Adhesion and cohesion properties of diamond-like-carbon coatings deposited on biomaterials by saddle field neutral fast atom beam source: measurement and modelling

Diamond-like-carbon (DLC) has been shown to be strategically important in respect to biomedical applications due to its biocompatibility. Despite decades of work on film deposition there is an insufficient understanding in respect of the film’s adhesion characteristics, particularly on biomaterial substrates. The central aim of this study is two pronged. A programme of work has been undertaken to set-up, study, understand and optimise the production technique for DLC deposition, while on the other hand diamond like carbon films have been characterised to investigate the strength of adhesion and cohesive strength with particular reference to biomedical applications. DLC films have been deposited on to substrates of 316L stainless steel, cobalt chrome (CoCr) and Ti6AI4V alloy using a saddle field neutral beam deposition system (Microvac 1200DB, Ion Tech Ltd) with acetylene and acetyleneargon mixture as the process gas. It is noted that numerous parameters influence coating adhesion including the stress in the film, contamination and chemical bonding between the film and the substrate, and the physical properties and roughness of the substrate. Discharge current vs. discharge voltage characteristics were investigated with different pressure and process gas. Uv absorption spectra were used to measure the photon energy and optical band gap of the films. The optical band gap was found in the range of -0.85 and 0.85 -0.97 eV for lower and higher deposition current respectively. The adhesion of the films has been measured as a function of the duration of in-situ etching by a neutral argon beam and also as a function of source current, system pressure and process gas (pure C2H2 and C2H2+Ar gas mixture). The studies were performed on DLC films with thickness -0 .4 |im. The adhesion of the film was measured using pull-off and Rockwell C tests whereas four point bend (FPB) test was used to measure the cohesive strength of the films. Argon pre etching for 15 minutes is recommended to guarantee an optimal adhesion. The etching process also influenced the film structure in terms of the sp3/sp2 ratio and stress. It was also found that this optimisation of the adhesion is correlated with a change in the structure and thickness of the native oxide layer on the steel surface of the substrates. Substrate surface temperature during etching and deposition also influenced film structure and adhesion. Correlation between the residual stress and the adhesion of the films has also been established which helped to identify optimum process parameters for substrate-film adhesion properties. No significant change with deposition pressure has been observed but high anode currents may lead to higher sp3 content. The adhesion strength has been found to be inversely proportional to residual stress and to increase at low deposition pressures. At source anode current of 0.6A, the adhesion is a monotonic function of pressure in the range examined where as with 1.0A source current the behaviour is more complex. The relationship between the stress and the sp3 content of the films measured by analysis of Raman signature has also been investigated. The experimental work of FPB has been used to support and develop a numerical (Finite Element) model for the determination and prediction of the film's cohesive strength. The model takes into account the film hardness, Young’s modulus and thickness and has been shown to be capable of predicting the film’s cohesive strength when combined with a theoretical formulation for brittle fracture. It has been observed that maximum stress developed at the outer surface of film during the bend test, which influenced the initiation of cracks at the outer surface of the film and their propagation through the film-substrate interface. This result has only been valid for films with higher Young's modulus compared with the substrate

A Study on Street Hawkers and Their Willing Towards Continuation of Hawking Business in Bangladesh: A Statistical Analysis

This study is an attempt to examine the association of various socio-demographic characteristics on the willing concerning continuation of hawking business for the respondents of Chattogram metropolitan area in Bangladesh. The association of the selected variables with the willing concerning continuation of hawking business were examined using bivariate and logistic regression analyses. The result shows that the respondents who are male, married, come from the rural areas, secondary and less than secondary educated are more involved in street hawking than those who are female, unmarried, urban areas residents, higher secondary and above educated. Again, logistic regression analysis for the willing regarding continuation of hawking business shows that sex, marital status, educational qualification, age, monthly income, rural urban migration, savings’ ability, fathers’ survival status are highly significantly associated with willing towards continuation of respondents’ business.Street hawke

Efficient Finite-difference Methods for Sensitivity Analysis of Stiff Stochastic Discrete Models of Biochemical Systems

