Shear layer excitation, experiment versus theory

The acoustical excitation of shear layers is investigated. Acoustical excitation causes the so-called orderly structures in shear layers and jets. Also, the deviations in the spreading rate between different shear layer experiments are due to the same excitation mechanism. Measurements in the linear interaction region close to the edge from which the shear layer is shed are examined. Two sets of experiments (Houston 1981 and Berlin 1983/84) are discussed. The measurements were carried out with shear layers in air using hot wire anemometers and microphones. The agreement between these measurements and the theory is good. Even details of the fluctuating flow field correspond to theoretical predictions, such as the local occurrence of negative phase speeds

The contribution of tyrosine water=hydrogen bonds to protein stability

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 30-32).The goal of this research was to determine how protein stability is affected when tyrosines form specific inter and/or intramolecular hydrogen bonds in the folded state. Our model protein, the enzyme RNase Sa, contains four Tyr residues believed to form one or more intermolecular hydrogen bonds to surface or partially buried water molecules. To study these interactions the single mutants Tyr 30, 49, 55, 81 ʾPhe were prepared and their conformational stability and thermodynamics of folding analyzed. From thermal denaturation data the free energy of unfolding, DGu, enthalpy of unfolding, DH, the melting temperature, Tm, and heat capacity change associated with unfolding, DCp, have been calculated. Initial analysis of Tyr 30, 49, 55, 81 predicted that each residue formed hydrogen bonds to one or more water molecules; however, thermodynamic and NMR data from this study support the surprising results that Tyr 81 actually makes an atypical intramolecular bond contributing 1.2 KcaI/mol to stability. Data for Tyr 30, 49, 55 support the prediction that intermolecular hydrogen bonds to water molecules are formed

Unraveling radial dependency effects in fiber thermal drawing

Fiber-based devices with advanced functionalities are emerging as promising solutions for various applications in flexible electronics and bioengineering. Multimaterial thermal drawing, in particular, has attracted strong interest for its ability to generate fibers with complex architectures. Thus far, however, the understanding of its fluid dynamics has only been applied to single material preforms for which higher order effects, such as the radial dependency of the axial velocity, could be neglected. With complex multimaterial preforms, such effects must be taken into account, as they can affect the architecture and the functional properties of the resulting fiber device. Here, we propose a versatile model of the thermal drawing of fibers, which takes into account a radially varying axial velocity. Unlike the commonly used cross section averaged approach, our model is capable of predicting radial variations of functional properties caused by the deformation during drawing. This is demonstrated for two effects observed, namely, by unraveling the deformation of initially straight, transversal lines in the preform and the dependence on the draw ratio and radial position of the in-fiber electrical conductivity of polymer nanocomposites, an important class of materials for emerging fiber devices. This work sets a thus far missing theoretical and practical understanding of multimaterial fiber processing to better engineer advanced fibers and textiles for sensing, health care, robotics, or bioengineering applications

Recent advances concerning an understanding of sound transmission through engine nozzles and jets

Experiments on the interaction between a turbulent jet and pure tone sound coming from inside the jet nozzle are reported. This is a model representing the sound transmission from sound sources in jet engines through the nozzle and the jet flow into the far field. It is shown that pure tone sound at low frequencies is considerably attenuated by the jet flow, whereas it is conserved at higher frequencies. On the other hand, broadband jet noise can be amplified considerably by a pure tone excitation. Both effects seem not to be interdependent. Knowledge on how they are created and on relevant parameter dependences allow new considerations for the development of sound attenuators

La influencia de ritmos musicales sobre la percepción de los estados subjetivos de pacientes adultos en hemodiálisis

