Synthesis and spectral analysis of (±)-cis-N-[1-(2-hydroxy-2-phenyl-ethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide and (±)-cis-N-[1-(2-hydroxy-1-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide

Treatment of (±)-cis-N-(3-methyl-4-piperidyl)-N-phenylpropanamide (2) with styrene oxide (1) yielded a mixture of (±)-cis-N-[1-(2-hydroxy-2-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide (3) and (±)-cis-N-[1-(2-hydroxy-1-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide (4) . The structure of compound 3 was confirmed by an unambiguous synthesis via (±)-cis-N-[1-(2-oxo-2-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide (6) . The proton and carbon-13 resonances of compounds 3 and 4 were assigned with the aid of two-dimensional heteronuclear correlation experiments.     

Observation of a new phosphorus-containing reactive intermediate: electronic spectroscopy and excited-state dynamics of the HPBr free radical

The A (2)A(')-X (2)A(") electronic spectra of jet-cooled HPBr and DPBr have been obtained for the first time using the pulsed electric discharge technique with a precursor mixture of PBr(3) and H(2)/D(2). Laser-induced fluorescence and single vibronic level emission spectra gave the bending and P-Br stretching frequencies in the ground and excited states of both isotopomers. Rotational analyses of the HPBr and DPBr 0(0) (0) bands showed small spin splittings characteristic of a doublet-doublet transition of an asymmetric-top molecule. From the ground- and excited-state rotational constants, effective (r(0)) structures were derived with r(")(PH)=1.4307(86) A, r(")(PBr)=2.2021(9) A, and theta(")=95.2(8) degrees, and r(')(PH)=1.434(31) A, r(')(PBr)=2.1669(26) A, and theta(')=115.5(16) degrees . In a few favorable cases, further hyperfine splitting of the spin-rotation energy levels has been observed, due to the excited-state Fermi contact interaction of the unpaired electron with the spin magnetic moment of the (31)P nucleus, with a(F) (')=0.064(9) cm(-1) for HPBr. Fluorescence depletion spectroscopy and lifetime measurements indicate that higher vibrational levels of the A (2)A(') state are predissociated by a X (2)A(") dissociative continuum. CCSD(T)/aug-cc-pVTZ calculations predict that the most likely dissociation process is HPBr (X (2)A("))-->PH((3)Sigma(-))+Br((2)P(u)).     

A metallocene-complexed dibismuthene: Cp2Zr(BiR)2 (Cp = C5H5; R = C6H3-2,6-Mes2)

The zirconocene-complexed dibismuthene, Cp2Zr(BiR)2 (Cp = C5H5; R = C6H3-2,6-Mes2), was prepared by the reaction of sodium metal with Cp2ZrCl2 and RBiCl2. The air- and moisture-sensitive dark reddish/brown compound is the first organometallic compound containing Bi-Zr bonds and the only example of a ZrBi2 ring. Moreover, our computations on associated model systems offer insight into the nature of the interaction of the heaviest dipnictene with a metallocene center.     

Finite Euclidean graphs over rings

We consider graphs attached to , where , for an odd prime , using an analogue of the Euclidean distance. These graphs are shown to be mostly non-Ramanujan, in contrast to the case of Euclidean graphs over finite fields.

     

A tandem Jackson network with feedback to the first node

AnN-node tandem queueing network with Bernoulli feedback to the end of the queue of thefirst node is considered. We first revisit the single-nodeM/G/1 queue with Bernoulli feedback, and derive a formula forEL(n), the expected queue length seen by a customer at his nth feedback. We show that, asn becomes large,EL(n) tends to /(l ), being the effective traffic intensity. We then treat the entire queueing network and calculate the mean value ofS, the total sojourn time of a customer in theN-node system. Based on these results we study the problem ofoptimally ordering the nodes so as to minimize ES. We show that this is a special case of a general sequencing problem and derive sufficient conditions for an optimal ordering. A few extensions of the serial queueing model are also analyzed. We conclude with an appendix in which we derive an explicit formula for the correlation coefficient between the number of customers seen by an arbitrary arrival to anM/G/1 queue, and the number of customers he leaves behind him upon departure. For theM/M/1 queue this coefficient simply equals the traffic intensity .     

Metallic thin film growth on vicinal Cu substrates

In this study we have investigated the heteroepitaxial growth of nickel and silver on vicinal copper substrates. Nickel was deposited onto a (211) substrate. The low lattice mismatch between copper and nickel of 2.5% enables epitaxial bidimensional growth in the substrate's orientation, where the strain can be accommodated in the overlaying film. On the contrary, copper and silver have a much larger mismatch of about 13% which usually cannot be accommodated in the film. In general, Ag is known to form alloys or to induce faceting on a stepped Cu surfaces. Here, silver was deposited onto a Cu(311) facet covered with a monatomic layer of NaCl. For the first time we show that Ag can be grown as ultrathin film in the substrates's orientation on a stepped surface using NaCl as a novel surfactant material.     

Stress communication and filtering of viscoelastic layers in oscillatory shear

We revisit a classical topic: response functions of viscoelastic layers in large amplitude oscillatory shear. Motivated by questions concerning protective biological layers, we focus on boundary stresses in a parallel plate geometry with imposed oscillatory strain or stress. These features are gleaned from resolution and analysis of coupled standing waves of deformation and stress. We identify a robust non-monotone variation in boundary stress signals with respect to all experimental controls: viscoelastic moduli of the layer, layer thickness, and driving frequency. This structure of peaks and valleys in boundary values of shear and normal stress indicates redundant mechanisms for stress communication (by tuning to the peaks) and stress filtering (by tuning to the valleys). In this paper, we first restrict to a single-mode non-linear Maxwell model for the viscoelastic layer, where analysis renders a transparent explanation of the phenomena. We then consider a Giesekus constitutive model of the layer, where analysis is supplanted by numerical simulations of coupled non-linear partial differential equations. Parametric studies of wall stress values from standing waves confirm persistence of the Maxwell model phenomena. The analysis and simulations rely on and extend our recent studies of shear waves in a micro parallel plate rheometer [S.M. Mitran, M.G. Forest, L. Yao, B. Lindley, D. Hill, Extenstions of the Ferry shear wave model for active linear and nonlinear microrheology, J. Non-Newtonian Fluid Mech. 154 (2008) 120–135; D.B. Hill, B. Lindley, M.G. Forest, S.M. Mitran, R. Superfine, Experimental and modeling protocols from a micro-parallel plate rheometer, UNC Preprint, 2008].     

Methodology for measuring conformation of solvent-disrupted protein subunits using T-WAVE ion mobility MS: An investigation into eukaryotic initiation factors

The methodology developed in the research presented herein makes use of chaotropic solvents to gently dissociate subunits from an intact macromolecular complex and subsequently allows for the measurement of collision cross section (CCS) for both the recombinant (R-eIF3k) and solvent dissociated form of the subunit (S-eIF3k). In this particular case, the k subunit from the eukaryotic initiation factor 3 (eIF3) was investigated in detail. Experimental and theoretical CCS values show both the recombinant and solvent disrupted forms of the protein to be essentially the same. The ultimate goal of the project is to structurally characterize all the binding partners of eIF3, determine which subunits interact directly, and investigate how subunits may change conformation when they form complexes with other proteins. Research presented herein is the first report showing retention of solution conformation of a protein as evidenced by CCS measurements of both recombinant and solvent disrupted versions of the same protein.     

Flow transition in dual bell nozzles

The dual bell nozzle is a concept of altitude adaptive nozzles. The flow adapts to the altitude by separation at the wall inflection at low altitude, and full flowing at high altitude. To understand the phenomenology of the flow by the transition from sea-level mode to high altitude mode, a series of tests have been made at the cold flow test bench P6.2 at DLR Lampoldshausen. A dual bell nozzle have been successively shorten and driven in the same conditions for each length. Hence it was possible to observe the flow in the vicinity of the wall inflection using Schlieren optics. Furthermore this study yields the influence of the length ratio between basis and extension on the transition conditions.

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