185 research outputs found
Switching Intentions of Service Providers and Cultural Orientation
This study performs a cross-cultural comparison to understand how the drivers of switching intentions differ between countries that vary in their long-term orientation (LTO). The authors hypothesize how LTO moderates the influence of the drivers of switching intentions for a mobile phone subscription service. Structural invariance tests between consumer samples of the United States (low LTO) and the Netherlands (high LTO) reveal that, consumers from high LTO nation attribute more importance to relational quality but care less about service recovery in their formation of switching intentions. The theoretical and managerial implications of how differences in time orientation affect the pathways to loyalty are discussed
The Dynamic Crust of Northern Afar and Adjacent Rift Margins: New Evidence From Receiver Function Analysis in Eritrea and Ethiopia
Afar is undergoing the final stages of continental rifting and hosts the triple junction between the Red Sea, Gulf of Aden, and Main Ethiopian rifts. To better understand the nature of the crust and continental breakup in the region, we calculate teleseismic receiver functions across northeastern Afar and the Danakil microplate, using new data from a regional deployment in Eritrea. We estimate the Moho depth and bulk crustal V P /V S ratio using the HâÎș stacking method. The heterogeneity of our crustal thickness estimates (âŒ19â35 km) indicates that the Danakil microplate has undergone stretching and crustal thinning. By investigating the relationship between crustal thickness and topographic elevation, we estimate the regional crustal bulk density as Ï c â 2,850 ± 20 kg mâ3, which is higher than expected, given the crustal thickness of the region. We show that topography is 1.5 ± 0.4 km higher than would be expected due to crustal isostasy alone. We propose that this topography is supported by the same hot mantle upwelling suggested to be responsible for the onset of rifting in East Africa. Uplift is generated due to the presence of a hot thermal anomaly beneath the plate and by thinning of the lithospheric mantle. Our results are consistent with a number of independent constraints on the thermal structure of the asthenospheric and lithospheric mantle. Evidence of melt within the crust is provided by anomalously high V P /V S ratios of >1.9, demonstrating that magmaâassisted extension continues to be important in the final stages of continental breakup
Lanthanum from a modified clay used in eutrophication control is bioavailable to the marbled crayfish (Procambarus fallax f. virginalis)
To mitigate eutrophication in fresh standing waters the focus is on phosphorus (P) control, i.e. on P inflows to a lake as well as a lake's sediment as internal P source. The in-lake application of the lanthanum (La) modified clays â i.e. La modified bentonite (Phoslock) or La modified kaolinite, aim at dephosphatising the water column and at reducing the release of P from a lake's sediment. Application of these clays raises the question whether La from these clays can become bioavailable to biota. We investigated the bioavailability of La from Phoslock in a controlled parallel groups experiment in which we measured the La in carapace, gills, ovaries, hepatopancreas and abdominal muscle after 0, 14 and 28 days of exposure to Phoslock. Expressing the treatment effect as the difference of the median concentration between the two treatment groups (Phoslock minus control group) yield the following effects, the plus sign (+) indicating an increase, concentrations in ”g g-1 dry weight: Day 14: carapace +10.5 ”g g-1, gills +112 ”g g-1, ovaries +2.6 ”g g-1, hepatopancreas +32.9 ”g g-1 and abodminal muscle +3.2 ”g g-1. Day 28: carapace +17.9 ”g g-1; gills +182 ”g g-1; ovaries +2.2 ”g g-1; hepatopancreas +41.9 ”g g-1 and abodminal muscle +7.6 ”g g-1, all effects were statistically significant. As La from Phoslock is bio-available to and taken up by the marbled crayfishes (Procambarus fallax f. virginalis), we advocate that the application of in-lake chemical water treatments to mitigate eutrophication should be accompanied by a thorough study on potential side effect
A little data goes a long way: automating seismic phase arrival picking at Nabro Volcano with transfer learning
Supervised deep learning models have become a popular choice for seismic phase arrival detection. However, they do not always perform well on out-of-distribution data and require large training sets to aid generalization and prevent overfitting. This can present issues when using these models in new monitoring settings. In this work, we develop a deep learning model for automating phase arrival detection at Nabro volcano using a limited amount of training data (2,498 event waveforms recorded over 35 days) through a process known as transfer learning. We use the feature extraction layers of an existing, extensively trained seismic phase picking model to form the base of a new all-convolutional model, which we call U-GPD. We demonstrate that transfer learning reduces overfitting and model error relative to training the same model from scratch, particularly for small training sets (e.g., 500 waveforms). The new U-GPD model achieves greater classification accuracy and smaller arrival time residuals than off-the-shelf applications of two existing, extensively-trained baseline models for a test set of 800 event and noise waveforms from Nabro volcano. When applied to 14 months of continuous Nabro data, the new U-GPD model detects 31,387 events with at least four P-wave arrivals and one S-wave arrival, which is more than the original base model (26,808 events) and our existing manual catalog (2,926 events), with smaller location errors. The new model is also more efficient when applied as a sliding window, processing 14 months of data from seven stations in less than 4 h on a single graphics processing unit
