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Machining industries are moving towards sustainable production processes. Nanofluid assisted minimum quantity lubrication is the perfect combination in the field of ecological machining process. The objective of current investigation is to evaluate the influence of Cu nanofluid on bearing steel turning operation. L9 orthogonal array employed to perform the experimentation. The output parameters surface roughness and cutting zone temperature were selected. The cutting speed, feed rate and depth of cut are utilized as a machining input parameters. For multi-objective optimization, the grey relational analysis technique was performed to identify the optimum condition. Investigation resulted that Cu nanofluid with minimum quantity lubrication observed as the most significant cooling environment as compared to vegetable cutting fluid. The output parameters surface roughness and cutting zone temperature effectively reduced under Cu nanofluid MQL as compared to vegetable oil centered cutting fluid cooling environment.

Blood clots form at the site of vascular injury to seal the wound and prevent bleeding. Clots are in tension as they perform their biological functions and withstand hydrodynamic forces of blood flow, vessel wall fluctuations, extravascular muscle contraction and other forces. There are several mechanisms that generate tension in a blood clot, of which the most well-known is the contraction/retraction caused by activated platelets. Here we show through experiments and modeling that clot tension is generated by the polymerization of fibrin. Our mathematical model is built on the hypothesis that the shape of fibrin monomers having two-fold symmetry and off-axis binding sites is ultimately the source of inherent tension in individual fibers and the clot. As the diameter of a fiber grows during polymerization the fibrin monomers must suffer axial twisting deformation so that they remain in register to form the half-staggered arrangement characteristic of fibrin protofibrils. This deformation results in a pre-strain that causes fiber and network tension. Our results for the pre-strain in single fibrin fibers is in agreement with experiments that measured it by cutting fibers and measuring their relaxed length. We connect the mechanics of a fiber to that of the network using the 8-chain model of polymer elasticity. By combining this with a continuum model of swellable elastomers we can compute the evolution of tension in a constrained fibrin gel. The temporal evolution and tensile stresses predicted by this model are in qualitative agreement with experimental measurements of the inherent tension of fibrin clots polymerized between two fixed rheometer plates. These experiments also revealed that increasing thrombin concentration leads to increasing internal tension in the fibrin network. Our model may be extended to account for other mechanisms that generate pre-strains in individual fibers and cause tension in three-dimensional proteinaceous polymeric networks.

We study the isometric conical deformation of an inextensible elastic sheet in response to a distributed external loading that is normal to the deformed sheet. The sheet is planar in the reference configuration and it deforms into a cone with a flower-shaped cross-section under load. These deformed configurations are distinguished by the number of lobes. We focus on the geometry and energetics of various lobed-cones in the deformed configuration and discuss their relative stability. First, we assume that the displacements are small which leads to linear governing equations for the curvature that we solve analytically to yield sinusoidal solutions. Then, we relax this restriction on the magnitude of the displacement which leads to nonlinear governing equations, which we again solve analytically using Jacobi elliptic functions which are periodic but not sinusoidal. We show that the sinusoidal solution can be recovered in the limit that the external loads are small.

The purpose of this paper is to deliver a review of the implementation of the minimum quantity lubrication (MQL) system for manufacturing method, centring on the application of the MQL during the metal-cutting of workpiece. The application of MQL system was implemented & studied by various eminent investigators in last two decades. Thus, in this paper, experimental investigations of prior research work were discussed and analysed to light on review with significant facts for investigators and industries to optimize the metal-cutting process. During metal-cutting process, previous investigators considered three independent parameters like cutting speed, depth of cut and feed rate. Out of these parameters, feed rate was found to be most influencing parameter for response variables. But, for specific metal-cutting operation specific types of feed rate is required. Hence, the selection of optimum value & type of feed rate for specific machining operation is yet to investigated. This paper explored an evaluation of industry-socio based trial and error approaches and propose scope for improvement from both an economic and an environmental viewpoint. This paper delivers an outline of formerly conducted analysis to propose zones of enhancement in metal-cutting process employing minimum quantity lubrication system

A number of biological tissues and synthetic gels consist of a fibrous network infused with liquid. There have been a few experimental studies of the rheological properties of such gels under applied compressive strain. Their results suggest that a plot of rheological moduli as a function of applied compressive strain has a long plateau flanked by a steeply increasing curve for large compressive strains and a slowly decreasing curve for small strains. In this paper we explain these trends in rheological properties using a chemo-elastic model characterized by a double-well strain energy function for the underlying fibrous network. The wells correspond to rarefied and densified phases of the fibrous network at low and high strains, respectively. These phases can co-exist across a movable transition front in the gel in order to accommodate overall applied compression. We find that the rheological properties of fibrous gels share similarities with a Kelvin–Voigt visco-elastic solid. The storage modulus has its origins in the elasticity of the fibrous network, while the loss modulus is determined by the dissipation caused by liquid flow through pores. The rheological properties can depend on the number of phase transition fronts present in a compressed sample. Our analysis may explain the dependence of storage and loss moduli of fibrin gels on the loading history. We also point to the need for combining rheological measurements on gels with a microstructural analysis that could shed light on various dissipation mechanisms.

Cellulose-based materials are increasingly finding applications in technology due to their sustainability and biodegradability. The sensitivity of cellulose fiber networks to environmental conditions such as temperature and humidity is well known. Yet, there is an incomplete understanding of the dependence of the fracture toughness of cellulose networks on environmental conditions. In the current study, we assess the effect of moisture content on the out-of-plane (i.e., z-dir.) fracture toughness of a particular cellulose network, specifically Whatman cellulose filter paper. Experimental measurements are performed at 16% RH along the desorption isotherm and 23, 37, 50, 75% RH along the adsorption isotherm using out-of-plane tensile tests and double cantilever beam (DCB) tests. Cohesive zone modeling and finite element simulations are used to extract quantitative properties that describe the crack growth behavior. Overall, the fracture toughness of filter paper decreased with increasing humidity. Additionally, a novel model is developed to capture the high peak and sudden drop in the experimental force measurement caused by the existence of an initiation region. This model is found to be in good agreement with experimental data. The relative effect of each independent cohesive parameter is explored to better understand the cohesive zone-based humidity dependence model. The methods described here may be applied to study rupture of other fiber networks with weak bonds.

