A rabbit shaped bidirectional linear ultrasonic motor driven by single-phase signal.

A rabbit shaped block, single-phase, linear, ultrasonic motor is proposed. The motor is 17.7 × 9.1 × 6 mm3 in size, and the overall mass is 2.3 g. The motor is designed by referring to the rabbit running mode and the principle of a Langevin vibrator concentrator. It can realize bidirectional driving without changing the constraint position. First, the basic structure of the motor is introduced, and the working principle of the motor is discussed. Then, the motion trajectory and driving force of the motor driving foot are theoretically deduced and simulated, and the simulation results are verified by the modal impedance characteristic test. Finally, the mechanical characteristics of the motor prototype are tested. The results show that under the excitation voltage of 5 N preload and 200 Vpp, the motor is driven to the right in B1 mode, the no-load speed is 42.3 mm/s, the maximum driving force is 0.28 N, and the stall torque is 0.27 Nm. Correspondingly, the motor is driven in reverse in B2 mode, the no-load speed is 118 mm/s, the maximum driving force is 1.48 N, and the stall torque is 1.41 Nm.

Grid-Scale Impact of Climate Change and Human Influence on Soil Erosion within East African Highlands (Kagera Basin).

Under global climate change and pressure from human activities, soil erosion is becoming a major concern in the quest for regional sustainable development in the Kagera basin (KB). However, few studies in this region have comprehensively considered the impact of climate change and human influence on soil erosion, and the associated processes are unclear. Based on the premise of quantifying climate change, human influence, and soil erosion, this study undertook a neighborhood analysis as the theoretical support, for a grey relation analysis which was conducted to realize the qualitative assessment of the influence of climate change and human activities on soil erosion. The results show that 90.32% of the KB saw climate change as having a greater influence on soil erosion than human influence, with the remaining area 9.68% seeing human influence having a greater impact than climate change, mainly as a result of the effect of rangeland and farmland. The average soil erosion rate of the KB shows a very low level (10.54 t ha-1 yr-1), with rangeland and farmland being the main land use/land cover (LULC) types that see soil loss, followed by forest, wetland, and built-up areas. The climate change trends of the KB show the most dramatic changes in the northeast and southwest, gradually decreasing towards the line crossing from the Birunga National Park (Rwanda) to the Keza district (Tanzania). The human influence intensity (HII) shows a high level in the KB (21.93), where it is higher in the west and lower in the east of the basin.

RPL21 siRNA Blocks Proliferation in Pancreatic Cancer Cells by Inhibiting DNA Replication and Inducing G1 Arrest and Apoptosis.

BACKGROUND: Our previous study showed that the ribosomal protein L21 (RPL21) may play an important role in the development and survival of pancreatic cancer. In this article, RNA interference (RNAi) experiments were performed with RPL21-specific small interfering RNA (siRNA) to elucidate the mechanism by which RPL21 controls PC PANC-1 and BxPC-3 cell proliferation. METHODS: In the present study, PANC-1, BxPC-3 cells, and BALB/c nude mice were used to investigate antitumor effect and mechanism by which RPL21 controls cell proliferation and apoptosis in vitro and in vivo. The effects of RPL21 knockdown on PANC-1 and BxPC-3 cell proliferation, cell cycle and cell apoptosis in vitro were determined using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assays and flow cytometry assay. The mechanism of RPL21 regulating cell proliferation was investigated using transcriptome sequencing analysis and luciferase reporter assay. The effects of RPL21 knockdown on PANC-1 and BxPC-3 cell proliferation in vivo were determined using BALB/c nude mice tumor model. RESULTS: In PANC-1 and BxPC-3 cells, the knockdown of RPL21 expression with corresponding siRNA suppressed cell proliferation in vitro and in vivo, inhibited DNA replication, and induced arrests in the G1 phase of the cell cycle. Further results showed that the mini-chromosome maintenance (MCM) protein family (MCM2-7), CCND1 and CCNE1 were down-regulated significantly in PANC-1 and BxPC-3 cells after transfected with RPL21 siRNA, which suggests that the suppression of DNA replication is due to the reduced expression of MCM2-7 family, and the induction of G1 arrest is correlated with the inhibition of CCND1 and CCNE1. Luciferase reporter assay showed that RPL21 controls the DNA replication and G1-S phase progression possibly through the regulation of E2F1 transcription factor in PC cells. Moreover, RPL21 siRNA showed an apoptosis-inducing effect only in BxPC-3 and PANC-1 cells but not in normal HPDE6-C7 cells. The increase of caspase-8 activities and the loss of mitochondrial membrane potential after RPL21 silencing indicates that the RPL21 gene may be involved in caspase-8-related mitochondrial apoptosis. CONCLUSION: Our findings suggest that siRNA against the RPL21 gene possesses a potential anti-cancer activity for PC cells by inhibiting their proliferation and DNA replication, as well as inducing cell cycle G1 arrest and cell apoptosis.

A novel high thrust-weight ratio linear ultrasonic motor driven by single-phase signal.

This paper presents an ultrasonic motor with a high thrust-weight ratio. The miniaturized motor is 13 mm × 5 mm × 3.8 mm in size and uses the first-order bending vibration mode (B1 mode) and second-order bending vibration mode (B2 mode) to realize bidirectional movement through a single-phase driving signal. The theoretical trajectory and output thrust of the motor driving foot are initially studied. Subsequently, a finite-element model of the motor is established, and its dynamic performance is studied. Next, the prototype of the motor is fabricated and tested. The results show that errors in the B1 and B2 modes are 1.976% and 0.436%, respectively. Finally, an experimental setup is constructed to test the mechanical properties of the motor. The maximum output velocities of the motor is approximately 158 mm/s at 58.917 kHz in the B1 mode and approximately 137 mm/s at 113.581 kHz in the B2 mode. The maximum thrust force values of the motor in the B1 and B2 modes are approximately 1.32 N and 1.08 N, respectively, with 7 N preload and 120 Vpp voltage. The overall mass of the motor stator is 1.0 g, so the motor thrust-weight ratio reaches 134.69.

An Equivalent Circuit of Longitudinal Vibration for a Piezoelectric Structure with Losses.

Equivalent circuits of piezoelectric structures such as bimorphs and unimorphs conventionally focus on the bending vibration modes. However, the longitudinal vibration modes are rarely considered even though they also play a remarkable role in piezoelectric devices. Losses, especially elastic loss in the metal substrate, are also generally neglected, which leads to discrepancies compared with experiments. In this paper, a novel equivalent circuit with four kinds of losses is proposed for a beamlike piezoelectric structure under the longitudinal vibration mode. This structure consists of a slender beam as the metal substrate, and a piezoelectric patch which covers a partial length of the beam. In this approach, first, complex numbers are used to deal with four kinds of losses-elastic loss in the metal substrate, and piezoelectric, dielectric, and elastic losses in the piezoelectric patch. Next in this approach, based on Mason's model, a new equivalent circuit is developed. Using MATLAB, impedance curves of this structure are simulated by the equivalent circuit method. Experiments are conducted and good agreements are revealed between experiments and equivalent circuit results. It is indicated that the introduction of four losses in an equivalent circuit can increase the result accuracy considerably.

Design and experiment of a small-scale walking robot employing stick-slip motion principle.

We describe the design and control of a four legged walking robot, 45 g in weight and 130 mm × 105 mm × 25 mm in size. Each leg consists of two piezoelectric bimorph actuators that are bonded at the free end by a flexure and an end-effector. The robot generates stick-slip locomotion when applying sawtooth shaped voltage signals. Friction between legs and a contact surface is analyzed by using the Coulomb friction model. Locomotion characteristics are measured in several experiments. The robot was driven with frequencies up to 75 Hz, and a maximum velocity of 65 mm/s was obtained at two frequencies: 45 Hz with 190 Vpp driving voltage and 60 Hz with 170 Vpp driving voltage, respectively.

Knockdown of ribosomal protein L39 by RNA interference inhibits the growth of human pancreatic cancer cells in vitro and in vivo.

