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Sample records for gan prime yu

  1. Effects of Gan lian Yu ping feng powder on the antibody titers to infectious laryngotracheitis vaccine and some nonspecific immune indexes in chickens.

    PubMed

    Chunmei, Kong; Zhujun, Zhao; Xiuhui, Zhong

    2013-01-01

    The study was conducted in order to investigate the immuno-enhancing property of the Chinese herbal formula, Gan lian Yu ping feng powder. Three hundred and thirty six 45-day-old chicks were randomly divided into eight groups. The chicks in groups A, B, C were orally given 0.25 g/mL (low-), 0.5 g/mL (middle-) and 1.0 g/mL (high) dose of Gan lian Yu ping feng powder in the drinking water respectively for 3 days consecutively. They were then immunised with infectious laryngotracheitis vaccine (ILTV) on the 4th day. Groups D, E, F were given 0.25 g/mL, 0.5 g/mL and 1.0 g/mL dose of Gan lian Yu ping feng powder respectively after the immunisation for three days consecutively. Group G was Wen du qing (a government approved herbal product for ILT) control group, and group H was blank control group. At 52, 59, 73, 87 days of age, 8 chicks of each group were selected randomly for blood sampling to determine the levels of IFN-γ, IL-4 and the antibody of ILT. Then the chickens were sacrificed, with the thymus, spleen and Bursa of Fabricius being weighed for the calculation of immune organ indexes. The results showed that high and middle dosages of Gan lian Yu ping feng powder given at the day before immunisation and 3 days after immunisation elevated not only the contents of IFN-γ, the antibody titers of ILT (P<0.01) and the immune organ indexes (P<0.05) significantly, but also reduced the contents of IL-4. There was a significantly different degree of enhancement in the content of IFN-γ, the antibody of ILT (P<0.01) and the immune organ index (P<0.05). The results indicate that Gan lian Yu ping feng powder effectively improves the immunity in chickens. PMID:24146504

  2. Prime Knowledge about Primes

    ERIC Educational Resources Information Center

    Eisenberg, Theodore

    2007-01-01

    Several proofs demonstrating that there are infinitely many primes, different types of primes, tests of primality, pseudo primes, prime number generators and open questions about primes are discussed in Section 1. Some of these notions are elaborated upon in Section 2, with discussions of the Riemann zeta function and how algorithmic complexity…

  3. Swift Captures Asteroid 2005 YU55 Flyby

    NASA Video Gallery

    Asteroid 2005 YU55 whisks through the field of view of Swift's Ultraviolet/Optical Telescope (UVOT) on Nov. 9, just hours after the space rock made its closest approach to Earth. The video plays on...

  4. Immunity of PCB transplacental Yu-Cheng children in Taiwan

    SciTech Connect

    Lan, Shou Jen; Yen, Yea Yin; Chen, Eng Rin; Ko, Ying Chin ); Lan, Joung Liang )

    1990-02-01

    Up to now, there has been no studies about the immune status of PCB transplacental Yu-Cheng babies. In an earlier study, Yu-Cheng babies were reported to have a high infant mortality rate. It was reported that these babies would easily catch cold, experience diarrhea and abdominal pains. Recently, it was found that the bronchitis rate of Yu-Cheng babies is higher than in control babies. Because of high risk of infection, it is presumed that these babies might suffer immunosuppression to a certain extent. According to these findings, investigations into the immune functions of PCB transplacental Yu-Cheng babies are needed.

  5. Kelly Yu, PhD, MPH | Division of Cancer Prevention

    Cancer.gov

    Dr. Kelly J Yu is an Epidemiologist with the Early Detection Research Group for the Division of Cancer Prevention. Her research has primarily been focused on screening as a mode of cancer prevention. |

  6. [Zheng Meijian's Sha yu yi yu (Random Medical Talks in Leisure Time) and his new ideas on pulse-taking].

    PubMed

    Zhang, H M; Zheng, R X; Lu, X; Chen, X G; Wu, F; Liu, K K

    2016-03-01

    Zheng Meijian, a doctor of Xin'an district in the reign of Qianlong Emperor of the Qing Dynasty, left his manuscript Sha yu yi yu (Random Medical Talks in Leisure Time), and was handed down in his family for generations. Sha yu yi yu was published in the Anhui Yixue of Issue 20, 1959, with horizontal layout and punctuation. The book records Zheng Meijian's understanding for the medicine, especially his new ideas on the cunkou pulse, with its underlying corresponding relationship among cun-guan-chi and zang-fu which should be combined with meridian and collateral system, claiming that the pulse taken superficially was corresponding to fu, while that taken deeply, to zang. He classified the strength of the fingers in pulse-taking into 8 levels, and advocated flexible application of pulse-taking. All his opinions had an important reference value for theoretical research and clinical application of pulse-taking. PMID:27255196

  7. Correction to Yu et al (2015).

    PubMed

    2015-06-01

    Reports an error in "Dynamics of postdecisional processing of confidence" by Shuli Yu, Timothy J. Pleskac and Matthew D. Zeigenfuse (Journal of Experimental Psychology: General, 2015[Apr], Vol 144[2], 489-510). The paragraph before the Conclusion section states: "To investigate when this occurs, we simulated Model 8 using the best fitting parameters for each participant in Study 2 and extended the IJT duration." "Model 8" should be "Model 1." (The following abstract of the original article appeared in record 2015-13746-006.) Most cognitive theories assume that confidence and choice happen simultaneously and are based on the same information. The 3 studies presented in this article instead show that confidence judgments can arise, at least in part, from a postdecisional evidence accumulation process. As a result of this process, increasing the time between making a choice and confidence judgment improves confidence resolution. This finding contradicts the notion that confidence judgments are biased by decision makers seeking confirmatory evidence. Further analysis reveals that the improved resolution is due to a reduction in confidence in incorrect responses, while confidence in correct responses remains relatively constant. These results are modeled with a sequential sampling process that allows evidence accumulation to continue after a choice is made and maps the amount of accumulated evidence onto a confidence rating. The cognitive modeling analysis reveals that the rate of evidence accumulation following a choice does slow relative to the rate preceding choice. The analysis also shows that the asymmetry between confidence in correct and incorrect choices is compatible with state-dependent decay in the accumulated evidence: Evidence consistent with the current state results in a deceleration of accumulated evidence and consequently evidence appears to have a decreasing impact on observed confidence. In contrast, evidence inconsistent with the current state

  8. Prime Time.

    ERIC Educational Resources Information Center

    Piele, Donald T.

    1982-01-01

    The design of a computer program to efficiently generate prime numbers is discussed. Programs for many different brands of home computers are listed, with suggestions of ways the programs can be speeded up. It is noted everyone seems to have a favorite program, but that every program can be improved. (MP)

  9. Atomic Composition of the Positron-Sensitive Vacancy Complexes in GaN

    NASA Astrophysics Data System (ADS)

    Arutyunov, Nikolai; Emtsev, Vadim

    2004-03-01

    The positron probing of the as-grown point defects in GaN and related materials has been conducted by the one-dimensional angular correlation of the annihilation radiation (1D-ACAR) as well as by some other positron annihilation techniques. It has been established that the electron density around the positron is lowered suggesting that positrons are trapped by the defects of a vacancy type in the crystal lattice of GaN. The electron-positron radii fitted to the conventional ion radii for the relevant anion and cation sites have formed a basis for a comparative analysis of the obtained results. The electron-positron cation core radius whose length is determined by the atoms in the nearest environment of the annihilating positrons has been estimated by the parameters of the high-momentum component of 1D-ACAR curves. The electron-positron momentum distribution outside the cation cores has been used for the estimations of the electron-positron anion core radius. A comparison of the electron-positron ion radii with a certain standards obtained for B, Al, Ga, related III-V compounds GaP, GaAs, GaSb, BN, and AlN has been done systematically at the processing of results. A plausible explanation of the experimental data obtained for GaN may be given assuming that the positron annihilation occurs in the complex of a vacancy-type where the nitrogen atom is shifted from its regular position and, probably, is trapped by the gallium vacancy forming the antisite configuration (N.Yu. Arutyunov, A.V.Mikhailin, V.Yu. Davidov, V.V.Emtsev, G.A. Oganesyan, and E.E.Haller, Semiconductors, 36 (2002) 1106.) (N.Yu. Arutyunov, V.V.Emtsev, A.V.Mikhailin, and C.J. Humphreys, Physica B, (2003), in press.) Similar complexes in GaN have been discussed theoretically. (D.J. Chadi, Appl. Phys. Lett. 71 (1997) 2970.) In this connection the results of the positron annihilation studies in GaN:Mg are also considered.

  10. Bao-yu: a mental disorder or a cultural icon?

    PubMed

    Huang, Flora; Gillett, Grant

    2014-06-01

    The embodied human subject is dynamically connected to his or her historico-sociocultural context, the soil from which a person's psyche is nourished as multiplex meanings are absorbed and enable personal development. In each culture certain towering artistic works embody this perspective. The Dream of the Red Chamber introduces Jia Bao-yu--a scion of the prestigious Jia family--and his relationships with a large cast of characters. Bao-yu is controversial but, at the time of the family's tragic collapse, he can be seen as embodying a spiritual struggle in which his instinct, nature, sensitivity, and creativity are grounded in his transcendent relationship with a fragment of the world stone, an eternal source of energy and creativity. We are invited to draw on a metaphysical level of thought to consider his struggles with man-made hierarchies and a situated historico-sociocultural order in such a way as to live out his spiritual being. As such, the novel is closely relevant to questions of spirituality in bioethics. Through personal experiences, passions, creativity, and relationships with others, the body is inscribed, forming the soul, which may be misconstrued (for instance, through a medical or Cartesian reformulation of events) but which can be seen as the site of ethical and spiritual thought. PMID:24744176

  11. Problems with Primes

    ERIC Educational Resources Information Center

    Melrose, Tim; Scott, Paul

    2005-01-01

    This article discusses prime numbers, defined as integers greater than 1 that are divisible only by only themselves and the number 1. A positive integer greater than 1 that is not a prime is called composite. The number 1 itself is considered neither prime nor composite. As the name suggests, prime numbers are one of the most basic but important…

  12. Learning about Primes

    ERIC Educational Resources Information Center

    McEachran, Alec

    2008-01-01

    In this article, the author relates his unhappy experience in learning about prime numbers at secondary school. To introduce primes, a teacher first told students a definition of a prime number, then students were taught how to find prime numbers. Students defined and listed them and at some later point were tested on their memory of both the…

  13. Phenolic component profiles of mustard greens, yu choy and 15 other Brassica vegatables

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A liquid chromatography-mass spectrometry (LC-MS) profiling method was used to characterize the phenolic components of 17 leafy vegetables from Brassica species other than Brassica oleracea. The vegetables studied were mustard green, baby mustard green, gai choy, baby gai choy, yu choy, yu choy tip...

  14. Unconventional Yu-Shiba-Rusinov states in hydrogenated graphene

    NASA Astrophysics Data System (ADS)

    Lado, J. L.; Fernández-Rossier, J.

    2016-06-01

    Conventional in-gap Yu-Shiba-Rusinov (YSR) states require two ingredients: magnetic atoms and a superconducting host that, in the normal phase, has a finite density of states at the Fermi energy. Here we show that hydrogenated graphene can host YSR states without any of those two ingredients. Atomic hydrogen chemisorbed in graphene is known to act as paramagnetic center with a weakly localized magnetic moment. Our calculations for hydrogenated graphene in proximity to a superconductor show that individual adatoms induce in-gap YSR states with an exotic spectrum whereas chains of adatoms result in a gapless YSR band. Our predictions can be tested using state of the art techniques, combining recent progress of atomic manipulation of atomic hydrogen on graphene together with the well tested proximity effect in graphene.

  15. Motor Priming in Neurorehabilitation

    PubMed Central

    Stoykov, Mary Ellen; Madhavan, Sangeetha

    2014-01-01

    Priming is a type of implicit learning wherein a stimulus prompts a change in behavior. Priming has been long studied in the field of psychology. More recently, rehabilitation researchers have studied motor priming as a possible way to facilitate motor learning. For example, priming of the motor cortex is associated with changes in neuroplasticity that are associated with improvements in motor performance. Of the numerous motor priming paradigms under investigation, only a few are practical for the current clinical environment, and the optimal priming modalities for specific clinical presentations are not known. Accordingly, developing an understanding of the various types of motor priming paradigms and their underlying neural mechanisms is an important step for therapists in neurorehabilitation. Most importantly, an understanding of the methods and their underlying mechanisms is essential for optimizing rehabilitation outcomes. The future of neurorehabilitation is likely to include these priming methods, which are delivered prior to or in conjunction with primary neurorehabilitation therapies. In this Special Interest article we discuss those priming paradigms that are supported by the greatest amount of evidence including: (i) stimulation-based priming, (ii) motor imagery and action observation, (iii) sensory priming, (iv) movement-based priming, and (v) pharmacological priming. PMID:25415551

  16. Ba4GaN3O

    PubMed Central

    Hashimoto, Takayuki; Yamane, Hisanori

    2014-01-01

    Red transparant platelet-shaped single crystals of tetra­barium gallium trinitride oxide, Ba4GaN3O, were synthesized by the Na flux method. The crystal structure is isotypic with Sr4GaN3O, containing isolated triangular [GaN3]6− anionic groups. O2− atoms are inserted between the slabs of [Ba4GaN3]2+, in which the [GaN3]6− groups are surrounded by Ba2+ atoms. PMID:24940188

  17. Repetition Priming in Music

    ERIC Educational Resources Information Center

    Hutchins, Sean; Palmer, Caroline

    2008-01-01

    The authors explore priming effects of pitch repetition in music in 3 experiments. Musically untrained participants heard a short melody and sang the last pitch of the melody as quickly as possible. Each experiment manipulated (a) whether or not the tone to be sung (target) was heard earlier in the melody (primed) and (b) the prime-target distance…

  18. Repetition priming in music.

    PubMed

    Hutchins, Sean; Palmer, Caroline

    2008-06-01

    The authors explore priming effects of pitch repetition in music in 3 experiments. Musically untrained participants heard a short melody and sang the last pitch of the melody as quickly as possible. Each experiment manipulated (a) whether or not the tone to be sung (target) was heard earlier in the melody (primed) and (b) the prime-target distance (measured in events). Experiment 1 used variable-length melodies, whereas Experiments 2 and 3 used fixed-length melodies. Experiment 3 changed the timbre of the target tone. In all experiments, fast-responding participants produced repeated tones faster than nonrepeated tones, and this repetition benefit decreased as prime-target distances increased. All participants produced expected tonic endings faster than less expected nontonic endings. Repetition and tonal priming effects are compared with harmonic priming effects in music and with repetition priming effects in language. PMID:18505332

  19. An ERP investigation of orthographic priming with superset primes.

    PubMed

    Ktori, Maria; Midgley, Katherine; Holcomb, Phillip J; Grainger, Jonathan

    2015-01-12

    Prime stimuli formed by inserting unrelated letters in a given target word (called "superset" primes) provide a means to modify the relative positions of the letters shared by prime and target. Here we examined the time-course of superset priming effects in an ERP study using the sandwich-priming paradigm. We compared the effects of superset primes formed by the insertion of unrelated letters (e.g., maurkdet-MARKET), or by the insertion of hyphens (e.g., ma-rk-et-MARKET), with identity priming (e.g., market-MARKET), all measured relative to unrelated control primes. Behavioral data revealed significantly greater priming in the hyphen-insert condition compared with the letter-insert condition. In the ERP signal, letter-insert priming emerged later than hyphen-insert priming and produced a reversed priming effect in the N400 time-window compared with the more typical N400 priming effects seen for both hyphen-insert priming and identity priming. The different pattern of priming effects seen for letter-insert primes and hyphen-insert primes suggests that compared with identity priming, letter superset priming reflects the joint influence of: (1) a disruption in letter position information, and (2) an inhibitory influence of mismatching letters. PMID:25451126

  20. PRIME Lab Radiocarbon Measurements

    NASA Astrophysics Data System (ADS)

    Hillegonds, D. J.; Mueller, K. A.; Ma, X.; Lipschutz, M. E.

    1996-03-01

    The Purdue Rare Isotope Measurement Laboratory (PRIME Lab) is one of three NSF national facilities for accelerator mass spectrometry (AMS), and is the only one capable of determining six cosmogenic radionuclides: 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I. This abstract describes the current status of the radiocarbon analysis program at PRIME Lab.

  1. Building Numbers from Primes

    ERIC Educational Resources Information Center

    Burkhart, Jerry

    2009-01-01

    Prime numbers are often described as the "building blocks" of natural numbers. This article shows how the author and his students took this idea literally by using prime factorizations to build numbers with blocks. In this activity, students explore many concepts of number theory, including the relationship between greatest common factors and…

  2. Discovery: Prime Numbers

    ERIC Educational Resources Information Center

    de Mestre, Neville

    2008-01-01

    Prime numbers are important as the building blocks for the set of all natural numbers, because prime factorisation is an important and useful property of all natural numbers. Students can discover them by using the method known as the Sieve of Eratosthenes, named after the Greek geographer and astronomer who lived from c. 276-194 BC. Eratosthenes…

  3. Priming Gestures with Sounds

    PubMed Central

    Lemaitre, Guillaume; Heller, Laurie M.; Navolio, Nicole; Zúñiga-Peñaranda, Nicolas

    2015-01-01

    We report a series of experiments about a little-studied type of compatibility effect between a stimulus and a response: the priming of manual gestures via sounds associated with these gestures. The goal was to investigate the plasticity of the gesture-sound associations mediating this type of priming. Five experiments used a primed choice-reaction task. Participants were cued by a stimulus to perform response gestures that produced response sounds; those sounds were also used as primes before the response cues. We compared arbitrary associations between gestures and sounds (key lifts and pure tones) created during the experiment (i.e. no pre-existing knowledge) with ecological associations corresponding to the structure of the world (tapping gestures and sounds, scraping gestures and sounds) learned through the entire life of the participant (thus existing prior to the experiment). Two results were found. First, the priming effect exists for ecological as well as arbitrary associations between gestures and sounds. Second, the priming effect is greatly reduced for ecologically existing associations and is eliminated for arbitrary associations when the response gesture stops producing the associated sounds. These results provide evidence that auditory-motor priming is mainly created by rapid learning of the association between sounds and the gestures that produce them. Auditory-motor priming is therefore mediated by short-term associations between gestures and sounds that can be readily reconfigured regardless of prior knowledge. PMID:26544884

  4. Priming Ability Emotional Intelligence

    ERIC Educational Resources Information Center

    Schutte, Nicola S.; Malouff, John M.

    2012-01-01

    Two studies examined whether priming self-schemas relating to successful emotional competency results in better emotional intelligence performance. In the first study participants were randomly assigned to a successful emotional competency self-schema prime condition or a control condition and then completed an ability measure of emotional…

  5. GaN High Power Devices

    SciTech Connect

    PEARTON,S.J.; REN,F.; ZHANG,A.P.; DANG,G.; CAO,X.A.; LEE,K.P.; CHO,H.; GILA,B.P.; JOHNSON,J.W.; MONIER,C.; ABERNATHY,C.R.; HAN,JUNG; BACA,ALBERT G.; CHYI,J.-I.; LEE,C.-M.; NEE,T.-E.; CHUO,C.-C.; CHI,G.C.; CHU,S.N.G.

    2000-07-17

    A brief review is given of recent progress in fabrication of high voltage GaN and AlGaN rectifiers, GaN/AlGaN heterojunction bipolar transistors, GaN heterostructure and metal-oxide semiconductor field effect transistors. Improvements in epitaxial layer quality and in fabrication techniques have led to significant advances in device performance.

  6. Mechanism of Torrential Rain Associated with the Mei-yu Development during SCSMEX-98

    NASA Technical Reports Server (NTRS)

    Qian, Jian-Hua; Tao, Wei-Kuo; Lau, K.-M.; Starr, David OC. (Technical Monitor)

    2002-01-01

    A case of torrential precipitation process in the Mei-yu front, an Asian monsoon system east to the Tibetan Plateau, is studied with the coupled Penn State University/NCAR MM5 and NASA/GSFC PLACE (Parameterization for Land - Atmosphere - Cloud Exchange) models. Remote and local impacts of water vapor on the location and intensity of Mei-yu precipitation are studied by numerical experiments. Results demonstrate that the water vapor source for this heavy precipitation case in Yangtze river basin is derived mostly from the Bay of Bengal, transported by the southwesterly low-level Jet (LLJ) southeast to the Tibetan Plateau. The moist convection is a critical process in the development and maintenance of the front. The meridional and zonal secondary circulations resulted from Mei-yu condensation heating both act to increase the wind speed in the LLJ. The condensation induced local circulation strengthens the moisture transport in the LLJ, providing a positive feedback to sustain the Mei-yu precipitation system. It is found that local precipitation recycling shifts heavy rain toward the warm side of the Mei-yu front. This shift of rainfall location is due to the pronounced increase of atmospheric moisture and decrease of surface temperature over the warm side of the front.

  7. Bandgap engineering of GaN nanowires

    NASA Astrophysics Data System (ADS)

    Ming, Bang-Ming; Wang, Ru-Zhi; Yam, Chi-Yung; Xu, Li-Chun; Lau, Woon-Ming; Yan, Hui

    2016-05-01

    Bandgap engineering has been a powerful technique for manipulating the electronic and optical properties of semiconductors. In this work, a systematic investigation of the electronic properties of [0001] GaN nanowires was carried out using the density functional based tight-binding method (DFTB). We studied the effects of geometric structure and uniaxial strain on the electronic properties of GaN nanowires with diameters ranging from 0.8 to 10 nm. Our results show that the band gap of GaN nanowires depends linearly on both the surface to volume ratio (S/V) and tensile strain. The band gap of GaN nanowires increases linearly with S/V, while it decreases linearly with increasing tensile strain. These linear relationships provide an effect way in designing GaN nanowires for their applications in novel nano-devices.

  8. Musculoskeletal changes in children prenatally exposed to polychlorinated biphenyls and related compounds (Yu-Cheng children)

    SciTech Connect

    Guo, Y.L.; Lin, C.J.; Yao, W.J.; Hsu, C.C. ); Ryan, J.J. )

    1994-01-01

    Fifty-five Yu-Cheng (oil-disease) children born between 1978 and 1985 to mothers who ate PCB-contaminated rice oil in 1978-1979 were studied and compared to age- and sex-matched control subjects in 1991. The children's growth profiles, bone mineral density and soft tissue composition, joint laxity, and serum parathyroid hormone, vitamin D, calcium, alkaline phosphatase, and phosphate were compared. The Yu-Cheng children were 3.1 cm (p < .05) smaller and had less total lean mass and soft tissue mass as compared to the matched control subjects. All other parameters studied were similar in both groups. The shorter height and decreased total lean mass and soft tissue control were only seen in the Yu-Cheng children who were the first born after the ingestion, but not in subsequent children. This was most likely due to decreased body burdens of the PCBs and related contaminants over time in the mothers.

  9. Musculoskeletal changes in children prenatally exposed to polychlorinated biphenyls and related compounds (Yu-Cheng children).

    PubMed

    Guo, Y L; Lin, C J; Yao, W J; Ryan, J J; Hsu, C C

    1994-01-01

    Fifty-five Yu-Cheng (oil-disease) children born between 1978 and 1985 to mothers who ate PCB-contaminated rice oil in 1978-1979 were studied and compared to age- and sex-matched control subjects in 1991. The children's growth profiles, bone mineral density and soft tissue composition, joint laxity, and serum parathyroid hormone, vitamin D, calcium, alkaline phosphatase, and phosphate were compared. The Yu-Cheng children were 3.1 cm (p < .05) smaller and had less total lean mass and soft tissue mass as compared to the matched control subjects. All other parameters studied were similar in both groups. The shorter height and decreased total lean mass and soft tissue content were only seen in the Yu-Cheng children who were the first born after the ingestion, but not in subsequent children. This was most likely due to decreased body burdens of the PCBs and related contaminants over time in the mothers. PMID:8277528

  10. Conscious contributions to subliminal priming.

    PubMed

    Jaśkowski, Piotr

    2008-03-01

    Choice reaction times to visual stimuli (targets) may be influenced by preceding subliminal stimuli (primes). Some authors reported a straight priming effect i.e., responses were faster when primes and targets called for the same response than when they called for different responses. Others found the reversed pattern of results. Eimer and Schlaghecken [Eimer, M. & Schlaghecken, F. (2002). Links between conscious awareness and response inhibition: evidence from masked priming. Psychonomic Bulletin &Review, 9, 514-520.] showed recently that straight priming occurs whenever a prime is not efficiently masked thereby the information provided by the prime is accessible for consciousness. In the present study, a hypothesis is tested that straight priming is due to mediation of consciousness. To test this hypothesis, prime validity was manipulated. We showed that even when no mask was used so that participants could fully and consciously perceive the prime and participants were informed that primes were mostly invalid, for the short prime-target ISI interval (100 ms) straight priming occurred. The priming was inverse when the ISI was 800 ms. This indicates that participants were able to use the information provided by the prime to prepare the response opposite to that cued by the prime but only if the time between the prime and the target was long enough. PMID:17126565

  11. Largest known twin primes and Sophie Germain primes

    NASA Astrophysics Data System (ADS)

    Indlekofer, Karl-Heinz; Járai, Antal

    The numbers 242206083* 2^38880+-1 are twin primes. The number p=2375063906985* 2^19380-1 is a Sophie Germain prime, i.e. p and 2p+1 are both primes. For p=4610194180515* 2^ 5056-1, the numbers p, p+2 and 2p+1 are all primes.

  12. Palomar Spectroscopy of 2001 FM129, 2004 FG11, and 2005 YU55.

    NASA Astrophysics Data System (ADS)

    Hicks, M.; Lawrence, K.; Benner, L.

    2010-04-01

    We obtained long-slit CCD spectrograms of the near-Earth asteroids 8254 (2001 FM129), 2004 FG11, and 2005 YU55 using the Palomar 5-m Hale Telescope equipped with the facility dual-channel spectrometer ("Double-Spec") on April 07 2010. 88254 (2001 FM129) and 2004 FG11 have been designated as Potentially Hazardous Asteroids by the Minor Planets Center. 2005 YU55 in noteworthy as a "virtual impactor", with a cumulative Earth-impact probability of 7.4e-6 between 2071 and 2109 (http://neo.jpl.nasa.gov/risk/).

  13. How important is a prime's gestalt for subliminal priming?

    PubMed

    Jaśkowski, Piotr; Slósarek, Maciej

    2007-06-01

    Masked stimuli (primes) can affect the preparation of a motor response to subsequently presented target stimuli. Under some conditions, reactions to the main stimulus can be facilitated (straight priming) or inhibited (inverse priming) when preceded by a compatible prime (calling for the same response). In the majority of studies in which inverse priming was demonstrated arrows pointing left or right were used as prime and targets. There is, however, evidence that arrows are special overlearned stimuli which are processed in a favorable way. Here we report three experiments designated to test whether the "arrowness" of primes/targets is a sufficient condition for inverse priming. The results clearly show that although inverse priming appeared when non-arrow shapes were used, the magnitude of the priming effect was larger with arrows. The possible reasons for this effect are discussed. PMID:16919477

  14. Microcomputer-Assisted Discoveries: Primes.

    ERIC Educational Resources Information Center

    Kimberling, Clark

    1983-01-01

    Four computer programs (Applesoft Basic) on prime numbers are described, including programs for factoring a positive integer as a product of primes, listing all divisors of a given A, and for exploring primes representable as prescribed sums/differences involving squares, cubes, Fibonnaci numbers, or other primes. Program listings are included.…

  15. Nano-clustered Pd catalysts formed on GaN surface for green chemistry

    NASA Astrophysics Data System (ADS)

    Hirayama, Motoi; Ueta, Yukiko; Konishi, Tomoya; Tsukamoto, Shiro

    2011-05-01

    We have succeeded in observing Pd nano-clusters, catalytic prime elements, on a GaN(0 0 0 1) surface by a scanning tunneling microscope for the first time. After the sample was reused, we found that nano-clusters (width: 11 nm, height: 2.2 nm) existed on the surface which still kept the catalytic activity, resulting that the neutral Pd atoms formed the nano-cluster. Moreover, the S-termination contributed to the formation of the dense and flat structure consisting of the Pd nano-clusters.

  16. Synthesis, structure, and reactivity of 1,2-(1{prime},1{prime},2{prime},2{prime}-tetramethyldisilane-1{prime},2{prime})carborane

    SciTech Connect

    Rege, F.M. de; Kassebaum, J.D.; Scott, B.L.; Abney, K.D.; Balaich, G.J.

    1999-02-08

    The novel strained compound 1,2-(1{prime},1{prime},2{prime},2{prime}-tetramethyldisilane-1{prime},2{prime})carborane (1) was synthesized by the reaction of 1,2-dilithiocarborane and dichlorotetramethyldisilane. Compound 1 was characterized by solution methods and its structure determined by single-crystal X-ray diffraction. In contrast to its organic analogue o-(disilanyl)-phenylene, the reaction of 1 with ethanol leads to cleavage of a Si-C bond rather than a Si-Si bond. Similarly to other cyclic disilanes, exposure of a solution of 1 to oxygen leads to the insertion of an oxygen atom into the Si-Si bond. The structure of the oxygen inserted product was also determined by X-ray crystallography. The general chemistry and attempts at polymerizing 1 are briefly discussed.

  17. Some "Prime" Comparisons.

    ERIC Educational Resources Information Center

    Brown, Stephen I.

    Topics that deal with prime numbers are presented with the intent of allowing the student to re-create the excitement of the original investigation. Suitable for advanced high school students as an introduction to number theory at the college level or as a text for courses in teacher education, the book covers the following topics: (1) the number…

  18. "Fell" Primes "Fall", but Does "Bell" Prime "Ball"? Masked Priming with Irregularly-Inflected Primes

    ERIC Educational Resources Information Center

    Crepaldi, Davide; Rastle, Kathleen; Coltheart, Max; Nickels, Lyndsey

    2010-01-01

    Recent masked priming experiments have brought to light a morphological level of analysis that is exclusively based on the orthographic appearance of words, so that it breaks down corner into corn- and -er, as well as dealer into deal- and -er (Rastle, Davis, & New, 2004). Being insensitive to semantic factors, this morpho-orthographic…

  19. Prime Retrieval of Motor Responses in Negative Priming

    ERIC Educational Resources Information Center

    Mayr, Susanne; Buchner, Axel; Dentale, Sandra

    2009-01-01

    Three auditory identification experiments were designed to specify the prime-response retrieval model of negative priming (S. Mayr & A. Buchner, 2006), which assumes that the prime response is retrieved in ignored repetition trials and interferes with probe responding. In Experiment 1, shortly before (in Experiment 1A) or after (in Experiment 1B)…

  20. Priming Ditransitive Structures in Comprehension

    ERIC Educational Resources Information Center

    Arai, Manabu; van Gompel, Roger P. G.; Scheepers, Cristoph

    2007-01-01

    Many studies have shown evidence for syntactic priming during language production (e.g., Bock, 1986). It is often assumed that comprehension and production share similar mechanisms and that priming also occurs during comprehension (e.g., Pickering & Garrod, 2004). Research investigating priming during comprehension (e.g., Branigan et al., 2005 and…

  1. Rhizosphere priming: a nutrient perspective

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rhizosphere priming is the change in decomposition of soil organic matter (SOM) caused by root activity. Rhizosphere priming plays a crucial role in soil carbon (C) dynamics and their response to global climate change. Rhizosphere priming may be affected by soil nutrient availability, but rhizospher...

  2. Masked Repetition Priming Using Magnetoencephalography

    ERIC Educational Resources Information Center

    Monahan, Philip J.; Fiorentino, Robert; Poeppel, David

    2008-01-01

    Masked priming is used in psycholinguistic studies to assess questions about lexical access and representation. We present two masked priming experiments using MEG. If the MEG signal elicited by words reflects specific aspects of lexical retrieval, then one expects to identify specific neural correlates of retrieval that are sensitive to priming.…

  3. The Near-Earth Encounter of 2005 YU55: Thermal Infrared Observations from Gemini North

    NASA Technical Reports Server (NTRS)

    Lim, Lucy F.; Emery, Joshua P.; Moskovitz, Nicholas A.; Granvik, Mikael

    2012-01-01

    As part of a multi-observatory campaign to observe 2005 YU55 during its November 2011 encounter with the Earth, thermal infrared photometry and spectroscopy (7.9- 14 and 18-22 micron) were conducted using the Michelle instrument at Gemini North. Reduction of the 8.8 flm photometry and the spectroscopy from UT Nov-IO as well as of all the Gemini data from UT Nov-9 is in progress. Results will be discussed.

  4. Selective-area growth of GaN on non- and semi-polar bulk GaN substrates

    NASA Astrophysics Data System (ADS)

    Okada, Shunsuke; Miyake, Hideto; Hiramatsu, Kazumasa; Enatsu, Yuuki; Nagao, Satoru

    2014-01-01

    We carried out the selective-area growth of GaN and fabricated InGaN/GaN MQWs on non- and semi-polar bulk GaN substrates by MOVPE. The differences in the GaN structures and the In incorporation of InGaN/GaN MQWs grown on non- and semi-polar GaN substrates were investigated. In the case of selective-area growth, different GaN structures were obtained on (20\\bar{2}1) GaN, (20\\bar{2}\\bar{1}) GaN, and (10\\bar{1}0) GaN substrates. A repeating pattern of \\{ 1\\bar{1}01\\} and \\{ 1\\bar{1}0\\bar{1}\\} facets appeared on (20\\bar{2}1) GaN. Then, we fabricated InGaN/GaN MQWs on the facet structures on (20\\bar{2}1) GaN. The emission properties characterized by cathodoluminescence were different for \\{ 1\\bar{1}01\\} and \\{ 1\\bar{1}0\\bar{1}\\} facets. On the other hand, for InGaN/GaN MQWs on non- and semi-polar GaN substrates, steps along the a-axis were observed by AFM. In particular on (20\\bar{2}1) GaN, undulations and undulation bunching appeared. Photoluminescence characterization indicated that In incorporation increased with the off-angle from the m-plane and also depended on the polarity.

  5. The Near-Earth Encounter of Asteroid 308635 (2005 YU55): Thermal IR Observations

    NASA Technical Reports Server (NTRS)

    Lim, Lucy F.; Emery, J. P.; Moskovitz, N. A.; Busch, N. W.; Yang, B.; Granvik, M.

    2012-01-01

    The near-Earth approach (0.00217 AU, or 0.845 lunar distances) of the C-type asteroid 308635 (2005 YU55) in November 2011 presented a rare opportunity for detailed observations of a low-albedo NEA in this size range. As part of a multi-telescope campaign to measure visible and infrared spectra and photometry, we obtained mid-infrared (approx. 8 to 22 micron) photometry and spectroscopy of 2005 YU55 using Michelle on the Gemini North telescope on UT November 9 and 10,2011. An extensive radar campaign together with optical light-curves established the rotation state of YU55. In addition, the radar imaging resulted in a shape model for the asteroid, detection of numerous boulders on its surface, and a preliminary estimate of its equatorial diameter at 380 +/- 20 m. In a preliminary analysis, applying the radar and lightcurve-derived parameters to a rough-surface thermophysical model fit to the Gemini/Michelle thermal emission photometry results in a thermal inertia range of approximately 500 to 1500 J/sq m/0.5s/K, with the low-thermal-inertia solution corresponding to the small end of the radar size range and vice versa. Updates to these results will be presented and modeling of the thermal contribution to the measured near-infrared spectra from Palomar/Triplespec and IRTF/SpeX will also be discussed.

  6. Generation of large prime numbers from a sequence of previous prime numbers

    NASA Astrophysics Data System (ADS)

    Samir, Brahim Belhaouari; Rezk, Youssef A. Y.

    2012-09-01

    A prime number is co-prime with all the primes as well. This paper utilizes this fact by generating larger prime numbers based on a set of smaller prime numbers. The prime numbers are ordered and each two consecutive primes are coupled to generate their co-prime number formula extending this process larger prime sequence is established. Will the process help us produce larger prime numbers faster and more efficiently? This paper investigates the described process.

  7. Heterologous prime-boost vaccination.

    PubMed

    Lu, Shan

    2009-06-01

    An effective vaccine usually requires more than one time immunization in the form of prime-boost. Traditionally the same vaccines are given multiple times as homologous boosts. New findings suggested that prime-boost can be done with different types of vaccines containing the same antigens. In many cases such heterologous prime-boost can be more immunogenic than homologous prime-boost. Heterologous prime-boost represents a new way of immunization and will stimulate better understanding on the immunological basis of vaccines. PMID:19500964

  8. Silicon doping of HVPE GaN bulk-crystals avoiding tensile strain generation

    NASA Astrophysics Data System (ADS)

    Hofmann, Patrick; Röder, Christian; Habel, Frank; Leibiger, Gunnar; Beyer, Franziska C.; Gärtner, Günter; Eichler, Stefan; Mikolajick, Thomas

    2016-02-01

    Doped GaN:Si crystals were grown in a commercially available vertical HVPE reactor. The templates used for the HVPE heteroepitaxy were so-called FACELO seeds, with a starting GaN layer thickness of 3-4 μm. The FWHM of the 0002 and the 30\\bar{3}2 reflection of the HVPE-grown GaN:Si crystals with a thickness of 3 mm are {{31}\\prime\\prime} and {{78}\\prime\\prime} , respectively, indicating excellent crystal quality. Hall measurements resulted in a charge carrier concentration of 1.5× {{10}18} cm-3, while exhibiting a mobility of 250 cm-2V-1 s-1. These values coincide with the values extracted from FTIR measurements and the lineshape fitting of the A1(LO)/plasmon coupled phonon mode of the confocal Raman measurements. SIMS investigations yielded a silicon atom concentration of 1.8× {{10}18} cm-3. This indicates an activation of the dopant atoms of approximately 90%. The TDD determined by CL dark spot counting was 2× {{10}6} cm-2. Within the measurement accuracy, the confocal Raman measurements did not show a tensile strain generation due to the silicon doping with resulting charge carrier concentrations of 1.5× {{10}18} cm-3.

  9. Piezotronic Effect in Polarity-Controlled GaN Nanowires.

    PubMed

    Zhao, Zhenfu; Pu, Xiong; Han, Changbao; Du, Chunhua; Li, Linxuan; Jiang, Chunyan; Hu, Weiguo; Wang, Zhong Lin

    2015-08-25

    Using high-quality and polarity-controlled GaN nanowires (NWs), we studied the piezotronic effect in crystal orientation defined wurtzite structures. By applying a normal compressive force on c-plane GaN NWs with an atomic force microscopy tip, the Schottky barrier between the Pt tip and GaN can be effectively tuned by the piezotronic effect. In contrast, the normal compressive force cannot change the electron transport characteristics in m-plane GaN NWs whose piezoelectric polarization axis is turned in the transverse direction. This observation provided solid evidence for clarifying the difference between the piezotronic effect and the piezoresistive effect. We further demonstrated a high sensitivity of the m-plane GaN piezotronic transistor to collect the transverse force. The integration of c-plane GaN and m-plane GaN indicates an overall response to an external force in any direction. PMID:26256533

  10. Experimental evidence of homonuclear bonds in amorphous GaN

    SciTech Connect

    Ishimaru, Dr. Manabu; Zhang, Yanwen; Wang, Xuemei; Chu, Wei-Kan; Weber, William J

    2011-01-01

    Although GaN is an important semiconductor material, its amorphous structures are not well understood. Currently, theoretical atomistic structural models which contradict each other, are proposed for the chemical short-range order of amorphous GaN: one characterizes amorphous GaN networks as highly chemically ordered, consisting of heteronuclear Ga-N atomic bonds; and the other predicts the existence of a large number of homonuclear bonds within the first coordination shell. In the present study, we examine amorphous structures of GaN via radial distribution functions obtained by electron diffraction techniques. The experimental results demonstrate that amorphous GaN networks consist of heterononuclear Ga-N bonds, as well as homonuclear Ga-Ga and N-N bonds.

  11. Impaired production priming and intact identification priming in Alzheimer's disease.

    PubMed

    Fleischman, D A; Monti, L A; Dwornik, L M; Moro, T T; Bennett, D A; Gabrieli, J D

    2001-11-01

    This study examined the distinction between identification and production processes in repetition priming for 16 patients with Alzheimer's disease (AD) and 16 healthy old control participants (NC). Words were read in three study phases. In three test phases, participants (1) reread studied words, along with unstudied words, in a word-naming task (identification priming); (2) completed 3-letter stems of studied and unstudied words into words in a word-stem completion task (production priming); and (3) answered yes or no to having read studied and unstudied words in a recognition task (explicit memory). Explicit memory and word-stem completion priming were impaired in the AD group compared to the NC group. After correcting for baseline slowing, word-naming priming magnitude did not differ between the groups. The results suggest that the distinction between production and identification processes has promise for explaining the pattern of preservation and failure of repetition priming in AD. PMID:11771621

  12. Prime time sexual harrassment.

    PubMed

    Grauerholz, E; King, A

    1997-04-01

    This study explores the explicit and implicit messages of sexual harassment that viewers receive when viewing prime-time television in the US. A content analysis of 48 hours of prime-time television reveals that sexual harassment on television is both highly visible and invisible. Sexual harassment is rendered visible simply by its prominence in these programs. Incidents involving quid-pro-quo harassment and environmental harassment occur with regularity on television. Furthermore, about 84% of the shows studied contained at least one incident of sexual harassment; yet these acts of sexual harassment remained largely invisible because none of the behaviors were labeled as sexual harassment. These incidents are presented in humorous ways, and victims are generally unharmed and very effective at ending the harassment. Although such programs may actually reflect the reality of many women's lives in terms of prevalence of sexual harassment, they perpetuate several myths about sexual harassment, such as that sexual harassment is not serious and that victims should be able to handle the situations themselves. PMID:12294811

  13. Past tense route priming.

    PubMed

    Cohen-Shikora, Emily R; Balota, David A

    2013-03-01

    The present research examined whether lexical (whole word) or more rule-based (morphological constituent) processes can be locally biased by experimental list context in past tense verb inflection. In Experiment 1, younger and older adults completed a past tense inflection task in which list context was manipulated across blocks containing regular past tense verbs (e.g. REACH-REACHED) or irregular past tense verbs (TEACH-TAUGHT). Critical targets, consisting of half regular and half irregular verbs, were embedded within blocks and participants' inflection response latency and accuracy were assessed. The results yielded a cross-over interaction in response latencies for both young and older adults. In the regular context there was a robust regularity effect: regular target verbs were conjugated faster than irregular target verbs. In contrast, in the irregular context, irregular target verbs were conjugated faster than regular target verbs. Experiment 2 used the same targets but in the context of either standard nonwords or nonwords ending in "-ED" to test the possibility of a phonological basis for the effect. The effect of context was eliminated. The results support the notion that distinct processes in past tense verb production can be locally biased by list context and, as shown in Experiment 2, this route priming effect was not due to phonological priming. PMID:23291293

  14. The Near-Earth Encounter of Asteroid 308635 (2005 YU55): Thermal IR Observations

    NASA Astrophysics Data System (ADS)

    Lim, Lucy F.; Emery, J. P.; Moskovitz, N. A.; Busch, M. W.; Yang, B.; Granvik, M.

    2012-10-01

    The near-Earth approach (0.00217 AU, or 0.845 lunar distances) of the C-type asteroid 308635 (2005 YU55) in November 2011 presented a rare opportunity for detailed observations of a low-albedo NEA in this size range. As part of a multi-telescope campaign to measure visible and infrared spectra and photometry, we obtained mid-infrared ( 8 to 22 micron) photometry and spectroscopy of 2005 YU55 using Michelle [1] on the Gemini North telescope on UT November 9 and 10, 2011. An extensive radar campaign [2] together with optical lightcurves [3,4] established the rotation state of YU55. In addition, the radar imaging resulted in a shape model for the asteroid, detection of numerous boulders on its surface, and a preliminary estimate of its equatorial diameter at 380 +/- 20 m. In a preliminary analysis, applying the radar and lightcurve-derived parameters to a rough-surface thermophysical model fit to the Gemini/Michelle thermal emission photometry results in a thermal inertia range of approximately 500 to 1500 J m-2 s-1/2 K-1, with the low-thermal-inertia solution corresponding to the small end of the radar size range and vice versa. Updates to these results will be presented and modeling of the thermal contribution to the measured near-infrared spectra from Palomar/Triplespec and IRTF/SpeX will also be discussed. The authors gratefully acknowledge the assistance of observatory staff and the support of the NASA NEOO program (LFL and JPE), the Carnegie fellowship (NAM), and NASA AES, NSF, and the NRAO Jansky Fellowship (MWB). [1] De Buizer, J. and R. Fisher, Proc. Hris (2005), pp. 84-87. [2] Busch, M.W. et al., ACM (2012), abstract #6179. [3] Warner, B., MPBull 39 (2), 84 [4] Pravec, P.

  15. Evaluation of external Q of the superconducting cavity using Kroll-Yu method

    SciTech Connect

    Dhavale, A. S.; Mittal, K. C.

    2006-06-15

    Design and development of superconducting (SC) cavity having {beta}{sub g}>0.42 has been taken up as a part of the accelerator driven subcritical system project. An input coupler is designed for the SC, elliptical cavity operating at 1.056 GHz, using the Kroll-Yu method. The evaluation procedure is optimized and the method has been successfully implemented for the evaluation of high Q external. The effect of beam pipe radius, coupler dimensions, penetration depth, and the position of the coupler on the external Q has also been studied.

  16. Transposed-Letter Priming Effects with Masked Subset Primes: A Re-Examination of the "Relative Position Priming Constraint"

    ERIC Educational Resources Information Center

    Stinchcombe, Eric J.; Lupker, Stephen J.; Davis, Colin J.

    2012-01-01

    Three experiments are reported investigating the role of letter order in orthographic subset priming (e.g., "grdn"-GARDEN) using both the conventional masked priming technique as well as the sandwich priming technique in a lexical decision task. In all three experiments, subset primes produced priming with the effect being considerably larger when…

  17. A Study of Relative-Position Priming with Superset Primes

    ERIC Educational Resources Information Center

    Van Assche, Eva; Grainger, Jonathan

    2006-01-01

    Four lexical decision experiments are reported that use the masked priming paradigm to study the role of letter position information in orthographic processing. In Experiments 1 and 2, superset primes, formed by repetition of 1 or 2 letters of the target (e.g., jusstice-JUSTICE) or by insertion of 1 or 2 unrelated letters (e.g., juastice-JUSTICE),…

  18. 5[prime] to 3[prime] nucleic acid synthesis using 3[prime]-photoremovable protecting group

    DOEpatents

    Pirrung, M.C.; Shuey, S.W.; Bradley, J.C.

    1999-06-01

    The present invention relates, in general, to a method of synthesizing a nucleic acid, and, in particular, to a method of effecting 5[prime] to 3[prime] nucleic acid synthesis. The method can be used to prepare arrays of oligomers bound to a support via their 5[prime] end. The invention also relates to a method of effecting mutation analysis using such arrays. The invention further relates to compounds and compositions suitable for use in such methods.

  19. Exodus: Prime Mover

    NASA Technical Reports Server (NTRS)

    Bauer, Nikkol; Conwell, Pete; Johnson, Matt; Shields, Wendy; Thornton, Tim; Tokarz, Rob; Mcmanus, Rich

    1992-01-01

    The Exodus Prime Mover is an overnight package delivery aircraft designed to serve the Northern Hemisphere of Aeroworld. The preliminary design goals originated from the desire to produce a large profit. The two main driving forces throughout the design process were first to reduce the construction man-hours by simplifying the aircraft design, thereby decreasing the total production cost of the aircraft. The second influential factor affecting the design was minimizing the fuel cost during cruise. The lowest fuel consumption occurs at a cruise velocity of 30 ft/s. Overall, it was necessary to balance the economic benefits with the performance characteristics in order to create a profitable product that meets all specified requirements and objectives.

  20. [Textual research on Guang dong xin yu (New Sayings of Guangdong) quoted in Ben cao gang mu shi yi (Supplements to Compendium of Materia Medica].

    PubMed

    Zhang, Ruixian; Zhang, Wei; Li, Jian; Liang, Fei

    2014-05-01

    Altogether 15 terms for Guang dong xin yu (New Sayings of Guangdong) were used in Ben cao gang mu shi yi (Supplements to Compendium of Materia Medica), including Yue yu (Cantonese sayings), Chong yu (Sayings from Insect Drug), Jie yu (Sayings from Crustacean Drug), Xin yu (New Sayings), Yue hai xiang yu (Fragrant Sayings from Cantonese Region), Yue zhi mu yu (Sayings from Plants in Cantonese Annals), Guang dong suo yu (Trivial Sayings from Guangdong), Yue shan lu (Records of Cantonese Mountains), Yue lu (Cantonese Records), Jiao guang lu (Joint Guangdong Records), Yue cao zhi (Records of Cantonese Grasses), Guang guo lu (Records of Guangdong Fruits), Nan yue suo ji (Trivial Records of Southern Canton), Guang zhi (Guangdong Records), Yue zhi (Cantonese Records) etc. dealing with 57 sorts of drugs (with individual overlapping ones), the author of Xin yu was Qu Dajun, a surviving fogy of the Ming Dynasty actively involved in the activities to restore the old dynasty and resist the Qing Dynasty, and was persecuted in the literary inquisition in which his works were burnt so that Zhao Xuemin, when quoting his texts, had to go in a roundabout way. PMID:25208840

  1. Nanoscale anisotropic plastic deformation in single crystal GaN

    PubMed Central

    2012-01-01

    Elasto-plastic mechanical deformation behaviors of c-plane (0001) and nonpolar GaN single crystals are studied using nanoindentation, cathodoluminescence, and transmission electron microscopy. Nanoindentation tests show that c-plane GaN is less susceptible to plastic deformation and has higher hardness and Young's modulus than the nonpolar GaN. Cathodoluminescence and transmission electron microscopy characterizations of indent-induced plastic deformation reveal that there are two primary slip systems for the c-plane GaN, while there is only one most favorable slip system for the nonplane GaN. We suggest that the anisotropic elasto-plastic mechanical properties of GaN are relative to its anisotropic plastic deformation behavior. PACS: 62.20.fq; 81.05.Ea; 61.72.Lk. PMID:22353389

  2. Investigating Home Primes and Their Families

    ERIC Educational Resources Information Center

    Herman, Marlena; Schiffman, Jay

    2014-01-01

    The process of prime factor splicing to generate home primes raises opportunity for conjecture and exploration. The notion of "home primes" is relatively new in the chronicle of mathematics. Heleen (1996-97) first described a procedure called "prime factor splicing" (PFS). The exploration of home primes is interesting and…

  3. Priming Macho Attitudes and Emotions.

    ERIC Educational Resources Information Center

    Beaver, Erik D.; And Others

    1992-01-01

    Investigated the effects of reading one of four priming stimuli stories (control, consenting sex, rape, or family) on males' evaluations of, and emotional reactions to, two videotaped date-rape scenarios. Results supported the concepts of a macho personality and revealed interactive effects for both the rape and family prime. (RJM)

  4. Immediate Priming and Cognitive Aftereffects

    ERIC Educational Resources Information Center

    Huber, David E.

    2008-01-01

    Three forced-choice perceptual word identification experiments tested the claim that transitions from positive to negative priming as a function of increasing prime duration are due to cognitive aftereffects. These aftereffects are similar in nature to perceptual aftereffects that produce a negative image due to overexposure and habituation to a…

  5. Rhizosphere priming: a nutrient perspective

    PubMed Central

    Dijkstra, Feike A.; Carrillo, Yolima; Pendall, Elise; Morgan, Jack A.

    2013-01-01

    Rhizosphere priming is the change in decomposition of soil organic matter (SOM) caused by root activity. Rhizosphere priming plays a crucial role in soil carbon (C) dynamics and their response to global climate change. Rhizosphere priming may be affected by soil nutrient availability, but rhizosphere priming itself can also affect nutrient supply to plants. These interactive effects may be of particular relevance in understanding the sustained increase in plant growth and nutrient supply in response to a rise in atmospheric CO2 concentration. We examined how these interactions were affected by elevated CO2 in two similar semiarid grassland field studies. We found that an increase in rhizosphere priming enhanced the release of nitrogen (N) through decomposition of a larger fraction of SOM in one study, but not in the other. We postulate that rhizosphere priming may enhance N supply to plants in systems that are N limited, but that rhizosphere priming may not occur in systems that are phosphorus (P) limited. Under P limitation, rhizodeposition may be used for mobilization of P, rather than for decomposition of SOM. Therefore, with increasing atmospheric CO2 concentrations, rhizosphere priming may play a larger role in affecting C sequestration in N poor than in P poor soils. PMID:23908649

  6. Representing Numbers: Prime and Irrational

    ERIC Educational Resources Information Center

    Zazkis, Rina

    2005-01-01

    This article draws an analogy between prime and irrational numbers with respect to how these numbers are defined and how they are perceived by learners. Excerpts are presented from two research studies: a study on understanding prime numbers by pre-service elementary school teachers and a study on understanding irrational numbers by pre-service…

  7. Phenolic Component Profiles of Mustard Greens, Yu Choy, and 15 Other Brassica Vegetables

    PubMed Central

    Lin, Long-Ze; Harnly, James M

    2013-01-01

    A liquid chromatography–mass spectrometry (LC-MS) profiling method was used to characterize the phenolic components of 17 leafy vegetables from Brassica species other than Brassica oleracea. The vegetables studied were mustard green, baby mustard green, gai choy, baby gai choy, yu choy, yu choy tip, bok choy, bok choy tip, baby bok choy, bok choy sum, Taiwan bok choy, Shanghai bok choy, baby Shanghai bok choy, rapini broccoli, turnip green, napa, and baby napa. This work led to the tentative identification of 71 phenolic compounds consisting of kaempferol 3-O-diglucoside-7-O-glucoside derivatives, isorhamnetin 3-O-glucoside-7-O-glucoside hydroxycinnamoyl gentiobioses, hydroxycinnamoylmalic acids, and hydroxycinnamoylquinic acids. Ten of the compounds, 3-O-diacyltriglucoside-7-O-glucosides of kaempferol and quercetin, had not been previously reported. The phenolic component profiles of these vegetables were significantly different than those of the leafy vegetables from B. oleracea. This is the first comparative study of these leafy vegetables. Ten of the vegetables had never been previously studied by LC-MS. PMID:20465307

  8. Phenolic component profiles of mustard greens, yu choy, and 15 other brassica vegetables.

    PubMed

    Lin, Long-Ze; Harnly, James M

    2010-06-01

    A liquid chromatography-mass spectrometry (LC-MS) profiling method was used to characterize the phenolic components of 17 leafy vegetables from Brassica species other than Brassica oleracea. The vegetables studied were mustard green, baby mustard green, gai choy, baby gai choy, yu choy, yu choy tip, bok choy, bok choy tip, baby bok choy, bok choy sum, Taiwan bok choy, Shanghai bok choy, baby Shanghai bok choy, rapini broccoli, turnip green, napa, and baby napa. This work led to the tentative identification of 71 phenolic compounds consisting of kaempferol 3-O-diglucoside-7-O-glucoside derivatives, isorhamnetin 3-O-glucoside-7-O-glucoside hydroxycinnamoyl gentiobioses, hydroxycinnamoylmalic acids, and hydroxycinnamoylquinic acids. Ten of the compounds, 3-O-diacyltriglucoside-7-O-glucosides of kaempferol and quercetin, had not been previously reported. The phenolic component profiles of these vegetables were significantly different than those of the leafy vegetables from B. oleracea. This is the first comparative study of these leafy vegetables. Ten of the vegetables had never been previously studied by LC-MS. PMID:20465307

  9. Chaotic Nonlinear Prime Number Function

    NASA Astrophysics Data System (ADS)

    Mateos, Luis A.

    2011-06-01

    Dynamical systems in nature, such as heartbeat patterns, DNA sequence pattern, prime number distribution, etc., exhibit nonlinear (chaotic) space-time fluctuations and exact quantification of the fluctuation pattern for predictability purposes has not yet been achieved [1]. In this paper a chaotic-nonlinear prime number function P(s) is developed, from which prime numbers are generated and decoded while composite numbers are encoded over time following the Euler product methodology, which works on sequences progressively culled from multiples of the preceding primes. By relating this P(s) to a virtually closed 2D number line manifold, it is possible to represent the evolving in time of nonlinear (chaotic) systems to a final value where the system becomes stable, becomes linear. This nonlinear prime number function is proposed as a chaotic model system able to describe chaotic systems.

