bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Methods for Calculation the Load Angle of a Synchronous Generator Based on PMU Data
Authors: Tepikin Y.E. , Rafikov V.R. , Gaydamakin F.N.
Published: April 2023

The development of the Wide Area Measurement Systems (WAMS) in the Unified Electric Power System (UES) of Russia and using phasor measurement technology (or PMU technology) open up new prospects in the electric power system (EPS) operational dispatch and automatic control. PMU devices installation on synchronous generators (SG) allows to obtain information not only about currents and stator voltages phasors, but also information about the excitation current and excitation voltage. This set of high-precision measurements of the network state parameters, in the presence of generators mathematical models, provides the possibility of calculating such parameters, the direct measurements of which are very difficult. One of these parameters, which can be determined using PMU, is the load angle of the SG (the angle between the generalized voltage phasor and the generator EMF phasor in the dq axis system) in the steady states and transients. The value of the load angle can be used to analyze the static and dynamic stability, as well as to quantify the damping properties of the SG at low-frequency oscillations (LFO) of the power systems electrical parameters. This study analyzes the possibilities for calculating the load angle based on a typical set of generator PMU signals: stator current and voltage vectors, excitation current and voltage. Two methods for calculating the load angle in steady states and transients have been developed and implemented. The first method is based on solving a system of nonlinear algebraic equations, and the basis of the second method is the mathematical model of the SG. The presented methods were tested using the SimInTech software package. Further, using the developed methods, the load angles of two turbogenerators installed at the plants of the Russian UES were calculated according to the PMU data of the parameters of the electromechanical transient process.
Coherence indicators of generators for express assessment of electric power system transient stability
Authors: Efimov Dmitry , Stashkevich Sergey
Published: April 2023

A brief overview of the generator coherence indicators is presented, the areas and limitations of their applicability are indicated. The application of the area method for the rapid assessment of the transient stability of complex multi-machine electric power system based on the features of the dynamics of the system behavior, determined by the heterogeneous structure of the electrical network, is considered. A distinctive feature of the proposed approach is the use of the characteristics of the heterogeneity of the power system structure, which determine the presence of weak links (or cut-sets) of the electrical network, which are critical from the point of view of a possible violation of the system stability.
Investigation the influence of the parameters of the computational scheme on detecting the source of low-frequency oscillations
Authors: Butin Kirill , Popov Aleksandr , Rodionov Andrey
Published: April 2023

The dispatching control requires the ability to detect the source of low-frequency oscillations in the power system based on the online processing of synchrophasor measurements data. This is a complex task; therefore, new approaches to its solution and variations of existing ones are constantly emerging. As a rule, a short expression of the criterion of a particular method hides a number of stages of computational data processing. The number of possible implementations of these stages increases during the investigation. The set, settings, implementation of the stages of the computational scheme, and combination of these stages affect the final result. Earlier, the authors developed a high-performance software platform that allows describing computational schemes in a general way, and then performing calculations with specified sets of algorithms. In this paper, a generalized calculation scheme for the dissipating energy method is constructed, and experiments are performed showing the influence of details of the implementation of data processing stages on the result of the online detection of the source of lowfrequency oscillations.
The innovative EHV line and its main indicators
Authors: Tatyana Krasilnikova , Karomatullo Makhmudov , German Samorodov , Nikolay Novikov
Published: April 2023

Single-circuit EHV lines widely used all over the world have a significant drawback, consisting in the fact that with the most probable single-phase stable failures, the line is completely taken out of operation. In this paper, a single-circuit EHV line is considered, one phase of which is made in the form of two parallel semi-phases, any of which is used as a backup phase in emergency modes. To symmetrize the conditions in the middle of the line, the Series Capasitor (SC) are included in the two usual phases. The article presents an algorithm for calculating normal modes, the main indicators of an innovative 500 kV line, consisting in its increased capacity, reliability and economic efficiency. The main provisions are illustrated by the example of a 500 kV line with a length of 500 km.
Modelling of laboratory work in the science “Fundamentals of power supply” using an educational simulator based on a programmed logic controller
Authors: Kholikhmatov B.B. , Samiev Sh.S. , Erejepov M.T. , Nematov L.A.
Published: April 2023

Today, the use of programmable logic controller devices in the educational process brings great results. This study demonstrated the effectiveness of using a programmable logic controller (PLC)-based training simulator in modeling laboratory work on the subject of "Power Supply Fundamentals". The results show that the training simulator was considered effective in providing students with a flexible and safe way to learn PLC and power supply systems. Also, this article presents the working principle and algorithm of a model virtual simulator based on PLC that meets the requirements of modern education in the field of "Basics of Power Supply" developed during our research. At the same time, the methodologies used for the research are also widely covered.
Determination of the service area and location of transformer substations in the city power supply system
Authors: Melikuziev M.V.
Published: April 2023

