加载——感应DAC的应用

加载-感应D/A转换器（Force/Sence DAC）是一类独特、极具吸引力的DAC，可以利用其输出缓冲放大器的反相输入端，设置输出增益，或改造成其它有用电路，所需外部元件很少，具有很大的设计灵活性。     

Roles of the Na+/H+ Exchanger Isoform 1 and Urokinase in Prostate Cancer Cell Migration and Invasion

Prostate cancer is a leading cause of cancer-associated deaths in men over 60 years of age. Most patients are killed by tumor metastasis. Recent evidence has implicated a role of the tumor microenvironment and urokinase plasminogen activator (uPA) in cancer cell migration, invasion, and metastasis. Here, we examine the role of the Na⁺/H⁺ exchanger isoform 1 (NHE1) and uPA in DU 145 prostate cancer cell migration and colony formation. Knockout of NHE1 reduced cell migration. The effects of a series of novel NHE1/uPA hexamethylene-amiloride-based inhibitors with varying efficacy towards NHE1 and uPA were examined on prostate cancer cells. Inhibition of NHE1—alone, or with inhibitors combining NHE1 or uPA inhibition—generally did not prevent prostate cancer cell migration. However, uPA inhibition—but not NHE1 inhibition—prevented anchorage-dependent colony formation. Application of inhibitors at concentrations that only saturate uPA inhibition decreased tumor invasion in vivo. The results suggest that while knockout of NHE1 affects cell migration, these effects are not due to NHE1-dependent proton translocation. Additionally, while neither NHE1 nor uPA activity was critical in cell migration, only uPA activity appeared to be critical in anchorage-dependent colony formation of DU 145 prostate cancer cells and invasion in vivo.     

Exploring the Biomaterial-Induced Secretome: Physical Bone Substitute Characteristics Influence the Cytokine Expression of Macrophages

In addition to their chemical composition various physical properties of synthetic bone substitute materials have been shown to influence their regenerative potential and to influence the expression of cytokines produced by monocytes, the key cell-type responsible for tissue reaction to biomaterials in vivo. In the present study both the regenerative potential and the inflammatory response to five bone substitute materials all based on β-tricalcium phosphate (β-TCP), but which differed in their physical characteristics (i.e., granule size, granule shape and porosity) were analyzed for their effects on monocyte cytokine expression. To determine the effects of the physical characteristics of the different materials, the proliferation of primary human osteoblasts growing on the materials was analyzed. To determine the immunogenic effects of the different materials on human peripheral blood monocytes, cells cultured on the materials were evaluated for the expression of 14 pro- and anti-inflammatory cytokines, i.e., IL-6, IL-10, IL-1β, VEGF, RANTES, IL-12p40, I-CAM, IL-4, V-CAM, TNF-α, GM-CSF, MIP-1α, Il-8 and MCP-1 using a Bio-Plex^® Multiplex System. The granular shape of bone substitutes showed a significant influence on the osteoblast proliferation. Moreover, smaller pore sizes, round granular shape and larger granule size increased the expression of GM-CSF, RANTES, IL-10 and IL-12 by monocytes, while polygonal shape and the larger pore sizes increased the expression of V-CAM. The physical characteristics of a bone biomaterial can influence the proliferation rate of osteoblasts and has an influence on the cytokine gene expression of monocytes in vitro. These results indicate that the physical structure of a biomaterial has a significant effect of how cells interact with the material. Thus, specific characteristics of a material may strongly affect the regenerative potential in vivo.     

Understanding risk-taking behavior of groups: A “decision analysis” perspective

Past research has extensively investigated the effect of media, especially focusing on how anonymity increases risk-related behaviors of groups when using computer-mediated communication (CMC). This study extends prior research by examining the differences in group risk-taking behaviors between face-to-face groups and completely non-anonymous CMC groups (i.e., groups working in a fully identified, synchronous CMC environment similar to popular instant messaging systems utilized widely within organizations). Drawing on the “decision analysis” perspective, a key framework for understanding organizational decision-making, the study also examines the effects of the firm's risk preferences as well as the type of information distribution among group members (i.e., full information known to all group members versus partial information know by only some of the members) on the groups' risk-taking behaviors. Results from a laboratory experiment using student subjects found no differences in risk-taking behaviors between CMC and face-to-face groups; additionally, no differences were found related to how information was distributed among group members. A significant effect was found, however, for the risk preference of the firm, showing that risk-neutral firms influenced groups to make riskier decisions than groups from risk-averse firms. Finally, groups within risk-neutral firms receiving partial information made riskier decisions than groups receiving full information. The implications of these results for future research and practice are examined.     

