Refrigeration Temperature Research Articles

Machine Learning Methodologies Applied to Magnetocaloric Perovskites Discovery.

Traditionally, designing novel materials involves exploring new compositions guided by insights from previous work, relying on a trial-and-error approach, where continuous synthesis and characterization proceed until the properties meet the improvements. This method is inefficient due to the challenges of exploring vast chemical spaces. In this study, a machine-learning-based methodology is developed to assist the design from available data in the literature, allowing us to test in silico more than 1.2 million compositions. Two databases with 1227 inputs were created from published studies. Four machine learning (ML) models were trained over the feature sets using 517 compositional features (generated from 58 atomic properties) to predict magnetocaloric properties of perovskites: Curie temperature (TC), magnetic entropy change (ME), and relative cooling power (RCP). The best model-feature combinations were used to explore the chemical space of lanthanum, praseodymium, and neodymium manganites, identifying composition trends for different temperature applications, including room temperature refrigeration, where the most suitable combinations of doping elements were highlighted. The study offers valuable guidelines for future research insights on magnetocaloric materials, and the methodology can be transferred to other perovskite related material areas, such as catalysts and solar cell materials.

The impact of temperature on the shear bond strength of conventional multi-step and self-adhesive orthodontic adhesive systems: an in-vitro study

BackgroundA recurring issue during orthodontic treatment is the detachment of brackets from the tooth surface, which proves problematic for both the patient and the orthodontist. This study aimed to evaluate the impact of various temperatures on the shear bond strength of metal molar tubes, using conventional multi-step and self-adhesive orthodontic adhesive systems.MethodsA total of 112 extracted human molars were randomly divided into eight groups (n = 14) for bonding tubes with two orthodontic adhesive systems (Transbond XT and GC Ortho Connect) at different temperatures: refrigeration temperature (4 °C), room temperature (20 °C), human body temperature (37 °C), and high temperature (55 °C). The shear bond strength (SBS) test was conducted using a universal testing machine set to a crosshead speed of 0.5 mm/min. The adhesive remnant index (ARI) was used to evaluate the amount of adhesive remnants on the molar surfaces. ARI scores were assessed under Carl Zeiss Stemi 2000-CS stereomicroscope with image recording camera AxioCam Mrc5 at ×10 magnification. The data were analyzed using Student’s t-test, parametric analysis of variance (ANOVA), the intra-class correlation coefficient (ICC), the Kruskal-Wallis test, and the chi-square test.ResultsHigher mean SBS values were obtained with Transbond XT compared to GC Ortho Connect resin; however, the difference was not statistically significant (p > 0.05). The SBS results were lowest at 20 °C and highest at 55 °C in the Transbond XT group, and lowest at 37 °C and highest at 20 °C in the GC Ortho Connect group with no statistically significant difference (p > 0.05). The distribution of the ARI scores between the two materials showed a statistically significant difference (p = 0.002), with higher ARI scores found in the Transbond XT group.ConclusionsPre-heating orthodontic adhesives prior to bonding does not affect the shear bond strength.

The Coating Effect of Persian Gum (Zedo Gum) Containing Lactobacillus sakei on the Beef Quality Parameters During Storage at Refrigerator Temperature.

