Siddhartha Pathak

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This study demonstrates a novel approach to characterizing hydrated bone's viscoelastic behavior at lamellar length scales using dynamic indentation techniques. We studied the submicron-level viscoelastic response of bone tissue from two different inbred mouse strains, A/J and B6, with known differences in whole bone and tissue-level mechanical properties.(More)
We report mechanical behavior and strain rate dependence of recoverability and energy dissipation in vertically aligned carbon nanotube (VACNT) bundles subjected to quasi-static uniaxial compression. We observe three distinct regimes in their stress-strain curves for all explored strain rates from 4 × 10(-2) down to 4 × 10(-4)/sec: (1) a short initial(More)
The dynamical cluster approximation (DCA) is a method which systematically incorporates nonlocal corrections to the dynamical mean-field approximation. Here we present a pedagogical discussion of the DCA by describing it as a ̊-derivable coarse-graining approximation in k-space, which maps an infinite lattice problem onto a periodic finite-sized cluster(More)
We report the mechanical behavior of vertically aligned carbon nanotube films, grown on Si substrates using atmospheric pressure chemical vapor deposition, subjected to in situ large displacement (up to 70 lm) flat-punch indentations. We observed three distinct regimes in their indentation stress–strain curves: (i) a short elastic regime, followed by (ii) a(More)
In this work, we demonstrate the viability of using our recently developed data analysis procedures for spherical nanoindentation in conjunction with Raman spectroscopy for studying lamellar-level correlations between the local composition and local mechanical properties in mouse bone. Our methodologies allow us to convert the raw load-displacement datasets(More)
Micromechanical experiments, image analysis, and theoretical modeling revealed that local failure events and compressive stresses of vertically aligned carbon nanotubes (VACNTs) were uniquely linked to relative density gradients. Edge detection analysis of systematically obtained scanning electron micrographs was used to quantify a microstructural(More)
0008-6223/$ see front matter Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.carbon.2013.06.083 * Corresponding author. Present address: MPA-CINT Center for Integrated Nanotechnologies, Los Alamos National Laborator 1663, MS-K771, Los Alamos, NM 87545, USA. Fax: +1 (505) 665 9030. E-mail addresses: pathak@caltech.edu, siddharthapathak@gmail.com (S.(More)
In this article, we report on the application of our spherical nanoindentation data analysis protocols to study the mechanical response of grain boundary regions in as-cast and 30% deformed polycrystalline Fe–3%Si steel. In particular, we demonstrate that it is possible to investigate the role of grain boundaries in the mechanical deformation of(More)
The electronic states of CF3I have been investigated using photon and electron energy loss spectroscopy from 4 to 20 eV (310 nm > λ > 60 nm). Assignments have been suggested for each of the observed absorption bands incorporating both valence and Rydberg transitions. Vibrational structure in each of these bands is observed for the first time. Absolute(More)
A quantum critical point (QCP), separating the non-Fermi liquid region from the Fermi liquid, exists in the phase diagram of the two-dimensional Hubbard model [Vidhyadhiraja et al., Phys. Rev. Lett. 102, 206407 (2009)]. Due to the vanishing of the critical temperature associated with a phase separation transition, the quantum critical point is characterized(More)