Phase effects in the diffraction of light: beyond the grating equation

Diffraction gratings affect the absolute phase of light in a way that is not obvious from the usual derivation of optical paths using the grating equation. For example, consider light which encounters first one and then the second of two parallel gratings. If one grating is moved parallel to its surface, the phase of the light diffracted from the grating pair is shifted by 2pi each time the grating is moved by one grating constant, even though the geometric path length is not altered by the motion. This additional phase shift must be included when incorporating diffraction gratings in interferometers.     

Phase diagrams of lyotropic cholesteric fluids

Experimental investigations of lyotropic cholesterics fluids are presented which show that changes in the shape anisotropy and chirality of the micellar population determine the topology of the temperature-concentration phase diagrams. For given amounts of the substances which induce the chirality and modify the shape anisotropy of the micelles, two distinct biaxial cholesteric phases are disclosed in the phase diagrams. This is interpreted in the framework of the catastrophe theory of phase transitions.     

Thermally activated stress relief in garnet layers grown by liquid phase epitaxy

The lattice misfit of (Lu, Tb)₃Fe₅O₁₂ epitaxial layers grown in compression on Gd₃Ga₅O₁₂ substrates has been found to decrease as a result of annealing at temperatures between 1000 and 1300°C. The deformation rate is thermally activated and depends on the degree of compressive misfit stress at the annealing temperature, the layer thickness and the reducing nature of the anneal atmosphere. Layers which were in tension at the annealing temperature (obtained by using Y₃Fe₅O₁₂ as the substrate material) did not exhibit stress relief. The process has been found to occur nonhomogeneously by the formation of regions of almost total relief which grow and multiply with continued annealing. The shape symmetry of these regions is consistent with dislocation climb in {112} planes. The results are interpreted in terms of a mechanism involving dislocation climb loops (∽1μm diameter) which develop as a result of the formation of oxygen vacancies.     

Optical measurement of magnetic anisotropy in thin garnet films

This paper describes an improved optical method for measuring locally the cubic and uniaxial magnetic anisotropy fields in thin garnet films. The derivative of the in-plane component of the magnetization is measured, using a double modulation technique which combines polarization modulation with field modulation. A simple graphical method is devised to calculateH _k andH _u from the extrema in this derivative curve. The results of measurements on magnetic garnet films obtained by different methods are compared. Local measurements of the anisotropy induced by substrate facet strain are described.     

Sulfated poly-amido-saccharides (sulPASs) are anticoagulants in vitro and in vivo

Anticoagulant therapeutics are a mainstay of modern surgery and of clotting disorder management such as venous thrombosis, yet performance and supply limitations exist for the most widely used agent – heparin. Herein we report the first synthesis, characterization, and performance of sulfated poly-amido-saccharides (sulPASs) as heparin mimetics. sulPASs inhibit the intrinsic pathway of coagulation, specifically FXa and FXIa, as revealed by ex vivo human plasma clotting assays and serine protease inhibition assays. sulPASs activity positively correlates with molecular weight and degree of sulfation. Importantly, sulPASs are not degraded by heparanases and are non-hemolytic. In addition, their activity is reversed by protamine sulfate, unlike small molecule anticoagulants. In an in vivo murine model, sulPASs extend clotting time in a dose dependent manner with bleeding risk comparable to heparin. These findings support continued development of synthetic anticoagulants to address the clinical risks and shortages associated with heparin.

Heparin mimicking sulfated poly-amido-saccharides (sulPASs) are anticoagulants resistant to heparanases and reversed by protamine sulfate. In an in vivo murine model, sulPASs extend clotting time without the increased risk of bleeding.     

Biotin functionalized poly(sulfonic acid)s for bioconjugation: In situ binding monitoring by QCM‐D

We describe the synthesis of biotin end functionalized poly(sulfonic acid)s via living radical polymerization (LRP) for conjugation to Avidin. Quartz crystal microbalance (QCM‐D) and competitive binding studies were used to confirm this conjugation. A biotin initiator for copper‐mediated LRP was used to provide acrylamide and methacrylate based polymers with the functional end group. This investigation revealed that 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid was not a suitable monomer in its acid form but was successfully used in its sodium salt form. A second monomer, 3‐sulfopropylmethacrylate as the potassium salt was also studied and both monomers produced polymers with polydispersities <1.3 and 1.4, respectively. Evolution of molecular weight with respect to time indicated that the polymerization of the acrylamide polymer is controlled. Quartz crystal microbalance with dissipation monitoring was used to confirm that the biotinylated polymers were able to bind to Avidin in situ. The gold surface of a quartz crystal was chemically modified resulting in a stable monolayer of Avidin; the biotinylated polymers were passed over the functionalized surface and their grafting ability was examined. A competitive binding evaluation was undertaken with 2‐(4‐hydroxyphenylazo)benzoic acid (HABA) dye to provide visual verification of conjugation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Instrumental neutron activation analysis,a technique for measurement of Se,Hg, Fe,Zn, K,Mn, Br,and the Hg:Se ratio in brain tissue samples with results from the Memory and Aging Project (MAP)

An INAA method for measurement of Se, Hg, Fe, Cr, Zn, Mn, K, and Br in autopsy cerebellum, anterior putamen, white matter, mid-frontal cortex, and inferior temporal lobe. Se, Hg, Fe, Cr, and Zn were measured autopsy samples collected from participants of the Memory and Aging Project. The first study examined the association between seafood consumption, brain Hg and Se, Apolipoprotein E (APOE-ε4) status, and brain neuropathology. Following the initial study, the samples were archived. A subsequent method was developed to measure Mn, K, and Br in the archived brain tissue samples.     

Catalytic asymmetric bromolactonization reactions using (DHQD)2PHAL-benzoic acid combinations

Catalytic (DHQD)₂PHAL as modified by added benzoic acid, is an off-the-shelf catalyst-additive combination for effecting catalytic asymmetric bromolactonization reactions. This combination delivers bromolactones with asymmetric induction at a comparable level to bespoke catalysts previously optimized for particular substrate classes.     

An integrated quantum chemical and experimental approach for exploring the structures and properties of insensitive munitions interacting with ions in bulk water

Structural Chemistry - Alternatives to legacy munitions and explosives, materials that feature increased stability against external stimuli without compromising their energetic yields are currently...