrared rotational lines of HF and HCl were observed at elevation angles of 25, 18 and 8 deg by a far-infrared Fourier-transform spectrometer on board a balloon platform at 28.5 km. Analysis of line intensities yields an average HF/HCl ratio of 0.18 + or - 0.02 at an effective altitude of 33 km, with a water vapor mixing ratio of about 4 ppmv. Results are noted to be in reasonable agreement with the calculated profile of Sze and Ko (1981) with 4.5 ppmv H2O.

  9. Pulsed HF laser ablation of dentin

    NASA Astrophysics Data System (ADS)

    Papagiakoumou, Eirini I.; Papadopoulos, Dimitris N.; Makropoulou, Mersini I.; Khabbaz, Maruan G.; Serafetinides, Alexander A.

    2005-03-01

    The interaction of a TEA (Transversally Excited Atmospheric pressure) corona preionized oscillator double amplifier HF (hydrogen fluoride) laser beam with dentin tissue is reported. Pulses of 39 ns in the wavelength range of 2.65-3.35 μm and output energies in the range of 10-45 mJ, in a predominantly TEM00 beam were used to interact with dentin tissue. Ablation experiments were conducted with the laser beam directly focused on the tissue. Several samples of freshly extracted human teeth were used, cut longitudinally in facets of about 1mm thick and stored in phosphate buffered saline after being cleaned from the soft tissue remains. The experimental data (ablation thresholds, ablation rates) are discussed with respect to the ablation mechanism(s). Adequate tissue removal was observed and the ablation behavior was, in the greates part of the available fluences, almost linear. From the microscopic examination of teh samples, in a scanning electron microscope (SEM), the irradiated surfaces displayed oval craters (reflecting the laser beam shape) with absence of any melting or carbonization zone. It is suggested that the specific laser removes hard tissue by a combined photothermal and plasma mediated ablation mechanism, leaving a surface free from thermal damage and with a well-shaped crater.

  10. Theoretical Assessment of 178m2Hf De-Excitation

    SciTech Connect

    Hartouni, E P; Chen, M; Descalle, M A; Escher, J E; Loshak, A; Navratil, P; Ormand, W E; Pruet, J; Thompson, I J; Wang, T F

    2008-10-06

    This document contains a comprehensive literature review in support of the theoretical assessment of the {sup 178m2}Hf de-excitation, as well as a rigorous description of controlled energy release from an isomeric nuclear state.

  11. Superconducting properties of the noncentrosymmetric superconductor Re6Hf

    NASA Astrophysics Data System (ADS)

    Singh, D.; Hillier, A. D.; Thamizhavel, A.; Singh, R. P.

    2016-08-01

    We report synthesis and detailed characterization of the noncentrosymmetric superconductor Re6Hf using powder x-ray diffraction (XRD), magnetization, transport, and thermodynamic measurements. XRD confirmed the noncentrosymmetric, α -Mn cubic structure in Re6Hf with the cubic cell parameter a =9.6850 (3 ) Å. Resistivity, DC, and AC magnetization measurements confirmed the type-II superconductivity in Re6Hf with the transition temperature Tconset˜5.96 K, having the lower critical field Hc 1(0 ) 5.6 mT and upper critical field Hc 2(0 ) 12.2 T. The electronic specific heat data fits well with the single-gap BCS model. The Sommerfeld coefficient (γ ) also shows linear relation with the magnetic field. All above results suggest s -wave superconductivity in Re6Hf .

  12. Low-Frequency Waves in HF Heating of the Ionosphere

    NASA Astrophysics Data System (ADS)

    Sharma, A. S.; Eliasson, B.; Milikh, G. M.; Najmi, A.; Papadopoulos, K.; Shao, X.; Vartanyan, A.

    2016-02-01

    Ionospheric heating experiments have enabled an exploration of the ionosphere as a large-scale natural laboratory for the study of many plasma processes. These experiments inject high-frequency (HF) radio waves using high-power transmitters and an array of ground- and space-based diagnostics. This chapter discusses the excitation and propagation of low-frequency waves in HF heating of the ionosphere. The theoretical aspects and the associated models and simulations, and the results from experiments, mostly from the HAARP facility, are presented together to provide a comprehensive interpretation of the relevant plasma processes. The chapter presents the plasma model of the ionosphere for describing the physical processes during HF heating, the numerical code, and the simulations of the excitation of low-frequency waves by HF heating. It then gives the simulations of the high-latitude ionosphere and mid-latitude ionosphere. The chapter also briefly discusses the role of kinetic processes associated with wave generation.

  13. Amorphous powders of Al-Hf prepared by mechanical alloying

    SciTech Connect

    Schwarz, R.B.; Hannigan, J.W.; Sheinberg, H.; Tiainen, T.

    1988-01-01

    We synthesized amorphous Al/sub 50/Hf/sub 50/ alloy powder by mechanically alloying an equimolar mixture of crystalline powders of Al and Hf using hexane as a dispersant. We characterized the powder as a function of mechanical-alloying time by scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry. Amorphous Al/sub 50/Hf/sub 50/ powder heated at 10 K s/sup /minus/1/ crystallizes polymorphously at 1003 K into orthorhombic AlHf (CrB-type structure). During mechanical alloying, some hexane decomposes and hydrogen and carbon are incorporated into the amorphous alloy powder. The hydrogen can be removed by annealing the powder by hot pressing at a temperature approximately 30 K below the crystallization temperature. The amorphous compacts have a diamond pyramidal hardness of 1025 DPH. 24 refs., 7 figs., 1 tab.

  14. Lu-Hf constraints on the evolution of lunar basalts

    NASA Technical Reports Server (NTRS)

    Fujimaki, H.; Tatsumoto, M.

    1984-01-01

    It is shown that a cumulate-remelting model best explains the recently acquired data on the Lu-Hf systematics of lunar mare basalts. The model is constructed using Lu and Hf concentration data and is strengthened by Hf isotopic evidence of Unruh et al. (1984). It is shown that the similarity in MgO/FeO ratios and Cr2O3 content in high-Ti and low-Ti basalts are not important constraints on lunar basalt petrogenesis. The model demonstrates that even the very low Ti or green glass samples are remelting products of a cumulate formed after at least 80-90 percent of the lunar magma ocean had solidified. In the model, all the mare basalts and green glasses were derived from 100-150 km depth in the lunar mantle. The Lu-Hf systematics of KREEP basalts clearly indicate that they would be the final residual liquid of the lunar magma ocean.

  15. Application of HF radar currents to oil spill modelling.

    PubMed

    Abascal, Ana J; Castanedo, Sonia; Medina, Raul; Losada, Inigo J; Alvarez-Fanjul, Enrique

    2009-02-01

    In this work, the benefits of high-frequency (HF) radar currents for oil spill modeling and trajectory analysis of floating objects are analyzed. The HF radar performance is evaluated by means of comparison between a drifter buoy trajectory and the one simulated using a Lagrangian trajectory model. A methodology to optimize the transport model performance and to calculate the search area of the predicted positions is proposed. This method is applied to data collected during the Galicia HF Radar Experience. This experiment was carried out to explore the capabilities of this technology for operational monitoring along the Spanish coast. Two long-range HF radar stations were installed and operated between November 2005 and February 2006 on the Galician coast. In addition, a drifter buoy was released inside the coverage area of the radar. The HF radar currents, as well as numerical wind data were used to simulate the buoy trajectory using the TESEO oil spill transport model. In order to evaluate the contribution of HF radar currents to trajectory analysis, two simulation alternatives were carried out. In the first one, wind data were used to simulate the motion of the buoy. In the second alternative, surface currents from the HF radar were also taken into account. For each alternative, the model was calibrated by means of the global optimization algorithm SCEM-UA (Shuffled Complex Evolution Metropolis) in order to obtain the probability density function of the model parameters. The buoy trajectory was computed for 24h intervals using a Monte Carlo approach based on the results provided in the calibration process. A bivariate kernel estimator was applied to determine the 95% confidence areas. The analysis performed showed that simulated trajectories integrating HF radar currents are more accurate than those obtained considering only wind numerical data. After a 24h period, the error in the final simulated position improves using HF radar currents. Averaging the

  16. Phase control of HF chemical lasers for coherent optical recombination.

    PubMed

    Wang, C P; Smith, P L

    1979-05-01

    A servo system for phase-locking two HF chemical lasers has been designed and simulated. A steady-state phase error is achieved that is adequate for coherent optical recombination. The results are based on the measured frequency drift of a small HF chemical laser and the measured frequency response of a piezoelectric transducer (PZT) mirror driver. A major innovation is the use of rate feedback with a laser Doppler sensor to extend the useful frequency response of the PZT driver.

  17. Few-layer HfS2 transistors

    PubMed Central

    Kanazawa, Toru; Amemiya, Tomohiro; Ishikawa, Atsushi; Upadhyaya, Vikrant; Tsuruta, Kenji; Tanaka, Takuo; Miyamoto, Yasuyuki

    2016-01-01

    HfS2 is the novel transition metal dichalcogenide, which has not been experimentally investigated as the material for electron devices. As per the theoretical calculations, HfS2 has the potential for well-balanced mobility (1,800 cm2/V·s) and bandgap (1.2 eV) and hence it can be a good candidate for realizing low-power devices. In this paper, the fundamental properties of few-layer HfS2 flakes were experimentally evaluated. Micromechanical exfoliation using scotch tape extracted atomically thin HfS2 flakes with varying colour contrasts associated with the number of layers and resonant Raman peaks. We demonstrated the I-V characteristics of the back-gated few-layer (3.8 nm) HfS2 transistor with the robust current saturation. The on/off ratio was more than 104 and the maximum drain current of 0.2 μA/μm was observed. Moreover, using the electric double-layer gate structure with LiClO4:PEO electrolyte, the drain current of the HfS2 transistor significantly increased to 0.75 mA/μm and the mobility was estimated to be 45 cm2/V·s at least. This improved current seemed to indicate superior intrinsic properties of HfS2. These results provides the basic information for the experimental researches of electron devices based on HfS2. PMID:26926098

  18. Few-layer HfS2 transistors

    NASA Astrophysics Data System (ADS)

    Kanazawa, Toru; Amemiya, Tomohiro; Ishikawa, Atsushi; Upadhyaya, Vikrant; Tsuruta, Kenji; Tanaka, Takuo; Miyamoto, Yasuyuki

    2016-03-01

    HfS2 is the novel transition metal dichalcogenide, which has not been experimentally investigated as the material for electron devices. As per the theoretical calculations, HfS2 has the potential for well-balanced mobility (1,800 cm2/V·s) and bandgap (1.2 eV) and hence it can be a good candidate for realizing low-power devices. In this paper, the fundamental properties of few-layer HfS2 flakes were experimentally evaluated. Micromechanical exfoliation using scotch tape extracted atomically thin HfS2 flakes with varying colour contrasts associated with the number of layers and resonant Raman peaks. We demonstrated the I-V characteristics of the back-gated few-layer (3.8 nm) HfS2 transistor with the robust current saturation. The on/off ratio was more than 104 and the maximum drain current of 0.2 μA/μm was observed. Moreover, using the electric double-layer gate structure with LiClO4:PEO electrolyte, the drain current of the HfS2 transistor significantly increased to 0.75 mA/μm and the mobility was estimated to be 45 cm2/V·s at least. This improved current seemed to indicate superior intrinsic properties of HfS2. These results provides the basic information for the experimental researches of electron devices based on HfS2.

  19. What Value "Value Added"?

    ERIC Educational Resources Information Center

    Richards, Andrew

    2015-01-01

    Two quantitative measures of school performance are currently used, the average points score (APS) at Key Stage 2 and value-added (VA), which measures the rate of academic improvement between Key Stage 1 and 2. These figures are used by parents and the Office for Standards in Education to make judgements and comparisons. However, simple…

  20. Synthesis of freestanding HfO2 nanostructures

    PubMed Central

    2011-01-01

    Two new methods for synthesizing nanostructured HfO2 have been developed. The first method entails exposing HfTe2 powders to air. This simple process resulted in the formation of nanometer scale crystallites of HfO2. The second method involved a two-step heating process by which macroscopic, freestanding nanosheets of HfO2 were formed as a byproduct during the synthesis of HfTe2. These highly two-dimensional sheets had side lengths measuring up to several millimeters and were stable enough to be manipulated with tweezers and other instruments. The thickness of the sheets ranged from a few to a few hundred nanometers. The thinnest sheets appeared transparent when viewed in a scanning electron microscope. It was found that the presence of Mn enhanced the formation of HfO2 by exposure to ambient conditions and was necessary for the formation of the large scale nanosheets. These results present new routes to create freestanding nanostructured hafnium dioxide. PACS: 81.07.-b, 61.46.Hk, 68.37.Hk. PMID:21711786

  1. Thermal stability of HfO2 nanotube arrays

    SciTech Connect

    Qiu, Xiaofeng; Howe, Jane Y; Meyer III, Harry M; Tuncer, Enis; Paranthaman, Mariappan Parans

    2010-01-01

    Thermal stability of highly ordered hafnium oxide (HfO2) nanotube arrays prepared through an electrochemical anodization method in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900 C in flowing argon atmosphere. The formation of the HfO2 nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as-grown and post-annealed HfO2 nanotube arrays were analyzed by powder Xray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Although monoclinic HfO2 is thermally stable up to 2000K in bulk, the morphology of HfO2 nanotube arrays degraded at 900 C. A detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impacted the composition and the chemical environment of the core elements (Hf and O), as well as F content coming from the electrolyte. Possible reasons for the degradation of the nanotube at high temperature were discussed based on XPS study and possible future improvements have also been suggested. Moreover, dielectric measurements were carried out on both the as-grown amorphous film and 500 C post-annealed crystalline film. This study will help us to understand the temperature impact on the morphology of nanotube arrays, which is important to its further applications at elevated temperatures.

  2. Tracking magmatic processes through Zr/Hf ratios in rocks and Hf and Ti zoning in zircons: An example from the Spirit Mountain batholith, Nevada

    USGS Publications Warehouse

    Lowery, Claiborne L.E.; Miller, C.F.; Walker, B.A.; Wooden, J.L.; Mazdab, F.K.; Bea, F.

    2006-01-01

    Zirconium and Hf are nearly identical geochemically, and therefore most of the crust maintains near-chondritic Zr/Hf ratios of ???35-40. By contrast, many high-silica rhyolites and granites have anomalously low Zr/Hf (15-30). As zircon is the primary reservoir for both Zr and Hf and preferentially incorporates Zr, crystallization of zircon controls Zr/ Hf, imprinting low Zr/Hf on coexisting melt. Thus, low Zr/Hf is a unique fingerprint of effective magmatic fractionation in the crust. Age and compositional zonation in zircons themselves provide a record of the thermal and compositional histories of magmatic systems. High Hf (low Zr/ Hf) in zircon zones demonstrates growth from fractionated melt, and Ti provides an estimate of temperature of crystallization (TTiZ) (Watson and Harrison, 2005). Whole-rock Zr/Hf and zircon zonation in the Spirit Mountain batholith, Nevada, document repeated fractionation and thermal fluctuations. Ratios of Zr/Hf are ???30-40 for cumulates and 18-30 for high-SiO2 granites. In zircons, Hf (and U) are inversely correlated with Ti, and concentrations indicate large fluctuations in melt composition and TTiZ (>100??C) for individual zircons. Such variations are consistent with field relations and ion-probe zircon geochronology that indicate a >1 million year history of repeated replenishment, fractionation, and extraction of melt from crystal mush to form the low Zr/Hf high-SiO2 zone. ?? 2006 The Mineralogical Society.

  3. Introducing ADS Labs

    NASA Astrophysics Data System (ADS)

    Accomazzi, Alberto; Henneken, E.; Grant, C. S.; Kurtz, M. J.; Di Milia, G.; Luker, J.; Thompson, D. M.; Bohlen, E.; Murray, S. S.

    2011-05-01

    ADS Labs is a platform that ADS is introducing in order to test and receive feedback from the community on new technologies and prototype services. Currently, ADS Labs features a new interface for abstract searches, faceted filtering of results, visualization of co-authorship networks, article-level recommendations, and a full-text search service. The streamlined abstract search interface provides a simple, one-box search with options for ranking results based on a paper relevancy, freshness, number of citations, and downloads. In addition, it provides advanced rankings based on collaborative filtering techniques. The faceted filtering interface allows users to narrow search results based on a particular property or set of properties ("facets"), allowing users to manage large lists and explore the relationship between them. For any set or sub-set of records, the co-authorship network can be visualized in an interactive way, offering a view of the distribution of contributors and their inter-relationships. This provides an immediate way to detect groups and collaborations involved in a particular research field. For a majority of papers in Astronomy, our new interface will provide a list of related articles of potential interest. The recommendations are based on a number of factors, including text similarity, citations, and co-readership information. The new full-text search interface allows users to find all instances of particular words or phrases in the body of the articles in our full-text archive. This includes all of the scanned literature in ADS as well as a select portion of the current astronomical literature, including ApJ, ApJS, AJ, MNRAS, PASP, A&A, and soon additional content from Springer journals. Fulltext search results include a list of the matching papers as well as a list of "snippets" of text highlighting the context in which the search terms were found. ADS Labs is available at http://adslabs.org

  4. Challenging the assumptions of Lu-Hf dating in spinel-peridotites

    NASA Astrophysics Data System (ADS)

    Byerly, B. L.; Lassiter, J. C.

    2013-12-01

    Lu-Hf 'pseudoisochrons' using peridotite-derived clinopyroxene separates are commonly used to constrain timing of melt depletion and lithosphere formation. However, cpx-based pseudoisochrons are only valid if 1) almost all Hf and Lu is hosted in the cpx, or 2) the system is below the mineral closure temperature. We tested these assumptions by examining Lu and Hf partitioning and Hf-isotope variations in cpx, opx, and bulk peridotite in xenoliths from the eastern Colorado Plateau and Rio Grande Rift. The samples primarily derive from Proterozoic SCLM, span a range of fertility (spinel Cr# range from 0.1-0.5), and have equilibration temperatures ranging from 950-1050°C, similar to temperatures reported for other xenoliths utilized in Lu-Hf isotope studies. Cpx have Hf and Lu concentrations ranging from 40-1000 ppb and 80-290 ppb, respectively. Opx have much lower Hf and Lu concentrations (5-60 ppb and 21-51 ppb). Concentrations of Lu, Hf, and other trace elements are well correlated between cpx and opx, indicating mineral equilibrium. DLucpx/opx and DHfcpx/opx range from 3.5-6.1 and 7.0-20, and are negatively correlated with cpx MgO content and other indices of peridotite fertility (e.g., spinel Cr#). Our results agree with (and extend the compositional range of) partition coefficients estimated following the formulation of [1]. The fraction of Lu and Hf hosted in opx increases in highly refractory samples. Although Lu/Hf in cpx is close to WR Lu/Hf in fertile samples, in refractory samples it is much lower. Hf isotopes in cpx are well correlated with cpx Lu/Hf (r2 = 0.998) and yield a pseudoisochron age of ~1.6 Ga (initial ɛHf of +30). Opx have systematically higher Lu/Hf than cpx, but in most samples have identical Hf isotopes. Some opx and WR have lower 176Hf/177Hf, similar to the host magma, likely reflecting melt contamination. The identical Hf isotopes in cpx and opx indicate that xenoliths evolved above the Lu-Hf closure temperature. Therefore, cpx (and opx

  5. Role of Hf on Phase Formation in Ti45Zr(38-x)Hf(x)Ni17 Liquids and Solids

    NASA Technical Reports Server (NTRS)

    Wessels, V.; Sahu, K. K.; Gangopadhyay, A. K.; Huett, V. T.; Canepari, S.; Goldman, A. I.; Hyers, R. W.; Kramer, M. J.; Rogers, J. R.; Kelton, K. F.; Robinson, D.

    2008-01-01

    Hafnium and zirconium are very similar, with almost identical sizes and chemical bonding characteristics. However, they behave differently when alloyed with Ti and Ni. A sharp phase formation boundary near 18-21 at.% Hf is observed in rapidly-quenched and as-cast Ti45Zr38-xHfxNi17 alloys. Rapidly-quenched samples that contain less than 18 at.% Hf form the icosahedral quasicrystal phase, whiles samples containing more than 21 at.% form the 3/2 rational approximant phase. In cast alloys, a C14 structure is observed for alloys with Hf lower than the boundary concentration, while a large-cell (11.93 ) FCC Ti2Ni-type structure is found in alloys with Hf concentrations above the boundary. To better understand the role of Hf on phase formation, the structural evolution with supercooling and the solidification behavior of liquid Ti45Zr38-xHfxNi17 alloys (x=0, 12, 18, 21, 38) were studied using the Beamline Electrostatic Levitation (BESL) technique using 125keV x-rays on the 6ID-D beamline at the Advanced Photon Source, Argonne National Laboratory. For all liquids primary crystallization was to a BCC solid solution phase; interestly, an increase in Hf concentration leads to a decrease in the BCC lattice parameter in spite of the chemical similarity between Zr and Hf. A Reitveld analysis confirmed that as in the cast alloys, the secondary phase that formed was the C14 below the phase formation boundary and a Ti2Ni-type structure at higher Hf concentrations. Both the liquidus temperature and the reduced undercooling change sharply on traversing the phase formation boundary concentration, suggesting a change in the liquid structure. Structural information from a Honeycutt-Anderson index analysis of reverse Monte Carlo fits to the S(q) liquid data will be presented to address this issue.

  6. 182Hf-182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System.

    PubMed

    Holst, Jesper C; Olsen, Mia B; Paton, Chad; Nagashima, Kazuhide; Schiller, Martin; Wielandt, Daniel; Larsen, Kirsten K; Connelly, James N; Jørgensen, Jes K; Krot, Alexander N; Nordlund, Ake; Bizzarro, Martin

    2013-05-28

    Refractory inclusions [calcium-aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., (26)Al, (41)Ca, and (182)Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of (26)Al corresponding to (26)Al/(27)Al of ∼5 × 10(-5), rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and (26)Al/(27)Al of <5 × 10(-6), possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the (182)Hf-(182)W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with (26)Al/(27)Al of ∼3 × 10(-6). The decoupling between (182)Hf and (26)Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for (182)Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for (26)Al. Admixing of stellar-derived (26)Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the (26)Al-(26)Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support (182)Hf homogeneity and chronological significance of the (182)Hf-(182)W clock. PMID:23671077

  7. 182Hf-182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System.

    PubMed

    Holst, Jesper C; Olsen, Mia B; Paton, Chad; Nagashima, Kazuhide; Schiller, Martin; Wielandt, Daniel; Larsen, Kirsten K; Connelly, James N; Jørgensen, Jes K; Krot, Alexander N; Nordlund, Ake; Bizzarro, Martin

    2013-05-28

    Refractory inclusions [calcium-aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., (26)Al, (41)Ca, and (182)Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of (26)Al corresponding to (26)Al/(27)Al of ∼5 × 10(-5), rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and (26)Al/(27)Al of <5 × 10(-6), possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the (182)Hf-(182)W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with (26)Al/(27)Al of ∼3 × 10(-6). The decoupling between (182)Hf and (26)Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for (182)Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for (26)Al. Admixing of stellar-derived (26)Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the (26)Al-(26)Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support (182)Hf homogeneity and chronological significance of the (182)Hf-(182)W clock.

  8. Serpentinization Changes Nd, but not Hf Isotopes of Abyssal Peridotites

    NASA Astrophysics Data System (ADS)

    Bizimis, M.; Frisby, C. P.; Mallick, S.

    2015-12-01

    Serpentinization of the oceanic lithosphere is a known sink for fluid mobile elements (B, Cl, Li, Sr, etc.), while high field strength elements (HFSE: e.g., Hf, Zr, Ti, Nb) are thought to be unaffected by it. In contrast, the fate of REE during serpentinization is equivocal. Correlations between REE and HFSE concentrations in abyssal peridotites suggest control by magmatic processes (Niu, 2004, J. Pet), while some LREE enrichments in serpentinized peridotites compared to their clinopyroxene (cpx) and Nd, Sr isotope data (Delacour et al., 2008, Chem. Geol.) imply seawater-derived REE addition to the mantle protolith (Paulick et al., 2006, Chem. Geol). To further constrain peridotite-seawater interaction during serpentinization we compare bulk rock and cpx Hf and Nd isotope data in partially (up to ~70%) serpentinized abyssal peridotites (9-16°E South West Indian Ridge). We also present a new method that improves yields in Hf, Nd and Pb separations from depleted (<0.03 ppm Hf) ultramafic rocks, which includes coprecipitation of metals with Al-Fe hydroxides and ether-HCl liquid-liquid exchange for Fe removal. Nd isotopes in the bulk peridotite are up to 7ɛNd units less radiogenic than their cpx (i.e., the magmatic value) while Hf isotopes remain equal to cpx within 1 ɛHf. Melt-rock reaction by the local lavas cannot generate this decoupling. The largest Nd isotopic difference between cpx and bulk is seen in the most LREE-depleted samples, while refertilized samples show little change. Leaching experiments show that 30-60% of REE are mobilized from the rock, but >90% of Hf, Zr, Ti are retained in the residue. LA-ICPMS data shows that serpentine after olivine typically has higher LREE/HREE ratios than cpx, pronounced negative Ce anomalies, high U, Sr concentrations and low HFSE, unlike the coexisting cpx. These data are consistent with some seawater-derived LREE addition to peridotite during serpentinization, localized in the serpentine and other secondary phases

  9. Investigation and Development of Data-Driven D-Region Model for HF Systems Impacts

    NASA Technical Reports Server (NTRS)

    Eccles, J. V.; Rice, D.; Sojka, J. J.; Hunsucker, R. D.

    2002-01-01

    Space Environment Corporation (SEC) and RP Consultants (RPC) are to develop and validate a weather-capable D region model for making High Frequency (HF) absorption predictions in support of the HF communications and radar communities. The weather-capable model will assimilate solar and earth space observations from NASA satellites. The model will account for solar-induced impacts on HF absorption, including X-rays, Solar Proton Events (SPE's), and auroral precipitation. The work plan includes: I . Optimize D-region model to quickly obtain ion and electron densities for proper HF absorption calculations. 2. Develop indices-driven modules for D-region ionization sources for low, mid, & high latitudes including X-rays, cosmic rays, auroral precipitation, & solar protons. (Note: solar spectrum & auroral modules already exist). 3. Setup low-cost monitors of existing HF beacons and add one single-frequency beacon. 4. Use PENEX HF-link database with HF monitor data to validate D-region/HF absorption model using climatological ionization drivers. 5. Develop algorithms to assimilate NASA satellite data of solar, interplanetary, and auroral observations into ionization source modules. 6. Use PENEX HF-link & HF-beacon data for skill score comparison of assimilation versus climatological D-region/HF absorption model. Only some satellites are available for the PENEX time period, thus, HF-beacon data is necessary. 7. Use HF beacon monitors to develop HF-link data assimilation algorithms for regional improvement to the D-region/HF absorption model.

  10. Hf-Zr anomalies in clinopyroxene from mantle xenoliths from France and Poland: implications for Lu-Hf dating of spinel peridotite lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Downes, Hilary; de Vries, Caja; Wittig, Nadine

    2014-09-01

    Clinopyroxenes in some fresh anhydrous spinel peridotite mantle xenoliths from the northern Massif Central (France) and Lower Silesia (Poland), analysed for a range of incompatible trace elements by laser ablation inductively coupled plasma mass spectrometry, show unusually strong negative anomalies in Hf and Zr relative to adjacent elements Sm and Nd, on primitive mantle-normalised diagrams. Similar Zr-Hf anomalies have only rarely been reported from clinopyroxene in spinel peridotite mantle xenoliths worldwide, and most are not as strong as the examples reported here. Low Hf contents give rise to a wide range of Lu/Hf ratios, which over geological time would result in highly radiogenic ɛHf values, decoupling them from ɛNd ratios. The high 176Lu/177Hf could in theory produce an isochronous relationship with 176Hf/177Hf over time; an errorchron is shown by clinopyroxene from mantle xenoliths from the northern Massif Central. However, in a review of the literature, we show that most mantle spinel peridotites do not show such high Lu/Hf ratios in their constituent clinopyroxenes, because they lack the distinctive Zr-Hf anomaly, and this limits the usefulness of the application of the Lu-Hf system of dating to garnet-free mantle rocks. Nevertheless, some mantle xenoliths from Poland or the Czech Republic may be amenable to Hf-isotope dating in the future.

  11. Hf-Zr anomalies in clinopyroxene from mantle xenoliths from France and Poland: implications for Lu-Hf dating of spinel peridotite lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Downes, Hilary; de Vries, Caja; Wittig, Nadine

    2015-01-01

    Clinopyroxenes in some fresh anhydrous spinel peridotite mantle xenoliths from the northern Massif Central (France) and Lower Silesia (Poland), analysed for a range of incompatible trace elements by laser ablation inductively coupled plasma mass spectrometry, show unusually strong negative anomalies in Hf and Zr relative to adjacent elements Sm and Nd, on primitive mantle-normalised diagrams. Similar Zr-Hf anomalies have only rarely been reported from clinopyroxene in spinel peridotite mantle xenoliths worldwide, and most are not as strong as the examples reported here. Low Hf contents give rise to a wide range of Lu/Hf ratios, which over geological time would result in highly radiogenic ɛHf values, decoupling them from ɛNd ratios. The high 176Lu/177Hf could in theory produce an isochronous relationship with 176Hf/177Hf over time; an errorchron is shown by clinopyroxene from mantle xenoliths from the northern Massif Central. However, in a review of the literature, we show that most mantle spinel peridotites do not show such high Lu/Hf ratios in their constituent clinopyroxenes, because they lack the distinctive Zr-Hf anomaly, and this limits the usefulness of the application of the Lu-Hf system of dating to garnet-free mantle rocks. Nevertheless, some mantle xenoliths from Poland or the Czech Republic may be amenable to Hf-isotope dating in the future.

  12. Two Virasoro symmetries in stringy warped AdS3

    NASA Astrophysics Data System (ADS)

    Compère, Geoffrey; Guica, Monica; Rodriguez, Maria J.

    2014-12-01

    We study three-dimensional consistent truncations of type IIB supergravity which admit warped AdS3 solutions. These theories contain subsectors that have no bulk dynamics. We show that the symplectic form for these theories, when restricted to the non-dynamical subsectors, equals the symplectic form for pure Einstein gravity in AdS3. Consequently, for each consistent choice of boundary conditions in AdS3, we can define a consistent phase space in warped AdS3 with identical conserved charges. This way, we easily obtain a Virasoro × Virasoro asymptotic symmetry algebra in warped AdS3; two different types of Virasoro × Kač-Moody symmetries are also consistent alternatives.

  13. Latitudinal distributions and temporal changes of stratospheric HCl and HF

    NASA Technical Reports Server (NTRS)

    Mankin, W. G.; Coffey, M. T.

    1983-01-01

    Hydrogen chloride and hydrogen fluoride are important sinks in the stratosphere for free halogens. The major sources of chlorine and fluorine in the stratosphere are anthropogenic; therefore, a measurement of HCl and HF gives information about the magnitude of anthropogenic effects on stratospheric chemistry and may give some information about the stratospheric hydroxyl concentration as well. The total column amount of HCl and HF above 12 km has been determined by measuring infrared absorption spectra with a high-resolution Fourier transform spectrometer flown on a jet aircraft. The HCl column varies from 0.7 x 10 to the 15th molecules/ sq cm near the equator to 2.7 x 10 to the 15th molecules/sq cm at 70 N; the HF column is about a factor of 5 lower. The HCl:HF ratio is almost independent of latitude, and neither constituent shows substantial seasonal or diurnal variation. At mid-latitudes, the data from 1978 to 1982 show an annual increase of 5 percent per year for HCl and 12 percent per year for HF.

  14. Developments in HF equipment and systems mobile and portable terminals

    NASA Astrophysics Data System (ADS)

    Wilson, Q. C.

    1986-03-01

    Before the advent of satellite platforms, sophisticated high frequency (HF) propagation and system research promised improved capability during disturbed ionospheric propagation conditions. However, satellite relays captured the imaginations and pocketbooks of the communications community in the mid-1960s. Consequently, extant HF systems aged while satellite systems were implemented. During peacetime, satellite systems transmit quality low data rate communications and navigation aids to mobile users, but there is now renewed interest in the low cost and survivability attributes of HF radio. At this time, when old HF prime systems need replacement for logistical reasons, the need for low cost communications that can survive jamming, nuclear effects, and space warfare is not satisfied. The HF renaissance is the response to this challenge. Logistical replacement procurements that provide new capabilities are redressing the attrition of vacuum-tube radio equipment over the last decade. Procuring organizations typically compile specifications comprising state-of-the-art and new capabilities offered by competing vendors. Integrated circuits, which include microprocessors, synthesizer ele ments, and other evolving components, have led to new circuit architectures. The first of the following three sections describes: Receivers; Transceivers and Antenna Couplers; Antenna Kits; and Audio Channel Peripherals.

  15. Leading Change, Adding Value.

    PubMed

    Evans, Nick

    2016-09-12

    Essential facts Leading Change, Adding Value is NHS England's new nursing and midwifery framework. It is designed to build on Compassion in Practice (CiP), which was published 3 years ago and set out the 6Cs: compassion, care, commitment, courage, competence and communication. CiP established the values at the heart of nursing and midwifery, while the new framework sets out how staff can help transform the health and care sectors to meet the aims of the NHS England's Five Year Forward View. PMID:27615573

  16. Development of Creep-Resistant NiAl(Ti,Hf) Single-Crystal Alloys

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Nickel-base superalloys are the current choice for high-temperature jet engine applications such as turbine blades and vanes. However, after more than five decades of use, nickel-base superalloys have reached their limit, since the operating temperatures in gas turbine engines are now approaching the melting temperature of these alloys. Thus alternative materials, such as lightweight NiAl intermetallic alloys with superior properties, (e.g., high melting temperature, high thermal conductivity, and excellent chemical stability and oxidation resistance) are required for the next generation of high-temperature structural materials for more efficient 21st century civil transport systems. The two major disadvantages that have historically prevented the application of NiAl as a high-temperature structural material are its poor creep resistance and low room-temperature ductility. Alloying strategies similar to those used for nickel-base superalloys are being used to improve the high-temperature strength via solid-solution and precipitate-hardening effects. This study highlights the potent role of Ti and Hf as potential solid-solution strengtheners in NiAl and also the added effect of second-phase particles when Ti and Hf are both used.

  17. Effect of HF leaching on 14C dates of pottery

    NASA Astrophysics Data System (ADS)

    Goslar, Tomasz; Kozłowski, Janusz; Szmyt, Marzena; Czernik, Justyna

    2013-01-01

    This paper presents the experiments with 14C dating of two potsherds, which contained carbon dispersed rather homogeneously in their clay fabric. After AAA treatment, the potsherds still appeared to be contaminated with young carbon, presumably connected with humic acids. To make removal of humic acids more effective, we treated the sherds with HF acid of different concentration. The 14C results obtained demonstrate that HF treatment indeed helps to remove humic contaminants, but it also mobilizes carbon bound to raw clay, which may make 14C dates too old. We conclude therefore, that using a simple combination of HF and AAA treatment seems insufficient in reliable 14C dating of carbon homogeneously dispersed in the volume of potsherds.

  18. Nonlinear realization of local symmetries of AdS space

    SciTech Connect

    Clark, T.E.; Love, S.T.; Nitta, Muneto; Veldhuis, T. ter

    2005-10-15

    Coset methods are used to construct the action describing the dynamics associated with the spontaneous breaking of the local symmetries of AdS{sub d+1} space due to the embedding of an AdS{sub d} brane. The resulting action is an SO(2,d) invariant AdS form of the Einstein-Hilbert action, which in addition to the AdS{sub d} gravitational vielbein, also includes a massive vector field localized on the brane. Its long wavelength dynamics is the same as a massive Abelian vector field coupled to gravity in AdS{sub d} space.

  19. Feature Modeling of HfO2 Atomic Layer Deposition Using HfCl4/H2O

    NASA Astrophysics Data System (ADS)

    Stout, Phillip J.; Adams, Vance; Ventzek, Peter L. G.

    2003-03-01

    A Monte Carlo based feature scale model (Papaya) has been applied to atomic layer deposition (ALD) of HfO2 using HfCl_4/H_20. The model includes physical effects of transport to surface, specular and diffusive reflection within feature, adsorption, surface diffusion, deposition and etching. Discussed will be the 3D feature modeling of HfO2 deposition in assorted features (vias and trenches). The effect of feature aspect ratios, pulse times, cycle number, and temperature on film thickness, feature coverage, and film Cl fraction (surface/bulk) will be discussed. Differences between HfO2 ALD on blanket wafers and in features will be highlighted. For instance, the minimum pulse times sufficient for surface reaction saturation on blanket wafers needs to be increased when depositing on features. Also, HCl products created during the HfCl4 and H_20 pulses are more likely to react within a feature than at the field, reducing OH coverage within the feature (vs blanket wafer) thus limiting the maximum coverage attainable for a pulse over a feature.

  20. Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

    USGS Publications Warehouse

    Patchett, P.J.

    1983-01-01

    The 176Lu-176Hf isotope method and its applications in earth sciences are discussed. Greater fractionation of Lu/Hf than Sm/Nd in planetary magmatic processes makes 176Hf 177Hf a powerful geochemical tracer. In general, proportional variations of 176Hf 177Hf exceed those of 143Nd l44Nd by factors of 1.5-3 in terrestrial and lunar materials. Lu-Hf studies therefore have a major contribution to make in understanding of terrestrial and other planetary evolution through time, and this is the principal importance of Lu-Hf. New data on basalts from oceanic islands show unequivocally that whereas considerable divergences occur in 176Hf 177Hf- 87Sr 86Sr and 143Nd l44Nd- 87Sr 86Sr diagrams, 176Hf 177Hf and 143Nd 144Nd display a single, linear isotopic variation in the suboceanic mantle. These discordant 87Sr 86Sr relationships may allow, with the acquisition of further Hf-Nd-Sr isotopic data, a distinction between processes such as mantle metasomatism, influence of seawater-altered material in the magma source, or recycling of sediments into the mantle. In order to evaluate the Hf-Nd isotopic correlation in terms of mantle fractionation history, there is a need for measurements of Hf distribution coefficients between silicate minerals and liquids, and specifically for a knowledge of Hf behavior in relation to rareearth elements. For studying ancient terrestrial Hf isotopic variations, the best quality Hf isotope data are obtained from granitoid rocks or zircons. New data show that very U-Pb discordant zircons may have upwardly-biased 176Hf 177Hf, but that at least concordant to slightly discordant zircons appear to be reliable carriers of initial 176Hf 177Hf. Until the controls on addition of radiogenic Hf to zircon are understood, combined zircon-whole rock studies are recommended. Lu-Hf has been demonstrated as a viable tool for dating of ancient terrestrial and extraterrestrial samples, but because it offers little advantage over existing methods, is unlikely to find

  1. Field operations with cesium clocks in HF navigation systems

    NASA Technical Reports Server (NTRS)

    Christy, E. H.; Clayton, D. A.

    1982-01-01

    Networks of HF phase comparison marine navigation stations employing cesium clocks are discussed. The largest permanent network is in the Gulf of Mexico where some fourteen base stations are continuously active and others are activated as needed. These HF phase comparison systems, which operate on a single transmission path, require a clock on the mobile unit as well. Inventory consists of upwards of 70 clocks from two different manufacturers. The maintenance of this network as an operating system requires a coordinated effort involving clock preparation, clock environment control, station performance monitoring and field service.

  2. European coordination for coastal HF radar data in EMODnet Physics

    NASA Astrophysics Data System (ADS)

    Mader, Julien; Novellino, Antonio; Gorringe, Patrick; Griffa, Annalisa; Schulz-Stellenfleth, Johannes; Montero, Pedro; Montovani, Carlo; Ayensa, Garbi; Vila, Begoña; Rubio, Anna; Sagarminaga, Yolanda

    2015-04-01

    Historically, joint effort has been put on observing open ocean, organizing, homogenizing, sharing and reinforcing the impact of the acquired information based on one technology: ARGO with profilers Argo floats, EuroSites, ESONET-NoE, FixO3 for deep water platforms, Ferrybox for stations in ships of opportunities, and GROOM for the more recent gliders. This kind of networking creates synergies and makes easier the implementation of this source of data in the European Data exchange services like EMODnet, ROOSs portals, or any applied services in the Blue economy. One main targeted improvement in the second phase of EMODnet projects is the assembling of data along coastline. In that sense, further coordination is recommended between platform operators around a specific technology in order to make easier the implementation of the data in the platforms (4th EuroGOOS DATAMEQ WG). HF radar is today recognized internationally as a cost-effective solution to provide high spatial and temporal resolution current maps (depending on the instrument operation frequency, covering from a few kilometres offshore up to 200 km) that are needed for many applications for issues related to ocean surface drift or sea state characterization. Significant heterogeneity still exists in Europe concerning technological configurations, data processing, quality standards and data availability. This makes more difficult the development of a significant network for achieving the needed accessibility to HF Radar data for a pan European use. EuroGOOS took the initiative to lead and coordinate activities within the various observation platforms by establishing a number of Ocean Observing Task Teams such as HF-Radars. The purpose is to coordinate and join the technological, scientific and operational HF radar communities at European level. The goal of the group is on the harmonization of systems requirements, systems design, data quality, improvement and proof of the readiness and standardization of

  3. Concerted hydrogen atom exchange between three HF molecules

    NASA Technical Reports Server (NTRS)

    Komornicki, Andrew; Dixon, David A.; Taylor, Peter R.

    1992-01-01

    The termolecular reaction involving concerted hydrogen-atom exchange between three HF molecules was investigated with particular attention given to the effects of correlation at the various stationary points along the reaction. Using large segmented Gaussian basis sets to locate the (HF)3 stationary points at the SCF level, the geometries of the stable hydrogen-bonded trimer, which is of C(3h) symmetry, were located, together with the transition state for hydrogen exchange, which is of D(3h) symmetry. Then, using a large atomic natural orbital basis and correlating all valence electrons, the energetics of the exchange reaction were evaluated at the correlated level.

  4. Ca + HF - The anatomy of a chemical insertion reaction

    NASA Technical Reports Server (NTRS)

    Jaffe, R. L.; Pattengill, M. D.; Mascarello, F. G.; Zare, R. N.

    1987-01-01

    A comprehensive first-principles theoretical investigation of the gas phase reaction Ca + HF - CaF + H is reported. Ab initio potential energy calculations are first discussed, along with characteristics of the computed potential energy surface. Next, the fitting of the computed potential energy points to a suitable analytical functional form is described, and maps of the fitted potential surface are displayed. The methodology and results of a classical trajectory calculation utilizing the fitted potential surface are presented. Finally, the significance of the trajectory study results is discussed, and generalizations concerning dynamical aspects of Ca + HF scattering are drawn.

  5. Dressing phases of AdS3/CFT2

    NASA Astrophysics Data System (ADS)

    Borsato, Riccardo; Ohlsson Sax, Olof; Sfondrini, Alessandro; Stefański, Bogdan, Jr.; Torrielli, Alessandro

    2013-09-01

    We determine the all-loop dressing phases of the AdS3/CFT2 integrable system related to type IIB string theory on AdS3×S3×T4 by solving the recently found crossing relations and studying their singularity structure. The two resulting phases present a novel structure with respect to the ones appearing in AdS5/CFT4 and AdS4/CFT3. In the strongly coupled regime, their leading order reduces to the universal Arutyunov-Frolov-Staudacher phase as expected. We also compute their subleading order and compare it with recent one-loop perturbative results and comment on their weak-coupling expansion.

  6. Bubbling geometries for AdS2× S2

    NASA Astrophysics Data System (ADS)

    Lunin, Oleg

    2015-10-01

    We construct BPS geometries describing normalizable excitations of AdS2×S2. All regular horizon-free solutions are parameterized by two harmonic functions in R 3 with sources along closed curves. This local structure is reminiscent of the "bubbling solutions" for the other AdS p ×S q cases, however, due to peculiar asymptotic properties of AdS2, one copy of R 3 does not cover the entire space, and we discuss the procedure for analytic continuation, which leads to a nontrivial topological structure of the new geometries. We also study supersymmetric brane probes on the new geometries, which represent the AdS2×S2 counterparts of the giant gravitons.

  7. A routine high-precision method for Lu-Hf isotope geochemistry and chronology

    USGS Publications Warehouse

    Patchett, P.J.; Tatsumoto, M.

    1981-01-01

    A method for chemical separation of Lu and Hf from rock, meteorite and mineral samples is described, together with a much improved mass spectrometric running technique for Hf. This allows (i) geo- and cosmochronology using the176Lu???176Hf+??- decay scheme, and (ii) geochemical studies of planetary processes in the earth and moon. Chemical yields for the three-stage ion-exchange column procedure average 90% for Hf. Chemical blanks are <0.2 ng for Lu and Hf. From 1 ??g of Hf, a total ion current of 0.5??10-11 Ampere can be maintained for 3-5 h, yielding 0.01-0.03% precision on the ratio176Hf/177Hf. Normalisation to179Hf/177Hf=0.7325 is used. Extensive results for the Johnson Matthey Hf standard JMC 475 are presented, and this sample is urged as an international mass spectrometric standard; suitable aliquots, prepared from a single batch of JMC 475, are available from Denver. Lu-Hf analyses of the standard rocks BCR-1 and JB-1 are given. The potential of the Lu-Hf method in isotope geochemistry is assessed. ?? 1980 Springer-Verlag.

  8. Infrared overtone spectroscopy of hydrogen fluoride van der Waals complexes at upsilon (HF) = 3

    NASA Astrophysics Data System (ADS)

    Tsang, Susy Ngan Ping

    1998-11-01

    The dependence of weak intermolecular forces on valence bond excitations is investigated by the spectroscopy and vibrational predissociation dynamics of four hydrogen fluoride van der Waals complexes, N2HF, (HF)2, Ar2HF and Ar3HF, at the second overtone vibrational excitation of the hydrogen bonded HF intramolecular stretch, v HF=3. The formation and detection of these weakly bound complexes are achieved by the unique combination of slit supersonic jet expansion and intracavity Ti:sapphire laser-induced fluorescence. For the four complexes studied, an increase in the red- shift as a function of v HF was observed in the hydrogen bonded HF valence stretch as a result of the strengthening of the hydrogen bond. In addition, changes in the anisotropies of the intermolecular potentials of these weakly bound systems are in accord with those observed in the prototypical studies of ArHF at v HF=3 in this laboratory. However, the van der Waals soft modes have only been completely characterized for N2HF at v HF=3. Moreover, the frequencies of these intermolecular modes were experimentally determined for the first time in the N2HF complex. Of major interest in the N2HF studies is the intermolecular state dependence of the vibrational predissociation in this complex at v HF=3. Intermolecular state dependent vibrational predissociation dynamics is also observed in the (HF)2 studies. In order to further understand the complex internal dynamics in N2HF, ab initio calculations for a highly accurate four-dimensional potential energy surface using the symmetry adapted perturbation theory (SAPT) method were performed at v HF=0 and at v HF=3. A preliminary analysis of the ab initio data for both vibrational states and bound state calculations for the ground state potential energy surface are presented. The work on the Ar2HF and Ar3HF clusters tests the accuracy of pairwise additive intermolecular potentials for these two systems at v HF=3. In particular, the data obtained on these

  9. [Value-Added--Adding Economic Value in the Food Industry].