  10. Transfer characteristics in a GaN MFSFET: comparison with a conventional GaN MOSFET

    NASA Astrophysics Data System (ADS)

    Ran, Jinzhi; Ying, Wei; Cai, Xueyuan; Yang, Jianhong

    2012-07-01

    Based on the Miller model, we develop an analytical model for the GaN-based metal-ferroelectric-semiconductor field-effect transistors (MFSFETs). In this article, we investigate the effects of ferroelectric film on the maximum drain current, transconductance and memory window of GaN MFSFET at the different hierarchical thickness values of 10, 30, 50, 100, 200 and 300 nm, as well as the polarisation influence. The results indicate that the thickness of ferroelectric film is one of the critical parameters, and certain trade-off should be made for various potential applications. Moreover, the advantages of GaN MFSFET are also investigated in detail, compared with the conventional GaN metal-oxide-semiconductor field-effect transistor under the conditions of similar design. Our results of simulation shows that GaN MFSFETs hold the numerous advantages in electrical characteristics, such as the maximal drain current reaching 69 mA, and the threshold voltage and the subthreshold slope as low as 1.5 V and 58 mV/decade, respectively. In general, these theoretical predictions not only indicate that GaN MFSFET devices have wide applicational perspectives, but also they provide some important references to the empirical research and the design of new electron devices in the future.

  11. GaN substrate and GaN homo-epitaxy for LEDs: Progress and challenges

    NASA Astrophysics Data System (ADS)

    Wu, Jie-Jun; Wang, Kun; Yu, Tong-Jun; Zhang, Guo-Yi

    2015-06-01

    After a brief review on the progresses in GaN substrates by ammonothermal method and Na-flux method and hydride vapor phase epitaxy (HVPE) technology, our research results of growing GaN thick layer by a gas flow-modulated HVPE, removing the GaN layer through an efficient self-separation process from sapphire substrate, and modifying the uniformity of multiple wafer growth are presented. The effects of surface morphology and defect behaviors on the GaN homo-epitaxial growth on free standing substrate are also discussed, and followed by the advances of LEDs on GaN substrates and prospects of their applications in solid state lighting. Project supported by the National High Technology Research and Development Program of China (Grant No. 2014AA032605), the National Key Basic Research and Development Program of China (Grant Nos. 2012CB619304 and 2011CB301904), and the National Natural Science Foundation of China (Grant Nos. 61376012, 61474003, and 61327801).

  12. Self-catalyzed anisotropic growth of GaN spirals

    NASA Astrophysics Data System (ADS)

    Patsha, Avinash; Sahoo, Prasana; Dhara, S.; Tyagi, A. K.

    2012-06-01

    GaN spirals with homogeneous size are grown using chemical-vapor-deposition technique in a self catalytic process. Raman and photoluminescence (PL) studies reveal wurtzite GaN phase. Nucleation of GaN sphere takes place with the agglomeration Ga clusters and simultaneous reaction with NH3. A growth mechanism involving diffusion limited aggregation process initiating supersaturation and subsequent neck formation along with possible role of thermodynamic fluctuation in different crystalline facets of GaN, is described for the anisotropic spiral structures. Temperature dependent PL spectra show strong excitonic emissions along with the presence of free-to-bound transition.

  13. Dislocation core in GaN

    SciTech Connect

    Liliental-Weber, Zuzanna; Jasinski, Jacek B.; Washburn, Jack; O'Keefe, Michael A.

    2002-02-20

    Light emitting diodes and blue laser diodes grown on GaN have been demonstrated despite six orders of magnitude higher dislocation density than that for III-V arsenide and phosphide diodes. Understanding and determination of dislocation cores in GaN is crucial since both theoretical and experimental work are somewhat contradictory. Transmission Electron Microscopy (TEM) has been applied to study the layers grown by hydride vapor-phase epitaxy (HVPE) and molecular beam epitaxy (MBE) (under Ga rich conditions) in plan-view and cross-section samples. This study suggests that despite the fact that voids are formed along the dislocation line in HVPE material, the dislocations have closed cores. Similar results of closed core are obtained for the screw dislocation in the MBE material, confirming earlier studies.

  14. Amphoteric arsenic in GaN

    SciTech Connect

    Wahl, U.; Correia, J. G.; Araujo, J. P.; Rita, E.; Soares, J. C.

    2007-04-30

    The authors have determined the lattice location of implanted arsenic in GaN by means of conversion electron emission channeling from radioactive {sup 73}As. They give direct evidence that As is an amphoteric impurity, thus settling the long-standing question as to whether it prefers cation or anion sites in GaN. The amphoteric character of As and the fact that As{sub Ga} 'antisites' are not minority defects provide additional aspects to be taken into account for an explanantion of the so-called miscibility gap in ternary GaAs{sub 1-x}N{sub x} compounds, which cannot be grown with a single phase for values of x in the range of 0.1

  15. Mechanisms of subliminal response priming

    PubMed Central

    Kiesel, Andrea; Kunde, Wilfried; Hoffmann, Joachim

    2008-01-01

    Subliminal response priming has been considered to operate on several stages, e.g. perceptual, central or motor stages might be affected. While primes’ impact on target perception has been clearly demonstrated, semantic response priming recently has been thrown into doubt (e.g. Klinger, Burton, & Pitts, 2000). Finally, LRP studies have revealed that subliminal primes evoke motor processes. Yet, the premises for such prime-evoked motor activation are not settled. A transfer of priming to stimuli that have never been presented as targets appears particularly interesting because it suggests a level of processing that goes beyond a reactivation of previously acquired S-R links. Yet, such transfer has not always withstood empirical testing. To account for these contradictory results, we proposed a two-process model (Kunde, Kiesel, & Hoffmann, 2003): First, participants build up expectations regarding imperative stimuli for the required responses according to experience and/or instructions. Second, stimuli that match these “action triggers” directly activate the corresponding motor responses irrespective of their conscious identification. In line with these assumptions, recent studies revealed that non-target primes induce priming when they fit the current task intentions and when they are expected in the experimental setting. PMID:20517516

  16. TEM characterization of GaN nanowires

    SciTech Connect

    Liliental-Weber, Zuzanna; Gao, Y.H.; Bando, Y.

    2002-02-21

    Transmission electron microscopy was applied to study GaN nanowires grown on carbon nanotube surfaces by chemical reaction between Ga{sub 2}O and NH{sub 3} gas in a conventional furnace. These wires grew in two crystallographic directions, <2{und 11}0> and <01{und 1}0> (fast growth directions of GaN), in the form of whiskers covered by small elongated GaN platelets. The morphology of these platelets is similar to that observed during the growth of single crystals from a Ga melt at high temperatures under high nitrogen pressure. It is thought that growth of nanowires in two different crystallographic directions and the arrangement of the platelets to the central whisker may be influenced by the presence of Ga{sub 2}O{sub 3} (based on the observation of the energy dispersive x-ray spectra), the interplanar spacings in the wire, and the presence of defects on the interface between the central part of the nanowire and the platelets surrounding it.

  17. Space Place Prime

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, Austin J.; Novati, Alexander; Fisher, Diane K.; Leon, Nancy J.; Netting, Ruth

    2013-01-01

    Space Place Prime is public engagement and education software for use on iPad. It targets a multi-generational audience with news, images, videos, and educational articles from the Space Place Web site and other NASA sources. New content is downloaded daily (or whenever the user accesses the app) via the wireless connection. In addition to the Space Place Web site, several NASA RSS feeds are tapped to provide new content. Content is retained for the previous several days, or some number of editions of each feed. All content is controlled on the server side, so features about the latest news, or changes to any content, can be made without updating the app in the Apple Store. It gathers many popular NASA features into one app. The interface is a boundless, slidable- in-any-direction grid of images, unique for each feature, and iconized as image, video, or article. A tap opens the feature. An alternate list mode presents menus of images, videos, and articles separately. Favorites can be tagged for permanent archive. Face - book, Twitter, and e-mail connections make any feature shareable.

  18. Prime focus instrument of prime focus spectrograph for Subaru telescope

    NASA Astrophysics Data System (ADS)

    Wang, Shiang-Yu; Braun, David F.; Schwochert, Mark A.; Huang, Pin-Jie; Kimura, Masahiko; Chen, Hsin-Yo; Reiley, Daniel J.; Mao, Peter; Fisher, Charles D.; Tamura, Naoyuki; Chang, Yin-Chang; Hu, Yen-Sang; Ling, Hung-Hsu; Wen, Chih-Yi; Chou, Richard C.-Y.; Takato, Naruhisa; Sugai, Hajime; Ohyama, Youichi; Karoji, Hiroshi; Shimono, Atsushi; Ueda, Akitoshi

    2014-07-01

    The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph design for the prime focus of the 8.2m Subaru telescope. PFS will cover 1.3 degree diameter field with 2394 fibers to complement the imaging capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber positioners are located. In addition, the acquisition and guiding (AG) cameras, the optical fiber positioner system, the cable wrapper, the fiducial fibers, illuminator, and viewer, the field element, and the telemetry system are located inside the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match those of the HSC's Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations within the required accuracy.

  19. PREFACE: SANS-YuMO User Meeting at the Start-up of Scientific Experiments on the IBR-2M Reactor: Devoted to the 75th anniversary of Yu M Ostanevich's birth

    NASA Astrophysics Data System (ADS)

    Gordely, Valentin; Kuklin, Alexander; Balasoiu, Maria

    2012-03-01

    The Second International Workshop 'SANS-YuMO User Meeting at the Start-up of Scientific Experiments on the IBR-2M Reactor', devoted to the 75th anniversary of the birth of Professor Yu M Ostanevich (1936-1992), an outstanding neutron physicist and the founder of small-angle neutron scattering (field, group, and instrument) at JINR FLNPh, was held on 27-30 May at the Frank Laboratory of Neutron Physics. The first Workshop was held in October 2006. Research groups from different neutron centers, universities and research institutes across Europe presented more than 35 oral and poster presentations describing scientific and methodological results. Most of them were obtained with the help of the YuMO instrument before the IBR-2 shutdown in 2006. For the last four years the IBR-2 reactor has been shut down for refurbishment. At the end of 2010 the physical launch of the IBR-2M reactor was finally realized. Nowadays the small-angle neutron scattering (SANS) technique is applied to a wide range of scientific problems in condensed matter, soft condensed matter, biology and nanotechnology, and despite the fact that there are currently over 30 SANS instruments in operation worldwide at both reactor and spallation sources, the demand for beam-time is considerably higher than the time available. It must be remembered, however, that as the first SANS machine on a steady-state reactor was constructed at the Institute Laue Langevin, Grenoble, the first SANS instrument on a 'white' neutron pulsed beam was accomplished at the Joint Institute for Nuclear Research at the IBR-30 reactor, beamline N5. During the meeting Yu M Ostanevich's determinative and crucial contribution to the construction of spectrometers at the IBR-2 high-pulsed reactor was presented, as well as his contribution to the development of the time-of-flight (TOF) small-angle scattering technique, and a selection of other scientific areas. His leadership and outstanding scientific achievements in applications of the

  20. [Zheng Yu-lin, a founder of the acupuncture and moxibustion cause of new China].

    PubMed

    Tian, Da-zhe; Liu, Jun-chi; Zhao, Juan; Zheng, Jun-jiang

    2007-07-01

    Mr. ZHENG Yu-lin is one of the most outstanding acupuncture scientists in the modern times in our country. He inherits the learning handed down in a family and is bold in making innovations, successfully combines the exercises to benefit the internal organs with Chinese traditional acupuncture needling methods, forming a set of unique Zheng's needling methods, which is used for treatment of severe ophthalmopathy with excellent therapeutic effects, and is famed the world over. Main achievements: took on scientific researches of acupuncture and moxibustion, teaching and clinical works in the first stage of establishment of China Academy of Traditional Chinese Medicinel trains a large number of famous specificities of acupuncture and moxibustion for new China; advocates study on channel essence; cures stubborn diseases for leaders of friend countries undertaking the great trust of the central leaders for many times, becoming an important ties of Chinese political foreign affairs. PMID:17722840

  1. The complete mitochondrial genome of Bombyx mori strain Yu39 (Lepidoptera: Bombycidae).

    PubMed

    Zhang, Yong-Liang; Zhao, Jin-Hui; Zhou, Qi-Ming

    2016-09-01

    The complete mitochondrial genome of Bombyx mori strain Yu39 (Lepidoptera: Bombycidae) is a circular molecule of 15,652 bp in length, containing 37 typical mitochondrial genes: 13 protein-coding genes (PCGs), 22 transfer RNAs, 2 ribosomal RNAs and a non-coding AT-rich region. Its gene order and arrangement are identical to the common type found in most insect mitogenomes. All PCGs start with a typical ATN codon, except for the cox1 gene, which begins with uncertained codon. All PCGs terminate in the common stop codon TAA, except for the cox1 and cox2, which use single T as their stop codons. The non-coding AT-rich region is 494-bp long, located between rrnS and trnM genes. It contains some structures of repeated motifs and microsatellite-like elements characteristic of the other lepidopterons. PMID:25676361

  2. [Shi Ji Yao Yu, the earliest extant monograph on TCM nursery].

    PubMed

    Fu, W

    1999-07-01

    Nursery of traditional Chinese medicine (NTCM) has a long history. However, due to the change and influence of the era, society, life style, and many other factors, NTCM did not become an independent discipline for a long period. Although there have been many articles about NTCM appearing in various historical books of traditional Chinese medicine, books specializing on NTCM were not available until later. The earliest ancient book, which is still currently available, describing NTCM in details is the "Shi Ji Yao Yu" written by Qian Xiang in the Qing Dynasty. The book explains the key issues of taking care of a patient's emotional well-being, life style, diet, illness, and drug administration which are of great practical significance now and for the future. PMID:11624096

  3. Self-organized topological superconductivity in a Yu-Shiba-Rusinov chain

    NASA Astrophysics Data System (ADS)

    Schecter, Michael; Flensberg, Karsten; Christensen, Morten H.; Andersen, Brian M.; Paaske, Jens

    2016-04-01

    We study a chain of magnetic moments exchange coupled to a conventional three-dimensional superconductor. In the normal state the chain orders into a collinear configuration, while in the superconducting phase we find that ferromagnetism is unstable to the formation of a magnetic spiral state. Beyond weak exchange coupling the spiral wave vector greatly exceeds the inverse superconducting coherence length as a result of the strong spin-spin interaction mediated through the subgap band of Yu-Shiba-Rusinov states. Moreover, the simple spin-spin exchange description breaks down as the subgap band crosses the Fermi energy, wherein the spiral phase becomes stabilized by the spontaneous opening of a p -wave superconducting gap within the band. This leads to the possibility of electron-driven topological superconductivity with Majorana boundary modes using magnetic atoms on superconducting surfaces.

  4. Main features of the new software control system for the YuMO instrument

    NASA Astrophysics Data System (ADS)

    Kirilov, A. S.

    2012-03-01

    During the last years the new software instrumental complex Sonix+ has been developed at FLNP JINR to replace the former Sonix control system [1]. This complex has been tested at a number of IBR-2 instruments (REMUR, NERA-PR) and on instruments at other centers - KIA, Moscow (MOND), etc. We plan to install the new complex at the YuMO instrument as well. The Sonix+ is implemented on the PC/Windows XP platform, whereas the Sonix is based on the VME/Os-9 obsolete platform. The Sonix+ [1] has been designed considering the experience of long-term operation of the predecessor and recent trends. The paper is devoted to the main features of the new software and the comparison with the former one.

  5. P-type doping of GaN

    SciTech Connect

    Wong, R.K.

    2000-04-10

    After implantation of As, As + Be, and As + Ga into GaN and annealing for short durations at temperatures as high as 1500 C, the GaN films remained highly resistive. It was apparent from c-RBS studies that although implantation damage did not create an amorphous layer in the GaN film, annealing at 1500 C did not provide enough energy to completely recover the radiation damage. Disorder recovered significantly after annealing at temperatures up to 1500 C, but not completely. From SIMS analysis, oxygen contamination in the AIN capping layer causes oxygen diffusion into the GaN film above 1400 C. The sapphire substrate (A1203) also decomposed and oxygen penetrated into the backside of the GaN layer above 1400 C. To prevent donor-like oxygen impurities from the capping layer and the substrate from contaminating the GaN film and compensating acceptors, post-implantation annealing should be done at temperatures below 1500 C. Oxygen in the cap could be reduced by growing the AIN cap on the GaN layer after the GaN growth run or by depositing the AIN layer in a ultra high vacuum (UHV) system post-growth to minimize residual oxygen and water contamination. With longer annealing times at 1400 C or at higher temperatures with a higher quality AIN, the implantation drainage may fully recover.

  6. GaN Electronics For High Power, High Temperature Applications

    SciTech Connect

    PEARTON,S.J.; REN,F.; ZHANG,A.P.; DANG,G.; CAO,X.A.; LEE,K.P.; CHO,H.; GILA,B.P.; JOHNSON,J.W.; MONIER,C.; ABERNATHY,C.R.; HAN,JUNG; BACA,ALBERT G.; CHYI,J.-I.; LEE,C.-M.; NEE,T.-E.; CHUO,C.-C.; CHU,S.N.G.

    2000-06-12

    A brief review is given of recent progress in fabrication of high voltage GaN and AlGaN rectifiers. GaN/AlGaN heterojunction bipolar transistors and GaN metal-oxide semiconductor field effect transistors. Improvements in epitaxial layer quality and in fabrication techniques have led to significant advances in device performance.

  7. Prime Diagnosticity in Short-Term Repetition Priming: Is Primed Evidence Discounted, Even when It Reliably Indicates the Correct Answer?

    ERIC Educational Resources Information Center

    Weidemann, Christoph T.; Huber, David E.; Shiffrin, Richard M.

    2008-01-01

    The authors conducted 4 repetition priming experiments that manipulated prime duration and prime diagnosticity in a visual forced-choice perceptual identification task. The strength and direction of prime diagnosticity produced marked effects on identification accuracy, but those effects were resistant to subsequent changes of diagnosticity.…

  8. The Pharmacology of Nociceptor Priming

    PubMed Central

    Kandasamy, Ram

    2015-01-01

    Nociceptors and neurons in the central nervous system (CNS) that receive nociceptive input show remarkable plasticity in response to injury. This plasticity is thought to underlie the development of chronic pain states. Hence, further understanding of the molecular mechanisms driving and maintaining this plasticity has the potential to lead to novel therapeutic approaches for the treatment of chronic pain states. An important concept in pain plasticity is the presence and persistence of “hyperalgesic priming.” This priming arises from an initial injury and results in a remarkable susceptibility to normally subthreshold noxious inputs causing a prolonged pain state in primed animals. Here we describe our current understanding of how this priming is manifested through changes in signaling in the primary nociceptor as well as through memory like alterations at CNS synapses. Moreover, we discuss how commonly utilized analgesics, such as opioids, enhance priming therefore potentially contributing to the development of persistent pain states. Finally we highlight where these priming models draw parallels to common human chronic pain conditions. Collectively, these advances in our understanding of pain plasticity reveal a variety of targets for therapeutic intervention with the potential to reverse rather than palliate chronic pain states. PMID:25846612

  9. Implant activation and redistribution of dopants in GaN

    SciTech Connect

    Zolper, J.C.; Pearton, S.J.; Wilson, R.G.; Stall, R.A.

    1996-07-01

    GaN and related III-Nitride materials (IN, an) have recently been the focus of extensive research for photonic and electronic device applications. As this material system matures, ion implantation doping and isolation is expected to play an important role in advance device demonstrations. To this end, we report the demonstration of implanted p-type doping with Mg+P and Ca as well as n-type doping with Si in GaN. These implanted dopants require annealing 105 approximately1100 {degrees}C to achieve electrical activity, but demonstrate limited redistribution at this temperature. The redistribution of other potential dopants in GaN (such as Be, Zn, and Cd) will also be reported. Results for a GaN junction field effect transistor (JFET), the first GaN device to use implantation doping, will also be presented.

  10. Response Priming with More or Less Biological Movements as Primes.

    PubMed

    Eckert, David; Bermeitinger, Christina

    2016-07-01

    Response priming in general is a suitable tool in cognitive psychology to investigate motor preactivations. Typically, compatibility effects reflect faster reactions in cases in which prime and target suggest the same response (i.e., compatible trials) compared with cases in which prime and target suggest opposite responses (i.e., incompatible trials). With moving dots that were horizontally aligned, Bermeitinger (2013) found a stable pattern of results: with short SOAs, faster responses in compatible trials were found; with longer SOAs up to 250 ms, faster responses in incompatible trials were found. It is unclear whether these results are specific to the special motion used therein or whether it generalizes to other motions. We therefore used other motions realized by arrangements of dots. In four experiments, we tested point-light displays (biological coherent walkers vs. less biological scrambled/split displays) as primes. In two experiments, eye gaze motions realized by moving dots representing irises and pupils (i.e., biological) versus the same motion either without surrounding face information or integrated in an abstract line drawing (i.e., less biological) were used. We found overall large positive compatibility effects with biological motion primes and also positive-but smaller-compatibility effects with less biological motion primes. Most important, also with very long SOAs (up to 1320 ms), we did not find evidence for negative compatibility effects. Thus, the pattern of positive-followed-by-negative-compatibility effects found in Bermeitinger (2013) seems to be specific to the materials used therein, whereas response priming in general seems an applicable tool to study motion perception. PMID:27150613

  11. Atomic force microscopy studies of homoepitaxial GaN layers grown on GaN template by laser MBE

    NASA Astrophysics Data System (ADS)

    Choudhary, B. S.; Singh, A.; Tanwar, S.; Tyagi, P. K.; Kumar, M. Senthil; Kushvaha, S. S.

    2016-04-01

    We have grown homoepitaxial GaN films on metal organic chemical vapor deposition (MOCVD) grown 3.5 µm thick GaN on sapphire (0001) substrate (GaN template) using an ultra-high vacuum (UHV) laser assisted molecular beam epitaxy (LMBE) system. The GaN films were grown by laser ablating a polycrystalline solid GaN target in the presence of active r.f. nitrogen plasma. The influence of laser repetition rates (10-30 Hz) on the surface morphology of homoepitaxial GaN layers have been studied using atomic force microscopy. It was found that GaN layer grown at 10 Hz shows a smooth surface with uniform grain size compared to the rough surface with irregular shape grains obtained at 30 Hz. The variation of surface roughness of the homoepitaxial GaN layer with and without wet chemical etching has been also studied and it was observed that the roughness of the film decreased after wet etching due to the curved structure/rough surface.

  12. Test Sequence Priming in Recognition Memory

    ERIC Educational Resources Information Center

    Johns, Elizabeth E.; Mewhort, D. J. K.

    2009-01-01

    The authors examined priming within the test sequence in 3 recognition memory experiments. A probe primed its successor whenever both probes shared a feature with the same studied item ("interjacent priming"), indicating that the study item like the probe is central to the decision. Interjacent priming occurred even when the 2 probes did not…

  13. Serotonin levels influence patterns of repetition priming.

    PubMed

    Burgund, E Darcy; Marsolek, Chad J; Luciana, Monica

    2003-01-01

    Repetition priming in a word-stem completion task was examined in a group of control subjects and in a group of experimental subjects under conditions of acute tryptophan depletion (T-) and tryptophan augmentation (T+). Experimental subjects ingested amino acid compounds that depleted or loaded the body with tryptophan, and word-stem completion priming performance was measured. Results indicate differential effects of T- and T+ manipulations on word-stem completion priming. In the control group, both specific-visual and amodal priming were observed. Conversely, in the T+ condition, specific-visual priming, but no amodal priming, was observed, whereas in the T- condition, amodal priming, but no specific-visual priming, was observed. The authors conclude that serotonin (5-hydroxytryptamine) plays a critical role in repetition priming by helping to modulate which neural systems contribute to priming effects. PMID:12597085

  14. Priming mortality salience: supraliminal, subliminal and "double-death" priming techniques.

    PubMed

    Mahoney, Melissa B; Saunders, Benjamin A; Cain, Nicole M

    2014-01-01

    The study examined whether successively presented subliminal and supraliminal morality salience primes ("double death" prime) would have a stronger influence on death thought accessibility than subliminal or supraliminal primes alone. A between-subjects 2 (subliminal prime/control) × 2 (supraliminal prime/control) design was used. The supraliminal prime prompted participants to answer questions about death. For the subliminal prime, the word death was presented outside of awareness. Both priming techniques differed significantly from a control in ability to elicit mortality salience. There was an interactive influence of both primes. Implications for unconscious neutral networks relating to death are discussed. PMID:24592974

  15. The Intervenor Effect in Masked Priming: How Does Masked Priming Survive across an Intervening Word?

    ERIC Educational Resources Information Center

    Forster, Kenneth I.

    2009-01-01

    Four masked priming experiments are reported investigating the effect of inserting an unrelated word between the masked prime and the target. When the intervening word is visible, identity priming is reduced to the level of one-letter-different form priming, but form priming is largely unaffected. However, when the intervening word is itself…

  16. On the Control of Single-Prime Negative Priming: The Effects of Practice and Time Course

    ERIC Educational Resources Information Center

    Chao, Hsuan-Fu

    2009-01-01

    Single-prime negative priming refers to the phenomenon wherein repetition of a prime as the probe target results in delayed response. Sometimes this effect has been found to be contingent on participants' unawareness of the primes, and sometimes it has not. Further, sometimes this effect has been found to be eliminated when the prime could predict…

  17. Repeated Masked Category Primes Interfere With Related Exemplars: New Evidence for Negative Semantic Priming

    ERIC Educational Resources Information Center

    Wentura, Dirk; Frings, Christian

    2005-01-01

    In 4 experiments, the authors found evidence for negatively signed masked semantic priming effects (with category names as primes and exemplars as targets) using a new technique of presenting the masked primes. By rapidly interchanging prime and mask during the stimulus onset asynchrony, they increased the total prime exposure to a level…

  18. Early dynamics of the semantic priming shift

    PubMed Central

    Lavigne, Frédéric; Chanquoy, Lucile; Dumercy, Laurent; Vitu, Françoise

    2013-01-01

    Semantic processing of sequences of words requires the cognitive system to keep several word meanings simultaneously activated in working memory with limited capacity. The real- time updating of the sequence of word meanings relies on dynamic changes in the associates to the words that are activated. Protocols involving two sequential primes report a semantic priming shift from larger priming of associates to the first prime to larger priming of associates to the second prime, in a range of long SOAs (stimulus-onset asynchronies) between the second prime and the target. However, the possibility for an early semantic priming shift is still to be tested, and its dynamics as a function of association strength remain unknown. Three multiple priming experiments are proposed that cross-manipulate association strength between each of two successive primes and a target, for different values of short SOAs and prime durations. Results show an early priming shift ranging from priming of associates to the first prime only to priming of strong associates to the first prime and all of the associates to the second prime. We investigated the neural basis of the early priming shift by using a network model of spike frequency adaptive cortical neurons (e.g., Deco & Rolls, 2005), able to code different association strengths between the primes and the target. The cortical network model provides a description of the early dynamics of the priming shift in terms of pro-active and retro-active interferences within populations of excitatory neurons regulated by fast and unselective inhibitory feedback. PMID:23717346

  19. GaN: Defect and Device Issues

    SciTech Connect

    Pearton, S.J.; Ren, F.; Shul, R.J.; Zolper, J.C.

    1998-11-09

    The role of extended and point defects, and key impurities such as C, O and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

  20. Nanoplasmonics of prime number arrays.

    PubMed

    Forestiere, Carlo; Walsh, Gary F; Miano, Giovanni; Dal Negro, Luca

    2009-12-21

    In this paper, we investigate the plasmonic near-field localization and the far-field scattering properties of non-periodic arrays of Ag nanoparticles generated by prime number sequences in two spatial dimensions. In particular, we demonstrate that the engineering of plasmonic arrays with large spectral flatness and particle density is necessary to achieve a high density of electromagnetic hot spots over a broader frequency range and a larger area compared to strongly coupled periodic and quasi-periodic structures. Finally, we study the far-field scattering properties of prime number arrays illuminated by plane waves and we discuss their angular scattering properties. The study of prime number arrays of metal nanoparticles provides a novel strategy to achieve broadband enhancement and localization of plasmonic fields for the engineering of nanoscale nano-antenna arrays and active plasmonic structures. PMID:20052140

  1. Priming in Systemic Plant Immunity

    SciTech Connect

    Jung, Ho Won; Tschaplinski, Timothy J; Wang, Lin; Glazebrook, Jane; Greenberg, Jean T.

    2009-01-01

    Upon local infection, plants possess inducible systemic defense responses against their natural enemies. Bacterial infection results in the accumulation to high levels of the mobile metabolite C9-dicarboxylic acid azelaic acid in the vascular sap of Arabidopsis. Azelaic acid confers local and systemic resistance against Pseudomonas syringae. The compound primes plants to strongly accumulate salicylic acid (SA), a known defense signal, upon infection. Mutation of a gene induced by azelaic acid (AZI1) results in the specific loss in plants of systemic immunity triggered by pathogen or azelaic acid and of the priming of SA induction. AZI1, a predicted secreted protein, is also important for generating vascular sap that confers disease resistance. Thus, azelaic acid and AZI1 comprise novel components of plant systemic immunity involved in priming defenses.

  2. Structural Priming: A Critical Review

    PubMed Central

    Pickering, Martin J.; Ferreira, Victor S.

    2009-01-01

    Repetition is a central phenomenon of behavior, and researchers make extensive use of it to illuminate psychological functioning. In the language sciences, a ubiquitous form of such repetition is structural priming, a tendency to repeat or better process a current sentence because of its structural similarity to a previously experienced (“prime”) sentence (Bock, 1986). The recent explosion of research in structural priming has made it the dominant means of investigating the processes involved in the production (and increasingly, comprehension) of complex expressions such as sentences. This review considers its implications for the representation of syntax and the mechanisms of production, comprehension, and their relationship. It then addresses the potential functions of structural priming, before turning to its implications for first language acquisition, bilingualism, and aphasia We close with theoretical and empirical recommendations for future investigations. PMID:18444704

  3. The Affective Regulation of Cognitive Priming

    PubMed Central

    Storbeck, Justin; Clore, Gerald L.

    2008-01-01

    Semantic and affective priming are classic effects observed in cognitive and social psychology, respectively. We discovered that affect regulates such priming effects. In Experiment 1, positive and negative moods were induced prior to one of three priming tasks; evaluation, categorization, or lexical decision. As predicted, positive affect led to both affective priming (evaluation task) and semantic priming (category and lexical decision tasks). However, negative affect inhibited such effects. In Experiment 2, participants in their natural affective state completed the same priming tasks as in Experiment 1. As expected, affective priming (evaluation task) and category priming (categorization and lexical decision tasks) were observed in such resting affective states. Hence, we conclude that negative affect inhibits semantic and affective priming. These results support recent theoretical models, which suggest that positive affect promotes associations among strong and weak concepts, and that negative affect impairs such associations (Kuhl, 2000; Clore & Storbeck, 2006). PMID:18410195

  4. Inductively coupled plasma etching of GaN

    SciTech Connect

    Shul, R.J.; McClellan, G.B.; Casalnuovo, S.A.; Rieger, D.J.; Pearton, S.J.; Constantine, C.; Barratt, C.; Karlicek, R.F. Jr.; Tran, C.; Schurman, M.

    1996-08-01

    Inductively coupled plasma (ICP) etch rates for GaN are reported as a function of plasma pressure, plasma chemistry, rf power, and ICP power. Using a Cl{sub 2}/H{sub 2}/Ar plasma chemistry, GaN etch rates as high as 6875 A/min are reported. The GaN surface morphology remains smooth over a wide range of plasma conditions as quantified using atomic force microscopy. Several etch conditions yield highly anisotropic profiles with smooth sidewalls. These results have direct application to the fabrication of group-III nitride etched laser facets. {copyright} {ital 1996 American Institute of Physics.}

  5. Screw dislocations in GaN

    SciTech Connect

    Liliental-Weber, Zuzanna; Jasinski, Jacek B.; Washburn, Jack; O'Keefe, Michael A.

    2002-02-15

    GaN has received much attention over the past few years because of several new applications, including light emitting diodes, blue laser diodes and high-power microwave transistors. One of the biggest problems is a high density of structural defects, mostly dislocations, due to a lack of a suitable lattice-matched substrate since bulk GaN is difficult to grow in large sizes. Transmission Electron Microscopy (TEM) has been applied to study defects in plan-view and cross-sections on samples prepared by conventional techniques such as mechanical thinning and precision ion milling. The density of dislocations close to the sample surface of a 1 mm-thick HVPE sample was in the range of 3x109 cm-2. All three types of dislocations were present in these samples, and almost 50 percent were screw dislocations. Our studies suggest that the core structure of screw dislocations in the same material might differ when the material is grown by different methods.

  6. Longitudinal Excitons in GaN

    NASA Astrophysics Data System (ADS)

    Reynolds, D. C.; Jogai, B.; Collins, T. C.

    2002-05-01

    Many of the previous investigations of longitudinal excitons have involved reflection and absorption measurements rather than emission. In these measurements it is more difficult to resolve the longitudinal exciton from the Γ5 and Γ6 free excitons in wurtzite material. The longitudinal excitons have energies and oscillator strengths that depend on the direction of propagation and they are not observable along the principal axis of the crystal. In the wurtzite structure, such as GaN, the Γ5 exciton is the pure transverse mode, whereas the longitudinal is a mixed mode going from pure longitudinal, for the propogation direction K perpendicular to C, to pure transverse for K parallel to C. If more than one orientation is present in the sample, it is clear that more than one longitudinal exciton may be seen since it is a mixed mode. In the current experiment we observe more than one mode, which we associate with more than one crystal orientation. This may result from the columnar growth often observed in GaN.

  7. GaN for LED applications

    NASA Technical Reports Server (NTRS)

    Pankove, J. I.

    1973-01-01

    In order to improve the synthesis of GaN the effect of various growth and doping parameters has been studied. Although Be, Li, Mg, and Dy can be used to overcompensate native donors, the most interesting acceptor element is Zn. The emission spectrum and the luminescence efficiency depend on the growth temperature (below 800 C), on the partial pressure of the doping impurity, and on the duration of growth. Blue-green electroluminescence with a power efficiency of 0.1 percent and a brightness of 850 fL (at 0.6 mA and 22.5 V) was obtained. Some diodes allow the color of the emitted light to change by reversing the polarity of the bias. Continuous operation of a diode over a period of 5 months showed no evidence of degradation. The luminescence properties of ion-implanted GaN were studied. Delay effects were found in the electroluminescence of diodes, although, with a dc bias, a 70-MHz modulation was possible.

  8. Oligomerizations of deoxyadenosine bis-phosphates and of their 3-prime-5-prime, 3-prime-3-prime, and 5-prime-5-prime dimers - Effects of a pyrophosphate-linked, poly(T) analog

    NASA Technical Reports Server (NTRS)

    Visscher, J.; Bakker, C. G.; Schwartz, Alan W.

    1990-01-01

    The effect of a 3-prime-5-prime pyrophosphate-linked oligomer of pTp on oligomerizations of pdAp and of its 3-prime-5-prime, 3-prime-3-prime, and 5-prime-5-prime dimers was investigated, using HPLC to separate the reaction mixtures; peak detection was by absorbance monitoring at 254 nm. It was expected that the dimers would form stable complexes with the template, with the degree of stability depending upon the internal linkage of each dimer. It was found that, although the isomers differ substantially in their oligomerization behavior in the absence of template, the analog-template catalyzes the oligomerization to about the same extent in all three cases.

  9. Priming and Habituation for Faces: Individual Differences and Inversion Effects

    ERIC Educational Resources Information Center

    Rieth, Cory A.; Huber, David E.

    2010-01-01

    Immediate repetition priming for faces was examined across a range of prime durations in a threshold identification task. Similar to word repetition priming results, short duration face primes produced positive priming whereas long duration face primes eliminated or reversed this effect. A habituation model of such priming effects predicted that…

  10. Barotropic processes associated with the development of the Mei-yu precipitation system

    NASA Astrophysics Data System (ADS)

    Li, Tingting; Li, Xiaofan

    2016-05-01

    The barotropic processes associated with the development of a precipitation system are investigated through analysis of cloud-resolving model simulations of Mei-yu torrential rainfall events over eastern China in mid-June 2011. During the model integration period, there were three major heavy rainfall events: 9-12, 13-16 and 16-20 June. The kinetic energy is converted from perturbation to mean circulations in the first and second period, whereas it is converted from mean to perturbation circulations in the third period. Further analysis shows that kinetic energy conversion is determined by vertical transport of zonal momentum. Thus, the prognostic equation of vertical transport of zonal momentum is derived, in which its tendency is associated with dynamic, pressure gradient and buoyancy processes. The kinetic energy conversion from perturbation to mean circulations in the first period is mainly associated with the dynamic processes. The kinetic energy conversion from mean to perturbation circulations in the third period is generally related to the pressure gradient processes.

  11. New opportunities provided by modernized small-angle neutron scattering two-detector system instrument (YuMO)

    NASA Astrophysics Data System (ADS)

    Kuklin, A. I.; Soloviov, D. V.; Rogachev, A. V.; Utrobin, P. K.; Kovalev, Yu S.; Balasoiu, M.; Ivankov, O. I.; Sirotin, A. P.; Murugova, T. N.; Petukhova, T. B.; Gorshkova, Yu E.; Erhan, R. V.; Kutuzov, S. A.; Soloviev, A. G.; Gordeliy, V. I.

    2011-04-01

    Main features of the modernized small-angle neutron scattering spectrometer (YuMO) at IBR-2M pulsed reactor are described. New installations for sample environment of the spectrometer are highlighted. The modernized SANS instrument (YuMO) is equipped with a new type of position sensitive detector as well as two detector system which provide a unique dynamic range (Qmax/Qmin ratio is about 90). Sample environment is extended with a magnetic system (magnetic field about 2.5 Tesla), automated high pressure setup which allows simultaneous SANS and volumetric high pressure studies and light illumination system. In particular, these developments led to considerable improvements of resolution of the instrument (about 1%) and opened the possibility to study anisotropic materials and perform efficient high pressure studies.

  12. On Techniques of Prime Factorization

    ERIC Educational Resources Information Center

    Cohen, David B.

    1977-01-01

    This article gives two methods of resolving natural numbers into prime factors. Depending upon the number that is being resolved, one method may be better to use than the other. However, it is difficult to tell beforehand which is the better method to employ. Examples are given. (Author/MA)

  13. Apollo 13 prime crew portrait

    NASA Technical Reports Server (NTRS)

    1969-01-01

    Apollo 13 prime crew portrait. From left to right are Astronauts James A. Lovell, Thomas K. Mattingly, and Fred W. Haise in their space suits. On the table in front of them are (l-r) a model of a sextant, the Apollo 13 insignia, and a model of an astrolabe. The sextant and astrolabe are two ancient forms of navigation.

  14. Prime Suspect, Second Row Center

    ERIC Educational Resources Information Center

    Laird, Ellen A.

    2011-01-01

    His father had been hacked to death in his own bed with an ax the previous November. His mother was similarly brutalized and left for dead with her husband but survived. On the last Monday of that August, after several months and many investigative twists, turns, and fumbles, there sat the son--the prime suspect--in Ellen Laird's literature class,…

  15. The Search for Prime Numbers.

    ERIC Educational Resources Information Center

    Pomerance, Carl

    1982-01-01

    Until recently the testing of a 100-digit number to determine whether it is prime or composite could have taken a century. However, in the past two years a method has been developed enabling a computer to determine the primality of an arbitrary number in about 40 seconds of running time. (Author/JN)

  16. Spirit's Prime-Mission Traverse

    NASA Technical Reports Server (NTRS)

    2004-01-01

    A traverse map for NASA's Mars Exploration Rover Spirit traces the path Spirit drove during its prime mission of 90 sols. The base image for this map was taken seconds before landing by Spirit's downward-looking descent image motion estimation system camera.

  17. Structural Priming: A Critical Review

    ERIC Educational Resources Information Center

    Pickering, Martin J.; Ferreira, Victor S.

    2008-01-01

    Repetition is a central phenomenon of behavior, and researchers have made extensive use of it to illuminate psychological functioning. In the language sciences, a ubiquitous form of such repetition is "structural priming," a tendency to repeat or better process a current sentence because of its structural similarity to a previously experienced…

  18. GaN grown on nano-patterned sapphire substrates

    NASA Astrophysics Data System (ADS)

    Jing, Kong; Meixin, Feng; Jin, Cai; Hui, Wang; Huaibing, Wang; Hui, Yang

    2015-04-01

    High-quality gallium nitride (GaN) film was grown on nano-patterned sapphire substrates (NPSS) and investigated using XRD and SEM. It was found that the optimum thickness of the GaN buffer layer on the NPSS is 15 nm, which is thinner than that on micro-patterned sapphire substrates (MPSS). An interesting phenomenon was observed for GaN film grown on NPSS:GaN mainly grows on the trench regions and little grows on the sidewalls of the patterns at the initial growth stage, which is dramatically different from GaN grown on MPSS. In addition, the electrical and optical properties of LEDs grown on NPSS were characterized. Project supported by the Suzhou Nanojoin Photonics Co., Ltd and the High-Tech Achievements Transformation of Jiangsu Province, China (No.BA2012010).

  19. Epitaxy of GaN Nanowires on Graphene.

    PubMed

    Kumaresan, Vishnuvarthan; Largeau, Ludovic; Madouri, Ali; Glas, Frank; Zhang, Hezhi; Oehler, Fabrice; Cavanna, Antonella; Babichev, Andrey; Travers, Laurent; Gogneau, Noelle; Tchernycheva, Maria; Harmand, Jean-Christophe

    2016-08-10

    Epitaxial growth of GaN nanowires on graphene is demonstrated using molecular beam epitaxy without any catalyst or intermediate layer. Growth is highly selective with respect to silica on which the graphene flakes, grown by chemical vapor deposition, are transferred. The nanowires grow vertically along their c-axis and we observe a unique epitaxial relationship with the ⟨21̅1̅0⟩ directions of the wurtzite GaN lattice parallel to the directions of the carbon zigzag chains. Remarkably, the nanowire density and height decrease with increasing number of graphene layers underneath. We attribute this effect to strain and we propose a model for the nanowire density variation. The GaN nanowires are defect-free and they present good optical properties. This demonstrates that graphene layers transferred on amorphous carrier substrates is a promising alternative to bulk crystalline substrates for the epitaxial growth of high quality GaN nanostructures. PMID:27414518

  20. Novel high frequency devices with graphene and GaN

    NASA Astrophysics Data System (ADS)

    Zhao, Pei

    This work focuses on exploring new materials and new device structures to develop novel devices that can operate at very high speed. In chapter 2, the high frequency performance limitations of graphene transistor with channel length less than 100 nm are explored. The simulated results predict that intrinsic cutoff frequency fT of graphene transistor can be close to 2 THz at 15 nm channel length. In chapter 3, we explored the possibility of developing a 2D materials based vertical tunneling device. An analytical model to calculate the channel potentials and current-voltage characteristics in a Symmetric tunneling Field-Effect-Transistor (SymFET) is presented. The symmetric resonant peak in SymFET is a good candidate for high-speed analog applications. Rest of the work focuses on Gallium Nitride (GaN), several novel device concepts based on GaN heterostructure have been proposed for high frequency and high power applications. In chapter 4, we compared the performance of GaN Schottky diodes on bulk GaN substrates and GaN-on-sapphire substrates. In addition, we also discussed the lateral GaN Schottky diode between metal/2DEGs. The advantage of lateral GaN Schottky diodes is the intrinsic cutoff frequency is in the THz range. In chapter 5, a GaN Heterostructure barrier diode (HBD) is designed using the polarization charge and band offset at the AlGaN/GaN heterojunction. The polarization charge at AlGaN/GaN interface behaves as a delta-doping which induces a barrier without any chemical doping. The IV characteristics can be explained by the barrier controlled thermionic emission current. GaN HBDs can be directly integrated with GaN HEMTs, and serve as frequency multipliers or mixers for RF applications. In chapter 6, a GaN based negative effective mass oscillator (NEMO) is proposed. The current in NEMO is estimated under the ballistic limits. Negative differential resistances (NDRs) can be observed with more than 50% of the injected electrons occupied the negative

  1. Fabrication of bamboo-shaped GaN nanorods

    NASA Astrophysics Data System (ADS)

    Li, H.; Li, J. Y.; He, M.; Chen, X. L.; Zhang, Z.

    Bamboo-shaped GaN nanorods were formed through a simple sublimation method. They were characterized by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). The TEM image showed that the nanorods were bamboo-like. XRD, HRTEM and SAED patterns indicated that the nanorods were single-crystal wurtzite GaN.

  2. Modeling of temperature sensor built on GaN nanostructures

    NASA Astrophysics Data System (ADS)

    Asgari, A.; Taheri, S.

    2011-03-01

    A GaN nanostructure based temperature sensor has been modeled using the minority-carrier exclusion theory. The model takes into account the effects of temperature, carrier concentrations and electric field on carrier mobilities. The model also consists of different carrier scattering mechanisms such as phonon and natural ionized scattering. The calculation results show that the resistance of modeled GaN nanostructure based temperature sensor is strongly dependent on the sensor structural parameters such as doping density and device size.

  3. ARM MJO Investigation Experiment on Gan Island (AMIE-Gan) Science Plan

    SciTech Connect

    Long, CL; Del Genio, A; Deng, M; Fu, X; Gustafson, W; Houze, R; Jakob, C; Jensen, M; Johnson, R; Liu, X; Luke, E; May, P; McFarlane, S; Minnis, P; Schumacher, C; Vogelmann, A; Wang, Y; Webster, P; Xie, S; Zhang, C

    2011-04-11

    The overarching campaign, which includes the ARM Mobile Facility 2 (AMF2) deployment in conjunction with the Dynamics of the Madden-Julian Oscillation (DYNAMO) and the Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011) campaigns, is designed to test several current hypotheses regarding the mechanisms responsible for Madden-Julian Oscillation (MJO) initiation and propagation in the Indian Ocean area. The synergy between the proposed AMF2 deployment with DYNAMO/CINDY2011, and the corresponding funded experiment on Manus, combine for an overarching ARM MJO Investigation Experiment (AMIE) with two components: AMF2 on Gan Island in the Indian Ocean (AMIE-Gan), where the MJO initiates and starts its eastward propagation; and the ARM Manus site (AMIE-Manus), which is in the general area where the MJO usually starts to weaken in climate models. AMIE-Gan will provide measurements of particular interest to Atmospheric System Research (ASR) researchers relevant to improving the representation of MJO initiation in climate models. The framework of DYNAMO/CINDY2011 includes two proposed island-based sites and two ship-based locations forming a square pattern with sonde profiles and scanning precipitation and cloud radars at both island and ship sites. These data will be used to produce a Variational Analysis data set coinciding with the one produced for AMIE-Manus. The synergy between AMIE-Manus and AMIE-Gan will allow studies of the initiation, propagation, and evolution of the convective cloud population within the framework of the MJO. As with AMIE-Manus, AMIE-Gan/DYNAMO also includes a significant modeling component geared toward improving the representation of MJO initiation and propagation in climate and forecast models. This campaign involves the deployment of the second, marine-capable, AMF; all of the included measurement systems; and especially the scanning and vertically pointing radars. The campaign will include sonde

  4. High nitrogen pressure solution growth of GaN

    NASA Astrophysics Data System (ADS)

    Bockowski, Michal

    2014-10-01

    Results of GaN growth from gallium solution under high nitrogen pressure are presented. Basic of the high nitrogen pressure solution (HNPS) growth method is described. A new approach of seeded growth, multi-feed seed (MFS) configuration, is demonstrated. The use of two kinds of seeds: free-standing hydride vapor phase epitaxy GaN (HVPE-GaN) obtained from metal organic chemical vapor deposition (MOCVD)-GaN/sapphire templates and free-standing HVPE-GaN obtained from the ammonothermally grown GaN crystals, is shown. Depending on the seeds’ structural quality, the differences in the structural properties of pressure grown material are demonstrated and analyzed. The role and influence of impurities, like oxygen and magnesium, on GaN crystals grown from gallium solution in the MFS configuration is presented. The properties of differently doped GaN crystals are discussed. An application of the pressure grown GaN crystals as substrates for electronic and optoelectronic devices is reported.

  5. Effect of photocatalytic oxidation technology on GaN CMP

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Wang, Tongqing; Pan, Guoshun; Lu, Xinchun

    2016-01-01

    GaN is so hard and so chemically inert that it is difficult to obtain a high material removal rate (MRR) in the chemical mechanical polishing (CMP) process. This paper discusses the application of photocatalytic oxidation technology in GaN planarization. Three N-type semiconductor particles (TiO2, SnO2, and Fe2O3) are used as catalysts and added to the H2O2-SiO2-based slurry. By optical excitation, highly reactive photoinduced holes are produced on the surface of the particles, which can oxidize OH- and H2O absorbed on the surface of the catalysts; therefore, more OH* will be generated. As a result, GaN MRRs in an H2O2-SiO2-based polishing system combined with catalysts are improved significantly, especially when using TiO2, the MRR of which is 122 nm/h. The X-ray photoelectron spectroscopy (XPS) analysis shows the variation trend of chemical composition on the GaN surface after polishing, revealing the planarization process. Besides, the effect of pH on photocatalytic oxidation combined with TiO2 is analyzed deeply. Furthermore, the physical model of GaN CMP combined with photocatalytic oxidation technology is proposed to describe the removal mechanism of GaN.

  6. GaN Technology for Power Electronic Applications: A Review

    NASA Astrophysics Data System (ADS)

    Flack, Tyler J.; Pushpakaran, Bejoy N.; Bayne, Stephen B.

    2016-06-01

    Power semiconductor devices based on silicon (Si) are quickly approaching their limits, set by fundamental material properties. In order to address these limitations, new materials for use in devices must be investigated. Wide bandgap materials, such as silicon carbide (SiC) and gallium nitride (GaN) have suitable properties for power electronic applications; however, fabrication of practical devices from these materials may be challenging. SiC technology has matured to point of commercialized devices, whereas GaN requires further research to realize full material potential. This review covers fundamental material properties of GaN as they relate to Si and SiC. This is followed by a discussion of the contemporary issues involved with bulk GaN substrates and their fabrication and a brief overview of how devices are fabricated, both on native GaN substrate material and non-native substrate material. An overview of current device structures, which are being analyzed for use in power switching applications, is then provided; both vertical and lateral device structures are considered. Finally, a brief discussion of prototypes currently employing GaN devices is given.

  7. GaN Technology for Power Electronic Applications: A Review

    NASA Astrophysics Data System (ADS)

    Flack, Tyler J.; Pushpakaran, Bejoy N.; Bayne, Stephen B.

    2016-03-01

    Power semiconductor devices based on silicon (Si) are quickly approaching their limits, set by fundamental material properties. In order to address these limitations, new materials for use in devices must be investigated. Wide bandgap materials, such as silicon carbide (SiC) and gallium nitride (GaN) have suitable properties for power electronic applications; however, fabrication of practical devices from these materials may be challenging. SiC technology has matured to point of commercialized devices, whereas GaN requires further research to realize full material potential. This review covers fundamental material properties of GaN as they relate to Si and SiC. This is followed by a discussion of the contemporary issues involved with bulk GaN substrates and their fabrication and a brief overview of how devices are fabricated, both on native GaN substrate material and non-native substrate material. An overview of current device structures, which are being analyzed for use in power switching applications, is then provided; both vertical and lateral device structures are considered. Finally, a brief discussion of prototypes currently employing GaN devices is given.

  8. Affective Priming with Associatively Acquired Valence

    ERIC Educational Resources Information Center

    Aguado, Luis; Pierna, Manuel; Saugar, Cristina

    2005-01-01

    Three experiments explored the effect of affectively congruent or incongruent primes on evaluation responses to positive or negative valenced targets (the "affective priming" effect). Experiment 1 replicated the basic affective priming effect with Spanish nouns: reaction time for evaluative responses (pleasant/unpleasant) were slower on…

  9. Affective Priming with Auditory Speech Stimuli

    ERIC Educational Resources Information Center

    Degner, Juliane

    2011-01-01

    Four experiments explored the applicability of auditory stimulus presentation in affective priming tasks. In Experiment 1, it was found that standard affective priming effects occur when prime and target words are presented simultaneously via headphones similar to a dichotic listening procedure. In Experiment 2, stimulus onset asynchrony (SOA) was…

  10. Structural Priming and Second Language Learning

    ERIC Educational Resources Information Center

    Shin, Jeong-Ah; Christianson, Kiel

    2012-01-01

    Structural priming (or syntactic priming) is a speaker's tendency to reuse the same structural pattern as one that was previously encountered (Bock, 1986). This study investigated (a) whether the implicit learning processes involved in long-lag structural priming lead to differential second language (L2) improvement in producing two structural…

  11. Priming Lexical Stress in Reading Italian Aloud

    ERIC Educational Resources Information Center

    Sulpizio, Simone; Job, Remo; Burani, Cristina

    2012-01-01

    Two experiments using a lexical priming paradigm investigated how stress information is processed in reading Italian words. In both experiments, prime and target words either shared the stress pattern or they had different stress patterns. We expected that lexical activation of the prime would favour the assignment of congruent stress to the…

  12. Competition Effects in Phonological Priming: The Role of Mismatch Position between Primes and Targets

    ERIC Educational Resources Information Center

    Dufour, Sophie; Peereman, Ronald

    2009-01-01

    In three experiments, we examined lexical competition effects using the phonological priming paradigm in a shadowing task. Experiments 1A and 1B showed that an inhibitory priming effect occurred when the primes mismatched the targets on the last phoneme (/bagar/-/bagaj/). In contrast, a facilitatory priming effect was observed when the primes…

  13. Priming motivation through unattended speech.

    PubMed

    Radel, Rémi; Sarrazin, Philippe; Jehu, Marie; Pelletier, Luc

    2013-12-01

    This study examines whether motivation can be primed through unattended speech. Study 1 used a dichotic-listening paradigm and repeated strength measures. In comparison to the baseline condition, in which the unattended channel was only composed by neutral words, the presence of words related to high (low) intensity of motivation led participants to exert more (less) strength when squeezing a hand dynamometer. In a second study, a barely audible conversation was played while participants' attention was mobilized on a demanding task. Participants who were exposed to a conversation depicting intrinsic motivation performed better and persevered longer in a subsequent word-fragment completion task than those exposed to the same conversation made unintelligible. These findings suggest that motivation can be primed without attention. PMID:23432056

  14. Maglev ready for prime time.

    SciTech Connect

    Rote, D. M.; Johnson, L. R.; Energy Systems

    2003-01-01

    Putting Maglev on Track' (Issues, Spring 1990) observed that growing airline traffic and associated delays were already significant and predicted that they would worsen. The article argued that a 300-mile-per-hour (mph) magnetic levitation (maglev) system integrated into airport and airline operations could be a part of the solution. Maglev was not ready for prime time in 1990, but it is now.

