Cellulose, Chitosan, and Keratin Composite Materials. Controlled Drug Release

A method was developed in which cellulose (CEL) and/or chitosan (CS) were added to keratin (KER) to enable [CEL/CS+KER] composites to have better mechanical strength and wider utilization. Butylmethylimmidazolium chloride ([BMIm+Cl–]), an ionic liquid, was used as the sole solvent, and because the [BMIm+Cl–] used was recovered, the method is green and recyclable. Fourier transform infrared spectroscopy results confirm that KER, CS, and CEL remain chemically intact in the composites. Tensile strength results expectedly show that adding CEL or CS into KER substantially increases the mechanical strength of the composites. We found that CEL, CS, and KER can encapsulate drugs such as ciprofloxacin (CPX) and then release the drug either as a single or as two- or three-component composites. Interestingly, release rates of CPX by CEL and CS either as a single or as [CEL+CS] composite are faster and independent of concentration of CS and CEL. Conversely, the release rate by KER is much slower, and when incorporated into CEL, CS, or CEL+CS, it substantially slows the rate as well. Furthermore, the reducing rate was found to correlate with the concentration of KER in the composites. KER, a protein, is known to have secondary structure, whereas CEL and CS exist only in random form. This makes KER structurally denser than CEL and CS; hence, KER releases the drug slower than CEL and CS. The results clearly indicate that drug release can be controlled and adjusted at any rate by judiciously selecting the concentration of KER in the composites. Furthermore, the fact that the [CEL+CS+KER] composite has combined properties of its components, namely, superior mechanical strength (CEL), hemostasis and bactericide (CS), and controlled drug release (KER), indicates that this novel composite can be used in ways which hitherto were not possible, e.g., as a high-performance bandage to treat chronic and ulcerous wounds

Determination of land policy in Zimbabwe

A paper presented by a Minister of Lands & Agriculture on Zimbabwe's land policy during the aftermath of independence.This paper which focuses on the determinants of land policy will consist of two sections. The first section will attempt to desribe the background or context in which Zimbabwe’s land policy has evolved since independence in 1980. It will try to show that the formulation of a land policy1 has been more of a process rather than a political event. The ensuing policy has been a result of the interplay of several factors, such as the inherited natural resources, opposed political class interests and economic imperatives. It will be shown that, in trying to meet its political and economic objectives, the Government has had to grapple with several existing constraints, some of which were inherited as part of the previous socio-economic system, while others such as shortage of suitable agricultural land, climate and population were more or less naturally given. The evolving policy can, therefore, be regarded as a pragmatic and reconciliatory attempt to resolve contradictions and conflict in a transition of continuing social and economic struggle. The second section is a brief outline of the actual policy as it has evolved so far in Zimbabwe

Supramolecular Biopolymeric Composite Materials: Green Synthesis, Characterization and Applications

Macrocycles, such as crown ethers (CRs) and resorcinarenes (RESs), exhibit selective complexation of heavy metal ions and organic pollutants respectively. Consequently, they have been investigated for their suitability in adsorbing these aqueous pollutants. However, they are difficult to handle and recycle for reuse because, by themselves, they can only be fabricated in powder form. To alleviate this challenge, we developed a method to encapsulate these macrocycles into film-forming polysaccharides--cellulose (CEL) and chitosan (CS). This was achieved by using a green and recyclable solvent, an ionic liquid, to dissolve both macrocycles and polysaccharides and regenerate corresponding composites in water. Resultant composites were characterized by FTIR, UV-Visible, X-ray powder diffraction and scanning electron microscopy. These polysaccharides are attractive because they are naturally abundant, biodegradable and biocompatible. The composites retained desirable properties of their individual constituents, namely superior mechanical strength (from CEL), excellent adsorption capability for cadmium and zinc ions (from CRs and CS) and organic solutes (from RESs and CS). Specifically, increasing the concentration of CEL from 50% to 90% in [CEL+CR] resulted in almost 2X increase in tensile strength. Adding 40% benzo 15-crown-5 ether (B15C5) to CS led to a 4X enhancement in the amount of cadmium ions adsorbed by [CS+B15C5]. Interestingly, RES-based composites exhibited selectivity amongst dinitrobenzene (DNB) isomers. For example, one g of [CEL+RES] adsorbed more 1,2-DNB (5.37±0.05 mol L-1) than 1,3-DNB (4.52±0.03 mol L-1) and 1,4-DNB (2.74±0.04 mol L-1). These results help to extend the potential applications of supramolecular composites in water remediation. We also successfully synthesized hydroxyapatite (HAp) in situ by alternately soaking [CEL+CS] composite films in calcium and phosphate salt solutions. These composites will be expected to be osteoconductive (due to HAp), thereby necessitating their use in bone tissue engineering. In another related study, we developed a simple, one step process to encapsulate an antibiotic, ciprofloxacin (CPX) in composites containing various proportional concentrations of CEL, CS, and keratin (KER). KER was found to slow down the release of CPX from the composites. These results clearly indicate that the release of CPX can be controlled by judicious adjustment of the concentrations of KER in the composites

