Moderate Depth Research Articles

Analyzing Effects of Crops on SMAP Satellite-Based Soil Moisture Using a Rainfall–Runoff Model in the U.S. Corn Belt

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> -band microwave satellite missions provide soil moisture information potentially useful for streamflow and, hence, flood predictions. However, these observations are also sensitive to the presence of vegetation that makes satellite soil moisture estimations prone to errors. In this study, the authors evaluate satellite soil moisture estimations from Soil Moisture Active Passive (SMAP) and Soil Moisture Ocean Salinity and two distributed hydrologic models with measurements from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> sensors in the Corn Belt state of Iowa, a region dominated by annual row crops of corn and soybean. First, the authors compare model and satellite soil moisture products across Iowa using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> data for more than 30 stations. Then, they compare satellite soil moisture products with state-wide model-based fields to identify regions of low and high agreement. Finally, the authors analyze and explain the resulting spatial patterns with Moderate Resolution Imaging Spectroradiometer vegetation indices and SMAP vegetation optical depth. The results indicate that satellite soil moisture estimations are drier than those provided by the hydrologic model, and the spatial bias depends on the intensity of row-crop agriculture. The work highlights the importance of developing a revised SMAP algorithm for regions of intensive row-crop agriculture to increase SMAP utility in the real-time streamflowpredictions.

Evaluation of Water seepage Along Proposed Baghdad Metro Tunnel Across Tigris River

Water seepage can cause serious problems in geotechnical engineering especially for construction under the water level. Baghdad metro tunnel is one of the leading vital projects to solve the major problem of crowding roadways in a highly population increase city like Baghdad. In this study, the seepage rate that will flow toward different selected points along the tunnel section across Tigris River was calculated during the excavation process, with the consideration of three different water levels of River at maximum, moderate, and minimum water depths. A three-dimensional model of the study has been modeled using the finite element software (PLAXIS 3D V20). The water seepage was observed for six different locations on each route of the tunnel. The study showed that the change of water depth in the river has no significant effect on the seepage – time curve shape. However, increasing the water level in River from minimum to maximum leads to increase the seepage rate about 15%.

Examining and applying the theory of “exploring petroleum inside source kitchens” for continental shale oil: A case study from the Kong 2 member of the Cangdong sag in the Bohai Bay Basin, China

Continental shale oil to be studied urgently is an important unconventional “source rock oil and gas” and key domain of “exploring petroleum inside source kitchens”. Based on the “source rock oil and gas” theory and the thought of “exploring petroleum inside source kitchens”, this paper established the ”six determination” exploration workflow for continental shale oil (i.e., determining the background, source rock, reservoir, play, resources, and sweet spot), which geological characteristics and exploration workflow are significantly different from conventional hydrocarbon. A case study was conducted by the workflow in the Kong 2 member (Ek2) of the Cangdong sag in the Bohai Bay Basin, China. Semi-deep to deep lacustrine facies belts and many gentle slope structures (belts) were widespread during Kongdian Formation depositing, thus providing favorable conditions for the formation and large-area accumulation of shale oil. Ek2 developed broader-distributed, and thick-bedded dark mudstone and oil shale, which exhibit high TOC, a good kerogen type, and great hydrocarbon-generating potential. Siltstone to fine sandstone and mud to micritic dolomite reservoirs were found within the low-dip slopes and central zone, which are thick, overlapped, abundant high-angle fractures, and exhibit low porosity and ultra-low permeability. Sandstone-type and dolomite-type shale oil of Ek2 characterized source–reservoir integration and five types of sources–reservoir configurations. They mainly overlapped at the front end of the braided river delta in the slope zone and in the sag center, where are superimposed vertically, and are connected horizontally with conventional structural–lithological oil pools in the up-dip slope. The median geological resources of the two classes shale oil were 5.26×108/t, with the remaining resources accounting for 90% of the total and moderate buried depths, thus the exploration potential is great. Several special exploration wells have obtained industrial oil flow. There are two types of sweet spots: low permeability sandstone layers and interbedded layers of oil shale and dolomite. A few favorable sweet spots were identified as targets for subsequent exploration. Then, three aspects of thinking and recommendations to solve the next exploration direction and technical problems were proposed, which will provide important reference and theoretical guidance for the further exploration of the same type of shale system in China and the world.