Submeter-se à Hemodiálise quatro horas por dia, três vezes por semana, pode configurar-se uma experiência carregada de tédio, além de causar desconforto durante sua realização. É comum os pacientes relatarem que o tempo parece se arrastar ou durar mais. O objetivo deste estudo foi conhecer a influência de dois diferentes ritmos musicais nos estados subjetivos e na percepção tempo-sensorial de pacientes adultos submetidos à hemodiálise, uma vez que a literatura sobre essa temática é escassa. O estudo foi realizado em um hospital privado, com 43 pacientes em hemodiálise, que se submeteram a duas sessões de improvisação musical em um teclado, nas quais os estados subjetivos e a percepção temporal foram avaliados pré e pós-intervenção. Mais de 80% dos pacientes sentiu o tempo passar mais rápido após as intervenções em ambos os ritmos. No entanto, o ritmo influenciou o tipo de experiência emocional que os pacientes apresentaram.Being submitted to dialysis four hours a day, three times a week can mean experiencing boredom, besides discomfort. Patients often report that the time seems to take longer to go by. The purpose of this study was to explore the influence of two different musical rhythms in the states of mind and perception of adult patients undergoing dialysis, since the literature on this subject is scarce. The study was performed at a private hospital with 43 patients, who participated in two sessions of musical improvisation with a keyboard. The subjective states and perception were evaluated before and after the intervention. Over 80% of the patients felt that time went by faster after the interventions in both rhythms. However, the pace was a decisive factor in the kind of emotional experience that the patients had.Someterse a la Hemodiálisis cuatro horas por día, tres veces por semana, puede configurarse en una experiencia cargada de tedio, además de causar incomodidad durante su realización. Es común que los pacientes relaten que el tiempo parece arrastrarse o durar más. El objetivo de este estudio fue conocer la influencia de dos diferentes ritmos musicales en los estados subjetivos y en la percepción del tiempo sensorial de pacientes adultos sometidos a la hemodiálisis, una vez que la literatura sobre esa temática es escasa. El estudio fue realizado en un hospital privado, con 43 pacientes en hemodiálisis, que se sometieron a dos sesiones de improvisación musical en un teclado, en las cuales los estados subjetivos y la percepción temporal fueron evaluados antes y después de la intervención. Más de 80% de los pacientes sintió el tiempo pasar más rápido después de las intervenciones en ambos ritmos. Sin embargo, el ritmo influenció el tipo de experiencia emocional que los pacientes presentaron

Biomimetic bluff body drag reduction by self-adaptive porous flaps

The performances of an original passive control system based on a biomimetic approach are assessed by investigating the flow over a bluff-body. This control device consists in a couple of flaps made from the combination of a rigid plastic skeleton coated with a porous fabric mimicking the shaft and the vane of the bird's feathers, respectively. The sides of a square cylinder have been fitted with this system so as to enable the flaps to freely rotate around their leading edge. This feature allows the movable flaps to self-adapt to the flow conditions. Comparing both the uncontrolled and the controlled flow, a significant drag reduction (up to 22%) has been obtained over a broad range of Reynolds number. The investigation of the mean flow reveals a noticeable modification of the flow topology at large scale in the vicinity of the controlled cylinder accounting for the increase of the pressure base in comparison with the natural flow. Meanwhile, the study of the relative motion of both flaps points out that their dynamics is sensitive to the Reynolds number. Furthermore, the comparative study of the flow dynamics at large scale suggest a lock-in coupling of the flap motion and the vortex shedding.Comment: 19 pages, 17 figures, submitted to Comptes-Rendus de l' Acad\'emie des Sciences (M\'ecanique

The Laws of the Buddhist Sangha : An Early Juridical System in Indian Tradition

departmental bulletin pape

CPT\cal CPT-invariant two-fermion Dirac equation with extended hyperfine operator

For the S-states of muonium and positronium, the hyperfine shifts to the order $\alpha^6$ of a recently derived two-fermion equation with explicit $\cal CPT$-invariance are checked against the results of a nonrelativistic reduction, and the leading $\alpha^8$ shifts are calculated. An additional hyperfine operator is discovered which can milden the singularity for $r\to 0$ of the Dirac hyperfine operator, such that the resulting extended operator can be used nonperturbatively. The binding correction to magnetic moments is mentioned