Amit Kumar

• Analyst at Tata Consultancy Services Limited

In this paper, we study the weighted $k$-server problem on the uniform metric in both the offline and online settings. We start with the offline setting. In contrast to the (unweighted) $k$-server problem which has a polynomial-time solution using min-cost flows, there are strong computational lower bounds for the weighted $k$-server problem, even...

This new investigation deals with the synthesis of an organic-inorganic nanohybrid using SNC with magnificent flower bud-shaped ZnO, termed SNC-ZnO by precipitation method. The nanohybrid (with concentrations 1 wt%, 3 wt%, and 5 wt%) was in situ incorporated into the PLA matrix to prepare the electrospun solution. The functionalized PLA composite n...

This present study demonstrated the preparation of a highly crystalline anatase (ana) form of titanium oxide (TiO 2 ) doped silk nanocrystal (SNC) nanohybrid (ana-TCS) of diameter (7.5 ± 1.4 nm) by the sol–gel method using titanium (IV) butoxide as the hydrolysis material. This prepared nanohybrid with surface hydroxyl groups acted as a co-initiato...

Acellular scaffold from buffalo pericardium was prepared by continuously stirring the tissues in 4% sodium deoxycholate for 2–4 h, followed by treatment with 2000 Kunitz units DNase–I suspended in 1 M sodium chloride solution for 2 h. The process was repeated twice. The acellular goat pericardium was prepared by continuously stirring the tissues in...

An environmentally friendly non-woven nanotextile has been prepared using enantiomeric pairs of poly (lactic acid) PLA by electrospinning technique. Solution blending of synthesized high molecular weight (⁓10⁵ Da) poly (L-lactic acid) PLLA and poly (D-lactic acid), PDLA for prolonged time stirring produce solely stereocrystallites (sc). The high cr...

We study the $k$-server problem with time-windows. In this problem, each request $i$ arrives at some point $v_i$ of an $n$-point metric space at time $b_i$ and comes with a deadline $e_i$. One of the $k$ servers must be moved to $v_i$ at some time in the interval $[b_i, e_i]$ to satisfy this request. We give an online algorithm for this problem wit...

The vector-balancing problem is a fundamental problem in discrepancy theory: given T vectors in $[-1,1]^n$, find a signing $\sigma(a) \in \{\pm 1\}$ of each vector $a$ to minimize the discrepancy $\| \sum_{a} \sigma(a) \cdot a \|_{\infty}$. This problem has been extensively studied in the static/offline setting. In this paper we initiate its study...

This study endeavoured to explore and fabricate antiviral and antibacterial facemasks using zinc (oligo-lactate) (ZL), developed through a microwave synthesis technique. The prepared nano-fabric layer has excellent antiviral and antibacterial properties against Newcastle Disease Virus (NDV) and E. coli and S. aureus, respectively. Thermogravimetric...

We consider online scheduling to minimize weighted completion time on related machines, where each job consists of several tasks that can be concurrently executed. A job gets completed when all its component tasks finish. We obtain an $O(K^3 \log^2 K)$-competitive algorithm in the non-clairvoyant setting, where $K$ denotes the number of distinct ma...

The Metric $k$-median problem over a metric space $(\mathcal{X}, d)$ is defined as follows: given a set $L \subseteq \mathcal{X}$ of facility locations and a set $C \subseteq \mathcal{X}$ of clients, open a set $F \subseteq L$ of $k$ facilities such that the total service cost, defined as $\Phi(F, C) \equiv \sum_{x \in C} \min_{f \in F} d(x, f)$, i...

We consider the online carpooling problem: given $n$ vertices, a sequence of edges arrive over time. When an edge $e_t = (u_t, v_t)$ arrives at time step $t$, the algorithm must orient the edge either as $v_t \rightarrow u_t$ or $u_t \rightarrow v_t$, with the objective of minimizing the maximum discrepancy of any vertex, i.e., the absolute differe...

This book discusses synthesis and characterization of sustainable polymers. The book covers opportunities and challenges of using sustainable polymers to replace existing petroleum based feedstock. This volume provides insights into the chemistry of polymerization, and discusses tailoring the properties of the polymers at the source in order fit re...

In the modern age, humans with their demanding nature along with comfort and fashion are also oriented toward flourishing functional textile products which have led researchers to focus toward the development of smart textiles. Scientists are now trying to introduce extraordinary properties like durable pressing performance, ultraviolet resistance,...

Sutures are known to facilitate wound healing and recently, a significant attention has been laid on the development of different classes of materials, their properties to enhance tissue approximation and wound closure. The advancements in the suture technology have introduced different types of sutures such as barbed sutures, antimicrobial sutures...

The present study describes the fabrication and characterization of eco-friendly composites based on high density polyethylene (HDPE), poly (lactic acid) (PLA) with microcrystalline cellulose (MCC) fibres via melt extrusion followed by injection moulding. The morphology of PLA in both HDPE/PLA blends and HDPE/MCC fibres composites was irregular and...

We give a 3-pass, polylog-space streaming PTAS for the constrained binary $k$-means problem and a 4-pass, polylog-space streaming PTAS for the binary $\ell_0$-low rank approximation problem. The connection between the above two problems has recently been studied. We design a streaming PTAS for the former and use this connection to obtain streaming...

We show that the span of $\Omega(\frac{1}{\varepsilon^4})$ rows of any matrix $A \subset \mathbb{R}^{n \times d}$ sampled according to the length-squared distribution contains a rank-$1$ matrix $\tilde{A}$ such that $||A - \tilde{A}||_F^2 \leq (1 + \varepsilon) \cdot ||A - \pi_1(A)||_F^2$, where $\pi_1(A)$ denotes the best rank-$1$ approximation of...

We generalise the results of Bhattacharya et al. (Journal of Computing Systems, 62(1):93-115, 2018) for the list-$k$-means problem defined as -- for a (unknown) partition $X_1, ..., X_k$ of the dataset $X \subseteq \mathbb{R}^d$, find a list of $k$-center sets (each element in the list is a set of $k$ centers) such that at least one of $k$-center s...

We consider the online problem of scheduling jobs on identical machines, where jobs have precedence constraints. We are interested in the demanding setting where the jobs sizes are not known up-front, but are revealed only upon completion (the non-clairvoyant setting). Such precedence-constrained scheduling problems routinely arise in map-reduce an...

This study focuses on novel fabrication of bionanocomposites of poly lactic acid (PLA) and crystalline silk nanodisc (CSN) via melt extrusion process aiming its application in high strength biomedical research and also for high gas barrier food packaging. We report novel fabrication of crystalline silk nanodiscs using wild silk variety, Antheraea a...

The present work investigates the effect of novel biofiller, ‘crystalline silk nano-discs (CSNs)’, on thermal stability and crystallization behaviour of melt-processed poly (lactic acid) (PLA)/CSN nanobiocomposites which are very much important for polymer processing. The PLA/CSN nanobiocomposites are obtained through melt extrusion technique. Ther...

Exacerbated environmental concerns about petroleum‐based plastics provide the impetus to foster sustainable poly(lactic acid) (PLA) based food packaging. Nonetheless, PLA has its foibilities such as its brittleness, higher gas permeability, and slow crystallization. With the intent to mitigate the above shortcomings, we report a maiden effort for t...

Graphene nanoscrolls (GNS), due to their remarkably interesting properties, have attracted significant interest with applications in various engineering sectors. However, uncontrolled morphologies, poor yield and low quality GNS produced through traditional routes are major challenges associated. We demonstrate sustainable approach of utilizing bio...

In the weighted flow-time problem on a single machine, we are given a set of n jobs, where each job has a processing requirement p_j, release date r_j and weight w_j. The goal is to find a preemptive schedule which minimizes the sum of weighted flow-time of jobs, where the flow-time of a job is the difference between its completion time and its rel...

The classical center based clustering problems such as $k$-means/median/center assume that the optimal clusters satisfy the locality property that the points in the same cluster are close to each other. A number of clustering problems arise in machine learning where the optimal clusters do not follow such a locality property. Consider a variant of...

In this work, novel biodegradable crystalline silk nano‐discs (CSNs) having a disc‐like morphology have been utilized for fabrication of poly(lactic acid) (PLA) nanocomposites by melt‐extrusion. The main focus is to investigate the effect of CSN on isothermal melt crystallization kinetics, spherulitic growth rates, morphology, and hydrolytic degrad...

The notion of competitive ratio often turns out to be too pessimistic for the analysis of online algorithms. Although the approach of resource augmentation (introduced by Kalyanasundaram and Pruhs) has been very successful in dealing with a variety of objective functions, there are problems for which even a (arbitrary) constant speedup cannot lead...

This study explores the plasticizing effect of coconut oil (CO) on PLA for evaluating its suitability for flexible packaging. Changes in morphological, mechanical, thermal, rheological, barrier and optical properties of melt compounded Poly(lactic acid)–Coconut oil (PLA–CO) blend were investigated by varying the mixing ratio. Water vapor permeabili...

In this paper, we give new results for the set cover problem in the fully dynamic model. In this model, the set of “active” elements to be covered changes over time. The goal is to maintain a near-optimal solution for the currently active elements, while making few changes in each timestep. This model is popular in both dynamic and online algor...

In this paper we initiate the study of the heterogeneous capacitatedk-center problem: we are given a metric space \(X = (F \cup C, d)\), and a collection of capacities. The goal is to open each capacity at a unique facility location in F, and also to assign clients to facilities so that the number of clients assigned to any facility is at most the...

Ashtiani et al. proposed a Semi-Supervised Active Clustering framework (SSAC), where the learner is allowed to make adaptive queries to a domain expert. The queries are of the kind "do two given points belong to the same optimal cluster?" There are many clustering contexts where such same-cluster queries are feasible. Ashtiani et al. exhibited the...

In this study, we successfully demonstrate single step industrially scalable reactive extrusion of polylactic acid(PLA)/cellulose nanocrystal(CNC) based cast films which leads to reduced necking, improved processability, melt-strength, and rheological behaviour. PLA chains grafted onto CNCs, formed cross-linked gel-like structures of high molecular...

In this paper we initiate the study of job scheduling on related and unrelated machines so as to minimize the maximum flow time or the maximum weighted flow time (when each job has an associated weight). Previous work for these metrics considered only the setting of parallel machines, while previous work for scheduling on unrelated machines only co...

In this paper we initiate the study of the heterogeneous capacitated $k$-center problem: given a metric space $X = (F \cup C, d)$, and a collection of capacities. The goal is to open each capacity at a unique facility location in $F$, and also to assign clients to facilities so that the number of clients assigned to any facility is at most the capa...

This work reports the fabrication of four varieties of cellulose nanocrystals(CNCs) through hydrolysis with different acids which leads to their tailored physical, structural, thermal and surface characteristics. The hydroxyl groups of CNCs are substituted with anionic-moieties from acid which alters its interfacial interaction with PLA matrix, as...

This paper reports a single step co-precipitation method for fabrication of magnetic cellulose nanocrystals (MGCNCs) with high content of iron oxide nanoparticles (~51 wt. % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopic studies confirmed that the hydroxyl gro...

Significance Clinical hematologists have long known that antiinflammatory glucocorticoids such as dexamethasone and blood pressure-supporting catecholamines such as epinephrine cause leukocytes to demarginate from the vascular wall and microvasculature into the main circulation, significantly elevating the effective white blood cell count. Canonica...

This paper reports a single step reactive extrusion process for fabrication of thermally stable, polylactic acid grafted cellulose nanocrystal(PLA-g-CNC) nanocomposite films using dicumyl peroxide as crosslinking agent. PLA-g-CNC nanocomposites were recycled without significant breakage in the molecular structure of PLA. The grafted PLA chains shie...

This article reports a single-step “green protocol” for the environmentally friendly synthesis of zerovalent iron (ZVI) nanoparticles supported on cellulose nanocrystals (CNCs) fabricated from bamboo pulp. The high content of available hydroxyl groups on the CNC surfaces is utilized as an anchor point for the simultaneous reduction and stabilizatio...

The work focused on the formation of percolation network by cellulose nanocrystals (CNCs) in poly(3-hydroxybutyrate) (PHB) matrix, which affects the rheological and mechanical properties of the polymer. Rheological investigations revealed the formation of a percolation network in the fabricated PHB/CNC films with a percolation threshold at a CNC lo...

Cellulose nanocrystals (CNCs) using different polymorphs of cellulose were fabricated from raw bamboo pulp through alkali treatment followed by acid hydrolysis. The effect of CNC polymorphs, namely CNC I, CNC II and CNC:I→II (CNC II from cellulose I), on its morphology, crystal structure, degree of hydrogen bonding and thermal stability were studie...

This article reports the fabrication of poly (3-hydroxybutyrate) (PHB)/cellulose nanocrystal (CNC) based nanobiocomposite films with improved gas barrier and migration properties for food packaging applications. Acid hydrolysis of cellulose pulp from bamboo (Bambusabalcooa) yields CNCs with diameter of 15–20 nm and length of 400–600 nm. Evaluation...

In the classical k-median problem, we are given a metric space and want to open k centers so as to minimize the sum (over all the vertices) of the distance of each vertex to its nearest open center. In this paper we present the first constant-factor approximation algorithms for two natural generalizations of this problem that handle matroid or knap...

We give the first logarithmic approximation for minimizing average flow-time of jobs in the subset parallel machine setting (also called the restricted assignment setting) under a single knapsack constraint. In a knapsack constraint setting, each job has a profit, and the set of jobs which get scheduled must have a total profit of at least a quanti...

In this study in-vitro evaluation of cellular and acellular caprine pericardium following crosslinking with glutaraldehyde (GA), glyoxal (GO) diphenyl phosphoryl azide (DPPA), ethylene glycol diglycidyl ether (EGDGE) was carried out. The uncross-linked native and acellular pericardium was used as control. Fresh pericardium was divided into to equal...

We study the unsplittable flow on a path problem which has received a lot of attention in the research community recently. Given is a path with capacities on its edges and a set of tasks where each task is characterized by a source and a sink vertex, a demand, and a profit. The goal is to find a subset of the tasks of maximum total profit such that...

Blood is the archetype of a biological complex fluid. It is complex in the microstructural and mechanical sense, as a multiphase non-Newtonian viscoelastic fluid, and also in the biological sense, as a tissue that has a wide range of functions from delivery of oxygen and nutrients to response to injury and inflammation. These forms of complexity ar...

In the Steiner Forest problem, we are given terminal pairs si, ti, and need to find the cheapest subgraph which connects each of the terminal pairs together. In 1991, Agrawal, Klein, and Ravi gave a primal-dual constant-factor approximation algorithm for this problem. Until this work, the only constant-factor approximations we know are via linear p...

Online algorithms are usually analyzed using the notion of competitive ratio which compares the solution obtained by the algorithm to that obtained by an online adversary for the worst possible input sequence. Often this measure turns out to be too pessimistic, and one popular approach especially for scheduling problems has been that of "resource a...

Fabrication of biopolymers suitable for food packaging applications is currently an active area of research worldwide due to biodegradable and environmental-friendly nature of these polymers. Biodegradable polymers obtained from microbial fermentation, especially polyhydroxyalkaonates (PHAs), utilizing cheap biomass sources, can be tuned to incorpo...

This chapter focuses on emerging technologies developed for the fabrication of cellulose nanocrystal (CNC) based composite films for food packaging applications. Due to its strong reinforcing effect, CNC is a promising smart material for application in several fields such as healthcare, biomedical engineering, packaging etc. These bionanoparticles...

Space efficient algorithms play a central role in dealing with large amount of data. In such settings, one would like to analyse the large data using small amount of “working space”. One of the key steps in many algorithms for analysing large data is to maintain a (or a small number) random sample from the data points. In this paper, we consider tw...

