An experimental investigation into the stress-dependent mechanical behavior of cohesive soil with application to wellbore instability

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 397-406).This thesis investigates the mechanical behavior of cohesive soils with reference to the applications of wellbore instabilities through an extensive program of laboratory element and model borehole tests. The laboratory tests use Resedimented Boston Blue Clay (RBBC) as an analog test material. Undrained triaxial shear tests have been performed on specimens that were K0-consolidated to stress levels ranging from 0.15 to 10.0 MPa in both compression and extension shear modes. Compression tests were also performed on overconsolidated specimens. Model borehole tests make use of two new automated, high pressure Thick-Walled Cylinder (TWC) devices to study the effects of the following parameters on the borehole response: mode of loading, specimen geometry, preshear lateral stress ratio, drainage conditions, consolidation stress level, stress history, and cavity volumetric strain rate. This testing program has been performed using small and large TWC devices with outer diameter, Do=7.6cm and 15.2cm, respectively. Both devices allow for independent control of the vertical stress and the radial pressures acting on the inner and outer walls of the cylinder, as well as pore pressure. The triaxial compression and extension test results demonstrate remarkable reductions in the undrained strength ratio (su/[sigma]'vc) with consolidation stress level, notable reduction in the stiffness ratio (Eu/[sigma]'vc), increase in the strain to mobilize the peak resistance (ef), and a significant decrease in the large strain friction angle (f'). The model borehole data indicate that most of the reduction in cavity pressure occurs at volume strains less than 5% before the borehole becomes unstable.(cont.) Increases in outer diameter and strain rate lead to a reduction in the minimum borehole pressure. The initial cavity stiffness ratio decreases as consolidation stress level increases. Drained tests have larger cavity strain at a given cavity pressure and lower minimum pressure than the undrained tests. The borehole closure curves were analyzed using a framework originally developed for interpreting undrained shear properties in model pressuremeter tests (Silvestri, 1998). Backfigured undrained strength ratios from these analyses range from su/[sigma]'vc=0.19-0.21 corresponding to an average between the measured triaxial compression and extension strength ratios. The relationship between su/[sigma]'vc and overconsolidation ratio is consistent with element tests.by Naeem Omar Abdulhadi.Ph.D

Need and potential of digitalization in the development and production of polymers

Synthetic polymers are produced to achieve desired application properties tailored to customer needs. Today’s environment of rapidly accelerating technological innovation poses the challenge of bringing new products to market even faster. However, since the relationship between application property and polymer structure is not always understood, development of new polymers requires a significant number of iterative cycles. Furthermore, scale-up to industrial scale often needs additional steps. Please download the file below for full content

Portal vein thrombosis and arterioportal shunts : effects on tumor response after chemoembolization of hepatocellular carcinoma

AIM: To evaluate the effect of portal vein thrombosis and arterioportal shunts on local tumor response in advanced cases of unresectable hepatocellular carcinoma treated by transarterial chemoembolization. METHODS: A retrospective study included 39 patients (mean age: 66.4 years, range: 45-79 years, SD: 7) with unresectable hepatocellular carcinoma (HCC) who were treated with repetitive transarterial chemoembolization (TACE) in the period between March 2006 and October 2009. The effect of portal vein thrombosis (PVT) (in 19 out of 39 patients), the presence of arterioportal shunt (APS) (in 7 out of 39), the underlying liver pathology, Child-Pugh score, initial tumor volume, number of tumors and tumor margin definition on imaging were correlated with the local tumor response after TACE. The initial and end therapy local tumor responses were evaluated according to the response evaluation criteria in solid tumors (RECIST) and magnetic resonance imaging volumetric measurements. RESULTS: The treatment protocols were well tolerated by all patients with no major complications. Local tumor response for all patients according to RECIST criteria were partial response in one patient (2.6%), stable disease in 34 patients (87.1%), and progressive disease in 4 patients (10.2%). The MR volumetric measurements showed that the PVT, APS, underlying liver pathology and tumor margin definition were statistically significant prognostic factors for the local tumor response (P = 0.018, P = 0.008, P = 0.034 and P = 0.001, respectively). The overall 6-, 12- and 18-mo survival rates from the initial TACE were 79.5%, 37.5% and 21%, respectively. CONCLUSION: TACE may be exploited safely for palliative tumor control in patients with advanced unresectable HCC; however, tumor response is significantly affected by the presence or absence of PVT and APS

