Variation In Experimental Results Research Articles

Ratiometric Strategy Based on Intramolecular Internal Standard for Reproducible and Simultaneous Fingerprint Recognition of Diols via 19F NMR Spectroscopy.

19F NMR spectroscopy has been widely used as a convenient and noninvasive analytical technique for understanding complex natural phenomena at the atomic level. However, current NMR referencing techniques are most optimized for 1H NMR, which causes some limitations while referencing heteronuclear NMR. Despite its promising advantages, 19F NMR spectroscopy often exhibits large variations in experimental results and lacks consistency compared with 1H NMR. Herein, we propose a new strategy to improve the consistency of 19F NMR referencing using an internal standard method. As a proof-of-concept, BA-Py-TFP was applied as a sensor for diols via 19F NMR spectroscopy. This strategy proved to be a robust and reproducible referencing method with acceptable deviation (ΔδF = 43-58 ppb) across diverse NMR spectrometers at different institutions. In particular, this new strategy allows reliable fingerprint recognition for analytes and enables qualitative and quantitative analyses of mixtures of multiple analytes simultaneously. The high recovery rates for d-glucose in the human serum matrix suggest its potential suitability for a diverse range of applications, such as in diabetes-related diagnostics.

The Effect of Pitch on Heat Transfer to an Immersed Heat Exchanger in a Solar Thermal Storage Tank With and Without a Baffle

Abstract The effect of the pitch of a copper coil heat exchanger immersed in a hot water storage tank on heat transfer from the storage tank to the heat exchanger working fluid is investigated. The storage tank is initially quiescent and full of hot water. The heat exchanger located at the top of the tank has a coil diameter just under the tank diameter and has a pitch of 2, 3, 4, 6, or 12 times the heat exchanger diameter, D. The effect of the pitch is explored both with and without a cylindrical baffle, which creates an annular region with the tank wall that has a width of 1.5D and within which the heat exchanger is located. In experiments without the baffle, increasing the heat exchanger pitch improves the rate of heat transfer to the working fluid. The improved heat transfer is attributed to the increased thermal stratification generated by the larger pitches. In experiments with the baffle, the results for experiments with pitches of 2D, 3D, 4D, and 6D are all very similar, with 3D slightly outperforming the others. Heat transfer to the heat exchanger with a 12D pitch was significantly lower than the others. In experiments both with and without the baffle, the larger pitches resulted in more variation in experimental results, despite strict standards for initial and operating conditions. As in the prior work, the presence of the baffle resulted in significantly higher heat transfer rates compared to respective experiments without the baffle.

Heat transfer and fluid flow analysis of sinusoidal protrusion rib in solar air heater

Three dimensional (3D) simulation has been carried out to study the heat transfer and fluid flow phenomenon of sinusoidal protrusion rib (SPR) in solar air heater (SAH). The performance of SPR model has been compared with continuous transverse sinusoidal rib (CTSR) model for roughness pitch 10 mm, 14 mm and 18 mm. The thermohydraulic performance (THP) value of SPR model is obtained very near to the THP value of CTSR model whereas it has been observed that at roughness pitch 10 mm in the range of Reynolds number 5000–10,000, THP value for SPR model is greater than that of CTSR model. The optimal Computational Fluid Dynamics (CFD) results of SPR model has been validated with experimental results of SPR model. The variation of experimental results with CFD results for Nusselt number and friction factor are found 6.53% and 4.11% respectively. The thermal efficiency of SPR model has been found 69% at Re 15,000 in the range of Reynolds number investigated.

