Designing spatial correlation of quantum dots: towards self-assembled three-dimensional structures

Buried two-dimensional arrays of InP dots were used as a template for the lateral ordering of self-assembled quantum dots. The template strain field can laterally organize compressive (InAs) as well as tensile (GaP) self-assembled nanostructures in a highly ordered square lattice. High-resolution transmission electron microscopy measurements show that the InAs dots are vertically correlated to the InP template, while the GaP dots are vertically anti-correlated, nucleating in the position between two buried InP dots. Finite InP dot size effects are observed to originate InAs clustering but do not affect GaP dot nucleation. The possibility of bilayer formation with different vertical correlations suggests a new path for obtaining three-dimensional pseudocrystals.

Clinical evaluation of the association of noncarious cervical lesions, parafunctional habits, and TMD diagnosis

Objective: To verify a potential association between the presence of noncarious cervical lesions, parafunctional habits, and temporomandibular disorder (TMD) diagnosis. Method and Materials: Sample-size calculation provided a value of 130 participants with a confidence level of 95% and an error margin of 5%. A population of 132 volunteers (30 men: mean age, 23.7 +/- 3.05 years; 102 women: mean age, 24.9 +/- 5.86 years) underwent an oral examination and was interviewed by a trained dentist. The following parameters were registered: personal details, TMD diagnosis, parafunctional habits, and noncarious cervical lesion presence. The population was then divided into a noncarious cervical lesion group and a control group and subjected to the t test, chi-square test, Fisher exact test, and Spearman correlation (alpha = .05). Results: Noncarious cervical lesions were present in 39% of the population, with the largest concentrations found in the maxillary premolars (32%). The data showed a significant association between noncarious cervical lesion presence, tooth clenching (P = .03), and nail biting (P = .02), as well as a relation with TMD diagnosis (Fonseca Index [P = .01] and Research Diagnostic Criteria for TMD (RDC/TMD) [P = .004] ). In the noncarious cervical lesion group, direct rank correlation was found between maxillary premolars and clenching (P = .03), mandibular canines and nail biting (P = .05), and mandibular incisors and parafunctional habits without dental contacts (P = .02). Conclusion: Parafunctional habits and TMD presence should be taken into account in the diagnosis and treatment plan of noncarious cervical lesions.

Roadside vegetation: estimation and potential for carbon sequestration

The present paper reports the assessment of the vegetation occupancy rate of the roadside, through analysis of aerial photographs. Using such value the potential of these areas to be employed as carbon (C) sinks was also assessed. Moreover, for the areas suitable for afforestation, the potential for carbon sequestration was estimated considering different species of vegetation, both native (scenario 1) and exotic (formed by Pinus sp. and Eucalyptus sp. - scenario 2). The study was carried out through GIS techniques and two regions were considered. A set of equations was used to estimate the rate of occupancy over the study areas, as well as amounts of fixed C under the above scenarios. The average occupancy rate was 0.06%. The simulation showed a higher potential for C sequestration in scenario 2, being the estimated amounts of CO(2) sequestered from the atmosphere per km of roadside: 131 tons of CO(2) km(-1) of highway to native species and 655 tons of CO(2) km(-1) of highway for exotic species (over period of 10 years for both estimates). If we consider the whole road network of the São Paulo State (approximately 190 000 km) and that a considerable part of this road work is suitable to receive this kind of service, it is possible to predict the very high potential for C sequestration if managers and planners consider roadside as area for afforestation.

Theory of electrical characteristics for metal-oxide-insulator Schottky barrier and metal-insulator-metal structures

The metal-insulator or metal-amorphous semiconductor blocking contact is still not well understood. Here, the intimate metal-insulator and metal-oxide-insulator contact are discussed. Further, the steady-state characteristics of metal-oxide-insulator-metal structures are also discussed. Oxide is an insulator with wider energy band gap (about 50 Å thick). A uniform energetic distribution of impurities is considered in addition to impurities at a single energy level inside the surface charge region at the oxide-insulator interface. Analytical expressions are presented for electrical potential, field, thickness of the depletion region, capacitance, and charge accumulated in the surface charge region. The electrical characteristics are compared with reference to relative densities of two types of impurities. ln I is proportional to the square root of applied potential if energetically distributed impurities are relatively important. However, distribution of the electrical potential is quite complicated. In general energetically distributed impurities can considerably change the electrical characteristics of these structures.

