TY  - JOUR
A1  - Putra, Sulistyo Emantoko Dwi
A1  - Tsuprykov, Oleg
A1  - Von Websky, Karoline
A1  - Ritter, Teresa
A1  - Reichetzeder, Christoph
A1  - Hocher, Berthold
T1  - Dealing with large sample sizes: comparison of a new one spot dot blot method to western blot
JF  - Clinical laboratory : the peer reviewed journal for clinical laboratories and laboratories related to blood transfusion
N2  - Background: Western blot is the gold standard method to determine individual protein expression levels. However, western blot is technically difficult to perform in large sample sizes because it is a time consuming and labor intensive process. Dot blot is often used instead when dealing with large sample sizes, but the main disadvantage of the existing dot blot techniques, is the absence of signal normalization to a housekeeping protein.
 Methods: In this study we established a one dot two development signals (ODTDS) dot blot method employing two different signal development systems. The first signal from the protein of interest was detected by horseradish peroxidase (HRP). The second signal, detecting the housekeeping protein, was obtained by using alkaline phosphatase (AP).
 Results: Inter-assay results variations within ODTDS dot blot and western blot and intra-assay variations between both methods were low (1.04 - 5.71%) as assessed by coefficient of variation.
 Conclusions: ODTDS dot blot technique can be used instead of western blot when dealing with large sample sizes without a reduction in results accuracy.
KW  - one dot two development signals (ODTDS) dot blot
KW  - western blot
KW  - protein quantification
KW  - large sample size studies
KW  - comparison
Y1  - 2014
U6  - https://doi.org/10.7754/Clin.Lab.2014.140317
SN  - 1433-6510
VL  - 60
IS  - 11
SP  - 1871
EP  - 1877
PB  - Clin Lab Publ., Verl. Klinisches Labor
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Hoffmann, Anne
A1  - Osterloh, Lukas
A1  - Stone, Robert
A1  - Lampert, Astrid
A1  - Ritter, Christoph
A1  - Stock, Maria
A1  - Tunved, Peter
A1  - Hennig, Tabea
A1  - Böckmann, Christine
A1  - Li, Shao-Meng
A1  - Eleftheriadis, Kostas
A1  - Maturilli, Marion
A1  - Orgis, Thomas
A1  - Herber, Andreas
A1  - Neuber, Roland
A1  - Dethloff, Klaus
T1  - Remote sensing and in-situ measurements of tropospheric aerosol, a PAMARCMiP case study
JF  - Atmospheric environment : air pollution ; emissions, transport and dispersion, transformation, deposition effects, micrometeorology, urban atmosphere, global atmosphere
N2  - In this work, a closure experiment for tropospheric aerosol is presented. Aerosol size distributions and single scattering albedo from remote sensing data are compared to those measured in-situ. An aerosol pollution event on 4 April 2009 was observed by ground based and airborne lidar and photometer in and around Ny-Alesund, Spitsbergen, as well as by DMPS, nephelometer and particle soot absorption photometer at the nearby Zeppelin Mountain Research Station.
 The presented measurements were conducted in an area of 40 x 20 km around Ny-Alesund as part of the 2009 Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project (PAMARCMiP). Aerosol mainly in the accumulation mode was found in the lower troposphere, however, enhanced backscattering was observed up to the tropopause altitude. A comparison of meteorological data available at different locations reveals a stable multi-layer-structure of the lower troposphere. It is followed by the retrieval of optical and microphysical aerosol parameters. Extinction values have been derived using two different methods, and it was found that extinction (especially in the UV) derived from Raman lidar data significantly surpasses the extinction derived from photometer AOD profiles. Airborne lidar data shows volume depolarization values to be less than 2.5% between 500 m and 2.5 km altitude, hence, particles in this range can be assumed to be of spherical shape. In-situ particle number concentrations measured at the Zeppelin Mountain Research Station at 474 m altitude peak at about 0.18 mu m diameter, which was also found for the microphysical inversion calculations performed at 850 m and 1500 m altitude. Number concentrations depend on the assumed extinction values, and slightly decrease with altitude as well as the effective particle diameter. A low imaginary part in the derived refractive index suggests weakly absorbing aerosols, which is confirmed by low black carbon concentrations, measured at the Zeppelin Mountain as well as on board the Polar 5 aircraft.
KW  - Arctic
KW  - Aerosols
KW  - Lidar
KW  - Arctic haze
Y1  - 2012
U6  - https://doi.org/10.1016/j.atmosenv.2011.11.027
SN  - 1352-2310
VL  - 52
IS  - 3
SP  - 56
EP  - 66
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Ritter, Christoph
A1  - Ángeles Burgos, María
A1  - Böckmann, Christine
A1  - Mateos, David
A1  - Lisok, Justyna
A1  - Markowicz, Krzysztof M.
