bluuebunny/crossref_metadata_2025 huggingface dataset:
State factor relationships of dissolved organic carbon and nitrogen losses from unpolluted temperate forest watersheds
Authors: Perakis Steven S. , Hedin Lars O.
Published: May 2007

We sampled 100 unpolluted, old‐growth forested watersheds, divided among 13 separate study areas over 5 years in temperate southern Chile and Argentina, to evaluate relationships among dominant soil‐forming state factors and dissolved carbon and nitrogen concentrations in watershed streams. These watersheds provide a unique opportunity to examine broad‐scale controls over carbon (C) and nitrogen (N) biogeochemistry in the absence of significant human disturbance from chronic N deposition and land use change. Variations in the ratio dissolved organic carbon (DOC) to nitrogen (DON) in watershed streams differed by underlying soil parent material, with average C:N = 29 for watersheds underlain by volcanic ash and basalt versus C:N = 73 for sedimentary and metamorphic parent materials, consistent with stronger adsorption of low C:N hydrophobic materials by amorphous clays commonly associated with volcanic ash and basalt weathering. Mean annual precipitation was related positively to variations in both DOC (range: 0.2–9.7 mg C/L) and DON (range: 0.008–0.135 mg N/L) across study areas, suggesting that variations in water volume and concentration may act synergistically to influence C and N losses across dry to wet gradients in these forest ecosystems. Dominance of vegetation by broadleaf versus coniferous trees had negligible effects on organic C and N concentrations in comparison to abiotic factors. We conclude that precipitation volume and soil parent material are important controls over chemical losses of dissolved organic C and N from unpolluted temperate forest watersheds. Our results raise the possibility that biotic imprints on watershed C and N losses may be less pronounced in naturally N‐poor forests than in areas impacted by land use change and chronic N deposition.
Methyl halide and methane fluxes in the northern Alaskan coastal tundra
Authors: Rhew Robert C. , Teh Yit Arn , Abel Triffid
Published: May 2007

The Arctic tundra is a major source and sink of carbon‐containing gases, but the biogeochemical cycling of halocarbons in this ecosystem has been largely unexplored. In this study, coastal tundra fluxes of methyl halides (CH3Cl, CH3Br, and CH3I) and methane (CH4) were measured near Barrow, Alaska (71°N, 157°W) during the 2005 growing season. Sites covered a range of microtopographic features including drained lake basins, channels, and high‐ and low‐centered ice‐wedge polygons. CH3Cl and CH3Br fluxes varied significantly with hydrologic conditions, with progressively higher net uptake rates observed with decreasing soil saturation. Drained tundra sites averaged −620 nmol CH3Cl m−2 d−1 and −9.8 nmol CH3Br m−2 d−1 while flooded tundra sites averaged −14 nmol CH3Cl m−2 d−1 and +1.1 nmol CH3Br m−2 d−1. CH3Cl and CH3Br fluxes were positively correlated with each other as well as with CH4 emissions, suggesting that consumption of both compounds occurs primarily in aerobic environments. Average CH3I net emissions were relatively weak (4.0 nmol m−2 d−1). Average methane fluxes (2.0 mmol m−2 d−1) and their relationship with soil moisture were comparable to tundra emissions reported by prior studies. Methane fluxes showed a marked seasonality, with emissions tripling between early and late in the growing season, but methyl halide fluxes did not show a similar temporal trend. If these measurements are representative of the Arctic tundra, then the Arctic tundra is a regionally important sink for CH3Cl and CH3Br but a trivial source of CH3I.
Validation of the land water storage simulated by Organising Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) with Gravity Recovery and Climate Experiment (GRACE) data
Authors: Ngo‐Duc T. , Laval K. , Ramillien G. , Polcher J. , Cazenave A.
Published: May 2007

The Gravity Recovery and Climate Experiment (GRACE) mission provides measurements of spatiotemporal change in land water storage that may improve simulation results of land surface models (LSMs). We show that a transfer scheme recently developed within the Organising Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) LSM significantly improves the simulated land water storage. Over large tropical rivers basins, model results without the transfer scheme provide significantly smaller amplitudes of water storage than observed by GRACE. Including the transfer scheme that accounts for water stored in the river systems and aquifers during its transfer to the oceans leads to predicted land water storage that are comparable to GRACE observations. Water stored in aquifers contributes about half the seasonal variation of water storage over large basins such as the Amazon, Congo, Yangtze, Ganges, Brahmaputra, and Mekong.
Hot spots of soil respiration in an Asian tropical rainforest
Authors: Ohashi Mizue , Kume Tomonori , Yamane Seiki , Suzuki Masakazu
Published: May 2007

Little is known about the variability in carbon dioxide (CO2) emissions from soil (soil respiration) in tropical rainforests. We studied temporal and spatial fluctuations of soil respiration in an intact Asian tropical rainforest. The values of soil respiration were distributed lognormally with mean and median values of 5.32 and 4.65 μmol m−2 s−1, respectively. Soil respiration varied little over time though highly in space. CO2 hot spots (>10 μmol m−2 s−1) were found with extremely high values (15–25 μmol m−2 s−1). Each CO2 hot spot occurred sporadically at different times and locations. It is hypothesized that animal activities are responsible for the hot spots. The impact of CO2 hot spots on total soil respiration was 10%, which is comparable to the estimation of net C balance in tropical rainforests.
Basaltic andesite, altered basalt, and a TES‐based search for smectite clay minerals on Mars
Authors: Ruff S. W. , Christensen P. R.
Published: May 2007

