Introducing COZIGAM: An R Package for Unconstrained and Constrained Zero-Inflated Generalized Additive Model Analysis

Zero-inflation problem is very common in ecological studies as well as other areas. Nonparametric regression with zero-inflated data may be studied via the zero-inflated generalized additive model (ZIGAM), which assumes that the zero-inflated responses come from a probabilistic mixture of zero and a regular component whose distribution belongs to the 1-parameter exponential family. With the further assumption that the probability of non-zero-inflation is some monotonic function of the mean of the regular component, we propose the constrained zero-inflated generalized additive model (COZIGAM) for analyzingzero-inflated data. When the hypothesized constraint obtains, the new approach provides a unified framework for modeling zero-inflated data, which is more parsimonious and efficient than the unconstrained ZIGAM. We have developed an R package COZIGAM which contains functions that implement an iterative algorithm for fitting ZIGAMs and COZIGAMs to zero-inflated data basedon the penalized likelihood approach. Other functions included in the packageare useful for model prediction and model selection. We demonstrate the use ofthe COZIGAM package via some simulation studies and a real application.

Introducing COZIGAM: An R Package for Unconstrained and Constrained Zero-Inflated Generalized Additive Model Analysis

Zero-inflation problem is very common in ecological studies as well as other areas. Nonparametric regression with zero-inflated data may be studied via the zero-inflated generalized additive model (ZIGAM), which assumes that the zero-inflated responses come from a probabilistic mixture of zero and a regular component whose distribution belongs to the 1-parameter exponential family. With the further assumption that the probability of non-zero-inflation is some monotonic function of the mean of the regular component, we propose the constrained zero-inflated generalized additive model (COZIGAM) for analyzingzero-inflated data. When the hypothesized constraint obtains, the new approach provides a unified framework for modeling zero-inflated data, which is more parsimonious and efficient than the unconstrained ZIGAM. We have developed an R package COZIGAM which contains functions that implement an iterative algorithm for fitting ZIGAMs and COZIGAMs to zero-inflated data basedon the penalized likelihood approach. Other functions included in the packageare useful for model prediction and model selection. We demonstrate the use ofthe COZIGAM package via some simulation studies and a real application

Composition effects on macroscopic solidification segregation of superalloys

This research work investigates primarily the composition effects on solidification macrosegregation, i.e. freckles, in superalloys. First, the freckling mechanism of superalloys is developed using the physical simulation of freckle formation in specially designed model alloys. It is found that freckles originate from dendrite irregularities at the solidification front. The freckle channels flow downward in Nb-containing alloys and upward in T-containing alloy under horizontal solidification conditions. The horizontal solidification correctly simulates the horizontal component in remelt ingot where freckling potential is the highest. Based on the result, key control parameters for freckling are identified.;Thermodynamic simulation approach is employed to study the solidification behavior of superalloys. The theoretical prediction yields relative good agreement with experimental observations of freezing range, solidification sequence, and the occurrence of secondary phases. Solidification diagram of Ni-Cr-Fe-Nb alloy system is developed using the simulation approach to predict the phase relationship during solidification. The simulation results can be used as inputs for freckling criteria.;The sensitivity of freckling criteria relies on the accurate acquisition of the attributes that are critical to the key control parameters. These attributes include interdendritic liquid composition, temperature and fraction of solid. Two techniques are developed in the present study to obtain their correlation. From here, liquid composition and fraction solid at any temperature in the mushy zone can be obtained.;Composition effects on the key control parameters are investigated in detail. Liquid density during solidification depends on the composition and the temperature of the liquid. A significant temperature effect on density change is found. Regression analysis shows that Nb has more pronounced effect than Ti in reducing the fraction solid. The dendrite arm spacing and the solidification front angle are largely dependent on the processing conditions.;Freckling criterion in remelting of superalloys is developed at the end of this study. A composition related is proposed to account for the alloying effect on freckling tendency. The model correctly predicts the freckling pattern in Ti- and Nb-containing model alloys. It also correctly predicts the freckling tendency of industrial alloys

Floating Architecture: A Solution for the Char People of Bangladesh

The 21st century has been and will be shaped by decisions made in centuries prior. It is our responsibility today to design for tomorrow, recognizing this century’s environmental changes. With the assistance of futurist studies, architects are now equipped with the knowledge to build for a successful future. Sea level rise is one of the expected consequences of today’s drastic environmental changes. Thus, fl oating architecture will play an important role in our future. Bangladesh is one of the countries already experiencing the eff ects of sea level rise. It is one of the world’s most densely populated countries, and the further inundation of its land will only bring more devastation. Within this already poverty-stricken land, a subculture known as the Char people are among the poorest. This group of people resides on the Char lands, dangerous yet highly fertile land that often suff ers the most during natural disasters. The goal of this project is to design a system of living on Char lands to cope with inconsistent water levels by applying ideals held by the Char people. The design will consist of an economic plan, three alternative site plans, and a schematic architectural prototype of a fl oating home. This system of living will be designed in hopes of being implemented in settings needing such applications including the Netherlands and Japan. The work includes initial research conducted in the fi elds of Bangladesh regarding the Char people, sea level rise concerns, and case studies of both modern and historic examples of aquatic architecture. The end product will be a system designed for “Char Abhinava,” located in the Upper Meghna River

Measurement of the effective diffusivity of carbon monoxide in commercial catalytic monolith converters

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Investigation of injection moulding for novel drug delivery systems. An investigation into the use of injection moulding to produce pharmaceutical dosage forms and to understand the relationship between materials, processing conditions and performance, in particular drug release and stability

