Magnetic phase diagram of layered cobalt dioxide LixCoO2.

The magnetism of LixCoO2 (LCO), which has a similar structure to NaxCoO2 (NCO), has been investigated by muon-spin spectroscopy and susceptibility measurements using samples with x=0.1-1 prepared by an electrochemical reaction. In the x range below 0.75, LCO was found to be Pauli paramagnetic down to 1.8 K, suggesting an intermediate- or weak-coupling regime, although disordered local moments, with volume fractions below approximately 20%, appear at low T for LCO with x > or = 0.5. The phase diagram and interactions of LCO are thus strikingly different from NCO, while the differences cannot be explained simply by structural differences between the two systems.

Evidence of two dimensionality in quasi-one-dimensional cobalt oxides.

The quasi-one-dimensional (Q1D) cobalt oxides A(N + 2)Co(n + 1)O(3n + 3) (A = Ca, Sr, and Ba, n = 1 - infinity) were investigated by muon-spin spectroscopy under applied pressures of up to 1.1 GPa. The relationship between the onset Néel temperature T(on)(N) and the interchain distance (d(ic)), which increases monotonically with n, is well fitted by the formula T(N)/T(N,0) = (1 - d(ic)/d(ic,o)(beta), here for T(on)(N) approximately 100 K for Ca(3)Co(2)O(6) (n = 1) and approximately 15 for BaCoCoO(3) (n = infinity at ambient P. The T(on)(N) - d(ic) curve also predicts a large dependence of Y(N) for the compounds with n > or = 5, i.e., in the vicinity of , while the compounds show only a very small effect. Indeed, our high-pressure mu(+) results show that of BaCoO(3) is enhanced by with a slope of 2.2 K(Gpa), whereas no detectable changes by P for both Ca(3)Co(2)O(6) and Sr(4)Co(3)O(9) (n = 2). This clearly confirms the role of the 2D-antiferromagnetic interaction on T(on)(N) in the Q1D cobalt oxides.

Static magnetic order in metallic K0.49CoO2.

By means of muon-spin spectroscopy, we have found that K0.49CoO2 crystals undergo successive magnetic transitions from a high-T paramagnetic state to a magnetic ordered state below 60 K and then to a second ordered state below 16 K, even though K0.49CoO2 is metallic at least down to 4 K. An isotropic magnetic behavior and wide internal-field distributions suggest the formation of a commensurate helical spin density wave (SDW) state below 16 K, while a linear SDW state is likely to exist above 16 K. It was also found that exhibits a further transition at 150 K presumably due to a change in the spin state of the Co ions. Since the dependence of the internal-field below 60 K was similar to that for Na0.5CoO2, this suggests that magnetic order is more strongly affected by the Co valence than by the interlayer distance or interaction and/or the charge ordering.

Dome-shaped magnetic phase diagram of thermoelectric layered cobaltites.

Using muon spin spectroscopy we have found that, for both NaxCoO(2) (0.6

Influence of impurities on short range electron transport in GaAs.

The influence of Cr impurities on muonium atom formation in GaAs has been studied using muon spin relaxation techniques with alternating electric fields. The results suggest that electron transport to and capture by the muon is suppressed by capture/scattering on intervening Cr centers. The length scale involved is estimated to be about 3x10(-6) cm. This offers an opportunity to study electron transport to positive centers in semiconductors on a microscopic scale.

Evidence for static magnetism in the vortex cores of ortho-II YBa2Cu3O6.50.

Evidence for static alternating magnetic fields in the vortex cores of underdoped YBa2Cu3O6+x is reported. Muon spin rotation measurements of the internal magnetic field distribution of the vortex state of YBa2Cu3O6.50 in applied fields of H = 1 T and H = 4 T reveal a feature in the high-field tail of the field distribution which is not present in optimally doped YBa2Cu3O6.95 and which fits well to a model with static magnetic fields in the vortex cores. The magnitude of the fields is estimated to be 18(2) G and decreases above T = 10 K. We discuss possible origins of the additional vortex core magnetism within the context of existing theories.

Anomalous weak magnetism in superconducting YBa2Cu3O6+x.

For some time now, there has been considerable experimental and theoretical effort to understand the role of the normal-state "pseudogap" phase in underdoped high-temperature cuprate superconductors. Recent debate has centered on the question of whether the pseudogap is independent of superconductivity. We provide evidence from zero-field muon spin relaxation measurements in YBa2Cu3O6+x for the presence of small spontaneous static magnetic fields of electronic origin intimately related to the pseudogap transition. Our most significant finding is that, for optimal doping, these weak static magnetic fields appear well below the superconducting transition temperature. The two compositions measured suggest the existence of a quantum critical point somewhat above optimal doping.

Human herpesvirus 6 and multiple sclerosis: systemic active infections in patients with early disease.

By means of immunohistochemical staining, cells actively infected with human herpesvirus 6 (HHV-6) were found in central nervous system tissues from 8 (73%) of 11 patients with definite multiple sclerosis (MS). Interestingly, 17 (90%) of 19 tissue sections showing active demyelination were positive for HHV-6-infected cells compared with only 3 (13%) of 23 tissue sections free of active disease (P<.0001). Central nervous system tissues from 2 of 28 normal persons and patients with other inflammatory demyelinative diseases were positive for HHV-6-infected cells (P<.0001), and the 2 positive cases were diagnosed as having HHV-6 leukoencephalitis. By use of a rapid culture assay, blood samples from 22 (54%) of 41 patients with definite MS were found to contain active HHV-6 infections, compared with 0 of 61 normal controls (P<.0001). No significant difference was found between HHV-6 viremia-positive and HHV-6 viremia-negative MS patients with respect to type of disease (relapsing/remitting or progressive). In contrast, patients with active HHV-6 viremia were significantly younger and had shorter durations of disease than did HHV-6 viremia-negative patients.

