Rise In Head Research Articles

Discontinuous deformation analysis for subsidence of fractured formations under seepage: A case study

With the growing prominence of recycling projects of groundwater, the attention towards subsidence concerns in geological formations is intensifying. However, due to the long evolutionary time and complex underground discontinuities, the deformation field and subsidence mechanism are difficult to obtain. To this concern, this study implemented the Hydro-Mechanical Coupled Discontinuous Deformation Analysis (HM-DDA) in a groundwater recycling project located at a goaf mining site. The method for establishing numerical stratigraphic models and determining the required numerical parameters is introduced. This contributes to the comprehensive reconstruction of changes in in-situ stress within the goaf area, encompassing the initial stress equilibrium state, as well as the processes of water pumping and injection. The results indicated that the water injection process mitigated stress concentrations at both ends of the goaf area. Specifically, a 30-m rise in water head resulted in a corresponding elevation of the ground surface by 3.94 ​cm.

Investigation of Groundwater Withdrawal and Recharge Affecting Underground Structures in the Shanghai Urban Area

In this paper, the hydrogeological features of Quaternary deposits in Shanghai as well as the characteristics of groundwater withdrawal and recharge in urban areas are investigated. One phreatic aquifer and five confined aquifers (AqI to AqV) are present in Shanghai, and these aquifers are separated by five aquitards. Groundwater withdrawal from confined aquifers has resulted in land subsidence in Shanghai. To control land subsidence, the groundwater withdrawal volume has been decreased, and the groundwater recharge volume has been increased since 1965. Correspondingly, the pressure head in confined aquifers has risen. The groundwater head increases in shallow aquifers may impact underground structures and lead to the following issues: i) an increased risk of water in-rushing hazards caused by confined water pressure during structural excavations and ii) an increased instability risk caused by groundwater buoyancy. Both excavation anti-uprush and underground structure anti-floating are discussed in this paper. Based on the risk possibilities, the anti-uprush of the excavation is divided into six regions, and the structural anti-floating is divided into five regions in urban areas. To avoid geohazards caused by the rise in groundwater head, real-time monitoring of the pressure head in AqII is recommended.

Effects of surface loading on groundwater flow and skeletal deformation

Abstract This paper proposes a relationship for the physics and mechanics constants of porous media related to water storage rate and ground settlement under a surface load variation condition. This provides the basis for accurate calculation of ground subsidence. Traditional equations for vertical deformation, groundwater flow and land subsidence due to surface loading were developed using Jacob's assumptions. This paper derives a skeletal elastic specific storage rate. The new deformation and flow equations are similar to the traditional ones based on Jacob's assumptions except that the pore-water head in the traditional equations corresponds with the margin between the pore-water head and the water-column height given in the proposed equations representing the surface load. The analysis show that increasing the surface loading leads to land subsidence, rise in pore-water head and decrease in elastic water storage capacity. The maximum subsidence is equivalent to the subsidence triggered by lowering the water head to the equivalent water column height. The maximum rise of the water head is also equal to the equivalent water column height. The maximum water released to a specific volume of porous medium is close to that resulting from reduction in the water head by the equivalent column height.

