Room Temperature Water Research Articles

PO-03-042 A COOL DRINK OF WATER: CONVECTIVE ESOPHAGEAL COOLING PREVENTS THERMAL INJURY FROM RADIOFREQUENCY HEATING IN AN EX VIVO SWINE ESOPHAGUS MODEL

Esophageal heating and subsequent thermal injury are concerning adverse effects of radiofrequency (RF) energy ablation on the posterior wall of the left atrium. Active intraluminal esophageal cooling may provide thermal protection, allowing for effective delivery of RF energy to overlying myocardium without collateral damage to the underlying esophagus. To evaluate the impact of esophageal luminal cooling with a closed loop continuous flow irrigation on esophageal heating and thermal injury using an ex vivo model. A flexible tube was placed through the lumen of a swine esophagus and connected to a closed loop circuit consisting of a pump and water bath (Figure 1, panel A). The esophagus was submerged in a saline bath with a temperature of 36 °C and an impedance of 140 ohms. Ten non-contiguous RF lesions were delivered at 50 watts for 8 seconds directly on the outer esophageal wall with 4 mm irrigated RF ablation catheter. This was performed without irrigation (control), irrigation at 1.5 L/min with room temperature water (20 °C), and irrigation at 1.5 L/min with ice water (0 °C). Esophageal tissue samples were obtained from immunohistochemistry and the esophagus was cross sectioned and lesions were measured with digital calipers. Closed loop continuous flow esophageal irrigation with ice water yielded esophageal lesions with the smallest surface area (Figure 1, panel A), depth, and volume (Figure 1, panel B). Continuous esophageal irrigation with room temperature water resulted in the second smallest lesions. RF lesions without esophageal irrigation resulted in the largest and deepest lesion, as well as evidence of luminal esophageal injury (Figure 1, panel C & D). Histology showed preserved smooth muscle, glands, basement membrane and epithelium with cooled esophagus and transmural lesions with non-irrigated esophagus (Figure 1, panel C & D). Continuous endoluminal esophageal cooling reduced lesion size with RF energy delivery. There was no luminal injury with room temperature and ice water esophageal irrigation. Thus, both may be useful in prevention of endoluminal esophageal injury during poster wall RF ablation.

Germination and Early Seedling Growth of Three Arabica Coffee Varieties at Four Seed Soaking Water Temperatures

It takes three weeks to analyze the germination percentage of Arabica coffee seeds germinated using paper and a three-day water-soaking method. This 3- week period is considered too long for seed distribution to remote areas. Thus, we need to modify this germination test needs to be modified to have a shorter test time. Temperature treatment is one method to break the seed dormancy period for faster germination. This study aimed to obtain a faster and more precise method of germination test on Arabica coffee seeds. This study employed a 3 x 4 factorial complete randomized block design with three replications in which Arabica coffee varieties of Gayo-1, Kartika-1, and Sigararutang as the first factor and the temperature of the soaking water of the seeds (25 0C, 50 0C, 75 0C, and 90 0C) as the second factor. The research was conducted at the Plant Breeding Laboratory, Indonesian Coffee and Cocoa Research Institute (ICCRI), for four months. Findings showed that the interaction between treatments was only found in seed germination percentage. Soaking in room temperature water (control) for three days was better than using water at 50 0C, 75 0C, and 90 0C on the germination percentage, sprout length, and vigor index. Observations of Arabica seed germination could be shortened to 14 days compared to the standard 21-day observation. During the seedling phase, the shoot growth and root growth of the Arabica coffee seeds soaked in water at 50 0C showed no significant difference from the control. Soaking at 75 0C and 90 0C damaged the embryo and resulted in rotten seeds. Different varieties led to different germination percentages, sprout lengths, and fresh weight of seedling shoots. The method of soaking at 50 0C for 30 minutes could be used as an alternative in germination test of Arabica coffee seeds because it showed small negative effect on germinated seed and seedling quality but it shorten thetesting time for three days.

