bluuebunny/crossref_metadata_2025 huggingface dataset:
VERIFICATION OF SUBCRITICAL LIMITS IN ANSI/ANS-8.1-2014
Authors: Bowen Douglas G. , Greene Travis M.
Published: February 2021

The ANSI/ANS-8.1 standard, “Safety Standard for Operations with Fissionable Materials Outside Reactors,” has been available since 1964 as ASA N6.1-1964. In 1969, this standard was revised as ANSI N16.1-1969, “Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors.” This version of the standard includes a variety of subcritical limits (SCLs) for uniform aqueous solutions and metals containing fissile nuclides for 233U, 235U, and 239Pu. Furthermore, SCLs are also included for uranium-water lattices. In the 1983 version of ANSI/ANS-8.1 (a revision of ANSI N16.1-1975), the suite of SCLs in the standard expanded to include 235U enrichment limits for homogeneous uranium-water mixtures and dry/damp oxides, uniform aqueous solutions of low-enriched uranium, and uniform aqueous mixtures of Pu(NO3)4 containing 240Pu, in addition to the SCLs included in ANSI N16.1-1969. The SCLs have changed little in subsequent revisions (ANSI/ANS-8.1-1998 and ANSI/ANS-8.1-2014). The ANSI/ANS-8.1-2014 standard is currently being revised to include new SCLs (uranium metal and compounds with enrichments up to 20 wt. % 235U) and possible updates to the current SCLs already in the standard, although these SCLs will not be available to the nuclear criticality safety community for a number of years. The bases for these SCLs were documented in journal articles such as Nuclear Science and Engineering, and the American Nuclear Society’s meeting transactions; however, the bases were ambiguous enough that sites and regulators in the United States are reluctant to endorse them for safety purposes. The purpose of this paper is to present the results of a comparison study for the SCLs in the ANSI/ANS-8.1-2014 standard using modern codes and cross sections (SCALE/ENDF/B-VIII) to provide some assurance about their quality (bias and bias uncertainty) for use in nuclear criticality safety applications.
INTRODUCING BURNUP CREDIT FOR EXPANSION STAGE 2 OF THE EXTERNAL SPENT FUEL POOL AT GÖSGEN NPP
Authors: Hoefer Axel , Basler Martin , Buss Oliver , Girardin Gaëtan , Jatuff Fabian , Meyer Lukas , Ornot Leo , Rossbach Detlev , Stoll Wolf
Published: February 2021

We present a summary of the actinide-plus-fission-product burnup credit criticality safety licensing analysis for Expansion Stage 2 (ES2) of the external spent fuel pool at Gösgen nuclear power plant. In ES2, the nine Expansion Stage 1 storage racks currently installed in the external spent fuel pool are going to be supplemented by nine ES2 storage racks with a significantly reduced fuel assembly pitch. They are designed for loadings with fuel assemblies above a well-defined minimum required burnup. The objective of the criticality safety analysis is to calculate the minimum required burnup values for the uranium and MOX fuel assemblies to be stored in the ES2 storage racks. We use a methodology that allows us to take into account the reactivity effects due to variabilities and uncertainties of all relevant parameters involved in a burnup credit criticality safety assessment in a bounding manner. These include manufacturing tolerances of the fuel assemblies and storage racks, the irradiation histories and burnup profiles of the spent fuel assemblies, the bias of the depletion code used to calculate the isotopic inventories of the irradiated fuel, and the bias of the criticality code used to calculate the neutron multiplication factor of the considered storage configuration. A combination of different statistical procedures is used to evaluate and propagate the uncertainty information on the input parameters and translate it into statistical confidence statements about the neutron multiplication factor. It should be noted that the presented analysis is related to the first implementation of a significant burnup credit for wet storage of PWR fuel in Switzerland.
LOW TEMPERATURE EFFECTS ON PWR FUEL ASSEMBLY CRITICALITY CALCULATIONS
Authors: Behler Matthias , Hannstein Volker , Sommer Fabian
Published: February 2021

One of the parameters affecting the neutron multiplication factor keff of a system containing fissile material is the system temperature. Therefore, the effect of temperature on criticality safety analyses is an area of international interest. In this context, the Working Party on Nuclear Criticality Safety (WPNCS) of the OECD Nuclear Energy Agency (NEA) formed a subgroup to define and execute a code-to-code comparison benchmark to investigate the effect of temperature on keff for PWR fuel assemblies. Two configurations of a generic water-moderated PWR fuel assembly were analysed at different temperatures between 233 K and 588 K, and with different assembly burnups. Based on this benchmark, GRS performed an additional study to investigate the impact of the moderator densities, the neutron reaction cross sections and the thermal scattering data on keff separately.

