Showing papers by "University of Maine published in 2010"

Updated national birth prevalence estimates for selected birth defects in the United States, 2004–2006†

Abstract: BACKGROUND: The National Birth Defects Prevention Network collects state-specific birth defects surveillance data for annual publication of prevalence estimates and collaborative research projects. In 2006, data for 21 birth defects from 1999 through 2001 were presented as national birth prevalence estimates. The purpose of this report was to update these estimates using data from 2004 through 2006. METHODS: Population-based data from 11 active case-finding programs, 6 passive case-finding programs with case confirmation, and 7 passive programs without case confirmation were used in this analysis. Pooled birth prevalence estimates for 21 birth defects, stratified by case ascertainment approach, were calculated. National prevalence estimates, adjusted for maternal race/ethnicity and maternal age (trisomy 13, trisomy 18, and Down syndrome only) were determined using data from 14 programs. The impact of pregnancy outcomes on prevalence estimates was also assessed for five specific defects. RESULTS: National birth defects prevalence estimates ranged from 0.72 per 10,000 live births for common truncus to 14.47 per 10,000 live births for Down syndrome. Stratification by type of surveillance system showed that active programs had a higher prevalence of anencephaly, anophthalmia/microphthalmia, cleft lip with or without cleft palate, reduction defect of upper limbs, and trisomy 18. The birth prevalence of anencephaly, trisomy 13, and trisomy 18 also varied substantially with inclusion of elective terminations. CONCLUSION: Accurate and timely national estimates of the prevalence of birth defects are needed for monitoring trends, assessing prevention efforts, determining service planning, and understanding the burden of disease due to birth defects in the United States. Birth Defects Research (Part A) 88:1008–1016, 2010. 2010 Wiley-Liss, Inc.

Rising to the challenge of sustaining coral reef resilience.

Abstract: Phase-shifts from one persistent assemblage of species to another have become increasingly commonplace on coral reefs and in many other ecosystems due to escalating human impacts. Coral reef science, monitoring and global assessments have focused mainly on producing detailed descriptions of reef decline, and continue to pay insufficient attention to the underlying processes causing degradation. A more productive way forward is to harness new theoretical insights and empirical information on why some reefs degrade and others do not. Learning how to avoid undesirable phase-shifts, and how to reverse them when they occur, requires an urgent reform of scientific approaches, policies, governance structures and coral reef management.

The last glacial termination.

Abstract: A major puzzle of paleoclimatology is why, after a long interval of cooling climate, each late Quaternary ice age ended with a relatively short warming leg called a termination. We here offer a comprehensive hypothesis of how Earth emerged from the last global ice age. A prerequisite was the growth of very large Northern Hemisphere ice sheets, whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation. The Southern Hemisphere westerlies shifted poleward during each northern stadial, producing pulses of ocean upwelling and warming that together accounted for much of the termination in the Southern Ocean and Antarctica. Rising atmospheric CO2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres.

Phenotypic plasticity and population viability: the importance of environmental predictability.

Abstract: Phenotypic plasticity plays a key role in modulating how environmental variation influences population dynamics, but we have only rudimentary understanding of how plasticity interacts with the magnitude and predictability of environmental variation to affect population dynamics and persistence. We developed a stochastic individual-based model, in which phenotypes could respond to a temporally fluctuating environmental cue and fitness depended on the match between the phenotype and a randomly fluctuating trait optimum, to assess the absolute fitness and population dynamic consequences of plasticity under different levels of environmental stochasticity and cue reliability. When cue and optimum were tightly correlated, plasticity buffered absolute fitness from environmental variability, and population size remained high and relatively invariant. In contrast, when this correlation weakened and environmental variability was high, strong plasticity reduced population size, and populations with excessively strong plasticity had substantially greater extinction probability. Given that environments might become more variable and unpredictable in the future owing to anthropogenic influences, reaction norms that evolved under historic selective regimes could imperil populations in novel or changing environmental contexts. We suggest that demographic models (e.g. population viability analyses) would benefit from a more explicit consideration of how phenotypic plasticity influences population responses to environmental change.