Evaluation of thermoregulation of horses (Equus caballus) submitted to two methods of post-exercise cooling, in hot and humid climate conditions, in the Eastern Amazon.

In Brazil, the study on equine thermoregulation has not shown considerable advances, moreover, in the Amazon, this is a little explored aspect. This study aims to evaluate the thermoregulation of horses submitted to two methods of post-exercise cooling, in the climatic conditions of the Eastern Amazon. The experiment was conducted at Centro Hipico, Ananindeua, Para, for 15 days. Ten male horses, castrated of the Brazilian breed, aged 13 years and with an average weight of 482.3 kg were used. Equestrianism, which was exercised with pre-established protocol in the arena and track, for 30 min. After the exercise, the animals were divided into two groups for application of the treatments, which were two cooling methods, such as a bath with water at room temperature (about 25°C) and a hiper cooling method (6-9°C). During the experimental period, air temperature (AT) and relative humidity (RH) data were recorded and the Temperature and Humidity Index (THI) was calculated. Data from the rectal temperature (RT), heart rate (HR), respiratory rate (RR) and Body surface temperature (BST) of the animals were also measured at three moments: before exercise, after exercise and after applying the cooling methods. The adaptability index used was the Benezra Thermal Comfort Index (BTCI). The BST was performed with the help of infrared thermograph, which were the left side of the neck, thorax, rump, and right side to the armpi, before the exercise, after the exercise and after applying the cooling methods. The statistical design was completely randomized. Analysis of variance was performed using the GLM Procedure of SAS 9.1.3. After the application of the cooling techniques in the animals, the AT and THI were higher and the highest RH values were found before the exercise (87.21%). The highest RT, RR, HR, BST, and BTCI values were observed after exercise. There was no significant dierence (P > 0.05) between cooling methods. There was a highly significant and positive correlation (P < 0.01) between all physiological variables (RT, RR, HR, and BST) and the Iberian Index with AT and THI and negative with RH (P < 0.01), thus demonstrating the influence of the environment on the thermoregulation of animals. It is concluded the evaluation of stress, welfare and thermoregulation of horses submitted to two methods of post-exercise cooling, in the climatic conditions of the Eastern Amazon, demonstrated that the studied cooling methods showed to reduce the rectal temperature, the respiratory rate, the heart rate and the body surface temperature with equal efficiency. However, in terms of practical ease of use, the room temperature water cooling method has proven to be more practical.

One-Step Formation of Pharmaceuticals Having a Phenylacetic Acid Core Using Water Microdroplets.

The properties of water microdroplets strikingly differ from bulk water. Using room-temperature water microdroplets, we find that toluene can react with CO2 to form phenylacetic acid in one step without any catalyst with negative high voltage applied at the sprayer source. The chemical components of these microdroplets are identified by mass spectrometry, and product structures are confirmed by tandem mass spectrometry. In this manner, we generate three drug molecules in a single step: 4-aminophenylacetic acid (epithelial peptide transporter PepT1 inhibitor), 3,4-dihydroxyphenylacetic acid (dopamine metabolite neurotransmitter), and phenylacetic acid (sodium salt form; treatment of urea cycle disorder). Mechanistic studies show that benzyl radicals formed from hydroxyl radicals at the water microdroplet interface drive these carboxylation reactions. This water microdroplet chemistry is general, allowing activation and subsequent carboxylation of aryl α-C-H groups.

Harvest Stage and Brewing Conditions Impact Mineral Content, Phenolic Compounds, and Antioxidant Capacity of Lemon Balm (Melissa officinalis L.) Herbal Tea.

