97,119 research outputs found
Wonders of Technology-Teaching Physics to Non-Scientists
Wonders of Technology is a conceptual physics course developed for non—science majors. The approach taken here in the introduction of the physical concepts is to depict their role in today’s technology, specifically the technology familiar to the students, and also to emphasize the connection between technology, art, and culture from the historical perspective. Why this approach? The traditional method of teaching physics is perceived by many students as user-unfriendly — they think physics is difficult, abstract, and, in fact, of little or no relevance to everyday life. The course Wonders of Technology alleviates this perception by placing the students on familiar ground that provides a fertile environment for an easier assimilation of knowledge. By examining the technology students use on a daily basis to demonstrate how physics makes things work, students are motivated to seek understanding of the principles underlying their operation. The course was developed within the guidelines of the new general education requirements at Virginia Commonwealth University. This presentation highlights some of the highly successful features of the newly developed course, with emphasis on responses from the education majors who are enrolled in the course
Mean-value identities as an opportunity for Monte Carlo error reduction
In the Monte Carlo simulation of both Lattice field-theories and of models of
Statistical Mechanics, identities verified by exact mean-values such as
Schwinger-Dyson equations, Guerra relations, Callen identities, etc., provide
well known and sensitive tests of thermalization bias as well as checks of
pseudo random number generators. We point out that they can be further
exploited as "control variates" to reduce statistical errors. The strategy is
general, very simple, and almost costless in CPU time. The method is
demonstrated in the two dimensional Ising model at criticality, where the CPU
gain factor lies between 2 and 4.Comment: 10 pages, 2 tables. References updated and typos correcte
Coherent States for Unusual Potentials
The program to construct minimum-uncertainty coherent states for general
potentials works transparently with solvable analytic potentials. However, when
an analytic potential is not completely solvable, like for a double-well or the
linear (gravitational) potential, there can be a conundrum. Motivated by
supersymmetry concepts in higher dimensions, we show how these conundrums can
be overcome.Comment: 10 pages, 3 figures, added info in Ref.
Global deposition of total reactive nitrogen oxides from 1996 to 2014 constrained with satellite observations of NO2 columns
Reactive nitrogen oxides (NOy) are a major constituent of the nitrogen deposited from the atmosphere, but observational constraints on their deposition are limited by poor or nonexistent measurement coverage in many parts of the world. Here we apply NO2 observations from multiple satellite instruments (GOME, SCIAMACHY, and GOME-2) to constrain the global deposition of NOy over the last two decades. We accomplish this by producing top-down estimates of NOx emissions from inverse modeling of satellite NO2 columns over 1996–2014, and including these emissions in the GEOS-Chem chemical transport model to simulate chemistry, transport, and deposition of NOy. Our estimates of long-term mean wet nitrate (NO3−) deposition are highly consistent with available measurements in North America, Europe, and East Asia combined (r = 0.83, normalized mean bias = −7 %, N = 136). Likewise, our calculated trends in wet NO3− deposition are largely consistent with the measurements, with 129 of the 136 gridded model-data pairs sharing overlapping 95 % confidence intervals. We find that global mean NOy deposition over 1996–2014 is 56.0 Tg N yr−1, with a minimum in 2006 of 50.5 Tg N and a maximum in 2012 of 60.8 Tg N. Regional trends are large, with opposing signs in different parts of the world. Over 1996 to 2014, NOy deposition decreased by up to 60 % in eastern North America, doubled in regions of East Asia, and declined by 20 % in parts of Western Europe. About 40 % of the global NOy deposition occurs over oceans, with deposition to the North Atlantic Ocean declining and deposition to the northwestern Pacific Ocean increasing. Using the residual between NOx emissions and NOy deposition over specific land regions, we investigate how NOx export via atmospheric transport has changed over the last two decades. Net export from the continental United States decreased substantially, from 2.9 Tg N yr−1 in 1996 to 1.5 Tg N yr−1 in 2014. On the other hand, export from China more than tripled between 1996 and 2011 (from 1.0 Tg N yr−1 to 3.5 Tg N yr−1), before a striking decline to 2.5 Tg N yr−1 by 2014. We find that declines in NOx export from some Western European countries have counteracted increases in emissions from neighbouring countries to the east. A sensitivity study indicates that simulated NOy deposition is robust to uncertainties in NH3 emissions with a few exceptions. Our novel long-term study provides timely context on the rapid redistribution of atmospheric nitrogen transport and subsequent deposition to ecosystems around the world.https://www.atmos-chem-phys-discuss.net/acp-2016-1100/acp-2016-1100.pdfhttps://www.atmos-chem-phys-discuss.net/acp-2016-1100/acp-2016-1100.pdfhttps://www.atmos-chem-phys-discuss.net/acp-2016-1100/acp-2016-1100.pdfPublished versionPublished versio
