There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of accuracy, spectral coverage, additional absorption phenomena, added line-shape formalisms, and validity. Moreover, molecules, isotopologues, and perturbing gases have been added that address the issues of atmospheres beyond the Earth. Of considerable note, experimental IR cross-sections for almost 300 additional molecules important in different areas of atmospheric science have been added to the database. The compilation can be accessed through www.hitran.org. Most of the HITRAN data have now been cast into an underlying relational database structure that offers many advantages over the long-standing sequential text-based structure. The new structure empowers the user in many ways. It enables the incorporation of an extended set of fundamental parameters per transition, sophisticated line-shape formalisms, easy user-defined output formats, and very convenient searching, filtering, and plotting of data. A powerful application programming interface making use of structured query language (SQL) features for higher-level applications of HITRAN is also provided.

/pdf/the-hitran-2008-molecular-spectroscopic-database-1ud8clpej3.pdf

The HITRAN 2008 molecular spectroscopic database

Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

Monthly Notices of the Royal Astronomical Society

Molecular structure and energetics of the four isomers of CH2N, namely H2CN, trans-HCNH, cis-HCNH, and H2NC, have been investigated by means of a highly accurate level of theory, i.e., using the coupled cluster method in conjunction with correlation consistent basis sets ranging in size from triple to sextuple zeta. Extrapolation to the complete basis set limit, higher excitations in the cluster operator as well as core correlation and relativistic effects have been considered. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2483–2494, 2010

A theoretical study of the CH2N isomers: Molecular structure and energetics

A gas-phase formation route is proposed for the recently detected propargylimine molecule. In analogy to other imines, such as cyanomethanimine, the addition of a reactive radical (C$_2$H in the present case) to methanimine (CH$_2$NH}) leads to reaction channels open also in the harsh conditions of the interstellar medium. Three possible isomers can be formed in the C$H_2$NH + C$_2$H reaction: Z- and E-propargylimine (Z-,E-PGIM) as well as N-ethynyl-methanimine (N-EMIM). For both PGIM species, the computed global rate coefficient is nearly constant in the 20-300 K temperature range, and of the order of 2-3 $\times$ 10$^{-10}$ cm$^3$ molecule$^{-1}$ s$^{-1}$, while that for N-EMIM is about two orders of magnitude smaller. Assuming equal destruction rates for the two isomers, these results imply an abundance ratio for PGIM of [Z]/[E] $\sim$ 1.5, which is only slightly underestimated with respect to the observational datum.

Methanimine as a Key Precursor of Imines in the Interstellar Medium: The Case of Propargylimine

Interstellar complex organic molecules (iCOMs) are assumed to be mainly formed on dust-grain surfaces. However, neutral gas-phase reactions in the interstellar medium (ISM) can play an important role. In this paper, by investigating the reaction between aldehydes and the cyano radical, we show that both formaldehyde (CH$_2$O) and acetaldehyde (CH$_3$CHO) can lead to the formation of formyl cyanide (HCOCN). Owing to accurate quantum-chemical computations followed by rate constant evaluations, we have been able to suggest and validate an effective mechanism for the formation of HCOCN, one of the molecules observed in the ISM. Quite interestingly, the mechanism starting from CH$_2$O is very effective at low temperature, while that involving CH$_3$CHO becomes more efficient at temperatures above 200 K.

The quest for a plausible formation route of formyl cyanide in the interstellar medium: a state-of-the-art quantum-chemical and kinetic approach.

The gas-phase IR spectrum of 1-azaindolizine has been recorded in the range from 100 to 3200 cm–1, at the resolution of 0.05 cm–1, using a multipass cell heated to 80 °C. The spectrum analysis has been performed by comparing the experimental spectrum with the theoretical one, using both frequency and intensity matching as guidelines for the assignments. The theoretical spectrum of 1-azaindolizine has been calculated from the harmonic force field evaluated at the self consistent field (SCF) level followed by empirical scaling according to the scaled quantum mechanical (SQM) approach, with pyridine and imidazole as parent molecules. The final root-mean-square deviation (RMSD) of the computed and experimental frequencies is 18 cm–1.

Gas-phase IR spectrum of 1-azaindolizine: scaled quantum mechanical force field and spectrum assignment

Experiments on nuclear spin interconversion of ortho, para, and meta nuclear spin isomers of the methane molecule have been undertaken in gas phase and cryomatrices. Only the latter environment has led to the observation of the nuclear spin conversion. In this study, a quantitative explanation is given for the first time by considering the coupling of three relaxation paths: meta ⇔ para, meta ⇔ ortho, and ortho ⇔ para. The global evolution of the three populations of spin isomers is thus described by two characteristic times, which have been calculated using the best values of the energy levels for the vibrational ground state, of the intramolecular magnetic interactions, and of the collisional relaxation rates, and for different pressure and temperature conditions. Such calculations also provide an indication for the proper choice of reliable scenarios for experimental separation of the spin isomers of methane.

Cristina Puzzarini

Papers

A theoretical study of the CH2N isomers: Molecular structure and energetics

Methanimine as a Key Precursor of Imines in the Interstellar Medium: The Case of Propargylimine

The quest for a plausible formation route of formyl cyanide in the interstellar medium: a state-of-the-art quantum-chemical and kinetic approach.

Gas-phase IR spectrum of 1-azaindolizine: scaled quantum mechanical force field and spectrum assignment

Nuclear Spin Conversion in CH4: A Multichannel Relaxation Mechanism