Movement patterns of southern bell frogs (Litoria raniformis) in response to flooding

Within the semiarid regions of New South Wales, Australia, the endangered southern bell frog (Litoria raniformis) occupies a landscape that is characterised by unpredictable rainfall and periodic flooding. Limited knowledge of the movement and habitat-occupancy patterns of this species in response to flood events has hampered conservation efforts. We used radio-tracking to assess changes in movement patterns and habitat occupancy of L. raniformis (n = 40) over three different periods (November, January and April/May) that coincided with the flooding, full capacity and subsequent drying of waterbodies within an irrigation landscape. We assessed (1) the use of permanent and ephemeral habitats in response to flooding and drying and (2) distances moved, turning angles and dispersion of frogs during wetland flooding, full capacity and drying. Individuals remained in permanent waterbodies in November but had abandoned these areas in favour of flooded ephemeral waterbodies by January. As the ephemeral waterbodies dried, radio-tracked individuals moved back into permanent waterbodies. The movement patterns of radio-tracked individuals were significantly different in the three radio-tracking periods, but did not differ significantly between sexes. Individuals moved significantly greater distances over 24 h, in straighter lines and movements were more dispersed while they occupied ephemeral waterbodies during January than when they occupied permanent waterbodies during November and April/May. Local weather conditions did not influence movement patterns when all three tracking periods were modelled together using a single linear stepwise regression. The dynamic distribution of habitat patches over space and time, combined with changing patterns of resource utilisation and movement of L. raniformis, highlights the importance of incorporating both permanent and ephemeral habitat patches into conservation plans. Reductions in flood frequency and extent of ephemeral wetlands due to modified flooding regimes have the capacity to limit dispersal of this species, even when permanent waterbodies remain unchanged.

Interdependence and dynamic linkages between the emerging stock markets of South Asia

The present article examines the dynamic linkages between the stock markets
of Bangladesh, India, Pakistan and Sri Lanka using a temporal Granger causality
approach by binding the relationship among the stock price indices within a
multivariate cointegration framework. We also examine the impulse response
functions. Our main finding is that in the long run, stock prices in Bangladesh,
India and Sri Lanka Granger-cause stock prices in Pakistan. In the short run
there is unidirectional Granger causality running from stock prices in Pakistan
to India, stock prices in Sri Lanka to India and from stock prices in Pakistan to
Sri Lanka. Bangladesh is the most exogenous of the four markets, reflecting its
small size and modest market capitalization.

Dynamic addressing in wireless sensor networks without location awareness

Sensor Networks have applications in diverse fields. They can be deployed for habitat modeling, temperature monitoring and industrial sensing. They also find applications in battlefield awareness and emergency (first) response situations. While unique addressing is not a requirement of many data collecting applications of wireless sensor networks, it is vital for the success of applications such as emergency response. Data that cannot be associated with a specific node becomes useless in such situations. In this work we propose a novel dynamic addressing mechanism for wireless sensor networks that are not location-aware. The scheme enables successful reuse of addresses in event-driven wireless sensor networks introducing minimal latencies and efficiently addressing packet loss. It also eliminates the need for network-wide Duplicate Address Detection (DAD) to ensure uniqueness of network level addresses.

Comparison of corticomotor excitability during visuomotor dynamic and static tasks

The human central nervous system (CNS) has the ability to modulate its activity during the performance of different movements. Recent evidence, however, suggests that the CNS can also modulate its activity in the same movement but with increased precision during a visuomotor static task. This study aimed to extend on these findings by using transcranial magnetic stimulation (TMS) to measure the CNS during the performance of two visuomotor dynamic tasks. Twelve volunteers participated in this study, performing two separate motor tasks. Study I (“Position Tracking”) involved participants to perform a visuomotor tracking task using a dial potentiometer and matching their response icon to the computer generated tracking icon whilst holding a pincer grip. Study II (“Force Tracking”) involved participants to perform a similar visuomotor tracking task by applying or releasing pressure against a fixed force transducer. Tasks were conducted at two speeds (“slow” being one tracking cycle in 10 s; and “fast” being two tracking cycles in 10 s) and compared to a visuomotor static task at a similar muscle contraction level. Results showed corticospinal changes with significant increases (p = 0.002) in excitability demonstrated during Study I (42.3 ± 16.8%) and Study II (56.3 ± 34.2%) slow speed tasks. Moreover, significant reduction in corticospinal inhibition was also observed during both tracking tasks at slow (59.3 ± 13.7%; p = 0.001) and fast speeds (31.9 ± 12.3%; p = 0.001). The findings may provide information on the underlying physiology during the early stages of motor skill acquisition.