  15. Associative priming in perceptual identification: effects of prime-processing requirements.

    PubMed

    Burt, J S; Walker, M B; Humphreys, M S; Tehan, G

    1993-01-01

    Three experiments assessed the effects of prime-processing instructions on associative priming in word identification and episodic memory for primes. In Experiment 1, groups instructed to read the prime silently or generate silently an associate of the prime showed a larger accuracy benefit for related over unrelated targets than did a group that decided whether an asterisk was to the right or left of the prime. The asterisk-search group showed a weaker repetition effect on a subsequent identification test of primes, indicating that the weaker priming in this group was a result of poorer perceptual processing. On a cued-recall test for primes, the generate group was superior to the other groups. In Experiment 2, we found that with weak prime-target associations, priming was comparable for read and generate groups and stronger than estimated for a guessing strategy, on the basis of single predictions made from each prime by an additional group. In Experiment 3, we demonstrated that the read and generate instructions produced similar mispriming and inhibitory effects. The results suggest that the depths of prime-processing manipulations do not have parallel effects on priming and episodic memory, and that associative priming in word identification, as in other tasks, may involve an expectancy process. PMID:8433643

  16. Priming arithmetic facts in amnesic patients.

    PubMed

    Delazer, M; Ewen, P; Benke, T

    1997-05-01

    In this study, amnesic patients showed significant repetition priming effects in arithmetic fact retrieval tasks. The results indicate that repetition priming effects in arithmetic depend not on explicit recognition, but on the activation of specific long-term representations of arithmetic facts. Processing dissociations between easy and difficult items suggest that the priming effects results from the stage of fact retrieval and not from peripheral activation. This claim is also supported by encoding and naming tasks, which showed only slight priming effects as compared to the priming found in calculation tasks. Significant priming was found for identical (5 x 6 and 5 x 6) and complement problems (5 x 6 and 6 x 5), the latter showing a smaller magnitude of priming. PMID:9153025

  17. What determines the direction of subliminal priming

    PubMed Central

    Jaśkowski, Piotr; Verleger, Rolf

    2008-01-01

    Masked stimuli (primes) can affect the preparation of a motor response to subsequently presented target stimuli. Reactions to the target can be facilitated (straight priming) or inhibited (inverse priming) when preceded by a compatible prime (calling for the same response) and also when preceded by an incompatible prime. Several hypotheses are currently under debate. These are the self-inhibition (SI) hypothesis, the object-updating (OU) hypothesis, and mask-triggered inhibition (MTI) hypothesis. All assume that the initial activation of the motor response is elicited by the prime according to its identity. This activation inevitably leads to straight priming in some cases and the mechanisms involved are undisputed. The hypotheses differ, however, as to why inverse priming occurs. The self-inhibition (SI) hypothesis assumes that the motor activation elicited by a prime is automatically followed by an inhibition phase, leading to inverse priming if three conditions are fulfilled: perceptual evidence for the prime has to be sufficiently strong, it has to be immediately removed by the mask, and the delay between the prime and target has to be long enough for inhibition to become effective. The object-updating (OU) hypothesis assumes that inverse priming is triggered by the mask, provided that it contains features calling for the alternative response (i.e. the one contrasting with the response induced by the prime). The MTI hypothesis assumes that the inhibitory phase is triggered by each successive stimulus which does not support the perceptual hypothesis provided by the prime. Based mostly on our own experiments, we argue that (1) attempts to manipulate the three factors required by the SI hypothesis imply changes of other variables and that (2) indeed, other variables seem to affect priming: prime-mask perceptual interaction and temporal position of the mask. These observations are in favor of the MTI hypothesis. A limiting factor for all three hypotheses is that

  18. What determines the direction of subliminal priming.

    PubMed

    Jaśkowski, Piotr; Verleger, Rolf

    2007-01-01

    Masked stimuli (primes) can affect the preparation of a motor response to subsequently presented target stimuli. Reactions to the target can be facilitated (straight priming) or inhibited (inverse priming) when preceded by a compatible prime (calling for the same response) and also when preceded by an incompatible prime. Several hypotheses are currently under debate. These are the self-inhibition (SI) hypothesis, the object-updating (OU) hypothesis, and mask-triggered inhibition (MTI) hypothesis. All assume that the initial activation of the motor response is elicited by the prime according to its identity. This activation inevitably leads to straight priming in some cases and the mechanisms involved are undisputed. The hypotheses differ, however, as to why inverse priming occurs. The self-inhibition (SI) hypothesis assumes that the motor activation elicited by a prime is automatically followed by an inhibition phase, leading to inverse priming if three conditions are fulfilled: perceptual evidence for the prime has to be sufficiently strong, it has to be immediately removed by the mask, and the delay between the prime and target has to be long enough for inhibition to become effective. The object-updating (OU) hypothesis assumes that inverse priming is triggered by the mask, provided that it contains features calling for the alternative response (i.e. the one contrasting with the response induced by the prime). The MTI hypothesis assumes that the inhibitory phase is triggered by each successive stimulus which does not support the perceptual hypothesis provided by the prime. Based mostly on our own experiments, we argue that (1) attempts to manipulate the three factors required by the SI hypothesis imply changes of other variables and that (2) indeed, other variables seem to affect priming: prime-mask perceptual interaction and temporal position of the mask. These observations are in favor of the MTI hypothesis. A limiting factor for all three hypotheses is that

  19. Prospect of GaN light-emitting diodes grown on glass substrates

    NASA Astrophysics Data System (ADS)

    Choi, Jun-Hee; Lee, Yun Sung; Baik, Chan Wook; Ahn, Ho Young; Cho, Kyung Sang; Kim, Sun Il; Hwang, Sungwoo

    2013-03-01

    We report the enhanced electroluminescence (EL) of GaN light-emitting diodes (LEDs) on glass substrates. We found that GaN morphology affected the EL and achieved enhanced EL of GaN-LEDs on glass by identifying the optimal GaN morphology having both high crystallinity and compatibility for device fabrication. At proper growth temperature, GaN crystallinity was improved with increasing GaN crystal size irrespective of the GaN crystallographic orientation, as determined by spatially resolved cathodoluminescent spectroscopy. The optimized GaN LEDs on glass composed of the nearly single-crystalline GaN pyramid arrays exhibited excellent microscopic EL uniformity and luminance values of ~ 9100 cd/m2 at the peak wavelength of 495 nm. The EL color could be adjusted mainly by varying the quantum well temperature. In addition, new growth methods for achieving high GaN crystallinity at a low growth temperature (e.g. ~700°C) were briefly reviewed and attempted by adopting selective heating. We expect that performance of the GaN LEDs on glass can be much enhanced by enhancing GaN crystallinity and p-GaN coating, and evolvement of low-temperature growth of high-quality GaN might even customize ordinary glass as a substrate, which enables high-performance, low-cost lighting or display.

  20. Pulsed laser annealing of Be-implanted GaN

    SciTech Connect

    Wang, H.T.; Tan, L.S.; Chor, E.F.

    2005-11-01

    Postimplantation thermal processing of Be in molecular-beam-epitaxy-grown GaN by rapid thermal annealing (RTA) and pulsed laser annealing (PLA) was investigated. It has been found that the activation of Be dopants and the repair of implantation-induced defects in GaN films cannot be achieved efficiently by conventional RTA alone. On the other hand, good dopant activation and surface morphology and quality were obtained when the Be-implanted GaN film was annealed by PLA with a 248 nm KrF excimer laser. However, observations of off-resonant micro-Raman and high-resolution x-ray-diffraction spectra indicated that crystal defects and strain resulting from Be implantation were still existent after PLA, which probably degraded the carrier mobility and limited the activation efficiency to some extent. This can be attributed to the shallow penetration depth of the 248 nm laser in GaN, which only repaired the crystal defects in a thin near-surface layer, while the deeper defects were not annealed out well. This situation was significantly improved when the Be-implanted GaN was subjected to a combined process of PLA followed by RTA, which produced good activation of the dopants, good surface morphology, and repaired bulk and surface defects well.

  1. Native defects in GaN: a hybrid functional study

    NASA Astrophysics Data System (ADS)

    Diallo, Ibrahima Castillo; Demchenko, Denis

    Intrinsic defects play an important role in the performance of GaN-based devices. We present hybrid density functional calculations of the electronic and possible optical properties of interstitial N (Ni-Ni) , N antisite (NGa) , interstitial Ga (Gai) , Ga antisite (GaN) , Ga vacancy (VGa) , N vacancy (VN) and Ga-N divacancies (VGaVN) in GaN. Our results show that the vacancies display relatively low formation energies in certain samples, whereas antisites and interstitials are energetically less favorable. However, interstitials can be created by electron irradiation. For instance, in 2.5 MeV electron-irradiated GaN samples, a strong correlation between the frequently observed photoluminescence (PL) band centered around 0.85 eV accompanied with a rich phonon sideband of ~0.88 eV and the theoretical optical behavior of interstitial Ga is discussed. N vacancies are found to likely contribute to the experimentally obtained green luminescence band (GL2) peaking at 2.24 eV in high-resistivity undoped and Mg-doped GaN. National Science Foundation (DMR-1410125) and the Thomas F. and Kate Miller Jeffress Memorial Trust.

  2. Microbial stress priming: a meta-analysis.

    PubMed

    Andrade-Linares, Diana R; Lehmann, Anika; Rillig, Matthias C

    2016-04-01

    Microbes have to cope with complex and dynamic environments, making it likely that anticipatory responses provide fitness benefits. Mild, previous stressors can prepare microbes (stress priming) to further and potentially damaging stressors (triggering). We here quantitatively summarize the findings from over 250 trials of 34 studies including bacteria and fungi, demonstrating that priming to stress has a beneficial impact on microbial survival. In fact, survival of primed microbes was about 10-fold higher compared with that in non-primed microbes. Categorical moderators related to microbial taxonomy and the kind of stress applied as priming or as triggering revealed significant differences of priming effect size among 14 different microbial species, 6 stress categories and stressor combination. We found that priming by osmotic, physiological and temperature stress had the highest positive effect sizes on microbial response. Cross-protection was evident for physiological, temperature and pH stresses. Microbes are better prepared against triggering by oxidative, temperature and osmotic stress. Our finding of an overall positive mean effect of priming regardless of the microbial system and particular stressor provides unprecedentedly strong evidence of the broad ecological significance of microbial stress priming. These results further suggest that stress priming may be an important factor in shaping microbial communities. PMID:26768991

  3. The temporal dynamics of visual object priming

    PubMed Central

    Ko, Philip C.; Duda, Bryant; Hussey, Erin P.; Mason, Emily J.; Ally, Brandon A.

    2014-01-01

    Priming reflects an important means of learning that is mediated by implicit memory. Importantly, priming occurs for previously viewed objects (item-specific priming) and their category relatives (category-wide priming). Two distinct neural mechanisms are known to mediate priming, including the sharpening of a neural object representation and the retrieval of stimulus-response mappings. Here, we investigated whether the relationship between these neural mechanisms could help explain why item-specific priming generates faster responses than category-wide priming. Participants studied pictures of everyday objects, and then performed a difficult picture identification task while we recorded event-related potentials (ERP). The identification task gradually revealed random line segments of previously viewed items (Studied), category exemplars of previously viewed items (Exemplar), and items that were not previously viewed (Unstudied). Studied items were identified sooner than Unstudied items, showing evidence of item-specific priming, and importantly Exemplar items were also identified sooner than Unstudied items, showing evidence of category-wide priming. Early activity showed sustained neural suppression of parietal activity for both types of priming. However, these neural suppression effects may have stemmed from distinct processes because while category-wide neural suppression was correlated with priming behavior, item-specific neural suppression was not. Late activity, examined with response-locked ERPs, showed additional processes related to item-specific priming including neural suppression in occipital areas and parietal activity that was correlated with behavior. Together, we conclude that item-specific and category-wide priming are mediated by separate, parallel neural mechanisms in the context of the current paradigm. Temporal differences in behavior are determined by the timecourses of these distinct processes. PMID:25164991

  4. Diophantine equations in the primes

    NASA Astrophysics Data System (ADS)

    Cook, Brian; Magyar, Ákos

    2014-12-01

    Let $\\mathfrak{p}=(\\mathfrak{p}_1,...,\\mathfrak{p}_r)$ be a system of $r$ polynomials with integer coefficients of degree $d$ in $n$ variables $\\mathbf{x}=(x_1,...,x_n)$. For a given $r$-tuple of integers, say $\\mathbf{s}$, a general local to global type statement is shown via classical Hardy-Littlewood type methods which provides sufficient conditions for the solubility of $\\mathfrak{p}(\\mathbf{x})=\\mathbf{s}$ under the condition that each of the $x_i$'s is prime.

  5. Centaur G Prime modal test

    NASA Technical Reports Server (NTRS)

    Trubert, Marc; Cutler, Art; Miller, Robert; Page, Don; Engelhardt, Charles

    1987-01-01

    The Centaur G Prime modal test resulted in sets of modes (frequencies, mode shapes and damping) with an accuracy similiar to or better than that normally obtained from the modal testing of linear structures with no backlash and small damping. In other words, performing the test at high level greatly minimized the backlash effect and provided a valid, simple linearization of the trunnion friction problem for the Centaur in the Shuttle Cargo Bay. All the most important modes (target modes) were measured and provided the data base for updating the finite element model for the pre-flight verification loads analysis.

  6. Structural defects in bulk GaN

    NASA Astrophysics Data System (ADS)

    Liliental-Weber, Z.; dos Reis, R.; Mancuso, M.; Song, C. Y.; Grzegory, I.; Porowski, S.; Bockowski, M.

    2014-10-01

    Transmission Electron Microscopy (TEM) studies of undoped and Mg doped GaN layers grown on the HVPE substrates by High Nitrogen Pressure Solution (HNPS) with the multi-feed-seed (MFS) configuration are shown. The propagation of dislocations from the HVPE substrate to the layer is observed. Due to the interaction between these dislocations in the thick layers much lower density of these defects is observed in the upper part of the HNPS layers. Amorphous Ga precipitates with attached voids pointing toward the growth direction are observed in the undoped layer. This is similar to the presence of Ga precipitates in high-pressure platelets, however the shape of these precipitates is different. The Mg doped layers do not show Ga precipitates, but MgO rectangular precipitates are formed, decorating the dislocations. Results of TEM studies of HVPE layers grown on Ammonothermal substrates are also presented. These layers have superior crystal quality in comparison to the HNPS layers, as far as density of dislocation is concern. Occasionally some small inclusions can be found, but their chemical composition was not yet determined. It is expected that growth of the HNPS layers on these substrate will lead to large layer thickness obtained in a short time and with high crystal perfection needed in devices.

  7. High Voltage GaN Schottky Rectifiers

    SciTech Connect

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  8. Mg doping and its effect on the semipolar GaN(1122) growth kinetics

    SciTech Connect

    Lahourcade, L.; Wirthmueller, A.; Monroy, E.; Chauvat, M. P.; Ruterana, P.; Laufer, A.; Eickhoff, M.

    2009-10-26

    We report the effect of Mg doping on the growth kinetics of semipolar GaN(1122) synthesized by plasma-assisted molecular-beam epitaxy. Mg tends to segregate on the surface, inhibiting the formation of the self-regulated Ga film which is used as a surfactant for the growth of undoped and Si-doped GaN(1122). We observe an enhancement of Mg incorporation in GaN(1122) compared to GaN(0001). Typical structural defects or polarity inversion domains found in Mg-doped GaN(0001) were not observed for the semipolar films investigated in the present study.

  9. Conductivity based on selective etch for GaN devices and applications thereof

    SciTech Connect

    Zhang, Yu; Sun, Qian; Han, Jung

    2015-12-08

    This invention relates to methods of generating NP gallium nitride (GaN) across large areas (>1 cm.sup.2) with controlled pore diameters, pore density, and porosity. Also disclosed are methods of generating novel optoelectronic devices based on porous GaN. Additionally a layer transfer scheme to separate and create free-standing crystalline GaN thin layers is disclosed that enables a new device manufacturing paradigm involving substrate recycling. Other disclosed embodiments of this invention relate to fabrication of GaN based nanocrystals and the use of NP GaN electrodes for electrolysis, water splitting, or photosynthetic process applications.

  10. Temperature dependent growth of GaN nanowires using CVD technique

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Kumar, Vikram; Singh, R.

    2016-05-01

    Growth of GaN nanowires have been carried out on sapphire substrates with Au as a catalyst using chemical vapour deposition technique. GaN nanowires growth have been studied with the experimental parameter as growth temperature. Diameter of grown GaN nanowires are in the range of 50 nm to 100 nm while the nanowire length depends on growth temperature. Morphology of the GaN nanowires have been studied by scanning electron microscopy. Crystalline nature has been observed by XRD patterns. Optical properties of grown GaN nanowires have been investigated by photoluminescence spectra.

  11. Desorption Induced Formation of Negative Nanowires in GaN

    SciTech Connect

    Stach, E.A.; Kim, B.-J.

    2011-06-01

    We report in-situ transmission electron microscopy studies of the formation of negative nanowires created by thermal decomposition of single crystal GaN. During annealing, vertical negative nanowires are formed in [0 0 0 1] by preferential dissociation of GaN along the 1 0 {bar 1} 0 prism planes, while lateral negative nanowires grow in close-packed 1 0 {bar 1} 0 by the self-catalytic solid-liquid-vapor (SLV) mechanism. Our quantitative measurements show that the growth rates of the laterally grown negative nanowires are independent of the wire diameter, indicating that the rate-limiting step is the decomposition of GaN on the surface of the Ga droplets that catalyze their creation. These nanoscale features offer controllable templates for the creation and integration of a broad range of nanoscale materials systems, with potential applications in nanoscale fluidics.

  12. Gate stack engineering for GaN lateral power transistors

    NASA Astrophysics Data System (ADS)

    Yang, Shu; Liu, Shenghou; Liu, Cheng; Hua, Mengyuan; Chen, Kevin J.

    2016-02-01

    Developing optimal gate-stack technology is a key to enhancing the reliability and performance of GaN insulated-gate devices for high-voltage power switching applications. In this paper, we discuss current challenges and review our recent progresses in gate-stack technology development toward high-performance and high-reliability GaN power devices, including (1) interface engineering that creates a high-quality dielectric/III-nitride interface with low trap density; (2) barrier-layer engineering that enables optimal trade-off between performance and stability; (3) bulk quality and reliability enhancement of the gate dielectric. These gate-stack techniques in terms of new process development and device structure design are valuable to realize highly reliable and competitive GaN power devices.

  13. Curvature and bow of bulk GaN substrates

    NASA Astrophysics Data System (ADS)

    Foronda, Humberto M.; Romanov, Alexey E.; Young, Erin C.; Roberston, Christian A.; Beltz, Glenn E.; Speck, James S.

    2016-07-01

    We investigate the bow of free standing (0001) oriented hydride vapor phase epitaxy grown GaN substrates and demonstrate that their curvature is consistent with a compressive to tensile stress gradient (bottom to top) present in the substrates. The origin of the stress gradient and the curvature is attributed to the correlated inclination of edge threading dislocation (TD) lines away from the [0001] direction. A model is proposed and a relation is derived for bulk GaN substrate curvature dependence on the inclination angle and the density of TDs. The model is used to analyze the curvature for commercially available GaN substrates as determined by high resolution x-ray diffraction. The results show a close correlation between the experimentally determined parameters and those predicted from theoretical model.

  14. Strong atomic ordering in Gd-doped GaN

    SciTech Connect

    Ishimaru, Manabu; Higashi, Kotaro; Hasegawa, Shigehiko; Asahi, Hajime; Sato, Kazuhisa; Konno, Toyohiko J.

    2012-09-03

    Gd-doped GaN (Ga{sub 1-x}Gd{sub x}N) thin films were grown on a GaN(001) template by radio frequency plasma-assisted molecular beam epitaxy and characterized by means of x-ray diffraction (XRD) and transmission electron microscopy (TEM). Three samples with a different Gd composition were prepared in this study: x = 0.02, 0.05, and 0.08. XRD and TEM results revealed that the low Gd concentration GaN possesses the wurtzite structure. On the other hand, it was found that an ordered phase with a quadruple-periodicity along the [001] direction in the wurtzite structure is formed throughout the film with x = 0.08. We proposed the atomistic model for the superlattice structure observed here.

  15. Stability of Carbon Incorpoated Semipolar GaN(1101) Surface

    NASA Astrophysics Data System (ADS)

    Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori

    2011-08-01

    The structural stability of carbon incorporated GaN(1101) surfaces is theoretically investigated by performing first-principles pseudopotential calculations. The calculated surface formation energies taking account of the metal organic vapor phase epitaxy conditions demonstrate that several carbon incorporated surfaces are stabilized depending on the growth conditions. Using surface phase diagrams, which are obtained by comparing the calculated adsorption energy with vapor-phase chemical potentials, we find that the semipolar surface forms NH2 and CH2 below ˜1660 K while the polar GaN(0001) surface with CH3 is stabilized below ˜1550 K. This difference could be one of possible explanations for p-type doping on the semipolar GaN(1101) surface.

  16. Biosensors based on GaN nanoring optical cavities

    NASA Astrophysics Data System (ADS)

    Kouno, Tetsuya; Takeshima, Hoshi; Kishino, Katsumi; Sakai, Masaru; Hara, Kazuhiko

    2016-05-01

    Biosensors based on GaN nanoring optical cavities were demonstrated using room-temperature photoluminescence measurements. The outer diameter, height, and thickness of the GaN nanorings were approximately 750–800, 900, and 130–180 nm, respectively. The nanorings functioned as whispering-gallery-mode (WGM)-type optical cavities and exhibited sharp resonant peaks like lasing actions. The evanescent component of the WGM was strongly affected by the refractive index of the ambient environment, the type of liquid, and the sucrose concentration of the analyzed solution, resulting in shifts of the resonant wavelengths. The results indicate that the GaN nanorings can potentially be used in sugar sensors of the biosensors.

  17. Structure investigations of nonpolar GaN layers.

    PubMed

    Neumann, W; Mogilatenko, A; Wernicke, T; Richter, E; Weyers, M; Kneissl, M

    2010-03-01

    The microstructure of nonpolar m-plane (1100) oriented GaN layers deposited on (100)gamma-LiAlO(2) was analysed by transmission electron microscopy. This study shows that the films contain a large number of defects. The most dominant defects in the m-plane GaN are intrinsic I(1) basal plane stacking faults (approximately 10(4) cm(-1)), threading dislocations (approximately 10(9) cm(-2)) as well as a complex defect network consisting of planar defects located on prismatic {1010} GaN and differently inclined pyramidal planes. A large number of the stacking faults nucleate at the GaN/LiAlO(2) interface. Furthermore, the inclined planar defects act as additional nucleation sites for the basal plane stacking faults. A decreasing crystal quality with an increasing layer thickness can be explained by this defect formation mechanism. PMID:20500386

  18. Surface morphology of GaN: Flat versus vicinal surfaces

    SciTech Connect

    Xie, M.H.; Seutter, S.M.; Zheng, L.X.; Cheung, S.H.; Ng, Y.F.; Wu, H.; Tong, S.Y.

    2000-07-01

    The surface morphology of GaN films grown by molecular beam epitaxy (MBE) is investigated by scanning tunneling microscopy (STM). A comparison is made between flat and vicinal surfaces. The wurtzite structure of GaN leads to special morphological features such as step pairing and triangularly shaped islands. Spiral mounds due to growth at screw threading dislocations are dominant on flat surfaces, whereas for vicinal GaN, the surfaces show no spiral mound but evenly spaced steps. This observation suggests an effective suppression of screw threading dislocations in the vicinal films. This finding is confirmed by transmission electron microscopy (TEM) studies. Continued growth of the vicinal surface leads to step bunching that is attributed to the effect of electromigration.

  19. High-Sensitivity GaN Microchemical Sensors

    NASA Technical Reports Server (NTRS)

    Son, Kyung-ah; Yang, Baohua; Liao, Anna; Moon, Jeongsun; Prokopuk, Nicholas

    2009-01-01

    Systematic studies have been performed on the sensitivity of GaN HEMT (high electron mobility transistor) sensors using various gate electrode designs and operational parameters. The results here show that a higher sensitivity can be achieved with a larger W/L ratio (W = gate width, L = gate length) at a given D (D = source-drain distance), and multi-finger gate electrodes offer a higher sensitivity than a one-finger gate electrode. In terms of operating conditions, sensor sensitivity is strongly dependent on transconductance of the sensor. The highest sensitivity can be achieved at the gate voltage where the slope of the transconductance curve is the largest. This work provides critical information about how the gate electrode of a GaN HEMT, which has been identified as the most sensitive among GaN microsensors, needs to be designed, and what operation parameters should be used for high sensitivity detection.

  20. Priming effects in marine sediments

    NASA Astrophysics Data System (ADS)

    Gontikaki, Evina; Thornton, Barry; Witte, Ursula

    2013-04-01

    Continental margin sediments (<2000 m) cover merely 15 % of the ocean's seafloor but are responsible for more than 70 % of the global benthic mineralization. Understanding when these systems act as a source or sink of carbon (C) is thus of primary importance if we are to produce reliable global C budgets and predict the effects of future perturbations on the global C cycle. The chemical nature of organic matter (OM) is thought to be one of the major controls on the degradation/preservation balance in sediments; labile and refractory OM pools degrade at different rates but not independently. Priming effects (PE), i.e. changes in the decomposition of refractory organic matter following inputs of labile OM, have the potential to alter the C budget in sediments but have been largely ignored by marine scientists. Climate-driven changes in primary production, and land erosion and run-off are likely to change the quantity and composition of organic matter inputs in marine ecosystems and influence the magnitude and direction of PEs in seawater and sediments. Here, we attempt to evaluate the importance of priming effects on C cycling in marine sediments by use of labelled substrates of different quantity and quality in stable isotope tracer experiments and argue that PEs need to be incorporated in global change models.

  1. Can Faces Prime a Language?

    PubMed

    Woumans, Evy; Martin, Clara D; Vanden Bulcke, Charlotte; Van Assche, Eva; Costa, Albert; Hartsuiker, Robert J; Duyck, Wouter

    2015-09-01

    Bilinguals have two languages that are activated in parallel. During speech production, one of these languages must be selected on the basis of some cue. The present study investigated whether the face of an interlocutor can serve as such a cue. Spanish-Catalan and Dutch-French bilinguals were first familiarized with certain faces, each of which was associated with only one language, during simulated Skype conversations. Afterward, these participants performed a language production task in which they generated words associated with the words produced by familiar and unfamiliar faces displayed on-screen. When responding to familiar faces, participants produced words faster if the faces were speaking the same language as in the previous Skype simulation than if the same faces were speaking a different language. Furthermore, this language priming effect disappeared when it became clear that the interlocutors were actually bilingual. These findings suggest that faces can prime a language, but their cuing effect disappears when it turns out that they are unreliable as language cues. PMID:26209531

  2. On Anti-Elite Prime Numbers

    NASA Astrophysics Data System (ADS)

    M"Uller, Tom

    2007-09-01

    An odd prime number p is called anti-elite if only finitely many Fermat numbers are quadratic non-residues to p. This concept is the exact opposite to that of elite prime numbers. We study some fundamental properties of anti-elites and show that there are infinitely many of them. A computational search among all the numbers up to 100 billion yielded 84 anti-elite primes.

  3. All Elite Primes Up to 250 Billion

    NASA Astrophysics Data System (ADS)

    Chaumont, Alain; Müller, Tom

    2006-08-01

    A prime number p is called elite if only finitely many Fermat numbers 2^(2^n)+1 are quadratic residues of p. Previously only the interval up to 10^9 was systematically searched for elite primes and 16 such primes were found. We extended this research up to 2.5*10^11 and found five further elites, among which 1,151,139,841 is the smallest and 171,727,482,881 the largest.

  4. Study of photoemission mechanism for varied doping GaN photocathode

    NASA Astrophysics Data System (ADS)

    Qiao, Jianliang; Xu, Yuan; Niu, Jun; Gao, Youtang; Chang, Benkang

    2015-10-01

    Negative electron affinity (NEA) GaN photocathode has many virtues, such as high quantum efficiency, low dark current, concentrated electrons energy distribution and angle distribution, adjustive threshold and so on. The quantum efficiency is an important parameter for the preparation and evaluation of NEA GaN photocathode. The varied doping GaN photocathode has the directional inside electric field within the material, so the higher quantum efficiency can be obtained. The varied doping NEA GaN photocathode has better photoemission performance. According to the photoemission theory of NEA GaN photocathode, the quantum efficiency formulas for uniform doping and varied doping NEA GaN photocathodes were given. In the certain condition, the quantum efficiency formula for varied doping GaN photocathode consists with the uniform doping. The activation experiment was finished for varied doping GaN photocathode. The cleaning method and technics for varied doping GaN photocathode were given in detail. To get an atom clean surface, the heat cleaning must be done after the chemical cleaning. Using the activation and evaluation system for NEA photocathode, the varied doping GaN photocathode was activated with Cs and O, and the photocurrent curve for varied doping GaN photocathode was gotten.

  5. Complex architecture of primes and natural numbers.

    PubMed

    García-Pérez, Guillermo; Serrano, M Ángeles; Boguñá, Marián

    2014-08-01

    Natural numbers can be divided in two nonoverlapping infinite sets, primes and composites, with composites factorizing into primes. Despite their apparent simplicity, the elucidation of the architecture of natural numbers with primes as building blocks remains elusive. Here, we propose a new approach to decoding the architecture of natural numbers based on complex networks and stochastic processes theory. We introduce a parameter-free non-Markovian dynamical model that naturally generates random primes and their relation with composite numbers with remarkable accuracy. Our model satisfies the prime number theorem as an emerging property and a refined version of Cramér's conjecture about the statistics of gaps between consecutive primes that seems closer to reality than the original Cramér's version. Regarding composites, the model helps us to derive the prime factors counting function, giving the probability of distinct prime factors for any integer. Probabilistic models like ours can help to get deeper insights about primes and the complex architecture of natural numbers. PMID:25215780

  6. eta. prime -. eta. -. pi. sup 0 mixing

    SciTech Connect

    Bagchi, B. ); Lahiri, A. ); Niyogi, S. )

    1990-05-01

    We have examined the saturation of anomalous Ward identities by the low-lying pseudoscalars {pi}{sup 0}, {eta}, and {eta}{prime} to determine the sizes of {eta}{prime}-{eta}, {pi}{sup 0}-{eta}, and {pi}{sup 0}-{eta}{prime} mixing angles. The {eta}{prime}-{eta} mixing angle turns out to be about {minus}20{degree} which is consistent with the recent findings. Our estimate for the {pi}{sup 0}-{eta} mixing angle shows that it could be bigger than the older value obtained from the {rho}-{omega} mixing, baryon mass splittings, and kaon mass difference.

  7. Phasic affective modulation of semantic priming.

    PubMed

    Topolinski, Sascha; Deutsch, Roland

    2013-03-01

    The present research demonstrates that very brief variations in affect, being around 1 s in length and changing from trial to trial independently from semantic relatedness of primes and targets, modulate the amount of semantic priming. Implementing consonant and dissonant chords (Experiments 1 and 5), naturalistic sounds (Experiment 2), and visual facial primes (Experiment 3) in an (in)direct semantic priming paradigm, as well as brief facial feedback in a summative priming paradigm (Experiment 4), yielded increased priming effects under brief positive compared to negative affect. Furthermore, this modulation took place on the level of semantic spreading rather than on strategic mechanisms (Experiment 5). Alternative explanations such as distraction, motivation, arousal, and cognitive tuning could be ruled out. This phasic affective modulation constitutes a mechanism overlooked thus far that may contaminate priming effects in all priming paradigms that involve affective stimuli. Furthermore, this mechanism provides a novel explanation for the observation that priming effects are usually larger for positive than for negative stimuli. Finally, it has important implications for linguistic research, by suggesting that association norms may be biased for affective words. PMID:22732031

  8. Complex architecture of primes and natural numbers

    NASA Astrophysics Data System (ADS)

    García-Pérez, Guillermo; Serrano, M. Ángeles; Boguñá, Marián

    2014-08-01

    Natural numbers can be divided in two nonoverlapping infinite sets, primes and composites, with composites factorizing into primes. Despite their apparent simplicity, the elucidation of the architecture of natural numbers with primes as building blocks remains elusive. Here, we propose a new approach to decoding the architecture of natural numbers based on complex networks and stochastic processes theory. We introduce a parameter-free non-Markovian dynamical model that naturally generates random primes and their relation with composite numbers with remarkable accuracy. Our model satisfies the prime number theorem as an emerging property and a refined version of Cramér's conjecture about the statistics of gaps between consecutive primes that seems closer to reality than the original Cramér's version. Regarding composites, the model helps us to derive the prime factors counting function, giving the probability of distinct prime factors for any integer. Probabilistic models like ours can help to get deeper insights about primes and the complex architecture of natural numbers.

  9. GaN nanowire arrays by a patterned metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Wang, K. C.; Yuan, G. D.; Wu, R. W.; Lu, H. X.; Liu, Z. Q.; Wei, T. B.; Wang, J. X.; Li, J. M.; Zhang, W. J.

    2016-04-01

    We developed an one-step and two-step metal-assisted chemical etching method to produce self-organized GaN nanowire arrays. In one-step approach, GaN nanowire arrays are synthesized uniformly on GaN thin film surface. However, in a two-step etching processes, GaN nanowires are formed only in metal uncovered regions, and GaN regions with metal-covering show nano-porous sidewalls. We propose that nanowires and porous nanostructures are tuned by sufficient and limited etch rate, respectively. PL spectra shows a red-shift of band edge emission in GaN nanostructures. The formation mechanism of nanowires was illustrated by two separated electrochemical reactions occur simultaneously. The function of metals and UV light was illustrated by the scheme of potential relationship between energy bands in Si, GaN and standard hydrogen electrode potential of solution and metals.

  10. First-principles study of d0 ferromagnetism in alkali-metal doped GaN

    NASA Astrophysics Data System (ADS)

    Zhang, Yong

    2016-08-01

    The d0 ferromagnetism in GaN has been studied based on density functional theory. Our results show that GaN with sufficient hole become spin-polarized. Alkali-metal doping can introduce holes in GaN. Among them, both of Li- and Na-doping induce ferromagnetism in GaN and Na-doped GaN behaves as half-metallic ferromagnet. Moreover, at a growth temperature of 2000 K under N-rich condition, both concentrations can exceed 18%, which is sufficient to produce detectable macroscopic magnetism in GaN. The Curie temperature of Li- and Na-doped GaN is estimated to be 304 and 740 K, respectively, which are well above room temperature.

  11. Development of Partial-Charge Potential for GaN

    SciTech Connect

    Gao, Fei; Devanathan, Ram; Oda, Takuji; Weber, William J.

    2006-09-01

    Partial-charged potentials for GaN are systematically developed that describes a wide range of structural properties, where the reference data for fitting the potential parameters are taken from ab initial calculations or experiments. The present potential model provides a good fit to different structural geometries and high pressure phases of GaN. The high-pressure transition from wurtzite to rock-salt structure is correctly described yielding the phase transition pressure of about 55 GPa, and the calculated volume change at the transition is in good agreement with experimental data. The results are compared with those obtained by ab initio simulations.

  12. Ferromagnetism in undoped One-dimensional GaN Nanowires

    SciTech Connect

    Jeganathan, K. E-mail: jagan@physics.bdu.ac.in; Purushothaman, V.; Debnath, R.; Arumugam, S.

    2014-05-15

    We report an intrinsic ferromagnetism in vertical aligned GaN nanowires (NW) fabricated by molecular beam epitaxy without any external catalyst. The magnetization saturates at ∼0.75 × emu/gm with the applied field of 3000 Oe for the NWs grown under the low-Gallium flux of 2.4 × 10{sup −8} mbar. Despite a drop in saturation magnetization, narrow hysteresis loop remains intact regardless of Gallium flux. Magnetization in vertical standing GaN NWs is consistent with the spectral analysis of low-temperature photoluminescence pertaining to Ga-vacancies associated structural defects at the nanoscale.

  13. Femtosecond Studies of Carrier Dynamics in GaN

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuhong; Zeng, Wensheng; Xu, Su; Makinen, Antti J.; Wicks, Gary W.; Gao, Yongli

    1998-03-01

    Ultrafast carrier dynamics were measured in GaN by femtosecond two-color pump-probe technique with 150fs resolution. Undoped wurtzite GaN sample studied in this work was grown by moecular beam epitaxy on a (0001)-oriented sapphire substrate. Third harmonic wave from Ti:sapphire Regen was employed as pump and second harmonic as probe. Transient transmission measurement shows the electron-phonon scattering and longitutal optical phonons relaxation. A simply two temperature model is used to explain the results.

  14. Persistent photoconductivity in neutron irradiated GaN

    NASA Astrophysics Data System (ADS)

    Minglan, Zhang; Ruixia, Yang; Naixin, Liu; Xiaoliang, Wang

    2013-09-01

    Unintentionally doped GaN films grown by MOCVD were irradiated with neutrons at room temperature. In order to investigate the influence of neutron irradiation on the optical properties of GaN films, persistent photoconductivity (PPC) and low temperature photoluminescence (PL) measurements were carried out. Pronounced PPC was observed in the samples before and after neutron irradiation without the appearance of a yellow luminescence (YL) band in the PL spectrum, suggesting that the origin of PPC and YL are not related. Moreover, PPC phenomenon was enhanced by neutron irradiation and quenched by the followed annealing process at 900 °C. The possible origin of PPC is discussed.

  15. Dislocation luminescence in GaN single crystals under nanoindentation

    NASA Astrophysics Data System (ADS)

    Huang, Jun; Xu, Ke; Fan, Ying Min; Wang, Jian Feng; Zhang, Ji Cai; Ren, Guo Qiang

    2014-12-01

    This work presents an experimental study on the dislocation luminescence in GaN by nanoindentation, cathodoluminescence, and Raman. The dislocation luminescence peaking at 3.12 eV exhibits a series of special properties in the cathodoluminescence measurements, and it completely disappears after annealing at 500°C. Raman spectroscopy shows evidence for existence of vacancies in the indented region. A comprehensive investigation encompassing cathodoluminescence, Raman, and annealing experiments allow the assignment of dislocation luminescence to conduction-band-acceptor transition involving Ga vacancies. The nanoscale plasticity of GaN can be better understood by considering the dislocation luminescence mechanism.

  16. Numerical studies on Heavy Rainfall Events over Northern Taiwan in Mei-Yu Season

    NASA Astrophysics Data System (ADS)

    Lin, Pay-Liam

    2014-05-01

    convective systems drift inland, the orographic lifting of the pre-frontal southwesterly flow helps to produce higher simulated rainfall intensity in the southern slopes of the Taipei Basin. The simulated daily accumulated rainfall over the Taipei Basin and northwestern coast of Taiwan is about 200 and 400 mm, respectively, about 50 mm less than observed. In an experiment without Taiwan's topography (the NT run), the simulated rainfall intensity over the northern Taiwan Strait and the northwestern coast of Taiwan is much less. In contrast to the control run, despite the presence of favorable large-scale settings, no convective systems move to the northern part of Taiwan from the northern Taiwan Strait in the NT run without heavy rainfall simulated over northern Taiwan. Two events will be comparatively investigated by WRF on the formation and maintainence of heavy rainfall in Mai-Yu season.

  17. Synthesis of p-type GaN nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Sung Wook; Park, Youn Ho; Kim, Ilsoo; Park, Tae-Eon; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

    2013-08-01

    GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping. As a potential alternative p-type dopant, Cu has been recognized as an acceptor impurity for GaN. Herein, we report the fabrication of Cu-doped GaN nanowires (Cu:GaN NWs) and their p-type characteristics. The NWs were grown vertically via a vapor-liquid-solid (VLS) mechanism using a Au/Ni catalyst. Electrical characterization using a nanowire-field effect transistor (NW-FET) showed that the NWs exhibited n-type characteristics. However, with further annealing, the NWs showed p-type characteristics. A homo-junction structure (consisting of annealed Cu:GaN NW/n-type GaN thin film) exhibited p-n junction characteristics. A hybrid organic light emitting diode (OLED) employing the annealed Cu:GaN NWs as a hole injection layer (HIL) also demonstrated current injected luminescence. These results suggest that Cu can be used as a p-type dopant for GaN NWs.GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping. As a potential alternative p-type dopant, Cu has been recognized as an acceptor impurity for GaN. Herein, we report the fabrication of Cu-doped GaN nanowires (Cu:GaN NWs) and their p-type characteristics. The NWs were grown vertically via a vapor-liquid-solid (VLS) mechanism using a Au/Ni catalyst. Electrical characterization using a nanowire-field effect transistor (NW-FET) showed that the NWs exhibited n-type characteristics. However, with further annealing, the NWs showed p-type characteristics. A homo

  18. Tight coupling between positive and reversed priming in the masked prime paradigm

    PubMed Central

    Boy, Frederic; Sumner, Petroc

    2011-01-01

    When associations between certain visual stimuli and particular actions are learnt, those stimuli become capable of automatically and unconsciously activating their associated action plans. Such sensorimotor priming is assumed to be fundamental for efficient responses, and can be reliably measured in masked prime studies even when the primes are not consciously perceived. However, when the delay between prime and target is increased, reversed priming effects are often found instead (the negative compatibility effect, NCE). The main accounts of the NCE assume that it too is a sensorimotor phenomenon, predicting that it should occur only when the initial positive priming phase also occurs. Alternatively, reversed priming may reflect a perceptual process entirely independent from positive motor priming (which is simply evident at a different temporal delay), in which case no dependency is expected between the NCE and positive priming. We tested these predictions while new sensorimotor associations were learnt, and when learnt associations were suddenly reversed. We found a remarkable symmetry between positive and reversed priming during all such learning phases, supporting the idea that reversed priming represents a sensorimotor process that is contingent on, and automatically follows, the positive priming phase. We discuss also whether the NCE mechanism is subject to a trigger threshold. PMID:20695707

  19. Comparative Transcriptional Profiling of Primed and Non-primed Rice Seedlings under Submergence Stress.

    PubMed

    Hussain, Saddam; Yin, Hanqi; Peng, Shaobing; Khan, Faheem A; Khan, Fahad; Sameeullah, Muhammad; Hussain, Hafiz A; Huang, Jianliang; Cui, Kehui; Nie, Lixiao

    2016-01-01

    Submergence stress is a limiting factor for direct-seeded rice systems in rainfed lowlands and flood-prone areas of South and Southeast Asia. The present study demonstrated that submergence stress severely hampered the germination and seedling growth of rice, however, seed priming alleviated the detrimental effects of submergence stress. To elucidate the molecular basis of seed priming-induced submergence tolerance, transcriptome analyses were performed using 4-day-old primed (selenium-Se and salicylic acid-SA priming) and non-primed rice seedlings under submergence stress. Genomewide transcriptomic profiling identified 2371 and 2405 transcripts with Se- and SA-priming, respectively, that were differentially expressed in rice compared with non-priming treatment under submergence. Pathway and gene ontology term enrichment analyses revealed that genes involved in regulation of secondary metabolism, development, cell, transport, protein, and metal handling were over-represented after Se- or SA-priming. These coordinated factors might have enhanced the submergence tolerance and maintained the better germination and vigorous seedling growth of primed rice seedlings. It was also found that many genes involved in cellular and metabolic processes such as carbohydrate metabolism, cellular, and metabolic biosynthesis, nitrogen compound metabolic process, transcription, and response to oxidative stress were induced and overlapped in seed priming treatments, a finding which reveals the common mechanism of seed priming-induced submergence tolerance. Taken together, these results may provide new avenues for understanding and advancing priming-induced responses to submergence tolerance in crop plants. PMID:27516766

  20. Unconscious congruency priming from unpracticed words is modulated by prime-target semantic relatedness.

    PubMed

    Ortells, Juan J; Marí-Beffa, Paloma; Plaza-Ayllón, Vanesa

    2013-03-01

    Participants performed a 2-choice categorization task on visible word targets that were preceded by novel (unpracticed) prime words. The prime words were presented for 33 ms and followed either immediately (Experiments 1-3) or after a variable delay (Experiments 1 and 4) by a pattern mask. Both subjective and objective measures of prime visibility were used in all experiments. On 80% of the trials the primes and targets belonged to different categories (incongruent trials), whereas in the remaining 20% (congruent trials) they could be either strong or weak semantically related category members. Positive congruency effects (reaction times faster on congruent than on incongruent trials) were consistently found, but only when the mask immediately followed the primes, and participants reported being unaware of the identity of the primes. Primes followed by a delayed mask (such that participants reported being aware of their identity) produced either nonreliable facilitation or reliable reversed priming (strategic), depending on whether the prime-target stimulus onset asynchrony was either short (200 ms; Experiments 1 and 4) or long (1,000 ms; Experiment 4). Facilitatory priming with immediate mask was found strong (a) even for participants who performed at chance in prime visibility tests; and (b) for high but not for weakly semantically related category coordinates, irrespective of category size (animals, body parts). These findings provide evidence that unconscious congruency priming by unpracticed words from large stimulus sets critically depends on associative strength and/or semantic similarity between category coexemplars. PMID:22686850

  1. The Effect of Prime Duration in Masked Orthographic Priming Depends on Neighborhood Distribution

    ERIC Educational Resources Information Center

    Robert, Christelle; Mathey, Stephanie

    2012-01-01

    A lexical decision task was used with a masked priming procedure to investigate whether and to what extent neighborhood distribution influences the effect of prime duration in masked orthographic priming. French word targets had two higher frequency neighbors that were either distributed over two letter positions (e.g., "LOBE/robe-loge") or…

  2. Tight Coupling between Positive and Reversed Priming in the Masked Prime Paradigm

    ERIC Educational Resources Information Center

    Boy, Frederic; Sumner, Petroc

    2010-01-01

    When associations between certain visual stimuli and particular actions are learned, those stimuli become capable of automatically and unconsciously activating their associated action plans. Such sensorimotor priming is assumed to be fundamental for efficient responses, and can be reliably measured in masked prime studies even when the primes are…

  3. Comparative Transcriptional Profiling of Primed and Non-primed Rice Seedlings under Submergence Stress

    PubMed Central

    Hussain, Saddam; Yin, Hanqi; Peng, Shaobing; Khan, Faheem A.; Khan, Fahad; Sameeullah, Muhammad; Hussain, Hafiz A.; Huang, Jianliang; Cui, Kehui; Nie, Lixiao

    2016-01-01

    Submergence stress is a limiting factor for direct-seeded rice systems in rainfed lowlands and flood-prone areas of South and Southeast Asia. The present study demonstrated that submergence stress severely hampered the germination and seedling growth of rice, however, seed priming alleviated the detrimental effects of submergence stress. To elucidate the molecular basis of seed priming-induced submergence tolerance, transcriptome analyses were performed using 4-day-old primed (selenium-Se and salicylic acid-SA priming) and non-primed rice seedlings under submergence stress. Genomewide transcriptomic profiling identified 2371 and 2405 transcripts with Se- and SA-priming, respectively, that were differentially expressed in rice compared with non-priming treatment under submergence. Pathway and gene ontology term enrichment analyses revealed that genes involved in regulation of secondary metabolism, development, cell, transport, protein, and metal handling were over-represented after Se- or SA-priming. These coordinated factors might have enhanced the submergence tolerance and maintained the better germination and vigorous seedling growth of primed rice seedlings. It was also found that many genes involved in cellular and metabolic processes such as carbohydrate metabolism, cellular, and metabolic biosynthesis, nitrogen compound metabolic process, transcription, and response to oxidative stress were induced and overlapped in seed priming treatments, a finding which reveals the common mechanism of seed priming-induced submergence tolerance. Taken together, these results may provide new avenues for understanding and advancing priming-induced responses to submergence tolerance in crop plants. PMID:27516766

  4. Unconscious Congruency Priming from Unpracticed Words Is Modulated by Prime-Target Semantic Relatedness

    ERIC Educational Resources Information Center

    Ortells, Juan J.; Mari-Beffa, Paloma; Plaza-Ayllon, Vanesa

    2013-01-01

    Participants performed a 2-choice categorization task on visible word targets that were preceded by novel (unpracticed) prime words. The prime words were presented for 33 ms and followed either immediately (Experiments 1-3) or after a variable delay (Experiments 1 and 4) by a pattern mask. Both subjective and objective measures of prime visibility…

  5. A Paradox of Syntactic Priming: Why Response Tendencies Show Priming for Passives, and Response Latencies Show Priming for Actives

    PubMed Central

    Segaert, Katrien; Menenti, Laura; Weber, Kirsten; Hagoort, Peter

    2011-01-01

    Speakers tend to repeat syntactic structures across sentences, a phenomenon called syntactic priming. Although it has been suggested that repeating syntactic structures should result in speeded responses, previous research has focused on effects in response tendencies. We investigated syntactic priming effects simultaneously in response tendencies and response latencies for active and passive transitive sentences in a picture description task. In Experiment 1, there were priming effects in response tendencies for passives and in response latencies for actives. However, when participants' pre-existing preference for actives was altered in Experiment 2, syntactic priming occurred for both actives and passives in response tendencies as well as in response latencies. This is the first investigation of the effects of structure frequency on both response tendencies and latencies in syntactic priming. We discuss the implications of these data for current theories of syntactic processing. PMID:22022352

  6. Algorithmic and Experimental Computation of Higher-Order Safe Primes

    NASA Astrophysics Data System (ADS)

    Díaz, R. Durán; Masqué, J. Muñoz

    2008-09-01

    This paper deals with a class of special primes called safe primes. In the regular definition, an odd prime p is safe if, at least, one of (p±1)/2 is prime. Safe primes have been recommended as factors of RSA moduli. In this paper, the concept of safe primes is extended to higher-order safe primes, and an explicit formula to compute the density of this class of primes in the set of the integers is supplied. Finally, explicit conditions are provided permitting the algorithmic computation of safe primes of arbitrary order. Some experimental results are provided as well.

  7. Inverse Target- and Cue-Priming Effects of Masked Stimuli

    ERIC Educational Resources Information Center

    Mattler, Uwe

    2007-01-01

    The processing of a visual target that follows a briefly presented prime stimulus can be facilitated if prime and target stimuli are similar. In contrast to these positive priming effects, inverse priming effects (or negative compatibility effects) have been found when a mask follows prime stimuli before the target stimulus is presented: Responses…

  8. Amount of Priming in the Difference of Mental Transformation

    ERIC Educational Resources Information Center

    Kanamori, Nobuhiro; Yagi, Akihiro

    2005-01-01

    We examined in detail effects of priming in 2 mental rotation strategies: spinning (rotating in a picture plane) and flipping (rotating in depth around a horizontal axis) by using a priming paradigm of Kanamori and Yagi (2002). The priming paradigm included prime and probe tasks within 1 trial. In the prime task, 16 participants were asked to…

  9. Pure Mediated Priming: A Retrospective Semantic Matching Model

    ERIC Educational Resources Information Center

    Jones, Lara L.

    2010-01-01

    Mediated priming refers to the activation of a target (e.g., "stripes") by a prime (e.g., "lion") that is related indirectly via a connecting mediator (e.g., tiger). In previous mediated priming studies (e.g., McNamara & Altarriba, 1988), the mediator was associatively related to the prime. In contrast, pure mediated priming (e.g., "spoon" [right…

  10. 30 CFR 716.7 - Prime farmland.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Prime farmland. 716.7 Section 716.7 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS SPECIAL PERFORMANCE STANDARDS § 716.7 Prime farmland. (a) Applicability. (1) Permittees of surface coal mining and...

  11. Priming Addition Facts with Semantic Relations

    ERIC Educational Resources Information Center

    Bassok, Miriam; Pedigo, Samuel F.; Oskarsson, An T.

    2008-01-01

    Results from 2 relational-priming experiments suggest the existence of an automatic analogical coordination between semantic and arithmetic relations. Word pairs denoting object sets served as primes in a task that elicits "obligatory" activation of addition facts (5 + 3 activates 8; J. LeFevre, J. Bisanz, & L. Mrkonjic, 1988). Semantic relations…

  12. Perceptual learning can reverse subliminal priming effects.

    PubMed

    Przekoracka-Krawczyk, Anna; Jaśkowski, Piotr

    2007-05-01

    Masked primes presented prior to a target can result in inverse priming (i.e., benefits on trials in which the prime and the target are mapped onto opposite responses). In five experiments, time-of-task effects on subliminal priming of motor responses were investigated. First, we replicated Klapp and Hinkley's (2002) finding that the priming effect is initially straight (i.e., it benefits congruent trials, in which the prime and targets are mapped onto the same response) or absent, and only later reverses (i.e., faster responses in incongruent than in congruent trials). We show that the presentation of the mask plays a crucial role in this reversal and that the reversal occurs later if the mask pattern is very complex. We suggest that perceptual learning improves the recognition of task-relevant features. Once recognized, these features can trigger the preparation of the alternative response and/or inhibit the prime-activated response. These findings support an active role of the mask in priming. PMID:17727109

  13. Can False Memories Prime Problem Solutions?

    ERIC Educational Resources Information Center

    Howe, Mark L.; Garner, Sarah R.; Dewhurst, Stephen A.; Ball, Linden J.

    2010-01-01

    Previous research has suggested that false memories can prime performance on related implicit and explicit memory tasks. The present research examined whether false memories can also be used to prime higher order cognitive processes, namely, insight-based problem solving. Participants were asked to solve a number of compound remote associate task…

  14. Priming by the variability of visual information

    PubMed Central

    Michael, Elizabeth; de Gardelle, Vincent; Summerfield, Christopher

    2014-01-01

    According to recent theories, perception relies on summary representations that encode statistical information about the sensory environment. Here, we used perceptual priming to characterize the representations that mediate categorization of a complex visual array. Observers judged the average shape or color of a target visual array that was preceded by an irrelevant prime array. Manipulating the variability of task-relevant and task-irrelevant feature information in the prime and target orthogonally, we found that observers were faster to respond when the variability of feature information in the prime and target arrays matched. Critically, this effect occurred irrespective of whether the element-by-element features in the prime and target array overlapped or not, and was even present when prime and target features were drawn from opposing categories. This “priming by variance” phenomenon occurred with prime–target intervals as short as 100 ms. Further experiments showed that this effect did not depend on resource allocation, and occurred even when prime and target did not share the same spatial location. These results suggest that human observers adapt to the variability of visual information, and provide evidence for the existence of a low-level mechanism by which the range or dispersion of visual information is rapidly extracted. This information may in turn help to set the gain of neuronal processing during perceptual choice. PMID:24821803

  15. Does Verb Bias Modulate Syntactic Priming?

    ERIC Educational Resources Information Center

    Bernolet, Sarah; Hartsuiker, Robert J.

    2010-01-01

    In a corpus analysis of spontaneous speech Jaeger and Snider (2007) found that the strength of structural priming is correlated with verb alternation bias. This finding is consistent with an implicit learning account of syntactic priming: because the implicit learning model implemented by Chang (2002), Chang, Dell, and Bock (2006), and Chang,…

  16. A prime number approach to biological sequencing.

    PubMed

    Greer, W; Barrett, A N; Sowden, J M

    1985-03-01

    Computational sequencing of nucleic acid and amino acid sequences is placing increasing demands on computer resources. The use of prime numbers is explored as a convenient means of improving program speed and reducing storage requirements. It is concluded that the application of the prime number approach leads to significant increases in speed and some reduction in storage requirements. PMID:3840126

  17. Morphological Priming Effects on Children's Spelling

    ERIC Educational Resources Information Center

    Rosa, Joao Manuel; Nunes, Terezinha

    2008-01-01

    Previous research has suggested that children in the early grades of primary school do not have much awareness of morphemes. In this study, a priming paradigm was used to try to detect early signs of morphological representation of stems through a spelling task presented to Portuguese children (N = 805; age range 6-9 years). Primes shared the stem…

  18. Phasic Affective Modulation of Semantic Priming

    ERIC Educational Resources Information Center

    Topolinski, Sascha; Deutsch, Roland

    2013-01-01

    The present research demonstrates that very brief variations in affect, being around 1 s in length and changing from trial to trial independently from semantic relatedness of primes and targets, modulate the amount of semantic priming. Implementing consonant and dissonant chords (Experiments 1 and 5), naturalistic sounds (Experiment 2), and visual…

  19. 30 CFR 716.7 - Prime farmland.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Prime farmland. 716.7 Section 716.7 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS SPECIAL PERFORMANCE STANDARDS § 716.7 Prime farmland. (a) Applicability. (1) Permittees of surface coal mining and...

  20. 30 CFR 716.7 - Prime farmland.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Prime farmland. 716.7 Section 716.7 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS SPECIAL PERFORMANCE STANDARDS § 716.7 Prime farmland. (a) Applicability. (1) Permittees of surface coal mining and...

  1. Morphological Priming Survives a Language Switch

    ERIC Educational Resources Information Center

    Verdonschot, Rinus G.; Middelburg, Renee; Lensink, Saskia E.; Schiller, Niels O.

    2012-01-01

    In a long-lag morphological priming experiment, Dutch (L1)-English (L2) bilinguals were asked to name pictures and read aloud words. A design using non-switch blocks, consisting solely of Dutch stimuli, and switch-blocks, consisting of Dutch primes and targets with intervening English trials, was administered. Target picture naming was facilitated…

  2. 7 CFR 29.2290 - Premature primings.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Premature primings. 29.2290 Section 29.2290 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... 21) § 29.2290 Premature primings. Ground leaves harvested before reaching complete growth...

  3. 7 CFR 29.2290 - Premature primings.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Premature primings. 29.2290 Section 29.2290 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... 21) § 29.2290 Premature primings. Ground leaves harvested before reaching complete growth...

  4. Syntactic Priming in American Sign Language

    PubMed Central

    Hall, Matthew L.; Ferreira, Victor S.; Mayberry, Rachel I.

    2015-01-01

    Psycholinguistic studies of sign language processing provide valuable opportunities to assess whether language phenomena, which are primarily studied in spoken language, are fundamentally shaped by peripheral biology. For example, we know that when given a choice between two syntactically permissible ways to express the same proposition, speakers tend to choose structures that were recently used, a phenomenon known as syntactic priming. Here, we report two experiments testing syntactic priming of a noun phrase construction in American Sign Language (ASL). Experiment 1 shows that second language (L2) signers with normal hearing exhibit syntactic priming in ASL and that priming is stronger when the head noun is repeated between prime and target (the lexical boost effect). Experiment 2 shows that syntactic priming is equally strong among deaf native L1 signers, deaf late L1 learners, and hearing L2 signers. Experiment 2 also tested for, but did not find evidence of, phonological or semantic boosts to syntactic priming in ASL. These results show that despite the profound differences between spoken and signed languages in terms of how they are produced and perceived, the psychological representation of sentence structure (as assessed by syntactic priming) operates similarly in sign and speech. PMID:25786230

  5. A Generalization of the Prime Number Theorem

    ERIC Educational Resources Information Center

    Bruckman, Paul S.

    2008-01-01

    In this article, the author begins with the prime number theorem (PNT), and then develops this into a more general theorem, of which many well-known number theoretic results are special cases, including PNT. He arrives at an asymptotic relation that allows the replacement of certain discrete sums involving primes into corresponding differentiable…

  6. Negative Priming in Free Recall Reconsidered

    ERIC Educational Resources Information Center

    Hanczakowski, Maciej; Beaman, C. Philip; Jones, Dylan M.

