The nonexistence of spurious solutions to discrete, two-point boundary value problems

We investigate difference equations which arise as discrete approximations to two-point boundary value problems for systems of second-order, ordinary differential equations. We formulate conditions under which all solutions to the discrete problem satisfy certain a priori bounds which axe independent of the step-size. As a result, the nonexistence of spurious solutions are guaranteed. Some existence and convergence theorems for solutions to the discrete problem are also presented. (C) 2002 Elsevier Science Ltd. All rights reserved.

PsyCoLaUS: santé mentale et maladies cardiovasculaires: association fortuite [PsyCoLaus: mental disorders and cardiovascular diseases: spurious association?].

Cardio-vascular diseases (CVD), their well established risk factors (CVRF) and mental disorders are common and co-occur more frequently than would be expected by chance. However, the mechanisms underlying this association are still poorly understood. The main study questions of PsyCoLaus, the psychiatric arm of CoLaus, are: 1) Do mental disorders increase vulnerability to CVRF and CVD? 2) Do CVRF and CVD promote the development of mental disorders? 3) Do CVRF/ CVD and mental disorders share common pathogenetic processes? The longitudinal project adds a comprehensive psychiatric evaluation to the CoLaus investigation. A better understanding of the psychological, physiological and behavioral links underlying CVD/ CVRF and mental disorders will result in the development of more specific and efficient strategies of prevention and treatment for both psychiatric and CVD/CVRF, two major elements of burden of disease.

High occurrence of Calodium hepaticum (syn. Capillaria hepatica) spurious infection in a village in the Atlantic Forest of southern Brazil

Calodium hepaticum (syn. Capillaria hepatica) is a nematode of the Capillariidae family that infects rodents and other mammals. In Brazil, human spurious infections of C. hepaticum have been detected in indigenous or rural communities from the Amazon Basin, but not in the southern states of the country. Here, we report the highest occurrence (13.5% of 37 residents) of C. hepaticum human spurious infection detected in Brazil and the first record in a southern region, Guaraqueçaba. The finding is explained by the area being located in the Atlantic Forest of the state of Paraná, surrounded by preserved forests and because the inhabitants consume the meat of wild mammals.

The hardness profile as a tool to detect spurious stationary points in the potential energy surface

The energy and hardness profile for a series of inter and intramolecular conformational changes at several levels of calculation were computed. The hardness profiles were found to be calculated as the difference between the vertical ionization potential and electron affinity. The hardness profile shows the correct number of stationary points independently of the basis set and methodology used. It was found that the hardness profiles can be used to check the reliability of the energy profiles for those chemical system

Is the observed persistence spurious? A test for fractional integration versus short memory and structural breaks

Although it is commonly accepted that most macroeconomic variables are nonstationary, it is often difficult to identify the source of the non-stationarity. In particular, it is well-known that integrated and short memory models containing trending components that may display sudden changes in their parameters share some statistical properties that make their identification a hard task. The goal of this paper is to extend the classical testing framework for I(1) versus I(0)+ breaks by considering a a more general class of models under the null hypothesis: non-stationary fractionally integrated (FI) processes. A similar identification problem holds in this broader setting which is shown to be a relevant issue from both a statistical and an economic perspective. The proposed test is developed in the time domain and is very simple to compute. The asymptotic properties of the new technique are derived and it is shown by simulation that it is very well-behaved in finite samples. To illustrate the usefulness of the proposed technique, an application using inflation data is also provided.

Spurious hyperphosphatemia in a patient with alteplase-locked central venous catheter.

Alteplase has been shown to be effective in preventing central venous access clotting in patients on hemodialysis. Because of a high phosphorus content in its excipient, it can inadvertently contaminate blood samples, leading the physician in care of the patient to erroneously increase dialysis time or change diet in order to control the pseudo-hyperphosphatemia.

Understanding round-tripping phenomenon in Russian context – case Cyprus

Russian FDI has a few peculiarities. One of them is round-tripping. Round-tripping is defined as transfer of funds abroad, usually to offshore financial centers (OFCs), and then bringing all or some of the investment back as foreign investment. Russian context was chosen for this study because the share of round-tripping investments from country’s total FDI is extensive. However, it needs to be addressed that this is not just a Russian phenomenon. Round-tripping is used by many developed and developing countries, and most of the countries have their own designated destinations for this kind of capital, much like Cyprus is the main destination for Russian capital. It is important to study this phenomenon further, since it falsifies FDI statistics and can lead to poor decisions on state level. Theoretical part of the study tries to determine weather traditional FDI and internationalization theories fit to explain the Russian round-tripping phenomenon. Traditional FDI and internationalization theories are first introduced in general terms, and then further examined in Russian context. In traditional endogenic FDI theories, when the capital is formed in one country it goes abroad to find better profits. At a first glance, this seemed not to be the case in round-tripping. However, during the study it became rather clear that with few adjustments and changes in perspective, traditional theories could be used to explain round-tripping phenomenon. For example, OLI paradigm can be further developed into OLIH paradigm with ‘H’ representing the important home country institutions. Transaction based view and resource seeking theories were also seen well equipped to explain round-tripping with a change in perspective. The latter part of the study focused on holistic understanding of Russian –Cyprian investment relationship. Study aims to shed light into the determinants and consequences of this phenomenon for both countries involved. The two share historical, cultural and political ties, but most importantly common financial interests. Russian companies seek security and financial knowledge to maneuver their assets and Cyprian economy largely is dependent on their disproportionally large financial sector. Consequences for Cyprian economy were seen in current economic crisis, when the need for their financial services diminished. Russian government on the other hand is losing vast amounts of tax money due to this phenomenon. A rather extreme view was also introduced in this study. Round-tripping phenomenon and OFCs are an important reason why corruption exists, since if one does not have a way to make ill-gained money legitimate why try to ill-gain the money at the first place. The most important finding of the study is that round-tripping companies are in a better competitive position than genuine and purely domestic investor due to their institutional knowledge.

The hardness profile as a tool to detect spurious stationary points in the potential energy surface

The energy and hardness profile for a series of inter and intramolecular conformational changes at several levels of calculation were computed. The hardness profiles were found to be calculated as the difference between the vertical ionization potential and electron affinity. The hardness profile shows the correct number of stationary points independently of the basis set and methodology used. It was found that the hardness profiles can be used to check the reliability of the energy profiles for those chemical system

Controlling spurious diapycnal mixing in eddy-resolving height-coordinate ocean models: insights from virtual deliberate tracer release experiments

A perceived limitation of z-coordinate models associated with spurious diapycnal mixing in eddying, frontal flow, can be readily addressed through appropriate attention to the tracer advection schemes employed. It is demonstrated that tracer advection schemes developed by Prather and collaborators for application in the stratosphere, greatly improve the fidelity of eddying flows, reducing levels of spurious diapycnal mixing to below those directly measured in field experiments, ∼1 × 10−5 m2 s−1. This approach yields a model in which geostrophic eddies are quasi-adiabatic in the ocean interior, so that the residual-mean overturning circulation aligns almost perfectly with density contours. A reentrant channel configuration of the MIT General Circulation Model, that approximates the Antarctic Circumpolar Current, is used to examine these issues. Virtual analogs of ocean deliberate tracer release field experiments reinforce our conclusion, producing passive tracer solutions that parallel field experiments remarkably well.

Spurious shifts in the pattern of diurnal variation of sea level pressure of reanalysis datasets

The main purpose of this work is to report the presence of spurious discontinuities in the pattern of diurnal variation of sea level pressure of the three reanalysis datasets from: the National Centers for Environmental Prediction (NCEP) and National Center for Atmospheric Science (R1), the NCEP and Department of Energy (R2), and the European Centre for Medium Range Weather Forecasting (ERA-40). Such discontinuities can be connected to the major changes in the global observing system that have occurred throughout reanalyses years. In the R1, the richest period in discontinuities is 1956-1958, coinciding with the start of modern radiosonde observation network. Rapid increase in the density of surface-based observations from 1967 also had an important impact on both R1 and ERA-40, with larger impact on R1. The reanalyses show discontinuities in the 1970s related to the assimilation of radiances measured by the Vertical Temperature Profile Radiometer and TIROS-N Operational Vertical Sounders onboard satellites. In the ERA-40, which additionally assimilated Special Sensor Microwave/Imager data, there are discontinuities in 1987-1989. The R1 also presents further discontinuities, in 1988-1993 likely connected to replacement/introduction of NOAA-series satellites with different biases, and to the volcanic eruption of Mount Pinatubo in June 1991, which is known to have severely affected measurements of infrared radiances for several years. The discontinuities in 1996-1998 might be partially connected to change in the type of radiosonde, from VIZ-B to VIZ-B2. The R2, which covers only satellite era (1979-on), shows discontinuities mainly in 1992, 1996-1997, and 2001. The discontinuities in 1992 and 2001 might have been caused by change in the satellite measurements and those in 1996-1997 by some changes in land-based observations network. © 2012 Springer-Verlag.

Spurious transients of projection methods in microflow simulations

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

Reducing the spurious oscillations in the lumped parameters model using low-pass filter

Voltages and currents in the transmission line are described by differential equations that are difficult to solve due soil and skin effect that has to be considered for accurate results, but it increases their complexity. Therefore there are some models to study the voltages and currents along in transmission line. The distributed parameters model that transforms the equations in time domain to the frequency domain and once the solutions are obtained, they are converted to time domain using the Inverse Laplace Transform using numerical methods. Another model is named lumped parameters model and it considers the transmission line represented by a pi-circuit cascade and the currents and voltages are described by state equations. In the simulations using the lumped parameters model, it can be observed the presence of spurious oscillations that are independent of the quantity of pi-circuits used and do not represent the real value of the transient. In this work will be projected a passive low-pass filter directly inserted in the lumped parameters model to reduce the spurious oscillations in the simulations, making this model more accurate and reliable for studying the electromagnetic transients in power systems.