The feasibility of the injection moulding (IM) was explored for the development of novel drug delivery systems. Controlled release formulations were developed using a substituted cellulose derivative, hydroxypropyl methyl cellulose acetate succinate (HPMCAS) and a graft co-polymer (Soluplus®). BCS class II drugs ibuprofen and the felodipine were selected based on their physicochemical properties. In the present work, a homogenous dispersion of drugs in the polymer matrices was achieved using Hot Melt Extrusion (HME) and extruded pellets obtained were used for the development of the injection moulded systems. Four systems were developed using the IM consisting of ibuprofen-HPMCAS, ibuprofen-Soluplus®, felodipine-PEO-HPMCAS and felodipine-Soluplus®. The ibuprofen acts as a good plasticiser compared to felodipine therefore, felodipine containing IM systems required a plasticiser (PEO) when processed with HPMCAS. The analysis of extruded pellets and injection moulded systems using modulated DSC (MDSC) and Raman spectroscopy confirmed the formation of an amorphous molecular dispersion (i.e solid solution) in the case of all four systems. The phase separation behaviour and the amorphous stability of the systems was studied at various stress conditions. This revealed the “surface crystallisation” behaviour of the ibuprofen-HPMCAS systems. Temperature-composition phase diagram constructed based on the melting point depression and the Flory-Huggins lattice solution theory provided the explanation for the phase separation and crystallisation behaviour of ibuprofen-HPMCAS systems. The advanced characterisation techniques like DMA, 2D XRD and 3D laser microscopy provided the detailed understanding of crystal habits, phase seperation and surface crystallisation. The significant effect of the stress conditions on the rate of shrinkage was observed where, higher shrinkage tendency of a HPMCAS IM system was observed compared to Soluplus® IM systems. The extruded pellets provided the faster drug release compared to the moulded tablets suggests the effect of particle size as well as the densification during IM on the dissolution rate of the dosage form. The nature of the polymer and processing history were the contributing factors for the dissolution of the dosage forms.The thesis is hardbound in two volumes. Volume II starts at Chapter 5, page 135

A longitudinal study of cortical EEG to olfactory stimulation : involving inter- and intra- subjective responses

This thesis forms the largest and most systematic study of the topographical EEG response to odour. The evolutionary history of the olfactory sense is briefly presented and its relevance to humans in the present day is considered. This thesis examines the information processing that occurs in this sensory system. The type of processing that the olfactory system utilises at each anatomical stage is discussed. The character of olfactory information that may reach neocortical levels in humans is considered in the light of the technology available to detect such information. The neurogenesis of the EEG is considered, together with questions concerning its postulated functional significance. The empirical work carried out uses the most advanced methodology for this type of study. The large number of odourants and subjects, combined with the longitudinal element, make this the most ambitious study of this nature undertaken. The issues surrounding the analysis and interpretation of EEG data arc fully discussed and the impact of Chaos theory is considered. Five major analysis techniques were used on the data collected, but largely negative findings arc reported. The reasons for the failure of this experimental paradigm are discussed and improvements arc suggested for future work. The major contribution of this thesis lies in its exploration of the assumptions of the EEG response to odour. The thesis notes the lack of a conceptual framework that has hindered progress in the area of the "odour" EEG. Recent developments in neural network theory and Chaos theory are highlighted as possible alternative approaches to the modelling and understanding of the olfactory system

Beyond globalized visions : problematizing urban theory through spatial explorations of the Pearl River Delta

L'abstract è presente nell'allegato / the abstract is in the attachmen

The role of the envelope cytoplasmic tail in Lentiviral replication

The envelope glycoprotein (Env) of lentiviruses plays an essential role in viral replication. Env is expressed on the plasma membrane of infected cells and is incorporated into budding virions, where it acts as the viral entry protein, binding to the CD4 receptor and coreceptors (CCR5 or CXCR4) on target cells to mediate attachment, fusion and entry of the viral capsid. Functional Env is a heterotrimeric structure composed of the receptor- binding surface subunit (gp120) and the transmembrane subunit (gp41) that contains the fusion peptide, a transmembrane domain and a cytoplasmic tail (CT). The HIV EnvCT is approximately 150 amino acids long, whereas the EnvCT of retroviruses are considerably shorter (approximately 50 amino acids). Conservation of the length of lentiviral EnvCTs suggests the presence of key determinants, many of which remain undefined, that are essential for efficient viral replication and spread. Previous studies have reported that HIV-2 and several SIVs truncate their EnvCT in vitro in order to gain a replicative advantage, although how this provides an advantage is currently unknown. To explore the biology of the EnvCT, HIV-1 and HIV-2 viruses with a truncated EnvCT were produced by site-directed mutagenesis and the requirement of the EnvCT has been explored in the context of viral replication, evasion of antiviral restriction factors and activation of signalling pathways. Data in this thesis show that HIV-1 and HIV-2 viruses have differential requirements for the long EnvCT, in a cell-type dependent manner. Whilst HIV-1 required a long EnvCT for efficient replication and spread in T cells, HIV-2 replication was not dependent on the EnvCT. This difference primarily mapped to differences in Env incorporation into virions, which is known to be a key determinant of infectivity. Notably, EnvCT truncation conferred resistance to two potent virus entry- targeting restriction factors, SERINC5 and IFITM. Further, results suggest that truncation of the EnvCT alters the susceptibility of virions to inhibition by neutralising antibodies. Together, this work provides new mechanistic insight into the role of the EnvCT in evasion of innate antiviral defences, revealing how viruses balance competing factors to adapt to their niche in the presence of differing selection pressures