Upper Bounds on the Multiplicative Complexity of Symmetric Boolean Functions

A special metric of interest about Boolean functions is multiplicative complexity (MC): the minimum number of AND gates sufficient to implement a function with a Boolean circuit over the basis {XOR, AND, NOT}. In this paper we study the MC of symmetric Boolean functions, whose output is invariant upon reordering of the input variables. Based on the Hamming weight method from Muller and Preparata (1975), we introduce new techniques that yield circuits with fewer AND gates than upper bounded by Boyar et al. in 2000 and by Boyar and Peralta in 2008. We generate circuits for all such functions with up to 25 variables. As a special focus, we report concrete upper bounds for the MC of elementary symmetric functions $\Sigma^n_k$ and counting functions $E^n_k$ with up to n = 25 input variables. In particular, this allows us to answer two questions posed in 2008: both the elementary symmetric $\Sigma^8_4$ and the counting $E^8_4$ functions have MC 6. Furthermore, we show upper bounds for the maximum MC in the class of n-variable symmetric Boolean functions, for each n up to 132

Estimation of depth-dependent material properties of biphasic soft tissues through finite element optimization and sensitivity analysis

PubMedID: 31591078A knowledge of material properties of soft tissue, such as articular cartilage, is essential to assess its mechanical function. It is also increasingly more evident that the inhomogeneity of the tissues plays a significant role in its in vivo functioning. Hence, efficient and reliable tools are needed to accurately characterize the inhomogeneity of the soft tissue mechanical properties. The objective of this research is to propose a finite element optimization procedure to determine depth-dependent material properties of articular cartilage by processing experimental data. Cartilage is modeled as a biphasic continuum with a linear elastic solid phase. The optimization method is based on a sensitivity analysis where the sensitivity of the finite element results to a variation in the material properties is analytically evaluated. The elastic modulus and permeability of the tissue are assumed to vary either linearly or quadratically through the thickness of the cartilage layer. After adopting some initial estimates, these material properties are updated iteratively based on their sensitivities to the current results, and the difference between the actual experimental data and computational experimental data. The optimization method has been tested in two common experimental configurations of cartilage and found to be efficient to estimate the material properties. © 2019 IPE

Naturally occurring novel promoters for recombinant protein production around pyruvate branch-point in Pichia pastoris

Novel strong Pichia pastoris promoter discovery is crucial in metabolic engineering for recombinant protein (r-protein) production. Transcriptome and proteome data of P. pastoris were analysed and genes having higher expressions than glyceraldehyde-3-phosphate dehydrogenase (GAP) gene under limited-oxygen-transfer conditions were identified as promoter sources. Two promoters around pyruvate-node were determined as promising candidates, and in silico analysis of putative promoter regions was conducted. Promoter of pyruvate kinase (PPYK) has one transcription start-site with a minimum promoter-score of 0.99; while, promoter of pyruvate decarboxylase (PPDC) has two start-sites each having a minimum promoter-score of 0.91. To drive gene expression, putative promoter-regions were replaced with PGAP in parent plasmid pGAPZαA::hGH, harboring human-growth-hormone (hGH) gene. P. pastoris strains carrying single-copy hGH under PPYK, PPDC, and for comparison under PGAP were tested in high-cell-density rhGH fermentations abbreviated, respectively, as BRPYK, BRPDC, and BRGAP. Promoter strength was evaluated by mRNA transcription-copy-number (mTCN) results, rhGH concentration measurements, and calculated flux distributions. PPDC and PPYK performed higher activity compared to PGAP. Maximum rhGH production was obtained in BRPDC as 122 mg dm−3 at t = 15 h, and then in BRPYK as 101 mg dm−3 at t = 12 h, and in BRGAP as 58 mg dm−3 at t = 9 h; while, mTCN of hGH was the highest with PGAP at t = 15 h, and then with PPDC with the maximum at t = 12 h, and lowest with PPYK. Flux distributions demonstrated perturbation effects of the naturally-occurring-novel-promoters in the engineered systems and validated the cross-pathway regulatory interactions

Mass flux balance-based model and metabolic flux analysis for collagen synthesis in the fibrogenesis process of human liver

