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  • 1
    Publication Date: 2016-02-03
    Description: Background: Tyrosinase is an oxidoreductase that is very important in medicine and cosmetics because the excessive production of melanin causes hyperpigmentation. The development of novel, effective tyrosinase inhibitors has long been pursued. In preliminary tests, we found that an extract of the wood of Artocarpus heterophyllous (AH) potently inhibited tyrosinase activity. Results: Two new flavonoids, artocaepin E (1) and artocaepin F (2), were isolated from the wood of AH, together with norartocarpetin (3), artocarpanone (4), liquiritigenin (5), steppogenin (6), and dihydromorin (7). Their structures were elucidated using one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) and mass spectrometry. The absolute configuration of 2 was determined from the circular dichroism (CD) spectrum. Artocarpanone (4) had the most potent tyrosinase inhibitory effect, with an IC 50 of 2.0 ± 0.1 μM, followed by artocaepin E (1) and steppogenin (6), with IC 50 values of 6.7 ± 0.8 and 7.5 ± 0.5 μM, respectively. A kinetic investigation indicated that 1 showed competitive inhibition, with an inhibition constant (K i ) of 6.23 μM. Conclusions: These results demonstrate that extracts of the wood of AH and its phytochemical constituents are potential sources for skin-whitening agents.Graphical abstractArtocarmin E (1) and artocarmin F (2) were isolated from the wood of Artocarpus heterophyllous. Their structures were elucidated using nuclear magnetic resonance analysis and mass spectrometric methods
    Electronic ISSN: 1752-153X
    Topics: Chemistry and Pharmacology
    Published by Chemistry Central
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  • 2
    Publication Date: 2018-04-12
    Description: Sustainability, Vol. 10, Pages 1151: Determinants of Customer Satisfaction and Loyalty in Vietnamese Life-Insurance Setting Sustainability doi: 10.3390/su10041151 Authors: Ha Nguyen Hoang Nguyen Nhan Nguyen Anh Phan Sustainable services are often regarded as sustainable strategies and operations producing goods and services that satisfy customer needs and significantly improve social and environmental performance. To be sustainable, service providers must satisfy consumers’ needs or otherwise they will become redundant and economically irrelevant. This paper presents the results of an empirical study on the determinants of customer satisfaction and loyalty in life-insurance services in Vietnam based on a database collected through a questionnaire survey of 1476 customers during 2017. A path analysis technique is applied to test the proposed framework on the direct and indirect relationship between variables. The results of statistical analysis indicate that customer satisfaction in life-insurance services is significantly explained by such factors as corporate image, service quality and perceived value. Our findings suggest that a life-insurance service provider should focus on enhancing service quality and corporate image in order to obtain customer satisfaction that leads to customer loyalty.
    Electronic ISSN: 2071-1050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 3
    Publication Date: 2014-09-23
    Print ISSN: 1742-6588
    Electronic ISSN: 1742-6596
    Topics: Physics
    Published by Institute of Physics
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  • 4
    ISSN: 1573-7810
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Sociology
    Notes: Abstract The generation and management of urban solid waste is an urgent and growing problem in Hochiminh City, as elsewhere in the world. An important contribution to solving the city's waste management problem is made by the recycling industry. The well-organized private system of collection, trade and recycling includes door-to-door itinerant buyers, entirely women, who buy solid waste products from households; a range of small, medium, and big shopkeepers who purchase waste from the buyers; middle-men who link the shopkeepers with the recyclers; and the recycling or production units that transform products for sale to consumers. Earnings of itinerant buyers are low and may be declining. However, their self-employment is critical because they are often the main economic support of their families. Shopkeepers enjoy better standards of living but economic competition and recent environmental regulations threaten the survival of the industry. Policy options are offered for attempting to ensure the survival of recyclers and itinerant buyers, those
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 23 (1977), S. 305-345 
    ISSN: 1573-2878
    Keywords: Pursuit-evasion problems ; differential games ; zero-sum games ; singular surfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An approach, both analytical and numerical, is used to solve a two-dimensional pursuit-evasion game characterized by a difficulty level intermediate between that of thesimple motion game (with freely and instantaneously oriented velocities) and that of thegame of two cars (with lower bounds on curvature radii). Each player's velocity has a constant modulus. The maneuvers are penalized by introducing, in the performance index, an integral term for the squared velocity turning rate. The local problem solution is relatively easy to find: the equations of motion and the adjoint equations can be integrated by means of elliptic functions and integrals. The global problem is more delicate to solve, because of the existence of a dispersal singular surface requiring an important numerical search to be determined. Thesynthesis problem (how to express the optimal strategies as functions of state) is not explicitly solvable, but a numerical approach using successive approximations can be developed. Illustrative interception trajectories are given.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2018
