Top PDF Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

of crystal edges, or potentially by 3-D reconstruction of equilibrium crystals captured from multiple angles. We found that it was usually not possible to determine height profiles when structures are visible, but near the limit of the image resolution, or where pronounced roughness did not intersect a resolved crystal edge, a common feature in our observations. We also find that the hri metric, much like the subjective percep-

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Some effects of ice crystals on the FSSP measurements in mixed phase clouds

Some effects of ice crystals on the FSSP measurements in mixed phase clouds

In this context, this paper is a contribution to the interpre- tation of the effects of ice particles on FSSP measurements using a data set for Arctic mixed phase clouds. The data dis- cussed were obtained during the ASTAR 2007 (Arctic Study on Tropospheric Aerosol and Radiation, Engvall et al., 2008) and POLARCAT (Polar Study using Aircraft, Remote Sens- ing, Surface Measurements and Models, of Climate, Chem- istry, Aerosols, and Transport, Law et al., 2008) field exper- iments. During ASTAR, the cloud observations were carried out onboard the Polar2 (Do228) operated by AWI (Alfred Wegener Institute for Polar and Marine Research) whereas the ATR42 research aircraft operated by SAFIRE (Service des Avions Franc¸ais Instrument´es pour la Recherche en En- vironnement) was used during POLARCAT. A combination of cloud in situ instruments was installed on both aircraft, namely: a standard Forward Scattering Spectrometer Probe (FSSP-100), a Polar Nephelometer (Gayet et al., 1997), as well as a Cloud Particle Imager (CPI, Lawson et al., 2001), to measure cloud particle properties in terms of scattering, mor- phology and size, and in-cloud partitioning of ice/water con- tent. Standard 2D-C, 2D-P instruments as well as liquid wa- ter devices (i.e. King probe, Nevzorov and PVM-100) were used in addition to the ATR42 in situ cloud instrumentation. A short description of the instruments and the analysis of cloud situations are first presented in Sect. 2. Then the pa- per describes in detail the FSSP response in the presence of ice particles (Sect. 3). A presentation of the microphys- ical and optical properties of a mixed-phase boundary-layer cloud observed during the 8 April 2007 situation (ASTAR) will then be given. The interpretation of the measurements from independent techniques leads to a clear identification of the effects of ice crystals on FSSP particle size distributions. This feature is confirmed with additional data obtained dur- ing POLARCAT, studied in order to experience a wide range of ice crystal conditions. Section 4 discusses the implications on FSSP measurements and Sect. 5 attempts to explore dif- ferent causes explaining the second mode presence when ice crystals are present in clouds. The shattering ice crystal effect is then discussed.
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Surface transition on ice induced by the formation of a grain boundary.

Surface transition on ice induced by the formation of a grain boundary.

To the best of our knowledge, no theoretical model has been presented which describe the spreading of crystal dislocations away from a grain boundary. It is also beyond the scope of the present work to create such a model; the purpose of this report is the rapid communication of a qualitatively new finding. The finding will potentially improve the understanding of processes in nature where ice grain boundaries are involved; one example is the sintering of snow. In the case of snow sintering, it is unknown whether or not the surface structure varies over the ice-air surface of an individual grain [5]. Today’s theoretical snow sintering models assume that there are no variations in surface roughness and surface melting, when considering the surface of a single grain [5]. However, the results presented here show an example of ice crystals in contact where the ice-air surface structure varies strongly over each individual grain; a grain boundary-induced surface transition is observed, which does not propagate across facet edges. The results therefore suggest that it is possible that the probability of molecular surface disorder is increased in the vicinity of a grain boundary. At present, we do not know how generalizable the results are, e.g. if similar grain boundary-induced transitions can occur at conditions found in nature. We do not know how far the surface transition would spread if the crystal surface was slightly curved before transition (instead of a smooth facet), and we do not know if similar transitions can occur at ambient pressure. Unfortunately, those conditions can not be investigated with the present experimental setup. Nevertheless, the observed transitions are caused by the contact between two crystals,
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A technique for generating consistent ice sheet initial conditions for coupled ice-sheet/climate models

