Factors affecting piston ring friction

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This thesis was scanned as part of an electronic thesis pilot project.Cataloged from PDF version of thesis.Includes bibliographical references (p. 153-156).The piston ring pack friction is a major contributor to the internal combustion engine mechanical friction loss. The oil control ring decides the oil supply to the top two rings in addition to being the major friction contributor in the ring pack. This work concentrated on the oil control ring friction. A large range of ring land widths and tensions, liner finish, and oil viscosity were investigated both experimentally and numerically to reveal how different factors affect the piston ring friction. A floating liner engine (FLE) was modified for motoring tests. The engine system repeatability and self-consistency were demonstrated. The thesis then discussed proper methods to select and measure the rings, liners and oil, which were important to generating meaningful results from the experiment. The ranges of engine speeds and liner temperatures were designed to ensure that all the lubrication modes, namely, boundary, mixed and hydrodynamic, can become dominant in both the instantaneous friction over a cycle and the FMEP over the engine speed range for any combination of rings, liners and lubricants. A parallel modeling effort was made to the experiments. The work showed that with careful preparation of adequate information on rings, liners and lubricants, the model can match the friction trends observed in the experiment over a large range of operating parameters and designs on the ring, liner finish and lubricant viscosity. The ring friction change over the liner break-in was studied using liners covering a wide range of surface roughness. The hydrodynamic pressure generation ability of the liner appears to be decided by the large surface structure. Therefore, the break-in process, which removes individual asperities from the plateau, does not affect pure hydrodynamic lubrication, and only the mixed lubrication is affected by the plateau roughness change. By keeping the same hydrodynamic pressure - ring/liner clearance (P-h) correlation and changing the plateau roughness, the model can predict the ring friction change over different lubrication regimes during the break-in. Compared to the current industry norm, a new engine power cylinder system design using a smaller land width twin land oil control ring with a lower ring tension and accompanied by a smoother liner surface gives lower friction and better oil control at the same time.by Kai Liao.Ph.D

Modeling of the effects of lubricant chemistry on engine component wear and parametric analysis

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Page 75 blank.Includes bibliographical references (p. 71-72).Recently, due to the strengthened regulations on diesel engine emissions, the dynamic understanding of engines' antiwear processes has drawn renewed attention. Oil additives can help engines resist wear by forming a thin solid layer of antiwear film, and zinc dialkyldithiophosphate (ZDDP) is the most commonly used oil additive. There has been sufficient experimental effort in trying to understand the dynamics of ZDDP antiwear film formation and its effect on wear between engine components, but the effort of predicting antiwear film formation and the effect of lubricant chemistry on engine wear through modeling has just begun to emerge. The purpose of this research is going to improve such a model modeling ZDDP antiwear processes so that it can be used to understand the dynamics of antiwear film formation at different operating conditions, and use this model to gain insight into the antiwear film formation processes. The effect of different processes on antiwear film formation and the sensitivity of the film formation to different parameters have been demonstrated and analyzed.by Kai Liao.S.M

Practical electron cloaking in solids

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 71-72).The design and experimental realization of "metamaterials" in the past decade has opened up new venues to obtain artificial materials with exotic properties that are desirable but not commonly encountered in the nature. Optical metamaterials have shown great potentials in applications such as optoelectronics, subwavelength imaging, and optical information processing etc. The invisibility effect, or "cloaking effect", is one of the most striking demonstrations of the unprecedented ability of manipulating light provided by optical metamaterials. As a natural extension, the cloaking effect of acoustic waves and quantum matter waves has also been discussed recently. Currently the main strategy of designing "cloaks" is the so-called transformation optics, and the resulting continuous distribution of material properties, such as the refractive index for optical metamaterials, the effective mass and the potential profile for matter-wave metamaterials, requires the artificial structures be much smaller than the wavelength of corresponding waves. In this thesis, the strategy of cloaking artificial scattering centers from conducting electrons in solids is discussed theoretically. The wavelength of conducting electrons in solids is of the order of a few nanometers, rendering the transformation optics technique impractical in this circumstance. Instead, a method based on the expansion of partial waves, analogous to the Mie theory for electromagnetic waves, is proposed. As an example, the design of "invisible" core-shell nanoparticles is demonstrated, and its application in thermoelectrics is discussed, where it is shown a simultaneous enhancement of the Seebeck coefficient and the electrical conductivity can be achieved. The corresponding formalism in 2D (both normal 2D electron gas system and graphene) is also derived, based on which novel electronic switches and filters can be constructed using properly designed gates to achieve desired potential profiles.by Bolin Liao.S.M