The article proposes a theoretically based approach to determining the service areas and location of transformer substations (TS) in the case depending on the intensity of the electric load based on the area specified in the city power supply system. Rational use of service areas and determination of the optimal area by location will help regulate the city's power supply. As a result of the scientific approach in the article, the targeted use of a transformer substation in the municipal power supply system will achieve orderly development in the city, as well as a reduction in the waste of electricity in distribution power networks.
Regulation system by voltage booster transformer
Authors: Usmanov E.G.
Published: April 2023

In this article, the features of the oscillatory circuit are investigated in order to determine the possibility of their application for controlling thrusters when building new, simple and reliable circuits for regulating booster voltage stabilizers from the value of the supply voltage. In Ferro resonant circuits connected to a voltage source with low internal resistance, with a certain combination of parameters, oscillations are excited at the fundamental frequency, the initial phase of which has a shift relative to the initial phase of the applied voltage.
Modes and technological features of electrolysis consumers of electricity
Authors: Rasulov A.N. , Paxratdinov A.Dj.
Published: April 2023

The article analyzes the use of direct voltage and current for electrolysis consumers powered by valve controlled converters, generating higher harmonics into the network, consuming reactive power fr0om the network and significantly affecting the quality of electricity and the efficiency of the entire power supply system.
Reactive power compensation for sustainable development of power grids in cities of Uzbekistan
Authors: Saidkhodjaev A.G. , Bobojonov Y.M.
Published: April 2023

The article deals with relevant and much needed at this stage problems of reconstruction and modernization of urban power supply systems and issues of energy saving in urban power grids. For the first time, it is proposed to carry out energy saving in the residential and public sectors of the residential zone of cities on the basis of reactive power compensation. There are given an analysis of experimental studies and measurements of power consumption and based on them recommendations and ways of energy saving in urban power grids.
Improving the quality of 0.4 kV electricity in household appliances due to voltage regulation
Authors: Karimov Raxmatillo
Published: April 2023

The article discusses a way to improve the quality of electricity up to 0.4 kV household appliances through voltage regulation. As an actuator, a booster transformer with two secondary windings connected in accordance with the primary winding is used. High-speed non-contact voltage relays are used as a device that is sensitive to changes in the input voltage, as well as a device that switches the secondary windings of a booster transformer.
Ways to use intellectual platforms in the Republic of Uzbekistan
Authors: Salomova Sarvinoz
Published: April 2023

The article is scientifically based on the development of the activities of JSC “Ohangarontsement”, a cement producer in Uzbekistan in the digital economy, based on the use of intelligent platforms. Ways to reduce the cost and increase the efficiency of products based on digital information and communication technology are presented.
Early-Onset Pectus Excavatum Is More Likely to Be Part of a Genetic Variation
Authors: Billar Ryan , Heyman Stijn , Kant Sarina , Wijnen René , Sleutels Frank , Demirdas Serwet , Schnater J. Marco
Published: April 2023

Background Potential underlying genetic variations of pectus excavatum (PE) are quite rare. Only one-fifth of PE cases are identified in the first decade of life and thus are of congenital origin. The objective of this study is to test if early-onset PE is more likely to be part of genetic variations than PE that becomes apparent during puberty or adolescence.

Materials and Methods Children younger than 11 years who presented with PE to the outpatient clinic of the Department of Pediatric Surgery at our center between 2014 and 2020 were screened by two clinical geneticists separately. Molecular analysis was performed based on the differential diagnosis. Data of all young PE patients who already had been referred for genetic counseling were analyzed retrospectively.

Results Pathogenic genetic variations were found in 8 of the 18 participants (44%): 3 syndromic disorders (Catel–Manzke syndrome and two Noonan syndromes), 3 chromosomal disorders (16p13.11 microduplication syndrome, 22q11.21 microduplication syndrome, and genetic gain at 1q44), 1 connective tissue disease (Loeys–Dietz syndrome), and 1 neuromuscular disorder (pathogenic variation in BICD2 gene).

Conclusion Early-onset PE is more likely to be part of genetic variations than PE that becomes apparent during puberty or adolescence. Referral for genetic counseling should therefore be considered.

Trial Registration: NCT05443113
Electrical Stimulation for Children with Cerebral Palsy: A Meta-analysis for Randomized Controlled Trials
Authors: Liu Yu , Li Hongzhi
Published: April 2023

Background Different types of electrical stimulation (ES) showed diverse effects on children with cerebral palsy (CP). Previous studies reported inconsistent results for effects of ES on children with CP. The present study aimed to conduct a meta-analysis to summarize these diverse results.

Methods We searched for studies exploring effects of ES on children with CP in databases (PubMed and Web of Science) from their inception until December 2022. Standard mean differences (SMDs) and 95% confidence intervals (CIs) were computed using STATA 12.0 software.

