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HypothesisFoaming in diesel fuels is not well understood and leads to operational challenges. To combat deleterious effects of foaming, diesel formulations can include additives called antifoams. Existing antifoams, unfortunately, are inherently ash-generating when combusted, with unknown environmental impacts. They are prohibited in certain countries, so identifying effective alternative ash-free antifoam chemistries is needed. ExperimentsWe conduct systematic characterization of foam stabilization and antifoaming mechanisms in diesel for two different antifoams (silicone-containing & ashless chemistries). Employing a custom technique combining single-bubble/single-antifoam-droplet manipulation with white light interferometry, we also obtain mechanistic insights into foam stability and antifoam dynamics. ResultsCoalescence times from both bulk foam and single bubble experiments confirm ashless antifoams are effective at reducing foaming, demonstrating the potential of ashless antifoams. Further, we perform single-antifoam-droplet experiments and obtain direct experimental evidence revealing the elusive antifoaming mechanisms. Interestingly, the silicone-containing and ashless antifoams seemingly function via two different mechanisms: spreading and dewetting respectively. This surprising finding refutes conventional wisdom that spreading is likely the only antifoam mechanism in diesels. These results and the reported experimental framework significantly enhance the scientific understanding of non-aqueous foams and will accelerate the engineering of alternative antifoam chemistries for non-aqueous systems.
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Droplet interface bilayer (DIB) is a lipid bilayer formed when two lipid monolayer-coated aqueous droplets are brought in contact within an oil phase. DIBs, especially post functionalization, are a facile model system to study the biophysics of the cell membrane. Continued advances in enhancing and functionalizing DIBs to be a faithful cell membrane mimetic requires a deep understanding of the physicochemical characteristics of droplet interface bilayers. In this review, we provide a comprehensive overview of the current scientific understanding of DIB characteristics starting with the key experimental frameworks for DIB generation, visualization and functionalization. Subsequently we report experimentally measured physical, electrical and transport characteristics of DIBs across physiologically relevant lipids. Advances in simulations and mathematical modelling of DIBs are also discussed, with an emphasis on revealing principles governing the key physicochemical characteristics. Finally, we conclude the review with important outstanding questions in the field.
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Membrana Dobles de Lípidos , Agua , Biomimética , Membrana Celular , Modelos BiológicosRESUMEN
HYPOTHESIS: Although wetting agents have been developed to limit tear film dewetting over contact lenses, systematic analyses correlating wetting agent properties to mechanisms of the tear film destabilization are not readily available. Clarifying destabilization characteristics across key physio-chemical variables will provide a rational basis for identifying optimal wetting agents. EXPERIMENTS: We employ an in-house, in vitro platform to comprehensively evaluate drainage and dewetting dynamics of five wetting agents across seventeen different formulations and two model tear film solutions. We consider the film thickness evolution, film thickness at breakup, dewetted front propagation, and develop correlations to contact angle to compare the samples. FINDINGS: Zwitterionic wetting agents effectively stabilize the tear film by reducing the film thickness at the onset of dewetting, and delaying the propagation of dewetted regions across the lens. Furthermore, tuning wetting agent surface concentrations and utilizing binary mixtures of wetting agents can enhance wetting characteristics. Finally, despite disparities in wetting agent molecular properties, the time to dewet 50% of the lens scales linearly with the product of the receding contact angle and contact angle hysteresis. Hence, we fundamentally establish the importance of minimizing the absolute contact angle and contact angle hysteresis for effective wetting performance.