Coatings with antibacterial properties, integrated with biological agents, offer a novel and promising strategy for preserving meat products. This study investigates the effect of Persian gum (PG) coating containing Lactobacillus sakei bacteria on beef quality during refrigerated storage. Beef loin pieces were divided into five groups (control, 1% PG, 2% PG, and 1% and 2% PG with L. sakei bacteria). The groups were evaluated for microbial, chemical, and sensory tests at specific periods (days 0, 2, 4, 6, and 8). The results of the microbial analysis (the mean LAB count) revealed that the quality of meat significantly (p < 0.05) improved in the presence of L. sakei coatings, ranging from 6.08 to 7.31 log10 CFU/g in different treatment groups at the end of the experiment. Additionally, coatings containing L. sakei significantly (p < 0.05) reduced the microbial counts of mesophilic, psychrophilic, and Enterobacteriaceae bacteria, resulting in an extended shelf life of at least 8 days. The chemical findings indicated that increases in pH values (ranging from 5.98 to 6.57), total volatile basic nitrogen (TVB-N) levels (from 18.30 to 32.33 mg N/g), thiobarbituric acid reactive substances (TBARs) (from 2.16 to 4.12 mg MDA/kg), and protein carbonyl (PC) concentrations (from 1.33 to 2.05 nmol/mg protein) during storage at 4°C were ranked as follows: PG 2% + L. sakei < PG 1% + L. sakei < PG 2% < PG 1% < control. Additionally, overall acceptability, texture, odor, and color were significantly higher in the groups coated with L. sakei than in other groups. Based on the results, the groups covered with PG and L. sakei indicated that the quality and safety of beef increased and extended the shelf life of meat. In conclusion, PG solution containing L. sakei bacteria can be recommended as a new method for beef packaging.

Data-driven systematic methodology for predicting optimal heat pump integration based on temperature levels and refrigerants

Data-driven systematic methodology for predicting optimal heat pump integration based on temperature levels and refrigerants

A more rapid method for transformation of Helicobacter pylori.

Helicobacter pylori is a major causative agent in several upper gastroduodenal tract diseases, including gastric cancer. The development of methods to genetically manipulate H. pylori by natural transformation has allowed a greater understanding of its biology and role in these diseases. Nevertheless, the transformation methods used for H. pylori are time-consuming, requiring growth of these fastidious and slow-growing bacteria from -80°C stocks. The aim of the study was to develop a more rapid and convenient method for generating H. pylori mutants. We describe here a method in which competent H. pylori bacteria can be stored at -80°C and used in transformations on the day of resuscitation, similar to methods routinely used for Escherichia coli. This means that transformation can be performed at will and that transformants can be obtained within days, rather than weeks. Furthermore, we show that bacteria remain competent for at least six months storage at -80°C and that the method is applicable to strains with varying levels of natural competence. Transformation efficiencies of the bacteria varied between 101 and 106 transformants/total colony-forming units/µg donor DNA, depending on the strain. We suggest that this improved method will facilitate studies on H. pylori and, moreover, may be applicable to other naturally transformable pathogens with fastidious growth requirements and requiring ultra-low temperature refrigeration for long-term preservation.IMPORTANCEGenetic manipulation is an important tool in the study of pathogenic bacteria and their interactions with the host. Many pathogenic bacteria are naturally transformable; however, transformation experiments can be impeded by the slow-growing and fastidious nature of some species. One such bacterium is Helicobacter pylori, which requires resuscitation from -80°C and multiple subcultures prior to transformation. The method described in the current study uses a simple modification of a conventional method of natural transformation. Using this method, competent H. pylori bacteria can be stored for long periods (at least six months) and resuscitated as needed for use in experiments. The method circumvents the need for multiple and lengthy subcultures prior to transformation, nor does it involve costly materials, complicated procedures, or sophisticated equipment. Thus, we describe a simple, inexpensive, and time-efficient method that may have broader applications for use with other fastidious bacteria.

Stability, Fat Content and Protein Content Test of Instant Powder Protein Combination of Milk, Egg Yolk and Temulawak (Curcuma xanthorrhiza Roxb.) Eggs to Prevent Stunting