Cellulose-Chitosan-Keratin Composite Materials: Synthesis, Immunological and Antibacterial Properties

Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The method is recyclable because majority (\u3e88%) of [BMIm+Cl-], an ionic liquid (IL), used as the sole solvent, was recovered for reuse. Experimentally, it was confirmed that unique properties of each component remain intact in the composites, namely bactericide (from KER and CS) and anti-inflammatory property (from KER). Specifically, the composites were examined for their anti-inflammatory influence on macrophages. The cells were imaged and immunophenotyped to determine the quantity using the macrophage marker CD11b. The 75:25 [KER+CS] composite was found to have the least amount of CD11b macrophages compared to other composites. Bactericidal assays indicated that all composites, except the 25:75 [KER+CS], substantially reduce the growth of organisms such as vancomycin resistant Enterococcus (VRE) and Eschericia coli. The results clearly indicate that the composites possess all properties needed for effective use as a wound dressin

Effects of Digital Transformation Initiatives on IT Performance: Evidence from US State Governments

For governments around the world, digital transformation (DT) initiatives have been a cornerstone in a plan to gain strategic competitiveness in the global market. However, DT initiatives have a high failure rate, and prior studies have suggested that DT initiatives are disruptive and evolutionary by nature, requiring a longitudinal examination of DT initiatives to fully understand how their effects unfolded over time. In this exploratory study, we use an event study analysis to unveil the effects of DT initiatives on IT performance over a decade in 25 US state governments. The results suggest that DT initiatives only have a significant and positive effect on radical transformation of IT performance, but not for incremental transformation of IT performance. The findings support a revolutionary perspective on effects of DT initiatives and suggest that for public organization, radical transformation is worth considering despite of the risks

Retropharyngeal abscess coinfected with and after rhinoviral infection in a 1-month-old infant

A retropharyngeal abscess is a rare disease entity in young infants but can develop after nasopharyngeal viral infection. Group B Streptococcus and Staphylococcus aureus are the most common pathogens in young infants, however, Mycobacterium tuberculosis is very rare. We report the case of retropharyngeal abscess and coinfection with S. aureus and M. tuberculosis in a very young infant presenting with respiratory symptoms due to upper airway obstruction. Usually tuberculous retropharyngeal abscesses are caused by the direct invasion of the bacteria from the spine via anterior longitudinal ligament of the spine. However, in this case, no associated spinal disease was observed

Perilaku konsumen

xiv.412 hlm. : ilus. ; 25 cm

Characterisation of wet and dry summer seasons and their spatial modes of variability over Zimbabwe

In the face of a changing climate, knowledge on the characteristics of wet and dry summers and their modes of variability becomes of great importance to Zimbabwe so that proper policies and planning can be implemented to maximise the positive impacts of climate change while minimising its negative impacts. We used time series of rainfall anomaly index, empirical orthogonal function analysis and composite analysis to determine the temporal and spatial characteristics of summer rainfall in Zimbabwe between 1980 and 2013. Results indicate that there is a possible shortening in the length of the summer season, running from November to March. There were 14 anomalous summer seasons (7 dry and 7 wet) during the 33 summer seasons in the study period. Three dominant modes of variability were identified for Zimbabwean summer rainfall for the period under study: (1) an east–west gradient accounting for about 63% of the total variability, (2) a northeast–southwest oscillation accounting for about 18% of the variability and (3) a northwest–southeast oscillation accounting for about 6% of the variability. From the results, the high frequency of occurrence of above or below normal summer seasons is a major concern due to their far-reaching effects on Zimbabwe’s economic and social well-being. Circulation mechanisms influencing such characteristics should be studied and possible predictors identified for the development of short-term climate prediction models. If the forecasting of extreme events is reliable and done with sufficient lead time, the information can be utilised to mitigate the adverse effects while maximising their positive impacts. The findings of this study are important for informing economic activities in sectors such as farming, energy, mining, and tourism, which rely heavily on summer rainfall. However further studies must be carried out to identify the atmospheric and oceanic circulations which lead to such rainfall variability. Such information is critical in the development of reliable rainfall forecasts and early warning systems. Significance: Rainfall affects a variety of socio-economic activities, especially in Zimbabwe where rain-fed agriculture is a major contributor to the gross domestic product. Therefore, understanding spatial and temporal variations in rainfall enhances the formulation of strategies and decision-making to ensure sustainable development in the country

