Influence of micro-textures on antibacterial behaviour of titanium-based implant surfaces: In vitro studies

Titanium and its alloys have been widely used as implant materials owing to several favourable properties. Bacterial infections are one of the most prominent reasons for implant failure. Antibacterial drugs are a possible solution to bacterial infection but they kill the normal cells, and in many cases, some traces of the bacteria remain. The bacteria form a biofilm that can act as a conductive medium for regrowth of the bacteria. Customised implant surfaces that inhibit the formation of biofilms and retard the bacterial adherence have a significant potential in the design of futuristic implants. In this study, the antibacterial behaviour of textured titanium Grade-2 and Grade-5 surfaces is analysed and compared with a polished surface. The surface topography and its influence on the water wettability were investigated. A culture of Staphylococcus aureus was seeded on the prepared specimen and the bacterial adherence was compared. The results show that the bacterial adhesion and growth are reduced in textured specimens in comparison with a polished specimen. The fewer adherences of bacteria on the textured specimens are attributed to its surface topography and the presence of micro-dimples, which in turn influence the hydrophilicity of the surfaces

Effects of multi-level governance characteristics on resilient flood risk management: Case study of Kerala floods

Kerala is the South-western state in the Malabar coast of India that experiences floods. The disaster management in this state is response-centric and the 2018 floods indicated the need for a transition from a response-centric approach to a resilient flood risk management (FRM) approach. According to Vincent Ostrom, multi-level governance (MLG) is required for the effective provision of a public good or service and when considering FRM to be a public good/service, it can be inferred that MLG is required for the effective provision of FRM. Kochi, the largest urban agglomeration in Kerala and the location of interest for this research, has a MLG structure and yet does not have an effective resilient FRM system due to the governance issues within FRM. This research is aimed towards adding an additional layer to the existing researches within the domain linking MLG and FRM by taking a data-driven modelling perspective. In order to achieve this, the existing system is viewed as a complex adaptive system (CAS). The existing flood risk governance arrangements (FRGA) were modelled with the help of MAIA (Modelling Agent Systems based on Institutional Analysis) metamodel and Agent-Based Model (ABM) to derive insights about the characteristics of MLG relevant to the governance issues faced by the resilient FRM in Kochi. The results revealed that the existing power distribution among the State, District and Local authorities must be changed to ensure a better resilient FRM system. Furthermore, the results revealed that the network formation among local communities, non-governmental organizations (NGOs) must be encouraged. The research enabled to propose certain policy recommendations - the existing structure must acknowledge and incorporate the need for monitoring the implementation stage of the policies developed. The existing structure must acknowledge and accommodate the need for a better clarity on the responsibilities of decision-makers. The positive influence of networks is higher than the negative influence of the opportunistic behaviour shown by stakeholders. It is thus recommended to encourage network formation among community members, NGOs and government authorities. This encouragement can be provided through “triggering” events. This research looked into environmental damage which can be referred to as a negative “triggering” event. However, positive “triggering” events must be explored. With respect to the power allocation aspect of decentralization, the research gives three recommendations - when considering the definition of resilience to be the ability of system to absorb shocks and show the least fluctuations, the recommendation is to ensure a power distribution set up where the District authority has the highest power followed by the Local authority and State authority. When considering resilient FRM cycle to involve distinct phases, the recommendation is to adopt “policy switching” which is defined in this research as the approach of considering a combination of policies in terms of power distribution such that the requirement of each phase is addressed. In general, the District and Local authorities must be more involved in the decision-making within resilient FRM cycle.Engineering and Policy Analysi

Investigations on the Influence of Surface Textures on Optical Reflectance of Multi-crystalline Silicone (MC-Si) Crystal Surfaces-Simulations and Experiments

