Progressive Removal Research Articles

Aquatic invertebrate community structure along an intermittence gradient: Selwyn River, New Zealand

Changes in community structure and life-history traits of benthic invertebrates were examined along a longitudinal intermittence gradient in an alluvial river. The gradient was characterized with modeled and measured hydrologic, chemical, and physical environmental variables. The invertebrates were collected in the Selwyn River, southeastern New Zealand, at multiple sites in each of 4 river sections with distinct hydrological conditions (perennial-losing, ephemeral, intermittent, perennial-gaining). Values of hydrological metrics for each site were generated with an empirical model developed for the Selwyn River. The metrics included 4 that characterized intermittent flow (flow permanence, flow duration, drying frequency, distance to nearest perennial site). Most invertebrate richness and density metrics were significantly higher in the perennial-losing and perennial-gaining sections than in the ephemeral and intermittent sections. A principle components analysis (PCA) separated invertebrate samples from the 4 sections along 2 primary factors. Nine of 13 hydrological metrics, including the 4 intermittence metrics, were correlated with the PCA site scores. Linear regressions indicated that most taxon-richness metrics and some density metrics were related to flow permanence, flow duration, or both. Based on the regression analysis, we predicted that 1.9 taxa/m2 are added with each 10% increase in flow permanence, and 0.5 taxa/m2 are added with each 10-d increase in flow duration. Results from a nestedness analysis indicated that communities at ephemeral and intermittent sites were nested subsets of the communities at perennial sites, and the nesting order of sites was related to both flow permanence and flow duration. Assemblages of taxa with particular life-history traits (life span, fecundity, maximum size, and voltinism) varied linearly with flow permanence and flow duration. The variation in invertebrate communities along the Selwyn River was primarily the result of progressive removal of desiccation-sensitive taxa with increasing intermittence, not to selection for desiccation-resistant specialists. Quantitative intermittence–ecology relationships are needed to predict the consequences of future changes in flow intermittence, but such relationships are rare. The univariate relationships reported in our study contribute to a small but growing array of intermittence–ecology relationships.

CRUDE OIL BIODEGRADATION AND ENVIRONMENTAL FACTORS AT THE RIUTORT OIL SHALE MINE, SE PYRENEES

Liquid oil seeps from organic‐rich source rock intervals in the Eocene Armàncies Formation in the walls of the underground Riutort oil‐shale mine in the SE Pyrenees. The mine was excavated at the beginning of the last century for oil shale extraction. For this study, oil samples were recovered from fractures in the mine walls, and from pools of water on the mine floor. Some oil is present at the bottom of these pools; oil also floats on the surface of the water in association with emulsions colonized by microbial mats. The oils have undergone variable degrees of biodegradation.The physical and chemical environment in the mine was studied in order to establish the controls on biodegradation processes. The results show that the degree of biodegradation depended on factors including the location of the oil (i.e. floating on the top of the water or from the bottom of a pool), and the addition of fresh seepage oil. The biodegradation observed mainly involved the progressive removal of n‐alkanes, isoprenoids and some aromatics. Biodegradation was also assessed in terms of the sulphur content and by quantitative analyses of molecular markers in the aromatic fraction. These approaches indicated that at least 50% of the oil was lost as a result of biodegradation. Isotope studies were also undertaken but isotope signatures did not provide significant data.Microbiological data were consistent with data collected from chemical analyses. Evidence for the presence of hydrocarbon‐degrading bacteria were obtained from laboratory studies.

A Finite Element Analysis for the Characteristics of Cutting Parameters in 3D Oblique Milling Process

In the field of aeronautical and astronautical manufacturing, milling is a basic machining process by which a surface is generated by progressive chip removal. Therefore, this paper reports a complete procedure of the finite element model for the 3D oblique milling process using the commercial software package ABAQUS. Effect of various parameters on cutting forces is mainly discussed. The model correctly exhibits the observed transition from small to large force with increasing cutting speed and cutting depth.

