21,004 research outputs found
Atypical Ductal Hyperplasia at the Margin of Lumpectomy Performed for Early Stage Breast Cancer: Is there Enough Evidence to Formulate Guidelines?
Background. Negative margins are associated with a reduced risk of ipsilateral breast tumor recurrence (IBTR) in women with early stage breast cancer treated with breast conserving surgery (BCS). Not infrequently, atypical ductal hyperplasia (ADH) is reported as involving the margin of a BCS specimen, and there is no consensus among surgeons or pathologists on how to approach this diagnosis resulting in varied reexcision practices among breast surgeons. The purpose of this paper is to establish a reasonable approach to guide the treatment of ADH involving the margin after BCS for early stage breast cancer. Methods. the published literature was reviewed using the PubMed site from the US National Library of Medicine. Conclusions. ADH at the margin of a BCS specimen performed for early stage breast cancer is a controversial pathological diagnosis subject to large interobserver variability. There is not enough data evaluating this diagnosis to change current practice patterns; however, it is reasonable to consider reexcision for ADH involving a surgical margin, especially if it coexists with low grade DCIS. Further studies with longer followup and closer attention to ADH at the margin are needed to formulate treatment guidelines
The effects of Reynolds number, rotor incidence angle, and surface roughness on the heat transfer distribution in a large-scale turbine rotor passage
A combined experimental and computational program was conducted to examine the heat transfer distribution in a turbine rotor passage geometrically similiar to the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP). Heat transfer was measured and computed for both the full-span suction and pressure surfaces of the rotor airfoil as well as for the hub endwall surface. The primary objective of the program was to provide a benchmark-quality data base for the assessment of rotor passage heat transfer computational procedures. The experimental portion of the study was conducted in a large-scale, ambient temperature, rotating turbine model. Heat transfer data were obtained using thermocouple and liquid-crystal techniques to measure temperature distributions on the thin, electrically-heated skin of the rotor passage model. Test data were obtained for various combinations of Reynolds number, rotor incidence angle and model surface roughness. The data are reported in the form of contour maps of Stanton number. These heat distribution maps revealed numerous local effects produced by the three-dimensional flows within the rotor passage. Of particular importance were regions of local enhancement produced on the airfoil suction surface by the main-passage and tip-leakage vortices and on the hub endwall by the leading-edge horseshoe vortex system. The computational portion consisted of the application of a well-posed parabolized Navier-Stokes analysis to the calculation of the three-dimensional viscous flow through ducts simulating the a gas turbine passage. These cases include a 90 deg turning duct, a gas turbine cascade simulating a stator passage, and a gas turbine rotor passage including Coriolis forces. The calculated results were evaluated using experimental data of the three-dimensional velocity fields, wall static pressures, and wall heat transfer on the suction surface of the turbine airfoil and on the end wall. Particular attention was paid to an accurate modeling of the passage vortex and to the development of the wall boundary layers including crossflow
Localized Stress Fluctuations Drive Shear Thickening in Dense Suspensions
The mechanical response of solid particles dispersed in a Newtonian fluid
exhibits a wide range of nonlinear phenomena including a dramatic increase in
the viscosity \cite{1-3} with increasing stress. If the volume fraction of the
solid phase is moderately high, the suspension will undergo continuous shear
thickening (CST), where the suspension viscosity increases smoothly with
applied shear stress; at still higher volume fractions the suspension can
display discontinuous shear thickening (DST), where the viscosity changes
abruptly over several orders of magnitude upon increasing applied stress.
