On the Disintegration of Ice Shelves: The Role of Fracture

Crevasses can be ignored in studying the dynamics of most glaciers because they are only about 20 m deep, a small fraction of ice thickness. In ice shelves, however, s urface crevasses 20 m deep often reach sealevel and bottom crevasses can move upward to sea-level (Clough, 1974; Weertman, 1980). The ice shelf is fractured completely through if surface and basal crevasses meet (Barrett, 1975; Hughes, 1979). This is especially likely if surface melt water fills surface crevasses (Weertman, 1973; Pfeffer, 1982; Fastook and Schmidt, 1982). Fracture may therefore play an important role i n the disintegration of ice shelves. Two fracture criteria which can be evaluated experimentally and applied to ice shelves, are presented. Fracture is then examined for the general strain field of an ice shelf and for local strain fields caused by shear rupture alongside ice streams entering the ice shelf, fatigue rupture along ice shelf grounding lines, and buckling up-stream from ice rises. The effect of these fracture patterns on the stability of Antarctic ice shelves and the West Antarctic ice sheet is then discussed.

Three “Bali Deliverables” for more Food Security

As the clock is ticking for a positive outcome at the Ninth WTO Ministerial Conference to be held in Bali in December 2013, agricultural negotiators are scrambling to find solutions to issues such as tariff-rate quota (TRQ) administration and export competition in order to improve trade flows. The main issue seems to be whether WTO rules applying to public stockpiles in developing countries need to be changed or temporarily suspended as a means to enhance national food security. This paper is based on a note submitted to the ICTSD-IPC Expert Group “Meeting on Agriculture and Food Security – Policy Options for MC9 and beyond” (Geneva, June 2013). It lists the policy instruments impacting on global, national and (urban and rural) household food security – “The Food Security Tool Box” – and asks which immediate decisions the WTO Ministers might take in this field despite the political difficulties such as continued agro-dumping practices or the “land grab” issue. Three such “deliverables” are outlined: (i) regional and “virtual” food security schemes could be allowed to provide reserves to other countries without violating the obligation to “form an integral part of a food security programme identified in national legislation” (Agreement on Agriculture, Annex II, para 3); (ii) TRQ under-fills could be improved by mandatory enquiries into low fill rate situations; and (iii) World Food Program (WFP) and other non-commercial food purchases could be exempted from export restrictions and prohibitions. High ambitions for Bali seem to be misplaced. A more realistic yet real progress could restore the dwindling credibility of the WTO as a forum for trade negotiations.

Public service motivation and rational choice modeling

While most previous research has considered public service motivation (PSM) as the only motivational factor predicting (public) job choice, the authors present a novel, rational choice-based model which includes three motivational dimensions: extrinsic, enjoyment-based intrinsic and prosocial intrinsic. Besides providing more accurate person-job fit predictions, this new approach fills a significant research gap and facilitates future theory building.

A Model Study of the Circulation in the Pearl River Estuary (PRE) and Its Adjacent Coastal Waters: 2. Sensitivity Experiments

The Princeton Ocean Model is used to study the circulation in the Pear River Estuary (PRE) and the adjacent coastal waters in the winter and summer seasons. Wong et al. [2003] compares the simulation results with the in situ measurements collected during the Pearl River Estuary Pollution Project (PREPP). In this paper, sensitivity experiments are carried out to examine the plume and the associated frontal dynamics in response to seasonal discharges and monsoon winds. During the winter, convergence between the seaward spreading plume water and the saline coastal water sets up a salinity front that aligns from the northeast to the southwest inside the PRE. During the summer the plume water fills the PRE at the surface and spreads eastward in the coastal waters in response to the prevailing southwesterly monsoon. The overall alignment of the plume is from the northwest to the southeast. The subsurface front is similar to that in the winter and summer except that the summer front is closer to the mouth and the winter front closer to the head of the estuary. Inside the PRE, bottom flows are always toward the head of the estuary, attributed to the density gradient associated with the plume front. In contrast, bottom flows in the shelf change from offshore in winter to onshore in summer, reflecting respectively the wintertime downwelling and summertime upwelling. Wind also plays an essential role in controlling the plume at the surface. An easterly wind drives the plume westward regardless winter or summer. The eastward spreading of the plume during the summer can be attributed to the southerly component of the wind. On the other hand, the surface area of the plume is positively proportional to the amount of discharge.

