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Researcher profile

Sanjay Kumar

Sanjay Kumar contributes to research discovery and scholarly infrastructure.

ResearcherAffiliation not importedOpen to collaborate
cond-mat.softcond-mat.stat-mechBiological Physicsmath.DSmath.CVastro-ph.SRBiomoleculescond-mat.mes-hallmath.FAmath.GTComputer Visioncond-mat.mtrl-sciCryptography and Securityeess.ASMachine LearningMolecular Networksphysics.app-phphysics.flu-dynphysics.plasm-phphysics.soc-phSocial and Information NetworksSound

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Published work

37 published item(s)

preprint2026arXiv

Smart Railway Obstruction Detection System using IoT and Computer Vision

Railway track intrusions pose a critical safety challenge for Indian Railways, encompassing wildlife incursions and deliberate malicious obstructions. The December 2025 collision in Assam, in which seven elephants were killed by the Rajdhani Express, underscores the urgency of effective real-time detection. Existing solutions such as the optical fiber-based Gajraj system suffer from prohibitive costs (\$1000/km) and high false alarm rates, limiting deployment to only 20 of India's 101 elephant corridors. This paper proposes NETRA, a cost-effective, internet-independent intrusion detection system deployed on Raspberry Pi Zero W and Raspberry Pi 4 edge platforms. NETRA employs probabilistic sensor fusion integrating a PIR motion sensor and an HC-SR04 ultrasonic distance sensor with a tunable threshold (tau_c = 0.65), enabling event-driven camera activation that reduces unnecessary visual processing by 52%. Upon confirmed intrusion, edge-AI classification using MobileNet-SSD (Pi Zero) or YOLOv5 ONNX (Pi 4) identifies threats including humans, large animals, and track obstructions. Confirmed threats are transmitted via LoRa (868 MHz) to alert the locomotive driver within 2.4 seconds end-to-end. Experimental evaluation across 113 motion events demonstrated 95% detection accuracy with zero false alarms through probabilistic fusion, compared to 85% for binary methods. Raspberry Pi 4 with YOLOv5 achieved 83.5% elephant F1-score, a 5.6x improvement over Pi Zero's heuristic approach (14.8%). LoRa communication achieved 100% packet delivery across 1-2 km in field trials. NETRA reduces deployment cost by 75% (\$247/km vs \$1000/km for Gajraj) while providing unified detection of both wildlife and obstruction threats.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

Asymptotic additivity of the Turaev-Viro invariants for a family of $3$-manifolds

In this paper, we show that the Turaev-Viro invariant volume conjecture posed by Chen and Yang is preserved under gluings of toroidal boundary components for a family of $3$-manifolds. In particular, we show that the asymptotics of the Turaev-Viro invariants are additive under certain gluings of elementary pieces arising from a construction of hyperbolic cusped $3$-manifolds due to Agol. The gluings of the elementary pieces are known to be additive with respect to the simplicial volume. This allows us to construct families of manifolds with an arbitrary number of hyperbolic pieces such that the resultant manifolds satisfy an extended version of the Turaev-Viro invariant volume conjecture.

0 citations0 reviewsNo code linkedOpen access
preprint2021arXiv

Identifying Influential Nodes in Weighted Networks using k-shell based HookeRank Algorithm

Finding influential spreaders is a crucial task in the field of network analysis because of numerous theoretical and practical importance. These nodes play vital roles in the information diffusion process, like viral marketing. Many real-life networks are weighted networks, but relatively less work has been done for finding influential nodes in the case of weighted networks as compared to unweighted networks. In this paper, we propose a k-shell-based HookeRank (KSHR) algorithm to identify spreaders in weighted networks. First, we propose weighted k-shell centrality of the node u by using the k-shell value of $u$, the k-shell value of its neighbors ($v$), and edge weight ($w_{uv}$) between them. We model edges present in the network as springs and edge weights as spring constants. Based on the notion of Hooke's law of elasticity, we assume a force equal to the weighted k-shell value acts on each node. In this arrangement, we formulate the KSHR centrality of each node using associated weighted k-shell value and the equivalent edge weight by taking care of series and parallel combination of edges up to 3-hop neighbors from the source node. The proposed algorithm finds influential nodes that can spread the information to the maximum number of nodes in the network. We compare our proposed algorithm with popular existing algorithms and observe that it outperforms them on many real-life and synthetic networks suing Susceptible-Infected-Recovered (SIR) information diffusion model.

0 citations0 reviewsNo code linkedOpen access
preprint2020arXiv

Experimental investigations of acoustic curtains for hospital environment noise mitigations

The continuous increase of hospital noise levels has become a vital challenge for society. The complex soundscapes in the hospital produce unpleasant noise, which may exceed the prescribed noise level for the patients and healthcare professionals. Previous studies have reported that extended exposure to loud noise may cause auditory and nonauditory disorders in healthcare professionals, medical staff, and patients. Therefore, there is an increased interest for the design and fabrication of effective noise barriers for the hospital premises. Herein, we have performed the thorough experimental investigations on the acoustical performances for PVC coated polyester fabrics and 100 % pure PVC sheets. The performances of these potential acoustic curtains have found to be superior to that of existing acoustic curtains for hospitals. Also, the results showed that the sound transmission class rating of PVC curtains are much higher than the existing commercial acoustic curtains.

0 citations0 reviewsNo code linkedOpen access
preprint2020arXiv

Experimental investigations of psychoacoustic characteristics of household vacuum cleaners

Vacuum cleaners are one of the most widely used household appliances associated with unpleasant noises. Previous studies have indicated the severity of vacuum cleaner noise and its impact on the users nearby. The quantified measurements of the generated noise standalone are not sufficient for the selection or designing of vacuum cleaners. The human perception must also be included for a better assessment of the quality of sound. A hybrid approach known as psychoacoustics, which comprises subjective and objective evaluations of sounds, is widely used in recent times. This paper focuses on the experimental assessment of psychoacoustical matrices for household vacuum cleaners. Three vacuum cleaners with different specifications have been selected as test candidates, and their sound qualities have been analyzed. Besides, the annoyance index has been assessed for these vacuum cleaners.

0 citations0 reviewsNo code linkedOpen access
preprint2020arXiv

Magnetic reconnections in the presence of three-dimensional magnetic nulls and quasi-separatrix layers

Three-dimensional (3D) magnetohydrodynamic simulations are carried out to explore magnetic reconnections in the presence of 3D magnetic nulls and quasi-separatrix layers (QSLs). The initial magnetic fields are created by superposing uniform vertical magnetic fields of two different magnitudes on a linear force-free field. The interior of the numerical box contains two 3D nulls with separatrix domes separated by a quasi-separator (or hyperbolic flux tube) with QSLs. In the first simulation, the uniform vertical field is so large that the nulls are located at low heights and the domes are separate. Initially unbalanced Lorentz forces drive rotational flows that form strong electric currents and strong torsional fan reconnection at the 3D nulls and weak QSL reconnection at the hyperbolic flux tube. Flipping or slipping of field lines is observed in both cases. In the second simulation, with a weaker vertical field and larger domes, the separatrix surfaces meet at the central quasi-separator and their rotation drives stronger QSL reconnection than before.

0 citations0 reviewsNo code linkedOpen access
preprint2020arXiv

Transport and tumbling of polymers in viscoelastic shear flow

Polymers in shear flow are ubiquitous and we study their motion in a viscoelastic fluid under shear. Employing dumbbells as representative, we find that the center of mass motion follows: $\langle x^2_c(t) \rangle \sim \dotγ^2 t^{α+2}, ~0< α<1$, generalizing the earlier result: $\langle x^2_c(t) \rangle \sim \dotγ^2t^3 ~(α= 1)$. Motion of the relative coordinate, on the other hand, is quite intriguing in that $\langle x^2_r(t) \rangle \sim t^β$ with $β= 2(1-α)$ for small $α$. This implies nonexistence of the steady state. We remedy this pathology by introducing a nonlinear spring with FENE-LJ interaction and study tumbling dynamics of the dumbbell. The overall effect of viscoelasticity is to slow down the dynamics in the experimentally observed ranges of the Weissenberg number. We numerically obtain the characteristic time of tumbling and show that small changes in $α$ result in large changes in tumbling times.

0 citations0 reviewsNo code linkedOpen access
preprint2018arXiv

On Zeros and Growth of Solutions of Second Order Linear Differential Equations

For a second order linear differential equation $f&#39;&#39;+A(z)f&#39;+B(z)f=0$, with $ A(z)$ and $B(z)$ being transcendental entire functions under some restriction, we have established that all non-trivial solutions are of infinite order. In addition, we have proved that these solutions have infinite number of zeros. Also, we have extended these results to higher order linear differential equations.

0 citations0 reviewsNo code linkedOpen access
preprint2016arXiv

Effect of a Radiation Cooling and Heating Function on Standing Longitudinal Oscillations in Coronal Loops

Standing long-period (with the periods longer than several minutes) oscillations in large hot (with the temperature higher than 3 MK) coronal loops have been observed as the quasi-periodic modulation of the EUV and microwave intensity emission and the Doppler shift of coronal emission lines, and have been interpreted as standing slow magnetoacoustic (longitudinal) oscillations. Quasi-periodic pulsations of shorter periods, detected in thermal and non-thermal emissions in solar flares could be produced by a similar mechanism. We present theoretical modelling of the standing slow magnetoacoustic mode, showing that this mode of oscillation is highly sensitive to peculiarities of the radiative cooling and heating function. We generalised the theoretical model of standing slow magnetoacoustic oscillations in a hot plasma, including the effects of the radiative losses, and accounting for plasma heating. The heating mechanism is not specified and taken empirically to compensate the cooling by radiation and thermal-conduction. It is shown that the evolution of the oscillations is described by a generalised Burgers equation. Numerical solution of an initial value problem for the evolutionary equation demonstrates that different dependences of the radiative cooling and plasma heating on the temperature lead to different regimes of the oscillations, including growing, quasi-stationary and rapidly decaying. Our findings provide a theoretical foundation for probing the coronal heating function, and may explain the observations of decayless long-period quasi-periodic pulsations in flares. The hydrodynamic approach employed in this study should be considered with caution in the modelling of non-thermal emission associated with flares, as it misses potentially important non-hydrodynamic effects.

0 citations0 reviewsNo code linkedOpen access
preprint2016arXiv

Escaping set and Julia set of transcendental semigroups

We discuss the dynamics of semigroups of transcendental entire functions using Fatou-Julia theory and provide a condition for the complete invariance of escaping set and Julia set of transcendental semigroups. Results regarding limit functions and postsingular set are also derived. In addition, classes of hyperbolic and postsingularly bounded transcendental semigroups are given. We also provide certain criterion for non existence of wandering domains of transcendental semigroups.

0 citations0 reviewsNo code linkedOpen access
preprint2016arXiv

Periodically driven DNA: Theory and simulation

We propose a generic model of driven DNA under the influence of an oscillatory force of amplitude $F$ and frequency $ν$ and show the existence of a dynamical transition for a chain of finite length. We find that the area of the hysteresis loop, $A_{\rm loop}$, scales with the same exponents as observed in a recent study based on a much more detailed model. However, towards the true thermodynamic limit, the high-frequency scaling regime extends to lower frequencies for larger chain length $L$ and the system has only one scaling ($A_{\rm loop} \approx ν^{-1}F^2)$. Expansion of an analytical expression for $A_{\rm loop}$ obtained for the model system in the low-force regime revealed that there is a new scaling exponent associated with force ($A_{\rm loop} \approx ν^{-1}F^{2.5}$), which has been validated by high-precision numerical calculation. By a combination of analytical and numerical arguments, we also deduce that for large but finite $L$, the exponents are robust and independent of temperature and friction coefficient.

0 citations0 reviewsNo code linkedOpen access
preprint2016arXiv

Tangle Functors from Semicyclic Representations

Let $q$ be a $2N$th root of unity where $N$ is odd. Let $U_q(sl_2)$ denote the quantum group with large center corresponding to the lie algebra $sl_2$ with generators $E,F,K$, and $K^{-1}$. A semicyclic representation of $U_q(sl_2)$ is an $N$-dimensional irreducible representation $ρ:U_q(sl_2)\rightarrow M_N(\mathbb{C})$, so that $ρ(E^N)=aId$ with $a\neq 0$, $ρ(F^N)=0$ and $ρ(K^N)=Id$. We construct a tangle functor for framed homogeneous tangles colored with semicyclic representations, and prove that for $(1,1)$-tangles coming from knots, the invariant defined by the tangle functor coincides with Kashaev&#39;s invariant.

0 citations0 reviewsNo code linkedOpen access
preprint2016arXiv

Thickness and electric field dependent polarizability and dielectric constant in phosphorene

Based on extensive first principle calculations, we explore the thickness dependent effective di- electric constant and slab polarizability of few layer black phosphorene. We find that the dielectric constant in ultra-thin phosphorene is thickness dependent and it can be further tuned by applying an out of plane electric field. The decreasing dielectric constant with reducing number of layers of phosphorene, is a direct consequence of the lower permittivity of the surface layers and the in- creasing surface to volume ratio. We also show that the slab polarizability depends linearly on the number of layers, implying a nearly constant polarizability per phosphorus atom. Our calculation of the thickness and electric field dependent dielectric properties will be useful for designing and interpreting transport experiments in gated phosphorene devices, wherever electrostatic effects such as capacitance, charge screening etc. are important.

0 citations0 reviewsNo code linkedOpen access
preprint2015arXiv

Effective Doping of Monolayer Phosphorene by Surface Adsorption of Atoms for Electronic and Spintronic Applications

We study the effect of surface adsorption of 27 different adatoms on the electronic and magnetic properties of monolayer black phosphorus using density functional theory. Choosing a few representative elements from each group, ranging from alkali metals (group I) to halogens (group VII), we calculate the band structure, density of states, magnetic moment and effective mass for the energetically most stable location of the adatom on monolayer phosphorene. We predict that group I metals (Li, Na, K), and group III adatoms (Al, Ga, In) are effective in enhancing the n-type mobile carrier density, with group III adatoms resulting in lower effective mass of the electrons, and thus higher mobilities. Furthermore we find that the adatoms of transition metals Ti and Fe, produce a finite magnetic moment (1.87 and 2.31 $μ_B$) in monolayer phosphorene, with different band gap and electronic effective masses (and thus mobilities), which approximately differ by a factor of 10 for spin up and spin down electrons opening up the possibility for exploring spintronic applications.

0 citations0 reviewsNo code linkedOpen access
preprint2015arXiv

Rupture of DNA Aptamer: new insights from simulations

Base-pockets (non-complementary base-pairs) in a double-stranded DNA play a crucial role in biological processes. Because of thermal fluctuations, it can lower the stability of DNA, whereas, in case of DNA aptamer, small molecules e.g. adenosinemonophosphate(AMP), adenosinetriphosphate(ATP) etc, form additional hydrogen bonds with base-pockets termed as &#34;binding-pockets&#34;, which enhance the stability. Using the Langevin Dynamics simulations of coarse grained model of DNA followed by atomistic simulations, we investigated the influence of base-pocket and binding-pocket on the stability of DNA aptamer. Striking differences have been reported here for the separation induced by temperature and force, which require further investigation by single molecule experiments.

0 citations0 reviewsNo code linkedOpen access
preprint2015arXiv

Semigroups of transcendental entire functions and their dynamics

We study the dynamics of an arbitrary semigroup of transcendental entire functions using Fatou-Julia theory. Several results of the dynamics associated with iteration of a transcendental entire function have been extended to transcendental semigroups. We provide some conditions for connectivity of the Julia set of the transcendental semigroups. We also study finitely generated transcendental semigroups, abelian transcendental semigroups and limit functions of transcendental semigroups on its invariant Fatou components.

0 citations0 reviewsNo code linkedOpen access
preprint2015arXiv

The dynamics of semigroups of transcendental entire functions II

We introduce the concept of escaping set for semigroups of transcendental entire functions using Fatou-Julia theory. Several results of the escaping set associated with the iteration of one transcendental entire function have been extended to transcendental semigroups. We also investigate the properties of escaping sets for conjugate semigroups and abelian transcendental semigroups. Several classes of transcendental semigroups for which Eremenko&#39;s conjectures hold have been provided.

0 citations0 reviewsNo code linkedOpen access
preprint2014arXiv

Bifurcation in cell cycle dynamics regulated by p53

We study the regulating mechanism of p53 on the properties of cell cycle dynamics in the light of the proposed model of interacting p53 and cell cycle networks via p53. Irradiation (IR) introduce to p53 compel p53 dynamics to suffer different phases, namely oscillating and oscillation death (stabilized) phases. The IR induced p53 dynamics undergo collapse of oscillation with collapse time Δt which depends on IR strength. The stress p53 via IR drive cell cycle molecular species MPF and cyclin dynamics to different states, namely, oscillation death, oscillations of periods, chaotic and sustain oscillation in their bifurcation diagram. We predict that there could be a critical Δt_c induced by p53 via IR_c, where, if Δt < Δt_c the cell cycle may come back to normal state, otherwise it will go to cell cycle arrest (apoptosis).

0 citations0 reviewsNo code linkedOpen access
preprint2014arXiv

On dynamics of composite entire functions and singularities

We consider the dynamical properties of transcendental entire functions and their compositions. We give several conditions under which Fatou set of a transcendental entire function $f$ coincide with that of $f\circ g,$ where $g$ is another transcendental entire function. We also prove some result giving relationship between singular values of transcendental entire functions and their compositions.

0 citations0 reviewsNo code linkedOpen access
preprint2014arXiv

The dynamics of semigroups of transcendental entire functions I

We consider the dynamics associated with an arbitrary semigroup of transcendental entire functions. Fatou-Julia theory is used to investigate the dynamics of these semigroups. Several results of the dynamics associated with iteration of a transcendental entire function have been extended to transcendental semigroup case. We also investigate the dynamics of conjugate semigroups, Abelian transcendental semigroups and wandering and Baker domains of transcendental semigroups.

0 citations0 reviewsNo code linkedOpen access
preprint2013arXiv

A note on Schwarzian derivatives and normal families

We establish a criterion for local boundedness and hence normality of a family $\F$ of analytic functions on a domain $D$ in the complex plane whose corresponding family of derivatives is locally bounded. Furthermore we investigate the relation between domains of normality of a family $\F$ of meromorphic functions and its corresponding Schwarzian derivative family. We also establish some criterion for the Schwarzian derivative family of a family $\F$ of analytic functions on a domain $D$ in the complex plane to be a normal family.

0 citations0 reviewsNo code linkedOpen access
preprint2013arXiv

Dynamical phase transition of a periodically driven DNA

Replication and transcription are two important processes in living systems. To execute such processes, various proteins work far away from equilibrium in a staggered way. Motivated by this, aspects of hysteresis during unzipping of DNA under a periodic drive in non-equilibrium conditions are studied. A steady state phase diagram of a driven DNA is proposed which is experimentally verifiable. As a two state system, we also compare the results of DNA with that of an Ising magnet under an asymmetrical variation of magnetic field.

0 citations0 reviewsNo code linkedOpen access
preprint2013arXiv

Scaling of hysteresis loop of interacting polymers under a periodic force

Using Langevin Dynamics simulations, we study a simple model of interacting-polymer under a periodic force. The force-extension curve strongly depends on the magnitude of the amplitude $(F)$ and the frequency ($ν$) of the applied force. In low frequency limit, the system retraces the thermodynamic path. At higher frequencies, response time is greater than the external time scale for change of force, which restrict the biomolecule to explore a smaller region of phase space that results in hysteresis of different shapes and sizes. We show the existence of dynamical transition, where area of hysteresis loop approaches to a large value from nearly zero area with decreasing frequency. The area of hysteresis loop is found to scale as $F^α ν^β$ for the fixed length. These exponents are found to be the same as of the mean field values for a time dependent hysteretic response to periodic force in case of the isotropic spin.

0 citations0 reviewsNo code linkedOpen access
preprint2013arXiv

Statistical Mechanics of DNA unzipping under periodic force: Scaling behavior of hysteresis loop

A simple model of DNA based on two interacting polymers has been used to study the unzipping of a double stranded DNA subjected to a periodic force. We propose a dynamical transition, where without changing the physiological condition, it is possible to bring DNA from the zipped/unzipped state to a new dynamic (hysteretic) state by varying the frequency of the applied force. Our studies reveal that the area of the hystersis loop grows with the same exponents as of the isotropic spin systems. These exponents are amenable to verification in the force spectroscopic experiments.

0 citations0 reviewsNo code linkedOpen access
preprint2012arXiv

Effect of shear force on the separation of double stranded DNA

Using the Langevin Dynamics simulation, we have studied the effects of the shear force on the rupture of short double stranded DNA at different temperatures. We show that the rupture force increases linearly with the chain length and approaches to the asymptotic value in accordance with the experiment. The qualitative nature of these curves almost remains same for different temperatures but with a shift in the force. We observe three different regimes in the extension of covalent bonds (back bone) under the shear force.

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preprint2012arXiv

Stretching force dependent transitions in single stranded DNA

Mechanical properties of DNA, in particular their stretch dependent extension and their loop formation characteristics, have been recognized as an effective probe for understanding the possible biochemical role played by them in a living cell. Single stranded DNA (ssDNA), which, till recently was presumed to be an simple flexible polymer continues to spring surprises. Synthetic ssDNA, like polydA (polydeoxyadenosines) has revealed an intriguing force-extension (FX) behavior exhibiting two plateaus, absent in polydT (polydeoxythymidines) for example. Loop closing time in polydA had also been found to scale exponentially with inverse temperature, unexpected from generic models of homopolymers. Here we present a new model for polydA which incorporates both a helix-coil transition and a over-stretching transition, accounting for the two plateaus. Using transfer matrix calculation and Monte-Carlo simulation we show that the model reproduces different sets of experimental observations, quantitatively. It also predicts interesting reentrant behavior in the temperature-extension characteristics of polydA, which is yet to be verified experimentally.

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preprint2010arXiv

Shock-driven hydrodynamic instability induced by particle seeding

We report an experimental observation of an instability in gas of constant density (air) with an initial non-uniform seeding of small droplets that develops as a planar shock wave passes through the gas-droplet mix. The seeding non-uniformity is produced by vertical injection of a slow-moving jet of air pre-mixed with glycol droplets into the test section of a shock tube, with the plane of the shock parallel to the axis of the jet. After the shock passage, we observe development of two counter-rotating vortices in the plane normal to that axis. The physical mechanism of the instability we observe is peculiar to multiphase flow, where the shock acceleration causes the second (embedded) phase to move with respect to the embedding medium. With sufficient seeding concentration, this leads to entrainment of the embedding phase that acquires a relative velocity dependent on the initial seeding, resulting in vortex formation in the flow.

0 citations0 reviewsNo code linkedOpen access
preprint2009arXiv

Effects of Molecular Crowding on stretching of polymers in poor solvent

We consider a linear polymer chain in a disordered environment modeled by percolation clusters on a square lattice. The disordered environment is meant to roughly represent molecular crowding as seen in cells. The model may be viewed as the simplest representation of biopolymers in a cell. We show the existence of intermediate states during stretching arising as a consequence of molecular crowding. In the constant distance ensemble the force-extension curves exhibit oscillations. We observe the emergence of two or more peaks in the probability distribution curves signaling the coexistence of different states and indicating that the transition is discontinuous unlike what is observed in the absence of molecular crowding.

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preprint2009arXiv

Force induced unfolding of bio-polymers in a cellular environment: A model study

Effect of molecular crowding and confinement experienced by protein in the cell during unfolding has been studied by modeling a linear polymer chain on a percolation cluster. It is known that internal structure of the cell changes in time, however, they do not change significantly from their initial structure. In order to model this we introduce the correlation among the different disorder realizations. It was shown that the force-extension behavior for correlated disorder in both constant force ensemble (CFE) and constant distance ensemble (CDE) is significantly different than the one obtained in absence of molecular crowding.

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preprint2009arXiv

Stretching of a single-stranded DNA: Evidence for structural transition

Recent experiments have shown that the force-extension (F-x) curve for single-stranded DNA (ssDNA) consisting only of adenine [poly(dA)] is significantly different from thymine [poly(dT)]. Here, we show that the base stacking interaction is not sufficient to describe the F-x curves as seen in the experiments. A reduction in the reaction co-ordinate arising from the formation of helix at low forces and an increase in the distance between consecutive phosphates of unstacked bases in the stretched state at high force in the proposed model, qualitatively reproduces the experimentally observed features. The multi-step plateau in the F-x curve is a signature of structural change in ssDNA.

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preprint2007arXiv

Effects of Eye-phase in DNA unzipping

The onset of an &#34;eye-phase&#34; and its role during the DNA unzipping is studied when a force is applied to the interior of the chain. The directionality of the hydrogen bond introduced here shows oscillations in force-extension curve similar to a &#34;saw-tooth&#34; kind of oscillations seen in the protein unfolding experiments. The effects of intermediates (hairpins) and stacking energies on the melting profile have also been discussed.

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preprint2007arXiv

Force induced conformational transition in a system of interacting stiff polymer: Application to unfolding

We consider a stiff polymer chain in poor solvent and apply a force at one end of the chain. We find that by varying the stiffness parameter, polymer undergoes a transition from the globule state to the folded like state. The conformation of folded state mimics the $β$-sheet as seen in titin molecule. Using exact enumeration technique, we study the extension-force and force-temperature diagrams of such a system. Force-temperature diagram shows the re-entrance behaviour for flexible chain. However, for stiff chain this re-entrance behaviour is absent and there is an enhancement in $θ$-temperature with the rise of stiffness. We further propose that the internal information about the frozen structure of polymer can be read from the distribution of end-to-end distance which shows saw-tooth like behaviour.

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