    ERIC Educational Resources Information Center

    Welch, Mary A., Ed.

    1989-01-01

    This booklet focuses on the economic concept of "value added" to goods and services. A student activity worksheet illustrates how the steps involved in processing food are examples of the concept of value added. The booklet further links food processing to the idea of value added to the Gross National Product (GNP). Discussion questions, a student…

  10. Photon scattering experiments off 176Hf and the systematics of low-lying dipole modes in the stable even-even Hf isotopes 176,178,180Hf

    NASA Astrophysics Data System (ADS)

    Scheck, M.; Belic, D.; von Brentano, P.; Carroll, J. J.; Fransen, C.; Gade, A.; von Garrel, H.; Kneissl, U.; Kohstall, C.; Linnemann, A.; Pietralla, N.; Pitz, H. H.; Stedile, F.; Toman, R.; Werner, V.

    2003-06-01

    The low-lying dipole strength distribution in the rare isotope 176Hf was studied in nuclear resonance fluorescence experiments performed at the Stuttgart Dynamitron facility using bremsstrahlung beams with end- point energies of 4.1 and 2.4 MeV. In total, about 55 excited spin-1 states, unknown so far, were observed in the excitation energy range up to 4 MeV. Detailed spectroscopic information has been obtained on excitation energies, spins, decay widths, decay branchings, and transition probabilities. Ascribing a positive parity to all observed K=1 states, the detected total B(M1)↑ strength in the energy range of the scissors mode amounts to 2.56(6) μ2N, nearly as much as for well-deformed midshell rare-earth nuclei. The total strength is higher than in the heavier Hf isotopes 178,180Hf, but fits well into the systematics. The observed low-lying ΔK=0 transitions (with probable E1 character) lie in the energy range around 2 MeV, as expected from the systematics. The excitation probabilities correspond to values which are characteristic for nuclei in the transitional region from deformed rotors to more γ-soft nuclei.

  11. Processing and crystallographic structure of non-equilibrium Si-doped HfO{sub 2}

    SciTech Connect

    Hou, Dong; Fancher, Chris M.; Esteves, Giovanni; Jones, Jacob L.; Zhao, Lili

    2015-06-28

    Si-doped HfO{sub 2} was confirmed to exist as a non-equilibrium state. The crystallographic structures of Si-doped HfO{sub 2} were studied using high-resolution synchrotron X-ray diffraction and the Rietveld refinement method. Incorporation of Si into HfO{sub 2} and diffusion of Si out of (Hf,Si)O{sub 2} were determined as a function of calcination temperature. Higher thermal energy input at elevated calcination temperatures resulted in the formation of HfSiO{sub 4}, which is the expected major secondary phase in Si-doped HfO{sub 2}. The effect of SiO{sub 2} particle size (nano- and micron-sized) on the formation of Si-doped HfO{sub 2} was also determined. Nano-crystalline SiO{sub 2} was found to incorporate into HfO{sub 2} more readily.

  12. Composition effects on mechanical properties of HfC-strengthened molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Witzke, W. R.

    1976-01-01

    The mechanical properties of swaged rod thermomechanically processed from arc-melted Mo-2Re-Hf-C alloys containing as much as 0.9 mol pct HfC have been evaluated. The low temperature ductilities of these alloys were not influenced by the amount of HfC present but by the amount of Hf in excess of stoichiometry. Maximum ductility occurred at 0.2 to 0.3 at. pct excess Hf. At 0.3 to 0.5 mol pct HfC, alloy strength varied directly with the Mo content of extracted carbide particles, both decreasing as the amount of excess Hf increased. Additions of 2 at. pct Re had little effect on strength or ductility. Tensile and creep strengths of Mo-2Re-0.7Hf-0.5C alloy equaled or exceeded those of other high strength Mo alloys.

  13. Exploring space plasmas - The WISP/HF experiment

    SciTech Connect

    James, H.G.; Darlington, T.R.; Hersom, C.H.; Gruno, R.S.; Gore, J.V.

    1987-02-01

    WISP/HF is the high-frequency part of the collaborative U.S.-Canada investigation, Waves in Space Plasmas. Instrumentation is being developed that will be flown on NASA's Space Shuttle starting with the Space Plasma Lab missions in the 1990s. Using a high-inclination orbit at heights near the maximum density of the ionospheric F region, active experiments will be carried out on antennas, electromagnetic and electrostatic wave propagation, problems in linear and nonlinear plasma physics, large-scale ionospheric structures, ionospheric irregularities, and the interaction of charged-particle beams with the ionospheric plasma. The WISP/HF equipment will generate, receive, and process signals in the 0.1-to 30-MHz range. The Orbiter-based transmitter will have variable pulse-power levels up to 0.5 kW and will use a dipole of variable length up to 300 m tip-to-tip. WISP/HF receivers will be located both on the Orbiter and on a subsatellite. A high level of operational flexibility in the WISP/HF instrument design has been achieved through programmable digital control. The design also permits human control of experiments, both from the Orbiter and from the ground.

  14. Single source noise reduction of received HF audio: experimental study

    NASA Astrophysics Data System (ADS)

    Campbell, Eric C.; Alva, Carlos O.

    2014-05-01

    This paper visits the application of single-source noise reduction on received audio over a HF channel. The noise reduction algorithm is typically used in vocoder noise processing at the transmitter before encoding. This study presents the results of the algorithm effects by objectively measuring audio quality through the use of industry standard PESQ analysis.

  15. A Coupled Ionosphere-Raytrace Model for Artificial HF Heating

    NASA Astrophysics Data System (ADS)

    Zawdie, K.; Huba, J. D.; Drob, D. P.; Bernhardt, P. A.

    2015-12-01

    The first self-consistent 3D model of artificial HF ionospheric heating has been developed. The model combines the first principles ionosphere model SAMI3/ESF and the ray trace code MoJo-15. The location of HF heating is calculated by simulating the ray path through the ionosphere and determining the average heating location. This new model has been used to successfully simulate the snapback effect discovered in a Arecibo HF heating experiment described by Bernhardt et al. [1988]. The simulations provide new insight into the physical mechanism for snapback. As Bernhardt et al. [1988] hypothesized, the heater wave is refracted by the density cavity, thus causing the location of heating to drift in longitude. The cause of snapback, however, is not that the ray snaps back to its original configuration once the density cavity has convected out of range. Instead, the density cavity convects into the path of the refracted ray such that only a small portion of the ray near the original heating location is above the threshold for HF heating. The heating location thus suddenly snaps back to the original location but the ray itself is still refracted in longitude.

  16. First 100 ms of HF modification at Tromso, Norway

    NASA Astrophysics Data System (ADS)

    Djuth, F. T.; Isham, B.; Rietveld, M. T.; Hagfors, T.; La Hoz, C.

    Experiments were performed with the high-power high-frequency HF facility at Troms o Norway to test theoretical predictions for the excitation of ion and Langmuir oscillations in the ionosphere The principal diagnostic of wave-plasma interactions was the VHF radar at the European Incoherent Scatter EISCAT facility High resolution radar techniques were used to monitor the temporal development of the ion and Langmuir oscillations HF pulses 100 ms in duration were periodically transmitted into a smooth background F region plasma Measurements of the radar backscatter spectra show that all key spectral features predicted by strong Langmuir turbulence SLT theory modified Zakharov model are simultaneously present in the plasma and that their evolution is in agreement with theoretical expectations However several new features have been observed that cannot be anticipated by current theory because of limitations in the electric field strength within the simulations The experimental results reinforce the notion that new theoretical developments are needed to accommodate the large HF electric fields produced at Troms o and HAARP Gakona Alaska and to treat the electron acceleration process in a self-consistent fashion The F region response to two HF effective radiated power levels sim 58 MW and sim 125 MW was investigated at Troms o These ERP values include absorptive losses resulting from the sunlit D region In general the results at 58 MW ERP and 125 MW ERP are consistent with many of the SLT

  17. HF wire antennas over real ground: Computer simulation and measurement

    NASA Astrophysics Data System (ADS)

    Belrose, John S.; Royer, G. M.; Petrie, L. E.

    1989-09-01

    The considerable combined experience with numerical and experimental modeling, with fabricating, with measuring performance of and with using practical HF antennas for the low HF band (2 to 8 MHz) is examined. The antenna poses a particularly difficult problem for this frequency band, particularly if a broad-band antenna is wanted for frequency agile systems, because of the four-to-one change in wavelength over the band. A further complication is that as the frequency is reduced so is the electrical height of the antenna above the ground, and since the ground is an imperfect conductor, the finite conductivity of the ground introduces loss of gain, and detuning. There is great concern with antennas at low (electrical) heights, even with antennas very near to or actually lying on the ground. Antennas lying on or near the ground are of particular interest for military tactical communicators, since low profile antenna systems that require no support mast or masts are operationally and logistically an advantage for use in a tactical environment. HF radio operators in the Canadian north have frequently reported success with using HF dipoles lying on the ground. The reason that antennas perform at all under the circumstances is because of the very low ground conductivities found in the Canadian north. It is shown what gain to expect under such circumstances. The comparison between computer simulation with measurement is emphasized, and with the application of computers for both numerical modeling, measurement, and data analysis and presentation.

  18. Noble gas encapsulation: clathrate hydrates and their HF doped analogues.

    PubMed

    Mondal, Sukanta; Chattaraj, Pratim Kumar

    2014-09-01

    The significance of clathrate hydrates lies in their ability to encapsulate a vast range of inert gases. Although the natural abundance of a few noble gases (Kr and Xe) is poor their hydrates are generally abundant. It has already been reported that HF doping enhances the stability of hydrogen hydrates and methane hydrates, which prompted us to perform a model study on helium, neon and argon hydrates with their HF doped analogues. For this purpose 5(12), 5(12)6(8) and their HF doped analogues are taken as the model clathrate hydrates, which are among the building blocks of sI, sII and sH types of clathrate hydrate crystals. We use the dispersion corrected and gradient corrected hybrid density functional theory for the calculation of thermodynamic parameters as well as conceptual density functional theory based reactivity descriptors. The method of the ab initio molecular dynamics (AIMD) simulation is used through atom centered density matrix propagation (ADMP) techniques to envisage the structural behaviour of different noble gas hydrates on a 500 fs timescale. Electron density analysis is carried out to understand the nature of Ng-OH2, Ng-FH and Ng-Ng interactions. The current results noticeably demonstrate that the noble gas (He, Ne, and Ar) encapsulation ability of 5(12), 5(12)6(8) and their HF doped analogues is thermodynamically favourable. PMID:25047071

  19. ORIGIN OF EXCESS {sup 176}Hf IN METEORITES

    SciTech Connect

    Thrane, Kristine; Connelly, James N.; Bizzarro, Martin; Meyer, Bradley S.; The, Lih-Sin

    2010-07-10

    After considerable controversy regarding the {sup 176}Lu decay constant ({lambda}{sup 176}Lu), there is now widespread agreement that (1.867 {+-} 0.008) x 10{sup -11} yr{sup -1} as confirmed by various terrestrial objects and a 4557 Myr meteorite is correct. This leaves the {sup 176}Hf excesses that are correlated with Lu/Hf elemental ratios in meteorites older than {approx}4.56 Ga meteorites unresolved. We attribute {sup 176}Hf excess in older meteorites to an accelerated decay of {sup 176}Lu caused by excitation of the long-lived {sup 176}Lu ground state to a short-lived {sup 176m}Lu isomer. The energy needed to cause this transition is ascribed to a post-crystallization spray of cosmic rays accelerated by nearby supernova(e) that occurred after 4564.5 Ma. The majority of these cosmic rays are estimated to penetrate accreted material down to 10-20 m, whereas a small fraction penetrate as deep as 100-200 m, predicting decreased excesses of {sup 176}Hf with depth of burial at the time of the irradiation event.

  20. Action growth for AdS black holes

    NASA Astrophysics Data System (ADS)

    Cai, Rong-Gen; Ruan, Shan-Ming; Wang, Shao-Jiang; Yang, Run-Qiu; Peng, Rong-Hui

    2016-09-01

    Recently a Complexity-Action (CA) duality conjecture has been proposed, which relates the quantum complexity of a holographic boundary state to the action of a Wheeler-DeWitt (WDW) patch in the anti-de Sitter (AdS) bulk. In this paper we further investigate the duality conjecture for stationary AdS black holes and derive some exact results for the growth rate of action within the Wheeler-DeWitt (WDW) patch at late time approximation, which is supposed to be dual to the growth rate of quantum complexity of holographic state. Based on the results from the general D-dimensional Reissner-Nordström (RN)-AdS black hole, rotating/charged Bañados-Teitelboim-Zanelli (BTZ) black hole, Kerr-AdS black hole and charged Gauss-Bonnet-AdS black hole, we present a universal formula for the action growth expressed in terms of some thermodynamical quantities associated with the outer and inner horizons of the AdS black holes. And we leave the conjecture unchanged that the stationary AdS black hole in Einstein gravity is the fastest computer in nature.

  1. Effects of additive C{sub 4}F{sub 8} during inductively coupled BCl{sub 3}/C{sub 4}F{sub 8}/Ar plasma etching of TaN and HfO{sub 2} for gate stack patterning

    SciTech Connect

    Ko, J. H.; Kim, D. Y.; Park, M. S.; Lee, N.-E.; Lee, S. S.; Ahn, Jinho; Mok, Hyungsoo

    2007-07-15

    In this work, the authors investigated the etching characteristics of TaN and HfO{sub 2} layers for gate stack patterning in BCl{sub 3}/Ar and BCl{sub 3}/C{sub 4}F{sub 8}/Ar inductively coupled plasmas and the effects of C{sub 4}F{sub 8} addition on the etch selectivity of the TaN to the HfO{sub 2} layer. Addition of C{sub 4}F{sub 8} gas to the BCl{sub 3}/Ar chemistry improved the TaN/HfO{sub 2} etch selectivity because adding the C{sub 4}F{sub 8} gas enhances the formation of the CF{sub x}Cl{sub y} passivation layer on HfO{sub 2} surface and decreased the HfO{sub 2} etch rate more rapidly than the TaN etch rate in a disproportionate way. Reduction in the etch time for HfO{sub 2} layer also increases the TaN/HfO{sub 2} etch selectivity because the etch time gets closer to the initiation time for HfO{sub 2} etching.

  2. Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The sulfur hexafluoride tracer technique (SF**6) is a commonly used method for measuring CH**4 enteric emissions in ruminants. Studies using SF**6 have shown large variation in CH**4 emissions data, inconsistencies in CH**4 emissions across studies, and potential methodological errors. Therefore, th...

  3. Effects of Zr impurity on microscopic behavior of Hf metal

    NASA Astrophysics Data System (ADS)

    Dey, S. K.; Dey, C. C.; Saha, S.

    2016-08-01

    Hf metal with ∼ 3 wt% Zr impurity has been reinvestigated by perturbed angular correlation (PAC) spectroscopy using a LaBr3(Ce)-BaF2 detector set up to understand the microscopic behavior of this metal with temperature. From present measurements, five quadrupole interaction frequencies have been found at room temperature where both pure hcp fraction (∼33%) with 12 nearest neighbor Hf surrounding the probe 181Hf atom and the probe-impurity fraction (∼33%) corresponding to 11 nearest neighbor Hf plus one dissimilar Zr atom are clearly distinguished. At room temperature, the results for quadrupole frequency and asymmetry parameter are found to be ωQ=51.6(4) Mrad/s, η=0.20(4) for the impurity fraction and ωQ=46.8(2) Mrad/s, η=0 for the pure fraction with values of frequency distribution width δ=0 for both components. At 77 K, only 1 NN Zr impurity (∼93%) and pure hcp (∼7%) components have been found with a value of δ ∼ 10% for the impurity fraction. A drastic change in microstructural configuration of Hf metal is observed at 473 K where the impurity fraction increases to ∼ 50% and the pure hcp fraction reduces to ∼ 15% with abrupt changes in quadrupole frequencies for both components. The pure fraction then increases with temperature and enhances to ∼50% at 973 K. In the temperature range 473-973 K, quadrupole frequencies for both components are found to decrease slowly with temperature. Using the Arrhenius relation, binding energy (B) for the probe-impurity pair and the entropy of formation are measured from temperature dependent fractions of probe-impurity and pure hcp in the temperature range 473-773 K. The three other minor components found at different temperatures are attributed to crystalline defects.

  4. The stability of the bifluoride ion (HF - 2) in the gas phase

    NASA Astrophysics Data System (ADS)

    Heni, Martin; Illenberger, Eugen

    1985-12-01

    The bifluoride ion (HF-2) has been generated by dissociative electron attachment to trans-1,2-difluorethylene and cis-1,2-difluoroethylene. Evaluation of the energetics for these reactions leads to ΔH0f (HF-2) ≤-6.9 eV and E. A. (HF2)≥4.8 eV.

  5. 75 FR 10186 - Beauveria bassiana HF23; Amendment of Exemption from the Requirement of a Tolerance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-05

    ... granting a tolerance exemption for Beauveria bassiana HF23 (Unit III.A. and B., 72 FR 1177, January 10... AGENCY 40 CFR Part 180 Beauveria bassiana HF23; Amendment of Exemption from the Requirement of a... the need to establish a maximum permissible level for residues of Beauveria bassiana HF23. DATES:...

  6. 40 CFR 180.1273 - Beauveria bassiana HF23; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false Beauveria bassiana HF23; exemption... FOOD Exemptions From Tolerances § 180.1273 Beauveria bassiana HF23; exemption from the requirement of a tolerance. Residues of Beauveria bassiana HF23 are exempt from the requirement of a tolerance on all...

  7. 40 CFR 180.1273 - Beauveria bassiana HF23; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false Beauveria bassiana HF23; exemption... FOOD Exemptions From Tolerances § 180.1273 Beauveria bassiana HF23; exemption from the requirement of a tolerance. Residues of Beauveria bassiana HF23 are exempt from the requirement of a tolerance on all...

  8. Superstring theory in AdS(3) and plane waves

    NASA Astrophysics Data System (ADS)

    Son, John Sang Won

    This thesis is devoted to the study of string theory in AdS 3 and its applications to recent developments in string theory. The difficulties associated with formulating a consistent string theory in AdS3 and its underlying SL(2, R) WZW model are explained. We describe how these difficulties can be overcome by assuming that the SL(2, R) WZW model contains spectral flow symmetry. The existence of spectral flow symmetry in the fully quantum treatment is proved by a calculation of the one-loop string partition function. We consider Euclidean AdS 3 with the time direction periodically identified, and compute the torus partition function in this background. The string spectrum can be reproduced by viewing the one-loop calculation as the free energy of a gas of strings, thus providing a rigorous proof of the results based on spectral flow arguments. Next, we turn to spacetimes that are quotients of AdS 3, which include the BTZ black hole and conical spaces. Strings propagating in the conical space are described by taking an orbifold of strings in AdS3. We show that the twisted states of these orbifolds can be obtained by fractional spectral flow. We show that the shift in the ground state energy usually associated with orbifold twists is absent in this case, and offer a unified framework in which to view spectral flow. Lastly, we consider the RNS superstrings in AdS 3 x S3 x M , where M may be K3 or T 4, based on supersymmetric extensions of SL(2, R) and SU(2) WZW models. We construct the physical states and calculate the spectrum. A subsector of this theory describes strings propagating in the six dimensional plane wave obtained by the Penrose limit of AdS3 x S3 x M . We reproduce the plane wave spectrum by taking J and the radius to infinity. We show that the plane wave spectrum actually coincides with the large J spectrum at fixed radius, i.e. in AdS3 x S3. Relation to some recent topics of interest such as the Frolov-Tseytlin string and strings with critical tension

  9. Two-dimensional semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures by molecular beam epitaxy

    SciTech Connect

    Aretouli, K. E.; Tsipas, P.; Tsoutsou, D.; Marquez-Velasco, J.; Xenogiannopoulou, E.; Giamini, S. A.; Vassalou, E.; Kelaidis, N.; Dimoulas, A.

    2015-04-06

    Using molecular beam epitaxy, atomically thin 2D semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures are grown on AlN(0001)/Si(111) substrates. Details of the electronic band structure of HfSe{sub 2} are imaged by in-situ angle resolved photoelectron spectroscopy indicating a high quality epitaxial layer. High-resolution surface tunneling microscopy supported by first principles calculations provides evidence of an ordered Se adlayer, which may be responsible for a reduction of the measured workfunction of HfSe{sub 2} compared to theoretical predictions. The latter reduction minimizes the workfunction difference between the HfSe{sub 2} and MoSe{sub 2} layers resulting in a small valence band offset of only 0.13 eV at the MoSe{sub 2}/HfSe{sub 2} heterointerface and a weak type II band alignment.

  10. Entanglement entropy for free scalar fields in AdS

    NASA Astrophysics Data System (ADS)

    Sugishita, Sotaro

    2016-09-01

    We compute entanglement entropy for free massive scalar fields in anti-de Sitter (AdS) space. The entangling surface is a minimal surface whose boundary is a sphere at the boundary of AdS. The entropy can be evaluated from the thermal free energy of the fields on a topological black hole by using the replica method. In odd-dimensional AdS, exact expressions of the Rényi entropy S n are obtained for arbitrary n. We also evaluate 1-loop corrections coming from the scalar fields to holographic entanglement entropy. Applying the results, we compute the leading difference of entanglement entropy between two holographic CFTs related by a renormalization group flow triggered by a double trace deformation. The difference is proportional to the shift of a central charge under the flow.

  11. Asymptotically AdS spacetimes with a timelike Kasner singularity

    NASA Astrophysics Data System (ADS)

    Ren, Jie

    2016-07-01

    Exact solutions to Einstein's equations for holographic models are presented and studied. The IR geometry has a timelike cousin of the Kasner singularity, which is the less generic case of the BKL (Belinski-Khalatnikov-Lifshitz) singularity, and the UV is asymptotically AdS. This solution describes a holographic RG flow between them. The solution's appearance is an interpolation between the planar AdS black hole and the AdS soliton. The causality constraint is always satisfied. The entanglement entropy and Wilson loops are discussed. The boundary condition for the current-current correlation function and the Laplacian in the IR is examined. There is no infalling wave in the IR, but instead, there is a normalizable solution in the IR. In a special case, a hyperscaling-violating geometry is obtained after a dimensional reduction.

  12. New massive gravity and AdS(4) counterterms.

    PubMed

    Jatkar, Dileep P; Sinha, Aninda

    2011-04-29

    We show that the recently proposed Dirac-Born-Infeld extension of new massive gravity emerges naturally as a counterterm in four-dimensional anti-de Sitter space (AdS(4)). The resulting on-shell Euclidean action is independent of the cutoff at zero temperature. We also find that the same choice of counterterm gives the usual area law for the AdS(4) Schwarzschild black hole entropy in a cutoff-independent manner. The parameter values of the resulting counterterm action correspond to a c=0 theory in the context of the duality between AdS(3) gravity and two-dimensional conformal field theory. We rewrite this theory in terms of the gauge field that is used to recast 3D gravity as a Chern-Simons theory. PMID:21635026

  13. Detailed ultraviolet asymptotics for AdS scalar field perturbations

    NASA Astrophysics Data System (ADS)

    Evnin, Oleg; Jai-akson, Puttarak

    2016-04-01

    We present a range of methods suitable for accurate evaluation of the leading asymptotics for integrals of products of Jacobi polynomials in limits when the degrees of some or all polynomials inside the integral become large. The structures in question have recently emerged in the context of effective descriptions of small amplitude perturbations in anti-de Sitter (AdS) spacetime. The limit of high degree polynomials corresponds in this situation to effective interactions involving extreme short-wavelength modes, whose dynamics is crucial for the turbulent instabilities that determine the ultimate fate of small AdS perturbations. We explicitly apply the relevant asymptotic techniques to the case of a self-interacting probe scalar field in AdS and extract a detailed form of the leading large degree behavior, including closed form analytic expressions for the numerical coefficients appearing in the asymptotics.

  14. 176Lu-176Hf geochronology of garnet I: experimental determination of the diffusion kinetics of Lu3+ and Hf4+ in garnet, closure temperatures and geochronological implications

    NASA Astrophysics Data System (ADS)

    Bloch, Elias; Ganguly, Jibamitra; Hervig, Richard; Cheng, Weiji

    2015-02-01

    The 176Lu-176Hf and 147Sm-143Nd decay systems are routinely used to determine garnet (Grt)-whole-rock (WR) ages; however, the 176Lu-176Hf age of garnet is typically older than the 147Sm-143Nd age determined from the same aliquots. Here we present experimental data for Lu3+ and Hf4+ diffusion in garnet as functions of temperature, pressure and oxygen fugacity and show that the diffusivity of Hf4+ in almandine/spessartine garnet is significantly slower than that of Lu3+. The diffusive closure temperature ( T C) of Hf4+ is significantly higher than that of Nd3+, and although this property is partly responsible for the observed 176Lu-176Hf and 147Sm-143Nd Grt-WR age discrepancies, the difference between the T C-s of Lu3+ and Hf4+ could lead to apparent Grt-WR 176Lu-176Hf ages that are skewed from the age of Hf4+ closure in garnet. In addition, the slow diffusivity of Hf4+ indicates that the bulk of metamorphic garnets retain a substantial fraction of prograde radiogenic 176Hf throughout peak metamorphic conditions, a phenomenon that further complicates the interpretation of 176Lu-176Hf garnet ages and invalidates the use of analytical T C expressions. We argue that the diffusion of trivalent rare earth elements in garnet becomes much faster when their concentration level falls below a few hundred ppm, as in the experiments of Tirone et al. (Geochim Cosmochim Acta 69: 2385-2398, 2005), and further argue that this low-concentration mechanism is appropriate for modeling the susceptibility of 147Sm-143Nd garnet ages to diffusive resetting.

  15. Holography and AdS4 self-gravitating dyons

    NASA Astrophysics Data System (ADS)

    Lugo, A. R.; Moreno, E. F.; Schaposnik, F. A.

    2010-11-01

    We present a self-gravitating dyon solution of the Einstein-Yang-Mills-Higgs equations of motion in asymptotically AdS space. The back reaction of gauge and Higgs fields on the space-time geometry leads to the metric of an asymptotically AdS black hole. Using the gauge/gravity correspondence we analyze relevant properties of the finite temperature quantum field theory defined on the boundary. In particular we identify an order operator, characterize a phase transition of the dual theory on the border and also compute the expectation value of the finite temperature Wilson loop.

  16. AdS box graphs, unitarity and operator product expansions

    NASA Astrophysics Data System (ADS)

    Hoffmann, L.; Mesref, L.; Rühl, W.

    2000-11-01

    We develop a method of singularity analysis for conformal graphs which, in particular, is applicable to the holographic image of AdS supergravity theory. It can be used to determine the critical exponents for any such graph in a given channel. These exponents determine the towers of conformal blocks that are exchanged in this channel. We analyze the scalar AdS box graph and show that it has the same critical exponents as the corresponding CFT box graph. Thus pairs of external fields couple to the same exchanged conformal blocks in both theories. This is looked upon as a general structural argument supporting the Maldacena hypothesis.

  17. Phases of global AdS black holes

    NASA Astrophysics Data System (ADS)

    Basu, Pallab; Krishnan, Chethan; Subramanian, P. N. Bala

    2016-06-01

    We study the phases of gravity coupled to a charged scalar and gauge field in an asymptotically Anti-de Sitter spacetime ( AdS 4) in the grand canonical ensemble. For the conformally coupled scalar, an intricate phase diagram is charted out between the four relevant solutions: global AdS, boson star, Reissner-Nordstrom black hole and the hairy black hole. The nature of the phase diagram undergoes qualitative changes as the charge of the scalar is changed, which we discuss. We also discuss the new features that arise in the extremal limit.

  18. Characterization of nanostructured HfO 2 films using RBS and PAC

    NASA Astrophysics Data System (ADS)

    Cavalcante, F. H. M.; Gomes, M. R.; Carbonari, A. W.; Pereira, L. F. D.; Rossetto, D. A.; Costa, M. S.; Alves, E.; Barradas, N. P.; Franco, N.; Redondo, L. M.; Lopes, A. M. L.; Soares, J. C.

    2012-02-01

    The hyperfine field at 181Ta lattice sites in a nanostructured HfO 2 thin film doped with Fe was studied using Rutherford Backscattering Spectrometry and Perturbed Angular Correlation techniques. The 409 nm Hf film was deposited by Electron Beam Evaporation on a silicon substrate. The radioactive 181Hf ions were produced by neutron activation of the nanofilm in the Brazilian Research Reactor (IPEN IEA-R1) by the reaction 180Hf(n,γ) 181Hf. These studies provided an excellent opportunity to obtain unique information regarding local arrangement of the grains, structure, phase transformations of nanoparticles and interfaces of nanostructured materials and the thin film.

  19. Effect of substitutional carbon-doping in BNNTs on HF adsorption: DFT study

    NASA Astrophysics Data System (ADS)

    Kaur, Jasleen; Singhal, Sonal; Goel, Neetu

    2014-11-01

    We employed density functional calculations to investigate the adsorption behavior of HF gas on the side walls of pure and carbon-doped boron nitride nanotubes (BNNTs). The HF adsorption over the pure BNNT opens a door for its functionalization without causing significant changes in its electronic properties. The substitutional doping of carbon atom on the BNNT considerably enhances its affinity towards HF where the effect of the dopant concentration plays a vital role. The change in electronic properties of the doped BNNT on HF adsorption is significant enough to consider it a potential sensor for HF detection.

  20. Charge storage characteristics and tunneling mechanism of amorphous Ge-doped HfOx films

    NASA Astrophysics Data System (ADS)

    Qiu, X. Y.; Zhang, S. Y.; Zhang, T.; Wang, R. X.; Li, L. T.; Zhang, Y.; Dai, J. Y.

    2016-09-01

    Amorphous Ge-doped HfOx films have been deposited on p-Si(100) substrates by means of RF magnetron sputtering. Microstructural investigations reveal the partial oxidation of doped Ge atoms in the amorphous HfOx matrix and the existence of HfSiOx interfacial layer. Capacitance-voltage hysteresis of the Ag-/Ge-doped HfOx/Si/Ag memory capacitor exhibits a memory window of 3.15 V which can maintain for >5 × 104 cycles. Current-voltage characteristics reveal that Poole-Frenkel tunneling is responsible for electron transport in the Ge-doped HfOx film.

  1. The forecaster's added value

    NASA Astrophysics Data System (ADS)

    Turco, M.; Milelli, M.

    2009-09-01

    skill scores of two competitive forecast. It is important to underline that the conclusions refer to the analysis of the Piemonte operational alert system, so they cannot be directly taken as universally true. But we think that some of the main lessons that can be derived from this study could be useful for the meteorological community. In details, the main conclusions are the following: - despite the overall improvement in global scale and the fact that the resolution of the limited area models has increased considerably over recent years, the QPF produced by the meteorological models involved in this study has not improved enough to allow its direct use, that is, the subjective HQPF continues to offer the best performance; - in the forecast process, the step where humans have the largest added value with respect to mathematical models, is the communication. In fact the human characterisation and communication of the forecast uncertainty to end users cannot be replaced by any computer code; - eventually, although there is no novelty in this study, we would like to show that the correct application of appropriated statistical techniques permits a better definition and quantification of the errors and, mostly important, allows a correct (unbiased) communication between forecasters and decision makers.

  2. Electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials.

    PubMed

    Moon, Byung-Hak; Jeong, Yong-Hoon; Choe, Han-Cheol

    2011-08-01

    In this study, we investigated the electrochemical oxide nanotube formation on the Ti-35Ta-xHf alloys for dental materials. The Ti-35Ta-xHf alloys contained from 3 wt.% to 15 wt.% Hf were manufactured by arc melting furnace. The nanotube oxide layers were formed on Ti-35Ta-xHf alloy by anodic oxidation method in 1 M H3PO4 electrolytes containing 0.5 wt.% NaF and 0.8 wt.% NaF at room temperature. The surface characteristics of Ti-35Ta-xHf alloy and nanotube morphology were determined by FE-SEM, STEM, and XRD. The nano-porous surface of Ti-35Ta-xHf alloys showed in 0.5 wt% NaF solution and nanotubular surface showed in 0.8 wt% NaF solution, respectively. The highly ordered nanotube layer without regular knots was formed on the Ti-35Ta-15Hf alloy in the 0.5 wt% NaF solution compared to on Ti-35Ta-3Hf and Ti-35Ta-7Hf alloys in 0.8 wt% NaF solution. Also, the nanotube length of Ti-35Ta-xHf alloys increased as Hf content increased.

  3. Intrinsic metastability of orthorhombic HfTiO{sub 4} in thin film hafnia-titania

    SciTech Connect

    Cisneros-Morales, Massiel Cristina; Aita, Carolyn Rubin

    2011-01-31

    Orthorhombic (o) HfTiO{sub 4} is crystallized when sputter deposited hafnia-titania nanolaminates with ultrathin layers and bilayer (HfO{sub 2}){sub 0.5}(TiO{sub 2}){sub 0.5} composition are annealed between 573 and 1173 K. However, o-HfTiO{sub 4} demixes after annealing at 1273 K, a result not predicted from bulk thermodynamics. X-ray diffraction and Raman microscopy are used here to study structural changes as o-HfTiO{sub 4} demixes upon long-term annealing at 1273 K into Ti-doped monoclinic HfO{sub 2} and Hf-doped rutile TiO{sub 2}. We conclude that o-HfTiO{sub 4} crystallized at low temperature is intrinsically metastable. A space group symmetry analysis shows that demixing can be accomplished by a continuous phase transition chain.

  4. HF-LPLI-treated tumor cells induce NO production in macrophage

    NASA Astrophysics Data System (ADS)

    Lu, Cuixia; Zhou, Feifan; Wu, Shengnan; Xing, Da

    2013-02-01

    High fluence low-power laser irradiation (HF-LPLI) provides a new stimulator to trigger cell apoptosis, and it is well known that apoptotic cells provide antigens to effectively trigger recognition by the immune system. In order to investigate the effect of HF-LPLI on the professional antigen-presenting cell (APC) function, in our primary study, we focused our attention on the effect of HF-LPLI-treated tumor cells on macrophages phagocytosis and NO production. Both confocal microscopy and flowcytometry analysis showed that HF-LPLI (120 J/cm2) induced significantly EMT6 death. Further experiments showed that HF-LPLI-treated EMT6 cells could be phagocyted by the murine macrophage cells RAW264.7, and could induce NO production in macrophages. Taken together, our results indicate that HF-LPLI-treated tumor cells effectively regulated the immune system. The HF-LPLI effect on the APC function needs to be further studied.

  5. D-branes on AdS flux compactifications

    NASA Astrophysics Data System (ADS)

    Koerber, Paul; Martucci, Luca

    2008-01-01

    We study D-branes in Script N = 1 flux compactifications to AdS4. We derive their supersymmetry conditions and express them in terms of background generalized calibrations. Basically because AdS has a boundary, the analysis of stability is more subtle and qualitatively different from the usual case of Minkowski compactifications. For instance, stable D-branes filling AdS4 may wrap trivial internal cycles. Our analysis gives a geometric realization of the four-dimensional field theory approach of Freedman and collaborators. Furthermore, the one-to-one correspondence between the supersymmetry conditions of the background and the existence of generalized calibrations for D-branes is clarified and extended to any supersymmetric flux background that admits a time-like Killing vector and for which all fields are time-independent with respect to the associated time. As explicit examples, we discuss supersymmetric D-branes on IIA nearly Kähler AdS4 flux compactifications.

  6. Dyonic AdS black holes from magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Caldarelli, Marco M.; Dias, Óscar J. C.; Klemm, Dietmar

    2009-03-01

    We use the AdS/CFT correspondence to argue that large dyonic black holes in anti-de Sitter spacetime are dual to stationary solutions of the equations of relativistic magnetohydrodynamics on the conformal boundary of AdS. The dyonic Kerr-Newman-AdS4 solution corresponds to a charged diamagnetic fluid not subject to any net Lorentz force, due to orthogonal magnetic and electric fields compensating each other. The conserved charges, stress tensor and R-current of the fluid are shown to be in exact agreement with the corresponding quantities of the black hole. Furthermore, we obtain stationary solutions of the Navier-Stokes equations in four dimensions, which yield predictions for (yet to be constructed) charged rotating black strings in AdS5 carrying nonvanishing momentum along the string. Finally, we consider Scherk-Schwarz reduced AdS gravity on a circle. In this theory, large black holes and black strings are dual to lumps of deconfined plasma of the associated CFT. We analyze the effects that a magnetic field introduces in the Rayleigh-Plateau instability of a plasma tube, which is holographically dual to the Gregory-Laflamme instability of a magnetically charged black string.

  7. AdS Branes from Partial Breaking of Superconformal Symmetries

    SciTech Connect

    Ivanov, E.A.

    2005-10-01

    It is shown how the static-gauge world-volume superfield actions of diverse superbranes on the AdS{sub d+1} superbackgrounds can be systematically derived from nonlinear realizations of the appropriate AdS supersymmetries. The latter are treated as superconformal symmetries of flat Minkowski superspaces of the bosonic dimension d. Examples include the N = 1 AdS{sub 4} supermembrane, which is associated with the 1/2 partial breaking of the OSp(1|4) supersymmetry down to the N = 1, d = 3 Poincare supersymmetry, and the T-duality related L3-brane on AdS{sub 5} and scalar 3-brane on AdS{sub 5} x S{sup 1}, which are associated with two different patterns of 1/2 breaking of the SU(2, 2|1) supersymmetry. Another (closely related) topic is the AdS/CFT equivalence transformation. It maps the world-volume actions of the codimension-one AdS{sub d+1} (super)branes onto the actions of the appropriate Minkowski (super)conformal field theories in the dimension d.

  8. Worldsheet dilatation operator for the AdS superstring

    NASA Astrophysics Data System (ADS)

    Ramírez, Israel; Vallilo, Brenno Carlini

    2016-05-01

    In this work we propose a systematic way to compute the logarithmic divergences of composite operators in the pure spinor description of the AdS 5 × S 5 superstring. The computations of these divergences can be summarized in terms of a dilatation operator acting on the local operators. We check our results with some important composite operators of the formalism.

  9. Field emission from single-crystalline HfC nanowires

    SciTech Connect

    Yuan, Jinshi; Tang, Jie; Zhang Han; Shinya, Norio; Nakajima, Kiyomi; Qin, Lu-Chang

    2012-03-12

    Single HfC nanowire field emitter/electrode structures have been fabricated using nano-assembling and electron beam induced deposition. Field ion microscopy has been applied to study the atomic arrangement of facets formed on a field evaporation-modified HfC nanowire tip. Field evaporation and crystal form studies suggest that the {l_brace}111{r_brace} and {l_brace}110{r_brace} crystal planes have lower work functions, while the {l_brace}100{r_brace}, {l_brace}210{r_brace}, and {l_brace}311{r_brace} planes have higher work functions. Field emission measurement permits us to obtain that the work function of the {l_brace}111{r_brace} crystal plane is about 3.4 eV.

  10. HF Doppler observations of acoustic waves excited by the earthquake

    NASA Technical Reports Server (NTRS)

    Ichinose, T.; Takagi, K.; Tanaka, T.; Okuzawa, T.; Shibata, T.; Sato, Y.; Nagasawa, C.; Ogawa, T.

    1985-01-01

    Ionospheric disturbances caused by the earthquake of a relatively small and large epicentral distance have been detected by a network of HF-Doppler sounders in central Japan and Kyoto station, respectively. The HF-Doppler data of a small epicentral distance, together with the seismic data, have been used to formulate a mechanism whereby ionospheric disturbances are produced by the Urakawa-Oki earthquake in Japan. Comparison of the dynamic spectra of these data has revealed experimentally that the atmosphere acts as a low-pass filter for upward-propagating acoustic waves. By surveying the earthquakes for which the magnitude M is larger than 6.0, researchers found the ionospheric effect in 16 cases of 82 seismic events. As almost all these effects have occurred in the daytime, it is considered that it may result from the filtering effect of the upward-propagating acoustic waves.

  11. CMS HF calorimeter PMTs and Xi(c)+ lifetime measurement

    SciTech Connect

    Akgun, Ugur; /Iowa U.

    2003-12-01

    This thesis consists of two parts: In the first part we describe the Photomultiplier Tube (PMT) selection and testing processes for the Hadronic Forward (HF) calorimeter of the CMS, a Large Hadron Collier (LHC) experiment at CERN. We report the evaluation process of the candidate PMTs from three different manufacturers, the complete tests performed on the 2300 Hamamatsu PMTs which will be used in the HF calorimeter, and the details of the PMT Test Station that is in University of Iowa CMS Laboratories. In the second part we report the {Xi}{sub c}{sup +} lifetime measurement from SELEX, the charm hadro-production experiment at Fermilab. Based upon 301 {+-} 31 events from three di.erent decay channels, by using the binned maximum likelihood technique, we observe the lifetime of {Xi}{sub c}{sup +} as 427 {+-} 31 {+-} 13 fs.

  12. Dislocation structures in Ni{sub 3}(Al,Hf)

    SciTech Connect

    Kruml, T.; Viguier, B.; Bonneville, J.; Martin, J.L.; Spaetig, P.

    1997-12-31

    Single crystalline specimens of Ni{sub 74.8}Al{sub 21.9}Hf{sub 3.3} were subjected to compression tests at different temperatures. Thin foils for transmission electron microscopy observations were prepared from several specimens deformed within and above the yield stress anomaly domain. The dislocation microstructure was studied. The weak beam imaging and image simulation techniques followed by anisotropic elasticity calculations were used for the determination of antiphase boundary energies in both cube and octahedral planes, resulting in values of 237 mJm{sup {minus}2} and 252 mJm{sup {minus}2} respectively. The comparison of the present results with data taken from literature shows the influence of Hf on mechanical properties, dislocation microstructures and APB energies.

  13. Crossbar Nanoscale HfO2-Based Electronic Synapses

    NASA Astrophysics Data System (ADS)

    Matveyev, Yury; Kirtaev, Roman; Fetisova, Alena; Zakharchenko, Sergey; Negrov, Dmitry; Zenkevich, Andrey

    2016-03-01

    Crossbar resistive switching devices down to 40 × 40 nm2 in size comprising 3-nm-thick HfO2 layers are forming-free and exhibit up to 105 switching cycles. Four-nanometer-thick devices display the ability of gradual switching in both directions, thus emulating long-term potentiation/depression properties akin to biological synapses. Both forming-free and gradual switching properties are modeled in terms of oxygen vacancy generation in an ultrathin HfO2 layer. By applying the voltage pulses to the opposite electrodes of nanodevices with the shape emulating spikes in biological neurons, spike-timing-dependent plasticity functionality is demonstrated. Thus, the fabricated memristors in crossbar geometry are promising candidates for hardware implementation of hybrid CMOS-neuron/memristor-synapse neural networks.

  14. Entanglement temperature and perturbed AdS3 geometry

    NASA Astrophysics Data System (ADS)

    Levine, G. C.; Caravan, B.

    2016-06-01

    Generalizing the first law of thermodynamics, the increase in entropy density δ S (x ) of a conformal field theory (CFT) is proportional to the increase in energy density, δ E (x ) , of a subsystem divided by a spatially dependent entanglement temperature, TE(x ) , a fixed parameter determined by the geometry of the subsystem, crossing over to thermodynamic temperature at high temperatures. In this paper we derive a generalization of the thermodynamic Clausius relation, showing that deformations of the CFT by marginal operators are associated with spatial temperature variations, δ TE(x ) , and spatial energy correlations play the role of specific heat. Using AdS/CFT duality we develop a relationship between a perturbation in the local entanglement temperature of the CFT and the perturbation of the bulk AdS metric. In two dimensions, we demonstrate a method through which direct diagonalizations of the boundary quantum theory may be used to construct geometric perturbations of AdS3 .

  15. Solid Solubilities of Pu, U, Gd and Hf in Candidate Ceramic Nuclear Wasteforms

    SciTech Connect

    Vance, Eric R.; Carter, M. L.; Lumpkin, G. R.; Day, R. A.; Begg, B. D.

    2001-04-02

    This goal of this research project was to determine the solid solubility of Pu, U, Gd, and Hf in candidate ceramics for immobilization of high-level nuclear waste. The experimental approach was to saturate each phase by adding more than the solid solubility limit of the given cation, using a nominated substitution scheme, and then analyzing the candidate phase that formed to evaluate the solid solubility limit under firing conditions. Confirmation that the solid solution limit had been reached insofar as other phases rich in the cation of interest was also required. The candidate phases were monazite, titanite, zirconolite, perovskite, apatite, pyrochlore, and brannerite. The valences of Pu and U were typically deduced from the firing atmosphere, and charge balancing in the candidate phase composition as evaluated from electron microscopy, although in some cases it was measured directly by x-ray absorption and diffuse reflectance spectroscopies (for U). Tetravalent Pu and U have restricted (< 0.1 formula units) solid solubility in apatite, titanite, and perovskite. Trivalent Pu has a larger solubility in apatite and perovskite than Pu4+. U3+ appears to be a credible species in reduced perovskite with a solubility of {approximately} 0.25 f.u. as opposed to {approximately} 0.05 f.u. for U4+. Pu4+ is a viable species in monazite and is promoted at lower firing temperatures ({approximately} 800 C) in an air atmosphere. Hf solubility is restricted in apatite, monazite (< 0.1 f.u.), but is {approximately} 0.2 and 0.5 f.u. in brannerite and titanite, respectively. Gd solubility is extended in all phases except for titanite ({approximately} 0.3 f.u.). U5+ was identified by DRS observations of absorption bands in the visible/near infrared photon energy ranges in brannerite and zirconolite, and U4+ in zirconolite was similarly identified.

  16. Mapping high-latitude plasma convection with coherent HF radars

    NASA Technical Reports Server (NTRS)

    Ruohoniemi, J. M.; Greenwald, R. A.; Baker, K. B.; Villain, J.-P.; Hanuise, C.

