Mass-loss Parameters Research Articles

Microstructural and mechanical properties of fiber-reinforced seawater sea-sand concrete under elevated temperatures

Seawater sea-sand (SWSS) concrete is a promising sustainable construction material that could mitigate the detrimental environmental impact because of the overuse of freshwater and natural sand (FWNS). Physical and chemical properties of seawater sea-sand (SWSS) concrete are significantly different than those of conventional concrete due to a high concentration of certain destructive ions in seawater and sea sand. When a fire accident occurs, the elevated temperature could alter the chemical composition and microstructure of concrete material. This study first examined the effects of elevated temperatures on the pertinent properties of SWSS and FWNS concretes and then proposed methodologies for improving the fire-resistance capability of SWSS concrete by application of fibre additions. Polypropylene (PP) and polyvinyl alcohol (PVA) fibres with volume fractions of 0.1–0.5% were employed for the above purpose. All the parameters of mass loss, residual thermal strain, compressive strength, elastic modulus, splitting tensile and flexural strength, and fracture toughness of the concrete specimens were examined after exposure to different elevated temperatures ranging from 100 to 750 °C. Furthermore, the alterations in the microstructure of the mixes after exposure to the elevated temperatures were investigated by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) images, water absorption and porosity tests. From the experimental results, the SWSS mix exhibited a lower mass loss, a higher residual thermal strain, and a slightly lower residual compressive strength and elastic modulus and tensile strength than those of conventional FWNS concrete. Additional porosity created by fibre decomposition appears to provide extra rooms for concrete expansion, which led to the formation of finer and lower number of cracks. Generally, incorporation of PP or PVA fibres improved SWSS concrete properties after exposure to the elevated temperatures tested. Compared with PP fibres, PVA fibre was more efficient for improving all the tested concrete properties after the exposure of high temperatures.

Hydrodynamic Model of Decaying Radial Oscillations in RU Cam

Calculations of stellar evolution up to the early white dwarf stage were carried out for stars with mass on the main sequence $M_0=0.82M_\odot$, $0.85M_\odot$, $0.9M_\odot$ and with initial abundances of helium and heavier elements $Y=0.25$ and $Z=10^{-3}$, respectively. For each value of $M_0$ the AGB and post--AGB evolutionary phases were computed with three values of the mass loss parameter in the Bl\"ocker formula: $\eta_B=0.02$, 0.05 and 0.1. The variable star RU~Cam with pulsation period $\Pi\approx 22$ day is shown to be in the post--AGB stage and the pulsation amplitude decrease in years 1962--1963 is due to movement of the star across the HR diagram beyond the pulsation instability region. Theoretical estimates of the mass and the luminosity of RU~Cam are $0.524M_\odot\le M\le 0.532M_\odot$ and $2.20\times 10^3L_\odot\le L\le 2.33\times 10^3L_\odot$, respectively. Hydrodynamic calculations of nonlinear stellar pulsations show that while the star approaches the instability boundary a significant reduction ($\approx 90\%$) in the pulsation amplitude occurs for nearly two years with subsequent slow decay of low--amplitude oscillations. Solution of the equations of hydrodynamics with time--dependent inner boundary conditions describing evolutionary changes in the radius and the luminosity at the bottom of the pulsating envelope allows us to conclude that decay of radial oscillations in RU~Cam is accompanied by the effect of oscillation hysteresis. In particular, the stage of large--amplitude limit cycle oscillations extends by $\approx 12$ years and the subsequent stage of decaying small--amplitude oscilations spreads beyond the formal boundary of pulsation instability.

Life in the Wheat Litter: Effects of Future Climate on Microbiome and Function During the Early Phase of Decomposition

