Well-defined Limits Research Articles

On the electrodynamics of moving bodies at low velocities

We discuss an article by Le Bellac and Lévy-Leblond in which they have identified two Galilean limits of electromagnetism (1973 Nuovo Cimento B 14 217–33). We use their results to point out some confusion in the literature, and in the teaching of special relativity and electromagnetism. For instance, it is not widely recognized that there exist two well-defined non-relativistic limits, so that researchers and teachers are likely to utilize an incoherent mixture of both. Recent works have shed new light on the choice of gauge conditions in classical electromagnetism. We retrieve the results of Le Bellac and Lévy-Leblond first by examining orders of magnitudes and then with a Lorentz-like manifestly covariant approach to Galilean covariance based on a five-dimensional Minkowski manifold. We emphasize the Riemann–Lorenz approach based on the vector and scalar potentials as opposed to the Heaviside–Hertz formulation in terms of electromagnetic fields.

Theory of Recurrent Neural Network with Common Synaptic Inputs

We discuss the effects of common synaptic inputs in a recurrent neural network. Because of the effects of these common synaptic inputs, the correlation between neural inputs cannot be ignored, and thus the network exhibits sample dependence. Networks of this type do not have well-defined thermodynamic limits, and self-averaging breaks down. We therefore need to develop a suitable theory without relying on these common properties. While the effects of the common synaptic inputs have been analyzed in layered neural networks, it was apparently difficult to analyze these effects in recurrent neural networks due to feedback connections. We investigated a sequential associative memory model as an example of recurrent networks and succeeded in deriving a macroscopic dynamical description as a recurrence relation form of a probability density function.

Heat Capacities and Volumes of Aqueous Dicarboxylate Salt Solutions of Relevance to the Bayer Process

Apparent molar volumes (Vφ) and heat capacities at constant pressure (Cpφ) of aqueous solutions of sodium oxalate (Na2Ox), sodium succinate (Na2Suc), sodium malonate (Na2Mal), and potassium oxalate (K2Ox) were determined at 25 °C up to their saturation limits using vibrating tube densitometry and flow calorimetry. These data were fitted using the Redlich−Rosenfeld−Meyer and Pitzer models. It was established using literature data that Vφ and Cpφ of Na+ and K+ salts with a common anion are additive within well-defined limits even up to high concentrations. This was used to estimate hypothetical values of Cpφ and Vφ at high ionic strengths for the sparingly soluble Na2Ox, which are required for the thermodynamic modeling of concentrated electrolyte mixtures such as Bayer process solutions. These values were in reasonable agreement with those estimated using a Pitzer model with parameters for Na2SO4(aq).

Imaging characteristics of two subtypes of congenital hemangiomas: rapidly involuting congenital hemangiomas and non-involuting congenital hemangiomas

Common infantile hemangiomas (COMMON) occur in approximately 10% of infants by the age of 1 year, with a female predominance. Some hemangiomas can be fully developed at birth and are thus called congenital hemangiomas (CH). Within this population, two courses have been identified: rapidly involuting CH (RICH) and non-involuting CH (NICH). Little has been reported on the clinical prognosis and imaging features of these entities. To describe the imaging characteristics of two subtypes of CH, i.e. RICH and NICH, and to compare them with COMMON. We retrospectively gathered data on 26 children presenting with CH, i.e. lesions fully developed at birth. These lesions were divided into two groups according to the clinical course: suspected RICH (n=8) and suspected NICH (n=18). We used US, CT or MRI and angiography to identify the gross anatomy and structure and the vascularization. Imaging findings were compared with the clinical course and pathology results, when available. The imaging findings in these patients were compared retrospectively with those in 26 patients with COMMON randomly chosen from the database of our multidisciplinary clinic. When compared with COMMON imaging characteristics, NICH and RICH had distinctive features on US such as being heterogeneous (72% of NICH and 62.5% of RICH vs 42.3% of COMMON), visible vessels (72% of NICH and 62.5% of RICH vs 15.4% of COMMON), calcifications (17% of NICH and 37.5% of RICH vs no case of COMMON). On CT and/or MRI, we compared imaging features such as well-defined limits (67% of NICH and 60% of RICH vs 100% of COMMON), and fat stranding (29.4% of NICH and RICH vs 7.7% of COMMON). Distinctive imaging characteristics are observed in cases of CH with US findings of visible vessels and calcifications statistically significant.

