765 research outputs found
Investigating event-specific drought attribution using self-organizing maps
Previous studies evaluating anthropogenic influences on the meteorological drivers of drought have found mixed results owing to (1) the complex physical mechanisms which lead to the onset of drought, (2) differences in the characteristics and time scales of drought for different regions of the world, and (3) different approaches to the question of attribution. For a midlatitude, temperate climate like New Zealand, strongly modulated by oceanic influences, summer droughts last on the order of 3âmonths, and are less strongly linked to persistent temperature anomalies than continental climates. Here we demonstrate the utility of a novel approach for characterizing the meteorological conditions conducive to extreme drought over the North Island of New Zealand, using the JanuaryâMarch 2013 event as a case study. Specifically, we consider the use of selfâorganizing map techniques in a multimember coupled climate model ensemble to capture changes in daily circulation, between two 41âyear periods (1861â1901 and 1993â2033). Comparisons are made with seasonal pressure and precipitation indices. Our results demonstrate robust (>99% confidence) increases in the likelihood of observing circulation patterns like those of the 2013 drought in the recentâclimate simulations when compared with the earlyâclimate simulations. Best guess estimates of the fraction of attributable risk range from 0.2 to 0.4, depending on the metric used and threshold considered. Contributions to uncertainty in these attribution statements are discussed
RV Sonne Cruise 198-1, 03 May-14 Jun 2008. Singapore - Merak, Indonesia
All plate boundaries are divided into segments -
pieces of fault that are distinct from one another, either separated by gaps or with different orientations. The maximum size of an earthquake on a fault system is controlled by the degree to which the propagating rupture can cross the boundaries between such segments. A large earthquake may rupture a whole segment
of plate boundary, but a great earthquake usually ruptures more than one segment at once.
Earthquakes offshore of Sumatra on December 26th 2004 (MW=9.3) and March 28th 2005 (MW=8.7) ruptured, respectively, 1200-1300 km and 300-400 km of the subduction boundary between the Indian-Australian plate and
the Burman and Sumatra blocks. Rupture in the 2004 event started at the southern end of the fault segment, and propagated northwards. The observation that the slip did not propagate significantly southwards in December 2004, even though the magnitude of slip was high at the southern end of the rupture strongly suggests a barrier at that place. Maximum slip in the March 2005 earthquake occurred within ~100 km of the barrier between the 2004 and 2005
ruptures, confirming both the physical importance of the
barrier, and the loading of the March 2005 rupture zone by
the December 2004 earthquake.
Cruise SO198-1, from Singapore to Merak between 3rd May and
14th June 2008 is the first of three cruises, funded by
the Natural Environment Research Council (NERC), which will form a coherent set of geophysical observations in the source regions of the 2004 and 2005 great Sumatra earthquakes. Arrays of 50 ocean-bottom seismometers (OBS) were deployed at each of two locations â between the 2004 and 2005 ruptures, and at the southern end of the 2005 rupture - to record shots from a large-capacity airgun array. Approximately 7 days of continuous airgun shooting at 60s interval was completed at each location. 10 OBS were reconfigured for earthquake recording and deployed with a planned retrieval in early 2009. Gravity, Parasound,
and swath bathymetry data were recorded continuously while in the permitted area, with magnetic field data recorded throughout the airgun shooting, and 101 XBT casts taken at the OBS deployment locations
Quantum dots in magnetic fields: thermal response of broken symmetry phases
We investigate the thermal properties of circular semiconductor quantum dots
in high magnetic fields using finite temperature Hartree-Fock techniques. We
demonstrate that for a given magnetic field strength quantum dots undergo
various shape phase transitions as a function of temperature, and we outline
possible observable consequences.Comment: In Press, Phys. Rev. B (2001
Dental Caries, Fluorosis, and Fluoride Exposure in Michigan Schoolchildren
This study relates the prevalence of caries and fluorosis among Michigan children, residing in four different areas, to the various concentrations of F in the communities' water supplies. Demographic information, details of F history, and dental attendance data were collected by a questionnaire form filled out by parents. Children ages six to 12 were screened for caries by means of the NIDR criteria and for fluorosis by means of the TSIF index. Results pertain only to continuous residents and the permanent dentition. The prevalence of both caries and fluorosis was significantly associated with the F concentration in the community water supply. Approximately 65% of all children were caries-free, ranging from 55.1 % in fluoride-deficient Cadillac to 73.7% in Redford (1. 0 ppm F). About 36% of all children had dental fluorosis, ranging from 12.2 in Cadillac to 51.2 in Richmond (1.2 ppm). All of the fluorosis was very mild. From logistic regression, the prevalence of caries was significantly associated with age, dental attendance, and the use of a water supply fluoridated at 1.0 ppm. The odds of experiencing fluorosis increased at every F level above the baseline (Cadillac), with the use of topical F rinses, and with age. Results suggest that children in the four communities may be ingesting a similar level of F from sources such as dentifrices, dietary supplements, and professional applications, but the factor that differentiates them with respect to the prevalence of caries and fluorosis is the F concentration in the community water supply.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66926/2/10.1177_00220345880670050101.pd
