greenteg-core-axillary

Core body temperature measures from a single subject with a non-24 circadian rhythm disorder, aged 33 years old at the start of measurements, weight between 72 and 77.5 kg.<br>The core body temperature measurements were done non-invasively with the GreenTEG CORE Research device, attached to the side of a Polar Pro chest strap band, placed on the axillary per the manufacturer's recommendations. The device captures core body temperature and skin temperature every second (1Hz sampling rate). It can store up to 3.5 days of data and takes 3h30 to 7h for data download, hence the gaps, which are placed during circadian daytime whenever possible. This device is able to measure the core body temperature using dual heat flux method (DHFM) with an in-house AI algorithm that replaces the standard DHFM equation to obtain more reliable readings according to the manufacturer. At the time of this experiment, this was the first and only wearable thermometer using heat flux technology.<br>The measurements are much more reliable since January 2021 so prefer to analyze the data from this date onwards. The device was changed in January 2021 for a new one because the old one broke due to a mechanical pressure flaw in the design. Since January 2021, an experimental attachment design using velcro sticked vertically on the CORE and with a loop around the Polar Pro band was conceived by the author/subject to avoid this mechanical flaw, and this had the unexpected side effect of improving significantly the reliability and extent of the surface of the CORE being in contact with the skin, so that measures are much more reliable and systematically reflect the circadian rhythm. Usually, the circadian night can be detected simply as being periods with a temperature below 36.5°C with this new attachment system.<br>Along with the sleep diaries, this is the most reliable circadian rhythm monitoring marker so far from preliminary results.<br>Note on data columns: most columns are encrypted gibberish data. Only the core body temperature, skin temperature flux 1, and timestamp are accessible and should be processed, the other columns can and should be discarded. More precisely, only the following columns are available (from the manufacturer's documentation):<br>* time [UTC-OFS=+0100] Timestamp of the data point in the format ‘DD:MM:YYYY hh:mm:ss’* timestamp [us] Timestamp in UNIX time in us (microseconds elapsed since January 1th 1970).* Hf_a0 Raw heat flux sensor signal of heat path A in ADC counts (unitless).* Temp_a0 [mC] Uncorrected temperature signal of heat path A in millidegree Celsius.* Cbt [mC] Core body temperature estimation output in millidegrees.<br><br>Note: Cbt needs to be divided by 1000 to get the core body temperature value in celsius degrees.<br>The following columns are not available and can be dropped as they are filled with random values: hf_a1, Temp_a1, ax, ay, az, Battery_voltage [mV].<br>Heat flux sensor A value can be obtained as follows:<br>Heat flux sensor A voltage [in uV] = hf_a0 [in counts] * 1.953125 uV<br><br>Skin temperature for sensor A can be obtained as follows:<br>Skin Temperature A [in °C] = (temp_a0 [in mC] – T0off) /1000<br><br>T0off is an offset that is defined once in the header of each CSV file.<br>There is a gap during January 2021, as this is the period the 1st device broke, before getting replaced by the manufacturer. The new dataset with the new device starts on 21th January 2021, with a new vertically oriented velcro attachment system devised by the author, which prevents the device from breaking and improves skin contact and hence data quality. It is recommended to analyze data after 21th January 2021 as it is likely the least noisy.<br>Each file represents one acquisition session of up to 3.5 days, hence they can be concatenated to study a longer time period.<br>Note: On 2021-05-29T21_25_00, an attempt to optimize further the disposition of the velcro was done by changing the orientation from vertical to diagonal, so that the CORE device was oriented on skin as a losange instead of a square, which would theoretically further increase skin contact and data quality, since the chest strap now pushes on the two corners in the horizontal middle, with much less chances that it gets stuck in a local equilibrium at either of the vertical corners. Unfortunately, the data quality was worse (the high and low phases were not correlated with empirical sleep-wake data anymore, there were no high nor low phases anymore), suggesting that the two heat flux sensors are vertically positioned in the middle line of the device (one temperature sensor at the top and one at the bottom), and hence that a vertical orientation is likely the most optimal orientation despite reduced skin contact compared to diagonal. Hence, on 2021-06-06T01_00_00, the disposition of the velcro band was reverted back to vertical. Only one session was acquired with the diagonal orientation, the file is named accordingly.<br>To postprocess the data for analysis, ensure that the first 30 min of each file / new data collection session is removed, as the sensor takes some time to converge to the true current body temperature. It will always start too high at first (because the equation for dual heat flux will show a high value when the sensor is cold when it was not worn), and then gradually lowers until it converges to the equilibrium which represents the current core body temperature.<br>

