Band Gap Formation and Tunability in Stretchable Serpentine Interconnects

Serpentine interconnects are highly stretchable and frequently used in flexible electronic systems. In this work, we show that the undulating geometry of the serpentine interconnects will generate phononic band gaps to manipulate elastic wave propagation. The interesting effect of `bands-sticking-together' is observed. We further illustrate that the band structures of the serpentine interconnects can be tuned by applying pre-stretch deformation. The discovery offers a way to design stretchable and tunable phononic crystals by using metallic interconnects instead of the conventional design with soft rubbers and unfavorable damping.Comment: 12 pages, 8 figure

Hyperelastic antiplane ground cloaking

Hyperelastic materials possess the appealing property that they may be employed as elastic wave manipulation devices and cloaks by imposing pre-deformation. They provide an alternative to microstructured metamaterials and can be used in a reconfigurable manner. Previous studies indicate that exact elastodynamic invariance to pre-deformation holds only for neo-Hookean solids in the antiplane wave scenario and the semi-linear material in the in-plane compressional/shear wave context. Furthermore, although ground cloaks have been considered in the acoustic context they have not yet been discussed for elastodynamics, either by employing microstructured cloaks or hyperelastic cloaks. This work therefore aims at exploring the possibility of employing a range of hyperelastic materials for use as antiplane ground cloaks (AGCs). The use of the popular incompressible Arruda-Boyce and Mooney-Rivlin nonlinear materials is explored. The scattering problem associated with the AGC is simulated via finite element analysis where the cloaked region is formed by an indentation of the surface. Results demonstrate that the neo-Hookean medium can be used to generate a perfect hyperelastic AGC as should be expected. Furthermore, although the AGC performance of the Mooney-Rivlin material is not particularly satisfactory, it is shown that the Arruda-Boyce medium is an excellent candidate material for this purpose

H-Diplo ISSF round table: Steven Ward. status and the challenge of rising powers. Cambridge: Cambridge University Press, 2017.

Published versio

EIE: Efficient Inference Engine on Compressed Deep Neural Network

State-of-the-art deep neural networks (DNNs) have hundreds of millions of connections and are both computationally and memory intensive, making them difficult to deploy on embedded systems with limited hardware resources and power budgets. While custom hardware helps the computation, fetching weights from DRAM is two orders of magnitude more expensive than ALU operations, and dominates the required power. Previously proposed 'Deep Compression' makes it possible to fit large DNNs (AlexNet and VGGNet) fully in on-chip SRAM. This compression is achieved by pruning the redundant connections and having multiple connections share the same weight. We propose an energy efficient inference engine (EIE) that performs inference on this compressed network model and accelerates the resulting sparse matrix-vector multiplication with weight sharing. Going from DRAM to SRAM gives EIE 120x energy saving; Exploiting sparsity saves 10x; Weight sharing gives 8x; Skipping zero activations from ReLU saves another 3x. Evaluated on nine DNN benchmarks, EIE is 189x and 13x faster when compared to CPU and GPU implementations of the same DNN without compression. EIE has a processing power of 102GOPS/s working directly on a compressed network, corresponding to 3TOPS/s on an uncompressed network, and processes FC layers of AlexNet at 1.88x10^4 frames/sec with a power dissipation of only 600mW. It is 24,000x and 3,400x more energy efficient than a CPU and GPU respectively. Compared with DaDianNao, EIE has 2.9x, 19x and 3x better throughput, energy efficiency and area efficiency.Comment: External Links: TheNextPlatform: http://goo.gl/f7qX0L ; O'Reilly: https://goo.gl/Id1HNT ; Hacker News: https://goo.gl/KM72SV ; Embedded-vision: http://goo.gl/joQNg8 ; Talk at NVIDIA GTC'16: http://goo.gl/6wJYvn ; Talk at Embedded Vision Summit: https://goo.gl/7abFNe ; Talk at Stanford University: https://goo.gl/6lwuer. Published as a conference paper in ISCA 201

Dynamic GATA4 enhancers shape the chromatin landscape central to heart development and disease.

