Convection-compensating PGSE experiment incorporating excitation-sculpting water suppression (CONVEX)

We present a new diffusion experiment which provides simultaneous suppression of an on-resonance solvent peak and compensation for convection. The experiment, which we name CONVEX, exploits similarities between two functionally different pulse sequences to enable the same sequence to be used simultaneously for two different purposes. The CONVEX pulse sequence combines a double-echo PGSE with double excitation-sculpting water suppression, using unequal gradient pulse-pair amplitudes (g1 and g2) and unequal diffusion intervals (Del1 and Del2). Convection compensation is achieved by setting g1 : g2 = Del2 : Del1. The new experiment provides the spectral quality, flat baseline, and water-suppression power characteristic of excitation-sculpting experiments, combined with excellent compensation for convection. The resulting Stejskal–Tanner plots are linear over a greater range of signal attenuation than in the absence of water suppression. Possible applications include protein NMR; NMR of cellular or colloidal systems; and the monitoring of technological processes

Magnetic Susceptibility: Solutions, Emulsions, and Cells

Differences in magnetic susceptibility between various compartments in heterogeneous samples can introduce unanticipated complications to NMR spectra. On the other hand, an understanding of these effects at the level of the underlying physical principles has led to the development of several experimental techniques that provide data on cellular function that are unique to NMR spectroscopy. To illustrate some key features of susceptibility effects we present, among a more general overview, results obtained with red blood cells and a recently described model system involving diethyl phthalate in water. This substance forms a relatively stable emulsion in water and yet it has a significant solubility of 5 mmol/L at room temperature; thus, the NMR spectrum has twice as many resonances as would be expected for a simple solution. What determines the relative intensities of the two families of peaks and can their frequencies be manipulated experimentally in a predictable way? The theory used to interpret the NMR spectra from the model system and cells was first developed in the context of electrostatics nearly a century ago, and yet some of its underlying assumptions now warrant closer scrutiny. While this insight is used in a practical way in this article, the accompanying article deals with the mathematics and physics behind this new analysis.Comment: 15 pages, 9 figures, v2: updated to resemble the published versio

Models of the human metabolic network: aiming to reconcile metabolomics and genomics

The metabolic syndrome, inborn errors of metabolism, and drug-induced changes to metabolic states all bring about a seemingly bewildering array of alterations in metabolite concentrations; these often occur in tissues and cells that are distant from those containing the primary biochemical lesion. How is it possible to collect sufficient biochemical information from a patient to enable us to work backwards and pinpoint the primary lesion, and possibly treat it in this whole human metabolic network? Potential analyses have benefited from modern methods such as ultra-high-pressure liquid chromatography, mass spectrometry, nuclear magnetic resonance spectroscopy, and more. A yet greater challenge is the prediction of outcomes of possible modern therapies using drugs and genetic engineering. This exposes the notion of viewing metabolism from a completely different perspective, with focus on the enzymes, regulators, and structural elements that are encoded by genes that specify the amino acid sequences, and hence encode the various interactions, be they regulatory or catalytic. The mainstream view of metabolism is being challenged, so we discuss here the reconciling of traditionally quantitative chemocentric metabolism with the seemingly 'parameter-free' genomic description, and vice versa

From Dust to Dust? A Legislator\u27s View of California\u27s Coming Water Crisis

Fortunately, there exists a spectrum of possibilities for supplying the projected requirements for additional water. The gravity of the situation dictates that all of these possibilities be examined in detail. We must learn to control and abate pollution where it has despoiled water sources. We must develop and improve our techniques of waste-water reclamation, since, although we have only a fixed amount of water, by reuse we might multiply the supply many fold. We must continue the development of techniques for desalination of sea water and brackish water. We must continue our research into weather modification in the hope that every available ounce of moisture can be wrung from the clouds in the most advantageous locations and then conserved for human use. Finally, we must put aside narrow sectional bias and seriously study the feasibility of major interbasin transfers of water. Let us examine each of these areas in more detail

Henri Temianka Correspondence; (kuchel)

This collection contains material pertaining to the life, career, and activities of Henri Temianka, violin virtuoso, conductor, music teacher, and author. Materials include correspondence, concert programs and flyers, music scores, photographs, and books.https://digitalcommons.chapman.edu/temianka_correspondence/3852/thumbnail.jp

Frustrated Settlements: Common Problems and Solutions in Liability Settlements Invoking the Medicare Secondary Payer Statutes

Frustrated Settlements: Common Problems and Solutions in Liability Settlements Invoking the Medicare Secondary Payer Statute