In the study of Systems Biology it is necessary to simulate cellular processes and chemical reactions that comprise biochemical systems. This is achieved through a range of mathematical modeling approaches. Standard methods use deterministic differential equations, but because many biological processes are inherently probabilistic, stochastic models must be used to capture the random fluctuations observed in these systems. The presence of noise in a system can be a significant factor in determining its behavior. The Chemical Master Equation is a valuable stochastic model of biochemical kinetics. Models based on this formalism rely on physically motivated parameters, but often these parameters are not well constrained by experiments. One important tool in the study of biochemical systems is sensitivity analysis, which aims to quantify the dependence of a system's dynamics on model parameters. Several approaches to sensitivity analysis of these models have been developed. We proposed novel methods for estimating sensitivities of discrete stochastic models of biochemical reaction systems. We used finite-difference approximations and adaptive tau-leaping strategies to estimate the sensitivities for stiff stochastic biochemical kinetics models, resulting in significant speed-up in comparison with previously published approaches for a similar accuracy. We also developed an approach for estimating sensitivity coefficients involving adaptive implicit tau-leaping strategies. We provide a comparison of these methodologies in order to identify which approach is most efficient depending of the features of the model. These results can facilitate efficient sensitivity analysis, which can serve as a foundation for the formulation, characterization, verification and reduction of models as well as further applications to identifiability analysis

Overheating and energy use in urban office buildings in a warming climate

Buildings are responsible for one‐third of the UK's greenhouse gas (GHG) emissions. The move to reduce emissions has resulted in recent stringent building regulations primarily aimed at reducing heating and associated energy use, often by improving the building fabric's airtightness. However, internal gains dominated, highly–insulated and airtight non‐domestic buildings will likely overheat in the projected warming climate, requiring energy‐intensive cooling, thus diminishing the effectiveness of heating efficiency focused regulations. This research investigated the effects of the warming climate on overheating and energy use and resulting emissions in representative urban office spaces in London in the present‐day and projected future climates using hourly dynamic thermal simulations. Findings suggest that airtight and highly–insulated office buildings in the temperate UK will overheat in the 2050s. Heating demand reduces by at least 36% in the 2050s but electricity consumption and summertime space conditioning will increase by at least 13% and 55% respectively when hybrid cooling is adopted to ameliorate overheating. Despite the increase, a mixed‐mode ventilation strategy is one of the ways of achieving overall energy efficiency while meeting benchmark overheating and emissions targets. Current heating‐focused legislation needs to be re‐evaluated to account for the effects of the warming climate and overheating risks

Adaptive Time-Stepping Using Control Theory for the Chemical Langevin Equation

Stochastic modeling of biochemical systems has been the subject of intense research in recent years due to the large number of important applications of these systems. A critical stochastic model of well-stirred biochemical systems in the regime of relatively large molecular numbers, far from the thermodynamic limit, is the chemical Langevin equation. This model is represented as a system of stochastic differential equations, with multiplicative and noncommutative noise. Often biochemical systems in applications evolve on multiple time-scales; examples include slow transcription and fast dimerization reactions. The existence of multiple time-scales leads to mathematical stiffness, which is a major challenge for the numerical simulation. Consequently, there is a demand for efficient and accurate numerical methods to approximate the solution of these models. In this paper, we design an adaptive time-stepping method, based on control theory, for the numerical solution of the chemical Langevin equation. The underlying approximation method is the Milstein scheme. The adaptive strategy is tested on several models of interest and is shown to have improved efficiency and accuracy compared with the existing variable and constant-step methods

Analysis of Heat Transfer in Channel Flow Subject to Sine-Bump Heating

AbstractConvection in a channel subject to a distributed sinusoidal bump like heating applied at the lower wall has been studied. It is found that small wave number heating provides large plumes whereas large wave number heating provides a uniform temperature distribution at the upper part of the channel. Heat transfer is more efficient at low Reynolds number with small wave number heating

EFFECT OF SCOURING AND BLEACHING TREATMENT ON KNITTED COTTON FABRICS FOR ECONOMIC STUDY

Cotton is the leading fibre in Textile Industry. Cotton is still the "King" of fibers because most of the world's apparel is made of Cotton. Apart from its fairly good strength, it is considered to provide comfort due to good moisture absorption and wicking properties. It is estimated that approx. 20 million tons of Cotton is processed worldwide yearly. Unlike man made cellulosic fibers such as Rayon and Lyocell, Cotton must be properly prepared for Dyeing, printing and finishing. To prepare the cotton fabric ready for Dyeing, printing and finishing scouring & bleaching is the fundamental step. Scouring of cotton textiles is an essential treatment in textile wet processing in order to obtain a sufficiently hydrophilic fabric. During scouring, waxes and other hydrophobic materials are removed from the cotton fibers. cotton fibres are off-white in color due to having colour bodies with it and the process of destruction these colour bodies from fibres is known as bleaching. The problems involved in normal scouring & bleaching using H2O2 is requirement of higher amount of alkali that will result higher cost in Effluent Treatment Plant to remove the alkalinity, use of wetting agent, sequestering agent, detergent & stabilizer and also require acetic acid to neutral the fabric. The aim of our work is to reduce the amount of alkali that is used in scouring , no use of acetic acid after scouring for neutralization and use of single chemical in place of that is cost effective. To fulfill our aim we use Imerol Blue Liquid in place of wetting agent, sequestering agent, detergent & stabilizer that is supplied by Clairiant and compare the Imerol Blue process with classical scouring & bleaching process using stabilizer

