How to improve nature: study of the electrostatic properties of the surface of alpha-lactalbumin

It was recently shown that alpha-lactalbumin interacts with histones and simple models of histone proteins such as positively charged polyamino acids, suggesting that some fundamental aspects of the protein surface electrostatics may come into play. In the present work, the energies of charge-charge interaction in apo- and Ca(2+)-loaded alpha-lactalbumin were calculated using a Tanford-Kirkwood algorithm with either solvent accessibility correction or using a finite difference Poisson-Boltzmann method. The analysis revealed two major regions of alpha-lactalbumin that possessed highly unfavorable electrostatic potentials: (a) the Ca(2+)-binding loop and its neighboring residues and (b) the N-terminal region of the protein. Several individual mutants were prepared to neutralize specific individual surface acidic amino acids at both the N-terminus and Ca(2+)-binding loop of bovine alpha-lactalbumin. These mutants were characterized by intrinsic fluorescence, differential scanning microcalorimetry and circular dichroism. The structural and thermodynamic data agree in every case with the theoretical predictions, confirming that the N-terminal region is very sensitive to changes in charge. For example, desMet D14N mutation destabilizes protein and decreases its calcium affinity. On the other hand, desMet E1M and desMet D37N substitutions increase the thermal stability and calcium affinity. The Met E1Q is characterized by a marked increase in protein stability, whereas desMet E7Q and desMet E11L display a slight increase in calcium affinity and thermal stability. Examination of the unfavorable energy contributed by Glu1 and the energetically favorable consequences of neutralizing this residue suggests that nature may have made an error with bovine alpha-lactalbumin from the viewpoint of stabilizing structure and conformation.     

Assessment of manual assembly complexity: a theoretical and empirical comparison of two methods

There are several theoretical methods for assessment of assembly complexity but there are few practically applicable methods. One of the methods, CompleXity Index (CXI), aims at assessing operators’ perception of manual assembly complexity in running production. Another recently developed method, Basic Assembly Complexity (CXB) is intended for predictive assessment of basic manual assembly complexity in early product and production development. Both CXI and CXB aim to improve assembly conditions for operators, reduce assembly-related errors and the costs for corrective measures as well as increase assembly quality although in different ways and at different organisational levels and life cycle stages. The purpose of this study was to compare the two methods to obtain feedback and learn from operators experience in order to develop better predictive assessment criteria. The method comparison showed that about 50% of the CXB assessment approaches were similar to CXI but other covered different aspects. In comparison of the complexity values of the methods no significant results were obtained. However, some CXI issues that were not taken into account in CXB should be considered. CXB and CXI could be used in conjunction but further assessment criteria are probably needed.     

Proactive assessment of basic complexity in manual assembly: development of a tool to predict and control operator-induced quality errors

A major challenge for manufacturing companies today is to manage a huge amount of product variants and build options at the same time in manufacturing engineering and in production. The overall complexity and risk of quality errors in manual assembly will increase placing high demands on the operators who must manage many different tasks in current production. Therefore, methods for decreasing and controlling assembly complexity are urgent because managing complex product and installation conditions will result in distinct competitive advantages. The objective of this paper is to present a method for predictive assessment of basic manual assembly complexity and explain how included complexity criteria were arrived at. The verified method includes 16 high complexity and 16 low complexity criteria to aid designers in preventing costly errors during assembly and create good basic assembly conditions in early design phases of new manufacturing concepts.     

Fracture dilation during grouting

Sealing underground excavations from ingress of water constitutes a large part of both the cost and the risk for many infrastructure projects. In this paper we present a mechanical model for the rock mass response when grouting hard jointed rock. The model predicts a stiff and a non-stiff behaviour and a transition between them that is dependent on the relationship between the grouting pressure and the in situ stress conditions. The predictions are consistent with previously published measurements and explain grouting behaviour that has been difficult to model with previous methods.     

Tolerancing: Managing uncertainty from conceptual design to final product

Variability is unavoidable in the realization of products. While design must specify ideal geometry, it shall also describe limits of variability (tolerances) that must be met in order to maintain proper product function. Although tolerancing is a mature field, new manufacturing processes and design methodologies are creating new avenues of research, and modelling standards must also evolve to support these processes. In addition, the study of uncertainty has produced widely-accepted methods of quantifying variability, and modern tolerancing tools should support these methods. The challenges introduced by new processes and design methodologies continue to make tolerancing research a fertile and productive area.     

An information and simulation framework for increased quality in welded components

The recent trend toward using simulation models with real-time data as digital twins is rapidly increasing in industry. In this paper, a digital framework supporting real-time geometrical quality control of welded components, is presented. The concept is based on a structured process model for all operations included in typical welding, strategies for selective assembly, automatic adjustment of fixtures and optimization of weld sequence. The concept utilizes recently developed algorithms for fast welding simulation and in-line scanning to be used in the optimization loop of an automated welding station—a digital twin for a welding cell.     

Off-axis transformation of the composite laminate stiffness properties

Most composite structures are orthotropic with respect to the major structural loading direction, i.e. the 0 ° fibres are along the principal bending axes of an aircraft wing (the spar line). The laminate stiffness properties are given with the laminate orthotropic axes aligned with the structural axes. If the orthotropic axes are not aligned to the structural axes, then the laminate stiffness properties are generated from classical laminated plate theory with individual ply angles rotated through the appropriae angle of transformation. In this discussion, the transformation of a laminate's stiffness from the on-axis position to an off-axis position is accomplished in one step. Two typical examples are shown to illustrate where and why such a transformation is used.     

The Absolute Configuration of the Sex Pheromone of the Citrophilous Mealybug, <Emphasis Type="Italic">Pseudococcus calceolariae</Emphasis>

The absolute configuration of the sex pheromone of the citrophilous mealybug, Pseudococcus calceolariae, was determined to be (1R,3R)-[2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropyl]methyl (R)-2-acetoxy-3-methylbutanoate. NMR, derivatization reactions, chiral gas chromatography-mass spectrometry, and comparison with synthetic chiral reference compounds, were used to determine the absolute configuration of this compound. This activity of this compound was further confirmed by testing synthetic stereoisomers of the compound as lures in traps for adult male mealybugs. Traps baited with 1,000 μg of the pheromone compound caught 36 times more males than traps baited with virgin females. A mixture of stereoisomers of the pheromone compound can be used for field trapping without adverse effects on trap catch. A comparison with the structures of other sex pheromones of mealybugs is presented.