Experimental Study on the Aging of Sands

Aging effects in sand, such as increases in cone penetration resistance with time after deposition and/or densification, are known to occur in the field, but the causes of these effects are not fully understood. A laboratory testing program was designed to study mechanisms responsible for aging effects under controlled conditions. The testing program included measurements of the small strain shear modulus, electrical conductivity, pore fluid chemistry, and minicone penetration resistance after different periods of aging. Two different sands were tested, and aging effects were evaluated for different combinations of relative density, temperature, and pore fluid composition. Increases in the small strain shear modulus were observed throughout most of the tests, and chemical analyses suggest that precipitation of carbonate and silica occurred in two tests. Despite these changes, there was no corresponding increase in the minicone penetration resistance with time in any of the tests. It is unlikely that precipitation of carbonate or silica is responsible for aging effects in sands; other possible mechanisms include arching due to dissipation of blast gases and redistribution of stresses through the soil skeleton. An additional possibility is that the boundary conditions imposed by the laboratory tests obscure changes in penetration resistance that would be measured had the volume of sand tested been much larger. The implications of these findings in terms of other published field and laboratory studies are discussed.     

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Topological equivalence in the theory of trapped ions

Abstract

We consider an ion whose motion is confined to a plane perpendicular to a constant magnetic field. A harmonic trapping field is applied within the plane of the ion's motion, together with some unspecified irradiating probe beam. By determining the dynamics of the ion we show that the particle theory is formally equivalent to that of a coupled massive (1 + 2)-dimensional vector Boson field. The field characteristics of current and Proca mass take on the roles of the interaction and harmonic potential respectively of the ion. The topological mass appropriate to the restricted configuration space, which in the case of the vector Boson field is given by the Chern-Simons term, is provided by the constant magnetic field.     

Gelation properties of previously cooked minced meat from Jonah crab (Cancer borealis) as affected by washing treatment and salt concentration

The influence of washing treatment (dewatered only, one wash, and three washes) and sodium chloride (NaCl) concentration (0%, 2%, and 4%) on the gelation properties of crab mince was investigated. This previously cooked muscle mince is a low-value by-product of the crab processing industry, considered to have little or no functional properties. Crab mince gels were produced and tested for water-holding capacity (WHC), gel strength, colour, and electrophoretic profile. Wash treatment and NaCl concentration significantly affected gelation. Washed samples exhibited significantly higher WHC than dewatered samples. The 4% NaCl treatment decreased WHC compared to lower NaCl levels. Multiple washing steps increased the force to gel deformation. Wash treatment and NaCl concentration also affected the colour of gels. Based on these results, cooked crab meat mince treated with three washes and 0% NaCl resulted in the strongest gels with the best water-holding capacity, which can be used in the development of value-added products.     

Steroidogenesis in bovine granulosa cells: the effect of short-term changes in dietary intake

The nutritional status of a cow is a key factor in the regulation of both follicle growth and oocyte quality. In this study, the effect of diets designed to increase circulating insulin and insulin-like growth factor I (IGF-I) concentrations on steroid production by granulosa cells in vitro was examined to analyse the mechanisms through which these changes occur. Hereford x Friesian heifers (n = 24) were offered maintenance or twice maintenance diets during the experimental period (17 days). Circulating concentrations of FSH did not differ between the two dietary groups, whereas insulin and IGF-I concentrations showed significant diet x day of oestrous cycle interactions. Ovaries were collected on day 3 of the first follicle wave after synchronization of oestrus. Granulosa cells were isolated from small (1-4 mm) and medium-sized (4-8 mm) follicles and cultured in the presence of long R3-IGF-I or bFSH or both. After 4 days in culture, granulosa cells isolated from small follicles, but not medium-sized follicles, collected from cattle offered the twice maintenance diet secreted significantly higher (P < 0.05) amounts of oestradiol compared with granulosa cells collected from cattle offered the maintenance diet. The effect was apparent in either the presence or absence of FSH and long R3-IGF-I. This nutritional effect on aromatase activity in granulosa cells was not apparent after day 6 of culture. There was no effect of diet on progesterone production by granulosa cells after 4 or 6 days of culture. These results support the hypothesis that dietary-induced changes in circulating insulin and IGF-I concentrations have a direct effect on the steroidogenic potential of bovine granulosa cells from small follicles. The dietary-induced increases in aromatase activity in small follicles combined with the increased concentration of metabolic hormones are possible mechanisms through which short-term changes in nutrition may affect follicle dynamics.     