The benchmark results show the expected decrease of keff with temperature and a considerable jump in keff at the phase transition of the moderator. The additional investigation demonstrates that the jump in keff is mainly caused by the change of the moderator density due to the phase transition. The change of the thermal scattering data due to the phase transitions leads to a similar but smaller jump in keff. Furthermore, the actual impact of the different parameters on keff depend strongly on the considered fuel assembly configuration.
CHARACTERIZATION AND COMPARSION OF NEUTRON GENERATORS OF IEC AND LINEAR D-T BY THE SPECTROMETRIC SYSTEM NGA-01
Authors: Matej Zdenek , Kostal Michal , Novak Evzen , Alexa Petr , Uhlar Radim , Mravec Filip , Jancar Ales , Cvachovec Frantisek , Prenosil Vaclav , Jancar Petr
Published: February 2021

This article focuses on description of two different neutron fields from linear and cylindrical Inertial Electrostatic Confinement (IEC) neutron generators. Both of these generators are well defined and commonly used. They use a deuterium-tritium reaction that produces neutrons with energies in the range 13 – 16 MeV, depending on the direction and the energy of the incoming deuterium nucleus. Two-parametric spectrometric system for neutron/gamma mixed fields NGA-01 was used to characterize neutron spectra in the proximity of generators. The cylindrical 45x45 mm stilbene scintillator was connected to this device using an active voltage divider. This way, we were able to measure neutron energies in the range 1 - 15 MeV while filtering out gamma radiation, even when counts per second is high. For the neutron spectrum calculation recoil spectra using deconvolution through maximum likelihood estimation was used. Measured neutron spectra have been compared with simulations realized via MCNP6. According to the theoretical prediction, these two types of generators produce different neutron fields. In case of the linear generator the target is very close to point located tritium bombarded by deuterons. Thus the neutron spectrum varies depending on the angle between the detector axis and the axis of the generator. Both experimental results and simulation show a shift of the neutron energy peak in pulse height histogram. For IEC type generators the neutron spectrum is more complicated. The shape and the position of the neutron energy peak depend heavily on the position of the detector. The most prominent effect is in the position in the plane perpendicular to the generator axis. In this case, the peak splits into two peaks that can be measured and distinguished. These results were verified by the diamond detector which was also used for characterization of the IEC type generator.
APPLICATION OF SUPERMC3.2 TO PRELIMINARY NEUTRONICS ANALYSIS FOR EUROPEAN HCPB DEMO
Authors: Li Bin , Wu Bin , Sun Guangyao , Hao Lijuan , Song Jing , Fischer Ulrich
Published: February 2021

In the D-T fueled tokamak, the neutrons not only carry the approximately 80% energy released in the per fusion reaction, but also are the source of radioactivity in the fusion system. Therefore, high-fidelity neutronics simulation is required to support such reactor design and safety analysis. In the present work, taking European HCPB DEMO (Helium Cooled Pebble Bed demonstration fusion plant) developed by KIT (Karlsruhe Institute of Technology) as an example, the preliminary neutronics analysis covering the assessments of NWL (neutron wall loading), TBR (tritium breeding ratio), nuclear power generation, radiation loads on PFCs (plasma-facing components) and TFCs (toroidal field coils) has been carried out by using SuperMC in the case of both unbiased and biased simulations. The preliminary results indicate that the blanket scheme could satisfy the design requirements in terms of TBR and shielding of inboard blankets. Specially, a speed-up by ~164 times in the calculation for thick shielding region (TFC region) is achieved by using global weight windows generated via GWWG in SuperMC. In addition, compared to MCNP, SuperMC shows advantages in accurate and efficient modeling of complex system, efficient calculation and 3D interactive visualization.
Shallow defects found in 2D semiconductors can ionize enough carriers to enable various applicationS
Authors: McConnon Aili
Published: February 2021

An investigation of the physical origin of intrinsic p-type conductivity in black phosphorene and black arsenene reveals large lattice-like intrinsic shallow acceptor defects.
A common parametrization for finite mode Gaussian states, their symmetries, and associated contractions with some applications
Authors: John Tiju Cherian , Parthasarathy K. R.
Published: February 2021

Let Γ(H) be the boson Fock space over a finite dimensional Hilbert space H. It is shown that every Gaussian symmetry admits a Klauder–Bargmann integral representation in terms of coherent states. Furthermore, Gaussian states, Gaussian symmetries, and second quantization contractions belong to a weakly closed self-adjoint semigroup E2(H) of bounded operators in Γ(H). This yields a common parametrization for these operators. It is shown that the new parametrization for Gaussian states is a fruitful alternative to the customary parametrization by position–momentum mean vectors and covariance matrices. This leads to a rich harvest of corollaries: (i) every Gaussian state ρ admits a factorization ρ=Z1†Z1, where Z1 is an element of E2(H) and has the form Z1=cΓ(P)exp∑r=1nλrar+∑r,s=1nαrsaras on the dense linear manifold generated by all exponential vectors, where c is a positive scalar, Γ(P) is the second quantization of a positive contractive operator P in H, ar, 1 ≤ r ≤ n, are the annihilation operators corresponding to the n different modes in Γ(H), λr∈C, and [αrs] is a symmetric matrix in Mn(C); (ii) an explicit particle basis expansion of an arbitrary mean zero pure Gaussian state vector along with a density matrix formula for a general Gaussian state in terms of its E2(H)-parameters; (iii) a class of examples of pure n-mode Gaussian states that are completely entangled; (iv) tomography of an unknown Gaussian state in Γ(Cn) by the estimation of its E2(Cn) parameters using O(n2) measurements with a finite number of outcomes.
Volume-scaled common nearest neighbor clustering algorithm with free-energy hierarchy
Authors: Weiß R. Gregor , Ries Benjamin , Wang Shuzhe , Riniker Sereina
Published: February 2021

