High Specific Gravity Research Articles

Lignin-Induced CaCO3 Vaterite Structure for Biocatalytic Artificial Photosynthesis.

The vaterite phase of CaCO3 exhibits unique characteristics, such as high porosity, surface area, dispersivity, and low specific gravity, but it is the most unstable polymorph. Here, we report lignin-induced stable vaterite as a support matrix for integrated artificial photosynthesis through the encapsulation of key active components such as the photosensitizer (eosin y, EY) and redox enzyme (l-glutamate dehydrogenase, GDH). The lignin-vaterite/EY/GDH photobiocatalytic platform enabled the regeneration of the reduced nicotinamide cofactor under visible light and facilitated the rapid conversion of α-ketoglutarate into l-glutamate (initial conversion rate, 0.41 mM h-1; turnover frequency, 1060 h-1; and turnover number, 39,750). The lignin-induced vaterite structure allowed for long-term protection and recycling of the active components while facilitating the photosynthesis reaction due to the redox-active lignin. Succession of stability tests demonstrated a significant improvement of GDH's robustness in the lignin-vaterite structure against harsh environments. This work provides a simple approach for solar-to-chemical conversion using a sustainable, integrated light-harvesting system.

Softening Behaviour of Indonesian Wood Species

This paper deals with softening behaviour measurements of Indonesian wood species by static bending tests. Wood samples with a size of 110mm (R) x 10mm (T) x 4mm (L) were bending tested in air-dry at 20°C and 65% relative humidity (RH), in water saturation at 20°C, and in water saturation at 80°C to know the decreasing of modulus of elasticity (MOE) and modulus of rupture (MOR) due to moisture content (MC) and both moisture content and temperature (MCT) changes. The wood samples represented Randu (Bombax ceiba. L) as the lowest specific gravity, i.e. 0.27 to Lamtoro (Leucaena glauca (Willd) Benth) as the highest specific gravity, i.e. 0.81. The three-point static bending test was carried out by a mechanical testing machine with a load capacity of 100kgf, loading deflection speed of 5mm/min, a span distance of 80mm at a room with a temperature of 20°C and 65% RH for air-dry wood samples, and that for wet wood samples were conducted in a water bath at 20°C (change in MC) and 80°C (change in MCT), respectively. MOE and MOR increased linearly with specific gravity regardless of wood species. On the other hand, maximum deflection did not correlate with specific gravity for any MCT conditions. The relative MOE and MOR which were calculated in wet 20°C to air-dry were affected from hardly to strongly depending on the wood species. Meanwhile, they decreased extremely when saturated in water at 80°C regardless of wood species. The relative MOE and MOR due to the change in MC or MCT was independent of specific gravity, as well. Furthermore, chemical compositions of the wood species were analysed to clarify the main factors that affected the decreasing of MOE and MOR due to MC and MCT changes. The results showed that the percentage of lignin and hemicelluloses in each wood played an important role in decreasing the static bending properties. Relative MOE and MOR decreased with increasing lignin and hemicellulose contents. It can be concluded that the hygrothermal properties of lignin and hemicelluloses significantly affect the changes of elastic and strength properties of wood in softening conditions.

Utilization of Quarry Dust as a Partial Replacement of Sand in Concrete Making

The use of crushed quarry dust as a partial replacement of river sand in concrete production was investigated in this study. This is expedient as quarry dust can be available at some locations with insufficient river sand for construction purposes. The use of quarry dust is also in concrete is also a measure necessary for improvement of concrete strength. River sand was replaced with quarry dust for different mix designs of concrete for 0% to 25% replacement levels with 5% intervals. The physical properties of river sand and quarry dust were tested and reported and the workability as well as compressive strengths of the concrete mixtures were also tested. It was observed that the slump values increased with increase in percentage replacement of sand with quarry dust. The compressive strength of cubes at 28 day curing for control mixture of 1:3:6 at 0% partial replacement of river sand with quarry dust was 12.6N/mm2 but compressive strengths of 21.5 N/mm2 and 26.0 N/mm2 were gotten for 1:2:4 concrete and 1:1.5:3 concrete respectively. As the quarry dust content increased to 25%, the 28day compressive strength increased to 13.58 N/mm2 and 21.57 N/mm2 for the 1:3:6 and 1:2:4 mixes respectively. Compressive strength values decreased to a value of 25.72N/mm2 for the 1:1.5:3 concrete mix. The maximum compressive strength values were reached at 20% quarry dust content at the age of 28 days for the three concrete grades investigated. The increase in compressive strength with inclusion of quarry dust was attributed to the higher specific gravity of quarry dust above river sand. The compressive strength of quarry dust concrete continued to increase with age for all the percentages of quarry dust contents. Quarry dust was recommended as a suitable partial replacement for river bed sand in concrete production.