A1  - Moroni, Beatrice
A1  - Cappelletti, David
A1  - Udisti, Roberto
A1  - Maturilli, Marion
A1  - Neuber, Roland
T1  - Microphysical properties and radiative impact of an intense biomass burning aerosol event measured over Ny-angstrom lesund, Spitsbergen in July 2015
JF  - Tellus - Series B, Chemical and Physical Meteorology
N2  - In this work, an evaluation of an intense biomass burning event observed over Ny-angstrom lesund (Spitsbergen, European Arctic) in July 2015 is presented. Data from the multi-wavelengths Raman-lidar KARL, a sun photometer and radiosonde measurements are used to derive some microphysical properties of the biomass burning aerosol as size distribution, refractive index and single scattering albedo at different relative humidities. Predominantly particles in the accumulation mode have been found with a bi-modal distribution and dominance of the smaller mode. Above 80% relative humidity, hygroscopic growth in terms of an increase of particle diameter and a slight decrease of the index of refraction (real and imaginary part) has been found. Values of the single scattering albedo around 0.9 both at 355nm and 532nm indicate some absorption by the aerosol. Values of the lidar ratio are around 26sr for 355nm and around 50sr for 532nm, almost independent of the relative humidity. Further, data from the photometer and surface radiation values from the local baseline surface radiation network (BSRN) have been applied to derive the radiative impact of the biomass burning event purely from observational data by comparison with a clear background day. We found a strong cooling for the visible radiation and a slight warming in the infra-red. The net aerosol forcing, derived by comparison with a clear background day purely from observational data, obtained a value of -95 W/m(2) per unit AOD500.
KW  - aerosol
KW  - lidar
KW  - retrieval of aerosol properties
KW  - radiative forcing
KW  - Arctic aerosol
Y1  - 2018
U6  - https://doi.org/10.1080/16000889.2018.1539618
SN  - 1600-0889
VL  - 70
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - GEN
A1  - Böckmann, Christine
A1  - Ritter, Christoph
A1  - Cappelletti, David
T1  - Mathematical tool for a closure study of aerosol microphysical property retrieval using lidar and photometer data
T2  - IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium
N2  - We present a project combining lidar, photometer and particle counter data with a regularization software tool for a closure study of aerosol microphysical property retrieval. In a first step only lidar data are used to retrieve the particle size distribution (PSD). Secondly, photometer data are added, which results in a good consistency of the retrieved PSDs. Finally, those retrieved PSDs may be compared with the measured PSD from a particle counter. The data here were taken in Ny Alesund, Svalbard, as an example.
KW  - Aerosol
KW  - Raman lidar
KW  - photometer
KW  - inversion
KW  - regularization
KW  - particle microphysics
Y1  - 2018
SN  - 978-1-5386-7150-4
U6  - https://doi.org/10.1109/IGARSS.2018.8518674
SN  - 2153-6996
SP  - 5575
EP  - 5578
PB  - IEEE
CY  - New York
ER  - 
TY  - JOUR
A1  - Dube, Jonas
A1  - Böckmann, Christine
A1  - Ritter, Christoph
T1  - Lidar-Derived Aerosol Properties from Ny-Ålesund, Svalbard during the MOSAiC Spring 2020
JF  - Remote sensing / Molecular Diversity Preservation International (MDPI)
N2  - In this work, we present Raman lidar data (from a Nd:YAG operating at 355 nm, 532 nm and 1064 nm) from the international research village Ny-Alesund for the time period of January to April 2020 during the Arctic haze season of the MOSAiC winter. We present values of the aerosol backscatter, the lidar ratio and the backscatter Angstrom exponent, though the latter depends on wavelength. The aerosol polarization was generally below 2%, indicating mostly spherical particles. We observed that events with high backscatter and high lidar ratio did not coincide. In fact, the highest lidar ratios (LR > 75 sr at 532 nm) were already found by January and may have been caused by hygroscopic growth, rather than by advection of more continental aerosol. Further, we performed an inversion of the lidar data to retrieve a refractive index and a size distribution of the aerosol. Our results suggest that in the free troposphere (above approximate to 2500 m) the aerosol size distribution is quite constant in time, with dominance of small particles with a modal radius well below 100 nm. On the contrary, below approximate to 2000 m in altitude, we frequently found gradients in aerosol backscatter and even size distribution, sometimes in accordance with gradients of wind speed, humidity or elevated temperature inversions, as if the aerosol was strongly modified by vertical displacement in what we call the "mechanical boundary layer". Finally, we present an indication that additional meteorological soundings during MOSAiC campaign did not necessarily improve the fidelity of air backtrajectories.
