Acoustofluidics along inclined surfaces based on AlN/Si Rayleigh surface acoustic waves

Conventional acoustofluidics are restricted to manipulation of droplets on a flat surface, and there is an increasing demand for acoustofluidic devices to be performed at inclined surfaces to facilitate multilayered microfluidic device design and enhance system compactness. This paper reports theoretical and experimental studies of acoustofluidic behaviors (including transportation/pumping and jetting) along inclined surfaces using AlN/Si Rayleigh surface acoustic waves (SAWs). It has been demonstrated that for droplets with volume smaller than 3 μL, they could be efficiently transported on arbitrary inclined surfaces. The gravity effect would play a more and more important role in uphill climbing with the increased inclination angle. When the inclination angle was increased up to 90°, a higher threshold power was needed to transport the droplet and the maximum droplet volume which can be pumped also reached its minimum value. Effects of surface inclination angle on droplet jetting angles could be neglected for their volumes less than 2 μL. Moreover, microfluidic and acoustic heating performances of AlN/Si SAWs were further studied and compared with those conventional ZnO/Si SAWs with the same electrode configurations

Bacterial endosymbiont Cardinium cSfur genome sequence provides insights for understanding the symbiotic relationship in Sogatella furcifera host

Background: Sogatella furcifera is a migratory pest that damages rice plants and causes severe economic losses. Due to its ability to annually migrate long distances, S.furcifera has emerged as a major pest of rice in several Asian countries. Symbiotic relationships of inherited bacteria with terrestrial arthropods have significant implications. The genus Cardinium is present in many types of arthropods, where it influences some host characteristics. We present a report of a newly # identified strain of the bacterial endosymbiont Cardinium cSfur in S. furcifera. Result: From the whole genome of S. furcifera previously sequenced by our laboratory, we assembled the whole genome sequence of Cardinium cSfur. The sequence comprised 1,103,593 bp with a GC content of 39.2%. The phylogenetic tree of the Bacteroides phylum to which Cardinium cSfur belongs suggests that Cardinium cSfur is closely related to the other strains (Cardinium cBtQ1 and cEper1) that are members of the Amoebophilaceae family. Genome comparison between the host-dependent endosymbiont including Cardinium cSfur and freeliving bacteria revealed that the endosymbiont has a smaller genome size and lower GC content, and has lost some genes related to metabolism because of its special environment, which is similar to the genome pattern observed in other insect symbionts. Cardinium cSfur has limited metabolic capability, which makes it less contributive to metabolic and biosynthetic processes in its host. From our findings, we inferred that, to compensate for its limited metabolic capability, Cardinium cSfur harbors a relatively high proportion of transport proteins, which might act as the hub between it and its host. With its acquisition of the whole operon related to biotin synthesis and glycolysis related genes through HGT event, Cardinium cSfur seems to be undergoing changes while establishing a symbiotic relationship with its host. Conclusion: A novel bacterial endosymbiont strain (Cardinium cSfur) has been discovered. A genomic analysis of the endosymbiont in S. furcifera suggests that its genome has undergone certain changes to facilitate its settlement in the host. The envisaged potential reproduction manipulative ability of the new endosymbiont strain in its S. furcifera host has vital implications in designing eco-friendly approaches to combat the insect pest

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Variability of the phytoplankton biomass in the southwestern Bay of Bengal from 2003 to 2018

The Bay of Bengal (BoB) has distinctive hydrological characteristics, and various physical mechanisms strongly influence the growth of phytoplankton in this region. In this work, we investigated the monthly and interannual variations of phytoplankton biomass (PB) in the southwestern (SW) BoB (78–88°E, 0–15°N) utilizing satellite data from 2003 to 2018. Bivariate wavelet coherence (BWC) and multiple wavelet coherence (MWC) analyses were conducted to assess the temporal fluctuations in various physical oceanographic parameters. The findings revealed that wind speed (WSP) and sea surface temperature (SST) were the main drivers for the monthly variations of chlorophyll-a (Chl-a). The southwest monsoon promoted the formation of upwelling by offshore Ekman transport via the southwest monsoon current (SMC) and the upward Ekman pumping induced by the strong positive wind stress curl, which brought nutrient-rich, cold waters from the subsurface to the surface, stimulating phytoplankton growth. The BWC analysis results identified WSP as the most effective individual factor accounting for the interannual fluctuations in Chl-a concentrations. The MWC analysis results unraveled that the combinations of WSP–SST, WSP–Niño 3.4, WSP–EPV, and WSP–DMI exhibited the strongest relationships with the changes in Chl-a in the SW BoB. The PB in 2015 demonstrated abnormally low values. The El Niño event in 2015 substantially weakened the southwest monsoon and current, possibly weakening the Ekman transport on the southern coast of Sri Lanka and India. Moreover, an abnormally intensified anticyclonic eddy occurred in this region. These processes disrupted the vertical exchange of nutrients, obstructing the vertical transport of nutrient-enriched subsurface waters and leading to abnormally decreased levels of Chl-a in 2015

Discrete-Time Noise-Suppression Neural Dynamics for Optical Remote Sensing Image Extraction

Optical remote sensing is an important method of observing objects over large areas. Naturally, it is essential to extract the target from optical remote sensing images. Most existing methods, such as thresholding methods and texture analysis-based methods, have some limitations. Additionally, most methods are generally not robust to noise, which tends to affect extraction results to some extent. Thus, how to extract the target object from optical remote sensing images conveniently and robustly is a challenge. To make up for the shortcomings of most methods, a constrained energy minimization (CEM) scheme is applied to extract the target object. Then, a discrete-time noise-suppression neural dynamics (DTNSND) model with an error-accumulation term is proposed to aid the CEM scheme for extracting the target object, which restrains the effects of noises in the extraction process. Theoretical analyses demonstrate that the DTNSND model suppresses noise in diverse noisy environments. Furthermore, numerical simulations are provided to illustrate that the maximal steady-state residual error generated by the DTNSND model is markedly lower than those of comparative algorithms. Finally, extraction experiments, using an optical remote sensing image of the Arctic sea ice as an experimental material, are executed in zero noise and random noise environments, respectively. Comparative results confirm that the DTNSND model is able to extract the remote sensing image stably and accurately in noisy environments, further demonstrating the feasibility of the DTNSND model in practice