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Polypyrrole/carbon (PPy/C) composites have been synthesized using varying concentration of p-toluenesulfonate (pTS) dopant by surface initiated in-situ chemical oxidative polymerization. The synthesis and influence of pTS on the structure of the PPy/C composites are confirmed by Fourier transform infrared studies and the morphological features have...

This study was undertaken for the identification of matrix metalloproteinases (MMPs) in extracts obtained from native, acellular and crosslinked bovine pericardium (in vitro), as well as in the plasma after implantation of these biomaterials in rabbits (in vivo). Native pericardium expressed a 72 kDa (MMP-2) band; whereas, in acellular pericardium...

Polypyrrole/carbon (PPy/C) composites have been synthesized using varying concentration of p-toluenesulfonate (pTS) dopant by surface initiated in-situ chemical oxidative polymerization with the purpose to develop an electrode material for supercapacitors. The influence of pTS on the structure of the composite is observed through Fourier transform...

Consider the following edge-orientation problem: edges of a graph appear online one-by-one and they to be directed- given an "orientation". We want to ensure that the in- degree of each vertex remains low. (This is a simple case of scheduling unit-sized jobs on machines, where each job can only go on one of two machines.) If the edge-orientations w...

The effects of particle size and rigidity on segregation behaviour in confined simple shear flow of binary suspensions of fluid-filled elastic capsules are investigated in a model system that resembles blood. We study this problem with direct simulations as well as with a master equation model that incorporates two key sources of wall-normal partic...

In the online Steiner tree problem, the input is a set of vertices that appear one-by-one, and we have to maintain a Steiner tree on the current set of vertices. The cost of the tree is the total length of edges in the tree, and we want this cost to be close to the cost of the optimal Steiner tree at all points in time. If we are allowed to only ad...

It is a well known fact that LabVIEW is one of the finest tools for measurement and control applications. Requirement of intelligent controller tuning methods like Genetic Algorithm (GA) has been felt at times in the LabVIEW environment as there is no standard LabVIEW GA toolkit supplied with the package. In this paper, a GA Toolkit developed in La...

Polypyrrole (PPy) and polypyrrole p-toluenesulfonate (PPy/pTS) supported cobalt (Co) catalysts have been synthesized using in situ surfactant modified chemical oxidative polymerization. These catalysts have been characterized for their structure and electrocatalytic activity employing FT-IR, Raman, SEM, HRTEM, and electrochemical techniques. The in...

After treatment with glucocorticoids (e.g. dexamethasone) or catecholamines (e.g. epinephrine), the white blood cell (WBC) count substantially increases. This is primarily due to WBCs shifting from the marginated to circulating pools (Nakagawa et al., Circulation, 2008) and is traditionally attributed to down-regulation of adhesion molecule express...

Electrochemically synthesized polypyrrole (PPy) films degrade under anodic polarization in aqueous solution. PPy is irreversibly oxidized leading to subsequently to an insulating material. This article highlights the degradation behavior of electrochemically synthesized PPy films using inorganic (perchlorate, ClO4−), organic (p-toluenesulfonate, pT...

Biological materials are increasingly used in the repair of tissue defects. To reduce antigenicity, biological tissues have to be acellularized and or fixed with a crosslinking agent before implantation. In this study, an acellularization process was employed to remove the cellular components from swim bladder of fish (Labeo rohita) using 0.5% ioni...

In the online Steiner tree problem, a sequence of points is revealed one-by-one: when a point arrives, we only have time to add a single edge connecting this point to the previous ones, and we want to minimize the total length of edges added. Here, a tight bound has been known for two decades: the greedy algorithm maintains a tree whose cost is O(l...

We initiate the study of job scheduling on related and unrelated machines so as to minimize the maximum flow time or the maximum weighted flow time (when each job has an associated weight). Previous work for these metrics considered only the setting of parallel machines, while previous work for scheduling on unrelated machines only considered L p ,...

