Royal Society Open Science Physics
http://rsos.royalsocietypublishing.org
Royal Society Open Science RSS feed -- recent Physics articles2054-5703Royal Society Open Science<![CDATA[The leading-edge vortex on a rotating wing changes markedly beyond a certain central body size]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/7/172197?rss=1
Stable attachment of a leading-edge vortex (LEV) plays a key role in generating the high lift on rotating wings with a central body. The central body size can affect the LEV structure broadly in two ways. First, an overall change in the size changes the Reynolds number, which is known to have an influence on the LEV structure. Second, it may affect the Coriolis acceleration acting across the wing, depending on the wing-offset from the axis of rotation. To investigate this, the effects of Reynolds number and the wing-offset are independently studied for a rotating wing. The three-dimensional LEV structure is mapped using a scanning particle image velocimetry technique. The rapid acquisition of images and their correlation are carefully validated. The results presented in this paper show that the LEV structure changes mainly with the Reynolds number. The LEV-split is found to be only minimally affected by changing the central body radius in the range of small offsets, which interestingly includes the range for most insects. However, beyond this small offset range, the LEV-split is found to change dramatically.
]]>2018-07-11T00:09:56-07:00info:doi/10.1098/rsos.172197hwp:master-id:royopensci;rsos.1721972018-07-11Physics57172197172197<![CDATA[Effect of high-frequency electric field on the tissue sticking of minimally invasive electrosurgical devices]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/7/180125?rss=1
Generally minimally invasive surgery is performed using an endoscope and other instruments including electrosurgical units (ESUs), and the adhesion of tissue to electrodes is a major concern. The mechanism governing this tissue sticking, especially the influence of high-frequency electric field, is still unclear. In this study, the effect of high-frequency electric field on the tissue sticking upon electrodes was investigated. The electrosurgical cutting test was performed on ex vivo fresh porcine liver under blend mode using a monopolar ESU. A heat-adherence test without electric field was used as a control. For the control group, the electrode was heated and maintained at a certain temperature and directly in contact with porcine liver. Both sticking tissues obtained from these two tests are partially carbonized porcine liver tissue, but their microstructure and bonding with electrode are obviously different. The sticking tissue formed just under heat is composed of biggish nanoparticles of different sizes which are loosely aggregated and has a weak bonding with the electrode, while the sticking tissue from the electrosurgical cutting test consists of tightly packed fine nanoparticles of equable size as a result of thermo-electric coupling and has a strong bonding with the electrode. Obviously, high-frequency electric field plays an extremely important role in the formation of the sticking tissue. It is the thermo-electric coupling that underlies the function of minimally invasive electrosurgical devices, and the effect of high-frequency electric field cannot be ignored in the tissue sticking study and anti-sticking strategies.
]]>2018-07-11T00:09:56-07:00info:doi/10.1098/rsos.180125hwp:master-id:royopensci;rsos.1801252018-07-11Physics57180125180125<![CDATA[Imaging of nuclear magnetic resonance spin-lattice relaxation activation energy in cartilage]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/7/180221?rss=1
Samples of human and bovine cartilage have been examined using magnetic resonance imaging to determine the proton nuclear magnetic resonance spin–lattice relaxation time, T_{1}, as a function of depth within through the cartilage tissue. T_{1} was measured at five to seven temperatures between 8 and 38°C. From this, it is shown that the T_{1} relaxation time is well described by Arrhenius-type behaviour and the activation energy of the relaxation process is quantified. The activation energy within the cartilage is approximately 11 ± 2 kJ mol^{–1} with this notably being less than that for both pure water (16.6 ± 0.4 kJ mol^{–1}) and the phosphate-buffered solution in which the cartilage was immersed (14.7 ± 1.0 kJ mol^{–1}). It is shown that this activation energy increases as a function of depth in the cartilage. It is known that cartilage composition varies with depth, and hence, these results have been interpreted in terms of the structure within the cartilage tissue and the association of the water with the macromolecular constituents of the cartilage.
]]>2018-07-11T00:09:56-07:00info:doi/10.1098/rsos.180221hwp:master-id:royopensci;rsos.1802212018-07-11Physics57180221180221<![CDATA[Analytical solution for bending vibration of a thin-walled cylinder rolling on a time-varying force]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/7/180639?rss=1
This paper presents the analytical solution of radial vibration of a rolling cylinder submitted to a time-varying point force. In the simplest situation of simply supported edges and zero in-plane vibration, the cylinder is equivalent to an orthotropic pre-stressed plate resting on a visco-elastic foundation. We give the closed-form solution of vibration as a series of normal modes whose coefficients are explicitly calculated. Cases of both deterministic and random forces are examined. We analyse the effect of rolling speed on merging of vibrational energy induced by Doppler's effect for the example of rolling tyre.