Extension and stress during continental breakup: seismic anisotropy of the crust in Northern Afar
Studies that attempt to simulate continental rifting and subsequent breakup require detailed knowledge of crustal stresses, however observational constraints from continental rifts are lacking. In addition, a knowledge of the stress field around active volcanoes can be used to detect sub-surface changes to the volcanic system. Here we use shear wave splitting to measure the seismic anisotropy of the crust in Northern Afar, a region of active, magma-rich continental breakup. We combine shear wave splitting tomography with modelling of gravitational and magmatic induced stresses to propose a model for crustal stress and strain across the rift. Results show that at the Ethiopian Plateau, seismic anisotropy is consistently oriented NâS. Seismic anisotropy within the rift is generally oriented NNWâSSE, with the exception of regions north and south of the Danakil Depression where seismic anisotropy is rift-perpendicular. These results suggest that the crust at the rift axis is characterized by rift-aligned structures and melt inclusions, consistent with a focusing of tectonic extension at the rift axis. In contrast, we show that at regions within the rift where extension rate is minimal the seismic anisotropy is best explained by the gravitationally induced stress field originating from variations in crustal thickness. Seismic anisotropy away from the rift is controlled by a combination of inherited crustal structures and gravitationally induced extension whereas at the Dabbahu region we show that the stress field changes orientation in response to magmatic intrusions. Our proposed model provides a benchmark of crustal stress in Northern Afar which will aid the monitoring of volcanic hazard. In addition we show that gravitational forces play a key role in measurements of seismic anisotropy, and must be considered in future studies. We demonstrate that during the final stages of continental rifting the stress field at the rift axis is primarily controlled by tectonic extension, but that gravitational forces and magmatic intrusions can play a key role in the orientation of the stress field
Application of biostimulant products and biological control agents in sustainable viticulture: A review
Current and continuing climate change in the Anthropocene epoch requires sustainable agricultural practices. Additionally, due to changing consumer preferences, organic approaches to cultivation are gaining popularity. The global market for organic grapes, grape products, and wine is growing. Biostimulant and biocontrol products are often applied in organic vineyards and can reduce the synthetic fertilizer, pesticide, and fungicide requirements of a vineyard. Plant growth promotion following application is also observed under a variety of challenging conditions associated with global warming. This paper reviews different groups of biostimulants and their effects on viticulture, including microorganisms, protein hydrolysates, humic acids, pyrogenic materials, and seaweed extracts. Of special interest are biostimulants with utility in protecting plants against the effects of climate change, including drought and heat stress. While many beneficial effects have been reported following the application of these materials, most studies lack a mechanistic explanation, and important parameters are often undefined (e.g., soil characteristics and nutrient availability). We recommend an increased study of the underlying mechanisms of these products to enable the selection of proper biostimulants, application methods, and dosage in viticulture. A detailed understanding of processes dictating beneficial effects in vineyards following application may allow for biostimulants with increased efficacy, uptake, and sustainability.KJ wishes to acknowledge financial support (3710473400); MS-M thanks to RTI2018-099417-B-I00 (Spanish Ministry of Science, Innovation and Universities cofunded with EU FEDER funds); JB wish to acknowledge the Conselho Nacional de Desenvolvimento CientĂfico e TecnolĂłgico/Brasil (CNPQ process number 309477/2021-2); RO-H is supported by the RamĂłn y Cajal program from the MICINN (RYC-2017 22032), PAIDI 2020 (Ref. 20_00323), AEI GGOO 2020 (GOPC-CA-20-0001), âJosĂ© Castillejoâ program from the âMinisterio de Universidadesâ (CAS21/00125) and PID2019-106004RA-I00/AEI/10.13039/501100011033. SM and GT thanks to Ministerio de Ciencia e InnovaciĂłn (grant PID2020-114330GB-100). PAIDI2020 from Junta de AndalucĂa, grant P18-RT-1401 to SM, MD, and GT is also acknowledged. GT acknowledge the support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)
