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Dissertations / Theses on the topic 'Ice crystals'
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1
Bacon, Neil J. "Laboratory studies of the growth, sublimation, and light-scattering properties of single levitated ice particles /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9735.
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Baker, Kristina M. Verlinde Johannes. "Microwave scattering from melting ice crystals." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4465/index.html.
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Slaughterbeck, Clifford R. "Force microscopy of ice surfaces /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9670.
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Siow, Lee Fong, and n/a. "Cryostability of large unilamellar vesicles in relation to the effect of cryoprotective agents on ice matrix." University of Otago. Department of Food Science, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080213.110706.
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Freeze-injury at the plasma membrane level has been identified as being crucial for the survival of living matter. Since plasma membranes consist of several micro domains that make the structure rather complex, this study attempted to use simple model membranes to investigate the changes of phospholipid bilayers at sub-zero temperatures. Egg yolk L-α-phosphatidylcholine (EPC) and 1, 2-dipalmitoyl-rac-glycero-3-phosphocholine (DPPC) that mimic plasma membranes in their unique ways were used to prepare large unilamellar vesicles (LUV), which were the model membranes of this study.
At cooling rates of 0.5 and 10�C/min, LUV were freeze-concentrated in the unfrozen matrix as a result of the advancing extraliposomal ice front and the decreasing phase volume of the unfrozen matrix, both of which led to membrane lesion. At the slow cooling rate of 0.5�C/min, an additional freezing stress imposed by the osmotic gradient across the bilayers, due to the increase of solute concentration in the unfrozen matrix, promoted leakage of LUV.
The gel-liquid crystal phase transition temperature of phospholipids played an important role in determining if the LUV could withstand freezing stress when the LUV were held at a defined sub-zero temperature for a given period of holding time. EPC LUV were more leaky than DPPC LUV when they were held at the high sub-zero temperatures and their leakage increased with increasing holding time. The leakiness of EPC LUV could be related to the fluid and deformable nature of the EPC above its phase transition temperature. In contrast, DPPC LUV with a higher gel-liquid crystal phase transition temperature compared to EPC may become increasingly fragile at lower sub-zero temperatures, which led to the increase of leakage when the DPPC LUV were held at the lower sub-zero temperatures. These results indicated that the determination of the fatty acid profile of the plasma membranes was essential to aid in developing the most suitable holding temperature and time during the cryopreservation of biological specimens. Adding to the integrity of LUV that depended on the gel-liquid crystal phase transition temperature of phospholipids, intraliposomal ice formation also depended on the phase transition temperature of phospholipids. Intraliposomal ice formation was only observed for DPPC LUV but not for EPC LUV.
In addition to the extraliposomal ice formation, other physical changes such as the eutectic crystallization of sodium chloride (NaCl) and ice mixture on the stability of LUV were also investigated. The eutectic crystallization of NaCl/ice mixture was governed by the intra- and extraliposomal distribution of NaCl and was more likely to occur at the physiological NaCl concentrations compared to lower NaCl concentrations. The eutectic crystallization of NaCl/ice mixture further increased the leakage of LUV.
The understanding of the freezing behaviour and the mechanisms of freeze-injury of LUV allowed the use of the current model membranes for further investigations of the cryoprotective actions of cryoprotective agents (CPA). Partial phase diagrams of sugar-salt-water, dimethyl sulfoxide (DMSO)-salt-water and ethylene glycol (EG)-salt-water systems that resembled extraliposomal solute compositions were constructed and the phase volume of ice and unfrozen matrix was estimated from the freezing curves. Ice reduction was the major mechanism by which the non-permeable and permeable CPA protected the LUV from freeze-injury. Other cryoprotective mechanisms of the non-permeable and permeable CPA through the dilution and spacing out of the LUV in the unfrozen matrix as well as the suppression of the eutectic crystallization of NaCl/ice mixture were not ruled out. Non-permeable CPA were more effective in preventing leakage of DPPC than EPC LUV. Unlike the non-permeable CPA, permeable CPA were more effective for EPC than DPPC LUV that had been subjected to freezing and thawing processes. At room temperature, however, DMSO and EG were detrimental to the stability of DPPC LUV. The choice of CPA is strictly dependent on the type of phospholipids that varied in their acyl chain length and phase transition temperature.
In summary, this study provides insights of the freeze-injury of LUV and the cryoprotective mechanisms of the non-permeable and permeable CPA which are beneficial to the field of cryopreservation that often depends on empirical trial and error methods. By integrating a comprehensive molecular-based understanding, an optimal cryopreservation procedure could be designed.
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Newyear, Karl D. "A comparison of theory with laboratory and field observations of wave propagation in grease ice /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/11057.
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Ritter, Georg. "The growth and morphology of small ice crystals in a diffusion chamber." Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/16329.
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Small water ice crystals are the main component of cold tropospheric clouds such as cirrus. Because these clouds cover large areas of our planet, their role in the radiation budget of incoming and outgoing radiation to the planet's surface is important. At present, the representation of these clouds in climate and weather models is subject to improvements: a large part of the uncertainty error stems from the lack of precise micro-physical and radiation model schemes for ice crystal clouds. To improve the cloud representations, a better understanding of the life time dynamics of the clouds and their composition is necessary, comprising a detailed understanding of the ice particle genesis, and development over their lifetime. It is especially important to understand how the development of ice crystals over time is linked to the changes in observable variables such as water vapour content and temperature and how they change the light scattering properties of the crystals. Recent remote and aircraft based in-situ measurements have shown that many ice particles show a light scattering behaviour typical for crystals having rough surfaces or being of complex geometrical shapes. The aim of this thesis was to develop the experimental setup and experiments to investigate this further by studying the surface morphology of small water ice crystals using scanning electron microscopy (SEM). The experiments I developed study the growth of water ice crystals inside an SEM chamber under controlled environmental conditions. The influence of water vapour supersaturation, pressure and temperature is investigated. I demonstrate how to retrieve the surface topology from observed crystals for use as input to computational light scattering codes to derive light scattering phase functions and asymmetry parameters, which can be used as input into atmospheric models. Difficulties with the method for studying the growth of water ice crystals, such as the effect of the electron beam-gas ionization and charging effects, the problem of facilitating repeated and localized ice growth, and the effect of radiative influences on the crystal growth are discussed. A broad set of nucleation target materials is studied. In a conclusion, I demonstrate that the method is suitable to study the surface morphologies, but is experimentally very challenging and many precautions must be taken, such as imaging only once and preventing radiative heat exchange between the chamber walls and the crystals to avoid unwanted effects on the crystal morphology. It is also left as a question if a laboratory experiment, where crystals will need to be grown in connection to a substrate, can represent the real world well enough. Deriving the required light scattering data in-situ might be an alternative, easier way to collect data for modelling use.
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Zhang, Zhibo. "Computation of the scattering properties of nonspherical ice crystals." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1267.
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This thesis is made up of three parts on the computation of scattering properties of nonspherical
particles in the atmosphere. In the first part, a new crystal type-droxtal-is introduced to make a better
representation of the shape of small ice crystals in the uppermost portions of midlatitude and tropical cirrus
clouds. Scattering properties of droxtal ice crystals are investigated by using the Improved-Geometric Optic
(IGO) method. At the visible wavelength, due to the presence of the hexagonal structure, all elements of the
phase matrix of droxtal ice crystals share some common features with hexagonal ice crystals, such as 220
and 460 halos. In the second part of this thesis, the possibility of enhancing the performance of current
Anomalous Diffraction Theory (ADT) is investigated. In conventional ADT models, integrations are
usually carried out in the domain of the particle projection. By transforming the integration domain to the
domain of scaled projectile length, the algorithm of conventional ADT models is enhanced. Because the
distribution of scaled projectile length is independent of the particle's physical size as long as the shape
remains the same, the new algorithm is especially efficient for the calculation of a large number of particles
with the same shape but different sizes. Finally, in the third part, the backscattering properties of
nonspherical ice crystals at the 94GHz frequency are studied by employing the Finite-Difference Time-
Domain (FDTD) method. The most important factor that controls the backscattering cross section is found
to be the ratio of the volume-equal radius to the maximum dimension of the ice crystal. Substantial
differences in backscattering cross sections are found between horizontal orientated and randomly oriented
ice crystals. An analytical formula is derived for the relationship between the ice water (IWC) content and
the radar reflectivity ( e Z ). It is shown that a change to the concentration of ice crystals without any
changes on the size distribution or particle habits leads only to a linear e Z IWC - relationship. The famous
power law e Z IWC - relationship is the result of the shift of the peak of particle size distribution.