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Lentes de Contacto Hidrofílicos , Agentes Mojantes , Lágrimas/química , Humectabilidad , Agentes Mojantes/análisisRESUMEN
Droplet interface bilayers are a convenient model system to study the physio-chemical properties of phospholipid bilayers, the major component of the cell membrane. The mechanical response of these bilayers to various external mechanical stimuli is an active area of research because of its implications for cellular viability and the development of artificial cells. In this article, we characterize the separation mechanics of droplet interface bilayers under step strain using a combination of experiments and numerical modelling. Initially, we show that the bilayer surface energy can be obtained using principles of energy conservation. Subsequently, we subject the system to a step strain by separating the drops in a step-wise manner, and track the evolution of the bilayer contact angle and radius. The relaxation time of the bilayer contact angle and radius along with the decay magnitude of the bilayer radius were observed to increase with each separation step. By analysing the forces acting on the bilayer and the rate of separation, we show that the bilayer separates primarily through the peeling process with the dominant resistance to separation coming from viscous dissipation associated with corner flows. Finally, we explain the intrinsic features of the observed bilayer separation by means of a mathematical model comprising the Young-Laplace equation and an evolution equation. We believe that the reported experimental and numerical results extend the scientific understanding of lipid bilayer mechanics, and that the developed experimental and numerical tools offer a convenient platform to study the mechanics of other types of bilayers.
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Membrana Dobles de Lípidos , Fosfolípidos , Membrana Celular , Modelos Teóricos , FosfatidilcolinasRESUMEN
The physics of foams and emulsions has traditionally been studied using bulk foam/emulsion tests and single film platforms such as the Scheludko cell. Recently there has been a renewed interest in a third class of techniques that we term as single bubble/drop tests, which employ isolated whole bubbles and drops to probe the characteristics of foams and emulsions. Single bubble and drop techniques provide a convenient framework for investigating a number of important characteristics of foams and emulsions, including the rheology, stabilization mechanisms, and rupture dynamics. In this review we provide a comprehensive discussion of the various single bubble/drop platforms and the associated experimental measurement protocols including the construction of coalescence time distributions, visualization of the thin film profiles and characterization of the interfacial rheological properties. Subsequently, we summarize the recent developments in foam and emulsion science with a focus on the results obtained through single bubble/drop techniques. We conclude the review by presenting important venues for future research.
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Surfactants in aqueous solutions self-assemble in the presence of salt, to form long, flexible, wormlike micelles (WLM). WLM solutions exhibit viscoelastic properties and are used in many applications, such as for cosmetic products, drag reduction, and hydraulic fracturing. Understanding the coalescence stability of bubbles in WLM solutions is important for the development of WLM based products that require a stable dispersion of bubbles. In this paper, we investigate the thin film drainage dynamics leading up to the coalescence of bubbles at flat WLM solution-air interfaces. The salts and surfactant type and concentrations were chosen so as to have the viscoelastic properties of the tested WLM solutions span over 2 orders of magnitude in moduli and relaxation times. The various stages in drainage and coalescence, the formation of a thick region at the apex (a dimple), the thinning and washout of this dimple, and the final stages of drainage before rupture, are modified by the viscoelasticity of the wormlike micellar solutions. As a result of the unique viscoelastic properties of the WLM solutions, we also observe a number of interesting fluid dynamic phenomena during the drainage processes including elastic recoil, thin film ripping, and single-step terminal drainage.
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Dynamic thin film interferometry is a technique used to non-invasively characterize the thickness of thin liquid films that are evolving in both space and time. Recovering the underlying thickness from the captured interferograms, unconditionally and automatically is still an open problem. Here we report a compact setup employing a snapshot hyperspectral camera and the related algorithms for the automated determination of thickness profiles of dynamic thin liquid films. The proposed technique is shown to recover film thickness profiles to within 100 nm of accuracy as compared to those profiles reconstructed through the manual color matching process. Subsequently, we discuss the characteristics and advantages of hyperspectral interferometry including the increased robustness against imaging noise as well as the ability to perform thickness reconstruction without considering the absolute light intensity information.
