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Comparison of double sensor, skin, and rectal temperature recording for determining circadian rhthm
No full textBackground: In chronobiology studies, the circadian rhythm of core body temperature has often been monitored via rectal temperature recordings. Compliance with rectal recordings, however, limits voluntary participation and prevents a broader spectrum of investigations. With the progress of technology, systems have been developed which allow a measurement of the core body temperature from an intact skin surface, such as the Double Sensor [1], a skin surface temperature and heat-flux combining device. Studies regarding how well such systems reflect the circadian rhythm of core body temperature, however, are lacking.
Material & Methods: As part of the 2nd Berlin BedRest Study (BBR2-2), subjects underwent micro-g simulated conditions, i.e. 6° head-down tilt bed-rest. On bed-rest day 49, 24 hours temperature profiles were obtained in seven health men by a single skin surface temperature sensor and the Double Sensor, each placed at forehead (Tfhd, DSfhd) and sternum (Tste, DSste), and by a rectal probe (Trec). The degree of parallelism between measured temperature variables was assessed by calculating the Pearson correlation coefficient r. Rhythm characteristics determined by fitting a single cosine curve included MESOR, amplitude, and acrophase, and were statistically tested for significance by Student's paired t- test.
Results: Averaged value (± SD) of Pearson’s r was .867 (.059), .797 (.097), .519 (.373), -.021 (.549) for correlation between Trec with DSfhd, Tfhd, DSste, and Tste, respectively. The correlation mean demonstrated a good parallelism between Trec and temperatures obtained from the forehead. Regarding the rhythm parameters MESOR, amplitude, and acrophase, no significant difference was found between Trec and DSfhd, but between Tfhd and DSfhd as well as between Tfhd and Trec.
Discussion & Conclusions: Not the skin surface temperature recordings, but the temperatures of the Double Sensor from the forehead seem promising for determining the circadian rhythm of core body temperature in occupational and environmental medicine on earth and space, where the use of rectal probes is not feasible or desired.
References: 1. Gunga HC, Sandsund M, Reinertsen RE, Sattler F and Koch J. A non-invasive device to continuously determine heat strain in humans. Journal of Thermal Biology 33: 297-307, 2008
Comparison of double sensor, skin, and rectal temperature recordings for determining circadian rhythm
No full textIntroduction
In chronobiology studies, the circadian rhythm of core body temperature has often been monitored via rectal
temperature recordings. Compliance with rectal recordings, however, limits voluntary participation and prevents a
broader spectrum of investigations. With the progress of technology, systems have been developed which allow a
measurement of the core body temperature from an intact skin surface, such as the Double Sensor [1], a skin
surface temperature and heat-flux combining device. Studies regarding how well such systems reflect the
circadian rhythm of core body temperature, however, are lacking.
Material & Methods
As part of the 2nd Berlin BedRest Study (BBR2-2), subjects underwent micro-g simulated conditions, i.e. 6° headdown
tilt bed-rest. On bed-rest day 49, 24 hours temperature profiles were obtained in seven healthy men by a
single skin surface temperature sensor and the Double Sensor, each placed at forehead (Tfhd, DSfhd) and sternum
(Tste, DSste), and by a rectal probe (Trec). The degree of parallelism between measured temperature variables was
assessed by calculating the Pearson correlation coefficient r. Rhythm characteristics determined by fitting a single
cosine curve included MESOR, amplitude, and acrophase, and were statistically tested for significance by
Student's paired t-test.
Results
Averaged value (± SD) of Pearson’s r was .867 (.059), .797 (.097), .519 (.373), -.021 (.549) for correlation
between Trec with DSfhd, Tfhd, DSste, and Tste, respectively. The correlation mean demonstrated a good parallelism
between Trec and temperatures obtained from the forehead. Regarding the rhythm parameters MESOR,
amplitude, and acrophase, no significant difference was found between Trec and DSfhd, but between Tfhd and DSfhd
as well as between Tfhd and Trec.