8
Bacer, Sara [Verfasser]. "Global numerical simulations of atmospheric ice crystals / Sara Bacer." Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/1187868744/34.
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Tymkovych, M. Y., О. Г. Аврунін, O. Gryshkov, K. G. Selivanova, V. Mutsenko, and B. Glasmacher. "Multiscale quantitative analysis of microscopic images of ice crystals." Thesis, The International Journal of Artificial Organs, 2019. http://openarchive.nure.ua/handle/document/9879.
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It was analyzed multiple images. The results in the first approximation show a 2-fold increase in speed when using our implementation of active contours. At the same time, the segmented areas of crystals correspond to the approach without the use of multi-scale image representation.
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Thorsteinsson, Throstur. "Anisotropy of ice Ih : development of fabric and effects of anisotropy on deformation /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/6844.
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Nicolet, Mathieu. "Characterization of ice crystals and water droplets with the ice optical detector device (IODE) using depolarization measurements /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17659.
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Nilamdeen, Mohamed Shezad. "An uncoupled multiphase approach towards modeling ice crystals in jet engines." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92185.
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Taylor, Laurence Charles. "A beam tracing model for electromagnetic scattering by atmospheric ice crystals." Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17645.
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While exact methods, such as DDA or T-matrix, can be applied to particles withsizes comparable to the wavelength, computational demands mean that they are size limited. For particles much larger than the wavelength, the Geometric Optics approximation can be employed, but in doing so wave effects, such as interference and diffraction, are ignored. In between these two size extremes there exists a need for computational techniques which are capable of handling the wide array of ice crystal shapes and sizes that are observed in cirrus clouds. The Beam Tracing model developed within this project meets these criteria. It combines aspects of geometric optics and physical optics. Beam propagation is handled by Snell's law and the law of reflection. A beam is divided into reflected and transmitted components each time a crystal facet is illuminated. If the incident beam illuminates multiple facets it is split, with a new beam being formed for each illuminated facet. The phase-dependent electric field amplitude of the beams is known from their ampli- tude (Jones) matrices. These are modified by transmission and reflection matrices, whose elements are Fresnel amplitude coefficients, each time a beam intersects a crystal facet. Phase tracing is carried out for each beam by considering the path that its 'centre ray' would have taken. The local near-field is then mapped, via a surface integral formulation of a vector Kirchhoff diffraction approximation, to the far-field. Once in the far-field the four elements of the amplitude matrix are trans- formed into the sixteen elements of the scattering matrix via known relations. The model is discussed in depth, with details given on its implementation. The physical basis of the model is given through a discussion of Ray Tracing and how this leads to the notion of Beam Tracing. The beam splitting algorithm is described for convex particles followed by the necessary adaptations for concave and/or ab- sorbing particles. Once geometric aspects have been established details are given as to how physical properties of beams are traced including: amplitude, phase and power. How diffraction is implemented in the model is given along with a review of existing diffraction implementations. Comparisons are given, first against a modified Ray Tracing code to validate the geometric optics aspects of the model. Then, specific examples are given for the cases of transparent, pristine, smooth hexagonal columns of four different sizes and orientations; a highly absorbing, pristine, smooth hexagonal column and a highly absorbing, indented, smooth hexagonal column. Analysis of two-dimensional and one-dimensional intensity distributions and degree of linear polarisation results are given for each case and compared with results acquired through use of the Amster- dam Discrete-Dipole Approximation (ADDA) code; with good agreement observed. To the author's best knowledge, the Beam Tracer developed here is unique in its ability to handle concave particles; particles with complex structures and the man- ner in which beams are divided into sub-beams of quasi-constant intensity when propagating in an absorbing medium. One of the model's potential applications is to create a database of known particle scattering patterns, for use in aiding particle classification from images taken by the Small Ice Detector (SID) in-situ probe. An example of creating such a database for hexagonal columns is given.
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Collier, Christopher Thomas. "Experimental and computational investigation into light scattering by atmospheric ice crystals." Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/16359.
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An investigation was carried out into light scattering by Gaussian rough ice crystals. Gaussian rough crystal geometries were generated using roughness parameters derived from mineral dust grains, which have been reported to be suitable proxies for rough ice crystals. Light scattering data for these geometries was computed using the discrete dipole approximation (DDA) method. Phase functions, 2D scattering patterns, degree of linear polarisation patterns and asymmetry parameters were computed for smooth, moderately rough and highly rough crystals with a variety of orientations and size parameters. A sodium fluorosilicate ice analogue crystal with three partially roughened prism facets was created using focused ion beam (FIB) milling and 2D scattering patterns were collected from it using the small ice detector (SID) 3 cloud probe. It was found that roughness reduces features in the phase function compared to scattering by smooth hexagonal prisms, particularly when the roughness features were horizontally much larger than the wavelength. However, the most effective roughness model also takes account of horizontal features whose size is closer to that of the wavelength. Horizontal features smaller than the wavelength have very little effect.
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Pope, Shelly Kay. "Laboratory measurements of the single-scattering properties of ammonia ice crystals." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185372.
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This work presents scattering measurements and photographs of ammonia ice crystals grown at temperatures from 130 to 180 Kelvins. The prime candidate for the material making up the visible clouds of Jupiter and Saturn is ammonia ice. Spacecraft observations of these planets have constrained the single-scattering properties of the cloud particles. To further investigate the nature of these particles, ammonia ice crystals were grown under conditions simulating the atmosphere of Jupiter and Saturn. The experimental apparatus used to make these measurements includes a glass-walled cylindrical chamber which permits measurement of the scattered light over a wide range of scattering angles and a temperature control system which uses a liquid nitrogen reservoir combined with heaters. The chamber is illuminated by a tungsten lamp through a rapidly spinning filter/polarizer wheel which yields measurements of intensity and linear polarization in each of three colors. A photographic record of the crystals is obtained with a microscope objective, and six linear array detectors measure the scattered light. A variety of crystal shapes and phase functions were seen. A representative selection of scattering measurements and photographs are presented. The data do not resemble theoretical calculations for ammonia cubes, tetrahedra, or octahedra. They do appear similar to microwave analog measurements of the scattering properties of a mix of particle shapes as well as of fluffy particles. The ammonia measurements fall into two groups: one has wavelength-dependent polarization and for size parameters up to about seven the scattering properties can be fit by Mie theory. The second group has wavelength-independent phase functions, implying size parameters of 10 to 50, and has a characteristic signature of polarization varying from -10% to +10%. The data can be used to rule out some models for Jupiter's and Saturn's atmospheres and to guide future modelling efforts. For Jupiter, models with a cloud of ammonia crystals of size parameter equal to about 5 (in the red) are suggested. For Saturn, a model is suggested that has a thin layer of small ammonia crystals (in the Mie range) over a thicker ammonia cloud with the wavelength-independent polarization that is characteristic of larger crystals.
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Smith, Sharon Lee Carleton University Dissertation Geology. "Ice lens formation and frost heave from a thermodynamic rheologic perspective." Ottawa, 1992.
