Span morphing using the compliant spar

This paper develops and models the Compliant Spar concept that allows the wing span to be varied to provide roll control and enhance the operational performance for a medium altitude long endurance (MALE) UAV. The wing semi-span is split into morphing partitions and the concept maybe incorporated in each partition; however only the tip partition is considered here. The Compliant Spar is made of compliant joints arrange in series to allow the partition to be flexible under axial (spanwise) loads but at the same time stiff enough to resist bending loads. Each compliant joint consists of two concentric overlapping AL 2024-T3 tubes joined together using elastomeric material. Under axial (spanwise) loading, the elastomeric material deforms in shear allowing the overlapping distance between the tubes to vary and hence the length (in the spanwise direction) of the joint/spar to vary. High fidelity modelling of the concept is performed. Then, structural optimisation studies are performed to minimise the axial stiffness and the structural mass of the concept for various design constraints. The flexible skin and actuation system to be used are also addressed

Multi-resolution texture classification based on local image orientation

The aim of this paper is to evaluate quantitatively the discriminative power of the image orientation in the texture classification process. In this regard, we have evaluated the performance of two texture classification schemes where the image orientation is extracted using the partial derivatives of the Gaussian function. Since the texture descriptors are dependent on the observation scale, in this study the main emphasis is placed on the implementation of multi-resolution texture analysis schemes. The experimental results were obtained when the analysed texture descriptors were applied to standard texture databases

The causal boundary of wave-type spacetimes

A complete and systematic approach to compute the causal boundary of wave-type spacetimes is carried out. The case of a 1-dimensional boundary is specially analyzed and its critical appearance in pp-wave type spacetimes is emphasized. In particular, the corresponding results obtained in the framework of the AdS/CFT correspondence for holography on the boundary, are reinterpreted and very widely generalized. Technically, a recent new definition of causal boundary is used and stressed. Moreover, a set of mathematical tools is introduced (analytical functional approach, Sturm-Liouville theory, Fermat-type arrival time, Busemann-type functions).Comment: 41 pages, 1 table. Included 4 new figures, and some small modifications. To appear in JHE

Constitutive heterochromatin polymorphisms in human chromosomes identified by whole comparative genomic hybridization

Whole comparative genomic hybridization (W-CGH) is a new technique that reveals cryptic differences in highly repetitive DNA sequences, when different genomes are compared using metaphase or interphase chromosomes. W-CGH provides a quick approach to identify differential expansion of these DNA sequences at the single-chromosome level in the whole genome. In this study, we have determined the frequency of constitutive chromatin polymorphisms in the centromeric regions of human chromosomes using a whole-genome in situ cross-hybridization method to compare the whole genome of five different unrelated individuals. Results showed that the pericentromeric constitutive heterochromatin of chromosome 6 exhibited a high incidence of polymorphisms in repetitive DNA families located in pericentromeric regions. The constitutive heterochromatin of chromosomes 5 and 9 was also identified as highly polymorphic. Although further studies are necessary to corroborate and assess the overall incidence of these polymorphisms in human populations, the use of W-CGH could be pertinent and of clinical relevance to assess rapidly, from a chromosomal viewpoint, genome similarities and differences in closely related genomes such as those of relatives, or in more specific situations such as bone marrow transplantation where chimerism is produced in the recipient

Chromosomal damage as prognosis marker in cervical carcinogenesis

Cancer of the uterine cervix is the third most common cancer in women worldwide and the most common cancer among Mexican and Latin American women. Risk factors that have been associated with the development of cervical intraepithelial neoplasia suggest that Human Papillomavirus (HPV) types 16, 18, 31, and 33 entail a high risk of developing a malignancy of this type. The accumulation of genetic alterations allows the growth of neoplastic cells; chromosomal instability is an event that occurs in the precancerous stages. The candidate cancer risk biomarkers include cytogenetic endpoints, such as chromosomal aberrations, sister chromatid exchange, micronuclei, and the outcomes of comet assay and DNA breakage detection-fluorescence in situ hybridization. The patterns identified in these cytogenetic studies indicate that chromosomal instability is a transient and chromosomally unstable intermediate in the development of cervical lesions. In this context, the mechanisms that may underlie the progressive increase in genetic instability in these patients seem to be related directly to HPV infection. The studies discussed in this paper show that chromosomal instability may serve as a biomarker by predicting the progression of cervical intraepithelial neoplasia. Nevertheless, these results should be validated in larger, prospective studies.Рак шейки матки является третьим по распространенности в мире типов рака у женщин и наиболее часто встречающимся у женщин Мексики и Латинской Америки. Факторы риска, связанные с развитием интраэпителиальной цервикальной неоплазии, предполагают, что папилломавирус человека (HPV) типов 16, 18, 31 и 33 влечет за собой высокий риск развития опухолей этого типа. Накопление генетических изменений делает возможным рост опухолевых клеток, хромосомная нестабильность является событием, которое предшествует предраковым стадиям. Возможные биомаркеры риска опухоли включают цитогенетические критерии, такие как хромосомные аберрации, обмен сестринских хроматид, микроядра, и заканчиваются Comet-анализом и детекцией поломок ДНК с помощью флюоресцентной гибридизации in situ. Образцы, идентифицированные в таких цитогенетических исследованиях, показывают, что хромосомная нестабильность является транзиентным промежуточным звеном в развитии цервикальных нарушений. В этой связи механизмы, которые могут лежать в основе прогрессирующей генетической нестабильности у таких пациентов, кажутся непосредственно связанными с инфекцией HPV. Настоящее исследование показывает, что хромосомная нестабильность может служить биомаркером для предсказания развития интраэпителиальной цервикальной неоплазии, тем не менее эти результаты должны быть оценены в более масштабных исследованиях

