Comparison of acoustic travel-time measurement of solar meridional circulation from SDO/HMI and SOHO/MDI

Time-distance helioseismology is one of the primary tools for studying the solar meridional circulation. However, travel-time measurements of the subsurface meridional flow suffer from a variety of systematic errors, such as a center-to-limb variation and an offset due to the P-angle uncertainty of solar images. Here we apply the time-distance technique to contemporaneous medium-degree Dopplergrams produced by SOHO/MDI and SDO/HMI to obtain the travel-time difference caused by meridional circulation throughout the solar convection zone. The P-angle offset in MDI images is measured by cross-correlating MDI and HMI images. The travel-time measurements in the south-north and east-west directions are averaged over the same observation period for the two data sets and then compared to examine the consistency of MDI and HMI travel times after correcting the systematic errors. The offsets in the south-north travel-time difference from MDI data induced by the P-angle error gradually diminish with increasing travel distance. However, these offsets become noisy for travel distances corresponding to waves that reach the base of the convection zone. This suggests that a careful treatment of the P-angle problem is required when studying a deep meridional flow. After correcting the P-angle and the removal of the center-to-limb effect, the travel-time measurements from MDI and HMI are consistent within the error bars for meridional circulation covering the entire convection zone. The fluctuations observed in both data sets are highly correlated and thus indicate their solar origin rather than an instrumental origin. Although our results demonstrate that the ad hoc correction is capable of reducing the wide discrepancy in the travel-time measurements from MDI and HMI, we cannot exclude the possibility that there exist other systematic effects acting on the two data sets in the same way.Comment: accepted for publication in A&

Solar meridional circulation from twenty-one years of SOHO/MDI and SDO/HMI observations: Helioseismic travel times and forward modeling in the ray approximation

The south-north travel-time differences are measured by applying time-distance helioseismology to the MDI and HMI medium-degree Dopplergrams covering May 1996-April 2017. Our data analysis corrects for several sources of systematic effects: P-angle error, surface magnetic field effects, and center-to-limb variations. An interpretation of the travel-time measurements is obtained using a forward-modeling approach in the ray approximation. The travel-time differences are similar in the southern hemisphere for cycles 23 and 24. However, they differ in the northern hemisphere between cycles 23 and 24. Except for cycle 24's northern hemisphere, the measurements favor a single-cell meridional circulation model where the poleward flows persist down to $\sim$0.8 $R_\odot$, accompanied by local inflows toward the activity belts in the near-surface layers. Cycle 24's northern hemisphere is anomalous: travel-time differences are significantly smaller when travel distances are greater than 20$^\circ$. This asymmetry between northern and southern hemispheres during cycle 24 was not present in previous measurements (e.g., Rajaguru & Antia 2015), which assumed a different P-angle error correction where south-north travel-time differences are shifted to zero at the equator for all travel distances. In our measurements, the travel-time differences at the equator are zero for travel distances less than $\sim$30$^\circ$, but they do not vanish for larger travel distances. This equatorial offset for large travel distances need not be interpreted as a deep cross-equator flow; it could be due to the presence of asymmetrical local flows at the surface near the end points of the acoustic ray paths.Comment: accepted for publication in A&

Time-distance helioseismology of solar Rossby waves

Context. Solar Rossby waves (r modes) have recently been discovered in the near-surface horizontal flow field using the techniques of granulation-tracking and ring-diagram analysis applied to six years of SDO/HMI data. Aims. Here we apply time-distance helioseismology to the combined SOHO/MDI and SDO/HMI data sets, which cover 21 years of observations from May 1996 to April 2017. The goal of this study is to provide an independent confirmation over two solar cycles and in deeper layers of the Sun. Methods. We have measured south-north helioseismic travel times along the equator, which are sensitive to subsurface north-south flows. To reduce noise, the travel times were averaged over travel distances from 6$^\circ$ to 30$^\circ$; the mean distance corresponds to a p-mode lower turning point of 0.91 $R_\odot$. The 21-year time series of travel-time measurements was split into three seven-year subsets and transformed to obtain power spectra in a corotating frame. Results. The power spectra all show peaks near the frequencies of the classical sectoral Rossby waves for azimuthal wavenumbers in the range $3 \leq m \leq 15$. The mode frequencies and linewidths of the modes with $m \leq 9$ are consistent with a previous study whereas modes with $m \geq 10$ are shifted toward less negative frequencies by 10--20 nHz. While most of these modes have e-folding lifetimes on the order of a few months, the longest lived mode, $m=3$, has an e-folding lifetime of more than one year. For each mode, the rms velocity at the equator is in the range of 1--3 m s$^{-1}$ , with the largest values for $m\sim10$. No evidence for the $m=2$ sectoral mode is found in the power spectrum, implying that the rms velocity of this mode is below $\sim$0.5 m s$^{-1}$.Comment: accepted for publication in A&

Serotonin promotes the proliferation of serum-deprived hepatocellular carcinoma cells via upregulation of FOXO3a

BACKGROUND: Peripheral serotonin is involved in tumorigenesis and induces a pro-proliferative effect in hepatocellular carcinoma (HCC) cells; however, the intracellular mechanisms by which serotonin exerts a mitogenic effect remain unclear. In this research, we examined whether FOXO3a, a transcription factor at the interface of crucial cellular processes, plays a role downstream of serotonin in HCC cells. RESULTS: The cell viability and expression of FOXO3a was assessed in three HCC cell lines (Huh7, HepG2 and Hep3B) during serum deprivation in the presence or absence of serotonin. Serum free media significantly inhibited HCC proliferation and led to reduced expression and nuclear accumulation of FOXO3a. Knockdown of FOXO3a enhanced the ability of serum deprivation to inhibit HCC cells proliferation. And overexpression of non-phosphorylated FOXO3a in HCC cells reversed serum-deprivation-induced growth inhibition. Serotonin reversed the serum-deprivation-induced inhibition of cell proliferation and upregulated FOXO3a in Huh7 cells; however, serotonin had no effect on the proliferation of serum-deprived HepG2 or Hep3B cells. In addition to proliferation, serotonin also induced phosphorylation of AKT and FOXO3a in serum-deprived Huh7 cells but not in HepG2 and Hep3B cells. However, the phosphorylation of FOXO3a induced by serotonin did not export FOXO3a from nucleus to cytoplasm in serum-deprived Huh7 cells. Consequently, we demonstrated that serotonin promoted the proliferation of Huh7 cells by increasing the expression of FOXO3a. We also provide preliminary evidence that different expression levels of the 5-HT2B receptor (5-HT(2B)R) may contribute to the distinct effects of serotonin in different serum-deprived HCC cells. CONCLUSIONS: This study demonstrates that FOXO3a functions as a growth factor in serum-deprived HCC cells and serotonin promotes the proliferation of serum-deprived HCC cells via upregulation of FOXO3a, in the presence of sufficient levels of the serotonin receptor 5-HT(2B)R. Drugs targeting the serotonin-5-HT(2B)R-FOXO3a pathway may provide a novel target for anticancer therapy

Energy dependence of J/ψJ/\psi production in pp collisions with the PACIAE model

In this work we investigate the $J/\psi$ production in proton-proton collisions at the center-of-mass energy ($\sqrt{s}$) equal to 2.76, 5.02, 7, 8 and 13 TeV with a parton and hadron cascade model PACIAE 2.2a. It is based on PYTHIA but extended considering the partonic and hadronic rescatterings before and after hadronization, respectively. In the PYTHIA sector the $J/\psi$ production quantum chromodynamics processes are selected specially and a bias factor is proposed correspondingly. The calculated total cross sections, the differential cross sections as a function of the transverse momentum and the rapidity of $J/\psi$ in the forward rapidity region reproduce the corresponding experimental measurements reasonably well. In the mid-rapidity region, the double differential cross sections at $\sqrt{s}=$ 5.02, 7 and 13 TeV are also in a good agreement with the experimental data. Moreover, we predict the double differential cross section as well as the total cross section of $J/\psi$ at $\sqrt{s}=$ 8 TeV, which could be validated when the experimental data is available.Comment: 6 pages, 8 figures, 3 table

Effect of Revaccination Using Different Schemes among Adults with Low or Undetectable Anti-HBs Titers after Hepatitis B Virus Vaccination