Observed 20th century desert dust variability: impact on climate and biogeochemistry

Abstract: Desert dust perturbs climate by directly and in- directly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and tempera- ture, in addition to modifying ocean and land biogeochem- istry. While we know that desert dust is sensitive to pertur- bations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on pa- leodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these ob- servational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of at- mosphere) over the 20th century to be 0.14± 0.11 W/m 2 (1990-1999 vs. 1905-1914). The estimated radiative change

Rapid circulation of warm subtropical waters in a major glacial fjord in East Greenland

Abstract: The recent rapid increase in mass loss from the Greenland ice sheet is primarily attributed to an acceleration of outlet glaciers. Oceanographic data obtained in summer 2008 show that subtropical waters that reside year-round in the shelf ocean off Greenland continuously enter a large glacial fjord in East Greenland and contribute to melting at the glacier terminus. The recent rapid increase in mass loss from the Greenland ice sheet1,2 is primarily attributed to an acceleration of outlet glaciers3,4,5. One possible cause of this acceleration is increased melting at the ice–ocean interface6,7, driven by the synchronous warming8,9,10 of subtropical waters offshore of Greenland. However, because of the lack of observations from Greenland’s glacial fjords and our limited understanding of their dynamics, this hypothesis is largely untested. Here we present oceanographic data collected in Sermilik Fjord, East Greenland, by ship in summer 2008 and from moorings. Our data reveal the presence of subtropical waters throughout the fjord. These waters are continuously replenished through a wind-driven exchange with the shelf, where they are present all year. The temperature and renewal of these waters indicate that they currently cause enhanced submarine melting at the glacier terminus. Key controls on the melting rate are the volume and properties of the subtropical waters on the shelf, and the patterns of along-shore winds, suggesting that the glaciers’ acceleration has been triggered by a combination of atmospheric and oceanic changes. Our measurements provide evidence for a rapid advective pathway for the transmission of oceanic variability to the ice-sheet margins.

A Census of Eddy Activities in the South China Sea During 1993-2007

Abstract: [1] Numerous mesoscale eddies occur each year in the South China Sea (SCS), but their statistical characteristics are still not well documented. A Pacific basin-wide three-dimensional physical-biogeochemical model has been developed and the result in the SCS subdomain is used to quantify the eddy activities during the period of 1993–2007. The modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method. On average, there are about 32.9 ± 2.4 eddies predicted by the model and 32.8 ± 3.4 eddies observed by satellite each year, and about 52% of them are cyclonic eddies. The radius of these eddies ranges from about 46.5 to 223.5 km, with a mean value of 87.4 km. More than 70% of the eddies have a radius smaller than 100 km. The mean area covered by these eddies each year is around 160,170 km2, equivalent to 9.8% of the SCS area with water depths greater than 1000 m. Linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude, showing that strong eddies usually last longer and penetrate deeper than weak ones. Interannual variations in eddy numbers and the total eddy-occupied area indicate that eddy activities in the SCS do not directly correspond to the El Nino–Southern Oscillation events. The wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the SCS.

Rapid landscape transformation in South Island, New Zealand, following initial Polynesian settlement

Abstract: Humans have altered natural patterns of fire for millennia, but the impact of human-set fires is thought to have been slight in wet closed-canopy forests. In the South Island of New Zealand, Polynesians (Māori), who arrived 700–800 calibrated years (cal y) ago, and then Europeans, who settled ∼150 cal y ago, used fire as a tool for forest clearance, but the structure and environmental consequences of these fires are poorly understood. High-resolution charcoal and pollen records from 16 lakes were analyzed to reconstruct the fire and vegetation history of the last 1,000 y. Diatom, chironomid, and element concentration data were examined to identify disturbance-related limnobiotic and biogeochemical changes within burned watersheds. At most sites, several high-severity fire events occurred within the first two centuries of Māori arrival and were often accompanied by a transformation in vegetation, slope stability, and lake chemistry. Proxies of past climate suggest that human activity alone, rather than unusually dry or warm conditions, was responsible for this increased fire activity. The transformation of scrub to grassland by Europeans in the mid-19th century triggered further, sometimes severe, watershed change, through additional fires, erosion, and the introduction of nonnative plant species. Alteration of natural disturbance regimes had lasting impacts, primarily because native forests had little or no previous history of fire and little resilience to the severity of burning. Anthropogenic burning in New Zealand highlights the vulnerability of closed-canopy forests to novel disturbance regimes and suggests that similar settings may be less resilient to climate-induced changes in the future.

