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•Seasonal shifts in groundwater recharge processes influence groundwater temperature.•Increased surface water recharge during floods influence groundwater temperature.•Increased ...groundwater recharge in comparatively “cool seasons”.•Waste heat from underground structures impact urban groundwater temperature.•Global warming adaptation strategies can influence groundwater temperature.
Climate change will have both quantitative and qualitative effects on groundwater resources. These impacts differ for aquifers in solid and unconsolidated rock, in urban or rural locations, and in the principal processes of groundwater recharge.
Having knowledge about the intrinsic key parameters (aquifer geometries, storage properties, groundwater renewal rates, residence times, etc.), the principal groundwater recharge processes, and the temperature imprinting makes it possible to compare and forecast the sensitivity of individual aquifers to climate change.
The sensitivity of future groundwater temperature development for selected climate projections was qualitatively investigated for representative Swiss unconsolidated rock groundwater resources in the Central Plateau as well as the Jura and Alpine region.
For non-urban and rural areas, climate change is expected to have a strong overall impact on groundwater temperatures. In urban areas, however, direct anthropogenic influences are likely to dominate. Increased thermal subsurface use and waste heat from underground structures, as well as adaptation strategies to mitigate global warming, increase groundwater temperatures. Likewise, measurements for the city of Basel show that groundwater temperatures increased by an average of 3.0 ± 0.7 °C in the period from 1993 to 2016, and that they can exceed 18 °C, especially in densely urbanized areas. Similarly, regarding shallow aquifers with low groundwater saturated zone thicknesses, such as in Davos (Canton Grisons), groundwater temperatures will strongly be influenced by changes in groundwater recharge regimes. In contrast, groundwater temperature changes within deep aquifers with large groundwater saturated zone thicknesses, such as in Biel/Bienne (Canton Bern), or in some cases in aquifers with large distances from the land surface to the groundwater table and extended unsaturated zones, such as in Winterthur (Canton Zurich), are strongly attenuated and can only be expected over long time periods.
In the context of the presented research we hypothesized that quantitative groundwater recharge and the associated temperature imprinting of aquifers is primarily determined by infiltrating surface waters (i.e. “river-fed aquifers”). We show that seasonal shifts in groundwater recharge processes could be an important factor affecting future groundwater temperatures. Moreover, the interaction with surface waters and increased groundwater recharge during high runoff periods are likely to strongly influence groundwater temperatures. Accordingly, for the “business as usual” climate change scenario and for the end of the century, a shift in precipitation and river flood events from summer to winter months could be accompanied by an increase in groundwater recharge in comparatively cool seasons, which would be accompanied by a tendency to “cool down” groundwater resources.
The primary stability of the acetabular cup (AC) implant is an important determinant for the long term success of cementless hip surgery. However, it remains difficult to assess the AC implant ...stability due to the complex nature of the bone-implant interface. A compromise should be found when inserting the AC implant in order to obtain a sufficient implant stability without risking bone fracture. The aim of this study is to evaluate the potential of impact signals analyses to assess the primary stability of AC implants inserted in cadaveric specimens.
AC implants with various sizes were inserted in 12 cadaveric hips following the same protocol as the one employed in the clinic, leading to 86 different configurations. A hammer instrumented with a piezoelectric force sensor was then used to measure the variation of the force as a function of time produced during the impact between the hammer and the ancillary. Then, an indicator I was determined for each impact based on the impact momentum. For each configuration, twelve impacts were realized with the hammer, the value of the maximum amplitude being comprised between 2500 and 4500 N, which allows to determine an averaged value IM of the indicator for each configuration. The pull-out force F was measured using a tangential pull-out biomechanical test.
A significant correlation (R2 = 0.69) was found between IM and F when pooling all data, which indicates that information related to the AC implant biomechanical stability can be retrieved from the analysis of impact signals obtained in cadavers.
These results open new paths in the development of a medical device that could be used in the future in the operative room to help orthopedic surgeons adapt the surgical protocol in a patient specific manner.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Polycrystalline UO2 discs were implanted with 500 keV helium ions at different temperatures (200, 400 and 600 °C) and fluences (1 and 3 × 1016 at cm−2), and further characterised by transmission ...electron microscopy (TEM). Examinations performed on the more concentrated sample implanted at 600 °C allowed us to observe platelets for the first time in the UO2 material in planes parallel to {111}UO2. A complete study was undertaken in grains oriented along <1 0 0>, <1 1 0> and <1 1 1> directions to determine {1 1 1} variant equivalence on platelet formation. Their features like density and size have been characterised with an appropriate statistic.
