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C Ulrich

Publications and source records attributed to C Ulrich.

At least 19 recordsLinked to original sources
PubMed2006

Raman scattering in the Mott insulators LaTiO3 and YTiO3: evidence for orbital excitations.

Raman scattering is used to observe pronounced electronic excitations around 230 meV--well above the two-phonon range--in the Mott insulators LaTiO3 and YTiO3. Based on the temperature, polarization, and photon energy dependence, the modes are identified as orbital excitations. The observed profiles bear a striking resemblance to magnetic Raman modes in the insulating parent compounds of the superconducting cuprates, indicating an unanticipated universality of the electronic excitations in transition metal oxides.

Journal Article↗
PubMed2006

Doping dependence of bilayer resonant spin excitations in (Y, Ca)Ba2Cu3O6+x.

Resonant magnetic modes with odd and even symmetries were studied by inelastic neutron scattering experiments in the bilayer high-Tc superconductor Y1-xCa+Ba2Cu3O6+y over a wide doping range. The threshold of the spin excitation continuum in the superconducting state, deduced from the energies and spectral weights of both modes, is compared with the superconducting d-wave gap, deduced from electronic Raman scattering in the B1g symmetry on the same samples. Above a critical doping level of delta approximately =0.19, both mode energies and the continuum threshold coincide. We find a simple scaling relationship between the characteristic energies and spectral weights of both modes, which indicates that the resonant modes are bound states in the superconducting energy gap, as predicted by the spin-exciton model of the resonant mode.

Journal Article↗
PubMed2006

Oral retinoids for chemoprevention of skin cancers in organ transplant recipients: results of a survey.

Systemic retinoid therapy is thought to be beneficial for chemosuppression of skin cancers in solid organ transplant recipients. We present the results of a survey of 28 dermatologists with experience managing transplant recipients to clarify when and how systemic retinoids are used in this population. Almost 80% of respondents use retinoids in some transplant recipients. Factors influencing the use of retinoids include the incidence and aggressiveness of cutaneous squamous cell carcinomas and the extent of concomitant actinic keratoses. Patients are monitored more closely during periods of dose adjustment than during the maintenance phase of therapy. Adverse effects are variably managed symptomatically, with dose adjustment, by discontinuation of retinoids, or by referral to another specialist for further evaluation. In the absence of large randomized controlled trials, the practice habits of experienced physicians serve as a useful guide for the use of oral retinoids in transplant recipients.

Administration, Oral↗
PubMed2006

Reduction of immunosuppression for transplant-associated skin cancer: expert consensus survey.

BACKGROUND: Reduction of immunosuppression is considered a reasonable adjuvant therapeutic strategy in solid-organ transplant recipients experiencing multiple or high-risk skin cancers. However, the literature provides no guidance about what threshold of cancer development would warrant initiation of reduction of immunosuppression. OBJECTIVES: To develop expert consensus guidelines for initiation of reduction of transplant-associated immunosuppression for solid-organ transplant recipients with severe skin cancer. METHODS: An expert consensus panel was convened by the International Transplant Skin Cancer Collaborative and Skin Care for Organ Transplant Patients Europe Reduction of Immunosuppression Task Force. Thirteen hypothetical patient scenarios with graduated morbidity and mortality risks were presented and mean and mode expert opinions about appropriate level of reduction of systemic immunosuppression (mild, moderate, severe) were generated. RESULTS: Mild reduction of transplant-associated immunosuppression was considered warranted once multiple skin cancers per year developed or with individual high-risk skin cancers. Moderate reduction was considered appropriate when patients experienced > 25 skin cancers per year or for skin cancers with a 10% 3-year risk of mortality. Severe reduction was considered warranted only for life-threatening skin cancers. CONCLUSIONS: Reduction of immunosuppression is considered a reasonable adjuvant management strategy for transplant recipients with numerous or life-threatening skin cancers. Proposed guidelines are presented for the graduated reduction of immunosuppression coincident with the increasing skin cancer risks.

Drug Administration Schedule↗
PubMed2006

Successful treatment of multiple actinic keratoses in organ transplant patients with topical 5% imiquimod: a report of six cases.

BACKGROUND: Nonmelanoma skin cancer represents a significant cause of morbidity in organ transplant recipients (OTRs). Cutaneous malignancies, mainly invasive squamous cell carcinoma and its precursor actinic keratosis (AK), appear approximately 5-10 years after organ transplantation. Impaired wound healing and high recurrence rates in immunocompromised patients treated with destructive therapies such as cryosurgery or topical 5-fluorouracil represent frequently known complications. OBJECTIVES: To evaluate the safety and efficacy of imiqimod 5% in the treatment of AKs in OTRs. METHODS: Six OTRs (two kidney, two heart, one lung and one liver) with extensive AKs were treated with imiquimod 5% cream two to three times weekly in an open-label uncontrolled, nonrandomized pilot study. RESULTS: In five of six patients treated with imiquimod 5% cream all AK lesions were cleared after 12-16 weeks. One patient showed partial response. Local adverse events at the site of application included erythema, oedema and mild erosion. No wound infection or scarring was observed in any of these patients. All graft-related laboratory parameters were stable during and after treatment. Immunosuppressive therapy remained unchanged throughout the treatment. CONCLUSIONS: These results suggest that imiquimod 5% cream may be useful for the local treatment of precancerous AK lesions in OTRs.

