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  • 1
    Electronic Resource
    Electronic Resource
    A survey of the signal-induced noise in photomultiplier detection of wide dynamics luminous signals (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3274-3280 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In the LIDAR sounding of wide atmospheric ranges, as in middle atmospheric probing, signal-induced noise (SIN) from the photomultiplier (PMT) has been known since long time as a challenging problem for scientists. In this article the results of investigations on SIN are reported and strategies to minimize its amount proposed. Three different types of PMTs have been tested and their response to pulsed light signals of various duration and amplitude, comparable with close range LIDAR return, have been studied. An analysis of the time properties and spectral characteristics of SIN has been performed, and a method to reduce SIN effects in photon counting acquisition has been proposed. The method is based on a careful choice of discriminator threshold level settings, and exploits differences observed between SIN and signal cumulative pulse height distributions. The method shows dependency on single PMT behavior. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147408
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  • 2
    Electronic Resource
    Electronic Resource
    Periodontal pathogens in atheromatous plaques. A controlled clinical and laboratory trial (2004)
    Oxford, UK : Munksgaard International Publishers
    Journal of periodontal research 39 (2004), S. 0 
    Details
    ISSN: 1600-0765
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective:  A possible relationship between periodontitis and cardiovascular disease has been suggested. The aims of this controlled clinical study were: (i) to ascertain the presence of periodontal bacteria DNA [Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis (formerly Bacteroides forsythus)] in carotid atheromatous plaques and (ii) to assess the concomitant presence of the same periodontal bacteria DNA, if any, in periodontal pockets and in carotid atheroma in the same patient.Methods:  A total of 52 patients scheduled for carotid endarderectomy were enrolled in this study. The test group consisted of 26 dentate patients; the control group included 26 edentulous patients. A complete periodontal examination, including radiographic orthopanoramic and subgingival plaque sample, was performed in the test population. Oral and X-ray examinations were performed in the control group. Atheromatous plaques were harvested during surgical procedure for each dentate and edentulous patient and then sent to the microbiological laboratory. Subgingival plaque samples and carotid specimens were examined using the polymerase chain reaction (PCR) technique by means of specific primers for periodontal bacteria. Amplification of extracted DNA was tested using human beta-globin specific-primers.Results:  Out of 52 endarterectomy samples, 12 (seven dentate, five edentulous patients) were excluded as negative to DNA amplification. In subgingival plaque samples of 19 test patients, T. forsythensis (79%), F. nucleatum (63%), P. intermedia (53%), P. gingivalis (37%) and A. actinomycetemcomitans (5%) were found. No periodontal bacteria DNA was detected by PCR in any of the carotid samples in either patient group.Conclusion:  The presence of periodontal bacteria DNA in atheromatous plaques could not be confirmed by this study and thus no correlation could be established between species associated with periodontal disease and putative bacteria contributing to atheromatous plaques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0765.2004.00761.x
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  • 3
    Electronic Resource
    Electronic Resource
    Stratospheric background aerosol and polar cloud observations by laser backscattersonde within the framework of the European project “Stratospheric Regular Sounding” (1999)
    Springer
    Annales geophysicae 17 (1999), S. 1352-1360 
    Details
    ISSN: 0992-7689
    Keywords: Atmospheric composition and structure (aerosols and particles; middle atmosphere - composition and chemistry; instruments and techniques)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The Stratospheric Regular Sounding project was planned to measure regularly the vertical profiles of several tracers like ozone, water vapor, NOx, ClOx and BrOx radicals, aerosol, pressure and temperature, at three latitudes, to discriminate between the transport and photochemical terms which control their distribution. As part of this project, the “Istituto di Fisica dell’Atmosfera” launched nine laser backscattersondes (LABS) on board stratospheric balloons to make observations of background aerosol and PSCs. LABS was launched with an optical particle counter operated by the University of Wyoming. Observations have been performed in the arctic, mid-latitudes and tropical regions in different seasons. Polar stratospheric clouds have been observed in areas inside and outside the polar vortex edge. A background aerosol was observed both in mid-latitudes and in arctic regions with a backscattering ratio of 1.2 at 692 nm. Very stratified aerosol layers, possibly transported into the lower stratosphere by deep convective systems, have been observed in the lower stratosphere between 20 and 29 km in the tropics in the Southern Hemisphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-1352-2
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  • 4
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    ANTARTIDE. Un osservatorio naturale per comprendere la Terra (2009)
    Details
    Publication Date: 2017-04-04
    Description: Molto è noto delle particolarissime condizioni che rendono l'Antartide un laboratorio veramente speciale per tante discipline. Tuttavia, per le Scienze della Terra il continente antartico ha un doppio interesse. Oltre ad essere un luogo poco conosciuto dove avvengono processi straordinari ed unici per il nostro pianeta, esso occupa anche una posizione privilegiata per la registrazione di dati geofisici. Questi dati sono essenziali per la comprensione globale di molti processi fisici e ci aiutano dunque a capire come la Terra "funziona" nel suo insieme. L'Antartide è, quindi, un luogo di osservazione cruciale per la conoscenza del pianeta in cui viviamo. I processi geofisici presentano variazioni su lunghi periodi. Di conseguenza, la registrazione di lunghe e ininterrotte serie temporali è un impegno basilare per gli osservatori geofisici. Come noi traiamo vantaggio dalle registrazioni della declinazione del campo magnetico fatte dai marinai del XVIII secolo, dalle cronologie degli effetti dei terremoti trovate in archivi storici e dalle informazioni sul tempo e sulle temperature dell'aria scritte negli antichi almanacchi, così dobbiamo impegnarci per acquisire ed allo stesso tempo conservare le registrazioni strumentali secondo i migliori livelli consentiti dalla tecnologia odierna. Seguendo queste considerazioni, il programma antartico Italiano - in modo simile ai programmi di altre nazioni - si sta prodigando in uno sforzo continuo nel mantenimento e nel miglioramento degli osservatori geofisici permanenti. Forse alcune di queste attività non forniscono dati con forte impatto immediato, ma la loro vera importanza si evidenzierà certamente in futuro. Il funzionamento degli osservatori geofisici antartici è anche un obbligo verso le prossime generazioni, per metterle in condizione di comprendere quello che a noi sfugge ancora.
    Description: PNRA
    Description: Published
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: open
    Keywords: Antartide ; Osservatori permanenti ; PNRA ; 01. Atmosphere::01.03. Magnetosphere::01.03.99. General or miscellaneous ; 03. Hydrosphere::03.03. Physical::03.03.05. Instruments and techniques ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.04. Instrumentation and techniques of general interest::05.04.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: report
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  • 5
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    Polar Stratospheric Clouds in the Arctic and Antarctic - A Statistical Approach (2005)
    In:  EPIC3Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 4-9 March, Berlin, Germany.
    Details
    Publication Date: 2019-07-16
    Description: Polar stratospheric clouds (PSCs) play a crucial role for the stratospheric ozone layer in the polar regions. Their various forms of appearance - e.g. the state of aggregation and size of their particles- have a decisive influence on the amount of activated chlorine leading to ozone destruction. Differences in Arctic and Antarctic PSC occurrence are to be expected due to the different vortex stability and temperatures. Our study is based on PSC lidar observations from Ny-Alesund [79°N, 12°E] and McMurdo [78°S, 167°E]. As expected, we find large differences in the occurrence frequency of the various PSC types. Yet, the statistical analysis reveals some surprises, e.g. it is found that the most common PSC type at the Antarctic station is made from solid NAT particles, while only a small fraction of the observed cloud layers consist of ice particles. On the other hand, the majority of PSCs at the Arctic station is found to consist of liquid particles. As the PSC type has an influence on the heterogeneous activation rate, these results have to be carefully validated and taken into account by ozone chemistry models.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 6
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    Optical measurements of atmospheric particles from airborne platforms: in situ and remote sensing instruments for balloons and aircrafts (2006)
    Details
    Publication Date: 2019-11-04
    Description: Multiwavelength laser backscattersondes (MAS) have been widely used from a variety of airborne platforms for in situ measurements of optical properties of clouds and atmospheric particulate as well as their phase and composition. Recently, a new miniaturized LIDAR (MULID) has been developed using state-of-art technology for balloon borne profiling of the same quantities. A description of the two instruments, a survey of preliminary results obtained during test flights and indications for future use are given.
    Description: JCR Journal
    Description: open
    Keywords: remote sensing ; LIDAR ; backscattersonde ; aerosol ; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques ; 04. Solid Earth::04.02. Exploration geophysics::04.02.05. Downhole, radioactivity, remote sensing, and other methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 3161955 bytes
    Format: application/pdf
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  • 7
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    Differences in Arctic and Antarctic PSC Occurrence as observed by lidar in Ny-Ålesund [79ºN, 12ºE] and McMurdo [78ºS, 167ºE] (2005)
    In:  EPIC3Atmospheric chemistry and physics, 5, pp. 2081-2090
    Details
    Publication Date: 2019-07-16
    Description: The extent of springtime Arctic ozone lossdoes not reach Antarctic "ozone hole" dimensionsbecause of the generally higher temperaturesin the northern hemisphere vortex and consequentless polar stratospheric cloud (PSC) particlesurface for heterogeneous chlorine activation.Yet, with increasing greenhouse gases stratospherictemperatures are expected to further decrease.To infer if present Antarctic PSC occurrence canbe applied to predict future Arctic PSC occurrence,lidar observations from McMurdo station (78ºS, 167ºE)and Ny Ålesund (79ºN, 12ºE) have been analysed forthe 9 winters between 1995 (1995/1996) and 2003(2003/2004). Although the statistics may notcompletely cover the overall hemispheric PSCoccurrence, the observations are considered torepresent the main synoptic cloud features asboth stations are mostly situated in the centreor at the inner edge of the vortex. Since thefocus is set on the occurrence frequency of solidand liquid particles, the analysis has beenrestricted to volcanic aerosol free conditions.In McMurdo, by far the largest part of PSCobservations is associated with PSC type Ia.The observed constant background of NATparticles and their potential ability to causedenoxification and irreversible denitrificationis presumably more important to Antarctic ozonechemistry than the scarcely observed PSC type II.Meanwhile in Ny-Ålesund, PSC type II has neverbeen observed, while type Ia and Ib both occurin large fraction. Although they are also foundsolely, the majority of observations revealssolid and liquid particle layers in the sameprofile. For the Ny-Ålesund measurements, thefrequent occurrence of liquid PSC particlesyields major significance in terms of ozonechemistry, as their chlorine activation ratesare more efficient. The relationship betweentemperature, PSC formation, and denitrificationis nonlinear and the McMurdo and Ny-Ålesund PSCobservations imply that for predictedstratospheric cooling it is not possible todirectly apply current Antarctic PSC occurrencedirectly to the Arctic stratosphere. FutureArctic PSC occurrence, and thus ozone loss,will depend on the shape and barotropy of thevortex rather than on the minimum temperatures.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions (RECONCILE): activities and results (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Atmospheric Chemistry and Physics, COPERNICUS GESELLSCHAFT MBH, 13, pp. 9233-9268, ISSN: 1680-7316
