bluuebunny/crossref_metadata_2025 huggingface dataset:
Intramammary infusion of a live culture ofLactococcus lactisfor treatment of bovine mastitis: comparison with antibiotic treatment in field trials
Authors: Klostermann Katja , Crispie Fiona , Flynn James , Ross R Paul , Hill Colin , Meaney William
Published: August 2008

A treatment containing a live food-grade organism,Lactococcus lactisDPC3147, was compared with conventional antibiotic therapy for its potential to treat bovine chronic subclinical or clinical mastitis in two separate field trials. Effects on disease symptoms and bacteriology were monitored in response to infusion with the culture in each trial. In the first trial, the live culture treatment was compared with an intramammary antibiotic (n=11 quarters for each treatment). Results from this small trial demonstrated that the live culture had potential to be as effective at eliminating chronic subclinical infections as an antibiotic treatment. By day 12, 7 of the 11 quarters treated with the live culture were pathogen-free compared with 5 of the 11 antibiotic-treated infected quarters. Somatic cell counts (SCC) remained relatively unchanged regardless of treatment: average log SCC pre- and post-treatment in the lactococci-treated group were 6·33±0·41 (day 0) and 6·27±0·43 cells/ml (day 12) and average log SCC pre- and post-treatment in the antibiotic-treated group were 6·34±0·37 and 6·22±0·46 cells/ml on day 0 and on day 12, respectively. In the second trial, the live culture was compared with an intramammary antibiotic for the treatment of naturally occurring clinical mastitis cases (n=25 quarters for each treatment). Following a 14-d experimental period, similar bacteriological responses were observed in 7 out of 25 live culture treated quarters and 9 out of 25 antibiotic-treated quarters. Additionally, 15 of 25 cases treated with the culture and 18 of 25 cases treated with the antibiotic did not exhibit clinical signs of the disease following treatment. The results of these trials suggest that live culture treatment withLc. lactisDPC3147 may be as efficacious as common antibiotic treatments in some instances.
Evaluation of breed-dependent differences in the innate immune responses of Holstein and Jersey cows toStaphylococcus aureusintramammary infection
Authors: Bannerman Douglas D , Springer Hayley R , Paape Max J , Kauf Adam CW , Goff Jesse P
Published: August 2008

Mastitis is one of the most prevalent diseases of cattle. Various studies have reported breed-dependent differences in the risk for developing this disease. Among two major breeds, Jersey cows have been identified as having a lower prevalence of mastitis than Holstein cows. It is well established that the nature of the initial innate immune response to infection influences the ability of the host to clear harmful bacterial pathogens. Whether differences in the innate immune response to intramammary infections explain, in part, the differential prevalence of mastitis in Holstein and Jersey cows remains unknown. The objective of the current study was to evaluate several parameters of the innate immune response of Holstein and Jersey cows to intramammary infection withStaphylococcus aureus, a common mastitis-inducing pathogen. To control for non-breed related factors that could influence these parameters, all cows were of the same parity, in similar stages of milk production, housed and managed under identical conditions, and experimentally infected and sampled in parallel. The following parameters of the innate immune response were evaluated: acute phase protein synthesis of serum amyloid A and lipopolysaccharide-binding protein; total and differential circulating white blood cell counts; milk somatic cell counts; mammary vascular permeability; milk N-acetyl-beta-d-glucosaminidase (NAGase) activity; and production of the cytokines, interferon (IFN)-γ, interleukin (IL)-12, tumour growth factor(TGF)-α, and TGF-β1. The temporal response of all of these parameters following infection was similar between Holstein and Jersey cows. Further, with the exception of changes in circulating neutrophils and NAGase activity, the overall magnitude of these parameters were also comparable. Together, these data demonstrate that the innate immune response of Holstein and Jersey cows toStaph. aureusintramammary infection remains highly conserved despite previously reported differences in mastitis prevalence, as well as genotypic and phenotypic traits, that exist between the two breeds.
Effects of experimental challenge of ewes with Mannheimia haemolytica on subsequent milk composition
Authors: Fragkou Ilectra A , Solomakos Nikos , Dagleish Mark P , Cripps Peter J , Papaioannou Nikos , Boscos Costas M , Ververidis Haris N , Billinis Charalambos , Orfanou Denise C , Govaris Alexander , Kyriazakis Ilias , Fthenakis George C
Published: August 2008

