Facile Synthesis of Fluorinated Polysilazanes and Their Durable Icephobicity on Rough Al Surfaces

Superhydrophobic Al surfaces with excellent durability and anti-icing properties were fabricated by coating dual-scale rough Al substrates with fluorinated polysilazane (FPSZ). Flat Al plates were etched using an acidic solution, followed by immersion in boiling water to generate hierarchical micro-nano structures on their surfaces. The FPSZ coatings were synthesized by grafting 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS-17), a fluoroalkyl silane), onto methylpolysilazane, an organopolysilazane (OPSZ) backbone. The high water contact angle (175°) and low sliding angle (1.6°) of the FPSZ-coated sample with an FAS-17 content of 17.3 wt% promoted the efficient removal of a frozen ice column with a low ice adhesion strength of 78 kPa at −20.0 °C (70% relative humidity), which was 4.3 times smaller than that of an OPSZ-coated surface. The FPSZ-coated Al surface suppressed ice nucleation, leading to a decrease in ice nucleation temperature from −19.5 to −21.9 °C and a delay in freezing time from 334 to 4914 s at −19.0 °C compared with the OPSZ-coated Al surface. Moreover, after 40 icing–melting cycles the freezing temperature of a water droplet on the FPSZ-coated Al surface remained unchanged, whereas that on the FAS-17-coated Al surface increased from −22.3 to −20.7 °C. Therefore, the durability of the polymeric FPSZ coating was superior to that of the FAS-17 monolayer coating.

Impact of freezing temperature (Tfr) of Al2O3 and molecular diameter (H2O)d on thermal enhancement in magnetized and radiative nanofluid with mixed convection

The dynamics of nanofluid by considering the role of imposed Lorentz forces, thermal radiations and velocity slip effects over a vertically convectively heated surface is a topic of huge interest. Therefore, the said study is conducted for Al2O3-H2O nanofluid. Mathematical modelling of the problem is done via nanofluid effective correlations comprising the influences of freezing temperature, molecular diameter and similarity transformations. The results for multiple parameters are plotted and provide comprehensive discussion. From the analysis, it is examined that Al2O3-H2O nanofluid motion drops by strengthening Lorentz forces. The temperature in the nanofluid (Al2O3-H2O) is improved by inducing viscous dissipation effects (Ec number), surface convection (Biot number) and thermal radiations (Rd). Moreover, the shear stresses at the surface decreased due to higher magnetic field effects and rises due to velocity slip. A significant rise in Local Nusselt number is observed due to thermal radiations and Biot effects. Finally, enhanced heat transport mechanism in Al2O3-H2O is examined than a conventional liquid. Therefore, nanofluids are better for industrial applications and the uses of conventional liquids are limited due to low thermal conductivity.

Influence of freezing temperature on semen quality of rainbow trout (Oncorhynchus mykiss)

Trout production in Peru has export potential. However, there are no fry available to maintain production throughout the year and there is also a lack of egg production at certain times of the year. Therefore, the alternative is to cryopreserve semen for the non-reproductive season. The objective of the study was to determine the influence of freezing temperature on the quality of rainbow trout semen. The semen of 12 reproductive males was collected in the facilities of the Chucuito Research and Production Center of the National University of the Altiplano of Puno, which underwent a macroscopic, microscopic pre and post thaw seminal evaluation and the fertility rate was measured. Due to the effect of three freezing temperatures (-80 °C, -100 °C, -120 °C), cryopreservation had a decline curve of -20 °C / min. The fresh seminal parameters were similar to those reported by other researchers. While freezing had unfavorable effects on semen quality, the best results for activation time (51.33 sec) and vitality (35.33%) were obtained with -100 °C, but the higher motility was obtained with -120 °C (36.33%). Regarding fertility, the higher rate was obtained with -100 °C (70.97%), followed by -80 °C and -120 °C in which 68.86% and 64.34% were obtained, respectively. In conclusion, the results suggest that the tolerable freezing temperature of rainbow trout semen is around -100 °C, which is shown as a favorable alternative for the reproductive management of rainbow trout under natural hypobaric conditions of the Peruvian highlands

