Middle Depths Research Articles

Advancements in nearshore wave modeling: A unified one-layer nonhydrostatic approach

This work presents a novel one-layer nonhydrostatic formulation and model for nearshore waves. The proposed governing equations define velocities and pressures at arbitrary distances from the still water and only contain spatial derivatives of maximum second order. The formulation can be unified into the existing nonhydrostatic models by defining the variables at the middle depth and neglecting certain additional terms. A Stokes-type Fourier analysis was performed to analyze the formulations' properties and determine the location of variables. The proposed formulation exhibited a clear superiority in describing both the linear and nonlinear properties of the coastal waves. The equations were numerically solved using a hybrid-finite, volume-finite difference scheme. The resulting model accurately described the wave-breaking and runup processes that occurred due to the adoption of a shock-capturing scheme and seabed elevation reconstruction. The suggested novel numerical model was validated against two theoretical benchmark tests and three wave transformation experiments.

One-dimensional self-weight consolidation of layered soil under variable load and semi-permeable boundary condition

In this study, an analytical solution is proposed to describe one-dimensional self-weight consolidation of two-layer soil under variable load and semi-permeable boundary condition. The analytical solution is comprehensively validated against existing field test, analytical solution and numerical simulation results. The influence of drainage capacity of boundary, self-weight, load rate, and soil layering features are then investigated. The difference of consolidation ratio between the complete pervious boundary condition and the semi-permeable boundary condition decreases with increasing semi-permeability coefficient R. Considering the self-weight will increase the excess pore pressure and make the maximum pressure appear below the middle depth, especially at the early time. The effect will be weaker and weaker and finally disappear. The dissipation of excess pore pressure is significantly impeded if the soil layer with lower consolidation coefficient is at the bottom. Finally, the design curve of the time for practical completion of consolidation (tst) is provided. An almost flat part can be observed in the curve if the relative thickness of the layer with lower consolidation coefficient ranges from 0.1 to 0.23, indicating that the influence of relative thickness on tst is negligible over this range, which provides a helpful reference for two-layer soil consolidation in engineering practices.

Digital assessments of soil organic carbon storage using digital maps provided by static and dynamic environmental covariates

AbstractUnderstanding the vertical and lateral distribution of soil organic carbon (SOC) and soil organic carbon density (SOCD) is indispensable for soil use and environmental management because of their vital role in soil quality assessments. Primarily, they are needed in calculating soil organic carbon storage (SOCS). The objective of this research was to provide digital maps of SOC and SOCD variation as well as their uncertainties at multiple standardized depths (H1: 0–5, H2: 5–15, H3: 15–30, H4: 30–60 and H5: 60–100 cm) using a parsimonious model with optimized terrain‐related attributes and satellite‐derived data. SOCS were evaluated at soil subgroup levels. An area of about 808 km2 with varying elevation, plant cover and lithology from the Miandoab region, West Azerbaijan Province, Iran was selected as a case study area. A total of 386 soil samples were collected from 104 profiles comprising various soil genetic horizons. A continuous spline function was then fitted to the target properties in advance of creating a dataset at five standard depth intervals (following the GlobalSoilMap project). These were then grouped into three classes including top (H1), middle (H2, H3 and H4) and bottom (H5) depths to ease interpretation. Static and dynamic covariates (30‐m resolution) were derived from a digital elevation model (DEM) and a suite of Landsat‐8 spectral imageries, respectively. Four candidate models including stepwise multiple linear regression (SMLR), random forest (RF), cubist (CU) and extreme gradient boosting (XGBoost) Tree were tested in this study. Finally, the digital maps at 30‐m resolution of SOC and SOCD and their uncertainties were prepared using the best‐fit model and the bootstrapping method, respectively. Four soil subgroups (Gypsic Haploxerepts, Typic Calcixerepts, Typic Haploxerepts and Xeric Haplocalcids) were identified across the study area. The covariates had variable contributions on the evaluated models. The XGBoost Tree model generally outperformed other models for prediction of SOC and SOCD (R2 = 0.60, on average). Regardless of soil subgroups, the uncertainty analysis showed that the SOCD map had a low prediction interval range value indicating high accuracy. Additionally, the highest SOCS and SOCD was observed at the top followed by middle and bottom depths in the study area. All subgroups exhibited a decreasing trend of SOCD with increasing depth. A similar trend was also observed for SOCS. The highest SOCD (on average) was observed in Gypsic Haploxerepts (4.71 kg C/m2) followed by Typic Calcixerepts (4.46 kg C/m2), Typic Haploxerepts (4.45 kg C/m2) and Xeric Haplocalcids (4.40 kg C/m2). Overall, the SOCS normalized by area within soil order boundaries was greater in Inceptisols than Aridisols across the study area. The findings of this study provide critical information for sustainable management of soil resources in the area for agricultural production and environmental health in the Miandoab region of Iran.

Evaluating Long-Term Performance of a Residential Ground-Source Heat Pump System under Climate Change in Cold and Warm Cities of Japan

A residential ground-source heat pump system often requires a long payback time to recover the capital cost. Long-term uncertainty in such a system’s performance increases as the climate changes. This study compares 20-years hourly heating/cooling demands of a typical residence in the present (2000–2020) and in the future (2076–2095) for two locations in Japan. This study also calculated soil temperatures as heat sources through 1D heat-transfer simulation based on the A1B climate scenario in the Intergovernmental Panel on Climate Change’s Special Report. System performance and simple payback times were compared in one cold and one warm city in Japan (Sapporo and Tokyo, respectively). Soil temperatures at a middle depth of a borehole heat exchanger were predicted to increase in the future by ~1 °C, with insignificant effects on a borehole heat exchanger. Seasonal performance factors increased in Sapporo because thermal demands would be kept even in the future, but decreased in Tokyo, which has a higher ratio of the energy used in operating the system in cooling mode compared with its small heating demand. The simple payback time was estimated at 16.2 and >20 years in Sapporo and Tokyo, respectively, both in the present and future, with the constant energy prices. If oil and gas prices doubled, the payback time would be halved in Sapporo to 8.4 years but remain around 20 years or more in Tokyo.

Origin and implication of two newly identified peraluminous A-type granites in the early Paleozoic orogeny, Southeast Asia

Abstract: The amalgamation of the Yangtze and the Cathaysia Block in Neoproterozoic time led to the formation of the South China Block (SCB) and generated the Jiangnan Orogen with the occurrences of juvenile magmatic rocks. After this orogeny, a typical collisional orogen formed during the early Paleozoic period in Southeast Asia which is mainly distributed in the Wuyi-Nanling-Yunkai area in the SCB. However, the transitional time from syn-collisional compression to post-collisional extension is debatable. Here, we present new data on zircon U-Pb zircon ages, Lu-Hf isotopes, and geochemistry for the Guzhang and Shadi granites from the Nanling area, South China. Both plutons have similar zircon 238U/206Pb ages of ca. 430 Ma. Petrographic and geochemical characteristics (e.g., FeOt/(FeOt+MgO) = 0.82–0.95) indicate that both granites are peraluminous A-type, with high Ga/Al ratios (2.43–2.91) as well as high concentrations of Zr, Nb, Ce, Y (sum values from 327 to 527 ppm), and formation temperature (820°C–845°C). Shadi granite exhibit high positive εHf(t) values (clustering within 0 to +6) while Guzhang granite show relatively lower εHf(t) values (−8.7 to −2.9). Their mildly negative to positive zircon εHf(t) values are higher than that of many coeval granites and can be derived from anhydrous melting of tonalitic genesis in the middle crustal depth, with the Shadi pluton having more orthometamorphite in the source. The ages and Hf isotopic compositions of inherited zircons (εHf(t = 960 Ma) = 9.2, εHf(t = 950 Ma) = 7.3) suggest that the Neoproterozoic juvenile magmatic rocks in the Jiangnan Orogen were a significant source for these granites. We interpret these A-type granites derived at the post-collisional stage. Their occurrence indicates that the geological setting of this Paleozoic orogen shifted from compression to extension no later than 430 Ma.

