Miniature Cone Penetration Tests with Shear Wave Velocity and Electrical Resistivity Measurements in Characterization of Silica Sand

Geotechnical engineering design and analysis require sound identification and characterization of in-situ soil. To characterize is to gather information about the engineering properties of a particular soil which will affect the performance of any structure built on it. As a result of complications associated with the retrieving of undisturbed samples of cohesionless soils, calibration chamber-based experiments under controlled laboratory settings are used for the determination of several geotechnical engineering parameters. The capability of a reduced-scale calibration chamber-based cone penetration testing system along with shear wave velocity and electrical resistivity measurements, to better characterize in-situ soil is examined in this study. Reconstituted clean sand specimens are anisotropically consolidated to different levels of consolidation relative densities to ideally simulate in-situ field conditions. This measured parameters such as cone tip resistance (qc), sleeve friction (fs), shear wave velocity (Vs) and bulk electrical resistivity of soil (ρs) at different consolidation stresses and relative densities have been used to establish improved characterization techniques for any site-specific pre-design geotechnical engineering analyses on silica-based cohesionless soil

Tunable polarization components and electric field induced crystallization in polyvinylidenefluoride (PVDF); a piezo polymer

Polyvinylidenefluoride (PVDF) a semicrystalline pieozoelectric polymer was synthesized with varying process conditions and its ferroelectric domain orientations were studied using piezoresponse force microscope (PFM). PVDF thin films fabricated using tape casting technique with precursor solutions of varying viscosities reveal that the polarization components transform from a dominant planar component to an out-of-plane polarization components with increase in viscosity. Interestingly the planar components possessed a head to head or tail to tail kind of paired domains separated by a distance of ~ 380-400nm. The electrostatic energies computed by numerically solving the electrostatic equilibrium equation for the electrically inhomogeneous system are in good correlation with the experiments. On increment of electric field, the domains were observed to grow in size and shape which indicates amorphous to crystalline transformation in the case of PVDF. Such transformation was evident from x-ray diffraction studies performed in-situ in the presence of an applied electric field

Tunable polarization components and electric field induced crystallization in polyvinylidenefluoride: A piezo polymer

Polyvinylidenefluoride (PVDF) a semicrystalline pieozoelectric polymer was synthesized with varying process conditions and its ferroelectric domain orientations were studied using piezoresponse force microscope (PFM). PVDF thin films fabricated using tape casting technique with precursor solutions of varying viscosities reveal that the polarization components transform from a dominant planar to an out‐of‐plane configuration with increase in viscosity. Interestingly the planar components possessed a head to head or tail to tail kind of paired domains separated by a distance of ~ 380‐400 nm. Electrostatic energy minimization of an electrically inhomogeneous system containing similar domain arrangements as the experiments shows that the head to head and tail to tail arrangements with a minimum separation distance are more favorable than head to tail arrangements of domains. With increment of applied field, the domains grew in size and shape indicating amorphous to crystalline transformation of PVDF films. Such transformation was evident from X‐ray diffraction studies performed in‐situ in the presence of an applied electric field

Study of Stiffness and flexible sensing performance of poly-vinylidene fluoride (PVDF) a piezo polymer with varying polarization components

Free standing PVDF thin films synthesized from varying precursor viscosities was fabricated through solution casting method. Polarization tuning from dominant in-plane to out-of-plane for an optimum viscosity range was observed and further its effect on the stiffness property was also studied. It was found that young's modulus increases with enhancement in in-plane polarization within the optimum range, However beyond the optimum range where polarization was negligible the young's modulus was observed to be very high. Effects of polarization tuning also observed on the device performance. The device with dominant in-plane polarization has the high stiffness as well as piezoelectric response whereas device with out-of-plane polarization has least stiffness and piezoelectric response. Thus correlation between viscosity as well as polarization on stiffness and piezoelectric response of device was observed

Dielectric switching studies of polyvinylidene fluoride thin films with dominant planar ferroelectric domain configuration for flexible electronic devices

