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| 2. |
- Blunden, Jessica, et al.
(författare)
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State of the Climate in 2012
- 2013
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 94:8, s. S1-S258
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Tidskriftsartikel (refereegranskat)abstract
- For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Ni a dissipated to ENSOneutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern conditions. Nevertheless, other large-scale climate patterns and extreme weather events impacted various regions during the year. A negative phase of the Arctic Oscillation from mid-January to early February contributed to frigid conditions in parts of northern Africa, eastern Europe, and western Asia. A lack of rain during the 2012 wet season led to the worst drought in at least the past three decades for northeastern Brazil. Central North America also experienced one of its most severe droughts on record. The Caribbean observed a very wet dry season and it was the Sahel's wettest rainy season in 50 years. Overall, the 2012 average temperature across global land and ocean surfaces ranked among the 10 warmest years on record. The global land surface temperature alone was also among the 10 warmest on record. In the upper atmosphere, the average stratospheric temperature was record or near-record cold, depending on the dataset. After a 30-year warming trend from 1970 to 1999 for global sea surface temperatures, the period 2000-12 had little further trend. This may be linked to the prevalence of La Ni a-like conditions during the 21st century. Heat content in the upper 700 m of the ocean remained near record high levels in 2012. Net increases from 2011 to 2012 were observed at 700-m to 2000-m depth and even in the abyssal ocean below. Following sharp decreases in to the effects of La Ni a, sea levels rebounded to reach records highs in 2012. The increased hydrological cycle seen in recent years continued, with more evaporation in drier locations and more precipitation in rainy areas. In a pattern that has held since 2004, salty areas of the ocean surfaces and subsurfaces were anomalously salty on average, while fresher areas were anomalously fresh. Global tropical cyclone activity during 2012 was near average, with a total of 84 storms compared with the 1981-2010 average of 89. Similar to 2010 and 2011, the North Atlantic was the only hurricane basin that experienced above-normal activity. In this basin, Sandy brought devastation to Cuba and parts of the eastern North American seaboard. All other basins experienced either near-or below-normal tropical cyclone activity. Only three tropical cyclones reached Category 5 intensity-all in Bopha became the only storm in the historical record to produce winds greater than 130 kt south of 7 N. It was also the costliest storm to affect the Philippines and killed more than 1000 residents. Minimum Arctic sea ice extent in September and Northern Hemisphere snow cover extent in June both reached new record lows. June snow cover extent is now declining at a faster rate (-17.6% per decade) than September sea ice extent (-13.0% per decade). Permafrost temperatures reached record high values in northernmost Alaska. A new melt extent record occurred on 11-12 July on the Greenland ice sheet; 97% of the ice sheet showed some form of melt, four times greater than the average melt for this time of year. The climate in Antarctica was relatively stable overall. The largest maximum sea ice extent since records begain in 1978 was observed in September 2012. In the stratosphere, warm air led to the second smallest ozone hole in the past two decades. Even so, the springtime ozone layer above Antarctica likely will not return to its early 1980s state until about 2060. Following a slight decline associated with the global 2 emissions from fossil fuel combustion and cement production reached a record 9.5 +/- 0.5 Pg C in 2011 and a new record of 9.7 +/- 0.5 Pg C is estimated for 2012. Atmospheric CO2 concentrations increased by 2.1 ppm in 2012, to 392.6 ppm. In spring 2012, 2 concentration exceeded 400 ppm at 7 of the 13 Arctic observation sites. Globally, other greenhouse gases including methane and nitrous oxide also continued to rise in concentration and the combined effect now represents a 32% increase in radiative forcing over a 1990 baseline. Concentrations of most ozone depleting substances continued to fall.
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| 3. |
- Abrahamsson, Per, 1985, et al.
(författare)
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Parameter study of a kinetic-frictional continuum model of a disk impeller high-shear granulator
- 2013
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 238, s. 20-26
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Tidskriftsartikel (refereegranskat)abstract
- A disk impeller high shear granulator was modeled with a kinetic-frictional continuum model. A parameter study was made and the parameterization of the equations was assessed to investigate if the model is suited for modeling high shear granulation. A dry granule mixing was studied and the parameters investigated were the particle diameter, the angle of internal friction, the particle-particle restitution coefficient, the particle density, the particle velocity boundary condition, the packing limit and the numerical parameter frictional packing limit. All the particle related parameters can be expected to change during a granulation. The flow field prediction of the model is in agreement with the behavior described by Knight et al. (2001), showing a rigid torus. This is in contrast to a discrete element model simulation that predicts inner rotation within the torus (Gantt and Gatzke 2006). The general flow field of this system is fairly insensitive to all parameter changes, except a change to no slip boundary condition for the particle phase, even though several parameters significantly affect the solid phase viscosity. The model was used to predict the change in impeller torque when going from mixing a dry powder to a wet system. It is shown that the models have some potential for qualitative descriptions of the wet state. (
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| 7. |
- Ingelsson, Erik, et al.
