Photon-graviton scattering: A new way to detect anisotropic gravitational waves?

Gravitons are the quantum counterparts of gravitational waves in low-energy theories of gravity. Using Feynman rules one can compute scattering amplitudes describing the interaction between gravitons and other fields. Here, we consider the interaction between gravitons and photons. Using the quantum Boltzmann equation formalism, we derive fully general equations describing the radiation transfer of photon polarization, due to the forward scattering with gravitons. We show that the Q and U photon linear polarization modes couple with the V photon circular polarization mode, if gravitons have anisotropies in their power-spectrum statistics. As an example, we apply our results to the case of primordial gravitons, considering models of inflation where an anisotropic primordial graviton distribution is produced. Finally, we evaluate the effect on cosmic microwave background (CMB) polarization, showing that in general the expected effects on the observable CMB frequencies are very small. However, our result is promising, since it could provide a novel tool for detecting anisotropic backgrounds of gravitational waves, as well as for getting further insight on the physics of gravitational waves.Comment: 15 pages, 1 figure. v2: references added, typos corrected, replaced to match published version in PR

CMB VV modes from photon-photon forward scattering revisited

Recent literature has shown that photon-photon forward scattering mediated by Euler-Heisenberg interactions may generate some amount of the circular polarization ($V$ modes) in the cosmic microwave background (CMB) photons. However, there is an apparent contradiction among the different references about the predicted level of the amplitude of this circular polarization. In this work, we will resolve this discrepancy by showing that with a quantum Boltzmann equation formalism we obtain the same amount of circular polarization as using a geometrical approach that is based on the index of refraction of the cosmological medium. We will show that the expected amplitude of $V$ modes is expected to be $\approx$ 8 orders of magnitude smaller than the amplitude of $E$-polarization modes that we actually observe in the CMB, thus confirming that it is going to be challenging to observe such a signature. Throughout the paper, we also develop a general method to study the generation of $V$ modes from photon-photon and photon-spin-1-massive-particle forward scatterings without relying on a specific interaction, which thus represent possible new signatures of physics beyond the Standard Model.Comment: 22 pages, 2 figures; v2: minor corrections implemented in the text. Replaced to match published version in PR

Platelet Rich in Growth Factors (PRGF): A Suitable Replacement for Fetal Bovine Serum (FBS) in Mesenchymal Stem Cell Culture

Background: Due to high differentiation potential and self-renewality, Mesenchymal Stem Cells are now widely considered by researchers in several diseases. FBS is used as a supplement in culture media for proliferation, differentiation, and other culture processes of MSCs, which is associated with transmission risk of a variety of infections as well as immune responses. PRGF derived from platelets contains growth factors causing the growth and proliferation of MSCs. This study was conducted to compare the effect of PRGF in comparison to FBS on the expression of h-TERT gene, in umbilical cord derived MSCs. Materials and Methods: This study is an experimental research. Four expired platelet concentrate bags were obtained from Kerman blood transfusion center, and PRGF was prepared by multiple centrifugation rounds of the platelet bag. Calcium chloride was added as an anticoagulant to PRGF in order to prevent gelatinization of the culture medium. On the other hand, mesenchymal stem cells were isolated from the umbilical cord as a primary culture. The phenotype of the cells was confirmed by flow cytometry, and the cells were randomly cultured as control (using FBS) and experimental (using PRGF) groups. The expression of the gene involved in increasing cell longevity (h-TERT) was investigated by real-time PCR technique after six days. Results: Mesenchymal stem cells were successfully isolated from the umbilical cord. Morphologically, the mesenchymal cells cultured in the experimental group (using PRGF) were similar to the cells in the control medium. The cells exhibited a high expression level of CD73, CD90, and CD105, while the surface markers of hematopoietic cells such as CD45 and CD34 were slightly expressed. Therefore, there was no significant difference in the expression of cell surface markers between control and experimental groups. In this study, using the real-time PCR technique, it was shown that PRGF derived from the platelet could increase the expression of h-TERT gene in the umbilical cord mesenchymal stem cells compared with the control.(P = 0.034) Conclusion: PRGF have been shown to be effective in increasing expression of h-TERT gene in the umbilical cord mesenchymal stem cells and may also be an appropriate substitute for FBS in cell culture media. &nbsp

Accurate model based on artificial intelligence for prediction of carbon dioxide solubility in aqueous tetra-n-butylammonium bromide solutions

This study highlights the application of radial basis function (RBF) neural networks, adaptive neuro-fuzzy inference systems (ANFIS), and gene expression programming (GEP) in the estimation of solubility of CO2 in aqueous solutions of tetra-n-butylammonium bromide (TBAB). The experimental data were gathered from a published work in literature. The proposed RBF network was coupled with genetic algorithm (GA) to access a better prediction performance of model. The structure of ANFIS model was trained by using hybrid method. The input parameters of the model were temperature, pressure, mass fraction of TBAB in feed aqueous solution (wTBAB), and mole fraction of TBAB in aqueous phase (xTBAB). The solubility of CO2 (xCO2) was the output parameter. Statistical and graphical analyses of the results showed that the proposed GA-RBF, Hybrid-ANFIS, and GEP models are robust and precise in the estimation of literature solubility data

Seroepidemiology of Hepatitis B in Pregnant Women in Sari, Iran 2018- 2020

Background and purpose: Hepatitis B vaccination is recommended in HBsAg-positive mothers to prevent hepatitis B in infants. Mother-to-infant transmission of HBV causes many health problems and it is important to identify HBV positive mothers. This investigation aimed at studying the prevalence of HBV and the immunogenicity of HBV vaccination in pregnant women to prevent HBV at birth in Sari, Iran. Materials and methods: This descriptive observational study was conducted in pregnant women attending Sari Birth Cohort (SBC) Center, 2018-2020. A total of 1018 samples were investigated for HBV serological markers by enzyme-linked immunosorbent assay (ELISA). Results: The prevalence of HBV was 1.57% and 46.6% (n=474) of expectant mothers had received HBV vaccine. Immunogenicity of HBV vaccination was 51.9%. HBV prevalence was found to be significantly associated with increase in age and gestational age (P= 0.009 and P= 0.005, respectively). HBV infection in women who were not immunized was significantly associated with family history of HBV and unprotected sex (P= 0.000 and P= 0.008, respectively). Conclusion: Family history of HBV, maternal age, gestational age, and unprotected intercourse were the risk factors for HBV infection in pregnant women in Sari