Dynamics and morphology of droplet penetrating a soap film

This work reports experimental observation and theoretical explanation of the dynamics and morphology of a droplet passing through a soap film. During the process, the film undergoes four sequential responses: (1) film deformation upon droplet impact; (2) drop–film detachment; (3) coalescence of the film shell with the drop; (4) peel-off of the film shell. Physical models and the corresponding analytical expressions are developed to reveal the underlying physics for the observed four responses. It is identified that the film is an elongated catenoid under continuous stretch by the droplet, and that they separate at the fixed height of 5.8 times of the droplet radius while the detach point is located at the centre of the height. After separation, the droplet is wrapped with a film shell, which is then punctured by the ring tip of the converging surface wave at the impacting Weber number range of [45, 225]. The film shell then coalesces with the droplet, falls off with a fixed velocity and is eventually ejected as a bubble leaving the droplet with a transplanted surface of the soap solution.

Super liquid repellent surfaces for anti-foaming and froth management

Wet and dry foams are prevalent in many industries, ranging from the food processing and commercial cosmetic sectors to industries such as chemical and oil-refining. Uncontrolled foaming results in product losses, equipment downtime or damage and cleanup costs. To speed up defoaming or enable anti-foaming, liquid oil or hydrophobic particles are usually added. However, such additives may need to be later separated and removed for environmental reasons and product quality. Here, we show that passive defoaming or active anti-foaming is possible simply by the interaction of foam with chemically or morphologically modified surfaces, of which the superamphiphobic variant exhibits superior performance. They significantly improve retraction of highly stable wet foams and prevention of growing dry foams, as quantified for beer and aqueous soap solution as model systems. Microscopic imaging reveals that amphiphobic nano-protrusions directly destabilize contacting foam bubbles, which can favorably vent through air gaps warranted by a Cassie wetting state. This mode of interfacial destabilization offers untapped potential for developing efficient, low-power and sustainable foam and froth management.

Analysis of the liquids composition by the sound produced by their heating

When a liquid is heated and the power of the heater is high enough (about 1MW/m2), bubbles are formed at the surface of the heater. Their expansion and collapse are the source of a specific sound, known to everybody who uses a kettle to prepare water for tea or coffee. The main goal of this study is to investigate whether it is possible to judge about the composition of the heated liquid by this sound. A specialized experimental set up is assembled and a systematic study of all known factors, influencing the sound is carried out. It is found out that the most crucial parts of the set up are the container for the liquids and the heater. They are discussed in detail and considerations for further improvements are given. It is demonstrated that with the present apparatus it is possible to detect changes in the sound spectrum when changing the composition of the liquid. For example, one can distinguish between pure water and water with less than 0.1% of ethanol. Along with admixtures of different alcohols, experiments with a soap solution in water and carbonated water are performed.

The Way of Laryngoscope Disinfection: A Survey of Practice in Various Hospitals and Clinics

Background and Aims: During general anaesthesia, laryngoscope is a common equipment for intubation used by anaesthesiologists. Laryngoscope has been identified as a potential source of cross infection. Though guidelines exist for appropriate disinfection practices, recent reviews suggested that current methods of disinfection areless effective and compliance is poor with the established protocols. We conducted a questionnaire-based survey to study the current disinfection practices being followed by a cross section of anaesthesiologists. Methods: A simple questionnaire containing 14 questions was distributed amongst anaesthesiologists through online as well as direct contact. Data were analyzed with percentage analysis. Results: Out of 150 anaesthesiologists, 120 submitted the completed questionnaires. Residents constituted 41% and 46% were consultants. Eighteen (12%) used only tap water for cleaning and 132 (88%) used a chemical agent after rinsing with water. Out of 132, 76 (51%) used detergent/soap solution, 29 (19%) would wash and then soak in disinfectant or germicidal agents (glutaraldehyde, povidone iodine and chlorhexidine) and 18 (12%) would wipe the blade with an alcohol swab. With respect to disinfection of laryngoscope handles, 70% respondents said they used an alcohol swab, 18% did not use any method, 9% were not aware of the method being used, while 3% did not respond. Conclusion: Our results indicate wide variation in methods of decontamination of laryngoscopes. Awareness regarding laryngoscope as a potential source of infection was high. We need to standardize and implement guidelines on a national level and make available resources which will help to improve patient safety. CBMJ 2020 January: Vol. 09 No. 01 P: 04-10

