bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Study of Small Modular Reactor Class Super Fast Reactor Core for In-Vessel Retention
Authors: Sasaki Ryotaro , Yamaji Akifumi , Uchimura Kyota
Published: February 2022

The small modular reactor (SMR) class core design concept of once-through supercritical light water-cooled reactor (SCWR) with fast neutron spectrum (super fast reactor (FR)) is being developed at Waseda University. For the 300 MWel class design, complete core meltdown may need to be considered in case of a severe accident. This study proposes the new in-vessel retention (IVR) concept of the SMR class super FR (super FR-IVR), which can avoid recriticality even if the whole core relocates to the lower plenum of the reactor pressure vessel (RPV). The core characteristics with a given set of design specifications and criteria are evaluated based on fully coupled neutronics and thermal-hydraulics core burnup calculations. The debris criticality is evaluated based on Monte Carlo based method to consider the RPV lower plenum and debris configurations. The relationships between the 300 MWel class core design with the inner vessel diameter of 2.32 m and the IVR design are revealed. By reducing the operation cycle length from 720 days to 360 days and increasing the core inlet temperature from 280 °C to 370 °C, the required IVR submergence level could be reduced from 2.18 m to 1.38 m, assuming that the debris bed (melt pool) is homogeneous. However, when fully stratified debris configurations are assumed, the required disperser height and the corresponding IVR submergence level may increase to about 2.70 m.
Defect and Cluster Characterization: A Python-Based Plugin for Wellbore Intergrity Analysis
Authors: Nuhn Zachary , Leong Chad , Kolomytsev Leonid , Le Calvez Joel , Valstar Dirk
Published: February 2022

Over time, corrosion in a pipe causes metal loss which reduces the amount of stress a pipe can be exposed to before failure. A radial thickness measurement of the corroded pipe allows for a quantitative analysis of the pipe's strength by identifying areas of significant material loss. The effects of metal loss defects on a pipe compound when the defects are close enough to interact. Thus, the identification and characterization of interacting defects as a defect cluster is required when calculating the remaining pipe strength. A Python-based Techlog* wellbore software platform plugin was developed to provide an analytical workflow to detect and characterize the impact of metal loss defects and defect clusters on remaining pipe strength for downhole wellbore integrity applications. The developed plugin is a fully customizable workflow which can be adapted to any well integrity scenario and pipeline regulatory body standards such as ASME B31G, subsequently meeting clients' reporting requirements. The innovative workflow has additional potential to be ported to completely new applications utilizing various alternative downhole measurements.
Investigation of the Flow Field and the Pressure Recovery in a Gas Turbine Exhaust Diffuser at Design, Part-Load, and Over-Load Conditions
Authors: Bauer Maximilian , Hummel Simon , Schatz Markus , Kegalj Martin , Vogt Damian M.
Published: February 2022

The performance of axial diffusers installed downstream of heavy duty gas turbines is mainly affected by the turbine load. Thereby the outflow varies in Mach number, total pressure distribution, swirl and its tip leakage flow in particular. To investigate the performance of a diffuser at different load conditions, a generic diffuser geometry has been designed at ITSM which is representative for current heavy duty gas turbine diffusers. Results are presented for three different operating conditions, each with and without tip flow, respectively. Part-load (PL), design-load (DL) and over-load (OL) operating conditions are defined and varied at the diffuser inlet in terms of Mach number, total pressure distribution, and swirl. Each operating point is investigated experimentally and numerically and assessed based on its flow field as well as the pressure recovery. The diffuser performance shows a strong dependency on the inlet swirl and total pressure profile. A superimposed tip flow only influences the flow field significantly when the casing flow is weakened due to casing separation. In those cases, pressure recovery increases with additional tip flow. There is a reliable prediction of the computational fluid dynamics (CFD) simulations at design-load. At part-load, CFD overpredicts the strut separation, resulting in an underpredicted overall pressure recovery. At over-load, CFD underpredicts the separation extension in the annular diffuser but overpredicts the hub wake. This leads to a better flow control in CFD with the result of an overpredicted overall pressure recovery.
Hydrodynamic Coupling of Viscous and Nonviscous Numerical Wave Solutions Within the Open-Source Hydrodynamics Framework reef3d
Authors: Wang Weizhi , Pákozdi Csaba , Kamath Arun , Martin Tobias , Bihs Hans
Published: February 2022

A comprehensive understanding of the marine environment in the offshore area requires phase-resolved wave information. For far-field wave propagation, computational efficiency is crucial, as large spatial and temporal scales are involved. For the near-field extreme wave events and wave impacts, high resolution is required to resolve the flow details and turbulence. The combined use of a computationally efficient large-scale model and a high-resolution local-scale solver provides a solution that combines accuracy and efficiency. This article introduces a coupling strategy between the efficient fully nonlinear potential flow (FNPF) solver REEF3D::FNPF and the high-fidelity computational fluid dynamics (CFD) model REEF3D::CFD within the open-source hydrodynamics framework REEF3D. REEF3D::FNPF solves the Laplace equation together with the boundary conditions on a sigma-coordinate. The free surface boundary conditions are discretized using high-order finite difference methods. The Laplace equation for the velocity potential is solved with a conjugated gradient solver preconditioned with a geometric multigrid provided by the open-source library Hypre. The model is fully parallelized following the domain decomposition strategy and the message passing interface protocol. The waves calculated with the FNPF solver are used as wave generation boundary conditions for the CFD-based numerical wave tank REEF3D::CFD. The CFD model employs an interface capturing two-phase flow approach that can resolve complex wave structure interaction, including breaking wave kinematics and turbulent effects. The presented hydrodynamic coupling strategy is tested for various wave conditions and the accuracy is fully assessed.
Development of a Three-Component Micro Force Sensor/Calibration Device
Authors: Jin W. L. , Mote C. D.
Published: February 2022

