Plain Samples Research Articles

Hydration kinetics and performance of sodium carbonate-activated slag-based systems containing reactive MgO and metakaolin under carbonation

The hydration mechanism and strength development of sodium carbonate-activated slag-based systems mainly depend on the additives used. Although the effects of mineral additives in such systems have been extensively investigated, the effects of Mg2+, Al3+, and Si4+ ions increasing with the addition of reactive MgO (Mg) and metakaolin (Mk) on the hydration mechanism of such systems have not been established yet. This study investigated the hydration kinetics and performance of sodium carbonate-activated ternary blended slag-based binder systems. The hydration mechanism was revealed by isothermal calorimetry and mechanical performance was evaluated with the measurement of compressive strength at different ages up to 56 days. The reaction mechanisms were investigated through X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and 29Si and 27Al solid-state nuclear magnetic resonance (NMR). C-(A)-S-H, Na and Al-enriched C-(N,A)-S-H and hydrotalcite were the main reaction products responsible for the strength development of the samples, accompanied by the minor contribution of other carbonate-containing phases. Partial replacement of slag with Mg and Mk led to high early-age strengths compared to plain samples when Mk was used at 5%. Samples incorporating Mg and Mk achieved similar or higher strengths than ordinary Portland cement-based samples. However, an increase in replacement ratio of Mk beyond 5% led to a significant decrease in compressive strength. Furthermore, the performance of samples under accelerated carbonation was studied. The use of Mg and Mk enhanced carbonation resistance due to enhanced hydrotalcite and C-(N,A)-S-H gel formation, highlighting the potential of using slag-Mg-Mk blends as an alternative binder system.

A combined contour lines iteration algorithm and Delaunay triangulation for terrain modeling enhancement

ABSTRACT Digital Elevation Models (DEMs) play a crucial role in civil and environmental applications, such as hydrologic and geologic analyses, hazard monitoring, natural resources exploration, etc. Generally, DEMs can be generated from various data sources, such as ground surveys, photogrammetric stereo methods, satellite images, laser scanning, and digitized contour lines. Compared with other data sources, contour lines are still the cheapest and more common data source becausethey cover all areas, at different scales, in most countries. Although there are different algorithms and technologies for interpolation in between contour lines, DEMs extracted solely from contours still suffer from poor terrain quality representation, which in turn negatively affects the quality of analytical applications results. In this paper, an approach for improving the digital terrain modeling based on contour line densification and Delaunay triangulation is presented to acquire a more suitable DEM for hydrographic modeling and its applications. The proposed methodology was tested using a variety of terrain patterns in terms of intensity: hilly, undulated, and plain (1:25,000 topographic map, 5 m contour interval). The precision of the extracted GRID model increases as the number of added contours increases. Adding four contour lines, the Root Mean Square Error (RMSE) of examining points were 0.26 m, 0.29 m, and 0.05 m for hilly, undulated, and plain samples, respectively, and the Mean Absolute Error (MAE) were 0.50 m, 0.48 m, and 0.17 m. The convergence probabilities between extracted and original flow lines for the same regions were 96.91%, 94.93%, and 84.03%. Applying the methodology, experimental results indicate that the developed approach provides a significant advantage in terrain modeling enhancement, generates DEMs smoothly and effectively from contours, mitigates problems and reduces uncertainties.

Effect of Lycopene on Selected Electrolytes in Sprague Dawley Rats Exposed to Dimethoate

