Academic literature on the topic 'AlGaN/AlGaN Duv Leds'
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Journal articles on the topic "AlGaN/AlGaN Duv Leds"
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Wang, Tien-Yu, Wei-Chih Lai, Syuan-Yu Sie, Sheng-Po Chang, Cheng-Huang Kuo, and Jinn-Kong Sheu. "Deep Ultraviolet AlGaN-Based Light-Emitting Diodes with p-AlGaN/AlGaN Superlattice Hole Injection Structures." Processes 9, no. 10 (2021): 1727. http://dx.doi.org/10.3390/pr9101727.
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The p-AlGaN/AlGaN superlattice (SL) hole injection structure was introduced into deep ultraviolet (DUV) light-emitting diodes (LEDs) to enhance their performances. The period thicknesses of the p-Al0.8Ga0.2N/Al0.48Ga0.52N SLs affected the performances of the DUV LEDs. The appropriate period thickness of the p-Al0.8Ga0.2N/Al0.48Ga0.52N SL may enhance the hole injection of DUV LEDs. Therefore, compared with the reference LEDs, the DUV LEDs with the 10-pair Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL presented forward voltage reduction of 0.23 V and light output power improvement of 15% at a current of 350 mA. Furthermore, the 10-pair Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL could slightly suppress the Auger recombination and current overflow of the DUV LEDs in a high-current operation region. In addition to improved carrier injection, the DUV LEDs with the p-Al0.8Ga0.2N/Al0.48Ga0.52N SL hole injection structure showed reduced light absorption at their emission wavelength compared with the reference LEDs. Therefore, the DUV LEDs with p-Al0.8Ga0.2N/Al0.48Ga0.52N SL may exhibit better light extraction efficiency than the reference LEDs. The enhancement of p-Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL may contribute to improvements in light extraction and hole injection.
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Gong, Mingfeng, Xuejiao Sun, Cheng Lei, et al. "Study on the Degradation Performance of AlGaN-Based Deep Ultraviolet LEDs under Thermal and Electrical Stress." Coatings 14, no. 7 (2024): 904. http://dx.doi.org/10.3390/coatings14070904.
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AlGaN-based deep-ultraviolet (DUV) LEDs could realize higher optical power output when adopting a p-AlGaN contact layer instead of a p-GaN contact layer. However, this new type DUV LEDs exhibit poor reliability. Thus, this study thoroughly investigates the degradation behaviors of AlGaN-based DUV LEDs with a p-AlGaN contact layer through different aging tests, including single thermal stress, single electrical stress with air-cooling, single electrical stress, and thermoelectric complex stress. It can be found that both high temperature and large working current play crucial roles in accelerating the degradation of optoelectronic properties of the DUV LEDs, and the single high thermal stress without electrical stress can also bring obvious performance degradation to the DUV LEDs, which is a significantly different finding from previous studies. This is because thermal stress on DUV LED could bring some metal electrode elements entering the p-AlGaN layer. Thus, the degradation of optical and electrical properties under the thermal and electrical stress could be not only attributed to the degradation of the device’s ohmic contacts, but also due to the metal electrode elements entering the p-AlGaN layer through thermal diffusion, leading to the generation of tunneling current and the generation of defects within or around the active region. Despite that the peak wavelengths of the DUV LEDs remained stable, the turn-on voltage and series resistance increased. Particularly worth mentioning is that the value of the optical power degradation under thermoelectric conditions is larger than the sum of the single thermal and single electrical optical power degradation, which is a result of the mutual reinforcement of thermal and electrical stresses to exacerbate the defect generation and ohmic contact degradation. Based on the study above, preparing p-AlGaN layers with hyperfine gradient aluminum fractions and reducing the junction temperature may help to improve the reliability of AlGaN-based DUV LEDs with the p-AlGaN contact layer.
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Xu, Ruiqiang, Qiushi Kang, Youwei Zhang, Xiaoli Zhang, and Zihui Zhang. "Research Progress of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes." Micromachines 14, no. 4 (2023): 844. http://dx.doi.org/10.3390/mi14040844.
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AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) have great application prospects in sterilization, UV phototherapy, biological monitoring and other aspects. Due to their advantages of energy conservation, environmental protection and easy miniaturization realization, they have garnered much interest and been widely researched. However, compared with InGaN-based blue LEDs, the efficiency of AlGaN-based DUV LEDs is still very low. This paper first introduces the research background of DUV LEDs. Then, various methods to improve the efficiency of DUV LED devices are summarized from three aspects: internal quantum efficiency (IQE), light extraction efficiency (LEE) and wall-plug efficiency (WPE). Finally, the future development of efficient AlGaN-based DUV LEDs is proposed.
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Băjenescu, Titu-Marius I. "DEEP ULTRAVIOLET LIGHT EMITTING DIODES (DUV LEDS)." Journal of Engineering Science XXV (2) (June 15, 2018): 6–19. https://doi.org/10.5281/zenodo.2559253.
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There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; the device-quality material, is deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates.
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Wang, Tien-Yu, Wei-Chih Lai, Qiao-Ju Xie, et al. "The influences of AlGaN barrier epitaxy in multiple quantum wells on the optoelectrical properties of AlGaN-based deep ultra-violet light-emitting diodes." RSC Advances 13, no. 8 (2023): 5437–43. http://dx.doi.org/10.1039/d2ra07368d.
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Liu, Cheng, Bryan Melanson, and Jing Zhang. "AlGaN-Delta-GaN Quantum Well for DUV LEDs." Photonics 7, no. 4 (2020): 87. http://dx.doi.org/10.3390/photonics7040087.
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AlGaN-delta-GaN quantum well (QW) structures have been demonstrated to be good candidates for the realization of high-efficiency deep-ultraviolet (DUV) light-emitting diodes (LEDs). However, such heterostructures are still not fully understood. This study focuses on investigation of the optical properties and efficiency of the AlGaN-delta-GaN QW structures using self-consistent six-band k⸱p modelling and finite difference time domain (FDTD) simulations. Structures with different Al contents in the AlxGa1−xN sub-QW and AlyGa1−yN barrier regions are examined in detail. Results show that the emission wavelength (λ) can be engineered through manipulation of delta-GaN layer thickness, sub-QW Al content (x), and barrier Al content (y), while maintaining a large spontaneous emission rate corresponding to around 90% radiative recombination efficiency (ηRAD). In addition, due to the dominant transverse-electric (TE)-polarized emission from the AlGaN-delta-GaN QW structure, the light extraction efficiency (ηEXT) is greatly enhanced when compared to a conventional AlGaN QW. Combined with the large ηRAD, this leads to the significant enhancement of external quantum efficiency (ηEQE), indicating that AlGaN-delta-GaN structures could be a promising solution for high-efficiency DUV LEDs.
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Chang, Jih-Yuan, Man-Fang Huang, Chih-Yung Huang, Shih-Chin Lin, Ching-Chiun Wang, and Yen-Kuang Kuo. "Band-Engineered Structural Design of High-Performance Deep-Ultraviolet Light-Emitting Diodes." Crystals 11, no. 3 (2021): 271. http://dx.doi.org/10.3390/cryst11030271.
