Path dependence or convergence? The evolution of corporate ownership around the world

We offer a theory that sheds light on the current debate over whether the form of corporate ownership converges to the Berle-Means image. Our analytical results are threefold. First, legal rules and firm-specific protective arrangements are complementary. Secondly, corporate ownership patterns can be convergent or path dependent depending on the relative importance of these protective arrangements. We predict, for example, diffuse stock ownership in countries that impose legal limits on blockholders’ power to expropriate minority investor rights. Thirdly, we find that convergence toward diffuse share ownership is a movement towards the social optimum. Our empirical results suggest a case for the co-existence of path dependence and functional convergence (convergence to the diffuse form of share ownership through cross-listings on U.S. stock exchanges that impose more stringent disclosure and listing requirements). These results have implications for the design of executive compensation, the case for institutional investor activism and the proposal to increase shareholder power

Use of Dispersion Imaging for Grating-Coupled Surface Plasmon Resonance Sensing of Multilayer Langmuir–Blodgett Films

We report grating-coupled surface plasmon resonance measurements involving the use of dispersion images to interpret the optical response of a metal-coated grating. Optical transmission through a grating coated with a thin, gold film exhibits features characteristic of the excitation of surface plasmon resonance due to coupling with the nanostructured grating surface. Evidence of numerous surface plasmon modes associated with coupling at both front (gold/air) and back (gold/substrate) grating interfaces is observed. The influence of wavelength and angle of incidence on plasmon coupling can be readily characterized via dispersion images, and the associated image features can be indexed to matching conditions associated with several diffracted orders at both the front and back of the grating. These features collapse onto a set of global dispersion curves when plotted as peak energy versus the grating wavevector, with feature locations clustered according to the refractive index values of the neighboring dielectric material, either air or polycarbonate. Coating of the grating with multilayer arachidic acid films via Langmuir–Blodgett deposition results in red-shifting of some, but not all, of the plasmon features. The magnitude of the shift is a function of the film thickness, wavelength, and angle of incidence. Dispersion images clearly depict the red-shifting and also broadening of the front side features with increasing film thickness. In contrast, little change is observed in features associated with the back-side of the grating. The nature and magnitude of the interaction between the plasmon modes appearing at the front and back sides of the grating are discussed and analyzed in terms of the predicted interactions determined via optical modeling calculations

Structure and sequence analyses of Bacteroides proteins BVU_4064 and BF1687 reveal presence of two novel predominantly-beta domains, predicted to be involved in lipid and cell surface interactions.

BackgroundN-terminal domains of BVU_4064 and BF1687 proteins from Bacteroides vulgatus and Bacteroides fragilis respectively are members of the Pfam family PF12985 (DUF3869). Proteins containing a domain from this family can be found in most Bacteroides species and, in large numbers, in all human gut microbiome samples. Both BVU_4064 and BF1687 proteins have a consensus lipobox motif implying they are anchored to the membrane, but their functions are otherwise unknown. The C-terminal half of BVU_4064 is assigned to protein family PF12986 (DUF3870); the equivalent part of BF1687 was unclassified.ResultsCrystal structures of both BVU_4064 and BF1687 proteins, solved at the JCSG center, show strikingly similar three-dimensional structures. The main difference between the two is that the two domains in the BVU_4064 protein are connected by a short linker, as opposed to a longer insertion made of 4 helices placed linearly along with a strand that is added to the C-terminal domain in the BF1687 protein. The N-terminal domain in both proteins, corresponding to the PF12985 (DUF3869) domain is a β-sandwich with pre-albumin-like fold, found in many proteins belonging to the Transthyretin clan of Pfam. The structures of C-terminal domains of both proteins, corresponding to the PF12986 (DUF3870) domain in BVU_4064 protein and an unclassified domain in the BF1687 protein, show significant structural similarity to bacterial pore-forming toxins. A helix in this domain is in an analogous position to a loop connecting the second and third strands in the toxin structures, where this loop is implicated to play a role in the toxin insertion into the host cell membrane. The same helix also points to the groove between the N- and C-terminal domains that are loosely held together by hydrophobic and hydrogen bond interactions. The presence of several conserved residues in this region together with these structural determinants could make it a functionally important region in these proteins.ConclusionsStructural analysis of BVU_4064 and BF1687 points to possible roles in mediating multiple interactions on the cell-surface/extracellular matrix. In particular the N-terminal domain could be involved in adhesive interactions, the C-terminal domain and the inter-domain groove in lipid or carbohydrate interactions

Resonance Quenching and Guided Modes Arising from the Coupling of Surface Plasmons with a Molecular Resonance