The relationship of chronic mucin secretion to airway disease in normal and CFTR-deficient mice

In the cystic fibrosis (CF) patient, lung function decreases throughout life as a result of continuous cycles of infection, particularly with Pseudomonas aeruginosa and Staphylococcus aureus. The mechanism underlying the pathophysiology of the disease in humans has not been established. However, it has been suggested that abnormal, tenacious mucus, resulting perhaps from improper hydration from loss of Cl- secretion via the cystic fibrosis transmembrane conductance regulator (CFTR) protein, impairs clearance of bacteria from the CF airway and provides an environment favorable to bacterial growth. If this hypothesis is correct, it could explain the absence of respiratory disease in CFTR-deficient mice, since mice have only a single submucosal gland and display few goblet cells in their lower airways, even when exposed to bacteria. To test this hypothesis further, we induced allergic airway disease in CFTR-deficient mice. We found that induction of allergic airway disease in mice, unlike bacterial infection, results in an inflammatory response characterized by goblet cell hyperplasia, increased mucin gene expression, and increased production of mucus. However, we also found that disease progression and resolution is identical in Cftr-/- mice and control animals. Furthermore, we show that the presence of mucus in the Cftr-/- airway does not lead to chronic airway disease, even upon direct inoculation with S. aureus and P. aeruginosa. Therefore, factors in addition to the absence of high levels of mucus secretion protect the mouse from the airway disease seen in human CF patients.     

Meta-analysis of multiple outcomes by regression with random effects

Earlier work showed how to perform fixed-effects meta-analysis of studies or trials when each provides results on more than one outcome per patient and these multiple outcomes are correlated. That fixed-effects generalized-least-squares approach analyzes the multiple outcomes jointly within a single model, and it can include covariates, such as duration of therapy or quality of trial, that may explain observed heterogeneity of results among the trials. Sometimes the covariates explain all the heterogeneity, and the fixed-effects regression model is appropriate. However, unexplained heterogeneity may often remain, even after taking into account known or suspected covariates. Because fixed-effects models do not make allowance for this remaining unexplained heterogeneity, the potential exists for bias in estimated coefficients, standard errors and p-values. We propose two random-effects approaches for the regression meta-analysis of multiple correlated outcomes. We compare their use with fixed-effects models and with separate-outcomes models in a meta-analysis of periodontal clinical trials. A simulation study shows the advantages of the random-effects approach. These methods also facilitate meta-analysis of trials that compare more than two treatments.     

Is preoperative chemotherapy in locally advanced non-small-cell bronchial carcinoma of value?

Although surgeons are able to resect completely locally advanced non-small cell lung cancer with mediastinal lymph node involvement (stage IIIA), the majority of patients succumb from metastatic disease. Therefore, neoadjuvant therapy was introduced in the management of this disease in order to eradicate distant metastases at an early stage. Phase II trials with preoperative chemotherapy in stage IIIA patients have shown that the pathological response (amount of tumour necrosis) and the clearance of mediastinal lymph node correlate with a better survival and is the best predictor for eradication of distant metastases. Indeed, three small randomised phase III studies have demonstrated a survival advantage for preoperative chemotherapy compared to surgery alone. Further studies are required to determine the best neoadjuvant regimen inducing the largest amount of tumour necrosis.