The combination of Markov state modeling (MSM) and molecular dynamics (MD) simulations has been shown in recent years to be a valuable approach to unravel the slow processes of molecular systems with increasing complexity. While the algorithms for intermediate steps in the MSM workflow such as featurization and dimensionality reduction have been specifically adapted to MD datasets, conventional clustering methods are generally applied to the discretization step. This work adds to recent efforts to develop specialized density-based clustering algorithms for the Boltzmann-weighted data from MD simulations. We introduce the volume-scaled common nearest neighbor (vs-CNN) clustering that is an adapted version of the common nearest neighbor (CNN) algorithm. A major advantage of the proposed algorithm is that the introduced density-based criterion directly links to a free-energy notion via Boltzmann inversion. Such a free-energy perspective allows a straightforward hierarchical scheme to identify conformational clusters at different levels of a generally rugged free-energy landscape of complex molecular systems.
Stability of the boundary layer expansion for the 3D plane parallel MHD flow
Authors: Ding Shijin , Lin Zhilin , Niu Dongjuan
Published: February 2021

In this paper, we establish the mathematical validity of the Prandtl boundary layer theory for a class of nonlinear plane parallel flows of viscous incompressible magnetohydrodynamic flow with the no-slip boundary condition of velocity and perfectly conducting walls for magnetic fields. The convergence is shown under various Sobolev norms, including the physically important space–time uniform norm L∞(H1). In addition, similar convergence results are also obtained under the case with uniform magnetic fields. This implies the stabilizing effects of magnetic fields. Besides, the higher-order expansion is also considered.
Cryogenic GaAs high-electron-mobility-transistor amplifier for current noise measurements
Authors: Lee Sanghyun , Hashisaka Masayuki , Akiho Takafumi , Kobayashi Kensuke , Muraki Koji
Published: February 2021

We show that a cryogenic amplifier composed of a homemade GaAs high-electron-mobility transistor (HEMT) is suitable for current-noise measurements in a mesoscopic device at dilution-refrigerator temperatures. The lower noise characteristics of our homemade HEMT lead to a lower noise floor in the experimental setup and enable more efficient current-noise measurement than is available with a commercial HEMT. We present the dc transport properties of the HEMT and the gain and noise characteristics of the amplifier. With the amplifier employed for current-noise measurements in a quantum point contact, we demonstrate the high resolution of the measurement setup by comparing it with that of the conventional one using a commercial HEMT.
Cryogen-free one hundred microkelvin refrigerator
Authors: Yan Jiaojie , Yao Jianing , Shvarts Vladimir , Du Rui-Rui , Lin Xi
Published: February 2021

A temperature below 100 µK is achieved in a customized cryogen-free dilution refrigerator with a copper-nuclear demagnetization stage. The lowest temperature of conduction electrons of the demagnetization stage is below 100 µK as measured by using a pulsed platinum nuclear magnetic resonance thermometer, and the temperature can remain below 100 µK for over 10 h. A demagnetization magnetic field of up to 9 T and a research magnetic field of up to 12 T can be controlled independently, provided by a coaxial room-temperature-bore cryogen-free magnet.
Infrared spectroscopy of CO3•−(H2O)1,2 and CO4•−(H2O)1,2
Authors: Münst Maximilian G. , Ončák Milan , Beyer Martin K. , van der Linde Christian
Published: February 2021

Hydrated molecular anions are present in the atmosphere. Revealing the structure of the microsolvation is key to understanding their chemical properties. The infrared spectra of CO3•−(H2O)1,2 and CO4•−(H2O)1,2 were measured via infrared multiple photon dissociation spectroscopy in both warm and cold environments. Redshifted from the free O–H stretch frequency, broad, structured spectra were observed in the O–H stretching region for all cluster ions, which provide information on the interaction of the hydrogen atoms with the central ion. In the C–O stretching region, the spectra exhibit clear maxima, but dissociation of CO3•−(H2O)1,2 was surprisingly inefficient. While CO3•−(H2O)1,2 and CO4•−(H2O) dissociate via loss of water, CO2 loss is the dominant dissociation channel for CO4•−(H2O)2. The experimental spectra are compared to calculated spectra within the harmonic approximation and from analysis of molecular dynamics simulations. The simulations support the hypothesis that many isomers contribute to the observed spectrum at finite temperatures. The highly fluxional nature of the clusters is the main reason for the spectral broadening, while water–water hydrogen bonding seems to play a minor role in the doubly hydrated species.
(Dis)Similarities of adsorption of diverse functional groups over alumina and hematite depending on the surface state
Authors: Blanck Sarah , Martí Carles , Loehlé Sophie , Steinmann Stephan N. , Michel Carine
Published: February 2021

To accelerate the conversion to more sustainable lubricants, there is a need for an improved understanding of the adsorption at the solid/liquid interface. As a first step, the density functional theory computed adsorption energies can be used to screen the ability of additives to cover a surface. Analogously to what has been found in catalysis with the universal scaling relations, we investigate here if a general universal ranking of additives can be found, independently of the surface considered. We divided our set of 25 diverse representative molecules into aprotic and protic molecules. We compared their adsorption over alumina and hematite, which are models of surface oxidized aluminum and steel, respectively. The adsorption energy ranking of our set is not strongly affected by alumina hydration. In contrast, adsorption on hematite is more strongly affected by hydration since all exposed Fe Lewis acid sites are converted into hydroxylated Brønsted basic sites. However, the ranking obtained on hydrated hematite is close to the one obtained on dry alumina, paving the road to a fast screening of additives. In our library, protic molecules are more strongly adsorbed than non-protic molecules. In particular, methyl and dimethyl phosphates are the most strongly adsorbed ones, followed by N-methyldiethanolamine, succinimide, and ethanoic acid. Additives combining these functional groups are expected to strongly adsorb at the solid/liquid interface and, therefore, likely to be relevant components of lubricant formulations.
Improving insulation and thermal conductivity of anodic coating by plasma discharge treatment
Authors: Wei Song , Dong-jie Liu , Can-can Liu , Bai-ling Jiang
Published: February 2021

