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Biomedical subjects

J Gustafson

Publications and source records attributed to J Gustafson.

At least 19 recordsLinked to original sources
PubMed2006

Kinetics of the reduction of the Rh(111) surface oxide: linking spectroscopy and atomic-scale information.

The reduction of the surface oxide on Rh(111) by H(2) was observed in situ by scanning tunneling microscopy (STM) and high-resolution core level spectroscopy (HRCLS). At room temperature, H(2) does not adsorb on the oxide, only in reduced areas. Reduction starts in very few sites, almost exclusively in stepped areas. One can also initiate the reduction process by deliberately creating defects with the STM tip allowing us to examine the reduction kinetics in detail. Depending on the size of the reduced area and the hydrogen pressure, two growth regimes were found. At low H(2) pressures or small reduced areas, the reduction rate is limited by hydrogen adsorption on the reduced area. For large reduced areas, the reduction rate is limited by the processes at the border of the reduced area. Since a near-random distribution of the reduction nuclei was found and the reduction process at defects starts at a random time, one can use Johnson-Mehl-Avrami-Kolmogoroff (JMAK) theory to describe the process of reduction. The microscopic data from STM agree well with spatially averaged data from HRCLS measurements.

Journal Article↗
PubMed2006

Structure of Ag(111)-p(4 x 4)-O: no silver oxide.

The structure of the oxygen-induced p(4 x 4) reconstruction of Ag(111) is determined by a combination of scanning tunneling microscopy, surface x-ray diffraction, core level spectroscopy, and density functional theory. We demonstrate that all previous models of this surface structure are incorrect and propose a new model which is able to explain all our experimental findings but has no resemblance to bulk silver oxide. We also shed some light on the limitations of current density functional theories and the potential role of van der Waals interactions in the stabilization of oxygen-induced surface reconstructions of noble metals.

Journal Article↗
PubMed2005

One-dimensional PtO2 at Pt steps: formation and reaction with CO.

Using core-level spectroscopy and density functional theory we show that a one-dimensional (1D) oxide structure forms at the steps of the Pt(332) surface after exposure. The 1D oxide is found to be stable in an oxygen pressure range, where bulk oxides are only metastable, and is therefore argued to be a precursor to the Pt oxidation. As an example of the consequences of such a precursor exclusively present at the steps, we investigate the reaction of CO with oxygen covered Pt(332). Albeit more strongly bound, the oxidic oxygen is found to react more easily with CO than oxygen chemisorbed on the Pt terraces.

Journal Article↗
PubMed2005

A surface x-ray study of the structure and morphology of the oxidized Pd001 surface.

The oxidation of Pd(100) and the formation of PdO was studied in situ using surface x-ray diffraction. A bulklike, epitaxial PdO film is formed at oxygen partial pressures beyond 1 mbar and sample temperatures exceeding 650 K. The main orientation is PdO(001)/Pd(001), based upon bulk reflections from the PdO film. By comparing with measurements from the Pd crystal truncation rods, we estimate an rms surface roughness of 6 A, in good agreement with previous high pressure scanning tunneling microscopy measurements. Finally, we observed the transformation from the (radical5 x radical5) surface oxide to PdO bulk oxide at 675 K and 50 mbar O(2) pressure.

Journal Article↗
PubMed2004

High-coverage oxygen structures on Rh111: adsorbate repulsion and site preference is not enough.

A new O induced structure on Rh(111) displaying a (2 sqaureroot[3] x 2sqaureroot[3])R30 degrees periodicity with an oxygen coverage of 2/3 has been studied by high resolution core level spectroscopy, scanning tunneling microscopy, and density functional theory. Although O favors fcc hollow sites in all other known phases, it occupies both fcc and hcp sites in this structure, which cannot be explained by pairwise adsorbate repulsion only. Both the (2sqaureroot[3] x 2sqaureroot[3])R30 degrees and (2 x 2)-3O structures also exemplify that density-of-states contrast can lead to oxygen adatoms appearing as protrusions in scanning tunneling microscopy images.

Journal Article↗
PubMed2004

Self-limited growth of a thin oxide layer on Rh(111).

The oxidation of the Rh(111) surface at oxygen pressures from 10(-10) mbar to 0.5 bar and temperatures between 300 and 900 K has been studied on the atomic scale using a multimethod approach of experimental and theoretical techniques. Oxidation starts at the steps, resulting in a trilayer O-Rh-O surface oxide which, although not thermodynamically stable, prevents further oxidation at intermediate pressures. A thick corundum like Rh2O3 bulk oxide is formed only at significantly higher pressures and temperatures.

Journal Article↗
PubMed2004

Kinetic hindrance during the initial oxidation of Pd(100) at ambient pressures.

