Locust Flight Muscle Activity and Body Orientation in Response to Objects Moving within Different Backgrounds

Locusts are ideal model systems to study complex behaviours, such as flight responses to objects approaching on a collision course. Previous studies have described the flight muscle activity, wing kinematics and aerodynamic forces during collision avoidance behaviour of locusts flying in the wind tunnel. Neural recordings have revealed the influence of backgrounds on the responses of the descending contralateral movement detector (DCMD). Flow field backgrounds delay DCMD responses to looming stimuli that are known to evoke collision avoidance and muscle asynchrony during flight. Therefore, I hypothesize that the flow field background will delay behavioural responses and affect the timing of flight muscle activity. To test for this hypothesis, I placed a loosely-tethered flying locust inside a flight simulator, and presented visual stimuli composed of disks looming within different backgrounds. Concurrent electromyogram (EMG) and videos were recorded before and during the approach. My results show that against both simple and flow field backgrounds, the locust performed collision avoidance behaviours, by exiting the area defining the pre-response epoch, in most of the trials. The time of behaviour (TOB) varied among trials, and neither depressor asymmetry (DA) nor LM97 firing rate changed at TOB. The linear correlation between rotational degrees of freedom [RDOF, including roll (η), pitch(χ), and yaw(ψ)], or the changes in RDOF from the previous frame (ΔRDOF), and DA was calculated to investigate the relationship between depressor asymmetry and behaviours. In the presence of a simple background, more trials showed a significant correlation between RDOF and DA, compared to a flow field background. In the simple background, the time when the correlation between RDOF/ΔRDOF (η, Δη, Δχ, and Δψ) and DA became significant occurred during the interquartile range of TOB. In the flow field background, the correlation between certain RDOF/ΔRDOF (η, ψ, Δη) and DA became significant, while the correlation between DA and χ became insignificant, during the interquartile range of TOB. These results suggest that the background types affected the correlation between RDOF (or ΔRDOF) and DA, and the time when the significance of the correlation changes could be related to TOB

The dynamic behaviour of flexible oscillators rocking and sliding on concentrated springs

This study presents the Flexible Rocking Model on Concentrated Springs (FRMCS), developed to investigate 2D laterally flexible oscillators rocking and sliding on deformable support media during ground excitations. In this model, concentrated vertical springs and viscous dampers simulate the contact forces from support medium at the corners of the body; the tensionless vertical contact element is linear in compression. Horizontal concentrated springs and linear viscous dampers simulate the frictional behaviour at the corners; the constitutive law for the springs models elastic deformations and sliding (according to Coulomb's friction law). With these elements, FRMCS can model the response of a rocking body which can experience sliding and free‐flight phases of motion. The consideration of the flexibility of the support medium enables the evaluation of the forces exerted by the support medium on the structure during an impact. In this study, the FRMCS response is first compared to a previous model where the support medium deformability and the effects of sliding and free‐flight are ignored. Then, the responses of four configurations, which feature either stiff or soft lateral springs and stiff or soft high‐grip support media, are examined under the influence of pulse excitations. Finally, to understand the potential influence of sliding, a configuration with a low‐grip support medium is explored. The comparative influence of lateral flexibility and support medium deformability and sliding is quantified with stability diagrams and various response spectra, describing structural force and moment demands

3D Printed Subject Models for Measurement of Head-related Transfer Function (HRTF)

This disclosure describes techniques to determine individual head-related transfer functions (HRTFs) using a large number of three-dimensional (3D) printed human subject models. Per techniques of this disclosure, 3D printing technology is utilized to generate multiple head model structures, ear model structure, and neck and torso structures of different sizes and shapes to mimic heads and ears observed in human subjects. The head models and ear models are combined in different ways with different neck and torso structures and accessories to create hundreds to thousands customized subject models. The created subject models are used to measure HRTFs. In some examples, the heads and pinnae are directly printed in soft silicone rubber by utilizing specialized 3D printers that can precisely create models that accurately mimic how sound reflects off human skin. In other examples, a female mold casting shell is first 3D printed, which can be filled with materials of varying shore hardness. The use of 3D printed components that can be combined to generate a large number of subject models enables accurate measurement of a large number of high-quality HRTFs at scale without requiring human subjects

