Decline In Tc Research Articles

Critical environmental core temperature limits and heart rate thresholds across the adult age span (PSU HEAT Project).

The frequency, duration, and severity of extreme heat events have increased and are projected to continue to increase throughout the next century. As a result, there is an increased risk of excessive heat- and cardiovascular-related morbidity and mortality during these extreme heat events. Therefore, the purposes of this investigation were to establish 1) critical environmental core temperature (Tc) limits for middle-aged adults (MA), 2) environmental thresholds that cause heart rate (HR) to progressively rise in MA and older (O) adults, and 3) examine critical environmental Tc limits and HR environmental thresholds across the adult age span. Thirty-three young (Y) (15 F; 23 ± 3 yr), 28 MA (17 F; 51 ± 6 yr), and 31 O (16 F; 70 ± 3 yr) subjects were exposed to progressive heat stress in an environmental chamber in a warm-humid (WH, 34-36°C, 50-90% rh) and a hot-dry (HD, 38°C-52°C, <30% rh) environment while exercising at a low metabolic rate reflecting activities of daily living (∼1.8 METs). In both environments, there was a main effect of age on the critical environmental Tc limit and environmental HR thresholds (main effect of age all P < 0.001). Across the lifespan, critical environmental Tc and HR thresholds decline linearly with age in HD environments (R2 ≥ 0.3) and curvilinearly in WH environments (R2 ≥ 0.4). These data support an age-associated shift in critical environmental Tc limits and HR thresholds toward lower environmental conditions and can be used to develop evidence-based safety guidelines to minimize future heat-related morbidity and mortality across the adult age span.NEW & NOTEWORTHY This study is the first to identify critical environmental core temperature and heart rate thresholds across the adult age spectrum. In addition, our data demonstrate that the rate of decline in Tc and HR limits with age is environmental-dependent. These findings provide strong empirical data for the development of safety guidelines and policy decisions to mitigate excessive heat- and cardiovascular-related morbidity and mortality for impending heat events.

Reduced A–B super exchange interaction in zirconium doped cobalt ferrite due to laser irradiation

The impact of Nd:YAG laser irradiation and the addition of zirconium ions (Zr4+) on the physical properties of CoFe2O4 spinel nano-ferrites has been studied. The co-precipitation method was used to synthesize the samples. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were employed to examine the structure and morphology. The decrease in the Curie temperature Tc is due to the laser irradiation and the increase in the Zr content of the sample. This decline in Tc is a result of an increase in the canting of the spins, leading to a change in the thermal energy needed for compensate the spin alignment. The difference in the Tc between the non irradiated and the irradiated samples is about 7%, 43% and 34% for CoFe2O4, Co1.1Zr0.1Fe1.8O4, and Co1.3Zr0.3Fe1.4O4, respectively. The decrease in the coercivity of the laser irradiated sample is due to a reduction in the magnetic anisotropy and an altered distribution of the cations (Co2+, Fe3+, Zr4+). The observed trend indicates that laser irradiation, and Zr substitution, can be used to modify the magnetic hardness of the samples. The low coercivity of irradiated Co1.1Zr0.1Fe1.8O4 makes it suitable for a range of applications. The high-frequency response of the Co1+xZrxFe2–2xO4 NPs shows that they can operate within the frequency range of 7.5 GHz–11.56 GHz.

Pressure-dependent magnetic properties of FeNi alloy: Theoretical study

The influence of external pressures on the structural and magnetic properties of the FeNi alloy is elucidated using density functional theory (DFT) and Monte Carlo simulation. Utilizing a range of pressures, the study showcases compressive behavior in lattice constants, with both a and c exhibiting reductions. A sharp decline in magnetic moments is recorded at a critical pressure of 54 GPa. Indicating a magnetic phase transition from ferro to paramagnetic phase. Beyond this critical pressure, dynamical instability becomes evident, attributable to the aforementioned magnetic phase transition. Further examination of exchange interaction parameters reveals that while Fe–Fe interactions exhibited a consistent decrease with pressure, the FeNi and NiNi interactions remained relatively stable across the examined pressure range. At pressures close to 0 GPa, the Curie temperature (TC) was found to be around 838 K. As the external pressure is applied, a consequential decline in TC is witnessed, suggesting a significant sensitivity of the magnetic phase transition to external pressures. In particular, this study indicates that the FeNi alloy is sensitive to external pressures, emphasizing some relation between structural and magnetic properties.

