Pathway selection by an active droplet.

We report the movement of an active 1-pentanol drop within a closed Y-shaped channel subjected to geometrical and chemical asymmetry. A Y-shaped channel was configured with an angle of 120° between any two arms, which serves as the closed area of movement for the active drop. The arm where the 1-pentanol drop is introduced in the beginning is considered the source arm, and the center of the Y-shaped structure is the decision region. The drop always selects a specific route to move away from the decision region. The total probability of pathway selection excludes the possibility of the drop choosing the source channel. Remarkably, the active drop exhibits a strong sense of navigation for both geometrically and chemically asymmetric environments with accuracy rates of 80% and 100%, respectively. The pathway selection in a chemically asymmetric channel is a demonstration of the artificial negative chemotaxis, where the extra confined drop acts as a chemo-repellent. To develop a better understanding of our observations, a numerical model is constructed, wherein the particle is subjected to a net force which is a combined form of - (i) Yukawa-like repulsive interaction force (acting between the drop and the walls), (ii) a self-propulsion force, (iii) a drag, and (iv) a stochastic force. The numerics can capture all the experimental findings both qualitatively and quantitatively. Finally, a statistical analysis validates conclusions derived from both experiments and numerics.

Quenching of oscillations via attenuated coupling for dissimilar electrochemical systems.

The coupled dynamics of two similar and disparate electrochemical cells oscillators are analyzed. For the similar case, the cells are intentionally operated at different system parameters such that they exhibit distinct oscillatory dynamics ranging from periodic to chaotic. It is observed that when such systems are subjected to an attenuated coupling, implemented bidirectionally, they undergo a mutual quenching of oscillations. The same holds true for the configuration wherein two entirely different electrochemical cells are coupled via bidirectional attenuated coupling. Therefore, the attenuated coupling protocol seems to be universally efficient in achieving oscillation suppression in coupled oscillators (similar or heterogeneous oscillators). The experimental observations were verified by numerical simulations using appropriate electrodissolution model systems. Our results indicate that quenching of oscillations via attenuated coupling is robust and therefore could be ubiquitous in coupled systems with a large spatial separation prone to transmission losses.

Phase-flip transition in volume-mismatched pairs of coupled 1-pentanol drops.

We have explored a variety of synchronization domains and observed phase-flip transition in a pair of coupled 1-pentanol drops as a function of the volume mismatch. Both experimental observations and numerical studies are presented. The experiments were carried out in a rectangular channel in a ferroin deionized water solution premixed with some volume of pentanol. A single pentanol drop (≥ 3µL) performs back and forth oscillations along the length of the channel due to the well-known Marangoni forces. In the present work, for a pair of drops, the drop 1 volume was changed from 3 to 5 µL in steps of 1µL, whereas the drop 2 volume was varied from 1 to 3 µL in steps of 0.5µL. A systematic investigation of all the possible combinations of the drop volumes showed the presence of three different types of synchrony-in-phase, antiphase, and phase-switched. In-phase synchronization was robust for a volume mismatch of >3.0µL between the two drops. On the other hand, antiphase synchronization was robust when the volume mismatch was <2.0µL. The phase-switched state is a synchronized state involving a phase-flip transition in the time domain. This state was observed for the intermediate range of volume mismatch. Numerically, the system has been investigated using two Stuart-Landau oscillators interacting via a coupling function in the form of Lennard-Jones potential. The numerical results suitably capture both in-phase and antiphase oscillations for a pair of volume-mismatched pentanol drops.

An alternate approach to simulate the dynamics of perturbed liquid drops.

