Coherent two-dimensional nanoscopy

We introduce a spectroscopic method that determines nonlinear quantum mechanical response functions beyond the optical diffraction limit and allows direct imaging of nanoscale coherence. In established coherent two-dimensional (2D) spectroscopy, four-wave-mixing responses are measured using three ingoing waves and one outgoing wave; thus, the method is diffraction-limited in spatial resolution. In coherent 2D nanoscopy, we use four ingoing waves and detect the final state via photoemission electron microscopy, which has 50-nanometer spatial resolution. We recorded local nanospectra from a corrugated silver surface and observed subwavelength 2D line shape variations. Plasmonic phase coherence of localized excitations persisted for about 100 femtoseconds and exhibited coherent beats. The observations are best explained by a model in which coupled oscillators lead to Fano-like resonances in the hybridized dark- and bright-mode response.     

Second-harmonic generation from magnetic metamaterials

We observe second-harmonic generation from metamaterials composed of split-ring resonators excited at 1.5-micrometer wavelength. Much larger signals are detected when magnetic-dipole resonances are excited, as compared with purely electric-dipole resonances. The experiments are consistent with calculations based on the magnetic component of the Lorentz force exerted on metal electrons-an intrinsic second-harmonic generation mechanism that plays no role in natural materials. This unusual mechanism becomes relevant in our work as a result of the enhancement and the orientation of the local magnetic fields associated with the magnetic-dipole resonances of the split-ring resonators.     

Inheritance of potato chip color at the 24-chromosome level

Potato chip color is an important trait in determining quality and acceptability of cultivars for processing. Therefore, the genetics of potato chip color is important in varietal breeding. The use of 2xS. tuberosum Group Tuberosum haploid × 2x wild species hybrids provides disomic inheritance for genetic analysis of chip color. Two hundred forty haploid-species hybrids representing crosses between 15 haploids and 10 species were evaluated for potato chip color after 21 days reconditioning (18 to 20C) following 6 months at 4C. Phenotypic variation for chip color was found among the haploid-species hybrids. Crosses between good, medium, and poor performing clones were made in all combinations and 136 families were obtained. Progeny were evaluated for reversion resistance (chipping direct from 10C storage) and reconditioning (chipping from 4C after tuber warming) chip color. Variation for chip color was found among the progeny for each trait. Significant correlations between reversion resistance and reconditioning were found. Yet, the use of at least two chip tests (one for reversion resistance and one for reconditioning) is more informative than the use of one test and subsequent predictions made, regarding the other trait. A three locus hypothesis for both reversion resistance and reconditioning is proposed for the inheritance of each trait. One dominant allele at each of the three loci is necessary for good chipping. One or two loci may be common to both characteristics. Good chipping 2x hybrids that produce 2n pollen can be used to transfer this trait to the 4x level through use of 4x × 2x crosses.     

Vertical variability of spectral ratios in a mature mixed forest stand

The quality and quantity of solar radiation are crucial for growth and competition within forest ecosystems. The spectral waveband between 400 and 700 nm is mainly responsible for photosynthesis and thus for plant growth. Spectral ratios such as red/far red (R/FR) and blue/red (B/R) give important information about the light quality within stands. Changes in R/FR and B/R trigger or inhibit effects such as seed germination, stem growth, dormancy, leaf expansion and flowering. Blue light strongly influences development and growth of plants e.g. an increase of B/R may lead to higher photosynthetic rates per unit leaf area. In addition to spectral properties, a higher fraction of diffuse radiation on overcast days can be used more effectively by plant organs. In this study, the spectral composition and variability of solar radiation were analyzed for different sky conditions and solar angles in six different vertical layers of a mixed European beech and Norway spruce stand in Southern Germany. The results showed lower R/FR ratios in beech than in spruce. Spruce showed markedly higher B/R values in comparison to beech under clear sky conditions. A steep increase of the B/R ratio at the height of the sun crown in both species was observed. Cloud cover had a major effect, elevating R/FR and reducing B/R values compared to clear sky days, due to a higher fraction of diffuse, unattenuated radiation within the canopy. The penetration of blue and red light into the canopy strongly depends on both the diffuse index and solar elevation angle.     

The cholesterol-lowering property of soybeans fed to rats is related to the fasting duration

Numerous factors affect plasma cholesterol and, therefore, representpotential interferences with the specific effects of diet on lipid metabolism.After casein intake, serum cholesterol levels depend on many experimentalconditions in rats, such as the type of casein, the presence or absence ofcholesterol in the diet, the age and strain of rat, the diet composition, thenutritional status. The effect of fasting duration on selected parameters wasstudied in adult male Wistar rats fed a 20% casein and 1% cholesterol-based diet. No changes were observed in total serum, lipoproteins-B andHDL cholesterol and in triglyceride values after an 8 h-fast compared tonon-fasted animals. A significant decrease was induced in total andlipoproteins-B cholesterol with a 12 h-fast. A prolonged fast resulted ina significant decrease in these parameters and in triglycerides and inHDL-cholesterol levels.Fasted animals fed heated soybean meal instead of casein did not display amarked decrease in serum lipids. It appeared that the fasting effect wasmore marked in animals fed casein than in animals fed soybeans. Theseresults showed the importance of experimental conditions such as nutritional status ofanimals when blood samples are taken in studies of the hypocholesterolemiceffect of soy protein compared to casein.     

Human guanylate-binding protein 1 as a model system investigated by several surface techniques

In medical technologies concerning the surface immobilization of proteins in a defined orientation, maintaining their activity is a critical aspect. Therefore, in this study, the authors have investigated the activity of an elongated protein attached to a self-assembled monolayer supported streptavidin layer for different relative orientations of the protein with regard to the surface. Several mutants of this protein, human guanylate-binding protein 1 (hGBP1) showing GTPase catalytic activity, have been furnished with either one or two biotin anchors. Various independent methods that are based on different biophysical properties such as surface plasmon resonance, atomic force microscopy, and quartz crystal microbalance have been used to determine the orientation of the hGBP1 variants after anchoring them via a streptavidin-linker to a biotinylated surface. The activity of guanosine-triphosphate hydrolysis of hGBP1 monomers bound on the surface is found to depend on their orientation relative to the substrate, relating to their ability to form dimers with other neighboring anchored mutants; the maximum activity is lower than that observed in solutions, as might be expected from diffusion limitations at the solid/liquid interface on the one hand and prevention from homodimer formation due to immobilization on the other hand.