Even though it is widely acknowledged that litter decomposition can be impacted by climate change, the functional roles of microbes involved in the decomposition and their answer to climate change are less understood. This study used a field experimental facility settled in Central Germany to analyze the effects of ambient vs. future climate that is expected in 50–80 years on mass loss and physicochemical parameters of wheat litter in agricultural cropland at the early phase of litter decomposition process. Additionally, the effects of climate change were assessed on microbial richness, community compositions, interactions, and their functions (production of extracellular enzymes), as well as litter physicochemical factors shaping their colonization. The initial physicochemical properties of wheat litter did not change between both climate conditions; however, future climate significantly accelerated litter mass loss as compared with ambient one. Using MiSeq Illumina sequencing, we found that future climate significantly increased fungal richness and altered fungal communities over time, while bacterial communities were more resistant in wheat residues. Changes on fungal richness and/or community composition corresponded to different physicochemical factors of litter under ambient (Ca2+, and pH) and future (C/N, N, P, K+, Ca2+, pH, and moisture) climate conditions. Moreover, highly correlative interactions between richness of bacteria and fungi were detected under future climate. Furthermore, the co-occurrence networks patterns among dominant microorganisms inhabiting wheat residues were strongly distinct between future and ambient climates. Activities of microbial β-glucosidase and N-acetylglucosaminidase in wheat litter were increased over time. Such increased enzymatic activities were coupled with a significant positive correlation between microbial (both bacteria and fungi) richness and community compositions with these two enzymatic activities only under future climate. Overall, we provide evidence that future climate significantly impacted the early phase of wheat litter decomposition through direct effects on fungal communities and through indirect effects on microbial interactions as well as corresponding enzyme production.

The response of an ethanol pool fire to transverse acoustic waves

To investigate the response of a pool fire perturbed by acoustic waves to guide the technology for fire extinguishing by acoustic waves, combustion tests on an ethanol pool fire perturbed by acoustic waves were conducted at acoustic frequencies of 20–100 Hz and acoustic pressures of up to 1.2585 Pa. Firstly, acoustic parameters at the position of the pool flame perturbed by acoustic waves were tested. Secondly, the mass loss rate of the fuel, shape characteristics and oscillation characteristics of the area and height of the pool flames under acoustic perturbance were studied. A modified model of the flame height of the pool fire correlated with mass loss and acoustic parameters was established. The results indicate that, in comparison with situations without acoustic perturbance, the acoustic perturbance suppresses and promotes the dimensionless consumption rate of fuel for the pool fire, while the shape of flames is in stable or disordered state. The dimensionless combustion rate of fuel for the pool fire increases quasi-linearly with the amplitude of sound–induced local periodic displacement. The instability of the pool fire perturbed by acoustic waves is mainly caused by suppressing the dominant frequency and promoting the secondary frequency of flame pulsation.

Influence of running-in operating conditions on the steady-state torque loss of ground spur gears

The influence of gear running-in operating conditions on the steady-state efficiency of ground spur gears is not well established. However, it is accepted that less rough surfaces promote better efficiency. Five ground spur gears with similar surface finishing were submitted to two distinct test stages: (i) running-in stage and (ii) torque loss stage. During the running-in stage, five different running-in operating conditions were conducted to ascertain the influence of the load and temperature on the subsequent steady-state gear torque loss test. The mass loss and surface roughness parameters were influenced by the running-in operating conditions. However, different surface conditions after running-in had only a transient effect on the torque loss measured subsequently. So, the test campaign allow to conclude that even after a severe running-in operating condition, the gears surface still evolves in a significant way during the torque loss tests.

Protection of mild steel corrosion by three new quinazoline derivatives: experimental and DFT studies

The corrosion inhibition ability of three newly synthesized quinazoline derivatives namely, 2-chloro-N-(1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinazoline-3-carbonothioyl) propanamide (Q1), 2-methoxy-N-(1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinazoline-3-carbonothioyl) acetamide (Q2) and N-(1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinazoline-3-carbonothioyl) propionamide (Q3) on the mild steel (MS) in 0.5 M HCl medium have been examined by mass loss and electrochemical parameters. The obtained results of all the quinazoline derivatives exhibit excellent corrosion inhibition for MS and exhibited the maximum inhibition efficiencies (η %) of 95.50% (Q1), 91.33% (Q2) and 86.71 (Q3) at optimum concentrations. From electrochemical impedance spectroscopy (EIS) result, it is proved that, corrosion inhibition was achieved due to adsorption of quinozoline derivatives at the metal/electrolyte interface, on the other hand the studied derivatives fall under a category of mixed inhibitor as suggested by polarization results. The quinazoline derivatives adsorption on MS has been compiled well with Langmuir isotherm model. Scanning electron microscopy (SEM) was used to analyse the protective layer of inhibitors formed on MS surface. The efficiency of corrosion inhibition from mass loss and electrochemical measurements were in good agreement with each other. The correlation of molecular structures and inhibition efficiencies of three quinazoline derivatives was studied by using density function theory (DFT) method.