Data-based dynamic haptic interaction model with deformable 3D objects

The data-based modeling of the haptic interaction simulation is a growing trend in research. These techniques offer a quick alternative to parametric modeling of the simulation. So far, most of the use of the data-based techniques was applied to static simulations. This paper introduces how to use data-based model in dynamic simulations. This ensures realistic behavior and produce results that are very close to parametric modeling. The results show that a quick and accurate response can be achieved using the proposed methods.

Impact response and energy absorption of aluminium foam-filled tubes

The effect of foam fillers on the impact behaviour and energy absorption of an aluminium tube is investigated. Both experimental test and computational simulation are employed in current study. For comparison, hollow tubes and foams are also tested, respectively. Foam filler is found to be ineffective in increasing the crushing loads of the composite tubes over the simple superposition of the crushing loads of hollow tube and foam. Also, foam filler increases the tendency for the concertina mode of folding. The foam fillers of tubes additionally result in increasing the SAE values over those of hollow tubes.

Force amplification response of actin filaments under confined compression

Actin protein is a major component of the cell cytoskeleton, and its ability to respond to external forces and generate propulsive forces through the polymerization of filaments is central to many cellular processes. The mechanisms governing actin's abilities are still not fully understood because of the difficulty in observing these processes at a molecular level. Here, we describe a technique for studying actin–surface interactions by using a surface forces apparatus that is able to directly visualize and quantify the collective forces generated when layers of noninterconnected, end-tethered actin filaments are confined between 2 (mica) surfaces. We also identify a force-response mechanism in which filaments not only stiffen under compression, which increases the bending modulus, but more importantly generates opposing forces that are larger than the compressive force. This elastic stiffening mechanism appears to require the presence of confining surfaces, enabling actin filaments to both sense and respond to compressive forces without additional mediating proteins, providing insight into the potential role compressive forces play in many actin and other motor protein-based phenomena.

Hyaluronic acid–collagen network interactions during the dynamic compression and recovery of cartilage

A compression cell designed to fit inside an NMR spectrometer was used to investigate (i) the in situ dynamic strain response and structural changes of the internal pore network, and (ii) the diffusion and flow of interstitial water, in full thickness cartilage samples as they were mechanically deformed under a constant compressive load (pressure) and then allowed to recover (swell again) when the load was removed. Selective enzymatic digestion of the collagen fibril network and the glycopolysaccharide hyaluronic acid (HA) was performed to mimic some of the structural and compositional changes associated with osteoarthritis. Digestion of collagen gave rise to mechanical ‘dynamic softening’ and—perhaps more importantly—nearly complete loss in the ability to recover through swelling, both effects due to the disruption of the hierarchical structure and fibril interconnectivity in the collagen network which adversely affects its ability to deform reversibly and to properly regulate the pressurization and resulting rate and direction of interstitial fluid flow. In contrast, digestion of HA inside the collagen pore network caused the cartilage to ‘dynamically stiffen’ which is attributed to the decrease in the osmotic (entropic) pressure of the digested HA molecules confined in the cartilage pores that causes the network to contract and thereby become less permeable to flow. These digestioninduced changes in cartilage’s properties reveal a complex relationship between the molecular weight and concentration of the HA in the interstitial fluid, and the structure and properties of the collagen fibril pore network, and provide new insights into how changes in either could influence the onset and progression of osteoarthritis.

Lipidomic profiling of chylomicron triacylglycerols in response to high fat meals

Using lipidomic methodologies the impact that meal lipid composition and metabolic syndrome (MetS) exerts on the postprandial chylomicron triacylglycerol (TAG) response was examined. Males (9 control; 11 MetS) participated in a randomised crossover trial ingesting two high fat breakfast meals composed of either dairy-based foods or vegetable oil-based foods. The postprandial lipidomic molecular composition of the TAG in the chylomicron-rich (CM) fraction was analysed with tandem mass spectrometry coupled with liquid chromatography to profile CM TAG species and targeted TAG regioisomers. Postprandial CM TAG concentrations were significantly lower after the dairy-based foods compared with the vegetable oil-based foods for both control and MetS subjects. The CM TAG response to the ingested meals involved both significant and differential depletion of TAG species containing shorter-and medium-chain fatty acids (FA) and enrichment of TAG molecular species containing C16 and C18 saturated, monounsaturated and diunsaturated FA. Furthermore, there were significant changes in the TAG species between the food TAG and CM TAG and between the 3- and 5-h postprandial samples for the CM TAG regioisomers. Unexpectedly, the postprandial CM TAG concentration and CM TAG lipidomic responses did not differ between the control and MetS subjects. Lipidomic analysing of CM TAG molecular species revealed dynamic changes in the molecular species of CM TAG during the postprandial phase suggesting either preferential CM TAG species formation and/or clearance.

