We present optical spectra of 10 Galactic Wolf-Rayet(WR)stars that consist of five WN and five WC stars.The optical observation was conducted using a low-resolution spectrograph NEO-R1000(λ/Δλ~1000)at GAO-ITB RTS(2...We present optical spectra of 10 Galactic Wolf-Rayet(WR)stars that consist of five WN and five WC stars.The optical observation was conducted using a low-resolution spectrograph NEO-R1000(λ/Δλ~1000)at GAO-ITB RTS(27.94 cm,F/10.0),Bosscha Observatory,Lembang.We implemented stellar atmosphere Postdam Wolf-Rayet(PoWR)grid modeling to derive stellar parameters.The normalized optical spectrum can be used to find the best model from the available PoWR grid,then we could derive stellar temperature and transformation radius.To derive luminosity,stellar radius and color excess,we conducted a Spectral Energy Distribution(SED)analysis with additional data on the near-ultraviolet spectrum from the International Ultraviolet Explorer(IUE)database,and UBV and 2MASS JHK broadband filter data.Additional analysis to derive asymptotic terminal wind velocity was conducted from the P-Cygni profile analysis of the high-resolution IUE ultraviolet spectrum.With previously derived parameters,we could determine the mass loss rate of the WR stars.Furthermore,we compared our results with previous work that used PoWR code and the differences are not more than 20%.We conclude that the PoWR spectral grid is sufficient to derive WR stellar parameters quickly and could provide more accurate initial parameter input to the PoWR program code.展开更多
With a one-dimensional stellar evolution model,we find that massive main sequence stars can accrete mass at very high mass accretion rates without expanding much if they lose a significant fraction of this mass from t...With a one-dimensional stellar evolution model,we find that massive main sequence stars can accrete mass at very high mass accretion rates without expanding much if they lose a significant fraction of this mass from their outer layers simultaneously with mass accretion.We assume the accretion process is via an accretion disk that launches powerful jets from its inner zones.These jets remove the outer high-entropy layers of the mass-accreting star.This process operates in a negative feedback cycle,as the jets remove more envelope mass when the star expands.With the one-dimensional model,we mimic the mass removal by jets by alternating mass addition and mass removal phases.For the simulated models of 30M☉and 60M☉,the star does not expand much if we remove more than about half of the added mass in not-too-short episodes.This holds even if we deposit the energy the jets do not carry into the envelope.As the star does not expand much,its gravitational potential well stays deep,and the jets are energetic.These results are relevant to bright transient events of binary systems powered by accretion and the launching of jets,e.g.,intermediate luminosity optical transients,including some luminous red novae,the grazing envelope evolution,and the 1837–1856 Great Eruption of Eta Carinae.展开更多
目的调查分析办公室职员肌肉质量减少发生率及影响因素,构建并验证风险预测模型,为制定干预方案提供参考。方法选取2023年3月至2023年12月在四川大学华西医院健康管理中心体检的事业单位、机关单位办公室职员和退休者286人,采用食物频...目的调查分析办公室职员肌肉质量减少发生率及影响因素,构建并验证风险预测模型,为制定干预方案提供参考。方法选取2023年3月至2023年12月在四川大学华西医院健康管理中心体检的事业单位、机关单位办公室职员和退休者286人,采用食物频率调查问卷、运动情况调查问卷、体格检查、人体成分分析、实验室检查等进行分析。使用R语言(R Studio,版本4.4.1)分析肌肉质量影响因素,建立风险预测模型并进行验证。结果肌肉质量减少发生率26.22%;高血糖、低体质量指数(body mass index,BMI)为肌肉质量减少的危险因素,高血尿素/血肌酐(blood urea nitrogen to serum creatinine,BUN/Cr)、每天实际摄入能量/每日推荐摄入能量比、高新鲜水果、高握力评分、超重是肌肉质量减少的保护因素,并构建模型;验证该模型的ROC曲线下面积为0.83,Youden指数为0.52,最佳风险阈值取14.40%。Hosmer-Lemeshow检验和校准曲线评估模型拟合度较高(χ^(2)=11.98,P=0.152),预测模型的阈值概率值在0.07~0.93。结论本研究预测模型具有较好的预测效果和拟合程度,利于医技护人员评估发生肌肉质量减少的风险,有助于为办公室职员肌肉质量减少高危人群提供参考尽早预防。展开更多
基金supported through HLM’s Program Penelitian Pengabdian Masyarakat ITB(P2MI)Astronomy Division,FMIPA ITB grant 2022-2023Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts。
文摘We present optical spectra of 10 Galactic Wolf-Rayet(WR)stars that consist of five WN and five WC stars.The optical observation was conducted using a low-resolution spectrograph NEO-R1000(λ/Δλ~1000)at GAO-ITB RTS(27.94 cm,F/10.0),Bosscha Observatory,Lembang.We implemented stellar atmosphere Postdam Wolf-Rayet(PoWR)grid modeling to derive stellar parameters.The normalized optical spectrum can be used to find the best model from the available PoWR grid,then we could derive stellar temperature and transformation radius.To derive luminosity,stellar radius and color excess,we conducted a Spectral Energy Distribution(SED)analysis with additional data on the near-ultraviolet spectrum from the International Ultraviolet Explorer(IUE)database,and UBV and 2MASS JHK broadband filter data.Additional analysis to derive asymptotic terminal wind velocity was conducted from the P-Cygni profile analysis of the high-resolution IUE ultraviolet spectrum.With previously derived parameters,we could determine the mass loss rate of the WR stars.Furthermore,we compared our results with previous work that used PoWR code and the differences are not more than 20%.We conclude that the PoWR spectral grid is sufficient to derive WR stellar parameters quickly and could provide more accurate initial parameter input to the PoWR program code.
基金A grant from the Pazy Foundation supported this research.
文摘With a one-dimensional stellar evolution model,we find that massive main sequence stars can accrete mass at very high mass accretion rates without expanding much if they lose a significant fraction of this mass from their outer layers simultaneously with mass accretion.We assume the accretion process is via an accretion disk that launches powerful jets from its inner zones.These jets remove the outer high-entropy layers of the mass-accreting star.This process operates in a negative feedback cycle,as the jets remove more envelope mass when the star expands.With the one-dimensional model,we mimic the mass removal by jets by alternating mass addition and mass removal phases.For the simulated models of 30M☉and 60M☉,the star does not expand much if we remove more than about half of the added mass in not-too-short episodes.This holds even if we deposit the energy the jets do not carry into the envelope.As the star does not expand much,its gravitational potential well stays deep,and the jets are energetic.These results are relevant to bright transient events of binary systems powered by accretion and the launching of jets,e.g.,intermediate luminosity optical transients,including some luminous red novae,the grazing envelope evolution,and the 1837–1856 Great Eruption of Eta Carinae.
文摘目的调查分析办公室职员肌肉质量减少发生率及影响因素,构建并验证风险预测模型,为制定干预方案提供参考。方法选取2023年3月至2023年12月在四川大学华西医院健康管理中心体检的事业单位、机关单位办公室职员和退休者286人,采用食物频率调查问卷、运动情况调查问卷、体格检查、人体成分分析、实验室检查等进行分析。使用R语言(R Studio,版本4.4.1)分析肌肉质量影响因素,建立风险预测模型并进行验证。结果肌肉质量减少发生率26.22%;高血糖、低体质量指数(body mass index,BMI)为肌肉质量减少的危险因素,高血尿素/血肌酐(blood urea nitrogen to serum creatinine,BUN/Cr)、每天实际摄入能量/每日推荐摄入能量比、高新鲜水果、高握力评分、超重是肌肉质量减少的保护因素,并构建模型;验证该模型的ROC曲线下面积为0.83,Youden指数为0.52,最佳风险阈值取14.40%。Hosmer-Lemeshow检验和校准曲线评估模型拟合度较高(χ^(2)=11.98,P=0.152),预测模型的阈值概率值在0.07~0.93。结论本研究预测模型具有较好的预测效果和拟合程度,利于医技护人员评估发生肌肉质量减少的风险,有助于为办公室职员肌肉质量减少高危人群提供参考尽早预防。
文摘锂离子电池(LIB)的高效热管理对其性能和寿命至关重要,浸没式冷却技术因其优异的散热能力成为研究热点.然而,现有研究在浸没介质选择和减少质量损失方面存在不足.为此,本研究构建了一个实验平台,测试放电倍率为10 C的电池在浸没式冷却下的热管理性能,并提出了一种密封性能优异的双腔换热器(DCHE),探究了三种冷凝换热模式(自然对流、冷却液自然对流、循环冷却液强制对流)和三种电子氟化液(EFL:D2、FW-92、HFE-347)对温控特性的影响.结果表明,DCHE的循环冷却液强制对流能够兼顾潜热传导和减少质量损失,而HFE-347在三种EFL中表现最优,可将电池模组的平均温度(AT)控制在44.44℃,最大温差(MTD)控制在4.4℃,质量损失(ML)仅为21.4 g.
文摘[目的]比较极外侧腰椎间融合术(extreme lateral interbody fusion, XLIF)结合侧卧位单侧椎弓钉固定(unilateral pedicle screw fixation, UPSF)与俯卧位双侧椎弓钉固定(bilateral pedicle screw fixation, BPSF)治疗骨量减少腰椎退变患者的临床疗效。[方法]回顾性分析接受XLIF手术治疗伴有骨量减少的单节段腰椎退变75例患者的临床资料。依据术前医患沟通结果,25例采用UPSF,50例采用BPSF,比较两组围手术期、随访、影像资料。[结果]两组手术均顺利完成,UPSF组手术时间[(73.6±10.6) min vs (84.8±12.2) min, P<0.001]、切口长度[(9.9±1.3) cm vs (14.0±1.4) cm, P<0.001]、术中出血量[(63.4±17.2) ml vs(86.7±10.8) ml, P<0.001]、术中透视次数[(6.2±1.2)次vs (13.1±1.6)次, P<0.001]均显著少于BPSF组。随访时间13~24个月,两组恢复完全负重活动时间的差异无统计学意义(P>0.05)。随时间推移,两组患者腰痛VAS评分、腿痛VAS评分、ODI评分均显著改善(P<0.05)。术后1周,UPSF组腰痛的VAS评分[(2.5±0.9) vs (2.9±0.7), P<0.001]显著优于BPSF组。影像方面,与术前相比,末次随访时两组椎管面积、椎间隙高度、腰椎前凸角、融合评级均显著改善(P<0.05),相应时间点,两组间上述影像指标的差异均无统计学意义(P>0.05)。末次随访两组内固定松动的差异无统计学意义(P>0.05)。[结论] XLIF结合BPSF和计算机辅助导航的侧卧位UPSF治疗骨量减少的腰椎退行性疾病患者均安全有效。与BPSF相比,UPSF组术中出血量少、透视次数少、手术时间短,术后恢复快。