Syndromic Surveillance Data for Accidental Fall Injury

Background:Fall injuries (FI) are a priority for public health planning. Syndromic surveillance (SS) is used to detect outbreaks, environmental exposures, and bioterrorism in real time. Since information is gathered on patients, the utility of using this system for FI should be evaluated. Methods:Strategies to integrate FI medical and SS data were compared using a cohort versus case control (CC) study design. Results:The CC study was accurate 77.7% (57.7-91.3) of the time versus 100% for a cohort design. The CC study design found FI increased for older age groups, female gender, November, and December months. Dates with any freezing temperature had a higher case fatality rate. Repeat acute care visits increased the risk of FI diagnosis by over 6% and trended upward with each visit (R=.333, p<.001). Conclusions:The CC diagnostic quality of FI were better for age and gender than for area. The CC study found the indicators of increased risk of FI including: Freezing temperature, repeat acute care visits, older age groups, female gender, November, and December months. A gradient of increasing odds of FI with the number of acute care visits provides proof that community fall prevention programs should focus on those most likely to fall. A CC design of SS data can quickly identify indicators of FI with a lower accuracy but with less cost than a full cohort study, thus providing a method to focus local public health interventions.

The effect of weather conditions in southern Russia on the frost resistance of apricot generative buds

One of the reasons limiting the apricot expansion in the world is the short period of winter dormancy in the plants and the rapid development of generative buds in the spring. Apricot flower buds often die even after small spring return frosts that limit the commercial culture of this fruit crop. The aim of this investigation was to study collection-breeding plantations and select frost-resistant genotypes that have promise for commercial and breeding use. To solve this problem, the frost resistance of generative buds in 50 apricot cultivars and the breeding forms of various origins were studied by freezing treatments of the branches in a climatic chamber. The Czech cultivar ‘Leala’ was selected due to its best frost resistance. In late winter 2020–2021, six cultivars and breeding forms, which kept 41.8 to 65.9% of the generative buds alive, were identified. These genotypes are characterised by a slow development that prevents any negative freezing temperature effects. Thus, the results of the study confirmed the dependence of the adaptation mechanisms in apricot plants on the rates of their morphogenesis and abiotic factor pressures.

Pengaruh Penyimpanan Beku terhadap Karakteristik Kimia dan Fisik Caulerpa racemosa, Drip, dan Filtratnya

Caulerpa racemosa merupakan rumput laut hijau dengan kandungan air yang tinggi sehingga mudah mengalami kerusakan. Penyimpanan dalam suhu beku merupakan salah satu cara untuk memperpanjang masa simpan suatu produk. Namun, pembekuan produk juga dapat menyebabkan terjadinya berbagai perubahan yang tidak dikehendaki. Penelitian ini bertujuan untuk menganalisis pengaruh penyimpanan pada suhu beku terhadap karakteristik kimia dan fisik C. racemosa, drip, dan filtrat yang dihasilkan. Sampel berupa C. rasemosa disimpan dalam ruangan penyimpan beku (cold storage) dan diamati setiap minggunya hingga minggu ke-4. Parameter uji yang diamati meliputi rendemen, komposisi proksimat, kadar garam, uji warna (L*, a*, b*), dan viskositas, masing-masing pada C. racemosa yang ditiriskan, drip, dan filtrat C. racemosa. Hasil penelitian menunjukkan bahwa penyimpanan beku C. racemosa dapat mengurangi berat pada sampel akhir karena sebagian besar drip keluar setelah pelelehan/thawing, yaitu sekitar 77,88-84,81%. Karakteristik fisik maupun kimia C. racemosa yang disimpan selama 1 hingga 4 minggu tidak berbeda nyata antar waktu penyimpanan, namun berbeda nyata pada C. racemosa tanpa disimpan beku, yaitu pada kadar air, abu, dan garam.ABSTRACTCaulerpa racemosa is a green seaweed that has a high moisture content, so it is easily damaged. Frozen storage is one way to extend the shelf life of a product. However, freezing the product can cause various undesirable changes to occur. This study was aimed to analyze the effect of storage at freezing temperature on the chemical and physical characteristics of C. racemosa, drip, and the resulting filtrate. C. racemosa samples were stored in cold storage and observed every week until the 4th week. The test parameters observed were yield, proximate composition, salt content, color (L*, a*, b*), and viscosity on drained C. racemosa, drip, and C. racemosa filtrate. The results showed that frozen storage of C. racemosa could cause weight loss in the final sample because most of the drip came out after thawing, which was around 77.88 - 84.81%. Physical and chemical characteristics of C. racemosa stored for 1 to 4 weeks were not significantly different from unfrozen C. racemosa, i.e. water, ash, and salt content.

