Aims To determine the antimicrobial potency of a surface‐anchored quaternary ammonium salt (SAQAS)‐based biocide during in vitro wet and dry fomite assays and to determine the mechanism of killing bacteria on the surface. Methods and Results Wet and dry fomite assays were established in vitro for a commercially available biocide (SAQAS‐A) applied to glass and low‐density polyethylene (LDPE) surfaces. Both wet and dry fomite tests showed the active killing of Gram‐positive and Gram‐negative bacteria but not endospores. Assays measuring membrane permeability (ATP and DNA release), bacterial membrane potential and bacterial ROS production were correlated with the time‐to‐kill profiles to show SAQAS‐A activity in suspension and applied to a surface. Conclusions SAQAS‐A is an effective biocide against model strains of vegetative bacteria. The killing mechanism for SAQAS‐A observed minimal membrane depolarization, a surge in ROS production and assessment of membrane permeability supported the puncture of cells in both suspension and surface attachment, leading to cell death. Significance and Impact of the study SAQAS represents effective surface biocides against single challenges with bacteria through a mechanical killing ability that supports real‐world application if their durability can be demonstrated to maintain residual activity.

The Sonia Sandstone of Proterozoic Jodhpur Group, Marwar Supergroup, exposed around the Sursagar dam area of Jodhpur town, Rajasthan exposes two varieties of nodular features, often spectacular in shape and size. On the basis of mode of occurrence (intra-or interbed) and stratal involvement (single or multiple) the features are classified as Type I and II. From granulometric and microscopic (optical and scanning electron) studies carried out on sandstones from the nodules and their host sandstones, geochemical analysis (SEM-EDAX) of intragranular cement present within Type I nodules, and appreciation of control of associated fracture system within Type II nodules, it is proposed that the two types of nodules vary in their formative mechanism and stage of formation. While Type I nodules are identified as product of processes operative at the early diagenetic, pre-lithification stage, the Type II nodules are undoubtedly the result of post-lithification origin triggered by formation of fracture system. Here we propose generation of vapour pressure (not exceeding the overlying hydrostatic pressure) by decay of thin, laterally impersistent organic mat as the causal factor for intrabed nodule (Type I) formation, which forced rarefication of local grain packing visa -vis early diagenetic silica cementation. The study warrants necessity of more studies on nodules to understand possible roles of organic matter and bedtransgressive fracture systems in their formation, going beyond the generalised secondary mineralisation hypothesis. 1981; McBride et al. 1994; Banerjee et al. 2006b; Banerjee and Jeevankumar 2007), although claims favouring burial and mechanical compaction origin can also be found in literature (Raiswell 1971). Within the carbonate sediments, studies of nodules progressed further as it is felt that the results will help in understanding the nature of fluid flow through heterogeneous calcareous sediments, evolution in petrophysical properties and in course, may guide in improved management of aquifers and

The control of pH of a process plays an important role in many chemical or biological reactions. The monitoring and control of pH of processes like wastewater treatment, manufacturing food and leather making facilitate to reduce pollution and improve the quality of the final product. The focus of this study is to optimize the usage of lime and recycling of spent liquor through continuous monitoring system of pH to achieve near zero residue from liming operation. But the challenges are nonlinear behaviour of the system and frequent fouling of pH sensors. The system developed monitors the pH values and controls the cycling time and the addition of lime as per the user set profile. The real time data of pH values in the process is logged on to the PC for further analysis. The efficacy of the system developed was validated at lab level and can be easily scaled up for implementation in industries. The results showed that the effluent from leather making can be minimized by adopting automated pH monitoring and control systems.

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