Terrestrial Planet Formation I. The Transition from Oligarchic Growth to Chaotic Growth

We use a hybrid, multiannulus, n-body-coagulation code to investigate the growth of km-sized planetesimals at 0.4-2 AU around a solar-type star. After a short runaway growth phase, protoplanets with masses of roughly 10^26 g and larger form throughout the grid. When (i) the mass in these `oligarchs' is roughly comparable to the mass in planetesimals and (ii) the surface density in oligarchs exceeds 2-3 g/sq cm at 1 AU, strong dynamical interactions among oligarchs produce a high merger rate which leads to the formation of several terrestrial planets. In disks with lower surface density, milder interactions produce several lower mass planets. In all disks, the planet formation timescale is roughly 10-100 Myr, similar to estimates derived from the cratering record and radiometric data.Comment: Astronomical Journal, accepted; 22 pages + 15 figures in ps format; eps figures at http://cfa-www.harvard.edu/~kenyon/dl/ revised version clarifies evolution and justifies choice of promotion masse

Risk factors for sporadic human infection with shiga toxin-producing Escherichia coli in South Australia

This paper reports the findings from a preliminary study seeking to identify risk factors for sporadic human infection with shiga toxin-producing Escherichia coli (STEC) in South Australia. This phase of the study, conducted between February and September 2002, aimed to make recommendations regarding study methodology, and provided an opportunity to identify any potential risk factors for STEC infections in South Australia. The study design was a prospective age-matched case control study. A case was defined as a person with macroscopic or microscopic evidence of blood in a faecal specimen, and in which a gene associated with the production of shiga toxin (stx 1 or 2) was identified. Two community controls per case were randomly selected from the Social Environmental Risk Context Information System database. Eleven cases and 22 controls were enrolled in the pilot phase of the case control study. Cases were more likely than controls to have eaten berries, including strawberries, blueberries, and blackberries, in the 10 days preceding illness (Mantel Haenszel matched OR 11; 95 per cent CI 1.26-96.12). No other exposures were significantly associated with illness. Due to the small number of study participants, the power of the study was insufficient to expect any significant results. National participation will be vital to obtain sufficient cases in a realistic time, however this would necessitate more consistent ascertainment and reporting of STEC disease between the states and territories

Dates of birth and seasonal changes in well-being among 4904 subjects completing the seasonal pattern assessment questionnaire

Background: Abnormal distributions of birthdates, suggesting intrauterine aetiological factors, have been found in several psychiatric disorders, including one study of out-patients with Seasonal Affective Disorder (S.A.D.). We investigated birthdate distribution in relation to seasonal changes in well-being among a cohort who had completed the Seasonal Pattern Assessment Questionnaire (SPAQ). Method: A sample of 4904 subjects, aged 16 to 64, completed the SPAQ. 476 were cases of S.A.D. on the SPAQ and 580 were cases of sub-syndromal S.A.D. (S-S.A.D.). 92 were interview confirmed cases of S.A.D. Months and dates of birth were compared between S.A.D. cases and all others, between S.A.D. and S-S.A.D. cases combined and all others, and between interview confirmed cases and all others. Seasonality, as measured through seasonal fluctuations in well-being on the Global Seasonality Scores (GSS) of the SPAQ, was compared for all subjects by month and season of birth. Results: There was no evidence of an atypical pattern of birthdates for subjects fulfilling criteria for S.A.D., for the combined S.A.D. / S-S.A.D. group or for interview confirmed cases. There was also no relationship between seasonality on the GSS and month or season of birth. Limitations: Diagnoses of S.A.D. made by SPAQ criteria are likely to be overinclusive. Conclusion: Our findings differ from studies of patients with more severe mood disorders, including psychiatric out-patients with S.A.D. The lack of association between seasonality and birthdates in our study adds credence to the view that the aetiology of S.A.D. relates to separable factors predisposing to affective disorders and to seasonality

Stochastic Gradient Annealed Importance Sampling for Efficient Online Marginal Likelihood Estimation

We consider estimating the marginal likelihood in settings with independent and identically distributed (i.i.d.) data. We propose estimating the predictive distributions in a sequential factorization of the marginal likelihood in such settings by using stochastic gradient Markov Chain Monte Carlo techniques. This approach is far more efficient than traditional marginal likelihood estimation techniques such as nested sampling and annealed importance sampling due to its use of mini-batches to approximate the likelihood. Stability of the estimates is provided by an adaptive annealing schedule. The resulting stochastic gradient annealed importance sampling (SGAIS) technique, which is the key contribution of our paper, enables us to estimate the marginal likelihood of a number of models considerably faster than traditional approaches, with no noticeable loss of accuracy. An important benefit of our approach is that the marginal likelihood is calculated in an online fashion as data becomes available, allowing the estimates to be used for applications such as online weighted model combination

