Rate Of Temperature Decline Research Articles

Influence of design parameters on heat production of a multilateral butted closed loop geothermal system

To efficiently develop hot dry rock and other geothermal energy, a multilateral butted closed loop geothermal system (MBCLGS) is presented in this paper to replace the U-shaped closed-loop geothermal system (UCLGS). Besides, a casing-cement-formation transient heat transfer model is established to investigate the influences of key factors on the heat production of MBCLGS. After thermal-fluid-structural coupling analysis, we can find that higher injected rate and lower fluid temperature can improve heat power but reduce output temperature. In addition, the output temperature and heat power do not increase continuously with the increasing of branch well number. There is an optimal value of branch well number. Longer well pair distance can improve both output temperature and heat power. Considering the drilling technology level and design purpose, the recommended injected flow rate of MBCLGS is 90 m3/h, the injected fluid temperature is 42.5 °C, the number of branch wells is 10 and the well pair distance is 200m. Finally, by comparing MBCLGS and UCLGS, it is found that MBCLGS has a lower temperature decline rate and higher output temperature than UCLGS under the same conditions. It works more stable and has better economy. Overall, the proposal of MBCLGS is expected to promote the efficient development of deep geothermal resources.

Spatial and Temporal Freezing Dynamics of Leaves Revealed by Time-Lapse Imaging.

Freezing air temperatures kill most leaves, yet the leaves of some species can survive these events. Tracking the temporal and spatial dynamics of freezing remains an impediment to characterizing frost tolerance. Here we deploye time-lapse imaging and image subtraction analysis, coupled with fine wire thermocouples, to discern the in situ spatial dynamics of freezing and thawing. Our method of analysis of pixel brightness reveals that ice formation in leaves exposed to natural frosts initiates in mesophyll before spreading to veins, and that while ex situ xylem sap freezes near 0°C, in situ xylem sap has a freezing point of -2°C in our model freezing-resistant species of Lonicera. Photosynthetic rates in leaves that have been exposed to a rapid freeze or thaw do not recover, but leaves exposed to a slow, natural freezing and thawing to -10°C do recover. Using this method, we are able to quantify the spatial formation and timing of freezing events in leaves, and suggest that in situ and ex situ freezing points for xylem sap can differ by more than 4°C depending on the rate of temperature decline.

Investigating infrared Radiation, Energy, and fracture evolution features of dry and wet coal under cyclic loading

The continuous mining activities at the working face cause periodic disturbances to the surrounding coal rock mass. Investigating the response characteristics of surface infrared radiation temperature, energy evolution features, and fracture development patterns in coal rock under cyclic loading and unloading is crucial for enhancing our understanding of the mechanisms of damage, degradation, and instability in rocks associated with mining operations. In this research work, we conducted infrared radiation observation experiments on both dry and wet coal samples subjected to uniaxial cyclic loading and unloading. Furthermore, we carried out a thorough analysis of the resulting temperature variations, energy changes, and fracture evolution patterns. It was found that the average infrared radiation temperature (AIRT) generally increases during the loading phase and decreases during the unloading phase, with the variance of successive minus infrared image temperature (VSMIT) exhibiting a sharp change just prior to failure. Energy analysis indicates that dissipated energy during the pore compaction and elastic deformation stages is minimal, while in the plastic deformation stage, the proportion of dissipated energy to total energy increases, displaying a “concave” upward trend. Additionally, fitting results show that the AIRT follows a single exponential decay relationship with dissipated energy, with wet coal exhibiting a greater decay coefficient, highlighting that moisture accelerates the rate of temperature decline. The Particle Flow Code (PFC) simulation results further demonstrate that the number of cracks in dry coal samples significantly exceeds that in wet coal samples, showing a single exponential relationship between the number of fractures and dissipated energy, which indicates that the development of fractures in dry coal rock occurs at a faster rate with increasing dissipated energy compared to wet coal rock.

