Prolonged Immersion Research Articles

Hierarchically structured composite with superhydrophobicity and radiative cooling for energy-saving buildings

Passive daytime radiative cooling (PDRC) with zero energy consumption and green is regarded as one of the most feasible solutions to replace conventional electrical cooling by reflecting sunlight spontaneously and radiating excess heat through atmospheric transparency windows to universe natural heat sink. However, traditional cool building materials are still very limited in practical applications due to contamination by dust, rain, etc., which reduces the cooling capacity in outdoor environments. Herein, we fabricate a hierarchically designed superhydrophobic daytime radiative composite (Al2O3-PDMS/Al2O3-PDMS@Ag/Al2O3-PDMS/SiO2) via facile bladeing film and electroless Ag plating methods, which have strong visible light reflectivity ∼91 % and high mid-infrared emissivity ∼97 %, effectively producing an ambient temperature drop of 13.8 °C on sunny days in direct outdoor sunlight. What's more, the composite has satisfactory superhydrophobicity with a water contact angle of 154°, making the composite self-cleaning so that the composite is not contaminated and effectively maintains splendid radiative cooling properties. Meanwhile, after prolonged immersion in hydrochloric acid and water shock, the composite retains superhydrophobicity and significant radiative cooling properties, which are of great significance for the sustainable development of energy-saving buildings.

Direct writing immersion laser lithography on graphene monolayers using two-photon absorption

Direct writing laser lithography has become increasingly attractive due to its mask-free nature, offering significant design flexibility and minimizing additional costs associated with new exposure masks. Among the various direct laser writing techniques, two-photon absorption direct laser writing stands out for its ability to fabricate very small features through nonlinear optical effects. Operating this technique in immersion, where the air gap between the lens and photoresist or probe is liquid-filled, has been shown to enable reduced feature sizes [D. P. Sanders, Chem. Rev. 110, 321 (2010).]. Previous studies have typically employed an immersion oil for this purpose [Jakkinapalli et al., J. Micromech. Microeng. 30, 125014 (2020).]. However, our experiments revealed that prolonged immersion times can lead to oil interacting with the photoresist, resulting in the formation of new compounds that are challenging to remove. Consequently, the altered photoresist becomes unresponsive to both exposure and development. In light of these findings, we conducted tests using alternative immersion liquids and propose a combination of different immersion liquids and air direct writing as a means to achieve optimal writing results.

Investigating in-vitro degradation, fatigue behavior, and fracture toughness of electrical discharge-processed Mg alloys for biodegradable implant applications

Biodegradable magnesium (Mg) alloys hold great potential for revolutionizing the field of biomedical engineering by offering temporary support during tissue healing and degrading without leaving permanent residues. However, their clinical applications have been limited due to their relatively high degradation rate. This study focuses on evaluating the in-vitro degradation, fatigue resistance, and fracture toughness properties of Mg alloys under cyclic loading conditions, mimicking real-life scenarios. Wire Electrical Discharge Machining (WEDM) was used to prepare spark-processed Mg samples with complex surface texture, and fine-polished Mg samples were used for comparison. The structural characterization, electrochemical corrosion behavior, degradation assessment, and mechanical integrity of the samples were comprehensively analysed. The results show that the Electrical Discharge processed (EDed) Mg sample exhibited uniformly distributed overlapped craters on the surface, which led to a lower charge transfer resistance and higher corrosion potential compared to the Pristine Mg sample. The rough surface topography and alkaline pH microenvironment of the EDed Mg sample facilitated rapid apatite mineralization, but the resulting Ca-deficient apatite compromised its structural stability. Both EDed and Pristine Mg samples exhibited a significant reduction in fatigue life and lower fracture toughness with prolonged immersion. These findings provide valuable insights into the performance of Mg alloys and their potential applications in biodegradable implants, guiding the design of robust implant materials for enhanced patient outcomes.