A sub-millimeter three-component force sensor is developed using silicon microfabrication technology. A polysilicon cross-beam, 300μm by 300μm, with twelve piezoresistive strain gauges integrated on it, is the elastic element of the sensor. The strains detected by the strain gauges are measures of the three orthogonal components of the force applied at the center of the cross-beam. Calibration of the sensor is achieved by generating electromagnetic forces on an aluminum cross-beam that is suspended over the sensor structure.
Artificial Micropatterns of Cells on Biocompatible Surfaces
Authors: Folch Albert , Toner Mehmet
Published: February 2022

The geometrically selective attachment of cells on surfaces is an on-going technological challenge. Biotechnological applications of man-made cellular micropatterns range from tissue engineering and wound healing to single-cell assays and biosensors for toxic compounds. Recently, silicon microfabrication techniques and advances in surface chemistry have allowed for selectively tailoring cellular adhesiveness on a micrometer scale [1–8]. Usually, a micropattern of a self-assembled monolayer (SAM) of organic molecules promotes or inhibits cell adhesion on certain areas of the substrate depending on the end functional group of the SAM. Unfortunately, the specialized SAM chemistries, e.g. functionalized alkylsiloxanes on silicon oxide or alkanethiols on gold, are not easily combined with most tissue culture or implantable (“biocompatible”) materials such as polymers or heteregeneous surfaces and, most importantly, can result in undesirable biointeraction [9].
A Micro Valve Made of PSPI
Authors: Wang Xiaohao , Zhou Zhaoying , Zhang Wendong
Published: February 2022

A novel micro valve made of photosensitive polyimide (PSPI) was designed, fabricated and demonstrated. The dimension of chip of microvalve is less than 5 × 4 × 0.5mm3. It is designed for flow rate of about 20ml/min at a system pressure level of about 1 bar. The open pressure in positive direction is less than 250Pa while the leakage of reverse direction is almost zero. The strength of the valve is enough to withstand the reverse pressure level of more than 5 bar. The micro valve was used in a micropump as the flow direction control element. Almost all of its fabrication processes are compatible with IC processes.

At the meanwhile, the design and fabrication of polysilicon microvalve and single crystallite silicon microvalve are discussed in the same paper as contrast.
Numerical Simulation of Radiant Thermal Processing of Bilayer Microcantilevers
Authors: Tada Haruna , Miaoulis Ioannis N. , Wong Peter Y.
Published: February 2022

Multilayered thin-film structures in microelectro-mechanical systems (MEMS) and other microscale devices affect the radiative properties of the structures due to microscale heat transfer effects, which include thin-film interference, diffraction, and scattering. The difference between the radiative properties of the wafer and those of the structures creates a non-uniform wafer temperature during radiant thermal processing. This temperature non-uniformity may lead to defects and non-uniform processing. This paper presents the results of a numerical investigation of the radiative properties of bilayer microcantilever beams consisting of SiO2 and Si3N4 layers, separated from a Si substrate by an air gap created by etching. The study focuses on the effects of changes in the absorptivity (α) and emissivity (ε) of the beams due to varying etching depth (η). The radiative Properties calculated with numerical models are used in a simulation of the radiant heating of patterned wafers, studying the effects of Pattern size and separation on the temperature uniformity of the wafer. For a beam with Si3N4 thickness of 2000 Å and SiO2 thickness of 5000 Å, the results show that the total absorptivity and emissivity are highly dependent on the etch depth (η) for values less than approximately 1.5 μm. For larger η, the radiative properties remain constant, approximately equal to those of the Si substrate. The temperature distributions for a patterned wafer become more uniform as the pattern size and spacing decrease. When the patterning size decrease for a given separation, the result is a better thermal interaction between the die and the wafer resulting in a smaller temperature gradient. This, however, creates a large temperature difference between the wafer patterning area and the outer edge region, which results in an increased temperature gradient along the wafer edge. These heat transfer effects should be taken into consideration when creating fabrication mask sets for radiant thermal processing to design a pattern layout that would hest avoid the problems caused by thermal gradients.
Viscous Effects in Supersonic MEMS-Fabricated Micronozzles
Authors: Bayt Robert L. , Breuer Kenneth S.
Published: February 2022

A contoured converging-diverging micronozzle has been created for the acceleration of gas flows to supersonic velocities. Extruded two-dimensional devices, with minimum throat widths averaging 19 microns and 35 microns, are etched using deep reactive ion etching. Mass flow efficiencies through the nozzles range from 87% to 98% and are within experimental error to those predicted by a 2-D Navier-Stokes fluid simulation for Reynolds numbers 350–3800. The thrust of a 16.9 to 1 expansion ratio nozzle was measured to be 11.3 mN at 97 psia chamber pressure. This corresponds to an exit velocity of 590 m/s, which is Mach 3.8 for a chamber temperature of 300 K. Thrust efficiency is found to deviate considerably from the 2-D numerical model at low Reynolds numbers due to the development of sidewall boundary layers.
Silicon-Micromachined Vortex-Controlled Thrusters
Authors: Cho Changho , Kim Jongpal , Choi Byung-gwi , Kim Dongjoo , Choi Haecheon , Cho Dong-il Dan
Published: February 2022