The influence of technological parameters on the hygroscopic properties of textiles

In this paper the method of wet chemistry used for hydrophobization of coarse calico surface was described. It was found that hydrophobicity of coarse calico surface is achieved by the formation of aluminum oxide on the surface. The effect of soap solution temperature, aluminum chloride solution concentration, sample treatment time in aluminum chloride solution and heat treatment temperature on water absorption, contact angle, capillary absorption and calico moisture content was studied. The dependences of gyroscopic properties on the process parameters were obtained. Capillary absorption and water absorption of the test samples increased with increasing concentration of aluminum chloride solution. An increase in the processing time of coarse calico samples in an aluminum chloride solution of lead to a decrease in the hydrophobicity of the samples. The characters of the dependences of hygroscopic properties on the temperature of heat treatment and the temperature of the soap solution are similar.

Bio-efficacy of Millettia pinnata oil soap in the suppression of brinjal fruit and shoot borer, Leucinodes orbonalis Guenee

A field experiment to evaluate the efficacy of pungam (Millettia/Pongamia) oil soap at four different concentrations against brinjal fruit and shoot borer (BFSB), Leucinodes orbonalis Guenee and its effect on spiders of brinjal field revealed that application of 3% pungam oil soap brought down fruit damage to minimum level (12.94% on 7 days after third spray) followed by chlorantraniliprole 18.5% SC (0.3 mL/L), 2, 1 and 0.6% pungam oil soap and neem oil soap 0.6%. Efficacy of chlorantraniliprole persisted up to 14th day of spray followed by pungam oil soap. None of the botanical or chemical pesticides found to influence the spider population until seven days. After 14 days of application soap solution either alone or with pungam oil increased spiders over the control whereas 14 DAS it was minimum in standard check.

Alternative insecticides in the control of the brown citrus aphid Toxoptera citricida (Hemiptera: Aphididae)

The objective of this study was to evaluate the efficacy of alternative insecticides to control the brown citrus aphid Toxoptera citricida (Hemiptera: Aphididae). The treatments consisted of neem oil Azadirachta indica (Sapindales: Meliaceae); smoke syrup Nicotiana tabacum (Solanales: Solanaceae); coconut soap solution (commercial product); black pepper extract Piper nigrum (Piperales: Piperaceae); chemical insecticide Decis® 25 EC; and distilled water. Ten adult insects were placed on a filter paper in a Petri dish, applying 1.5 mL of each treatment to each dish, kept in a BOD-type air-conditioned chamber at a temperature of 25 ± 1 °C and a photophase of 12 hours. The experimental design used was completely randomized, using six treatments with six repetitions, consisting of 10 aphids. Survival assessment were performed at 6, 12, 18 and 24 hours after application of treatments. The alternative insecticides coconut soap and the smoke syrup caused the mortality of 45% and 38.3%, respectively, of the T. citricida at 24 hours after application, showing promising in the control of this pest.

Pongamia oil soap for managing the cowpea aphid, Aphis craccivora Koch

Efficacy of pongamia oil soap against cowpea aphid, Aphis craccivora infesting vegetable cowpea, Vigna unguiculata was evaluated during rabi and summer seasons in comparison with neem oil soap, spinosad, soap solution and absolute control. Pongamia oil soap 2 per cent showed the highest efficacy without phytotoxicity followed by 1 per cent while neem oil soap 0.6 per cent was on par with pongamia oil soap 0.6 per cent. All treatments having pongamia oil soap were significantly superior to absolute control.

Evaluation of Hardness of Ground Drinking Water in Vehari, Pakistan

Ground water contamination has become a major concern in recent years. Hard water is considered aprimary cause of many health-relating issues due to its unsuitability for drinking, domestic, industrial and agriculturalpurposes. Current studies were performed to explore the degree of hardness in drinking water of the selected areas ofVehari city, Pakistan. For this purpose, ten water samples were collected and analyzed. This research involves presentpractices and easy approaches to evaluate the quality of drinking water. The tested samples have shown pH 7.3-7.7,temperature 27-320C and TDS value of 545-1155 mg/L. The hardness of tested water samples was found in the rangeof 110-530 mg/L by titration method. The soap solution method demonstrated the degree of hardness (dᵒTH) in therange of 19.8-35.41. The obtained results were compared with the national and international standards worldwide. Thedrinking water of investigated areas was found hard, contaminated and unsuitable.