Critical Point Analysis Research Articles

On the prediction of glucose concentration under intra-patient variability in type 1 diabetes: A monotone systems approach

Insulin therapy in type 1 diabetes aims to mimic the pattern of endogenous insulin secretion found in healthy subjects. Glucose–insulin models are widely used in the development of new predictive control strategies in order to maintain the plasma glucose concentration within a narrow range, avoiding the risks of high or low levels of glucose in the blood. However, due to the high variability of this biological process, the exact values of the model parameters are unknown, but they can be bounded by intervals. In this work, the computation of tight glucose concentration bounds under parametric uncertainty for the development of robust prediction tools is addressed.A monotonicity analysis of the model states and parameters is performed. An analysis of critical points, state transformations and application of differential inequalities are proposed to deal with non-monotone parameters. In contrast to current methods, the guaranteed simulations for the glucose–insulin model are carried out by considering uncertainty in all the parameters and initial conditions. Furthermore, no time-discretisation is required, which helps to reduce the computational time significantly. As a result, we are able to compute a tight glucose envelope that bounds all the possible patient's glycemic responses with low computational effort.

Métodos de diagnóstico e pontos críticos de bem-estar de bovinos leiteiros

O bem-estar de animais de produção tem sido discutido nos âmbitos comercial, social e acadêmico, sendo que tal discussão pode ser enriquecida pela elaboração de protocolos de diagnóstico de bem-estar animal bem definidos, favorecendo a regulamentação de uma legislação específica. O objetivo desta revisão é discutir os métodos de diagnóstico de bem-estar animal e apontar os principais pontos críticos que afetam o bem-estar dos bovinos leiteiros. O diagnóstico de bem-estar compreende a observação do comportamento animal e de indicadores fisiológicos e sanitários, como análise hematológica e dosagem de hormônios, análise do escore de locomoção, a observação de lesões corporais e o estado geral de saúde dos animais. Tais ferramentas permitem verificar quais são os principais pontos críticos que afetam o bem-estar dos animais e construir estratégias de melhoria. As vacas em lactação podem sofrer restrições ambientais, nutricionais e sanitárias. Os bezerros passam pelo distresse do desmame precoce e do isolamento social. Alguns pontos críticos de bem-estar de gado leiteiro reconhecidos internacionalmente parecem prováveis no cenário brasileiro. Entretanto, é possível a existência de diferenças importantes em relação aos sistemas de produção praticados no Brasil e no exterior, uma vez que o acesso ao pasto é um fator comum na produção brasileira e pode estar associado a um maior grau de bem-estar animal. Dessa forma, é importante a condução de trabalhos de diagnóstico de bem-estar específico para os animais envolvidos com a produção de leite no Brasil.

Monitoring of cleanliness and disinfection in dairies: Comparison of traditional microbiological and ATP bioluminescence methods

The levels of aerobic contamination at different points in the production chain (curd vat, filler, mould, table and tank) at five cheese factories were analysed using contact plates, dipslides and bioluminescence methods. Almost all the cheese factories showed similar levels of contamination.ATP bioluminescence detected the largest number of unacceptable surfaces (47.7%), followed by the contact plates (41%) and dipslides (34.2%). The dipslide and contact plate methods showed moderate concordance and significant differences (p < 0.001) between the various surfaces sampled. The points in the production chain were classified according to contamination rates, being minimal in the curd vats–fillers and maximal in tables–moulds. The same surfaces were also sampled to determine total Enterobacteriaceae, mould and yeast growth using contact plates and dipslides and no concordance between these two methods was detected. These results were analysed and discussed taking into account the importance of cleanliness and disinfection in cheese factories, as a prerequisite of the HACCP (Hazard Analysis of Critical Control Points) quality assurance system.