    2016-01-01

    Negative priming in free recall is the finding of impaired memory performance when previously ignored auditory distracters become targets of encoding and retrieval. This negative priming has been attributed to an aftereffect of deploying inhibitory mechanisms that serve to suppress auditory distraction and minimize interference with learning and…

  7. Understanding Primes: The Role of Representation

    ERIC Educational Resources Information Center

    Zazkis, Rina; Liljedahl, Peter

    2004-01-01

    In this article we investigate how preservice elementary school (K-7) teachers understand the concept of prime numbers. We describe participants' understanding of primes and attempt to detect factors that influence their understanding. Representation of number properties serves as a lens for the analysis of participants' responses. We suggest that…

  8. One version of direct response priming requires automatization of the relevant associations but not awareness of the prime.

    PubMed

    Klapp, Stuart T

    2015-07-01

    Priming is the influence of one event on performance during a second event. One type of priming is known as semantic priming because it biases interpretation of the subsequent stimulus. Another type, direct response priming, biases responding directly without semantic mediation. Research reviewed in this article indicates that two versions of the second type, direct response priming, can be distinguished. One version, explicit priming, requires awareness of the prime. The other version, associative response priming, occurs even if the prime is masked and not phenomenally visible. This version, which is attributed to associations relating specific sensory events to movements of particular muscles, is enabled only if the association has previously been automatized by brief practice in which the to-be-primed response is made to the stimulus that subsequently appears as the prime. Associative response priming can be explained by a simple stimulus-response interpretation; other varieties of priming are more theoretically challenging. PMID:25167776

  9. Structural and vibrational properties of GaN

    NASA Astrophysics Data System (ADS)

    Deguchi, T.; Ichiryu, D.; Toshikawa, K.; Sekiguchi, K.; Sota, T.; Matsuo, R.; Azuhata, T.; Yamaguchi, M.; Yagi, T.; Chichibu, S.; Nakamura, S.

    1999-08-01

    Structural and vibrational properties of device quality pure GaN substrate grown using a lateral epitaxial overgrowth (LEO) technique were studied using x-ray diffraction, Brillouin, Raman, and infrared spectroscopy. Lattice constants were found to be a=3.1896±0.0002 Å and c=5.1855±0.0002 Å. Comparing the results with those on GaN epilayer directly grown on sapphire substrate, it is shown that the GaN substrate is indeed of high quality, i.e., the lattice is relaxed. However the GaN substrate has a small enough but finite residual strain arising from the pileup of the lateral growth front on SiO2 masks in the course of LEO. It was also found that the elastic stiffness constants C13 and C44, are more sensitive to the residual strain than the optical phonon frequencies. The high frequency and static dielectric constants were found to be 5.14 and 9.04. The Born and Callen effective charges were found to be 2.56 and 0.50.

  10. Growth of ZnO and GaN Films

    NASA Astrophysics Data System (ADS)

    Chang, J.; Hong, S.-K.; Matsumoto, K.; Tokunaga, H.; Tachibana, A.; Lee, S. W.; Cho, M.-W.

    . Zinc oxide (ZnO) and gallium nitride (GaN) are wide bandgap semi conductors applicable to light emitting diodes (LEDs) and laser diodes (LDs) with wavelengths ranging from ultraviolet to blue light. Now ZnO and GaN are key ma terials for optoelectronic device applications and their applications are being rapidly expanded to lots of other technology including electronics, biotechnology, nanotech-nology, and fusion technology among all these. As a fundamental starting point for the development of this new technique, epitaxy of ZnO and GaN films is one of the most important key technology. Hence, development of the growth technique for high quality epitaxial films is highly necessary. Among the various kinds of epi taxy technique for semiconductor films developed so far, physical vapor deposition (PVD)-based epitaxy technique has been revealed to be the appropriate way for the high quality ZnO film and related alloy growths, while chemical vapor deposition (CVD)-based epitaxy technique has been proved to be the best method for the high quality GaN film and related alloy growths.

  11. Properties of H, O and C in GaN

    SciTech Connect

    Pearton, S.J.; Abernathy, C.R.; Lee, J.W.

    1996-04-01

    The electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at {ge} 450 C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until > 800 C, and its diffusivity is relatively high ({approximately} 10{sup {minus}11} cm{sup 2}/s) even at low temperatures (< 200 C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30--40 meV. It is essentially immobile up to 1,100 C. Carbon can produce low p-type levels (3 {times} 10{sup 17} cm{sup {minus}3}) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.

  12. NQRS Data for GaN (Subst. No. 2219)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume B 'Substances Containing C10H16 … Zn' of Volume 48 'Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains an extract of Section '3.2 Data tables' of the Chapter '3 Nuclear quadrupole resonance data' providing the NQRS data for GaN (Subst. No. 2219)

  13. Photoluminescence of Zn-implanted GaN

    NASA Technical Reports Server (NTRS)

    Pankove, J. I.; Hutchby, J. A.

    1974-01-01

    The photoluminescence spectrum of Zn-implanted GaN peaks at 2.87 eV at room temperature. The emission efficiency decreases linearly with the logarithm of the Zn concentration in the range from 1 x 10 to the 18th to 20 x 10 to the 18th Zn/cu cm.

  14. Crystallization of free standing bulk GaN by HVPE

    NASA Astrophysics Data System (ADS)

    Ucznik, B.; Pastuszka, B.; Grzegory, I.; Bokowski, M.; Kamler, G.; Domagaa, J.; Nowak, G.; Prystawko, P.; Krukowski, S.; Porowski, S.

    2006-06-01

    Gallium nitride was crystallized on 2 inch MOVPE GaN/sapphire substrates by Hydride Vapor Phase Epitaxy. A stable growth has been achieved in long duration (>10 h) processes at growth rates bigger than 100 m/h. As a result, entirely transparent and colorless bulk crystals with thickness exceeding 2 mm were obtained. The cracks in the thick HVPE GaN layers deposited on the MOVPE GaN/sapphire substrates can appear especially during cooling of the system after crystallization. It is shown that the formation of cracks at cooling is dependent on the gradients in the layer thickness The relaxation of strains in the resulting crystal coupled to the substrate leads to the self separation of GaN from sapphire. (At present 30 x 30 x 2 mm free standing bulk GaN crystals are obtained). The GaN crystals are characterized by defect selective etching (DSE) and X-ray diffraction. The density of threading dislocations (measured by DSE of (0001) surface) decreases with the thickness of the HVPE layer and becomes lower than 107 cm-2 in the layers thicker than app. 1 mm. The X-ray rocking curves for (0002) reflection (slit 0.5 x 0.1 mm) are in the range of 80-95 arcsec. However, larger scans reveal bending of crystallographic {0001} planes. The behavior of these deformed free standing crystals used as substrates for HVPE re-growth is also analyzed.

  15. Refractive index of erbium doped GaN thin films

    SciTech Connect

    Alajlouni, S.; Sun, Z. Y.; Li, J.; Lin, J. Y.; Jiang, H. X.; Zavada, J. M.

    2014-08-25

    GaN is an excellent host for erbium (Er) to provide optical emission in the technologically important as well as eye-safe 1540 nm wavelength window. Er doped GaN (GaN:Er) epilayers were synthesized on c-plane sapphire substrates using metal organic chemical vapor deposition. By employing a pulsed growth scheme, the crystalline quality of GaN:Er epilayers was significantly improved over those obtained by conventional growth method of continuous flow of reaction precursors. X-ray diffraction rocking curve linewidths of less than 300 arc sec were achieved for the GaN (0002) diffraction peak, which is comparable to the typical results of undoped high quality GaN epilayers and represents a major improvement over previously reported results for GaN:Er. Spectroscopic ellipsometry was used to determine the refractive index of the GaN:Er epilayers in the 1540 nm wavelength window and a linear dependence on Er concentration was found. The observed refractive index increase with Er incorporation and the improved crystalline quality of the GaN:Er epilayers indicate that low loss GaN:Er optical waveguiding structures are feasible.

  16. Priming analogical reasoning with false memories.

    PubMed

    Howe, Mark L; Garner, Sarah R; Threadgold, Emma; Ball, Linden J

    2015-08-01

    Like true memories, false memories are capable of priming answers to insight-based problems. Recent research has attempted to extend this paradigm to more advanced problem-solving tasks, including those involving verbal analogical reasoning. However, these experiments are constrained inasmuch as problem solutions could be generated via spreading activation mechanisms (much like false memories themselves) rather than using complex reasoning processes. In three experiments we examined false memory priming of complex analogical reasoning tasks in the absence of simple semantic associations. In Experiment 1, we demonstrated the robustness of false memory priming in analogical reasoning when backward associative strength among the problem terms was eliminated. In Experiments 2a and 2b, we extended these findings by demonstrating priming on newly created homonym analogies that can only be solved by inhibiting semantic associations within the analogy. Overall, the findings of the present experiments provide evidence that the efficacy of false memory priming extends to complex analogical reasoning problems. PMID:25784574

  17. Luminescence properties of defects in GaN

    SciTech Connect

    Reshchikov, Michael A.; Morkoc, Hadis

    2005-03-15

    Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The point defects include native isolated defects (vacancies, interstitial, and antisites), intentional or unintentional impurities, as well as complexes involving different combinations of the isolated defects. Further improvements in device performance and longevity hinge on an in-depth understanding of point defects and their reduction. In this review a comprehensive and critical analysis of point defects in GaN, particularly their manifestation in luminescence, is presented. In addition to a comprehensive analysis of native point defects, the signatures of intentionally and unintentionally introduced impurities are addressed. The review discusses in detail the characteristics and the origin of the major luminescence bands including the ultraviolet, blue, green, yellow, and red bands in undoped GaN. The effects of important group-II impurities, such as Zn and Mg on the photoluminescence of GaN, are treated in detail. Similarly, but to a lesser extent, the effects of

  18. Individual Differences in Working Memory Capacity Modulates Semantic Negative Priming from Single Prime Words

    PubMed Central

    Ortells, Juan J.; Noguera, Carmen; Álvarez, Dolores; Carmona, Encarna; Houghton, George

    2016-01-01

    The present study investigated whether semantic negative priming from single prime words depends on the availability of cognitive control resources. Participants with high vs. low working memory capacity (as assessed by their performance in complex span and attentional control tasks) were instructed to either attend to or ignore a briefly presented single prime word that was followed by either a semantically related or unrelated target word on which participants made a lexical decision. Individual differences in working memory capacity (WMC) mainly affected the processing of the ignored primes, but not the processing of the attended primes: While the latter produced reliable positive semantic priming for both high- and low-WMC participants, the former gave rise to reliable semantic negative priming only for high WMC participants, with low WMC participants showing the opposite positive priming effect. The present results extend previous findings in demonstrating that (a) single negative priming can reliably generalize to semantic associates of the prime words, and (b) a differential availability of cognitive control resources can reliably modulate the negative priming effect at a semantic level of representation. PMID:27621716

  19. Individual Differences in Working Memory Capacity Modulates Semantic Negative Priming from Single Prime Words.

    PubMed

    Ortells, Juan J; Noguera, Carmen; Álvarez, Dolores; Carmona, Encarna; Houghton, George

    2016-01-01

    The present study investigated whether semantic negative priming from single prime words depends on the availability of cognitive control resources. Participants with high vs. low working memory capacity (as assessed by their performance in complex span and attentional control tasks) were instructed to either attend to or ignore a briefly presented single prime word that was followed by either a semantically related or unrelated target word on which participants made a lexical decision. Individual differences in working memory capacity (WMC) mainly affected the processing of the ignored primes, but not the processing of the attended primes: While the latter produced reliable positive semantic priming for both high- and low-WMC participants, the former gave rise to reliable semantic negative priming only for high WMC participants, with low WMC participants showing the opposite positive priming effect. The present results extend previous findings in demonstrating that (a) single negative priming can reliably generalize to semantic associates of the prime words, and (b) a differential availability of cognitive control resources can reliably modulate the negative priming effect at a semantic level of representation. PMID:27621716

  20. Masked priming by misspellings: Word frequency moderates the effects of SOA and prime-target similarity.

    PubMed

    Burt, Jennifer S

    2016-02-01

    University students made lexical decisions to eight- or nine-letter words preceded by masked primes that were the target, an unrelated word, or a typical misspelling of the target. At a stimulus onset asynchrony (SOA) of 47 ms, primes that were misspellings of the target produced a priming benefit for low-, medium-, and high-frequency words, even when the misspelled primes were changed to differ phonologically from their targets. At a longer SOA of 80 ms, misspelled primes facilitated lexical decisions only to medium- and low-frequency targets, and a phonological change attenuated the benefit for medium-frequency targets. The results indicate that orthographic similarity can be preserved over changes in letter position and word length, and that the priming effect of misspelled words at the shorter SOA is orthographically based. Orthographic-priming effects depend on the quality of the orthographic learning of the target word. PMID:26530310

  1. Reading a standing wave: figure-ground-alternation masking of primes in evaluative priming.

    PubMed

    Bermeitinger, Christina; Kuhlmann, Michael; Wentura, Dirk

    2012-09-01

    We propose a new masking technique for masking word stimuli. Drawing on the phenomena of metacontrast and paracontrast, we alternately presented two prime displays of the same word with the background color in one display matching the font color in the other display and vice versa. The sequence of twenty alterations (spanning approx. 267 ms) was sandwich-masked by structure masks. Using this masking technique, we conducted evaluative priming experiments with positive and negative target and prime words. Significant priming effects were found - for primes and targets drawn from the same as well as from different word sets. Priming effects were independent of prime discrimination performance in direct tests and they were still significant after the sample was restricted to those participants who showed random responding in the direct test. PMID:22521264

  2. GaN as a radiation hard particle detector

    NASA Astrophysics Data System (ADS)

    Grant, J.; Bates, R.; Cunningham, W.; Blue, A.; Melone, J.; McEwan, F.; Vaitkus, J.; Gaubas, E.; O'Shea, V.

    2007-06-01

    Semiconductor tracking detectors at experiments such as ATLAS and LHCb at the CERN Large Hadron Collider (LHC) will be subjected to intense levels of radiation. The proposed machine upgrade, the Super-LHC (SLHC), to 10 times the initial luminosity of the LHC will require detectors that are ultra-radiation hard. Much of the current research into finding a detector that will meet the requirements of the SLHC has focused on using silicon substrates with enhanced levels of oxygen, for example Czochralski silicon and diffusion oxygenated float zone silicon, and into novel detector structures such as 3D devices. Another avenue currently being investigated is the use of wide band gap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN). Both SiC and GaN should be intrinsically more radiation hard than silicon. Pad and guard ring structures were fabricated on three epitaxial GaN wafers. The epitaxial GaN thickness was either 2.5 or 12 μm and the fabricated detectors were irradiated to various fluences with 24 GeV/c protons and 1 MeV neutrons. Detectors were characterised pre- and post-irradiation by performing current-voltage ( I- V) and charge collection efficiency (CCE) measurements. Devices fabricated on 12 μm epitaxial GaN irradiated to fluences of 1016 protons cm-2 and 1016 neutrons cm-2 show maximum CCE values of 26% and 20%, respectively, compared to a maximum CCE of 53% of the unirradiated device.

  3. Wafer-scale epitaxial lift-off of optoelectronic grade GaN from a GaN substrate using a sacrificial ZnO interlayer

    NASA Astrophysics Data System (ADS)

    Rajan, Akhil; Rogers, David J.; Ton-That, Cuong; Zhu, Liangchen; Phillips, Matthew R.; Sundaram, Suresh; Gautier, Simon; Moudakir, Tarik; El-Gmili, Youssef; Ougazzaden, Abdallah; Sandana, Vinod E.; Teherani, Ferechteh H.; Bove, Philippe; Prior, Kevin A.; Djebbour, Zakaria; McClintock, Ryan; Razeghi, Manijeh

    2016-08-01

    Full 2 inch GaN epilayers were lifted off GaN and c-sapphire substrates by preferential chemical dissolution of sacrificial ZnO underlayers. Modification of the standard epitaxial lift-off (ELO) process by supporting the wax host with a glass substrate proved key in enabling full wafer scale-up. Scanning electron microscopy and x-ray diffraction confirmed that intact epitaxial GaN had been transferred to the glass host. Depth-resolved cathodoluminescence (CL) analysis of the bottom surface of the lifted-off GaN layer revealed strong near-band-edge (3.33 eV) emission indicating a superior optical quality for the GaN which was lifted off the GaN substrate. This modified ELO approach demonstrates that previous theories proposing that wax host curling was necessary to keep the ELO etch channel open do not apply to the GaN/ZnO system. The unprecedented full wafer transfer of epitaxial GaN to an alternative support by ELO offers the perspective of accelerating industrial adoption of the expensive GaN substrate through cost-reducing recycling.

  4. Transcriptomic Profiling Reveals Complex Molecular Regulation in Cotton Genic Male Sterile Mutant Yu98-8A

    PubMed Central

    Xie, Deyi; Sun, Li; Xu, Zhenzhen; Zhu, Wei; Yang, Lirong; Zhao, Yuanming; Lv, Shuping; Tang, Zhongjie; Nie, Lihong; Li, Wu; Hou, Jianan; Duan, Zhengzheng; Yu, Yuebo; Yang, Xiaojie

    2015-01-01

    Although cotton genic male sterility (GMS) plays an important role in the utilization of hybrid vigor, its precise molecular mechanism remains unclear. To characterize the molecular events of pollen abortion, transcriptome analysis, combined with histological observations, was conducted in the cotton GMS line, Yu98-8A. A total of 2,412 genes were identified as significant differentially expressed genes (DEGs) before and during the critical pollen abortion stages. Bioinformatics and biochemical analysis showed that the DEGs mainly associated with sugars and starch metabolism, oxidative phosphorylation, and plant endogenous hormones play a critical and complicated role in pollen abortion. These findings extend a better understanding of the molecular events involved in the regulation of pollen abortion in genic male sterile cotton, which may provide a foundation for further research studies on cotton heterosis breeding. PMID:26382878

  5. NK Cell-Dependent Growth Inhibition of Lewis Lung Cancer by Yu-Ping-Feng, an Ancient Chinese Herbal Formula

    PubMed Central

    Luo, Yingbin; Wu, Jianchun; Zhu, Xiaowen; Gong, Chenyuan; Yao, Chao; Ni, Zhongya; Wang, Lixin; Ni, Lulu; Li, Yan; Zhu, Shiguo

    2016-01-01

    Little is known about Yu-Ping-Feng (YPF), a typical Chinese herbal decoction, for its antitumor efficacy in non-small-cell lung cancer (NSCLC). Here, we found that YPF significantly inhibited the growth of Lewis lung cancer, prolonged the survival of tumor-bearing mice, promoted NK cell tumor infiltration, increased the population of NK cells in spleen, and enhanced NK cell-mediated killing activity. The growth suppression of tumors by YPF was significantly reversed by the depletion of NK cells. Furthermore, we found that YPF significantly downregulated the expression of TGF-β, indoleamine 2,3-dioxygenase, and IL-10 in tumor microenvironment. These results demonstrated that YPF has a NK cell-dependent inhibitory effect on Lewis lung cancer. PMID:27034590

  6. [From custody to scientific therapy: Wei Yu-lin's contribution to the founding of the Peiping Municipal Psychopathic Hospital].

    PubMed

    Fan, Ting-Wei

    2013-11-01

    In August 1908, the Ministry of Civil Affairs of the Qing Dynasty established a pauper reformatory, attached to it was a lunatic asylum, which was the first of its kind set up by the Government. In December 1917, with the restructuring of the pauper reformatory, the asylum became an independent organization called asylum for the maniac which was jointly reorganized by Peping Union Medical College (PUMC) and the Bureau of Public Welfare and renamed it as Peiping Municipal Psychopathic Hospital, with Wei Yu-lin as the director. Led by Dr. Wei Yun-lin, tremendous efforts were made to improve sanitary condition and physical comfort of the patients. Professional treatment system was set up, including psychiatric social service, occupational therapy, and psychotherapy, symbolizing the transformation of an old asylum to a modern mental hospital. PMID:24524637

  7. Contrasts of atmospheric circulation and associated tropical convection between Huaihe River valley and Yangtze River valley mei-yu flooding

    NASA Astrophysics Data System (ADS)

    Hong, Jieli; Liu, Yimin

    2012-07-01

    The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu (i.e., the East Asian rainy season in June) and the related tropical convection were investigated. During the both flooding cases, although the geopotential height anomalies always exhibit equivalent barotropic structures in middle to high latitudes at middle and upper troposphere, the phase of the Rossby wave train is different over Eurasian continent. During flooding in the Huaihe River valley, only one single blocking anticyclone is located over Baikal Lake. In contrast, during flooding in the Yangtze River valley, there are two blocking anticyclones. One is over the Ural Mountains and the other is over Northeast Asia. In the lower troposphere a positive geopotential height anomaly is located at the western ridge of subtropical anticyclone over Western Pacific (SAWP) in both flooding cases, but the location of the height anomaly is much farther north and west during the Huaihe River mei-yu flooding. Furthermore, abnormal rainfall in the Huaihe River valley and the regions north of it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian peninsula. However, the rainfall in the Yangtze River valley and the regions to its south in China is strongly related to the convection over the western tropical Pacific. Numerical experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River valley extending to Japan Sea with enhanced precipitation; and vapor divergence over the Yangtze River valley and the regions to its south with deficient precipitation. While the weakened convection in the tropical West Pacific results in moisture converging over the Yangtze River and the region to its south, along with abundant rainfall.

  8. Priming effects in a subtropical forest soil

    NASA Astrophysics Data System (ADS)

    Li, Qianru; Sun, Yue; Xu, Xingliang

    2015-04-01

    Priming effects can accelerate decomposition of soil organic carbon (SOC) and thus have great potential to change SOC dynamics. Although temperature and addition of fresh substrates could affect the intensity and direction of priming, it remains unclear how their interactions affect priming. Therefore we conducted an incubation experiment using a subtropical forest soil. We incubated the soil for 10 days at two temperatures: 15oC and 25oC, with four treatments: CK (only adding water), G (13C-glucose addition), NT (13C-glucose and nitrate additions) and AM (13C-glucose and ammonium additions). The results showed that glucose addition significantly accelerated the decomposition of SOC in both temperatures, indicates that positive priming occurs in this subtropical soil. While negative priming was observed in soils with simultaneous additions of glucose and nitrogen addition, especially at 25oC. The effect of temperature on PE was not significant. This indicates that mining of nitrogen is a major mechanism responsible for priming in this subtropical soil and there is no strong interaction between temperature and substrate additions to induce priming.

  9. Nonconscious and conscious color priming in schizophrenia.

    PubMed

    Jahshan, Carol; Wynn, Jonathan K; Breitmeyer, Bruno G; Green, Michael F

    2012-10-01

    Deficits in visual processing are well established in schizophrenia. However, there is conflicting evidence about whether these deficits start before the formation of percepts because visual processing studies in schizophrenia have typically examined the processing of consciously registered stimuli. In this study, we used nonconscious color priming to evaluate the very early visual processing stages in schizophrenia. Nonconscious and conscious color priming was assessed in 148 schizophrenia patients and 54 healthy control subjects. In both conditions, subjects identified the color of a ring preceded by a disk (prime) in the same color (congruent) or a different color (incongruent). The ring rendered the disk invisible in the nonconscious condition (SOA of 62.5 ms) or did not mask the disk (SOA of 200 ms) in the conscious condition. Schizophrenia patients exhibited a color priming effect (longer reaction times in the incongruent vs. congruent trials) that was similar to healthy controls in both the nonconscious and conscious priming conditions. Healthy controls had a significantly larger priming effect in the nonconscious vs. conscious condition, but patients did not show a significant difference in priming effects between the two conditions. Our results indicate that schizophrenia patients do not have deficits at the nonconscious, pre-perceptual stages of visual processing, suggesting that the feed forward sweep of information processing (from retina to V1) might be intact in schizophrenia. These results imply that the well-documented visual processing deficits in this illness likely occur at later, percept-dependent stages of processing. PMID:22785333

  10. Re-naming D Double Prime

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.

    1999-01-01

    "Knowledge about the dynamics of the D double prime region is a key to unlock some fundamental mysteries of the Earth heat engine which governs a wide range of global geophysical processes from tectonics to geodynamo." This benign sentence makes complete sense to many geophysicists. But for many others, it makes sense all except the odd nomenclature "D double prime". One knows about the crust, upper and lower mantle, outer and inner core, but where is the D double prime region? What meaning does it try to convey? Where is D prime region, or D, or A, B, C regions for that matter, and are there higher-order primes? How does such an odd name come about anyway? D double prime, or more "simply" D", is a generic designation given to the thin shell, about 200 km thick, of the lowermost mantle just above the core-mantle boundary inside the Earth. Incidentally, whether D" is "simpler" than "D double prime" depends on whether you are pronouncing it or writing/typing it; and D" can be confusing to readers in distinguishing quotation marks (such as in the above sentences) and second derivatives, and to word processors in spelling check and indexing.

  11. Complete Genome Sequence of Salmonella enterica Serovar Typhimurium Strain YU15 (Sequence Type 19) Harboring the Salmonella Genomic Island 1 and Virulence Plasmid pSTV

    PubMed Central

    Calva, Edmundo; Puente, José L.; Zaidi, Mussaret B.

    2016-01-01

    The complete genome of Salmonella enterica subsp. enterica serovar Typhimurium sequence type 19 (ST19) strain YU15, isolated in Yucatán, Mexico, from a human baby stool culture, was determined using PacBio technology. The chromosome contains five intact prophages and the Salmonella genomic island 1 (SGI1). This strain carries the Salmonella virulence plasmid pSTV. PMID:27081132

  12. Cherry Pit Primes Brad Pitt

    PubMed Central

    Burke, Deborah M.; Locantore, Jill Kester; Austin, Ayda A.; Chae, Bryan

    2008-01-01

    This study investigated why proper names are difficult to retrieve, especially for older adults. On intermixed trials, young and older adults produced a word for a definition or a proper name for a picture of a famous person. Prior production of a homophone (e.g., pit) as the response on a definition trial increased correct naming and reduced tip-of-the-tongue experiences for a proper name (e.g., Pitt) on a picture-naming trial. Among participants with no awareness of the homophone manipulation, older but not young adults showed these homophone priming effects. With a procedure that reduced awareness effects (Experiment 2), prior production of a homophone improved correct naming only for older adults, but speeded naming latency for both age groups. We suggest that representations of proper names are susceptible to weak connections that cause deficits in the transmission of excitation, impairing retrieval especially in older adults. We conclude that homophone production strengthens phonological connections, increasing the transmission of excitation. PMID:15016287

  13. Electromagnetic decays of radially excited mesons {pi}{sup 0 Prime }, {rho}{sup 0 Prime }, {omega}{sup 0 Prime }, and production of {pi}{sup 0 Prime} at lepton colliders

    SciTech Connect

    Arbuzov, A. B. Kuraev, E. A.; Volkov, M. K.

    2011-05-15

    Radiative decays {pi}{sup 0}({pi}{sup 0 Prime }) {yields} {gamma} + {gamma}, {pi}{sup 0 Prime} {yields} {rho}{sup 0}({omega}) + {gamma}, {rho}{sup 0 Prime }({omega} Prime ) {yields} {pi}{sup 0} + {gamma}, {rho}{sup 0 Prime }({omega} Prime ) {yields} {pi}{sup 0 Prime} + {gamma}, and some processes of {pi}{sup 0 Prime} production at lepton colliders are considered in the framework of the nonlocal SU(2) Multiplication-Sign SU(2) Nambu-Jona-Lasinio model. Mixing of the radially excited and the ground meson states is taken into account. Numerical results for the decay and production processes are presented.

  14. Phonological and Orthographic Overlap Effects in Fast and Masked Priming

    PubMed Central

    Frisson, Steven; Bélanger, Nathalie N.; Rayner, Keith

    2014-01-01

    We investigated how orthographic and phonological information is activated during reading, using a fast priming task, and during single word recognition, using masked priming. Specifically, different types of overlap between prime and target were contrasted: high orthographic and high phonological overlap (track-crack), high orthographic and low phonological overlap (bear-gear), or low orthographic and high phonological overlap (fruit-chute). In addition, we examined whether (orthographic) beginning overlap (swoop-swoon) yielded the same priming pattern as end (rhyme) overlap (track-crack). Prime durations were 32 and 50ms in the fast priming version, and 50ms in the masked priming version, and mode of presentation (prime and target in lower case) was identical. The fast priming experiment showed facilitatory priming effects when both orthography and phonology overlapped, with no apparent differences between beginning and end overlap pairs. Facilitation was also found when prime and target only overlapped orthographically. In contrast, the masked priming experiment showed inhibition for both types of end overlap pairs (with and without phonological overlap), and no difference for begin overlap items. When prime and target only shared principally phonological information, facilitation was only found with a long prime duration in the fast priming experiment, while no differences were found in the masked priming version. These contrasting results suggest that fast priming and masked priming do not necessarily tap into the same type of processing. PMID:24365065

  15. Phonological and orthographic overlap effects in fast and masked priming.

    PubMed

    Frisson, Steven; Bélanger, Nathalie N; Rayner, Keith

    2014-01-01

    We investigated how orthographic and phonological information is activated during reading, using a fast priming task, and during single-word recognition, using masked priming. Specifically, different types of overlap between prime and target were contrasted: high orthographic and high phonological overlap (track-crack), high orthographic and low phonological overlap (bear-gear), or low orthographic and high phonological overlap (fruit-chute). In addition, we examined whether (orthographic) beginning overlap (swoop-swoon) yielded the same priming pattern as end (rhyme) overlap (track-crack). Prime durations were 32 and 50 ms in the fast priming version and 50 ms in the masked priming version, and mode of presentation (prime and target in lower case) was identical. The fast priming experiment showed facilitatory priming effects when both orthography and phonology overlapped, with no apparent differences between beginning and end overlap pairs. Facilitation was also found when prime and target only overlapped orthographically. In contrast, the masked priming experiment showed inhibition for both types of end overlap pairs (with and without phonological overlap) and no difference for begin overlap items. When prime and target only shared principally phonological information, facilitation was only found with a long prime duration in the fast priming experiment, while no differences were found in the masked priming version. These contrasting results suggest that fast priming and masked priming do not necessarily tap into the same type of processing. PMID:24365065

  16. Fabrication and characterization of GaN nanowire doubly clamped resonators

    NASA Astrophysics Data System (ADS)

    Maliakkal, Carina B.; Mathew, John P.; Hatui, Nirupam; Rahman, A. Azizur; Deshmukh, Mandar M.; Bhattacharya, Arnab

    2015-09-01

    Gallium nitride (GaN) nanowires (NWs) have been intensely researched as building blocks for nanoscale electronic and photonic device applications; however, the mechanical properties of GaN nanostructures have not been explored in detail. The rigidity, thermal stability, and piezoelectric properties of GaN make it an interesting candidate for nano-electromechanical systems. We have fabricated doubly clamped GaN NW electromechanical resonators on sapphire using electron beam lithography and estimated the Young's modulus of GaN from resonance frequency measurements. For wires of triangular cross section with side ˜90 nm, we obtained values for the Young's modulus to be about 218 and 691 GPa, which are of the same order of magnitude as the values reported for bulk GaN. We also discuss the role of residual strain in the nanowire on the resonant frequency and the orientation dependence of the Young's modulus in wurtzite crystals.

  17. Growth of GaN micro/nanolaser arrays by chemical vapor deposition.

    PubMed

    Liu, Haitao; Zhang, Hanlu; Dong, Lin; Zhang, Yingjiu; Pan, Caofeng

    2016-09-01

    Optically pumped ultraviolet lasing at room temperature based on GaN microwire arrays with Fabry-Perot cavities is demonstrated. GaN microwires have been grown perpendicularly on c-GaN/sapphire substrates through simple catalyst-free chemical vapor deposition. The GaN microwires are [0001] oriented single-crystal structures with hexagonal cross sections, each with a diameter of ∼1 μm and a length of ∼15 μm. A possible growth mechanism of the vertical GaN microwire arrays is proposed. Furthermore, we report room-temperature lasing in optically pumped GaN microwire arrays based on the Fabry-Perot cavity. Photoluminescence spectra exhibit lasing typically at 372 nm with an excitation threshold of 410 kW cm(-2). The result indicates that these aligned GaN microwire arrays may offer promising prospects for ultraviolet-emitting micro/nanodevices. PMID:27454350

  18. Photo-induced Doping in GaN Epilayers with Graphene Quantum Dots

    PubMed Central

    Lin, T. N.; Inciong, M. R.; Santiago, S. R. M. S.; Yeh, T. W.; Yang, W. Y.; Yuan, C. T.; Shen, J. L.; Kuo, H. C.; Chiu, C. H.

    2016-01-01

    We demonstrate a new doping scheme where photo-induced carriers from graphene quantum dots (GQDs) can be injected into GaN and greatly enhance photoluminescence (PL) in GaN epilayers. An 8.3-fold enhancement of PL in GaN is observed after the doping. On the basis of time-resolved PL studies, the PL enhancement is attributed to the carrier transfer from GQDs to GaN. Such a carrier transfer process is caused by the work function difference between GQDs and GaN, which is verified by Kelvin probe measurements. We have also observed that photocurrent in GaN can be enhanced by 23-fold due to photo-induced doping with GQDs. The improved optical and transport properties from photo-induced doping are promising for applications in GaN-based optoelectronic devices. PMID:26987403

  19. Atomic-Level Study of Melting Behavior of GaN Nanotubes

    SciTech Connect

    Wang, Zhiguo; Zu, Xiaotao; Gao, Fei; Weber, William J.

    2006-09-20

    Molecular dynamics simulations with a Stillinger-Weber potential have been used to investigate the melting behavior of wurtzite-type single crystalline GaN nanotubes. The simulations show that the melting temperature of GaN nanotubes is much lower than that of bulk GaN, which may be associated with the large surface-to-volume ratio of the nanotubes. The melting temperature of the GaN nanotubes increases with the thickness of the nanotubes to a saturation value, which is close to the melting temperature of a GaN slab. The results reveal that the nanotubes begin to melt at the surface, and then the melting rapidly extends to the interior of the nanotubes as the temperature increases. The melting temperature of a single-crystalline GaN nanotube with [100]-oriented lateral facets is higher than that with [110]-oriented lateral facets for the same thickness.

  20. Photo-induced Doping in GaN Epilayers with Graphene Quantum Dots.

    PubMed

    Lin, T N; Inciong, M R; Santiago, S R M S; Yeh, T W; Yang, W Y; Yuan, C T; Shen, J L; Kuo, H C; Chiu, C H

    2016-01-01

    We demonstrate a new doping scheme where photo-induced carriers from graphene quantum dots (GQDs) can be injected into GaN and greatly enhance photoluminescence (PL) in GaN epilayers. An 8.3-fold enhancement of PL in GaN is observed after the doping. On the basis of time-resolved PL studies, the PL enhancement is attributed to the carrier transfer from GQDs to GaN. Such a carrier transfer process is caused by the work function difference between GQDs and GaN, which is verified by Kelvin probe measurements. We have also observed that photocurrent in GaN can be enhanced by 23-fold due to photo-induced doping with GQDs. The improved optical and transport properties from photo-induced doping are promising for applications in GaN-based optoelectronic devices. PMID:26987403

  1. Photo-induced Doping in GaN Epilayers with Graphene Quantum Dots

    NASA Astrophysics Data System (ADS)

    Lin, T. N.; Inciong, M. R.; Santiago, S. R. M. S.; Yeh, T. W.; Yang, W. Y.; Yuan, C. T.; Shen, J. L.; Kuo, H. C.; Chiu, C. H.

    2016-03-01

    We demonstrate a new doping scheme where photo-induced carriers from graphene quantum dots (GQDs) can be injected into GaN and greatly enhance photoluminescence (PL) in GaN epilayers. An 8.3-fold enhancement of PL in GaN is observed after the doping. On the basis of time-resolved PL studies, the PL enhancement is attributed to the carrier transfer from GQDs to GaN. Such a carrier transfer process is caused by the work function difference between GQDs and GaN, which is verified by Kelvin probe measurements. We have also observed that photocurrent in GaN can be enhanced by 23-fold due to photo-induced doping with GQDs. The improved optical and transport properties from photo-induced doping are promising for applications in GaN-based optoelectronic devices.

  2. Computational synthesis of single-layer GaN on refractory materials

    SciTech Connect

    Singh, Arunima K.; Hennig, Richard G.

    2014-08-04

    The synthesis of single-layer materials relies on suitable substrates. In this paper, we identify suitable substrates for the stabilization and growth of single-layer GaN and characterize the effect of the substrate on the electronic structure of single-layer GaN. We identify two classes of epitaxial substrates, refractory metal diborides and transition-metal dichalcogenides. We find that the refractory diborides provide epitaxial stabilization for the growth and functionalization of single layer GaN. We show that chemical interactions of single layer GaN with the diboride substrates result in n-type doping of the single-layer GaN. Transition-metal dichalcogenides, on the other hand, although epitaxially matched, cannot provide sufficient thermodynamic stabilization for the growth of single layer GaN. Nonetheless, energy band alignments of GaN/metal chalcogenides show that they make good candidates for heterostructures.

  3. Growth of GaN micro/nanolaser arrays by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, Haitao; Zhang, Hanlu; Dong, Lin; Zhang, Yingjiu; Pan, Caofeng

    2016-09-01

    Optically pumped ultraviolet lasing at room temperature based on GaN microwire arrays with Fabry–Perot cavities is demonstrated. GaN microwires have been grown perpendicularly on c-GaN/sapphire substrates through simple catalyst-free chemical vapor deposition. The GaN microwires are [0001] oriented single-crystal structures with hexagonal cross sections, each with a diameter of ∼1 μm and a length of ∼15 μm. A possible growth mechanism of the vertical GaN microwire arrays is proposed. Furthermore, we report room-temperature lasing in optically pumped GaN microwire arrays based on the Fabry–Perot cavity. Photoluminescence spectra exhibit lasing typically at 372 nm with an excitation threshold of 410 kW cm‑2. The result indicates that these aligned GaN microwire arrays may offer promising prospects for ultraviolet-emitting micro/nanodevices.

  4. Fabrication and characterization of GaN nanowire doubly clamped resonators

    SciTech Connect

    Maliakkal, Carina B. Mathew, John P.; Hatui, Nirupam; Rahman, A. Azizur; Deshmukh, Mandar M.; Bhattacharya, Arnab

    2015-09-21

    Gallium nitride (GaN) nanowires (NWs) have been intensely researched as building blocks for nanoscale electronic and photonic device applications; however, the mechanical properties of GaN nanostructures have not been explored in detail. The rigidity, thermal stability, and piezoelectric properties of GaN make it an interesting candidate for nano-electromechanical systems. We have fabricated doubly clamped GaN NW electromechanical resonators on sapphire using electron beam lithography and estimated the Young's modulus of GaN from resonance frequency measurements. For wires of triangular cross section with side ∼90 nm, we obtained values for the Young's modulus to be about 218 and 691 GPa, which are of the same order of magnitude as the values reported for bulk GaN. We also discuss the role of residual strain in the nanowire on the resonant frequency and the orientation dependence of the Young's modulus in wurtzite crystals.

  5. Enhancing the field emission properties of Se-doped GaN nanowires

    NASA Astrophysics Data System (ADS)

    Li, Enling; Wu, Guishuang; Cui, Zhen; Ma, Deming; Shi, Wei; Wang, Xiaolin

    2016-07-01

    Pure and Se-doped GaN nanowires (NWs) are synthesized on Pt-coated Si(111) substrates via chemical vapor deposition. The GaN NWs exhibit a uniform density with an average diameter of 20–120 nm. The structure of the NWs is wurtzite hexagonal, and the growth direction is along [0001]. Field emission measurements show that the Se-doped GaN NWs possess a low turn-on field (2.9 V μm‑1) compared with the pure GaN NWs (7.0 V μm‑1). In addition, density functional theory calculations indicate that the donor states near the Fermi level are mainly formed through the hybridization between Se 4p and N 2p orbitals and that the Fermi level move towards the vacuum level. Consequently, the work functions of Se-doped GaN NWs are lower than those of pure GaN NWs.

  6. Study of radiation detection properties of GaN pn diode

    NASA Astrophysics Data System (ADS)

    Sugiura, Mutsuhito; Kushimoto, Maki; Mitsunari, Tadashi; Yamashita, Kohei; Honda, Yoshio; Amano, Hiroshi; Inoue, Yoku; Mimura, Hidenori; Aoki, Toru; Nakano, Takayuki

    2016-05-01

    Recently, GaN, which has remarkable properties as a material for optical devices and high-power electron devices, has also attracted attention as a material for radiation detectors. We previously suggested the use of BGaN as a neutron detector material. However, the radiation detection characteristics of GaN itself are not yet adequately understood. For realizing a BGaN neutron detector, the understanding of the radiation detection characteristics of GaN, which is a base material of the neutron detector, is important. In this study, we evaluated the radiation detection characteristics of GaN. We performed I-V and energy spectrum measurements under alpha ray, gamma ray, and thermal neutron irradiations to characterize the radiation detection characteristics of a GaN diode. The obtained results indicate that GaN is an effective material for our proposed new BGaN-based neutron detector.

  7. Construction of monomers and chains assembled by 3d/4f metals and 4 Prime -(4-carboxyphenyl)-2,2 Prime :6 Prime ,2 Double-Prime -terpyridine

    SciTech Connect

    Yang, Juan; Hu, Rui-Xiang; Zhang, Man-Bo

    2012-12-15

    A series of transition metal and lanthanide complexes of 4 Prime -(4-carboxyphenyl)-2,2 Prime :6 Prime ,2 Double-Prime -terpyridine (HL, 1), namely [M(L){sub 2}]{center_dot}5H{sub 2}O (M=Ni, 2; Co, 3), [Zn(L){sub 2}]{sub n}{center_dot}0.5nH{sub 2}O (4) and [Ln(L){sub 3}]{sub n} (Ln=Nd, 5; Gd, 6; Er, 7) were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Isomorphic compounds 2 and 3 are mononuclear molecules with two ligand chelating to the metal centers via tridentate terpyridyl, while compound 4 adopts 1D chain-like structure, in which five-coordinate zinc centers are surrounded by three ligands. Compounds 5-7 also display 1D chain-like structure, but the nine-coordinate lanthanide centers bonded by four ligands. Luminescent property indicates that compound 4 exhibits photoluminescence in the solid state at room temperature. - Graphical abstract: Six complexes of 4 Prime -(4-carboxyphenyl)-2,2 Prime :6 Prime ,2 Double-Prime -terpyridine were synthesized via assembly with transition metal and lanthanide ions, respectively. Among them, [Ni(L){sub 2}]{center_dot}5H{sub 2}O and [Co(L){sub 2}]{center_dot}5H{sub 2}O are monomers, while [Zn(L){sub 2}]{sub n}{center_dot}0.5nH{sub 2}O and [Ln(L){sub 3}]{sub n} display chain-like structures. Highlights: Black-Right-Pointing-Pointer Compounds of 4 Prime -(4-carboxyphenyl)-2,2 Prime :6 Prime ,2 Double-Prime -terpyridine were synthesized. Black-Right-Pointing-Pointer [Ni(L){sub 2}]{center_dot}5H{sub 2}O and [Co(L){sub 2}]{center_dot}5H{sub 2}O are monomers. Black-Right-Pointing-Pointer [Zn(L){sub 2}]{sub n}{center_dot}0.5nH{sub 2}O and [Ln(L){sub 3}]{sub n} display chain-like structures.

  8. Gas source molecular beam epitaxy of GaN with hydrazine on spinel substrates

    NASA Astrophysics Data System (ADS)

    Nikishin, S. A.; Temkin, H.; Antipov, V. G.; Guriev, A. I.; Zubrilov, A. S.; Elyukhin, V. A.; Faleev, N. N.; Kyutt, R. N.; Chin, A. K.

    1998-05-01

    Growth of high quality wurtzite-structure GaN layers on (111) MgAl2O4 by gas source molecular beam epitaxy is described. Hydrazine was used as a source of active nitrogen. In situ reflection high energy electron diffraction was used to monitor the growth mode. Two-dimensional growth was obtained at temperatures above 750 °C on multi-step GaN buffer layers. The resulting GaN films show excellent luminescence properties.

  9. Graphene oxide assisted synthesis of GaN nanostructures for reducing cell adhesion

    NASA Astrophysics Data System (ADS)

    Yang, Rong; Zhang, Ying; Li, Jingying; Han, Qiusen; Zhang, Wei; Lu, Chao; Yang, Yanlian; Dong, Hongwei; Wang, Chen

    2013-10-01

    We report a general approach for the synthesis of large-scale gallium nitride (GaN) nanostructures by the graphene oxide (GO) assisted chemical vapor deposition (CVD) method. A modulation effect of GaN nanostructures on cell adhesion has been observed. The morphology of the GaN surface can be controlled by GO concentrations. This approach, which is based on the predictable choice of the ratio of GO to catalysts, can be readily extended to the synthesis of other materials with controllable nanostructures. Cell studies show that GaN nanostructures reduced cell adhesion significantly compared to GaN flat surfaces. The cell-repelling property is related to the nanostructure and surface wettability. These observations of the modulation effect on cell behaviors suggest new opportunities for novel GaN nanomaterial-based biomedical devices. We believe that potential applications will emerge in the biomedical and biotechnological fields.We report a general approach for the synthesis of large-scale gallium nitride (GaN) nanostructures by the graphene oxide (GO) assisted chemical vapor deposition (CVD) method. A modulation effect of GaN nanostructures on cell adhesion has been observed. The morphology of the GaN surface can be controlled by GO concentrations. This approach, which is based on the predictable choice of the ratio of GO to catalysts, can be readily extended to the synthesis of other materials with controllable nanostructures. Cell studies show that GaN nanostructures reduced cell adhesion significantly compared to GaN flat surfaces. The cell-repelling property is related to the nanostructure and surface wettability. These observations of the modulation effect on cell behaviors suggest new opportunities for novel GaN nanomaterial-based biomedical devices. We believe that potential applications will emerge in the biomedical and biotechnological fields. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02770h

  10. Transfer of processing in repetition priming: some inappropriate findings.

    PubMed

    Brown, A S; Neblett, D R; Jones, T C; Mitchell, D B

    1991-05-01

    Transfer effects in repetition priming were found with both picture and word naming, but varied with the type of prime list. Unmixed lists of word or picture primes produced equivalent intra-modal and cross-modal repetition priming in both picture-naming (Experiment 1) and word-naming (Experiment 5) tasks. However, mixing word and picture primes resulted in greater intra-modal than cross-modal priming for both picture-naming (Experiment 2) and word-naming (Experiment 6) tasks. This mixed-list difference between intra-modal and cross-modal priming was reduced by blocking prime types at input (Experiment 3). These findings suggest that differences in priming as a function of prime stimulus format should be cautiously interpreted when mixed prime lists are used. PMID:1829475

  11. Structural defects in GaN revealed by Transmission Electron Microscopy

    DOE PAGESBeta

    Liliental-Weber, Zuzanna

    2014-09-08

    This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Lastly, some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

  12. Structural defects in GaN revealed by Transmission Electron Microscopy

    SciTech Connect

    Liliental-Weber, Zuzanna

    2014-04-18

    This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

  13. Russian Prime Minister Calls the Station Crew

    NASA Video Gallery

    Russian Prime Minister Vladimir Putin called the International Space Station from the Russian Mission Control Center in Korolev, Russia, on Jan. 11, 2011. Putin also offered his condolences to ISS ...

  14. OVATION Prime Model and "Aurorasaurus" Auroral Observations

    NASA Video Gallery

    This video shows the auroral oval, as modeled using OVATION Prime (2013), along with citizen science reports collected by the Aurorasaurus project for the St. Patrick’s Day storm over March 17-19, ...

  15. Riemann equation for prime number diffusion

    NASA Astrophysics Data System (ADS)

    Chen, Wen; Liang, Yingjie

    2015-05-01

    This study makes the first attempt to propose the Riemann diffusion equation to describe in a manner of partial differential equation and interpret in physics of diffusion the classical Riemann method for prime number distribution. The analytical solution of this equation is the well-known Riemann representation. The diffusion coefficient is dependent on natural number, a kind of position-dependent diffusivity diffusion. We find that the diffusion coefficient of the Riemann diffusion equation is nearly a straight line having a slope 0.99734 in the double-logarithmic axis. Consequently, an approximate solution of the Riemann diffusion equation is obtained, which agrees well with the Riemann representation in predicting the prime number distribution. Moreover, we interpret the scale-free property of prime number distribution via a power law function with 1.0169 the scale-free exponent in respect to logarithmic transform of the natural number, and then the fractal characteristic of prime number distribution is disclosed.

  16. NASA and OPTIMUS PRIME Team Up

    NASA Video Gallery

    NASA and OPTIMUS PRIME have teamed up to educate! Kids everywhere created videos showing how NASA technology is truly more than meets the eye, and now you can vote on your favorite! Visit http://ip...

  17. Negative priming in free recall reconsidered.

    PubMed

    Hanczakowski, Maciej; Beaman, C Philip; Jones, Dylan M

    2016-05-01

    Negative priming in free recall is the finding of impaired memory performance when previously ignored auditory distracters become targets of encoding and retrieval. This negative priming has been attributed to an aftereffect of deploying inhibitory mechanisms that serve to suppress auditory distraction and minimize interference with learning and retrieval of task-relevant information. In 6 experiments, we tested the inhibitory account of the effect of negative priming in free recall against alternative accounts. We found that ignoring auditory distracters is neither sufficient nor necessary to produce the effect of negative priming in free recall. Instead, the effect is more readily accounted for by a buildup of proactive interference occurring whenever 2 successively presented lists of words are drawn from the same semantic category. (PsycINFO Database Record PMID:26595066

  18. Cannabis use, schizotypy, and negative priming.

    PubMed

    Albertella, Lucy; Le Pelley, Mike E; Copeland, Jan

    2015-08-30

    The present study examined the effects of frequency of cannabis use, schizotypy, and age on cognitive control, as measured using a location-based negative priming task in a sample of 124 Australians aged 15-24 who had ever used cannabis. This study found that the schizotypy dimension of Impulsive Nonconformity had a significant effect on negative priming such that participants with higher scores on this dimension showed reduced negative priming. Also, higher levels of psychological distress were associated with greater negative priming. Finally, there was a significant age by cannabis use interaction indicating that younger, frequent users of cannabis may be more susceptible to its effects on cognitive control and perhaps at greater risk of developing a disorder on the psychosis dimension. PMID:26154815

  19. Amygdala priming results in conditioned place avoidance.

    PubMed

    Thielen, Shelley K; Shekhar, Anantha

    2002-03-01

    Priming involves daily stimulation of the basolateral nucleus of the amygdala (BLA) for 5 days using a dose of the GABA(A) receptor antagonist, bicuculline methiodide (BMI), that is subthreshold to generate anxiogenic-like responses. The coordinated physiological and behavioral response of the primed rat is similar to the symptoms of human panic disorder and has been used as a model to study panic attacks. If the priming procedure is indeed similar to human panic disorder, then the context in which priming occurs should become associated with aversive conditioning and avoidance as seen in secondary agoraphobia following panic attacks in humans. Therefore, the purpose of this study was to further characterize the behavioral response of priming using the conditioned place avoidance (CPA) task that utilizes distinct tactile cues of a grid floor (Grid+) or hole floor (Grid-). Male Wistar rats (275-300 g) were implanted bilaterally with guide cannulae positioned 1 mm above the BLA. Grid+ animals were placed in the conditioning chamber containing grid floors immediately after a 6-pmol (in 250 nl) BMI injection into the BLA and on hole floors following a sham (250 nl vehicle) injection. Grid animals were placed in the chamber containing hole floors after the BMI injection and on grid floors following the sham injection. Animals were placed in the chamber for 20 min following each injection and injections were separated by 4 h. After 5 days of this treatment, the animals were primed. Two days later, during avoidance testing, each animal was placed in the chamber containing both floors for 30 min. Priming with daily 6-pmol BMI injections into the BLA results in CPA or an aversion to the floor paired with the BMI injection. These results suggest that priming may result in phobic-like responses, similar to the avoidance behavior exhibited by panic disorder patients. PMID:11830174

  20. Adaptive and maladaptive mechanisms of cellular priming.

    PubMed Central

    Meldrum, D R; Cleveland, J C; Moore, E E; Partrick, D A; Banerjee, A; Harken, A H

    1997-01-01

    OBJECTIVE: The mechanisms of cellular priming resulting in both adaptive and maladaptive responses to subsequent injury and strategies for manipulating this priming to constructive therapeutic advantage are explored. BACKGROUND DATA: A cell is prepared or educated by an initial insult (priming stimulus). Investigations in both laboratory animals and humans indicate that cells, organs, and perhaps even whole patients respond differently to a proximal second insult ("second hit") by virtue of this prior environmental history. The opportunity to achieve the primed state appears to be conserved across almost all cell types. The initial stimulus transmits a message to the cellular machinery that influences the cell's response to a subsequent challenge. This response may result in an exaggerated inflammatory response in the case of the neutrophil (an often maladaptive process) or an improved tolerance to injury by the myocyte (adaptive response). Our global hypothesis is that cellular priming is a conserved, receptor-dependent process that invokes common intracellular targets across multiple cell types. We further postulate that these targets create a language based on the transient phosphorylation and dephosphorylation of intracellular enzymes that is therapeutically accessible. CONCLUSIONS: Priming is a conserved, receptor-dependent process transduced by means of intracellular targets across multiple cell types. The potential therapeutic strategies outlined involve the receptor-mediated manipulation of cellular events. These events are transmitted through an intracellular language that instructs the cell regarding its behavior in response to subsequent stimulation. Understanding these intracellular events represents a realistic goal of priming and preconditioning biology and will likely lead to clinical control of the primed state. PMID:9389392

  1. Priming addition facts with semantic relations.

    PubMed

    Bassok, Miriam; Pedigo, Samuel F; Oskarsson, An T

    2008-03-01

    Results from 2 relational-priming experiments suggest the existence of an automatic analogical coordination between semantic and arithmetic relations. Word pairs denoting object sets served as primes in a task that elicits "obligatory" activation of addition facts (5 + 3 activates 8; J. LeFevre, J. Bisanz, & L. Mrkonjic, 1988). Semantic relations between the priming words were either aligned or misaligned with the structure of addition (M. Bassok, V. M. Chase, & S. A. Martin, 1998). Obligatory activation of addition facts occurred when the digits were primed by categorically related words (tulips-daisies), which are aligned with addition, but did not occur when the digits were primed by unrelated words (hens-radios, Experiment 1) or by functionally related words (records-songs, Experiment 2), which are misaligned with addition. These findings lend support to the viability of automatic analogical priming (B. A. Spellman, K. J. Holyoak, & R. G. Morrison, 2001) and highlight the relevance of arithmetic applications to theoretical accounts of mental arithmetic. PMID:18315410

  2. Cathodoluminescence of GaN implanted with Sm and Ho

    SciTech Connect

    Lozykowski, H.J.; Jadwisienczak, W.M.; Brown, I.

    1999-04-01

    We report the first observation of visible cathodoluminescence of the rare earth (RE) elements Sm, Ho implanted in GaN. The implanted samples were given isochronal thermal annealing treatments at a temperature of 1100 degrees C in N2, at atmospheric pressure to recover implantation damages and activate the RE ions. The sharp characteristic emission lines corresponding to Sm{sup 3+} and Ho{sup 3+} intra-4f{sup n}-shell transitions are resolved in the spectral range from 400 to 1000 nm, and observed over the temperature range of 11-411 K. The cathodoluminescence emission is only weakly temperature dependent. The results indicate that RE doped GaN epilayers are suitable as a material for visible optoelectronic devices.

  3. Hydrogen-dependent lattice dilation in GaN

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Ping; Wang, Xiao-Liang; Sun, Dian-Zhao; Kong, Mei-Ying

    2000-06-01

    Using Raman spectroscopy we have analysed the strain status of GaN films grown on sapphire substrates by NH3 source molecular beam epitaxy (MBE). In addition to the expected compressive biaxial strain, in some cases GaN films grown on c-face sapphire substrates suffer from serious tensile biaxial strain. This anomalous behaviour has been well interpreted in terms of interstitial hydrogen-dependent lattice dilation. The hydrogen concentration in the films is measured by nuclear reaction analysis (NRA). With increasing hydrogen incorporation, the residual compressive biaxial strain is first further relaxed, and then turns into tensile strain when the hydrogen contaminant exceeds a critical concentration. The hydrogen incorporation during the growth process is found to be growth-rate dependent, and is supposed to be strain driven. We believe that the strain-induced interstitial incorporation is another way for strain relaxation during heteroepitaxy, besides the two currently well known mechanisms: formation of dislocations and growth front roughening.

  4. Anharmonic phonon decay in cubic GaN

    NASA Astrophysics Data System (ADS)

    Cuscó, R.; Domènech-Amador, N.; Novikov, S.; Foxon, C. T.; Artús, L.