The global‐scale surface type 2 unit first identified with the Mars Global Surveyor Thermal Emission Spectrometer (TES) remains enigmatic. Competing hypotheses suggest that it represents either basaltic andesite or some form of altered basalt rich in dioctahedral smectite clay minerals and/or spectrally similar amorphous silica phases. Common dioctahedral smectites contain a diagnostic feature in a portion of TES spectra that has been excluded in previous studies because of atmospheric CO2 absorption. We exploit the relative transparency of this spectral region to develop two indices that in tandem, distinguish between certain smectites and amorphous phases. Smectites are not detected in northern lowlands type 2 settings, consistent with other datasets, but the case for primary or secondary amorphous silica phases is strengthened. Separately, one index reveals an abundance of isolated type 2 occurrences in the southern high‐latitudes (>50°) associated with dunes, the other shows olivine concentrations between −40° and +30°.
Model‐based directed drifter launches in the Adriatic Sea: Results from the DART experiment
Authors: Haza A. C. , Griffa A. , Martin P. , Molcard A. , Özgökmen T. M. , Poje A. C. , Barbanti R. , Book J. W. , Poulain P. M. , Rixen M. , Zanasca P.
Published: May 2007

A high‐resolution numerical model of the Adriatic Sea is used to predict Lagrangian coherent structure boundaries, quantified by finite‐size Lyapunov exponents (FSLE), for flow features in the region of the Gargano Peninsula during the course of the Dynamics of the Adriatic in Real Time (DART) observational program. FSLE fields computed from two‐day model forecasts of the surface velocity indicate distinct regions of high relative drifter dispersion. Model predictions of such regions located on available ship‐tracks were used to direct the launching of pairs of surface drifters on three days during March 2006, with the goal of maximize coverage of the sampling area. For two of the three launches, the observed trajectories separated at locations and along directions closely approximated by those predicted from the model FSLE fields. The third case acted as an inadvertent control experiment. Model predictions at release‐time showed minimal FSLE structure at the launch locations and the observed drifter pair advected in a coherent fashion for two days. While there are considerable differences between individual drifter observations and trajectory envelopes computed from ensembles of synthetic drifters, the experiment confirms the model's ability to approximate the location and shape of energetic flow features controlling the near‐time fate of quasi‐Lagrangian particles. Overall, the combined use of FSLEs with realistic coastal circulation models appears to be a promising avenue to aid real‐time‐directed drifter launches in observational programs.
Crystal growth and properties of LiAlO2 and nonpolar GaN on LiAlO2 substrate
Authors: Chou Mitch M. C. , Hang D. R. , Kalisch H. , Jansen R. H. , Dikme Y. , Heuken Michael , Yablonskii G. P.
Published: May 2007

In this study, the growth and properties of LiAlO2 material and a nonpolar GaN-based light-emitting-diode (LED) structure on LiAlO2 have been investigated. The LiAlO2 material is grown by the Czochralski pulling technique and is used as a substrate for nonpolar nitride growth. An improved surface roughness can be obtained by a four-step polishing process. With subsequent nitridation treatment, a pure M-plane (101̱0) GaN can be obtained. An electron microscope shows an abundance of cracks that are oriented parallel to the (001) and (100) planes of the LiAlO2 substrate on the rear surface of GaN. The absence of the polarization-induced electric field of a GaN-based LED structure on LiAlO2 was shown by using photoluminescence measurements. Therefore, this approach is promising to further increase the luminescence performance of GaN-based LEDs.
Perturbation expansion and Nth order Fermi golden rule of the nonlinear Schrödinger equations
Authors: Zhou Gang
Published: May 2007

In this paper we consider generalized nonlinear Schrödinger equations with external potentials. We find the expressions for the fourth and the sixth order Fermi golden rules (FGRs), conjectured in Gang and Sigal [Rev. Math. Phys. 17, 1143–1207 (2005); Geom. Funct. Anal. 16, No. 7, 1377–1390 (2006)]. The FGR is a key condition in a study of the asymptotic dynamics of trapped solitons.
Mutually unbiased bases and Hadamard matrices of order six
Authors: Bengtsson Ingemar , Bruzda Wojciech , Ericsson Åsa , Larsson Jan-Åke , Tadej Wojciech , Życzkowski Karol
Published: May 2007

We report on a search for mutually unbiased bases (MUBs) in six dimensions. We find only triplets of MUBs, and thus do not come close to the theoretical upper bound 7. However, we point out that the natural habitat for sets of MUBs is the set of all complex Hadamard matrices of the given order, and we introduce a natural notion of distance between bases in Hilbert space. This allows us to draw a detailed map of where in the landscape the MUB triplets are situated. We use available tools, such as the theory of the discrete Fourier transform, to organize our results. Finally, we present some evidence for the conjecture that there exists a four dimensional family of complex Hadamard matrices of order 6. If this conjecture is true the landscape in which one may search for MUBs is much larger than previously thought.
Optically pumped mid-infrared light emitter on silicon
Authors: Elizondo L. A. , Li Y. , Sow A. , Kamana R. , Wu H. Z. , Mukherjee S. , Zhao F. , Shi Z. , McCann P. J.
Published: May 2007