Energy efficient resource allocation for NOMA in cellular IoT with energy harvesting

© 2017 IEEE. The Internet of Things (IoT) offers connectivity of massive low-power devices and sensors through the Internet which requires spectrum and energy efficient solutions. Recently, non-orthogonal multiple access (NOMA) has been investigated to address the challenges associated with spectral efficiency and dense deployment of a large number of devices in 5G cellular networks. Further, energy harvesting can enhance the energy efficiency of IoT devices. In this paper, we propose an energy-efficient resource allocation scheme for NOMA (EERA-NOMA) in cellular IoT with RF energy harvesting to address the above mentioned challenges. We model a framework to optimize user grouping of IoT devices in most appropriate resource blocks, power allocation, and time allocation for information transfer and energy harvesting. The objective is to maximize energy efficiency while satisfying constraints on the minimum data rate requirement of each user and transmit power. We adopted mesh adaptive direct search (MADS) algorithm to solve the formulated problem. Simulation results are presented to show the performance of proposed framework in comparison with existing work

The nutritional composition of mayonnaise and salad dressing in the Malaysian market

Mayonnaise and salad dressing are fast becoming popular condiments for Malaysian. The aim of this study was to obtain the nutritional composition of mayonnaise and salad dressing commercially available in the Malaysian market. The data will be used to update the Malaysian Food Composition Database which was last updated in 1997. A total of six brands from each type of mayonnaise and salad dressing were sampled from local supermarkets in the Klang Valley and analysed using standard methods. The validity of test data was monitored with the application of internal quality controls in line with the requirements of ISO 17025. The energy contents of mayonnaise and salad dressings were up to 626.40 kcal/100 g. Our findings were also in agreement with the energy labelling on the packaging. Sodium was high in mayonnaise and salad dressing because it is used in the final mixture of both condiments to improve their characteristics for certain reasons. Mayonnaise and salad dressing have been identified as potent sources of vitamin A and vitamin E and both condiments were found to contain high levels of these antioxidants. It can be concluded that this study are useful not only in providing information on the nutritional content of several commercial types of mayonnaise and salad dressing, but also in improving the public understanding of healthy food choices

Mapping a multiplexed zoo of mRNA expression

In situ hybridization methods are used across the biological sciences to map mRNA expression within intact specimens. Multiplexed experiments, in which multiple target mRNAs are mapped in a single sample, are essential for studying regulatory interactions, but remain cumbersome in most model organisms. Programmable in situ amplifiers based on the mechanism of hybridization chain reaction (HCR) overcome this longstanding challenge by operating independently within a sample, enabling multiplexed experiments to be performed with an experimental timeline independent of the number of target mRNAs. To assist biologists working across a broad spectrum of organisms, we demonstrate multiplexed in situ HCR in diverse imaging settings: bacteria, whole-mount nematode larvae, whole-mount fruit fly embryos, whole-mount sea urchin embryos, whole-mount zebrafish larvae, whole-mount chicken embryos, whole-mount mouse embryos and formalin-fixed paraffin-embedded human tissue sections. In addition to straightforward multiplexing, in situ HCR enables deep sample penetration, high contrast and subcellular resolution, providing an incisive tool for the study of interlaced and overlapping expression patterns, with implications for research communities across the biological sciences

Physiological and anthocyanin biosynthesis genes response induced by vanadium stress in mustard genotypes with distinct photosynthetic activity

The present study aimed to elucidate the photosynthetic performance, antioxidant enzyme activities, anthocyanin contents, anthocyanin biosynthetic gene expression, and vanadium uptake in mustard genotypes (purple and green) that differ in photosynthetic capacity under vanadium stress. The results indicated that vanadium significantly reduced photosynthetic activity in both genotypes. The activities of the antioxidant enzymes were increased significantly in response to vanadium in both genotypes, although the purple exhibited higher. The anthocyanin contents were also reduced under vanadium stress. The anthocyanin biosynthetic genes were highly expressed in the purple genotype, notably the genes TT8, F3H, and MYBL2 under vanadium stress. The results indicate that induction of TT8, F3H, and MYBL2 genes was associated with upregulation of the biosynthetic genes required for higher anthocyanin biosynthesis in purple compared with the green mustard. The roots accumulated higher vanadium than shoots in both mustard genotypes. The results indicate that the purple mustard had higher vanadium tolerance