Studies of pseudoachondroplasia chondrocytes and knockdown of the cartilage oligomeric matrix protein

Cartilage oligomeric matrix protein (COMP) is a large, homopentameric, extracellular matrix glycoprotein. Mutations in COMP cause two skeletal dysplasias: pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (EMD1). These dwarfing conditions are caused by retention of misfolded mutant COMP with type IX collagen and matrilin-3 (MATN3) in the rough endoplasmic reticulum (rER) of the chondrocyte. These proteins form a matrix in the rER that continues to expand until it fills the entire cell, eventually causing cell death. Interestingly, loss of COMP in COMP null mice does not affect normal bone development or growth, suggesting that elimination of COMP (wildtype and mutant) expression may prevent PSACH. The hypothesis of these studies was that a hammerhead ribozyme could eliminate or knockdown COMP mRNA expression in PSACH chondrocytes . To test this hypothesis, a human chondrocyte model system that recapitulates the PSACH chondrocyte phenotype was developed by over-expressing mutant (mt-) COMP in normal chondrocytes using a recombinant adenovirus. Chondrocytes over-expressing mt-COMP developed giant rER cisternae containing COMP, type IX collagen and MATN3. Deconvolution microscopy and computer modeling showed that these proteins formed an ordered matrix surrounding a type II pro-collagen core. Additionally, the results show that a hammerhead ribozyme, ribozyme 56 (Ribo56) reduced over-expressed mt-COMP in COS cells and endogenous COMP in normal chondrocytes and mt-COMP in three PSACH chondrocytes cell line (with different mutations) by 40-70%. Altogether, these studies show that the PSACH cellular phenotype can be created in vitro and that the mt-COMP protein burden can be reduced by the presence of a COMP-specific ribozyme. Future studies will focus on designing ribozymes or short interfering RNA (siRNA) technologies that will result in better knockdown of COMP expression as well as the temporal constraints imposed by the PSACH phenotype. ^

The role of a nursing home administrator's education in influencing quality of care in US nursing homes

Nursing home literature links poor management practices to poor quality of care and resident outcomes. Since Nursing Home Administrators (NHAs) require an array of skills to perform their role, it is important to explore what makes a NHA effective. This research fills a gap in the literature and provides a possible option to improve the quality of care in nursing homes. Purpose of the study. The study examines whether NHAs with advanced education (defined as a Masters degree or more) are associated with better quality of care in licensed nursing homes (NHs). Design and Methods. Data was derived from the CDC’s 2004 National Nursing Home Survey, which is a representative sample of NHs across the US. A Donabedian- inspired structure-process-outcomes study model was created to explain how education relates to quality of care. Quality of care was defined as onsite oral care, employee influenza vaccination rates and staff recognition programs. Statistical analyses included multivariate logistic regression; covariates included facility-level variables used in similar peer-reviewed research but also included select measures from the Area Resource File to control for county-level factors. Results. Descriptive and analytical analyses confirm that NHAs with a Bachelor’s degree, Associate degree or high school diploma perform less well than NHAs with a Masters degree or more. NHAs with advanced education are more likely to have onsite dental care and recognition programs for staff than NHAs with a Bachelor’s degree (or less). Also NHAs with less than graduate education are more likely to provide off-site dental care. Employee vaccination rates are not impacted by education. Adding certification, tenure or years of experience to a NHA with advanced education gives them an advantage. In fact, certification and experience alone do not have a positive relationship to care indicators; however adding these to advanced education produces a significant result. Implications. This research provides preliminary evidence that advanced education for the NHA is associated with better quality of care. If future research can confirm these findings, there is merit in revisiting the qualifications. Education can be a legitimate option to support quality improvement efforts in US nursing homes. ^

Addressing teenage pregnancy in rural areas: A case study from Liberty County, Texas