本数据集包含一名患有非24小时昼夜节律紊乱（non-24 circadian rhythm disorder）的受试者的核心体温测量数据，测量开始时受试者年龄为33岁，体重介于72至77.5千克之间。
核心体温采用非侵入式方式测量，使用GreenTEG CORE Research设备，该设备安装于Polar Pro胸带侧面，按照制造商建议放置于腋窝区域。该设备以每秒1次（1Hz采样率）的频率采集核心体温与皮肤温度数据，可存储最长3.5天的测量数据，数据下载耗时3.5小时至7小时，因此存在数据间隙，这些间隙尽可能安排在昼夜节律的日间时段。该设备采用双热通量法（dual heat flux method, DHFM）进行核心体温测量，内置人工智能（AI）算法替代标准DHFM方程，以获取更可靠的测量结果；据制造商称，这是当时首款且唯一一款采用热通量技术的可穿戴体温计。
自2021年1月起，测量数据的可靠性大幅提升，建议优先分析该日期之后的数据。2021年1月因旧设备存在设计上的机械压力缺陷损坏，更换了新设备。自2021年1月起，受试者/研究者自行设计了采用魔术贴的新型固定方案：将CORE设备垂直粘贴，并通过魔术贴环固定于Polar Pro胸带上，解决了原设备的机械损坏问题，同时意外显著提升了设备与皮肤的接触可靠性和接触面积，使测量结果更为可靠，且能系统性反映昼夜节律。采用该新型固定方案后，可通过体温低于36.5℃的时段直接识别昼夜节律的夜间阶段。
结合睡眠日记来看，本数据集是目前初步研究中最可靠的昼夜节律监测标志物之一。
关于数据列的说明：多数列均为加密的无意义数据，仅核心体温、热通量传感器1的皮肤温度和时间戳可用于后续处理，其余列均可且应当丢弃。具体而言，仅以下列数据可用（源自制造商文档）：
* time [UTC-OFS=+0100]：数据点时间戳，格式为「DD:MM:YYYY hh:mm:ss」
* timestamp [us]：UNIX时间戳（单位为微秒，即自1970年1月1日起经过的微秒数）
* Hf_a0：热通路A的原始热通量传感器信号，以ADC计数为单位（无量纲）
* Temp_a0 [mC]：热通路A的未校正温度信号，单位为毫摄氏度
* Cbt [mC]：核心体温估计输出值，单位为毫摄氏度

注意：需将Cbt值除以1000，即可得到以摄氏度为单位的核心体温数值。
以下列数据不可用，且因填充随机值可直接丢弃：hf_a1、Temp_a1、ax、ay、az、Battery_voltage [mV]。
热通量传感器A的电压计算方式如下：
热通量传感器A电压（单位为微伏）= hf_a0（单位为计数）× 1.953125 μV

传感器A的皮肤温度计算方式如下：
皮肤温度A（单位为℃）= (temp_a0 [单位为mC] – T0off) / 1000
其中T0off为偏移量，在每个CSV文件的文件头中一次性定义。
2021年1月存在数据间隙，该时段为第一台设备损坏至制造商更换设备的期间。搭载新设备的新数据集始于2021年1月21日，搭配受试者自行设计的垂直魔术贴固定方案，该方案可防止设备损坏，并优化了设备与皮肤的接触，进而提升数据质量。建议优先分析2021年1月21日之后的数据，该部分数据的噪声水平最低。
每个文件代表一次最长3.5天的采集会话，因此可通过拼接文件以研究更长的时间周期。
补充说明：2021年5月29日T21:25:00，尝试对魔术贴的固定方式进行优化，将垂直方向改为斜向，使CORE设备在皮肤上呈菱形而非方形排布，理论上可进一步提升皮肤接触面积与数据质量——此时胸带将在水平中线的两个角施加压力，减少设备卡在垂直方向角落的局部平衡状态的概率。但实际数据质量反而下降（体温高低相位不再与实测睡眠-觉醒数据相关，且无明显高低相位变化），这表明设备的两个热通量传感器沿设备中线垂直布置（顶部与底部分别设有一个温度传感器），因此尽管斜向固定的皮肤接触面积更大，垂直固定仍为最优方案。因此在2021年6月6日T01:00:00，魔术贴带的固定方式重新改回垂直方向。仅存在一次采用斜向固定方式的采集会话，对应文件名也已标注。
数据后处理建议：为进行分析，需移除每个文件/新采集会话的前30分钟数据，因为传感器需要一定时间才能收敛至真实的当前核心体温。初始阶段传感器读数总是偏高（因为当传感器处于未佩戴的低温状态时，双热通量方程会显示较高数值），随后会逐渐降低直至平衡，此时的平衡值即为当前核心体温。