Development of lab-on-a-chip technology for the analysis of ions in natural waters

There is a demand for portable in-situ measurement systems for measuring ions in environmental water samples. Commercially available flow injection analysis systems are not easy to install, have high power requirements, and use large volumes of reagents. Miniaturising the measurements is promising, and quite successful microfluidic automated systems have been developed. These systems, however, tend to only measure one species at a time, and what is really required is a portable system that simultaneously measures several anions and cations. The aim of this thesis was, therefore, to develop a novel analytical device that has the ability to measure several nutrient levels in water samples in-situ, at high-frequency measurements, by miniaturising the sample preparation and measurement. The system involved: ion extraction, ion separation, and detection with a C4D contactless conductivity detector. This analytical system to be developed needs to be able to replace the current, typical system being used in the field.To avoid the effects of the sample matrix on the separation process, the extraction of ions from the sample before separation, was investigated. Different ion extraction approaches were explored, including ion extraction through a potassium silicate monolith and electrodialysis. The potassium silicate monolith was used to extract ions from water samples; this worked as a barrier to prevent unwanted materials present in the river water from entering the measurement system. The presence of these materials would influence the separation process.Extraction techniques using the potassium silicate monolith were investigated, using both glass chips and glass capillaries. To prevent the electroosmotic flow (EOF) caused by the negative charge on the surface of the glass and the monolith, the surface was silanised. Three different silanisation methods were investigated: trichloro perfluorooctyl silane (FDTS), a commercial coating, and an end-capping procedure. The extraction of the ions was achieved with all three of the silanisation methods but greater reproducibility was needed.Electrodialysis (ED) was examined to see if it could provide a more reproducible sample introduction method. The advantage of this method was that it could be effectively combined with electrophoresis (CE) for rapid pre-concentration and the subsequent determination of inorganic ions in the river water. Different ED techniques were investigated for extracting the inorganic ions. This involved exploring different membranes including polytetrafluoroethylene (PTFE), Parafilm, cellulose acetate, and ion-exchange membranes. Different ED systems were evaluated, including a commercial flow design and microfluidic chips manufactured from cyclic olefin copolymers (COC), with both single and multiple membranes.The cellulose acetate membrane provided good results for cation extraction from a real river water sample. Sodium, calcium, potassium and magnesium were extracted at 85%, 45%, 23%, and 10%, respectively. The anion-exchange (AEX) membrane in the ED system was successful and demonstrated good results. Cation extraction with a single cation-exchange (CEX) membrane also provided good results.Several ED microfluidic chips were designed to improve the extraction, using the ion-exchange membranes. In this system, a gold electrode was used and positive results were obtained for both anions and cations, and the anion extraction was demonstrated using a real river water sample. Five anions were extracted: respectively comprised sulphate 65%, phosphate with 31%, 82% for chloride, nitrite with 10% and nitrate with 6%.Initial work on the separation of the inorganic ions concentrated on a monolithic column, as reported in the literature. For the separation of anions, two different anion exchangers were investigated, lysine and DDAB. The monoliths were prepared in-house and were then coated with the anion exchanger. A commercial C18 monolith was used to compare the results obtained from the homemade monolithic column. Problems were encountered with the coated monoliths, especially in terms of high back pressures, and it was decided that capillary electrophoresis (CE) would provide a better separation solution and would more easily integrate with the ED ion extraction.A proposed design of an integrated system was presented including the pumps that are required, the reagents, and the energy use. The proposed integrated system only required one buffer for all processes in the system, which reduces the environmental impact of the chemical reagents. The suitability of the buffer (MES/His) was extensively investigated, and the amount needed for a month was also calculated to be less than 3 L, which is ideal for the system portability. It was also calculated that the required power could be provided by a battery, although the inclusion of solar panels would be advantageous.The proposed integrated system meets most of the requirements of the project, and promising results were obtained. Further optimisation of the design will focus on increasing the robustness of field applications

The relationship between nurse managers' leadership style and patients' perception of the quality of the care provided by nurses: Cross sectional survey