Characterization of a IV-VI semiconductor structure consisting of a PbSe/PbSrSe multiple quantum well (MQW) active region between distributed Bragg reflectors grown by molecular beam epitaxy on a Si(111) substrate is described. Pulsed photoluminescence (PL) spectra exhibited interband electronic transition energies ranging linearly with temperature from 231.4 meV at 150 K to 299.4 meV at 300 K, while continuous wave (cw) PL spectra exhibited only the vertical optical cavity mode with emission varying between 299.2 meV at 150 K to 301.1 meV at 300 K. A maximum PL emission power of approximately 1.8 mW was obtained for cw diode laser pumping when the heat sink temperature was 200 K. Data are consistent with a localized epilayer heating effect of about 100 deg where the interband electronic transition energy is coincident with the vertical optical cavity mode. In spite of significant sample heating and associated thermal expansion mismatch stress, cw PL emission intensity was stable with no noticeable degradation in intensity after repeated measurements. These results show that IV-VI epitaxial layers on silicon are viable materials for fabricating reliable light emitters for on-chip optical interconnects.
Depth profile high-energy spectroscopic study of Mn-doped GaN prepared by thermal diffusion
Authors: Hwang J. I. , Osafune Y. , Kobayashi M. , Ebata K. , Ooki Y. , Ishida Y. , Fujimori A. , Takeda Y. , Okane T. , Saitoh Y. , Kobayashi K. , Tanaka A.
Published: May 2007

We have performed an in situ depth profile study of Mn-doped GaN prepared by a low temperature thermal diffusion method using photoemission and x-ray absorption spectroscopy. It was revealed from the core-level photoemission measurements that Mn ions are diffused into a deep (∼70 Å) region of the GaN substrates and that the line shapes of Mn 3d partial density of states obtained by resonant photoemission measurements were close to that of Ga1−xMnxN thin films grown by molecular-beam epitaxy. From x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements at the Mn L edge, it was revealed that the doped Mn ions were in the divalent Mn2+ state and primarily paramagnetic. In magnetization measurements, weak hysteresis was detected in samples prepared using p-type GaN substrates while samples using n-type GaN substrates showed only paramagnetism.
Stress field induced by swift heavy ion irradiation in cubic yttria stabilized zirconia
Authors: Sattonnay G. , Lahrichi M. , Herbst-Ghysel M. , Garrido F. , Thomé L.
Published: May 2007

X-ray diffraction (XRD) was used to investigate the damage and the correlated stress induced by the slowing down of swift heavy ions in cubic zirconia polycrystals doped with 10 mol % Y2O3. Samples were irradiated at room temperature with 940 MeV Pb ions at fluences ranging from 5×1011 to 4×1013 cm−2. Changes of XRD profiles were examined at increasing fluences. Residual macroscopic stresses induced by irradiation were determined using XRD by the “sin2 ψ method.” The state of stress in the irradiated layer was described by a combination of: (i) a hydrostatic stress caused by the formation of damaged tracks leading to swelling and (ii) a biaxial stress imposed by the bulk undamaged material, which controls the lateral expansion of the surface damaged layer. The evolution of the stress as a function of irradiation fluence was also determined: the intensity of the hydrostatic stress increases from 80 to 460 MPa when the fluence is increased from 5×1011 to 4×1013 cm−2 and that of the biaxial stress increases correlatively from −80 to −1630 MPa.
Intra- and intermolecular vibrational energy transfer in tungsten carbonyl complexes W(CO)5(X) (X=CO, CS, CH3CN, and CD3CN)
Authors: Banno Motohiro , Iwata Koichi , Hamaguchi Hiro-o
Published: May 2007

Vibrational energy relaxation of degenerate CO stretches of four tungsten carbonyl complexes, W(CO)6, W(CO)5(CS), W(CO)5(CH3CN), and W(CO)5(CD3CN), is observed in nine alkane solutions by subpicosecond time-resolved infrared (IR) pump-probe spectroscopy. Between 0 and 10ps after the vibrational excitation, the bleaching signal of the ground-state IR absorption band shows anisotropy. Decay of the anisotropic component corresponds either to the rotational diffusion of the molecule or to the intramolecular vibrational energy transfer among the degenerate CO stretch modes. The time constant of the anisotropy decay, τaniso, shows distinct solvent dependence. By comparing the results for the T1u CO stretch of W(CO)6 and the A1 CO stretch of W(CO)5(CS), the time constant of the rotational diffusion, τr, and the time constant of the intramolecular energy transfer among the three degenerate vibrational modes, τe, are determined as 12 and 8ps, respectively. The τaniso value increases as the number of carbon atoms in the alkane solvent increases. After 10ps, the recovery of the bleaching becomes isotropic. The isotropic decay represents the vibrational population relaxation, from v=1 to v=0. In heptane, the time constant for the isotropic decay, τ1, for W(CO)5(CS) and W(CO)6 was 140ps. The τ1 for the two acetonitrile-substituted complexes, however, shows a smaller value of 80ps. The vibrational energy relaxation of W(CO)5(CH3CN) and W(CO)5(CD3CN) is accelerated by the intramolecular energy redistribution from the CO ligand to the acetonitrile ligand. In the nine alkane solutions, the τ1 value of W(CO)6 ranges between 124 and 158ps, showing the apparent V-shaped solvent dependence with its minimum in decane, while the τ1 value shows little solvent dependence for W(CO)5(CH3CN) and W(CO)5(CD3CN).
Spatially indirect excitons in type-II quantum dots
Authors: Madureira Justino R. , de Godoy Márcio P. F. , Brasil Maria J. S. P. , Iikawa Fernando
Published: May 2007