This study explores the issue of teenage pregnancy in a case study of Liberty County, a rural area in Texas with no public health department. It also describes the decision-making process and barriers faced in the beginning phases of adopting a sexual education program, and sets forth an implementation plan for two school districts on disseminating an evidence-based, comprehensive curriculum. Methods include a review of epidemiological data surrounding teenage pregnancy on the national, state, and county level; a literature review of factors related to teenage pregnancy and past interventions implemented in a rural community; a policy review of past and current bills in Legislature; and an analysis of barriers and decision making in implementing an evidence based program through qualitative observations, discussions with community members during meetings, presentations, and discussions. Results of this study indicate that there is a lack of research conducted in rural areas in the field of teenage pregnancy prevention and sexual education programs. Barriers experienced in Liberty County are shown to be consistent in scientific literature such as funding, logistical issues, and problems approaching the School Board in adopting a comprehensive sexual education program. This study fills a large gap in the literature on rural adolescents and attempts to analyze the process of decision-making in a rural area related to adoption of sexual education programming. In order to relieve this health disparity, further research should focus on rural areas to gain insight on the attitudes and behaviors of rural adolescents and beliefs among community stakeholders.^

Sedimentology, magnetics and chemistry on palaeolake core D100 from the Gobi Desert

The Gaxun Nur Basin in arid China is tectonically influenced by the left-lateral displacements along the Gobi-Altay and Qilian Shan shear zones, resulting in a large pull-apart basin with strong subsidence in the interior. The up to 300 m thick basin fills consist of fluvio-lacustrine fine-grained deposits mainly transported by river discharges from the Tibetan Plateau. They led to a large depositional area of more than 28,000 qkm in size with presently dry terminal lakes at the outer edges. This vast area serves as a main source for loess transport to south-eastern regions of China (Loess Plateau) caused by the variable winter monsoon. Based on geochemical and sedimentological analyses of the sediment core D100 retrieved from a deep drilling in the centre of the Gaxun Nur Basin following questions have to be answered: 1. Reconstruction of the water balance and determination of hydrological cycles during interglacial and glacial periods. 2. Reconstructing variations in lacustrine environment and aeolian activities with respect to transitional phases fro, warm to cold stages (MIS 4 to 5 and older stages). 3. Establishing a sustainable chronology for the last 250 ka.

Mineralogical and geochemical data from five lake sediment cores of Lake Donggi Cona

Sediments of Lake Donggi Cona on the northeastern Tibetan Plateau were studied to infer changes in the lacustrine depositional environment, related to climatic and non-climatic changes during the last 19 kyr. The lake today fills a 30 X 8 km big and 95 m deep tectonic basin, associated with the Kunlun Fault. The study was conducted on a sediment-core transect through the lake basin, in order to gain a complete picture of spatiotemporal environmental change. The recovered sediments are partly finely laminated and are composed of calcareous muds with variable amounts of carbonate micrite, organic matter, detrital silt and clay. On the basis of sedimentological, geochemical, and mineralogical data up to five lithological units (LU) can be distinguished that document distinct stages in the development of the lake system. The onset of the lowermost LU with lacustrine muds above basal sands indicates that lake level was at least 39 m below the present level and started to rise after 19 ka, possibly in response to regional deglaciation. At this time, the lacustrine environment was characterized by detrital sediment influx and the deposition of siliciclastic sediment. In two sediment cores, upward grain-size coarsening documents a lake-level fall after 13 cal ka BP, possibly associated with the late-glacial Younger Dryas stadial. From 11.5 to 4.3 cal ka BP, grainsize fining in sediment cores from the profundal coring sites and the onset of lacustrine deposition at a litoral core site (2m water depth) in a recent marginal bay of Donggi Cona document lake-level rise during the early tomid-Holocene to at least modern level. In addition, high biological productivity and pronounced precipitation of carbonate micrites are consistent with warm and moist climate conditions related to an enhanced influence of summer monsoon. At 4.3 cal ka BP the lake system shifted from an aragonite- to a calcite-dominated system, indicating a change towards a fully open hydrological lake system. The younger clay-rich sediments are moreover non-laminated and lack any diagenetic sulphides, pointing to fully ventilated conditions, and the prevailing absence of lake stratification. This turning point in lake history could imply either a threshold response to insolation-forced climate cooling or a response to a non-climatic trigger, such as an erosional event or a tectonic pulse that induced a strong earthquake, which is difficult to decide from our data base.