Citizens’ participation in the Italian health‐care system: the experience of the Mixed Advisory Committees

In 1994, the region of Emilia-Romagna recognized the importance of citizens' participation in the regional health-care system and recommended the institution of Mixed Advisory Committees in the health districts and hospitals with the objective of monitoring and assessing health-care quality from the users' perspective. This paper reports findings from a qualitatively based evaluation involving direct observations of the committees and 39 semi-structured interviews: 20 with representatives of patients and users' associations and 19 with health professionals and managers involved in the activities of the committees. The Mixed Advisory Committees introduced for the first time in the Italian health system an ongoing deliberative approach that gave patients and users' representatives the opportunity to be involved in health service governance. The committees enabled the creation of a method of collective participation that overcame the reductive individualistic 'approach' to health-care participation. MAC participants evaluated the committees positively for their mixed composition, which integrated different cultures, experiences and professional profiles with the potential to contribute to solving health-care problems, in a consultative role. Although patients and users' representatives were able to exert some form of influence, their expectations were greater than the results obtained. The study illuminated some weak points of public consultation, such as a decline in participation by citizen representatives and a weak influence on decision making. MACs developed a mechanism of participation that provides health-care users' representatives with the opportunity to contribute to the identification and analysis of critical points of the health-care system. A strength of the MACs is their level of institutionalization within the health system in the region of Emilia-Romagna. However, they contain a problem of representativeness, lacking a formal system of determining a representative composition from among patients and users' associations. The case study also illustrates that participation without the cooperation of the health service, and financial and organizational support, will result in a decline in citizen participation, given the resources required of these volunteer citizens in return for limited results.

Towards a fair degrowth-society: Justice and the right to a ‘good life’ beyond growth

A critical scrutiny is presented of the ethical assumptions of growth and degrowth theories with respect to distributive justice and the normative conditions for a ‘good human life’. An argument is made in favor of Sen's and Nussbaum's ‘capabilities approach’ as the most suitable theoretical framework for addressing these questions. Since industrialization economic growth has played a key-role as an attraction pole, around which issues of social justice, political stability, and welfare protection seemed to gravitate. Accordingly, it is considered as a necessary condition for both intragenerational and intragenerational justice. These assumptions have been subjected to substantial critique by degrowth-thinkers, according to which economic growth is rather a threat than a condition for intragenerational and intergenerational justice. However, a theoretical underpinning of these assumptions is missing so far. In the paper I analyze the ethical and moral assumptions in both approaches by focusing on the theories of justice that are implicitly laid down as a background for their arguments (welfarism, resourcism, and the capabilities-approach). In a detailed analysis of the main critical points formulated by degrowth advocates I take the capabilities approach perspective and show why it can offer a more adequate normative underpinning for the conceptualization of a degrowth society.

Sr7Ge6, Ba7Ge6 and Ba3Sn2 –Three new binary compounds containing dumbbells and four-membered chains of tetrel atoms with considerable Ge–Ge π-bonding character

The germanides Sr7Ge6 and Ba7Ge6 as well as the stannide Ba3Sn2 were prepared by arc melting and annealing in welded tantalum ampoules using induction as well as resistance furnaces. The compounds were investigated by powder and single crystal X-ray diffraction. Sr7Ge6 and Ba7Ge6 crystallize in the Ca7Sn6 structure type (space group Pmna, Z=4: a=7.777(2)Å, b=23.595(4)Å, c=8.563(2)Å, wR2=0.081 (all data), 2175 independent reflections, 64 variable parameters for Sr7Ge6 and a=8.0853(6)Å, b=24.545(2)Å, c=8.9782(8)Å, wR2=0.085 (all data), 2307 independent reflections, 64 variable parameters for Ba7Ge6). Ba3Sn2 crystallizes in an own structure type with the space group P43212, Z=4, a=6.6854(2)Å, c=17.842(2)Å, wR2=0.037 (all data), 1163 independent reflections, 25 variable parameters.In Sr7Ge6 and Ba7Ge6 the Ge atoms are arranged as Ge2 dumbbells and Ge4 four-membered atom chains. Their crystal structures cannot be rationalized according to the (8-N) rule. In contrast, Ba3Sn2 presents Sn2 dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. The chemical bonding situation in these structures is discussed on the basis of partial and total Density Of States (DOS) curves, band structures including fatbands, topological analysis of the Electron Localization Function (ELF) as well as Bader analysis of the bond critical points using the programs TB-LMTO-ASA and Wien2k. While Ba3Sn2 reveals semiconducting behaviour, all germanides Ae7Ge6 (Ae=Ca, Sr, and Ba) show metallic properties and a considerable π-bonding character between the Ge atoms of the four-membered chains and the dumbbells. The π-bonding character of the germanides is best reflected by the resonance hybrid structures {[Ge–Ge]6−/[Ge–....Ge–....Ge–....Ge]8−}↔{[Ge=Ge]4−/[Ge–Ge–Ge–Ge]10−}.