Lemon balm (Melissa officinalis L.) is commonly consumed as an herbal tea for its antioxidant health benefits. Young seedlings known as microgreens are popular for their distinct flavors and can contain higher mineral content on a dry weight basis compared to their adult counterparts. However, the use of microgreens for herbal teas has not been previously investigated. In this study, lemon balm was grown to adult and microgreen harvest stages and prepared as herbal teas by brewing with boiled (100°C) water for 5minutes and room temperature water (22°C) for 2hours. The effects of harvest time and brewing method on the mineral content, phenolic compounds, and antioxidant capacity of lemon balm herbal teas were assessed. Results showed that adult lemon balm tea contained higher total phenolics, total flavonoids, rosmarinic acid, and antioxidant capacity than microgreen teas, with hot preparations containing the highest amounts (p ≤ 0.05). In contrast, microgreen lemon balm teas contained higher amounts of minerals (p ≤ 0.05), including calcium, potassium, magnesium, sodium, phosphorus, copper, and zinc. In general, brewing conditions did not impact the content of most minerals. Overall, the results support the potential of using dried microgreens as herbal teas. Microgreen lemon balm teas prepared hot and cold offer antioxidant compounds and are richer sources of minerals than adult teas. The ease of growth for microgreens offers consumers the opportunity for home preparation of a novel herbal tea beverage.

Sulfide oxidation during the simulated weathering of pyrrhotite-rich tailings: Impacts of freeze-thaw cycles and chloride salinity

Kinetic leached columns (KLCs) were used to simulate the weathering of pyrrhotite-rich tailings from Raglan Mine (QC, Canada) and evaluate the effects of freeze-thaw cycles and salinity on long-term trends in sulfide oxidation. This study focuses on the results of a series of oxygen consumption tests (OCTs) with additional observations from the dismantlement of the KLCs. Four treatments were evaluated in duplicate in the KLCs: (1) room-temperature and deionized water; (2) room-temperature and saline water; (3) freeze-thaw cycles and deionized water; and (4) freeze-thaw cycles and saline water. Oxygen fluxes showed no reproducible differences over the course of the study when comparing between deionized and saline water columns within each thermal regime. However, fluxes may have differed slightly at several timepoints. The room-temperature and freeze-thaw columns displayed somewhat different oxidative behaviors. Notably, all columns stabilized at similar oxygen fluxes, though the amount of time until stability differed for the two thermal regimes. Visual observations made upon dismantlement of the columns revealed extensive oxidation and cementation throughout the entire depth of the columns with no significant differences noted between the room-temperature and freeze-thaw columns. This study provides novel insights into the long-term evolution of sulfide oxidation in mine tailings weathering under conditions relevant to northern mine sites.

Влияние сублимационной сушки на качественные показатели клубней картофеля

Freeze-dried vegetable production is intensively developing due to its advantages - a four-time decrease in the weight of supplied freeze-dried potatoes, increased shelf life by dozens of times, and the resistance of freeze-dried products to temperature fluctuations. To study the quality indicators of potato tubers before freeze-drying and after it using standard techniques, the authors analyzed domestic and foreign varieties including those with pigmented flesh and peel. Freeze-drying of potato tubers was carried out in the vacuum-sublimation machine USS‑5 in two stages: rapid freezing of 2 to 3 cm thick sample plates to -30°C during 4 h and heating to +50°C during 2.5 h. Raw potato tubers and freeze-dried samples were tested for antioxidant, phenolic and flavonoid content using standard methods. The results of biochemical analysis showed the total content of alcoholsoluble flavonoids in fresh potato pulp in recalculation on quercetin 0.08 to 1.13 mg/g raw weight, in freeze-dried samples - 0.22 to 1.46 mg/g dry weight; total content of low-molecular antioxidants in fresh pulp from 0.12 to 1.92 mg/g raw weight, phenolic compounds in freeze-dried samples from 0.55 to 4.63 mg/g dry weight in gallic acid equivalents. The study also focused on the determination of the moisture absorption level of freeze-dried potato tuber slices. Moisture saturation of freeze-dried potato slices when immersed in room temperature water occurred within 60 min. Freeze drying had no effect on the antioxidant content of the potato tubers. Therefore, this method can be used to produce healthy foods.