The combined effect of hydroxyapatite and zirconia coatings on magnesium-based-implant to improve corrosion resistance and induce antibacterial activity

In this research, zirconium has been used in two methods of, single-step and double-step, to improve the anticorrosion properties of Hydroxyapatite (HA) coating. The corrosion behavior of the samples and the performance of the coatings in the physiological environment were investigated by EIS and DC polarization tests in 3.5 wt% sodium chloride and SBF solution, respectively. The results of the electrochemical assays showed that the best resistance against corrosion and biocorrosion is obtained for the sample prepared by the double-step method (HAopt/Zropt sample). FE-SEM and XRD were used to examine the morphology and composition of the coatings that confirmed the formation of HA crystals and the amorphous zirconium layer. According to the antibacterial results, HA/zirconia coating provided a remarkable antibacterial performance (RP =99.9%) against Staphylococcus aureus gram-positive and Escherichia coli gram-negative bacteria. Also, HAopt/Zropt sample provided the highest corrosion resistance of about 9000 ohm.cm2 in NaCl, and |Z|0.01 Hz= 3.5 × 105 ohm.cm2 in SBF solution in a prolonged immersion period.

Stage changes in the oxidizing properties of long-term water-soaked coal and analysis of key reactive groups

To elucidate the impact of prolonged water immersion on the evolution of key active functional groups during the low-temperature oxidation of coal, the programmed temperature ramping method, in-situ Fourier transform infrared spectroscopy (in-situ FTIR), microcalorimetry (C80) experiments, thermodynamic analysis, and gray and Pearson correlation analysis were performed. The analysis involved coal samples exposed to different immersion durations (3, 6, 9, and 12 months). The results reveal that long-term water immersion exerts a stage-wise influence on the oxidation characteristics of coal, with the critical time point being 6 months. Before this period, the gradual accumulation of active sites progressively enhances the oxidation characteristics. However, after 6 months, the generation of active sites is suppressed, resulting in a gradual weakening of the coal's oxidation behavior. Correlation analysis revealed that the correlation between free hydroxyl groups and gaseous products is strongest in coal immersed for 6 months (A6), with a correlation coefficient of 0.91. During the accelerated oxidation stage, the heat released from the soaked coal is significantly greater than that in other stages, which promotes the formation of C=O and –COOH functional groups and further reduces the apparent activation energy. According to the Coats–Redfern method, A6 exhibits the smallest apparent activation energy—only 30 % of the original value of coal. The correlation between free hydroxyl groups and apparent activation energy is strongest at this stage, with a correlation coefficient of 0.92. This indicates that free hydroxyl groups and the accelerated oxidation stage are, respectively, the key active functional groups and critical phases in the coal oxidation process.

Validation of a human thermoregulatory model during prolonged immersion in warm water

This study validates the Six Cylinder Thermoregulatory Model (SCTM) during prolonged warm water immersion, which underpins the Probability of Survival Decision Aid (PSDA) currently in use by the United States Coast Guard (USCG). PSDA predicts survival time for hypothermia and dehydration. USCG has been using PSDA for search and rescue operation since 2010. In 2019, USCG organized a workshop to review PSDA performance and concluded that PSDA is an essential tool for operation, although it occasionally overestimates survival times in warm waters above 16 °C. Forty-six human subjects were immersed from the neck down in 18, 22, and 26 °C water for 45 min up to 10 h. Rectal temperature (Tcore), 10-site mean skin temperature (Tsk), and water loss were measured. At the end of immersion, Tcore ranged from 35.2 to 38.0 °C, and Tsk ranged from 19.7 to 27.4 °C. The SCTM-predicted Tcore, Tsk and water loss were compared to the measured values. Root mean squared deviation (RMSD) was used to test for acceptable predictions. Tcore RMSDs were 0.2, 0.14, and 0.3 °C in 18, 22, and 26 °C water respectively. Tsk RMSDs were 1.44, 0.76, and 1.1 °C in 18, 22, and 26 °C water respectively. SCTM underpredicted water loss by 84%. Overall, SCTM predicted Tcore and Tsk with acceptable accuracy in 18 and 22 °C water for up to 10 h, but overpredicted in 26 °C water. Future studies and algorithm development are required to improve water loss prediction as well as Tcore and Tsk prediction in 26 °C water.