CORE™ wearable sensor: Comparison against gastrointestinal temperature during cold water ingestion and a 5 km running time-trial

Five km running time-trials (TT) are associated with rapid and significant increases in core body temperature (TC). For such races, real-time feedback from pre-exercise and exercise TC may be helpful in the design of an optimal pacing strategy aimed at limiting the possibility of developing heat-related illnesses. This study compared measurements of TC obtained with a wearable device, the CORE™, to those of a gastrointestinal pill (GI pill), during cold water ingestion and a 5 km running TT. Twelve participants (25 ± 4 yrs) ingested 7.5 mL/kg fat-free mass of 4 °C water over the first 5 min of a 120 min sitting period, after which they completed a 5 km running TT at 30 °C, 50% relative humidity. A TC difference > ± 0.25 °C between sensors was deemed clinically unacceptable. Prior to water ingestion, the CORE-derived TC was 0.49 ± 0.25 °C lower than the GI pill. The CORE was irresponsive to the 0.26 ± 0.22 °C peak decline in TC captured with the GI pill 40 min following water ingestion. Prior to the TT, TC was 0.30 ± 0.25 °C lower with the CORE than the GI pill. During the TT, the CORE underestimated the rate of increase in TC by 0.0125 ± 0.019 °C/min compared with the GI pill, and mean absolute difference in TC between sensors was of 0.47 ± 0.34 °C. In conclusion, the CORE does not capture the cooling effect of cold water ingestion and provides a clinically relevant underestimation of TC during a 5 km running TT in the heat.

When music compensates language: a case study of severe aphasia in dementia and the use of music by a spousal caregiver

ABSTRACTBackground: There is accumulating evidence of the preservation of music skills in people with Alzheimer’s dementia (AD), including spared memory for familiar music and the ability to produce music by singing or playing an instrument. Music can also be used to alleviate symptoms of dementia, leading to reduced agitation, improved positive mood, memory, and expressive language functions.Aims: We evaluated the rate of decline of expressive language and music skills in TC, a 77 year old woman with aphasia in the context of severe AD, and her husband’s use of music in caregiving. Neither TC nor her husband had any formal music training. We also explored whether the preservation of music skills had implications for treating a symptom of her dementia, specifically her misidentification delusion.Methods & Procedures: A retrospective comparison of the progressive decline in TC’s expressive music and language skills was obtained through interviews with her husband. He also completed a purposefully developed questionnaire regarding his use of music during caregiving. Assessment of TC’s language skills was attempted using the Sydney Language Battery, and her music engagement skills were evaluated with the Music Engagement Questionnaire (MusEQ, informant version). Her behaviour and verbal communication was observed during four different conditions, presented by her husband; (1) reading a newspaper article, (2) reading familiar song lyrics, (3) singing familiar song lyrics, and (4) listening to the original version of the familiar song.Outcomes & Results: TC exhibited a gradual deterioration of her expressive language abilities, whereas her music skills (singing and music engagement), were relatively preserved. Her overall score on the MusEQ was in keeping with age matched healthy controls (50–55 percentile) and she had a high average (80–85 percentile) score on the “emotion” subscale. The impact of preserved music engagement was powerfully demonstrated when TC developed a transient misidentification delusion and believed that her husband was an intruder. Her delusion was only resolved after her husband repeatedly sang a significant song that they had shared as a couple for close to 60 years. By singing this special song (“Unchained Melody”), TC eventually “came back” and recognised him. During behavioural observations under different language and music conditions, TC’s verbal communication did not appear to change.Conclusions: This case study illustrates that when language skills deteriorate in AD, music functions may persist, providing a vital tool in coping with the symptoms of severe dementia.

Firefighter feedback during active cooling: A useful tool for heat stress management?

Monitoring an individual's thermic state in the workplace requires reliable feedback of their core temperature. However, core temperature measurement technology is expensive, invasive and often impractical in operational environments, warranting investigation of surrogate measures which could be used to predict core temperature. This study examines an alternative measure of an individual's thermic state, thermal sensation, which presents a more manageable and practical solution for Australian firefighters operating on the fireground. Across three environmental conditions (cold, warm, hot & humid), 49 Australian volunteer firefighters performed a 20-min fire suppression activity, immediately followed by 20min of active cooling using hand and forearm immersion techniques. Core temperature (Tc) and thermal sensation (TS) were measured across the rehabilitation period at five minute intervals. Despite the decline in Tc and TS throughout the rehabilitation period, there was little similarity in the magnitude or rate of decline between each measure in any of the ambient conditions. Moderate to strong correlations existed between Tc and TS in the cool (0.41, p<0.05) and hot & humid (0.57, p<0.05) conditions, however this was resultant in strong correlation during the earlier stages of rehabilitation (first five minutes), which were not evident in the latter stages. Linear regression revealed TS to be a poor predictor of Tc in all conditions (SEE=0.45–0.54°C) with a strong trend for TS to over-predict Tc (77–80% of the time). There is minimal evidence to suggest that ratings of thermal sensation, which represent a psychophysical assessment of an individual's thermal comfort, are an accurate reflection of the response of an individual's core temperature. Ratings of thermal sensation can be highly variable amongst individuals, likely moderated by local skin temperature. In account of these findings, fire managers require a more reliable source of information to guide decisions of heat stress management.