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Understanding the mechanics of detrimental convective instabilities in drying polymer solutions is crucial in many applications such as the production of film coatings. It is well known that solvent evaporation in polymer solutions can lead to Rayleigh-Bénard or Marangoni-type instabilities. Here, we reveal another mechanism, namely that evaporation can cause the interface to display Rayleigh-Taylor instabilities due to the build-up of a dense layer at the air-liquid interface. We study experimentally the onset time (tp) of the instability as a function of the macroscopic properties of aqueous polymer solutions, which we tune by varying the polymer concentration (c0), molecular weight and polymer type. In dilute solutions, tp shows two limiting behaviours depending on the polymer diffusivity. For high diffusivity polymers (low molecular weight), the pluming time scales as [Formula: see text]. This result agrees with previous studies on gravitational instabilities in miscible systems where diffusion stabilizes the system. On the other hand, in low diffusivity polymers the pluming time scales as [Formula: see text]. The stabilizing effect of an effective interfacial tension, similar to those in immiscible systems, explains this strong concentration dependence. Above a critical concentration, [Formula: see text], viscosity delays the growth of the instability, allowing time for diffusion to act as the dominant stabilizing mechanism. This results in tp scaling as (ν/c0)2/3. This article is part of the theme issue 'Stokes at 200 (Part 1)'.
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Lubricant formulations are filtered to remove deleterious particulate matter. An unintended consequence of this important process is the detrimental effect of fine filtration on the foaming performance of lubricants with antifoam additives. Here we outline a method to study this phenomenon in detail by probing the coalescence stability of single bubbles in filtered antifoam laden lubricants. Initially, we establish the validity of Garrett's hypothesis for the tested antifoam laden lubricants. Subsequently, we show that the bubble stability in filtered lubricants are positively correlated to the number of filtration cycles - with the most dramatic changes in bubble stability accompanying the initial few cycles of filtration. Further, we show that post filtration, the stability of bubbles in lubricants is inversely correlated to the pore size of the filter and the volume fraction of antifoam in the lubricant prior to filtration. The results also reveal that in the presence of antifoam additives, the bubble coalescence times span multiple Rayleigh distributions. We also provide visual evidence that shows the tested antifoams employ a bridging-stretching mechanism to rupture non-aqueous foams. Finally, a simple probabilistic model is introduced that helps in analyzing the distribution of coalescence times of single bubbles to obtain insights into the volume fraction of antifoams in the lubricant. We believe these results are valuable in guiding the design of lubricants with robust and superior foaming performance.
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Chronic inflammatory disorders of the upper airways are extremely prevalent and have a major impact on public health. Sinusitis and bronchial asthma are closely interrelated diseases and sinusitis is known to influence bronchial asthma in its severity and chronicity. Causal relationships have been proposed but not yet proved. The relationship between sinusitis and asthma is academically interesting and has important diagnostic and therapeutic implications. The present study is designed to evaluate the efficacy of functional endoscopic sinus surgery done as treatment for chronic rhinosinusitis on bronchial asthma patients, in terms of quality of life and pattern of improvement. Objectives of the study were to determine whether bronchial asthma and quality of life improved after functional endoscopic sinus surgery. This was an open labelled randomised control trial, done at ENT Department of Medical College, Thiruvananthapuram. Those in Group A underwent functional endoscopic sinus surgery and group B patients were given only medicines as per standard protocol. All of them received asthma treatment depending on asthma attacks and severity and followed up at specific intervals. Quality of life status and pattern of improvement of bronchial asthma among these patients were evaluated. Patients of chronic rhinosinusitis treated by functional endoscopic sinus surgery showed significant improvement in the mean asthma symptom score, asthma medication use score, pulmonary function test results, and quality of life assessment scores. Functional endoscopic sinus surgery could be considered early in the natural course of chronic rhinosinusitis with concomitant bronchial asthma.
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Foaming in liquids is ubiquitous in nature. Whereas the mechanism of foaming in aqueous systems has been thoroughly studied, nonaqueous systems have not enjoyed the same level of examination. Here we study the mechanism of foaming in a widely used class of nonaqueous liquids: lubricant base oils. Using a newly developed experimental technique, we show that the stability of lubricant foams can be evaluated at the level of single bubbles. The results obtained with this single-bubble technique indicate that solutocapillary flows are central to lubricant foam stabilization. These solutocapillary flows are shown to originate from the differential evaporation of multicomponent lubricants-an unexpected result given the low volatility of nonaqueous liquids. Further, we show that mixing of some combinations of different lubricant base oils, a common practice in the industry, exacerbates solutocapillary flows and hence leads to increased foaming.