Research on the use of agricultural waste to manufacture highly hygroscopic materials for agricultural applications

Material based on hydrogel from rice-straw with high absorption capacity and slow water release was prepared by cryogenic method, using citric acid as cross-linker and without creating waste stream to the environment. The structure and properties of the material were characterized by SEM, XRD, FTIR and TGA method. The results showed that the largest water absorbency of the material reached 30.67g/g, 4.48 times higher than the original rice-straw. The material was able to slowly release water in 6 days at room temperature and return water absorption of 3.97 g/g when reusing the material. In addition, the material is biodegradable and biocompatible. With the obtained results and simple, inexpensive, environmentally friendly method, this is a material that can be industrially produced and widely used in green agriculture.

A phytochemical screening, antioxidant and antibacterial activity analysis in the leaves, stems and roots of Portulacaria afra

Introduction: Portulacaria afra is a medicinal plant commonly used among African traditional healers to treat skin conditions and dehydration. The aim of this study was to scientifically validate the use of P. afra among traditional healers. Methods: Standard phytochemical colour tests were used to determine the presence of ten phytochemicals, using four solvents of varying polarities (hexane, ethyl acetate, methanol, and water). The antioxidant activity was determined using 1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide scavenging assays. An agar-well diffusion assay was used to determine the antibacterial activities of the leaves, stems, and roots of P. afra against Staphylococcus aureus and Escherichia coli. Results: P. afra exhibited a high phytochemical presence in the methanolic extracts, with seven out of the 10 phytochemical groups present. Flavonoids and phlobatannins were absent in all of the plant’s extracts. The methanolic root extract exhibited the highest DPPH scavenging activity (IC50=0.39) whilst the hexane leaf extract (IC50= 14.83) was the only extract to exceed the acceptable upper limit. The scavenging activity of the plant was stronger against hydrogen peroxide than it was against DPPH. The methanolic and hot water stem extracts displayed the largest zone of inhibition (of 20 mm) against E. coli. The cold-water and room-temperature water extracts, of all three plant parts, showed no zone of inhibition against either bacterial strain. Conclusion: P. afra has the capacity to be used as a nutritional supplement for its antioxidant properties, while the antibacterial properties may provide relief against E. coli infections.

Investigate the physics of instant noodles in a hot cup using Arduino temperature sensors

The study explores the physics of cooking instant noodles in a hot cup using low-cost Arduino sensors developed as a thermocouple and an infrared thermometer. By pouring room temperature water onto a bag of calcium oxide (CaO) contained in the outside cup of the noodles, the exothermic reaction of CaO generates. Its energy is released into the water of the outside cup. This cooks the noodles, which are put into an inside cup. The amount of heat transferred to the water is measured. Moreover, the change in the temperature of the hot cooked noodles with time is investigated using Newton’s law of cooling. The experiment using the Arduino temperature sensors encourages undergraduate students to learn thermodynamics concepts from the instant noodles in a hot cup, primarily found in groceries.

Characterization and split-split-plot analysis of steamed factors affecting the swimming crab (Portunus trituberculatus) flavor quality

Swimming crab (Portunus trituberculatus) is a kind of popular crab for being rich in nutrition and intense in flavor. The time and heat exposure cause differences in flavor during steaming, dramatically affecting first impression and acceptability. The quality of P. trituberculatus with different steaming methods (steam with Room Temperature Water, RTW and steam with Boiling Water, BW) was evaluated using consumer acceptability, sensory characterization, and instrumental analysis. The split-split plot analysis was employed to compared the effects of the edible parts, steaming methods and steaming time. The results demonstrated that the hedonic score of crab meat was 1.3 times higher than that of hepatopancreas. Edible parts were the most important factor followed by the steaming method without interaction. The female crab meat (F-M) and male crab meat (M-M) were correlated with positive emotions, while opposite for hepatopancreas. RTW was more likely to evoke positive emotions, while BW followed the opposite trend. Instrumental analysis revealed that the types of volatiles produced with BW were similar to those by RTW, but their contents are generally 1.5–2.5 times higher. In sum, P. trituberculatus which were steamed for 25 min using RTW may be more acceptable.