In this paper, we describe experimental and modeling results that illucidate the nature of coupling between surface plasmon polaritons in a thin silver film with the molecular resonance of a zinc phthalocyanine dye film. This coupling leads to several phenomena not generally observed when plasmons are coupled to transparent materials. The increased absorption coefficient near a molecular resonance leads to a discontinuity in the refractive index, which causes branching of the plasmon resonance condition and the appearance of two peaks in the p-polarized reflectance spectrum. A gap exists between these peaks in the region of the spectrum associated with the molecular resonance and reflects quenching of the plasmon wave due to violation of the resonance condition. A second observation is the appearance of a peak in the s-polarized reflection spectra. The initial position of this peak corresponds to where the refractive index of the adsorbate achieves its largest value, which occurs at wavelengths just slightly larger than the maximum in the molecular resonance. Although this peak initially appears to be nondispersive, both experimental data and optical modeling indicate that increasing the film thickness shifts the peak position to longer wavelengths, which implies that this peak is not associated with the molecular resonance but, rather, is dispersive in nature. Indeed, modeling shows that this peak is due to a guided mode in the film, which appears in these conditions due to the abnormally high refractive index of the film near the absorbance maximum. Results also show that, with increasing film thickness, numerous additional guided modes appear and move throughout the visible spectrum for both s- and p-polarized light. Notably, these guided modes are also quenched near the location of the molecular resonance. The quenching of both the plasmon resonance and the guided modes can be explained by a large decrease in the in-plane wave propagation length that occurs near the molecular resonance, which is a direct result of the film’s large absorption coefficient

Diffraction-Based Tracking of Surface Plasmon Resonance Enhanced Transmission Through a Gold-Coated Grating

Surface plasmon resonance enhanced transmission through metal-coated nanostructures represents a highly sensitive yet simple method for quantitative measurement of surface processes and is particularly useful in the development of thin film and adsorption sensors. Diffraction-induced surface plasmon excitation can produce enhanced transmission at select regions of the visible spectrum, and wavelength shifts associated with these transmission peaks can be used to track adsorption processes and film formation. In this report, we describe a simple optical microscope-based method for monitoring the first-order diffracted peaks associated with enhanced transmission through a gold-coated diffraction grating. A Bertrand lens is used to focus the grating’s diffraction image onto a CCD camera, and the spatial position of the diffracted peaks can be readily transformed into a spectral signature of the transmitted light without the use of a spectrometer. The surface plasmon peaks appear as a region of enhanced transmission when the sample is illuminated with p-polarized light, and the peak position reflects the local dielectric properties of the metal interface, including the presence of thin films. The ability to track the position of the plasmon peak and, thus, measure film thickness is demonstrated using the diffracted peaks for samples possessing thin films of silicon oxide. The experimental results are then compared with calculations of optical diffraction through a model, film-coated grating using the rigorously coupled wave analysis simulation method

Interstellar solid hydrogen

We consider the possibility that solid molecular hydrogen is present in interstellar space. If so cosmic-rays and energetic photons cause ionization in the solid leading to the formation of H+6. This ion is not produced by gas-phase reactions and its radiative transitions therefore provide a signature of solid H2 in the astrophysical context. The vibrational transitions of H+6 are yet to be observed in the laboratory, but we have characterized them in a quantum-theoretical treatment of the molecule; our calculations include anharmonic corrections, which are large. Here we report on those calculations and compare our results with astronomical data. In addition to the H+6 isotopomer, we focus on the deuterated species (HD)+3 which is expected to dominate at low ionization rates as a result of isotopic condensation reactions. We can reliably predict the frequencies of the fundamental bands for five modes of vibration. For (HD)+3 all of these are found to lie close to some of the strongest of the pervasive mid-infrared astronomical emission bands, making it difficult to exclude hydrogen precipitates on observational grounds. By the same token these results suggest that (HD)+3 could be the carrier of the observed bands. We consider this possibility within the broader picture of interstellar medium photo-processes and we conclude that solid hydrogen may indeed be abundant in astrophysical environments

Doctors of osteopathic medicine (DO): a Canadian perspective

Background: Doctors of osteopathic medicine (DO) are one of the fastest growing segments of health care professionals in the United States. Although Canada has taken significant leaps in the acknowledgment of US trained DOs, there continues to be a lack of understanding of the profession by Canadian trained physicians. In this article, we provide a brief overview of osteopathic medical education and training in the United States.Method: Current information of osteopathic training by American Association of Colleges of Osteopathic Medicine (AACOM) and American Osteopathic Association (AOA) was presented. Data pertaining to Canadians enrolled in osteopathic colleges was compared with allopathic (MD) and international medical graduates (IMGs).Results: Doctors of osteopathic medicine programs provide an additional pathway for students interested in pursuing a medical education. Canadian applications to osteopathic colleges are expected to grow due to successful post-graduate US residency matching, increased difficulty of matriculating at Canadian medical schools, and a greater awareness of the profession in Canada.Conclusions: Given the increasing enrollment of Canadian students in US osteopathic medical schools, we expect that Canadian DOs will play a significant role in shaping health care in both the US and Canada