]]>2018-07-11T00:09:56-07:00info:doi/10.1098/rsos.180639hwp:master-id:royopensci;rsos.1806392018-07-11Physics57180639180639<![CDATA[How silanization influences aggregation and moisture sorption behaviours of silanized silica: analysis of porosity and multilayer moisture adsorption]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/6/180206?rss=1
Based on the results of nitrogen adsorption and dynamic vapour sorption as well as analysis by the Hailwood–Horrobin (H-H) model, the effects of -methacryloxypropyltrimethoxysilane (MPTS) on the agglomeration and moisture sorption properties of fumed silica particles were investigated. After adding various concentrations (2%, 4%, 6% and 8%) of MPTS, different degrees of silanization were obtained by showing various OH group contents on the silica surface, which resulted in silica agglomerates with different porous structures. The bigger mesopores in the unmodified silica agglomerates became smaller and finally disappeared after MPTS modification and the Bruanuer–Emmett–Teller surface area decreased more gradually with an increase in MPTS concentration. The H-H model fitted the sorption isotherms very well, and both hydrated water and dissolved water showed decreasing trends with the increase in MPTS concentration, showing reduced hygroscopicity. Up to 6% MPTS, the OH groups decreased with increasing MPTS concentration, as indicated by reduced K_{h} and W parameters, while at 8% MPTS an extensive self-condensation of MPTS occurred. Adsorption hysteresis appeared for moisture sorption on silanized silica, especially at low relative humidity values and at low MPTS concentrations, which could be explained by a synergistic effect of the surface OH group content and pore characteristics. These results could aid our understanding of the applications of silane-modified silica particles.
]]>2018-06-06T00:10:11-07:00info:doi/10.1098/rsos.180206hwp:master-id:royopensci;rsos.1802062018-06-06Physics56180206180206<![CDATA[Quantum correlations are weaved by the spinors of the Euclidean primitives]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/5/180526?rss=1
The exceptional Lie group E_{8} plays a prominent role in both mathematics and theoretical physics. It is the largest symmetry group associated with the most general possible normed division algebra, namely, that of the non-associative real octonions, which—thanks to their non-associativity—form the only possible closed set of spinors (or rotors) that can parallelize the 7-sphere. By contrast, here we show how a similar 7-sphere also arises naturally from the algebraic interplay of the graded Euclidean primitives, such as points, lines, planes and volumes, which characterize the three-dimensional conformal geometry of the ambient physical space, set within its eight-dimensional Clifford-algebraic representation. Remarkably, the resulting algebra remains associative, and allows us to understand the origins and strengths of all quantum correlations locally, in terms of the geometry of the compactified physical space, namely, that of a quaternionic 3-sphere, S^{3}, with S^{7} being its algebraic representation space. Every quantum correlation can thus be understood as a correlation among a set of points of this S^{7}, computed using manifestly local spinors within S^{3}, thereby extending the stringent bounds of ±2 set by Bell inequalities to the bounds of ±22 on the strengths of all possible strong correlations, in the same quantitatively precise manner as that predicted within quantum mechanics. The resulting geometrical framework thus overcomes Bell’s theorem by producing a strictly deterministic and realistic framework that allows a locally causal understanding of all quantum correlations, without requiring either remote contextuality or backward causation. We demonstrate this by first proving a general theorem concerning the geometrical origins of the correlations predicted by arbitrarily entangled quantum states, and then reproducing the correlations predicted by the EPR-Bohm and the GHZ states. The raison d’être of strong correlations turns out to be the Möbius-like twists in the Hopf bundles of S^{3} and S^{7}.
]]>2018-05-30T00:34:31-07:00info:doi/10.1098/rsos.180526hwp:master-id:royopensci;rsos.1805262018-05-30Physics55180526180526<![CDATA[A worldwide model for boundaries of urban settlements]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/5/180468?rss=1
The shape of urban settlements plays a fundamental role in their sustainable planning. Properly defining the boundaries of cities is challenging and remains an open problem in the science of cities. Here, we propose a worldwide model to define urban settlements beyond their administrative boundaries through a bottom-up approach that takes into account geographical biases intrinsically associated with most societies around the world, and reflected in their different regional growing dynamics. The generality of the model allows one to study the scaling laws of cities at all geographical levels: countries, continents and the entire world. Our definition of cities is robust and holds to one of the most famous results in social sciences: Zipf’s law. According to our results, the largest cities in the world are not in line with what was recently reported by the United Nations. For example, we find that the largest city in the world is an agglomeration of several small settlements close to each other, connecting three large settlements: Alexandria, Cairo and Luxor. Our definition of cities opens the doors to the study of the economy of cities in a systematic way independently of arbitrary definitions that employ administrative boundaries.
