333 research outputs found
For and against; should doctors advise young people to abstain from sex?
No full textAgainst a background of high rates of teenage pregnancy and an increasing prevalence of sexually transmitted infections, the sexual conduct of young people is vigorously debated. Many teenagers later say that they had sexual intercourse "too early" but should doctors be advising young people to abstain from sex? Trevor Stammers, who is a tutor in general practice and an author and broadcaster on sexual health, and Roger Ingham, who has done research on sexual conduct and sex education in Britain and other countries, consider whether advising abstinence is an effective response to declining teenage sexual health
A vectorial Ingham-Beurling type theorem
No full textInternational audienceBaiocchi et al. generalized a few years ago a classical theorem of Ingham and Beurling by means of divided differences. The optimality of their assumption has been proven by the third author of this note. The purpose of this note to extend these results to vector coefficient sum
A compleat collection of devotions : both publick and private : taken from the apostolical constitutions, the ancient liturgies, and the Common prayer book of the Church of England ... [etc.].
No full textSignatures: [pi]¹, A?, A-Y?, Z?, a-h?, i? (final verso blank).; Attributed to Thomas Deacon.; Label: Library of the Congregation of U.B. of the Borough of Bethlehem and its vicinity, no. 877.; Signature; B. Ingham.; An appendix in justification of the foregoing undertaking ... has separate title and pagings.; BM,; ESTC
The saline Interface of a Shallow Unconfined Aquifer, Rangitikei Delta
No full textThe coastal communities of Tangimoana and Scott's Ferry have a long history of using shallow groundwater bores. The cumulative effect of pumping over decades could influence the saline interface given the close proximity of the communities to the seashore and river estuary. It is important to quantify the effects of pumping on both the shallow groundwater system and the dynamics of the saline interface. This is
necessary to protect the groundwater system against saline intrusion especially given the increasing number of high volume groundwater consents to support dairying. Resistivity soundings and traverses, coupled with chemical analyses of groundwater samples, were found to be an effective method for defining the saline interface of the shallow groundwater aquifer under the Rangitikei delta. The saline interface extends from the salt marsh to beneath the farmland north of Tangimoana. The interface is a
zone of diffusion with freshwater and brackish water mixing from the estuary. The interface is currently located on the outskirts of Tangimoana, and it is likely to extend beneath the township. The infiltration of brackish surface waters into sediments of the salt marsh form a surficial mixing zone that decreases with distance from the salt marsh. There is no indication of salinity in the area to the north of the Rangitikei delta.
This area is most at risk of contamination from saline intrusion because of high volume
groundwater abstractions, even though these abstractions are from deeper aquifers. The shallow groundwater beneath Tangimoana showed high concentrations of Ca and HCO3 ions. This may be a result of carbonate dissolution, which can occur when saline and freshwater mix. This creates groundwater that is under-saturated with calcium. The mixing water dissolves carbonates and increases the concentrations of Ca and HCO3.
The major source of sodium and chloride was likely rainwater with evaporated solutes
from seawater. The saline interface near Tangimoana appears to be relatively static, but the estuary and salt marsh are areas of low relief. There are preferential flows paths across the salt
marsh to the farmland. These factors make the shallow groundwater in the Rangitikei delta vulnerable to saline intrusion
Geophysical Investigations of the South-Western Wairarapa Region of New Zealand
No full textA model of the sub-surface structure of the south-western part of the Wairarapa sedimentary basin in central New Zealand was constructed from geophysical data obtained by the author during the period 1990-1991. A total of 122 new gravity observations, eight magnetotelluric (MT) stations and approximately two kilometres of seismic refraction lines were established in the study area. All methods complemented each other in the determination of the final result. The gravity data provided the depth for the basement layer of the basin, and determined the position of a fossil fault in the region of the Wharepapa River channel. The MT and seismic data confirmed the fossil nature of the fault. The results for the boundaries determined by the MT surveys were also shown to agree with the upper layers of the gravity model. The final model presented is of a sedimentary basin with thickness of approximately 2km, with a fossil fault dividing the basin near the vicinity of the Wharepapa River. To the west of the study area is a highly anomalous region which could not be fully modelled in this study because of lack of data in this particular area
El Tlacuache Núm. 504 (2012). 504 Año 13 (2012) enero. El Tlacuache
No full textJohn M. Ingham donó su valioso archivo Etnográfico sobre Tlayacapan (1960-1980) al Centro INAH Morelos por Miguel Morayta Mendoza. -Mary, Michel and Lucifer. Folk catholicism in central Mexico por John Mary Ingham. -Arqueología en el Santuario de Jesús Nazareno en Tepalcingo por José Cuauhtli A. Medina Romero, Antonio Vázquez Martínez. -Arqueología en el Santuario de Jesús en Tepalcingo por José Cuauhtli A. Medina Romero Nazareno. -Catalogo: fondo de fotografía antigua de Cuautla Morelos por Erick Alvarado Tenorio
Structural and Hydrothermal Inferences from a Magnetotelluric Survey across Mt. Ruapehu, New Zealand
No full textThis thesis explains the electrical conductivity structure of Mt. Ruapehu. To identify
hydrothermal or volcanic components of the volcano, data from 25 magnetotelluric
sites are analyzed.
