bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term evaluation of HVDC transmission line audible noise and its correlation with background noise
Authors: Shin Koo Yong , Oh Joon Arm , Kwon Gu Min , Ju Mun No , Woo Jeong Min
Published: September 2019

The audible noise (AN) generated by corona discharge from a full-scale, high-voltage direct-current (HVDC) transmission line was evaluated over a one-year period from December 2017 to November 2018. The double bipolar HVDC transmission line using a metallic return conductor was demonstrated using a full-scale tower having a height of 21 m in Gochang, Korea. The measured AN in an outdoor environment was statistically evaluated and compared in different seasons and weather conditions. The A-weighted spectrum of the HVDC corona noise exhibited a greater distribution than the background noise above 1.0 kHz in the frequency domain. Various background noises were considered and eliminated to improve the measurement accuracy. The highest AN levels were exhibited during the spring season. Individuals in the age range of 18–60 years were randomly selected to conduct a human-perception test. The results indicated that 15% of the participants became aware of the AN from the corona discharge when it was >5 dBA greater than the background noise. The AN was <36 dBA when the conductor surface gradient was <18 kV/cm with a six-bundle sub-conductor.
Argon metastable and resonant level densities in Ar and Ar/Cl2 discharges used for the processing of bulk niobium
Authors: Peshl Jeremy , McNeill Roderick , Sukenik Charles I. , Nikolić Milka , Popović Svetozar , Vŭsković Leposava
Published: September 2019

A comparative analysis of two popular spectroscopy techniques is conducted in a coaxial cylindrical capacitively coupled discharge designed for the plasma processing of superconducting radio frequency (SRF) cavities. The density of the metastable and resonant levels in Ar is measured in both Ar and Ar/Cl2 discharges to properly characterize the unique discharge system and aid in the development of a cavity etching routine. The first method, deemed the “branching fraction method,” utilizes the sensitivity of photon reabsorption of radiative decay to measure the lower state (metastable and resonant) densities by taking ratios of spectral lines with a common upper level. This method has been gaining popularity as it does not require any a priori knowledge about the electron energy distribution. The second method is a tunable diode laser absorption spectroscopy technique that measures the thermal Doppler broadening of spectral lines, from which the neutral gas temperature and lower state density of the transition can be evaluated. The two methods were conducted in tandem, while external parameters that were empirically determined to be important to the etching mechanism of SRF cavities are varied. Relationships between the excited state densities and the external parameters are presented for both spectroscopy methods and conclusions about the effects of these parameters on the discharge are stated when appropriate.
Almost pinning-free bismuth/Ge and /Si interfaces
Authors: Nishimura Tomonori , Luo Xuan , Matsumoto Soshi , Yajima Takeaki , Toriumi Akira
Published: September 2019

In this work, we investigated the band alignment at bismuth (Bi)/germanium (Ge) and Bi/silicon (Si) interfaces to understand the mechanism of strong Fermi level pinning (FLP) at element metal/Ge and/Si interfaces. Bi/Ge and/Si interfaces exhibit almost ideal alignment deviating from the trend of strong FLP at element metal/Ge and/Si interfaces. This result suggests that the strong FLP at element metal/Ge and/Si interfaces is mainly caused by the metal-induced gap states (MIGS) in case of the free electron density of metal, and that the weak FLP at direct metal/Ge and/Si interfaces including germanide/Ge and silicide/Si interfaces is comprehensively understandable from the MIGS in case of low electron density. Furthermore, we also discuss impacts of interface structures on the band alignment at the MIGS-weakened interface.
One-dimensional multiperiodic photonic structures: A new route in photonics (four-component media)
Authors: Panyaev I. S. , Yafarova L. R. , Sannikov D. G. , Dadoenkova N. N. , Dadoenkova Y. S. , Lyubchanskii I. L.
Published: September 2019

We study the transmittivity spectra of one-dimensional finite three-periodic photonic crystals of the structure [(ab)N(cd)M]K composed of four different layers a, b, c, and d being dielectric oxides Al2O3, SiO2, TiO2, and ZrO2, respectively. We analyze modification of the transmittivity spectra of near-infrared electromagnetic waves of the TE and TM polarizations in the vicinity of the photonic bandgaps with variations of the sub-cell numbers N and M and super-cell number K, the incidence angle, and the order of the layers in the structure. We propose the classification of three-periodic photonic crystals by the magnitude and sign of the optical contrast between the layers in pairs (ab) and (cd) forming the sub-cells and discuss common spectral properties as well as their differences in these structures.
Transport properties of topologically non-trivial bismuth tellurobromides BinTeBr
Authors: Pabst Falk , Hobbis Dean , Alzahrani Noha , Wang Hsin , Rusinov I. P. , Chulkov E. V. , Martin Joshua , Ruck Michael , Nolas George S.
Published: September 2019