The authors have calculated the electronic structure for type-II InP∕GaAs quantum dot systems considering a three-dimensional geometry including the wetting layer and the electron-hole interaction, which is the only responsible for the hole localization. Their results for the InP∕GaAs structure show the electron confined inside the dot and the hole in the GaAs layer, partially above and below the dot. The authors propose structures with InGaAs or InGaP layers, where the hole wave function forms a ring around the dot walls. The electron-hole overlap, and therefore, the carrier lifetimes are very sensitive to the structural geometry, which is an important tool for device engineering.
Diffraction of plane compressional wave by a nanosized spherical cavity with surface effects
Authors: Wang G. F.
Published: May 2007

For nanostructured materials and devices, the effects of surface energy become prominent due to the increasing ratio of surface area to volume. In the present letter, based on the surface elasticity theory, the authors analyzed the diffraction of plane harmonic compressional wave (P wave) by a spherical cavity. The results show that once the radius of cavity reduces to nanometers, surface energy significantly affects the diffraction of elastic waves. For incident waves with different frequencies, the surface effects on dynamic stress concentrations around the spherical cavity are discussed in detail.
Enhanced switching current density due to resonant precession in current-induced magnetization switching
Authors: Kim Woojin , Lee Taek-Dong , Lee Jang-Eun , Oh Se-Chung , Shin Kyung-Ho , Suh Hong-Ju , Lee Kyung-Jin
Published: May 2007

Micromagnetic investigation was performed on the influence of neighboring cells in a conventional rectangular array to the switching current density (Jc) in the current-induced magnetization switching. We found that the Jc was increased regardless of the relative switching direction to the overall stray field. It is because the precession of the magnetization in the switching cell induces a resonant precession in neighboring cells through magnetostatic interaction. The resonant precession disturbs a fast reversal and results in the enhanced Jc for a fixed pulse width. The enhancement increases as the distance between the cells decreases. Here we proposed a zigzag array which significantly suppresses the enhancement of Jc due to the resonant precession.
Nearest-neighbor coordination and chemical ordering in multicomponent bulk metallic glasses
Authors: Ma D. , Stoica A. D. , Yang L. , Wang X.-L. , Lu Z. P. , Neuefeind J. , Kramer M. J. , Richardson J. W. , Proffen Th.
Published: May 2007

The authors report complementary use of high-energy x-ray and neutron diffraction to probe the local atomic structure in a Zr-based bulk metallic glass. By analyzing the partial coordination numbers, the authors demonstrate the presence of multiple types of solute-centered clusters in the multicomponent glass and efficient packing of the amorphous structure at atomic scale. The authors’ findings provide a basis for understanding how local structures change during phase transformation and mechanical deformation of multicomponent amorphous alloys.
Single crystalline ZnS nanotubes and their structural degradation under electron beam irradiation
Authors: Shi L. , Xu Y. M. , Li Quan , Wu Z. Y. , Chen F. R. , Kai J. J.
Published: May 2007

ZnS nanotubes were synthesized using wet-chemistry method. These nanotubes appear to be extremely unstable under electron beam irradiation. Time dependent transmission electron diffraction patterns disclose the appearance of additional diffraction spots that belong to ZnO, with the prolonged e-beam irradiation duration. The experimental results suggest that displacement damage followed by oxidation is mainly responsible for the structural degradation of these ZnS nanotubes.
Adaptation of Central Pitch-Specific Mechanisms
Authors: Phillips Dennis P , Scovil Susan J , Carmichael Martha E , Hall Susan E
Published: May 2007

Three previous psychophysical studies have demonstrated that interaural time difference (ITD) coding mechanisms can undergo frequency-specific, selective adaptation. We sought to determine whether this phenomenon extends to the pitch domain, by employing the same psychophysical paradigm as one used previously, but with harmonic tone complexes lacking energy at the fundamental frequency. Ten normal listeners participated in experiment 1. Psychometric functions for ITDs were obtained for harmonic tone complexes with fundamental frequencies of 110 Hz and 185 Hz, before and after selective adaptation with complexes of the same fundamental frequencies lateralised to opposite sides. In experiment 1, each subject was tested twice. On separate days, subjects were tested with 110 Hz and 185 Hz stimuli that were either partially resolvable complexes or unresolvable ones. Both partially resolved and unresolved stimuli supported adaptation, and at both fundamental frequencies. In experiment 2, which employed nine listeners, the adaptor tone complexes were presented in conjunction with a diotic noise background designed to mask difference tones generated by the adaptor stimuli. The use of the masker had little effect on the mean strength of the adaptation effected by the unresolved adaptor stimuli, and only slightly weakened the adaptation effect found with the partially resolved adaptor stimuli. Taken together, these data constitute the first demonstration of selective adaptation exerted on a central mechanism in the pitch domain.
Neural signature of fictive learning signals in a sequential investment task
Authors: Lohrenz Terry , McCabe Kevin , Camerer Colin F. , Montague P. Read
Published: May 2007