•Helium platelets have been observed by TEM for the first time in uranium dioxide.•Platelets form from 600 °C and from 0.95 at. % of helium.•Platelet distribution in {1 1 1} habit planes depends on UO2 crystallographic orientation.•High helium concentration and high internal pressure are contained in platelets.
Highlights • Acetabular cup implants were inserted into 20 bovine bone samples with different cavity diameter. • An impact hammer was designed and was used to measure the impact momentum. • ...Tangential stability tests were performed. • The AC implant stability and the impact momentum were significantly correlated (R2 = 0.83).
The implant primary stability of the acetabular cup (AC) is an important parameter for the surgical success of press-fit procedures used for the insertion of cementless hip prostheses. In previous ...studies by our group (Mathieu, V., Michel, A., Lachaniette, C. H. F., Poignard, A., Hernigou, P., Allain, J., and Haiat, G., 2013, "Variation of the Impact Duration During the in vitro Insertion of Acetabular Cup Implants," Med. Eng. Phys., 35(11), pp. 1558-1563) and (Michel, A., Bosc, R., Mathieu, V., Hernigou, P., and Haiat, G., 2014, "Monitoring the Press-Fit Insertion of an Acetabular Cup by Impact Measurements: Influence of Bone Abrasion," Proc. Inst. Mech. Eng., Part H, 228(10), pp. 1027-1034), the impact momentum and duration were shown to carry information on the press-fit insertion of the AC within bone tissue. The aim of the present study is to relate the impact momentum recorded during the AC insertion to the AC biomechanical primary stability. The experimental protocol consisted in testing 13 bovine bone samples that underwent successively series of 15 reproducible mass falls impacts (5 kg, 5 cm) followed by tangential stability testing. Each bone sample was tested with different hole sizes in order to obtain different stability configurations. The impact momentum and the tangential primary stability reach a maximum value for an interference fit equal to around 1 mm. Moreover, a correlation between the impact momentum and the stability was obtained with all samples and all configuration (R2 = 0.65). The implant primary stability can be assessed through the measurement of the impact force signal analysis. This study opens new paths for the development of a medical device which could be used as a decision support system to assist the surgeon during the insertion of the AC implant.
Water vapor transport has been highlighted as a critical process in Arctic snowpacks, shaping the snow cover structure in terms of density, thermal conductivity, and temperature profile among others. ...Here, we present an attempt to describe the thermally-induced vertical diffusion of water vapor in the snow cover and its effects of the snowpack structure using the SNOWPACK model. Convection, that may also constitute a significant part of vapor transport, is not addressed. Assuming saturated conditions at the upper boundary of the snowpack and as initial condition, the vapor flux between snow layers is expressed by a 1-dimensional transient diffusion equation, which is solved with a finite difference routine. The implications on the snowpack of this vertical diffusive flux, are analyzed using metrics such as the cumulative density change due to diffusive vapor transport, the degree of over- or undersaturation, the instantaneous snow density change rate, and the percentage of snow density change. We present results for four different regions sampling the space of natural snow cover variability: Alpine, Subarctic, Arctic, and Antarctic sea ice. The largest impact of diffusive water vapor transport is observed in snow on sea ice in the Weddell Sea and the shallow Arctic snowpack. The simulations show significant density reductions upon inclusion of diffusive water vapor transport: cumulative density changes from diffusive vapor transport can reach −62 and −66 kg m−3 for the bottom layer in the shallow Arctic snowpack and snow on sea ice, respectively. For comparison, in deeper snow covers, they rarely exceed −40 kg m−3. This leads to changes in density for shallow snowpacks at the soil-snow interface in the range of −5 to −21%. Mirroring the density decease at depth is a thicker deposition layer above it with increase in density around 7.5%. Similarly, for the sea ice, the density decreased at the sea ice-snow interface by −20%. We acknowledge that vapor transport by diffusion may in some snow covers—such as in thin tundra snow—be small compared to convective transport, which will have to be addressed in future work.