Are fungal strains from salinized streams adapted to salt-rich conditions?

Anthropogenic salinization of freshwater is a global problem with largely unknown consequences for stream functions. We compared the effects of salt addition (6 g l-1 NaCl) in microcosms on leaf mass loss and microbial parameters in single- and multispecies assemblages of fungal strains (Heliscus lugdunensis, HELU; Tetracladium marchalianum, TEMA; Flagellospora curta, FLCU) isolated from a reference (R) or salinized (S) stream. Fungal growth and interactions were also assessed. Salinization inhibited leaf decomposition and fungal biomass, but no differences were observed between species, strains or species combinations. Sporulation rates in monocultures were not affected by added salt, but differed among species (FLCU > HELU > TEMA), with S strains releasing more conidia. Fungal assemblages did not differ significantly in total conidia production (either between strains or medium salt concentration). HELU was the dominant species, which also had highest growth and most pronounced antagonistic behaviour. Fungal species, irrespective of origin, largely maintained their function in salinized streams. Strains from salt-contaminated streams did not trade-off conidial production for vegetative growth at high salt levels. The expected reduction of fungal diversity and potential changes in nutritional litter quality owing to salinization may impact leaf incorporation into secondary production in streams.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Influence of hybrid fibers on serviceability of RC beams under loading and steel corrosion

This paper presents an investigation of the behavior of reinforced concrete (RC) beams containing steel, Polyolefin (PO), Polypropylene (PP), and their combinations under the simultaneous effect of accelerated corrosion and sustained loading. A new setup was designed that made possible the corrosion test of tensile reinforcement and the monitoring of the adjacent concrete cover during loading. During the corrosion test, the parameters of theoretical mass loss, corrosion crack width and cracking area, deflection, and corrosion potential were monitored. After the end of the test, the affected bars were extracted from concrete and gravimetry was done to determine the actual corrosion level. A new method known as “volumetric mass loss” was proposed to determine the profile of corrosion along the corroded bars.The results show that the presence of fibers decreases the corrosion level of bars, but fibers do not affect the corrosion potential. The assessment of corroded bars by the volumetric mass loss method reveals that the presence of fibers mitigate the severity of localized corrosion. The fibers reduce the corrosion cracking and deflection in comparison to the beam made of plain concrete. The observation indicates that the selection of a proper combination of fibers can significantly improve the service life of beams from structural and aesthetic viewpoints.

Preparation and Ablation Performance of Lightweight Phenolic Composite Material under Oxyacetylene Torch Environment

The present study investigates the influence of fiber content on thermal properties of short silica fiber (SSF) reinforced modified resole resin (MRR) composites. For this purpose, different SSF loading composites were prepared: 40, 55, and 65 wt.%. The ablation resistance related to mass loss parameters was quantified by testing under an oxyacetylene flame up to 2300 °C for 30 s. The thermal conductivity of the composite was studied via experimental steady state technique. Thermal stability of the composite material was estimated by means of thermo-gravimetric analysis (TGA), both in air and nitrogen atmosphere. The ablated composite material was characterized by different techniques (XRD, FTIR, and SEM). The results showed that the backface surface temperature of SSF/MRR composites follows the typical variation curve, and linear ablation rate, mass ablation rate, and char yield decrease with increasing silica fiber content. This confirms that 55 and 65 wt.% SSF loading exhibited the best anti-ablation performance and the lowest percentage of char yield. XRD and FTIR analysis of the ablated specimen zone showed the absence of new phase. The thermo-gravimetric analysis confirmed the thermal resistance of SSF/MRR composites in comparison with MRR matrix and the decrease of char with increasing SSF loading. The thermal conductivity of these composites was significantly enhanced by the SSF into the modified resole matrix. This thermal conductivity follows both the rule of mixture and Maxwell models. The overall thermal characteristics of the SSF/MRR composites meet most of the necessary high temperature application criteria.

