741 research outputs found
Wave attenuation in glasses: Rayleigh and generalized-Rayleigh scattering scaling
The attenuation of long-wavelength phonons (waves) by glassy disorder plays a
central role in various glass anomalies, yet it is neither fully characterized,
nor fully understood. Of particular importance is the scaling of the
attenuation rate with small wavenumbers in the
thermodynamic limit of macroscopic glasses. Here we use a combination of theory
and extensive computer simulations to show that the macroscopic low-frequency
behavior emerges at intermediate frequencies in finite-size glasses, above a
recently identified crossover wavenumber , where phonons are no
longer quantized into bands. For , finite-size effects
dominate , which is quantitatively described by a theory of
disordered phonon bands. For , we find that is
affected by the number of quasilocalized nonphononic excitations, a generic
signature of glasses that feature a universal density of states. In particular,
we show that in a frequency range in which this number is small,
follows a Rayleigh scattering scaling ( is the spatial
dimension), and that in a frequency range in which this number is sufficiently
large, the recently observed generalized-Rayleigh scaling of the form
emerges ( is a characteristic
wavenumber). Our results suggest that macroscopic glasses --- and, in
particular, glasses generated by conventional laboratory quenches that are
known to strongly suppress quasilocalized nonphononic excitations --- exhibit
Rayleigh scaling at the lowest wavenumbers and a crossover to
generalized-Rayleigh scaling at higher . Some supporting experimental
evidence from recent literature is presented.Comment: 15 pages, 10 figures (including appendices). v2 includes a new
appendix with 2 figures (Fig.7 & Fig.8
Bostonia. Volume 5
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
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Wavelet Decomposition of Forced Turbulence: Applicability of the Iterative Donoho-Johnstone Threshold
We examine the decomposition of forced Taylor-Green and Arn’old-Beltrami- Childress (ABC) flows into coherent and incoherent components using an orthonormal wavelet decomposition. We ask whether wavelet coefficient thresh- olding based on the Donoho-Johnstone criterion can extract a coherent vortex signal while leaving behind Gaussian random noise. We find that no threshold yields a strictly Gaussian incoherent component, and that the most Gaussian incoherent flow is found for data compression lower than that achieved with the fully iterated Donoho-Johnstone threshold. Moreover, even at such low compression, the incoherent component shows clear signs of large-scale spatial correlations that are signatures of the forcings used to drive the flows
The presence of γ′ chain impairs fibrin polymerization
A fraction of fibrinogen molecules contain an alternatively spliced variant chain called γ’. Plasma levels of this variant have been associated with both myocardial infarction and venous thrombosis. Because clot structure has been associated with cardiovascular risk, we examined the effect of γ’ chain on clot structure
Bostonia: The Boston University Alumni Magazine. Volume 11
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
The Maine Annex, vol. 2, no. 2
Maine Annex editor Roy W. Nickerson faced flack after disrupting a talk about American-Russian relations by Russian revolutionary, leader of the social-democratic Trudovik faction of the Socialist Revolutionary Party, and president of the short-lived provinsional government following the overthrow of the Czar, Dr. Alexander Kerensky. Kerensky was ousted by the Bolshevisks lead by Vladamir Lenin
Epirubicin With Cyclophosphamide Followed by Docetaxel With Trastuzumab and Bevacizumab as Neoadjuvant Therapy for HER2-Positive Locally Advanced Breast Cancer or as Adjuvant Therapy for HER2-Positive Pathologic Stage III Breast Cancer: A Phase II Trial of the NSABP Foundation Research Group, FB-5
Background The purpose of this study was to determine the cardiac safety and clinical activity of trastuzumab and bevacizumab with docetaxel after epirubicin with cyclophosphamide (EC) in patients with HER2-positive locally advanced breast cancer (LABC) or pathologic stage 3 breast cancer (PS3BC). Patients and Methods Patients received every 3 week treatment with 4 cycles of EC (90/600 mg/m2) followed by 4 cycles of docetaxel (100 mg/m2). Targeted therapy with standard-dose trastuzumab with bevacizumab 15 mg/kg was given for a total of 1 year. Coprimary end points were (1) rate of cardiac events (CEs) in all patients defined as clinical congestive heart failure with a significant decrease in left ventricular ejection fraction or cardiac deaths; and (2) pathologic complete response (pCR) in breast and nodes in the neoadjuvant cohort. An independent cardiac review panel determined whether criteria for a CE were met. Results A total of 105 patients were accrued, 76 with LABC treated with neoadjuvant therapy and 29 with PS3BC treated with adjuvant therapy. Median follow-up was 59.2 months. Among 99 evaluable patients for cardiac safety, 4 (4%; 95% confidence interval [CI], 1.1%-10.0%) met CE criteria. The pCR percentage in LABC patients was 46% (95% CI, 34%-59%). Five-year recurrence-free survival (RFS) and overall survival (OS) for all patients was 79.9% and 90.8%, respectively. Conclusion The regimen met predefined criteria for activity of interest with an acceptable rate of CEs. Although the pCR percentage was comparable with chemotherapy regimens with trastuzumab alone the high RFS and OS are of interest in these high-risk populations
Object Relations in the Museum: A Psychosocial Perspective
This article theorises museum engagement from a psychosocial perspective. With the aid of selected concepts from object relations theory, it explains how the museum visitor can establish a personal relation to museum objects, making use of them as an ‘aesthetic third’ to symbolise experience. Since such objects are at the same time cultural resources, interacting with them helps the individual to feel part of a shared culture. The article elaborates an example drawn from a research project that aimed to make museum collections available to people with physical and mental health problems. It draws on the work of the British psychoanalysts Donald Winnicott and Wilfred Bion to explain the salience of the concepts of object use, potential space, containment and reverie within a museum context. It also refers to the work of the contemporary psychoanalyst Christopher Bollas on how objects can become evocative for individuals both by virtue of their intrinsic qualities and by the way they are used to express personal idiom
Simple Viscous Flows: from Boundary Layers to the Renormalization Group
The seemingly simple problem of determining the drag on a body moving through
a very viscous fluid has, for over 150 years, been a source of theoretical
confusion, mathematical paradoxes, and experimental artifacts, primarily
arising from the complex boundary layer structure of the flow near the body and
at infinity. We review the extensive experimental and theoretical literature on
this problem, with special emphasis on the logical relationship between
different approaches. The survey begins with the developments of matched
asymptotic expansions, and concludes with a discussion of perturbative
renormalization group techniques, adapted from quantum field theory to
differential equations. The renormalization group calculations lead to a new
prediction for the drag coefficient, one which can both reproduce and surpass
the results of matched asymptotics
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