Biomedical subjects

Georg Müller

Publications and source records attributed to Georg Müller.

4 recordsLinked to original sources

PubMed2006

Developing quantitative, multiscale models for microgravity crystal growth.

Crystal growth conducted under microgravity conditions has had a profound impact on improving our understanding of melt crystal growth processes. Here, we present a brief history of microgravity crystal growth and discuss the development of appropriate models to interpret and optimize these growth experiments. The need for increased model realism and predictive capability demands new approaches for describing phenomena important at several disparate length scales. Of special importance is the ability to represent three-dimensional and transient continuum transport (flows, heat, and mass transfer), phase-change phenomena (thermodynamics and kinetics), and system design (such as furnace heat transfer during melt growth). An overview of mathematical models and numerical algorithms employed to represent such multiscale effects is presented.

Journal Article↗

PubMed2004

The reaction of M(CO)3(Ph2PCH2CH2PPh2)(M = Fe, Ru) with parahydrogen: probing the electronic structure of reaction intermediates and the internal rearrangement mechanism for the dihydride products.

The photochemical reaction of Ru(CO)(3)(dppe) and Fe(CO)(3)(dppe)(dppe = Ph(2)PCH(2)CH(2)PPh(2)) with parahydrogen has been studied by in situ-photochemistry resulting in NMR spectra of Ru(CO)(2)(dppe)(H)(2) that show significant enhancement of the hydride resonances while normal signals are seen in Fe(CO)(2)(dppe)(H)(2). This effect is associated with a singlet electronic state for the key intermediate Ru(CO)(2)(dppe) while Fe(CO)(2)(dppe) is a triplet. DFT calculations reveal electronic ground states consistent with this picture. The fluxionality of Ru(CO)(2)(dppe)(H)(2) and Fe(CO)(2)(dppe)(H)(2) has been examined by NMR spectroscopy and rationalised by theoretical methods which show that two pathways for ligand exchange exist. In the first, the phosphorus and carbonyl centres interchange positions while the two hydride ligands are unaffected. A second pathway involving interchange of all three ligand sets was found at slightly higher energy. The H-H distances in the transition states are consistent with metal-bonded dihydrogen ligands. However, no local minimum (intermediate) was found along the rearrangement pathways.

Journal Article↗

PubMed2003

Bone mineral density and urine calcium excretion among subjects with and without nephrolithiasis.

BACKGROUND: Bone mineral density (BMD) is reduced among patients with idiopathic hypercalciuria (IH) and nephrolithiasis. To disentangle effects of diet, stone formation, and physiology upon BMD, we studied vertebral and femoral neck BMD among relatives of hypercalciuric stone formers, and contrasted those with to those without stones. METHODS: Among 59 subjects from 11 families, vertebral and femoral neck BMD, diet calcium intake, urine excretions of calcium, sodium, ammonium, titratable acid, sulfate, urea nitrogen, and serum levels of calcitriol and markers of bone turnover were studied. RESULTS: Stone formers (SF) consumed less calcium than non-stone formers (NSF). Spine and femoral neck BMD z-scores varied inversely with urine calcium loss and urine ammonium excretion among SF but not NSF. No correlations of BMD z-score were found for bone markers, calcitriol, or any of the other measurements. CONCLUSION: SF consumed less calcium, presumably to prevent more stones, and displayed a bone mineral responsiveness to calcium loss and ammonium excretion not present among NSF, who ate more calcium. Lowered calcium consumption in IH, perhaps in response to stone formation, alters bone responses in a direction that can predispose to mineral loss and eventual fracture.

Adult↗

PubMedDate not supplied

Serial proton MR spectroscopy and diffusion imaging findings in HIV-related herpes simplex encephalitis.

We report the case of pathologically proved atypical herpes simplex encephalitis (HSE) in a 40-year-old male patient with AIDS who was followed up by MR imaging, which included diffusion-weighted imaging and proton MR spectroscopy ((1)H-MRS). MR revealed sparing of hippocampi and limbic cortices, necrosis of both cingulate gyri, and cerebellar involvement. Increased diffusivity and severe metabolic alterations were compatible with biopsy findings of necrotizing inflammation. Clinical recovery corresponded with partial metabolite and diffusion normalization and a myo-inositol increase that indicated evolving gliosis formation further corroborated by immunohistochemistry results. (1)H-MRS and diffusion-weighted imaging may both support the diagnosis of HSE in patients with AIDS and help in the follow-up of necrotizing inflammation.

Adult↗