Search

Research which makes possible a quantification of the size, composition, and growth of the underclass is discussed. Trends in the quality of life and the growth of the underclass are presented. (CW)

Cites evidence supporting the author's view that the present national approach to standardizing measurement methods is inadequate. Discusses needs for adequate estimates of precision and evaluation of interlaboratory bias in the mandated measurement methods required by regulatory agencies and other governmental groups. (Author/CS)

Presents the influence that science has had and is having on contemporary society. The author suggests that science is a subculture of the human race and occupies a unique habitat in a social ecosystem that does not conform to its values. (Author/SA)

The article focuses on naturalist Alexander von Humboldt and his combination of humanism with science in his studies. It comments on his use of systematic measurements and observations and talks about how he relied on a world-wide network of correspondents and collaborators to increase his observational abilities. It describes his pursuit of knowledge as part of a greater vision that included both the human mind and nature and discusses his impact on scientific research.

The article discusses the proposal of a global-scale metric to assess the impact of mercury emissions policies. Topics include the Minamata Convention on Mercury's efforts to protect human health and the environment from anthropogenic emissions and releases of mercury, failure of the proposed effective anthropogenic mercury deposition (EAMD) metric to distinguish between emission of different forms of mercury, and the need for periodic effectiveness evaluations.

The article discusses the measurement of academic achievement at universities and colleges and its impact on faculty and faculty employment. Emphasis is given to topics such as the development of metrics for research impact assessment, the implementation of dashboard systems for tracking academic and clinical performance, and the inclusion of infographics and social media in professional development.

The phylogenetic relationships among most metazoan phyla remain uncertain. We obtained large numbers of gene sequences from metazoans, including key understudied taxa. Despite the amount of data and breadth of taxa analyzed, relationships among most metazoan phyla remained unresolved. In contrast, the same genes robustly resolved phylogenetic relationships within a major clade of Fungi of approximately the same age as the Metazoa. The differences in resolution within the two kingdoms suggest that the early history of metazoans was a radiation compressed in time, a finding that is in agreement with paleontological inferences. Furthermore, simulation analyses as well as studies of other radiations in deep time indicate that, given adequate sequence data, the lack of resolution in phylogenetic trees is a signature of closely spaced series of cladogenetic events., Detailed knowledge of the phylogenetic relationships among Metazoa and their eukaryotic relatives is critical for understanding the history of life and the evolution of molecules, phenotypes, and developmental mechanisms. Currently, [...]

Previous predictions of sea-level change subsequent to the last glacial maximum show significant, systematic discrepancies between observations at Tahiti, Huon Peninsula, and Sunda Shelf during Lateglacial time (~14,000 to 9000 calibrated years before the present). We demonstrate that a model of glacial isostatic adjustment characterized by both a high-viscosity lower mantle (4 x 1022 Pa s) and a large contribution from the Antarctic ice sheet to meltwater pulse IA (~15-meters eustatic equivalent) resolves these discrepancies. This result supports arguments that an early and rapid Antarctic deglaciation contributed to a sequence of climatic events that ended the most recent glacial period of the current ice age., The evolution of high-latitude global ice volumes, as inferred from observations of far-field sea-level change, serves as a fundamental constraint on ice-age climate models (1). In this regard, data from [...]

Satellite radar altimetry measurements indicate that the East Antarctic ice-sheet interior north of 81.6% increased in mass by 45 ± 7 billion metric tons per year from 1992 to 2003. Comparisons with contemporaneous meteorological model snowfall estimates suggest that the gain in mass was associated with increased precipitation. A gain of this magnitude is enough to slow sea-level rise by 0.12 ± 0.02 millimeters per year., Recent studies report substantial contributions from the Greenland (1, 2) and Antarctic (3, 4) ice sheets to present-day sea-level rise of ~1.8 mm/year (5). Rapid increases in near-coastal Greenland ice-sheet [...]

The magnetic field signature obtained by Cassini during its first close encounter with Titan on 26 October 2004 is presented and explained in terms of an advanced model. Titan was inside the saturnian magnetosphere. A magnetic field minimum before closest approach marked Cassini's entry into the magnetic ionopause layer. Cassini then left the northern and entered the southern magnetic tail lobe. The magnetic field before and after the encounter was approximately constant for ~20 Titan radii, but the field orientation changed exactly at the location of Titan's orbit. No evidence of an internal magnetic field at Titan was detected., We report results from the Cassini magnetometer experiment obtained during the first close encounter [closest approach (CA) altitude: 1174 km] of Cassini with Saturn's moon Titan on 26 October 2004. [...]

