Is the Jaw Bone Micro-Structure Altered in Response to Osteoporosis and Bisphosphonate Treatment? A Micro-CT Analysis

The aim of the study was to quantify the micro-architectural changes of the jaw bone in response to ovariectomy, exposed or not to bisphosphonate treatment. A total of 47 Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and exposed to osteoporosis preventive treatment for eight weeks either with bisphosphonates (alendronate, ALN; group OVX-ALN) three days/week at a dose of 2 mg/kg or with saline solution (untreated control condition; group OVX). The bone morphometric parameters of the trabecular jaw bone were assessed using ex vivo micro-computed tomography. The regions of interest investigated in the maxilla were the inter-radicular septum of the second molar and the tuber. The regions quantified in the mandible included the three molar regions and the condyle. A one-way analysis of variance followed by pairwise comparison using Tukey’s HSD and the Games–Howell test was conducted to explore significant differences between the groups. In the maxilla, OVX decreased the bone volume in the inter-radicular septum of the second molar. Bisphosphonate treatment was able to prevent this deterioration of the jaw bone. The other investigated maxillary regions were not affected by (un)treated ovariectomy. In the mandible, OVX had a significant negative impact on the jaw bone in the buccal region of the first molar and the inter-radicular region of the third molar. Treatment with ALN was able to prevent this jaw bone loss. At the condyle site, OVX significantly deteriorated the trabecular connectivity and shape, whereas preventive bisphosphonate treatment showed a positive effect on this trabecular bone region. No significant results between the groups were observed for the remaining regions of interest. In summary, our results showed that the effects of ovariectomy-induced osteoporosis are manifested at selected jaw bone regions and that bisphosphonate treatment is capable to prevent these oral bone changes.     

M- S-H formation in MgO-SiO2slurries via wet milling for magnesia based castables

It is believed that the formation of hydration phase, MgO-SiO₂-H₂O (M-S-H), contributes to good workability and reliable comprehensive properties for magnesia based castables. In order to stimulate the formation of M-S-H in magnesia based castables and understand the minimum introduction of microslica amount, wet milling process was used to promote the dissolution of MgO and SiO₂ in this work. The slurry containing different content of microsilica with wet milling technology and the castables with/without wet milling slurry were prepared. The effects of microsilica content on the formation of hydration phases were analyzed by XRD, FT-IR and TG/DSC and the properties of magnesia based castables were evaluated by explosion resistance, CMOR, HMOR and so on. The results showed that the formation of M-S-H was accelerated because of the dissolution of Mg²⁺ and HSiO₃^? in wet milling process. Higher amount of M-S-H led to a tight bonding in the early stage, and a denser structure after firing at high temperature due to the limited formation of brucite and in-situ formation of evenly distributed forsterite phase. In addition, much higher HMOR were obtained when less microsilica was added, attributing to the suppressed formation of low-melting-point liquid. Therefore, 2–3 wt% microsilica addition was recommended in this process.     

Unimportance of geometric nonlinearity in analysis of flanged joints with metal-to-metal contact

Gasketless flanged joints with metal to metal contact offer some advantages over gasketed joints such as lower weight and better fatigue life. Design of such joints is often based on finite element analyses, and complicated by the fact that the area of contact between the flanges changes upon application of loads. Such analyses can be done using commercial software, which can incorporate geometrical nonlinearities as well as contact nonlinearities. Engineering intuition suggests that the role of geometrical nonlinearities might be small for such problems. However, many engineers continue to use the fully nonlinear analyses. Our aim in this paper is simply to put on record that significant savings in time can be obtained by “turning off” geometric nonlinearities in such analyses, with negligible loss of accuracy. To this end, a nonautomated implementation of the basic ideas is first demonstrated for a simple geometry; more automated analyses for a more general geometry follow.     

COMPOSITIONAL ANALYSIS OF NORTH SEA OILS

ABSTRACT

The molar fluid composition of either the reservoir fluid or the well stream is determined by combining the true boiling point (TBP’) distillation data with gas chromatographic (GC) analysis of the light ends. For the purpose of thermodynamic simulation of phase behavior of petroleum reservoir fluids, in addition to the compositional data, physical properties of the pseudo fractions, i.e. density and molecular weight are required. A major drawback of the TBP distillation is the fact that the fractions contain typically 20 -30 % of the material outside the defined boiling range. Another significant issue is the use of generalized density and molecular weight data in the absence of experimentally determined values. This can introduce major inaccuracies in the phase behavior calculations because the generalized value of density and molecular weight significantly differ in each oil based on the paraffin-naphthene-aromatic distribution and its geographic origin.

In this work we have performed the true TBP distillation of 7 stabilized North Sea oil samples. All the oils were distilled from carbon number 6 to 19 and the distillation was terminated at C₂₀₊, which was termed as the residue. We have performed analysis of the Cm fraction of each oil by gas chromatography. Subsequently, the specific gravity and molecular weights of the TBP fractions were determined and compared with the generalized values, which indicated major differences. In addition, the superiority of the PVT calculations for a volatile oil and a gas condensate using the experimentally determined specific gravity and molecular weight of the pseudo fractions against the generalized properties is also demonstrated.     