High Resolution Crystal Structures of the Wild Type and Cys-55 right-arrow Ser and Cys-59 right-arrow Ser Variants of the Thioredoxin-like [2Fe-2S] Ferredoxin from Aquifex aeolicus

The [2Fe-2S] ferredoxin (Fd4) from Aquifex aeolicus adopts a thioredoxin-like polypeptide fold that is distinct from other [2Fe-2S] ferredoxins. Crystal structures of the Cys-55 right-arrow Ser (C55S) and Cys-59 right-arrow Ser (C59S) variants of this protein have been determined to 1.25 Å and 1.05 Å resolution, respectively, whereas the resolution of the wild type (WT) has been extended to 1.5 Å. The improved WT structure provides a detailed description of the [2Fe-2S] cluster, including two features that have not been noted previously in any [2Fe-2S] cluster-containing protein, namely, pronounced distortions in the cysteine coordination to the cluster and a Calpha -H-Sgamma hydrogen bond between cluster ligands Cys-55 and Cys-9. These features may contribute to the unusual electronic and magnetic properties of the [2Fe-2S] clusters in WT and variants of this ferredoxin. The structures of the two variants of Fd4, in which single cysteine ligands to the [2Fe-2S] cluster are replaced by serine, establish the metric details of serine-ligated Fe-S active sites with unprecedented accuracy. Both the cluster and its surrounding protein matrix change in subtle ways to accommodate this ligand substitution, particularly in terms of distortions of the Fe2S2 inorganic core from planarity and displacements of the polypeptide chain. These high resolution structures illustrate how the interactions between polypeptide chains and Fe-S active sites reflect combinations of flexibility and rigidity on the part of both partners; these themes are also evident in more complex systems, as exemplified by changes associated with serine ligation of the nitrogenase P cluster

Characterization of a novel weak cation-exchange hydrogel membrane through the separation of lysozyme from egg white

Membrane chromatography was investigated as an alternative method to packed-bed chromatography for protein recovery. The purification of lysozyme from egg white with Natrix adseptTM weak cation-exchange membranes was investigated under two different binding configurations: (1) a non-flow, static set-up with variable pH and sodium chloride (NaCl) concentrations during the binding and elution steps, and (2) a dynamic, cross-flow set-up with recycle at pH 7.5 and no NaCl addition during binding. The weak cation-exchange membrane consisted of a carboxylic acid-based, environmentally-responsive hydrogel layer bonded to a polymer matrix. Lysozyme was chosen to illustrate protein-membrane binding interactions due to its well-characterized nature and positive surface charge over a large pH range. For the static binding set-up, two sources of lysozyme were studied: pure lysozyme and egg whites treated with 60 % (v/v) ethanol (ESEW). Elution of bound protein was performed with 1 M NaCl under two pH strategies: binding and elution at a constant pH, and binding at pH 4.5 and variable elution pH. The highest maximum total protein binding capacity for pure lysozyme and ESEW was observed at pH 4.5 with no NaCl addition; however, poor total protein and lysozyme activity recovery were achieved during separation. As well, other egg white proteins, such as ovomucoid, were observed to bind to the membrane surface at pH 4.5, despite possessing similar charge polarity to the anionic membrane surface, indicating a non-electrostatic binding mechanism during operation below the membrane’s pKa (4.7). Based on the conditions tested, the highest total protein and lysozyme activity recovery was demonstrated for the separation of lysozyme from ESEW at pH 7.5 binding and elution and no NaCl addition. In the dynamic binding study, very high pure lysozyme dynamic binding capacity was achieved at 10 % breakthrough (167.3 mg/ml membrane for a 0.35 mg/ml lysozyme solution). The lysozyme dynamic binding capacity was 2.2 times greater than the static binding capacity under similar conditions, significantly higher than published results for other cation-exchange membranes. The separation of lysozyme from four lysozyme sources was tested: pure lysozyme, ESEW, and aqueous egg whites with (ASEW) and without (AEW) 100 mM NaCl. The highest lysozyme activity recovery during separation and lysozyme purity was achieved from the ESEW feed. Lysozyme separation from aqueous egg whites was not as effective, likely due to a high concentration of negatively-charged protein impurities fouling the surface of the membrane. Competitive binding to the membrane limited lysozyme binding and reduced the purity of the recovery elution stream. The application of feed-side pressure during the separation of ESEW produced a high purity, high recovery lysozyme elution stream with a significant reduction in processing time; however, protein aggregates were observed to form on the membrane surface, limiting the applicability of high-pressure operation and reducing protein functionality in the elution stream. The weak cation-exchange membrane system was shown to successfully separate out a target protein from a low concentration protein mixture through electrostatic interactions, and may be further applied to other protein systems