    Description: Herein, we present a low-power cyclic Vernier two-step time-to-digital converter (TDC) that achieves a wide input range with good linearity. Since traditional approaches require a large area or high power to achieve an input range 〉300 ns, we solve this problem by proposing a simple yet efficient TDC suitable for time-of-flight (TOF) sensors. In previous studies using the cyclic structure, the effect of startup time on the linearity of the TDC is not described. Thus, the achievable linearity has been limited when the TDC is used for applications requiring a high input range. We solve this problem by using a simple yet effective technique to compensate. The proposed technique is realized using (1) digitally-controlled oscillators (DCOs) that have dual frequency control and matched startup time; (2) an alignment detector that performs startup time correction by proper timing control; and (3) a fully symmetric arbiter that precisely detects the instant of edge alignment. To achieve a fine resolution for the cyclic Vernier TDC, we design two closely-matched DCOs with dual frequency control. The alignment detector performs the critical task of cancelling startup time via timing control. The detector is delay-compensated by using a dummy to provide matched loading for the two DCOs. To enhance the detection speed under low power, a current-reuse approach is employed for the arbiter. The TDC is fabricated using a 0.18 μm complementary metal–oxide–semiconductor (CMOS) process in a compact chip area of 0.028 mm2. Measured results show a dynamic range of 355 ns and a resolution of 377 ps. When the result is applied for TOF sensing, it corresponds to a distance range of 53.2 m and a resolution of 5.65 cm. Over a relatively large input range, good linearity is achieved, which is indicated by a DNL of 0.28 LSBrms and an INL of 0.96 LSBrms. The result corresponds to root mean square (RMS) error distance of 5.42 cm. The result is achieved by consuming a relatively low power of 0.65 mW.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by MDPI
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  • 7
    Publication Date: 2015-06-25
    Description: Online service providers often use challenge questions (a.k.a. knowledge‐based authentication) to facilitate resetting of passwords or to provide an extra layer of security for authentication. While prior schemes explored both static and dynamic challenge questions to improve security, they do not systematically investigate the problem of designing challenge questions and its effect on user recall performance. Interestingly, as answering different styles of questions may require different amount of cognitive effort and evoke different reactions among users, we argue that the style of challenge questions itself can have a significant effect on user recall performance and usability of such systems. To address this void and investigate the effect of question types on user performance, this paper explores location‐based challenge question generation schemes where different types of questions are generated based on users’ locations tracked by smartphones and presented to users. For evaluation, we deployed our location tracking application on users’ smartphones and conducted two real‐life studies using four different kinds of challenge questions. Each study was approximately 30 days long and had 14 and 15 users respectively. Our findings suggest that the question type can have a significant effect on user performance. Finally, as individual users may vary in terms of performance and recall rate, we investigate and present a Bayesian classifier based authentication algorithm that can authenticate legitimate users with high accuracy by leveraging individual response patterns while reducing the success rate of adversaries.
    Electronic ISSN: 2192-1962
    Topics: Computer Science
    Published by SpringerOpen
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  • 8
    Publication Date: 2015-12-17
    Description: Software update messages are commonly used to inform users about software updates, recent bug fixes, and various system vulnerabilities, and to suggest recommended actions (e.g., updating software). While various design features (e.g., update options, message layout, update message presentation) of these messages can influence the actions taken by users, no prior study can be found that investigated users opinions regarding various design alternatives. To address this void, this paper focuses on identifying software update message design features (e.g., layout, color, content) that may affect users positively or negatively. Toward that, we conducted a user study where users are shown 13 software update messages along with 1 virus warning message. We collect responses from 155 users through an online survey. Participants gave a total of 809 positive comments and 866 negative comments along with ranking of each image in terms of perceived importance, noticeability, annoyance and confusion. As many of the comments are repetitive and often contain multiple themes, we manually analyzed and performed a bottom-up, inductive coding to identify and refine the underlying themes. Over multiple iterations, positive comments were grouped into 52 categories which were subsequently grouped under four themes. Similarly, negative comments were first grouped into 38 categories which were subsequently grouped under four themes. Based on our analysis, we present the list of design features that are found to be highly correlated to confusion, annoyance, noticeability, and importance, either positively or negatively.
    Electronic ISSN: 2192-1962
    Topics: Computer Science
    Published by SpringerOpen
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  • 9
    Publication Date: 2016-02-24
    Description: Software update messages are commonly used to inform users about software updates, recent bug fixes, and various system vulnerabilities, and to suggest recommended actions (e.g., updating software). While vari...
    Electronic ISSN: 2192-1962
    Topics: Computer Science
    Published by SpringerOpen
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  • 10
    Publication Date: 2002-09-01
    Print ISSN: 0362-546X
    Electronic ISSN: 1873-5215
    Topics: Mathematics
    Published by Elsevier
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