Results The meta-analysis included 19 randomized controlled trials (including 265 CP patients in test group and 263 CP patients in corresponding control group). The study showed an increased improvement in gross motor function, walking speed, step length, and daily living activities in ES group compared with corresponding control group with random effects models (gross motor function: SMD = 2.04, 95% CI = 1.43–2.65; walking speed: SMD = 3.71, 95% CI = 1.49–5.92; step length: SMD = 1.89, 95% CI = 0.65–3.13; daily living activities: SMD = 5.18, 95% CI = 3.04–7.31), whereas the study showed no significant difference in change of muscle strength between ES group and the corresponding control group with a random effects model (SMD = 0.42, 95% CI = −0.12 to 0.97).

Conclusion The study demonstrated that ES might be used as therapy to improve gross motor function, gait, and daily living activities in children with CP.
Decarboxylative, Radical C–C Bond Formation with Alkyl or Aryl Carboxylic Acids: Recent Advances
Authors: Tibbetts Joshua D. , Cresswell Alexander J. , Askey Hannah E. , Cao Qiao , Grayson James D. , Hobson Sophie L. , Johnson George D. , Turner-Dore Jacob C.
Published: April 2023

The ubiquity of carboxylic acids as naturally derived or man-made chemical feedstocks has spurred the development of powerful, decarboxylative C–C bond-forming transformations for organic synthesis. Carboxylic acids benefit not only from extensive commercial availability, but are stable surrogates for organohalides or organometallic reagents in transition-metal-catalysed cross-coupling. Open shell reactivity of carboxylic acids (or derivatives thereof) to furnish carbon-centred radicals is proving transformative for synthetic chemistry, enabling novel and strategy-level C(sp3)–C bond disconnections with exquisite chemoselectivity. This short review will summarise several of the latest advances in this ever-expanding area.

1 Introduction

2 Improved Decarboxylative Arylations

3 sp3–sp3 Cross-Coupling of Carboxylic Acids with Aliphatic Bromides

4 sp3–sp3 Cross-Coupling of Carboxylic Acids with Aliphatic Alcohols and Amines

5 Doubly Decarboxylative sp3–sp3 Cross-Coupling of Carboxylic Acids

6 Decarboxylative C–C Bond Formation from (Hetero)aryl Carboxylic Acids

7 Conclusions
External Validation of a Prediction Model Assessing Risk of Delivery in Fetuses with Growth Restriction after Diagnosis of Abnormal Umbilical Artery Doppler
Authors: Yu Hope Y. , Wang Wei , Benson Carol B. , Doubilet Peter , Rouse Dwight J. , Little Sarah E.
Published: April 2023

Objective We have previously described a model using maternal, antenatal, and ultrasonographic characteristics to assess the risk of delivery within 7 days following diagnosis of abnormal umbilical artery Doppler (UAD) in pregnancies affected by fetal growth restriction (FGR). Therefore, we sought to validate this model in an independent cohort.

Study Design Retrospective, single referral center study of liveborn singleton pregnancies from 2016 to 2019 complicated by FGR and abnormal UAD (systolic/diastolic ratio ≥95th percentile for gestational age [GA]). Prediction probabilities were calculated by applying the original model (Model 1) to the current cohort (Brigham and Women's Hospital [BWH] cohort). The variables of this model include GA at first abnormal UAD, severity of first abnormal UAD, oligohydramnios, preeclampsia, and prepregnancy body mass index. Model fit was assessed with area under the curve (AUC). Two alternative models (Models 2 and 3) were created to identify a model with better predictive characteristics than Model 1. The receiver operating characteristics curves were compared using the DeLong test.

Results A total of 306 patients were assessed for eligibility, 223 of whom were included in the BWH cohort. Median GA at eligibility was 31.3 weeks, and median interval from eligibility to delivery was 17 days (interquartile range: 3.5–33.5). Eighty-two (37%) patients delivered within 7 days of eligibility. Applying Model 1 to the BWH cohort resulted in an AUC of 0.865. Using the previously determined probability cutoff of 0.493, the model was 62% sensitive and 90% specific in predicting the primary outcome in this independent cohort. Models 2 and 3 did not perform better than Model 1 (p = 0.459).

Conclusion A previously described prediction model to predict risk of delivery in patients with FGR and abnormal UAD performed well in an independent cohort. With high specificity, this model could assist in identifying low-risk patients and improve antenatal corticosteroid timing.

Key Points
Clinical Factors Associated with Intrapartum Presentation Change after Mechanical Cervical Ripening
Authors: Wilkie Gianna , Leung Katherine , Lauring Julianne
Published: April 2023

Objective The use of mechanical cervical ripening with balloon devices is common during induction of labor; however, there is risk for displacement of the fetal presenting part during its insertion. This study sought to investigate the clinical risk factors associated with an intrapartum presentation change from cephalic to noncephalic presentation after mechanical cervical ripening.

Study Design Data were obtained from the Consortium on Safe Labor, a multicenter retrospective study that abstracted detailed labor and delivery information from electronic medical records in 19 hospitals across the United States. All women with fetal cephalic confirmed position on admission undergoing induction of labor with mechanical cervical ripening were included. Women who had a cesarean delivery for noncephalic presentation were compared with women who had a vaginal delivery or cesarean delivery for other indications. Models were adjusted for nulliparity, multiple gestation, and gestational age.