Local Earthquake Magnitude Scale and bâValue for the Danakil Region of Northern Afar
The Danakil region of northern Afar is an area of ongoing seismic and volcanic activity caused by the final stages of continental breakup. To improve the quantification of seismicity, we developed a calibrated local earthquake magnitude scale. The accurate calculation of earthquake magnitudes allows the estimation of b?values and maximum magnitudes, both of which are essential for seismic?hazard analysis. Earthquake data collected between February 2011 and February 2013 on 11 three?component broadband seismometers were analyzed. A total of 4275 earthquakes were recorded over hypocentral distances ranging from 0 to 400 km. A total of 32,904 zero?to?peak amplitude measurements (A) were measured on the seismometerâs horizontal components and were incorporated into a direct linear inversion that solved for all individual local earthquake magnitudes (ML), 22 station correction factors (C), and 2 distance?dependent factors (n, K) in the equation ML=log(A)?log(A0)+C. The resultant distance correction term is given by ?log(A0)=1.274336log(r/17)?0.000273(r?17)+2. This distance correction term suggests that attenuation in the upper and mid?crust of northern Afar is relatively high, consistent with the presence of magmatic intrusions and partial melt. In contrast, attenuation in the lower crust and uppermost mantle is anomalously low, interpreted to be caused by a high melt fraction causing attenuation to occur outside the seismic frequency band. The calculated station corrections serve to reduce the ML residuals significantly but do not show a correlation with regional geology. The cumulative seismicity rate produces a b?value of 0.9±0.06, which is higher than most regions of continental rifting yet lower than values recorded at midocean ridges, further supporting the hypothesis that northern Afar is transitioning to seafloor spreading
Initiation of a protoâtransform fault prior to seafloor spreading
Transform faults are a fundamental tenet of plate tectonics, connecting offset extensional segments of midâocean ridges in ocean basins worldwide. The current consensus is that oceanic transform faults initiate after the onset of seafloor spreading. However, this inference has been difficult to test given the lack of direct observations of transform fault formation. Here, we integrate evidence from surface faults, geodetic measurements, local seismicity, and numerical modelling of the subaerial Afar continental rift and show that a protoâtransform fault is initiating during the final stages of continental breakup. This is the first direct observation of protoâtransform fault initiation in a continental rift, and sheds unprecedented light on their formation mechanisms. We demonstrate that they can initiate during lateâstage continental rifting, earlier in the rifting cycle than previously thought. Future studies of volcanic rifted margins cannot assume that oceanic transform faults initiated after the onset of seafloor spreading
Effectiveness of Monovalent Rotavirus Vaccine in Mozambique, a Country with a High Burden of Chronic Malnutrition
Funding Information: Funding: This research was funded by GAVI through the Centers for Disease Control and Prevention (CDC), Atlanta and World Health Organization, Regional Office for Africa (WHO/AFRO). African Research in Neglected Tropical Diseases (EFINTD, grant number 89539); Deutsche Forschungsge-meinschaft (DFG; grant number JO369/5-1); Fundo Nacional de Investigação (FNI); United States Agency for International Development (USAID; grant number AID-656-F-16-00002); the Calouste Gulbenkian Foundation from where A.C., F.M., and J.S. have a PhD fellowship. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Mozambique introduced monovalent rotavirus vaccine (RotarixÂź ) in September 2015. We evaluated the effectiveness of RotarixÂź under conditions of routine use in Mozambican children hospitalized with acute gastroenteritis (AGE). A test negative case-control analysis was performed on data collected during 2017â2019 from children <5 years old, admitted with AGE in seven sentinel hospital sites in Mozambique. Adjusted VE was calculated for â„1 dose of vaccine vs. zero doses using unconditional logistic regression, where VE = (1 â aOR) Ă 100%. VE estimates were stratified by age group, AGE severity, malnutrition, and genotype. Among 689 children eligible for analysis, 23.7% were rotavirus positive (cases) and 76.3% were negative (controls). The adjusted VE of â„1 dose in children aged 6â11 months was 52.0% (95% CI, â11, 79), and â24.0% (95% CI, â459, 62) among children aged 12â23 months. Estimated VE was lower in stunted than non-stunted children (14% (95% CI, â138, 66) vs. 59% (95% CI, â125, 91)). Rotavirus vaccination appeared moderately effective against rotavirus gastroenteritis hospitalization in young Mozambican children. VE point estimates were lower in older and stunted children, although confidence intervals were wide and overlapped across strata. These findings provide additional evidence for other high-mortality countries considering rotavirus vaccine introduction.publishersversionpublishe
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