Geophysical evidence for lithospheric scale asymmetry and inherited mantle in the SE Brazilian-Angola and Newfoundland-Iberia rifted margins

Rift systems in the central South Atlantic and the southern Northern Atlantic margins exhibit anomalous wide ocean-continent transitions, extreme thinning of the continental crust, and scarce volcanism indicative of low magmatic budgets during rifting and breakup, characteristic of magma-poor rifted margins. While numerous studies investigated the crustal architecture at these magma-poor rifted margins, the nature of the underlying mantle lithosphere remains virtually unknown. In this work, we have interpreted seismic tomography and electromagnetic data with the aim of comparing large-scale aspects and mantle geophysical anomalies at these conjugate rifted margins. The data exhibits low electrical conductivity and high P-wave velocity in the mantle underlying the Iberia and the Angolan margins, while the Newfoundland and SE-Brazil margins show a lack of high-velocity mantle and exhibit higher electrical conductivity. The P-wave tomography values at middle lithospheric depths are suggestive of an oceanward lateral continuity of rigid lithospheric mantle at both the Iberian and Angola margins that may correspond to an anomalous mantle. Rifting-induced delamination at the onset of Atlantic opening is supported by previous geochemical studies. In addition, low electrical conductivity areas may indicate dry mantle conditions, which can be caused by inherited subcontinental mantle, and/or pre-to syn-rift magmatic extraction. A lack of high-velocity and high electrical conductivity in the mantle under the Newfoundland and Santos-Campos margins suggest a relatively weaker and newly formed mantle, in agreement with the removing and/or initial absence of a strong middle-to-lower inherited lithosphere beneath those margins. Therefore, the geophysical observations support different types of the nature of the middle mantle lithospheres flooring the two conjugate, magma-poor rifted margins.

Fish community characterization of mid-shelf and shelf- edge mesophotic coral ecosystems in the expanded Flower Garden Banks National Marine Sanctuary

The mid to outer continental shelf in the northern Gulf of Mexico is composed of a patchy distribution of coral and rock reefs designated high priority for marine protection. To better understand the influence of deepwater habitat on fish community dynamics and conservation needs, we compared altiphotic-mesophotic transition (20– 40 m), upper mesophotic (40–60 m), and middle mesophotic (60–80 m) fish communities between mid-shelf (Sonnier Bank) and outer-shelf (McGrail Bank) banks from before their inclusion into the Flower Garden Banks National Marine Sanctuary. Surveys performed over two years with a remotely operated vehicle indicated that each bank and depth zone had distinct fish communities. Both banks were dominated by planktivores and piscivores, with an increase in depth specialists (e.g., deepwater anthiids and serranids) at the deeper zones surveyed, particularly in middle mesophotic depths at McGrail. An increased frequency of snappers, groupers, and amberjack was observed at Sonnier Bank, predominately in mesophotic depths, indicating the Sonnier Mesophotic Coral Ecosystem as either a hotspot or potential refuge for meso- and apex predators. This study fills a temporal gap in fish community dynamics of these two banks, serving to create a more continuous dataset available to assist in conservation assessments of the Flower Garden Banks National Marine Sanctuary.

Fabrication of Rigid Polyurethane Foam Lumbar Spine Model for Surgical Training using Indirect Additive Manufacturing