Vortex-controlled thrusters are silicon micromachined for the first time. Vortex thrusters are fluidic devices that convert a pressure signal into a flow or force signal. These micro-fluidic thrusters are micromachined on a 500 μm-thick silicon wafer. The vortex chamber and inlet ports are deep reactive ion etched to a 300 μm depth from the topside, and the output nozzle is deep reactive ion etched from the backside to a 200 μm depth. For a fixed vortex chamber radius and control port width, varying the output nozzle and supply port sizes are investigated. The maximum attainable thruster force at a 300 kPa supply pressure is 21.0 mN, which is a very large force for a microdevice.
Microfluidics of a Planar Microfabricated Fluid Filter
Authors: Ki Yit-shun Leung , Maillefer Didier , Rey-Mermet Gilles , Monkewitz Peter A. , Renaud Philippe , van Lintel Harald T. G.
Published: February 2022

Design and characterization of a planar microfabricated liquid filter for implantable drug delivery applications is presented. An on-chip liquid filter is required at the inlet of a micromachined membrane pump [1] to ensure trouble-free operation of pump components. The filter, bulk micromachined in silicon, consists of a slightly etched long filtration barrier within a deep wet-etched cavity with asymmetrically offset inlet and exit encapsulated by bonding a pyrex coverslip over the silicon substrate. Minimum filtrate size is thus controlled by the depth h of the barrier etch and can be as slim as 0.1 μm. Flow resistance of the filter is minimized by winding the filtration barrier into a zig-zag. Effects observed during priming of the filters are described here and a model is presented which led to a filter design with vastly improved priming characteristics. The filter fulfills design specifications with respect to proper operation of the micropump, and successfully blocks the transport of 0.48 μm particles as visualized using blue fluorescent microbeads. The gap size achieved in practice was of 0.18 μm for a desired gap size of 0.2 μm. The filter design can also be used as a test structure for the exploration of liquid transport effects in submicron channels. Preliminary results show that in accordance with previous theoretical and experimental work [2,3], there is an increase in apparent viscosity for the flow of aqueous NaCl solutions through submicron-sized gaps.
Pressure Drop Measurements in a Microchannel
Authors: Pfund David , Shekarriz Alireza , Popescu Aristotel , Welty James R.
Published: February 2022

This paper presents the results of experiments performed on single-phase flow in microchannels. Channel depths ranged between 100 and 500 microns, with a W:H ratio greater than 20:1. Water was the primary working fluid in these studies, with the Reynolds numbers (based on the hydraulic diameter of the channel) ranging between 40 and 4000. The experimental setup used allowed measurements of the local pressure drop as well as visualization of the flow patterns within the channel using microscopy. Data presented include friction factors for various channel geometry and surface conditions. We found that the surface roughness tended to increase the laminar friction factor within the channel. Further, for the smoothest channel, as the channel height (or hydraulic diameter) decreased, the laminar friction factor did not depart from the continuum theory predictions. Further, our pressure drop measurements, corroborated with careful flow visualization tests, reveal that the transition Reynolds number is nearly half of what is previously reported for macroscopic channels.
Tribology on the Macro- to Nanoscales of MEMS Materials: A Review
Authors: Bhushan Bharat
Published: February 2022

Silicon-based MEMS devices are made from single-crystal silicon, LPCVD polysilicon films and other ceramic films (Bhushan, 1998). For high temperature applications, SiC films are being developed to replace polysilicon films. Tribology in the MEMS devices requiring relative motion is of importance. Atomic force/friction force microscopy (AFM/FFM) and nanoindentation techniques (Bhushan et al., 1995; Bhushan, 1995, 1998) have been used for tribological studies on micro- to nanoscale on materials of interest. These techniques have been used to study surface roughness, friction, scratching/wear, indentation and boundary lubrication of bulk and treated silicon, polysilicon films and SiC films (Bhushan, 1996a, b; Bhushan et al., 1994, 1997a, b, 1998; Koinkar and Bhushan, 1997; Li and Bhushan, 1998; Sundararajan and Bhushan, 1998; Zhao and Bhushan, 1998). Macroscale friction and wear tests have also been conducted using the ball-on-flat tribometer. (Bhushan and Venkatesan, 1993; Gupta et al., 1993, 1994a, b; Venkatesan and Bhushan, 1993, 1994). Measurements of microscale and macroscale friction forces show that friction values on both scales of all the silicon samples are about the same among different silicon materials and higher than that of SiC. The microscale values are lower than the macroscale values as there is less ploughing contribution in the microscale measurements. Surface roughness has an effect on friction. In microscale and macroscale tests, C+-implanted, oxidized and PECVD oxide-coated single-crystal silicon samples exhibit much larger scratching and wear resistance as compared to untreated samples. Polysilicon films and undoped single-crystal silicon show similar friction and wear characteristics. Doping of polysilicon film does not affect its tribological properties. Microscratching, microwear and nanoindentation, and macroscale friction and wear studies indicate that SiC films are superior when compared to the other materials currently used in MEMS devices. Higher hardness and fracture toughness of the SiC film is believed to be responsible for its superior mechanical integrity and lower friction. Chemically grafted self-assembled monolayers and chemically-bonded liquid lubricants show promising performance for boundary lubrication in MEMS devices.
Cyclic Fatigue Testing of Surface-Micromachined Thermal Actuators
Authors: Conant Robert A. , Muller Richard S.
Published: February 2022