International development: exploring the gap between organisations’ development policy and practice—a Southern perspective

International development policies inevitably encounter a conflict in their implementation, representing the gap between universal goals and grass-roots practice. The aim of this study was to explore and understand the significance of this gap, and to apply knowledge management principles as a lens to suggest bridging solutions. The research focuses on non-governmental organisations, which are a sub-section of the civil society. The study was unique as it took a Southern perspective—the views and experiences of policy-makers, practitioners and beneficiaries in Kenya form the basis of the empirical research. Consequently, the research and its findings provide some answers as to how systems of knowledge can be aligned with the core values of organisational and societal culture in order to positively influence international stability.     

Low metal levels in emotionally disturbed children.

Investigated possible relationships of metal levels to childhood behavioral disorders. Hair-metal concentrations in 22 emotionally disturbed children (mean age 8.72 yrs) were compared to hair-metal levels in 25 control Ss (mean age 8.4 yrs) drawn from the general school population. Each S was also rated on the Walker Problem Behavior Identification Checklist (WPBIC). Disturbed Ss had significantly higher hair-lead levels. Correlations were run between hair-metal levels and WPBIC ratings for the 2 groups. Arsenic, cadmium, and aluminum levels correlated positively and significantly with the WPBIC total scale score for the disturbed group. A continuing reexamination of metal-poisoning concentrations is needed because metals levels previously thought harmless may be associated with behavioral impairments in children. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Robust Adaptive Terminal Sliding Mode Control for Rigid Robotic Manipulators

In this paper, a robust adaptive terminal sliding mode controller is developed for n-link rigid robotic manipulators with uncertain dynamics. An MIMO terminal sliding mode is defined for the error dynamics of a closed loop robot control system, and an adaptive mechanism is introduced to estimate the unknown parameters of the upper bounds of system uncertainties in the Lyapunov sense. The estimates are then used as controller parameters so that the effects of uncertain dynamics can be eliminated and a finite time error convergence in the terminal sliding mode can be guaranteed. Also, a useful bounded property of the derivative of the inertial matrix is explored, the convergence rate of the terminal sliding variable vector is investigated, and an experiment using a five bar robotic manipulator is carried out in support of the proposed control scheme.     

The Impact of an Agile Methodology on the Well Being of Development Teams

This paper describes an empirical study, which addresses the aspect of well being amongst members of the software development teams. The question of interest is whether an agile methodology has any distinct effect on the well being of the software developers. Both quantitative and qualitative methods were utilised, including the participative observation, focus group interviews, close-ended questionnaires and simple statistical tests such as Spearman Correlation and Mann–Whitney test. Initial results showed that an agile methodology (XP) has a positive effect on the level of enthusiasm of the software developers in the most dynamic project. To understand why XP can increase enthusiasm, results are interpreted with references to cognitive, affective and managerial properties of the practices studied. This result needs further investigation on the individual effects of each practice on the wellbeing and attitudes of Software Engineering (SE) teams.     

THE PAPER ENIGMA MACHINE

The Enigma Machine is a complex electromechanical device used by the Germans in World War II to achieve what they thought was complete communications security. While the original machine weighed over 20?lbs, the central mechanics of the machine can be simulated manually by manipulating strips of paper. A Paper Enigma is presented that can be cut out of a single sheet of paper. The resulting simulator is compatible with the electromechanical original in that messages can be encoded on one, and decoded on the other. Copies of The Paper Enigma can be downloaded from http://mckoss.com/crypto/enigma.htm.