Reinforcement learning models now provide principled guides for a wide range of reward learning experiments in animals and humans. One key learning (error) signal in these models is experiential and reports ongoing temporal differences between expected and experienced reward. However, these same abstract learning models also accommodate the existence of another class of learning signal that takes the form of a fictive error encoding ongoing differences between experienced returns and returns that “could-have-been-experienced” if decisions had been different. These observations suggest the hypothesis that, for all real-world learning tasks, one should expect the presence of both experiential and fictive learning signals. Motivated by this possibility, we used a sequential investment game and fMRI to probe ongoing brain responses to both experiential and fictive learning signals generated throughout the game. Using a large cohort of subjects (
n
= 54), we report that fictive learning signals strongly predict changes in subjects' investment behavior and correlate with fMRI signals measured in dopaminoceptive structures known to be involved in valuation and choice.
Cystic fibrosis transmembrane conductance regulator is vital to sperm fertilizing capacity and male fertility
Authors: Xu Wen Ming , Shi Qi Xian , Chen Wen Ying , Zhou Chen Xi , Ni Ya , Rowlands Dewi Kenneth , Yi Liu Guo , Zhu Hu , Ma Ze Gang , Wang Xiao Fei , Chen Zhang Hui , Zhou Si Chang , Dong Hong Shan , Zhang Xiao Hu , Chung Yiu Wa , Yuan Yu Ying , Yang Wan Xi , Chan Hsiao Chang
Published: May 2007

Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel, mutations of which cause cystic fibrosis, a disease characterized by defective Cl−and HCO3−transport. Although >95% of all CF male patients are infertile because of congenital bilateral absence of the vas deferens (CBAVD), the question whether CFTR mutations are involved in other forms of male infertility is under intense debates. Here we report that CFTR is detected in both human and mouse sperm. CFTR inhibitor or antibody significantly reduces the sperm capacitation, and the associated HCO3−-dependent events, including increases in intracellular pH, cAMP production and membrane hyperpolarization. The fertilizing capacity of the sperm obtained from heterozygous CFTR mutant mice is also significantly lower compared with that of the wild-type. These results suggest that CFTR in sperm may be involved in the transport of HCO3−important for sperm capacitation and that CFTR mutations with impaired CFTR function may lead to reduced sperm fertilizing capacity and male infertility other than CBAVD.
Selectivity in K
+
channels is due to topological control of the permeant ion's coordinated state
Authors: Bostick David L. , Brooks Charles L.
Published: May 2007

The selectivity filter of K
+
channels provides specific coordinative interactions between dipolar carbonyl ligands, water, and the permeant cation, which allow for selective flow of K
+
over (most importantly) Na
+
across the cell membrane. Although a structural viewpoint attributes K
+
selectivity to coordination geometry provided by the filter, recent molecular dynamics simulation studies attribute it to dynamic and unique chemical/electrostatic properties of the filter's carbonyl ligands. Here we provide a simple theoretical analysis of K
+
and Na
+
complexation with water in the context of simplified binding site models and bulk solution. Our analysis reveals that water molecules and carbonyl groups can both provide K
+
selective environments if equivalent constraints are imposed on the coordination number of the complex. Absence of such constraints annihilates selectivity, demonstrating that whether a coordinating ligand is a water molecule or a carbonyl group, “external” or “topological” constraints/forces must be imposed on an ion-coordinated complex to elicit selective binding. These forces must inevitably originate from the channel protein, because in bulk water, which, by definition, presents a nonselective medium, the coordination number is allowed to relax to suit the ion. We show that the coordination geometry of K
+
channel binding sites is replicated by 8-fold complexation of K
+
in both water and simplified binding site models due to dominance of local interactions within a complex and is thus a requirement for topologically constraining the coordination number to a specific value.
GPR37 associates with the dopamine transporter to modulate dopamine uptake and behavioral responses to dopaminergic drugs
Authors: Marazziti Daniela , Mandillo Silvia , Di Pietro Chiara , Golini Elisabetta , Matteoni Rafaele , Tocchini-Valentini Glauco P.
Published: May 2007

The orphan G protein-coupled receptor 37 (GPR37) is a substrate of parkin; its insoluble aggregates accumulate in brain samples of Parkinson's disease patients. We report here that GPR37 interacts with the dopamine transporter (DAT) and modulates DAT activity. GPR37 and DAT were found colocalized in mouse striatal presynaptic membranes and in transfected cells and their interaction was confirmed by coimmunoprecipitation assays.Gpr37-null mutant mice showed enhanced DAT-mediated dopamine uptake in striatal membrane samples, with a significant increase in the number of plasma membrane DAT molecules. The null mutant mice also exhibited a decrease in cocaine-induced locomotor activity and in catalepsy induced by dopamine receptor antagonists. These results reveal the specific role of GPR37, a putative peptidergic G protein-coupled receptor, in modulating the functional expression of DAT and the behavioral responses to dopaminergic drugs.
Innateness as Closed Process Invariance
Authors: Mallon Ron , Weinberg Jonathan M.
Published: May 2007

Controversies over the innateness of cognitive structures play a persistent role in driving research in philosophy as well as cognitive science, but the appropriate way to understand the category of the innate remains in dispute. The invariantist approaches of Stich and Sober face counterexample cases of traits that, though developing invariantly across different environments, nonetheless are not held by nativism partisans to count as innate. Appeals to canalization (Ariew) or to psychological primitiveness (Samuels) fail to handle this liberalism problem. We suggest a novel approach to innateness:closed process invariantism.
The distribution functions of 𝜎(𝑛)/𝑛 and 𝑛/𝜑(𝑛)
Authors: Weingartner Andreas
Published: May 2007

Let

σ
(
n
)