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The articular release of the metacarpophalangeal joint produces a typical cracking sound, resulting in what is commonly referred to as the cracking of knuckles. Despite over sixty years of research, the source of the knuckle cracking sound continues to be debated due to inconclusive experimental evidence as a result of limitations in the temporal resolution of non-invasive physiological imaging techniques. To support the available experimental data and shed light onto the source of the cracking sound, we have developed a mathematical model of the events leading to the generation of the sound. The model resolves the dynamics of a collapsing cavitation bubble in the synovial fluid inside a metacarpophalangeal joint during an articular release. The acoustic signature from the resulting bubble dynamics is shown to be consistent in both magnitude and dominant frequency with experimental measurements in the literature and with our own experiments, thus lending support for cavitation bubble collapse as the source of the cracking sound. Finally, the model also shows that only a partial collapse of the bubble is needed to replicate the experimentally observed acoustic spectra, thus allowing for bubbles to persist following the generation of sound as has been reported in recent experiments.
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Articulación Metacarpofalángica/fisiología , Modelos Teóricos , Sonido , Líquido Sinovial/fisiología , Acústica , Humanos , Hidrodinámica , Presión , ViscosidadRESUMEN
An experimental and theoretical investigation is conducted to understand the role of compressibility on the quasi-static expansion and contraction of a bubble that is pinned at the opening of a small capillary. The results show that there are two regimes of expansion and contraction depending on the values of two dimensionless parameters which correspond to a dimensionless volume and maximum capillary pressure. In one regime, not all bubble sizes are accessible during expansion and contraction, and the bubbles exhibit a hysteretic behavior when cycling through expansion and contraction. We call this the bubble shape hysteresis. The magnitude of the bubble shape hysteresis is computed for a realistic range of the nondimensional parameters. In the other regime, the bubble size can be varied continuously, but compressibility can still make it difficult to smoothly control the size of the bubble. The theoretical analysis shows that compressibility affects the evolution of the bubbles, even when the bubble is smaller than a hemispherical cap. The analysis also provides the infusion and withdrawal rates that a syringe pump must supply to expand and contract the bubble at a desired rate, accounting for compressibility. The validity of the assumptions used in the model is verified by comparison against experimental data.
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A 41-year-old HIV positive woman was started on highly active antiretroviral therapy when her CD(4) count was 54/cu mm. Three weeks later, she developed erythematous to skin-colored plaques over the face. Investigations revealed a moderate eosinophilia, raised ESR, elevated 24-hour urinary calcium and hyperglobulinemia. Skin biopsy of the facial plaque revealed prominent epithelioid cell granulomas in the dermis. Reticulin stain showed reticulin fibers within the granulomas. Five months later, all the facial lesions regressed with continuation of HAART, with no specific treatment for facial plaques. Repeat CD(4) count was 104/cu mm. A diagnosis of cutaneous sarcoidosis occurring as a part of immune reconstitution inflammatory syndrome was made. Although systemic sarcoidosis has been reported, the occurrence of cutaneous sarcoidosis as part of immune reconstitution inflammatory syndrome has not been elucidated conclusively.
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A 26-year-old man presented with swelling of his face and nose of three months duration. He had multiple hyperpigmented, hyperkeratotic plaques over the swelling, of one-month duration and an erythematous indurated plaque below the left nostril for two weeks. Based on a biopsy taken from the antral mass with special stain for fungus, he was treated as fungal sinusitis with intravenous amphotericin-B, but the lesion did not regress. Later a skin biopsy from the indurated lesion showed moderately differentiated squamous cell carcinoma. A diagnosis of sinonasal carcinoma was made and chemotherapy was started.
