bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calmodulin regulates the olfactory performance in Drosophila melanogaster
Authors: Jain Kalpana , Lavista-Llanos Sofia , Grabe Veit , Hansson Bill S. , Wicher Dieter 
Published: February 2021

AbstractInsect odorant receptors (ORs) detect volatile chemical cues with high sensitivity. These ORs operate as ligand-gated ion channels and are formed by heptahelical OrX and Orco (co-receptor) proteins. A highly conserved calmodulin (CaM) binding site (CBS) 336SAIKYWVER344 within the second intracellular loop of Drosophila melanogaster Orco constitutes a target for regulating OR performance. Here we asked how a point mutation K339N in this CBS affects the olfactory performance of Drosophila melanogaster. We first asked how this mutation would affect the odor responses of olfactory sensory neurons (OSNs). Using Ca2+ imaging in an ex-vivo antenna preparation, we activated all OR (OrX/Orco) expressing neurons using the synthetic agonist VUAA1. In a next attempt, we restricted the OR spectrum to Or22a expressing neurons (Or22a/Orco) and stimulated these OSNs with the ligand ethyl hexanoate. In both approaches, we found that flies carrying the K339N point mutation in Orco display a reduced olfactory response. We also found that the mutation abolishes the capability of OSNs to sensitize by repeated weak odor stimuli. Next, we asked whether OrcoK339N might affect the odor localization performance. Using a wind tunnel bioassay, we found that odor localization in flies carrying the OrcoK339N mutation was severely diminished.
Tracking Advanced Planetary Systems (TAPAS) with HARPS-N
Authors: Niedzielski A. , Villaver E. , Adamów M. , Kowalik K. , Wolszczan A. , Maciejewski G. 
Published: February 2021

Context. We present the current status of and new results from our search for exoplanets in a sample of solar-mass evolved stars observed with the HARPS-N and the 3.6 m Telescopio Nazionale Galileo (TNG), and the High-Resolution Spectrograph (HRS) and the 9.2 m Hobby-Eberly Telescope (HET).
Aims. The aim of this project is to detect and characterize planetary-mass companions to solar-mass stars in a sample of 122 targets at various stages of evolution from the main sequence to the red giant branch, mostly subgiants and giants, selected from the Pennsylvania-Toruń Planet Search sample, and to use this sample to study relations between stellar properties, such as metallicity, luminosity, and the planet occurrence rate.
Methods. This work is based on precise radial velocity (RV) measurements. We have observed the program stars for up to 14 yr with the HET/HRS and the TNG/HARPS-N.
Results. We present the analysis of RV measurements with the HET/HRS and the TNG/HARPS-N of four solar-mass stars, HD 4760, HD 96992, BD+02 3313, and TYC 0434-04538-1. We found that HD 4760 hosts a companion with a minimum mass of 13.9 MJ (a = 1.14 au, e = 0.23); HD 96992 is a host to a m sin i = 1.14 MJ companion on an a = 1.24 au and e = 0.41 orbit, and TYC 0434-04538-1 hosts an m sin i = 6.1 MJ companion on an a = 0.66 au and e = 0.08 orbit. In the case of BD+02 3313 we found a correlation between the measured RVs and one of the stellar activity indicators, suggesting that the observed RV variations may either originate in stellar activity or be caused by the presence of an unresolved companion. We also discuss the current status of the project and a statistical analysis of the RV variations in our sample of target stars.
Conclusions. In our sample of 122 solar-mass stars, 49 ± 5% of them appear to be single and 16 ± 3% spectroscopic binaries. The three giants hosting low-mass companions presented in this paper join the six previously identified giants in the sample.
A search for a fifth planet around HR 8799 using the star-hopping RDI technique at VLT/SPHERE
Authors: Wahhaj Z. , Milli J. , Romero C. , Cieza L. , Zurlo A. , Vigan A. , Peña E. , Valdes G. , Cantalloube F. , Girard J. , Pantoja B. 
Published: February 2021