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In this study, systematic structural design was investigated numerically to probe into the cross-relating influences of n-AlGaN layer, quantum barrier (QB), and electron-blocking layer (EBL) on the output performance of AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) with various Al compositions in quantum wells. Simulation results show that high-Al-composition QB and high-Al-composition EBL utilized separately are beneficial for the enhancement of carrier confinement, while the wall-plug efficiency (WPE) degrades dramatically if both high-Al-composition QB and EBL are existing in a DUV LED structure simultaneously. DUV LEDs may be of great optical performance with appropriate structural design by fine-tuning the material parameters in n-AlGaN layer, QB, and EBL. The design curves provided in this paper can be very useful for the researchers in developing the DUV LEDs with a peak emission wavelength ranging from 255 nm to 285 nm.
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Amano, Hiroshi, Masataka Imura, Motoaki Iwaya, Satoshi Kamiyama, and Isamu Akasaki. "AlN and AlGaN by MOVPE for UV Light Emitting Devices." Materials Science Forum 590 (August 2008): 175–210. http://dx.doi.org/10.4028/www.scientific.net/msf.590.175.
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The fundamental growth issues of AlN and AlGaN on sapphire and SiC using metalorganic vapor phase epitaxy, particularly the growth of AlN and AlGaN on a groove-patterned template are reviewed. In addition, the conductivity control of AlGaN is shown. The conductivity control of p-type AlGaN, particularly the realization of a high hole concentration, is essential for realizing high-efficiency UV and DUV LEDs and LDs.
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Yang, Sipan, Miao He, Jianchang Yan, et al. "Enhanced electrical performance by modulation-doping in AlGaN-based deep ultraviolet light-emitting diodes." Modern Physics Letters B 33, no. 08 (2019): 1950088. http://dx.doi.org/10.1142/s021798491950088x.
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Through the silicon modulation-doping (MD) growth method, the electrical performance of AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) is improved by replacing the commonly uniform-doped (UD) method of n-AlGaN layer. The electroluminescence characterisic measurements demonstrate the MD growth method could effectively enhance the light emission intensity. Both the forward voltage and reverse leakage current of the MD samples are obviously reduced compared to those of the UD sample. Due to the existence of periodic Si-MD superlattices in n-AlGaN layers, which may behave like a series of capacitors, the built-in electric fields are formed. Both the measured capacitance–voltage (C–V) characteristics, and related photoluminescence (PL) intensity with the Si-MD growth method are enhanced. In detail, the effects of these capacitors can enhance the peak internal capacitance up to 370 pF in the MD sample, whereas the UD sample is only 180 pF. The results also mean that with better current spreading ability in the MD sample, the MD processes can effectively enhance the efficiency and reliability of DUV-LEDs. Thus, the investigations of the Si-MD growth methods may be useful for improving the electrical performance of DUV-LEDs in future works. Meanwhile, this investigation may partly suggest the minor crystalline quality improvements in the epi-layers succeeding the MD n-AlGaN layer.
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Nagasawa, Yosuke, and Akira Hirano. "A Review of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on Sapphire." Applied Sciences 8, no. 8 (2018): 1264. http://dx.doi.org/10.3390/app8081264.
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This paper reviews the progress of AlGaN-based deep-ultraviolet (DUV) light emitting diodes (LEDs), mainly focusing in the work of the authors’ group. The background to the development of the current device structure on sapphire is described and the reason for using a (0001) sapphire with a miscut angle of 1.0° relative to the m-axis is clarified. Our LEDs incorporate uneven quantum wells (QWs) grown on an AlN template with dense macrosteps. Due to the low threading dislocation density of AlGaN and AlN templates of about 5 × 108/cm2, the number of nonradiative recombination centers is decreased. In addition, the uneven QW show high external quantum efficiency (EQE) and wall-plug efficiency, which are considered to be boosted by the increased internal quantum efficiency (IQE) by enhancing carrier localization adjacent to macrosteps. The achieved LED performance is considered to be sufficient for practical applications. The advantage of the uneven QW is discussed in terms of the EQE and IQE. A DUV-LED die with an output of over 100 mW at 280–300 nm is considered feasible by applying techniques including the encapsulation. In addition, the fundamental achievements of various groups are reviewed for the future improvements of AlGaN-based DUV-LEDs. Finally, the applications of DUV-LEDs are described from an industrial viewpoint. The demonstrations of W/cm2-class irradiation modules are shown for UV curing.
Dissertations / Theses on the topic "AlGaN/AlGaN Duv Leds"
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Ichikawa, Shuhei. "Fundamental Study on Carrier Recombination Processes in AlGaN-related Materials and their Structural Designs toward Highly Efficient Deep-UV Emitters." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225608.
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Lachèze, Ludovic. "Etude et simulation physique des effets parasites dans les HEMTs AlGaN/GaN." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13975/document.
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Le développement des systèmes de télécommunication et de transfert d’informations motive la mise au point de systèmes de transmission qui permettent des débits plus élevés sur des distances plus grandes. De ce fait, les transistors utilisés dans ces systèmes doivent fonctionner à des fréquences et des puissances plus élevées. Différents transistors sont apparus pour répondre au mieux aux contraintes des applications visées par ces systèmes. Les transistors à haute mobilité électronique, HEMT, en nitrure de gallium (GaN) répondent actuellement aux applications allant de 1GHz à 30GHz. Pour ces applications, les HEMT GaN concurrencent avantageusement les technologies bipolaires et BiCMOS basées sur SiGe, les LDMOS Si et SiC, ainsi que les PHEMT GaAs. Même si la filière technologique GaN est encore récente, les HEMT GaN semblent prometteurs. A l’image des autres technologies III-V (InP, GaAs), les procédés de fabrication utilisés pour les HEMT AlGaN/GaN sont complexes et entraînent la formation de nombreux défauts cristallins. Des effets parasites de fonctionnement sont induits par des mécanismes physiques qui pénalisent le transport des porteurs dans la structure. De ce fait, à l’heure actuelle, ces effets parasites ont une influence négative sur les performances de ce transistor. Ils sont principalement liés aux pièges à électrons induits par des impuretés présentes dans le matériau ou des défauts cristallins. Malgré cela, les performances sont très prometteuses et rivalisent déjà avec d’autres technologies hyperfréquences (InP, GaAs, SiC et Si) puisque les HEMTs AlGaN/GaN débitent des puissances de 4W/mm à 30GHz [ITRS08]. Les travaux présentés dans ce manuscrit sont consacrés à l'étude des phénomènes parasites dans les HEMTs AlGaN/GaN. Les composants étudiés dans ce travail proviennent du programme blanc ANR CARDYNAL et ont été fabriqués par III-V Lab Alcatel-Thales. Une méthodologie a été développer afin de permettre la simulation TCAD d’un HEMT GaN dans l’objectif de valider ou d’invalider les origines des mécanismes de dégradation ainsi que des effets parasites. Le courant de grille a été spécialement étudié et un modèle analytique permettant de le décrire en fonction de la température a été développé. Les mécanismes de transport à travers la grille ont aussi été étudiés par simulation TCAD afin de les localiser géographiquement dans la structure du transistor<br>III-V nitrides have attracted intense interest recently for applications in high-temperature, high-power electronic devices operating at microwave frequencies. Great progress has been made in recent years to improve the characteristics of nitride High Electron Mobility Transistors (HEMTs). However, it's necessary to study the mecanisms involved in the electron transport as the mechanic strain on the AlGaN layer, the fixed charge distribution and leakage currents. In this goal, from DC I-V measurements, pulsed I-V measurements and DCTS measurements, TCAD simulation are used to validate the assumption on the origin of the parasitic mechanisms on the electron transport. I-V measurement in temperature (from 100K to 200K) are used to identify the nature of mechanisms (Poole-Frenkel, band-to-band tunneling, thermionic,..). With this method, an accurate study of the gate current was done. To choose the different physical phenomena and which model to implement in the TCAD simulations, an analytical model was developed with a compraison with measurements. These mechanisms are validated by TCAD simulation. The comparaison between I-V measurements and simulation permit to localize (in the transistor) these parasitic mechanisms. In conclusion of this work, a high density of traps in a thin layer under the gate increase the probability of tunnelling current through the gate. When the gate bias increases, the high density of traps in AlGaN layer is using by electrons to leak by the gate. When the gate bias increases, the valence band in AlGaN layer is aligned with the conduction band in the channel. The very thin thickness of this layer (about 25nm) makes possible a band-to-band tunneling
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Küller, Viola [Verfasser], Markus [Akademischer Betreuer] Weyers, Michael [Akademischer Betreuer] Kneissl, and Detlef [Akademischer Betreuer] Hommel. "Versetzungsreduzierte AlN- und AlGaN-Schichten als Basis für UV LEDs / Viola Küller. Gutachter: Michael Kneissl ; Markus Weyers ; Detlef Hommel. Betreuer: Markus Weyers." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1066546606/34.