Sensitivity Analysis of Interfacial Tension Predictions for Hydrocarbon Fluids

The interfacial tension (IFT) of hydrocarbon fluids is commonly predicted by either the parachor method or the scaling law. The methods require equilibrium liquid and vapor phase composition and density. An equation of state would normally be required if experimental values are not available. However, the computation of density for simple hydrocarbons and reservoir fluids, despite the important advances achieved by cubic equations of state, still remains a weak link in these types of calculations. Thus, there exists a need to investigate the qualitative and quantitative effects, of such inaccuracies in the density, on IFT predictions. Moreover, the study presented in this work would be useful in reservoir engineering and enhanced oil recovery calculations. The results presented in this work indicate that the methods are highly sensitive to the inaccuracies in the density of both the liquid and the vapor phases. An error of around 10% in the liquid or the vapor density can result in an error of up to 200% in the estimated IFT. Two binary and one ternary mixture for which measured data on IFT, composition and density is reported in the literature form the basis of this study.     

Optimization of conditions for hydrogen production from complex dairy wastewater by anaerobic sludge using desirability function approach

Present study deals with the multiple-response optimization for biohydrogen production using anaerobic sludge and outstanding approach to overcome the drawbacks of conventional response surface methodology (RSM). Dairy wastewater was used as source in batch fermentation was followed for this study. Response surface methodology (RSM), based on a three level, four variable Box–Behnken design, was employed to obtain the best possible combination of substrate concentration, pH, COD/N ratio and COD/P ratio for maximum H₂ yield (HY) and specific hydrogen production rate (SHPR). Experimental data were evaluated by applying RSM integrating a desirability function approach. The optimum H₂ yield and SHPR conditions were: substrate concentration 15.3 g COD/L, pH 5.5, COD/N ratio 100.5 and COD/P ratio 120 with maximum overall desirability D of 0.94. The confirmation experiment under these optimal condition showed a HY and SHPR of 13.54 mmol H₂/g COD and 29.91 mmol H₂/g-VSS.d, respectively. This was only 0.22% and 0.20%, respectively, different from the predicted values, suggesting that the desirability function approach with RSM was a useful technique to get the maximum H₂ yield and SHPR simultaneously.     

Experimental Investigation of the Effect of Tube-to-Tube Porous Medium Interconnectors on the Thermohydraulics of Confined Tube Banks

This experimental study investigates the effect of tube-to-tube copper porous interconnectors on the thermohydraulic performance of an in-line and staggered confined tube bank. The porous medium, having a transverse thickness equal to that of the diameter of the tube (9 mm), connects longitudinally six successive tubes kept as in-line and staggered arrangements with a square pitch of 2.0. The tubes are subjected to a constant and uniform heat flux and are cooled by forced convection under laminar-transition flow range (200 < Reynolds number < 1500) using air with a Prandtl number of 0.71 as cooling fluid. Experimental data presented here establish that by introducing tube-to-tube porous medium interconnectors for the maximum Reynolds number tested here, a reduction in the pressure drop by 18% is observed in the in-line configuration while the heat transfer is enhanced by 100% in the staggered configuration, when compared to their respective configurations without the porous medium. Defining an overall energy gain as the ratio of the heat transfer enhancement due to the presence of the porous inserts to the pressure drop incurred, it is seen that fixing the porous inserts in the in-line configuration is advantageous.     

Wavelet Bootstrap Multiple Linear Regression Based Hybrid Modeling for Daily River Discharge Forecasting

A new hybrid model, the wavelet–bootstrap–multiple linear regression (WBMLR) is proposed to explore the potential of wavelet analysis and bootstrap resampling techniques for daily discharge forecasting. The performance of the developed WBMLR model is also compared with five more models: multiple linear regression (MLR), artificial neural network (ANN), wavelet-based MLR (WMLR), wavelet-based ANN (WANN) and wavelet–bootstrap–ANN (WBANN) models. Seven years of discharge data from seven gauging stations in the middle reaches of Mahanadi river basin in India are applied in this study. Significant input vectors are decomposed into discrete wavelet components (DWCs) using discrete wavelet transformation (DWT) to generate wavelet sub time series that are used as inputs to the MLR and ANN models to develop the WMLR and WANN models, respectively. Effective wavelets are selected by considering several types of wavelets with different vanishing moments. WBMLR and WBANN models are developed as ensemble of different WMLR and WANN models, respectively, developed using different realizations of the training dataset generated using bootstrap resampling technique. The results show that the wavelet bootstrap hybrid models (i.e. WBMLR and WBANN) produce significantly better results than the traditional MLR and ANN models. Hybrid models based on MLR (WMLR, WBMLR) perform better than the ANN based hybrid models (WBANN, WANN). The WBMLR and WMLR models simulate the peak discharges better than the WBANN, WANN, MLR and ANN models, whereas the overall performance of WBMLR model is found to be more accurate and reliable than the remaining five models.     

Heat Transfer Analysis for Gas-to-Liquids Transportation Through Trans Alaska Pipeline

Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations.