An interpretation of glass chemistry in terms of the optical basicity concept

The basicity of an oxide glass can be measured experimentally from the frequency shifts in the ultra-violet (UV) (s-p) spectra of probe ions such as Pb²⁺ and can be expressed on the numerical scale of optical basicity Λ (ideally Λ lies between zero and unity). It is possible to relate Λ with (i) the constitution, and (ii) the electronegativity of the cations (e.g. Na⁺, Si⁴⁺, etc.) of the glass, and the relationship allows microscopic optical basicities λ to be assigned to individual oxides and oxy-groups in the glass. These microscopic optical basicities are used for interpreting various aspects of the physics and chemistry of glass including refractivity, network coordination number changes, chemical durability, the glass electrode, UV transparency and the host behaviour of glass towards metal ions generally. Changes in glass basicity in going from one alkali metal oxide to another are also discussed. Finally, the concept of optical basicity, both as an experimentally obtained quantity and as a number calculated from glass constitution and electronegativity, is discussed in relation to the traditional approach to acid-base behaviour in glass.     

Evidence for exchange-coupled quadratic nets in CTS

Measurements of the low temperature heat capacity and powder magnetic susceptibility of CTS (Cu(NH₃)₄SO₄·H₂O) are shown to be consistent with quadratic nets of Heisenberg exchange-coupled spins ($\text{s =}\text{1}\text{2}$).     

A neutrino (antineutrino)-induced four lepton event

We report observation of a neutrino (antineutrino)-induced event with two electrons, one positron, one positively charged muon, a neutral K meson, and seven gammas in an experiment performed in the FNAL 15-ft. bubble chamber with a 47% atomic mixture of neon in hydrogen. Estimated experimental electron backgrounds are ～10^?4 per track. At present we have no plausible interpretation of this event.     

Tomentosones A and B, hexacyclic phloroglucinol derivatives from the Thai shrub Rhodomyrtus tomentosa

Two phloroglucinols named tomentosones A and B (1 and 2) that each possess a novel hexacyclic ring system were isolated from the CH(2)Cl(2) extract of Rhodomyrtus tomentosa leaves. Their structures were elucidated from analyses of 2D NMR spectroscopic data. Tomentosone A inhibited the growth of chloroquine-resistant and -sensitive strains of the malaria parasite Plasmodium falciparum, with IC(50) values of 1.49 μM and 1.0 μM, respectively, while tomentosone B was significantly less active.     

Isolation and detection of single molecules on paramagnetic beads using sequential fluid flows in microfabricated polymer array assemblies

We report a method for isolating individual paramagnetic beads in arrays of femtolitre-sized wells and detecting single enzyme-labeled proteins on these beads using sequential fluid flows in microfabricated polymer array assemblies. Arrays of femtolitre-sized wells were fabricated in cyclic olefin polymer (COP) using injection moulding based on DVD manufacturing. These arrays were bonded to a complementary fluidic structure that was also moulded in COP to create an enclosed device to allow delivery of liquids to the arrays. Enzyme-associated, paramagnetic beads suspended in aqueous solutions of enzyme substrate were delivered fluidically to the array such that one bead per well was loaded by gravity. A fluorocarbon oil was then flowed into the device to remove excess beads from the surface of the array, and to seal and isolate the femtolitre-sized wells containing beads and enzyme substrate. The device was then imaged using standard fluorescence imaging to determine which wells contained single enzyme molecules. The analytical performance of this device as the detector for digital ELISA compared favourably to the standard method, i.e., glass arrays mechanically sealed against a silicone gasket; prostate specific antigen (PSA) could be detected from 0.011 pg mL(-1) up to 100 pg mL(-1). The use of an enclosed fluidic device to isolate beads in single-molecule arrays offers a multitude of advantages for low-cost manufacturing, ease of automation, and instrument development to enable applications in biomarker validation and medical diagnosis.     

Binding efficiency and transport properties of molecularly imprinted polymer thin films

A model system for the characterization of molecular recognition events in molecularly imprinted polymers (MIPs) is presented. The use of a biologically inspired, three-point hydrogen-bonding motif and a thin film polymeric matrix allows for pre- and post-polymerization binding properties to be characterized by infrared spectroscopy. A method to determine binding constants was developed and utilized before and after cross-linking. These values showed a 10-fold decrease in binding after polymerization, which was attributed to an increase in molecular confinement after polymerization and a change in the local structural environment of the binding cavity. Transport of the guest molecule was shown to be reversible.     

Flow of a liquid with an anisotropic viscosity tensor

This paper presents a simple model of an anisotropic incompressible viscous fluid, whose equations of state involve one anisotropic physical constant tensor (in the sense of Oldroyd [1]). Attention is restricted to the case of a fluid that is everywhere transversely isotropic at some given instant, so that the model is essentially one of a liquid with initially just one privileged direction at each point. Transverse isotropy does not persist, however, in some flow situations.Predictions are made for simple shearing flows and for channel and pipe flows with different initial directions of orientation. In some cases, the volume rate of flow under constant pressure-gradient decreases steadily and tends to zero after a long time.