Aim: This study was aimed at evaluating the effect of lycopene on some selected electrolytes in Sprague Dawley rats exposed to Dimethoate.
 Experimental Design: A completely randomized experimental design using standard methods for analysis.
 Location and Duration of Study: This study was carried out in the Department of Biology, Ignatius Ajuru University of Education Rumuolumeni, Port Harcourt, Rivers State, Nigeria. GPS 4o48ʹ14ʹʹ N 6o59ʹ12ʹʹ E. The study lasted for 28days.
 Methodology: Thirty male rats were randomly selected into five (5) groups A-E (n=6/group). Groups B, C and D recieved 10,20 and 30 mg/kg/bw/day of dimethoate respectively co-administered 10mg/kg/bw of lycopene daily. Group E were administered 30mg/kg/bw/day of dimethoate without lycopene. All animals were allowed access to cool clean water and standard rat pellet ad libitum. Twenty-four hours to the termination of the experiment, feed was withdrawn from the animals. Blood samples for electrolytes analysis were collected through ocular puncture between the hours of 7:00am and 9:00am into plain sample tubes according to the approved protocol of blood collection techniques, while statistical analysis was carried out using one-way Analysis of Variance (ANOVA) and expressed as their respective units using SPSS 20 software.
 Results: Result showed a significant (P=0.05) increase in the concentrations of sodium, calcium, potassium and bicarbonate with increase in the concurrent administration of lycopene. The highest concentration of all electrolytes was observed at the concentration of 30mg/kg/bw/day with coadministration of lycopene. Administration of lycopene at the concentration of 10mg/kg/bw appeared not to have any significant effect on production of electrolytes since all the electrolytes assessed increased with increased concentration of the pesticides. However, further work is required to make any conclusive statement with lycopene effect on electrolyte.

Pyrolysis of anaerobic digested residues in the presence of catalyst-sorbent bifunctional material: Pyrolysis characteristics, kinetics and evolved gas analysis

We investigated the potential application of anaerobically digested residues for generating bioenergy in the presence of alkali bifunctional material, sodium zirconate (Na2ZrO3, NZ) using a thermogravimetric analyzer connected to a mass spectrometer. Isoconversional kinetic models, compensation effect and master-plots method were used on data obtained under multiple heating rates (10, 15 and 20 °C min−1) to calculate the activation energy (Eα) and pre-exponential value (A) and reaction mechanism. The average Eα for blend samples C-DSW (NZ mixed with digested municipal solid waste (DSW)), and C-DSM (NZ mixed with digested swine manure (DSM)) were 172.24 and 171.63 kJ mol−1, which were much lower when compared to plain samples, DSW (202.51 kJ mol−1) and DSM (215.22 kJ mol−1). The total gas yields increased by 19.5 and 17.1% for NZ blended samples C-DSW and C-DSM, respectively. In addition, the hydrogen yields also increased by 79 and 44% for C-DSW and C-DSM, respectively.

Hormonal Profile Evaluation in Swiss Male Mice Administered Lambda Cyhalothin and Extracts of Some Local Spices

Aim: This study was aimed at evaluating the hormonal profile of Swiss male mice administered lambda cyhalothin and extracts of some local spices.
 Experimental Design: A completely randomized experimental design using standard methods for analysis. 
 Location and Duration of Study: This study was carried out in the Department of Animal and Environmental Biology, Rivers State University, Port Harcourt, Rivers State, Nigeria. GPS 4o47'50''N 6o58'49''E The study lasted for 35 days.
 Methodology: Forty-two male mice were randomly selected into six (6) groups A-F (n=7/group). Group B were gavage Cyhalothin LCT) alone. Group C, D, and E were gavaged 10 mg/kg/bw of LCT and 20 mg/kg/bw/day of Tetrepleura tetraptera, Piper guineense, and Xylopia aethiopica respectively, while group F received 10 mg/kg/bw of LCT together with the combination of the three spices. All animals were allowed access to cool clean water and standard rat pellet ad libitum. Twenty-four hours to the termination of the experiment, feed was withdrawn from the animals. Blood samples for hormonal profile evaluation were collected through ocular puncture between the hours of 7:00 and 9:00am into plain sample tubes according to the approved protocol of blood collection techniques. Analysis for the quantitative determination of all androgens was carried out using enzyme-linked immunosorbent assay (ELISA), while statistical analysis was carried out using one-way Analysis of Variance (ANOVA) and expressed as their respective units. Where significant differences were found, Pair-wise comparisons conducted with Tukey test using SPSS 20 software.
 Results: Result showed a significant (P=0.05) decrease in the concentration of all androgens in group B animals treated with LCT alone. The level of these hormones were also reduced although not as low as the level in group B, with administration of the combination of all three spices in group F. This implies that the consumption of these spices might have had an antagonistic effect on the level of hormone produced when combined. Exposure to lambda cyhalothrin, affects reproductive hormones in males leading to infertility and other reproductive dysfunctions. Using spices such as tetrapleura tetraptera and Piper guineense singly as remedy can ameliorate the toxic effect of insecticide related hormonal changes under the guidance of a doctor or any healthcare professional. However, high and frequent intake of Xylopia aethiopica or the concomitant consumption of these three spices is not advised for males.