Lumbar model is an artificial bone that is commonly used in surgical training to simulate working with the human-like bone for the trainer. The common lumbar model is made of rigid polyurethane (PU) foam and is produced using casting. However, the current lumbar model is expensive and has limitations in representing the real human lumbar, especially in geometry, visuals, and haptics. Therefore, an alternative method of fabricating lumbar models made of rigid polyurethane for surgical training using indirect additive manufacturing will be investigated in this paper. The proposed indirect additive manufacturing is a combination of 3D printing and casting methods. The main process of this method is started by fabricating a mold made of polyvinyl alcohol (PVA) using fused deposition modeling (FDM) 3D printing and subsequently casting PU foam material into the 3D printed PVA mold. Accordingly, the aim of this study is to find the optimized casting process parameters, especially for injecting the material into the mold, to achieve a better quality of lumbar model. The study was conducted using a Design of Experiment (DoE) Taguchi Orthogonal Array to optimize the casting process. The geometrical measurements of middle end-plate depth, upper end-plate width, spinal canal width, spinal canal depth, and lower pedicle length show the error ranged from 0.14% to 0.85%. The average porosity, measured from the body, lamina, and spinous, was found to be non-uniform. It is ranged from 19.58% to 21.94% on the middle part and 39.78% to 45.41% on the subsurface of lumbar model. The density was increased by 64.89% compared to the reference open molded PU foam.

Study on Temperature Correction of Asphalt Pavement Deflection Based on the Deflection Change Rate

The pavement deflection measured by falling weight deflectometer (FWD) detection equipment can be used to determine the bearing capacity of a pavement structure through modulus backcalculation to provide suggestions for pavement structure maintenance. However, because asphalt mixtures are temperature-sensitive materials, they are greatly affected by temperature, and changes in temperature can cause their mechanical properties to vary and affect the structural bearing capacity. Therefore, this paper conducts a pavement deflection test on an in-service highway asphalt pavement at different temperatures in different seasons. The representative temperature of the asphalt layer was determined through comparative analysis. The temperature’s effective influence distance on the deflection basin was found, and a more suitable temperature correction model for the deflection basin of asphalt pavement was established. The results showed that the temperature at the middle layer depth of the asphalt layer is more suitable as the representative temperature of the asphalt layer. The effective influence range of temperature on the deflection basin is 90 cm. The deflection change rate before and after the temperature correction at a radial distance of 20 cm is more appropriate for the temperature correction of the deflection basin.

Kanningar av gongdini hjá fjarðarsild í Føroyum gjøgnum samdøgrið

In october 1968 investigations on plankton and 1, 2 and 3 years old herring were carried out during 24 hours in Funningsfjørður, Faroe Islands. Plankton as well as herring showed vertical migration.
 In daytime the main part of the herring and the plankton stayed from the bottom up to a level of 10 m below the surface, in the night they moved up from bottom coming to íhe surface entirely.
 The echograms showing the movements of the herring form a picture corresponding with Ball's (1951) three step movement described for middle depths in the North Sea. The only factor which the day and night migrations could be correlated with was the light intensity.
 Stomach contents was found in the afternoon, whereas a sample of herring taken at 730 GMT, at sunrise, had empty stomachs only. The herring feed was composed of Acartia sp. besides some few Temora longicornis. Acartia longiremis and Acartia Clausii were dominating in the plankton samples, ohiefly females with egg sacks.

Effect of the notch depth on fracture behavior of TC4 titanium alloy sheets

To evaluate the low-stress brittle fracture of TC4 titanium alloy sheet structures, the effect of notch depth (d) on the fracture behavior of the 1.8 mm thick TC4 titanium alloy sheets was investigated combied with tensile tests and digital image correlation method. The results show that the ductile–brittle transition (DBT) occurs with increasing notch depths. Ductile fracture occurs for the notched samples with d = 0.5–1.5 mm, and a uniform plastic deformation stage is observed in the load–displacement (P-L) curves, and there are stretch zone and the stable crack propagation zone in the fracture surfaces. Brittle fracture occurs for the notched samples with d = 3.0–5.0 mm, and there is only the linear elastic stage in the P-L curves, and no stretch zone in the fracture surfaces. The samples at the middle notch depths (d = 2.0–2.5 mm) are in the transition from ductile to brittle fracture, and there exists the elastoplastic deformation stage in the P-L curves, and the stretch zone and stable crack propagation zone are both decreased. The analysis of notch fracture parameters shows that fracture of notched samples is controlled by the stress concentration and the stress field intensity of an imaginary crack with the same notch depth. The effect of crack gradually increases with increasing d, which results in increased brittle fracture tendency. Moreover, the fracture energy γf can characterize the DBT of notched TC4 titanium alloy sheets, and the γf is proportional tothe ratio of critical plastic zone size to d (rpc/d). Finally, the rpc/d is proposed to characterize the DBT of the notched TC4 titanium alloy sheets, and the criterion of the DBT for the notched TC4 titanium alloy sheets is obtained.

