Uso de DES y RANS no estacionario para la simulación del flujo alrededor de una carena Wigley - Use of Unsteady RANS and DES to simulate flows around a Wigley Hull)

Computer Fluid Dynamics tools have already become a valuable instrument for Naval Architects during the ship design process, thanks to their accuracy and the available computer power. Unfortunately, the development of RANSE codes, generally used when viscous effects play a major role in the flow, has not reached a mature stage, being the accuracy of the turbulence models and the free surface representation the most important sources of uncertainty. Another level of uncertainty is added when the simulations are carried out for unsteady flows, as those generally studied in seakeeping and maneuvering analysis and URANS equations solvers are used. Present work shows the applicability and the benefits derived from the use of new approaches for the turbulence modeling (Detached Eddy Simulation) and the free surface representation (Level Set) on the URANS equations solver CFDSHIP-Iowa. Compared to URANS, DES is expected to predict much broader frequency contents and behave better in flows where boundary layer separation plays a major role. Level Set methods are able to capture very complex free surface geometries, including breaking and overturning waves. The performance of these improvements is tested in set of fairly complex flows, generated by a Wigley hull at pure drift motion, with drift angle ranging from 10 to 60 degrees and at several Froude numbers to study the impact of its variation. Quantitative verification and validation are performed with the obtained results to guarantee their accuracy. The results show the capability of the CFDSHIP-Iowa code to carry out time-accurate simulations of complex flows of extreme unsteady ship maneuvers. The Level Set method is able to capture very complex geometries of the free surface and the use of DES in unsteady simulations highly improves the results obtained. Vortical structures and instabilities as a function of the drift angle and Fr are qualitatively identified. Overall analysis of the flow pattern shows a strong correlation between the vortical structures and free surface wave pattern. Karman-like vortex shedding is identified and the scaled St agrees well with the universal St value. Tip vortices are identified and the associated helical instabilities are analyzed. St using the hull length decreases with the increase of the distance along the vortex core (x), which is similar to results from other simulations. However, St scaled using distance along the vortex cores shows strong oscillations compared to almost constants for those previous simulations. The difference may be caused by the effect of the free-surface, grid resolution, and interaction between the tip vortex and other vortical structures, which needs further investigations. This study is exploratory in the sense that finer grids are desirable and experimental data is lacking for large α, especially for the local flow. More recently, high performance computational capability of CFDSHIP-Iowa V4 has been improved such that large scale computations are possible. DES for DTMB 5415 with bilge keels at α = 20º were conducted using three grids with 10M, 48M and 250M points. DES analysis for flows around KVLCC2 at α = 30º is analyzed using a 13M grid and compared with the results of DES on the 1.6M grid by. Both studies are consistent with what was concluded on grid resolution herein since dominant frequencies for shear-layer, Karman-like, horse-shoe and helical instabilities only show marginal variation on grid refinement. The penalties of using coarse grids are smaller frequency amplitude and less resolved TKE. Therefore finer grids should be used to improve V&V for resolving most of the active turbulent scales for all different Fr and α, which hopefully can be compared with additional EFD data for large α when it becomes available.

Ribozyme-mediated high resistance against potato spindle tuber viroid in transgenic potatoes

A hammerhead ribozyme [R(-)] targeting the minus strand RNA of potato spindle tuber viroid (PSTVd) and a mutated nonfunctional ribozyme [mR(-)] were designed, cloned, and transcribed. As predicted, both monomer and dimer transcripts of the active R(-) ribozyme gene could cleave the PSTVd minus strand dimer RNA into three fragments of 77, 338, and 359 bases in vitro at 25 and 50°C. The tandem dimer genes of R(-) and mR(-) were subcloned separately into the plant expression vector pROK2. Transgenic potato plants (cultivar Desirée) were generated by Agrobacterium tumefaciens-mediated transformation. Twenty-three of 34 independent transgenic plant lines expressing the active ribozyme R(-) resulted in having high levels of resistance to PSTVd, being free of PSTVd accumulation after challenge inoculation with PSTVd, but the remaining lines showed weaker levels of resistance to PSTVd with low levels of PSTVd accumulation. In contrast, 59 of 60 independent transgenic lines expressing the mutated ribozyme mR(-) were susceptible to PSTVd inoculation and had levels of PSTVd accumulation similar to that of the control plants transformed with the empty vector. The resistance against PSTVd replication was stably inherited to the vegetative progenies.

