Direct observation of muonium reacting with uncapped gold nanoparticles in porous silica and nature of the final state.

We report the reaction of muonium (Mu = [µ+e-]), a light isotopic analog of hydrogen, with uncapped gold nanoparticles embedded in mesoporous silica. Using the radio-frequency muon spin rotation (RF-µSR) technique, we directly observe and characterize the resulting final state on the nanoparticle surface, showing conclusively its diamagnetic nature. The magnetic environment experienced by the reacted muons is only weakly perturbed compared to that of muons in a silica reference, consistent with the surface of the gold nanoparticles being metallic and non-magnetic. We demonstrate the potential of RF-µSR for the investigation of the surface properties of nanoparticles and show the feasibility of Knight shift measurements of muons on metal surfaces.

Communication: Chemisorption of muonium on gold nanoparticles: A sensitive new probe of surface magnetism and reactivity.

Chemisorption of muonium onto the surface of gold nanoparticles has been observed. Muonium (µ+e-), a light hydrogen-like atom, reacts chemically with uncapped 7 nm gold nanoparticles embedded in mesoporous silica (SBA-15) with a strong temperature-dependent rate. The addition rate is fast enough to allow coherent spin transfer into a diamagnetic muon state on the nanoparticle surface. The muon is well established as a sensitive probe of static or slowly fluctuating magnetic fields in bulk matter. These results represent the first muon spin rotation signal on a nanoparticle surface or any metallic surface. Only weak magnetic effects are seen on the surface of these Au nanoparticles consistent with Pauli paramagnetism.

The erosion of physician-patient privilege and patient confidentiality.

With the proliferation of third party payers for health care who exercise utilization management, there has been an erosion of the physician-patient privilege and patient confidentiality. The kinds of medical information obtained by third party payers under the guise of claims administration violate the spirit if not the actual laws pertaining to physician-patient communication. It presents three episodes involving the first author in which that communication was violated by third parties administering health care benefits. Recommendations are made to protect that confidentiality in this era of increasing cost management.

Approaches to primary care. Physician capitation.

The first author, as a consultant to the Office of Prepaid Health Care, reviewed the financial status of nine IPAs for federal qualification in 1987. He found little to suggest any methodology being used for constructing primary care physician (PCP) capitation reimbursement systems. This article draws upon statistical theory and presents hypothetical examples to structure better financial arrangements based on five criteria: stop-loss reinsurance deductible levels, capitation of services related to physician practice, minimum panel size (number of patients) for capitation, stratified capitation, and inclusion of all PCPs in the capitation arrangement.

Spectrophotometric investigation of pulsatile blood flow for transcutaneous reflectance oximetry.

A new method to estimate arterial oxygen saturation is suggested based on the presence of the plethysmographic pulse. A prototype skin reflectance oximeter system utilizing a miniature solid state optical transducer has been constructed. Preliminary data collected from a group of volunteers indicated good quantitative correlation between skin reflectance and arterial oxygen saturation as determined by an earlobe oximeter. We are now investigating the dependency of the measurements on various physiological conditions and skin characteristics in order to determine appropriate calibration procedures. This study has demonstrated for the first time that arterial hemoglobin oxygen saturation can be measured quantitatively using transcutaneous reflectance techniques. However, more extensive work is needed to further develop this technique into a viable clinical tool.

Intracranial pressure telemetry system. II. Animal testing.

A small, implantable, telemetric device for the long-term monitoring of intracranial pressure has been described in part I of this article. This portion of the study is designed to demonstrate the in vivo operational characteristics of that implant device in experimental animals. Results indicate that this system can provide long-term in vivo operation with rapid and accurate responses to acute changes in pressure. Data also indicate some drift in the baseline measurement of pressure. No signs of abnormal body reactions to the units were observed.

Echocardiographic abnormalities in patients with cystic fibrosis.

An echographic study was undertaken to evaluate left (LV) and right ventricular (RV) function in 30 patients with cystic fibrosis. Echographic recording of the pulmonary and aortic valve echogram permitted measurement of the phases of right and left ventricular systole. The ratio of the LV preejection period/LV ejection time (LPEP/LVET) and shortening of the LV internal dimension %SID was employed to reflect LV function, while RV preejection period/RV ejection time (RPEP/RVET) has excellent correlation with pulmonary artery diastolic pressure. RPEP/RVET and two other echographic measurements, right ventricular wall (RVW) and internal dimension (RVD) were compared with pulmonary function tests and clinical scores. RPEP/RVET correlated well with percent vital capacity(%VC), r = -0.73, percent residual volume (%RVol) r = +0.72, and clinical score, r = -0.77. Multilinear regression of RPEP/RVET, RVD, and RVW improved correlation for %VC (r = -0.80), %RVol, r = +0.82, and clinical score, r = -0.84. Patients in overt right heart failure exhibited elevated RPEP/RVET (mean = 0.48) when compared to patients not in right heart failure (mean = .33). Marked diminution of LV function was present in two patients. A variety of cardiovascular abnormalities were demonstrated echographically and were valuable in assessing the degree of cardiac involvement in patients with cystic fibrosis.