Breakage of needle-shaped particles in a combination of compressive and shearing stress field

In-silico experiments of needle-shaped particles breakage during shearing have been carried out using DEM simulation. Results of preliminary studies with variation of individual particle strength, compaction ratio, and shearing rate are presented

Humidity sensor utilizing a photonic multilayer structure

Táto bakalárska práca sa zaoberá ako javom povrchovej plazmónovej rezonancie (surface plasmon resonance alebo SPR), tak aj javom rezonancie vedených módov (guided mode resonance alebo GMR). Najskôr je prevedená teoretická analýza pre viacvrstvovú štruktúru substrát-zlato-fotorezist v Kretschmannovom usporiadaní. Následne sú pre rôzne indexy lomu vyjadrené spektrálne závislosti odrazivostí s a p polarizovaných vĺn. Ďalej je navrhnutý a realizovaný experiment demonštrujúci využitie GMR pri meraní odozvy danej štruktúry na zmeny relatívnej vlhkosti vzduchu.This bachelor thesis deals with both surface plasmon resonance (SPR) and guided mode resonance (GMR) phenomena. First, a theoretical analysis is performed for a multilayer substrate-gold-photoresist structure in the Kretschmann configuration. Then, the spectral dependences of the reflectances s and p polarized waves are expressed for different refractive indices. Furthermore, an experiment demonstrating the use of GMR in measuring the response of a given structure to changes in relative humidity is designed and implemented.480 - Katedra fyzikyvelmi dobř

Svojstva višeslojnih materijala ozračenih jakim neutronskim tokovima

Multilayer materials based on silicon were exposed to fast neutrons with fluences ranging from 1015 to 1019 n/cm2. C-V, deep level transient spectroscopy (DLTS) and I-V measurements were carried out to analyse the properties of the respective layers as well as the SiO2-(n-type)silicon and metal-(n-type)silicon interfaces. The detected divacancies and E-centres are likely the main cause of carrier reduction that has been found to depend on the initial doping concentration of the layer. This study has proven that both investigated interfaces exhibit radiation induced interface traps.Višeslojni materijali na osnovi silicija izloženi su brzim neutronima tokovima od 1015 do 1019 n/cm2 . Mjerenja C − V , prijelazna spektroskopija dubokih stanja i I − V mjerenja načinjeni su radi analize svojstava višeslojeva kao i SiO2 – (nsilicij) te metal – (n-silicij) granice. Cini se da su glavni razlog smanjenja nositelja opažene dvojne šupljine i E-centri, koji ovise o početnoj koncentraciji dodataka (dopanata) u sloju. Pokazano je da obje istraživane granice sadrže klopke uzrokovane ozračivanjem

Unified network model for adsorption–desorption in systems with hysteresis

The problem of equilibrium and kinetics for adsorption–desorption of condensable vapors in porous media is studied experimentally and theoretically. For adsorption, the network model for diffusion based on pore blocking theory with percolation (in the network) added by effective medium approximation is further improved. A new predictive model based on properties of the Bethe lattices is proposed to account for the existence of liquid-filled “blind” pores that result in a decrease in the total diffusion rate. For desorption, a new “shell and core” (or shrinking core) representation of the network model is proposed. Information from adsorption–desorption equilibria is needed to compute the thickness of the shell in which desorption/evaporation occurs for concentrations higher than the percolation threshold. These models form a unified equilibrium-kinetics theory for gas-porous solid systems that exhibit hysteresis. The models are applied to the systems silica gel-water vapor and Vycor glass-nitrogen. Concentration-dependent Fickian diffusivities for these systems have been measured for both adsorption and desorption branches. The adsorption model successfully predicts the experimental data with a maximum in diffusivity. The desorption model correctly predicts the concentration dependence of diffusivity with a steep minimum at the percolation threshold.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49313/1/690450409_ftp.pd

Modelling of co-rotating twin-screw extruders in the pharmaceutical industry I : single component model

Twin-screw extruders are being increasingly applied in the pharmaceutical industry for the manufacture of solid dispersions. In particular, Hot Melt Extrusion (HME) is a viable manufacturing alternative for poorly soluble drugs that are difficult to process. This is due to the high shear stress applied in the process, which enhances mixing of the base polymer with the dispersed API. Delivery systems that can be obtained using this technology include pellets, granules, sustained release tablets and implants. Experiments for HME are typically very labour-intensive, involving the use of highly viscous polymers, high pressures, and require proper cleaning between runs. Identifying the critical experiments to perform based on model simulations would thus be highly desirable. Single-component modelling of twin-screw extrusion processes could be beneficial in the following areas: identifying optimal screw configurations, tracking the degree of melting and when identifying the area within the extruder where the polymer becomes completely melted