The objective was to describe the physicochemical changes during the early phase of subclinical mastitis and to associate them with pathological findings. A Mannheimia haemolytica strain was deposited into one teat duct of 25 ewes and the clinical, bacteriological, cytological, physicochemical (pH, milk composition), gross-pathological and histological findings were subsequently recorded. The organism was consistently isolated from samples of teat duct material (140/150) but not from mammary secretion (50/150). California Mastitis Test (CMT) scores increased (>1) and remained high (143/150 samples) after challenge; polymorphonuclear neutrophils (PMN) predominated in milk films, but the proportion of lymphocytes and macrophages progressively increased. Increased pH values (>7·0) were recorded in the mammary secretion from the challenged side. Furthermore, content of fat, total proteins and lactose therein decreased markedly. Histological changes (leucocytic infiltration, destruction of epithelial cells) were observed in the mammary parenchyma of the ewes. The present results confirm that the reduction of milk constituents is the effect of cellular damage and can occur soon after infection.
Effects of stocking density and supplement level on milk production and cheese characteristics in Brown cows grazing on mountain pasture
Authors: Bovolenta Stefano , Saccà Elena , Corazzin Mirco , Gasperi Flavia , Biasioli Franco , Ventura Walter
Published: August 2008

Twenty-eight Brown cows were maintained on a mountain pasture for a period of 40 days and assigned to 4 groups following a factorial design 2 stocking density (0·7 and 1·4 cows/ha)×2 supplement levels (2·4 and 4·8 kg organic matter (OM)/d). Herbage intake, animal body condition score (BCS), milk yield, milk chemical and coagulation properties, cheese composition, rheology and sensory characteristics were measured. The average herbage intake was 12·2 kg OM/d, with a significant effect related to stocking density (low, 13·1v. high, 11·4 kg OM/d). BCS variation was always negative and changed with supplement level, although with no statistical significance (−0·43 points on average). Milk yield was lower for the group with lower availability of herbage (low supplement and high stocking density: 15·9 kg/d), whereas it was comparable among others groups (16·9 kg/d on average). The group with high supplement and low stocking density produced milk with worse cheese making properties. Cheese composition analyses showed an effect of supplement level on calcium content, and on parameters for degree of ripening, such as nitrogen fractions and lipolysis index. As for the textural parameters, hardness and gumminess were found to be higher with the low level of supplement. The different level of supplementation could differentiate the groups on the basis of the sensory perception of cheese.
Hydroids symbiotic with octocorals from the Sulawesi Sea, Indonesia
Authors: Puce Stefania , Di Camillo Cristina Gioia , Bavestrello Giorgio
Published: August 2008

Hydroids symbiotic with octocorals in the Bunaken Marine Park and in the Lembeh Strait (North Sulawesi, Indonesia) were studied. Four species,Hydrichthella epigorgia,Ralpharia neira,Pteroclava krempfiandZanclea timidasp. nov. were recorded and are described. The new speciesZ. timidais the only one of the genus associated with an octocoral. It is characterized by a naked hydrorhiza producing nematocyst knobs and by polyps which are able to retract into their own rigid, cup-shaped, basal region. The relationship between epibiontic hydroids and their octocoral hosts affects the morphology of both partners. The hydrorhiza ofHydrichthella epigorgiais naked when associated withAnthoplexaura dimorpha, but perisarc-covered when growing on other gorgonian host species. Vice versa, the hydroid is also able to affect the host morphology:Ralpharia neirainducesEllisellasp. to develop new branches, with the inner skeleton enveloping the hydroid stem.
Cetacean diversity at the west coast of La Palma Island (Canary Islands)
Authors: Pérez-Vallazza Claudia , Álvarez-Vázquez Rosana , Cardona Laura , Pintado Clara , Hernández-Brito Joaquín
Published: August 2008

Little is known about cetacean communities around La Palma Island. Therefore, and in order to determine the presence and distribution of the cetacean species on its west coast, daily censuses were carried out from November 2003 to April 2005. The platform used was a whale watching vessel certified by the Canary Government. Data collected included time, position, species identity, group size and, in some cases, the presence of calves and/or any other outstanding parameter. During the study period, 570 sightings were made, with a mean sighting success of 1.7 sightings per day, showing a high cetacean presence in the area. Thirteen species and one genus (Globicephalaspp.) were positively matched, three of them included in the Mysticeti suborder and the other ten in the Odontoceti one. The four most sighted species, in decreasing order, correspond toTursiops truncatus,Steno bredanensis,Globicephalaspp. andStenella frontalis. Diversity of sighted species shows a moderate peak during spring time, which is in agreement with the presence of occasional species. Most sightings were located off the central west coast of the island, exceeding 1.5 nautical miles. This is particularly outstanding in relation to Franja Marina de Fuencaliente SCI, where 90% of all sightings were located outside its boundaries. High cetacean presence and diversity off the west coast of La Palma Island seem to be connected with oceanographic and ecological features. Results gained provide, for this region, baseline data on cetacean populations and a useful tool in conservation plans.
The ecology of protists epibiontic on marine hydroids
Authors: Bavestrello Giorgio , Cerrano Carlo , Di Camillo Cristina , Puce Stefania , Romagnoli Tiziana , Tazioli Silvia , Totti Cecilia
Published: August 2008

