Sylvone, a new furanoid lignan of

The structure of a novel 2,3,4- trisubstituted furanoid lignan, designated sylvone, was established as from detailed spectroscopical and chemical studies.     

Conventionality of Simultaneity and the Tippe Top Paradox in Relativity

In this paper we critically examine a recently posed paradox (tippe top paradox in relativity) and its suggested resolution. A tippe top when spun on a table, tips over after a few rotations and eventually stands spinning on its stem. The ability of the top to demonstrate this charming feat depends on its geometry (all tops are not tippe tops). To a rocket-bound observer the top geometry should change because of the Lorentz contraction. This gives rise to the possibility that for a sufficiently fast observer the geometry of the top may get altered to such an extent that the top may not tip over! This is certainly paradoxical since a mere change of the observer cannot alter the fact that the top tips over on the table. In an effort to resolve the issue the authors of the paradox compare the equations of motion of the particles of the top from the perspective of the inertial frames of the rocket and the table and observe among other things that (1) the relativity of simultaneity plays an essential role in resolving the paradox and (2) the puzzle in some way is connected with one of the corrolaries of special relativity that the notion of rigidity is inconsistent with the theory. We show here that the question of the incompatibility of the notion of rigidity with special relativity has nothing to do with the current paradox and the role of the lack of synchronization of clocks in the context of the paradox is grossly over-emphasized. The conventionality of simultaneity of special relativity and the notion of the standard (Einstein) synchrony in the Galilean world have been used to throw light on some subtle issues concerning the paradox.     

The effect of aryl nitration on gas sorption and permeation in polysulfone

CO_2, CH_4, O_2, and N₂ permeability and solubility of unmodified and aryl-nitrated polysulfone were determined at 35°C and pressures up to 20 atm. The degree of nitration was varied from 0 to 2 nitro groups per repeat unit. The permeability and diffusion coefficients for all gases decreased with increasing degree of nitro substitution. The decrease in gas diffusivity is attributed to a combination of decreased fractional free volume and decreased torsional mobility with increasing degree of substitution. The solubilities of N_2, O_2, and CH₄ do not show a systematic dependence on degree of substitution. However, CO₂ solubility apparently goes through a minimum as the degree of substitution is increased. CO₂ solubility may be influenced by a competition between increases in polymer polarity (favoring higher solubility) and lower free volume (favoring lower solubility) that accompanies increases in the polar nitro substituent concentration. CO₂/CH₄ solubility selectivity increases monotonically as the degree of substitution increases. CO₂/CH₄ permselectivity and diffusivity selectivity increased with increasing degree of substitution. © 1995 John Wiley & Sons, Inc.     

Asymptotic distributions of M-estimators in a spatial regression model under some fixed and stochastic spatial sampling designs

In this paper, we consider M-estimators of the regression parameter in a spatial multiple linear regression model. We establish consistency and asymptotic normality of the M-estimators when the data-sites are generated by a class of deterministic as well as a class of stochastic spatial sampling schemes. Under the deterministic sampling schemes, the data-sites are located on a regular grid but may have aninfill component. On the other hand, under the stochastic sampling schemes, locations of the data-sites are given by the realizations of a collection of independent random vectors and thus, are irregularly spaced. It is shown that scaling constants of different orders are needed for asymptotic normality under different spatial sampling schemes considered here. Further, in the stochastic case, the asymptotic covariance matrix is shown to depend on the spatial sampling density associated with the stochastic design. Results are established for M-estimators corresponding to certain non-smooth score functions including Huber’s ψ-function and the sign functions (corresponding to the sample quantiles). Research of Lahiri is partially supported by NSF grant no. DMS-0072571. Research of Mukherjee is partially supported by the Academic Research Grant R-155-000-003-112 from the National University of Singapore.     