Effect of progressive removal of ground tissue with increasing plant population on the growth and yield of yan (<i><u>Discorea sp</i></u> grown from minisetts

Effect of progressive removal of ground tissue with increasing plant population on the growth and yield of yan (<i><u>Discorea sp</i></u> grown from minisetts

Partially pyrolyzed membranes ( PPMs) derived from copolyimides having carboxylic acid groups. Preparation and gas transport properties

A series of partially pyrolyzed membranes ( PPMs) were prepared from a copolyimide having carboxylic acid pendant groups ( PIA). The effect of the final pyrolysis temperature (425, 450 and 475 °C) on the gas separation properties was investigated and compared with those of PIA. The thermal treatments caused a progressive removal of the carboxylic acid pendant groups of PIA and a simultaneous increase of the fractional free volume of the PPMs. Thus, it was found that the permeability coefficients of PPMs were higher than that of PIA, between 6.5 and 25 times higher, depending on the gas tested and the final pyrolysis temperature, while the selectivity slightly decreased. All PPMs were attractive materials to separate CO 2 from CH 4 since were inside the commercially interesting region and are close to the present Robeson trade-off limit line. The pyrolysis at 475 °C yielded the PPM with the best performance: CO 2/CH 4 selectivity of 47 and CO 2 permeability close to 95 barrers.

Seafloor structural geomorphic evolution of the accretionary frontal wedge in response to seamount subduction, Poverty Indentation, New Zealand

High quality swath bathymetry and seismic reflection data reveal that the steep forearc slope along the northern sector of the obliquely convergent Hikurangi subduction zone is characteristic of non-accretionary and tectonically eroding continental margins, with reduced sediment supply in the trench relative to further south, and the presence of subducting seamount relief on the Hikurangi Plateau. These seamounts influence the subduction process and the structurally-driven geomorphic development of the over-riding margin of the Australian Plate frontal wedge. The origin of the Poverty Indentation, on the inboard trench slope, is attributed to multiple seamount impacts over the last c. 1 Myr period, accompanied by canyon incision, thrust fault propagation into the trench fill, and numerous large-scale gravitational collapse structures with multiple debris flow and avalanche deposits ranging in downslope length from a few hundred metres to more than 40 km. The indentation is directly offshore of the Waipaoa River which is currently estimated to have a high sediment yield into the marine system. The Poverty Canyon stretches 70 km from the continental shelf edge directly offshore from the Waipaoa to the trench floor, incising into the axis of the indentation. The sediment delivered to the margin from the Waipaoa catchment and elsewhere during sea-level high-stands, including the Holocene, has remained largely trapped in a large depocentre on the Poverty shelf, while during low-stand cycles, sediment bypassed the shelf to develop a prograding clinoform sequence out onto the upper slope. The formation of the indentation and the development of the upper branches of the Poverty Canyon system has led to the progressive removal of a substantial part of this prograding wedge by mass movements and gully incision. Sediment has also accumulated in the head of the Poverty Canyon and episodic mass flows contribute significantly to continued modification of the indentation by driving canyon incision and triggering instability in the adjacent slopes. Prograding clinoforms lying seaward of active faults beneath the shelf, and overlying a buried inactive thrust system beneath the upper slope, reveal a history of deformation accompanied by the creation of accommodation space. The middle to lower Poverty Canyon represents a structural transition zone within the indentation coincident with the indentation axis. The lower to mid-slope south of the canyon conforms more closely to a classic accretionary slope deformation style with a series of east-facing thrust-propagated asymmetric anticlines, separated by early-stage slope basins. North of the canyon system, seamount impact has resulted in frontal tectonic erosion associated with the development of an over-steepened lower to mid-slope margin, fault reactivation and structural inversion and over-printing.

