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A Biophysical Model Uncovers the Size Distribution of Migrating Cell Clusters across Cancer Types
No full textMigration from the primary tumor is a crucial step in the metastatic cascade. Cells with various degrees of adhesion and motility migrate and are launched into the bloodstream as single circulating tumor cells (CTC) or multicellular CTC clusters. The frequency and size distributions of these clusters have been recently measured, but the underlying mechanisms enabling these different modes of migration remain poorly understood. We present a biophysical model that couples the phenotypic plasticity enabled by the epithelial-mesenchymal transition (EMT) and cell migration to explain the modes of individual and collective cancer cell migration. This reduced physical model captures how cells undergo a transition from individual migration to collective cell migration and robustly recapitulates CTC cluster fractions and size distributions observed experimentally across several cancer types, thus suggesting the existence of common features in the mechanisms underlying cancer cell migration. Furthermore, we identify mechanisms that can maximize the fraction of CTC clusters in circulation. First, mechanisms that prevent a complete EMT and instead increase the population of hybrid epithelial/mesenchymal (E/M) cells are required to recapitulate CTC size distributions with large clusters of 5 to 10 cells. Second, multiple intermediate E/M states give rise to larger and heterogeneous clusters formed by cells with different epithelial-mesenchymal traits. Overall, this biophysical model provides a platform to continue to bridge the gap between the molecular and biophysical regulation of cancer cell migration and highlights that a complete EMT might not be required for metastasis. Significance: A biophysical model of cancer cell invasion integrates phenotypic heterogeneity and cell migration to interpret experimental observations of circulating tumor cell clusters and provides new predictions
Fluctuation relations for flow-driven trapped colloids and implications for related polymeric systems
No full textThis paper is a theoretical study of the stochastic thermodynamics of a single, optically trapped particle that is initially in equilibrium at temperature T and is then subjected to a steady 2D extensional flow. Specifically, it is an attempt to show how fluctuation theorems arise in systems governed by thermal noise and the opposing effects of harmonic confinement and hydrodynamic driving. Among the paper's findings are the following: (i) that at long times, following the imposition of the flow, the system settles into an equilibrium stationary state that obeys detailed balance and that is characterized by an effective Boltzmann potential, such that the free energy change Delta F between the initial and final states is determined by the ratio of the corresponding partition functions, (ii) that the work done in the process w and the accompanying change in total entropy of system and surroundings, Delta S-tot, both satisfy fluctuation theorems, the first the Jarzynski equality ⟨e(-w/kBT)⟩ = e(-Delta F/kBT), and the second the integral fluctuation theorem, ⟨e(-Delta Stot/kB)⟩ = 1, and (iii) that under a frame-invariant version of thermodynamics used to describe flow-driven particle motion, the work done W satisfies the Bochkov-Kuzovlev relation, ⟨e(-W/kBT)⟩ = 1, while the associated total entropy change continues to satisfy the integral fluctuation theorem. These results have an immediate bearing on prior results from this lab on the dynamics of flow-driven polymers; in particular, they highlight the need to revise a number of our earlier conclusions
Partial informational correlation-based band selection for hyperspectral image classification
No full textHyperspectral (HS) data are enriched with highly resourceful abundant spectral bands. However, analyzing and interpreting these ample amounts of data is a challenging task. Optimal spectral bands should be chosen to address the issue of redundancy and to capitalize on the absolute advantages of HS data. Partial informational correlation (PIC)-based band selection approach is proposed for feature selection-based classification of HS images. PIC measure appears to be more skillful compared to mutual information for estimation of nonparametric conditional dependency. In this proposed approach, HS narrow bands are selected in an innovative way utilizing the PIC. This approach is more efficient in terms of computational time and in generalizing the applicability of selected spectral bands. Further, these optimal spectral bands are used in the support vector machine (SVM) and random forest classifier for performance evaluation. The optimum performance is accomplished with SVM classifier, and the achieved average overall accuracies are 82.89%, 91.4%, and 91.29% for the Indian Pines, Pavia University, and Botswana datasets, respectively. The proposed band selection approach is compared with different state-of-the-art techniques. This methodology improves the classification performances compared to the existing techniques, and the advancement in performances is proven to be statistically significant
Two-Dimensional Algebraic Codes for Multiple Burst Error Correction
No full textWe construct native binary 2D binary cyclic codes capable of correcting multiple occurrences of multiple non-overlapping <italic>pre-defined</italic> 2D error shapes using frequency domain techniques. The starting location of each error shape is determined using a novel decoding algorithm based on a careful selection of the common zero set. The proposed code construction is generic and offers <italic>superior</italic> coding rates compared to the native 2D BCH code with the same error correction ability
Storm characteristics and precipitation estimates of monsoonal clouds using C-band polarimetric radar over Northwest India
No full textStorm is a convective cell much smaller than a mesoscale convective system (MCS) but typically larger than a cumulonimbus cloud and heavy precipitation and lightning are often associated with it. Storms contribute major fraction of the convective precipitation in MCSs. Storm characteristics and precipitation estimates around New Delhi (28.6 degrees N, 77.2 degrees E; an Indian land location) during June-September period of the year 2013 are reported here using data of C-band polarimetric Doppler weather radar. Storms, defined based on radar reflectivity thresholds (30 dBZ for simple storms and 40 dBZ for intense storms), are tracked and their properties are extracted. Our results show that about 80% of storms exist for 1 h or less. The areas of 90% of simple storms are less than 100 km(2) and the largest area averaged over storm lifespan does not exceed 400 km(2). The majority of storms (> 80%) move with speeds less than 30 km h(-1). About 60-65% of simple/intense storms have echo top heights between 6 and 10 km, while only few of them exceed 17 km. The values of average thickness of simple and intense storms lie between similar to 2-10 and similar to 1-7 km, respectively. It is not the vertical extent of a storm but its area-time integral that correlates better with the total precipitation amount. Around the New Delhi area, daily accumulated precipitation derived from relations incorporating polarimetric variables is in good agreement with the rain gauge measurements while that obtained from relations based on radar reflectivity factor (Z(h)) alone highly underestimates precipitation. This suggests that polarimetric capability is needed in Doppler weather radars to get the realistic precipitation estimates. The mean precipitation water content derived from Z(h) (similar to 0.96 g m(-3)) is about 30-40% less compared to that derived from polarimetric relations. Our findings on storm properties have implications for cloud parameterizations and in short-term weather forecasting
Numerical investigation of an evaporating meniscus in a heated capillary slot
No full textThis paper numerically studies heat transfer and fluid flow from an evaporating meniscus of a wetting fluid within a heated capillary. A simplified steady state mathematical model is developed for predicting the wicking height of the meniscus and the evaporation mass flow rate which includes: (1) one-dimensional flow and energy equations for the liquid and vapor regions, (2) one-dimensional model for the evaporating meniscus region, and (3) two-dimensional energy equation for the capillary wall. Three parameters, namely, apparent contact angle, cumulative heat transfer, and evaporating meniscus height characterize the evaporating meniscus region. In this paper, the apparent contact angle in the evaporating meniscus is uniquely deduced from the meniscus curvature at the centre of the capillary using the thickness profile obtained from standard extended meniscus theory (which includes the evaporating thin film and bulk meniscus regions). Correlations are obtained for the cumulative heat transfer, apparent contact angle and evaporating meniscus height as a function of the difference between the wall and saturation temperatures from the evaporating thin film theory for the meniscus region, which is called as micromodel. The macroscopic model accounts for wall heat conduction and heat transfer with fluid flow in the liquid and vapor regions. The micromodel deals with heat transfer and fluid flow in the evaporating meniscus region. In this paper, a novel scheme to link the ``macroscopic'' momentum and energy equations in the capillary slot and the evaporating meniscus through the correlations developed above is proposed. Using this numerical model, the wicking height and the evaporation mass flow rate are estimated and the results are compared with previously conducted experiments. The trends in the numerical results of the mathematical model correlate reasonably well with the experimental data
