Growth and kinetics of in vitro poly([R]‐(–)‐3‐hydroxybutyrate) granules interpreted as particulate polymerization with coalescence

Transmission electron microscopy (TEM) and Cryo‐TEM were used to study the growth kinetics of poly(3‐hydroxybutyrate) granules produced by in vitro polymerization. The in vitro formation of poly(3‐hydroxybutyrate) uses a recombinant form of the PHA synthase to polymerize [R]‐(–)‐3‐hydroxybutyryl‐CoA. Since the in vitro reaction contains only synthase and monomer, it is a simpler system than the in vivo biosynthesis of poly(3‐hydroxybutyrate). TEM and Cryo‐TEM were used in conjunction with image analysis to examine the granules that were formed in the in vitro reaction. The in vitro reaction yielded spherical granules of rapidly increasing size; the initially observed granules were already larger than 0.1 μm. While the average granule diameter and volume increased with reaction time, the number of granules decreased throughout the reaction due to coalescence. Basic kinetic parameters, including K_M and V_max were determined and compared to those reported for the in vivo biosynthesis of poly(3‐hydroxybutyrate). In addition it was found that the granules formed by this process were essentially noncrystalline. A computer simulation of the reaction, based on initial formation of relatively large microporous granules that consolidate by expulsion of water during polymerization, accounted for the shape of the kinetic curves.     

Induced crystallization and orientation of poly(ethylene terephthalate) during uniaxial and biaxial elongation

Stretching PET at a high strain rate above the glass transition temperature has a positive effect on the strength of the material. In a recent paper^[1], we presented the influence of stretch and blow molding parameters on the properties of the final product, especially on the crystallinity induced by stretching. In this paper, we focus on the effects of loading, temperature, elongation and strain rate on macromolecular orientation and crystallization kinetics. We present experimental results from uniaxial and biaxial elongation tests carried out on injected PET specimens. To minimize the effect of quiescent crystallization, specimens are quickly heated with infrared lamps before the test and temperature is regulated during the test. Both uniaxial and biaxial tests are analyzed using a cross correlation technique^[2] that compares a picture used as reference and the picture of the deformed specimen. This technique allows us to determine all strain components at each point of the specimen, even when the strain field is not homogeneous. In a second part, we present measurements of macromolecular orientation and crystallinity ratio performed after each test. The infrared dichroïsm technique is used to determine the orientation of the microscopic morphology of PET before and after the testing. DSC measurements and density measurements are carried out to calculate the crystallinity ratio. Influences of strain rate, temperature and strain path sequence are evaluated in order to build a database for recent models of induced crystallization^[3],[4],[5].     

Affect-Logic,Embodiment, Synergetics,and the Free Energy Principle: New Approaches to the Understanding and Treatment of Schizophrenia

This theoretical paper explores the affect-logic approach to schizophrenia in light of the general complexity theories of cognition: embodied cognition, Haken’s synergetics, and Friston’s free energy principle. According to affect-logic, the mental apparatus is an embodied system open to its environment, driven by bioenergetic inputs of emotions. Emotions are rooted in goal-directed embodied states selected by evolutionary pressure for coping with specific situations such as fight, flight, attachment, and others. According to synergetics, nonlinear bifurcations and the emergence of new global patterns occur in open systems when control parameters reach a critical level. Applied to the emergence of psychotic states, synergetics and the proposed energetic understanding of emotions lead to the hypothesis that critical levels of emotional tension may be responsible for the transition from normal to psychotic modes of functioning in vulnerable individuals. In addition, the free energy principle through learning suggests that psychotic symptoms correspond to alternative modes of minimizing free energy, which then entails distorted perceptions of the body, self, and reality. This synthetic formulation has implications for novel therapeutic and preventive strategies in the treatment of psychoses, among these are milieu-therapeutic approaches of the Soteria type that focus on a sustained reduction of emotional tension and phenomenologically oriented methods for improving the perception of body, self, and reality.     

The magid-ryan conjecture for 4-dimensional affine spheres

In this paper we prove the Magid-Ryan conjecture for 4-dimensional affine hyperspheres in R⁵. This conjecture states that every affine hypersphere with non-zero Pick invariant and constant sectional curvature is affinely equivalent with either (x ₁ ² ±x ₂ ² )(x ₃ ² ±x ₄ ² ...(x _2m−1 ² ±x _2m ² ) = 1 or (x ₁ ² ±x ₂ ² (x ₃ ² ±x ₄ ² )...(x _2m−1 ² ±x _2m ² )x _2m+1 = 1 where the dimensionn satisfiesn = 2m orn =2m + 1. This conjecture was proved in [11] in case the metric is positive definite and in [2] in case the metric is Lorentzian.     