Improving the insulation layer’s thermal conductivity is a key technology when concerning conquering the bottleneck of electronic device development. For improving the insulation layer’s thermal conductivity on the surface of aluminum alloy substrates, anodizing and MAO technology had been combined to prepare thick compact crystalline alumina ceramic. In addition, the influence of current density on the coating performances had been studied. Then, results showed that after plasma discharge treatment, amorphous alumina with thickness reaching 143 µm had been transformed into crystalline alumina and the through holes were sealed. The influence of current density on the crystallinity, compactness, and adhesion of the coating had been studied, and results showed as the current density increased from 10 mA/cm2 to 50 mA/cm2, the crystallinity of the coating increased and the compactness of the coating decreased. Moreover, when the current density was lower than 30 mA/cm2, the coating had good adhesion to the substrate. The impedance, breakdown voltage, and thermal conductivity of the coating were observed for comparison with those of the anodic coating. Then from the results, it was found that after the coating had been treated with this method, the impedance increased from 60 kΩ/cm2 to 120 kΩ/cm2, while the breakdown voltage increased from 0.89 kV to 3.24 kV as the thermal conductivity increased from 10.2 W/m K to 23.7 W/m K.
A critical perspective on Markov state model treatments of protein–protein association using coarse-grained simulations
Authors: He Ziwei , Paul Fabian , Roux Benoît
Published: February 2021

Atomic-level information is essential to explain the specific interactions governing protein–protein recognition in terms of structure and dynamics. Of particular interest is a characterization of the time-dependent kinetic aspects of protein–protein association and dissociation. A powerful framework to characterize the dynamics of complex molecular systems is provided by Markov State Models (MSMs). The central idea is to construct a reduced stochastic model of the full system by defining a set of conformational featured microstates and determining the matrix of transition probabilities between them. While a MSM framework can sometimes be very effective, different combinations of input featurization and simulation methods can significantly affect the robustness and the quality of the information generated from MSMs in the context of protein association. Here, a systematic examination of a variety of MSMs methodologies is undertaken to clarify these issues. To circumvent the uncertainties caused by sampling issues, we use a simplified coarse-grained model of the barnase–barstar protein complex. A sensitivity analysis is proposed to identify the microstates of an MSM that contribute most to the error in conjunction with the transition-based reweighting analysis method for a more efficient and accurate MSM construction.
Recent progress in simulating microscopic ion transport mechanisms at liquid–liquid interfaces
Authors: Morita Akihiro , Koizumi Ai , Hirano Tomonori
Published: February 2021

Transport of ions through liquid–liquid interfaces is of fundamental importance to a wide variety of applications. However, since it is quite challenging for experimentalists to directly and selectively observe molecules at the interfaces, microscopic mechanisms of ion transport have been largely presumed from kinetic information. This Perspective illustrates recent examples that molecular dynamics simulations with proper free energy surfaces clarified mechanistic pictures of ion transport. The key is a proper choice of coordinates and defining/calculating free energy surfaces in multidimensional space. Once the free energy surfaces for realistic systems are available, they naturally provide new insight into the ion transport in unprecedented details, including water finger, transient ion pairing, and electron transfer.
High-Q perfect absorption induced by the coupling of LSP and SPP modes
Authors: Zhou Yuan-Cheng , Zhang Xue-Chun , Hu Ya-Xin , Tang Li-Li , Cao Yue , Li Jia-Qi , Wang Jin , Dong Zheng-Gao
Published: February 2021

At optical frequencies, we design an anisotropic metasurface to realize high-Q perfect absorption in numerical calculation. By establishing the Norton equivalent network model, we first reveal that the root cause of this phenomenon is the coupling excitation of the localized surface plasmon (LSP) mode and the surface plasmon polariton (SPP) mode. This absorber can realize bifunctional switching and is expected to realize the energy conversion of photons–SPP–photons. Meanwhile, we analyze the control of the structural design on high-Q perfect absorption. This research will provide theoretical guidance for the further development of applications related to high-Q perfect absorption such as absorption filters with specific wavelengths and narrow band photon emitters.
Tunable Pr3+:LiYF4 lasers in the green-red spectral region
Authors: Liu Huilong , Zhao Zhexian , Xia Jing , Lü Yanfei
Published: February 2021