Endosonographic characteristics of perigastrointestinal lymphnodes studied ex-corpore

Objectives Assessment of morphological characteristics of lymphnodes studied ex-corpore by echoendoscopy—shape, sharpness of limits, echogenicity and dimensions—to categorize them either as metastatic or non-metastatic. Material and methods Fifty-four lymphnodes were studied. They were identified and studied by echoendoscopy in fresh surgical specimens of oesophagus, stomach and rectum. Eight nodal characteristics were evaluated. The data obtained were studied by multivariate analysis using the logistical estimate method in two different statistical models. Results In model 1, logistical estimate demonstrated that well-defined limits (WDL) of the lymphnodes and the association of hypoechogenicity and round shape were the most significant variables suggesting the presence of invasion. In model 2, the most significant variables were WDL, round shape and association of round shape with WDL. The first model had a high sensitivity of 93.1% and specificity of 68% whereas the second model had a greater specificity of 84%, with a slight fall in sensitivity. Conclusion These models might have an application to clinical practice particularly in the pre-operative assessment of patients with oesophageal carcinoma, gastric carcinoma or rectal carcinoma.

Variation in ultraviolet reflectance by carotenoid-bearing feathers of tanagers (Thraupini: Emberizinae: Passeriformes)

Avian visual sensitivity encompasses both the human visible range (400–700 nm) and also near-ultraviolet (UV) wavelengths (320–400 nm) invisible to normal humans. I used reflectance spectrophotometry to assess variation in UV reflectance for yellow, orange and red plumage in 67 species of tanager (Passeriformes). Previous chemical studies, and my analysis of reflectance minima, suggest that carotenoids are the dominant pigments in yellow, orange and red tanager plumage. Spectra recorded over the range of wavelengths to which birds are sensitive (320–700 nm) were invariably bimodal, with both a plateau of high reflectance at longer (> 500 nm) wavelengths and a distinct secondary peak at UV (< 400 nm) wavelengths. Within this overall framework, variation in UV reflectance was expressed within well-defined quantitative limits: (1) peak reflectance was always lower than the corresponding plateau of reflectance at longer visible wavelengths; (2) the intensity of peak reflectance declined steadily below 350 nm; (3) wavelengths of peak reflectance clustered between 350 and 370 nm. Significant correlations were detected between various measures of total reflectance in the UV and visible wavebands, but not between various measures of spectral location of UV and visible reflectance. I propose that the strong absorption band at short visible wavelengths (∼ 380–550 nm) responsible for bimodal spectra of carotenoids in vitro is also responsible for bimodal reflectance by carotenoid-based plumage colours. The construction of the UV and visible reflectance bands from different sides of this same absorbance band provides a mechanism for the observed covariation between UV and visible wavelengths. Lack of an association between the spectral locations of the UV and visible reflectance bands may result from the limited variation in spectral location of the UV band. These patterns suggest that plumage colours are subject to constraints, just as are more traditional morphological characters. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84, 243–257.

Quantum and dynamical effects of proton donor-acceptor vibrational motion in nonadiabatic proton-coupled electron transfer reactions

This paper presents a general theoretical formulation for proton-coupled electron transfer (PCET) reactions. The solute is represented by a multistate valence bond model, and the active electrons and transferring proton(s) are treated quantum mechanically. This formulation enables the classical or quantum mechanical treatment of the proton donor-acceptor vibrational mode, as well as the dynamical treatment of the proton donor-acceptor mode and the solvent. Nonadiabatic rate expressions are presented for PCET reactions in a number of well-defined limits for both dielectric continuum and molecular representations of the environment. The dynamical rate expressions account for correlations between the fluctuations of the proton donor-acceptor distance and the nonadiabatic PCET coupling. The quantities in the rate expressions can be calculated with a dielectric continuum model or a molecular dynamics simulation of the full system. The significance of the quantum and dynamical effects of the proton donor-acceptor mode is illustrated with applications to model PCET systems.

