The Flipside of Ubiquitous Connectivity by Smartphone-based Social Networking Service (SNS): Social Presence and Privacy Concern

The spread of smartphones triggers the universal use of smartphone-based social networking services (SNS) from younger generations in their teens and twenties to older ones in their fifties and sixties. SNS would no longer be the preserve of younger generations. Smartphone-based SNS can be enjoyed by everyone irrespective of age or gender. Under the circumstances, this study attempts to shed light on the sources of enjoyment, which has been argued as a key determinant of hedonic IS use, assuming that ubiquitous connectivity is a foundation of using smartphone-based SNS. This is because the main reason that people use smartphone-based SNS is to maintain seamless connection with others such as family, friends and acquaintances. Furthermore, the study examines factors related to enjoyment considering both sides of ubiquitous connectivity due to smartphone-based SNS use (i.e., social presence and privacy concern) and also verifies the effects of these variables on SNS continuance intention. Our results show that first, ubiquitous connectivity increases social presence and privacy concern. Second, enjoyment comes from not only ubiquitous connectivity but also social presence and privacy concern. Finally, smartphone-based SNS continuance intention is determined by enjoyment, social presence and privacy concern. Discussion and implications on the results are presented

Velocity-Space Reasoning for Interactive Simulation of Dynamic Crowd Behaviors

The problem of simulating a large number of independent entities, interacting with each other and moving through a shared space, has received considerable attention in computer graphics, biomechanics, psychology, robotics, architectural design, and pedestrian dynamics. One of the major challenges is to simulate the dynamic nature, variety, and subtle aspects of real-world crowd motions. Furthermore, many applications require the capabilities to simulate these movements and behaviors at interactive rates. In this thesis, we present interactive methods for computing trajectory-level behaviors that capture various aspects of human crowds. At a microscopic level, we address the problem of modeling the local interactions. First, we simulate dynamic patterns of crowd behaviors using Attribution theory and General Adaptation Syndrome theory from psychology. Our model accounts for permanent, stable disposition and the dynamic nature of human behaviors that change in response to the situation. Second, we model physics-based interactions in dense crowds by combining velocity-based collision avoidance algorithms with external forces. Our approach is capable of modeling both physical forces and interactions between agents and obstacles, while also allowing the agents to anticipate and avoid upcoming collisions during local navigation. We also address the problem at macroscopic level by modeling high-level aspects of human crowd behaviors. We present an automated scheme for learning and predicting individual behaviors from real-world crowd trajectories. Our approach is based on Bayesian learning algorithms combined with a velocity-based local collision avoidance model. We further extend our method to learn time-varying trajectory behavior patterns from pedestrian trajectories. These behavior patterns can be combined with local navigation algorithms to generate crowd behaviors that are similar to those observed in real-world videos. We highlight their performance for pedestrian navigation, architectural design and generating dynamic behaviors for virtual environments.Doctor of Philosoph

Vascular Disrupting Agent Drug Classes Differ in Effects on the Cytoskeleton

Vascular disrupting agents (VDAs), anti-cancer drugs that target established tumor blood vessels, fall into two main classes: microtubule targeting drugs, exemplified by combretastatin A4 (CA4), and flavonoids, exemplified by 5,6-dimethylxanthenone-4-acetic acid (DMXAA). Both classes increase permeability of tumor vasculature in mouse models, and DMXAA in particular can cause massive tumor necrosis. The molecular target of CA4 is clearly microtubules. The molecular target(s) of DMXAA remains unclear. It is thought to promote inflammatory signaling in leukocytes, and has been assumed to not target microtubules, though it is not clear from the literature how carefully this assumption has been tested. An earlier flavone analog, flavone acetic acid, was reported to promote mitotic arrest suggesting flavones might possess anti-microtubule activity, and endothelial cells are sensitive to even mild disruption of microtubules. We carefully investigated whether DMXAA directly affects the microtubule or actin cytoskeletons of endothelial cells by comparing effects of CA4 and DMXAA on human umbilical vein endothelial cells (HUVEC) using time-lapse imaging and assays for cytoskeleton integrity. CA4 caused retraction of the cell margin, mitotic arrest and microtubule depolymerization, while DMXAA, up to 500 µM, showed none of these effects. DMXAA also had no effect on pure tubulin nucleation and polymerization, unlike CA4. We conclude that DMXAA exhibits no direct anti-microtubule action and thus cleanly differs from CA4 in its mechanism of action at the molecular level

Effect of geopolymer composition and curing conditions on efflorescence in lightweight porous geopolymers

Lightweight geopolymers are more readily produced and give higher fire resistant performance than foam cement concrete. The fly ash-based lightweight geopolymers stones could be used for decoration due to the similarity in appearance and color to natural vesicular basalts. Efflorescence can be even more nettlesome issue in commercialization of lightweight porous geopolimers. Lowering the density of solid geopolymers can be achieved by inducing chemical reactions that entrain gases to foam the geopolymer structure. The apparent density of lightweight porous geopolymers has a range from 0.7 to 1.2 g/m3 with 0.025, 0.05 and 0.10 wt% of Al powder concentration, which corresponds to about 37~60 % of the apparent density, 1.96 g/cm3, of solid geopolymers. The compressive strength of cellular structured geopolymers decreased to 6~18 % of the compressive strength, 45 MPa of solid geopolymers. The microstructure of geopolymers gel was equivalent for both solid and cellular structured geopolymers. The efflorescence can be controlled by reducing targeted Na/Al molar ratio less than 1.0 or water content in geopolymers or curing at high temperature. Please click Additional Files below to see the full abstract