Ultrahigh resolution mass spectrometry and indicator species analysis to identify marker components of soil- and plant biomass- derived organic matter fractions.

Abstract: The chemical properties of organic matter affect important soil processes such as speciation, solubilization, and transport of plant nutrients and metals. This work uses ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry to determine the molecular composition of three organic matter fractions of soils and aqueous extracts of crop biomass. Comparison of the van Krevelen plots allowed tracking the changes in organic matter with increasing humification. Aqueous plant biomass extracts contain a diverse mixture of lipids, proteins, and lignins. Soil aqueous extracts were marked by increases in lignin and carbohydrate components and decrease in the protein component as compared to the plant extract. Refractory humic acid fractions were marked by decrease in the lignin component and increases in the lipid and condensed aromatic components. The multivariate indicator species analysis was used to identify marker components of the four organic matter types inves...

Marine plankton phenology and life history in a changing climate: current research and future directions

Abstract: Increasing availability and extent of biological ocean time series (from both in situ and satellite data) have helped reveal significant phenological variability of marine plankton. The extent to which the range of this variability is modified as a result of climate change is of obvious importance. Here we summarize recent research results on phenology of both phytoplankton and zooplankton. We suggest directions to better quantify and monitor future plankton phenology shifts, including (i) examining the main mode of expected future changes (ecological shifts in timing and spatial distribution to accommodate fixed environmental niches vs. evolutionary adaptation of timing controls to maintain fixed biogeography and seasonality), (ii) broader understanding of phenology at the species and community level (e.g. for zooplankton beyond Calanus and for phytoplankton beyond chlorophyll), (iii) improving and diversifying statistical metrics for indexing timing and trophic synchrony and (iv) improved consideration of spatio-temporal scales and the Lagrangian nature of plankton assemblages to separate time from space changes.

Effect of varying feedstock-pretreatment chemistry combinations on the formation and accumulation of potentially inhibitory degradation products in biomass hydrolysates.

Abstract: A variety of potentially inhibitory degradation products are produced during pretreatment of lignocellulosic biomass. Qualitative and quantitative interrogation of pretreatment hydrolysates is paramount to identifying potential correlations between pretreatment chemistries and microbial inhibition in downstream bioconversion processes. In the present study, corn stover, poplar, and pine feedstocks were pretreated under eight different chemical conditions, which are representative of leading pretreatment processes. Pretreatment processes included: 0.7% H(2)SO(4), 0.07% H(2)SO(4), liquid hot water, neutral buffer solution, aqueous ammonia, lime, lime with oxygen pressurization, and wet oxidation. Forty lignocellulosic degradation products resulting from pretreatment were analyzed using high performance liquid chromatography in combination with UV spectroscopy or tandem mass spectrometry detection (HPLC-PDA-MS/MS) and ion chromatography (IC). Of these compounds, several have been reported to be inhibitory, including furfural, hydroxymethyl furfural, ferulic acid, 3,4-dihydroxybenzaldehyde, syringic acid among others. Formation and accumulation of monitored compounds in hydrolysates is demonstrated to be a function of both the feedstock and pretreatment conditions utilized.

Glacier advance in southern middle-latitudes during the Antarctic Cold Reversal

Abstract: The geographic extent of cooling associated with the Antarctic Cold Reversal is unclear. Dating of glacial moraines in New Zealand suggests that the cooling extended into the southern mid-latitudes, possibly as a result of the northward migration of the southern subtropical front.