A technique for generating consistent ice sheet initial conditions for coupled ice-sheet/climate models

thickness due to climate model forcing biases existed around the margins. However, these do not preclude the effectiveness of the spin-up procedure. They rather empha- size that improvement to the climate-side SMB generation are an important component of generating more realistic spun-up ice sheets. Thus, we are confident that the tech- nique described here is a feasible approach to for generating consistent ice sheet initial

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Monitoring device of ice formation in evaporator surface of refrigeration systems

Monitoring device of ice formation in evaporator surface of refrigeration systems

The ice formation monitoring has been investigated from different research areas, among these, aviation engineering due to the huge risk for the safety of passengers and crew that ice formation may have in the normal operation of an aircraft [8-9]. In this application area, the sensors must have high reliability and sensitivity, being its cost a secondary question. On the other hand, a sensor developed for monitoring the ice formation in refrigeration application has the cost as determining factor. Thus, any prototype to be developed must be inexpensive and have reasonable sensitivity and reliability [7]. Currently the most widely used defrost system in the refrigeration industry is time controlled. The defrost system is triggered periodically during predefined periods [10]. Although not obtaining the desired results, it continues to be the most selected systems due to its simplicity and inexpensiveness, although with compromised reliability [7]. Taking into account these factors, the ice formation monitoring system to be developed will use a resistive sensor. This sensor type is cheap and has the potential to achieve good results. In addition, it does not require special equipment for data acquisition and can be simple and cheaply automated.
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Drumlins and related glaciogenic landforms of the Madliena Tilted Plain, Central Latvian Lowland

Drumlins and related glaciogenic landforms of the Madliena Tilted Plain, Central Latvian Lowland

Landforms situated in the western part of the MTP were separated from drumlins by Aboltinš (1970), who attributed them to the Linkuva marginal formations and related landforms westerly from them as end moraines of the Plieni glacial phase. Landforms which were attributed to the Plieni glacial phase (ibid.) in the rest of the Central Latvian glacial lowland were re-interpreted as ribbed moraines by Zelcs & Dreimanis (1998). Later the Plieni glacial phase was no more recognized in the deglaciation history of Latvia (Zelcs & Markots, 2004; Zelcs et al., 2011). It is suggested by author that end moraines that are situated westerly from the Linkuva marginal formations due to their lower topography, spatial arrangement and orientation of the longitudinal axes can be termed as recessional moraines, which formed during the subsequent ice retreat from the Linkuva ice-marginal zone. Recessional moraines are few hundreds to 5 km long and by tens up to one thousand metres wide. A few hundreds of metres wide landforms are predomi- nant. They are orientated on average from N to S. The distance between individual crests of recessional moraines is a few hundreds of metres. It is supposed to be equal to the retreat rate of the ice margin in a year. It also coincides with a rate of the deglaciation of the Onega area from the Luga moraine (between 14 250 and 12 750 cal. BP), which was 200 m per annum on average (Saarnisto & Saarinen, 2001). Above mentioned also supports the interpretation of recessional moraines, which formed by seasonal re-advance of the ice margin as suggested also by Bennett (2001) who defined such moraines as recessional push moraines.
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Surface Morphology And Photoluminescence Properties Of A-GaAsSe Detector

Surface Morphology And Photoluminescence Properties Of A-GaAsSe Detector

3-2 P HOTOLUMINESCENCE SPECTRA OF A -G A A S :S E FILMS The dependence of PLspectra of a-GaAs:Se films on annealing temperature was shown in figure (2). The PL peak located at(832.215),(829.87) and(827.538) for (RT,100 and 200)oCwhich corresponding to an energy (1.49),(1.494) and(1.498) eV respectively. This may be associated to the electron in bottom of Ecrecombine with hole in the Ev This behavior can beinteroperate in term the improvement the

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Distributions of grain parameters on the surface of aircraft engine turbine blades

Distributions of grain parameters on the surface of aircraft engine turbine blades