Modified functional ocular impression of post-enucleation socket: A case report

Introduction: The disfigurement associated with the loss of an eye can cause significant physical and psychological problems. Therefore, a good ocular prosthesis is needed to restore the patient's quality of life. One of the factors that determine the quality of an ocular prosthesis is accurately impression. In the case of enucleation where the eyes socket has a soft and movable tissue bad will result inaccurate impression. The difficulty of post enuclation impression in such case is the compression of the tissue eyes socket. This case report will discuss the modification in functional impression technique using a modified custom tray. Case: A 39-year-old male patient came to Dental Hospital Universitas Sumatera Utara with chief complaint an unaesthetic and loose left stock eye that had been used for 10 years. Clinical examination shows moderate depth eye socket with soft and movable tissue. Management: The functional impression technique was modified using a self-curing clear acrylic sclera without handle as a custom tray with 2 mm reduction on the intaglio surface and light body polyvinyl siloxane as impression material. Discussion: The aim of this modification is to avoid the tendency of the eye socket to compress during impression taking and to achieve a natural contour of the eyelid convexity because of the absence of the tray handle so the patient can close their eyes. Conclusion: This technique produces an ocular prosthesis that has a good retention with excellent aesthetic result.

Environmental effects caused by the Mw 8.2, September 8, 2017, and Mw 7.4, June 23, 2020, Chiapas-Oaxaca (Mexico) subduction events: Comparison of large intraslab and interface earthquakes

Earthquake Environmental Effects (EEEs) such as surface faulting, landslides, liquefaction and tsunamis are widely distributed following strong seismic events and may account for a significant part of the overall damage. Here, we investigate EEEs generated by two earthquakes with different source parameters, both occurring along the Mexican subduction zone: the Sept. 8, 2017, Mw 8.2, moderate depth, normal fault, intraslab event; and the June 23, 2020, Mw 7.0, shallow depth, thrust fault, interface event. We document the EEEs for each event, assign an intensity value using the Environmental Seismic Intensity (ESI-2007) scale, and derive the macroseismic fields. Finally, we compute the attenuation of intensity with distance and we compare it with other subduction zone earthquakes worldwide, demonstrating the repeatability of EEEs. This work represents the first application of the ESI-2007 scale to an intraslab earthquake and documents its wide applicability in different seismotectonic settings. We argue that EEEs provide useful information that should not be neglected in seismic hazard assessment procedures.

In situ U-Pb dating and geochemical characterization of multi-stage dolomite cementation in the Ediacaran Dengying Formation, Central Sichuan Basin, China: Constraints on diagenetic, hydrothermal and paleo-oil filling events

Improved understanding of subsurface paleo-fluid circulation history can assist in reconstructing associated pore evolution of carbonate reservoirs. Multi-stage dolomite cements generated by basinal fluids over time were investigated using a combination of petrography, geochemistry, fluid-inclusion studies, LA-ICP-MS U-Pb geochronology, and seismic interpretation. This study aims to gain clues about diagenetic, hydrothermal and paleo-oil filling events within the Ediacaran Dengying Formation, Sichuan Basin, China.Four main phases of dolomite cementation were petrographically, geochemically and geochronologically distinguished that can be ascribed to major tectonic events throughout the basin evolution. The earliest dolomite generation occurs as fibrous dolomite crust (FDC) growing along the karst vug wall, interpreted as marine diagenetic cement formed in a submarine environment during the Late Ediacaran, most likely from the influx of seawaters following the uplift and subaerial exposure related to the Tongwang movement. In situ U-Pb ages obtained from the other three generations of cement dolomites are interpreted to coincide with the timing of repeated strike-slip fault movements as indicated by the seismic data, suggesting a direct link between cement emplacement and regional tectonic-thermal events. Sub-vertical extension dolomite veins (EDV), representing the second generation, are considered as being syntectonic, generated from slightly modified connate seawaters at a shallow to moderate burial depth in a transtensional stress regime during the Cambrian taphrogenesis. Two generations of saddle dolomite cements, SD1 and SD2, have recorded two major episodes of hot fluids circulating in the Dengying Formation. The SD1, filling in hydraulic fractures and vugs, formed during the third phase of cementation, as a result of a hydrothermal event associated with Caledonian exhumation. Deep-seated hot brines squeezed into the Dengying reservoirs along the sub-vertical strike-slip faults combined with some meteoric waters that percolated downward, are deemed responsible for precipitating SD1. The SD2 is the youngest cement present, which is interpreted to have formed during the ingress of deeper, hot, hypersaline brines arising from the late Permian hydrothermal activity likely triggered by the eruption of Emeishan flood basalts.Cross-cutting relationships between bitumen phases and different dolomite generations indirectly define the dates of two paleo-oil charging events. The first episode of paleo-oil charging occurred during the Late Ediacaran to Early Cambrian, likely sourced from underlying Ediacaran Doushantuo shales. Late oil emplacement occurred after the Late Permian, in agreement with the reported bitumen Re-Os age and the age inferred through fluid-inclusion analysis. Primary source rocks generating this phase of oil were considered as the Cambrian Qiongzhusi shales, because basin modeling-derived date of oil window matches with the second oil filling time.

