Variational approach to hard sphere segregation under gravity

It is demonstrated that the minimization of the free energy functional for hard spheres and hard disks yields the result that excited granular materials under gravity segregate not only in the widely known "Brazil nut" fashion, i.e., with the larger particles rising to the top, but also in reverse "Brazil nut" fashion. Specifically, the local density approximation is used to investigate the crossover between the two types of segregation occurring in the liquid state, and the results are found to agree qualitatively with previously published results of simulation and of a simple model based on condensation.     

Design Flow Methodology for Radiation Hardened by Design CMOS Enclosed-Layout-Transistor-Based Standard-Cell Library

Ionizing radiation degrades the electrical characteristics of MOS devices, reducing their reliability, performance, and lifetime; therefore, hardening techniques are required for the proper functioning of those devices when exposed to harsh environments. Nonetheless, in the context of design flow automation, necessary to synthesize complex digital circuits, there is a lack of reliable foundry-provided Radiation Hardening by Design (RHBD) cell libraries. In this work, a complete RHBD flow methodology employing enclosed-layout transistors (ELTs) and guard rings, transparent to the designer, and fully compatible with commercial CAD tools and standard fabrication processes is presented. The proposed flow includes the automated calculation of the effective aspect ratio of the ELTs for annular and rectangular topologies, and a template proposal for digital cells, as well as series and parallel arrangements. Moreover, calculation of aspect ratio between pull-up and down networks and output buffers sizing using Logical Effort (LE) methodology, i.e., timing optimization accounting for typical commercial digital design constraints, is considered. Test structures, enclosing single n,pMOS devices, series and parallel arrangements, inverter cells, ring oscillators, and output buffers, were fabricated in two different technology nodes (600 nm and 180 nm). The experimental results were compared to SPICE simulations performed using the models here implemented. The results indicate that the flow methodology is feasible to implement and fully compatible with the CAD tools employed for circuit design. Besides, two case studies were first silicon-proven, presenting fully functional behavior under typical conditions.     

Whole‐Cell Biocatalysts for Stereoselective C−H Amination Reactions

Enantiomerically pure chiral amines are ubiquitous chemical building blocks in bioactive pharmaceutical products and their synthesis from simple starting materials is of great interest. One of the most attractive strategies is the stereoselective installation of a chiral amine through C?H amination, which is a challenging chemical transformation. Herein we report the application of a multienzyme cascade, generated in a single bacterial whole‐cell system, which is able to catalyze stereoselective benzylic aminations with ee values of 97.5 %. The cascade uses four heterologously expressed recombinant enzymes with cofactors provided by the host cell and isopropyl amine added as the amine donor. The cascade presents the first example of the successful de novo design of a single whole‐cell biocatalyst for formal stereoselective C?H amination.     

Measurement of the thermal impedance of laser diodes via thermal transients

The thermal impedance of laser diodes was determined by the measurement of thermal transients. The parameters of an equivalent R-C network were synthesized from the transient response. The network was compared with the real layer structure of the device. The effects of structure, mounting and aging on the temperature distribution were investigated with this method.

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Zusammenfassung Mittels Messung thermischer Einschwingvorgänge wurde die thermische Impedanz von Laserdioden bestimmt. Auf Grundlage des Sprungverhaltens wurden die Parameter eines äquivalentenR-C-Gliedes ermittelt, das mit der wahren Schichtenstruktur verglichen wurde. Mittels dieser Methode wurde der Einfluss von Struktur, Aufbau und Alterung auf die Temperaturverteilung untersucht.

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Fast XYT imaging of elementary calcium release events in muscle with multifocal multiphoton microscopy and wavelet denoising and detection

We used multifocal multiphoton microscopy to image fast, localized elevations of the cytosolic Ca2+ concentration in two spatial dimensions plus time (XYT). This technique extends the common spatially 1-D XT imaging and allows the acquisition of more than ten times longer time series (>500 images) and ten times larger areas of interest than for previously used confocal XYT imaging techniques due to lower phototoxicity and fast multifocal scanning. We recorded spontaneously occurring elementary Ca2+ release events in chemically permeabilized adult mammalian skeletal muscle fibers using two-photon excitation of the fluorescent dye Fluo-4. The resulting time series were analyzed with an automated denoising and detection algorithm based on the à trous implementation of the discrete wavelet transform. Wavelet coefficient hard-thresholding is used for denoising and event detection is performed across several wavelet scales. The spatiotemporal characteristics of the detected Ca2+ release events are followed throughout the XYT stack and are parametrized using a biophysically valid anisotropic Gaussian event model. The proposed method allows a detailed spatiotemporal analysis of elementary Ca2+ release events underlying the excitation-contraction coupling process in muscle.     

Quality of experience and quality of service-aware handover for video transmission in heterogeneous networks

Heterogeneous networks offer a wide range of multimedia services, such as entertainment, advertising, and video conferences. In this multimedia scenario, users can access video content via heterogeneous wireless networks, such as LTE macro and small cells. Users also expect to receive real-time videos with Quality of Experience (QoE) support, which is a challenging task due to the great diversity of radio base stations in such heterogeneous environments. In this article, we introduce a Quality of Service (QoS-)/QoE- and Radio-aware (SER) handover management algorithm for heterogeneous networks to provide video dissemination with QoS/QoE support. SER algorithm considers the analytic hierarchy process (AHP) to adjust the degree of importance of each criterion in order to select the appropriate radio base station that the mobile node must connect, allowing efficient handover decision making for video transmission with high user experience. Simulation results show that the SER algorithm delivered videos with significant improvement on QoE than existing handover algorithms.     

Evaluation of an Adaptive Resource Allocation for LoRaWAN

Long Range Wide Area Network (LoRaWAN) emerges to connect devices that require long-range and low-cost (bandwidth and power) communication services. In this context, the adoption of this technology brings new challenges due to the densification of IoT devices, which causes signal interference and affects the QoS directly. On the other hand, the LoRaWAN transmission configurations’ flexibility allows higher management to use end-device parameters, allowing better resource utilization and improve network scalability. We evaluate an adaptive solution that defines the best LoRaWAN parameter settings to reduce the channel utilization and, consequently, maximize the number of packets delivered. Additionally, to validate the method, we used a mixed-integer linear programming solution and compared the results obtained with those given by the heuristics. The results achieved by the heuristics were very close to those provided by the optimal result, demonstrating the effectiveness of the heuristics.