Highlights of This Issue

The American Indian and Alaska Native (AI/AN) population bears a disproportionate burden of cancer incidence in the United States. To describe cancer incidence rates and trends in the AI/AN population compared with the non-Hispanic white population, Melkonian and colleagues used data from the central cancer registries linked with the Indian Health Service patient registration databases to identify cancers diagnosed between 2010 and 2015. The authors reported elevated rates of lung, colorectal, liver, kidney, and stomach cancer in the AI/AN population that varied by geographic region. This confirmed widening cancer disparities and highlighted missed opportunities for targeted interventions to reduce AI/AN cancer incidence.Over the last two decades, there has been a rise in head and neck cancers in the oropharynx, due to the human papillomavirus (HPV). These cancers require aggressive treatment with radiation, surgery, or chemotherapy. This study by Mahal and colleagues is the largest study to date on the incidence of HPV-positive oropharyngeal head and neck squamous cell carcinoma in the United States, finding that 75% of oropharynx cancers are related to HPV. The U.S. incidence of HPV-related throat cancer is 4.6 per 100,000 people, peaking amongst those ages 60 to 64, and highest in white men where it is the 6th most common incident nonskin cancer. The study shows that the favorable prognosis associated with Hp. is restricted to oropharynx cancer rather than other head and neck cancers and provides data to support education and prevention strategies, including vaccination.Helicobacter pylori (H. pylori) eradication has been shown to decrease gastric adenocarcinoma risk. The epidemiology of gastric lymphoma, which is also associated with H. pylori, and other rare subtypes of gastric cancer is less clear. This study by Chang and colleagues comprehensively evaluated the incidence trend and the survival of gastric cancer in Taiwan by histologic subtype. The incidence trends of gastric cancer in Taiwan from 1996 to 2013 were evaluated using data from the Taiwan Cancer Registry. The incidence of all gastric cancers in Taiwan decreased. However, the incidence of adenocarcinoma and lymphoma, both of which are associated with H. pylori, showed diverging trends. The disparity in the incidence trends warrants the need to search for additional risk factors of gastric lymphoma.The etiology of intrahepatic cholangiocarcinoma (ICC) is less well- known compared to hepatocellular carcinoma (HCC). As ICC has poor prognosis and response to conventional therapy, identifying diagnostic and prognostic biomarkers of this form of liver cancer is warranted. Liquid chromatography coupled to tandem mass spectrometry was used to measure non-invasively detected urinary metabolites in subjects from the U.S. (NCI-MD cohort) and Thailand (TIGER-LC cohort). Haznadar and colleagues found that metabolites were significantly increased in both, HCC and ICC in urine, but were significantly higher in ICC in urine and in tissue. Metabolite profile was robust at classifying ICC in combination with a clinically utilized marker, CA19-9, holding promise for diagnostic and prognostic evaluation of ICC.

Failure mechanism of unsaturated landslide dam under seepage loading – Model tests and corresponding numerical simulations

Due to the rapid cracking, sliding and packing of its geomaterials, a landslide dam (LD) is usually weaker in structure than the undisturbed ground and is more vulnerable to seepage loading. In addition, since the naturally packed geomaterials of an LD are mostly in an unsaturated state, it is necessary to use a suitable constitutive model that can describe the mechanical behaviour of the soils under an unsaturated/saturated state in a unified way and whose material parameters can be determined in a rational way in order to accurately simulate the failure mechanism of the LD. In this paper, water retention tests and flume tests were conducted on model LDs prepared with three different ground materials. An unsaturated soil constitutive model was selected for the corresponding numerical simulations. Based on the results of water retention tests and triaxial tests, the parameters of the LD materials were properly determined. Using these parameters, soil-water-air coupling finite element analyses were conducted to simulate the flume tests on the model LDs. By comparing the calculated results with the test results, it was found that the numerical method used in this paper has satisfactory accuracy for describing the different failure mechanisms of the model LDs under seepage loading. The results indicate that the material properties of the LDs, especially the strength and the difference in void ratio between the unsaturated and the saturated states, play important roles. In addition, the influence of the rate of the rise in water head was also investigated by numerical tests. The purpose of this research is to provide a scientific basis for decision-making in the disaster mitigation process of LDs with a comprehensive method for understanding the failure mechanism of these LDs.

Modeling the Spatial and Seasonal Variations of Groundwater Head in an Urbanized Area under Low Impact Development

Increasing impervious land cover has great impacts on groundwater regimes in urbanized areas. Low impact development (LID) is generally regarded as a sustainable solution for groundwater conservation. However, the effects of LID on the spatial-temporal distribution of groundwater are not yet fully understood. In this case study, a coupled Storm Water Management Model (SWMM) and Finite Element Subsurface FLOW system (FEFLOW) model was used to simulate surface and groundwater flow in an urbanized area in Shenzhen, China. After verification, the model was used to analyze the spatial-seasonal variations of groundwater head and hydrological processes under different LID scenarios. The results indicate that if the runoff from 7.5% and 15% of impervious area is treated by LID facilities, the annual surface runoff decreases by 5% and 9%, respectively, and the spatial average groundwater head relative to sea level pressure increases by 0.9 m and 1.7 m in the study area, respectively. The rise in groundwater head generally decreases from the recharge zones to the discharge zones surrounded by the streams and coastal waters. However, the groundwater head change is determined not only by the location in the catchment, but also by the hydraulic conductivity of underlying aquifer and LID infiltration intensity. Moreover, LID significantly enhances groundwater recharge and aquifer storage in the wet seasons; in turn it increases aquifer release and groundwater discharge in the dry seasons. However, LID has the potential to increase the risk of groundwater flooding during wet seasons in areas with poor aquifer drainage capacity and shallow groundwater depth. The findings from this study provide the basis for further assessing the benefit and risk of LID infiltration for groundwater supplementation in the urbanized areas.