Injector Effects on Hybrid Polymethylmethacrylate Combustion Assessed by Thermochemical Tomography

In this work, two representative hybrid rocket injector designs, a single-port and an axial showerhead design, were examined experimentally to determine the comparative influence on the development of the downstream combustion zone with polymethylmethacrylate (PMMA) fuel. One-dimensional laser absorption tomography was employed to obtain the thermochemical structure of the PMMA–gaseous oxygen reaction layer via quantitative in situ species and temperature measurements. Optical measurements were performed with tunable semiconductor lasers in the midwave infrared to target absorption features in the fundamental vibrational bands of CO, , and . Planar measurements were conducted at the exit plane of cylindrical fuel grains () at axial distances () ranging from 2 to 11 with a constant gaseous oxygen flow for each of the injectors. Assuming azimuthal symmetry, a Tikhonov-regularized Abel inversion technique was used to obtain the radially resolved absorption coefficient, from which temperature and mole fractions were extracted. One-dimensional measurements over all fuel-grain lengths were consolidated to obtain spatially resolved two-dimensional images of the reaction layer thermochemical structure in a hybrid rocket motor geometry. Significant variations in experimental results were observed between the two injectors, suggesting the importance of injection fluid dynamics in hybrid rocket combustion performance. Explanations of the variations are offered from both a theoretical and a computational analysis.

Additional methodological considerations regarding optimization of the dose of intracerebroventricular streptozotocin A response to: "Optimization of intracerebroventricular streptozotocin dose for the induction of neuroinflammation and memory impairments in rats" by Ghosh et al., Metab Brain Dis 2020 July 21.

A recent article by Ghosh et al. entitled "Optimization of intracerebroventricularstreptozotocin dose for the induction of neuroinflammation and memory impairments inrats" provides an important new set of information on neuroinflammation and cognitivedeficit in a rat model of sporadic Alzheimer's disease (sAD) based onintracerebroventricular administration of streptozotocin (STZ-icv) in Charles-Foster ratsin the early post-treatment period of 21 days.This comment is supposed to supplement the aforementioned manuscript by providingadditional perspective on important factors that should be taken into account in theprocess of optimization of the streptozotocin (STZ) dose for intracerebroventriculartreatment, and provides a brief overview of possible sources of variation ofexperimental results reported by different groups working with STZ-icv rodent models.

Systems biology analysis of the Clostridioides difficile core-genome contextualizes microenvironmental evolutionary pressures leading to genotypic and phenotypic divergence

Hospital acquired Clostridioides (Clostridium) difficile infection is exacerbated by the continued evolution of C. difficile strains, a phenomenon studied by multiple laboratories using stock cultures specific to each laboratory. Intralaboratory evolution of strains contributes to interlaboratory variation in experimental results adding to the challenges of scientific rigor and reproducibility. To explore how microevolution of C. difficile within laboratories influences the metabolic capacity of an organism, three different laboratory stock isolates of the C. difficile 630 reference strain were whole-genome sequenced and profiled in over 180 nutrient environments using phenotypic microarrays. The results identified differences in growth dynamics for 32 carbon sources including trehalose, fructose, and mannose. An updated genome-scale model for C. difficile 630 was constructed and used to contextualize the 28 unique mutations observed between the stock cultures. The integration of phenotypic screens with model predictions identified pathways enabling catabolism of ethanolamine, salicin, arbutin, and N-acetyl-galactosamine that differentiated individual C. difficile 630 laboratory isolates. The reconstruction was used as a framework to analyze the core-genome of 415 publicly available C. difficile genomes and identify areas of metabolism prone to evolution within the species. Genes encoding enzymes and transporters involved in starch metabolism and iron acquisition were more variable while C. difficile distinct metabolic functions like Stickland fermentation were more consistent. A substitution in the trehalose PTS system was identified with potential implications in strain virulence. Thus, pairing genome-scale models with large-scale physiological and genomic data enables a mechanistic framework for studying the evolution of pathogens within microenvironments and will lead to predictive modeling to combat pathogen emergence.

Experimental Investigation on the Impact Resistance of Carbon Fibers Reinforced Coral Concrete.

