An improved fitting algorithm for parametric macromodeling from tabulated data

This paper introduces a new scheme for the identification of multivariate behavioral maeromodels from tabulated frequencydomain data. The method produces closed-form parametric expressions that reproduce with excellent accuracy the external port behavior of the structure, both as function of frequency and one or more external parmeters. The numerical robustness of the main algorithm is demonstrated on two significant examples

Stability, Causality, and Passivity in Electrical Interconnect Models

Modern packaging design requires extensive signal integrity simulations in order to assess the electrical performance of the system. The feasibility of such simulations is granted only when accurate and efficient models are available for all system parts and components having a significant influence on the signals. Unfortunately, model derivation is still a challenging task, despite the extensive research that has been devoted to this topic. In fact, it is a common experience that modeling or simulation tasks sometimes fail, often without a clear understanding of the main reason. This paper presents the fundamental properties of causality, stability, and passivity that electrical interconnect models must satisfy in order to be physically consistent. All basic definitions are reviewed in time domain, Laplace domain, and frequency domain, and all significant interrelations between these properties are outlined. This background material is used to interpret several common situations where either model derivation or model use in a computer-aided design environment fails dramatically.We show that the root cause for these difficulties can always be traced back to the lack of stability, causality, or passivity in the data providing the structure characterization and/or in the model itsel

Palladium-Catalyzed Carboamination and Carboetherification Reactions for the Synthesis of Heterocycles.

Investigation of the Pd-catalyzed carboamination reaction for the synthesis of substituted piperidines from delta-amino olefins and piperazine heterocycles from amino acid derivatives is described. These reactions are believed to proceed via an unprecedented insertion into a Pd–N bond of the key Pd-amido species. These reactions also proceed with excellent levels of 2,6-diastereocontrol (in many cases, >20:1 dr has been observed). The diastereoselectivity of these reactions is also dependent on the protecting group on the cyclizing nitrogen, where more electron rich aryl protecting groups provide more of the cis-diastereomer, whereas less electron rich protecting groups provide slightly lower diastereoselectivity, still favoring the cis-diastereomer. Our stereochemical model differs from related pyrrolidine cyclizations which also provide the cis-diastereomer. We hypothesized that the nitrogen is pyramidalized in the transition state leading to the piperazine and therefore the alpha-substituent can lie in the pseudoequatorial orientation. In addition to 2,6-disubstituted aryl-protected piperazines coupled with aryl halides, we also extended the methodology to include vinyl-halide coupling partners, Boc-protected piperazines, 2,3-disubstituted piperazines, bicyclic piperazines, and benzopiperazines. The second part of this thesis details intramolecular Pd-catalyzed carboetherification and carboamination reactions for the synthesis of 2-indanyl tetrahydrofurans and 2-indanyl pyrrolidines. These reactions are believed to proceed through an unprecedented macrocyclic insertion into a Pd–O or Pd–N bond to afford products resulting from syn-addition across the olefin. Surprisingly, in the optimization of the carboetherification reactions, we discovered an unprecedented catalyst control on the stereochemical outcome of the reaction. In cases where a monodentate ligand was used in combination with a Pd(0) source, we observed selective formation of the syn-addition diastereomer. When we switched to a catalyst system composed of Pd(0) and a bidentate ligand, we observed formation of the anti-addition diasteromer. We reasoned we were observing a catalyst control of mechanism in the oxypalladation reaction. In the analogous carboamination reactions, we did not observe a complete reversal of diastereoselectivity, but instead erosion of diastereoselectivity. We reasoned this was due to several factors, including the reduced pKa of the aniline versus the alcohol. Further studies to expand the scope of the intramolecular carboetherification and carboamination were also demonstrated.Ph.D.ChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60696/1/jnakhla_1.pd

Neutrophil-derived microparticles are released into the coronary circulation following percutaneous coronary intervention in acute coronary syndrome patients.

To evaluate (i) local coronary and systemic levels of microparticles (MP) in acute coronary syndrome (ACS) and stable angina pectoris (SAP) patients and (ii) their release after plaque disruption with percutaneous coronary intervention (PCI). MP are small vesicles originating from plasma membranes of cells after activation or apoptosis and are implicated in the pathogenesis of atherosclerosis. Neutrophils play a role in plaque destabilization and shed neutrophil-derived MP that have the potential to drive significant proinflammatory and thrombotic downstream effects. Eight ACS and eight SAP patients were included. Coronary sinus (CS) samples pre-intervention (CS1), 45 s following balloon angioplasty (CS2) and at 45 s intervals following stent deployment (CS3, CS4 and CS5), together with peripheral vein samples, pre- and post-PCI were analysed for neutrophil-derived (CD66b+), endothelial-derived (CD144+), platelet-derived (CD41a+), monocyte-derived (CD14+) and apoptotic (Annexin V+) MP. ELISA for interleukin (IL)-6, myeloperoxidase (MPO) and P-selectin was also performed. CD66b+ MP levels were similar in both groups pre-intervention. Post-PCI, CS levels rose significantly in ACS but not SAP patients (ACS area under the curve (AUC): 549 ± 83, SAP AUC: 24 ± 29, P<0.01). CS CD41a+, CD144+, CD14+ and Annexin V+ MP levels did not differ between groups. Acute neutrophil-derived MP release post-PCI occurs in ACS compared with stable patients, likely to be reflective of plaque MP content in vulnerable lesions