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Celik, Yeliz. "Experimental Investigation of the Interactions of Hyperactive Antifreeze Proteins with Ice Crystals." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1268166115.
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Groves, Ronald William. "O17 spin-lattice relaxation solid state NMR studies of pure and doped ices." Columbus, Ohio : Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1021903674.
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Thesis (Ph. D.)--Ohio State University, 2002.<br>Title from first page of PDF file. Document formatted into pages; contains xx, 128 p.; also contains graphics. Includes abstract and vita. Co-advisors: Charles H. Pennington and James V. Coe, Dept. of Chemistry. Includes bibliographical references (p. 124-128).
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Peterson, Harold S. "NOx formation through electrical processes in the middle atmosphere and subsequent effects on ice crystals." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3316372.
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Petersen, Danyal A. "Laboratory study of electrical discharges on vapor grown ice crystals subjected to strong electric fields." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3387817.
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Bickerstaffe, Anna Kristina. "Crystallisation at the solid/liquid interface : carboxylic acids on graphite and ice crystals in solution." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613988.
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Kornelsen, Kevin E. "Far-infrared reflectivity measurements including thin films of ice and a mosaic of TTF-TCNQ crystals." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25905.
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The main objective of this thesis project involved the design and construction of a reflectance module to be used with a far infrared Fourier spectrometer. This module would be used for specular reflectivity measurements with small samples at temperatures between liquid helium and room temperature.
Early tests of this reflectance module were used to investigate some of the interesting changes in the far infrared spectrum which result from ice condensation on the sample surface. With the condensing substrate at temperatures between 130 and 200K the condensation is in a crystalline phase and can drastically reduce the intensity of the reflected radiation. The effects are most significant in the spectral range between 150 and 300cm⁻¹. Substrate temperatures lower than 130K lead to condensation of ice in a vitreous phase which does not have such a large effect on the far infrared spectrum.
Modifications were made to the reflectance module design to eliminate the unpredictable effects of ice condensation and a final set of tests were performed measuring the reflectance of a mosaic of TTF-TCNQ crystals. The resulting data shows much of the fine structure which has been observed in other measurements using bolometric techniques.<br>Science, Faculty of<br>Physics and Astronomy, Department of<br>Graduate
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Clarke, Adrian Jonathan Miles. "Modelling of light scattering by cirrus ice crystals using geometric optics combined with diffraction of facets." Thesis, University of Hertfordshire, 2005. http://hdl.handle.net/2299/14268.
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A new 3D model of light scattering applicable to dielectric faceted objects is presented. The model combines Geometric Optics with diffraction on individual facets yet maintains the low computational expense of standard Geometric Optics. The current implementation of the model is explained and then applied to the problem of light scattering by ice crystals in cirrus clouds. Accurate modelling of the scattering properties of such crystals is crucial to better understanding of cirrus radiative properties and hence to climate modelling and weather forecasting. Calculations using the new model are compared to a separation of variables method and the Improved Geometric Optics method with encouraging results. The model shows significant improvements over standard Geometric Optics. The size applicability of the new model is discussed. The model is applied to a range of crystal geometries that have been observed in cirrus including the hexagonal column, the hollow column, the droxtal and the bullet rosette. For each geometry the phase function and degree of linear polarization are presented and discussed. Ice analogue crystals grown at the University of Hertfordshire have optical properties very close to ice but are stable at room temperature. The geometries of three ice analogue crystals are reconstructed and the single scattering properties of the reconstructions are presented. 2D scattering patterns calculated using the model are compared to laboratory photographs of scattering patterns on a screen created by an ice analogue hexagonal column. The agreement is shown to be very good. By applying the model to a range of geometries, it is shown that the results in the form of 2D scattering patterns can potentially be used to aid particle characterization. By combining the model with a Monte Carlo radiative transfer code, comparisons are made with aircraft radiance measurements of cirrus provided by the Met Office. The improvements over standard Geometric Optics are found to persist following a radiative transfer treatment.
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Myagkov, Alexander. "Shape-temperature relationship of ice crystals in mixed-phase clouds based on observations with polarimetric cloud radar." Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-216598.
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This thesis is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data is obtained using a newly developed 35-GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing backscattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes.
In the thesis the first quantitative estimations of ice particle shape at the top of liquid-topped clouds are presented. Analyzed ice particles were formed in the presence of supercooled water and in the temperature range from -20 °C to -3 °C. The estimation is based on polarizability ratios of ice particles measured by the MIRA-35 with hybrid polarimetric configuration, manufactured by METEK GmbH. For the study, 22 cases observed during the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign were used. Polarizability ratios retrieved for cloud layers with cloud-top temperatures of about -5, -8, -15, and -20 °C were 1.6, 0.9, 0.6, and 0.9, respectively. Such values correspond to prolate, quasi-isotropic, oblate, and quasi-isotropic particles, respectively. Data from a free-fall chamber were used for the comparison. A good agreement of detected shapes with well-known shape{temperature dependencies observed in laboratories was found.
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Higgins, Adam Zachary. "Intracellular ice formation in tissue constructs and the effects of mass transport across the cell membrane." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/28166.
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Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Karlsson, Jens; Committee Co-Chair: Nerem, Robert; Committee Member: Meda, Paolo; Committee Member: Prausnitz, Mark; Committee Member: Sands, Jeff; Committee Member: Zhu, Cheng.
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Jaffeux, Louis. "Automatic Classification Tool for Optical Array Probes to Understand Ice Cloud Mechanisms." Electronic Thesis or Diss., Université Clermont Auvergne (2021-...), 2023. http://www.theses.fr/2023UCFA0155.
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L'objectif de la thèse est l'identification des processus de croissance de la glace dans les nuages en utilisant l'information morphologique extraite de la forme des particules de glaces. Pour réaliser cette tâche, des outils de classification ont été développés durant la thèse en utilisant une technique innovante d'apprentissage automatique sur des images de sondes à acquisition rapide (2DS et PIP), communément utilisée à bord des avions de recherche. Ces réseaux de neurones à convolution, développés pour chacune des sondes, ont été évalués et utilisés pour analyser les données récoltées durant la campagne ICE GENESIS. Tout d'abord, la morphologie et les propriétés microphysiques ont été extraites sur l'ensemble de ces données. Puis, l'étude des processus microphysiques et des structures nuageuses ont été réalisés avec ces outils. D'autres mesures effectuées à bord de l'ATR-42 durant la campagne ont été utilisées, notamment la réflectivité et la vitesse Doppler moyenne mesurées grâce au radar RASTA, la présence de gouttelettes surfondues grâce à la sonde CDP-2, et l'humidité via l'hygromètre WVSS-2. Le potentiel des algorithmes de classification a pu ainsi être exploré, et des contributions remarquables ont pu être apportées dans le cadre du projet ICE GENESIS. Une large part des données obtenues durant cette campagne ont pu être interprétées, d'un point de vue de la microphysique du nuageuse. Un schéma conceptuel rassemblant les connaissances existantes dans la littérature, des intuitions nouvelles, et la théories des structures dissipatives, a été proposé afin de formaliser ces interprétations et d'approfondir l'étude de la consommation de la vapeur d'eau et la formation des précipitations au sein des nuages observés. Le réalisme de ce schéma conceptuel a finalement été confronté à un cas d'étude exceptionnel de la campagne ICE GENESIS, observé le 30 Janvier 2021<br>The objective of the thesis is to identify the ice growth processes occurring in clouds by using morphological data provided by the shapes of the ice particles and crystals. To accomplish this task, classification tools were developed during this thesis using innovative machine learning on 2D images from two fast imaging probes routinely mounted onboard research aircraft: the 2DS and PIP probes. This set of tools, namely convolutional neural networks (CNN) developed for both imaging probes, was evaluated and used to analyze data gathered during the ICE GENESIS Swiss Jura campaign. First, ice particle morphological and microphysical properties were extracted from the whole data. Then, the extraction of cloud properties allowed to study microphysical processes and cloud structures. Other measurements made onboard the ATR-42 during the campaign were used, notably reflectivity and MDV from the vertically pointing w-band radar RASTA, total water content from the CVI-Snow, supercooled droplets observations from the CDP-2, and humidity measurements from the WVSS-2 hygrometer. The potential of the classification tools was thereby explored, and significant contributions were achieved within the ICE GENESIS project. Microphysical interpretation of morphological data was proposed for a significant part of the ICE GENESIS data set. In addition, a conceptual scheme was developed combining the knowledge from the literature, new intuitions, and the theory of dissipative structures in order to study consumption of water vapor and precipitation formation in deep stratiform ice clouds using quantitative morphological information. This framework was mainly developed with the overall goal, to extract information from observed in situ observations, beyond a state of the art extraction of microphysical properties (crystal number and mass size distributions, without morphological distinction). The realism of the framework was confronted to an exceptional case study from the ICE GENESIS campaign, observed on the 30th of January 2021
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Myagkov, Alexander [Verfasser], Andreas [Akademischer Betreuer] Macke, and Herman [Gutachter] Russchenberg. "Shape-temperature relationship of ice crystals in mixed-phase clouds based on observations with polarimetric cloud radar : Shape-temperature relationship of ice crystals in mixed-phase cloudsbased on observations with polarimetric cloud radar / Alexander Myagkov ; Gutachter: Herman Russchenberg ; Betreuer: Andreas Macke." Leipzig : Universitätsbibliothek Leipzig, 2017. http://d-nb.info/1240696310/34.