Vertical characterisation of phylogenetic divergence of microbial community structures, interaction, and sustainability in estuary and marine ecosystems

The changes in the aquatic environmental conditions often influence the microbial community assemblages and genome repertoire. Studies investigating the aquatic diversity and ecosystem services were primarily conducted in horizontal environments while neglecting the microbial phylogenetic divergences, biotrophic interactions, and eco-sustainability at water vertical layers. We investigated the mechanisms of microbial transitions, and the ecological significance of water depth layers in the estuary and marine ecosystems. The results demonstrated that the salinity and turbidity increased with increasing water depth (0–50 m), while temperature and pH decreased significantly. The bacterial and eukaryotic diversity and composition significantly increased with an elevating water depth. Bacterial phyla such as Desulfobacterota, Acidobacteriota, Myxococcota, Gemmatimonadota, Campilobacterota, and Latescibacterota were increased significantly. However, niche preference occurred, and some microbes showed differential nestedness at water vertical layers. In the eukaryotic community, Eustigmatales group were the only clades predominantly phylogenetically nested at the surface water depth. c_Conoidasida, o_Gregarinasina, f_Eugregarinorida, and g_Lankesteria were the most predominant at the middle depth. While Mediophyceae clades, p_SAR, and the Animalia clades were the most predominant groups nested at the bottom depths. The microbial interaction, structure, and stability were increased with increasing depth. The vertical phylogenetic turnover of the microbial community was related to the feeding mechanisms. Phototrophic organisms were particularly adapted at the surface, and middle depth by parasitic and pathogenic organisms, while the bottom was inhabited by diatoms, decomposers, and detritus protists. This study demonstrated that the bottom depth was the most ecologically stable area with more profound ecosystem services.

Elastic Contrast, Rupture Directivity, and Damage Asymmetry in an Anisotropic Bimaterial Strike‐Slip Fault at Middle Crustal Depths

Mature faults with large cumulative slip often separate rocks with dissimilar elastic properties and show asymmetric damage distribution. Elastic contrast across such bimaterial faults can significantly modify various aspects of earthquake rupture dynamics, including normal stress variations, rupture propagation direction, distribution of ground motions, and evolution of off-fault damage. Thus, analyzing elastic contrasts of bimaterial faults is important for understanding earthquake physics and related hazard potential. The effect of elastic contrast between isotropic materials on rupture dynamics is relatively well studied. However, most fault rocks are elastically anisotropic, and little is known about how the anisotropy affects rupture dynamics. We examine microstructures of the Sandhill Corner shear zone, which separates quartzofeldspathic rock and micaceous schist with wider and narrower damage zones, respectively. This shear zone is part of the Norumbega fault system, a Paleozoic, large-displacement, seismogenic, strike-slip fault system exhumed from middle crustal depths. We calculate elastic properties and seismic wave speeds of elastically anisotropic rocks from each unit having different proportions of mica grains aligned sub-parallel to the fault. Our findings show that the horizontally polarized shear wave propagating parallel to the bimaterial fault (with fault-normal particle motion) is the slowest owing to the fault-normal compliance and therefore may be important in determining the elastic contrast that affects rupture dynamics in anisotropic media. Following results from subshear rupture propagation models in isotropic media, our results are consistent with ruptures preferentially propagated in the slip direction of the schist, which has the slower horizontal shear wave and larger fault-normal compliance.

