Creating Standardized Guides for Pottery Temper Characterization

BackgroundThe virtual reality (VR) content market is rapidly growing due to an increased supply of VR devices such as head-mounted displays (HMDs), whereas VR sickness (reported to occur while experiencing VR) remains an unsolved problem. The most widely used method of reducing VR sickness is the use of a rest frame that stabilizes the user's viewpoint by providing fixed visual stimuli in VR content (including video). However, the earth-fixed grid and natural independent visual background that are widely used as rest frames cannot maintain VR fidelity, as they reduce the immersion and the presence of the user. A visual guide is a visual element (eg, a crosshair of first-person shooter [FPS]) that induces a user's gaze movement within the VR content while maintaining VR fidelity, whereas there are no studies on the correlation of visual guide with VR sickness.ObjectiveThis study aimed to analyze the correlation between VR sickness and crosshair, which is widely used as a visual guide in FPS games.MethodsEight experimental scenarios were designed and evaluated, including having the visual guide on/off, the game controller on/off, and varying the size and position of the visual guide to determine the effect of visual guide on VR sickness.ResultsThe results showed that VR sickness significantly decreased when visual guide was applied in an FPS game. In addition, VR sickness was lower when the visual guide was adjusted to 30% of the aspect ratio and positioned in the head-tracking direction.ConclusionsThe experimental results of this study indicate that the visual guide can achieve VR sickness reduction while maintaining user presence and immersion in the virtual environment. In other words, the use of a visual guide is expected to solve the existing limitation of distributing various types of content due to VR sickness.

Assessment of atherosclerotic luminal narrowing of coronary arteries based on morphometrically generated visual guides.

Usually we steer a car using mainly visual information to perceive road's shape and bends. We developed a driving simulator with visual and/or tactile information guides to virtually present drivers' lateral position and to enhance their steering performance. The purpose of this study was to test effects of the cross-modal guide information on the driving performance. We found that the tactile guide improved driving accuracy more than the visual guide without any tradeoff of driving loads. Thus, the tactile information of virtual position of a car is useful for assisting and improving driver's performance with fewer loads.

Learning to play the guitar is difficult. We proposed a system that assists people learning to play the guitar using augmented reality. This system shows a learner how to correctly hold the strings by overlaying a virtual hand model and lines onto a real guitar. The player learning to play the guitar can easily understand the required position by overlapping their hand on a visual guide. An important issue for this system to address is the accurate registration between the visual guide and the guitar, therefore we need to track the pose and the position of the guitar. We also proposed a method to track the guitar with a visual marker and natural features of the guitar. Since we used marker information and edge information as natural features, the system could continually track the guitar. Accordingly, our system can constantly display visual guides at the required position to enable a player to learn to play the guitar in a natural manner.

We devised and tested two new visual guides to help users comprehend distorted sketched information in magnification lenses. Distortion techniques, such as fisheye lenses, have the advantage of magnifying information without occluding the surrounding content. However distorted information in the transition region requires extra mental workload to understand: this can lead to frustration and rejection of magnification lenses. Our evaluation shows any visual guide is better than none and identifies strengths and weaknesses of the new guides. We tested for the four visual properties important for understanding distorted information: scale, alignment, distance and direction. Surprisingly grids are not as effective in many contexts as our new lenses.

Low density lipoprotein (LDL) is the main carrier of plasma cholesterol and a major component of atherosclerotic plaque [1]. Lowering LDL cholesterol reduces coronary events and mortality from coronary artery disease (CAD) [2–4], however, the relation between LDL cholesterol concentration and (CAD) is complex. Many patients with CAD have plasma LDL cholesterol concentrations in the normal rangefor the general population [5]. Thus, it could be that coronary risk goes beyond LDL cholesterol concentration to the characteristics of the LDL particles themselves. The purpose of this communication is to address the issue of whether LDL particle size and density influences its atherogenecity and how this might be modified by drug therapy. Human LDL particles can be isolated by density gradient centrifugation in the density range of 1.019–1.063 g ml−1 and contain approximately 50% cholesterol (free and esterified), 25% proteins, 20% phospholipids and 5% triglycerides. Over 95% of the LDL protein mass is apolipoprotein B-100 (apo B-100, 549 kDa) [6, 7], each LDL particle containing only one molecule of apo B-100. The molecular mass of LDL is in the range from 2.4– 3.9 MDa [8]. The particles are usually described as spherical, containing a central core of non-polar cholesteryl esters and triglycerides while free cholesterol intercalates between the phospholipid fatty acid chains providing a degree of rigidity to the phospholipid monolayer that is the LDL outer coat which interfaces with plasma. ApoB-100 is exposed at the surface allowing receptor recognition [9]. More recent studies using cryoelectron microscopy suggest that human LDL is discoidal with diameter 21.4±1.3 nm, height 12.1±1.1 nm and average volume of 4352 nm3 [10]. The LDL particle population is heterogeneous with the respect to size, density and composition. Distinct subpopulations vary in isoelectric point, electrical charge, hydrodynamic properties and immunoreactivity [11]. This heterogeneity has been identified through the use of density gradient, rate zonal and analytical ultracentrifugation as well as with nondenaturing gradient gel electrophoresis [12]. Depending on the methodology used, from 2 to 38 LDL subfractions have been separated [13]. Measurements of LDL subfraction diameters using negative staining electron microscopy have established that mean particle diameter decreases with increasing density [14]. The structure of LDL particles of different densities varies with respect both to the size of the core and the width of the surface shell [15]. LDL subfraction composition varies between individuals. Of the various phenotypic classifications of LDL subfraction patterns, two of the most widely used are those of Musliner & Krauss [16] and Austin et al. [17]. The former divide subjects into one of four main groups (LDL I to LDL IV) with properties shown in Table 1. In an alternative classification based on particle diameter Austin et al. [17] suggested two major patterns of LDL profile, pattern A (particle diameter 25.5 nm or greater) and pattern B (particle diameter less than 25.5 nm). In kinetic turnover studies, where the rate of urinary excretion of radioactive products of labelled LDL were measured, two LDL pools were demonstrated. A rapidly cleared pool A (probably consisting of large LDL particles) and a slowly cleared pool B (small LDL particles) [18]. LDL subfractions share several common features. Cholesteryl ester is the principal lipid (38.3–42.8%) and free cholesterol (8.5–11.6%) tends to diminish as density increases. Triglycerides are a minor component (3–5%). Density increases with increasing protein content. ApoB-100 is the major protein in all subfractions. ApoE constitutes 0.1–1.3% and 0.2–1.9% of LDL proteins in subfractions of low and high density, respectively. The ratio of apoE to apoB changes from 1:60 to a maximum of 1:8 in denser subfractions possibly accounting for differences in binding affinities for LDL receptors. Apo C-III is present in subfractions with densities greater than 1.0358 g ml−1. Calculation of the number of each chemical component per LDL subspecies showed the presence of one molecule of apoB per particle in association with decreasing amount of cholesteryl esters, free cholesterol and phospholipids [11]. The diameter of human LDL particles correlates positively with the molar ratio of phospholipid/apo B in LDL but not with the molar ratio of either cholesterol/apoB or triglyceride/apo B suggesting that phospholipid content is also an important determinant of LDL size [19]. There are distinct and constant differences in the electrical charge of LDL subfractions at neutral pH of 7.4 arising as a result of either dissimilarities in the relative proportions of charged phospholipids or of sialytion of associated proteins [11, 20]. Negative charge increases with increasing density of LDL particles. Small LDL particles have significantly lower neutral carbohydrate and sialic acid content [20, 21]. LDL particles with lower sialic acid content have greater affinity for proteoglycans in the arterial wall and could be preferentially involved in the development of atherosclerosis [21, 22]. The biochemical processes that underlie the formation of distinct LDL subfractions are incompletely understood. Most LDL particles originate from larger triglyceride rich apo-B containing particles such as VLDL that are secreted from the liver. However some kinetic studies suggest that LDL particles are also normally secreted from the liver [23]. Lipoprotein lipase (LPL) progressively removes triglycerides from the core of VLDL to form intermediate density lipoprotein (IDL) particles which can be either degraded directly by the liver via receptor-mediated binding or further metabolised by LPL and hepatic lipase (HL) to LDL particles. Some of the surface constituents (cholesterol, phospholipids, apo-C and apoE) are released and transferred to HDL. Cholesteryl ester remains and the remnant lipoprotein is a cholesteryl ester-enriched large LDL. Cholesterol ester transfer protein (CETP) transfers cholesteryl esters from the LDL back to VLDL in exchange for triglycerides. During lipolysis VLDL loses much of its apo-C, so the proportion of apo-E increases which is of importance as hepatic LDL receptors have a particularly strong affinity for apo-E [24]. The triglyceride content of the precursor lipoproteins is a major determinant of the size of the LDL product formed by lipolysis [25], larger triglyceride-rich VLDL particles giving rise to smaller LDL particles. This apparent paradox is explained by the fact that large triglyceride rich VLDL particles provide a ready substrate for the CETP. It transfers cholesteryl esters from LDL particles in exchange for triglycerides from VLDL. Triglyceride enriched LDL has its acquired triglycerides removed by the actions of the enzymes LPL and hepatic lipase (HL) leading to continued particle size reduction. High HL activity is associated with an increased concentration of small LDL even at lower plasma triglyceride levels [23, 25]. Accordingly, deficiency of HL is associated with increased large LDL particles whereas raised HL activity is associated with a predominance of smaller LDL [26]. The distribution of LDL particle size is determined by both genetic and environmental factors. Phenotype B (predominance of small LDL particles) is found in 30-35% of adult Caucasian men but is less prevalent in men younger than 20 years and in premenopausal women. The data are consistent with either an autosomal dominant or codominant model for inheritance of the pattern B phenotype with additional polygenic effects of variable magnitude. Pattern B is linked to the LDL receptor gene locus on chromosome 19 [27]. Estimates of heritability of LDL particle size range from 30-50% confirming the importance of environmental influences in determining the LDL profile [12]. Such environmental factors include diet, obesity, exercise and drugs (lipid lowering drugs, beta adrenergic receptor antagonists) as well as age and hormonal status. The pattern B phenotype correlates strongly with insulin resistance [28]. The explanation for this association is not fully known. It is possible that failure of insulin to suppress free fatty acid release from adipose tissue, in subjects with insulin resistance, causes increased influx of free fatty acids to the liver. This would result in an increased secretion of VLDL and transfer of its triglycerides to LDL. Furthermore, insulin activation of LPL is suppressed in insulin resistance affecting hydrolysis of triglyceride-rich lipoproteins including large VLDL, leading to further LDL particle size reduction [28]. The predominance of small, dense LDL particles is correlated with an increased risk for CAD [17, 29], and small LDL subfractions are more prevalent among patients with CAD. The predominance of small LDL subfractions is generally associated with increased triglyceride concentrations and often with low HDL cholesterol concentrations. Hence the risk associated with small LDL subfractions is reduced after adjusting for these parameters in multivariate analyses. However, three recent studies have shown an increased risk of CAD associated with the predominance of small LDL particles independent of other lipid parameters, including triglycerides [30–32]. Griffin and colleagues (1994) were first to demonstrate that the predominance of small, dense LDL particles in patients with CAD was independent of triglyceride concentrations. However, in their study patients with CAD had significantly higher triglyceride concentrations than the control subjects [30]. The only study of LDL subfraction profiles in normotriglyceridaemic men with established CAD, showed that LDL particles were significantly smaller in men with CAD than in controls, regardless of other plasma lipid parameters, including triglycerides and HDL cholesterol. Furthermore, LDL subfraction profile was the strongest predictive factor for the presence of CAD when compared to other lipid parameters [31]. Finally, in the first large prospective study of LDL subfractions followed over 5 years, LDL particle size was predictive of CAD independently of other lipid parameters including triglyceride concentrations [32]. Taken together these studies suggest that triglyceride concentration is not the only factor in determining LDL particle size. LDL subfraction analysis may further define risk of CAD, particularly in men with relatively normal lipid profiles. Although the cited cross-sectional studies suggest that small, dense LDL particles are especially atherogenic, there are additional possibilities to be considered. For example, this atherogenic lipoprotein phenotype often clusters with insulin resistance which may be an etiological factor leading to enhanced CAD risk in many patients with the small dense LDL phenotype [33]. The predominance of small LDL particles over other LDL particles, is also strongly correlated with high plasma fibrinogen concentrations in men. The reason for this association (which is independent of cholesterol, triglycerides, body mass index, age and insulin resistance) is unknown but since hyperfibrinogenaemia is an independent risk factor for CAD this could account for some of the effects of small, dense LDL particles on CAD [34]. There are several mechanisms by which small dense LDL is likely to play a causal role in promoting atherosclerosis and thrombosis. These are discussed below. Native LDL increases superoxide generation (O2−) from the endothelium and decreases basal nitric oxide (NO) production [35] and stimulated NO production [36]. It is likely that small dense LDL is more potent in this regard. Inhibition of NO production is atherogenic [37] and O2− inactivates NO [38] and can oxidise LDL (see below). The filtration rate of LDL particles into subendothelium is inversely proportional to particle size, thus small LDL particles are transported more effectively from the circulation to the subendothelial space of artery wall than are large LDL particles [39]. Oxidized LDL plays an important role in atherogenesis since it is taken up by scavenger receptors on macrophages leading to cholesterol accumulation and foam cell formation in the evolving fatty streak [40]. Small, dense LDL particles are more susceptible to oxidation in vitro than large LDL particles [41]. This is attributable to several factors. The content of antioxidants including vitamin E and ubiquinol-10 is lower in small than in large LDL particles. The structure of small, dense LDL may expose their polyunsaturated fatty acids (PUFA) to free radical attack and lipid peroxidation [40]. Small, dense LDL particles have a higher content of PUFA, including arachidonic acid, than do large LDL particles. PUFA are degraded to conjugated dienes and other oxidation products during oxidation [42]. Non-enzymatic oxidation of arachidonic acid yields the isoprostanes, some of which are biologically active (e.g. 8-epi-PGF2α ) and may contribute to atherogenesis as well as providing an in vivo measure of oxidative stress [43]. Lipid peroxidation starts by oxidation of the PUFA component of the phospholipids in the particle surface and propagates towards the particle core. Free cholesterol of the particle limits access of oxidants to PUFA in the particle surface thus stabilising LDL particles against initial oxidative attack. Small LDL particles are relatively depleted of free cholesterol and may therefore be less protected by this mechanism [44]. In the kinetic turnover studies, two LDL pools were demonstrated. Rapidly cleared pool A (probably consisting of large LDL particles) and slowly cleared pool B (small LDL particles) [18]. This observation is consistent with in vitro studies demonstrating that small, dense LDL particles have a lower affinity for LDL receptors than do larger LDL particles [45]. This results in reduced hepatic clearance and a longer residence time in plasma of small versus large LDL particles, increasing the likelihood that small LDL particles will be filtered into the arterial wall followed by oxidation and uptake via scavenger receptors [45]. This lower affinity of small, dense LDL particles for the LDL receptor is independent of their triglyceride content [46]. ApoB-100 in small, dense LDL particles has additional cleavage sites and different accessibility to protease attack, suggesting that the conformation of apoB-100 in small, dense LDL particles differs from that in other LDL particles. This may reduce their affinity for LDL receptors [47]. Small, dense LDL particles have greater affinity for intimal proteoglycans than do other LDL particles [48]. This may be related to their lower sialic acid content and to different exposures of the apoB region that influences interactions with proteoglycans. Binding to intimal proteoglycans leads to extracellular lipid accumulation which is an important component of atherogenesis [49]. LDL particle size is related to endothelial vasodilator dysfunction in patients with CAD, independent of other lipoprotein variables [50]. Small, dense LDL particles stimulate thromboxane (TX) A2 synthesis in vitro, more than large LDL particles [51]. Since TXA2 stimulates platelet aggregation and is a potent vasoconstrictor this could contribute to the progression of CAD. Production of 8-epi-PGF2α as a result of non-enzymatic oxidation of arachidonic acid in small, dense LDL particles could also promote vasoconstriction and platelet aggregation. Generally, heterogeneity of LDL is investigated using either density gradient ultracentrifugation or polyacrylamide gel electrophoresis [29]. Several DGUC procedures have been developed to characterise LDL subfractions [29, 52]. The procedures differ both in the construction of the gradient and in the fractionation profile and no single method has yet assumed general usage. The main disadvantages of all DGUC procedures for investigation of LDL subfractions are: a) expensive equipment (ultracentrifuges and appropriate rotors), b) time required for separation to be completed is very long (except when vertical rotors are used), c) lipoprotein degradation during ultracentrifugation (lipids and proteins tend to separate during centrifugation), d) complicated gradient preparation, e) large volumes of plasma are required for an adequate analysis of lipoprotein distributions, f) fractionation requires special gradient fractionator or punching a hole at the bottom of the tube and collecting subfractions; both techniques are time consuming and require great care as the gradient is easily disturbed. However, DGUC allows good resolution between lipoprotein subfractions and analysis of the chemical composition of each subfraction. Electrophoresis method is relatively inexpensive, faster than centrifugation and can be used for analyses of small amounts of material. Furthermore, it enables different subfractions of LDL and HDL to be separated directly and with better resolution than when using other techniques. Electrophoresis separates lipoproteins according to their charge and size. Lipoproteins have an isoelectric point at about pH 5.5 above which they are negatively charged. Analysis of LDL subfractions is usually performed by using nondenaturing polyacrylamide gradient gel electrophoresis. Lipoproteins migrate in an electric field through a gradient of increasing polyacrylamide concentration. The pore size of the matrix progressively decreases as the concentration of acrylamide increases. Migration of the particles stops when they reach their exclusion limit. Gradient slab gels of 2–16% polyacrylamide have commonly been used [53]. Electrophoresis for separation of LDL subfractions using these gels requires less than 25 ml of plasma and may last for up to 24 h depending on voltage used. After electrophoresis gels need to be stained and destained. So the whole procedure lasts for more than 24 h and is time consuming and labour intensive. Continuous polyacrylamide disc gels were introduced to simplify the method. These gels are a modification of the disc gels as described by Naito et al. [54] and Muniz [55]. In order to achieve desirable separation of LDL subfractions they were modified by increasing the gel length and optimising the electrolyte buffers and gel composition. These gels allow separation of up to 7 LDL subfractions within 70 min using prestained serum samples [56]. The advantages of separation of LDL subfractions by using electrophoretic methods compared with DGUC are as follows: a) less expensive and less complicated equipment is required, b) generally, separations is achieved in shorter time, particularly if the prestained disc gels are used (still over 24 h if staining and destaining procedures applied), c) lipoprotein degradation does not occur during electrophoresis, d) technique is simpler to perform, e) small volume of sample is needed for the analysis (not more than 25 μl). In view of the strong relationship between elevated plasma triglycerides and the small dense LDL phenotype, triglyceride lowering therapies could be expected to have a greater impact on LDL size and density than predominantly cholesterol lowering therapies. The HMG CoA reductase inhibitors (statins) lower LDL cholesterol substantially and their value in reducing CAD mortality and morbidity has been demonstrated conclusively [2–4]. These drugs have little effect on particle size when tested in patients with the small dense LDL phenotype. Simvastatin caused a decrease in both large and small LDL particles in combined hyperlipidaemic patients, with no overall improvement in the subclass phenotype [57]. Pravastatin reduced total and LDL cholesterol in combined hyperlipidaemic patients but LDL particle size was either unchanged or became even smaller [58, 59]. In familial hypercholesterolaemia, lovastatin and simvastatin decrease cholesterol more in the light LDL than in dense particles [60]. These statins cause little or no decrease in plasma triglycerides in the combined and familial hyperlipidaemic patients, which may explain why there is generally no reduction of small, dense LDL particles. Any apparent worsening of LDL phenotype by statins may be due to up-regulation of LDL receptors, preferentially increasing clearance of larger LDL particles which have a higher affinity for LDL receptors. As a result, small LDL particles come to dominate the plasma LDL subfraction profile. Potentially adverse effects of statins on LDL density profiles are