Abstract The use of tricalcium silicate-based cement (TSBC) as bone substitute material for implant stabilization is promising. However, its mechanical behavior under fatigue loading in presence of a ...dental implant was not reported so far because of the difficulty of measuring TSBC properties around a dental implant in a nondestructive manner. The aim of this study is to investigate the evolution of the 10 MHz ultrasonic response of a dental implant embedded in TSBC versus fatigue time. Seven implants were embedded in TSBC following the same experimental protocol used in clinical situations. One implant was left without any mechanical solicitation after its insertion in TSBC. The ultrasonic response of all implants was measured during 24 h using a dedicated device deriving from previous studies. An indicator I based on the temporal variation of the signal amplitude was derived and its variation as a function of fatigue time was determined. The results show no significant variation of I as a function of time without mechanical solicitation, while the indicator significantly increases ( p <10−5 , F =199.1) at an average rate of 2.2 h−1 as a function of fatigue time. The increase of the indicator may be due to the degradation of the Biodentine–implant interface, which induces an increase of the impedance gap at the implant surface. The results are promising because they show the potentiality of ultrasonic methods to (i) investigate the material properties around a dental implant and (ii) optimize the conception of bone substitute materials in the context of dental implant surgery.
Abstract The acetabular cup (AC) is an implant impacted into a bone cavity and used for hip prosthesis surgery. Initial stability of the AC is an important factor for long term surgical success. The ...aim of this study is to determine the variations of the impact duration during AC implant insertion. Twenty-two bone samples taken from bovine femurs were prepared ex vivo for the insertion of an acetabular cup implant, following the surgical procedure used in the clinic. For each bone sample, ten impacts were applied using reproducible mass falls (3.5 kg) in order to insert the AC implant. Each impact duration was recorded using a wide bandwidth force sensor. For all bone samples, the impact duration was shown to first decrease as a function of the impact number, then reaching a stationary value equal in average to 4.2 ± 0.7 ms after an average number of 4.1 ± 1.7 impacts. The impact duration may be related to variations of the bone–implant interface contact rigidity because of an increase the amount of bone tissue in contact with the AC implant. Measurements of impact duration have a good potentiality for clinical application to assist the surgeon during the insertion of the AC implant, providing valuable information on the bone–implant interface contact properties.
Quantitative ultrasound techniques can be used to retrieve cortical bone quality. The aim of this study was to investigate the anatomic variations in speed of sound (SOS) in the radial direction of ...cortical bone tissue. SOS measurements were realized in 17 human cortical bone samples with a 3.5-MHz transverse transmission device. The radial dependence of SOS was investigated in a direction perpendicular to the periosteum. For each sample, bone porosity was measured using an X-ray micro-computed tomography device. The mean SOS was 3586 ± 255 m/s. For 16 of 17 specimens, similar radial variations in SOS were observed. In the periosteal region, SOS first decreased in the direction of the endosteum and reached a minimum value approximately in the middle of the cortical bone. SOS then increased, moving to the endosteal region. A significant negative correlation was obtained between SOS and porosity (R = -0.54, p = 0.02).
Many physically‐based models for climate change impact studies require sub‐daily temporal resolution of the forcing data to provide meaningful predictions. However, climate scenarios are typically ...available at daily time step, severely limiting the application of such physically‐based models. In this study, we propose an enhanced delta‐change method for downscaling climate change scenarios from daily to hourly resolution. The approach presented provides objective criteria for assessing the quality of the determined delta and downscaled time series, while also fixing issues of common quantile mapping methods used for spatial downscaling related to the decrease of correlation between different variables. However, this new approach has limitations in correctly representing statistically extreme events and changes in the frequency of discontinuous events such as precipitation. Smoothing of historical and future data is required prior to applying the delta‐change method, and the related parameters are found to have a subtle impact on the correctness of the representation of the seasonal means as well as the resulting (artificial) variability in the scenario data product. This new method is universal and can be applied with smoothing approaches apart from the harmonic fitting used in this work and in the past. In this study, the assessment suggested the use of seven harmonics for the smoothing of the input data as a best choice of this parameter for the data used. The method is applied to a Swiss climate change scenario data set, CH2018, and to a complement of this set to a Swiss alpine measurement network obtained by spatial transfer of CH2018, resulting in a set of 68 climate change scenarios at hourly resolution for 188 stations over Switzerland significantly expanding upon the spatial and temporal resolution of the CH2018 data set. All source code to perform such an analysis and the complete data product are provided open access.
The CH2018 climate change scenarios are spatially extended to cover a Swiss alpine measurement network. This extended data set is then downscaled to hourly resolution. The employed downscaling method (delta‐change approach) is explained and a new assessment method for choosing optimal parameters for the downscaling process is presented. All the downscaled time series together with the code to perform the assessment and the downscaling are publicly available.
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