Quantification of Self-Healing Effect of Bacillus Subtilis on Cementitious Material

In this paper, the self-healing ability of the bacterial concrete is tested and compared numerically with the conventional concrete. Micro-cracks cause degradation of strength which leads to deterioration of structures. To improve the life span of structures, self-healing techniques are used. One such technique is bacterial concrete which remediates cracks in concrete by using microbes as the self-healing agent. The self-healing agent is embedded into the cement mortar and its behaviour is studied. Control and bacterial specimens are cast and the tests like compressive strength, porosity, UPV test, ESEM, EDAX are done. ESEM and EDAX results show that the calcium precipitates formed in the micro-cracks at micron levels, to initiate the self-healing of mortar. UPV results show 3.90% of healing at the end of 45 days

Effect of the Intrinsic Width on the Piezoelectric Force Microscopy of a Single Ferroelectric Domain Wall

Intrinsic domain wall width is a fundamental parameter that reflects bulk ferroelectric properties and governs the performance of ferroelectric memory devices. We present closed-form analytical expressions for vertical and lateral piezoelectric force microscopy (PFM) profiles for the conical and disc models of the tip, beyond point charge and sphere approximations. The analysis takes into account the finite intrinsic width of the domain wall, and dielectric anisotropy of the material. These analytical expressions provide insight into the mechanisms of PFM image formation and can be used for quantitative analysis of the PFM domain wall profiles. PFM profile of a realistic domain wall is shown to be the convolution of its intrinsic profile and resolution function of PFM.Comment: 25 pages, 5 figures, 3 tables, 3 Appendices, To be submitted to J. Appl. Phy

Relativistic spin precession in the binary PSR J1141−-6545

PSR J1141$-$6545 is a precessing binary pulsar that has the rare potential to reveal the two-dimensional structure of a non-recycled pulsar emission cone. It has undergone $\sim 25 \deg$ of relativistic spin precession in the $\sim18$ years since its discovery. In this paper, we present a detailed Bayesian analysis of the precessional evolution of the width of the total intensity profile, to understand the changes to the line-of-sight impact angle ($\beta$) of the pulsar using four different physically motivated prior distribution models. Although we cannot statistically differentiate between the models with confidence, the temporal evolution of the linear and circular polarisations strongly argue that our line-of-sight crossed the magnetic pole around MJD 54000 and that only two models remain viable. For both these models, it appears likely that the pulsar will precess out of our line-of-sight in the next $3-5$ years, assuming a simple beam geometry. Marginalising over $\beta$ suggests that the pulsar is a near-orthogonal rotator and provides the first polarization-independent estimate of the scale factor ($\mathbb{A}$) that relates the pulsar beam opening angle ($\rho$) to its rotational period ($P$) as $\rho = \mathbb{A}P^{-0.5}$ : we find it to be $> 6 \rm~deg~s^{0.5}$ at 1.4 GHz with 99\% confidence. If all pulsars emit from opposite poles of a dipolar magnetic field with comparable brightness, we might expect to see evidence of an interpulse arising in PSR J1141$-$6545, unless the emission is patchy.Comment: Accepted for publication in Astrophysical Journal Letter

Progressive cavitating leukoencephalopathy: Case report of a rare childhood onset neurodegenerative disease

The leukoencephalopathies with cystic changes form a distinct subtype of childhood onset neurodegenerativedisorders. This group has heterogeneous etiological differentials that primarily include mitochondrial disorders, someleukodystrophies and central nervous system infections. We report this case of a 17-month old girl who presented withseizures, episodic encephalopathy, elevated blood lactate level and lactate peak on magnetic resonance spectroscopy,a typical imaging picture noted on cranial magnetic resonance imaging and absence of deletions or duplications ofmitochondrial deoxyribonucleic acid. Progressive cavitating leukoencephalopathy (PCL) is a recently described entitywith only a few cases reported so far. We report the first case of PCL from India. Accurate diagnosis can be made, notonly, by the presence of typical clinicoradiological findings of PCL, but also by the awareness of, and, ruling out of,the various other differential diagnoses that are discussed in detail below

Automated Defect Detection and Characterization on Pulse Thermography Images Using Computer Vision Techniques

