Peroxide‐mediated crosslinking of poly(ethylene oxide)

The crosslinking of poly(ethylene oxide) (PEO) with a difunctional peroxide such as 2,5‐bis(tert‐butylperoxy)‐2,5‐dimethylhexane (Luperox 101) may proceed through at least two different pathways. Thus, the thermally formed alkoxy radicals abstract hydrogen from PEO, and the resulting PEO radicals may combine or react with the peroxide radicals to give ether or acetal crosslinks. However, these reactions also produce noncrosslinking acetals and vinyl ethers. The acetals may react further with peroxy or other radicals and yield orthoesters and ketene acetals. These and similar groups, in the presence of dilute acids, are susceptible to acid hydrolysis, leading to the disintegration of the gels. The gels, upon swelling in dilute acids, undergo a slow degradation process that is not observed for unmodified PEO. The acid hydrolysis is confirmed by a combination of size exclusion chromatography and dynamic mechanical analysis. IR analysis shows the presence of hydroxyl end groups and the presence of carboxylates rather than aldehyde groups, this is consistent with orthoesters and ketene acetal intermediates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3021–3026, 2002     

Paradox in Wave-Particle Duality

We report on the simultaneous determination of complementary wave and particle aspects of light in a double-slit type “welcher-weg” experiment beyond the limitations set by Bohr’s Principle of Complementarity. Applying classical logic, we verify the presence of sharp interference in the single photon regime, while reliably maintaining the information about the particular pinhole through which each individual photon had passed. This experiment poses interesting questions on the validity of Complementarity in cases where measurements techniques that avoid Heisenberg’s uncertainty principle and quantum entanglement are employed. We further argue that the application of classical concepts of waves and particles as embodied in Complementarity leads to a logical inconsistency in the interpretation of this experiment. A Preliminary version of this paper was presented by S.S.A. at a Seminar titled “Waving Copenhagen Good-bye: Were the Founders of Quantum Mechanics Wrong?,” Department of Physics, Harvard University, Cambridge, MA 02138, 23 March, 2004.     

Demonstration of a spectrally scanned holographic Stokesmeter

A holographic Stokesmeter (HSM) utilizes the inherent polarization sensitivity of volume gratings to determine all the Stokes parameters of input beams. A unique feature of the HSM is that it can be designed for spectral multiplexing at a high speed. Here, we report the demonstration of such a spectrally scanning HSM for two different wavelengths. Integration of such an HSM with a polarimetric imaging system will produce a device of potentially significant practical usage: a multi-spectral Stokes parameter camera (MSPC).     

Synthesis of chiral 2-(4-phenoxyphenylsulfonylmethyl)thiiranes as selective gelatinase inhibitors

[reactions: see text] Compound 1, 2-(4-phenoxyphenylsulfonylmethyl)thiirane, is a selective inhibitor of gelatinases, which is showing high promise in studies of animal models for cancer metastasis and stroke. The (R)-1 and (S)-1 enantiomers of compound 1 were each synthesized in this study and were shown to be equally active in inhibition of gelatinases.     

Thermodynamic Studies of Myelin Basic Protein upon Interaction with Zinc

The interaction of myelin basic protein (MBP) from bovine central nervous system with divalent zinc ion was studied by UV‐Vis titration spectrophotometry and isothermal titration calorimetry techniques at 27°C in Tris buffer solution at pH = 7.2. MBP has one binding site for a zinc ion. The binding of a zinc ion is endothermic (ΔH = + 159 kJ mol^?1) with a dissociation binding constant of 0.445 μM. The results obtained by two previous methods of isothermal titration spectrophotometry and calorimetry are similar and consistent with the result obtained from a new calculation method of calorimetric data analysis according to the Scatchard plot.     

On Uniform f-vectors of Cutsets in the Truncated Boolean Lattice

and let be the collection of all subsets of [n] ordered by inclusion. is a cutset if it meets every maximal chain in , and the width of is the minimum number of chains in a chain decomposition of . Fix . What is the smallest value of such that there exists a cutset that consists only of subsets of sizes between m and l, and such that it contains exactly k subsets of size i for each ? The answer, which we denote by , gives a lower estimate for the width of a cutset between levels m and l in . After using the Kruskal–Katona Theorem to give a general characterization of cutsets in terms of the number and sizes of their elements, we find lower and upper bounds (as well as some exact values) for . Received September 4, 1997