14 research outputs found
Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015
With the rapidly growing number of automated single-wavelength backscatter
lidars (ceilometers), their potential benefit for aerosol remote sensing
received considerable scientific attention. When studying the accuracy of
retrieved particle backscatter coefficients, it must be considered that most
of the ceilometers are influenced by water vapor absorption in the spectral
range around 910 nm. In the literature methodologies have been proposed to correct for this
effect; however, a validation was not yet performed. In
the framework of the ceilometer intercomparison campaign CeiLinEx2015 in
Lindenberg, Germany, hosted by the German Weather Service, it was possible to
tackle this open issue. Ceilometers from Lufft (CHM15k and CHM15kx, operating
at 1064 nm), from Vaisala (CL51 and CL31) and from Campbell Scientific
(CS135), all operating at a wavelength of approximately 910 nm, were
deployed together with a multi-wavelength research lidar (RALPH) that served
as a reference. In this paper the validation of the water vapor correction is
performed by comparing ceilometer backscatter signals with measurements of
the reference system extrapolated to the water vapor regime. One inherent
problem of the validation is the spectral extrapolation of particle optical
properties. For this purpose AERONET measurements and inversions of RALPH
signals were used. Another issue is that the vertical range where validation
is possible is limited to the upper part of the mixing layer due to incomplete
overlap and the generally low signal-to-noise ratio and signal artifacts
above that layer. Our intercomparisons show that the water vapor correction
leads to quite a good agreement between the extrapolated reference signal and
the measurements in the case of CL51 ceilometers at one or more wavelengths
in the specified range of the laser diode's emission. This ambiguity is due
to the similar effective water vapor transmission at several wavelengths. In
the case of CL31 and CS135 ceilometers the validation was not always
successful. That suggests that error sources beyond the water vapor
absorption might be dominant. For future applications we recommend monitoring
the emitted wavelength and providing “dark” measurements on a regular
basis.</p
A Pre-clinical Animal Model of Trypanosoma brucei Infection Demonstrating Cardiac Dysfunction
African trypanosomiasis (AT), caused by Trypanosoma brucei species, results in both neurological and cardiac dysfunction and can be fatal if untreated. Research on the pathogenesis and treatment of the disease has centred to date on the characteristic neurological symptoms, whereas cardiac dysfunction (e.g. ventricular arrhythmias) in AT remains largely unstudied. Animal models of AT demonstrating cardiac dysfunction similar to that described in field cases of AT are critically required to transform our understanding of AT-induced cardiac pathophysiology and identify future treatment strategies. We have previously shown that T. brucei can interact with heart muscle cells (cardiomyocytes) to induce ventricular arrhythmias in ex vivo adult rat hearts. However, it is unknown whether the arrhythmias observed ex vivo are also present during in vivo infection in experimental animal models. Here we show for the first time the characterisation of ventricular arrhythmias in vivo in two animal models of AT infection using electrocardiographic (ECG) monitoring. The first model utilised a commonly used monomorphic laboratory strain, Trypanosoma brucei brucei Lister 427, whilst the second model used a pleomorphic laboratory strain, T. b. brucei TREU 927, which demonstrates a similar chronic infection profile to clinical cases. The frequency of ventricular arrhythmias and heart rate (HR) was significantly increased at the endpoint of infection in the TREU 927 infection model, but not in the Lister 427 infection model. At the end of infection, hearts from both models were isolated and Langendorff perfused ex vivo with increasing concentrations of the β-adrenergic agonist isoproterenol (ISO). Interestingly, the increased frequency of arrhythmias observed in vivo in the TREU 927 infection model was lost upon isolation of the heart ex vivo, but re-emerged with the addition of ISO. Our results demonstrate that TREU 927 infection modifies the substrate of the myocardium in such a way as to increase the propensity for ventricular arrhythmias in response to a circulating factor in vivo or β-adrenergic stimulation ex vivo. The TREU 927 infection model provides a new opportunity to accelerate our understanding of AT-related cardiac pathophysiology and importantly has the required sensitivity to monitor adverse cardiac-related electrical dysfunction when testing new therapeutic treatments for AT
Estudo etnobotânico como subsídio para elaboração de plano de manejo da reserva florestal Embrapa/Epagri no município de Caçador, Santa Catarina
Orientador: Raquel Rejane Bonato NegrelleMonografia (Bacharelado) - Universidade Federal do Paraná. Setor de Ciencias Biológicas. Curso de Graduaçao em Ciencias Biológica
Late Stage Infection in Sleeping Sickness