Transcriptional regulatory network triggered by oxidative signals configures the early response mechanisms of japonica rice to chilling stress.

Abstract: The transcriptional regulatory network involved in low temperature response leading to acclimation has been established in Arabidopsis. In japonica rice, which can only withstand transient exposure to milder cold stress (10°C), an oxidative-mediated network has been proposed to play a key role in configuring early responses and short-term defenses. The components, hierarchical organization and physiological consequences of this network were further dissected by a systems-level approach. Regulatory clusters responding directly to oxidative signals were prominent during the initial 6 to 12 hours at 10°C. Early events mirrored a typical oxidative response based on striking similarities of the transcriptome to disease, elicitor and wounding induced processes. Targets of oxidative-mediated mechanisms are likely regulated by several classes of bZIP factors acting on as1/ocs/TGA-like element enriched clusters, ERF factors acting on GCC-box/JAre-like element enriched clusters and R2R3-MYB factors acting on MYB2-like element enriched clusters. Temporal induction of several H2O2-induced bZIP, ERF and MYB genes coincided with the transient H2O2 spikes within the initial 6 to 12 hours. Oxidative-independent responses involve DREB/CBF, RAP2 and RAV1 factors acting on DRE/CRT/rav1-like enriched clusters and bZIP factors acting on ABRE-like enriched clusters. Oxidative-mediated clusters were activated earlier than ABA-mediated clusters. Genome-wide, physiological and whole-plant level analyses established a holistic view of chilling stress response mechanism of japonica rice. Early response regulatory network triggered by oxidative signals is critical for prolonged survival under sub-optimal temperature. Integration of stress and developmental responses leads to modulated growth and vigor maintenance contributing to a delay of plastic injuries.

Distance to Retirement and Older Workers‘ Employment: The Case for Delaying the Retirement Age

Abstract: This paper presents empirical evidence and a theoretical foundation in favor of the view that the retirement age decision affects older workers' employment prior to retirement. To the extent that there are search frictions on the labor market, the return on jobs is determined by their expected duration: The time to retirement is then key to understanding older workers' employment. Countries with a retirement age of 60 are indeed characterized by lower employment rates for workers aged 55–59. Based on the French Labor Force Survey, we show that the likelihood of employment is significantly affected by the distance to retirement, in addition to age and other relevant variables. We then extend McCall's job search model by explicitly integrating life-cycle features with the retirement decision. Using simulations, we show that the distance effect in interaction with the generosity of unemployment benefits and the depressed demand for older workers explains the low rate of employment just before the eligibility age for the Social Security pension. Finally, we show that implementing actuarially fair schemes not only extends the retirement age, but also encourages a more intensive job search by older unemployed workers. (JEL: J22, J26, H55)

Peer experiences of anxious and socially withdrawn youth: an integrative review of the developmental and clinical literature.

Abstract: Prior research indicates that both anxious youth and socially withdrawn youth tend to experience challenges and difficulties in various aspects of their peer relationships and social functioning. While clinical psychology researchers have examined how anxiety relates to peer experiences using normative and clinically anxious samples, developmental psychologists have focused primarily on the peer experiences of shy and withdrawn children. Research from these two fields has progressed on related yet separate paths, producing similar results despite using different terminology and assessment techniques. The purpose of this review is to bring together the developmental and clinical bodies of literature on the peer experiences of anxious and socially withdrawn youth by identifying common themes and unique contributions of each discipline. Studies reviewed focus specifically on the peer constructs of acceptance, friendship, peer victimization, social skills, and social-cognitive processes. Limitations including methodological inconsistencies and insufficient examination of age-, gender-, and ethnicity-related issues are identified. Recommendations for future collaborations between developmental and clinical researchers as well as implications for interventions targeting the peer relations of anxious and withdrawn youth are discussed.

Climate control of terrestrial carbon exchange across biomes and continents

Abstract: Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate–carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45°N). The sensitivity of NEE to mean annual temperature breaks down at ~ 16 °C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.