Theory of Critical Distances and static/dynamic fracture behaviour of un-reinforced concrete: length scale parameters vs. material meso-structural features

The Theory of Critical Distances (TCD) groups together a number of approaches that make use of specific length scale parameters to model and estimate the strength of cracked/notched engineering materials. In the TCD framework, the critical distance is assumed to be an intrinsic property and this length is somehow related to the material micro-/meso-/macro-structural features. In recent years, a number of comprehensive theoretical/experimental investigations have proven that the TCD is successful also in assessing the static/dynamic Mode I/Mixed-Mode I-II strength of unreinforced concrete containing geometrical features of all kinds. However, the scientific community has not yet agreed on a commonly accepted answer to the most obvious fundamental research question, i.e. “what is the physical meaning of the TCD critical distance?” In order to answer this question, a number of experimental results were generated by testing specimens of unreinforced concrete under static and dynamic Mode I bending. According to what is recommended by RILEM for the determination of fracture parameters of plain concrete, this comprehensive experimental work involved not only plain samples, but also specimens containing crack-like saw-cut notches. The specimens being tested were manufactured by using different bespoke mixes so that the meso-structural features of the concrete materials being tested could be controlled and then modelled in a very accurate way. The results from this systematic experimental/theoretical study led to the conclusion that the TCD critical length approaches the average distance between the crack-like saw-cut notch tip line and the first aggregates, with these aggregates acting as barriers slowing down/affecting the crack propagation process.

Plain and notch fatigue strength of ductile cast iron GJS600: The role of defect sensitivity

The present work is aimed at exploring the applicability of the theory of critical distances (TCD) to the plain and notch fatigue prognosis of the ductile cast iron GJS600. Particular attention is paid to investigating how defectiveness influences material critical length. It was found that fatigue damage is triggered by microshrinkage porosity in plain samples and by graphite nodules in notched samples. This evidence makes cumbersome the applicability of TCD, which postulates the notch-crack equivalence. According to this postulate, the critical distance can be inferred from a plain and a notched or cracked specimen configuration. Since the plain variants examined in this paper exhibit a fatigue damage phenomenon different from the notched ones, the critical distance inferred in this way leads to inaccurate predictions of the fatigue strength of independent notched variants. To overcome this shortcoming, we explore here the possibility of inferring the critical distance from two notched variants with different notch severity.

Physicochemical characteristics, sensory profile, probiotic, and starter culture viability of synbiotic yogurt.

This study aimed to envisage the effectiveness of adding three particular prebiotics (inulin, β-glucan, and Hi-maize) to synbiotic yogurt's physicochemical properties, sensory characteristics, and survivability of the probiotic and starter cultures. The yogurt's gross composition, syneresis, water-holding capacity (WHC), viscosity, sensorial properties, and probiotic and starter cell stability were analyzed. The Lactobacillus delbrueckii subsp. bulgaricus M240-5 and Streptococcus thermophilus M140-2 were employed as yogurt starter bacteria, and Lactobacillus acidophilus LA-5 as probiotic culture. The synbiotic yogurt was formulated with 5% sucrose and 0.7% artificial vanilla flavor. The findings showed that when prebiotic ingredients were added to synbiotic yogurt, it had a significant impact on its sensory qualities, WHC, syneresis, and viscosity when compared to plain yogurt samples. The prebiotics did not affect the pH and titratable acidity of the yogurt samples. Additionally, the prebiotic supplementation did not influence the protein and fat content of synbiotic yogurt (p < 0.05). Prebiotics had an impact on the probiotic cell viability and total viable count (p < 0.05) compared to the plain sample, the 2.5% β-glucan, 1.5% and 2.5% Hi-maize samples had the highest mean viability (8.95 Log CFU/ml). The starter culture ratio remained stable in response to the prebiotic levels. In summary, the production of synbiotic yogurts supplemented with Hi-maize and β-glucan at 1.5% and 2.5%, respectively, is highly advised because these supplementations provide yogurt with acceptable syneresis, viscosity, WHC, and sensory attributes.