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Sadot, Mathieu. "Etudes numérique et expérimentale d'un procédé de congélation assisté par micro-ondes." Thesis, Nantes, Ecole nationale vétérinaire, 2018. http://www.theses.fr/2018ONIR111F/document.
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Ce travail s’inscrit dans le cadre duprojet européen FREEZEWAVE (ERA-NetSUSFOOD) et porte sur l’étude et lamodélisation d’un procédé de congélationassistée par micro-ondes. Il a pour objectif unemeilleure compréhension des phénomènesphysiques associés à ce procédé. Un modèlecouplant thermique, changement de phase etélectromagnétisme a été développé. Une étudenumérique préliminaire a permis d’appréhenderles interactions complexes entre micro-ondes etmatière durant le changement de phase,notamment l’importance de la diminution despropriétés diélectriques sur la modification desphénomènes de résonance entrainant ledéplacement des « points chauds » et sur laquantité de chaleur générée.Un gel modèle a été caractérisé puis utilisé pourvalider le modèle sur un pilote développé pourl’étude. La micro-tomographie à rayon X apermis la mesure de la taille des cristaux et amis en évidence, lors d’une congélationconventionnelle, l’impact du tempscaractéristique de congélation et du gradient detempérature sur la taille des cristaux de glace.Cette étude a permis de constater une nettediminution de la taille des cristaux de glace lorsd’une congélation assistée par micro-ondes parrapport à une congélation conventionnelle. EnfinIl a été montré que la réduction de taille descristaux n’était pas due aux oscillations detempérature provoquées par des créneaux depuissance micro-ondes mais à la quantitéd’énergie apportée<br>This work was performed in thecontext of the European project FREEZEWAVE(ERA-net SUSFOOD) and focuses on studyingand modelling the microwave assisted freezingprocess. The main objective was to acquire abetter understanding of the correspondingphysical phenomena. A model coupling thermal,phase change and electromagnetism wasdeveloped. A preliminary numerical studypermitted to grasp the complex interactionsbetween microwaves and matter, especially theimportance of the dielectric properties reductionon resonance phenomena, leading to the movingof “hot spots”, and on the generated heat.A methylcellulose gel was characterised andused for the model validation on a prototype pilotspecially designed for this study. A protocolbased on X ray tomography was developed todetermine the ice crystal size. It highlighted, fora conventional freezing process, that thethermal gradient and characteristic freezing timeimpacts the ice crystals sizes.In the case of microwave assisted freezing, thestudy permitted to show a clear decrease in icecrystal size compared to conventional freezing.Finally, it has been shown that the ice crystalsize reduction was not a consequence oftemperature oscillations due to microwavespulses but the consequence of the energyquantity brought to the system by microwaves
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Tsay, Gabriela Salles. "Composição microbiológica cultivável do granizo de uma tempestade no sudoeste do Paraná." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2562.
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A queda de granizo é um fenômeno muito recorrente nas tempestades que atingem a Região Sul do Brasil, região do país que registra a maior incidência do fenômeno. Ainda assim, pouca investigação científica foi conduzida até o momento para se compreender as principais características do fenômeno e os mecanismos nele envolvidos. Desta forma, o presente trabalho tem como objetivo apresentar, pela primeira vez, uma caracterização da composição microbiológica cultivável do granizo de uma tempestade ocorrida no sudoeste do estado do Paraná. Após terem seus diâmetro, massa e volume mensurados fisicamente, amostras de granizo de uma tempestade ocorrida em julho de 2016 foram submetidas a um protocolo de descontaminação estabelecido neste trabalho, e cultivadas em meio MHA para o isolamento de bactérias. As UFC foram caracterizadas e contabilizadas e os 76 isolados representativos obtidos foram submetidos a análise morfotintorial com a técnica coloração de Gram. Um agrupamento fenotípico utilizando o software UPGMA permitiu a seleção de 22 isolados representativos para serem enviados ao sequenciamento genético. O DNA total destes isolados foi extraído por kit comercial e na sequência foi realizada PCR para amplificação da região 16S de RNA ribossômico (RNAr). O amplicon gerado foi encaminhado para sequenciamento em empresa especializada, e as sequências genéticas obtidas foram submetidas a buscas de similaridades com sequências gênicas presentes no GenBank, por meio do BLAST. Como resultado foram identificadas 11 espécies de bactérias pertencentes a 8 gêneros distintos, todas características de ambiente natural, com predominância de espécies em formato de bacilo, Gram-positivas e formadoras de esporos. Os gêneros Bacillus e Paenibacillus representaram 50% das espécies identificadas e foram apontados em outros estudos como potenciais nucleadores de gelo. Identificou-se ainda o gênero Sporosarcina como o único não encontrado em buscas feitas na literatura para estudos relacionados a amostras de ar, água de nuvem ou granizo. Com relação às propriedades físicas, as pedras de granizo apresentaram diâmetros médios entre 1,15 e 1,75cm, e densidades médias variando entre 0,8 a 1,0g/mL, condizentes com a literatura. Por fim, sugestões para estudos futuros foram apresentadas nas conclusões.<br>The hailfall is a recurrent phenomenon in storms that reach Brazil´s South Region. Nevertheless, little scientific investigation has been conducted in order to understand the main characteristics and involved mechanisms. Physical, chemical and microbiological characterization of hailstones consists on an important stage to understand processes associated to events that culminate in hail. Thus, this work aims to present, for the first time, a characterization of microbiological composition of hail from a hailstorm occurred in southwestern of Paraná state. Hailstones from a storm occurred in July 2016 were physically characterized (mass, diameter, volume, density), and submitted to a decontamination protocol established in this work. Melt hailstone water was plated to grow in MHA medium for bacteria isolation. We counted and characterized CFU, resulting in 76 representative isolates that were submitted to morphotintorial analysis by Gram stain technique. UPGMA software delivered a phenotypic grouping that enabled the selection of 22 representative isolates to be forwarded to the genetic sequencing service. We extracted total DNA from these isolates by commercial extraction kit and performed a PCR for amplification of ribosomal RNA (rRNA) 16S region. A specialized company provided the genetic sequences to the generated amplicon. The genetic sequences were submitted to BLAST for similarity search in GenBank. As a result, we identified 8 genera and 11 species of environmental bacteria, which were predominantly rod-shaped, Gram-positive, and spore-forming. Bacillus and Paenibacillus represented 50% of the species identified and they were mentioned in other studies as potential ice nucleators. Sporosarcina was the only genus that could not be found in our literature searches regarding air, cloud water or hail samples. Regarding the physical properties, hailstones had average diameters between 1.15 and 1.75cm, and mean densities ranging from 0.8 to 1.0g / mL, consistent with the literature. Finally, we present suggestions for future studies in the conclusion.
