Wind tunnel investigations of model rotor noise at low tip speeds

Experimental and related analytical results on model rotor rotational and broadband noise obtained in the anechoic wind tunnel and rotor facility are summarized. Factors studied include various noise sources, effects of helicopter performance parameters on noise generated by a model main rotor, appropriate scaling laws for the various types of main rotor noise, and the effects of intensity and size scales of injected turbulence on the intensity and spectra of broadband noise

Prediction and reduction of rotor broadband noise

Prediction techniques which can be or have been applied to subsonic rotors, and methods for designing helicopter rotors for reduced broadband noise generation are summarized. It is shown how detailed physical models of the noise source can be used to identify approaches to noise control

Back-mixing Studies in the Presence of an Unstable Density Gradient in a Reciprocating Plate Extraction Column

The efficient design of extraction columns calIs for the accounting of flow non idealities, collectively termed axial mixing, in the phases involved. Axial mixing occurs mainly through back-mixing caused by circulation, wake transport with dispersed drops and induced turbulence due to mechanical agitation. Non uniform velocity profiles and forward mixing due to drops of different sizes are the other factors. A new factor identified to significantly enhance back-mixing, is the increase in the density of the continuous phase with column height termed as the unstable density gradient. In this thesis, attention was focussed on this factor using a 5 cm reciprocating plate extraction column (RPC). A new approach based on the Kohnogoroff isotropic turbulence theory was developed to model the continuous phase back-mixing under two phase flow conditions. The contribution due to mechanical agitation, dispersed phase flow and the unstable density gradient were accounted in the model in terms of their respective energy dissipation rates and mixing lengths. The parameters were estimated by fitting the model to the experimental data obtained through the steady state tracer injection technique under non mass transfer conditions. The results showed that the unstable density gradient played an important role in enhancing the back-mixing even though its energy dissipation rate was very small relative to the other two contributing factors. This was due to the large mixing length associated with the unstable density gradient effect. At high mechanical agitations, the contributions of the dispersed phase and the density gradient declined. A preliminary study was also performed to investigate the unstable density gradient effect under mass transfer condition. Water was used as the solvent to extract i-propanol from lsopar M drops in the extractor. As increasing amount of alcohol was extracted, the density of water decreased leading to an unstable density gradient. To ensure the reliability of the estimation of the back-mixing coefficient (Ec), a non transferring tracer dye was also injected steadily into the continuous phase. Ec values were determined simultaneously from the concentration profiles of the tracer and the solute, thereby providing two independent estimates for each experiment. The results were comparable under most operating conditions thereby validating the tracer technique. The dispersed phase hold-up, drop size and the mass transfer coefficient were also estimated and compared critically with the models available in literature. The hydrodynamics in the column were significantly altered by the interfacial effects associated with the transfer of solute from the dispersed phase to the continuous phase. In particular coalescence was promoted leading to large drops. Under these conditions the Kolmogoroff model could not isolate the influence of the density gradient from other contributing factors. However the experimental results clearly showed an enhancement in the back-mixing relative to the non mass transfer case. Based on these observations it is concluded that care must be taken to avoid the unstable density gradient created either inadvertently during tracer measurements involving ionic compounds or during mass transfer.Doctor of Philosophy (PhD

Oxidative stress-induced mitochondrial dysfunction drives inflammation and airway smooth muscle remodeling in patients with chronic obstructive pulmonary disease

BackgroundInflammation and oxidative stress play critical roles in patients with chronic obstructive pulmonary disease (COPD). Mitochondrial oxidative stress might be involved in driving the oxidative stress–induced pathology.ObjectiveWe sought to determine the effects of oxidative stress on mitochondrial function in the pathophysiology of airway inflammation in ozone-exposed mice and human airway smooth muscle (ASM) cells.MethodsMice were exposed to ozone, and lung inflammation, airway hyperresponsiveness (AHR), and mitochondrial function were determined. Human ASM cells were isolated from bronchial biopsy specimens from healthy subjects, smokers, and patients with COPD. Inflammation and mitochondrial function in mice and human ASM cells were measured with and without the presence of the mitochondria-targeted antioxidant MitoQ.ResultsMice exposed to ozone, a source of oxidative stress, had lung inflammation and AHR associated with mitochondrial dysfunction and reflected by decreased mitochondrial membrane potential (ΔΨm), increased mitochondrial oxidative stress, and reduced mitochondrial complex I, III, and V expression. Reversal of mitochondrial dysfunction by the mitochondria-targeted antioxidant MitoQ reduced inflammation and AHR. ASM cells from patients with COPD have reduced ΔΨm, adenosine triphosphate content, complex expression, basal and maximum respiration levels, and respiratory reserve capacity compared with those from healthy control subjects, whereas mitochondrial reactive oxygen species (ROS) levels were increased. Healthy smokers were intermediate between healthy nonsmokers and patients with COPD. Hydrogen peroxide induced mitochondrial dysfunction in ASM cells from healthy subjects. MitoQ and Tiron inhibited TGF-β–induced ASM cell proliferation and CXCL8 release.ConclusionsMitochondrial dysfunction in patients with COPD is associated with excessive mitochondrial ROS levels, which contribute to enhanced inflammation and cell hyperproliferation. Targeting mitochondrial ROS represents a promising therapeutic approach in patients with COPD

How can power discourses be changed? - Contrasting the ‘daughter deficit’ policy of the Delhi government with Gandhi and King’s transformational reframing

Social policy impact is partly determined by how policy is articulated and advocated, including which values are highlighted and how. In this paper, we examine the influence of policy framing and reframing on outcomes, with particular reference to the policies of the Delhi state government in India that target the practices of female feticide, infanticide and neglect that underlie the ‘daughter deficit’. Using Snow and Benford’s categories for understanding reframing processes, the paper outlines and applies a ‘model’ of reframing disputed issues derived from looking at two famous campaigns – Gandhi’s 1930 Salt March in the struggle for Indian freedom from British rule and the African-American civil rights struggle of the 1950s and 1960s. It argues that ‘carrot and stick’ policy measures, such as financial incentives and legal prohibitions, to counteract the ‘daughter deficit’ must be complemented by well crafted discursive interventions

Time-Course of Changes in the Myonuclear Domain During Denervation in Young-Adult and Old Rat Gastrocnemius Muscle

If myonuclear loss initiates muscle wasting, it should precede the loss of muscle mass. As aging affects muscle plasticity, the time-course of muscle atrophy during disuse may differ between young and old animals. To investigate this, gastrocnemius muscles of 5- and 25-month-old rats were exposed to 1, 2, or 4 weeks of denervation, whereas the contralateral gastrocnemius muscles served as controls. Muscle fibers of each type responded similarly to 4 weeks of denervation. For both ages most of the atrophy (36%; P < 0.001) occurred in the first 2 weeks. In young-adult muscles, the myonuclear number remained constant, but in old muscles it decreased to below control level after 4 weeks of denervation (P < 0.05). Despite this differential response, myonuclear domain size decreased similarly at both ages (P < 0.001). In both young-adult and old rats, denervation-induced atrophy was not preceded by a loss of myonuclei. © 2011 Wiley Periodicals, Inc

Caveolae in Rabbit Ventricular Myocytes: Distribution and Dynamic Diminution after Cell Isolation

Caveolae are signal transduction centers, yet their subcellular distribution and preservation in cardiac myocytes after cell isolation are not well documented. Here, we quantify caveolae located within 100 nm of the outer cell surface membrane in rabbit single-ventricular cardiomyocytes over 8 h post-isolation and relate this to the presence of caveolae in intact tissue. Hearts from New Zealand white rabbits were either chemically fixed by coronary perfusion or enzymatically digested to isolate ventricular myocytes, which were subsequently fixed at 0, 3, and 8 h post-isolation. In live cells, the patch-clamp technique was used to measure whole-cell plasma membrane capacitance, and in fixed cells, caveolae were quantified by transmission electron microscopy. Changes in cell-surface topology were assessed using scanning electron microscopy. In fixed ventricular myocardium, dual-axis electron tomography was used for three-dimensional reconstruction and analysis of caveolae in situ. The presence and distribution of surface-sarcolemmal caveolae in freshly isolated cells matches that of intact myocardium. With time, the number of surface-sarcolemmal caveolae decreases in isolated cardiomyocytes. This is associated with a gradual increase in whole-cell membrane capacitance. Concurrently, there is a significant increase in area, diameter, and circularity of sub-sarcolemmal mitochondria, indicative of swelling. In addition, electron tomography data from intact heart illustrate the regular presence of caveolae not only at the surface sarcolemma, but also on transverse-tubular membranes in ventricular myocardium. Thus, caveolae are dynamic structures, present both at surface-sarcolemmal and transverse-tubular membranes. After cell isolation, the number of surface-sarcolemmal caveolae decreases significantly within a time frame relevant for single-cell research. The concurrent increase in cell capacitance suggests that membrane incorporation of surface-sarcolemmal caveolae underlies this, but internalization and/or micro-vesicle loss to the extracellular space may also contribute. Given that much of the research into cardiac caveolae-dependent signaling utilizes isolated cells, and since caveolae-dependent pathways matter for a wide range of other study targets, analysis of isolated cell data should take the time post-isolation into account

