bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of Multi‐Component Reactions: From Libraries of Compounds to Libraries of Reactions
Authors: Mironov Maxim A. 
Published: April 2006

AbstractMulti‐Component Reactions (MCRs) constitute a methodology to shorter syntheses of natural products or complex molecules similar to natural. Due to the large number of accessible compounds and other advantages, this type of chemistry has become very popular in the community of combinatorial chemists. In the last 5 years combinatorial chemistry is has evolved from the synthesis of libraries based on one scaffold to the synthesis of structurally diverse compounds, better known as diversity‐oriented synthesis. Following this trend, the design of MCRs is becoming a tool kit for chemists to explore chemistry space broadly with complex and diverse structures. Various approaches to the creation of novel MCRs including “union of MCRs”, “substrate design”, and “reaction operator” are discussed here.
Matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight tandem mass spectra of poly(butylene adipate)
Authors: Rizzarelli Paola , Puglisi Concetto , Montaudo Giorgio 
Published: April 2006

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight tandem mass spectrometry (MALDI‐TOF/TOF‐MS/MS) was employed to analyze four poly(butylene adipate) (PBAd) oligomers and to investigate their fragmentation pathways as a continuation of our work on the MALDI‐TOF/TOF‐MS/MS study of synthetic polymers. MALDI‐TOF/TOF‐MS/MS analysis was performed on oligomers terminated by carboxyl and hydroxyl groups, methyl adipate and hydroxyl groups, dihydroxyl groups, and dicarboxyl groups. The sodium adducts of these oligomers were selected as precursor ions. Different end groups do not influence the fragmentation of sodiated polyester oligomers and similar series of product ions were observed in all the MALDI‐TOF/TOF‐MS/MS spectra. According to the structures of the most abundant product ions identified in the present work, three fragmentation pathways have been proposed to occur most frequently in PBAd: β‐hydrogen‐transfer rearrangement, leading to the selective cleavage of the OCH2 bonds; CH2CH2 (ββ) bond cleavage in the adipate moiety; and ester bond scission. Copyright © 2006 John Wiley & Sons, Ltd.
Induced smoothing for rank regression with censored survival times
Authors: Brown B. M. , Wang You‐Gan 
Published: April 2006

AbstractAdaptions of weighted rank regression to the accelerated failure time model for censored survival data have been successful in yielding asymptotically normal estimates and flexible weighting schemes to increase statistical efficiencies. However, for only one simple weighting scheme, Gehan or Wilcoxon weights, are estimating equations guaranteed to be monotone in parameter components, and even in this case are step functions, requiring the equivalent of linear programming for computation. The lack of smoothness makes standard error or covariance matrix estimation even more difficult. An induced smoothing technique overcame these difficulties in various problems involving monotone but pure jump estimating equations, including conventional rank regression. The present paper applies induced smoothing to the Gehan–Wilcoxon weighted rank regression for the accelerated failure time model, for the more difficult case of survival time data subject to censoring, where the inapplicability of permutation arguments necessitates a new method of estimating null variance of estimating functions. Smooth monotone parameter estimation and rapid, reliable standard error or covariance matrix estimation is obtained. Copyright © 2006 John Wiley & Sons, Ltd.
Quality audit roles and skills: Perceptions of non‐financial auditors and their clients
Authors: Power Damien , Terziovski Milé 
Published: April 2006

AbstractA major development in Operations Management over the past two decades has been the use of quality audits to gauge the effectiveness of quality management systems in manufacturing and service organizations. Achieving optimal benefits from non‐financial audits will, however, require that auditors and their clients obtain a greater understanding of and appreciation for the appropriate roles, responsibilities and skills of the non‐financial auditor. This research uses data obtained from surveys of 126 practicing non‐financial auditors and 400 non‐financial audit clients in Australasia to test two propositions about the roles and requirements of non‐financial auditors. The results indicate that non‐financial auditors believe they are providing a style of auditing that is strongly focused on developing continuous improvement of client's quality systems. Non‐financial auditors also appear to have a desire to meet what they perceive to be the requirements of certified organizations by emphasizing the importance of continuous improvement focused auditing. However, their clients have the opposite perception believing that they are getting less continuous improvement focused auditing than they would like, and more compliance auditing than they need. The results show that client organizations are, in general, looking for a more balanced approach to non‐financial auditing in terms of compliance and continuous improvement. The evidence also suggests that a major constraint identified relates to some fundamental issues of auditor independence. This dilemma created is apparent both in the understanding of what the appropriate role of the auditor is (in both the mind of the client and the auditor), and in the nature of the different roles each plays as a stakeholder in a quality system.
Report of a Symposium on Mechanics of Fluidized Beds
Authors: Homsy G. M. , Jackson R. , Grace J. R. 
Published: April 2006

Fluidized beds are widely used in industry for carrying out a variety of chemical reactions and physical processes. Applications are frequently impeded by a lack of fundamental understanding of the mechanical behaviour of fluidized beds. Despite intensive experimental and theoretical study over the last four decades, there are still many aspects of fluidized beds and related fluid—particle systems that remain obscure. Further work is needed to understand interactions between the particles, influence of particle physical properties, development of non-obtrusive experimental techniques, and study of high-velocity beds and of novel-geometry beds in which particulate solids interact with interstitial fluid.An international symposium was held at Stanford University on 1–4 July 1991 to discuss recent developments and the current state of knowledge and understanding of the mechanical behaviour of fluidized beds and related fluid—particle systems. The symposium was sponsored by the International Union of Theoretical and Applied Mechanics, and co-funded by the US Department of Energy, National Science Foundation and Electric Power Research Institute. The symposium was attended by 58 specialists representing academic institutions, industry and government research organizations in 11 countries. The diversity of background, coupled with differences in approach, ranging from purely theoretical to fully experimental, led to interesting exchanges where participants were often groping to understand the viewpoint of those involved. The result was frequently rewarding, occasionally perplexing, but certainly stimulating of thought and encouraging for further meetings of this nature.The scientific committee for the Symposium were G. K. Batchelor (Cambridge University), J. J. H. Brouwers (Trent University), J. Gibilaro (University College London), J. R. Grace (University of British Columbia), G. M. Homsy (Stanford University) (Chairman), R. Jackson (Princeton University), R. I. Nigmatulin (Moscow University) and W. Schneider (Techische Universität Wien).Each session began with an invited talk for one hour. This was followed by a series of 20-minute presentations. Participants were able at the end of each session to give brief (5 minute) unscheduled mini-presentations. Except for the latter, abstracts were submitted for the presentations, compiled by the organizers and distributed to participants. The meeting also included an informal workshop and a series of video and cinephotographic presentations not reported here. No formal proceedings of the meeting are being published; instead, this report is intended to summarize key findings and areas of discussion.The titles of all formal presentations are identified with asterisks in the list of References. The report is organized around common themes, and the sequence of presentations may not be that in which they were given. The authors have endeavoured to interpret and extract the essence of the presentations, and apologize if any of the presentations have been misinterpreted or overlooked.
Turbulence: the filtering approach
Authors: Germano M. 
Published: April 2006

Explicit or implicit filtered representations of chaotic fields like spectral cut-offs or numerical discretizations are commonly used in the study of turbulence and particularly in the so-called large-eddy simulations. Peculiar to these representations is that they are produced by different filtering operators at different levels of resolution, and they can be hierarchically organized in terms of a characteristic parameter like a grid length or a spectral truncation mode. Unfortunately, in the case of a general implicit or explicit filtering operator the Reynolds rules of the mean are no longer valid, and the classical analysis of the turbulence in terms of mean values and fluctuations is not so simple.In this paper a new operatorial approach to the study of turbulence based on the general algebraic properties of the filtered representations of a turbulence field at different levels is presented. The main results of this analysis are the averaging invariance of the filtered Navier—Stokes equations in terms of the generalized central moments, and an algebraic identity that relates the turbulent stresses at different levels. The statistical approach uses the idea of a decomposition in mean values and fluctuations, and the original turbulent field is seen as the sum of different contributions. On the other hand this operatorial approach is based on the comparison of different representations of the turbulent field at different levels, and, in the opinion of the author, it is particularly fitted to study the similarity between the turbulence at different filtering levels. The best field of application of this approach is the numerical large-eddy simulation of turbulent flows where the large scale of the turbulent field is captured and the residual small scale is modelled. It is natural to define and to extract from the resolved field the resolved turbulence and to use the information that it contains to adapt the subgrid model to the real turbulent field. Following these ideas the application of this approach to the large-eddy simulation of the turbulent flow has been produced (Germano et al. 1991). It consists in a dynamic subgrid-scale eddy viscosity model that samples the resolved scale and uses this information to adjust locally the Smagorinsky constant to the local turbulence.
Temperature fluctuation spectrum in the dissipation range for statistically isotropic turbulent flow
Authors: Tatarskii V. I. , Dubovikov M. M. , Praskovsky A. A. , Karyakin M. Yu. 
Published: April 2006

In the present paper we obtain a theoretical expression for the temperature fluctuation spectrum for a Prandtl number of approximately one and for the region where both viscosity and molecular heat conductivity are important. An asymptotic theory for very large wavenumbers of the temperature spectrum in the turbulent flow is developed. The assumption of smallness of the correlation coefficient between the product of small-scale components of velocities at two points and the corresponding product of small-scale components of temperatures is used. The results of simultaneous measurements of streamwise velocity fluctuations and temperature fluctuations carried out in the plane of symmetry of a two-dimensional wake behind a slightly heated cylinder (Rλ = 270) in a wind tunnel is consistent with this assumption.The main result of the theory developed is the appearance of a bump in the temperature spectrum for a Prandtl number of approximately one.
Natural convection and dispersion in a tilted fracture
Authors: Woods Andrew W. , Linz Stefan J. 
Published: April 2006

In many geophysical situations, fluid is contained in long narrow fractures embedded within an impermeable medium of different thermal conductivity: and there may be a uniform vertical temperature gradient imposed upon the system. We show that whenever the slot is tiled to the vertical, convection develops in the fluid, even if the background temperature increases with height. We then investigate the transport of passive material governed by this flow. The dispersion coefficient of a passive contaminant transported by this flow DT = f[R sin2ϕ] k2 cot2 ϕ/D, where k and D are the thermal and compositional diffusivities, ϕ is the angle of tilt and R is a Rayleigh number for the slot.Using typical values for the physical properties of a water-filled fracture, we show that the Earth's geothermal gradient produces a convective flow in a fracture through the mechanism above; this has an associated dispersion coefficient DT ∼ 102-103D in fractures about a centimetre wide. We show that this shear dispersion could transport radioactive material, of half-life 104 years, tens of metres along the fracture within one half-life; without this dispersion, the material would only diffuse a few metres along the fracture within one half-life.If there is a background salinity gradient along the slot in addition to the thermal gradient, analogous steady flow solutions exist; if the flow is stable, the salinity may either enhance or reduce the steady flow and associated dispersion of passive tracer.
Multiple equilibria in two-dimensional thermohaline circulation
Authors: Cessi Paola , Young W. R. 
Published: April 2006

As a model of the thermohaline circulation of the ocean we study the two-dimensional Boussinesq equations forced by prescribing the surface temperature and the surface salinity flux. We simplify the equations of motion using an expansion based on the small aspect ratio of the domain. The result is an amplitude equation governing the evolution of the depth averaged salinity field. This amplitude equation has multiple, linearly stable equilibria. The simplified dynamics has a Lyapunov functional and this variational structure permits a simple characterization of the relative stability of the alternative steady solutions.Even when the thermal and salinity surface forcing functions are symmetric about the equator there are asymmetric solutions, representing pole to pole circulations. These asymmetric solutions are stable to small perturbations and are always found in conjunction with symmetric solutions, also stable to small perturbations. Recent numerical solutions of the full two-dimensional equations have shown very similar flow patterns.
The structure of a turbulent free shear layer in a rotating fluid
Authors: Bidokhti A. A. , Tritton D. J. 
Published: April 2006

An experimental investigation has been carried out on the effects of rotation on the development and structure of turbulence in a free shear layer, oriented so that its mean vorticity is parallel or antiparallel to the system vorticity. The effective local Rossby number extended down to about 1/3. The experimental methods were hydrogen-bubble flow visualization and hot-film anemometry.In summarizing the results we refer to stabilized flow when the system vorticity has the same sign as the shear vorticity and destabilized and subsequently restabilized when it has the opposite sign (Tritton 1992). The roller eddy pattern, familiar in non-rotating flow, was observed in all stabilized flows, but was almost completely disrupted by even weak destabilization. Notable features of the quantitative results were: reorientation by Coriolis effects of the Reynolds stress tensor (inferred from the ratio of the cross-stream to longitudinal turbulence intensity and the normalized shear stress); changes in the ratio of spanwise to longitudinal intensity similar to but weaker than changes in the ratio of cross-stream to longitudinal; a gradual decrease, with increasing stabilization, of the Reynolds shear stress leading ultimately to its changing sign; an increase of the Reynolds shear stress in the destabilized range followed by rapid collapse to almost zero with restabilization. Absolute intensities did not change in line with the turbulence energy production, implying enhancement of dissipation in destabilized flow and inhibition in stabilized and restabilized. Correlation measurements indicated changes of lengthscale in the spanwise direction, and spectra indicated changes in the longitudinal direction that suggest that this enhancement and inhibition are associated with variations between fully three-dimensional and partially two-dimensional turbulence. Data for a wake in a rotating fluid (Witt & Joubert 1985) show similarities to some of the above observations and can be incorporated into the interpretation.
Experimental investigation of the field of velocity gradients in turbulent flows
Authors: Tsinober A. , Kit E. , Dracos T. 
Published: April 2006

We present results of experiments on a turbulent grid flow and a few results on measurements in the outer region of a boundary layer over a smooth plate. The air flow measurements included three velocity components and their nine gradients. This was done by a twelve-wire hot-wire probe (3 arrays × 4 wires), produced for this purpose using specially made equipment (micromanipulators and some other auxiliary special equipment), calibration unit and calibration procedure. The probe had no common prongs and the calibration procedure was based on constructing a calibration function for each combination of three wires in each array (total 12) as a three-dimensional Chebishev polynomial of fourth order. A variety of checks were made in order to estimate the reliability of the results.Among the results the most prominent are the experimental confirmation of the strong tendency for alignment between vorticity and the intermediate eigenvector of the rate-of-strain tensor, the positiveness of the total enstrophy-generating term ωiωjsij (sij = ½(∂ui/∂xj+∂uj/∂xi), ωi = εijk∂uj/∂xk) even for rather short records and the tendency for alignment in the strict sense between vorticity and the vortex stretching vector Wi = ωjsij. An emphasis is put on the necessity to measure invariant quantities, i.e. independent of the choice of the system of reference (e.g. sijsij and ωiωjsij) as the most appropriate to describe physical processes. From the methodological point of view the main result is that the multi-hot-wire technique can be successfully used for measurements of all the nine velocity derivatives in turbulent flows, at least at moderate Reynolds numbers.
Instability of a solid-body rotating vortex in a two-layer model
Authors: Ripa P. 
Published: April 2006

The instability of an anticyclonic solid-body rotating eddy embedded on a quiescent environment is studied, for all possible values of the parameters of the unperturbed state, i.e. the vortex's relative thickness and rotation rate. The Coriolis force is fundamental for the existence of the eddy (because the pressure force has a centrifugal direction) and therefore this analysis pertains to the study of mesoscale vortices in the ocean or the atmosphere, as well as those in other planets.These eddies are known to be stable when the ‘second’ layer is assumed imperturbable (infinitely deep); however, here these vortices are found to be unstable in the more realistic case of an active environment layer, which may be arbitrarily thick.Three basic types of instability are found, classified according to the dynamic structure of the growing perturbation field, in both layers: baroclinic instability (Rossby-like in both layers), Sakai instability (Poincaré-like in the vortex layer and Rossby-like in the environment), and Kelvin–Helmholtz instability (Poincaré-like in both layers). In addition, there is a hybrid instability, which goes continuously from the baroclinic to the Sakai types, as the rotation rate is increased.The problem is constrained by the conservation of pseudoenergy and angular pseudomomentum, which are quadratic (to lowest order) in the perturbation. The requirement that both integrals of motion vanish for a growing disturbance, determines the structure of the latter in both layers. Furthermore, that constraint restricts the region, in parameter space, where each type of instability is present.
Dynamics and transport of a localized soluble surfactant on a thin film
Authors: Halpern D. , Grotberg J. B. 
Published: April 2006

The flow induced by a localized droplet of soluble surfactant on the surface of a thin film is analysed, motivated by an interest in the interaction between inhaled droplets and the lung's thin liquid lining after an aerosol lands on its surface. The spreading is driven by gradients of surface tension and results in flow of the droplet and underlying liquid film. This induced flow field plays an important role in the transport of dissolved species from the droplet, through the film, and to the tissue for absorption.Evolution equations for the film thickness, surface and bulk liquid concentrations are derived using lubrication theory, since the depth of the film is much smaller than the characteristic radius of the droplet. Solutions are obtained numerically using the method of lines for a variety of surface Péclet numbers.We find that the effect of solubility is to decrease both film disturbances and surface concentrations, and to induce an absorption-driven backflow. In addition, there is a gravity-driven backflow from hydrostatics. At large surface Péclet numbers, large film disturbances are obtained and more surfactant is able to diffuse across the rigid permeable wall, while surface diffusion causes more rapid spreading and decreases film disturbances. Gravity acts as a restoring force by creating a bidirectional flow, and hence disenhances the vertical flux of surfactant across the air-liquid interface. This model may have implications for the delivery of drugs by aerosol inhalation.
Orbital flow around a circular cylinder. Part 1. Steady streaming in non-uniform conditions
Authors: Chaplin John R. 
Published: April 2006

This work is concerned with the source of an important component of nonlinear loading on a horizontal cylinder beneath waves that is not present in conventional diffraction calculations. Earlier measurements (Chaplin 1984b) have suggested that circulation induced by steady streaming around the cylinder may be responsible for loading which in some cases reduces the perceived inertia force by 50%. The present work is aimed at studying the steady streaming around a cylinder in general non-uniform orbital flow, and determining whether in the particular case of wave-induced flow it could be related quantitatively to the loading.The steady outer flow has been obtained numerically for cases where the steady streaming does not have a reversal, and for cases where a weak reversal is compatible with a uniform outer circulation. It is found that the outer circulation is closely related to the mean streaming velocity around the cylinder at the outer edge of the shear-wave layer. Results for conditions corresponding to previous measurements of force on a horizontal cylinder beneath waves suggest that separation, turbulence, transient effects and organized three-dimensional instabilities should also be considered.