Phenylethanoid glycosides isolated from Paraboea paniculata

Phytochemical studies of the leaves and rhizomes of Paraboea pa niculata (Gesneriaceae) are reported for the first time. Three phenylethanoid glycosides were isolated and characterized as 3,4-dihydroxyphenethyl-(3"-O-beta-D-apiofuranosyl)-beta-D-glucopyranoside, calceoralarioside E, and acteoside. These isolates exhibited weak cytotoxic activity against the K-562 cell line with a 50% of cell killing rate of 40.18 microM, 27.05 microM, and 27.24 microM, respectively. In the DPPH free radical scavenging assay, their IC50 values were determined as 75.89 microM, 25.00 microM, and 26.04 microM, respectively.     

A compact and highly fluorescent orange-emitting polymer dot for specific subcellular imaging

We demonstrate a new compact CN-PPV dot, which emits in the orange wavelength range with high brightness. The small particle size, high brightness, and the ability to highly specifically target subcellular structures make the CN-PPV dots promising probes for biological imaging and bioanalytical applications.     

Novel synthesis and functionalization of ortho-ortho disubstituted biphenyls and a highly condensed novel heterocycle using radical cyclization reaction

This paper describes a novel synthetic route for the preparation of ortho-ortho disubstituted biphenyls and compounds possessing highly condensed ring system represented by structures X and Y, respectively. Several approaches, such as intermolecular Grubb's olefin metathesis, Heck and, Suzuki reactions were incorporated to functionalize the core structures of X and Y making it suitable for the preparation of a library of compounds.     

Measurement and analysis of forces in bubble and droplet systems using AFM

The use of atomic force microscopy to measure and understand the interactions between deformable colloids - particularly bubbles and drops - has grown to prominence over the last decade. Insight into surface and structural forces, hydrodynamic drainage and coalescence events has been obtained, aiding in the understanding of emulsions, foams and other soft matter systems. This article provides information on experimental techniques and considerations unique to performing such measurements. The theoretical modelling frameworks which have proven crucial to quantitative analysis are presented briefly, along with a summary of the most significant results from drop and bubble AFM measurements. The advantages and limitations of such measurements are noted in the context of other experimental force measurement techniques.     

Facing the change and meeting the challenge: mathematics curriculum of Tongwen Guan in China in the second half of the nineteenth century

It is commonly recognized that the second wave of transmission of Western science and mathematics into China took place in the second half of the nineteenth century, thereby starting a process of modernization which has become synonymous with ??westernization?? of the country. In this context mathematics education in China also went through a process of modernization. During this period of great change reformers faced serious challenge and went through a ??mental struggle??. This paper discusses this challenge and mental struggle by taking a close look at the controversy over the establishment of Tianwen Suanxue Guan (School of Astronomy and Mathematics) in Tongwen Guan (School of Combined Learning), one of the schools of Western learning at the time. The attempt to integrate Western mathematics with Chinese traditional mathematics is also discussed through the study of some questions sampled from examinations and students?? homework assignments of this school.     

Momentum and heat transport in a finite-length cylinder wake

This paper reports an experimental study of turbulent momentum and heat transport in the wake of a wall-mounted finite-length square cylinder, with its length-to-width ratio L/d = 3–7. The cylinder was slightly heated so that heat produced could be considered as a passive scalar. A moveable three-wire probe (a combination of an X-wire and a cold wire) was used to measure velocity and temperature fluctuations at a Reynolds number of 7,300 based on d and the free-stream velocity. Measurements were performed at 10 and 20d downstream of the cylinder at various spanwise locations. Results indicate that L/d has a pronounced effect on Reynolds stresses, temperature variance and heat fluxes. The downwash flow from the free end of the cylinder acts to suppress spanwise vortices and, along with the upwash flow from the cylinder base, makes the finite-length cylinder wake highly three-dimensional. Reynolds stresses, especially the lateral normal stress, are significantly reduced as a result of suppressed spanwise vortices at a small L/d. The downwash flow acts to separate the two rows of spanwise vortices further apart from the wake centerline, resulting in a twin-peak distribution in temperature variance. While the downwash flow entrains high-speed fluid into the wake, responsible for a small deficit in the time-averaged streamwise velocity near the free end, it does not alter appreciably the distribution of time-averaged temperature. It has been found that the downwash flow gives rise to a counter-gradient transport of momentum about the central region of the wake near the free end of the cylinder, though such a counter-gradient transport does not occur for heat transport.     

One Pot Phase Transfer Synthesis of Trithiocarbonates from Carbon Bisulphide and Alkyl Halides

Symmetrical and cyclic alkyl trithiocarbonates were synthesized by reacting CS₂ and 33% aqueous NaOH with alkyl hal-ides under phase transfer catalysis conditions     

1,4-Addition Reactions of Alkynyl Fischer Carbene Complexes with Azides-Synthesis of β-Amino Alkenyl Carbene Complexes

Seredipitious 1, 4-additon reactions of alkynyl tungsten Fischer carbene complex with azides with the exclusion of nitrogen to form βamino carbene complexes were found.     

Synthesis of 1,3-Diynes Using Palladium-Copper Catalysis

1,3-Diynes were synthesized by a facile palladium-copper catalyzed coupling of 1-alkynes with 1-iodoalkynes.     

The three body interaction energy between optically active molecules

An account is given of a steady-state molecular dynamics method for the calculation of the shear viscosity of a dense fluid. The method is applied to the case of a system described by a Lennard-Jones potential with parameters appropriate to argon. Satisfactory agreement with experimental data is found over a range of temperature and density for which the viscosity varies by a factor of approximately 8. The results are interpreted in terms of a modified hard-sphere model and it is shown that the Lennard-Jones fluid obeys a Stokes-type relation in which the effective molecular diameter is close to that deduced from equilibrium structural properties.