Electrical switching characteristics of the polymer chains of polyvinylidene fluoride (PVDF) thin films with dominant planar domain configuration were investigated in this work. PVDF a semi-crystalline piezoelectric polymer is known to undergo structural transformation when subjected to electric field. In this study, the I-V characteristics of PVDF was analyzed by varying the delay time from 0.1 to 0.001 seconds in order to understand the response of switching behavior; a promising attribute that governs the operational speed of the device. A hysteretic behavior in the I-V characteristics was observed at different drive voltages. The ferroelectric polarization domains responds at different voltages and give rise to polarization switching currents. In addition to this, at relatively larger voltages (> 10 V) the amorphous intermediate regions of PVDF is expected to undergo an amorphous to crystalline transformation. Hence, the switching characteristics of the ferroelectric domains in the form of switching currents and the dipolar re-orientation arising due to the amorphous to crystalline transformation by rotation of polymer chains are captured at different voltages. Furthermore, a longer delay time (0.1 seconds) is employed to capture the current arising from a reversible amorphous to crystalline transformation. The dielectric relaxation time for the rotation of polymer chains in PVDF was inferred from independent studies and observed to be between 100 to 500 μS

Characterization of the N-Terminal Domain of BteA: A <em>Bordetella</em> Type III Secreted Cytotoxic Effector

<div><p>BteA, a 69-kDa cytotoxic protein, is a type III secretion system (T3SS) effector in the classical <em>Bordetella</em>, the etiological agents of pertussis and related mammalian respiratory diseases. Currently there is limited information regarding the structure of BteA or its subdomains, and no insight as to the identity of its eukaryotic partners(s) and their modes of interaction with BteA. The mechanisms that lead to BteA dependent cell death also remain elusive. The N-terminal domain of BteA is multifunctional, acting as a docking platform for its cognate chaperone (BtcA) in the bacterium, and targeting the protein to lipid raft microdomains within the eukaryotic host cell. In this study we describe the biochemical and biophysical characteristics of this domain (BteA287) and determine its architecture. We characterize BteA287 as being a soluble and highly stable domain which is rich in alpha helical content. Nuclear magnetic resonance (NMR) experiments combined with size exclusion and analytical ultracentrifugation measurements confirm these observations and reveal BteA287 to be monomeric in nature with a tendency to oligomerize at concentrations above 200 µM. Furthermore, diffusion-NMR demonstrated that the first 31 residues of BteA287 are responsible for the apparent aggregation behavior of BteA287. Light scattering analyses and small angle X-ray scattering experiments reveal a prolate ellipsoidal bi-pyramidal dumb-bell shape. Thus, our biophysical characterization is a first step towards structure determination of the BteA N-terminal domain.</p> </div

Secondary structure prediction of BteA superposed on established experimental data.

<p>The sequence of BteA was subjected to secondary structure meta-server analysis which was plotted as line for coil, spring for alpha-helix and arrow for beta sheet. Vertical arrows mark the boundaries of BteA287 fragment. Experimentally-derived secondary structure topology (PDB code 2JPF, aa 121–220) is shown in red. BteA-derived peptides from peptide fingerprinting MS/MS experiment (see Materials and Methods) were plotted as blue lines.</p

Circular dichroism analysis of BteA287 and 2D ¹H,¹⁵N-TROSY-HSQC spectrum of BteA287.

<p>(<b>A</b>) Dichroic spectra for BteA287 (black line) and BteA32-287 (blue line). <b>(B)</b> Melting curve of BteA287, measured at 222 nm (blue line indicates calculated Tm). (<b>C</b>) Spectrum was acquired for a triply-labeled [²H,¹³C,¹⁵N]-BteA287 0.4 mM sample in 100 mM NaCl, 20 mM NaPi pH 7.3 at 303 K and 16.4 T. The inset shows an outlying indole NH peak.</p

SDS-PAGE analysis of BteA purification and limited proteolysis experiments.

<p>(<b>A</b>) Ni²⁺-affinity chromatography purification of BteA showing fractions of: 1, pellet; 2, flow through; 3, wash 1; 4, wash 2; 5, wash 3; Elutions, selected elution fractions; M, marker. Black and white arrows indicate BteA monomer and oligomer respectively. (<b>B</b>) Limited proteolysis experiment was conducted on purified BteA after which the reaction was quenched by the addition of sample buffer and separated on 12.5% SDS-polyacrylamide.</p