“Viscosity is the most ubiquitous dissipative mechanical behavior” ( Maugin, 1999 ). Despite its ubiquity, even for those systems where the mechanisms causing viscous and other forms of dissipation are known there are only a few quantitative models that extract the macroscopic rheological response from these microscopic mechanisms. One such mechanism is the stochastic breaking and forming of bonds which is present in polymer networks with transient cross-links, strong inter-layer bonding between graphene sheets, and sliding dry friction. In this paper we utilize a simple yet flexible model to show analytically how stochastic bonds can induce an array of rheological behaviors at the macroscale. We find that varying the bond interactions induces a Maxwell-type macroscopic material behavior with Newtonian viscosity, shear thinning, shear thickening, or solid like friction when subjected to shear at constant rates. When bond rupture is independent of the force applied, Newtonian viscosity is the predominant behavior. When bond breaking is accelerated by the applied force, a shear thinning response becomes most prevalent. Further connections of the macroscopic response to the interaction potential and rates of bonding and unbonding are illustrated through phase diagrams and analysis of limiting cases. Finally, we apply this model to polymer networks and to experimental data on “solid bridges” in polydisperse granular media. We imagine possible applications to material design through engineering bonds with specific interactions to bring about a desired macroscopic behavior.

Inorganic salt hydrates as a phase change material have the advantage of high latent heat values, high thermal conductivity and are not flammable. Phase segregation is the key downside feature that restricts its application in thermal energy storage application. A PU-PCM composite was prepared by incorporating aqueous saturated sodium sulphate solution, inorganic phase change material (PCM), within open pores of polyurethane (PU) foam. Experimental study on the thermal insulation performance of this composite, aqueous sodium sulphate solution embedded in open cell polyurethane foam, was discussed. This paper presents the computational solving approach for the thermal analysis of this composite having crystallization of sodium sulphate decahydrate, from its aqueous solution, within open pores of PU foam. Thermal study of salt solution in a porous material that undergoes phase change was done using COMSOL Multiphysics software and results were compared with experimental result.

Curvature mediated elastic interactions between inclusions in lipid membranes have been analyzed using both theoretical and computational methods. Entropic corrections to these interactions have also been studied. Here we show that elastic and entropic forces between inclusions in membranes can compete under certain conditions to a yield a maximum in the free energy at a critical separation. If the distance between the inclusions is less than this critical separation then entropic interactions dominate and there is an attractive force between them, while if the distance is more than the critical separation then elastic interactions dominate and there is a repulsive force between them. We assume the inclusions to be rigid and use a previously developed semi-analytic method based on Gaussian integrals to compute the free energy of a membrane with inclusions. We show that the critical separation between inclusions decreases with increasing bending modulus and with increasing tension. We also compute the projected area of a membrane with rigid inclusions under tension and find that the trend of the effective bending modulus as a function of area fraction occupied by inclusions is in agreement with earlier results. Our technique can be extended to account for entropic effects in other methods which rely on quadratic energies to study the interactions of inclusions in membranes.

The present investigation emphasizes seed germination and growth performance of an important medicinal herb Paeonia emodi Wall. ex Royle (family Paeoniaceae) under different microclimatic conditions for sustainable utilization in the Garhwal Himalayan region. The species is used largely in edible, medicinal and economical aspects, but due to its vulnerable status required conservation/cultivation interventions. The study was carried out for storage period, presoaking time, viability and germination/growth performance. Maximum viability (87 %) was found in fresh seeds and minimum at room temperature (16 %). The imbibitions duration of 48 h was observed appropriate for water soaking or chemicals pretreatments in seeds. Germination percentage was significantly higher under shade net (48.16 ± 1.65 %) as compared to polyhouse and open (46.00 ± 3.26 % and 32.16 ± 2.35 %). Mean Germination Time was obtained minimum (144.15 ± 0.93 days) whereas, it was shown maximum (165.15 ± 0.80 days) for open condition. Plant height and stem diameter was recorded highest (19.96 ± 0.52 and 0.64 ± 0.01 cm, respectively) under polyhouse and lowest (13.31 ± 0.37 and 0.48 ± 0.01 cm, respectively) in open condition. Above ground and below ground fresh weight, (10.77 ± 0.44 and 9.69 ± 0.19 g, respectively) were found maximum under shade net, while minimum in open and polyhouse (9.48 ± 0.32 and 9.09 ± 0.26 g, respectively). Seedlings of P. emodi showed average growth and good survival rate (65 %). Microclimatic condition provides the higher concentrations of the photosynthetic pigments. Therefore, study suggests that polyhouses and shade net are the best option for the large scale cultivation and conservation of P. emodi at high altitude.

Architected metastructures offer unprecedented mechanical characteristics due to particular design and assembly of engineered local structures. Here, we study the out-of-plane deflection of plate-like metastructures designed with hexagonal corrugation. Due to the out-of-plane asymmetry of the corrugation, our metaplates develop out-of-plane deflection when put under tension. A theoretical model is developed to analyze the tensile response of the corrugated metaplates, and experiments are conducted on the metaplates made of silicone rubber. The tensile modulus of the silicone rubber is calibrated and the rubber metaplates are then measured under tension. Numerical simulations validate the theoretical and experimental results, and satisfactory agreements are obtained for the force–displacement relations (i.e., effective tensile modulus) and out-of-plane deflection. Parametric studies are carried out to investigate the influences of the geometry (e.g., height h and thickness t ) and the corrugation pattern (e.g., hexagonal diameter D h e x and rib width W r i b ) on the tensile response of the metaplates. The presented corrugated metaplates are envisioned as a promising path to optimize structures for multifunctional applications (e.g., wings in flying robots or light sails for interstellar space travel).