Hot Carcass Fabrication Intervention for Managing Top Round Quality in Heavy Weight Beef Carcasses

Chilling-related meat quality issues have been observed in the deep portion of the top round due to the increase of average beef carcass size. The current study examines the impact of an alternative fabrication method aimed at alleviating top round quality in heavy weight beef carcasses (n = 11; 510 kg average weight). Prior to rigor, the knuckle subprimal was partially fabricated to expose the femur on alternating sides of each carcass (TRT), and each adjacent intact side served as a control (CON). All sides were air chilled (2°C) for 48 h before further fabricating. Temperature loggers placed at approximately 2.54 cm below the top round surface was the superficial (SP) location while loggers for the deep (DP) location were inserted at the midline sagittal center of the round until in contact with the femur bone. Temperature and pH decline were monitored for 48 h. The top rounds were collected, aged under vacuum packaging until 14 d postmortem, and then cut into steaks (2.54 cm). Each steak was separated into SP and DP portions and subjected to Warner-Bratzler shear force (WBSF), consumer sensory panel, and a 3-d retail display analysis which included lipid oxidation and objective color evaluation. The TRT accelerated the rate of temperature decline at the DP location (P < 0.001) and increased the pH decline rate at the SP location (P = 0.029). Retail day and location were more impactful than TRT on objective color traits. SP steaks were more tender (P = 0.001) than DP steaks. Consumer taste panel indicated TRT improved overall acceptability (P = 0.042) and flavor (P = 0.035) of top round steaks regardless of locations. TRT accelerated top round DP chilling rate and elevated steak palatability attributes. Findings of the present study report an improvement of top round steaks due to the innovative fabrication treatment.

Optimum moment to heal cracks in asphalt pavement by means of waste carbon fiber-enhanced electromagnetic induction heating during multiple damage-healing cycles

This study investigated the optimal timing for healing asphalt pavement cracks using waste carbon fibers (WCFs) reinforced electromagnetic induction (EMI) technology through multiple "damage-healing" cycles, focusing on mechanical and fatigue performance. Initially, an extensive research project was carried out to evaluate the rate of induction heating, surface temperature decline rate, and effective heating depth of the asphalt mixture. Subsequently, from a mechanical performance perspective, semi-circular bending (SCB) tests were employed. By setting four different load termination conditions, the extent of cracking in the specimens was quantitatively controlled, followed by multiple "damage-healing" tests to analyze the impact of healing timing on the mechanical properties and healing efficiency of the asphalt mixture. Lastly, from the perspective of fatigue performance, using the four-point bending fatigue test (4 PB), the fatigue damage extent of specimens was quantitatively controlled through the attenuation rate of stiffness modulus. Multiple "damage-healing" tests were carried out at four different healing timings to study the effect of healing timing on the fatigue performance and healing efficiency of the asphalt mixture. The results indicated that WCFs improved the heating performance of asphalt mixture, enabling 5 cm-thick specimens to be fully heated within 6 min. Both SCB and 4 PB tests yielded similar conclusions: in the process of multiple "damage-healing" cycles, earlier healing interventions were beneficial for the recovery and maintenance of the mechanical properties of asphalt mixtures and effectively extended their service life. However, the fatigue tests also revealed that overly early self-healing interventions, where cracks were insufficiently formed, did not fully exploit the potential of the healing process. Conversely, healing interventions conducted too late were extremely detrimental to the restoration of mechanical characteristics and the prolongation of the asphalt mixture's lifespan.

Study on the Modified Ventilation Network on the Ventilation Effect and Ozone Migration Characteristics in Grain Pile

Grain is an important material for human survival. However, the expanding world population is contributing to a growing grain shortage. In order to reduce the loss of grain due to pests and mold during storage, mechanical ventilation as the main method of ventilation has crucial research significance. This article proposed and analyzed the ventilation effect and the migration characteristics of ozone in the grain pile under the modified ventilation network (MVN) and compared it with the original ventilation network (OVN). The study found that the temperature, moisture, and ozone concentration in the grain pile of the two ventilation networks are not evenly distributed in the vertical direction, showing a layered pattern. That is, with an increase in grain stack height, the temperature and moisture content of the grain stack are higher, and the ozone concentration is lower. Moreover, in the pre-ventilation period, the average temperature decline rate of the MVN was 1.25 °C/d, which was better than that of the OVN (0.84 °C/d), and the maximum temperature difference between the MVN and the OVN was 0.89 °C. The vertical ducts added to the MVN improved the ventilation effect, maintaining high ozone concentrations within the grain pile. Notably, on the sixth day of fumigation, the average ozone concentration of the MVN exceeded that of the OVN. The MVN can solve the shortcomings of the OVN, where air intake and fumigation gas rise slowly in the vertical direction. These findings hold substantial significance for optimizing ventilation network structures, devising effective fumigation strategies, and enhancing the insecticidal effects of grain storage.