How stage-specific enhancer dynamics modulate gene expression patterns essential for organ development, homeostasis and disease is not well understood. Here, we addressed this question by mapping chromatin occupancy of GATA4--a master cardiac transcription factor--in heart development and disease. We find that GATA4 binds and participates in establishing active chromatin regions by stimulating H3K27ac deposition, which facilitates GATA4-driven gene expression. GATA4 chromatin occupancy changes markedly between fetal and adult heart, with a limited binding sites overlap. Cardiac stress restored GATA4 occupancy to a subset of fetal sites, but many stress-associated GATA4 binding sites localized to loci not occupied by GATA4 during normal heart development. Collectively, our data show that dynamic, context-specific transcription factors occupancy underlies stage-specific events in development, homeostasis and disease

Optimization of Genome Engineering Approaches with the CRISPR/Cas9 System

Designer nucleases such as TALENS and Cas9 have opened new opportunities to scarlessly edit the mammalian genome. Here we explored several parameters that influence Cas9-mediated scarless genome editing efficiency in murine embryonic stem cells. Optimization of transfection conditions and enriching for transfected cells are critical for efficiently recovering modified clones. Paired gRNAs and wild-type Cas9 efficiently create programmed deletions, which facilitate identification of targeted clones, while paired gRNAs and the Cas9D10A nickase generated smaller targeted indels with lower chance of off-target mutagenesis. Genome editing is also useful for programmed introduction of exogenous DNA sequences at a target locus. Increasing the length of the homology arms of the homology-directed repair template strongly enhanced targeting efficiency, while increasing the length of the DNA insert reduced it. Together our data provide guidance on optimal design of scarless gene knockout, modification, or knock-in experiments using Cas9 nuclease

WT1 regulates epicardial epithelial to mesenchymal transition through β-catenin and retinoic acid signaling pathways

AbstractAn epithelial sheet, the epicardium, lines the surface of the heart. In the developing embryo, the epicardium expresses the transcriptional regulator Wilm's Tumor Gene 1 (Wt1). Through incompletely understood mechanisms, Wt1 inactivation derails normal heart development. We investigated mechanisms by which Wt1 regulates heart development and epicardial epithelial to mesenchymal transition (EMT). We used genetic lineage tracing approaches to track and isolate epicardium and epicardium derivatives in hearts lacking Wt1 (Wt1KO). Wt1KO hearts had diminished proliferation of compact myocardium and impaired coronary plexus formation. Wt1KO epicardium failed to undergo EMT. Wt1KO epicardium expressed reduced Lef1 and Ctnnb1 (β-catenin), key components of the canonical Wnt/β-catenin signaling pathway. Wt1KO epicardium expressed decreased levels of canonical Wnt downstream targets Axin2, Cyclin D1, and Cyclin D2 and exhibited decreased activity of the Batgal Wnt/β-catenin reporter transgene, suggestive of diminished canonical Wnt signaling. Hearts with epicardium-restricted Ctnnb1 loss of function resembled Wt1KO hearts and also failed to undergo epicardial EMT. However, Ctnnb1 inactivation did not alter WT1 expression, positioning Wt1 upstream of canonical Wnt/β-catenin signaling. Wnt5a, a prototypic non-canonical Wnt with enriched epicardial expression, and Raldh2, a key regulator of retinoic acid signaling confined to the epicardium, were also markedly downregulated in Wt1KO epicardium. Hearts lacking Wnt5a or Raldh2 shared phenotypic features with Wt1KO. Although Wt1 has been proposed to regulate EMT by repressing E-cadherin, we detected no change in E-cadherin in Wt1KO epicardium. Collectively, our study shows that Wt1 regulates epicardial EMT and heart development through canonical Wnt, non-canonical Wnt, and retinoic acid signaling pathways

Density Functional Theory Study of Pt_3M Alloy Surface Segregation with Adsorbed O/OH and Pt_3Os as Catalysts for Oxygen Reduction Reaction

Using quantum mechanics calculations, we have studied the segregation energy with adsorbed O and OH for 28 Pt_3M alloys, where M is a transition metal. The calculations found surface segregation to become energetically unfavorable for Pt_3Co and Pt_3Ni, as well as for the most other Pt binary alloys, in the presence of adsorbed O and OH. However, Pt_3Os and Pt_3Ir remain surface segregated and show the best energy preference among the alloys studied for both adsorbed species on the surface. Binding energies of various oxygen reduction reaction (ORR) intermediates on the Pt(111) and Pt_3Os(111) surfaces were calculated and analyzed. Energy barriers for different ORR steps were computed for Pt and Pt_3Os catalysts, and the rate-determining steps (RDS) were identified. It turns out that the RDS barrier for the Pt_3Os alloy catalyst is lower than the corresponding barrier for pure Pt. This result allows us to predict a better ORR performance of Pt_3Os compared to that of pure Pt