In this study, the impact resistance of coral concrete with different carbon fiber (CF) dosages subjected to drop-weight impact test was investigated. For this purpose, three concrete strength grades (C20, C30, C40) and six CF dosages (0.0%, 0.3%, 0.6%, 1.0%, 1.5%, and 2.0% by weight of the binder) were considered, and a total of 18 groups of carbon fibers reinforced coral concrete (CFRCC) were cast. For each group, eight specimens were tested following the drop-weight impact test suggested by CECS 13. Then, the two-parameter Weibull distribution theory was adopted to statistically analyze the variations in experimental results. The results indicated that the addition of CFs could transform the failure pattern from obvious brittleness to relatively good ductility and improve the impact resistance of coral concrete. Moreover, the impact resistance of CFRCC increases with the CF dosage increasing. The statistical analysis showed that the probability distribution of the blow numbers at the initial crack and final failure of CFRCC approximately follows the two-parameter Weibull distribution.

Combustion and Emission Characteristics of Hydrous Ethanol–Gasoline Blends with Co-solvents in Spark-ignited Single cylinder Engine

In Brazil, hydrous ethanol is blended with gasoline and is successfully implemented in flexi fuel engines and it has the potential to directly compete with fossil fuels. However, the Ethanol Blending Program of India has not been successful due to non-availability of sugarcane molasses and could not achieve its 5% blending target based on the literature review study. Hydrous ethanol with co-solvent is proposed in this work as a promising blending oxidant instead of energy-intensive anhydrous ethanol in gasoline. This research work also delves into the challenges of using hydrous ethanol in gasoline blended fuel such as water tolerance, fuel properties, and fuel selection. The selected fuel sample 2EW30TBA10, which contains 30% hydrous ethanol and 10% TBA (t-butyl alcohol), and gasoline was selected based on water tolerance of the blended sample and stability. The combustion and emission characteristics of the selected fuel sample 2EW30TBA10 are studied in 4-stroke, single cylinder, water cooled engine, and the performances are compared to base fuel (E0) and reference fuel (E10). The significant contributions of the present research work are the development of combustion model using MATLAB using: Apparent heat release model (Model1) and Combustion pressure method (Model-2) and the results are validated using modified Wiebe function. There was an increase in brake thermal efficiency by 5% compared to base fuel (E0) and the specific fuel consumption (sfc) for 2EW30TBA10 fuel sample is 290 g/KWh as compared to E10, which is 300 g/KWh and for Petrol (E0), sfc is 360 g/KWh. There was a reduction in CO and HC emission compared to base fuel (E0) and an increase in NOx emissions. The cyclic variations of experimental results are validated using a non-linear regression model.

Effects of Cage Enrichment on Behavior, Welfare and Outcome Variability in Female Mice

The manner in which laboratory rodents are housed is driven by economics (minimal use of space and resources), ergonomics (ease of handling and visibility of animals), hygiene, and standardization (reduction of variation). This has resulted in housing conditions that lack sensory and motor stimulation and restrict the expression of species-typical behavior. In mice, such housing conditions have been associated with indicators of impaired welfare, including abnormal repetitive behavior (stereotypies, compulsive behavior), enhanced anxiety and stress reactivity, and thermal stress. However, due to concerns that more complex environmental conditions might increase variation in experimental results, there has been considerable resistance to the implementation of environmental enrichment beyond the provision of nesting material. Here, using 96 C57BL/6 and SWISS female mice, respectively, we systematically varied environmental enrichment across four levels spanning the range of common enrichment strategies: (1) bedding alone; (2) bedding + nesting material; (3) deeper bedding + nesting material + shelter + increased vertical space; and (4) semi-naturalistic conditions, including weekly changes of enrichment items. We studied how these different forms of environmental enrichment affected measures of animal welfare, including home-cage behavior (time–budget and stereotypic behavior), anxiety (open field behavior, elevated plus-maze behavior), growth (food and water intake, body mass), stress physiology (glucocorticoid metabolites in fecal boluses and adrenal mass), brain function (recurrent perseveration in a two-choice guessing task) and emotional valence (judgment bias). Our results highlight the difficulty in making general recommendations across common strains of mice and for selecting enrichment strategies within specific strains. Overall, the greatest benefit was observed in animals housed with the greatest degree of enrichment. Thus, in the super-enriched housing condition, stereotypic behavior, behavioral measures of anxiety, growth and stress physiology varied in a manner consistent with improved animal welfare compared to the other housing conditions with less enrichment. Similar to other studies, we found no evidence, in the measures assessed here, that environmental enrichment increased variation in experimental results.