Heat transfer characteristics of rectangular/triangular/convex-shaped fins filled with hybrid nanoparticles under dry and wet conditions

Numerous researchers have been interested in nanofluids because of their improved thermal characteristics and heat transmission capabilities. Recently, it has been possible to create a novel nanofluid with exceptional thermal properties by combining ternary nanoparticles of various shapes. In this respect, it is believed that the thickness of the fin will change with the length of the fin and that the impacts of thermal radiation, convection on a heat transfer mechanism, and internal heat production in a fin wetted with ternary hybrid nanofluid will depend on the length of the fin. As a result, several fin profiles, including triangular, convex, and rectangular, have been taken into consideration. This study also investigates the comparison of heat and thermal energy fluctuations in both wet and dry conditions. In order to examine the porous nature, Darcy's model is required. With the aid of the Maple computer program, the resultant nonlinear partial differential equation and boundary conditions are non-dimensionalized and numerically resolved using the implicit finite difference approach, the graphic explanation of fin efficiency, and transient thermal response for different values of the essential parameters. The investigation yielded the novel discovery that the effectiveness of the fins is enhanced by the presence of a ternary hybrid nanofluid. Three fins with varied shapes have been compared in both wet and dry circumstances. The study has discovered that triangular fins have a quicker rate of temperature decline, whereas rectangular fins have a greater efficiency. The investigation's results have a significant impact on improving heat transmission in industrial operations.

Field Evaluation of Tiletamine-Zolazepam-Medetomidine for Immobilization of Raccoons (Procyon lotor) and Striped Skunks (Mephitis mephitis).

The effectiveness of tiletamine-zolazepam (1.7 mg/kg) plus medetomidine (0.07 mg/kg; TZM) as an immobilizing combination in raccoons (Procyon lotor; n=43) and striped skunks (Mephitis mephitis; n=7) was evaluated during October 2019. Mean (±SD) induction time for raccoons was 15.0±6.6 min. First signs of recovery (head up) occurred 12.9±6.0 min after receiving atipamezole reversal (0.35 mg/kg) and animals were standing in 30.3±16.1 min. Mean induction time for skunks was 11.7±5.8 min. Following reversal, skunks first raised their heads in 6.7±4.3 min and stood in 17.1±12.9 min. Recovery in skunks and female raccoons was not related to length of time immobilized, but male raccoons that were immobilized for longer periods of time stood faster after reversal. Raccoon heart rate (HR) remained steady during immobilization, but respiration rate (RR) and rectal temperature (RT) declined. The HR and RR were similar among males and females, but RT of male raccoons were, on average, 0.5 C higher than those of females, and rate of temperature decline was slower for males. The HR, RR, and RT of skunks declined during immobilization. Although induction times for both raccoons and skunks were longer than expected, induction and recovery were smooth, side effects were few, analgesia was adequate for nonsurgical procedures, and reversal reduced time in captivity.

Numerical study on seasonal operation of solar assisted hybrid borehole heat exchange array

The combined use of solar energy and ground-source heat pump system may provide a reasonable solution to the energy crisis and low utilization efficiency of single energy. Herein, a numerical model of a solar assisted hybrid ground-source heat pump (SAHGSHP) system composed of multiple types and lengths of borehole heat exchanger (BHE) array was developed. The effectiveness of this model was validated by experimental data of a SAHGSHP system located in Tongzhou, Beijing. The verified model was used to study the performance sustainability of SAHGSHP system under different seasonal operation modes and its influence on the temperature of rock and soil. It was shown that for different types of BHEs in heat extraction periods of SAHGSHP systems, the outlet temperature decline rate decreases by an average of 2.30%, the temperature decline rate of rock and soil at the reference point under single-season operation decreases by an average of 0.78%, and the temperature increase rate of rock and soil at the reference point under double-season operation increases by an average of 0.53% compared with that of hybrid ground-source heat pump (HGSHP). The results of this study could provide a further understanding for analyzing the seasonal operation mode of SAHGSHP.