Effects of post materials and length on the stress distribution of endodontically treated maxillary central incisors: a 3D finite element analysis

Traditionally, using a long post can cause progressive removal of the root structure, complicate the ability to re-treat the tooth if necessary and make it difficult to apply an adhesive bonding agent into the root canal. It is unclear if a shorter post length can be applied when a light translucent glass fibre post and adhesive resin cement are used. The aim of this study was to evaluate the biomechanical performance of endodontically treated teeth restored with three post materials, glass-fibre, stainless steel and cast-nickel chromium posts and cores of different lengths of 7, 10 and 13 mm. A 3D finite element analysis model of the maxillary central incisor was constructed. An occlusal load of 300 N was applied to a node at the palatal surface of the crown at 45 degrees to the long axis of the tooth. von Mises stress analyses were carried out in three regions. Simulated data were collected for plotting various pattern graphics and conducting statistical tests. The pattern graphics showed that when the post length changed from 13 to 7 mm, the stress patterns were even and flat in all fibre-post groups, while the stress patterns of the metal-post groups showed an M-shaped peak and trough. Statistical tests showed that the shorter fibre post was superior to the longer metal post in some situations. Within the limitations of this study, it was concluded that when a metal post is used, the post should be as long as possible, while the biomechanical performance of a glass-fibre post combined with a composite resin core was less sensitive to post length.

Contribution by different organic fractions to triazines sorption in Calcaric Regosol amended with raw and biotransformed olive cake

A soil, olive cake, compost and vermicompost of olive cake, were subjected to sequential laboratory extraction to progressively remove water-soluble, lipid and alkali-soluble (humic-type) fractions. Sorption experiments with triazines were carried out with non-amended and amended soil and with soil residues in the intermediate stages during the laboratory removal of the different organic fractions. Herbicide sorption in soil amended with olive cake was between two and three times higher than sorption in composted substrates. In non-amended soil, the removal of humic and fulvic acids led to a decrease of triazines sorption indicating the importance of these fractions in the sorption of these pesticides. The greater triazines sorption in soil amended with olive cake could be associated with the high concentration of water-soluble substances. In contrast, olive cake lipids did not favour the sorption of the more hydrophobic herbicides as indicated by the fact that the sorbed amount increased 30–40% when this fraction was removed. No significant ( P > 0.05) differences in K oc values were found in soils amended with compost and vermicompost in the course of the progressive removal of the different organic fractions, indicating triazine sorption was related more with the total amount of organic matter than with its chemical composition.

Age‐related improvement in reproductive performance in a long‐lived raptor: a cross‐sectional and longitudinal study

In numerous iteroparous species, mean fecundity increases with age. Such improvement has been explained by: a) progressive removal of inferior breeders from the breeding population (selection‐hypothesis); b) delayed breeding of higher‐quality phenotypes (delayed‐breeder‐hypothesis); c) longitudinal enhancement of skills associated with age per se (age‐hypothesis); d) progressive improvement in the capability to conduct specific tasks facilitated by accumulated experience (breeding‐experience‐hypothesis); and e) increasing parental investment promoted by declining residual reproductive values (restraint‐hypothesis). To date, there have been few comprehensive tests of these hypotheses. Here, we provide such a study using a long‐term dataset on a long‐lived raptor, the black kite Milvus migrans (maximum lifespan 23 yr). Kites delayed breeding for 1–7 yr and all measures of breeding performance increased linearly or quadratically up to 11 yr of age. There was no support for the delayed‐breeder‐hypothesis: superior phenotypes did not delay breeding longer. Superior breeders were retained longer in the breeding population, consistent with the selection‐hypothesis. All measures of breeding performance increased longitudinally within individuals, supporting the age‐hypothesis, while some of them increased with accumulated previous experience, supporting the breeding‐experience‐hypothesis. Some analyses suggested the existence of trade‐offs between reproduction in the early years of life and subsequent survival, partially supporting the restraint‐hypothesis. The pattern of age‐related improvements in breeding rates observed at the population‐level could be ascribed to the combined effect of the progressive removal of inferior phenotypes from the breeding population and the individual‐level lack of specific skills which are progressively acquired with time and experience. It was also compatible with a longitudinal increase in reproductive investment. Results from previous studies suggest that different mechanisms may operate in different species and that age‐related improvements in reproduction may be frequently promoted by the complex interplay between longitudinal improvements and changes in the relative frequency of productive phenotypes in the breeding population.

