Illustrating field emission theory by using Lauritsen plots of transmission probability and barrier strength

This technical note relates to the theory of cold field electron emission (CFE). It starts by suggesting that, to emphasize common properties in relation to CFE theory, the term 'Lauritsen plot' could be used to describe all graphical plots made with the reciprocal of barrier field (or the reciprocal of a quantity proportional to barrier field) on the horizontal axis. It then argues that Lauritsen plots related to barrier strength (G) and transmission probability (D) could play a useful role in discussion of CFE theory. Such plots would supplement conventional Fowler-Nordheim (FN) plots. All these plots would be regarded as particular types of Lauritsen plot. The Lauritsen plots of -G and lnD can be used to illustrate how basic aspects of FN tunnelling theory are influenced by the mathematical form of the tunnelling barrier. These, in turn, influence local emission current density and emission current. Illustrative applications used in this note relate to the well-known exact triangular and Schottky-Nordheim barriers, and to the Coulomb barrier (i.e., the electrostatic component of the electron potential energy barrier outside a model spherical emitter). For the Coulomb barrier, a good analytical series approximation has been found for the barrier-form correction factor; this can be used to predict the existence (and to some extent the properties) of related curvature in FN plots.Comment: Based on a poster presented at the 25th International Vacuum Nanoelectronics Conference, Jeju, S. Korea, July 2012. Version 3 incorporates small changes made at proof stag

How to avoid potential pitfalls in recurrence plot based data analysis

Recurrence plots and recurrence quantification analysis have become popular in the last two decades. Recurrence based methods have on the one hand a deep foundation in the theory of dynamical systems and are on the other hand powerful tools for the investigation of a variety of problems. The increasing interest encompasses the growing risk of misuse and uncritical application of these methods. Therefore, we point out potential problems and pitfalls related to different aspects of the application of recurrence plots and recurrence quantification analysis

Finite element analysis of protective bicycle helmet & dummy head under dynamic loading

Cycling is a good activities particularly for recreation, exercise, and transportation. However, cycling related to the head injury is a significant contributor to hospitalization and death. Previous literatures indicates that the available helmets have less effective in preventing head injuries among cyclists. Moreover, most of the available helmets have been tested for only a few loading conditions. Therefore, the purpose of this study is to use finite element models to evaluate the protective effect of a helmet against various impact velocities. The head and helmet model has been developed using computational software. This study focus on the explicit dynamic analysis which performed in ANSY-WORKBENCH with loading condition in term of various impact velocity impacted on front and side of the head model. The results indicates the differences between the frontal and side simulations. They have been compared to identify the protective effect of the helmet and head

Ocena stężeń adiponektyny i leptyny w surowicy u pacjentów z chorobą niedokrwienną serca — związek z frakcją wyrzutową, wskaźnikiem uwapnienia tętnic i angiogramem tętnic wieńcowych

Introduction. Adiponectin is an adipose tissue-derived adipocytokine protein, while leptin is the protein that maintains the body weight in humans via its effect on the hypothalamus. These hormones interact at different levels of cardio-metabolic risk factors. This study aimed to assess the serum levels of adiponectin and leptin in patients with ischaemic heart disease and subjected to coronary calcium scoring (CCS) and coronary angiography. Material and methods. We included 59 patients with ischaemic heart disease and 20 healthy subjects served as a control in this study. The patients were assessed by electrocardiograph, echocardiograph, coronary angiogram and coronary computerised tomography (CCT) for the assessment of CCS. Serum levels of adiponectin and leptin were determined by using enzyme-linked immunosorbent assay (ELISA) technique. Results. Coronary computed tomography (CT) investigation explored, that 30.5% of patients had positive calcium score and 67.8% of patients did not show evidence of coronary changes by CT angiograph. The patients had significantly high leptin and low adiponectin levels compared with healthy subjects. Serum leptin levels were significantly low in patients with positive CCS and angiogram, compared with those who had no abnormal CCT. Significant positive correlation between ejection fraction and serum leptin (r = 0.285, p &lt; 0.05) and non-significant correlation with serum adiponectin were observed. Conclusions. Serum leptin and adiponectin levels are useful determinants in patients with ischaemic heart disease, as high serum leptin levels are associated with negative coronary CT and positively correlated with left ventricular ejection fraction.Wstęp. Adiponektyna jest adipocytokiną, białkiem produkowanym przez tkankę tłuszczową, natomiast leptyna jest białkiem przyczyniającym się u ludzi do utrzymania masy ciała przez wpływ na przysadkę mózgową. Hormony te oddziałują na siebie na różnych poziomach czynników ryzyka sercowo-naczyniowego. Badanie przeprowadzono w celu oceny stężeń adiponektyny i leptyny w surowicy pacjentów z niedokrwienną chorobą serca, których poddano koronarografii i u których określono wskaźnik uwapnienia tętnic (CCS). Materiał i metody. Do badania włączono 59 pacjentów z chorobą niedokrwienną serca i 20 zdrowych osób tworzących grupę kontrolną. U chorych wykonano badania elektrokardiograficzne, echokardiograficzne, koronarografię i tomografię tętnic wieńcowych (CCT) w celu oceny CCS. Surowicze stężenia adiponektyny i leptyny oznaczono metodą immunoenzymatyczną (ELISA). Wyniki. W ocenie uwapnienia tętnic, dokonanej za pomocą tomografii komputerowej (CT) tętnic wieńcowych, u 30,5% chorych uzyskano wynik dodatni, a u 67,8% chorych nie stwierdzono zmian w tętnicach wieńcowych w angiografii CT. U osób z chorobą niedokrwienną stężenia leptyny były istotnie wyższe, a adiponektyny — niższe niż w grupie kontrolnej. U chorych z dodatnim CCS i zmianami w angiogramie stężenie leptyny w surowicy było istotnie niższe niż u osób bez nieprawidłowości w CCT. Stwierdzono istotną dodatnią korelację frakcji wyrzutowej ze stężeniem leptyny w surowicy (r = 0,285; p < 0,05) oraz nieistotną korelację ze stężeniem adiponektyny w surowicy. Wnioski. Surowicze stężenia leptyny i adiponektyny są użytecznymi wskaźnikami u pacjentów z chorobą niedokrwienną serca, ponieważ wysokie stężenie leptyny wiązało się z ujemnym wynikiem CCT i korelowało dodatnio z frakcją wyrzutową lewej komory

Recurrence-based time series analysis by means of complex network methods

Complex networks are an important paradigm of modern complex systems sciences which allows quantitatively assessing the structural properties of systems composed of different interacting entities. During the last years, intensive efforts have been spent on applying network-based concepts also for the analysis of dynamically relevant higher-order statistical properties of time series. Notably, many corresponding approaches are closely related with the concept of recurrence in phase space. In this paper, we review recent methodological advances in time series analysis based on complex networks, with a special emphasis on methods founded on recurrence plots. The potentials and limitations of the individual methods are discussed and illustrated for paradigmatic examples of dynamical systems as well as for real-world time series. Complex network measures are shown to provide information about structural features of dynamical systems that are complementary to those characterized by other methods of time series analysis and, hence, substantially enrich the knowledge gathered from other existing (linear as well as nonlinear) approaches.Comment: To be published in International Journal of Bifurcation and Chaos (2011

Treatment of olive mill based wastewater by means of magnetic nanoparticles: Decolourization, dephenolization and COD removal

AbstractOlive mill wastewater (OMW) is an environmental concern that has been highlighted as a serious environmental problem in the Mediterranean basin countries because of its high organic load and phytotoxic and antibacterial phenolic compounds, which resist biological degradation. Consequently, this type of wastewater represents a huge challenge for the conventional wastewater treatment techniques as it can impact the lifetime of bacteria needed for the treatment. Iron-oxide nanoparticles are attractive for wastewater treatment for two important reasons. First, nanoparticles can remove pollutants from wastewater rapidly. Second, this magnetic type of nanoparticles could be separated easily using a magnet after finishing treatment process. In this study, we aimed at investigating the effectiveness of the magnetic iron oxide nanoparticles in the removal of large organic contaminants from OMW. Batch and continuous mode processes were applied on OMW treatment to determine the effect of contact time, solution pH, coexisting contaminants and the adsorption isotherm.The results showed that the adsorption was fast and the adsorption reached equilibrium within less than 30min. The adsorption equilibrium data fit very well to the Brunauer–Emmett–Teller (BET) Model, indicating multi-layers adsorption. The adsorption of major pollutants was associated to an efficient removal of coexisting contaminants such as heavy metals and free ions. The adsorption of OMW pollutants was dependent on pH of the solution. Finally, continuous-mode process was tested successfully using a packed bed column that combined sand filtration with magnetic nanoparticles to decolourize OMW effluent. This study will provide valuable insight on the effect of nanoparticles toward the treatment and recyclability of olive mill wastewater, which is crucial for the local olive mill industry. After seeing the successful achievement of integrating nanoparticles with fixed bed filtration, a preliminary process description and cost estimation of stand-alone plant (with a capacity of 4m3/h) for OMW treatment were considered in this study. Process capital and annual operating costs were estimated to be $12,306 and$476/year, respectively

Scale-free brain functional networks

Functional magnetic resonance imaging (fMRI) is used to extract {\em functional networks} connecting correlated human brain sites. Analysis of the resulting networks in different tasks shows that: (a) the distribution of functional connections, and the probability of finding a link vs. distance are both scale-free, (b) the characteristic path length is small and comparable with those of equivalent random networks, and (c) the clustering coefficient is orders of magnitude larger than those of equivalent random networks. All these properties, typical of scale-free small world networks, reflect important functional information about brain states.Comment: 4 pages, 5 figures, 2 table

Investigating the topology of interacting networks - Theory and application to coupled climate subnetworks

Network theory provides various tools for investigating the structural or functional topology of many complex systems found in nature, technology and society. Nevertheless, it has recently been realised that a considerable number of systems of interest should be treated, more appropriately, as interacting networks or networks of networks. Here we introduce a novel graph-theoretical framework for studying the interaction structure between subnetworks embedded within a complex network of networks. This framework allows us to quantify the structural role of single vertices or whole subnetworks with respect to the interaction of a pair of subnetworks on local, mesoscopic and global topological scales. Climate networks have recently been shown to be a powerful tool for the analysis of climatological data. Applying the general framework for studying interacting networks, we introduce coupled climate subnetworks to represent and investigate the topology of statistical relationships between the fields of distinct climatological variables. Using coupled climate subnetworks to investigate the terrestrial atmosphere's three-dimensional geopotential height field uncovers known as well as interesting novel features of the atmosphere's vertical stratification and general circulation. Specifically, the new measure "cross-betweenness" identifies regions which are particularly important for mediating vertical wind field interactions. The promising results obtained by following the coupled climate subnetwork approach present a first step towards an improved understanding of the Earth system and its complex interacting components from a network perspective