An investigation of laboratory sound transmission loss testing for steel-framed partitions

Laboratory sound transmission loss (STL) test reports and research publications may be used to validate partition designs as valid and code-compliant sound isolation treatments in buildings. However, longitudinal and cross-laboratory analyses of the sound transmission loss of steel-framed building partitions have revealed such a wide variation in experimental results and calculated ratings that design validation is impossible. There are multiple possible explanations for this variation in results. Steel manufacturers list a variety of mil-thicknesses under the same “gauge” specification, for example. This research study investigates laboratory testing parameters and material components such as the repeated use of the same steel framing for varying panel configurations, screw length and spacing, and steel mil-thickness, regarding the effect that each of these aspects of sample assembly design and testing have on the sound transmission loss of steel-framed partitions.

Impact of bedding volume on physiological and behavioural parameters in laboratory mice.

The standard housing temperature in animal facilities is substantially below the lower critical temperature of mice. This does not only endanger animal welfare, it can also jeopardize scientific research as cold stress has a major impact on mouse physiology. There is some evidence that deep bedding, comparable to nesting material, can help mice to reduce heat loss. Whenever changes are applied to the cage environment, the potential impact on experimental results, including variation, needs to be assessed. An increased variation can result in a conflict between reduction and refinement, when more animals are needed for significance due to the housing design. The aim of this study was to assess the impact of different bedding volumes (0.5 L, 1.5 L and 6 L per type III cage) on mean values and coefficient of variation (CV) of physiological (pentobarbital sleeping time, blood and anatomical parameters) and behavioural parameters (open-field and novel object recognition tests) of group-housed female and male BALB/c and C57BL/6 mice. A larger bedding volume did not interfere with the CVs, but influenced mean values of organ weights and tail lengths. Mice housed on deeper bedding showed a significant reduction in adrenal, liver, kidney and heart weights as well as an increase in tail lengths; these anatomical changes are akin to warm adaptation, and were previously observed for mice housed under warmer environments. A larger bedding volume appears to be a sensible way to reduce cold stress for laboratory mice without increasing variation in experimental results.

Hybrid-fiber reinforced engineered cementitious composite under tensile and impact loading

The behavior under impact loading of an innovative hybrid fiber-reinforced engineered cementitious composite incorporating short randomly dispersed shape memory alloy (HECC-SMAF) and PVA fibers was explored using a drop weight impact test. Test specimens were also heat-treated to investigate possible pre-stressing effects of SMA fibers on the impact resistance of the ECC. Uniaxial tensile testing on ECC coupon specimens was also conducted. A two-parameter Weibull distribution was used to analyze variations in experimental results in terms of reliability function. Results indicate that SMA fibers significantly enhanced the tensile and impact performance of the ECC. Adding fibers beyond a certain dosage led to fiber clustering, thus, no further gain in tensile and impact performance was measured. The impact resistance of HECC-SMAF specimens was further improved after exposure to heat treatment. This highlights the significant contribution imparted by the local pre-stressing effect of SMA fibers to the impact resistance of the composite. The Weibull distribution was adequate to predict the impact failure strength of ECC, allowing to avert additional costly experiments. This research underscores the potential to engineer new cementitious composites with superior tensile properties and impact resistance for the protection of critical infrastructure in the event of explosive or impact loading.