In this paper we describe experiments and a continuum phase transition model for the compression of carbon nanotube (CNT) forests. Our model is inspired by the observation of one or more moving interfaces across which densified and rarefied phases of the CNT forests co-exist. We use a quasi-static version of the Abeyaratne-Knowles theory of phase transitions for continua with a stick-slip type kinetic law and a nucleation criterion based on the critical stress for buckling of CNT forests to describe the formation and motion of these interfaces in uniaxial compression experiments. We investigate micropillars made from bare CNTs, as well as those coated with different thicknesses of alumina using atomic layer deposition (ALD). The coating thickness affects the moduli of individual CNTs as well as the adhesion energy per contact between CNTs. In order to test the applicability of our model to more complex stress states, we carry out nanoindentation experiments on the CNT pillars and interpret the load-indentation data by incorporating a constitutive law allowing for phase transitions into solutions for the indentation of a linearly elastic half-space. Even though the state of stress in a nanoindentation experiment is more complex than that in a uniaxial compression test, we find that the parameters extracted from the nanoindentation experiments are close to those from uniaxial compression. Our models could therefore aid the design of CNT forests to have engineered mechanical properties, and guide further understanding of their behavior under large deformations.

Blood clots are required to stem bleeding and are subject to a variety of stresses, but they can also block blood vessels and cause heart attacks and ischemic strokes. We measured the compressive response of human platelet-poor plasma (PPP) clots, platelet-rich plasma (PRP) clots and whole blood clots and correlated these measurements with confocal and scanning electron microscopy to track changes in clot structure. Stress-strain curves revealed four characteristic regions, for compression-decompression: (1) linear elastic region; (2) upper plateau or softening region; (3) non-linear elastic region or re-stretching of the network; (4) lower plateau in which dissociation of some newly made connections occurs. Our experiments revealed that compression proceeds by the passage of a phase boundary through the clot separating rarefied and densified phases. This observation motivates a model of fibrin mechanics based on the continuum theory of phase transitions, which accounts for the pre-stress caused by platelets, the adhesion of fibrin fibers in the densified phase, the compression of red blood cells (RBCs), and the pumping of liquids through the clot during compression/decompression. Our experiments and theory provide insights into the mechanical behavior of blood clots that could have implications clinically and in the design of fibrin-based biomaterials. Statement of Significance The objective of this paper is to measure and mathematically model the compression behavior of various human blood clots. We show by a combination of confocal and scanning electron microscopy that compression proceeds by the passage of a front through the sample that separates a densified region of the clot from a rarefied region, and that the compression/decompression response is reversible with hysteresis. These observations form the basis of a model for the compression response of clots based on the continuum theory of phase transitions. Our studies may reveal how clot rheology under large compression in vivo due to muscle contraction, platelet retraction and hydrodynamic flow varies under various pathophysiological conditions and could inform the design of fibrin based biomaterials.

Inorganic salt hydrates as phase change material (PCM) offers high energy storage density, low heat of combustion and relatively high thermal conductivity than organic PCMs at a reasonable cost. Moreover, these are nonflammable and also available in the large temperature range for the thermal energy storage (TES) application. However, phase segregation, supercooling and incongruent melting are the main disadvantages which confine them for TES application. In this present study, open cell polyurethane foam (PU foam) as a heterogeneous surface was introduced to mitigate the problem of phase segregation during its repeated thermal cycles. Composite (PU-PCM) having a combination of porous polyurethane foam sheet and saturated inorganic salt solution, by soaking different saturated salt solutions within pores, was prepared. Solution crystallization process was carried out to develop inorganic salt hydrate crystals within the pores from their aqueous solutions. For thermal insulation application, a model experimental setup was constructed and performance of PU-PCM composite sheet compared with the performance of dry PU foam. Various melting and freezing cycles of salt hydrates inside the porous structure were analyzed and the results are discussed.

In the first phase of axon growth, axons sprout from neuron bodies and are extended by the pull of the migrating growth cones towards their targets. Thereafter, once the target is reached, a lesser known second phase of axon growth ensues as the mechanical forces from the growth of the animal induce extension of the integrated axons in the process of forming tracts and nerves. Although there are several microscopic physics based models of the first phase of axon growth, to date, there are no models of the very different second phase. Here we propose a mathematical model for stretch growth of axon tracts in which the rate of production of proteins required for growth is dependent on the membrane tension. We assume that growth occurs all along the axon, and are able to predict the increase in axon cross-sectional area after they are rapidly stretched and held at a constant length for several hours. We show that there is a length dependent maximum stretching rate that an axon can sustain without disconnection in steady state when the axon length is primarily increased near the cell body. Our results could inform better design of stretch growth protocols to create transplantable axon tracts to repair the nervous system.

The aim of this paper is to provide a framework for the integration of internet of things with minimum quantity lubrication system during metal-cutting process, focusing to provide cleaner environment to manpower at shop floor. In last decade, minimum quantity lubrication system was studied and implemented effectively to optimize the metal cutting process at shop floor. Minimum quantity lubrication system was found to be most promising technique with respect to technical, economic and environmental aspects. Internet of things was also implemented in various domains of industry & delivered excellent outcomes. The internet of things has reduced production cost, cycle time and provides assistance to machine operator for improvement method insights. Thus, in this paper, prior research work of eminent investigators related to internet of things and minimum quantity lubrication were discussed and analysed. After review, it was found that if internet of things is integrate with minimum quantity lubrication system then it leads to new research area in the field of smart manufacturing. Internet of things-minimum quantity lubrication (IoT-MQL) integration provides a platform to automatic control the effect of cutting temperature generated during metal cutting process, due to which tool life and productivity affects significantly. This paper briefed an evaluation of manufacturing – socio based manual operation of minimum quantity lubrication system and propose scope for integration of it with internet of things for an economic and an environmental viewpoint. This investigation provides an outline of integration of internet of things with minimum quantity lubrication system. Proposed framework can be used to create an architecture based on lab-scale system with usually accessible, small cost electronic devices like sensors. Micro Electro-Mechanical System is the main base for this integrated framework of IoT-MQL system. This integrated framework represent a kind of key thing for empowering the ‘Smart Factory’ revolution.

