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  • 1
    Online Resource
    Online Resource
    The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance
    American Association for the Advancement of Science (AAAS) ; 2022
    In:  Science Vol. 378, No. 6615 ( 2022-10-07)
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 378, No. 6615 ( 2022-10-07)
    Abstract: Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century. Expanse of SARS-CoV-2 sequencing capacity in Africa. ( A ) African countries (shaded in gray) and institutions (red circles) with on-site sequencing facilities that are capable of producing SARS-CoV-2 whole genomes locally. ( B ) The number of SARS-CoV-2 genomes produced per country and the proportion of those genomes that were produced locally, regionally within Africa, or abroad. ( C ) Decreased turnaround time of sequencing output in Africa to an almost real-time release of genomic data.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.abq5358
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2022
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    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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  • 2
    Online Resource
    Online Resource
    AlN and AlN/Al2O3 seed layers from atomic layer deposition for epitaxial growth of AlN on sapphire
    American Vacuum Society ; 2019
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 37, No. 2 ( 2019-03-01)
    Details
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 37, No. 2 ( 2019-03-01)
    Abstract: The annealing of amorphous AlN and AlN/Al2O3 seed layers from atomic layer deposition (ALD) on sapphire substrates and their application as starting layers for metal-organic vapor phase epitaxial growth on sapphire was investigated. During annealing in hydrogen, the amorphous ALD layers become crystalline with epitaxial relation to the underlying sapphire substrate. In contrast to the pure AlN ALD seed layers, mixed layers containing Al2O3 help to avoid the formation of polycrystalline material. Additionally, such mixed ALD seeds support void formation at the AlN/sapphire interface resulting in the formation of a smooth AlN surface. This void formation can be seen in situ during AlN growth in the reflectivity at 405 nm. The tilt and twist component of the AlN grains could be decreased by increasing the annealing time at 1290 °C from 1.5 to 40 min.
    Type of Medium: Online Resource
    ISSN: 0734-2101 , 1520-8559
    URL: Article
    DOI: 10.1116/1.5079473
    RVK:
    UA 4921
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2019
    detail.hit.zdb_id: 1475424-1
    detail.hit.zdb_id: 797704-9
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  • 3
    Online Resource
    Online Resource
    Atmospheric pressure plasma enhanced spatial atomic layer deposition of SnOx as conductive gas diffusion barrier
    American Vacuum Society ; 2018
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 36, No. 1 ( 2018-01-01)
    Details
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 36, No. 1 ( 2018-01-01)
    Abstract: The authors report the preparation of transparent conductive gas permeation barriers based on thin films of tin oxide (SnOx) grown by spatial atomic layer deposition (ALD) at atmospheric pressure. They present a comparative study using tetrakis(dimethylamino)tin(IV) and various oxidants (atmospheric pressure oxygen plasma, ozone, and water) at process temperatures in the range of 80–165 °C. Specifically, for oxygen plasma or ozone as oxidant, the authors confirm self-limited ALD growth with a growth per cycle (GPC) of 0.16 and 0.11 nm for 80 and 150 °C, respectively, comparable to the classical vacuum-based ALD of SnOx. On the contrary, for water-based processes the GPC is significantly lower. Very notably, while SnOx grown with water as oxidant shows only a very limited electrical conductivity [10−3 (Ω cm)−1], atmospheric pressure oxygen plasma affords SnOx layers with an electrical conductivity up to 102 (Ω cm)−1. At the same time, these layers are excellent gas permeation barriers with a water vapor transmission rate as low as 7 × 10−4 g m−2 day−1 (at 60 °C and 60% rH). ALD growth will be demonstrated at substrate velocities up to 75 mm/s (i.e., 4.5 m/min), which renders spatial plasma assisted ALD an excellent candidate for the continuous manufacturing of transparent and conductive gas permeation barriers based on SnOx.
    Type of Medium: Online Resource
    ISSN: 0734-2101 , 1520-8559
    URL: Article
    DOI: 10.1116/1.5006781
    RVK:
    UA 4921
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2018
    detail.hit.zdb_id: 1475424-1
    detail.hit.zdb_id: 797704-9
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  • 4
    Online Resource
    Online Resource
    Identification of genetic risk loci and causal insights associated with Parkinson's disease in African and African admixed populations: a genome-wide association study
    Elsevier BV ; 2023
    In:  The Lancet Neurology Vol. 22, No. 11 ( 2023-11), p. 1015-1025
    Details
    In: The Lancet Neurology, Elsevier BV, Vol. 22, No. 11 ( 2023-11), p. 1015-1025
    Type of Medium: Online Resource
    ISSN: 1474-4422
    URL: Article
    DOI: 10.1016/S1474-4422(23)00283-1
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
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  • 5
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    Online Resource
    Hazardous materials and CBRN incidents: Fundamentals of pre-hospital readiness in the State of Qatar
    Hamad bin Khalifa University Press (HBKU Press) ; 2021
    In:  Journal of Emergency Medicine, Trauma and Acute Care Vol. 2021, No. 2 ( 2021-08-09)
    Details
    In: Journal of Emergency Medicine, Trauma and Acute Care, Hamad bin Khalifa University Press (HBKU Press), Vol. 2021, No. 2 ( 2021-08-09)
    Type of Medium: Online Resource
    ISSN: 1999-7086 , 1999-7094
    URL: Article
    DOI: 10.5339/jemtac.2021.qhc.35
    Language: English
    Publisher: Hamad bin Khalifa University Press (HBKU Press)
    Publication Date: 2021
    detail.hit.zdb_id: 2771295-3
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  • 6
    Online Resource
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    Ag films grown by remote plasma enhanced atomic layer deposition on different substrates
    American Vacuum Society ; 2016
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 34, No. 1 ( 2016-01-01)
    Details
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 34, No. 1 ( 2016-01-01)
    Abstract: Silver (Ag) layers were deposited by remote plasma enhanced atomic layer deposition (PALD) using Ag(fod)(PEt3) (fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato) as precursor and hydrogen plasma on silicon substrate covered with thin films of SiO2, TiN, Ti/TiN, Co, Ni, and W at different deposition temperatures from 70  to 200 °C. The deposited silver films were analyzed by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive x-ray spectroscopy, four point probe measurement, ellipsometric measurement, x-ray fluorescence (XRF), and x-ray diffraction (XRD). XPS revealed pure Ag with carbon and oxygen contamination close to the detection limit after 30 s argon sputtering for depositions made at 120 and 200 °C substrate temperatures. However, an oxygen contamination was detected in the Ag film deposited at 70 °C after 12 s argon sputtering. A resistivity of 5.7 × 10−6 Ω cm was obtained for approximately 97 nm Ag film on SiO2/Si substrate. The thickness was determined from the SEM cross section on the SiO2/Si substrate and also compared with XRF measurements. Polycrystalline cubic Ag reflections were identified from XRD for PALD Ag films deposited at 120 and 200 °C. Compared to W surface, where poor adhesion of the films was found, Co, Ni, TiN, Ti/TiN and SiO2 surfaces had better adhesion for silver films as revealed by SEM, TEM, and AFM images.
    Type of Medium: Online Resource
    ISSN: 0734-2101 , 1520-8559
    URL: Article
    DOI: 10.1116/1.4936221
    RVK:
    UA 4921
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2016
    detail.hit.zdb_id: 1475424-1
    detail.hit.zdb_id: 797704-9
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  • 7
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    Online Resource
    Low-temperature growth of gallium oxide thin films by plasma-enhanced atomic layer deposition
    American Vacuum Society ; 2020
    In:  Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Vol. 38, No. 2 ( 2020-03-01)
    Details
    In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, American Vacuum Society, Vol. 38, No. 2 ( 2020-03-01)
    Abstract: Gallium oxide (Ga2O3) thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) applying a capacitively coupled plasma source where trimethylgallium (TMGa) as the gallium precursor and oxygen (O2) plasma were used in a substrate temperature (Ts) in range of 80–200 °C. TMGa exhibits high vapor pressure and therefore facilitates deposition at lower substrate temperatures. The Ga2O3 films were characterized by spectroscopic ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), and capacitance-voltage (C-V) measurements. The SE data show linear thickness evolution with a growth rate of ∼0.66 Å per cycle and inhomogeneity of ≤2% for all samples. The refractive index of the Ga2O3 thin films is 1.86 ± 0.01 (at 632.8 nm) and independent of temperature, whereas the bandgap slightly decreases from 4.68 eV at Ts of 80 °C to 4.57 eV at 200 °C. XPS analysis revealed ideal stoichiometric gallium to oxygen ratios of 2:3 for the Ga2O3 layers with the lowest carbon contribution of ∼10% for the sample prepared at 150 °C. The permittivity of the layers is 9.7 ± 0.2 (at 10 kHz). In addition, fixed and mobile oxide charge densities of 2–4 × 1012 and 1–2 × 1012 cm−2, respectively, were observed in the C-V characteristics. Moreover, the Ga2O3 films show breakdown fields in the range of 2.2–2.7 MV/cm. Excellent optical and electrical material properties are maintained even at low substrate temperatures as low as 80 °C. Hence, the TMGa/O2 PEALD process is suitable for electronic and optoelectronic applications where low-temperature growth is required.
    Type of Medium: Online Resource
    ISSN: 0734-2101 , 1520-8559
    URL: Article
    DOI: 10.1116/1.5134800
    RVK:
    UA 4921
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2020
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    detail.hit.zdb_id: 797704-9
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  • 8
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    Online Resource
    Ellipsometry and XPS comparative studies of thermal and plasma enhanced atomic layer deposited Al 2 O 3 -films
    Beilstein Institut ; 2013
    In:  Beilstein Journal of Nanotechnology Vol. 4 ( 2013-11-08), p. 732-742
    Details
    In: Beilstein Journal of Nanotechnology, Beilstein Institut, Vol. 4 ( 2013-11-08), p. 732-742
    Abstract: We report on results on the preparation of thin ( 〈 100 nm) aluminum oxide (Al 2 O 3 ) films on silicon substrates using thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) in the SENTECH SI ALD LL system. The T-ALD Al 2 O 3 layers were deposited at 200 °C, for the PE-ALD films we varied the substrate temperature range between room temperature (rt) and 200 °C. We show data from spectroscopic ellipsometry (thickness, refractive index, growth rate) over 4” wafers and correlate them to X-ray photoelectron spectroscopy (XPS) results. The 200 °C T-ALD and PE-ALD processes yield films with similar refractive indices and with oxygen to aluminum elemental ratios very close to the stoichiometric value of 1.5. However, in both also fragments of the precursor are integrated into the film. The PE-ALD films show an increased growth rate and lower carbon contaminations. Reducing the deposition temperature down to rt leads to a higher content of carbon and CH-species. We also find a decrease of the refractive index and of the oxygen to aluminum elemental ratio as well as an increase of the growth rate whereas the homogeneity of the film growth is not influenced significantly. Initial state energy shifts in all PE-ALD samples are observed which we attribute to a net negative charge within the films.
    Type of Medium: Online Resource
    ISSN: 2190-4286
    URL: Article
    DOI: 10.3762/bjnano.4.83
    Language: English
    Publisher: Beilstein Institut
    Publication Date: 2013
    detail.hit.zdb_id: 2583584-1
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  • 9
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    A monolithic micro-optical interferometer deep etched into fused silica
    Elsevier BV ; 2017
    In:  Microelectronic Engineering Vol. 174 ( 2017-04), p. 40-45
    Details
    In: Microelectronic Engineering, Elsevier BV, Vol. 174 ( 2017-04), p. 40-45
    Type of Medium: Online Resource
    ISSN: 0167-9317
    URL: Article
    DOI: 10.1016/j.mee.2017.01.002
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
    detail.hit.zdb_id: 1497065-X
    detail.hit.zdb_id: 605230-7
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  • 10
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    Deep etching of Zerodur glass ceramics in a fluorine-based plasma
    Elsevier BV ; 2018
    In:  Microelectronic Engineering Vol. 185-186 ( 2018-01), p. 1-8
    Details
    In: Microelectronic Engineering, Elsevier BV, Vol. 185-186 ( 2018-01), p. 1-8
    Type of Medium: Online Resource
    ISSN: 0167-9317
    URL: Article
    DOI: 10.1016/j.mee.2017.10.013
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
    detail.hit.zdb_id: 1497065-X
    detail.hit.zdb_id: 605230-7
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