Search

Materials exhibiting auxetic behavior have garnered significant interest due to their potential applications across various fields, with synthetic auxetic materials being one such group. Theoretical studies have demonstrated the potential for various organic polymeric systems to exhibit auxetic behavior. However, to date, only a few synthesized molecular systems have shown some degree of auxetic behavior. Among the theoretical classes of molecular systems that have attracted attention are calix[4]arene systems in the "egg‐rack" conformation. While the theoretical systems proposed in the literature have been deemed difficult to synthesize, calix[4]arene chemistry has advanced tremendously in recent years. In fact, a number of molecular systems with configurations similar to those predicted to exhibit a negative Poisson's ratio have been synthesized, albeit with different chemical moieties. Consequently, it is deemed valuable to study the potential of these synthesized systems to exhibit a negative Poisson's ratio through force‐field‐based simulations. This study is extended to include theoretical calix[4]arene systems linked by acetylene moieties, which are also potentially synthesizable through known methods. It is suggested that these materials can exhibit auxetic behavior when subjected to on‐axis loading in the [001] direction. A detailed mechanistic study of these systems is also conducted. [ABSTRACT FROM AUTHOR]

This study was part of a project designed to simulate the long-term landform equilibrium of a rehabilitated mine site. The project utilized event Fine Suspended Sediment (FSS) fluxes in a receiving stream following a rainfall event as an indicator of landform stability. The aim of this study was to use HEC-HMS to determine sediment and discharge quantity upstream to determine how it affects the downstream development of the catchment landform, in terms of sediment changes and geomorphology. Thus, the study focused on hydrology and sediment modelling of the upper catchment with HEC-HMS (Hydrologic Engineering Centre-Hydrologic Modelling System) to determine the daily discharge and sediment output at the catchment outlet. HEC-HMS was used to calibrate the stream discharge and FSS quantities at the catchment outlet to observed continuous discharge and FSS values. The calibration of the HEC-HMS model was carried out for two water years and then the same model parameters were used to validate the model for a third water year. The catchment discharge and FSS were calibrated and validated for continuous rainfall events against observed discharge and FSS data at the catchment outlet. The model was then run for a projected rainfall of 50 years. The denudation rate predicted by the model was 0.0245 mm per year, which falls in the range previously determined for the region. The simulated sediment output was compared to the rainfall trends over the years. As a result, the sediment spikes following a rainfall-runoff event gradually decreased over time. Reducing FSS spikes indicates that the landform gradually attains stability. This modelling study can be used for long-term simulations to determine erosion equilibrium over the years and to quantify sediment yield in catchments for projected time periods. [ABSTRACT FROM AUTHOR]

Self-folding behavior is an exciting property of weft-knit fabrics that can be created using just front and back stitches. This behavior is easy to create, but not easy to anticipate and currently cannot be predicted by the existing computer-aided design software that controls industrial knitting machines. This work identifies the edge deformation behaviors that lead to self-folding in weft knits, and methods to characterize the mechanical forces driving these behaviors with regard to chosen manufacturing parameters. With this data and analysis of the fabric deformations, the self-folding behavior was purposely controlled using calculated scaling factors. Furthermore, theoretical equations were developed to mathematically predict these scaling factors, minimizing the trial and error required to design with self-folding behavior and create textiles with novel engineered properties. By understanding the mechanisms responsible for creating these three-dimensional self-folding textiles, they can then be designed in a programmable manner for use in technical applications. [ABSTRACT FROM AUTHOR]

An analytical model for a general Star‐4 system, having different ligament lengths, angles, and ligament thickness, is derived using Castigliano's second theorem. The analytical model is validated through finite element analysis and experimental work. The results obtained show that, depending on the parameters used, the general Star‐4 system can show a wide range of Poisson's ratios with the potential of obtaining giant negative Poisson's ratios (in the order of −8) for certain conformations. The wide range of Poisson's ratio is explained in terms of the different geometrical conformations obtainable by the system, where the star‐ligaments can also describe rhombi, irregular octagons, rectangles, and accordion‐like systems, together with changes in the deformation mechanism due to variations in parameters. For example, if one set of star‐ligaments is much thicker than the other, the deformation of the star would be akin to that of the hexagonal reentrant unit cell. [ABSTRACT FROM AUTHOR]

Materials with a negative Poisson's ratio (auxetic materials) have the fascinating property of becoming fatter when stretched. This article describes some of the consequences of this phenomenon and some of the routes for making polymers with this property. Potential applications for these materials are reviewed.