The 2D Disk Structure with Advective Transonic Inflow–Outflow Solutions around Black Holes

Abstract We solved analytically viscous two-dimensional (2D) fluid equations for accretion and outflows in spherical polar coordinates (r, θ, ϕ) and obtained explicitly flow variables in r- and θ-directions around black holes (BHs). We investigated global transonic advection-dominated accretion flow (ADAF) solutions in an r-direction on an equatorial plane using Paczyński–Wiita potential. We used radial flow variables of ADAFs with symmetric conditions on the equatorial plane as initial values for integration in the θ-direction. In the study of 2D disk structure, we used two azimuthal components of viscous stress tensors—namely, and . Interestingly, we found that the whole advective disk does not participate in outflow generation, and the outflows form close to the BHs. Normally, outflow strength increased with increasing viscosity parameter (α 1), mass-loss parameter (s), and decreasing gas pressure ratio (β). The outflow region increased with increasing s, α 1 for and decreasing α 2 for . The is effective in angular momentum transportation at high latitude and outflows collimation along an axis of symmetry, since it changes polar velocity ( ) of the flow. The outflow emission is also affected by the ADAF size and decreases with it. Transonic surfaces formed for both inflows ( , very close to BH) and outflows ( ). We also explored no outflows, outflows, and failed outflows regions, which mainly depend on the viscosity parameters.

Modelling the carbon AGB star R Sculptoris

Context. On the asymptotic giant branch (AGB), Sun-like stars lose a large portion of their mass in an intensive wind and enrich the surrounding interstellar medium with nuclear processed stellar material in the form of molecular gas and dust. For a number of carbon-rich AGB stars, thin detached shells of gas and dust have been observed. These shells are formed during brief periods of increased mass loss and expansion velocity during a thermal pulse, and open up the possibility to study the mass-loss history of thermally pulsing AGB stars. Aims. We study the properties of dust grains in the detached shell around the carbon AGB star R Scl and aim to quantify the influence of the dust grain properties on the shape of the spectral energy distribution (SED) and the derived dust shell mass. Methods. We modelled the SED of the circumstellar dust emission and compared the models to observations, including new observations of Herschel/PACS and SPIRE (infrared) and APEX/LABOCA (sub-millimeter). We derived present-day mass-loss rates and detached shell masses for a variation of dust grain properties (opacities, chemical composition, grain size, and grain geometry) to quantify the influence of changing dust properties to the derived shell mass. Results. The best-fitting mass-loss parameters are a present-day dust mass-loss rate of 2 × 10−10 M⊙ yr−1 and a detached shell dust mass of (2.9 ± 0.3) × 10−5 M⊙. Compared to similar studies, the uncertainty on the dust mass is reduced by a factor of 4. We find that the size of the grains dominates the shape of the SED, while the estimated dust shell mass is most strongly affected by the geometry of the dust grains. Additionally, we find a significant sub-millimeter excess that cannot be reproduced by any of the models, but is most likely not of thermal origin.

Decomposition dynamic of two aquatic macrophytes Trapa bispinosa Roxb. and Nelumbo nucifera detritus.

In freshwater ecosystems, aquatic macrophytes play significant roles in nutrient cycling. One problem in this process is nutrient loss in the tissues of untimely harvested plants. In this study, we used two aquatic species, Nelumbo nucifera and Trapa bispinosa Roxb., to investigate the decomposition dynamics and nutrient release from detritus. Litter bags containing 10g of stems (plus petioles) and leaves for each species detritus were incubated in the pond from November 2016 to May 2017. Nine times litterbags were retrieved on days 6, 14, 25, 45, 65, 90, 125, 145, and 165 after the decomposition experiment for the monitoring of biomass loss and nutrient release. The results suggested that the dry masses of N. nucifera and T. bispinosa decomposed by 49.35-69.40 and 82.65-91.65%, respectively. The order of decomposition rate constants (k) is as follows: leaves of T. bispinosa (0.0122day-1) > stems (plus petioles) of T. bispinosa (0.0090day-1) > leaves of N. nucifera (0.0060day-1) > stems (plus petioles) of N. nucifera (0.0030day-1). Additionally, the orders of time for 50% dry mass decay, time for 95% dry mass decay, and turnover rate are as follows: leaves < stems (plus petioles) and T. bispinosa < N. nucifera, respectively. This result indicated that the dry mass loss, k values, and other parameters related to k values are significantly different in species- and tissue-specific. The C, N, and P concentration and the C/N, C/P, and N/P ratios presented the irregular temporal changes trends during the whole decay period. In addition, nutrient accumulation index (AI) was significantly changed depending on the dry mass remaining and C, N, and P concentration in detritus at different decomposition times. The nutrient AIs were 36.72, 8.08, 6.35, and 2.56% for N; 31.25, 9.85, 4.00, and 1.63% for P; 25.15, 16.96, 7.36, and 6.16% for C in the stems (plus petioles) of N. nucifera, leaves of N. nucifera, stems (plus petioles) of T. bispinosa, and leaves of T. bispinosa, respectively, at the day 165. These results indicated that 63.28-97.44% of N, 68.75-98.37% of P, and 74.85-93.84% of C were released from the plant detritus to the water at the day 165 of the decomposition period. The initial detritus chemistry, particularly the P-related parameters (P concentration and C/P and N/P ratios), strongly affected dry mass loss, decomposition rates, and nutrient released from detritus into water. Two-way ANOVA results also confirm that the effects on the species were significant for decomposition dynamics (dry mass loss), nutrient release (nutrient concentration, their ratios, and nutrient AI) (P < 0.01), and expected N concentration (P > 0.05). In addition, the decomposition time had also significant effects on the detritus decomposition dynamic and nutrient release. However, the contributors of species and decomposition time on detritus decomposition were significantly different on the basis of their F values of two-way ANOVA results. This study can provide scientific bases for the aquatic plant scientific management in freshwater ecosystems of the East region of China.