    2015-08-01

    We present a Raman-scattering study of optical phonons in zinc-blende (cubic) GaN for temperatures ranging from 80 to 750 K. The experiments were performed on high-quality, cubic GaN films grown by molecular-beam epitaxy on GaAs (001) substrates. The observed temperature dependence of the optical phonon frequencies and linewidths is analyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light of density-functional-theory calculations. The longitudinal-optical (LO) mode relaxation is found to occur via asymmetric decay into acoustic phonons, with an appreciable contribution of higher-order processes. The transverse-optical mode linewidth shows a weak temperature dependence and its frequency downshift is primarily determined by the lattice thermal expansion. The LO phonon lifetime is derived from the observed Raman linewidth and an excellent agreement with previous theoretical predictions is found.

  5. High-Temperature Growth of GaN Single Crystals Using Li-Added Na-Flux Method

    NASA Astrophysics Data System (ADS)

    Honjo, Masatomo; Imabayashi, Hiroki; Takazawa, Hideo; Todoroki, Yuma; Matsuo, Daisuke; Murakami, Kosuke; Maruyama, Mihoko; Imade, Mamoru; Yoshimura, Masashi; Sasaki, Takatomo; Mori, Yusuke

    2012-12-01

    The Na-flux method is a promising for fabricating GaN crystals with high quality. In our previous study, we found that the surface morphology and transparency of these crystals were improved by raising the growth temperature. Increasing the threshold pressure of nitrogen for GaN growth, however, made GaN growth at high temperatures difficult. In this study, we attempted to grow GaN crystals by the Na-flux method with the addition of Li to the flux, which promoted the solubility of nitrogen in the flux. As a result, the threshold pressure of nitrogen for GaN growth decreased, and GaN crystals with high crystallinity were grown at 900 °C. In addition, we found that the crystallinity of the grown GaN crystals was improved and the concentration of impurities in the grown GaN crystals was decreased by raising the growth temperature.

  6. Positron annihilation in AlN and GaN

    NASA Astrophysics Data System (ADS)

    Arutyunov, N. Yu.; Emtsev, V. V.; Mikhailin, A. V.; Davidov, V. Yu.

    2001-12-01

    The measurements of one-dimensional angular correlation of the annihilation radiation (1D-ACAR) have been carried out for AlN and GaN as well as for some related materials (Al, Ga, GaP, GaAs, GaSb) which have been used as samples of references the analysis of results. The numeral values of characteristic length of radius of spherical volume to be occupied by annihilating electron ( rs‧) have differed significantly from the corresponding values ( rs) calculated by the conventional independent-particle-model (IPM) for ideal Fermi-gas: rs‧ (AlN)≃1.28 rs, where rs (AlN)≃1.61 a.u., and rs‧ (GaN)≃1.66 rs, where rs (GaN)≃1.64 a.u. The electron-positron “ion radii” reconstructed by the high-momentum components (HMC) of 1D-ACAR for Al 3+, Ga 3+ cores as well as numeral rs‧ values provide some reasons to believe that Ga- and Al-vacancies and their impurity complexes are effective centers of the positron localization in AlN and GaN; it is assumed that these complexes include V Ga, V Al, and N atom (V Ga-N Ga in GaN and V Al-N Al in AlN) where the nitrogen atom is likely to be in the configuration of substitution (anti-site), N +Ga and N +Al, respectively.

  7. GaN blue diode lasers: a spectroscopist's view

    NASA Astrophysics Data System (ADS)

    Leinen, H.; Glässner, D.; Metcalf, H.; Wynands, R.; Haubrich, D.; Meschede, D.

    We have characterized the spectroscopic properties of one of the first samples of blue-emitting diode lasers based on GaN. With such a laser diode operated inside a standard extended cavity arrangement we find a mode-hop free tuning range of more than 20 GHz and a linewidth of 10 MHz. Doppler-free spectroscopy on an indium atomic beam reveals the isotope shift between the two major indium isotopes as well as efficient optical pumping.

  8. Photoluminescence of ion-implanted GaN

    NASA Technical Reports Server (NTRS)

    Pankove, J. I.; Hutchby, J. A.

    1976-01-01

    Thirty-five elements were implanted in GaN. Their photoluminescence spectra were measured and compared to those of an unimplanted control sample. Most impurities emit a peak at about 2.15 eV. Mg, Zn, Cd, Ca, As, Hg, and Ag have more characteristic emissions. Zn provides the most efficient recombination center. A set of midgap states is generated during the damage-annealing treatment.

  9. Ammonothermal bulk GaN substrates for LEDs

    NASA Astrophysics Data System (ADS)

    Jiang, W.; Ehrentraut, D.; Kamber, D. S.; Downey, B. C.; Cook, J.; Grundmann, M.; Pakalapati, R. T.; Yoo, H.; D'Evelyn, M. P.

    2014-02-01

    Soraa has developed a novel ammonothermal approach for growth of high quality, true bulk GaN crystals at a greatly reduced cost. Soraa's patented approach, known as SCoRA (Scalable Compact Rapid Ammonothermal) utilizes internal heating to circumvent the material-property limitations of conventional ammonothermal reactors. The SCoRA reactor has capability for temperatures and pressures greater than 650 °C and 500 MPa, respectively, enabling higher growth rates than conventional ammonothermal techniques, yet is less expensive and more scalable than conventional autoclaves fabricated from nickel-based superalloys. SCoRA GaN growth has been performed on c-plane and m-plane seed crystals with diameters between 5 mm and 2" to thicknesses of 0.5-4 mm. The highest growth rates are greater than 40 μm/h and rates in the 10-30 μm/h range are routinely observed. These values are significantly larger than those achieved by conventional ammonothermal GaN growth and are sufficient for a cost-effective manufacturing process. Two-inch diameter, crack-free, free-standing, n-type bulk GaN crystals have been grown. The crystals have been characterized by a range of techniques, including x-ray diffraction rocking-curve (XRC) analysis, optical microscopy, cathodoluminescence (CL), optical spectroscopy, and capacitance-voltage measurements. The crystallinity of the grown crystals is very good, with FWHM values of 15-80 arc-sec and average dislocation densities below 5 x 105 cm-2.

  10. Thermal functionalization of GaN surfaces with 1-alkenes.

    PubMed

    Schwarz, Stefan U; Cimalla, Volker; Eichapfel, Georg; Himmerlich, Marcel; Krischok, Stefan; Ambacher, Oliver

    2013-05-28

    A thermally induced functionalization process for gallium nitride surfaces with 1-alkenes is introduced. The resulting functionalization layers are characterized with atomic force microscopy and X-ray photoelectron spectroscopy and compared to reference samples without and with a photochemically generated functionalization layer. The resulting layers show very promising characteristics as functionalization for GaN based biosensors. On the basis of the experimental results, important characteristics of the functionalization layers are estimated and a possible chemical reaction scheme is proposed. PMID:23617559

  11. Growth of GaN epilayers on c-, m-, a-, and (20.1)-plane GaN bulk substrates obtained by ammonothermal method

    NASA Astrophysics Data System (ADS)

    Rudziński, M.; Kudrawiec, R.; Janicki, L.; Serafinczuk, J.; Kucharski, R.; Zając, M.; Misiewicz, J.; Doradziński, R.; Dwiliński, R.; Strupiński, W.

    2011-08-01

    GaN epilayers were grown by metalorganic chemical vapor deposition (MOCVD) on c-, m-, a-, and (20.1)-plane GaN substrates obtained by the ammonothermal method. The influence of (i) the surface preparation of substrates, (ii) MOCVD growth parameters, and (iii) the crystallographic orientation of substrates on the structural and optical properties of GaN epilayers was investigated and carefully analyzed. It was observed that the polishing of substrates and their misorientation have strong impact on the quality of GaN epilayers grown on these substrates. The MOCVD growth process was optimized for epilayers grown on m-plane GaN substrates. The best structural and optical properties were achieved for epilayers deposited at 1075 °C and the total reactor pressure of 50 mbar. These conditions were applied to grow GaN epilayers on substrates with other ( c-, a-, and (20.1)-plane) crystallographic orientations in the same MOCVD process. Particularly good optical properties were obtained for GaN epilayers deposited on polar and non-polar ( m- and a-plane) substrates, whereas slightly worse optical properties were observed for epilayers deposited on the semi-polar substrate. It therefore means that MOCVD growth conditions optimized for a given crystallographic direction ( m-plane direction in this case) work rather well also for other crystallographic directions.

  12. Characterization of Flavonoid 3[prime],5[prime]-Hydroxylase in Microsomal Membrane Fraction of Petunia hybrida Flowers.

    PubMed Central

    Menting, JGT.; Scopes, R. K.; Stevenson, T. W.

    1994-01-01

    We have detected a flavonoid 3[prime],5[prime]-hydroxylase (F3[prime],5[prime]H) in the microsomal fraction of Petunia hybrida flowers. Activity varied with the development of flowers, peaking immediately prior to and during anthesis, but was absent in mature flowers. F3[prime],5[prime]H activity in flower extracts from genetically defined floral color mutants correlated strictly with the genotypes Hf1 and Hf2. No activity was detected in flowers from mutants homozygous recessive for both alleles. F3[prime],5[prime]H activity was dependent on NADPH and molecular oxygen; there was only slight activity with NADH. The enzyme catalyzes the hydroxylation of 5,7,4[prime]-trihydroxyflavonone at the 3[prime] and 5[prime] positions, and of 5,7,3[prime],4[prime]-tetrahydroxyflavonone and dihydroquercetin at the 5[prime] position. Hydroxylase activity was inhibited by plant growth regulators (1-aminobenzotriazole and tetcyclacis) and by CO, N-ethylmaleimide, diethyldithiocarbamate, and cytochrome (Cyt) c. Activity was not affected by diethylpyrocarbonate or phenylmethylsulfonyl fluoride, but was enhanced by 2-mercaptoethanol. A polyclonal antibody that inhibits higher plant NADPH-Cyt P450 reductase inhibited the F3[prime],5[prime]H. The data are consistent with the suggestion that the P. hybrida F3[prime],5[prime]H is a monooxygenase consisting of a Cyt P450 and a NADPH-Cyt P-450 reductase. Cyts P450 were detected in microsomal membranes and in solubilized detergent extracts of these membranes. F3[prime],5[prime]H activity was sensitive to low concentrations of all detergents tested, and therefore solubilization of the active enzyme was not achieved. Reaction products other than flavanones were observed in F3[prime],5[prime]H assays and these may be formed by enzymic oxidation of flavanones. The possibility of a microsomal flavone synthase of a type that has not been described in P. hybrida is discussed. PMID:12232356

  13. Priming Ability-Relevant Social Categories Improves Intellectual Test Performance

    ERIC Educational Resources Information Center

    Lin, Phoebe S.; Kennette, Lynne N.; Van Havermaet, Lisa R.; Frank, Nichole M.; McIntyre, Rusty B.

    2012-01-01

    Research shows that priming affects behavioral tasks; fewer studies, however, have been conducted on how social category primes affect cognitive tasks. The present study aimed to examine the effects of social category primes on math performance and word recall. It was hypothesized that Asian prime words would improve math performance and word…

  14. An Electrophysiological Investigation of Early Effects of Masked Morphological Priming

    ERIC Educational Resources Information Center

    Morris, Joanna; Grainger, Jonathan; Holcomb, Phillip J.

    2008-01-01

    This experiment examined event-related responses to targets preceded by semantically transparent morphologically related primes (e.g., farmer-farm), semantically opaque primes with an apparent morphological relation (corner-corn), and orthographically, but not morphologically, related primes (scandal-scan) using the masked priming technique…

  15. Masked Priming from Orthographic Neighbors: An ERP Investigation

    ERIC Educational Resources Information Center

    Massol, Stephanie; Grainger, Jonathan; Dufau, Stephane; Holcomb, Phillip

    2010-01-01

    Two experiments combined masked priming with event-related potential (ERP) recordings to examine effects of primes that are orthographic neighbors of target words. Experiment 1 compared effects of repetition primes with effects of primes that were high-frequency orthographic neighbors of low-frequency targets (e.g., faute-faune [error-wildlife]),…

  16. Semantic Priming for Coordinate Distant Concepts in Alzheimer's Disease Patients

    ERIC Educational Resources Information Center

    Perri, R.; Zannino, G. D.; Caltagirone, C.; Carlesimo, G. A.

    2011-01-01

    Semantic priming paradigms have been used to investigate semantic knowledge in patients with Alzheimer's disease (AD). While priming effects produced by prime-target pairs with associative relatedness reflect processes at both lexical and semantic levels, priming effects produced by words that are semantically related but not associated should…

  17. Masked Inhibitory Priming in English: Evidence for Lexical Inhibition

    ERIC Educational Resources Information Center

    Davis, Colin J.; Lupker, Stephen J.

    2006-01-01

    Predictions derived from the interactive activation (IA) model were tested in 3 experiments using the masked priming technique in the lexical decision task. Experiment 1 showed a strong effect of prime lexicality: Classifications of target words were facilitated by orthographically related nonword primes (relative to unrelated nonword primes) but…

  18. Processing Speaker Variability in Repetition and Semantic/Associative Priming

    ERIC Educational Resources Information Center

    Lee, Chao-Yang; Zhang, Yu

    2015-01-01

    The effect of speaker variability on accessing the form and meaning of spoken words was evaluated in two short-term priming experiments. In the repetition priming experiment, participants listened to repeated or unrelated prime-target pairs, in which the prime and target were produced by the same speaker or different speakers. The results showed…

  19. Decomposition of Repetition Priming Components in Picture Naming

    ERIC Educational Resources Information Center

    Francis, Wendy S.; Corral, Nuvia I.; Jones, Mary L.; Saenz, Silvia P.

    2008-01-01

    Cognitive mechanisms underlying repetition priming in picture naming were decomposed in several experiments. Sets of encoding manipulations meant to selectively prime or reduce priming in object identification or word production components of picture naming were combined factorially to dissociate processes underlying priming in picture naming.…

  20. Cytokinin primes plant responses to wounding and reduces insect performance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report a potential role of endogenous cytokinin supply in priming plant defense against herbivory. Cytokinin priming significantly reduced weight gain by insect larvae. Unlike previously described priming by volatile compounds, priming by cytokinin did not overcome vascular restrictions on system...

  1. Ca and O ion implantation doping of GaN

    SciTech Connect

    Zolper, J.C.; Wilson, R.G.; Pearton, S.J.; Stall, R.A.

    1996-04-01

    {ital p}- and {ital n}-type doping of GaN have been realized by ion implantation of Ca and O, respectively. Rapid thermal annealing at 1100{degree}C or higher is required to achieve {ital p}-type conduction in Ca or Ca+P implanted samples with an estimated ionization level of 169 meV and a corresponding activation efficiency of {approximately}100{percent}. This is the first experimental report of an acceptor species in GaN, other than Mg, with an ionization energy level less than 180 meV. O-implanted GaN displays an ionization level of {approximately}29 meV but with an activation efficiency of only 3.6{percent} after a 1050{degree}C anneal that may result from insufficient vacancy generation for the lighter O ion or from the existence of a second, deeper O energy level. Neither Ca or O displayed measurable redistribution, based on secondary ion mass spectrometry measurements, even after a 1125{degree}C anneal. {copyright} {ital 1996 American Institute of Physics.}

  2. In situ nanomechanics of GaN nanowires.

    PubMed

    Huang, Jian Yu; Zheng, He; Mao, S X; Li, Qiming; Wang, George T

    2011-04-13

    The deformation, fracture mechanisms, and the fracture strength of individual GaN nanowires were measured in real time using a transmission electron microscope-scanning probe microscope (TEM-SPM) platform. Surface mediated plasticity, such as dislocation nucleation from a free surface and plastic deformation between the SPM probe (the punch) and the nanowire contact surface were observed in situ. Although local plasticity was observed frequently, global plasticity was not observed, indicating the overall brittle nature of this material. Dislocation nucleation and propagation is a precursor before the fracture event, but the fracture surface shows brittle characteristic. The fracture surface is not straight but kinked at (10-10) or (10-11) planes. Dislocations are generated at a stress near the fracture strength of the nanowire, which ranges from 0.21 to 1.76 GPa. The results assess the mechanical properties of GaN nanowires and may provide important insight into the design of GaN nanowire devices for electronic and optoelectronic applications. PMID:21417390

  3. UV-Photoassisted Etching of GaN in KOH

    SciTech Connect

    Abernathy, C.R.; Auh, K.H.; Cho, H.; Donovan, S.M.; Han, J.; Lambers, E.S.; Pearton, S.J.; Ren F.; Shul, R.J.

    1998-11-12

    The etch rate of GaN under W-assisted photoelectrochemical conditions in KOH solutions is found to be a strong function of illumination intensity, solution molarity, sample bias and material doping level. At low e-h pair generation rates, grain boundaries are selectively etched, while at higher illumination intensities etch rates for unintentionally doped (n - 3x 10^12Gcm-3) GaN are 2 1000 .min-l. The etching is diffusion limited under our conditions with an activation energy of - 0.8kCal.mol-1. The etched surfaces are rough, but retain their stoichiometry. PEC etching is found to selectively reveal grain boundaries in GaN under low light illumination conditions. At high lamp powers the rates increase with sample temperature and the application of bias to the PEC cell, while they go through a maximum with KOH solution molarity. The etching is diffusion-limited, producing rough surface morphologies that are suitable in a limited number of device fabrication steps. The surfaces however appear to remain relatively close to their stoichiometric composition.

  4. Oxidation of GaN: An ab initio thermodynamic approach

    NASA Astrophysics Data System (ADS)

    Jackson, Adam J.; Walsh, Aron

    2013-10-01

    GaN is a wide-band-gap semiconductor used in high-efficiency light-emitting diodes and solar cells. The solid is produced industrially at high chemical purities by deposition from a vapor phase, and oxygen may be included at this stage. Oxidation represents a potential path for tuning its properties without introducing more exotic elements or extreme processing conditions. In this work, ab initio computational methods are used to examine the energy potentials and electronic properties of different extents of oxidation in GaN. Solid-state vibrational properties of Ga, GaN, Ga2O3, and a single substitutional oxygen defect have been studied using the harmonic approximation with supercells. A thermodynamic model is outlined which combines the results of ab initio calculations with data from experimental literature. This model allows free energies to be predicted for arbitrary reaction conditions within a wide process envelope. It is shown that complete oxidation is favorable for all industrially relevant conditions, while the formation of defects can be opposed by the use of high temperatures and a high N2:O2 ratio.

  5. Theoretical and Experiment Study of Cathodoluminescence of GaN

    NASA Astrophysics Data System (ADS)

    Ben Nasr, F.; Matoussi, A.; Salh, R.; Boufaden, T.; Guermazi, S.; Fitting, H.-J.; Eljani, B.; Fakhfakh, Z.

    2007-09-01

    In this work, we report the theoretical and experimental results of cathodoluminescence (CL) from GaN layers with thickness (1-3) micron grown at 800 °C by MOVPE on silicon substrate. The CL measurements were performed in a digital scanning electron microscope DSM 960 at room temperature. The CL spectra recorded at room temperature (RT) show the main UV peak at 3.42 eV of the fundamental transition and a broad yellow band at 2.2 eV attributed the intrinsic defects and extrinsic dopants and impurities. The simulation of the CL excitation and intensity is developed using consistent 2-D model based on the electron beam energy dissipation and taking into account the effects of carrier diffusion, internal absorption and the recombination processes in GaN. Then, we have investigated the evolution of the CL intensity from GaN as a function the electron beam energy in the range Eo = (5-20) keV. A comparative study between experimental and simulated CL spectra at room temperature is presented.

  6. Epitaxially-Grown GaN Junction Field Effect Transistors

    SciTech Connect

    Baca, A.G.; Chang, P.C.; Denbaars, S.P.; Lester, L.F.; Mishra, U.K.; Shul, R.J.; Willison, C.G.; Zhang, L.; Zolper, J.C.

    1999-05-19

    Junction field effect transistors (JFET) are fabricated on a GaN epitaxial structure grown by metal organic chemical vapor deposition (MOCVD). The DC and microwave characteristics of the device are presented. A junction breakdown voltage of 56 V is obtained corresponding to the theoretical limit of the breakdown field in GaN for the doping levels used. A maximum extrinsic transconductance (gm) of 48 mS/mm and a maximum source-drain current of 270 mA/mm are achieved on a 0.8 µ m gate JFET device at VGS= 1 V and VDS=15 V. The intrinsic transconductance, calculated from the measured gm and the source series resistance, is 81 mS/mm. The fT and fmax for these devices are 6 GHz and 12 GHz, respectively. These JFETs exhibit a significant current reduction after a high drain bias is applied, which is attributed to a partially depleted channel caused by trapped hot-electrons in the semi-insulating GaN buffer layer. A theoretical model describing the current collapse is described, and an estimate for the length of the trapped electron region is given.

  7. Pit assisted oxygen chemisorption on GaN surfaces.

    PubMed

    Mishra, Monu; Krishna T C, Shibin; Aggarwal, Neha; Kaur, Mandeep; Singh, Sandeep; Gupta, Govind

    2015-06-21

    A comprehensive analysis of oxygen chemisorption on epitaxial gallium nitride (GaN) films grown at different substrate temperatures via RF-molecular beam epitaxy was carried out. Photoemission (XPS and UPS) measurements were performed to investigate the nature of the surface oxide and corresponding changes in the electronic structure. It was observed that the growth of GaN films at lower temperatures leads to a lower amount of surface oxide and vice versa was observed for a higher temperature growth. The XPS core level (CL) and valence band maximum (VBM) positions shifted towards higher binding energies (BE) with oxide coverage and revealed a downward band bending. XPS valence band spectra were de-convoluted to understand the nature of the hybridization states. UPS analysis divulged higher values of electronic affinity and ionization energy for GaN films grown at a higher substrate temperature. The surface morphology and pit structure were probed via microscopic measurements (FESEM and AFM). FESEM and AFM analysis revealed that the film surface was covered with hexagonal pits, which played a significant role in oxygen chemisorption. The favourable energetics of the pits offered an ideal site for oxygen adsorption. Pit density and pit depth were observed to be important parameters that governed the surface oxide coverage. The contribution of surface oxide was increased with an increase in average pit density as well as pit depth. PMID:25991084

  8. Dislocation core structures in Si-doped GaN

    SciTech Connect

    Rhode, S. L. Fu, W. Y.; Sahonta, S.-L.; Kappers, M. J.; Humphreys, C. J.; Horton, M. K.; Pennycook, T. J.; Dusane, R. O.; Moram, M. A.

    2015-12-14

    Aberration-corrected scanning transmission electron microscopy was used to investigate the core structures of threading dislocations in plan-view geometry of GaN films with a range of Si-doping levels and dislocation densities ranging between (5 ± 1) × 10{sup 8} and (10 ± 1) × 10{sup 9} cm{sup −2}. All a-type (edge) dislocation core structures in all samples formed 5/7-atom ring core structures, whereas all (a + c)-type (mixed) dislocations formed either double 5/6-atom, dissociated 7/4/8/4/9-atom, or dissociated 7/4/8/4/8/4/9-atom core structures. This shows that Si-doping does not affect threading dislocation core structures in GaN. However, electron beam damage at 300 keV produces 4-atom ring structures for (a + c)-type cores in Si-doped GaN.

  9. Understanding the pyramidal growth of GaN

    SciTech Connect

    Rouviere, J.L.; Arlery, M.; Bourret, A.

    1996-11-01

    By a combination of conventional, HREM and CBED TEM experiments the authors have studied wurtzite GaN layers grown by Metal-Organic Chemical Vapor Deposition (MOCVD) on (0001)Al{sub 2}O{sub 3}. They experimentally determine the structure of the macroscopic hexagonal pyramids that are visible at the surface of the layers when no optimized buffer is introduced. These pyramids look like hexagonal volcanoes with one hexagonal microscopic chimney (up to 75 nm wide) at their core. The crystal inside the chimney is a pure GaN crystal with a polarity opposed to the one of the neighboring material: the GaN layers grown on (0001)Al{sub 2}O{sub 3} are everywhere Ga-terminated except in the chimneys where they are N-terminated. Some of the N-terminated chimneys grow faster and form macroscopic hexagonal pyramids. Chimneys bounded by Inversion Domains Boundaries (IDBs) originate from steps at the surface of the substrate and may be suppressed by an adapted buffer layer.

  10. Magnesium diffusion profile in GaN grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Benzarti, Z.; Halidou, I.; Bougrioua, Z.; Boufaden, T.; El Jani, B.

    2008-07-01

    The diffusion of magnesium has been studied in GaN layers grown on sapphire substrate by atmospheric pressure metalorganic vapor-phase-epitaxy (MOVPE) in a "home-made" reactor. Secondary Ion Mass Spectroscopy (SIMS) was used to visualise the Mg profiles in two kinds of multi-sublayer GaN structures. One structure was grown with a variable flow of Ga precursor (TMG) and the second one with a variable growth temperature. In both cases, the Mg dopant precursor (Cp 2Mg) flow was kept constant. Using the second Fick's law to fit the experimental SIMS data, we have deduced an increasing then a saturating Mg diffusion coefficient versus the Mg concentration. Mg incorporation was found to get higher for lower growth rate, i.e. when TMG flow is reduced. Furthermore, based on the temperature-related behaviour we have found that the activation energy for Mg diffusion coefficient in GaN was 1.9 eV. It is suggested that Mg diffuses via substitutional sites.

  11. Self-assembled GaN nanowires on diamond.

    PubMed

    Schuster, Fabian; Furtmayr, Florian; Zamani, Reza; Magén, Cesar; Morante, Joan R; Arbiol, Jordi; Garrido, Jose A; Stutzmann, Martin

    2012-05-01

    We demonstrate the nucleation of self-assembled, epitaxial GaN nanowires (NWs) on (111) single-crystalline diamond without using a catalyst or buffer layer. The NWs show an excellent crystalline quality of the wurtzite crystal structure with m-plane faceting, a low defect density, and axial growth along the c-axis with N-face polarity, as shown by aberration corrected annular bright-field scanning transmission electron microscopy. X-ray diffraction confirms single domain growth with an in-plane epitaxial relationship of (10 ̅10)(GaN) [parallel] (01 ̅1)(Diamond) as well as some biaxial tensile strain induced by thermal expansion mismatch. In photoluminescence, a strong and sharp excitonic emission reveals excellent optical properties superior to state-of-the-art GaN NWs on silicon substrates. In combination with the high-quality diamond/NW interface, confirmed by high-resolution transmission electron microscopy measurements, these results underline the potential of p-type diamond/n-type nitride heterojunctions for efficient UV optoelectronic devices. PMID:22506554

  12. Metal contacts on ZnSe and GaN

    SciTech Connect

    Duxstad, K J

    1997-05-01

    Recently, considerable interest has been focused on the development of blue light emitting materials and devices. The focus has been on GaN and ZnSe, direct band gap semiconductors with bands gaps of 3.4 and 2.6 eV, respectively. To have efficient, reliable devices it is necessary to have thermally and electrically stable Ohmic contacts. This requires knowledge of the metal-semiconductor reaction behavior. To date few studies have investigated this behavior. Much information has accumulated over the years on the behavior of metals on Si and GaAs. This thesis provides new knowledge for the more ionic wide band gap semiconductors. The initial reaction temperatures, first phases formed, and phase stability of Pt, Pd, and Ni on both semiconductors were investigated. The reactions of these metals on ZnSe and GaN are discussed in detail and correlated with predicted behavior. In addition, comparisons are made between these highly ionic semiconductors and Si and GaAs. The trends observed here should also be applicable to other II-VI and III-Nitride semiconductor systems, while the information on phase formation and stability should be useful in the development of contacts for ZnSe and GaN devices.

  13. Fabrication of GaN structures with embedded network of voids using pillar patterned GaN templates

    NASA Astrophysics Data System (ADS)

    Svensk, O.; Ali, M.; Riuttanen, L.; Törmä, P. T.; Sintonen, S.; Suihkonen, S.; Sopanen, M.; Lipsanen, H.

    2013-05-01

    In this paper we report on the MOCVD growth and characterization of GaN structures and InGaN single quantum wells grown on pillar patterned GaN/sapphire templates. During the regrowth a network of voids was intentionally formed at the interface of sapphire substrate and GaN epitaxial layer. The regrowth process was found to decrease the threading dislocation density of the overgrown layer. The quantum well sample grown on patterned template showed significantly higher optical output in photoluminescence measurements compared to the reference sample with identical internal quantum efficiency characteristics. We attribute the increase to enhanced light extraction efficiency caused by strong scattering and redirection of light from the scattering elements.

  14. Implicit phonological priming during visual word recognition

    PubMed Central

    Wilson, Lisa B.; Tregellas, Jason R.; Slason, Erin; Pasko, Bryce E.; Rojas, Donald C.

    2011-01-01

    Phonology is a lower-level structural aspect of language involving the sounds of a language and their organization in that language. Numerous behavioral studies utilizing priming, which refers to an increased sensitivity to a stimulus following prior experience with that or a related stimulus, have provided evidence for the role of phonology in visual word recognition. However, most language studies utilizing priming in conjunction with functional magnetic resonance imaging (fMRI) have focused on lexical-semantic aspects of language processing. The aim of the present study was to investigate the neurobiological substrates of the automatic, implicit stages of phonological processing. While undergoing fMRI, eighteen individuals performed a lexical decision task (LDT) on prime-target pairs including word-word homophone and pseudoword-word pseudohomophone pairs with a prime presentation below perceptual threshold. Whole-brain analyses revealed several cortical regions exhibiting hemodynamic response suppression due to phonological priming including bilateral superior temporal gyri (STG), middle temporal gyri (MTG), and angular gyri (AG) with additional region of interest (ROI) analyses revealing response suppression in left lateralized supramarginal gyrus (SMG). Homophone and pseudohomophone priming also resulted in different patterns of hemodynamic responses relative to one another. These results suggest that phonological processing plays a key role in visual word recognition. Furthermore, enhanced hemodynamic responses for unrelated stimuli relative to primed stimuli were observed in midline cortical regions corresponding to the default-mode network (DMN) suggesting that DMN activity can be modulated by task requirements within the context of an implicit task. PMID:21159322

  15. Modulation of 2{prime}-5{prime} oligoadenylate synthetase by environmental stress in the marine sponge Geodia cydonium

    SciTech Connect

    Schroeder, H.C.; Wiens, M.; Mueller, W.E.G.; Kuusksalu, A.; Kelve, M.

    1997-07-01

    Recently the authors established the presence of relatively high amounts of 2{prime}-5{prime} oligoadenylates (2{prime}-5{prime} A) and 2{prime}-5{prime} oligoadenylate synthetase (2{prime}-5{prime} A synthetase) in the marine sponge Geodia cydonium. Here they determined by applying radioimmunoassay and high-performance liquid chromatographical methods that the concentration of 2{prime}-5{prime} A synthetase change following exposure of G. cydonium tissue to environmental stress. The 2{prime}-5{prime} A content and the activity of 2{prime}-5{prime} A synthetase, present in crude sponge extract, increase by up to three-fold after treating sponge cubes for 2 h with natural stressors including heat shock (26 C), cold shock (6 C), pH shock (pH 6), and hypertonic shock and subsequent incubation for 18 h under ambient conditions (16 C). No response was observed after exposure of sponges to an alkaline (pH 10) or hypotonic environment. Similar changes have been found for the expression of heat shock protein HSP70 in G. cydonium. These results show that 2{prime}-5{prime} A in sponges may be useful as a novel biomarker for environmental monitoring.

  16. Invariance to Rotation in Depth Measured by Masked Repetition Priming is Dependent on Prime Duration

    PubMed Central

    Eddy, Marianna D.; Holcomb, Phillip J.

    2011-01-01

    The current experiment examined invariance to pictures of objects rotated in depth using event-related potentials (ERPs) and masked repetition priming. Specifically we rotated objects 30°, 60° or 150° from their canonical view and, across two experiments, varied the prime duration (50 or 90 milliseconds (ms)). We examined three ERP components, the P/N190, N300 and N400. In Experiment 1, only the 30° rotation condition produced repetition priming effects on the N/P190, N300 and N400. The other rotation conditions only showed repetition priming effects on the early perceptual component, the N/P190. Experiment 2 extended the prime duration to 90 ms to determine whether additional exposure to the prime may produce invariance on the N300 and N400 for the 60° and 150° rotation conditions. Repetition priming effects were found for all rotation conditions across the N/P190, N300 and N400 components. We interpret these results to suggest that whether or not view invariant priming effects are found depends partly on the extent to which representation of an object has been activated. PMID:22005687

  17. Prime and prejudice: co-occurrence in the culture as a source of automatic stereotype priming.

    PubMed

    Verhaeghen, Paul; Aikman, Shelley N; Van Gulick, Ana E

    2011-09-01

    It has been argued that stereotype priming (response times are faster for stereotypical word pairs, such as black-poor, than for non-stereotypical word pairs, such as black-balmy) is partially a function of biases in the belief system inherent in the culture. In three priming experiments, we provide direct evidence for this position, showing that stereotype priming effects associated with race, gender, and age can be very well explained through objectively measured associative co-occurrence of prime and target in the culture: (a) once objective associative strength between word pairs is taken into account, stereotype priming effects disappear; (b) the relationship between response time and associative strength is identical for social primes and non-social primes. The correlation between associative-value-controlled stereotype priming and self-report measures of racism, sexism, and ageism is near zero. The racist/sexist/ageist in all of us appears to be (at least partially) a reflection of the surrounding culture. PMID:21884547

  18. Early Morphological Decomposition of Suffixed Words: Masked Priming Evidence with Transposed-Letter Nonword Primes

    ERIC Educational Resources Information Center

    Beyersmann, Elisabeth; Dunabeitia, Jon Andoni; Carreiras, Manuel; Coltheart, Max; Castles, Anne

    2013-01-01

    Many studies have previously reported that the recognition of a stem target (e.g., "teach") is facilitated by the prior masked presentation of a prime consisting of a derived form of it (e.g., "teacher"). We conducted two lexical decision experiments to investigate masked morphological priming in Spanish. Experiment 1 showed…

  19. Smelly primes – when olfactory primes do or do not work

    PubMed Central

    Smeets, M. A. M.; Dijksterhuis, G. B.

    2014-01-01

    In applied olfactory cognition the effects that olfactory stimulation can have on (human) behavior are investigated. To enable an efficient application of olfactory stimuli a model of how they may lead to a change in behavior is proposed. To this end we use the concept of olfactory priming. Olfactory priming may prompt a special view on priming as the olfactory sense has some unique properties which make odors special types of primes. Examples of such properties are the ability of odors to influence our behavior outside of awareness, to lead to strong affective evaluations, to evoke specific memories, and to associate easily and quickly to other environmental stimuli. Opportunities and limitations for using odors as primes are related to these properties, and alternative explanations for reported findings are offered. Implications for olfactory semantic, construal, behavior and goal priming are given based on a brief overview of the priming literature from social psychology and from olfactory perception science. We end by formulating recommendations and ideas for a future research agenda and applications for olfactory priming. PMID:24575071

  20. Prime time advertisements: repetition priming from faces seen on subject recruitment posters.

    PubMed

    Bruce, V; Carson, D; Burton, A M; Kelly, S

    1998-05-01

    Repetition priming is defined as a gain in item recognition after previous exposure. Repetition priming of face recognition has been shown to last for several months, despite contamination by everyday exposure to both experimental and control faces in the interval. Here we show that gains in face recognition in the laboratory are found from faces initially seen in a rather different context--on subject recruitment posters, even when the advertisements make no specific mention of experiments involving face recognition. The priming was greatest when identical pictures were shown in the posters and in the test phase, although different views of faces did give significant priming in one study. Follow-up studies revealed poor explicit memory for the faces shown on the posters. The results of these experiments are used to develop a model in which repetition priming reflects the process of updating representations of familiar faces. PMID:9610121

  1. Opportunities and challenges in GaN metal organic chemical vapor deposition for electron devices

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koh; Yamaoka, Yuya; Ubukata, Akinori; Arimura, Tadanobu; Piao, Guanxi; Yano, Yoshiki; Tokunaga, Hiroki; Tabuchi, Toshiya

    2016-05-01

    The current situation and next challenge in GaN metal organic chemical vapor deposition (MOCVD) for electron devices of both GaN on Si and GaN on GaN are presented. We have examined the possibility of increasing the growth rate of GaN on 200-mm-diameter Si by using a multiwafer production MOCVD machine, in which the vapor phase parasitic reaction is well controlled. The impact of a high-growth-rate strained-layer-superlattice (SLS) buffer layer is presented in terms of material properties. An SLS growth rate of as high as 3.46 µm/h, which was 73% higher than the current optimum, was demonstrated. As a result, comparable material properties were obtained. Next, a typical result of GaN doped with Si of 1 × 1016 cm‑3 grown at the growth rate of 3.7 µm/h is shown. For high-voltage application, we need a thick high-purity GaN drift layer with a low carbon concentration, of less than 1016 cm‑3. It is shown that achieving a high growth rate by precise control of the vapor phase reaction is still challenge in GaN MOCVD.

  2. Nanoheteroepitaxy of GaN on AlN/Si(111) nanorods fabricated by nanosphere lithography

    NASA Astrophysics Data System (ADS)

    Lee, Donghyun; Shin, In-Su; Jin, Lu; Kim, Donghyun; Park, Yongjo; Yoon, Euijoon

    2016-06-01

    Nanoheteroepitaxy (NHE) of GaN on an AlN/Si(111) nanorod structure was investigated by metal-organic chemical vapor deposition. Silica nanosphere lithography was employed to fabricate a periodic hexagonal nanorod array with a narrow gap of 30 nm between the nanorods. We were successful in obtaining a fully coalesced GaN film on the AlN/Si(111) nanorod structure. Transmission electron microscopy revealed that threading dislocation (TD) bending and termination by stacking faults occurred near the interface between GaN and the AlN/Si(111) nanorods, resulting in the reduction of TD density for the NHE GaN layer. The full width at half-maximum of the X-ray rocking curve for (102) plane of the NHE GaN was found to decrease down to 728 arcsec from 1005 arcsec for the GaN layer on a planar AlN/Si(111) substrate, indicating that the crystalline quality of the NHE GaN was improved. Also, micro-Raman measurement showed that tensile stress in the NHE GaN layer was reduced significantly as much as 70% by introducing air voids between the nanorods.

  3. Preparation and characterization of one-dimensional GaN nanorods with Tb intermediate layer

    SciTech Connect

    Shi, Feng; Xue, Chengshan

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► GaN nanorods have been prepared on Si substrates by magnetron sputtering. ► GaN nanorods are single crystal with hexagonal wurtzite structure. ► GaN nanorods are high-quality crystalline after ammoniating at 950 °C for 15 min. ► Ammoniating temperatures and times affect the growth of GaN nanorods significantly. -- Abstract: GaN nanorods have been successfully prepared on Si(1 1 1) substrates by magnetron sputtering through ammoniating Ga{sub 2}O{sub 3}/Tb thin films. X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), FT-IR spectrophotometer, scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and photoluminescence (PL) spectroscopy were used to characterize the microstructures, morphologies compositions and optical properties of the GaN samples. The results demonstrate that the nanorods are single crystal GaN with hexagonal wurtzite structure and high-quality crystalline after ammoniating at 950 °C for 15 min, which have the size of 100–150 nm in diameter. Ammoniating temperatures and times affect the growth of GaN nanorods significantly. The growth procedure mainly follows the Tb catalyst-assisted VLS mechanism.

  4. Terahertz study of m-plane GaN thin fims

    NASA Astrophysics Data System (ADS)

    Quadir, Shaham; Jang, Der-Jun; Lin, Ching-Liang; Lo, Ikai

    2014-03-01

    We investigate the optical properties of m-plane GaN thin films using the terahertz time domain spectroscopy. The m-plane GaN thin films were grown on γ-LiAlO2 substrates with buffer layers of low temperature grown GaN. The thin films were illuminated with terahertz radiation generated by a LT-GaAs antenna and the transmitted signal was detected by a ZnTe crystal. The polarization of the terahertz wave was chosen to be either parallel or perpendicular to the GaN [0001] direction. We compared the transmitted signals of the m-plane GaN thin films to that of the LAO substrate. The samples as well as the LAO substrate exhibited polarization dependence of absorption in terahertz spectrum. The carrier densities and the mobilities were derived from the transmittance of the THz wave using extended Drude model. We found, in all samples, both the carrier densities and mobilities along the GaN [0001] direction were smaller than those along the GaN [1120] direction due to the stripe formation along the GaN [1120].

  5. A computational approach to negative priming

    NASA Astrophysics Data System (ADS)

    Schrobsdorff, H.; Ihrke, M.; Kabisch, B.; Behrendt, J.; Hasselhorn, M.; Herrmann, J. Michael

    2007-09-01

    Priming is characterized by a sensitivity of reaction times to the sequence of stimuli in psychophysical experiments. The reduction of the reaction time observed in positive priming is well-known and experimentally understood (Scarborough et al., J. Exp. Psycholol: Hum. Percept. Perform., 3, pp. 1-17, 1977). Negative priming—the opposite effect—is experimentally less tangible (Fox, Psychonom. Bull. Rev., 2, pp. 145-173, 1995). The dependence on subtle parameter changes (such as response-stimulus interval) usually varies. The sensitivity of the negative priming effect bears great potential for applications in research in fields such as memory, selective attention, and ageing effects. We develop and analyse a computational realization, CISAM, of a recent psychological model for action decision making, the ISAM (Kabisch, PhD thesis, Friedrich-Schiller-Universitat, 2003), which is sensitive to priming conditions. With the dynamical systems approach of the CISAM, we show that a single adaptive threshold mechanism is sufficient to explain both positive and negative priming effects. This is achieved by comparing results obtained by the computational modelling with experimental data from our laboratory. The implementation provides a rich base from which testable predictions can be derived, e.g. with respect to hitherto untested stimulus combinations (e.g. single-object trials).

  6. Modal Analysis Using Co-Prime Arrays

    NASA Astrophysics Data System (ADS)

    Pakrooh, Pooria; Scharf, Louis L.; Pezeshki, Ali

    2016-05-01

    Let a measurement consist of a linear combination of damped complex exponential modes, plus noise. The problem is to estimate the parameters of these modes, as in line spectrum estimation, vibration analysis, speech processing, system identification, and direction of arrival estimation. Our results differ from standard results of modal analysis to the extent that we consider sparse and co-prime samplings in space, or equivalently sparse and co-prime samplings in time. Our main result is a characterization of the orthogonal subspace. This is the subspace that is orthogonal to the signal subspace spanned by the columns of the generalized Vandermonde matrix of modes in sparse or co-prime arrays. This characterization is derived in a form that allows us to adapt modern methods of linear prediction and approximate least squares, such as iterative quadratic maximum likelihood (IQML), for estimating mode parameters. Several numerical examples are presented to demonstrate the validity of the proposed modal estimation methods, and to compare the fidelity of modal estimation with sparse and co-prime arrays, versus SNR. Our calculations of Cram\\'{e}r-Rao bounds allow us to analyze the loss in performance sustained by sparse and co-prime arrays that are compressions of uniform linear arrays.

  7. Priming Intelligent Behavior: An Elusive Phenomenon

    PubMed Central

    Shanks, David R.; Newell, Ben R.; Lee, Eun Hee; Balakrishnan, Divya; Ekelund, Lisa; Cenac, Zarus; Kavvadia, Fragkiski; Moore, Christopher

    2013-01-01

    Can behavior be unconsciously primed via the activation of attitudes, stereotypes, or other concepts? A number of studies have suggested that such priming effects can occur, and a prominent illustration is the claim that individuals' accuracy in answering general knowledge questions can be influenced by activating intelligence-related concepts such as professor or soccer hooligan. In 9 experiments with 475 participants we employed the procedures used in these studies, as well as a number of variants of those procedures, in an attempt to obtain this intelligence priming effect. None of the experiments obtained the effect, although financial incentives did boost performance. A Bayesian analysis reveals considerable evidential support for the null hypothesis. The results conform to the pattern typically obtained in word priming experiments in which priming is very narrow in its generalization and unconscious (subliminal) influences, if they occur at all, are extremely short-lived. We encourage others to explore the circumstances in which this phenomenon might be obtained. PMID:23637732

  8. Avoid self-priming centrifugal pump

    SciTech Connect

    Reeves, G.G.

    1987-01-01

    The self-priming horizontal centrifugal pump becomes known to its operator either as a good pump or a bad pump. The latter is usually replaced by another type of pump, even though a properly specified self-priming centrifugal pump might have been a good choice. Use of the guidelines described in this article are intended to help in the purchase and installation of a good pump. Self-priming centrifugal pumps are used for removing liquids from below grade sumps or pits that may also contain solids, fibers and/or muck. Alternate pumps for this service include submersible pumps, vertical turbine pumps and positive displacement pumps. These alternate pumps do not pass solid particles as large as self-priming pumps do without damage. Positive displacement pumps are not normally cost-effective when pumping liquid at rates in excess of 500 gallons per minute in low-head applications. Vertical and submersible pumps must be removed when cleaning of the pump is required. Self-priming pumps are easily cleaned by opening the access plates without moving the pump; and they cost less than the other types.

  9. Radar-observed diurnal cycle and propagation of convection over the Pearl River Delta during Mei-Yu season

    NASA Astrophysics Data System (ADS)

    Chen, Xingchao; Zhao, Kun; Xue, Ming; Zhou, Bowen; Huang, Xuanxuan; Xu, Weixin

    2015-12-01

    Using operational Doppler radar and regional reanalysis data from 2007-2009, the climatology and physical mechanisms of the diurnal cycle and propagation of convection over the Pearl River Delta (PRD) region of China during the Mei-Yu seasons are investigated. Analyses reveal two hot spots for convection: one along the south coastline of PRD and the other on the windward slope of mountains in the northeastern part of PRD. Overall, convection occurs most frequently during the afternoon over PRD due to solar heating. On the windward slope of the mountains, convection occurrence frequency exhibits two daily peaks, with the primary peak in the afternoon and the secondary peak from midnight to early morning. The nighttime peak is shown to be closely related to the nocturnal acceleration and enhanced lifting on the windward slope of southwesterly boundary layer flow, in the form of boundary layer low-level jet. Along the coastline, nighttime convection is induced by the convergence between the prevailing onshore wind and the thermally induced land breeze in the early morning. Convection on the windward slope of the mountainous area is more or less stationary. Convection initiated near the coastline along the land breeze front tends to propagate inland from early morning to early afternoon when land breeze cedes to sea breeze and the prevailing onshore flow.

  10. Ancient Chinese Formula Qiong-Yu-Gao Protects Against Cisplatin-Induced Nephrotoxicity Without Reducing Anti-tumor Activity

    PubMed Central

    Teng, Zhi-Ying; Cheng, Xiao-Lan; Cai, Xue-Ting; Yang, Yang; Sun, Xiao-Yan; Xu, Jin-Di; Lu, Wu-Guang; Chen, Jiao; Hu, Chun-Ping; Zhou, Qian; Wang, Xiao-Ning; Li, Song-Lin; Cao, Peng

    2015-01-01

    Cisplatin is a highly effective anti-cancer chemotherapeutic agent; however, its clinical use is severely limited by serious side effects, of which nephrotoxicity is the most important. In this study, we investigated whether Qiong-Yu-Gao (QYG), a popular traditional Chinese medicinal formula described 840 years ago, exhibits protective effects against cisplatin-induced renal toxicity. Using a mouse model of cisplatin-induced renal dysfunction, we observed that pretreatment with QYG attenuated cisplatin-induced elevations in blood urea nitrogen and creatinine levels, ameliorated renal tubular lesions, reduced apoptosis, and accelerated tubular cell regeneration. Cisplatin-mediated elevations in tumor necrosis factor alpha (TNF-α) mRNA, interleukin-1 beta (IL-1β) mRNA, and cyclooxygenase-2 (COX-2) protein in the kidney were also significantly suppressed by QYG treatment. Furthermore, QYG reduced platinum accumulation in the kidney by decreasing the expression of copper transporter 1 and organic cation transporter 2. An in vivo study using implanted Lewis lung cancer cells revealed that concurrent administration of QYG and cisplatin did not alter the anti-tumor activity of cisplatin. Our findings suggest that the traditional Chinese medicinal formula QYG inhibits cisplatin toxicity by several mechanisms that act simultaneously, without compromising its therapeutic efficacy. Therefore, QYG may be useful in the clinic as a protective agent to prevent cisplatin-induced nephrotoxicity. PMID:26510880

  11. Metabolic profiling of Shu-Yu capsule in rat serum based on metabolic fingerprinting analysis using HPLC-ESI-MSn.

    PubMed

    Li, Fang; Zhang, You-Bo; Wei, Xia; Song, Chun-Hong; Qiao, Ming-Qi; Zhang, Hui-Yun

    2016-05-01

    The Chinese herbal formula, Shu-Yu capsule (SYC), has been successfully used to treat depression-like disorders in clinical settings. To rapidly identify the chemical constituents of SYC and its metabolites in rat serum, a simple and sensitive liquid chromatography-tandem mass spectrometry method was established in the present study. By comparing the retention times, MS and MSn spectra data in the literature and reference standards, a total of 73 compounds were identified from SYC. In rat serum, 62 components, including 13 prototype compounds and 49 metabolites were identified. Of these components, 14 metabolites were confirmed as novel metabolites of SYC. The results of the present study indicated that certain flavonoid glycosides and monoterpene glycosides were absorbed directly. Glucuronidation and sulfation were identified as the predominant metabolic pathways of the components in SYC. In addition, certain phase I reactions, including hydrolysis, demethylation and hydroxylation occurred in the rats. These results provide scientific evidence, which support further investigations of the pharmacology and mechanism of SYC. PMID:27052341

  12. Metabolic profiling of Shu-Yu capsule in rat serum based on metabolic fingerprinting analysis using HPLC-ESI-MSn

    PubMed Central

    LI, FANG; ZHANG, YOU-BO; WEI, XIA; SONG, CHUN-HONG; QIAO, MING-QI; ZHANG, HUI-YUN

    2016-01-01

    The Chinese herbal formula, Shu-Yu capsule (SYC), has been successfully used to treat depression-like disorders in clinical settings. To rapidly identify the chemical constituents of SYC and its metabolites in rat serum, a simple and sensitive liquid chromatography-tandem mass spectrometry method was established in the present study. By comparing the retention times, MS and MSn spectra data in the literature and reference standards, a total of 73 compounds were identified from SYC. In rat serum, 62 components, including 13 prototype compounds and 49 metabolites were identified. Of these components, 14 metabolites were confirmed as novel metabolites of SYC. The results of the present study indicated that certain flavonoid glycosides and monoterpene glycosides were absorbed directly. Glucuronidation and sulfation were identified as the predominant metabolic pathways of the components in SYC. In addition, certain phase I reactions, including hydrolysis, demethylation and hydroxylation occurred in the rats. These results provide scientific evidence, which support further investigations of the pharmacology and mechanism of SYC. PMID:27052341

  13. Majorana fermions in topological Yu-Shiba-Rusinov chains and lattices with or without spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Kotetes, Panagiotis

    Recent spin polarized scanning tunneling microscopy (SPSTM) experiments in magnetic chains (S. Nadj-Perge et al., Science 2014) opened new routes for detecting the elusive Majorana fermions (MFs). Within the deep Yu-Shiba-Rusinov (YSR) limit we calculate the spatially resolved tunneling conductance of topological ferromagnetic chains measured by means of SPSTM. Our analysis reveals novel signatures of MFs arising from the interplay of their strongly anisotropic spin-polarization and the magnetization content of the tip. We investigate the occurrence and evolution of zero/finite bias peaks for a single or two coupled chains forming a Josephson junction, when a preexisting chiral symmetry controlling the number of MFs per chain edge is preserved or weakly broken. We also reveal alternative pathways for engineering MFs without spin-orbit interaction (SOI). On one hand, we highlight that antiferromagnetic YSR chains become topological by inducing an artificial SOI using external fields, while on the other, we pursue mechanisms for stabilizing magnetic textures and topological YSR lattices following the self-organization principle for topological spiral chains.

  14. Characterization and quantification of major constituents of Xue Fu Zhu Yu by UPLC-DAD-MS/MS.

    PubMed

    Zhang, Lei; Zhu, Lin; Wang, Yuefei; Jiang, Zhenzuo; Chai, Xin; Zhu, Yan; Gao, Xiumei; Qi, Aidi

    2012-03-25

    Xue Fu Zhu Yu (XFZY), a classic recipe in traditional Chinese medicine (TCM), has been demonstrated to show protective effects on cardiovascular system. For quality control of XFZY products, qualitative analysis using ultra high performance liquid chromatography with diode-array detector-tandem mass spectrometry (UPLC-DAD-MS) was undertaken. Twenty-eight compounds from XFZY were simultaneously detected; among them, seventeen compounds were unequivocally identified, and another eight compounds were tentatively characterized. According to qualitative results, a new method for quantitative analysis of XFZY has been established by ultra high performance liquid chromatography coupled with diode array detector (UPLC-DAD). Twelve representative compounds unequivocally identified were used as chemical markers in quantitative analysis, including 5-hydroxymethyl-2-furaldehyde (5-HMF), hydroxysafflor yellow A (HSYA), amygdalin, albiflorin, paeoniflorin, liquiritin, ferulic acid (FA), naringin, hesperidin, neohesperidin (NH), isoliquiritigenin (IL) and glycyrrhizic acid (GA), which were derived from nine of eleven herbs of XFZY except Platycodon grandiflorum (Jacq.) A. DC. (Jiegeng) and Bupleurum chinense DC. (Chaihu). This UPLC method was validated in terms of linearity, LOD and LOQ, precision, repeatability, stability, and recovery tests. Quality control of XFZY products in total fourteen samples by four dosage forms was examined by this method, and results confirmed its feasibility and reliability in practice. PMID:22264846

  15. [A brief textual research on circulated versions of Dan tai yu an (Jade Case Records of Red Stage].

    PubMed

    Xu, Gao; Zhu, Jianping

    2014-03-01

    Dan tai yu an (Jade Case Records of Red Stage) was compiled by a doctor of the Ming Dynasty Sun Wenyin, including 6 volumes. This book involves Chinese internal medicine, paediatrics, gynaecology, external medicine, and Department of the sense organs (ENT) classified into 73 categories, each of which contains 80 kinds of disease. The total number of disease was 157. Each kind of disease is discussed under the order of etiology, syndrome, pulse condition and treatment. The range of traditional Chinese prescriptions in this book is rather extensive with its indications, administrations and modification of main prescriptions given concretely. Both internal and external treatment are included, and the individual drug and proved recipe are practical and effective, which is a significant reference to clinical practice. There are many versions of this book extant. According to our investigation and research, we replenished some information to the"General Catalogue of TCM Ancient Books", and at the same time, correct some mistakes, providing the basis for further collation and publishing. PMID:24989811

  16. Priming for novel object associations: Neural differences from object item priming and equivalent forms of recognition.

    PubMed

    Gomes, Carlos Alexandre; Figueiredo, Patrícia; Mayes, Andrew

    2016-04-01

    The neural substrates of associative and item priming and recognition were investigated in a functional magnetic resonance imaging study over two separate sessions. In the priming session, participants decided which object of a pair was bigger during both study and test phases. In the recognition session, participants saw different object pairs and performed the same size-judgement task followed by an associative recognition memory task. Associative priming was accompanied by reduced activity in the right middle occipital gyrus as well as in bilateral hippocampus. Object item priming was accompanied by reduced activity in extensive priming-related areas in the bilateral occipitotemporofrontal cortex, as well as in the perirhinal cortex, but not in the hippocampus. Associative recognition was characterized by activity increases in regions linked to recollection, such as the hippocampus, posterior cingulate cortex, anterior medial frontal gyrus and posterior parahippocampal cortex. Item object priming and recognition recruited broadly overlapping regions (e.g., bilateral middle occipital and prefrontal cortices, left fusiform gyrus), even though the BOLD response was in opposite directions. These regions along with the precuneus, where both item priming and recognition were accompanied by activation, have been found to respond to object familiarity. The minimal structural overlap between object associative priming and recollection-based associative recognition suggests that they depend on largely different stimulus-related information and that the different directions of the effects indicate distinct retrieval mechanisms. In contrast, item priming and familiarity-based recognition seemed mainly based on common memory information, although the extent of common processing between priming and familiarity remains unclear. Further implications of these findings are discussed. © 2015 Wiley Periodicals, Inc. PMID:26418396

  17. GaN: From three- to two-dimensional single-layer crystal and its multilayer van der Waals solids

    NASA Astrophysics Data System (ADS)

    Onen, A.; Kecik, D.; Durgun, E.; Ciraci, S.