Reinforcement Learning Based Relay Selection for Underwater Acoustic Cooperative Networks

In the complex and dynamically varying underwater acoustic (UWA) channel, cooperative communication can improve throughput for UWA sensor networks. In this paper, we design a reasonable relay selection strategy for efficient cooperation with reinforcement learning (RL), considering the characteristics of UWA channel variation and long transmission delay. The proposed scheme establishes effective state and reward expression to better reveal the relationship between RL and UWA environment. Meanwhile, simulated annealing (SA) algorithm is integrated with RL to improve the performance of relay selection, where exploration rate of RL is dynamically adapted by SA optimization through the temperature decline rate. Furthermore, the fast reinforcement learning (FRL) strategy with pre-training process is proposed for practical UWA network implementation. The whole proposed SA-FRL scheme has been evaluated by both simulation and experimental data. The simulation and experimental results show that the proposed relay selection scheme can converge more quickly than classical RL and random selection with the increase of the number of iterations. The reward, access delay and data rate of SA-FRL can converge at the highest value and are close to the ideal optimum value. All in all, the proposed SA-FRL relay selection scheme can improve the communication efficiency through the selection of the relay nodes with high link quality and low access delay.

The impact of carcass size, chilling, and electrical stimulation on beef postmortem temperature and pH decline

Variability in carcass size can influence carcass chilling rates which could result in issues associated with beef tenderness and color. Moreover, the usage of electrical stimulation can affect postmortem metabolism and meat quality. However, few studies have looked at the combined impact of chilling and electrical stimulation on temperature decline, postmortem biochemistry, and color among the current consist of US beef. Beef carcasses (N =162, < 30 months) were randomly selected from two beef processing plants. One side of each carcass was electrically stimulated (ES), while the opposing side was not electrically stimulated (NES). Matched sides were subjected to either conventional spray chilling (CONV) or delayed-spray chilling (DELAY). Deep tissue (10.5-cm under the pelvic bone) and surface temperature (1.5-cm under the loin fat) were continuously monitored during chilling in addition to temperature and pH measurements from the semimembranosus (SM), longissimus lumborum (LL), and psoas major (PM) muscles at an initial time (45 to 60 min), 6 h, 12 h, and after chilling (28 to 36 h) postmortem. Further, the instrumental (L*, a*, and b*) and visual color of the PM were evaluated. For data analysis, carcasses with hot carcass weights above or below the average were considered heavy or light, respectively. A nonlinear regression model was fitted to the continuous deep and surface temperatures, whereas other parameters were evaluated using a mixed model. Electrical stimulation improved (P < 0.05) the color of PM in light weight carcasses, but not (P > 0.05) in heavy weight carcasses. Temperature decline was faster (P < 0.05), and pH decline slower (P < 0.05) in the SM and LL of light weight carcasses under CONV. Exponential decay models for deep and surface temperatures indicated the rate of cooling differed (P < 0.05) due to the combination of treatment factors. Heavy weight carcasses in DELAY had slower rates of temperature decline (P < 0.05). Overall, the variability in carcass size affected temperature decline and postmortem metabolism. Therefore, postmortem management practices should consider carcass weights to ensure homogeneous meat quality.

Predictive control using a hybrid data-based artificial neural network model: a case study on the construction of massive concrete structures

Traditionally, temperature control for massive concrete structures during the construction phase is based on experience instead of using advanced methods such as predictive control method. In this paper, a predictive control method with a hybrid data-based artificial neural network (ANN) model is proposed. The main parameters of the numerical model are identified based on the data measured from the site. Since the limitation of the measured data, a rich dataset is generated by the numerical model with the identified parameters. Finally, a hybrid data-based ANN model for predicting the temperature indicator of massive concrete is developed. A case study in which the temperature control of concrete in a real bridge anchorage foundation construction in Southwestern China is conducted. Results show that the maximum temperature of concrete can be controlled around the target temperature by the proposed method. The average temperature decline rate decreases from 0.19 °C/h to 0.14 °C/h in the period of 120 h (i.e., from 60 h to 180 h after the concrete pouring) at a sudden decrease of 8 °C in environmental temperature, thereby enabling a significant reduction in the risk of concrete cracking.