Long-term testing of surface-micromachincd U-shaped thermal actuators has been carried out. Actuators operated at power levels lower than 8 mW (12 μm of displacement) operated satisfactorally for more than 100 million cycles at 660 Hz, with a failure defined as the point at which the displacement decreases by 20%. Plastic deformation had been observed in actuators operated above 8 mW, and the plastic deformation has been shown to be associated with the high temperatures encountered during operation. The failure rate of the actuators is dependent on the total time the actuators are at the elevated temperatures encountered during operation, rather than on the number of actuation cycles. This paper provides a guide for MEMS designers that shows the lifetime of a thermal actuator as a function of its drive power.
Computer-Aided Micro-Mechanism Design
Authors: Sacks Elisha , Allen James
Published: February 2022

This paper describes computer-aided design tools for micro-mechanisms that help designers validate correct function, detect design flaws, and assess the effects of part clearances. The domain characteristics of curved geometry, joint play, and higher pairs render traditional software inappropriate. Our software uses configuration spaces to model the kinematic function of micro-mechanisms. It uses the configuration spaces to perform real-time simulation, to compute functional kinematic tolerances, and to support parametric design. Designers can visualize system function under a range of operating conditions, can find and correct design flaws, and can optimize dynamical function. The software is demonstrated on a surface micromachined counter meshing gear discrimination device developed at Sandia National Laboratory.
Influence of Fabrication and Crystal Orientation on the Strength of Silicon Microridges
Authors: Chen Quanfang , Yao Da-Jeng , Kim Chang-Jin “CJ” , Carman Greg P.
Published: February 2022

The shear strength of microridges fabricated using both anisotropic wet etching (KOH, TMAH and EDP) and dry-etching methods (chlorine RIE) is presented in this paper. Shear strengths obtained using a KOH wet etching is concentration dependent, that is the microridges made with a 45% KOH solution has a strength 65% larger than those by 30% KOH. EDP and TMAH wet etching produce structures whose average strengths are similar to the 30% KOH solution. On the other hand, dry etching chlorine RIE produces structures with strength values 95% higher than the wet etching approaches containing similar crystal orientations. Strength variations are attributed to local stress concentrations. RIE is also used to manufacture structures with different crystal orientations. Test results indicate that microridges with a {110} sidewall has the highest strength because for this case the loading direction (perpendicular to sidewall) has one of the smallest component along the {111} plane (sliding plane of silicon). Microridges made with a sidewall of {100} plane produce the lowest strength value among the three crystal orientations studied.
MHD (Magnetohydrodynamic) Micropump Using Lorentz Force
Authors: Jang Jaesung , Lee Seung S.
Published: February 2022

We present a novel micropump of which pumping mechanism is based upon MHD (Magnetohydrodynamic) principle. The MHD micropump uses Lorentz force as the pumping source. In the micropump, Lorentz force is applied into initially stagnant conducting fluid to drive it in magnetic and electric field to flow in both directions. The performance of the micropump is obtained by measuring the pressure head difference and flow rate as the applied voltage changes from 10 to 60 V DC at 0.19 and 0.44 Tesla. The pressure head difference is 18 mm at 38 mA and the flow rate is 63 μl/min at 1.8 mA when the inside diameter of inlet/outlet tube is 2 mm and the magnetic flux density is 0.44 Tesla.
Flow Past a Micro-Sphere in a Pipe: Effects of Rarefaction
Authors: Liu Hsin-Chih F. , Beskok Ali , Gatsonis Nikolaos , Karniadakis George E.
Published: February 2022

The canonical problem of rarefied gas flow past a sphere in a pipe has been studied in a wide range of Knudsen number (Kn), covering the continuum, slip, and transitional flow regimes. The blockage effects are studied by varying the pipe to sphere diameter ratio H/D, as well as the Knudsen number. The numerical results in the continuum and slip flow regimes are obtained by ΝεκΤαr and μFlow, based on spectral element algorithms for incompressible continuum, and for compressible continuum/slip flows, respectively. The transitional flow regime is investigated by the code F3, based on the direct simulation Monte Carlo (DSMC) method of Bird. Our results show that the drag coefficient CD is inversely proportional to Kn, the Reynolds number Re and H/D. The blockage effects are shown to become negligible for high Knudsen number regime (Kn ≥ 3.5) even for small values of H/D. The sphere in a pipe configuration can be used in designing electro-magnetically driven micro-valve systems.
A Micromechanical Actuator With Capacitive Position Correction for Phase Shifting Diffraction Interferometry
Authors: McConaghy Charles F. , Lee Abraham P. , Sommargren Gary , Phillion Don , Campbell Eugene W. , Trevino Jimmy
Published: February 2022

An electrostatically-actuated micro phase shifter with capacitive position feedback for linearization is presented in this paper. The travel range of the micro phase shifter is 1.2 μm, and a lock-in amplifier capacitive sensing circuit capable of 1.5 nm position accuracy is developed and with a digital signal processor generates a position feedback correction curve to achieve a linearized travel trajectory. The eventual application for this microactuator is to provide linear phase shifting in the phase shifting diffraction interferometer (PSDI) developed at LLNL Which can perform optical metrology down to 2Å accuracy.
First Discrete Time Full-System Inertial Microsensor Performance Simulation Tool
Authors: Pottenger Michael D. , Kaiser William J.
Published: February 2022

