Nitrate source identification in the Baltic Sea using its isotopic ratios in combination with a Bayesian isotope mixing model

Nitrate (NO3-) is the major nutrient responsible for coastal eutrophication worldwide and its production is related to intensive food production and fossil-fuel combustion. In the Baltic Sea NO3- inputs have increased 4-fold over recent decades and now remain constantly high. NO3- source identification is therefore an important consideration in environmental management strategies. In this study focusing on the Baltic Sea, we used a method to estimate the proportional contributions of NO3- from atmospheric deposition, N-2 fixation, and runoff from pristine soils as well as from agricultural land. Our approach combines data on the dual isotopes of NO3- (delta N-15-NO3- and delta O-18-NO3-) in winter surface waters with a Bayesian isotope mixing model (Stable Isotope Analysis in R, SIAR). Based on data gathered from 47 sampling locations over the entire Baltic Sea, the majority of the NO3- in the southern Baltic was shown to derive from runoff from agricultural land (33-100 %), whereas in the northern Baltic, i.e. the Gulf of Bothnia, NO3- originates from nitrification in pristine soils (34-100 %). Atmospheric deposition accounts for only a small percentage of NO3- levels in the Baltic Sea, except for contributions from northern rivers, where the levels of atmospheric NO3- are higher. An additional important source in the central Baltic Sea is N-2 fixation by diazotrophs, which contributes 49-65% of the overall NO3- pool at this site. The results obtained with this method are in good agreement with source estimates based upon delta N-15 values in sediments and a three-dimensional ecosystem model, ERGOM. We suggest that this approach can be easily modified to determine NO3- sources in other marginal seas or larger near-coastal areas where NO3- is abundant in winter surface waters when fractionation processes are minor

Simultaneous effects on parvalbumin-positive interneuron and dopaminergic system development in a transgenic rat model for sporadic schizophrenia

To date, unequivocal neuroanatomical features have been demonstrated neither for sporadic nor for familial schizophrenia. Here, we investigated the neuroanatomical changes in a transgenic rat model for a subset of sporadic chronic mental illness (CMI), which modestly overexpresses human full-length, non-mutant Disrupted-in-Schizophrenia 1 (DISC1), and for which aberrant dopamine homeostasis consistent with some schizophrenia phenotypes has previously been reported. Neuroanatomical analysis revealed a reduced density of dopaminergic neurons in the substantia nigra and reduced dopaminergic fibres in the striatum. Parvalbumin-positive interneuron occurrence in the somatosensory cortex was shifted from layers II/III to V/VI, and the number of calbindin-positive interneurons was slightly decreased. Reduced corpus callosum thickness confirmed trend-level observations from in vivo MRI and voxel-wise tensor based morphometry. These neuroanatomical changes help explain functional phenotypes of this animal model, some of which resemble changes observed in human schizophrenia post mortem brain tissues. Our findings also demonstrate how a single molecular factor, DISC1 overexpression or misassembly, can account for a variety of seemingly unrelated morphological phenotypes and thus provides a possible unifying explanation for similar findings observed in sporadic schizophrenia patients. Our anatomical investigation of a defined model for sporadic mental illness enables a clearer definition of neuroanatomical changes associated with subsets of human sporadic schizophrenia

Noncovalent Interactions by QMC: Speedup by One-Particle Basis-Set Size Reduction

While it is empirically accepted that the fixed-node diffusion Monte-Carlo (FN-DMC) depends only weakly on the size of the one-particle basis sets used to expand its guiding functions, limits of this observation are not settled yet. Our recent work indicates that under the FN error cancellation conditions, augmented triple zeta basis sets are sufficient to achieve a benchmark level of 0.1 kcal/mol in a number of small noncovalent complexes. Here we report on a possibility of truncation of the one-particle basis sets used in FN-DMC guiding functions that has no visible effect on the accuracy of the production FN-DMC energy differences. The proposed scheme leads to no significant increase in the local energy variance, indicating that the total CPU cost of large-scale benchmark noncovalent interaction energy FN-DMC calculations may be reduced.Comment: ACS book chapter, accepte

Observations of the longitudinal spread of solar energetic particle events in solar cycle 24

With the twin STEREO spacecraft, significantly separated from L1-based satellites such as ACE, simultaneous multi-point measurements of solar energetic particle (SEP) events can be made for H-Fe ions from a few hundred keV/nuc to over 100 MeV/nuc and for electrons from tens to hundreds of keV. These observations allow studies of the longitudinal characteristics of SEP events to advance beyond statistical analysis of single point measurements. Although there have been few large SEP events thus far in cycle 24, there have been a number of smaller events that have been detected by more than one spacecraft. The composition of these SEP events, as indicated by the H/He and Fe/O abundance ratios, shows a dependence on longitudinal distance from the solar source in some events, at times with ratios varying by an order of magnitude. However, these variations are not organized by either the speed or width of the associated coronal mass ejections