Reaction monitoring is crucial in order to guide pharmaceutical chemical processes towards successful outcomes. Many drug substances require the application of water/additive-free solvents to guide process efforts which are intrinsically incompatible with reversed phase liquid chromatography (RPLC) conditions. Sub/supercritical fluid chromatography (SFC) helps to overcome many of these challenges delivering unmatched speed, with low cost, high-efficiency and an additive-free environment ideal for reaction monitoring of species chemically susceptible to water. Herein, we provide several examples where traditional RPLC fails or delivers sub-optimal performance in monitoring processes. These examples include using additive-free SFC-UV and SFC-MS methodologies to overcome difficulties associated with: 1) on-column RPLC hydrolysis, 2) improving normal phase liquid chromatography, replacing capillary zone electrophoresis methods, and 3) avoiding the use of tedious pre-column derivatization procedures.

Flexible mechanical metamaterials have been recently shown to support a rich nonlinear dynamic response. In particular, it has been demonstrated that the behavior of rotating-square architected systems in the continuum limit can be described by nonlinear Klein–Gordon equations. Here, we report on a general class of solutions of these nonlinear Klein–Gordon equations, namely cnoidal waves based on the Jacobi elliptic functions sn, cn and dn. By analyzing theoretically and numerically their validity and stability in the design- and wave-parameter space, we show that these cnoidal wave solutions extend from linear waves (or phonons) to solitons, while covering also a wide family of nonlinear periodic waves. The presented results thus reunite under the same framework different concepts of linear and non-linear waves and offer a fertile ground for extending the range of possible control strategies for nonlinear elastic waves and vibrations.

Mass–spring chains with only extensional degrees of freedom have provided insights into the behavior of crystalline solids, including those capable of phase transitions. Here we add rotational degrees of freedom to the masses in a chain and study the dynamics of phase boundaries across which both the twist and stretch can jump. We solve impact and Riemann problems in the chain by numerical integration of the equations of motion and show that the solutions are analogous to those in a phase transforming rod whose stored energy function depends on both twist and stretch. From the dynamics of phase boundaries in the chain we extract a kinetic relation whose form is familiar from earlier studies involving chains with only extensional degrees of freedom. However, for some combinations of parameters characterizing the energy landscape of our springs we find propagating phase boundaries for which the rate of dissipation, as calculated using isothermal expressions for the driving force, is negative. This suggests that we cannot neglect the energy stored in the oscillations of the masses in the interpretation of the dynamics of mass–spring chains. Keeping this in mind we define a local temperature of our chain and show that it jumps across phase boundaries, but not across sonic waves. Hence, impact problems in our mass–spring chains are analogous to those on continuum thermoelastic bars with Mie–Gruneisen type constitutive laws. At the end of the paper we use our chain to shed some light on experiments involving yarns that couple twist and stretch to perform useful work in response to various stimuli.

The thermal fluctuations of lipid bi-layer membranes are key to their interaction with cellular components as well as the measurement of their mechanical properties. Typically, membrane fluctuations are analyzed by decomposing into normal modes or by molecular simulations. Here we propose two new approaches to calculate the partition function of a membrane. In the first approach we view the membrane as a fluctuating von Karman plate and discretize it into triangular elements. We express its energy as a function of nodal displacements, and then compute the partition function and co-variance matrix using Gaussian integrals. We recover well-known results for the dependence of the projected area of the membrane on the applied tension and recent simulation results on the dependence of membrane free energy on geometry, spontaneous curvature and tension. As new applications we compute the fluctuations of the membrane of a malaria infected cell and analyze the effects of boundary conditions on fluctuations. Our second approach is based on the cell model of Lennard-Jones and Devonshire. This model, which was developed for liquids, assumes that each molecule fluctuates within a cell on which a potential is imposed by all the surrounding molecules. We adapt the cell model to a lipid membrane by recognizing that it is a 2D liquid with the ability to deform out of plane whose energetic penalty must be factored into the partition function of a cell. We show, once again, that some results on membrane fluctuations can be recovered using this new cell model. However, unlike some well established results, our cell model gives an entropy that scales with the number of molecules in a membrane. Our model makes predictions about the heat capacity of the membrane that can be tested in experiments.

Pulmonary embolism occurs when blood flow to a part of the lungs is blocked by a venous thrombus that has traveled from the lower limbs. Little is known about the mechanical behavior of emboli under compressive forces from the surrounding musculature and blood pressure. We measured the stress-strain responses of human pulmonary emboli under cyclic compression, and showed that emboli exhibit a hysteretic stress-strain curve. The fibrin fibers and red blood cells (RBCs) are damaged during the compression process, causing irreversible changes in the structure of the emboli. We showed using electron and confocal microscopy that bundling of fibrin fibers occurs due to compression, and damage is accumulated as more cycles are applied. The stress-strain curves depend on embolus structure, such that variations in composition give quantitatively different responses. Emboli with a high fibrin component demonstrate higher normal stress compared to emboli that have a high RBC component. We compared the compression response of emboli to that of whole blood clots containing various volume fractions of RBCs, and found that RBCs rupture at a certain critical stress. We describe the hysteretic response characteristic of foams, using a model of phase transitions in which the compressed foam is segregated into coexisting rarefied and densified phases whose fractions change during compression. Our model takes account of the rupture of RBCs in the compressed emboli and stresses due to fluid flow through their small pores. Our results can help in classifying emboli as rich in fibrin or rich in red blood cells, and can help in understanding what responses to expect when stresses are applied to thrombi in vivo.

The study of causes and cures for ultraviolet B radiation (UVB)-induced non-melanoma skin cancers (NMSC) has been greatly facilitated by use of the albino SKH-1 hairless mice. These mice develop multiple tumors of different sizes and the severity of cancer is often measured by one or more of the four criteria, namely the prevalence, multiplicity, area and volume of tumors. However, there are inherent limitations of each criterion: the prevalence and number do not account for size differences among tumors, area measurement ignores the tumor height, and volume measurement overcompensates for the height at the cost of planar dimensions. Here, using our dataset from an ongoing NMSC study, we discuss the limitations of these four criteria, and suggest refinements in measuring prevalence. We recommend the use of three more criteria, namely the Knud Thomsen tridimensional surface that apportions optimal weightage to three tumor dimensions, weekly occurrence of new tumors and tumor growth-rate to reveal initiation and growth of tumors in early and late phase of NMSC development, respectively. Together, use of this comprehensive panel of seven criteria can provide an accurate assessment of severity of NMSC and lead to a testable hypothesis whether the experimental manipulation of mice has affected the early initiation or growth phase of NMSC tumors.

Lipid membranes form the outer covering of all biological cells. Embedded on the lipid membrane are numerous proteins that can diffuse on its surface due to its fluid nature. The proteins can also interact with each other through elastic and entropic forces that have their origin in the membrane’s resistance to bending deformations. These interactions can be attractive or repulsive, and they likely play a role in self-assembly of proteins on the surface of the membrane to form scaffolds for exo- and endo-cytosis and also viruses. Thus, it is crucial to understand these elastic and entropic forces in detail and how they affect self-assembly of inclusions on the surface of membranes. Although most analyses of these phenomena utilize various simulation techniques, we use a semi-analytical method based on Gaussian integrals to compute the elastic and entropic interactions of inclusions. Once we have determined the interaction forces between inclusions, we use Langevin dynamics to study how they diffuse under the influence of these interaction forces. We focus first on two inclusions and cast their self-assembly as a first passage time problem. We show that an analytical treatment of the first passage time problem starting from a Fokker-Planck equation leads to a partial differential equation that can be solved numerically, and gives results which are in excellent agreement with the first passage time estimated from Langevin dynamics simulations. We are also able to account for hydrodynamic interactions between inclusions and show that they speed up the self-assembly. Finally, we use these insights to study how interaction forces influence the self-assembly of more than two inclusions. Our methods provide a different view of self-assembly that could be utilized for developing more advanced and efficient computational techniques.

Plate mechanical metamaterials with nanoscale thickness demonstrate significantly enhanced mechanical properties compared to solid plates that lack micropatterning. We have previously reported how the honeycomb corrugation greatly increases the bending stiffness, but any functional applications also require a full understanding of the tensile properties. Here we report that, surprisingly, the tensile properties of alumina plates with nanoscale thickness can be measured using conventional materials testing tools and that the tensile stiffness of honeycomb corrugated plates is greatly reduced, providing an unusual combination of high bending stiffness and low tensile stiffness that cannot be achieved with unpatterned plates. These measurements, along with finite-element (FE) simulations, provide validation for our analytical model that fully characterizes the tensile response of the corrugated nanoplates, thus enabling predictable tuning of their mechanical properties by changing the corrugation geometry. Plates optimized for high bending stiffness and low tensile stiffness can find applications as wings of microflyers or deployable aerospace components.

A solid is said to be flexoelectric when it polarizes in proportion to strain gradients. Since strain gradients are large near defects, we expect the flexoelectric effect to be prominent there and decay away at distances much larger than a flexoelectric length scale. Here, we quantify this expectation by computing displacement, stress and polarization fields near defects in flexoelectric solids. For point defects we recover some well known results from strain gradient elasticity and non-local piezoelectric theories, but with different length scales in the final expressions. For edge dislocations we show that the electric potential is a maximum in the vicinity of the dislocation core. We also estimate the polarized line charge density of an edge dislocation in an isotropic flexoelectric solid which is in agreement with some measurements in ice. We perform an asymptotic analysis of the crack tip fields in flexoelectric solids and show that our results share some features from solutions in strain gradient elasticity and piezoelectricity. We also compute the energy release rate for cracks using simple crack face boundary conditions and use them in classical criteria for crack growth to make predictions. Our analysis can serve as a starting point for more sophisticated analytic and computational treatments of defects in flexoelectric solids which are gaining increasing prominence in the field of nanoscience and nanotechnology.

Summary Background Ultrasound accelerates tissue-type plasminogen activator (t-PA)–induced fibrinolysis of clots in vitro and in vivo. Objective To identify mechanisms for the enhancement of t-PA–induced fibrinolysis of clots. Methods Turbidity is an accurate and convenient method, not previously used, to follow the effects of ultrasound. Deconvolution microscopy was used to determine changes in structure, while fluorescence recovery after photobleaching was used to characterize the kinetics of binding/unbinding and transport. Results The ultrasound pulse repetition frequency affected clot lysis times, but there were no thermal effects. Ultrasound in the absence of t-PA produced a slight but consistent decrease in turbidity, suggesting a decrease in fibrin diameter due solely to the action of the ultrasound, likely caused by an increase in protofibril tension because of vibration from ultrasound. Changes in fibrin network structure during lysis with ultrasound were visualized in real time by deconvolution microscopy, revealing that the network becomes unstable when 30–40% of the protein in the network was digested, whereas without ultrasound, the fibrin network was digested gradually and retained structural integrity. Fluorescence recovery after photobleaching during lysis revealed that the off-rate of oligomers from digesting fibers was little affected, but the number of binding/unbinding sites was increased. Conclusions Ultrasound causes a decrease in the diameter of the fibers due to tension as a result of vibration, leading to increased binding sites for plasmin(ogen)/t-PA. The positive feedback of this structural change together with increased mixing/transport of t-PA/plasmin(ogen) is likely to account for the observed enhancement of fibrinolysis by ultrasound.

Neurons are cells that carry electrical impulses. The growth of axons in these cells has been of interest for some time. Experiments have been performed to understand the tension dependent growth of axons but there are few models in the literature that can explain the characteristics of axon growth. Here we propose a growth model that is based on diffusion limited polymerization of microtubules in the axon. The tension in the axonal membrane determines the compressive force on the polymerizing microtubules and this controls the rate of growth. We show that the growth process of an axon that is coupled to a device which can measure and apply forces on it can be described by an ordinary differential equation. Solutions of this equation for various loading conditions reproduces the data in many recent experiments.

World over large reserves of low grade coals are available. The use of low-grade coal in various industries like power plants, metallurgical plants, cement units, etc. creates environmental pollution because of generation of large amount of solid and gaseous pollutants. Therefore, it is of paramount importance to clean the coal before its utilization. A number of upgrading technologies are being followed to produce clean coal. The current paper reviews demineralization/desulfurization of coals containing high ash and/or sulfur by physical, microwave, bio- and chemical beneficiation methods. Physical beneficiation of coal is not very effective in separation of the finely dispersed minerals, whereas microwave processing requires lesser time but is not favoured energetically. Bio-processing is mainly used for the desulfurization of high sulfur coal, although it is usually slow and requires long incubation period. Chemical beneficiation uses expensive reagents and leads to the generation of large amount of wastewater which is to be purified before discharge. Thus, a combined approach consisting of physical beneficiation followed by chemical cleaning of coal appears to have a potential for significant reduction of ash with less investment while generating less amount of wastewater.

Idiopathic or immune thrombocytopenia (ITP) is a serious clinical disorder involving the destruction of platelets by macrophages. Small molecule therapeutics are highly sought after to ease the burden on current therapies derived from human sources. Earlier, we discovered that dimers of five-membered heterocycles exhibited potential to inhibit phagocytosis of human RBCs by macrophages. Here, we reveal a structure–activity relationship of the bis-pyrazole class of molecules with –C–C–, –C–N– and –C–O– linkers, and their evaluation as inhibitors of phagocytosis of antibody-opsonized human RBCs as potential therapeutics for ITP. We have uncovered three potential candidates, 37 , 47 and 50 , all carrying a different linker connecting the two pyrazole moieties. Among these compounds, hydroxypyrazole derivative 50 is the most potent compound with an IC 50 of 14 ± 9 μM for inhibiting the phagocytosis of antibody-opsonized human RBCs by macrophages. None of the compounds exhibited significant potential to induce apoptosis in peripheral blood mononuclear cells (PBMCs). Current study has revealed specific functional features, such as up to 2-atom spacer arm and alkyl substitution at one of the N 1 positions of the bivalent pyrazole core to be important for the inhibitory activity.

Small molecules that mimic IFN-α epitopes that interact with the cell surface receptor, IFNAR, would be useful therapeutics. One such 8-amino acid region in IFN-α2, designated IRRP-1, was used to derive 11 chemical compounds that belong to 5 distinct chemotypes, containing the molecular features represented by the key residues Leu30, Arg33, and Asp35 in IRRP-1. Three of these compounds exhibited potential mimicry to IRRP-1 and, in cell based assays, as predicted, effectively inhibited IFNAR activation by IFN-α. Of these, compound 3 did not display cell toxicity and reduced IFN-α-inducible STAT1 phosphorylation and STAT-DNA binding. Based on physicochemical properties’ analyses, our data suggest that moieties with acidic p K a on the small molecule may be a necessary element for mimicking the carboxyl group of Asp35 in IRRP-1. Our data confirm the relevance of this strategy of molecular mimicry of ligand–receptor interaction domains of protein partners for small molecule drug discovery.

We discuss the statistical mechanics of a heterogeneous elastic rod with bending, twisting and stretching. Our model goes beyond earlier works where only homogeneous rods were considered in the limit of high forces and long lengths. Our methods allow us to consider shorter fluctuating rods for which boundary conditions can play an important role. We use our theory to study structural transitions in torsionally constrained DNA where there is coexistence of states with different effective properties. In particular, we examine whether a newly discovered left-handed DNA conformation called L-DNA is a mixture of two known states. We also use our model to investigate the mechanical effects of the binding of small molecules to DNA. For both these applications we make experimentally falsifiable predictions.

Cloning, over-expression, characterization and structural and functional analysis of two alkaline proteases from the newly isolated haloalkaliphilic bacteria: Oceanobacillus iheyensis O.M.A18 and Haloalkaliphilic bacterium O.M.E12 were carried out. The cloned protease genes were over-expressed in Escherichia coli within 6 h of the IPTG induction. The protease genes were sequenced and the sequence submitted to the GenBank with the accession numbers, HM219179 and HM219182 . The recombinant proteases were active in the range of pH 8–11 and temperature 30–50 °C. The amino acid sequences of the alkaline proteases displayed hydrophobic character and stable configurations. The amino acids Asp 141, His 171 and Ser 324 formed the catalytic triad, while Ile, Leu and Ser were other amino acid moieties present in the active site. The characteristics of the recombinant proteases were compared and found to be similar to their native counterparts. On the basis of the in-silico analysis and inhibitor studies, the enzymes were confirmed as serine proteases. The study hold significance as only limited enzymes from the haloalkaliphilic bacteria have been cloned, sequenced and analyzed for the structure and function analysis.