Post‐depositional memory record of mercury in sediment near the effluent disposal site of a chlor‐alkali plant in Thane Creek–Mumbai Harbour, India

A mercury‐cell chlor‐alkali plant, operating for 40 years at Airoli (eastern bank of Thane Creek), India, has caused widespread contamination of the surrounding environment. Untreated wastewater from the plant was discharged to Thane Creek for several years. Thane Creek joins the Ulhas Estuary by a narrow arm and opens to the Arabian Sea through Mumbai Harbour. The Ulhas Estuary is impacted by mercury (Hg) released from several industries including two chlor‐alkali industries. In order to understand the historical record of anthropogenic Hg and its association to Al, Fe and total organic carbon (TOC), estimation of Hg, Al, Fe and TOC was made in surface sediments and cores from Thane Creek–Mumbai Harbour and the adjacent coastal area. Though 70% of the chlor‐alkali plant has been changed to membrane cell technology, surficial sediment in the vicinity of effluent release contains a high concentration (up to 1.19 µg g−1 dry wt) of Hg compared with its background value (0.10 µg g−1 dry wt). The contaminated creek sediments are prone to current‐driven resuspension and are acting as a strong source of Hg to the sediment of the coastal region. Several rocks and sediments from the catchment area were analysed to find out the natural background level of Hg. A high suspended load transported from the catchment region provides natural dilution to the Hg‐contaminated sediment of the Bay. Lithogenic and anthropogenic Hg buried in marine sediments is quantified based on normalization with Al, Fe and TOC, and inter‐comparisons of the results indicate comparable values obtained by using Al and Fe, while discernible deviations are found when normalization is carried out using TOC. The Hg profile in the core, from the effluent release site for which sedimentation rate has been established, is discussed in terms of the progressive removal of Hg from the effluent after the mid‐1970s and partial changeover of the manufacturing process from Hg cell to membrane cell production subsequent to 1992. Based on the reported sedimentation rate in the locality, a maximum concentration (49.19 µg g−1 dry wt) of Hg corresponds to the year 1967, when the chlor‐alkali plant started discharging its untreated effluent to the creek. Results indicate that more than 80% of Hg settles in the vicinity of its discharge and, once deposited in the sediment, it is not affected to any substantial degree by diagenesis.

Comparative Analysis of Extensions of Transbasal Approaches: Effect on Access to Midline and Paramedian Structures

We sought to quantitate the effect of extensions of transbasal approaches (TBAs) on midline and paramedian targets of the cranial base. Eight silicone-injected cadaveric heads were dissected with extensions of TBA level I removal of the orbital bar. Objective measures were the comparisons of the accessibility of midline and paramedian targets with progressive dissections by level II detachment of the medial canthal ligaments and removal of the nasal bone and by level III removal of the lateral orbital walls with lateral orbital retraction. Mean areas of freedom increased for most targets with progressive bone removal. For midline targets, the most effective freedom increment was at the pituitary gland (level II: 28.8%, p = 0.05; level III: 107.1%, p < 0.001). For paramedian targets, the best freedom increment was for the foramen rotundum (level II: 56.4%; level III: 134.5%, all p < 0.001). Extensions of the TBA can increase the surgical corridor to midline and paramedian structures, especially for pituitary and maxillary regions. Level II exposure offers no clear benefit for most targets except the foramen rotundum. With level III exposure, all targets are effectively exposed compared with levels I and II.

Sludge dewatering and stabilization in drying reed beds: Characterization of three full-scale systems in Catalonia, Spain