Data collected are first analyzed in the time domain prior to conversion into the frequency
domain. Here, data are remote referenced, and the impedance tensors, tippers,
apparent resistivity and phase values are calculated. These components are then analyzed
to identify major features within the data. The new phase tensor ellipse method
is applied to identify influential features and determine the dimensionality of data.
This analysis indicates where it is appropriate to apply 1 or 2 dimensional inversion
schemes.
Dimensionality analysis led to 1-D modelling of the determinant impedance at each
site; and limited 2-D profiles across the Tongariro Volcanic Centre boundaries. These
models are used to create a simple 3-D structural model of the volcano that is then
forward modelled. The results of the 3-D forward modelling indicate that the dominating
features of the volcano's electrical structure have been identified in the previous
models.
Crater Lake is the only possible hydrothermal system on Mt. Ruapehu identified
in this study. It is also very unlikely that any large coherent bodies of magma exist
in the near surface. However, a second thin conductor laying somewhere between 10
and 30 km deep beneath the eastern flank may contain 13% melt and is the probable
driving heat force beneath the volcano.
The structure of Mt. Ruapehu can be split into seven layers.
A resistive surface layer (100 ohm m) of young volcanic debris within the Tongariro
Volcanic Centre that is up to 500 m thick near the crater.
A conductive layer (10 - 30 ohm m) of wet, fractured and altered volcanic debris
underlaying the younger debris throughout the Tongariro Volcanic Centre.
A layer of Tertiary sediment under the Tongariro Volcanic Centre that extends to
the south and west. This layer is electrically indistinguishable from the previous
layer and extends to approximately sea level.
A resistive layer (400 ohm m), and consistent with greywacke basement covers the
entire field area.
A second conductive layer (20 ohm m) is identified under the eastern flank of the
volcano somewhere between the depths of 10 and 30 km. This layer is likely to
be the heat and magma source driving the volcanic activity.
A surrounding resistive layer extends beyond and below the second conductive
layer mentioned above. This surrounding layer is electrically similar to the
greywacke above.
A very high resistivity layer (7000 ohm m) is identified below 80 km deep, and may
be associated with the land/sea boundary or subduction zone to the east
Design, construction and testing of an EMAP system for high resolution electrical conductivity studies
No full textThe ElectroMagnetic Array Profiling (EMAP) technique was developed by Bostick (1986) as a method of removing static shift from magnetotelluric (MT) soundings. An additional benefit of EMAP is the high resolution of near vertical electrical conductivity contrasts that the method offers. This is the primary reason for developing an EMAP system at Victoria University.
The EMAP system required the development of both hardware and software. Hardware was developed on Protel98TM an electronics computer aided design program with the PCB boards being manufactured commercially. The software for processing EMAP data EDGE (Emap Data processinG Engine) was written on MatlabTM with a GUI (Graphical User Interface) for easy of use.
A field test for the EMAP system was performed in Waitarere forest, approximately 10km north-west of Levin. The area has simple geology with sand and gravel overlaying basement, a previous seismic survey 6 km to the south west found an average basement depth of approximately 380 m.
The data were processed using EDGE to give apparent resistivity and phase plots and a simple 1-D Bostick inversion of structure. The apparent resistivity and phase were also used in a 1-D Occam inversion scheme. The results from this were in good agreement with the previous survey, with EMAP giving a value of between 450-500 m for the depth to basement.