Improving the Performance of Solar Heat Collector Using Molten Salts

An individual solar collector and two partly freight cylinders filled with molten salts embedded storage tank were connected to each other and forced circulated water by electric pump to improve the thermal performance of residential solar hot water tank. Multi flow rates of 25, 50 and 70 l/h. used to achieve an appropriate flow rate of circulating water. The calcium nitrate tetra hydrate Ca(NO3)2-4H2O and magnesium nitrate hex hydrate Mg(NO3)2-6H2O were mixed to form cheap binary molten salts base on different weight ratios. These molten salts combined could be used as both sensible heat materials and latent heat storage materials, besides they can directly use as heat transfer fluid due to freezing temperature. Six samples of different mixing ratio of molten salts had tested to assess the thermal analysis of each sample. The result indicated that the mixture 60%Ca(NO3)2+40%Mg(NO3)2 had the best performance for thermal storage tank with melting point of 38°C and the thermal value is 8.7 mW, and thermal stability of molten salts were noticed by DSC 60 SHIMADZSU devise.

Metal Emulsion-Based Synthesis, Characterization, and Properties of Sn-Based Microsphere Phase Change Materials

A comparative study of the metal emulsion-based synthesis of Sn-based materials in two different types of molten salts (namely LiCl–KCl–CsCl and LiNO3-NaNO3-KNO3 eutectics) is presented, and the properties of Sn, Sn-Cu and Sn-Cu-Zn microsphere phase change materials prepared in chloride salts are evaluated by differential scanning calorimetry (DSC) to understand the effect of element doping. Despite a high ultrasonic power (e.g., 600 W or above) being required for dispersing liquid Sn in the chloride system, well-shaped Sn microspheres with a relatively narrow size range, e.g., about 1 to 15 µm or several micrometers to around 30 µm, can be prepared by adjusting the ultrasonic power (840–1080 W), sonication time (5–10 min) and the volume ratio of salts to metal (25:1–200:1). Such a method can be extended to the synthesis of Sn-based alloy microspheres, e.g., Sn-Cu and Sn-Cu-Zn microspheres. In the nitrate system, however, a very low ultrasonic power (e.g., 12 W) can be used to disperse liquid Sn, and the particles obtained are much smaller. At low ultrasonic power (e.g., 12 W), the particle size is generally less than 10 or 4 µm when the sonication time reaches 2 or 5 min, and at high ultrasonic power, it is typically in the range of hundreds of nanometers to 2 µm, regardless of the change in ultrasonic power (480–1080 W), irradiation time (5–10 min), or volume ratio of salts to metal (25:1–1000:1). In addition, the appearance of a SnO phase in the products prepared under different conditions hints at the occurrence of a reaction between Sn droplets and O2 in situ generated by the ultrasound-induced decomposition of nitrates, and such an interfacial reaction is believed to be responsible for these differences observed in two different molten salt systems. A DSC study of Sn, Sn-Cu, and Sn-Cu-Zn microspheres encapsulated in SiO2 reveals that Cu (0.3–0.9 wt.%) or Cu-Zn (0.9 wt.% Cu and 0.6% Zn) doping can raise the onset freezing temperature and thus suppress the undercooling of Sn, but a broad freezing peak observed in these doped microspheres, along with a still much higher undercooling compared to those of reported Sn-Cu or Sn-Cu-Zn solders, suggests the existence of a size effect, and that a low temperature is still needed for totally releasing latent heat. Since the chloride salts can be recycled by means of the evaporation of water and are stable at high temperature, our results indicate that the LiCl–KCl–CsCl salt-based metal emulsion method might also serve as an environmentally friendly method for the synthesis of other metals and their alloy microspheres.