Global human papilloma virus vaccine implementation: An update.

Human papillomavirus (HPV) infections continue to be one of the most common sexually transmitted infections worldwide. The oncogenic potential of this virus was well established in anogenital malignancies and oropharyngeal cancers. Even though a fall in cervical cancer rates has been reported worldwide, the subsequent rise in HPV-associated head and neck cancers among men and women have been reported from developed countries, necessitating the vaccination of adolescent boys as well. The objective of this narrative review is to provide an update on the current status of HPV vaccination worldwide. This will be helpful for clinicians in counseling parents and guardians as this vaccine mainly targets sexually naïve preadolescents. An electronic search of the databases was carried out to retrieve information concerning HPV vaccine implementation between July 2006 and 2017, with special emphasis on the current viewpoints, controversies and ethical issues. Globally, 74 countries have implemented the HPV vaccine in the national immunization schedule, and this vaccine is listed as an essential medicine by WHO. About 60% of the low- and lower-middle-income countries have implemented the vaccine with financial assistance from Gavi and WHO. The HPV vaccine is a safe vaccine with no serious adverse effects as per the data available from developed nations as well as low/lower middle/upper middle-income countries. However, long-term follow-up is essential to substantiate the impact of the vaccination programs in cancer prevention.

High-resolution InSAR constraints on flood-related subsidence and evaporite dissolution along the Dead Sea shores: Interplay between hydrology and rheology

Sinkhole generation and land subsidence are commonly attributed to dissolution of subsurface layers by under-saturated groundwater and formation of cavities. Along the Dead Sea (DS) shorelines, this process also involves seasonal flash floods that are drained into the subsurface by existing and newly formed sinkholes. We quantify the contribution of flash-floods to salt dissolution and land subsidence using high-resolution interferometric synthetic aperture radar (InSAR). Subsidence rates during a 3-year period (2012–2015) were calculated from 57 COSMO SkyMed X-band interferograms bracketing major flood events and intra-flood periods in 21 sinkhole sites. The sites are located within channels and alluvial fans along the western shores of the Dead Sea, Israel. The observed subsidence reaches maximum rates of ~2.5mm/day, accumulating in specific sites to 500mm/year. In most of the sinkhole sites a gradual increase in the annual subsidence rate is observed during the 3-year study period. Three different modes of response to floods were observed: (1) sites where floodwater is not directly channeled into sinkholes do not respond to floods; (2) sites adjacent to active channels with sinkholes are unaffected by specific floods but their subsidence rates increase gradually from early winter to mid-summer, and decay gradually until the following winter; and (3) sites in active channels with sinkholes are characterized by an abrupt increase in subsidence rates immediately after each flood (by a factor of up to 20) and by a subsequent quasi-exponential subsidence decay over periods of several months. In these latter sites, subsidence rates after each flood are temporally correlated with alternating groundwater levels in adjacent boreholes. The rapid rise in groundwater head following floods increases the hydraulic gradient of the under-saturated groundwater and hence also the groundwater discharge and the dissolution rate of the subsurface salt layer. A subsequent quasi-exponential water level drop results in similar deceleration in dissolution and subsidence rates, with a similar characteristic decay time of about 150days. The observed subsidence decay pattern may also be explained by viscoelastic relaxation of the overburden in response to instantaneously-formed dissolution cavities. Utilizing a Kelvin viscoelastic model, we show that the contribution of this process is most probably <30% of the total observed subsidence and is sensitive to the sediment mechanical properties. On a broader scale, this study demonstrates how high-resolution InSAR measurements can improve our understanding of subsurface dissolution and subsidence processes and provide independent constraints on the mechanical properties of heterogeneous alluvial sediments.

Squamous Cell Carcinoma DNA Detection Using Ultrabright SERS Nanorattles and Magnetic Beads for Head and Neck Cancer Molecular Diagnostics.