Several hydroid species have an epibiontic lifestyle, living associated with organisms of many different phyla. On the other hand, hydroids can also host dense assemblages of microflora and microfauna, mainly composed of protists and bacteria. Among protists, diatoms are the most abundant and diversified group, followed by foraminifera and sessile ciliata such asVorticellaand suctorians. Regarding the spatial distribution of epibionts, hydroid colonies represent a mosaic of different microhabitats: in some species, each colony portion (base of the stem, branches, pedicels, inner space between the polyp and the theca) hosts different diatom species. Moreover, three foram species have been shown to occupy different positions according to the plasticity of their shell. A host specificity has been also observed: some epibionts are typical of only one or a group of species, such asVorticellaliving on the teeth of theAglaopheniathecae or coralline algae that cover mainlyAglaopheniaandSertularellacolonies. The microassemblage associated toEudendrium racemosumshowed a typical seasonal cycle and a vertical distribution which reflects the selective advantage of the different life forms. Experiments with plastic structures miming hydroid colonies demonstrated that the living hydroid affects the assemblage structure. Probably, the perisarc composition and secondary metabolites play a crucial role in the relationships between hydroids and their microassemblage.
Decomposing diversity patterns of a soft-bottom macroinvertebrate community in the tropical eastern Pacific
Authors: Godínez-Domínguez E. , Freire J. , Franco-Gordo C. , González-Sansón G.
Published: August 2008

Diversity is one of the most frequently used attributes of ecological communities, and there is a long-standing discussion about their adequate use, calculus and interpretation. One of the most conspicuous and simple diversity estimators is species richness, but it has been criticized by recurrent pitfalls, which has biased comparisons and the testing of hypotheses. Otherwise, synthetic ecological indices of diversity are difficult to interpret due to the underlying complex or cryptic concepts. Most of the studies in soft-bottom macroinvertebrate communities trying to estimate species richness, have actually quantified species diversity as species density; the number of species per unit area. In the present study, the diversity of a tropical Pacific soft bottom community is analytically decomposed using two null models to assess species richness and evenness, and the slope of species–area curves to estimate species density. A declining trend of species richness was observed along a 2-year period and could be related to the cumulative effects of interannual environmental variability and fishing disturbance. The species–area relationship could be considered a good indicator of spatial heterogeneity, specifically to illustrate the depth gradient. Local abundance was negatively correlated with evenness, showing that high-density communities are the result of increases in abundance of a few dominant species. Here we demonstrate that seasonality, depth and abundance could explain diversity in soft-bottom macroinvertebrate communities of coastal waters and propose a robust procedure to survey diversity as a part of monitoring programmes of coastal management.
Long-term tributyltin (TBT)-induced sterilization of neogastropods: persistence of effects in Ocenebra erinacea over 20 years in the vicinity of Falmouth (Cornwall, UK)
Authors: Gibbs P.E.
Published: August 2008

A population of the neogastropod Ocenebra erinacea sited close to the shipyard at Falmouth (Cornwall: south-west England) has been monitored over a period of 20 years for the effects of exposure to the antifouling agent tributyltin (TBT). During the years 1986 to 1995 the proportion of females sterilized through abnormal development of the oviduct increased from 36% to 87%. Despite legislative restrictions on TBT paints, in 2006 there was little improvement in the reproductive capacity of the population in that over 75% of females still showed the same abnormality. At the sampling site, levels of TBT in surface water had a background of around 2 ng Sn l−1 throughout the period of study with higher peaks up to 50 ng Sn l−1. Much of the TBT pollution in the Fal estuary and environs in recent years appears to be the result of discharges from the shipyard at Falmouth within the estuary.
The semantics of sense perception in Berkeley
Authors: PEARCE KENNETH L.
Published: August 2008

George Berkeley's linguistic account of sense perception is one of the most central tenets of his philosophy. It is intended as a solution to a wide range of critical issues in both metaphysics and theology. However, it is not clear from Berkeley's writings just how this ‘universal language of the Author of Nature’ is to be interpreted. This paper discusses the nature of the theory of sense perception as language, together with its metaphysical and theological motivations, then proceeds to develop an account of the semantics of the perceptual language, using Berkeley's theory of reference for human language as a guide.
Schleiermacher and Otto on religion: a reappraisal
Authors: SMITH A. D.
Published: August 2008

An interpretation of the work of Schleiermacher and Otto recently offered by Andrew Dole, according to which these two thinkers differed over the extent to which religion can be explained naturalistically, and over the sense in which the supernatural can be admitted, is examined and refuted. It is argued that there is no difference between the two thinkers on this issue. It is shown that Schleiermacher's claim that a supernatural event is at the same time a natural event does not invite, but rather forecloses the possibility of, a naturalistic explanation of the event. It is further demonstrated that Otto, like Schleiermacher, denied the existence of supernatural events interpreted as events that infringe the laws of nature.
Response to Tucker on hiddenness
Authors: SCHELLENBERG J. L.
Published: August 2008

Chris Tucker's paper on the hiddenness argument seeks to turn aside a way of defending the latter which he calls the value argument. But the value argument can withstand Tucker's criticisms. In any case, an alternative argument capable of doing the same job is suggested by his own emphasis on free will.
Role of bioregionalism in Bookmark Biosphere Reserve, Australia
Authors: PFUELLER SHARRON L.
Published: August 2008