Fatigue life assessment of polyamide 12 processed by selective laser sintering. Damage modelling according to fracture mechanics

PurposePolyamide 12 (PA12) processed by the additive manufacturing technique of selective laser sintering (SLS) is acquiring a leading role in cutting-edge technological sectors pertaining to transport and biomedical among others. In many of these applications, design requirements must ensure fatigue structural integrity. One of the characteristic features of these SLS PA12 is the layer-wise structure that may influence the mechanical response. Therefore, this paper aims to assess the fatigue life behavior of PA12, focusing on the effect of the load direction with respect to the load orientation.Design/methodology/approachWith the aim of analyzing the effect of the load direction with respect to the layer wise structure, fatigue tests on plain samples of SLS PA12 were carried out with the load applied parallel and perpendicular to the layer planes. The S-N stress life curves and the fatigue limit at 106 cycles were determined at room temperature and at a stress ratio of 0.1. The fracture surfaces were inspected to evaluate the damage evolution, modeled via the fracture mechanics methodology to obtain the fracture parameters.FindingsThe fatigue resistance was better when the load was applied parallel than when was applied perpendicularly to the layered structure. The analysis of the postmortem specimens evidenced three regions. The inspection of the fatigue macro crack growth region revealed that crazing was the mechanism responsible of nucleation and growth of damage till a macroscopic crack was generated, as well as of the consequent crack advancement. The calculated fracture parameters computed from the application of the fracture mechanics approach were similar to those obtained from standardized fracture tests, except when the stress levels were close to the yield strength.Originality/valueThe fatigue knowledge of polymers, and especially of polymers processed via additive manufacturing techniques, is still scarce. Therefore, the value of this investigation is not only to obtain fatigue data that could be used for structural design with SLS PA12 materials but also to advance in the knowledge of damage evolution during the fatigue process.

Study on dynamic mechanical properties of carbon nanotubes reinforced concrete subjected to freeze–thaw cycles

AbstractAs a nanometer material, carbon nanotubes can inhibit the expansion of microcracks and is of great significance to improve the mechanical properties and durability of concrete. In order to explore the mechanism of dynamic mechanical properties enhancement of carbon nanotube reinforced concrete under impact load after freeze–thaw cycles, the dynamic compression test of carbon nanotube reinforced concrete samples was carried out by using the control variable method with freeze–thaw cycles and impact air pressure as variables. The results showed that under the same impact pressure, the peak stress of carbon nanotube reinforced concrete sample decreased gradually with the increase of freeze–thaw cycles. The corresponding strain increased slightly, and the stress–strain curve moved to the right and down as a whole. Under the same freeze–thaw cycle, the peak stress of carbon nanotube reinforced concrete sample increased with the increase of strain rate, and the dynamic strength growth factor DIF also increased, showing an obvious strain rate strengthening effect. In addition, under the same freeze–thaw cycles and external impact load, the dynamic strength of carbon nanotube concrete is 41.97 and 54.21 MPa, respectively, which is 22.27 and 25.81% higher than that of ordinary plain concrete. The results show that carbon nanotube reinforced concrete samples have higher dynamic mechanical properties and freeze–thaw cycle resistance than ordinary plain concrete samples.

Screening of Asymptomatic Healthcare Workers for SARS-COV-2 for Occult Infections: A Cross-Sectional Study.

IntroductionThe SARS-CoV-2 illness (COVID-19) has spread around the world, primarily through person-to-person transmission, and is a serious public health concern. Based on the severity of illness symptoms, SARS-CoV-2 infection can be classified as either apparent or occult. To date, real-time reverse transcription polymerase chain reaction (RT-PCR) on respiratory specimens, particularly nasopharyngeal and oropharyngeal swabs, or nasopharyngeal wash or aspirate, has been the gold standard for the identification of COVID-19. A negative RT-PCR does not necessarily rule out SARS-CoV-2 infection. Occult COVID-19 infections could least be identified with RT-PCR.Aims and objectivesTo assess the prevalence of possible occult COVID-19 infection in healthcare personnel by RT-PCR and serology testing for SARS-CoV-2 virus.MethodsA cross-sectional study was conducted on health care workers at a tertiary care hospital in South India during the period from October 2020 to January 2021. None of the study participants were vaccinated against COVID-19 during the study period. Nasopharyngeal swabs collected for RT-PCR were tested using Cobas 480 platform (Roche, Basel, Switzerland). Peripheral blood venous sampling was performed to collect EDTA (ethylenediaminetetraacetic acid) and plain samples. SARS-CoV-2 IgG antibodies against spike proteins were estimated using ECI Vitros platform (Ortho Clinical Diagnostics, Raritan, USA).ResultsThe mean age of study participants was 34.78 years (SD±9.51) with an age range of 19-69 years. The study participants were stratified into age groups of 19-25 years, 26-40 years, 41-60 years, and above 60 years, gender, ABO and Rh blood groups, and occupational and further based on their area of work as Covid and Non-Covid for the purpose of statistical analysis. Total 190 samples from healthcare workers (HCWs) were tested for RT-PCR using nasopharyngeal swabs collected at the time of enrolment into the study, and all the 190 samples tested negative for RT-PCR. Among 190 HCW samples screened for SARS-CoV-2-IgG antibodies, 48 (25.3%) were found reactive for IgG antibodies while 142 (74.7%) were found non-reactive.ConclusionOur study findings suggested that using RT-PCR testing, which may only identify those with a prolonged viral shedding period and minimum viral loads, the proportion of asymptomatic/occult infections could be underestimated.

Investigating the Strength and Durability Properties of One Way Slabs Incorporating Marble Dust as Cement Replacement Material

To reduce the environmental pollution caused by cement manufacturing and to save both the economy and resources, it is required to use alternative waste materials of pozzolanic nature to partially replace cement in the construction industry. Among different cement replacement materials being used now-a-days, marble dust is the one on which limited research has been done especially on the performance of structural members like RC slabs. In this paper, marble dust has been used in different ratios as partial replacement of cement in concrete mix. RC one-way slabs as well as plain concrete standard samples were cast to determine their mechanical properties i.e. compressive, tensile and flexural strengths, stiffness, first &amp; ultimate load, crack patterns, modulus of elasticity, maximum deflection and durability etc. It was found that by increasing the dosage of marble dust in plain concrete samples, workability was decreased. Compressive and tensile strengths of concrete increased up to 7.5% replacement but decreased on further replacement. The permeability of concrete decreased with the addition of marble dust up to 10% replacement, then it increased. The behavior of one-way slabs showed an increase in the first crack load and ultimate failure capacity. Moreover, decrease in the deflection of slabs was observed with the increasing replacement of cement with marble dust. The resistance of concrete against corrosion of steel reinforcement also increased due to less migration of chloride ions. Ultrasonic Pulse Velocity (UPV) tests showed improved homogeneity and stiffness of concrete structure with the replacement of cement by marble dust.

Metaheuristically optimized nano-MgO additive in freeze-thaw resistant concrete: a charged system search-based approach

With progressive advances in the synthesis, characterization, and commercialization of nanoparticles and nanomaterials, these modern engineered materials are becoming an ingredient of innovative structural materials for various applications in civil and construction engineering. In this research, MgO nanoparticles were systematically added to normal concrete samples in order to investigate the effect of these nanomaterials on the durability of the samples under freeze and thaw conditions. The compressive and tensile strengths as well as the permeability of concrete samples containing nanoparticles were measured and compared with the corresponding values of control samples without nanoparticles. The curing time of the concrete samples, the amount of nanoparticles, and the water-cement ratios (w/c) were the variables of the experiments. Moreover, data clustering and the Charged System Search (CSS) algorithm were utilized as the numerical analysis and optimization methods. The regression analysis before clustering and after clustering proved the process of clustering is a prerequisite of regression analysis. Furthermore, the CSS optimization method showed that the optimum amount of nano MgO is 1% of the weight of cement, which can increase the compressive strength of concrete by 9.12% more than plain samples over 34 days.