Global deposition of total reactive nitrogen oxides from 1996 to 2014 constrained with satellite observations of NO2 columns
Reactive nitrogen oxides (NOy) are a major constituent of the nitrogen deposited from the atmosphere, but observational constraints on their deposition are limited by poor or nonexistent measurement coverage in many parts of the world. Here we apply NO2 observations from multiple satellite instruments (GOME, SCIAMACHY, and GOME-2) to constrain the global deposition of NOy over the last 2 decades. We accomplish this by producing top-down estimates of NOx emissions from inverse modeling of satellite NO2 columns over 1996–2014, and including these emissions in the GEOS-Chem chemical transport model to simulate chemistry, transport, and deposition of NOy. Our estimates of long-term mean wet nitrate (NO3−) deposition are highly consistent with available measurements in North America, Europe, and East Asia combined (r = 0.83, normalized mean bias  = −7%, N = 136). Likewise, our calculated trends in wet NO3− deposition are largely consistent with the measurements, with 129 of the 136 gridded model–data pairs sharing overlapping 95% confidence intervals. We find that global mean NOy deposition over 1996–2014 is 56.0TgNyr−1, with a minimum in 2006 of 50.5TgN and a maximum in 2012 of 60.8TgN. Regional trends are large, with opposing signs in different parts of the world. Over 1996 to 2014, NOy deposition decreased by up to 60% in eastern North America, doubled in regions of East Asia, and declined by 20% in parts of western Europe. About 40% of the global NOy deposition occurs over oceans, with deposition to the North Atlantic Ocean declining and deposition to the northwestern Pacific Ocean increasing. Using the residual between NOx emissions and NOy deposition over specific land regions, we investigate how NOx export via atmospheric transport has changed over the last 2 decades. Net export from the continental United States decreased substantially, from 2.9TgNyr−1 in 1996 to 1.5TgNyr−1 in 2014. Export from China more than tripled between 1996 and 2011 (from 1.0 to 3.5TgNyr−1), before a striking decline to 2.5TgNyr−1 by 2014. We find that declines in NOx export from some western European countries have counteracted increases in emissions from neighboring countries to the east. A sensitivity study indicates that simulated NOy deposition is robust to uncertainties in NH3 emissions with a few exceptions. Our novel long-term study provides timely context on the rapid redistribution of atmospheric nitrogen transport and subsequent deposition to ecosystems around the world.This work was supported by NSERC and Environment and Climate Change Canada. We acknowledge the free use of tropospheric NO2 column data from the GOME, SCIAMACHY, and GOME-2 sensors from www.temis.nl. We further acknowledge the NADP, CAPMoN, EMEP, and EANET regional monitoring networks as well as the World Data Centre for Precipitation Chemistry for access to wet deposition data. (NSERC; Environment and Climate Change Canada)https://www.atmos-chem-phys.net/17/10071/2017/acp-17-10071-2017.pdfhttps://www.atmos-chem-phys.net/17/10071/2017/acp-17-10071-2017.pdfhttps://www.atmos-chem-phys.net/17/10071/2017/acp-17-10071-2017.pdfPublished versionPublished versio
Raising the Higgs mass with Yukawa couplings for isotriplets in vector-like extensions of minimal supersymmetry
Extra vector-like matter with both electroweak-singlet masses and large
Yukawa couplings can significantly raise the lightest Higgs boson mass in
supersymmetry through radiative corrections. I consider models of this type
that involve a large Yukawa coupling between weak isotriplet and isodoublet
chiral supermultiplets. The particle content can be completed to provide
perturbative gauge coupling unification, in several different ways. The impact
on precision electroweak observables is shown to be acceptably small, even if
the new particles are as light as the current experimental bounds of order 100
GeV. I study the corrections to the lightest Higgs boson mass, and discuss the
general features of the collider signatures for the new fermions in these
models.Comment: 30 page
Information from leading neutrons at HERA
In principle, leading neutrons produced in photoproduction and deep-inelastic
scattering at HERA have the potential to determine the pion structure function,
the neutron absorptive cross section and the form of the pion flux. To explore
this potential we compare theoretical predictions for the x_L and p_t spectra
of leading neutrons, and the Q^2 dependence of the cross section, with the
existing ZEUS data.Comment: 17 pages, 8 figure
Checking formalism for central exclusive production in the first LHC runs
We discuss how the early LHC data runs can provide crucial tests of the
formalism used to predict the cross sections of central exclusive production.Comment: 7 pages, 6 figures; Based on a talk by A.D. Martin at the CERN - DESY
Workshop "HERA and the LHC", 26 - 30 May 2008, CER
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