Some general properties of the renormalized stress-energy tensor for static quantum states on (n+1)-dimensional spherically symmetric black holes
We study the renormalized stress-energy tensor (RSET) for static quantum
states on (n+1)-dimensional, static, spherically symmetric black holes. By
solving the conservation equations, we are able to write the stress-energy
tensor in terms of a single unknown function of the radial co-ordinate, plus
two arbitrary constants. Conditions for the stress-energy tensor to be regular
at event horizons (including the extremal and ``ultra-extremal'' cases) are
then derived using generalized Kruskal-like co-ordinates. These results should
be useful for future calculations of the RSET for static quantum states on
spherically symmetric black hole geometries in any number of space-time
dimensions.Comment: 9 pages, no figures, RevTeX4, references added, accepted for
publication in General Relativity and Gravitatio
Separation of Flip and Non-Flip parst of Charge Exchange np->pn at energies Tn = 0.5 - 2.0 GeV
The new Delta-Sigma experimental data on the ratio allowed
separating the Flip and Non-Flip parts of the differential cross section of
charge exchange process at the zero angle by the Dean formula. The
PSA solutions for the elastic scattering are transformed to the
charge exchange representation using unitary transition, and good
agreement is obtain.Comment: 7 pages, 2 figure
Emergence of Anti-Cancer Drug Resistance: Exploring the Importance of the Microenvironmental Niche via a Spatial Model
Practically, all chemotherapeutic agents lead to drug resistance. Clinically,
it is a challenge to determine whether resistance arises prior to, or as a
result of, cancer therapy. Further, a number of different intracellular and
microenvironmental factors have been correlated with the emergence of drug
resistance. With the goal of better understanding drug resistance and its
connection with the tumor microenvironment, we have developed a hybrid
discrete-continuous mathematical model. In this model, cancer cells described
through a particle-spring approach respond to dynamically changing oxygen and
DNA damaging drug concentrations described through partial differential
equations. We thoroughly explored the behavior of our self-calibrated model
under the following common conditions: a fixed layout of the vasculature, an
identical initial configuration of cancer cells, the same mechanism of drug
action, and one mechanism of cellular response to the drug. We considered one
set of simulations in which drug resistance existed prior to the start of
treatment, and another set in which drug resistance is acquired in response to
treatment. This allows us to compare how both kinds of resistance influence the
spatial and temporal dynamics of the developing tumor, and its clonal
diversity. We show that both pre-existing and acquired resistance can give rise
to three biologically distinct parameter regimes: successful tumor eradication,
reduced effectiveness of drug during the course of treatment (resistance), and
complete treatment failure
Phenotypic Diversity for Seed Mineral Concentration in North American Dry Bean Germplasm of Middle American Ancestry
Dry bean (Phaseolus vulgaris L.) seeds are a major protein, carbohydrate, and mineral source in the human diet of peoples in multiple regions of the world. Seed mineral biofortification is an ongoing objective to improve this important food source. The objective of this research was to assess the seed mineral concentration of five macroelements and eight microelements in a large panel (n = 277) of modern race Durango and race Mesoamerica genotypes to determine if variability existed that could be exploited for targeted seed biofortification. Varieties that derive from these races are found in many diets throughout the world. The panel was grown in replicated trials under typical production conditions in the major bean growing regions of the United States, and a subset of the panel was also grown in replicated trials at three locations under control and terminal drought conditions. Except for K, seed mineral concentrations were higher for race Mesoamerica genotypes. Significantly higher seed concentrations for the majority of the minerals were observed for white-seeded genotypes and race Durango genotypes with the now preferred indeterminate, upright growth habit. Modern genotypes (since 1997) had equal or increased mineral concentrations compared with older genotypes. Drought affected mineral content differentially, having no effect on the microelement content but increased Co, Fe, and Ni concentrations. The correlation of Ca and Mn concentrations suggests that these elements may share seed deposition mechanisms. The high heritability for seed mineral concentration implies that breeding progress can be achieved by parental selection from this panel
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