Analyzing the structure of biodiversity

Thierry de Meeûs et al. [1] recently discussed some of the limitations of the biological species concept, and they argue that the nonexistence of a single-species concept that satisfactorily reflects the complexity of natural diversity illustrates the futility of the search for such a concept. de Meeûs et al. consider the species as a taxonomic category (which was also stated by Kunz [2] from a parasitological context). We believe that this consideration could mean: (i) identification of the concept with the object to which it refers (i.e. the species entity); (ii) negation of the said object; or (iii) recognition of an object, although it cannot be conceptualized because of a lack of well-defined limits. The first is the product of confusion, the second of radicalization because the definition involves adoption of a purely nominalist principle, and the third is a hypothesis that requires confirmation. We think it is premature to invalidate any of the species concepts, or to suggest that classic concepts such as the biological species concept are not useful at a time when we are just beginning to understand the genetics of the speciation process.

Uncertainties in estimates of the risks of late effects from space radiation

Methods used to project risks in low-Earth orbit are of questionable merit for exploration missions because of the limited radiobiology data and knowledge of galactic cosmic ray (GCR) heavy ions, which causes estimates of the risk of late effects to be highly uncertain. Risk projections involve a product of many biological and physical factors, each of which has a differential range of uncertainty due to lack of data and knowledge. Using the linear-additivity model for radiation risks, we use Monte-Carlo sampling from subjective uncertainty distributions in each factor to obtain an estimate of the overall uncertainty in risk projections. The resulting methodology is applied to several human space exploration mission scenarios including a deep space outpost and Mars missions of duration of 360, 660, and 1000 days. The major results are the quantification of the uncertainties in current risk estimates, the identification of factors that dominate risk projection uncertainties, and the development of a method to quantify candidate approaches to reduce uncertainties or mitigate risks. The large uncertainties in GCR risk projections lead to probability distributions of risk that mask any potential risk reduction using the “optimization” of shielding materials or configurations. In contrast, the design of shielding optimization approaches for solar particle events and trapped protons can be made at this time and promising technologies can be shown to have merit using our approach. The methods used also make it possible to express risk management objectives in terms of quantitative metrics, e.g., the number of days in space without exceeding a given risk level within well-defined confidence limits.

Ouverture de ‘Marketing Research and Global Markets’

Global markets express a new vision of market research and of marketing research, consistent with the information needs of complex organisations (generally network-based) working with several decision-making points (characterised by high-level delegations and responsibilities) and with very brief action-reaction times. Marketing research and market research represent two distinct information support domains for corporate management, with well-defined theoretical and practical limits. Market research concerns, on the one hand, uncontrollable environmental phenomena (such as demographic and social composition and trends). On the other, it regards influenceable environmental phenomena (e.g. overall product consumption trends, degree of competition, distribution channels, etc.). On the contrary, marketing research tends to develop when increased competition obliges a company to perform analysis of market opportunities and threats. In general terms, marketing research can be defined as the systematic collection and analysis of relevant quantitative and qualitative data and information for a specific marketing situation that a company must face for product, price, place and promotion.

The Fornax Cluster Spectroscopic Survey: a sample of confirmed cluster dwarfs

The Fornax Cluster Spectroscopic Survey (FCSS) project utilizes the Two-degree Field (2dF) multi-object spectrograph on the Anglo-Australian Telescope (AAT). Its aim is to obtain spectra for a complete sample of all 14 000 objects with 16.5 ⩽bj⩽ 19.7 irrespective of their morphology in a 12 deg2 area centred on the Fornax cluster. A sample of 24 Fornax cluster members has been identified from the first 2dF field (3.1 deg2 in area) to be completed. This is the first complete sample of cluster objects of known distance with well-defined selection limits. Nineteen of the galaxies (with −15.8 < MB < −12.7) appear to be conventional dwarf elliptical (dE) or dwarf S0 (dS0) galaxies. The other five objects (with −13.6 < MB < −11.3) are those galaxies which were described recently by Drinkwater et al. and labelled ‘ultracompact dwarfs’ (UCDs). A major result is that the conventional dwarfs all have scale sizes α≳ 3 arcsec (≃300 pc). This apparent minimum scale size implies an equivalent minimum luminosity for a dwarf of a given surface brightness. This produces a limit on their distribution in the magnitude–surface brightness plane, such that we do not observe dEs with high surface brightnesses but faint absolute magnitudes. Above this observed minimum scale size of 3 arcsec, the dEs and dS0s fill the whole area of the magnitude–surface brightness plane sampled by our selection limits. The observed correlation between magnitude and surface brightness noted by several recent studies of brighter galaxies is not seen with our fainter cluster sample. A comparison of our results with the Fornax Cluster Catalog (FCC) of Ferguson illustrates that attempts to determine cluster membership solely on the basis of observed morphology can produce significant errors. The FCC identified 17 of the 24 FCSS sample (i.e. 71 per cent) as being ‘cluster’ members, in particular missing all five of the UCDs. The FCC also suffers from significant contamination: within the FCSS's field and selection limits, 23 per cent of those objects described as cluster members by the FCC are shown by the FCSS to be background objects.