In the quality assurance system for components cast using the lost wax method, the object of evaluation is the grain size on the surface of the casting. This paper describes a new method for evaluating the primary grain parameters on the surface of aircraft engine turbine blades. Effectiveness of the method has been tested on two macrostructures distinguished by a high degree of diversity in the grain size. The grounds for evaluating the grain parameters consist of geometric measurement of the turbine blade using a laser profilometer and of approximation of the measurement results using a polynomial of a proper degree. The so obtained analytical non-planar surface serves as a reference point for an assessment of the parameters of grains observed on the real blade surface of a variable curvature. The aspects subjected to evaluation included: the grain areas, shape and elongation coefficients of grains on a non-planar surface of the blade airfoil, using measurements taken on a perpendicular projection by means of a stereoscopic microscope and image analysis methods, and by making calculations using the Mathematica ® package.
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The relation between sea ice thickness and freeboard in the Arctic

The relation between sea ice thickness and freeboard in the Arctic

Use of the hydrostatic equilibrium equation to estimate ice thickness from freeboard data requires data on snow and ice density as well as snow depth, which exhibit regional and seasonal variability. Climatic snow cover data from Russian North Pole drifting stations have been published by War- ren et al. (1999), but there are few available data sets that provide statistics on snow and ice density, snow depth, ice freeboard and thickness over large parts of the Arctic ice cover. Therefore, the main objective of this paper is to inves- tigate the relation between ice freeboard and ice thickness using extensive in-situ measurements from Arctic field ex- peditions. First, an empirical relation between ice thickness and freeboard is derived from direct measurements during the Sever expeditions in the 1980s. Furthermore, published data on snow and ice densities are reviewed and errors are estimated. These data are used in the hydrostatic equilibrium equation to assess the relations between thickness and free- board for first-year (FY) and multiyear (MY) ice. Finally, the error sources in ice thickness retrieval from freeboard mea- surements are discussed and recommendations for in-situ ob- servations in forthcoming CryoSat-2 post-launch calibration- validation experiments are provided.
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An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data

An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data

ous regional versions of the algorithm (Gades et al., 2000; MacGregor et al., 2007; Jacobel et al., 2009; Fujita et al., 2012; Matsuoka et al., 2012b). These included using a wave- form processing procedure that is specifically tuned for the evaluation of bulk material properties, incorporating a prior Arrhenius model estimate for the spatial variation in attenu- ation to constrain the sample area, standardising the power within each sample area and introducing an automated qual- ity control approach based on the underlying radar equa- tion. We demonstrated regions of attenuation solution con- vergence for two different input temperature fields and for independently analysed field seasons. A feature of the algo- rithm is that the uncertainty, as measured by standard devi- ation of the attenuation solution difference distribution for different input temperature fields and separate field seasons, is tunable. Subsequently, we suggested that the algorithm could be used for the discrimination of bulk material prop- erties over selected regions of ice sheets. Notably, assuming a total loss uncertainty of ∼ 5 dB to be approximately suffi- cient for basal melt discrimination, we demonstrated that, on the scale of a major drainage basin, the attenuation solution produces a physically realistic ( ∼ 20 dB) range for the basal reflection coefficient.
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Ice nucleation by surrogates for atmospheric mineral dust and mineral dust/sulfate particles at cirrus temperatures

Ice nucleation by surrogates for atmospheric mineral dust and mineral dust/sulfate particles at cirrus temperatures

temperature range than those reported by Hung et al. (2003). Uncertainties in nucleation rate due to uncertainties in ag- glomerate particle surface area and CFDC residence times do not explain this difference. It is possible that the Hung et al. (2003) data may not reflect as large a variation in par- ticle size nucleating ice as assumed from the mode size of the input particle distributions. For example, the small frac- tions nucleated from the polydisperse populations (0.000003 to 0.003%) may represent primarily the largest particles in the distributions. It is also possible that the particles used in the respective studies were not of entirely similar mor- phology. For example, it is possible that our agglomerated particles may provide additional active sites for freezing in concave dimensions which are not present for the approxi- mately spherical particles used Hung et al. (2003). Finally, the different solutes (sulfuric acid in this study versus ammo- nium sulfate in Hung et al. (2003)) and coating amounts (rel- atively small weight fractions in this study versus relatively large weight fractions in Hung et al. (2003)) used may have had different impacts. This is not expected based on what is understood about solute impacts on freezing and the fact that even the low weight percent coatings of acid in this study would induce a typical 1.3 diameter particle growth factor by water uptake at the point of ice nucleation. Nevertheless, this discussion is not intended to distract from the fact that the general agreement between the two studies is quite good and the results in the current study extend the nucleation rate ob- servations over a wider range of J hetf for potential use in nu-
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Effect of uncertainty in surface mass balance elevation feedback on projections of the future sea level contribution of the Greenland ice sheet – Part 2: Projections

