Organic contaminants levels, distribution and risk assessment in Jeddah marine coastal zone sediments.

Herein, various organic contaminants were determined in surface sediments collected from the Jeddah coastal zone, Saudi Arabia, to assess their levels, origin and probable toxic effects on marine organisms. High hydrocarbons concentrations, indicative of an enhanced pollutant burden, were recorded in the Jeddah Lagoon (mean value 4100 mg/kg for total aliphatic hydrocarbons (∑AHC) and 5800 µg/kg for total polycyclic aromatic hydrocarbons (∑PAH)), whereas mean values in Mena Jeddah were 258 mg/kg for ∑AHC and 615 µg/kg for ∑PAH. By using molecular diagnostic ratios/indices and applying Positive Matrix Factorization, petroleum related pollution seems to predominate in Jeddah lagoons, whereas carcinogenic contaminants of pyrolytic origin were dominant in Mena Jedda. Additionally, municipal wastewaters were identified as a major source of pollution in Jeddah lagoons. Comparison of the concentrations of individual PAHs and polychlorinated biphenyls with sediment quality guidelines indicates that, despite their high total values, adverse biological effects are unlikely to occur.

Nonlinear gravity electro-capillary waves in two-fluid systems: solitary and periodic waves and their stability.

Starting from the Euler equations governing the flow of two immiscible incompressible fluids in a horizontal channel, allowing gravity and surface tension, and imposing an electric field across the channel, a nonlinear long-wave analysis is used to derive a 2 × 2 system of evolution equations describing the interface position and a modified tangential velocity jump across it. Travelling waves of permanent form are shown to exist and are constructed in the periodic case producing wave trains and the infinite case yielding novel gravity electro-capillary solitary waves. Various regimes are analysed including a hydrodynamically passive but electrically active upper layer, pairs of perfect dielectric fluids and a perfectly conducting lower fluid. In all cases, the presence of the field produces both depression and elevation waves travelling at the same speed, for given sets of parameters. The stability of the non-uniform travelling waves is investigated by numerically solving appropriate linearised eigenvalue problems. It is found that depression waves are neutrally stable whereas elevation ones are unstable unless the surface tension is large. Stability or instability is shown to be linked mathematically to the type of local eigenvalues of the nonlinear flux matrix used to obtain travelling and solitary waves; if these are real (hyperbolic flux matrix), the system is stable, and if they are complex (elliptic), the system is unstable. The latter is a manifestation of Kelvin-Helmholtz instability in electrified flows.

Analysis and computations of a non-local thin-film model for two-fluid shear driven flows.

This paper is concerned with analysis and computations of a non-local thin-film model developed in Kalogirou & Papageorgiou (J. Fluid Mech. 802, 5-36, 2016) for a perturbed two-layer Couette flow when the thickness of the more viscous fluid layer next to the stationary wall is small compared to the thickness of the less viscous fluid. Travelling wave solutions and their stability are determined numerically, and secondary bifurcation points are identified in the process. We also determine regions in parameter space where bistability is observed with two branches being linearly stable at the same time. The travelling wave solutions are mathematically justified through a quasi-solution analysis in a neighbourhood of an empirically constructed approximate solution. This relies in part on precise asymptotics of integrals of Airy functions for large wave numbers. The primary bifurcation about the trivial state is shown rigorously to be supercritical, and the dependence of bifurcation points, as a function of Reynolds number R and the primary wavelength 2πν -1/2 of the disturbance, is determined analytically.

Nonlinear dynamics of a dispersive anisotropic Kuramoto-Sivashinsky equation in two space dimensions.

