793 research outputs found
On FPL configurations with four sets of nested arches
The problem of counting the number of Fully Packed Loop (FPL) configurations
with four sets of a,b,c,d nested arches is addressed. It is shown that it may
be expressed as the problem of enumeration of tilings of a domain of the
triangular lattice with a conic singularity. After reexpression in terms of
non-intersecting lines, the Lindstr\"om-Gessel-Viennot theorem leads to a
formula as a sum of determinants. This is made quite explicit when
min(a,b,c,d)=1 or 2. We also find a compact determinant formula which generates
the numbers of configurations with b=d.Comment: 22 pages, TeX, 16 figures; a new formula for a generating function
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Observation of the Dependence of Scintillation from Nuclear Recoils in Liquid Argon on Drift Field
We have exposed a dual-phase Liquid Argon Time Projection Chamber (LAr-TPC)
to a low energy pulsed narrowband neutron beam, produced at the Notre Dame
Institute for Structure and Nuclear Astrophysics to study the scintillation
light yield of recoiling nuclei in a LAr-TPC. A liquid scintillation counter
was arranged to detect and identify neutrons scattered in the LAr-TPC target
and to select the energy of the recoiling nuclei.
We report the observation of a significant dependence on drift field of
liquid argon scintillation from nuclear recoils of 11 keV. This observation is
important because, to date, estimates of the sensitivity of noble liquid TPC
dark matter searches are based on the assumption that electric field has only a
small effect on the light yield from nuclear recoils.Comment: v3 updated to reflect published version, including a set of plots for
49.9 keV dat
Discovery of underground argon with low level of radioactive 39Ar and possible applications to WIMP dark matter detectors
We report on the first measurement of 39Ar in argon from underground natural
gas reservoirs. The gas stored in the US National Helium Reserve was found to
contain a low level of 39Ar. The ratio of 39Ar to stable argon was found to be
<=4x10-17 (84% C.L.), less than 5% the value in atmospheric argon
(39Ar/Ar=8x10-16). The total quantity of argon currently stored in the National
Helium Reserve is estimated at 1000 tons. 39Ar represents one of the most
important backgrounds in argon detectors for WIMP dark matter searches. The
findings reported demonstrate the possibility of constructing large multi-ton
argon detectors with low radioactivity suitable for WIMP dark matter searches.Comment: 6 pages, 2 figures, 2 table
Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon
We have measured the scintillation and ionization yield of recoiling nuclei
in liquid argon as a function of applied electric field by exposing a
dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy
pulsed narrow band neutron beam produced at the Notre Dame Institute for
Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged
to detect and identify neutrons scattered in the TPC and to select the energy
of the recoiling nuclei. We report measurements of the scintillation yields for
nuclear recoils with energies from 10.3 to 57.3 keV and for median applied
electric fields from 0 to 970 V/cm. For the ionization yields, we report
measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486
V/cm. We also report the observation of an anticorrelation between
scintillation and ionization from nuclear recoils, which is similar to the
anticorrelation between scintillation and ionization from electron recoils.
Assuming that the energy loss partitions into excitons and ion pairs from
Kr internal conversion electrons is comparable to that from Bi
conversion electrons, we obtained the numbers of excitons () and ion
pairs () and their ratio () produced by nuclear recoils from
16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in
LAr-TPC signals due to columnar recombination, a comparison of the light and
charge yield of recoils parallel and perpendicular to the applied electric
field is presented for the first time.Comment: v2 to reflect published versio
Long-Term Functionality of Rural Water Services in Developing Countries: A System Dynamics Approach to Understanding the Dynamic Interaction of Causal Factors
Research has shown that sustainability of rural water infrastructure in developing countries is largely affected by the dynamic and systemic interactions of technical, social, financial, institutional, and environmental factors that can lead to premature water system failure. This research employs systems dynamic modeling, which uses feedback mechanisms to understand how these factors interact dynamically to influence long-term rural water system functionality. To do this, the research first identified and aggregated key factors from literature, then asked water sector experts to indicate the polarity and strength between factors through Delphi and cross impact survey questionnaires, and finally used system dynamics modeling to identify and prioritize feedback mechanisms. The resulting model identified 101 feedback mechanisms that were dominated primarily by three and four-factor loops that contained some combination of the factors: Water System Functionality, Community, Financial, Government, Management, and Technology. These feedback mechanisms were then scored and prioritized, with the most dominant feedback mechanism identified as Water System Functionality – Community – Finance – Management. This research offers insight into the dynamic interaction of factors impacting sustainability of rural water infrastructure through the identification of these feedback mechanisms and makes a compelling case for future research to longitudinally investigate the interaction of these factors in various contexts
Capacidade combinatória de linhagens e seleção de hibridos de sorgo granÃfero.
