102,248 research outputs found
Chapter 2. Symmetry and Long-lived Spin Order
No full textA permutation symmetry theory for nuclear long-lived spin states is examined. The theory predicts the number of expected long-lived states (LLS), which are described as population imbalances of states belonging to different irreducible representations
Entrapment of the sciatic nerve at the linea aspera: A case report and literature review
No full textNontraumatic, non-neoplastic sciatic nerve entrapment at the level of the thigh is extremely rare. In its course, in proximity of the linea aspera, the nerve is exposed to unexpected neuropathic syndromes associated with bone disorders
Alternating Delays Achieve Polarization Transfer (ADAPT) to heteronuclei in PHIP experiments
No full textA new methodology for producing hyperpolarized 13C nuclei in small organic systems via parahydrogen induced polarization (PHIP) is proposed: ADAPT (Alternating Delays Achieve Polarization Transfer). The theoretical foundation of the process is investigated in some detail and experimental examples demonstrating the viability of the approach are provided as well. The number of adjustable parameters is fewer than most of other conversion schemes. The achieved theoretical heteronuclear polarization is close to unity for any examined magnetic equivalence regime. The duration of the pulse sequence, which was successfully implemented, can be shorter than other established methods reducing possible relaxation losses. The conversion scheme is robust to B1 inhomogeneities, but more sensitive to off-resonance RF irradiation
Chapter 11: Converting Spin Order from Singlet to Heteronuclear Magnetisation
No full textSome singlet to heteronuclear polarization transfer strategies are presented. The NMR sequences and relative parameters are described
Homonuclear ADAPT: A general preparation route to long-lived nuclear singlet order
No full textWe introduce a simple strategy to access and readout nuclear singlet order based on the alternate repetition of hard pulses and delays. We demonstrate the general applicability of the method by accessing nuclear singlet order in spin systems characterized by diverse coupling regimes. We show that the method is highly efficient in the strong-coupling and chemical equivalence regimes, and can overcome some limitations of other well-established and more elaborated pulse sequences. A simulation package is provided which allows the determination of pulse sequence parameters
Bovine serum amine oxidase activity and substrate structure: physical control of the activity
No full textA steady-state kinetic study of bovine serum amine oxidase activity was performed, over a wide range of pH values (5.4–10.2) and ionic strength (10–200mM), using various (physiological and analogue) substrates as specific probes of the active-site binding region. Relatively small changes in kcat values (approx. one order of magnitude) accompanied by marked changes in Km and kcat/Km values (approx. six orders of magnitude) were observed. This behaviour was correlated with the presence of positively charged groups or apolar chains in the substrates. In particular, it was found that the docking of the physiological polyamines, i.e. spermidine and spermine, appears to be modulated by three amino acid residues of the active site, which we have named L-H+, G-H+ and IH+, characterized by pKa values of 6.2±0.2 [Di Paolo, Scarpa, Corazza, Stevanato and Rigo (2002) Biophys. J. 83, 2231–2239], 8.2±0.3 and 7.8±0.4 respectively. The electrostatic interaction between the protonated substrates and the enzyme containing the residues L-H+, G-H+ and IH+ in the deprotonated form, the on/off role of the IH+ residue and the role of hydrophobic interactions with substrates characterized by apolar chains are discussed
A rapid photometric micromethod for serum lipase determination.
No full textA new micromethod for the determination of serum lipase activity is presented. Small quantities of serum are incubated for 30 min at 40° in a substrate consisting of an olive oil suspension in the presence of deoxycholic acid. The pH is 8.5. The hydrolyzed fatty acids are determined with a photometric technique, with a slight modification of the method of Duncombe. The normal values are lower than 20 I.U. © 1972
Biobjective combinatorial optimization and the TSP with profits – Methods and Algorithms
No full textBi-objective combinatorial optimization (BOCO) deals with mathematical programming models where two competing objectives have to be minimised subject to constraints. A number of real world applications may be cast in this setting, where the objective and constraint functions are linear and the variables are binary. In a BOCO problem usually there is no solution that simultaneously minimise both objectives, so it is necessary to describe a set of Pareto optimal solutions, or solutions such that it is not possible to improve one objective without worsening the other. In this work we review the exact, heuristic and approximated methods developed to date for the construction of the Pareto optimal set in BOCO problems. Emphasis is given to exact and to approximate methods where a subset of the exact set of Pareto optimal solutions is given. We apply all the analysed methods to a hard BOCO problem: the Traveling Salesman Problem with Profits (TSPP). Specific approaches for the TSPP on graphs with special metrics and/or with time windows are also discussed. Finally, the approaches studied are suggested as a methodology to face a case study connecting Medicine and Computer Science
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