    2016-02-01

    Three-dimensional (3D) GaN is a III-V compound semiconductor with potential optoelectronic applications. In this paper, starting from 3D GaN in wurtzite and zinc-blende structures, we investigated the mechanical, electronic, and optical properties of the 2D single-layer honeycomb structure of GaN (g -GaN ) and its bilayer, trilayer, and multilayer van der Waals solids using density-functional theory. Based on high-temperature ab initio molecular-dynamics calculations, we first showed that g -GaN can remain stable at high temperature. Then we performed a comparative study to reveal how the physical properties vary with dimensionality. While 3D GaN is a direct-band-gap semiconductor, g -GaN in two dimensions has a relatively wider indirect band gap. Moreover, 2D g -GaN displays a higher Poisson ratio and slightly less charge transfer from cation to anion. In two dimensions, the optical-absorption spectra of 3D crystalline phases are modified dramatically, and their absorption onset energy is blueshifted. We also showed that the physical properties predicted for freestanding g -GaN are preserved when g -GaN is grown on metallic as well as semiconducting substrates. In particular, 3D layered blue phosphorus, being nearly lattice-matched to g -GaN , is found to be an excellent substrate for growing g -GaN . Bilayer, trilayer, and van der Waals crystals can be constructed by a special stacking sequence of g -GaN , and they can display electronic and optical properties that can be controlled by the number of g -GaN layers. In particular, their fundamental band gap decreases and changes from indirect to direct with an increasing number of g -GaN layers.

  18. The role of AlN encapsulation of GaN during implant activation annealing

    SciTech Connect

    Zolper, J.C.; Rieger, D.J.; Baca, A.G.; Pearton, S.J.; Lee, J.W.; Vartulli, C.R.; Stall, R.A.

    1996-09-01

    With the demonstration of implant doping of GaN and the resulting need to perform the activation anneal at 1100 C, details of thermal stability of the GaN surface needs to be understood. This work reports on the use of a sputtered AlN encapsulant to preserve the surface of GaN during such annealing. The surface was characterized by formation of Pt/Au Schottky contacts and by AES. Schottky contacts deposited an GaN annealed wtih the AlN encapsulant displayed good rectification properties while those formed on GaN annealed uncapped approached ohmic behavior. AES analysis supports the hypothesis that the uncapped sample has lost N from the very near surface which creates N-vacancies that act as donors and thereby form an n{sup +}-surface layer.

  19. GaN microdomes for broadband omnidirectional antireflection for concentrator photovoltaics

    NASA Astrophysics Data System (ADS)

    Han, Lu; McGoogan, Matthew R.; Piedimonte, Tyler A.; Kidd, Ian V.; French, Roger H.; Zhao, Hongping

    2013-03-01

    GaN microdomes are studied as a broadband omnidirectional anti-reflection structure for high efficiency multi-junction concentrated photovoltaics. Comprehensive studies of the effect of GaN microdome sizes and shapes on the light collection efficiency were studied. The three dimensional finite difference time domain (3-D FDTD) method was used to calculate the surface reflectance of GaN microdomes as compared to that of the flat surface. Studies indicate significant reduction of the surface reflectance is achievable by properly designing the microdome structures. Formation of the GaN microdomes with the flexibility to tune the size and shape has been demonstrated by using reactive ion etching (RIE) of both GaN and the self-assembled silica monolayer microspheres. Characterizations of the angle-dependence light surface reflectance for both micro-domes and flat surface show the similar trend as the simulation.

  20. Electronic structure and magnetic properties of substitutional transition-metal atoms in GaN nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Shi, Jun-Jie

    2014-01-01

    The electronic structure and magnetic properties of the transition-metal (TM) atoms (Sc—Zn, Pt and Au) doped zigzag GaN single-walled nanotubes (NTs) are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6-16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Co-doped GaN NTs induce the largest local moment of 4μB among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it.

  1. Step-induced misorientation of GaN grown on r-plane sapphire

    SciTech Connect

    Smalc-Koziorowska, J.; Dimitrakopulos, G. P.; Sahonta, S.-L.; Komninou, Ph.; Tsiakatouras, G.; Georgakilas, A.

    2008-07-14

    In the growth of nonpolar (1120) a-plane GaN on r-plane (1102) sapphire by plasma-assisted molecular beam epitaxy, misoriented crystallites are observed close to the substrate. They have average diameter {approx}10 nm and are oriented with the (0001){sub GaN} plane approximately parallel to the (2113){sub sapph.} plane and [0110]{sub GaN} parallel [1101]{sub sapph.}. This semipolar orientation is promoted by a low misfit (2.4%) between (1011){sub GaN} and (1210){sub sapph.} planes. Its introduction, after nitridation treatment, is due to GaN nucleation on (2113){sub sapph.} step facets inclined at 26 deg. relative to the r-plane. Two variants are observed, leading to twinning when they abut inside the epilayer.

  2. Hydrogen sensing characteristics of semipolar (112{sup ¯}2) GaN Schottky diodes

    SciTech Connect

    Hyeon Baik, Kwang; Kim, Hyonwoong; Jang, Soohwan; Lee, Sung-Nam; Lim, Eunju; Pearton, S. J.; Ren, F.

    2014-02-17

    The hydrogen detection characteristics of semipolar (112{sup ¯}2) plane GaN Schottky diodes were investigated and compared to c-plane Ga- and N-polar and nonpolar a-plane (112{sup ¯}0) GaN diodes. The semipolar GaN diodes showed large current response to 4% hydrogen in nitrogen gas with an accompanying Schottky barrier reduction of 0.53 eV at 25 °C, and the devices exhibited full recovery to the initial current level upon switching to a nitrogen ambient. The current-voltage characteristics of the semipolar devices remained rectifying after hydrogen exposure, in sharp contrast to the case of c-plane N-polar GaN. These results show that the surface atom configuration and polarity play a strong role in hydrogen sensing with GaN.

  3. Time-resolved photoluminescence study of m-plane GaN thin films

    NASA Astrophysics Data System (ADS)

    Pan, Ji-Hong; Jang, Der-Jun; Quadir, Shaham; Lo, Ikai

    2014-03-01

    The optical properties and the carrier relaxation of GaN thin films were studied by time-resolved photoluminescence apparatus. The m-plane GaN thin films were grown on GaN buffer layer and γ-LiAlO2 substrates by molecular beam epitaxy with variation of N/Ga ratio. We found that the PL associated with defect is prominent for large N/Ga ratio due to the increasing of stacking faults. The intensity of PL perpendicular to the GaN [0001] direction is more intensive than that of PL parallel to the perpendicular to the GaN [0001] direction. The PL decay times exhibit dependence on the direction of the PL polarizations.

  4. Vertical nonpolar growth templates for light emitting diodes formed with GaN nanosheets

    NASA Astrophysics Data System (ADS)

    Yeh, Ting-Wei; Lin, Yen-Ting; Ahn, Byungmin; Stewart, Lawrence S.; Daniel Dapkus, P.; Nutt, Steven R.

    2012-01-01

    We demonstrate that nonpolar m-plane surfaces can be generated on uniform GaN nanosheet arrays grown vertically from the (0001)-GaN bulk material. InGaN/GaN multiple quantum wells (MQWs) grown on the facets of these nanosheets are demonstrated by cross-sectional transmission electron microscopy. Owing to the high aspect ratio of the GaN nanosheet structure, the MQWs predominantly grow on nonpolar GaN planes. The results suggest that GaN nanosheets provide a conduction path for device fabrication and also a growth template to reduce the piezoelectric field inside the active region of InGaN-based light emitting diodes.

  5. Prospects for the application of GaN power devices in hybrid electric vehicle drive systems

    NASA Astrophysics Data System (ADS)

    Su, Ming; Chen, Chingchi; Rajan, Siddharth

    2013-07-01

    GaN, a wide bandgap semiconductor successfully implemented in optical and high-speed electronic devices, has gained momentum in recent years for power electronics applications. Along with rapid progress in material and device processing technologies, high-voltage transistors over 600 V have been reported by a number of teams worldwide. These advances make GaN highly attractive for the growing market of electrified vehicles, which currently employ bipolar silicon devices in the 600-1200 V class for the traction inverter. However, to capture this billion-dollar power market, GaN has to compete with existing IGBT products and deliver higher performance at comparable or lower cost. This paper reviews key achievements made by the GaN semiconductor industry, requirements of the automotive electric drive system and remaining challenges for GaN power devices to fit in the inverter application of hybrid vehicles.

  6. Surface morphology evolution of m-plane (1100) GaN during molecular beam epitaxy growth: Impact of Ga/N ratio, miscut direction, and growth temperature

    SciTech Connect

    Shao Jiayi; Tang Liang; Malis, Oana; Edmunds, Colin; Gardner, Geoff; Manfra, Michael

    2013-07-14

    We present a systematic study of morphology evolution of [1100] m-plane GaN grown by plasma-assisted molecular beam epitaxy on free-standing m-plane substrates with small miscut angles towards the -c [0001] and +c [0001] directions under various gallium to nitrogen (Ga/N) ratios at substrate temperatures T = 720 Degree-Sign C and T = 740 Degree-Sign C. The miscut direction, Ga/N ratio, and growth temperature are all shown to have a dramatic impact on morphology. The observed dependence on miscut direction supports the notion of strong anisotropy in the gallium adatom diffusion barrier and growth kinetics. We demonstrate that precise control of Ga/N ratio and substrate temperature yields atomically smooth morphology on substrates oriented towards +c [0001] as well as the more commonly studied -c [0001] miscut substrates.

  7. Polarity of semipolar wurtzite crystals: X-ray photoelectron diffraction from GaN(101⁻1) and GaN(202⁻1) surfaces

    SciTech Connect

    Romanyuk, O. Jiříček, P.; Bartoš, I.; Paskova, T.

    2014-09-14

    Polarity of semipolar GaN(101⁻1) (101⁻1⁻) and GaN(202⁻1) (202⁻1⁻) surfaces was determined with X-ray photoelectron diffraction (XPD) using a standard MgKα source. The photoelectron emission from N 1s core level measured in the a-plane of the crystals shows significant differences for the two crystal orientations within the polar angle range of 80–100° from the (0001) normal. It was demonstrated that XPD polar plots recorded in the a-plane are similar for each polarity of the GaN(101⁻1) and GaN(202⁻1) crystals if referred to (0001) crystal axes. For polarity determinations of all important GaN(h0h⁻l) semipolar surfaces, the above given polar angle range is suitable.

  8. Initial growth control of GaN on Si with physical-vapor-deposition-AlN seed layer for high-quality GaN templates

    NASA Astrophysics Data System (ADS)

    Wang, Hongbo; Sodabanlu, Hassanet; Daigo, Yoshiaki; Seino, Takuya; Nakagawa, Takashi; Sugiyama, Masakazu

    2016-05-01

    An ex situ AlN seed layer was formed by physical vapor deposition (PVD) on a Si substrate, aiming at the production of high-quality GaN on Si by metal–organic vapor-phase epitaxy. A low density of initial GaN islands were obtained by reducing the trimethylgallium (TMGa) flow rate. The dislocation density of GaN was dramatically reduced with 3D growth compared with 2D growth, as indicated by measurements of XRD rocking curves (FWHM of 384 and 461 arcsec for 0002 and 10\\bar{1}0 diffractions, respectively) and cathodoluminescence (CL) mapping (dark-spot density of 3.4 × 108 cm‑2) for 1-µm-thick crack-free GaN on a Si substrate. The values were almost equivalent to those of the layers grown on sapphire substrates.

  9. Semantic priming revealed by mouse movement trajectories.

    PubMed

    Xiao, Kunchen; Yamauchi, Takashi

    2014-07-01

    Congruency effects are taken as evidence that semantic information can be processed automatically. However, these effects are often weak, and the straightforward association between primes and targets can exaggerate congruency effects. To address these problems, a mouse movement method is applied to scrutinize congruency effects. In one experiment, participants judged whether two numbers were the same ("3\\3") or different ("3\\5"), preceded by briefly presented pictures with either positive or negative connotations. Participants indicated their responses by clicking a "Same" or "Different" button on the computer screen, while their cursor trajectories were recorded for each trial. The trajectory data revealed greater deviation to unselected buttons in incongruent trials (e.g., "3\\5" preceded by a green traffic light picture). This effect was influenced by the type of responses but not by prime durations. We suggest that the mouse movement method can complement the reaction time to study masked semantic priming. PMID:24797040

  10. Congruent numbers with many prime factors

    PubMed Central

    Tian, Ye

    2012-01-01

    Mohammed Ben Alhocain, in an Arab manuscript of the 10th century, stated that the principal object of the theory of rational right triangles is to find a square that when increased or diminished by a certain number, m becomes a square [Dickson LE (1971) History of the Theory of Numbers (Chelsea, New York), Vol 2, Chap 16]. In modern language, this object is to find a rational point of infinite order on the elliptic curve . Heegner constructed such rational points in the case that m are primes congruent to 5,7 modulo 8 or twice primes congruent to 3 modulo 8 [Monsky P (1990) Math Z 204:45–68]. We extend Heegner's result to integers m with many prime divisors and give a sketch in this report. The full details of all the proofs will be given in ref. 1 [Tian Y (2012) Congruent Numbers and Heegner Points, arXiv:1210.8231]. PMID:23213259

  11. A small world network of prime numbers

    NASA Astrophysics Data System (ADS)

    Chandra, Anjan Kumar; Dasgupta, Subinay

    2005-11-01

    According to Goldbach conjecture, any even number can be broken up as the sum of two prime numbers: n=p+q. We construct a network where each node is a prime number and corresponding to every even number n, we put a link between the component primes p and q. In most cases, an even number can be broken up in many ways, and then we chose one decomposition with a probability |p-q|α. Through computation of average shortest distance and clustering coefficient, we conclude that for α>-1.8 the network is of small world type and for α<-1.8 it is of regular type. We also present a theoretical justification for such behaviour.

  12. Riemann zeros, prime numbers, and fractal potentials.

    PubMed

    van Zyl, Brandon P; Hutchinson, David A W

    2003-06-01

    Using two distinct inversion techniques, the local one-dimensional potentials for the Riemann zeros and prime number sequence are reconstructed. We establish that both inversion techniques, when applied to the same set of levels, lead to the same fractal potential. This provides numerical evidence that the potential obtained by inversion of a set of energy levels is unique in one dimension. We also investigate the fractal properties of the reconstructed potentials and estimate the fractal dimensions to be D=1.5 for the Riemann zeros and D=1.8 for the prime numbers. This result is somewhat surprising since the nearest-neighbor spacings of the Riemann zeros are known to be chaotically distributed, whereas the primes obey almost Poissonlike statistics. Our findings show that the fractal dimension is dependent on both level statistics and spectral rigidity, Delta(3), of the energy levels. PMID:16241330

  13. Stronger suboptimal than optimal affective priming?

    PubMed

    Rotteveel, M; de Groot, P; Geutskens, A; Phaf, R H

    2001-12-01

    The finding of stronger affective priming in less conscious (suboptimal) conditions than in fully conscious (optimal) conditions (S. T. Murphy & R. B. Zajonc, 1993) is theoretically important because it contradicts notions that emotions are primarily reflected by conscious states. In 2 experiments, this pattern of results was obtained. Happy and angry faces were presented both optimally and suboptimally and were masked by unknown ideographs. In Experiment 1, instructions for the conscious and less conscious affective priming conditions were matched, and affective ratings of ideographs were determined. In Experiment 2, a more implicit affective measure (facial electromyography of musculus zygomaticus major and musculus corrugator supercilii) served as the dependent variable. Stronger suboptimal than optimal affective priming was found in both experiments. It is concluded that stronger suboptimal than optimal processing is characteristic for affective processing and that it can also be found when instructions are matched and when a more implicit measure is assessed. PMID:12901397

  14. A model study of the coupled water quality and hydrodynamics in YuQiao Reservoir of Haihe River Basin, People's Republic of China

    NASA Astrophysics Data System (ADS)

    Liu, X.; Liu, J.; Peng, W.; Wang, Y.

    2007-05-01

    In recent years, eutrophication has become one of the most serious of global water pollution problems, especially in reservoirs, which is menacing the security of domestic water supplies. As the unique drinking water source of Tianjin within the Haihe River basin of Hebei Province, China, YuQiao Reservoir has been polluted and its eutrophic state is serious. To make clear the physical and chemical relationship between transport and transformation of the polluted water, a model package was developed to compute the hydrodynamic field and mass transport processes including total nitrogen (TN) and total phosphorus (TP) for YuQiao Reservoir. The hydrodynamic model was driven by observed winds and daily measured flow data to simulate the seasonal water cycle of the reservoir. The mass transport and transformation processes of TN and TP was based on the unsteady diffusion equations, driven by observed meteorological forcings and external loadings, with the fluxes through the bottom of the reservoir, plant (algal) photosynthesis, and respiration as internal sources and sinks. The solution of these equations uses the finite volume method and alternating direction implicit (ADI) scheme. The model was calibrated and verified by using the data observed from YuQiao Reservoir in two different years. The results showed that in YuQiao Reservoir, the wind-driven current is an important style of lake current, while the water quality is decreasing from east to west because of the external polluted loadings. There was good agreement between the simulated and measured values. Advection is the main process driving the water quality impacts from the inflow river, and diffusion and biochemical processes dominate in center of the reservoir. So it is necessary to build a pre-pond to reduce the external loadings into the reservoir.

  15. Mare Orientale Prime Meridian lunar coordinate system

    NASA Astrophysics Data System (ADS)

    Walden, B.; York, C.; McGown, R.; Billings, T.

    The Moon was the first extraterrestrial body to be mapped. From 1514 to 1840, navigators sailing the open seas needed accurate lunar maps to determine longitude by the "lunar-distance" method. For the convenience of early navigators, astronomers and selenographers, the lunar prime meridian was made to bisect the lunar disk as seen from Earth, formalized as the present Mean Earth / Polar Axis system. In 1961, the International Astronomical Union reversed lunar east and west to avoid confusion by astronauts and their controllers, so that now Mare Orientale -- the Eastern Sea -- lies on the Moon's western limb. By international agreement in 1974, lunar longitude was defined to increase eastward from zero to 360 degrees and prime meridians are generally defined by an observable feature. Examination of popular lunar maps indicates these newer standards are not widely accepted. Modern navigation no longer relies on the Moon. Lunar maps are now made by satellite imagery from lunar orbit. Today, humankind anticipates navigating the Moon itself. A relatively simple change to the lunar coordinate system could benefit upcoming lunar activities and promote acceptance of a 360 degree standard: move the lunar prime meridian. We propose the lunar prime meridian intersect some natural monument that most nearly represents the center longitude of Mare Orientale (perhaps crater Hohmann), and longitude increase eastward from zero to 360 degrees. Mare Orientale is a dramatic large "target," easily identifiable from space. Nearside traffic will use low longitude numbers from zero to r ughly 180 degrees,o and will not frequently cross this prime meridian. Earth's angle above the eastern horizon equals approximate longitude. Low and high longitude numbers will reflect the distinctive nearside and farside geological domains. The face of the Moon as seen from Earth will no longer be split in two. Calculations are simplified and sources of error eliminated. This system is more convenient and

  16. Rokumi-jio-gan-Containing Prescriptions Attenuate Oxidative Stress, Inflammation, and Apoptosis in the Remnant Kidney

    PubMed Central

    Park, Chan Hum; Lee, Sul Lim; Okamoto, Takuya; Tanaka, Takashi; Yokozawa, Takako

    2012-01-01

    Two Rokumi-jio-gan-containing prescriptions (Hachimi-jio-gan and Bakumi-jio-gan) were selected to examine their actions in nephrectomized rats. Each prescription was given orally to rats for 10 weeks after the excision of five-sixths of their kidney volumes, and its effect was compared with non-nephrectomized and normal rats. Rats given Hachimi-jio-gan and Bakumi-jio-gan showed an improvement of renal functional parameters such as serum urea nitrogen, creatinine, creatinine clearance, and urinary protein. The nephrectomized rats exhibited the up-regulation of nicotinamide adenine dinucleotide phosphate oxidase subunits, c-Jun N-terminal kinase (JNK), phosphor-JNK, c-Jun, transforming growth factor-β1, nuclear factor-kappa B, cyclooxygenase-2, inducible nitric oxide synthase, monocyte chemotactic protein-1, intracellular adhesion molecule-1, Bax, cytochrome c, and caspase-3, and down-regulation of NF-E2-related factor 2, heme oxygenase-1, and survivin; however, Bakumi-jio-gan administration acts as a regulator in inflammatory reactions caused by oxidative stress in renal failure. Moreover, the JNK pathway and apoptosis-related protein expressions, Bax, caspase-3, and survivin, were ameliorated to the normal levels by Hachimi-jio-gan administration. The development of renal lesions, glomerular sclerosis, tubulointerstitial damage, and arteriolar sclerotic lesions, estimated by histopathological evaluation and scoring, was strong in the groups administered Hachimi-jio-gan rather than Bakumi-jio-gan. This study suggests that Rokumi-jio-gan-containing prescriptions play a protective role in the progression of renal failure. PMID:23243456

  17. Fabrication of low-density GaN/AlN quantum dots via GaN thermal decomposition in MOCVD

    PubMed Central

    2014-01-01

    With an appropriate high anneal temperature under H2 atmosphere, GaN quantum dots (QDs) have been fabricated via GaN thermal decomposition in metal organic chemical vapor deposition (MOCVD). Based on the characterization of atomic force microscopy (AFM), the obtained GaN QDs show good size distribution and have a low density of 2.4 × 108 cm-2. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the GaN QDs were formed without Ga droplets by thermal decomposition of GaN. PMID:25136276

  18. Comprehensive Qualitative Ingredient Profiling of Chinese Herbal Formula Wu-Zhu-Yu Decoction via a Mass Defect and Fragment Filtering Approach Using High Resolution Mass Spectrometry.

    PubMed

    Xu, Huarong; Niu, Huibin; He, Bosai; Cui, Chang; Li, Qing; Bi, Kaishun

    2016-01-01

    The Wu-Zhu-Yu decoction is a traditional Chinese medicine formula for the treatment of headache. To reveal its material basis, a rapid and reliable liquid chromatography-high resolution mass spectrometry method was established for comprehensive profiling of the chemical ingredients in the Wu-Zhu-Yu decoction. The method was used on a quadrupole time-of-flight mass spectrometer along with an advanced data processing procedure consisting of mass accuracy screening, mass defect filtering and fragment filtering. After eliminating interference with a filtering approach, the MS data profiling was made more distinct and accurate. With the optimized conditions of only 35 min LC separation and single sample injection of each positive or negative ion mode, a total of 168 compounds were characterized, including 23 evodiamine and its analogous alkaloids, 12 limonoids, 17 gingerols, 38 ginsenosides, 15 flavonoids, 16 organic acids, 14 alkaloids, 5 saponins, 3 2,2-dimethylchromenes and 25 other compounds. The fragmentation patterns of representative compounds were illustrated as well. Integrative qualitative analysis of the Wu-Zhu-Yu decoction by high resolution mass spectrometry was accomplished and reported for the first time. The study demonstrated that the established method was a powerful and reliable strategy for comprehensive detection and would be widely applicable for identification of complicated components from herbal prescriptions, and may provide a basis for chemical analysis of other complex mixtures. PMID:27213316

  19. On the role of mask structure in subliminal priming.

    PubMed

    Jaśkowski, Piotr; Przekoracka-Krawczyk, Anna

    2005-01-01

    Choice reaction times to visual stimuli may be influenced by preceding subliminal stimuli (primes). Some authors reported a straight priming effect i.e., responses were faster when primes and targets called for the same response than when they called for different responses. Other authors found a reversed pattern of results. Our results suggest that the sign of the priming effect depends on mask structure. Inverse priming was obtained only for masks containing the searched-for feature even though informational content of the masks was neutral. With masks of irrelevant structure, straight priming effects were found. Thus, masks are not passive stimuli whose roles are limited to rendering the prime invisible. Processing of the mask may interact with prime and target processing. Implications of the results are discussed for two hypotheses trying to account for straight and inverse priming (the self-inhibition hypothesis and object-updating hypothesis). PMID:16366393

  20. Schoolbook Texts: Behavioral Achievement Priming in Math and Language

    PubMed Central

    Engeser, Stefan; Baumann, Nicola; Baum, Ingrid

    2016-01-01

    Prior research found reliable and considerably strong effects of semantic achievement primes on subsequent performance. In order to simulate a more natural priming condition to better understand the practical relevance of semantic achievement priming effects, running texts of schoolbook excerpts with and without achievement primes were used as priming stimuli. Additionally, we manipulated the achievement context; some subjects received no feedback about their achievement and others received feedback according to a social or individual reference norm. As expected, we found a reliable (albeit small) positive behavioral priming effect of semantic achievement primes on achievement in math (Experiment 1) and language tasks (Experiment 2). Feedback moderated the behavioral priming effect less consistently than we expected. The implication that achievement primes in schoolbooks can foster performance is discussed along with general theoretical implications. PMID:26938446

  1. Fabrication of GaN Microporous Structure at a GaN/Sapphire Interface as the Template for Thick-Film GaN Separation Grown by HVPE

    NASA Astrophysics Data System (ADS)

    Chen, Jianli; Cheng, Hongjuan; Zhang, Song; Lan, Feifei; Qi, Chengjun; Xu, Yongkuan; Wang, Zaien; Li, Jing; Lai, Zhanping

    2016-06-01

    In this paper, a microporous structure at the GaN/sapphire interface has been obtained by an electrochemical etching method via a selective etching progress using an as-grown GaN/sapphire wafer grown by metal organic chemical vapor deposition. The as-prepared GaN interfacial microporous structure has been used as a template for the following growth of thick-film GaN crystal by hydride vapor phase epitaxy (HVPE), facilitating the fabrication of a free-standing GaN substrate detached from a sapphire substrate. The evolution of the interfacial microporous structure has been investigated by varying the etching voltages and time, and the formation mechanism of interfacial microporous structure has been discussed in detail as well. Appropriate interfacial microporous structure is beneficial for separating the thick GaN crystal grown by HVPE from sapphire during the cooling down process. The separation that occurred at the place of interfacial microporous can be attributed to the large thermal strain between GaN and sapphire. This work realized the fabrication of a free-standing GaN substrate with high crystal quality and nearly no residual strain.

  2. Influence of prime lexicality, frequency, and pronounceability on the masked onset priming effect.

    PubMed

    Dimitropoulou, Maria; Duñabeitia, Jon Andoni; Carreiras, Manuel

    2010-09-01

    The present study investigates the origins of the masked onset priming effect (MOPE). There are two alternative interpretations that account for most of the evidence reported on the MOPE, so far. The speech planning account (SP) identifies the locus of the MOPE in the preparation of the speech response. In contrast, the dual-route theory proposes that the effect arises as a result of the processing of the prime by the nonlexical route. In a series of masked onset priming word naming experiments we test the validity of these accounts by manipulating the primes' frequency, their lexical status, and pronounceability. We found consistent MOPEs of similar magnitude with high- and low-frequency prime words as well as with pronounceable nonwords. Contrarily, when primes consisted of unpronounceable consonantal strings the effect disappeared, suggesting that pronounceability of the prime is a prerequisite for the emergence of the MOPE. These results are in accordance with the predictions of the SP account. The pattern of effects obtained in the present study further defines the origins of the MOPE. PMID:20221948

  3. The roles of scene priming and location priming in object-scene consistency effects

    PubMed Central

    Heise, Nils; Ansorge, Ulrich

    2014-01-01

    Presenting consistent objects in scenes facilitates object recognition as compared to inconsistent objects. Yet the mechanisms by which scenes influence object recognition are still not understood. According to one theory, consistent scenes facilitate visual search for objects at expected places. Here, we investigated two predictions following from this theory: If visual search is responsible for consistency effects, consistency effects could be weaker (1) with better-primed than less-primed object locations, and (2) with less-primed than better-primed scenes. In Experiments 1 and 2, locations of objects were varied within a scene to a different degree (one, two, or four possible locations). In addition, object-scene consistency was studied as a function of progressive numbers of repetitions of the backgrounds. Because repeating locations and backgrounds could facilitate visual search for objects, these repetitions might alter the object-scene consistency effect by lowering of location uncertainty. Although we find evidence for a significant consistency effect, we find no clear support for impacts of scene priming or location priming on the size of the consistency effect. Additionally, we find evidence that the consistency effect is dependent on the eccentricity of the target objects. These results point to only small influences of priming to object-scene consistency effects but all-in-all the findings can be reconciled with a visual-search explanation of the consistency effect. PMID:24910628

  4. The growth and characterization of GaN films on cone-shaped patterned sapphire by MOCVD

    NASA Astrophysics Data System (ADS)

    Liang, Jing; Hongling, Xiao; Xiaoliang, Wang; Cuimei, Wang; Qingwen, Deng; Zhidong, Li; Jieqin, Ding; Zhanguo, Wang; Xun, Hou

    2013-11-01

    GaN films are grown on cone-shaped patterned sapphire substrates (CPSSs) by metal-organic chemical vapor deposition, and the influence of the temperature during the middle stage of GaN growth on the threading dislocation (TD) density of GaN is investigated. High-resolution X-ray diffraction (XRD) and cathode-luminescence (CL) were used to characterize the GaN films. The XRD results showed that the edge-type dislocation density of GaN grown on CPSS is remarkably reduced compared to that of GaN grown on conventional sapphire substrates (CSSs). Furthermore, when the growth temperature in the middle stage of GaN grown on CPSS decreases, the full width at half maximum of the asymmetry (102) plane of GaN is reduced. This reduction is attributed to the enhancement of vertical growth in the middle stage with a more triangular-like shape and the bending of TDs. The CL intensity spatial mapping results also showed the superior optical properties of GaN grown on CPSS to those of GaN on CSS, and that the density of dark spots of GaN grown on CPSS induced by nonradiative recombination is reduced when the growth temperature in the middle stage decreases.

  5. Retro-priming, priming, and double testing: psi and replication in a test–retest design

    PubMed Central

    Rabeyron, Thomas

    2014-01-01

    Numerous experiments have been conducted in recent years on anomalous retroactive influences on cognition and affect (Bem, 2010), yet more data are needed to understand these processes precisely. For this purpose, we carried out an initial retro-priming study in which the response times of 162 participants were measured (Rabeyron and Watt, 2010). In the current paper, we present the results of a second study in which we selected those participants who demonstrated the strongest retro-priming effect during the first study, in order to see if we could replicate this effect and therefore select high scoring participants. An additional objective was to try to find correlations between psychological characteristics (anomalous experiences, mental health, mental boundaries, trauma, negative life events) and retro-priming results for the high scoring participants. The retro-priming effect was also compared with performance on a classical priming task. Twenty-eight participants returned to the laboratory for this new study. The results, for the whole group, on the retro-priming task, were negative and non-significant (es = −0.25, ns) and the results were significant on the priming task (es = 0.63, p < 0.1). We obtained overall negative effects on retro-priming results for all the sub-groups (students, male, female). Ten participants were found to have positive results on the two retro-priming studies, but no specific psychological variables were found for these participants compared to the others. Several hypotheses are considered in explaining these results, and the author provide some final thoughts concerning psi and replicability. PMID:24672466

  6. Crack-free GaN substrates grown by the Na-flux method with a sapphire dissolution technique

    NASA Astrophysics Data System (ADS)

    Yamada, Takumi; Imanishi, Masayuki; Nakamura, Kosuke; Murakami, Kosuke; Imabayashi, Hiroki; Matsuo, Daisuke; Honjo, Masatomo; Maruyama, Mihoko; Imade, Mamoru; Yoshimura, Masashi; Mori, Yusuke

    2016-07-01

    GaN wafers are generally fabricated by separating a foreign substrate from a GaN layer using thermal stress; however, thermal stress also leads to the cracking of the GaN layer. In this study, we first succeeded in dissolving a sapphire substrate just after Na-flux growth by successively changing the flux content for GaN growth (Ga–Na–C) to that for dissolving sapphire (Ga–Na–C–Li) at the considered growth temperature. Hence, no thermal stress was induced in the grown GaN crystals, resulting in a crack-free GaN substrate. We concluded that this process is a good candidate technique for supplying free-standing GaN substrates.

  7. Cross-language positive priming disappears, negative priming does not: evidence for two sources of selective inhibition.

    PubMed

    Neumann, E; McCloskey, M S; Felio, A C

    1999-11-01

    The authors used a unilingual and bilingual primed lexical decision task to investigate priming effects produced by attended and ignored words. In the unilingual experiment, accelerated lexical decisions to probe target words resulted when the word matched the preceding target word, whereas slowed lexical decisions to probe target words resulted when the word matched the preceding ignored nontarget word. In the bilingual (English-Spanish) experiment, between-language, rather than within-language, priming manipulations were used. Although the ignored repetition negative priming effect replicated across languages, cross-language attended repetition positive priming did not. This dissociation of priming effects in the inter- versus intralanguage priming conditions contradicts episodic retrieval accounts of negative priming that deny the existence of selective inhibitory processes. On the other hand, these results support an extension of inhibition-based accounts of negative priming, because they indicate that inhibition can operate at two levels of abstraction--local word and global language--simultaneously. PMID:10586580

  8. Devices for medical diagnosis with GaN lasers

    NASA Astrophysics Data System (ADS)

    Kwasny, Miroslaw; Mierczyk, Zygmunt

    2003-10-01

    This paper presents laser-induced fluroescence method (LIF) employing endogenous ("autofluroescence") and exogenous fluorophores. LIF is applied for clinical diagnosis in dermatology, gynaecology, urology, lung tumors as well as for early dentin caries. We describe the analysers with He-Ne, He-Cd, and SHG Nd:YAG lasers and new generation systems based on blue semiconductor GaN lasers that have been implemented into clinical practice till now. The LIF method, fundamental one for many medical applications, with excitation radiation of wavelength 400 nm could be appl,ied only using tunable dye lasers or titanium lasers adequte for laboratory investigations. Development of GaN laser shows possibility to design portable, compact diagnostic devices as multi-channel analysers of fluorescence spectra and surface imaging devoted to clinical application. The designed systems used for spectra measurement and registration of fluorescence images include lasers of power 5-30 mW and generate wavelengths of 405-407 nm. They are widely used in PDT method for investigation of superficial distribution of accumulation kinetics of all known photosensitizers, their elimination, and degradation as well as for treatment of superficial lesions of mucosa and skin. Excitation of exogenous porphrins in Soret band makes possible to estimate their concentration and a period of healthy skin photosensitivity that occurs after photosensitiser injections. Due to high sensitivity of spectrum analysers, properties of photosensitisers can be investigated in vitro (e.g. their aggregation, purity, chromatographic distributions) when their concentrations are 2-3 times lower in comparison to concentrations investigated with typical spectrofluorescence methods. Dentistry diagnosis is a new field in which GaN laser devices can be applied. After induction with blue light, decreased autofluorescence intensity can be observed when dentin caries occur and strong characteristic bands of endogenous porphyrines

  9. Visible fiber lasers excited by GaN laser diodes

    NASA Astrophysics Data System (ADS)

    Fujimoto, Yasushi; Nakanishi, Jun; Yamada, Tsuyoshi; Ishii, Osamu; Yamazaki, Masaaki

    2013-07-01

    This paper describes and discusses visible fiber lasers that are excited by GaN laser diodes. One of the attractive points of visible light is that the human eye is sensitive to it between 400 and 700 nm, and therefore we can see applications in display technology. Of course, many other applications exist. First, we briefly review previously developed visible lasers in the gas, liquid, and solid-state phases and describe the history of primary solid-state visible laser research by focusing on rare-earth doped fluoride media, including glasses and crystals, to clarify the differences and the merits of primary solid-state visible lasers. We also demonstrate over 1 W operation of a Pr:WPFG fiber laser due to high-power GaN laser diodes and low-loss optical fibers (0.1 dB/m) made by waterproof fluoride glasses. This new optical fiber glass is based on an AlF3 system fluoride glass, and its waterproof property is much better than the well known fluoride glass of ZBLAN. The configuration of primary visible fiber lasers promises highly efficient, cost-effective, and simple laser systems and will realize visible lasers with photon beam quality and quantity, such as high-power CW or tunable laser systems, compact ultraviolet lasers, and low-cost ultra-short pulse laser systems. We believe that primary visible fiber lasers, especially those excited by GaN laser diodes, will be effective tools for creating the next generation of research and light sources.

  10. GaN Nanowire Devices: Fabrication and Characterization

    NASA Astrophysics Data System (ADS)

    Scott, Reum

    The development of microelectronics in the last 25 years has been characterized by an exponential increase of the bit density in integrated circuits (ICs) with time. Scaling solid-state devices improves cost, performance, and power; as such, it is of particular interest for companies, who gain a market advantage with the latest technology. As a result, the microelectronics industry has driven transistor feature size scaling from 10 μm to ~30 nm during the past 40 years. This trend has persisted for 40 years due to optimization, new processing techniques, device structures, and materials. But when noting processor speeds from the 1970's to 2009 and then again in 2010, the implication would be that the trend has ceased. To address the challenge of shrinking the integrated circuit (IC), current research is centered on identifying new materials and devices that can supplement and/or potentially supplant it. Bottom-up methods tailor nanoscale building blocks---atoms, molecules, quantum dots, and nanowires (NWs)---to be used to overcome these limitations. The Group IIIA nitrides (InN, AlN, and GaN) possess appealing properties such as a direct band gap spanning the whole solar spectrum, high saturation velocity, and high breakdown electric field. As a result nanostructures and nanodevices made from GaN and related nitrides are suitable candidates for efficient nanoscale UV/ visible light emitters, detectors, and gas sensors. To produce devices with such small structures new fabrication methods must be implemented. Devices composed of GaN nanowires were fabricated using photolithography and electron beam lithography. The IV characteristics of these devices were noted under different illuminations and the current tripled from 4.8*10-7 A to 1.59*10 -6 A under UV light which persisted for at least 5hrs.

  11. Ion implantation processing of GaN epitaxial layers

    SciTech Connect

    Tan, H.H.; Williams, J.S.; Zou, J.; Cockayne, D.J.H.; Pearton, S.J.; Yuan, C.

    1996-12-31

    Ion implantation induced-damage build up in epitaxial GaN layers grown on sapphire has been analyzed by ion channeling and electron microscopy techniques. The epitaxial layers are extremely resistant to ion beam damage in that substantial dynamic annealing of implantation disorder occurs even at liquid nitrogen temperatures. Amorphous layers can be formed in some cases if the implantation dose is high enough. However, the damage (amorphous or complex extended defects) that is formed is also extremely difficult to remove during annealing and required temperatures in excess of 1,100 C.

  12. Memristive GaN ultrathin suspended membrane array.

    PubMed

    Dragoman, Mircea; Tiginyanu, Ion; Dragoman, Daniela; Braniste, Tudor; Ciobanu, Vladimir

    2016-07-22

    We show that ultrathin GaN membranes, with a thickness of 15 nm and planar dimensions of 12 × 184 μm(2), act as memristive devices. The memristive behavior is due to the migration of the negatively-charged deep traps, which form in the volume of the membrane during the fabrication process, towards the unoccupied surface states of the suspended membranes. The time constant of the migration process is of the order of tens of seconds and varies with the current or voltage sweep. PMID:27291970

  13. H enhancement of N vacancy migration in GaN.

    SciTech Connect

    Wixom, Ryan R.; Wright, Alan Francis

    2005-06-01

    We have used density functional theory to investigate diffusion of V{sub N}{sup +} in the presence of H{sup +}. Optimal migration pathways were determined using the climbing image nudged elastic band and directed dimer methods. Our calculations indicate that the rate-limiting barrier for VN{sub N}{sup +} migration will be reduced by 0.58 eV by interplay with H{sup +}, which will enhance migration by more than an order of magnitude at typical GaN growth temperatures.

  14. Memristive GaN ultrathin suspended membrane array

    NASA Astrophysics Data System (ADS)

    Dragoman, Mircea; Tiginyanu, Ion; Dragoman, Daniela; Braniste, Tudor; Ciobanu, Vladimir

    2016-07-01

    We show that ultrathin GaN membranes, with a thickness of 15 nm and planar dimensions of 12 × 184 μm2, act as memristive devices. The memristive behavior is due to the migration of the negatively-charged deep traps, which form in the volume of the membrane during the fabrication process, towards the unoccupied surface states of the suspended membranes. The time constant of the migration process is of the order of tens of seconds and varies with the current or voltage sweep.

  15. High field effects of GaN HEMTs.

    SciTech Connect

    Barker, Joy; Shul, Randy John

    2004-09-01

    This report represents the completion of a Laboratory-Directed Research and Development (LDRD) program to develop and fabricate geometric test structures for the measurement of transport properties in bulk GaN and AlGaN/GaN heterostructures. A large part of this study was spent examining fabrication issues related to the test structures used in these measurements, due to the fact that GaN processing is still in its infancy. One such issue had to do with surface passivation. Test samples without a surface passivation, often failed at electric fields below 50 kV/cm, due to surface breakdown. A silicon nitride passivation layer of approximately 200 nm was used to reduce the effects of surface states and premature surface breakdown. Another issue was finding quality contacts for the material, especially in the case of the AlGaN/GaN heterostructure samples. Poor contact performance in the heterostructures plagued the test structures with lower than expected velocities due to carrier injection from the contacts themselves. Using a titanium-rich ohmic contact reduced the contact resistance and stopped the carrier injection. The final test structures had an etch constriction with varying lengths and widths (8x2, 10x3, 12x3, 12x4, 15x5, and 16x4 {micro}m) and massive contacts. A pulsed voltage input and a four-point measurement in a 50 {Omega} environment was used to determine the current through and the voltage dropped across the constriction. From these measurements, the drift velocity as a function of the applied electric field was calculated and thus, the velocity-field characteristics in n-type bulk GaN and AlGaN/GaN test structures were determined. These measurements show an apparent saturation velocity near to 2.5x10{sup 7} cm/s at 180 kV/cm and 3.1x10{sup 7} cm/s, at a field of 140 kV/cm, for the bulk GaN and AlGaN heterostructure samples, respectively. These experimental drift velocities mark the highest velocities measured in these materials to date and confirm

  16. Radiation enhanced basal plane dislocation glide in GaN

    NASA Astrophysics Data System (ADS)

    Yakimov, Eugene B.; Vergeles, Pavel S.; Polyakov, Alexander Y.; Lee, In-Hwan; Pearton, Stephen J.

    2016-05-01

    A movement of basal plane segments of dislocations in GaN films grown by epitaxial lateral overgrowth under low energy electron beam irradiation (LEEBI) was studied by the electron beam induced current (EBIC) method. Only a small fraction of the basal plane dislocation segments were susceptible to irradiation and the movement was limited to relatively short distances. The effect is explained by the radiation enhanced dislocation glide (REDG) in the structure with strong pinning. A dislocation velocity under LEEBI with a beam current lower than 1 nA was estimated as about 10 nm/s. The results assuming the REDG for prismatic plane dislocations were presented.

  17. Shape dependent electronic properties of wurzite GaN nanowire

    NASA Astrophysics Data System (ADS)

    Srivastava, Pankaj; Kumar, Avaneesh; Jaiswal, Neeraj K.; Sharma, Varun

    2016-05-01

    In the present work, energetic stability and electronic behavior of triangular and square shaped wurzite GaN NW oriented along [1100] and [11 2 0] direction has been investigated by employing ab-initio DFT calculation. Structural analysis suggests that triangular shaped NW undergoes strong surface reconstruction compared to square shaped NW. However, binding energy reveals that square shaped NW is energetically more feasible than triangular NW. Further, from electronic band structure we observe that both structures are metallic with higher metallicity for triangular shaped NW.

  18. Stress related aspects of GaN technology physics

    NASA Astrophysics Data System (ADS)

    Suhir, Ephraim

    2015-03-01

    Simple, easy-to-use and physically meaningful analytical models have been developed for the assessment of the combined effect of the lattice and thermal mismatch on the induced stresses in an elongated bi-material assembly, as well as on the thermal mismatch on the thermal stresses in a tri-material assembly, in which the lattice mismatched stresses are eliminated in one way or another. This could be done, e.g., by using a polished or an etched substrate. The analysis is carried out in application to Gallium Nitride (GaN)-Silicon Carbide (SiC) and GaN-diamond (C) filmsubstrate assemblies. The calculated data are obtained, assuming that no annealing or other stress reduction means is applied. The data agree reasonably well with the reported (available) in-situ measurements. The most important conclusion from the computed data is that even if a reasonably good lattice match takes place (as, e.g., in the case of a GaN film fabricated on a SiC substrate, when the mismatch strain is only about 3%) and, in addition, the temperature change (from the fabrication/growth temperature to the operation temperature) is significant (as high as 1000 °C), the thermal stresses are still considerably lower than the lattice-mismatch stresses. Although there are structural and technological means for further reduction of the lattice-mismatch stresses (e.g., by high temperature annealing or by providing one or more buffering layers, or by using patterned or porous substrates), there is still a strong incentive to eliminate completely the lattice mismatch stresses. This seems to be indeed possible, if polished or otherwise flattened (e.g., chemically etched) substrates and sputter deposited GaN film is employed. In such a case only thermal stresses remain, but even these could be reduced, if necessary, by using compliant buffering layers, including layers of variable compliance, or by introducing variable compliance into the properly engineered substrate. In any event, it is expected

  19. Predicting the Unbeaten Path through Syntactic Priming

    ERIC Educational Resources Information Center

    Arai, Manabu; Nakamura, Chie; Mazuka, Reiko

    2015-01-01

    A number of previous studies showed that comprehenders make use of lexically based constraints such as subcategorization frequency in processing structurally ambiguous sentences. One piece of such evidence is lexically specific syntactic priming in comprehension; following the costly processing of a temporarily ambiguous sentence, comprehenders…

  20. Maple Explorations, Perfect Numbers, and Mersenne Primes

    ERIC Educational Resources Information Center

    Ghusayni, B.

    2005-01-01

    Some examples from different areas of mathematics are explored to give a working knowledge of the computer algebra system Maple. Perfect numbers and Mersenne primes, which have fascinated people for a very long time and continue to do so, are studied using Maple and some questions are posed that still await answers.

  1. Thematic Mathematics: The Combinatorics of Prime Factorizations

    ERIC Educational Resources Information Center

    Griffiths, Martin

    2010-01-01

    In this article, we use a particular example to illustrate a thematic approach to the teaching and learning of mathematics. Our theme, suitable for undergraduates and able sixth-form students, is the enumeration of mathematical objects associated with the prime factorizations of integers. It is shown in detail how this gives rise to some beautiful…

  2. Riemann equation for prime number diffusion.

    PubMed

    Chen, Wen; Liang, Yingjie

    2015-05-01

    This study makes the first attempt to propose the Riemann diffusion equation to describe in a manner of partial differential equation and interpret in physics of diffusion the classical Riemann method for prime number distribution. The analytical solution of this equation is the well-known Riemann representation. The diffusion coefficient is dependent on natural number, a kind of position-dependent diffusivity diffusion. We find that the diffusion coefficient of the Riemann diffusion equation is nearly a straight line having a slope 0.99734 in the double-logarithmic axis. Consequently, an approximate solution of the Riemann diffusion equation is obtained, which agrees well with the Riemann representation in predicting the prime number distribution. Moreover, we interpret the scale-free property of prime number distribution via a power law function with 1.0169 the scale-free exponent in respect to logarithmic transform of the natural number, and then the fractal characteristic of prime number distribution is disclosed. PMID:26026319

  3. Values in Prime Time Alcoholic Beverage Commercials.

    ERIC Educational Resources Information Center

    Frazer, Charles F.

    Content analysis was used to study the values evident in televised beer and wine commercials. Seventy-seven prime time commercials, 7.6% of a week's total, were analyzed along value dimensions adapted from Gallup's measure of popular social values. The intensity of each value was coded on a five-point scale. None of the commercials in the beer and…

  4. Attentional Control and Asymmetric Associative Priming

    ERIC Educational Resources Information Center

    Hutchison, Keith A.; Heap, Shelly J.; Neely, James H.; Thomas, Matthew A.

    2014-01-01

    Participants completed a battery of 3 attentional control (AC) tasks (OSPAN, antisaccade, and Stroop, as in Hutchison, 2007) and performed a lexical decision task with symmetrically associated (e.g., "sister-brother") and asymmetrically related primes and targets presented in both the forward (e.g., "atom-bomb") and backward…

  5. A Fresh Approach to Prime Numbers.

    ERIC Educational Resources Information Center

    Hampton, Homer F.

    1979-01-01

    The introduction of prime numbers in the intermediate grades should be handled with care or the concept will appear arbitrary, artificial, and unreal to the pupils. The approach suggested here is in the form of a game-like activity. A knowledge of multiplication and factors is a prerequisite. (BB)

  6. Emergence, Self-Organization and Prime Numbers

    NASA Astrophysics Data System (ADS)

    Berezin, Alexander A.

    1998-04-01

    Pattern of primes (PP) is critical for dynamics of universal emergence, self-organization and complexity ascendance [1-3]. Due to gradual logarithmic dilution of primes (prime number theorem), PP gives only base envelop for above effects. More informative are full factorizational spectra (FS) of all intermediate composites. Tower exponential mappings like f(N) = 10(N)10 with (N) indicating N vertical arrows [4] lead to infinite fractal-like hierarchy of integer trails; say, FS of intervals between f(N) and f(N+1). This allows FAPP-infinite informational content of PP and FS be "used" as catalyzer of emergence dynamics. This is "Platonic pressure effect" (physical embodiments of PP and FS). Said effect may provide more direct picture for cosmogenesis than traditional quantum tunneling ("Big Bang") and/or inflationary scenarios. Furthermore, we can speculate that metrics of (Mega)universe at tower exponential scales becomes asymptotically Euclidean (multi or infinitely dimensional), due to unchangability of PP and FS. - [1] Arnold Arnold, "The Corrupted Sciences", Paladin (Harper Collins), 1992; [2] Peter Plichta, "God's Secret Formula: Deciphering the Riddle of the Universe and the Prime Number Code", Element, 1997; [3] Alexander Berezin, URAM Journal, 20, 72 (1997); [4] Donald E. Knuth, Science, 194, 1235, 17 Dec 1976. abstract.

  7. Priming effects on the perceived grouping of ambiguous dot patterns.

    PubMed

    Kurylo, Daniel D; Bukhari, Farhan

    2015-09-01

    For ambiguous stimuli, complex dynamics guide processes of perceptual grouping. Previous studies have suggested two opposing effects on grouping that are produced by the preliminary stimulus state: one that enhances grouping towards the existing structure, and another that opposes this structure. To examine effects of the preliminary state on grouping directly, measurements were made of perceived grouping of dot patterns that followed a visual prime. Three stimuli were presented in sequence: prime, target, and mask. Targets were composed of an evenly spaced dot grid in which grouping was established by similarity in luminance. Subjects indicated the dominant perceived grouping. The prime either corresponded to or opposed the prevailing organization of the target. Contrary to the hypothesis, solid-line primes biased grouping away from the structure of the prime, even when the prevailing organization of dot patterns strongly favored the primes' structure. This effect occurred, although to a lesser extent, when primes did not occupy the same location of targets, but were presented in a marginal area surrounding the grid. Priming effects did not occur for primes constructed of dot patterns. Effects found here may be attributed to a forward masking effect by primes, which more effectively disrupts grouping of patterns matched to the prime. Effects may also be attributed to a type of pattern contrast, in which a grouped pattern dissimilar to primes gains salience. For the pattern contrast model, the partial activation of multiple grouped configurations is compared to the pattern of the solid-line primes. PMID:25281427

  8. Screening Active Components from Yu-Ping-Feng-San for Regulating Initiative Key Factors in Allergic Sensitization

    PubMed Central

    Zhu, Zhijie; Yu, Xi; Liu, Hailiang; Wang, Huizhu; Fan, Hongwei; Wang, Dawei; Jiang, Guorong; Hong, Min

    2014-01-01

    Yu-ping-feng-san (YPFS) is a Chinese medical formula that is used clinically for allergic diseases and characterized by reducing allergy relapse. Our previous studies demonstrated that YPFS efficiently inhibited T helper 2 cytokines in allergic inflammation. The underlying mechanisms of action of YPFS and its effective components remain unclear. In this study, it was shown that YPFS significantly inhibited production of thymic stromal lymphopoietin (TSLP), an epithelial cell-derived initiative factor in allergic inflammation, in vitro and in vivo. A method of human bronchial epithelial cell (16HBE) binding combined with HPLC-MS (named 16HBE-HPLC-MS) was established to explore potential active components of YPFS. The following five components bound to 16HBE cells: calycosin-7-glucoside, ononin, claycosin, sec-o-glucosylhamaudol and formononetin. Serum from YPFS-treated mice was analyzed and three major components were detected claycosin, formononetin and cimifugin. Among these, claycosin and formononetin were detected by 16HBE-HPLC-MS and in the serum of YPFS-treated mice. Claycosin and formononetin decreased the level of TSLP markedly at the initial stage of allergic inflammation in vivo. Nuclear factor (NF)-κB, a key transcription factor in TSLP production, was also inhibited by claycosin and formononetin, either in terms of transcriptional activation or its nuclear translocation in vitro. Allergic inflammation was reduced by claycosin and formononetin when they are administered only at the initial stage in a murine model of atopic contact dermatitis. Thus, epithelial cell binding combined with HPLC-MS is a valid method for screening active components from complex mixtures of Chinese medicine. It was demonstrated that the compounds screened from YPFS significantly attenuated allergic inflammation probably by reducing TSLP production via regulating NF-κB activation. PMID:25198676

  9. Evolution of the Li-Yu Lake at Eastern Taiwan: Evidences from Magnetic Proxies and Pollen Analysis

    NASA Astrophysics Data System (ADS)

    Lee, T.; Wang, L.; Chen, S.

    2008-12-01

    The Li-Yu Lake located at Hua-Lien County of eastern Taiwan seems to be originally a river and was trapped by a landslide to form a lake after. To investigate the truth, a lacustrine sediment core of about 8 meters was raised from the lake and magnetic proxies and pollen analysis were employed to analyze it. Based on the C- 14 dating, this core provides the information for the last 7000 years Magnetic proxies point out that the records could be clearly distinguished into two parts from the depth of about 2.6 meters : the deeper part dominates very coarse grained with higher oxidized magnetic minerals and vice versa at the shallower part. This boundary corresponds an ages of about 2300 yrB.P. Pollen analysis reveals that no pollen could be found at the depths below 2.8 meters; only aquatic plant pollens, such as Poaceae, Cyperaceae and Mynophyllum, were found at the depth between 2.8-2.5 meters; tree and shrub pollens began to appear at about 2.5 m in depth. These results proposed that sediments below 2.8 m (before 2400 yrBP) might be a river deposit; the river was blocked at its northern end to form a lake between 2300-2400 yrBP in consideration of the topography, and regular lake deposits occurred after 2300 yrBP. Furthermore, magnetic proxies were found to have a clear change during the age interval of about 900-600 yrBP. Pollen patterns also support this point. It is proposed that the river piracy might have happened at the southern area of the lake at this time. The literatures recording the human activity in this area seem to support this point of view.

  10. Rhizosphere priming effects in two contrasting soils

    NASA Astrophysics Data System (ADS)

    Lloyd, Davidson; Kirk, Guy; Ritz, Karl

    2015-04-01

    Inputs of fresh plant-derived carbon may stimulate the turnover of existing soil organic matter by so-called priming effects. Priming may occur directly, as a result of nutrient 'mining' by existing microbial communities, or indirectly via population adjustments. However the mechanisms are poorly understood. We planted C4 Kikuyu grass (Pennisetum clandestinum) in pots with two contrasting C3 soils (clayey, fertile TB and sandy, acid SH), and followed the soil CO2 efflux and its δ13C. The extent of C deposition in the rhizosphere was altered by intermittently clipping the grass in half the pots; there were also unplanted controls. At intervals, pots were destructively sampled for root and shoot biomass. Total soil CO2 efflux was measured using a gas-tight PVC chamber fitted over bare soil, and connected to an infra-red gas analyser; the δ13C of efflux was measured in air sub-samples withdrawn by syringe. The extent of priming was inferred from the δ13C of efflux and the δ13C of the plant and soil end-members. In unclipped treatments, in both soils, increased total soil respiration and rhizosphere priming effects (RPE) were apparent compared to the unplanted controls. The TB soil had greater RPE overall. The total respiration in clipped TB soil was significantly greater than in the unplanted controls, but in the clipped SH soil it was not significantly different from the controls. Clipping affected plant C partitioning with greater allocation to shoot regrowth from about 4 weeks after planting. Total plant biomass decreased in the order TB unclipped > SH unclipped >TB clipped > SH clipped. The results are consistent with priming driven by microbial activation stimulated by rhizodeposits and by nitrogen demand from the growing plants under N limited conditions. Our data suggest that photosynthesis drives RPE and soil differences may alter the rate and intensity of RPE but not the direction.

  11. Study on photoemission surface of varied doping GaN photocathode

    NASA Astrophysics Data System (ADS)

    Qiao, Jianliang; Du, Ruijuan; Ding, Huan; Gao, Youtang; Chang, Benkang

    2014-09-01

    For varied doping GaN photocathode, from bulk to surface the doping concentrations are distributed from high to low. The varied doping GaN photocathode may produce directional inside electric field within the material, so the higher quantum efficiency can be obtained. The photoemission surface of varied doping GaN photocathode is very important to the high quantum efficiency, but the forming process of the surface state after Cs activation or Cs/O activation has been not known completely. Encircling the photoemission mechanism of varied GaN photocathode, considering the experiment phenomena during the activation and the successful activation results, the varied GaN photocathode surface model [GaN(Mg):Cs]:O-Cs after activation with cesium and oxygen was given. According to GaN photocathode activation process and the change of electronic affinity, the comparatively ideal NEA property can be achieved by Cs or Cs/O activation, and higher quantum efficiency can be obtained. The results show: The effective NEA characteristic of GaN can be gotten only by Cs. [GaN(Mg):Cs] dipoles form the first dipole layer, the positive end is toward the vacuum side. In the activation processing with Cs/O, the second dipole layer is formed by O-Cs dipoles, A O-Cs dipole includes one oxygen atom and two Cs atoms, and the positive end is also toward the vacuum side thus the escape of electrons can be promoted.

  12. Fabrication of GaN nanotubular material using MOCVD with aluminum oxide membrane

    NASA Astrophysics Data System (ADS)

    Jung, Woo-Gwang; Jung, Se-Hyuck; Kung, Patrick; Razeghi, Manijeh

    2006-02-01

    GaN nanotubular material is fabricated with aluminum oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminum oxide membrane with ordered nano holes is used as template. Gallium nitride is deposited at the inner wall of the nano holes in aluminum oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis condition in MOCVD is obtained successfully for the gallium nitride nanotubular material in this research. The diameter of GaN nanotube fabricated is approximately 200 ~ 250 nm and the wall thickness is about 40 ~ 50 nm. GaN nanotubular material consists of numerous fine GaN particulates with sizes ranging 15 to 30 nm. The composition of gallium nitride is confirmed to be stoichiometrically 1:1 for Ga and N by EDS. XRD and TEM analyses indicate that grains in GaN nanotubular material have nano-crystalline structure. No blue shift is found in the PL spectrum on the GaN nanotubular material fabricated in aluminum oxide template.

  13. Fabrication of GaN nanotubular material using MOCVD with an aluminium oxide membrane

    NASA Astrophysics Data System (ADS)

    Jung, Woo-Gwang; Jung, Se-Hyuck; Kung, Patrick; Razeghi, Manijeh

    2006-01-01

    GaN nanotubular material is fabricated with an aluminium oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminium oxide membrane with ordered nanoholes is used as a template. Gallium nitride is deposited at the inner wall of the nanoholes in the aluminium oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis conditions in MOCVD are obtained successfully for the gallium nitride nanotubular material in this research. The diameter of the GaN nanotube fabricated is approximately 200-250 nm and the wall thickness is about 40-50 nm. GaN nanotubular material consists of numerous fine GaN particulates with size range 15-30 nm. The composition of gallium nitride is confirmed to be stoichiometrically 1:1 for Ga and N by EDS. XRD and TEM analyses indicate that the grains in GaN nanotubular material have a nano-crystalline structure. No blue shift is found in the PL spectrum on the GaN nanotubular material fabricated in an aluminium oxide template.

  14. Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

    NASA Astrophysics Data System (ADS)

    Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong; Zhao, Degang; Zhang, Baolin; Du, Guotong

    2016-01-01

    KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 × 1017 cm-3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

  15. Influence of surface scattering on the thermal properties of spatially confined GaN nanofilm

    NASA Astrophysics Data System (ADS)

    Hou, Yang; Zhu, Lin-Li

    2016-08-01

    Gallium nitride (GaN), the notable representative of third generation semiconductors, has been widely applied to optoelectronic and microelectronic devices due to its excellent physical and chemical properties. In this paper, we investigate the surface scattering effect on the thermal properties of GaN nanofilms. The contribution of surface scattering to phonon transport is involved in solving a Boltzmann transport equation (BTE). The confined phonon properties of GaN nanofilms are calculated based on the elastic model. The theoretical results show that the surface scattering effect can modify the cross-plane phonon thermal conductivity of GaN nanostructures completely, resulting in the significant change of size effect on the conductivity in GaN nanofilm. Compared with the quantum confinement effect, the surface scattering leads to the order-of-magnitude reduction of the cross-plane thermal conductivity in GaN nanofilm. This work could be helpful for controlling the thermal properties of GaN nanostructures in nanoelectronic devices through surface engineering. Project supported by the National Natural Science Foundation of China (Grant Nos. 11302189 and 11321202) and the Doctoral Fund of Ministry of Education of China (Grant No. 20130101120175).

  16. Growth of GaN nanowall network on Si (111) substrate by molecular beam epitaxy

    PubMed Central

    2012-01-01

    GaN nanowall network was epitaxially grown on Si (111) substrate by molecular beam epitaxy. GaN nanowalls overlap and interlace with one another, together with large numbers of holes, forming a continuous porous GaN nanowall network. The width of the GaN nanowall can be controlled, ranging from 30 to 200 nm by adjusting the N/Ga ratio. Characterization results of a transmission electron microscope and X-ray diffraction show that the GaN nanowall is well oriented along the C axis. Strong band edge emission centered at 363 nm is observed in the spectrum of room temperature photoluminescence, indicating that the GaN nanowall network is of high quality. The sheet resistance of the Si-doped GaN nanowall network along the lateral direction was 58 Ω/. The conductive porous nanowall network can be useful for integrated gas sensors due to the large surface area-to-volume ratio and electrical conductivity along the lateral direction by combining with Si micromachining. PMID:23270331

  17. Synthesis of GaN nanocrystallites by pulsed laser ablation in pure nitrogen background gases

    NASA Astrophysics Data System (ADS)

    Yoshida, Takehito; Kakumoto, Soichiro; Sugimura, Akira; Umezu, Ikurou

    2011-09-01

    GaN is a promising material not only for electronic devices but also for photocatalysts. Synthesis of GaN nanocrystal is a key issue to improve performance for these applications. In the present study, GaN nanocrystallites have been synthesized by pulsed laser ablation (PLA), where safe and inactive pure N2 gases were used as reactive background gases. The third harmonics beam of a Q-switched Nd:YAG laser (355 nm, 10 mJ/pulse, 4 J/(cm2 pulse)) was used to ablate a sintered high purity GaN target. The deposition substrates were not heated. It was clarified that the formed GaN nanoparticles contained a hexagonal system with the wurtzite structure. The diameter of the nanocrystallites was about 10 nm, and showed only little dependence on the background gas pressure, while the porosity of the assembly of nanocrystallites and content of GaN nanocrystallites in the assembly increased with background gas pressure. Highly porous nanometer-sized GaN film obtained at higher gas pressure is considered to be candidate structures for the photocatalysts.

  18. Fabrication of photonic crystal circuits based on GaN ultrathin membranes by maskless lithography

    NASA Astrophysics Data System (ADS)

    Volciuc, Olesea; Braniste, Tudor; Sergentu, Vladimir; Ursaki, Veaceslav; Tiginyanu, Ion M.; Gutowski, Jürgen

    2015-06-01

    We report on maskless fabrication of photonic crystal (PhC) circuits based on ultrathin (d ~ 15 nm) nanoperforated GaN membranes exhibiting a triangular lattice arrangement of holes with diameters of 150 nm. In recent years, we have proposed and developed a cost-effective technology for GaN micro- and nanostructuring, the so-called surface charge lithography (SCL), which opened wide possibilities for a controlled fabrication of GaN ultrathin membranes. SCL is a maskless approach based on direct writing of negative charges on the surface of a semiconductor by a focused ion beam (FIB). These charges shield the material against photo-electrochemical (PEC) etching. Ultrathin GaN membranes suspended on specially designed GaN microstructures have been fabricated using a technological route based on SCL with two selected doses of ion beam treatment. Calculation of the dispersion law in nanoperforated membranes in the approximation of scalar waves is indicative of the occurrence of surface and bulk modes, and there is a range of frequencies where only surface modes can exist. Advantages of the occurrence of two types of modes in ultrathin nanoperforated GaN membranes from the point of view of their incorporation in photonic and optoelectronic integrated circuits are discussed. Along with this, we present the results of a comparative analysis of persistent photoconductivity (PPC) and optical quenching (OQ) effects occurring in continuous and nanoperforated ultrathin GaN suspended membranes, and assess the mechanisms behind these phenomena.

  19. Assessment of GaN chips for culturing cerebellar granule neurons.

    PubMed

    Young, Tai-Horng; Chen, Chi-Ruei

    2006-06-01

    In this work, the behaviors of cerebellar granule neurons prepared from 7-day-old Wistar rats on gallium nitride (GaN) were investigated. We believe that this is the first time that the GaN has been used as a substrate for neuron cultures to examine its effect on cell response in vitro. The GaN surface structure and its relationship with cells were examined by atomic force microscopy (AFM), metallography microscopy, scanning electron microscopy (SEM), lactate dehydrogenase (LDH) release and Western blot analysis. GaN is a so-called III-V compound semiconductor material with a wide bandgap and a relatively high bandgap voltage. Compared with silicon used for most neural chips, neurons seeded on GaN were able to form an extensive neuritic network and expressed very high levels of GAP-43 coincident with the neurite outgrowth. Therefore, the GaN structure may spatially mediate cellular response that can promote neuronal cell attachment, differentiation and neuritic growth. The favorable biocompatibility characteristics of GaN can be used to measure electric signals from networks of neuronal cells in culture to make it a possible candidate for use in a microelectrode array. PMID:16516287

  20. Priming effects on cooperative behavior in social dilemmas: considering the prime and the person.

    PubMed

    Prentice, Mike; Sheldon, Kennon M

    2015-01-01

    ABSTRACT. We test whether people with a relatively more intrinsic vs. extrinsic value orientation (RIEVO) are particularly likely to enact cooperative behavior in resource dilemmas when they are primed with relatedness goals. In Study 1, high RIEVO participants primed with relatedness exhibited more restrained fishing behavior in a resource dilemma than their unprimed counterparts or participants low in RIEVO. Study 2 replicated this effect and further showed that the prime must signal the possibility of satisfying a valued goal (relatedness satisfaction) in order to elicit the value-consistent behavior. We discuss these results in the context of recent process models of goal priming, and also discuss how these findings contribute to our understanding of cooperative behavior and the predictive power of value constructs more broadly. PMID:25329359

  1. Surface chemistry and electronic structure of nonpolar and polar GaN films

    NASA Astrophysics Data System (ADS)

    Mishra, Monu; Krishna, T. C. Shibin; Aggarwal, Neha; Gupta, Govind

    2015-08-01

    Photoemission and microscopic analysis of nonpolar (a-GaN/r-Sapphire) and polar (c-GaN/c-Sapphire) epitaxial gallium nitride (GaN) films grown via RF-Molecular Beam Epitaxy is reported. The effect of polarization on surface properties like surface states, electronic structure, chemical bonding and morphology has been investigated and correlated. It was observed that polarization lead to shifts in core level (CL) as well as valence band (VB) spectra. Angle dependent X-ray Photoelectron Spectroscopic analysis revealed higher surface oxide in polar GaN film compared to nonpolar GaN film. On varying the take off angle (TOA) from 0° to 60°, the Gasbnd O/Gasbnd N ratio varied from 0.11-0.23 for nonpolar and 0.17-0.36 for polar GaN film. The nonpolar film exhibited N-face polarity while Ga-face polarity was perceived in polar GaN film due to the inherent polarization effect. Polarization charge compensated surface states were observed on the polar GaN film and resulted in downward band bending. Ultraviolet photoelectron spectroscopic measurements revealed electron affinity and ionization energy of 3.4 ± 0.1 eV and 6.8 ± 0.1 eV for nonpolar GaN film and 3.8 ± 0.1 eV and 7.2 ± 0.1 eV for polar GaN film respectively. Field Emission Scanning Electron Microscopy measurements divulged smooth morphology with pits on polar GaN film. The nonpolar film on the other hand showed pyramidal structures having facets all over the surface.

  2. Annealing effects on polycrystalline GaN using nitrogen and ammonia ambients

    NASA Astrophysics Data System (ADS)

    Ariff, A.; Zainal, N.; Hassan, Z.

    2016-09-01

    This paper describes effects of using post-annealing treatment in different conditions on the properties of polycrystalline GaN layer grown on m-plane sapphire substrate by electron beam (e-beam) evaporator. Without annealing, GaN surface was found to have a low RMS roughness with agglomeration of GaN grains in a specific direction and the sample consisted of gallium oxide (Ga2O3) material. When the post-annealing treatment was carried out in N2 ambient at 650 °C, initial re-crystallization of the GaN grains was observed while the evidence of Ga2O3 almost disappeared. As the NH3 annealing was conducted at 950 °C, more effect of re-crystallization occurred but with less grains coalescence. Three dominant XRD peaks of GaN in (10 1 bar 0) , (0002) and (10 1 bar 1) orientations were evident. Near band edge (NBE) related emission in GaN was also observed. The significant improvement was attributed to simultaneous recrystallization and effective reduction of N deficiency density. The post-annealing in a mixture of N2 and NH3 ambient at 950 °C was also conducted, but has limited the effectiveness of the N atoms to incorporate on the GaN layer due to 'clouding' effect by the inert N2 gas. Further increase in the annealing temperature at 980 °C and 1100 °C, respectively caused severe deteriorations of the structural and optical properties of the GaN layer. Overall, this work demonstrated initial potential in improving polycrystalline GaN material in simple and inexpensive manner.

  3. Repetition priming of nonwords in young and older adults.

    PubMed

    Light, L L; La Voie, D; Kennison, R

    1995-03-01

    In 3 experiments, a pronunciation task was used to examine repetition priming of novel nonwords in young and older adults. The contributions of item and associative priming to the total repetition priming effect were assessed. In Experiment 1, age consistency was found in both components of repetition priming after 9 repetitions of nonwords. Experiment 2 established that young and older adults were similar in item and associative priming after as few as 2 repetitions of nonwords. Finally, Experiment 3 demonstrated that associative priming persists for at least 3 min and that it is dissociable from cued recall. The overall pattern of results strongly argues that elaborative processing is not necessary to obtain associative priming in indirect memory tasks and that young and older adults show similar magnitudes of associative priming. PMID:7738504

  4. Odd perfect numbers have at least nine distinct prime factors

    NASA Astrophysics Data System (ADS)

    Nielsen, Pace P.

    2007-12-01

    An odd perfect number, N , is shown to have at least nine distinct prime factors. If 3nmid N then N must have at least twelve distinct prime divisors. The proof ultimately avoids previous computational results for odd perfect numbers.

  5. Prime time news: the influence of primed positive and negative emotion on susceptibility to false memories.

    PubMed

    Porter, Stephen; ten Brinke, Leanne; Riley, Sean N; Baker, Alysha

    2014-01-01

    We examined the relation between emotion and susceptibility to misinformation using a novel paradigm, the ambiguous stimuli affective priming (ASAP) paradigm. Participants (N = 88) viewed ambiguous neutral images primed either at encoding or retrieval to be interpreted as either highly positive or negative (or neutral/not primed). After viewing the images, they either were asked misleading or non-leading questions. Following a delay, memory accuracy for the original images was assessed. Results indicated that any emotional priming at encoding led to a higher susceptibility to misinformation relative to priming at recall. In particular, inducing a negative interpretation of the image at encoding led to an increased susceptibility of false memories for major misinformation (an entire object not actually present in the scene). In contrast, this pattern was reversed when priming was used at recall; a negative reinterpretation of the image decreased memory distortion relative to unprimed images. These findings suggest that, with precise experimental control, the experience of emotion at event encoding, in particular, is implicated in false memory susceptibility. PMID:24552271

  6. Highly c-axis oriented growth of GaN film on sapphire (0001) by laser molecular beam epitaxy using HVPE grown GaN bulk target

    SciTech Connect

    Kushvaha, S. S.; Kumar, M. Senthil; Maurya, K. K.; Dalai, M. K.; Sharma, Nita D.

    2013-09-15

    Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001) substrates by laser molecular beam epitaxy (LMBE) were investigated in the range of 500–750 °C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). The x-ray rocking curve full width at a half maximum (FWHM) value for (0002) reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 °C to 600 °C and the value further decreased with increase of growth temperature up to 720 °C. A highly c-axis oriented GaN epitaxial film was obtained at 720 °C with a (0002) plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 °C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 °C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE.

  7. Size dependence of melting of GaN nanowires with triangular cross sections

    SciTech Connect

    Wang, Zhiguo; Zu, Xiaotao; Gao, Fei; Weber, William J.

    2007-02-15

    Molecular dynamics simulations have been used to study the melting of GaN nanowires with triangular cross-sections. The curve of the potential energy, along with the atomic configuration is used to monitor the phase transition. The thermal stability of GaN nanowires is dependent on the size of the nanowires. The melting temperature of the GaN nanowires increases with the increasing of area cross-section of the nanowires to a saturation value. An interesting result is that of the nanowires start to melt from the edges, then the surface, and extends to the inner regions of nanowires as temperature increases.

  8. Stress and Defect Control in GaN Using Low Temperature Interlayers

    SciTech Connect

    Akasaki, I.; Amano, H.; Chason, E.; Figiel, J.; Floro, J.A.; Han, J.; Hearne, S.; Iwaya, M.; Kashima, T.; Katsuragcawa, M.

    1998-12-04

    In organometallic vapor phase epitaxial growth of Gail on sapphire, the role of the low- temperature-deposited interlayers inserted between high-temperature-grown GaN layers was investigated by in situ stress measurement, X-ray diffraction, and transmission electron microscopy. Insertion of a series of low temperature GaN interlayers reduces the density of threading dislocations while simultaneously increasing the tensile stress during growth, ultimately resulting in cracking of the GaN film. Low temperature AIN interlayers were found to be effective in suppressing cracking by reducing tensile stress. The intedayer approach permits tailoring of the film stress to optimize film structure and properties.

  9. Some effects of oxygen impurities on AlN and GaN

    NASA Astrophysics Data System (ADS)

    Slack, Glen A.; Schowalter, Leo J.; Morelli, Donald; Freitas, Jaime A.

    2002-12-01

    Oxygen is a common substitutional impurity in both AlN and GaN crystals. In the wurtzite 2H phase it can be present in AlN up to concentrations of 1×10 21/cm 3 while in GaN it can reach concentrations of 3×10 22/cm 3. These high concentrations of oxygen affect the luminescence, the optical absorption, the thermal conductivity, and the crystal perfection. The effects are somewhat similar in AlN and GaN. Representative experimental data will be presented to demonstrate the similarities, and to show how the oxygen content may be estimated from these property measurements.

  10. Density Functional Theory for Green Chemical Catalyst Supported on S-Terminated GaN(0001)

    NASA Astrophysics Data System (ADS)

    Yokoyama, Mami; Tsukamoto, Shiro; Ishii, Akira

    2011-12-01

    A novel function of nitried-based semiconductor is successfully developed for organic synthesis, in which palladium supported on the surface of S-terminated GaN(0001) serves as a unique green chemical catalyst. In this study we determined the structure of Pd-catalyst supported on S-terminated GaN(0001) surface by means of the density functional theory (DFT) within a Local Density Approximation (LDA). The important role of S on the case of GaN substrate is to make the number of the valence electron to be close to 0, it happened same way for GaAs substrate.

  11. Ion implantation doping and isolation of GaN

    SciTech Connect

    Pearton, S.J.; Vartuli, C.B.; Zolper, J.C.; Yuan, C.; Stall, R.A.

    1995-09-04

    {ital N}- and {ital p}-type regions have been produced in GaN using Si{sup +} and Mg{sup +}/P{sup +} implantation, respectively, and subsequent annealing at {similar_to}1100 {degree}C. Carrier activation percentages of 93% for Si and 62% for Mg were obtained for implant doses of 5{times}10{sup 14} cm{sup {minus}2} of each element. Conversely, highly resistive regions ({gt}5{times}10{sup 9} {Omega}/{D`Alembertian}) can be produced in initially {ital n}- or {ital p}- type GaN by N{sup +} implantation and subsequent annealing at {similar_to}750 {degree}C. The activation energy of the deep states controlling the resistivity of these implant-isolated materials is in the range 0.8--0.9 eV. These process modules are applicable to the fabrication of a variety of different GaN-based electronic and photonic devices. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  12. Dielectrics for GaN based MIS-diodes

    SciTech Connect

    Ren, F.; Abernathy, C.R.; MacKenzie, J.D.

    1998-02-01

    GaN MIS diodes were demonstrated utilizing AlN and Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) as insulators. A 345 {angstrom} of AlN was grown on the MOCVD grown n-GaN in a MOMBE system using trimethylamine alane as Al precursor and nitrogen generated from a wavemat ECR N2 plasma. For the Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) growth, a multi MBE chamber was used and a 195 {angstrom} oxide is E-beam evaporated from a single crystal source of Ga{sub 5}Gd{sub 3}O{sub 12}. The forward breakdown voltage of AlN and Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) diodes are 5V and 6V, respectively, which are significantly improved from {approximately} 1.2 V of schottky contact. From the C-V measurements, both kinds of diodes showed good charge modulation from accumulation to depletion at different frequencies. The insulator GaN interface roughness and the thickness of the insulator were measured with x-ray reflectivity.

  13. High Quality, Low Cost Ammonothermal Bulk GaN Substrates

    SciTech Connect

    Ehrentraut, D; Pakalapati, RT; Kamber, DS; Jiang, WK; Pocius, DW; Downey, BC; McLaurin, M; D'Evelyn, MP

    2013-12-18

    Ammonothermal GaN growth using a novel apparatus has been performed on c-plane, m-plane, and semipolar seed crystals with diameters between 5 mm and 2 in. to thicknesses of 0.5-3 mm. The highest growth rates are greater than 40 mu m/h and rates in the 10-30 mu m/h range are routinely observed for all orientations. These values are 5-100x larger than those achieved by conventional ammonothermal GaN growth. The crystals have been characterized by X-ray diffraction rocking-curve (XRC) analysis, optical and scanning electron microscopy (SEM), cathodoluminescence (CL), optical spectroscopy, and capacitance-voltage measurements. The crystallinity of the grown crystals is similar to or better than that of the seed crystals, with FWHM values of about 20-100 arcsec and dislocation densities of 1 x 10(5)-5 x 10(6) cm(-2). Dislocation densities below 10(4) cm(-2) are observed in laterally-grown crystals. Epitaxial InGaN quantum well structures have been successfully grown on ammonothermal wafers. (C) 2013 The Japan Society of Applied Physics

  14. Orthodox etching of HVPE-grown GaN

    SciTech Connect

    Weyher, J.L.; Lazar, S.; Macht, L.; Liliental-Weber, Z.; Molnar,R.J.; Muller, S.; Nowak, G.; Grzegory, I.

    2006-08-10

    Orthodox etching of HVPE-grown GaN in molten eutectic of KOH + NaOH (E etch) and in hot sulfuric and phosphoric acids (HH etch) is discussed in detail. Three size grades of pits are formed by the preferential E etching at the outcrops of threading dislocations on the Ga-polar surface of GaN. Using transmission electron microscopy (TEM) as the calibration tool it is shown that the largest pits are formed on screw, intermediate on mixed and the smallest on edge dislocations. This sequence of size does not follow the sequence of the Burgers values (and thus the magnitude of the elastic energy) of corresponding dislocations. This discrepancy is explained taking into account the effect of decoration of dislocations, the degree of which is expected to be different depending on the lattice deformation around the dislocations, i.e. on the edge component of the Burgers vector. It is argued that the large scatter of optimal etching temperatures required for revealing all three types of dislocations in HVPE-grown samples from different sources also depends upon the energetic status of dislocations. The role of kinetics for reliability of etching in both etches is discussed and the way of optimization of the etching parameters is shown.

  15. X-ray detectors based on GaN

    NASA Astrophysics Data System (ADS)

    Duboz, J. Y.; Frayssinet, E.; Chenot, Sebastien; Reverchon, J. L.; Idir, M.

    2013-03-01

    The potential of GaN for X-ray detection in the range from 5 to 40 keV has been assessed. The absorption coefficient has been measured as a fonction of photon energy. Various detectors have been fabricated including MSM and Schottky diodes. They were tested under polychromatic X-ray illumination and under monochromatic irradiation from 6 to 22 keV in the Soleil synchrotron facility. The vertical Schottky diodes perform better as their geometry is better suited to the thick layers required by the low absorption coefficient. The operation mode is discussed in terms of photoconductive and photovoltaic behaviors. Some parasitic effects related to the electrical activation of defects by high energy photons and to the tunnel effect in lightly doped Schottky diodes have been evidenced. These effects disappear in diodes where the doping profile has been optimized. The spectral response is found to be very consistent with the spectral absorption coefficient. The sensitivity of GaN Schottky diodes is evaluated and found to be on the order of 40 photons per second. The response is fast nd linear.

  16. GaN and ZnO Light Emitters

    NASA Astrophysics Data System (ADS)

    Ha, J.-S.

    In the recent several decades, there are huge concerns in solid-state light emitters based on semiconductor compound materials, which emit light of ultraviolet to red light. Light-emitting diode (LED) fabrication technology for this application is now relatively mature. Currently, the lifetime of blue or green light-emitter are apparently determined mostly by light-induced degradation of a packaging unit encapsulating the LED. New renaissance is taking place in research societies and industries of LEDs because of the straight possibilities and needs for LED-based solid-state lighting in human life instead of the conventional ones employing incandescent, halogen, fluorescent lightings etc. Among various semiconductor compounds applicable to LEDs, GaN and ZnO are regarded as promising materials for solid-state lighting because ultraviolet- or blue-light emitters, which are applicable to white-light LEDs, based on these materials are possible. In this chapter, current technologies and researches on GaN- and ZnO-based LEDs are described. A special emphasis is given to the efficiency of the LEDs in the review of the GaN-based LEDs, while current status technologies in LED applications of ZnO-based materials have been reviewed.

  17. Si Donor Incorporation in GaN Nanowires.

    PubMed

    Fang, Zhihua; Robin, Eric; Rozas-Jiménez, Elena; Cros, Ana; Donatini, Fabrice; Mollard, Nicolas; Pernot, Julien; Daudin, Bruno

    2015-10-14

    With increasing interest in GaN based devices, the control and evaluation of doping are becoming more and more important. We have studied the structural and electrical properties of a series of Si-doped GaN nanowires (NWs) grown by molecular beam epitaxy (MBE) with a typical dimension of 2-3 μm in length and 20-200 nm in radius. In particular, high resolution energy dispersive X-ray spectroscopy (EDX) has illustrated a higher Si incorporation in NWs than that in two-dimensional (2D) layers and Si segregation at the edge of the NW with the highest doping. Moreover, direct transport measurements on single NWs have shown a controlled doping with resistivity from 10(2) to 10(-3) Ω·cm, and a carrier concentration from 10(17) to 10(20) cm(-3). Field effect transistor (FET) measurements combined with finite element simulation by NextNano(3) software have put in evidence the high mobility of carriers in the nonintentionally doped (NID) NWs. PMID:26426262

  18. Integrative Priming Occurs Rapidly and Uncontrollably during Lexical Processing

    ERIC Educational Resources Information Center

    Estes, Zachary; Jones, Lara L.

    2009-01-01

    Lexical priming, whereby a prime word facilitates recognition of a related target word (e.g., "nurse" [right arrrow] "doctor"), is typically attributed to association strength, semantic similarity, or compound familiarity. Here, the authors demonstrate a novel type of lexical priming that occurs among unassociated, dissimilar, and unfamiliar…

  19. Do Stimulus-Action Associations Contribute to Repetition Priming?

    ERIC Educational Resources Information Center

    Dennis, Ian; Perfect, Timothy J.

    2013-01-01

    Despite evidence that response learning makes a major contribution to repetition priming, the involvement of response representations at the level of motor actions remains uncertain. Levels of response representation were investigated in 4 experiments that used different tasks at priming and test. Priming for stimuli that required congruent…

  20. The Role of Polysemy in Masked Semantic and Translation Priming

    ERIC Educational Resources Information Center

    Finkbeiner, Matthew; Forster, Kenneth; Nicol, Janet; Nakamura, Kumiko

    2004-01-01

    A well-known asymmetry exists in the bilingual masked priming literature in which lexical decision is used: namely, masked primes in the dominant language (L1) facilitate decision times on targets in the less dominant language (L2), but not vice versa. In semantic categorization, on the other hand, priming is symmetrical. In Experiments 1-3 we…

  1. Cognitive Conflict and Inhibition in Primed Dichotic Listening

    ERIC Educational Resources Information Center

    Saetrevik, Bjorn; Specht, Karsten

    2009-01-01

    In previous behavioral studies, a prime syllable was presented just prior to a dichotic syllable pair, with instructions to ignore the prime and report one syllable from the dichotic pair. When the prime matched one of the syllables in the dichotic pair, response selection was biased towards selecting the unprimed target. The suggested mechanism…

  2. A Statistical Argument for the Weak Twin Primes Conjecture

    ERIC Educational Resources Information Center

    Bruckman, P. S.

    2006-01-01

    Certain definitions introduce appropriate concepts, among which are the definitions of the counting functions of the primes and twin primes, along with definitions of the correlation coefficient in a bivariate sample space. It is argued conjecturally that the characteristic functions of the prime "p" and of the quantity "p"+2 are highly…

  3. Identifiable Orthographically Similar Word Primes Interfere in Visual Word Identification

    ERIC Educational Resources Information Center

    Burt, Jennifer S.

    2009-01-01

    University students participated in five experiments concerning the effects of unmasked, orthographically similar, primes on visual word recognition in the lexical decision task (LDT) and naming tasks. The modal prime-target stimulus onset asynchrony (SOA) was 350 ms. When primes were words that were orthographic neighbors of the targets, and…

  4. Persistent Structural Priming from Language Comprehension to Language Production

    ERIC Educational Resources Information Center

    Bock, Kathryn; Dell, Gary S.; Chang, Franklin; Onishi, Kristine H.

    2007-01-01

    To examine the relationship between syntactic processes in language comprehension and language production, we compared structural persistence from sentence primes that speakers heard to persistence from primes that speakers produced. [Bock, J. K., & Griffin, Z. M. (2000). The persistence of structural priming: transient activation or implicit…

  5. 48 CFR 45.501 - Prime contractor alternate locations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Prime contractor alternate... CONTRACT MANAGEMENT GOVERNMENT PROPERTY Support Government Property Administration 45.501 Prime contractor alternate locations. The property administrator assigned to the prime contract may request support...

  6. Does "Darkness" Lead to "Happiness"? Masked Suffix Priming Effects

    ERIC Educational Resources Information Center

    Dunabeitia, Jon Andoni; Perea, Manuel; Carreiras, Manuel

    2008-01-01

    Masked affix priming effects have usually been obtained for words sharing the initial affix (e.g., "reaction"-"REFORM"). However, prior evidence on masked suffix priming effects (e.g., "baker"-"WALKER") is inconclusive. In the present series of masked priming lexical decision experiments, a target word was briefly preceded by a morphologically or…

  7. Prospective and Retrospective Processing in Associative Mediated Priming

    ERIC Educational Resources Information Center

    Jones, Lara L.

    2012-01-01

    Mediated priming refers to the faster word recognition of a target (e.g., milk) following presentation of a prime (e.g., pasture) that is related indirectly via a connecting "mediator" (e.g., cow). Association strength may be an important factor in whether mediated priming occurs prospectively (with target activation prior to its presentation) or…

  8. 7 CFR 29.1166 - Primings (P Group).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    .... Grades, Grade Names, Minimum Specifications, and Tolerances P2L—Fine Quality Lemon Primings Prematurely... tolerance 25 percent, of which not over 10 percent may be waste. P3L—Good Quality Lemon Primings Prematurely... tolerance 40 percent, of which not over 20 percent may be waste. P4L—Fair Quality Lemon Primings...

  9. 7 CFR 29.1166 - Primings (P Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    .... Grades, Grade Names, Minimum Specifications, and Tolerances P2L—Fine Quality Lemon Primings Prematurely... tolerance 25 percent, of which not over 10 percent may be waste. P3L—Good Quality Lemon Primings Prematurely... tolerance 40 percent, of which not over 20 percent may be waste. P4L—Fair Quality Lemon Primings...

  10. 7 CFR 29.1166 - Primings (P Group).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    .... Grades, Grade Names, Minimum Specifications, and Tolerances P2L—Fine Quality Lemon Primings Prematurely... tolerance 25 percent, of which not over 10 percent may be waste. P3L—Good Quality Lemon Primings Prematurely... tolerance 40 percent, of which not over 20 percent may be waste. P4L—Fair Quality Lemon Primings...

  11. 7 CFR 29.1166 - Primings (P Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    .... Grades, Grade Names, Minimum Specifications, and Tolerances P2L—Fine Quality Lemon Primings Prematurely... tolerance 25 percent, of which not over 10 percent may be waste. P3L—Good Quality Lemon Primings Prematurely... tolerance 40 percent, of which not over 20 percent may be waste. P4L—Fair Quality Lemon Primings...

  12. 7 CFR 29.1166 - Primings (P Group).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    .... Grades, Grade Names, Minimum Specifications, and Tolerances P2L—Fine Quality Lemon Primings Prematurely... tolerance 25 percent, of which not over 10 percent may be waste. P3L—Good Quality Lemon Primings Prematurely... tolerance 40 percent, of which not over 20 percent may be waste. P4L—Fair Quality Lemon Primings...

  13. Structural Priming and Frequency Effects Interact in Chinese Sentence Comprehension.

    PubMed

    Wei, Hang; Dong, Yanping; Boland, Julie E; Yuan, Fang

    2016-01-01

    Previous research in several European languages has shown that the language processing system is sensitive to both structural frequency and structural priming effects. However, it is currently not clear whether these two types of effects interact during online sentence comprehension, especially for languages that do not have morphological markings. To explore this issue, the present study investigated the possible interplay between structural priming and frequency effects for sentences containing the Chinese ambiguous construction V NP1 de NP2 in a self-paced reading experiment. The sentences were disambiguated to either the more frequent/preferred NP structure or the less frequent VP structure. Each target sentence was preceded by a prime sentence of three possible types: NP primes, VP primes, and neutral primes. When the ambiguous construction V NP1 de NP2 was disambiguated to the dispreferred VP structure, participants experienced more processing difficulty following an NP prime relative to following a VP prime or a neutral baseline. When the ambiguity was resolved to the preferred NP structure, prime type had no effect. These results suggest that structural priming in comprehension is modulated by the baseline frequency of alternative structures, with the less frequent structure being more subject to structural priming effects. These results are discussed in the context of the error-based, implicit learning account of structural priming. PMID:26869954

  14. Transposed-Letter Priming of Prelexical Orthographic Representations

    ERIC Educational Resources Information Center

    Kinoshita, Sachiko; Norris, Dennis

    2009-01-01

    A prime generated by transposing two internal letters (e.g., jugde) produces strong priming of the original word (judge). In lexical decision, this transposed-letter (TL) priming effect is generally weak or absent for nonword targets; thus, it is unclear whether the origin of this effect is lexical or prelexical. The authors describe the Bayesian…

  15. Attentional Control and the Relatedness Proportion Effect in Semantic Priming

    ERIC Educational Resources Information Center

    Hutchison, Keith A.

    2007-01-01

    In 2 experiments, participants completed both an attentional control battery (OSPAN, antisaccade, and Stroop tasks) and a modified semantic priming task. The priming task measured relatedness proportion (RP) effects within subjects, with the color of the prime indicating the probability that the to-be-named target would be related. In Experiment…

  16. Structural Priming and Frequency Effects Interact in Chinese Sentence Comprehension

    PubMed Central

    Wei, Hang; Dong, Yanping; Boland, Julie E.; Yuan, Fang

    2016-01-01

    Previous research in several European languages has shown that the language processing system is sensitive to both structural frequency and structural priming effects. However, it is currently not clear whether these two types of effects interact during online sentence comprehension, especially for languages that do not have morphological markings. To explore this issue, the present study investigated the possible interplay between structural priming and frequency effects for sentences containing the Chinese ambiguous construction V NP1 de NP2 in a self-paced reading experiment. The sentences were disambiguated to either the more frequent/preferred NP structure or the less frequent VP structure. Each target sentence was preceded by a prime sentence of three possible types: NP primes, VP primes, and neutral primes. When the ambiguous construction V NP1 de NP2 was disambiguated to the dispreferred VP structure, participants experienced more processing difficulty following an NP prime relative to following a VP prime or a neutral baseline. When the ambiguity was resolved to the preferred NP structure, prime type had no effect. These results suggest that structural priming in comprehension is modulated by the baseline frequency of alternative structures, with the less frequent structure being more subject to structural priming effects. These results are discussed in the context of the error-based, implicit learning account of structural priming. PMID:26869954

  17. Novel Word Lexicalization and the Prime Lexicality Effect

    ERIC Educational Resources Information Center

    Qiao, Xiaomei; Forster, Kenneth I.

    2013-01-01

    This study investigates how newly learned words are integrated into the first-language lexicon using masked priming. Two lexical decision experiments are reported, with the aim of establishing whether newly learned words behave like real words in a masked form priming experiment. If they do, they should show a prime lexicality effect (PLE), in…

  18. Masked Translation Priming with Semantic Categorization: Testing the Sense Model

    ERIC Educational Resources Information Center

    Wang, Xin; Forster, Kenneth I.

    2010-01-01

    Four experiments are reported which were designed to test hypotheses concerning the asymmetry of masked translation priming. Experiment 1 confirmed the presence of L2-L1 priming with a semantic categorization task and demonstrated that this effect was restricted to exemplars. Experiment 2 showed that the translation priming effect was not due to…

  19. Subchronic toxicity of 2,2{prime},3,3{prime},4,4{prime}-hexachlorobiphenyl in rats

    SciTech Connect

    Lecavalier, P.; Chu, I.; Feeley, M.

    1997-06-27

    The subchronic toxicity of 2,2{prime},3,3{prime},4,4{prime}-hexachlorobiphenyl (PCB 128) was investigated in rats following dietary exposure at 0, 0.05, 0.5, 5, or 50 ppm for 13 wk. The growth rate was not affected by treatment and no apparent clinical signs of toxicity were observed. There was a significant increase in liver weight in the 50 ppm females. The liver ethoxy-resorufin deethylase (EROD) activity was increased by five- and fourfold in the highest dose males and females, respectively, while aminopyrine demethylase (ADPM) activity was significantly increased only in the highest dose females. Liver vitamin A was significantly reduced in the highest dose females. No other biochemical or hematological effects were observed. Treatment-related histopathological changes were seen in the thyroid and liver, and to a lesser extent in the bone marrow and thymus. Residue data showed a dose-dependent accumulation of PCB 128 in the following tissues: fat, liver, kidney, brain, spleen, and serum, with the highest concentration being found in fat followed by liver and kidney. Based on these data, the no-observable-adverse-effect level of PCB 128 was judged to be 0.5 ppm in diet or 42 {mu}g/kg body weight. 29 refs., 1 fig., 5 tabs.

  20. Microstructural properties and dislocation evolution on a GaN grown on patterned sapphire substrate: A transmission electron microscopy study

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Ruh, H.; Noh, Y. K.; Kim, M. D.; Oh, J. E.

    2010-03-01

    The microstructural properties of a GaN layer grown on a patterned sapphire substrate (PSS) were studied in detail using transmission electron microscope techniques to determine dislocation and growth behaviors. Regular and uniform recrystallized GaN islands were observed on the protruding pattern. On a flat sapphire surface, the crystallographic orientation relationship of ⟨1¯21¯0⟩GaN on FS//⟨11¯00⟩sapphire and {11¯01}GaN on FS//{12¯13}sapphire existed between the GaN and the substrate. On the other hand, the orientation relationship of ⟨1¯21¯0⟩GaN layer//⟨1¯21¯0⟩GaN island on IS//⟨11¯00⟩sapphire and {11¯01}GaN layer//{0002}GaN island on IS//{12¯13}sapphire was confirmed among the GaN layer, the recrystallized GaN islands on an inclined sapphire surface and the PSS. The flat surface among the protruding patterns began to fill rapidly with GaN. Then, the GaN gradually overgrew the protruding pattern and coalesced near the summit as the growth time increased. The generation of threading dislocations was observed in the vicinity of the coalescence points near the top of the protruding patterns.

  1. The Original Gemini 9 Prime Crew

    NASA Technical Reports Server (NTRS)

    1966-01-01

    The original Gemini 9 prime crew, astronauts Elliot M. See Jr. (left), command pilot, and Charles A. Bassett II, pilot, in space suits with their helmets on the table in front of them. On February 28, 1966 the prime crew for the Gemini 9 mission were killed when their twin seat T-38 trainer jet aircraft crashed into a building in which the Gemini spacecraft were being manufactured. They were on final approach to Lambert-Saint Louis Municipal Airport when bad weather conditions hampered pilot See's ability to make a good visual contact with the runway. Noticing the building at the last second as he came out of the low cloud cover, See went to full afterburner and attempted to nose-up the aircraft in an attempt to miss the building. He clipped it and his plane crashed.

  2. Average prime-pair counting formula

    NASA Astrophysics Data System (ADS)

    Korevaar, Jaap; Riele, Herman Te

    2010-04-01

    Taking r>0 , let π_{2r}(x) denote the number of prime pairs (p, p+2r) with p≤ x . The prime-pair conjecture of Hardy and Littlewood (1923) asserts that π_{2r}(x)˜ 2C_{2r} {li}_2(x) with an explicit constant C_{2r}>0 . There seems to be no good conjecture for the remainders ω_{2r}(x)=π_{2r}(x)- 2C_{2r} {li}_2(x) that corresponds to Riemann's formula for π(x)-{li}(x) . However, there is a heuristic approximate formula for averages of the remainders ω_{2r}(x) which is supported by numerical results.

  3. Repetition priming results in sensitivity attenuation

    PubMed Central

    Allenmark, Fredrik; Hsu, Yi-Fang; Roussel, Cedric; Waszak, Florian

    2015-01-01

    Repetition priming refers to the change in the ability to perform a task on a stimulus as a consequence of a former encounter with that very same item. Usually, repetition results in faster and more accurate performance. In the present study, we used a contrast discrimination protocol to assess perceptual sensitivity and response bias of Gabor gratings that are either repeated (same orientation) or alternated (different orientation). We observed that contrast discrimination performance is worse, not better, for repeated than for alternated stimuli. In a second experiment, we varied the probability of stimulus repetition, thus testing whether the repetition effect is due to bottom-up or top-down factors. We found that it is top-down expectation that determines the effect. We discuss the implication of these findings for repetition priming and related phenomena as sensory attenuation. This article is part of a Special Issue entitled SI: Prediction and Attention. PMID:25819554

  4. The Actual Apollo 13 Prime Crew

    NASA Technical Reports Server (NTRS)

    1970-01-01

    The actual Apollo 13 lunar landing mission prime crew from left to right are: Commander, James A. Lovell Jr., Command Module pilot, John L. Swigert Jr.and Lunar Module pilot, Fred W. Haise Jr. The original Command Module pilot for this mission was Thomas 'Ken' Mattingly Jr. but due to exposure to German measles he was replaced by his backup, Command Module pilot, John L. 'Jack' Swigert Jr.

  5. Detecting Prime Numbers via Roots of Polynomials

    ERIC Educational Resources Information Center

    Dobbs, David E.

    2012-01-01

    It is proved that an integer n [greater than or equal] 2 is a prime (resp., composite) number if and only if there exists exactly one (resp., more than one) nth-degree monic polynomial f with coefficients in Z[subscript n], the ring of integers modulo n, such that each element of Z[subscript n] is a root of f. This classroom note could find use in…

  6. Detecting prime numbers via roots of polynomials

    NASA Astrophysics Data System (ADS)

    Dobbs, David E.

    2012-04-01

    It is proved that an integer n ≥ 2 is a prime (resp., composite) number if and only if there exists exactly one (resp., more than one) nth-degree monic polynomial f with coefficients in Z n , the ring of integers modulo n, such that each element of Z n is a root of f. This classroom note could find use in any introductory course on abstract algebra or elementary number theory.

  7. Trans-generational immune priming in honeybees

    PubMed Central

    Hernández López, Javier; Schuehly, Wolfgang; Crailsheim, Karl; Riessberger-Gallé, Ulrike

    2014-01-01

    Maternal immune experience acquired during pathogen exposure and passed on to progeny to enhance resistance to infection is called trans-generational immune priming (TgIP). In eusocial insects like honeybees, TgIP would result in a significant improvement of health at individual and colony level. Demonstrated in invertebrates other than honeybees, TgIP has not yet been fully elucidated in terms of intensity and molecular mechanisms underlying this response. Here, we immune-stimulated honeybee queens with Paenibacillus larvae (Pl), a spore-forming bacterium causing American Foulbrood, the most deadly bee brood disease worldwide. Subsequently, offspring of stimulated queens were exposed to spores of Pl and mortality rates were measured to evaluate maternal transfer of immunity. Our data substantiate the existence of TgIP effects in honeybees by direct evaluation of offspring resistance to bacterial infection. A further aspect of this study was to investigate a potential correlation between immune priming responses and prohaemocytes–haemocyte differentiation processes in larvae. The results point out that a priming effect triggers differentiation of prohaemocytes to haemocytes. However, the mechanisms underlying TgIP responses are still elusive and require future investigation. PMID:24789904

  8. Trans-generational immune priming in honeybees.

    PubMed

    Hernández López, Javier; Schuehly, Wolfgang; Crailsheim, Karl; Riessberger-Gallé, Ulrike

    2014-06-22

    Maternal immune experience acquired during pathogen exposure and passed on to progeny to enhance resistance to infection is called trans-generational immune priming (TgIP). In eusocial insects like honeybees, TgIP would result in a significant improvement of health at individual and colony level. Demonstrated in invertebrates other than honeybees, TgIP has not yet been fully elucidated in terms of intensity and molecular mechanisms underlying this response. Here, we immune-stimulated honeybee queens with Paenibacillus larvae (Pl), a spore-forming bacterium causing American Foulbrood, the most deadly bee brood disease worldwide. Subsequently, offspring of stimulated queens were exposed to spores of Pl and mortality rates were measured to evaluate maternal transfer of immunity. Our data substantiate the existence of TgIP effects in honeybees by direct evaluation of offspring resistance to bacterial infection. A further aspect of this study was to investigate a potential correlation between immune priming responses and prohaemocytes-haemocyte differentiation processes in larvae. The results point out that a priming effect triggers differentiation of prohaemocytes to haemocytes. However, the mechanisms underlying TgIP responses are still elusive and require future investigation. PMID:24789904

  9. Initial models in conditionals: evidence from priming.

    PubMed

    Espino, Orlando; Santamaría, Carlos

    2008-05-01

    We examined the comprehension of different types of conditionals. We measured the reading time of sentences primed by different types of conditionals (Experiments 1 and 2). We found that the participants read not-p and not-q faster when it was primed by the conditional form p if q and they were slower to read p and q when it was primed by the conditional form p only if q. This effect disappeared in the second experiment, where the order of the elements was reversed (q and p and not-q and not-p). These results suggest that the conditional form p if q elicits an initial representation "from p to q" with two possibilities, while the conditional form p only if q elicits a reverse representation with only one possibility. The third experiment showed that there were effects of the order only for the conditional if p then q, which confirms the reverse representation hypothesis. We discuss the implications of these results for different theories of conditional comprehension. PMID:18630646

  10. Congruent numbers with many prime factors.

    PubMed

    Tian, Ye

    2012-12-26

    Mohammed Ben Alhocain, in an Arab manuscript of the 10th century, stated that the principal object of the theory of rational right triangles is to find a square that when increased or diminished by a certain number, m becomes a square [Dickson LE (1971) History of the Theory of Numbers (Chelsea, New York), Vol 2, Chap 16]. In modern language, this object is to find a rational point of infinite order on the elliptic curve my2 = x3 - x. Heegner constructed such rational points in the case that m are primes congruent to 5,7 modulo 8 or twice primes congruent to 3 modulo 8 [Monsky P (1990) Math Z 204:45-68]. We extend Heegner's result to integers m with many prime divisors and give a sketch in this report. The full details of all the proofs will be given in ref. 1 [Tian Y (2012) Congruent Numbers and Heegner Points, arXiv:1210.8231]. PMID:23213259

  11. Controlled morphology of regular GaN microrod arrays by selective area growth with HVPE

    NASA Astrophysics Data System (ADS)

    Lekhal, Kaddour; Bae, Si-Young; Lee, Ho-Jun; Mitsunari, Tadashi; Tamura, Akira; Deki, Manato; Honda, Yoshio; Amano, Hiroshi

    2016-08-01

    The selective area growth (SAG) of GaN was implemented on patterned GaN/sapphire templates by hydride vapor phase epitaxy (HVPE) to fabricate regular arrays of Ga-polar GaN microrods. The control of growth parameters such as H2/N2 carrier gas ratio, growth temperature, and absolute NH3/HCl gas flow resulted in changes in the growth morphology. In particular, for an optimized mixed-carrier gas ratio of H2 to N2, we achieved vertically well-aligned microrods. The topmost regions of the GaN microrods were terminated with pyramidal facets, indicating typical Ga polarity. The optical properties of the grown microrods were characterized by cathodoluminescence (CL) at a low temperature. This revealed that the GaN microrods had high crystal quality since they exhibited suppressed yellow luminescence as well as strong band edge emission.

  12. Doping of Si into GaN nanowires and optical properties of resulting composites.

    PubMed

    Xu, Congkang; Chung, Sangyong; Kim, Misuk; Kim, Dong Eon; Chon, Bonghwan; Hong, Sangsu; Joo, Taiha

    2005-04-01

    Doping of Si into GaN nanowires has been successfully attained via thermal evaporation in the presence of a suitable gas atmosphere. Analysis indicated that the Si-doped GaN nanowire is a single crystal with a hexagonal wurtzite structure, containing 2.2 atom % of Si. The broadening and the shift of Raman peak to lower frequency are observed, which may be attributed to surface disorder and various strengths of the stress. The band-gap emission (358 nm) of Si-doped GaN nanowires relative to that (370 nm) of GaN nanowires has an apparent blue shift (approximately 12 nm), which can be ascribed to doping impurity Si. PMID:16004115

  13. High-resistance GaN epilayers with low dislocation density via growth mode modification

    NASA Astrophysics Data System (ADS)

    Xu, Z. Y.; Xu, F. J.; Wang, J. M.; Lu, L.; Yang, Z. J.; Wang, X. Q.; Shen, B.

    2016-09-01

    High-resistance GaN with low dislocation density adopting growth mode modification has been investigated by metalorganic chemical vapor deposition. The sheet resistance of the order of 1016 Ω/sq has been achieved at room temperature by diminishing the oxygen impurity level close to the substrate with an AlN blocking layer. Attributed to this method which offers more freedom to tailor the growth mode, a three-dimensional (3D) growth process is introduced by adjusting the growth pressure and temperature at the initial stage of the GaN epitaxy to improve the crystalline quality. The large 3D GaN grains formed during this period roughen the surface, and the following coalescence of the GaN grains causes threading dislocations bending, which finally remarkably reduces the dislocation density.

  14. A liftoff process of GaN layers and devices through nanoporous transformation

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Leung, Benjamin; Han, Jung

    2012-04-01

    A process to slice and separate GaN device layers for vertical light emitting diodes (LEDs) is presented through a developed electrochemical anodization process to create nanoporous (NP) GaN of designed porosity profiles. The NP GaN serves dual purposes of supporting subsequent overgrowth of LED structures while undergoing, during growth, shape transformation into a largely voided morphology. It is shown that this voided region decreases the lateral fracture resistance and enables large-area separation of the LED structures after appropriate wafer bonding. The separated LED layers are shown to have comparable material quality before and after the liftoff process. Blue emitting GaN LEDs are transferred to silicon substrates with vertical configuration by this unique process.

  15. Swelling or erosion on the surface of patterned GaN damaged by heavy ion implantation

    SciTech Connect

    Gao, Yuan; Lan, Chune; Xue, Jianming; Yan, Sha; Wang, Yugang; Xu, Fujun; Shen, Bo; Zhang, Yanwen

    2010-06-08

    Wurtzite undoped GaN epilayers (0 0 0 1) was implanted with 500 keV Au+ ions at room temperature under different doses, respectively. Ion implantation was performed through photoresist masks on GaN to produce alternating strips. The experimental results showed that the step height of swelling and decomposition in implanted GaN depended on ion dose and annealing temperature, i.e., damage level and its evolution. This damage evolution is contributed to implantation-induced defect production, and defect migration/accumulation occurred at different levels of displacement per atom. The results suggest that the swelling is due to the formation of porous structures in the amorphous region of implanted GaN. The decomposition of implanted area can be attributed to the disorder saturation and the diffusion of surface amorphous layer.

  16. GaN growth using gallium hydride generated by hydrogenation of liquid gallium

    NASA Astrophysics Data System (ADS)

    Nagayoshi, H.; Nishimura, S.; Takeuchi, T.; Hirai, M.; Terashima, K.

    2005-02-01

    The novel growth method of GaN using hydrogen radicals has been investigated. This paper is the first report of gallium hydrogenation reaction and deposition of GaN using hydrogenated gallium. We found that gallium (Ga) could be volatilized at low temperature by hydrogenation reaction with hydrogen radicals. In this reaction, Ga assumed to be volatilized as GaH 3. The GaN deposition was attempted by using gas phase reaction of NH 3 and GaH 3 generated by the reaction between liquid Ga and hydrogen radicals. Hydrogen radicals were generated by hot tungsten filament, which works as a catalyst during hydrogen cracking, whose temperature was 1600 °C. Surface morphology, deposition rate, and film structure were investigated. It was confirmed that GaN could be deposited by this method. The source materials of this method are safe and of low cost compared to the conventional methods.

  17. Leakage mechanism in GaN and AlGaN Schottky interfaces

    NASA Astrophysics Data System (ADS)

    Hashizume, Tamotsu; Kotani, Junji; Hasegawa, Hideki

    2004-06-01

    Based on detailed temperature-dependent current-voltage (I-V-T) measurements the mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed. The experiments were compared to calculations based on thin surface barrier model in which the effects of surface defects were taken into account. Our simulation method reproduced the experimental I-V-T characteristics of the GaN and AlGaN Schottky diodes, and gave excellent fitting results to the reported Schottky I-V curves in GaN for both forward and reverse biases at different temperatures. The present results indicate that the barrier thinning caused by unintentional surface-defect donors enhances the tunneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces.

  18. Droplet heteroepitaxy of zinc-blende vs. wurtzite GaN quantum dots

    NASA Astrophysics Data System (ADS)

    Reese, C.; Jeon, S.; Hill, T.; Jones, C.; Shusterman, S.; Yacoby, Y.; Clarke, R.; Deng, H.; Goldman, Rs

    We have developed a GaN droplet heteroepitaxy process based upon plasma-assisted molecular-beam epitaxy. Using various surface treatments and Ga deposition parameters, we have demonstrated polycrystalline, zinc-blende (ZB), and wurtzite (WZ) GaN quantum dots (QDs) on Si(001), r-Al2O3, Si(111), and c-GaN substrates. For the polar substrates (i.e. Si(111) and c-GaN), high-resolution transmission electron microscopy and coherent Bragg rod analysis reveals the formation of coherent WZ GaN QDs with nitridation-temperature-dependent sizes and densities. For the non-polar substrates (i.e. Si(001) and r-Al2O3) , QDs with strong near-band photoluminescence emission are observed and ZB GaN QD growth on Si(001) is demonstrated for the first time.

  19. Formation of helical dislocations in ammonothermal GaN substrate by heat treatment

    NASA Astrophysics Data System (ADS)

    Horibuchi, Kayo; Yamaguchi, Satoshi; Kimoto, Yasuji; Nishikawa, Koichi; Kachi, Tetsu

    2016-03-01

    GaN substrate produced by the basic ammonothermal method and an epitaxial layer on the substrate was evaluated using synchrotron radiation x-ray topography and transmission electron microscopy. We revealed that the threading dislocations present in the GaN substrate are deformed into helical dislocations and the generation of the voids by heat treatment in the substrate for the first observation in the GaN crystal. These phenomena are formed by the interactions between the dislocations and vacancies. The helical dislocation was formed in the substrate region, and not in the epitaxial layer region. Furthermore, the evaluation of the influence of the dislocations on the leakage current of Schottky barrier diodes fabricated on the epitaxial layer is discussed. The dislocations did not affect the leakage current characteristics of the epitaxial layer. Our results suggest that the deformation of dislocations in the GaN substrate does not adversely affect the epitaxial layer.

  20. High breakdown single-crystal GaN p-n diodes by molecular beam epitaxy

    SciTech Connect

    Qi, Meng; Zhao, Yuning; Yan, Xiaodong; Li, Guowang; Verma, Jai; Fay, Patrick; Nomoto, Kazuki; Zhu, Mingda; Hu, Zongyang; Protasenko, Vladimir; Song, Bo; Xing, Huili Grace; Jena, Debdeep; Bader, Samuel

    2015-12-07

    Molecular beam epitaxy grown GaN p-n vertical diodes are demonstrated on single-crystal GaN substrates. A low leakage current <3 nA/cm{sup 2} is obtained with reverse bias voltage up to −20 V. With a 400 nm thick n-drift region, an on-resistance of 0.23 mΩ cm{sup 2} is achieved, with a breakdown voltage corresponding to a peak electric field of ∼3.1 MV/cm in GaN. Single-crystal GaN substrates with very low dislocation densities enable the low leakage current and the high breakdown field in the diodes, showing significant potential for MBE growth to attain near-intrinsic performance when the density of dislocations is low.