    1989-01-01

    Several methods developed for mapping high-latitude plasma convection with a high-latitude HF radar are described, which utilize coherent backscatter from electron density irregularities at F-region altitudes to observe convective plasma motion. Several examples of two-dimensional convection-velocity maps are presented, showing instances of L-shell-aligned flow in the dusk sector, the reversal of convection near magnetic midnight, and counterstreaming in the dayside cleft.

  17. Gas consumption characteristics of a recirculating HF-laser.

    PubMed

    Willis, C; Dosi, M; James, D J

    1979-05-01

    The gas consumption characteristics of a recirculating HF TE-laser have been defined. The stoichiometry varies from close to H(2):SF(6):1:1 at low H(2) concentration to 3:1 above 30% H(2). The output energy shows a broad maximum in its dependence on pressure and H(2) concentration and, as a result fairly stable output can be maintained with recirculation using only a simple make-up control system.

  18. Interface and bulk properties of HfO2 films

    NASA Astrophysics Data System (ADS)

    Biswas, Nivedita; Harris, Harlan; Choi, Kisik; Temkin, Henryk; Gangopadhyay, Shubhra

    2003-03-01

    HfO2 films of varying thickness were deposited on silicon and titanium by reactive electron beam evaporation. Metal gates of Titanium were deposited to form MIS and MIM structures. Capacitance-voltage and conductance-voltage measurements were performed to analyze the HfO2/Si interface and HfO2 bulk. For samples having thickness between 30 and 300 Å the C-V curves of the as-deposited samples were marked by charge leakage, huge hysteresis and frequency dispersion. However, annealing the sample in H2 ambient reduced charge leakage, hysteresis and the frequency dispersion of the C-V curves. A dielectric constant of the annealed films was calculated to be 17. The interface state density as calculated using the method of Nicollian and Brews was 2-3E10 cm-2eV-1 close to the midgap. To study the bulk properties, HfO2 films of thickness 2100 Å with platinum electrodes were deposited on silicon and titanium nitride. The C-V and G-V curves of both as-deposited and annealed samples were measured. Interface state density was found to be comparable to that of the thin samples. Thus the passivation of bulk and interface states with hydrogen annealing is independent of thickness. The gap state densities were found compatible with the observed hysteresis of the as-deposited ( 1E16-1E17 eV-1cm-3) and annealed sample (1E14-1E15eV-1cm-3).

  19. Ionosphere Transient Response To Solar Flares: Hf Radio Monitoring Observations

    NASA Astrophysics Data System (ADS)

    Lebreton, J.-P.; Telljohann, U.; Witasse, O.; Sanderson, T. R.

    We use a simple and low cost method to monitor the ionospheric reflection of commer- cial HF radio transmissions. It only requires a standard HF radio receiver with Single Side Band capability, a computer with a sound card, and appropriate audio signal spectral analysis software. We tune the radio receiver such that the carrier frequency of the transmission appears as a ~ 1kHz tone at the output of the radio receiver. The output signal of the radio receiver is processed with appropriate software that allows real time recording of high frequency resolution dynamic spectrograms of the audio spectrum in the 0-5 kHz range. Voice modulation is also present in the audio spectrum and appears as both upper and lower side bands but it is not considered in this study. HF radio signals reach the receiving station after being reflected by ionospheric layers. Any change in the ionospheric layers that affects HF wave reflection is detectable. In this paper, we particularly discuss our observations related to the transient response of the ionosphere to solar flare ionizing radiation. Enhanced ionization due to EUV and soft X-rays may produce a transient perturbation of the ionosphere which lasts typically one to few minutes. The signature of the transient response depends upon local time, solar flare intensity and the rise time of the solar flare ionizing radiation. We discuss both a few typical examples and a preliminary analysis of our 1-year sta- tistical analysis of observed events at 17.640 MHz. The method is easily accessible to amateur scientists. Possible use of the method for spaceweather-related research and outreach and educational activities is discussed.

  20. Solidification Effects in MAR-M246(Hf) Alloy

    NASA Technical Reports Server (NTRS)

    Johnston, M. H.; Parr, R. A.

    1987-01-01

    Fatigue properties degraded with crystallographic orientations greater than 10 degrees from {001} axis. Influence of solidification and heat-treatment parameters on structure and fatigue properties of nickel-based superalloy MAR-M246(Hf) described in 24-page report. Superalloys have high strength and corrosion resistance at temperatures up to 1,400 degrees C; their uses range from petrochemical equipment to marine, industrial, aircraft, and vehicular gas turbines.

  1. Ferroelectric HfO2 for Emerging Ferroelectric Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Florent, Karine

    The spontaneous polarization in ferroelectrics (FE) makes them particularly attractive for non-volatile memory and logic applications. Non-volatile FRAM memories using perovskite structure materials, such as Lead Zirconate Titanate (PZT) and Strontium Bismuth Tantalate (SBT) have been studied for many years. However, because of their scaling limit and incompatibility with CMOS beyond 130 nm node, floating gate Flash memory technology has been preferred for manufacturing. The recent discovery of ferroelectricity in doped HfO2 in 2011 has opened the door for new ferroelectric based devices compatible with CMOS technology, such as Ferroelectric Field Effect Transistor (FeFET) and Ferroelectric Tunnel Junctions (FTJ). This work began with developing ferroelectric hysteresis characterization capabilities at RIT. Initially reactively sputtered aluminum doped HfO 2 films were investigated. It was observed that the composition control using co-sputtering was not achievable within the existing capabilities. During the course of this study, collaboration was established with the NaMLab group in Germany to investigate Si doped HfO2 deposited by Atomic Layer Deposition (ALD). Metal Ferroelectric Metal (MFM) devices were fabricated using TiN as the top and bottom electrode with Si:HfO2 thickness ranging from 6.4 nm to 22.9 nm. The devices were electrically tested for P-E, C-V and I-V characteristics. Structural characterizations included TEM, EELS, XRR, XRD and XPS/Auger spectroscopy. Higher remanant polarization (Pr) was observed for films of 9.3 nm and 13.1 nm thickness. Thicker film (22.9 nm) showed smaller Pr. Devices with 6.4 nm thick films exhibit tunneling behavior showing a memristor like I-V characteristics. The tunnel current and ferroelectricity showed decrease with cycling indicating a possible change in either the structure or the domain configurations. Theoretical simulations using the improved FE model were carried out to model the ferroelectric behavior of

  2. Electrochemical characterization of cast Ti-Hf binary alloys.

    PubMed

    Cai, Z; Koike, M; Sato, H; Brezner, M; Guo, Q; Komatsu, M; Okuno, O; Okabe, T

    2005-05-01

    This study characterized the electrochemical behavior of Ti-Hf binary alloys in a simulated oral environment. Ti-Hf alloys (10, 20, 25, 30, 35 and 40 mass% Hf) were prepared by arc-melting titanium sponge and hafnium sponge. Specimens of each alloy (n = 4) were prepared using a dental titanium casting system with a MgO-based investment. Specimens were inspected with X-ray radiography to ensure minimal internal porosity. Castings (n = 4) made from pure titanium and commercially pure titanium were used as controls. The ground flat surface (10 mm x 10 mm) on each specimen where approximately 30 microm was removed was used for the characterization. Sixteen-hour open-circuit potential (OCP) measurement, linear polarization and potentiodynamic cathodic polarization were performed sequentially in aerated (air + 10% CO2) MTZ synthetic saliva at 37 degrees C. Potentiodynamic anodic polarization was conducted in the same medium but deaerated (N2 + 10% CO2) 2 h before and during testing. Polarization resistance (R(P)) and Tafel slopes were determined, as were corrosion current density (I(CORR)) and passive current density (I(PASS)). Results were subjected to nonparametric statistical analysis (alpha = 0.05). The OCP stabilized (mean values -229 mV to -470 mV vs. SCE) for all specimens after the 16-h immersion. Similar passivation was observed for all the metals on their anodic polarization diagrams. The Kruskal-Wallis test showed significant differences in OCP among the test groups (p = 0.006). No significant differences were found in R(P), I(CORR) or I(PASS) among all the metals (p>0.3). Results indicate that the electrochemical behavior of the Ti-Hf alloys examined resembles that of pure titanium. PMID:16701813

  3. Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using HfO2 ceramic target

    SciTech Connect

    Aguirre, B.; Vemuri, R. S.; Zubia, David; Engelhard, Mark H.; Shutthanandan, V.; Kamala Bharathi, K.; Ramana, Chintalapalle V.

    2011-01-01

    Hafnium oxide (HfO₂) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO₂ ceramic target has been employed for sputtering while varying the Ts from room temperature to 500⁰C during deposition. The effect of Ts on the growth and microstructure of deposited HfO₂ films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO₂ films. Structural characterization indicates that the HfO₂ films grown at Ts<200 ⁰C are amorphous while films grown at Ts>200 ⁰C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 ⁰C. Nanocrystalline HfO₂ films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO₂ films. An interface layer (IL) formation occurs due to reaction at the HfO₂-Si interface for HfO₂ films deposited at Ts>200 ⁰C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO₂-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.

  4. Spectroscopic ellipsometry studies of HF treated Si (100) surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

    1993-06-01

    Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effect of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that, after a 20-sec 9:1 HF dip without rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed, in an ultrahigh vacuum chamber (UHV), and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface layer, after being heated to about 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

  5. Spectroscopic ellipsometry studies of HF treated Si (100) surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

    1993-08-01

    Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effects of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that after a 20-s 9:1 HF dip without rinse, the Si(100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si(100) surface was observed, in an ultrahigh vacuum (UHV) chamber, and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface-layer, after being heated to approximately 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

  6. Oxidation behavior of FeAl+Hf,Zr,B

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Doychak, Joseph

    1988-01-01

    The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

  7. Superconductivity in the noncentrosymmetric compound Re6Hf

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Guo, Yang; Wang, Hangdong; Su, Qiping; Mao, Qianhui; Du, Jianhua; Zhou, Yuxing; Yang, Jinhu; Fang, Minghu

    2016-07-01

    Re6Hf , which crystallizes in α -Mn structure(space group I 4 ¯3 m ) without a spatial inversion center, is a superconductor with a superconducting transition temperature Tc≈6.2 K . The measurements of magnetic susceptibility (χ ), resistivity (ρ ), and specific heat capacity (C ) were carried out. Bulk superconductivity is revealed by the jump at Tc of the specific heat with Δ C /γnTc≈1.63 , suggesting moderate electron-electron coupling strength in this system. The upper critical field μ0Hc2 W H H(0 ) was estimated to be of 89 kOe, and μ0Hc2 G L(0 ) =107 kOe, which is close to the Pauli limiting field. The Ginzburg Landau parameter κG L=50.2 , indicates that Re6Hf is a type-II superconductor. The temperature dependence of the electronic specific heat Ce l(T ) in the superconducting state can be explained by BCS theory. Furthermore, the magnetic-field dependence of γ (H ) is found to be linear with respect to H . These results imply a dominant s -wave superconductivity in Re6Hf .

  8. Detection of HCl and HF by TTFMS and WMS.

    PubMed

    De Luca, Anna Chiara; Pesce, Giuseppe; Rusciano, Giulia; Sasso, Antonio

    2006-04-01

    In this work we discuss on a compact spectrometer based on DFB diode lasers for detection of chloridric and fluoridric acids. HCl and HF concentrations are determined through optical absorption of the P(4) line (lambda=1.7 microm) and the R(3) line (lambda=1.3 microm), respectively. Both lines belong to first overtone vibrational bands and their line strengths are 7.8 x 10(-21)cm/molecule for HCl and 2.8 x 10(-20)cm/molecule for HF. We chose these lines for their relative high intensities and because they are quite far from water vapour lines which represent the main interfering gas for trace-gases analysis. To detect these species we used two different high frequency modulation techniques: two-tone frequency modulation spectroscopy (f(1)=800 MHz and f(2)=804 MHz) was used for HCl while for HF we followed a simpler approach based on wavelength modulation spectroscopy (f=600 kHz). We demonstrate that the two techniques provide comparable detection limit of about 80 ppbV at atmospheric pressure. Positive testing of our spectrometer makes it suitable for in situ measurements of exhaust gases coming from waste incinerators.

  9. Effective Ad-Hoc Committees.

    ERIC Educational Resources Information Center

    Young, David G.

    1983-01-01

    Ad-hoc committees may be symbolic, informational, or action committees. A literature survey indicates such committees' structural components include a suprasystem and three subsystems involving linkages, production, and implementation. Other variables include size, personal factors, and timing. All the factors carry implications about ad-hoc…

  10. Lorentzian AdS geometries, wormholes, and holography

    SciTech Connect

    Arias, Raul E.; Silva, Guillermo A.; Botta Cantcheff, Marcelo

    2011-03-15

    We investigate the structure of two-point functions for the quantum field theory dual to an asymptotically Lorentzian Anti de Sitter (AdS) wormhole. The bulk geometry is a solution of five-dimensional second-order Einstein-Gauss-Bonnet gravity and causally connects two asymptotically AdS spacetimes. We revisit the Gubser-Klebanov-Polyakov-Witten prescription for computing two-point correlation functions for dual quantum field theories operators O in Lorentzian signature and we propose to express the bulk fields in terms of the independent boundary values {phi}{sub 0}{sup {+-}} at each of the two asymptotic AdS regions; along the way we exhibit how the ambiguity of normalizable modes in the bulk, related to initial and final states, show up in the computations. The independent boundary values are interpreted as sources for dual operators O{sup {+-}} and we argue that, apart from the possibility of entanglement, there exists a coupling between the degrees of freedom living at each boundary. The AdS{sub 1+1} geometry is also discussed in view of its similar boundary structure. Based on the analysis, we propose a very simple geometric criterion to distinguish coupling from entanglement effects among two sets of degrees of freedom associated with each of the disconnected parts of the boundary.

  11. One-loop diagrams in AdS space

    SciTech Connect

    Hung Lingyan; Shang Yanwen

    2011-01-15

    We study the complex scalar loop corrections to the boundary-boundary gauge two-point function in pure AdS space in Poincare coordinates, in the presence of boundary quadratic perturbations to the scalar. These perturbations correspond to double-trace perturbations in the dual CFT and modify the boundary conditions of the bulk scalars in AdS. We find that, in addition to the usual UV divergences, the one-loop calculation suffers from a divergence originating in the limit as the loop vertices approach the AdS horizon. We show that this type of divergence is independent of the boundary coupling; making use of this we extract the finite relative variation of the imaginary part of the loop via Cutkosky rules as the boundary perturbation varies. Applying our methods to compute the effects of a time-dependent impurity to the conductivities using the replica trick in AdS/CFT, we find that generally an IR-relevant disorder reduces the conductivity and that in the extreme low frequency limit the correction due to the impurities overwhelms the planar CFT result even though it is supposedly 1/N{sup 2} suppressed. We also comment on the more physical scenario of a time-independent impurity.

  12. Lu-Hf and PbSL geochronology of apatites from Proterozoic terranes: A first look at Lu-Hf isotopic closure in metamorphic apatite

    NASA Astrophysics Data System (ADS)

    Barfod, Gry Hoffmann; Krogstad, Eirik Jens; Frei, Robert; Albarède, Francis

    2005-04-01

    The mineral apatite is characterized by elevated and highly variable Lu/Hf ratios that, in some cases, allow for single-crystal dating by the Lu-Hf isotopic system. Apatites from the Adirondack Lowlands and Otter Lake area in the Grenville Province, and from the Black Hills, South Dakota, yield Lu-Hf ages that are consistently older than their respective Pb step leaching ages. Isotopic closure for the Lu-Hf system, therefore, occurs before U-Pb system closure in this mineral. In the Adirondack Lowlands, where H 2O activity was low, Lu-Hf systematics of cm-sized apatite crystals remained undisturbed during upper amphibolite facies metamorphism (˜700 to 675 °C) at 1170-1130 Ma. The relatively old Lu-Hf ages of 1270 and 1230 Ma observed for these apatites correlate with decreasing crystal size. In contrast, apatite from the fluid-rich Otter Lake area and Black Hills yields unrealistically low apparent Lu-Hf closure temperatures, implying that in these apatites, fluids facilitated late exchange. The Lu-Hf ages for the metamorphic apatites were thus controlled either by the prevailing temperature and grain size, or by fluid activity.

  13. Anion Exchange Behavior Of Ti, Zr, Hf, Nb And Ta As Homologues Of Rf And Db In Mixed HF--Acetone Solutions

    SciTech Connect

    Aksenov, N. V.; Bozhikov, G. A.; Starodub, G. Ya.; Dmitriev, S. N.; Filosofov, D. V.; Sun Jin, Jon; Radchenko, V. I.; Lebedev, N. A.; Novgorodov, A. F.

    2010-04-30

    We studied in detail the sorption behavior of Ti, Zr, Hf, Nb and Ta on AG 1 anion exchange resin in HF-acetone mixed solutions as a function of organic cosolvent and acid concentrations. Anion exchange behavior was found to be strongly acetone concentration dependent. The distribution coefficients of Ti, Zr, Hf and Nb increased and those of Ta decreased with increasing content of acetone in HF solutions. With increasing HF concentration anion exchange equilibrium analysis indicated the formation of fluoride complexes of group 4 elements with charge-3 and Ta---2. For Nb the slope of-2 increased up to-5. Optimal conditions for separation of the elements using AIX chromatography were found. Group 4 elements formed MF{sub 7}{sup 3-} (M = Ti, Zr, Hf) complexes whose sorption decreased Ti>Hf>Zr in reverse order of complex stability. This fact is of particular interest for studying ion exchange behavior of Rf compared to Ti. The advantages of studying chemical properties of Rf and Db in aqueous HF solutions mixed with organic solvents are briefly discussed.

  14. Hf isotope compositions and chronology of magmatic zircons from Tarim continental flood basalts: implications for magmatic evolution of the Early Permian Tarim Large Igneous Province in NW China

    NASA Astrophysics Data System (ADS)

    Li, Y.; Li, Z.; Yu, X.; Langmuir, C. H.; Yang, S.; Chen, H.

    2013-12-01

    they may have a similar mantle source region. The relatively higher ɛHf(t) values of the basalts than zircons further indicate that more depleted mantle components have been added into their parent magmas during the extrusion of basalts. Although the effect of crustal contamination needs further studies, most TCFB have not suffered significant crustal contamination. The TCFB with relatively low ɛNd(t) values (<1) and high 87Sr/86Sri ratios (<0.705) were probably derived from a modified SCLM source with a non-negligible mix of some amounts of plume and/or asthenospheric-derived mantle components and variable extents of assimilation and fractional crystallization. Compared to the basalts, the late formed intrusive rocks (~280 Ma) have positive ɛNd(t) values (1.0~5.0) and most of them exhibit lower 87Sr/86Sri ratios (0.703~0.705) than the Bulk Silicate Earth. Based on the coherently depleting trend on Sr-Nd-Hf isotopic compositions from the earlier erupted basalts , and then to later emplaced intrusive rocksin the TLIP, a magmatic evolution model is suggested, which a rising mantle plume was continuously injecting depleted mantle components to the magma source region of the TLIP at the bottom of the SCLM under the Tarim block, then produced the various igneous rock units in the TLIP.

  15. Kolmogorov-Zakharov spectrum in AdS gravitational collapse.

    PubMed

    de Oliveira, H P; Pando Zayas, Leopoldo A; Rodrigues, E L

    2013-08-01

    We study black hole formation during the gravitational collapse of a massless scalar field in asymptotically D-dimensional anti-de Sitter AdS(D) spacetimes for D = 4, 5. We conclude that spherically symmetric gravitational collapse in asymptotically AdS spaces is turbulent and characterized by a Kolmogorov-Zakharov spectrum. Namely, we find that after an initial period of weakly nonlinear evolution, there is a regime where the power spectrum of the Ricci scalar evolves as ω(-s) with the frequency, ω, and s ≈ 1.7 ± 0.1.

  16. H-shuttling within a Hf-defect complex in Si/SiO2/HfO2 structures

    NASA Astrophysics Data System (ADS)

    Marinopoulos, A. G.; Batyrev, I.; Zhou, X.; Schrimpf, R.; Fleetwood, D.; Pantelides, S. T.

    2008-03-01

    It was recently shown that, following irradiation of Si-SiO2/HfO2 structures by X-rays or constant-voltage stress, both oxide- and interface-trap densities exhibit oscillations with switch-bias annealing that are much larger than those previously observed in Si/SiO2 devices. Here we describe a particular defect complex that can account for the observations. The complex comprises a suboxide Hf-Si bond and an interfacial dangling bond (Pb center). With the aid of first-principles calculations we show that this defect possesses a symmetric double-well minimum and can provide trapping sites for H atoms near the interface. In the first site, the H atom passivates the dangling bond; in the second site the H atom resides near the center of the Hf-Si bond. A moderate intervening barrier (1.2 eV) suggests a relatively easy hopping of H atoms between these two energy minima, aided by the applied field and temperature. This shuttling mechanism can explain the observed oscillations in the interface trap densities during switched-bias conditions. This work was supported in part by the AFOSR and the DOE.

  17. Empirical Study of the Multiaxial, Thermomechanical Behavior of NiTiHf Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Shukla, Dhwanil; Noebe, Ronald D.; Stebner Aaron P.

    2013-01-01

    An empirical study was conducted to characterize the multiaxial, thermomechanical responses of new high temperature NiTiHf alloys. The experimentation included loading thin walled tube Ni(sub 50.3)Ti(sub 29.7)Hf(sub 20) alloy samples along both proportional and nonproportional axial-torsion paths at different temperatures while measuring surface strains using stereo digital image correlation. A Ni(sub 50.3)Ti(sub 33.7)Hf(sub 16) alloy was also studied in tension and compression to document the effect of slightly depleting the Hf content on the constitutive responses of NiTiHf alloys. Samples of both alloys were made from nearly texture free polycrystalline material processed by hot extrusion. Analysis of the data shows that very small changes in composition significantly alter NiTiHf alloy properties, as the austenite finish (Af) temperature of the 16-at Hf alloy was found to be approximately 60 C less than the 20-at Hf alloy (approximately 120 C vs. 180 C). In addition, the 16-at Hf alloy exhibited smaller compressive transformation strains (2 vs. 2.5 percent). Multi-axial characterization of the 20-at % Hf alloy showed that while the random polycrystal transformation strains in tension (4 percent) and compression (2.5 percent) are modest in comparison with binary NiTi (6 percent, 4 percent), the torsion performance is superior (7 vs. 4 shear strain width to the pseudoelastic plateau).

  18. Vertically oriented few-layered HfS2 nanosheets: growth mechanism and optical properties

    NASA Astrophysics Data System (ADS)

    Zheng, Binjie; Chen, Yuanfu; Wang, Zegao; Qi, Fei; Huang, Zhishuo; Hao, Xin; Li, Pingjian; Zhang, Wanli; Li, Yanrong

    2016-09-01

    For the first time, large-area, vertically oriented few-layered hafnium disulfide (V-{{{HfS}}}2) nanosheets have been grown by chemical vapor deposition. The individual {{{HfS}}}2 nanosheets are well [001] oriented, with highly crystalline quality. Far different from conventional van der Waals epitaxial growth mechanism for two-dimensional transition metal dichalcogenides, a novel dangling-bond-assisted self-seeding growth mechanism is proposed to describe the growth of V-{{{HfS}}}2 nanosheets: difficult migration of {{{HfS}}}2 adatoms on substrate surface results in {{{HfS}}}2 seeds growing perpendicularly to the substrate; V-{{{HfS}}}2 nanosheets inherit the growth direction of {{{HfS}}}2 seeds; V-{{{HfS}}}2 nanosheets further expand in the in-plane direction with time evolution. Moreover, the V-{{{HfS}}}2 nanosheets show strong and broadened photons absorption from near infrared to ultraviolet; the V-{{{HfS}}}2-based photodetector exhibits an ultrafast photoresponse time of 24 ms, and a high photosensitivity ca. 103 for 405 nm laser.

  19. Hafnium sulfate prenucleation clusters and the Hf(18) polyoxometalate red herring.

    PubMed

    Ruther, Rose E; Baker, Brenna M; Son, Jung-Ho; Casey, William H; Nyman, May

    2014-04-21

    In prior studies, aqueous Hf sulfate-peroxide solutions were spin-coated, dehydrated, patterned by electron-beam lithography, ion-exchanged (OH(-) for SO4(2-)), and finally converted to HfO2 hard masks via annealing. The atomic-level details of the underlying aqueous chemistries of these processes are complex and yet to be understood. Yet a thorough understanding of this specific chemical system will inspire development of design rules for other aqueous-precursor-to-solid-state metal oxide systems. Often-observed crystallization of the Hf18 polyoxometalate from aqueous Hf sulfate-peroxide precursor solutions has led us to believe that Hf18 may represent an important intermediate step in this process. However, via detailed solution studies described here (small-angle X-ray scattering, electrospray ionization mass spectrometry, and Raman spectroscopy), we ascertained that Hf18 is in fact not a prenucleation cluster of Hf sulfate coatings. Rather, the Hf tetramers, pentamers, and hexamers that are the core building blocks of Hf18 are robustly persistent over variable compositions and aging time of precursor solutions, and therefore they are likely the rudimentary building blocks of the deposited thin-film materials. These Hf clusters are capped and linked by sulfate and peroxide anions in solution, which probably prevents crystallization of Hf18 during the rapid dehydration process of spin-coating. In fact, crystallization of Hf18 from the amorphous gel coating would be detrimental to formation of a high-density conformal coating that we obtain from precursor solutions. Therefore, this study revealed that the well-known Hf18 polyoxometalate is not likely to be an important intermediate in the thin-film process. However, its subunits are, confirming the universal importance of deriving information from the solid state, albeit judiciously and critically, to understand the solution state.

  20. Reliability assessment of ultra-thin HfO2 films deposited on silicon wafer

    NASA Astrophysics Data System (ADS)

    Fu, Wei-En; Chang, Chia-Wei; Chang, Yong-Qing; Yao, Chih-Kai; Liao, Jiunn-Der

    2012-09-01

    Ultra-thin hafnium dioxide (HfO2) is used to replace silicon dioxide to meet the required transistor feature size in advanced semiconductor industry. The process integration compatibility and long-term reliability for the transistors depend on the mechanical performance of ultra-thin HfO2 films. The criteria of reliability including wear resistance, thermal fatigue, and stress-driven failure rely on film adhesion significantly. The adhesion and variations in mechanical properties induced by thermal annealing of the ultra-thin HfO2 films deposited on silicon wafers (HfO2/SiO2/Si) are not fully understood. In this work, the mechanical properties of an atomic layer deposited HfO2 (nominal thickness ≈10 nm) on a silicon wafer were characterized by the diamond-coated tip of an atomic force microscope and compared with those of annealed samples. The results indicate that the annealing process leads to the formation of crystallized HfO2 phases for the atomic layer deposited HfO2. The HfSixOy complex formed at the interface between HfO2 and SiO2/Si, where the thermal diffusion of Hf, Si, and O atoms occurred. The annealing process increases the surface hardness of crystallized HfO2 film and therefore the resistance to nano-scratches. In addition, the annealing process significantly decreases the harmonic contact stiffness (or thereafter eliminate the stress at the interface) and increases the nano-hardness, as measured by vertically sensitive nano-indentation. Quality assessments on as-deposited and annealed HfO2 films can be thereafter used to estimate the mechanical properties and adhesion of ultra-thin HfO2 films on SiO2/Si substrates.

  1. Semiclassical Virasoro blocks from AdS3 gravity

    NASA Astrophysics Data System (ADS)

    Hijano, Eliot; Kraus, Per; Perlmutter, Eric; Snively, River

    2015-12-01

    We present a unified framework for the holographic computation of Virasoro conformal blocks at large central charge. In particular, we provide bulk constructions that correctly reproduce all semiclassical Virasoro blocks that are known explicitly from conformal field theory computations. The results revolve around the use of geodesic Witten diagrams, recently introduced in [1], evaluated in locally AdS3 geometries generated by backreaction of heavy operators. We also provide an alternative computation of the heavy-light semiclassical block — in which two external operators become parametrically heavy — as a certain scattering process involving higher spin gauge fields in AdS3; this approach highlights the chiral nature of Virasoro blocks. These techniques may be systematically extended to compute corrections to these blocks and to interpolate amongst the different semiclassical regimes.

  2. AdS6 solutions of type II supergravity

    NASA Astrophysics Data System (ADS)

    Apruzzi, Fabio; Fazzi, Marco; Passias, Achilleas; Rosa, Dario; Tomasiello, Alessandro

    2014-11-01

    Very few AdS6 × M 4 supersymmetric solutions are known: one in massive IIA, and two IIB solutions dual to it. The IIA solution is known to be unique; in this paper, we use the pure spinor approach to give a classification for IIB supergravity. We reduce the problem to two PDEs on a two-dimensional space Σ. M 4 is then a fibration of S 2 over Σ; the metric and fluxes are completely determined in terms of the solution to the PDEs. The results seem likely to accommodate near-horizon limits of ( p, q)-fivebrane webs studied in the literature as a source of CFT5's. We also show that there are no AdS6 solutions in eleven-dimensional supergravity.

  3. Crystallography of the NiHfSi Phase in a NiAl (0.5 Hf) Single-Crystal Alloy

    NASA Technical Reports Server (NTRS)

    Garg, A.; Noebe, R. D.; Darolia, R.

    1996-01-01

    Small additions of Hf to conventionally processed NiAl single crystals result in the precipitation of a high density of cuboidal G-phase along with a newly identified silicide phase. Both of these phases form in the presence of Si which is not an intentional alloying addition but is a contaminant resulting from contact with the ceramic shell molds during directional solidification of the single-crystal ingots. The morphology, crystal structure and Orientation Relationship (OR) of the silicide phase in a NiAl (0.5 at.%Hf) single-crystal alloy have been determined using transmission electron microscopy, electron microdiffraction and energy dispersive X-ray spectroscopy. Qualitative elemental analysis and indexing of the electron microdiffraction patterns from the new phase indicate that it is an orthorhombic NiHfSi phase with unit cell parameters, a = 0.639 nm, b = 0.389 nm and c = 0.72 nm, and space group Pnma. The NiHfSi phase forms as thin rectangular plates on NiAl/111/ planes with an OR that is given by NiHfSi(100))(parallel) NiAl(111) and NiHfSi zone axes(010) (parallel) NiAl zone axes (101). Twelve variants of the NiHfSi phase were observed in the alloy and the number of variants and rectangular morphology of NiHfSi plates are consistent with symmetry requirements. Quenching experiments indicate that nucleation of the NiHfSi phase in NiAI(Hf) alloys is aided by the formation of NiAl group of zone axes (111) vacancy loops that form on the NiAl /111/ planes.

  4. Conserved higher-spin charges in AdS4

    NASA Astrophysics Data System (ADS)

    Gelfond, O. A.; Vasiliev, M. A.

    2016-03-01

    Gauge invariant conserved conformal currents built from massless fields of all spins in 4d Minkowski space-time and AdS4 are described in the unfolded dynamics approach. The current cohomology associated with non-zero conserved charges is found. The resulting list of charges is shown to match the space of parameters of the conformal higher-spin symmetry algebra in four dimensions.

  5. On information loss in AdS3/CFT2

    DOE PAGES

    Fitzpatrick, A. Liam; Kaplan, Jared; Li, Daliang; Wang, Junpu

    2016-05-18

    We discuss information loss from black hole physics in AdS3, focusing on two sharp signatures infecting CFT2 correlators at large central charge c: ‘forbidden singularities’ arising from Euclidean-time periodicity due to the effective Hawking temperature, and late-time exponential decay in the Lorentzian region. We study an infinite class of examples where forbidden singularities can be resolved by non-perturbative effects at finite c, and we show that the resolution has certain universal features that also apply in the general case. Analytically continuing to the Lorentzian regime, we find that the non-perturbative effects that resolve forbidden singularities qualitatively change the behavior ofmore » correlators at times t ~SBH, the black hole entropy. This may resolve the exponential decay of correlators at late times in black hole backgrounds. By Borel resumming the 1/c expansion of exact examples, we explicitly identify ‘information-restoring’ effects from heavy states that should correspond to classical solutions in AdS3. Lastly, our results suggest a line of inquiry towards a more precise formulation of the gravitational path integral in AdS3.« less

  6. Strong photoluminescence of the porous silicon with HfO{sub 2}-filled microcavities

    SciTech Connect

    Jiang, Ran; Wu, Zhengran; Du, Xianghao; Han, Zuyin; Sun, Weideng

    2015-06-22

    Greatly enhanced blue emission was observed at room temperature in the single-crystal silicon with HfO{sub 2} filled into its microcavities. The broad blue band light was emitted from both the HfO{sub 2} dielectric and the porous Si. The ferroelectricity of HfO{sub 2} enhances the blue emission from Si by its filling into the microcaivities. At the same time, HfO{sub 2} contributes to the light emission for the transitions of the defect levels for oxygen vacancy. The observation of greatly enhanced blue light emission of the porous Si filled with HfO{sub 2} dielectric is remarkable as both HfO{sub 2} and Si are highly compatible with Si-based electronic industry.

  7. Corrosion characteristics of anodized Ti-(10-40wt%)Hf alloys for metallic biomaterials use.

    PubMed

    Jeong, Yong-Hoon; Choe, Han-Cheol; Brantley, William A

    2011-01-01

    The effect of anodizing on corrosion resistance of Ti-xHf alloys has been investigated. Ti-xHf alloys were prepared and anodized at 120, 170 and 220 V in 1 M H(3)PO(4) solution, and crystallized at 300 and 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution at 36.5 ± 1°C. The Ti-xHf alloys exhibited the α' and anatase phases. The pore size on the anodized surface increases as the applied voltage is increased, whereas the pore size decreases as the Hf content is increased. The anodized Ti-xHf alloys exhibited better corrosion resistance than non-anodized Ti-xHf alloys.

  8. Microstructure dependent filament forming kinetics in HfO2 programmable metallization cells

    NASA Astrophysics Data System (ADS)

    Clarke, Heidi; Brown, Timothy; Hu, Jianjun; Ganguli, Raj; Reed, Amber; Voevodin, Andrey; Shamberger, Patrick J.

    2016-10-01

    Variability remains the principal concern for commercialization of HfO2 based resistance switching devices. Here, we investigate the role of thermal processing conditions on internal structure of atomic layer deposited HfO2 thin films, and the impact of that structure on filament forming kinetics of p+ Si/HfO2/Cu and TiN/HfO2/Cu devices. Regardless of bias polarity or electrode metal, filament formation times are at least one order of magnitude shorter in polycrystalline than in amorphous films, which we attribute to the presence of fast ion migration along grain boundaries. Within polycrystalline films, filament formation times are correlated with degree of crystalline orientation. Inter-device variability in forming time is roughly equivalent across HfO2 film processing conditions. The kinetics of filament forming are shown to be highly dependent on HfO2 microstructure, with possible implications for the inter-device variability of subsequent switching cycles.

  9. A coupled ionosphere-raytrace model for high-power HF heating

    NASA Astrophysics Data System (ADS)

    Zawdie, K. A.; Huba, J. D.; Drob, D. P.; Bernhardt, P. A.

    2015-11-01

    The first 3-D model of artificial HF ionospheric heating to self-consistently calculate the modification in heating location due to evolving ionospheric gradients has been developed. The model combines the ionosphere model SAMI3/ESF and the HF propagation code MoJo-15. At each time step, the simulated path of the HF wave through the ionosphere is used to determine the HF heating location. These calculations have been used to explain the physical mechanism responsible for the snapback effect observed in an Arecibo HF heating experiment described by Bernhardt et al. (1988). The heater wave is refracted by the density cavity, which causes the heating location to drift in longitude. Eventually, the density cavity convects into the path of the refracted ray, such that only a small portion of the ray is above the threshold for HF heating and the heating location snaps back even though the ray itself is still refracted in longitude.

  10. Simultaneous measurements of HF-enhanced plasma waves and artificial field-aligned irregularities at Arecibo

    NASA Astrophysics Data System (ADS)

    Noble, S. T.; Djuth, F. T.

    1990-09-01

    A study aimed at examining the coupling between HF-induced Langmuir waves and artificially produced field-aligned irregularities is presented. The HF-enhanced plasma lines (HFPLs) were monitored with the Arecibo 430-MHz radar while simultaneous measurements of artificial geomagnetic field-aligned irregularities (AFAIs) were made with a mobile 49.92-MHz radar. The HF power was systematically increased and then decreased during the experimental period when a single data set was obtained under nearly ideal observing conditions. As the HF power is increased, the HFPL backscatter power starts to saturate at about 70 MW effective radiated power (ERP). However, the backscatter from AFAIs is linearly dependent on HF power, even at the greatest (120 MW ERP) HF power levels available at Arecibo.

  11. Microstructure dependent filament forming kinetics in HfO2 programmable metallization cells.

    PubMed

    Clarke, Heidi; Brown, Timothy; Hu, Jianjun; Ganguli, Raj; Reed, Amber; Voevodin, Andrey; Shamberger, Patrick J

    2016-10-21

    Variability remains the principal concern for commercialization of HfO2 based resistance switching devices. Here, we investigate the role of thermal processing conditions on internal structure of atomic layer deposited HfO2 thin films, and the impact of that structure on filament forming kinetics of p+ Si/HfO2/Cu and TiN/HfO2/Cu devices. Regardless of bias polarity or electrode metal, filament formation times are at least one order of magnitude shorter in polycrystalline than in amorphous films, which we attribute to the presence of fast ion migration along grain boundaries. Within polycrystalline films, filament formation times are correlated with degree of crystalline orientation. Inter-device variability in forming time is roughly equivalent across HfO2 film processing conditions. The kinetics of filament forming are shown to be highly dependent on HfO2 microstructure, with possible implications for the inter-device variability of subsequent switching cycles.

  12. ADS/CFT and QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U. /SLAC

    2007-02-21

    The AdS/CFT correspondence between string theory in AdS space and conformal .eld theories in physical spacetime leads to an analytic, semi-classical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. Although QCD is not conformally invariant, one can nevertheless use the mathematical representation of the conformal group in five-dimensional anti-de Sitter space to construct a first approximation to the theory. The AdS/CFT correspondence also provides insights into the inherently non-perturbative aspects of QCD, such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of AdS space z and a specific impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions, the fundamental entities which encode hadron properties and allow the computation of decay constants, form factors, and other exclusive scattering amplitudes. New relativistic lightfront equations in ordinary space-time are found which reproduce the results obtained using the 5-dimensional theory. The effective light-front equations possess remarkable algebraic structures and integrability properties. Since they are complete and orthonormal, the AdS/CFT model wavefunctions can also be used as a basis for the diagonalization of the full light-front QCD Hamiltonian, thus systematically improving the AdS/CFT approximation.

  13. Meteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth.

    PubMed

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

    2015-04-28

    Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The (176)Lu-(176)Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day (176)Hf/(177)Hf and (176)Lu/(177)Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess (176)Hf due to the accelerated decay of (176)Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu-Hf system. Herein we report the first, to our knowledge, high-precision Lu-Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial (176)Hf/(177)Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess (176)Hf and accurately represent the Lu-Hf system of the bulk Earth ((176)Hf/(177)Hf = 0.282793 ± 0.000011; (176)Lu/(177)Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago.

  14. Meteorite zircon constraints on the bulk Lu−Hf isotope composition and early differentiation of the Earth

    PubMed Central

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

    2015-01-01

    Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The 176Lu−176Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day 176Hf/177Hf and 176Lu/177Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess 176Hf due to the accelerated decay of 176Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu−Hf system. Herein we report the first, to our knowledge, high-precision Lu−Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial 176Hf/177Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess 176Hf and accurately represent the Lu−Hf system of the bulk Earth (176Hf/177Hf = 0.282793 ± 0.000011; 176Lu/177Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago. PMID:25870298

  15. Meteorite zircon constraints on the bulk Lu-Hf isotope composition and early differentiation of the Earth.

    PubMed

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Hibiya, Yuki; Amelin, Yuri

    2015-04-28

    Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The (176)Lu-(176)Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day (176)Hf/(177)Hf and (176)Lu/(177)Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess (176)Hf due to the accelerated decay of (176)Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu-Hf system. Herein we report the first, to our knowledge, high-precision Lu-Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial (176)Hf/(177)Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess (176)Hf and accurately represent the Lu-Hf system of the bulk Earth ((176)Hf/(177)Hf = 0.282793 ± 0.000011; (176)Lu/(177)Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago. PMID:25870298

  16. Coalescence of silver clusters by immersion in diluted HF solution

    SciTech Connect

    Milazzo, R. G.; Mio, A. M.; D’Arrigo, G.; Spinella, C.; Grimaldi, M. G.; Rimini, E.

    2015-07-14

    The galvanic displacement deposition of silver on H-terminated Si (100) in the time scale of seconds is instantaneous and characterized by a cluster density of 10{sup 11}-10{sup 12} cm{sup −2}. The amount of deposited Ag follows a t{sup 1/2} dependence in agreement with a Cottrell diffusion limited mechanism. At the same time, during the deposition, the cluster density reduces by a factor 5. This behavior is in contrast with the assumption of immobile clusters. We show in the present work that coalescence and aggregation occur also in the samples immersed in the diluted hydrofluoric acid (HF) solution without the presence of Ag{sup +}. Clusters agglomerate according to a process of dynamic coalescence, typical of colloids, followed by atomic redistribution at the contact regions with the generation of multiple internal twins and stacking-faults. The normalized size distributions in terms of r/r{sub mean} follow also the prediction of the Smoluchowski ripening mechanism. No variation of the cluster density occurs for samples immersed in pure H{sub 2}O solution. The different behavior might be associated to the strong attraction of clusters to oxide-terminated Si surface in presence of water. The silver clusters are instead weakly bound to hydrophobic H-terminated Si in presence of HF. HF causes then the detachment of clusters and a random movement on the silicon surface with mobility of about 10{sup −13} cm{sup 2}/s. Attractive interaction (probably van der Waals) among particles promotes coarsening.

  17. Temporal Development of HF-Excited Langmuir and Ion Turbulence at Arecibo

    NASA Astrophysics Data System (ADS)

    Djuth, F. T.; DuBois, D. F.

    2015-10-01

    The Arecibo high-power, high-frequency (HF) facility and 430 MHz radar are used to examine the temporal development of the HF-induced Langmuir and ion turbulences from 1 ms to many minutes after the turn-on of the HF beam in the F region. All HF observations begin in a smooth, stratified, stable plasma. "Cold start" HF transmissions are employed to avoid remnant irregularities from prior HF transmissions. HF-excited plasma line (HFPL) and ion line echoes are used to monitor the evolution of the turbulence. In the evening/nighttime the HFPL develops in three reproducible stages. Over time scales of 0 to 10-20 ms (possibly 40 ms), the smooth plasma conditions are maintained, and the results are consistent with theoretical models of the excitation of strong Langmuir turbulence near HF reflection. This entails the initiation of the so-called "caviton production cycle." The turbulence from the parametric decay instability is detected at lower altitudes where the radar wave vector matches those of the HF-enhanced waves. The data suggests that the two processes coexist in the region in between. After ~40 ms the "overshoot process" begins and consists of a downward extension of the HFPL from the HF reflection region to heights ~1.1 km below followed by a retreat back to the reflection region. The whole overshoot process takes place over a time scale of ~3 s. Thereafter the echo remains near HF reflection for 20-90 s after HF turn-on. The HFPL echo subsequently breaks up into patches because of the formation of large-scale electron density structures in the plasma. New kinetic models indicate that suprathermal electrons excited in the plasma by, for example, caviton burn-out serve to regulate plasma turbulence in the modified ionospheric volume.

  18. Silicon/HfO2 interface: Effects of gamma irradiation

    NASA Astrophysics Data System (ADS)

    Maurya, Savita

    2016-05-01

    Quality of MOS devices is a strong function of substrate and oxide interface. In this work we have studied how gamma photon irradiation affects the interface of a 13 nm thick, atomic layer deposited hafnium dioxide deposited on silicon wafer. CV and GV measurements have been done for pristine and irradiated samples to quantify the effect of gamma photon irradiation. Gamma photon irradiation not only introduces positive charge in the oxide and at the interface of Si/HfO2 interface but also induce phase change of oxide layer. Maximum oxide capacitances are affected by gamma photon irradiation.

  19. Survey reveals nature of corrosion in HF alky units

    SciTech Connect

    Dobis, J.D. ); Clarida, D.R. ); Richert, J.P. )

    1995-03-06

    The results of a National Association of Corrosion Engineers survey of 62 HF alkylation units reveal relatively low incidence of service-related cracking of carbon steel. Hydrogen blistering, however, is prevalent, especially in the main acid circuit and overhead condensers. Based on these and other survey results, several recommendations are made to enable refiners to monitor and reduce corrosion in these special units. The paper discusses the survey results, construction materials, post-weld heat treatments, small-diameter piping, construction inspection, bolting, gaskets, block valves, maintenance practices, cracking, blistering, areas of vulnerability, and recommendations.

  20. Enhanced resistive switching and multilevel behavior in bilayered HfAlO/HfAlO{sub x} structures for non-volatile memory applications

    SciTech Connect

    Faita, F. L.; Silva, J. P. B.; Pereira, M.; Gomes, M. J. M.

    2015-12-14

    In this work, hafnium aluminum oxide (HfAlO) thin films were deposited by ion beam sputtering deposition technique on Si substrate. The presence of oxygen vacancies in the HfAlO{sub x} layer deposited in oxygen deficient environment is evidenced from the photoluminescence spectra. Furthermore, HfAlO(oxygen rich)/HfAlO{sub x}(oxygen poor) bilayer structures exhibit multilevel resistive switching (RS), and the switching ratio becomes more prominent with increasing the HfAlO layer thickness. The bilayer structure with HfAlO/HfAlO{sub x} thickness of 30/40 nm displays the enhanced multilevel resistive switching characteristics, where the high resistance state/intermediate resistance state (IRS) and IRS/low resistance state resistance ratios are ≈10{sup 2} and ≈5 × 10{sup 5}, respectively. The switching mechanisms in the bilayer structures were investigated by the temperature dependence of the three resistance states. This study revealed that the multilevel RS is attributed to the coupling of ionic conduction and the metallic conduction, being the first associated to the formation and rupture of conductive filaments related to oxygen vacancies and the second with the formation of a metallic filament. Moreover, the bilayer structures exhibit good endurance and stability in time.

  1. Reduced-temperature processing and consolidation of ultra-refractory Ta4HfC5

    SciTech Connect

    Gaballa, Osama; Cook, B. A.; Russell, A. M.