The objective of the present study was to test the efficacy of bladder acellular matrix graft (BAMG) as cell delivery vehicle and to evaluate the process of bladder regeneration with and without cell seeding in rabbits. Rabbit bladder smooth muscle cells were grown in culture, and seeded on BAMG of porcine origin. Partial cystectomy was performed o...

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process err...

In this study, a decellularization process was employed to remove the cellular components from small intestine of buffalo (Bubalus bubalis) using 2% ionic biological detergent. The acellular matrix then was cross linked with 0.6% glutaraldehyde (GA), 1% 1, 4-butanediol diglycidyl ether (BDDGE) and 1% 1- ethyl-3 - (3 - dimethylaminopropyl) carbodiim...

Decellularization and cross-linking approach minimize the host immune response to the bioprosthetic tissue. The present study was carried out to evaluate the in-vivo biocompatibility of native and acellular scaffolds, using 0.6% Glutaraldeyde (GA) and 0.5% Hexamethylene discarnate (HMDC) as crosslinking agents. Thirty six adult New Zealand white ra...

a b s t r a c t Lipophilic chalcones and their conformationally restricted analogues were synthesized and evaluated for their antitubercular efficacy against Mycobacterium tuberculosis H37Rv strain. Compounds 16, 24, 25a and 25c were found to be active MIC at 60, 30, 3.5 and 7.5 lg-mL À1 . In vitro cytotoxicity of compounds 16, 24, 25a, 25c and 26...

In recent experimental studies, it has been shown that introducing drag reducing polymers (DRP) to blood in nanomolar concentration has many beneficial physiological effects, including the prevention of lethality from hemorrhagic shock in animals. In micro-channel experiments, with suspensions of red blood cells (RBCs), DRPs have been shown to redu...

Blood and many other multicomponent suspensions display a segregation behavior in which different components of the suspension are differentially distributed in the cross-stream direction during flow in a confined geometry such as an arteriole or a microfluidic device. Specifically, in blood the platelets and leukocytes are strongly segregated to t...

Flowing blood displays a phenomenon called margination, in which leukocytes and platelets are preferentially found near blood vessel walls, while erythrocytes are depleted from these regions. Here margination is investigated using direct hydrodynamic simulations of a binary suspension of stiff (s) and floppy (f) capsules, as well as a stochastic mo...

We propose a general dual-fitting technique for analyzing online scheduling algorithms in the unrelated machines setting where the objective function involves weighted flow-time, and we allow the machines of the on-line algorithm to have (1 + ε)-extra speed than the offline optimum (the so-called speed augmentation model). Typically, such algorithm...

Highly conducting polypyrrole (PPY) films, doped with various anions [pTS-, ClO4-, and NO3- and mixed electrolyte system (pTS- ClO4-)], have been electrochemically synthesized in aqueous solution at ∼275 K in an inert atmosphere. PPY exhibits metallic order dc conductivity at room temperature and shows variation of conductivity with respect to time...

Given a set of points $P \subset \mathbb{R}^d$, the $k$-means clustering problem is to find a set of $k$ {\em centers} $C = \{c_1,...,c_k\}, c_i \in \mathbb{R}^d,$ such that the objective function $\sum_{x \in P} d(x,C)^2$, where $d(x,C)$ denotes the distance between $x$ and the closest center in $C$, is minimized. This is one of the most prominent...

Poly(2,5-dimethoxyaniline) (PDMA) has been synthesized by chemical oxidative polymerization technique using varying ratio (wt/wt) of binary oxidants; ferric chloride (FeCl3) and ammonium persulfate (APS). Fourier transform infrared (FT-IR) and ultraviolet-visible (Uv-vis) spectroscopic investigations provide the evidence of the presence of both ben...

We consider a natural generalization of the Partial Vertex Cover problem. Here an instance consists of a graph G = (V,E), a positive cost function c: V-> Z^{+}, a partition $P_1,..., P_r$ of the edge set $E$, and a parameter $k_i$ for each partition $P_i$. The goal is to find a minimum cost set of vertices which cover at least $k_i$ edges from the...