Fully-Echoed Q-Routing With Simulated Annealing Inference for Flying Adhoc Networks

Current networking protocols deem inefficient in accommodating the two key challenges of Unmanned Aerial Vehicle (UAV) networks, namely the network connectivity loss and energy limitations. One approach to solve these issues is using learning-based routing protocols to make close-to-optimal local decisions by the network nodes, and Q-routing is a bold example of such protocols. However, the performance of the current implementations of Q-routing algorithms is not yet satisfactory, mainly due to the lack of adaptability to continued topology changes. In this paper, we propose a full-echo Q-routing algorithm with a self-adaptive learning rate that utilizes Simulated Annealing (SA) optimization to control the exploration rate of the algorithm through the temperature decline rate, which in turn is regulated by the experienced variation rate of the Q-values. Our results show that our method adapts to the network dynamicity without the need for manual re-initialization at transition points (abrupt network topology changes). Our method exhibits a reduction in the energy consumption ranging from 7% up to 82%, as well as a 2.6 fold gain in successful packet delivery rate, compared to the state of the art Q-routing protocols.

Comparison of the effect of isopropyl alcohol and chlorhexidine solution rinses on body temperature of female cats undergoing sterilization surgery.

Isopropyl alcohol 70% as a rinse agent for chlorhexidine scrub has been shown to decrease body temperature more quickly than chlorhexidine solution in mice prepared aseptically prior to surgery. For this reason, some high-quality, high-volume (HQHV) surgical sterilization clinics use chlorhexidine solution rather than alcohol. We sought to determine if temperature upon entry to recovery, heat loss per kg and rate of temperature decline during surgery were different between cats rinsed with chlorhexidine solution vs 70% isopropyl alcohol following surgical scrub, and if there were significant predictors of recovery temperature. Female cats admitted for surgery to trap-neuter-return (TNR) clinics at a veterinary college were assigned chlorhexidine solution or alcohol rinse agents via block randomization. Veterinary students and veterinarians performed spay surgeries using HQHV techniques. In recovery, heat support and reversal agents were available for cats with a low body temperature or that were slow to recover. Baseline values, outcome variables and duration of each stage (preparation, surgery, recovery) were assessed using Wilcoxon rank-sum and t-tests. Recovery temperature was evaluated using random effects multiple linear regression. The recovery temperature, heat loss per kg, heat loss per min, need for reversal and need for heat support in recovery were not significantly different between rinse groups. Weight <2.3 kg, body condition score <4, duration of surgery and postinduction temperature were predictors of recovery temperature. The rate of heat loss in the first 30 mins of surgery was slightly lower for cats in the alcohol rinse group and the recovery duration was shorter for cats weighing less <2.3 kg in the alcohol rinse group. There were no clinically meaningful differences in body temperature between chlorhexidine and alcohol rinses. Both chlorhexidine solution and isopropyl alcohol 70% are appropriate rinse agents for aseptic preparation of feline spay surgeries.

Effect of hot carcass weight on the rate of temperature decline of pork hams and loins in a blast-chilled commercial abattoir123.

Adequate carcass chilling is required to optimize pork quality and food safety. The rate at which carcasses chill is dependent on their mass. Hot carcass weight has increased steadily over the years, certainly affecting the chilling rate of the average carcass in contemporary abattoirs. Therefore, the objective was to model the effect of HCW on temperature decline of a contemporary population of pork carcasses slaughtered at a commercial abattoir that used a blast-chilling method. In addition, carcasses were sorted into HCW classes, and the effect of HCW group was tested on the rate of temperature decline of the longissimus dorsi and semimembranosus. Hot carcass weight, internal temperature of the loin muscle (at the 10th rib) and ham, as well as ambient temperature, were recorded from 40 to 1,320 min postmortem (45 time points) on 754 pork carcasses. An exponential decay model based on Newton's law of cooling, T(t)=Ta+(T0-Ta)e-kt, was fit to temperature decline of the ham and loin of the whole population using PROC MODEL of SAS. The initial models for the decline of both ham and loin temperature displayed significant autocorrelation of errors based on evaluation of the autocorrelation function plots and Durbin-Watson test (P < 0.0001). Therefore, second- and third-order autocorrelation parameters were tested. Based on Durbin-Watson test, the use of second-order autocorrelation model with lags of 1 and 2 was deemed adequate and was therefore included in all subsequent models. This base model and its respective parameter estimates were all significant (P < 0.01) for the whole population. Carcasses approximating 85, 90, 95, 100, and 105 kg (± 1 kg) were selected and binned into their respective weight classes. Dummy variables were used to compare the effect of HCW class on parameter estimate of ham and loin models. The developed model significantly fit all weight classes (P < 0.01) for both ham and loin temperature decline. For both loin and ham models, estimates of the rate constant (k) generally decreased as HCW increased. For loin temperature, k estimate for 105-kg carcasses was 0.00124 less (P = 0.02) than 85-kg carcasses, with the intermediate HCW classes not differing from the 85-kg class. For ham temperature, estimates of k for 90, 95, 100, and 105 kg HCW were all significantly and successively less than the k estimate for 85 kg class. For perspective, loins of 95-kg carcasses were estimated to reach 2 °C in 17 h, whereas loins from 105-kg carcasses would not reach 2 °C until 27 h. For hams, 95-kg carcasses were projected to reach 2 °C in 21 h, whereas those from 105-kg carcasses would take 28 h. Overall, HCW significantly affects the rate of temperature decline of pork hams, but not loins from pork carcasses weighing between 85 and 100 kg.