Results A total of 3,462 women met inclusion criteria, with 1.3% (n = 46) having an intrapartum presentation change from cephalic to noncephalic presentation after mechanical cervical ripening. Those who had a cesarean delivery for an intrapartum presentation change were more likely to be nulliparous (82.6 vs. 65.4%, p = 0.01), less than 34 weeks' gestation (6.5 vs. 1.3%, p = 0.02), and have twins (6.5 vs. 1.2%, p = 0.02). In adjusted analysis, twins were associated with an increased odds of cesarean delivery for intrapartum presentation change (adjusted odds ratio [aOR]: 4.43; 95% confidence interval [CI]: 1.25–15.77), whereas multiparity reduced the odds (aOR: 0.38; 95% CI: 0.17–0.82).

Conclusion Nulliparity and multifetal gestation are associated with a cesarean delivery for an intrapartum presentation change after mechanical cervical ripening.

Key Points
Synthesis of a Heavy-Atom-Free BODIPY and its Photooxygenation of 1-Naphthol to 1,4-Naphthoquinone
Authors: Jiang Xin-Dong , Zhou Meizhu , Hu Xinhu , Zhang Dongxiang , Cui Tianfang
Published: April 2023

By using 1,5,6,7-dihydro-4H-indol-4-one, a carbonyl group was introduced onto a BODIPY photosensitizer. The resulting heavy-atom-free BODIPY is a highly effective producer of singlet oxygen with a calculated quantum yield (ΦΔ) of 0.68, compared with that of methylene blue (ΦΔ = 0.57). Photooxygenation of 1-naphthol to 1,4-naphthoquinone was achieved by using this heavy-atom-free BODIPY catalyst in the presence of white-light irradiation under air atmosphere. Our work demonstrated a practical example of the design of a heavy-atom-free BODIPY, capable of efficient singlet-oxygen generation, with a potential in photocatalysis.
A Rare Case of Fallopian Tube Metastasis Presenting as a Solitary Breast Mass
Authors: Sharma Swati , Padilla Rebekah , Marji Noor , Sharma Smita
Published: April 2023

Metastases to the breast from a nonmammary primary are rare. Primary fallopian tube carcinoma is one of the rarest malignancies of the female genital tract. Therefore, breast metastases from primary fallopian tube carcinoma are considered extremely rare.

In this article, we shared the case of serous carcinoma of fallopian tube with metastasis to an intramammary lymph node, presenting as a solitary breast mass. On initial staging 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography for this patient with serous carcinoma of fallopian tube, a solitary FDG avid breast mass was found, along with FDG avid multistation nodes. The breast mass was evaluated with diagnostic mammogram and ultrasound and eventually biopsy of this mass revealed metastatic lymph node from carcinoma of fallopian tube origin.
Surgical and Patient-Reported Outcomes of Open Perforator-Preserving Anterior Component Separation for Ventral Hernia Repair
Authors: Bustos Samyd S. , Kuruoglu Doga , Truty Mark J. , Sharaf Basel A.
Published: April 2023

Background Abdominal wall reconstruction is challenging for surgeons and may be life altering for patients. There are scant high-quality studies on patient-reported outcomes following abdominal wall reconstruction. We assess long-term surgical and patient-reported outcomes of perforator-preserving open anterior component separation (OPP-ACS) following large ventral hernia repair.

Methods A retrospective review of patients with large ventral hernia defects who underwent OPP-ACS performed by the authors (B.A.S., M.J.T.) was conducted between 2015 and 2019. Demographics, surgical history, operative details, outcomes, and complications were extracted. A validated questionnaire, Carolinas Comfort Scale (CCS), was used to assess postoperative quality of life.

Results Twenty-two patients (12 males and 10 females) with a mean age and BMI of 60.9 ± 10 years and 28.9 ± 4.8 kg/m2, respectively, were included. Mean follow-up was 28.5 ± 16.3 months. All had prior abdominal surgery; 15 (68%) for abdominopelvic malignancy, 3 (14%) for previous failed hernia repair, and 8 (36%) had history of abdominopelvic radiation. Overall, 16 (73%) hernias were in the midline, 4 (18%) in the right lower quadrant, 1 (4.5%) in the right upper quadrant, and 1 (4.5%) in the left lower quadrant. Mean hernia defect surface area was 145 ± 112 cm2. A total of 9 patients (40.9%) underwent bilateral component separation, whereas 13 (59.1%) had unilateral. Bioprosthetic mesh was used in all patients as underlay. Mean mesh size and thickness were 545.6 ± 207.7 cm2 and 3.4 ± 0.5 mm, respectively. One patient presented with a minor wound dehiscence, and two presented with seromas not requiring aspiration/evacuation. One patient had hernia recurrence 22 months after surgery. One patient was readmitted for partial small bowel obstruction and one required wound revision. A total of 14 (65%) patients responded to the CCS questionnaire. At 12 months, mean score for all 23 items was 0.29 ± 0.21 (0.08–0.62), which corresponds to absence or minimal symptoms.