Consuming foods or drinks that contain animal protein, such as milk and yolks, is one way to prevent stunting. In addition, the addition of temulawak in the formula can enhance appetite. Innovation is needed to turn milk, yolks, and temulawak into powder because their high protein content makes the products prone to spoilage. Information about the stability and content of products is very important to ensure that the products are safe for consumption. One way to determine the stability of a formulation is to conduct tests at various storage temperatures. The purpose of this research is to determine the storage stability (temperature and shelf life), fat content, and protein content of the instant powder preparation combining milk, yolk, and temulawak. Stability testing using the accelerated stability testing method or Accelerated Shelf Life Testing (ASLT) to determine shelf life. This method uses temperature variations, namely T1: refrigerator temperature 4°C ± 2°C, T2: room temperature 30°C ± 2°C, and T3: warm temperature 40°C ± 2°C for a duration of 2 weeks. The parameters used are moisture content, redispersibility time, and the pH of the preparation. Stability data analysis is calculated using the Arrhenius model and reaction order. The fat content and protein content are determined using the method outlined in the SNI-01-2970-2006 attachment for powdered milk. The research results show that the instant powder combination of milk, yolk, and temulawak has a fat content of 10.09% and a protein content of 71.07%. The stability test of the preparation conducted at storage temperatures of 4°C ± 2°C, 30°C ± 2°C, and 40°C ± 2°C, respectively, showed results based on moisture content (54 days, 26 days, 20 days), redispersibility time (371 days, 99 days, 63 days), and pH of the preparation. (247 hari, 72 hari, 47 hari). The decrease in stability is directly proportional to the increase in storage temperature. In conclusion, the instant powder combination of milk, yolk, and temulawak is stable at storage temperatures below 30°C, with a fat content of 10.09% and a protein content of 71.07%.

High Entropy: A General Strategy for Broadening the Operating Temperature of Magnetic Refrigeration.

Lattice distortion and disorder in the chemical environment of magnetic atoms within high-entropy compounds present intriguing issues in the modulation of magnetic functional compounds. However, the complexity inherent in high-entropy disordered systems has resulted in a relative scarcity of comprehensive investigations exploring the magnetic functional mechanisms of these alloys. Herein, we investigate the magnetocaloric effect (MCE) of the high-entropy intermetallic compound Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Co2. Notably, the operating temperature range of the MCE broadens by an order of magnitude from 9 to 83 K while maintaining the refrigeration capacity compared to ErCo2. Atomic-scale microstructure analysis and atomic pair distribution function measurements reveal that lattice distortion stabilizes the cubic structure and induces disorder in the chemical environment of magnetic atoms. First-principles calculations point out that the enhanced average correlation energy raises the Curie temperature. The random distribution of elements across these sites induces local magnetic disorder around magnetic atoms with lower correlation energy, broadening the operating temperature range of MCE. This study not only significantly advances the understanding of the magnetic behavior of high-entropy alloys but also promotes the research progress of high-entropy functional compounds.

Storage Stability and Probiotic Viability of Foxtail Millet Probiotic Powder Enriched with High Protein and Fiber

Aims: The study aimed to evaluate the storage stability of foxtail millet probiotic powder enriched with high protein and dietary fiber under two storage conditions: room temperature (27 ± 1°C) and refrigeration temperature (7 ± 1°C). Study Design: This was an experimental, laboratory-based study. Place and Duration of Study: The study was conducted at the Department of Dairy Microbiology, Dairy Science College, Hebbal, Bengaluru, Karnataka, India, between January 2024 and October 2024. Methodology: Foxtail millet probiotic powder enriched with high protein and dietary fiber was stored in polypropylene sachets under two storage conditions: room temperature and refrigeration temperature. Samples were systematically drawn at 7-day intervals and analyzed for key quality parameters, including probiotic viability, microbial contaminants, water activity, moisture content, alcoholic acidity, and pH. Statistical analyses were performed using Analysis of Variance (ANOVA), with a 5% significance level. A critical difference (CD) value was employed to determine the statistical significance of observed variations between treatments over the storage period. Results: The storage stability of the optimized foxtail millet probiotic dry mix was assessed at both room temperature (27 ± 1°C) and refrigeration (7 ± 1°C) until spoilage or decline in probiotic viability below the threshold value. Probiotic viability declined significantly under both conditions, with a reduction from 11.04 log₁₀ CFU/g to 8.88 log₁₀ CFU/g at room temperature and 8.81 log₁₀ CFU/g under refrigeration. Water activity and moisture content increased over time, reflecting the hygroscopic nature of the mix, while alcoholic acidity rose significantly in both storage conditions. Despite these changes, the mix maintained probiotic viability above the therapeutic threshold (9 log₁₀ CFU/g) for 84 days at room temperature and 105 days under refrigeration, demonstrating its potential as a stable functional food product. Conclusion: The storage study of foxtail millet probiotic powder demonstrated its stability under both refrigeration and ambient conditions, with probiotic viability exceeding the 1 billion CFU/g threshold for up to 105 days and 84 days, respectively. Significant changes in water activity, moisture content, alcoholic acidity, and pH were observed, highlighting the product’s dynamic response to storage conditions.These results support the feasibility of developing shelf-stable, high-protein, high-fiber probiotic millet powders for the health-conscious market.