Upper-Cretaceous and Paleocene Biostratigraphy of Nkporo Shales, Calabar Flank, Southern Benue Trough

The present study Biostratigraphic (foraminiferal and palynological), paleoenvironment and paleoecological evaluations are aimed at interpreting the lithology, age, paleoenvironmental as well as the paleoecological condition of the deposited sediments newly exposed along Ikot Okpara Otopy, Southeastern Nigeria. Lithological descriptions of the samples reveal that this section is predominantly shale. This shale is dark grey to light brown, fossiliferous with minor occurrence of silts and sandstones. Foraminiferal analysis reveals a Paleocene interval within the Nkporo Formation for the first time. The sediments have low to moderate number of taxa with 96% benthic and 4% planktics, while a total of 196 microflora were recovered and identified. The microfloral species contain 60% of continental plants with 40% of marine counterparts. Key foraminiferal taxa used in this study include Bolivina afra, Bolivina explicata, Globigerina fringe and Haplophragmoides talokaense, while their microfloral counterparts encountered within the section include Cingulatisporites ornatus, Auriculidites reticulates Ephedripites ambonoides, Retidiporites magdalenensis, Synolocolporites marginatus, Constructipollenites ineffectus, Foveotriletes margaritae, Buttinia andreevi, Proxapertites operculatus, Zlivisporis blanensis and Paleocystodinium sp. These assemblages (Foraminiferal and Palynological) depict the deposition of these sediments during the Maastrichtian Paleocene age. The combination of lithologic and biostratigraphic data reveal paleoenvironment interpretation of the study section to range from marginal - shallow to Middle neritic paleo-water depths, while the paleoecological studies depicts a fluctuation in the salinity from brackish to marine settings deposited within a tropical to subtropical warm and humid climate.

Effects of fiddler crab bioturbation on the geochemical migration and bioavailability of heavy metals in coastal wetlands

Fiddler crabs, found in coastal wetlands worldwide, function as ecosystem engineers. Their burrowing activity can significantly alter biogeochemistry at the local scale, however, the mobility of heavy metals (HMs) in burrow sediments remains unclear. Here, we used diffusive gradients in thin-film probes to obtain bioavailable Fe and HMs (Cu, Zn, Ni, Cd, Pb, Co, and Mo) in crab burrows from coastal wetlands (mudflats, salt marshes, and mangroves). The depth-profile results showed that most HMs were enriched at shallow and deep depths but deficient at middle depths. We highlighted that bioturbation improved oxic conditions, enhanced HM concentrations, and favored dissolved HM retention in burrow sediments, which served as a sink for overlying water HMs via burrow flushing but a potential source of particle HMs via enhanced resuspension. In deep anoxic layers, Fe(III) reduction drove the remobilization of HMs, except Cu and Mo, leading to the co-release of HMs with Fe. This Fe-HM coupling/decoupling was verified using enhanced two-dimensional high-resolution imaging, which revealed highly spatial heterogeneity of multiple HMs. Moreover, the hydrological conditions regulating bioturbation effects on HM behavior varied across different coastal wetlands. With coastal environmental changes, the key role of ubiquitous bioturbation in HM migration and bioavailability should be reconsidered.

Soil Depth Significantly Shifted Microbial Community Structures and Functions in a Semiarid Prairie Agroecosystem.

The North American Great Plains cover a large area of the Nearctic ecozone, and an important part of this biome is semiarid. The sustainable intensification of agriculture that is necessary to produce food for an ever-increasing world population requires knowledge of the taxonomic and functional structure of the soil microbial community. In this study, we investigated the influence of soil depth on the composition and functions of the microbial communities hosted in agricultural soils of a semiarid agroecosystem, using metagenomic profiling, and compared them to changes in soil chemical and physical properties. Shotgun sequencing was used to determine the composition and functions of the soil microbial community of 45 soil samples from three soil depths (0–15 cm, 15–30 cm, and 30–60 cm) under different agricultural land use types (native prairie, seeded prairie, and cropland) in southwest Saskatchewan. Analysis of community composition revealed the declining abundance of phyla Verrucomicrobia, Bacteroidetes, Chlorophyta, Bacillariophyta, and Acidobacteria with soil depth, whereas the abundance of phyla Ascomycota, Nitrospirae, Planctomycetes, and Cyanobacteria increased with soil depth. Soil functional genes related to nucleosides and nucleotides, phosphorus (P) metabolism, cell division and cell cycle, amino acids and derivatives, membrane transport, and fatty acids were particularly abundant at 30–60 cm. In contrast, functional genes related to DNA and RNA metabolism, metabolism of nitrogen, sulfur and carbohydrates, and stress response were more abundant in the top soil depth. The RDA analysis of functional genes and soil physico-chemical properties revealed a positive correlation between phages and soil organic P concentrations. In the rooting zone of this semiarid agroecosystem, soil microbes express variable structural patterns of taxonomic and functional diversity at different soil depths. This study shows that the soil microbial community is structured by soil depth and physicochemical properties, with the middle soil depth being an intermediate transition zone with a higher taxonomic diversity. Our results suggest the co-existence of various microbial phyla adapted to upper and lower soil depths in an intermediate-depth transition zone.