    2013-04-26

    TaC, HfC, and WC powders were subjected to high-energy milling and hot pressing to produce Ta4HfC5, a composite of Ta(4)HfC5 + 30 vol.% WC, and a composite of Ta4HfC5 + 50 vol.% WC. Sub-micron powders were examined after four different milling intervals prior to hot pressing. XRD was used to verify proper phase formation. SEM, relative density, and hardness measurements were used to examine the resulting phases. Hot pressed compacts of Ta4HfC5 showed densification as high as 98.6% along with Vickers hardness values of 21.4 GPa. Similarly, Ta4HfC5 + 30 vol.% WC exhibited 99% densification with a Vickers hardness of 22.5 GPa. These levels of densification were achieved at 1500 degrees C, which is lower than any previously reported sintering temperature for Ta4HfC5. Microhardness values measured in this study were higher than those previously reported for Ta4HfC5. The WC additions to Ta4HfC5 were found to improve densification and increase microhardness. (C) 2013 Elsevier Ltd. All rights reserved.

  2. Characterization of nanostructured HfO2 films using Perturbed Angular Correlation (PAC) technique

    NASA Astrophysics Data System (ADS)

    Cavalcante, F. H. M.; Gomes, M. R.; Carbonari, A. W.; Pereira, L. F. D.; Rossetto, D. A.; Costa, M. S.; Redondo, L. M.; Mestnik-Filho, J.; Saxena, R. N.; Soares, J. C.

    2010-06-01

    The hyperfine field at 181Ta lattice sites in nanostructured HfO2 thin films was studied by the Perturbed Angular Correlation (PAC) technique. Thin oxide films were deposited by Electron Beam Evaporation on a silicon substrate. The thickness of the films was ~100 nm and ~250 nm. Radioactive 181Hf nuclei were produced by neutron activation of the film samples in the Brazilian Research Reactor (IPEN IEA-R1) by the reaction 180Hf(n, γ)181Hf. PAC measurements were carried out after annealing at 1473 K. The PAC technique allows the determination of the electric field gradient (EFG) at the probe sites.

  3. Electron beam induced local crystallization of HfO2 nanopores for biosensing applications

    PubMed Central

    Shim, Jiwook; Rivera, Jose; Bashir, Rashid

    2013-01-01

    We report the development of single, locally crystallized nanopores in HfO2 membranes for biosensing applications. HfO2 is chosen for its isoelectric point of 7.0, mechanical and chemical stability in solution, and for its potential as a high-k material for nanopore ionic field effect transistor applications. The HfO2 membrane is deposited on a graphene layer suspended over a 300 nm FIB hole, where graphene is used as the mechanical support. Exposure of the membrane to a focused electron beam causes crystallization in the vicinity of the nanopore during pore formation. We investigate the effects of crystallization on the electrical and surface properties of HfO2 films. Our surface analysis of HfO2 reveals improved hydrophilicity of crystallized HfO2, a notable advantage over the hydrophobicity of as-deposited HfO2. We also demonstrate detection of dsDNA translocation through HfO2 nanopores under various applied bias levels. In addition, our device architecture also presents a promising first step toward the realization of high-k HfO2 nanopore transistors. PMID:23945603

  4. Importance of the Lu-Hf isotopic system in studies of planetary chronology and chemical evolution

    NASA Technical Reports Server (NTRS)

    Patchett, P. J.

    1983-01-01

    The Lu-176-Hf-176 isotope method and its applications in earth sciences are discussed with regard to planetary-evolution studies. From new data on basalts from oceanic islands, Hf-176/Hf-177 and Nd-143/Nd-144 are found to display a single linear isotopic variation in the suboceanic mantle, whereas considerable divergences occur in Hf-176/Hf-177-Sr-87/Sr-86 and Nd-143/Nd-144-Sr87/Sr-86 diagrams. With the acquisition of further Hf-Sr-Nd isotopic data, these discordant Sr-87/Sr-86 relationships may allow a distinction between processes such as mantle metasomatism, influence of sea-water altered material in the magma source, or recycling of sediments into the mantle. The best quality Hf isotope data are obtained from granitoid or zircons, and are most suitable for studying ancient terrestrial Hf isotopic variations. Lu-Hf is shown to be a viable method for dating ancient terrestrial and extraterrestrial samples, but is unlikely to find wide application in pure chronological studies because it offers little advantage over existing methods.

  5. Hf isotope compositions of U.S. Geological Survey reference materials

    NASA Astrophysics Data System (ADS)

    Weis, Dominique; Kieffer, Bruno; Hanano, Diane; Nobre Silva, Inês; Barling, Jane; Pretorius, Wilma; Maerschalk, Claude; Mattielli, Nadine

    2007-06-01

    A systematic multi-isotopic and trace element characterization of U.S. Geological Survey reference materials has been carried out at the Pacific Centre for Isotopic and Geochemical Research, University of British Columbia. Values of 176Hf/177Hf are recommended for the following reference materials (mean ±2 SD): G-2: 0.282523 ± 6; G-3: 0.282518 ± 1; GSP-2: 0.281949 ± 8; RGM-1: 0.283017 ± 13; STM-1: 0.283019 ± 12; STM-2: 0.283021 ± 5; BCR-1: 0.282875 ± 8; BCR-2: 0.282870 ± 8; BHVO-1: 0.283106 ± 12; BHVO-2: 0.283105 ± 11; AGV-1: 0.282979 ± 6; and AGV-2: 0.282984 ± 9. Reproducibility is better than 50 ppm for the granitoid compositions and better than 40 ppm for the basaltic/andesitic compositions. For the isotopic analyses acquired early in this project on glass columns, Hf isotopic analyses from several of the reference materials were significantly less reproducible than Nd and Sr isotopic analyses determined from the same sample dissolution. The 176Hf/177Hf ratios for relatively radiogenic compositions (BCR-1, 2; BHVO-1, 2; RGM-1) were shifted systematically toward lower values by 100-150 ppm when a borosilicate primary column was used. Although systematic, the shift for felsic compositions was generally within analytical error, except for GSP-2, which has a very low Hf isotopic ratio, where the shift was to higher 176Hf/177Hf. Trace element and isotopic characterization of the borosilicate glass column, borosilicate frits, and quartz columns reveals extremely variable levels of trace elements. The 176Hf/177Hf ratios for these materials are very unradiogenic (borosilicate glass <0.28220 frit = 0.28193 ± 4). The borosilicate frit material appears to be the most variable in elemental concentration and isotopic composition. The quartz material has very low levels (Hf/177Hf and high Hf concentrations of the borosilicate glass column (16 ppm) and frit material (22 ppm) indicate that only small amounts of such unradiogenic

  6. Lu-Hf total-rock age for the Amîtsoq gneisses, West Greenland

    USGS Publications Warehouse

    Pettingill, H.S.; Patchett, P.J.

    1981-01-01

    Lu-Hf total-rock data for the Amîtsoq gneisses of West Greenland yield an age of 3.55±0.22Gy(2σ), based on the decay constant λ176Lu=1.96×10−11y−1, and an initial176Hf/177Hf ratio of 0.280482±33. The result is in good agreement with Rb-Sr total-rock and U-Pb zircon ages. In spite of severe metamorphism of the area at 2.9 Gy, zircons from two of the samples have remained on the total-rock line, and define points close to the initial Hf ratio. The initial176Hf/177Hf lies close to a chondritic Hf isotopic evolution curve from 4.55 Gy to present. This is consistent with the igneous precursors to the Amîtsoq gneisses having been derived from the mantle at or shortly before 3.6 Gy. Anomalous relationships between Hf concentration and the176Lu/177Hf ratio may suggest that trace element abundances in the Amîtsoq gneisses are partly controlled by processes related to metamorphism.

  7. Electron beam induced local crystallization of HfO2 nanopores for biosensing applications.

    PubMed

    Shim, Jiwook; Rivera, Jose A; Bashir, Rashid

    2013-11-21

    We report the development of single, locally crystallized nanopores in HfO2 membranes for biosensing applications. HfO2 is chosen for its isoelectric point of 7.0, mechanical and chemical stability in solution, and for its potential as a high-k material for nanopore ionic field effect transistor applications. The HfO2 membrane is deposited on a graphene layer suspended over a 300 nm FIB hole, where graphene is used as the mechanical support. Exposure of the membrane to a focused electron beam causes crystallization in the vicinity of the nanopore during pore formation. We investigate the effects of crystallization on the electrical and surface properties of HfO2 films. Our surface analysis of HfO2 reveals improved hydrophilicity of crystallized HfO2, a notable advantage over the hydrophobicity of as-deposited HfO2. We also demonstrate detection of dsDNA translocation through HfO2 nanopores under various applied bias levels. In addition, our device architecture also presents a promising first step toward the realization of high-k HfO2 nanopore transistors.

  8. Lu-Hf total-rock age for the Amitsoq gneisses, West Greenland

    NASA Technical Reports Server (NTRS)

    Pettingill, H. S.; Patchett, P. J.

    1981-01-01

    Lu-Hf total-rock data for the Amitsoq gneisses of West Greenland yield an age of 3.55 + or - 0.22 billion years, based on the decay constant for Lu-176 of 1.96 x 10 to the -11th/year, and an initial Hf-176/Hf-177 ratio of 0.280482 + or - 33. The result is in good agreement with Rb-Sr total-rock and U-Pb zircon ages. In spite of severe metamorphism of the area at 2.9 billion years, zircons from two of the samples have remained on the total-rock line, and define points close to the initial Hf ratio. The initial Hf-176/Hf-177 lies close to a chondritic Hf isotopic evolution curve from 4.55 billion years to present. This is consistent with the igneous precursors to the Amitsoq gneisses having been derived from the mantle at or shortly before 3.6 billion years. Anomalous relationships between Hf concentration and the Lu-176/Hf-177 ratio may suggest that trace element abundances in the Amitsoq gneisses are partly controlled by processes related to metamorphism.

  9. Ferroelectric phase stabilization of HfO2 by nitrogen doping

    NASA Astrophysics Data System (ADS)

    Xu, Lun; Nishimura, Tomonori; Shibayama, Shigehisa; Yajima, Takeaki; Migita, Shinji; Toriumi, Akira

    2016-09-01

    We report that nitrogen (N) doping can drive the ferroelectricity of HfO2. It was found that N doping can cause the transition from a monoclinic phase to a highly symmetric phase. The role of N doping is discussed from the viewpoints of charge balance and bond-constraining effects. The former is responsible for the structural transformation from a paraelectric phase to a ferroelectric phase by forming an oxygen vacancy. In addition, Hf-N and N-O bonds with covalent characteristics have strong effects on HfO2 structural and electrical properties, and thus contribute to a marked HfO2 para-/ferroelectric transition.

  10. Lu-hf total-rock isochron for the eucrite meteorites

    USGS Publications Warehouse

    Patchett, P.J.; Tatsumoto, M.

    1980-01-01

    The isotope 176Lu (2.6% of natural lutetium) decays by ??- to 176Hf, with a long half life. We present here the first Lu-Hf isochron. The eucrite meteorites, a suite of planetary igneous rocks of known age, 4,550 Myr, define a 10-point total-rock isochron with a slope of 0.0934 ?? 40, leading to a value of 3.53 ?? 0.14 ??1010yr for the ??--decay half life of 176Lu. The isochron intercept of 0.27973 ?? 12 gives the initial 176Hf/177Hf for the inner Solar System at the time of accretion. ?? 1980 Nature Publishing Group.

  11. Cathodoluminescence guided zircon Hf isotope depth profiling: Mobilization of the Lu-Hf system during (U)HP rock exhumation in the Woodlark Rift, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Zirakparvar, N. A.

    2015-04-01

    Cathodoluminescence image guided Hf isotope depth profiling by laser ablation of zircons from two quartzofeldspathic host gneisses constrains the Lu-Hf system's behavior during rapid exhumation of (U)HP rocks in the Woodlark Rift, Papua New Guinea. Investigation of the depth profiling technique in individual and composite zircon standards demonstrates that it is possible to resolve ~ 8 μm thick domains in which εHf(present) differs by as little as 4 units. In a metasedimentary gneiss, 2.89 ± 0.29 Ma zircon overgrowths on Cretaceous aged inherited cores have radiogenic εHf(present) indicating growth in a medium that was originally in equilibrium with garnet undergoing recrystallization (the 'garnet effect' of Zheng et al., 2005). In a separate gneiss sample that originated as an exhumation related anatectic melt, 3.66 ± 0.13 Ma zircons lacking inheritance contain sub-domains that differ from each other by > 15 εHf(present). Some of these sub-domains are radiogenic and can be explained by the 'garnet effect', whereas others also contain highly elevated Lu and Yb in addition to their radiogenic Hf compositions, thus necessitating a medium derived from the complete breakdown of garnet. Zircons in this sample also contain non-radiogenic sub-domains that grew in the presence of Hf mobilized from the surrounding rocks of the subducted and metamorphosed remnants of the Australian continental margin. The results confirm that rapid exhumation of (U)HP rocks can result in the following: 1) transmission of radiogenic Hf (and sometimes Lu and the other HREE) from garnet bearing mafic lithologies into the quartzofeldspathic gneisses, and 2) mobilization and transport of unradiogenic Hf present within the quartzofeldspathic remnants of subducted continental crust.

  12. Euclidean and Noetherian entropies in AdS space

    SciTech Connect

    Dutta, Suvankar; Gopakumar, Rajesh

    2006-08-15

    We examine the Euclidean action approach, as well as that of Wald, to the entropy of black holes in asymptotically AdS spaces. From the point of view of holography these two approaches are somewhat complementary in spirit and it is not obvious why they should give the same answer in the presence of arbitrary higher derivative gravity corrections. For the case of the AdS{sub 5} Schwarzschild black hole, we explicitly study the leading correction to the Bekenstein-Hawking entropy in the presence of a variety of higher derivative corrections studied in the literature, including the Type IIB R{sup 4} term. We find a nontrivial agreement between the two approaches in every case. Finally, we give a general way of understanding the equivalence of these two approaches.

  13. New Features in ADS Labs

    NASA Astrophysics Data System (ADS)

    Accomazzi, Alberto; Kurtz, M. J.; Henneken, E. A.; Grant, C. S.; Thompson, D.; Di Milia, G.; Luker, J.; Murray, S. S.

    2013-01-01

    The NASA Astrophysics Data System (ADS) has been working hard on updating its services and interfaces to better support our community's research needs. ADS Labs is a new interface built on the old tried-and-true ADS Abstract Databases, so all of ADS's content is available through it. In this presentation we highlight the new features that have been developed in ADS Labs over the last year: new recommendations, metrics, a citation tool and enhanced fulltext search. ADS Labs has long been providing article-level recommendations based on keyword similarity, co-readership and co-citation analysis of its corpus. We have now introduced personal recommendations, which provide a list of articles to be considered based on a individual user's readership history. A new metrics interface provides a summary of the basic impact indicators for a list of records. These include the total and normalized number of papers, citations, reads, and downloads. Also included are some of the popular indices such as the h, g and i10 index. The citation helper tool allows one to submit a set of records and obtain a list of top 10 papers which cite and/or are cited by papers in the original list (but which are not in it). The process closely resembles the network approach of establishing "friends of friends" via an analysis of the citation network. The full-text search service now covers more than 2.5 million documents, including all the major astronomy journals, as well as physics journals published by Springer, Elsevier, the American Physical Society, the American Geophysical Union, and all of the arXiv eprints. The full-text search interface interface allows users and librarians to dig deep and find words or phrases in the body of the indexed articles. ADS Labs is available at http://adslabs.org

  14. Anticooperativity of FHF hydrogen bonds in clusters of the type F- × (HF)n, RF × (HF)n and XF × (HF)n, R = alkyl and X = H, Br, Cl, F

    NASA Astrophysics Data System (ADS)

    Kucherov, S. Yu.; Bureiko, S. F.; Denisov, G. S.

    2016-02-01

    Properties of twenty five hydrogen-bonded complexes, namely, F- × (HF)n (n = 1-6), RF × (HF)n (R = t-Bu, i-Pr, Et, Me; n = 1-3), XF × (HF)n (X = H, Br, Cl; n = 1-2), and FF…HF with the hydrogen bond energy varying in a wide range have been calculated using ab initio methods at the MP2/6-31++G** level. For the first time, the energies, geometrical parameters and vibrational frequencies are obtained for the series of clusters, where the bonding character changes from covalent to van der Waals on the variation of proton-acceptor ability of the base, and the energies are in the range of 45-1 kcal/mol. The mutual influence of multiple hydrogen bonds of F…HF type in clusters, in which a fluorine anion or an atom participates in hydrogen bond formation as the acceptor, is systematically investigated. The relative changes in the values of the considered parameters on the sequential addition of an HF molecule (anticooperativity) were determined. It was shown that non-additivity of the interaction is most strongly pronounced in the energy and vibrational frequency values, geometrical parameters of hydrogen bonds are less sensitive to the mutual influence. The anticooperative effect is more pronounced on the hydrogen bridge length R(F...F) than on the geometry of proton donor r(HF). The hydrogen bond formation and the increase of the number n of ligands lead to successive lengthening of the r(XF) bond adjacent to the hydrogen bridge. The length of an XF bond changes stronger on formation of each hydrogen bond than the HF bond length.

  15. Most general AdS3 boundary conditions

    NASA Astrophysics Data System (ADS)

    Grumiller, Daniel; Riegler, Max

    2016-10-01

    We consider the most general asymptotically anti-de Sitter boundary conditions in three-dimensional Einstein gravity with negative cosmological constant. The metric contains in total twelve independent functions, six of which are interpreted as chemical potentials (or non-normalizable fluctuations) and the other half as canonical boundary charges (or normalizable fluctuations). Their presence modifies the usual Fefferman-Graham expansion. The asymptotic symmetry algebra consists of two sl{(2)}_k current algebras, the levels of which are given by k = ℓ/(4 G N ), where ℓ is the AdS radius and G N the three-dimensional Newton constant.

  16. Microstructure And Oxidation Properties Of Laser Clad Ni70AL20Cr7Hf3 Alloys With Extended Solid Solution Of Hf

    NASA Astrophysics Data System (ADS)

    Mazumder, J.; Sircar, S.; Ribaudo, C.; Kar, A.,

    1989-01-01

    Alloys coatings for superalloys for improved higher temperature (1200°C) service life under aggressive atmospheres are of great interest at present. There is a general consensus that addition of rare earths such as hafnium (Hf) to these alloys has a pronounced effect on the oxidation resistance properties at high temperatures. In situ laser cladding technique was used to produce Ni-Al-Cr-Hf alloys with extended solid solution of Hf in a near stoichiometric Ni3Al matrix. A 10 kW CW CO2 laser was used in conjunction with a screw-feed powder dispenser to perform the in situ cladding process.

  17. Introducing ADS 2.0

    NASA Astrophysics Data System (ADS)

    Accomazzi, Alberto; Kurtz, M. J.; Henneken, E. A.; Grant, C. S.; Thompson, D.; Luker, J.; Chyla, R.; Murray, S. S.

    2014-01-01

    In the spring of 1993, the Smithsonian/NASA Astrophysics Data System (ADS) first launched its bibliographic search system. It was known then as the ADS Abstract Service, a component of the larger Astrophysics Data System effort which had developed an interoperable data system now seen as a precursor of the Virtual Observatory. As a result of the massive technological and sociological changes in the field of scholarly communication, the ADS is now completing the most ambitious technological upgrade in its twenty-year history. Code-named ADS 2.0, the new system features: an IT platform built on web and digital library standards; a new, extensible, industrial strength search engine; a public API with various access control capabilities; a set of applications supporting search, export, visualization, analysis; a collaborative, open source development model; and enhanced indexing of content which includes the full-text of astronomy and physics publications. The changes in the ADS platform affect all aspects of the system and its operations, including: the process through which data and metadata are harvested, curated and indexed; the interface and paradigm used for searching the database; and the follow-up analysis capabilities available to the users. This poster describes the choices behind the technical overhaul of the system, the technology stack used, and the opportunities which the upgrade is providing us with, namely gains in productivity and enhancements in our system capabilities.

  18. Resonance Ionization Instability in HF and Microwave Discharges

    NASA Astrophysics Data System (ADS)

    Dvinin, Sergey; Dovzhenko, Vitaliy

    2013-09-01

    For the first time ionization instability of HF plasma has been described in. Later it has been shown that in the spatially limited low pressure microwave discharge the given instability leads not only to change plasma structure, but to appearance of resonances at electron densities, when the size of plasma becomes multiple to some number of half waves of the standing surface wave, exciting on plasma boundary. Evolution of electron density perturbation is defined by two processes - negative feedback owing to a total current continuity (as in striations) and positive one due to excitation of a wave, which is close to a resonance. In the given work the theory has been improved with accounting of both processes that has allowed to reach better coincidence with experiment. In addition, the general theory of ionization instability has been developed. Application of the model to CCP HF (100 MHz and higher) discharge with large electrodes has shown that excitation of the instability accompanied by surface waves, propagating along plasma-sheath-electrodes interface, is possible.

  19. Multianode Photomultiplier Testing for 2013 CMS Hadronic Forward (HF) Upgrades

    NASA Astrophysics Data System (ADS)

    Funk, Garrett; Jia, Zhe; Onel, Yasar

    2012-03-01

    The Hadronic Forward (HF) section of the Compact Muon Solenoid, a detector at the Large Hadron Collider at CERN, will undergo various upgrades in 2013. HF requires photomultiplier tubes (PMTs) to detect the energy signatures of hadronic collisions. The University of Iowa High Energy Physics group is responsible for testing new PMTs for the upgrade. These tests provide seven different operational parameters that will be used for calibration and quality control before installation. The dark current test checks the noise generated by the PMTs at different voltages when there is no light source. The after pulse test measures the degradation of the vacuum chamber of each PMT as it relates to pulse noise. The gain test measures the degree of amplification provided by the PMT. This is the most vital test, as it allows for the reconstruction of the energies observed by the PMT. The surface non-uniformity test checks the active face of the PMTs for signal uniformity and ``hot spot'' sensitivity to light. The timing test observes the PMT's reading and recovery speed. The linearity test measures the tube's output under varying levels of light. The double pulse test checks the linearity of the PMT with two signals occurring 25 nanoseconds apart.

  20. Concerted hydrogen atom exchange between three HF molecules

    NASA Technical Reports Server (NTRS)

    Komornicki, Andrew; Dixon, David A.; Taylor, Peter R.

    1992-01-01

    We have investigated the termolecular reaction involving concerted hydrogen exchange between three HF molecules, with particular emphasis on the effects of correlation at the various stationary points along the reaction. Using an extended basis, we have located the geometries of the stable hydrogen-bonded trimer, which is of C(sub 3h) symmetry, and the transition state for hydrogen exchange, which is of D(sub 3h) symmetry. The energies of the exchange reation were then evaluated at the correlated level, using a large atomic natural orbital basis and correlating all valence electrons. Several correlation treatments were used, namely, configration interaction with single and double excitations, coupled-pair functional, and coupled-cluster methods. We are thus able to measure the effect of accounting for size-extensivity. Zero-point corrections to the correlated level energetics were determined using analytic second derivative techniques at the SCF level. Our best calculations, which include the effects of connected triple excitations in the coupled-cluster procedure, indicate that the trimer is bound by 9 +/- 1 kcal/mol relative to three separate monomers, in excellent agreement with previous estimates. The barrier to concerted hydrogen exchange is 15 kcal/mol above the trimer, or only 4.7 kcal/mol above three separated monomers. Thus the barrier to hydrogen exchange between HF molecules via this termolecular process is very low.

  1. Observations of HF backscatter decay rates from HAARP generated FAI

    NASA Astrophysics Data System (ADS)

    Bristow, William; Hysell, David

    2016-07-01

    Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

  2. Identification of triaxial strongly deformed band in {sup 168}Hf.

    SciTech Connect

    Yadav, R. B.; Ma, W. C.; Hagemann, G. B.; Bengtsson, R.; Ryde, H.; Carpenter, M. P.; Janssens, R. V. F.; Khoo, T. L.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; Mississippi State Univ.; Niels Bohr Inst.; Lund Inst. of Tech.; Lund. Univ.; Univ. di Milano; Univ. of Bonn; U.S. Naval Academy; Univ. of Oslo; Univ. of Tennessee

    2008-01-01

    Possible decay pathways associated with three candidates for triaxial strongly deformed (TSD) bands in {sup 168}Hf have been investigated. The spin and excitation energy of the strongest band, TSD1, were determined approximately based on {gamma}-ray coincidence relationships. Discrete links were established for the second band. The overall agreement between the observed properties of the bands and cranking calculations using the ULTIMATE CRANKER code provides strong support for an interpretation where band TSD1 is associated with a TSD minimum, ({var_epsilon}{sub 2},{gamma}) {approx} (0.43,20{sup o}), involving the {pi}(i{sub 13/2}){sup 2} and the {nu}(j{sub 15/2}) high-j orbitals. This constitutes the first identification of a TSD band in Hf isotopes, which has been long-predicted by theoretical studies. The second band is understood as being associated with a near-prolate shape and a deformation enhanced with respect to the normal deformed bands. It is proposed to be built on the {pi}(i{sub 13/2}h{sub 9/2}) {nu}(i{sub 13/2}){sup 2} configuration.

  3. Recent observations of HF and HCl in the upper stratosphere

    NASA Technical Reports Server (NTRS)

    Zander, R.

    1981-01-01

    Concentrations of gas phase hydrofluoric acid and hydrochloric acid have been determined in the upper stratosphere from near-infrared solar spectra recorded in the course of balloon flights from Palestine, Texas, in October 1978 and in September 1979. The average mixing ratios for HF deduced respectively from these flights are (4.8 plus or minus .3) x 10 to the -10th ppv above 30.3km and (6.2 plus or minus .5) x 10 to the -10th ppv above 36.8km. This observed difference is ascribed to an increase in the HF concentration out to at least 37km. The HCl mixing ratios deduced from the 1978 flight yield (4.5 plus or minus .6) x 10 to the -10th ppv at 21.7km, (7.5 plus or minus .7) x 10 to the -10th ppv at 27.5 km and (2.1 plus or minus .4) x 10 to the -9th ppv above 30.5km. Observations in 1979 imply an average HCl mixing ratio above 36.8km of (2.4 plus or minus .4) x 10 to the -9th ppv. Our data do not indicate a measurable temporal trend of the HCl concentration above 30km.

  4. Chemistry of H2O and HF Under Extreme Conditions

    SciTech Connect

    Fried, L; Goldman, N; Kuo, I W; Mundy, C

    2005-11-28

    The predicted high pressure superionic phases of water and HF are investigated via ab initio molecular dynamics. These phases could potentially be achieved through either static compression with heating or through shock compression. We study water at densities of 2.0-3.0 g/cc (34-115 GPa) along the 2000K isotherm.We find that extremely rapid (superionic) diffusion of protons occurs in a fluid phase at pressures between 34 and 58 GPa. A transition to a stable body-centered cubic (bcc) O lattice with superionic proton conductivity is observed between 70 and 75 GPa, a much higher pressure than suggested in prior work. We find that all molecular species at pressures greater than 75 GPa are too short lived to be classified as bound states. Up to 95 GPa, we find a solid superionic phase characterized by covalent O-H bonding. Above 95 GPa, a transient network phase is found characterized by symmetric O-H hydrogen bonding with nearly 50% covalent character. Ab initio molecular dynamics simulations of HF were conducted at densities of 1.8-4.0 g/cc along the 900 K isotherm. According to our simulations, a unique form of (symmetric) hydrogen bonding could play a significant role in superionic conduction. Our work shows that superionic phases could be more prevalent in hydrogen bonded systems than previously thought, such as HCl and HBr.

  5. Electron Microprobe Analysis of Hf in Zircon: Suggestions for Improved Accuracy of a Difficult Measurement

    NASA Astrophysics Data System (ADS)

    Fournelle, J.; Hanchar, J. M.

    2013-12-01

    It is not commonly recognized as such, but the accurate measurement of Hf in zircon is not a trivial analytical issue. This is important to assess because Hf is often used as an internal standard for trace element analyses of zircon by LA-ICPMS. The issues pertaining to accuracy revolve around: (1) whether the Hf Ma or the La line is used; (2) what accelerating voltage is applied if Zr La is also measured, and (3) what standard for Hf is used. Weidenbach, et al.'s (2004) study of the 91500 zircon demonstrated the spread (in accuracy) of possible EPMA values for six EPMA labs, 2 of which used Hf Ma, 3 used Hf La, and one used Hf Lb, and standards ranged from HfO2, a ZrO2-HfO2 compound, Hf metal, and hafnon. Weidenbach, et al., used the ID-TIMS values as the correct value (0.695 wt.% Hf.), for which not one of the EPMA labs came close to that value (3 were low and 3 were high). Those data suggest: (1) that there is a systematic underestimation error of the 0.695 wt% Hf (ID-TIMS Hf) value if Hf Ma is used; most likely an issue with the matrix correction, as the analytical lines and absorption edges of Zr La, Si Ka and Hf Ma are rather tightly packed in the electromagnetic spectrum. Mass absorption coefficients are easily in error (e.g., Donovan's determination of the MAC of Hf by Si Ka of 5061 differs from the typically used Henke value of 5449 (Donovan et al, 2002); and (2) For utilization of the Hf La line, however, the second order Zr Ka line interferes with Hf La if the accelerating voltage is greater than 17.99 keV. If this higher keV is used and differential mode PHA is applied, only a portion of the interference is removed (e.g., removal of escape peaks), causing an overestimation of Hf content. Unfortunately, it is virtually impossible to apply an interference correction in this case, as it is impossible to locate Hf-free Zr probe standard. We have examined many of the combinations used by those six EPMA labs and concluded that the optimal EPMA is done with Hf

  6. The role of Upper Hybrid Turbulence on HF Artificial Ionization

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Konstantinos Dennis; Najmi, Amir; Eliasson, Bengt; Milikh, Gennady

    2016-07-01

    One of the most fascinating and scientifically interesting phenomena of active space experiments is the discovery of artificial ionization by Todd Pedersen when the HAARP ERP reached the GW level. The phenomenon has been well documented experimentally. A theoretical model based on ionization by energetic electrons accelerated by 50-100 V/m localized electric fields due to Strong Langmuir Turbulence (SLT) near the reflection surface of the HF pump wave, reproduced the observed dynamics of the descending plasma layer quite accurately. A major defect of the model was that the electron temperature in the SLT region was a free parameter. When taken as the 2000 K representing the ambient electron temperature the SLT driven electron flux was insufficient to produce ionization. An equivalent electron temperature of 5000 K or higher was necessary to reproduce the observations. The needed electron heating was attributed to the interaction of the HF at the Upper Hybrid (UH) resonant layer, approximately 5 Km below the reflection region where the HF electric field is perpendicular to the ambient magnetic field. The heated electrons expanded upwards along the magnetic field line and interacted with SLT fields near the resonance region. A consequence of this defect was that the theory could not explain the puzzling double resonance effect. Namely the observation that the ionization level was much stronger when the HF frequency and the UH resonance were a multiple of the electron cyclotron frequency. To remedy this we used a series of Vlasov simulations to explore the HF-plasma interaction in the vicinity of the UH resonance. The simulations followed the evolution of the spectral density of the electric field over a 7.5 MHz frequency band and cm scale lengths and of the electron distribution function over one millisecond for both double resonant and non-resonant cases. Many new features were revealed by the analysis of the simulations such as: 1. Broadening of the wave

  7. Conserved charges in timelike warped AdS3 spaces

    NASA Astrophysics Data System (ADS)

    Donnay, L.; Fernández-Melgarejo, J. J.; Giribet, G.; Goya, A.; Lavia, E.

    2015-06-01

    We consider the timelike version of warped anti-de Sitter space (WAdS), which corresponds to the three-dimensional section of the Gödel solution of four-dimensional cosmological Einstein equations. This geometry presents closed timelike curves (CTCs), which are inherited from its four-dimensional embedding. In three dimensions, this type of solution can be supported without matter provided the graviton acquires mass. Here, among the different ways to consistently give mass to the graviton in three dimensions, we consider the parity-even model known as new massive gravity (NMG). In the bulk of timelike WAdS3 space, we introduce defects that, from the three-dimensional point of view, represent spinning massive particlelike objects. For this type of source, we investigate the definition of quasilocal gravitational energy as seen from infinity, far beyond the region where the CTCs appear. We also consider the covariant formalism applied to NMG to compute the mass and the angular momentum of spinning particlelike defects and compare the result with the one obtained by means of the quasilocal stress tensor. We apply these methods to special limits in which the WAdS3 solutions coincide with locally AdS3 and locally AdS2×R spaces. Finally, we make some comments about the asymptotic symmetry algebra of asymptotically WAdS3 spaces in NMG.

  8. Evolution of continental crust and mantle heterogeneity: Evidence from Hf isotopes

    USGS Publications Warehouse

    Jonathan, Patchett P.; Kouvo, O.; Hedge, C.E.; Tatsumoto, M.

    1982-01-01

    We present initial 176Hf/177 Hf ratios for many samples of continental crust 3.7-0.3 Gy old. Results are based chiefly on zircons (1% Hf) and whole rocks: zircons are shown to be reliable carriers of essentially the initial Hf itself when properly chosen on the basis of U-Pb studies. Pre-3.0 Gy gneisses were apparently derived from an unfractionated mantle, but both depleted and undepleted mantle are evident as magma sources from 2.9 Gy to present. This mantle was sampled mainly from major crustal growth episodes 2.8, 1.8 and 0.7 Gy ago, all of which show gross heterogeneity of 176Hf/177Hf in magma sources from ??Hf=0 to +14, or about 60% of the variability of the present mantle. The approximate ??Hf=2??Nd relationship in ancient and modern igneous rocks shows that 176Lu/177Hf fractionates in general twice as much as 147Sm/144Nd in mantle melting processes. This allows an estimation of the relative value of the unknown bulk solid/liquid distribution coefficient for Hf. DLu/DHf=??? 2.3 holds for most mantle source regions. For garnet to be an important residual mantle phase, it must hold Hf strongly in order to preserve Hf-Nd isotopic relationships. The ancient Hf initials are consistent with only a small proportion of recycled older cratons in new continental crust, and with quasi-continuous, episodic growth of the continental crust with time. However, recycling of crust less than 150 My old cannot realistically be detected using Hf initials. The mantle shows clearly the general positive ??Hf resulting from a residual geochemical state at least back to 2.9 Gy ago, and seems to have repeatedly possessed a similar degree of heterogeneity, rather than a continuously-developing depletion. This is consistent with a complex dynamic disequilibrium model for the creation, maintenance and destruction of heterogeneity in the mantle. ?? 1981 Springer-Verlag.

  9. Influence of coagulation factor x on in vitro and in vivo gene delivery by adenovirus (Ad) 5, Ad35, and chimeric Ad5/Ad35 vectors.

    PubMed

    Greig, Jenny A; Buckley, Suzanne Mk; Waddington, Simon N; Parker, Alan L; Bhella, David; Pink, Rebecca; Rahim, Ahad A; Morita, Takashi; Nicklin, Stuart A; McVey, John H; Baker, Andrew H

    2009-10-01

    The binding of coagulation factor X (FX) to the hexon of adenovirus (Ad) 5 is pivotal for hepatocyte transduction. However, vectors based on Ad35, a subspecies B Ad, are in development for cancer gene therapy, as Ad35 utilizes CD46 (which is upregulated in many cancers) for transduction. We investigated whether interaction of Ad35 with FX influenced vector tropism using Ad5, Ad35, and Ad5/Ad35 chimeras: Ad5/fiber(f)35, Ad5/penton(p)35/f35, and Ad35/f5. Surface plasmon resonance (SPR) revealed that Ad35 and Ad35/f5 bound FX with approximately tenfold lower affinities than Ad5 hexon-containing viruses, and electron cryomicroscopy (cryo-EM) demonstrated a direct Ad35 hexon:FX interaction. The presence of physiological levels of FX significantly inhibited transduction of vectors containing Ad35 fibers (Ad5/f35, Ad5/p35/f35, and Ad35) in CD46-positive cells. Vectors were intravenously administered to CD46 transgenic mice in the presence and absence of FX-binding protein (X-bp), resulting in reduced liver accumulation for all vectors. Moreover, Ad5/f35 and Ad5/p35/f35 efficiently accumulated in the lung, whereas Ad5 demonstrated poor lung targeting. Additionally, X-bp significantly reduced lung genome accumulation for Ad5/f35 and Ad5/p35/f35, whereas Ad35 was significantly enhanced. In summary, vectors based on the full Ad35 serotype will be useful vectors for selective gene transfer via CD46 due to a weaker FX interaction compared to Ad5.

  10. Evolution of E 2 transition strength in deformed hafnium isotopes from new measurements on 172Hf,174Hf, and 176Hf

    NASA Astrophysics Data System (ADS)

    Rudigier, M.; Nomura, K.; Dannhoff, M.; Gerst, R.-B.; Jolie, J.; Saed-Samii, N.; Stegemann, S.; Régis, J.-M.; Robledo, L. M.; Rodríguez-Guzmán, R.; Blazhev, A.; Fransen, Ch.; Warr, N.; Zell, K. O.

    2015-04-01

    Background: The available data for E 2 transition strengths in the region between neutron-deficient hafnium and platinum isotopes are far from complete. More and precise data are needed to enhance the picture of structure evolution in this region and to test state-of-the-art nuclear models. In a simple model, the maximum collectivity is expected at the middle of the major shell. However, for actual nuclei, particularly in heavy-mass regions, which should be highly complex, this picture may no longer be the case, and one should use a more realistic nuclear-structure model. We address this point by studying the spectroscopy of Hf as a representative case. Purpose: We remeasure the 21+ half-lives of 172,174,176Hf, for which there is some disagreement in the literature. The main goal is to measure, for the first time, the half-lives of higher-lying states of the rotational band. The new results are compared to a theoretical calculation for absolute transition strengths. Method: The half-lives were measured using γ -γ and conversion-electron-γ delayed coincidences with the fast timing method. For the determination of half-lives in the picosecond region, the generalized centroid difference method was applied. For the theoretical calculation of the spectroscopic properties, the interacting boson model is employed, whose Hamiltonian is determined based on microscopic energy-density functional calculations. Results: The measured 21+ half-lives disagree with results from earlier γ -γ fast timing measurements, but are in agreement with data from Coulomb excitation experiments and other methods. Half-lives of the 41+ and 61+ states were measured, as well as a lower limit for the 81+ states. Conclusions: This work shows the importance of a mass-dependent effective boson charge in the interacting boson model for the description of E 2 transition rates in chains of nuclei. It encourages further studies of the microscopic origin of this mass dependence. New experimental

  11. Passive all-sky imaging radar in the HF regime with WWV and the first station of the Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Helmboldt, J. F.; Clarke, T. E.; Craig, J.; Dowell, J. D.; Ellingson, S. W.; Hartman, J. M.; Hicks, B. C.; Kassim, N. E.; Taylor, G. B.; Wolfe, C. N.

    2013-09-01

    We present a new passive, bistatic high-frequency (HF) radar system consisting of the transmitters for the radio station WWV and the dipole antenna array that comprises the first station of the Long Wavelength Array (LWA) or "LWA1." We demonstrate that these two existing facilities, which are operated for separate purposes, can be used together as a unique HF radar imager, capable of monitoring the entire visible sky. In this paper, we describe in detail the techniques used to develop all-sky radar capability at 10, 15, and 20 MHz. We show that this radar system can be a useful tool for probing ionospheric structure and its effect on over-the-horizon (OTH) geolocation. The LWA1+WWV radar system appears to be especially adept at detecting and characterizing structures associated with sporadic-E. In addition, we also demonstrate how this system may be used for long-distance, OTH mapping of terrain/ocean HF reflectivity. Finally, we discuss the potential improvements in the utility of these applications as more LWA stations are added.

  12. Air sensitivity of MoS2, MoSe2, MoTe2, HfS2, and HfSe2

    NASA Astrophysics Data System (ADS)

    Mirabelli, Gioele; McGeough, Conor; Schmidt, Michael; McCarthy, Eoin K.; Monaghan, Scott; Povey, Ian M.; McCarthy, Melissa; Gity, Farzan; Nagle, Roger; Hughes, Greg; Cafolla, Attilio; Hurley, Paul K.; Duffy, Ray

    2016-09-01

    A surface sensitivity study was performed on different transition-metal dichalcogenides (TMDs) under ambient conditions in order to understand which material is the most suitable for future device applications. Initially, Atomic Force Microscopy and Scanning Electron Microscopy studies were carried out over a period of 27 days on mechanically exfoliated flakes of 5 different TMDs, namely, MoS2, MoSe2, MoTe2, HfS2, and HfSe2. The most reactive were MoTe2 and HfSe2. HfSe2, in particular, showed surface protrusions after ambient exposure, reaching a height and width of approximately 60 nm after a single day. This study was later supplemented by Transmission Electron Microscopy (TEM) cross-sectional analysis, which showed hemispherical-shaped surface blisters that are amorphous in nature, approximately 180-240 nm tall and 420-540 nm wide, after 5 months of air exposure, as well as surface deformation in regions between these structures, related to surface oxidation. An X-ray photoelectron spectroscopy study of atmosphere exposed HfSe2 was conducted over various time scales, which indicated that the Hf undergoes a preferential reaction with oxygen as compared to the Se. Energy-Dispersive X-Ray Spectroscopy showed that the blisters are Se-rich; thus, it is theorised that HfO2 forms when the HfSe2 reacts in ambient, which in turn causes the Se atoms to be aggregated at the surface in the form of blisters. Overall, it is evident that air contact drastically affects the structural properties of TMD materials. This issue poses one of the biggest challenges for future TMD-based devices and technologies.

  13. Measurement of thermal neutron cross-sections and resonance integrals for 164Dy(n,γ) 165Dy and 180Hf(n,γ) 181Hf reactions

    NASA Astrophysics Data System (ADS)

    Cho, Hyun-Je; Kobayashi, Katsuhei; Yamamoto, Shuji; Seo, Kyung-Won; Hwang, Han Yull; Nha, Sang Kyun; Ko, Seung Kook

    2001-04-01

    The thermal neutron cross-sections for the 164Dy(n,γ) 165Dy and the 180Hf(n,γ) 181Hf reactions have been measured by the activation method at the heavy water thermal neutron facility of the Kyoto University Reactor, KUR. The results measured at 0.0253 eV are 2656±98 b for the 164Dy(n,γ) 165Dy reaction and 13.04±0.47 b for the 180Hf(n,γ) 181Hf reaction, respectively. The results have been obtained relative to the reference value of 98.65±0.09 b for the 197Au(n,γ) 198Au reaction. For dysprosium, most of the experimental data and the evaluated ones in ENDF/B-VI and JEF-2.2 are in good agreement with the present value. For hafnium, the previous measurements and the evaluated ones in ENDF/B-VI and JENDL-3.2 are in good agreement with the present result. The resonance integrals for the 164Dy(n,γ) 165Dy and the 180Hf(n,γ) 181Hf reactions have also been measured relative to the reference value of 1550±28 b for the 197Au(n,γ) 198Au reaction using a 1/ E standard neutron spectrum field of the Kinki University Reactor, UTR-KINKI. The present resonance integral for the 164Dy(n,γ) 165Dy reaction is 649±24 b, and the existing experimental and the evaluated data are distributed from 335 to 820 b. The present result for the 180Hf(n,γ) 181Hf reaction is 32.4±1.2 b, and most of the previous measurements and the evaluated values are close to the present measurement. Gryntakis et al. reported the resonance integrals for both reactions, whose results were also in good agreement with the measurements.

  14. Structural characterization of Nd-doped Hf-zirconolite Ca 1-xNd xHfTi 2-xAl xO 7 ceramics

    NASA Astrophysics Data System (ADS)

    Caurant, Daniel; Loiseau, Pascal; Bardez, Isabelle

    2010-12-01

    Because of its high incorporation capacity and of the high thermal neutron capture cross-section of hafnium, Hf-zirconolite (CaHfTi 2O 7) ceramic can be envisaged as a potential waste form for minor actinides (Np, Am, Cm) and plutonium immobilization. In this work, Nd-doped Hf-zirconolite Ca 1-xNd xHfTi 2-xAl xO 7 ( x = 0; 0.01 and 0.2) ceramics have been prepared by solid state reaction. Neodymium has been used as trivalent actinide surrogate. The ceramic samples structure has been studied by X-ray diffraction and refined by the Rietveld method. This revealed that Nd 3+ ions only enter the Ca site, whereas part of Hf 4+ ions substitute titanium into Ti(1) sites and Al 3+ ions mainly occupy the Ti(2) split sites and Ti(3) sites of the zirconolite structure. Using various spectroscopic techniques (electron spin resonance, optical absorption and fluorescence), the environment of Nd 3+ cations in Hf-zirconolite has been studied and compared with that of Nd 3+ cations in Zr-zirconolite (CaZrTi 2O 7). Different local environments of Nd 3+ cations have been detected in Hf-zirconolite that can be attributed to the existence of an important disorder around Nd in the Ca site probably due to the statistical occupancy of the next nearest cationic site of neodymium (a split Ti site) by Ti 4+, Al 3+ cations and vacancies. No significant differences were observed concerning Nd 3+ cations environment and distribution in Hf- and Zr-zirconolite ceramics.

  15. Forward physics in CMS: Simulation of PMT hits in HF and Higgs mass reconstruction methods with a focus on forward jet tagging

    NASA Astrophysics Data System (ADS)

    Moeller, Anthony Richard

    Abnormally high energy events were seen in the Hadronic Forward (HF) calorimeter for pion and muon data during testbeam in 2004. Analysis of testbeam data suggested that such events were caused by particles traveling the entire length of HF and striking the photomultiplier (PMT) windows in the readout box behind HF. Charged particles traversing the window of the PMT emit cerenkov radiation, which creates abnormally high energy events in the data. To further study these events, a modification of the existing official CMS HF simulation was created that added the PMT windows to the simulation as sensitive detectors. In agreement with testbeam data, abnormally high energy events in the PMTs were seen in the simulation for muons and pions. The simulation was then extended to jets simulated with Pythia, and then for collision like events as well. PMT hits were seen in both of these cases. Energy sharing between PMTs for long and short fibers in HF as well as timing differences between normal HF events and PMT events were investigated as methods to tag such abnormal events. While both methods were somewhat successful, it was determined that they were not sufficient. The simulation was also modified to use thinner PMT windows. Reducing the thickness of the window reduced the number of PMT hits, and drastically reduced the energy of these hits, bringing most of them below standard jet energy thresholds. These results led to the replacement of the existing PMTs with new PMTs with a smaller, thinner window. Higgs mass reconstruction methods were applied to Monte Carlo datasets for 115 and 130 GeV Higgs produced through vector boson fusion. In these datasets, the Higgs boson decayed to two tau particles, each of which decayed leptonically. The mass reconstruction methods successfully created a peak at the proper mass for both datasets. In addition to creating a Higgs, the vector boson fusion signal also has two forward jets. These jets are not found in the signal of the

  16. Added Value in Electronic Publications.

    ERIC Educational Resources Information Center

    Bothma, Theo J. D.