Optical constants of layered structured Ga0.75In0.25Se crystals from the ellipsometric measurements

We have carried out the spectroscopic ellipsometry measurements on Ga0.75In0.25Se single crystals in the 1.2–6.0 eV spectral range at room temperature. The optical constants, real and imaginary parts of the dielectric function, refractive index and extinction coefficient, were found as a result of analysis of ellipsometric data. The critical point analysis of the second derivative spectra of the dielectric function revealed four interband transition structures with critical point energy values of 3.19, 3.53, 4.10 and 4.98 eV. The results of the analysis were compared with those of the ellipsometric studies performed on GaSe which is the main constituent of the Ga0.75In0.25Se crystal. The obtained critical point energies are in good agreement with the energies of the GaSe crystal reported in the literature.

The Nature of Bond Critical Points in Dinuclear Copper(I) Complexes

Closed-shell contacts between two copper(I) ions are expected to be repulsive. However, such contacts are quite frequent and are well documented. Crystallographic characterization of such contacts in unsupported and bridged multinuclear copper(I) complexes has repeatedly invited debates on the existence of cuprophilicity. Recent developments in the application of Bader's theory of atoms-in-molecules (AIM) to systems in which weak hydrogen bonds are involved suggests that the copper(I)-copper(I) contacts would benefit from a similar analysis. Thus the nature of electron-density distributions in copper(I) dimers that are unsupported, and those that are bridged, have been examined. A comparison of complexes that are dimers of symmetrical monomers and those that are dimers of two copper(I) monomers with different coordination spheres has also been made. AIM analysis shows that a bond critical point (BCP) between two Cu atoms is present in most cases. The nature of the BCP in terms of the electron density, ρ, and its Laplacian is quite similar to the nature of critical points observed in hydrogen bonds in the same systems. The ρ is inversely correlated to Cu-Cu distance. It is higher in asymmetrical systems than what is observed in corresponding symmetrical systems. By examining the ratio of the local electron potential-energy density (V(c)) to the kinetic energy density (G(c)), |V(c)|/G(c) at the critical point suggests that these interactions are not perfectly ionic but have some shared nature. Thus an analysis of critical points by using AIM theory points to the presence of an attractive metallophilic interaction similar to other well-documented weak interactions like hydrogen bonding.

Optical Properties of Ultrathin Copper Thin Films Sandwiched between Nb-Doped TiO2 Films Studied with Spectroscopic Ellipsometry

Cu thin films sandwiched between Nb-doped TiO2 (NTO) thin films were grown on glass substrates using tilted-dual target DC magnetron sputtering deposition. The thicknesses of the top and bottom NTOs were nominally 30 nm, and the thicknesses of the Cu films (t) varied between 1.5 nm and 50 nm. We measured the ellipsometric angles (Ψ,Δ) of the NTO/Cu/NTO/glass by using spectroscopic ellipsometry and estimated the thicknesses and dielectric functions of the Cu films by using a multi-layer model analysis. Transmission electron microscopy measurements showed that the Cu layers evolved from aggregates of Cu nanoparticles to coalesced Cu thin films as the Cu film thickness increased. Sheet resistance data also showed that the t = 8 nm film was near the percolation threshold, suggesting that films thinner than 8 nm were aggregations of Cu nanoparticles that were not well-connected. The films thicker than 8 nm were above the percolation threshold. From the Drude model, we estimated the plasmon frequency (ωp) and the electron relaxation time (τ), which were found to increase with increasing film thickness. By applying standard critical point analysis to the second derivatives of the dielectric function spectra, we found several peaks near 1.5, 2.1, 2.5, 3.5, and 4.3 eV, and attributed to interband transitions. The peak energies (except 1.5 eV) matched to the band structure calculations of bulk Cu found in the literature.