Systemic delivery of microRNA-101 potently inhibits hepatocellular carcinoma in vivo by repressing multiple targets

Targeted therapy based on adjustment of microRNA (miRNA)s activity takes great promise due to the ability of these small RNAs to modulate cellular behavior. However, the efficacy of miR-101 replacement therapy to hepatocellular carcinoma (HCC) remains unclear. In the current study, we first observed that plasma levels of miR-101 were significantly lower in distant metastatic HCC patients than in HCCs without distant metastasis, and down-regulation of plasma miR-101 predicted a worse disease-free survival (DFS, P<0.05). In an animal model of HCC, we demonstrated that systemic delivery of lentivirus-mediated miR-101 abrogated HCC growth in the liver, intrahepatic metastasis and distant metastasis to the lung and to the mediastinum, resulting in a dramatic suppression of HCC development and metastasis in mice without toxicity and extending life expectancy. Furthermore, enforced overexpression of miR-101 in HCC cells not only decreased EZH2, COX2 and STMN1, but also directly down-regulated a novel target ROCK2, inhibited Rho/Rac GTPase activation, and blocked HCC cells epithelial-mesenchymal transition (EMT) and angiogenesis, inducing a strong abrogation of HCC tumorigenesis and aggressiveness both in vitro and in vivo. These results provide proof-of-concept support for systemic delivery of lentivirus-mediated miR-101 as a powerful anti-HCC therapeutic modality by repressing multiple molecular targets. © 2015 Zheng et al.published_or_final_versio

ERK1/2 signaling dominates over RhoA signaling in regulating early changes in RNA expression induced by endothelin-1 in neonatal rat cardiomyocytes

Cardiomyocyte hypertrophy is associated with changes in gene expression. Extracellular signal-regulated kinases 1/2 (ERK1/2) and RhoA [activated by hypertrophic agonists (e.g. endothelin-1)] regulate gene expression and are implicated in the response, but their relative significance in regulating the cardiomyocyte transcriptome is unknown. Our aim was to establish the significance of ERK1/2 and/or RhoA in the early cardiomyocyte transcriptomic response to endothelin-1.Cardiomyocytes were exposed to endothelin-1 (1 h) with/without PD184352 (to inhibit ERK1/2) or C3 transferase (C3T, to inhibit RhoA). RNA expression was analyzed using microarrays and qPCR. ERK1/2 signaling positively regulated approximately 65% of the early gene expression response to ET-1 with a small (approximately 2%) negative effect, whereas RhoA signaling positively regulated approximately 10% of the early gene expression response to ET-1 with a greater (approximately 14%) negative contribution. Of RNAs non-responsive to endothelin-1, 66 or 448 were regulated by PD184352 or C3T, respectively, indicating that RhoA had a more significant effect on baseline RNA expression. mRNAs upregulated by endothelin-1 encoded a number of receptor ligands (e.g. Ereg, Areg, Hbegf) and transcription factors (e.g. Abra/Srf) that potentially propagate the response.ERK1/2 dominates over RhoA in the early transcriptomic response to endothelin-1. RhoA plays a major role in maintaining baseline RNA expression but, with upregulation of Abra/Srf by endothelin-1, RhoA may regulate changes in RNA expression over longer times. Our data identify ERK1/2 as a more significant node than RhoA in regulating the early stages of cardiomyocyte hypertrophy

New Solution for Neutrino Masses and Leptogenesis in Adjoint SU(5)