Optimization of sludge management can help reducing sludge handling costs in wastewater treatment plants. Sludge drying reed beds appear as a new and alternative technology which has low energy requirements, reduced operating and maintenance costs, and causes little environmental impact. The objective of this work was to evaluate the efficiency of three full-scale drying reed beds in terms of sludge dewatering, stabilization and hygienisation. Samples of influent sludge and sludge accumulated in the reed beds were analysed for pH, Electrical Conductivity, Total Solids (TS), Volatile Solids (VS), Chemical Oxygen Demand, Biochemical Oxygen Demand, nutrients (Total Kjeldahl Nitrogen (TKN) and Total Phosphorus (TP)), heavy metals and faecal bacteria indicators ( Escherichia coli and Salmonella spp.). Lixiviate samples were also collected. There was a systematic increase in the TS concentration from 1–3% in the influent to 20–30% in the beds, which fits in the range obtained with conventional dewatering technologies. Progressive organic matter removal and sludge stabilization in the beds was also observed (VS concentration decreased from 52–67% TS in the influent to 31–49% TS in the beds). Concentration of nutrients of the sludge accumulated in the beds was quite low (TKN 2–7% TS and TP 0.04–0.7% TS), and heavy metals remained below law threshold concentrations. Salmonella spp. was not detected in any of the samples, while E. coli concentration was generally lower than 460 MPN/g in the sludge accumulated in the beds. The studied systems demonstrated a good efficiency for sludge dewatering and stabilization in the context of small remote wastewater treatment plants.

Excimer laser removal of beeswax from galician granite monuments

Abstract The paper presents the use of laser radiation for cleaning of beeswax treated granite stone. In the early sixties, prestigious restorers decided to apply molten beeswax on the granite surface of valuable monuments with the aim of preventing the erosive action of atmospheric agents. An interesting example of this treatment is the Renaissance Frieze in the Cloister of the Cathedral of Santiago de Compostela in Galicia (Northwest Spain). With time, salt accumulation beneath the beeswax layer has caused an intense surface disintegration of granite. Conventional cleaning methods can destroy sculptured details of these emblematic monuments. For this reason, excimer laser cleaning has been chosen as a promising non contact, selective and environmentally friendly cleaning technique to be studied. The cleaning tests have been carried out using an excimer laser (ArF, 193 nm), with fluences between 0.5 and 2 J cm −2 pulse −1 and a spot area of 0.025 cm 2 . Samples representing beeswax films over Roan granite have been irradiated and their degree of cleaning has been studied as a function of the number of pulses and the laser fluence. Cleaning efficiency has been evaluated by FT-Raman Spectroscopy, allowing to establish the beeswax ablation threshold and the ablation rate. Excimer laser cleaning allows a progressive and controlled removal of a few tenths of micrometers of beeswax per pulse without damaging the underlying granite stone.

Structural changes induced by dehydration in the crystalline layered silicate Na-RUB-18: a computational/experimental combined study

Na-RUB-18 layered silicate (Na8Si32O64(OH)8·32H2O) is prepared following the procedure reported in the literature (: K. Kosuge and A. Tsunashima, J. Chem. Soc., Chem. Commun., 1995, 2427) and its significant structural modifications induced by progressive removal of hydration water molecules are studied for the first time by a combined experimental (TGA and variable temperature XRD and FTIR) and theoretical approach. A novel structure of a partially de-hydrated Na-RUB-18 obtained upon heating at 75 °C under inert gas flow, which leads to a reversible phase transformation in agreement with XRD and FTIR results, is found. TGA indicates that at this stage, two of the four hydration water molecules per Na ion are lost. Theoretical results based on DFT calculations suggest that the apical water molecules of the solvated octahedrally coordinated sodium ion, forming weak H-bonds with the silicate oxygen atoms, are removed at this stage. As a consequence of the dehydration, the silicate layers get closer, and, similarly to that observed for zeolites, the sodium ions move towards lattice oxygen atoms, to restore their coordination shell. A combination of IR spectroscopy and computational models is used to describe the vibrational properties of silanol/silanolate (SiOH⋯SiO)−1 bridges, which are responsible for the proton conduction of Na-RUB-18. The method described can be of general utility to refine structures which are not fully accessible to standard X-ray structure analysis.