Background:  In healthcare systems, human resources play a strategic role that has a significant impact on the whole caring process. When the wellbeing of professionals is low their performance decreases, counterproductive work behaviours may became more likely, and as a result the quality of care is compromised. Studies have shown that leadership style is particularly relevant in relation to the quality of work environments in healthcare organizations. Objective:  The main purpose of this study is to test a model that investigates the relationships between nurse managers’ leadership style and patients’ perception of the quality of the care provided by the nurses, through the mediation of the quality of the working environment (in terms of burnout, interpersonal strain and counterproductive work behaviour). Design:  A multi-centre cross-sectional study was conducted. Setting:  The study was conducted in five hospitals located two in the north, two in the centre and one in the south of Italy. Participants:  Participants were 479 registered nurses (working as staff nurses, while head nurses and nurse managers were excluded) and 829 patients aged 18 years or older, able to read and write Italian and hospitalized for at least 3 days. Severely ill or mentally disabled patients who were not able to fill in the questionnaire were excluded. Methods:  The data were collected through two different questionnaires, one for the nurses and one for the patients. A multilevel analysis was conducted to examine the hypothesized model. Results:  Results confirmed the hypothesis that, when nurses were satisfied with leadership, they felt less burned-out and strained in interpersonal relationships, they engaged less in misbehaviour, and, in turn, patients were more satisfied with the quality of the care provided by the nurses. Conclusions:  The results of this study showed that the characteristics of the organizational context, the leadership, and the behaviours of nurses, influenced patients’ perceptions of nurses’ care. Therefore, managers of healthcare services should take these results into account seriously in order to improve the quality of care provided to patients

Rainfall Characteristics of Johor Bahru and Kota Bharu, Malaysia

Characteristics of rainfall was influenced by climate variability. Occurrence of extreme events due to climate variability may lead to flash floods or monsoonal flooding. This paper discusses on characteristics and trend of monthly and annual rainfall at Johor Bahru and Kota Bharu. Daily rainfall observations at the stations that spans over 13 years, i.e. from year 2004 to year 2016 was used. Minimum and maximum total annual rainfall recorded at Johor Bahru and Kota Bharu are 1708.0 mm and 3455.5 mm, and 1036.3 mm and 3037.0 mm, respectively. Mann-Kendall test has showed that the monthly and annual rainfall trends at both stations are insignificant. Longer period of rainfall observations should be considered to obtain more significant trends. The longest dry and wet days within a month observed over the 13-year rainfall are 26 days and 17 days at Johor Bahru, and 29 days and 25 days at Kota Bharu. Both Johor Bahru and Kota Bharu receives higher rain during the beginning of north-east monsoon, i.e. in November and December

Bending and Buckling of FG-GRNC Laminated Plates via Quasi-3D Nonlocal Strain Gradient Theory

To improve the structural stiffness, strength and reduce the weight of nanoplate structure, functionally graded (FG) graphene-reinforced nanocomposite (GRNC) laminated plates are exploited in this paper. The bending and buckling behaviors of FG-GRNC laminated nanoplates are investigated by using novel quasi-3D hyperbolic higher order shear deformation plate theory in conjunction with modified continuum nonlocal strain gradient theory, which considered both length and material scale parameters. The modified model of Halpin–Tsai is employed to calculate the effective Young’s modulus of the GRNC plate along the thickness direction, and Poisson’s ratio and mass density are computed by using the rule of mixture. An analytical approach of the Galerkin method is developed to solve governing equilibrium equations of the GRNC nanoplate and obtain closed-form solutions for bending deflection, stress distributions and critical buckling loads. A detailed parametric analysis is carried out to highlight influences of length scale parameter (nonlocal), material scale parameter (gradient), distribution pattern, the GPL weight fraction, thickness stretching, geometry and size of GPLs, geometry of the plate and the total number of layers on the stresses, deformation and critical buckling loads. Some details are studied exclusively for the first time, such as stresses and nonlocality effect

Bending and Buckling of FG-GRNC Laminated Plates via Quasi-3D Nonlocal Strain Gradient Theory