Optimization of Multi-Vehicle Cold Chain Logistics Distribution Paths Considering Traffic Congestion

Urban road traffic congestion has become a serious issue for cold chain logistics in terms of delivery time, distribution cost, product freshness, and even organization revenue and reputation. This study focuses on the cold chain distribution path by considering road traffic congestion with transportation, real-time vehicle delivery speeds, and multiple-vehicle conditions. Therefore, a vehicle routing optimization model has been established with the objectives of minimizing costs, reducing carbon emissions, and maintaining cargo freshness, and a multi-objective hybrid genetic algorithm has been developed in combination with large neighborhood search (LNSNSGA-III) for leveraging strong local search capabilities, optimizing delivery routes, and enhancing delivery efficiency. Moreover, by reasonably adjusting departure times, product freshness can be effectively enhanced. The vehicle combination strategy performs well across multiple indicators, particularly the three-type vehicle strategy. The results show that costs and carbon emissions are influenced by environmental and refrigeration temperature factors, providing a theoretical basis for cold chain management. This study highlights the harmonious optimization of cold chain coordination, balancing multiple constraints, ensuring efficient logistic system operation, and maintaining equilibrium across all dimensions, all of which reflect the concept of symmetry. In practice, these research findings can be applied to urban traffic management, delivery optimization, and cold chain logistics control to improve delivery efficiency, minimize operational costs, reduce carbon emissions, and enhance corporate competitiveness and customer satisfaction. Future research should focus on integrating complex traffic and real-time data to enhance algorithm adaptability and explore customized delivery strategies, thereby achieving more efficient and environmentally friendly logistics solutions.

Effect of packaging materials and storage temperature on the shelf stability of Awaze paste.

It is well known that deterioration is a big concern in the food supply chain. The problem is more serious in handling of traditional foods in developing country such as Ethiopia, due to the limited knowledge about the optimum processing, packaging and storage conditions. This study aimed to investigate the effect of packaging material and storage condition on the shelf life of Ethiopian traditional Awaze paste. Six types of packaging materials were employed: Shekella pot, Gourd (Qelle), high-density polyethylene (plastic bag), plastic bottle, glass bottle and metal can. These packaging materials are traditionally used by household producers and cottage industries in Ethiopia. The paste was stored at two temperatures: room temperature (21 ± 2°C) and refrigeration temperature (4°C). Physical changes, color (a) value, pH, acidity, yeast and mold levels, total bacterial count (TBC), and lactic acid bacteria count (LAB) were assessed every 60 days over a period of 300 days. pH value, acidity, yeast and mold, TBC, and LAB count were significantly (p < 0.05) affected by packaging material, storage temperature and storage period. After 300 days of storage, the highest yeast and mold count, 4.06 log CFU/g, was observed in samples stored in plastic bags. The highest total bacterial count (TBC), 4.12 log CFU/g, was found in samples stored in metal cans. The samples stored in glass bottles at refrigeration temperature (4°C) were found to have a color (a*) value difference of 11.5 to 13.85, a yeast and mold count value of 3.2 log cfu/g, and a TBC value of 2.97 log cfu/g, which were acceptable after 300 days of storage as per the international food standards. Taking into account all parameters including physical changes (color, mold growth, texture), acidity, yeast and mold, TBC, and LAB count, Awaze paste could be stored in glass bottles at 4°C for up to 300 days.