Different roles of N‐ and C‐ termini in the functional activity of FGF21

Fibroblast growth factor 21 is a member of endocrine FGFs subfamily, along with FGF19 and FGF23. It is emerging as a novel regulator with beneficial effects on a variety of metabolic parameters, including glucose and lipid control. FGF21 activity depends on membrane protein betaKlotho that physically complexes with various FGF receptors, thus conferring them the ability to bind FGF21 and activate downstream signaling pathways. FGF21, like other FGFs, folds to a beta-trefoil-like core region, with disordered N- and C-termini. In order to investigate their role in the activity of FGF21, we have constructed a series of deletion mutants and tested them for their ability to (1) bind betaKlotho, analyzed by surface plasmon resonance spectroscopy (2) signal through MAPK phosphorylation and inhibit apoptosis in 3T3-L1/betaKlotho fibroblasts (3) stimulate GLUT1 mRNA upregulation and glucose uptake in 3T3-L1 adipocytes. Binding studies with betaKlotho revealed that the interaction with the co-receptor involves the C-terminus, as progressive removal of amino acids from the carboxy end decreased affinity for betaKlotho. By contrast, removal of up to 17 amino acids from the N-terminus had no effect on the interaction with betaKlotho. Terminal deletions had greater effect on function, as deletions of six amino acids from the amino-terminus and only four from the carboxy-terminus each significantly impacted activity (10-fold). Of the extreme terminal truncations, with no detectable activity, DeltaN17 acted as competitive antagonist while DeltaC20 did not. Our structure/function studies show that the C-terminus is important for betaKlotho interaction whereas the N-terminus likely interacts directly with FGF receptors.

Enhanced osteoblast function on ultraviolet light-treated zirconia

Unlike titanium, surface roughening of zirconia for enhanced bone integration has been technically challenging. The photochemical reaction of semiconductor oxides, e.g., titanium dioxide, has earned considerable and broad interest in environmental and clean energy sciences. This study determined whether ultraviolet (UV) light treatment of zirconia enhances its bioactivity on osteoblasts. Machined zirconia disks were treated with UV light for various time periods up to 48 h. UV light treatment for 48 h increased the rates of attachment, spread, and proliferation of rat bone marrow-derived osteoblasts. Alkaline phosphatase-positive and mineralized nodule areas doubled on UV light-treated zirconia. The expression of osteoblastic genes, such as osteopontin and osteocalcin, was not modulated by UV light treatment. X-ray diffraction and X-ray photoelectron spectroscopy analyses showed that zirconia disks consisted of monoclinic and tetragonal phases of ZrO 2 and Y 2O 3 having a wide light absorption band of 200–400 nm with its peak at <250 nm. UV light treatment transformed the zirconia surface from hydrophobic to hydrophilic status and reduced the atomic percentage of surface carbon in a UV light dose-dependent manner. These results suggest that UV treatment of yttrium-containing partially stabilized zirconia enhances its bioactivity on osteoblasts, in terms of their attachment, proliferation, and eventually mineralization. This biofunctionalization was associated with UV light-catalytic hydrophilic conversion of zirconia surfaces and progressive removal of hydrocarbons.

On the etching of silica and mesoporous silica films determined by X-ray reflectivity and atomic force microscopy

X-ray reflectometry and atomic force microscopy were used to characterize the etching effect of 0.1 mol dm − 3 NaOH solution on mesoporous silica films < 100 nm thick produced by the evaporation induced self assembly route using a nonionic triblock co-polymer as the template. The effect of this treatment on films that had been partly condensed at 80 °C or fired at 400 °C in air are compared to non-porous films produced using conventional sol–gel technique. The evolution of film structure was monitored by atomic force microscopy and X-ray reflectometry. Thicknesses obtained from these measurements were used as an order parameter to determine the etch rate. For the mesoporous films, distinct stages corresponding to (a) film compression; (b) removal of the weakly organised caplayer; (c) progressive removal of bilayers of pores/silicated layres; and finally film collapse were revealed.