MC-Si is the most widely used material for making solar PV cells. In spite of the considerable research on improving the conversion efficiency of MC-Si solar PV cells still it remains well within the range of 15-20%. Optical reflectance being the major loss of incident solar energy, efforts are being made to reduce the optical reflectance of solar cell surfaces. Among the several methods proposed, creation of well-defined surface topography on the cell surface remains a promising option. Micro/nano level features with various dimensions and distributions have been created on MC-Si crystal surfaces using a femto-second pulsed laser and the influence of surface topography on optical reflectance in the incident light wave length of 350 – 1000 nm have been studied and compared with the simulation results obtained using OPAL2 software. Experimental results indicate that surface textures on the wafer surface lead to the reduction of optical reflectance in the range of 20-35% in comparison with plain surface. Width of micro grooves have less significant effect on the optical reflectance in comparison with pitch between the micro grooves. Best reduction in reflectance is exhibited by the texture having a groove width of 30 mm and a pitch of 100 mm. A post texturing etching operation is found to have detrimental effect on the ability of micro/nano level features in decreasing the optical reflectance in the preferred wavelength of solar spectrum due to the flattening of nano level features created within the micro grooves due to laser texturing

Defect-Rich Brown TiO_2–<i>x</i> Porous Flower Aggregates: Selective Photocatalytic Reversibility for Organic Dye Degradation

A low-temperature, Mn­(II)-assisted sol-solvothermal strategy has been developed for the synthesis of positively surface-charged defective brown TiO_2–<i>x</i> flower aggregates with porous nature. The porous structure possessed enormous surface defect states such as trivalent titanium ion (Ti³⁺) and oxygen vacancy (V_o) sites. The defect states present in the brown TiO_2–<i>x</i> facilitated enhanced absorption even in the NIR region of the solar spectrum, whereas for the negatively surface-charged TiO₂ sample, synthesized in the absence of Mn­(II), the absorption was limited to the visible region. Obviously, band-gap narrowing occurred for brown TiO_2–<i>x</i> as compared to the yellow TiO₂ synthesized in the absence of Mn­(II). Interestingly, studying the photocatalytic efficiency of these materials using a methyl orange–methylene blue (MO-MB) dye mixture model system under solar illumination revealed selective photocatalytic reversibility, with MB and MO photodegradation performed by yellow TiO₂ and brown TiO_2–<i>x</i>, respectively. This is the first report on the use of surface-charged brown TiO_2–<i>x</i> with porous flower aggregate morphology for selective photocatalysis

Defect minimized Ag-ZnO microneedles for photocatalysis

A facile solution processing strategy has been developed for the formation of Ag-modified ZnO microneedles at various calcination temperatures such as 300, 500, and 700 °C (AZ3, AZ5, and AZ7 respectively). Due to the heavy doping of AgNO3, Ag+ ions have been incorporated in to the crystal lattice of ZnO in all the Ag-ZnO samples, which facilitated the formation of Ag-ZnO microneedle morphology with minimized defect states, and obviously, the plasmon peaks were observed due to Ag modification. These Ag-ZnO microneedle structures have been evaluated for their photocatalytic performance using methylene blue as model target contaminant and their activity was compared with the commercially available titania P25 photocatalyst. The photoactivity of all the Ag-ZnO microneedle structures was significantly higher than that of the commercially available P25 photocatalyst with the most active Ag-ZnO material having a photocatalytic activity ~ 1.4 times greater than that of P25 titania.Other Information Published in: Environmental Science and Pollution Research License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s11356-020-09433-5</p

Defective Grey TiO2 with Minuscule Anatase&ndash;Rutile Heterophase Junctions for Hydroxyl Radicals Formation in a Visible Light-Triggered Photocatalysis

The novelty of this work was to prepare a series of defect-rich colored TiO2 nanostructures, using a peroxo solvothermal-assisted, high-pressure nitrogenation method. Among these solids, certain TiO2 materials possessed a trace quantity of anatase&ndash;rutile heterojunctions, which are beneficial in obtaining high reaction rates in photocatalytic reactions. In addition, high surface area (above 100 m2/g), even when utilizing a high calcination temperature (500 &deg;C), and absorption of light at higher wavelengths, due to the grey color of the synthesized titania, were observed as an added advantage for photocatalytic hydroxyl radical formation. In this work, we adopted a photoluminescent probe method to monitor the temporal evolution of hydroxyl radicals. As a result, promising hydroxyl radical formations were observed for all the colored samples synthesized at 400 and 500 &deg;C, irrespective of the duration of calcination