Modeling the dynamics of E. coli populations in the three-dimensional turbulent field of a stirred-tank bioreactor—A structured-segregated approach

In the present work, an Euler-Lagrange approach has been applied to characterize the behavior of a heterogeneous cell population in a stirred-tank bioreactor with non-ideal mixing. It allows one to describe population behavior as the outcome of the interaction between the intracellular state of its individual cell and the turbulent flow field in the reactor. The modeling approach and the numerical method employed are based on an Euler-Lagrange formulation of the system combined with a fractional-step method to allow for a stable, accurate, and numerically efficient solution of the underlying equations. This strategy permits one to account for the heterogeneity present in real reactors in both the abiotic and biotic phases. The example of sugar uptake (phosphotransferase system, PTS) of E. coli cells growing in a fed-batch culture is used to illustrate the application of the approach. The activity of the uptake system depends on the local concentration of glucose as well as the ratio of the intracellular concentrations of phosphoenolpyruvate and pyruvate, which in turn is a function of the history of the individual cell. The simulation results point to distinct differences in the viability of the cells at different scale of operation.     

A Tikhonov Regularizing Algorithm for Processing Multiwave Lidar Data in the Absence of Information on the Measurement Error

An algorithm is considered for recovering the aerosol size distribution and also the mean (effective) radius and quantitative concentration from optical data: back-scattering and total attenuation coefficients as measured with a certain error δ at various wavelengths. These quantities are connected by a linear integral Fredholm equation of the first kind. A solution is provided by the modified discrepancy, which enables one to estimate the regularization parameter in the absence of information on the error δ. __________ Translated from Izmeritel'naya Tekhnika, No. 10, pp. 8–14, October, 2005.     

Change in Iron Powder Properties with Treatment in Rolls

Conditioned iron powders are prepared by carbothermal reduction of “Blue Dust” (India) ore concentrate followed by compaction treatment in rolling mill and a decarburizing anneal. The properties of powder prepared by grinding in a vibration and rolling mill are determined. The method makes it possible to control the bulk density of the powder from 1.75 to 2.75 g/cm³. Determination of the production properties of the powders obtained and powder NC.100.24 by the same procedure established satisfactory conformity of the results. The technological desirability of preparing conditioned iron powder by treatment in a rolling mill is demonstrated.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 12–16, March–April, 2005.     

Morphology and Growth Kinetics of 3He Crystals Below 1 mK

The shapes as well as the growth and melting properties of bcc-³He single crystals have been investigated with a low temperature Fabry-Pérot interferometer. Eleven types of facets were clearly identified during slow crystal growth at the temperature of 0.55 mK, where the solid is in the antiferromagnetically ordered u2d2 phase. The growth rates of the individual facets have been measured and the results indicate significant growth anisotropy. The observed linear dependence of the growth velocity on the driving force shows that facets grow due to the presence of screw dislocations, while the step velocity is limited by the spin wave velocity due to the strong interaction of the moving step with magnons in the solid. The measured growth rates of the facets and the assumed growth mechanism gave us the unique opportunity to obtain the step free energies for ten different types of facets observed during a single growth sequence. The dependence of the free energy of the step on the step height is compared with predictions of the weak- and strong-coupling models. Our results suggest that ³He crystals have rather strong coupling of the liquid/solid interface to the crystal lattice and that the step-step interactions are of elastic origin.     

Search for the most stable folds of protein chains: I. Application of a self-consistent molecular field theory to a problem of protein three-dimensional structure prediction

We present a general approach to the prediction of 3-D foldsof protein chains from their amino acid sequences. The approachis based on the use of the self-consistent molecular field theoryfor long-range interactions, the use of 1-D statistical mechanicsfor short-range interactions and on the discovery that thereis and should only be a relatively small discrete set of foldingpatterns. This makes it possible to examine the full varietyof ‘potentially stable’ folds and to determine thethermodynamically stable structure. In this paper, we give thegeneral theoretical background of the approach. The encouragingresults of the application of this approach to ß-domainsare described in another paper.     

高氯酸杂环配合物金属盐的激光起爆（英）

1 IntroductionNowadays the electrical way of blast-caps initiation istraditional. But the devices used for this process are in-herently susceptible to an accident initiation by externalstimuli such as an electrostatic discharge (ESD), elec-tromagnetic interference (EMI), and radio wave irradia-tion (RI). Pulse laser initiation of explosives is a newperspective method. Pulse lasers provide practical meansof electrical isolation of the energetic materials, therebyeliminating hazards associat…     

Information content of multiwavelength lidar data with respect to microphysical particle properties derived from eigenvalue analysis

The multiwavelength Raman lidar technique in combination with sophisticated inversion algorithms has been recognized as a new tool for deriving information about the microphysical properties of atmospheric aerosols. The input optical parameter sets, provided by respective aerosol Raman lidars, are at the theoretical lower limit at which these inversion algorithms work properly. For that reason there is ongoing intense discussion of the accuracy of these inversion methods and the possibility of simultaneous retrieval of the particle size distribution and the complex refractive index. We present results of the eigenvalue analysis, used to study the information content of multiwavelength lidar data with respect to microphysical particle properties. Such an analysis provides, on a rather mathematical basis, more insight into the limitations of these inversion algorithms regarding the accuracy of the retrieved parameters. We show that the effective radius may be retrieved to 50% accuracy and the real and imaginary part of the complex refractive index to +/- 0.05 and +/- 0.005i, if the imaginary part is < 0.02i. These results are in accordance with the classic approach of simulation studies with synthetic particle size distributions. Major difficulties are found with a particle effective radius of < 0.15 microm. In that case the complex refractive index may not be derived with sufficient accuracy. The eigenvalue analysis also shows that the accuracy of the derived parameters degrades if the imaginary part is > 0.02i. Furthermore it shows the importance of the simultaneous use of backscatter and extinction coefficients for the retrieval of microphysical parameters.     

Non-Enzymatic Template-Directed Recombination of RNAs

RNA non-enzymatic recombination reactions are of great interest within the hypothesis of the “RNA world”, which argues that at some stage of prebiotic life development proteins were not yet engaged in biochemical reactions and RNA carried out both the information storage task and the full range of catalytic roles necessary in primitive self-replicating systems. Here we report on the study of recombination reaction occuring between two 96 nucleotides (nts) fragments of RNAs under physiological conditions and governed by a short oligodeoxyribonucleotide template, partially complementary to sequences within each of the RNAs. Analysis of recombination products shows that ligation is predominantly template-directed, and occurs within the complementary complex with the template in “butt-to-butt” manner, in 1- or 3- nts bulges or in 2–3 nts internal loops. Minor recombination products formed in the template-independent manner are detected as well.     

Temperature- and pH-sensitive core–shell nanogels as efficient carriers of doxorubicin with potential application in lung cancer treatment

Temperature- and pH-sensitive core–shell nanogels were prepared by one-pot soapless emulsion polymerization of N-isopropylacrylamide and 2-methacryloyloxy benzoic acid with the aid of a crosslinker (core) using poly(ethylene glycol) methyl ether methacrylate as stabilizer (shell). The size of nanogels depended on the crosslinker used, being considerable smaller (around 100?nm) with the use of the acid-labile crosslinker 9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane (DVA). Doxorubicine (DOX) was loaded in nanogels with good efficiency. The empty nanogels were biocompatible for a lung cancer cell line (NCI-H1437), while the DOX-loaded, DVA-crosslinked nanogels resulted with efficient cytotoxicity for that cell line.