The Cassini Radio and Plasma Wave Science (RPWS) Langmuir probe (LP) sensor observed the cold plasma environment around Titan during the first two flybys. The data show that conditions in Saturn's magnetosphere affect the structure and dynamics deep in the ionosphere of Titan. The maximum measured ionospheric electron number density reached 3800 per cubic centimeter near closest approach, and a complex chemistry was indicated. The electron temperature profiles are consistent with electron heat conduction from the hotter Titan wake. The ionospheric escape flux was estimated to be [10.sup.25] ions per second., The giant planet Saturn and its magnetosphere rotate with a period of ~ 11 hours, which can be inferred from radio measurements (1). At the distance of the large moon [...]

Diapycnal mixing plays a significant role in the ocean's circulation and uptake of heat and carbon dioxide, but has not been quantified in salt finger-driven thermohaline staircases. We recently performed a tracer release experiment in the western tropical Atlantic staircase at ~400 m depth. The observed dispersion implies an effective diapycnal diffusivity for tracer and salt of 0.8 to 0.9 x [10.sup.-4] [m.sup.2]/s. Temperature microstructure data interpreted in terms of a vertical production-dissipation balance yields a smaller effective diffusivity for heat of 0.45 (± 02) x [10.sup.-4] [m.sup.2]/s, consistent with salt fingers and well above the mixing ascribable to mechanical turbulence., Since the discovery of salt fingers by Stern (1) in 1960, there has been much speculation about their role in oceanic mixing (2, 3). Fieldwork has suggested the importance of [...]

It has been hypothesized that changes in the marine biological pump caused a major portion of the glacial reduction of atmospheric carbon dioxide by 80 to 100 parts per million through increased iron fertilization of marine plankton, increased ocean nutrient content or utilization, or shifts in dominant plankton types. We analyze sedimentary records of marine productivity at the peak and the middle of the last glacial cycle and show that neither changes in nutrient utilization in the Southern Ocean nor shifts in plankton dominance explain the C[O.sub.2] drawdown. Iron fertilization and associated mechanisms can be responsible for no more than half the observed drawdown., The causes of the 80- to 100-ppm atmospheric C[O.sub.2] fluctuations during glacial cycles remain elusive despite more than 20 years of research (1). Oceanic processes must account for the observed [...]

Albert Einstein postulated the equivalence of energy and mass, developed the theory of special relativity, explained the photoelectric effect, and described Brownian motion in five papers, all published in 1905, 100 years ago. With these papers, Einstein provided the framework for understanding modern astrophysical phenomena. Conversely, astrophysical observations provide one of the most effective means for testing Einstein's theories. Here, I review astrophysical advances precipitated by Einstein's insights, including gravitational redshifts, gravitational lensing, gravitational waves, the Lense-Thirring effect, and modern cosmology. A complete understanding of cosmology, from the earliest moments to the ultimate fate of the universe, will require developments in physics beyond Einstein, to a unified theory of gravity and quantum physics., Einstein's 1905 theories form the basis for much of modern physics and astrophysics. In 1905, Einstein postulated the equivalence of mass and energy (1), which led Sir Arthur Eddington to [...]

Rayleigh scattering spectra were obtained from individual single-walled carbon nanotubes with the use of a laser-generated visible and near-infrared supercontinuum. This diagnostic method is noninvasive and general for nanoscale objects. The approach permits clear identification of excited states in arbitrary metallic and semiconducting nanotubes. We analyzed spectral lineshapes in relation to the role of excitonic effects and correlated the results with Raman scattering data on individual tubes. The nanotube structure remained the same over distances of tens of micrometers. Small nanotube bundles retained distinct Rayleigh spectroscopic signatures of their component nanotubes, thus allowing the probing of nanotube-nanotube interactions., Single-walled carbon nanotubes (SWNTs) comprise a family of more than 200 structures characterized by different chiral angles and diameters, each having a distinct electronic structure that can be either metallic [...]

Over the past half-century, there has been a shift away from standards based on particular artifacts toward those based on physical effects, the most stable being based on quantum properties of systems. This change was proposed at the end of the 19th century but is still not complete at the start of the 21st. We discuss how this vision has been implemented through recent advances in science and metrology and how these may soon lead to an SI system finally free from artifact standards, with a consistency based on fundamental constants., Quantities, Units, and Standards To investigate any physical phenomena, we must make measurements, communicate them to others, and record them in a way that will be understandable in the future. [...]

Recent aircraft and satellite laser altimeter surveys of the Amundsen Sea sector of West Antarctica show that local glaciers are discharging about 250 cubic kilometers of ice per year to the ocean, almost 60% more than is accumulated within their catchment basins. This discharge is sufficient to raise sea level by more than 0.2 millimeters per year. Glacier thinning rates near the coast during 2002-2003 are much larger than those observed during the 19905. Most of these glaciers flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way., Perhaps half the present increase in global sea level of ~1.8 mm/year is caused by melting of terrestrial ice (1). During the 1990s, nonpolar glaciers accounted for an estimated 0.4 [...]

The middle Miocene climate transition (MMCT), 14.2 to 13.8 million years ago (Ma), is one of the three major steps in Earth's Cenozoic climate evolution (1-3). The ~1 ‰ increase [...], Magnesium/calcium data from Southern Ocean planktonic foraminifera demonstrate that high-latitude (-55°S) southwest Pacific sea surface temperatures (SSTs) cooled 6° to 7°C during the middle Miocene climate transition (14.2 to 13.8 million years ago). Stepwise surface cooling is paced by eccentricity forcing and precedes Antarctic cryosphere expansion by ~60 thousand years, suggesting the involvement of additional feedbacks during this interval of inferred low-atmospheric partial pressure of C[O.sub.2] (pC[O.sub.2]). Comparing SSTs and global carbon cycling proxies challenges the notion that episodic pC[O.sub.2] drawdown drove this major Cenozoic climate transition. SST, salinity, and ice-volume trends suggest instead that orbitally paced ocean circulation changes altered meridional heat/vapor transport, triggering ice growth and global cooling.

The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive Lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead Loss. The U/Pb age of the main pulse of the extinction is 252.6 ± 0.2 million years, synchronous with the Siberian flood volcanism, and it occurred within the quoted uncertainty., Despite intensive study, the cause and timing of events associated with the Permian-Triassic (P-T) extinction--the most profound such extinction known over the history of life on Earth--remain uncertain. Most scenarios [...]

We observed the in situ growth of a grain during recrystallization in the bulk of a deformed sample. We used the three-dimensional x-ray diffraction microscope located at the European Synchrotron Radiation Facility in Grenoble, France. The results showed a very heterogeneous growth pattern, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical characterization of microstructures. For recrystallization, the in situ method includes direct measurements of nucleation and boundary migration through a deformed matrix., When a material is deformed plastically, excess line defects (dislocations) and some excess point defects are introduced into the material. The density of these excess defects can be reduced by [...]

Identifying leads and lags between high- and low-latitude abrupt climate shifts is needed to understand where and how such events were triggered. Vascular plant biomarkers preserved in Cariaco basin sediments reveal rapid vegetation changes in northern South America during the last deglaciation, 15,000 to 10,000 years ago. Comparing the biomarker records to climate proxies from the same sediment core provides a precise measure of the relative timing of changes in different regions. Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades., In order to evaluate the relative roles of high and low latitudes in initiating and propagating abrupt global climate changes, we need precise information regarding the relative timing of abrupt [...]

Noise, or random fluctuations, in gene expression may produce variability in cellular behavior. To measure the noise intrinsic to eukaryotic gene expression, we quantified the differences in expression of two alleles in a diploid cell. We found that such noise is gene-specific and not dependent on the regulatory pathway or absolute rate of expression. We propose a model in which the balance between promoter activation and transcription influences the variability in messenger RNA levels. To confirm the predictions of our model, we identified both cis- and trans-acting mutations that alter the noise of gene expression. These mutations suggest that noise is an evolvable trait that can be optimized to balance fidelity and diversity in eukaryotic gene expression., The stochastic, or random and probabilistic, nature of chemical reactions may create variation in an identical population of cells (1). The reactions underlying gene expression involve small numbers of molecules [...]

We demonstrate two approaches that use the recently developed helium spin-echo technique to measure surface potential energy landscapes. For helium-lithium fluoride (100), we use the selective adsorption phenomenon to obtain the complete experimental band structure of atoms in a corrugated surface potential. For carbon monoxide-copper (001), we measure the diffusion-induced energy broadening in the scattered helium beam and extract properties of the adsorbate-substrate potential The measurements are made possible by the resolution of our new spectrometer, which improves on existing resolution by three orders of magnitude. We show that it is possible to produce benchmark energy landscapes to assist evaluation and development of first-principles theory in the problematic van der Waals/weak chemisorption regime., First-principle calculations provide powerful tools for assisting in the design of new catalysts for the chemical industry and helping elucidate critical steps in semiconductor device growth and development (1). However, [...]

We present measurements of the dust particle flux and mass distribution from the Stardust Dust Flux Monitor Instrument (DFMI) throughout the flyby of comet 81P/Wild 2. In the particle mass regime from [10.sup.-14] to [10.sup.-7] kilograms, the spacecraft encountered regions of intense swarms of particles, together with bursts of activity corresponding to clouds of particles only a few hundred meters across. This fine-scale structure can be explained by particle fragmentation. We estimate that 2800 ± 500 particles of diameter 15 micrometers or larger impacted the aerogel collectors, the largest being ~6 x [10.sup.-7] kilograms, which dominates the total collected mass., Comets are one of the primary sources of interplanetary dust as sublimating gases from their nuclei release and accelerate particles, ranging in size from submicrometer grains to objects many meters [...]

Images taken by the Stardust mission during its flyby of 81P/Wild 2 show the comet to be a 5-kilometer oblate body covered with remarkable topographic features, including unusual circular features that appear to be impact craters. The presence of high-angle slopes shows that the surface is cohesive and self-supporting. The comet does not appear to be a rubble pile, and its rounded shape is not directly consistent with the comet being a fragment of a larger body. The surface is active and yet it retains ancient terrain. Wild 2 appears to be in the early stages of its degradation phase as a small volatile-rich body in the inner solar system., Jupiter family comets (JFCs) such as 81 P/Wild 2 typically range from the orbit of Jupiter to inner regions of the solar system. These subliming-disintegrating bodies have inner solar system [...]

We interpret the nucleus properties and jet activity from the Stardust spacecraft imaging and the onboard dust monitoring system data. Triangulation of 20 jets shows that 2 emanate from the nucleus dark side and 16 emanate from sources that are on slopes where the Sun's elevation is greater than predicted from the fitted triaxial ellipsoid. Seven sources, including five in the Mayo depression, coincide with relatively bright surface spots. Fitting the imaged jets, the spikelike temporal distribution of dust impacts indicates that the spacecraft crossed thin, densely populated sheets of particulate ejecta extending from small sources on the rotating nucleus, consistent with an emission cone model., Cometary activity is characterized by solar energy-driven sublimation of water ice and other volatile substances from the nucleus into the coma, while refractory material (dust particles of various sizes) is [...]

The Mars Rover is looking for evidence that life existed in martian soil. This is perhaps the only extraterrestrial foothold for life we will be able to directly observe for [...], Soil is the most complicated biomaterial on the planet. As with any material, the physical habitat is of prime importance in determining and regulating biological activity. However, until recently the opaque nature of soil has meant that any interrogation of its interior architecture has been relatively rudimentary, restricted to simple qualitative expressions of the physical heterogeneity that fail to relate to any specific function. However, new techniques and insights into the biophysical and biochemical processes of this inner space are leading to the developments of theoretical frameworks and experimental approaches that will allow us to sustainably manage Earth's most important resource. We introduce the concept that the soil-microbe system is self-organized and suggest new priorities for research based on an integrative approach that combines biochemistry and biophysics.

Ship-borne ozone ([O.sub.3]) measurements over the Atlantic Ocean during the period from 1977 to 2002 show that [O.sub.3] trends in the northern mid-latitudes are small In contrast, remarkably large [O.sub.3] [...]

The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic add, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide., The Southern Ocean exerts a major control on the partial pressure of carbon dioxide (pC[O.sub.2]) in the atmosphere. Because rates of photosynthesis and biological carbon export are low in Antarctic [...]

