554 research outputs found
Some relations for one-part double Hurwitz numbers
In this very short note we slightly generalize some relations for one-part
double Hurwitz numbers from math.AG/0209282.Comment: 3 page
Predicting the effects of climate change on water yield and forest production in the northeastern United States
Rapid and simultaneous changes in temperature, precipitation and the atmospheric concentration of CO2 are predicted to occur over the next century. Simple, well-validated models of ecosystem function are required to predict the effects of these changes. This paper describes an improved version of a forest carbon and water balance model (PnET-II) and the application of the model to predict stand- and regional-level effects of changes in temperature, precipitation and atmospheric CO2 concentration. PnET-II is a simple, generalized, monthly time-step model of water and carbon balances (gross and net) driven by nitrogen availability as expressed through foliar N concentration. Improvements from the original model include a complete carbon balance and improvements in the prediction of canopy phenology, as well as in the computation of canopy structure and photosynthesis. The model was parameterized and run for 4 forest/site combinations and validated against available data for water yield, gross and net carbon exchange and biomass production. The validation exercise suggests that the determination of actual water availability to stands and the occurrence or non-occurrence of soil-based water stress are critical to accurate modeling of forest net primary production (NPP) and net ecosystem production (NEP). The model was then run for the entire NewEngland/New York (USA) region using a 1 km resolution geographic information system. Predicted long-term NEP ranged from -85 to +275 g C m-2 yr-1 for the 4 forest/site combinations, and from -150 to 350 g C m-2 yr-1 for the region, with a regional average of 76 g C m-2 yr-1. A combination of increased temperature (+6*C), decreased precipitation (-15%) and increased water use efficiency (2x, due to doubling of CO2) resulted generally in increases in NPP and decreases in water yield over the region
From Hurwitz numbers to Kontsevich-Witten tau-function: a connection by Virasoro operators
In this letter,we present our conjecture on the connection between the
Kontsevich--Witten and the Hurwitz tau-functions. The conjectural formula
connects these two tau-functions by means of the group element. An
important feature of this group element is its simplicity: this is a group
element of the Virasoro subalgebra of . If proved, this conjecture
would allow to derive the Virasoro constraints for the Hurwitz tau-function,
which remain unknown in spite of existence of several matrix model
representations, as well as to give an integrable operator description of the
Kontsevich--Witten tau-function.Comment: 13 page
Quantum curves for Hitchin fibrations and the Eynard-Orantin theory
We generalize the topological recursion of Eynard-Orantin (2007) to the
family of spectral curves of Hitchin fibrations. A spectral curve in the
topological recursion, which is defined to be a complex plane curve, is
replaced with a generic curve in the cotangent bundle of an arbitrary
smooth base curve . We then prove that these spectral curves are
quantizable, using the new formalism. More precisely, we construct the
canonical generators of the formal -deformation family of -modules
over an arbitrary projective algebraic curve of genus greater than ,
from the geometry of a prescribed family of smooth Hitchin spectral curves
associated with the -character variety of the fundamental
group . We show that the semi-classical limit through the WKB
approximation of these -deformed -modules recovers the initial family
of Hitchin spectral curves.Comment: 34 page
ABCD of Beta Ensembles and Topological Strings
We study beta-ensembles with Bn, Cn, and Dn eigenvalue measure and their
relation with refined topological strings. Our results generalize the familiar
connections between local topological strings and matrix models leading to An
measure, and illustrate that all those classical eigenvalue ensembles, and
their topological string counterparts, are related one to another via various
deformations and specializations, quantum shifts and discrete quotients. We
review the solution of the Gaussian models via Macdonald identities, and
interpret them as conifold theories. The interpolation between the various
models is plainly apparent in this case. For general polynomial potential, we