\sigma (n)

be the sum of the positive divisors of

n
n

. We show that the natural density of the set of integers

n
n

satisfying

σ
(
n
)

/

n
≥
t

\sigma (n)/n\ge t

is given by

exp
⁡

{
−

e

t

e

−
γ

(
1
+
O

(

t

−
2

)

)

}

\exp \left \{ -e^{t \, e^{-\gamma }} \left (1+O\left ({t^{-2}}\right )\right ) \right \}

, where

γ
\gamma

denotes Euler’s constant. The same result holds when

σ
(
n
)

/

n

\sigma (n)/n

is replaced by

n

/

φ
(
n
)

n/\varphi (n)

, where

φ
\varphi

is Euler’s totient function.
Row and column finite matrices
Authors: Nielsen Pace
Published: May 2007

Consider the ring of all

κ
×
κ

\kappa \times \kappa

column finite matrices over a ring

R
R

. We prove that each such matrix is conjugate to a row and column finite matrix if and only if

R
R

is right Noetherian and

κ
\kappa

is countable. We then demonstrate that one can perform this conjugation on countably many matrices simultaneously. Some applications and limitations are given.
Moment problem with contractive solutions: the regular case
Authors: Jablonski Zenon
Published: May 2007

An operator multivariate moment problem with contractive solutions having regular unitary dilation is characterized in terms of the initial data. This extends a recent result of Sebestyén and Popovici, but the ideas of our proof differ from those used by them. The connection between the operator multivariate moment problem and harmonizable multivariate discrete processes is mentioned.
The Lempert function of the symmetrized polydisc in higher dimensions is not a distance
Authors: Nikolov Nikolai , Pflug Peter , Zwonek Wlodzimierz
Published: May 2007

We prove that the Lempert function of the symmetrized polydisc in dimension greater than two is not a distance.
Uniqueness for boundary blow-up problems with continuous weights
Authors: García-Melián Jorge
Published: May 2007

In this paper, we prove that forp>1p>1the problemΔu=a(x)up\Delta u=a(x)u^pin a boundedC2C^2domainΩ\OmegaofRN\mathbb R^Nhas a unique positive solution withu=∞u=\inftyon∂Ω\partial \Omega. The nonnegative weighta(x)a(x)is continuous inΩ¯\overline {\Omega }, but is only assumed to verify a “bounded oscillations" condition of local nature near∂Ω\partial \Omega, in contrast with previous works, where a definite behavior ofaanear∂Ω\partial \Omegawas imposed.
The conformal deformation detour complex for the obstruction tensor
Authors: Branson Thomas , Gover A.
Published: May 2007

On pseudo-Riemannian manifolds of even dimension

n
≥
4

n\geq 4

, with everywhere vanishing (Fefferman-Graham) obstruction tensor, we construct a complex of conformally invariant differential operators. The complex controls the infinitesimal deformations of obstruction-flat structures, and, in the case of Riemannian signature the complex is elliptic.
Recombination-filtered genomic datasets by information maximization
Authors: Woerner August E. , Cox Murray P. , Hammer Michael F.
Published: May 2007

Summary: With the increasing amount of DNA sequence data available from natural populations, new computational methods are needed to efficiently process raw sequences into formats that are applicable to a variety of analytical methods. One highly successful approach to inferring aspects of demographic history is grounded in coalescent theory. Many of these methods restrict themselves to perfectly tree-like genealogies (i.e. regions with no observed recombination), because theoretical difficulties prevent ready statistical evaluation of recombining regions. However, determining which recombination-filtered dataset to analyze from a larger recombination-rich genomic region is a non-trivial problem. Current applications primarily aim to quantify recombination rates (rather than produce optimal recombination-filtered blocks), require significant manual intervention, and are impractical for multiple genomic datasets in high-throughput, automated research environments. Here, we present a fast, simple and automatable command-line program that extracts optimal recombination-filtered blocks (no four-gamete violations) from recombination-rich genomic re-sequence data.

Availability:  http://hammerlab.biosci.arizona.edu/software.html

Contact:  mpcox@email.arizona.edu
Assortative mixing in Protein Contact Networks and protein folding kinetics
Authors: Bagler Ganesh , Sinha Somdatta
Published: May 2007

Motivation: Starting from linear chains of amino acids, the spontaneous folding of proteins into their elaborate 3D structures is one of the remarkable examples of biological self-organization. We investigated native state structures of 30 single-domain, two-state proteins, from complex networks perspective, to understand the role of topological parameters in proteins’ folding kinetics, at two length scales—as ‘Protein Contact Networks (PCNs)’ and their corresponding ‘Long-range Interaction Networks (LINs)’ constructed by ignoring the short-range interactions.

Results: Our results show that, both PCNs and LINs exhibit the exceptional topological property of ‘assortative mixing’ that is absent in all other biological and technological networks studied so far. We show that the degree distribution of these contact networks is partly responsible for the observed assortativity. The coefficient of assortativity also shows a positive correlation with the rate of protein folding at both short- and long-contact scale, whereas, the clustering coefficients of only the LINs exhibit a negative correlation. The results indicate that the general topological parameters of these naturally evolved protein networks can effectively represent the structural and functional properties required for fast information transfer among the residues facilitating biochemical/kinetic functions, such as, allostery, stability and the rate of folding.