The NEWFIRM HETDEX Survey: Photometric Catalog and a Conservative Sample of Massive Quiescent Galaxies at z = 3–5 over 17.5 deg2 in the SHELA Field

Abstract We present the results of a deep K s -band (2.1 μm) imaging survey of the Spitzer/HETDEX Exploratory Large-Area (SHELA) field using the NEWFIRM near-infrared camera on the KPNO Mayall 4 m telescope. This NEWFIRM HETDEX Survey reaches a 5σ depth of 22.4 AB mag (2″-diameter apertures corrected to total), is ∼50% and 90% complete at K ∼ 22.65 and K ∼ 22.15, respectively, and covers 22 deg2 of the 24 deg2 SHELA Spitzer/IRAC footprint (within “Stripe 82” of the Sloan Digital Sky Survey). We present a K s -band-selected catalog that includes deep ugriz imaging from the Dark Energy Camera and 3.6 and 4.5 μm imaging from Spitzer/IRAC, with forced photometry of 1.7 million sources across 17.5 deg2. The large area and moderate depth of this catalog enable the study of the most massive galaxies at high redshift and minimize uncertainties associated with counting statistics and cosmic variance. As a demonstration, we derive stellar masses (M *) and star formation rates (SFRs) for candidate galaxies at 3 ≲ z ≲ 5 and select a conservative sample of nine candidate massive (M * &gt; 1011 M ⊙) quiescent galaxies, which have measured SFRs significantly below the main sequence at this redshift. Five are ultramassive with M * &gt; 1012, though uncertainties in IRAC blending, gravitational lensing, or active galactic nucleus emission could result in true masses that are lower. Simulations predict that these galaxies should be extremely rare; thus, we conclude by discussing what physical processes in models could be altered to allow the formation of such massive quiescent galaxies at such early times.

Pinning effects in a two-dimensional cluster glass

We study numerically the glass formation and depinning transition of a system of two-dimensional cluster-forming monodisperse particles in presence of pinning disorder. The pairwise interaction potential is nonmonotonic, and is motivated by the intervortex forces in type-$1.5$ superconductors. Such systems can form cluster glasses due to the intervortex interactions following a thermal quench, without underlying disorder. We study the effects of vortex pinning in these systems. We find that a small density of pinning centers of moderate depth has limited effect on vortex glass formation, i.e., formation of vortex glasses is dominated by intervortex interactions. At higher densities pinning can significantly affect glass formation. The cluster glass depinning, under a constant driving force, is found to be plastic, with features distinct from non-cluster-forming systems such as clusters merging and breaking. We find that in general vortices with cluster-forming interaction forces can exhibit stronger pinning effects than regular vortices.

