Programming Strain Rate Dependency into Mechanical Metamaterials

This work presents an approach to introduce significant strain rate sensitivity into metallic metamaterials that are manufactured via additive manufacturing, where the base material employed will typically have a weak strain rate sensitivity. Here, we employ friction between the rough surfaces as the strain-rate dependent mechanism, whose magnitude is tunable by optimizing the geometry. The design along with the preliminary simulation results of the friction unit cell is presented. This work will quantify the effects of geometrical parameters on the dissipated energy

A simple glassy polymer model: A practical framework for the strain-rate and temperature dependent behaviour of polycarbonate

This work presents a simple and robust material model, suitable for dynamic simulations of glassy polymers such as Polycarbonate. The new model reduces the complex stress/strain behavior and its dependence on strain rate and temperature to a simple set of characteristics. Utilizing a time–temperature superposition principle, these characteristics serve as input for a purely empirical fitting approach, which provides an accurate representation of the material behaviour over a wide range of strain rates and temperatures. Calibration data including failure at high rates is obtained using a split Hopkinson tension bar. To demonstrate the applicability of the new model, it is parameterized using high strain rate data and its simulation predictions compared to a gas gun impact experiment wherein a Polycarbonate plate is subjected to the impact of a steel sphere at temperatures between 23–80 °C and 56–75 m/s

A comparative study on colour and surface parameters of current esthetic restorative CAD/CAM materials

With the development of newer technologies, computer aided design and computer aided manufacturing help immensely in designing, planning and creating a dental prosthesis with the precise 3-D printing technology. Recently, patients are at increasing demand for everlasting colour stability of restorations in such a way that it improves the aesthetic appearance of teeth. CAD/CAM systems are developed to assemble all ceramic materials which restores the aesthetic zone, attributing to the aesthetics and its clinical long-term survivability.A well-known fact that the type, thickness, composition, curing protocols, and polishing methods of resin composites influences the colour characteristics of the restorations. 99 all-ceramic samples with both glazed or polished CAD/CAM were taken into study. The samples were assessed for the surface roughness (Ra) and colour change after immersion in hot and coffee drink and then were subjected to thermocycling for about 30 days. Total samples of 99 among which 33 samples were manufactured from   Vita Enamic, Vitablocs Mark II, and Vita Suprinity.  All the disc were milled uniformly to obtain a standard dimension of 10mm ×10 mm±0.2 diameter and the thickness of the block ranges from 2.0±0.2 mm based on the manufacturer’s instructions using a CAD/CAM machine (Amann Girrbach, Germany) and then glazed

Identification of novel regulatory small RNAs in Acinetobacter baumannii.

Small RNA (sRNA) molecules are non-coding RNAs that have been implicated in regulation of various cellular processes in living systems, allowing them to adapt to changing environmental conditions. Till date, sRNAs have not been reported in Acinetobacter baumannii (A. baumannii), which has emerged as a significant multiple drug resistant nosocomial pathogen. In the present study, a combination of bioinformatic and experimental approach was used for identification of novel sRNAs. A total of 31 putative sRNAs were predicted by a combination of two algorithms, sRNAPredict and QRNA. Initially 10 sRNAs were chosen on the basis of lower E- value and three sRNAs (designated as AbsR11, 25 and 28) showed positive signal on Northern blot. These sRNAs are novel in nature as they do not have homologous sequences in other bacterial species. Expression of the three sRNAs was examined in various phases of bacterial growth. Further, the effect of various stress conditions on sRNA gene expression was determined. A detailed investigation revealed differential expression profile of AbsR25 in presence of varying amounts of ethidium bromide (EtBr), suggesting that its expression is influenced by environmental or internal signals such as stress response. A decrease in expression of AbsR25 and concomitant increase in the expression of bioinformatically predicted targets in presence of high EtBr was reverberated by the decrease in target gene expression when AbsR25 was overexpressed. This hints at the negative regulation of target genes by AbsR25. Interestingly, the putative targets include transporter genes and the degree of variation in expression of one of them (A1S_1331) suggests that AbsR25 is involved in regulation of a transporter. This study provides a perspective for future studies of sRNAs and their possible involvement in regulation of antibiotic resistance in bacteria specifically in cryptic A. baumannii

A Comparative Study on Colour and Surface Parameters of Current Esthetic Restorative CAD/CAM Materials

With the development of newer technologies, computer aided design and computer aided manufacturing help immensely in designing, planning and creating a dental prosthesis with the precise 3-D printing technology. Recently, patients are at increasing demand for everlasting colour stability of restorations in such a way that it improves the aesthetic appearance of teeth. CAD/CAM systems are developed to assemble all ceramic materials which restores the aesthetic zone, attributing to the aesthetics and its clinical long-term survivability.A well-known fact that the type, thickness, composition, curing protocols, and polishing methods of resin composites influences the colour characteristics of the restorations. 99 all-ceramic samples with both glazed or polished CAD/CAM were taken into study. The samples were assessed for the surface roughness (Ra) and colour change after immersion in hot and coffee drink and then were subjected to thermocycling for about 30 days. Total samples of 99 among which 33 samples were manufactured from   Vita Enamic, Vitablocs Mark II, and Vita Suprinity.  All the disc were milled uniformly to obtain a standard dimension of 10mm ×10 mm±0.2 diameter and the thickness of the block ranges from 2.0±0.2 mm based on the manufacturer's instructions using a CAD/CAM machine (Amann Girrbach, Germany) and then glazed

Selected target genes for expression analysis by qRT-PCR.

<p>Selected target genes for expression analysis by qRT-PCR.</p

Effect of AbsR25 sRNA overexpression.

<p>Comparison of expression of predicted putative target genes in <i>A. baumannii</i> cells harbouring recombinant plasmid over-expressing AbsR25 sRNA. Expression of target genes was studied under arabinose induced and uninduced conditions. The experiments were performed in triplicates.</p

List of putative 31 sRNAs and their features.

<p>Up ORF: Upstream Open Reading frame; dist Up ORF: distance of sRNA from Upstream Open Reading frame; UpORF dir: Upstream Open Reading frame direction; dir sRNA: direction of small RNA expression; len sRNA: length of sRNA; dist Dn ORF: distance of sRNA from downstream open reading frame.</p

Oligonucleotides used in this study.

<p>Oligonucleotides used in this study.</p

The expression of novel <i>A. baumannii</i> small RNA in different growth phases.

<p>Northern blot was used for determining the intracellular abundance of AbsRs over the course of growth (lag phase, L; early exponential phase, EE; exponential phase, E; stationary phase, S). Riborular low range RNA ladder (Fermentas, USA) sizes are shown to the left of the blot. Corresponding ethidium bromide stained 5S rRNA was used as loading control to ensure equal loading and shown below each Northern blot. (A) Northern blot of AbsR11, (B) Northern blot of AbsR25, (C) Northern blot of AbsR28.</p