A combined extrusion, retrogradation, and cross-linking strategy for preparing starch-based straws with desirable mechanical properties

This work developed a novel strategy for producing starch straws with desirable mechanical properties by a combination of extrusion, retrogradation, and sodium trimetaphosphate (STMP) cross-linking. The straws were prepared by first extruding starch, glycerin, and water (10:1:1) with a double screw extruder, then retrograding the resulting straws at 4 °C for 6 h, and finally cross-linking the straws. Rapid visco-analyzer profiles showed decreases in the viscosity of milled straws with increases in the cross-linking duration, perhaps reflecting a higher degree of crosslinking. Fourier transform infrared spectroscopy showed evidence of more hydrogen bonds in the straws with a longer cross-linking duration, while thermogravimetric analysis indicated higher thermal stability for the cross-linked straws than for the controls. The straw cross-linked for 3 h showed 1.52 times higher stiffness after soaking in room-temperature water for 30 min (4967.56 g/s), and 1.88 times higher stiffness after soaking in 60 °C hot water for 5 min (5371.89 g/s) than the original straw. STMP cross-linking also improved the starch straw mechanical properties after soaking in common soft drinks. These findings identify a potential new way to produce biodegradable straws with desirable properties from starch, an affordable biomaterial, while also addressing the problem of petroleum-based plastic pollution.

Isolated Effects of Plasma Freezing versus Thawing on Metabolite Stability.

Freezing and thawing plasma samples is known to perturb metabolite stability. However, no study has systematically tested how different freezing and thawing methods affect plasma metabolite levels. The objective of this study was to isolate the effects of freezing from thawing on mouse plasma metabolite levels, by comparing a matrix of freezing and thawing conditions through 10 freeze-thaw cycles. We tested freezing with liquid nitrogen (LN2), at -80 °C, or at -20 °C, and thawing quickly in room temperature water or slowly on ice. Plasma samples were extracted and the relative abundance of 87 metabolites was obtained via liquid chromatography-mass spectrometry (LC-MS). Observed changes in metabolite abundance by treatment group correlated with the amount of time it took for samples to freeze or thaw. Thus, snap-freezing with LN2 and quick-thawing with water led to minimal changes in metabolite levels. Conversely, samples frozen at -20 °C exhibited the most changes in metabolite levels, likely because freezing required about 4 h, versus freezing instantaneously in LN2. Overall, our results show that plasma samples subjected to up to 10 cycles of LN2 snap-freezing with room temperature water quick-thawing exhibit remarkable metabolomic stability.

Synthesis and Characterization of a Coumarin Antimicrobial Polymer Fluorescent Coating

Polymer materials are widely used in medical materials, food packaging, coatings, and other fields. However, the surface of the materials is easily contaminated by microorganisms, resulting in serious problems. To solve this issue, a new type of antibacterial polymer fluorescent coating was successfully synthesized by copolymerization of divinylbenzene with 7-methacryloxy-4-methyl coumarin, dodecafluoroheptyl methacrylate, and other monomers. The surface structure and thermal stability of the coating were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. Fluorine was polymerized into the polymer, improving the thermal stability compared to polystyrene and polydivinylbenzene. The bactericidal and antibacterial adhesion properties of the coating materials were studied by a contact germicidal test and antibacterial adhesion test. The polymer had a strong inhibitory effect on Staphylococcus aureus. After immersion in room temperature water, the film maintained its strong inhibitory effect on S. aureus fluorescence intensity and had high fluorescence stability.

A comparative study on precipitation behavior of a sand-cast Al–Li–Cu alloy with the different quenching rates

The performance of large-size structural components with varied wall thickness is mainly determined by the quench sensitivity, while there was a blank of the studies on the quench sensitivity of cast Al–Li alloys. In this study, the precipitation behavior of sand-cast Al–2Li–2Cu-0.5Mg-0.15Sc-0.15Zr-0.05Ti alloy subjected to different quenching conditions in room temperature water, boiling water and air was compared. The effect of the quenching rates on the formation mechanisms of δ΄ (Al3Li) and T1 (Al2CuLi) precipitates was discussed. It was found that a rapid quenching rate facilitated the precipitation of T1 phases and the refinement of δ′ phases, which contributes to the improvement of the mechanical properties. During the subsequent ageing, the strength and ductility were enhanced with the quenching rate increasing, but the strength did not vary by more than 15%, indicating that the sand-cast Al–Li–Cu alloy owns a lower quench sensitivity. This work is expected to enlighten the understanding of the evolution mechanisms of precipitates during quenching and provide a reference for the heat treatment of complex structural components for cast Al–Li alloys.