Mapping a multiplexed zoo of mRNA expression

In situ hybridization methods are used across the biological sciences to map mRNA expression within intact specimens. Multiplexed experiments, in which multiple target mRNAs are mapped in a single sample, are essential for studying regulatory interactions, but remain cumbersome in most model organisms. Programmable in situ amplifiers based on the mechanism of hybridization chain reaction (HCR) overcome this longstanding challenge by operating independently within a sample, enabling multiplexed experiments to be performed with an experimental timeline independent of the number of target mRNAs. To assist biologists working across a broad spectrum of organisms, we demonstrate multiplexed in situ HCR in diverse imaging settings: bacteria, whole-mount nematode larvae, whole-mount fruit fly embryos, whole-mount sea urchin embryos, whole-mount zebrafish larvae, whole-mount chicken embryos, whole-mount mouse embryos and formalin-fixed paraffin-embedded human tissue sections. In addition to straightforward multiplexing, in situ HCR enables deep sample penetration, high contrast and subcellular resolution, providing an incisive tool for the study of interlaced and overlapping expression patterns, with implications for research communities across the biological sciences

Effects of a high-dose 24-h infusion of tranexamic acid on death and thromboembolic events in patients with acute gastrointestinal bleeding (HALT-IT): an international randomised, double-blind, placebo-controlled trial

Background: Tranexamic acid reduces surgical bleeding and reduces death due to bleeding in patients with trauma. Meta-analyses of small trials show that tranexamic acid might decrease deaths from gastrointestinal bleeding. We aimed to assess the effects of tranexamic acid in patients with gastrointestinal bleeding. Methods: We did an international, multicentre, randomised, placebo-controlled trial in 164 hospitals in 15 countries. Patients were enrolled if the responsible clinician was uncertain whether to use tranexamic acid, were aged above the minimum age considered an adult in their country (either aged 16 years and older or aged 18 years and older), and had significant (defined as at risk of bleeding to death) upper or lower gastrointestinal bleeding. Patients were randomly assigned by selection of a numbered treatment pack from a box containing eight packs that were identical apart from the pack number. Patients received either a loading dose of 1 g tranexamic acid, which was added to 100 mL infusion bag of 0·9% sodium chloride and infused by slow intravenous injection over 10 min, followed by a maintenance dose of 3 g tranexamic acid added to 1 L of any isotonic intravenous solution and infused at 125 mg/h for 24 h, or placebo (sodium chloride 0·9%). Patients, caregivers, and those assessing outcomes were masked to allocation. The primary outcome was death due to bleeding within 5 days of randomisation; analysis excluded patients who received neither dose of the allocated treatment and those for whom outcome data on death were unavailable. This trial was registered with Current Controlled Trials, ISRCTN11225767, and ClinicalTrials.gov, NCT01658124. Findings: Between July 4, 2013, and June 21, 2019, we randomly allocated 12 009 patients to receive tranexamic acid (5994, 49·9%) or matching placebo (6015, 50·1%), of whom 11 952 (99·5%) received the first dose of the allocated treatment. Death due to bleeding within 5 days of randomisation occurred in 222 (4%) of 5956 patients in the tranexamic acid group and in 226 (4%) of 5981 patients in the placebo group (risk ratio [RR] 0·99, 95% CI 0·82–1·18). Arterial thromboembolic events (myocardial infarction or stroke) were similar in the tranexamic acid group and placebo group (42 [0·7%] of 5952 vs 46 [0·8%] of 5977; 0·92; 0·60 to 1·39). Venous thromboembolic events (deep vein thrombosis or pulmonary embolism) were higher in tranexamic acid group than in the placebo group (48 [0·8%] of 5952 vs 26 [0·4%] of 5977; RR 1·85; 95% CI 1·15 to 2·98). Interpretation: We found that tranexamic acid did not reduce death from gastrointestinal bleeding. On the basis of our results, tranexamic acid should not be used for the treatment of gastrointestinal bleeding outside the context of a randomised trial

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure < 100 mmHg (n = 1127), estimated glomerular filtration rate < 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation