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。
核心体温测量采用非侵入式方式，使用GreenTEG CORE Research研究级设备，该设备安装于Polar Pro胸带侧面，按照制造商推荐的方式置于腋窝区域。该设备以每秒1次（1Hz采样率）的频率同步采集核心体温与皮肤温度数据，最多可存储3.5天的测量数据，数据下载耗时3小时30分钟至7小时，因此存在数据间隙；为尽可能减少对昼夜节律日间时段的干扰，间隙均尽量安排在该时段内。
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）算法替代了标准双热通量法公式，可根据制造商描述获取更可靠的测量结果。在本实验开展时，这是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，测量数据的可靠性显著提升，建议优先分析该日期之后的数据集。2021年1月，原设备因设计存在机械压力缺陷损坏，因此更换为新设备。更换后，受试者本人设计了一款实验性固定附件：采用魔术贴（velcro）垂直粘贴于CORE设备本体，并通过环绕Polar Pro胸带的绑带固定，以规避原有的机械缺陷；该附件意外带来了额外增益：显著提升了设备与皮肤的接触可靠性与接触面积，使得测量结果更为可靠，且能系统性地反映昼夜节律特征。借助该新型固定系统，通常可直接将体温低于36.5℃的时段判定为昼夜节律夜间。
结合睡眠日记来看，该数据集是目前初步研究结果中最可靠的昼夜节律监测标志物之一。
关于数据列的说明：绝大多数列均为加密的乱码数据，仅核心体温、热通量传感器相关皮肤温度以及时间戳三类数据可被正常读取并用于处理，其余列均可且应当直接丢弃。具体而言，根据制造商文档，仅以下列有效：
* time [UTC-OFS=+0100]：数据点的时间戳，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日起累计的微秒数）
* 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（mC）
* Cbt [mC]：核心体温估计输出值，单位为毫摄氏度（mC）
注意：需将Cbt值除以1000，方可得到以摄氏度为单位的核心体温数值。
以下列无有效数据，均为随机填充值，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（单位为微伏，uV）可通过如下公式计算：
热通量传感器A电压 [uV] = hf_a0 [计数] × 1.953125 uV
传感器A的皮肤温度可通过如下公式计算：
皮肤温度A [°C] = (Temp_a0 [mC] – T0off) / 1000
其中T0off为偏移量，仅在每个CSV文件的文件头中定义一次。
2021年1月存在数据间隙，该时段为原设备损坏至制造商更换新设备的间隔期。搭载新型固定系统的新数据集起始于2021年1月21日，建议优先分析该日期之后的数据，因其噪声水平最低。
每个文件对应一段最长3.5天的采集会话，因此可通过拼接多个文件以研究更长时间跨度的数据集。
注意：2021年5月29日T21_25_00时段，受试者尝试进一步优化魔术贴的固定方式，将垂直方向调整为斜向，使CORE设备在皮肤上呈菱形而非方形排布；理论上该调整可进一步提升皮肤接触面积与数据质量，因胸带将在水平中线的两个拐角处施加压力，降低了设备卡在垂直拐角局部平衡状态的概率。但实际效果适得其反：数据质量显著下降（体温高低相位不再与实测睡眠-觉醒数据相关，且无明显高低相位波动），这表明设备内部的两个热通量传感器沿设备中线垂直排布（一个位于顶部，一个位于底部），因此尽管斜向排布的皮肤接触面积更大，垂直方向仍为最优取向。据此，2021年6月6日T01_00_00时段，魔术贴绑带的固定方式被重新调整回垂直方向。本次斜向固定仅开展了一次采集会话，对应文件名也已标注该调整。
如需对数据进行后处理以用于分析，需移除每个文件/新采集会话的前30分钟数据。这是因为传感器需要一定时间收敛至真实的当前体温：初始阶段传感器读数会偏高（因当传感器处于未佩戴的低温状态时，双热通量法公式会输出偏高值），随后会逐步降低直至收敛至代表当前核心体温的平衡值。