We present the first report on a full-system integrated microsensor simulation model, based on discrete-time methods and implemented in SPICE. Included are all electrical and thermomechanical noise sources, proof mass dynamics, differential capacitive transducer bridge, interface circuit, and feedback control. Complete microsensor system performance can be simulated in the time domain, incorporating flicker noise models based on measured data from a commercial CMOS process. Simulation results for two complete inertial sensor system are presented: System I has an open loop resonant frequency of 100Hz, Q factor of 1000, and has a critically damped closed-loop resonance at 1.67kHz; System II is a critically damped open loop sensor with resonance at 1.67kHz. Closed loop operation is demonstrated to improve sensitivity by 106dB at 100Hz.
Automatic Model Order Reduction of a Microdevice Using the Arnoldi Approach
Authors: Wang Frank , White Jacob
Published: February 2022

In this paper we demonstrate that Arnoldi based model-order reduction can be used to generate accurate reduced-order models from linear systems generated by coupled-domain simulation of MEMS devices. In particular, we examine the well-known fixed-fixed beam example and show that when the device is in the linear regime, we can automatically generate a tenth order model that faithfully, reproduces the device characteristics. We also show the limitations of this linearized model approach.
Automatic Model Generation and Analysis for MEMS
Authors: Ljung Per B. , Bächtold Martin
Published: February 2022

Simulating large, realistic MEMS models has previously been prohibitive due to both the extensive user effort required to generate models and the computational cost of such analyses [1]. This work robustly automates efficient and accurate MEMS analysis by eliminating substantially all user interaction required to generate accurate 3D simulations of devices described by photolithographic masks. This automatic procedure allows large, realistic MEMS devices to be accurately simulated in less than one hour on personal computers.
Utilizing Existing TCAD Simulation Tools to Create Solid Models for the Simulation Based Design of MEMS Devices
Authors: Wilson Nathan M. , Dutton Robert W. , Pinsky Peter M.
Published: February 2022

This paper gives an overview of MEMS simulation and the computational requirements in the field from the prospective of creating realistic geometry based on process simulation. We motivate the needs for such geometry, and discuss in detail one approach to create pseudo 3-D geometry from 2-D process simulation. Three different methods to perform booleans critical to the pseudo-3D technique are discussed in detail.
Optimized Compliance With Supplemental Indication Requirements: Leveraging Non-Intrusive Techniques, Preexisting Line-Ups and Programs to Meet 10CFR50.55a(b)(3)(xi)
Authors: Arnold Eli , Cruz Domingo
Published: February 2022

To ensure safe operation of the United States’ nuclear power plants, the Nuclear Regulatory Commission enacted 10CFR50.55a(b)(3)(xi) requiring the verification of valves’ capability to control plant process conditions. Palo Verde Generating Station implemented the requirement with a focus on crediting existing operational and testing activities, iterating to optimize implementation. The station credits valve diagnostics, operational activities, and component testing programs wherever possible. Where testing and operations are insufficient to meet the requirement, phased-array ultrasonic equipment is used to verify stem-disc connection integrity. Palo Verde is fully compliant with the requirements of 10CFR50.55a(b)(3)(xi). This suggests compliance at other pressurized water reactors can be achieved primarily by documenting existing plant activities with minimal new testing activities required.
NRC Inspection Manual Inspection Procedure 71111 Attachment 21N.02: Design-Basis Capability of Power-Operated Valves Under 10 CFR 50.55a Requirements Inspection Implementation Update and Lessons Learned
Authors: Bollock Douglas
Published: February 2022

On July 26, 2019, the NRC issued Inspection Procedure 71111, Attachment 21N.02 (IP 71111.21N.02), “Design-Basis Capability of Power-Operated Valves Under 10 CFR 50.55a Requirements.” The objective of this inspection procedure is to assess the reliability, functional capability, and design basis of risk-important power-operated valves (POVs) as required by Section 55a, “Codes and Standards,” in Part 50, “Domestic Licensing of Production and Utilization Facilities,” of Title 10, “Energy,” in the Code of Federal Regulations (10 CFR 50.55a). The NRC staff has implemented this inspection procedure at operating nuclear power plants in the United States (U.S.) since January 2020 and has gained lessons learned through implementation of and feedback from the inspections. The staff has held a public meeting with nuclear power plant licensees to discuss the lessons learned from the inspection activities in December 2020. This paper describes the status of the ongoing NRC staff activities for POV inspections at operating U.S. nuclear power plants and the lessons learned through implementation of the inspections.
Collegiate Student-Athlete Psychological Distress and Counseling Utilization During COVID-19
Authors: Slavin Lindsey E. , Palmateer Tess M. , Petrie Trent A. , Moore E. Whitney G.
Published: February 2022

The onset of COVID-19 and cancellation of collegiate sports may have exacerbated student-athletes’ psychological distress. Within a national sample of collegiate athletes (N = 5,755; 66.7% women), we determined how gender and race related to rates of depression, stress, and counseling use at the beginning of the pandemic (April/May 2020). Overall, 26.5% (n = 1,526) and 10.6% (n = 612) endorsed clinical levels of depression and stress, respectively; 25.1% (n = 1,443) and 69.7% (n = 4,014) reported subclinical levels. Few athletes (2.3%–17.1%) reported counseling use before or after the onset of COVID-19; those who did reported higher levels of depression and stress than those who never sought services. The female athletes reported higher rates of depression, stress, and counseling use than the male athletes. There were no race effects. Athletic departments must address their student-athletes’ psychological distress by facilitating a higher use of mental health services.
Apparent sunk cost effect in rational agents
Authors: Ott Torben , Masset Paul , Gouvêa Thiago S. , Kepecs Adam
Published: February 2022