We have developed a chemical ionization mass spectrometry technique for precise in situ measurements of hydrochloric acid (HCl) from a high-altitude aircraft. In measurements at subtropical latitudes, minimum HCl values found in the upper troposphere (UT) were often near or below the detection Limit of the measurements (0.005 parts per billion by volume), indicating that background HCl values are much Lower than a global mean estimate. However, significant abundances of HCl were observed in many UT air parcels, as a result of stratosphere-to-troposphere transport events. We developed a method for diagnosing the amount of stratospheric ozone in these UT parcels using the compact linear correlation of HCl with ozone found throughout the lower stratosphere (LS). Expanded use of this method will Lead to improved quantification of cross-tropopause transport events and validation of global chemical transport models., Ozone ([O.sub.3]) that is produced in the stratosphere and transported into the upper troposphere (UT) is a substantial but uncertain contribution to the tropospheric [O.sub.3] budget (1-5). The increase in [...]

Real-time feedback performed during a quantum nondemolition measurement of atomic spin-angular momentum allowed us to influence the quantum statistics of the measurement outcome. We showed that it is possible to harness measurement backaction as a form of actuation in quantum control, and thus we describe a valuable tool for quantum information science. Our feedback-mediated procedure generates spin-squeezing, for which the reduction in quantum uncertainty and resulting atomic entanglement are not conditioned on the measurement outcome., Quantum systems evolve deterministically when no one is looking. Free from observation, knowledge of a quantum state at one point in time is in principle sufficient to predict its entire [...]

By coupling a single-electron transistor to a high-quality factor, 19.7-megahertz nanomechanical resonator, we demonstrate position detection approaching that set by the Heisenberg uncertainty principle limit. At millikelvin temperatures, position resolution a factor of 4.3 above the quantum limit is achieved and demonstrates the near-ideal performance of the single-electron transistor as a linear amplifier. We have observed the resonator's thermal motion at temperatures as low as 56 millikelvin, with quantum occupation factors of [N.sub.TH] = 58. The implications of this experiment reach from the ultimate limits of force microscopy to qubit readout for quantum information devices., Since the development of quantum mechanics, it has been appreciated that there is a fundamental limit to the precision of repeated position measurements (1). This is a consequence of the [...]

Oxygen isotopes in marine sulfate ([δ.sup.18][O.sub.SO4]) measured in marine barite show variability over the past 10 million years, including a 5 per mil decrease during the Plio-Pleistocene, with near-constant values during the Miocene that are slightly enriched over the modern ocean. A numerical model suggests that sea level fluctuations during Plio-Pleistocene glacial cycles affected the sulfur cycle by reducing the area of continental shelves and increasing the oxidative weathering of pyrite. The data also require that sulfate concentrations were 10 to 20% lower in the late Miocene than today., Sulfate plays an important role in the modern ocean, serving as the primary oxidant for much of the organic matter and nearly all of the methane produced in ocean sediments [...]

A transect of 68 acid grasslands across Great Britain, covering the lower range of ambient annual nitrogen deposition in the industrialized world (5 to 35 kg N [ha.sup.-1] [year.sup.-1]), indicates that long-term, chronic nitrogen deposition has significantly reduced plant species richness. Species richness declines as a linear function of the rate of inorganic nitrogen deposition, with a reduction of one species per 4-[m.sup.2] quadrat for every 2.5 kg N [ha.sup.-1] [year.sup.-1] of chronic nitrogen deposition. Species adapted to infertile conditions are systematically reduced at high nitrogen deposition. At the mean chronic nitrogen deposition rate of central Europe (17 kg N [ha.sup.-1] [year.sup.-1]), there is a 23% species reduction compared with grasslands receiving the lowest levels of nitrogen deposition., Conservation of biodiversity underpins some of the largest and most ambitious environmental legislation in the world (1). Most of the focus of this legislation is on mitigating damage to ecological [...]

We used force-clamp atomic force micoscopy to measure the end-to-end length of the small protein ubiquitin during its folding reaction at the single-molecule level. Ubiquitin was first unfolded and extended at a high force, then the stretching force was quenched and protein folding was observed. The folding trajectories were continuous and marked by several distinct stages. The time taken to fold was dependent on the contour length of the unfolded protein and the stretching force applied during folding. The folding collapse was marked by large fluctuations in the end-to-end length of the protein, but these fluctuations vanished upon the final folding contraction. These direct observations of the complete folding trajectory of a protein provide a benchmark to determine the physical basis of the folding reaction., Resolving the folding pathway of a protein remains a challenge in biology (1-9). Here, we demonstrate a method by which the entire folding trajectory of a single protein can be [...]