Amphiphilic Surface‐Active Methacrylic Urethane Additives for the Design of Photopolymerized Coatings with Great Potential for Marine Fouling‐Release Applications

AbstractAmphiphilic photopolymerized network films are prepared, based on a hexyl acrylate (HA) hydrophobic matrix containing varied amounts of urethane dimethacrylates bearing a hydrophilic poly(ethylene glycol) segment and terminated with hydrophobic, low surface energy groups, i.e., a short perfluorohexyl chain (for EF) or a fluorine‐free heptamethyltrisiloxane group (for ES). These films are extensively characterized in bulk and at the surface by thermal, mechanical, solvent and water uptake, contact angle, and X‐ray photoelectron spectroscopy measurements. On one hand, surface characterizations reveal that the amphiphilic chains of the additives enrich the topmost layer of the films, thus generating a water‐responsive surface. The reconstruction process is found to be faster for the perfluorinated additive EF and slower for the fluorine‐free ES ones. On the other hand, HA provides a hydrophobic matrix with low elastic modulus, dimensional stability, and adhesion to the substrates even after the absorption of water after prolonged immersion. A field immersion trial carried out in a touristic harbor in Leghorn points out that the films, although being ineffective in preventing organism settlement, are easily cleaned by a water jet after three months of immersion, showing a final residual coverage of panels as low as 15%.

A smart sol-gel coating incorporating pH-responsive BTA-ZIF-8 MOF assembled hexagonal boron nitride for active/passive corrosion protection of 1060 aluminum alloy

Integration of both passive and active corrosion-protecting mechanisms is an effective method for endowing sol-gel derived coatings with long-term anticorrosion performance. To provide “smart” functionality for sol-gel coating, a novel self-healing nanocontainer is fabricated via the in-situ growth of 1H-benzotriazole-inbuilt zeolitic imidazolate framework (BTA-ZIF-8) on hydroxylated hexagonal boron nitride nanosheets (BN-OH), which exhibits efficient pH-dependent inhibitor release behavior at both acidic and alkaline media. Electrochemical measurements reveal that sol-gel coating containing the BTA-ZIF-8@BN-OH nanocontainers exhibits superior anticorrosion performance and long-term corrosion protective capability, with |Z|0.01Hz increased by nearly three orders of magnitude (∼2 × 108 Ω·cm2) compared to that of pure sol-gel coating after 28 days of saline solution immersion. In addition, the EIS measurements on sol-gel coating surfaces with artificial scratches show increased impedance values after prolonged immersion in saline solution, indicative of effective active inhibiting effect. This phenomenon is the result of the synergistic effect of both passive and active corrosion protection. The active protection (inhibiting effect) is provided by the on-demand release of inbuilt BTA inhibitor from ZIF-8 frameworks, whereas the passive protection (barrier performance) is achieved through the “labyrinth effect” of BN-OH nanosheets as well as the improved interfacial compatibility of nanocontainers with surrounding sol-gel matrix by surface hydroxylation of h-BN nanosheets. This nanocontainer design offers a facile strategy for fabricating self-healing sol-gel coatings with the exceptional anticorrosion properties.

Mechanical properties, corrosion and degradation behaviors, and in vitro cytocompatibility of a biodegradable Zn-5La alloy for bone-implant applications.

Zinc (Zn) and its alloys are used in bone-fixation devices as biodegradable bone-implant materials due to their good biosafety, biological function, biodegradability, and formability. Unfortunately, the clinical application of pure Zn is hindered by its insufficient mechanical properties and slow degradation rate. In this study, a Zn-5 wt.% lanthanum (Zn-5La) alloy with enhanced mechanical properties, suitable degradation rate, and cytocompatibility was developed through La alloying and hot extrusion. The hot-extruded (HE) Zn-5La alloy showed ultimate tensile strength of 286.3MPa, tensile yield strength of 139.7MPa, elongation of 35.7%, compressive yield strength of 262.7MPa, and microhardness of 109.7 HV. The corrosion resistance of the HE Zn-5La in Hanks' and Dulbecco's modified Eagle medium (DMEM) solutions gradually increased with prolonged immersion time. Further, the HE Zn-5La exhibited an electrochemical corrosion rate of 36.7μm/y in Hanks' solution and 11.4μm/y in DMEM solution, and a degradation rate of 49.5μm/y in Hanks' solution and 30.3μm/y in DMEM solution, after 30 d of immersion. The corrosion resistance of both HE Zn and Zn-5La in DMEM solution was higher than in Hanks' solution. The 25% concentration extract of the HE Zn-5La showed a cell viability of 106.5%, indicating no cytotoxicity toward MG-63 cells. We recommend the HE Zn-5La alloy as a promising candidate material for biodegradable bone-implant applications. STATEMENT OF SIGNIFICANCE: This work reports the mechanical properties, corrosion and degradation behaviors, in vitro cytocompatibility and antibacterial ability of biodegradable Zn-5La alloy for bone-implant applications. Our findings demonstrate that the hot-extruded (HE) Zn-5La alloy showed an ultimate tensile strength of 286.3MPa, a yield strength of 139.7MPa, an elongation of 35.7%, compressive yield strength of 262.7MPa, and microhardness of 109.7 HV. HE Zn-5La exhibited appropriate degradation rates in Hanks' and DMEM solutions. Furthermore, the HE Zn-5La alloy showed good cytocompatibility toward MG-63 and MC3T3-E1 cells and greater antibacterial ability against S. aureus.

