Retention Coefficient Research Articles

Study of resistance of potato varieties to drought in the conditions of the Central Polissya of Ukraine

Objective. To determine and evaluate the indicators of changes in the water regime of the most common varieties of potatoes (on the 60th and 85th day of germination) in the conditions of central Polissya of Ukraine, namely the coefficients of water recovery, water retention, drought resistance and water deficit. Methods. Field and laboratory-based, selection and statistical. Results. The coefficients of water retention, water recovery capacity and drought resistance and water deficit of plant leaves are determined. The highest water content of potato leaves was observed among the following varieties: Tyras, Nahoroda, Serpanok, Slovianka and Chervona Ruta. It is established that the mechanism of water recovery in potato varieties of different maturity groups is different, the highest percentage of this indicator in early-maturing varieties is observed on the 60th day from germination, in the mid ripening group on the 85th day from germination. High value of the integrated indicator of water recovery was demonstrated by the following varieties: Tyras, Vyhoda, Yavir, Lietana, Slovianka Volodarka, Bazaliia and Chervona Ruta. It was found that on the 60th day from germination among the following potato varieties: Chervona Ruta, Serpanok, Avanhard, Mezhyrichka, Nahoroda, Oleksandryt, Radomysl and Bazaliia, the drought resistance coefficient was ≤ 80%. It was found that only in the varieties Tyras and Slovianka, on the 85th day after germination, there is an increase in the numerical expression of the drought resistance coefficient, which indicates an increased degree of adaptation of plants to soil moisture deficiency. In the first and second record the indicator of water deficit of the most of the studied varieties of potatoes was within acceptable limits, indicating a slight negative effect of weather conditions on the physiological state of plants. A slightly increased indicator of water deficit was observed on the 60th day of germination among the following potato varieties: Tyras, Volodarka and Levada, but within two weeks it decreased to a safe level. Conclusions. We recommend growing potato varieties that have shown high values of integrated indicators of water regime in the area of central Polissya and use as a source material for breeding purposes in the creation of new drought-resistant genotypes.

Effects of Supplementing Intestinal Autochthonous Bacteria in Plant-Based Diets on Growth, Nutrient Digestibility, and Gut Health of Bullfrogs (Lithobates catesbeianus).

Poor utilization efficiency of plant protein diets always leads to intestinal barrier dysfunction and growth inhibition in animals. Probiotics have shown promise in improving growth performance and gut health of the host. However, obtaining the host-beneficial probiotic from thousands of bacterial phylotypes is challenging. Here, four intestinal autochthonous bacteria were isolated from fast-growing bullfrog after a 60-day feeding on a soybean meal (SM)-based diet. Another feeding trial was conducted to evaluate the effects of supplementing these strains in an SM-based diet on growth, nutrient digestibility, immunity, and gut health of bullfrog. A high-SM basal diet was used as a non-supplemented control group (NC), and four other diets were prepared by supplementing the basal diet with 1 × 107 CFU/g of Bacillus siamensis, Bacillus tequilensis (BT), Bacillus velezensis, and Lactococcus lactis (LL). Results showed that weight gain, feed efficiency, nitrogen retention, and apparent digestibility coefficients of dry matter and protein were significantly higher in the LL group compared with the NC group (p < 0.05). Furthermore, compared with the NC group, both BT and LL groups showed markedly higher jejunal protease and amylase activities, serum complement 4 and immunoglobulin M levels, jejunal muscularis thickness (p < 0.05), and up-regulated expression of il-10 and zo-1 genes (p < 0.05). High-throughput sequencing revealed higher abundances of Bacillus and Cetobacterium in BT and LL groups, respectively, accompanied with decreased abundances of Enterobacter and Escherichia–Shigella. Besides, KEGG pathways related to metabolisms were significantly enhanced by the LL diet relative to the NC diet (p < 0.05). Overall, the beneficial effects of two frog-derived probiotics were determined: supplementation of L. lactis in SM-based diet promoted growth and nutrient digestibility; both B. tequilensis and L. lactis supplementation improved immune response and intestinal barrier function of bullfrogs.