Effects of impregnating PTFE filled with added graphite on wear behavior of sintered bronze plain bearings

Abstract In this study, self-lubricating porous bronze plain bearing samples were manufactured differently from conventional plain bearings and the wear behaviours were investigated. Plain bearing samples were manufactured by sintering of pre-alloyed spherical CuSn11 bronze powders with grain size of 100– 200 μm. Then, special polymeric composite mixtures were prepared as PTFE (polytetrafluoroethylene) and graphite (GR) additive PTFE mixtures. The GR additive PTFE mixtures were prepared by addition of the GR powder with an average particle size of 200 μm at ratios of 10 wt.% and 20 wt.% into the PTFE solution. Next, the polymeric composite mixtures were impregnated into the porous structure of samples by the spray pulverization coating method. The purpose of the impregnation process was to minimise wear at a longer sliding distance by the gain of self-lubricating property to the samples. The plain bearing samples were produced as three different types (PTFE, PTFE + 10% GR and PTFE + 20% GR). Wear tests were carried out using a plain bearing test rig at different sliding speeds (0.5, 1.0 and 1.5 m s–1) and under applied loads (30, 50 and 70 N). Wear values were determined as weight loss of the samples. Scanning electron microscopy and energy dispersive X-ray spectroscopy were used for the wear analysis of the samples. The results show that the mixtures of PTFE with GR significantly reduced the wear loses of plain bearing surfaces under dry sliding conditions. The PTFE + 10% GR sample had the lowest wear loss under 0.5 m s–1 sliding speed and 30 N applied load conditions after 2.5 hour in comparison with other samples. In other words, the PTFE + 10% GR sample showed lower wear than (31.25%) PTFE sample (without GR additive) and (2.65%) PTFE + 20% GR sample. Also, the wear loss of the PTFE + 20% GR sample (3.67 mg) was slightly increased (difference 1.27 mg/53%) compared to the PTFE + 10% GR sample (2.40 mg) under average load and sliding speed conditions.

Impact of Coenzyme Q10 on Hormonal Profile in Male Sprague-Dawley Rat Exposed to Sub-Chronic Concentrations of Cypermethrin

Aim: This study was aimed at evaluating the impact of Coenzyme Q10 on hormonal profile in male Sprague-Dawley rat exposed to sub-chronic concentrations of Cypermethrin.&#x0D; Experimental Design: A completely randomized experimental design using standard methods for analysis. Hormonal assay was carried out by Microplate Enzyme Immunoassay using their respective test kits. Including AccuBindTM Microplate EIA Test system from Monobind Inc. Lake Forest CA 92630 USA while statistical analysis was carried out using one-way Analysis of Variance (ANOVA); where significant differences were found, Pair-wise comparisons conducted with Tukey test using SPSS 20 software.&#x0D; Location and Duration of Study: This study was carried out in the Department of Biology, Ignatius Ajuru University of Education Rumuolumeni, Port Harcourt, Rivers State, Nigeria. GPS 4o48ʹ14ʹʹ N 6o59ʹ12ʹʹ E. The study lasted for 28days.&#x0D; Methodology: Thirty male Sprague-Dawley rats were randomly assigned to five groups, A-E(n=6/group).Group A was given cool clean water and standard rat pellet ad libitum. Group B,C and D were administered Cypermethrin @ 10mg/kg/bw,20mg/kg/bw,30mg/kg/bw respectively along with 10mg/kg/bw of coenzyme Q10 (CoQ10). Group E received 30mg/kg/bw of cypermethrin only without Coenzyme Q10. All animals were allowed access to cool clean water and standard rat pellet ad libitum. Bodyweight of the animals were taken twice a week and recorded in grams. Twenty-four hours before the animals were euthanized with ethyl ether inhalation, feed was withdrawn from the animals. Blood samples were collected by cardiac puncture between the hours of 7:00 and 9:00am into plain sample tubes according to the approved protocol of blood collection techniques. Analysis for the quantitative determination of all androgens was by Microplate Enzyme Immunoassay using the AccuBindTM Microplate EIA Test system from Monobind Inc. Lake Forest CA 92630 USA and expressed as their respective units. The animals were latter dissected and the vital organs harvested and weighed. The values were subjected to statistical analysis using SPSS software 20.&#x0D; Results: Results showed that there was no significant difference between the bodyweight and organ weight of animals in the treatment group compared with the control. Also, treatment with Cypermethrin only in group E, reduced the level of all the androgens considered in exposed animals. However, with concurrent administration of coenzyme Q10, the production of all androgens especially the production of Follicle Stimulating Hormone, Luteinizing Hormone and Progesterone in groups B,C,D and Estrogen in group B were significantly (P=.05) increased to values higher than the control.&#x0D; Conclusion: This elevation indicates the role of Coenzyme Q10 as an effective antioxidant to boost hormonal level production especially the level of androgens.

