Cooperation-dominant Situations in SNS-norms Game on Complex and Facebook Networks

We propose an SNS-norms game to model behavioral strategies in social networking services (SNSs) and investigate the conditions required for the evolution of cooperation-dominant situations. SNSs such as Facebook and Google+ are indispensable social media for a variety of social communications ranging from personal chats to business and political campaigns, but we do not yet fully understand why they thrive and whether these currently popular SNSs will remain in the future. A number of studies have attempted to understand the conditions or mechanisms that keep social media thriving by using a meta-rewards game that is the dual form of a public goods game or by analyzing user roles. However, the meta-rewards game does not take into account the unique characteristics of current SNSs. Hence, in this work we propose an SNS-norms game that is an extension of Axelrod’s metanorms game, similar to meta-rewards games, but that considers the cost of commenting on an article and who is most likely to respond to it. We then experimentally investigated the conditions for a cooperation-dominant situation, by which we mean many users continuing to post articles on an SNS. Our results indicate that relatively large rewards compared to the cost of posting articles and comments are required to evolve cooperation-dominant situations, but optional responses with lower cost, such as “Like!” buttons, facilitate the evolution. This phenomenon is of interest because it is quite different from those shown in previous studies using meta-rewards games. We also confirmed the same phenomenon in an additional experiment using a network structure extracted from real-world SNS data.     

Poly(lactide) nanofibers produced by a melt‐electrospinning system with a laser melting device

A new melt‐electrospinning system equipped with a CO₂‐laser melting device was developed. Rod‐like samples were prepared from poly(lactide) pellets, and then fibers were produced from the samples using the new system. The effects of producing conditions on the fiber diameter were investigated. Furthermore, the physical properties of the fibers were investigated. The following conclusions were obtained: (i) in a special case, fibers having an average fiber diameter smaller than 1 μm could be obtained using the system developed; (ii) the fiber diameter could be decreased with increased laser output power, but the physical properties of the fibers such as the melting point and the molecular weight were decreased; and (iii) the electrospun fibers exhibited an amorphous state, and the annealed fibers exhibited an isotropic crystal orientation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1640–1645, 2007     

TEM image simulation study of small carbon nanotubes and carbon nanowire

Recent findings of extremely small diameter carbon nanotube and nanowire in the core of a multi-walled carbon nanotube (MWCNT) have attracted interests from broad range of researchers. Direct observation of carbon nanotube is usually done using a transmission electron microscope (TEM). When nanotubes become smaller, it becomes harder to correctly understand the TEM images, not only because of the weak scattering, but also due to the artifact that starts to appear because of the interference effect and the inappropriate defocus condition.In this study, we have shown that the artifact such as ghost fringes due to inappropriate defocus conditions of the TEM appear in the core of an MWCNT, and can be misinterpreted as either carbon nanowire or small carbon nanotube. It is also shown that, in the TEM image, it is hard to distinguish a single-walled nanotube bundle from a double-walled carbon nanotube bundle. Finally, we propose that the cross-sectional observation is necessary for the correct characterization of single- and double-walled carbon nanotube bundles.     

Novel biobased nanocomposites from functionalized vegetable oil and organically-modified layered silicate clay

The new biobased nanocomposites are processed from anhydride-cured epoxidized linseed oil (ELO)/ or octyl epoxide linseedate (OEL)/diglycidyl ether of bisphenol F (DGEBF) epoxy matrix and organomontmorillonite clay. The selection of anhydride curing agent and biobased epoxy resulted in an excellent combination to provide an epoxy matrix having high elastic modulus, high glass transition temperature, and high heat distortion temperature (HDT), with higher amounts of functionalized vegetable oil (FVO), compared with amine-cured biobased epoxy. The sonication technique was utilized to process the organically-modified clay nanoplatelets in the glassy biobased epoxy network resulting in nanocomposites where the clay nanoplatelets are almost completely exfoliated and homogeneously dispersed in the epoxy network. The processed exfoliated clay nanocomposites showed higher storage modulus compared with the neat epoxy containing the same amount of FVO. Therefore, the lost storage modulus with larger amount of FVO can be regained with exfoliated clay nanoreinforcement.     

