Project scheduling with generalized precedence relations: a new method to analyze criticalities and flexibilities

In this paper, we illustrate a new method to overcome the failures of the theory proposed by Elmaghraby and Kamburowski (1992) and De Reyck (1998) for the analysis of activity criticalities and flexibilities in non-preemptive project scheduling with generalized precedence relations under unlimited resources. These failures, discussed in detail in this paper, call for a new approach to study this problem. We provide new definitions of criticalities and consequently new tools for their identification within a more general framework without ambiguities

Clustering methods for Mode S stations: Evaluation and perspectives

Grouping of a set of Secondary Surveillance Radar (SSR) Mode S stations into functional entities called clusters has significant operational facets; it calls for a constrained optimization, an important significant constraint being the scarcity of Interrogation Identifier (II) codes. This clustering problem can be approached by two ways, i.e., integer programming methods and heuristic approaches. The definition of a general, usable decision support tool to build up and evaluate clustering strategies in any operational airspace, e.g. the one of a nation or, even more complicated, of a system such as the European one, is a very challenging task. This paper describes some steps toward this envisaged result proposing a mathematical formulation and a heuristic approach for the problem

Scheduling activities in project network with feeding precedence relations: an earliest start forward recursion algorithm

In some production processes, the effort associated with a certain activity for its execution can vary over time. In this case, the amount of work per time unit devoted to each activity, so as its duration, is not univocally determined. This kind of problem can be represented by an activity project network with the so-called feeding precedence relations, and activity variable execution intensity. In this paper, we propose a forward recursion algorithm able to find the earliest start and finish times of each activity, in O(m log n) time, with n and m being the number of activities and the number of precedence relations, respectively. In particular, this requires the calculation of the (optimal) execution intensity profile, for each activity, that warrants the earliest start schedule and the minimum completion time of the project

Structural and catalytic insights into HoLaMa, a derivative of Klenow DNA polymerase lacking the proofreading domain

We report here on the stability and catalytic properties of the HoLaMa DNA polymerase, a Klenow sub-fragment lacking the 3\u2019-5\u2019 exonuclease domain. HoLaMa was overexpressed in Escherichia coli, and the enzyme was purified by means of standard chromatographic techniques. High-resolution NMR experiments revealed that HoLaMa is properly folded at pH 8.0 and 20C. In addition, urea induced a cooperative folding to unfolding transition of HoLaMa, possessing an overall thermodynamic stability and a transition midpoint featuring \u394G and C M equal to (15.7 \ub1 1.9) kJ/mol and (3.5 \ub1 0.6) M, respectively. When the catalytic performances of HoLaMa were compared to those featured by the Klenow enzyme, we did observe a 10-fold lower catalytic efficiency by the HoLaMa enzyme. Surprisingly, HoLaMa and Klenow DNA polymerases possess markedly different sensitivities in competitive inhibition assays performed to test the effect of single dNTPs

Flash-memories in Space Applications: Trends and Challenges

Nowadays space applications are provided with a processing power absolutely overcoming the one available just a few years ago. Typical mission-critical space system applications include also the issue of solid-state recorder(s). Flash-memories are nonvolatile, shock-resistant and power-economic, but in turn have different drawbacks. A solid-state recorder for space applications should satisfy many different constraints especially because of the issues related to radiations: proper countermeasures are needed, together with EDAC and testing techniques in order to improve the dependability of the whole system. Different and quite often contrasting dimensions need to be explored during the design of a flash-memory based solid- state recorder. In particular, we shall explore the most important flash-memory design dimensions and trade-offs to tackle during the design of flash-based hard disks for space applications

Electrically conductive and high temperature resistant superhydrophobic composite films from colloidal graphite

Electrically conductive and self-cleaning superhydrophobic films (water contact angles >160°, droplet roll off angles <5°) were fabricated by simply solution casting sub-micron polytetrafluoroethylene (Teflon) particle dispersed alcohol-based colloidal graphite solutions. The process is very suitable for forming conductive superhydrophobic coatings on glasses, metals, ceramics and high performance polymers such as polyimide (Kapton®). The solutions were deposited on microscope glass slides and Kapton® films by drop casting. After solvent evaporation under ambient conditions, the coatings were annealed to melt Teflon. Upon melting, Teflon particles fused into one another forming a hydrophobic polymer matrix. The degree of superhydrophobicity and the surface morphology of the coatings together with their electrical conductivity were studied in detail by varying Teflon-to-graphite weight fractions. A number of applications can be envisioned for these coatings such as electrode materials for energy conversion devices, high performance electromagnetic shielding materials, flexible electronic components and heat exchanger surfaces, to name a few

Patients with chronic migraine without history of medication overuse are characterized by a peculiar white matter fiber bundle profile

Background: We investigated intracerebral fiber bundles using a tract-based spatial statistics (TBSS) analysis of diffusion tensor imaging (DTI) data to verify microstructural integrity in patients with episodic (MO) and chronic migraine (CM). Methods: We performed DTI in 19 patients with MO within interictal periods, 18 patients with CM without any history of drug abuse, and 18 healthy controls (HCs) using a 3 T magnetic resonance imaging scanner. We calculated diffusion metrics, including fractional anisotropy (FA), axial diffusion (AD), radial diffusion (RD), and mean diffusion (MD). Results: TBSS revealed no significant differences in the FA, MD, RD, and AD maps between the MO and HC groups. In comparison to the HC group, the CM group exhibited widespread increased RD (bilateral superior [SCR] and posterior corona radiata [PCR], bilateral genu of the corpus callosum [CC], bilateral posterior limb of internal capsule [IC], bilateral superior longitudinal fasciculus [LF]) and MD values (tracts of the right SCR and PCR, right superior LF, and right splenium of the CC). In comparison to the MO group, the CM group showed decreased FA (bilateral SCR and PCR, bilateral body of CC, right superior LF, right forceps minor) and increased MD values (bilateral SCR and right PCR, right body of CC, right superior LF, right splenium of CC, and right posterior limb of IC). Conclusion: Our results suggest that chronic migraine can be associated with the widespread disruption of normal white matter integrity in the brain

Tailoring the morphology of poly(ethylene oxide)/silver triflate blends: from crystalline to self-assembled nanofibrillar structures.

Interaction of polyethylene oxide (PEO) with transition metal triflates is a newly emerging research area due to its numerous application fields, such as thin-film power conversion devices and sensors. In the present study, we demonstrate, for the first time, that PEO can solvate silver triflate organic salts in large quantities when formic acid is used as a common solvent for both. Nanocomposites with unique structural and electrical properties are fabricated by simply drop casting formic acid solutions of PEO and silver triflate salts. We present a detailed experimental study on the characterization of morphological and electrical properties of PEO–silver triflate nanocomposite films as a function of silver triflate concentration and discuss their potential applications as humidity sensors. In particular, by increasing the concentration of the salt in the initial solution the morphological features of the formed nanocomposites can be varied from well defined microcrystals to amorphous nanofibers. Of special interest are the nanocomposite films fabricated from a 1:1 (PEO-unit:Ag+) molar ratio, since they consist of self-assembled nanofibrillar structures, which exhibit good electrical conductivity as well as highly repeatable sensitivity towards humidity

Novel standards in the measurement of rat insulin granules combining electron microscopy, high-content image analysis and in silico modelling

Knowledge of number, size and content of insulin secretory granules is pivotal for understanding the physiology of pancreatic beta cells. Here we re-evaluated key structural features of rat beta cells, including insulin granule size, number and distribution as well as cell size

Ownership and control in a competitive industry

We study a differentiated product market in which an investor initially owns a controlling stake in one of two competing firms and may acquire a non-controlling or a controlling stake in a competitor, either directly using her own assets, or indirectly via the controlled firm. While industry profits are maximized within a symmetric two product monopoly, the investor attains this only in exceptional cases. Instead, she sometimes acquires a noncontrolling stake. Or she invests asymmetrically rather than pursuing a full takeover if she acquires a controlling one. Generally, she invests indirectly if she only wants to affect the product market outcome, and directly if acquiring shares is profitable per se. --differentiated products,separation of ownership and control,private benefits of control