Our objective was to investigate the effect of various reimmunization schemes for hepatitis B in adults with low or undetectable anti-HBs titers. Over 2 years, 10 g of Saccharomyces cerevisiae-recombinant hepatitis B virus (HBV) vaccine (synthesized in China) was used in at least one standardized scheme to immunize 2,310 healthy male and nonpregnant female adults. Of these, 240 subjects tested negative for hepatitis B markers. These 240 subjects were equally divided into 4 groups. The first group, designated Engerix-40, was revaccinated with 40 g Engerix-B; the second, Engerix-20, was revaccinated with 20 g Engerix-B; the third, Chinese-20, was revaccinated with 20 g Chinese-made yeast-recombinant vaccine; and the last group, Chinese-10, was revaccinated with 10 g Chinese-made yeast-recombinant vaccine. Blood samples were collected before and 1, 2, 8, and 12 months after the first injection. The anti-HBs-positive conversion rates of the Engerix-40, Engerix-20, and Chinese-20 groups were higher than that of the Chinese-10 group (P < 0.01). Over time, the anti-HBs conversion rate increased in all groups, but values were significantly different from those for the other groups only in the Chinese-10 group (P < 0.001). The anti-HBs geometric mean titers (GMTs) of the Engerix-40, Engerix-20, and Chinese-20 groups were higher than in the Chinese-10 group (P < 0.05). Increased doses raise and maintain anti-HBs titers in subjects with low or undetectable titers after HBV vaccination. Viral hepatitis B is a worldwide public health problem, and there are no specific drugs to treat hepatitis B virus (HBV) infection. For susceptible populations, the most effective preventive measure is to improve immune competence by immunizing with a hepatitis B vaccine (7). Yet, 5 to 15% of subjects have low or undetectable anti-HBs titers after an entire course of Heptavax-B vaccination following standardized immunization programs (0, 1, and 6 months), as recommended by the WHO (17, 26). Subjects with low or undetectable anti-HBs titers remain susceptible to HBV (23). Many studies have probed for the reasons why subjects fail to develop adequate anti-HBs titers after hepatitis B vaccination (5, 6, 9), but no formal recommendations regarding standardized, normalized reimmunization programs have been made. To develop an effective enhanced hepatitis B vaccination program, we reimmunized 240 subjects with low or undetectable anti-HBs titers using 4 schemes and report and compare the results here. MATERIALS AND METHODS (i) Subjects. Between September 2006 and August 2009, 2,310 healthy male and nonpregnant female adults were selected from among outpatients at the Infectious Department of the Third Affiliated Hospital, Sun Yat-sen University. The subjects were immunized by hypodermic injection of 10 g Chinese-made Saccharomyces cerevisiae-recombinant HBV vaccine using at least 1 standardized scheme over 2 years. Of the original 2,310 immunized outpatients, 240 healthy subjects tested negative for hepatitis B markers (HBV surface antigen [HBsAg], anti-HBs, HBeAg, anti-HBe, and anti-HBc), as detected by enzyme-linked immunosorbent assay (ELISA), and were enrolled in this study. The enrollees had no history of hepatitis and had normal liver function. Informed consent was obtained from all subjects. (ii) Research methods and revaccination schemes. The 240 healthy adult subjects were randomly divided into 4 groups of 60, and each group was assigned to a different revaccination scheme. Revaccination was administered in each group by intramuscular injection into the deltoid muscle at 0, 1, and 6 months. The baseline statistical differences between subjects in the 4 groups were insignificant (P Ͼ 0.05). (iii) Sources of vaccines. The Chinese-made yeast-recombinant hepatitis B vaccine (10 g and 20 g) was produced by Shenzhen Kangtai Biological Products Co., Ltd. (batch no. 20051131, 5 g/0.5 ml). The imported yeast-recombinant hepatitis B vaccine (20 g Engerix-B) was produced by Shanghai GlaxoSmithKline Biological Products Co., Ltd. (batch no. XHBVB270AA, 20 g/ml). The vaccines were used within the dates of validity. (iv) Blood collection and detection. Five milliliters of venous blood was collected from all subjects before the first injection, ϳ28 to ϳ30 days after the first injection (time 1 [T1]), ϳ28 to ϳ30 days after the second injection (T2), 2 months after the third injection (T8), and 13 to 15 months after the first injection (T12). Anti-HBs was detected according to the manufacturer's instructions for the anti-HBs assay kit (Abbot Axsym AUSAB) by a single investigator in a single laboratory, using the same equipment and methods; the reagents were purchased from the same supplier. (v) Definition of anti-HBs levels. Anti-HBs titers of Ͻ10 mIU/ml were considered negative; anti-HBs titers of Ն10 mIU/ml were considered positive. (vi) Statistical analysis. The statistical software SPSS 13.0 was used for statistical analysis. Mean comparisons between groups were made by single-facto