Contact:  sinha@ccmb.res.in

Supplementary information: Supplementary data are available at Bioinformatics online.
The evolutionary forest algorithm
Authors: Leman Scotland C. , Uyenoyama Marcy K. , Lavine Michael , Chen Yuguo
Published: May 2007

Motivation: Gene genealogies offer a powerful context for inferences about the evolutionary process based on presently segregating DNA variation. In many cases, it is the distribution of population parameters, marginalized over the effectively infinite-dimensional tree space, that is of interest. Our evolutionary forest (EF) algorithm uses Monte Carlo methods to generate posterior distributions of population parameters. A novel feature is the updating of parameter values based on a probability measure defined on an ensemble of histories (a forest of genealogies), rather than a single tree.

Results: The EF algorithm generates samples from the correct marginal distribution of population parameters. Applied to actual data from closely related fruit fly species, it rapidly converged to posterior distributions that closely approximated the exact posteriors generated through massive computational effort. Applied to simulated data, it generated credible intervals that covered the actual parameter values in accordance with the nominal probabilities.

Availability: A C++ implementation of this method is freely accessible at http://www.isds.duke.edu/~scl13

Contact:  scotland@stat.duke.edu
Virtual Laryngoscopy: a Noninvasive Tool for the Assessment of Laryngeal Tumor Extent
Authors: Yan Yuling , Luo Shouhua , McWhorter Andrew
Published: May 2007

Objectives: Present a clinical application of virtual laryngoscopy (VL) in the assessment of laryngeal tumor and its extent.

Study Design: CT data from two subjects are acquired for this preliminary study. One subject is a healthy volunteer and the other is a patient with laryngeal tumor. The laryngeal framework and upper airway are reconstructed using CT data, which allows for computer‐aided internal and external anatomical views and interactive fly‐through.

Methods: These CT data are reconstructed into 0.5 mm slice images, resulting in a total of 200–300 image slices. An advanced commercial visualization software (AMIRA) is used for 3D image segmentation, reconstruction and surface rendering of laryngeal anatomical structures.

Results: The 3D laryngeal framework and upper airway are reconstructed for both the tumor patient and the healthy subject. The conventional views of the reconstructed vocal folds are compared with those obtained from fiber‐optic laryngoscope. Additionally, unique views of the vocal folds obtained from retrograde visualization and fly‐through are presented, which are not possible to obtain using conventional endoscope imaging. The segmented anatomical model and the tumor from the patient's CT images were displayed individually to show the distribution of the tumor and its extent as well as spatial and contextual relationships to the larynx and airway anatomical structures.

Conclusions: This study demonstrated the potential application of VL as a noninvasive clinical diagnostic tool for the assessment of laryngeal tumor and its extent. Our preliminary results demonstrated that the VL may provide valuable insights for the diagnosis and treatment planning for laryngeal and airway tumors. The noninvasive VL may complement the invasive laryngoscopic examinations for the staging of tumors and follow‐ups on surgical interventions.
Upper Lateral Cartilage‐Sparing Component Dorsal Hump Reduction in Primary Rhinoplasty
Authors: Arslan Emrah , Aksoy Alper
Published: May 2007

Background: Dorsal hump reduction is a critical step in rhinoplasty. Most of the reasons behind revisional procedures are related to incorrect hump reduction.

Methods: The authors used a modified dorsal hump reduction method in their primary cases, the steps of which are as follows: 1) dissection of the nasal vault; 2) bilateral submucoperichondrial dissections to free the cartilaginous septum; 3) separation of the upper lateral cartilages from the cartilaginous septum; 4) partial dissection of the upper lateral cartilages from the inner surfaces of the nasal bones bilaterally; 5) separation of the bony septum from the nasal bones bilaterally; 6) reduction of the partially isolated nasal bones; 7) en bloc cartilaginous and bony septum removal. The authors have operated on 68 primary cases over a 2 year period (30 mo).

Results: In the great majority of cases, the results were satisfactory. No revisions were performed in this patient group.

Conclusions: This method is a good alternative to traditional techniques in noses with a high and narrow roof, thin skin, and weak middle nasal vault. Revision could be performed more easily when required. Initially, wide noses may not seem good candidates for this procedure; however, careful case‐based preoperative planning may overcome this difficulty.
Salvage Surgery with Free Flap Reconstruction: Factors Affecting Outcome After Treatment of Recurrent Head and Neck Squamous Carcinoma
Authors: Kim Alyn J. , Suh Jeffrey D. , Sercarz Joel A. , Abemayor Elliot , Head Christian , Funk Gerry , Blackwell Keith E.
Published: May 2007

Objective: To determine factors predicting the outcome after salvage surgery with microvascular flap reconstruction for recurrent squamous cell cancer (SCC) of the head and neck.

Study Design: This is a retrospective analysis of patients treated at an academic medical center.

Methods. One hundred six patients underwent salvage surgery and microvascular flap reconstruction after prior unsuccessful cancer treatment using surgery, radiation, or chemotherapy. All patients had a follow‐up interval after salvage surgery of at least 24 months unless cancer rerecurrence occurred within 24 months after salvage surgery. Factors including age, sex, comorbidity level, tobacco use, alcohol use, disease‐free interval since prior therapy, prior radiation, prior chemotherapy, prior surgery, recurrent tumor T class, recurrent tumor N class, recurrent cancer stage, and tumor location were examined to determine their association with cancer rerecurrence after salvage surgery. Successful treatment was defined as patients who remained free from cancer rerecurrence for a minimum 2 year period after salvage surgery.