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Carcinoma de Células Escamosas/diagnóstico , Micosis , Neoplasias Nasales/diagnóstico , Neoplasias de los Senos Paranasales/diagnóstico , Sinusitis/diagnóstico , Sinusitis/microbiología , Adulto , Carcinoma de Células Escamosas/patología , Diagnóstico Diferencial , Humanos , Masculino , Micosis/diagnóstico , Neoplasias Nasales/patología , Neoplasias de los Senos Paranasales/patologíaRESUMEN
BACKGROUND: Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are a group of severe life threatening drug reactions. The drugs commonly implicated as the cause of these drug reactions vary depending on host factors and the prescription pattern of drugs in that particular area. AIM: The aim of the study was to find the drugs implicated as the cause of SJS/TEN in the patients admitted in the dermatology ward at the Medical College, Thrissur and to find the clinical outcome. METHODS: It was a retrospective study of 7 years from 1997 to 2004. The case records of all patients with a clinical diagnosis of TEN or SJS were studied in detail regarding the drugs implicated as the cause, the management and the clinical outcome. RESULTS: During the study period, 41 patients in the age group ranging from 12 to 72 years were treated as inpatients, of which 20 were males and 21 were females. The commonest drug implicated as the cause of SJS/TEN was carbamazepine (44%). The indication for carbamazepine was control of pain in more than 50% of the cases. Presence of a major systemic disease before the onset of SJS/TEN was associated with a bad prognosis. CONCLUSION: The increased use of carbamazepine, especially for control of pain, may be the reason for the increased incidence of SJS/TEN due to the same drug. Awareness about the drugs implicated in life threatening drug reactions will help physicians in preventing them by judicious use of the drugs.
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Anticonvulsivantes/efectos adversos , Carbamazepina/efectos adversos , Síndrome de Stevens-Johnson/inducido químicamente , Síndrome de Stevens-Johnson/etiología , Adolescente , Adulto , Anciano , Amoxicilina/efectos adversos , Antibacterianos/efectos adversos , Antiinflamatorios no Esteroideos/efectos adversos , Antipsicóticos/efectos adversos , Niño , Clorpromazina/efectos adversos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios RetrospectivosRESUMEN
Liv.100 is an improvised herbal formulation of Liv.52. Liv.52 is an important component of the ayurvedic system of medicine. This report highlights on the protective effect of Liv.52 and Liv.100 against in vitro peroxidation induced by hydrogen peroxide in rat liver homogenate. Addition of the two herbal formulations reduced the peroxidation effect of hydrogen peroxide in the dose- and time-dependent manner. The protective effect of the drugs is attributed to the enhanced supply of reduced glutathione that inhibit the deleterious process of lipid peroxidation. The results suggest on the antioxidant potential of Liv.52 and Liv.100.
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Peroxidación de Lípido/efectos de los fármacos , Medicina Ayurvédica , Extractos Vegetales/farmacología , Animales , Combinación de Medicamentos , Glutatión/metabolismo , Peróxido de Hidrógeno/farmacología , Técnicas In Vitro , Masculino , Plantas Medicinales , RatasRESUMEN
A 60-year old man with squamous cell carcinoma of hypopharynx and acrokeratosis paraneoplastica (Bazex syndrome) is reported.
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Embelin, a plant-based benzoquinone derivative, has been found to exhibit significant antitumor activity in methylcholanthrene-induced fibrosarcoma in albino rats besides enhancing their survival time. The drug also has an appreciable action on pain and inflammation. The changes in DNA, RNA and protein levels in various organs in the tumor-bearing control and the drug-treated animals were also studied.
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Analgésicos/uso terapéutico , Antiinflamatorios no Esteroideos/uso terapéutico , Benzoquinonas/uso terapéutico , Fibrosarcoma/tratamiento farmacológico , Extractos Vegetales/uso terapéutico , Analgésicos/farmacología , Animales , Antiinflamatorios no Esteroideos/farmacología , Benzoquinonas/farmacología , ADN/metabolismo , Masculino , Dolor/tratamiento farmacológico , Extractos Vegetales/farmacología , Proteínas/metabolismo , ARN/metabolismo , Ratas , Ratas WistarRESUMEN
Twenty five cases suspected to have milker's dertiatitiswere clinically studied including tests with various self-made antigens. Eight cases showed positive patch tests results. Two cases showed cay saliva and one case showed under shaves as the allergen.