Temperature-dependent transport properties of the recently discovered layered bismuth-rich tellurobromides BinTeBr (n = 2, 3) are investigated for the first time. Dense homogeneous polycrystalline specimens prepared for different electrical and thermal measurements were synthesized by a ball milling-based process. While the calculated electronic structure classifies Bi2TeBr as a semimetal with a small electron pocket, its transport properties demonstrate a semiconductorlike behavior. Additional bismuth bilayers in the Bi3TeBr crystal structure strengthens the interlayer chemical bonding thus leading to metallic conduction. The thermal conductivity of the semiconducting compositions is low, and the electrical properties are sensitive to doping with a factor of four reduction in resistivity observed at room temperature for only 3% Pb doping. Investigation of the thermoelectric properties suggests that optimization for thermoelectrics may depend on particular elemental substitution. The results presented are intended to expand on the research into tellurohalides in order to further advance the fundamental investigation of these materials, as well as investigate their potential for thermoelectric applications.
Electronic and vibrational relaxation dynamics of NH3 Rydberg states probed by vacuum-ultraviolet time-resolved photoelectron imaging
Authors: Svoboda Vít , Wang Chuncheng , Waters Max D. J. , Wörner Hans Jakob
Published: September 2019

Time-resolved dynamics of high-lying Rydberg states of ammonia (NH3) prepared by using a vacuum ultraviolet (VUV) pump (∼9.3 eV) and an ultraviolet (UV) probe (∼4.7 eV) pulse are reported using photoelectron imaging detection. After photoexcitation, two main features appear in the photoelectron spectrum with vertical binding energies of ∼1.8 eV and ∼3.2 eV and with distinctly different anisotropy parameters β of ∼1.3 and ∼0.7, respectively. This information allows the unambiguous assignment of the respective Rydberg states and disentangles the induced electronic and vibrational dynamics. The combination of velocity-map imaging with femtosecond VUV and UV pulses is shown to offer an attractive approach for studying the dynamics of high-lying Rydberg states of small molecules.
Efficient computation of demagnetizing fields for magnetic multilayers using multilayered convolution
Authors: Lepadatu Serban
Published: September 2019

As research into magnetic thin films and spintronics devices is moving from single to multiple magnetic layers, there is a need for micromagnetics modeling tools specifically designed to efficiently handle magnetic multilayers. Here, we show an exact method of computing demagnetizing fields in magnetic multilayers, which is able to handle layers with arbitrary spacing, arbitrary thicknesses, and arbitrary relative positioning between them without impacting the computational performance. The multilayered convolution method is a generalization of the well-known fast Fourier transform-based convolution method used to compute demagnetizing fields in a single magnetic body. In typical use cases, such as multilayered stacks used to study skyrmions, we show that the multilayered convolution method can be up to 8 times faster, implemented both for central processors and graphics processors, compared to the simple convolution method.
Improvements of mechanical properties of multilayer open-hole graphene papers
Authors: Xia Yuxuan , Li Yeyuan , Zhu Chunhua , Wei Ning , Zhao Junhua
Published: September 2019

Holes and defects can greatly reduce the mechanical properties of multilayer graphene sheets under different loading conditions due to the stress concentration near the hole edge in each in-plane sheet and the lack of interlayer carbon–carbon bonds between the layers. Here, we report a novel design of multilayer open-hole graphene papers (MLGPs) formed through interlayer covalent bonding at the hole edges of multilayer open-hole graphene sheets (MLGSs) under high temperature using molecular dynamics (MD) simulations. Our MD results show that the hybrid sp2–sp3 interlayer bonds of MLGPs can significantly improve their both tensile strength and interlayer shear strength. The tensile strength and interlayer shear strength of MLGPs increase by around 20% and 3 times by comparison with those of MLGSs with the same number of layers, respectively, which mainly depends on the uniformity of their interlayer bond distribution. This study can provide an effective way to improve the mechanical performances of multilayer graphene sheets with flaws and also offer corresponding guidance for the design of MLGS-based nanocomposites.
Statistical sensorless short-circuit fault detection algorithm for photovoltaic arrays
Authors: Maleki Amir , Sadeghkhani Iman , Fani Bahador
Published: September 2019

One of the main challenges for the conventional protection system of a photovoltaic (PV) array is the occurrence of light fault conditions including a low location mismatch fault, a fault with a high fault path resistance, and a fault under low solar irradiance because the fault current increment is not enough for triggering current-based protective devices. The operation of the maximum power point tracking system and utilizing blocking diodes may also result in a light fault condition. An undetected fault condition causes a potential fire hazard and energy loss. This paper proposes a waveshape based statistical fault detection algorithm for light fault detection. The proposed algorithm quantifies the waveshape tailedness of superimposed PV array power by the kurtosis function. The proposed algorithm is able to discriminate the light fault condition from severe partial shading and is also effective for open-circuit faults. In addition to no need for additional sensors, it does not require a training dataset and prior information about the PV array. The merits of the proposed algorithm are corroborated through several case studies on a simulation model of a test PV array considering the parameter uncertainty and the presence of noise in the signals.
Gaussian approximation potential for studying the thermal conductivity of silicene
Authors: Zhang Cunzhi , Sun Qiang
Published: September 2019