Magnetic and structural studies on nanostructured Gd/Cr multilayer films

Investigations of magnetic phases, transition temperatures and coercivity were performed in multilayered Gd/Cr films as a function of the crystalline state and morphology of the Gd layers. The films were deposited by dc magnetron sputtering at three substrate temperatures, Ts, (room temperature, 300 and 500°C). The Gd and Cr thicknesses were of 10 and 30nm, respectively. Two series of three films were prepared. In one of the series, the films had a single Gd/Cr bilayer; in the other, 15 bilayers. The discontinuous or granular nature of the Gd layers was revealed by scanning electron microscopy Grazing incidence angle x-ray diffraction was used to investigate the crystalline state of the Gd and Cr layers. These techniques revealed that grain average size and crystalline order increase with increasing Ts. From dc magnetic measurements, the co-existence of ferromagnetic and superferromagnetic phases in the Gd layers was observed, and Curie transition temperatures, TC, were determined. High coercive fields at low temperature (2K) were measured in hysteresis cycles. Field-cooled and zero field-cooled magnetizations as functions of temperature curves exhibited, for some of the samples, a low temperature peak suggesting a freezing transition to a cluster glass state. This was confirmed by complementary ac-susceptibility measurements carried out as a function of temperature, for various frequencies of the ac field. Some results of this work – the decline in TC for decreasing Gd grain size, the high coercive field and its dependence on particle size, and the behavior of the magnetization at low temperatures for the sample deposited at room temperature – are discussed in terms of finite size and surface effects in nanosized particles.

Clinical significance of serum lipids in idiopathic pulmonary alveolar proteinosis

BackgroundIt is well known that pulmonary alveolar proteinosis(PAP) is characterised by accumulation of surfactant lipids and proteins within airspaces. However, few previous data describe the serum lipid levels associated with PAP.Materials and methodsWe retrospectively reviewed 25 patients with idiopathic PAP(iPAP). The serum lipid levels of patients with idiopathic PAP were compared with those of the healthy volunteers. In patients and healthy subjects, the LDL-C/HDL-C ratios were 2.94 ± 1.21 and 1.60 ± 0.70, respectively (p < 0.001), HDL-C were 1.11 ± 0.27 and 1.71 ± 0.71 respectively (p < 0.001). The values of LDL-C correlated significantly with those of PaO2 and PA-aO2 (r = -0.685, p = 0.003, and r = 0.688, p = 0.003, respectively). The values of LDL-C/HDL-C ratios also correlated with PaO2 levels and PA-aO2 levels (r = -0.698, p = 0.003, and r = 0.653, p = 0.006, respectively). 11 and 13 patients experienced respectively a decline in TC and LDL-C levels following whole lung lavage(WLL), the median decline was 0.71 mmol/L(p < 0.009) and 0.47 mmol/L(p < 0.003), respectively.Conclusionsthe serum lipid levels, especially the levels of LDL-C and LDL-C/HDL-C, may reflect the severity of the disease in PAP patients, and predict the therapeutic effect of WLL.

Thermal responses for men with different fat compositions during immersion in cold water at two depths: prediction versus observation

A cold thermoregulatory model (CTM) was applied to data from partially immersed subjects divided into normal (NF) or low fat (LF) groups in order to validate CTM during immersion at two depths and to examine mechanisms underlying the individual differences. CTM defines thermal characteristics, e.g. surface area and maximal shivering intensity, using height, weight, fat %, age and VO(2max). Ten clothed subjects, 5 NF (15-19%) and 5 LF (8.1-14.7%), were immersed in both 10 and 15 degrees C water at chest (CH) and waist (WA) level. Environmental and clothing inputs for CTM were weighted to adjust for the ratio of skin surface area covered by either air or water at various immersion depths. Predicted core temperature (Tc) responses for each individual trial were compared with measured data. There were no significant differences (P > 0.05) between measured Tc and predicted Tc for NF at all four conditions. In contrast, for the LF group, the predicted Tc responses were all higher than measured (P < 0.05). However, predicted Tc agreed closer with measured Tc for LF when leg muscle blood flow was increased in the simulation. This suggests that blood flow may contribute to the rapid decline in Tc observed in LF and its variance may cause in part the individual differences in Tc responses. CTM predicts Tc responses to immersion at various depths with acceptable accuracy for NF individuals in this study and can be adapted to non-uniform environments.