Preparation and characterisation of CeSt3-modified Zn-Ni-B4C composite superhydrophobic coatings

CeSt3-modified Zn-Ni-B4C composite superhydrophobic coatings were prepared via two-step deposition. First, Zn-Ni-B4C coatings with microstructures were prepared through electrodeposition, and then cerium stearate deposited on surface successfully by electrophoretic deposition to obtain superhydrophobic coatings. The effects of electrophoretic deposition time on the hydrophobicity and corrosion resistance of coatings were investigated. The coatings obtained at 10 min deposition have a water contact angle of 161°, exhibiting superior superhydrophobicity. The corrosion current density of this coatings in 3.5 wt% NaCl solution is 9.139 × 10−7 A·cm−2, demonstrating outstanding corrosion resistance. Electrochemical tests of the samples after prolonged immersion in 3.5 wt% NaCl solution exhibited better corrosion resistance in the samples immersed for 96 h compared to those immersed for 48 h, suggesting that the existence of cerium acted as a corrosion inhibitor after the superhydrophobic coatings failed.

Elevated brain temperature under severe heat exposure impairs cortical motor activity and executive function

BackgroundExcessive heat exposure can lead to hyperthermia in humans, which impairs physical performance and disrupts cognitive function. While heat is a known physiological stressor, it is unclear how severe heat stress affects brain physiology and function. MethodsEleven healthy participants were subjected to heat stress from prolonged exercise or warm water immersion until their rectal temperatures (Tre) attained 39.5°C, inducing exertional or passive hyperthermia, respectively. In a separate trial, blended ice was ingested before and during exercise as a cooling strategy. Data were compared to a control condition with seated rest (normothermic). Brain temperature (Tbr), cerebral perfusion, and task-based brain activity were assessed using magnetic resonance imaging techniques. ResultsTbr in motor cortex was found to be tightly regulated at rest (37.3°C ± 0.4°C (mean ± SD)) despite fluctuations in Tre. With the development of hyperthermia, Tbr increases and dovetails with the rising Tre. Bilateral motor cortical activity was suppressed during high-intensity plantarflexion tasks, implying a reduced central motor drive in hyperthermic participants (Tre = 38.5°C ± 0.1°C). Global gray matter perfusion and regional perfusion in sensorimotor cortex were reduced with passive hyperthermia. Executive function was poorer under a passive hyperthermic state, and this could relate to compromised visual processing as indicated by the reduced activation of left lateral-occipital cortex. Conversely, ingestion of blended ice before and during exercise alleviated the rise in both Tre and Tbr and mitigated heat-related neural perturbations. ConclusionSevere heat exposure elevates Tbr, disrupts motor cortical activity and executive function, and this can lead to impairment of physical and cognitive performance.

A novel approach using vinegar to eradicate recalcitrant skin flukes in koi fish: a case report

Parasites such as skin flukes and gill flukes can be a problem for koi carp owners – particularly hobbyists – for a number of reasons. Although they can theoretically be treated with one application of medication, factors such as water quality, drug resistance and degradation of medications can make these parasites more diffcult to eradicate. Acetic acid can be used as a method of killing ectoparasites on fish, though traditionally this is performed by dipping the fish into the acid, not as a prolonged immersion. This case report concerns a hobbyists pond with a long-term skin fluke infestation and the treatment of the infestation by using household vinegar to acidify the water over a prolonged period.