Rational decision makers aim to maximize their gains, but humans and other animals often fail to do so, exhibiting biases and distortions in their choice behavior. In a recent study of economic decisions, humans, mice, and rats were reported to succumb to the sunk cost fallacy, making decisions based on irrecoverable past investments to the detriment of expected future returns. We challenge this interpretation because it is subject to a statistical fallacy, a form of attrition bias, and the observed behavior can be explained without invoking a sunk cost–dependent mechanism. Using a computational model, we illustrate how a rational decision maker with a reward-maximizing decision strategy reproduces the reported behavioral pattern and propose an improved task design to dissociate sunk costs from fluctuations in decision valuation. Similar statistical confounds may be common in analyses of cognitive behaviors, highlighting the need to use causal statistical inference and generative models for interpretation.
The pore conformation of lymphocyte perforin
Authors: Ivanova Marina E. , Lukoyanova Natalya , Malhotra Sony , Topf Maya , Trapani Joseph A. , Voskoboinik Ilia , Saibil Helen R.
Published: February 2022

Perforin is a pore-forming protein that facilitates rapid killing of pathogen-infected or cancerous cells by the immune system. Perforin is released from cytotoxic lymphocytes, together with proapoptotic granzymes, to bind to a target cell membrane where it oligomerizes and forms pores. The pores allow granzyme entry, which rapidly triggers the apoptotic death of the target cell. Here, we present a 4-Å resolution cryo–electron microscopy structure of the perforin pore, revealing previously unidentified inter- and intramolecular interactions stabilizing the assembly. During pore formation, the helix-turn-helix motif moves away from the bend in the central β sheet to form an intermolecular contact. Cryo–electron tomography shows that prepores form on the membrane surface with minimal conformational changes. Our findings suggest the sequence of conformational changes underlying oligomerization and membrane insertion, and explain how several pathogenic mutations affect function.
Ionic heat dissipation in solid-state pores
Authors: Tsutsui Makusu , Arima Akihide , Yokota Kazumichi , Baba Yoshinobu , Kawai Tomoji
Published: February 2022

Energy dissipation in solid-state nanopores is an important issue for their use as a sensor for detecting and analyzing individual objects in electrolyte solution by ionic current measurements. Here, we report on evaluations of heating via diffusive ion transport in the nanoscale conduits using thermocouple-embedded SiN

x

pores. We found a linear rise in the nanopore temperature with the input electrical power suggestive of steady-state ionic heat dissipation in the confined nanospace. Meanwhile, the heating efficiency was elucidated to become higher in a smaller pore due to a rapid decrease in the through-water thermal conduction for cooling the fluidic channel. The scaling law suggested nonnegligible influence of the heating to raise the temperature of single-nanometer two-dimensional nanopores by a few kelvins under the standard cross-membrane voltage and ionic strength conditions. The present findings may be useful in advancing our understanding of ion and mass transport phenomena in nanopores.
The chemical evolution of solid electrolyte interface in sodium metal batteries
Authors: Gao Lina , Chen Juner , Chen Qinlong , Kong Xueqian
Published: February 2022

The solid electrolyte interface (SEI) formed on the anode is one of the key factors that determine the life span of sodium metal batteries (SMBs). However, the continuous evolution of SEI during charging/discharging processes complicates the fundamental understanding of its chemistry and structure. In this work, we studied the underlying mechanisms of the protection effect offered by the SEI derived from sodium difluoro(oxalato)borate (NaDFOB). In situ nuclear magnetic resonance (NMR) shows that the prior reduction of DFOB anion contributes to the SEI formation, and it suppresses the decomposition of carbonate solvents. Depth-profiling x-ray photoelectron spectroscopy and high-resolution solid-state NMR reveal that the DFOB anion is gradually turned into borate and fluoride-rich SEI with cycling. The protection effect of SEI reaches the optimum at 50 cycles, which triples the life span of SMB. The detailed investigations provide valuable guidelines for the SEI engineering.
Secondary cratering on Earth: The Wyoming impact crater field
Authors: Kenkmann Thomas , Müller Louis , Fraser Allan , Cook Doug , Sundell Kent , Rae Auriol S.P.
Published: February 2022

A large number of small impact structures have been discovered in Wyoming, USA, and we raise the question of how this accumulation occurred. We document 31 crater structures of 10–70 m diameter with corresponding shock features but missing meteorite relics. All craters occur along the outcrops of the uppermost Permo-Pennsylvanian Casper Sandstone Formation and are ~280 m.y. old. Their spatial arrangement shows clusters and ray-like alignments. Several craters have elliptical crater morphologies that allow the reconstruction of impact trajectories. The radial arrangement of the trajectories indicates that the craters are secondary craters formed by ejecta from a primary crater whose likely position and size are reconstructed. Modeling ballistic trajectories and secondary crater formation indicates that impacts occurred at around 700–1000 m/s and caused small shock volumes with respect to crater volumes. This is the first field of secondary craters found on Earth, and we disentangle its formation conditions.
Reassessment of ocean paleotemperatures during the Late Ordovician
Authors: Barney Bryce B. , Grossman Ethan L.
Published: February 2022

The Late Ordovician is a paradox, with a greenhouse climate shifting to an icehouse climate during a time of presumably high CO2 levels. We used clumped isotope (Δ47) microanalysis of fossil brachiopod shells to determine paleotemperatures of North America (Cincinnati Arch) during the Katian (453–443 Ma). Microanalyses of fossil brachiopods yielded a right-skewed distribution of clumped isotope temperatures [T(Δ47)] ranging from 25 °C to 55 °C with a mode of 32 °C and a mean of 36 °C. To test the impact of Δ47 reordering (reequilibration of 13C-18O bonding) at burial temperatures on T(Δ47), we applied a Monte Carlo simulation to a Δ47 reordering model based on the burial history. Because the reordering simulation indicated partial reordering, we used the simulation results to back-calculate T(Δ47) and correct the reordering effect. Correcting for reordering decreased the mean T(Δ47) by only ~1 °C, to 35 °C, and did not change the mode (32 °C). These temperatures are lower than those of previous studies, but still suggest that the Late Ordovician climate of the Cincinnati Arch was warmer than the modern subtropical seas. However, carbonate facies in these strata argue for upwelling of cool water; thus, typical subtropical surface waters may have been as warm as 35 °C approaching the Hirnantian glaciation. Seawater δ18O values derived from back-calculated T(Δ47) and brachiopod δ18O values average −0.3‰ ± 0.6‰ relative to Vienna standard mean ocean water (VSMOW), consistent with the value expected for subtropical surface waters in a greenhouse Earth, assuming a constant seawater-δ18O model.
Implications for Ediacaran biological evolution from the ca. 602 Ma Lantian biota in China
Authors: Yang Chuan , Li Yang , Selby David , Wan Bin , Guan Chengguo , Zhou Chuanming , Li Xian-Hua
Published: February 2022

The morphologically differentiated benthic macrofossils of algae and putative animal affinities of the Lantian biota in China represents the oldest known Ediacaran macroscopic eukaryotic assemblage. Although the biota provides remarkable insights into the early evolution of complex macroeukaryotes in the Ediacaran, the uncertainty in its age has hampered any robust biological evaluation. We resolve this issue by applying a petrographic-guided rhenium-osmium (Re-Os) organic-bearing sedimentary unit study on the Lantian biota. This work confines a minimum age for the first appearance of the Lantian biota to 602 ± 7 Ma (2σ, including decay constant uncertainty). This new Re-Os date confirms that the Lantian biota is of early–mid Ediacaran age and temporally distinct from the typical Ediacaran macrobiotas. Our results indicate that the differentiation and radiation of macroscopic eukaryotes, and the evolution of the primitive, erect epibenthic ecosystem, occurred in the early–mid Ediacaran and were associated with highly fluctuating oceanic redox conditions. The radiogenic initial 187Os/188Os ratios derived from the Lantian (1.14 ± 0.02) and other Ediacaran shales invoke oxidative weathering of upper continental crust in the early–middle Ediacaran, which may have stimulated the evolution of life and oceanic-atmospheric oxygenation. Integrated with published Ediacaran chronological and geochemical data, our new Re-Os geochemical study of the Lantian black shale provides a refined, time-calibrated record of environment and eukaryote evolution during the Ediacaran.
Multicentre point-prevalence survey of antibiotic use and healthcare-associated infections in Ethiopian hospitals
Authors: Fentie Atalay Mulu , Degefaw Yidnekachew , Asfaw Getachew , Shewarega Wendosen , Woldearegay Mengistab , Abebe Ephrem , Gebretekle Gebremedhin Beedemariam
Published: February 2022

Objective

Effective antimicrobial containment strategies such as Antimicrobial Stewardship Programs (ASPs) require comprehensive data on antibiotics use which are scarce in Ethiopia. This study sought to assess antibiotics use and healthcare-associated infections (HCAIs) in Ethiopian public hospitals.

Design

We conducted a cross-sectional study using the WHO point-prevalence survey protocol for systemic antibiotics use and HCAIs for low/middle-income countries.

Setting

The study was conducted among 10 public hospitals in 2021.

Participants

All patients admitted to adult and paediatric inpatient and emergency wards before or at 08:00 on the survey date were enrolled.

Outcome measure

The primary outcome measures were the prevalence of antibiotic use, HCAIs and the hospitals’ readiness to implement ASP.

Results

Data were collected from 1820 patient records. None of the surveyed hospitals had functional ASP. The common indication for antibiotics was for HCAIs (40.3%). Pneumonia was the most common bacterial infection (28.6%) followed by clinical sepsis (17.8%). Most treatments were empiric (96.7%) and the overall prevalence of antibiotic use was 63.8% with antibiotics prescription per patient ratio of 1.77. Ceftriaxone was the most commonly prescribed antibiotic (30.4%) followed by metronidazole (15.4%). Age, having HIV infection, ward type, type of hospital, catheterisation and intubation history had significant association with antibiotic use. Patients who were treated in paediatric surgical wards were about four times more likely to be on antibiotics compared with patients treated at an adult emergency ward. Patients on urinary catheter (adjusted OR (AOR)=2.74, 95% CI: 2.04 to 3.68) and intubation device (AOR=2.62, 95% CI: 1.02 to 6.76) were more likely to be on antibiotics than their non-intubated/non-catheterised counterparts. Patients treated at secondary-level hospitals had 0.34 times lower odds of being on antibiotics compared with those in tertiary hospitals.