Effect of Ultrafine Metakaolin on the Properties of Mortar and Concrete

This study investigated the influence of ultrafine metakaolin replacing cement as a cementitious material on the properties of concrete and mortar. Two substitution levels of ultrafine metakaolin (9% and 15% by mass) were chosen. The reference samples were plain cement concrete sample and silica fume concrete sample with the same metakaolin substitution rates and superplasticizer contents. The results indicate that simultaneously adding ultrafine metakaolin and a certain amount of polycarboxylate superplasticizer can effectively ensure the workability of concrete. Additionally, the effect of adding ultrafine metakaolin on the workability is better than that of adding silica fume. Adding ultrafine metakaolin or silica fume can effectively increase the compressive strength, splitting tensile strength, resistance to chloride ion penetration and freeze–thaw properties of concrete due to improved pore structure. The sulphate attack resistance of mortar can be improved more obviously by simultaneously adding ultrafine metakaolin and prolonging the initial moisture curing time.

Evaluation of fiber-reinforced and cement-stabilized rammed-earth composite under cyclic loading

In this paper, the cyclic behavior of Rammed Earth (RE) elements is investigated by imposing strain-controlled cyclic loads. RE samples comprise plain soil, Waste Tire Textile Fiber (WTTF)-reinforced specimens (FR), cement-stabilized specimens (CS), and simultaneously reinforced and stabilized (CSFR) specimens. Cyclic properties and responses such as maximum stress, plastic strain, dynamic elastic modulus, damage, and plastic strain energy are evaluated. Two models are also proposed and tested against the experimental data for predicting the plastic strain and damage in different loading cycles. CT-Scan images are also provided for visual inspection of fractures and crack growth. Based on the results, plain and CS samples are found to show the weakest cyclic behavior, since they experience high maximum stress reduction, dynamic elastic modulus deterioration, damage, and plastic strain energy. Extensive and continuous cracks are also detected in these specimens according to CT-Scan images. On the other hand, CSFR specimens enjoy both high strengths induced by cement stabilization and ductility imparted as a result of fiber reinforcement. CSFR specimens with high fiber contents undergo relatively low maximum strength reduction, dynamic elastic modulus deterioration, damage, and plastic strain energy. FR specimens are also found to display relatively decent cyclic behavior. As a result, it is deduced that among the tested soil mixtures, CSFR specimens (with a WTTF content higher than 2%) have the most suitable performance under cyclic loadings.

Changes in serum biochemical parameters of experimental Trypanosoma brucei brucei-infected Nigerian indigenous dogs administered multispecies probiotic and diminazene aceturate.