Investigation into the Strength Properties of Plain Cotton Fabrics after Water Immersion for Upcycling Textiles

Abstract This study utilized SEM to examine the fiber structure of cotton stock fabrics and tested their durability based on ISO standards. Two types of cotton stock fabrics were evaluated: natural-colored (162 cm width, 120.8 g/m2 weight, 281/10 in × 252/10 in density) and black-colored (157 cm width, 136.1 g/m2 weight, 482/10 in × 210/10 in density). Prolonged water immersion caused surface yarns to loosen, fibers to expand, and the cross-sectional area to increase. Residual pulp and impurities on the fabric adhered to fibers. After 27 days, fiber looseness peaked, leading to complete breakdown after 30 days. Natural-colored fabric experienced significant weft strength loss within 12 days, while black fabric showed slightly higher weft strength loss after 36 days. Color changes were prominent in natural-colored fabric during the initial 21 days, while black fabric displayed noticeable changes after 12 days of immersion.

Strength and acoustic emission weakening mechanism of sandstone after prolonged water immersion: Insights from micro-fracture

In this study, a series of uniaxial compression and acoustic emission (AE) tests were conducted on sandstone specimens immersed in water for different durations (0–720 h). The mechanical properties and AE characteristics of dry, unsaturated, saturated, and long-term saturated sandstone specimens were comparatively analyzed. The experimental results show that with the passage of immersion time, the uniaxial compressive strength and elastic modulus of the specimens both decrease, while the Poisson’s ratio increase; the mechanical parameters change exponentially with the immersion time and are linearly related to the water content; the dominant failure mode evolves from tensile failure to shear failure gradually; and the AE intensity and frequency both weaken. Besides, the mechanism of long-term water–rock interaction was explored. It was proposed that the weakening of rock strength and AE signals is largely attributed to the transformation in the micro-fracture form (from transgranular fracture to intergranular fracture), which is induced by the deterioration of grain cementation. This view is supported by optical microscopic observations on micro-fracture behavior as well as AE response.

Corrosion inhibition behaviour of synthetic 2-(phenylsulphonamido)-3-methylbutanoic acid on mild steel in alkaline solution

The corrosion inhibiting behaviour of synthetic 2-(phenylsulphonamido)-3-methylbutanoic acid (PSMBA) on mild steel in the presence of 0.1 M KOH was investigated using combined gravimetric, electrochemical and theoretical simulation corrosion monitoring methods. The gravimetric data showed that the inhibitor effectively protected the metal from alkaline corrosion and that the inhibition ability depended on concentration increase and reduced gradually with prolonged immersion time. The electrochemical impedance spectroscopy results show that the charge transfer resistance increased with the addition of the inhibitor while potentiodynamic polarization results showed that the corrosion current density decreased upon the addition of the inhibitor, theoretical simulation results revealed a low and comparable energy gap between the LUMO and HOMO energies. All these showed that 2-(phenylsulphonamido)-3-methylbutanoic acid functioned as a good corrosion inhibitor for mild steel in alkaline medium.

Effect of functional groups on spontaneous combustion characteristics of high water-rich coal after long-term soaking and drying

ABSTRACT Spontaneous combustion of waterlogged coal accounts for many coal mine fire accidents. The soaking process affects the chemical properties of the coal, causing it to be highly susceptible to spontaneous combustion. Changes in functional groups of highly water-rich coals after flooding and drying are discussed, and the structural parameters were characterized by infrared spectroscopy (FTIR). The results show that the highest aliphatic hydrocarbons, oxygenated functional groups, and aromatic hydrocarbons are reached when air-dried after soaking for 30 days. The substitution of the dumb ring is changed with growing immersion time. C-O rose from 13% to 26% at 30 days and remained constant. Methyl and self-conjugated hydroxyl groups are increasing. Analysis of the structural parameters revealed that aromaticity decreases and increases with soaking time, while the degree of fatty chaining increases and decreases. Prolonged water immersion and air-drying change the coal’s aromatization and aliphatic chain structure, resulting in the continuous loss of the branched chains, thus making the skeleton of coal more sparse and the low-temperature oxidation reactions easier to carry out. It is sufficient to show that the theoretical basis for prevention and control of highly water-rich coal combustion after long-term immersion and drying is provided.

