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.     

Polyvinylpyrrolidone thin film pyrolysis as accessed by the real-time optical transmission measurements

Present results reveal basic features of the optical transmission thermo-analytical method in its employment to investigate the oxidative pyrolysis of supported thin polyvinylpyrrolidone films. The OT curves naturally vary in shapes and positions on the time/temperature scales, respective to the examined rate of sample heating, to the wavelengths of radiation as well as to the film thickness. Recorded OT curves exhibit characteristic shapes with well-expressed OT minima. The temperatures at which the OT minima appear are in a linear relationship with heating rates of samples, at a frequency of radiation as well as a film thickness kept constant. Similarly, the OT values at which the OT minima appear are in a linear relationship with film thickness, at a frequency of the radiation and sample heating rate unchanged.     

Weak MV-algebras

In a recent paper [CHAJDA, I.—KüHR, J.: A non-associative generalization of MV-algebras, Math. Slovaca 57, (2007), 301–312], authors introduced and studied a non-associative generalization of MV-algebras called NMV-algebras. In contrast to MV-algebras, sections (i.e. principal filters) in NMV-algebras which are proper (i.e. are not MV-algebras), do not admit a structure of an NMV-algebra with respect to the operations defined in a natural way. The aim of the paper is to present a new class of algebras generalizing MV-algebras but sharing the above property. The financial support by the grant of Czech Government MSM 6198959214 is gratefully acknowledged.     

К ТЕОРИИ СПОНТАННОЙ Н АМАГНИЧЕННОСТИ ТОНКИХ СЛОЕВ. II. ЧАСТЬ)

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Synthesis and characterization of low dimensional ZnS- and PbS-semiconductor particles on a montmorillonite template

Low dimensional metal sulfide particles have been prepared in the interlayers of montmorillonites via reactions of the metal ion-exchanged clay minerals in aqueous dispersions with gaseous hydrogen sulfide. The montmorillonites separated from the Wyoming (USA) and Jel?ovy Potok (Slovakia) bentonites were saturated with Pb(2+) or Zn(2+). In the final nanohybrids, the smectite mineral can be incorporated with metal sulfide pillars and/or nanoparticles. Properties of the prepared materials were investigated by various analytical techniques. The formation of metal sulfide nanoparticles in the interlayer galleries was indicated by X-ray diffraction and energy dispersive X-ray analysis. About 50% of Pb(2+) or Zn(2+) present in montmorillonite has formed metal sulfide semiconducting units. Infrared spectroscopy and thermogravimetric analysis were used for characterization of starting materials and products. Ultraviolet-visible absorption and photoluminescence spectroscopies confirmed that final composite systems acquired the optical properties of the incorporated quantum low dimensional systems exhibiting blue shift of the energy gap and higher oscillator strength excitonic peaks. Larger amounts of metal sulfide nanoparticles were formed in montmorillonite Jel?ovy Potok probably as a consequence of its higher cation exchange capacity.     

Observation of the spin alignment of the ϱ0-meson produced in ¯pp interactions at 22.4 and 5.7 GeV/c

Studying the ⁰-meson production in ¯pp interactions at 22.4 GeV/c and in 4-prong anníhilation channels of ¯pp interactions at 5.7 GeV/c, we have observed an essential ⁰-meson spin alignment. The values of the ₀₀ element of the ⁰-meson spin density matrix (thez-axis is directed along the normal to the production plane) are equal to 0.08 ± 0.07 and 0.55 ± 0.03, respectively, i.e. the ⁰-meson spin lies preferably in the production plane. The absence of such an effect in pp interactions at 12 and 24 GeV/c and also the essentially larger ⁰ production cross section in ¯pp interactions at these energies make it possible to connect the observed ⁰-meson spin alignment with the annihilation processes. The character of the observed spin alignment is unexpected from the point of view of usual models, e.g. multiperipheral models. This effect could be described by the spontaneous polarization of quarks and antiquarks during the state preceding their recombination into mesons.Dedicated to Professor Ivan Úlehla on the occasion of his sixtieth birthday.The authors would like to express their gratitude to the CERN-Prague collaboration for permission to use their data on ¯pp interactions at 5.7 GeV/c. The authors are also indebted to A. M. Baldin, S. B. Gerasimov and H. I. Miettinen for valuable discussions, to the technicians and assistants at all laboratories for their work.     

Boundary trace inequalities and rearrangements

A new approach to boundary trace inequalities for Sobolev functions is presented, which reduces any trace inequality involving general rearrangement-invariant norms to an equivalent, considerably simpler, one-dimensional inequality for a Hardy-type operator. In particular, improvements of classical boundary trace embeddings and new optimal trace embeddings are derived. This research was partially supported by the Italian research project “Geometric properties of solutions to variational problems” of GNAMPA (INdAM) 2006, by the research project MSM 0021620839 of the Czech Ministry of Education, by grants 201/03/0935, 201/05/2033 and 201/07/0388 of the Grant Agency of the Czech Republic and by the Nečas Center for Mathematical Modeling project no. LC06052 financed by the Czech Ministry of Education.     

The complexity of cover graph recognition for some varieties of finite lattices

We address the following decision problem: Instance: an undirected graphG. Problem: IsG a cover graph of a lattice? We prove that this problem is NP-complete. This extends results of Brightwell [5] and Ne?et?il and Rödl [12]. On the other hand, it follows from Alvarez theorem [2] that recognizing cover graphs of modular or distributive lattices is in P. An important tool in the proof of the first result is the following statement which may be of independent interest: Given an integerl, l?3, there exists an algorithm which for a graphG withn vertices yields, in time polynomial inn, a graphH with the number of vertices polynomial inn, and satisfying girth(H)?l and χ(H)=χ(G).     

On the theory of the spontaneous magnetization of thin films. Part I

Conclusion From (3) it is seen that the quantum-mechanical theory of thin films leads to quite analogous results as for massive specimens. It is obvious that we should arrive at the same results as in (3) if from the very beginning we solved the whole problem by means of the theory of molecular fields putting the molecular fields of the individual atomic planes proportional to their magnetization. We shall therefore make use of this fact in the future by working with the method of molecular fields which permits of a somewhat more flexible procedure than the quantum-mechanical solution. At the same time, however, there appear in the equations constants of the molecular fields which are not more closely defined and which, as we know, are proportional to the exchange interaction energy between neighbours but with the present state of the theory this is not a disadvantage in comparison with the quantum-mechanical procedure, since the exchange integrals have not yet been calculated.A comparison of (3) with experiment will be left to the second part of this paper, where we shall compare the results of measurement with the equivalent equations in the molecular-field form.This paper was read at the international conference on magnetic phenomena in Moscow, 1956.