Abstract P6-12-11: Feasibility and biomarker modulation due to high levels of moderate to vigorous physical activity as part of a weight loss intervention in older, sedentary, obese breast cancer survivors

Abstract We sought to demonstrate that older, sedentary, obese breast cancer survivors could achieve &amp;gt; 200 minutes per week of moderate to vigorous physical activity (MVI PA) as part of a weight loss intervention; and to assess modulation of risk biomarkers. This level of PA in combination with moderate calorie restriction is associated with weight losses of &amp;gt;10% in women without cancer, which in turn is associated with significant modulation of cancer risk biomarkers. Eleven participants with BMI &amp;gt; 30 kg/m2 enrolled in a 12-week program that consisted of moderate caloric restriction, weekly phone group behavioral sessions, and individualized exercise plans based on measured heart rate reserve. Women were provided an accelerometer with heart rate monitor linked to GarminConnect, membership to a YMCA, twice weekly supervised exercise sessions with a personal trainer, and weekly feedback regarding weight and physical activity progress. The goal was to increase MVI PA (≥45% heart rate reserve) gradually from &amp;lt;60 to &amp;gt;200 minutes per week. The median age was 61, 5/11 women had received prior chemotherapy, and 7/11 were currently taking aromatase inhibitors. Median values of baseline anthropomorphic measures acquired by dual energy x-ray absorptiometry (GE Lunar iDXA) included BMI, 37.3 kg/m2; total mass, 97.5 kg; fat mass, 47.6 kg; visceral fat, 1.7 kg (range 1.4-3.0); and fat mass index, 17.6 kg/m2. The majority had a baseline VO2 peak in the poor range for their age. All 11 participants completed the intervention, with no reported serious adverse events. Median MVI PA achieved over weeks 5-12 was 161 minutes/week (range 48-320). VO2 peak was increased in 10/11 with a median relative change of 12% from baseline. All but one lost weight with an overall median of 8% total mass loss, which was associated with 13% total fat mass loss and 21% visceral fat mass loss. For those with MVI PA above the median, values were 11%, 17%, and 40%, respectively. Visceral fat mass loss was linearly correlated with minutes per week of MVI PA (p=0.032); these parameters in turn were associated with changes in a number of serum biomarkers, including adiponectin-leptin ratio, TNF-alpha, as well as circulating adipose stromal cells, a potential marker for metastasis. Insulin and hs-CRP were favorably modulated in almost all participants but change was not linearly correlated with activity or mass loss parameters; thus these may not be ideal biomarkers to document a dose response to level of MVI PA. Conclusion: These results demonstrate that older, sedentary, obese breast cancer survivors can safely achieve a high level of MVI PA when provided a structured program that includes an exercise trainer. It is feasible to design a clinical trial for such breast cancer survivors to examine biomarker modulation as a function of level of physical activity. Citation Format: Fabian CJ, Klemp JR, Burns JM, Vidoni ED, Nydegger JL, Kreutzjans AL, Phillips TL, Baker HA, Hendry B, John C, Amin AL, Khan QJ, Mitchell MP, O'Dea AP, Sharma P, Wagner JL, Hursting SD, Kimler BF. Feasibility and biomarker modulation due to high levels of moderate to vigorous physical activity as part of a weight loss intervention in older, sedentary, obese breast cancer survivors [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-12-11.

Theoretical investigation on the mass loss impact on asteroseismic grid-based estimates of mass, radius, and age for RGB stars

Aims.We aim to perform a theoretical evaluation of the impact of the mass loss indetermination on asteroseismic grid based estimates of masses, radii, and ages of stars in the red giant branch (RGB) phase.Methods.We adopted the SCEPtER pipeline on a grid spanning the mass range [0.8; 1.8]M⊙. As observational constraints, we adopted the star effective temperatures, the metallicity [Fe/H], the average large frequency spacing Δν,and the frequency of maximum oscillation powerνmax. The mass loss was modelled following a Reimers parametrization with the two different efficienciesη= 0.4 andη= 0.8.Results.In the RGB phase, the average random relative error (owing only to observational uncertainty) on mass and age estimates is about 8% and 30% respectively. The bias in mass and age estimates caused by the adoption of a wrong mass loss parameter in the recovery is minor for the vast majority of the RGB evolution. The biases get larger only after the RGB bump. In the last 2.5% of the RGB lifetime the error on the mass determination reaches 6.5% becoming larger than the random error component in this evolutionary phase. The error on the age estimate amounts to 9%, that is, equal to the random error uncertainty. These results are independent of the stellar metallicity [Fe/H] in the explored range.Conclusions.Asteroseismic-based estimates of stellar mass, radius, and age in the RGB phase can be considered mass loss independent within the range (η∈ [0.0,0.8]) as long as the target is in an evolutionary phase preceding the RGB bump.

Corrosion Resistance of 1.4362 Steel in Boiling 65% Nitric Acid

Lean duplex stainless steels were developed for use in environments where high strength and corrosion resistance are required. Duplex stainless steels offer a cost-effective solution with high strength and corrosion resistance. Due to high chromium content and a balanced composition, 1.4362 ferritic-austenitic stainless steel possesses excellent corrosion resistance in acidic environments. General corrosion problems in duplex stainless steels at 475°C have been widely researched. Steels are most degraded at 475°C, but corrosion can still occur at both lower and higher temperatures. Corrosion resistance is influenced by chromium content and microstructural morphology. The percentage of each phase and its properties are determined by composition, technological processing and heat treatments. Machining and fabrication practices, such as welding, are also vital for performance. The objective of this study was to determine the effects of 30-minute isothermal heat treatments at 535°C and exposure time on relative mass loss and roughness parameters of 1.4362 lean duplex stainless steel. The influence of boiling nitric acid on the corrosion resistance of steel was investigated based on mass loss and roughness parameters. Corrosion properties and roughness of 1.4362 alloys are discussed in this paper.

X-ray and radio emission from the luminous supernova 2005kd.

SN 2005kd is among the most luminous supernovae (SNe) to be discovered at X-ray wavelengths. We have re-analysed all good angular resolution (better than 20 arcsec full width at half-maximum point spread function) archival X-ray data for SN 2005kd. The data reveal an X-ray light curve that decreases as t -1.62±0.06. Our modelling of the data suggests that the early evolution is dominated by emission from the forward shock in a high-density medium. Emission from the radiative reverse shock is absorbed by the cold dense shell formed behind the reverse shock. Our results suggest a progenitor with a mass-loss rate towards the end of its evolution of ≥4.3 × 10-4 M⊙ yr-1, for a wind velocity of 10 km s-1, at 4.0 × 1016 cm. This mass-loss rate is too high for most known stars, except perhaps hypergiant stars. A higher wind velocity would lead to a correspondingly higher mass-loss rate. A luminous blue variable star undergoing a giant eruption could potentially fulfill this requirement, but would need a high mass-loss rate lasting for several hundred years, and need to explain the plateau observed in the optical light curve. The latter could perhaps be due to the ejecta expanding in the dense circum-stellar material at relatively small radii. These observations are consistent with the fact that Type IIn SNe appear to expand into high-density and high mass-loss rate environments, and also suggest rapid variability in the wind mass-loss parameters within at least the last 5000 yr of stellar evolution prior to core-collapse.