  1. Depth dependence of defect density and stress in GaN grown on SiC

    NASA Astrophysics Data System (ADS)

    Faleev, N.; Temkin, H.; Ahmad, I.; Holtz, M.; Melnik, Yu.

    2005-12-01

    We report high resolution x-ray diffraction studies of the relaxation of elastic strain in GaN grown on SiC(0001). The GaN layers were grown with thickness ranging from 0.29to30μm. High level of residual elastic strain was found in thin (0.29to0.73μm thick) GaN layers. This correlates with low density of threading screw dislocations of 1-2×107cm-2, observed in a surface layer formed over a defective nucleation layer. Stress was found to be very close to what is expected from thermal expansion mismatch between the GaN and SiC. A model based on generation and diffusion of point defects accounts for these observations.

  2. Microstructure of GaN Grown on (111) Si by MOCVD

    SciTech Connect

    Fleming, J.G.; Follstaedt, D.M.; Han, J.; Provencio, P.

    1998-12-17

    Gallium nitride was grown on (111) Si by MOCVD by depositing an AIN buffer at 108O"C and then GaN at 1060 {degrees}C. The 2.2pm layer cracked along {1-100} planes upon cooling to room temperature, but remained adherent. We were able to examine the microstructure of material between cracks with TEM. The character and arrangement of dislocation are much like those of GaN grown on Al{sub 2}O{sub 3}: -2/3 pure edge and - 1/3 mixed (edge + screw), arranged in boundaries around domains of GaN that are slightly disoriented with respect to neighboring material. The 30 nm AIN buffer is continuous, indicating that AIN wets the Si, in contrast to GaN on Al{sub 2}O{sub 3}.

  3. Rare earth 4f hybridization with the GaN valence band

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Mei, Wai-Ning; McHale, S. R.; McClory, J. W.; Petrosky, J. C.; Wu, J.; Palai, R.; Losovyj, Y. B.; Dowben, P. A.

    2012-11-01

    The placement of the Gd, Er and Yb 4f states within the GaN valence band has been explored by both experiment and theory. The 4d-4f photoemission resonances for various rare-earth(RE)-doped GaN thin films (RE = Gd, Er, Yb) provide an accurate depiction of the occupied 4f state placement within the GaN. The resonant photoemission show that the major Er and Gd RE 4f weight is at about 5-6 eV below the valence band maximum, similar to the 4f weights in the valence band of many other RE-doped semiconductors. For Yb, there is a very little resonant enhancement of the valence band of Yb-doped GaN, consistent with a large 4f14-δ occupancy. The placement of the RE 4f levels is in qualitative agreement with theoretical expectations.

  4. The rare earth 4 f hybridization with the GaN valence band

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Mei, Wai-Ning; McHale, Steve; McClory, John; Petrosky, James; Wu, J.; Palai, Ratnakar; Losovyj, Yaroslav; Dowben, Peter

    2013-03-01

    The placement of the Gd, Er, and Yb 4f states within the GaN valence band has been explored by both experiment and theory. The 4 d - 4 f photoemission resonances for various rare earth doped GaN thin films (RE = Gd, Er, Yb) provide an accurate depiction of the occupied 4 f state placement within the GaN. The resonant photoemission show that the major Er and Gd rare earth 4 f weight is at about 5-6 eV below the valence band maximum, similar to the 4 f weights in the valence band of many other rare earth doped semiconductors. For Yb, there is very little resonant enhancement of the valence band of Yb doped GaN, consistent with a largely 4f 14 - δ occupancy. The placement of the rare earth 4 f levels is in qualitative agreement with theoretical expectations.

  5. Depth dependence of defect density and stress in GaN grown on SiC

    SciTech Connect

    Faleev, N.; Temkin, H.; Ahmad, I.; Holtz, M.; Melnik, Yu.

    2005-12-15

    We report high resolution x-ray diffraction studies of the relaxation of elastic strain in GaN grown on SiC(0001). The GaN layers were grown with thickness ranging from 0.29 to 30 {mu}m. High level of residual elastic strain was found in thin (0.29 to 0.73 {mu}m thick) GaN layers. This correlates with low density of threading screw dislocations of 1-2x10{sup 7} cm{sup -2}, observed in a surface layer formed over a defective nucleation layer. Stress was found to be very close to what is expected from thermal expansion mismatch between the GaN and SiC. A model based on generation and diffusion of point defects accounts for these observations.

  6. GaN grown on (1 1 1) single crystal diamond substrate by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Dussaigne, A.; Malinverni, M.; Martin, D.; Castiglia, A.; Grandjean, N.

    2009-10-01

    GaN epilayers are grown on (1 1 1) oriented single crystal diamond substrate by ammonia-source molecular beam epitaxy. Each step of the growth is monitored in situ by reflection high energy electron diffraction. It is found that a two-dimensional epitaxial wurtzite GaN film is obtained. The surface morphology is smooth: the rms roughness is as low as 1.3 nm for 2×2 μm 2 scan. Photoluminescence measurements reveal pretty good optical properties. The GaN band edge is centred at 3.469 eV with a linewidth of 5 meV. These results demonstrate that GaN heteroepitaxially grown on diamond opens new rooms for high power electronic applications.

  7. Surface potential barrier in m-plane GaN studied by contactless electroreflectance

    NASA Astrophysics Data System (ADS)

    Janicki, Lukasz; Misiewicz, Jan; Cywiński, Grzegorz; Sawicka, Marta; Skierbiszewski, Czeslaw; Kudrawiec, Robert

    2016-02-01

    Contactless electroreflectance (CER) is used to study the surface potential barrier in m-plane GaN UN+ [GaN (d = 20,30,50,70 nm)/GaN:Si] structures grown by using molecular beam epitaxy. Clear bandgap-related transitions followed by Franz-Keldysh oscillations (FKO) have been observed in the CER spectra of all samples at room temperature. The built-in electric fields in the undoped cap layers have been determined from the FKO period. From the built-in electric field and the undoped GaN layer thickness, the Fermi level location at the air-exposed m-plane GaN surface has been estimated as 0.42 ± 0.05 eV below the conduction band.

  8. Radiative defects in GaN nanocolumns: Correlation with growth conditions and sample morphology

    SciTech Connect

    Lefebvre, P.; Fernandez-Garrido, S.; Grandal, J.; Ristic, J.; Sanchez-Garcia, M.-A.; Calleja, E.

    2011-02-21

    Low-temperature photoluminescence is studied in detail in GaN nanocolumns (NCs) grown by plasma-assisted molecular beam epitaxy under various conditions (substrate temperature and impinging Ga/N flux ratio). The relative intensities of the different emission lines, in particular those related to structural defects, appear to be correlated with the growth conditions, and clearly linked to the NC sample morphology. We demonstrate, in particular, that all lines comprised between 3.10 and 3.42 eV rapidly lose intensity when the growth conditions are such that the NC coalescence is reduced. The well-known line around 3.45 eV, characteristic of GaN NC samples, shows, however, a behavior that is exactly the opposite of the other lines, namely, for growth conditions leading to reduced NC coalescence, this line tends to become more prominent, thus proving to be intrinsic to individual GaN NCs.

  9. Thermal Conductivity and Large Isotope Effect in GaN from First Principles

    SciTech Connect

    Lindsay, L.; Broido, D. A.; Reinecke, T. L.

    2012-08-28

    We present atomistic first principles results for the lattice thermal conductivity of GaN and compare them to those for GaP, GaAs, and GaSb. In GaN we find a large increase to the thermal conductivity with isotopic enrichment, ~65% at room temperature. We show that both the high thermal conductivity and its enhancement with isotopic enrichment in GaN arise from the weak coupling of heat-carrying acoustic phonons with optic phonons. This weak scattering results from stiff atomic bonds and the large Ga to N mass ratio, which give phonons high frequencies and also a pronounced energy gap between acoustic and optic phonons compared to other materials. Rigorous understanding of these features in GaN gives important insights into the interplay between intrinsic phonon-phonon scattering and isotopic scattering in a range of materials.

  10. In situ studies of the effect of silicon on GaN growth modes.

    SciTech Connect

    Munkholm, A.; Stephenson, G. B.; Eastman, J. A.; Auciello, O.; Murty, M. V. R.; Thompson, C.; Fini, P.; Speck, J. S.; DenBaars, S. P.; Northern Illinois Univ.; Univ. of California at Santa Barbara

    2000-12-01

    We present real-time X-ray scattering studies of the influence of silicon on the homoepitaxial growth mode of GaN grown by metal-organic vapor-phase epitaxy. Both annealing of Si-doped GaN and surface dosing of GaN with disilane are shown to change the mode of subsequent growth from step-flow to layer-by-layer. By comparing the growth behavior induced by doped layers which have been annealed to that induced by surface dosing, we extract an approximate diffusion coefficient for Si in GaN of 3.5 x 10{sup -18} cm{sup 2}/s at 810{sup o}C.

  11. Above room-temperature ferromagnetism of Mn delta-doped GaN nanorods

    SciTech Connect

    Lin, Y. T.; Wadekar, P. V.; Kao, H. S.; Chen, T. H.; Chen, Q. Y.; Tu, L. W.; Huang, H. C.; Ho, N. J.

    2014-02-10

    One-dimensional nitride based diluted magnetic semiconductors were grown by plasma-assisted molecular beam epitaxy. Delta-doping technique was adopted to dope GaN nanorods with Mn. The structural and magnetic properties were investigated. The GaMnN nanorods with a single crystalline structure and with Ga sites substituted by Mn atoms were verified by high-resolution x-ray diffraction and Raman scattering, respectively. Secondary phases were not observed by high-resolution x-ray diffraction and high-resolution transmission electron microscopy. In addition, the magnetic hysteresis curves show that the Mn delta-doped GaN nanorods are ferromagnetic above room temperature. The magnetization with magnetic field perpendicular to GaN c-axis saturates easier than the one with field parallel to GaN c-axis.

  12. Hydrothermal syntheses, crystal structures and luminescence properties of zinc(II) and cadmium(II) coordination polymers based on bifunctional 3,2 Prime :6 Prime ,3 Prime Prime -terpyridine-4 Prime -carboxylic acid

    SciTech Connect

    Li, Na; Guo, Hui-Lin; Hu, Huai-Ming; Song, Juan; Xu, Bing; Yang, Meng-Lin; Dong, Fa-Xin; Xue, Gang-Lin

    2013-02-15

    Five new coordination polymers, [Zn{sub 2}(ctpy){sub 2}Cl{sub 2}]{sub n} (1), [Zn{sub 2}(ctpy){sub 2}(ox)(H{sub 2}O){sub 2}]{sub n} (2), [Zn{sub 2}(ctpy)(3-btc)(H{sub 2}O)]{sub n}{center_dot}0.5nH{sub 2}O (3), [Cd(ctpy){sub 2}(H{sub 2}O)]{sub n} (4), [Cd{sub 4}(ctpy){sub 2}(2-btc){sub 2}(H{sub 2}O){sub 2}]{sub n}{center_dot}2nH{sub 2}O (5), (Hctpy=3,2 Prime :6 Prime ,3 Prime Prime -terpyridine-4 Prime -carboxylic acid, H{sub 2}ox=oxalic acid, H{sub 3}(3-btc)=1,3,5-benzenetricarboxylic acid, H{sub 3}(2-btc)=1,2,4-benzenetricarboxylic acid) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. Compounds 1-2 are a one-dimensional chain with weak interactions to form 3D supramolecular structures. Compound 3 is a 4-nodal 3D topology framework comprised of binuclear zinc units and (ctpy){sup -} anions. Compound 4 shows two dimensional net. Compound 5 is a (4,5,6)-connected framework with {l_brace}4{sup 4}{center_dot}6{sup 2}{r_brace}{l_brace}4{sup 6}{center_dot}6{sup 4}{r_brace}{sub 2}{l_brace}4{sup 9}{center_dot}6{sup 6}{r_brace} topology. In addition, the thermal stabilities and photoluminescence properties of 1-5 were also studied in the solid state. - Graphical abstract: Five new Zn/Cd compounds with 3,2 Prime :6 Prime ,3 Prime Prime -terpyridine-4 Prime -carboxylic acid were prepared. The photoluminescence and thermal stabilities properties of 1-5 were investigated in the solid state. Highlights: Black-Right-Pointing-Pointer Five new zinc/cadmium metal-organic frameworks have been hydrothermal synthesized. Black-Right-Pointing-Pointer The structural variation is attributed to the diverse metal ions and auxiliary ligand. Black-Right-Pointing-Pointer Compounds 1-5 exhibit 1D ring chain, 2D layer and 3D open-framework, respectively. Black-Right-Pointing-Pointer These compounds exhibit strong solid state luminescence emission at room temperature.

  13. The study of in situ scanning tunnelling microscope characterization on GaN thin film grown by plasma assisted molecular beam epitaxy

    SciTech Connect

    Yang, R.; Krzyzewski, T.; Jones, T.

    2013-03-18

    The epitaxial growth of GaN by Plasma Assisted Molecular Beam Epitaxy was investigated by Scanning Tunnelling Microscope (STM). The GaN film was grown on initial GaN (0001) and monitored by in situ Reflection High Energy Electron Diffraction and STM during the growth. The STM characterization was carried out on different sub-films with increased thickness. The growth of GaN was achieved in 3D mode, and the hexagonal edge of GaN layers and growth gradient were observed. The final GaN was of Ga polarity and kept as (0001) orientation, without excess Ga adlayers or droplets formed on the surface.

  14. [HUANG Yu-jie, the famous traditional Chinese medical physician of Taiwan in the late Qing dynasty and early republican period of China].

    PubMed

    Xiao, Lin-rong; Zhang, Yong-xian

    2009-07-01

    HUANG Yu-jie, the famous TCM physician of Taiwan in the late Qing dynasty and early Republican period of China, was a physician with noble medical morality and perfect medical skill. He made distinguished contributions especially to the prevention and treatment of epidemic disease. During the time he undertook the medical work, he also actively took part in the social activities and made changes in customs and traditions to promote the development of society. His medical morality and skill not only were the model for the medical field at that time but also had an extensive and profound impact on the common people. PMID:19930943

  15. Novel word lexicalization and the prime lexicality effect.

    PubMed

    Qiao, Xiaomei; Forster, Kenneth I

    2013-07-01

    This study investigates how newly learned words are integrated into the first-language lexicon using masked priming. Two lexical decision experiments are reported, with the aim of establishing whether newly learned words behave like real words in a masked form priming experiment. If they do, they should show a prime lexicality effect (PLE), in which less priming is obtained due to form similarity when the prime is a word. In the first experiment, subjects were taught the meanings of novel words that were neighbors of real words, but no PLE was observed; that is, equally strong form priming was obtained for both trained and untrained novel primes. In the second experiment, 4 training sessions were spread over 4 weeks, and under these conditions, a clear PLE was obtained in the final session. It is concluded that lexicalization requires multiple training sessions. Possible explanations of the PLE are discussed. PMID:23088548

  16. Intact Conceptual Priming in the Absence of Declarative Memory

    PubMed Central

    Levy, D.A.; Stark, C.E.L.; Squire, L.R.

    2009-01-01

    Priming is an unconscious (nondeclarative) form of memory whereby identification or production of an item is improved by an earlier encounter. It has been proposed that declarative memory and priming might be related—for example, that conceptual priming results in more fluent processing, thereby providing a basis for familiarity judgments. In two experiments, we assessed conceptual priming and recognition memory across a 5-min interval in 5 memory-impaired patients. All patients exhibited fully intact priming in tests of both free association (study tent; at test, provide an association to canvas) and category verification (study lemon; at test, decide: Is lemon a type of fruit?). Yet the 2 most severely amnesic patients performed at chance on matched tests of recognition memory. These findings count against the notion that conceptual priming provides feelings of familiarity that can support accurate recognition judgments. We suggest that priming is inaccessible to conscious awareness and does not influence declarative memory. PMID:15447639

  17. Task-Dependent Masked Priming Effects in Visual Word Recognition

    PubMed Central

    Kinoshita, Sachiko; Norris, Dennis

    2012-01-01

    A method used widely to study the first 250 ms of visual word recognition is masked priming: These studies have yielded a rich set of data concerning the processes involved in recognizing letters and words. In these studies, there is an implicit assumption that the early processes in word recognition tapped by masked priming are automatic, and masked priming effects should therefore be invariant across tasks. Contrary to this assumption, masked priming effects are modulated by the task goal: For example, only word targets show priming in the lexical decision task, but both words and non-words do in the same-different task; semantic priming effects are generally weak in the lexical decision task but are robust in the semantic categorization task. We explain how such task dependence arises within the Bayesian Reader account of masked priming (Norris and Kinoshita, 2008), and how the task dissociations can be used to understand the early processes in lexical access. PMID:22675316

  18. P- and N-type implantation doping of GaN with Ca and O

    SciTech Connect

    Zolper, J.C.; Wilson, R.G.; Pearton, S.J.; Stall, R.A.

    1996-05-01

    III-N photonic devices have made great advances in recent years following the demonstration of doping of GaN p-type with Mg and n-type with Si. However, the deep ionization energy level of Mg in GaN ({approximately} 160 meV) limits the ionized of acceptors at room temperature to less than 1.0% of the substitutional Mg. With this in mind, the authors used ion implantation to characterize the ionization level of Ca in GaN since Ca had been suggested by Strite to be a shallow acceptor in GaN. Ca-implanted GaN converted from n-to-p type after a 1,100 C activation anneal. Variable temperature Hall measurements give an ionization level at 169 meV. Although this level is equivalent to that of Mg, Ca-implantation may have advantages (shallower projected range and less straggle for a given energy) than Mg for electronic devices. In particular, the authors report the first GaN device using ion implantation doping. This is a GaN junction field effect transistor (JFET) which employed Ca-implantation. A 1.7 {micro}m JFET had a transconductance of 7 mS/mm, a saturation current at 0 V gate bias of 33 mA/mm, a f{sub t} of 2.7 GHz, and a f{sub max} of 9.4 GHz. O-implantation was also studied and shown to create a shallow donor level ({approximately} 25 meV) that is similar to Si. SIMS profiles of as-implanted and annealed samples showed no measurable redistribution of either Ca or O in GaN at 1,125 C.

  19. High efficiency DC-DC converter using GaN transistors

    NASA Astrophysics Data System (ADS)

    Tómaş, Cosmin-Andrei; Grecu, Cristian; Pantazicǎ, Mihaela; Marghescu, Ion

    2015-02-01

    The paper presents a new high-efficiency power switching supply using the Gallium Nitride (GaN) technology. There are compared two solutions, the first using standard MOS transistors and the second using the new GaN transistor. The actual green technologies for obtaining the maximum energy and minimum losses have pushed the semiconductor industry into a continuous research regarding high power and high frequency devices, having uses in both digital communications and switching power supplies.

  20. Femtosecond dynamics of exciton bleaching in bulk GaN at room temperature

    NASA Astrophysics Data System (ADS)

    Huang, Yin-Chieh; Chern, Gia-Wei; Lin, Kung-Hsuan; Liang, Jian-Chin; Sun, Chi-Kuang; Hsu, Chia-Chen; Keller, Stacia; DenBaars, Steven P.

    2002-07-01

    Femtosecond transient transmission pump-probe technique was used to investigate exciton dynamics in a nominally undoped GaN thin film at room temperature. An exciton ionization time of 100-250 femtoseconds was observed by the time-resolved pump-probe measurement. A comparison experiment with pre-excited free carriers also confirmed the observation of the exciton ionization process in bulk GaN.

  1. GaN Stress Evolution During Metal-Organic Chemical Vapor Deposition

    SciTech Connect

    Amano, H.; Chason, E.; Figiel, J.; Floro, J.A.; Han, J.; Hearne, S.; Hunter, J.; Tsong, I.

    1998-10-14

    The evolution of stress in gallium nitride films on sapphire has been measured in real- time during metal organic chemical vapor deposition. In spite of the 161%0 compressive lattice mismatch of GaN to sapphire, we find that GaN consistently grows in tension at 1050"C. Furthermore, in-situ stress monitoring indicates that there is no measurable relaxation of the tensile growth stress during annealing or thermal cycling.

  2. The dispersion of BED ° in unintentional doped GaN crystals

    NASA Astrophysics Data System (ADS)

    Qingcheng, Bao; Fungleng, Zhang; Ke, Shi; Rensong, Dai; Xurong, Xu

    1986-09-01

    The polarization and the wavelength of the photoluminescence of BED ° in not intentionaly doped GaN crystal wafers are observed to be dependent on the excitation intensity (I-exc). When I-exc increases from 1 KW/CM 2 to 1000 KW/CM 2, they vary at first quadratically, and then, appear saturated. This phenomenon is resulted from dispersion effect of BED ° in GaN crystal wafers, which is proposed earlier (1).

  3. Evolution of deep centers in GaN grown by hydride vapor phaseepitaxy

    SciTech Connect

    Fang, Z.-Q.; Look, D.C.; Jasinski, J.; Benamara, M.; Liliental-Weber, Z.; Molnar, R.J.

    2001-04-18

    Deep centers and dislocation densities in undoped n GaN, grown by hydride vapor phase epitaxy (HVPE), were characterized as a function of the layer thickness by deep level transient spectroscopy and transmission electron microscopy, respectively. As the layer thickness decreases, the variety and concentration of deep centers increase, in conjunction with the increase of dislocation density. Based on comparison with electron irradiation induced centers, some dominant centers in HVPE GaN are identified as possible point defects.

  4. Mass transport, faceting and behavior of dislocations in GaN

    SciTech Connect

    Nitta, S.; Kashima, T.; Kariya, M.; Yukawa, Y.; Yamaguchi, S.; Amano, H.; Akasaki, I.

    2000-07-01

    The behavior of threading dislocations during mass transport of GaN was investigated in detail by transmission electron microscopy. Mass transport occurred at the surface. Therefore, growing species are supplied from the in-plane direction. The behavior of threading dislocations was found to be strongly affected by the mass transport process as well as the high crystallographic anisotropy of the surface energy of the facets particular to GaN.

  5. Atomistic Simulation of Brittle to Ductile Transition in GaN Nanotubes

    SciTech Connect

    Wang, Zhiguo; Zu, Xiaotao; Gao, Fei; Weber, William J.

    2006-12-11

    Molecular dynamics methods with a Stillinger-Weber potential have been used to investigate the mechanical properties of wurtzite-type single crystalline GaN nanotubes under applied tensile stresses. At lower temperatures, the nanotubes show brittle properties; whereas at higher temperatures, they behave as ductile materials. The brittle to ductile transition (BDT) is systemically investigated, and the corresponding transition temperatures have been determined in GaN. The BDT temperature generally increases with increasing thickness of nanotubes and strain rate.

  6. Strain dependent electron spin dynamics in bulk cubic GaN

    SciTech Connect

    Schaefer, A.; Buß, J. H.; Hägele, D.; Rudolph, J.; Schupp, T.; Zado, A.; As, D. J.

    2015-03-07

    The electron spin dynamics under variable uniaxial strain is investigated in bulk cubic GaN by time-resolved magneto-optical Kerr-rotation spectroscopy. Spin relaxation is found to be approximately independent of the applied strain, in complete agreement with estimates for Dyakonov-Perel spin relaxation. Our findings clearly exclude strain-induced relaxation as an effective mechanism for spin relaxation in cubic GaN.

  7. Influence of initial growth conditions and Mg-surfactant on the quality of GaN film grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Junsong, Cao; Xin, Lü; Lubing, Zhao; Shuang, Qu; Wei, Gao

    2015-02-01

    The initial growth conditions of a 100 nm thick GaN layer and Mg-surfactant on the quality of the GaN epilayer grown on a 6H-SiC substrate by metal-organic vapor phase epitaxy have been investigated in this research. Experimental results have shown that a high V/III ratio and the initially low growth rate of the GaN layer are favorable for two-dimension growth and surface morphology of GaN and the formation of a smoother growth surface. Mg-surfactant occurring during GaN growth can reduce the dislocations density of the GaN epilayer but increase the surface RMS, which are attributed to the change of growth mode.

  8. An ultra-thin compliant sapphire membrane for the growth of less strained, less defective GaN

    NASA Astrophysics Data System (ADS)

    Moon, Daeyoung; Jang, Jeonghwan; Choi, Daehan; Shin, In-Su; Lee, Donghyun; Bae, Dukkyu; Park, Yongjo; Yoon, Euijoon

    2016-05-01

    An ultra-thin (26 nm) sapphire (Al2O3) membrane was used as a compliant substrate for the growth of high quality GaN. The density of misfit dislocations per unit length at the interface between the GaN layer and the sapphire membrane was reduced by 28% compared to GaN on the conventional sapphire substrate. Threading dislocation density in GaN on the sapphire membrane was measured to be 2.4×108/cm2, which is lower than that for GaN on the conventional sapphire substrate (3.2×108/cm2). XRD and micro-Raman results verifed that the residual stress in GaN on the sapphire membrane was as low as 0.02 GPa due to stress absorption by the ultra-thin compliant sapphire membrane.

  9. Probing deep level centers in GaN epilayers with variable-frequency capacitance-voltage characteristics of Au /GaN Schottky contacts

    NASA Astrophysics Data System (ADS)

    Wang, R. X.; Xu, S. J.; Shi, S. L.; Beling, C. D.; Fung, S.; Zhao, D. G.; Yang, H.; Tao, X. M.

    2006-10-01

    Under identical preparation conditions, Au /GaN Schottky contacts were prepared on two kinds of GaN epilayers with significantly different background electron concentrations and mobility as well as yellow emission intensities. Current-voltage (I-V) and variable-frequency capacitance-voltage (C-V) characteristics show that the Schottky contacts on the GaN epilayer with a higher background carrier concentration and strong yellow emission exhibit anomalous reverse-bias I-V and C-V characteristics. This is attributed to the presence of deep level centers. Theoretical simulation of the low-frequency C-V curves leads to a determination of the density and energy level position of the deep centers.

  10. Nanoheteroepitaxial lateral overgrowth of GaN on nanoporous Si(111)

    NASA Astrophysics Data System (ADS)

    Zang, K. Y.; Wang, Y. D.; Chua, S. J.; Wang, L. S.; Tripathy, S.; Thompson, C. V.

    2006-04-01

    Nanoheteroepitaxial (NHE) lateral overgrowth of GaN on nanoporous Si(111) substrates has been demonstrated. Nanopore arrays in Si(111) surfaces were fabricated using anodized aluminum oxide templates as etch masks, resulting in an average pore diameter and depth of about 60 and 160-180nm, respectively. NHE growth of AlN and GaN was found to result in a significant reduction in the threading dislocation density (<108cm-2) compared to that on flat Si(111). Most dislocations that originate at the Si interface bent to lie in the GaN (0001) basal plane during lateral growth over the pore openings. E2 phonon blueshifts in the Raman spectra indicate a significant relaxation of the tensile stress in the coalesced GaN films, due to three-dimensional stress relaxation mechanisms on porous substrates. Our results show that a single step lateral overgrowth of GaN on nanopatterned Si(111) substrates without a dielectric mask is a simple way to improve the crystalline quality of GaN layers for microelectronic applications.

  11. Successive selective growth of semipolar (11-22) GaN on patterned sapphire substrate

    NASA Astrophysics Data System (ADS)

    Tendille, Florian; Hugues, Maxime; Vennéguès, Philippe; Teisseire, Monique; De Mierry, Philippe

    2015-06-01

    Thanks to the use of two successive selective growths by metal organic chemical vapor deposition reactor, high quality semipolar (11-22) GaN with a homogenous defect repartition over the surface was achieved. The procedure starts with a first selective growth on a patterned sapphire substrate, leading to continuous stripes of three dimensional (3D) GaN crystals of low defect density. Then, a second selective growth step is achieved by depositing a SiNx nano-mask and a low temperature GaN nano-layer on the top of the GaN stripes. Hereby, we demonstrate an original way to obtain a homoepitaxial selective growth on 3D GaN crystals by taking advantage of the different crystallographic planes available. Basal stacking faults (BSFs) are generated during this second selective growth but could be eliminated by using a three-step growth method in which elongated voids are created above the defective area. For a fully coalesced sample grown using the 2 step method, dislocation density of 1.2 × 108 cm-2 and BSFs density of 154 cm-1 with a homogenous distribution have been measured by cathodoluminescence at 80 K. Consequently the material quality of this coalesced semipolar layer is comparable to the one of polar GaN on c-plane sapphire.

  12. Behavior of aluminum adsorption and incorporation at GaN(0001) surface: First-principles study

    SciTech Connect

    Qin, Zhenzhen; Xiong, Zhihua Wan, Qixin; Qin, Guangzhao

    2013-11-21

    First-principles calculations are performed to study the energetics and atomic structures of aluminum adsorption and incorporation at clean and Ga-bilayer GaN(0001) surfaces. We find the favorable adsorption site changes from T4 to T1 as Al coverage increased to 1 monolayer on the clean GaN(0001) surface, and a two-dimensional hexagonal structure of Al overlayer appears. It is interesting the Al atoms both prefer to concentrate in one deeper Ga layer of clean and Ga-bilayer GaN(0001) surface, respectively, while different structures could be achieved in above surfaces. For the case of clean GaN(0001) surface, corresponding to N-rich and moderately Ga-rich conditions, a highly regular superlattice structure composed of wurtzite GaN and AlN becomes favorable. For the case of Ga-bilayer GaN(0001) surface, corresponding to extremely Ga-rich conditions, the Ga bilayer is found to be sustained stable in Al incorporating process, leading to an incommensurate structure directly. Furthermore, our calculations provide an explanation for the spontaneous formation of ordered structure and incommensurate structure observed in growing AlGaN films. The calculated results are attractive for further development of growth techniques and excellent AlGaN/GaN heterostructure electronic devices.

  13. GaN etching in BCl{sub 3}Cl{sub 2} plasmas

    SciTech Connect

    Shul, R.J.; Ashby, C.I.H.; Willison, C.G.; Zhang, L.; Han, J.; Bridges, M.M.; Pearton, S.J.; Lee, J.W.; Lester, L.F.

    1998-04-01

    GaN etching can be affected by a wide variety of parameters including plasma chemistry and plasma density. Chlorine-based plasmas have been the most widely used plasma chemistries to etch GaN due to the high volatility of the GaCl{sub 3} and NCl etch products. The source of Cl and the addition of secondary gases can dramatically influence the etch characteristics primarily due to their effect on the concentration of reactive Cl generated in the plasma. In addition, high-density plasma etch systems have yielded high quality etching of GaN due to plasma densities which are 2 to 4 orders of magnitude higher than reactive ion etch (RIE) plasma systems. The high plasma densities enhance the bond breaking efficiency of the GaN, the formation of volatile etch products, and the sputter desorption of the etch products from the surface. In this study, the authors report GaN etch results for a high-density inductively coupled plasma (ICP) as a function of BCl{sub 3}:Cl{sub 2} flow ratio, dc-bias, chamber-pressure, and ICP source power. GaN etch rates ranging from {approximately}100 {angstrom}/min to > 8,000 {angstrom}/min were obtained with smooth etch morphology and anisotropic profiles.

  14. Growth and characterization of horizontal GaN wires on silicon

    SciTech Connect

    Zou, Xinbo; May Lau, Kei; Lu, Xing; Lucas, Ryan; Kuech, Thomas F.; Choi, Jonathan W.; Gopalan, Padma

    2014-06-30

    We report the growth of in-plane GaN wires on silicon by metalorganic chemical vapor deposition. Triangular-shaped GaN microwires with semi-polar sidewalls are observed to grow on top of a GaN/Si template patterned with nano-porous SiO{sub 2}. With a length-to-thickness ratio ∼200, the GaN wires are well aligned along the three equivalent 〈 112{sup ¯}0 〉 directions. Micro-Raman measurements indicate negligible stress and a low defect density inside the wires. Stacking faults were found to be the only defect type in the GaN wire by cross-sectional transmission electron microscopy. The GaN wires exhibited high conductivity, and the resistivity was 20–30 mΩ cm, regardless of the wire thickness. With proper heterostructure and doping design, these highly aligned GaN wires are promising for photonic and electronic applications monolithically integrated on silicon.

  15. Strain-induced step bunching in orientation-controlled GaN on Si

    NASA Astrophysics Data System (ADS)

    Narita, Tetsuo; Iguchi, Hiroko; Horibuchi, Kayo; Otake, Nobuyuki; Hoshi, Shinichi; Tomita, Kazuyoshi

    2016-05-01

    We report a technique for the fabrication of high-quality GaN-on-silicon (Si) substrates for use in various power applications. GaN epitaxial layers were generated on Si(111) vicinal faces that had been previously covered with a thin coating of Al2O3 to control the orientation of the AlN seed layers. We obtained orientation-controlled GaN layers and found a linear relationship between the GaN c-axis and Si[111] tilt angles. As a result, the threading dislocation density in the AlN seed layer was reduced and high-quality GaN layers were generated. The X-ray rocking curves for these layers exhibited full width at half maximum values of 390‧‧ and 550‧‧ for the (004) and (114) reflections, respectively. Significant step bunching was observed on a GaN(0001) vicinal face produced using this technique, attributed to strain-induced attractive interactions between steps. Thus, by controlling the strain near the surface layer, we achieved the step flow growth of GaN on Si.

  16. Layered transition metal dichalcogenides: promising near-lattice-matched substrates for GaN growth

    PubMed Central

    Gupta, Priti; Rahman, A. A.; Subramanian, Shruti; Gupta, Shalini; Thamizhavel, Arumugam; Orlova, Tatyana; Rouvimov, Sergei; Vishwanath, Suresh; Protasenko, Vladimir; Laskar, Masihhur R.; Xing, Huili Grace; Jena, Debdeep; Bhattacharya, Arnab

    2016-01-01

    Most III-nitride semiconductors are grown on non-lattice-matched substrates like sapphire or silicon due to the extreme difficulty of obtaining a native GaN substrate. We show that several layered transition-metal dichalcogenides are closely lattice-matched to GaN and report the growth of GaN on a range of such layered materials. We report detailed studies of the growth of GaN on mechanically-exfoliated flakes WS2 and MoS2 by metalorganic vapour phase epitaxy. Structural and optical characterization show that strain-free, single-crystal islands of GaN are obtained on the underlying chalcogenide flakes. We obtain strong near-band-edge emission from these layers, and analyse their temperature-dependent photoluminescence properties. We also report a proof-of-concept demonstration of large-area growth of GaN on CVD MoS2. Our results show that the transition-metal dichalcogenides can serve as novel near-lattice-matched substrates for nitride growth. PMID:27025461

  17. Enhancing the field emission properties of Se-doped GaN nanowires.

    PubMed

    Li, Enling; Wu, Guishuang; Cui, Zhen; Ma, Deming; Shi, Wei; Wang, Xiaolin

    2016-07-01

    Pure and Se-doped GaN nanowires (NWs) are synthesized on Pt-coated Si(111) substrates via chemical vapor deposition. The GaN NWs exhibit a uniform density with an average diameter of 20-120 nm. The structure of the NWs is wurtzite hexagonal, and the growth direction is along [0001]. Field emission measurements show that the Se-doped GaN NWs possess a low turn-on field (2.9 V μm(-1)) compared with the pure GaN NWs (7.0 V μm(-1)). In addition, density functional theory calculations indicate that the donor states near the Fermi level are mainly formed through the hybridization between Se 4p and N 2p orbitals and that the Fermi level move towards the vacuum level. Consequently, the work functions of Se-doped GaN NWs are lower than those of pure GaN NWs. PMID:27197556

  18. Influence of Annealing Conditions on Dopant Antirotation of Si+ and Mg+ Implanted GaN

    SciTech Connect

    Suvkhanov, A.; Parikh, N.; Usov, I.; Hunn, J.D.; Withrow, S.; Thomson, D.; Herke, T.; Davis, R.F.; Krasnobaev, L.

    1999-10-12

    This report reflects the results of heat treatment under various conditions on as-grown and ion implanted GaN. The PL spectrums of as-grown GaN and GaN with 400 A AlN cap were almost identical. This fact allows one to use PL analysis without AlN stripping. As-grown GaN and ion implanted with Mg and Si crystals were annealed at 1300 C for 10 minutes in three different conditions: in flowing argon gas; in flowing ultra high purity nitrogen; and in a quartz capsule sealed with nitrogen gas. The results of PL, RBS, SEM and TEM analysis show an advantage of GaN high temperature annealing in quartz capsules with nitrogen ambient as compared to annealing in argon and nitrogen gas flow. Encapsulation with nitrogen over-pressure prevents the decomposition of the GaN crystal and the AlN capping film, and allows one to achieve optical activation of implanted Mg and Si after 1300 C annealing.

  19. Hybrid device based on GaN nanoneedles and MEH-PPV/PEDOT:PSS polymer

    SciTech Connect

    Shin, Min Jeong; Gwon, Dong-Oh; Lee, Chan-Mi; Lee, Gang Seok; Jeon, In-Jun; Ahn, Hyung Soo; Yi, Sam Nyung; Ha, Dong Han

    2015-08-15

    Highlights: • A hybrid device was demonstrated by using MEH-PPV, PEDOT:PSS, and GaN nanoneedles. • I–V curve of the hybrid device showed its rectification behaviour, similar to a diode. • EL peak originated by the different potential barriers at MEH-PPV and GaN interface. - Abstract: A hybrid device that combines the properties of organic and inorganic semiconductors was fabricated and studied. It incorporated poly[2-methoxy-5-(2-ethylhexyloxy)- 1,4-phenylenevinylene] (MEH-PPV) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as organic polymers and GaN nanoneedles as an inorganic semiconductor. Layers of the two polymers were spin coated on to the GaN nanoneedles. The one peak in the electroluminescence spectrum originated from the MEH-PPV layer owing to the different potential barriers of electrons and holes at its interface with the GaN nanoneedles. However, the photoluminescence spectrum showed peaks due to both GaN nanoneedles and MEH-PPV. Such hybrid structures, suitably developed, might be able to improve the efficiency of optoelectronic devices.

  20. A comparative DFT study of the structural and electronic properties of nonpolar GaN surfaces

    NASA Astrophysics Data System (ADS)

    González-Hernández, Rafael; González-García, Alvaro; Barragán-Yani, Daniel; López-Pérez, William

    2014-09-01

    A comparative analysis of the geometry and the electronic characteristics of nonpolar GaN surfaces was carried out using density-functional theory (DFT) with different approximations for the exchange-correlation energy (LDA, PBE, PBEsol, RPBE, TPSS, revTPSS, and HSE). The obtained data show that the GaN(1 0 1bar 0) (m-plane) is more energetically stable than the GaN(1 1 2bar 0) (a-plane) surface. However, these surfaces have similar surface relaxation geometry, with a Ga-N surface bond-length contraction of around 6-7% and a Ga-N surface rotational angle in the range of 6-9°. Our results show that the use of different exchange-correlation functionals does not significantly change the surface energy and surface geometry. In addition, we found the presence of surface intra-gap states that reduce the band gap of the nonpolar GaN surface with respect to the bulk value, in agreement with recent photoelectron and surface optical spectroscopy experiments.

  1. Layered transition metal dichalcogenides: promising near-lattice-matched substrates for GaN growth

    NASA Astrophysics Data System (ADS)

    Gupta, Priti; Rahman, A. A.; Subramanian, Shruti; Gupta, Shalini; Thamizhavel, Arumugam; Orlova, Tatyana; Rouvimov, Sergei; Vishwanath, Suresh; Protasenko, Vladimir; Laskar, Masihhur R.; Xing, Huili Grace; Jena, Debdeep; Bhattacharya, Arnab

    2016-03-01

    Most III-nitride semiconductors are grown on non-lattice-matched substrates like sapphire or silicon due to the extreme difficulty of obtaining a native GaN substrate. We show that several layered transition-metal dichalcogenides are closely lattice-matched to GaN and report the growth of GaN on a range of such layered materials. We report detailed studies of the growth of GaN on mechanically-exfoliated flakes WS2 and MoS2 by metalorganic vapour phase epitaxy. Structural and optical characterization show that strain-free, single-crystal islands of GaN are obtained on the underlying chalcogenide flakes. We obtain strong near-band-edge emission from these layers, and analyse their temperature-dependent photoluminescence properties. We also report a proof-of-concept demonstration of large-area growth of GaN on CVD MoS2. Our results show that the transition-metal dichalcogenides can serve as novel near-lattice-matched substrates for nitride growth.

  2. Using the kinetic Wulff plot to design and control nonpolar and semipolar GaN heteroepitaxy

    NASA Astrophysics Data System (ADS)

    Leung, Benjamin; Sun, Qian; Yerino, Christopher D.; Han, Jung; Coltrin, Michael E.

    2012-02-01

    For nonpolar and semipolar orientations of GaN heteroepitaxially grown on sapphire substrates, the development of growth procedures to improve surface morphology and microstructure has been driven in a largely empirical way. This work attempts to comprehensively link the intrinsic properties of GaN faceted growth, across orientations, in order to understand, design and control growth methods for nonpolar (1 1 2 0) GaN and semipolar (1 1 2 2) GaN on foreign substrates. This is done by constructing a comprehensive series of kinetic Wulff plots (or v-plots) by monitoring the advances of convex and concave facets in selective area growth. A methodology is developed to apply the experimentally determined v-plots to the interpretation and design of evolution dynamics in nucleation and island coalescence. This methodology offers a cohesive and rational model for GaN heteroepitaxy along polar, nonpolar and semipolar orientations, and is broadly extensible to the heteroepitaxy of other materials. We demonstrate furthermore that the control of morphological evolution, based on invoking a detailed knowledge of the v-plots, holds a key to the reduction of microstructural defects through effective bending of dislocations and blocking of stacking faults. The status and outlook of semipolar and nonpolar GaN growth on sapphire substrates will be presented.

  3. The hydride vapor phase epitaxy of GaN on silicon covered by nanostructures

    NASA Astrophysics Data System (ADS)

    Jahn, U.; Musolino, M.; Lähnemann, J.; Dogan, P.; Fernández Garrido, S.; Wang, J. F.; Xu, K.; Cai, D.; Bian, L. F.; Gong, X. J.; Yang, H.

    2016-06-01

    GaN several tens of μm thick has been deposited on a silicon substrate using a two-step hydride vapor phase epitaxy (HVPE) process. The substrates were covered by AlN layers and GaN nanostructures grown by plasma-assisted molecular-beam epitaxy. During the first low-temperature (low-T) HVPE step, stacking faults (SF) form, which show distinct luminescence lines and stripe-like features in the cathodoluminescence images of the cross-section of the layers. These cathodoluminescence features provide an insight into the growth process. During a second high-temperature (high-T) step, the SFs disappear, and the luminescence of this part of the GaN layer is dominated by the donor-bound exciton. For templates consisting of both a thin AlN buffer and GaN nanostructures, the incorporation of silicon into the GaN grown by HVPE is not observed. Moreover, the growth mode of the (high-T) HVPE step depends on the specific structure of the AlN/GaN template, where in the first case, epitaxy is dominated by the formation of slowly growing facets, while in the second case, epitaxy proceeds directly along the c-axis. For templates without GaN nanostructures, cathodoluminescence spectra excited close to the Si/GaN interface show a broadening toward higher energies, indicating the incorporation of silicon at a high dopant level.

  4. Reduction of stress at the initial stages of GaN growth on Si(111)

    NASA Astrophysics Data System (ADS)

    Dadgar, A.; Poschenrieder, M.; Reiher, A.; Bläsing, J.; Christen, J.; Krtschil, A.; Finger, T.; Hempel, T.; Diez, A.; Krost, A.

    2003-01-01

    GaN growth on heterosubstrates usually leads to an initially high dislocation density at the substrate/seed layer interface. Due to the initial growth from small crystallites, tensile stress is generated at the coalescence boundaries during GaN growth. In addition, with tensile thermal stress this leads to cracking of GaN on Si and SiC substrates when cooling to room temperature. By partially masking the typically applied AlN seed layer on Si(111) with an in situ deposited SiN mask a reduction in tensile stress can be achieved for the subsequently grown GaN layer. Additionally, the 6 K GaN band edge photoluminescence is increased by about an order of magnitude and shifts by 21 meV, which can be attributed to a change in tensile stress of ˜0.8 GPa, in good agreement with x-ray diffractometry measurements. This improvement in material properties can be attributed to a reduction of grain boundaries by the growth of larger sized crystallites and lateral overgrowth of less defective GaN.

  5. Semantic Priming from Letter-Searched Primes Occurs for Low- but Not High-Frequency Targets: Automatic Semantic Access May Not Be a Myth

    ERIC Educational Resources Information Center

    Tse, Chi-Shing; Neely, James H.

    2007-01-01

    Letter-search (LS) within a prime often eliminates semantic priming. In 2 lexical decision experiments, the authors found that priming from LS primes occurred for low-frequency (LF) but not high-frequency (HF) targets whether the target's word frequency was manipulated between or within participants and whether the prime-target pairs were…

  6. GaN Metal Oxide Semiconductor Field Effect Transistors

    SciTech Connect

    Ren, F.; Pearton, S.J.; Abernathy, C.R.; Baca, A.; Cheng, P.; Shul, R.J.; Chu, S.N.G.; Hong, M.; Lothian, J.R.; Schurman, M.J.

    1999-03-02

    A GaN based depletion mode metal oxide semiconductor field effect transistor (MOSFET) was demonstrated using Ga{sub 2}O{sub 3}(Gd{sub 2}O{sub 3}) as the gate dielectric. The MOS gate reverse breakdown voltage was > 35V which was significantly improved from 17V of Pt Schottky gate on the same material. A maximum extrinsic transconductance of 15 mS/mm was obtained at V{sub ds} = 30 V and device performance was limited by the contact resistance. A unity current gain cut-off frequency, f{sub {tau}}, and maximum frequency of oscillation, f{sub max} of 3.1 and 10.3 GHz, respectively, were measured at V{sub ds} = 25 V and V{sub gs} = {minus}20 V.

  7. Stacking fault related luminescence in GaN nanorods.

    PubMed

    Forsberg, M; Serban, A; Poenaru, I; Hsiao, C-L; Junaid, M; Birch, J; Pozina, G

    2015-09-01

    Optical and structural properties are presented for GaN nanorods (NRs) grown in the [0001] direction on Si(111) substrates by direct-current reactive magnetron sputter epitaxy. Transmission electron microscopy (TEM) reveals clusters of dense stacking faults (SFs) regularly distributed along the c-axis. A strong emission line at ∼3.42 eV associated with the basal-plane SFs has been observed in luminescence spectra. The optical signature of SFs is stable up to room temperatures with the activation energy of ∼20 meV. Temperature-dependent time-resolved photoluminescence properties suggest that the recombination mechanism of the 3.42 eV emission can be understood in terms of multiple quantum wells self-organized along the growth axis of NRs. PMID:26267041

  8. Inversion domains in GaN grown on sapphire

    SciTech Connect

    Romano, L.T.; Northrup, J.E.; OKeefe, M.A.

    1996-10-01

    Planar defects observed in GaN films grown on (0001) sapphire have been identified as inversion domain boundaries (IDBs) by a combination of high resolution transmission electron microscopy, multiple dark field imaging, and convergent beam electron diffraction techniques. Films grown by molecular beam epitaxy (MBE), metalorganic vapor deposition (MOCVD), and hydride vapor phase epitaxy (HVPE) were investigated and all were found to contain IDBs. The IDBs in the MBE and HVPE films extended from the interface to the film surface and formed columnar domains that ranged in width from 3 to 20 nm in the MBE films and up to 100 nm in the HVPE films. For the films investigated, the MBE films had the highest density, and the MOCVD films had the lowest density of IDBs. The nucleation of inversion domains (IDs) may result from step-related inhomogeneities of the GaN/sapphire interface. {copyright} {ital 1996 American Institute of Physics.}

  9. GaN directional couplers for integrated quantum photonics

    SciTech Connect

    Zhang Yanfeng; McKnight, Loyd; Watson, Ian M.; Gu, Erdan; Calvez, Stephane; Dawson, Martin D.; Engin, Erman; Cryan, Martin J.; Thompson, Mark G.; O'Brien, Jeremy L.

    2011-10-17

    Large cross-section GaN waveguides are proposed as a suitable architecture to achieve integrated quantum photonic circuits. Directional couplers with this geometry have been designed with aid of the beam propagation method and fabricated using inductively coupled plasma etching. Scanning electron microscopy inspection shows high quality facets for end coupling and a well defined gap between rib pairs in the coupling region. Optical characterization at 800 nm shows single-mode operation and coupling-length-dependent splitting ratios. Two photon interference of degenerate photon pairs has been observed in the directional coupler by measurement of the Hong-Ou-Mandel dip [C. K. Hong, et al., Phys. Rev. Lett. 59, 2044 (1987)] with 96% visibility.

  10. Spontaneous emission enhancement in micropatterned GaN

    NASA Astrophysics Data System (ADS)

    Niehus, M.; Sanguino, P.; Monteiro, T.; Soares, M. J.; Schwarz, R.

    2004-10-01

    With two interfering pulses from the fourth harmonic of a Nd-YAG laser we burnt a periodic lattice structure into the surface of GaN thin films. The lattice period of this permanent grating could be controlled between less than one and several tens of microns. Above the decomposition threshold, nitrogen evades from the sample surface, and the residual metallic gallium accumulates in the form of tiny droplets at the surfaces. The patterned structure shows structural similarities with microcavities. The question arises if the residual metallic gallium may act as a partially reflecting mirror. To test this hypothesis, we studied the steady-state and transient photoluminescence through the modulation of light emerging from the ubiquitous broad "yellow" photoluminescence band. The microlattice is evidenced by energy-equidistant spontaneous emission enhancement peaks in the steady-state photoluminescence spectra. We suggest that the partial reflection due to the residual metallic gallium leads to the observed enhancement effect.

  11. Influence of dopants on defect formation in GaN

    SciTech Connect

    Liliental-Weber, Z.; Jasinski, J.; Benamara, M.; Grzegory, I.; Porowski, S.; Lampert, D.J.H.; Eiting, C.J.; Dupuis R.D.

    2001-10-15

    Influence of p-dopants (Mg and Be) on the structure of GaN has been studied using Transmission Electron Microscopy (TEM). Bulk GaN:Mg and GaN:Be crystals grown by a high pressure and high temperature process and GaN:Mg grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering in bulk GaN:Mg on c-plane (formation of Mg-rich planar defects with characteristics of inversion domains) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects empty inside (pinholes) were observed. Both these defects were also observed in MOCVD grown crystals. Pyramidal defects were also observed in the bulk GaN:Be crystals.

  12. Intrinsic polarization control in rectangular GaN nanowire lasers

    DOE PAGESBeta

    Li, Changyi; Liu, Sheng; Luk, Ting S.; Figiel, Jeffrey J.; Brener, Igal; Brueck, S. R. J.; Wang, George T.

    2016-02-01

    In this study, we demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444kW/cm2 and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control overmore » the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates.« less

  13. Intrinsic polarization control in rectangular GaN nanowire lasers.

    PubMed

    Li, Changyi; Liu, Sheng; Luk, Ting S; Figiel, Jeffrey J; Brener, Igal; Brueck, S R J; Wang, George T

    2016-03-01

    We demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444 kW cm(-2) and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control over the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates. PMID:26899502

  14. Enhanced water splitting with silver decorated GaN photoelectrode

    NASA Astrophysics Data System (ADS)

    Hou, Y.; Syed, Z. A.; Smith, R.; Athanasiou, M.; Gong, Y.; Yu, X.; Bai, J.; Wang, T.

    2016-07-01

    By means of a cost-effective approach, we demonstrate a GaN-based photoelectrode decorated with self-organized silver nano-islands employed for solar powered hydrogen generation, demonstrating 4 times increase in photocurrent compared with a reference sample without using any silver. Our photoelectrode exhibits a 60% incident photon-to-electron conversion efficiency. The enhanced hydrogen generation is attributed to a significantly increased carrier generation rate as a result of strongly localized electric fields induced by surface plasmon coupling effect. The silver coating also contributes to the good chemical stability of our photoelectrode in a strong alkali electrolyte. This work paves the way for the development of GaN and also InGaN based photoelectrodes with ultra-high solar hydrogen conversion efficiency.

  15. Intrinsic polarization control in rectangular GaN nanowire lasers

    NASA Astrophysics Data System (ADS)

    Li, Changyi; Liu, Sheng; Luk, Ting. S.; Figiel, Jeffrey J.; Brener, Igal; Brueck, S. R. J.; Wang, George T.

    2016-03-01

    We demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444 kW cm-2 and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control over the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates.

  16. Defect Donor and Acceptor in GaN

    SciTech Connect

    Look, D.C.; Reynolds, D.C.; Hemsky, J.W.; Sizelove, J.R.; Jones, R.L.

    1997-09-01

    High-energy (0.7{endash}1MeV) electron irradiation in GaN grown on sapphire produces shallow donors and deep or shallow acceptors at equal rates, 1{plus_minus}0.2 cm{sup {minus}1}. The data, in conjunction with theory, are consistent only with the shallow donor being the N vacancy, and the acceptor the N interstitial. The N-vacancy donor energy is 64{plus_minus}10 meV, much larger than the value of 18meV found for the residual donor (probably Si) in this material. The Hall-effect measurements also reveal a degenerate n -type layer at the GaN/sapphire interface which must be accounted for to get the proper donor activation energy. {copyright} {ital 1997} {ital The American Physical Society}

  17. Surface photovoltage in undoped n-type GaN

    NASA Astrophysics Data System (ADS)

    Reshchikov, M. A.; Foussekis, M.; Baski, A. A.

    2010-06-01

    Steady-state and transient surface photovoltage (SPV) in undoped GaN is studied in vacuum and air ambient at room temperature and 400 K with a Kelvin probe. The results are explained within a phenomenological model accounting for the accumulation of photogenerated holes at the surface, capture of free electrons from the bulk over the near-surface potential barrier, and emission of electrons from surface states into the bulk. Simple analytical expressions are obtained and compared with experimental results. In particular, the proposed model explains the logarithmic decay of the SPV after stopping illumination. Internal and external mechanisms of the SPV are discussed in detail. It is shown that an internal mechanism dominates at low illumination intensity and/or small photon energies, while external mechanisms such as charging of a surface oxide layer and photoinduced processes play a significant role for above-bandgap illumination with sufficient intensity.

  18. Spatial distribution of defect luminescence in GaN nanowires.

    PubMed

    Li, Qiming; Wang, George T

    2010-05-12

    The spatial distribution of defect-related and band-edge luminescence from GaN nanowires grown by metal-organic chemical vapor deposition was studied by spatially resolved cathodoluminescence imaging and spectroscopy. A surface layer exhibiting strong yellow luminescence (YL) near 566 nm in the nanowires was revealed, compared to weak YL in the bulk. In contrast, other defect-related luminescence near 428 nm (blue luminescence) and 734 nm (red luminescence), in addition to band-edge luminescence (BEL) at 366 nm, were observed in the bulk of the nanowires but were largely absent at the surface. As the nanowire width approaches a critical dimension, the surface YL layer completely quenches the BEL. The surface YL is attributed to the diffusion and piling up of mobile point defects, likely isolated gallium vacancies, at the surface during growth. PMID:20392110

  19. Persistent photoconductivity in n-type GaN

    SciTech Connect

    Hirsch, M.T.; Wolk, J.A.; Walukiewicz, W.; Haller, E.E.

    1997-08-01

    We report on the spectral and temperature dependence of persistent photoconductivity (PPC) in metal-organic chemical vapor deposition grown unintentionally doped n-type GaN. The PPC effect is detectable up to temperatures of at least 352 K, the highest temperature used in this study. At 77 K, the conduction persists at a level 80{percent} higher than the equilibrium dark conduction for over 10{sup 4} s after removing the excitation. We have determined the spectral dependence for the optical cross section for PPC and obtain an optical ionization energy of {approximately}2.7 eV. The temperature dependence of the photoconductivity decay and its nonexponential shape are explained by a distribution of capture barriers with a mean capture barrier of 0.2 eV and a width of {approximately}26 meV. {copyright} {ital 1997 American Institute of Physics.}

  20. Microstructure of laterally overgrown GaN layers

    SciTech Connect

    Liliental-Weber, Zuzanna; Cherns, David

    2001-04-03

    Transmission electron microscopy study of plan-view and cross-section samples of epitaxial laterally overgrown (ELOG) GaN samples is described. Two types of dislocation with the same type of Burgers vector but different line direction have been observed. It is shown that threading edge dislocations bend to form dislocation segments in the c-plane as a result of shear stresses developed in the wing material along the stripe direction. It is shown that migration of these dislocations involves both glide and climb. Propagation of threading parts over the wing area is an indication of high density of point defects present in the wing areas on the ELOG samples. This finding might shed new light on the optical properties of such samples.