Glacier retreat in New Zealand during the Younger Dryas stadial

Abstract: The Younger Dryas — a period of sudden cooling in the Northern Hemisphere about 12,900 years ago — is perhaps the best-known example of abrupt climate change. But the global extent of the Younger Dryas is a topic of intense debate, particularly in the record of glacial behaviour in New Zealand. A new reconstruction of the growth and retreat patterns of glaciers in the Southern Alps in New Zealand at the time of the Younger Dryas supports the suggestion that temperature reductions in the north caused warming and glacial retreat in the Southern Hemisphere through a series of climate feedbacks. The Younger Dryas — during which Northern Hemisphere temperatures cooled drastically in just a few years — is perhaps the best-known example of abrupt climate change, but its global extent is under debate, particularly in the record of glacial behaviour in New Zealand. These authors present evidence for glacial retreat in New Zealand during the Younger Dryas, supporting the hypothesis that Northern Hemisphere climate changes caused Southern Hemisphere warming through a series of climate feedbacks. Millennial-scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions. The presence of the Younger Dryas stadial (∼12.9 to ∼11.7 kyr ago) is established throughout much of the Northern Hemisphere, but the global timing, nature and extent of the event are not well established. Evidence in mid to low latitudes of the Southern Hemisphere, in particular, has remained perplexing1,2,3,4,5,6. The debate has in part focused on the behaviour of mountain glaciers in New Zealand, where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent1,2,3. The interhemispheric behaviour of the climate system during the Younger Dryas thus remains an open question, fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period. Here we show that New Zealand’s glaciers retreated after ∼13 kyr bp, at the onset of the Younger Dryas, and in general over the subsequent ∼1.5-kyr period. Our evidence is based on detailed landform mapping, a high-precision 10Be chronology7 and reconstruction of former ice extents and snow lines from well-preserved cirque moraines. Our late-glacial glacier chronology matches climatic trends in Antarctica, Southern Ocean behaviour and variations in atmospheric CO2. The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand’s cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient8 during late-glacial times, in turn leading to increased upwelling and CO2 release from the Southern Ocean9, thereby triggering Southern Hemisphere warming during the northern Younger Dryas.

Hemicellulose Removal from Hardwood Chips in the Pre-Hydrolysis Step of the Kraft-Based Dissolving Pulp Production Process

Abstract: A pre-hydrolysis step to remove hemicelluloses from mixed hardwood chips consisting of maple, aspen, and birch with a ratio of 7:2:1 has been carried out. The effects of parameters on the pre-hydrolysis such as time, temperature, acetic acid addition, and raw material species, were determined. Different sugars, acetic acid, and furfural formation in the pre-hydrolysis liquor were quantified. The results showed that the pre-hydrolysis is a dynamic process, in which the removal of hemicelluloses increased with time while the conversion of extracted hemicelluloses to monosaccharides due to acid hydrolysis increased and part of the xylose was converted to furfural. The maximum temperature was the most critical parameter for hemicelluloses extraction and conversion, and a temperature of 170°C was the optimum for hemicelluloses extraction with relatively low conversion of xylose to furfural. About 11% of the xylan (in both monomeric and oligomeric forms) was removed at 170°C. Due to the presence of a h...

In situ evaluation of the initiation of the North Atlantic phytoplankton bloom

Abstract: [1] Two years of continuous physical and optical measurements from a profiling float in the western subarctic North Atlantic are used to analyze seasonal phytoplankton dynamics. The observed annual cycle challenges the traditional view that initiation of spring accumulations of phytoplankton in the upper water column requires a critical stratification threshold (known as the ‘Gran effect’ or the ‘Sverdrup Hypothesis’). Instead, we find that biomass accumulation begins in mid-winter when light levels are minimal and near-surface mixing is deepest. These observations are consistent with the recently proposed dilution–recoupling hypothesis which states that deep winter mixing in the North Atlantic is essential for bloom formation as it decouples phytoplankton growth from grazing losses, thereby allowing net biomass accumulation despite low-light conditions.