Higher-Order Allan Variance for Atomic Clocks of Arbitrary Order

In this paper, we perform a time-domain analysis of the higher-order Allan variance for atomic clock models of arbitrary order. Adopting a standard atomic clock model where the time series of the clock reading deviation is expressed as a Wiener or integrated Wiener process, we define the higher-order Allan variance as the mean squared higher-order difference of the clock reading deviation. The main results of this paper are threefold. First, we prove that the higher-order difference operation of the clock reading deviation, which can be interpreted as a linear aggregation with binomial coefficients, is not only sufficient, but also necessary for a resulting aggregated time series to be an independent and identically distributed Gaussian process. Second, we derive a complete analytical expression of the higher-order Allan variance, which consists of both time-dependent and time-independent terms. Third and finally, we prove that the higher-order Allan variance is time-independent if and only if the order of difference operation is greater than or equal to the order of the atomic clock model

パルス励起によるCoherent Population Trapping原子発振器の特性改善に関する研究

Coherent Population Trapping（以下 CPT）共鳴を利用した原子発振器は，小型かつ省電力でありながら原子の遷移周波数を基準とするため高い周波数安定度を有することが特徴である．近年では，小型情報端末，センサーネットワーク，測位衛星，車載向けなど体積と消費電力が制限される機器への搭載に向けてCPT原子発振器の小型化，省電力化，高安定化の研究，開発が進められている．一般に，原子発振器には高い周波数安定度が要求され，安定度を高める方法として Double-Λ法 [6] やPush-Pull光ポンピング法 [7] など，種々提案されている [8]．しかし，これまでの提案法は複雑な光学系と高い消費電力を要するため，小型原子発振器への適用は困難であった．そこで本研究は小型原子発振器に適用できる小型で低電力動作可能な改善法として，パルス励起に着目した．一般的に周波数安定度はアラン標準偏差で表される [9;10;11]．原子発振器の場合には，安定度は平均化時間により短期と長期の２つに分類される [12]．短期安定度は共鳴のS/N比とQ値の積で理論的性能が決まる [13]．S/N比改善のためには高い光強度で励起する必要があるが，高い光強度はパワーブロードニングによるQ値低下を招くため，S/N比とQ値を同時に改善するのは難しい [14]．長期安定度は，共鳴の測定条件が時間的に変化し，周波数が変動することで劣化する．周波数変動の支配的な要因はライトシフトであり，光学素子類の経年劣化により光強度変化が生じた際に周波数が変動する [15;16;17] したがって，周波数安定度を改善するためには，S/N比とQ値の向上とライトシフトの低減が求められる．近年，パルス励起による特性改善が注目されている [6;18;19;20;21]．パルス励起は，ラムゼイ干渉を利用する方法で，パワーブロードニング抑制とライトシフト低減が可能となり，短期，長期ともに高い安定度が得られる [18]．しかし，パルス励起で使用される音響光学変調器は体積と消費電力が大きく，小型原子発振器への適用は困難である．また，ライトシフトは長期安定度劣化の主要因であるが，その低減効果は実験による報告のみで，理論的解明は行われていなかった．それゆえ，最適な実験条件は明らかでなく，更なる長期安定度改善のため，ライトシフトの理論的な解明が望まれていた．そこで本研究は，小型原子発振器に適用できる小型で低電力動作可能な改善法として，パルス励起に関する研究を行った．パルス励起が小型かつ省電力動作可能なこと，提案する解析法によりライトシフトの振る舞いを定量的に解析可能なことを示した．本論文では，まず，パルス励起によるCPT共鳴の解析および実験からパワーブロードニング抑制効果とライトシフト低減効果を明らかにし，パルス励起の有効性を確認する．次に，小型で低消費電力な改善方法として透過型液晶を用いたパルス励起を提案し，共鳴特性が改善されることを示す．加えて，発振器の更なる省電力化を目指し，高次高調波による励起を検討し，RF回路の大幅な省電力化を図る．最後に，S/N比改善法として直交偏光子法を提案する．首都大学東

Heterogeneous Effects of Intensive Glycemic and Blood Pressure on Cardiovascular Events Among Diabetes by Living Arrangements

糖尿病患者における厳格な血糖・血圧管理の効果が、居住形態によって異なることが明らかに. 京都大学プレスリリース. 2024-07-03.Background: Although living alone versus with others is a key social element for cardiovascular prevention in diabetes, evidence is lacking about whether the benefit of intensive glycemic and blood pressure (BP) control differs by living arrangements. We thus aim to investigate heterogeneity in the joint effect of intensive glycemic and BP control on cardiovascular events by living arrangements among participants with diabetes. Methods and results: This study included 4731 participants with diabetes in the ACCORD-BP (Action to Control Cardiovascular Risk in Diabetes-Blood Pressure) trial. They were randomized into 4 study arms, each with glycated hemoglobin target (intensive, <6.0% versus standard, 7.0-7.9%) and systolic BP target (intensive, <120 mm Hg versus standard <140 mm Hg). Cox proportional hazard models were used to estimate the joint effect of intensive glycemic and BP control on the composite cardiovascular outcome according to living arrangements. At a mean follow-up of 4.7 years, the cardiovascular outcome was observed in 445 (9.4%) participants. Among participants living with others, intensive treatment for both glycemia and BP showed decreased risk of cardiovascular events compared with standard treatment (hazard ratio [HR], 0.68 [95% CI, 0.51-0.92]). However, this association was not found among participants living alone (HR, 0.96 [95% CI, 0.58-1.59]). P for interaction between intensive glycemic and BP control was 0.53 among participants living with others and 0.009 among those living alone (P value for 3-way interaction including living arrangements was 0.049). Conclusions: We found benefits of combining intensive glycemic and BP control for cardiovascular outcomes among participants living with others but not among those living alone. Our study highlights the critical role of living arrangements in intensive care among patients with diabetes

Racial Differences in Abnormal Ambulatory Blood Pressure Monitoring Measures: Results From the Coronary Artery Risk Development in Young Adults (CARDIA) Study

Background: Several ambulatory blood pressure monitoring (ABPM) measures have been associated with increased cardiovascular disease risk independent of clinic blood pressure (BP). African Americans have higher clinic BP compared with Whites but few data are available on racial differences in ABPM measures. Methods: We compared ABPM measures between African American (n = 178) and White (n = 103) participants at the Year 5 Coronary Artery Risk Development in Young Adults study visit. BP was measured during a study visit and the second and third measurements were averaged. ABPM was conducted over the following 24 hours. Results: Mean ± SD age of participants was 29.8±3.8 years and 30.8±3.5 years for African Americans and Whites, respectively. Mean daytime systolic BP (SBP) was 3.90 (SD 1.18) mm Hg higher among African Americans compared with Whites (P < 0.001) after age–gender adjustment and 1.71 (SD 1.03) mm Hg higher after multivariable adjustment including mean clinic SBP (P = 0.10). After multivariable adjustment including mean clinic SBP, nighttime SBP was 4.83 (SD 1.11) mm Hg higher among African Americans compared with Whites (P < 0.001). After multivariable adjustment, the African Americans were more likely than Whites to have nocturnal hypertension (prevalence ratio: 2.44, 95% CI: 0.99–6.05) and nondipping (prevalence ratio: 2.50, 95% CI: 1.39–4.48). The prevalence of masked hypertension among African Americans and Whites was 4.4% and 2.1%, respectively, (P = 0.49) and white coat hypertension was 3.3% and 3.9%, respectively (P = 0.99). Twenty-four hour BP variability on ABPM was higher among African Americans compared with Whites. Conclusions: These data suggest racial differences in several ABPM measures exist

Associations of cortisol/testosterone and cortisol/sex hormone-binding globulin ratios with atherosclerosis in middle-age women

AbstractBackground and aimsThe cortisol/testosterone (C/T) ratio has been hypothesized to be a better predictor of atherosclerosis than cortisol alone. No study has assessed whether the C/T and C/sex hormone-binding globulin (SHBG) ratios are associated with atherosclerosis in a U.S. population sample.MethodsThis substudy included 367 women who had both cortisol from year 15 and testosterone and SHBG at year 16 of the Coronary Artery Risk Development in Young Adults study, an ongoing observational cohort in the United States. Of these, intima-media thickness (IMT) was available at follow-up year 20 in 339 (n = 332 with measurement at carotid bulb), and 303 were free of prevalent coronary artery calcium (CAC) at year 15. Area under the curve (AUC) of salivary cortisol was available in 302 individuals. Ratios of AUCs of cortisol to total testosterone, free testosterone, and SHBG were categorized into tertiles. Associations with CAC and IMT were assessed by regression models adjusted for age, race, body mass index, systolic blood pressure, menopause, oral contraceptive use, diabetes, alcohol, and smoking.ResultsOnly the highest tertile of the AUC/free testosterone ratio was positively associated with carotid bulb IMT (β = 0.088, P = 0.006). This tertile was also positively associated with new onset CAC between year 15 and 25 (OR 3.45, 95% CI 1.18–10.06). Tertiles of cortisol or testosterone alone were not associated with new onset CAC.ConclusionAUC/Free testosterone ratio may be more associated with atherosclerosis in women than either indicator alone. The ratio may serve as a suitable biomarker of cortisol-linked stress