clearly more than offset by the beneficial effects of reducing the total plasma LDL cholesterol pool, as evidenced by the reduction of CAD events which has been demonstrated in recent clinical trials [2–4]. A new member of the HMG CoA reductase inhibitor, atorvastatin, lowers plasma triglycerides more than other marketed statins at licensed doses [61]. As a result it may have greater beneficial effects on LDL density profiles than other currently licensed statins. The impact of aggressive lipid lowering on CAD progression and the relationship to small dense LDL was evaluated in a retrospective analysis of data from the Familial Atherosclerosis Treatment Study, FATS [62]. Patients treated with nicotinic acid plus cholestyramine or lovastatin plus cholestyramine experienced a significant reduction in coronary stenosis compared to There was a strong relationship between the changes in LDL density and coronary The reduction of small, dense LDL was a of disease progression than was reduction of LDL cholesterol. of nicotinic acid plus cholestyramine and lovastatin plus cholestyramine plasma triglycerides which to the improvement in the small dense LDL phenotype. to the of small, dense LDL This is due to up-regulation of LDL receptors. These preferentially larger more LDL particles. acid reduces the concentration of small dense LDL acid is more at lowering plasma triglycerides than cholesterol and in patients the in LDL phenotype caused by nicotinic acid is both correlated with triglyceride levels and the reduction in triglycerides after It causes only a reduction of LDL particle diameter in with normal plasma triglycerides but a more reduction in particle size in subjects with the most widely used triglyceride lowering are Several of these including and decrease small dense LDL in patients with combined increased LDL particle size and particle density in patients with triglycerides in the range of The effect was strongly correlated with the reduction of triglycerides. had no effect on LDL density profile in patients with normal triglyceride levels in LDL particles were larger and less dense In patients with higher triglycerides LDL to the larger and less dense phenotype in association with reduced triglycerides Thus, the effect of and the other on LDL size and density on the triglyceride plasma triglycerides the transfer of VLDL triglycerides to LDL by CETP. The hydrolysis of LDL triglyceride small dense LDL reducing plasma triglycerides, the amount of substrate for transfer to LDL and decrease the formation of small dense LDL. In was found to decrease mass and transfer which further limits the formation of small dense LDL only a effect on may reduce progression of coronary atherosclerosis and coronary events in men a analysis of patients in the study demonstrated a reduced number of events in patients to effects suggest that with a and could be of in patients with a of small dense a that to be tested by clinical As discussed small dense LDL profile is associated with insulin that insulin include exercise and possibly receptor while on resistance, and small dense LDL particles and together form the which is strongly associated with atherosclerosis on these factors could LDL particle size. The causes a small in LDL cholesterol in due to an in less dense LDL. This may explain the observation that increases the resistance of LDL particles to oxidation It is possible that is against The in the LDL particle density is associated with a decrease in plasma triglycerides, larger effects on triglycerides are generally in patients treated with Since the small, dense LDL profile is associated with insulin resistance, the improvement caused by may be related to its to insulin studies will be required to the relative of enhanced insulin and of reducing plasma triglyceride in the effects of on LDL and other their effects by binding to the receptor found predominantly in The mechanism by which they insulin is not fully but is at attributable to increased of a involved in fatty acid The triglyceride lowering effects of also to effects on gene triglyceride lowering their major activity by binding to a in this which is in the liver the and decrease plasma concentrations of small dense LDL. mechanisms at the of plasma triglycerides but there may be additional by which they LDL density including effects on CETP. were described that both and These decrease plasma triglycerides and insulin in It is that such may have greater effects on small dense LDL than or that decrease plasma concentrations of triglycerides or transfer triglycerides between lipoprotein may the formation of small dense LDL. Thus, inhibitors of and triglyceride transfer protein which are currently development may decrease small dense LDL. The value of these or other to LDL size and density profiles be Finally, studies in patients with of insulin resistance and allow effects on particle size to be from effects on other factors. Such studies are needed to whether LDL particle size plays a role in the effects of different drug on particle size will play an increasing in clinical of not only in but in and

