Light modulation of electric field driven semiconductor micromotors

The future micro/nanorobots require high degrees of freedom in motion control to perform complex tasks by individuals or by a swarm. It remains a great challenge to control the motions of an individual nanomachine amidst many, to switch the operation modes facilely, and it is even more difficult to actuate several components of a nanomachine coordinately for purposed actions. This high degree of versatility is essential for the future micro/nanorobots and requires investigation of innovative actuation mechanisms. In this dissertation, we report our recent finding about a new approach combining two types of stimulation to achieve such goal. The micromotors being studied are made of semiconductor silicon nanowires. Mechanical motion of the motors is driven by several types of AC electric field. Meanwhile, the electrical property of the nanowires can be locally and instantaneously modulated by visible light illumination in a reversible manner. We demonstrate that visible light is able to change the electric polarization of semiconductor nanowires under AC electric field, and reflected by the dramatic change of mechanical motions with very rich configurations. Under a rotating electric field, the rotation speed of semiconductor Si nanowires in electric fields can instantly increase, decrease, and even reverse the orientation by light illumination in the visible to infrared regime at various AC E-field frequencies. Under a linear AC electric field, instantaneous change of alignment direction and speed of semiconductor nanowires is observed under visible-light exposure. With theoretical analysis and simulation, the working principle can be attributed to the optically tuned imaginary-part (out-phase) and real-part (in-phase) electrical polarization of a semiconductor nanowire in aqueous suspension. Based on the understanding of this system, we further propose a new approach to control the semiconductor micromotor via light tunable dielectrophoresis. Localized control of collective behavior in a highly density silicon nanowire suspension is also investigated. Finally, we demonstrated how to utilize the mechanical motion at microscale for practical application of biosensing.Materials Science and Engineerin

Karyotype Analysis of Diploid and Spontaneously Occurring Tetraploid Blood Orange [Citrus sinensis (L.) Osbeck] Using Multicolor FISH With Repetitive DNA Sequences as Probes

Blood orange [Citrus sinensis (L.) Osbeck] has been increasingly appreciated by consumers worldwide owing to its brilliant red color, abundant anthocyanin and other health-promoting compounds. However, there is still relatively little known about its cytogenetic characteristics, probably because of the small size and similar morphology of metaphase chromosomes and the paucity of chromosomal landmarks. In our previous study, a naturally occurring tetraploid blood orange plant was obtained via seedling screening. Before this tetraploid germplasm can be manipulated into a citrus triploid seedless breeding program, it is of great importance to determine its chromosome characterization and composition. In the present study, an integrated karyotype of blood orange was constructed using sequential multicolor fluorescence in situ hybridization (FISH) with four satellite repeats, two ribosomal DNAs (rDNAs), a centromere-like repeat and an oligonucleotide of telomere repeat (TTTAGGG)3 as probes. Satellite repeats were preferentially located at the terminal regions of the chromosomes of blood orange. Individual somatic chromosome pairs of blood orange were unambiguously identified by repetitive DNA-based multicolor FISH. These probes proved to be effective chromosomal landmarks. The karyotype was formulated as 2n = 2x = 18 = 16m+2sm (1sat) with the karyotype asymmetry degree belonging to 2B. The chromosomal distribution pattern of these repetitive DNAs in this spontaneously occurring tetraploid was identical to that of the diploid, but the tetraploid carried twice the number of hybridization sites as the diploid, indicating a possible pathway involving the spontaneous duplication of chromosome sets in nucellar cells. Our work may facilitate the molecular cytogenetic study of blood orange and provide chromosomal characterization for the future utilization of this tetraploid germplasm in the service of seedless breeding programs

Laziness, barren plateau, and noises in machine learning

We define laziness to describe a large suppression of variational parameter updates for neural networks, classical or quantum. In the quantum case, the suppression is exponential in the number of qubits for randomized variational quantum circuits. We discuss the difference between laziness and barren plateau in quantum machine learning created by quantum physicists in McClean et al (2018 Nat. Commun.9 1–6) for the flatness of the loss function landscape during gradient descent. We address a novel theoretical understanding of those two phenomena in light of the theory of neural tangent kernels. For noiseless quantum circuits, without the measurement noise, the loss function landscape is complicated in the overparametrized regime with a large number of trainable variational angles. Instead, around a random starting point in optimization, there are large numbers of local minima that are good enough and could minimize the mean square loss function, where we still have quantum laziness, but we do not have barren plateaus. However, the complicated landscape is not visible within a limited number of iterations, and low precision in quantum control and quantum sensing. Moreover, we look at the effect of noises during optimization by assuming intuitive noise models, and show that variational quantum algorithms are noise-resilient in the overparametrization regime. Our work precisely reformulates the quantum barren plateau statement towards a precision statement and justifies the statement in certain noise models, injects new hope toward near-term variational quantum algorithms, and provides theoretical connections toward classical machine learning. Our paper provides conceptual perspectives about quantum barren plateaus, together with discussions about the gradient descent dynamics in Liu et al (2023 Phys. Rev. Lett.130 150601)

Portable Bulk-Water Disinfection by Live Capture of Bacteria with Divergently Branched Porous Graphite in Electric Fields