Enhanced all-optical cavity-tuning using graphene
No full textAll-optical tuning of the resonance of an optical cavity is used to realise optical signal-processing including modulation, switching, and signal-routing. The tuning of optical resonance is dictated by the two primary effects induced by optical absorption: charge-carrier-generation and heat-generation. Since these two effects shift the resonance in opposite directions in a pure silicon-on-insulator (SOI) micro-ring resonator as well as in a graphene-on-SOI system, the efficiency and the dynamic range of all-optical resonance-tuning is limited. In this work, in a graphene-oxide-silicon waveguide system, we demonstrate an exceptional resonance-tuning-efficiency of 300 pm/mW (0.055 pi/mW), with a large dynamic range of 1.2 nm (0.22 pi) from linear resonance to optical bistability. The dynamics of the resonance-tuning indicates that the superior resonance-tuning is due to large linear-absorption-induced thermo-optic effect. Competing free-carrier dispersion is suppressed as a result of the large separation between graphene and the silicon core. This work reveals new ways to improve the performance of graphene-on-waveguide systems in all-optical cavity-tuning, low-frequency all-optical modulation, and switching
On the Regge limit of Fishnet correlators
No full textWe study the Regge trajectories of the Mellin amplitudes of the 0-,1- and 2-magnon correlators of the Fishnet theory. Since fishnet theory is both integrable and conformal, the correlation functions are known exactly. We find that while for 0 and 1 magnon correlators, the Regge poles can be exactly determined as a function of coupling, 2-magnon correlators can only be dealt with perturbatively. We evaluate the resulting Mellin amplitudes at weak coupling, while for strong coupling we do an order of magnitude calculation
Magnetic Properties of MFeCrO4 (M = Co/Ni) Prepared by Solution Combustion Method
No full textSingle phase MFeCrO4 (M = Co/Ni) nanosized samples are prepared by solution combustion method using glycine as fuel. Lattice parameter obtained after Rietveld refinement of the powder x-ray diffraction pattern of CoCrFeO4 and NiCrFeO4 samples are 8.374 and 8.325 angstrom and corresponding crystallite sizes are 40 and 27 nm, respectively. FTIR spectra of both samples show tetrahedral and octahedral metal oxygen bond stretching peaks at 596 and 488 cm(-1), indicating spinel phase formation. DC magnetisation study indicates that both samples are ferrimagnetic at room temperature, with CoCrFeO4 having a higher value of saturation magnetisation. Mossbauer spectra indicate the presence of magnetic relaxation in the samples. Also, the strength of interaction with nearest neighbour Fe3+ cations is higher in NiCrFeO4
Automatic schemes for including generator Q and transformer tap limits in the fast decoupled load flow method
No full textThis study proposes a modified formulation for the popular fast decoupled load flow method to facilitate automatic incorporation of reactive power flow related constraints, i.e. generator reactive power and in-phase transformer tap limits. This formulation has been developed by viewing each device constraint as a set of complementary conditions and adopting the complementarity framework to define one equation to represent this set. The original set of load flow equations is augmented with this set of new equations representing the device constraints and solved to get the adjusted solutions directly. This approach is a significant departure from all the earlier approaches. The earlier approaches generally adopt a two-stage scheme. In the first stage, an approximate unadjusted solution is obtained and in the next stage, adjustments are attempted by ad hoc schemes. The new formulation presented here permits handling both the reactive power related constraints simultaneously. However, it can also be used in situations where only one type of adjustment is needed. Two alternate algorithms in complementarity framework based on mixed complementarity problem and non-linear complementarity problem formulations are presented here. Simulation results are presented to provide evidence of the impressive performance of the new algorithms as compared with the existing ones