Characterization of dust activation and their prevailing transport over East Asia based on multi-satellite observations

Mineral dust from the deserts and arid areas in East Asia plays a critical role in regional climate and air quality. Based on integrated satellite observations and MERRA-2 reanalysis, we provide an observational insight into dust activities governing spatial patterns of dust aerosols over East Asia. With Moderate resolution Imaging Spectroradiometer Aerosol Optical Depth (AOD) and Ozone Monitoring Ultraviolet Aerosol Index (UVAI), fixed dust-active areas with distinct spatial-temporal differences are revealed. Besides the few dust storms mostly in spring, unnoticeable but frequent dust plumes are found to be the predominant sources of prevailing dust particles over East Asia. Compared with the active dust sources in Taklimakan Desert throughout the year, dust activities in Gobi deserts are at a much lower frequency. The elevated dust plumes are concentrated within 2–6 km over the deserts with large seasonal variations, and can be transported downstream to eastern China and Sichuan Basin within 3–5 days. Moreover, owing to the lack of enough strong winds, these dust plumes tend to be concentrated above the haze layers near surface in eastern China. The intense temperature inversion during winter and early spring can delay the mixing of dust-pollution. Despite a generally reasonable performance in dust AOD, MERRA-2 reanalysis exhibits some uncertainties in reproducing spatial locations of dust hotspots, dust concentration, and transport process. Our results emphasize significant role of the inapparent but prevalent dust plumes in air quality and in climate effects of East Asia.

Sequence stratigraphy and coal accumulation model of the Taiyuan Formation in the Tashan Mine, Datong Basin, China

Abstract Datong Basin is a platform uplift formed in the Cenozoic era and has a significant coal-bearing geological unit in China. Tashan Mine is located in the middle-eastern part of the Datong Basin, the coal resources of the Taiyuan Formation are abundant, and the research value is enormous. Of the coal resources, coal seams 3–5 and 8 are the main. The lack of research in sequence stratigraphy, coal-forming environment, coal-accumulating model limits the layout efficiency of working face and the exploration and development efficiency of coal measures associated resources. This study used sedimentary and sequence stratigraphy and calculated and measured field drilling data to investigate the sequence stratigraphic characteristics, paleogeographic pattern, and coal accumulation model of the Taiyuan Formation. The sequence boundary and system tract boundary were identified, and the Taiyuan Formation was divided into four third-order sequences. The paleogeographic pattern was reconstructed with the third-order sequence as a unit by applying the single-factor analysis and multifactor comprehensive mapping. Additionally, the distribution characteristics of the main coal seams were clarified, and the corresponding coal accumulation model was reconstructed. The results exhibit that the sedimentary facies transformed from carbonate platform–tidal flat–lagoon–shallow water delta facies to shallow water delta facies from SQ1 to SQ2, coal seam 8 formed in interdistributary bay microfacies and peat swamp microfacies in SQ1. Transgression further expanded in SQ3, and the sedimentary facies were still dominated by the shallow water delta facies. Coal seams 3–5 are formed in distributary channel microfacies, which consist of interdistributary bay microfacies and peat swamp microfacies. The paleogeographic pattern was still dominated by shallow water delta in SQ4, in which interdistributary depressions and peat swamp microfacies widely developed. The thickness of coal seams 3–5 is in the range of 2.40–25.90 m, in which the northwestern study area is characterized by moderate water depth and sufficient fine sediment, and the widely developed distributary bay and peat swamp deposited a thick coal seam. The thickness of coal seam 8 is in the range of 0.5–10.5 m, and the thickness is stable (mostly thicker than 6 m) controlled by the widely developed lagoon, mud flat, and peat swamp microfacies and reduction water environment.

Dynamic Responses for WindFloat Floating Offshore Wind Turbine at Intermediate Water Depth Based on Local Conditions in China

Offshore wind energy, a clean energy resource, is considered to be a possible alternative to fossil energy. Floating offshore wind technology is considered to be a proper concept to develop abundant wind energy in deep water. Considering the reality of offshore wind energy development in China, the floating offshore wind turbine concept is expected to be developed at moderate water depths. In this paper, a mooring system of the WindFloat semisubmersible floating offshore wind turbine (SFOWT) at a water depth of 60 m is designed. The dynamic responses of the WindFloat SFOWT under different wind–wave combination conditions are investigated using the coupled method and the simplified method, which do not include the effect of the tower top motion in the aerodynamic calculation. The results show that the dynamic responses of the WindFloat SFOWT, including the platform motions, tower loads, and mooring line tensions, perform fairly well at a moderate water depth. A comparison between the coupled method and simplified method shows that the calculated results are slightly different between the different conditions for the time domain results, response spectra results, and fatigue results. In addition, mooring line 1 (ML 1) suffers higher fatigue damage than ML2, which should be paid more attention.