Conclusion The OPP-ACS is a safe surgical option for large, complex ventral hernias. Our cases showed minimal complication rate and hernia recurrence, and our patients reported significant improvement in life quality.
Patient-Reported Outcome–Based Prediction for Postdischarge Complications after Lung Surgery
Authors: Yang Ding , Wei Xing , Hong Qian , Zhao Chenguang , Mu Juwei
Published: April 2023

Background Patients undergoing lung tumor surgery may experience various complications after discharge from the hospital. Using patient-reported outcomes (PROs), this study attempted to identify relevant indicators of postdischarge complications after lung tumor surgery and develop a predictive nomogram model to evaluate the risk for individual patients.

Methods Patients who underwent lung tumor surgery between December 2021 and June 2022 were included in this study. PROs were assessed using the Perioperative Symptom Assessment for Lung Surgery scale and were assessed preoperatively at baseline, on postoperative day 1 (POD1) 1 to POD4, and then weekly until the fourth week. A random forest machine learning prediction model was built to rank the importance of each PRO score of patients on POD1 to POD4. We then selected the top 10 variables in terms of importance for the multivariable logistic regression analysis. Finally, a nomogram was developed.

Results PROs, including coughing (POD3 and POD4), daily activity (POD1), and pain (POD1 and POD2), were associated with postdischarge complications in patients undergoing lung tumor surgery. The predictive model showed good performance in estimating the risk of postdischarge complications, with an area under the curve of 0.833 (95% confidence interval: 0.753–0.912), while maintaining good calibration and clinical value.

Conclusion We found that PRO scores on POD1 to POD4 were associated with postdischarge complications after lung tumor surgery, and we developed a helpful nomogram model to predict the risk of postdischarge complications.
Grand strategy and the construction of the national interest: the underpinnings of Sino-US strategic competition
Authors: Mokry Sabine
Published: April 2023

The ubiquity of Sino-US strategic competition calls for uncovering its underpinnings by systematically comparing their grand strategies. This article examines how both governments have constructed their countries’ national interest since the 2008 global financial crisis. Through quantitative content analysis, it traces the relative salience of different components of the construction of the national interest detailing differences and shifts in emphasis and divergences within both governments. Whereas the Chinese government increasingly emphasized taking on a leadership role in international affairs, the US government became more concerned about the country’s security and economic standing. Between Chinese actors, the most pronounced divergence appeared regarding the importance of territorial defense. US actors disagreed about the importance of promoting the country’s values abroad. These findings suggest that a long-term perspective is needed to uncover the underpinnings of great power competition. Researchers and policy-makers must listen to different foreign policy actors, even under centralized authoritarian rule.
Cs2KMnCl6: A possible half-metallic double perovskite for spintronics
Authors: Ramawat Surbhi , Kukreti Sumit , Kale Abhijeet J. , Dutt Rajeev , Chakrabarti Aparna , Dixit Ambesh
Published: April 2023

Materials with 100% spin polarisation, high-speed conduction electrons, high Curie temperatures, and ferromagnetic ground state are known for spintronics. Double perovskites (DPs) with these features are becoming popular nowadays. Herein, introducing another halide-based DP, we determined that Cs2KMnCl6 is a robust intrinsic 3d ferromagnetic half-metal with a 4 μB magnetic moment per unit cell. It exhibits the metallic band for the spin-up configuration, enabling their smooth transport, together with a massive gap of ∼4.51 eV for the spin-down states, thus protecting it from spin–flip transitions. The calculated structural and elastic stability criteria substantiate the stability of the cubic Cs2KMnCl6 double perovskite with a F m 3 ¯ m symmetry. The 3d states of Mn mainly contribute to the robust ferromagnetism above room temperature and show Tc ∼ 534 K. The different Fermi surface topologies within the Brillouin zone establish its conducting nature for up-spin channels and favor the spin-polarized transport. Moreover, the spin-polarized dielectric constant and absorption coefficient also evidenced the half-metallic characteristics. Therefore, our findings offer a novel DP system for investigating spintronic application.
Quantifying burned area of wildfires in the western United States from polar-orbiting and geostationary satellite active-fire detections
Authors: Berman Melinda T. , Ye Xinxin , Thapa Laura H. , Peterson David A. , Hyer Edward J. , Soja Amber J. , Gargulinski Emily M. , Csiszar Ivan , Schmidt Christopher C. , Saide Pablo E.
Published: April 2023

Background Accurately estimating burned area from satellites is key to improving biomass burning emission models, studying fire evolution and assessing environmental impacts. Previous studies have found that current methods for estimating burned area of fires from satellite active-fire data do not always provide an accurate estimate. Aims and methods In this work, we develop a novel algorithm to estimate hourly accumulated burned area based on the area from boundaries of non-convex polygons containing the accumulated Visible Infrared Imaging Radiometer Suite (VIIRS) active-fire detections. Hourly time series are created by combining VIIRS estimates with Fire Radiative Power (FRP) estimates from GOES-17 (Geostationary Operational Environmental Satellite) data. Conclusions, key results and implication We evaluate the performance of the algorithm for both accumulated and change in burned area between airborne observations, and specifically examine sensitivity to the choice of the parameter controlling how much the boundary can shrink towards the interior of the area polygon. Results of the hourly accumulation of burned area for multiple fires from 2019 to 2020 generally correlate strongly with airborne infrared (IR) observations collected by the United States Forest Service National Infrared Operations (NIROPS), exhibiting correlation coefficient values usually greater than 0.95 and errors <20%.
Biogenic carbon pool production maintains the Southern Ocean carbon sink
Authors: Huang Yibin , Fassbender Andrea J. , Bushinsky Seth M.
Published: April 2023

Through biological activity, marine dissolved inorganic carbon (DIC) is transformed into different types of biogenic carbon available for export to the ocean interior, including particulate organic carbon (POC), dissolved organic carbon (DOC), and particulate inorganic carbon (PIC). Each biogenic carbon pool has a different export efficiency that impacts the vertical ocean carbon gradient and drives natural air–sea carbon dioxide gas (CO
2
) exchange. In the Southern Ocean (SO), which presently accounts for ~40% of the anthropogenic ocean carbon sink, it is unclear how the production of each biogenic carbon pool contributes to the contemporary air–sea CO
2
exchange. Based on 107 independent observations of the seasonal cycle from 63 biogeochemical profiling floats, we provide the basin-scale estimate of distinct biogenic carbon pool production. We find significant meridional variability with enhanced POC production in the subantarctic and polar Antarctic sectors and enhanced DOC production in the subtropical and sea-ice-dominated sectors. PIC production peaks between 47°S and 57°S near the “great calcite belt.” Relative to an abiotic SO, organic carbon production enhances CO
2
uptake by 2.80 ± 0.28 Pg C y
−
1
, while PIC production diminishes CO
2
uptake by 0.27 ± 0.21 Pg C y
−
1
. Without organic carbon production, the SO would be a CO
2
source to the atmosphere. Our findings emphasize the importance of DOC and PIC production, in addition to the well-recognized role of POC production, in shaping the influence of carbon export on air–sea CO
2
exchange.
Secretory MPP3 reinforce myeloid differentiation trajectory and amplify myeloid cell production
Authors: Kang Yoon-A , Paik Hyojung , Zhang Si Yi , Chen Jonathan J. , Olson Oakley C. , Mitchell Carl A. , Collins Amelie , Swann James W. , Warr Matthew R. , Fan Rong , Passegué Emmanuelle
Published: April 2023

Hematopoietic stem cells (HSC) and downstream lineage-biased multipotent progenitors (MPP) tailor blood production and control myelopoiesis on demand. Recent lineage tracing analyses revealed MPPs to be major functional contributors to steady-state hematopoiesis. However, we still lack a precise resolution of myeloid differentiation trajectories and cellular heterogeneity in the MPP compartment. Here, we found that myeloid-biased MPP3 are functionally and molecularly heterogeneous, with a distinct subset of myeloid-primed secretory cells with high endoplasmic reticulum (ER) volume and FcγR expression. We show that FcγR+/ERhigh MPP3 are a transitional population serving as a reservoir for rapid production of granulocyte/macrophage progenitors (GMP), which directly amplify myelopoiesis through inflammation-triggered secretion of cytokines in the local bone marrow (BM) microenvironment. Our results identify a novel regulatory function for a secretory MPP3 subset that controls myeloid differentiation through lineage-priming and cytokine production and acts as a self-reinforcing amplification compartment in inflammatory stress and disease conditions.
Deciphering mechanically activated ion channels at the single-channel level in dorsal root ganglion neurons
Authors: Murthy Swetha E.
Published: April 2023

Mechanically activated (MA) ion channels confer somatosensory neurons with the ability to sense a wide range of mechanical stimuli. MA ion channel activity in somatosensory neurons is best described by the electrophysiological recordings of MA currents in cultured dorsal root ganglion (DRG) neurons. Biophysical and pharmacological characterization of DRG MA currents has guided the field in screening/confirming channel candidates that induce the currents and facilitate the mechanosensory response. But studies on DRG MA currents have relied mostly on whole-cell macroscopic current properties obtained by membrane indentation, and little is known about the underlying MA ion channels at the single-channel level. Here, by acquiring indentation-induced macroscopic currents as well as stretch-activated single-channel currents from the same cell, we associate macroscopic current properties with single-channel conductance. This analysis reveals the nature of the MA channel responsible for the ensemble response. We observe four different conductances in DRG neurons with no association with a specific type of macroscopic current. Applying this methodology to a Piezo2 expressing DRG neuronal subpopulation allows us to identify PIEZO2-dependent stretch-activated currents and conductance. Moreover, we demonstrate that upon Piezo2 deletion, the remaining macroscopic responses are predominantly mediated by three different single-channel conductances. Collectively, our data predict that at least two other MA ion channels exist in DRG neurons that remain to be discovered.
On uniqueness and ill-posedness for the deautoconvolution problem in the multi-dimensional case
Authors: Hofmann Bernd , Werner Frank , Deng Yu
Published: April 2023