Geosynchronous inclined orbits for high-latitude communications

We present and discuss a solution to the growing demand for satellite telecommunication coverage in the high-latitude geographical regions (beyond N), where the signal from geostationary satellites is limited or unavailable. We focus on the dynamical issues associated to the design, the coverage, the maintenance and the disposal of a set of orbits selected for the purpose. Specifically, we identify a group of highly inclined, moderately eccentric geosynchronous orbits derived from the Tundra orbit (geosynchronous, eccentric and critically inclined). Continuous coverage can be guaranteed by a constellation of three satellites in equally spaced planes and suitably phased. By means of a high-precision model of the terrestrial gravity field and the relevant environmental perturbations, we study the evolution of these orbits. The effects of the different perturbations on the ground track (which is more important for coverage than the orbital elements themselves) are isolated and analyzed. The physical model and the numerical setup are optimized with respect to computing time and accuracy. We show that, in order to maintain the ground track unchanged, the key parameters are the orbital period and the argument of perigee. Furthermore, corrections to the right ascension of the ascending node are needed in order to preserve the relative orientation of the orbital planes. A station-keeping strategy that minimizes propellant consumption is then devised, and comparisons are made between the cost of a solution based on impulsive maneuvers and one with continuous thrust. Finally, the issue of end-of-life disposal is discussed

Lubricated revolute joints in rigid multibody systems

The main purpose of this work is to present a general methodology for modeling lubricated revolute joints in constrained rigid multibody systems. In the dynamic analysis of journal-bearings, the hydrodynamic forces, which include both squeeze and wedge effects, generated by the lubricant fluid, oppose the journal motion. The hydrodynamic forces are obtained by integrating the pressure distribution evaluated with the aid of Reynolds’ equation, written for the dynamic regime. The hydrodynamic forces built up by the lubricant fluid are evaluated from the system state variables and included into the equations of motion of the multibody system. Numerical examples are presented in order to demonstrate the use of the methodologies and procedures described in this work.Fundação para a Ciência e a Tecnologia (FCT

Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity

Volatile esters, a major class of compounds contributing to the aroma of many fruit, are synthesized by alcohol acyl-transferases (AAT). We demonstrate here that, in Charentais melon (Cucumis melo var. cantalupensis), AAT are encoded by a gene family of at least four members with amino acid identity ranging from 84% (Cm-AAT1/Cm-AAT2) and 58% (Cm-AAT1/Cm-AAT3) to only 22% (Cm-AAT1/Cm-AAT4). All encoded proteins, except Cm-AAT2, were enzymatically active upon expression in yeast and show differential substrate preferences. Cm-AAT1 protein produces a wide range of short and long-chain acyl esters but has strong preference for the formation of E-2-hexenyl acetate and hexyl hexanoate. Cm-AAT3 also accepts a wide range of substrates but with very strong preference for producing benzyl acetate. Cm-AAT4 is almost exclusively devoted to the formation of acetates, with strong preference for cinnamoyl acetate. Site directed mutagenesis demonstrated that the failure of Cm-AAT2 to produce volatile esters is related to the presence of a 268-alanine residue instead of threonine as in all active AAT proteins. Mutating 268-A into 268-T of Cm-AAT2 restored enzyme activity, while mutating 268-T into 268-A abolished activity of Cm-AAT1. Activities of all three proteins measured with the prefered substrates sharply increase during fruit ripening. The expression of all Cm-AAT genes is up-regulated during ripening and inhibited in antisense ACC oxidase melons and in fruit treated with the ethylene antagonist 1-methylcyclopropene (1-MCP), indicating a positive regulation by ethylene. The data presented in this work suggest that the multiplicity of AAT genes accounts for the great diversity of esters formed in melon

Hyperon semileptonic decays and quark spin content of the proton

We investigate the hyperon semileptonic decays and the quark spin content of the proton $\Delta \Sigma$ taking into account flavor SU(3) symmetry breaking. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. As a result we predict the unmeasured decay constants, particularly for $\Xi^0 \to \Sigma^+$, which will be soon measured and examine the effect of the SU(3) symmetry breaking on the spin content $\Delta \Sigma$ of the proton. Unfortunately large experimental errors of $\Xi^-$ decays propagate in our analysis making $\Delta \Sigma$ and $\Delta s$ practically undetermined. We conclude that statements concerning the values of these two quantities, which are based on the exact SU(3) symmetry, are premature. We stress that the meaningful results can be obtained only if the experimental errors for the $\Xi$ decays are reduced.Comment: The final version accepted for publication in Phys. Rev. D. 18 pages, RevTex is used with 4 figures include