KW  - aerosol
KW  - Arctic haze
KW  - lidar
KW  - microphysical properties
KW  - backtrajectories;
KW  - Ny-Alesund
KW  - Svalbard
KW  - MOSAiC
KW  - aerosol-boundary layer interactions
Y1  - 2022
U6  - https://doi.org/10.3390/rs14112578
SN  - 2072-4292
VL  - 14
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Nakoudi, Konstantina
A1  - Ritter, Christoph
A1  - Stachlewska, Iwona Sylwia
T1  - Properties of cirrus clouds over the European Arctic (Ny-Alesund, Svalbard)
JF  - Remote sensing / Molecular Diversity Preservation International (MDPI)
N2  - Cirrus is the only cloud type capable of inducing daytime cooling or heating at the top of the atmosphere (TOA) and the sign of its radiative effect highly depends on its optical depth. However, the investigation of its geometrical and optical properties over the Arctic is limited. In this work the long-term properties of cirrus clouds are explored for the first time over an Arctic site (Ny-Alesund, Svalbard) using lidar and radiosonde measurements from 2011 to 2020. The optical properties were quality assured, taking into account the effects of specular reflections and multiple-scattering. Cirrus clouds were generally associated with colder and calmer wind conditions compared to the 2011-2020 climatology. However, the dependence of cirrus properties on temperature and wind speed was not strong. Even though the seasonal cycle was not pronounced, the winter-time cirrus appeared under lower temperatures and stronger wind conditions. Moreover, in winter, geometrically- and optically-thicker cirrus were found and their ice particles tended to be more spherical. The majority of cirrus was associated with westerly flow and westerly cirrus tended to be geometrically-thicker. Overall, optically-thinner layers tended to comprise smaller and less spherical ice crystals, most likely due to reduced water vapor deposition on the particle surface. Compared to lower latitudes, the cirrus layers over Ny-Alesund were more absorbing in the visible spectral region and they consisted of more spherical ice particles.
KW  - Arctic clouds
KW  - cirrus clouds
KW  - ice clouds
KW  - lidar
Y1  - 2021
U6  - https://doi.org/10.3390/rs13224555
SN  - 2072-4292
VL  - 13
IS  - 22
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Wang, Chaoxuan
A1  - Enssle, Jörg
A1  - Pietzner, Anne
A1  - Schmöcker, Christoph
A1  - Weiland, Linda
A1  - Ritter, Oliver
A1  - Jaensch, Monique
A1  - Elbelt, Ulf
A1  - Pagonas, Nikolaos
A1  - Weylandt, Karsten-Henrich
T1  - Essential polyunsaturated fatty acids in blood from patients with and without catheter-proven coronary artery disease
JF  - International journal of molecular sciences
N2  - Coronary artery disease (CAD) is the leading cause of death worldwide. 
Statins reduce morbidity and mortality of CAD. Intake of n-3 polyunsaturated fatty acid (n-3 PUFAs), particularly eicosapentaenoic acid (EPA), is associated with reduced morbidity and mortality in patients with CAD. Previous data indicate that a higher conversion of precursor fatty acids (FAs) to arachidonic acid (AA) is associated with increased CAD prevalence. 
Our study explored the FA composition in blood to assess n-3 PUFA levels from patients with and without CAD. We analyzed blood samples from 273 patients undergoing cardiac catheterization. Patients were stratified according to clinically relevant CAD (n = 192) and those without (n = 81). FA analysis in full blood was performed by gas chromatography. Indicating increased formation of AA from precursors, the ratio of dihomo-gamma-linolenic acid (DGLA) to AA, the delta-5 desaturase index (D5D index) was higher in CAD patients. CAD patients had significantly lower levels of omega-6 polyunsaturated FAs (n-6 PUFA) and n-3 PUFA, particularly EPA, in the blood. 
Thus, our study supports a role of increased EPA levels for cardioprotection.
KW  - coronary artery disease
KW  - triglycerides
KW  - polyunsaturated fatty acids
KW  - n-3 PUFA
KW  - statins
KW  - arachidonic acid
Y1  - 2022
U6  - https://doi.org/10.3390/ijms23020766
SN  - 1422-0067
SN  - 1661-6596
VL  - 23
IS  - 2
PB  - Molecular Diversity Preservation International
CY  - Basel
ER  - 
TY  - JOUR
A1  - Nakoudi, Konstantina
A1  - Stachlewska, Iwona S.