Due to the compatibility with the well-developed Si-based semiconductor technology, the properties of silicene and silicene-based materials have attracted tremendous attention. Among them, the thermal conductivity (TC) is of special importance for electronic devices. However, unlike graphene, the poor quality of empirical potentials hinders the reliable evaluation of TC for silicene using molecular dynamics (MD). Here, we present a Gaussian approximation potential (GAP) for silicene based on ab initio derived training data. The potential can precisely describe the geometries, mechanical properties, as well as phonon dispersion of free-standing sheet, outperforming any other empirical ones. Using sinusoidal approach-to-equilibrium MD simulations based on the GAP potential, the TC of silicene is found to be 32.4±2.9W/mK at room temperature. Importantly, our result achieves a good agreement with Boltzmann transport equation (BTE) based first-principles predictions (∼30W/mK), such that the TC value of silicene is confirmed via both MD and BTE; thus, we prove that the accuracy of machine learning potentials, like GAP, can enable a faithful prediction of TC at a density functional theory (DFT) level.
Revisiting the protomotive vectorial motion of F
0
-ATPase
Authors: Bai Chen , Warshel Arieh
Published: September 2019

Significance

The F
0
F
1
-adenosin triphosphate (ATP) synthase energy conversion under a proton gradient is fundamental in living cells. However, the detailed mechanism has been poorly understood due to the lack of structural information near subunit a. Here, we explored the free energy landscape of the proton transfer pathway at F
0
in the recent cryoelectron microscopy cF
1
F
0
structure of spinach chloroplast ATP synthase by using our coarse-grained model. Our calculated landscape reproduced the correct unidirectionality of the rotation of F
0
. It is found that the directionality is mainly due to the coupling between the change in the electrostatic energy of the c-ring conformational change and the proton transfer pathway. This work provides guidance for investigating other proton-driven mechanochemical processes.
Mechanism of activation of the human cysteine desulfurase complex by frataxin
Authors: Patra Shachin , Barondeau David P.
Published: September 2019

Significance

In humans, essential iron-sulfur (Fe-S) cluster cofactors are synthesized using an assembly complex that depends on the protein frataxin (FXN). The physiological function of FXN, which is linked to the fatal neurodegenerative disease Friedreich’s ataxia (FRDA), is still under debate. Here, we show that FXN accelerates Fe-S cluster formation by positioning a mobile loop cysteine of the assembly complex to interact with the substrate and function as an acid, nucleophile, and sulfur carrier during the reaction. Our architectural switch model suggests that FXN controls Fe-S cluster biosynthesis by inducing an unusual rearrangement of protein subunits in the assembly complex. These results provide mechanistic insights into this critical biological process and establish a foundation for the design of new FRDA treatments.
La variación lingüística del vocativo en el lenguaje juvenil madrileño
Authors: De Latte Fien , Enghels Renata
Published: September 2019

This paper investigates the formal and functional variation of the vocative in contemporary Spanish teenage talk. For this purpose, all vocative occurrences found in conversations between teenagers in theCorpus Oral de Madrid-2016are analyzed. The vocative is known to be highly productive in Spanish teenage talk, on both formal and functional levels. First, we provide the inventory of vocative forms used by Madrilenian teenagers, examine their origin and describe their semantic-pragmatic features, with special attention for the nominal vocative expressions used as symbols of in-group identity. The second part disentangles the pragmatic-discursive functions assumed by these forms, by taking into account the vocative’s multifunctionality. Teenagers tend to use vocatives as a phatic mechanism which allows them to control the contact with their interlocutor(s).
Microstructural evolution and strain hardening mechanism of a boron-containing metastable austenitic steel
Authors: Li Cheng , Li Feng , Liang Juhua , Cao Ronghua , Zhao Zhengzhi
Published: September 2019

Quantitative tensile tests were carried out to study the microstructural evolution and strain hardening mechanism of a boron-containing metastable austenitic steel with 13 wt-% Mn and 0.30 wt-% B. The results indicate that the great mechanical properties come from two-stage TRIP effect and the true stress–strain curve can be divided into three stages during the tensile process. In the initial stage, part of the initial austenite transformed to ϵ-martensite through the stacking faults. Then, α’-martensite was formed from austenite directly or through the ϵ-martensite formation, which led to a great rise on the strain hardening rate in this stage. In the last stage, decline of the strain hardening rate was observed due to the co-work between multiple phases and voids.
Improved iterative tomographic reconstruction for x-ray imaging with edge-illumination
Authors: Modregger Peter , Meganck Jeff , Hagen Charlotte K , Massimi Lorenzo , Olivo Alessandro , Endrizzi Marco
Published: September 2019

Iterative tomographic reconstruction has been established as a viable alternative for data analysis in phase-sensitive x-ray imaging based on the edge-illumination principle. However, previously published approaches did not account for drifts of optical elements during a scan, which can lead to artefacts. Up to now, the strategy to reduce these artefacts was to acquire additional intermediate flat field images, which were used to correct the sinograms. Here, we expand the theoretical model to take these effects into account and demonstrate a significant reduction of (ring)-artefacts in the final reconstructions, while allowing for a significant reduction of scan time and dose. We further improve the model by including the capability to reconstruct combined absorption and phase contrast slices, which we experimentally demonstrate to deliver improved contrast to noise ratios compared to previously employed single shot approaches.
Helicity transport and dynamo sustainment for helical plasma states
Authors: Paccagnella R
Published: September 2019