A rise in head and neck cancers in low and middle countries over recent years has prompted the need for low-cost, resource-efficient diagnostic technologies. Standard diagnosis with histopathology is often not feasible due to the low number of trained pathologists in these regions, resulting in delayed diagnosis and treatment. This study presents an alternative diagnostic method to standard histopathology. We developed a surface enhanced raman scattering (SERS) based method to distinguish squamous cell carcinoma from other cell lines. Using a "sandwich" method employing ultrabright SERA nanorattles and magnetic beads, we directly targeted specific nucleic acid markers of squamous cells. Our method was able to detect the presence of squamous cells with high sensitivity and specificity, supporting its potential for use as a diagnostic tool in head and neck fine needle aspirations (FNA).

Investigations of hydraulic operating conditions of air lift pump with three types of air-water mixers

Abstract: Investigations of hydraulic operating conditions of air lift pump with three types of air-water mixers. The paper presents the analysis of results of the investigations concerning the influence of various constructive solutions of the air-water mixers on hydraulic operating conditions of the air lift pump. The scope of the investigations encompassed the determination of characteristics of delivery head and delivery rate for three types of air-water mixers applied in the constructed air lift pump. Using the obtained results, the efficiency of the three types of air-water mixers applied in this air lift pump was determined. The analysis was carried out and there was checked whether the improved analytical Stenning-Martin model can be used to design air lift pumps with the air-water mixers of these types. The highest capacity in the water transport was reached by the air lift pump with the 1st type air-water mixer, the lowest one – with the 3rd type air-water mixer. The water flow in the air lift pump increases along with the rise in the air flow. The lower are the hydraulic losses generated during flow of the air flux by the air-water mixer, the higher is the air lift pump capacity. Along with the rise in the water delivery head, the capacity of the air lift pump decreases. The highest efficiency is reached by the air lift pump with the 1st type air-water mixer, the lowest – with the 3st type air-water mixer. The efficiency of the air lift pump for the three investigated types of air-water mixers decreases along with the rise in air flow rate and water delivery head. The values of submergence ratio (h/L) of the delivery pipe, calculated with the use of the improved analytical Stenning-Martin model, coincide quite well with the values of h/L determined from the measurements.

SAR and temperature distribution in the rat head model exposed to electromagnetic field radiation by 900 MHz dipole antenna

Rats are often used in the electromagnetic field (EMF) exposure experiments. In the study for the effect of 900 MHz EMF exposure on learning and memory in SD rats, the specific absorption rate (SAR) and the temperature rise in the rat head are numerically evaluated. The digital anatomical model of a SD rat is reconstructed with the MRI images. Numerical method as finite difference time domain has been applied to assess the SAR and the temperature rise during the exposure. Measurements and simulations are conducted to characterize the net radiated power of the dipole to provide a precise dosimetric result. The whole-body average SAR and the localized SAR averaging over 1, 0.5 and 0.05 g mass for different organs/tissues are given. It reveals that during the given exposure experiment setup, no significant temperature rise occurs. The reconstructed anatomical rat model could be used in the EMF simulation and the dosimetric result provides useful information for the biological effect studies.

Evaluating Frictional Temperature Rise in Sliding Surface of Artificial Hip Joint Materials with Different Loading Conditions

Friction between articulating surfaces cause temperature rise in acetabular cup and femoral head. This heating may in uence the rate of wear, fatigue, creep, oxidative degradation of bearing materials and may terminate surrounding tissue. The objective of this study is to determine temperature rise with di erent applied load for the articulating surfaces of conventional ultra high molecular weight polyethylene (UHMWPE) and vitamin E blended ultra high molecular weight polyethylene (VE-UHMWPE) acetabular components paired with a ceramic femoral component in bovine calf serum lubrication condition. Additionally frictional torque between the bearing surfaces was measured and friction coe cient was calculated. Frictional measurements of the joints were carried out on a custom made hip joint friction simulator. Various levels of static loads were applied on 28 mm diameter prostheses. In exion-extension plane, a simple harmonic oscillatory motion between ±24◦ was applied to the UHMWPE acetabular component. The period of motion was 1 Hz and the tests were run up to 12,000 cycles. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. The results were compared in terms of UHMWPE and vitamin E blended UHMWPE.