A Kuramoto-Sivashinsky equation in two space dimensions arising in thin film flows is considered on doubly periodic domains. In the absence of dispersive effects, this anisotropic equation admits chaotic solutions for sufficiently large length scales with fully two-dimensional profiles; the one-dimensional dynamics observed for thin domains are structurally unstable as the transverse length increases. We find that, independent of the domain size, the characteristic length scale of the profiles in the streamwise direction is about 10 space units, with that in the transverse direction being approximately three times larger. Numerical computations in the chaotic regime provide an estimate for the radius of the absorbing ball in [Formula: see text] in terms of the length scales, from which we conclude that the system possesses a finite energy density. We show the property of equipartition of energy among the low Fourier modes, and report the disappearance of the inertial range when solution profiles are two-dimensional. Consideration of the high-frequency modes allows us to compute an estimate for the analytic extensibility of solutions in [Formula: see text]. We also examine the addition of a physically derived third-order dispersion to the problem; this has a destabilizing effect, in the sense of reducing analyticity and increasing amplitude of solutions. However, sufficiently large dispersion may regularize the spatio-temporal chaos to travelling waves. We focus on dispersion where chaotic dynamics persist, and study its effect on the interfacial structures, absorbing ball and properties of the power spectrum.

Dynamics of fully nonlinear capillary-gravity solitary waves under normal electric fields.

Two-dimensional capillary-gravity waves travelling under the effect of a vertical electric field are considered. The fluid is assumed to be a dielectric of infinite depth. It is bounded above by another fluid which is hydrodynamically passive and perfectly conducting. The problem is solved numerically by time-dependent conformal mapping methods. Fully nonlinear waves are presented, and their stability and dynamics are studied.

An in-depth numerical study of the two-dimensional Kuramoto-Sivashinsky equation.

The Kuramoto-Sivashinsky equation in one spatial dimension (1D KSE) is one of the most well-known and well-studied partial differential equations. It exhibits spatio-temporal chaos that emerges through various bifurcations as the domain length increases. There have been several notable analytical studies aimed at understanding how this property extends to the case of two spatial dimensions. In this study, we perform an extensive numerical study of the Kuramoto-Sivashinsky equation (2D KSE) to complement this analytical work. We explore in detail the statistics of chaotic solutions and classify the solutions that arise for domain sizes where the trivial solution is unstable and the long-time dynamics are completely two-dimensional. While we find that many of the features of the 1D KSE, including how the energy scales with system size, carry over to the 2D case, we also note several differences including the various paths to chaos that are not through period doubling.

Controlling spatiotemporal chaos in active dissipative-dispersive nonlinear systems.

We present an alternative methodology for the stabilization and control of infinite-dimensional dynamical systems exhibiting low-dimensional spatiotemporal chaos. We show that with an appropriate choice of time-dependent controls we are able to stabilize and/or control all stable or unstable solutions, including steady solutions, traveling waves (single and multipulse ones or bound states), and spatiotemporal chaos. We exemplify our methodology with the generalized Kuramoto-Sivashinsky equation, a paradigmatic model of spatiotemporal chaos, which is known to exhibit a rich spectrum of wave forms and wave transitions and a rich variety of spatiotemporal structures.

On the generation of nonlinear travelling waves in confined geometries using electric fields.

We investigate electrostatically induced interfacial instabilities and subsequent generation of nonlinear coherent structures in immiscible, viscous, dielectric multi-layer stratified flows confined in small-scale channels. Vertical electric fields are imposed across the channel to produce interfacial instabilities that would normally be absent in such flows. In situations when the imposed vertical fields are constant, interfacial instabilities emerge due to the presence of electrostatic forces, and we follow the nonlinear dynamics via direct numerical simulations. We also propose and illustrate a novel pumping mechanism in microfluidic devices that does not use moving parts. This is achieved by first inducing interfacial instabilities using constant background electric fields to obtain fully nonlinear deformations. The second step involves the manipulation of the imposed voltage on the lower electrode (channel wall) to produce a spatio-temporally varying voltage there, in the form of a travelling wave with pre-determined properties. Such travelling wave dielectrophoresis methods are shown to generate intricate fluid-surface-structure interactions that can be of practical value since they produce net mass flux along the channel and thus are candidates for microfluidic pumps without moving parts. We show via extensive direct numerical simulations that this pumping phenomenon is a result of an externally induced nonlinear travelling wave that forms at the fluid-fluid interface and study the characteristics of the generated velocity field inside the channel.

Thermal degradation kinetics and decomposition mechanism of PBSu nanocomposites with silica-nanotubes and strontium hydroxyapatite nanorods.

Novel poly(butylene succinate) (PBSu) nanocomposites containing 5 and 20 wt% mesoporous strontium hydroxyapatite nanorods (SrHNRs) and silica nanotubes (SiNTs) were prepared by melt-mixing. A systematic investigation of the thermal stability and decomposition kinetics of PBSu was performed using pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS) and thermogravimetry (TG). Thorough studies of evolving decomposition compounds along with the isoconversional and model-fitting analysis of mass loss data led to the proposal of a decomposition mechanism for PBSu. Moreover, the effects of SrHNRs and SiNTs on the thermal stability and decomposition kinetics of PBSu were also examined in detail. The complementary use of these techniques revealed that the incorporation of SiNTs in PBSu does not induce significant effects neither on its thermal stability nor on its decomposition mechanism. In contrast, the addition of SrHNRs resulted in the catalysis of the initial decomposition steps of PBSu and also in modified decomposition mechanisms and activation energies. The evolving gaseous products of PBSu and their evolution pattern in the SiNT nanocomposites were the same as in neat PBSu, while they were slightly modified for the SrHNR nanocomposites, confirming the findings from thermogravimetric analysis.

Private duty nurses in Greek hospitals: a literature review.

AIM: The study aims to provide an overview of the practice of private duty nurses in Greek hospitals. BACKGROUND: For several decades, it has been a necessity for some hospital patients to hire private duty nurses (PDNs) to counterbalance the inadequacies of hospital infrastructures. In the current economic crisis in Greece, the majority of patients will not be able to afford to pay for private nursing care. METHODS: Databases such as PubMed, CINAHL, ScienceDirect, Wiley Online Library, Google Scholar and national sources were searched for relevant literature through a range of keywords. Information gathered was evaluated for relevance and grouped on a thematic basis. FINDINGS: Five articles met the inclusion criteria. Nearly 90% of PDNs have secondary levels of education or below. Approximately 15% of patients use PDNs at night due to nurse shortages and inability of their families to stay with them. Fifty per cent of the relatives reported being very unsatisfied with PDN services, while the cost for the use of a PDN is rather high. CONCLUSION: The existence of private duty nursing has been largely responsible for protecting healthcare authorities from the need to develop effective care infrastructures. In the current economic climate, nursing and healthcare authorities must staff wards appropriately for safe, free and efficient care for all patients. Effective utilization of the national nursing and healthcare workforce--including PDNs with appropriate qualifications--and matching demand with the necessary skills is essential.

Breakup of an electrified, perfectly conducting, viscous thread in an AC field.

We study the axisymmetric breakup and satellite formation of slender jets surrounded by a concentrically placed cylindrical electrode and subjected to time-dependent AC electric fields. The jet is assumed to be a perfectly conducting viscous fluid and surrounded by a dielectric inviscid gas. We use the long-wave approximation to derive coupled evolution equations for the interface position and the axial velocity component, which accounts for electrostatic forcing. The electrostatic force in this case is large and competes with capillary forces near the rupture point, causing the interface to oscillate and the satellite to have shapes that are distinct from the DC case. In particular, our results indicate that it may be possible to use the AC field to control the number of satellites accompanying breakup as well as their size.

Noise induced state transitions, intermittency, and universality in the noisy Kuramoto-Sivashinksy equation.

Consider the effect of pure additive noise on the long-time dynamics of the noisy Kuramoto-Sivashinsky (KS) equation close to the instability onset. When the noise acts only on the first stable mode (highly degenerate), the KS solution undergoes several state transitions, including critical on-off intermittency and stabilized states, as the noise strength increases. Similar results are obtained with the Burgers equation. Such noise-induced transitions are completely characterized through critical exponents, obtaining the same universality class for both equations, and rigorously explained using multiscale techniques.