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Targino, Admir Créso. "Regional studies of the optical, chemical and microphysical properties of atmospheric aerosols : Radiative impacts and cloud formation." Doctoral thesis, Stockholm University, Department of Meteorology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-740.
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<p>Atmospheric particles are ubiquitous in the Earth’s atmosphere and have potential to influence atmospheric chemistry, visibility, global climate and human health, particularly downwind from major pollution sources. The main objective of this thesis was to investigate questions pertaining to the microphysical, chemical and optical properties of aerosol particles by using in situ data collected during four experiments carried out in different regions of the Northern Hemisphere.</p><p>The first two papers of this thesis reports on airborne measurements of the aerosol optical properties performed over the North Atlantic and the Los Angeles basin. Airmasses from Europe and North Africa are usually advected in over the North Atlantic, alternating with the background marine conditions. The results showed that the aerosols are not uniformly distributed in the area and variability in the aerosol fields occurs at sub-synoptic scales. It was also observed that the single scattering coefficient varied as the polluted plumes aged, suggesting a relationship between this quantity and transport time. The measurements performed around the Los Angeles basin showed that the area’s complex topography and local meteorological circulations exert a strong control on the distribution of the aerosol in the basin. Large spatio-temporal gradients in the aerosol optical properties were observed along a transect flown from the shore towards the mountains. Profiles flown over sites located on the mountains displayed a stratified configuration with elevated aerosol layers.</p><p>Airborne data of residual particles collected in orographic wave clouds over Scandinavia were analyzed using a single particle analysis technique. Mineral dust, organic aerosols and sea salt were the main group of particles identified. Residuals composed predominantly of mineral dust were found in glaciated clouds while organic residuals were found in liquid clouds. The results suggest that organic material may inhibit freezing and have considerable influence on supercooled clouds that form through heterogeneous pathways.</p><p>The partitioning of the aerosol particles between cloud droplets and interstitial air has been addressed in terms of their microphysical properties using data obtained at a mountain-top site in Sweden during a stratocumulus event. The results showed that the scavenging efficiency varied during the cloud event, and Aitken-mode particles were also efficiently scavenged in addition to accumulation-mode particles. It is hypothesized that alterations of the aerosol chemical composition occurred during the measurement period, modifying the hygroscopic nature of the particles and decreasing their activation diameter.</p>
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Coutris, Pierre. "Analyse des propriétés dimensionnelles et massiques des cristaux de glace pour l’étude des processus microphysiques dans les systèmes convectifs à méso-échelle." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC007/document.
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L’étude des propriétés et processus microphysiques caractérisant la phase glace permet de mieux définir le rôle des nuages dans le cycle de l’eau et sur bilan radiatif de l’atmosphère. Les modèles atmosphériques et les codes d’inversion des données de télédétection utilisent des paramétrisations établies à partir de mesures in situ. Ces mesures servent également des besoins industriels en lien avec la problématique du givrage en aéronautique. L’étude présentée se base sur les données de deux campagnes aéroportées réalisées dans le cadre de la collaboration internationale HAIC-HIWC, ciblant les zones à fort contenu en glace que l’on peut observe rau sein des systèmes convectifs à méso-échelle (MCS) tropicaux. Sur la question des relations « masse-diamètre » (m - D) d’abord, une nouvelle approche est présentée. Basée sur la résolution d’un problème inverse, elle permet de restituer la masse des cristaux à partir de mesures colocalisées classiques en s’affranchissant de la traditionnelle hypothèse de loi puissance, et montre que cette dernière ne permet pas de représenter correctement les propriétés massiques de populations de cristaux hétérogènes (morphologie et tailles différentes) typiques des MCS. La variabilité horizontale des distributions de tailles permet d’étudier le vieillissement de l’enclume d’un point de vue microphysique et de souligner le rôle essentiel du processus d’agrégation dans l’élimination des petits cristaux apportés dans la haute troposphère par la convection profonde et dans la formation d’agrégats supra-millimétriques, précurseurs glacés des précipitations stratiformes. Les relations m - D restituées permettent d’identifier des régimes microphysiques distincts et ouvre la voie aux développement d’une paramétrisation de la masse volumique des hydrométéores en fonction de critères environnementaux<br>The detailed characterization of ice cloud microphysics is key to understand their role in theEarth’s hydrological cycle and radiation budget. The developement of atmospheric models and remote sensingalgorithms relies on parametrisations derived from in situ measurements. These measurements are also usedby the aviation industry to handle the problem of ice crystal icing. This PhD work presents an analysis of themass and size properties of ice crystals observed in high ice water content areas embedded in tropical mesoscaleconvective systems (MCS) during two airborne field campaigns of the HAIC-HIWC international project.A new approach is developped to derive mass-size relationships (m - D) from size distributions and icewater contents. The retrieval is formulated as an inverse problem which waives the power law constraint, aclassical assumption that proves to be an oversimplification when applied to heterogeneous populations of iceparticules typical of MCS anvils.The horizontal variability of size distributions and the aging of MCS anvils is described in terms of microphysicalprocesses. The importance of the aggregation growth process is emphasized as it efficiently removessmall ice particles brought into the upper troposphere by deep convection and significantly contributes to theformation of large agregates, precusor of the stratiform precipitations. The analysis of mass properties revealsthat distinctive microphysical regimes may be identified from the m-D relationship retrieved in various conditions.It paves the way toward a statistical model of the effective density of ice particles as a function of environmentalparameters
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Mladenov, Bilyan. "Klimatologisk analys av mätningar från Abisko för den inre snöstrukturen." Thesis, Uppsala University, LUVAL, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-111334.