A low-cost time-hopping impulse radio system for high data rate transmission

We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are: (i) all-baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A/D conversion, and digital signal processing, (iii) fast acquisition due to novel search algorithms, (iv) spectral shaping that can be adapted to accommodate different spectrum regulations and interference environments. Computer simulations show that this system can provide 110Mbit/s at 7-10m distance, as well as higher data rates at shorter distances under FCC emissions limits. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple simultaneous users, and can suppress narrowband interference effectively.Comment: To appear in EURASIP Journal on Applied Signal Processing (Special Issue on UWB - State of the Art

New Insight into the Anti-liver Fibrosis Effect of Multitargeted Tyrosine Kinase Inhibitors: From Molecular Target to Clinical Trials

Tyrosine kinases (TKs) is a family of tyrosine protein kinases with important functions in the regulation of a broad variety of physiological cell processes. Overactivity of TK disturbs cellular homeostasis and has been linked to the development of certain diseases, including various fibrotic diseases. In regard to liver fibrosis, several TKs, such as vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), fibroblast growth factor receptor (FGFR) and epidermal growth factor receptor (EGFR) kinases, have been identified as central mediators in collagen production and potential targets for anti-liver fibrosis therapies. Given the essential role of TKs during liver fibrogenesis, multitargeted inhibitors of aberrant TK activity, including sorafenib, erlotinib, imatinib, sunitinib, nilotinib, brivanib and vatalanib, have been shown to have potential for treating liver fibrosis. Beneficial effects are observed by researchers of this field using these multitargeted TK inhibitors in preclinical animal models and in patients with liver fibrosis. The present review will briefly summarize the anti-liver fibrosis effects of multitargeted TK inhibitors and molecular mechanisms

The effect of nanoparticle softness on the interfacial dynamics of a model polymer nanocomposite

The introduction of soft organic nanoparticles (NPs) into polymer melts has recently expanded the material design space for polymer nanocomposites, compared to traditional nanocomposites that utilize rigid NPs, such as silica, metallic NPs, and other inorganic NPs. Despite advances in the fabrication and characterization of this new class of materials, the effect of NP stiffness on the polymer structure and dynamics has not been systematically investigated. Here, we use molecular dynamics to investigate the segmental dynamics of the polymer interfacial region of isolated NPs of variable stiffness in a polymer matrix. When the NP-polymer interactions are stronger than the polymer-polymer interactions, we find that the slowing of segmental dynamics in the interfacial region is more pronounced for stiff NPs. In contrast, when the NP-polymer interaction strength is smaller than the matrix interaction, the NP stiffness has relatively little impact on the changes in the polymer interfacial dynamics. We also find that the segmental relaxation time τα of segments in the NP interfacial region changes from values lower than to higher than the bulk material when the NP-polymer interaction strength is increased beyond a "critical"strength, reminiscent of a binding-unbinding transition. Both the NP stiffness and the polymer-surface interaction strength can thus greatly influence the relative segmental relaxation and interfacial mobility in comparison to the bulk material

Periodontal health: A national cross‐sectional study of knowledge, attitudes and practices for the public oral health strategy in China

Aim To assess the status of periodontal health knowledge, attitudes and practices (KAP) among Chinese adults. Materials and Methods A cross‐sectional study was conducted in a nationally representative sample of adults (N = 50,991) aged 20 years or older from ten provinces, autonomous regions, and municipalities. Percentages of Chinese adults with correct periodontal knowledge, positive periodontal attitudes, and practices were estimated. Multiple logistic regression analyses were used to examine the related factors. Results Less than 20% of Chinese adults were knowledgeable about periodontal disease. Very few (2.6%) of Chinese adults use dental floss ≥once a day and undergo scaling ≥once a year and visit a dentist (6.4%) in the case of gingival bleeding. Periodontal health KAP was associated with gender, age, body mass index, marital status, place of residence, education level, income, smoking status, and history of periodontal disease. Conclusions Periodontal health KAP are generally poor among the Chinese adult population. Community‐based health strategies to improve periodontal health KAP need to be implemented. Increasing knowledge of periodontal disease, the cultivation of correct practices in response to gingival bleeding, and the development of good habits concerning the use of dental floss and regular scaling should be public oral health priorities