Experimental Investigation of Grinding Force in Microgrinding of Ceramic Materials Using Small Grinding Tool

An experimental study of grinding force in microgrinding zirconia ceramics using small grinding tool is presented. In the experiments, the grinding tool used is electroplated diamond microgrinding wheels of 0.41, 0.63 and 0.76 μm in diameter, and the machining operations were conducted in side grinding under dry cutting. The process parameters include the diameter of the microgrinding wheel, feedrate, and rotational speed of the grinding spindle. The microgrinding forces were measured by a Kistler three-component dynamometer. The experimental results show that the normal forces are much larger than the tangential forces, the effects of process parameters selected on the variation of experimental results is almost the same for tangential forces, and that is the feedrate, diameter of the microgrinding wheel and rotational speed of the grinding spindle in turn for normal forces. As the feedrate increases or diameter of the wheel increases, the microgrinding forces increase, and the magnitudes of increase are more significant at higher radial grinding depth.

Statistical Evaluation for Impact Resistance of Steel Fiber Reinforced Lightweight Aggregate Concrete

The impact resistance of steel fiber reinforced lightweight aggregate concrete was presented in a drop weight test. In this test, 5 groups of disc specimens with different steel fiber volumes including 0.0%, 0.5%, 1.0%, 1.5% and 2.0% were tested. The experimental results indicated that the impact resistance of lightweight aggregate concrete is improved with the increase in fiber volume. As the variation in experimental results, a statistical evaluation was performed to study the influence of impact resistance of steel fiber reinforced lightweight aggregate concrete with different steel fiber volumes. Further more, the impact resistance was simulated with probability distribution by Log-normal method. And the goodnees-of-fit tests indicate that the Log-normal method has good fitness to the impact resistance of steel fiber reinforced lightweight aggregate concrete.

Patterns and mechanisms of conspecific and heterospecific interactions in a dry perennial grassland

Summary 1. Models of local stable coexistence require negative feedbacks, i.e. intraspecific interactions must be more negative than interspecific interactions. However, most competition experiments, often done in the glasshouse, have found evidence for competitive hierarchies. Measurement of interactions under realistic field conditions is necessary to assess their contribution to community dynamics, and explicit measurement of intermediaries thought to be important in interactions may allow studies to account for any variation in experimental results. 2. In this study, we compare conspecific and heterospecific interactions in a field experiment in a dry sand prairie in Michigan. We study the four dominant species at two different stages, germination and adult growth. Using seed addition and adult transplant experiments, we ask whether plants perform best in natural field monocultures of conspecifics, heterospecifics or no neighbour plots. We also measure abiotic environmental characteristics associated with each neighbourhood type and test whether performance can be explained by environmental effects. We hypothesize that plants will create competitive hierarchies because our experimental design is similar to classic competition experiments. 3. Neighbour species created consistent hierarchies in their effects on germination of all four target species, which is likely due to light limitation. However, interestingly, adult plant biomass for two of the three species (one species did not survive) was lower in conspecific monocultures compared to heterospecific or no neighbour plots, thus producing negative feedbacks. For two species, the effects of neighbours on adult growth are likely due to reduction of light and soil nitrate; for the third, however, resources could not explain the pattern that conspecific interactions were more negative than heterospecific. 4. Synthesis. These results suggest that patterns in the relative strength of conspecific and heterospecific competition depend on life‐history stage. Moreover, resource uptake could explain some, but not all, of the interactions among species, suggesting that other factors such as microbial communities or other forms of niche partitioning may play a role and that field experiments are necessary to gauge their relative importance.

Target Loading from a Submerged Explosion

The pressure on a flat plate suspended over a submerged detonation is measured and simulated. Calculation and experiment are in relatively good agreement, although there is variation in experimental results and simulations are sensitive, near the centerline, to the computational details. This sensitivity is linked to the instability of the accelerating plume, typical of a Richtmyer-Meshkov instability. The plate loading features an initial force at plate center, followed by an expanding circular loading pattern. The initial load is due to plume impact, while the circular load arises from the impact of water transported up the edges of the explosion cavity.

