A Transition State Theory for Calculating Hopping Times and Diffusion in Highly Confined Fluids

Monte Carlo simulation is used to study the dynamical crossover from single file diffusion to normal diffusion in fluids confined to narrow channels. We show that the long time diffusion coefficients for a series of systems involving hard and soft interaction potentials can be described in terms of a hopping time that measures the time it takes for a particle to escape the cage formed by its neighbors in the pore. Free energy barriers for the particle hopping process are calculated and used to show that transition state theory effectively describes the hopping time for all the systems studied, over a range of pore diameters. Our work suggests that the combination of hopping times and transition state theory offers a useful and general framework to describe the dynamics of these highly confined fluids.Comment: 6 figure

Localized Fibrous Tumors of the Pleura: Experience With 7 Recent Cases

OBJECTIVE: Localized fibrous tumors of the pleura are rare. We report 7 cases and review the literature in order to define the range of clinical characteristics of these tumors, treatment options, and prognosis. METHODS: A retrospective review of 7 cases treated between 1997 and 2003, focusing on clinical presentation, diagnostic tests, and treatment. The tumor was removed surgically in all cases, by thoracotomy in 6 cases and by video-assisted thoracoscopic surgery in 1 patient. RESULTS: All patients recovered fully after surgery, with no postoperative complications. One patient experienced recurrence twice, 33 and 67 months after the initial resection. All are alive at the time of writing, after a mean follow up period of 19 months (range 1 month to 5 years and 10 months). CONCLUSIONS: The treatment of choice for a fibrous tumor of the pleura is full resection and follow up to detect possible late recurrence

Resultados a medio y largo plazo de la utilización de videotoracoscopia en la cirugía de resección de las metástasis pulmonares

The surgical resection of pulmonary metastases is a method of treatment accepted as habitual in thoracic surgery. However, it continues to be a source of controversy if this resection must be realised by thoracotomy or by modern video-assisted techniques. With the aim of finding a response to this controversy in our work milieu, a review was made of the surgical interventions carried out in order to resect pulmonary metastases. Between January 1997 and December 2001, 56 patients were found whose pulmonary metastases had been resected by videothorascopy out of a total of 252 metastasectomies (22.2%). The primary tumours were classified in 4 groups: sarcoma (n=11); colorectal (n=25); renal (n=5); and others (n=15). Videothoroscopy was carried out on the right hemithorax (n=28), left hemithorax (n=22) or on both at once (n=6). Operational mortality was nil and the only morbidity attributable to the technique was a defect of re-expansion following the removal of the thoracic drainage in one patient. Using the Kaplan-Meier method, the probability of survival in this series of patients was 60.4% after 5 years, with an average survival time of 48 months. All of this data supports the use of videothorascopy in our milieu on patients with pulmonary metastases. However, in the light of the results, it is important in using this technique to place special emphasis on obtaining good margins of resection, due to the real risk of local recurrence on these margins in the medium term

Mathematical modeling of auxetic systems : bridging the gap between analytical models and observation

The Poisson’s ratio, a property which quantifies the changes in thickness when a material is stretched and compressed, can be determined as the negative of the transverse strain over the applied strain. In the scientific literature, there are various ways how strain may be defined and the actual definition used could result in a different Poisson’s ratio being computed. This paper will look in more detail at this by comparing the more commonly used forms of strain and the Poisson’s ratio that is computable from them. More specifically, an attempt is made to assess through examples on the usefulness of the various formulations to properly describe what can actually be observed, thus providing a clearer picture of which form of Poisson’s ratio should be used in analytical modelling.peer-reviewe

A novel mechanical metamaterial exhibiting auxetic behavior and negative compressibility

Auxetics (negative Poisson’s ratio) and materials with negative linear compressibility (NLC) exhibit the anomalous mechanical properties of getting wider rather than thinner when stretched and expanding in at least one direction under hydrostatic pressure, respectively. A novel mechanism—termed the ‘triangular elongation mechanism’—leading to such anomalous behavior is presented and discussed through an analytical model. Amongst other things, it is shown that this novel mechanism, when combined with the well-known ‘rotating squares’ model, can generate giant negative Poisson’s ratios when the system is stretched.peer-reviewe

The multidirectional auxeticity and negative linear compressibility of a 3D mechanical metamaterial

In this work, through the use of a theoretical model, we analyse the potential of a specific three-dimensional mechanical metamaterial composed of arrowhead-like structural units to exhibit a negative Poisson’s ratio for an arbitrary loading direction. Said analysis allows us to assess its suitability for use in applications where materials must be able to respond in a desired manner to a stimulus applied in multiple directions. As a result of our studies, we show that the analysed system is capable of exhibiting auxetic behaviour for a broad range of loading directions, with isotropic behaviour being shown in some planes. In addition to that, we show that there are also certain loading directions in which the system manifests negative linear compressibility. This enhances its versatility and suitability for a number of applications where materials exhibiting auxetic behaviour or negative linear compressibility are normally implemented.peer-reviewe

Auxetic-inspired honeycomb macrostructures with anomalous tailormade thermal expansion properties including “negative” heat-shrinking characteristics

Negative thermal expansion (NTE) materials and structures exhibit the anomalous property of shrinking rather than expanding when heated. This work examines the potential of multimaterial planar re-entrant and non-re-entrant honeycombs to exhibit anomalous thermal expansion properties. Expressions for the coefficient of thermal expansion as a function of the geometric parameters and intrinsic thermal expansion properties were derived for any in-plane direction. It was shown that re-entrant honeycombs, a metamaterial which is well known for its auxetic characteristics, can be made to exhibit NTE in specific directions when constructed from conventional positive thermal expansion (PTE) materials, provided that the slanting ligaments expand more than the vertical ligaments when heated and that the geometry is amenable. Conversely, it was shown that the construction of such honeycombs from NTE components will not necessarily result in a system which exhibits NTE in all directions. Furthermore, conditions which result in honeycombs demonstrating zero thermal expansion (ZTE) coefficients in specific directions were also explored.peer-reviewe

Angiomiolipoma epitelioide hepático

Abstract: We describe the case of a hepatic epithelioid angiomyolipoma in a 50-year-old woman with epigastric pain and well-circumscribed 47 mm hepatic mass detected by ultrasonography. Angiomyolipoma is a rare benign mesenchymal tumor of the liver, composed of variable amounts of smooth muscle cells, abnormal blood vessels and adipose tissue. Preoperative diagnosis is difficult. Immunoreactivity with HMB-45 antibody helps to distinguish this tumor from other benign and malignant tumors of the liver

Gastritis and gastroesophageal reflux disease are strongly associated with non-allergic nasal disorders

Background: Gastroesophageal reflux disease (GERD) has been reported to be significantly associated with chronic rhinosinusitis, but the strength of the association is still debated. Aims: To evaluate the strength of the association between gastritis/GERD and non-allergic rhinitis (NAR)/allergic rhinitis (AR)/sinusitis. Methods: We investigated 2887 subjects aged 20–84 years, who underwent a clinical visit in seven Italian centres (Ancona, Palermo, Pavia, Terni, Sassari, Torino, Verona) within the study on Gene Environment Interactions in Respiratory Diseases, a population-based multicase-control study between 2008 and 2014. Subjects were asked if they had doctor-diagnosed “gastritis or stomach ulcer (confirmed by gastroscopy)” or “gastroesophageal reflux disease, hiatal hernia or esophagitis”. The association between NAR/AR/sinusitis and either gastritis or GERD was evaluated through relative risk ratios (RRR) by multinomial logistic regression. Results: The prevalence of gastritis/GERD increased from subjects without nasal disturbances (22.8% = 323/1414) to subjects with AR (25.8% = 152/590) and further to subjects with NAR (36.7% = 69/188) or sinusitis (39.9% = 276/691). When adjusting for centre, sex, age, education level, BMI, smoking habits and alcohol intake, the combination of gastritis and GERD was associated with a four-fold increase in the risk of NAR (RRR = 3.80, 95% CI 2.56–5.62) and sinusitis (RRR = 3.70, 2.62–5.23) with respect to controls, and with a much smaller increase in the risk of AR (RRR = 1.79, 1.37–2.35). Conclusion: The study confirmed the association between gastritis/GERD and nasal disturbances, which is stronger for NAR and sinusitis than for AR