    Details
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Lagrangian analysis of microphysical and chemical processes in the Antarctic stratosphere: a case study (2015)
    In:  EPIC3Atmospheric Chemistry and Physics, 15(12), pp. 6651-6665, ISSN: 1680-7324
    Details
    Publication Date: 2016-07-25
    Description: We investigated chemical and microphysical processes in the late winter in the Antarctic lower stratosphere, after the first chlorine activation and initial ozone depletion. We focused on a time interval when both further chlorine activation and ozone loss, but also chlorine deactivation, occur. We performed a comprehensive Lagrangian analysis to simulate the evolution of an air mass along a 10-day trajectory, coupling a detailed microphysical box model to a chemistry model. Model results have been compared with in situ and remote sensing measurements of particles and ozone at the start and end points of the trajectory, and satellite measurements of key chemical species and clouds along it. Different model runs have been performed to understand the relative role of solid and liquid polar stratospheric cloud (PSC) particles for the heterogeneous chemistry, and for the denitrification caused by particle sedimentation. According to model results, under the conditions investigated, ozone depletion is not affected significantly by the presence of nitric acid trihydrate (NAT) particles, as the observed depletion rate can equally well be reproduced by heterogeneous chemistry on cold liquid aerosol, with a surface area density close to background values. Under the conditions investigated, the impact of denitrification is important for the abundances of chlorine reservoirs after PSC evaporation, thus stressing the need to use appropriate microphysical models in the simulation of chlorine deactivation. We found that the effect of particle sedimentation and denitrification on the amount of ozone depletion is rather small in the case investigated. In the first part of the analyzed period, when a PSC was present in the air mass, sedimentation led to a smaller available particle surface area and less chlorine activation, and thus less ozone depletion. After the PSC evaporation, in the last 3 days of the simulation, denitrification increases ozone loss by hampering chlorine deactivation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    Polar Stratospheric Clouds in the Arctic and Antarctic - A Statistical Approach (2004)
    In:  EPIC3XXVIII SCAR Meeting, 25-31 July 2004, Bremen, Germany.
    Details
    Publication Date: 2019-07-16
    Description: A phenomenon known also beyond atmospheric sciences is the springtimeAntarctic ozone hole and the fact that ozone is catalytically destroyedby products of man-made CFCs. Yet, ozone depletion is tightly connectedwith natural processes in the polar stratosphere. Below a certainthreshold temperature, polar stratospheric clouds (PSCs) can form which provide the surface for heterogeneous reactions that lead to theactivation of initially bound chemical reservoir species. As theactivation is a key process for consequent succeeding ozone depletion, polarstratospheric clouds are a main factor for ozone chemistry in the polar stratosphere.PSCs occur at very low temperatures found in the stratosphere duringpolar night. Different cloud types, consisting of ice crystals, nitricacid trihydrate (NAT) particles, or H2O/HNO3/H2SO4 droplets form underdifferent temperature conditions and cause different chemical effects.In the Antarctic stratosphere, wintertime temperatures are much lowerthan in the Arctic due to different atmospheric wave patterns. Thedifference in temperature is reflected in frequency and persistence ofPSC types.By ground-based lidar it is possible to determine altitude and extent ofPSCs, and the retrieved backscatter ratio and depolarisation allow todistinguish the observed cloud type. Our study is based on lidarobservations from Ny-?lesund in the Arctic [79°N, 12°E] and McMurdo inthe Antarctic [78°S, 167°E].As expected, we find large differences in the occurrence frequency ofthe various PSC types. Yet, the statistical analysis reveals somesurprises. It is found that the most common PSC type at the Antarcticstation is made from solid NAT particles, while only a small fraction ofthe observed cloud layers consist of ice particles. On the other hand,the majority of PSCs at the Arctic station is found to consist of liquidparticles.As the PSC type has an influence on the heterogeneous activation rate,these results have to be carefully validated and taken into account byozone chemistry models.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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