Proposed models to explain this phenomenon are based in two distinct types of
particle interactions, hydrodynamic\cite{2,4,5} and frictional\cite{6-10}. In
both cases, the increase in the bulk viscosity is attributed to some form of
localized clustering\cite{11,12}. However, the physical properties and
dynamical behavior of these heterogeneities remains unclear. Here we show that
continuous shear thickening originates from dynamic localized well defined
regions of particles with a high viscosity that increases rapidly with
concentration. Furthermore, we find that the spatial extent of these regions is
largely determined by the distance between the shearing surfaces. Our results
demonstrate that continuous shear thickening arises from increasingly frequent
localized discontinuous transitions between coexisting low and high viscosity
Newtonian fluid phases. Our results provide a critical physical link between
the microscopic dynamical processes that determine particle interactions and
bulk rheological response of shear thickened fluids
A review of the mallet impact test for small scale explosive formulations
Presented at 19th Seminar on New Trends of Energetic Materials (NTREM 2016); 20-22/04/2016, Pardubice Czech RepublicDevelopment of new explosive formulations begins with the generation of only a few milligrams of material which is investigated using a number of small scale tests such as DSC, TGA, response to flame, mallet impact (mallet friction either glancing or direct blow) to determine whether the formulation is safe to scale up to 10 g. The latter of these tests, mallet impact, can be particularly subjective as the result is directly influenced by the operator carrying out the assessment. Not only can there be a change from one operator to another but there can also be a change in the force applied during each strike potentially leading to inconsistent results. This study highlights this encountered variation and assesses the load applied by a variety of operators with varying levels of explosive experience. This paper also proposes the use of a small scale laboratory based impact test which would provide improved confidence in the assessment of impact sensitiveness of explosive formulations and assist in justifying whether a formulation can be taken to the next scale. A small scale version of the BAM impact test (EMTAP Test 43) has been devised that allows the comparison of the sensitiveness of small scale formulations relative to RDX (8.7 J, EMTAP Test 43B) whilst also ensuring a reproducible result
Is There Selection Bias in Laboratory Experiments? The Case of Social and Risk Preferences
Laboratory experiments are frequently used to examine the nature of individual preferences and inform economic theory. However, it is unknown whether the preferences of volunteer participants are representative of the population from which the participants are drawn or whether they differ due to selection bias. We examine whether the social and risk preferences of participants in a laboratory experiment represent the preferences of the population from which they are recruited. To answer this question, we measured the preferences of 1,173 students in a classroom experiment. Separately, we invited all students to participate in a laboratory experiment. We find that the social and risk preferences of students who attend the laboratory experiment do not differ significantly from the preferences of the population from which they were recruited. Moreover, participation decisions based on social and risk preferences do not differ significantly across most subgroups, with the exception that female participants are on average less risk averse than female non-participants, and male participants are more risk averse than male non-participants.selection bias, laboratory experiments, external validity, social preferences, risk preferences
Polymer matrix composites on LDEF experiments M0003-9 and M0003-10
Over 250 polymer matrix composites were exposed to the natural space environment on Long Duration Exposure Facility (LDEF) experiments M0003-9 and 10. The experiments included a wide variety of epoxy, thermoplastic, polyimide, and bismalimide matrix composites reinforced with graphite, glass, or organic fibers. A review of the significant observations and test results obtained to date is presented. Estimated recession depths from atomic oxygen exposure are reported and the resulting surface morphologies are discussed. The effects of the LDEF exposure on the flexural strength and modulus, short beam shear strength, and coefficient of thermal expansion of several classes of bare and coated composites are reviewed. Lap shear data are presented for composite-to-composite and composite-to-aluminum alloy samples that were prepared using different bonding techniques and subsequently flown on LDEF
Is There Selection Bias in Laboratory Experiments?*
Do the social and risk preferences of participants in laboratory experiments represent the preferences of the population from which they are recruited? To answer this question, we conducted a classroom experiment with a population of 1,173 students using a trust game and a lottery choice task to measure individual preferences. Separately, all 1,173 students were invited to participate in a laboratory experiment. To determine whether selection bias exists, we compare the preferences of the individuals who eventually participated in a laboratory experiment to those in the population. We find that the social and risk preferences of the students participating in the laboratory experiment are not significantly different from the preferences of the population from which they were recruited. We further show that participation decisions across most subgroups (e.g., men vs. women) do not differ significantly. We therefore fail to find selection bias based on social and risk preferences.external validity; social preferences; selection bias; laboratory experiments; risk preferences
Bottom-Up Reconstruction Scenarios for (un)constrained MSSM Parameters at the LHC
We consider some specific inverse problem or "bottom-up" reconstruction
strategies at the LHC for both general and constrained MSSM parameters,
starting from a plausibly limited set of sparticle identification and mass
measurements, using mainly gluino/squark cascade decays, plus eventually the
lightest Higgs boson mass. For the three naturally separated sectors of:
gaugino/Higgsino, squark/slepton, and Higgs parameters, we examine different
step-by-step algorithms based on rather simple, entirely analytical, inverted
relations between masses and basic MSSM parameters. This includes also
reasonably good approximations of some of the relevant radiative correction
calculations. We distinguish the constraints obtained for a general MSSM from
those obtained with universality assumptions in the three different sectors.
Our results are compared at different stages with the determination from more
standard "top-down" fit of models to data, and finally combined into a global
determination of all the relevant parameters. Our approach gives complementary
information to more conventional analysis, and is not restricted to the
specific LHC measurement specificities. In addition, the bottom-up
renormalization group evolution of general MSSM parameters, being an important
ingredient in this framework, is illustrated as a new publicly available option
of the MSSM spectrum calculation code "SuSpect".Comment: 52 pages, 22 figures. Slight reorganization of sections, a few more
results for the neutralino sector, one appendix added on neutralino sector
calculation details. Version to appear in Phys. Rev.
- âŠ