Effects of various curing methods on the compressive strength and microstructure of blast furnace slag-fly ash-based cementitious material activated by alkaline solid wastes

The large-scale stacking of alkaline industrial solid wastes such as soda residue (SR) and calcium carbide residue (CCR) has caused serious environmental problems. Therefore, a new type of cementitious material was developed in our previous study by using SR-CCR synergistically activated blast furnace slag (BFS)-fly ash (FA), which abbreviated as SCBF. This paper further studied the effects of various curing methods on the compressive strength and microstructure of SCBF, which was expected to provide guidance for its application in the field of non-reinforced products such as baking-free brick. The results show that the optimal curing scheme was heat curing at 75 °C for 12 h. The optimal scheme significantly promoted an early hydration reaction and provided the 3d/28d strength values of 16.4/24.7 MPa, exceeding those of room-temperature (RT) sealed curing and water curing by 154/24.5 % and 264/31 %, respectively. Besides, the optimal scheme accelerated the formation of CSH gel, Hydrotalcite (6MgO·Al2O3·CO2·12H2O), Hydrocalumite (3CaO·Al2O3·CaCl2·10H2O), and other crystal products, as well as increased the consolidation rate of chlorine ion from 37.9 % (in RT sealed curing) to 64.3 %. These hydration products were evenly distributed, effectively filling the pores and reducing the macroporosity from 9.30 (in RT sealed curing) to 1.54 %, thus improving the early and later-age strength. Too high curing temperature (exceeding 75 ℃) or prolong heat curing period (exceeding 12 h) would cause microstructure deterioration, significantly increase the number of macropores and microcracks in the matrix, ultimately leading to strength retrogression.

Environmentally friendly etchant of in situ plasmon-activated water to improve SERS sensing of pesticides

Wet etching, the most commonly used technology in the etching industry, is simple and convenient to use, and is currently the most widely used technical method of etching. However, etching solvents used in etching technology are harmful to living organisms and the environment. Another frequently used etching technique is dry etching. Dry etching is often used to prepare array substrates for surface-enhanced Raman scattering (SERS). However, the disadvantage of dry etching technology is its complicated operation and expensive equipment required. In order to resolve the shortcomings of the above etching technologies, we propose a new technical concept, in situ vapor etching with room-temperature plasmon-activated water (PAW). The vapor of traditional deionized water (DIW) cannot perform etching of SERS-active substrates. In situ PAW vapor has characteristics of high energy and doping electrons which enable in situ PAW vapor to perform nanostructured treatment of SERS-active substrates. In addition, many properties of PAW vapor are also superior to those of DIW. Application of PAW vapor to the rhodamine 6 G (R6G) probe molecule and the imidacloprid (IM), acetamiprid (AC), and flusilazole (FL) pesticides resulted in higher signal acquisitions and lower relative standard deviations (RSDs). In our proposed innovative technique, the limit of detection (LOD) of IM was determined to be 10 ppb. Application of this technique yielded the same or better results than SERS-array substrates. This environmentally friendly etching method is an innovative technology that can provide a wider range of SERS applications.