Forensic analysis of automotive paints by Raman spectroscopy

In this work, the possible contribution of Raman spectroscopy in forensic science is evaluated, more specifically for the analysis of automotive paint samples. Spectra from paint flakes as well as from cross sections were examined, in order to identify not only the pigments but also binders and extenders in all paint layers. Moreover, the possibility of distinguishing paint samples from different cars was evaluated to assess the use of vibrational spectroscopic techniques in the investigation of a hit-and-run accident. The presence of rutile and extenders, such as calcite and barium sulphate, could be demonstrated by their characteristic Raman bands. However, the identification of the binder by Raman spectroscopy was hampered: only with additional information from IR analysis could most of the bands in the spectrum be assigned to molecular vibrations of the binders. In contrast, organic pigments, having very distinctive and well-resolved characteristic bands, could easily be identified by comparing the spectra from the basecoat of the sample with spectra from a reference database. Because of these characteristic bands, the basecoat seems to provide the best spectra to distinguish paint samples. Moreover, some paints can also be distinguished by the absence or presence of the bands from calcium carbonate and barium sulphate in the primer surfacer. When recording spectra from paint flakes, Raman bands from the spectra of the clearcoat as well as from the basecoat are obtained. Copyright © 2005 John Wiley & Sons, Ltd.     

Natural and Synthetic Xanthones as Monoamine Oxidase Inhibitors: Biological Assay and 3D‐QSAR

Fifty‐nine xanthones (=9H‐xanthen‐9‐ones) of natural or synthetic origin were investigated for their inhibitory activity toward monoamine‐oxidase A (MAO‐A) and MAO‐B. The compounds demonstrated reversible, time‐independent activities, with selectivity toward MAO‐A. The most active inhibitor had an IC₅₀ of 40 nM . Electron absorption spectroscopy revealed the formation of a 1 : 1 charge‐transfer complex between lumiflavine and xanthones. 3D‐QSAR Studies according to the CoMFA/GOLPE procedure provided information on the relationship between steric and electrostatic fields and MAO‐A inhibition. The ALMOND procedure yielded additional topographical information on structural factors favoring activity.     

Surface organization of hyperbranched polymer molecules,as studied by atomic force microscopy

The recent emergence of hyperbranched polymers has opened the door for the design of a large variety of novel, well‐controlled chain architectures. For instance, «comb‐like» and “dendritic‐like” polymers can be obtained from hyperbranched poly(chloroethyl vinyl ether)‐g‐polystyrene (PCEVE‐g‐PS) copolymers, with excellent control over the dimensions of the polystyrene lateral branches and the PCEVE backbone. In this work, the nanometer scale organization of these materials is studied by means of Tapping Mode Atomic Force Microscopy. We focus on the influence of the intrinsic molecular architecture of the hyperbranched PCEVE‐g‐PS on the organization of the material. In the case of thin deposits, we observe a layer‐by‐layer organization. On the free surface, it is possible to image single polymer molecules and to analyze their size in terms of polymer molecular weight. In most cases, the molecules are found to adopt an extended conformation and to form lamellar arrangements. We observe that the degree of lateral ordering of these molecules strongly depends on their intrinsic architecture.     

Three-dimensional centrifugal instabilities development inside a parallelepipedic open cavity of various shape

This experimental study reports flow developments inside a parallelepipedic cavity of variable shape and dimensions. That flow is generated by the interaction between a laminar boundary layer and the cavity, which creates shear-layer oscillations. The aim is to understand the three-dimensional flow morphology varying the Reynolds number and the cavity shape. Flow visualizations are obtained in a plane situated inside the cavity in order to get the dynamical structures. Dimensional analysis of the cavity flow teaches that three dimensionless numbers are necessary for the flow reduction. This is confirmed by experimental results pointing thresholds of appearance of instabilities identified for some combinations of Reynolds number and geometric parameters. The key mechanisms for their existence are centrifugal effects induced by a vortex of spanwise axis with sufficient intensity, and viscous effects due to the wall confinement of the cavity. Their destruction is linked to flow transition to turbulence above a limiting convective velocity generated by the vortex of spanwise axis. These instabilities are generally present in a spanwise row of counter-rotating pairs of vortices, but for some cases, isolated pairs are also identified. Secondary modulations of primary instabilities are also present for particular parameters. Results permit to discriminate the relevant scales associated with the shear layer and the inner cavity flow.