The Waitarere forest site had a large amount of 50 Hz mains hum and associated harmonics present which had a degrading effect on the high frequency data. This led to the high frequency band data not being included in the final Occam inversion (an approach to the regularized inversion of nonlinear problems)
High frequency magnetotelluric survey of the volcanic vent and hydrothermal system on Mount Ruapehu New Zealand
No full textPrevious magnetotelluric (MT) studies (Dravitzki, 2005; Cairns, 2006) carried out by Victoria University of Wellington (VUW) and GNS Science identified a shallow low resistivity anomaly on the summit plateau of Mount Ruapehu. It was inferred that the low resistivity was most likely to be related to the volcanic hydrothermal system (Dravitzki, 2005).
This current study builds on this earlier work with the aim of modelling the electrical resistivity structure of the volcanic vent and hydrothermal system of Mount Ruapehu. Data from high frequency MT measurements made at nine sites around the summit plateau, combined with data from previous studies were used to derive both one and three dimensional models.
The 3D models show two vertical pipe-like structures of relatively high resistivity compared to their surroundings. The first of these is located to the magnetic south of the centre of the model at depths of 150m to 500m. The second of these pipe-like structures is located to the magnetic north of the centre of the model, at depths of between 800m and 2,000m. The resistivity of these two structures is ~30Ωm and ~100Ωm respectively, with surrounding resistivities of 0.3Ω 10Ωm.
At these depths it is inferred that these pipe like structures indicate regions of resistive high temperature alteration mineral, which are possible candidates for a heat pipe structure as proposed by Hurst et. al. (1991).
Additional three dimensional modelling of the wider area was carried out using MT data collected in the Tongariro Volcanic Centre during the previous VUW and GNS Science studies. These models displayed a region of low resistivity (0.3Ωm - 10Ωm) located to the magnetic north of Ruapehu, continuing northward for ~72km and ranging in depth from 1,500m to around 10,000m.
Phase tensor analysis carried out in previous studies (Cairns, 2006) also indicated the existence of a deep conductive zone on the NE (with respect to true north) side of Ruapehu. In these studies it was suggested that this region was associated with the southern termination of the Taupo Volcanic Zone
Coastal Groundwater Dynamics - Investigation of Using Geoelectrical and Hydrochemical Tools for Saline Intrusion Monitoring
No full textWith over 65 % of the global population currently living in areas near a coast, increasing fresh groundwater demands within these areas, shifted precipitation patterns, and rising mean sea levels, increased seawater intrusion into coastal aquifers has become a major issue for groundwater resources in many coastal countries all around the world. Although there are many past studies researching the saline interface in affected aquifers from a modelling, laboratory or field perspective with different hydrological and geophysical approaches, little is known about real field dynamics over various time spans and in different geological settings. This PhD project aims at detecting and characterising seawater intrusion into a shallow coastal Holocene sand and gravel aquifer at New Zealand's west coast with respect to seasonally changing aquifer resistivity and hydrochemical tracers, as well as investigating resistivity and hydraulic property changes within a tidal time frame. Seawater mixing behaviour over different time spans was monitored with electrical resistivity tomography (ERT) over the course of two years, and additional hydrochemical sampling was carried out during the second year of the long-term seawater intrusion monitoring study. During two consecutive years, repeat ERT measurements were able to determine seasonal and shorter-term cycles in seawater mixing behaviour within the shallow coastal aquifer. There are strong indications that increasing urbanisation has a major influence on seasonal seawater intrusion patterns, and the dominant processes at the field locations were identified to be tied to the amount of freshwater available over the course of a year, as well as enhanced evapotranspiration / evaporation during summer. Hydrochemical data backed these observations and were also able to characterise seawater intrusion as a function of depth at the field location. Within the smaller tidal cycle investigations, similarly behaving parts of the aquifer could be identified from resistivity ratios and time series analyses. Varying amplitudes in resistivity changes led to the conclusion that saline mixing within a diurnal tidal cycle is strongly dependent on the recharge regime of the aquifer and decreases significantly for times during the year when recharge is continuous as opposed to times with little general recharge but intense, isolated rainfall events. In addition, tidal time series were used to qualitatively infer hydraulic properties of the aquifer and ultimately delineate preferential flow paths for seawater intrusion at the field site. The results of this project support findings of previous modelling, laboratory and short-term field studies, and put the concepts into a much broader time frame. For the first time the dynamics of seawater mixing in a shallow coastal sand aquifer were conclusively studied at the same location and within different time frames, and are thus of great value for sustainable groundwater management in the area of investigation and similar coastal environments
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