Hypochlorite‐Mediated Modulation of Photoinduced Electron Transfer in a Phenothiazine–Boron dipyrromethene Electron Donor–Acceptor Dyad: A Highly Water Soluble “Turn‐On” Fluorescent Probe for Hypochlorite

A highly water‐soluble phenothiazine (PTZ)–boron dipyrromethene (BODIPY)‐based electron donor–acceptor dyad ( WS‐Probe ), which contains BODIPY as the signaling antennae and PTZ as the OCl^? reactive group, was designed and used as a fluorescent chemosensor for the detection of OCl^?. Upon addition of incremental amounts of NaOCl, the quenched fluorescence of WS‐Probe was enhanced drastically, which indicated the inhibition of reductive photoinduced electron transfer (PET) from PTZ to ¹BODIPY*; the detection limit was calculated to be 26.7 nm . Selectivity studies with various reactive oxygen species, cations, and anions revealed that WS‐Probe was able to detect OCl^? selectively. Steady‐state fluorescence studies performed at varied pH suggested that WS‐Probe can detect NaOCl and exhibits maximum fluorescence in the pH range of 7 to 8, similar to physiological conditions. ESI‐MS analysis and ¹H NMR spectroscopy titrations showed the formation of sulfoxide as the major oxidized product upon addition of hypochlorite. More interestingly, when WS‐Probe was treated with real water samples, the fluorescence response was clearly visible with tap water and disinfectant, which indicated the presence of OCl^? in these samples. The in vitro cell viability assay performed with human embryonic kidney 293 (HEK 293) cells suggested that WS‐probe is non‐toxic up to 10 μm and implicates the use of the probe for biological applications.     

Sylvone,a new furanoid lignan ofpiper sylvaticum

The structure of a novel 2,3,4- trisubstituted furanoid lignan, designated sylvone, was established as $\text{1}$ from detailed spectroscopical and chemical studies.     

Soluble substituted poly-p-phenylenes—A new material for application in light-emitting diodes

Poly-p-phenylenes have attracted a great deal of attention with respect to their applications in displays, light-emitting devices, and batteries. However, the polymer poly-p-phenylene obtained by the Kovacic method is insoluble and intractable. The present study reports the preparation of soluble poly(p-phenylenes) by polymerization of derivatives of benzene in the presence of a specific aromatic nuclei. The resultant copolymer so obtained is soluble in common organic solvents such as chloroform and toluene. Preliminary studies have indicated that the polymer shows orange photoluminescence and electroluminescence when a potential of 7–10 V is applied to the device.     

Dithioannulation of Alkynes

A direct method for the preparation of 2,3-diphenyl-1,4-dithiins has been developed. The process involves treating alkynes with nickel bisdiphenyl-dithiolene in refluxing chlorobenzene in the presence of pyridine. Pyridine appears to be essential in order to avoid further transformation of 1,4-dithiins to thiophenes.     

Theoretical study of the electronic nonadiabatic transitions in the photoelectron spectroscopy of F2O

The photoelectron spectrum of F2O pertaining to ionizations to the ground (X2B1) and low-lying excited electronic states (A2B2, B2A1, and C2A2) of F2O+ is investigated theoretically. The near equilibrium potential energy surfaces of the ground electronic state (X2B1) of F2O and the mentioned ground and excited electronic states of F2O+ reported by Wang et al. ( J. Chem. Phys. 2001, 114, 10682) for the C2v configuration are extended for the Cs geometry assuming a harmonic vibration along the asymmetric stretching mode. The vibronic interactions between the A2B2 and B2A1 electronic states of F2O+ are treated within a linear coupling approach, and the strength of the vibronic coupling parameter is calculated by an ab initio method. The nuclear dynamics is simulated by both time-independent quantum mechanical and time-dependent wave packet approaches. Although the first photoelectron band exhibits resolved vibrational progression along the symmetric stretching mode, the second one is highly overlapping. The latter is attributed to the nonadiabatic interactions among the energetically close A2B2, B2A1, and C2A2 electronic states of F2O+. The theoretical findings are in good accord with the available experimental results.     

A convergent total synthesis of a new antiepileptic ceramide and its triacetyl derivative using olefin cross metathesis

A convergent total synthesis of a new antiepileptic ceramide 1b and its triacetyl derivative 1b′ was completed by using two important C-C bond forming reactions, Wittig methylenation and olefin cross metathesis as the key steps. The easily available 3,4,6-tri-O-benzyl-d-galactal was used as a chiral pool for the synthesis of highly functionalized amide 3 and the commercially available 1,12-dodecanediol for the long chain olefin counterpart 4. The long hydrocarbon chain of the new ceramide 1b was installed by using olefin cross metathesis between amide 3 and long chain terminal olefin 4 followed by hydrogenation.