This paper analyzes the inverse problem of deautoconvolution in the multi-dimensional case with respect to solution uniqueness and ill-posedness. Deautoconvolution means here the reconstruction of a real-valued L
2-function with support in the n-dimensional unit cube

[
0
,
1

]
n

from observations of its autoconvolution either in the full data case (i.e. on

[
0
,
2

]
n

) or in the limited data case (i.e. on

[
0
,
1

]
n

). Based on multi-dimensional variants of the Titchmarsh convolution theorem due to Lions and Mikusiński, we prove in the full data case a twofoldness assertion, and in the limited data case uniqueness of non-negative solutions for which the origin belongs to the support. The latter assumption is also shown to be necessary for any uniqueness statement in the limited data case. A glimpse of rate results for regularized solutions completes the paper.
Charge relaxation associated with photon-induced deactivation of various traps in MAPbI3 films
Authors: Chien F S-S , Herawati A , Ho C-M , Hsiao H-L , Lim T-S , Wang C R , Ng K-K , Das S , Kao F-J , Wu M-C
Published: April 2023

Photon-induced deactivation of traps in MAPbI3 can strongly affect charge relaxation behavior. Charge relaxation associated with photo-induced deactivation of various traps in MAPbI3 films was investigated through steady-state and time-resolved photoluminescence (PL) spectroscopy under laser excitation at 635 and 430 nm to investigate the properties of the traps. Three types of traps that could be deactivated by photons were observed in the MAPbI3 films, namely TL, TH, and TGB. TL and TH, which were related to MAPbI3 bulk, had low and high photon energy thresholds (red and blue photons) for deactivation, respectively. TGB was related to the traps at grain boundaries in MAPbI3 and had a low photon energy threshold (red photons) for deactivation. The energy level of TGB was higher than that of the conduction band of MAPbI3. Under blue excitation, TGB mediated a fast nonradiative recombination at few nanoseconds, and TL and TH mediated a slow nonradiative recombination at few 100 ns. The fast nonradiative recombination led to a significantly low initial normalized photoluminescence quantum yield (PLQY) (1/22) under blue excitation, compared with that obtained under red excitation (1/4). The deactivation of TL and TH resulted in increases in both the amplitude of PL and recombination time. The deactivation of TGB resulted only in a significant increase in PLQY of blue excitation.
Carrier removal rates in 1.1 MeV proton irradiated α-Ga2O3 (Sn)
Authors: Polyakov A Y , Nikolaev V I , Pechnikov A I , Lagov P B , Shchemerov I V , Vasilev A A , Chernykh A V , Kochkova A I , Guzilova L , Pavlov Yu S , Kulevoy T V , Doroshkevich A S , Isaev R Sh , Panichkin A V , Pearton S J
Published: April 2023

Films of α-Ga2O3 (Sn) grown by halide vapor phase epitaxy on sapphire with donor densities in the range 5 × 1015–8.4 × 1019 cm−3 were irradiated at 25 °C with 1.1 MeV protons to fluences from 1013 to 1016 cm−2. For the lowest doped samples, the carrier removal rate was ∼35 cm−1 at 1014 cm−2 and ∼1.3 cm−1 for 1015 cm−2 proton fluence. The observed removal rate could be accounted for by introduction of deep acceptors with optical ionization energies of 2 eV, 2.8 eV and 3.1 eV. For samples doped at 4 × 1018 cm−3, the initial electron removal rate was 5 × 103 cm−1 for 1015 cm−2 fluence and ∼300 cm−1 for 1016 cm−2 fluence. The same deep acceptors were observed in photocapacitance spectra, but their introduction rate was orders of magnitude lower than the carrier removal rate. For the heaviest doped samples, the electron removal rate was close to that for the 4 × 1018 cm−3 sample. The radiation tolerance of lightly doped α-Ga2O3 is higher than for similarly doped β-Ga2O3 layers.
Resistive switching study on diffusive memristors using electrochemical impedance spectroscopy
Authors: Gabbitas A , Pattnaik D P , Zhou Z , Borisov P
Published: April 2023