A mass flux balance-based stoichiometric model for human liver metabolism has been set up. The model considers 125 reaction fluxes, and there are 83 metabolites that are assumed to be in pseudo-steady state. Theoretical metabolic flux distributions in the fibrotic and healthy liver cells were determined by maximizing respectively the collagen and palmitate synthesis in the objective function for the solution of the model, The flux distribution maps of the analysis for the collagen synthesis showed that the glycolysis pathway was active down to fructose-6-phosphate and the gluconeogenesis pathway was active up to glyceraldehyde 3-phosphate synthesis. However, the flux distribution maps for the palmitate synthesis revealed that both the glycolysis pathway and the gluconeogenesis pathway were active towards 3-phospho glycerate. The TCA cycle operated from citrate towards oxalacetate, and the anaplerotic reactions that connect the TCA cycle to the gluconeogenesis pathway were active in both analyses. Metabolic flux analysis shows that the amino acid fluxes are indeed important in the collagen synthesis. The results of the comparative analyses for the occurrence of the collagen synthesis in the fibrotic liver cells reveal that among the non-essential amino acids three, namely glycine, proline and aspartic acid, and among the essential amino acids one, methionine, are respectively the potential metabolic bottlenecks and the limiting amino acid. The diversions in the pathways and certain metabolic reactions are also presented, and potential strategies for controlling the collagen synthesis and consequently the fibrosis are also discussed. (C) 2000 Harcourt Publishers Ltd

Relevance of inhomogeneous–anisotropic models of human cortical bone: a tibia study using the finite element method

Cortical bone is an inhomogeneous and anisotropic tissue subjected to large loads during typical daily activities. While studies assuming isotropic material properties are frequent, anisotropy and inhomogeneity of cortical bone have been rarely taken into account. Moreover, the question, whether an assumption of anisotropy and inhomogeneity has an impact in the mechanical analysis of cortical bone, has not been explored in the literature. This study explores the relevance of anisotropy in human cortical bone. The cortical bone model has been divided into six radial regions and a different set of orthotropic material properties has been assigned to each region. This inhomogeneous and anisotropic elastic tibia model has been compared with a corresponding isotropic model under various loading modes using the finite element method. In particular, the variation in the maximum von Mises stress and strain values has been observed along the bone axis. We have observed that the isotropic model may overestimate the maximum von Mises strain up to 15% under pure compression and underestimate up to 50% under pure torsion relative to the inhomogeneous–anisotropic model. Our results suggest that consideration of anisotropy and inhomogeneity of the bone may make a significant difference in the predicted maximum von Mises strain values, which can be important for strain-based damage accumulation studies and fracture risk evaluation. © 2016 The Author(s). Published by Taylor & Francis

Regulatory effects of alanine-group amino acids on serine alkaline protease production by recombinant Bacillus licheniformis

Influences of the concentration and addition time of alanine-group amino acids, i.e. alanine, leucine and valine, on serine alkaline protease (SAP) synthesis were investigated by Bacillus licheniformis (DSM 1969) carrying pHV1431::subC in a defined medium to identify the amino acids creating intracellular reaction-rate limitation in SAP production. While the precursors of alanine-group amino acids, pyruvate and alanine, did not affect SAP production considerably within the range 0-15 mM, the addition of leucine decreased both SAP production and cell formation, because of the inhibition of valine synthesis. Although valine inhibits reactions starting with pyruvate towards 2-oxo-isovalerate, due to conversion of valine into 2-oxoisovalerate and from 2-oxo-isovalerate to leucine, valine did not inhibit leucine synthesis. Val (7.5 mM) supply at t = 0 h increased SAP activity to an activity of 1070 units - cm-' which was 1.3-fold higher than that of the reference production medium. The highest cell growth yield on substrate (Y-X/S) was obtained as 0.24 g . g(-1) with the supply of alanine; and the highest product formation yield on substrate was obtained as 0.134 units . g(-1) with the supply of valine. By using the results obtained, strategies for increasing SAP production and complex medium design were also discussed

The effect of heat treatment on mechanical properties of 42CrMo4 steel

Purpose: In this study, the effect of heat treatment on the microstructure and mechanical properties of 42CrMo4 steel were investigated. Design/methodology/approach: The samples were annealed at 860°C for 120 min. followed by oil quenching and then tempered at temperatures between 480 and 570°C for 120 min. The microstructure of untreated 42CrMo4 steel mainly consists of pearlite and ferrite whereas the microstructure was found to be as a martensitic structure with a quenching process. Findings: The results showed that there is an increase in yield stress, ultimate tensile stress, hardness and impact energy, while elongation decreases at the end of the quenching process. Conversely, yield stress, ultimate tensile stress and hardness decrease slightly with the increasing of tempering temperature, while elongation and impact energy increase. Research limitations/implications: Other types of steels can be heat treated in a wider temperature range and the results can be compared. Practical implications: It is a highly effective method for improving the mechanical properties of heat treatment materials. Originality/value: A relationship between the mechanical properties and the microstructure of materials can be developed. The heat treatment is an effective method for this process

Phosphate enrichment and fed-batch operation for prolonged beta-lactamase production by Bacillus licheniformis

Aims: Investigation of the phosphate effect and feeding strategy, i.e. linear and exponential feeding, to improve beta-lactamase production by Bacillus licheniformis considering the viability of the cells

Preface to the special issue section on “International Mediterranean Science and Engineering Congress (IMSEC 2017), 25–27 October 2017, Adana, Turkey”

[No abstract available