Electric and magnetic dipole antennas of a directional resistivity logging-while-drilling tool for “look-around” boundary detection

Directional resistivity logging-while-drilling tools play an important role in geosteering. In contrast to the widely used tool with magnetic dipole transmitters and receivers, tools are investigated with electric and magnetic dipoles as transmitters and/or receivers for “look-around” boundary detection. Measurement schemes are selected based on their look-around boundary detection abilities. Those measurement schemes are studied regarding the sensitivity and depths of boundary detection, the optimal transmitter-receiver distance and frequency, and the effects of a drill collar using the coefficient propagator method and the finite-difference method. Higher sensitivity to a boundary often implies a shallower depth of investigation. More specifically, the measurement schemes using an electric dipole transmitter and receiver are the least sensitive to the boundary; however, such schemes have the maximum depth of detection and the strongest signal strength. The schemes using electric and magnetic dipole transmitters and receivers have a moderate depth of detection and signal strength. The measurement schemes with a magnetic dipole transmitter and receiver have the highest sensitivity to the boundary and the weakest signal strength. The drill collar affects the response of all of the measurement schemes. However, this effect cannot be corrected with a simple coefficient for the schemes using an axial electric dipole transmitter, but it can be corrected for others. The optimal frequencies and optimal transmitter-receiver distances of those schemes have two types: the changing one that changes with the distance to boundaries and the fixed one that usually has the lowest frequency or the shortest transmitter-receiver distance. The characteristics of each measurement scheme will guide the tool designs and determine its role in the application and method of interpretation.

Effective wavelength of envelope waves on the water surface beneath an ice sheet: small amplitudes and moderate depths

Effective wavelength of envelope waves on the water surface beneath an ice sheet: small amplitudes and moderate depths

Experimental investigation and fuzzy TOPSIS optimisation of Ti6Al4V finish milling

ABSTRACT Ti6A14V is a well-known ‘Difficult to Cut’ material in the aerospace industry. Ti6Al4V shows strain hardening, poor thermal conductivity and chemical reactivity at elevated temperatures, which implies low machinability. This work presents an experimental investigation of 3D finish milling of Ti6Al4V material by Taguchi design of experiments, having L25 array. The considered process parameters are cutting speed, feed, depth of cut, tool type, coolant type and computer aided manufacturing strategy. The experimentation is conducted on the 3D finish milling process, and the performance in terms of tool life, tool wear and surface integrity were recorded. The fuzzy technique for order of preference by similarity to ideal solution, a multiple-criteria decision-making tool, was applied on experimental responses. The yielded optimum results are derived at minimum cutting speed, moderate depth of cut, feed rate per tooth and collaboration under high concentrated wet lubrication using a PVD-TiAlN cutting tool driven by streamline computer aided manufacturing strategy. In addition, analysis of variance confirms the influential process parameter contribution on the respective performance. Finally, optimised process parameters were applied for the gear bracket finish milling through streamline CAM strategy, which results in minimum flank and crater wear with an average surface roughness of 0.17 microns.

Эффективные длины волн огибающей на поверхности воды под ледяным покровом: малые амплитуды и умеренные глубины