Abstract 5129: Identification of therapeutic targets for HPV-positive and HPV-negative head and neck cancers using high throughput RNAi screening

Abstract Cancers of the head and neck account for three percent of all malignancies in the United States and is the sixth most common type of cancer worldwide. Historically, the two most common risk factors for head and neck squamous cell carcinomas (HNSCC) were tobacco use and/or heavy alcohol consumption. Recent growing evidence strongly supports a role for human papillomavirus (HPV) in a subset (15-30%) of HNSCC and there is currently a rise in HPV-related head and neck cancers. In order to improve treatment of head and neck cancers and identify etiology-specific therapeutic targets, we applied a functional genomics based approach utilizing high-throughput RNAi (HT-RNAi) to identify genes specifically involved in growth of either HPV-positive or HPV-negative HNSCC cells. A HT-RNAi assay was developed to quantify the effects of gene specific siRNA on growth inhibition of two HPV-positive (SCC-090 and UMSCC-047) and two HPV-negative (SCC-25 and CAL-27) HNSCC cell lines. For HT-RNAi screening, the four cell lines were reverse-transfected with siRNA from a library targeting 7000 druggable genes with four siRNA per gene and assessed for growth modulation at 96 hours post transfection. The data was normalized using Z-score analysis and statistical cut-offs were set. Following data analysis, we generated a hit list of gene targets that are involved in growth of HPV-positive or HPV-negative HNSCC cells. Validation of these genes will identify potential therapeutic targets for head and neck tumors depending on their HPV status. Furthermore, these findings demonstrate the effectiveness of using HT-RNAi as a tool for the identification of etiologic-specific targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5129. doi:1538-7445.AM2012-5129

Water losses through paddy bunds: Methods, experimental data, and simulation studies

Summary Irrigated rice landscapes increasingly experience water scarcity, and the bunds surrounding paddy rice fields (also referred to as dikes, banks or levees) have been pointed out as possible causes for low water productivities. Yet, detailed experimental data to confirm this assumption is missing, as well as an identification of the most decisive factors for bund infiltration. The objective of this study was therefore to quantify water fluxes through bunds in a terraced paddy landscape both experimentally and by numerical analysis. Two bunds with a respective age of 20 (young bund: BY) and 100 years (old bund: BO) were investigated at the end of the rice-growing season. Soil core samples revealed a compacted hard pan at 30 cm depth in both bunds. Hydraulic conductivity was very high and variable especially in the upper part of the bunds. For direct measurements of infiltration into the bund, a double-frame infiltrometer was introduced analogous to a double ring infiltrometer. Measured infiltration rates in bund BO at ponding water depths (PWDs) of 3, 5 and 7 cm amounted to 480, 270 and 550 cm2 d−1, respectively, and no cross-flow was observed. At bund BY, the infiltrating water resulted in an increasing water level on the lower field, and the cross-flow was 807, 4205 and 5506 cm2 d−1 at corresponding PWDs. However, no reliable infiltration measurements could be recorded. Tensiometers installed in the bunds during the infiltration experiments revealed a nearly instantaneous rise in pressure head after flooding throughout the profile in bund BY, indicating preferential water fluxes. In bund BO, contrarily, pressure heads underneath the hard pan rose slowly and with a time lag and thus show dominant matrix fluxes. Different infiltration rates in the investigated bunds could be mainly attributed to a lower bulk density and enhanced macroporosity in the young bund BY. The existence of a hard pan in a bund does not necessarily reduce percolation losses, as it might become perforated by macropores originating from bio-activity. A sensitivity analysis realized with HYDRUS 1.05 revealed that under-bund percolation is most strongly influenced by the hydraulic conductivity in the upper and middle bund. Ponding water depth and groundwater table are less important, while soybean cultivation, bund width and elevation difference only play a minor role. For each conductivity profile, there is a critical bund width underneath which cross-flow occurred. A detailed description of the bunds’ water fluxes needs to be included in hydrologic modelling of irrigated rice landscapes.