    Electronic publications are flooding the market. Some of these publications are created specifically for the electronic environment, but many are conversions of existing material to electronic format. It is not worth the time and effort merely to publish existing material in electronic format if no value is added in the conversion process. The…

  17. 47 CFR 73.758 - System specifications for digitally modulated emissions in the HF broadcasting service.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... emissions in the HF broadcasting service. 73.758 Section 73.758 Telecommunication FEDERAL COMMUNICATIONS... § 73.758 System specifications for digitally modulated emissions in the HF broadcasting service. (a... digital audio broadcasting and datacasting are authorized. The RF requirements for the DRM system...

  18. 47 CFR 73.758 - System specifications for digitally modulated emissions in the HF broadcasting service.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... emissions in the HF broadcasting service. 73.758 Section 73.758 Telecommunication FEDERAL COMMUNICATIONS... § 73.758 System specifications for digitally modulated emissions in the HF broadcasting service. (a... digital audio broadcasting and datacasting are authorized. The RF requirements for the DRM system...

  19. 47 CFR 73.758 - System specifications for digitally modulated emissions in the HF broadcasting service.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... emissions in the HF broadcasting service. 73.758 Section 73.758 Telecommunication FEDERAL COMMUNICATIONS... § 73.758 System specifications for digitally modulated emissions in the HF broadcasting service. (a... digital audio broadcasting and datacasting are authorized. The RF requirements for the DRM system...

  20. Interfacial and structural properties of sputtered HfO{sub 2} layers

    SciTech Connect

    Aygun, G.; Yildiz, I.

    2009-07-01

    Magnetron sputtered HfO{sub 2} layers formed on a heated Si substrate were studied by spectroscopic ellipsometer (SE), x-ray diffraction (XRD), Fourier transform infrared (FTIR), and x-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO{sub x} suboxide layer at the HfO{sub 2}/Si interface is unavoidable. The HfO{sub 2} thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O{sub 2}/Ar gas ratio during sputtering, sputtering time, and substrate temperature. XRD spectra show that the deposited film has (111) monoclinic phase of HfO{sub 2}, which is also supported by FTIR spectra. The atomic concentration and chemical environment of Si, Hf, and O have been measured as a function of depth starting from the surface of the sample by XPS technique. It shows that HfO{sub 2} layers of a few nanometers are formed at the top surface. Below this thin layer, Si-Si bonds are detected just before the Si suboxide layer, and then the Si substrate is reached during the depth profiling by XPS. It is clearly understood that the highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO{sub 2} to form HfO{sub 2}, leaving Si-Si bonds behind.

  1. Lu-Hf and Sm-Nd evolution in lunar mare basalts

    NASA Technical Reports Server (NTRS)

    Unruh, D. M.; Tatsumoto, M.; Stille, P.; Patchett, P. J.

    1984-01-01

    Existing cumulate remelting models for mare basalt genesis are evaluated in light of Lu-Hf, Rb-Sr, Sm-Nd data and overall REE characteristics in order to determine the simplest model that can account for these data. A data base for comparing Lu-Hf evolution in the lunar mantle as inferred from Lu-Hf analyses of oceanic basalts is presented along with a preliminary comparison of Lu-Hf and Sm-Nd evolution betwee mare basalts and terrestrial oceanic basalts. It is found that Lu/Hf characteristics of mare basalts cannot be explained in terms of modal melting of cumulate sources formed from a magma ocean with chondritic Lu/Hf. The data are consistent with a model in which the cumulate sources formed from a light REE + HF-enriched magma ocean. Nonmodal melting of ilmenite in the sources is also required. The Lu-Hf data suggest that even the high-Ti basalt sources contained no more than about 3 percent ilmenite.

  2. Interface properties of Ge on cubic SrHfO3 (001)

    NASA Astrophysics Data System (ADS)

    Wang, Jianli; Wang, Chenxiang; Tang, Gang; Zhang, Junting; Guo, Sandong; Han, Yujia

    2016-06-01

    High quality Ge-on-high-k oxide interface is essential to facilitate the high performance metal-oxide semiconductor field-effect transistors and monolithically integrated optoelectronics device performance. The atomic structure and electronic properties of Ge on perfect and defective (001) SrHfO3 are investigated by first-principle calculations. The amplitude of the surface rumpling for the SrO-terminated surface is much larger than that for HfO2-terminated surface, although both SrO- and HfO2-terminated surfaces are stable for a comparable range of the HfO2 chemical potential. The distance between the first and second planes compresses while that of the second and third planes expands due to the relaxation of the slab. We investigated systematically the specific adsorption sites and the atomic structure at the initial growth stage of Ge on the SrHfO3 (001) substrate. The top sites of the oxygen atoms are favorable for 1/2 (1/3) monolayer Ge adsorbate at SrO (HfO2)-terminated surface. We calculated the surface grand potential and presented the complete surface phase diagram. We also pointed out the energetically favorable interfaces among the atomic arrangements of the Ge/SrHfO3 (001) interfaces. The atomic structure and electronic properties of the intrinsic point defects were calculated and analyzed for the Ge/SrHfO3 (001) interfaces.

  3. Schirmwirkung von Hochfrequenz (HF)-Schutzkleidung: Untersuchung verschiedener Konstruktionsmerkmale

    NASA Astrophysics Data System (ADS)

    Arps, V.; Scheibe, K.

    2005-05-01

    Die Messverfahren zur Bestimmung der Schutzwirkung von HF-Schutzkleidung sind in der Norm DIN 32780-100 festgelegt. Entsprechend diesen Anforderungen wird die elektrische und magnetische Schirmdämpfung bestimmt und daraus als Maß für die Schutzwirkung die elektromagnetische Schirmdämpfung berechnet. Diese ist eine der SAR vergleichbare Größe. In diesem Beitrag werden die Einflüsse verschiedener Konstruktionsmerkmale von HF-Schutzanzügen auf die elektromagnetische Schirmdämpfung untersucht. Zu diesen gehören die nach MIL STD 285 vermessene elektrische Schirmdämpfung der verwendeten Gewebe. Weiter werden verschiedene Teilbereiche der HF-Schutzkleidung auf ihre Schutzwirkung untersucht. Der Schwerpunkt liegt hierbei auf der Fragestellung inwieweit Verschlüsse, Reißverschlüsse oder leitfähiges Klettband, die Schutzwirkung beeinträchtigen. Zu diesem Zweck werden zwei Schutzanzüge unterschiedlicher Konstruktion vergleichend vermessen. Es handelt sich dabei um einen bereits im Handel befindlichen und entsprechend der Norm zertifizierten Anzug und einen neuen Prototyp, welcher nach verschiedenen Gesichtspunkten optimiert wurde. Schwachstellen der Konstruktion werden herausgearbeitet und Ansatzpunkte für weitere Verbesserungen erarbeitet. The measuring methods for determining the shielding effectiveness of radiofrequency (RF)-protective clothing are defined in German Standard DIN 32780-100. According to this standard, both the electric and the magnetic shielding effectiveness are measured in order to calculate the electromagnetic shielding effectiveness. The electromagnetic shielding effectiveness is an adequate quality criterion for the degree of protection and also compares well with the Specific Absorption Rate (SAR). In this article, the impact of different design features on the electromagnetic shielding effectiveness is analyzed. The electric shielding effectiveness of the used shielding materials is measured according to MIL STD 285 and thereupon

  4. Comparison of HfO2 films grown by atomic layer deposition using HfCl4 and H2O or O3 as the oxidant

    NASA Astrophysics Data System (ADS)

    Park, Hong Bae; Cho, Moonju; Park, Jaehoo; Lee, Suk Woo; Hwang, Cheol Seong; Kim, Jong-Pyo; Lee, Jong-Ho; Lee, Nae-In; Kang, Ho-Kyu; Lee, Jong-Cheol; Oh, Se-Jung

    2003-09-01

    HfO2 gate dielectric thin-films were deposited on Si wafers using an atomic-layer deposition (ALD) technique with HfCl4 and either H2O or O3 as the precursor and oxidant, respectively. Although the ALD reactions using either H2O or O3 were successfully confirmed at a deposition temperature of 300 °C, the structural and electrical properties of the HfO2 films grown using the two oxidants were quite different. The stronger oxidation power of the O3 compared to H2O increased the oxygen concentration in the HfO2 film and the rate of interfacial SiO2 formation even at the as-deposited state. Because of the larger oxygen concentration, the decrease in the capacitance density of the film grown with O3 after rapid thermal annealing at 750 °C under N2 atmosphere was slightly larger than that of the HfO2 film grown with H2O. Apart from this weakness, all the other electrical properties, including the fixed charge density, the interface trap density, the leakage current density and the hysteresis in the capacitance-voltage plot of the film grown with O3 were superior to those of the film grown with H2O. Therefore, O3 appears to be a better oxidant for the HfO2 film growth using the ALD method.

  5. Thermodynamics of charged Lovelock: AdS black holes

    NASA Astrophysics Data System (ADS)

    Prasobh, C. B.; Suresh, Jishnu; Kuriakose, V. C.

    2016-04-01

    We investigate the thermodynamic behavior of maximally symmetric charged, asymptotically AdS black hole solutions of Lovelock gravity. We explore the thermodynamic stability of such solutions by the ordinary method of calculating the specific heat of the black holes and investigating its divergences which signal second-order phase transitions between black hole states. We then utilize the methods of thermodynamic geometry of black hole spacetimes in order to explain the origin of these points of divergence. We calculate the curvature scalar corresponding to a Legendre-invariant thermodynamic metric of these spacetimes and find that the divergences in the black hole specific heat correspond to singularities in the thermodynamic phase space. We also calculate the area spectrum for large black holes in the model by applying the Bohr-Sommerfeld quantization to the adiabatic invariant calculated for the spacetime.

  6. An investigation of AdS2 backreaction and holography

    NASA Astrophysics Data System (ADS)

    Engelsöy, Julius; Mertens, Thomas G.; Verlinde, Herman

    2016-07-01

    We investigate a dilaton gravity model in AdS2 proposed by Almheiri and Polchinski [1] and develop a 1d effective description in terms of a dynamical boundary time with a Schwarzian derivative action. We show that the effective model is equivalent to a 1d version of Liouville theory, and investigate its dynamics and symmetries via a standard canonical framework. We include the coupling to arbitrary conformal matter and analyze the effective action in the presence of possible sources. We compute commutators of local operators at large time separation, and match the result with the time shift due to a gravitational shockwave interaction. We study a black hole evaporation process and comment on the role of entropy in this model.

  7. Superconformal algebras on the boundary of AdS3

    NASA Astrophysics Data System (ADS)

    Rasmussen, Jørgen

    1999-07-01

    Motivated by recent progress on the correspondence between string theory on nti-de Sitter space and conformal field theory, we provide an explicit construction of an infinite dimensional class of superconformal algebras on the boundary of AdS3. These space-time algebras are N extended superconformal algebras of the kind obtainable by hamiltonian reduction of affine SL(2|N/2) current superalgebras for N even, and are induced by the same current superalgebras residing on the world sheet. Thus, such an extended superconformal algebra is generated by N supercurrents and an SL(N/2) current algebra in addition to a U(1) current algebra. The results are obtained within the framework of free field realizations.

  8. Systematics of Coupling Flows in AdS Backgrounds

    SciTech Connect

    Goldberger, Walter D.; Rothstein, Ira Z.

    2003-03-18

    We give an effective field theory derivation, based on the running of Planck brane gauge correlators, of the large logarithms that arise in the predictions for low energy gauge couplings in compactified AdS}_5 backgrounds, including the one-loop effects of bulk scalars, fermions, and gauge bosons. In contrast to the case of charged scalars coupled to Abelian gauge fields that has been considered previously in the literature, the one-loop corrections are not dominated by a single 4D Kaluza-Klein mode. Nevertheless, in the case of gauge field loops, the amplitudes can be reorganized into a leading logarithmic contribution that is identical to the running in 4D non-Abelian gauge theory, and a term which is not logarithmically enhanced and is analogous to a two-loop effect in 4D. In a warped GUT model broken by the Higgs mechanism in the bulk,we show that the matching scale that appears in the large logarithms induced by the non-Abelian gauge fields is m_{XY}^2/k where m_{XY} is the bulk mass of the XY bosons and k is the AdS curvature. This is in contrast to the UV scale in the logarithmic contributions of scalars, which is simply the bulk mass m. Our results are summarized in a set of simple rules that can be applied to compute the leading logarithmic predictions for coupling constant relations within a given warped GUT model. We present results for both bulk Higgs and boundary breaking of the GUT gauge

  9. Crystal structure of Si-doped HfO{sub 2}

    SciTech Connect

    Zhao, Lili; Nelson, Matthew; Fancher, Chris M.; Aldridge, Henry; Iamsasri, Thanakorn; Forrester, Jennifer S.; Jones, Jacob L.; Nishida, Toshikazu; Moghaddam, Saeed

    2014-01-21

    Si-doped HfO{sub 2} was prepared by solid state synthesis of the starting oxides. Using Rietveld refinement of high resolution X-ray diffraction patterns, a substitutional limit of Si in HfO{sub 2} was determined as less than 9 at. %. A second phase was identified as Cristobalite (SiO{sub 2}) rather than HfSiO{sub 4}, the latter of which would be expected from existing SiO{sub 2}-HfO{sub 2} phase diagrams. Crystallographic refinement with increased Si-dopant concentration in monoclinic HfO{sub 2} shows that c/b increases, while β decreases. The spontaneous strain, which characterizes the ferroelastic distortion of the unit cell, was calculated and shown to decrease with increasing Si substitution.

  10. Effect of hydrofluoric acid (HF) concentration to pores size diameter of silicon membrane.

    PubMed

    Burham, Norhafizah; Hamzah, Azrul Azlan; Majlis, Burhanuddin Yeop

    2014-01-01

    This paper studies parameters which affect the pore size diameter of a silicon membrane. Electrochemical etching is performed in characterise the parameter involved in this process. The parameter has been studied is volume ratio of hydrofluoric acid (HF) and ethanol as an electrolyte aqueous for electrochemical etch. This electrolyte aqueous solution has been mixed between HF and ethanol with volume ratio 3:7, 5:5, 7:3 and 9:1. As a result, the higher volume of HF in this electrolyte gives the smallest pore size diameter compared to the lower volume of HF. These samples have been dipped into HF and ethanol electrolyte aqueous with supplied 25 mA/cm2 current density for 20, 30, 40, and 50 minutes. The samples will inspect under Scanning Electron Microscope (SEM) to execute the pore formations on silicon membrane surface.

  11. Perturbed angular correlation study of a nanostructured HfO2 film

    NASA Astrophysics Data System (ADS)

    Pasquevich, A. F.; Cavalcante, F. H. M.; Soares, J. C.

    The hyperfine field at 181Ta lattice sites in a nanostructured Hf02 thin film was studied by the perturbed angular correlation (PAC) technique. The thin oxide film was deposited by pulsed laser ablation on a silicon substrate kept at 673 K. The thickness was about 25 nm. The radioactive 181Hf ions were produced by neutron activation of the very thin film in the Portuguese research reactor by the reaction 180Hf(n,γ)181Hf. PAC measurements were carried out at room temperature after annealing at different temperatures up to 1,473 K in air. The PAC technique allows determining the electric field gradient at the 181Ta probe sites. The 181Ta isotopes appear in the sample as disintegration product of 181 Hf.

  12. Perturbed angular correlation study of a nanostructured HfO2 film

    NASA Astrophysics Data System (ADS)

    Pasquevich, A. F.; Cavalcante, F. H. M.; Soares, J. C.

    2007-09-01

    The hyperfine field at 181Ta lattice sites in a nanostructured HfO2 thin film was studied by the perturbed angular correlation (PAC) technique. The thin oxide film was deposited by pulsed laser ablation on a silicon substrate kept at 673 K. The thickness was about 25 nm. The radioactive 181Hf ions were produced by neutron activation of the very thin film in the Portuguese research reactor by the reaction 180Hf(n, γ)181Hf. PAC measurements were carried out at room temperature after annealing at different temperatures up to 1,473 K in air. The PAC technique allows determining the electric field gradient at the 181Ta probe sites. The 181Ta isotopes appear in the sample as disintegration product of 181Hf.

  13. Synthesis of polymorph A-enriched beta zeolites in a HF-concentrated system.

    PubMed

    Zhang, Guanqun; Wang, Bingchun; Zhang, Weiping; Li, Mingrun; Tian, Zhijian

    2016-04-21

    Polymorph A-enriched beta zeolites were synthesized by employing high HF concentrations in the synthesis medium. The polymorphic compositions of the synthesized beta zeolites were determined by the complementary characterization methods (19)F NMR analysis and PXRD simulation. With a variety of SDAs, a high HF concentration (HF/SDA > 1.0) in the synthesis medium results in the A-rich feature (55-65% A) of beta zeolites, while a moderate HF concentration only results in typical beta zeolites. A systematic study on the synthesis conditions reveals the existence of a buffered system of H(+) and F(-) formed in the highly HF-concentrated medium. This buffer results in a small but continuous supply of F(-) during zeolite crystallization, in contrast to the conventional fluoride route where all F(-) are discharged all-at-once at the initial stage. PMID:26974286

  14. Directionally solidified pseudo-binary eutectics of Ni-Cr-/Hf,Zr/

    NASA Technical Reports Server (NTRS)

    Kim, Y. G.; Ashbrook, R. L.

    1975-01-01

    This report is concerned with the experimental determination of pseudo binary eutectic compositions and the directional solidification of the Ni-Cr-Hf,Zr, and Ni-Cr-Zr eutectic alloys. To determine unknown eutectics, chemical analyses were made of material bled from near eutectic ingots during incipient melting. Nominal compositions in weight per cent of Ni-18.6Cr-24.0Hf, Ni-19.6Cr-12.8Zr-2.8Hf, and Ni-19.2Cr-14.8Zr formed aligned pseudo-binary eutectic structures. The melting points were about 1270 C. The reinforcing intermetallic phases were identified as noncubic (Ni,Cr)7Hf2 and (Ni,Cr)7(Hf,Zr)2, and face centered cubic (Ni,Cr)5Zr. The volume fraction of the reinforcing phases were about 0.5.

  15. Ab initio characterization of the Mg-HF van der Waals complex.

    PubMed

    Koput, Jacek; Makarewicz, Jan

    2010-10-28

    The equilibrium structure and the three-dimensional potential energy surface of the Mg-HF van der Waals complex in its ground electronic state have been determined from accurate ab initio calculations using the coupled-cluster method, CCSD(T), in conjunction with the basis sets of triple- through quintuple-zeta quality. The core-electron correlation, high-order valence-electron correlation, and scalar relativistic effects were investigated. The Mg-HF complex was confirmed to be linear at equilibrium, with a vibrationless dissociation energy (into Mg and HF) D(e) of 280 cm(-1). The vibration-rotation energy levels of two isotopologues, (24)Mg-HF and (24)Mg-DF, were predicted using the variational method. The predicted spectroscopic constants can be useful in a further analysis of high-resolution vibration-rotation spectra of the Mg-HF complex.

  16. Shape memory effect of the Ni-Ti-Hf high temperature shape memory alloy

    SciTech Connect

    Wu, K.H.; Pu, Z.; Tseng, H.K.; Biancaniello, F.S.

    1995-11-17

    The one-way shape memory effect of the newly-developed TiNi-Hf high temperature shape memory alloys has been investigated. The results of the study show that TiNi-Hf high temperature alloys possess a relatively high shape memory effect. All the alloys, even those with an Hf content as high as 30at%, exhibit complete strain recovery behavior. However, as the Hf content increases, the fully reversible strain of the alloys decreases. The increase of the second phase as the Hf content increases is the primary reason for the deterioration of the shape memory effect and ductility. The shape memory properties also deteriorate as the deformation temperature increases.

  17. Thermal decomposition of HfCl{sub 4} as a function of its hydration state

    SciTech Connect

    Barraud, E.; Begin-Colin, S. . E-mail: begin@ipcms.u-strasbg.fr; Le Caer, G.; Villieras, F.; Barres, O.

    2006-06-15

    The thermogravimetric behavior of HfCl{sub 4} powders with different hydration states has been compared. Strongly hydrated powders consist of HfOCl{sub 2}.nH{sub 2}O with n>4. Partially hydrated powders consist of particles with a HfCl{sub 4} core and a hydrated outerlayer of HfOCl{sub 2}.nH{sub 2}O with n in the range of 0-8. Hydrated powders decomposed at temperature lower than 200 deg. C whereas the decomposition of partially hydrated powders was completed at a temperature of around 450 deg. C. The observed differences in decomposition temperature is related to the structure of HfOCl{sub 2}.nH{sub 2}O, which is different if n is higher or smaller than 4 and leads to intermediate compounds, which decompose at different temperatures.

  18. Holography beyond conformal invariance and AdS isometry?

    SciTech Connect

    Barvinsky, A. O.

    2015-03-15

    We suggest that the principle of holographic duality be extended beyond conformal invariance and AdS isometry. Such an extension is based on a special relation between functional determinants of the operators acting in the bulk and on its boundary, provided that the boundary operator represents the inverse propagators of the theory induced on the boundary by the Dirichlet boundary value problem in the bulk spacetime. This relation holds for operators of a general spin-tensor structure on generic manifolds with boundaries irrespective of their background geometry and conformal invariance, and it apparently underlies numerous O(N{sup 0}) tests of the AdS/CFT correspondence, based on direct calculation of the bulk and boundary partition functions, Casimir energies, and conformal anomalies. The generalized holographic duality is discussed within the concept of the “double-trace” deformation of the boundary theory, which is responsible in the case of large-N CFT coupled to the tower of higher-spin gauge fields for the renormalization group flow between infrared and ultraviolet fixed points. Potential extension of this method beyond the one-loop order is also briefly discussed.

  19. Toward an european Med HF-radar coastal monitoring

    NASA Astrophysics Data System (ADS)

    Molcard, A.; Fraunie, P.

    2010-12-01

    The monitoring of coastal areas through HF radar is developping in the european Mediterranean coasts, through national and international projects. Surface current maps may be used for process studies, forecast correction through assimilation, or for practical applications in transport studies (jellyfish, oil-spill, search-and-rescue operations). Results of radar campaigns in the North-western Mediterranean (evidence of mesoscale eddy in the Gulf of Lions and identification of dynamical structures by FSLE in the Ligurian Sea) are shown, as well as techniques for current reconstruction using a single site. A new inter-regional european project started in summer 2010, regrouping 5 countries for an integrated oil-spill coastal awarness network is presented.

  20. Observation of weak HF electrostatic turbulence in the auroral ionosphere

    NASA Astrophysics Data System (ADS)

    Pottelette, R.; Illiano, J. M.

    1982-07-01

    A numerical calculation of the cross spectrum of random signals received by two small antennas that were immersed in a two-component magnetoplasma has been conducted, for the case of a plasma model consisting of a cool and a warm component. The data were compiled by the HF electrostatic wave detection experiment of the Porcupine F3 rocket. A linear calculation of the natural electrostatic emissions detected around the electron gyrofrequency three-halves harmonic and around the upper hybrid frequency shows that their amplitudes are above the plasma thermal noise level. It is noted that the low energy precipitating suprathermal electrons present are highly anisotropic and enhance the three-halves electron gyrofrequency noise, although the electron distribution function remains stable and the most intense emissions are observed around the upper hybrid frequency.

  1. Development of HF radar inversion algorithm for spectrum estimation (HIAS)

    NASA Astrophysics Data System (ADS)

    Hisaki, Yukiharu

    2015-03-01

    A method for estimating ocean wave directional spectra using an HF (high-frequency) ocean radar was developed. This method represents the development of work conducted in previous studies. In the present method, ocean wave directional spectra are estimated on polar coordinates whose center is the radar position, while spectra are estimated on regular grids. This method can be applied to both single and multiple radar cases. The area for wave estimation is more flexible than that of the previous method. As the signal to noise (SN) ratios of Doppler spectra are critical for wave estimation, we develop a method to exclude low SN ratio Doppler spectra. The validity of the method is demonstrated by comparing results with in situ observed wave data that it would be impossible to estimate by the methods of other groups.

  2. Digital hf radar observations of equatorial spread-F

    SciTech Connect

    Argo, P.E.

    1984-01-01

    Modern digital ionosondes, with both direction finding and doppler capabilities can provide large scale pictures of the Spread-F irregularity regions. A morphological framework has been developed that allows interpretation of the hf radar data. A large scale irregularity structure is found to be nightward of the dusk terminator, stationary in the solar reference frame. As the plasma moves through this foehn-wall-like structure it descends, and irregularities may be generated. Localized upwellings, or bubbles, may be produced, and they drift with the background plasma. The spread-F irregularity region is found to be best characterized as a partly cloudy sky, due to the patchiness of the substructures. 13 references, 16 figures.

  3. Alternatives for satellite sound broadcast systems at HF and VHF

    NASA Technical Reports Server (NTRS)

    Leroy, B. E.

    1985-01-01

    The National Aeronautics and Space Administration and the United States Information Agency (USIA) are currently engaged in a joint program to assess the technical and economic feasibility of direct sound broadcast satellite systems to meet USIA mission needs. The cooperative effort calls for a series of interrelated studies to provide the respective Agency managements with information on the potential role of direct broadcast satellites. Initial studies focused on HF propagation phenomena and broadcast coverage requirements. These studies served as the basis for parallel systems studies currently in progress. The systems studies are to provide a data base on various satellite configurations and systems concepts capable of supporting potential broadcast requirements ranging from a small fraction to a substantial addition to USIA requirements. Antenna concepts for LEO and GEO orbits are briefly described.

  4. Josephson parametric amplifiers for the ADMX-HF experiment

    NASA Astrophysics Data System (ADS)

    Malnou, Maxime; Palken, Daniel; Hilton, Gene; Vale, Leila; Lehnert, Konrad

    2016-03-01

    Dark matter search in the ADMX-HF experiment aims at detecting power generated by the axion-photon conversion, of a few hundred of yoctowatts, in the 4 - 12 GHz band. The sensitivity of detection directly depends on the amplifier noise temperature, and therefore requires state of the art microwave amplifiers. In contrast to amplifiers with dissipation on-chip, superconducting Josephson parametric amplifiers (JPA) reach and even circumvent the quantum limit. Over the past years, we have developed JPAs fabricated with arrays of superconducting quantum interference devices. Their gain, bandwidth and tunability are particularly well suited for efficient amplification in the band of interest. In this talk we will present numerical modeling of the behavior of our amplifiers, along with the first results from new designs that cover the 4-12 GHz band. Finally, we will present the ongoing work to increase the gain-bandwidth product and gain stability of our amplifiers.

  5. Ternary ceramic alloys of Zr-Ce-Hf oxides

    DOEpatents

    Becher, P.F.; Funkenbusch, E.F.

    1990-11-20

    A ternary ceramic alloy is described which produces toughening of zirconia and zirconia composites through the stress transformation from tetragonal phase to monoclinic phase. This alloy, having the general formula Ce[sub x]Hf[sub y]Zr[sub 1[minus]x[minus]y]O[sub 2], is produced through the addition of appropriate amounts of ceria and hafnia to the zirconia. Typically, improved toughness is achieved with about 5 to about 15 mol % ceria and up to about 40 mol % hafnia. The preparation of alloys of these compositions are given together with data as to the densities, tetragonal phase content, hardness and fracture toughness. The alloys are useful in preparing zirconia bodies as well as reinforcing ceramic composites. 1 fig.

  6. Ternary ceramic alloys of ZR-CE-HF oxides

    DOEpatents

    Becher, Paul F.; Funkenbusch, Eric F.

    1990-01-01

    A ternary ceramic alloy which produces toughening of zirconia and zirconia composites through the stress transformation from tetragonal phase to monoclinic phase. This alloy, having the general formula Ce.sub.x Hf.sub.y Zn.sub.1-x-y O.sub.2, is produced through the addition of appropriate amounts of ceria and hafnia to the zirconia. Typically, improved toughness is achieved with about 5 to about 15 mol % ceria and up to about 40 mol % hafnia. The preparation of alloys of these compositions are given together with data as to the densities, tetragonal phase content, hardness and fracture toughness. The alloys are useful in preparing zirconia bodies as well as reinforcing ceramic composites.

  7. Mixing and melt sources in the Miocene Aztec Wash pluton (Nevada, USA) as revealed by zircon Hf and O and whole rock Sr, Nd, and Hf isotopes

    NASA Astrophysics Data System (ADS)

    Ryan, M.; Miller, J. S.; Miller, C. F.; Bromley, S.; Davies, G. R.; Schmitt, A. K.

    2011-12-01

    The 15.6 Ma Aztec Wash Pluton (AWP) is one of several Miocene intrusions located within the northern Colorado River extensional corridor. Extensive E-W tilting of fault blocks has exposed the pluton from the roof to 5 km structural depth. Earlier field and petrologic studies subdivided the AWP into two distinct zones: (1) a Granite Zone (GZ) comprised of relatively homogeneous granite with subtle differences in textures and mineralogy; (2) a Heterogeneous Zone (HZ), which interfingers the GZ, contains evidence for mafic and felsic magma input with a wide compositional range (42-78 wt% SiO2), and abundant field evidence for hybridization. Previous whole rock geochemistry and zircon trace element analyses indicated that compositional variation was produced by multi-component mixing between mafic and felsic melts within the HZ. New whole rock Sr, Nd, and Hf isotope data from the HZ show that all rocks (including high-silica granites) formed by mixing Precambrian crust and enriched mantle, with mixtures having a large mantle fraction (≥50%). New Hf (n=189) and O (n=241) isotope analyses of zircon from samples in the HZ confirm these melt sources and provide a broader perspective on hybridization processes within the AWP. Zircon grains from all samples show heterogeneous Hf and O isotopic compositions (-5 to -18 ɛHf; 4.5-7.5% δ18O), but despite the clear signature of Precambrian crust in the whole rock data, obvious Precambrian zircons (or cores) were mostly absent; only one zircon was clearly Precambrian (ɛHf = -25). Resolvable intragrain variability is relatively limited (including the Precambrian grain, which is unzoned). Zircons from hand samples and from compositional groups also show heterogeneous ɛHf and δ18O values, although the spreads are more restricted than in the whole data set (6-10 ɛHf in granites, 5-7 ɛHf in intermediate "hybrids", 5-6 ɛHf in gabbro/diorite sheets). Oxygen isotope values for the zircons also show intra-handsample heterogeneity

  8. ADS's Dexter Data Extraction Applet

    NASA Astrophysics Data System (ADS)

    Demleitner, M.; Accomazzi, A.; Eichhorn, G.; Grant, C. S.; Kurtz, M. J.; Murray, S. S.

    The NASA Astrophysics Data System (ADS) now holds 1.3 million scanned pages, containing numerous plots and figures for which the original data sets are lost or inaccessible. The availability of scans of the figures can significantly ease the regeneration of the data sets. For this purpose, the ADS has developed Dexter, a Java applet that supports the user in this process. Dexter's basic functionality is to let the user manually digitize a plot by marking points and defining the coordinate transformation from the logical to the physical coordinate system. Advanced features include automatic identification of axes, tracing lines and finding points matching a template. This contribution both describes the operation of Dexter from a user's point of view and discusses some of the architectural issues we faced during implementation.

  9. Scattering States in AdS/CFT

    SciTech Connect

    Fitzpatrick, A.Liam; Kaplan, Jared; /SLAC

    2012-02-14

    We show that suitably regulated multi-trace primary states in large N CFTs behave like 'in' and 'out' scattering states in the flat-space limit of AdS. Their transition matrix elements approach the exact scattering amplitudes for the bulk theory, providing a natural CFT definition of the flat space S-Matrix. We study corrections resulting from the AdS curvature and particle propagation far from the center of AdS, and show that AdS simply provides an IR regulator that disappears in the flat space limit.

  10. Hf and Nd isotopes in marine sediments: Constraints on global silicate weathering

    NASA Astrophysics Data System (ADS)

    Bayon, G.; Burton, K. W.; Soulet, G.; Vigier, N.; Dennielou, B.; Etoubleau, J.; Ponzevera, E.; German, C. R.; Nesbitt, R. W.

    2009-01-01

    The combined use of Lu-Hf and Sm-Nd isotope systems potentially offers a unique perspective for investigating continental erosion, but little is known about whether, and to what extent, the Hf-Nd isotope composition of sediments is related to silicate weathering intensity. In this study, Hf and Nd elemental and isotope data are reported for marine muds, leached Fe-oxide fractions and zircon-rich turbidite sands collected off the Congo River mouth, and from other parts of the SE Atlantic Ocean. All studied samples from the Congo fan (muds, Fe-hydroxides, sands) exhibit indistinguishable Nd isotopic composition (ɛ Nd ~ - 16), indicating that Fe-hydroxides leached from these sediments correspond to continental oxides precipitated within the Congo basin. In marked contrast, Hf isotope compositions for the same samples exhibit significant variations. Leached Fe-hydroxide fractions are characterized by ɛ Hf values (from - 1.1 to + 1.3) far more radiogenic than associated sediments (from - 7.1 to - 12.0) and turbidite sands (from - 27.2 to - 31.6). ɛ Hf values for Congo fan sediments correlate very well with Al/K (i.e. a well-known index for the intensity of chemical weathering in Central Africa). Taken together, these results indicate that (1) silicate weathering on continents leads to erosion products having very distinctive Hf isotope signatures, and (2) a direct relationship exists between ɛ Hf of secondary clay minerals and chemical weathering intensity. These results combined with data from the literature have global implications for understanding the Hf-Nd isotope variability in marine precipitates and sediments. Leached Fe-hydroxides from Congo fan sediments plot remarkably well on an extension of the 'seawater array' (i.e. the correlation defined by deep-sea Fe-Mn precipitates), providing additional support to the suggestion that the ocean Hf budget is dominated by continental inputs. Fine-grained sediments define a diffuse trend, between that for igneous

  11. Design for human factors (DfHF): a grounded theory for integrating human factors into production design processes.

    PubMed

    Village, Judy; Searcy, Cory; Salustri, Filipo; Patrick Neumann, W

    2015-01-01

    The 'design for human factors' grounded theory explains 'how' human factors (HF) went from a reactive, after-injury programme in safety, to being proactively integrated into each step of the production design process. In this longitudinal case study collaboration with engineers and HF Specialists in a large electronics manufacturer, qualitative data (e.g. meetings, interviews, observations and reflections) were analysed using a grounded theory methodology. The central tenet in the theory is that when HF Specialists acclimated to the engineering process, language and tools, and strategically aligned HF to the design and business goals of the organisation, HF became a means to improve business performance. This led to engineers 'pulling' HF Specialists onto their team. HF targets were adopted into engineering tools to communicate HF concerns quantitatively, drive continuous improvement, visibly demonstrate change and lead to benchmarking. Senior management held engineers accountable for HF as a key performance indicator, thus integrating HF into the production design process. Practitioner Summary: Research and practice lack explanations about how HF can be integrated early in design of production systems. This three-year case study and the theory derived demonstrate how ergonomists changed their focus to align with design and business goals to integrate HF into the design process.

  12. Magnetic mass in 4D AdS gravity

    NASA Astrophysics Data System (ADS)

    Araneda, René; Aros, Rodrigo; Miskovic, Olivera; Olea, Rodrigo

    2016-04-01

    We provide a fully covariant expression for the diffeomorphic charge in four-dimensional anti-de Sitter gravity, when the Gauss-Bonnet and Pontryagin terms are added to the action. The couplings of these topological invariants are such that the Weyl tensor and its dual appear in the on-shell variation of the action and such that the action is stationary for asymptotic (anti-)self-dual solutions in the Weyl tensor. In analogy with Euclidean electromagnetism, whenever the self-duality condition is global, both the action and the total charge are identically vanishing. Therefore, for such configurations, the magnetic mass equals the Ashtekhar-Magnon-Das definition.

  13. Canonical energy and hairy AdS black holes

    NASA Astrophysics Data System (ADS)

    Hyun, Seungjoon; Park, Sang-A.; Yi, Sang-Heon

    2016-08-01

    We propose the modified version of the canonical energy which was introduced originally by Hollands and Wald. Our construction depends only on the Euler-Lagrange expression of the system and thus is independent of the ambiguity in the Lagrangian. After some comments on our construction, we briefly mention on the relevance of our construction to the boundary information metric in the context of the AdS/CFT correspondence. We also study the stability of three-dimensional hairy extremal black holes by using our construction.

  14. Lifshitz-like systems and AdS null deformations

    SciTech Connect

    Narayan, K.

    2011-10-15

    Following K. Balasubramanian and K. Narayan [J. High Energy Phys. 08 (2010) 014], we discuss certain lightlike deformations of AdS{sub 5}xX{sup 5} in type IIB string theory sourced by a lightlike dilaton {Phi}(x{sup +}) dual to the N=4 super Yang-Mills theory with a lightlike varying gauge coupling. We argue that, in the case where the x{sup +} direction is noncompact, these solutions describe anisotropic 3+1-dim Lifshitz-like systems with a potential in the x{sup +} direction generated by the lightlike dilaton. We then describe solutions of this sort with a linear dilaton. This enables a detailed calculation of two-point correlation functions of operators dual to bulk scalars and helps illustrate the spatial structure of these theories. Following this, we discuss a nongeometric string construction involving a compactification along the x{sup +} direction of this linear dilaton system. We also point out similar IIB axionic solutions. Similar bulk arguments for x{sup +}-noncompact can be carried out for deformations of AdS{sub 4}xX{sup 7} in M theory.

  15. AdS black holes from duality in gauged supergravity

    NASA Astrophysics Data System (ADS)

    Halmagyi, Nick; Vanel, Thomas

    2014-04-01

    We study and utilize duality transformations in a particular STU-model of four dimensional gauged supergravity. This model is a truncation of the de Wit-Nicolai =8 theory and as such has a lift to eleven-dimensional supergravity on the seven-sphere. Our duality group is U(1)3 and while it can be applied to any solution of this theory, we consider known asymptotically AdS4, supersymmetric black holes and focus on duality transformations which preserve supersymmetry. For static black holes we generalize the supersymmetric solutions of Cacciatori and Klemm from three magnetic charges to include two additional electric charges and argue that this is co-dimension one in the full space of supersymmetric static black holes in the STU-model. These new static black holes have nontrivial profiles for axions. For rotating black holes, we generalize the known two-parameter supersymmetric solution to include an additional parameter. When lifted to M-theory, these black holes correspond to the near horizon geometry of a stack of BPS rotating M2-branes, spinning on an S 7 which is fibered non-trivially over a Riemann surface.

  16. Stability of charged global AdS4 spacetimes

    NASA Astrophysics Data System (ADS)

    Arias, Raúl; Mas, Javier; Serantes, Alexandre

    2016-09-01

    We study linear and nonlinear stability of asymptotically AdS4 solutions in Einstein-Maxwell-scalar theory. After summarizing the set of static solutions we first examine thermodynamical stability in the grand canonical ensemble and the phase transitions that occur among them. In the second part of the paper we focus on nonlinear stability in the microcanonical ensemble by evolving radial perturbations numerically. We find hints of an instability corner for vanishingly small perturbations of the same kind as the ones present in the uncharged case. Collapses are avoided, instead, if the charge and mass of the perturbations come to close the line of solitons. Finally we examine the soliton solutions. The linear spectrum of normal modes is not resonant and instability turns on at extrema of the mass curve. Linear stability extends to nonlinear stability up to some threshold for the amplitude of the perturbation. Beyond that, the soliton is destroyed and collapses to a hairy black hole. The relative width of this stability band scales down with the charge Q, and does not survive the blow up limit to a planar geometry.

  17. Photocurrent generation in carbon nanotube/cubic-phase HfO2 nanoparticle hybrid nanocomposites.

    PubMed

    Rauwel, Protima; Galeckas, Augustinas; Salumaa, Martin; Ducroquet, Frédérique; Rauwel, Erwan

    2016-01-01

    A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs) and cubic-phase HfO2 nanoparticles (NPs) with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV-vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications. PMID:27547626

  18. Photocurrent generation in carbon nanotube/cubic-phase HfO2 nanoparticle hybrid nanocomposites

    PubMed Central

    Galeckas, Augustinas; Salumaa, Martin; Ducroquet, Frédérique; Rauwel, Erwan

    2016-01-01

    Summary A hybrid material consisting of nonfunctionalized multiwall carbon nanotubes (MWCNTs) and cubic-phase HfO2 nanoparticles (NPs) with an average diameter of 2.6 nm has been synthesized. Free standing HfO2 NPs present unusual optical properties and a strong photoluminescence emission in the visible region, originating from surface defects. Transmission electron microscopy studies show that these NPs decorate the MWCNTs on topological defect sites. The electronic structure of the C K-edge in the nanocomposites was probed by electron energy loss spectroscopy, highlighting the key role of the MWCNT growth defects in anchoring HfO2 NPs. A combined optical emission and absorption spectroscopy approach illustrated that, in contrast to HfO2 NPs, the metallic MWCNTs do not emit light but instead expose their discrete electronic structure in the absorption spectra. The hybrid material manifests characteristic absorption features with a gradual merger of the MWCNT π-plasmon resonance band with the intrinsic defect band and fundamental edge of HfO2. The photoluminescence of the nanocomposites indicates features attributed to combined effects of charge desaturation of HfO2 surface states and charge transfer to the MWCNTs with an overall reduction of radiative recombination. Finally, photocurrent generation under UV–vis illumination suggests that a HfO2 NP/MWCNT hybrid system can be used as a flexible nanodevice for light harvesting applications. PMID:27547626

  19. The ADS All Sky Survey

    NASA Astrophysics Data System (ADS)

    Goodman, Alyssa

    We will create the first interactive sky map of astronomers' understanding of the Universe over time. We will accomplish this goal by turning the NASA Astrophysics Data System (ADS), widely known for its unrivaled value as a literature resource, into a data resource. GIS and GPS systems have made it commonplace to see and explore information about goings-on on Earth in the context of maps and timelines. Our proposal shows an example of a program that lets a user explore which countries have been mentioned in the New York Times, on what dates, and in what kinds of articles. By analogy, the goal of our project is to enable this kind of exploration-on the sky-for the full corpus of astrophysical literature available through ADS. Our group's expertise and collaborations uniquely position us to create this interactive sky map of the literature, which we call the "ADS All-Sky Survey." To create this survey, here are the principal steps we need to follow. First, by analogy to "geotagging," we will "astrotag," the ADS literature. Many "astrotags" effectively already exist, thanks to curation efforts at both CDS and NED. These efforts have created links to "source" positions on the sky associated with each of the millions of articles in the ADS. Our collaboration with ADS and CDS will let us automatically extract astrotags for all existing and future ADS holdings. The new ADS Labs, which our group helps to develop, includes the ability for researchers to filter article search results using a variety of "facets" (e.g. sources, keywords, authors, observatories, etc.). Using only extracted astrotags and facets, we can create functionality like what is described in the Times example above: we can offer a map of the density of positions' "mentions" on the sky, filterable by the properties of those mentions. Using this map, researchers will be able to interactively, visually, discover what regions have been studied for what reasons, at what times, and by whom. Second, where

  20. Authigenic phases and biomass contents drive Zr, Hf and REE distributions in anoxic lake sediments

    NASA Astrophysics Data System (ADS)

    Censi, P.; Saiano, F.; Zuddas, P.; Nicosia, A.; Mazzola, S.; Raso, M.

    2013-05-01

    REE, Zr and Hf distributions in seafloor sediments collected from the hypersaline, anoxic Thetis, Kryos, Medee and Tyro deep-sea basins from the Eastern Mediterranean were determined in light of their mineralogical composition, and biomass contents. Mineralogical investigations demonstrate that all the studied sediments show a similar mineralogy. Detritic assemblages mainly consist of quartz, gypsum and calcite with Mg contents ranging from 0 to about 7%, often of a bioclastic nature. On the contrary, authigenic parageneses are formed by halite, bischofite, dolomite and calcite, with Mg contents up to 22%. Textural evidences of biological activity were also identified. In sediments from the Medee and Tyro basins, REE, Zr and Hf distributions were analysed in the fraction soluble in nitric acid, whereas in materials coming from the Thetis and Kryos basins, the water-soluble sediment fraction had been previously removed and REE, Zr and Hf distributions were investigated in the residue. This approach evidenced that shale-normalised REE patterns of the whole fraction soluble in nitric acid show strong intermediate REE (MREE) enrichments that give way to positive Gd anomalies once water-soluble minerals are removed. Y/Ho ratios are clustered around chondritic values justified by the occurrence of detritic minerals whereas Zr/Hf values span a~wider range from slightly subchondritic to superchondritic terms. Negative Gd anomalies, subchondritic Y/Ho and Zr/Hf values are found in Mg-carbonate rich samples suggesting that authigenic Mg-carbonates partition Ho and Hf with respect to Y and Zr during their crystallization from brines. Textural observations and biomass analyses highlighted effects of biological activities in sediments involving Zr and Hf enrichments and the highest Zr/Hf values according to the preferential Zr removal onto biological surfaces, without partitioning Y with respect to Ho. These first data suggest that Zr/Hf ratio and REE distributions can

  1. High precision Lu and Hf isotope analyses of both spiked and unspiked samples: A new approach

    NASA Astrophysics Data System (ADS)

    Lapen, Thomas J.; Mahlen, Nancy J.; Johnson, Clark M.; Beard, Brian L.

    2004-01-01

    The functional form of instrumentally produced mass fractionation associated with MC-ICP-MS analysis is not accurately known and therefore cannot be fully corrected by traditional approaches of internal normalization using power, linear, or exponential mass-bias laws. We present a method for robust correction of instrumentally produced mass-fractionation of both spiked and unspiked samples that can be applied to mass analysis of Hf as well as Nd, Sr, Os, etc. Correction of 176Hf/177Hf for unspiked samples follows a traditional approach of internal normalization using an exponential law, followed by normalization to a standard of known composition, such as JMC-475. For spiked samples, standards are used to characterize a linear instrumental mass-bias coefficient; the mass-bias coefficient is defined by the slope of a tie-line between measured and true values of a standard. This approximation results in identical precision and accuracy of measurements for spiked and unspiked samples (±0.005% 2σ, external reproducibility). The effects of the spike on the 176Hf/177Hf ratio and calculation of the molar spike-sample ratio is determined by a closed-form solution modified from the double-spike approach used for Fe isotope analysis by TIMS [Johnson and Beard, 1999]. The measured 176Lu/175Lu ratios are corrected by doping the sample with Er and using the 167Er/166Er ratio to externally normalize the 176Lu/175Lu ratio using an exponential law. Finally, spike-sample equilibration is confirmed for our sample dissolution protocol through analysis of varying physical mixtures of 1 Ga garnet and hornblende, where all the data lie on a mixing-line, within error, on a 176Lu/177Hf-176Hf/177Hf diagram. Precision of 176Lu/177Hf ratios is determined to be ±0.2% (2σ) for standards and for physical mixtures of garnet and hornblende.