Defect detection and characterization plays a vital role in predicting the life span of materials. Defect detection using appropriate inspection technologies at various phases has gained huge importance in metal production lines. It can be accomplished through wise application of non-destructive testing and evaluation (NDE). It is important to characterize defects at an early stage in order to be able to overcome them or take corrective measures. Pulse thermography is a modern NDE method that can be used for defect detection in metal objects. Only a limited amount of work has been done on automated detection and characterization of defects due to thermal diffusion. This paper proposes a system for automatic defect detection and characterization in metal objects using pulse thermography images as well as various image processing algorithms and mathematical tools. An experiment was carried out using a sequence of 250 pulse thermography images of an AISI 316 L stainless steel sheet with synthetic defects. The proposed system was able to detect and characterize defects sized 10 mm, 8 mm, 6 mm, 4 mm and 2 mm with an average accuracy of 96%, 95%, 84%, 77%, 54% respectively. The proposed technique helps in the effective and efficient characterization of defects in metal objects

Response properties of neighboring neurons in the auditory midbrain

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2006.Includes bibliographical references (p. 171-175).The inferior colliculus, the primary nucleus in the mammalian auditory midbrain, occupies a central position in the ascending auditory pathway. Nearly all ascending neural pathways converge and synapse in the central nucleus of the inferior colliculus (ICC). Further, the anatomical arrangement of axons and neurons in the ICC suggests the existence of functional regions which may play a role in organizing different types of physiological information. To investigate this organization, we characterized the response properties of neighboring neurons in the ICC. To record reliably from neighboring neurons, we adopted a relatively new electrophysiological technique, tetrode recordings. Tetrodes have four closely spaced recording sites (<20[mu]m) which record multi-unit activity from a small number of neighboring neurons. The recorded signals contain action potentials originating from more than one neuron. Based on action potential wave shape differences across the four channels, we can reconstruct the contributions of individual neurons. Applying tetrode recordings to the ICC of anesthetized cats, we successfully reconstructed individual spike trains for 190 neurons at 52 recording sites.(cont.) To quantify the advantage of tetrodes, we compared our multi-channel recording results with waveform sorting from single-channel electrode recordings. At best, only 32% of the single-units from tetrode sorting were correctly identified using single-channel recordings. We used tetrode to characterize pure tone responses of neighboring neurons in the ICC in terms of frequency selectivity, level dependence, temporal discharge patterns, and sensitivity to interaural time differences. We find similarities in best frequency and pure-tone threshold among neighboring neurons; however, we find large disparities in bandwidth, level dependence, temporal discharge patterns, and sensitivity to interaural time differences. These results suggest that neighboring neurons in ICC can greatly differ in membrane properties and/or their patterns of synaptic input from different brainstem nuclei and tonotopic regions. Using tetrode recordings, we investigated how well multi-unit responses represent the response properties of the contributing single-unit responses.(cont.) We find that multi-unit responses represent single-unit best frequency, pure-tone threshold and level dependence well, and they represent single-unit bandwidth and interaural phase sensitivity poorly. These results suggest caution must be used not to infer single-unit responses from multi-unit recordings.by Chandran V. Seshagiri.Ph.D

Thermodynamics of nanodomain formation and breakdown in Scanning Probe Microscopy: Landau-Ginzburg-Devonshire approach

Thermodynamics of tip-induced nanodomain formation in scanning probe microscopy of ferroelectric films and crystals is studied using the Landau-Ginzburg-Devonshire phenomenological approach. The local redistribution of polarization induced by the biased probe apex is analyzed including the effects of polarization gradients, field dependence of dielectric properties, intrinsic domain wall width, and film thickness. The polarization distribution inside subcritical nucleus of the domain preceding the nucleation event is very smooth and localized below the probe, and the electrostatic field distribution is dominated by the tip. In contrast, polarization distribution inside the stable domain is rectangular-like, and the associated electrostatic fields clearly illustrate the presence of tip-induced and depolarization field components. The calculated coercive biases of domain formation are in a good agreement with available experimental results for typical ferroelectric materials. The microscopic origin of the observed domain tip elongation in the region where the probe electric field is much smaller than the intrinsic coercive field is the positive depolarization field in front of the moving counter domain wall. For infinitely thin domain walls local domain breakdown through the sample depth appears. The results obtained here are complementary to the Landauer-Molotskii energetic approach.Comment: 35 pages, 8 figures, suplementary attached, to be submitted to Phys. Rev.