The production of a cellular graphene array by scanning probe lithography and its ability to store electrical charge

A graphene cellular array on an insulating SiO₂ layer was fabricated by scanning probe lithography. The graphene layer was oxidized by an electric field which was applied between the cantilever tip and Si substrate without any electrode directly connected to the graphene layer. When the bias voltage was applied on a cell of patterned graphene through the cantilever tip, charge was accumulated on the cell and preserved for a long time without decay. The accumulated charge and the surface potential were measured by an electrostatic force microscope. The charge retention was measured as a function of time, and the decay time constant was estimated to be ～70 min.     

Three-dimensional Petersen-torus network: a fixed-degree network for massively parallel computers

A two-dimensional (2D) Petersen-torus network is a mesh-class fixed-degree network designed using a Petersen graph, which has a maximum of 10 nodes when the degree is 3 and the diameter is 2 in a (d,k)-graph problem. Here, I propose a new three-dimensional (3D) Petersen-torus network that extends the 2D Petersen-torus network without increasing the degree. The 3D Petersen-torus has the same number of nodes (N). The 3D Petersen-torus is better than the well-known 3D torus and 3D honeycomb mesh in terms of diameter and network cost. The 3D Petersen-torus network is better than the hypercube-like and star graph-like networks in terms of extendibility. Hence, the proposed network may serve as the foundation for realizing a high-performance multicomputer. In this paper, the optimal routing algorithm, Hamilton cycle, and several basic attributes are discussed. Furthermore, a comparison with a mesh-class fixed-degree 3D network is made for degree, diameter, and network cost.     

Effects of additives on phase transitions of Poloxamer 407/Poloxamer 188 mixture and release property of monoolein cubic phase containing the poloxamers

The gelling temperature of Poloxamer 407/Poloxamer 188 (16%/10%) mixture solution increased with increasing amount of surfactants. Among surfactants tested, the order of effectiveness in increasing the gelling temperature was sodium dodecyl sulfate (SDS) > tween 20 > cetyltrimethylammonium chloride (CTAC). The gelling temperature increased with the increasing concentration of cyclodextrin (CD). The order of effectiveness in increasing the gelling temperature was gamma CD > beta CD > alpha CD. The gelling temperature increased with increasing concentration of alcohols (ethanol and propylene glycol (PG)). On the contrary, dimethyl sulfoxide (DMSO) decreased the gelling temperature of P407/P188 (16%/10%) mixture solution. On the other hand, the gelling temperature decreased upon addition of NaCl but it increased by addition of MgCl₂. With P407/P188-loaded monoolein cubic phase, the degrees of release in 40 hr were about 52% at 25 °C and 37.5% at 47 °C. The suppressed release at 47 °C is possibly because P407/P188 in the water channel of cubic phase is in gel state at the temperature.     

Oxygen-dependent enhancement of hydrogen production by engineering bacterial hemoglobin in Escherichia coli

H₂ production under aerobic conditions has been proposed as an alternative method to overcome the fundamentally low yield of H₂ production by fermentative bacteria by maximizing the number of electrons that are available for H₂. Here, we engineered Vitreoscilla hemoglobin (VHb) in Escherichia coli to study the effects of this versatile oxygen (O₂)-binding protein on oxic H₂ production in a closed batch system that was supplemented with glucose. The H₂ yields that were obtained with the VHb-expressing E. coli were greatly enhanced in comparison to the negative control cells in culture that started with high O₂ tensions. The formate hydrogen lyase (FHL) activity of oxically cultured, VHb-expressing cells was also much higher than that of the negative control cells. Through inhibitor studies and time-course experiments, VHb was shown to contribute to the improved H₂ yield primarily by increasing the efficiency of cellular metabolism during the aerobic phase before the onset of H₂ production and not by working as an O₂-scavenger during H₂ production. This new approach allowed more substrate to remain to be further utilized for the production of more H₂ from limited resources. We expect that VHb can be successfully engineered in potential aerobic H₂-producing microbial systems to enhance the overall H₂ production yield. In addition, the remarkably high FHL activity of oxically grown, VHb-expressing cells may make this engineered strain an attractive whole-cell biocatalyst for converting formate to H₂.     

Joint Optimization of User Set Selection and Transmit Power Allocation for Orthogonal Random Beamforming in Multiuser MIMO Systems

When the number of users is finite, the performance improvement of the orthogonal random beamforming (ORBF) scheme is limited in high signal‐to‐noise ratio regions. In this paper, to improve the performance of the ORBF scheme, the user set and transmit power allocation are jointly determined to maximize sum rate under the total transmit power constraint. First, the transmit power allocation problem is expressed as a function of a given user set. Based on this expression, the optimal user set with the maximum sum rate is determined. The suboptimal procedure is also presented to reduce the computational complexity, which separates the user set selection procedure and transmit power allocation procedure.     

Hybrid approach of parallel implementation on CPU–GPU for high-speed ECDSA verification

The Journal of Supercomputing - Since the advent of deep belief network deep learning technology in 2006, artificial intelligence technology has been utilized in various convergence areas, such as...