Development of an apparatus to measure thermophysical properties of wind tunnel heat transfer models

The apparatus and technique for measuring the thermophysical properties of models used with the phase-change paint method for obtaining wind tunnel heat transfer data are described. The method allows rapid measurement of the combined properties in a transient manner similar to an actual wind tunnel test. An effective value of the thermophysical properties can be determined which accounts for changes in thermal properties with temperature or with depth into the model surface. The apparatus was successfully tested at various heating rates between 19,000 and 124,000 watts per square meter

Introduction: The emergence of ‘trans’

No abstract available

Making Good Lawyers

Today, the criticism of law schools has become an industry. Detractors argue that legal education fails to effectively prepare students for the practice of law, that it is too theoretical and detached from the profession, that it dehumanizes and alienates students, too expensive and inapt in helping students develop a sense of professional identity, professional values, and professionalism. In this sea of criticisms it is hard to see the forest from the trees. “There is so much wrong with legal education today,” writes one commentator, “that it is hard to know where to begin.” This article argues that any reform agenda will fall short if it does not start by recognizing the dominant influence of the culture of autonomous self-interest in legal education. Law schools engage in a project of professional formation and instill a very particular brand of professional identity. They educate students to become autonomously self-interested lawyers who see their clients and themselves as pursuing self-interest as atomistic actors. As a result, they understand that their primary role is to serve as neutral partisans who promote the narrow self-interest of clients without regard to the interests of their families, neighbors, colleagues, or communities and to the exclusion of counseling clients on the implications of those interests. They view as marginal their roles as an officer of the legal system and as a public citizen and accordingly place a low priority on traditional professional values, such as the commitment to the public good, that conflict with their primary allegiance to autonomous self-interest. In this work of professional formation, law schools are reflecting the values and commitments of the autonomously self-interested culture that is dominant in the legal profession. Therefore, even if law schools sought to form a professional identity outside of the mold of autonomous self-interest, such a commitment would require much more than curricular reform. It would, at minimum, require the construction of a persuasive alternative understanding of the lawyer’s role. The article seeks to offer such an understanding grounded in a relational perspective on lawyers and clients. Part I offers workable definitions of professionalism and professional identity that enable an informed discussion of the formation of professional identity in and by law schools. Part II explores what and how legal education teaches students showing that both institutionally (at the law school level) and individually (at the law professor level) legal education is proactively engaged in the formation of a professional identity of autonomous self-interest. Part II further explains that its dominance in legal education notwithstanding, autonomous self-interest is but one, often unpersuasive, account of professionalism and professional identity. Part III turns to the competing vision of relationally self-interested professionalism and professional identity and develops an outline for legal education grounded in these conceptions. Because legal education reflects a deep commitment to the dominant culture of autonomous self-interest, it is unlikely that reform proposals that are inconsistent with that culture are likely to succeed in the near future. Yet proposing an alternative account of professional identity that exposes the assumptions of the dominant culture, explains their limitations, and develops a more persuasive understanding is a necessary step toward providing a workable framework for reformers committed to promoting professional values in the long term

Parametric Generation of Second Sound by First Sound in Superfluid Helium

We report the first experimental observation of parametric generation of second sound (SS) by first sound (FS) in superfluid helium in a narrow temperature range in the vicinity of $T_\lambda$. The temperature dependence of the threshold FS amplitude is found to be in a good quantitative agreement with the theory suggested long time ago and corrected for a finite geometry. Strong amplitude fluctuations and two types of the SS spectra are observed above the bifurcation. The latter effect is quantitatively explained by the discreteness of the wave vector space and the strong temperature dependence of the SS dissipation length.Comment: 4 pages, 4 postscript figures, REVTE

Structural and Compositional Changes in Aging Bone: Osteopenia in Lumbar Vertebrae of Wistar Female Rats

Changes in vertebral bone mineral content and density during aging were quantified in female Wistar rats. This study represents a longitudinal follow up utilizing single photon absorptiometry for the measurement of bone mineral content (BMC), quantitative computed tomography (OCT) for the measurement of bone mineral density (BMD), and image analysis histomorphometry for the measurement of trabecular bone volume (TBV) and bone cortical area (BCA). The above measurements were accompanied by biochemical assays of calcium concentrations in the respective bones. All aging animals experienced significant decreases in BMC, BMD, TBV, BCA and in the calcium content of their bones. The above features have been further emphasized through the use of scanning electron micrographs showing the age-related structural changes in a three-dimentional fashion. New, advanced technologies will enable the quantitation of 3-dimensional images that are currently obtained from the scanning electron micrograph; thus will provide new consideration as related to trabecular bone compactness (density). Energy dispersive x-ray spectroscopy indicated that the nature of crystals in aging bones does not differ markedly from that encountered in young specimens. Data are also provided with regard to the health of the animals, and it became apparent that aging rats undergo changes in their kidneys yet do not show any significant change in renal functional parameters as measured in both the serum and the urine. Hence, new noninvasive methodologies are currently available for longitudinal studies related to the skeleton in laboratory animals enabling reliable monitoring of age-related and hormonally induced changes in bones (spine and hip) of well defined experimental models

Elastic turbulence in curvilinear flows of polymer solutions

Following our first report (A. Groisman and V. Steinberg, \sl Nature $\bf 405$, 53 (2000)) we present an extended account of experimental observations of elasticity induced turbulence in three different systems: a swirling flow between two plates, a Couette-Taylor (CT) flow between two cylinders, and a flow in a curvilinear channel (Dean flow). All three set-ups had high ratio of width of the region available for flow to radius of curvature of the streamlines. The experiments were carried out with dilute solutions of high molecular weight polyacrylamide in concentrated sugar syrups. High polymer relaxation time and solution viscosity ensured prevalence of non-linear elastic effects over inertial non-linearity, and development of purely elastic instabilities at low Reynolds number (Re) in all three flows. Above the elastic instability threshold, flows in all three systems exhibit features of developed turbulence. Those include: (i)randomly fluctuating fluid motion excited in a broad range of spatial and temporal scales; (ii) significant increase in the rates of momentum and mass transfer (compared to those expected for a steady flow with a smooth velocity profile). Phenomenology, driving mechanisms, and parameter dependence of the elastic turbulence are compared with those of the conventional high Re hydrodynamic turbulence in Newtonian fluids.Comment: 23 pages, 26 figure

Sub-femtosecond determination of transmission delay times for a dielectric mirror (photonic bandgap) as a function of angle of incidence

Using a two-photon interference technique, we measure the delay for single-photon wavepackets to be transmitted through a multilayer dielectric mirror, which functions as a ``photonic bandgap'' medium. By varying the angle of incidence, we are able to confirm the behavior predicted by the group delay (stationary phase approximation), including a variation of the delay time from superluminal to subluminal as the band edge is tuned towards to the wavelength of our photons. The agreement with theory is better than 0.5 femtoseconds (less than one quarter of an optical period) except at large angles of incidence. The source of the remaining discrepancy is not yet fully understood.Comment: 5 pages and 5 figure

Correlation energy of an electron gas in strong magnetic fields at high densities

The high-density electron gas in a strong magnetic field B and at zero temperature is investigated. The quantum strong-field limit is considered in which only the lowest Landau level is occupied. It is shown that the perturbation series of the ground-state energy can be represented in analogy to the Gell-Mann Brueckner expression of the ground-state energy of the field-free electron gas. The role of the expansion parameter is taken by r_B= (2/3 \pi^2) (B/m^2) (\hbar r_s /e)^3 instead of the field-free Gell-Mann Brueckner parameter r_s. The perturbation series is given exactly up to o(r_B) for the case of a small filling factor for the lowest Landau level.Comment: 10 pages, Accepted for publication in Phys.Rev.

Solitary vortex couples in viscoelastic Couette flow

We report experimental observation of a localized structure, which is of a new type for dissipative systems. It appears as a solitary vortex couple ("diwhirl") in Couette flow with highly elastic polymer solutions. A unique property of the diwhirls is that they are stationary, in contrast to the usual localized wave structures in both Hamiltonian and dissipative systems which are stabilized by wave dispersion. It is also a new object in fluid dynamics - a couple of vortices that build a single entity somewhat similar to a magnetic dipole. The diwhirls arise as a result of a purely elastic instability through a hysteretic transition at negligible Reynolds numbers. It is suggested that the vortex flow is driven by the same forces that cause the Weissenberg effect. The diwhirls have a striking asymmetry between the inflow and outflow, which is also an essential feature of the suggested elastic instability mechanism.Comment: 9 pages (LaTeX), 5 Postscript figures, submitte

Conditional probabilities in quantum theory, and the tunneling time controversy

It is argued that there is a sensible way to define conditional probabilities in quantum mechanics, assuming only Bayes's theorem and standard quantum theory. These probabilities are equivalent to the ``weak measurement'' predictions due to Aharonov {\it et al.}, and hence describe the outcomes of real measurements made on subensembles. In particular, this approach is used to address the question of the history of a particle which has tunnelled across a barrier. A {\it gedankenexperiment} is presented to demonstrate the physically testable implications of the results of these calculations, along with graphs of the time-evolution of the conditional probability distribution for a tunneling particle and for one undergoing allowed transmission. Numerical results are also presented for the effects of loss in a bandgap medium on transmission and on reflection, as a function of the position of the lossy region; such loss should provide a feasible, though indirect, test of the present conclusions. It is argued that the effects of loss on the pulse {\it delay time} are related to the imaginary value of the momentum of a tunneling particle, and it is suggested that this might help explain a small discrepancy in an earlier experiment.Comment: 11 pages, latex, 4 postscript figures separate (one w/ 3 parts