Bioregionalism claims that interaction between the biophysical and human components of a region generates place-based environmental and social understanding and concern, which lead to locally shared power and responsibility in cooperative land management and governance. The Man and the Biosphere Programme's Seville Strategy calls for local community participation in a multi-stakeholder ecosystem-based approach to conservation, but it is unclear if tenets of bioregionalism play a role in its implementation. Bookmark Biosphere Reserve (BBR) in Australia has substantially succeeded in scientific research and monitoring, conservation, environmental education and sustainable land-use initiatives. Aspects of bioregionalism (for example recognition of the region's unique identity, local community sense of responsibility, integration of local knowledge, presence of motivated local leaders and cooperative community-based management through a network of groups) have contributed to success. Other crucial factors were funding, technical and scientific information and support from government agencies, leadership from members of state and federal government and from private philanthropic foundations, community capacity-building for sustainable land management and availability of volunteers from outside the region. Nevertheless, conflict arose in relation to governance, originating from the recognized difficulties of reconciling a diversity of allegiances, motivations, management styles and personalities, and resulted in division of BBR into two, one section being managed largely through the private sector and community volunteers, the other (renamed Riverland Biosphere Reserve) coordinated by a committee with more diverse affiliations. Bioregionalism can play a role in biosphere reserves but motivations and resources of external public and private organizations are also vital. Avoiding weaknesses of bioregional approaches requires greater attention to social aspects of environmental management. Governance structures and processes need to be inclusive, flexible and equitable in decision making and access to funds. They should support both agency and community-initiated activities and include conflict resolution mechanisms.
Inputs of glacially derived dissolved and colloidal iron to the coastal ocean and implications for primary productivity
Authors: Statham Peter J. , Skidmore Mark , Tranter Martyn
Published: August 2008

Glacial meltwaters draining shield bedrock under the Greenland Ice Sheet (GIS) contain <0.4 μm “total dissolved” Fe (TDFe) with an average flow weighted concentration of ∼53 nM. The concentrations of <0.03 and 0.03–0.4 μm Fe vary over the ablation period, with weighted means for each of these fractions being respectively 22.4 nM and 30.8 nM. These concentrations are lower estimates as an adjacent larger glacier (a more representative source of glacial meltwater) had higher dissolved Fe concentrations, and reactions of meltwaters with proglacial sediments could also enhance dissolved Fe concentrations. This source of TDFe is additional to the reactive (oxyhydr)oxide phases identified by Raiswell et al. (2006) that are also introduced to adjacent polar seas from glaciers. The Fe concentrations in the shield bedrock underlying the GIS are lower than those of other crustal rocks (4.0% cf. 6.2%), but we argue that these Fe concentrations are not limiting on the total dissolved Fe concentrations we measure. The biogeochemical weathering processes operating on the subglacial debris and suspended sediment in our catchment are likely to be similar to those in other glaciated catchments. Therefore the meltwater Fe concentrations reported here can be used to give a first estimate of global fluxes of meltwater dissolved Fe to coastal polar waters. A lower estimate of the global flux of TDFe from glacial meltwaters is ∼75 × 106 moles Fe/a. This glacial meltwater input of Fe to adjacent polar waters will be greatest around Greenland where there are highest annual meltwater discharges. However, the greatest impact of this source of glacial meltwater Fe is anticipated to be in Antarctic high nutrient low chlorophyll (HNLC) waters where phytoplankton productivity is typically limited by availability of Fe. For Antarctic waters the estimated meltwater Fe (TDFe) input is about 10% of that suggested to come from sea ice melting, but glacial inputs continue throughout the austral summer ablation period after sea ice melt is complete.
Implications of “peak oil” for atmospheric CO2and climate
Authors: Kharecha Pushker A. , Hansen James E.
Published: August 2008

Unconstrained CO2emission from fossil fuel burning has been the dominant cause of observed anthropogenic global warming. The amounts of “proven” and potential fossil fuel reserves are uncertain and debated. Regardless of the true values, society has flexibility in the degree to which it chooses to exploit these reserves, especially unconventional fossil fuels and those located in extreme or pristine environments. If conventional oil production peaks within the next few decades, it may have a large effect on future atmospheric CO2and climate change, depending upon subsequent energy choices. Assuming that proven oil and gas reserves do not greatly exceed estimates of the Energy Information Administration, and recent trends are toward lower estimates, we show that it is feasible to keep atmospheric CO2from exceeding about 450 ppm by 2100, provided that emissions from coal, unconventional fossil fuels, and land use are constrained. Coal‐fired power plants without sequestration must be phased out before midcentury to achieve this CO2limit. It is also important to “stretch” conventional oil reserves via energy conservation and efficiency, thus averting strong pressures to extract liquid fuels from coal or unconventional fossil fuels while clean technologies are being developed for the era “beyond fossil fuels”. We argue that a rising price on carbon emissions is needed to discourage conversion of the vast fossil resources into usable reserves, and to keep CO2beneath the 450 ppm ceiling.
Analysis of slip‐weakening frictional laws with static restrengthening and their implications on the scaling, asymmetry, and mode of dynamic rupture on homogeneous and bimaterial interfaces
Authors: Olsen‐Kettle L. M. , Weatherley D. , Saez E. , Gross L. , Mühlhaus H.‐B. , Xing H. L.
Published: August 2008