Coupled effects of initial water content with refrigeration temperature and freeze-thaw cycles on dewatering of sludge.

Many studies have displayed that freeze-thaw (F/T) conditioning is an environmentally friendly approach of improving sludge dewaterability. However, Initial water content (IWC) has a strong influence on the efficiency of the F/T method in conditioning sludge dewatering performance. Finding the most suitable F/T parameters for sludge with different IWCs is a critical issue that needs to be solved. Therefore, the coupled effects of different IWCs, refrigeration temperatures and the number of F/T cycles on sludge dewatering characteristics were explored. Single and multiple F/T cycles were performed on sludge from each group of IWCs at the same temperature. The coupling mechanism was analyzed by comparing the changes in sludge dewatering capacity before and after conditioning. The outcomes show that the F/T method is more suitable for sludge with a higher IWC. At -28 °C, the specific resistance to filtration of sludge with 87.5% IWC was reduced to 65.8 × 1012 m/kg, and the post-filtration water content was only 63.1%. After repeated F/T cycles, the water content of the sludge gradually decreased, and the post-filtration water content of sludge with 87.5% IWC dropped to 58.8% after 7 cycles. Appropriate refrigeration temperatures can improve the effectiveness of ice crystal cracking, especially for sludge with a water content of less than 82.5%. The results of research provide a guide for the selection of F/T parameters in the operation of deep dewatering of sludge with different IWCs.

Formulation development of highly stable collagenase-containing hydrogels for wound healing.

Collagenases are enzymes that break down collagen and are used in wound healing and treating various disorders. Currently, collagenase is commercially available in only ointment and injectable forms and is sensitive to various environmental factors. In the present study, different hydrogel formulations of collagenase have been prepared at pH 6.5 using carboxymethylcellulose sodium and zinc acetate with and without humectants such as propylene glycol (PG) and glycerin (GL) in varying concentrations. The formulated gels were stored at room temperature (25±2°C, 60±5% RH) and refrigerator temperature (5±3°C) for six months to evaluate their physical and up to six years for chemical stability. The gels were subjected to various tests, including organoleptic studies, spreadability, moisture content, swelling index, swelling/de-swelling, syneresis, viscosity, gelation time, and weight variation. The purity and molecular weight of collagenase have been determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). At the same time, its activity during the storage period was evaluated by gelatin zymography. Casein zymography was also performed to detect any caseinase contamination in the formulations. The release of the enzyme from different gel formulations was assessed using the Franz diffusion apparatus and analyzed by gelatin zymography. The results showed some physical changes that were more prominent in gels stored at room temperature than those kept refrigerated. The difference in humectant concentration was also found to affect the stability of gels. PG was found to be a better humectant than GL, particularly in a concentration of 25%. The zymography results indicated that collagenase was stable in all formulations kept in the refrigerator. In contrast, its complete degradation was noted in the preparations stored at room temperature within a month. The data generated in this study will help the formulators to commercialize a relatively economical gel formulation of collagenase that is highly stable for up to six years at refrigerator temperature (5±3°C).

Investigating the effects of citric acid concentrations on acidification, rheological, and microbial properties of fermented soy protein isolate yogurts.

