Discrete Conditional Phase-type models utilising classification trees: Application to modelling health service capacities

Discrete Conditional Phase-type models (DC-Ph) consist of a process component (survival distribution) preceded by a set of related conditional discrete variables. This paper introduces a DC-Ph model where the conditional component is a classification tree. The approach is utilised for modelling health service capacities by better predicting service times, as captured by Coxian phase-type distributions, interfaced with results from a classification tree algorithm. To illustrate the approach, a case-study within the healthcare delivery domain is given, namely that of maternity services. The classification analysis is shown to give good predictors for complications during childbirth. Based on the classification tree predictions, the duration of childbirth on the labour ward is then modelled as either a two or three-phase Coxian distribution. The resulting DC-Ph model is used to calculate the number of patients and associated bed occupancies, patient turnover, and to model the consequences of changes to risk status.     

Quantum-state resolved reaction dynamics at the gas-liquid interface: direct absorption detection of HF(v,J) product from F(2P)+squalane

Exothermic reactive scattering of F atoms at the gas-liquid interface of a liquid hydrocarbon (squalane) surface has been studied under single collision conditions by shot noise limited high-resolution infrared absorption on the nascent HF(v,J) product. The nascent HF(v,J) vibrational distributions are inverted, indicating insufficient time for complete vibrational energy transfer into the surface liquid. The HF(v=2,J) rotational distributions are well fit with a two temperature Boltzmann analysis, with a near room temperature component (T(TD) approximately equal to 290 K) and a second much hotter scattering component (T(HDS) approximately equal to 1040 K). These data provide quantum state level support for microscopic branching in the atom abstraction dynamics corresponding to escape of nascent HF from the liquid surface on time scales both slow and fast with respect to rotational relaxation.     

Tedanolide C: a potent new 18-membered-ring cytotoxic macrolide isolated from the Papua New Guinea marine sponge Ircinia sp

Cytotoxicity-guided fractionation of the crude methanol extract of a marine sponge, Ircinia sp., yielded tedanolide C (1), a new 18-membered macrolide. The structure was solved by interpreting NMR and MS data, and the relative stereochemistry was determined from a combination of homo- and heteronuclear coupling constants in conjunction with molecular modeling. Compound 1 exhibited potent cytotoxicity against HCT-116 cells in vitro. Cell cycle analysis showed that treatment of cells with compound 1 arrested cells in the S-phase.     

Locational analysis: highlights of growth to maturity

Locational analysis has grown to maturity over the last decades, from its earliest roots, to fruitfulness in a wide-ranging number of strands that join with other disciplines and applications such as environmental planning and supply chain management. This paper charts the progress of location theory in three stages: a period of early contributions, when a number of seminal geometrical and geographical problems were studied; a ‘coming of age’ with the development of defining or classical problems that have proved fundamental to much later research and a third period of new models and new applications.     

3,7-Dimethylguanine, a new purine from a Philippine sponge Zyzzya fuliginosa.

A new purine 3,7-dimethylguanine (1) has been isolated from the marine sponge Zyzzya fuliginosa, along with the known metabolites, makaluvamines A, C, K (2--4), 4-hydroxyphenylacetic acid (5), methyl ester of 4-hydroxyphenylacetic acid (6), 4-hydroxyphenethyl alcohol (7), L-phenylalanine (8) and L-tryptophan (9). The structure of 3,7-dimethylguanine (1) was elucidated by analysis of 1D and 2D (one- and two-dimensional) NMR [HMQC (heteronuclear multiple quantum coherence), gHMBC (heteronuclear multiple bond connectivity), 1H-15N gHMBC] data, mass spectroscopy data, and by comparison with 3,7-dimethylisoguanine (10).     

Vibrational spectra of cyclic C8 in solid argon

Vapors from solid and powdered carbon, emitted from an oven cycled between 2000 and 3000 K, were co-condensed with argon onto a CsI substrate maintained at 10 K. The cycling process produced a multilayered matrix with regions of high carbon density alternating with layers of argon. FTIR measurements including ¹³C isotopic data, supported by ab initio calculations, allow the assignment of a band observed at 1817.8 cm⁻¹ to the ν₁₂(e_u) fundamental of cyclic C₈.     

Modified Spectral Editing Methods for C CP/MAS Experiments in Solids

The spectral editing approach of Zilm and coworkers utilizes polarization, polarization inversion, and spin depolarization methods for enhancing or suppressing NMR spectral lines in solids. The proposed pulse sequences allow nonprotonated C, CH, CH₂, and CH₃ types of carbon resonances to be separated from one another and identified accordingly. The former method tentatively separates the nonprotonated C and CH₃ peaks with a cutoff shift of 35 ppm. This shift is a reasonable demarcation shift for a preponderance of organic molecules, but exceptions do exist that could constitute a serious drawback in a few instances. The new approach separates the nonprotonated C and CH₃ carbon peaks unequivocally using modified pulse sequences similar to those of Zilm. Further, both the CH only and CH₂ only spectra, respectively, can be acquired directly from combining so called (+) and (−) sequences using different spectral delay periods and pulse parameters. The (+) and the (−) pulse sequences produce signals for the nonprotonated and methyl carbons that have essentially the same amplitude but opposite phases. These spectra, combined with the previously reported CH₃ and nonprontonated C only spectra, offer a complete spectral editing technique for solid samples. Examples of these spectral editing methods are provided for 3-methylglutaric acid, fumaric acid monoethyl ester, and two complex natural products: methyl o-methylpodocarpate and 10-deacetylbaccatin III.     

Electron density modeling and reconstruction of infinite periodic minimal surfaces (IPMS) based phases in lipid-water systems. II. Reconstruction of D surface based phases

This is the second of two papers dealing with the structure of lipid-water phases based on Infinite Periodic Minimal Surfaces (IPMS). The first paper describes mathematical modeling of such phases. In this paper, a new reconstruction method, called the methyl trough search, is described and used to solve the structures based on powder pattern X-ray diffraction data. Structures are derived for both a single chain lipid-water system (mono-olein) and a diacyl phospholipid-water system (2-2 methyl butyl 16:0 phosphatidylcholine). The methyl trough search uses the low electron density of the lipid methyl tails to determine the correct phasing for the electron density reconstruction. The data are consistent with a structure based on the IPMS D surface. The results are compared to other methods used to solve the mono-olein structure; the structure of the diacyl lipid has never before been solved. We discuss the subtleties involved in reconstruction of D surface based phases and the substantial artifacts that arise in low-resolution reconstructions of hydrocarbon lipids lacking heavy-atom sites. Received 15 January 1999 and Received in final form 20 October 1999     

Scalable Electrochemical Decarboxylative Olefination Driven by Alternating Polarity**

A mild, scalable (kg) metal-free electrochemical decarboxylation of alkyl carboxylic acids to olefins is disclosed. Numerous applications are presented wherein this transformation can simplify alkene synthesis and provide alternative synthetic access to valuable olefins from simple carboxylic acid feedstocks. This robust method relies on alternating polarity to maintain the quality of the electrode surface and local pH, providing a deeper understanding of the Hofer-Moest process with unprecedented chemoselectivity.