Ultra-Fine Centrifugal Concentration of Bastnaesite Ore

Historically, the ability to effectively separate carbonate gangue from bastnaesite via flotation has frequently proven to be challenging without sacrificing significant rare earth oxide (REO) grade or recovery. However, in light of the fact that the rare earth bearing minerals often exhibit higher specific gravities than the carbonate gangue, the possibility exists that the use of gravity separation could be used to achieve such a selective separation. This however is complicated by the fact that, in cases such as this study when the liberation size is finer than 50 µm, most traditional gravity separation methods become increasingly challenging. The purposes of this study is to determine the applicability of gravity concentrators to beneficiate bastnaesite from deleterious calcite bearing flotation feed material. Via the use of a UF Falcon, it was possible to achieve rougher gravity REO recoveries approaching the upper 80% range while rejecting on the order of 30% of the total calcium. In terms of purely REO recovery, this represents a significant improvement over results obtained via a traditional Falcon in previously reported studies.

Recovery of Rare Earth Oxides from Flotation Concentrates of Bastnaesite Ore by Ultra-Fine Centrifugal Concentration

Historically, the ability to effectively separate carbonate gangue from bastnaesite via flotation has frequently proven to be challenging without sacrificing significant rare earth oxide (REO) grade or recovery. However, in light of the fact that the rare earth bearing minerals often exhibit higher specific gravities than the carbonate gangue, the possibility exists that the use of gravity separation could be used to achieve such a selective separation. This however is complicated by the fact that, in cases such as this study when the liberation size is finer than 50 microns, most traditional gravity separation methods become increasingly challenging. The aim of this study is to determine the applicability of centrifugal concentrators to beneficiate ultra-fine (UF) bastnaesite and calcite bearing flotation concentrates. By using a UF Falcon, it was possible to achieve initial gravity REO recoveries exceeding 90% while rejecting on the order of 25% to 35% of the total calcium from an assortment of rougher and cleaner flotation concentrates. Additionally, when additional stages of cleaner UF Falcon gravity separation were operated in an open circuit configuration, it was possible, from an original fine feed of 35 microns containing 50.5% REO and 5.5% Ca, to upgrade up to approximately 59% REO and 2.0% calcium. While not the goal of this study, these results also support previous limited data to suggest that UF Falcons are potentially capable of treating a wider range of materials than they were originally designed for, including feeds rich in heavy mineral content.

Assessing inter and intra-variation in the characteristics of faecal sludge from Vadgaon Maval, Maharashtra: For better faecal sludge management in India