Caveolin contributes to the modulation of basal and β-adrenoceptor stimulated function of the adult rat ventricular myocyte by simvastatin: A novel pleiotropic effect

The number of people taking statins is increasing across the globe, highlighting the Importance of fully understanding statins effects on the cardiovascular system. The beneficial impact of statins extends well beyond regression of atherosclerosis to include direct effects on tissues of the cardiovascular system (pleiotropic effects). Pleiotropic effects on the cardiac myocyte are often overlooked. Here we consider the contribution of the caveolin protein, whose expression and cellular distribution is dependent on cholesterol, to statin effects on the cardiac myocyte. Caveolin is a structural and regulatory component of caveolae, and is a key regulator of cardiac contractile function and adrenergic responsiveness. We employed an experimental model in which inhibition of myocyte HMG CoA reductase could be studied in the absence of paracrine influences from non-myocyte cells. Adult rat ventricular myocytes were treated with 10 μM simvastatin for 2 days. Simvastatin treatment reduced myocyte cholesterol, caveolin 3 and caveolar density. Negative inotropic and positive lusitropic effects (with corresponding changes in [Ca2]¡) were seen in statin-treated cells. Simvastatin significantly potentiated the inotropic response to β2-, but not β1-, adrenoceptor stimulation. Under conditions of β2-adrenoceptor stimulation, phosphorylation of phospholamban at Ser16and troponin I at Ser23/24was enhanced with statin treatment. Simvastatin increased NO production without significant effects on eNOS expression or phosphorylation (Ser1177), consistent with the reduced expression of caveolin 3, its constitutive Inhibitor. In conclusion, statin treatment can reduce caveolin 3 expression, with functional consequences consistent with the known role of caveolae in the cardiac cell. These data are likely to be of significance, particularly during the early phases of statin treatment, and in patients with heart failure who have altered ß-adrenoceptor signalling. In addition, as caveolin is ubiquitously expressed and has myriad tissue-specific functions, the impact of statin-dependent changes in caveolin is likely to have many other functional sequelae

Photoelectrochemical properties of metal-cluster oxide compounds, A<SUB>2</SUB>Mo<SUB>3</SUB>O<SUB>8</SUB> and (LiY)Mo<SUB>3</SUB>O<SUB>8</SUB>

PEC studies on the single crystals of the metal-cluster oxide compounds. A2Mo3O8 (A = Zn, Mg, Fe), and polycrystalline LiYMo3O8 are reported. The photoresponse behaviour is attributed to the Mo d-d transition. The photopotential, the photocurrent vs applied voltage and the wavelength data indicate that n-Zn2Mo3O8 is stable and possesses a small and indirect band gap of 1.55 eV and a direct band gap of 1.9 eV. With change in A ions in A2Mo3O8, there is no significant change in the PEC properties. LiYMo3O8 is found to be of p-type. PEC studies show that excepting for poor electronic conductivity, A2Mo3O8 possesses all the requisitie characteristics of an ideal photoanode for PAE of water for trapping solar energy

Global Joyce

James Joyce’s interest in accessing the global through the core of the local makes him a particularly suggestive example for writers interested in a cosmopolitan vernacular, particularly for those writing, as Joyce did, from the margins of Europe. Postcolonial studies have extended Joyce criticism through new readings of the global multiplicity of his work and through study of the translations that brought Joyce to new readerships, but have only recently begun to examine writers outside of Europe and North America who both followed and challenged Joyce’s example. This article discusses Joyce’s global influence in the accounts of critics and novelists, including Mulk Raj Anand, Salman Rushdie, Derek Walcott and Orhan Pamuk. Attention to Joyce as a postcolonial writer should serve to call attention to other international writers, rather than to overwrite them; the effect should be centripetal and should expand and dislocate our ideas of influence rather than situate them in a stable centre. Joyce’s global circulation, reception, imitation and adaptation comprises an odyssey of reading engaged both with the revisioning of the literary past and the future of literary studies