To improve the structural stiffness, strength and reduce the weight of nanoplate structure, functionally graded (FG) graphene-reinforced nanocomposite (GRNC) laminated plates are exploited in this paper. The bending and buckling behaviors of FG-GRNC laminated nanoplates are investigated by using novel quasi-3D hyperbolic higher order shear deformation plate theory in conjunction with modified continuum nonlocal strain gradient theory, which considered both length and material scale parameters. The modified model of Halpin–Tsai is employed to calculate the effective Young’s modulus of the GRNC plate along the thickness direction, and Poisson’s ratio and mass density are computed by using the rule of mixture. An analytical approach of the Galerkin method is developed to solve governing equilibrium equations of the GRNC nanoplate and obtain closed-form solutions for bending deflection, stress distributions and critical buckling loads. A detailed parametric analysis is carried out to highlight influences of length scale parameter (nonlocal), material scale parameter (gradient), distribution pattern, the GPL weight fraction, thickness stretching, geometry and size of GPLs, geometry of the plate and the total number of layers on the stresses, deformation and critical buckling loads. Some details are studied exclusively for the first time, such as stresses and nonlocality effect

NDM Production as a Dominant Feature in Carbapenem-Resistant Enterobacteriaceae Isolates from a Tertiary Care Hospital

The worldwide spread and increasing prevalence of carbapenem-resistant Enterobacteriaceae (CRE) is of utmost concern and a problem for public health. This resistance is mainly conferred by carbapenemase production. Such strains are a potential source of outbreaks in healthcare settings and are associated with high rates of morbidity and mortality. In this study, we aimed to determine the dominance of NDM-producing Enterobacteriaceae at a teaching hospital in Karachi. A total of 238 Enterobacteriaceae isolates were collected from patients admitted to Jinnah Postgraduate Medical Centre (Unit 4) in Karachi, Pakistan, a tertiary care hospital. Phenotypic and genotypic methods were used for detection of metallo-β-lactamase. Out of 238 isolates, 52 (21.8%) were CRE and 50 isolates were carbapenemase producers, as determined by the CARBA NP test; two isolates were found negative for carbapenemase production by CARB NP and PCR. Four carbapenemase-producing isolates phenotypically appeared negative for metallo-β-lactamase (MBL). Of the 52 CRE isolates, 46 (88.46%) were blaNDM positive. Most of the NDM producers were Klebsiella pneumoniae, followed by Enterobacter cloacae and Escherichia coli. In all the NDM-positive isolates, the blaNDM gene was found on plasmid. These isolates were found negative for the VIM and IPM MBLs. All the CRE and carbapenem-sensitive isolates were sensitive to colistin. It is concluded that the NDM is the main resistance mechanism against carbapenems and is dominant in this region

Sulfhydryl Functionalized Magnetic Chitosan as an Efficient Adsorbent for High-Performance Removal of Cd(II) from Water: Adsorption Isotherms, Kinetic, and Reusability Studies

In this study, dimercaptosuccinic acid-functionalized magnetic chitosan (Fe3O4@CS@DMSA) was synthesized via in situ coprecipitation process and amidation reaction, aiming to eliminate cadmium (Cd(II)) ions from an aqueous environment. The structure, morphology, and particle size of the Fe3O4@CS@DMSA adsorbent were investigated using FTIR, TEM, EDX, TGA, zeta potential, and XRD techniques, and the obtained results approved the successful synthesis of the Fe3O4@CS@DMSA nanocomposite. The influence of external adsorption conditions such as pH solution, adsorbent mass, initial Cd(II) concentration, temperature, and contact time on the adsorption process was successfully achieved. Accordingly, pH: 7.6, contact time: 210 min, and adsorbent mass:10 mg were found to be the optimal conditions for best removal. The adsorption was analyzed using nonlinear isotherm and kinetic models. The outcomes revealed that the adsorption process obeyed the Langmuir and the pseudo-first-order models. The maximum adsorption capacity of Fe3O4@CS@DMSA toward Cd(II) ion was 314.12 mg/g. The adsorption mechanism of Cd(II) on Fe3O4@CS@DMSA nanocomposite is the electrostatic interaction. The reusability test of Fe3O4@CS@DMSA nanocomposite exhibited that the adsorption efficiency was 72% after the 5th cycle. Finally, this research indicates that the Fe3O4@CS@DMSA exhibited excellent characteristics such as high adsorption capacity, effective adsorption-desorption results, and easy magnetic separation and thus could be an effective adsorbent for removing Cd(II) ions from aqueous solutions

Antifungal Activity of Soft Tissue Extract from the Garden Snail Helix aspersa (Gastropoda, Mollusca)

