Minimizing the sum of the k largest functions in linear time

Given a collection of n functions defined on , and a polyhedral set , we consider the problem of minimizing the sum of the k largest functions of the collection over Q. Specifically we focus on collections of linear functions and several classes of convex, piecewise linear functions which are defined by location models. We present simple linear programming formulations for these optimization models which give rise to linear time algorithms when the dimension d is fixed. Our results improve complexity bounds of several problems reported recently by Tamir [Discrete Appl. Math. 109 (2001) 293-307], Tokuyama [Proc. 33rd Annual ACM Symp. on Theory of Computing, 2001, pp. 75-84] and Kalcsics, Nickel, Puerto and Tamir [Oper. Res. Lett. 31 (1984) 114-127].     

The properties of elastohydrodynamic grease films

The results of investigations of elastohydrodynamic grease films are reported. The elastic deformation of the rolling elements and changes in the grease properties due to pressure were considered. The theoretical results were confirmed by optical interference measurements of the film thickness. A formula for the film thickness as a function of the rheological grease parameters is given. The effects of breakdown of the grease structure and of starvation conditions on the film thickness are discussed.     

Aminopropylsilane treatment for the surface of porous glasses suitable for enzyme immobilisation

During silylation of porous glass with 3-aminopropyltriethoxysilane, the properties of the carrier affected the concentration of bound amino groups, the formation of aminopolysiloxane mono- or multilayer on the surface, and the hydrolytic stability of the layer formed. The influence of the carrier depended on the specific surface area and the size of pores. In contrast to silylation performed in organic solvents, in aqueous solutions a monolayer of aminopolysiloxane of high hydrolytic stability was formed on the surface of porous glass. Tetraethoxysilane modification of porous glass prior to silylation with aminosilane yields carriers of increased hydrolytic stability. Glucoamylase immobilised on carriers, that were modified in aqueous solutions, exhibit higher enzymatic activity.     

Fuzzy elements

On the basis of the theory of fuzzy sets, the fuzzy element concept is introduced. Several fuzzy elements are presented, and the stiffness matrix of fuzzy element is derived. These elements are used to modelling of infinite systems, and they don't affect the number of degrees of freedom of the system.     

Single-Strand Annealing in Cancer

DNA double-strand breaks (DSBs) are among the most serious forms of DNA damage. In humans, DSBs are repaired mainly by non-homologous end joining (NHEJ) and homologous recombination repair (HRR). Single-strand annealing (SSA), another DSB repair system, uses homologous repeats flanking a DSB to join DNA ends and is error-prone, as it removes DNA fragments between repeats along with one repeat. Many DNA deletions observed in cancer cells display homology at breakpoint junctions, suggesting the involvement of SSA. When multiple DSBs occur in different chromosomes, SSA may result in chromosomal translocations, essential in the pathogenesis of many cancers. Inhibition of RAD52 (RAD52 Homolog, DNA Repair Protein), the master regulator of SSA, results in decreased proliferation of BRCA1/2 (BRCA1/2 DNA Repair Associated)-deficient cells, occurring in many hereditary breast and ovarian cancer cases. Therefore, RAD52 may be targeted in synthetic lethality in cancer. SSA may modulate the response to platinum-based anticancer drugs and radiation. SSA may increase the efficacy of the CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 (CRISPR associated 9) genome editing and reduce its off-target effect. Several basic problems associated with SSA, including its evolutionary role, interplay with HRR and NHEJ and should be addressed to better understand its role in cancer pathogenesis and therapy.     

VISCOSITY OF BITUMEN-CRUMB RUBBER BLEND (NEW PAVING MATERIAL)

The feasibility of blending scrap tire rubber with Asphalt Ridge and Circle Cliffs (Utah, USA) tar sand bitumens was studied. Viscosity of the blended mixtures was analyzed as a function of composition, and coprocessing variables including processing temperature and time. Coprocessing of tar sand bitumens with crumb rubber at elevated temperatures has been shown to increase the viscosity of the bitumens with the exception of the bitumen-rubber sample prepared at 380°C. Optimum viscosity behavior was exhibited for an oil-extended bitumen blended with crumb rubber at 200°C for 0.5 hours. The viscosity of the bitumen-rubber blend prepared under these conditions met ASTM specifications of a viscosity-graded AC-30 asphalt binder. Viscosity increase was most noticeable at low temperature, providing the benefit of high viscosity at pavement temperatures experienced during summer months without concession of processability at pavement construction temperatures. A difference in viscosity was observed between bitumen modified with whole-tire crumb and tread-rubber crumb, due to the compositional differences that exist between the two materials.     

Study and development of a high temperature process of multi-reformation of CH4 with CO2 for remediation of greenhouse gas

A new carbon capture and recycle (CCR) system based on multi-reforming of CH₄ with CO₂ is proposed in this study. The aim was to develop a novel method to remediate greenhouse gases (CO₂) using a high temperature (over 1173 K) process of reforming CH₄ and/or O₂, and/or H₂O without catalysts. Using this novel method, the reactants are individually preheated to over 1173 K using a ceramic honeycomb heat exchanger, and then these high temperature streams enter the reactor to start the reforming reactions. Both thermodynamic and experimental studies were carried out on this novel method. Thermodynamic equilibrium models were built for four types of reforming, including dry reforming, bi-reforming, auto-thermal reforming, and tri-reforming. Only dry reforming was experimentally tested. The feasibility of this novel technology was proven by simulated and experimental results. High temperatures significantly promoted the multi-reforming process while avoiding the problem of catalyst deactivation. The experimental results on the direct system also showed that potential improvements in the efficiency of the novel technology could be achieved by optimizing the reforming reactants. Therefore, a continuous system was proposed. Moreover, the power source for the application of CCR systems was also discussed.     

Thermochemical treatment of E-waste from small household appliances using highly pre-heated nitrogen-thermogravimetric investigation and pyrolysis kinetics

The EU directive on waste of electrical and electronic equipment (WEEE) 2002/96/EC has set a goal of recovering 70–80% in terms of materials and energy. Nowadays, thermal cracking (pyrolysis) of such waste streams is receiving renewed attention, due to the energy and material recovery that can be achieved and therefore the sustainable waste management. However, it still lacks the kinetic background which is of great importance for a successful design of thermochemical processes. In this study the kinetic parameters of WEEE (originating from small household appliances) pyrolysis using highly pre-heated nitrogen under six different heating rates (1–2.5 K/s) have been estimated using a combination of model-free and model fitted methods. Even though WEEE is heterogeneous material, similar behavior at each of the six different heating rates applied was observed. The activation energy of the pyrolysis process determined with two different model-free methods gave comparable results. Pre-exponential factor and reaction order were determined using the Coats-Redfern method. The estimated kinetic parameters for the WEEE pyrolysis are: E = 95.54 kJ/mol, A = 1.06 × 10⁸ and n = 3.38.     

The Aging Stress Response and Its Implication for AMD Pathogenesis

Aging induces several stress response pathways to counterbalance detrimental changes associated with this process. These pathways include nutrient signaling, proteostasis, mitochondrial quality control and DNA damage response. At the cellular level, these pathways are controlled by evolutionarily conserved signaling molecules, such as 5’AMP-activated protein kinase (AMPK), mechanistic target of rapamycin (mTOR), insulin/insulin-like growth factor 1 (IGF-1) and sirtuins, including SIRT1. Peroxisome proliferation-activated receptor coactivator 1 alpha (PGC-1α), encoded by the PPARGC1A gene, playing an important role in antioxidant defense and mitochondrial biogenesis, may interact with these molecules influencing lifespan and general fitness. Perturbation in the aging stress response may lead to aging-related disorders, including age-related macular degeneration (AMD), the main reason for vision loss in the elderly. This is supported by studies showing an important role of disturbances in mitochondrial metabolism, DDR and autophagy in AMD pathogenesis. In addition, disturbed expression of PGC-1α was shown to associate with AMD. Therefore, the aging stress response may be critical for AMD pathogenesis, and further studies are needed to precisely determine mechanisms underlying its role in AMD. These studies can include research on retinal cells produced from pluripotent stem cells obtained from AMD donors with the mutations, either native or engineered, in the critical genes for the aging stress response, including AMPK, IGF1, MTOR, SIRT1 and PPARGC1A.