EFFECT OF SCOURING AND BLEACHING TREATMENT ON KNITTED COTTON FABRICS FOR ECONOMIC STUDY

Cotton is the leading fibre in Textile Industry. Cotton is still the "King" of fibers because most of the world's apparel is made of Cotton. Apart from its fairly good strength, it is considered to provide comfort due to good moisture absorption and wicking properties. It is estimated that approx. 20 million tons of Cotton is processed worldwide yearly. Unlike man made cellulosic fibers such as Rayon and Lyocell, Cotton must be properly prepared for Dyeing, printing and finishing. To prepare the cotton fabric ready for Dyeing, printing and finishing scouring & bleaching is the fundamental step. Scouring of cotton textiles is an essential treatment in textile wet processing in order to obtain a sufficiently hydrophilic fabric. During scouring, waxes and other hydrophobic materials are removed from the cotton fibers. cotton fibres are off-white in color due to having colour bodies with it and the process of destruction these colour bodies from fibres is known as bleaching. The problems involved in normal scouring & bleaching using H2O2 is requirement of higher amount of alkali that will result higher cost in Effluent Treatment Plant to remove the alkalinity, use of wetting agent, sequestering agent, detergent & stabilizer and also require acetic acid to neutral the fabric. The aim of our work is to reduce the amount of alkali that is used in scouring , no use of acetic acid after scouring for neutralization and use of single chemical in place of that is cost effective. To fulfill our aim we use Imerol Blue Liquid in place of wetting agent, sequestering agent, detergent & stabilizer that is supplied by Clairiant and compare the Imerol Blue process with classical scouring & bleaching process using stabilizer

Effect of genotype on proximate composition and biological yield of maize (Zea mays L.)

An experiment was conducted to study the proximate composition of five released maize varieties (Zea mays L.) of Bangladesh Agricultural Research Institute (BARI), which was popularly growing in Bangladesh namely BHM-5, BHM-8, BHM-13, BHM-15, and Barnali. There was none a single variety performed best in all nutrient parameters. Among these maize varieties, the highest grain weight of 100 seeds, and yield was found in BHM-15 (32.84g and 12.6 ton/ha). In the case of proximate analysis, the highest protein, ash, and fat content was recorded from BHM-15 (13.11%, 2.33%, and 5.44%), the highest carbohydrate content was recorded from BHM-13 (82.40%), and the highest amount of fiber was recorded from BHM-5 (2.07%). On the other hand, the lowest amount of carbohydrate and protein was recorded from BHM-15 (77.67%) and BHM-8 (10.96%), respectively. BHM-13 contained the lowest amount of fiber (1.24%) and fat (4.27%). Barnali and BHM-15 showed better performance for most of the minerals. The findings concluded that the different genotypes of maize differ substantially in their chemical and mineral compositions

EFFECT OF FABRIC STRUCTURE ON RIB FABRIC PROPERTIES

In this work,1×1Rib,1×1Skeleton rib, 2×2English rib, 2×2Swiss rib, 6×3Derby rib were produced with 20/2 Ne and 32/2 Ne combed ring yarn and V-bed knitting machine of 14 Gauge. In addition, Wales per 3cm, Course per 3cm, Stitch density, Stitch length, Tightness factor, GSM, Dimensional Stability of fabric were tested. According to test result, Wales per 3cm, Stitch density, Cover factor, GSM of 1×1Rib were higher than the 1×1Skeleton rib;Wales per 3cm, Course per 3cm, Stitch density, Stitch length, Cover factor, Shrinkage%, extension% of 2×2English rib were higher than the 1×1Rib; Wales per 3cm, Stitch density, GSM, Shrinkage%, extension% of 2×2Swiss rib were higher than the 1×1Rib; in 6×3Derby Rib values of the properties were higher than other structure; shrinkage and extension percentage increase with the increase of needle drop in knitting