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Carosella, Francesca. "Étude théorique des phénomènes de transport électronique dans les puits quantiques AlGaN/GaN." Lille 1, 2005. http://www.theses.fr/2005LIL10125.
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Les hétérostructures AlGaN/GaN ont la particularité de supporter à leur interface des puits quantiques, dont la densité électronique peut atteindre des valeurs aussi élevées que 10 ^13 cm-2 sans dopage volontaire. Ils offrent ainsi la possibilité de fabriquer des composants électroniques de puissance ainsi que des composants hyperfréquences, dans la mesure où leur qualité cristalline permet également aux porteurs de charge d'avoir une bonne mobilité. Nous nous sommes intéressés à l'étude théorique des mécanismes de diffusion présents dans ces matériaux, de façon à identifier la nature des défauts responsables des faibles valeurs de mobilité mesurées sur des échantillons obtenus dans l'état de l'art de la croissance épitaxiale. Nous avons, avant tout, montré par des calculs auto-cohérents, que ces puits quantiques étaient caractérisés par la présence de plusieurs sous-bandes notablement peuplées, ce qui nous a ensuite amené à devoir établir une méthode de résolution de l'équation de Boltzmann, permettant de tenir compte de la possibilité de transitions interbandes, et à devoir établir un formalisme permettant de calculer la réponse diélectrique de ces systèmes multi sous bandes, nécessaire à la détermination des potentiels diffuseurs écrantés<br>Nous avons ensuite abordé l'étude des mécanismes de diffusion intrinsèques, en établissant pour ces systèmes bidimensionnels le potentiel diffuseur associé aux pseudo particules hybrides, résultant de l'interaction entre les phonons optiques et les plasmons. Fort de cette base, qui a permis pour la première fois le calcul de la mobilité théorique maximum, nous avons pu enfin aborder l'étude des centres diffuseurs extrinsèques les plus déterminants Nous avons démontré qu'ils étaient liés à la présence de dislocations ainsi qu'à la qualité des interfaces présentant des rugosités (ou des fluctuations) liées aussi bien à leur structure géométrique qu'à la répartition hétérogène des charges d'interface La comparaison de nos résultats théoriques avec différents résultats expérimentaux a permis de démontrer que les dislocations introduisent des niveaux extrinsèques légers situés à environ 110 meV sous la bande de conduction de GaN et que leur potentiel détermine en grande partie la mobilité des échantillons contenant de faibles valeurs de densité de porteurs, alors que les mécanismes de rugosité, caractérisés par le biais d'un paramètre de corrélation, sont responsables de la chute des valeurs de mobilité dans le domaine des hautes densités de porteurs libres. Ces résultats devraient permettre d'affiner les méthodes de croissance cristalline selon le domaine de densité de porteurs qui sera choisi pour la réalisation des composants
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Enslin, Johannes-Tobias [Verfasser], Michael [Akademischer Betreuer] Kneissl, Michael [Gutachter] Kneissl, Åsa [Gutachter] Haglund, and Ferdinand [Gutachter] Scholz. "MOVPE growth of (In)AlGaN-based heterostructures for thin-film LEDs and VCSELs in the UVB spectral range / Johannes-Tobias Enslin ; Gutachter: Michael Kneissl, Åsa Haglund, Ferdinand Scholz ; Betreuer: Michael Kneissl." Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1230468498/34.
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Liuolia, Vytautas. "Localization effects in ternary nitride semiconductors." Doctoral thesis, KTH, Optik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104290.
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InGaN based blue and near-ultraviolet light emitting diodes and laser diodes have been successfully commercialized for many applications such as general lighting, display backlighting and high density optical storage devices. Despite having a comparably high defect density, these devices are known for their efficient operation, which is attributed to localization in potential fluctuations preventing carriers from reaching the centers of nonradiative recombination. Nitride research is currently headed towards improving deep ultraviolet AlGaN and green InGaN emitters with higher Al and In molar fractions. The efficiency of these devices trails behind the blue counterparts as the carrier localization does not seem to aid in supressing nonradiative losses. In addition, the operation of ternary nitride heterostructure based devices is further complicated by the presence of large built-in electric fields. Although the problem can be ameliorated by growing structures in nonpolar or semipolar directions, the step from research to production still awaits. In this thesis, carrier dynamics and localization effects have been studied in three different nitride ternary compounds: AlGaN epitaxial layers and quantum wells with high Al content, nonpolar m-plane InGaN/GaN quantum wells and lattice matched AlInN/GaN heterostructures. The experimental methods of this work mainly consist of spectroscopy techniques such as time-resolved photoluminescence and differential transmission pump-probe measurements as well as spatial photoluminescence mapping by means of scanning near-field microscopy. The comparison of luminescence and differential transmission measurements has allowed estimating the localization depth in AlGaN quantum wells. Additionally, it has been demonstrated that the polarization degree of luminescence from m-InGaN quantum wells decreases as carriers diffuse to localization centers.What is more, dual-scale localization potential has been evidenced by near-field measurements in both AlGaN and m-InGaN. Larger scale potential fluctuation have been observed directly and the depth of nanoscopic localization has been estimated theoretically from the recorded linewidth of the near-field spectra. Lastly, efficient carrier transport has been observed through AlInN layer despite large alloy inhomogeneities evidenced by broad luminescence spectra and the huge Stokes shift. Inhomogeneous luminescence from the underlying GaN layer has been linked to the fluctuations of the built-in electric field at the AlInN/GaN interface.<br><p>QC 20121101</p>
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Guéno, Josselin. "Détermination et différenciation sexuelle chez les algues brunes." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS629.
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Chez de nombreux eucaryotes, le sexe est déterminé génétiquement par des chromosomes sexuels tels que XY, ZW et UN. Chez de nombreuses algues brunes, le sexe est déterminé génétiquement par les chromosomes IJ et V, plus précisément par la présence de régions spécifiques U (femelles) ou V (mâles) sur ces chromosomes. Un gène candidat pour la détermination du sexe mâle a été découvert dans la région spécifique du chromosome V. Ce gène appartient à la famille des gènes codant pour les protéines à domaine HMG, qui intervient notamment dans la détermination du sexe chez les mammifères et les champignons. Bien que la détermination du sexe soit déclenchée par un gène présent sur les chromosomes sexuels, la différenciation sexuelle est principalement déterminée par l'expression de gènes sexuellement biaisés au niveau des autosomes, qui sont donc présents chez les mâles et les femelles, mais dont le niveau d'expression diffère entre les deux sexes. Le but de ma thèse était d'améliorer notre compréhension des mécanismes qui sous-tendent la détermination et la différenciation du sexe chez les algues brunes. J'ai étudié la protéine HMG liée à la région spécifique mâles chez Ectocarpus, par des techniques de double hybride en levures et de DAP-seq. Par ailleurs, afin de comprendre comment les programmes de développement sexuel sont établis et régulés chez les algues brunes, j'ai examiné les paysages chromatiniens entre les deux sexes à différentes échelles que ce soit au niveau du génome, au niveau chromosomique et au niveau des gènes sexuellement biaisés par une méthode ChlP-seq contre des modifications post-traductionnelles d'histone<br>In many eukaryotes, sex is genetically determined by sex chromosomes such as XY, ZW and IJIV. In many brown algae, sex is genetically determined by the U and V chromosomes, more precisely by the presence of U (female) or V (male)-specific regions on these chromosomes. A candidate gene for male sex deterrnination has been discovered at the V (male)-specific region. This gene belongs to the HMG-domain protein coding gene family, that is involved in gender determination in mammals and fungi. Although sex determination is triggered by a gene present on the sex chromosomes, sexual differentiation is mainly driven by autosomal sex-biased gene expression, which are therefore present in both males and females. My thesis's goal was to increase our understanding of the mechanisms underlying sex determination and differentiation in brown algae. I studied the HMG protein linked to the (male)-specific regions in Ectocarpus, by a yeast two hybrid method and DAP-seq. In order to understand how sex-specific developmental programs are established and regulated in the brown algae, I examined the sex- and chromosome-specific chromatin landscapes by a ChlP-seq method, and explored variant lines that are impaired in the expression of their sex-specific developmental programs
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Di, Giacomo Michael. "Les pentecôtistes québécois, 1966-1995 : histoire d'un réveil." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0017/NQ47564.pdf.
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Borderie, Fabien. "Utilisation du rayonnement UV-C comme méthode alternative aux produits chimiques dans la lutte et le contrôle de la prolifération des micro-organismes sur les matériaux du patrimoine." Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2038/document.
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L’objectif général de cette thèse est d’étudier et d’analyser l’effet du rayonnement UV-C comme méthodealternative aux produits chimiques dans la lutte et le contrôle de la prolifération des micro-organismesphotosynthétiques dans les grottes touristiques. Dans un premier temps, l’effet des UV-C a été analysé surdifférentes souches cavernicoles de micro-algues cultivées au laboratoire. Des analyses à l’échelle moléculaire,cellulaire et à l’échelle du biofilm d’algues ont permis de mettre en évidence un ensemble de dommages causépar l’irradiation aux UV-C (diminution de la viabilité et de l’activité photosynthétique, dégradation desmembranes, décoloration des cellules par destruction des pigments chlorophylliens, fragmentation de l’ADN,diminution de la surface d’occupation des biofilms d’algues cultivés sur support solide). Ceux-ci sont soit directs(réactions de photooxydation) soit indirects (liés à un stress oxydatif important). L’ensemble de ces résultats ontservi à la sélection de différentes durées d’exposition aux UV-C (traduites en doses d’UV-C) efficaces en termesd’éradication et de décoloration des micro-algues. Ces doses d’UV-C ont dans un deuxième temps été testées enconditions réelles sur le site d’étude de la grotte des Moidons (Jura, France). Une étude préalable à ces tests a étémenée afin de comprendre les dynamiques et les facteurs favorisant l’installation et la prolifération des biofilmsde micro-organismes photosynthétiques dans la grotte. L’étude des facteurs environnementaux mesurés àl’échelle du biofilm (quantité de lumière, type de support, localisation dans la grotte) ainsi que ceux mesurés àl’échelle de la cavité (circulation horizontale et verticale des eaux, vitesse des courants d’air, temps d’allumagedes lampes et temps de présence des visiteurs) ont permis de distinguer des zones de colonisation préférentielle.Plusieurs biofilms ont ensuite été sélectionnés pour tester l’efficacité des UV-C. Selon les caractéristiques desbiofilms (intensité de colonisation) et en fonction de leur emplacement dans la grotte (variations des facteurspréalablement déterminés), nous avons pu mettre en évidence une efficacité des UV-C variable dans le temps.Avec l’appui de résultats complémentaires obtenus sur deux souches de champignons et sur plusieurs types dematières picturales, l’ensemble des données collectées au cours de la thèse souligne l’intérêt et l’applicabilité destraitements aux UV-C dans divers contextes de conservation des matériaux du patrimoine<br>The aim of this thesis is to study and analyze the effect of UV-C radiation as an alternative method tochemicals to combat phototrophic microorganisms’ proliferation in show caves. First, the effect of UV-C wasanalyzed on several cave-dwelling unicellular green algae sub-cultured in laboratory conditions. Analysis at themolecular, cellular and biofilm scale highlighted several damages (decrease of viability and photosyntheticactivity, membrane degradation, chlorophyll bleaching, DNA fragmentation, decrease of the biofilms’ colonizedarea…) both direct (photooxydation reaction) or indirect (oxidative stress). These results helped to selectefficient UV-C exposure times (traduced in UV-C doses) both to eradicate and bleach green micro-algae.Second, these efficient UV-C doses were used to test the efficiency of UV-C treatments on natural phototrophicbiofilms proliferating in the Moidons Cave (Jura, France). Previous study to the UV-C tests was performed tounderstand the dynamics and factors that promote algal proliferation in this cave. Factors measured at the biofilmscale (quantity of light, type of the physical support, localization in the cave…) and at the cavity scale(horizontal and vertical circulation of waters, air currents, illumination time and visitors’ presence time) allowedto distinguish several preferential areas where growth-supporting conditions were present for algal proliferation.Then, several biofilms were selected to test the efficiency of UV-C treatments. According to the characteristicsof the biofilms (colonization intensity) and their localization in the cave (variations of the factors promotingcolonization) UV-C efficiency varied over time. Supplementary results obtained on filamentous fungi andmineral pigments used for prehistoric paintings, emphasize the interest and the applicability
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Rousseeuw, Kévin. "Modélisation de signaux temporels hautes fréquences multicapteurs à valeurs manquantes : Application à la prédiction des efflorescences phytoplanctoniques dans les rivières et les écosystèmes marins côtiers." Thesis, Littoral, 2014. http://www.theses.fr/2014DUNK0374/document.
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La prise de conscience des problèmes d'environnement et des effets directs et indirects des activités humaines a conduit à renforcer la surveillance haute fréquence des écosystèmes marins par l'installation de stations de mesures multicapteurs autonomes. Les capteurs, installés dans des milieux hostiles, sont sujets à des périodes de calibration, d'entretien voire des pannes et sont donc susceptibles de générer des données bruitées, manquantes voire aberrantes qu'il est nécessaire de filtrer et compléter avant toute exploitation ultérieure. Dans ce contexte, l'objectif du travail est de concevoir un système numérique automatisé robuste capable de traiter de tel volume de données afin d’améliorer les connaissances sur la qualité des systèmes aquatiques, et plus particulièrement en considérant le déterminisme et la dynamique des efflorescences du phytoplancton. L'étape cruciale est le développement méthodologique de modèles de prédiction des efflorescences du phytoplancton permettant aux utilisateurs de disposer de protocoles adéquats. Nous proposons pour cela l'emploi du modèle de Markov caché hybridé pour la détection et la prédiction des états de l'environnement (caractérisation des phases clefs de la dynamique et des caractéristiques hydrologiques associées). L'originalité du travail est l'hybridation du modèle de Markov par un algorithme de classification spectrale permettant un apprentissage non supervisé conjoint de la structure, sa caractérisation et la dynamique associée. Cette approche a été appliquée sur trois bases de données réelles : la première issue de la station marine instrumentée MAREL Carnot (Ifremer) (2005-2009), la seconde d’un système de type Ferry Box mis en œuvre en Manche orientale en 2012 et la troisième d’une station de mesures fixe, installée le long de la rivière Deûle en 2009 (Agence de l’Eau Artois Picardie - AEAP). Le travail s’inscrit dans le cadre d’une collaboration étroite entre l'IFREMER, le LISIC/ULCO et l'AEAP afin de développer des systèmes optimisés pour l’étude de l’effet des activités anthropiques sur le fonctionnement des écosystèmes aquatiques et plus particulièrement dans le contexte des efflorescences de l’algue nuisible, Phaeocystis globosa<br>Because of the growing interest for environmental issues and to identify direct and indirect effects of anthropogenic activities on ecosystems, environmental monitoring programs have recourse more and more frequently to high resolution, autonomous and multi-sensor instrumented stations. These systems are implemented in harsh environment and there is a need to stop measurements for calibration, service purposes or just because of sensors failure. Consequently, data could be noisy, missing or out of range and required some pre-processing or filtering steps to complete and validate raw data before any further investigations. In this context, the objective of this work is to design an automatic numeric system able to manage such amount of data in order to further knowledge on water quality and more precisely with consideration about phytoplankton determinism and dynamics. Main phase is the methodological development of phytoplankton bloom forecasting models giving the opportunity to end-user to handle well-adapted protocols. We propose to use hybrid Hidden Markov Model to detect and forecast environment states (identification of the main phytoplankton bloom steps and associated hydrological conditions). The added-value of our approach is to hybrid our model with a spectral clustering algorithm. Thus all HMM parameters (states, characterisation and dynamics of these states) are built by unsupervised learning. This approach was applied on three data bases: first one from the marine instrumented station MAREL Carnot (Ifremer) (2005-2009), second one from a Ferry Box system implemented in the eastern English Channel en 2012 and third one from a freshwater fixed station in the river Deûle in 2009 (Artois Picardie Water Agency). These works fall within the scope of a collaboration between IFREMER, LISIC/ULCO and Artois Picardie Water Agency in order to develop optimised systems to study effects of anthropogenic activities on aquatic systems functioning in a regional context of massive blooms of the harmful algae, Phaeocystis globosa
Book chapters on the topic "AlGaN/AlGaN Duv Leds"
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Dai, Jiangnan, Jingwen Chen, Jun Zhang, et al. "Solar-Blind AlGaN Devices." In Handbook of Solid-State Lighting and LEDs. CRC Press, 2017. http://dx.doi.org/10.1201/9781315151595-15.
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Stutzmann, M. "Novel Algan Heterostructures for UV Sensors and Leds." In UV Solid-State Light Emitters and Detectors. Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2103-9_10.
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Li, Jinmin, Junxi Wang, Xiaoyan Yi, et al. "AlGaN-Based Multiple-Quantum-Well Materials and UV LEDs." In Springer Series in Materials Science. Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-7949-3_6.
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Tamulaitis, Gintautas. "Influence of Carrier Localization on Efficiency Droop and Stimulated Emission in AlGaN Quantum Wells." In Handbook of Solid-State Lighting and LEDs. CRC Press, 2017. http://dx.doi.org/10.1201/9781315151595-14.
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Nakamura, Shuji, Stephen Pearton, and Gerhard Fasol. "Zn and Si Co-Doped InGaN/AlGaN Double-Heterostructure Blue and Blue-Green LEDs." In The Blue Laser Diode. Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-662-04156-7_9.
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Nakamura, Shuji, and Gerhard Fasol. "Zn and Si Co-Doped InGaN / AlGaN Double-Heterostructure Blue and Blue-Green LEDs." In The Blue Laser Diode. Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-662-03462-0_9.
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Robidas, Dipika, and D. Arivuoli. "Reduction of Electron Overflow Problem by Improved InGaN/GaN Based Multiple Quantum Well LEDs Structure with p- AlInGaN/AlGaN EBL Layer." In Physics of Semiconductor Devices. Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-03002-9_47.
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Chichibu, Shigefusa F., Hideto Miyake, Kazumasa Hiramtsu, and Akira Uedono. "Impacts of Dislocations and Point Defects on the Internal Quantum Efficiency of the Near-Band-Edge Emission in AlGaN-Based DUV Light-Emitting Materials." In III-Nitride Ultraviolet Emitters. Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-24100-5_5.
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Suzuki, Masakatsu, and Takeshi Uenoyama. "Electronic and optical properties of GaN-based quantum wells." In Group Ill Nitride Semiconductor Compounds. Oxford University PressOxford, 1998. http://dx.doi.org/10.1093/oso/9780198501596.003.0008.
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Abstract There is increasing interest in the use of GaN and related materials for opto-electronic devices in the short wavelength region, due to their wide direct bandgap and physical hardness. During the past few years, remarkable progress has been made in the development of optical devices based on wurtzite (WZ) GaN. At present, high-brightness blue light-emitting diodes (LEDs), based on WZ InGaN / AlGaN doublehetero (DH) (Nakamura et al. 1994) or single quantum well (SOW) (Nakamura et al. 1995) structures, are commercially available. Very recently the pulse-lasing action of multi-quantum well (MOW) laser diodes (LDs) by current injection at room temperature was reported for the first time (Nakamura et al. 1996). Furthermore, the recent development of crystal growth techniques has made it possible to obtain high-quality zincblende (ZB) crystals as well as WZ ones (Mizuta et al. 1986). However, many fundamental material and device characteristics of the III-V nitrides are less understood than conventional ZB compounds.
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Hirayama, Hideki. "Recent Progress in AlGaN Deep-UV LEDs." In Light-Emitting Diode - An Outlook On the Empirical Features and Its Recent Technological Advancements. InTech, 2018. http://dx.doi.org/10.5772/intechopen.79936.
Full textConference papers on the topic "AlGaN/AlGaN Duv Leds"
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Marouf, Ibrahim, Friedhard Römer, Marcel Schilling, et al. "Analysis of effective carrier mobility in the multi-quantum wells of DUV AlGaN LEDs by carrier transport simulations." In Physics and Simulation of Optoelectronic Devices XXXIII, edited by Marek Osiński, Yasuhiko Arakawa, and Bernd Witzigmann. SPIE, 2025. https://doi.org/10.1117/12.3042015.
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Wang, Rui, Huabin Yu, Muhammad Hunain Memon, Wei Chen, and Haiding Sun. "Superior AlGaN-Based Deep Ultraviolet Light- Emitting Diodes Incorporated with a Tunnel Junction Located on the N-Side of the Device." In CLEO: Science and Innovations. Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_si.2024.sm1o.3.
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We propose an AlGaN-based DUV LED incorporated with a n-side located tunnel junction to reverse the carrier injection direction, which can improve the light output power and internal quantum efficiency while reducing the efficiency droop.
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Boisvere, Jacob, Bryan Melanson, Matthew Seitz, and Jing Zhang. "Demonstration of a novel full structure electrically driven AlGaN-delta-GaN QW DUV LED." In Light-Emitting Devices, Materials, and Applications XXIX, edited by Martin Strassburg, Jong Kyu Kim, and Michael R. Krames. SPIE, 2025. https://doi.org/10.1117/12.3041254.
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Kirste, Ronny, James Loveless, Jack Almeter, et al. "AlGaN based UVC LEDs on AlN with reflective contacts." In Gallium Nitride Materials and Devices XX, edited by Hadis Morkoç, Hiroshi Fujioka, and Ulrich T. Schwarz. SPIE, 2025. https://doi.org/10.1117/12.3042261.
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Nicholls, Jordan, Liam Anderson, Darren Aung, et al. "AlGaN short-period superlattice based far-UVC LEDs on AlN templates." In Gallium Nitride Materials and Devices XX, edited by Hadis Morkoç, Hiroshi Fujioka, and Ulrich T. Schwarz. SPIE, 2025. https://doi.org/10.1117/12.3041460.
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Korte, Jannik, Johanna Meier, Hehe Zhang, Umut Kaya, Wolfgang Mertin, and Gerd Bacher. "Graphene as a current spreading layer in top-emitting AlGaN-based UVC-LEDs." In Light-Emitting Devices, Materials, and Applications XXIX, edited by Martin Strassburg, Jong Kyu Kim, and Michael R. Krames. SPIE, 2025. https://doi.org/10.1117/12.3042668.
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Wang, Xin, Wenlan Ma, Aoxiang Zhang, Fang Wang, and Yuhuai Liu. "Optimization of AlGaN-Based Deep Ultraviolet LEDs with a Graded Superlattice Electron Blocking Layer." In 2024 21st China International Forum on Solid State Lighting & 2024 10th International Forum on Wide Bandgap Semiconductors (SSLCHINA: IFWS). IEEE, 2024. https://doi.org/10.1109/sslchinaifws64644.2024.10835362.
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Mazumder, Indrani, Kashish Sapra, Ashok Chauhan, Manish Mathew, and Kuldip Singh. "Effect of AlGaN/ AlInGaN Super-Lattice Based Periodically Altered Carrier Injection Layers for UV-C LEDs." In 2023 IEEE Workshop on Recent Advances in Photonics (WRAP). IEEE, 2023. http://dx.doi.org/10.1109/wrap59682.2023.10713042.
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Brault, Julien, Mohamed Al Khalfioui, Mathieu Leroux, et al. "DUV LEDs based on AlGaN quantum dots." In Gallium Nitride Materials and Devices XVI, edited by Hadis Morkoç, Hiroshi Fujioka, and Ulrich T. Schwarz. SPIE, 2021. http://dx.doi.org/10.1117/12.2576135.
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Ippommatsu, Masamichi, Akira Hirano, Isamu Akasaki, and Hiroshi Amano. "Development of AlGaN DUV-LED." In 2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR). IEEE, 2013. http://dx.doi.org/10.1109/cleopr.2013.6599921.
Full textReports on the topic "AlGaN/AlGaN Duv Leds"
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Han, J., and M. H. Crawford. MOCVD growth of AlGaN UV LEDs. Office of Scientific and Technical Information (OSTI), 1998. http://dx.doi.org/10.2172/658459.
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Pandori, Lauren, Lauren Strope, and Linh Cat. Rocky intertidal community shift over 30 years: 1990–2020 rocky intertidal long term trend report. National Park Service, 2023. http://dx.doi.org/10.36967/2297397.
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Cabrillo National Monument (CABR) is a unit of the National Park System located on the Point Loma peninsula in San Diego, CA, USA. Despite its small size (0.65 terrestrial km2), the monument attracts 851,000 annual visitors (IRMA SRSS Reports 2011-2020), and acts as an “urban island”, providing habitat for unique algal, plant and animal species in an area of increasing development and urbanization. The coastal area of the park also leads to the rocky intertidal zone, which is regarded by many as the best conserved shorelines in mainland southern California. Due to the high-quality habitat and proximity to an urban area, it is critical to monitor community composition and visitor use of the rocky intertidal area. We leveraged over 30 years of long-term monitoring data of both rocky intertidal communities and visitation to investigate: (1) whether visitation has increased over time, (2) if community composition has changed over time across intertidal management zones. We found that visitation to management Zone I has increased over time. Additionally, we found that visitation doesn’t scale linearly across management zones: 73% of people were observed in Zone I, 19% of people in Zone II, and 4% of people in Zone III. PERMANOVA analyses indicated that community composition differed over time and across management zones for all plot types. Documenting community shifts, rather than changes in populations of single species, allows NPS staff to capture, and respond to, ecological transformation. Using the Resist-Accept-Direct (RAD) framework, we recommend that CABR either accept or direct changes to the rocky intertidal (e.g., directing changes in higher visitation areas by implementing a timed entry or shuttle system, and accepting changes in closed or very low visitation areas). Looking forward, long-term rocky intertidal monitoring will inform the effectiveness of resisting, accepting, or directing actions the park takes to uphold the NPS mission at CABR and other NPS units with rocky intertidal habitat, which span the Pacific coast.
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Hackbarth, Carolyn, and Rebeca Weissinger. Water quality in the Northern Colorado Plateau Network: Water years 2016–2018 (revised with cost estimate). National Park Service, 2023. http://dx.doi.org/10.36967/nrr-2279508.
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Water-quality monitoring in National Park Service units of the Northern Colorado Plateau Network (NCPN) is made possible through partnerships between the National Park Service Inventory & Monitoring Division, individual park units, the U.S. Geological Survey, and the Utah Division of Water Quality. This report evaluates data from site visits at 62 different locations on streams, rivers, and reservoirs in or near ten NCPN park units between October 1, 2015 and September 30, 2018. Data are compared to state water-quality standards for the purpose of providing information to park managers about potential water-quality problems. The National Park Service does not determine the regulatory status of surface waters; state water quality agencies determine whether waters comply with the Clean Water Act. Evaluation of water-quality parameters relative to state water-quality standards indicated that 17,997 (96.8%) of the 18,583 total designated beneficial-use evaluations completed for the period covered in this report met state water-quality standards. The most common exceedances or indications of impairment, in order of abundance, were due to elevated nutrients, elevated bacteria (E. coli), elevated water temperature, elevated trace metals, elevated total dissolved solids (and sulfate), elevated pH, and low dissolved oxygen. While some exceedances were recurring and may have been caused by human activities in the watersheds, many were due to naturally occurring conditions characteristic of the geographic setting. This is most apparent with phosphorus, which can be introduced into surface water bodies at elevated levels by natural weathering of the geologic strata found throughout the Colorado Plateau. Higher phosphorus concentrations could also be attributed to anthropogenic activities that can accelerate erosion and transport of phosphorus. Some activities that can increase erosional processes include grazing, logging, mining, pasture irrigation, and off-highway vehicle (OHV) use. Exceedances for total phosphorus were common occurrences at nine out of ten NCPN park units, where at least one site in each of these parks had elevated phosphorus concentrations. At these sites, high levels of nutrients have not led to algal blooms or other signs of eutrophication. Sites monitored in Arches National Park (NP), Black Canyon of the Gunnison NP (BLCA), Bryce Canyon NP (BRCA), Capitol Reef NP (CARE), Curecanti National Recreation Area (CURE), Dinosaur National Monument (DINO), and Zion NP (ZION) all had E. coli ex-ceedances that could be addressed by management actions. While many of these sites already have management actions underway, some of the actions necessary to bring these waters into compliance are beyond the control of the National Park Service. Changes to agricultural practices to improve water quality involves voluntary participation by landowners and/or grazing permittees and their respective states. This could be the case with lands upstream of several parks with E. coli contamination issues, including Red Rock Canyon (BLCA); Sul-phur, Oak, and Pleasant creeks (CARE); Blue Creek and Cimarron River (CURE); Brush and Pot creeks (DINO); and North Fork Virgin River (ZION). Issues with E. coli contamination at Yellow Creek (BRCA) seemed to be resolved after the park boundary fence downstream of the site was repaired, keeping cattle out of the park. At North Fork Virgin River, E. coli exceedances have been less frequent since the State of Utah worked with landowners and grazing permittees to modify agricultural practices. Continued coordination between the National Park Service, state agencies, and local landowners will be necessary to further re-duce E. coli exceedances and, in turn, improve public health and safety in these streams. Selenium concentrations in Red Rock Canyon (BLCA) continued to exceed the state aquat-ic-life standard at both the upstream and downstream sites. Although selenium weathers naturally from bedrock and...
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Desiderati, Christopher. Carli Creek Regional Water Quality Project: Assessing Water Quality Improvement at an Urban Stormwater Constructed Wetland. Portland State University, 2022. http://dx.doi.org/10.15760/mem.78.
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Stormwater management is an ongoing challenge in the United States and the world at-large. As state and municipal agencies grapple with conflicting interests like encouraging land development, complying with permits to control stormwater discharges, “urban stream syndrome” effects, and charges to steward natural resources for the long-term, some agencies may turn to constructed wetlands (CWs) as aesthetically pleasing and functional natural analogs for attenuating pollution delivered by stormwater runoff to rivers and streams. Constructed wetlands retain pollutants via common physical, physicochemical, and biological principles such as settling, adsorption, or plant and algae uptake. The efficacy of constructed wetlands for pollutant attenuation varies depending on many factors such as flow rate, pollutant loading, maintenance practices, and design features. In 2018, the culmination of efforts by Clackamas Water Environment Services and others led to the opening of the Carli Creek Water Quality Project, a 15-acre constructed wetland adjacent to Carli Creek, a small, 3500-ft tributary of the Clackamas River in Clackamas County, OR. The combined creek and constructed wetland drain an industrialized, 438-acre, impervious catchment. The wetland consists of a linear series of a detention pond and three bioretention treatment cells, contributing a combined 1.8 acres of treatment area (a 1:243 ratio with the catchment) and 3.3 acre-feet of total runoff storage. In this study, raw pollutant concentrations in runoff were evaluated against International Stormwater BMP database benchmarks and Oregon Water Quality Criteria. Concentration and mass-based reductions were calculated for 10 specific pollutants and compared to daily precipitation totals from a nearby precipitation station. Mass-based reductions were generally higher for all pollutants, largely due to runoff volume reduction on the treatment terrace. Concentration-based reductions were highly variable, and suggested export of certain pollutants (e.g., ammonia), even when reporting on a mass-basis. Mass load reductions on the terrace for total dissolved solids, nitrate+nitrite, dissolved lead, and dissolved copper were 43.3 ± 10%, 41.9 ± 10%, 36.6 ± 13%, and 43.2 ± 16%, respectively. E. coli saw log-reductions ranging from -1.3 — 3.0 on the terrace, and -1.0 — 1.8 in the creek. Oregon Water Quality Criteria were consistently met at the two in-stream sites on Carli Creek for E. coli with one exception, and for dissolved cadmium, lead, zinc, and copper (with one exception for copper). However, dissolved total solids at the downstream Carli Creek site was above the Willamette River guidance value 100 mg/L roughly 71% of the time. The precipitation record during the study was useful for explaining certain pollutant reductions, as several mechanisms are driven by physical processes, however it was not definitive. The historic rain/snow/ice event in mid-February 2021 appeared to impact mass-based reductions for all metals. Qualitatively, precipitation seemed to have the largest effect on nutrient dynamics, specifically ammonia-nitrogen. Determining exact mechanisms of pollutant removals was outside the scope of this study. An improved flow record, more targeted storm sampling, or more comprehensive nutrient profiles could aid in answering important questions on dominant mechanisms of this new constructed wetland. This study is useful in establishing a framework and baseline for understanding this one-of-a-kind regional stormwater treatment project and pursuing further questions in the future.
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Whitaker, Stephen. Rocky intertidal community monitoring at Channel Islands National Park: 2018–19 annual report. National Park Service, 2023. http://dx.doi.org/10.36967/2299674.