A1  - Ritter, Christoph
T1  - An extended lidar-based cirrus cloud retrieval scheme
BT  - first application over an Arctic site
JF  - Optics express : the international electronic journal of optics / Optica
N2  - Accurate and precise characterization of cirrus cloud geometrical and optical properties is essential for better constraining their radiative footprint. A lidar-based retrieval scheme is proposed here, with its performance assessed on fine spatio-temporal observations over the Arctic site of Ny-Alesund, Svalbard. Two contributions related to cirrus geometrical (dynamic Wavelet Covariance Transform (WCT)) and optical properties (constrained Klett) are reported. The dynamic WCT rendered cirrus detection more robust, especially for thin cirrus layers that frequently remained undetected by the classical WCT method. Regarding optical characterization, we developed an iterative scheme for determining the cirrus lidar ratio (LRci) that is a crucial parameter for aerosol - cloud discrimination. Building upon the Klett-Fernald method, the LRci was constrained by an additional reference value. In established methods, such as the double-ended Klett, an aerosol-free reference value is applied. In the proposed constrained Klett, however, the reference value was approximated from cloud-free or low cloud optical depth (COD up to 0.2) profiles and proved to agree with independent Raman estimates. For optically thin cirrus, the constrained Klett inherent uncertainties reached 50% (60-74%) in terms of COD (LRci). However, for opaque cirrus COD (LRci) uncertainties were lower than 10% (15%). The detection method discrepancies (dynamic versus static WCT) had a higher impact on the optical properties of low COD layers (up to 90%) compared to optically thicker ones (less than 10%). The constrained Klett presented high agreement with two established retrievals. For an exemplary cirrus cloud, the constrained Klett estimated the COD355 (LRci355) at 0.28 +/- 0.17 (29 +/- 4 sr), the double-ended Klett at 0.27 +/- 0.15 (32 +/- 4 sr) and the Raman retrievals at 0.22 +/- 0.12 (26 +/- 11 sr). Our approach to determine the necessary reference value can also be applied in established methods and increase their accuracy. In contrast, the classical aerosol-free assumption led to 44 sr LRci overestimation in optically thin layers and 2-8 sr in thicker ones. The multiple scattering effect was corrected using Eloranta (1998) and accounted for 50-60% extinction underestimation near the cloud base and 20-30% within the cirrus layers.
Y1  - 2021
U6  - https://doi.org/10.1364/OE.414770
SN  - 1094-4087
VL  - 29
IS  - 6
SP  - 8553
EP  - 8580
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Grassl, Sandra
A1  - Ritter, Christoph
A1  - Schulz, Alexander
T1  - The nature of the Ny-Alesund wind field analysed by high-resolution windlidar data
JF  - Remote sensing
N2  - In this work we present windlidar data for the research village Ny-Alesund located on Svalbard in the European Arctic (78.923 degrees N, 11.928 degrees F) from 2013 to 2021. 
The data have a resolution of 50 m and 10 min with an overlapping height of about 150 m. 
The maximum range depends on the meteorologic situation. Up to 1000 m altitude the data availability is better than 71%. 
We found that the highest wind speeds occur in November and December, the lowest ones in June and July, up to 500 m altitude the wind is channelled strongly in ESE to NW direction parallel to the fjord axis and the synoptic conditions above 1000 m altitude already dominate. 
While the fraction of windy days (v > 10 m/s) varies significantly from month to month, there is no overall trend of the wind visible in our data set. 
We define gusts and jets by the requirement of wind maxima v > 2 m/s above and below a wind maximum. In total, more than 24,000 of these events were identified (corresponding to 6% of the time), of which 223 lasted for at least 100 min ("Long Jets"). All of these events are fairly equally distributed over the months relatively to the available data. 
Further, gusts and jets follow different distributions (in terms of altitude or depths) and occur more frequently for synoptic flow from roughly a southerly direction. Jets do not show a clear correlation between occurrence and synoptic flow. Gusts and jets are not related to cloud cover. 
We conclude that the atmosphere from 400 m to 1000 m above Ny-Alesund is dominated by a turbulent wind shear zone, which connects the micrometeorology in the atmospheric boundary layer (ABL) with the synoptic flow.
KW  - windlidar
KW  - wind field
KW  - wind channelling
KW  - jets
KW  - Ny-Alesund
KW  - Svalbard
KW  - Kongsfjord
KW  - wind speed
KW  - wind direction
KW  - turbulent wind shear zone
Y1  - 2022
U6  - https://doi.org/10.3390/rs14153771
SN  - 2072-4292
VL  - 14
IS  - 15
PB  - MDPI
CY  - Basel
ER  -