Administration, Cutaneous↗
PubMed2005

[Value of early somatosensory evoked potentials in intubated and mechanically ventilated patients with craniocerebral trauma].

The objective of this study was to evaluate the prognostic value of early somatosensory evoked potentials (SEP) in patients with brain injury. A total of 85 patients who had been intubated and mechanically ventilated were investigated retrospectively. The results were compared to the Glasgow Coma Scale (GCS). The Glasgow Coma Scale as determined by the emergency doctor at the accident site, an SEP score, and the outcome of the patient were compared. There was no correlation of the Glasgow Coma Scale with the outcome. Probably the reason for this finding is the short interval of time between accident and evaluation of the GCS so that an awakening of the patient a short time after the accident is not reflected by the GCS. On the other hand, there was a significant correlation of the SEP score in the first examination after the accident with the outcome (p<0.001). SEP gave no false pessimistic prognoses. All patients without cortical responses either in one hemisphere or both hemispheres remained in coma vigile or died because of their brain injury. If cortical responses over both hemispheres remained normal, it was highly probable that the patients were later not severely handicapped. A reliable prognosis based on SEP is possible at a time when the clinical examination of the patient is limited due to sedating drugs. Repetitive examinations can monitor the course of recovery and correct false optimistic prognoses. The method may be applied at bedside and requires minimal time and little financial effort.

Adolescent↗
PubMed2004

Effects of arousing emotional scenes on the distribution of visuospatial attention: changes with aging and early subcortical vascular dementia.

BACKGROUND: The modulation of attention by emotionally arousing stimuli is highly important for each individual's social function. Disturbances of emotional processing are a supportive feature for the diagnosis of subcortical vascular dementia (SVD). We address here whether these disturbances might be useful as an early disease marker. METHODS: In order to examine the modulation of visual attention by emotionally arousing stimuli of different valence, 12 elderly patients with early SVD, 12 age-comparable healthy adults and 12 young healthy subjects were studied while looking at pairs of pictures from the International Affective Picture Battery that were either neutral-neutral, neutral-positive or neutral-negative in terms of emotional content. Eye movements were recorded with an infrared eye-tracking system. The direction of the first saccade and the dwell time during the 10 s of presentation were measured and compared among groups with parametric tests. RESULTS: All subjects showed a modulation of initial attentional orienting as well as a higher percentage of dwell time towards the pictures containing emotional material. Patients with SVD and old controls did not differ in either experimental measure. Young patients showed a stronger bias towards emotionally negative material than both groups of older individuals. CONCLUSIONS: Modulation of visuospatial attention is preserved in early SVD. This might have implications for therapeutic interventional approaches. A weakened sustained attention towards negative but not positive emotional pictures in the elderly is in accordance with the socioemotional selectivity theory, describing a relative selection of positive stimuli with aging.

Adult↗
PubMed2004

Resonant magnetic excitations at high energy in superconducting YBa2Cu3O6.85.

A detailed inelastic neutron scattering study of the high temperature superconductor YBa2Cu3O6.85 provides evidence of new resonant magnetic features, in addition to the well-known resonant mode at 41 meV: (i) a commensurate magnetic resonance peak at 53 meV with an even symmetry under exchange of two adjacent CuO2 layers, and (ii) high-energy incommensurate resonant spin excitations whose spectral weight is around 54 meV. The locus and the spectral weight of these modes provides unrevealed insight about the momentum shape of the electron-hole spin-flip continuum of d-wave superconductors.

Journal Article↗
PubMed2004

Magnetism, charge order, and giant magnetoresistance in SrFeO(3-delta) single crystals.

The electronic and magnetic properties of SrFeO(3-delta) single crystals with controlled oxygen content (0< or =delta< or =0.19) have been studied systematically by susceptibility, transport, and spectroscopic techniques. An intimate correlation between the spin-charge ordering and the electronic transport behavior is found. Giant negative as well as positive magnetoresistance are observed.

Journal Article↗
PubMed2003

Magnetic neutron scattering study of YVO3: evidence for an orbital Peierls state.

Neutron spectroscopy has revealed a highly unusual magnetic structure and dynamics in YVO3, an insulating pseudocubic perovskite that undergoes a series of temperature-induced phase transitions between states with different spin and orbital ordering patterns. A good description of the neutron data is obtained by a theoretical analysis of the spin and orbital correlations of a quasi-one-dimensional model. This leads to the tentative identification of one of the phases of YVO3 with the "orbital Peierls state," a theoretically proposed many-body state comprised of orbital singlet bonds.

Journal Article↗
PubMed2003

Two resonant magnetic modes in an overdoped high T(c) superconductor.

A detailed inelastic neutron scattering study of the overdoped high temperature copper oxide superconductor Y(0.9)Ca(0.1)Ba(2)Cu(3)O(7) reveals two-distinct magnetic resonant modes in the superconducting state. The modes differ in their symmetry with respect to exchange between adjacent copper oxide layers. Counterparts of the mode with odd symmetry, but not the one with even symmetry, had been observed before at lower doping levels. The observation of the even mode resolves a long-standing puzzle, and the spectral weight ratio of both modes yields an estimate of the onset of particle-hole spin-flip excitations.

Journal Article↗
PubMed2003

Viral warts in organ transplant recipients: new aspects in therapy.

The long-term success of organ transplantation depends on the prevention of allograft rejection and improvement in quality of life for the patients. This has been achieved through better immunosuppressive regimens with lower dosages and a new generation of immunosuppressive drugs. However, these immunosuppressive agents not only impair the patient's reactivity to the graft, but also to infectious organisms, thereby making them more susceptible to opportunistic pathogens. Because of this, organ transplant recipients are predisposed to epithelial malignancies and infections. The majority of transplant recipients will develop warts induced by human papillomavirus (HPV). Some of these viral warts may present with atypical histological features and may progress into squamous cell carcinomas. The risk for cutaneous cancers after transplantation is much higher than in the immunocompetent population. Current therapies for HPV-associated skin tumours mainly depend on the destruction of affected skin areas. These treatment modalities are of limited efficacy and are usually painful for the patients. A promising novel therapeutic agent is imiquimod, an immune response modifier. Clinical efficacy of imiquimod has been observed for different skin lesions, including viral warts in both immunocompetent and immunosuppressed patients.

Adjuvants, Immunologic↗
PubMed2003

Induction of apoptosis by Toll-like receptor-7 agonist in tissue cultures.

Toll-like receptor (TLR)-7 agonists represent a new group of immune response modifiers, which include imiquimod and resiquimod (R-848). Topically applied imiquimod is used for the treatment of both external and perianal genital warts, and benign and malignant epithelial lesions. Based on the induction of interferons and other cytokines in vitro and in vivo, regression of epithelial lesions probably depends on induction of both innate and cellular immune responses. As clinical remission is not always associated with inflammation, other mechanisms may also be involved. Using two different assays for detection of apoptosis (TUNEL test and gel analysis of DNA fragmentation), we observed induction of apoptosis by imiquimod in human epithelial cell lines (HeLa S3) and keratinocytes (HaCaT, A431 cells), as well as in mouse fibroblasts (McCoy cells). These findings suggest that the mode of action of imiquimod to eliminate virus-infected, dysplastic or neoplastic epithelial cells may also include the induction of apoptotic processes.

Aminoquinolines↗
PubMed2003

Cutaneous precancers in organ transplant recipients: an old enemy in a new surrounding.

Premalignant and malignant epithelial lesions are acknowledged as being the most frequent neoplasia in long-term immunosuppressed patients such as organ-transplant recipients. Paralleling the constant improvement in modern transplant techniques, their incidence increases together with the growing survival time post-transplantation, reaching 40% to 60% after 20 years. Against the background of lifelong immunosuppression, the impact of accepted cancer inducers and promoters such as ultraviolet radiation, oncogenic viruses and individual susceptibility has to be closely scrutinized. Precancerous lesions such as actinic keratoses in transplant patients progress more rapidly into squamous cell carcinomas, showing an increased tendency to metastasize. As it remains impossible to identify and consequently treat those lesions that may progress into invasive carcinoma, the best prophylaxis for nonmelanoma skin cancer in organ-transplant recipients may be the treatment of all existing precancerous lesions. As reduction of the immunosuppressive therapy is rarely practicable, other terms of prophylaxis and treatment, such as immune response modifiers, have to be considered.

Adjuvants, Immunologic↗
PubMed2002

Magnetic order and dynamics in an orbitally degenerate ferromagnetic insulator.

Neutron scattering was used to determine the spin structure and the magnon spectrum of the Mott-Hubbard insulator YTiO3. The magnetic structure is complex, comprising substantial G-type and A-type antiferromagnetic components in addition to the predominant ferromagnetic component. The magnon spectrum, on the other hand, is gapless and nearly isotropic. We show that these findings are inconsistent with the orbitally ordered states thus far proposed for YTiO3 and discuss general implications for a theoretical description of exchange interactions in orbitally degenerate systems.

Journal Article↗
PubMed2002

Magnetic resonant mode in the single-layer high-temperature superconductor Tl2Ba2CuO(6+delta).

An unusual spin excitation mode observed by neutron scattering has inspired numerous theoretical studies of the interplay between charged quasiparticles and collective spin excitations in the copper oxide high-temperature superconductors. The mode has, thus far, only been observed in materials with crystal structures consisting of copper oxide bilayers, and it is absent in the single-layer compound La(2-x)Sr(x)CuO(4+delta). Neutron-scattering data now show that the mode is present in Tl(2)Ba(2)CuO(6+delta), a single-layer compound with a superconducting transition temperature of approximately 90 kelvin, demonstrating that it is a generic feature of the copper oxide superconductors, independent of the layer sequence. This restricts the theoretical models for the origin of the resonant mode and its role in the mechanism of high-temperature superconductivity.

Journal Article↗