Characterization and in vitro bioactivity analysis of apatite growth on modified calcium borate silicate ceramic

Bioactive glasses are considered biocompatible materials that form a hydroxyapatite-like layer on the surface that allows strong adhesion to soft and hard tissues. This study aims to develop a method to fabricate a borate silicate ceramic biomaterial with a chemical composition of Ca11Si4B2O22 using sodium metaborate (NaBO2) as a flux. X-ray diffraction (XRD), scanning electron microscopy energy distribution spectrometer (SEM-EDS), and Fourier transform infrared spectrometer (FTIR) were used to analyze the structure, surface composition and chemical bonding of the bioactive borate silicate. In addition, the pH measurements and biodegradability behavior of the fabricated glass structures were investigated after immersion in simulated body fluid for 2, 7, 14, and 21 days, respectively. The results showed that the glass-ceramic structure, which was transferred from the crystalline phase Ca11Si4B2O22 to a hydroxyapatite phase after incubation, started on the second day. In addition, the formed hydroxyapatite crystals developed due to the prolonged immersion time, reflecting biodegradable behavior. The antimicrobial activity of the prepared ceramic showed high inhibitory activity against Enterococcus faecalis and Streptococcus mutans.

A Multiple Case Study of Career Construction and Career Development Processes of People with Adventitious Blindness

A Multiple Case Study of Career Construction and Career Development Processes of People with Adventitious Blindness

Social Maintenance and Cultural Continuity—Folk Religion among the Tu Ethnic Group in Northwest China

Despite economic development and social changes, folk religion in China has not died out, but has survived and has even experienced a revival. Oscillating state policies have in general had a strong impact on religion in China. Though there is no official recognition of ethnic folk-religions, the state classifies them positively as manifestations of local cultural heritage and in this context has supported—not stifled—public folk religious practices among the Tu. This study deals with folk religious’ practice among the Tu ethnic group in Northwest China. The article highlights animist ontology as a theoretical perspective for analyzing the religious practices of the Tu ethnic group in China. The authors carried out anthropological procedures of participant observation and interviewing in the Tu community distributed in Qinghai Province and now present a portrait of the folk religion in typical Tu communities located in Minhe County and Huzhu County. The article also discusses the tripartite cosmology of the Tu and the positive interactions with national authorities. Quite apart from the issue of the impact of the state, the authors document, via prolonged ethnographic immersion in two regions, that the folk religion of the Tu is also closely linked to, and continues to have an impact on, daily life, particularly with regard to the construction and maintenance of ethnic community structure. This paper is organized as follows. First, we present ethnographic information on the religious beliefs and ritual practices of the Tu. The subsequent section then discusses how public folk-religious performances receive support from the state in the context of tourism and local economic development and how they contribute to the maintenance of community structure and social order. The conclusion summarizes the process by which ethnic folk religions have not only survived, but, in part as a result of state support for ethnic cultural heritage, experienced a revival.

Tough, Reprocessable, and Recyclable Dynamic Covalent Polymers with Ultrastable Long-Lived Room-Temperature Phosphorescence.

Room-temperature phosphorescence (RTP) polymers, whose emission can persist for a long period after photoexcitation, are of great importance for practical applications. Herein, dynamic covalent boronic ester linkages with internal B-N coordination are incorporated into a commercial epoxy matrix. The reversible dissociation of B-N bonds upon loading provides an efficient energy dissipation pathway for the epoxy network, while the rigid epoxy matrix can inhibit the quenching of triplet excitons in boronic esters. The obtained polymers exhibit enhanced mechanical toughness (12.26 MJ m-3 ), ultralong RTP (τ=540.4 ms), and shape memory behavior. Notably, there is no apparent decrease in the RTP property upon prolonged immersion in various solvents because the networks are robust. Moreover, the dynamic bonds endow the polymers with superior reprocessablity and recyclability. These novel properties have led to their potential application for information encryption and anti-counterfeiting.