At the turn of the 19th century, trypanosomes were identified as the causative agent of sleeping sickness and their presence within the cerebrospinal fluid of late stage sleeping sickness patients was described. However, no definitive proof of how the parasites reach the brain has been presented so far. Analyzing electron micrographs prepared from rodent brains more than 20 days after infection, we present here conclusive evidence that the parasites first enter the brain via the choroid plexus from where they penetrate the epithelial cell layer to reach the ventricular system. Adversely, no trypanosomes were observed within the parenchyma outside blood vessels. We also show that brain infection depends on the formation of long slender trypanosomes and that the cerebrospinal fluid as well as the stroma of the choroid plexus is a hostile environment for the survival of trypanosomes, which enter the pial space including the Virchow-Robin space via the subarachnoid space to escape degradation. Our data suggest that trypanosomes do not intend to colonize the brain but reside near or within the glia limitans, from where they can re-populate blood vessels and disrupt the sleep wake cycles
Trois lents effondrements
We present the development of the PathfinderTURB algorithm for the analysis of ceilometer backscatter data and the real-time detection of the vertical structure of the planetary boundary layer. Two aerosol layer heights are retrieved by PathfinderTURB: the convective boundary layer (CBL) and the continuous aerosol layer (CAL). PathfinderTURB combines the strengths of gradient- and variance-based methods and addresses the layer attribution problem by adopting a geodesic approach. The algorithm has been applied to 1 year of data measured by two ceilometers of type CHM15k, one operated at the Aerological Observatory of Payerne (491 m a.s.l.) on the Swiss plateau and one at the Kleine Scheidegg (2061 m a.s.l.) in the Swiss Alps. The retrieval of the CBL has been validated at Payerne using two reference methods: (1) manual detections of the CBL height performed by human experts using the ceilometer backscatter data; (2) values of CBL heights calculated using the Richardson's method from co-located radio sounding data. We found average biases as small as 27 m (53 m) with respect to reference method 1 (method 2). Based on the excellent agreement between the two reference methods, PathfinderTURB has been applied to the ceilometer data at the mountainous site of the Kleine Scheidegg for the period September 2014 to November 2015. At this site, the CHM15k is operated in a tilted configuration at 71° zenith angle to probe the atmosphere next to the Sphinx Observatory (3580 m a.s.l.) on the Jungfraujoch (JFJ). The analysis of the retrieved layers led to the following results: the CAL reaches the JFJ 41 % of the time in summer and 21 % of the time in winter for a total of 97 days during the two seasons. The season-averaged daily cycles show that the CBL height reaches the JFJ only during short periods (4 % of the time), but on 20 individual days in summer and never during winter. During summer in particular, the CBL and the CAL modify the air sampled in situ at JFJ, resulting in an unequivocal dependence of the measured absorption coefficient on the height of both layers. This highlights the relevance of retrieving the height of CAL and CBL automatically at the JFJ.ISSN:1680-7375ISSN:1680-736
PathfinderTURB: an automatic boundary layer algorithm. Development, validation and application to study the impact on in-situ measurements at the Jungfraujoch
We present the development of the PathfinderTURB algorithm for the analysis
of ceilometer backscatter data and the real-time detection of the vertical
structure of the planetary boundary layer. Two aerosol layer heights are
retrieved by PathfinderTURB: the convective boundary layer (CBL) and the
continuous aerosol layer (CAL). PathfinderTURB combines the strengths of
gradient- and variance-based methods and addresses the layer attribution
problem by adopting a geodesic approach. The algorithm has been applied to
1 year of data measured by two ceilometers of type CHM15k, one operated at
the Aerological Observatory of Payerne (491 m a.s.l.) on the Swiss plateau
and one at the Kleine Scheidegg (2061 m a.s.l.) in the Swiss Alps. The
retrieval of the CBL has been validated at Payerne using two reference
methods: (1) manual detections of the CBL height performed by human experts
using the ceilometer backscatter data; (2) values of CBL heights calculated
using the Richardson's method from co-located radio sounding data. We found
average biases as small as 27 m (53 m) with respect to reference method 1
(method 2). Based on the excellent agreement between the two reference
methods, PathfinderTURB has been applied to the ceilometer data at the
mountainous site of the Kleine Scheidegg for the period September 2014 to
November 2015. At this site, the CHM15k is operated in a tilted configuration
at 71° zenith angle to probe the atmosphere next to the Sphinx
Observatory (3580 m a.s.l.) on the Jungfraujoch (JFJ). The analysis of the
retrieved layers led to the following results: the CAL reaches the JFJ
41 % of the time in summer and 21 % of the time in winter for a total
of 97 days during the two seasons. The season-averaged daily cycles show that
the CBL height reaches the JFJ only during short periods (4 % of the
time), but on 20 individual days in summer and never during winter. During
summer in particular, the CBL and the CAL modify the air sampled in situ at
JFJ, resulting in an unequivocal dependence of the measured absorption
coefficient on the height of both layers. This highlights the relevance of
retrieving the height of CAL and CBL automatically at the JFJ
Jahresganglinien 1989 - Langzeitzaehlstellen
TIB: RN 5590(48) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman