Mathematical modeling heat transfer in closed two-phase thermosyphon

Проведен численный анализ теплопереноса в замкнутом двухфазном термосифоне цилиндрической формы в условии подвода теплоты на нижней крышке. Для описания исследуемого процесса предложена упрощенная математическая модель, отличающаяся от известной описанием только процессов теплопроводности в системе "корпус термосифона - паровой канал - пленка конденсата". Сформулированная краевая задача решена методом конечных разностей. Получены поля температур в термосифоне для типичных тепловых нагрузок и режимов работы

Bias-Variation Dilemma Challenges Clinical Trials: Inherent Limitations of Randomized Controlled Trials and Meta-Analyses Comparing Hernia Therapies

Purpose: Evaluation of hernia therapies according to the current rules of Evidence Based Medicine is widely reduced to results of RCTs or meta-analyses. RCTs have been accepted as a most important tool to confirm a superior effect of an intervention. Unfortunately, in hernia surgery, comparisons of RCTs and correspondingly their use in meta-analyses, are not, surprisingly often, able to confirm any significant impact of a specific procedure due to intrinsic restrictions in a multi-causal\ud setting with its web of influences. Methods: Based on our own experiences of clinical studies in surgery, the present article outlines several situations, with their respective reasons, which argue the severe limitations of RCTs and meta-analysis to define an optimum treatment. Results: Metaanalyses accumulate the variations of each trial, which then may cover any clear causal relationship. RCTs usually are dealing with subgroups of standard patients thus excluding the majority of our patients. Low statistical power of current cohort sizes restricts the analysis of subgroups or of effects with low incidences. Simple comparisons of means frequently are hampered by nonlinear relationships to outcome. The relevance of a specific variable is difficult to separate from other influences. The limited surveillance period of studies ignores a delayed change in outcome. Randomization cannot guarantee a standardized patient’s condition. All the arguments have to be considered as a crucial and fundamental consequence of the bias-variance dilemma or principle of uncertainty in medicine, and underline the many limitations of RCTs to evaluate any specific impact of hernia therapies on e.g. infection, pain or recurrence. Conclusions: Many surgical issues\ud cannot be and should not be investigated by RCTs, in particular, if a marked patients’ heterogeneity\ud has to be considered or the low incidences of the outcome readout cannot be addressed with sufficient statistical power without getting lost in the variation mire. Registries with their non-restricted data-acquisition should be regarded as reliable alternatives for postoperative outcome quality surveillance studies

Formation of translational risk score based on correlation coefficients as an alternative to Cox regression models for predicting outcome in patients with NSCLC

<p>Abstract</p> <p>Background</p> <p>Personalised cancer therapy, such as that used for bronchial carcinoma (BC), requires treatment to be adjusted to the patient's status. Individual risk for progression is estimated from clinical and molecular-biological data using translational score systems. Additional molecular information can improve outcome prediction depending on the marker used and the applied algorithm. Two models, one based on regressions and the other on correlations, were used to investigate the effect of combining various items of prognostic information to produce a comprehensive score. This was carried out using correlation coefficients, with options concerning a more plausible selection of variables for modelling, and this is considered better than classical regression analysis.</p> <p>Methods</p> <p>Clinical data concerning 63 BC patients were used to investigate the expression pattern of five tumour-associated proteins. Significant impact on survival was determined using log-rank tests. Significant variables were integrated into a Cox regression model and a new variable called integrative score of individual risk (ISIR), based on Spearman's correlations, was obtained.</p> <p>Results</p> <p>High tumour stage (TNM) was predictive for poor survival, while CD68 and Gas6 protein expression correlated with a favourable outcome. Cox regression model analysis predicted outcome more accurately than using each variable in isolation, and correctly classified 84% of patients as having a clear risk status. Calculation of the integrated score for an individual risk (ISIR), considering tumour size (T), lymph node status (N), metastasis (M), Gas6 and CD68 identified 82% of patients as having a clear risk status.</p> <p>Conclusion</p> <p>Combining protein expression analysis of CD68 and GAS6 with T, N and M, using Cox regression or ISIR, improves prediction. Considering the increasing number of molecular markers, subsequent studies will be required to validate translational algorithms for the prognostic potential to select variables with a high prognostic power; the use of correlations offers improved prediction.</p

Angiotensin II induced inflammation in the kidney and in the heart of double transgenic rats

BACKGROUND: We are investigating a double transgenic rat (dTGR) model, in which rats transgenic for the human angiotensinogen and renin genes are crossed. These rats develop moderately severe hypertension but die of end-organ cardiac and renal damage by week 7. The heart shows necrosis and fibrosis, whereas the kidneys resemble the hemolytic-uremic syndrome vasculopathy. Surface adhesion molecules (ICAM-1 and VCAM-1) are expressed early on the endothelium, while the corresponding ligands are found on circulating leukocytes. Leukocyte infiltration in the vascular wall accompanies PAI-1, MCP-1, iNOS and Tissue Factor expression. Furthermore we show evidence that Ang II causes the upregulation of NF-{kappa}B in our model. METHODS: We started PDTC-treatment on four weeks old dTGR (200 mg/kg sc) and age-matched SD rats. Blood-pressure- and albuminuria- measurements were monitored during the treatment period (four weeks). The seven weeks old animals were killed, hearts and kidneys were isolated and used for immunohistochemical-and electromobility shift assay analysis. RESULTS: Chronic treatment with the antioxidant PDTC decreased blood pressure (162 plus minus 8 vs. 190 plus minus 7 mm Hg, p = 0.02). Cardiac hypertrophy index was significantly reduced (4.90 plus minus 0.1 vs. 5.77 plus minus 0.1 mg/g, p < 0.001) compared to dTGR. PDTC reduced 24 h albuminuria by 85 % (2.7 plus minus 0.5 vs. 18.0 plus minus 3.4 mg/d, p < 0.001) and prevented death significantly. Vascular injury was ameliorated in small renal and cardiac vessels. PDTC inhibited NF-{kappa}B binding activity in heart and kidney. Immunohistochemical analysis shows increased expression of the p65 NF-{kappa}B subunit in the endothelium, smooth muscles cells of damaged small vessels, infiltrated cells, glomeruli, tubuli and collecting ducts of dTGR. PDTC markedly reduced the immunoreactivity of p65. CONCLUSION: Our data show that inhibition of NF-{kappa}B by PDTC markedly reduces inflammation, iNOS expression in the dTGR most likely leading to decreased cytotoxicity, and cell proliferation. Thus, NF-{kappa}B activation plays an important role in ANG II-induced end-organ damage

Evaluation of the collaborative network of highly correlating skin proteins and its change following treatment with glucocorticoids

<p>Abstract</p> <p>Background</p> <p>Glucocorticoids (GC) represent the core treatment modality for many inflammatory diseases. Its mode of action is difficult to grasp, not least because it includes direct modulation of many components of the extracellular matrix as well as complex anti-inflammatory effects. Protein expression profile of skin proteins is being changed with topical application of GC, however, the knowledge about singular markers in this regard is only patchy and collaboration is ill defined.</p> <p>Material/Methods</p> <p>Scar formation was observed under different doses of GC, which were locally applied on the back skin of mice (1 to 3 weeks). After euthanasia we analyzed protein expression of collagen I and III (picrosirius) in scar tissue together with 16 additional protein markers, which are involved in wound healing, with immunhistochemistry. For assessing GC's effect on co-expression we compared our results with a model of random figures to estimate how many significant correlations should be expected by chance.</p> <p>Results</p> <p>GC altered collagen and protein expression with distinct results in different areas of investigation. Most often we observed a reduced expression after application of low dose GC. In the scar infiltrate a multivariate analysis confirmed the significant impact of both GC concentrations. Calculation of Spearman's correlation coefficient similarly resulted in a significant impact of GC, and furthermore, offered the possibility to grasp the entire interactive profile in between all variables studied. The biological markers, which were connected by significant correlations could be arranged in a highly cross-linked network that involved most of the markers measured. A marker highly cross-linked with more than 3 significant correlations was indicated by a higher variation of all its correlations to the other variables, resulting in a standard deviation of > 0.2.</p> <p>Conclusion</p> <p>In addition to immunohistochemical analysis of single protein markers multivariate analysis of co-expressions by use of correlation coefficients reveals the complexity of biological relationships and identifies complex biological effects of GC on skin scarring. Depiction of collaborative clusters will help to understand functional pathways. The functional importance of highly cross-linked proteins will have to be proven in subsequent studies.</p

Проектирование автоматизированной системы управления блочно-кустовой насосной станции

Данная работа является проектом разработки автоматизированной компьютерной системы управления. Представлен выбор технических и программных средств, математический аппарат и программное обеспечение при проектирование автоматизированных систем управления SCADA. В работе отражены физические основы работы устройств АС, протоколов и интерфейсов систем автоматизации технологических процессов, требования ГОСТ по разработке технической документации проектов АС.This work is a project for the development of an automated computer control system. The choice of hardware and software, mathematical apparatus and software for the design of automated control systems SCADA. The work reflects the physical basis of the AC devices, protocols and interfaces of process automation systems, the requirements of GOST for the development of technical documentation of AC projects

Технологические решения для строительства разведочной вертикальной скважины глубиной 2650 метров на нефтяном месторождении (Тюменская область)

Объектом исследования является разведочная вертикальная скважина глубиной 2650 метров на нефтяном месторождении (Тюменская область). Целью работы является – спроектировать технологическое решения для бурения вертикальной разведочной скважины, геолого-технический наряд, компоновки низа бурильной колонны, интервалы бурении и спуск обсадных колонн, интервалы цементирования.The object of the study is a vertical exploratory well with a depth of 2,650 meters in an oil field (Tyumen Oblast). The aim of the work is to design technological solutions for drilling a vertical exploration well, geological and technical outfit, layouts of the bottom of the drill string, drilling intervals and running of the casing strings, cementing intervals

Why are mineralocorticoid receptor antagonists cardioprotective?

Two clinical trials, the Randomized ALdosterone Evaluation Study (RALES) and the EPlerenone HEart failure and SUrvival Study (EPHESUS), have recently shown that mineralocorticoid receptor (MR) antagonists reduce mortality in patients with heart failure on top of ACE inhibition. This effect could not be attributed solely to blockade of the renal MR-mediated effects on blood pressure, and it has therefore been proposed that aldosterone, the endogenous MR agonist, also acts extrarenally, in particular in the heart. Indeed, MR are present in cardiac tissue, and possibly aldosterone synthesis occurs in the heart. This review critically addresses the following questions: (1) is aldosterone synthesized at cardiac tissue sites, (2) what agonist stimulates cardiac MR normally, and (3) what effects are mediated by aldosterone/MR in the heart that could explain the beneficial effects of MR blockade in heart failure? Conclusions are that most, if not all, of cardiac aldosterone originates in the circulation (i.e., is of adrenal origin), and that glucocorticoids, in addition to aldosterone, may serve as the endogenous agonist of cardiac MR. MR-mediated effects in the heart include effects on endothelial function, cardiac fibrosis and hypertrophy, oxidative stress, cardiac inotropy, coronary flow, and arrhythmias. Some of these effects occur via or in synergy with angiotensin II, and involve a non-MR-mediated mechanism. This raises the possibility that aldosterone synthase inhibitors might exert beneficial effects on top of MR blockade