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<p>Snö har en stor betydelse för oss inom hydrologin samt ekologin. Inom hydrologin har snön inverkan på våra vattendrag under vinter och vår dessutom har den en stor betydande roll för elektricitetsproduktionen via vattenkraft. För ekologin ger snön isolering för växter, marken och skydd för mindre djur arter. Snöförhållanden förklarar också ofta naturkatastrofer, så som lavinrisker och översvämningar i vattendragen. Ökad kunskap om snöegenskaper skulle kunna hjälpa oss att förstå alla ovan nämnda skeenden bättre.</p><p>På Abiskos naturvetenskapliga forskningsstation har det sedan år 1961 till nu gjorts snöprofilsmätningar, där snötäckets egenskaper, tjocklek, snölagrets täthet/hårdhet, snö kristallernas fasthet, snökornens storlek och snöns torrhet uppskattas. Dessa mätningar utgör grunden till denna studie där syftet är att klimatologiskt undersöka den inre snöstrukturen.</p><p>Undersökningen av snöns inre struktur ger oss en tydlig bild av att kategorin is förekommer mycket ofta i snötäcket och att dess tjocklek är mycket tunn. Under de senaste 15-åren (1993-2007) har kategorin is utgjorts till 25% av alla egenskaper i snötäckets översta lager. Vi kan även se att snön har blivit mycket blötare under våren för perioden 1993-2007 (senaste 15 åren) speciellt under maj månad. Att detta är klara och distinkta spår på den ökade lufttemperaturen är det inga tvivel på. Tydliga spår av metamorfosen i snötäcket ses när kategorin mycket lucker och lucker har ökat kraftigt i det understa lagret de senaste åren, något som även förklarar ökade lavinrisker i området.</p><p>Snödjupet har minskat under de senaste 15 åren (1993-2007) under hösten (oktober och november) i jämförelse med de andra två 15-års perioderna (1961-1992), men snölagrets tjocklek har däremot ökat under våren.</p><br><p>Snow is of great importance to our environment in ways such as hydrological and ecological. When speaking in terms of hydrology, snow affects our water streams and has a great influence on hydropower. In ecological purposes, snow is a good isolator for vegetation, soil and it also gives shelter for smaller animals. Snow conditions often explain natural disaster, such as risks for avalanches and submergence in the streams. Understanding the fundamentals of snow properties would give scientist a greater understanding of snow and its effects on our environment.</p><p>Snow profile measurements have been made in Abisko research centre since 1961 until present time. Measurements have been done on snow cover properties, such as the thickness of the snow layer, grain size, snow layer hardness, grain compactness and the dryness of the snow. Collected data from Abisko research centre is the foundation of this study where our objective is to analyze the inner snow structure. This will give us a greater understanding of how snow has been behaving historically.</p><p>Result of this study illustrates that category ice occurs very frequent in the snow cover and its thickness is very thin. During the last 15-years (1993-2007) has the category ice constitute up to 25% of all the properties in the snow cover in the upper layer. We can also see that the snow cover has drastically become more wet during spring specially for the month may and there is no doubt that the increased air temperature is behind it. There are also distinct signs of metamorphoses in the snow cover which can explain the increased risks for avalanches in the area.</p><p>Results also shows that the snow depth has decreased during the last 15 years (1993-2007) in autumn (October and November) in comparison with the other 15-year periods (1961-1992), but on the other hand the snow layer thickness has increased during the spring.</p>
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Xie, Yu. "The effect of ice crystal surface roughness on the retrieval of ice cloud microphysical and optical properties." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5970.
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The effect of the surface roughness of ice crystals is not routinely accounted for in
current cloud retrieval algorithms that are based on pre-computed lookup libraries. In this
study, we investigate the effect of ice crystal surface roughness on the retrieval of ice
cloud effective particle size, optical thickness and cloud-top temperature. Three particle
surface conditions, smooth, moderately rough and deeply rough, are considered in the
visible and near-infrared channels (0.65 and 3.75 õm). The discrete ordinates radiative
transfer (DISORT) model is used to compute the radiances for a set of optical
thicknesses, particle effective sizes, viewing and illumination angles, and cloud
temperatures. A parameterization of cloud bi-directional reflectances and effective
emittances is then developed from a variety of particle surface conditions. This
parameterization is applied in a 3-channel retrieval method for Moderate Resolution
Imaging Spectroradiometer (MODIS) data at 0.65, 3.75, and 10.8 õm. Cloud optical
properties are derived iteratively for each pixel that contains ice clouds. The impact of ice
crystal surface roughness on the cloud parameter retrievals is examined by comparing the
results for particles with smooth surfaces and rough surfaces. Retrieval results from two
granules of MODIS data indicate that the retrieved cloud optical thickness is significantly reduced if the parameterization for roughened particles is used, as compared with the case
of smooth particles. For the retrieval of cloud effective particle size, the inclusion of the
effect of surface roughness tends to decrease the retrieved effective particle size if ice
crystals are small. The reversed result is noticed for large ice crystals. It is also found that
surface roughness has a very minor effect on the retrieval of cloud-top temperatures.
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Smith, Helen. "Scattering ice clouds." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/scattering-ice-clouds(949032cc-fbdd-4fde-a942-163d870a5ddd).html.
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The 2013 meeting of the Intergovernmental Panel on Climate Change concluded that the coupling of clouds to the Earth's climate is one of the biggest uncertainties faced in predicting climate change today. Cirrus clouds are of particular interest because the extensive variability in particle size, shape and complexity poses a number of challenges in the accurate modelling of optical properties. The dependence of the single-scattering properties on particle shape demand accurate representation of the crystal geometries in scattering models, geometries which can vary from simple hexagonal prisms to complex multi-branched aggregates. This work, presented as a series of papers, uses laboratory studies to investigate the single scattering properties of ice crystals. Of particular focus here are columns with internal cavities. The first paper investigates the phase function, P11 and asymmetry parameter, g of varying crystal habits, whilst the second paper focuses on polarised scattering. One of the main findings is the difference in internal structure between hollow columns grown at warmer temperatures (-7 degrees C) and those grown at colder temperatures (-30 degrees C). Measurements were used to create new particle geometries for use in scattering models. The third paper makes use of findings from papers 1 & 2 to create an optical parametrization for cirrus, utilizing the new particle geometry.
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Choi, Young Eun. "A Study on the Hyperactive Antifreeze Proteins from the Insect Tenebrio molitor." Ohio : Ohio University, 2007. http://www.ohiolink.edu/etd/view.cgi?ohiou1195953014.
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Stopford, C. "Ice crystal classification using two dimensional light scattering patterns." Thesis, University of Hertfordshire, 2010. http://hdl.handle.net/2299/4797.
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An investigation is presented into methods of characterising cirrus ice crystals from in-situ light scattering data. A database of scattering patterns from modelled crystals was created using the Ray Tracing with Diffraction on Facets (RTDF) model from the University of Hertfordshire, to which experimental and modelled data was fitted. Experimental data was gathered in the form of scattering patterns from ice analogue crystals with similar optical properties and hexagonal symmetry to ice, yet stable at room temperature. A laboratory rig is described which images scattering patterns from single particles while allowing precise control over the orientation of the particle with respect to the incident beam. Images of scattering patterns were captured and compared to patterns from modelled crystals with similar geometry. Methods for introducing particles en-masse and individually to the Small Ice Detector (SID) instruments are discussed, with particular emphasis on the calibration of the gain of the SID-2 instrument. The variation in gain between detector elements is found to be significant, variable over the life of the detector, and different for different detectors. Fitting was performed by comparison of test scattering patterns (either modelled or experimental) to the reference database. Representation of the two dimensional scattering patterns by asymmetry factor, moment invariants, azimuthal intensity patterns (AIP) and the Fourier transform of the AIP are compared for fitting accuracy. Direct comparison of the AIP is found to be the most accurate method. Increased resolution of the AIP is shown to improve the fitting substantially. Case studies are presented for the fitting of two ice analogue crystals to the modelled database. Fitting accuracy is found to be negatively influenced by small amounts of surface roughness and detail not currently considered by the RTDF model. Fitting of in-situ data gathered by the SID-3 instrument during the HALO 02 campaign at the AIDA cloud chamber in Germany is presented and discussed. Saturation of detector pixels is shown to affect pattern fitting. In-flight operation of the instrument involves the variation of gain of the whole detector (as opposed to individual elements) in order to obtain unsaturated images of both large and small particles.
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Berdeklis, Peter. "The ice crystal-graupel collision charging mechanism of thunderstorm electrification." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0007/NQ41402.pdf.
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Evans, Jeannette M. "The control effects of ice crystal growth in a mycelial system." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294730.
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Meyer, Jessica [Verfasser]. "Ice Crystal Measurements with the New Particle Spectrometer NIXE-CAPS / Jessica Meyer." Wuppertal : Universitätsbibliothek Wuppertal, 2013. http://d-nb.info/1033621218/34.
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SANTOS, ROBINSON A. dos. "Otimização da metodologia de preparação do cristal de brometo de tálio para sua aplicação como detector de radiação." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10085.
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Made available in DSpace on 2014-10-09T12:34:35Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:00:07Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Fulford, Maxwell. "Investigating the snow crystal : a computational study of the molecular mechanisms of hexagonal ice growth." Thesis, King's College London (University of London), 2017. https://kclpure.kcl.ac.uk/portal/en/theses/investigating-the-snow-crystal(146ee9b7-e4b0-4e6a-96f8-f9c542b8fd84).html.