Characterisation of wet and dry summer seasons and their spatial modes of variability over Zimbabwe

In the face of a changing climate, knowledge on the characteristics of wet and dry summers and their modes of variability becomes of great importance to Zimbabwe so that proper policies and planning can be implemented to maximise the positive impacts of climate change while minimising its negative impacts. We used time series of rainfall anomaly index, empirical orthogonal function analysis and composite analysis to determine the temporal and spatial characteristics of summer rainfall in Zimbabwe between 1980 and 2013. Results indicate that there is a possible shortening in the length of the summer season, running from November to March. There were 14 anomalous summer seasons (7 dry and 7 wet) during the 33 summer seasons in the study period. Three dominant modes of variability were identified for Zimbabwean summer rainfall for the period under study: (1) an east–west gradient accounting for about 63% of the total variability, (2) a northeast–southwest oscillation accounting for about 18% of the variability and (3) a northwest–southeast oscillation accounting for about 6% of the variability. From the results, the high frequency of occurrence of above or below normal summer seasons is a major concern due to their far-reaching effects on Zimbabwe’s economic and social well-being. Circulation mechanisms influencing such characteristics should be studied and possible predictors identified for the development of short-term climate prediction models. If the forecasting of extreme events is reliable and done with sufficient lead time, the information can be utilised to mitigate the adverse effects while maximising their positive impacts. The findings of this study are important for informing economic activities in sectors such as farming, energy, mining, and tourism, which rely heavily on summer rainfall. However further studies must be carried out to identify the atmospheric and oceanic circulations which lead to such rainfall variability. Such information is critical in the development of reliable rainfall forecasts and early warning systems. Significance: Rainfall affects a variety of socio-economic activities, especially in Zimbabwe where rain-fed agriculture is a major contributor to the gross domestic product. Therefore, understanding spatial and temporal variations in rainfall enhances the formulation of strategies and decision-making to ensure sustainable development in the country

Circulation mechanisms responsible for wet or dry summers over Zimbabwe

Climate change has resulted in increased rainfall variability over many parts of the world including Southern Africa. As such, droughts and floods have become a frequent phenomenon in Zimbabwe and have potential to intensify socio-economic stressors. This study examined possible forcing factors behind the occurrence of extreme summer events using re-analysis datasets. Composite analysis and correlation methods were used to identify circulation mechanisms and their strength in determining rainfall patterns in Zimbabwe. Predominantly northerly airflow in the lower troposphere was found to favor wet while southerly airflow favors dry seasons. Negative geopotential anomalies (minimum of −20 hPa) to the west of Zimbabwe in the middle levels characterize wet summers which swing to positive anomalies (+24 hPa) during dry summers. Positive SST anomalies (maximum of 0.4) exist to the southwest of Madagascar extending to the western shore on the Angola-Namibian border characterize wet summers which swing to negative anomalies (−0.2 ºC) during dry summer seasons. SST anomalies in the South western Indian and South eastern Atlantic oceans are crucial in the determination of the strength of both the South Indian and Atlantic Ocean high pressure systems which in turn control moisture advection and convergence into Zimbabwe during the summer period. If these SST anomalies at lag times of about 3 months can be used to predict the incoming summer circulation patterns then the accuracy of summer seasonal outlook forecasts can be improved. Studying the mechanisms behind drought and flood occurrence is important to the country which is in the process of downscaling regional prediction products to improve the accuracy of seasonal forecasts. These findings are useful in crafting relevant measures to maximize the benefits and minimize the risks of extreme rainfall events