Benefits of adding calcium hydroxide to metakaolin-based geopolymers on fast setting and strength enhancement

Ca compounds are used in geopolymers and alkali-activated materials to accelerate setting. The effectiveness, however, can be erratic and the mechanism of fast setting is not clearly understood. It might be because the unstandardized, different combination of feedstocks in each case and the reaction products still include substantial amount of amorphous phases. We investigated the effect of some calcium compounds on the setting time in metakaolin-based geopolymers having the fixed ratio of ingredients (Na2O : Al2O3 : SiO2 : H2O = 1 : 1 : 4 : 10). Calcium compounds were added at dosages from 1% to 4% of the total mix weight. The final setting time of the 1:1:4:10 composition geopolymers was presumed to be over 24 hours at ambient temperature. Ca hydroxide was vastly superior to Ca oxide and carbonate in accelerating setting, and Ca carbonate even retarded the setting of geopolymers. Adding 2% of Ca(OH)2 concurrently increased the compressive strength by about 12% from 68 MPa to 76 MPa. Calcium hydroxide probably decreases the modulus of the alkaline activator at low dosage and resulted in gaining higher strength. An overdose of calcium, a glass modifier, might depolymerize the molecular structure of geopolymers and cause dehydration cracking

Characterization of system status signals for multivariate time series discretization based on frequency and amplitude variation

Many fault detection methods have been proposed for monitoring the health of various industrial systems. Characterizing the monitored signals is a prerequisite for selecting an appropriate detection method. However, fault detection methods tend to be decided with user???s subjective knowledge or their familiarity with the method, rather than following a predefined selection rule. This study investigates the performance sensitivity of two detection methods, with respect to status signal characteristics of given systems: abrupt variance, characteristic indicator, discernable frequency, and discernable index. Relation between key characteristics indicators from four different real-world systems and the performance of two fault detection methods using pattern recognition are evaluated

Mitochondria-mediated defense mechanisms against pathogens in Caenorhabditis elegans

Mitochondria are crucial organelles that generate cellular energy and metabolites. Recent studies indicate that mitochondria also regulate immunity. In this review, we discuss key roles of mitochondria in immunity against pathogen infection and underlying mechanisms, focusing on discoveries using Caenorhabditis elegans. Various mitochondrial processes, including mitochondrial surveillance mechanisms, mitochondrial unfolded protein response (UPRmt), mitophagy, and reactive oxygen species (ROS) production, contribute to immune responses and resistance of C. elegans against pathogens. Biological processes of C. elegans are usually conserved across phyla. Thus, understanding the mechanisms of mitochondria-mediated defense responses in C. elegans may provide insights into similar mechanisms in complex organisms, including mammals.110Ysciescopuskc

View-dependent dynamics of articulated bodies

Special Issue: CASA'2008 Special IssueInternational audienceWe propose a method for view-dependent simplification of articulated-body dynamics, which enables an automatic trade-off between visual precision and computational efficiency. We begin by discussing the problem of simplifying the simulation based on visual criteria, and show that it raises a number of challenging questions. We then focus on articulated-body dynamics simulation, and propose a semi-predictive approach which relies on a combination of exact, a priori error metrics computations, and visibility estimations. We suggest several variants of semi-predictive metrics based on hierarchical data structures and the use of graphics hardware, and discuss their relative merits in terms of computational efficiency and precision. Finally, we present several benchmarks and demonstrate how our view-dependent articulated-body dynamics method allows an animator (or a physics engine) to finely tune the visual quality and obtain potentially significant speedups during interactive or off-line simulations

Potential of IGCC slag as an alkali activated material

Integrated gasification combined cycle (IGCC) is a next generation energy production technology that converts coal into syngas with enhanced power generation efficiency and environmental performance. IGCC produces coal gasification slag as the solid by-product. Recycling of IGCC slag is still in the early stages, but the recycling process has been around the cement and concrete industry. We calculated the reactive Si/Al ratio of IGCC slag which is generated from a pilot plant in South Korea, and evaluated the potential of it as an alkali-activated material. Samples which were activated with the combined activator of sodium silicate solution and caustic soda had an average compressive strength of 4.5 MPa, showing swelling on the top free surface. Expansion of the alkali-activated slag was possibly caused by free CaO and MgO in the slag. While the samples that were activated with the combined activator of sodium aluminate and caustic soda had an average compressive strength of 10 MPa. Hydroxy sodalite and C3AH6 were found to be the new crystalline phases. IGCC slag can be used as an alkali-activated material, but the strength performance should be improved with proper mix design approach which can alleviate the expansion issue at the same time. Acknowledgement This study was supported by Korea Western Power Co., Ltd. in South Korea