Evaluating the climate effects of mid-1800s deforestation in New England, USA, using a Weather, Research, and Forecasting (WRF) Model Multi-Physics Ensemble

The New England region of the northeastern United States has a land use history characterized by forest clearing for agriculture and other uses during European colonization and subsequent reforestation following widespread farm abandonment. Despite these broad changes, the potential influence on local and regional climate has received relatively little attention. This study investigated wintertime (December through March) climate impacts of reforestation in New England using a high-resolution (4 km) multiphysics ensemble of the Weather Research and Forecasting Model. In general, the conversion from mid-1800s cropland/grassland to forest led to warming, but results were sensitive to physics parameterizations. The 2-m maximum temperature (T2max) was most sensitive to choice of land surface model, 2-m minimum temperature (T2min) was sensitive to radiation scheme, and all ensemble members simulated precipitation poorly. Reforestation experiments suggest that conversion of mid-1800s cropland/grassland to present-day forest warmed T2max +0.5 to +3 K, with weaker warming during a warm, dry winter compared to a cold, snowy winter. Warmer T2max over forests was primarily the result of increased absorbed shortwave radiation and increased sensible heat flux compared to cropland/grassland. At night, T2min warmed +0.2 to +1.5 K where deciduous broadleaf forest replaced cropland/grassland, a result of decreased ground heat flux. By contrast, T2min of evergreen needleleaf forest cooled –0.5 to –2.1 K, primarily owing to increased ground heat flux and decreased sensible heat flux

FIT-MART: Quantum Magnetism with a Gentle Learning Curve

We present a new open-source software package, FIT-MART, that allows non-experts to quickly get started simulating quantum magnetism. FIT-MART can be downloaded as a platform-idependent executable Java (JAR) file. It allows the user to define (Heisenberg) Hamiltonians by electronically drawing pictures that represent quantum spins and operators. Sliders are automatically generated to control the values of the parameters in the model, and when the values change, several plots are updated in real time to display both the resulting energy spectra and the equilibruim magnetic properties. Several experimental data sets for real magnetic molecules are included in FIT-MART to allow easy comparison between simulated and experimental data, and FIT-MART users can also import their own data for analysis and compare the goodness of fit for different models

The Development of a Detailed Abundance Analysis Method Intended for the Integrated Light Spectra of Extragalactic Globular Clusters.

Globular
 clusters
 are
 stellar
 systems
 that
 possess
 an
 astrophysically
 rare
 combination
 of
 theoretical
 and
 observational
 simplicity,
 which
 make
 them
 ideal
 diagnostic
 tracers 
of
 astrophysical
 processes 
in 
both
 space
 and
 time.

 Capitalizing 
on
 this
 simplicity,
 this
 dissertation
 develops
 and
 demonstrates
 a
 detailed
 abundance
 analysis 
method
 that 
is
 capable 
of
 computing 
all
 observable
 line
 abundances
 (i.e. 
Fe‐ peak
 elements,
 alpha‐elements,
 neutron‐capture
 elements,
 and
 light‐elements) 
from
 the
 integrated
 light
 spectra
 of
 extragalactic
 globular
 clusters
 (GCs).
 
 The
 premise
 behind
 the
 method
 is
 that
 the
 precise
 and
 accurate
 techniques
 used
 for
 single
 star
 abundance
 analysis
 can
 be
 combined
 with
 theoretical
 simple
 stellar
 population
 (SSP)
 models
 to
 synthesize
 light‐weighted
 absorption
 line
 equivalent
 widths
 (EWs).
 By
 iterating 
on
 the
 assumed
 abundance
 for
 a
 line 
until 
its 
synthesized 
EW
 equals
 its
 observed
 EW
 allows
 its
 line
 abundance
 to
 be
 determined.
 
 The
 development

 and demonstration of
 this
 method
 is
 carried
 out
 using
 a
 training
 set
 of
 seven
 Milky
 Way
 GCs
 (NGC
104,
 NGC
362,
 NGC
2808,
 NGC
6093,
 NGC
6388,
 NGC
6397,
 NGC
6752),
 which
 were
 observed
 using
 a
 spectrograph
 scanning
 technique
 that
 produces
 integrated
 light
 spectra
 that
 mimic
 extragalactic
 GC
 spectra.
 
 The
 role
 of
 the
 training
 set
 is
 two
 fold.
 