(författare)
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Detailed Physiologic Characterization Reveals Diverse Mechanisms for Novel Genetic Loci Regulating Glucose and Insulin Metabolism in Humans
- 2010
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Ingår i: Diabetes. - 0012-1797 .- 1939-327X. ; 59:5, s. 1266-1275
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Konferensbidrag (refereegranskat)abstract
- OBJECTIVE-Recent genome-wide association studies have revealed loci associated with glucose and insulin-related traits. We aimed to characterize 19 such loci using detailed measures of insulin processing, secretion, and sensitivity to help elucidate their role in regulation of glucose control, insulin secretion and/or action. RESEARCH DESIGN AND METHODS-We investigated associations of loci identified by the Meta-Analyses of Glucose and Insulin-related traits Consortium (MAGIC) with circulating proinsulin, measures of insulin secretion and sensitivity from oral glucose tolerance tests (OGTTs), euglycemic clamps, insulin suppression tests, or frequently sampled intravenous glucose tolerance tests in nondiabetic humans (n = 29,084). RESULTS-The glucose-raising allele in MADD was associated with abnormal insulin processing (a dramatic effect on higher proinsulin levels, but no association with insulinogenic index) at extremely persuasive levels of statistical significance (P = 2.1 x 10(-71)). Defects in insulin processing and insulin secretion were seen in glucose-raising allele carriers at TCF7L2, SCL30A8, GIPR, and C2CD4B. Abnormalities in early insulin secretion were suggested in glucose-raising allele carriers at MTNR1B, GCK, FADS1, DGKB, and PROX1 (lower insulinogenic index; no association with proinsulin or insulin sensitivity). Two loci previously associated with fasting insulin (GCKR and IGF1) were associated with OGTT-derived insulin sensitivity indices in a consistent direction. CONCLUSIONS-Genetic loci identified through their effect on hyperglycemia and/or hyperinsulinemia demonstrate considerable heterogeneity in associations with measures of insulin processing, secretion, and sensitivity. Our findings emphasize the importance of detailed physiological characterization of such loci for improved understanding of pathways associated with alterations in glucose homeostasis and eventually type 2 diabetes. Diabetes 59:1266-1275, 2010
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| 8. |
- Karlsson, Stina, 1975, et al.
(författare)
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Characterization and mathematical modelling of single fluidised particle coating
- 2011
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 207:1-3, s. 245-256
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Tidskriftsartikel (refereegranskat)abstract
- A study was made of coating single particles with water-based dispersions under realistic fluid dynamic and well-defined operating conditions. The surfaces of the coated particles were observed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM was used to study the latex particle packing and the colloid particle coalescence at the nanoscale, while SEM was used to study the film at the droplet size level. The influence of temperature, moisture content and spray rate were investigated. The experiments showed a coating layer built up of rings of colloid particles for all cases studied except for high spray rate. A variation in the degree of coalescence between colloid particles with different glass transition temperatures, T-g, was shown in AFM. Cracks in the coating layer were observed when the temperature was lower than T-g. Mechanism evaluation using dimensionless numbers showed that a droplet will spread to the equilibrium angle without splashing; the colloid particles accumulate at the interface between the liquid and the air for all cases studied except air with 90% RH and 20 degrees C and a wet-bulb temperature in the coating layer. The evaluation indicated that no skin forms in any of the cases. A model of the drying of a single droplet was developed to describe the experimental results with rings of colloid particles. The simulation of the shape and height of the dried droplet agrees well with the experimental results. (C) 2010 Elsevier B.V. All rights reserved.
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| 9. |
- Nguyen, Duy, 1986, et al.
(författare)
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CFD simulation of transient particle mixing in a high shear mixer
- 2014
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 258, s. 324-330
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Tidskriftsartikel (refereegranskat)abstract
- Particle mixing is one of the key operations in pharmaceutical processing. In this work, an Eulerian-Eulerian multiphase framework has been employed to model and simulate particulate flow and mixing behaviour in the blending of dry powders for inhalation. The kinetic theory of granular flow and the frictional stress model are used to close the transport equations of dense particulate flow in a high shear mixer. The transient mixing dynamics, including start-up, within the mixer are captured by adding a scalar transport equation as a tracer. The solid velocity profile at the wall is experimentally determined by using a high speed camera and particle image velocimetry (PIV) evaluation. The evolution of a tracer movement is experimentally tracked using an imaging technique that is processed in the Matlab image toolbox to obtain the local particle concentration. The model can capture the main features in granular flow motion, e.g. bed height and the dominating flow direction. The mixing mechanism is found to be a combination of azimuthal, axial and radial mixing at the same order of magnitude. Rapid mixing is captured in the simulation and is in agreement with experimental data. Even though the continuum-based model can predict well some flow features and the transient mixing time, there is a need for further development of the continuum description of dense particulate flows.
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| 10. |
- Nguyen, Duy, 1986, et al.
(författare)
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Numerical modelling of breakage and adhesion of loose fine-particle agglomerates
- 2014
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 116, s. 91-98
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Tidskriftsartikel (refereegranskat)abstract
- In this study, discrete element method (DEM) simulations are used to examine the breakage and capturing behaviour of loose fine-particle agglomerates on impact with a target particle. The model system is an agglomerate composed of 5 mu m fine particles and a 200 gm target particle. The cohesion between fine particles was modelled using the Johnson, Kendall and Roberts (JKR) theory. In contrast to the breakage of hard agglomerates which break in large fragments, as commonly investigated, loose agglomerates break in finer fragments. Impact velocity was found to be a significant parameter not only for the adhesion strength but also for the structure of the particles captured on the target. The capture ratio of the agglomerate as well as the thickness of the particle layer covering the target decreases with increasing impact velocity. High impact velocity results in finer fragments attached to the target with greater tensile strength due to the re-structuring mechanism that occurs during impact. Accordingly, impact velocity is one of the critical parameters governing the structure resulting after collision. However, the effect of material properties, e.g. surface energy, material hardness and plasticity, on adhesion behaviour should be investigated to obtain a full picture of the breakage-adhesion regime map.
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