Vacuum assisted flow initiation in arching powders

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The discharge of powders from hoppers usually takes place in open atmosphere. However, in powder pressing industries (e.g. manufacturing of pharmaceutical tablets, detergents, ceramics, powder metallurgy etc.) there are handling operations where powders are filled into closed cavities such as dies. During this process the air pressure is increased as powder is delivered into the die. At the same time typical tablet production equipment creates a suction effect. A critical orifice measurement apparatus was developed to study powder flow initiation from an arching state into an enclosure where the air pressure is reduced. It was shown that a very small reduction of pressure changed the critical orifice diameter significantly. Dimensional analysis was carried out to relate powder properties (particle size and density) and processing parameters (geometry of the system and differential pressure necessary to break the arch). A relationship was developed to calculate the pressure difference necessary to initiate powder flow. The relationship has two empirical parameters which are calibrated by performing simple experiments using the testing rig developed

Time scale analysis for fluidizedbedmeltgranulation-II: binder spreading rate

The spreading time of liquid binder droplet on the surface a primary particle is analyzed for Fluidized Bed Melt Granulation (FBMG). As discussed in the first paper of this series (Chua et al., in press) the droplet spreading rate has been identified as one of the important parameters affecting the probability of particles aggregation in FBMG. In this paper, the binder droplet spreading time has been estimated using Computational Fluid Dynamic modeling (CFD) based on Volume of Fluid approach (VOF). A simplified analytical solution has been developed and tested to explore its validity for predicting the spreading time. For the purpose of models validation, the droplet spreading evolution was recorded using a high speed video camera. Based on the validated model, a generalized correlative equation for binder spreading time is proposed. For the operating conditions considered here, the spreading time for Polyethylene Glycol (PEG1500) binder was found to fall within the range of 10-2 to 10-5 s. The study also included a number of other common binders used in FBMG. The results obtained here will be further used in paper III, where the binder solidification rate is discussed

The Arabidopsis thaliana N-recognin E3 ligase PROTEOLYSIS1 influences the immune response.

N-degron pathways of ubiquitin-mediated proteolysis (formerly known as the N-end rule pathway) control the stability of substrate proteins dependent on the amino-terminal (Nt) residue. Unlike yeast or mammalian N-recognin E3 ligases, which each recognize several different classes of Nt residues, in Arabidopsis thaliana, N-recognin functions of different N-degron pathways are carried out independently by PROTEOLYSIS (PRT)1, PRT6, and other unknown proteins. PRT1 recognizes type 2 aromatic Nt-destabilizing residues and PRT6 recognizes type 1 basic residues. These two N-recognin functions diverged as separate proteins early in the evolution of plants, before the conquest of the land. We demonstrate that loss of PRT1 function promotes the plant immune system, as mutant prt1-1 plants showed greater apoplastic resistance than WT to infection by the bacterial hemi-biotroph Pseudomonas syringae pv tomato (Pst) DC3000. Quantitative proteomics revealed increased accumulation of proteins associated with specific components of plant defense in the prt1-1 mutant, concomitant with increased accumulation of salicylic acid. The effects of the prt1 mutation were additional to known effects of prt6 in influencing the immune system, in particular, an observed over-accumulation of pipecolic acid (Pip) in the double-mutant prt1-1 prt6-1. These results demonstrate a potential role for PRT1 in controlling aspects of the plant immune system and suggest that PRT1 limits the onset of the defense response via degradation of substrates with type 2 Nt-destabilizing residues

A translational synthetic biology platform for rapid access to gram-scale quantities of novel drug-like molecules

Plants are an excellent source of drug leads. However availability is limited by access to source species, low abundance and recalcitrance to chemical synthesis. Although plant genomics is yielding a wealth of genes for natural product biosynthesis, the translation of this genetic information into small molecules for evaluation as drug leads represents a major bottleneck. For example, the yeast platform for artemisinic acid production is estimated to have taken >150 person years to develop. Here we demonstrate the power of plant transient transfection technology for rapid, scalable biosynthesis and isolation of triterpenes, one of the largest and most structurally diverse families of plant natural products. Using pathway engineering and improved agro-infiltration methodology we are able to generate gram-scale quantities of purified triterpene in just a few weeks. In contrast to heterologous expression in microbes, this system does not depend on re-engineering of the host. We next exploit agro-infection for quick and easy combinatorial biosynthesis without the need for generation of multi-gene constructs, so affording an easy entrée to suites of molecules, some new-to-nature, that are recalcitrant to chemical synthesis. We use this platform to purify a suite of bespoke triterpene analogs and demonstrate differences in anti-proliferative and anti-inflammatory activity in bioassays, providing proof of concept of this system for accessing and evaluating medicinally important bioactives. Together with new genome mining algorithms for plant pathway discovery and advances in plant synthetic biology, this advance provides new routes to synthesize and access previously inaccessible natural products and analogs and has the potential to reinvigorate drug discovery pipelines