Self-Assembly and Temperature-Driven Chirality Inversion of Cholesteryl-Based Block Copolymers

Block copolymers (BCPs), comprising a poly(methyl methacrylate) (PMMA) block and a poly(cholesteryloxyhexyl methacrylate) (PChMA) block, were synthesized via reversible addition–fragmentation chain transfer polymerization. The self-assembly of the liquid crystalline BCPs was characterized by differential scanning calorimetry, polarized optical microscopy, and synchrotron-based small/wide-angle X-ray scattering. The results indicate the formation of both tilted and nontilted chiral smectic (SmC* and SmA*) phases. A phase transition from the SmA* to SmC* phase on cooling was observed for BCPs but not for PChMA homopolymers. The layer spacing (5.00 ± 0.18 nm) between those can be controlled to maintain the number of ChMA units while varying the lengths of the PMMA block, thus introducing systematically the SmC* phase. Furthermore, BCPs with the short PMMA block showed inversion of chirality at specific temperatures; however, for PChMA attached with the long PMMA block, no chirality inversion was observed. This mode of chirality switching, investigated by circular dichroism, NMR, and theoretical studies, is associated with the methyl substituents in the backbone affecting the packing of the polymers. The basic rules, described here, have the potential to be implemented for the design of a wide range of functional materials, where helix–helix conversion is of use

Oprimización y paralelización de un algoritmo de sincronización mediante el uso de GPUs y la tecnología CUDA

En el presente documento se hablará acerca del desarrollo de un proyecto para la mejora de un programa de análisis de señales; con ese fin, se hará uso de técnicas de optimización del software y de tecnologías de aceleración, mediante el aprovechamiento del paralelismo del programa. Además se hará un análisis de acerca del uso de dos tecnologías basadas en diferentes paradigmas de programación paralela; una mediante múltiples hilos con memoria compartida y la otra mediante el uso de GPUs como dispositivos de coprocesamiento. This paper will talk about the development of a Project to improve a program that does signals analysis; to that end, it will make use of software optimization techniques and acceleration technologies by exploiting parallelism in the program. In Addition will be done an analysis on the use of two technologies based on two different paradigms; one using multiple threads with shared memory and the other using GPU as co-processing devices

Bean-dreg-derived carbon materials used as superior anode material for lithium-ion batteries

The structures of modified carbons from bean dregs were regulated via graphitization treatment and chemical activation. The microstructure and electrochemical performance were studied using X-ray diffraction, Raman spectrometer, SEM and TEM techniques. The electrochemical performance was investigated using electrochemical methods. After heat-treatment at 2800 °C, the obtained BDC-2800 possessed a high degree of graphitization and showed an outstanding cycling performance, delivering capacity decay from 423 to 396 mAh g at 0.1 C after 100 cycles. The chemical-treated carbons also demonstrated enhanced electrochemical performance, especially for the KOH-treated sample. The BDC-K displayed superior specific charge capacity of 801 mAh g at 0.1 C, and showed an impressive rate capability of 643 mAh g at 1 C. In addition, this sample delivered capacity retention of 94% after 500 cycles at 1 C. This good electrochemical performance was mainly due to its high surface area and abundant mesoporous structure

Robust passivity-based dynamical systems for compliant motion adaptation

Motivated by human compliant behaviors during interacting with unknown environments and how motions and impedance to are adapted skilfully complete a task, this article develops a motion planning scheme that is capable of generating a compliant trajectory online such that tracking desired contacting forces under a predefined motion task. First, an improved dynamical system (DS) is designed to generate an adaptive compliant scanning trajectory online from the original DS in terms of the contact forces and the desired scanning forces. Inspired by passivity analysis for the robot control system, a robust term is formulated to guarantee stability by considering the balance between environmental and robotic energy. Furthermore, we develop a state-constrained controller based on barrier Lyapunov function to track the compliant DS motion and to ensure safety during scanning for the patient. Finally, comparative simulations are conducted to validate the general compliant capability of the proposed framework. We also instantiate our methodology through a use case of liver ultrasound scanning to demonstrate the stable and dynamic force tracking performance

Rapid assessment of disaster damage using social media activity

Could social media data aid in disaster response and damage assessment? Countries face both an increasing frequency and an increasing intensity of natural disasters resulting from climate change. During such events, citizens turn to social media platforms for disaster-related communication and information. Social media improves situational awareness, facilitates dissemination of emergency information, enables early warning systems, and helps coordinate relief efforts. In addition, the spatiotemporal distribution of disaster-related messages helps with the real-time monitoring and assessment of the disaster itself. We present a multiscale analysis of Twitter activity before, during, and after Hurricane Sandy. We examine the online response of 50 metropolitan areas of the United States and find a strong relationship between proximity to Sandy's path and hurricane-related social media activity. We show that real and perceived threats, together with physical disaster effects, are directly observable through the intensity and composition of Twitter's message stream. We demonstrate that per-capita Twitter activity strongly correlates with the per-capita economic damage inflicted by the hurricane. We verify our findings for a wide range of disasters and suggest that massive online social networks can be used for rapid assessment of damage caused by a large-scale disaster.Publicad

Collaborative virtual environment for knowledge management: a new paradigm for distributed communications

© 2012 Dr. Haohui ChenOrganizations gain competiveness through knowledge management. However, knowledge management in the context of distributed environment has two main issues, geographical distance and cognitive distance. This research adopted the concepts of Web 2.0 and designed a knowledge management system, iFarming, based on the technology of collaborative virtual environment for reducing these two distances in the context of Australian agriculture. A case study involving real farmer, scientist and agricultural consultant was carried out to assess the value of iFarming, through which a new paradigm for distributed communications was achieved