17βH-Periplogenin, a cardiac aglycone from the root bark of Periploca sepium Bunge

The title compound {systematic name: 4-[(3S,5S,8R,9S,10R,13R,14S,17S)-3,5,14-trihy­droxy-10,13-dimethyl­hexa­deca­hydro-1H-cyclo­penta­[a]phenanthren-17-yl]furan-2(5H)-one}, C23H34O5, was isolated from the roots of Periploca sepium Bunge, a famous Chinese traditional herbal medicine. The three six-membered rings adopt chair conformations, the cyclo­pentane ring displays an approximate envelope conformation (with the C atom bearing the methyl substituent at the flap) and the five-membered lactone ring adopts an essentially planar [maximum deviation of 0.004 (8) Å] conformation. In the crystal, mol­ecules are linked into helical chains along [010] by O—H⋯O hydrogen bonds and weak C—H⋯O inter­actions. Two intra­molecular O—H⋯O hydrogen bonds are also present

A LITERATURE REVIEW OF SUSTAINABLE TOURISM (1990-2016): DEVELOPMENT TRAJECTORY AND FRAMEWORK

Purpose of the study—Tourism is one of the largest and fastest growing industries in the world. Just like an enterprise today, sustainability is the long-term objective pursued by tourism industry. However, little effort has been made to systematically provide sufficient information to academicians and practitioners who have great research interests in sustainable tourism. Therefore, this paper aims to figure out the knowledge mapping of sustainable tourism and to indicate its research hot spots and trends for future research. Methodology—This paper surveys the development trajectory of sustainable tourism using a literature review and classification of articles retrieved from 5 online databases with solo keyword “sustainable tourism” from 1900 to 2016. Main findings—Based on the scope of 641 articles, this study reveals that the number of publication on sustainable tourism has significantly increased since 2006. In addition, these articles are scattered across 125 journals and mostly published in 23 academic journals. The majority of targeted countries/regions for sustainable tourism focus on Asia, Europe and America. Limitation—Restricted to limited knowledge, we make a brief literature survey on sustainable tourism from 1990-2016 to explore how sustainable tourism and its applications have developed in this period. Originality/value—In fact, sustainable tourism is a belief and an overall concept in every tourism activities. Though this research has done lots, it still has rooms to make more complete. Finally, we present a conceptual framework integrating 13 classifications criteria derived from our analysis with 3247 keywords. Most interestingly, we further present a conceptual framework with a visual effect to operationalize the coverage of sustainable tourism. Based on our analysis, any researcher can easily find the popular and right journal to get into it, if he/she is in need, he/she also can roughly know its applications so far and completely get a whole picture of sustainable tourism quickly

RNACompress: Grammar-based compression and informational complexity measurement of RNA secondary structure

<p>Abstract</p> <p>Background</p> <p>With the rapid emergence of RNA databases and newly identified non-coding RNAs, an efficient compression algorithm for RNA sequence and structural information is needed for the storage and analysis of such data. Although several algorithms for compressing DNA sequences have been proposed, none of them are suitable for the compression of RNA sequences with their secondary structures simultaneously. This kind of compression not only facilitates the maintenance of RNA data, but also supplies a novel way to measure the informational complexity of RNA structural data, raising the possibility of studying the relationship between the functional activities of RNA structures and their complexities, as well as various structural properties of RNA based on compression.</p> <p>Results</p> <p><it>RNACompress </it>employs an efficient grammar-based model to compress RNA sequences and their secondary structures. The main goals of this algorithm are two fold: (1) present a robust and effective way for RNA structural data compression; (2) design a suitable model to represent RNA secondary structure as well as derive the informational complexity of the structural data based on compression. Our extensive tests have shown that <it>RNACompress </it>achieves a universally better compression ratio compared with other sequence-specific or common text-specific compression algorithms, such as <it>Gencompress, winrar </it>and <it>gzip</it>. Moreover, a test of the activities of distinct GTP-binding RNAs (aptamers) compared with their structural complexity shows that our defined informational complexity can be used to describe how complexity varies with activity. These results lead to an objective means of comparing the functional properties of heteropolymers from the information perspective.</p> <p>Conclusion</p> <p>A universal algorithm for the compression of RNA secondary structure as well as the evaluation of its informational complexity is discussed in this paper. We have developed <it>RNACompress</it>, as a useful tool for academic users. Extensive tests have shown that <it>RNACompress </it>is a universally efficient algorithm for the compression of RNA sequences with their secondary structures. <it>RNACompress </it>also serves as a good measurement of the informational complexity of RNA secondary structure, which can be used to study the functional activities of RNA molecules.</p

Sesquiterpenes and Dimeric Sesquiterpenoids from Sarcandra glabra

Two new sesquiterpenes, sarcandralactones A (1) and B (2), and five new dimeric sesquiterpenoids, sarcandrolides A-E (3-7), along with 10 known compounds were isolated from the whole plants of Sarcandra glabra. Their structures were elucidated on the basis of spectroscopic analysis. Some of the new isolates exhibit significant cytotoxicities when tested against a small panel of tumor cell lines

1-(But-2-enyl­idene)-2-(2-nitro­phen­yl)hydrazine

The mol­ecule of the title Schiff base compound, C10H11N3O2, adopts an E geometry with respect to the C=N double bond. The mol­ecule is roughly planar, with the largest deviation from the mean plane being 0.111 (2) Å, The enyl­idene-hydrazine group is, however, slightly twisted with respect to the phenyl ring, making a dihedral angle of 6.5 (3)°. An intra­molecular N—H⋯O hydrogen bond may be responsible for the planar conformation. An inter­molecular N—H⋯O hydrogen bond links two mol­ecules around an inversion center, building a pseudo dimer

N′-(2-Furylmethyl­ene)nicotinohydrazide

The asymmetric unit of the title compound, C11H9N3O2, contains two independent mol­ecules: the dihedral angles between the pyridine ring and the furyl ring are 17.00 (16) and 34.12 (15)°. The crystal structure involves inter­molecular C—H⋯O, N—H⋯N and N—H⋯O hydrogen bonds

2-Eth­oxy-4-{[(2-nitro­phen­yl)hydrazono]meth­yl}phenol

The title compound, C15H15N3O4, a Schiff base, was obtained from a condensation reaction of 3-eth­oxy-4-hydroxy­benzaldehyde and 2-nitro­phenyl­hydrazine. The mol­ecule is approximately planar, the largest deviation from the mean plane being 0.1449 (16) Å. An intramolecular N—H⋯O inter­action is also present. In the crystal, inter­molecular O—H⋯O hydrogen bonds link the mol­ecules, forming chain parallel to the b axis