Dynamics of an electrostatically modified Kuramoto-Sivashinsky-Korteweg-de Vries equation arising in falling film flows.

The gravity-driven flow of a liquid film down a vertical flat plate in the presence of an electric field acting in a direction perpendicular to the wall is investigated. The film is assumed to be a perfect conductor, and the bounding region of air above the film is taken to be a perfect dielectric. A strongly nonlinear long-wave evolution equation is developed for flow parameters near the critical instability conditions. The equation retains terms up to second order in the slenderness parameter in order to incorporate the effects of shear-induced growth, short-wave damping due to surface tension, electric stress effects, and dispersive effects. In the additional asymptotic limit of small but finite interfacial perturbations the dynamics are shown to be governed by a Kuramoto-Sivashinsky (KS) equation with Korteweg-de Vries dispersion, also known as the Kawahara or the generalized Kuramoto-Sivashinsky (gKS) equation, which also includes a nonlocal energy growth term that arises from the electrostatics. Extensive numerical experiments are carried out to characterize solutions to this equation. Using perturbation theory and numerical solutions, it is shown that the electric field alters the far-field decay characteristics of bound states of the gKS equation from exponential to algebraic behavior. In addition, it is demonstrated numerically that chaotic solutions of the KS equation that are regularized into traveling-wave pulses when sufficient dispersion is added can in turn become chaotic by applying a sufficiently strong electric field. It is suggested, therefore, that electric fields can be utilized to enhance interfacial turbulence and in turn increase heat or mass transfer in applications. A physical example involving electrified falling film flows of ethelene glycol fluids is furnished and shows that the theory is within reach of experiments.

Deformation induced directional amorphization in Zr2Ni systems: a remedy for the mechanical failure of nano-crystalline alloys.

We report on Molecular Dynamics results referring to the mechanical properties of crystalline, amorphous and nanocrystalline Zr2Ni. In addition, nanocrystals of the same alloy having various sizes were also considered. With the exception of the amorphous system, we found that upon tensile deformation these systems exhibit lattice instability along the [110] direction. In addition, we found that the nanocrystals exhibit small decrease in the bulk moduli and yielding points as their sizes increased from 2 nm to 12 nm. Furthermore, it came out that in the nanocrystalline models the catastrophic failure is prevented via partial amorphization of the nanocrystals and their incorporation into the amorphous matrix, resulting in significant elongation of the plastic region. This effect results also in the increase of the triple junctions present in the system, thus altering the grain's migration angles and mobility. These findings could be used for remedying the yielding to fracture of nanostructured materials and for tailoring nanograined systems to exhibit enhanced ductility.

Chromogranin a levels in diagnosis, treatment and follow-up of 42 patients with non-functioning pancreatic endocrine tumours.

BACKGROUND/AIMS: Non-functioning pancreatic endocrine tumours (NFPET) constitute the largest component (35-50%) of pancreatic endocrine tumours. They are characterized by the absence of symptoms of hormone hypersecretion and frequently have clinical manifestations similar to the more common exocrine pancreatic adenocarcinoma. The present studyaims toevaluate the clinical features, diagnostic approach and, in particular, the significance of serum chromogranin A levels (CgA) in the management and outcome of 42 patients with NFPET (from a series of 121 patients with pancreatic endocrine tumours). METHODS: Twenty-five males and 17 females were included, and the mean age at diagnosis was 52.3 years (range: 26-68 years). The diagnosis for each patient was established by histopathological examination and immunohistochemistry. After the histopathological confirmation of diagnosis and during the follow-up period, patients were evaluated clinically and radiologically (including OctreoScan), whilst fasting gut hormones (including CgA) were also estimated. At diagnosis, all patients were checked for the presence of multiple endocrine neoplasia type I syndrome. The follow-up was complete and ranged from 12 to 86 months (mean: 49 months). RESULTS: Dyspepsia (66.5%) and weight loss (47.6%) were the most common symptoms at diagnosis, while in 21.4% of patients tumour lesions were revealed incidentally. Plasma CgA levels were significantly or moderately elevated in all patients with liver metastases at diagnosis (64.3%). The levels also reflected tumour progression or response to treatment during the follow-up period. OctreoScan showed avid uptake in 77.8% of patients with hepatic metastases. Moreover, in 2 patients OctreoScan revealed unexpected metastatic mesenteric deposits, which had not been found by the other studies. However, it was negative in 6 patients with liver metastases, in whom tumours were proved to be poorly differentiated (high-grade). CONCLUSIONS: (1) NFPET may present with clinical manifestations similar to those of an exocrine pancreatic tumour; (2) plasma CgA levels reflect tumour load, and also seem to correlate with tumour progression or response to treatment; (3) surgeryin patients with localized disease at presentation can be curative, while it can also reduce tumour burden in patients with metastases; (4) long-acting somatostatin analogues provide good quality of life and temporary disease stabilization in patients with low-grade tumours; (5) systemic chemotherapy or chemoembolization seem to be beneficial in high-grade and progressive tumours.

Non-lactic acid, contaminating microbial flora in ready-to-eat foods: a potential food-quality index.

The bacteriological profile of 87 samples of commercially available ready-to-eat (RTE) dairy and meat-products, packaged sandwiches and salads was obtained by testing for aerobic colony count, for lactic acid bacterial (LAB) count, for the presence and the extent of non-LAB microflora (contaminating microflora), and by testing for certain food-borne pathogens. The pathogens Listeria monocytogenes, Salmonella spp. and sulfite-reducing clostridia were not detected in any of the analysed samples. Whereas only three samples (3.4%) were deemed unacceptable for consumption for exceeding the established pathogen tolerance levels (for Staphylococcus aureus and Escherichia coli), several samples were found to contain non-lactic acid contaminating microflora of considerable magnitude. The log10 cfu g(-1) counts for contaminating microflora in the food categories examined were as follows: hard cheeses 4.85 (SD 1.17); semi-hard cheeses 5.39 (SD 1.37); soft cheeses 5.13 (SD 1.03); whey cheeses 6.55 (1.24); fermented meat-products 4.18 (SD 1.48); heat-treated meat-products 3.47 (SD 1.99); salads 3.37 (SD 1.56) and sandwiches 5.04 (SD 0.96). Approximately 1 in every 30 to 80 bacterial cells found on different types of cheeses and salads was a non-LAB microorganism; the respective ratios for fermented meat-products, heat-treated meat-products and sandwiches were 1 in 6, 2.5 and 15. The assessment of the contaminating microflora magnitude at various steps during the manufacture and distribution of RTE foods can serve as an index for monitoring the microbiological quality of the starting materials, the sanitation efficacy during processing and possible temperature abuse during processing, transportation or storage.

Monodisperse drop formation in square microchannels.

The electrohydrodynamic instability of the interface between two liquids with different physical and electrical properties in plane Poiseuille flow is used to form monodisperse droplets in a square channel. The drop size and formation rate are controlled by simply controlling the flow rates and the amplitude of the electric field applied across the channel.

Neural-network methods for boundary value problems with irregular boundaries.

Partial differential equations (PDEs) with boundary conditions (Dirichlet or Neumann) defined on boundaries with simple geometry have been successfully treated using sigmoidal multilayer perceptrons in previous works. This article deals with the case of complex boundary geometry, where the boundary is determined by a number of points that belong to it and are closely located, so as to offer a reasonable representation. Two networks are employed: a multilayer perceptron and a radial basis function network. The later is used to account for the exact satisfaction of the boundary conditions. The method has been successfully tested on two-dimensional and three-dimensional PDEs and has yielded accurate results.

Enumeration and confirmation of Aeromonas hydrophila, Aeromonas caviae, and Aeromonas sobria isolated from raw milk and other milk products in Northern Greece.