Experimental Study on Dynamic Heat Release Performance of Water Tank with Phase Change Materials

Solar heating system has raised much attention due to the global energy shortage and environment pollution. The dynamic heat release performance of water tank (WT) with phase change materials (PCM) plays an important role in the operation of solar heating system, while seldom available literatures focused on this research topic. In this paper, an experimental system for heat release of the WT-PCM was established. The temperature variations of the water and the PCM during heat release of the WT-PCM and the traditional water tank were measured respectively, and their dynamic heat release performance were also analyzed based on the measured data. The results are as follows: the heat release of the WT-PCM can be divided into three phases: sensible heat before phase change, latent heat during phase change and sensible heat after phase change, and the water temperature will be temporarily heated after the sudden drop; the water supply temperature decline rate of both tanks will increase dramatically at the initial stage of heat release, when the PCM temperature is reduced to 50℃, the water supply decline rate of the WT-PCM is less than that of the traditional water tank, while when PCM is completely solidified, the water supply temperature decline rate of the WT-PCM is more than that of the traditional water tank. The heat release performance of the WT-PCM is much better than that of the traditional water tank. The research results can provide useful reference for engineering application of the WT-PCM.

Stability of an aluminum salt-adjuvanted protein D-conjugated pneumococcal vaccine after exposure to subzero temperatures

ABSTRACTAccidental exposure of a vaccine containing an aluminum-salt adjuvant to temperatures below 0°C in the cold chain can lead to freeze damage. Our study evaluated the potential for freeze damage in a licensed aluminum-salt-containing protein-D-conjugated pneumococcal vaccine (PHiD-CV; Synflorix, GSK) in conditions that included static storage, single subzero-temperature excursions, and simulated air-freight transportation. Several parameters were assessed including freezing at subzero temperatures, aluminum-salt-particle size, antigen integrity and immunogenicity in the mouse. The suitability of the WHO's shake test for identifying freeze-damaged vaccines was also assessed. During subzero-temperature excursions, the mean temperatures at which PHiD-CV froze (−16.7°C to −18.1°C) appeared unaffected by the type of vaccine container (two-dose or four-dose vial, or single-dose syringe), vaccine batch, rotational agitation, or the rate of temperature decline (−0.5 to −10°C/hour). At constant subzero temperature and in simulated air-freight transportation, the freezing of PHiD-CV appeared to be promoted by vibration. At −5°C, no PHiD-CV sample froze in static storage (>1 month), whereas when subjected to vibration, a minority of samples froze (7/21, 33%) within 18 hours. At −8°C with vibration, nearly all (5/6, 83%) samples froze. In these vibration regimes, the shake test identified most samples that froze (10/12, 93%) except two in the −5°C regime. Nevertheless, PHiD-CV-antigen integrity appeared unaffected by freezing up to −20°C or by vibration. And although aluminum-salt-particle size was increased only by freezing at −20°C, PHiD-CV immunogenicity appeared only marginally affected by freezing at −20°C. Therefore, our study supports the use of the shake test to exclude freeze-damaged PHiD-CV in the field.

