REEVALUATION OF THE C4H ABUNDANCE BASED ON THE REVISED DIPOLE MOMENT

C$_{n}$H molecules are the simplest linear carbon chains in space. They are crucial for not only probes of young clouds but also benchmarks of calculations of chemical reaction network. However, their abundances occasionally show anomaly. For example, observed column densities of \chem{C_4H} in various sources are one order of magnitude higher than theoretically estimated values. Herbst \& Osamura suggested that these excesses of \chem{C_4H} come from the theoretically determined dipole moment of \chem{C_4H}.\footnote{Herbst \& Osamura, 2008, $ApJ$, {\bf 679}, 1670. $^b$Woon, 1995, $Chem$. $Phys$. $Lett$. {\bf 244}, 45. $^c$Oyama $et$ $al$., 2020, $ApJ$, {\bf 890}, 39.} The dipole moment in the electronic ground state of $^{2}\Sigma^+$ was calculated to be 0.87 D by the RCCSD(T)/aug-cc-pVDZ level of $ab$ $initio$ theory.$^b$ However, the mixing of wavefunctions between the ground state and the low-lying electronic excited state of $^{2}\Pi$ having the large dipole moment of 4.4 D occurs, giving a higher dipole moment to the ground state. By using a higher dipole moment, a smaller column density is derived via observed line intensities. In the present study, we re-calculated the dipole moment of \chem{C_4H} by quantum chemical calculations including the mixing.$^c$ The calculations were carried out by the multi-reference configuration interaction level of $ab$ $initio$ theory using the cc-pVQZ basis set. The new dipole moment was derived to be 2.10 D, which is about 2.4 times larger than the value of 0.87 D used so far. Reported lines of \chem{C_4H} were analyzed to revise column densities by using the new dipole moment. Revised values are about a factor of 6 smaller than those in the previous works. Using the revised column density of \chem{C_4H}, abundances of the C$_{2n}$H ($n = 1–4$) series show exponential smooth decreases with carbon-chain length in various sources

A SEARCH FOR THE HOCO RADICAL IN THE MASSIVE STAR-FORMING REGION Sgr B2(M)

Despite importance of the origin of life, long lasting challenges to detect the simplest amino acid glycine (chem{H_2NCH_2COOH}) in interstellar medium has not been successful. As a preliminary step toward search for glycine, detection of its precursor has received attention. It is considered that glycine is produced by the reaction of the chem{HOCO} radical and the aminomethyl radical(chem{CH_2NH_2}) on interstellar grain surface:_x000d_ \_x000d_ _x000d_ chem{HOCO} + chem{CH_2NH_2} $rightarrow$ chem{H_2NCH_2COOH}.hspace{15pt} (1)_x000d_ \_x000d_ \_x000d_ chem{HOCO} is produced by the reaction of chem{OH} + chem{CO} $rightarrow$ chem{HOCO} and/or chem{HCOOH} $rightarrow$ chem{HOCO} + chem{H}. However, chem{HOCO} and chem{CH_2NH_2} have not been investigated in interstellar medium. Recently, we determined the accurate molecular constants of chem{HOCO}.footnote{T. Oyama $et$ $al$., $J$. $Chem$. $Phys$. {bf 134}, 174303 (2011).} Thus, accurate rest frequencies were derived from the constants. In the present study, we carried out the observations of chem{HOCO} in the massive star-forming region Sgr B2(M), having variety of interstellar molecules, with Nobeyama 45 m radio telescope. Although chem{HOCO} could not be detected in Sgr B2(M), the upper limit of the column density was derived to be 9.0$times$10$^{12}$ cm$^{-2}$ via the spectrum in the 88 GHz region by the rotational diagram method. If the reaction (1) is a main process of the glycine production in this region, an extremely deep search is needed to detect glycine. _x000d

Sarcomere Imaging by Quantum Dots for the Study of Cardiac Muscle Physiology

We here review the use of quantum dots (QDs) for the imaging of sarcomeric movements in cardiac muscle. QDs are fluorescence substances (CdSe) that absorb photons and reemit photons at a different wavelength (depending on the size of the particle); they are efficient in generating long-lasting, narrow symmetric emission profiles, and hence useful in various types of imaging studies. Recently, we developed a novel system in which the length of a particular, single sarcomere in cardiomyocytes can be measured at ~30 nm precision. Moreover, our system enables accurate measurement of sarcomere length in the isolated heart. We propose that QDs are the ideal tool for the study of sarcomere dynamics during excitation-contraction coupling in healthy and diseased cardiac muscle