Detailed organic analysis of natural aerosols from the Amazonian rain forest showed considerable quantities of previously unobserved polar organic compounds, which were identified as a mixture of two diastereoisomeric 2-methyltetrols: 2-methylthreitol and 2-methylerythritol. These polyols, which have the isoprene skeleton, can be explained by OH radical--initiated photooxidation of isoprene. They have low vapor pressure, allowing them to condense onto preexisting particles. It is estimated that photooxidation of isoprene results in an annual global production of about 2 teragrams of the polyols, a substantial fraction of the Intergovernmental Panel on Climate Change estimate of between 8 and 40 teragrams per year of secondary organic aerosol from biogenic sources., Aerosols are of climatic interest because they act as cloud condensation nuclei (1) and scatter and absorb solar radiation (2). It has been well established that photooxidation products of monoterpenes [...]

Four-year averages of 25-kilometer-resolution measurements of near-surface wind speed and direction over the global ocean from the QuikSCAT satellite radar scatterometer reveal the existence of surprisingly persistent small-scale features in the dynamically and thermodynamically important curl and divergence of the wind stress. Air-sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields, as are the influences of islands and coastal mountains. Ocean currents such as the Gulf Stream generate distinctive patterns in the curl field. These previously unresolved features have important implications for oceanographic and air-sea interaction research., The stress of the wind on the sea surface forces upper-ocean currents in a nonintuitive manner. Except near the equator, where the Coriolis acceleration from Earth's rotation vanishes, ocean currents [...]

The viscosities of aqueous fluids with 10 to 80 weight percent dissolved silicates have been measured at 600° to 950°C and 1.0 to 2.0 gigapascals by in situ observation of falling spheres in the diamond anvil celt. The viscosities at 800°C range from [10.sup.-4] to [10.sup.0.5] pascal seconds. The combination of low viscosities with a favorable wetting angle makes silicate-rich fluid an efficient agent for material transport at low-volume fractions. Our results therefore suggest that there may be a direct relationship between the position of the volcanic front and the onset of complete miscibility between water and silicate melt in the subducting slab., Understanding the formation of Earth's crest and the associated element fractionation between crust and mantle requires detailed knowledge of the mechanisms of melt production and material transport in subduction zone [...]

The article presents the discussion on project catalyzing an international effort in measuring all the world's birds. Topics include living bird species not just passerines such as robins but everything from ducks and penguins to vultures and ostriches; and studying bird evolution and ecology as well as the impact of changes in climate and habitat on vulnerable species.

Brine rejection that accompanies ice formation in coastal polynyas is responsible for ventilating several globally important water masses in the Arctic and Antarctic. However, most previous studies of this process have been indirect, based on heat budget analyses or on warm-season water column inventories. Here, we present direct measurements of brine rejection and formation of North Pacific Intermediate Water in the Okhotsk Sea from moored winter observations. A steady, nearly linear salinity increase unambiguously caused by local ice formation was observed for more than a month., The global thermohaline circulation is primed by dense water formation in high latitudes, which leads to the gradual renewal of the deep ocean. The densest bottom water is formed in [...]

Water isotope ratios have been measured by laser absorption spectroscopy in and out of cirrus clouds formed in situ and convectively generated in anvils over subtropical regions. Water vapor in the tropical and subtropical upper troposphere shows a wide range of isotopic depletion not observed previously. The range suggests that dehydration of upper tropospheric air occurs both by convective dehydration and by gradual dehydration mechanisms. Twenty-five percent of upper tropospheric water sampled is in ice particles whose isotopic signatures are used to identify those grown in situ from those lofted from below., Tropospheric water vapor is the most important greenhouse gas and a key component of the climate system (1). In the upper troposphere (UT) and lower stratosphere (LS), water vapor, liquid [...]

The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarem, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites., The terrestrial biosphere currently sequesters 20 to 30% of global anthropogenic C[O.sub.2] emissions (1, 2). Amazonia has been suggested to be a major contributor to observed interannual variations in this [...]