 First,
 because
 the
 training
 set
 clusters
 are
 spatially
 resolved,
 their
 stellar 
populations
 are
 known
 a
 priori 
in
 the
 form
 of 
color‐magnitude
 diagrams.
 
 The
 use
 of
 these
 known
 stellar
 populations
 in
 the
 analysis
 method
 serve
 to
 initially
 test
 the
 feasibility
 of
 the
 method
 without
 encountering
 any
 of
 the
 potential 
complications
 that 
may
 stem
 from
 using
 theoretical
 SSPs.

 Second,
 because
 the
 clusters
 are
 spatially
 resolved,
 their
 stellar
 abundances
 are
 known
 a
 priori from
 single
 star
 abundance
 analysis.
 These
 stellar
 abundances
 critically
 serve
 as
 fiducial
 abundances
 against
 which
 the
 dissertation's
 abundance
 results
 are
 tested.
 
 The
 major
 conclusion
 from
 this
 dissertation
 is
 that
 its
 abundance
 analysis
 method
 using
 theoretical
 SSPs
 is
 capable
 of
 deriving
 the
 detailed
 abundances
 of
 extragalactic
 GCs
 with
 an
 accuracy
 and
 precision
 that
 are
 competitive
 with
 standard
 stellar
 abundance 
analysis. 


The 
method 
produces
 abundances 
that
 are
 on
 average
 only

 <
 0.1
 dex larger
 than
 the
 abundances
 from
 stellar
 analysis,
 and
 their
 statistical
 uncertainties
 are 
on
 average
 ~
0.2
 dex.
Ph.D.Astronomy and AstrophysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64633/1/sacamero_1.pd

Winter Harbor Dredge Channel Data Report

Winter Harbor is a tidal creek that flows between a sandy barrier system and an eroding marsh shoreline. It is an important waterway that provides access to the Chesapeake Bay from the Winter Harbor watershed. In the past, Winter Harbor Inlet was the only hydraulic connection from the Winter Harbor watershed and Chesapeake Bay. The two open water areas of Winter Harbor were separated by marsh channels that hydraulically connected to the mouth at the present-day Winter Harbor Inlet. The federally-defined channel at Winter Harbor was authorized by Congress in 1950. It was authorized as a 12 feet (ft) deep, 100 ft wide channel extending to the 12-ft contour in Chesapeake Bay into Winter Harbor to a point just east of the public landing, a distance of about 7,600 ft. A mooring and turning basin were constructed 12 ft deep and 400 feet2 with a flared entranced 300 ft long. A traffic survey in 1982 found that the 12 ft depth was not justified and a 6 ft deep channel was maintained. (...

Cedarbush Creek Dredge Channel Data Report

Cedarbush Creek is located in Gloucester County, Virginia. It is a long, but narrow creek that empties into the York River. The mouth is a wide embayment, but farther north, the creek narrows to about 400 feet wide and extends for about 1.5 miles to its marshy headwaters. Cedarbush Creek has never been dredged, but due to shoaling within the creek, it needs dredging to accommodate vessel traffic. Oliver’s Landing, located near the mouth of Cedarbush Creek, is a working waterfront that supports commercial and recreational boaters in Gloucester. (...

Differential effects of food availability and nest predation risk on avian reproductive strategies

Spatial and temporal variation in resource abundance and predation risk can favor the evolution of phenotypic plasticity as a means of tracking changing environments. However, because food abundance and predation risk often covary in nature, few studies have separated their effects or tested whether different phenotypic traits respond to the same sources of environmental variation. We investigated patterns of parental investment and behavior over a 7-year period in 2 island populations of orange-crowned warblers (Oreothlypis celata) that showed little genetic divergence but experienced dramatic temporal variation in rainfall and spatial variation in nest predation risk. The amount of rainfall in each year was correlated with food abundance, and birds on both islands initiated breeding earlier and laid larger clutches in wetter years. In contrast, the rate at which parents visited their nests was not affected by rainfall but was negatively correlated with nest predation risk both within and between islands. Our results suggest that although the effects of food availability and nest predation have been viewed as mutually exclusive drivers of entire suites of life-history and behavioral traits, these traits can differ in their sensitivity to resource abundance or mortality risk, and traits that are often correlated can be decoupled under appropriate environmental conditions.Fil: Sofaer, Helen R.. State University Of Colorado-fort Collins. Dept.of Biology; Estados UnidosFil: Sillett, T. Scott. No especifíca;Fil: Peluc, Susana Ines. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Zoología Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Morrison, Scott A.. No especifíca;Fil: Ghalambor, Cameron K.. State University Of Colorado-fort Collins. Dept.of Biology; Estados Unido