Context.Direct imaging of extrasolar giant planets demands the highest possible contrasts (ΔH ≳ 10 mag) at the smallest angular separations (∼0.1″) from the star. We present an adaptive optics observing method, called star-hopping, recently offered as standard queue observing (service mode) for the SPHERE instrument at the VLT. The method uses reference difference imaging (RDI) but, unlike earlier RDI applications, images of a reference star for PSF subtraction are obtained within minutes of observing the target star.Aims.We aim to significantly gain in contrast beyond the conventional angular differencing imaging (ADI) method to search for a fifth planet at separations less than 10 au, interior to the four giant planets of the HR 8799 system. The most likely semimajor axes allowed for this hypothetical planet, which were estimated via dynamical simulations in earlier works, were 7.5 au and 9.7 au within a mass range of 1–8MJup.Methods.We obtained 4.5 h of simultaneous low-resolution integral field spectroscopy (R ∼ 30,Y − Hband with IFS) and dual-band imaging (K1 andK2 bands with IRDIS) of the HR 8799 system, interspersed with observations of a reference star. The reference star was observed for about one-third of the total time and generally needs to be of similar brightness (ΔR ≲ 1 mag) and separated on sky by ≲1–2°. The hops between stars were made every 6–10 min, with only 1 min gaps in on-sky integration per hop.Results.We did not detect the hypothetical fifth planet at the most plausible separations, 7.5 and 9.7 au, down to mass limits of 3.6MJupand 2.8MJup, respectively, but attained an unprecedented contrast limit of 11.2 magnitudes at 0.1″. We detected all four planets with high signal-to-noise ratios. TheYJHspectra for planetsc,dwere detected with redderH-band spectral slopes than found in earlier studies. As noted in previous works, the planet spectra are matched very closely by some red field dwarfs. Finally, comparing the current locations of the planets to orbital solutions, we found that planetseandcare most consistent with coplanar and resonant orbits. We also demonstrated that with star-hopping RDI, the contrast improvement at 0.1″ separation can be up to 2 mag.Conclusions.Since ADI, meridian transit and the concomitant sky rotation are not needed, the time of observation can be chosen from within a window that is two to three times larger. In general, star-hopping can be used for stars fainter thanR = 4 magnitudes, since for these a reference star of suitable brightness and separation is usually available.
Infrared photometry and CaT spectroscopy of globular cluster M 28 (NGC 6626)
Authors: Moni Bidin C. , Mauro F. , Contreras Ramos R. , Zoccali M. , Reinarz Y. , Moyano M. , González-Díaz D. , Villanova S. , Carraro G. , Borissova J. , Chené A.-N. , Cohen R. E. , Geisler D. , Kurtev R. , Minniti D. 
Published: February 2021

Context. Recent studies show that the inner Galactic regions host genuine bulge globular clusters, but also halo intruders, complex remnants of primordial building blocks, and objects likely accreted during major merging events.
Aims. In this study we focus on the properties of M 28, a very old and massive cluster currently located in the Galactic bulge.
Methods. We analysed wide-field infrared photometry collected by the VVV survey, VVV proper motions, and intermediate-resolution spectra in the calcium triplet range for 113 targets in the cluster area.
Results. Our results in general confirm previous estimates of the cluster properties available in the literature. We find no evidence of differences in metallicity between cluster stars, setting an upper limit of Δ[Fe/H] < 0.08 dex to any internal inhomogeneity. We confirm that M 28 is one of the oldest objects in the Galactic bulge (13–14 Gyr). From this result and the literature data, we find evidence of a weak age–metallicity relation among bulge globular clusters that suggests formation and chemical enrichment. In addition, wide-field density maps show that M 28 is tidally stressed and that it is losing mass into the general bulge field.
Conclusions. Our study indicates that M 28 is a genuine bulge globular cluster, but its very old age and its mass loss suggest that this cluster could be the remnant of a larger structure, possibly a primeval bulge building block.
Sub-10 nm spatial resolution for electrical properties measurements using bimodal excitation in electric force microscopy
Authors: Kaja Khaled , Mariolle Denis , Chevalier Nicolas , Naja Adnan , Jouiad Mustapha 
Published: February 2021

We demonstrate that under ambient and humidity-controlled conditions, operation of bimodal excitation single-scan electric force microscopy with no electrical feedback loop increases the spatial resolution of surface electrical property measurements down to the 5 nm limit. This technical improvement is featured on epitaxial graphene layers on SiC, which is used as a model sample. The experimental conditions developed to achieve such resolution are discussed and linked to the stable imaging achieved using the proposed method. The application of the herein reported method is achieved without the need to apply DC bias voltages, which benefits specimens that are highly sensitive to polarization. Besides, it allows the simultaneous parallel acquisition of surface electrical properties (such as contact potential difference) at the same scanning rate as in amplitude modulation atomic force microscopy (AFM) topography measurements. This makes it attractive for applications in high scanning speed AFM experiments in various fields for material screening and metrology of semiconductor systems.
Generation of third-order parametric down-conversion photons via weak nonlinearities
Authors: He Ying-Qiu , Ding Dong , Yan Feng-Li , Gao Ting 
Published: February 2021

Abstract
A higher-order parametric down-conversion (PDC) photon state is amazingly different from the states involving independent photon pairs. We focus on the third-order PDC photons. Firstly, we present a symmetry detector which is capable of analyzing twin-beam six-photon symmetric states in the regime of weak nonlinearities. By cascading symmetry detectors, then, it is shown that one can generate third-order PDC photons from a class of twin-beam six-photon symmetric states. Finally, as an example, we describe an application of third-order PDC photons for exploring six-mode-photon entangled states with linear optics.
Plasma defocusing in dual-pulse laser ignition
Authors: Tropina Albina A , Pokharel Sagar , New-Tolley Matthew R , Shneider Mikhail N 
Published: February 2021

Abstract
The paper presents simulation results of hydrogen-air mixture ignition by an ultraviolet followed by a near-infrared laser pulse. We used the three-temperature plasma model in a combination with the beam propagation method. Effect of plasma defocusing on the ignition kernel development is reported. It is shown that the plasma generated by the pre-ionizing pulse affects the position of the focal region of the second heating pulse with resulting changes in the distribution of the laser energy absorption, electron and radical production and ignition kernel dynamics. For the case with the defocusing effect we observed a shift of the peaks of translational and vibrational temperatures towards the direction of the laser pulse and two peaks on the axial profile of the electron temperature, reflecting local changes both in Joule heating and electron energy losses.
Coercivity analysis of cubic and tetragonal (Cu,Co) ferrite particles within the global model
Authors: Latiff Hawa , Eslava Gabriel Gomez , Devillers Thibaut , Yanagihara Hideto , Dempsey Nora M , Givord Dominique 
Published: February 2021

Abstract
We analyzed the coercivity of both cubic and tetragonally distorted Co
x
Cu1−x
Fe2O4 particles (x = 0.2 and 0.1, respectively) using the global model. According to magnetic viscosity measurements, the size of the activation volumes v
a increases from around 2000 nm3 (v
a
1/3 ≈ 13 nm) at 10 K for both samples, to close to 175 000 nm3 for the cubic sample and 5400 nm3 for the tetragonally distorted sample at 300 K. The microstructure-related phenomenological parameters obtained from the global model analysis are α= 0.29 and N
eff = −0.01 and α= 0.39 and N
eff = −0.24 for the cubic and tetragonal samples, respectively. High-resolution transmission electron microscopy images of the tetragonal sample showed that nanograins are connected through a thin amorphous layer (∼1 nm), which could account for the intergranular exchange interactions indicated by the negative value of N
eff as well as values of M
r/M
s > 0.5 for such isotropic samples. Low temperature discrepancies are tentatively attributed to magnetic reversal being governed by a local heating process following thermal activation.
Data augmentation for rolling bearing fault diagnosis using an enhanced few-shot Wasserstein auto-encoder with meta-learning
Authors: Pei Zeyu , Jiang Hongkai , Li Xingqiu , Zhang Jianjun , Liu Shaowei 
Published: February 2021

Abstract
Despite the advance of intelligent fault diagnosis for rolling bearings, in industries, data-driven methods still suffer from data acquisition and imbalance. We propose an enhanced few-shot Wasserstein auto-encoder (fs-WAE) to reverse the negative effect of imbalance. Firstly, an enhanced WAE is proposed for data augmentation, in which squeeze-and-excitation blocks are applied to calibrate channel-wise feature responses adaptively, strengthening the representational power of encoder. Secondly, a meta-learning strategy called Reptile is utilized to further enhance the mapping ability of WAE from prior distribution to vibration signals in the face of small dataset. Finally, gradient penalty is introduced as a regularization term to provide a flexible optimization function. The proposed method is applied to the pattern recognition based on experimental and engineering datasets. Moreover, comparative results demonstrate the utility and superiority of fs-WAE over other models in terms of efficiency and the resilience to imbalance degree.
Monte Carlo study of Cu precipitation in bcc-Fe: temperature-dependent cluster expansion versus local chemical environment potentials
Authors: Redermeier A , Kozeschnik E 
Published: February 2021