Plasma states dominated by single helical modes are often observed in the Reverse Field Pinch (RFP) plasma confinement devices. In this paper the properties of these states are studied on the basis of a relaxation model that assumes the existence of several topological invariants related to the dominant mode. It is hypothesized that the value of the first invariant in this chain, is determined by the existence of a plasma dynamo mechanism that transport helicity. This hypothesis enables us to determine the steady state properties of the plasma equilibrium and some other interesting physical consequences. Further, by considering the properties of the transfer of helicity from the mesoscale (fluctuations) to the macroscale (equilibrium), through the dynamo field, a nonlinear dynamical model can be constructed, that evolves in time to a steady state with a non-vanishing dynamo field, when helicity is injected in the system, as in the case of the ohmic sustained RFP, while the dynamo oscillates initially, but is damped later in time, for vanishing helicity input.
Two-axis cavity optomechanical torque characterization of magnetic microstructures
Authors: Hajisalem G , Losby J E , de Oliveira Luiz G , Sauer V T K , Barclay P E , Freeman M R
Published: September 2019

Significant new functionality is reported for torsion mechanical tools aimed at full magnetic characterizations of both spin statics and dynamics in micro- and nanostructures. Specifically, two orthogonal torque directions are monitored and the results co-analyzed to separate magnetic moment and magnetic susceptibility contributions to torque, as is desired for characterization of anisotropic three-dimensional structures. The approach is demonstrated through application to shape and microstructural disorder-induced magnetic anisotropies in lithographically patterned permalloy, and will have utility for the determination of important magnetic thin-film and multilayer properties including interface anisotropy and exchange bias. The results reflect remarkable sensitivity of the out-of-plane magnetic torque to the nature of small edge domains perpendicular to the applied field direction, and also contain tantalizing indications of direct coupling to spin dynamics at the frequency of the mechanics.
Spin-valley filter effect and Seebeck effect in a silicene based antiferromagnetic/ferromagnetic junction
Authors: Niu Zhi Ping
Published: September 2019

The presence of the coupled spin and valley degrees of freedom makes silicene an important material for spintronics and valleytronics. Here we report a spin-valley filter effect in a silicene based antiferromagnetic/ferromagnetic junction. It is found that at zero Fermi level a valley locked bipolar spin filter effect is observed, where in a broad gate voltage range in one valley one spin (the other spin) electrons contribute to the current under the positive (negative) bias, but in the other valley the transport is forbidden. At the finite Fermi level a valley locked fully spin-polarized current can exist under both the positive and negative biases. Furthermore, at the high Fermi level by reversing the bias direction, the spin filter effect can switch to the valley filter effect. In addition, by changing the sign of the Fermi level, the spin polarization direction of the current can be reversed. If a temperature bias is applied, the spin-dependent Seebeck effect (SSE) always exists. With increasing the temperature bias, the system undergoes three regions: valley locked SSE, normal SSE and valley Seebeck effect. Moreover, by tuning the interlayer electric field, three phases: thermally induced valley locked spin filter effect, valley Seebeck effect and valley mixed Seebeck effect are observed.
Numerical simulation of critical dissipative non-equilibrium quantum systems with an absorbing state
Authors: Gillman Edward , Carollo Federico , Lesanovsky Igor
Published: September 2019

The simulation of out-of-equilibrium dissipative quantum many body systems is a problem of fundamental interest to a number of fields in physics, ranging from condensed matter to cosmology. For unitary systems, tensor network methods have proved successful and extending these to open systems is a natural avenue for study. In particular, an important question concerns the possibility of approximating the critical dynamics of non-equilibrium systems with tensor networks. Here, we investigate this by performing numerical simulations of a paradigmatic quantum non-equilibrium system with an absorbing state: the quantum contact process. We consider the application of matrix product states and the time-evolving block decimation algorithm to simulate the time-evolution of the quantum contact process at criticality. In the Lindblad formalism, we find that the Heisenberg picture can be used to improve the accuracy of simulations over the Schrödinger approach, which can be understood by considering the evolution of operator-space entanglement. Furthermore, we also consider a quantum trajectories approach, which we find can reproduce the expected universal behaviour of key observables for a significantly longer time than direct simulation of the average state. These improved results provide further evidence that the universality class of the quantum contact process is not directed percolation, which is the class of the classical contact process.
Fibre-optic based particle sensing via deep learning
Authors: Grant-Jacob James A , Jain Saurabh , Xie Yunhui , Mackay Benita S , McDonnell Michael D T , Praeger Matthew , Loxham Matthew , Richardson David J , Eason Robert W , Mills Ben
Published: September 2019

We demonstrate the capability for the identification of single particles, via a neural network, directly from the backscattered light collected by a 30-core optical fibre, when particles are illuminated using a single mode fibre-coupled laser light source. The neural network was shown to be able to determine the specific species of pollen with ∼97% accuracy, along with the distance between the end of the 30-core sensing fibre and the particles, with an associated error of ±6 μm. The ability to be able to classify particles directly from backscattered light using an optical fibre has potential in environments in which transmission imaging is neither possible nor suitable, such as sensing over opaque media, in the deep sea or outer space.
Altered Collection Interfaces in Hematopoietic Progenitor Collection of Sickle Cell Patients
Authors: Tsai Jonathan , Manis John , Ching Kimberly
Published: September 2019

Sickle cell disease (SCD) results from a point mutation in the beta globin gene leading to abnormal hemoglobin production and, correspondingly, abnormal sickling of erythrocytes that result in chronic anemia and vaso-occlusive crises. Patients with sickle cell are commonly treated with lifelong transfusions or hydroxyurea to increase fetal hemoglobin to ameliorate sickling. Evolving therapies are aimed at correcting known mutations with gene therapy on autologous hematopoietic stem and progenitor cells (HSCs), indicating a growing need for optimal stem cell collections from SCD patients. Recent studies have shown the safety and efficacy of plerixafor to increase peripheral CD34+ cells, enhancing collection. Here we show that standard apheresis collection procedures from sickle cell patients are inefficient when compared to healthy donors. Eleven patients with SCD were recruited to receive plerixafor and followed by peripheral CD34+ cell monitoring and apheresis collection. Overall, efficiency ranged from 2% to 55% with no correlation to total peripheral CD34+ cell count. To better understand where the CD34+ cells sedimented in the apheresis instrument, we collected different layers of the interface ranging from 3% to 10% estimated Hct and found that deeper layers with higher hematocrit (7.5%-10%) are enriched for CD34+ cells when compared to historical donors with healthy red cells. All patients had undergone red cell exchange prior to collection, yet this intervention did not prevent the altered sedimentation of CD34+ cells. These findings indicate that CD34+ cells from SCD patients sediment at a deeper, higher Hct interface layer during apheresis and support the altered collection practices for the efficient collection of HSCs for cellular therapies.
Thromboelastography in Trauma: A 1-Year Institutional Experience
Authors: Wells David , Hess John R , Sabath Daniel E
Published: September 2019

Viscoelastic testing to assess the overall clotting ability of a patient’s whole blood, such as thromboelastography (TEG), has risen in popularity over the past several years due its holistic assessment and rapid turnaround time, most notably in the realm of liver transplants and complex cardiac surgery. In the setting of trauma and assessing the concomitant coagulopathy, the rapid turnaround time and ability to assess for hyperfibrinolytic states had led to it being requested at our institution despite variable result interpretation and lack of reproducibility in previous studies. In response, our institution’s laboratory made this available at our hospital, which includes a large level 1 trauma center serving multiple states, with the aim of reassessing its utility after a 1-year period. Following the first year of use, data that were evaluated included TEG values and conventional laboratory testing temporally associated with the TEG order, including platelet count and fibrinogen level. Retrospective chart review was also performed to determine indication and context of testing, as well as for assessment of resulting interventions. Seventy-three samples from 58 patients were tested during the 1-year period, 30 of whom were admitted for trauma and 20 of whom were evaluated during the critical initial acute resuscitation period. Among the trauma patients, the majority of TEG samples (75.6%) did not demonstrate any abnormality. A primary reason cited by trauma surgeons for the need for TEG was its ability to accurately identify states of hyperfibrinolysis to determine the need for therapeutic agents such as tranexamic acid. In this regard, no evidence of hyperfibrinolysis was identified in any of the trauma patients. In fact, only a single hyperfibrinolytic sample was identified, corresponding to a nontrauma patient who had received a thrombolytic agent (alteplase) prior to TEG testing. Additionally, 75% of acute trauma patients received tranexamic acid, which was nearly always administered prior to the TEG sample being drawn. No evidence of TEG results affecting patient management was identified. As a result of the retrospective review of the data, use of TEG in the trauma population at our institution dramatically declined. We present this institutional review as an example of performing data review to influence test utilization practices.
Pending Log Monitors: Implementation for Improved Lab Efficiency
Authors: Perrone Marie , Behrens Caitlin , Lee Arthur , Pac Lincoln , Hoffman Noah
Published: September 2019

Hospital labs are increasingly consolidating into larger hospital systems with centralized testing locations. Specimens collected at disparate sites need to be transported to different locations for testing. Our LIS (Sunquest FlexiLab) does not provide a real-time display of specimens in need of transport to other locations. The current system lists pending specimens in paper printouts. The printouts have a difficult-to-read format, fail to account for certain add-on tests, and leave room for human error. In addition, IT staff must maintain test groups that are specific to each sending and receiving facility pair. This is a costly use of IT resources and is error prone due to test menu differences at each facility. In the current study, we evaluated the current system of batching specimens for transport and then designed a web-based application to provide a dynamic display of transport batches. The web-based application that we developed is called a “transport batch monitor” (TBM). The TBM displays specimens that need to be sent to another location for testing. This application was implemented in Python using the Flask microframework. Data are transferred in JSON format from Sunquest every 3 minutes using custom Caché ObjectScript routines. The application can be accessed with a secure login from any computer with Internet access and is displayed on large, fixed monitors in locations where transport batches are assembled. The display shows pertinent information for lab techs to be able to locate specimens that need to be sent out and is color-coded for ease of use. Metrics used to evaluate the current system included timing studies, surveys of lab staff performing the task, and paper usage. The process of collecting and batching specimens for transport to another facility took on average 24 minutes and required on approximately 22 sheets of paper. Anecdotally, specimens had historically been missed, especially when clinicians ordered add-on tests on specimens from days prior due to the way the LIS generated the printouts. Although 74% of techs surveyed reported that the task was somewhat easy or very easy, 32% were somewhat dissatisfied with the current system, and 40% said that the current paper printouts were either very unclear or somewhat unclear. Postimplementation metrics will be collected once the TBM has been implemented. We hypothesize that the transport batch monitor is a simple, inexpensive web-based tool that can greatly improve the day-to-day functioning of the lab. We hope it will improve efficiency and tech satisfaction, and reduce errors.
Genetic Testing to Resolve the Source of Hemolytic Antibody in Solid Organ Transplantation
Authors: Samraj Annie N , Morse Ryan , Krumm Niklas , Pagano Monica B , Hess John R , Tsang Hamilton
Published: September 2019

Introduction

Antibody-mediated hemolysis arising in the face of solid organ transplant can be devastating. Some degree of passenger lymphocyte syndrome is said to occur in up to 10% of ABO mismatched renal transplants, 40% of ABO mismatched liver transplants, and 70% of ABO mismatched heart-lung transplants, a reflection of the number of memory B-cells transplanted with the organ. Passenger lymphocyte syndrome is less common with minor antigens but can still be severe.

Materials and Methods

A series of patients developed immune hemolytic anemia after solid organ transplantation. Conventional serologic testing was performed using tube and solid-phase testing. Molecular testing was performed using gene-chip array.

Results

In patients receiving a minor antigen mismatched organ transplant and multiple allogenic red cell transfusions, serologic methods proved insufficient to resolve the source of minor blood group antibodies that arose in the aftermath of transplant. Genetic testing was able to clearly resolve donor and recipient types.

Conclusions

Passenger lymphocyte syndrome after mismatched organ transplantation is not rare. The mixtures of organ donor, recipient, and other transfused RBCs profoundly limit the usefulness of serologic testing. Genetic assignment of minor blood types to donor and recipient can guide therapy and inform prognosis.
Accuracy of Nanosphere Verigene Gram-Negative Blood Culture (BC-GN) Test for Rapid Detection of Extended-Spectrum Beta-Lactamases (ESBLs) From Positive Blood Cultures
Authors: Otero Dennise , Patros Clay , McElvania Erin , Singh Kamaljit
Published: September 2019

Background

The rapid and accurate detection of ESBL production in Gram-negative rod (GNR) bacteremia is critical as recent data suggest that carbapenem treatment decreases mortality. At the same time, avoiding widespread empiric carbapenem prescribing is an important goal of antimicrobial stewardship teams. The aim of this retrospective review was to determine the accuracy of a nucleic acid–based test, Luminex Verigene BC-GN panel, to detect ESBL-positive GNRs direct from blood cultures.

Methods

The Verigene BC-GN was performed on all first positive GNR blood cultures. In addition, routine antibiotic susceptibility testing was performed on all isolates by the disk-diffusion method and included phenotypic ESBL testing using cefotaxime and ceftazidime with and without clavulanate. Escherichia coli, Klebsiella spp., and Proteus mirabilis–positive blood cultures were identified as ESBL producers through either Verigene or phenotypic disk testing. Positive GNR blood cultures from February 2016 to July 2017 were included for review. The primary objective was to determine the sensitivity and specificity of Verigene for detection of ESBLs. The secondary objective was assessing the percent of community-onset and hospital-acquired ESBL-positive blood cultures.

Results

There were 83 positive blood cultures with ESBL producing GNR included in the primary review. A total of 82 of 83 positive GNR blood cultures were CTX-M gene positive via Verigene (sensitivity 98.8%). All 83 cultures were confirmed as ESBL producers via phenotypic tests. There were no positive Verigene cases with negative phenotypic results. All 68 ESBL E coli–positive cultures were detected by Verigene (100%), 10 ESBL K pneumoniae (100%), and four of the five ESBL P mirabilis–positive cultures (80%). Of the 73 results available for review in the secondary objectives, 68 were community onset (93%) and five were hospital acquired (7%).

Conclusion

The majority of ESBL-positive blood cultures in a low-prevalence setting were due to CTX-M producers. The Luminex Verigene BC-GN was accurate in detecting ESBL-producing Enterobacteriaceae from blood cultures and can be reliably used to guide antimicrobial therapy.
Evaluation of the Clinical Utility of Factor V, VII, and VIII Assays in Assessment of DIC
Authors: Carll Timothy , Mikrut Krzysztof , Wool Geoffrey
Published: September 2019

