Re: Signal Simulator Update V1 7 7-PLAZA
Anaias Bunz
Game inspired by SETI. Take the role of a scientist to find an extraterrestrial signal .Control massive Radio Antennas by using interactive control in your Observatory. Detect , download and decode unknown or story telling signals. Manage and Maintain an electrical system to improve your systems and make it more efficient.
A list of audible signals divided by city is below. Each row has a link to Google Street View to explore the intersection virtually. You can search for a road or city name, or look at the entire list below.
IMAC is a conference and exposition focusing on structural dynamics and has evolved to encompass the latest technologies supporting structural dynamics. This broad focus on structural dynamics includes topics in simulation and modeling, nonlinear dynamics, sensors, signal processing and control spanning the full range of engineering disciplines.
IMAC remains a friendly conference where exhibitors, presenters and attendees spend several days exchanging the ideas that fuel the coming year.
(A) A schematic diagram illustrating the advantage of material-based optical stimulation tools for the study of transient bacterial signaling. Existing tools are only suitable for the study of prolonged and large-scale bacterial communications, e.g., quorum sensing and K+ signaling, due to their induction of slow or global changes in a microbial environment. Optical modulation techniques, using nongenetic transducers, can introduce local, transient, and physical perturbations to the microbial community. These new platforms have the potential to uncover transient microbial signaling. (B) Schematic illustrating the utility of interfacing biological systems with functional materials. Such biointerface not only allows the probing of new biological behaviors but also creates new opportunities to form dynamic hybrid living matters. (C) SEM image of a mesostructured Si nanowire (left) synthesized via chemical vapor deposition (CVD) and subsequent defect-selective wet etching. Pseudocolored SEM image (right) showing that the nanowire (purple) scale is similar to that of a bacterial cell (green). The rough surface topography of the nanowire can be well anchored by the bacteria pili. Scale bars, 0.5 μm. (D) SEM image (left) of 2D Si discs (2-μm thickness) made from top-down fabrications. Overlaid confocal microscope image (right) showing an Si disc (blue) on the top of a B. subtilis biofilm (green) after 1 day of coculture. Bacteria were stained with LIVE/DEAD bacterial viability kit. Scale bars, 10 μm (left) and 5 μm (right).
For interfaces with quasi-2D biofilms (fig. S4), we selected Si microplates (Fig. 1D). Using top-down microfabrication on silicon-on-insulator (SOI) wafers, we built a broad spectrum of Si microplates that were 2 μm in thickness, with defined shapes (e.g., circles, squares, triangles, and crescents) (fig. S5). These geometry variations with deterministic properties are essential to mechanistic studies of biofilm signaling. Biofilms cultured over Si microplates were healthy and continuous (Fig. 1D). To manipulate the macroscopic activities of biofilms, we constructed centimeter-scale Si meshes (fig. S6). With the open network design, the mesh can conform to the surface of a mature biofilm and integrate seamlessly with individual cells following coculture (fig. S6).
Beyond dimension-matched interfaces (19), Si materials need to effectively transduce light energy into localized signals that cells can respond to, especially given that no genetic modification is used here to enable light sensitivity in bacteria. We used a previously described patch-clamp setup (22) to assess the photoresponses of different Si structures (fig. S7). Representative current dynamics (Fig. 2A) recorded from a mesostructured Si nanowire showed that it generated a 4.1-K increase in the local temperature (pipette tip 5 μm above the nanowire center) from a 1-ms laser pulse with negligible photoelectrochemical responses (Fig. 2A and fig. S7). In contrast, a smooth nanowire can only heat up the surrounding medium by 1.1 K (fig. S7). Nanowires with different roughness have quite narrow temperature distributions, suggesting a good uniformity of the materials (fig. S8). Consistent with previous studies on mesoporous Si (17, 30), the hierarchical cavities in the mesostructured nanowire likely contribute to enhanced light absorption, reduced thermal conductivity, and reduced heat capacity of Si. According to the Fourier thermal conduction equation, these trends will lead to its enhanced photothermal response in the mesostructured nanowire, which was also confirmed by finite element simulation (fig. S9).