  2. Hf isotope systematics of seamounts near the East Pacific Rise (EPR) and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Meng, Fanxue; Niu, Yaoling

    2016-10-01

    We report new Hf isotopic data for basaltic glasses from seamounts flanking the East Pacific Rise (EPR) between 5° and 15°N that have been previously analyzed for Sr-Nd-Pb isotopes as well as major and trace elements. The Hf isotopic data offer new perspectives on the petrogenesis of these samples in a broader context on mantle dynamics. The Hf isotope compositions show significant correlations with Sr-Nd-Pb isotopes and with both abundances and ratios of incompatible elements. The seamount lavas are thus best interpreted as products of melting-induced mixing in a two-component mantle. The range in composition of EPR seamount lavas cannot be generated by simple mixing of melt and melting of variably heterogeneous mantle in which enriched and depleted materials contribute equally to melting (source mixing). Instead, the trace element and isotope compositions of seamount lavas can be reproduced by melting models in which more enriched, fertile mantle component are preferentially melted during mantle upwelling. At progressively lower degrees of melting, erupted lavas are thus more enriched in incompatible trace elements, have higher 87Sr/86Sr, 208Pb/204Pb ratios and lower 143Nd/144Nd, 176Hf/177Hf ratios. The "EM1" and "pyroxenite" endmember might be the suitable enriched component. The Hf-Nd isotopic variations on global scale might result from the variations in amounts of residual continental lithospheric mantle that detached into upper mantle during continental rifting. The significant correlations of Rb/Sr vs 87Sr/86Sr, Sm/Nd vs 143Nd/144Nd and Lu/Hf vs 176Hf/177Hf give pseudochron ages of 182 ± 33 Ma, 276 ± 50 Ma and 387 ± 93 Ma, respectively. These different "ages" have no significance, but result from melting-induced mixing with the pseudochron slopes controlled by the compositions of enriched component and depleted end-member.

  3. DIRECT DETERMINATION OF THE HF/H{sub 2} ABUNDANCE RATIO IN INTERSTELLAR GAS

    SciTech Connect

    Indriolo, Nick; Neufeld, D. A.; Seifahrt, A.; Richter, M. J.

    2013-02-20

    We report the first detection of the v = 1-0, R(0) ro-vibrational transition of HF at 2.499385 {mu}m arising from interstellar gas. The line is seen in absorption toward three background sources-HD 154368, Elias 29, and AFGL 2136 IRS 1-all of which have reported H{sub 2} column densities determined from observations of H{sub 2}. This allows for the first direct determination of the HF/H{sub 2} abundance ratio. We find values of N(HF)/N(H{sub 2}) = 1.15 Multiplication-Sign 10{sup -8} and 0.69 Multiplication-Sign 10{sup -8} for HD 154368 and Elias 29, respectively. The sight line toward AFGL 2136 IRS 1 also shows absorption from the v = 1-0, R(1) transition of HF, indicating warm, dense (n {sub H} {approx}> 10{sup 9} cm{sup -3}) gas, likely very close to the central protostar. Ascribing portions of the HF absorption to warm and cold gas, we find N(HF)/N(H{sub 2}) = (1.7-2.9) Multiplication-Sign 10{sup -8} and (0.33-0.58) Multiplication-Sign 10{sup -8} for the two components, respectively. Except for the warm component toward AFGL 2136 IRS 1, all observed HF/H{sub 2} ratios are well below N(HF)/N(H{sub 2}) = 3.6 Multiplication-Sign 10{sup -8}, the value predicted if nearly all gas phase fluorine is in the form of HF. Models of fluorine chemistry that account for depletion onto grains are able to reproduce the results toward HD 154368, but not in the cold, dense gas toward AFGL 2136 IRS 1 and Elias 29. Most likely, some combinations of simplifying assumptions made in the chemical models are responsible for these discrepancies.

  4. Microstructure and Phase Stability of Single Crystal NiAl Alloyed with Hf and Zr

    NASA Technical Reports Server (NTRS)

    Locci, I. E.; Dickerson, R. M.; Garg, A.; Noebe, R. D.; Whittenberger, J. D.; Nathal, M. V.; Darolia, R.

    1996-01-01

    Six near stoichiometric, NiAl single-crystal alloys, with 0.05-1.5 at.% of Hf and Zr additions plus Si impurities, were microstructurally analyzed in the as-cast, homogenized, and aged conditions. Hafnium-rich interdendritic regions, containing the Heusler phase (Ni2AlHf), were found in all the as-cast alloys containing Hf. Homogenization heat treatments partially reduced these interdendritic segregated regions. Transmission electron microscopy (TEM) observations of the as-cast and homogenized microstructures revealed the presence of a high density of fine Hf (or Zr) and Si-rich precipitates. These were identified as G-phase, Nil6X6Si7, or as an orthorhombic NiXSi phase, where X is Hf or Zr. Under these conditions the expected Heusler phase (beta') was almost completely absent. The Si responsible for the formation of the G and NiHfSi phases is the result of molten metal reacting with the Si-containing crucible used during the casting process. Varying the cooling rates after homogenization resulted in the refinement or complete suppression of the G and NiHfSi phases. In some of the alloys studied, long-term aging heat treatments resulted in the formation of Heusler precipitates, which were more stable at the aging temperature and coarsened at the expense of the G-phase. In other alloys, long-term aging resulted in the formation of the NiXSi phase. The stability of the Heusler or NiXSi phases can be traced to the reactive element (Hf or Zr) to silicon ratio. If the ratio is high, then the Heusler phase appears stable after long time aging. If the ratio is low, then the NiHfSi phase appears to be the stable phase.

  5. Equilibrium and rate constants, and reaction mechanism of the HF dissociation in the HF(H2O)7 cluster by ab initio rare event simulations.

    PubMed

    Elena, Alin Marin; Meloni, Simone; Ciccotti, Giovanni

    2013-12-12

    We perform restrained hybrid Monte Carlo (MC) simulations to compute the equilibrium constant of the dissociation reaction of HF in HF(H2O)7. We find that the HF is a stronger acid in the cluster than in the bulk, and its acidity is higher at lower T. The latter phenomenon has a vibrational entropic origin, resulting from a counterintuitive balance of intra- and intermolecular terms. We find also a temperature dependence of the reactions mechanism. At low T (≤225 K) the dissociation reaction follows a concerted path, with the H atoms belonging to the relevant hydrogen bond chain moving synchronously. At higher T (300 K), the first two hydrogen atoms move together, forming an intermediate metastable state having the structure of an eigen ion (H9O4(+)), and then the third hydrogen migrates completing the reaction. We also compute the dissociation rate constant, kRP. At very low T (≤75 K) kRP depends strongly on the temperature, whereas it gets almost constant at higher T’s. With respect to the bulk, the HF dissociation in the HF(H2O)7 is about 1 order of magnitude faster. This is due to a lower free energy barrier for the dissociation in the cluster.

  6. Ti insertion in the MTe(5) (M = Zr, Hf) structure type: Hf(0.78)Ti(0.22)Te(5).

    PubMed

    Yu, Jaemin; Yun, Hoseop

    2012-03-01

    The group 5 mixed-metal telluride, Hf(0.78)Ti(0.22)Te(5) (hafnium titanium penta-telluride), is isostructural with the binary phases HfTe(5) and ZrTe(5) and forms a layered structure extending parallel to (010). The layers are made up from chains of bicapped metal-centered trigonal prisms and zigzag Te chains. The metal site (site symmetry m2m) is occupied by statistically disordered Hf [78.1 (5)%] and Ti [21.9 (5)%]. In addition to the regular Te-Te pair [2.7448 (13) Å] forming the short base of the equilateral triangle of the trigonal prism, an inter-mediate Te⋯Te separation [2.9129 (9) Å] is also found. The classical charge balance of the compound can be described as [M(4+)][Te(2-)][Te(2) (2-)][Te(2) (0)] (M = Hf, Ti). The individual metal content can vary in different crystals, apparently forming a random substitutional solid solution (Hf(1-x)Ti(x))Te(5), with 0.15 ≤ x ≤ 0.22.

  7. Characterization of Backbending in Even-Even Isotopes of 164-174Hf and 154-164Dy Nuclei by a Modified Phenomenological Model

    NASA Astrophysics Data System (ADS)

    Najim, L. A.; Kheder, Malek. H.

    2013-07-01

    A modified phenomenological model is used to calculate nuclear energy levels and describe successfully the backbending of the moment of inertia for the ground state bands in even-even isotopes of Hf and Dy nuclei. The model is a combination of the Myers and Swiatecki model with variable moment inertia (VMI) model. Since the Myers and Swiatecki model has a deviation from experimental energies in which it takes into account pairing effect with constant moment of inertia, in the rotation of nuclei, the Coriolis force acts to de-pair the nucleons pair and align their angular momentum with nuclei total angular momentum, thus Coriolis force increasing and decrease the rotational energy. So, the moment of inertia varies with the angular momentum. Therefore, we modified this model by adding a term to make the moment of inertia vary with angular momentum in the same manner of the VMI model which has a term added to the rotational energy equation. The modified model fits remarkably with the experimental observation and other models in many cases with the use of few parameters especially in rotational nuclei regions similar to Hf and Dy nuclei.

  8. Artificial Ionization and UHF Radar Response Associated with HF Frequencies near Electron Gyro-Harmonics (Invited)

    NASA Astrophysics Data System (ADS)

    Watkins, B. J.; Fallen, C. T.; Secan, J. A.

    2013-12-01

    We present new results from O-mode ionospheric heating experiments at the HAARP facility in Alaska to demonstrate that the magnitude of artificial ionization production is critically dependent on the choice of HF frequency near gyro-harmonics. For O-mode heating in the lower F-region ionosphere, typically about 200 km altitude, artificial ionization enhancements are observed in the lower ionosphere (about 150 - 220 km) and also in the topside ionosphere above about 500 km. Lower ionosphere density enhancements are inferred from HF-enhanced ion and plasma-line signals observed with UHF radar. Upper ionospheric density enhancements have been observed with TEC (total electron content) experiments by monitoring satellite radio beacons where signal paths traverse the HF-modified ionosphere. Both density enhancements and corresponding upward plasma fluxes have also been observed in the upper ionosphere via in-situ satellite observations. The data presented focus mainly on observations near the third and fourth gyro-harmonics. The specific values of the height-dependent gyro-harmonics have been computed from a magnetic model of the field line through the HF heated volume. Experiments with several closely spaced HF frequencies around the gyro-harmonic frequency region show that the magnitude of the lower-ionosphere artificial ionization production maximizes for HF frequencies about 1.0 - 1.5 MHz above the gyro-harmonic frequency. The response is progressively larger as the HF frequency is increased in the frequency region near the gyro-harmonics. For HF frequencies that are initially greater than the gyro-harmonic value the UHF radar scattering cross-section is relatively small, and non-existent or very weak signals are observed; as the signal returns drop in altitude due to density enhancements the HF interaction region passes through lower altitudes where the HF frequency is less than the gyro-harmonic value, for these conditions the radar scattering cross-section is

  9. High local disorder in Tb2Hf2O7 pyrochlore oxide nanocrystals

    NASA Astrophysics Data System (ADS)

    Kabanova, V. A.; Popov, V. V.; Zubavichus, Ya V.; Kulik, E. S.; Yaroslavtsev, A. A.; Chernikov, R. V.; Menushenkov, A. P.

    2016-05-01

    The process of Tb2Hf2O7 nanocrystals formation upon annealing to 1600°C was investigated by means of X-ray absorption fine structure (XAFS) spectroscopy combined with X-ray diffraction (XRD) and pair distribution function (PDF) analysis. The structure ordering and the growth of nanocrystals upon annealing were estimated independently from XRD patterns and PDF. The probable content of Tb4+ ions in Tb2Hf2O7 was estimated from XANES. All studies indicate a high disorder and a large number of local structure defects in Tb2Hf2O7 pyrochlore oxide.

  10. PARTITION COEFFICIENTS OF Hf, Zr, AND REE BETWEEN PHENOCRYSTS AND GROUNDMASSES.

    USGS Publications Warehouse

    Fujimaki, Hirokazu; Tatsumoto, Mitsunobu; Aoki, Ken-ichiro

    1984-01-01

    Partition coefficients of Hf, Zr, and REE between olivine, orthopyroxene, clinopyroxene, plagioclase, garnet, amphibole, ilmenite, phlogopite, and liquid are presented. Samples consist of megacrysts in kimberlite, phenocrysts in alkaline basalts, tholeiitic basalts and andesitic to dacitic rocks, and synthetic garnet and clinopyroxene in Hawaiian tholeiites. The Hf-Lu and Zr-Lu elemental fractionations are as large as the Lu-Sm or Lu-Nd fractionation. The Hf and Zr partition coefficients between mafic phenocrysts and liquids are smaller than the Lu partition coefficients, but are similar to the Nd or Sm partition coefficients.

  11. Simulation of a two-frequency cw chemical HF-HBr laser

    SciTech Connect

    Aleksandrov, B P; Katorgin, B I; Stepanov, A A

    2008-10-31

    An autonomous cw chemical HF-HBr laser emitting simultaneously at {approx}2.7 {mu}m (HF molecules) and {approx}4.2 {mu}m (HBr molecules) is studied numerically by using complete Navier-Stokes equations. It is shown that the output power of the HBr laser per unit area of the nozzle array can achieve {approx}20 W cm{sup -2} for the laser region length {approx}20 cm. The relation between the radiation intensities emitted by HF and HBr molecules is controlled by diluting the secondary fuel by bromine. (lasers)

  12. Initial characterization of partially stabilized HfO/sub 2/ single crystals

    SciTech Connect

    Ingel, R.P.; Lewis, D.; Bender, B.A.; Rice, R.W.

    1982-09-01

    Results are presented for initial characterization of physical properties, microstructure, and phase structure of partially stabilized HfO/sub 2/ single crystals. These results, for crystals prepared by skull melting, are compared with those for ZrO/sub 2/ single crystals of similar composition and for fully stabilized ZrO/sub 2/ and HfO/sub 2/ single crystals. The observed microstructures and mechanical properties suggest that partially stabilized HfO/sub 2/ crystals may be useful high temperature structural ceramics.

  13. Crystal structure of Na2HfSi2O7 by Rietveld refinement

    PubMed Central

    Massoni, Nicolas; Chevreux, Pierrick

    2016-01-01

    The structure of triclinic disodium hafnium disilicate, Na2HfSi2O7, has been determined by laboratory powder X-ray diffraction and refined by the Rietveld refinement. The structure is a framework made of alternate layers of HfO6 octa­hedra and SiO4 tetra­hedra linked by common O atoms. Sodium atoms are located in the voids of the framework, aligned into tunnels along the [010] direction. Na2HfSi2O7 is isostructural with the parakeldyshite Na2ZrSi2O7 phase. PMID:27746936

  14. Dielectric and complex impedance properties of tetravalent hafnium (HF 4+) integrated cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Sanchez, Luis

    The work presented in this thesis was carried out to understand the effects of tetravalent hafnium (Hf4+) ion on the crystal structure and phase, surface morphology, electrical, dielectric and complex impedance properties of cobalt ferrite (CoFe2O4; CFO). Hafnium incorporated cobalt ferrite, CoFe2-xHfxO4, with x = 0.00, 0.05, 0.075, 0.10, 0.15 and 0.20 were prepared by the standard solid state ceramic synthesis method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations were performed to determine the structural properties. Most important aspect of this study is to explore the dielectric and complex impedance properties as a function of variable temperature (T=300-1000 K) and frequency (f=20 Hz -1 MHz). Room temperature and the temperature dependence of dielectric constant, loss factor, complex impedance, and the ac resistivity measurements enabled us to understand the effect of temperature and frequency on the electrical and dielectric properties on CoFe2-xHfxO4 and, thus, to derive structure-property relation. X-ray diffraction (XRD) patterns for Hf-incorporated CFO confirm the formation of majority of CFO spinel [with space group Fd3m (227)] phase, in addition to the small amount of HfO2 monoclinic [space group, P1 21/c (14)] phase leading to formation of CFO-Hf composites. The lattice constant values derived from XRD for CFO-Hf were found to increase from 8.374 A (x = 0.000) to 8.391 A (x = 0.200). The lattice expansion is significant at the very first step of Hf-incorporation and then slows down with progressive Hf-incorporation. SEM imaging analysis indicates that Hf resides at the grain boundaries for CFO-Hf. The dielectric constant (epsilon') of CFO-Hf is T-independent at T<450 K, at which point increasing trend prevails. A grain bulk-boundary based two-layer model, where semiconducting-grains separated by insulating-grain boundaries, satisfactorily accounts for epsilon- T (>450 K) variation. Correspondingly, electrical

  15. Lu-Hf isotope systematics of fossil biogenic apatite and their effects on geochronology

    NASA Astrophysics Data System (ADS)

    Herwartz, Daniel; Münker, Carsten; Tütken, Thomas; Hoffmann, J. Elis; Wittke, Andreas; Barbier, Bruno

    2013-01-01

    Reliable methods for direct dating of biogenic apatite from pre-Pleistocene fossils are currently not available, and recent attempts using the Lu-Hf decay system yielded highly inaccurate ages for both bones and teeth. The geological processes accounting for this poor accuracy of Lu-Hf chronometry are not yet understood. Here we explore Lu-Hf systematics in fossil bones and teeth in detail, by applying five different sample digestion techniques that are tested on bones and composites of bone and sediment. Our current dataset implies that dissolution methods only slightly affect the resulting Lu-Hf ages, while clear differences between the individual digestion techniques became apparent for element concentrations. By analysing the insoluble leftovers from incomplete sample dissolution, four main reservoirs of Hf in fossil bones were identified: (1) a radiogenic end-member associated with apatite; (2) an unradiogenic end-member represented by the authigenic minerals or the embedding sediment; (3) a highly unradiogenic end-member that can be attributed to detrital zircon; and (4) a moderately soluble phase (probably a Zr(Hf)-phosphate) that yielded very low Lu/Hf but a highly radiogenic Hf isotope composition at the same time. This Zr(Hf)-phase must have been precipitated within the fossil bone sample at a late stage of burial history, thereby incorporating radiogenic 176Hf released from apatite surfaces over geological timescales. A second focus of our study is the effect of different sediment matrices and of crystal size on the preservation of pristine Lu-Hf isotope compositions in bioapatite. Because near-depositional Lu-Hf ages of phosphate fossils have previously been reported for the London Clay (England) and a calcareous marl from Tendaguru (Tanzania), we herein investigate specimens fossilised in carbonate matrices (calcareous marl from Oker, Germany; carbonate concretions from the Santana Formation, Brazil; carbonate from the Eifel, Germany) and argillaceous

  16. Condom ads slated for TV.

    PubMed

    1987-02-20

    3 CBS-owned television stations and NBC's New York television station announced yesterday that they would begin accepting condom advertising. In addition, the ABC network announced it will begin running a 30-second public service message with Dr. C. Everett Koop, the US surgeon general, saying that condoms are the best protection against sexual transmission of AIDS. CBS said it will allow the 4 television stations and 18 radio stations it owns to accept condom advertising based on the attitudes of the local viewing or listening community. WCBS-TV in New York, WCAU-TV in Philadelphia and KCBS-TV in Los Angeles said they would accept such ads. CBS also owns a television station in Chicago. WCAU will air condom ads after 11 p.m. only, beginning probably next week, said Paul Webb, a station spokesman. "We recognize the legitimate sensitivities of some members of the community in regard to this issue," said Steve Cohen, the WCAU general manager. "However, it is the judgment of this station that the importance of providing information about the AIDS epidemic and means of prevention is an overriding consideration." NBC's New York television station, WNBC, announced that it will accept condom advertising and public service announcements. PMID:12269166

  17. Mixed cation phases in sputter deposited HfO{sub 2}-TiO{sub 2} nanolaminates

    SciTech Connect

    Cisneros-Morales, M. C.; Aita, C. R.

    2008-07-14

    Nanolaminate HfO{sub 2}-TiO{sub 2} films are grown by reactive sputter deposition on unheated fused SiO{sub 2}, sequentially annealed at 573 to 973 K, and studied by x-ray diffraction. A nanocrystalline structure of orthorhombic (o) HfTiO{sub 4} adjacent to an interface followed by monoclinic (m) Hf{sub 1-x}Ti{sub x}O{sub 2} is identified. m-Hf{sub 1-x}Ti{sub x}O{sub 2}, a metastable phase, is isomorphous with m-HfO{sub 2} and a high pressure phase, m-HfTiO{sub 4}. A Vegard's law analysis shows that the Ti atomic fraction in m-Hf{sub 1-x}Ti{sub x}O{sub 2} is much greater than Ti equilibrium solubility in m-HfO{sub 2}. A space group-subgroup argument proposes that m-Hf{sub 1-x}Ti{sub x}O{sub 2} arises from an o/m-HfTiO{sub 4} second order phase transition to accommodate the larger Hf atom.

  18. Lu-Hf and Sm-Nd Isotopic Studies of Shergottites and Nakhlites: Implications for Martian Mantle Sources

    NASA Technical Reports Server (NTRS)

    Debaille, V.; Yin, Q.-Z.; Brandon, A. D.; Jacobsen, B.; Treiman, A. H.

    2007-01-01

    We present a new Lu-Hf and Sm-Nd isotope systematics study of four enriched shergottites (Zagami, Shergotty, NWA856 and Los Angeles), and three nakhlites (Nakhla, MIL03346 and Yamato 000593) in order to further understand processes occurring during the early differentiation of Mars and the crystallization of its magma ocean. Two fractions of the terrestrial petrological analogue of nakhlites, the Archaean Theo's flow (Ontario, Canada) were also measured. The coupling of Nd and Hf isotopes provide direct insights on the mineralogy of the melt sources. In contrast to Sm/Nd, Lu/Hf ratios can be very large in minerals such as garnet. Selective partial melting of garnet bearing mantle sources can therefore lead to characteristic Lu/Hf signatures that can be recognized with Hf-176/Hf-177Hf ratios.

  19. Effects of C and Hf concentration on phase relations and microstructure of a wrought powder-metallurgy superalloy

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.

    1977-01-01

    NASA IIB-11, a candidate alloy for advanced temperature turbine engine disks, and four modifications with varying C and Hf concentrations were produced from prealloyed powders. Several notable effects of C and Hf concentration in the alloys were observed. Both the amount of the gamma-prime phase and its solvus temperature increased with decreasing C, but only the gamma-prime solvus was affected by Hf, increasing with increasing Hf. Hf also promoted a cellular gamma-prime precipitation. Hf was, however, about equally distributed between gamma-prime and gamma. Hf and C both affected the carbides formed. Increasing both promoted formation of an MC relative to that of an M6C.

  20. The Li···HF van der Waals minimum and the barrier to the deep HF-Li potential well

    NASA Astrophysics Data System (ADS)

    Fan, Qunchao; Feng, Hao; Sun, Weiguo; Xie, Yaoming; Wu, Chia-Hua; Allen, Wesley D.; Schaefer, Henry F., III

    2014-03-01

    Molecular beam experiments (lithium atom plus hydrogen fluoride) by both Becker and co-workers (C.H. Becker, P. Casavecchia, P.W. Tiedemann, J.J.Valentini, and Y.T. Lee, J. Chem. Phys. 73, 2833 (1980)) and Loesch and Stienkemeier (H.J. Loesch and F. Stienkemeier, J. Chem. Phys. 98, 9570 (1993)) deduced a van der Waals complex of type Li...HF. In this research, molecular electronic structure theory [aug-cc-pCVQZ CCSD(T)] has been used to predict a well depth of 0.86 kcal mol-1 relative to separated Li + HF. However, the barrier from this vdW well to the more strongly bound (∼6.2 kcal mol-1) HFLi complex lies 0.43 kcal mol-1 below separated Li + HF. Special Issue of Molecular Physics: Seventh Molecular Quantum Mechanics Conference, Lugano, Switzerland, 2-7 June 2013.

  1. Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment

    NASA Astrophysics Data System (ADS)

    Maruyama, T.; Kawamura, M.

    2006-07-01

    A transequatorial radio-wave propagation experiment at shortwave frequencies (HF-TEP) was done between Shepparton, Australia, and Oarai, Japan, using the radio broadcasting signals of Radio Australia. The receiving facility at Oarai was capable of direction finding based on the MUSIC (Multiple Signal Classification) algorithm. The results were plotted in azimuth-time diagrams (AT plots). During the daytime, the propagation path was close to the great circle connecting Shepparton and Oarai, thus forming a single line in the AT plots. After sunset, off-great-circle paths, or satellite traces in the AT plot, often appeared abruptly to the west and gradually returned to the great circle direction. However, there were very few signals across the great circle to the east. The off-great-circle propagation was very similar to that previously reported and was attributed to reflection by an ionospheric structure near the equator. From the rate of change in the direction, we estimated the drift velocity of the structure to range mostly from 100 to 300 m/s eastward. Multiple instances of off-great-circle propagation with a quasi-periodicity were often observed and their spatial distance in the east-west direction was within the range of large-scale traveling ionospheric disturbances (LS-TIDs). Off-great-circle propagation events were frequently observed in the equinox seasons. Because there were many morphological similarities, the events were attributed to the onset of equatorial plasma bubbles.

  2. Anomalous phenomena on HF radio paths during geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskii, D. V.

    2016-07-01

    We analyze ionospheric oblique sounding data on three high-latitude and one high-latitude-midlatitude HF radio paths for February 15 and 16, 2014, when two substorms and one magnetic storm occurred. We investigate cases of anomalous propagation of signals: their reflection from sporadic layer Es, lateral reflections, type "M" or "N" modes, the presence of traveling ionospheric disturbances, and the diffusivity of signals and triplets. The most significant results are the following. In geomagnetically undisturbed times, sporadic Es-layers with reduced maximum observed frequencies (MOF Es) on three high-latitude paths were observed in both days. The values of MOF Es during disturbances are large, which leads to the screening of other oblique sounding signals reflected from the ionosphere. On all four paths, the most frequently traveling ionospheric disturbances due to the terminator were observed in quiet hours from 03:00 to 15:00 UT on the first day and from 06:00 to 13:00 UT on the second day of the experiment. In addition, both the sunset terminator and the magnetic storm on the high-latitude-mid-latitude path were found to generate traveling ionospheric disturbances jointly. No such phenomenon was found on high-latitude paths.

  3. LU-HF Age of Martian Meteorite Larkman Nunatek 06319

    NASA Technical Reports Server (NTRS)

    Shafer, J. T.; Brandon, A. D.; Lapen, T. J.; Righter, M.; Beard, B.; Peslier, A. H.

    2009-01-01

    Lu-Hf isotopic data were collected on mineral separates and bulk rock powders of LAR 06319, yielding an age of 197+/- 29 Ma. Sm-Nd isotopic data and in-situ LA-ICP-MS data from a thin section of LAR 06319 are currently being collected and will be presented at the 2009 LPSC. These new data for LAR 06319 extend the existing data set for the enriched shergottite group. Martian meteorites represent the only opportunity for ground truth investigation of the geochemistry of Mars [1]. At present, approximately 80 meteorites have been classified as Martian based on young ages and distinctive isotopic signatures [2]. LAR 06319 is a newly discovered (as part of the 2006 ANSMET field season) martian meteorite that represents an important opportunity to further our understanding of the geochemical and petrological constraints on the origin of Martian magmas. Martian meteorites are traditionally categorized into the shergottite, nakhlite, and chassignite groups. The shergottites are further classified into three distinct isotopic groups designated depleted, intermediate, and enriched [3,4] based on the isotope systematics and compositions of their source(s).

  4. Tactical HF field expedient antenna performance, volume 2

    NASA Astrophysics Data System (ADS)

    Turkes, Gurkan

    1990-03-01

    This thesis investigates the performance of various configurations of tactical high frequency (HF) field deployable antennas in the presence of lossy earth. Antennas investigated include horizontal dipoles, short sloping wires, inverted vees, and monopoles with buried and elevated radials. Numerical models of the antennas are exercised via the Numerical Electromagnetic Code (NEC) for radiation pattern performance. Antennas are analyzed for applicability to the following: (1) short-range near vertical incident skywave (NVIS), where high elevation radiation angles are required; (2) medium- and long-range low radiation angle use; and (3) vertically polarized low-angle radiation for ground wave communication. Good NVIS and ground wave performance occurs for horizontal dipoles. Sloping wires and sloping dipoles are similar to horizontal dipoles but exhibit a moderate amount of azimuth plane directivity. Vertical monopoles with at least 15 buried radials produce medium- and long-range skywave coverage and good ground wave performance. Four elevated radials for quarter-wavelength monopoles are shown to out-perform 15 buried radials and are much easier to erect. The larger and more difficult-to-erect inverted vee dipole slightly outperforms a monopole by virtue of modest azimuth plane directivity. The results of this study can be included in an antenna engineering handbook and can be used to interface with existing ionospheric propagation codes in order to obtain optimum communication effectiveness

  5. Tactical HF field expedient antenna performance, volume 1

    NASA Astrophysics Data System (ADS)

    Turkes, Gurkan

    1990-03-01

    This thesis investigates the performance of various configurations of tactical High Frequency (HF) field deployable antennas in the presence of lossy earth. Antennas investigated include horizontal dipoles, short sloping wires, inverted vees, and monopoles with buried and elevated radials. Numerical models of the antennas are exercised via the Numerical Electromagnetics Code (NEC) for radiation pattern performance. Antennas are analyzed for applicability to (1) short-range Near Vertical Incident Skywave (NVIS), where high elevation radiation angles are required; (2) medium-and long-range low radiation angle use; and (3) vertically polarized low-angle radiation for ground wave communication. Good NVIS and ground wave performance occurs for horizontal dipoles. Sloping wires and sloping dipoles are similar to horizontal dipoles but exhibit a moderate amount of azimuth plane directivity. Vertical monopoles with at least 15 buried radials produce medium-and long-range skywave coverage and good ground wave performance. Four elevated radials for quarter-wavelength monopoles are shown to out-perform 15 buried radials and are much easier to erect. The larger and more difficult-to-erect inverted vee dipole slightly outperforms a monopole by virtue of modest azimuth plane directivity. The results of this study can be included in an antenna engineering handbook and can be used to interface with existing ionospheric propagation codes in order to obtain optimum communication effectiveness.

  6. Development of Hf(4+)-immobilized polydopamine-coated magnetic graphene for highly selective enrichment of phosphopeptides.

    PubMed

    Lin, Haizhu; Deng, Chunhui

    2016-01-01

    In this work, we first designed and synthesized an IMAC material with Hf(4+) immobilized on polydopamine-coated magnetic graphene and applied it to phosphopeptides enrichment successfully. The newly prepared material gathered the advantages of large specific surface area of graphene, good hydrophilicity and biocompatibility of polydopamine and superparamagnetism of Fe3O4. We investigated the performance of Hf(4+)-immobilized polydopamine-coated magnetic graphene (denoted as magG@PDA-Hf(4+)) in phosphopeptides enrichment and the results showed high selectivity and sensitivity of the new material. Finally, we successfully applied magG@PDA-Hf(4+) to phosphopeptides enrichment from non-fat milk digests and human serum, further demonstrating excellent performance of this new material in phosphopeptides enrichment.

  7. Two-dimensional electron gas in GaAs/SrHfO3 heterostructure

    NASA Astrophysics Data System (ADS)

    Wang, Jianli; Yuan, Mengqi; Tang, Gang; Li, Huichao; Zhang, Junting; Guo, Sandong

    2016-06-01

    The III-V/perovskite-oxide system can potentially create new material properties and new device applications by combining the rich properties of perovskite-oxides together with the superior optical and electronic properties of III-Vs. The structural and electronic properties of the surface and interface are studied using first-principles calculations for the GaAs/SrHfO3 heterostructure. We investigate the specific adsorption sites and the atomic structure at the initial growth stage of GaAs on the SrHfO3 (001) substrate. Ga and As adsorption atoms preferentially adsorb at the top sites of oxygen atoms under different coverage. The energetically favorable interfaces are presented among the atomic arrangements of the GaAs/SrHfO3 interfaces. Our calculations predict the existing of the two-dimensional electron gas in the GaAs/SrHfO3 heterostructure.

  8. Modulation of auroral electrojet currents using dual HF beams with ELF phase offset

    NASA Astrophysics Data System (ADS)

    Golkowski, M.; Cohen, M.; Moore, R. C.

    2012-12-01

    The modulation of naturally occuring ionospheric currents with high power radio waves in the high frequency (HF, 3-10 MHz) band is a well known technique for generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) waves. We use the heating facility of the High Frequency Active Auroral Research Program (HAARP) to investigate the effect of using dual HF beams with an ELF/VLF phase offset between the modulation waveforms. Experiments with offset HF beams confirm the model of independent ELF/VLF sources. Experiments with co-located HF beams exhibit interaction between the first and second harmonics of the modulated tones when square and sine wave modulation waveforms are employed. Using ELF/VLF phase offsets for co-loacted beams is also shown to be a potential diagnostic for the D-region ionospheric profile.

  9. Long haul communications in the HF spectrum utilizing high speed modems

    NASA Astrophysics Data System (ADS)

    Ellis, Robert H.

    1988-03-01

    In the past ten years reliable high-speed satellite systems have pushed slower less reliable communication systems to the bottom of the list for development programs. Concern over reduced budgets, vulnerability of expensive satellite systems, and recent advances in HF technology are creating new interest in upgrading existing HF communication systems. Nondevelopment Items (NDI) are defined as the use of off-the-shelf commercial items instead of costly, time-consuming conventional research and development programs. The Navy Department's current policies are designed to insure the maximum use of NDI to fulfill Navy requirements. The speed of HF systems can be improved using current signaling and modulation techniques, and reliability can be increased by error-correcting codes or error detection used in conjunction with automatic repeat request (ARQ) schemes. Improved HF systems not only provide survivable back-up capability, but increased capacity for present communication needs.

  10. Reconciling Hf-W Model Ages of IVB Parent Body with Numerical Models

    NASA Astrophysics Data System (ADS)

    Neumann, W.; Breuer, D.; Kleine, T.; Kruijer, T.

    2016-08-01

    We calculated the differentiation of the parent body of IVB iron meteorites comparing its evolution to the metal separation data. Our models are consistent with the separation ages inferred from the Hf-W chronology.

  11. Oxidation of several corrosion-resistant metals in HF-DMF

    SciTech Connect

    Chulkevich, A.K.; Smolina, E.V.; Lavrent'ev, I.P.; Khidekel', M.L.

    1987-02-20

    The oxidative dissolution of transition metals in organic and aqueous organic media yields a broad range of complexes. In work, data are given on the dissolution of Ti, Zr, Nb, Ta, Cr, and Mn in HF-DMF and HF-DMF-H/sub 2/O/sub 2/ systems. The dimethylammonium oxyfluoride complexes were isolated and characterized. Metals of groups IV-VI may be oxidized in HF-DMF and HF-DMF-H/sub 2/O/sub 2/ systems. The dimethylammonium oxyfluoride complexes of titanium(IV), zirconium(IV), niobium(V), tantalum(V), and the oxyfluorides of chromium(III) and manganese(II) were isolated and characterized.

  12. Partition coefficients of Hf, Zr, and REE between zircon, apatite, and liquid

    USGS Publications Warehouse

    Fujimaki, H.

    1986-01-01

    Concentration ratios of Hf, Zr, and REE between zircon, apatite, and liquid were determined for three igneous compositions: two andesites and a diorite. The concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient. Although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients, those for the apatite in the diorite may deviate from the partition coefficients. The HREE partition coefficients between zircon and liquid are very large (100 for Er to 500 for Lu), and the Hf partition coefficient is even larger. The REE partition coefficients between apatite and liquid are convex upward, and large (D=10-100), whereas the Hf and Zr partition coefficients are less than 1. The large differences between partition coefficients of Lu and Hf for zircon-liquid and for apatite-liquid are confirmed. These partition coefficients are useful for petrogenetic models involving zircon and apatite. ?? 1986 Springer-Verlag.

  13. Lu-Hf total-rock isochron for the eucrite meteorites

    NASA Technical Reports Server (NTRS)

    Patchett, P. J.; Tatsumoto, M.

    1980-01-01

    The isotope Lu-176 (2.6% of natural lutetium) decays by beta(-) to Hf-176, with a long half life. The first Lu-Hf isochron is presented. The eucrite meteorites, a suite of planetary igneous rocks of known age, 4,550 Myr, define a 10-point total-rock isochron with a slope of 0.0934 + or - 40, leading to a value of 3.53 + or - 0.14 x 10 to the 10th yr for the beta(-) decay half life of Lu-176. The isochron intercept of 0.27973 + or - 12 gives the initial Hf-176/Hf-177 for the inner solar system at the time of accretion.

  14. Strongly reduced Si surface recombination by charge injection during etching in diluted HF/HNO3.

    PubMed

    Greil, Stefanie M; Schöpke, Andreas; Rappich, Jörg

    2012-08-27

    Herein, we investigate the behaviour of the surface recombination of light-induced charge carriers during the etching of Si in alkaline (KOH) and acidic etching solutions of HF/HNO(3)/CH(3)COOH (HNA) or HF/HNO(3)/H(3)PO(4) (HNP) at different concentration ratios of HF and HNO(3) by means of photoluminescence (PL) measurements. The surface recombination velocity is strongly reduced during the first stages of etching in HF/HNO(3)-containing solutions pointing to a interface well passivated by the etching process, where a positive surface charge is induced by hole injection from NO-related surface species into the Si near-surface region (back surface field effect). This injected charge leads to a change in band bending by about 150 mV that repulses the light-induced charge carriers from the surface and therefore enhances the photoluminescence intensity, since non-radiative surface recombination is reduced.

  15. Recent Terrestrial Disturbance of the 176Lu-176Hf Systematics in Meteorites

    NASA Astrophysics Data System (ADS)

    Bast, R.; Scherer, E. E.; Sprung, P.; Mezger, K.; Bischoff, A.

    2016-08-01

    The Lu-Hf isotope systematics of many achondrites exhibit excessive scatter above a solar system isochron that cannot be explained by early solar system processes but by recent terrestrial weathering or contamination.

  16. Optical detection of concentrations for mixed acid: HF and HNO3

    NASA Astrophysics Data System (ADS)

    Kang, Gumin; Kim, Kyoungsik

    2009-02-01

    Mixed acid, which consist of HF and HNO3, is used as a good etchant for silicon dioxide in the wet etching and pickling process of stainless steel. The optical detection of concentration for such mixed acids is crucial to optimize and cut costs in the manufacturing process. Optical detection in the IR regime has been utilized to measure the concentration of the mixed acid for HF and HNO3, because that has several strong absorption peaks, which is contributed by vibrational mode of each acid molecular in this spectrum. In this research, we observed the concentrations of mixed acid to consist of HF and HNO3, as we measured the absorption intensity of OH- stretch and NO3 - stretch band by optical spectroscopy. The concentration range of HF over 1.5-3 wt% and that of HNO3 over 2-10 wt% were studied in room temperature.

  17. Subduction Controls of Hf and Nd Isotopes in Lavas of the Aleutian Island Arc

    SciTech Connect

    Yogodzinski, Gene; Vervoort, Jeffery; Brown, Shaun Tyler; Gerseny, Megan

    2010-08-29

    The Hf and Nd isotopic compositions of 71 Quaternary lavas collected from locations along the full length of the Aleutian island arc are used to constrain the sources of Aleutian magmas and to provide insight into the geochemical behavior of Nd and Hf and related elements in the Aleutian subduction-magmatic system. Isotopic compositions of Aleutian lavas fall approximately at the center of, and form a trend parallel to, the terrestrial Hf-Nd isotopic array with {var_epsilon}{sub Hf} of +12.0 to +15.5 and {var_epsilon}{sub Nd} of +6.5 to +10.5. Basalts, andesites, and dacites within volcanic centers or in nearby volcanoes generally all have similar isotopic compositions, indicating that there is little measurable effect of crustal or other lithospheric assimilation within the volcanic plumbing systems of Aleutian volcanoes. Hafnium isotopic compositions have a clear pattern of along-arc increase that is continuous from the eastern-most locations near Cold Bay to Piip Seamount in the western-most part of the arc. This pattern is interpreted to reflect a westward decrease in the subducted sediment component present in Aleutian lavas, reflecting progressively lower rates of subduction westward as well as decreasing availability of trench sediment. Binary bulk mixing models (sediment + peridotite) demonstrate that 1-2% of the Hf in Aleutian lavas is derived from subducted sediment, indicating that Hf is mobilized out of the subducted sediment with an efficiency that is similar to that of Sr, Pb and Nd. Low published solubility for Hf and Nd in aqueous subduction fluids lead us to conclude that these elements are mobilized out of the subducted component and transferred to the mantle wedge as bulk sediment or as a silicate melt. Neodymium isotopes also generally increase from east to west, but the pattern is absent in the eastern third of the arc, where the sediment flux is high and increases from east to west, due to the presence of abundant terrigenous sediment in the

  18. Deformation and its influence on K isomerism in neutron-rich Hf nuclei

    SciTech Connect

    Liu, H. L.; Bertulani, C. A.; Xu, F. R.; Walker, P. M.

    2011-06-15

    We investigate the influence of deformation on the possible occurrence of long-lived K isomers in Hf isotopes around N=116, using configuration-constrained calculations of potential-energy surfaces. Despite having reduced shape elongation, the multiquasiparticle states in {sup 186,188}Hf remain moderately robust against triaxial distortion, supporting the long expected occurrence of exceptionally long-lived isomers. The calculations are compared with available experimental data.

  19. Evolution of magnetic properties and microstructure of Hf2Co11B alloys

    DOE PAGES

    McGuire, Michael A.; Rios, Orlando

    2015-02-05

    Amorphous Hf2Co11B alloys produced by melt-spinning have been crystallized by annealing at 500-800 °C, and the products have been investigated using magnetization measurements, x-ray diffraction, and scanning electron microscopy. The results reveal the evolution of the phase fractions, microstructure, and magnetic properties with both annealing temperature and time. Crystallization of the phase denoted HfCo7, which is associated with the development of coercivity, occurs slowly at 500 °C. Annealing at intermediate temperatures produces mixed phase samples containing some of the HfCo7 phase with the highest values of remanent magnetization and coercivity. The equilibrium structure at 800 °C contains HfCo3B2, Hf6Co23 andmore » Co, and displays soft ferromagnetism. Maximum values for the remanent magnetization, intrinsic coercivity, and magnetic energy product among the samples are approximately 5.2 kG, 2.0 kOe, and 3.1 MGOe, respectively, which indicates that the significantly higher values observed in crystalline, melt-spun Hf2Co11B ribbons are a consequence of the non-equilibrium solidification during the melt-spinning process. Application of high magnetic fields during annealing is observed to strongly affect the microstructural evolution, which may provide access to higher performance materials in Zr/Hf-Co hard ferromagnets. The crystal structure of HfCo7 and the related Zr analogues is unknown, and without knowledge of atomic positions powder diffraction cannot distinguish among proposed unit cells and symmetries found in the literature.« less

  20. CE8N -- A new generation of HF modified stainless steel for refinery service

    SciTech Connect

    Gapinski, G.E.

    1995-11-01

    A new generation of HF Modified stainless steel has been developed for hydrocracker/hydrotreater transfer line piping system applications. The new alloy, CE8N, contains lower carbon and higher nitrogen than previous versions of HF Modified. This new alloy offers improved aged toughness, increased resistance to sensitization, and enhanced polythionic acid-stress corrosion cracking resistance. Strength levels of the new alloy are somewhat below CE20N at temperatures up to 850 F (454 C).

  1. Evolution of magnetic properties and microstructure of Hf2Co11B alloys

    NASA Astrophysics Data System (ADS)

    McGuire, Michael A.; Rios, Orlando

    2015-02-01

    Amorphous Hf2Co11B alloys produced by melt-spinning have been crystallized by annealing at 500-800 °C, and the products have been investigated using magnetization measurements, x-ray diffraction, and scanning electron microscopy. The results reveal the evolution of the phase fractions, microstructure, and magnetic properties with both annealing temperature and time. Crystallization of the phase denoted HfCo7, which is associated with the development of coercivity, occurs slowly at 500 °C. Annealing at intermediate temperatures produces mixed phase samples containing some of the HfCo7 phase with the highest values of remanent magnetization and coercivity. The equilibrium structure at 800 °C contains HfCo3B2, Hf6Co23, and Co, and displays soft ferromagnetism. Maximum values for the remanent magnetization, intrinsic coercivity, and magnetic energy product among the samples are approximately 5.2 kG, 2.0 kOe, and 3.1 MGOe, respectively, which indicates that the significantly higher values observed in crystalline, melt-spun Hf2Co11B ribbons are a consequence of the non-equilibrium solidification during the melt-spinning process. Application of high magnetic fields during annealing is observed to strongly affect the microstructural evolution, which may provide access to higher performance materials in Zr/Hf-Co hard ferromagnets. The crystal structure of HfCo7 and the related Zr analogues is unknown, and without knowledge of atomic positions powder diffraction cannot distinguish among proposed unit cells and symmetries found in the literature.

  2. Evolution of magnetic properties and microstructure of Hf2Co11B alloys

    SciTech Connect

    McGuire, Michael A.; Rios, Orlando

    2015-02-05

    Amorphous Hf2Co11B alloys produced by melt-spinning have been crystallized by annealing at 500-800 °C, and the products have been investigated using magnetization measurements, x-ray diffraction, and scanning electron microscopy. The results reveal the evolution of the phase fractions, microstructure, and magnetic properties with both annealing temperature and time. Crystallization of the phase denoted HfCo7, which is associated with the development of coercivity, occurs slowly at 500 °C. Annealing at intermediate temperatures produces mixed phase samples containing some of the HfCo7 phase with the highest values of remanent magnetization and coercivity. The equilibrium structure at 800 °C contains HfCo3B2, Hf6Co23 and Co, and displays soft ferromagnetism. Maximum values for the remanent magnetization, intrinsic coercivity, and magnetic energy product among the samples are approximately 5.2 kG, 2.0 kOe, and 3.1 MGOe, respectively, which indicates that the significantly higher values observed in crystalline, melt-spun Hf2Co11B ribbons are a consequence of the non-equilibrium solidification during the melt-spinning process. Application of high magnetic fields during annealing is observed to strongly affect the microstructural evolution, which may provide access to higher performance materials in Zr/Hf-Co hard ferromagnets. The crystal structure of HfCo7 and the related Zr analogues is unknown, and without knowledge of atomic positions powder diffraction cannot distinguish among proposed unit cells and symmetries found in the literature.