Effect of uncertainty in surface mass balance elevation feedback on projections of the future sea level contribution of the Greenland ice sheet – Part 2: Projections

projections. Our method allows ISMs to be forced with the more physically realistic simulations of SMB from RCMs, rather than their own simpler PDD schemes, while incorporating the elevation feedback and exploring model uncertainties. Another use would be to correct low resolution MAR simulations onto a high resolution digital ele- vation map; the difference in elevation between the two topographies is analogous to

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Which circulating antioxidant vitamins are confounded by socioeconomic deprivation? The MIDSPAN family study.

Which circulating antioxidant vitamins are confounded by socioeconomic deprivation? The MIDSPAN family study.

The socioeconomic and lifestyle circumstance of the partic- ipants in adulthood were derived from self-reported question- naire responses and physical examination measures. For simplicity, these were primarily used as dichotomous variables, although secondary analyses, using variables in a continuous fashion are also reported. Socioeconomic factors were: occupa- tional social class coded according to the registrar general’s classification (manual vs. non-manual); Carstairs deprivation index (‘‘DepCat’’: an index of deprivation in a specific postcode based on census data comprising information on low social class, lack of car ownership, overcrowding and male unemployment; a score of 1 is most affluent, a score of 7 is most deprived) [22] (continuous scores and categories 5–7 vs. 1–4 were used); highest educational level (secondary or lower vs. tertiary); housing tenure (rented vs. owner occupier); domestic over- crowding (number of people sharing accommodation $ number of available rooms vs. otherwise); access to cars (none vs. one or more). Lifestyle factors were: high alcohol intake (.28 [men] or 21 [women] units per week vs. otherwise); low fibre intake (,18 g/day vs. $18 g/day); high fat intake [.35% of total food energy intake vs. #35%]; low physical activity [not very/not at all physically active during usual daily activities, and physically active for at least 20 minutes on less than one occasion a week during non-working time, vs. otherwise]; current smoking habit (smoker vs. non-smoker); two measures of obesity (body mass index (BMI) .30 kg/m 2 vs. #30 kg/m 2 ; waist-hip ratio (WHR) .1.0 [men] or 0.9 [women] vs. otherwise). Participant’s log- transformed cholesterol levels were expressed as continuous variables only.
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Surface undulations of Antarctic ice streams tightly controlled by bedrock topography

Surface undulations of Antarctic ice streams tightly controlled by bedrock topography

each profile; the lower limit corresponds to its value for temperate ice whereas the up- per limit is computed for a uniform ice column at −20 ◦ C. Despite a substantial amount of scatter, the plot indicates an increasing trend of about 350 % over the considered range of slip ratios. This increasing trend is supported by theory (dashed line in Fig. 4), although the flow-line model predicts a more rapid increase and a peak amplitude

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Ice water content of arctic, midlatitude, and tropical cirrus – Part 2: Extension of the database and new statistical analysis

Ice water content of arctic, midlatitude, and tropical cirrus – Part 2: Extension of the database and new statistical analysis

role in that system through its effect on terrestrial and solar radiation, but it is diffi- cult to parameterize owing to the large variability in IWC values possible for a given set of atmospheric conditions. Here, we have presented the extension of a cirrus IWC climatology originally developed by Schiller et al. This extension provides a highly com- prehensive dataset in terms of covering the temperature, altitude, and latitude ranges

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3D Mapping of the SPRY2 domain of ryanodine receptor 1 by single-particle cryo-EM.

3D Mapping of the SPRY2 domain of ryanodine receptor 1 by single-particle cryo-EM.