]]>2018-05-23T00:10:35-07:00info:doi/10.1098/rsos.180468hwp:master-id:royopensci;rsos.1804682018-05-23Physics55180468180468<![CDATA[Predicting double negativity using transmitted phase in space coiling metamaterials]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/5/171042?rss=1
Metamaterials are engineered materials that offer the flexibility to manipulate the incident waves leading to exotic applications such as cloaking, extraordinary transmission, sub-wavelength imaging and negative refraction. These concepts have largely been explored in the context of electromagnetic waves. Acoustic metamaterials, similar to their optical counterparts, demonstrate anomalous effective elastic properties. Recent developments have shown that coiling up the propagation path of acoustic wave results in effective elastic response of the metamaterial beyond the natural response of its constituent materials. The effective response of metamaterials is generally evaluated using the ‘S’ parameter retrieval method based on amplitude of the waves. The phase of acoustic waves contains information of wave pressure and particle velocity. Here, we show using finite-element methods that phase reversal of transmitted waves may be used to predict extreme acoustic properties in space coiling metamaterials. This change is the difference in the phase of the transmitted wave with respect to the incident wave. This method is simpler when compared with the more rigorous ‘S’ parameter retrieval method. The inferences drawn using this method have been verified experimentally for labyrinthine metamaterials by showing negative refraction for the predicted band of frequencies.
]]>2018-05-16T00:11:14-07:00info:doi/10.1098/rsos.171042hwp:master-id:royopensci;rsos.1710422018-05-16Physics55171042171042<![CDATA[Crystalline modification of a rare earth nucleating agent for isotactic polypropylene based on its self-assembly]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/5/180247?rss=1
In this paper, the crystalline modification of a rare earth nucleating agent (WBG) for isotactic polypropylene (PP) based on its supramolecular self-assembly was investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. In addition, the relationship between the self-assembly structure of the nucleating agent and the crystalline structure, as well as the possible reason for the self-assembly behaviour, was further studied. The structure evolution of WBG showed that the self-assembly structure changed from a needle-like structure to a dendritic structure with increase in the content of WBG. When the content of WBG exceeded a critical value (0.4 wt%), it self-assembled into a strip structure. This revealed that the structure evolution of WBG contributed to the K_{β} and the crystallization morphology of PP with different content of WBG. In addition, further studies implied that the behaviour of self-assembly was a liquid–solid transformation of WBG, followed by a liquid–liquid phase separation of molten isotactic PP and WBG. The formation of the self-assembly structure was based on the free molecules by hydrogen bond dissociation while being heated, followed by aggregation into another structure by hydrogen bond association while being cooled. Furthermore, self-assembly behaviour depends largely on the interaction between WBG themselves.
]]>2018-05-16T00:11:14-07:00info:doi/10.1098/rsos.180247hwp:master-id:royopensci;rsos.1802472018-05-16Physics55180247180247<![CDATA[Comparison of vacuum static quadrupolar metrics]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/5/170826?rss=1
We investigate the properties of static and axisymmetric vacuum solutions of Einstein equations which generalize the Schwarzschild spherically symmetric solution to include a quadrupole parameter. We test all the solutions with respect to elementary and asymptotic flatness and curvature regularity. Analysing their multipole structure, according to the relativistic invariant Geroch definition, we show that all of them are equivalent up to the level of the quadrupole. We conclude that the q-metric, a variant of the Zipoy–Voorhees metric, is the simplest generalization of the Schwarzschild metric, containing a quadrupole parameter.