Two Cohorts of Severely Injured Trauma Patients, Nearly Two Decades Apart: Unchanged Mortality But Improved Quality of Life Despite Higher Age

The care for trauma patients has undergone major changes during the last decades. Additionally, many injury prevention measures have been established. The objective of these efforts was to reduce the number of traumatic incidents and to reduce mortality and morbidity in injured patients. The aim of our study was to assess how these measures and improved care have altered trauma mechanisms, occurrence of injuries, treatment, and outcome in the trauma population treated at our trauma center. Two cohorts of trauma patients with an Injury Severity Score >15, treated at the University Medical Center Groningen were compared. The first cohort was treated from 1985 to 1990, the second cohort from September 2002 to January 2005. The annual mean number of severely injured patients increased by 76%. Fourteen percent more patients had sustained an injury at home. The mean age increased from 33 +/- 22 years to 41 +/- 23 years. The presence of severe head and neck injuries in the patients increased from 62% to 73%. Inhospital mortality remained unchanged at 25%. The outcome of survivors improved; 67% of patients made a moderate or good recovery versus 40% almost 20 years ago. Striking are the consequences of the aging of the Dutch population: an almost 10-year increase in mean age and a rise in severe head and neck injuries in the population treated at our trauma center. The unchanged mortality and improved outcome of survivors represented the enhanced trauma care.

六郷扇状地における地下水人工涵養の実施と成果

The Rokugo alluvial fan lies around 39° 25' N and 140° 34' E in northern Japan. The distance between the proximal fan at 90 meters above sea level and the distal fan at 45 meters is about four kilometers. The unconfined aquifer of the fan consists mainly of gravel and sand. Four artificial recharge basins were constructed on the central part of the fan. Observation in struments are wells and piezometers installed in depths of 20 m and 50 m. In this paper, the author discusses the effects of artificial recharge using the basin No.2 at the center of the fan. The recharge experience was done during the period when ground water level was affected by melting snow, from April 8 to May 2, 1998. Results obtained are as follows : first, artificial recharging caused a rise in the hydraulic head, which was related to the Rokugo town area situated on the distal fan, and second, because the author supplied the basin No.2 with water with a low water temperature after snow melted, the characteristic phenomenon of ground water temperature was recorded by piezometers in a depth of 20 m at both sites of central and distal fan. Consideration of this point is a theme for future studies. As a synthetic judgment, the artificial recharge of ground water contributes to sustainable aquifer management in the alluvial fan.

DECOVALEX III BMT3/BENCHPAR WP4: The thermo-hydro-mechanical responses to a glacial cycle and their potential implications for deep geological disposal of nuclear fuel waste in a fractured crystalline rock mass

A number of studies related to past and on-going deep repository performance assessments have identified glaciation/deglaciation as major future events in the next few hundred thousand years capable of causing significant impact on the long term performance of the repository system. Benchmark Test 3 (BMT3) of the international DECOVALEX III project has been designed to provide an illustrative example that explores the mechanical and hydraulic response of a fractured crystalline rock mass to a period of glaciation . The primary purpose of this numerical study is to investigate whether transient events associated with a glacial cycle could significantly influence the performance of a deep geological repository in a crystalline Shield setting. A conceptual site-scale (tens of kilometres) hydro-mechanical (HM) model was assembled based primarily on site-specific litho-structural, hydrogeological and geomechanical data from the Whiteshell Research Area in the Canadian Shield, with simplification and generalization. Continental glaciological modelling of the Laurentide ice sheet through the last glacial cycle lasting approximately 100,000 years suggests that this site was glaciated at about 60 ka and between about 22.5 and 11 ka before present with maximum ice sheet thickness reaching 2500 m and maximum basal water pressure head reaching 2000 m. The ice-sheet/drainage model was scaled down to generate spatially and temporally variable hydraulic and mechanical glaciated surface boundary conditions for site-scale subsurface HM modelling and permafrost modelling. Under extreme periglacial conditions permafrost was able to develop down to the assumed 500-m repository horizon. Two- and three-dimensional coupled HM finite-element simulations indicate: during ice-sheet advance there is rapid rise in hydraulic head, high transient hydraulic gradients and high groundwater velocities 2–3 orders of magnitude higher than under nonglacial conditions; surface water recharges deeper than under nonglacial conditions; upon ice-sheet retreat, the gradients reverse; fracture zone network geometry, interconnectivity and hydraulic properties significantly influence flow domain response; residual elevated heads are preserved for 10,000 s in the low-diffusivity rock; and no hydraulic jacking or shear failure occurs at depth. It was found that transient coupled modelling is necessary to capture the essence of glacial effects on Performance Assessment. Model dimensionality also significantly affects simulated results.

