Cycloalkylpyranones and cycloalkyldihydropyrones as HIV protease inhibitors: exploring the impact of ring size on structure-activity relationships

Previously, 3-substituted cycloalkylpyranones, such as 2d, have proven to be effective inhibitors of HIV protease. In an initial series of 3-(1-phenylpropyl) derivatives with various cycloalkyl ring sizes, the cyclooctyl analog was the most potent. We became interested in exploring the influence of other structural changes, such as substitution on the phenyl ring and saturation of the 5,6-double bond, on the cycloalkyl ring size structure-activity relationship (SAR). Saturation of the 5,6-double bond in the pyrone ring significantly impacts the SAR, altering the optimal ring size from eight to six. Substitution of a sulfonamide at the meta position of the phenyl ring dramatically increases the potency of these inhibitors, but it does not change the optimal ring size in either the cycloalkylpyranone or the cycloalkyldihydropyrone series. This work has led to the identification of compounds with superb binding affinity for the HIV protease (Ki values in the 10-50 pM range). In addition, the cycloalkyldihydropyrones showed excellent antiviral activity in cell culture, with ED50 values as low as 1 microM.     

Constrained minimum-time path planning for robot manipulators viavirtual knots of the cubic B-spline functions

The B-spline functions are used to generate the constrained minimum-time path for a robot manipulator. The interpolated path via B-spline functions is determined via a unique set of virtual knots so that the robot path can pass every intermediate knot and satisfy the boundary conditions. The local control property of the B-spline functions can also be utilized to simplify the involved computational complexities. The flexible polyhedron search algorithm is used to generate the near minimum-time path with velocity, acceleration, and jerk constraints on every intermediate point. This approach can simplify the formulation and procedures for generating the near minimum-time cubic B-spline path. The use of this method to generate the constrained minimum-time joint trajectories for a PUMA 560 robot is discussed as an example     

Determination of the operating range of CO2 conversion and syngas production in dry auto-thermal reforming

A porous medium-catalyst hybrid reformer for CO₂ conversion by dry auto-thermal reforming (DATR) was investigated in this study, and its operating range was discovered. The hybrid design was used to enhance the oxidative heat release by internal heat recirculation during exothermic reaction conditions, thereby increasing the CO₂ conversion efficiency. The experimental results show that the CO₂ conversion could be enhanced with higher catalyst inlet temperatures. The examination of the operating range of DATR showed that the CO₂ conversion efficiency increased at higher reaction temperatures and CO₂/CH₄ ratios (≧1). Moreover, DATR in high temperature conditions must be carried out with high O₂/CH₄ ratios. Under these conditions of high oxygen content, CO₂ generation and reduction reactions occur simultaneously. Overall, optimal CO₂ conversion can be obtained with an O₂/CO₂ ratio of approximately 0.5. At these conditions, CO₂ conversion efficiency can reach approximately 13% without external heat addition.     

A new authentication based cheating prevention scheme in Naor–Shamir’s visual cryptography

Visual cryptography (VC), first presented by Naor and Shamir, is a variant of secret sharing, thus it also called visual secret sharing. It can be widely used in many applications such as encrypting large data efficiently. In the literature, the problem of cheating is under consideration in secret sharing. Recently, Horng et al. pointed out that cheating is possible in k-out-of-n VC schemes, and presented two kinds of the cheating prevention schemes for protecting honest participants. One of them is the authentication based cheating prevention scheme. In this paper, we analyze the definition of cheating prevention and propose a new authentication based cheating prevention scheme. This scheme is constructed with Naor–Shamir’s VC scheme. Finally, we give the security analysis to prove that the proposed scheme is immune to cheating.     

Interface effect of oxygen doping in polythiophene

Long-time evolution of the electrical characteristics for two-terminal and transistor of poly(3-hexylthiophene) film with various gate dielectric interfaces are measured. The oxygen doping is found to depend sensitively on the amount of hydroxyl groups of the interface and irreversible after long time in vacuum except for quartz. For a given interface, dip-coated film always has a higher doping level and slower de-doping than spin-coated films because of higher porosity. With careful control of the oxygen level transistor with mobility of 0.12 cm²/V s and on–off ratio of 29,000 are obtained for dip-coated film on glass substrate.     

Personality, safety attitudes and risky driving behaviors—Evidence from young Taiwanese motorcyclists

This paper's main objective is to explore the relationships between personality factors, attitudes toward traffic safety and risky driving behaviors among young Taiwanese motorcyclists. A second objective is to examine the gender difference in the effects of personality and safety attitudes on risky driving behaviors. The study sample consisted of 257 student participants from a Taiwanese university. The results show attitudes toward traffic safety are directly associated with risky driving behaviors while having direct effects on attitudes toward traffic safety, personality traits are also found to influence risky driving behaviors indirectly mediated by traffic safety attitudes. Practical implications for traffic safety of young motorcyclists are also discussed.     

Poly(ethylene terephthalate)/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate)/clay nanocomposites: Mechanical properties,optical transparency,and barrier properties

Poly(ethylene terephthalate) (PET)/clay, PET/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG), and PET/PETG/clay nanocomposites were fabricated using the twin‐screw extrusion technique. The spherulitic morphologies, thermomechanical, mechanical, and gas‐barrier properties, as well as the effect of clay on the transparency of the resulting nanocomposites were identified. The clay induced the heterogeneous nucleation of the nanocomposites during the cold crystallization process, thereby increasing the crystallinities and melting temperatures of the resulting nanocomposites. The incorporation of clay increased the storage moduli, Young's moduli, impact strengths, and barrier properties of the PET, PETG, and PET/PETG blend. Regarding the optical transparency, the inclusion of clay can make the crystallizable PET matrix crystalline opaque. However, the amorphous PETG maintained its transparency. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39869.     

A model to simulate surface roughness in the pad dressing process

Pad dressing, which is one of the most important planarization processes, is widely used in CMP. The estimation of surface roughness under various machining parameters (such as dressing force, diamond density of the dresser, rotational speed of the dresser, different machining paths, etc.) is essential to the pad dressing process. In this study, elastic-plastic theory and the wear model are used to construct the expression for the magnitude of material removal as a function of the indentation depth. The deformation of the pad is obtained by using elastic-plastic theory, and the material removal caused by individual micro-contacts is calculated with the help of wear theory. Finally, the macroscopic wear volume is found by summing the volumetric wear of each individual micro-contact. A parametric study is conducted to explore the influence on the surface roughness results and the pad dressing interfacial phenomena of operational parameters. The results reveal that a rapid initial improvement followed by a leveling off, manifesting a saturation effect. Moreover, the model shows that a higher dressing force with a dresser speed close to the pad speed and a moderate translation speed increase the material removal rate corresponding with a lower surface roughness dressing.