Range Of Core Temperatures Research Articles

Magnetars and axion-like particles: probes with the hard X-ray spectrum

Quiescent hard X-ray and soft gamma-ray emission from neutron stars constitute a promising frontier to explore axion-like-particles (ALPs). ALP production in the core peaks at energies of a few keV to a few hundreds of keV; subsequently, the ALPs escape and convert to photons in the magnetosphere. The emissivity goes as ∼ T 6 while the conversion probability is enhanced for large magnetic fields, making magnetars, with their high core temperatures and strong magnetic fields, ideal targets for probing ALPs. We compute the energy spectrum of photons resulting from conversion of ALPs in the magnetosphere and then compare it against hard X-ray data from NuSTAR, INTEGRAL, and XMM-Newton for a set of eight magnetars for which such data exists. Upper limits are placed on the product of the ALP-nucleon and ALP-photon couplings. For the production in the core, we perform a calculation of the ALP emissivity in degenerate nuclear matter modeled by a relativistic mean field theory. The reduction of the emissivity due to improvements to the one-pion exchange approximation is incorporated, as is the suppression of the emissivity due to proton superfluidity in the neutron star core. A range of core temperatures is considered, corresponding to different models of the steady heat transfer from the core to the stellar surface. For the subsequent conversion, we solve the coupled differential equations mixing ALPs and photons in the magnetosphere. The conversion occurs due to a competition between the dipolar magnetic field and the photon refractive index induced by the external magnetic field. Semi-analytic expressions are provided alongside the full numerical results. We also present an analysis of the uncertainty on the axion limits we derive due to the uncertainties in the magnetar masses, nuclear matter equation of state, and the proton superfluid critical temperature.

Managing perioperative hypothermia.

surrounds this thermal core. The peripheral temperature ranges between 31° and 35°C, whereas skin temperature is generally 28° to 32°C [2,4]. The peripheral shell protects the thermal core by either absorbing heat from or releasing heat to the environment. The range of core temperatures that are tolerated without triggering a thermoregulatory response is known as the interthreshold range. This range is normally 0.2°C. Within this range, no autonomic responses to cold or warmth occur. Below the hypothermia threshold, vasoconstriction is triggered, followed by shivering as the temperature decreases further. Peripheral vasoconstriction takes place in arteriovenous shunts located primarily in the fingers and toes. These are controlled by centrally mediated α1-adrenergic receptors, but the vasoconstriction triggered by local hypothermia is augmented by α2adrenergic receptors [3]. Shivering is an involuntary muscular activity that increases metabolic rate and oxygen consumption. The response to body temperatures above the hyperthermia threshold is perspiration. Reliable sites for monitoring the core temperature include the tympanic membrane, the nasopharynx, the distal esophagus, the rectum, and the pulmonary arteries. These reflect core temperature even during rapid cooling or rewarming [5]. The tympanic membrane temperature reflects that of the blood supplying the hypothalamus [6]. Measurement of temperature in the ear canal avoids the risk of tympanic membrane perforation. Esophageal probes are a popular means of temperature monitoring, and the results correlate well with tympanic membrane temperature [7]. It is important to note that the inspired air temperature affects the esophageal temperature and that the esophagus has a large temperature gradient along its length [8]. For investigative purposes, the esophageal probe is placed 12 to 16 cm distal to the best heart–lung sounds [9], but for clinical use it should be placed at the point of maximal heart sounds. Rectal probes have slow response rates and may give inaccurate readings.

The etiology and management of inadvertent perioperative hypothermia.

Mild perioperative hypothermia is a frequent complication of anesthesia and surgery. Core temperature should be monitored during general anesthesia and during regional anesthesia for large operations. Reliable sites of core temperature monitoring include the tympanic membrane, nasopharynx, esophagus, bladder, rectum, and pulmonary artery. The skin surface is not an acceptable site for monitoring core temperature. Anesthetic-induced vasodilation initially rapidly decreases core temperature secondary to an internal redistribution of heat rather than an increased heat loss to the environment. Both general and regional anesthetics impair thermoregulation, increasing the interthreshold range; that is, the range of core temperatures over which no autonomic response to cold or warmth occurs. Preinduction skin surface warming is the only means to prevent this initial redistribution hypothermia. Forced-air warming is the most effective method of rewarming hypothermic patients intraoperatively.

Seasonal variation in heart rate response to core temperature changes

1. 1. The heart rate of normal, intact, unrestrained, unanesthetized, adult male Rana pipiens was studied over a range of core temperatures (16–32°C) throughout a 12-month period. 2. 2. During the summer heart rate response to increasing temperature was linear with a slope of 4·5. 3. 3. During the winter the heart rate response was linear with a slope of 2·9 up to a core temperature of 26°C. At temperatures above this point the response was not as large with a calculated slope of 1·61. Also the linearity above 26°C was not as marked. 4. 4. During intermediate months the response was intermediate with no predictable patterns.