Abstract Background The epithelial to mesenchymal transition (EMT) is a molecular process through which an epithelial cell undergoes transdifferentiation into a mesenchymal phenotype. The role of EMT in embryogenesis is well-characterized and increasing evidence suggests that elements of the transition may be important in other processes, including metastasis and drug resistance in various different cancers. Methods Agilent 4 × 44 K whole human genome arrays and selected reaction monitoring mass spectrometry were used to investigate mRNA and protein expression in A2780 cisplatin sensitive and resistant cell lines. Invasion and migration were assessed using Boyden chamber assays. Gene knockdown of snail and slug was done using targeted siRNA. Clinical relevance of the EMT pathway was assessed in a cohort of primary ovarian tumours using data from Affymetrix GeneChip Human Genome U133 plus 2.0 arrays. Results Morphological and phenotypic hallmarks of EMT were identified in the chemoresistant cells. Subsequent gene expression profiling revealed upregulation of EMT-related transcription factors including snail, slug, twist2 and zeb2. Proteomic analysis demonstrated up regulation of Snail and Slug as well as the mesenchymal marker Vimentin, and down regulation of E-cadherin, an epithelial marker. By reducing expression of snail and slug, the mesenchymal phenotype was largely reversed and cells were resensitized to cisplatin. Finally, gene expression data from primary tumours mirrored the finding that an EMT-like pathway is activated in resistant tumours relative to sensitive tumours, suggesting that the involvement of this transition may not be limited to in vitro drug effects. Conclusions This work strongly suggests that genes associated with EMT may play a significant role in cisplatin resistance in ovarian cancer, therefore potentially leading to the development of predictive biomarkers of drug response or novel therapeutic strategies for overcoming drug resistance.

Abstract Multiple myeloma (MM) is the second most common hematological malignancy in adults. It is characterized by clonal proliferation of terminally differentiated B lymphocytes and over-production of monoclonal immunoglobulins. Recurrent genomic aberrations have been identified to contribute to the aggressiveness of this cancer. Despite a wealth of knowledge describing the molecular biology of MM as well as significant advances in therapeutics, this disease remains fatal. The identification of biomarkers, especially through the use of mass spectrometry, however, holds great promise to increasing our understanding of this disease. In particular, novel biomarkers will help in the diagnosis, prognosis and therapeutic stratification of MM. To date, results from mass spectrometry studies of MM have provided valuable information with regards to MM diagnosis and response to therapy. In addition, mass spectrometry was employed to study relevant signaling pathways activated in MM. This review will focus on how mass spectrometry has been applied to increase our understanding of MM.

An extensive investigation is carried out on the missing rib square grid structure using finite element simulations. This showed that, in the cases considered in this study, the type of deformation is primarily dependent on the ratio of the thickness of different ribs with the structure behaving like an anti-tetrachiral at particular ratios. The analysis also showed that the ability of the structure to deform predominantly through the bending of the ligament allows it to achieve much more negative values of the Poisson's ratio than previously reported. Confirmation of the numerical results is obtained through experimental methods involving the 3D printing of representative structures which are subsequently subjected to compression. [ABSTRACT FROM AUTHOR]

Vibrating structures, such as gas turbine engines, are assemblages of multiple components interfaced with each other through physical contact. The friction produced at these contact interfaces, by sliding or slipping at the interface, is a source of energy dissipation, resulting in damping effects. This passive approach to damping is exploited by engineers to provide optimal energy dissipation to attenuate vibration in a variety of systems (such as bladed disc assemblies and airfoils), to prevent wear and premature failure. However, the highly nonlinear nature of friction renders accurate predictive modeling of such a problem challenging. This article gives an overview of the current state of the art, and the methods used for mathematical and predictive computational modeling of vibrating systems under the influence of dry friction. [ABSTRACT FROM AUTHOR]

This study examines the recycling of polytetrafluoroethylene (PTFE)/glass fiber (GF) printed circuit boards (PCB) laminates through mechanical grinding and the re-manufacture of new composites incorporating PTFE/GF recyclate using sintering processes with and without pressure (SWOP and SWP). The PTFE/GF recyclate was tested for mechanical and dielectric performance. Experimental data were fitted to modified Lichtenecker and Effective-Medium Theory (EMT) theoretical equations to estimate the dielectric constant of PTFE/GF recyclate subsheets for further use in new PTFE/GF laminates. It was found that the experimental values were inside of the Wiener bounds and fitted well the two theories for both manufacturing methods proposed. Overall, the results showed that PTFE/GF recyclate could be used as replacement for virgin PTFE/GF when incorporated in specific concentrations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) is the second most common hematological malignancy in adults. It is characterized by clonal proliferation of terminally differentiated B lymphocytes and over-production of monoclonal immunoglobulins. Recurrent genomic aberrations have been identified to contribute to the aggressiveness of this cancer. Despite a wealth of knowledge describing the molecular biology of MM as well as significant advances in therapeutics, this disease remains fatal. The identification of biomarkers, especially through the use of mass spectrometry, however, holds great promise to increasing our understanding of this disease. In particular, novel biomarkers will help in the diagnosis, prognosis and therapeutic stratification of MM. To date, results from mass spectrometry studies of MM have provided valuable information with regards to MM diagnosis and response to therapy. In addition, mass spectrometry was employed to study relevant signaling pathways activated in MM. This review will focus on how mass spectrometry has been applied to increase our understanding of MM. [ABSTRACT FROM AUTHOR]