Effect of Electron-Withdrawing Substituents on the Epoxide Ring: An Experimental and Theoretical Electron Density Analysis of a Series of Epoxide Derivatives

A series of acceptor-substituted epoxide derivatives is scrutinized by means of experimental and theoretical electron-density investigations. Due to the possibility of nucleophilic ring-opening, the epoxide ring is not only a very useful functional group in organic synthesis, but acceptor-substituted epoxides are valuable building blocks for the design of protease inhibitors. Therefore, the electron-density analysis in this work focuses on two main aspects that can contribute to rational drug design: (i) the quantification of the electron-withdrawing substituent effects on the epoxide ring and (ii) the intermolecular interactions involving the epoxide ring in combination with different substituents. It can be shown that the electron-withdrawing properties of the substituents cause an elongation of the C-C bonds in the epoxide rings and the loss of electron density can be measured by an analysis of critical points, atomic charges, and the source function. The different strengths of the substituents are reflected in these properties. Covalent and electrostatic contributions to the intermolecular interactions and thus the lattice energies are depicted on different molecular surfaces.

Icing Certification of Civil Aircraft Engines

Aeroengine icing is an unwanted phenomenon which can normally lead to the hazardous effect to the power of aircraft during routine flight. To be on the safe side, each civil aircraft engine model must fully meet the strict requirements of icing operation and ice ingestion in the authoritative certification program, and usually this could be demonstrated by using the experimental approach. Base on a concrete engine model, this paper aims to provide an acceptable method of compliance to the engine icing operation and ice ingestion requirements which are demanded by the US airworthiness standards of aircraft engines, i.e., Federal Aviation Administration 14 CFR Part 33, and introduce the application of critical point analysis and experimental arrangement in engine icing certification. Through the textual description, it would be greatly helpful to the industrial community to evaluate the engine anti-icing capability and conduct the ice-slab ingestion demonstration in engine design process.

A novel methodological approach to systematically analyse pandemic influenza response programs within health systems

Background: Pandemic influenza preparedness plans exist in most countries yet the health systems operational capacity to actually implement these is a challenge. Diverse approaches to evaluate pandemic influenza programmes like guidelines, checklists or table top exercises exist yet they do not see the broader health system context in which programs have to function. Here we present an evaluation framework which helps to systematically determine how health systems and pandemic programmes interact, whether, where and which weak points exist; and how and where pandemic response programmes can be improved effectively. Method: The applied evaluation framework draws upon two existing approaches, the Systemic Rapid Assessment Toolkit (SYSRA) and the Hazard Analysis of Critical Control Points (HACCP) modified to systematically assess pandemic preparedness programmes in context. The assessment process can be divided into four basic phases i) data collection, ii) data synthesis, iii) hazard analysis and iv) generating recommendations. Results: The SYSRA is a systematic approach to analyse the interplay between pandemic control programmes and the broader health systems context within which they operate i.e. the meso level. Program functionality is for e.g. influenced by the political, economical, social and legal background of the health system environment. The HACCP methodology extends this to the micro level (service delivery) and builds upon a systematic analysis of predefined successive process steps within a pandemic programme to identify and localise likely hazards and to develop control measures to address them. Discussion: The combination of a systematic data collection tool with an analytical evaluation method provides a simple and rapid means for developing a contextual understanding and for identifying frailties in programmes that need to be responded to. Data collection from different sources (interviews, documents and guidelines) and data triangulation aims to display programme and system functionality as accurately as possible yet as with all models it can only represent reality.

Fur animal botulism hazard due to feed

To assess the botulism hazard in fur animal feed production, 236 fur animal feed components and feed samples were analysed for Clostridium botulinum by detecting BoNT-encoding genes ( botA, botB, botC, botE or botF) by PCR and for sulphite-reducing clostridia (SRC) by iron sulphite agar. The quality of the hazard analysis of critical control points (HACCP) –based in-house control system (IHCS) was evaluated with respect to botulism risk in feed plants ( n = 32). The overall prevalence of C. botulinum was 13% in different feed components and 5% in feed. The estimated MPN count of C. botulinum in feed components was 6.4 × 10 3/kg at the highest and was shown to poorly correlate with SRC count. The critical control points in IHCSs were variable, and control limits were improperly set in most feed-producing plants. C. botulinum possesses a persistent safety hazard for fur animals by feed production, and control practices should be reassessed.