Metagenomics has opened new horizon to unlock the biotechnological potential for novel enzymes. An alkaline protease gene was obtained from the total environmental DNA extracted from a saline habitat. After cloning and sequencing, it was identified that the protease gene related to uncultivable bacteria (HM219181). The protease was over expressed at 6h of induction with optimum induction at 1mM IPTG and 27°C. The purified enzyme was characterized with respect to various factors; temperature, pH, NaCl and chemical denaturant. The sequence analysis indicated a hydrophobic tendency of the protein, while the predicted 3D structure indicated the enzyme as a serine protease.

We develop an elastic–isotropic rod model for twisted DNA in the plectonemic regime. We account for DNA elasticity, electrostatic interactions and entropic effects due to thermal fluctuations. We apply our model to single-molecule experiments on a DNA molecule attached to a substrate at one end, while subjected to a tensile force and twisted by a given number of turns at the other end. The free energy of the DNA molecule is minimized subject to the imposed end rotations. We compute values of the torsional stress, radius, helical angle and key features of the rotation–extension curves. We also include in our model the end loop energetic contributions and obtain estimates for the jumps in the external torque and extension of the DNA molecule seen in experiments. We find that, while the general trends seen in experiments are captured simply by rod mechanics, the details can be accounted for only with the proper choice of electrostatic and entropic interactions. We perform calculations with different ionic concentrations and show that our model yields excellent fits to mechanical data from a large number of experiments. Our methods also allow us to consider scenarios where we have multiple plectonemes or a series of loops forming in the DNA instead of plectonemes. For a given choice of electrostatic and entropic interactions, we find there is a range of forces in which the two regimes can coexist due to thermal motion.

We model long rod-like molecules, such as DNA and coiled-coil proteins, as one-dimensional continua with a multi-well stored energy function. These molecules suffer a structural change in response to large forces, characterized by highly typical force-extension behavior. We assume that the structural change proceeds via a moving folded/unfolded interface, or phase boundary, that represents a jump in strain and is governed by the Abeyaratne–Knowles theory of phase transitions. We solve the governing equations using a finite difference method with moving nodes to represent phase boundaries. Our model can reproduce the experimental observations on the overstretching transition in DNA and coiled-coils and makes predictions for the speed at which the interface moves. We employ different types of kinetic relations to describe the mobility of the interface and show that this leads to different classes of experimentally observed force-extension curves. We make connections with several existing theories, experiments and simulation studies, thus demonstrating the effectiveness of the phase transitions-based approach in a biological setting.

In Saccharomyces cerevisiae, non-coding RNAs, including cryptic unstable transcripts (CUTs), are subject to degradation by the exosome. The Trf4/5-Air1/2-Mtr4 polyadenylation (TRAMP) complex in S. cerevisiae is a nuclear exosome cofactor that recruits the exosome to degrade RNAs. Trf4/5 are poly(A) polymerases, Mtr4 is an RNA helicase, and Air1/2 are putative RNA-binding proteins that contain five CCHC zinc knuckles (ZnKs). One central question is how the TRAMP complex, especially the Air1/2 protein, recognizes its RNA substrates. To characterize the function of the Air1/2 protein, we used random mutagenesis of the AIR1/2 gene to identify residues critical for Air protein function. We identified air1-C178R and air2-C167R alleles encoding air1/2 mutant proteins with a substitution in the second cysteine of ZnK5. Mutagenesis of the second cysteine in AIR1/2 ZnK1–5 reveals that Air1/2 ZnK4 and -5 are critical for Air protein function in vivo. In addition, we find that the level of CUT, NEL025c, in air1 ZnK1–5 mutants is stabilized, particularly in air1 ZnK4, suggesting a role for Air1 ZnK4 in the degradation of CUTs. We also find that Air1/2 ZnK4 and -5 are critical for Trf4 interaction and that the Air1-Trf4 interaction and Air1 level are critical for TRAMP complex integrity. We identify a conserved IWRXY motif in the Air1 ZnK4-5 linker that is important for Trf4 interaction. We also find that hZCCHC7, a putative human orthologue of Air1 that contains the IWRXY motif, localizes to the nucleolus in human cells and interacts with both mammalian Trf4 orthologues, PAPD5 and PAPD7 (PAP-associated domain containing 5 and 7), suggesting that hZCCHC7 is the Air component of a human TRAMP complex.

We aimed to analyze the clinical, radiological, surgicopathological and clinical outcome data of patients who underwent surgery for central nervous system (CNS) hemangioblastoma (HBL) with or without von Hippel-Lindau (VHL) disease. The clinico pathological and radiological findings, management and clinical outcome of patients with CNS HBL (operated between 2000 and 2009) were analyzed retrospectively. The differences between sporadic and VHL-associated HBL were analyzed. Forty-nine patients (28 male, 21 female) underwent surgery for CNS hemangioblastoma. Thirty-nine patients (80%) harbored sporadic HBL whereas 10 (20%) had VHL disease. The mean age at diagnosis for VHL-associated HBL was 32 years when compared to 40 years in sporadic HBL. The lesions were solitary in 41 patients and multiple in eight. The cerebellum was the most common site of HBL (35/49, 71%). Six patients with sporadic and two with VHL disease had spinal lesions. On imaging (available in 43/49 patients), a cyst with a mural nodule was the most common finding, seen in 16 patients (37.2%) whereas nine patients (21%) had solid and cystic lesions. Clinical presentation, radiological features, and histomorphology of HBL with or without VHL disease were similar. Multiple cysts in the pancreas, kidney, broad ligament, epididymis, clear cell renal cell carcinoma, phaeochromocytoma and retinal angiomas were the visceral manifestations seen in patients with VHL disease. Of all patients with VHL disease, three required multiple surgeries for new lesions and one died of renal failure and sepsis. Among the patients with sporadic disease (31/39), two died of surgical complications, one died of postoperative sepsis, three were lost to follow-up and the remainder had resolution of symptoms at 1year following surgery. We concluded that the diagnosis of VHL disease is important as management is more difficult and lifelong follow-up and counseling are required in these patients and for their at-risk relatives.