Liquid drops when subjected to external periodic perturbations can execute polygonal oscillations. In this work, a simple model is presented that demonstrates these oscillations and their characteristic properties. The model consists of a spring-mass network such that masses are analogous to liquid molecules and the springs correspond to intermolecular links. Neo-Hookean springs are considered to represent these intermolecular links. The restoring force of a neo-Hookean spring depends nonlinearly on its length such that the force of a compressed spring is much higher than the force of the spring elongated by the same amount. This is analogous to the incompressibility of liquids, making these springs suitable to simulate the polygonal oscillations. It is shown that this spring-mass network can imitate most of the characteristic features of experimentally reported polygonal oscillations. Additionally, it is shown that the network can execute certain dynamics, which so far have not been observed in a perturbed liquid drop. The characteristics of dynamics that are observed in the perturbed network are polygonal oscillations, rotation of network, numerical relations (rational and irrational) between the frequencies of polygonal oscillations and the forcing signal, and that the shape of the polygons depends on the parameters of perturbation.

Modes of synchrony in self-propelled pentanol drops.

We report various modes of synchrony observed for a population of two, three and four pentanol drops in a rectangular channel at the air-water interface. Initially, the autonomous oscillations of a single 1-pentanol drop were studied in a ferroin DI water solution pre-mixed with some volume of pentanol. A pentanol drop performs continuous motion on the air-water interface due to Marangoni forces. A linear channel was prepared to study the uniaxial movement of the drop(s). Thereafter, a systematic study of the self-propelled motion of a 1-pentanol drop was reported as a function of the drop volume. Subsequently, the coupled dynamics were studied for two, three and four drops, respectively. We observed anti-phase oscillations in a pair of pentanol drops. In the case of three drops, relay synchronization was observed, wherein consecutive pairs of drops were exhibiting out-of-phase oscillations and alternate drops were performing in-phase oscillations. Four pentanol drops showed two different modes of synchrony: one was relay synchrony and the other was out-of-phase oscillations between two pairs of drops (within a pair, the drops exhibit in-phase oscillations).

Velocity controlled pattern writing: An application of stochastic resonance.

In the present work, the concept of stochastic resonance is employed for pattern fabrication. In particular, the interplay of noise amplitudes and intrinsic system time scales is investigated. This interplay enabled us to obtain preordained patterns. Experiments were performed galvanostatically in a two electrode electrochemical cell onto a n-type Si substrate using a coherent wavelength laser source of 5 mW intensity. A focused laser beam was swept along the silicon substrate unidirectionally by moving the electrochemical cell at different velocities. By systematic tuning of the velocity, we have observed a unimodal variation in the contrast of the pattern. This indicates the occurrence of the stochastic resonance phenomena. Corresponding numerical simulations, performed on a spatial array of diffusively coupled FitzHugh-Nagumo oscillators in the presence of external noise, reveal good agreement with the experimental observations.

Methotrexate Aspasomes Against Rheumatoid Arthritis: Optimized Hydrogel Loaded Liposomal Formulation with In Vivo Evaluation in Wistar Rats.

Aspasomes of methotrexate with antioxidant, ascorbyl palmitate, were developed and optimized using factorial design by varying parameters such as lipid molar ratio, drug to lipid molar ratio, and type of hydration buffer for transdermal delivery for disease modifying activity in rheumatoid arthritis (RA). Aspasomes were characterized by drug-excipients interaction, particle size analysis, determination of zeta potential, entrapment efficiency, and surface properties. The best formulation was loaded into hydrogel for evaluation of in vitro drug release and tested in vivo against adjuvant induced arthritis model in wistar rats, by assessing various physiological, biochemical, hematological, and histopathological parameters. Optimized aspasome formulation exhibited smooth surface with particle size 386.8 nm, high drug loading (19.41%), negative surface potential, and controlled drug release in vitro over 24 h with a steady permeation rate. Transdermal application of methotrexate-loaded aspasome hydrogel for 12 days reduced rat paw diameter (21.25%), SGOT (40.43%), SGPT (54.75%), TNFα (33.99%), IL ß (34.79%), cartilage damage (84.41%), inflammation (82.37%), panus formation (84.38%), and bone resorption (80.52%) as compared to arthritic control rats. Free methotrexate-treated group showed intermediate effects. However, drug-free aspasome treatment did not show any effect. The experimental results indicate a positive outcome in development of drug-loaded therapeutically active carrier system which presents a non-invasive controlled release transdermal formulation with good drug loading, drug permeation rate, and having better disease modifications against RA than the free drug, thereby providing a more attractive therapeutic strategy for rheumatoid disease management.