Pancreatic cancer remains a major unsolved health problem lacking a potent therapeutic option. Our previous studies showed that the ribosomal protein L39 (RPL39) gene was up-regulated after long-term silencing of oncogenic KRAS in pancreatic cancer PANC-1 cells, which indicated that RPL39 may be important for pancreatic cancer development and survival. In the current study, small interfering RNA (siRNA) targeting of the RPL39 gene was performed to determine the effects of the RPL39 gene on growth of pancreatic cancer PANC-1 and BxPC-3 cells in vitro and in vivo. Results from in vitro experiments showed that knockdown of RPL39 expression with RPL39-siRNA suppressed cell proliferation and specifically enhanced cell apoptosis significantly in both PANC-1 and BxPC-3 cells. The increase of caspase-8 activities and the loss of mitochondrial membrane potential after RPL39 silencing indicated that the RPL39 gene may be involved in caspase-8-related mitochondrial apoptosis. Further, treatment with the RPL39-siRNA inhibited the growth of a human pancreatic cancer xenograft in BALB/c nude mice, accompanied by a decreased expression of RPL39. In the xenograft tumors with injection of RPL39-siRNA, the expressions of Ki-67 and CD31 were significantly down-regulated, and apoptosis was markedly induced. Our findings suggested that siRNA against the RPL39 gene may be of value for gene therapy of pancreatic cancer.

Silencing expression of ribosomal protein L26 and L29 by RNA interfering inhibits proliferation of human pancreatic cancer PANC-1 cells.

Oncogenic KRAS, an important target for antitumor therapy, contributes to pancreatic cancer tumorigenesis, progression and maintenance. However, intracellular compensation regulation can help cells to resist the targeted therapy. Gene knockdown method such as RNAi may help to understand this intracellular regulatory system and discover novel therapeutic approach. In this study, two stable transfected cell lines were constructed through lentivirus-mediated shRNA targeting KRAS of PANC-1 cells, to investigate cell response to the knockdown of KRAS. Human whole genome microarray was then used to compare the gene expression profile. As a result, ribosomal proteins L26 and L29 (RPL26 and RPL29) were dramatically upregulated by KRAS-shRNA specifically. To identify whether RPL26 or RPL29 was critical for PANC-1 cells, siRNAs against RPL26 and RPL29 were designed and transfected in vitro. The results showed that knockdown of RPL26 or RPL29 expression significantly suppressed cell proliferation, induced cell arrest at G0/G1 phase and enhanced cell apoptosis. Reactive oxygen species (ROS) assay indicated that silencing of RPL26 or RPL29 markedly decreased the intracellular ROS generation. Our findings imply that siRNA interference against RPL26 and RPL29 is of potential value for intervention of pancreatic cancer.

Highly sensitive method for assay of drug-induced apoptosis using fluorescence correlation spectroscopy.

Apoptosis plays a crucial role in many biological processes and pathogenesis of various malignancies and diseases of the immune system. In this paper, we described a novel method for sensitive detection of drug-induced apoptosis by using fluorescence correlation spectroscopy (FCS). The principle of this method is based on the assay of DNA fragmentation in the process of the drug-induced apoptosis. FCS is a single molecule method, and it can be used for sensitive and selective assay of DNA fragmentation without separation. We first developed a highly sensitive method for characterization of DNA fragments using a home-built FCS system and SYBR Green I as fluorescent DNA-intercalating dye, and then established a model of drug-induced apoptosis using human pancreatic cancer cells and a drug lidamycin. Furthermore, FCS method established was used to directly detect the fragmentation of DNA extracted from apoptotic cells or in the apoptotic cell lysate. In FCS assay, the single-component model and the multiple-components model were used to fit raw FCS data. The characteristic diffusion time of DNA fragments was used as an important parameter to distinguish the apoptotic status of cells. The obtained data documented that the characteristic diffusion time of DNA fragments from apoptotic cells significantly decreased with an increase of lidamycin concentration, which implied that DNA fragmentation occurred in lidamycin-induced apoptosis. The FCS results are well in line with the data obtained from flow cytometer and gel electrophoresis. Compared to current methods, the method described here is sensitive and simple, and more importantly, our detection volume is less than 1 fL, and the sample requirement can easily be reduced to nL level using a droplets array technology. Therefore, our method probably becomes a high throughput detection platform for early detection of cell apoptosis and screening of apoptosis-based anticancer drugs.

