Surface plasmons in terahertz metamaterials.

We characterize terahertz metamaterials by applying apertureless near-field microscopy with a bandwidth that covers the entire spectral response of the structures. The observations agree with the interpretation of the fundamental mode of the metamaterial. But the high frequency resonance shows properties that deviate from the common interpretation. We show that the high frequency response is governed by surface Plasmon excitations, which have a comparable oscillator strength as the fundamental mode.

Shear force control for a terahertz near field microscope.

We report on the advancement of apertureless terahertz microscopy by active shear force control of the scanning probe. Extreme subwavelength spatial resolution and a maximized image contrast are achieved by maintaining a tip-surface distance of about 20 nm. The constant distance between scanning tip and surface results in terahertz images that mirror the dielectric permittivity of the surface.

Millimeter wave probing of the acoustic phase for concealed object detection.

We developed a far infrared technique for detecting objects that are concealed behind a barrier, which is opaque for visible light. The technique makes use of the fact that mechanically coupled objects can be distinguished by their acoustic phase during a driven vibration. The pattern of the acoustic phase is imaged using 70 GHz radiation. The experimental data demonstrate that virtually all objects can be sensed, which includes metals as well as dielectric materials.

Identification of a resonant imaging process in apertureless near-field microscopy.

We report on apertureless near-field microscopy in the far infrared. We identify a configurational resonance of the scanning tip-surface system to be the dominating mechanism that forms the image. Experimental data such as the high imaging contrast and its spectral properties can be well explained and make the framework of a mesoscopic resonance an alternative to conventional scattering models that are used to interpret near-field data. Our findings are plausibly not restricted to the far infrared and may impact on near-field spectroscopy in general.

Few-cycle THz generation for imaging and tomography applications.

The methods for generating few-cycle THz radiation from semiconductors without external applied fields are reviewed. Their spectral characteristics, efficiency and prospects for imaging and tomography at terahertz frequencies are discussed.

Time-domain differentiation of terahertz pulses.

We report on the time-domain differentiation of light waves by metallic transmission gratings. Time-resolved terahertz experiments show that the first time derivative of an arbitrary waveform can be achieved by use of gratings of subwavelength period. The results are in accord with classical diffraction theory and may permit novel applications for tailoring few-cycle light pulses and ultrahigh-frequency optoelectronics.

Impact of social support, diversity, and poverty on nursing home utilization in a nationally representative sample of older Americans.

This study examined the effects of social support, poverty, functional status, and demographic variables (age, race, gender) on nursing home admission using Cox proportional hazard models with time varying covariates on the Longitudinal Study on Aging (1984-1990). The Behavioral Model of Health Care Utilization was used to organize the study. Living with a spouse or children reduced the risk as did being socially active. High income reduced the risk but there were problems in the measurement of income. Higher levels of functional disability predicted higher risk. Being Black or being female reduced the risk of admission. Age was a predictor of increased risk. Beyond these findings this paper provides support for the importance of gathering and utilizing data that allows for predictor variables to vary with time.

Sampling a terahertz dipole transition with subcycle time resolution.

We present a time-resolved technique to measure optical excitation processes with a time resolution shorter than the oscillation period of the exciting light. Our terahertz (THz) experiments fully resolve the polarization dynamics of electrons in semiconductor heterostructures when they are excited by a THz pulse. The time resolution of the polarization enables us to deduce the population dynamics of the excited state, which includes the dynamics of a virtual population in the case of off-resonant excitation.

Stress, social support, and distress in a statewide population of persons with AIDS in New Jersey.

This study examined the effects of stress, social support, and health status on distress in a sample of 79 persons with AIDS in New Jersey. The study used New Jersey's AIDS Registry as a geographically based list sampling frame, with data gathered through in-person interviews. The study examined the effects of health status (operationalized as symptom burden), stress (operationalized with a stressful-life-events scale), social support from friends, and social support from family on depression as measured by the Center for Epidemiological Studies-Depression (CES-D) scale. We examined the differential effects of friend support and of family support at differing levels of stressful life events. Results indicate that health status and stressful life events both have substantial impact on distress. Friend support reduced distress under lower-stress conditions, while family support reduced distress under high-stress conditions. These results suggest that social support from peers is critical for emotional well-being of persons with HIV in many circumstances, but that in periods of crisis family support becomes a more important determinant of emotional well-being.

Erythropoietin immunolocalization in renal cell carcinoma.

Erythropoietin (EPO) is a well-recognized hormone that induces erythrocytosis in a wide range of physiologic and pathologic situations in mammals. One of these situations is a paraneoplastic erythrocytosis, which might be seen in association with various neoplasms, including renal cell carcinoma (RCC), hepatoma, and cerebellar hemangioblastoma. Although there have been multiple studies confirming the association between this erythrocytosis and the production of EPO by tumor cells, immunohistochemical detection of EPO in formalin-fixed, paraffin-embedded tissue was not described. We report on the use of microwave antigen retrieval to detect EPO in RCCs in such routinely processed tissues. We selected 19 RCCs received as nephrectomy specimens, fixed in formalin, and routinely processed. These cases were previously diagnosed on the basis of morphologic, immunohistochemical, and clinical features. We examined the immunoreactivity of these specimens with a monoclonal anti-EPO antibody. Fetal (20 wk gestational age) liver served as a positive control. Intense positive immunoreactivity was observed as cytoplasmic, granular staining in fetal hepatocytes. Fourteen RCCs (10 clear cell and 4 tubulopapillary types) demonstrated unequivocal cytoplasmic immunoreactivity. Additionally, two clear cell tumors were only focally positive, whereas three (16%) were negative. EPO immunoreactivity might thus prove to be of value in the diagnosis or confirmation of RCC, particularly in the context of routinely processed material.

[Sarmiento function fracture treatment of the tibia]. / Die funktionelle Knochenbruch-Behandlung am Unterschenkel (nach Sarmiento).

Sarmiento's functional brace treatment of tibial bone fractures is introduced and discussed. After fixation with a plaster cast and extension, the injured limb is fitted into a synthetic brace until complete bony union is achieved. Our four years of experience with 73 patients and the distribution of age, sex, localization, and cause are presented, as are the reexamination results. The possible complications and their treatment are demonstrated. The results justify extensive use of this method.