Dynamic simulations of homogeneous, heterogeneous and bimaterial fault rupture using modified slip‐weakening frictional laws with static restrengthening are presented giving rise to both crack‐like and pulse‐like rupture. We demonstrate that pulse‐like rupture is possible by making a modification of classical slip‐weakening friction to include static restrengthening. We employ various slip‐weakening frictional laws to examine their effect on the resulting earthquake rupture speed, size and mode. More complex rupture characteristics were produced with more strongly slip‐weakening frictional laws, and the degree of slip‐weakening had to be finely tuned to reproduce realistic earthquake rupture characteristics. Rupture propagation on a fault is controlled by the constitutive properties of the fault. We provide benchmark tests of our method against other reported solutions in the literature. We demonstrate the applicability of our elastoplastic fault model for modeling dynamic rupture and wave propagation in fault systems, and the rich array of dynamic properties produced by our elastoplastic finite element fault model. These are governed by a number of model parameters including: the spatial heterogeneity and material contrast across the fault, the fault strength, and not least of all the frictional law employed. Asymmetric bilateral fault rupture was produced for the bimaterial case, where the degree of material contrast influenced the rupture speed in the different propagation directions.
A physical model of the low‐frequency electrical polarization of clay rocks
Authors: Cosenza Philippe , Ghorbani Ahmad , Revil André , Zamora Maria , Schmutz Myriam , Jougnot Damien , Florsch Nicolas
Published: August 2008

Low‐frequency (0.18 Hz to 1.5 kHz) effective dielectric spectra have been measured on a set of near‐saturated samples of argillite. The measured spectra of the real part of the complex apparent permittivity did not show significant correlation with cation exchange capacity (CEC) per unit mass of rock values. They satisfied a power law relationship with the frequency, at least for samples with CEC values lower than 10 cmol/kg. The Maxwell‐Wagner‐Hanai‐Bruggeman formulation used for a two‐phase mixture has been modified to account for mutual polarization between the pockets of water located in the micropores and those located in the macropores. The results of the modeling calculations illustrate (1) the ability of this new formulation to reproduce the power law relationships of the measured spectra of the real and imaginary components of the complex permittivity and (2) the strong impact of the pore electrical conductivity.
Aerosol‐cloud relationships in continental shallow cumulus
Authors: Lu Miao‐Ling , Feingold Graham , Jonsson Haflidi H. , Chuang Patrick Y. , Gates Harmony , Flagan Richard C. , Seinfeld John H.
Published: August 2008

Aerosol‐cloud relationships are derived from 14 warm continental cumuli cases sampled during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) by the Center for Interdisciplinary Remotely‐Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. Cloud droplet number concentration is clearly proportional to the subcloud accumulation mode aerosol number concentration. An inverse correlation between cloud top effective radius and subcloud aerosol number concentration is observed when cloud depth variations are accounted for. There are no discernable aerosol effects on cloud droplet spectral dispersion; the averaged spectral relative dispersion is 0.30 ± 0.04. Aerosol‐cloud relationships are also identified from comparison of two isolated cloud cases that occurred under different degrees of anthropogenic influence. Cloud liquid water content, cloud droplet number concentration, and cloud top effective radius exhibit subadiabaticity resulting from entrainment mixing processes. The degree of LWC subadiabaticity is found to increase with cloud depth. Impacts of subadiabaticity on cloud optical properties are assessed. It is estimated that owing to entrainment mixing, cloud LWP, effective radius, and cloud albedo are decreased by 50–85%, 5–35%, and 2–26%, respectively, relative to adiabatic values of a plane‐parallel cloud. The impact of subadiabaticity on cloud albedo is largest for shallow clouds. Results suggest that the effect of entrainment mixing must be accounted for when evaluating the aerosol indirect effect.
Kinematic structure of convective‐scale elements in the rainbands of Hurricanes Katrina and Rita (2005)
Authors: Hence Deanna A. , Houze Robert A.
Published: August 2008