Target Loading from a Submerged Explosion

The pressure on a flat plate suspended over a submerged detonation is measured and simulated. Calculation and experiment are in relatively good agreement, although there is variation in experimental results and simulations are sensitive, near the centerline, to the computational details. This sensitivity is linked to the instability of the accelerating plume, typical of a Richtmyer-Meshkov instability. The plate loading features an initial force at plate center, followed by an expanding circular loading pattern. The initial load is due to plume impact, while the circular load arises from the impact of water transported up the edges of the explosion cavity.

The open hole tensile test: a challenge for virtual testing of composites

The open hole tension strength is an important parameter for composite structures since it is can be a limiting factor in design. It is also difficult to characterise and predict through analytical or numerical methods since there exists a wide variation in experimental results depending on testing configuration. Here a range of such variations are presented and the behaviour explained in terms of the development of sub-critical damage in the form of intra-ply splits and inter-ply delaminations and their interaction with each other and also with fibre failure. A finite element based numerical analysis technique has been developed and applied to each case in turn, successfully predicting the failure modes, trends and strengths. This is sufficiently robust to form the basis for a virtual testing framework for the open hole tensile strength of composite materials.

Effects of Environmental Enrichment for Mice: Variation in Experimental Results

This study focused on the effects of different enriched environments for mice in a number of behavioral and physiological parameters in 2 routine laboratory testing procedures: potency testing for tetanus vaccine and stress-induced hyperthermia. The variability in the results was studied by calculating and analyzing mean absolute deviations. Mice from enriched conditions weighed more and consumed more food than mice from standard housing conditions. However, mice from enriched conditions lost more body weight after being housed individually. Other physiological parameters showed no differences. Mice from standard conditions were more active in an open field, suggesting a tendency to overrespond to various stimuli in a testing environment. Mice from enriched environments were more tranquil and easier to handle. The enrichment did not influence the variability in any of the parameters measured, although earlier results and results of other studies suggest that the effects on the variability in results are parameter dependent. When enrichment does not influence variability, there is no reason for not introducing cage enrichment and by doing so contributing to the animals' welfare.

(2-22) Numerical Analysis of the Interaction between Thermo-Fluid Dynamics and Auto-Ignition Reaction in Spark Ignition Engines((SI-7)S. I. Engine Combustion 7-Modeling)

The interaction between thermo-fluid dynamics and auto-ignition reaction was analyzed by the CFD simulation integrating the low temperature oxidation reaction. In the first analysis, a compression auto-ignition of a premixed mixture in a rapid compression machine was solved in a laminar axisymmetric field. The computed results show that the temperature field becomes non-uniform at the end of compression, being higher in the outer region and lower in the central region ana near wan regions, This is due to the vortex induced in the piston-liner corner and wall heat transfer. It is shown that the auto-ignition initiates different places depending on whether local temperatures are outside or inside the negative temperature coefficient regime of the low temperature oxidation reaction. In the second, the auto-ignition in an s. i. engine was analyzed in a three dimensional turbulent field by solving the spatially filtered transport equations instead of the Reynolds averaged ones in consideration of the strong non-linearity to temperature in the reaction terms in the fluctuating temperature field. The computed results for a disk-shaped combustion chamber with a central spark plug show that temperature fluctuations appear during compression due to random variations in the wall heat transfer which were generated by the random motion flow, though a uniform temperature field was assumed as the initial condition. Figure 1 shows the computed pressure compared with the experimental results. The calculation terminated at the auto-ignition initiation, which was assumed as the time when any local temperature of the unburned mixture reached 1100 K. The predicted time of the first local auto-ignition appearance is seen to be 1.1 deg. BTDC, which falls in the range of the cycle variation in experimental results. The computed temperature fields of the unburned mixture at this time are shown in Figure 2. The figure demonstrates that the auto-ignition sites appear sporadically as seen in the high-speed photographs presented in the literature.