EFFECT OF DIFFERENT SALIVA DECONTAMINATION PROCEDURES ON THE SHEAR BOND STRENGTH OF A UNIVERSAL EIGHTH GENERATION ADHESIVE SYSTEM TO DENTIN AFTER POLYMERIZATION - AN IN VITRO STUDY

Aim: To evaluate and compare the effect of saliva decontamination procedure on the shear bond strength of a Universal eighth generation adhesive system to dentin after polymerization. Materials & Method: Forty extracted non-carious premolars were mounted on a acrylic block and their occlusal surfaces were grounded flat to exposed the middle depth dentin. The teeth were then randomly divided into five Groups: Group A(control), Group B(Bonding, Saliva, Air-dried), Group C(Bonding, Saliva, Air-dried, Rinse), Group D(Bonding, Saliva, Air-dried, Re-bonding) & Group E (Bonding, Saliva, Air-dried, Rinse, Re-bonding). A teflon tube of 2x3 mm dimension was used to pack composite on the treated dentin surface and light cured for 40s. Shear Bond strength was then measured using instron testing machine at a crosshead speed of 1mm/min. Data were statistically analysed using ONE WAY-ANOVA and TUKEYS test. Result: It was observed that, the highest mean shear bond strength was found in Group D(Bonding, Saliva, Air-dried, Re-bonding) & Group E(Bonding, Saliva, Air-dried, Rinse, Re-bonding) with a mean value of 23.87 each. The least mean value was seen in Group C(Bonding, Saliva, Air-dried, Rinse), 13.25. When an intergroup comparision was made, statistically significant difference was seen between the various groups except Group A(control)-Group D(Bonding, Saliva, Air-dried, Re-bonding)-Group E(Bonding, Saliva, Air-dried, Rinse, Re-bonding) and Group B(Bonding, Saliva, Air-dried)-Group C(Bonding, Saliva, Air-dried, Rinse). Conclusion: Salivary contamination significantly decreases the bond strength of the adhesive to dentin after polymerization. Rinsing and Air-drying of the cured contaminated dentin surface was not sufficient to restore the shear bond strength. However reapplication of adhesive system after rinsing and air-drying of the cured contaminated dentin surface fully restored the bond strength.

Technical note: Comparison of arithmetic mean and energy-weighted mean flood histogram generation methods for dual-ended readout positron emission tomography detectors.