FDTD computation of temperature rise in the human head for portable telephones

Temperature rises in the human head for portable telephones were computed with an anatomically based head model at 900 MHz and 1.5 GHz. The specific absorption rate (SAR) in the human head was determined using the finite-difference time-domain (FDTD) method, while a bioheat equation was numerically solved also using the FDTD method. The portable telephone was modeled by a quarter-wavelength monopole antenna on a dielectric covered metal box. The source geometries considered were the telephone barely touching the ear and the telephone pressing the ear, both having a vertical alignment at the side of the head. The antenna output power was set to be consistent with the portable telephones of today: 0.6 W at 900 MHz and 0.27 W at 1.5 GHz. Computed results show that a phone time of 6-7 min yields a temperature rise of approximately 90% of the steady-state value. Application of the ANSZ/IEEE safety guidelines restricting the 1-g-averaged spatial peak SAR to 1.6 W/kg results in the maximum temperature rise in the brain of 0.06/spl deg/C, and application of the ICNIRP/Japan safety guidelines restricting the 10-g-averaged spatial peak SAR to 2 W/kg results in the maximum temperature rise in the brain of 0.11/spl deg/C, both at 900 MHz and 1.5 GHz.

On the long-term hydraulic gradient in the thick clayey aquitard in the Sarnia region, Ontario

Much of the southwestern part of Ontario between Lake Huron and Lake Erie has a thin freshwater aquifer overlain by an aquitard of Late Pleistocene clayey glaciolacustrine deposits and underlain by a thick Devonian shale aquitard. In a large area east of the St. Clair River, where the Quaternary aquitard is 30-50 m thick, groundwater of Pleistocene origin (identified by 18O and 2H signature) occurs in the aquifer and in the bottom part of the Quaternary aquitard. Numerous piezometer nests in the aquitard show a downward hydraulic gradient with depth. In some areas, the aquitard has downward gradients only in the upper part and upward gradient in the lower part, indicating a transient condition. The piezometer nests in the clayey aquitard also show an increase in Cl- concentration with depth. Long-term piezometer monitoring at two sites show a major shift in the aquitard hydraulic gradient since 1983 and a large rise in head in the underlying aquifer. Analyses of initial aquifer water levels, reported in well drilling records, indicate a large decline in the potentiometric surface of the aquifer between the 1940's and the 1970's followed by a recent rise in the surface in part of the region. This pattern is consistent with well drilling and water use records indicating that 7000 wells were installed in the aquifer in the three decades since 1940 and that groundwater use has greatly diminished in the past 10-15 years due to rural pipeline distribution of lake and river water. The hydraulic gradient in the aquitard is slowly adjusting to the rise in the aquifer potentiometric surface. One-dimensional solute transport modelling provides close matches to the vertical profiles of Cl- migrating upward from the aquifer since deglaciation, 15 000 - 18 000 years before present, by diffusion with little or no advection. The lack of advection indicates a near-neutral long-term hydraulic gradient. As the withdrawal rate of water from the aquifer continues to decline, it is expected that the hydraulic head in the aquitard in much of the area westward of the recharge area will continue to adjust for many decades.Key words: clay, aquitard, aquifer, water use, hydraulic gradient.

Deformation‐Induced Changes in Hydraulic Head During Ground‐Water Withdrawal

AbstractGround‐water withdrawal from a confined or semiconfined aquifer causes three‐dimensional deformation in the pumped aquifer and in adjacent layers (overlying and underlying aquifers and aquitards). In response to the deformation, hydraulic head in the adjacent layers could rise or fall almost immediately after the start of pumping. This deformation‐induced effect is analyzed by a linear poroelasticity model using properties typical of unconsolidated sedimentary materials. Model simulations suggest that an adjacent layer undergoes horizontal compression and vertical extension when pumping begins. Hydraulic head initially drops in a region near the well and close to the pumped aquifer, but rises outside this region. Magnitude of head change varies from a few centimeters to more than 10 centimeters. Factors that influence the development of deformation‐induced effects includes matrix rigidity (shear modulus), the arrangement of aquifer and aquitards, their thicknesses, and proximity to land surface. Induced rise in hydraulic head is prominent in an aquitard that extends from land surface to a shallow pumped aquifer. Induced drop in hydraulic head is likely observed close to the well in an aquifer that is separated from the pumped aquifer by a relatively thin aquitard. Induced effects might last for hours in an aquifer, but could persist for many days in an aquitard. Induced effects are eventually dissipated by fluid flow from regions of higher head to regions of lower head, and by propagation of drawdown from the pumped aquifer into adjacent layers.