A new mass and radius determination of the ultra-short period planet K2-106b and the fluffy planet K2-106c

Ultra-short period planets have orbital periods of less than one day. Since their masses and radii can be determined to a higher precision than long-period planets, they are the preferred targets to determine the density of planets which constrains their composition. The K2-106 system is particularly interesting because it contains two planets of nearly identical masses. One is a high density USP, the other is a low-density planet that has an orbital period of 13 days. Combining the Gaia DR3 results with new ESPRESSO data allows us to determine the masses and radii of the two planets more precisely than before. We find that the USP K2-106b has a density consistent with an Earth-like composition, and K2-106c is a low-density planet that presumably has an extended atmosphere. We measure a radius of Rp=1.676-0.037+0.037 REarth, a mass of Mp=7.80-0.70+0.71 MEarth and a density of rho=9.09-0.98+0.98 gcm-3 for K2-106b. For K2-106c, we derive Rp=2.84-0.08+0.10 REarth, Mp=7.3-2.4+2.5 MEarth, and a density of rho= 1.72-0.58+0.66 gcm-3. We finally discuss the possible structures of the two planets with respect to other low-mass planets.Comment: 16 pages with 12 figure

A new mass and radius determination of the ultra-short period planet K2-106b and the fluffy planet K2-106c

Ultra-short period planets have orbital periods of less than one day. Since their masses and radii can be determined to a higher precision than long-period planets, they are the preferred targets to determine the density of planets which constrains their composition. The K2-106 system is particularly interesting because it contains two planets of nearly identical masses. One is a high density USP, the other is a low-density planet that has an orbital period of 13 days. Combining the Gaia DR3 results with new ESPRESSO data allows us to determine the masses and radii of the two planets more precisely than before. We find that the USP K2-106b has a density consistent with an Earth-like composition, and K2-106c is a low-density planet that presumably has an extended atmosphere. We measure a radius of Rp = 1.676-0.037+0.037 R⊕, a mass of Mp = 7.80-0.70+0.71 M⊕ and a density of ρ = 9.09-0.98+0.98 gcm-3 for K2-106b. For K2-106c, we derive Rp = 2.84-0.08+0.10 R⊕, Mp = 7.3-2.4+2.5 M⊕, and a density of ρ = 1.72-0.58+0.66 gcm-3. We finally discuss the possible structures of the two planets with respect to other low-mass planets

Characteristics of the plasma distribution in Mercury's equatorial magnetosphere derived from MESSENGER Magnetometer observations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96228/1/jgra22273.pd

Re-Evaluation of Sinocastor (Rodentia: Castoridae) with Implications on the Origin of Modern Beavers

The extant beaver, Castor, has played an important role shaping landscapes and ecosystems in Eurasia and North America, yet the origins and early evolution of this lineage remain poorly understood. Here we use a geometric morphometric approach to help re-evaluate the phylogenetic affinities of a fossil skull from the Late Miocene of China. This specimen was originally considered Sinocastor, and later transferred to Castor. The aim of this study was to determine whether this form is an early member of Castor, or if it represents a lineage outside of Castor. The specimen was compared to 38 specimens of modern Castor (both C. canadensis and C. fiber) as well as fossil specimens of C. fiber (Pleistocene), C. californicus (Pliocene) and the early castorids Steneofiber eseri (early Miocene). The results show that the specimen falls outside the Castor morphospace and that compared to Castor, Sinocastor possesses a: 1) narrower post-orbital constriction, 2) anteroposteriorly shortened basioccipital depression, 3) shortened incisive foramen, 4) more posteriorly located palatine foramen, 5) longer rostrum, and 6) longer braincase. Also the specimen shows a much shallower basiocciptal depression than what is seen in living Castor, as well as prominently rooted molars. We conclude that Sinocastor is a valid genus. Given the prevalence of apparently primitive traits, Sinocastor might be a near relative of the lineage that gave rise to Castor, implying a possible Asiatic origin for Castor

Observations of Mercury's northern cusp region with MESSENGER's Magnetometer

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95510/1/grl29143.pd

Mercury's Surface Magnetic Field Determined from Proton-Reflection Magnetometry

Solar wind protons observed by the MESSENGER spacecraft in orbit about Mercury exhibit signatures of precipitation loss to Mercury's surface. We apply proton-reflection magnetometry to sense Mercury's surface magnetic field intensity in the planet's northern and southern hemispheres. The results are consistent with a dipole field offset to the north and show that the technique may be used to resolve regional-scale fields at the surface. The proton loss cones indicate persistent ion precipitation to the surface in the northern magnetospheric cusp region and in the southern hemisphere at low nightside latitudes. The latter observation implies that most of the surface in Mercury's southern hemisphere is continuously bombarded by plasma, in contrast with the premise that the global magnetic field largely protects the planetary surface from the solar wind