We investigate baryogenesis via leptogenesis and generation of neutrino masses and mixings through the Type I plus Type III seesaw plus an one-loop mechanism in the context of Renormalizable Adjoint SU(5) theory. One light neutrino remains massless, because the contributions of three heavy Majorana fermions \rho_0, \rho_3 and \rho_8 to the neutrino mass matrix are not linearly independent. However none of these heavy fermions is decoupled from the generation of neutrino masses. This opens a new range in parameter space for successful leptogenesis, in particular, allows for inverted hierarchy of the neutrino masses.Comment: 16 pages, 4 figures; references added and typos fixe

Psychometric precision in phenotype definition is a useful step in molecular genetic investigation of psychiatric disorders

Affective disorders are highly heritable, but few genetic risk variants have been consistently replicated in molecular genetic association studies. The common method of defining psychiatric phenotypes in molecular genetic research is either a summation of symptom scores or binary threshold score representing the risk of diagnosis. Psychometric latent variable methods can improve the precision of psychiatric phenotypes, especially when the data structure is not straightforward. Using data from the British 1946 birth cohort, we compared summary scores with psychometric modeling based on the General Health Questionnaire (GHQ-28) scale for affective symptoms in an association analysis of 27 candidate genes (249 single-nucleotide polymorphisms (SNPs)). The psychometric method utilized a bi-factor model that partitioned the phenotype variances into five orthogonal latent variable factors, in accordance with the multidimensional data structure of the GHQ-28 involving somatic, social, anxiety and depression domains. Results showed that, compared with the summation approach, the affective symptoms defined by the bi-factor psychometric model had a higher number of associated SNPs of larger effect sizes. These results suggest that psychometrically defined mental health phenotypes can reflect the dimensions of complex phenotypes better than summation scores, and therefore offer a useful approach in genetic association investigations

Clinical Validation of Integrated Nucleic Acid and Protein Detection on an Electrochemical Biosensor Array for Urinary Tract Infection Diagnosis

BACKGROUND: Urinary tract infection (UTI) is a common infection that poses a substantial healthcare burden, yet its definitive diagnosis can be challenging. There is a need for a rapid, sensitive and reliable analytical method that could allow early detection of UTI and reduce unnecessary antibiotics. Pathogen identification along with quantitative detection of lactoferrin, a measure of pyuria, may provide useful information towards the overall diagnosis of UTI. Here, we report an integrated biosensor platform capable of simultaneous pathogen identification and detection of urinary biomarker that could aid the effectiveness of the treatment and clinical management. METHODOLOGY/PRINCIPAL FINDINGS: The integrated pathogen 16S rRNA and host lactoferrin detection using the biosensor array was performed on 113 clinical urine samples collected from patients at risk for complicated UTI. For pathogen detection, the biosensor used sandwich hybridization of capture and detector oligonucleotides to the target analyte, bacterial 16S rRNA. For detection of the protein biomarker, the biosensor used an analogous electrochemical sandwich assay based on capture and detector antibodies. For this assay, a set of oligonucleotide probes optimized for hybridization at 37°C to facilitate integration with the immunoassay was developed. This probe set targeted common uropathogens including E. coli, P. mirabilis, P. aeruginosa and Enterococcus spp. as well as less common uropathogens including Serratia, Providencia, Morganella and Staphylococcus spp. The biosensor assay for pathogen detection had a specificity of 97% and a sensitivity of 89%. A significant correlation was found between LTF concentration measured by the biosensor and WBC and leukocyte esterase (p<0.001 for both). CONCLUSION/SIGNIFICANCE: We successfully demonstrate simultaneous detection of nucleic acid and host immune marker on a single biosensor array in clinical samples. This platform can be used for multiplexed detection of nucleic acid and protein as the next generation of urinary tract infection diagnostics

Age-Related Attenuation of Dominant Hand Superiority

The decline of motor performance of the human hand-arm system with age is well-documented. While dominant hand performance is superior to that of the non-dominant hand in young individuals, little is known of possible age-related changes in hand dominance. We investigated age-related alterations of hand dominance in 20 to 90 year old subjects. All subjects were unambiguously right-handed according to the Edinburgh Handedness Inventory. In Experiment 1, motor performance for aiming, postural tremor, precision of arm-hand movement, speed of arm-hand movement, and wrist-finger speed tasks were tested. In Experiment 2, accelerometer-sensors were used to obtain objective records of hand use in everyday activities