With the transformed dataset having all particles with an anti- SPRY antibody bound to repeat 1 of RyR1, we followed two different approaches to obtain a 3D reconstruction, without and with symmetry enforcement. Figure 3D shows both the symmetry- free and the fourfold symmetrized 3D reconstructions of the RyR1 with anti-SPRY2 antibodies bound. The 3D reconstruction without the use of symmetry shows the signal of the antibody concentrated in the first repeat of RyR1, while the fourfold symmetry distributes the signal of the antibody originating from one corner into the four symmetrically-related repeats. In both cases the quality of both reconstructions is poor because of (i) the low number of particles, and (ii) the noise introduced by the flexibility and the diversity of orientations that is adopted by bound antibodies [34]. Nevertheless, a clear signal emerges in the vicinity of domain 6 of RyR1 in both cases. To better illustrate these features, we used a one-pixel thick slice of the 3D reconstruction (dashed line in Fig. 3D) and color-coded the density gradient above a threshold level, thus revealing the more intense regions (Fig. 3E). In the case of the symmetry-free reconstruction, the density is most intense in domain 6 of the first and third repeats but some intensity is also measurable in domains 5 and 10 in the second and fourth repeats (Fig. 3E top left). When fourfold symmetry is applied, the maximum intensity appears in domain 6, followed by domain 5 and 10 with less intensity (Fig. 3E top right). As a control, the same slice is represented for the reference 3D volume (without antibody) showing that the maximum intensity is restricted to domain 5 (Fig. 3E, bottom).
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A minimal, statistical model for the surface albedo of Vestfonna ice cap, Svalbard

A minimal, statistical model for the surface albedo of Vestfonna ice cap, Svalbard

FAM profile indeed shows a slighly wider spread for the values of all individual eleva- tion bins, but the overall bias pattern appears to be the same for both IAM and FAM. No systematic elevation-dependency is obvious except for the uppermost parts of the ice cap above 500 m a.s.l. (Fig. 5). The systematic bias is thus limited to regions where only very little ablation occurs (M ¨oller et al., 2011a). As the presented albedo model is

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Protein Adsorption to Surface Chemistry and Crystal Structure Modification of Titanium Surfaces

Protein Adsorption to Surface Chemistry and Crystal Structure Modification of Titanium Surfaces

In living systems, blood (plasma) is the irst component to come in contact with biomaterials such as a titanium implant during surgery [1]. It is known that immediately after contact with plasma, rapid adsorption of plasma proteins onto the biomaterial takes place [2], which inluences subsequent cell attachment, spreading, proliferation, and differentiation [3]. In bone-to-implant binding, i.e. osseointegration, the attachment of blood- derived proteins such as plasma ibronectin to the implant surface enhances the chemotaxis [4] and focal adhesion of osteogenic cells [5]. Fibronectin is a high- molecular weight extracellular matrix (ECM) protein (approximately 440 kDa) that binds to integrins, which are membrane-spanning receptor proteins [6]. One form of ibronectin, the plasma ibronectin, is produced by hepatocytes in the liver and circulates in the blood [7]. It activates signaling pathways that direct cell-cycle progression, gene expression, matrix mineralization [8], and the regulation of the survival of osteoblasts [9]. In addition, plasma ibronectin is known to be a regulator for bone density, and bone biomechanical properties [7 ], and it has been reported that plasma ibronectin interacts with bone morphogenetic protein 1, indicating that it has an important role in osteogenesis [10]. Ever since the importance of a moderately roughened surface was proposed, the rate of osseointegration has been enhanced by surface modiication [ 11], and further, in recent times, surface modiication is being carried out even at the nano-level. It is therefore reasonable that implant surfaces should be modiied at this level, given that it has been proven that cells react sensitively to nano-topographies [12]. Several studies have investigated the effect of the modiied surfaces on osteogenic cell reactions, and surface modiications aimed at enhancing cell responses have been carried out [13,14 ]. However, few modiications have actually focused on the protein reactions underlying such cell reactions.
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Simulating the Greenland ice sheet under present-day and palaeo constraints including a new discharge parameterization

Simulating the Greenland ice sheet under present-day and palaeo constraints including a new discharge parameterization

narrow outlet glaciers. As a result, although ice discharge into the ocean currently accounts for more than half of surface accumulation, over most of Greenland the ice sheet margin is located several tens of kilometres away from the ocean. Since current ice-sheet models do not resolve outlet glaciers and their interaction with the ocean in the fjords, the modelled GIS needs too much contact with the ocean to produce

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