Производится сравнение длин волн огибающих, монохроматических волн и скоростей так называемых уединенных волн огибающей на поверхности идеальной жидкости (воды) под ледяным покровом, находящимся в напряженном состоянии, для жидкости умеренной глубины в рамках двух формулировок. Во-первых, используются двумерные уравнения Эйлера для описания слоя воды конечной глубины, а ледяной покров моделируется упругой геометрически нелинейной пластиной Кирхгофа-Лява (эта формулировка называется полностью нелинейной). Бегущие уединенные волны огибающей малой амплитуды, для которых фазовая скорость равна групповой скорости и соответствует возникновению минимума скорости при конечном волновом числе на дисперсионной кривой, можно асимптотически описать в этой формулировке с помощью редукции базовых уравнений на центральное многообразие и анализа квазинормальной формы уравнений на центральном многообразии. Во-вторых, для малоамплитудных и длинных волн можно использовать слабонелинейную формулировку и формально вывести нелинейное уравнение Шредингера. В этих двух формулировках однозначно определяются длины волн огибающей, монохроматической волны и фазовая скорость волны. Эти параметры сравниваются для огибающих волновых пакетов и оказывается, что они близки для небольших глубин водоемов. Обсуждается существование сингулярного предела в уравнениях полностью нелинейной формулировки, когда изгибная жесткость ледяной пластины стремится к нулю, и формально получается случай гравитационно-капиллярных волн. Обсуждается также возможность теоретического определения длин волн и скоростей волн для существенно нестацинарных уединенных волн огибающих с помощью слабонелинейной формулировки.

Recent Advances in Reactive Ion Etching and Applications of High-Aspect-Ratio Microfabrication.

This paper reviews the recent advances in reaction-ion etching (RIE) for application in high-aspect-ratio microfabrication. High-aspect-ratio etching of materials used in micro- and nanofabrication has become a very important enabling technology particularly for bulk micromachining applications, but increasingly also for mainstream integrated circuit technology such as three-dimensional multi-functional systems integration. The characteristics of traditional RIE allow for high levels of anisotropy compared to competing technologies, which is important in microsystems device fabrication for a number of reasons, primarily because it allows the resultant device dimensions to be more accurately and precisely controlled. This directly leads to a reduction in development costs as well as improved production yields. Nevertheless, traditional RIE was limited to moderate etch depths (e.g., a few microns). More recent developments in newer RIE methods and equipment have enabled considerably deeper etches and higher aspect ratios compared to traditional RIE methods and have revolutionized bulk micromachining technologies. The most widely known of these technologies is called the inductively-coupled plasma (ICP) deep reactive ion etching (DRIE) and this has become a mainstay for development and production of silicon-based micro- and nano-machined devices. This paper will review deep high-aspect-ratio reactive ion etching technologies for silicon, fused silica (quartz), glass, silicon carbide, compound semiconductors and piezoelectric materials.

Dynamic analysis of a novel semi-submersible platform for a 10 MW wind turbine in intermediate water depth

A conceptual semi-submersible platform in the moderate water depth is proposed through fully coupled analysis using aeeo-hydro-servo-elastic code to support the Technical University of Denmark (DTU) 10 MW wind turbine. The intact stability of the newly designed semi-submersible floating offshore wind turbine (FOWT) is assessed based on DNV structure, and comparison with LIFES 50+ OO-Star platform is presented to verify the numerical model. The effect of mooring line damping on the dynamic behaviors of the conceptual FOWT is investigated. Additionally, the dynamic responses of the conceptual FOWT under different fault conditions is examined, including grid loss, blade seize without shutdown and blade seize with the shutdown, and a comparative study on the dynamic behaviors of the conceptual FOWT under operational and fault conditions is implemented. The results show that the proposed concept FOWT has a good stability, and the shutdown fault conditions have the most significant impact on its dynamic behaviors.

Oriented stochastic loss descent algorithm to train very deep multi-layer neural networks without vanishing gradients

Deep multi-layer neural networks represent hypotheses of very high degree polynomials to solve very complex problems. Gradient descent optimization algorithms are utilized to train such deep networks through backpropagation, which suffers from permanent problems such as the vanishing gradient problem. To overcome the vanishing problem, we introduce a new anti-vanishing back-propagated learning algorithm called oriented stochastic loss descent (OSLD). OSLD updates a random-initialized parameter iteratively in the opposite direction of its partial derivative sign by a small positive random number, which is scaled by a tuned ratio of the model loss. This paper compares OSLD to stochastic gradient descent algorithm as the basic backpropagation algorithm and Adam as one of the best backpropagation algorithms in five benchmark models. Experimental results show that OSLD is very competitive to Adam in small and moderate depth models, and OSLD outperforms Adam in very long models. Moreover, OSLD is compatible with current backpropagation architectures except for learning rates. Finally, OSLD is stable and opens more choices in front of the very deep multi-layer neural networks.