Water chemistry, and biological traits and mercury content of Salvelinus alpinus and S. namaycush in Laflamme and Pingualuit lake

Pingualuk Lake fills a deep crater in the Parc National des Pingualuit on the Ungava Peninsula (Nunavik, Canada) and is isolated from nearby surface waters. The main objectives of this study were to determine and compare the concentrations of two atmospherically derived contaminants, mercury and perfluorinated chemicals (PFCs), in the lake water column and fish of Pingualuk Lake and to assess the physical and biological factors influencing contaminant concentrations. Mercury concentrations in arctic char muscle tissue were comparable to those of char in other Arctic lakes, while the total amount of PFCs was below reported levels for remote lakes in the Arctic and elsewhere. Stable isotope and stomach content analyses were made to investigate the feeding ecology of the Pingualuk Lake arctic char population and indicated the possibility of multiple feeding groups. Genetics characteristics (MH and mtDNA) of fish from Pingualuk Lake revealed that this population is likely distinct from that of nearby Laflamme Lake. However, both arctic char populations exhibit differential variation of their allele families. Physical characteristics determined for Lake Pingualuk revealed that the water column was inversely stratified beneath the ice and extremely transparent to visible and ultraviolet radiation. The highest mercury concentrations (3- 6 pg/mL THg) occurred just beneath the ice surface in each lake. Pingualuk Lake, given its near pristine state and exceptional limnological features, may serve as a most valuable reference ecosystem for monitoring environmental stressors, such as contaminants, in the Arctic.

Sedimentology of the Vietnam shelf

On the Vietnam Shelf more than 1000 miles of shallow high-resolution seismics were analyzed to unravel post-glacial evolution in a tropical, siliciclastic environment together with 25 sediment cores from water depths between 21 and 169 m to determine stratigraphy, distribution and style of sedimentation. Fourty-seven samples were dated with the AMS-14C technique. The shelf was grouped into three regions: a southern part, a central part, and a northern part. On the broad Southern Shelf, sedimentation is influenced by the Mekong River, which drains into the SCS in this area. Here, incised valley fills are abundant that were cut into the late Pleistocene land surface by the Paleo-Mekong River during times of sea level lowstand. Those valleys are filled with transgressive deposits. The Holocene sedimentation rate in this low gradient accommodation-dominated depositional system is in the range of 5-10 and 25-40 cm/ky at locations sheltered from currents. The Central Shelf is narrow and the sedimentary strata are conformable. Here, numerous small mountainous rivers reach the SCS and transport large amounts of detrital sediment onto the shelf. Therefore, the Holocene sedimentation rate is high with values of 50-100 cm/ky in this supply-dominated depositional system. The broad Northern Shelf in the vicinity of the Red River Delta shows, as on the Southern Shelf, incised valleys cut into the Pleistocene land surface by paleo river channels. In this accommodation-dominated shelf area, the sedimentation rate is low with values of 5-10 cm/ky. Where applicable, we assigned the sampled deposits to different paleo-facies. The latter are related to certain intervals of water depths at their time of deposition. Comparison with the sea-level curve of (Hanebuth et al., 2000, doi:10.1126/science.288.5468.1033) indicates subsidence on the Central Shelf, which is in agreement with the high sedimentation rates in this area. In contrast, data from the Northern Shelf suggest tectonic uplift that might be related to recent tectonic movements along the Ailao Shan-Red River Fault zone. Data from the Southern Shelf are generally in agreement with the sea-level curve mentioned above.

Mala gente que camina : De la expropiación a la reconstrucción de la memoria

Las indagaciones de la última década sobre el robo de niños en la dictadura franquista y el silencio por parte de los gobiernos democráticos españoles, han despertado el interés tanto de historiadores como de escritores. Quienes no vivieron directamente el exterminio físico e ideológico del régimen dictatorial, recomponen las identidades que quedaron sepultadas en fosas comunes, pero también esclarecen las apropiaciones por parte del Estado, para que aquellos que aún viven engañados puedan saberlo. Benjamín Prado con Mala gente que camina, se inscribe en el conjunto de autores que trabajan por escribir una memoria histórica capaz de llenar los vacíos que han dejado las generaciones anteriores

