Low-Cost UAV Swarm for Real-Time Object Detection Applications

With unmanned aerial vehicles (UAVs), also known as drones, becoming readily available and affordable, applications for these devices have grown immensely. One type of application is the use of drones to fly over large areas and detect desired entities. For example, a swarm of drones could detect marine creatures near the surface of the ocean and provide users the location and type of animal found. However, even with the reduction in cost of drone technology, such applications result costly due to the use of custom hardware with built-in advanced capabilities. Therefore, the focus of this thesis is to compile an easily customizable, low-cost drone design with the necessary hardware for autonomous behavior, swarm coordination, and on-board object detection capabilities. Additionally, this thesis outlines the necessary network architecture to handle the interconnection and bandwidth requirements of the drone swarm. The drone on-board system uses a PixHawk 4 flight controller to handle flight mechanics, a Raspberry Pi 4 as a companion computer for general-purpose computing power, and a NVIDIA Jetson Nano Developer Kit to perform object detection in real-time. The implemented network follows the 802.11s standard for multi-hop communications with the HWMP routing protocol. This topology allows drones to forward packets through the network, significantly extending the flight range of the swarm. Our experiments show that the selected hardware and implemented network can provide direct point-to-point communications at a range of up to 1000 feet, with extended range possible through message forwarding. The network also provides sufficient bandwidth for bandwidth intensive data such as live video streams. With an expected flight time of about 17 minutes, the proposed design offers a low-cost drone swarm solution for mid-range aerial surveillance applications

Blastocystis Isolates from Patients with Irritable Bowel Syndrome and from Asymptomatic Carriers Exhibit Similar Parasitological Loads, but Significantly Different Generation Times and Genetic Variability across Multiple Subtypes.

Blastocystis spp is a common intestinal parasite of humans and animals that has been associated to the etiology of irritable bowel syndrome (IBS); however, some studies have not found this association. Furthermore, many biological features of Blastocystis are little known. The objective of present study was to assess the generation times of Blastocystis cultures, from IBS patients and from asymptomatic carriers. A total of 100 isolates were obtained from 50 IBS patients and from 50 asymptomatic carriers. Up to 50 mg of feces from each participant were cultured in Barret's and in Pavlova's media during 48 h. Initial and final parasitological load were measured by microscopy and by quantitative PCR. Amplicons were purified, sequenced and submitted to GenBank; sequences were analysed for genetic diversity and a Bayesian inference allowed identifying genetic subtypes (ST). Generation times for Blastocystis isolates in both media, based on microscopic measures and molecular assays, were calculated. The clinical symptoms of IBS patients and distribution of Blastocystis ST 1, 2 and 3 in both groups was comparable to previous reports. Interestingly, the group of cases showed scarce mean nucleotide diversity (π) as compared to the control group (0.011±0.016 and 0.118±0.177, respectively), whilst high gene flow and small genetic differentiation indexes between different ST were found. Besides, Tajima's D test showed negative values for ST1-ST3. No statistical differences regarding parasitological load between cases and controls in both media, as searched by microscopy and by qPCR, were detected except that parasites grew faster in Barret's than in Pavlova's medium. Interestingly, slow growth of isolates recovered from cases in comparison to those of controls was observed (p<0.05). We propose that generation times of Blastocystis might be easily affected by intestinal environmental changes due to IBS probably because virulent strains with slow growth may be selected, reducing their genetic variability

Population genetic indexes between different <i>Blastocystis</i> ST sequences.

<p>^a95%CI, 95% Confidence interval.</p><p>Population genetic indexes between different <i>Blastocystis</i> ST sequences.</p

Parasitological loads estimated at the beginning of the study between cases and controls.

<p>Plots drew with all sample data according to the number of <i>Blastocystis</i> organisms/mg feces by microscopy (A) and number of <i>Blastocystis</i> DNA copies/mg feces by qPCR (B). The black bars mean the average in each group.</p

Generation times data in Blastocystis by qPCR and by microscopy

<p>Generation time (Tg) data of Blastocystis cultures in Barret’s and in Pavlova’s media during 48 h., from IBS patients and from asymptomatic carriers, measured by microscopy and by quantitative PCR are shown in present table. The generation times of Blastocystis isolates, were calculated according to Zhang et al. [17], with the following equation: Tg=(T2-T1)/(log2(n2/n1)), where Tg denotes the generation time, n1 represents the number of cultured parasitic organisms at the initial time (T1), and n2 represents the number of parasitic cells at subsequent time (T2). Thus, (T2-T1) = 48 hours of in vitro culture. Besides, for to absolute quantification by qPCR, it was necessary to consider i) the size of the Blastocystis genome ~ 18.8Mbp[36]; ii) 1pg of DNA ~ 978Mbp[37] and iii) the concentration of DNA control was 160ng/µL; thus, by cross multiplications, the number of copies of the genetic marker amplified were estimated.</p> <p> </p

Generation time (<i>T</i>_<i>g</i>) values of <i>Blastocystis</i> isolates between case and control groups.

<p>Average and standard deviation of <i>T</i>_{<b><i>g</i></b>} in Barret’s and Pavlova media, based on microscopic measures and qPCR assays.</p

Characteristics of the carriers and of <i>Blastocystis</i> ST identified in IBS patients and in the control group.

<p>^a<i>p</i> = 0.043,</p><p>OR(95%IC) = 0.43(0.17–1.06).</p><p>Characteristics of the carriers and of <i>Blastocystis</i> ST identified in IBS patients and in the control group.</p

Phylogenetic inference of <i>Blastocystis</i> spp.

<p>Bayesian phylogenetic tree using a fragment of SSUrDNA sequences; the values of the nodes indicate posterior probabilities values using 10 million generations. GenBank accession numbers are included, as well as if correspond to a case or a control; each ST clade is shown in different branch colors.</p