Association of Lipoprotein Subfractions and Coronary Artery Calcium In Patient at Intermediate Cardiovascular Risk

We devised and tested two new visual guides to help users comprehend distorted sketched information in magnification lenses. Distortion techniques, such as fisheye lenses, have the advantage of magnifying information without occluding the surrounding content. However distorted information in the transition region requires extra mental workload to understand: this can lead to frustration and rejection of magnification lenses. Our evaluation shows any visual guide is better than none and identifies strengths and weaknesses of the new guides. We tested for the four visual properties important for understanding distorted information: scale, alignment, distance and direction. Surprisingly grids are not as effective in many contexts as our new lenses.

Physiotherapy patients exercising at home alone are at risk of re-injury since they do not have corrective guidance from a therapist. To explore solutions to this problem, we designed Physio@Home, a prototype that guides people through prerecorded physiotherapy exercises using real-time visual guides and multi-camera views. Our design addresses several aspects of corrective guidance, including: plane and range of movement, joint positions and angles, and extent of movement. We evaluated our design, com-paring how closely people could follow exercise movements under various feedback conditions. Participants were most accurate when using our visual guide and multi-views. We provide suggestions for exercise guidance systems drawn from qualitative findings on visual feedback complexity.

Entrainment has become a significant issue nowadays with fine grinding being used to liberate valuable minerals from low grade and complex ores to increase “true flotation”. Entrainment results in large amounts of fine gangue materials reporting to flotation concentrates along with recovered valuable minerals and reduces the final product quality. In froth flotation, entrainment is the dominant recovery mechanism for fine gangue mineral particles, and it is influenced by a number of factors in both the pulp and froth phase, including particle properties (e.g. particle size and density) and flotation operational variables (e.g. gas flowrate, froth depth, impeller speed and reagent dosage). A number of models incorporating different factors have been developed to estimate entrainment recovery. Most of these models relate entrainment recovery to two parameters: the water recovery to concentrate, and the degree of entrainment, a classification factor to account for the degree of drainage of entrained particles with respect to the water in the pulp and froth phases of a flotation cell. However, there are still significant barriers to be overcome before they can be applied for routine estimation of entrainment in industrial applications. There is no consensus as to the variables which significantly affect the entrainment process and should therefore be included in the model as well as to the mechanisms involved. This thesis investigated the effect of flotation operational factors and particle properties on the entrainment parameters (i.e. degree of entrainment and water recovery) and the mechanisms underpinning the observed effects. The objective of the thesis was to develop a comprehensive understanding of the key operating conditions and particle attributes influencing the entrainment of gangue minerals in flotation, which should enable the development of a more sophisticated predictive entrainment model by more accurately predicting the degree of entrainment and water recovery. A two level factorial experimental program was adopted to investigate the effect of impeller speed, gas flowrate, froth height and specific gravity of gangue minerals on the degree of entrainment. Batch flotation experiments were performed in a 3.5 L conventional Agitair flotation cell using a feed which was a mixture of liberated chalcopyrite and one of two liberated gangue minerals, quartz and hematite. Results show that there was no direct correlation between the degree of entrainment and water recovery, indicating that the key drivers of water recovery were not the same as those that affected the degree of entrainment. The degree of entrainment was significantly influenced by particle size, particle density, frother and the interaction between gas flowrate and froth height. The mechanisms underpinning the effect of these significant influencing factors were investigated. Results suggest that the classification of gangue mineral particles mainly occurs at the pulp/froth interface region. Whether a particle moves upward into the froth and subsequently follows the water phase depends on whether the drag force acting on the solids is greater than the apparent immersed weight of the particles which promotes particle settling. Particle size and density are two variables that affect apparent immersed weight and drag force. Frother, gas flowrate and froth height can alter the liquid velocity at the interface and hence the drag force, and therefore also have a significant impact on the degree of entrainment. The results from the two level factorial experiment were also analysed with respect to water recovery. It was found that water recovery was significantly affected by (1) froth height, (2) gas flowrate, (3) impeller speed, (4) the interaction between impeller speed and particle density, and (5) the interaction between gas flowrate and froth height (in the order of reducing effects). These effects resulted from these factors affecting the water motion in a flotation cell: water drainage in the froth phase and water flow into the froth from the pulp phase. Moreover, the results show that water recovery could be modelled effectively using an exponential function, incorporating water drainage and water entering into the froth. The outcomes of this work can provide plant operators with information they can use to minimise entrainment in their flotation operations as well as providing relationships that could be used to develop an improved predictive entrainment model.

