Quantitative analysis of ferroelectric domain imaging with piezoresponse force microscopy

The contrast mechanism for ferroelectric domain imaging via piezoresponse force microscopy (PFM) is investigated. A novel analysis of PFM measurements is presented which takes into account the background caused by the experimental setup. This allows, for the first time, a quantitative, frequency independent analysis of the domain contrast which is in good agreement with the expected values for the piezoelectric deformation of the sample and satisfies the generally required features of PFM imaging

Sol-Gel Derived Ferroelectric Nanoparticles Investigated by Piezoresponse Force Microscopy

Piezoresponse force microscopy (PFM) was used to investigate the ferroelectric properties of sol-gel derived LiNbO$_3$ nanoparticles. To determine the degree of ferroelectricity we took large-area images and performed statistical image-analysis. The ferroelectric behavior of single nanoparticles was verified by poling experiments using the PFM tip. Finally we carried out simultaneous measurements of the in-plane and the out-of-plane piezoresponse of the nanoparticles, followed by measurements of the same area after rotation of the sample by 90$^{\circ}$ and 180$^{\circ}$. Such measurements basically allow to determine the direction of polarization of every single particle

Multi-excitonic complexes in single InGaN quantum dots

Cathodoluminescence spectra employing a shadow mask technique of InGaN layers grown by metal organic chemical vapor deposition on Si(111) substrates are reported. Sharp lines originating from InGaN quantum dots are observed. Temperature dependent measurements reveal thermally induced carrier redistribution between the quantum dots. Spectral diffusion is observed and was used as a tool to correlate up to three lines that originate from the same quantum dot. Variation of excitation density leads to identification of exciton and biexciton. Binding and anti-binding complexes are discovered.Comment: 3 pages, 4 figure

Spectral properties and geology of bright and dark material on dwarf planet Ceres

Variations and spatial distributions of bright and dark material on dwarf planet Ceres play a key role in understanding the processes that have led to its present surface composition. We define limits for bright and dark material in order to distinguish them consistently, based on the reflectance of the average surface using Dawn Framing Camera data. A systematic classification of four types of bright material is presented based on their spectral properties, composition, spatial distribution, and association with specific geomorphological features. We found obvious correlations of reflectance with spectral shape (slopes) and age; however, this is not unique throughout the bright spots. Although impact features show generally more extreme reflectance variations, several areas can only be understood in terms of inhomogeneous distribution of composition as inferred from Dawn Visible and Infrared Spectrometer data. Additional material with anomalous composition and spectral properties are rare. The identification of the composition and origin of the dark, particularly the darkest material, remains to be explored. The spectral properties and the morphology of the dark sites suggest an endogenic origin, but it is not clear whether they are more or less primitive surficial exposures or excavated subsurface but localized material. The reflectance, spectral properties, inferred composition, and geologic context collectively suggest that the bright and dark material tends to gradually change toward the average surface over time. This could be because of multiple processes, i.e., impact gardening/space weathering, and lateral mixing, including thermal and aqueous alteration, accompanied by changes in composition and physical properties such as grain size, surface temperature, and porosity (compaction).Comment: Meteoritics and Planetary Science; Dawn at Ceres special issu

Dual-path state reconstruction scheme for propagating quantum microwaves and detector noise tomography

Quantum state reconstruction involves measurement devices that are usually described by idealized models, but not known in full detail in experiments. For weak propagating microwaves, the detection process requires linear amplifiers which obscure the signal with random noise. Here, we introduce a theory which nevertheless allows one to use these devices for measuring all quadrature moments of propagating quantum microwaves based on cross-correlations from a dual-path amplification setup. Simultaneously, the detector noise properties are determined, allowing for tomography. We demonstrate the feasibility of our novel concept by proof-of-principle experiments with classical mixtures of weak coherent microwaves.Comment: 11 pages, 3 figure

Ruminal Fermentation Kinetics of Moringa and Peltiphyllum Supplements During Early Incubation Period in the in Vitro Reading Pressure Technique

This experiment was aimed to observe rumen fermentation kinetics of alternative supplements, i.e.Moringa oleifera and Peltiphyllum peltatum leaves added to maize silage diet as compared to aconventional supplement (barley-soya). A total of six treatments were investigated in the present study,which consisted of: maize silage (A), M. oleifera (B), P. peltatum (C), maize silage + concentrate (56:44,w/w; D), maize silage + M. oleifera (56:44, w/w; E), and maize silage + concentrate + P. peltatum(47:37:16, w/w/w; F). The feeds were incubated in vitro in three replicates (completely randomized)using the Reading Pressure Technique system. Approximately 800 mg of the feeds were mixed by 75 mlof buffered rumen liquor. The incubation was carried out up to 12 h in bottles and gas pressure wasrecorded and released in regular intervals. Repeated sampling was conducted for analysis offermentation products at 1, 6 and 12 h of incubation period. The results showed that the nutritionalquality of Moringa and its fermentation pattern was comparable to that of barley-soya concentrate. PlainMoringa incubation resulted the highest production of iso-SCFA and soluble protein concentrationamong all treatments after 12 h incubation (P<0.05). Incubation of sole Peltiphyllum peltatum highlyhampered the fermentation rate. Production of iso-SCFA both for plain Peltiphyllum and its mixturewere comparatively low. Supplementation of Peltiphyllum increased significantly soluble proteinconcentration during 12 h incubation (P<0.05). Peltiphyllum also had a very low C2+C4/C3 ratiocompared to other treatments. It could be concluded that Moringa oleifera is a potential alternativesupplement to replace either partially or completely concentrate as a conventional supplement, andPeltiphyllum peltatum supplementation could reduce excessive protein degradation and fermentation ofthe concentrate in the rumen

T Cell-Tumor Interaction Directs the Development of Immunotherapies in Head and Neck Cancer

The competent immune system controls disease effectively due to induction, function, and regulation of effector lymphocytes. Immunosurveillance is exerted mostly by cytotoxic T-lymphocytes (CTLs) while specific immune suppression is associated with tumor malignancy and progression. In squamous cell carcinoma of the head and neck, the presence, activity, but also suppression of tumor-specific CTL have been demonstrated. Functional CTL may exert a selection pressure on the tumor cells that consecutively escape by a combination of molecular and cellular evasion mechanisms. Certain of these mechanisms target antitumor effector cells directly or indirectly by affecting cells that regulate CTL function. This results in the dysfunction or apoptosis of lymphocytes and dysregulated lymphocyte homeostasis. Another important tumor-escape mechanism is to avoid recognition by dysregulation of antigen processing and presentation. Thus, both induction of functional CTL and susceptibility of the tumor and its microenvironment to become T cell targets should be considered in CTL-based immunotherapy