We describe the mechanical behavior of isotropic fibrin networks at the macroscopic scale in terms of the nanoscale force response of fibrin molecules that are its basic building blocks. We show that the remarkable extensibility and compressibility of fibrin networks have their origins in the unfolding of fibrin molecules. The force-stretch behavior of a single fibrin fiber is described using a two-state model in which the fiber has a linear force-stretch relation in the folded phase and behaves like a worm-like-chain in the unfolded phase. The nanoscale force-stretch response is connected to the macro-scale stress-stretch response by means of the eight-chain model. This model is able to capture the macroscopic response of a fibrin network in uniaxial tension and appears remarkably simple given the molecular complexity. We use the eight-chain model to explain why fibrin networks have negative compressibility and Poisson’s ratio greater than one due to unfolding of fibrin molecules.

The variability of total electron content (TEC) over the crest of equatorial anomaly station Bhopal has been studied during the low solar activity period (2005–2006) using global positioning system (GPS) data. Diurnal variation of TEC is studied for different seasons. Interesting features like the winter anomaly, semiannual anomaly and noon bite out in TEC have been reported. GPS derived TEC is then compared with International Reference Ionosphere (IRI) 2001 model and the difference between predictions and observation is being studied. Using the variability index we have also studied the TEC variability for different seasons and also during quiet and disturbed conditions. A higher variability is observed on quiet days as compared to disturbed days during daytime and nighttime hours.

Hemangiopericytomas (HPC) of the central nervous system (CNS) are uncommon dural-based tumors that mimic meningiomas clinically and radiologically. Because there are few reports about these tumors from India, we aimed to study the clinico-pathological and immunohistochemical features of CNS HPC. During 2000 to 2008 all 23 patients diagnosed with HPC of CNS at our Institution were reviewed in the study (11 males and 12 females, mean age of 46 years). Clinical, radiological and histopathological features were reviewed. There were 14 patients with grade II and nine with grade III tumors. Immunohistochemistry with antibodies to epithelial membrane antigen (EMA), vimentin, S-100, CD34 and Ki-67 was done on routinely processed, paraffin-embedded sections of 20 tumors. All patients were EMA and S-100 negative, and vimentin positive. CD34 was positive in only five out of 20 patients. The mean Ki-67 labeling index was 4.25% in grade II tumors and 7.8% in grade III tumors. We concluded that HPC are distinct from meningiomas in morphology, immunohistochemistry and biologic behavior, although they resemble each other clinically and radiologically, HPCs need to be differentiated from meningiomas.

In this paper we present a theory to efficiently calculate the thermo-mechanical properties of fluctuating heterogeneous rods and chains. The central problem is to evaluate the partition function and free energy of a general heterogeneous chain under the assumption that its energy can be expressed as a quadratic function in the kinematic variables that characterize the configurations of the chain. We analyze the effects of various types of boundary conditions on the fluctuations of the rods and chains and show that our results are in agreement with recent work on homogeneous rods. The results for the heterogeneous chains are verified through Monte Carlo simulations. Finally, we consider a special heterogeneous chain with only two bending moduli and use it as a model to interpret experiments on partially unfolded protein oligomers.

We describe and solve a two-state kinetic model for the forced unfolding of proteins. The protein oligomer is modeled as a heterogeneous, freely jointed chain with two possible values of Kuhn length and contour length representing its folded and unfolded configurations. We obtain analytical solutions for the force–extension response of the protein oligomer for different types of loading conditions. We fit the analytical solutions for constant-velocity pulling to the force–extension data for ubiquitin and fibrinogen and obtain model parameters, such as Kuhn lengths and kinetic coefficients, for both proteins. We then predict their response under a linearly increasing force and find that our solutions for ubiquitin are consistent with a different set of experiments. Our calculations suggest that the refolding rate of proteins at low forces is several orders larger than the unfolding rate, and neglecting it can lead to lower predictions for the unfolding force, especially at high stretching velocities. By accounting for the refolding of proteins we obtain a critical force below which equilibrium is biased in favor of the folded state. Our calculations also suggest new methods to determine the distance of the transition state from the energy wells representing the folded and unfolded states of a protein.

We describe an analytic method for the computation of equilibrium shapes for two-dimensional vesicles characterized by a Helfrich elastic energy. We derive boundary value problems and solve them analytically in terms of elliptic functions and elliptic integrals. We derive solutions by prescribing length and area, or displacements and angle boundary conditions. The solutions are compared to solutions obtained by a boundary integral equation-based numerical scheme. Our method enables the identification of different configurations of deformable vesicles and accurate calculation of their shape, bending moments, tension, and the pressure jump across the vesicle membrane. Furthermore, we perform numerical experiments that indicate that all these configurations are stable minima.

The rapid development of single molecule experimental techniques in the last two decades has made it possible to accurately measure the force–extension response as well as the transverse fluctuations of individual rod-like macromolecules. This information is used in conjunction with a statistical mechanical model based on the treatment of the molecule as a fluctuating elastic rod to extract its bending and extension moduli. The models most commonly used to interpret the experimental data assume that the magnitude of the Brownian fluctuations are independent of the length of the macromolecule, an assumption that holds only in the asymptotic limit of infinitely long rods, and is violated in most experiments. As an alternative, we present a theoretical treatment of a finite length, fluctuating rod and determine its mechanical behavior by measuring the transverse Brownian fluctuations under the action of large stretching forces. To validate our theory, we have applied our methods to an experiment on short actin filaments whose force–extension relation is difficult to measure, but whose transverse deflections can be captured by current microscopy techniques. An important consequence of the short contour lengths is that the boundary conditions applied in the experiment affect the fluctuations and can no longer be neglected as is commonly done when interpreting data from force–extension measurements. Our theoretical methods account for boundary conditons and can therefore be deployed in conjunction with force–extension measurements to obtain detailed information about the mechanical response of rod-like macromolecules.