As consumer awareness grows regarding the environmental and health impacts of animal-based products, plant-based alternatives are gaining popularity in developed countries. Plant-based proteins, like soy protein isolate (SPI), are valued for their sustainability and ability to complement animal proteins. SPI is commonly used in plant-based yogurts due to its high-quality protein, strong gelling capacity, and support for lactic acid bacteria (LAB) growth. Typically, plant-based yogurts use citric acid (CA) as a preservative, but its effect on LAB quality and effects is not fully understood. This study examines how different CA concentrations (0%, 1%, 1.5%, 2%, and 3%) influence the physicochemical, rheological, and microbial properties of fermented SPI yogurts under various temperature conditions over time (0, 15, and 24h at 45°C and 48h readings at 4°C). Higher CA concentrations led to lower pH, higher total titratable acidity, a loss modulus (G″) exceeding the storage modulus (G'), and increased viscosity. LAB growth was significant at refrigeration temperatures across all samples, indicating LAB adaptation to produce more lactic acid during storage. The study highlights that fermentation duration, temperature, storage conditions, and CA concentration significantly affect the properties of plant-based yogurts. Yogurts with 1% CA exhibited the best quality attributes while maintaining a pH below 4.6 as a food safety process control. This research provides insights into the preservation, safety, and quality of plant-based yogurts. PRACTICAL APPLICATION: This research aims to help food manufacturers improve the quality and safety of plant-based yogurts by optimizing citric acid levels. By balancing acidity and probiotic content, producers can create healthier, more sustainable yogurt alternatives that appeal to environmentally conscious consumers.

Formulation optimization of the powder for suspension of flixweed seeds (Descurainia sophia L.), a Persian medicinal drink

Background/Aim. Flixweed (Descurainia sophia L.) beverage has been used in Persian medicine as an effective remedy for constipation. Allyl isothiocyanate (AITC), the main ingredient of flixweed essential oil, has been claimed to regulate gastrointestinal contractility. The aim of the study was to stabilize the flixweed beverage, enhance its flavor, and determine the AITC content in the flixweed seeds (FS). Methods. To prepare a stable formulation of flixweed with desirable organoleptic properties, the optimal amount of tragacanth as a stabilizer, stevia as a sweetener, and lime and cinnamon powders as flavoring agents were mixed with flixweed solution. The shelf lives of the suspensions at room temperature (25?C) and refrigerator temperature (5?C) were evaluated. The viscosity and pH of the suspen-sions were also investigated. Finally, flixweed essential oil was obtained using the Clevenger apparatus. The amount of AITC in FS essential oil was determined by gas chromatography coupled with mass spectroscopy (GC-MS). Results. Based on our findings, two formulas, including FS (5 g), stevia (3 g), cinnamon (300 mg) or lime (400 mg), and 100 mL of water, had the optimum textural and organoleptic properties. Furthermore, adding 0.5% tragacanth gum as a suspending agent was able to stabilize the FS beverage. From 200 g of FS, 0.14 mL of essential oil was extracted, which corresponded to 0.07% (v/w). GC-MS analysis revealed that each 100 g of FS contained 24.85 mg of AITC, equating to 0.025% w/w AITC. Conclusion. Due to the presence of AITC in FS and the favorable characteristics of the FS suspension, this formulation, in the form of a sachet, can be suggested as an herbal supplement product for industrial production.

Magnetic refrigeration properties of Gd20Tb20Er20Cu20M20 (M=Fe, Co) high-entropy metallic glasses with refrigeration temperature span of exceeding 130 K

Magnetic refrigeration properties of Gd20Tb20Er20Cu20M20 (M=Fe, Co) high-entropy metallic glasses with refrigeration temperature span of exceeding 130 K

Investigating the energetic and exergetic performance of a solar based cooling-heating-low temperature refrigeration system

Investigating the energetic and exergetic performance of a solar based cooling-heating-low temperature refrigeration system

Investigating the Energetic and Exergetic Performance of a Solar Based Cooling-Heating-Low Temperature Refrigeration System

Investigating the Energetic and Exergetic Performance of a Solar Based Cooling-Heating-Low Temperature Refrigeration System

Effect of Enhanced Antimicrobial Fish Gelatin and Lactic Acid Coating on the Shelf Life of Fresh and Previously Frozen Shrimp