  3. Ultrathin Hf0.5Zr0.5O2 Ferroelectric Films on Si.

    PubMed

    Chernikova, Anna; Kozodaev, Maksim; Markeev, Andrei; Negrov, Dmitrii; Spiridonov, Maksim; Zarubin, Sergei; Bak, Ohheum; Buragohain, Pratyush; Lu, Haidong; Suvorova, Elena; Gruverman, Alexei; Zenkevich, Andrei

    2016-03-23

    Because of their immense scalability and manufacturability potential, the HfO2-based ferroelectric films attract significant attention as strong candidates for application in ferroelectric memories and related electronic devices. Here, we report the ferroelectric behavior of ultrathin Hf0.5Zr0.5O2 films, with the thickness of just 2.5 nm, which makes them suitable for use in ferroelectric tunnel junctions, thereby further expanding the area of their practical application. Transmission electron microscopy and electron diffraction analysis of the films grown on highly doped Si substrates confirms formation of the fully crystalline non-centrosymmetric orthorhombic phase responsible for ferroelectricity in Hf0.5Zr0.5O2. Piezoresponse force microscopy and pulsed switching testing performed on the deposited top TiN electrodes provide further evidence of the ferroelectric behavior of the Hf0.5Zr0.5O2 films. The electronic band lineup at the top TiN/Hf0.5Zr0.5O2 interface and band bending at the adjacent n(+)-Si bottom layer attributed to the polarization charges in Hf0.5Zr0.5O2 have been determined using in situ X-ray photoelectron spectroscopy analysis. The obtained results represent a significant step toward the experimental implementation of Si-based ferroelectric tunnel junctions.

  4. The molecular frame electric dipole moment and hyperfine interactions in hafnium fluoride, HfF.

    PubMed

    Le, Anh; Steimle, Timothy C; Skripnikov, Leonid; Titov, Anatoly V

    2013-03-28

    The (1,0) [17.9]2.5-X(2)Δ(3∕2) band of hafnium monofluoride (HfF) has been recorded using high-resolution laser-induced fluorescence spectroscopy both field-free and in the presence of a static electric field. The field-free spectra of (177)HfF, (179)HfF, and (180)HfF were modeled to generate a set of fine and hyperfine parameter for the X(2)Δ(3∕2)(v = 0) and [17.9]2.5 (v = 1) states. The observed optical Stark shifts for the (180)HfF isotopologue were analyzed to produce the molecular frame electric dipole moments of 1.66(1) D and 0.419(7) D for the X(2)Δ(3∕2) and [17.9]2.5 state, respectively. Both the generalized effective core potential and all-electron four component approaches were used in ab initio calculations to predict the properties of ground state HfF including equilibrium distance, dipole moments, quadrupole coupling, and magnetic hyperfine constants.

  5. Quadrupole moment measurements for strongly deformed bands in {sup 171,172}Hf

    SciTech Connect

    Mukhopadhyay, S.; Ma, W. C.; Ijaz, Q. A.; Marsh, J.; Yadav, R. B.; Janssens, R. V. F.; Carpenter, M. P.; Khoo, T. L.; Lauritsen, T.; Zhu, S.; Chiara, C. J.; Chowdhury, P.; Hota, S. S.; Lakshmi, S.; Cullen, D. M.; Hagemann, G. B.; Hartley, D. J.; Kondev, F. G.; Riedinger, L. L.; Toh, Y.

    2011-04-15

    A lifetime experiment, using the Doppler-shift attenuation method, has been performed at Gammasphere to measure the transition quadrupole moments Q{sub t} of strongly deformed bands in {sup 171}Hf and {sup 172}Hf. The measured value of Q{sub t} {approx} 9.5 e b for the band labeled ED in {sup 171}Hf strongly supports the recent suggestion that this sequence and several structures with similar properties in neighboring Hf isotopes are associated with a near-prolate shape with a deformation enhanced relative to that of normal deformed structures. The measured values of Q{sub t} {approx} 14 e b for the bands labeled SD1 and SD3 in {sup 172}Hf confirm that these sequences are associated with a prolate superdeformed shape, a property inferred in earlier work from other measured characteristics of the bands. Similar bands in {sup 173-175}Hf are also likely to be associated with superdeformed shapes. The observations are in contrast to predictions of cranking calculations performed with the ultimate cranker code.

  6. Epidermal lipids and the natural history of hydrofluoric acid (HF) injury.

    PubMed

    Noonan, T; Carter, E J; Edelman, P A; Zawacki, B E

    1994-06-01

    To explain several fortuitous observations, we hypothesized that there is a naturally occurring lipid 'barrier' to HF injury in guinea-pig skin and sought to characterize both the barrier and its role in the natural history of such injuries. Under anaesthesia, the dorsal trunk skin of groups of guinea-pigs was gently clipped of hair, washed with chloroform, soap and water, acetone or nothing (controls), and examined histologically for the presence of neutral lipid. Thereafter, in animal groups similarly washed, 1.5 in x 1.5 in (38 mm x 38 mm) areas were exposed to 40 per cent HF for up to 50 min and: (a) mean percentages of exposed areas with gross necrosis 5 days postinjury plotted on dose-response curves; or (b) less than 4 h after exposure to HF, intra-aortic India ink was injected and skin specimens examined to discern depth of ischaemia and necrosis. In contrast to controls, washing reduced neutral lipid in epidermis and significantly (at P < 0.001) increased susceptibility to injury by HF. With very rare (but interesting) exceptions, HF injury was found to be full thickness in depth with ischaemia and coagulative necrosis. In this study, development of guinea-pig skin necrosis due to HF was typically an 'all-or-nothing' 'barrier-penetration' phenomenon relating as much to the integrity of an epidermal lipid barrier as to the duration and intensity of noxious exposure.

  7. ELF/VLF wave generation from the beating of two HF ionospheric heating sources

    NASA Astrophysics Data System (ADS)

    Cohen, M. B.; Moore, R. C.; Golkowski, M.; Lehtinen, N. G.

    2012-12-01

    It is well established that Extremely Low Frequency (ELF, 0.3-3 kHz) and Very Low Frequency (VLF, 3-30 kHz) radio waves can be generated via modulated High Frequency (HF, 3-10 MHz) heating of the lower ionosphere (60-100 km). The ionospheric absorption of HF power modifies the conductivity of the lower ionosphere, which in the presence of natural currents such as the auroral electrojet, creates an `antenna in the sky.' We utilize a theoretical model of the HF to ELF/VLF conversion and the ELF/VLF propagation, and calculate the amplitudes of the generated ELF/VLF waves when two HF heating waves, separated by the ELF/VLF frequency, are transmitted from two adjacent locations. The resulting ELF/VLF radiation pattern exhibits a strong directional dependence (as much as 15 dB) that depends on the physical spacing of the two HF sources. This beat wave source can produce signals 10-20 dB stronger than those generated using amplitude modulation, particularly for frequencies greater than 5-10 kHz. We evaluate recent suggestions that beating two HF waves generates ELF/VLF waves in the F-region (>150 km), and conclude that those experimental results may have misinterpreted, and can be explained strictly by the much more well established D region mechanism.

  8. Power-Stepped HF Cross-Modulation Experiments: Simulations and Experimental Observations

    NASA Astrophysics Data System (ADS)

    Greene, S.; Moore, R. C.

    2014-12-01

    High frequency (HF) cross modulation experiments are a well established means for probing the HF-modified characteristics of the D-region ionosphere. The interaction between the heating wave and the probing pulse depends on the ambient and modified conditions of the D-region ionosphere. Cross-modulation observations are employed as a measure of the HF-modified refractive index. We employ an optimized version of Fejer's method that we developed during previous experiments. Experiments were performed in March 2013 at the High Frequency Active Auroral Research Program (HAARP) observatory in Gakona, Alaska. During these experiments, the power of the HF heating signal incrementally increased in order to determine the dependence of cross-modulation on HF power. We found that a simple power law relationship does not hold at high power levels, similar to previous ELF/VLF wave generation experiments. In this paper, we critically compare these experimental observations with the predictions of a numerical ionospheric HF heating model and demonstrate close agreement.

  9. HfO{sub x}N{sub y} gate dielectric on p-GaAs

    SciTech Connect

    Dalapati, G. K.; Sridhara, A.; Wong, A. S. W.; Chia, C. K.; Chi, D. Z.

    2009-02-16

    Plasma nitridation method is used for nitrogen incorporation in HfO{sub 2} based gate dielectrics for future GaAs-based devices. The nitrided HfO{sub 2} (HfO{sub x}N{sub y}) films on p-GaAs improve metal-oxide-semiconductor device characteristics such as interface state density, accumulation capacitance, hysteresis, and leakage current. An equivalent oxide thickness of 3.6 nm and a leakage current density of 10{sup -6} A cm{sup -2} have been achieved at V{sub FB}-1 V for nitrided HfO{sub 2} films. A nitride interfacial layer (GaAsO:N) was observed at HfO{sub 2}-GaAs interface, which can reduce the outdiffusion of elemental Ga and As during post-thermal annealing process. Such suppression of outdiffusion led to a substantial enhancement in the overall dielectric properties of the HfO{sub 2} film.

  10. Electronic structure characterization of La incorporated Hf-based high-k gate dielectrics by NEXAFS.

    PubMed

    Yamamoto, Takashi; Ogawa, Singo; Kunisu, Masahiro; Tsuji, Junichi; Kita, Koji; Saeki, Masayuki; Oku, Yudai; Arimura, Hiroaki; Kitano, Naomu; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2011-04-01

    The electronic structures of lanthunum (La) incorporated hafnium (Hf)-based oxides (HfLaO) and their silicate (HfLaSiO) films were investigated by the Near Edge X-ray Absorption Fine Structure (NEXAFS) technique. The oxygen (O) K-edge spectra, which reflected the hybridized Hf 5d state with the O 2p orbital, were found to reveal features of the unoccupied state of the metal oxides, as well as the conduction-band edge. We also found that, while La incorporation into the Hf-based oxides simply changed the features of the conduction-band structure, subsequent thermal annealing of the La-incorporated films led to a conduction-band edge shift due to an interface silicate reaction and/or local bond rearrangement depending on the La concentration and annealing temperature. The impact of La incorporation into the Hf-based high-k materials on the electronic structure is discussed by taking into account the intrinsic nature of these metal oxides.

  11. Hf, Zr, and REE partition coefficients between ilmenite and liquid - Implications for lunar petrogenesis

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.; Fujimaki, H.; Nakamura, N.; Tatsumoto, M.; Mckay, G. A.

    1986-01-01

    Partition coefficients (D) between ilmenite and coexisting liquid were determined under near-lunar conditions for Hf, Zr, and REE. Through isotope dilution analysis, ilmenite D values of 0.41 and 0.33 were obtained for Hf and Zr respectively, values significantly lower than those of ilmenite from a kimberlite megacryst. Partition coefficients of REE for the synthesized ilmenite are slightly smaller than those of ilmenite from the kimberlite megacryst, and the lunar (Lu) partition coefficient is 0.056. These results suggest that ilmenite was significant in the lunar-Hf evolution of lunar mare basalts. Using lunar and Hf D values for ilmenite, the Lu-Hf evolution of lunar cumulates and the coexisting magma was examined for various crystallization sequences. The Lu-Hf variation trend of most high-Ti mare basalts is explained by a small degree of partial cumulate melting, though a higher degree is required to explain the variation of very low-Ti basalts, green glass, and Apollo 12 low-Ti basalts. Apollo 15 low-Ti basalts may require chromite crystallization as well.

  12. Partition coefficients of Hf, Zr, and REE between phenocrysts and groundmasses

    NASA Technical Reports Server (NTRS)

    Fujimaki, H.; Tatsumoto, M.; Aoki, K.-I.

    1984-01-01

    Partition coefficients of Hf, Zr, and REE between olivine, orthopyroxene, clinopyroxene, plagioclase, garnet, amphibole, ilmenite, phlogopite, and liquid are presented. Samples consist of megacrysts in kimberlite, phenocrysts in alkaline basalts, tholeiitic basalts and andesitic to dacitic rocks, and synthetic garnet and clinopyroxene in Hawaiian tholeiites. The Hf-Lu and Zr-Lu elemental fractionations are as large as the Lu-Sm or Lu-Nd fractionation. The Hf and Zr partition coefficients between mafic phenocrysts and liquids are smaller than the Lu partition coefficients, but are similar to the Nd or Sm partition coefficients. The Hf and Zr partition coefficients between ilmenite, phlogopite, and liquid are larger than the Lu partition coefficients for these minerals and their corresponding liquids. The Hf-Zr elemental fractionation does not occur except for extreme fractionation involving Zr-minerals and extremely low fO2. These data have an important bearing on chronological and petrogenetic tracer studies involving the Lu-Hf isotopic system.

  13. HfCo7-Based Rare-Earth-Free Permanent-Magnet Alloys

    SciTech Connect

    Das, B; Balamurugan, B; Kumar, P; Skomski, R; Shah, VR; Shield, JE; Kashyap, A; Sellmyer, DJ

    2013-07-01

    This study presents the structural and magnetic properties of melt-spun HfCo7, HfCo7-xFex (0.25 <= x <=), and HfCo7Six (0.2 <= x <= 1.2) alloys. Appreciable permanent-magnet properties with a magnetocrystalline anisotropy of about 9.6-16.5, Mergs/cm(3), a magnetic polarization J(s) approximate to 7.2-10.6 kG, and coercivities H-c = 0.5-3.0 kOe were obtained by varying the composition of these alloys. Structural analysis reveals that the positions of x-ray diffraction peaks of HfCo7 show good agreement with those corresponding to an orthorhombic structure having lattice parameters of about a = 4.719 angstrom, b = 4.278 angstrom, and c = 8.070 angstrom. Based on these results, a model crystal structure for HfCo7 is developed and used to estimate the magnetic properties of HfCo7 using density-functional calculations, which agree with the experimental results.

  14. Microstructure of laser clad Ni- Cr- Al- Hf alloy on a γ' strengthened ni- base superalloy

    NASA Astrophysics Data System (ADS)

    Singh, Jogender; Mazumder, J.

    1988-08-01

    Alloys and coatings for alloys for improved high temperature service life under aggressive atmo-spheres are of great contemporary interest. There is a general consensus that the addition of rare earths such as Hf will provide many beneficial effects for such alloys. The laser cladding technique was used to produce Ni-Cr-AI-Hf alloys with extended solid solution of Hf. A 10 kW CO2 laser with mixed powder feed was used for laser cladding. Optical, scanning electron (SEM) and scanning transmission electron (STEM) microscopy were employed to characterize the microstructure of alloys produced during laser cladding processes. Microstructural studies revealed grain refinement, considerable in-crease in solubility of Hf in the matrix, Hf-rich precipitates, and new metastable phases. The size and morphology of γ' (Ni3Al) phase were discussed in relation to its microchemistry and the laser processing conditions. This paper will report the microstructural development in this laser clad Ni-Cr-AI-Hf alloy.

  15. Microstructure dependent filament forming kinetics in HfO2 programmable metallization cells.

    PubMed

    Clarke, Heidi; Brown, Timothy; Hu, Jianjun; Ganguli, Raj; Reed, Amber; Voevodin, Andrey; Shamberger, Patrick J

    2016-10-21

    Variability remains the principal concern for commercialization of HfO2 based resistance switching devices. Here, we investigate the role of thermal processing conditions on internal structure of atomic layer deposited HfO2 thin films, and the impact of that structure on filament forming kinetics of p+ Si/HfO2/Cu and TiN/HfO2/Cu devices. Regardless of bias polarity or electrode metal, filament formation times are at least one order of magnitude shorter in polycrystalline than in amorphous films, which we attribute to the presence of fast ion migration along grain boundaries. Within polycrystalline films, filament formation times are correlated with degree of crystalline orientation. Inter-device variability in forming time is roughly equivalent across HfO2 film processing conditions. The kinetics of filament forming are shown to be highly dependent on HfO2 microstructure, with possible implications for the inter-device variability of subsequent switching cycles. PMID:27632249

  16. The effect of silicon on the oxidation behavior of NiAlHf coating system

    NASA Astrophysics Data System (ADS)

    Dai, Pengchao; Wu, Qiong; Ma, Yue; Li, Shusuo; Gong, Shengkai

    2013-04-01

    Two types of NiAlHf coatings doped with different content of Si (1 at.% and 2 at.%) were deposited on a Ni3Al based single crystal superalloy IC32 by electron beam physical vapor deposition (EB-PVD) method, respectively. For comparison, NiAlHf coating with 0 at.% Si was also prepared. The oxidation tests were carried out at 1423 K in air. At the initial stage of oxidation, large amount of flake-like θ-Al2O3 was found on NiAlHf coating surface. However, no θ-Al2O3 was observed in 2 at.% Si doped NiAlHf coating except α-Al2O3. It revealed that the Si additions could contribute to the transformation from θ-Al2O3 to α-Al2O3. When oxidation time prolonged to 100 h, it was found that the degradation of NiAlHf coating was very severe with no residual β-phase, which was due to the serious inter-diffusion between the coating and substrate. In contrast, the inter-diffusion in Si-doped coating was reduced with some residual β-phase and R-Ni(Mo, Re) precipitates. The presence of Si could retard the inter-diffusion of elements between coating and substrate, indicating a barrier diffusion effect. As a result, the oxidation resistance of NiAlHf coating was improved significantly.

  17. Finishing and Commissioning the New Arecibo HF Facility

    NASA Astrophysics Data System (ADS)

    Sulzer, M. P.; Gonzalez, S. A.

    2011-12-01

    The imminent completion of the major tasks in the construction of the New Arecibo HF facility means that we must verify that the components are working as intended. The antenna system and the transmitters must be separately commissioned before they can be connected together so that we an be sure it will provide 83 dbW at 8.175 MHz, and 80 dbW at 5.1 MHz. The antenna system will be ready for initial testing in September. It Illuminates the 305 meter dish using dipoles near the surface of the dish transmitting upward to a wire mesh sub-reflector. There are three crossed dipoles for each of the two frequencies. The dipoles are supported on towers mounted on concrete pads underneath the dish. Each dipole element is connected to a transmitter through a three inch coax line. The tower foundations are nearly complete, and the towers will be erected in early September, and we expect to have at least one crossed dipole in place for initial testing by the end of September. We will need to make some measurements on the antenna system to ensure that it meets our requirements. One requirement is to match the antenna impedance to the transmission line and the transmitter closely enough to meet the transmitter specifications, the closer, the better. We have additional requirements; for example, it is necessary for efficient use of the facility that the polarization be close to circular. In most experiments, we want O mode excitation. If we were to transmit linear only half the power would reach the reflection height. The symmetry of the system assures that most of the conditions for achieving accurate circular polarization are met, but one condition is not: that exciting the transmitters driving the orthogonal elements at 90 degrees assures 90 degree separation in the corresponding antenna currents. One of the dipoles of each pair points toward the center of the array. If we think of the three crossed dipoles as consisting of a reference and two that are excited relative to it

  18. Dynamic NBTI effects in HfSiON.

    SciTech Connect

    Devine, Roderick A. B.; Kambour, Kenneth E.; Hjalmarson, Harold Paul; Mee, Jesse K.

    2010-12-01

    Negative bias temperature instability is an issue of critical importance as the space electronics industry evolves because it may dominate the reliability lifetime. Understanding its physical origin is therefore essential in determining how best to search for methods of mitigation. It has been suggested that the magnitude of the effect is strongly dependent on circuit operation conditions (static or dynamic modes). In the present work, we examine the time constants related to the charging and recovery of trapped charged induced by NBTI in HfSiON gate dielectric devices. In previous work, we avoided the issue of charge relaxation during acquisition of the I{sub ds}(V{sub gs}) curve by invoking a continuous stressing technique whereby {Delta}V{sub th} was extracted from a series of single point I{sub ds} measurements. This method relied heavily on determination of the initial value of the source-drain current (I{sub ds}{sup o}) prior to application of gate-source stress. In the present work we have used a new pulsed measurement system (Keithley SCS 4200-PIV) which not only removes this uncertainty but also permits dynamic measurements in which devices are AC stressed (Fig. 1a) or subjected to cycles of continued DC stresses followed by relaxation (Fig. 1b). We can now examine the charging and recovery characteristics of NBTI with higher precision than previously possible. We have performed NBTI stress experiments at room temperature on p-channel MOSFETs made with HfSiON gate dielectrics. In all cases the devices were stressed in the linear regime with V{sub ds}=-0.1V. We have defined two separate waveforms/pulse trains as illustrated in Fig 1. These were applied to the gate of the MOSFET. Firstly we examined the charging characteristics by applying an AC stress at 2.5MHz or 10Hz for different times. For a 50% duty cycle this corresponded to V{sub gs} = - 2V pulses for 200ns or 500ms followed by V{sub gs} = 0V pulses for 200ns or 500ms recovery respectively. In

  19. The New York Times ad.

    PubMed

    Hunt, M E; Kissling, F

    1993-01-01

    Feminization of patriarchal institutions is necessary in order to eliminate the exclusivity and mutuality of hierarchical, gender, class, and race stratification. The aim of this paper is to explain the history and activities surrounding the New York Times ad on Sunday, October 7, 1984 (the Catholic Statement on Pluralism and Abortion signed by Barbara Ferraro and Patricia Hussey of the Sisters of Note Dame de Namur, Rose Dominic Trapasso of the Maryknoll Sisters, and 67 other signers). The significance of this ad for Roman Catholic feminists and suggestions for new models of relationships between feminists is given. The Statement was written by Daniel Maguire and Frances Kissling and reviewed by 20 Roman Catholic ethicists. A sponsoring committee of early signers sought other support. Catholics for a Free Choice sponsored the funding for circulation of the Statement among professional societies, but not necessarily canonical communities. Publication of the entire statement in the Times was at the height of the presidential campaign. Conservative Bishops Bernard Law of Boston and John O'Connor of Boston publicly denounced Ferraro's position. The first institutional church response came on November 14, 1984, and stated that the Statement was personal opinion and contradictory to clear and constant church teachings about abortion. On November 30, 1984, Cardinal Jean Jerome Hamer of the Congregation for Religious and Secular Institutes responded to most presidents of canonical communities to request a public retraction from signers under threat of dismissal. The issue was obedience to the church. Several members of the canonical community and priests published retractions; negotiations with the Vatican began. Freedom of conscience and empowerment of canonical communities, as agents of their own lives, were given as reasons for the challenge to paternalism. The response was that women were subject to obedience within their communities and had taken public vows and were

  20. HfO{sub 2} dielectric thickness dependence of electrical properties in graphene field effect transistors with double conductance minima

    SciTech Connect

    Zhang, Cheng; Xie, Dan Xu, Jian-Long; Sun, Yi-Lin; Dai, Rui-Xuan; Li, Xian; Li, Xin-Ming; Zhu, Hong-Wei

    2015-10-14

    We investigate the electrical properties in back-gated graphene field effect transistors (GFETs) with SiO{sub 2} dielectric and different thickness of high-k HfO{sub 2} dielectric. The results show that transform characteristic (I{sub ds}–V{sub gs}) curves of GFETs are uniquely W-shaped with two charge neutrality point (left and right) in both SiO{sub 2} and HfO{sub 2} dielectric (SiO{sub 2}-GFETs and HfO{sub 2}-GFETs). The gate voltage reduces drastically in HfO{sub 2}-GFETs compared with that in SiO{sub 2}-GFETs, and it becomes much smaller with the decline of HfO{sub 2} thickness. The left charge neutrality point in I{sub d}–V{sub g} curves of all HfO{sub 2}-GFETs is negative, compared to the positive ones in SiO{sub 2}-GFETs, which means that there exists n-doping in graphene with HfO{sub 2} as bottom dielectric. We speculate that this n-doping comes from the HfO{sub 2} layer, which brings fixed charged impurities in close proximity to graphene. The carrier mobility is also researched, demonstrating a decreasing trend of hole mobility in HfO{sub 2}-GFETs contrast to that in SiO{sub 2}-GFETs. In a series of HfO{sub 2}-GFETs with different HfO{sub 2} dielectric thickness, the hole mobility shows a tendency of rise when the thickness decreases to 7 nm. The possible reason might be due to the introduced impurities into HfO{sub 2} film from atomic layer deposition process, the concentration of which varies from the thickness of HfO{sub 2} layer.

  1. HfO2 dielectric thickness dependence of electrical properties in graphene field effect transistors with double conductance minima

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Xie, Dan; Xu, Jian-Long; Li, Xin-Ming; Sun, Yi-Lin; Dai, Rui-Xuan; Li, Xian; Zhu, Hong-Wei

    2015-10-01

    We investigate the electrical properties in back-gated graphene field effect transistors (GFETs) with SiO2 dielectric and different thickness of high-k HfO2 dielectric. The results show that transform characteristic (Ids-Vgs) curves of GFETs are uniquely W-shaped with two charge neutrality point (left and right) in both SiO2 and HfO2 dielectric (SiO2-GFETs and HfO2-GFETs). The gate voltage reduces drastically in HfO2-GFETs compared with that in SiO2-GFETs, and it becomes much smaller with the decline of HfO2 thickness. The left charge neutrality point in Id-Vg curves of all HfO2-GFETs is negative, compared to the positive ones in SiO2-GFETs, which means that there exists n-doping in graphene with HfO2 as bottom dielectric. We speculate that this n-doping comes from the HfO2 layer, which brings fixed charged impurities in close proximity to graphene. The carrier mobility is also researched, demonstrating a decreasing trend of hole mobility in HfO2-GFETs contrast to that in SiO2-GFETs. In a series of HfO2-GFETs with different HfO2 dielectric thickness, the hole mobility shows a tendency of rise when the thickness decreases to 7 nm. The possible reason might be due to the introduced impurities into HfO2 film from atomic layer deposition process, the concentration of which varies from the thickness of HfO2 layer.

  2. Myths & Facts about Value-Added Analysis

    ERIC Educational Resources Information Center

    TNTP, 2011

    2011-01-01

    This paper presents myths as well as facts about value-added analysis. These myths include: (1) "Value-added isn't fair to teachers who work in high-need schools, where students tend to lag far behind academically"; (2) "Value-added scores are too volatile from year-to-year to be trusted"; (3) "There's no research behind value-added"; (4) "Using…

  3. Condom ads promote illicit sex.

    PubMed

    Kippley, J F

    1994-01-01

    Written in 1987, this opinion was republished in the wake of US President Bill Clinton's AIDS prevention media campaign promoting condom use which began January 1994, targeted at young adults aged 18-25. The author staunchly opposes condom use even though he admits that people do not consider abstinence from sex to be a serious option for the prevention of HIV/STD infection. He believes that there is no moral use of sex with a condom and that condoms have always been a sign of immorality, be it prostitution, adultery, fornication, or marital contraception. Likewise, the author laments the success enjoyed by Planned Parenthood in achieving the social acceptance of marital contraception and sex outside of marriage. The complete social acceptance of homosexual activity, however, remains to be achieved. Magazines, newspapers, and television receive income in exchange for publishing or airing advertisements. Finding offensive advertisements which promote the use of condoms against HIV infection, the author recommends writing letters of complaint to the responsible media sources. If the television stations or publications in question continue to advertise condoms to the public, stop watching them or end one's subscriptions to the particular printed media. Such action taken collectively among many individuals will reduce product sales and income, and potentially sway corporate policy against condom ads. PMID:12345946

  4. Condom ads promote illicit sex.

    PubMed

    Kippley, J F

    1994-01-01

    Written in 1987, this opinion was republished in the wake of US President Bill Clinton's AIDS prevention media campaign promoting condom use which began January 1994, targeted at young adults aged 18-25. The author staunchly opposes condom use even though he admits that people do not consider abstinence from sex to be a serious option for the prevention of HIV/STD infection. He believes that there is no moral use of sex with a condom and that condoms have always been a sign of immorality, be it prostitution, adultery, fornication, or marital contraception. Likewise, the author laments the success enjoyed by Planned Parenthood in achieving the social acceptance of marital contraception and sex outside of marriage. The complete social acceptance of homosexual activity, however, remains to be achieved. Magazines, newspapers, and television receive income in exchange for publishing or airing advertisements. Finding offensive advertisements which promote the use of condoms against HIV infection, the author recommends writing letters of complaint to the responsible media sources. If the television stations or publications in question continue to advertise condoms to the public, stop watching them or end one's subscriptions to the particular printed media. Such action taken collectively among many individuals will reduce product sales and income, and potentially sway corporate policy against condom ads.

  5. The Molecular Frame Electric Dipole Moment and Hyperfine Interactions in Hafnium Fluoride, HfF

    NASA Astrophysics Data System (ADS)

    Le, Anh; Steimle, Timothy C.; Skripnikov, Leonid; Titov, Anatoly V.

    2013-06-01

    The identification of HfF^{+} as a possible candidate for a d_{e}} measurement has stimulated new interest in the spectroscopy of both HfF^{+} and neutral HfF. Studies of the neutral are relevant because photoionization schemes can be used to produce the cations. More importantly, computational methodologies used to predict the electronic wavefunction of HfF^{+} can be effectively assessed by making a comparison of predicted and experimental properties of the neutral, which are more readily determinable. The (1,0)[17.9]2.5 -X^{2}Δ_{3/2} band of hafnium monofluoride (HfF) has been recorded using high-resolution laser-induced fluorescence spectroscopy both field-free and in the presence of a static electric field. The field-free spectra of ^{177}HfF, ^{179}HfF, and ^{180}HfF were model to generate a set of fine and hyperfine parameters for the X^{2}Δ_{3/2} (v=0) and [17.9]2.5 (v=1) states. The observed optical Stark shifts for the ^{180}HfF isotopologue were analyzed to produce the molecular frame electric dipole moments of 1.66(1)D and 0.419(7)D for the X^{2}Δ_{3/2} and [17.9]2.5 states, respectively. A two-step ab initio calculation consisting of a two-component generalized relativistic effective core potential calculation (GRECP) followed by a restoration of the proper four-component wavefunction was performed to predict the properties of ground state HfF. B. J. Barker, I. O. Antonov, V. E. Bondybey, and M. C. Heaven, J. Chem. Phys., 134, 201102 (2011). K. C. Cossel, D. N. Gresh, L. C. Sinclair, T. Coffey, L. V. Skripnikov, A. N. Petrov, N. S. Mosyagin, A. V. Titov, R. W. Field, E. R. Meyer, E. A. Cornell and J. Ye, Chem. Phys. Lett., 546, 1 (2012). M. Grau, A. E. Leanhardt, H. Loh, L. C. Sinclair, R. P. Stutz, T. S. Yahn, and E. A. Cornell, J. Mol. Spectroc., 272, 32 (2012). H. Loh, R. P. Stutz, T. S. Yahn, H. Looser, R. W. Field, and E. A. Cornell, J. Mol. Spectroc.,276-277, 49 (2012).

  6. Hf Isotope Geochemistry of USGS Reference Materials and Various Labware: Insight into Potential Contaminant Sources

    NASA Astrophysics Data System (ADS)

    Weis, D.; Nobre Silva, I.; Kieffer, B.; Barling, J.; Pretorius, W.; Maerschalk, C.

    2005-12-01

    We have undertaken a high-precision geochemical and isotopic study of USGS reference materials by HR-ICP-MS, TIMS and MC-ICP-MS, including basalt (BCR-1,2; BHVO-1,2), andesite (AGV-1,2), rhyolite (RGM-1), syenite (STM-1,2), granodiorite (GSP-2), and granite (G-2,3). Only a few 176Hf/177Hf results are published on these materials and with the increased use of MC-ICP-MS it is critical to build a solid reference database. Standard hotplate dissolution was used, except for granitoid compositions where it involved a high-pressure bomb procedure. The reproducibility of 176Hf/177Hf is better than 100 ppm for granitoid compositions (G-2: 0.282523±8; G-3: 0.282505±20; GSP-2: 0.282059±27) and better than 65 ppm for basaltic/andesitic compositions in glassware and better than 30 ppm in teflon (BCR-2: 0.282872±9; BHVO-2: 0.283103±6). Overall, our results agree with the rare published data (BCR-1&2, BHVO-1 and RGM-1). Slight differences appear depending on the chemical procedure used to separate Hf and the type of labware used. There are systematic shifts in 176Hf/177Hf for basaltic compositions towards lower values (by 100-150 ppm) when non-teflon material is used. As a result, we then carried out a systematic trace element and isotopic study of various labware, including borosilicate glass and quartz columns and frits. Maximum concentrations (in ppm) of these materials (in the order listed above) are: Hf=16-0.3-22, Nd=0.8-0.1-23, Sr=8-0.08-16, Pb=1.4-0.5-14. The frit material appears the most variable in elemental concentration and isotopic composition, which might reflect various accumulations resulting from column chemistry. 176Hf/177Hf is 0.282198±4 in borosilicate glass and even lower in some of the frit material (<0.28195). Only a small amount of such unradiogenic material can account for the shifts observed in basaltic rocks. Our systematic study shows that careful analyses of rock reference materials with different compositional matrices are necessary, in

  7. Hard magnetic property enhancement of Co{sub 7}Hf-based ribbons by boron doping

    SciTech Connect

    Chang, H. W.; Liao, M. C.; Shih, C. W.; Chang, W. C.; Yang, C. C.; Hsiao, C. H.; Ouyang, H.

    2014-11-10

    Hard magnetic property enhancement of melt spun Co{sub 88}Hf{sub 12} ribbons by boron doping is demonstrated. B-doping could not only remarkably enhance the magnetic properties from energy product ((BH){sub max}) of 2.6 MGOe and intrinsic coercivity ({sub i}H{sub c}) of 1.5 kOe for B-free Co{sub 88}Hf{sub 12} ribbons to (BH){sub max} = 7.7 MGOe and {sub i}H{sub c} = 3.1 kOe for Co{sub 85}Hf{sub 12}B{sub 3} ribbons but also improve the Curie temperature (T{sub C}) of 7:1 phase. The (BH){sub max} value achieved in Co{sub 85}Hf{sub 12}B{sub 3} ribbons is the highest in Co-Hf alloy ribbons ever reported, which is about 15% higher than that of Co{sub 11}Hf{sub 2}B ribbons spun at 16 m/s [M. A. McGuire, O. Rios, N. J. Ghimire, and M. Koehler, Appl. Phys. Lett. 101, 202401 (2012)]. The structural analysis confirms that B enters the orthorhombic Co{sub 7}Hf (7:1) crystal structure as interstitial atoms, forming Co{sub 7}HfB{sub x}, in the as-spun state. Yet B may diffuse out from the 7:1 phase after post-annealing, leading to the reduction of Curie temperature and the magnetic properties. The uniformly refined microstructure with B-doping results in high remanence (B{sub r}) and improves the squareness of demagnetization curve. The formation of interstitial-atom-modified Co{sub 7}HfB{sub x} phase and the microstructure refinement are the main reasons to give rise to the enhancement of hard magnetic properties in the B-containing Co{sub 7}Hf-based ribbons.

  8. A study of the structure of the ν1(HF) absorption band of the СH3СN…HF complex

    NASA Astrophysics Data System (ADS)

    Gromova, E. I.; Glazachev, E. V.; Bulychev, V. P.; Koshevarnikov, A. M.; Tokhadze, K. G.

    2015-09-01

    The ν1(HF) absorption band shape of the CH3CN…HF complex is studied in the gas phase at a temperature of 293 K. The spectra of gas mixtures CH3CN/HF are recorded in the region of 4000-3400 cm-1 at a resolution from 0.1 to 0.005 cm-1 with a Bruker IFS-120 HR vacuum Fourier spectrometer in a cell 10 cm in length with wedge-shaped sapphire windows. The procedure used to separate the residual water absorption allows more than ten fine-structure bands to be recorded on the low-frequency wing of the ν1(HF) band. It is shown that the fine structure of the band is formed primarily due to hot transitions from excited states of the low-frequency ν7 librational vibration. Geometrical parameters of the equilibrium nuclear configuration, the binding energy, and the dipole moment of the complex are determined from a sufficiently accurate quantum-chemical calculation. The frequencies and intensities for a number of spectral transitions of this complex are obtained in the harmonic approximation and from variational solutions of anharmonic vibrational problems.

  9. Laser-clad Ni70Al20Cr7Hf3 alloys with extended solid solution of Hf: Part I. Microstructure evolution

    NASA Astrophysics Data System (ADS)

    Sircar, S.; Ribaudo, C.; Mazumder, J.

    1989-11-01

    Coatings for superalloys for extended service in atmospheres at high temperature are of great interest at present. The addition of reactive elements (RE’s) such as Hf to these coatings has a pronounced effect on their high-temperature oxidation resistance. A laser-cladding technique was used to produce Ni-Al-Cr-Hf alloys with an extended solid solution of Hf in a nearstoichiometric Ni3Al matrix. A 10 kW CO2 laser with mixed powder feed was used for the cladding process. Scanning electron microscope (SEM), transmission electron microscope (TEM), and scanning transmission electron microscope (STEM) were employed for studies of microstructural evolution of alloys produced during the laser-cladding process. Microstructural studies reveal the formation of dendrites with a solid solubility of about 11 to 14 wt pct Hf and also a eutectic structure. Convergent-beam techniques and X-ray spectroscopy have been applied to characterize the phases formed during the cladding process.

  10. 27 CFR 19.456 - Adding denaturants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Adding denaturants. 19.456... Denaturation § 19.456 Adding denaturants. Denaturants and spirits shall be mixed in packages, tanks, or bulk... proprietor shall submit a flow diagram of the intended process or method of adding denaturants. (Sec....

  11. 16 CFR 460.18 - Insulation ads.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Insulation ads. 460.18 Section 460.18 Commercial Practices FEDERAL TRADE COMMISSION TRADE REGULATION RULES LABELING AND ADVERTISING OF HOME INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation...

  12. 16 CFR 460.18 - Insulation ads.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Insulation ads. 460.18 Section 460.18 Commercial Practices FEDERAL TRADE COMMISSION TRADE REGULATION RULES LABELING AND ADVERTISING OF HOME INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation...

  13. 16 CFR 460.18 - Insulation ads.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 1 2013-01-01 2013-01-01 false Insulation ads. 460.18 Section 460.18 Commercial Practices FEDERAL TRADE COMMISSION TRADE REGULATION RULES LABELING AND ADVERTISING OF HOME INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation...

  14. 16 CFR 460.18 - Insulation ads.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 1 2014-01-01 2014-01-01 false Insulation ads. 460.18 Section 460.18 Commercial Practices FEDERAL TRADE COMMISSION TRADE REGULATION RULES LABELING AND ADVERTISING OF HOME INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation...

  15. 16 CFR 460.18 - Insulation ads.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Insulation ads. 460.18 Section 460.18 Commercial Practices FEDERAL TRADE COMMISSION TRADE REGULATION RULES LABELING AND ADVERTISING OF HOME INSULATION § 460.18 Insulation ads. (a) If your ad gives an R-value, you must give the type of insulation...

  16. New Features in the ADS Abstract Service

    NASA Technical Reports Server (NTRS)

    Eichhorn, Guenther; Accomazzi, Alberto; Grant, Carolyn S.; Kurtz, Michael J.; Henneken, Edwin A.; Thompson, Donna M.; Murray, Stephen S.

    2005-01-01

    The NASA-ADS Abstract Service provides a sophisticated search capability for the literature in Astronomy, Planetary Sciences, Physics/Geophysics, and Space Instrumentation. The ADS is funded by NASA and access to the ADS services is free to anybody world-wide without restrictions. It allows the user to search the literature by author, title, and abstract text.

  17. Value Added and Other Related Matters.

    ERIC Educational Resources Information Center

    Whitla, Dean K.

    The term "value added" refers to the assessment of the amount of learning that takes place during the college years. Two experiments, Value Added I and Value Added II, attempted to measure college students' attainment of eight liberal education objectives: (1) writing ability; (2) analytical ability; (3) sensitivity to ethics, morals, and values;…

  18. High energy QCD from Planckian scattering in AdS space and the Froissart bound

    SciTech Connect

    Kang, Kyungsik; Nastase, Horatiu

    2005-11-15

    We reanalyze high-energy QCD scattering regimes from scattering in cutoff AdS space via gravity-gauge dualities (a la Polchinski-Strassler). We look at 't Hooft scattering, Regge behavior, and black hole creation in AdS space. Black hole creation in the gravity dual is analyzed via gravitational shockwave collisions. We prove the saturation of the QCD Froissart unitarity bound, corresponding to the creation of black holes of AdS size, as suggested by Giddings.

  19. REE and Hf distribution among mineral phases in the CV-CK clan: A way to explain present-day Hf isotopic variations in chondrites

    NASA Astrophysics Data System (ADS)

    Martin, Céline; Debaille, Vinciane; Lanari, Pierre; Goderis, Steven; Vandendael, Isabelle; Vanhaecke, Frank; Vidal, Olivier; Claeys, Philippe

    2013-11-01

    Chondrites are among the most primitive objects in the Solar System and constitute the main building blocks of telluric planets. Among the radiochronometers currently used for dating geological events, Sm-Nd and Lu-Hf are both composed of refractory, lithophile element. They are thought to behave similarly as the parent elements (Sm and Lu) are generally less incompatible than the daughter elements (Nd and Hf) during geological processes. As such, their respective average isotopic compositions for the solar system should be well defined by the average of chondrites, called Chondritic Uniform Reservoir (CHUR). However, while the Sm-Nd isotopic system shows an actual spread of less than 4% in the average chondritic record, the Lu-Hf system shows a larger variation range of 28% [Bouvier A., Vervoort J. D. and Patchett P. J. (2008) The Lu-Hf and Sm-Nd isotopic composition of CHUR: Constraints from unequilibrated chondrites and implications for the bulk composition of terrestrial planets. Earth Planet. Sci. Lett.273, 48-57]. To better understand the contrast between Sm-Nd and Lu-Hf systems, the REE and Hf distribution among mineral phases during metamorphism of Karoonda (CK) and Vigarano-type (CV) carbonaceous chondrites has been examined. Mineral modes were determined from elemental mapping on a set of five CK chondrites (from types 3-6) and one CV3 chondrite. Trace-element patterns are obtained for the first time in all the chondrite-forming minerals of a given class (CK chondrites) as well as one CV3 sample. This study reveals that REE are distributed among both phosphates and silicates. Only 30-50% of Sm and Nd are stored in phosphates (at least in chondrites types 3-5); as such, they are not mobilized during early stages of metamorphism. The remaining fraction of Sm and Nd is distributed among the same mineral phases; these elements are therefore not decoupled during metamorphism. Of the whole-rock total of Lu, the fraction held in phosphate decreases significantly

  20. The thermal and electrical properties of the promising semiconductor MXene Hf2CO2

    PubMed Central

    Zha, Xian-Hu; Huang, Qing; He, Jian; He, Heming; Zhai, Junyi; Francisco, Joseph S.; Du, Shiyu

    2016-01-01

    With the growing interest in low dimensional materials, MXenes have also attracted considerable attention recently. In this work, the thermal and electrical properties of oxygen-functionalized M2CO2 (M = Ti, Zr, Hf) MXenes are investigated using first-principles calculations. Hf2CO2 is determined to exhibit a thermal conductivity better than MoS2 and phosphorene. The room-temperature thermal conductivity along the armchair direction is determined to be 86.25~131.2 Wm−1 K−1 with a flake length of 5~100 μm. The room temperature thermal expansion coefficient of Hf2CO2 is 6.094 × 10−6 K−1, which is lower than that of most metals. Moreover, Hf2CO2 is determined to be a semiconductor with a band gap of 1.657 eV and to have high and anisotropic carrier mobility. At room temperature, the Hf2CO2 hole mobility in the armchair direction (in the zigzag direction) is determined to be as high as 13.5 × 103 cm2V−1s−1 (17.6 × 103 cm2V−1s−1). Thus, broader utilization of Hf2CO2, such as the material for nanoelectronics, is likely. The corresponding thermal and electrical properties of Ti2CO2 and Zr2CO2 are also provided. Notably, Ti2CO2 presents relatively lower thermal conductivity but much higher carrier mobility than Hf2CO2. According to the present results, the design and application of MXene based devices are expected to be promising. PMID:27302597

  1. The thermal and electrical properties of the promising semiconductor MXene Hf2CO2

    NASA Astrophysics Data System (ADS)

    Zha, Xian-Hu; Huang, Qing; He, Jian; He, Heming; Zhai, Junyi; Francisco, Joseph S.; Du, Shiyu

    2016-06-01

    With the growing interest in low dimensional materials, MXenes have also attracted considerable attention recently. In this work, the thermal and electrical properties of oxygen-functionalized M2CO2 (M = Ti, Zr, Hf) MXenes are investigated using first-principles calculations. Hf2CO2 is determined to exhibit a thermal conductivity better than MoS2 and phosphorene. The room-temperature thermal conductivity along the armchair direction is determined to be 86.25~131.2 Wm‑1 K‑1 with a flake length of 5~100 μm. The room temperature thermal expansion coefficient of Hf2CO2 is 6.094 × 10‑6 K‑1, which is lower than that of most metals. Moreover, Hf2CO2 is determined to be a semiconductor with a band gap of 1.657 eV and to have high and anisotropic carrier mobility. At room temperature, the Hf2CO2 hole mobility in the armchair direction (in the zigzag direction) is determined to be as high as 13.5 × 103 cm2V‑1s‑1 (17.6 × 103 cm2V‑1s‑1). Thus, broader utilization of Hf2CO2, such as the material for nanoelectronics, is likely. The corresponding thermal and electrical properties of Ti2CO2 and Zr2CO2 are also provided. Notably, Ti2CO2 presents relatively lower thermal conductivity but much higher carrier mobility than Hf2CO2. According to the present results, the design and application of MXene based devices are expected to be promising.