Effect of Residual Stress on Fatigue Failure of Carbonitrided Low-Carbon Steel

The effect of residual stress on fatigue behavior and mechanisms of carbonitrided AISI 1015 steel under uniaxial cyclic loading has been experimentally studied. By progressive removal of thin surface layers using an electropolishing technique and subsequent residual stress measurements using an x-ray diffraction technique, the compressive residual stress at the surface was approximately 900 MPa. The stress decreased toward the center, and became stable tensile residual stress of approximately 20 MPa. The fatigue resistance of carbonitrided AISI 1015 steel was higher than that of AISI 1015 steel due to the presence of compressive residual stress in case layer. The fatigue limit of AISI 1015 steels with and without carbonitriding was 340 and 300 MPa, respectively. Subsurface cracks initiated at the case-core interface, i.e. approximately 400 μm from the surface. With increasing number of stress cycles, the subsurface cracks coalesced and propagated intergranularly through the case layer. After some incubation cycles, the subsurface cracks reached the surface of specimen, and became a main crack. During this stage, the stress increased, and caused the formation of voids in core material. Consequently, the crack propagated through the core material, interacted with voids, and caused complete fracture.

The effect of ultraviolet functionalization of titanium on integration with bone

Titanium implants are used as a reconstructive anchor in orthopedic and dental diseases and problems. Recently, ultraviolet (UV) light-induced photocatalytic activity of titanium has earned considerable and broad interest in environmental and clean-energy sciences. This study determines whether UV treatment of titanium enhances its osteoconductive capacity. Machined and acid-etched titanium samples were treated with UV for various time periods up to 48 h. For both surfaces, UV treatment increased the rates of attachment, spread, proliferation and differentiation of rat bone marrow-derived osteoblasts, as well as the capacity of protein adsorption, by up to threefold. In vivo histomorphometry in the rat model revealed that new bone formation occurred extensively on UV-treated implants with virtually no intervention by soft tissue, maximizing bone–implant contact up to nearly 100% at week 4 of healing. An implant biomechanical test revealed that UV treatment accelerated the establishment of implant fixation 4 times. The rates of protein adsorption and cell attachment strongly correlated with the UV dose-responsive atomic percentage of carbon on TiO 2, but not with the hydrophilic status. The data indicated that UV light pretreatment of titanium substantially enhances its osteoconductive capacity, in association with UV-catalytic progressive removal of hydrocarbons from the TiO 2 surface, suggesting a photofunctionalization of titanium enabling more rapid and complete establishment of bone–titanium integration.

Paleomagnetic directions from mid-latitude sites in the southern hemisphere (Argentina): Contribution to time averaged field models

Back-arc volcanism located to the east of the Andean Cordillera was sampled in the Argentina provinces of Mendoza and Neuquen for paleomagnetic time average field and paleosecular investigations. The activity ranges from 2 Ma to very recent time, with a large variety of products, from basalts to highly differentiated lavas. After removal of sites affected by lightning, those with α 95 higher than 10°, and combining of nearby sites displaying close directions, we present new paleomagnetic results from 31 flows units belonging to two volcanic massifs: the Payun Matru and the Cerro Nevado. Previous and new K–Ar age determinations constrain the volcanic activity of these massifs from 300 to 0 ka, and from 1.9 to 0.9 Ma, respectively. Most paleomagnetic samples have NRM intensities between about 1 and 20 A/m and depict progressive removal of magnetization components in a consistent fashion during stepwise AF or thermal demagnetization. Nineteen flows yielded a normal direction (declination = 354.8°, inclination = −53.0°, α 95 = 6.8°) and 12 flows a reverse direction (declination = 181.0°, inclination = 52.3°, α 95 = 5.9°). The combined data yielded a mean direction (declination = 357.3°, inclination = −52.8°, α 95 = 4.6°), which is not statistically different from the axial dipole field ( g 1 0 ) expected at this latitude (36°S). The angular dispersion of virtual geomagnetic poles calculated from flows with normal directions (ASD = 16.5°) compares well with the observed value from global datasets for this site latitude, but flows with reverse directions display a surprisingly low dispersion (ASD = 12.5°). Since most reverse directions were sampled from flows ranging between 1.9 and 0.9 Ma, this can be interpreted as an interval of low paleomagnetic secular variation. Additional data, also with accurate time constraints, are obviously needed to better support this observation. Finally, no convincing evidence for a complex time average field significantly different from the axial dipole can be supported by this study for the last 2 Myr.