A tunable Pr3+:LiYF4 laser using a single birefringent filter (BF) plate under excitation with a frequency doubled optically pumped semiconductor laser was demonstrated to operate at nine different laser wavelengths of 523, 546, 604, 613, 639, 645, 670, 698, and 720 nm. Within these wavelengths, several new wavelengths of 613, 639, 645, and 670 nm were obtained. The total tuning range exceeded 190 nm in the visible spectral range on nine intervals between 523 nm and 720 nm. The highest output power of 2.32 W was achieved at an emission wavelength of 523 nm with a slope efficiency of 61.5% and an optical-to-optical efficiency of 52.1% with respect to the absorbed pump power. Moreover, by adjusting the rotation angle of the BF plate, a continuous-wave simultaneous dual-wavelength Pr3+:LiYF4 laser operating at 698 and 720 nm was also demonstrated. At an absorbed pump power of 4.45 W, the maximum output powers at 698 nm and 720 nm were 162 mW and 258 mW, respectively.
Solitons in complex systems of chiral fields with Kuramoto interactions
Authors: Lohe M. A.
Published: February 2021

We construct a complex system of N chiral fields, each regarded as a node or a constituent of a complex field-theoretic system, which interact by means of chirally invariant potentials across a network of connections. In the classical case, these interactions are identical or similar to Kuramoto interactions, leading to synchronization phenomena for the well-known Kuramoto model and its many extensions and generalizations to higher dimensions. We consider chiral systems of arbitrary size N, where each constituent carries a conserved charge of topological origin, which evolve according to a coupled system of second-order, Lorentz invariant, nonlinear partial differential equations. Stable soliton configurations occur as a consequence of the nonlinear network interactions, not necessarily from self-interactions of the fundamental fields. In 1+1 dimensions, these chirally invariant models allow for multi-soliton configurations that for N=2 are determined by the sine-Gordon equation and for N=3 reduce in special cases to the double sine-Gordon equation, which has exact double-kink static solutions consisting of solitons positioned at arbitrary locations. Planar and three-dimensional networked skyrmions appear in higher dimensions. Such configurations can be viewed for general N as bound states of the constituent fields, which exist together with the usual fundamental excitations. Whereas Kuramoto interactions in first-order systems lead to emergent classical phenomena such as synchronization, these same interactions in complex systems of chiral fields result in a rich variety of multi-soliton bound states.
ΔSCF Dyson orbitals and pole strengths from natural ionization orbitals
Authors: Harb Hassan , Hratchian Hrant P.
Published: February 2021

The calculation of photoionization cross sections can play a key role in spectral assignments using modeling and simulation. In this work, we provide formal relationships between pole strengths, which are proportional to the photoionization cross section, and terms related to the natural ionization orbital model for ΔSCF calculations. A set of numerical calculations using the developed models is carried out. Pole strength values computed using the two approaches developed for ΔSCF calculations demonstrate excellent agreement with an electron propagator theory model.
SARS COV-2 virus-laden droplets coughed from deep lungs: Numerical quantification in a single-path whole respiratory tract geometry
Authors: April Si Xiuhua , Talaat Mohamed , Xi Jinxiang
Published: February 2021

When an infected person coughs, many virus-laden droplets will be exhaled out of the mouth. Droplets from deep lungs are especially infectious because the alveoli are the major sites of coronavirus replication. However, their exhalation fraction, size distribution, and exiting speeds are unclear. This study investigated the behavior and fate of respiratory droplets (0.1–4 μm) during coughs in a single-path respiratory tract model extending from terminal alveoli to mouth opening. An experimentally measured cough waveform was used to control the alveolar wall motions and the flow boundary conditions at lung branches from G2 to G18. The mouth opening was modeled after the image of a coughing subject captured using a high-speed camera. A well-tested k-ω turbulence model and Lagrangian particle tracking algorithm were applied to simulate cough flow evolutions and droplet dynamics under four cough depths, i.e., tidal volume ratio (TVR) = 0.13, 0.20. 0.32, and 0.42. The results show that 2-μm droplets have the highest exhalation fraction, regardless of cough depths. A nonlinear relationship exists between the droplet exhalation fraction and cough depth due to a complex deposition mechanism confounded by multiscale airway passages, multiregime flows, and drastic transient flow effects. The highest exhalation fraction is 1.6% at the normal cough depth (TVR = 0.32), with a mean exiting speed of 20 m/s. The finding that most exhaled droplets from deep lungs are 2 μm highlights the need for more effective facemasks in blocking 2-μm droplets and smaller both in infectious source control and self-protection from airborne virus-laden droplets.
Can we define a unique microscopic pressure in inhomogeneous fluids?
Authors: Shi Kaihang , Santiso Erik E. , Gubbins Keith E.
Published: February 2021

The estimation of a microscopic pressure tensor in an adsorbed thin film on a planar surface remains a challenge in both experiment and theory. While the normal pressure is well-defined for a planar surface, the tangential pressure at a point is not uniquely defined at the nanoscale. We report a new method that allows us to calculate the local pressure tensor and its spatial integral using an arbitrary contour definition of the “virial-route” local pressure tensor. We show that by integrating the local tangential pressure over a small region of space, roughly the range of the intermolecular forces, it is possible to define a coarse-grained tangential pressure that appears to be unique and free from ambiguities in the definition of the local pressure tensor. We support our argument by presenting the results for more than ten types of contour definitions of the local pressure tensor. By defining the coarse-grained tangential pressure, we can also find the effective thickness of the adsorbed layer and, in the case of a porous material, the statistical pore width. The coarse-grained in-layer and in-pore tangential pressures are determined for Lennard-Jones argon adsorbed in realistic carbon slit pores, providing a better understanding of the pressure enhancement for strongly wetting systems.
The graphitization of a highly oriented graphite precursor prepared under a high magnetic field of 6 T
Authors: Hamasaki Atom , Sadohara Akito , Nakamura Hideki , Takeuchi Yuka , Katsuki Akio , Ozeki Sumio
Published: February 2021

