ENGENEERING ON THE (UN)PREDICATBLE ROADS

A scope is given on the past and future progress of the Engineering. The origin of the term Engineering is elaborated and followed through the past. A stress is put on the Latin Ingenium, as oposed to the frequently mismatched origin in the word Engine. Further development through the Military until the Civil Engineering (and other varieties in the contemporary world) is distinguished too. A forecast is given on the possible direction of development in future, based on the experienced trends in the pas

Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains

We study the quasiparticle band structure of isolated, infinite HF and HCl bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods "local molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.Comment: 11 pages, 6 figures, 6 tables, RevTeX4, corrected typoe

The Electrocrystallization of Metals. Investigation of Zinc

In electrodeposition of zinc depending on the condition of deposition, various effects of electrocrystallization can be observed. In acid solution of zinc sulfate the considerable surface diffusion overpotential appears at lower values of the total overpotential, indicating the surface diffusion of actions as the rate determining step. An interesting dependence of exchange current density on pH with a minimum at pH - 2 indicate the probable change in structure of the reacting particle. The mechanism of the reaction is evaluated. In alkaline zincate solutions no surface diffusion limitations can be detected. However, due to the rather low zincate ion concentration and high exchange current density zinc deposition proceeds practically always under the diffusion control. Morphology of zinc deposited depends considerably on the value of the electrode potential. This can be seen from the experiments in which the deposition morphology was observed with a scanning electron microscope. It was found possible to disrupt the deposition repeatedly for microscopic observation and than continue deposition. At low overpotentials (up to 50 mV) epitaxial layer type growth was observed with the linear increase of the microstep width with time. For this effect a theory is proposed which accounts also for the observed effects of substrate orientation. At larger overpotentials (50-100 mV) boulder type deposit was observed, most of which were not epitaxial with the substrate. They are suggested to be originated by nucleation. The boulder density per cm2 is first sharply increasing, and then slowly decreasing with time. A statistical calculation for this is given based on the model that large boulders consume the smaller ones. With further deposition a small fraction of the boulders develop into dendrites, their number being limited by the available total current

Hamiltonian walks on Sierpinski and n-simplex fractals

We study Hamiltonian walks (HWs) on Sierpinski and $n$--simplex fractals. Via numerical analysis of exact recursion relations for the number of HWs we calculate the connectivity constant $\omega$ and find the asymptotic behaviour of the number of HWs. Depending on whether or not the polymer collapse transition is possible on a studied lattice, different scaling relations for the number of HWs are obtained. These relations are in general different from the well-known form characteristic of homogeneous lattices which has thus far been assumed to hold for fractal lattices too.Comment: 22 pages, 6 figures; final versio

Thermodynamic Stability of the Transcription Regulator PaaR2 from Escherichia coli O157:H7

PaaR2 is a putative transcription regulator encoded by a three-component parDE-like toxin-antitoxin module from Escherichia coli O157:H7. Although this module’s toxin, antitoxin, and toxin-antitoxin complex have been more thoroughly investigated, little remains known about its transcription regulator PaaR2. Using a wide range of biophysical techniques (circular dichroism spectroscopy, size-exclusion chromatography-multiangle laser light scattering, dynamic light scattering, small-angle x-ray scattering, and native mass spectrometry), we demonstrate that PaaR2 mainly consists of α-helices and displays a concentration-dependent octameric build-up in solution and that this octamer contains a global shape that is significantly nonspherical. Thermal unfolding of PaaR2 is reversible and displays several transitions, suggesting a complex unfolding mechanism. The unfolding data obtained from spectroscopic and calorimetric methods were combined into a unifying thermodynamic model, which suggests a five-state unfolding trajectory. Furthermore, the model allows the calculation of a stability phase diagram, which shows that, under physiological conditions, PaaR2 mainly exists as a dimer that can swiftly oligomerize into an octamer depending on local protein concentrations. These findings, based on a thorough biophysical and thermodynamic analysis of PaaR2, may provide important insights into biological function such as DNA binding and transcriptional regulation

Aplinkos įtaka duoninių (Triticum aestivum L.) ir kietųjų (Triticum durum Desf.) kviečių albuminų kiekiui

Albumins or water soluble proteins (wsp) in wheat are important as nutrients containing high content of essential amino acids such as lysine, tryptophan, methionine, and also asparagine, glutamine, arginine, and proline in comparison to storage proteins-glutenins and gliadins. Fifteen bread wheat (Triticum aestivum L.) and 15 durum wheat (Triticum durum Desf.) genotypes were evaluated across six different environments for two years to determine the content of albumins in grains. The purpose of this research was to determine the variability of the albumins content of the tested bread wheat and durum wheat genotypes, effects of environment, genotype and their interaction (GEI) on the trait of interest, heritability in a broad sense, stability, and also to interpret GEI by climatic factors modelling. The statistical procedure included analysis of variance, sites regression and factorial regression. The mean content of albumins was 20.23 g kg-1 in bread wheat and 23.12 g kg-1 in durum wheat. Environment followed by GEI was the most important in determining albumins content. The heritability in a broad sense was low, i.e. 31.3% for bread wheat and only 2.4% for durum wheat. GEI for the albumins content was explained with the efficacy of 94.7% and 94.2% of sum of squares, for bread wheat and durum wheat, respectively, by the following models: mean temperature in May, winter moisture reserves, minimum temperature in April and March for bread wheat; and precipitation sum in April, sunshine hours sum in March, maximum temperature in May, and winter moisture reserves for durum wheat. The simultaneous selection for high albumins content and good stability proved to be possible for bread wheat genotypes, but less for durum wheat genotypes due to unsatisfactory stability

A dual role in regulation and toxicity for the disordered N-terminus of the toxin GraT.

Bacterial toxin-antitoxin (TA) modules are tightly regulated to maintain growth in favorable conditions or growth arrest during stress. A typical regulatory strategy involves the antitoxin binding and repressing its own promoter while the toxin often acts as a co-repressor. Here we show that Pseudomonas putida graTA-encoded antitoxin GraA and toxin GraT differ from other TA proteins in the sense that not the antitoxin but the toxin possesses a flexible region. GraA auto-represses the graTA promoter: two GraA dimers bind cooperatively at opposite sides of the operator sequence. Contrary to other TA modules, GraT is a de-repressor of the graTA promoter as its N-terminal disordered segment prevents the binding of the GraT2A2 complex to the operator. Removal of this region restores operator binding and abrogates Gr aT toxicity. GraTA represents a TA module where a flexible region in the toxin rather than in the antitoxin controls operon expression and toxin activity

Nanobody-aided crystallization of the transcription regulator PaaR2 from Escherichia coli O157:H7

paaR2–paaA2–parE2 is a three-component toxin–antitoxin module found in prophage CP-993P of Escherichia coli O157:H7. Transcription regulation of this module occurs via the 123-amino-acid regulator PaaR2, which forms a large oligomeric structure. Despite appearing to be well folded, PaaR2 withstands crystallization, as does its N-terminal DNA-binding domain. Native mass spectrometry was used to screen for nanobodies that form a unique complex and stabilize the octameric structure of PaaR2. One such nanobody, Nb33, allowed crystallization of the protein. The resulting crystals belong to space group F432, with unit-cell parameter a = 317 Å, diffract to 4.0 Å resolution and are likely to contain four PaaR2 monomers and four nanobody monomers in the asymmetric unit. Crystals of two truncates containing the N-terminal helix–turn–helix domain also interact with Nb33, and the corresponding co-crystals diffracted to 1.6 and 1.75 Å resolution