Abstract
Phase decomposition in binary Fe1−x
Cu
x
is studied using Monte Carlo simulations. Initially, density functional theory calculations are utilized to determine reference energies of various Fe–Cu compounds that serve as input for a temperature and composition-dependent cluster expansion. On this basis, the thermodynamic properties of the bcc Fe–Cu system are predicted and used to simulate the equilibrium constitution of bcc Cu-rich precipitates in an Fe-rich solid solution at various temperatures and supersaturations. Complementarily, computationally efficient pair potentials are developed in the local chemical environment approach that are calibrated on the first principles-cluster expansion results. These are then utilized in large-scale simulations for analysis of the multi-particle precipitate evolution. It is concluded that both approaches provide comparable information in terms of the precipitate radius as well as interface constitution. Whereas the cluster expansion (‘full-information’) path is especially useful in predicting energies of various ground state configurations for small systems, the local chemical environment approach (‘fast-computation’) path is particularly useful in evaluation of cluster formation kinetics and evolution statistics.
The microstructural refinement and performance improvement of a nanoporous Ag/CeO2 catalyst for NaBH4 oxidation
Authors: Ma Chen , Wen Yang , He Gege , Wang Liqun , Gao Lumei , Sun Zhanbo 
Published: February 2021

Abstract
In this paper, Cu and Ce were added to melt-spun Al–Ag precursor alloys to refine the microstructures of nanoporous Ag and Ag/CeO2 composite catalysts for NaBH4 oxidation. After the precursor alloys were dealloyed in 20% NaOH, calcined in air and corroded again in 50% NaOH, Ag2Al in the precursor alloys was completely removed, and refined nanoporous Ag could be obtained; from this process, the finest microstructures were exhibited by Al84Ag8Cu8. When more than 0.3% Ce was added to the Al84Ag8Cu8 ribbons, a refined nanoporous Ag material that consisted of CeO2 nanorods interspersed between Ag ligaments was obtained. Electrochemical measurements indicated that the catalytic properties were clearly increased due to the Cu addition to the Al–Ag alloy. After Ce was added to the Al84Ag8Cu8 ribbons, the catalytic properties of the resulting material were further improved. In regard to melt-spun Al84Ag8Cu8Ce0.5, the obtained nanoporous Ag/CeO2 presented the best properties, and its current density was 2.5 times that of Al84Ag8Cu8, 3.1 times that of Al90Ag8Cu2 and 2.3 times that of Ag/Ce from the Al79Ag15Ce6 precursor alloy without Cu. It was believed that the core–shell structure composed of Ag and Cu-rich phases formed during dealloying could limit the diffusion of Ag and prevent the coarsening of Ag ligaments. Thus, the refined microstructures could provide a large specific surface or additional active sites for the catalytic reaction. Strong interactions resulted from the many interfaces between the Ag ligaments and interspersed CeO2 nanorods, and the more effective utilization of Ag was due to the decomposition of Ag2Al; this result was the key reason for the clear improvement in catalytic performance.
Positron range-free and multi-isotope tomography of positron emitters
Authors: Beekman F J , Kamphuis C , Koustoulidou S , Ramakers R M , Goorden M C 
Published: February 2021

Abstract
Despite improvements in small animal PET instruments, many tracers cannot be imaged at sufficiently high resolutions due to positron range, while multi-tracer PET is hampered by the fact that all annihilation photons have equal energies. Here we realize multi-isotope and sub-mm resolution PET of isotopes with several mm positron range by utilizing prompt gamma photons that are commonly neglected. A PET-SPECT-CT scanner (VECTor/CT, MILabs, The Netherlands) equipped with a high-energy cluster-pinhole collimator was used to image 124I and a mix of 124I and 18F in phantoms and mice. In addition to positrons (mean range 3.4 mm) 124I emits large amounts of 603 keV prompt gammas that—aided by excellent energy discrimination of NaI—were selected to reconstruct 124I images that are unaffected by positron range. Photons detected in the 511 keV window were used to reconstruct 18F images. Images were reconstructed iteratively using an energy dependent matrix for each isotope. Correction of 18F images for contamination with 124I annihilation photons was performed by Monte Carlo based range modelling and scaling of the 124I prompt gamma image before subtracting it from the 18F image. Additionally, prompt gamma imaging was tested for 89Zr that emits very high-energy prompts (909 keV). In Derenzo resolution phantoms 0.75 mm rods were clearly discernable for 124I, 89Zr and for simultaneously acquired 124I and 18F imaging. Image quantification in phantoms with reservoirs filled with both 124I and 18F showed excellent separation of isotopes and high quantitative accuracy. Mouse imaging showed uptake of 124I in tiny thyroid parts and simultaneously injected 18F-NaF in bone structures. The ability to obtain PET images at sub-mm resolution both for isotopes with several mm positron range and for multi-isotope PET adds to many other unique capabilities of VECTor’s clustered pinhole imaging, including simultaneous sub-mm PET-SPECT and theranostic high energy SPECT.
Method for estimating charge breeder ECR ion source plasma parameters with short pulse 1+ injection of metal ions
Authors: Angot J , Luntinen M , Kalvas T , Koivisto H , Kronholm R , Maunoury L , Tarvainen O , Thuillier T , Toivanen V 
Published: February 2021

Abstract
A new method for determining plasma parameters from beam current transients resulting from short pulse 1+ injection of metal ions into a charge breeder electron cyclotron resonance ion source has been developed. The proposed method relies on few assumptions, and yields local values for the ionisation times

1
/

n

e

σ
v

q
→
q
+
1

inz

, charge exchange times

1
/

n

0

σ
v

q
→
q
−
1

cx

, the ion confinement times τ

q
, as well as estimates for the minimum plasma energy contents

n

e

E

e

and the plasma triple products

n

e

E

e

τ

q

. The method is based on fitting the current balance equation on the extracted beam currents of high charge state ions, and using the fitting coefficients to determine the postdictions for the plasma parameters via an optimisation routine. The method has been applied for the charge breeding of injected K+ ions in helium plasma. It is shown that the confinement times of K
q+ charge states range from 2.

6

−
0.4

+
0.8

ms to 16.

4

−
6.8

+
18.3

ms increasing with the charge state. The ionisation and charge exchange times for the high charge state ions are 2.

6

−
0.5

+
0.5

ms–12.

6

−
3.2

+
2.6

ms and 3.

7

−
1.6

+
5.0

ms–357.

7

−
242.4

+
406.7

ms, respectively. The plasma energy content is found to be

2
.

5

−
1.8

+
4.3

×
1

0

15

eV cm−3.
Modeling of fast ionization waves in pure nitrogen at moderate pressure
Authors: Chen Xiancong , Zhu Yifei , Wu Yun , Hao Jinbo , Ma Xiaoguang , Lu Pengfei 
Published: February 2021

Abstract
The fast ionization wave (FIW) discharges in pure nitrogen in a capillary tube at 27 mbar, initiated by positive polarity, high-voltage nanosecond pulses, are numerically studied by coupled two-dimensional plasma fluid modeling. The 2D fluid code based on local mean energy approximation is validated and used, an extended three-exponential Helmholtz photoionization model is proposed for pure nitrogen. The development and structure of the nitrogen FIW is analyzed, the electric field and current are calculated compared with experimental measurements. The evolution of radial distribution of electrons and N2(C
3Π
u
) during the FIW development stage and in the afterglow are analyzed, the radial profiles of electron density show a ‘hollow’ structure in the FIW development stage, the temporal-spatial evolution of N2(C
3Π
u
) is dominated by the competition between the pooling reaction of

N

2

(

A

3

Σ

u

+

)

and the quenching by electrons. The role of photoionization on the nitrogen FIW radial morphology is discussed, the equivalent background electron density of photoionization in nitrogen discharge is suggested to be (4–6) × 1013 m−3. Spatial distribution of specific energy deposition (SED), fast gas heating (FGH) energy and temperature rise are obtained, heating efficiency varies with electric field E/N and SED and tends to be 10% at high SED. The dominating reactions responsible for FGH and their fractional contribution in space and time are analyzed, in the near axis region, pooling reactions of

N

2

(

A

3

Σ

u

+

)

and N2(B
3Π
g
) contribute up to 80% FGH energy, electron impact dissociation of molecular nitrogen contributes about 10%, while e-

N

2

+

recombination and quenching of N(2
D) atoms by N2 molecules contribute rest.