The komatiite-mantle platinum-group element paradox

The platinum-group element (PGE) contents of komatiites have been used to estimate the PGE contents of their mantle sources and investigate temporal variations in the PGE systematics of the mantle throughout Earth history. However, the use of mantle melts to investigate source characteristics is critically dependent on understanding the fractionation of the elements in question between mantle sources and their derived magmas. We present new PGE and Re abundance data, together with Re-Os isotope data for the pristine 1.9 Ga Winnipegosis komatiites, Canada. Whole rock Re-Os isotope data define a 1865 ± 40 Ma isochron, consistent with previous age estimates, with initial γOs of +0.9 ± 1.4. The PGE and Re variations in these komatiites were controlled by fractionation of olivine, chromite, Os-Ir alloys, a Ru-Os rich phase (possibly laurite) from the komatiite melt. The calculated parental melt composition at 23.6 ± 1.6 wt% MgO has 1.1 ± 0.1 ppb Os, 0.91 ± 0.08 ppb Ir, 4.0 ± 0.5 ppb Ru, 7.0 ± 0.8 ppb Pt, 7.2 ± 0.7 ppb Pd, and 0.53 ± 0.06 ppb Re. The calculated PGE contents are low relative to many komatiites; using existing methods for calculating the PGE contents of mantle sources suggests the Winnipegosis source had PGE contents from 25 ± 19 wt% to 57 ± 7 wt% of primitive mantle values. This surprising finding substantiates a growing ‘PGE paradox’, where almost all komatiites appear to have formed from PGE-depleted mantle sources. We suggest the simplest resolution to this paradox is that current methods systematically underestimate mantle source PGE contents. We test the assumptions implicit in these methods by comparing detailed models of PGE behaviour during mantle melting to a large database of parental melt compositions of high degree melts. Ruthenium behaviour in high degree melts can be adequately modelled using our current understanding of Ru partitioning. However, the Ru contents of high degree mantle melts are strongly dependent on the degree of melting, as Ru-rich melts formed after sulphide exhaustion are increasingly mixed into early-formed Ru-poor melts. Platinum and Pd behaviour during mantle melting cannot be successfully modelled under the widespread assumption that they are strongly incompatible following sulphide exhaustion, suggesting that these elements cannot be used to estimate PGE contents of the mantle sources of high degree melts. Parental melt Pt and Pd in many high degree lavas are correlated with Al2O3/TiO2, suggesting a pressure control on their partitioning. We attribute the relatively low PGE contents of the Winnipegosis komatiites to their moderate degrees and depth of melting compared to other komatiites, rather than invoking a PGE-depleted mantle source. More broadly, the complex controls (T, P, fO2, S content, prior depletion) on the PGE contents of komatiites mean that most komatiites can be reconciled with being derived from sources with primitive mantle-like PGE contents, and few komatiites can be confidently asserted to come from PGE-depleted mantle sources. Pending a better understanding of PGE behaviour during mantle melting, we recommend caution when using komatiite PGE systematics to infer the highly siderophile element evolution and accretionary history of Earth’s mantle.

AWARENESS REGARDING USE OF LINING UNDER POSTERIOR COMPOSITE RESTORATIONS AMONG GENERAL DENTISTS OF LAHORE

Objective: To evaluate awareness among the General Dentists of Lahore regarding the use of lining materials under posterior resin restorations.&#x0D; Study Design: Cross-sectional study.&#x0D; Place and Duration of Study: The study was conducted in Lahore, from Sep 2019 to Jan 2020.&#x0D; Methodology: Non-probability consecutive sampling technique was used. A sample size of 271 was calculated. The questionnaires were distributed by 2 surveyors to the general dentists of Lahore, Pakistan.&#x0D; Results: The response rate was 100%. Amongst these dentists, 191 (63.87%) affirmed that they use lining materials in initial depth cavities, 248 (82.94%) used lining material under moderate depth restorations and 285 (95.31%) used lining materials under advanced depth cavities with calcium hydroxide being the most commonly used material.&#x0D; Conclusion: The findings of the present study indicate that general dentists of Lahore are unaware of the contemporary concepts regarding the placement of cavity liners and tend to place liners in initial and moderate depth cavities under posterior resin restorations.