Factors effecting construction contractors' performance

A number of interesting and important aspects have been achieved in this research; in particular, that quality of work should be of major concern to contractors and could become a pre-requisite in any selection process by the client body. Contract documentation should be clear and should not include ambiguous clauses and contradictory documentation, as this only leads to problems for all parties during the contract and a low performance rating from the contractor.     

Professional architectural/engineering consultancy practices in Saudi Arabia

The local architectural engineering firm in Saudi Arabia is handling projects up to 175m SR a year on average. It will have been in practice 13 years, employing 91 people, most holding a B.Sc. degree. Practices are mainly selected by competitive bidding and paid under a fixed fee arrangement. The authors found that the public authorities are the major employers of local A/E design services.     

Large blue shift of the biexciton state in tellurium doped CdSe colloidal quantum dots

The exciton-exciton interaction energy of tellurium doped CdSe colloidal quantum dots is experimentally investigated. The dots exhibit a strong Coulomb repulsion between the two excitons, which results in a huge measured biexciton blue shift of up to 300 meV. Such a strong Coulomb repulsion implies a very narrow hole wave function localized around the defect, which is manifested by a large Stokes shift. Moreover, we show that the biexciton blue shift increases linearly with the Stokes shift. This result is highly relevant for the use of colloidal QDs as optical gain media, where a large biexciton blue shift is required to obtain gain in the single exciton regime.     

Regulation of Secondary Metabolism in the Penicillium Genus

Penicillium, one of the most common fungi occurring in a diverse range of habitats, has a worldwide distribution and a large economic impact on human health. Hundreds of the species belonging to this genus cause disastrous decay in food crops and are able to produce a varied range of secondary metabolites, from which we can distinguish harmful mycotoxins. Some Penicillium species are considered to be important producers of patulin and ochratoxin A, two well-known mycotoxins. The production of these mycotoxins and other secondary metabolites is controlled and regulated by different mechanisms. The aim of this review is to highlight the different levels of regulation of secondary metabolites in the Penicillium genus.     

Time efficiency and physical workload in manual picking from large containers

A common task in both trade and manufacturing, manual picking from large containers often involves considerable physical workload, as well as low efficiency and varying picking times. With quantitative evidence from an industrial setting, the paper provides detailed insights into how physical workload and picking time vary in picking from large containers. Components at a short horizontal distance from the picker and at the top instead of the bottom of the pallet are associated with shorter picking time and lower physical workload. Moreover, pallets tilted 45° towards the picker are associated with picking times that are significantly shorter on average and display smaller variations than horizontal pallets. The effects that the tilting of the pallets has on physical workload differs depending on component characteristics and from which section of the containers picking was performed. In the study, the greatest values of physical workload were observed for the tilted pallets.     

Internal stability of dynamic quantised control for stochastic linear plants

Existing analyses of ‘zooming’ quantisation schemes for bit-rate-limited control systems rely on the encoder and controller being initialised with identical internal states. Due to the quantiser discontinuity and the plant instability, it was not clear if closed-loop stability was possible if the encoder and controller commenced from different initial conditions. In this article, we consider partially observed, unstable linear time-invariant plants, with unbounded and possibly non-Gaussian noise, and propose a modified zooming-like scheme with finite-dimensional internal encoder and controller states that may not initially be identical. Using a stochastic pseudo-norm, we prove that this scheme yields mean-square stability in all closed-loop state variables, not just the plant state, under a sufficient condition involving this initial error, the plant dynamics and the channel data rate. With diminishing initial error, this condition approaches a known universal lower bound on data rates and becomes tight. Furthermore, we show that the scheme automatically corrects itself, in the sense that the errors between the internal states of the encoder and controller tend to zero stochastically with time. This suggests that the policy will maintain stability in the presence of channel errors, for sufficiently low bit error rates. We support these conclusions with simulations.     

Chemical synthesis and expression of the HIV-1 Rev protein

The HIV-1 Rev protein is responsible for shuttling partially spliced and unspliced viral mRNA out of the nucleus. This is a crucial step in the HIV-1 lifecycle, thus making Rev an attractive target for the design of anti-HIV drugs. Despite its importance, there is a lack of structural, biophysical, and quantitative information about Rev. This is mainly because of its tendency to undergo self-assembly and aggregation; this makes it very difficult to express and handle. To address this knowledge gap, we have developed two new highly efficient and reproducible methods to prepare Rev in large quantities for biochemical and structural studies: 1) Chemical synthesis by using native chemical ligation coupled with desulfurization. Notably, we have optimized our synthesis to allow for a one-pot approach for the ligation and desulfurization steps; this reduced the number of purification steps and enabled the obtaining of desired protein in excellent yield. Several challenges emerged during the design of this Rev synthesis, such as racemization, reduced solubility, formylation during thioester synthesis, and the necessity for using orthogonal protection during desulfurization; solutions to these problems were found. 2) A new method for expression and purification by using a vector that contained an HLT tag, followed by purification with a Ni column, a cation exchange column, and gel filtration. Both methods yielded highly pure and folded Rev. The CD spectra of the synthetic and recombinant Rev proteins were identical, and consistent with a predominantly helical structure. These advances should facilitate future studies that aim at a better understanding of the structure and function of the protein.     

Scheduling with a common due-window: Polynomially solvable cases

The single machine scheduling problem to minimize maximum weighted absolute deviations of job completion times from a common due-date, is known to be NP-hard. However, two special cases have been shown to have polynomial time solutions: the case of unit processing time jobs, and the case of due-date assignment for a given job sequence. We extend both cases to a setting of a common due-window. We show that the unit-job problem includes 12 different sub-cases, depending on the size and location of the (given) due-window. Scheduling and due-window assignment for a given job sequence is solved for a single machine, for parallel identical machines and for flow-shops. For each of the above cases, an appropriate special-structured linear program is presented.     

Compressed Genotyping

Over the past three decades we have steadily increased our knowledge on the genetic basis of many severe disorders. Nevertheless, there are still great challenges in applying this knowledge routinely in the clinic, mainly due to the relatively tedious and expensive process of genotyping. Since the genetic variations that underlie the disorders are relatively rare in the population, they can be thought of as a sparse signal. Using methods and ideas from compressed sensing and group testing, we have developed a cost-effective genotyping protocol to detect carriers for severe genetic disorders. In particular, we have adapted our scheme to a recently developed class of high throughput DNA sequencing technologies. The mathematical framework presented here has some important distinctions from the 'traditional' compressed sensing and group testing frameworks in order to address biological and technical constraints of our setting.