Model Calculations for the Two-Fragment Electro-Disintegration of 4^4He

Differential cross sections for the electro-disintegration process $e + {^4He} \longrightarrow {^3H}+ p + e'$ are calculated, using a model in which the final state interaction is included by means of a nucleon-nucleus (3+1) potential constructed via Marchenko inversion. The required bound-state wave functions are calculated within the integrodifferential equation approach (IDEA). In our model the important condition that the initial bound state and the final scattering state are orthogonal is fulfilled. The sensitivity of the cross section to the input $p{^3H}$ interaction in certain kinematical regions is investigated. The approach adopted could be useful in reactions involving few cluster systems where effective interactions are not well known and exact methods are presently unavailable. Although, our Plane-Wave Impulse Approximation results exhibit, similarly to other calculations, a dip in the five-fold differential cross-section around a missing momentum of $\sim 450 MeV/c$, it is argued that this is an artifact of the omission of re-scattering four-nucleon processes.Comment: 16 pages, 6 figures, accepted for publication by Phys.Rev.

Studies in Molecular Recognition: Non-proteogenic Amino Acids for Antibiotic Studies and Chemosensors for Recognition and Reporting of Metal-ions

The field of molecular recognition focuses on the selective and reversible binding of small guest molecules to larger host molecules. This dissertation describes synthesis of small molecules as binding guests for enzymatic substrates as well as molecules as host chemosensors to detect and identify metal ions. Two approaches to new antibiotic drugs have been explored, and an array of sensors for the quantitation of aqueous metals is being commercialized. As strains of deadly bacteria emerge with evolved resistance to known antibiotics, new drugs are needed with novel mechanisms of action. Natural product antibiotics containing enduracididine, a non-canonical amino acid derived from arginine, have been found effective against resistant organisms. Recently, the biosynthesis of enduracididine has been elucidated by the Silvaggi group. Various derivatives of arginine are of interest as guest molecules for the Mpp family of proteins. We have developed a particularly succinct route to γ-hydroxy-arginine, which has also been used as a precursor to other oxidized arginine derivatives. Our route provides quantities of arginine derivatives which have been synthesized via a four step route utilizing an isoxazoline intermediate. The synthetic methods for formation and subsequent reduction of the isoxazoline have been studied extensively; and this succinct and versatile synthesis yields either γ-hydroxy-arginine or the keto acid derived from it by changing the conditions of the reduction. iii In another approach to developing new antibiotic treatment, we have pursued the inhibition of the β-barrel assembly machine (BAM), through a small molecule scaffold that binds β-sheets. BAMa is the only known β-barrel protein that spontaneously folds, while all others require the help of BAMa. The β-barrel membrane proteins include efflux pumps, proteins for active transport that allow bacterial survival by ejection of antibiotic drugs. Inhibition of BAMa may itself prove bactericidal, or used in combination therapy increase efficacy of drugs rendered previously ineffective due to acquired resistance. We have also developed metal ion chemosensors for simulataneous identification and quantitation of multiple metals. These are useful for monitoring metal ion concentrations in industrial wastewater. Current limitations in measuring metal concentration in wastewater can lead to increased costs and excess solid waste in order to meet compliance standards. Our goal is a simple system to allow continuous, real-time measurement of multiple metals on site to decrease over-treatment and detect spikes in pollutant metals. Utilizing UV/VIS absorption an array of semi-selective sensors each with its own spectral response to metal ions allows identification and concentration of pollutants to be determined. Toward this end, we have prepared chemosensors, demonstrated their sensing ability, and covalently attached them to transparent polymers and transparent supports in several ways that allow repeated use for metal-ion measurement. These dyes have been studied in solution and when covalently bound to polymers. Dyes with complementary metal-selectivity allow for high information from a few sensors; a model using three sensors has been demonstrated to simultaneously measure the concentration of seven metals in solution

Coherent Photoproduction of eta-mesons on Three-Nucleon Systems

A microscopic few-body description of near-threshold coherent photoproduction of the eta-meson on tritium and He3 targets is given. The photoproduction cross-section is calculated using the Finite Rank Approximation (FRA) of the nuclear Hamiltonian. The results indicate a strong final state interaction of the eta-meson with the residual nucleus. Sensitivity of the results to the choice of the eta-N T-matrix is investigated. The importance of obeying the two-body unitarity condition in the eta-N system is demonstrated.Comment: 17 pages, RevTeX, 5 eps-figures, submitted to Phys. Rev.

Four-Body Bound State Calculations in Three-Dimensional Approach

The four-body bound state with two-body interactions is formulated in Three-Dimensional approach, a recently developed momentum space representation which greatly simplifies the numerical calculations of few-body systems without performing the partial wave decomposition. The obtained three-dimensional Faddeev-Yakubovsky integral equations are solved with two-body potentials. Results for four-body binding energies are in good agreement with achievements of the other methods.Comment: 29 pages, 2 eps figures, 8 tables, REVTeX

Adult parasite burden and excretion of first-stage larvae of Angiostrongylus vasorum in dogs: Methodologically relevant diagnostic aspects and associations with serological detection of parasite antigen and specific antibodies

Angiostrongylus vasorum is a widely distributed cardiopulmonary parasite of canids in Europe. Clinical signs in dogs can be highly variable and diagnostically challenging. A correct and early diagnosis is hence indispensable to adequately manage affected patients. First-stage larvae (L1) are excreted in the faeces of definitive hosts and conventionally identified using the Baermann technique. Moreover, ELISAs for the detection of circulating antigen and specific antibodies have been presented. The current study aimed at i) quantitatively assessing larval migration in the Baermann funnel after 12 h and 24 h; ii) investigating the influence of sample storage at 4 °C over the course of three days on the number of detected L1; iii) evaluating potential associations of adult worm burdens with larval shedding in dogs and ELISA optical density (OD) values for circulating parasite antigen and specific antibodies. Faecal samples were obtained from naturally infected dogs (n = 21) and Baermann funnels were set up in duplicate over the course of four consecutive days (days 0–3) starting with the day of sample collection. Funnels were harvested on days 1–4 after 12 and 24 h, respectively, and the number of L1 per gram faeces (LPG) was determined. The LPG did not differ between larval harvest after 12 h from harvest after 24 h. Storage of faecal samples at 4 °C for two and three days entailed a considerable decrease in LPG. Adult worm burdens and larval excretion data from previous experiments demonstrated a correlation between worm burden and LPG. In contrast, no correlations between worm burden and the level of parasite antigen and specific antibody OD values, respectively, were identified. Thus, OD values of both antigen and antibody ELISA did not allow for conclusions on infection intensity reflected by the number of adult parasites. For the detection of L1 in faeces, 12 or 24 h of larval migration time was not discriminating for A. vasorum positivity. Thus, early processing of faecal samples is essential, since larval detection and hence sensitivity of the approach considerably decreased over the course of three days of storage. Therefore, the common recommendation to collect faecal samples for three consecutive days and to subsequently analyse them needs to be reconsidered. The results of this study can be readily translated into precise recommendations for daily practice to adequately assess A. vasorum infected dogs

Nicholas Oehm : personal interviews

Nicholas Oehm, Associate Professor, STEM Transformation Institute, College of Arts, Sciences and Education, Florida International University. History of Higher Education Oral History Interviews: International is our Middle Name. Personal interviews done by graduate students in the EDH 6061 History of Higher Education, Florida International University.https://digitalcommons.fiu.edu/international-oral-histories/1008/thumbnail.jp