Assessing the mechanical strength of interfacial atomic bonds by quantitative high-resolution transmission electron microscopy

Abstract A method is presented for quantitatively assessing the strength of interatomic bonding forces across interfaces between two dissimilar crystalline materials. At such interfaces, the mismatch of corresponding lattice parameters gives rise to a periodic pattern of linear regions of poor match, denoted as ‘misfit dislocations’. The atom displacements that occur in these regions constitute an ‘image’ of the bonding forces across the interface. By fitting a model of the displacement field to experimentally determined atom positions at misfit dislocation cores, therefore, it should be possible to assess the mechanical strength of the interatomic bonds across the interface. The feasibility of this approach is demonstrated for the cube-on-cube interface between a SrTiO3(001) substrate and an epitaxial layer of SrZrO3. The atom positions at the misfit dislocations in this interface were determined with small error limits (0.03 nm) by quantitative high-resolution transmission electron microscopy. By fitting a continuum model describing the displacement field of misfit dislocations as a function of elasticity parameters of the interfacial bond layer and the two juxtaposed crystals, it is possible to determine the shear stiffness of the interatomic bonds across this interface quantitatively and with well-defined error limits (30%). Moreover, the analysis enables determining Poisson's ratio and the shear modulus of epitaxial layers, in this case SrZrO3. The method introduced here has a broad range of applications.

Crossing the Secular Divide: Government and Faith-Based Organizations as Partners in Health

Recent debate over the relationship between government and faith-based organizations has renewed interest in the opportunities and challenges that are associated with change in this area of health care policy. Experience exists already that faith-based organizations can provide effective health education and services in the community. Limited infrastructure and liability are among the important barriers to their expansion. Spurred by the demographics of an aging population and increasing health care costs, we argue the necessity of further partnering, within well-defined limits, to maximize the availability of health care education and services throughout this nation.

The Most Luminous Protostars in Molecular Clouds: A Hint to Understand the Stellar Initial Mass Function

The maximum luminosity of protostars forming in molecular clouds is investigated as a function of the parent cloud mass on the basis of a rich cloud sample searched for in the literature. In total, we gathered 499 molecular clouds among the published data, out of which 243 clouds are found to be associated with candidates for protostars selected from the IRAS point source catalog. A diagram of the maximum stellar luminosity in each cloud and the parent cloud mass shows that the young stars in the clouds associated with regions are apparently more luminous than those in clouds away from H II regions over the entire cloud mass range investigated (1 M CL /M ⊙ 6 ). In addition, we found that there are well-defined upper and lower limits in the maximum stellar luminosity distribution with the lower limit having a steeper dependence on the cloud mass ( L MAX ∝ M CL 1.5 ) than the upper one ( L MAX ∝ M CL 0.8 ). All these features could be naturally accounted for if we assume that the luminosity function of protostars is controlled by the cloud mass and the external pressure imposed on the cloud surface. We introduce a simple model for the stellar luminosity function as a function of these quantities.

The US and Other Optically Selected Bright QSO Samples

AbstractThe US Bright Quasar Sample (UBQS) is a color-selected sample of quasars with B &lt; 17 that has been constructed with an eye towards completeness within well-defined selection limits. The redshift distribution of the UBQS shows an interesting spike at z ~ 0.55. The significance of this enhancement increases when the UBQS is combined with other bright quasar samples which also show evidence of high levels of completeness. Reconstitution of this combined bright quasar sample after removal of the emission-line flux from the B magnitudes indicates that the z ~ 0.55 spike is not caused by an emission-line selection bias. Rather, the largest effect of these sample corrections would be to depress the high end of the optical luminosity function that is derivable from this combined sample.

Hematopoiese extramedular intratorácica: relato de um caso

Os autores relatam o caso de um paciente do sexo masculino, de 40 anos de idade, portador de anemia falciforme, que desenvolveu a forma intratorácica de hematopoiese extramedular, apresentando lesões expansivas com densidade de partes moles, localizadas posteriormente, nas goteiras paravertebrais, na radiologia convencional. A tomografia computadorizada do tórax demonstrou massas bem delimitadas, de contornos lobulados, com densidade heterogênea à custa de áreas de tecido gorduroso e de densidade de partes moles, localizadas no terço inferior das goteiras paravertebrais. Os pulmões tinham coeficientes de atenuação preservados. A tomografia computadorizada de abdome revelou importante aumento da densidade e do volume do fígado, atribuídos à hemossiderose, e baço atrófico e calcificado devido a infartos esplênicos de repetição.

Interpolation from number states to chaotic states of the electromagnetic field

We introduce new two-parameter states of the quantized radiation field interpolating from number states to chaotic states. Instead of dealing with pure states, we consider truncated mixtures of number states - number-chaotic states (NCS) - which reduce to number and chaotic (thermal) states in two well-defined limits. We study the statistical and squeezing properties of such states and show that there is a value of the chaoticity parameter at which a transition from sub- to super-Poissonian characteristics occurs. Analysing the atomic population inversion in the Jaynes-Cummings model for these NCSs, we demonstrate the appearance of collapses and revivals as is increased. Their phase space representations are studied emphasizing the changes as the parameters are varied and we discuss the nonclassical depth.

Mesonic spectrum of two-dimensional supersymmetric theories

We consider a bound state problem for a family of supersymmetric gauge theories with fundamental matter. These theories can be obtained by a dimensional reduction of supersymmetric QCD from three dimensions to 1+1 and subsequent truncation of some of the fields. We find that the models without adjoint scalar converge to well-defined continuum limits and calculate the resulting spectra of these theories. We also find the critical value of coupling at which an additional massless state is observed. By contrast, the models containing adjoint scalars, seem to have a continuous mass spectrum in the limit of infinite volume.

Leiomioma renal voluminoso

Renal leiomyomas are uncommon between renal tumors, and they have a benign mesenchymatous origin. Because of their low incidence, unspecific symptomatololly an not well-defined iconographic semilogy, they often raise problems with differential diagnosis from kidney masses, although they are often big size lessionsWe report a patients with incidentally diagnosis of big solid left renal mass, who underwent radical nephrectomy resulting kidney pelvis leiomyoma. Diagnostic, hystological and therapeutic aspects are briefly review in literatureEmphasis is made on the relevance of a high index suspicion considering big solid asymptomatic renal masses in middle-age women. Specially in renal tumors with well-defined limits and abscense of locoregional and systemic disemination. We emphasized usefulness of Magnetic Angioresonance, immunohystochemical test and conservative surgery oportunity in small renal leiomyomas preoperatively confirmed

Quaternionic Projective Theory and Hadron Transformation Laws

A quaternionic projective theory based on the symmetry group Sl(2,H) allows one to identify various hadron models and many well-known particle transformation laws in its subgroup chains. Identifying the 16-dimensional Dirac algebra {γμ} with Sl(2,H), we use a well-established group-theoretic framework as well as the framework of projective geometry to classify elementary particles and describe their interactions at low energies. It is straightforward to derive Chiral Dynamics and explain the spinorial ('quark') structure of hadrons. Spontaneous symmetry breaking occurs naturally by coset reductions, whereas 'classical' physics is obtained via well-defined limits in terms of a group contraction. The Dirac equation can be identified within a Riemannian globally symmetric space and thus allows one to investigate the fermionic mass as a well-defined parameter. In addition, we suggest an identification of the second quantization scheme and an approach to sum up the perturbation series.