A total of 138 raw cow's and 57 raw ewe's milk samples; 80 pasteurized cow's milk samples; 39 Anthotyros cheese, 36 Manouri cheese, and 23 Feta cheese samples; and 15 rice pudding samples were examined for the presence and any countable population of Aeromonas species. Twenty-two (15.9%) of the 138 cow's milk samples analyzed were contaminated with A. hydrophila. In 13 of these samples, populations of 3.0x10(2) to 5.0x10(3) CFU/ml were counted in starch ampicillin agar (SAA). Eighteen cow's milk samples (13.0%) were contaminated with A. caviae, and in eight of these samples, populations of 2.0x10(2) to 3.0x10(3) CFU/ml were counted in SAA. Five cow's milk samples (3.6%) were contaminated with A. sobria, and in two of these samples, populations of 2.5x10(3) and 5.0x10(3) CFU/ml were counted in SAA. Eleven cow's milk samples (7.9%) were contaminated with other Aeromonas spp. not classified. Eight (14.0%) of the 57 ewe's milk samples analyzed were contaminated with A. hydrophila. In these samples, populations of 5.0x10(2) to 5.0x10(3) CFU/ml were counted in SAA. Six ewe's milk samples (10.5%) were contaminated with A. caviae, and populations of 1.5x10(2) to 1.0x10(3) CFU/ ml were counted in SAA. Two ewe's milk samples (3.5%) were contaminated with A. sobria, and populations counted in SAA were 5.0x10(2) and 1.0x10(3) CFU/ml. Four samples (7.0%) were contaminated with other Aeromonas spp. not classified. A. hydrophila was recovered in 4 (10.2%) and 3 (8.3%) of the Anthotyros and Manouri cheese samples analyzed, respectively, but no countable populations were noted in SAA. None of the pasteurized milk, Feta cheese, and rice pudding samples yielded Aeromonas spp. The results of this work indicate that motile Aeromonas are common in raw milk in Greece. Also, the presence of A. hydrophila in the whey cheeses Anthotyros and Manouri indicates that postprocessing contaminations of these products with motile Aeromonas may occur during production.

Chemical and bacteriological characteristics of Pichtogalo Chanion cheese and mesophilic starter cultures for its production.

Sixty-two samples of Pichtogalo Chanion cheese traditionally produced in Crete, a few (3 to 6) days old, were analyzed for some chemical and bacteriological characteristics. The results of physicochemical analyses were as follows: (1) moisture content 61.63% (standard deviation 4.67); (2) fat in dry matter 54.03% (SD 7.73); (3) protein content 14.23% (SD 1.72); (4) salt content 1.02% (SD 0.38); (5) water activity (aw) 0.990 (SD 0.003); and (6) pH 4.36 (SD 0.25). None of the samples yielded Salmonella spp. Listeria monocytogenes and coagulase-positive staphylococci were present in 6.45% of the samples. Bacillus cereus and sulfite-reducing clostridia were isolated from 14.51% and 40.32% of the samples, respectively. High populations of coliforms were determined in the cheese samples. In 11.3% of the samples, Escherichia coli was not detected, while 88.7% of the samples yielded E. coli most probable number levels from 1.32 to 5.66 log10/g. The log10 CFU/g counts of enterococci were 6.89 (SD 0.84), of yeasts 6.79 (SD 0.61), of molds 4.68 (SD 0.69), and of psychrotrophic bacteria 7.63 (SD 0.62). The log10 CFU/g counts of lactic acid streptococci and lactococci were 7.91 (SD 0.68) and of lactobacilli 8.11 (SD 0.65). Lactic acid bacteria, mainly mesophilic, were isolated and confirmed using API 50 CH test trips. A pasteurized mixture of ewe's and goat's milk was made into Pichtogalo Chanion cheese according to standard procedure at 23 degrees C, after the addition of 4% commercial mesophilic starter culture or 2%, 3%, and 4% starter culture of the isolated and confirmed lactic acid bacteria and the addition of rennet. Results of this work indicated that high quality of Pichtogalo Chanion cheese can be produced using a pasteurized mixture of ewe's and goat's milk and 4% (vol/vol) of mesophilic starter culture.