]]>2018-05-09T00:10:48-07:00info:doi/10.1098/rsos.170826hwp:master-id:royopensci;rsos.1708262018-05-09Physics55170826170826<![CDATA[Aspiration-based coevolution of link weight promotes cooperation in the spatial prisoner's dilemma game]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/5/180199?rss=1
In this article, we propose an aspiration-based coevolution of link weight, and explore how this set-up affects the evolution of cooperation in the spatial prisoner's dilemma game. In particular, an individual will increase the weight of its link to its neighbours only if the payoff received via this interaction exceeds a pre-defined aspiration. Conversely, if the received payoff is below this aspiration, the link weight with the corresponding neighbour will decrease. Our results show that an appropriate aspiration level leads to a high-cooperation plateau, whereas too high or too low aspiration will impede the evolution of cooperation. We explain these findings with a comprehensive analysis of transition points and with a systematic analysis of typical configuration patterns. The presented results provide further theoretical insights with regards to the impact of different aspiration levels on cooperation in human societies.
]]>2018-05-02T00:10:32-07:00info:doi/10.1098/rsos.180199hwp:master-id:royopensci;rsos.1801992018-05-02Physics55180199180199<![CDATA[Entrainment in the master equation]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/4/172157?rss=1
The master equation plays an important role in many scientific fields including physics, chemistry, systems biology, physical finance and sociodynamics. We consider the master equation with periodic transition rates. This may represent an external periodic excitation like the 24 h solar day in biological systems or periodic traffic lights in a model of vehicular traffic. Using tools from systems and control theory, we prove that under mild technical conditions every solution of the master equation converges to a periodic solution with the same period as the rates. In other words, the master equation entrains (or phase locks) to periodic excitations. We describe two applications of our theoretical results to important models from statistical mechanics and epidemiology.
]]>2018-04-25T00:10:32-07:00info:doi/10.1098/rsos.172157hwp:master-id:royopensci;rsos.1721572018-04-25Physics54172157172157<![CDATA[Applicability of Taylor's hypothesis in thermally driven turbulence]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/4/172152?rss=1
In this paper, we show that, in the presence of large-scale circulation (LSC), Taylor’s hypothesis can be invoked to deduce the energy spectrum in thermal convection using real-space probes, a popular experimental tool. We perform numerical simulation of turbulent convection in a cube and observe that the velocity field follows Kolmogorov’s spectrum (k^{–5/3}). We also record the velocity time series using real-space probes near the lateral walls. The corresponding frequency spectrum exhibits Kolmogorov’s spectrum (f^{–5/3}), thus validating Taylor’s hypothesis with the steady LSC playing the role of a mean velocity field. The aforementioned findings based on real-space probes provide valuable inputs for experimental measurements used for studying the spectrum of convective turbulence.
]]>2018-04-18T00:05:32-07:00info:doi/10.1098/rsos.172152hwp:master-id:royopensci;rsos.1721522018-04-18Physics54172152172152<![CDATA[Advances in synthetic gauge fields for light through dynamic modulation]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/4/172447?rss=1
Photons are weak particles that do not directly couple to magnetic fields. However, it is possible to generate a photonic gauge field by breaking reciprocity such that the phase of light depends on its direction of propagation. This non-reciprocal phase indicates the presence of an effective magnetic field for the light itself. By suitable tailoring of this phase, it is possible to demonstrate quantum effects typically associated with electrons, and, as has been recently shown, non-trivial topological properties of light. This paper reviews dynamic modulation as a process for breaking the time-reversal symmetry of light and generating a synthetic gauge field, and discusses its role in topological photonics, as well as recent developments in exploring topological photonics in higher dimensions.
]]>2018-04-18T00:05:32-07:00info:doi/10.1098/rsos.172447hwp:master-id:royopensci;rsos.1724472018-04-18Physics54172447172447<![CDATA[Generalized transformations and coordinates for static spherically symmetric general relativity]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/5/4/171109?rss=1
We examine a static, spherically symmetric solution of the empty space field equations of general relativity with a non-orthogonal line element which gives rise to an opportunity that does not occur in the standard derivations of the Schwarzschild solution. In these derivations, convenient coordinate transformations and dynamical assumptions inevitably lead to the Schwarzschild solution. By relaxing these conditions, a new solution possibility arises and the resulting formalism embraces the Schwarzschild solution as a special case. The new solution avoids the coordinate singularity associated with the Schwarzschild solution and is achieved by obtaining a more suitable coordinate chart. The solution embodies two arbitrary constants, one of which can be identified as the Newtonian gravitational potential using the weak field limit. The additional arbitrary constant gives rise to a situation that allows for generalizations of the Eddington–Finkelstein transformation and the Kruskal–Szekeres coordinates.
]]>2018-04-11T00:05:23-07:00info:doi/10.1098/rsos.171109hwp:master-id:royopensci;rsos.1711092018-04-11Physics54171109171109