A lineage-specific protein kinase crucial for myeloid maturation

To identify genes involved in macrophage development, we used the differential display technique and compared the gene expression profiles for human myeloid HL-60 leukemia cell lines susceptible and resistant to macrophage maturation. We identified a gene coding for a protein kinase, protein kinase X (PRKX), which was expressed in the maturation-susceptible, but not in the resistant, cell line. The expression of the PRKX gene was found to be induced during monocyte, macrophage, and granulocyte maturation of HL-60 cells. We also studied the expression of the PRKX gene in 12 different human tissues and transformed cell lines and found that, among these tissues and cell types, the PRKX gene is expressed only in blood. Among the blood cell lineages, the PRKX gene is specifically expressed in macrophages and granulocytes. Antisense inhibition of PRKX expression blocked terminal development in both the leukemic HL-60 cells and normal peripheral blood monocytes, implying that PRKX is a key mediator of macrophage and granulocyte maturation. Using the HL-60 cell variant deficient in protein kinase C-β (PKC-β) and several stable PKC-β transfectants, we found that PRKX gene expression is under control of PKC-β; hence PRKX is likely to act downstream of this PKC isozyme in the same signal transduction pathway leading to macrophage maturation.

A psychrophilic crenarchaeon inhabits a marine sponge: Cenarchaeum symbiosum gen. nov., sp. nov.

Archaea, one of the three major domains of extant life, was thought to comprise predominantly microorganisms that inhabit extreme environments, inhospitable to most Eucarya and Bacteria. However, molecular phylogenetic surveys of native microbial assemblages are beginning to indicate that the evolutionary and physiological diversity of Archaea is far greater than previously supposed. We report here the discovery and preliminary characterization of a marine archaeon that inhabits the tissues of a temperate water sponge. The association was specific, with a single crenarchaeal phylotype inhabiting a single sponge host species. To our knowledge, this partnership represents the first described symbiosis involving Crenarchaeota. The symbiotic archaeon grows well at temperatures of 10 degrees C, over 60 degrees C below the growth temperature optimum of any cultivated species of Crenarchaeota. Archaea have been generally characterized as microorganisms that inhabit relatively circumscribed niches, largely high-temperature anaerobic environments. In contrast, data from molecular phylogenetic surveys, including this report, suggest that some crenarchaeotes have diversified considerably and are found in a wide variety of lifestyles and habitats. We present here the identification and initial description of Cenarchaeum symbiosum gen. nov., sp. nov., a symbiotic archaeon closely related to other nonthermophilic crenarchaeotes that inhabit diverse marine and terrestrial environments.

Four p53 DNA-binding domain peptides bind natural p53-response elements and bend the DNA.

Recent structural studies of the minimal core DNA-binding domain of p53 (p53DBD) complexed to a single consensus pentamer sequence and of the isolated p53 tetramerization domain have provided valuable insights into their functions, but many questions about their interacting roles and synergism remain unanswered. To better understand these relationships, we have examined the binding of the p53DBD to two biologically important full-response elements (the WAF1 and ribosomal gene cluster sites) by using DNA circularization and analytical ultracentrifugation. We show that the p53DBD binds DNA strongly and cooperatively with p53DBD to DNA binding stoichiometries of 4:1. For the WAF1 element, the mean apparent Kd is (8.3 +/- 1.4) x 10(-8) M, and no intermediate species of lower stoichiometries can be detected. We show further that complex formation induces an axial bend of at least 60 degrees in both response elements. These results, taken collectively, demonstrate that p53DBD possesses the ability to direct the formation of a tight nucleoprotein complex having the same 4:1 DNA-binding stoichiometry as wild-type p53 which is accompanied by a substantial conformational change in the response-element DNA. This suggests that the p53DBD may play a role in the tetramerization function of p53. A possible role in this regard is proposed.

The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory

We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than 60 degrees, detected at the Pierre Auger Observatory. the geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the similar to 2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.