Grafting fluorocarbons to polyethylene in glow discharge

A systematic surface fluorination of high-density polyethylene was carried out using CF₄, CF₃H, CF₃Cl, and CF₃Br, in a radio-frequency glow discharge. Based on ESCA and wettability measurements, all of these compounds provided a fluorocarbon layer on high-density polyethylene surface, but the fluorine to carbon ratio and extractability of the films were strongly dependent on the starting materials and the location of the sample specimen in the reactor chamber as well as the duration of the reaction. The results with vertically held, CF₃H-treated samples showed a high level of nonextractable surface fluorination and very little change in wetting properties before and after extraction with CF₂ClCFCl₂.     

Generation of an Oncolytic Herpes Simplex Viral Vector Completely Retargeted to the GDNF Receptor GFRα1 for Specific Infection of Breast Cancer Cells

Oncolytic herpes simplex viruses (oHSV) are under development for the treatment of a variety of human cancers, including breast cancer, a leading cause of cancer mortality among women worldwide. Here we report the design of a fully retargeted oHSV for preferential infection of breast cancer cells through virus recognition of GFRα1, the cellular receptor for glial cell-derived neurotrophic factor (GDNF). GFRα1 displays a limited expression profile in normal adult tissue, but is upregulated in a subset of breast cancers. We generated a recombinant HSV expressing a completely retargeted glycoprotein D (gD), the viral attachment/entry protein, that incorporates pre-pro-GDNF in place of the signal peptide and HVEM binding domain of gD and contains a deletion of amino acid 38 to eliminate nectin-1 binding. We show that GFRα1 is necessary and sufficient for infection by the purified recombinant virus. Moreover, this virus enters and spreads in GFRα1-positive breast cancer cells in vitro and caused tumor regression upon intratumoral injection in vivo. Given the heterogeneity observed between and within individual breast cancers at the molecular level, these results expand our ability to deliver oHSV to specific tumors and suggest opportunities to enhance drug or viral treatments aimed at other receptors.     

Performance analysis of CSMA/CD‐DRC system

Multimedia communication systems must handle two types of messages, one is data type and the other is voice type. Data type messages can tolerate longer delay but voice type ones cannot. Though communication systems with huge capacity by optical fibers and ATM switches have little problem for multimedia communication, most of the present LANs cannot handle messages, especially voice type ones, satisfactorily because of their poor capacity. In this paper we propose a new protocol for LANs, CSMA/CD‐DRC (Carrier Sense Multiple Access with Collision Detection and Dynamic Retransmission Control). This protocol is for the multimedia communication systems which must handle those two types of messages but do not have enough channel capacity, and controls retransmission rates dynamically to achieve higher throughput and shorter delay for voice type message. Moreover, we analyze the protocol in order to confirm its performance. In analysis we derive Laplace–Stieltjes transform (LST) of the probability distribution function (PDF) of the performance measures. Through LSTs, we can calculate not only averages but also higher moments of performance measures as well as coefficients of variation. We also present some numerical results, from which we find the proposed protocol can improve the system performance. This revised version was published online in June 2006 with corrections to the Cover Date.     

Crystal structures of mutants of Thermus thermophilus IPMDH adapted to low temperatures

Random mutagenesis on thermophilic 3-isopropylmalate dehydrogenases(IPMDH; EC 1.1.1.85) produced mutant enzymes which adapt tolow temperatures. These mutants had higher activity at lowertemperatures than the wild-type enzyme without losing high thermostability.Here we report three structures of the mutants of Thermus thermophilusIPMDH determined by X-ray diffraction which was adapted to alow-temperature environment. Two of them have unstable coenzymebinding states and the other one probably has a stable substratebinding state. The present research suggests that the adaptationis correlated with the binding of either coenzyme or the substrate.