calculate the partition function in the multi-cut phase in a perturbative
fashion, beyond tree-level in the large-N limit. The relation to refined
topological string orientifolds on the corresponding local geometry is
discussed along the way.Comment: 33 pages, 1 figur
Psychosocial Factors Associated with Happiness
This chapter provides an overview of psychosocial factors associated with happiness. Using an ecological framework, we will begin with a discussion of broad-based cultural factors and move downward to social and individual level psychological factors. This includes social support, interpersonal relationships, and psychological factors such as personality characteristics and cognitive factors. The relationship between finding meaning, posttraumatic growth, and happiness will be discussed
Ecosystem carbon 7 dioxide fluxes after disturbance in forests of North America
Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events, insect infestations (gypsy moth, forest tent caterpillar, and mountain pine beetle), Hurricane Wilma, and silvicultural thinning (Arizona, California, and New Brunswick). Net ecosystem production (NEP) showed a carbon loss from all ecosystems following a stand-replacing disturbance, becoming a carbon sink by 20 years for all ecosystems and by 10 years for most. Maximum carbon losses following disturbance (g C m−2y−1) ranged from 1270 in Florida to 200 in boreal ecosystems. Similarly, for forests less than 100 years old, maximum uptake (g C m−2y−1) was 1180 in Florida mangroves and 210 in boreal ecosystems. More temperate forests had intermediate fluxes. Boreal ecosystems were relatively time invariant after 20 years, whereas western ecosystems tended to increase in carbon gain over time. This was driven mostly by gross photosynthetic production (GPP) because total ecosystem respiration (ER) and heterotrophic respiration were relatively invariant with age. GPP/ER was as low as 0.2 immediately following stand-replacing disturbance reaching a constant value of 1.2 after 20 years. NEP following insect defoliations and silvicultural thinning showed lesser changes than stand-replacing events, with decreases in the year of disturbance followed by rapid recovery. NEP decreased in a mangrove ecosystem following Hurricane Wilma because of a decrease in GPP and an increase in ER
Enumeration of simple random walks and tridiagonal matrices
We present some old and new results in the enumeration of random walks in one
dimension, mostly developed in works of enumerative combinatorics. The relation
between the trace of the -th power of a tridiagonal matrix and the
enumeration of weighted paths of steps allows an easier combinatorial
enumeration of the paths. It also seems promising for the theory of tridiagonal
random matrices .Comment: several ref.and comments added, misprints correcte
Activity and toxicity of intramuscular 1000 iu/m² polyethylene glycol-E. coli L-asparaginase in the UKALL 2003 and UKALL 2011 clinical trials
In successive UK clinical trials (UKALL 2003, UKALL 2011) for paediatric acute lymphoblastic leukaemia (ALL), polyethylene glycol-conjugated E. coli L-asparaginase (PEG-EcASNase) 1000 iu/m2 was administered intramuscularly with risk-stratified treatment. In induction, patients received two PEG-EcASNase doses, 14 days apart. Post-induction, non-high-risk patients (Regimens A, B) received 1–2 doses in delayed intensification (DI) while high-risk Regimen C patients received 6–10 PEG-EcASNase doses, including two in DI. Trial substudies monitored asparaginase (ASNase) activity, ASNase-related toxicity and ASNase-associated antibodies (total, 1112 patients). Median (interquartile range) trough plasma ASNase activity (14 ± 2 days post dose) following first and second induction doses and first DI dose was respectively 217 iu/l (144–307 iu/l), 265 iu/l (165–401 iu/l) and 292 iu/l (194–386 iu/l); 15% (138/910) samples showed subthreshold ASNase activity (<100 iu/l) at any trough time point. Older age was associated with lower (regression coefficient −9.5; p < 0.0001) and DI time point with higher ASNase activity (regression coefficient 29.9; p < 0.0001). Clinical hypersensitivity was observed in 3.8% (UKALL 2003) and 6% (UKALL 2011) of patients, and in 90% or more in Regimen C. A 7% (10/149) silent inactivation rate was observed in UKALL 2003. PEG-EcASNase schedule in UKALL paediatric trials is associated with low toxicity but wide interpatient variability. Therapeutic drug monitoring potentially permits optimisation through individualised asparaginase dosing
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