Effects of Electrical Stimulation, Chilling Rate, and Carcass Size on Rates of Temperature Decline and pH Decline, and Beef Quality

Effects of Electrical Stimulation, Chilling Rate, and Carcass Size on Rates of Temperature Decline and pH Decline, and Beef Quality

Effect of Hot Carcass Weight on the Rate of Temperature Decline of the Longissimus Dorsi and Semimembranosus of Pigs Slaughtered in a Blast-Chilled Commercial Abattoir

ObjectivesOver the last 30 yr, the average hot carcass weight (HCW) has consistently increased by approximately 0.5 kg per yr. This trend toward increased HCW causes engineering challenges for aging facilities designed when average HCW was 85 kg, in contrasts to today’s average HCW of 95 kg. The rate of carcass chilling is among the primary concerns. Larger carcasses have a smaller surface area to volume ratio, and almost certainly do not reach desired internal temperatures at the same rate as smaller carcasses. However, differences in rate have not been routinely reported, and to the authors’ knowledge, no such model has been reported for a large-scale, blast-chilled pork abattoir. Therefore, the objective of this study was to model the effect of HCW on temperature decline of a contemporary population of pork carcasses slaughtered at a commercial abattoir that used a blast-chilling method. Additionally, carcasses were sorted into HCW classes and the effect of HCW group was tested on the rate of temperature decline of the longissimus dorsi and semimembranosus.Materials and MethodsHot carcass weight, internal temperature of the loin muscle (at the 10th rib) and ham, as well as ambient temperature, were recorded from 40 to 1,320 min postmortem (45 time points) on 754 pork carcasses. An exponential decay model based on Newton’s Law of Cooling, was fit to temperature decline of the ham and loin of the whole population using PROC MODEL of SAS (SAS Inst. Inc., Cary, NC). The initial models for the decline of both ham and loin temperature displayed significant autocorrelation of errors based on evaluation of the autocorrelation function plots and Durbin-Watson test (P < 0.0001). Therefore, second and third order autocorrelation parameters were tested. Based on Durbin-Watson tests, the use of second order autocorrelation model with lags of 1 and 2 were deemed adequate and were therefore included in all subsequent models. This base model and its respective parameter estimates were all significant (P < 0.01) for the whole population. Carcasses approximating (± 1 kg) 85, 90, 95, 100, and 105 kg were selected and binned into their respective weight classes. Dummy variables were used to compare the effect of HCW class on parameter estimate of ham and loin models.ResultsThe developed model significantly fit all weight classes (P < 0.01) for both ham and loin temperature decline. For both loin and ham models, estimates of the rate constant (k) generally decreased as HCW increased. For loin temperature, k estimate for 105 kg carcasses was 0.00124 less (P = 0.02) than 85 kg carcasses, with the intermediate HCW classes not differing from the 85 kg class. For ham temperature, estimates of k for 90, 95, 100, and 105 kg HCW were all significantly and successively less than the k estimate for 85 kg class. For perspective, loins of 95 kg carcasses were estimated to reach 2°C in 17 h; whereas, loins from 105 kg carcasses would not reach 2°C until 27 h. For hams, 95 kg carcasses were projected to reach 2°C in 21 h; whereas, those from 105 kg carcasses would take 28 h. These estimates generally agreed with observed values.ConclusionOverall, HCW significantly affects the rate of temperature decline of pork hams, but not loins from pork carcasses weighing between 85 and 100 kg. This method of analysis can be used to model temperature decline in individual facilities.

Low-temperature tolerance of juvenile tarpon Megalops atlanticus

The tarpon Megalops atlanticus is a tropical to subtropical species whose pole-ward distribution is thought to be limited by low water temperatures. In the western north Atlantic Ocean juvenile tarpon occur in estuaries of the South Atlantic Bight (SAB) north of Florida near the northern limit of its distribution, but it is currently unknown whether these individuals can survive winter, grow to maturity, and contribute to the adult population. As a first step to determine whether juvenile tarpon can survive winter conditions in the SAB, we conducted laboratory experiments to estimate minimum lethal temperatures of tarpon exposed to 1) ambient fluctuating winter water conditions and 2) a constant rate of temperature decline. Juvenile tarpon exposed to ambient winter water conditions had a mean ± standard deviation (SD) minimum lethal temperature of 13.7 ± 3.4 °C. When exposed to a constant rate of temperature decline (2 °C day−1), mean ± SD minimum lethal temperature (9.2 ± 0.8 °C) was lower than when tarpon were exposed to ambient fluctuating conditions. A combination of our results with all published data on the cold tolerance of juvenile tarpon resulted in an overall mean ± SD minimum lethal temperature of 12.0 ± 2.8 °C. Based on available long-term temperature records from SAB estuaries, overwinter survival of juvenile tarpon is unlikely in most aquatic habitats (e.g., tidal creeks, flats, open water). Similar to other estuarine transient fishes, juvenile tarpon likely exploit seasonably favorable nursery habitats and then migrate to other locations to overwinter.