Airborne Doppler radar data collected during the Hurricane Rainband and Intensity Change Experiment (RAINEX) show the convective‐scale air motions embedded in the principal rainbands of hurricanes Katrina and Rita. These embedded convective cells have overturning updrafts and low‐level downdrafts (originating at 2–4 km) that enter the rainband on its radially outward side and cross over each other within the rainband as well as a strong downdraft emanating from upper levels (6+ km) on the radially inward side. These vertical motion structures repeat from one convective cell to another along each rainband. The resulting net vertical mass transport is upward in the upwind portion of the band and greatest in the middle sector of the principal rainband, where the updraft motions contribute generally to an increase of potential vorticity below the 3–4 km level. Because the convective cells in the middle sector are systematically located radially just inside the secondary horizontal wind maximum (SHWM), the local increase in vorticity implied by the convective mass transport is manifest locally as an increase in the strength of the SHWM at midlevels (∼4 km). The overturning updrafts of the convective cells tilt, stretch, and vertically transport vorticity such that the convergence of the vertical flux of vorticity strengthens the vorticity anomaly associated with the SHWM. This process could strengthen the SHWM by several meters per second per hour, and may explain how high wave number convective‐scale features can influence a low wave number feature such as the principal rainband, and subsequently influence the primary vortex.
Effect of stratospheric sudden warming and vortex intensification on the tropospheric climate
Authors: Kuroda Yuhji
Published: August 2008

The effect of stratospheric sudden warming (SSW) and vortex intensification (VI) on the tropospheric climate is examined through composite analysis of the observational data. Specifically examined in the present study is the Eulerian meridional circulations associated with SSW and VI. It is found that prominent signal in the troposphere tends to appear associated with the occurrence of SSW and VI. The patterns created are very similar between SSW and VI except for the polarity. In the high latitude region, the pattern similar to the Arctic Oscillation (AO) is created before and after the occurrence of SSW and VI with changing polarities. In the tropics, convection tends to enhance in the Southern Hemisphere (Northern Hemisphere) tropics after the occurrence of SSW (VI). These signals are created through three prominent cells of the anomalous Eulerian meridional circulation that extends from polar cap to the tropical Southern Hemisphere. The mechanism for the formation of the cells associated with SSW and VI is also discussed.
Strike‐slip faults on Mars: Observations and implications for global tectonics and geodynamics
Authors: Andrews‐Hanna Jeffrey C. , Zuber Maria T. , Hauck Steven A.
Published: August 2008

The tectonic evolution of Mars has been driven primarily by the interaction of Tharsis‐induced loading stresses with a uniform contractional stress field, leading to global assemblages of graben and wrinkle ridges. Until recently, strike‐slip faults have appeared to be largely absent from the tectonic record. We here present evidence for a new set of Noachian to Early Hesperian strike‐slip faults southwest of Tharsis. The best‐preserved fault in the newly mapped set has a length of ∼200 km and measured lateral offset of 5–9 km. We use the locations of both previously mapped and newly identified strike‐slip faults to investigate the tectonic and geodynamic evolution of Mars. We model the tectonic evolution of the planet in response to the evolving balance between the loading and contractional stresses, finding widespread regions in which strike‐slip faulting was favored. The observed tectonic history is consistent with a scenario in which loading‐induced stresses peaked early in Mars history, followed by the growth of contractional stresses, leading to a shift in the preferred locus of strike‐slip faulting from regions southwest of Tharsis in the Noachian to Early Hesperian, to northwest of Tharsis in the Early Amazonian. The contractional strain history inferred from the ages and locations of the strike‐slip faults is consistent with the strains calculated from models of the thermal evolution of Mars in which the gradual secular cooling of the planet over time was augmented by plume‐induced contraction during Tharsis formation in the Noachian.
Formation of silica by low‐temperature acid alteration of Martian rocks: Physical‐chemical constraints
Authors: McAdam Amy C. , Zolotov Mikhail Y. , Mironenko Mikhail V. , Sharp Thomas G.
Published: August 2008

Theoretical geochemical modeling has been used to evaluate the formation conditions of amorphous silica during aqueous alteration of typical Martian igneous rocks at 0°C. The models show that some silica can form during low‐temperature alteration of mafic to ultramafic rocks over a large range of pH and water/rock ratios. Silica‐dominated deposits, like those found at the Columbia Hills in Gusev crater on Mars, could form at solution pH below ∼2 and water/rock ratios of ∼102–104. High‐water/rock conditions could represent acid flow through rocks, solution discharge from an acid spring, and/or surface flow of released solutions. Low pH favors dissolution of silicates and saturation of solution with respect to relatively insoluble silica, which then precipitates. Partial evaporation or freezing of released solutions would also cause precipitation of amorphous silica. Modeling shows that Ti oxides are also present in silica‐rich deposits. More soluble minerals (e.g., ferric oxides, phyllosilicates) could precipitate downstream from partially neutralized, evaporated, or frozen solutions. Temperatures above ∼0°C are not required to form abundant silica through acid alteration of Martian rocks.
Modeling fluvial incision and transient landscape evolution: Influence of dynamic channel adjustment
Authors: Attal M. , Tucker G. E. , Whittaker A. C. , Cowie P. A. , Roberts G. P.
Published: August 2008

