Optimal streaks in a Falkner-Skan boundary layer

This paper deals with the optimal streaky perturbations (which maximize the perturbed energy growth) in a wedge flow boundary layer. These three dimensional perturbations are governed by a system of linearized boundary layer equations around the Falkner-Skan base flow. Based on an asymptotic analysis of this system near the free stream and the leading edge singularity, we show that for acute wedge semi-angle, all solutions converge after a streamwise transient to a single streamwise-growing solution of the linearized equations, whose initial condition near the leading edge is given by an eigenvalue problem first formulated in this context by Tumin (2001). Such a solution may be regarded as a streamwise evolving most unstable streaky mode, in analogy with the usual eigenmodes in strictly parallel flows, and shows an approximate self-similarity, which was partially known and is completed in this paper. An important consequence of this result is that the optimization procedure based on the adjoint equations heretofore used to define optimal streaks is not necessary. Instead, a simple low-dimensional optimization process is proposed and used to obtain optimal streaks. Comparison with previous results by Tumin and Ashpis (2003) shows an excellent agreement. The unstable streaky mode exhibits transient growth if the wedge semi-angle is smaller than a critical value that is slightly larger than $\pi/6$, and decays otherwise. Thus the cases of right and obtuse wedge semi-angles exhibit less practical interest, but they show a qualitatively different behavior, which is briefly described to complete the analysis

Neural Processes Underlying Tool Use in Humans, Macaques, and Corvids

It was thought that tool use in animals is an adaptive specialization. Recent studies, however, have shown that some non-tool-users, such as rooks and jays, can use and manufacture tools in laboratory settings. Despite the abundant evidence of tool use in corvids, little is known about the neural mechanisms underlying tool use in this family of birds. This review summarizes the current knowledge on the neural processes underlying tool use in humans, macaques and corvids. We suggest a possible neural network for tool use in macaques and hope this might inspire research to discover a similar brain network in corvids. We hope to establish a framework to elucidate the neural mechanisms that supported the convergent evolution of tool use in birds and mammals

Design of novel aqueous two-phase systems to be coupled in biological remediation processes

The ability of a biodegradable Deep Eutectic Solvent (DES) reline to induce phase segregation in aqueous solutions of polymeric non-ionic surfactants (Tween 20 and Tween 80) has been demonstrated as a preliminary step to be employed for assisting a biological degradation process of a model contaminant. The binodal curves for systems composed of (surfactants + reline + Water) have been determined at several temperatures, and the experimental data have been correlated using well-known equations. The equilibrium data have been analysed in the light of the operating temperature and the hydrophobicity of surfactants. Tie-lines of these systems have been determined, together with useful parameters such as tie-line length and tie-line slopes. Othmer-Tobias and Bancroft equations have been applied to provide an adequate description of the equilibrium data. Finally, the application of this new approach for the remediation of aqueous polluted effluent has proven to be highly efficient, with extraction percentages exceeding 99% for two model persistent contaminants (Acid Black 48 and Crystal Violet). Consequently, this ATPS is proposed as an extra-stage to enhance the remediation percentagesachieved through biological methods. Furthermore, the process has been simulated using commercial software.Universidade de Vigo/CISU

Influence of process parameters on the corrosion resistance of corrugated austenitic and duplex stainless steels

The main objective of this work is to study the influence of the forming process on two corrugated, lean, duplex stainless steels (DSSs): UNS S32001 and UNS S32304. Both grades have been recently proposed as alternative materials to the austenitic UNS S30403 grade for manufacturing reinforcement bars to be embedded in concrete structures, exposed to corrosive environments. Hot-worked (HW) corrugated bars of both DSSs are analyzed and their corrosion behaviour is compared with that of the HW and cold-worked (CW) corrugated bars of S30403. The corrosion performance is characterized through cyclic polarization curves in 8 different solutions that simulate those contained inside the pores of concrete in different circumstances. The obtained results justify a great interest in the studied lean DSS grades with respect to their use as reinforcements. Moreover, it is proved that the corrugated surface of a bar is clearly less corrosion resistant than the centre of the bar. The processing method of producing reinforcements influences not only the pitting susceptibility but also the pitting morphology.Publicad

Cycloidal Domains in the Magnetization Reversal Process of Ni80Fe20/Nd16Co84/Gd12Co88 Trilayers

The magnetization reversal of each individual layer in magnetic trilayers ( permalloy / Nd Co / Gd Co ) is investigated in detail with x-ray microscopy and micromagnetic calculations. Two sequential inversion mechanisms are identified. First, magnetic vortex-antivortex pairs move along the field direction while inverting the magnetization of magnetic stripes until they are pinned by defects. The vortex-antivortex displacements are reversible within a field interval which allows their controlled motion. Second, as the reversed magnetic field increases, cycloidal domains appear in the permalloy layer as a consequence of the dissociation of vortex-antivortex pairs due to pinning. The field range where magnetic vortices and antivortices are effectively guided by the stripe pattern is of the order of tens of mT for the Ni Fe layer, as estimated from the stability of cycloid domains in the sample

Zinc: What Is Its Role in Lung Cancer?

Recently, zinc emerged as an important signaling molecule, activating intracellular pathways and regulating cell fate, although our knowledge remains incomplete. Zinc is required in many enzymatic and metabolic pathways, playing roles as enzyme cofactors. In normal cell physiology, optimal zinc availability is essential for regular growth and proliferation. Zinc accumulation has varied effects: from stimulation to inhibition of cell growth, depending on type. There is evidence that zinc is capable of inducing apoptosis in some cancers, while others proved that zinc may act as apoptosis activator depending on the dose and cell type. Upregulation of telomerase in most cancer tissues is considered to be responsible for unlimited proliferation of cancer cells, and in some cell lines, it was induced by Zn. These suggest that Zn is highly involved in cell cycle and metabolism; whether it goes to the survival or the cancer pathway depends on the concentration and the cell type involved. Nevertheless, the conclusion is that Zn is not just another trace element; but a vital one and further studies are needed to elucidate the mechanisms involved in cancer and metastatic spread in order to identify potential therapies

Investigating Piezochromic Properties of πconjugated Materials: a combined Raman and DFT Study

Π-conjugated materials have been studied for decades due to their great interest in organic electronics. Among them, piezochromic materials, which exhibit color changes resulting from external pressure or mechanical grinding, become very attractive from a scientific viewpoint owing to their potential applications as pressure-sensing and opticalrecording systems1. The main target of the present work is to develop a joint experimental and theoretical approach able to deliver crucial information for the understanding of the structural effects causing piezochromic changes. To this end, we will focus our attention on two families of -conjugated materials with potential application as sensors. The first one is a family of 9,10-Bis((E)-n(pyrid-2-yl)vinyl) anthracene, BPnVA (n=2 orto-,3 metha- and 4 para-) compounds, see Figure 1. Interestingly, these three compounds with varying position of the nitrogen on the external pyridyl group exhibit different molecular packing modes. Grinding and the application of external pressure on the powder also led to a strong change in their photoluminescence color.2 The second familiy is based on the N,N’-Bis-Boc-3,3’-di(pyren-1yl)-2,2’-biindole compound (compound 1c in Figure 1) which also shows photoluminescence under pressure application. However, the molecular packing induced by this phenomenon is still under study 3. In both cases, it will be also very interesting to determine how temperature affects the vibrational structure of these systems.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Yellowtail Flounder Length at Maturity in the Grand Bank (1995-98)

In this paper yellowtail length at maturity estimates based data collected in the spring Spanish surveys in the Regulatory Area of Divisions 3NO are presented. Female length at 50 % maturity decreased from 35 cm in 1995 to 23 cm in 1998. In males, this parameter decreased from 23 cm in 1995 to 19 cm in 1998. The differences in L50 estimates in females were significant between 1997 and the previous years , and between 1998 and both 1996 and 1995, and were not significant between 1997 and 1998. In males, differences were significant between all the years, except between 1997 and 1998. The covariance analysis between the linearized maturity curves were highly significant in both sexes

Data on sharks in NAFO Divisions 3LMNO: 1991-1998

A review of the species composition, distribution and abundance of sharks in both the Spanish commercial catches (1991-98) and research surveys (1988-98) are carried out. Shark species are by-catches of Greenland halibut fishery. The proportion of shark species in the total catch is small and the main retained species is the black dogfish, whereas the main discard is the boreal shark. Since 1996 the retained proportion of black dogfish increase notably, as well as the proportion of total sharks. In the surveys this shark is the species with the highest biomass index. Black dogfish is found in the deepest waters. The length range of black dogfish is mainly between 50 and 80 cm, with a mode about 62-63 cm. No evident geographic pattern in the length distribution is observed during the studied period

N-Benzoyl-N′,N′-dimethyl­thio­urea

In the title compound, C10H12N2OS, the amide NCO group is twisted relative to the thio­ureido SCN2 group, forming a dihedral angle of 55.3 (2)°. The crystal packing shows inter­molecular N—H⋯S and weak C—H⋯O inter­actions, the former giving rise to the formation of centrosymmetric R 2 2(8) dimers