Evaluating health systems’ preparedness for emerging infectious diseases: A novel conceptual and analytic framework

In this article we present a novel conceptual framework for systematically assessing the national health system capacity to respond to pandemic influenza. This framework helps to determine how health systems and pandemic programmes interact, whether, where and which weak points exist, and how and where pandemic response health programmes can be improved effectively. This new conceptual framework draws upon two existing approaches for assessment and evaluation, the Systemic Rapid Assessment Toolkit (SYSRA) and the Hazard Analysis of Critical Control Points (HACCP). SYSRA is a systematic approach to analyse the interplay between communicable disease programmes and the broader health systems context within which they operate and the HACCP methodology builds upon a systematic analysis of process steps within a programme in order to identify likely hazards and to develop control measures to address them. The analytical framework that we have developed from the novel conceptualisation is simple, can be applied rapidly, and should, we believe, be low cost to implement. Thus, this provides a means for developing a contextual understanding of the broader health system in which a pandemic infectious disease programme operates, and for identifying frailties in programmes that need to be responded to.

ChemInform Abstract: Critical Point Representations of Electron Density Maps for the Comparison of Benzodiazepine-Type Ligands.

A procedure for the comparison of three-dimensional electron density distributions is proposed for similarity searches between pharmacological ligands at various levels of crystallographic resolution. First, a graph representation of molecular electron density distributions is generated using a critical point analysis approach. Pairwise as well as multiple comparisons between the obtained graphs of critical points are then carried out using a Monte Carlo/simulated annealing technique, and results are compared with genetic algorithm solutions.

Critical point analysis using domain lifting for fast geometry queries

In this paper, a general scheme for solving coherent geometric queries on freeform geometry is presented and demonstrated on a variety of problems common in geometric modeling. The underlying strategy of the approach is to lift the domain of the problem into a higher-dimensional space to enable analysis on the continuum of all possible configurations of the geometry. This higher-dimensional space supports analysis of changes to solution topology by solving for critical points using a B-spline-based constraint solver. The critical points are then used to guide fast, local methods to robustly update repeated queries. This approach effectively combines the speed of local updates with the robustness of global search solutions. The effectiveness of the domain lifting scheme (DLS) is demonstrated on several geometric computations, including accurately generating offset curves and finding minimum distances. Our approach requires a preprocessing step that computes the critical points, but once the topology is analyzed, an arbitrary number of geometry queries can be solved using fast local methods. Experimental results show that the approach solves for several hundred minimum distance computations between planar curves in one second and results in a hundredfold speedup for trimming self-intersections in offset curves.

New methods to monitor emerging chemicals in the drinkingwater production chain

New techniques enable a shift in monitoring chemicals that affect water quality from mainly at the end product, tap water, towards monitoring during the whole process along the production chain. This is congruent with the 'HACCP' system (hazard analysis of critical control points) that is fairly well integrated into food production but less well in drinking water production. This shift brings about more information about source quality, the efficiency of treatment and distribution, and understanding of processes within the production chain, and therefore can lead to a more pro-active management of drinking water production. At present, monitoring is focused neither on emerging chemicals, nor on detection of compounds with chronic toxicity. We discuss techniques to be used, detection limits compared to quality criteria, data interpretation and possible interventions in production.