Channel geometry exerts a fundamental control on fluvial processes. Recent work has shown that bedrock channel width depends on a number of parameters, including channel slope, and is not solely a function of drainage area as is commonly assumed. The present work represents the first attempt to investigate the consequences of dynamic, gradient‐sensitive channel adjustment for drainage‐basin evolution. We use the Channel‐Hillslope Integrated Landscape Development (CHILD) model to analyze the response of a catchment to a given tectonic perturbation, using, as a template, the topography of a well‐documented catchment in the footwall of an active normal fault in the Apennines (Italy) that is known to be undergoing a transient response to tectonic forcing. We show that the observed transient response can be reproduced to first order with a simple detachment‐limited fluvial incision law. Transient landscape is characterized by gentler gradients and a shorter response time when dynamic channel adjustment is allowed. The differences in predicted channel geometry between the static case (width dependent solely on upstream area) and dynamic case (width dependent on both drainage area and channel slope) lead to contrasting landscape morphologies when integrated at the scale of a whole catchment, particularly in presence of strong tilting and/or pronounced slip‐rate acceleration. Our results emphasize the importance of channel width in controlling fluvial processes and landscape evolution. They stress the need for using a dynamic hydraulic scaling law when modeling landscape evolution, particularly when the relative uplift field is nonuniform.
An investigation of the flow and scour mechanisms around isolated spur dikes in a shallow open channel: 1. Conditions corresponding to the initiation of the erosion and deposition process
Authors: Koken Mete , Constantinescu George
Published: August 2008

The present study investigates the flow physics and the role played by the main coherent structures in the scouring processes around a vertical spur dike in a straight channel at conditions corresponding to the start (flat bed) of the scouring process. Large eddy simulation (LES) is performed at a relatively low channel Reynolds number (Re = 18,000), in the range where most flume studies with clear water scour conditions are conducted. Similar to these studies, the incoming flow is fully turbulent and contains realistic turbulence fluctuations. Visualization experiments are conducted to better understand the nature of the interactions between the dominant coherent structures playing a role in the erosion process. It is found that the structure of the horseshoe vortex (HV) system at the base of the spur dike changes considerably in time and in vertical sections perpendicular to the trajectory defined by the axis of the main necklace vortex. However, its intensity is the largest at vertical sections situated around the tip of the spur dike. It is in this region that the core of the main necklace vortex oscillates aperiodically between two preferred modes. In one of them (zero‐flow mode), the necklace vortex is closer to the spur dike and more compact, and the near‐bed jet flow beneath it is weak. In the other one (back‐flow mode), a strong near‐bed jet flow convects the primary necklace vortex away from the spur dike, and its core is more elongated and less compact. This explains the large amplification (by about 1 order of magnitude compared to the surrounding turbulent flow) of the turbulent kinetic energy and pressure fluctuations inside the HV system in the region situated around the tip of the spur dike and the double‐peak distribution of the turbulent kinetic energy. Past the spur dike, in the legs of the necklace vortex, the intensity of the bimodal oscillations decreases such that they are not observed in spanwise sections situated at more than one channel depth behind the spur dike. It is found that the legs of the horseshoe vortices can interact, at times, with the vortex tubes shed in the detached shear layer (DSL) and with the tip of the spur dike. These events typically result in a significant change in the coherence of the HV system. The largest bed shear stress values in the mean flow are present in the strong acceleration region near the tip of the spur dike, but high bed shear stress values are also observed beneath the upstream part of the DSL. The bed shear stress fluctuations around the local mean values can be very high, especially in the region situated beneath the upstream part of the DSL. At random times, some of the vortices shed in the DSL merge or interact with eddies from the recirculation region. This leads to an increase in their strength and to a large increase of the bed shear stress along their path.
Use of CALIPSO lidar observations to evaluate the cloudiness simulated by a climate model
Authors: Chepfer H. , Bony S. , Winker D. , Chiriaco M. , Dufresne J.‐L. , Sèze G.
Published: August 2008

New space‐borne active sensors make it possible to observe the three‐dimensional structure of clouds. Here we use CALIPSO lidar observations together with a lidar simulator to evaluate the cloudiness simulated by a climate model: modeled atmospheric profiles are converted to an ensemble of subgrid‐scale attenuated backscatter lidar signals from which a cloud fraction is derived. Except in regions of persistent thick upper‐level clouds, the cloud fraction diagnosed through this procedure is close to that actually predicted by the model. A fractional cloudiness is diagnosed consistently from CALIPSO data at a spatio‐temporal resolution comparable to that of the model. The comparison of the model's cloudiness with CALIPSO data reveals discrepancies more pronounced than in previous model evaluations based on passive observations. This suggests that space‐borne lidar observations constitute a powerful tool for the evaluation of clouds in large‐scale models, including marine boundary‐layer clouds
Understanding the transportation process of tropospheric air entering the stratosphere from direct vertical air motion measurements over Gadanki and Kototabang
Authors: Narayana Rao T. , Uma K. N. , Narayana Rao D. , Fukao S.
Published: August 2008

Long‐term measurements of vertical air velocity (w) obtained with VHF wind profilers are utilized to study mean w features as a function of season at two key geographical locations. It is observed that the magnitude of w is always larger than the error/bias contributed by various contaminators. The seasonal mean w profiles at Gadanki and Kototabang show descending (ascending) motion below (above) 8–10 km in most of the seasons. The magnitude of w observed at the above locations is larger than those obtained from radiative budget estimations. The height of wind reversal seems to have a seasonal dependence at Gadanki. Present observations suggest the transportation of air from near surface to the stratosphere is a two‐step process: a rapid ascent from the surface to the middle‐upper troposphere in convective turrets, and a gentle ascent into the stratosphere. Also, the convection requires to reach an altitude of 10 km, at least at the above locations, and thereafter the prevailing ascent transports the air into the stratosphere.
An analysis of the environmental energetics associated with the transition of the first South Atlantic hurricane
Authors: Veiga José Augusto Paixão , Pezza Alexandre Bernardes , Simmonds Ian , Silva Dias Pedro L.
Published: August 2008

This study presents the first analysis of the energetics associated with a hybrid cyclone's transition in the Southern Hemisphere, Hurricane Catarina (March 2004). Catarina has earned a place in history as the first documented South Atlantic hurricane, but its unusual tropical transition is still poorly understood. Here we show that Catarina's transition was preceded by marked environmental changes in the Lorenz energy cycle, with an abrupt shift from a baroclinic to a predominantly barotropic state. Such changes help to explain the unusual vortex's growth until its transition was completed. Although the vortex's energy flux is not explicitly calculated, a likely mechanism linking the environmental energetics with Catarina is the extraction of eddy kinetic energy from horizontal momentum and heat transfers within the through component of the blocking. The results advance the understanding of this rare event and suggest that the technique has a great potential to study transitioning systems in general.
Extent of gas hydrate filled fracture planes: Implications for in situ methanogenesis and resource potential
Authors: Cook Ann E. , Goldberg David
Published: August 2008

High‐angle gas hydrate filled fracture planes were identified along a 31 m interval in logging while drilling images in two holes located ∼11 m apart drilled during the Indian National Gas Hydrate Program Expedition 01, offshore India. Using Monte Carlo simulations to account for uncertainty in hole location, hole deviation, strike and dip, we assert with 95% confidence that the fracture planes in the two holes are not the same. The gas hydrate filled fracture planes likely only extend a few meters laterally from each borehole and occur in an isolated interval in the middle of the gas hydrate stability zone. This suggests gas generated microbially within in the gas hydrate stability zone may have supplied the gas hydrate‐filled fracture interval. Production of methane from these reservoirs using conventional methods may be quite challenging.
Observations of parametric subharmonic instability of the diurnal internal tide in the South China Sea
Authors: Alford M. H.
Published: August 2008

Shipboard observations are presented that suggest the occurrence of parametric subharmonic instability (PSI) of diurnal K1 and O1 internal tides at “critical” latitudes of 14.52°N and 13.44°N, respectively. In a transect spanning 12.5–18°N, depth‐mean shear squared shows sharp peaks at 14.52°N (elevated relative to that at 15°N by a factor of ten) and at 13.44°N (by a factor of 7). Wind speed measured from the ship and Quikscat scatterometer during and before the transect was <10 m s−1 at these latitudes. Eight‐hour time series (about 1/6 of an inertial period) of shear and isopycnal depth at 14.52°N are sufficient to associate the elevated shear with alternating, clockwise‐rotating layers analogous to those observed at the M2 critical latitude of 28.8°N.
Implications of the differences between daytime and nighttime CloudSat observations over the tropics
Authors: Liu Chuntao , Zipser Edward J. , Mace Gerald G. , Benson Sally
Published: August 2008

Using 1 year of CloudSat level 2B Cloud Geometrical Profile product, the vertical structures, geographical distributions, and seasonal variations of cloud occurrence at the daytime (1330 LT) and the nighttime (0130 LT) overpasses and their differences over tropical land and ocean are presented separately. The differences between the cloud and precipitation occurrence at 0130 and 1330 LT and the 24 h mean are quantitatively evaluated using climatologies of diurnal variation from 9 years of TRMM observations. Then the vertical structures, geographical distributions, and seasonal variations of cloud and precipitation near the two CloudSat overpass times are generated from 9 years of TRMM observations and compared to those from CloudSat. Larger differences between cloud and precipitation occurrences at 0130 LT and those at 1330 LT were found at high altitudes because the amplitude of diurnal variation increases with height. Cloud and precipitation occurrences show day versus night differences which are opposite with respect to each other in the upper troposphere over the tropics. For example, near 1330 LT over tropical oceans, there are more clouds, but less precipitation at 13–14 km than near 0130 LT except over Panama. This may be explained with the phase lags between precipitation and clouds in the life cycles of the convective systems over land and ocean. The differences between the seasonal cycles of cloud and precipitation sampled at the 0130 and 1330 LT A‐Train overpass times and the seasonal cycles generated from full day samples are shown.