Retention characteristics of some antibiotic and anti-retroviral compounds in hydrophilic interaction chromatography using isocratic elution, and gradient elution with repeatable partial equilibration

© 2018 Elsevier B.V. The separation of some zwitterionic, basic and neutral antibiotic and antiretroviral compounds was studied using hydrophilic interaction chromatography (HILIC) on bare silica, bonded amide and urea superficially porous phases. The differences in the selectivity and retentivity of these stationary phases were evaluated for compounds with widely different physicochemical properties (logD −3.43 to 2.41 at ww pH 3.0). The mobile phase was acetonitrile-ammonium formate buffered at low ww pH. Compounds containing quinolone and serine groups showed poor peak shapes on all columns, attributed to metal-oxide interactions with system metals. Peak shapes were improved by addition of citrate buffers. Gradient elution, particularly with regard to column equilibration, was also studied due to the large differences in retention factors observed under isocratic conditions. Full equilibration in HILIC was slow for both ionogenic and neutral solutes, requiring as much as ∼40 column volumes. However, highly repeatable partial equilibration, suitable for gradient elution, was achieved in only a few minutes. Pronounced selectivity differences in the separations were shown dependent on the partial equilibration time

Special Order (12 February 1864)

Report on Major O.P. Chaffie\u27s assignment as Inspector of Field Transportation for the Army of Tennessee and his chain of command.https://egrove.olemiss.edu/ciwar_milrec/1015/thumbnail.jp

The Design of a Lumped Element Impedance-Matching Network with Reduced Parasitic Effects Obtained From Numerical Modeling

This paper presents an impedance-matching network design with numerical modeling of the parasitic effects. A modeling tool CEMPIE (a Circuit Extraction approach based on a Mixed Potential Integral Equation formulation) is used to model the hoard-level parasitics of surface mount technology (SMT) resistors for impedance-matching networks. A 3-layer design of impedance-matching network with 0402 SMT resistors is implemented according to the modeling results. And its performance is demonstrated

NACA Research Memorandums

Memorandum presenting a supersonic wind-tunnel investigation of the origin and distribution of store interference in the 4- by 4-foot supersonic pressure tunnel at a Mach number of 1.61 in which separate forces on a store, a fuselage, a swept wing, and a swept-wing-fuselage combination were measured. The report presents data on a configuration which simulated a fighter-bomber airplane with a large and a small external store

Quantifying Decoupling Capacitor Location

Decoupling capacitor location in DC power bus design is a critical design choice for which proven guidelines are not well established. The mutual inductance between two closely spaced vias can have a great impact on the coupling between an IC and a decoupling capacitor. This coupling is a function of the spacing between the IC and capacitor, and spacing between power and ground layers. The impact of the mutual inductance on decoupling, i.e., local versus global decoupling, was studied, using a circuit extraction approach based on a mixed-potential integral equation. Modeling indicates that local decoupling has benefits over global decoupling for certain ranges of IC/capacitor spacing and power layer thickness. Design curves for evaluating local decoupling benefits were generated, which can be used to guide surface mount technology (SMT) decoupling capacitor placement