O objetivo do presente trabalho foi selecionar parentais e hÃbridos de sorgo granÃfero para caracterÃsticas agronômicas. Foram avaliados 184 cruzamentos oriundos de um dialelo parcial envolvendo 16 linhagens machoestéreis e 12 restauradoras da fertilidade. Foram realizados 8 experimentos, com 23 hÃbridos cada e duas testemunhas adicionais (BRS 304 e BRS 330), em blocos casualizados, com duas repetições. Foram avaliadas as caracterÃsticas rendimento de grãos, florescimento e altura de plantas. Os efeitos de CGC e CEC foram significativos para as três caracterÃsticas, mostrando a importância dos efeitos aditivos e dominantes no controle destes caracteres. O quadrado médio para CGC foi superior ao da CEC. Todos os parentais que contribuÃram para aumentar o rendimento de grãos também o fizeram para altura de plantas, exceto pelos parentais femininos CMSXS 1006 e CMSXS 1011, mostrando a dificuldade de dissociar estas duas caracterÃsticas. Os hÃbridos mais produtivos apresentaram altura de plantas acima do recomendado para sorgo granÃfero, mesmo assim foi possÃvel a seleção de cruzamentos que apresentaram rendimento de grãos acima da média, florescimento abaixo da média e altura dentro do padrão exigido. Dentre estes, pode-se destacar os hÃbridos CMSXS 1002 x CMSXS 1102, CMSXS 1006 x RTx2907, ATx ARG 1 x SC1155 e CMSXS 1008 x Tx2741
Capacidade combinatória de linhagens de sorgo granÃfero cultivados em segunda safra.
Nos programas de melhoramento genético de sorgo é comum o desenvolvimento de elevado número de linhagens, sendo a escolha das mais promissoras um dos principais desafios enfrentados pelos melhoristas. A técnica de cruzamentos dialélicos permite a seleção daquelas linhagens detentoras de atributos de maior interesse identificados com base em algumas combinações hÃbridas, não necessitando a realização de todos os cruzamentos possÃveis. O objetivo do presente trabalho foi estimar as capacidades geral (CGC) e especÃfica de combinação (CEC), para as caracterÃsticas rendimento de grãos, altura de plantas e dias para florescimento de 50 linhagens de sorgo. Assim, foram avaliados 141 hÃbridos experimentais, oriundos do cruzamento de 47 linhagens macho-estéreis com 3 linhagens restauradoras. Como testemunha, utilizaram-se os hÃbridos comerciais BRS 330, DKB 550 e 1G244. Para a caracterÃstica rendimento de grãos, os efeitos da CEC foram bem superiores aos da CGC, evidenciando a importância dos efeitos de dominância. Para dias para florescimento e altura de plantas, os efeitos de CGC foram bem superiores aos efeitos de CEC. Vinte e cinco linhagens macho-estéreis apresentaram CGC positivas para rendimento de grãos, com destaque para 0803085, 1105405-2, 1105417-2, 1105419-1, 1105419-2, 1105521-2 e 1105451-2, com contribuições no rendimento de grãos acima de 0,5 t.ha-1 nos hÃbridos em que participaram. A linhagem 9910032 foi a melhor restauradora por contribuir para aumentar o rendimento de grãos, reduzir os dias para florescimento e não aumentar a altura de plantas, nos hÃbridos em que participa. Vários hÃbridos superaram as testemunhas para todas as caracterÃsticas.bitstream/item/142481/1/bol-127.pd
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