South America, 1902 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Rand, McNally & Co.'s new 14 x 21 map of South America. It was published by Rand, McNally & Co. in 1902. Scale [1:19,008,000]. The image inside the map neatline is georeferenced to the surface of the earth and fit to a non-standard 'World Sinusoidal' projection with the central meridian at 60 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. Relief shown by hachures. Includes inset of the Galapagos Islands. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

In vitro bioactivity of MOEP grafted ePTFE membranes for craniofacial applications

The bioactivity of three methacryloyloxyethyl phosphate (MOEP) grafted expanded polytetrafluoroethylene (ePTFE) membranes with varying surface coverage as well as unmodified ePTFE was investigated through a series of in vitro tests: calcium phosphate (CaP) growth in simulated body fluid (SBF), serum protein adsorption, and a morphology and attachment study of human osteoblast-like SaOS-2 cells. The graft copolymers were prepared by means of gamma irradiation induced grafting and displayed various surface morphologies and wettabilities depending on the grafting conditions used. Unmodified ePTFE did not induce nucleation of Cal? minerals, whereas all the grafted membranes revealed the growth of Cal? minerals after 7 days immersion in SBF. The sample with lowest surface grafting yield (24% coverage), a smooth graft morphology and relatively high hydrophobicity (theta(adv) = 120 degrees, theta(rec) = 80 degrees) showed carbonated hydroxyapatite growth covering the surface. On the other hand, the samples with high surface grafting yield (76% and 100%), a globular graft morphology and hydrophilic surfaces (theta(adv) = 60 degrees and 80 degrees, theta(rec) = 25 degrees and 15 degrees, respectively) exhibited irregular growth of non-apatitic Cap minerals. Irreversibly adsorbed protein measured after a 1 h immersion in serum solution was quantified by the amount of nitrogen on the surface using XPS, as well as by weight increase. All grafted membranes adsorbed 3-6 times more protein than the unmodified membrane. The sample with the highest surface coverage adsorbed the most protein. Osteoblast-like SaOS-2 cells cultured for 3 h revealed significantly higher levels of cell attachment on all grafted membranes compared to unmodified ePTFE. Although the morphology of the cells was heterogeneous, in general, the higher grafted surfaces showed a much better cell morphology than both the low surface-grafted and the control unmodified sample. The suite of in vitro tests confirms that a judicious choice of grafted monomer such as the phosphate-containing methacrylate monomer (MOEP) significantly improves the bioactivity of ePTFE in vitro. (c) 2005 Elsevier Ltd. All rights reserved.

Correlations between the satellite-derived seasonal cycle of phytoplankton biomass and aerosol optical depth in the Southern Ocean: Evidence for the influence of sea ice

The relationship between the production of dimethylsulfide (DMS) in the upper ocean and atmospheric sulfate aerosols has been confirmed through local shipboard measurements, and global modeling studies alike. In order to examine whether such a connection may be recoverable in the satellite record, we have analyzed the correlation between mean surface chlorophyll (CHL) and aerosol optical depth (AOD) in the Southern Ocean, where the marine atmosphere is relatively remote from anthropogenic and continental influences. We carried out the analysis in 5-degree zonal bands between 50 degrees S and 70 degrees S, for the period ( 1997 - 2004), and in smaller meridional sectors in the Eastern Antarctic, Ross and Weddell seas. Seasonality is moderate to strong in both CHL and AOD signatures throughout the study regions. Coherence in the CHL and AOD time series is strong in the band between 50 degrees S and 60 degrees S, however this synchrony is absent in the sea-ice zone (SIZ) south of 60 degrees S. Marked interannual variability in CHL occurs south of 60 degrees S, presumably related to variability in sea-ice production during the previous winter. We find a clear latitudinal difference in the cross correlation between CHL and AOD, with the AOD peak preceding the CHL bloom by up to 6 weeks in the SIZ. This suggests that substantial trace gas emissions ( aerosol precursors) are being produced over the SIZ in spring ( October - December) as sea ice melts. This hypothesis is supported by field data that record extremely high levels of sulfur species in sea ice, surface seawater, and the overlying atmosphere during ice melt.