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Channel Islands National Park includes the five northern islands off the coast of southern California (San Miguel, Santa Rosa, Santa Cruz, Anacapa, and Santa Barbara Islands) and the surrounding waters out one nautical mile. There are approximately 176 miles of coastline around the islands, about 80% of which is composed of rock. The diversity and undisturbed nature of the tidepools of this rocky coastline were recognized as special features of the islands in the enabling legislation. To conserve these communities unimpaired for future generations, the National Park Service has been monitoring the rocky intertidal communities at the islands since 1982. Sites were established between 1982 and 1998. Site selection considered visitation, accessibility, presence of representative organisms, wildlife disturbance, and safety. This report summarizes the 2018–2019 sampling year efforts (from November 2018 to April 2019) and findings of the Channel Islands National Park Rocky Intertidal Community Monitoring Program. Specific monitoring objectives are 1) to determine the long-term trends in percent cover of key sessile organisms in the rocky intertidal ecosystem, and 2) to determine population dynamics of black abalone (Haliotis cracherodii), owl limpets (Lottia gigantea), and ochre sea stars (Pisaster ochraceus). Objectives were met by monitoring percent cover of core species in target intertidal zones using photoplots and transects, and by measuring size frequency and abundance of black abalone, owl limpets, and sea stars using fixed plots or timed searches. Twelve key species or assemblages, as well as the substrate, tar, have been monitored twice per year at 21 sites on the five park islands as part of the rocky intertidal community monitoring program. Fixed photoplots were used to monitor the percent cover of thatched and acorn barnacles (Tetraclita rubescens, Balanus glandula/Chthamalus spp., respectively), mussels (Mytilus californianus), rockweeds (Silvetia compressa, and Pelvetiopsis californica (formerly Hesperophycus californicus), turfweed (Endocladia muricata), goose barnacles (Pollicipes polymerus) and tar. Point-intercept transects were used to determine the percent cover of surfgrass (Phyllospadix spp.). Information about size distribution (i.e., “size frequency” data) was collected for owl limpets in circular plots. Size distribution and relative abundance of black abalone and ochre sea stars were determined using timed searches. The maximum number of shorebirds and pinnipeds seen at one time were counted at each site. The number of concession boat visitors to the Anacapa tidepools was collected and reported. All sites were monitored in 2018–2019. This was the third year that we officially reduced our sampling interval from twice per year (spring and fall) to once in order to streamline the program and allow for the implementation of additional protocols. Weather conditions during the site visits were satisfactory, but high wind coupled with strong swell and surge limited or prevented the completion of some of the abalone and sea star searches. The percent cover for most key species or assemblages targeted in the photoplots was highly variable among sites. Mussel (Mytilus californianus) cover remained below average at Anacapa and Santa Barbara Islands. Record or near record low abundances for Mytilus were measured at Middle West Anacapa (Anacapa Island), Harris Point (San Miguel Island), Prisoner’s Harbor (Santa Cruz Island), and Sea Lion Rookery (Santa Barbara Island) sites. The only site that appeared to have above average Mytilus cover was Scorpion Rock on Santa Cruz Island. All other sites had mussel cover near or below the long-term mean. Qualitatively, Mytilus recruitment appeared low at most sites. Both rockweed species, Silvetia compressa and Pelvetiopsis californica (formerly Hesperophycus californicus), continued to decrease markedly in abundance this year at the majority of sites compared to combined averages for previous years. Fossil Reef and Northwest-Talcott on Santa Rosa Island, Sea Lion Rookery on Santa Barbara Island, and South Frenchy’s Cove on Anacapa Island were the only sites that supported Silvetia cover that was near the long-term mean. No sites exhibited above average cover of rockweed. Extremely high levels of recruitment for Silvetia and Pelvetiopsis were documented at many sites. Most sites exhibited marked declines in S. compressa abundances beginning in the early 2000s, with little recovery observed for the rockweed through this year. Barnacle (Chthamalus/Balanus spp.) cover fell below the long-term means at all islands except Anacapa, where barnacle cover was slightly above average. Endocladia muricata abundances remained comparable to the grand mean calculated for previous years at Santa Barbara, Santa Cruz, and Santa Rosa Islands, while cover of the alga decreased slightly below the long-term means at Anacapa and San Miguel Islands. Black abalone (Haliotis cracherodii) abundances at the islands remain less than one percent of 1985 population levels. Zero abalone were found throughout the entire site at Landing Cove on Santa Barbara Island and South Frenchy’s Cove on Anacapa Island. Above average abundances relative to the long-term mean generated from post-1995 data were observed at all but five sites. Juvenile black abalone were seen at all islands except Santa Barbara. Ochre sea star (Pisaster ochraceus) populations crashed in 2014 at all monitoring sites due to Sea Star Wasting Syndrome, an illness characterized by a suite of symptoms that generally result in death. The mortality event was widely considered to be the largest mortality event for marine diseases ever seen. Beginning in June 2013, the disease swiftly and significantly impacted P. ochraceus (among other species of sea stars) populations along the North American Pacific coast from Alaska to Baja California, Mexico. By the beginning of 2014, P. ochraceus abundances had declined by >95% at nearly all Channel Islands long-term intertidal monitoring sites, in addition to numerous other locations along the West Coast. At various times during the past decade, extremely high abundances (~ 500 P. ochraceus) have been observed at multiple sites, and most locations have supported >100 sea stars counted during 30-minute site-wide searches. This year, abundances ranged 0–13 individuals per site with all but one site having fewer than 10 P. ochraceus seen during routine searches. Insufficient numbers of sea stars were seen to accurately estimate the size structure of P. ochraceus populations. Only two juveniles (i.e., <50 mm) were observed at all sites combined. Giant owl limpet densities in 2018–2019 were comparable or slightly above the long-term mean at seven sites. Exceptionally high densities were measured at Northwest-Talcott on Santa Rosa Island, Otter Harbor on San Miguel Island, and Willows Anchorage on Santa Cruz Island. The sizes of L. gigantea this year varied among sites and islands. The smallest L. gigantea were observed at Otter Harbor followed closely by Willows Anchorage and Anacapa Middle West, and the largest were seen at Northwest-Talcott. Temporally, the mean sizes of L. gigantea in 2018–2019 decreased below the long-term mean at each island except Anacapa. Surfgrasses (Phyllospadix spp.) are typically monitored biannually at two sites each on Santa Cruz and Santa Rosa Islands. Beginning in 2015, all transects at each of the monitoring sites were only sampled once per year. At East Point on Santa Rosa Island, the conditions were not conducive to sampling the surfgrass transects, but qualitatively, percent cover of surfgrass appeared to be near 100% on all three transects. Relative to past years, cover of surfgrass increased above the long-term mean at Fraser Cove on Santa Cruz Island, fell slightly below the mean at Trailer on Santa Cruz Island, and remained approximately equivalent to the mean at the two Santa Rosa Island sites. Overall, the abundance and diversity of shorebirds in 2018–2019 at all sites appeared similar to observations made in recent years, with the exception of elevated numbers of brown pelicans (Pelecanus occidentalis) observed at East Point on Santa Rosa Island. Black oystercatchers (Haematopus bachmani) were the most ubiquitous shorebird seen at all sites. Black turnstones (Arenaria melanocephala) were not common relative to past years. Pinniped abundances remained comparable in 2018–2019 to historical counts for all three species that are commonly seen at the islands. Harbor seals (Phoca vitulina) were seen in the vicinity of eight sites this year. As in past years, harbor seals were most abundant at Otter Harbor and Harris Point on San Miguel Island. Elephant seals (Mirounga angustirostris) were seen at six sites during the year, where abundances ranged 1–5 individuals per location. California sea lions (Zalophus californianus) were common at Santa Barbara Island; 117 individuals were observed at Sea Lion Rookery. Sea lion abundances were higher than usual at Harris Point (N = 160) and Otter Harbor (N = 82) on San Miguel Island. Relative to past years, abundances this year were considered average at other locations.