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Hexagonal Ice (Ih) plays a number of essential roles in controlling and maintaining the natural environment on Earth. It is the predominant crystalline form of ice and permanently covers at least 10% of all land. Within the atmosphere ice forms cirrus clouds which are involved in the greenhouse e↵ect. The altitude and thickness of the clouds controls the balance of solar heating and infrared cooling from Earth to space, and is governed by the sizes and shapes of the constituent ice crystals. The shape of vapour grown ice crystals depends strongly on temperature and vapour pressure. At low vapour pressures, simple hexagonal prisms form with an aspect ratio that depends on the relative rate of growth of its two crystallographic surfaces - the basal and prism surface. The competing action of the two rates results in thin hexagonal plates at very low temperatures and elongated prisms at higher temperatures. Curiously, as temperature is increased further, thin plates form once again. The reasons why growth occurs preferentially along the basal and prism surfaces at different temperatures remain unknown. Progress in climate science is hindered by an incomplete grasp of the underlying mechanisms involved in ice growth in cirrus clouds. A comprehensive understanding of ice crystal growth is essential if we are to overcome the colossal climate change challenges we face. In this project we investigate the basal and secondary prism surfaces of hexagonal ice at a range of temperatures between 240 K and 270 K using molecular dynamics and metadynamics. Metadynamics is an enhanced sampling technique that enables efficient sampling of rare events and yields an estimate of the free energy as a function of selected collective variables. Our simulations show the formation of a disordered quasi-liquid layer (QLL) on the surfaces of ice. The QLL mediates crystal growth and has a thickness which varies with temperature. We investigate how the ice/QLL and QLL/vapour interfaces influence the water adsorption potential, surface diffusion properties and growth shape. Our findings reveal that the outer surface structure at the QLL/vapour interface depends weakly on the underlying crystal lattice. The desorption energy costs are equivalent for the basal and prism surfaces, however, the crystal lattice impacts the dynamics within the QLL. Our results show that there are distinct diffusion energy barriers at the basal and prismatic QLL/ice interfaces. The implication of our work is that the QLL/ice interface is key to the overall kinetics of ice growth in vapour whereas the QLL/vapour interface plays a secondary role.
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Riley, Emily Marie. "A Global Survey of Clouds by CloudSat." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/198.
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With the launch of CloudSat, direct observations of cloud vertical structure became possible on the global scale. This thesis utilizes over two years of CloudSat data to study large-scale variations of clouds. We compose a global data set of contiguous clouds (echo objects, EOs) and the individual pixels comprising each EO. For each EO many attributes are recorded. EOs are categorized according to cloud type, time of day, season, surface type, and region. From the categorization we first look at gross global climatology of clouds. Maps of cloud cover are subdivided by EO (cloud) type, and results compare well with previous CloudSat work. The seasonality of cloud cover is also examined. Focus topics studied in this thesis include: (1) mid-level clouds, (2) stratocumulus clouds, and (3) clouds across the Madden-Julian Oscillation (MJO). The mid-level cloud work found an unexpected frequency peak in EO top heights between 7-8 km in the tropics, further shown to correspond to a global peak in EO top temperature between -15°C ? -20°C. Hypotheses are discussed regarding cause of this feature. Stratocumulus clouds are defined as low-level (tops < 4.5 km), wide (width > 11 km) EOs. Stratocumulus cloud cover agrees (with understandable differences) with other estimates (ISCCP and CALIPSO). The seasonal cycle of stratocumulus over the main stratocumulus decks is examined. The Peruvian and Namibian decks have increased cloud cover in austral spring in 2007 vs. 2006, corresponding sensibly to sea surface temperature differences and changes in lower static stability. Looking at rain and drizzle statistics, wider EOs are found to drizzle more. Clouds across the MJO are defined relative to temporally filtered OLR data. Cloud cover (volume) doubles (triples) from suppressed to active MJO phases, with some shifts of the relative contributions of different EO types from the front to back of the MJO. Pixel statistics in dBZ-height space correspond to these cloud-type shifts. High anvils and low clouds in front lead deep convection followed by relatively lower anvils in the back.
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Diez, Anja [Verfasser], and T. [Akademischer Betreuer] Bohlen. "Effects of cold glacier ice crystal anisotropy on seismic data / Anja Diez. Betreuer: T. Bohlen." Karlsruhe : KIT-Bibliothek, 2013. http://d-nb.info/104738342X/34.
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Forster, Linda [Verfasser], and Bernhard [Akademischer Betreuer] Mayer. "Information content of halo displays for remote sensing of ice crystal properties / Linda Forster ; Betreuer: Bernhard Mayer." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1153338610/34.
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Belissont, Rémi. "Germanium and related elements in sulphide minerals : crystal chemistry, incorporation and isotope fractionation." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0049/document.
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Le germanium est un métalloïde « stratégique » dans l’industrie high-tech, notamment pour la transition énergétique et le secteur des communications. Étant distinctement sidérophile, lithophile, chalcophile et organophile, le Ge possède un fort potentiel comme traceur géochimique. Ces travaux de thèse visent à améliorer la compréhension de la géochimie du cycle du Ge et des facteurs qui contrôlent son incorporation dans les minéraux et les gisements métalliques. Les cibles de cette étude concernent le gisement filonien à Zn de Saint-Salvy (Massif Central, France), le gisement filonien à Cu de Barrigão (Ceinture pyriteuse ibérique, Portugal), et le gisement à Zn–Cu de Kipushi (R.D. Congo). Les porteurs de Ge les plus importants sont respectivement la sphalérite (jusqu’à 2580 ppm), la chalcopyrite (jusqu’à 5750 ppm) et la réniérite (5,0–9,1 %). Les résultats montrent qu’il existe une relation de premier ordre entre la concentration en Ge dans la sphalérite et le type de gisement. La spectroscopie XANES par rayonnement synchrotron met en évidence la présence de Ge4+ en site tétraédrique dans les sulfures analysés. Les corrélations élémentaires observées dans la sphalérite et la chalcopyrite suggèrent une incorporation du Ge par co-substitutions, e.g., 3Zn2+ ↔ Ge4+ + 2(Cu,Ag)+ et 3Fe3+ ↔ 2Ge4+ + Cu+, ou via la création de lacunes cristallographiques, e.g., 2Zn2+ ↔ Ge4+ + ?. La corrélation positive δ74Ge–[Ge]ZnS des sphalérites de Saint-Salvy indiquerait que coefficient de partage (KdGe) augmenterai avec T. Les compositions isotopiques δ74Ge des sulfures étudiés varient de –5,72‰ à +3,67‰. Les compositions légères mesurées dans les gisements de Saint-Salvy et Barrigão semblent liées à des variations de température des fluides (basse à moyennes T) lors de l’incorporation de Ge en système ouvert, alors que la tendance marquée vers les compositions isotopiques lourdes à Kipushi indiquerait un fractionnement de Rayleigh<br>Germanium is a critical metalloid in many high-tech industries, especially for the energy transition and the communication sector. Being distinctly siderophile, lithophile, chalcophile and organophile, Ge can be a particularly useful geochemical tracer. This thesis aims at understanding the Ge geochemistry and the factors controlling its concentration in Ge-bearing minerals and ore deposits. Three contrasted Ge-bearing deposits were studied, the Saint-Salvy Zn vein-type deposit, French Massif Central, the Barrigão Cu vein-type deposit, Iberian pyrite belt, Portugal, and the Kipushi Zn–Cu carbonate-hosted deposit, Central African copper-belt, D.R. Congo. The most important Ge-bearing minerals are sphalerite (up to 2580 ppm Ge), chalcopyrite (up to 5750 ppm Ge), and renierite (5.0–9.1 wt.% Ge). The results show a first order relation between the Ge content and the deposition temperature. Synchrotron-based XANES spectroscopy showed that Ge4+ occur in tetrahedral sites in the studied sulphides. Element correlations suggest that Ge is chiefly incorporated in sphalerite and chalcopyrite through coupled substitutions, e.g., 3Zn2+ ↔ Ge4+ + 2(Cu,Ag)+ and 3Fe3+ ↔ 2Ge4+ + Cu+, respectively, or via the creation of lattice vacancies, e.g., 2Zn2+ ↔ Ge4+ + ?. The positive δ74Ge–Ge content correlation observed in sphalerite from Saint-Salvy could indicate that Ge partition coefficient (KdGe) increases with temperature. Ge isotopes in sulphides yield δ74Ge values spanning from –5.72‰ to +3.67‰. The light δ74Ge compositions of Saint-Salvy and Barrigão ores appear to be related to variations in low to moderate fluid temperatures during Ge uptake in open system (e.g., fluid cooling), while the trend towards heavy δ74Ge compositions observed at Kipushi likely translates a Rayleigh fractionation effect during ore formation in closed system, associated with significant fluid modification
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Schäfer, M., E. Bierwirth, A. Ehrlich, F. Heyner, and M. Wendisch. "Retrieval of Cirrus Optical Thickness and Assessment of Crystal Shape from Ground-Based Imaging Spectrometry." Universität Leipzig, 2013. https://ul.qucosa.de/id/qucosa%3A16411.