BKEmission Spectra for MgB2and Al-doped MgB2

Recently, MgB2 has been shown to be a superconductor with Tc 1⁄4 39K by Nagamatsu et al. Since this discovery, the nature of the superconductivity in MgB2 has been studied using B isotope effect, neutron inelastic scattering and band calculations, among others. The results strongly suggest that MgB2 is a conventional BCS-type phononmediated superconductor. At the same time, a new superconductor from MgB2 as a starting material is being developed. Al-doped MgB2 (e.g. Mg1 xAlxB2) was one of the materials whose superconductivity was determined. Unfortunately, it could not attain a higher Tc, but it can contribute to the development of a new superconductor with a higher Tc. Band calculation is one of the methods used in such studies. Neaton and Perali showed that a decrease in the unit cell volume by Al doping decreases the density of states (DOS) at the Fermi level resulting in a decline in Tc. Suzuki et al. showed that holes disappear at about x 1⁄4 0:6, at which the Fermi level is equal to the top of the band. The B-NMR study by Kotegawa et al. showed that the decline in Tc by Al doping is due to the decrease in DOS at the Fermi level. To confirm these results, soft-X-ray emission (SXE) spectroscopy is a useful method. Since the SXE spectrum reflects the partial density of states (PDOS) of the valence band, B K emission for MgB2 shows the PDOS of the B 2p band. B 2p is a dominant component of the Fermi level, which is closely related with the Tc of superconductors. Thus, the B K emission spectra of MgB2 and related materials provide much information on the superconductivity of MgB2. B K emission spectra for MgB2, 13–15) AlB2 16) and other diborides have already been reported, but not yet for Al-doped MgB2. In this paper, we will show the B K emission spectra measured for MgB2 (x 1⁄4 0) and Mg0:8Al0:2B2 (x 1⁄4 0:2). We further discuss the spectra by comparing with those obtained by band calculations and soft-X-ray absorption (SXA), which show the PDOS of the conduction band. The samples were sintered polycrystals of MgB2 and Mg0:8Al0:2B2. Phase purity and the Tc of the samples were estimated before the SXE measurement. X-ray diffraction patterns showed that all the samples were of a hexagonal phase. The diffraction peaks for MgB2 were sharp, with the lattice constants a 1⁄4 0:3086 nm and c 1⁄4 0:3524 nm, and those for Mg0:8Al0:2B2 were broadened. Numerous reports showed that at this Al content region, Al-doped MgB2 tends to include another hexagonal phase with slightly different lattice constants, and its diffraction peaks are broadened or split. Broad diffraction peaks reflected these effects. The diffraction peaks shifted towards larger angles for Mg0:8Al0:2B2, denoting that lattice constants decreased in Mg0:8Al0:2B2. The temperature-dependent magnetization measurements showed that the Tc values of the samples were 39K for MgB2 and 29K for Mg0:8Al0:2B2, respectively. An SXE experiment was performed at BL-16B of the Photon Factory, KEK. The FWHM of the incident synchrotron radiation soft X-ray at an excitation energy of 191.1 eV was 0.5 eV. The SXE spectrometer utilized was a planefocusing type with a 1200-grooves/mm grating. The energy resolution of the spectrometer was about 0.8 eV around 200 eV near the B K emission. The sample preparation chamber was combined with the spectrometer. In this chamber, we can file the samples to remove surface contaminations without air exposure. Figure 1 shows the results of the SXE experiment. The solid and open circles show the B K SXE spectra for MgB2 and Mg0:8Al0:2B2, respectively, whereas the black and gray lines show the smoothed spectra respectively. These spectra were normalized using the height of the main peak of the smoothed spectra. Those for MgB2 (solid circles and black line) have a main peak at 183.5 eV and a slight shoulder at about 185 eV, and show a monotonic decrease towards the low-energy side of the main peak. The small peak at 191 eV is due to the elastic scattering of the incident soft X-rays (Rayleigh). The spectral feature almost resembles the PDOS obtained by band calculations for MgB2 and SXE spectra already reported. The spectrum for the Mg0:8Al0:2B2 is very similar to that of MgB2, but slightly shifted towards the lowenergy side. The inset in Fig. 1 shows the smoothed spectra used to estimate the peak shift, which was about 0.3 eV. The shift was also confirmed by the higher-order spectra we measured simultaneously. We ascertained that the spectra did not contain oxides after filing by comparing with the B K emission spectrum for B2O3. Thus, the shift is not related with the experimental error. We also measured the B K emission spectrum for Mg0:9Al0:1B2 (x 1⁄4 0:1). Although the