Disseminated intravascular coagulation (DIC) is a hematologic emergency that requires prompt diagnosis and intervention. The International Society of Thrombosis and Hemostasis (ISTH) has developed a scoring system to diagnose life-threatening DIC, which is based upon routine coagulation lab assays, including PT, D-dimer, fibrinogen, and platelet count. Laboratory assays for coagulation factors V (FV) and VII (FVII) are commonly used to evaluate for abnormal liver function in patients with abnormally elevated PT/INR. They are also frequently ordered as part of workup for DIC, in combination with factor VIII (FVIII), at UChicago Medicine. However, these coagulation factors are not part of the guideline-based DIC workup, and their utility in the evaluation of DIC is not clearly defined. A retrospective review of orders containing at least factors V, VII, and VIII was performed at UChicago Medicine ranging from December 1, 2016, through November 30, 2017. Results for corresponding coagulation lab results, anticoagulation therapy, and factor-replenishing therapy (vitamin K, plasma, cryoprecipitate, and factor concentrates) were pooled. Patient charts were reviewed for DIC diagnosis by clinical suspicion (defined by keyword searches of clinician documentation) and by ISTH scoring. In total, 117 patients were reviewed. Only 47 had complete coagulation data to perform ISTH scoring. Of these, 30 met ISTH criteria for DIC (64%). No patient was diagnosed with DIC based on abnormal coagulation factor assays in the absence of abnormal screening coagulation results. The most common underlying diagnosis in those meeting ISTH criteria was sepsis. A statistically significant lower FV level was observed in those meeting ISTH criteria (P < .001, one-tail), but no such differences were observed in FVII or FVIII levels (P = .059, .224). FVIII was only reduced in 2 of the 117 reviewed patients (2%), and FVIII levels were rarely repeated to trend for any decrease in FVIII levels. FVII was reduced in 88 patients, of which 57 also showed reduced FV levels. Twenty-eight patients received factor replenishing therapy shortly before their initial lab draw for factor testing. Of the 88 patients with reduced FVII, 61 received factor-replenishing therapy within 3 days following the lab draw. We concluded that at this institution, factor level assays are often ordered without first obtaining complete screening coagulation assays, which represents poor utilization of laboratory resources due to cost and time constraints placed by factor assay testing. Factors VII and VIII are ineffective at evaluation of DIC, and factor VIII levels as currently utilized are of particularly little value given its near-universal elevation in the inpatient setting and lack of repeat testing for trend. We also took this opportunity to review the clinical response to abnormal testing results and found that the majority of abnormal factor testing results in the reviewed setting prompted therapeutic correction.
Prothrombin Complex Concentrate Versus Plasma in Patients With Liver Disease
Authors: Knoeckel Christopher , Roberts Sammie , Pokrandt Paul , Stokes Amber , Berg Mary
Published: September 2019

Prothrombin complex concentrate (PCC) is FDA approved for warfarin reversal but is often used for coagulopathy and hemorrhage in patients with liver disease. While studies have explored its use during liver transplant, less is known about its safety and efficacy for other indications in patients with liver disease. Our objective was to retrospectively compare INR and mortality in patients with liver disease treated with PCC versus plasma. After obtaining institutional review board approval, we conducted retrospective chart review of patients with liver disease who received PCC. Control patients with liver disease who received plasma alone were matched based on indication for treatment. Outcomes were first post-PCC or post-plasma INR and mortality during admission. Twenty-one patients with liver disease who received PCC were identified; 21 who received plasma alone were matched. Two PCC patients and 1 plasma patient were excluded due to insufficient data in the medical record to calculate MELD scores. Statistics were calculated in Microsoft Excel (Version 1901). The most frequent indications were coagulopathy reversal and hemorrhage. The most common liver disease etiologies in both groups were alcohol and hepatitis C. The mean MELD score for the PCC group was higher than that for the plasma group (35 ± 7 vs 27 ± 9, P = .01). Mean baseline INR was similar between groups (PCC group, 4.0 ± 2.8 vs plasma group, 3.8 ± 3.8, P = .88). While INR decreased somewhat without a significant difference between groups (PCC group, 2.8 ± 1.5 vs plasma group, 2.4 ± 1.2, P = .44), mortality during admission was significantly higher in patients who received PCC (15 [71%] vs 5 [33%], P < .01). Of the 15 PCC patients who died, 5 died with hemorrhage as a contributing factor, 3 with disseminated intravascular coagulopathy, and 1 with both; 1 other patient died with TIPS thrombus as a contributing factor. Of the 5 plasma patients who died during admission, 2 died with hemorrhage as a contributing factor, and none died with clotting complications. The difference in mortality between groups is likely confounded by more severe disease in the PCC group as evidenced by higher mean MELD score. It is unclear whether the higher number of bleeding and clotting complications in the PCC group is related to PCC administration or is a consequence of more advanced liver disease in these patients. The higher mean MELD score in the PCC group may reflect a tendency for providers to prescribe PCC for patients with more severe liver disease, who may not tolerate the large fluid boluses required for coagulopathy reversal with plasma. In conclusion, PCC does not appear to be superior to plasma for INR reversal in patients with liver disease. Further study is needed to determine efficacy and safety of PCC in patients with liver disease and should include comparison of patient groups with similar disease severity.
Automated Clinical Chemistry Platform Performance Across Two Academic Medical Centers
Authors: Brown Megan , Colby Jennifer , Feldhammer Matthew , Nichols James
Published: September 2019