Application of Solid Paraffin Inhibitor in Fracturing of Kuqa Ultra Deep High Pressure and High Wax Content Tight Condensate Gas Reservoir

The buried depth of gas reservoir B is more than 6700m, the thickness of reservoir is about 180m, the porosity of reservoir matrix is mainly 5.0% - 7.0%, with an average of 6.3%, and the permeability of reservoir matrix is mainly 0.01-0.1mD, The average production capacity of the three wells is 0.08mD, the formation pressure is 116-126MPa, the formation temperature is 124-131°C, the wax content of the condensate oil is high, and the average wax content is 16.9%. In the early stage, the natural productivity of the three wells was low, and the daily gas production was 120000-180000 cubic meters after stimulation. During the production process, the wellhead temperature was 20°C-25°C, the wax freezing temperature was 35°C, and the wellbore wax plugging was serious, The wellbore was blocked, the gas well was forced to shut down, and the reserves of 100 billion cubic meters were unable to be used, so it was necessary to explore new wax control technology. Through investigation, a new type of solid particle paraffin inhibitor is introduced, which can enter the artificial fracture with proppant during fracturing. When the condensate gas passes through the fracture, it washes the solid paraffin inhibitor which enters with proppant, and becomes the condensate gas containing paraffin control components.Therefore,it is not easy to form wax after entering the wellbore, which makes the problem of wellbore paraffin formation change from "passive control" to "active control". Referring to the relevant experimental standards, the conductivity, crushing test, solid paraffin inhibitor and fracturing fluid compatibility test were carried out. The existing test standards of wax freezing point are all for waxy oil under normal pressure, but not for condensate gas. A set of innovative experimental method is designed to successfully test the wax freezing point of condensate gas containing wax control components, and obtain the wax control effect under different ratios of wax control agent and proppant, so as to optimize the amount of wax control agent used in the experiment. The results show that the solid paraffin inhibitor has good dispersibility and suspension, and has little influence on the conductivity of sand filled fractures. The paraffin control effect on condensate oil and gas in this block is good. The wax freezing point can be reduced by about 12°C-18°C, and the optimal dosage is proppant 1%-2%. Field test was carried out in B gas reservoir. After fracturing, 5mm nozzle was used for production, tubing pressure was 83.6MPa, wellhead temperature was 28.8°C, daily oil production was 10.72 cubic meters, daily gas production was 217000 cubic meters, wellhead temperature was lower than wax freezing temperature in this area. At present, it has been in production for 6 months, and there is no wax deposit in wellbore. The successful test of solid paraffin inhibitor in the fracturing of Kuqa ultra deep high pressure and high wax content tight condensate gas reservoir provides a powerful technical reference for the wellbore flow guarantee of condensate gas reservoir.

The migration law of magnesium ions during freezing and melting processes

To explore the migration law of magnesium ions (Mg2+) during freezing and melting processes, laboratory simulation experiments involving freezing and melting were carried out to investigate the influence of ice thickness, freezing temperature, initial concentration, and initial pH on the distribution of Mg2+ in the ice-water system. The distribution coefficient “K” (the ratio of the Mg2+ concentration in the ice layer to the Mg2+ concentration in the water layer under ice) was used to characterize the migration ability of Mg2+. The results showed that during the freezing process, the concentration distribution of Mg2+ in the ice and water two-phase system was as follows: ice layer < water before freezing < water layer under ice; in other words, it migrated from ice layer to the water layer under ice. “K” decreased with increasing ice thickness, freezing temperature, initial concentration, and initial pH; the higher the ice thickness, freezing temperature, initial concentration, and initial pH were, the higher the migration efficiency of Mg2+ into the water layer under ice was. During the melting process, Mg2+ was released in large amounts (50–60%) at the initial stage (0–25%) and in small amounts (25–100%) uniformly in the middle and later periods. According to the change of Mg2+ concentration in ice melt water, an exponential model was established to predict Mg2+ concentration in ice melt period. The migration law of Mg2+during the freezing and melting process was explained by using first principles.