The oxidation of the Pd(100) surface at oxygen pressures in the 10(-6) to 10(3) mbar range and temperatures up to 1000 K has been studied in situ by surface x-ray diffraction (SXRD). The results provide direct structural information on the phases present in the surface region and on the kinetics of the oxide formation. Depending on the (T,p) environmental conditions, we observe either a thin (sqrt[5]xsqrt[5])R27 degrees surface oxide or the growth of a rough, poorly ordered bulk oxide film of PdO predominantly with (001) orientation. By either comparison to the surface phase diagram from first-principles atomistic thermodynamics or by explicit time-resolved measurements we identify a strong kinetic hindrance to the bulk oxide formation even at temperatures as high as 675 K.

Journal Article↗
PubMed2003

Identification of step atoms by high resolution core level spectroscopy.

Vicinal Rh(111) surfaces are studied with high resolution core level photoemission. We demonstrate the possibility to distinguish between the different kinds of surface atoms on these surfaces by virtue of their 3d core level binding energies. In particular, the low coordinated step atoms are found to exhibit a clear fingerprint in Rh 3d spectra. We demonstrate how this may be used to show that initial oxygen adsorption occurs on the steps and not on the terraces of the vicinal surfaces.

Journal Article↗
PubMed1999

glmM operon and methicillin-resistant glmM suppressor mutants in Staphylococcus aureus.

The Staphylococcus aureus phosphoglucosamine mutase gene glmM was shown to be the last gene of a three-cistron operon, orf1-orf2-glmM. One transcriptional start was identified upstream of orf1, and a second start producing a monocistronic transcript was identified upstream of glmM. Disruption of glmM abolished GlmM production, decreased methicillin resistance, and resulted in teicoplanin hypersusceptibility without affecting the production of the endogenous penicillin-binding proteins and PBP 2'. Complementation of the glmM mutation by the complete glmM operon restored both methicillin resistance and normal teicoplanin susceptibility. In contrast, a highly methicillin-resistant suppressor mutant obtained by selection for growth in the presence of methicillin remained GlmM deficient and teicoplanin hypersusceptible. The suppressor mutation was not linked to the glmM operon but was correlated with decreased autolysis and increased production of a 49-kDa protein, suggesting that there is an alternative pathway for glucosamine-1-phosphate synthesis in S. aureus.

Bacterial Proteins↗
PubMed1994

The femC locus of Staphylococcus aureus required for methicillin resistance includes the glutamine synthetase operon.

Tn551 insertional inactivation of femC is known to reduce methicillin resistance levels in methicillin-resistant and -susceptible Staphylococcus aureus. By use of cotransductional crosses, femC was mapped close to thrB on the SmaI-A fragment of the S. aureus NCTC 8325 chromosome. The Tn551 insertion femC::omega 2005 was found to interrupt an open reading frame coding for a putative protein of 121 amino acids which is highly similar to the glutamine synthetase repressors (GlnR) of Bacillus spp. Downstream of femC, an open reading frame highly similar to Bacillus sp. glutamine synthetases (GlnA) was found. Northern (RNA) blots probed with putative glnR or glnA fragments revealed that 1.7- and 1.9-kb transcripts characteristic of wild-type cells were replaced by less abundant 7.0- and 7.2-kb transcripts in the femC::omega 2005 mutant. Total glutamine synthetase activity was also decreased in the mutant strain; the addition of glutamine to defined media restored the wild-type methicillin resistance phenotype of the femC mutant. This result suggests that the omega 2005 insertion in glnR has a polar effect on glnA and that glnR and glnA are transcribed together as an operon. These results suggest that the loss of wild-type levels of glutamine synthetase and the consequent decrease in glutamine availability cause a decreased level of methicillin resistance.

Amino Acid Sequence↗
PubMed1984

Experimental analysis of the adjunctive Z-plasty in the closure of fusiform defects.

Facial defects too large for primary closure can sometimes be repaired with the addition of a unilateral or bilateral adjunctive Z-plasty. In this study, the mechanics of the adjunctive Z-plasty are examined experimentally. In vivo experiments using piglets show that closure tension is decreased 30% by each Z-plasty. The true lengthening of the Z when transposed is 80% of that theoretically predicted. The deformation caused by fusiform excision and closure with and without undermining and with one or two Z-plasties is evaluated. In general, the Z-plasty exchanges deformation perpendicular to the long axis of excision for deformation parallel to that axis. A clinical case using the adjunctive Z-plasty for the repair of a large chin defect is reported.

Animals↗
PubMed1981

Rh hemolytic disease of the newborn: using incidence observations to evaluate the use of RH immune globulin.

During the 1970s, the crude incidence of Rh hemolytic disease of the newborn (RhHDN) in the United States dropped 65 per cent---from 40.5/10,000 total births in 1970 to 14.3/10,000 total births in 1979. Since the risk of RhHDN is directly associated with birth order, changes both in birth order-specific RhHDN incidence rates and in the birth order distribution would be expected to influence crude RhHDN incidence. Review of birth order-specific incidences ascertained in Connecticut, 1972-1977, shows that incidence was stable for first and second births, whereas it dropped significantly for third and fourth births. Due to the nearly complete use of Rh immune globulin (RhIG) in Connecticut during these years, the drop in these specific rates is best attributed to this prevention strategy. Nationwide, during the 1970s, the annual percentages of fourth and higher order births decreased from 18 per cent to 10 per cent. We estimate that some 30 per cent to 40 per cent of the 1970-1979 drop in the crude rate is attributed to changes in the birth order distribution, whereas 60 per cent to 70 per cent of the drop is attributed to RhIG. However, comparison of pooled incidences for 1972-1974 and 1975-1977 observed in Connecticut for first births and births to 15-19 year olds showed significant increases for both groups in 1975-1977. Further study of specific trends from other areas is needed to confirm these observations. Also needed is investigation of likely causes of sensitization among these teenaged, primiparous women.

Birth Order↗
PubMed1979

Combined modality treatment of Hodgkin's disease confined to lymph nodes. Results eight years later.

Eighty-seven patients with newly diagnosed Hodgkin's disease, pathologic stages IA, IIA, IIB and IIIA, were assigned at random to receive either extended field radiotherapy alone or that therapy followed by six cycles of MOPP (nitrogen mustard, Oncovin, procarbazine, prednisone) chemotherapy. Patients were entered into the study from January 1970 to January 1974. Patients were followed for a median of 69 + months from the end of all treatments. Patients whose disease was less than stage IIIA had a 31 per cent relapse rate with radiotherapy alone compared to a 6 per cent relapse rate with combined modality treatment (P = 0.04). No deaths from Hodgkin's disease have occurred in patients who received combined modality therapy, whereas 24 per cent of the patients who received radiotherapy alone have died with active disease. However, three patients with stage IIIA disease who were treated with both modalities have died from other causes (myocardial infarction, adenocarcinoma of lung, acute leukemia). Combined modality therapy of patients with early Hodgkin's disease may be superior to radiotherapy alone, especially for certain subgroups of patients discussed in detail.

Adolescent↗
PubMed1976

Ferric iron reduction by sulfur- and iron-oxidizing bacteria.

Acidophilic bacteria of the genera Thiobacillus and Sulfolobus are able to reduce ferric iron when growing on elemental sulfur as an energy source. It has been previously thought that ferric iron serves as a nonbiological oxidant in the formation of acid mine drainage and in the leaching of ores, but these results suggest that bacterial catalysis may play a significant role in the reactivity of ferric iron.

Acidithiobacillus thiooxidans↗
PubMed1976

The mirror transference in the psychoanalytic psychotherapy of alcoholism: a case report.

The development of a mirror transference in the successful outpatient psychoanalytic psychotherapy of an alcoholic patient is described in this paper. Important features of the case were a very severe initial period of resistance, a dramatic shift from a climate of bitterness and rancor to one of quiet and satisfaction that coincided with the establishment of the mirroring relationship, then recall of important genetic material, and finally, a period of many gains in the patient's contemporary relationships. Very few interpretations were given. The psychotherapy was chiefly an attempt to provide the object relationship that would be therapeutic, an archaic relationship of the grandiose self and the mirroring self-object. The theoretical work of Balint and Kohut was applied to this problem (with the alcoholic patient) and proved extremely helpful in predicting the major turning points in the psychotherapy and in guiding the strategy of the therapist. The principal difficulty not fully predicted was the extent and depth of the resistance to a positive transferace; once this resistance was overcome, the psychotherapy proceeded in a way similar to that generally described by Kohut with regard to patients who became involved in a mirror transference.

Adult↗
PubMedDate not supplied

Nodular poorly differentiated lymphocytic lymphoma: changes in histology and survival.

Lymphoma patients with a nodular pattern have a better prognosis than those with a diffuse pattern. Histologic evolution from nodular to diffuse may occur during the course of the disease in the same patient. This change in pattern may be of prognostic significance. We reviewed 56 patients with an initial diagnosis of nodular poorly differentiated lymphoma seen over a 12-year period (1966-1978). Thirty-five patients had biopsies after initial diagnosis, and 28 of the cases could be classified as nodular or diffuse. Eleven of the 56 cases evolved from a nodular to a diffuse pattern. Forty-four of the 56 patients achieved a complete remission and were evaluated for survival. The median survival (66+ months) for patients who have never relapsed is similar to that for patients who relapsed with a nodular pattern (70 months) and patients who relapsed with a diffuse pattern (73 months). Relapse with a nodular pattern occurred at a median of 27 months after initial diagnosis and relapse with a diffuse pattern (73 months). Relapse with a nodular pattern occurred at a median of 27 months after initial diagnosis and relapse with a diffuse pattern occurred at a median of 49 months. Although overall survival in patients relapsing with nodular or diffuse disease is similar, median survival from relapse with nodular disease is longer (32+ months) than median survival with diffuse disease (17 months) (P = 0.068).

Adult↗