The boiling suppression of liquid nitrogen

When He gas is injected from room temperature into boiling liquid N$_{2}$, boiling is suppressed, leaving liquid surface flat like a mirror. Although the qualitative explanation for this phenomenon is known [Minkoff G J \textit{et al}. Nature 1957;180(4599):1413-4.], it has not been studied quantitatively and comprehensively yet. In this report, we made careful simultaneous measurements of temperature and weight variation of the liquid. The results clearly indicate that the boiling suppression is caused by cooling of the liquid with "internal evaporation" of N$_{2}$ into the He bubbles.Comment: 14 pages, 7 figure

Hypernova Nucleosynthesis and Implications for Cosmic Chemical Evolution

We examine the characteristics of nucleosynthesis in 'hypernovae', i.e., supernovae with very large explosion energies (\gsim 10^{52} ergs). Implications for the cosmic chemical evolution and the abundances in M82 are discussed.Comment: To appear in 'Cosmic Evolution' Conference at IAP, Paris, honoring Jean Audouze and Jim Truran, 13-17 Nov 200

Formation of the Black Hole in Nova Scorpii

Israelian et al. (1999) showed that the stellar companion of the black-hole binary Nova Sco is polluted with material ejected in the supernova that accompanied the formation of the black-hole primary. Here we systematically investigate the implications of these observations for the black-hole formation process. Using a variety of supernova models, including both standard as well as hypernova models (for different helium-star masses, explosion energies, and explosion geometries) and a simple model for the evolution of the binary and the pollution of the secondary, we show that most of the observed abundance anomalies can be explained for a large range of model parameters (apart from the abundance of Ti). The best models are obtained for He star masses of 10 to 16 Msun, where spherical hypernova models are generally favoured over standard supernova ones. Aspherical hypernova models also produce acceptable fits, provided there is extensive lateral mixing. All models require substantial fallback and that the fallback material either reached the orbit of the secondary or was mixed efficiently with material that escaped. The black hole therefore formed in a two-step process, where the initial mass of the collapsed remnant was increased substantially by matter that fell back after the initial collapse. This may help to explain the high observed space velocity of Nova Sco either because of a neutrino-induced kick (if a neutron star was formed first) or by asymmetric mass ejection in an asymmetric supernova explosion.Comment: 16 pages, 3 Figures, 4 Tables. submitted to Ap

Decreased alveolar bone turnover is related to the occurrence of root resorption during experimental tooth movement in dogs

Objective:  To investigate the relationship between root resorption (RR) and bone turnover in two different types of tooth movement in dogs. Materials and Methods:  A total of 16 dogs in two different groups were used. Tooth movement of dog premolars resulted from approximately 200 g of force. Histomorphometric analysis of premolar roots was assessed after 4 and 12 weeks of tooth movement by comparing nonresorptive to resorptive surfaces. Results:  Histomorphometric analysis indicated a significant decrease in the bone formation rate in the root resorptive areas, which resulted in decreased bone volume after 12 weeks. The threshold to detect RR in periapical radiographs was about 1.0 mm2. Conclusions:  A sustained mechanical load, due to the prolonged stress and strain of continuous mechanics, induces elevated bone metabolic activity, such as the bone turnover (remodeling) and change in bone volume (modeling). Therefore, our data support the hypothesis that increased RR is related to decreased bone formation (turnover) in high stress areas exposed to prolonged orthodontic tooth movement

Chiral gravity in higher dimensions

We construct a chiral theory of gravity in 7 and 8 dimensions, which are equivalent to Einstein-Cartan theory using less variables. In these dimensions, we can construct such higher dimensional chiral gravity because of the existence of gravitational instanton. The octonionic-valued variables in the theory represent the deviation from the gravitational instanton, and from their non-associativity, prevents the theory to be SO(n) gauge invariant. Still the chiral gravity holds G_2 (7-D), and Spin(7) (8-D) gauge symmetry.Comment: 18 pages, no figures. Minor typos corrected. Updated reference

Isolated Diastolic Hypertension in the IDACO Study: An Age-Stratified Analysis Using 24-Hour Ambulatory Blood Pressure Measurements

The prognostic implications of isolated diastolic hypertension (IDH), as defined by 2017 American College of Cardiology (ACC)/American Heart Association (AHA) guidelines, have not been tested using ambulatory blood pressure (BP) monitor thresholds (ie, 24-hour mean systolic BP \u3c125 mm Hg and diastolic BP ≥75 mm Hg). We analyzed data from 11 135 participants in the IDACO (International Database on Ambulatory Blood Pressure in Relation to Cardiovascular Outcomes). Using 24-hour mean ambulatory BP monitor values, we performed Cox regression testing independent associations of IDH with death or cardiovascular events. Analyses were conducted in the cohort overall, as well as after age stratification (\u3c50 years versus ≥50 years). The median age at baseline was 54.7 years and 49% were female. Over a median follow-up of 13.8 years, 2836 participants died, and 2049 experienced a cardiovascular event. Overall, irrespective of age, IDH on 24-hour ambulatory BP monitor defined by 2017 American College of Cardiology/American Heart Association criteria was not significantly associated with death (hazard ratio, 0.95 [95% CI, 0.79–1.13]) or cardiovascular events (hazard ratio, 1.14 [95% CI, 0.94–1.40]), compared with normotension. However, among the subgroup \u3c50 years old, IDH was associated with excess risk for cardiovascular events (2.87 [95% CI, 1.72–4.80]), with evidence for effect modification based on age (P interaction \u3c0.001). In conclusion, using ambulatory BP monitor data, this study suggests that IDH defined by 2017 American College of Cardiology/American Heart Association criteria is not a risk factor for cardiovascular disease in adults aged 50 years or older but is a risk factor among younger adults. Thus, age is an important consideration in the clinical management of adults with IDH

Population-genetic nature of copy number variations in the human genome

Copy number variations (CNVs) are universal genetic variations, and their association with disease has been increasingly recognized. We designed high-density microarrays for CNVs, and detected 3000–4000 CNVs (4–6% of the genomic sequence) per population that included CNVs previously missed because of smaller sizes and residing in segmental duplications. The patterns of CNVs across individuals were surprisingly simple at the kilo-base scale, suggesting the applicability of a simple genetic analysis for these genetic loci. We utilized the probabilistic theory to determine integer copy numbers of CNVs and employed a recently developed phasing tool to estimate the population frequencies of integer copy number alleles and CNV–SNP haplotypes. The results showed a tendency toward a lower frequency of CNV alleles and that most of our CNVs were explained only by zero-, one- and two-copy alleles. Using the estimated population frequencies, we found several CNV regions with exceptionally high population differentiation. Investigation of CNV–SNP linkage disequilibrium (LD) for 500–900 bi- and multi-allelic CNVs per population revealed that previous conflicting reports on bi-allelic LD were unexpectedly consistent and explained by an LD increase correlated with deletion-allele frequencies. Typically, the bi-allelic LD was lower than SNP–SNP LD, whereas the multi-allelic LD was somewhat stronger than the bi-allelic LD. After further investigation of tag SNPs for CNVs, we conclude that the customary tagging strategy for disease association studies can be applicable for common deletion CNVs, but direct interrogation is needed for other types of CNVs

Ambulatory Hypertension Subtypes and 24-Hour Systolic and Diastolic Blood Pressure as Distinct Outcome Predictors in 8341 Untreated People Recruited From 12 Populations

Background—Data on risk associated with 24-hour ambulatory diastolic (DBP24) versus systolic (SBP24) blood pressure are scarce. Methods and Results—We recorded 24-hour blood pressure and health outcomes in 8341 untreated people (mean age, 50.8 years; 46.6% women) randomly recruited from 12 populations. We computed hazard ratios (HRs) using multivariable-adjusted Cox regression. Over 11.2 years (median), 927 (11.1%) participants died, 356 (4.3%) from cardiovascular causes, and 744 (8.9%) experienced a fatal or nonfatal cardiovascular event. Isolated diastolic hypertension (DBP24≥80 mm Hg) did not increase the risk of total mortality, cardiovascular mortality, or stroke (HRs≤1.54; P≥0.18), but was associated with a higher risk of fatal combined with nonfatal cardiovascular, cardiac, or coronary events (HRs≥1.75; P≤0.0054). Isolated systolic hypertension (SBP24≥130 mm Hg) and mixed diastolic plus systolic hypertension were associated with increased risks of all aforementioned end points (P≤0.0012). Below age 50, DBP24 was the main driver of risk, reaching significance for total (HR for 1-SD increase, 2.05; P=0.0039) and cardiovascular mortality (HR, 4.07; P=0.0032) and for all cardiovascular end points combined (HR, 1.74; P=0.039) with a nonsignificant contribution of SBP24 (HR≤0.92; P≥0.068); above age 50, SBP24 predicted all end points (HR≥1.19; P≤0.0002) with a nonsignificant contribution of DBP24 (0.96≤HR≤1.14; P≥0.10). The interactions of age with SBP24 and DBP24 were significant for all cardiovascular and coronary events (P≤0.043). Conclusions—The risks conferred by DBP24 and SBP24 are age dependent. DBP24 and isolated diastolic hypertension drive coronary complications below age 50, whereas above age 50 SBP24 and isolated systolic and mixed hypertension are the predominant risk factors

Outcome-Driven Thresholds for Ambulatory Pulse Pressure in 9938 People Recruited from 11 Populations

Evidence-based thresholds for risk stratification based on pulse pressure (PP) are currently unavailable. To derive outcome-driven thresholds for the 24–h ambulatory PP, we analyzed 9938 people randomly recruited from 11 populations (47.3% women). After age stratification (≥60 years) and using average risk as reference, we computed multivariable-adjusted hazard ratios (HRs) to assess risk by tenths of the PP distribution or risk associated with stepwise increasing (+1 mm Hg) PP levels. All adjustments included mean arterial pressure. Among 6028 younger participants (68,853 person-years), the risk of cardiovascular (HR, 1.58; P=0.011) or cardiac (HR, 1.52; P=0.056) events increased only in the top PP tenth (mean, 60.6 mm Hg). Using stepwise increasing PP levels, the lower boundary of the 95% confidence interval of the successive thresholds did not cross unity. Among 3910 older participants (39,923 person-years), risk increased (P≤0.028) in the top PP tenth (mean, 76.1 mm Hg). HRs were 1.30 and 1.62 for total and cardiovascular mortality, and 1.52, 1.69 and 1.40 for all cardiovascular, cardiac and cerebrovascular events. The lower boundary of the 95% confidence interval of the HRs associated with stepwise increasing PP levels crossed unity at 64 mm Hg. While accounting for all covariables, the top tenth of PP contributed less than 0.3% (generalized R2 statistic) to the overall risk among elderly. Thus, in randomly recruited people, ambulatory PP does not add to risk stratification below age 60; in the elderly, PP is a weak risk factor with levels below 64 mm Hg probably being innocuous