Spectral engineering of ultrathin germanium solar cells for combined photovoltaic and photosynthesis.

In densely populated areas, ground mounted photovoltaic power plants compete with agriculture for cultivable land. Agrivoltaic systems allow the combination of these two forms of land use by deliberately designed light sharing. In this contribution, we present a spectrally selective solar cell, for use in agrivoltaic systems, greenhouses, and photo-bioreactors. Our concept benefits from a solar cell with a transmission spectrum which can be easily tuned for the specific absorption requirements of algae and plants. This is achieved by a Fabry-Perot-type multilayer resonator as a back reflector, which determines the transmission and absorption spectrum of the solar cell. We demonstrate the extent of how this transmission spectrum can be engineered by varying the layer thicknesses of the reflector and we show how the reflecting metal layers in the back reflector influence the transmission and photocurrent generation of the spectrally selective solar cell. Finally, we analyze the optical loss mechanisms of the solar cell layer stack to address further optimization potential. Our work offers a spectrally selective solar cell which can be easily adjusted for the requirements of combining photovoltaic and photosynthesis.

Negative refraction observed in a metallic ferromagnet in the gigahertz frequency range.

It is generally believed that nature does not provide materials with negative refraction. Here we demonstrate experimentally that such materials do exist at least at GHz frequencies: ferromagnetic metals reveal a negative refraction index close to the frequency of the ferromagnetic resonance. The experimental realization utilizes a colossal magnetoresistance manganite La(2/3)Ca(1/3)MnO(3) as an example. In this material the negative refractive index can be achieved even at room temperature using external magnetic fields.

A-site ordering versus electronic inhomogeneity in colossally magnetoresistive manganite films.

Epitaxial La(3/4)Ca(1/4)MnO3/MgO(100) (LCMO) thin film shows an unusual rhombohedral (R-3c) structure with a new perovskite superstructure at room temperature due to the CE-type ordering of La and Ca with modulation vector q=1/4[011]. A-site ordered film was found to be electronically homogeneous down to the 1 nm scale as revealed by scanning tunnelling microscopy/spectroscopy. In contrast, orthorhombic and A-site disordered LCMO demonstrate a mesoscopic phase separation far below the Curie temperature (TC). Unique La/Ca ordering compensates the cation mismatch stress within one supercell, a(S) approximately 1.55 nm, and enhances the electronic homogeneity. The phase separation does not seem to be a unique mechanism for the colossal magnetoresistance (CMR) as very large CMR approximately 500% was also observed in A-site ordered films.

Effect of pentoxifylline in severe sepsis: results of a randomized, double-blind, placebo-controlled study.

OBJECTIVE: To evaluate the effect of pentoxifylline on organ dysfunction, survival, and mediator response in patients with severe sepsis. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Surgical intensive care units at 2 university hospitals. PATIENTS: Fifty-one surgical patients with severe sepsis were randomized to receive pentoxifylline continuously (27 patients) or saline infusion as placebo (24 patients). INTERVENTIONS: PATIENTS received pentoxifylline (1 mg/kg of body weight per hour; maximum, 1800 mg/d) during 28 days or until they were discharged from the intensive care unit or died. MEASUREMENTS AND MAIN RESULTS: Vital signs and organ function were determined at diagnosis; daily from day 1 to 7; on days 10, 14, 17, 21, and 24; and 28 days after diagnosis of sepsis. There were no differences in characteristics of patients at diagnosis in the Acute Physiology and Chronic Health Evaluation II (APACHE II) score (mean+/-SEM, 17+/-4 points for the pentoxifylline group and 18+/-5 points for the placebo group), the multiple organ dysfunction score (mean+/-SEM, 11.0+/-0.8 vs 11.8+/-1.0 points), tumor necrosis factor alpha and interleukin 6 bioactivity, serum endotoxin levels, or organ dysfunction. At study entrance, 23 of 27 patients in the pentoxifylline group and 21 of 24 patients in the placebo group experienced septic shock. No adverse effects of pentoxifylline treatment were observed. The 28-day mortality rate was 30% (8/27) in pentoxifylline-treated patients and 33% (8/24) in the placebo group. Hospital mortality was 41% (11/27) in the pentoxifylline group and 54% (13/24) in the placebo group. The multiple organ dysfunction score decreased in patients receiving pentoxifylline 4 days after diagnosis of sepsis compared with placebo-treated patients; a significant difference was reached on day 14 (P<.05; Student t test, Bonferoni correction). The PaO2/FIO2 (fraction of inspired oxygen) ratio was significantly improved in pentoxifylline-treated patients on days 14 and 17 (P<.05), and the pressure-adjusted heart rate was significantly improved on day 6 (P<.05) compared with the placebo group. Serum endotoxin levels, tumor necrosis factor alpha and interleukin 6 bioactivity were not different between the groups during the study. CONCLUSIONS: Continuous intravenous administration of pentoxifylline beneficially influenced cardiopulmonary dysfunction in patients with sepsis without adverse effects. Larger trials are needed to evaluate the efficacy in improving organ function in relation to the outcome for patients with severe sepsis.

Inexpensive upgrading of a FACS I and isolation of rare somatic variants by double-fluorescence sorting.

We have modified a FACS I by addition of a tunable dye laser and an optical system for fluorescence detection that allows physically independent measurement of green and red immunofluorescence. These modifications are inexpensive and should be applicable to most single-laser systems. By using the modified machine and double-fluorescence activated selection with H-2Kk-specific monoclonal antibodies labelled with FITC or Texas Red, we have isolated from a murine T-cell lymphoma line variant subclones expressing structurally altered histocompatibility class I (H-2Kk) molecules.