Magnetic properties of LaCo13-based systems

Four polycomponent systems based on LaCo13 have been studied: La(Co1−xFex)13, La(Co1−xAlx)13, La(Co1−x−yFexAly)13, and La0.7Nd0.3(Co0.7Fe0.3)13. These 1:13 systems were studied because of their potential for permanent magnet fabrication. LaCo13 has a high 3d metal content, the highest for any known rare-earth intermetallic, a 13 kG saturation induction, and a high Tc (1318 K). Unfortunately, it is cubic and lacks anisotropy. The substituted systems were examined as a portion of a program to find LaCo13-based systems of applications significance. Replacement of Co in LaCo13 by Fe and/or Al leads to a rapid decline in Tc for all systems studied. Replacement of Co by Al results in a decline in moment, whereas replacement by Fe leads to a rise in moment to 2.39μB/3d atom for La(Co0.4Fe0.6)13, as compared to 2.46μB/3d atom for Fe0.7Co0.3. Analysis of the magnetic data shows that vacancies occur in both half-bands for LaCo13 (4.8 spin up and 3.24 spin down) but in only one half-band in La(Co1−xAlx)13 for x≥0.2. Nd in these systems carries a moment of 3μB, close to that of the free tripositive ion.

Twenty‐four‐hour variations in activity, core temperature, metabolic rate, and respiratory quotient in captive chinese pangolins

AbstractThe circadian rhythms in activity, core temperature (Tc), O2 consumption, CO2 production, and respiratory quotient (RQ) were monitored in four captive Chinese pangolins (Manis pentadactyla). The pangolins were strictly nocturnal, never emerging from their nest before 1600 h, and their intermittent activity continued no later than 0230. As is usual in nocturnal mammals, the highest values observed in Tc, O2 consumption, and CO2 production occurred during the night; the lowest values occurred during the day. The magnitude of the variation in Tc, O2 consumption, CO2 production, and RQ averaged 1.2°C, 1.3 ml O2 kg−1 min−1, 1.2 ml CO2 kg−1 min−1, and 0.24, respectively. The circadian pattern in RQ was independent of activity, Tc, and the metabolic parameters and was of a different character than the patterns exhibited in the other variables. RQ remained constant at either a high or low level for long periods (8–10 h) and then increased or decreased relatively rapidly (1–2h) to the other level as in a square wave, whereas the rhythms in the other variables are similar to sine waves. The sharp increase in RQ was followed by a slow decline in Tc, and the sharp decline in RQ was followed by a slow increase in Tc.

Thermal effects of injecting norepinephrine into hypothalamus of the rat during rest and exercise

Norepinephrine (NE) was injected bilaterally through implanted guide cannulas into the anterior hypothalamus (AH) of conscious male Sprague-Dawley rats (300-360 g) at rest and just before treadmill exercise (21.5 m/min for 30 min). Colonic (Tc), tail-skin (Ts), and ambient (Ta) temperatures were monitored each minute by use of a telethermometer. At rest (Ta = 23 degrees C), intrahypothalamic injections of 0.5-40.0 micrograms of NE, in a total of 1.0 microliter delivered within 30 s, produced a dose-dependent hypothermia with a 3-5 degrees C rise in Ts. NE (10 micrograms) injected 2 min before exercise (Ta = 23 degrees C) caused an immediate rise in Ts and a mean decline in Tc of 0.9 +/- 0.1 degree C (SE) below resting levels during exercise. This decline in Tc was statistically the same as that observed after the injections of 10 micrograms of NE at rest. Under control exercise conditions, Tc rose approximately 1 degree C and was associated with an initial decline (0.5 degrees C) followed by a rise (4.0 degrees C) in Ts. When the alpha-adrenergic receptor blocker phentolamine was injected 5-15 min before exercise, it caused a significant (P < 0.01) elevation in Tc during the ensuing exercise compared with controls. These results indicate that 1) over a dose range 0.5-40.0 micrograms, NE microinjected into the AH of the rt produces only hypothermia; 2) alpha-adrenergic receptors in the AH participate in the mediation of heat dissipation when the thermoregulatory system is challenged by the endogenous heat stress of exercise; and 3) exercise per se provides a nonthermal input to the temperature regulatory system that enhances heat dissipation.