Full textAbstract:
An imaging spectrometer (AisaEAGLE) is applied for ground-based measurements of downward spectral radiance fields with high spatial (1024 spatial pixels within 36.7° field of view), spectral (488 spectral pixels, 400-970 nm, 1.25 nm full width at half maximum) and temporal (4-30 Hz) resolution. The calibration, measurement, and data evaluation procedures are introduced. A method is presented that retrieves the cirrus optical thickness tci using the spectral radiance data collected by AisaEAGLE. On the basis of four measurement cases during the second campaign of the Cloud Aerosol Radiation and tuRbulence of trade wInd cumuli over BArbados (CARRIBA) project in 2011 the spatial inhomogeneity of the investigated cirrus is characterized by the standard deviation of the retrieved tci, as well as the width of the frequency distribution of the retrieved tci. By comparing measured and simulated downward solar radiances as a function of scattering angle, a first estimation of the detected cirrus ice crystal shape is given and used in the retrieval of tci.<br>Ein abbildendes Spektrometer (AisaEAGLE) wurde bodengebunden zur Messung von Feldern abwärts gerichteter spektraler Strahldichten mit hoher räumlicher (1024 Raumpixel auf 36.7° FOV), spektraler (488 spektrale Pixel, 400-970 nm, 1.25 nm FWHM) und zeitlicher (4-30 Hz) Auflösung verwendet. Die Kalibrierungsprozedur, das Messverfahren sowie die Datenauswertung werden hier
vorgestellt. Weiter wird eine Methode zur Ableitung der Zirrus optischen Dicke tci unter Verwendung dieser bodengebundenen spektralen Strahldichtedaten vorgestellt. Auf der Grundlage von vier Messzeiträumen während der zweiten Kampagne des Cloud Aerosol Radiation and tuRbulence of trade wInd cumuli over BArbados (CARRIBA) Projektes in 2011 wird die räumliche Inhomogenität der untersuchten Zirren durch die Standardabweichung der abgeleiteten tci, wie auch der Breite ihrer
Häufigkeitsverteilungen charakterisiert. Vergleiche der gemessenen Strahldichten mit Simulationen abwärts gerichteter solarer Strahldichten als Funktion der Streuwinkel ermöglichen eine erste Abschätzung der Eiskristallform im detektierten Zirrus und gehen in die Ableitung der tci ein.
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HARGUINDEGUY, MAITE. "Infrared thermography for freeze-drying applications: from ice crystal size prediction to primary drying process monitoring and design space determination." Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2959955.
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Oliver, Michael James. "A STUDY ON THE PHYSICS OF ICE ACCRETION IN A TURBOFAN ENGINE ENVIRONMENT." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1363875844.
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Ori, Davide <1987>. "Study of the Optical Properties of Complex Ice Crystal Aggregates. Application to the remote sensing of dry and mixed-phase snowfall." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7521/1/Ori_Davide_tesi.pdf.
Full textAbstract:
Snowfall is a prominent component of the Earth’s hydrologic cycle. Global observations of snowfall are essential for the monitoring of the status of the Earth system, and because of their wide coverage, nowadays, remote sensing instruments are fundamental tools in the measurement of precipitation.
The principal uncertainty in the interpretation of radar data are the scattering properties of the hydrometeors which are strictly connected to their microphysical characteristics. The presented study propose a comprehensive approach that analyze the all snow physical characteristics: single particle modeling, snowfall automatic microphysical retrieval, scattering simulations and remote sensing.
A state of the art snow aggregation algorithm (SAM) has been implemented to model the snowflake accurate morphology, simulating the basic physical governing phenomena of snow formation and growth. The algorithm has been further extended to model the initial stage of snowflake melting. The snowflake models are used as input of computer scattering simulations.
The analysis of the radiative properties obtained with the spherical models and the complex aggregated particles produced by SAM shows that the former are inadequate to represent the scattering characteristics of large aggregated particles.
An innovative methodology has been developed to automatically estimate the mean snow mass-size relation using particle size distribution, velocity fits, snow accumulation and Rayleigh radar reflectivity. The radar reflectivities at Ka and W band simulated with T-matrix spheroidal models and using the retrieved mass-dimensional relation cannot match the observation. When the same simulation is performed with the usage of DDA scattering calculations the results reproduce better the observed radar reflectivities. This outcome gives validity to both the microphysical and the scattering model.
A multi-perspective approach, that simultaneously include the microphysical and scattering simulation of snowflake properties, is the way forward to solve the uncertainties related to snowfall remote sensing.
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Ori, Davide <1987>. "Study of the Optical Properties of Complex Ice Crystal Aggregates. Application to the remote sensing of dry and mixed-phase snowfall." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7521/.
Full textAbstract:
Snowfall is a prominent component of the Earth’s hydrologic cycle. Global observations of snowfall are essential for the monitoring of the status of the Earth system, and because of their wide coverage, nowadays, remote sensing instruments are fundamental tools in the measurement of precipitation.
The principal uncertainty in the interpretation of radar data are the scattering properties of the hydrometeors which are strictly connected to their microphysical characteristics. The presented study propose a comprehensive approach that analyze the all snow physical characteristics: single particle modeling, snowfall automatic microphysical retrieval, scattering simulations and remote sensing.
A state of the art snow aggregation algorithm (SAM) has been implemented to model the snowflake accurate morphology, simulating the basic physical governing phenomena of snow formation and growth. The algorithm has been further extended to model the initial stage of snowflake melting. The snowflake models are used as input of computer scattering simulations.
The analysis of the radiative properties obtained with the spherical models and the complex aggregated particles produced by SAM shows that the former are inadequate to represent the scattering characteristics of large aggregated particles.
An innovative methodology has been developed to automatically estimate the mean snow mass-size relation using particle size distribution, velocity fits, snow accumulation and Rayleigh radar reflectivity. The radar reflectivities at Ka and W band simulated with T-matrix spheroidal models and using the retrieved mass-dimensional relation cannot match the observation. When the same simulation is performed with the usage of DDA scattering calculations the results reproduce better the observed radar reflectivities. This outcome gives validity to both the microphysical and the scattering model.
A multi-perspective approach, that simultaneously include the microphysical and scattering simulation of snowflake properties, is the way forward to solve the uncertainties related to snowfall remote sensing.