(A) Experimental setup for the photoresponse measurement of Si nanowire with representative traces of local temperature (upper) and photocurrent (lower) dynamics of a mesostructured Si nanowire in response to laser illumination (532 nm, 5-μm spot size, 60.1 mW for 1 ms). Green-shaded area highlights the laser illumination period. (B) Bacterial cells from the suspension are repeatedly attracted onto the Si nanowire upon light stimulation. Red, E. coli expressing eforRed; yellow, Si nanowire scattering. Scale bars, 5 μm. (C) FEA simulation of convective water flow velocity distribution with the speed (map) and the directions (arrows) near the laser illumination spot on the Si nanowire; white dot represents Si nanowire (cross section). (D) Confocal microscope images of light-induced Ca2+ elevation in a B. subtilis biofilm before (left) and after (right) stimulation (592 nm, 22.3 mW, 1 ms). Green, Ca2+ fluorescence; yellow, nanowire scattering. Scale bars, 10 μm. (E) Ca2+ wave propagation after laser stimulation. Left: Contour plot showing the propagation of the Ca2+ wave front over time. (0, 0) coordinate denotes the laser illumination spot. Right: Radial average Ca2+ propagation profile showing activation up to 26.3 μm from the center with a 7.63-s time delay. Error bars denote SDs. (F) Ca2+ fluorescence intensity along the radial direction shows only slight signal decay within the propagation range. (G) Color-coded map showing the jumping activation of non-neighboring cells. Ca2+ signaling was initiated from the laser spot (back arrow, at t = 2.5 s) and then propagated to adjacent bacterial cells (up to t = 7.5 s). The color code indicates the time scale. Gray cells did not show fluorescence intensity change after the stimulation. Scale bar, 20 μm. (H) Statistical analysis of the Ca2+ propagation distances using different inhibitors. n = 5 for control, n = 6 for verapamil, n = 4 for amiloride, n = 6 for La3+, and n = 4 for suramin. Error bars denote SDs.
Given the critical role of calcium ions (Ca2+) as a secondary messenger in key physiological responses of the mammalian system cell physiology (e.g., proliferation, differentiation, and survival) (35) and the recent discovery of induced Ca2+ signal propagation in plants (36), we stained planktonic B. subtilis cells with a Ca2+ indicator Fluo-4 acetyloxymethyl ester (Fluo-4 AM) and illuminated a nanowire with a laser pulse (592 nm, 8.28 mW, 500-nm spot size, 1 ms). Immediately following the cell trapping onto the nanowire, the intracellular Ca2+ fluorescence intensity was raised (fig. S16), suggesting a possibility of induced Ca2+ signaling in bacterial community.
(A) Schematic illumination of Ca2+ signaling propagation mechanism stimulated by Si microplates. Si microplates with different sizes and various shapes were designed to investigate the stimulation mechanism. Absolute temperature (ΔT), temporal gradient of temperature (dT/dt), and spatial gradient of temperature (dT/dr) are three possible factors. (B) Confocal microscope time series showing the evolution of Ca2+ distribution over time. Upon light illumination at the center of the disc, cells near the disc edges first experienced intracellular elevations followed by bidirectional circular propagation toward the disc centroid and the rest of biofilm outside the disc. The laser (592 nm, 32.2 mW) was on for 1 ms right before the time point of 2.63 s. Scale bars, 30 μm. (C) Quantitative analysis of the fluorescence intensity of Ca2+ over time showing the immediate Ca2+ activation near the disc edge and a delayed onset near the disc center. The initial dip of the fluorescence intensity near the center is likely due to photobleaching by the stimulation laser. (D) FEA simulation (unfilled circles) and patch-clamp recording (filled circles) show an inverse relationship between the disc size and the photothermal effect. Numerical fitting of the simulated data points is plotted. (E) Minimal power required to evoke the Ca2+ signaling in biofilm gradually increases with larger discs. (F) Ca2+ propagation distances outside the discs are almost identical in all cases using the minimal powers required to elicit Ca2+ signaling. (G) Recorded final Ca2+ distribution patterns and simulated spatial gradient of temperature right after stimulation correlate well with each other for Si microplates of different sizes and geometries. Scale bars, 20 μm.
Furthermore, the dT/dr profile correlated highly with the static Ca2+ distribution, which could possibly explain the observed size-dependent Ca2+ patterns (fig. S26). For example, in a large-sized Si disc, temperature will first undergo an exponential decay from the heat source (i.e., the center of the disc under illumination) to the edge, followed by another substantial temperature drop at the Si/medium interface due to the large interfacial thermal resistance and the poor thermal conductivity of water. As a result, a bimodal time-dependent dT/dr distribution can be perceived, which is similar to the static Ca2+ pattern (fig. S26). In a smaller Si disc, however, heat is more uniformly confined within the disc such that only one major dT/dr peak is expected at the edge of the disc (fig. S26). In both scenarios, the dT/dr profiles are more or less the same in the regions outside the discs, consistent with the observation that maximum Ca2+ propagation to the rest of the biofilm (fig. S26) always stayed at the similar level (i.e., 6 μm from the disc edge under the current illumination condition) (Fig. 3F). This thermal gradient sensing is reminiscent of results from previous studies in which bacteria responded to the chemical gradient rather than the absolute chemical concentration (38), although the response time was quite different, i.e., milliseconds in our observation versus seconds in previous studies. To further support our model of dT/dr-dependent Ca2+ signaling, we conducted additional FEA and Ca2+ imaging using Si with a variety of shapes, e.g., triangle, square, and crescent, which consistently yielded good agreements between the simulated patterns and the experimental observations (Fig. 3G and fig. S30).
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