Kaolinite and illite colloid transport in saturated porous media

Understanding the transport of naturally abundant clay colloids is critical in colloid associated contaminant transport in porous media. This study was focused on the impact of the median size of sand grains and the ionic strength of solution on the transport and retention behavior of clay colloids. Two clay samples of kaolinite and illite colloids were selected to represent clay samples containing 1:1 and 2:1 clay minerals, respectively. The observed retention profiles and breakthrough curves demonstrated that the impact of ionic strength on the retention behavior of clay was consistent with other colloidal colloids such as latex colloids or graphene oxide. The quantity of the retained clay increased as the median sizes of sand decreased, and the ionic strength increased from 0 to 0.1 M. However, a similar quantity of retained illite at the ionic strength of 0.01 M and 0.1 M indicates the presence of threshold ionic strength in clay colloid retention. The exponential relationship between sand-to-clay size ratio and first-order retention coefficient at given ionic strength implies the chance in long-term prediction of clay colloid transport from the observed retention profiles. • Transport of kaolinite and illite was investigated in saturated sand column. • Quantity of retained clay does not increase for ionic strength greater than 0.01 M. • Porosity of sand can be a critical factor in clay particle transport. • Impact of aggregation and aspect ratio of clay particles should be considered.

Hydrological Performance of Green Roofs in Mediterranean Climates: A Review and Evaluation of Patterns

The capacity of green roofs to intercept rainfall, and consequently store and slow runoff resulting in a reduction in flood risk, is one of their main advantages. In this review, previous research related to the influence of green roofs on the hydrological cycle is examined with a special focus on studies for Mediterranean climate conditions (Csa and Csb according to the Köppen–Geiger climate classification). This climate is characterized by short and intense rainfall occurrences which, along with the increased area of impervious surface on Mediterranean regions, intensify the risk of flooding, particularly in the cities. The analysis covers the variables rainfall retention (R, %), runoff delay (RD, min or h), peak delay (PD, min or h), peak attenuation (PA, %), and runoff coefficient (RC, −), in relation to physical features of the green roof such as layers, substrate depth, slope, and vegetation, as well as, weather conditions, such as monthly temperature and monthly precipitation. Following a statistical analysis, some patterns for the average rainfall retention (%) were found in the published literature for green roofs under Mediterranean climate conditions—namely, that the most significant variables are related to the substrate depth, the existence of certain layers (root barrier, drainage layer), the origin of the vegetation, the types of green roofs (extensive, semi-intensive, intensive), and the precipitation and temperature of the location. Moreover, a multivariate analysis was conducted using multiple linear regression to identify the set of green roof features and weather conditions that best explain the rainfall retention (%), taking into consideration not only the studies under Mediterranean conditions but all climates, and a similar pattern emerged. Recommendations for future research include addressing the effect of physical features and weather conditions on the other variables (RD, PD, PA, RC) since, although present in some studies, they still do not provide enough information to reach clear conclusions.

Crosslinked Sodium Alginate as a Material for Nanolfiltration Protonic and Aprotonic Solvents

In this work, for the first time, salts of bivalent and trivalent metals were used as crosslinking agents for nanofiltration membranes based on sodium alginate. The developed membranes were investigated for chemical stability in protic and aprotic solvents, the dependence of the permeability of these solvents on their sorption into the membrane material was obtained. The separating properties of membranes based on sodium alginate crosslinked with metal cations were investigated. The retention coefficient of the model substance with a molecular weight of 626 g/mol, dissolved in ethanol, was 97%.

Trichostrongylus colubriformis infection negatively impacted phosphorus metabolism of lambs