An easy access to clean water pivots function and development of a modern society. However, it remains arduous to develop energy-efficient, facile, and portable water treatment systems for point-of-use (POU) applications, which is particularly imperative for the safety and resilience of a society during extreme weathers and critical events. Here, we report an innovative working scheme and device prototype for water disinfection via directly capturing and removing pathogen cells from bulk water using strategically designed three-dimensional (3D) porous dendritic graphite foams (PDGF) in an AC field. The prototype, integrated in a 3D-printed portable water-purification module, can reproducibly remove 99.997 % E-coli bacteria in bulk water at only a few voltages with among the lowest energy consumption of 435.5 J·L-1. The unique PDGF foams, costing at only $1.42 per piece, can robustly operate for at least 20 times without functional degradation. Furthermore, we successfully unveil the unique disinfection mechanism with one-dimensional Brownian dynamics simulation. Finally, the system is applied and practically brings natural water in the Waller Creek at UT Austin to the safe drinking level. This research, including the innovative working mechanism based on dendritically porous graphite and the design scheme, could inspire a new device paradigm for POU water treatment

Molecular cytogenetic analysis of genome-specific repetitive elements in Citrus clementina Hort. Ex Tan. and its taxonomic implications

Abstract Background Clementine mandarin (Citrus clementina Hort. ex Tan.) is one of the most famous and widely grown citrus cultivars worldwide. Variations in relation to the composition and distribution of repetitive DNA sequences that dominate greatly in eukaryote genomes are considered to be species-, genome-, or even chromosome-specific. Repetitive DNA-based fluorescence in situ hybridization (FISH) is a powerful tool for molecular cytogenetic study. However, to date few studies have involved in the repetitive elements and cytogenetic karyotype of Clementine. Results A graph-based similarity sequence read clustering methodology was performed to analyze the repetitive DNA families in the Clementine genome. The bioinformatics analysis showed that repetitive DNAs constitute 41.95% of the Clementine genome, and the majority of repetitive elements are retrotransposons and satellite DNAs. Sequential multicolor FISH using a probe mix that contained CL17, four satellite DNAs, two rDNAs and an oligonucleotide of (TTTAGGG)3 was performed with Clementine somatic metaphase chromosomes. An integrated karyotype of Clementine was established based on unequivocal and reproducible chromosome discriminations. The distribution patterns of these probes in several Citrus, Poncirus and Fortunella species were summarized through extensive FISH analyses. Polymorphism and heterozygosity were commonly observed in the three genera. Some asymmetrical FISH loci in Clementine were in agreement with its hybrid origin. Conclusions The composition and abundance of repetitive elements in the Clementine genome were reanalyzed. Multicolor FISH-based karyotyping provided direct visual proof of the heterozygous nature of Clementine chromosomes with conspicuous asymmetrical FISH hybridization signals. We detected some similar and variable distribution patterns of repetitive DNAs in Citrus, Poncirus, and Fortunella, which revealed notable conservation among these genera, as well as obvious polymorphism and heterozygosity, indicating the potential utility of these repetitive element markers for the study of taxonomic, phylogenetic and evolutionary relationships in the future

Biobased High-Performance Rotary Micromotors for Individually Reconfigurable Micromachine Arrays and Microfluidic Applications

In this work, we report an innovative type of rotary biomicromachines by using diatom frustules as integrated active components, including the assembling, operation, and performance characterization. We further investigate and demonstrate unique applications of the biomicromachines in achieving individually reconfigurable micromachine arrays and microfluidic mixing. Diatom frustules are porous cell walls of diatoms made of silica. We assembled rotary micromachines consisting of diatom frustules serving as rotors and patterned magnets serving as bearings in electric fields. Ordered arrays of micromotors can be integrated and rotated with controlled orientation and a speed up to ∼3000 rpm, one of the highest rotational speeds in biomaterial-based rotary micromachines. Moreover, by exploiting the distinct electromechanical properties of diatom frustules and metallic nanowires, we realized the first reconfigurable rotary micro/nanomachine arrays with controllability in individual motors. Finally, the diatom micromachines are successfully integrated in microfluidic channels and operated as mixers. This work demonstrated the high-performance rotary micromachines by using bioinspired diatom frustules and their applications, which are essential for low-cost bio-microelectromechanical system/nanoelectromechanical system (bio-MEMS/NEMS) devices and relevant to microfluidics

Development of SARS-CoV-2 Isothermal Amplification Detection Kits

The SARS-CoV-2 isothermal amplification detection kits based on loop-mediated isothermal amplification (LAMP) were developed and evaluated on three types samples of SARS-CoV-2. The kits included enzyme reaction mixtures and chromogenic agents. After the isothermal amplification reactions were completed, the reaction results were judged by using the chromogenic agents to determine whether SARS-CoV-2 exists in the samples to be tested. The detection kits have the advantages of convenient operation, fast detection speed and high sensitivity up to 1 copy of virus particles per reaction, which can speed up the detection speed of suspected cases, and avoid the missing detection problems caused by the low detection sensitivity

Designing a Novel Nano-Vaccine against SARS-CoV-2

The new coronavirus SARS-CoV-2 has become a global pandemic, which has had a huge impact on the lives of people around the world and has caused huge impacts and losses on global economic development. To now, there is still no effective drug or therapy against coronavirus. A large number of studies have shown that vaccines are the ultimate weapon to eliminate major infectious diseases. The development of new vaccines against new coronaviruses is the best way to prevent new coronavirus infections. In this study, we developed a new vaccine against the new coronavirus by combining our self-developed nano adjuvant loaded with carnosine graphene oxide adjuvant with loaded with CpG molecule and RBD protein antigen. Our results showed that this vaccine can produce high titer anti-SARS-CoV-2 RBD antibody neutralizing SARS-CoV-2 in mice within 2 weeks