Discussion & Conclusions
Not the skin surface temperature recordings, but the temperatures of the Double Sensor from the forehead seem
promising for determining the circadian rhythm of core body temperature in occupational and environmental
medicine on earth and space, where the use of rectal probes is not feasible or desired
Phase shifts of circadian core body temperature profiles during Mars500
No full textA growing body of research indicates that a misalignment of circadian rhythms can be detrimental
to mental and physical health. Long-term space missions may also potentially alter circadian rhythms,
and pose a critical risk to crew health and safety. The long-term impact of isolation and confinement on
circadian rhythms has not been fully characterized. We here assessed the impact of the Mars500 study
on the circadian phase of core body temperature (CBT). CBT was recorded continuously for 24 h at
the forehead using a recently proposed heat-flux technique (Double Sensor) [1] before (BDC) and during
(ISO-20, ISO-60, ISO-140, ISO-200, ISO-260, ISO-320, ISO-400, ISO-460) the mission. Each recording
was then subjected to cosinor analysis to determine acrophase for each subject and session. A linear mixed
model treating “Time” as fixed e↵ect was fit to phase, including random e↵ects (intercepts and slopes) to
account for individual subject variation. To analyze whether the rate of change in CBT was characterized
by nonlinear changes over time, quadratic and cubic models were also considered. In spite of substantial
inter-individual variation, visual inspection of the data indicated a phase advance during the first half of
the mission (+1.4 h), after which phase returned to baseline again (phase delay of about -1.2 h relative
to first mission half). At ISO-460 phase sharply advanced again to similar levels observed during the first
half of the mission. This pattern was confirmed by significant linear, quadratic and cubic components of
the mixed model (P<0.05). This third degree polynomial trend is well in line with recent data, showing
substantial di↵erences for sleep-wake cycles between the first and last the part of the 520-d mission [2].
We suggest that this specific pattern is related to a highly controlled diet, which was administered during
the first half of the mission. This diet required very strict meal times, which are well known to be strong
nonphotic cues for circadian entrainment [3]. In contrast, we speculate that the sudden phase advance
after 400 mission days could be related to the exposure of blue light, which was exclusively employed
during days 439-499 only. In conclusion, the present results indicate that long-term isolation can induce
significant changes in the circadian timing system, which might be attributed to specific nonphotic and
photic cues of the Mars500 experiment.
[1] Respir Physiol Neurobiol, 169 (2009) S63-S68 [2] PNAS, 110 (2013) 2635-2640 [3] Science, 320
(2008) 1074–107
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Physical Exercise : A Countermeasure Against Disruptions of the Circadian Timing System During Spaceflight?
No full textA growing body of research indicates that any de-synchronization of the circadian Timing system (CTS) can be detrimental to mental and physical health [1]. It has also been reported that space mission can induce a misalignment of the CTS, and substantially impact crew health and safety [2]. Physical exercise on the other hand has recently been outlined as a potential countermeasure to promote the entrainment of the CTS. Previous studies investigating the role of exercise on the CTS have, however, often lacked strictly controlled laboratory conditions isolating the effects that can be purely attributed to exercise. Bedrest offers an excellent model not only for simulating fluid shifts observed during micro-g exposure, but also exposes subjects to semi-isolation and confinement while allowing to strictly control various potential confounding effects. The aim of the present study was therefore (1) To investigate the effect of 60 days of bed-rest on circadian rhythm. (2) To investigate if any changes in circadian rhythm can be compensated by resistance exercise (RES) or resistance exercises superimposed by whole-body vibrations (RVE). 24 healthy men were exposed to 60 days of 6-degree head-down tilt bed-rest as part of the Berlin Bed-rest Study 2 (BBR2-2). Subjects were randomly allocated to a resistance (RES), a combined resistance and vibration exercise (RVE), or a control (CTR) group. Core body temperature profiles for 36 h (7.30 p.m. to +1d 6.30 a.m.) were determined at week 1 and week 7 using a non-invasive heatflux sensor (Double Sensor) positioned at the forehead. Cosinor analysis was employed to quantify circadian rhythm by mesor, acrophase, and amplitude. Bed-rest induced a phase delay of 45 min in CTR (P = 0.051). This delay was offset by both exercise groups, indicating that exercise may also induce a phase advance. In addition, CTR showed more variation in circadian rhythmicity compared to RVE and RE. The effect of exercise on advancing phase confirms previous findings [3,4], supporting the notion that exercise may potentially offset disruptions of circadian rhythm. Future studies should therefore consider investigating the role of exercise as a countermeasure when circadian rhythm is prone to misalignments during long-term spaceflight
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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