Intestinal endoparasite infection may promote a nutrient competition with host, reducing absorption and performance as consequence. Phosphorus could be more affected due to the main absorption site is the duodenum. Thus, the study measured the performance, phosphorus metabolism, bone density and blood markers in Santa Ines lambs infected Trichostrongylus colubriformis and fed with different phosphorus (P) levels were tested. Eighteen healthy six-month old, castrated male, Santa Ines lambs (initial body weight 22.4 ± 2.7 kg) were randomly assigned to 4 treatments in a 2 × 2 split-plot arrangement. Treatment factors were sufficient (SP) or deficient (DP) dietary P and uninfected (ui) or infected (i) resulting in 4 treatments: SPui, DPui, SPi, and Dpi). Five animals were assigned to each of the infected treatments and 4 to the uninfected treatments. Infection was established using a single oral dose of 40.000 T. colubriformis in the larval stage (L3). All the animals were fed Tifton 85 hay (Cynodon spp.; 60 %) supplemented with cassava and maize gluten meal (40 %). Animals were weighed and blood was sampled weekly. Body composition was estimated twice by computed tomography. P metabolism was assessed by isotope dilution after a bolus infusion of 32P (7.4 M Bq/0.5 mL). Fecal egg counts (FEC) were assessed every 3 days beginning d 18 post-infection, and adult nematodes were counted and characterized (gender, length, and eggs in reproductive tract) at slaughter. The experiment lasted 96 d, and 45 d after infeciton. Statistical procedures were performed using R studio. Infection was successful as evidenced by increased FEC, and the elevated counts were maintained longer with Dpi than SPi. Performance, feed intake, and blood parameters were not affected by treatments. Infected animals had reduced bone density and bone P concentrations as compared to uninfected ones. Endogenous P loss was reduced for DP. Plasma, saliva, and ruminal liquid P concentrations decreased in infected animals. Phosphorus absorption and retention coefficients did not differ by treatment, but the biological half-life (T1/2) of P was reduced for infected animals due to faster blood 32P removal. We concluded that T. colubriformis infection modified P metabolism, and blood P concentrations are an indicator of animal problems, connecting infection and bone mineralization.

Manure-induced carbon retention measured from long-term field studies in Canada

Accurate estimates of manure-induced carbon retention coefficients (MCR) in soil are required when assessing carbon (C) storage and the C footprint in agricultural production systems. Eight field studies using various types and rates of manure applications on different crop rotations with durations varying from 10 to 74 years were used to quantify MCRs across diverse climatic conditions in Canada. The rate of solid cattle and swine manure had no impact on MCR which averaged 26%, whereas the MCR for liquid manure, including swine and cattle liquid manures, was much smaller, at only 5%. Under semi-arid conditions, irrigation had no impact on MCR. Compared to stockpiled manures, composted manure had a higher MCR (~36%), due to the additional stabilization of C during the composting process. The MCRs can be effectively stratified based on the type of manure affecting soil organic C differently, and the approach has potential application in regional and national estimates of soil C storage in Canada and elsewhere.

The effects of the dietary replacement of soybean meal with yellow mealworm larvae (Tenebrio molitor) on the growth, nutrient digestibility and nitrogen output of fattening rabbits

The present study aimed to obtain novel information concerning the effects of the total dietary replacement of soybean meal (SBM) with yellow mealworm (Tenebrio molitor; TM) on the coefficients of total tract apparent digestibility (CTTAD) in the diet and on the nitrogen output of fattening rabbits. Two diets were formulated that included 60 g/kg SBM (SBM diet) or 30 g/kg TM (TM diet) as the main crude protein (CP) source. The TM diet had slightly lower CP content than the SBM diet (141 vs. 150 g/kg). A total of 30 rabbits (Hyplus PS 19 x Hyplus PS 40; males) weaned at the age of 32 day were randomly allocated into 2 groups (15 rabbits per group), individually housed, and fed one of the two diets ad libitum for 47 days. Feed intake was measured daily during the entire fattening period (between 32 and 79 day of age). The total faecal and urine output were individually measured between 57 and 61 day of age. A lower daily weight gain (ADWG) between 32 and 53 day of age (by 6.9 g/day, 12 %; P = 0.034), resulting in lower live weight (LW) at the age of 53 day, and a lower feed intake (ADFI) between 32 and 79 day of age (by 13 g/day, 7 %; P = 0.047) were recorded in rabbits fed the TM diet compared to rabbits fed the SBM diet. The ADWG or feed conversion ratio concerning the entire fattening period, the final LW of rabbits, or the CTTAD of the diets were not affected by treatments. Whatever the diet, on average, losses of nitrogen in faeces represented 26 % of the nitrogen intake. Lower losses of nitrogen in urine (by 0.35 g/day, 32 %; P = 0.007) and total excretion of nitrogen (by 0.53 g/day, 23 %; P = 0.003), as well as a higher nitrogen retention coefficient (by 0.06, 11 %; P = 0.026) were detected in rabbits fed the TM diet compared to rabbits fed the SBM diet. It can be concluded that fattening rabbits effectively utilized the diet containing TM without detrimental effects on the CTTAD of the diets or on their nitrogen output.

Rigid and flexible polyimide aerogels with less fatigue for use in harsh conditions

Polyimide aerogels possess various applications in harsh environment but are often limited by poor mechanical property. The ice template method to construct a layered aerogel has structural advantages, but there are still problems of insufficient compression recovery and anisotropy. We investigated the method of forming a spring-like bridge in layered structure, and verified the effect of bridges on the compression deformation, compressive strength, energy dissipation, and fatigue properties. Based on structural observations, a corresponding force mechanism was proposed. After 10,000-cyclic compression at 50% strain, PI aerogels had only 5.8% plastic deformation, 82% stress retention and stable energy dissipation coefficient below 0.3. Interestingly, the compressive performance was isotropic in horizontal direction. Combined with low thermal conductivity, PI aerogels had high structural stability when repeatedly used at 300 °C. This research may provide an available method for design of high-strength and high-toughness polymer aerogels suitable for harsh environment.

Effect of feed processing during the nursery rearing of the Nile tilapia (Oreochromis niloticus)

This study aimed to compare 5 feed processing for O. niloticus fingerlings: ME1: micro-extruded 1 mm; ED03: extruded and disintegrated 0.3 mm; ED06: extruded and disintegrated 0.6 mm; BF03: bran 0.3 mm and BF06: bran 0.6 mm. Feed conversion was lower in ME1 and ED06. The protein retention coefficient was statistically higher in ME1. The fish proximate composition did not differ among treatments. Although superior in ME1 weight gain did not differ statistically from ED06. ME1 resulted in nitrogen and phosphorus in water statistically lower. ME1, ED06 and BF06 obtained the highest partial net revenues. Thus, ME1 presented the best zootechnical indices, economic performance and reduced impact on water quality.

Nutritive value of dehydrated sainfoin (Onobrychis viciifoliae) for growing rabbits, according to the harvesting stage

In rabbit production, the use of dehydrated sainfoin, a Legume containing phenols and condensed tannins (CT), has received recent attention because of its nutraceutical properties. Here, we aimed to compare the nutritive value of dehydrated Perly cultivar sainfoin for a first cut (SC1: crude protein = 200 g/kg, Acid detergent fiber (ADFom) = 208 g/kg, CT = 11.8 g/kg), or a third cut (SC3: crude protein = 159 g/kg, ADFom = 228 g/kg, CT = 17.5 g/kg). The digestibility of two sets of 4 diets, made either with SC1 or with SC3, and containing either 0, 120, 240, or 360 g/kg of dehydrated sainfoin (DS0, DS120, DS240, DS360) in dilution with a basal mixture was compared based on a regression statistical procedure. A direct measure of the nutritive value of SC1 was performed with a supplemental diet containing 980 g/kg (DS980) of SC1. In trial 1, four groups of 12 growing rabbits received SC3 diets. In the trial 2, five groups of 8–9 rabbits received SC1 diets. Rabbits were allotted at weaning (35 days), housed individually in metabolism cages and fed ad libitum during six weeks. Sainfoin digestibility was measured for both trials in 6 weeks old rabbit, and in 8 weeks old rabbit only for trial 2. The digestibility of energy and particularly that of protein linearly decreased with the increase in SC3 incorporation in diets (P < 0.001). Using a regression procedure, SC3 digestible energy (DE) and protein (DP) concentrations were respectively 6.70 ± 0.15 MJ DE/kg and 53 ± 4 g DP/kg as fed, corresponding respectively to a 40 % and 33 % digestibility coefficient. On the contrary energy digestibility was relatively stable from 0 to 360 g/kg SC1 incorporation in diets, in both 6 wks. and 8 wks. old rabbits whereas the digestibility of protein decreased linearly with SC1 incorporation in diets (P < 0.001) as observed with SC3 incorporation. SC1 DE and DP concentration were respectively 8.84 ± 0.25 MJ DE/kg, corresponding to an energy digestibility of 58 %, and 79 ± 5 g DP/kg corresponding to a protein digestibility coefficient of 40 %. Nitrogen retention coefficients slightly decreased with SC3 incorporation. With SC1 incorporation, nitrogen retention coefficients were stable. With SC3 incorporation level the protein digestibility decreased sharper (P < 0.05) than for SC1. The DE content of SC1 calculated by regression gave similar results than a direct measurement (DS980), while the DP content was lower by regression compared to the direct measure (74 vs 92 g/kg). Thus for future assays of sainfoin nutritive value the use of a direct measure could be recommended for DE estimation.

Macromineral and trace element requirements for Santa Ines sheep

Minerals play an important role in animal metabolism. Knowledge of mineral requirements allows well-formulated diets to be provided, which is the main factor that affects performance. To determine the macromineral and trace element requirements for growth and maintenance, thirty-eight 2-month-old Santa Ines lambs with initial body weight (BW) of 13.0 ± 1.49 kg were distributed in a factorial design with feeding levels (ad libitum, 30% and 60% feed restriction) and sex classes [castrated (CM) and intact males (IM)]. The net mineral requirements for gain were higher (P < 0.05) with increasing BW and average daily gain, except for Ca and Na, which remained constant as the empty BW (EBW) increased. The macromineral net requirement for maintenance (g/kg EBW0.75) and the true retention coefficient (k; %) were 0.0784 and 65.2 for Ca, 0.0926 and 80.0 for P, and 0.0379 and 59.0 for K, respectively. The k of Mg was higher (P < 0.05) for IM (11.3 for IM and 7.9 for CM). Sex did not affect (P > 0.05) the maintenance requirement of the trace elements Co, Cu, Zn and Cr which were 0.0015, 0.037, 0.698, and 0.0055 (mg/kg EBW0.75), respectively. Our study indicated that the Santa Ines net mineral requirements are different from the main nutritional requirements established by committees for sheep, which may result in unbalanced diets.

Hydration of Nebular Minerals through the Implantation–Diffusion Process

Abstract Recent studies have detected structurally bound water in the refractory silicate minerals present in ordinary and enstatite chondrite meteorites. The mechanism for the incorporation of the hydrogen is not well defined. In this paper we quantitatively examine a two-fold process involving the implantation and diffusion of nebular hydrogen ions that is responsible for the hydration of the chondritic minerals. Our simulations show that depending on critical parameters, including the flux of the protons in nebular plasma, retention coefficient, temperature of the silicate minerals, and desorption rate of implanted hydrogen, the implantation of low-energy hydrogen ions can result in equivalent water contents of ∼0.1 wt% in chondritic silicates within 10 years. Thus, this novel mechanism operating in the nebula at 10−3 bar pressure and &lt;650 K temperatures can efficiently hydrate the free-floating chondritic minerals prior to the rapid formation of planetesimals inside the snow line, and agree well with the wet accretion scenario for the inner solar system objects.

Effect of By-Products from Selected Fruits and Vegetables on Gluten-Free Dough Rheology and Bread Properties

The aim of the study was to investigate the effect of using various by-products (orange and apple pomace, tomato peel, pepper peel, prickly pear peel, and prickly pear seed peel) on the dough rheology and properties of gluten-free bread. The by-products were incorporated into a gluten-free bread formulation based on corn and chickpea flours (2/1 w/w). Different levels of each by-product (0, 2.5, 5, and 7.5% in the basic replacement) were tested. Wheat bread and gluten-free bread without the addition of by-products were used as controls. The results indicated that the by-products increased the maximum dough height, the total CO2 production, and CO2 retention coefficient compared to unenriched gluten-free dough. The highest K-value consistency coefficient was observed for the dough enriched with the prickly pear peel. The addition of by-products significantly improved (p &lt; 0.0001) the specific volume of gluten-free bread, with values increasing from 1.48 to 2.50 cm3/g. The hierarchical cluster analysis and the constellation plot showed four groups: the wheat bread group, the second group containing the gluten-free control bread, the group with bread enriched by pomace, and the group with bread enriched with peels, exhibit the same effect on gluten-free bread and the peels exhibit the same effect on gluten-free bread.

Exchange Flow and Material Transport Along the Salinity Gradient of a Long Estuary

AbstractMost estuaries are characterized by non‐uniform axial topography with shallow shoals near the mouth. Previous studies have addressed the impacts of the axial topographic variations on mixing and estuarine circulations yet seldom on material transport and retention. This study investigates the longitudinal structure and mechanisms of exchange flow and material transport of Chesapeake Bay (CB), featuring a shallow sill in the lower bay, by applying total exchange flow (TEF) algorithm, tracer experiments, and partial residence time (PRT) using a validated 32‐years numerical model simulation. A retention coefficient was adopted to quantify the material retention rate using two characteristic PRTs: with and without incorporating water parcels returning to a concerned region. It is found that shoaling from the Rappahannock Shoal to the mouth causes persistent downwelling, strong reflux, and the highest material retention rate in the middle of the bay. The gravitational circulation and the river outflow dominate the transport of salt and riverine dissolved materials (RDMs), whereas the contribution of the tidal oscillatory process is localized near the mouth. The dominance of river outflow over the gravitational circulation for transporting RDMs is confined within the upper bay, where PRTs exhibit distinct seasonality. PRTs show small seasonality in the middle to the lower bay controlled by the exchange flow. The present analysis combining TEF, efflux/reflux theory, and PRT is applicable to other coastal aquatic ecosystems to characterize the water exchange and renewal efficiency along the salinity gradient and understand the contributions of transport to biogeochemical processes.

Physicochemical and sensory properties of Manchego-type cheese fortified with nanoemulsified curcumin

The effect of incorporating nanoemulsified curcumin in Manchego-type cheese on its physicochemical and sensory properties was investigated. Nanoemulsified curcumin was prepared by the thin-film hydration-emulsification and ultrasonication methods, and added to Pelibuey sheep milk at 5, 7.5, and 10 ppm of curcumin to make enriched Manchego-type cheeses. The curcumin content of the enriched cheeses was determined by high-performance liquid chromatography. The average curcumin retention coefficient was 0.83 ± 0.03. The total phenolic content and antioxidant activity according to the FRAP and DPPH assays increased in the curcumin-enriched cheeses as compared to the control cheese. No significant differences were observed in the moisture, protein, fat, and ash contents, nor in water activity and yield; however, significant differences were observed in the soluble nitrogen and free fatty acid contents and colour. According to surveyed panellists, the addition of nanoemulsified curcumin to cheese modified its colour, odour, and appearance, but not its flavour, texture, and overall acceptability. The present work highlights the potential of incorporating nanoemulsified curcumin in Manchego-type cheese to enhance its beneficial health effects.

True phosphorus digestibility of cottonseed meal and rice husk supplemented with microbial phytase in broiler chickens

This research aimed to determine effects of phytase in cottonseed meal (CM) and rice husk (RH) based diets on true phosphorus digestibility (TPD) by broiler chickens. Two studies were conducted with 576 one-day-old broiler chickens using regression analysis to determine the TPD in these diets and the response to phytase supplementation. Six semi-purified diets were formulated to contain 150 g, 300 g, and 450 g each of CM/kg (experiment 1) and RH/kg (experiment 2) with phytase supplied at 0 and 1000 units/kg. Titanium dioxide was added to the diets at the rate of 5 g/kg as an indigestible maker. A total of 288 broiler chickens in each study were weighed and allotted to the six diets with six replicates of eight birds in a randomized complete block design. The birds were fed the experimental diets until day 26 post hatch. The coefficients of true phosphorus retention (TPR) were 0.8 for CM and 0.78 for RH without phytase; 0.93 for CM and 0.92 for RH with phytase. True phosphorus digestibility was 0.82 for CM and 0.75 for RH without phytase; and 0.95 for CM and 0.92 for RH with phytase. Phytase supplementation resulted in 13.27 and 17.94 % increases in TPD; and 12.29 and 13.61 % increases in TPR by birds fed the CM and RH diets, respectively. Phytase supplementation of CM and RH based diets increased TPD and improved total TPR and true ileal phosphorus digestibility in broiler chickens.

Nutrient mass balance of a large riverine reservoir in the context of water residence time variability.

The excessive input of nitrogen (N) and phosphorus (P) from anthropogenic activities is the main reason behind the cultural eutrophication and algal blooms in freshwater ecosystems. Here, I present a comprehensive budget of N, P for a large reservoir (Lake Diefenbaker) within a highly cultivated watershed. I constructed a 4-year nutrient budget from 2011 to 2014, using grab samples and daily flow data, and a multi-decadal (1978 through 2014) budgeting to examine the effect of inter-annual variability of water residence time on retention of N and P, and if retention of N and P is affected differently. The 4-year budget showed that the reservoir was a net source of total nitrogen (TN) during 2011 and 2014, but a net sink during 2012 and 2013. This resulted in retention coefficients of - 35% and - 4% in 2011 and 2014, respectively. With respect to the total phosphorus (TP) budget, the reservoir acted as a net sink in all 4 years, with a mean retention coefficient of 87%. Consistent with findings of the 4-year budget, the results of the multi-decadal budgeting showed that the reservoir was a net sink for TP during the period of record with a mean retention of 81% (1583 t/year). Regarding TN, the mean retention was lower (49%, 4836 t/year) and more variable relative to TP over the long term. Unlike TP, the results showed that the retention of TN has been decreasing noticeably since 1978. Overall, the retention of TP in this lake is primarily controlled by in-lake sedimentation and most likely does not change substantially in response to inter-annual variation of hydraulic variables such as water residence time. For TN, the role of sedimentation could be minor in retention process in this reservoir (or similar reservoirs elsewhere), but in-lake biological processes could play a more important role. These findings are useful for understanding the role of larger reservoirs with water residence time of 1-3 years in nutrient retention and how changes in flow and water residence time due to climate variability and water management can influence the nutrient retention efficiency.

Effect of Aging Conditions and Rubber Waste Content on the Mechanical Properties and Structure of Montmorillonite/Acrylonitrile Butadiene Rubber Nanocomposites

The research described in the present work investigated the effect of thermal and photoaging and rubber waste content on the properties of acrylonitrile–butadiene rubber modified with montmorillonite (MMT). The MMT was mixed with plasticizer before the compounding in two roll mills. The modulus at 300% strain of samples without scrap maximally increased by 50% and 30% after thermal and photoaging, respectively, most probably due to an increase in the crosslink density. The maximum increases of the modulus, measured at 300% strain, of the unaged and aged rubber nanocomposite were exhibited by samples which each contained 10 wt.% of rubber waste. The MMT nanoparticles, well dispersed in the matrix, combined with good interfacial interaction between the different components, led to relative retention of the thermal and photo-oxidation aging coefficients and the large shape retention coefficient of the tested samples. Fourier transform infrared spectra showed that the crosslinking of the rubber nanocomposites containing waste occurred through the nitrile groups and C = C double bonds under the influence of aging. Scanning electron microscopy micrographs indicated that the MMT nanoparticles were uniformly embedded and well dispersed in the matrix. The rough and homogeneous fracture surfaces of the nanocomposite samples were not affected by incorporated waste. As a result of UV irradiation and thermal heating, aggregates were less visible and the fracture surfaces more homogeneous and compact.

Analysis of experimental data on the kinetic characteristics of milk whey purification using ultrafiltration elements of BTU 05/2 type

The paper presents the results of experimental data on the kinetic characteristics of ultrafiltration tubular elements, such as the output specific flow, retention coefficient, diffusion permeability coefficient, distribution coefficient. To study the purification of milk whey, we used tubular ultrafilters BTU 05/2 with membrane material fluoroplast (F), polyethersulfone (PESF), polysulfone (PS). For theoretical calculation of the retention coefficient, output specific flux, diffusion permeability coefficient, distribution coefficient, mathematical expressions were developed and empirical coefficients were obtained. The developed mathematical expression describes the experimental data with good reliability. The obtained experimental and calculated data can be used with high reliability in calculating mass-transfer fluxes of substances through a semi-permeable membrane, as well as in engineering methods for calculating and predicting efficiency, and using membrane processes for concentrating serum. The protein concentration in real milk whey was determined by formol titration. On the basis of the studies carried out, the dependence of the growth of the output specific flow on pressure was established, that the optimal pressure for concentrating milk whey on the ultrafiltration membranes we have chosen is 0.25 MPa. For three types of ultrafilters, the experimental value of the coefficient was within 99% for protein. For the theoretical calculation of the retention coefficient, a program in the MAXIMA language was developed and registered. Due to the method of applying the membrane to the reinforcing element, the membrane material polyethersulfone (PESF) and polysulfone (PS) have a substrate, due to which they sorb more substances on themselves, because of this, the diffusion permeability coefficient and the distribution coefficient are much higher than that of a filter element with membrane made of fluoroplastic (F), which does not have a substrate.