Gastropods comprise approximately 80% of molluscans, of which land snails are used variably as food and traditional medicines due to their high protein content. Moreover, different components from land snails exhibit antimicrobial activities. In this study, we evaluated the antifungal activity of soft tissue extracts from Helix aspersa against Candida albicans, Aspergillus flavus, and Aspergillus brasiliensis by identifying extract components using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Two concentrations of three extracts (methanol, acetone, and acetic acid) showed antifungal activity. Both acetone (1 g/3 mL) and acetic acid extracts (1 g/mL) significantly inhibited C. albicans growth (p = 0.0001, 5.2 +/- 0.2 mm and p = 0.02, 69.7 +/- 0.6 mm, respectively). A. flavus and A. brasiliensis growth were inhibited by all extracts at 1 g/mL, while inhibition was observed for acetic acid extracts against A. brasiliensis (p = 0.02, 50.3 +/- 3.5 mm). The highest growth inhibition was observed for A. flavus using acetic acid and acetone extracts (inhibition zones = 38 +/- 1.7 mm and 3.1 +/- 0.7 mm, respectively). LC-MS-MS studies on methanol and acetone extracts identified 11-alpha-acetoxyprogesterone with a parent mass of 372.50800 m/z and 287.43500 m/z for luteolin. Methanol extracts contained hesperidin with a parent mass of 611.25400 m/z, whereas linoleic acid and genistein (parent mass = 280.4 and 271.48900 m/z, respectively) were the main metabolites

The Influence of Microstructure on the Passive Layer Chemistry and Corrosion Resistance for Some Titanium-Based Alloys

The effect of microstructure and chemistry on the kinetics of passive layer growth and passivity breakdown of some Ti-based alloys, namely Ti-6Al-4V, Ti-6Al-7Nb and TC21 alloys, was studied. The rate of pitting corrosion was evaluated using cyclic polarization measurements. Chronoamperometry was applied to assess the passive layer growth kinetics and breakdown. Microstructure influence on the uniform corrosion rate of these alloys was also investigated employing dynamic electrochemical impedance spectroscopy (DEIS). Corrosion studies were performed in 0.9% NaCl solution at 37 °C, and the obtained results were compared with ultrapure Ti (99.99%). The different phases of the microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Chemical composition and chemistry of the corroded surfaces were studied using X-ray photoelectron spectroscopy (XPS) analysis. For all studied alloys, the microstructure consisted of α matrix, which was strengthened by β phase. The highest and the lowest values of the β phase’s volume fraction were recorded for TC21 and Ti-Al-Nb alloys, respectively. The susceptibility of the investigated alloys toward pitting corrosion was enhanced following the sequence: Ti-6Al-7Nb < Ti-6Al-4V << TC21. Ti-6Al-7Nb alloy recorded the lowest pitting corrosion resistance (Rpit) among studied alloys, approaching that of pure Ti. The obvious changes in the microstructure of these alloys, together with XPS findings, were adopted to interpret the pronounced variation in the corrosion behavior of these materials

Manganese Ferrite–Hydroxyapatite Nanocomposite Synthesis: Biogenic Waste Remodeling for Water Decontamination

Environmental pollution, especially water pollution caused by dyes, heavy metal ions and biological pathogens, is a root cause of various lethal diseases in human-beings and animals. Water purification materials and treatment methods are overpriced. Consequently, there is an imperative outlook observance for cheap materials for the purification of wastewaters. In order to fill up the projected demand for clean water, the present study aimed to make use of cost-effective and environmentally friendly methods to convert bone-waste from animals such as cows into novel composites for the decontamination of water. The bone-waste of slaughtered cows from the Najran region of Saudi Arabia was collected and used for the synthesis of hydroxyapatite based on the thermal method. The synthesized hydroxyapatite (Ca10(PO4)6(OH)2) was utilized to prepare a manganese ferrite/hydroxyapatite composite. The nanocomposite was categorized by diverse sophisticated procedures, for instance XRD, FE-SEM, EDX, TEM, UV, PL and FT-IR. This composite possesses outstanding photocatalytic activity against methylene blue dye, which is a common pollutant from industrial wastes. Moreover, the synthesised composite revealed exceptional bacteriostatic commotion towards E. coli and S. aureus bacteria, which are accountable for acute waterborne infections. The outcome of this study demonstrated that the integration of manganese ferrite into hydroxyapatite significantly intensified both antimicrobial and photocatalytic actions when compared to the virgin hydroxyapatite