Improving the eating quality of brown rice by defatting combined with hydrothermal treatment

Aiming at consumer acceptability of brown rice such as cooking difficulty and coarse taste, the effects of defatting and hydrothermal treatment alone or in combination on the texture and sensory score of cooked brown rice were studied, and the improvement mechanism was explored through cooking quality and microscopic morphology. The results showed that defatting combined with hydrothermal treatment could significantly improve the quality of brown rice, the hardness and chewiness of treated cooked brown rice decreased respectively from 20.385 N and 10.221 N to 14.494 N and 6.886 N, and the sensory score increased from 68.90 to 83.50. The room temperature water absorption rate of the treated brown rice increased from 10.72 % to 29.71 %, which was much higher than that of polished rice. The cooking quality of the treated brown rice was obviously improved, the optimal cooking time decreased from 30.33 min to 22.67 min, and the heating water absorption, volume expansion rate and solid loss increased from 147.32 %, 255.20 % and 13.35 mg/g to 219.15 %, 400.39 % and 22.49 mg/g, respectively. Scanning electron microscope showed that defatting combined with hydrothermal treatment significantly increased cracks and micropores of brown rice grains, which may be the intrinsic reason for the improvement in room temperature water absorption rate and cooking quality of brown rice and thus eating quality of cooked brown rice. The results are of great significance for promoting the staple consumption of whole-grain brown rice with broad application prospects.

Salivary uric acid reactivity and baseline associations with physiological stress response

Uric acid, an end product of the purinergic system, plays a role in several physiological systems that are responsive to stress. However, few studies have examined whether (1) uric acid concentrations change in response to acute stress, and (2) there are cross-system associations where uric acid might influence other physiological system responses to acute physical stress. The present study measured indices of the purinergic, hypothalamic-pituitary-adrenal axis, sympathetic, and parasympathetic systems (uric acid, cortisol, pre-ejection period, and root mean square of successive differences, respectively) in response to a standardized acute physical pain stressor, the cold pressor task. A diverse sample of participants (n = 67; mean age = 20.5 years, 52% female; 48% male) from a larger study completed anthropometric measurements and took part in a room temperature water task followed by the cold pressor task and sociodemographic questionnaires. Throughout the study, electrocardiography and impedance cardiography were measured continuously, and five saliva samples were collected that were later assayed for cortisol and uric acid. Descriptively, uric acid increased about 32 min following completion of the cold pressor. Resting uric acid concentrations were not associated with the autonomic nervous system response, but higher resting uric acid concentrations were associated with increased cortisol concentrations. Future research should examine the extent to which the purinergic system influences, and is influenced by, other types of stress and other physiological systems. The current findings highlight the potential role of an understudied biomarker and physiological system in the stress literature and have implications for basic and mechanistic researchers who study psychoneuroendocrinology, stress, and health.

Thermally induced fracturing in hot dry rock environments - Laboratory studies

In enhanced geothermal system (EGS) wells, where strong thermal gradients exist, hydraulic fracturing is the apparent driver for creating permeability in the reservoirs. Thermal effects, however, have been observed to accompany hydraulic loading and may further enhance the permeability of the reservoir. The mechanism of thermal fracturing in downhole conditions, however, is not well understood, limiting the efficient engineering of thermal effects on EGS stimulation. This laboratory study examines the behavior of thermal shock stimulation and temperature propagation by flowing room-temperature water through a borehole of a hot specimen block without confining stresses or borehole hydraulic loading. This condition isolates the effect of thermal shock from hydraulic pressure and confining stress. We monitored temperatures across the inside of the specimens and assessed fractures by visual inspection, bubble leakage, pressure decay, and acoustics. Thermal loading resulted in an enhancement of permeability by induced macro/microcracks. The profiles of borehole pressure decay obtained before and after each stage of stimulation show increased permeability of the treated specimens. The acoustic measurements indicate the extent of fractures, and the bubble leakage tests on the specimen surface visually indicate localized permeation paths created by newly created cracks. The maximum thermal gradient was achieved near the borehole surface at the start of the water flow. As the flow continued, the magnitude of the thermal gradient near the borehole decreased while that of the thermal gradient away from the borehole increased. Thermally driven fractures, initiated from the borehole walls, propagated perpendicular to the borehole surfaces. These “seed” fractures created during thermal stimulation, although they might be suppressed under very high stress, help reduce the levels of breakdown pressure in concurrent or subsequent pressure-based fracturing methods.