Our objective was to define the performance of automated chemistry platforms at two large academic medical centers by calculating and comparing sigma metrics for 28 analytes. Performance characteristics of chemistry assays on two Roche Cobas analyzers and four Abbott Architect analyzers were estimated using 12 months of Bio-Rad quality control (QC) data at two concentrations. Method imprecision was calculated as the cumulative QC coefficient of variation (CV) across analyzers at each QC concentration and percent bias was calculated by comparison of analyzer QC mean to peer group means. Sigma values were calculated for each method as [(TEa – Bias%)/CV%] using allowable total error (TEa) from two sources: the CLIA evaluation limits and desirable biological variation. Average sigma values were generated for each site and graded as optimal, >6 sigma; good, 5 to 6 sigma; marginal, 3 to 5 sigma; or poor, <3 sigma. Analysis of NIST SRM1950 standards for a subset of analytes allowed an estimation of absolute bias. Sigma metrics were highly comparable across both study sites. Considering CLIA TEa, just over half (Roche 57%; Abbott 54%) of the 28 analytes met the six-sigma standard of performance. The highest performing groups to meet or exceed the six-sigma standard were lipids (cholesterol, LDL, HDL, and triglycerides) and enzymes (ALP, ALT, AST, CK, GGT, LDH, and lipase). Electrolytes (Na, K, Cl, Mg) and metabolites (total bilirubin, BUN, CO2) failed to meet six-sigma. Notably, there were dramatic differences in sigma values calculated using CLIA and Ricos TEa criteria. Almost 40% of the analytes had at least one QC that performed poorly using Ricos criteria. Only 4 of the 28 assays (CK, GGT, lipase, and triglycerides) demonstrated optimal performance at both study sites using Ricos and CLIA criteria. Overall, 11 analytes at each institution exhibited unacceptable performance using Ricos criteria as opposed to only two analytes with the CLIA TEa limits. Analysis of NIST SRM1950 at both study sites gave comparable sigmas for all analytes except total bilirubin, cholesterol, Mg, and total protein. Neither Abbott nor Roche analyzers met six-sigma quality standards for all analytes tested. Overall assay performance across these two platforms at two major academic medical centers was almost identical. CLIA TEa and RICOS TEa criteria are significantly different, with wider limits of acceptability for CLIA. Variations between individual analyzers and manufacturers and limitations in automation would make tailored QC rules based on sigma metrics difficult to implement in a high-volume laboratory.
Amylase and Lipase Co-ordering in the Workup of Pancreatic Disorders Is Unnecessary and Costly: An Institutional Lab Utilization Study
Authors: Hupp Meghan , Peterson Nicholas , Buchner Sasha , Karger Amy B
Published: September 2019

Background

Acute pancreatitis is the most common gastrointestinal cause of hospitalization in the United States. Amylase and lipase are commonly ordered together in the workup of suspected pancreatitis at our institution (a large academic medical center), despite meta-analyses and evidence-based guidelines that recommend the use of lipase alone. Lipase has more diagnostic accuracy, rises earlier, and stays elevated longer than amylase. Co-ordering amylase has not been shown to increase sensitivity or specificity. This study aims to explore how well amylase and lipase correlate in our patient population, and which marker more accurately detects acute pancreatitis when the results are discrepant.

Methods

The laboratory information system was queried for co-orders of amylase and lipase during a 2-month period (November 1, 2016, to December 31, 2016). The overall agreement and Cohen’s kappa were calculated. Discrepant results were separated from concordant results. Clinical data were extracted from the electronic medical record, including the rationale for ordering and relevant diagnosis code.

Results

There were 962 instances of amylase and lipase co-orders in the 2-month period. Of these, 138 had high amylase and lipase, and 694 had normal amylase and lipase concentrations. The overall agreement was 86.5% and Cohen’s kappa was 0.596 (moderate agreement) (P < .0001). There were 88 cases in which the lipase was elevated and the amylase was normal. Of these, 12 were acute pancreatitis and 76 were not. There were 42 cases in which the amylase was elevated and the lipase was normal; only one case out of 42 was acute pancreatitis. Further investigation into this case revealed that the patient was approximately 7 months status-post pancreas transplant. During this admission, he was diagnosed with “graft pancreatitis” and, while amylase remained elevated above the reference range for longer than lipase after treatment, both enzymes were increased at diagnosis (lipase 831 U/L [73-393 U/L] and amylase 194 U/L [30-110 U/L]). These data show that, had only lipase been ordered, no cases of acute pancreatitis would have been missed.

Conclusion

Amylase has been shown to be an inferior marker of acute pancreatitis compared to lipase, and many guidelines recommend the use of lipase alone. However, these tests are commonly co-ordered at our institution; in a given 2-month period, there were 962 co-order events. Of these, there were no cases of pancreatitis that would have been missed by ordering lipase alone. Our laboratory charges $50 per amylase assay; therefore $48,100 was spent on unnecessary amylase orders during the 2 months of this study. Lab test overutilization has been identified as an important problem; if addressed and curtailed, labs and hospitals can increase efficiency and cost savings.