A carbocationic route to 3-substituted 1,4-cycloheptadienes

The Lewis acid catalysed reaction of 5-chloro-1, 3-cycloheptadiene 4 with silyl enol ethers yields -cycloheptadienyl substituted carbonyl compounds in high yield. Since 4 is easily prepared from cycloheptatriene, and the cycloheptadienyl cation 3 is preferably attacked at 3-position, this reaction opens an efficient access to 3-substituted 1,4-cycloheptadienes

Invariant Solution underlying Oblique Stripe Patterns in Plane Couette Flow

When subcritical shear flows transition to turbulence, laminar and turbulent flow often coexists in space, giving rise to turbulent-laminar patterns. Most prominent are regular stripe patterns with large-scale periodicity and oblique orientation. Oblique stripes are a robust phenomenon, observed in experiments and flow simulations, yet their origin remains unclear. We demonstrate the existence of an invariant equilibrium solution of the fully nonlinear 3D Navier-Stokes equations that resembles the oblique pattern of turbulent-laminar stripes in plane Couette flow. We uncover the origin of the stripe equilibrium and show how it emerges from the well-studied Nagata equilibrium via two successive symmetry-breaking bifurcations

Potenziamento delle stazioni di monitoraggio video esistenti e istallazione di nuove telecamere all’Osservatorio Astrofisico di “Serra la Nave”, a “La Montagnola” e a “Monte Vetore

Directed evolution is a method to tune the properties of enzymes for use in organic chemistry and biotechnology, to study enzyme mechanisms, and to shed light on Darwinian evolution in nature. In order to enhance its efficacy, iterative saturation mutagenesis (ISM) was implemented. This involves: 1) randomized mutation of appropriate sites of one or more residues; 2) screening of the initial mutant libraries for properties such as enzymatic rate, stereoselectivity, or thermal robustness; 3) use of the best hit in a given library as a template for saturation mutagenesis at the other sites; and 4) continuation of the process until the desired degree of enzyme improvement has been reached. Despite the success of a number of ISM-based studies, the question of the optimal choice of the many different possible pathways remains unanswered. Here we considered a complete 4-site ISM scheme. All 24 pathways were systematically explored, with the epoxide hydrolase from Aspergillus niger as the catalyst in the stereoselective hydrolytic kinetic resolution of a chiral epoxide. All 24 pathways were found to provide improved mutants with notably enhanced stereoselectivity. When a library failed to contain any hits, non-improved or even inferior mutants were used as templates in the continuation of the evolutionary pathway, thereby escaping from the local minimum. These observations have ramifications for directed evolution in general and for evolutionary biological studies in which protein engineering techniques are applied

Measuring stellar oscillations using equivalent widths of absorption lines

Kjeldsen et al. (1995, AJ 109, 1313; astro-ph/9411016) have developed a new technique for measuring stellar oscillations and claimed a detection in the G subgiant eta Boo. The technique involves monitoring temperature fluctuations in a star via their effect on the equivalent width of Balmer lines. In this paper we use synthetic stellar spectra to investigate the temperature dependence of the Balmer lines, Ca II, Fe I, the Mg b feature and the G~band. We present a list of target stars likely to show solar-like oscillations and estimate their expected amplitudes. We also show that centre-to-limb variations in Balmer-line profiles allow one to detect oscillation modes with l<=4, which accounts for the detection by Kjeldsen et al. of modes with degree l=3 in integrated sunlight.Comment: MNRAS (accepted); 7 pages, LaTeX with necessary style file and PostScript figures in a single uuencoded Z-compressed .tar fil

Water Quality in the West

Under the Western Water Policy Review Act of 1992 (P.L. 102-575, Title XXX), Congress directed the President to undertake a comprehensive review of Federal activities in the 19 Western States that directly or indirectly affect the allocation and use of water resources, whether surface or subsurface, and to submit a report of findings to the congressional committees having jurisdiction over Federal Water Programs

Travelling Islam - Madrasa Graduates from India and Pakistan in the Malay Archipelago

The phenomenon of travelling religious traditions has attracted the attention of various scholars, but a differentiated understanding of its nature and impact is still lacking. This essay addresses the transnational and transregional impact of educational traditions in Islam in the South-South direction. It traces the impact of two education networks based in South Asia on Islamic learning in South East Asia. Both the modernist institutions of the International Islamic University and the conservative Deoband schools together with the affiliated Tablighi Jama'at have made significant headway in Malaysia, Indonesia, Singapore and beyond. The case study argues that the impact is far from unidirectional and more multifaceted than often assumed. It is largely shaped by the social and cultural experience of local society and driven by its needs, rather than by a transnational agenda

Code-switching among Qaqet-speaking adults in Kamanakam, East New Britain Province, Papua New Guinea

This thesis provides a description of the code-switching practices of adult bilingual speakers of Qaqet and Tok Pisin in Kamanakam, East New Britain Province, Papua New Guinea. In this study, code-switching is approached from a sociolinguistic and conversation analytic perspective. It takes the distinction of situational and conversational code-switching as an overarching approach. The categories are an integral part of the major code-switching typologies of the last 50 years and have therefore proven to be very robust. The data collection process focused on two focal families and their social network, ranging from uncontrolled to controlled methods. They include participant observation, sociodemographic and sociolinguistic surveys, sociolinguistic interviews, wiring method, naturalistic audiovisual recordings, and staged audiovisual recordings. This study shows that Qaqet/Tok Pisin code-switching is dominantly observed in non-public settings, whereas in public settings, Tok Pisin is the dominant language. The major factor for situational code-switching is the language competence of the interlocutor, established between speaker and interlocutor in previous interactions through habitual language use. In addition, a number of conversational strategies are identified in monolingual and code-switched discourse. It is argued that code-switching serves here as a further cue to other already present cues (e.g., prosodic ones). For Qaqet/Tok Pisin speakers in Kamanakam, code-switching is an important means to facilitate daily communication in a multilingual environment, where people have different competencies of Qaqet. In addition, they use code-switching as a further tool to structure their discourse

Modeling many-particle mechanical effects of an interacting Rydberg gas

In a recent work [Phys. Rev. Lett. 98, 023004 (2007)] we have investigated the influence of attractive van der Waals interaction on the pair distribution and Penning ionization dynamics of ultracold Rydberg gases. Here we extend this description to atoms initially prepared in Rydberg states exhibiting repulsive interaction. We present calculations based on a Monte Carlo algorithm to simulate the dynamics of many atoms under the influence of both repulsive and attractive longrange interatomic forces. Redistribution to nearby states induced by black body radiation is taken into account, changing the effective interaction potentials. The model agrees with experimental observations, where the ionization rate is found to increase when the excitation laser is blue-detuned from the atomic resonance