Self-reported Age of Hypertension Onset and Hypertension-Mediated Organ Damage in Middle-Aged Individuals

BackgroundObjectively defined early onset hypertension, based on repeated blood pressure measurements, is a strong risk factor for cardiovascular disease (CVD). We aimed to assess if also self-reported hypertension onset age is associated with hypertension-mediated organ damage (HMOD). Additionally, we evaluated the agreement between self-reported and objectively defined hypertension onset age.MethodsWe studied 2,649 participants (50 4 years at the time of outcome assessment, 57% women) of the Coronary Artery Risk Development in Young Adults (CARDIA) study who underwent measurements for echocardiographic left ventricular hypertrophy (LVH), left ventricular diastolic dysfunction (LVDD), coronary calcification, and albuminuria. We divided the participants into groups according to self-reported hypertension onset age (= 45 years, and no hypertension). We used multivariable-adjusted logistic regression models to assess the relation between self-reported hypertension onset age with the presence of HMOD, with those who did not report hypertension as the referent group.ResultsCompared with individuals without self-reported hypertension, self-reported hypertension onset at = 45 years was only associated with LVDD (OR, 1.81; 95% CI, 1.06-3.08). The agreement between self-reported and objectively defined hypertension onset age groups was 78-79%.ConclusionsOur findings suggest that self-reported hypertension onset age, a pragmatically feasible assessment in clinical practice, is a reasonable method for assessing risk of HMOD and CVD

Resveratrol promotes expression of SIRT1 and StAR in rat ovarian granulosa cells: an implicative role of SIRT1 in the ovary

<p>Abstract</p> <p>Background</p> <p>Resveratrol is a natural polyphenolic compound known for its beneficial effects on energy homeostasis, and it also has multiple properties, including anti-oxidant, anti-inflammatory, and anti-tumor activities. Recently, silent information regulator genes (Sirtuins) have been identified as targets of resveratrol. Sirtuin 1 (SIRT1), originally found as an NAD⁺-dependent histone deacetylase, is a principal modulator of pathways downstream of calorie restriction, and the activation of SIRT1 ameliorates glucose homeostasis and insulin sensitivity. To date, the presence and physiological role of SIRT1 in the ovary are not known. Here we found that SIRT1 was localized in granulosa cells of the human ovary.</p> <p>Methods</p> <p>The physiological roles of resveratrol and SIRT1 in the ovary were analyzed. Immunohistochemistry was performed to localize the SIRT1 expression. SIRT1 protein expression of cultured cells and luteinized human granulosa cells was investigated by Western blot. Rat granulosa cells were obtained from diethylstilbestrol treated rats. The cells were treated with increasing doses of resveratrol, and subsequently harvested to determine mRNA levels and protein levels. Cell viability was tested by MTS assay. Cellular apoptosis was analyzed by caspase 3/7 activity test and Hoechst 33342 staining.</p> <p>Results</p> <p>SIRT1 protein was expressed in the human ovarian tissues and human luteinized granulosa cells. We demonstrated that resveratrol exhibited a potent concentration-dependent inhibition of rat granulosa cells viability. However, resveratrol-induced inhibition of rat granulosa cells viability is independent of apoptosis signal. Resveratrol increased mRNA levels of SIRT1, LH receptor, StAR, and P450 aromatase, while mRNA levels of FSH receptor remained unchanged. Western blot analysis was consistent with the results of quantitative real-time RT-PCR assay. In addition, progesterone secretion was induced by the treatment of resveratrol.</p> <p>Conclusions</p> <p>These results suggest a novel mechanism that resveratrol could enhance progesterone secretion and expression of luteinization-related genes in the ovary, and thus provide important implications to understand the mechanism of luteal phase deficiency.</p