Critical points bifurcation analysis of high-ℓ bending dynamics in acetylene

The bending dynamics of acetylene with pure vibrational angular momentum excitation and quantum number l not = 0 are analyzed through the method of critical points analysis, used previously [V. Tyng and M. E. Kellman, J. Phys. Chem. B 110, 18859 (2006)] for l = 0 to find new anharmonic modes born in bifurcations of the low-energy normal modes. Critical points in the reduced phase space are computed for continuously varied bend polyad number N(b) = n(4) + n(5) as l = l(4) + l(5) is varied between 0 and 20. It is found that the local L, orthogonal O, precessional P, and counter-rotator CR families persist for all l. In addition, for l > or = 8, there is a fifth family of critical points which, unlike the previous families, has no fixed relative phase ("off great circle" OGC). The concept of the minimum energy path in the polyad space is developed. With restriction to l=0 this is the local mode family L. This has an intuitive relation to the minimum energy path or reaction mode for acetylene-vinylidene isomerization. With l > or = 0 included as a polyad number, the l = 0 minimum energy path forms a troughlike channel in the minimum energy surface in the polyad space, which consists of a complex mosaic of L, O, and OGC critical points. There is a division of the complete set of critical points into layers, the minimum energy surface forming the lowest.

Theoretical study of halogen bonding between F nH 3−nCBr ( n = 0, 1, 2, 3) and HMgH

In this work, ab initio calculations have been performed to investigate the interaction between F n H 3− n CBr ( n = 0, 1, 2, 3) and HMgH at the MP2/aug-cc-pVTZ level. The results obtained from these calculations reveal the weak non-covalent Br⋯H interactions in all complexes. The calculated interaction energies for the complexes span from −2.17 to −8.98 kJ/mol. Upon complexation, the C–Br and H–Mg bonds are both elongated. Most C–Br stretches have a small red shift, whereas the H–Mg stretch exhibits a blue shift. These complexes are stabilized by the electrostatic interaction, charge transfer interaction and polarization interaction. The halogen-bonding nature of the Br⋯H interactions has been identified in terms of the bond critical point analysis within the theory of atoms in molecules.

Hydrogen bonding interactions in PN···HX complexes: DFT and ab initio studies of structure, properties and topology

Spin-restricted DFT (X3LYP and B3LYP) and ab initio (MP2(fc) and CCSD(fc)) calculations in conjunction with the Aug-CC-pVDZ and Aug-CC-pVTZ basis sets were performed on a series of hydrogen bonded complexes PN...HX (X = F, Cl, Br) to examine the variations of their equilibrium gas phase structures, energetic stabilities, electronic properties, and vibrational characteristics in their electronic ground states. In all cases the complexes were predicted to be stable with respect to the constituent monomers. The interaction energy (Delta E) calculated using a super-molecular model is found to be in this order: PN...HF > PN...HCl > PN...HBr in the series examined. Analysis of various physically meaningful contributions arising from the Kitaura-Morokuma (KM) and reduced variational space self-consistent-field (RVS-SCF) energy decomposition procedures shows that the electrostatic energy has significant contribution to the over-all interaction energy. Dipole moment enhancement (Delta mu) was observed in these complexes expected of predominant dipole-dipole electrostatic interaction and was found to follow the trend PN...HF > PN...HCl > PN...HBr at the CCSD level. However, the DFT (X3LYP and B3LYP) and MP2 levels less accurately determined these values (in this order HF < HCl < HBr). Examination of the harmonic vibrational modes reveals that the PN and HX bands exhibit characteristic blue- and red shifts with concomitant bond contraction and elongation, respectively, on hydrogen bond formation. The topological or critical point (CP) analysis using the static quantum theory of atoms in molecules (QTAIM) of Bader was considered to classify and to gain further insight into the nature of interaction existing in the monomers PN and HX, and between them on H-bond formation. It is found from the analysis of the electron density rho ( c ), the Laplacian of electron charge density nabla(2)rho(c), and the total energy density (H ( c )) at the critical points between the interatomic regions that the interaction N...H is indeed electrostatic in origin (rho(c) > 0, nabla(2)rho(c) > 0 and H(c) > 0 at the BCP) whilst the bonds in PN (rho(c) > 0, nabla(2)rho(c) > 0 and H(c) < 0) and HX ((rho(c) > 0, nabla(2)rho(c) < 0 and H(c) < 0)) are predominantly covalent. A natural bond orbital (NBO) analysis of the second order perturbation energy lowering, E((2)), caused by charge transfer mechanism shows that the interaction N...H is n(N) --> BD*(HX) delocalization.