Thermal effects on the catalysis by a magnetic field

We show that the formation of condensates in the presence of a constant magnetic field in 2+1 dimensions is extremely unstable. It disappears as soon as a heat bath is introduced with or without a chemical potential. The value of the condensate as well as other observables are shown to become nonanalytic at finite temperature.

Critical coupling for dynamical chiral-symmetry breaking with an infrared finite gluon propagator

We compute the critical coupling constant for the dynamical chiral-symmetry breaking in a model of quantum chromodynamics, solving numerically the quark self-energy using infrared finite gluon propagators found as solutions of the Schwinger-Dyson equation for the gluon, and one gluon propagator determined in numerical lattice simulations. The gluon mass scale screens the force responsible for the chiral breaking, and the transition occurs only for a larger critical coupling constant than the one obtained with the perturbative propagator. The critical coupling shows a great sensibility to the gluon mass scale variation, as well as to the functional form of the gluon propagator.

Infrared finite solutions for the gluon propagator and the QCD vacuum energy

Nonperturbative infrared finite solutions for the gluon polarization tensor have been found, and the possibility that gluons may have a dynamically generated mass is supported by recent Monte Carlo simulation on the lattice. These solutions differ among themselves, due to different approximations performed when solving the Schwinger-Dyson equations for the gluon polarization tensor. Only approximations that minimize energy are meaningful, and, according to this, we compute an effective potential for composite operators as a function of these solutions in order to distinguish which one is selected by the vacuum. © 1997 Elsevier Science B.V.

Closed expressions for Lie algebra invariants and finite transformations

A simple procedure to obtain complete, closed expressions for Lie algebra invariants is presented. The invariants are ultimately polynomials in the group parameters. The construction of finite group elements requires the use of projectors, whose coefficients are invariant polynomials. The detailed general forms of these projectors are given. Closed expressions for finite Lorentz transformations, both homogeneous and inhomogeneous, as well as for Galilei transformations, are found as examples.

Induced variational method from supersymmetric quantum mechanics and the screened Coulomb potential

The formalism of supersymmetric quantum mechanics supplies a trial wave function to be used in the variational method. The screened Coulomb potential is analyzed within this approach. Numerical and exact results for energy eigenvalues are compared.

Coherent atomic oscillations and resonances between coupled Bose-Einstein condensates with time-dependent trapping potential

The atomic tunneling between two tunnel-coupled Bose-Einstein condensates (BECs) in a double-well time-dependent trap was studied. For the slowly varying trap, synchronization of oscillations of the trap with oscillations of the relative population was predicted. Using the Melnikov approach, the appearance of the chaotic oscillations in the tunneling phenomena between the condensates was confirmed.

Two short peptides including segments of subunit A of Escherichia coli DNA gyrase as potential probes to evaluate the antibacterial activity of quinolones

Quinolones constitute a family of compounds with a potent antibiotic activity. The enzyme DNA gyrase, responsible for the replication and transcription processes in DNA of bacteria, is involved in the mechanism of action of these drugs. In this sense, it is believed that quinolones stabilize the so-called 'cleavable complex' formed by DNA and gyrase, but the whole process is still far from being understood at the molecular level. This information is crucial in order to design new biological active products. As an approach to the problem, we have designed and synthesized low molecular weight peptide mimics of DNA gyrase. These peptides correspond to sequences of the subunit A of the enzyme from Escherichia coli, that include the quinolone resistance-determining region (positions 75-92) and a segment containing the catalytic Tyr-122 (positions 116-130). The peptide mimic of the non-mutated enzyme binds to ciprofloxin (CFX) only when DNA and Mg2+ were present (Kd = 1.6 × 10 -6 m), a result previously found with DNA gyrase. On the other hand, binding was reduced when mutations of Ser-83 to Leu-83 and Asp-87 to Asn-87 were introduced, a double change previously found in the subunit A of DNA gyrase from several CFX-resistant clinical isolates of E. coli. These results suggest that synthetic peptides designed in a similar way to that described here can be used as mimics of gyrases (topoisomerases) in order to study the binding of the quinolone to the enzyme-DNA complex as well as the mechanism of action of these antibiotics. Copyright © 2001 European Peptide Society and John Wiley & Sons, Ltd.