Population densities, population fluctuations, yield loss and disease incidence caused by Nacobbus aberrans on tomato (Lycopersicon esculentum) were studied, using an epidemiological approach, in a field experiment that included three different control regimes: an integrated control (IC) scheme, which included fertilisation, nematicide (ethoprop) and chicken manure; a technical control (TC) scheme, based on the best local practices of fertilisation and use of carbofuran for nematode control; and a check treatment (AC), with no application of fertilisers or nematicide. At least three generations of N. aberrans occurred through the cropping season and the numbers of galls/plant and females/g of root through the crop season were used to define the area under a disease progress curve (AUDPC). The variables b-1 (Weibull's apparent infection rate), AUDPC and Yf (final disease incidence) indicated less crop damage under the IC scheme than under the other two schemes (TC and AC). The IC scheme resulted in increased plant height (41-49%), foliage dry weight (37-53%) and stem diameter (31-41%) compared with the TC and AC schemes. Tomato yields in IC surpassed those from TC and AC by 34 and 83%, respectively, while TC exceeded AC by 73%. The yield loss attributed to N. aberrans was 12, 29 and 83% in IC, TC and AC, respectively. The IC scheme improved commercial production by 20 and 81% in comparison to the TC and AC schemes. This was largely due to effective control of the initial inoculum density, which affects the first generation of the nematode population; control of this generation is essential for avoidance of yield loss. The first generation is completed during the period 0-60 dat (days after transplanting), i.e., during the critical stages of flowering, fruit initiation and fruit set (40, 50 and 60 dat). Data on plant performance taken every 10 days were used to derive a multiple point model for calculation of production loss. [ABSTRACT FROM AUTHOR]

Populations of potato cyst nematode (PCN) were assembled from all of the potato growing regions of Portugal, either by direct sampling of fields or from cyst samples sent to the University of Coimbra for identification. When 30 or more cysts were available, isoelectric focusing of species-specific protein bands was used to identify which PCN species were present. PCN was present in 35% of a set of 226 soil samples. PCN was also identified in a larger set of 423 populations. Of the 423 populations, 83% were pure Globodera rostochiensis, 8% were pure G. pallida and 9% were mixtures of the two. PCN was found in all of the main potato growing areas but G. pallida was not detected in Coimbra, Setúbal or Viana do Castelo districts. [ABSTRACT FROM AUTHOR]

A new software tool, GACOMP, for the optimal design of general and symmetric/balanced laminates (or sandwich panels) with specified mechanical properties has been developed. The approach taken relies on the analysis of a given laminate, of known materials and stacking sequence, and on an efficient genetic algorithm-based optimization procedure to come up with the best design with respect to single or multiple objectives and constraints. Required engineering constants or their ratios, weight, strength, anisotropy, isotropy, or twist, considered individually or in any combination, can be used as optimization objectives. Several improvements to the genetic algorithms were introduced to provide faster convergence and the ability to identify multiple optima in a single run. Two practical examples are presented to show the effective performance of GACOMP The first tackles the design of a composite laminate with specified in-plane and flexural engineering constants, while the second deals with the design of a laminate with specified stiffness ratios, minimum twisting under the load considered, and maximum strength. [ABSTRACT FROM AUTHOR]

Twelve populations of Nacobbus aberrans from Mexico and South America were cultured in the glasshouse on tomato plants. Second stage juveniles, males, young females and mature females were recovered from the cultures and studied using light microscopy. Morphometric data were analysed using canonical variate analysis. Many of the characters previously used to establish species or subspecific ranks were shown to be variable and all variants occurred in all populations studied, even if at low frequencies. Etude morphometrique de douze populations de Nacobbus aberrans (Thorne, 1935) Thorne & Allen, 1944 (Nematoda: Pratylenchidae) du Mexique et d'Amerique du Sud - Douze populations de Nacobbus aberrans du Mexique et d'Amerique du Sud ont ete elevees en serre sur plants de tomate. Les juveniles de deuxieme stade, les males, les femelles jeunes et les femelles matures ont ete recoltes a partir de ces elevages et etudies en microscopie photonique. Les donnees morphometriques ont ete analysees par analyse canonique. De nombreux caracteres precedemment utilises aux niveaux specifique ou subspecifique sont apparus variables, tous les variants etant presents dans toutes les populations etudiees, a des frequences parfois faibles mais jamais nulles. [ABSTRACT FROM AUTHOR]

Introduces and comments on articles on psychotherapy, published in the December 2001 issue of the 'European Journal of Psychotherapy, Counselling and Health.' Survey of European psychotherapy training; Subject benchmarking; Absence of a sociological perspective to the issue of psychotherapy.