Trypanosomosis is an infectious disease with great economic impact on livestock production. In this study, the effects of probiotic on serum biochemical changes of Nigerian indigenous dogs experimentally infected with Trypanosoma brucei brucei were investigated. Twenty (20) healthy dogs of both sexes (6-10kg body weight) following screening, were randomly divided into 5 groups of 4 dogs each. Dogs in group I (uninfected and untreated); group II (uninfected + multi species (Pet dophillus®) probiotic); group III (infected + multi species probiotic); group IV (infected + diaminazene aceturate); and group V (infected + probiotic + diminazene aceturate). Dogs were fed probiotic for 21 days before infection, and up to the last day post-infection (PI). Dogs in infected groups were inoculated intraperitonially with 2.5 × 106 trypanosomes on day 21 and diminazene aceturate was administered on day 5 post-infection (PI). Prepatent period and parasitaemia were determined. Blood was collected in plain sample bottles and serum harvested for serum biochemical analyses. Prepatent periods of T. brucei brucei were 4.75 ± 0.25 days (group III), 4.00 ± 0.41 days (group IV) and 4.25 ± 0.49 days (groups V); and parasitaemia was significantly decreased (P < 0.05) in groups IV and V compared to group III post-treatment. Mean serum total protein was significantly increased in group III from day 28 up to the end of the study. No significant (P > 0.05) differences existed in the mean serum albumin and creatinine levels in all groups of dogs. The mean serum activities of alanine aminotransferase (ALT), alkaline phosphatase (ALP) and aspartate aminotransferase (AST) were increased significantly (P < 0.05) in group III post infection up to the end of the study. In conclusion, the multispecies probiotic enhanced the efficacy of diaminazene aceturate in mitigating the serum biochemical changes due to experimental T. brucei brucei infection in dogs.

Alteration in biochemical parameters during plateletpheresis in healthy donors: A compendious analysis.

During plateletpheresis, citrate induces hypocalcemia and hypomagnesemia, which are usually transient and self-limiting, but they can lead to significant donor discomfort. The aim of study was to determine the effect of citrate infusion on a multitude of biochemical parameters during plateletpheresis in healthy donors and to correlate changes with adverse donor reactions. The study was conducted on 60 healthy plateletpheresis donors. Blood samples were drawn on three occasions, a baseline pre-donation sample, 30min at start of procedure and 30min post procedure. Heparinized samples were taken to measure ionized calcium and plain samples to measure serum calcium, serum magnesium, parathyroid hormone, total protein and serum albumin. There was statistically significant decline in mean total calcium (9.27±0.66mg/dl to 8.72±0.87mg/dl) and ionized calcium (3.8±0.51mg/dl to 2.9±0.67mg/dl) from baseline until 30min after the start of procedure respectively. A significant fall in serum magnesium, total protein and serum albumin was observed. The mean parathyroid hormone showed significant increase from baseline levels till at the completion of procedure (19.94±12.1pg/ml to 92.08±36.78pg/ml). If the yield was set constant, there was negative correlation between ACD used and pre-donation platelet count. Majority of adverse donor reactions were hypocalcemic reactions, which were more with Amicus double yield plateletpheresis and were managed with calcium supplementation. Plateletpheresis induces marked reduction in serum calcium and magnesium levels. Moreover, increase in parathyroid hormone levels was significant. In addition, decline in total protein and serum albumin may be a concern in donors also participating in plasmapheresis.

Hydrogeological and geochemical characterization of groundwater in the F'Kirina plain (eastern Algeria)

The F'Kirina plain in eastern Algeria is an endorheic basin suffering water scarcity due to a combination of natural and man-made causes. Its hydrogeological system is complex as made by interconnected aquifers represented by Mesozoic, Cenozoic, and Quaternary lithological units. The combination of drought indicators and water level data shows that a groundwater drought affected the plain during the last 15 years, which reflects on current water quality. The reported geochemical analyses, including major ions and trace elements, indicate that the groundwater resource is suffering from salinization, mainly due to evaporation and leaching of soil salts, a process that is coupled with simultaneous cation-exchange effects. In this framework, we observe a geochemical evolution from the fresh Ca–HCO3 facies, typical of springs bordering the plain, towards more saline groundwater characterized by chloride/sulphate-rich facies in the middle of the plain approaching the sebka. However, geochemical diagrams indicate that in few wells salinization is also influenced by upraising of deep groundwater. The water isotopic composition of the F'Kirina plain samples suggests that they diversely record both recharge and evaporation components. Moreover, the most 18O and D depleted compositions among the investigated ground-waters suggest recharge contributions by comparatively higher elevation or the involvement of old (fossil) water components.