Sputtering of Surfaces by Ion Irradiation: A Comparison of Molecular Dynamics and Binary Collision Approximation Models to Laboratory Measurements

We compare various sputtering simulation methods to experimental results in both the low energy (<1 keV) and high energy (≥1 keV) impact regimes for argon ions impacting a pure copper substrate at normal incidence. Our results indicate that for high energy impacts, both binary collision approximation (BCA) and molecular dynamics methods can be used to generate reasonable predictions for the yield and energy distribution of the sputtered atoms. We also find reasonable agreement between the theoretical and experimental results down to impact energies of 600 eV. However, at 200 eV impact energies, significant discrepancies appear between the experimental and theoretical ejecta energy distributions in the peak position, the width of the energy distribution, and the magnitude of the high energy tail. These discrepancies appear to arise from the experimental results being only for atoms sputtered normal to the substrate surface, whereas the theoretical results are integrated over all 2π solid angles above the surface. Using the BCA code SDTrimSP and limiting the results to only atoms emitted within ±15° of the surface normal brings theory and experiment into reasonable agreement. These results suggest that for low energy impacts, the energy distribution of sputtered atoms is highly dependent on the emission angle of the ejecta

Solar Wind Ion Sputtering of Sodium from Silicates Using Molecular Dynamics Calculations of Surface Binding Energies

For nearly 40 yr, studies of exosphere formation on airless bodies have been hindered by uncertainties in our understanding of the underlying ion collisional sputtering by the solar wind (SW). These ion impacts on airless bodies play an important role in altering their surface properties and surrounding environment. Much of the collisional sputtering data needed for exosphere studies come from binary collision approximation (BCA) sputtering models. These depend on the surface binding energy (SBE) for the atoms sputtered from the impacted material. However, the SBE is not reliably known for many materials important for planetary science, such as plagioclase feldspars and sodium pyroxenes. BCA models typically approximate the SBE using the cohesive energy for a monoelemental solid. We use molecular dynamics (MD) to provide the first accurate SBE data we are aware of for Na sputtered from the above silicate minerals, which are expected to be important for exospheric formation at Mercury and the Moon. The MD SBE values are ∼8 times larger than the Na monoelemental cohesive energy. This has a significant effect on the predicted SW ion sputtering yield and energy distribution of Na and the formation of the corresponding Na exosphere. We also find that the SBE is correlated with the coordination number of the Na atoms within the substrate and with the cohesive energy of the Na-bearing silicate. Our MD SBE results will enable more accurate BCA predictions for the SW ion sputtering contribution to the Na exosphere of Mercury and the Moon

Molecular characterization of a Moroccan isolate of Tomato yellow leaf curl Sardinia virus and differentiation of the Tomato yellow leaf curl virus complex by the polymerase chain reaction

The polymerase chain reaction (PCR) was used to identify an isolate of Tomato yellow leaf curl Sardinia virus (TYLCSV) from southwestern Morocco and to detect the members of the Tomato yellow leaf curl virus (TYLCV) complex. Thirty-five tomato samples with typical TYLCV symptoms were collected from infected tomato fields in the Souss-Massa region. PCR was performed with a general primer pair based on the coat protein (Cp) gene of the TYLCV complex, as well as with specific primer pairs for TYLCV and TYLCSV. Of the 35 samples tested, 29 generated a viral DNA product with the general primer pair, 29 samples gave a viral DNA product with the TYLCV-specific primers, and of these, 9 also gave a product with the TYLCSV primer pair; 6 samples did not give any PCR product with either primer pair. The full-length genome of TYLCSV was amplified with overlapping primers at the unique NcoI site in the TYLCSV genome (GenBank accession number X61153). The full-length genome of the TYLCSV isolate from Morocco is 2,777 nucleotides long (accession number AY702650) and is almost identical (97% nucleotide identity) to a TYLCSV isolate from Murcia, Spain (accession number Z25751). A PCR-based diagnostic method was developed to distinguish between TYLCV and TYLCSV in Morocco. To diagnose the TYLCV/TYLCSV complex a general primer pair was designed that anneals to a conserved region of the Cp gene. To diagnose TYLCSV exclusively, two primer pairs were designed to anneal specifically to the replication-associated protein gene (Rep) of TYLCSV from Morocco. To detect TYLCV exclusively, a primer pair previously described to amplify the intergenic region (IR) of TYLCV was used. The PCR primers were tested for their effectiveness using DNA clones of the TYLCSV from Morocco and of the TYLCV from the Dominican Republic. PCR using these primers offers a rapid means to detect the TYLCV complex and to distinguish between the two TYLCV species present in Morocco