Texture, geochemistry, isotope composition, petrography and epoch at DSDP Site 93-603

Abundant Fe-Mn carbonate concretions (mainly siderite, manganosiderite, and rhodochrosite) were found in the hemipelagic claystones of Site 603 on the eastern North American continental rise. They occur as nodules, micronodules, or carbonate-replaced burrow fills and layers at a subbottom depth of between ~ 120 (Pliocene) and 1160 m (Albian-Cenomanian). In general, the Fe-Mn carbonate concretions form from CO3- produced by the microbiological degradation of organic matter in the presence of abundant Fe + or Mn + and very low S- concentrations. However, there is also some evidence for diagenetic replacement of preexisting calcite by siderite. The carbon isotope composition of diagenetic Fe-Mn carbonate nodules is determined by CO2 reduction during methanogenesis. Carbonate nodules in Cretaceous sediments at sub-bottom depths of 1085 and 1160 m have distinctly lower d13C values (- 12.2 and - 12.9 per mil) than Neogene siderites, associated with abundant biogenic methane in the pore space (-8.9 to 1.7 per mil between 330 and 780 m depth). Since no isotopic zonation could be detected within individual nodules, we assume that the isotopic composition reflects more or less geochemical conditions at the present burial depth of the carbonate nodules. Carbonates did not precipitate within the zone of sulfate reduction (approximately 0.01 to 10 m), where all of the pyrite was formed. The oxygen isotope composition indicates precipitation from seawater-derived interstitial waters. The d18O values decrease with increasing burial depth from + 5.1 to - 1.2 per mil, suggesting successively higher temperatures during carbonate formation.

Mala gente que camina : De la expropiación a la reconstrucción de la memoria

Las indagaciones de la última década sobre el robo de niños en la dictadura franquista y el silencio por parte de los gobiernos democráticos españoles, han despertado el interés tanto de historiadores como de escritores. Quienes no vivieron directamente el exterminio físico e ideológico del régimen dictatorial, recomponen las identidades que quedaron sepultadas en fosas comunes, pero también esclarecen las apropiaciones por parte del Estado, para que aquellos que aún viven engañados puedan saberlo. Benjamín Prado con Mala gente que camina, se inscribe en el conjunto de autores que trabajan por escribir una memoria histórica capaz de llenar los vacíos que han dejado las generaciones anteriores

Chemistry of minerals of ODP Hole 103-637A peridotites

The Galicia margin lies northwest of the Iberian Peninsula and is a passive ocean margin with thin sedimentary cover. Altered peridotite was recovered from ODP Site 637, on the north-trending ridge at the western edge of the margin, near the oceanic/continental crust boundary. The altered ultramafics were originally clinopyroxene-rich upper mantle harzburgites and are now extensively serpentinized (>85%) and cut by very late-stage carbonate veins. Despite pervasive late, low-temperature alteration, evidence of early, high-temperature alteration remains. Alteration is apparent as (1) amphibole rims on clinopyroxene (>800°C), (2) hornblende + tremolite (450° to 800°C), (3) breakdown of hornblende to form tremolite + chlorite (<450°C), (4) zoned Cr-spinels, (5) hydration of orthopyroxene and olivine to serpentine, (6) serpentine veins, (7) replacement of pyroxene and olivine by calcite, and (8) calcite veins and vugs. Both the relict igneous and the high-temperature alteration minerals (amphiboles) show evidence of brittle deformation. Subsequent low-temperature alteration veins and minerals are deformed only in faulted and brecciated zones. This textural evidence suggests that the low-temperature alteration occurred after emplacement of the ultramafics at the surface. Serpentine fills tension fractures in orthopyroxene, and both serpentine and calcite fill tension cracks in olivine. The high-temperature alterations in these samples are similar to those found in oceanic fracture zone and ophiolite ultramafics. This widespread occurrence of high-temperature alteration suggests that hot fluids were pervasive in these ultramafic blocks. Localization of high-temperature alteration close to large carbonate veins suggests channelization of the late, low-temperature fluids. Earlier hydrations (e.g., high-temperature alterations and serpentinization) were pervasive.