Traditional carbon materials such as graphite are currently extremely useful and have recently been applied to cutting-edge materials. However, it is a concern that as production will increase much more in the future, the impact on the environment during preparation will become a problem. Recently, we have succeeded in obtaining an extremely high orientation structure using a carbonization process in a strong magnetic field [“Magnetic orientation of hexagonal carbon layers at high temperature” Chem. Lett. 41, 1576 (2012)]. Because graphite has a two-dimensional structure in which graphene sheets are laminated, we expect that graphitization should be easily performed by using a precursor that originally has an oriented structure. When two types of precursors prepared in the absence and presence of a magnetic field of 6 T were graphitized under the same conditions, graphitization was promoted by 50 to 100 K for the precursor to which a strong magnetic field was applied. If we fabricate products with the same degree of graphitization, it is calculated that the graphitization energy can be suppressed by as much as 10% by using a magnetic field. Applying this technology to the preparation of graphite in industry is proposed to result in substantial energy savings.
Cross-reactivity of a pathogenic autoantibody to a tumor antigen in GABA
A
receptor encephalitis
Authors: Brändle Simone M. , Cerina Manuela , Weber Susanne , Held Kathrin , Menke Amélie F. , Alcalá Carmen , Gebert David , Herrmann Alexander M. , Pellkofer Hannah , Gerdes Lisa Ann , Bittner Stefan , Leypoldt Frank , Teegen Bianca , Komorowski Lars , Kümpfel Tania , Hohlfeld Reinhard , Meuth Sven G. , Casanova Bonaventura , Melzer Nico , Beltrán Eduardo , Dornmair Klaus
Published: February 2021

Significance

Antibodies recognizing the neuronal gamma-aminobutyric acid A receptor (GABA
A
-R) cause severe encephalitis by triggering internalization of the antibody–receptor complexes in inhibitory synapses, which leads to hyperexcitability and dysfunction of neuronal networks. From the cerebrospinal fluid of a patient with GABA
A
-R encephalitis we cloned a highly expressed antibody and showed that it binds the GABA
A
-R and influences signal transduction in neurons, explaining clinical symptoms. Using several experimental techniques, we confirmed that the antibody cross-reacts to an oncoprotein which is known to be involved in several malignancies. We showed that cross-reactivity to this oncoprotein may also be detected in two other GABA
A
-R patients, suggesting that such cross-reactivity is presumably a key event in the pathogenesis of GABA
A
-R encephalitis.
On the evolutionary origins of host–microbe associations
Authors: Sieber Michael , Traulsen Arne , Schulenburg Hinrich , Douglas Angela E.
Published: February 2021

Significance

Animals can provide benefits to their associated microbes—and these can, in turn, positively affect their hosts. But how do such mutually beneficial associations arise in the first place? In particular, when animal and microbe initially have independent lifestyles, this is not clear. By developing a model of animal and microbial life cycles on patchy habitats, we show how their overlapping ecologies of development and dispersal can lead to the enrichment of certain microbes in the dispersing animals, even in the absence of specific mutualistic benefits. This enrichment can then set the stage for the evolution of more specific host–microbe associations, which also implies that host enrichment per se is not an indicator of a beneficial host–microbe symbiosis.
Risk of tipping the overturning circulation due to increasing rates of ice melt
Authors: Lohmann Johannes , Ditlevsen Peter D.
Published: February 2021

Significance

Ongoing greenhouse gas emissions put elements of the Earth system at risk for crossing critical thresholds (tipping points), leading to abrupt irreversible climate change. Measures for reducing emissions should keep Earth in the safe operating space away from tipping points. Here we show that increasing rates of change of ice melt can induce a collapse of the Atlantic Meridional Overturning Circulation in a global ocean model, while no critical threshold in ice melt is crossed and slower increases to the same level of ice melt do not induce tipping. Moreover, the chaotic dynamics of the climate make such a collapse hard to predict. This shows that the safe operating space of the Earth system might be smaller than previously thought.
Deep time diversity and the early radiations of birds
Authors: Yu Yilun , Zhang Chi , Xu Xing
Published: February 2021

Significance

Our lineage diversification rate through time analyses of three supertrees combining the published phylogenies of both stem and crown group birds reveal three distinct large-scale increases in the diversification rate across bird evolutionary history. The first two increases also are associated with rapid morphological evolution pertaining to the locomotory and cranial systems, respectively. The third increase needs further support from morphological data. Our study demonstrates that the bird biodiversity evolution was influenced mainly by long-term climatic changes and also by the Cretaceous–Paleogene extinction.
Glucagon blockade restores functional β-cell mass in type 1 diabetic mice and enhances function of human islets
Authors: Wang May-Yun , Dean E. Danielle , Quittner-Strom Ezekiel , Zhu Yi , Chowdhury Kamrul H. , Zhang Zhuzhen , Zhao Shangang , Li Na , Ye Reshing , Lee Young , Zhang Yiyi , Chen Shiuhwei , Yu Xinxin , Leonard Derek C. , Poffenberger Greg , Von Deylen Alison , McCorkle S. Kay , Schlegel Amnon , Sloop Kyle W. , Efanov Alexander M. , Gimeno Ruth E. , Scherer Philipp E. , Powers Alvin C. , Unger Roger H. , Holland William L.
Published: February 2021