Preparation and anode property of Pt-CeO2 electrodes supported on carbon black for direct methanol fuel cell applications

A platinum (Pt) on pure ceria (CeO2) supported by carbon black (CB) anode was synthesized using a combined process of precipitation and coimpregnation methods. The electrochemical activity of methanol oxidation reaction on synthesized Pt-CeO2/CB anodes was investigated by cyclic voltammetry and chronoamperometry experimentation. To improve the anode property on Pt-CeO2/CB, the influence of particle morphology and particle size on anode properties was examined. The morphology and particle size of the pure CeO2 particles could be controlled by changing the preparation conditions. The anode properties (i.e., peak current density and onset potential for methanol oxidation) were improved by using nanosize CeO2 particles. This indicates that a larger surface area and higher activity on the surface of CeO2 improve the anode properties. The influence of particle morphology of CeO2 on anode properties was not very large. The onset potential for methanol oxidation reaction on Pt-CeO2/CB, which consisted of CeO2 with a high surface area, was shifted to a lower potential compared with that on the anodes, which consisted of CeO2 with a low surface area. The onset potential on Pt-CeO2/CB at 60 degrees C became similar to that on the commercially available Pt-Ru/carbon anode. We suggest that the rate-determining steps of the methanol oxidation reaction on Pt-CeO2/CB and commercially available Pt-Ru/carbon anodes are different, which accounts for the difference in performance. In the reaction mechanism on Pt-CeO2/CB, we conclude that the released oxygen species from the surface of CeO2 particles contribute to oxidation of adsorbed CO species on the Pt surface. This suggests that the anode performance of the Pt-CeO2/CB anode would lead to improvements in the operation of direct methanol fuel cells at 80 degrees C by the enhancement of diffusion of oxygen species created from the surface of nanosized CeO2 particles. Therefore, we conclude that fabrication of nanosized CeO2 with a high surface area is a key factor for development of a high-quality Pt-CeO2/CB anode in direct methanol fuel cells.

Effect of knee joint angle on motor unit synchronization

Activity of the vasti has been argued to vary through knee range of movement due to changes in passive support of the patellofemoral joint and the relative contribution of these muscles to knee extension. Efficient function of the knee is dependent on optimal control of the patellofemoral joint, largely through coordinated activity of the medial and lateral quadriceps. Motor unit synchronization may provide a mechanism to coordinate the activity of vastus medialis (VMO) and vastus lateralis (VL), and may be more critical in positions of reduced passive support for the patellofemoral joint (i.e., full extension). Therefore, the aim of this study was to determine whether the degree of motor unit synchronization between the vasti muscles is dependent on joint angle. Electromyographic (EMG) recordings of single motor unit action potentials (MUAPs) were made from VMO and multiunit recordings from VL during isometric contractions of the quadriceps at 0 degrees, 30 degrees, and 60 degrees of knee flexion. The degree of synchronization between motor unit firing was evaluated by identification of peaks in the rectified EMG averages of VL, triggered from MUA-Ps in VMO. The proportion of cases in which there was a significant peak in the triggered averages was calculated. There was no significant difference in the degree of synchronization between the vasti at different knee angles (p = 0.57). These data suggest that this basic coordinative mechanism between the vasti muscles is controlled consistently throughout knee range of motion, and is not augmented at specific angles where the requirement for dynamic control of stability is increased. (D 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Screening, characterization and flocculating property of carbohydrate polymer from newly isolated Enterobacter cloacae WD7

A total of 188 carbohydrate polymer-producing bacterial strains were isolated from recycled sludge of five seafood processing plants. Among three selected isolates, identified as Enterobacter cloacae WD7, Enterobacter agglomerans WD50 and Pseudomonas alcaligenes WD22. E. cloacae WD7 generated a viscous culture broth exhibiting the highest flocculating activity and a crude polymer yield of 2.27 g/L after 3 days cultivation. Partial purification of this polymer was performed by precipitation with 95% ethanol, dialysis and freeze-drying. It was characterized as an acidic heteropolysaccharide, composed of neutral sugars (29.4%), uronic acids (14.2%) and amino sugars (0.93%). The functional group analysis by FT-IR spectroscopy showed the presence of hydroxyl, carboxyl, carbonyl and methoxyl groups. Thermal analysis by DSC showed the crystalline transition and the crystalline melting point (T-m) at 300 degrees C. This polysaccharide was soluble in water and insoluble in any organic solvents tested; gelation occurred under alkaline conditions in the presence of divalent cations in which copper as CuSO4 gave the best result. Studies on the flocculation property revealed that this polysaccharide was stable at 4-60 degrees C and pH 5-7. The optimal concentrations for the flocculating activity were 2 mg/L polysaccharide and 40 mM CaCl2 which played the synergistic effect on kaolin flocculation. Moreover, this polysaccharide could flocculate the kaolin suspension over a wide range of pH (pH 2-8) and temperature (4-50 degrees C) tested in the presence of CaCl2. (c) 2006 Elsevier Ltd. All rights reserved.

Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge-from a biological nutrient removal plant

A two-stage thermophilic-mesophilic anaerobic digestion pilot-plant was operated solely on waste activated sludge (WAS) from a biological nutrient removal (BNR) plant. The first-stage thermophilic reactor (HRT 2 days) was operated at 47, 54 and 60 degrees C. The second-stage mesophilic digester (HRT 15 days) was held at a constant temperature of 36-37 degrees C. For comparison with a single-stage mesophilic process, the mesophilic digester was also operated separately with an HRT of 17 days and temperature of 36-37 degrees C. The results showed a truly thermophilic stage (60 degrees C) was essential to achieve good WAS degradation. The lower thermophilic temperatures examined did not offer advantages over single-stage mesophilic treatment in terms of COD and VS removal. At a thermophilic temperature of 60 degrees C, the plant achieved 35% VS reduction, representing a 46% increase compared to the single-stage mesophilic digester. This is a significant level of degradation which could make such a process viable in situations where there is no primary sludge generated. The fate of the biologically stored phosphorus in this BNR sludge was also investigated. Over 80% of the incoming phosphorus remained bound up with the solids and was not released into solution during the WAS digestion. Therefore only a small fraction of phosphorus would be recycled to the main treatment plant with the dewatering stream.

On the Nature of Temporal Variability of the Gulf Stream Path from 75° to 55°W

The response of the Gulf Stream (GS) system to atmospheric forcing is generally linked either to the basin-scale winds on the subtropical gyre or to the buoyancy forcing from the Labrador Sea. This study presents a multiscale synergistic perspective to describe the low-frequency response of the GS system. The authors identify dominant temporal variability in the North Atlantic Oscillation (NAO), in known indices of the GS path, and in the observed GS latitudes along its path derived from sea surface height (SSH) contours over the period 1993-2013. The analysis suggests that the signature of interannual variability changes along the stream's path from 75 degrees to 55 degrees W. From its separation at Cape Hatteras to the west of 65 degrees W, the variability of the GS is mainly in the near-decadal (7-10 years) band, which is missing to the east of 60 degrees W, where a new interannual (4-5 years) band peaks. The latter peak (4-5 years) was missing to the west of 65 degrees W. The region between 65 degrees and 60 degrees W seems to be a transition region. A 2-3-yr secondary peak was pervasive in all time series, including that for the NAO. This multiscale response of the GS system is supported by results from a basin-scale North Atlantic model. The near-decadal response can be attributed to similar forcing periods in the NAO signal; however, the interannual variability of 4-5 years in the eastern segment of the GS path is as yet unexplained. More numerical and observational studies are warranted to understand such causality.

On the Nature of Temporal Variability of the Gulf Stream Path from 75° to 55°W

The response of the Gulf Stream (GS) system to atmospheric forcing is generally linked either to the basin-scale winds on the subtropical gyre or to the buoyancy forcing from the Labrador Sea. This study presents a multiscale synergistic perspective to describe the low-frequency response of the GS system. The authors identify dominant temporal variability in the North Atlantic Oscillation (NAO), in known indices of the GS path, and in the observed GS latitudes along its path derived from sea surface height (SSH) contours over the period 1993-2013. The analysis suggests that the signature of interannual variability changes along the stream's path from 75 degrees to 55 degrees W. From its separation at Cape Hatteras to the west of 65 degrees W, the variability of the GS is mainly in the near-decadal (7-10 years) band, which is missing to the east of 60 degrees W, where a new interannual (4-5 years) band peaks. The latter peak (4-5 years) was missing to the west of 65 degrees W. The region between 65 degrees and 60 degrees W seems to be a transition region. A 2-3-yr secondary peak was pervasive in all time series, including that for the NAO. This multiscale response of the GS system is supported by results from a basin-scale North Atlantic model. The near-decadal response can be attributed to similar forcing periods in the NAO signal; however, the interannual variability of 4-5 years in the eastern segment of the GS path is as yet unexplained. More numerical and observational studies are warranted to understand such causality.