Osmotic dehydration of yellow melon using red grape juice concentrate

The main objectives of this work were to study the effect of fruit ripening on the melon osmotic dehydration at reduced pressure and to model the mass transfer of moisture during melon dehydration with grape juice concentrate and sucrose solution. The ripening level had no relevant effect over the physical characteristics of the final product, with soluble solids, moisture and water activity without significant differences. Besides, the mass loss and solute gain parameters did not show significant differences, and only the solute gain had few variations. The process of the osmotic dehydration with grape juice concentrate was the most effective one, with higher dehydration and lowest solutes gain compared to the process carried out with sucrose solution. The water effective diffusivity calculated by the Fick’s equation for the process conduced with grape juice was lower than the one obtained for the sucrose solution, according to different equilibrium moisture content calculated by Peleg’s equation. The dehydrated melon with grape juice concentrate showed reduced water activity (~ 0.92) and low moisture content (~ 58%).

Low-frequency radio observations of SN 2011dh and the evolution of its post-shock plasma properties

We present late time, low frequency observations of SN 2011dh made using the Giant Metrewave Radio Telescope (GMRT). Our observations at $325\ \rm MHz$, $610\ \rm MHz$ and $1280\ \rm MHz$ conducted between $93-421\ \rm days$ after the explosion supplement the millimeter and centimeter wave observations conducted between $4-15 \ \rm days$ after explosion using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and extensive radio observations ($ 1.0-36.5\ \rm GHz$) conducted between $16-93\ \rm days$ after explosion using Jansky Very Large Array (JVLA). We fit a synchrotron self absorption model (SSA) to the $610\ \rm MHz$ and $1280\ \rm MHz$ radio light curves. We use it to determine the radius ($R_{\rm p}$) and magnetic field ($B_{\rm p}$) at $173$ \& $323$ days after the explosion. A comparison of the peak radio luminosity $L_{\rm op}$, with the product of the peak frequency $\nu_{\rm p}$ and time to peak $t_{\rm p}$ shows that the supernova evolves between the epochs of CARMA, JVLA and GMRT observations. It shows a general slowing down of the expansion speed of the radio emitting region on a timescale of several hundred days during which the shock is propagating through a circumstellar medium set up by a wind with a constant mass loss parameter, $\dot M/v_{\rm w}$. We derive the mass loss parameter ($A_{\star}$) based on $610\ \rm MHz$ and $1280\ \rm MHz$ radio light curves, which are found to be consistent with each other within error limits.

Ultrasonic guided waves for monitoring corrosion of FRP wrapped concrete structures

Reinforced concrete (RC) structures affected by corrosion of steel bars are often repaired and rehabilitated by wrapping fibre reinforced polymer (FRP) sheets. Most commonly available FRP materials are glass and carbon fibre composites. This paper uses ultrasonic guided waves as a non-destructive tool to monitor the initiation and progression of corrosion in reinforcing bars in concrete after repairing with bonded FRP sheets. Concrete cylinders embedded with reinforcing bars are subjected to accelerated impressed current corrosion in chloride environment. After specific days of exposure to corrosive environment the cylinders are repaired by wrapping with GFRP and CFRP sheets. Anodic current was further continued for specified times. Specific core and surface seeking guided wave modes were used to ultrasonically measure the resistance offered by FRP wraps to corrosion. The ultrasonic measurements were correlated with destructive parameters of pull-out strength and mass loss. This paper demonstrates that guided waves were able to discern the corrosion protection offered by the FRP. It is observed that Glass FRP gives better protection than Carbon FRP.

Using the X-ray Lightcurves of Young Supernovae to Probe the Stellar Environment and Supernova Progenitors

AbstractWe have aggregated together data available in the literature, or analysed by us, to compute the lightcurves of most young supernovae (SNe) that have been detected in X-rays. Currently the database contains about 60 SNe spanning all the various types, but it is expanding rapidly. We use this library of lightcurves and spectra to explore the diversity of SNe, the characteristics of the environment into which they are expanding, and the implications for their progenitors. X-ray spectra can provide insight into the density structure, composition and metallicity of the surrounding medium, and the ionization level, through the spectra themselves as well as the X-ray absorption. Since core-collapse SNe expand mainly in environments created by the progenitor star mass-loss, this can provide crucial information about the nature of the progenitor star, and its mass-loss parameters in the decades or centuries before its death. In a few cases, via detailed modelling, we can distinguish the composition of the SN ejecta from that of the environment. X-ray observations therefore provide an invaluable probe into the stellar environments of core-collapse SNe, complementing data available at other wavelengths. We provide an overview of the X-ray lightcurves of various SN types, the implications for their environment, and clues to their progenitor stars.