Gelatin coatings have been shown to successfully slow the oxidation of fresh foods. Furthermore, organic acids have proven effective in the inhibition of bacteria and the extension of product shelf life. The purpose of this study was to observe the effects of gelatin and lactic acid treatment combinations on fresh and previously frozen (thawed) wild-caught shrimp. The samples were separated into four treatment groups: control (C), gelatin coating (G), lactic acid followed by gelatin coating (L), and gelatin infused with lactic acid coating (LG). Half of each group was stored at refrigeration temperature (≤4 °C), while the other half was frozen (≤−18 °C) and thawed for the thawed study. Physical, chemical, and microbiological changes were observed in refrigeration storage for 8 days. Results showed that fresh and thawed shrimp exhibited darkening in color over time. Treatments with lactic acid were more blue than yellow. Treated samples developed less oxidation than the control. Psychrophilic counts for samples L and LG remained below the 7 log CFU/g threshold throughout the study. In fresh shrimp samples, the addition of just a gelatin coating was able to increase shelf life by three days, while the addition of lactic acid successfully lowered microbial counts and extended the shelf life by six days. The freeze–thaw cycle negatively affected the extension of shelf life in the G group.

Enterotoxigenic profile, biofilm production, and antimicrobial resistance of Bacillus cereus isolated from rice-based food marketed in southern Mexico

Bacillus cereus is responsible for food poisoning worldwide; thus, the characterization of strains isolated from food, in this case rice, is essential. The objective of this study was to identify the toxigenic profile, lytic enzymes, antimicrobial resistance, and biofilm production of B. cereus strains isolated from rice. The genetic profile of toxins and biofilm-related genes in the strains was determined by endpoint PCR. Biofilm formation was visualized using safranin staining, and the evaluation of lytic enzymes was conducted in culture media. Psychrophilic characteristics were monitored by assessing the growth of the strains at refrigeration temperature. The GTG5 technique was employed to determine the genetic diversity of the strains, and their antimicrobial resistance was validated through minimum inhibitory concentration testing. The strains of B. cereus s.l. isolated from rice contained genes for enterotoxins and genes associated with biofilm production. However, the strains did not possess the cereulide gene. The strain isolated from fried rice was the only one that contained the hbl toxin gene and the eps2 operon. Interestingly, this strain was the only one that did not produce biofilm. It exhibited intermediate sensitivity to erythromycin, was positive for amylase activity, showed high lecithinase activity, and was capable of growing at refrigeration temperature.

Studies of a Mechanically Pumped Two-Phase Loop with a Pressure-Controlled Accumulator Under Pulsed Evaporator Heat Loads

As avionics become more power dense, electronic device cooling has become a significant barrier to aircraft integration. A mechanically pumped two-phase loop (MPTL) is a thermal subsystem that enables near isothermal evaporator operation, which is desirable for electronics cooling. The goal of this study was to integrate an MPTL with a pressure-controlled accumulator and model a predictive control technique to demonstrate improvements for transient, isothermal evaporator operation for MPTLs under pulsed evaporator heat loads. The model predictive controller enables active control of MPTL compressible volume, which has not been demonstrated for pulsed evaporator heat loads. Experimental data were collected to validate a representative numerical model. A pressure-controlled accumulator was added to an MPTL to experimentally characterize the system thermodynamic response for three pulsed evaporator heat loads. Two statistical methods were used to assess the numerical model agreement with the experimental results. Under pulsed evaporator heat loads, the mean percent error agreed within 3.45% and the mean average percent error agreed within 0.74% for the three pulsed evaporator heat loads. Finally, a traditional proportional–integral (PI) controller and an advanced model predictive controller were developed and integrated into the validated numerical model. Both control methods were evaluated for an expanded set of evaporator heat load profiles to analyze transient behavior. For evaporator heat profiles with high heat transfer rates, the model predictive controller can maintain a target ±2 K refrigerant temperature at the evaporator exit throughout the evaporator heat load duration, whereas the PI-controlled MPTL cannot. Through this work, active control of a pressure-controlled accumulator within an MPTL is shown to improve refrigerant isothermal (±2 K) operation when compared to a traditional control technique.