Visual Information Alone Changes Behavior and Physiology during Social Interactions in a Cichlid Fish (Astatotilapia burtoni)

Social behavior can influence physiological systems dramatically yet the sensory cues responsible are not well understood. Behavior of male African cichlid fish, Astatotilapia burtoni, in their natural habitat suggests that visual cues from conspecifics contribute significantly to regulation of social behavior. Using a novel paradigm, we asked whether visual cues alone from a larger conspecific male could influence behavior, reproductive physiology and the physiological stress response of a smaller male. Here we show that just seeing a larger, threatening male through a clear barrier can suppress dominant behavior of a smaller male for up to 7 days. Smaller dominant males being “attacked” visually by larger dominant males through a clear barrier also showed physiological changes for up to 3 days, including up-regulation of reproductive- and stress-related gene expression levels and lowered plasma 11-ketotestesterone concentrations as compared to control animals. The smaller males modified their appearance to match that of non-dominant males when exposed to a larger male but they maintained a physiological phenotype similar to that of a dominant male. After 7 days, reproductive- and stress- related gene expression, circulating hormone levels, and gonad size in the smaller males showed no difference from the control group suggesting that the smaller male habituated to the visual intruder. However, the smaller male continued to display subordinate behaviors and assumed the appearance of a subordinate male for a full week despite his dominant male physiology. These data suggest that seeing a larger male alone can regulate the behavior of a smaller male but that ongoing reproductive inhibition depends on additional sensory cues. Perhaps, while experiencing visual social stressors, the smaller male uses an opportunistic strategy, acting like a subordinate male while maintaining the physiology of a dominant male

Mono/bidentate thiol oligoarylene-based self-assembled monolayers (SAMs) for interface engineering

A new set of linear oligoarylene thiol molecules, namely (4'-(Thiophen-2-yl) Biphenyl-3,5-diyl) Dimethanethiol (TBD), (4'-(Thiophen-2-yl) Biphenyl-4-yl) Methanethiol (TBM) and ([ 1,1'; 4',1''] Terphenyl-3,5-diyl) Dimethanethiol (TD), were synthesized and used for functionalizing the polycrystalline gold electrodes. Such molecules differ for the number of anchoring groups (TBM vs. TBD) and the terminal rings (TD vs. TBD). As shown by electrochemical measurements, they form homogeneous and pinholes-free self-assembly monolayers (SAMs) when deposited on the gold electrode. Moreover, the wettability of the functionalized surface and the morphological changes of pentacene films grown on SAMs were investigated by contact angle and atomic force microscopy, respectively. OTFT has been used as organic gauge for investigating the metal-SAM-organic semiconductor structure. Charge carriers mobility, threshold voltage, contact resistance were measured in both air and vacuum to assess the influence of the anchoring groups and the terminal rings to the transistor performance. Although these SAMs do not show an improvement of mobility due to an increase of contact resistance, they allow a better modulation of the current flowing across the electrode-organic semiconductor (OS) interface, pointing out the structural differences between the three SAMs in terms of resistance drop combined with the critical voltage

The emergence of multifrequency force microscopy

Atomic force microscopy uses the deflection of a cantilever with a sharp tip to examine surfaces, and conventional dynamic force microscopy involves the excitation and detection of a single frequency component of the tip’s motion. Information about the properties of a sample is, however, encoded in the motion of the probe and the dynamics of the cantilever are highly nonlinear. Therefore, information included in the other frequency components is irreversibly lost. Multifrequency force microscopy involves the excitation and/or detection of several frequencies of the probe’s oscillation, and has the potential to overcome limitations in spatial resolution and acquisition times of conventional force microscopes. It could also provide new applications in fields such as energy storage and nanomedicine. Here we review the development of multifrequency force microscopy methods, highlighting the five most prominent approaches. We also examine the range of applications offered by the technique, which include mapping the flexibility of proteins, imaging the mechanical vibrations of carbonbased resonators, mapping ion diffusion, and imaging the subsurface of cells.We are grateful for financial support from the Ministerio de Ciencia e Innovación (CSD2010-00024, MAT2009-08650).Peer reviewe