Characteristics of the steam flow in the end seals of high pressure cylinders in the state of vacuum augmentation

Разработан алгоритм определения параметров пара в концевых уплотнениях на режиме набора вакуума, который позволяет учесть утечки пара из камер с дренажами и найти характеристики течения в каждой камере. Определен характер течения пара в каждой секции концевых уплотнений цилиндра высокого давления (ЦВД) турбины К-325-23,5 на этапе набора вакуума. Распределение давлений и расходов пара по секциям переднего и заднего концевых уплотнений свидетельствует о нерациональной схеме прогрева ротора и возможности возникновения высокого уровня термических напряжений. По рассчитанным параметрам пара вычислены коэффициенты теплоотдачи при одно- и двухфазном течении пара на поверхности ротора ЦВД в области концевых уплотнений для последующего термопрочностного анализа

Strategic communication: An experimental investigation

In this paper we attempt to compare theoretically and experimentally three models of strategic information transmission. In particular we focus on the models by Crawford & Sobel (1982), Lai (2010) and Ehses-Friedrich (2011). These three models differ in the information that the receiver possesses and the sender´s knowledge about these information. Lai, 2010 introduce a partially informed decision maker into Crawford & Sobel´s model. Ehses-Friedrich (2011) makes the decision maker´s knowledge public knowledge. The experiment replicates the results of earlier experimental studies (Dickhaut et al., 1995, Cai & Wang, 2006, Wang et al., 2010): on the one hand experts usually give a too truthful advice, they overcommunicate. On the other hand the decision makers rely too much on the received information. Moreover, communication as well as payoffs decrease with increasing preference differences. We find that when decision makers are privately informed the messages from the expert to the decision maker are less precise than in the baseline setting. In the public information treatment, the communication is less biased. In all treatments, however, the messages are more precise than theoretically predicted

Sensitivity analysis of magnetic field measurements for magnetic resonance electrical impedance tomography (MREIT)

Purpose Clinical use of magnetic resonance electrical impedance tomography (MREIT) still requires significant sensitivity improvements. Here, the measurement of the current-induced magnetic field (ΔBz,c) is improved using systematic efficiency analyses and optimization of multi-echo spin echo (MESE) and steady-state free precession free induction decay (SSFP-FID) sequences. Theory and Methods Considering T1, T2, and math formula relaxation in the signal-to-noise ratios (SNRs) of the MR magnitude images, the efficiency of MESE and SSFP-FID MREIT experiments, and its dependence on the sequence parameters, are analytically analyzed and simulated. The theoretical results are experimentally validated in a saline-filled homogenous spherical phantom with relaxation parameters similar to brain tissue. Measurement of ΔBz,c is also performed in a cylindrical phantom with saline and chicken meat. Results The efficiency simulations and experimental results are in good agreement. When using optimal parameters, ΔBz,c can be reliably measured in the phantom even at injected current strengths of 1 mA or lower for both sequence types. The importance of using proper crusher gradient selection on the phase evolution in a MESE experiment is also demonstrated. Conclusion The efficiencies observed with the optimized sequence parameters will likely render in-vivo human brain MREIT feasible

Human In-vivo MR Current Density Imaging (MRCDI) Based on Optimized Multi-echo Spin Echo (MESE)

MRCDI aims at imaging an externally injected current flow in the human body, and might be useful for many biomedical applications. However, the method requires very sensitive measurement of the current-induced magnetic field component ?Bz,c parallel to main field. We systematically optimized MESE to determine its most efficient parameters. In one of the first human in-vivo applications of MRCDI, the optimized sequence was successfully used to image the ?Bz,c distribution in the brain caused by a two-electrode montage, as confirmed by finite-element calculations of ?Bz,c. Further improvements will be performed to increase its robustness to field drifts

Comparison of two alternative sequences for human in-vivo brain MR Current Density Imaging (MRCDI)

MRCDI is a novel technique, utilizing different phase-sensitive MR methods for non-invasive measurements of weak currents in the human body, which is important in several neuroscience applications. Here, we compare the in-vivo performance of two different MR methods, multi-echo spin echo (MESE) and steady-state free precession free induction decay (SSFP-FID), with single- vs. multi-gradient-echo readouts. We demonstrate that multi-gradient-echo readouts improve both methods. We validate the linear dependence of the measured current-induced magnetic field on the injected current strength for both methods, and propose the more efficient SSFP-FID method as being well suited for highly sensitive single-slice human in-vivo MRCDI

Human In-vivo Brain MR Current Density Imaging (MRCDI) based on Steady-state Free Precession Free Induction Decay (SSFP-FID)

MRCDI is a novel technique for non-invasive measurement of weak currents in the human head, which is important in several neuroscience applications. Here, we present reliable in-vivo MRCDI measurements in the human brain based on SSFP-FID, yielding an unprecedented accuracy. We demonstrate the destructive influences of stray magnetic fields caused by the current passing through feeding cables, and propose a correction method. Also, we show inter-individual differences in MRCDI measurements for two different current profiles, and compare the measurements with simulations based on individualized head models. The simulations of the current-induced magnetic fields show good agreement with in-vivo brain measurements

The complex interplay of RNA-binding proteins and RISC in neurons

An extensive network of RNA-binding proteins (RBPs) is at the center of posttranscriptional gene regulation. Importantly, different RBPs – including microRNA-loaded Argonaute (Ago) – can bind to a single mRNA resulting in antagonistic or cooperative mode of actions, thereby determining the fate and function of an mRNA. Here, I investigated the impact of two different RBPs, HuR and Staufen2 (Stau2), on microRNA/Ago-dependent gene expression homeostasis. The results of my thesis allow me to present a working model how these three RBPs might control neuronal function in a novel RNA-structure dependent manner. HuR protein binds to AU-rich elements within mRNAs. In the case of Regulator of G-protein signaling (Rgs4) mRNA, I find that HuR binding occurs close to a miR-26/RISC binding site, resulting in Rgs4 destabilization. As both binding sites are in close proximity within a predicted RNA hairpin structure, only synergistic action of HuR and miR-26 results in Rgs4 repression. I propose a novel mechanism involving the trifold combination of HuR, miR-26-loaded Ago and RNA secondary structure in governing functional regulation of Rgs4 mRNA in neurons. Certain RBPs such as Stau2 protein bind to double-stranded RNAs (dsRNAs), thereby shaping local and global secondary structures of mRNAs. Based on preliminary data linking Stau2 and the miRNA pathway, I investigated Stau2-dependent expression, localization and function of the miRNA-induced silencing complex (RISC) in neurons. Proteome and small RNA transcriptome analysis in Stau2 deficient primary neurons revealed significant upregulation of several RISC associated proteins, including Ago1/2, while global miRNA levels were unaffected. This upregulation was accompanied by decreased global translation and translocation of Ago2 from Processing-bodies, sites of mRNA storage, to translating polysomes. Phenotypically, depletion of Ago1/2 reduced dendritic branching. This effect could be rescued by simultaneous knockdown of Stau2, suggesting that Ago1/2 and Stau2 functionally counterbalance each other in neurons. I hypothesize that Stau2’s ability to bind to dsRNA stabilizes defined mRNA structures thereby governing association of RISC and mRNAs. Based on Stau2 hiCLIP experiments by our collaborator Jernej Ule, I was able to define a long-range RNA duplex in the 3’-untranslated region of Rgs4 mRNA bound by Stau2 in vivo. This RNA duplex is necessary and sufficient to drive Stau2-dependent ribonucleoprotein particle (RNP) assembly as well as dendritic RNA localization in neurons. Together, the data presented in my thesis support a model, in which balanced expression and interdependent action of RBPs, RISC and RNA structure shapes RNP assembly and gene expression homeostasis, important for neuronal function