Faecal Sludge (FS) produced in developing countries has become a significant source of water pollution. The optimal treatment of FS can lead to a sustainable economy. In India, the second phase of the open defecation free (ODF) initiative (energy recovery by providing city- or town-level centralised FS treatment plants) has begun from 2019 to sustain millions of toilets. However, to achieve this goal, India must address significant knowledge gaps such as the type of available on-site sanitation treatments (OSTs), optimal time of emptying the OSTs, and variations in the FS characteristics with age. Thus, the present study analysed FS samples collected from Vadgaon Maval, Maharashtra, India, to understand the inter- and intra-variation in FS characteristics. The pH, electrical conductivity, total solids (TS), specific gravity (SG), organic matter (OM), chemical oxygen demand (COD), and pathogen content of FS samples were observed to be in the range of 7–7.65, 1.19–4.01 mS/cm, 1–123 g/L, 0.88–1.26, 18.4%–100%, 960–6080 mg/L, and 105–109 number/L of FS, respectively. The inter-variation of FS characteristics exhibited that the pH, EC, TS, and SG increased, whereas OM, settling, and drying capacity decreased with an increase in age. Fresh FS (excreta degraded for ≤3 years) was yellowish-brown in colour and exhibited low TS, low SG, and high OM. On the other hand, older FS (excreta degraded for >3 years) was blackish-brown in colour and exhibited high TS, SG, and pathogen content. This observation indicates that FS vacuum pumping may be difficult in the sludge zone after 3 years of excreta degradation, which may encourage the manual scavenging practice. Additionally, the analysis of FS treatment plant (FSTP) process control parameters (settled sludge volume, sludge volume index, and sludge drying capacity) indicated that the treatment time required for older FS is long, which increases the FSTP cost. Furthermore, FS intra-variation in OST exhibited that effluent FS could be directly sent for effluent treatment without any solid–liquid separation process. Thus, the present study can help practitioners in establishing or modifying FS treatment systems for addressing conditions based on the variation in FS characteristics at the town level in India.

Study of the Effect of Fiber Composition on the Density and Unconfined Compressive Strength of Clay

In recent years, a lot of research has been done on fiber reinforced soil. However, in most of these studies, one type of fiber has been used and less attention has been paid to fiber composition issues. Also, the use of waste fibers has been less considered economically and environmentally. Therefore, in this study, the shear strength of soil clay has been investigated using 5 types of fibers including: industrial steel, scrap steel, glass, polypropylene and straw individually and in combination. The research process is that first a control design is prepared from fiber-free soil. Then, soil samples were prepared with the mentioned fibers individually in the amounts of 0.5, 0.75 and 1%. And in the third stage, samples of soil with fibers, in dual composition including: industrial steel and glass, industrial steel and polypropylene, glass and polypropylene, scrap steel and straw with weight percentages of 0.25 and 0.75, 0.5 and 5 / 0, 0.75 and 0.25, have been prepared. Finally, the maximum specific gravity and uniaxial compressive strength of all designs have been studied and compared.The results of this study showed that among the samples made with one type of fiber, glass with a value of 1%, the highest specific gravity and compressive strength, and among binary compounds, a combination of industrial steel and glass with a value of 0.75 and 25 0.%, the highest specific gravity and with 0.25 and 0.75%, the highest compressive strength is obtained.

Working Conditions and Urinalysis Dipstick Testing among Female Rice Farmers: A Preliminary Cross-Sectional Study.

This cross-sectional study aimed to assess working conditions and renal function among female rice farmers in Nan Province, Thailand. Purposive random sampling was used to select participants who met the inclusion criteria. Data were collected from 65 female rice farmers using in-depth interviews. A walk-through survey was performed to examine hazards in the rice farm and a dipstick test was used for urinalysis. The results demonstrated that all rice farming stages contained risks from physical, chemical, biological and ergonomic hazards and that no measures had been implemented to protect participants’ health from these risks. The screening test results showed low urinary pH (5–6) in 54 women (83.0%), but high urinary specific gravity (1.030) in 25 women (38.5%). Participants’ urine contained leukocytes in 15 women (23.1%), protein in 14 women (21.5%) and blood in 13 women (20%). This study results suggest that farming activities affect female rice farmers’ health and safety. Urinalysis dipstick tests, which can be administered at the local public health promoting hospital, should be used to assess the occupational health status. The results will be useful for health surveillance and follow-up of the participants. These preliminary findings need to be confirmed in a larger study including non-farmers.

Fabrication and characterization of W/Cu/Ni-based high specific gravity alloy with Zr and Ti combined addition

W/Cu/Ni-based high specific gravity alloys with Zr and Ti combined addition were successfully prepared through mechanical ball milling combined with spark plasma sintering. The morphologies, structural evolutions, and compositions of the W/Cu/Ni-based composites were thoroughly studied through scanning electron microscopy, energy dispersive spectrometry, and high-resolution transmission electron microscopy. Results reveal that the prepared (Zr, Ti)-doped W/Cu/Ni-based composite has completely compact structure and uniform element distribution after sintering, resulting in the W/Cu/Ni-based alloys with superior microhardness (up to 911.9). The Ti and Ni elements combined to form TixNiy intermetallic compounds, and the CuxZry intermetallic compounds were formed by the combination of Cu and Zr elements. The electrical properties of the W/Cu/Ni-based composites were also explored in detail. The electrical conductivity of the W/Cu/Ni composite increased from 13.2 MS/m to 19.9 MS/m, and the mass loss of electric ablation decreased from 6.20 mg to 1.21 mg through Zr and Ti combined addition. Hence, the W/Cu/Ni-based alloys with Zr and Ti combined addition provide an effective support for future electrical contact materials in electrical and electronic fields.

Dispersal limitation, soil, and fire affect functional properties of tropical secondary forests on abandoned cattle ranching landscapes

Forest age is a major predictor of secondary forest functional properties and through the chronosequence approach continues to be a principal focus in local, landscape, and regional-scale studies of secondary succession. Recent work has shown that patterns of temporal change in functional properties differ markedly between wet and seasonally dry lowland forests, suggesting that decreasing light and increasing water availability, respectively, are the main drivers of successional change. Meanwhile, however, the potentially marked effects of anthropogenic factors (especially fire), soils, climate, and dispersal limitation on the variation of forest characteristics over landscapes remain poorly understood. We studied the functional properties of seasonally dry secondary forests 5–35 years after pasture abandonment on the Nicoya Peninsula, Costa Rica. We measured 11 functional traits for 63 dominant tree and palm species in 52 plots of 0.12 ha. We used linear regression and variation partitioning to determine the relative importance of soil, climate, site use, fire history, spatial factors, and forest age in the determination of community weighted mean (CWM) trait values. CWM leaf trait and stem trait spectra of the 52 plots were orthogonal in a PCA ordination. Our seasonal forest hypothesis, that forest functional properties become more acquisitive with age as suggested by other authors, was not supported, perhaps because our chronosequence was relatively short. Our fire tolerance hypothesis was that bark thickness, wood specific gravity and resprouting capacity would increase with time of exposure to fires. This hypothesis was not supported for bark thickness. Rather, our results suggest that wood specific gravity and resprouting capacity are better predictors of fire tolerance. Also, our results suggest that >10 years of exposure to fire generates changes in forest fire tolerance strategies from high CWM bark thickness to high wood specific gravity. Finally, we tested our dispersal limitation hypothesis, that spatial variables, expressed as principal coordinates of neighbor matrices (PCNM) eigenfunctions, predict variation in forest functional properties, using variation partitioning analysis with matrices of climate, soil, anthropogenic and spatial variables. The results (overall model R2 = 0.46) indicated that spatial variables, followed by soil (acidity, depth, and extractable Mn), are the best overall predictors of forest functional traits values, supporting this hypothesis. Overall, fire, dispersal limitation and soil characteristics explain the functional properties of these secondary forests, with no effect of age in the 5–35 years range. This indicates a critical need for sampling designs and analytical approaches that take into account all these factors to advance understanding of tropical seasonal forest recovery at the landscape scale.

Urinary Specific Gravity Decreases over Time in Adult Sickle Cell Patients

▪Introduction: Altered urinary concentration is one of the earliest and most common features of kidney disease in patients with sickle cell disease (SCD). This phenomenon is reversible in early age by transfusion but becomes fixed with time. Little data exist as to which additional clinical features are associated with impaired urinary concentration. Further, longitudinal changes in urinary concentration over time in adults have not been examined.Methods: We conducted a retrospective study of adult sickle cell patients seen between January, 2004 and December, 2013 at a single center. Clinical and laboratory variables were abstracted from medical records. Specific gravity was assessed from random dipstick urinalysis results. Estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. Patients had confirmed SCD, were at least 18 years old, and were evaluated during routine clinic visits. Mixed effects models were fit to evaluate the change in specific gravity over time. Clinical and laboratory variables, including measures of kidney function or disease, hemolysis markers and associated comorbidities, were evaluated for their association with baseline specific gravity and on specific gravity over time in age- and sex-adjusted analyses. We also compared those with severe phenotypes (SS/Sβ0) to those with mild phenotypes (SC/Sβ+). A multivariable model was constructed utilizing covariates identified in univariate analyses with a final model produced via backward elimination with age and sex adjustment retained. We included interaction terms between covariates and to evaluate the longitudinal association of these variables on change in specific gravity. We also employed similar approaches in analyses stratified for those with SS and Sβ0 disease from those with milder SC and Sβ+disease.Results: Four hundred and forty-seven patients with SCD (SS = 280, SC = 102, Sβ0 = 22, Sβ+ = 33, SE = 2, SLepore = 2, SD = 2, SHPFH = 4) were followed over a median duration of 2.8 years (IQR: 0.99 - 6.3 years). Median age was 28.5 years (IQR: 20 - 40 years) and 238 were female (53%). Over time, specific gravity decreased (-0.00011 per year, SE 0.000030; p=0.0002). In stratified analysis, patients with SS/Sβ0 had a similar decrement (-0.00011, SE 0.000032; p=0.0005) while SC/Sb+ had a slightly lower decline (-0.00008, SE 0.000079; p=0.3) that was not statistically significant. Patients with SS/Sβ0 trended toward slightly higher baseline specific gravity (0.00079, SE 0.00035; p=0.03) compared to SC/Sb+ patients. At baseline, hemoglobin level (0.00017, SE 0.000079; p=0.03) and hemoglobinuria (0.00096, SE 0.00046; p=0.04) were associated with higher specific gravity. In multivariate modeling, only hemoglobinuria (0.0012; SE 0.00048; p=0.01) and SS/Sβ0 phenotypes (0.00096, SE 0. 00036; p=0.009) were associated with higher specific gravity. Over time, ferritin; (-0.00011, SE 0.000048; p=0.02) and priapism in men (-0.00029, SE 0.00010; p=0.006) were associated with annual decline in specific gravity. Use of angiotensin-converting-enzyme inhibitors/angiotensin receptor blockers (ACE-I/ARB) (0.00018, SE 0.000076; p=0.02) was associated with a rise in specific gravity. In multivariate analyses, only ferritin (-0.00012, SE 0.000048; p=0.01) was associated with annual decline in specific gravity When evaluated separately, SS/Sβ0 demonstrated nearly identical findings in multivariate analysis for ferritin (-0.00013, SE 0.000057; p=0.02).Conclusion: Even in adult patients with SCD, specific gravity declines over time, and decline may be more prominent in those with SS/β0. Higher ferritin, a measure of iron overload, is associated with greater decline in specific gravity. Future prospective studies of kidney disease in SCD patients should include measures of specific gravity to better understand this phenomenon and its long-term consequences. DisclosuresAtaga:Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Reprixys Pharmaceuticals Corporation (formerly known as Selexys Pharmaceuticals Corporation, which is not affiliated with Selexis S.A.): Research Funding; Global Blood Therapeutics: Research Funding; Global Blood Therapeutics: Honoraria; Novartis: Honoraria; Novartis: Membership on an entity's Board of Directors or advisory committees.

Geotechnical properties of unprocessed soil from abandoned Mamut mine in Sabah, Borneo

The issue related to the geotechnical stability of land mining area in Malaysia had become more critical after a strong earthquake struck Sabah, Borneo in 2015 centred in Ranau District where Mamut copper mine is located. As part of safety assessment and future planning, knowledge of soil characteristics in this risky area is necessary. This paper presents some findings on geotechnical properties of unprocessed soil obtained from the abandoned mine. Results found that Mamut soil can be classified as SW and has higher coarse-grained percentage (97.4%) compared to other copper mines elsewhere. The soil also has higher permeability (3.61 x 10−3 m/s), lower organic content (0.15%), lower pH (4.53), higher specific gravity (2.75) and higher maximum dry density (1780 kg/m3). Mamut soil is found to be cohesionless, while the angle of friction shows a variation with the relative compaction. Chemical analysis shows that SiO2 and C12H10MgO6S2 are the two predominant compounds of the soil. Morphologically, Mamut soil appears to be composed of powdered and hardened particles with dark brown colour. They contain higher amount of irregular-shaped particles but well-rounded and spherical shapes are also observed. Smooth surfaces with no agglomeration between particles indicates that the strength value of the soil is low due to the weak bonding between the loose grain structure. These findings suggest that Mamut soil is suitable for chemical stabilisation or remediation method such as microbiologically induced calcite precipitation (MICP).

Study on radon (222Rn) emanation coefficient and mass exhalation rate from heavy minerals of high specific gravity

A study on 222Rn emanation coefficient and mass exhalation rate was carried out for different minerals having high specific gravity collected from a natural high background radiation area of India. The mass exhalation rate varied from 31 ± 0.5 to 2366 ± 36 mBq kg−1 h−1 and the radon emanation coefficient varied from 1.02 × 10−2 to 2.04 × 10−1. The radon escape probability was highest in garnet mineral indicating the uniform distribution of radium atoms on the mineral surface and smaller grain size than other minerals. Statistical analysis revealed that the radon mass exhalation rate was positively correlated with the 226Ra activity whereas no such strong significant correlation was observed between radon emanation coefficient and 226Ra activity.

Performance of potato clones for processing in subtropical and high-altitude tropical regions of Brazil

This work evaluated the performance of potato clones for some agronomic and processing traits, in subtropical and high-altitude tropical regions, under conventional and organic production systems. Experiments were conducted in spring of 2017 and 2018 in Canoinhas-SC (subtropical), under the conventional system, and in winter of 2018 and 2019 in Brasília-DF (tropical), Brazil, under conventional and organic systems. Eleven advanced clones and cultivars Agata (fresh), Atlantic (chipping) and Asterix (French fry) were evaluated. RCBD with tree replications was used, and tuber yield and processing traits, plant vigor and cycle were evaluated. It was not possible to select high yielding and good processing quality clones with short cycle and less vigorous plants. It because higher yield and larger tuber size were attained by longer cycle genotypes, which had higher specific gravity, but darker frying color. The most outstanding clones differed with region and production system. For chipping, in the subtropical region, no clone had adequate quality, but in tropical F177-11-20 presented similar processing traits and higher or similar yield to 'Atlantic' in both systems, and also ORG7785 in organic. Comparing with ‘Asterix’, for French fry, in the subtropical region, superior or similar to the standard this cultivarwere F129-10-06 and F163-11-01; while in the tropical region and conventional system, were the clones ORG7785, F129-10-06, F163-11-01, F177-11-20, ORG6464, ORG 6377, F05-11-03, Odone 80-02 and F174-11-01; and in organicsystem, the best cloneswere F54-11-03, ORG7785, F129-10-06, F163-11-01, F177-11-20 and ORG6464.

Selective grinding of glass to remove resin for silicon-based photovoltaic panel recycling

Secondary grinding was investigated as a mean of liberating glass from locked particles of glass and resin obtained by the primary shredding from the silicon-based PV panels. Many previous studies on separating glass from resin have focused on chemical processes. However, a simple physical process—using an eccentric stirring mill to selectively grind the glass, separating the glass from the resin, and concentrating the glass into a narrower particle size group—resulted in successful liberation. Grinding rate analysis using the population balance model quantitatively confirmed that glass particles were more easily ground than resin particles and that locked particles were more easily ground than free particles. This is because the high specific gravity of the glass particles and the greater adhesiveness of the locked particles cause them to be located near the stirring blade of the mill. The selectivity of grinding became more significant and the grinding time shorter as the rotation speed increased. At the optimal grinding speed of 2500 rpm, 97% of the glass was concentrated into particles under 5.6 mm in size in 5 min. The resulting glass particles had a carbon content of 1% or less, which makes them suitable for the manufacture of glass fiber.

Design of asphalt mixes with steel slag aggregates using the Bailey method of gradation selection

It has been reported in the literature that the asphalt mixes containing a high percentage of Steel Slag Aggregates (SSA) are susceptible to high void space. This is one of the major reasons that SSA usage is limited to replacement of either the fine or coarse aggregates fraction, but not both by the road agencies. More void spaces in the asphalt mixes with a higher proportion of SSA can be attributed to the high specific gravity of the coarse aggregate (CA) of SSA and the adoption of weight-based gradation selection for mix design. This issue can be addressed by adopting the volume-based Bailey method. The present paper attempts to provide a framework to design asphalt mixes with a high proportion (up to 100%) SSA with aggregate fractions of varying specific gravity by employing the Bailey method of gradation selection. The study in the paper showed that by adopting the Bailey method for gradation selection, SSA mixes with Voids in Mineral Aggregates (VMA) similar to Natural Aggregate (NA) mixes can be produced despite the significant differences in specific gravities between the fine and coarse aggregate fractions. Test for mechanical properties on asphalt mixes suggested that the resilient modulus of SSA asphalt mixes can be 1.4 to 1.8 times that of NA asphalt mixes. Owing to the high particle strength of SSA combined with the predominantly cubical shape, SSA mixes were found to be relatively more resistant to rutting. Comparisons based on linear elastic analysis and design of hypothetical pavement sections indicate that the fatigue life of pavement with SSA asphalt base layers is comparable with the fatigue life of the pavement with NA asphalt mix bases. It was also observed that the asphalt mixes with SSA aggregates had shown relatively more resistance to the moisture damage.

Shielding Properties of Heavyweight Concrete.(Dept.C)

Heavyweight concrete can be used when particular properties, such as combined high strength and good radiation shielding, are required. Such concrete, using Ilmenite aggregates, can have a density in the range 4.2 t/m3, significantly higher than the density of concretes made with normal aggregate. The present paper deals with sand-llmenite heavy weight concrete, llmenite has been used as coarse aggregate because of high specific gravity compared with gravel. In the present work, 21 mixes were selected to achieve a slump above 5± 2 cm and strength up to 40 MPa at 56 days. The investigation used three levels of fine aggregates to total aggregates ratio (0.25, 0.4, 0.48), three cement content (350, 400, 450 kg/m3) and four levels of llmenite aggregate to total coarse aggregate (gravel + Ilmenite) ratio (0.25, 0.5, 0.75, 1) were used. The investigation provided information on compressive strength, shielding properties and indicated clear benefits from the use of lImenite as a coarse aggregate. For all type of coarse aggregate (gravel, Ilmenite), increasing the amount of fine aggregate leads to reduction in each of compressive strength and absorption co-efficient. Replacing the gravel with llmenite yields about 35% increase in absorption co-efficient.

Production and characterisation of new bioresorbable radiopaque Mg–Zn–Y alloy to improve X-ray visibility of polymeric scaffolds

For the medical diagnosis, radiopaque materials (RM) made from high specific gravity elements like Pt, Au, Ta, Iodine, Bromine are either attached or blended or coated on an implant to makes it detectable under X-ray/Fluoroscopy/CT-Scan. RM facilitate the surgeon in an operation theatre to position an implant during the surgery. Mainly, RM are non-degradable, thus in case of biodegradable implants, it may detach from the body and accumulate in vital organ cause serious health issue. Therefore, a new bioresorbable radiopaque material (BRM) was produced by alloying the high specific gravity elements Zn (35% w/w) and Y(4% w/w) with Mg metal. In this alloy, three main phases were identified, alpha Mg, Mg 7 Zn 3 and icosahedral quasicrystalline I-phase Mg 3 Zn 6 Y, which reinforce the Mg matrix. Hereafter, BRM was powdered to a size of less than 25microns and blended in different ratios with bioresorbable poly- l -lactic acid (PLLA) for fabricating PLLA/BRM bio-composite. BRM microparticles were uniformly distributed and interfacial bonded with the matrix. The X-ray was passed through bio-composite to capture µCT radiograph for evaluating linear attenuation co-efficient (µ) and optical density (OD). Thermal analysis reveals that BRM particles act as a nucleating site and enhance the crystallinity of the polymeric chain. During the In Vitro accelerated degradation study, the alkaline nature of BRM neutralise the acidity of PLLA and balance the pH of the body fluid to reduce the inflammatory reactions, but this compromises the stability of the polymer as it increases the decomposition rate.

К ВОПРОСУ О ДВУХ КУЛЬТУРНО-ХРОНОЛОГИЧЕСКИХ ГРУППАХ КРЕМНЕВОГО ИНВЕНТАРЯ СТОЯНКИ КРАСНЫЙ ГОРОДОК

The Krasny Gorodok site, explored in the late 1980s, has long attracted the attention of specialists in the Neolithic. There archaeologists discovered a small but very interesting collection of ceramics. At the same time, the flint complex of the site raised several questions even at the stage of primary comprehension of the material, and researchers made assumptions about the presence of two cultural-chronological groups of flint materials in the complex of the site. In connection with the expansion of the source base on the Early Neolithic and Mesolithic of the forest-steppe Volga region, as well as the acquisition of a significant array of natural science data, it became necessary to verify the conclusions drawn by more than a quarter of a century ago. In particular, the question of the homogeneity of the flint collection of the site and the possibility of identifying an early admixture remains relevant. During the reanalysis of the flint collection of the Krasny Gorodok site, about 600 units of stone artifacts were examined. This complex was divided into two groups depending on the color and quality characteristics of the flint. The first group is represented by artifacts made of high-quality flint of gray color and its various shades. The second group includes artifacts made of low-grade colored flint, mainly brown and of various shades of brown, without a stable shape. The first group is characterized by a large orientation towards obtaining plates of a regular shape and their relatively high specific gravity (23%). In addition, this type of raw material was used to make all the angular cutters on the plates found at the site and, in general, most of the tools were made from plate blanks. The collection of tools made of colored flint is less indicative, however, one can state a lesser orientation towards obtaining plates from this type of raw material and, predominantly, their irregular shape, while few tools were made on flakes and chips. In our opinion, the marked differences between the first and second groups of stone products from the site are of a cultural and chronological nature. The first group of flint, in terms of raw materials, shape and technique of making tools and applying retouching on them, can be attributed to the era of the late Mesolithic of the forest-steppe Volga region. The second group, in terms of the nature of the raw materials and the morphology of tools, belongs to the Early Neolithic.

Hydraulic conductivity and calcium carbonate content of biocemented heavy-metal contaminated mine waste soil

It is not uncommon for mining activity to generate wastes associated with negative engineering impacts include susceptibility to runoff due to the absence of vegetation, erosion, and sinkhole. Due to their high degree of permeability, movement of heavy metal contaminants in waste soils and aquifers occurs actively along with the hydrogeological parameters, and research on using biocementation methods such as enzyme induced calcite precipitation (EICP) to reduce the hydraulic conductivity is therefore beneficial. Mine waste soil collected from a copper mine in Lohan Dam, Sabah is characterized physically, morphologically, and chemically then treated with EICP under different operational parameters include curing duration (1,3,7 days), curing temperatures (5, 10, and 25 oC ), and relative density (70 and 80 %). The hydraulic conductivity was then tested using a constant head permeability test and the calcium carbonate content (%) is determined using the HCL washing method. Properties of the Lohan Dam wastes are found to be predominantly coarse grain soil of low plasticity, high specific gravity, high permeability, acidic in nature, and low organic content. Morphologically, they are composed of powdered and hardened particles with dark brown color with high amount of irregular-shaped particles. Mineralogical, Lohan Dam soil wastes contain a high level of heavy metals beyond the safety level of the Department of Environmental Malaysia. EICP treatment had to change the degree of permeability from ‘high and medium’ to ‘low’ with a 94-97% reduction in hydraulic conductivity corresponding to the amount of calcium carbonate content produced ranging 6.94-9.63%. In conclusion, relative density shows the marginal effect, curing duration, and temperature shows a more significant impact on the treatment effectiveness.