  2. The thermal and electrical properties of the promising semiconductor MXene Hf2CO2.

    PubMed

    Zha, Xian-Hu; Huang, Qing; He, Jian; He, Heming; Zhai, Junyi; Francisco, Joseph S; Du, Shiyu

    2016-01-01

    With the growing interest in low dimensional materials, MXenes have also attracted considerable attention recently. In this work, the thermal and electrical properties of oxygen-functionalized M2CO2 (M = Ti, Zr, Hf) MXenes are investigated using first-principles calculations. Hf2CO2 is determined to exhibit a thermal conductivity better than MoS2 and phosphorene. The room-temperature thermal conductivity along the armchair direction is determined to be 86.25~131.2 Wm(-1) K(-1) with a flake length of 5~100 μm. The room temperature thermal expansion coefficient of Hf2CO2 is 6.094 × 10(-6) K(-1), which is lower than that of most metals. Moreover, Hf2CO2 is determined to be a semiconductor with a band gap of 1.657 eV and to have high and anisotropic carrier mobility. At room temperature, the Hf2CO2 hole mobility in the armchair direction (in the zigzag direction) is determined to be as high as 13.5 × 10(3) cm(2)V(-1)s(-1) (17.6 × 10(3) cm(2)V(-1)s(-1)). Thus, broader utilization of Hf2CO2, such as the material for nanoelectronics, is likely. The corresponding thermal and electrical properties of Ti2CO2 and Zr2CO2 are also provided. Notably, Ti2CO2 presents relatively lower thermal conductivity but much higher carrier mobility than Hf2CO2. According to the present results, the design and application of MXene based devices are expected to be promising. PMID:27302597

  3. Critical Parameters for Obtaining Low Particle Densities on a Si Surface in an HF-Last Process

    NASA Astrophysics Data System (ADS)

    Alay, Josep-Lluís; Verhaverbeke, Steven; Vandervorst, Wilfried; Heyns, Marc

    1993-01-01

    A study was made on the relation between particle densities and the (remaining) degree of oxidation of a cleaned (100) Si surface following different HF-treatments (HF, HF/IPA, DI-rinse). A detailed comparison between (X-ray photoelectron spectroscopy) XPS and contact angle measurements of a water droplet with the Si surface shows that the latter method is sensitive to less than 1/10 of a SiO2 monolayer on the (100)Si surface. The results obtained with XPS point out that minute amounts of suboxides (a few percentage of a monolayer) are the dominant cause for particles. On the other hand, HF-dipping time and HF bath temperature are found to be the determinant parameters in an HF-last process. In addition the quality of the rinsing water as well as the initial roughness (Si vs polysilicon) play a major role.

  4. Microstructure and Corrosion Behavior of Hf-40 Wt Pct Ti Alloy in Nitric Acid Medium for Reprocessing Applications

    NASA Astrophysics Data System (ADS)

    Jayaraj, J.; Ravi, K. R.; Mallika, C.; Kamachi Mudali, U.

    2016-09-01

    The Hf-40 wt pct Ti (Hf-Ti) alloy was developed for neutron poison application in the spent nuclear fuel reprocessing plant. The furnace-cooled Hf-Ti sample exhibited the microstructure comprising equiaxed-α, lamellar-α, and feathery-α. The water-quenched Hf-Ti sample confirmed the presence of lath and internally twinned martensite. In comparison to the furnace-cooled sample, low corrosion current density and passivation current density values obtained for the water-quenched Hf-Ti in 6 M HNO3 at 298 K (25 °C) indicated better passivation ability. The martensitic structure exhibited high hardness (660 HV) and negligible corrosion rate in 6 M nitric acid at 298 K (25 °C). X-ray photoelectron spectroscopic (XPS) analysis confirmed that passivation behavior of this alloy was due to the protective passive film composed of TiO2 and HfO2.

  5. The study of single station inverting the sea surface current by HF ground wave radar based on adjoint assimilation technology

    NASA Astrophysics Data System (ADS)

    Han, Shuzong; Yang, Hua; Xue, Wenhu; Wang, Xingchi

    2016-10-01

    This paper introduces the assimilation technology in an ocean dynamics model and discusses the feasibility of inverting the sea surface current in the detection zone by assimilating the sea current radial velocity detected by single station HF ground wave radar in ocean dynamics model. Based on the adjoint assimilation and POM model, the paper successfully inverts the sea surface current through single station HF ground wave radar in the Zhoushan sea area. The single station HF radar inversion results are also compared with the bistatic HF radar composite results and the fixed point measured results by Annderaa current meter. The error analysis shows that acquisition of flow velocity and flow direction data from the single station HF radar based on adjoint assimilation and POM model is viable and the data obtained have a high correlation and consistency with the flow field observed by HF radar.

  6. Gas-phase reaction studies of dipositive hafnium and hafnium oxide ions: generation of the peroxide HfO2(2+).

    PubMed

    Lourenço, Célia; Michelini, Maria del Carmen; Marçalo, Joaquim; Gibson, John K; Oliveira, Maria Conceição

    2012-12-27

    Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the gas-phase reactivity of Hf dipositive ions, Hf(2+)and HfO(2+), toward several oxidants: thermodynamically facile O-atom donor N(2)O, ineffective donor CO, and intermediate donors O(2), CO(2), NO, and CH(2)O. The Hf(2+) ion exhibited electron transfer with N(2)O, O(2), NO, and CH(2)O, reflecting the high ionization energy of Hf(+). The HfO(2+) ion was produced by O-atom transfer to Hf(2+) from N(2)O, O(2), and CO(2), and the HfO(2)(2+) ion by O-atom transfer to HfO(2+) from N(2)O; these reactions were fairly efficient. Density functional theory revealed the structure of HfO(2)(2+) as a peroxide. The HfO(2)(2+) ion reacted by electron transfer with N(2)O, CO(2), and CO to give HfO(2)(+). Estimates were made for the second ionization energies of Hf (14.5 ± 0.5 eV), HfO (14.3 ± 0.5 eV), and HfO(2) (16.2 ± 0.5 eV), and also for the bond dissociation energies, D[Hf(2+)-O] = 686 ± 69 kJ mol(-1) and D[OHf(2+)-O] = 186 ± 98 kJ mol(-1). The computed bond dissociation energies, 751 and 270 kJ mol(-1), respectively, are within these experimental ranges. Additionally, it was found that HfO(2)(2+) oxidized CO to CO(2) and is thus a catalyst in the oxidation of CO by N(2)O and that Hf(2+) activates methane to produce a carbene, HfCH(2)(2+).

  7. Designer HF-Based Fluorination Reagent: Highly Regioselective Synthesis of Fluoroalkenes and gem-Difluoromethylene Compounds from Alkynes

    PubMed Central

    2015-01-01

    Hydrogen fluoride (HF) and selected nonbasic and weakly coordinating (toward cationic metal) hydrogen-bond acceptors (e.g., DMPU) can form stable complexes through hydrogen bonding. The DMPU/HF complex is a new nucleophilic fluorination reagent that has high acidity and is compatible with cationic metal catalysts. The gold-catalyzed mono- and dihydrofluorination of alkynes using the DMPU/HF complex yields synthetically important fluoroalkenes and gem-difluoromethlylene compounds regioselectively. PMID:25260170

  8. Appetite and food intake after consumption of sausages with 10% fat and added wheat or rye bran.

    PubMed

    Vuholm, Stine; Jakobsen, Louise Margrethe; Sørensen, Karina Vejrum; Kehlet, Ursula; Raben, Anne; Kristensen, Mette

    2013-10-25

    The use of dietary fibers as fat-replacers in sausages gives less energy-dense and thereby healthier foods. Also, dietary fibers have been shown to induce satiety. The objectives of this study were to investigate if appetite sensations and energy intake was affected by (1) addition of dietary fibers to sausages, (2) type of dietary fibers and (3) the food matrix of the dietary fibers. In this randomized cross-over study 25 young men were served four test meals; wheat bran sausages, rye bran sausages, rye bran bread and wheat flour sausages. The test meals were served as breakfast after an overnight fast. Appetite sensations were evaluated by visual analogue scales (VAS) assessed every 30 minutes for 240 minutes followed by an ad libitum lunch meal where energy intake was calculated. Both rye bran and wheat bran sausages increased satiety (P < 0.01) and fullness (P < 0.02) and decreased hunger (P < 0.001) and prospective consumption (P < 0.001) compared to wheat flour sausages. Furthermore, rye bran sausages increased satiety (P < 0.05) and fullness (P < 0.02) and decreased prospective consumption (P < 0.01) compared to rye bran bread. No differences in subsequent energy intake were observed. In conclusion, wheat and rye bran added to sausages decreased appetite sensations and thereby has a potential added health benefit beyond the role as fat-replacer. The satisfying effect of dietary fibers appears to be more pronounced when added to sausages than when added to bread, stressing the importance of food matrix and food processing.

  9. Appetite and food intake after consumption of sausages with 10% fat and added wheat or rye bran.

    PubMed

    Vuholm, Stine; Jakobsen, Louise Margrethe; Sørensen, Karina Vejrum; Kehlet, Ursula; Raben, Anne; Kristensen, Mette

    2013-10-25

    The use of dietary fibers as fat-replacers in sausages gives less energy-dense and thereby healthier foods. Also, dietary fibers have been shown to induce satiety. The objectives of this study were to investigate if appetite sensations and energy intake was affected by (1) addition of dietary fibers to sausages, (2) type of dietary fibers and (3) the food matrix of the dietary fibers. In this randomized cross-over study 25 young men were served four test meals; wheat bran sausages, rye bran sausages, rye bran bread and wheat flour sausages. The test meals were served as breakfast after an overnight fast. Appetite sensations were evaluated by visual analogue scales (VAS) assessed every 30 minutes for 240 minutes followed by an ad libitum lunch meal where energy intake was calculated. Both rye bran and wheat bran sausages increased satiety (P < 0.01) and fullness (P < 0.02) and decreased hunger (P < 0.001) and prospective consumption (P < 0.001) compared to wheat flour sausages. Furthermore, rye bran sausages increased satiety (P < 0.05) and fullness (P < 0.02) and decreased prospective consumption (P < 0.01) compared to rye bran bread. No differences in subsequent energy intake were observed. In conclusion, wheat and rye bran added to sausages decreased appetite sensations and thereby has a potential added health benefit beyond the role as fat-replacer. The satisfying effect of dietary fibers appears to be more pronounced when added to sausages than when added to bread, stressing the importance of food matrix and food processing. PMID:24512899

  10. Appetite and food intake after consumption of sausages with 10% fat and added wheat or rye bran.

    PubMed

    Vuholm, Stine; Arildsen Jakobsen, Louise Margrethe; Vejrum Sørensen, Karina; Kehlet, Ursula; Raben, Anne; Kristensen, Mette

    2014-02-01

    The use of dietary fibers as fat-replacers in sausages gives less energy-dense and thereby healthier foods. Also, dietary fibers have been shown to induce satiety. The objectives of this study were to investigate if appetite sensations and energy intake was affected by (1) addition of dietary fibers to sausages, (2) type of dietary fibers and (3) the food matrix of the dietary fibers. In this randomized cross-over study 25 young men were served four test meals; wheat bran sausages, rye bran sausages, rye bran bread and wheat flour sausages. The test meals were served as breakfast after an overnight fast. Appetite sensations were evaluated by visual analogue scales (VAS) assessed every 30 min for 240 min followed by an ad libitum lunch meal where energy intake was calculated. Both rye bran and wheat bran sausages increased satiety (P < 0.01) and fullness (P < 0.02) and decreased hunger (P < 0.001) and prospective consumption (P < 0.001) compared to wheat flour sausages. Furthermore, rye bran sausages increased satiety (P < 0.05) and fullness (P < 0.02) and decreased prospective consumption (P < 0.01) compared to rye bran bread. No differences in subsequent energy intake were observed. In conclusion, wheat and rye bran added to sausages decreased appetite sensations and thereby has a potential added health benefit beyond the role as fat-replacer. The satisfying effect of dietary fibers appears to be more pronounced when added to sausages than when added to bread, stressing the importance of food matrix and food processing. PMID:24511620

  11. Appetite and food intake after consumption of sausages with 10% fat and added wheat or rye bran.

    PubMed

    Vuholm, Stine; Arildsen Jakobsen, Louise Margrethe; Vejrum Sørensen, Karina; Kehlet, Ursula; Raben, Anne; Kristensen, Mette

    2014-02-01

    The use of dietary fibers as fat-replacers in sausages gives less energy-dense and thereby healthier foods. Also, dietary fibers have been shown to induce satiety. The objectives of this study were to investigate if appetite sensations and energy intake was affected by (1) addition of dietary fibers to sausages, (2) type of dietary fibers and (3) the food matrix of the dietary fibers. In this randomized cross-over study 25 young men were served four test meals; wheat bran sausages, rye bran sausages, rye bran bread and wheat flour sausages. The test meals were served as breakfast after an overnight fast. Appetite sensations were evaluated by visual analogue scales (VAS) assessed every 30 min for 240 min followed by an ad libitum lunch meal where energy intake was calculated. Both rye bran and wheat bran sausages increased satiety (P < 0.01) and fullness (P < 0.02) and decreased hunger (P < 0.001) and prospective consumption (P < 0.001) compared to wheat flour sausages. Furthermore, rye bran sausages increased satiety (P < 0.05) and fullness (P < 0.02) and decreased prospective consumption (P < 0.01) compared to rye bran bread. No differences in subsequent energy intake were observed. In conclusion, wheat and rye bran added to sausages decreased appetite sensations and thereby has a potential added health benefit beyond the role as fat-replacer. The satisfying effect of dietary fibers appears to be more pronounced when added to sausages than when added to bread, stressing the importance of food matrix and food processing.

  12. New Hf isotope data from the Jack Hills zircons: constraints on the Hadean crustal evolution

    NASA Astrophysics Data System (ADS)

    Amelin, Y.; Davis, D.; Lee, D.

    2004-05-01

    Here we present a follow-up of our study of the "older" population of detrital zircons from the Jack Hills metaconglomerate W-74 [1]. We report Lu-Hf data for zircon grains, which have been previously analyzed with a number of techniques: BSE and CL imaging, detailed U-Pb SHRIMP geochronology, trace element concentrations, and oxygen isotopic compositions. After completion of non-destructive SIMS analyses and imaging, the zircons were extracted from the mounts, dissolved and analyzed for U-Pb and Lu-Hf using isotope dilution. Twenty five grains were air abraded before digestion, and eight grains were digested without abrasion. Four grains were cut, and the fragments were analyzed for U-Pb and Lu-Hf separately. The 207Pb/206Pb ages determined by isotope dilution vary between 3788-4186 Ma; the maximum SHRIMP spot 207Pb/206Pb ages of the same grains are between 3871-4276 Ma. The spot 207Pb/206Pb ages averaged over each grain are close to the whole grain isotope dilution values. The U-Pb discordance depends mainly on whether the grains were abraded: the median discordance of 27 abraded grains and fragments is 2.7 (the range is -0.4 to 20.2), whereas the median discordance of 11 unabraded grains and fragments is 66.5 (the range is 20.5 to 83.5). The epsilon176Hf values, calculated using the whole grain TIMS 207Pb/206Pb ages and the 176Lu decay constant of 1.865*10-11, are between -1.4 and -10.6. Using maximum SHRIMP spot 207Pb/206Pb ages and the same decay constant yields the range of epsilon176Hf of 0.1 to -8.6. If the decay constant of 1.983*10-11 is used instead, then the range of epsilon176Hf becomes 4.7 to -5.0 using the whole grain ages, or 6.3 to -3.0 using the maximum SHRIMP spot ages. Grain fragment analyses show internal variations of initial 176Hf/177Hf in three grains out of five. This observation is consistent with multi-episodic zircon growth rather than with ancient Pb loss. In the presentation we shall discuss the prospect of reliable interpretation of

  13. Enhanced performance of supported HfO2 counter electrodes for redox couples used in dye-sensitized solar cells.

    PubMed

    Yun, Sining; Pu, Haihui; Chen, Junhong; Hagfeldt, Anders; Ma, Tingli

    2014-02-01

    Mesoporous-graphitic-carbon-supported HfO2 (HfO2 -MGC) nanohybrids were synthesized by using a soft-template route. Characterization and a systematic investigation of the catalytic properties, stability, and catalytic mechanism were performed for HfO2 -MGC counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The new HfO2 -MGC as a CE in DSSCs showed a surprisingly high efficiency of 7.75 % for the triiodide/iodide redox couple and 3.69 % for the disulfide/thiolate redox couple, greater than the Pt electrode in the corresponding electrolyte system, which opens up a possibility for its practical application.

  14. Transformation of amorphous TiO2 to a hydronium oxofluorotitanate and applications as an HF sensor

    SciTech Connect

    Appelhans, Leah N.; Finnegan, Patrick S.; Massey, Lee T.; Luk, Ting S.; Rodriguez, Mark A.; Brumbach, Michael T.; McKenzie, Bonnie; Craven, Julia M.

    2015-12-24

    We examined amorphous titania thin films for use as the active material in a polarimetry based HF sensor. The amorphous titania films were found to be sensitive to vapor phase HF and the reaction product was identified as a hydronium oxofluorotitanate phase, which has previously only been synthesized in aqueous solution. The extent of reaction varied both with vapor phase HF concentration, relative humidity, and the exposure time. HF concentrations as low as 1 ppm could be detected for exposure times of 120 h.

  15. Transformation of amorphous TiO2 to a hydronium oxofluorotitanate and applications as an HF sensor

    DOE PAGES

    Appelhans, Leah N.; Finnegan, Patrick S.; Massey, Lee T.; Luk, Ting S.; Rodriguez, Mark A.; Brumbach, Michael T.; McKenzie, Bonnie; Craven, Julia M.

    2015-12-24

    We examined amorphous titania thin films for use as the active material in a polarimetry based HF sensor. The amorphous titania films were found to be sensitive to vapor phase HF and the reaction product was identified as a hydronium oxofluorotitanate phase, which has previously only been synthesized in aqueous solution. The extent of reaction varied both with vapor phase HF concentration, relative humidity, and the exposure time. HF concentrations as low as 1 ppm could be detected for exposure times of 120 h.

  16. Measurements of hf auroral clutter using the verona ava linear array radar (VALAR). Report for June 1990-June 1991

    SciTech Connect

    Choi, D.S.; Weijers, B.; Myers, N.B.

    1994-03-01

    Measurements of high frequency (HF) auroral clutter using the Verona Ava Linear Array Radar (VALAR) system are presented. VALAR is an experimental HF backscatter system capable of obtaining high resolution synoptic mapping of HF auroral clutter. The receive system includes a 700 meter long linear array. providing the high azimuthal resolution required for determining the spatial distribution of HF auroral clutter. Since the completion of the system at the end of 1989, data acquisition campaigns have been carried out on a near-monthly basis. In this report, the authors provide a brief description of VALAR and present preliminary measurements of three types of phenomena: ground backscatter, slant-F, and auroral backscatter.

  17. Effect of native defects and Co doping on ferromagnetism in HfO2: first-principles calculations.

    PubMed

    Han, Chong; Yan, Shi-Shen; Lin, Xue-Ling; Hu, Shu-Jun; Zhao, Ming-Wen; Yao, Xin-Xin; Chen, Yan-Xue; Liu, Guo-Lei; Mei, Liang-Mo

    2011-05-01

    First-principles calculations of undoped HfO(2) and cobalt-doped HfO(2) have been carried out to study the magnetic properties of the dielectric material. In contrast to previous reports, it was found that the native defects in HfO(2) could not induce strong ferromagnetism. However, the cobalt substituting hafnium is the most stable defect under oxidation condition, and the ferromagnetic (FM) coupling between the cobalt substitutions is favorable in various configurations. We found that the FM coupling is mediated by the threefold-coordinated oxygen atoms in monoclinic HfO(2) and could be further enhanced in electron-rich condition.

  18. First-principles study of graphene under c-HfO2(111) layers: Electronic structures and transport properties

    NASA Astrophysics Data System (ADS)

    Kaneko, Tomoaki; Ohno, Takahisa

    2016-08-01

    We investigated the electronic properties, stability, and transport of graphene under c-HfO2(111) layers by performing first-principles calculations with special attention to the chemical bonding between graphene and HfO2 surfaces. When the interface of HfO2/graphene is terminated by an O layer, the linear dispersion of graphene is preserved and the degradation of transport is suppressed. For other interface structures, HfO2 is tightly adsorbed on graphene and the transport is strictly limited. In terms of the stability of the interface structures, an O-terminated interface is preferable, which is achieved under an O-deficient condition.

  19. The effect of Si impurities on the effective work function at TiN/tetragonal-HfO2 interface

    NASA Astrophysics Data System (ADS)

    Kim, Geun-Myeong; Oh, Young Jun; Chang, Kee Joo

    The TiN/monoclinc-HfO2 (TiN/m-HfO2) interface structure is widely used in high-k/metal gate stacks of metal-oxide-semiconductor field-effect transistors. As the device size is continuously reduced, high-k dielectric materials are required to reduce the gate leakage current. The tetragonal HfO2 (t-HfO2) is beneficial in high-k/metal gate stacks because its dielectric constant is much higher than that of m-HfO2. It is known that Si doping can reduces the crystalline temperature of t-HfO2. However, there is a lack of studies for the effect of Si impurities at TiN/t-HfO2 interface. Here we perform first-principles density functional calculations to investigate the effect of Si impurities on the work function at TiN/t-HfO2 interface. It is energetically favorable for Si atoms to substitutes for interface N atoms. The change of interface bonds by the Si atoms enhances the effective work function(EWF). On the other hand, when the Si atoms replace the N atoms in bulk region, the EWF is almost unchanged. Our results indicate that the Si impurities incorporated in the interface region mostly affect the work function at TiN/t-HfO2 interface.

  20. Effect of Hf-Rich Particles on the Creep Life of a High-strength Nial Single Crystal Alloy

    NASA Technical Reports Server (NTRS)

    Garg, A.; Raj, S. V.; Darolia, R.

    1995-01-01

    Additions of small amounts of Hf and Si to NiAl single crystals significantly improve their high-temperature strength and creep properties. However, if large Hf-rich dendritic particles formed during casting of the alloyed single crystals are not dissolved completely during homogenization heat treatment, a large variation in creep rupture life can occur. This behavior, observed in five samples of a Hf containing NiAl single crystal alloy tested at 1144 K under an initial stress of 241.4 MPa, is described in detail highlighting the role of interdendritic Hf-rich particles in limiting creep rupture life.

  1. The “zircon effect” as recorded by the chemical and Hf isotopic compositions of Lesser Antilles forearc sediments

    NASA Astrophysics Data System (ADS)

    Carpentier, Marion; Chauvel, Catherine; Maury, René C.; Mattielli, Nadine

    2009-09-01

    Oceanic sediments contain the products of erosion of continental crust, biologic activity and chemical precipitation. These processes create a large diversity of their chemical and isotopic compositions. Here we focus on the influence of the distance from a continental platform on the trace element and isotopic compositions of sediments deposited on the ocean floor and highlight the role of zircons in decoupling high-field strength elements and Hf isotopic compositions from other trace elements and Nd isotopic compositions. We report major and trace element concentrations as well as Sr and Hf isotopic data for 80 sediments from the Lesser Antilles forearc region. The trace-element characteristics and the Sr and Hf isotopic compositions are generally dominated by detrital material from the continental crust but are also variably influenced by chemical or biogenic carbonate and pure biogenic silica. Next to the South American continent, at DSDP Site 144 and on Barbados Island, sediments, coarse quartz arenites, exhibit marked Zr and Hf excesses that we attribute to the presence of zircon. In contrast, the sediments from DSDP Site 543, which were deposited farther away from the continental platform, consist of fine clay and they show strong deficiencies in Zr and Hf. The enrichment or depletion of Zr-Hf is coupled to large changes in Hf isotopic compositions (- 30 < ɛHf < + 4) that vary independently from the Nd isotopes. We interpret this feature as a clear expression of the "zircon effect" suggested by Patchett and coauthors in 1984. Zircon-rich sediments deposited next to the South American continent have very low ɛHf values inherited from old zircons. In contrast, in detrital clay-rich sediments deposited a few hundred kilometers farther north, the mineral fraction is devoid of zircon and they have drastically higher ɛHf values inherited from finer, clay-rich continental material. In the two DSDP sites, average Hf isotopes are very unradiogenic relative to

  2. Atomic layer deposition HfO2 capping layer effect on porous low dielectric constant materials

    NASA Astrophysics Data System (ADS)

    Cheng, Yi-Lung; Kao, Kai-Chieh; Huang, Chi-Jia; Chen, Giin-Shan; Fang, Jau-Shiung

    2015-11-01

    Low dielectric constant (low-k) materials are used as inter-level insulators between copper (Cu) conductors to improve the characteristics of integrated circuits. This work proposes a new method for improving the characteristics of porous low-k dielectric film by capping it with an HfO2 film by atomic layer deposition (ALD). Experimental results revealed that capping a porous low-k dielectric film with a ∼1.0 nm-thick HfO2 film increases its dielectric constant from 2.56 to 2.65 because the pores in the surface of the film are sealed by Hf precursors. The leakage current density and reliability of the porous low-k dielectrics are greatly improved. The HfO2 capping film also increased resistances against Cu diffusion and damage by oxygen plasma. Therefore, this ALD-deposited HfO2 capping film can be used as a pore-sealing layer and a Cu barrier layer for the porous low-k dielectric film in the future advanced technologies.

  3. Mixed Al and Si doping in ferroelectric HfO{sub 2} thin films

    SciTech Connect

    Lomenzo, Patrick D.; Nishida, Toshikazu; Takmeel, Qanit; Zhou, Chuanzhen; Chung, Ching-Chang; Jones, Jacob L.; Moghaddam, Saeed

    2015-12-14

    Ferroelectric HfO{sub 2} thin films 10 nm thick are simultaneously doped with Al and Si. The arrangement of the Al and Si dopant layers within the HfO{sub 2} greatly influences the resulting ferroelectric properties of the polycrystalline thin films. Optimizing the order of the Si and Al dopant layers led to a remanent polarization of ∼20 μC/cm{sup 2} and a coercive field strength of ∼1.2 MV/cm. Post-metallization anneal temperatures from 700 °C to 900 °C were used to crystallize the Al and Si doped HfO{sub 2} thin films. Grazing incidence x-ray diffraction detected differences in peak broadening between the mixed Al and Si doped HfO{sub 2} thin films, indicating that strain may influence the formation of the ferroelectric phase with variations in the dopant layering. Endurance characteristics show that the mixed Al and Si doped HfO{sub 2} thin films exhibit a remanent polarization greater than 15 μC/cm{sup 2} up to 10{sup 8} cycles.

  4. Characteristics of Hf-silicate thin films synthesized by plasma enhanced atomic layer deposition

    SciTech Connect

    Liu Jiurong; Martin, Ryan M.; Chang, Jane P.

    2008-09-15

    Hafnium silicate films were grown by alternating the deposition cycles of hafnium oxide and silicon oxide using a plasma enhanced atomic layer deposition process. The as-deposited and 900 deg. C annealed hafnium silicate films were determined to be amorphous using grazing incidence x-ray diffraction. This suggested that the formation of hafnium silicate suppressed the crystallization of HfO{sub 2} at high temperatures. The dielectric constants increased from {approx}5 to {approx}17 as the hafnium content increased from 9 to 17 at. % in the hafnium silicate films. The leakage currents through the Hf-rich Hf-silicate films were two to three orders of magnitude lower than that of SiO{sub 2} with the same equivalent oxide thickness in the range of 1.6-2.3 nm. The estimated band gap of Hf-silicate films from the O 1s plasma loss spectra increased with the increasing Si content due to the higher band gap of SiO{sub 2} than that of HfO{sub 2}.

  5. Growth and thermal annealing of Cu on HfO 2

    NASA Astrophysics Data System (ADS)

    Park, H. J.; Sun, Y.-M.; Troiani, H.; Santiago, P.; Yacaman, M. J.; White, J. M.

    2002-12-01

    The interface between Cu and HfO 2 synthesized using physical vapor deposition at 300 K has been examined with in situ low-energy ion scattering (LEIS), in situ X-ray photoelectron spectroscopy (XPS) and ex situ scanning transmission electron microscopy (STEM). Cu deposited on HfO 2 at 300 K readily forms three-dimensional clusters. LEIS and XPS data show that the Cu is not oxidized at the Cu-HfO 2 interface. A proposed model allows simulation of the coverage of Cu as a function of Cu dosing time before and after thermal annealing. At 300 K, the model fits the data when two-dimensional islands cover no more than 90% of the HfO 2 surface. After thermal annealing at 673 K for 10 min under vacuum (1×10 -8 Torr), large Cu clusters are formed from smaller ones, but there is no evident diffusion into the HfO 2. For this annealed sample, STEM shows a narrow cluster diameter distribution (10-12 nm). Strain fields at the hafnia-copper interface may help limit the cluster size distribution.

  6. Proposal for ionospheric tomography technique using a new HF radio source

    NASA Astrophysics Data System (ADS)

    Wang, L.; MacDougall, J. W.

    Ionospheric tomography has developed near 20 years from a theoretical concept to a powerful experimental method and it has been used successfully to image a wide range of ionospheric structures over altitude-versus-latitude planes Measurements of the line integral of the electron density along ray paths from ground transmitter to satellite i e TEC are inverted in a reconstruction algorithm to create an image of the spatial distribution of the density over the region of interest Recent ionospheric tomography experiments use VHF UHF signals transmitted from NNSS or GPS satellite networks We propose a new signal source using transmission from ground HF radar networks and received by a satellite HF signals carry rich information about the ionosphere and sensitive to small changes HF measurements such as signal amplitude group delay DOA and Doppler frequency shift provide a priori knowledge for the tomographic image reconstruction The initial phase problem inherent in the phase or TEC measurement can be eliminated by Faraday rotation measurements and the relative rotations on two adjacent frequencies solves the ambiguity problems at HF frequencies We are currently working on the simulations and the transmitter design A great opportunity to implement this idea will come from the launch of the CASSIOPE a multi-purpose small satellite that receives HF signals from ground radar fertilities in 2007

  7. Linear magnetoresistance and zero-field anomalies in HfNiSn single crystals

    NASA Astrophysics Data System (ADS)

    Steinke, Lucia; Kistner-Morris, Jedediah J.; Deng, Haiming; Geschwind, Gayle; Aronson, Meigan C.

    The Half-Heusler compound HfNiSn is probably best known as a candidate material for thermoelectric applications, and studies of its properties have mainly focused on polycrystalline samples and thin films. However, magnetotransport studies of HfNiSn show unusual transport properties like linear magnetoresistance (LMR), where single-crystalline samples of HfNiSn exhibit unexpected LMR at very low fields. In this work, we optimized the solution growth of HfNiSn to obtain high-quality single crystals, where electrical transport measurements show that it is a compensated semimetal below ~ 200 K, where the Hall voltage is zero. At higher temperatures, we see a finite Hall contribution from activated excess carriers. In the semimetallic regime, we observe transport anomalies like resistive signals that strongly depend on contact configuration, and LMR below 5 K. Both low-field DC and low frequency AC magntization measurements show pronounced diamagnetic behavior and the onset of paramagnetism below 4 K. High-frequency diamagnetic screening may be attributed to a decreased skin depth with decreased resistance, but this scenario seems unlikely in HfNiSn since the measured resistance increases steeply at the lowest temperatures This research was supported by the Army Research Office.

  8. Microstructure and thermal stability of HfO2 gate dielectric deposited on Ge (100)

    NASA Astrophysics Data System (ADS)

    Gusev, E. P.; Shang, H.; Copel, M.; Gribelyuk, M.; D'Emic, C.; Kozlowski, P.; Zabel, T.

    2004-09-01

    We report on physical and electrical characterization of ultrathin (3-10nm) high-κHfO2 gate stacks deposited on Ge (100) by atomic-layer deposition. It is observed that uniform films of HfO2 can be deposited on Ge without significant interfacial growth. The lack of an interlayer enables quasiepitaxial growth of HfO2 on the Ge surface after wet chemical treatment whereas a nitrided interface (grown by thermal oxynitridation in ammonia) results in an amorphous HfO2. The stacks exhibit surprisingly good thermal stability, up to temperatures only 150°C below the melting point of Ge. In terms of electrical properties, HfO2 on Ge shows significantly reduced (up to 4 decades) gate leakage currents in the ultrathin regime of equivalent electrical thickness down to ˜1.4nm due to the high-dielectric constant of ˜23. Nitrided interface is observed to be important for good insulating properties of the stack.

  9. Thermoelectric Properties of Microstructurally Modified CoSb3 Skutterudite by Hf-Addition

    NASA Astrophysics Data System (ADS)

    Elsheikh, Mohamed Hamid; Sabri, Mohd Faizul Mohd; Said, Suhana Mohd; Miyazaki, Yuzuru; Masjuki, H. H.; Shnawah, Dhafer Abdul Ameer; Long, Bui Duc; Naito, Shuma; Bashir, Mohamed Bashir Ali

    2016-06-01

    A polycrystalline phase of Hf-filled CoSb3 skutterudite was successfully prepared by the mechanical alloying technique followed by the spark plasma sintering process. X-ray diffraction and scanning electron microscopy linked with energy-dispersive x-ray spectroscopy were used to investigate the result filling the void spaces with Hf. HfCo4Sb12 skutterudite possesses a very low thermal conductivity [1.8 W/(m K)], lower than that of some lanthanide-filled skutterudites, while exhibiting p-type conduction. The anharmonicity of oscillation of the loosely bond Hf atoms, the point defects on the lattice microstructure and the large area fraction of the grain boundaries were the reasons for the significant drop in the thermal conductivity of Hf-filled CoSb3. Thus, this work is useful in deriving a pathway for improvement in thermoelectrics through the introduction of smaller rattling cations with higher mass to increase the disorder of the lattice structure.

  10. The microwave spectrum and properties of the propyne-HF complex

    NASA Astrophysics Data System (ADS)

    Shea, J. A.; Bumgarner, R. E.; Henderson, Giles

    1984-05-01

    The microwave spectrum of the weakly bound propyne-HF/DF complex was recorded in the region between 6 and 16 GHz. The J=0-1 and J=1-2 a-dipole lines, each with a torsional counterpart due to internal rotation of the methyl top, were observed. The spectrum was characteristic of a distorted T-shaped asymmetric top exhibiting torsional splitting caused by a low barrier to internal rotation of the methyl top relative to the propyne-HF frame. Deuterium substitution of HF confirms that the acidic hydrogen of HF is located between the F atom and the propyne triple bond. The spectroscopic constants given below are consistent with the fluorine atom's being displaced toward the methyl group from a line perpendicular to and bisecting the propyne triple bond, suggesting a weak hydrogen bond interaction between fluorine and the methyl protons. UFRULE2 Propyne-HF Propyne-DF UFRULE1 A(MHz) 8722(9) 8644(12) B(MHz) 3919(3) 3886(6) C(MHz) 2753(1) 2728(2) Daa(kHz) ṡ ṡ ṡ -23(6) χaa(kHz) ṡ ṡ ṡ 163(6) V3(cm-1) 100(50) 100(50) UFRULE2

  11. Oxygen vacancy effects in HfO2-based resistive switching memory: First principle study

    NASA Astrophysics Data System (ADS)

    Dai, Yuehua; Pan, Zhiyong; Wang, Feifei; Li, Xiaofeng

    2016-08-01

    The work investigated the shape and orientation of oxygen vacancy clusters in HfO2-base resistive random access memory (ReRAM) by using the first-principle method based on the density functional theory. Firstly, the formation energy of different local Vo clusters was calculated in four established orientation systems. Then, the optimized orientation and charger conductor shape were identified by comparing the isosurface plots of partial charge density, formation energy, and the highest isosurface value of oxygen vacancy. The calculated results revealed that the [010] orientation was the optimal migration path of Vo, and the shape of system D4 was the best charge conductor in HfO2, which effectively influenced the SET voltage, formation voltage and the ON/OFF ratio of the device. Afterwards, the PDOS of Hf near Vo and total density of states of the system D4_010 were obtained, revealing the composition of charge conductor was oxygen vacancy instead of metal Hf. Furthermore, the migration barriers of the Vo hopping between neighboring unit cells were calculated along four different orientations. The motion was proved along [010] orientation. The optimal circulation path for Vo migration in the HfO2 super-cell was obtained.

  12. Height dependence of the observed spectrum of radar backscatter from HF-induced ionospheric Langmuir turbulence

    NASA Astrophysics Data System (ADS)

    Fejer, J. A.; Sulzer, M. P.; Djuth, F. T.

    1991-09-01

    Results are presented of observations of the spectrum of the 430-MHz radar backscatter from HF-induced Langmuir turbulence with height discrimination. During very stable ionospheric conditions under which the height of the below-threshold backscatter spectrum changed by less than 300 m during a 7-min period, a 20-s-long temporary increase in the HF power from 3 MW ERP to 38-MW-equivalent-radiated HF power is found to result in subsequent strong above-threshold spectra extending to heights up to 1200 m greater than the height of the below-threshold spectrum for more than a minute. The generation of irregularities in the plasma density during the 20 s of enhanced HF power is suggested as a possible cause of this persistence of strong above-threshold spectra at greater heights. The initial temporal evolution of the backscatter spectrum from Langmuir turbulence after the start of HF transmissions is observed for different heights. The observational results are compared with the predictions of existing theories of Langmuir turbulence.

  13. Mixed Al and Si doping in ferroelectric HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Lomenzo, Patrick D.; Takmeel, Qanit; Zhou, Chuanzhen; Chung, Ching-Chang; Moghaddam, Saeed; Jones, Jacob L.; Nishida, Toshikazu

    2015-12-01

    Ferroelectric HfO2 thin films 10 nm thick are simultaneously doped with Al and Si. The arrangement of the Al and Si dopant layers within the HfO2 greatly influences the resulting ferroelectric properties of the polycrystalline thin films. Optimizing the order of the Si and Al dopant layers led to a remanent polarization of ˜20 μC/cm2 and a coercive field strength of ˜1.2 MV/cm. Post-metallization anneal temperatures from 700 °C to 900 °C were used to crystallize the Al and Si doped HfO2 thin films. Grazing incidence x-ray diffraction detected differences in peak broadening between the mixed Al and Si doped HfO2 thin films, indicating that strain may influence the formation of the ferroelectric phase with variations in the dopant layering. Endurance characteristics show that the mixed Al and Si doped HfO2 thin films exhibit a remanent polarization greater than 15 μC/cm2 up to 108 cycles.

  14. UV-assisted room-temperature gas sensing by HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Karaduman, Irmak; Barin, Özlem; Acar, Selim

    2016-06-01

    This research paper presents a detailed study of the influence of annealing temperature and UV irradiation on the sensitivity to NO2 of HfO2 thin films that can be used for the development of metal-oxide gas sensors. The HfO2 thin films were grown with a 3.3-nm thickness by using atomic layer deposition (ALD) and were annealed at different temperatures. The HfO2 thin films were characterized by using an atomic force microscope (AFM). The roughnesses of thin films were seen to have been affected by the annealing treatment. The effects of annealing temperature, as well as the operating temperature, on the response and the recovery characteristics of the HfO2 film were investigated. The results showed that both the annealing temperature and the operating temperature had significant effects on the sensing characteristics. Also, at room-temperature operation, the sensitivity of HfO2 thin films to 5 ppm of NO2 gas in air was investigated under UV irradiation. UV irradiation not only increased the response but also reduced the response and the recovery times during the gas-sensing measurements.

  15. HF treatment effect for carbon deposition on silicon (111) by DC sputtering technique

    SciTech Connect

    Aji, A. S. Darma, Y.

    2014-03-24

    Surface modifications of Si (111) substrate by HF solution for thin film carbon deposition have been systematically studied. Thin film carbon on Si (111) has been deposited using DC Unbalanced Magnetron Sputtering with carbon pellet doped by 5% Fe as the target. EDAX characterization confirmed that the carbon fraction on Si substrate much higher by dipping a clean Si substrate by HF solution before sputtering process in comparison with carbon fraction on Si substrate just after conventional RCA. Moreover, SEM and AFM images show the uniform thin film carbon on Si with HF treatment, in contrast to the Si without HF solution treatment. These experimental results suggest that HF treatment of Si surface provide Si-H bonds on top Si surface that useful to enhance the carbon deposition during sputtering process. Furthermore, we investigate the thermal stability of thin film carbon on Si by thermal annealing process up to 900 °C. Atomic arrangements during annealing process were characterized by Raman spectroscopy. Raman spectra indicate that thin film carbon on Si is remaining unchanged until 600 °C and carbon atoms start to diffuse toward Si substrate after annealing at 900 °C.

  16. Automatic modulation classification of digital modulations in presence of HF noise

    NASA Astrophysics Data System (ADS)

    Alharbi, Hazza; Mobien, Shoaib; Alshebeili, Saleh; Alturki, Fahd

    2012-12-01

    Designing an automatic modulation classifier (AMC) for high frequency (HF) band is a research challenge. This is due to the recent observation that noise distribution in HF band is changing over time. Existing AMCs are often designed for one type of noise distribution, e.g., additive white Gaussian noise. This means their performance is severely compromised in the presence of HF noise. Therefore, an AMC capable of mitigating the time-varying nature of HF noise is required. This article presents a robust AMC method for the classification of FSK, PSK, OQPSK, QAM, and amplitude-phase shift keying modulations in presence of HF noise using feature-based methods. Here, extracted features are insensitive to symbol synchronization and carrier frequency and phase offsets. The proposed AMC method is simple to implement as it uses decision-tree approach with pre-computed thresholds for signal classification. In addition, it is capable to classify type and order of modulation in both Gaussian and non-Gaussian environments.

  17. Spectroscopic analysis of Al and N diffusion in HfO{sub 2}

    SciTech Connect

    Lysaght, P. S.; Price, J.; Kirsch, P. D.; Woicik, J. C.; Weiland, C.; Sahiner, M. A.

    2012-09-15

    X-ray photoelectron core level spectroscopy, secondary ion mass spectroscopy, spectroscopic ellipsometry, and extended x-ray absorption fine structure measurements have been employed to distinguish the effects of Al and N diffusion on the local bonding and microstructure of HfO{sub 2} and its interface with the Si substrate in (001)Si/SiO{sub x}/2 nm HfO{sub 2}/1 nm AlO{sub x} film structures. The diffusion of Al from the thin AlO{sub x} cap layer deposited on both annealed and unannealed HfO{sub 2} has been observed following anneal in N{sub 2} and NH{sub 3} ambient. Both N{sub 2} and NH{sub 3} subsequent anneals were performed to decouple incorporated nitrogen from thermal reactions alone. Causal variations in the HfO{sub 2} microstructure combined with the dependence of Al and N diffusion on initial HfO{sub 2} conditions are presented with respect to anneal temperature and ambient.

  18. The Effect of Adding Corrosion Inhibitors into an Electroless Nickel Plating Bath for Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Hu, Rong; Su, Yongyao; Liu, Hongdong; Cheng, Jiang; Yang, Xin; Shao, Zhongcai

    2016-08-01

    In this work, corrosion inhibitors were added into an electroless nickel plating bath to realize nickel-phosphorus (Ni-P) coating deposition on magnesium alloy directly. The performance of five corrosion inhibitors was evaluated by inhibition efficiency. The results showed that only ammonium hydrogen fluoride (NH4HF2) and ammonium molybdate ((NH4)2MoO4) could be used as corrosion inhibitors for magnesium alloy in the bath. Moreover, compounding NH4HF2 and (NH4)2MoO4, the optimal concentrations were both at 1.5 ~ 2%. The deposition process of Ni-P coating was observed by using a scanning electron microscope (SEM). It showed corrosion inhibitors inhibited undesired dissolution of magnesium substrate during the electroless plating process. In addition, SEM observation indicated that the corrosion inhibition reaction and the Ni2+ replacement reaction were competitive at the initial deposition time. Both electrochemical analysis and thermal shock test revealed that the Ni-P coating exhibited excellent corrosion resistance and adhesion properties in protecting the magnesium alloy.

  19. The Effect of Adding Corrosion Inhibitors into an Electroless Nickel Plating Bath for Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Hu, Rong; Su, Yongyao; Liu, Hongdong; Cheng, Jiang; Yang, Xin; Shao, Zhongcai

    2016-10-01

    In this work, corrosion inhibitors were added into an electroless nickel plating bath to realize nickel-phosphorus (Ni-P) coating deposition on magnesium alloy directly. The performance of five corrosion inhibitors was evaluated by inhibition efficiency. The results showed that only ammonium hydrogen fluoride (NH4HF2) and ammonium molybdate ((NH4)2MoO4) could be used as corrosion inhibitors for magnesium alloy in the bath. Moreover, compounding NH4HF2 and (NH4)2MoO4, the optimal concentrations were both at 1.5 ~ 2%. The deposition process of Ni-P coating was observed by using a scanning electron microscope (SEM). It showed corrosion inhibitors inhibited undesired dissolution of magnesium substrate during the electroless plating process. In addition, SEM observation indicated that the corrosion inhibition reaction and the Ni2+ replacement reaction were competitive at the initial deposition time. Both electrochemical analysis and thermal shock test revealed that the Ni-P coating exhibited excellent corrosion resistance and adhesion properties in protecting the magnesium alloy.

  20. Reduction of oxidative stress by bioaugmented strain Pseudomonas sp. HF-1 and selection of potential biomarkers in sequencing batch reactor treating tobacco wastewater.

    PubMed

    Shao, Tiejuan; Yang, Guiqin; Wang, Meizhen; Lu, Zhenmei; Min, Hang; Zhao, Long

    2010-08-01

    Oxidative stress induced by toxic pollutants is generally responsible for the poor performance of many sequencing batch reactors (SBRs) treating organic wastewater. In this study, the oxidative stress in two SBR systems that dealt with tobacco wastewater was monitored by measuring four popular biomarkers (superoxide dismutase, SOD; catalase, CAT; glutathione, GSH; and malondialdehyde, MDA). In the non-BA (non-bio-augmented) system, more intense oxidative stress was induced by a higher concentration of nicotine in tobacco wastewater, and excessive oxidative stress was induced by 250 mg/l of nicotine at the final stage. However, when a nicotine-degrading bacterial strain Pseudomonas sp. HF-1 was added to the BA (bio-augmented) system, the oxidative stress was significantly reduced compared to the non-BA system (p < 0.01).These results suggested that the oxidative stress was mainly induced by nicotine in the SBR treatment of tobacco wastewater, and that bioaugmentation with strain HF-1 would be a potential strategy to reduce the oxidative stress and thereby improve the performance in SBRs. Additionally, the positive correlation between the nicotine content and CAT, GSH and MDA activity in both systems implied that these parameters can be used as biomarkers for reflecting the performance of SBR treatment of tobacco wastewater, and in monitoring nicotine environmental pollution. PMID:20396945