Surface-Mediated Solid Phase Reaction. IX. A Convenient Procedure for Aldol Reaction of Ketene Silyl Acetals with Aldehydes on the Solid Surface of Alumina

The aldol reaction of ketene silyl acetals with aldehydes proceeds efficiently on the solid surface of alumina impregnated with anhydrous zinc chloride under sonication providing aldol products in high yields and with good stereoselectivity.     

Toward numerical simulations of fluid–structure interactions for investigation of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a medical condition characterized by repetitive partial or complete occlusion of the airway during sleep. The soft tissues in the airway of OSA patients are prone to collapse under the low-pressure loads incurred during breathing. This paper describes efforts toward the development of a numerical tool for simulation of air–tissue interactions in the upper airway of patients with sleep apnea. A procedure by which patient-specific airway geometries are segmented and processed from dental cone-beam CT scans into signed distance fields is presented. A sharp-interface embedded boundary method based on the signed distance field is used on Cartesian grids for resolving the airflow in the airway geometries. For simulation of structure mechanics with large expected displacements, a cut-cell finite element method with nonlinear Green strains is used. The fluid and structure solvers are strongly coupled with a partitioned iterative algorithm. Preliminary results are shown for flow simulation inside the three-dimensional rigid upper airway of patients with obstructive sleep apnea. Two validation cases for the fluid–structure coupling problem are also presented.     

An efficient green protocol for the synthesis of coumarin fused highly decorated indenodihydropyridyl and dihydropyridyl derivatives

A simple, convenient, environmentally benign, and mild synthetic method has been established to afford highly decorated indenodihydropyridine and dihydropyridine derivatives employing a green solvent ethyl-l-lactate and an organo-catalyst (±)lactic acid. A wide range of functional groups were tolerated in the developed protocol. The target molecules were obtained in moderate to good yields applying the current method.     

Estimation of Phase and Its Higher Order Derivatives from a Single Complex Interferogram

This paper reports a method for the simultaneous estimation of unwrapped phase and higher order phase derivatives from a single phase fringe pattern recorded in an optical interferometric setup, thereby overcoming substantial barriers to achieving such measurements. The proposed method considers the interference phase as a weighted linear combination of Gaussian radial basis functions defined along a given row or column at a time. The Gaussian radial basis functions are defined with a constant standard deviation and equally spaced centers. Unscented Kalman filter is employed for the accurate estimation of the weights of the basis functions using the state space representation of the spatial evolution of the interferogram. The estimated weights along with the numerically computed gradients of the basis functions also provide the estimations of phase derivatives of arbitrary order. The proposed representation of interference phase along with the unscented Kalman filter provides high robustness against the speckle noise. Simulation study is preformed to evaluate the dependence of the phase and phase derivative estimation accuracy on the selection of basis dimension and the noise level. Experimental results demonstrate the practical applicability of the proposed method.     

Viscous flow in a mixed compression intake

Numerical simulation of the flow in a two‐dimensional mixed compression intake is carried out by solving unsteady viscous compressible equations using a stabilized finite element method. The effect of bleed in starting/unstarting of the intake and controlling the buzz instability is investigated in detail. Higher bleed leads to an increase in the ability of the intake to sustain larger back‐pressure for stable operation. The amount of bleed and its location is varied to understand its effect on the performance of the intake. Two kinds of unsteady oscillations are observed: ‘little’ and ‘big’ buzz. The frequency of the both kinds of buzz oscillations is found to be super‐harmonic of the fundamental acoustic frequency of intake modeled as an open‐closed organ pipe. The frequency as well as amplitudes of the big buzz cycles is larger than those of the little buzz. The little‐ and big‐buzz are found to occur for low‐ and high‐subcritical state of the intake and are very similar to Ferri and Dailey criteria, respectively. Buzz is eliminated when relatively high bleed is implemented, both, upstream and downstream of the throat. The effect of rate of change of back‐pressure on the start/unstart of the intake is investigated. Two situations are considered. The first case is that of an intake where the back‐pressure remains below the critical value. It is found that the intake remains started if the change in back‐pressure is gradual. However, it unstarts if the back‐pressure is changed relatively rapidly. The second set of simulations is an attempt to model the situation where the back‐pressure at the exit of the intake exceeds the critical value and a logic is incorporated in the feed back loop of the fuel modulation to start the intake. Low rate of change of pressure is unsuccessful in starting the intake. Relatively high rates result in either a quick starting of the intake or a slow unstart. Copyright © 2010 John Wiley & Sons, Ltd.     

Substituted Diorganotin(IV) O,O’-Alkylene Dithiophosphates: Synthesis and Spectral Aspects

Six new substituted diphenyltin(IV) O,O′-alkylene dithiophosphates, (C₆H₅)₂Sn(X)S(S) POGO [G = —CH₂C(CH₃)₂CH₂—, X = Cl (1), SCN (3), ClO₄ (5); G = —CH₂C (C₄H₉)(C₂H₅)CH₂—, X = Cl (2), SCN (4), ClO₄ (6)], were synthesized by the reaction of the corresponding ammonium salts of the O,O’-alkylene dithiophosphates with an appropriate organotin(IV) chloride. The compounds were characterized on the basis of elemental and spectral analyses (ESI mass spectrometry, IR, ¹H, ¹³C, ³¹P, and ¹¹⁹Sn NMR). The presence of a four-coordinated Sn atom and monodentate O,O’-alkylene dithiophosphate moiety in compounds 1–4 as well as bidentate O,O’-alkylene dithiophosphate unit in compounds 5,6 is established.     

Immobilized Carboxypeptidase A for Sequential Analysis

The use of carboxypeptidase for sequence determination is attractive because of its technical simplicity. In chemical methods all molecules of a peptide are made to go through a degradation cycle before a new cycle is started. In the enzymatic degradation of a protein, the order of the amino acid residues is not necessarily determined in a stepwise fashion but rather from the rate at which the amino acids appear in the digest, i.e., an amino acid appearing faster than another presumably precedes it in the sequence. Under favorable circumstances the rate of appearance of the amino acids released during digestion give sufficient evidence for the C-terminal sequence to be deduced. The present work pertains to a study on the use of immobilized carboxypeptidase A columns for sequential analyses.     

Low-Valent Titanium Mediated Deprotection of N-Allyl/Benzyl Amines: A New Approach

A novel low-valent titanium (LVT) mediated cleavage of N-allyl/benzyl amines is reported. Regio- and chemo-selective cleavages were also observed.     

RuCl3 · xH2O: A New Efficient Catalyst for Facile Preparation of 1,1‐Diacetates from Aldehydes

An efficient, facile preparation of aldehyde 1,1‐diacetates (acylals) in excellent yields catalyzed by RuCl₃ · xH₂O is described. Ketones do not react under these conditions.