Results: Advanced recurrent T class (P = .02) was significantly associated with cancer recurrence. Recurrent cancer stage and patient smoking status approached statistical significance (P = .06).

Conclusion: Patients with recurrent T1 and T2 class are the best candidates for salvage surgery and microvascular flap reconstruction for treatment of recurrent SCC of the head and neck. Patients with T3 and T4 class recurrent cancers and patients who continue to smoke after initial diagnosis and treatment of head and neck SCC are poor candidates to undergo salvage surgery.
Influence of Age on the Surgical Outcome After Endoscopic Sinus Surgery for Chronic Rhinosinusitis With Nasal Polyposis
Authors: Lee Jae Yong , Lee Seung Won
Published: May 2007

Objectives: To determine whether patient age is associated with the surgical outcome after endoscopic sinus surgery (ESS) with polypectomy.

Study Design: A prospective, controlled case series.

Materials and Methods: This study consisted of 60 patients who were diagnosed as having chronic rhinosinusitis (CRS) with nasal polyposis (NP) that was refractory to medical treatment. Three groups were classified according to patient age: pediatric (5–18 yr), adult (19–65 yr), and geriatric (over 65 yr). We collected 20 patients in each age group after applying the exclusion criteria. The extent of the polyps and the Lund‐Mackay score were calculated for each patient, and they underwent ESS with polypectomy. We compared the objective endoscopic findings and subjective improvements in symptoms among the groups 6 months after the procedure.

Results: There were no statistical differences in polyp extent or Lund‐Mackay score between the three age groups. The objective surgical outcome based on the endoscopic findings was worst in the pediatric group (45%), whereas the geriatric group showed the best results (90%). The differences in objective outcome among the three groups were significant, and patient age was a predictive variable for surgical result based on multiple logistic regression analysis. No major complications occurred, and the overall improvement in subjective symptoms was statistically significant in all three age groups at 6 months postoperatively. The subjective surgical outcome did not differ statistically between the groups, with the exception of olfactory disturbance.

Conclusions: The results of the present study suggest that patient age influences the objective postoperative outcome in the endoscopic treatment of CRS with NP, and that ESS is an effective and reliable method for improving the subjective symptoms in patients of all age groups despite the statistically different objective surgical outcomes between the groups.
Methane bubbling from northern lakes: present and future contributions to the global methane budget
Authors: Walter Katey M , Smith Laurence C , Stuart Chapin F
Published: May 2007

Large uncertainties in the budget of atmospheric methane (CH
4
) limit the accuracy of climate change projections. Here we describe and quantify an important source of CH
4
—point-source ebullition (bubbling) from northern lakes—that has not been incorporated in previous regional or global methane budgets. Employing a method recently introduced to measure ebullition more accurately by taking into account its spatial patchiness in lakes, we estimate point-source ebullition for 16 lakes in Alaska and Siberia that represent several common northern lake types: glacial, alluvial floodplain, peatland and thermokarst (thaw) lakes. Extrapolation of measured fluxes from these 16 sites to all lakes north of 45° N using circumpolar databases of lake and permafrost distributions suggests that northern lakes are a globally significant source of atmospheric CH
4
, emitting approximately 24.2±10.5 Tg CH
4
 yr
−1
. Thermokarst lakes have particularly high emissions because they release CH
4
produced from organic matter previously sequestered in permafrost. A carbon mass balance calculation of CH
4
release from thermokarst lakes on the Siberian yedoma ice complex suggests that these lakes alone would emit as much as approximately 49 000 Tg CH
4
if this ice complex was to thaw completely. Using a space-for-time substitution based on the current lake distributions in permafrost-dominated and permafrost-free terrains, we estimate that lake emissions would be reduced by approximately 12% in a more probable transitional permafrost scenario and by approximately 53% in a ‘permafrost-free’ Northern Hemisphere. Long-term decline in CH
4
ebullition from lakes due to lake area loss and permafrost thaw would occur only after the large release of CH
4
associated thermokarst lake development in the zone of continuous permafrost.
Critical issues in trace gas biogeochemistry and global change
Authors: Beerling David J , Nicholas Hewitt C , Pyle John A , Raven John A
Published: May 2007

The atmospheric composition of trace gases and aerosols is determined by the emission of compounds from the marine and terrestrial biospheres, anthropogenic sources and their chemistry and deposition processes. Biogenic emissions depend upon physiological processes and climate, and the atmospheric chemistry is governed by climate and feedbacks involving greenhouse gases themselves. Understanding and predicting the biogeochemistry of trace gases in past, present and future climates therefore demands an interdisciplinary approach integrating across physiology, atmospheric chemistry, physics and meteorology. Here, we highlight critical issues raised by recent findings in all of these key areas to provide a framework for better understanding the past and possible future evolution of the atmosphere. Incorporating recent experimental and observational findings, especially the influence of CO
2
on trace gas emissions from marine algae and terrestrial plants, into earth system models remains a major research priority. As we move towards this goal, archives of the concentration and isotopes of N
2
O and CH
4
from polar ice cores extending back over 650 000 years will provide a valuable benchmark for evaluating such models. In the Pre-Quaternary, synthesis of theoretical modelling with geochemical and palaeontological evidence is also uncovering the roles played by trace gases in episodes of abrupt climatic warming and ozone depletion. Finally, observations and palaeorecords across a range of timescales allow assessment of the Earth's climate sensitivity, a metric influencing our ability to decide what constitutes ‘dangerous’ climate change.