5,250 research outputs found
Weight Control System
Weight Control System, a set of linked computer programs which provides weight and balance reports from magnetic tape files, provides weight control and reporting on launch vehicle programs. With minor format modifications the program is applicable to aerospace, marine, automotive and other land transportation industries
Low-coverage heats of adsorption. iii - alkali metal ions on tungsten, atom-metal interaction theory
Heats of adsorption of sodium, rubidium, and cesium ions on tungsten substrat
Machine learning -- based diffractive imaging with subwavelength resolution
Far-field characterization of small objects is severely constrained by the
diffraction limit. Existing tools achieving sub-diffraction resolution often
utilize point-by-point image reconstruction via scanning or labelling. Here, we
present a new imaging technique capable of fast and accurate characterization
of two-dimensional structures with at least wavelength/25 resolution, based on
a single far-field intensity measurement. Experimentally, we realized this
technique resolving the smallest-available to us 180-nm-scale features with
532-nm laser light. A comprehensive analysis of machine learning algorithms was
performed to gain insight into the learning process and to understand the flow
of subwavelength information through the system. Image parameterization,
suitable for diffractive configurations and highly tolerant to random noise was
developed. The proposed technique can be applied to new characterization tools
with high spatial resolution, fast data acquisition, and artificial
intelligence, such as high-speed nanoscale metrology and quality control, and
can be further developed to high-resolution spectroscop
On the Prediction of Extreme Ecological Events
Ecological studies often focus on average effects of environmental factors, but ecological dynamics may depend as much upon environmental extremes. Ecology would therefore benefit from the ability to predict the frequency and severity of extreme environmental events. Some extreme events (e.g., earthquakes) are simple events: either they happen or they don\u27t, and they are generally difficult to predict. In contrast, extreme ecological events are often compound events, resulting from the chance coincidence of run-of-the-mill factors. Here we present an environmental bootstrap method for resampling short-term environmental data (rolling the environmental dice) to calculate an ensemble of hypothetical time series that embodies how the physical environment could potentially play out differently. We use this ensemble in conjunction with mechanistic models of physiological processes to analyze the biological consequences of environmental extremes. Our resampling method provides details of these consequences that would be difficult to obtain otherwise, and our methodology can be applied to a wide variety of ecological systems. Here, we apply this approach to calculate return times for extreme hydrodynamic and thermal events on intertidal rocky shores. Our results demonstrate that the co-occurrence of normal events can indeed lead to environmental extremes, and that these extremes can cause disturbance. For example, the limpet Lottia gigantea and the mussel Mytilus californianus are co-dominant competitors for space on wave-swept rocky shores, but their response to extreme environmental events differ. Limpet mortality can vary drastically through time. Average yearly maximum body temperature of L. gigantea on horizontal surfaces is low, sufficient to kill fewer than 5% of individuals, but on rare occasions environmental factors align by chance to induce temperatures sufficient to kill \u3e99% of limpets. In contrast, mussels do not exhibit large temporal variation in the physical disturbance caused by breaking waves, and this difference in the pattern of disturbance may have ecological consequences for these competing species. The effect of environmental extremes is under added scrutiny as the frequency of extreme events increases in response to anthropogenically forced climate change. Our method can be used to discriminate between chance events and those caused by long-term shifts in climate
Comprehension as social and intellectual practice: Rebuilding curriculum in low socioeconomic and cultural minority schools
This article reframes the concept of comprehension as a social and intellectual practice. It reviews current approaches to reading instruction for linguistically and culturally diverse and low socioeconomic students, noting an emphasis on comprehension as autonomous skills. The Four Resources model (Freebody & Luke, 1990) is used to make the case for the integration of comprehension instruction with an emphasis on student cultural and community knowledge, and substantive intellectual and sociocultural content in elementary school curricula. Illustrations are drawn from research underway on the teaching of literacy in primary schools in low SES communities
Elementary simulation of tethered Brownian motion
We describe a simple numerical simulation, suitable for an undergraduate
project (or graduate problem set), of the Brownian motion of a particle in a
Hooke-law potential well. Understanding this physical situation is a practical
necessity in many experimental contexts, for instance in single molecule
biophysics; and its simulation helps the student to appreciate the dynamical
character of thermal equilibrium. We show that the simulation succeeds in
capturing behavior seen in experimental data on tethered particle motion.Comment: Submitted to American Journal of Physic
Iron-catalysed C(sp<sup>2</sup>)-H borylation enabled by carboxylate activation
Arene C(sp2)-H bond borylation reactions provide rapid and efficient routes to synthetically versatile boronic esters. While iridium catalysts are well established for this reaction, the discovery and development of methods using Earth-abundant alternatives is limited to just a few examples. Applying an in situ catalyst activation method using air-stable and easily handed reagents, the iron-catalysed C(sp2)-H borylation reactions of furans and thiophenes under blue light irradiation have been developed. Key reaction intermediates have been prepared and characterised, and suggest two mechanistic pathways are in action involving both C-H metallation and the formation of an iron boryl species
Strong and Electromagnetic Decays of Two New Baryons
Two recently discovered excited charm baryons are studied within the
framework of Heavy Hadron Chiral Perturbation Theory. We interpret these new
baryons which lie 308 \MeV and 340 \MeV above the as
members of a P-wave spin doublet. Differential and total decay rates for their
double pion transitions down to the ground state are calculated.
Estimates for their radiative decay rates are also discussed. We find that the
experimentally determined characteristics of the baryons may be
simply understood in the effective theory.Comment: 16 pages with 4 figures not included but available upon request,
CALT-68-191
Renormalization group scaling in nonrelativistic QCD
We discuss the matching conditions and renormalization group evolution of
non-relativistic QCD. A variant of the conventional MS-bar scheme is proposed
in which a subtraction velocity nu is used rather than a subtraction scale mu.
We derive a novel renormalization group equation in velocity space which can be
used to sum logarithms of v in the effective theory. We apply our method to
several examples. In particular we show that our formulation correctly
reproduces the two-loop anomalous dimension of the heavy quark production
current near threshold.Comment: (27 pages, revtex
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