The affinity between continuous quality improvement and epidemic surveillance.

OBJECTIVE: To discuss the close affinity between the continuous quality improvement (CQI) concept of monitoring a process for the introduction of special causes and epidemic surveillance. DESIGN: A case study of a CQI tool for infection control epidemic surveillance. SETTING AND PATIENTS: A 668-bed acute care hospital with 5 intensive care units supporting heart, liver transplant, and trauma teams. The infection control department consists of 2.5 full-time employee nurse epidemiologists and a medical director who is an infectious disease specialist. RESULTS: The outbreak investigation illustrates principles of CQI and their relationship to epidemic surveillance through the use of applied statistical methods. CONCLUSIONS: The expanding role of hospital epidemiology is enhanced by applying CQI concepts to improving health care. The application of epidemiologic tools and principles to the problems of nosocomial infections is strongly connected to the CQI concept of using dependable data to improve processes.

Norwegian scabies in a patient with acquired immune deficiency syndrome.

A rare, severe form of scabies called Norwegian or keratotic scabies is described in a patient with acquired immune deficiency syndrome (AIDS). This is the first known description of this disease in an AIDS patient. The occurrence of secondary staphylococcal sepsis illustrates the importance of early correct diagnosis and treatment. Cutaneous hydration followed by aggressive application of gamma benzene hexachloride was safe and effective.

Chronic pulmonary histoplasmosis with an oral lesion.

Histoplasmosis is a fungal disease resulting from inhalation of airborne spores of the organism Histoplasma capsulatum. The disease is endemic to the Ohio and Mississippi river valleys. Oral lesions are not common, but when present, they are usually associated with the severe disseminated form of histoplasmosis. This particular case is presented as an example of chronic pulmonary histoplasmosis in which a localized gingival lesion represented the initial clinical manifestation of the disease. Diagnosis was based on a positive biopsy and the results of chest radiographic examination. If, as in this case, serologic, hematologic, and physical examination results are negative, the biopsy of suspicious lesions is of paramount importance to the clinical differential diagnosis.

Cutaneous mucormycosis in a heart transplant patient.

We present the first case of cutaneous mucormycosis reported in a patient who had undergone a heart transplant operation. This appeared to be a localized infection without a predisposing local factor such as a surgical adhesive and without evidence of dissemination. Prompt treatment with intravenous amphotericin B resulted in an apparent cure.

Posttraumatic Pasteurella multocida meningitis.

The patient described was immunologically compromised by multisystem trauma. Pasteurella multocida was isolated from the respiratory tract and subsequently from the cerebrospinal fluid; direct spread apparently occurred by way of a basilar skull fracture. Sepsis was absent. He was successfully treated but subsequently had hydrocephalus, which has not previously been reported to occur after P multocida meningitis. Because of the opportunistic nature of this infrequent human commensal and the significant morbidity and mortality associated with it, we believe that isolation of Pasteurella multocida from the respiratory tract justifies treatment, especially in the compromised host.

Cryptococcal cellulitis with multiple sites of involvement.

Cryptococcal cellulitis is an uncommon cutaneous manifestation of generalized cryptococcal disease. We describe the only reported incidence with multiple sites of cutaneous involvement. In an immunosuppressed patient an apparent cellulitis, even with multiple sites of involvement, that does not respond to appropriate antibiotics should alert one to the possible diagnosis of cryptococcal cellulitis.

Staphylococcus epidermidis ventriculitis treated with vancomycin and rifampin.

Two cases of ventriculitis with Staphylococcus epidermidis that failed on therapy with an antistaphylococcal penicillin are presented. Both infections responded to a combination of intravenous and intraventricular vancomycin and rifampin. Vancomycin and rifampin represent an important antibiotic regimen for the management of resistant infections of the central nervous system, especially with those due to S. epidermidis or methicillin-resistant Staphylococcus aureus.

Campylobacter septic abortion.

We have reported a case of a septic abortion caused by Campylobacter fetus ssp jejuni. This organism is best known for producing diarrhea, but is now being linked with more serious diseases, including pregnancy wastage.

Disseminated coccidioidomycosis in a heart transplant recipient.

A cardiac transplant patient developed disseminated coccidioidomycosis shortly after transplantation and institution of immunosuppressive therapy. The patient was maintained on intravenous and intrathecal amphotericin B for 19 months, but when therapy was discontinued, the disease relapsed and he died. At autopsy the cardiac allograft was without signs of rejection, but the patient had coccidioidomycotic lesions in multiple organs. There is an increasing number of reports of disseminated coccidioidomycosis in immunocompromised patients, especially those who receive steroids or immunosuppressive therapy. Coccidioidomycosis may represent a severe complication in the transplant patient.

Pericarditis in a patient with Legionnaires' disease.

Pericardial involvement with legionnaires' disease is rare. Pericarditis with legionnaires' pneumonia developed in a patient with previous mediastinal irradiation for Hodgkin's disease. Subsequently, the patient had progressive symptoms of pericardial constriction that required pericardiectomy. Acute infection with agents such as legionnaires' bacillus may precipitate the late appearance of pericardial disease in patients with previous mediastinal irradiation.