Effect of motivational context on conspecific song discrimination by brown-headed cowbirds (Molothrus ater).

Two experiments to examine the effects of motivational context on the perception of conspecific song by cowbirds were conducted. In the 1st experiment, sexual displays were elicited from females by playback of normal song and rearranged sequences of the component phrases. In a 2nd experiment, male and female cowbirds discriminated among the same songs in a food-rewarded operant procedure. In a sexual context, the birds were sensitive to both the beginning and end phrases of normal song, whereas in a food context, the birds were more sensitive to the beginning of normal song. In both experiments, 1-phrase songs were better discriminated from normal song than 2-phrase songs, and there was no effect of phrase order on discrimination. Similarities and differences in the results of the 2 experiments suggest that some aspects of cowbird song perception remain constant across motivational contexts, whereas others are unique to particular motivational contexts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Imaging nanoparticles in cells by nanomechanical holography

Nanomaterials have potential medical applications, for example in the area of drug delivery, and their possible adverse effects and cytotoxicity are curently receiving attention. Inhalation of nanoparticles is of great concern, because nanoparticles can be easily aerosolized. Imaging techniques that can visualize local populations of nanoparticles at nanometre resolution within the structures of cells are therefore important. Here we show that cells obtained from mice exposed to single-walled carbon nanohorns can be probed using a scanning probe microscopy technique called scanning near field ultrasonic holography. The nanohorns were observed inside the cells, and this was further confirmed using micro Raman spectroscopy. Scanning near field ultrasonic holography is a useful technique for probing the interactions of engineered nanomaterials in biological systems, which will greatly benefit areas in drug delivery and nanotoxicology.     

Spectroscopy and imaging of arrays of nanorods toward nanopolarimetry

The polarization dependence of the optical scattering properties of two-dimensional arrays of metal nanostructures with sub-wavelength dimensions (nanoantennas) has been investigated. Arrays of 500 nm × 100 nm gold nanorods covering a 100 × 100 μm(2) area were fabricated with varying orientations on an electrically conductive substrate. The experimental and computational analysis of the angularly organized nanorods suggest potential use toward the development of an integrated polarimeter. Using the gold nanorods on a transparent substrate as a preliminary system, we show that in the proper spectral range the scattering properties of the structures may be tuned for such an application.     

Enhanced Magnetism in Highly Ordered Magnetite Nanoparticle‐Filled Nanohole Arrays

A new approach to develop highly ordered magnetite (Fe₃O₄) nanoparticle‐patterned nanohole arrays with desirable magnetic properties for a variety of technological applications is presented. In this work, the sub‐100 nm nanohole arrays are successfully fabricated from a pre‐ceramic polymer mold using spin‐on nanoprinting (SNAP). These nanoholes a then filled with monodispersed, spherical Fe₃O₄ nanoparticles of about 10 nm diameter using a novel magnetic drag and drop procedure. The nanohole arrays filled with magnetic nanoparticles a imaged using magnetic force microscopy (MFM). Magnetometry and MFM measurements reveal room temperature ferromagnetism in the Fe₃O₄‐filled nanohole arrays, while the as‐synthesized Fe₃O₄ nanoparticles exhibit superparamagnetic behavior. As revealed by MFM measurements, the enhanced magnetism in the Fe₃O₄‐filled nanohole arrays originates mainly from the enhanced magnetic dipole interactions of Fe₃O₄ nanoparticles within the nanoholes and between adjacent nanoholes. Nanoparticle filled nanohole arrays can be highly beneficial in magnetic data storage and other applications such as microwave devices and biosensor arrays that require tunable and anisotropic magnetic properties.     

Nanometrology of delignified Populus using mode synthesizing atomic force microscopy

The study of the spatially resolved physical and compositional properties of materials at the nanoscale is increasingly challenging due to the level of complexity of biological specimens such as those of interest in bioenergy production. Mode synthesizing atomic force microscopy (MSAFM) has emerged as a promising metrology tool for such studies. It is shown that, by tuning the mechanical excitation of the probe-sample system, MSAFM can be used to dynamically investigate the multifaceted complexity of plant cells. The results are argued to be of importance both for the characteristics of the invoked synthesized modes and for accessing new features of the samples. As a specific system to investigate, we present images of Populus, before and after a holopulping treatment, a crucial step in the biomass delignification process.     

Spectroscopy and atomic force microscopy of biomass

Scanning probe microscopy has emerged as a powerful approach to a broader understanding of the molecular architecture of cell walls, which may shed light on the challenge of efficient cellulosic ethanol production. We have obtained preliminary images of both Populus and switchgrass samples using atomic force microscopy (AFM). The results show distinctive features that are shared by switchgrass and Populus. These features may be attributable to the lignocellulosic cell wall composition, as the collected images exhibit the characteristic macromolecular globule structures attributable to the lignocellulosic systems. Using both AFM and a single case of mode synthesizing atomic force microscopy (MSAFM) to characterize Populus, we obtained images that clearly show the cell wall structure. The results are of importance in providing a better understanding of the characteristic features of both mature cells as well as developing plant cells. In addition, we present spectroscopic investigation of the same samples.     

Atomic force microscopy of silica nanoparticles and carbon nanohorns in macrophages and red blood cells

The emerging interest in understanding the interactions of nanomaterial with biological systems necessitates imaging tools that capture the spatial and temporal distributions and attributes of the resulting nano–bio amalgam. Studies targeting organ specific response and/or nanoparticle-specific system toxicity would be profoundly benefited from tools that would allow imaging and tracking of in-vivo or in-vitro processes and particle-fate studies. Recently we demonstrated that mode synthesizing atomic force microscopy (MSAFM) can provide subsurface nanoscale information on the mechanical properties of materials at the nanoscale. However, the underlying mechanism of this imaging methodology is currently subject to theoretical and experimental investigation. In this paper we present further analysis by investigating tip-sample excitation forces associated with nanomechanical image formation. Images and force curves acquired under various operational frequencies and amplitudes are presented. We examine samples of mouse cells, where buried distributions of single-walled carbon nanohorns and silica nanoparticles are visualized.     

White-throated sparrows (Zonotrichia albicollis) can perceive pitch change in conspecific song by using the frequency ratio independent of the frequency difference.

In the ascending songs of white-throated sparrows, the 1st note (Phrase 1) is sung lower than the remaining notes (Phrase 2). The production of this frequency change is more reliably predicted by the frequency ratio (Phrase 2? ?Phrase 1) than by the frequency difference (Phrase 2?–?Phrase 1). To determine whether sparrows use the ratio rather than the difference to identify ascending songs, a low-frequency song was transposed upward in frequency, maintaining a normal frequency difference but altering the frequency ratio, and a high-frequency song was transposed downward in the same way. Territorial males tested in the wild sang more and approached more closely to songs with normal ratios than to songs with altered ratios, even when the frequency difference was identical in both. This is the first evidence that the perception of pitch change by songbirds is related to the frequency ratio independent of the difference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)