Conclusions

Antibiotic use across the surveyed hospitals was common and most were empiric which has both practical and policy implications for strengthening ASP and promoting rational antibiotics use.
TACTICS - Trial of Advanced CT Imaging and Combined Education Support for Drip and Ship: evaluating the effectiveness of an ‘implementation intervention’ in providing better patient access to reperfusion therapies: protocol for a non-randomised controlled stepped wedge cluster trial in acute stroke
Authors: Ryan Annika , Paul Christine L , Cox Martine , Whalen Olivia , Bivard Andrew , Attia John , Bladin Christopher , Davis Stephen M , Campbell Bruce C V , Parsons Mark , Grimley Rohan S , Anderson Craig , Donnan Geoffrey A , Oldmeadow Christopher , Kuhle Sarah , Walker Frederick R , Hood Rebecca J , Maltby Steven , Keynes Angela , Delcourt Candice , Hatchwell Luke , Malavera Alejandra , Yang Qing , Wong Andrew , Muller Claire , Sabet Arman , Garcia-Esperon Carlos , Brown Helen , Spratt Neil , Kleinig Timothy , Butcher Ken , Levi Christopher R
Published: February 2022

Introduction

Stroke reperfusion therapies, comprising intravenous thrombolysis (IVT) and/or endovascular thrombectomy (EVT), are best practice treatments for eligible acute ischemic stroke patients. In Australia, EVT is provided at few, mainly metropolitan, comprehensive stroke centres (CSC). There are significant challenges for Australia’s rural and remote populations in accessing EVT, but improved access can be facilitated by a ‘drip and ship’ approach. TACTICS (Trial of Advanced CT Imaging and Combined Education Support for Drip and Ship) aims to test whether a multicomponent, multidisciplinary implementation intervention can increase the proportion of stroke patients receiving EVT.

Methods and analysis

This is a non-randomised controlled, stepped wedge trial involving six clusters across three Australian states. Each cluster comprises one CSC hub and a minimum of three primary stroke centre (PSC) spokes. Hospitals will work in a hub and spoke model of care with access to a multislice CT scanner and CT perfusion image processing software (MIStar, Apollo Medical Imaging). The intervention, underpinned by behavioural theory and technical assistance, will be allocated sequentially, and clusters will move from the preintervention (control) period to the postintervention period.

Primary outcome

Proportion of all stroke patients receiving EVT, accounting for clustering.

Secondary outcomes

Proportion of patients receiving IVT at PSCs, proportion of treated patients (IVT and/or EVT) with good (modified Rankin Scale (mRS) score 0–2) or poor (mRS score 5–6) functional outcomes and European Quality of Life Scale scores 3 months postintervention, proportion of EVT-treated patients with symptomatic haemorrhage, and proportion of reperfusion therapy-treated patients with good versus poor outcome who presented with large vessel occlusion at spokes.

Ethics and dissemination

Ethical approval has been obtained from the Hunter New England Human Research Ethics Committee (18/09/19/4.13, HREC/18/HNE/241, 2019/ETH01238). Trial results will be disseminated widely through published manuscripts, conference presentations and at national and international platforms regardless of whether the trial was positive or neutral.

Trial registration number

ACTRN12619000750189; UTNU1111-1230-4161.
Complete loss of the X-linked geneCASKcauses severe cerebellar degeneration
Authors: Patel Paras A , Hegert Julia V , Cristian Ingrid , Kerr Alicia , LaConte Leslie E W , Fox Michael A , Srivastava Sarika , Mukherjee Konark
Published: February 2022

Background

Heterozygous loss of X-linked genes likeCASKand MeCP2 (Rett syndrome) causes developmental delay in girls, while in boys, loss of the only allele of these genes leads to epileptic encephalopathy. The mechanism for these disorders remains unknown.CASK-linked cerebellar hypoplasia is presumed to result from defects in Tbr1-reelin-mediated neuronal migration.

Method

Here we report clinical and histopathological analyses of a deceased 2-month-old boy with aCASK-null mutation. We next generated a mouse line whereCASKis completely deleted (hemizygous and homozygous) from postmigratory neurons in the cerebellum.

Result

TheCASK-null human brain was smaller in size but exhibited normal lamination without defective neuronal differentiation, migration or axonal guidance. The hypoplastic cerebellum instead displayed astrogliosis and microgliosis, which are markers for neuronal loss. We therefore hypothesise thatCASKloss-induced cerebellar hypoplasia is the result of early neurodegeneration. Data from the murine model confirmed that in CASK loss, a small cerebellum results from postdevelopmental degeneration of cerebellar granule neurons. Furthermore, at least in the cerebellum, functional loss fromCASKdeletion is secondary to degeneration of granule cells and not due to an acute molecular functional loss ofCASK. Intriguingly, female mice with heterozygous deletion ofCASKin the cerebellum do not display neurodegeneration.

Conclusion

We suggest that X-linked neurodevelopmental disorders likeCASKmutation and Rett syndrome are pathologically neurodegenerative; random X-chromosome inactivation in heterozygous mutant girls, however, results in 50% of cells expressing the functional gene, resulting in a non-progressive pathology, whereas complete loss of the only allele in boys leads to unconstrained degeneration and encephalopathy.