Dual-ended readout pixelated scintillator array detectors can provide a suitable crystal resolvability and satisfactory depth of interaction (DOI), energy, and timing resolutions. Usually, the flood histogram measured by one-sided readout is depth dependent, and the flood histogram quality degrades as the distance between the interaction site and photodetector increases. Information measured by two photodetectors must be combined to obtain an improved flood histogram yielding a better PET scanner spatial resolution. Two flood histogram generation algorithms for dual-ended readout of pixelated scintillator array detectors were compared by theoretical calculations and experimental measurements. The first algorithm is the arithmetic mean (AM) algorithm, which assigns the same weight to the flood histograms measured by photodetectors 1 and 2. The second algorithm is the energy-weighted mean (EWM) algorithm, which assigns each flood histogram a certain weight proportional to the energy measured by the photodetector. Theoretical equations were derived to determine the quality of the flood histograms obtained with these two algorithms. Experimental measurements were performed with an 18 × 18 lutetium-yttrium oxyorthosilicate (LYSO) array with a crystal size of 0.62 × 0.62 × 20 mm3 read out by two multi-anode photomultiplier tubes at both ends. Flood histograms of the whole array and five specific depths were compared between the above two algorithms. The theoretical results indicated that the flood histograms obtained with the EWM method matched those obtained with the AM method at the middle detector depth and were better at other detector depths when the distance (S) between the locations of the same crystal in the flood histograms measured by photodetectors 1 and 2 reached 0. The advantage of the EWM method decreased with increasing S value since the crystal position in the flood histogram obtained with the EWM method varies with the depth when S does not equal 0. The advantage of the EWM method decreased with increasing S value. The experimental results generally agreed with the theoretical predictions. Compared to the AM method, the EWM method provided a similar flood histogram at a depth of 10 mm but generated a better flood histogram at depths of 2 and 18 mm. Although an inverse correlation between Q (a quality factor representing the advantage of the EWM method) and S was observed, the variation in Q given the same S value was high. The average Q value at the same S still agreed with the theoretical predictions. Theoretical equations were derived, and experimental measurements were performed to compare two flood histogram generation algorithms for dual-ended readout PET detectors. The results indicated that the EWM method based on inverse variance weighting theory could provide better flood histograms than those provided by the AM method.

The effects of tree age, thickness, and depth of timber on density and mechanical properties of heat-treated black poplar wood (Populus nigra)

ThermoWood is a wood modification method that is used to improve the wood application and dimensional stability of wood. In this study, poplar wood (Populus nigra) was used in two age groups of 18- and 38-year-old trees to investigate the effect of tree age, thickness, and depth of heat-treated timbers on mechanical properties and density. In each age group, the timbers were prepared according to thickness of 40, 50, and 60 mm. The experimental samples were prepared from the surface (S) and middle (M) depth of heat-treated timbers based on age and thickness. Some properties of heat-treated and control wood such as density (oven-dry density, air-dry density, and basic density) and mechanical properties (modulus of rupture (MOR), modulus of elasticity (MOE), and impact strength) were measured. In general, density and mechanical properties of heat-treated wood were decreased compared with the control samples. Density and mechanical properties of heat-treated and control wood samples were increased from 18- to 38-year-old trees. There were no differences in density and mechanical properties after changing thickness. Surface and middle depth specimens of heat-treated timbers showed a positive effect on the impact strength but had no considerable effect on densities and other strengths of heat-treated wood timbers.

Investigating the Shallow to Mid-Depth (>100–300 °C) Continental Crust Evolution with (U-Th)/He Thermochronology: A Review

Quantifying geological processes has greatly benefited from the development and use of thermochronometric methods over the last fifty years. Among them is the (U-Th)/He dating method, which is based on the production and retention, within a crystal structure, of radiogenic 4He atoms associated with the alpha decay of U, Th and Sm nuclei. While apatite has been the main target of (U-Th)/He studies focusing on exhumation and burial processes in the upper levels of the continental crust (~50–120 °C), the development of (U-Th)/He methods for typical phases of igneous and metamorphic rocks (e.g., zircon and titanite) or mafic and ultramafic rocks (e.g., magnetite) over the last two decades has opened up a myriad of geological applications at higher temperatures (>100–300 °C). Thanks to the understanding of the role of radiation damage in He diffusion and retention for U-Th-poor and rich mineral phases, the application of (U-Th)/He thermochronometry to exhumation processes and continental evolution through deep time is now mainstream. This contribution reviews the (U-Th)/He thermochronometer principle and the influence of radiation damage in modifying the diffusion behavior. It presents applications of (U-Th)/He dating to problems in tectonic and surface processes at shallow to middle crustal depths (>100–300 °C). New and promising applications using a combination of methods will stimulate a research avenue in the future.