Effects of co-treatment with pioglitazone and methotrexate on experimentally induced rheumatoid arthritis in Wistar albino rats.

OBJECTIVES: Rheumatoid arthritis (RA) is a chronic inflammatory disease primarily affecting the synovial joints of the body. Methotrexate (MTX) is considered as a mainstay in the management of RA. However, monotherapy with MTX in RA is often limited by potential long-term toxicity. The present study was conducted to evaluate if MTX-pioglitazone combination therapy has an add-on benefit over monotherapy with MTX or pioglitazone on disease activity in male Wistar rats in adjuvant-induced arthritis model. MATERIALS AND METHODS: Arthritis was induced by single subcutaneous injection of complete Freund's adjuvant (CFA) in thirty male Wistar albino rats. They were then divided into five equal groups, which included two control groups (arthritic and nonarthritic), pioglitazone-treated (1.35 mg/kg daily), MTX-treated (0.225 mg/kg daily), and MTX + pioglitazone-treated. The disease-modifying action of the drugs was assessed by various physiological, hematological, and biochemical parameters along with histopathological and radiological analysis of affected joints. The experimental data were statistically assessed by one-way ANOVA. RESULTS: There was a significant reduction of disease activity in the MTX monotherapy group when compared with disease control. However, pioglitazone monotherapy group failed to demonstrate any significant effect on disease activity. The MTX-pioglitazone combination group demonstrated greater suppression of disease activity as compared to MTX and pioglitazone monotherapy and disease control group (P < 0.05). CONCLUSION: The present study demonstrates that the combination therapy of MTX with pioglitazone offers better control of disease activities in RA as compared to MTX or pioglitazone monotherapy.

Effect of fuel concentration and force on collective transport by a team of dynein motors.

Motor proteins are essential components of intracellular transport inside eukaryotic cells. These protein molecules use chemical energy obtained from hydrolysis of ATP to produce mechanical forces required for transporting cargos inside cells, from one location to another, in a directed manner. Of these motors, cytoplasmic dynein is structurally more complex than other motor proteins involved in intracellular transport, as it shows force and fuel (ATP) concentration dependent step-size. Cytoplasmic dynein motors are known to work in a team during cargo transport and force generation. Here, we use a complete Monte-Carlo model of single dynein constrained by in vitro experiments, which includes the effect of both force and ATP on stepping as well as detachment of motors under force. We then use our complete Monte-Carlo model of single dynein motor to understand collective cargo transport by a team of dynein motors, such as dependence of cargo travel distance and velocity on applied force and fuel concentration. In our model, cargos pulled by a team of dynein motors do not detach rapidly under higher forces, confirming the experimental observation of longer persistence time of dynein team on microtubule under higher forces.

A Rare Presentation of Os Odontoideum with Multiple Vertebral Fusion in Type III Klippel-Feil Syndrome (KFS) - A Case Report.

An abnormal atlas and axis with presence of os odontoideum and fusion of multiple vertebrae were noted in an intact skeleton, in the osteology museum of the Department of Anatomy of North Bengal Medical College, West Bengal, India.These multiple abnormalities at various levels along with increased thickness of antero-posterior arch of atlas pointed towards the congenital nature of the anomalies, possibly due to Klippel-Feil syndrome (KFS). These unusual findings denote a developmental background of the manifestations.The cervical instability, resultant neurodeficit and impairment of quality of life of the affected individuals, which are inherent in such cases, reveal their clinical importance.

Unilateral variations in upper limb arterial system: a case report with literature review.

In a female cadaver unilateral variations were found in upper limb arterial system - as (1) high-up origin of ulnar artery at arm, (2) persistent prominent arteria nervii mediana or median artery, (3) common interosseous artery branching out of brachial artery. Literature review revealed these coexistent anomalies as the consequence of aberrant finalization of the path chosen by axis arterial network in embryonic life.