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Ralf Ludwig

Publications and source records attributed to Ralf Ludwig.

25 records · Page 2Linked to original sources
PubMed2002

Narrowband UV-B phototherapy in the treatment of cutaneous graft versus host disease.

Graft versus host disease (GVHD) is an important problem following allogenic bone marrow transplantation (BMT). The beneficial effects of photochemotherapy with psoralens plus UVA irradiation (PUVA) have been described repeatedly; however, PUVA is limited by a wide range of unwanted effects. A novel improved form of UV-B phototherapy, narrowband UV-B, has been proven to be very effective in T-cell mediated dermatoses. Therefore, we investigated the effect of narrowband UV-B phototherapy (5 times per week) in 10 patients with cutaneous GVHD (grade 2-3) resistant to standard immunosuppressive drugs. It was tolerated well by all patients, and no side effects were observed. Skin lesions showed complete clearance in 7 out of 10 patients within 3 to 5 weeks. 3 patients showed significant improvement of GVHD. We suggest that narrowband UV-B phototherapy is a nonaggressive treatment that may benefit patients with cutaneous GVHD who already take high doses of immunosuppressive drugs.

Adult↗
PubMed2002

Formation of the magic cluster Na8 in noble gas matrixes.

The sodium molecules Na(2), Na(4), and Na(8) have been isolated in argon matrixes at 15 K and characterized for the first time by Raman spectroscopy. The vibrational frequencies are compared with density functional (DFT) calculations. The Na(4) cluster possesses a rhombic structure (D(2h)) with calculated d(Na-Na) = 307.2 and 347.4 pm, respectively. For octasodium, a hypertetrahedral structure (T(d)) is predicted in which each side of an inner tetrahedron with d(Na-Na) = 331.5 pm is capped by sodium atoms with a distance of d(Na-Na) = 348.7 pm. The green octasodium cluster is the first example of a matrix-isolated magic number cluster. Its formation from blue tetrasodium is discussed on the basis of the observed sequence of cluster growth.

Journal Article↗
PubMed2002

Enchondroma: a benign osseous lesion with high F-18 FDG uptake.

A woman was referred for fluorodeoxyglucose positron emission tomography for the staging of a malignant melanoma. Although no signs of metastatic melanoma were evident on the whole-body scan, focally increased uptake within the femoral metaphysis was noted. Radiographic and magnetic resonance examinations revealed an enchondroma as the cause of the increased uptake. Histopathologic verification was obtained. The final diagnosis was actively proliferating enchondroma. A grade I chondrosarcoma could be ruled out. Enchondromas may be responsible for focally increased FDG uptake in bone lesions and must be considered when positron emission tomographic scans obtained with FDG are evaluated in cancer staging.

Adult↗
PubMed2001

Water: From Clusters to the Bulk.

Water is of fundamental importance for human life and plays an important role in many biological and chemical systems. Although water is the most abundant compound on earth, it is definitely not a simple liquid. It possesses strongly polar hydrogen bonds which are responsible for a striking set of anomalous physical and chemical properties. For more than a century the combined importance and peculiarity of water inspired scientists to construct conceptual models, which in themselves reproduce the observed behavior of the liquid. The exploration of structural and binding properties of small water complexes provides a key for understanding bulk water in its liquid and solid phase and for understanding solvation phenomena. Modern ab initio quantum chemistry methods and high-resolution spectroscopy methods have been extremely successful in describing such structures. Cluster models for liquid water try to mimic the transition from these clusters to bulk water. The important question is: What cluster properties are required to describe liquid-phase behavior?

Journal Article↗
PubMed1999

Raman Spectroscopic Investigation of Matrix Isolated Rubidium and Cesium Molecules: Rb(2), Rb(3), Cs(2), and Cs(3)(,)(1).

The rubidium molecules Rb(2) and Rb(3) and the cesium molecules Cs(2) and Cs(3) were isolated in argon matrixes and characterized for the first time by Raman spectroscopy. The fundamental frequencies of the dimers were observed at 59.1 cm(-)(1) for the rubidium dimer and 45.8 cm(-)(1) for the cesium dimer. The Raman lines of the rubidium trimer appeared at 38.3 and 53.9 cm(-)(1), and the lines of the cesium trimer, at 24.4 and 39.5 cm(-)(1). The vibrational frequencies were compared with gas-phase frequencies and with density functional theory (DFT) calculations. Furthermore, the lowest vibrational levels of the (1)Pi(u) state of Cs(2) isolated in solid argon were observed by Raman matrix spectroscopy.

Journal Article↗
PubMed1997

Trifluoromethyl Hypobromite, CF(3)OBr.

The synthesis and isolation of the hypobromite CF(3)OBr is reported. CF(3)OBr is formed besides Me(4)N(+)BrF(2)(-) by the reaction of CF(3)OCl and Me(4)N(+)Br(3)(-) via an addition-elimination mechanism. The initially formed solid, [2CF(3)OBr.Me(4)N(+)BrF(2)(-)], was characterized by (13)C and (19)F NMR, Raman, IR, and mass spectra. The hypobromite was separated from the solid by high-vacuum condensation onto a cold surface and characterized by matrix isolation multichannel Raman spectroscopy. An ab initio calculation was performed, and a force field and the torsional barrier of CF(3)OBr were calculated. The calculation predicts an eclipsed conformation with a rotional barrier of 3.4 kcal/mol. The photolytic decomposition of CF(3)OBr in the solid state and in an argon matrix was investigated.

Journal Article↗