Influence of Particle Size and Density on Particulate Passage Through Alimentary Tract of Holstein Heifers

This study discusses component separation using a microfluidic device. Based on the separation principle, a method was adopted to generate an external force due to centrifugal force in a spirally designed channel. In this study, four types of polystyrene particles with different diameters ranging within 1–45 µm were used, and the separation performance was evaluated for each particle size. The centrifugal force increased as the flow velocity in the channel increased; however, this time, the test was conducted with the flow rate, which is an input parameter fixed at 100 µL/min. The results of the micro-channel observation using a high-speed camera indicated that the particle density might be a factor in the decrease in separation efficiency. Therefore, by conducting tests at three different particle densities, we were able to experimentally investigate the change in separation efficiency based on the particle size and density. In this study, we considered the separation efficiency due to the size and density of the particle diameter along with its application to an onsite-type separation device.

The particle settling velocity is the feature of separation in such processes as flowing classification and jigging. It characterizes material forwarded to the separation process and belongs to the so-called complex features because it is the function of particle density and size. i.e. the function of two simple features. The affiliation to a given subset is determined by the values of two properties and the distribution of such feature in a sample is the function of distributions of particle density and size. The knowledge about distribution of particle settling velocity in jigging process is as much important factor as knowledge about particle size distribution in screening or particle density distribution in dense media beneficiation. The paper will present a method of determining the distribution of settling velocity in the sample of spherical particles for the turbulent particle motion in which the settling velocity is expressed by the Newton formula. Because it depends on density and size of particle which are random variable of certain distributions, the settling velocity is a random variable. Applying theorems of probability, concerning distributions function of random variables, the authors present general formula of probability density function of settling velocity for the turbulent motion and particularly calculate probability density function for Weibull’s forms of frequency functions of particle size and density. Distribution of settling velocity will calculate numerically and perform in graphical form. The paper presents the simulation of calculation of settling velocity distribution on the basis of real distributions of density and projective diameter of particles assuming that particles are spherical.

Electrodeposition of gold nanoparticles on fluorine-doped tin oxide: Control of particle density and size distribution

Particle passage from the reticulorumen (RR) depends on particle density and size. Forage particle density and size are related and change over time in the RR. Particle density mainly influences sorting in the reticulum, whereas particle size influences particle retention in the fibre mat of stratified rumen contents ('filter-bed' effect). We investigated these effects independently, by inserting plastic particles of different sizes (1, 10 and 20mm) and densities (1·03, 1·20 and 1·44mg/ml) in the RR of cattle (Bos primigenius f. taurus) as a pilot study, and of muskoxen (Ovibos moschatus; n 4) and moose (Alces alces; n 2) both fed two diets (browse and grass). Faeces were analysed for plastic residues for 13d after dosing to calculate mean retention times (MRT). The results confirmed previous findings of differences in absolute MRT between species. Comparing muskoxen with moose, there was no difference in the effect of particle density on the MRT between species but particle size had a more pronounced effect on the MRT in muskoxen than in moose. This indicated a stronger 'filter-bed effect' in muskoxen, in accord with the reports of stratified RR contents in this species v. the absence of RR content stratification in moose. Low-density particles were retained longer in both species fed on grass diets, indicating a contribution of forage type to the 'filter-bed effect'. The results indicate that retention based on particle size may differ between ruminant species, depending on the presence of a fibre mat in the RR, whereas the density-dependent mechanism of sedimentation in the RR is rather constant across species.