Fiscal policy in Brazil: from counter-cyclical response to crisis

The main goal of this article is to identify the dynamic effects of fiscal policy on output in Brazil from 1997 to 2014, and, more specifically, to estimate those effects when the output falls below its potential level. To do so, we estimate VAR (vector autoregressive) models to generate impulse-response functions and causality/endogeneity tests. Our most remarkable results indicate the following channel of economic policy in Brazil: to foster output, government spending increases causing increases in both tax rates and revenue and the short-term interest rate. A fiscal stimulus via spending seems efficient for economic performance as well as monetary policy; however, the latter operates pro-cyclically in the way we defined here, while the former is predominantly countercyclical. As the monetary shock had a negative effect on GDP growth and GDP growth responded positively to the fiscal shock, it seems that the economic policy has given poise to growth with one hand and taken it with the other one. The monetary policy is only reacting to the fiscal stimuli. We were not able to find any statistically significant response of the output to tax changes, but vice versa seems work in the Brazilian case.

Changes in phytoplankton composition in response to tides, wind-induced mixing conditions, and freshwater outflows in an urbanised estuarine complex

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A high dynamic range method for the direct readout of a dynamic phase change in homodyne interferometers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On the dynamic behaviour of a mass supported by a parallel combination of a spring and an elastically connected damper

This paper presents a consistent and concise analysis of the free and forced vibration of a mass supported by a parallel combination of a spring and an elastically supported damper (a Zener model). The results are presented in a compact form and the physical behaviour of the system is emphasised. This system is very similar to the conventional single-degree-of freedom system (sdof)-(Voigt model), but the dynamics can be quite different depending on the system parameters. The usefulness of the additional spring in series with the damper is investigated, and optimum damping values for the system subject to different types of excitation are determined and compared.There are three roots to the characteristic equation for the Zener model; two are complex conjugates and the third is purely real. It is shown that it is not possible to achieve critical damping of the complex roots unless the additional stiffness is at least eight times that of the main spring. For a harmonically excited system, there are some possible advantages in using the additional spring when the transmitted force to the base is of interest, but when the displacement response of the system is of interest then the benefits are marginal. It is shown that the additional spring affords no advantages when the system is excited by white noise. (c) 2007 Elsevier Ltd. All rights reserved.

Optimal and robust modal control of a flexible structure using an active dynamic vibration absorber

This paper is concerned with feedback vibration control of a lightly damped flexible structure that has a large number of well-separated modes. A single active electrical dynamic absorber is used to reduce a particular single vibration mode selectively or multiple modes simultaneously. The absorber is realized electrically by feeding back the structural acceleration at one position to a collocated piezoceramic patch actuator via a controller consisting of one or several second order lowpass filters. A simple analytical method is presented to design a modal control filter that is optimal in that it maximally flattens the mobility frequency response of the target mode, as well as robust in that it works within a prescribed maximum control spillover of 2 dB at all frequencies. Experiments are conducted with a free-free beam to demonstrate its ability to control any single mode optimally and robustly. It is also shown that an active absorber with multiple such filters can effectively control multiple modes simultaneously.

Force and displacement transmissibility of a nonlinear isolator with high-static-low-dynamic-stiffness

Engineers often face the challenge of reducing the level of vibrations experienced by a given payload or those transmitted to the support structure to which a vibrating source is attached. In order to increase the range over which vibrations are isolated, soft mounts are often used in practice. The drawback of this approach is the static displacement may be too large for reasons of available space for example. Ideally, a vibration isolator should have a high-static stiffness, to withstand static loads without too large a displacement, and at the same time, a low dynamic stiffness so that the natural frequency of the system is as low as possible which will result in an increased isolation region. These two effects are mutually exclusive in linear isolators but can be overcome if properly configured nonlinear isolators are used. This paper is concerned with the characterisation of such a nonlinear isolator comprising three springs, two of which are configured to reduce the dynamic stiffness of the isolator. The dynamic behaviour of the isolator supporting a lumped mass is investigated using force and displacement transmissibility, which are derived by modelling the dynamic system as a single-degree-of-freedom system. This results in the system dynamics being approximately described by the Duffing equation. For a linear isolator, the dynamics of the system are the same regardless if the source of the excitation is a harmonic force acting on the payload (force transmissibility) or a harmonic motion of the base (displacement transmissibility) on which the payload is mounted. In this paper these two expressions are compared for the nonlinear isolator and it is shown that they differ. A particular feature of the displacement transmissibility is that the response is unbounded at the nonlinear resonance frequency unless the damping in the isolator is greater than some threshold value, which is not the case for force transmissibility. An explanation for this is offered in the paper. (C) 2011 Elsevier Ltd. All rights reserved.