Significance

Both type 1 and type 2 diabetes are associated with reduced β-cell mass or function, resulting from decreased proliferation and increased apoptosis. Understanding the signals governing β-cell survival and regeneration is critical for developing strategies to maintain healthy populations of these cells in individuals. Both forms of diabetes are associated with hyperglucagonemia and an increased plasma glucagon:insulin ratio. Glucagon excess contributes to metabolic dysregulation of the diabetic state and glucagon receptor antagonism is a potential target area for the treatment and prevention of diabetes. Our studies presented here suggest that blockade of glucagon signaling lowers glycemia in mouse models of type 1 diabetes while enhancing formation of functional β-cell mass and production of insulin-positive cells from α-cell precursors.
Compartmentalization of phosphatidylinositol 4,5-bisphosphate metabolism into plasma membrane liquid-ordered/raft domains
Authors: Myeong Jongyun , Park Cheon-Gyu , Suh Byung-Chang , Hille Bertil
Published: February 2021

Significance

Lipids of bilayer membranes can segregate laterally into distinct liquid phases of different composition called liquid ordered and liquid disordered, and corresponding in the plasma membrane of living cells to nanodomains called raft and nonraft domains. Using Förster resonance energy transfer and genetically expressible protein probes of lipid domains, we find that several steps of the metabolism of phosphoinositide lipids are concentrated in cholesterol-rich liquid-ordered domains of the plasma membrane. The receptor-mediated breakdown and the restoration of major phosphoinositide pools are faster in the liquid-ordered than in the liquid-disordered domains. Thus, the ordered domains host a key lipid signaling system of the cell.
The Role of Overdose Reversal Training in Knowing where to Get Naloxone: Implications for Improving Naloxone access among People who use Drugs
Authors: Schneider Kristin E. , Dayton Lauren , Winiker Abigail K. , Tobin Karin E. , Latkin Carl A.
Published: February 2021

Background

Naloxone distribution and training programs have been implemented to combat the opioid overdose crisis. While many individuals are trained, ongoing naloxone access is not ensured by these programs. We explored whether people who use drugs (PWUD) in Baltimore City, Maryland could identify a location where they would go to obtain naloxone and how training changed where they would be willing to access naloxone.

Methods

We surveyed 574 PWUD as to whether they had heard of, been trained to use, and knew where to get naloxone. Among participants who had heard of naloxone, we tested for differences in knowing where to get naloxone by training.

Results

The majority (95.3%) had heard of naloxone. Of these, 84.0% could name a location where they would access naloxone, but only 11.7% named multiple. Pharmacies (32.3%) and medical providers (excluding drug treatment providers) (22.9%) were the most commonly identified sources. Participants who had been trained to use naloxone were more likely to report that they would obtain naloxone from the needle exchange and were less likely to report they did not know where they would go to get it or that they would go to a medical provider (excluding drug treatment providers) for naloxone.

Conclusions

Naloxone training was associated with participants’ ability to name a location where they would obtain naloxone. Medicalized sources of naloxone remained the most commonly reported. These sources, however, may be associated with significant barriers to access, such as cost. Trainings should provide comprehensive education about low-cost/free sources to ensure ongoing naloxone access among people who use drugs.
Cannabis use in Adolescence and Risk of Psychosis: Are there Factors that Moderate this Relationship? A Systematic Review and Meta-Analysis
Authors: Kiburi Sarah Kanana , Molebatsi Keneilwe , Ntlantsana Vuyokazi , Lynskey Michael T.
Published: February 2021

Background

Previous research has reported increased risk for psychosis among individuals who use cannabis during adolescence. We conducted a systematic review and meta-analysis to investigate the interaction between adolescent cannabis use and other factors in moderating risk for psychosis later in life.

Method

We searched four electronic databases in June 2020 for articles that assessed adolescent cannabis use, had psychosis as an outcome and analyzed for the association between adolescent cannabis use and psychosis. Analysis was done using random-effects meta-analysis and narrative synthesis.

Results

A total of 63 studies were included in the narrative review and 18 studies were included in the meta-analysis. Adolescent cannabis use was found to increase risk for psychosis (RR = 1.71 (95%CI, 1.47–2.00, p < 0.00001) and predict earlier onset of psychosis. The following factors moderate the relationship between cannabis use and the risk of psychosis: age of onset of cannabis use, frequent cannabis use, exposure to childhood trauma, concurrent use of other substances and genetic factors.

Conclusion

Adolescent cannabis use is associated with an increased risk for psychosis later in life. In addition, there are factors that moderate this relationship; therefore there is a need for research to assess the interaction between these factors, adolescent cannabis use and psychosis risk.
Substance Consumption and Intoxication Patterns in a Medically Supervised Overdose Prevention Program for People Experiencing Homelessness
Authors: Wishik Gabriel , Gaeta Jessie M. , Racine Melanie W. , O'Connell James J. , Baggett Travis P.
Published: February 2021

Background

Opioid overdose is a leading cause of death among homeless individuals. Combining psychoactive substances with opioids increases overdose risk. This study aimed to describe intoxication patterns at a drop-in space offering medical monitoring and harm reduction services to individuals who arrive intoxicated and at risk of overdose.

Methods

We examined data from visits to the Supportive Place for Observation and Treatment at Boston Health Care for the Homeless Program between January 1, 2017 and December 31, 2017. We used k-means cluster analysis to characterize intoxication patterns based on clinically assessed sedation levels and vital sign parameters. Multinomial logistic regression analysis assessed demographic and substance consumption predictors of cluster membership. Linear and logistic regression models examined associations between cluster membership and care outcomes.

Results

Across 305 care episodes involving 156 unique patients, cluster analysis revealed 3 distinct intoxication patterns. Cluster A (26.6%) had mild sedation and normal vital signs. Cluster B (44.5%) featured greater sedation with bradycardia and/or hypotension. Cluster C (28.9%) was comparable to cluster B but with the addition of hypoxia. Self-reported consumption of non-opioid sedatives prior to arrival was common (63.3% of episodes) and predicted membership in cluster B (aOR 2.75, 95% CI 1.40, 5.40) and cluster C (aOR 3.38, 95% CI 1.48, 7.70). In comparison to cluster A episodes, cluster C episodes were longer (mean 4.8 vs. 2.3 hours, p < 0.001) and more likely to require supplemental oxygen (27.3% vs. 2.5%, p < 0.001). Few episodes required hospital transfer (4.7%) or naloxone (1.0%). No deaths occurred.

Conclusions

In a medically supervised overdose monitoring program, reported use of non-opioid sedatives strongly predicted more complex clinical courses and should be factored into overdose prevention efforts. Low-threshold medical monitoring in an ambulatory setting was sufficient for most episodes, suggesting a role for such programs in reducing harm and averting costly emergency services.
“The Assessment Really Helps you with the First Step in Recovery.” What do Clients Think Substance use Disorder Treatment Intake Assessments Should Look Like?
Authors: Treiman Katherine , Padwa Howard , Mark Tami L. , Tzeng Janice , Gilbert Marylou
Published: February 2021

Background

In general, research has found that patient-centered substance use disorder treatment is positively correlated with improved patient outcomes. However, little research has examined what factors make intake assessments—the first step in addiction treatment—patient-centered.

Methods

We conducted interviews with 30 Medicaid-enrolled individuals who received addiction treatment in California about their experiences with the intake assessment process.

Results

Participants reported that the intake assessment process evoked strong feelings, both positive and negative. Some participants said that answering detailed questions about their substance use, mental health, and social relationships, for example, was cathartic and gave them helpful insights. Other participants found the questions invasive, exhausting, and anxiety provoking. Participants also emphasized how critical it is for the person conducting the assessment to be supportive, nonjudgmental, and attentive. Participants recommended delaying the comprehensive assessment because they did not feel physically or emotionally ready to complete the intake.

Conclusions and recommendations

Patients’ introduction to addiction treatment is typically the intake assessment. By understanding how patients experience intake assessments, providers can make the process more patient-centered, which may lead to improved patient outcomes.
Tunable terahertz Dirac semimetal metamaterials
Authors: He Xiaoyong , Liu Feng , Lin Fangting , Shi Wangzhou
Published: February 2021

The tunable propagation properties of 3D Dirac semimetal (DSM) patterned metamaterial (MM) structures have been symmetrically investigated in the terahertz (THz) regime. The results demonstrate that the resonant properties are very sensitive to the thicknesses of DSM MMs, and hundreds of nanometers are required to excite strong resonant curves. The DSM MMs support both strong LC and dipolar resonances, quite different from graphene MM patterns which mainly depend on dipolar resonance. As the Fermi level increases, the resonant strength becomes stronger, and significant modulation can be achieved, e.g. the amplitude and frequency modulation depths of transmission curves are more than 99% and 80%, respectively. In addition, by utilizing asymmetrical resonators, a very sharp Fano resonant peak is achieved with a large Q-factor of more than 25, for which the figure of merit is about 20. The results are very helpful to understand the tunable mechanisms of DSM devices and design novel THz plasmonic components, such as modulators, filters, and sensors.
How to solve problems in micro- and nanofabrication caused by the emission of electrons and charged metal atoms during e-beam evaporation
Authors: Volmer Frank , Seidler Inga , Bisswanger Timo , Tu Jhih-Sian , Schreiber Lars R , Stampfer Christoph , Beschoten Bernd
Published: February 2021

We discuss how the emission of electrons and ions during electron-beam-induced physical vapor deposition can cause problems in micro- and nanofabrication processes. After giving a short overview of different types of radiation emitted from an electron-beam (e-beam) evaporator and how the amount of radiation depends on different deposition parameters and conditions, we highlight two phenomena in more detail: First, we discuss an unintentional shadow evaporation beneath the undercut of a resist layer caused by the one part of the metal vapor which got ionized by electron-impact ionization. These ions first lead to an unintentional build-up of charges on the sample, which in turn results in an electrostatic deflection of subsequently incoming ionized metal atoms toward the undercut of the resist. Second, we show how low-energy secondary electrons during the metallization process can cause cross-linking, blisters, and bubbles in the respective resist layer used for defining micro- and nanostructures in an e-beam lithography process. After the metal deposition, the cross-linked resist may lead to significant problems in the lift-off process and causes leftover residues on the device. We provide a troubleshooting guide on how to minimize these effects, which e.g. includes the correct alignment of the e-beam, the avoidance of contaminations in the crucible and, most importantly, the installation of deflector electrodes within the evaporation chamber.