Potential of Brazilian eugenia myrtaceae - As ornamental and as a fruit crop

Brazilian Myrtaceae comprises several genera of trees and shrubs used for ornamental and fruit production. In addition to the well known Guava, Pitanga and Jaboticaba, other species could be used for fruitculture, due the value and quality of their fruits and adaptation to some climate conditions mainly the subtropical one. Nine species of Eugenia were evaluated at Jaboticabal, located at 48° W and 21° S in São Paulo state in a germplasm bank. The average rain by year is 1431 mm and the temperature 22,2° C at an altitude of 575 m. The species are Eugenia klozschiana Berg. (Pero-do-campo), E. stipitata Mc Vaugh (Araça-boi), E. tomentosa Camb. (Cabeludinha), E. dysentherica DC. (Cagaita), E. brasiliensis Berg. (Grumixama), E.pitanga (Pitanga-anã), E. luchsnathiana Berg. (Pitomba), E. uvalha Camb. (Uvaia) and E. involucrata DC. (Cereja-do-rio-grande). The evaluations comprised tree development, fruit quality and leaf and flower morphological studies. The main results are: the trees of Pera-do-campo and Pitanga-anã are small shrubs of 1 to 2 m height, Araça-boi and Cabeludinha are small trees, 3 to 5 m high, and the other species are tall trees, with 5 to 10 m height. The species adapted well to the subtropical conditions, except for Araça-boi, which is native to the Amazonian region and exhibited a severe fungus disease infection. In relation to fruit quality, all the species had edible fruit, some were sweet and juicy, Cabeludinha, Grumixama, Pitomba, Cereja-do-rio grande and Pitanga-anã, while others had high acidity (Araça-boi, Pera-do-campo, Cagaita and Uvaia and were more suitable for processing. Simple, single leaves were characteristic of all species, but with different sizes and shapes., With the addition of color, smell and other characteristics, leaf size and shape were useful for comparative classification. Flower components and structure are described also.

In vitro propagation of Maytenus ilicifolia (Celastraceae) as potential source for antitumoral and antioxidant quinomethide triterpenes production. A rapid quantitative method for their analysis by reverse-phase high-performance liquid chromatography

Cell culture of Maytenus ilicifolia were established in order to produce and to quantify the antitumoral and antioxidant quinonemethide triterpenes. In vitro calli were induced from leaf explants of native plants and cultured in semi-solid medium under controlled conditions of humidity, temperature and photoperiod. The quinonemethide triterpenes showed maximum accumulation in the logarithmic phase growth of the cell culture. A rapid, sensitive and reliable reverse-phase HPLC method was used for quantitative determination of the antitumoral and antioxidant quinonemethide triterpenes, 22β-hydroxymaytenin and maytenin in callus of Maytenus ilicifolia. Well resolved peaks with good detection response and linearity in the range 1.0 - 100 μg/mL were obtained. This quantitative work was performed by an external standard method.

Final state and thermodynamics of a dark energy universe

As it follows from the classical analysis, the typical final state of a dark energy universe where a dominant energy condition is violated is a finite-time, sudden future singularity (a big rip). For a number of dark energy universes (including scalar phantom and effective phantom theories as well as specific quintessence models) we demonstrate that quantum effects play the dominant role near a big rip, driving the universe out of a future singularity (or, at least, moderating it). As a consequence, the entropy bounds with quantum corrections become well defined near a big rip. Similarly, black hole mass loss due to phantom accretion is not so dramatic as was expected: masses do not vanish to zero due to the transient character of the phantom evolution stage. Some examples of cosmological evolution for a negative, time-dependent equation of state are also considered with the same conclusions. The application of negative entropy (or negative temperature) occurrence in the phantom thermodynamics is briefly discussed.

Classification of petroleum well drilling operations using Support Vector Machine (SVM)

During the petroleum well drilling operation many mechanical and hydraulic parameters are monitored by an instrumentation system installed in the rig called a mud-logging system. These sensors, distributed in the rig, monitor different operation parameters such as weight on the hook and drillstring rotation. These measurements are known as mud-logging records and allow the online following of all the drilling process with well monitoring purposes. However, in most of the cases, these data are stored without taking advantage of all their potential. On the other hand, to make use of the mud-logging data, an analysis and interpretationt is required. That is not an easy task because of the large volume of information involved. This paper presents a Support Vector Machine (SVM) used to automatically classify the drilling operation stages through the analysis of some mud-logging parameters. In order to validate the results of SVM technique, it was compared to a classification elaborated by a Petroleum Engineering expert. © 2006 IEEE.