Performance evaluation of dual-frequency driving plate ultrasonic motor based on an analytical model.

An analytical model is presented to explain the effects of dual-frequency drive on the plate ultrasonic motor in this paper. The experimental prototype is a plate ultrasonic motor using single-phase asymmetric excitation, which can work under a single vibration or multiple vibration modes. Based on the linear superposition of vibrations with two different excitation frequencies, an analytical model is established using the classic Coulomb friction model, and the non-load rotation speed and maximum stall torque are deduced. Moreover, some crucial parameters such as preload and dead-zone in dual-frequency superposition model are identified or modified automatically by searching for the maximum correlation coefficient between simulation and experimental data using single-frequency drive. It is found that simulation and experiment results agree well when no excitation frequency component is at resonance.

Production of dihydrodaidzein and dihydrogenistein by a novel oxygen-tolerant bovine rumen bacterium in the presence of atmospheric oxygen.

The original bovine rumen bacterial strain Niu-O16, capable of anaerobically bioconverting isoflavones daidzein and genistein to dihydrodaidzein (DHD) and dihydrogenistein (DHG), respectively, is a rod-shaped obligate anaerobic bacterium. After a long-term domestication, an oxygen-tolerant bacterium, which we named Aeroto-Niu-O16 was obtained. Strain Aeroto-Niu-O16, which can grow in the presence of atmospheric oxygen, differed from the original obligate anaerobic bacterium Niu-O16 by various characteristics, including a change in bacterial shape (from rod to filament), in biochemical traits (from indole negative to indole positive and from amylohydrolysis positive to negative), and point mutations in 16S rRNA gene (G398A and G438A). We found that strain Aeroto-Niu-O16 not only grew aerobically but also converted isoflavones daidzein and genistein to DHD and DHG in the presence of atmospheric oxygen. The bioconversion rate of daidzein and genistein by strain Aeroto-Niu-O16 was 60.3% and 74.1%, respectively. And the maximum bioconversion capacity for daidzein was 1.2 and 1.6 mM for genistein. Furthermore, when we added ascorbic acid (0.15%, m/v) in the cultural medium, the bioconversion rate of daidzein was increased from 60.3% to 71.7%, and that of genistein from 74.1% to 89.2%. This is the first reported oxygen-tolerant isoflavone biotransforming pure culture capable of both growing and executing the reductive activity under aerobic conditions.

[C-ring cleavage of isoflavone daidzein by a newly-isolated facultative Enterococcus hirae AUH-HM195 from Crossoptilon mantchuricum feces].

OBJECTIVE: To isolate specific bacteria capable of biotransforming isoflavone daidzein. METHODS: Fresh crossoptilon mantchuricum feces was diluted serially from 10(-1) to 10(-8) in Brain Heart Infusion (BHI) liquid medium in the anaerobic chamber at 37 degrees C. Single colony was isolated and incubated in BHI liquid medium containing 0.1 mmol/L daidzein under anaerobic conditions. The culture medium was detected by HPLC method after being incubated for 3 days. RESULTS: A gram-positive facultative anaerobic bacterium designated strain AUH-HM195 capable of cleaving the C-ring of isoflavone daidzein was isolated. Basic Local Alignment Search Tool (BLAST) search on the GenBank revealed that the full-length of 16S rDNA gene sequence for strain AUH-HM195 has 100% similarity to that of Enterococcus hirae (DSM20160). Based on HPLC retention time, UV spectrum, 1H and 13C NMR analysis,the metabolite of daidzein by strain Enterococcus hirae AUH-HM195 was identified as O-desmethylangolensin. Two peaks were observed when purified O-desmethylangolensin was eluted on a chiral column. The enantiomeric excess (% e.e.) of O-desmethylangolensin was 66.9%. CONCLUSION: Bacterial strain Enterococcus hirae AUH-HM195 is the first reported Enterococcus bacterium with C-ring cleavage activity. It is also the first reported facultative bacterium capable of metabolizing isoflavones.