Diffusive memristors demonstrate volatile resistive switching powered by the diffusion of silver nanoparticles through the matrix of silicon dioxide. The equivalent circuit of the high resistance state has been studied via electrochemical impedance spectroscopy for two types of devices which demonstrate either analog or abrupt switching characteristics. It was found that the resistance component has a relatively good agreement with the differential resistance obtained from the I–V curves, whereas the capacitance visibly increases in the analog switching devices with increasing bias voltage as its conductive precursor filament starts forming with increasing voltage and redistribution of silver nanoparticles starts to occur at the top electrodes. Such an effect is not observed for abrupt switching device, which rapidly enters its conductive state for a small increase in bias voltage. This experimental approach allows for the identification of different types of electrical circuit behaviors in a memristive device, even before resistive switching takes place.
Intrinsic and extrinsic dopings in epitaxial films MnBi2Te4
Authors: He Mengyun , Fu Yu , Huang Yu , Sun Huimin , Guo Tengyu , Lin Wenlu , Zhu Yu , Zhang Yan , Liu Yang , Yu Guoqiang , He Qing Lin
Published: April 2023

The intrinsic antiferromagnetic topological insulator MnBi2Te4 and members of its family have been the subject of theoretical and experimental research, which has revealed the presence of a variety of defects and disorders that are crucial in determining the topological and magnetic properties. This also brings about challenges in realizing the quantum states like the quantum anomalous Hall and the axion insulator states. Here, utilizing cryogenic magnetoelectric transport and magnetic measurements, we systematically investigate the effects arising from intrinsic doping by antisite defects and extrinsic doping by Sb in MnBi2Te4 epitaxial films grown by molecular beam epitaxy. We demonstrate that the nonequilibrium condition in epitaxy allows a wide growth window for optimizing the crystalline quality and defect engineering. While the intrinsic antisite defects caused by the intermixing between Bi and Mn can be utilized to tune the Fermi level position as evidenced by a p-to-n conductivity transition, the extrinsic Sb-doping not only compensates for this doping effect but also modifies the magnetism and topology of the film, during which a topological phase transition is developed. Conflicting reports from the theoretical calculations and experimental measurements in bulk crystals versus epitaxial films are addressed, which highlights the intimate correlation between the magnetism and topology as well as the balance between the Fermi-level positioning and defect control. The present study provides an experimental support for the epitaxial growth of the intrinsic topological insulator and underlines that the topology, magnetism, and defect engineering should be revisited for enabling a steady and reliable film production.
Tunable electronic and optical properties of MoTe2/InSe heterostructure via external electric field and strain engineering
Authors: Liang Kanghao , Wang Jing , Wei Xing , Zhang Yan , Fan Jibin , Ni Lei , Yang Yun , Liu Jian , Tian Ye , Wang Xuqiang , Yuan Chongrong , Duan Li
Published: April 2023

Based on first-principles calculation under density functional theory, the geometry, electronic and optical properties of the MoTe2/InSe heterojunction have been investigated. The results reveal that the MoTe2/InSe heterojunction has a typical type-Ⅱ band alignment and exhibits an indirect bandgap of 0.99 eV. In addition, the Z-scheme electron transport mechanism is capable of efficiently separating photogenerated carriers. The bandgap of the heterostructure changes regularly under applied electric field and exhibits a significant Giant Stark effect. Under an applied electric field of 0.5 V Å−1, the band alignment of the heterojunction shifts from type-Ⅱ to type-I. The application of strain produced comparable changes in the heterojunction. More importantly, the transition from semiconductor to metal is completed in the heterostructure under the applied electric field and strain. Furthermore, the MoTe2/InSe heterojunction retains the optical properties of two monolayers and produces greater light absorption on this basis, especially for UV light. The above results offer a theoretical basis for the application of MoTe2/InSe heterostructure in the next generation of photodetectors.
Frustration shapes multi-channel Kondo physics: a star graph perspective
Authors: Patra Siddhartha , Mukherjee Abhirup , Mukherjee Anirban , Vidhyadhiraja N S , Taraphder A , Lal Siddhartha
Published: April 2023

We study the overscreened multi-channel Kondo (MCK) model using the recently developed unitary renormalisation group technique. Our results display the importance of ground state degeneracy in explaining various important properties like the breakdown of screening and the presence of local non-Fermi liquids (NFLs). The impurity susceptibility of the intermediate coupling fixed point Hamiltonian in the zero-bandwidth (or star graph) limit shows a power-law divergence at low temperature. Despite the absence of inter-channel coupling in the MCK fixed point Hamiltonian, the study of mutual information between any two channels shows non-zero correlation between them. A spectral flow analysis of the star graph reveals that the degenerate ground state manifold possesses topological quantum numbers. Upon disentangling the impurity spin from its partners in the star graph, we find the presence of a local Mott liquid arising from inter-channel scattering processes. The low energy effective Hamiltonian obtained upon adding a finite non-zero conduction bath dispersion to the star graph Hamiltonian for both the two and three-channel cases displays the presence of local NFLs arising from inter-channel quantum fluctuations. Specifically, we confirm the presence of a local marginal Fermi liquid in the two channel case, whose properties show logarithmic scaling at low temperature as expected. Discontinuous behaviour is observed in several measures of ground state entanglement, signalling the underlying orthogonality catastrophe associated with the degenerate ground state manifold. We extend our results to underscreened and perfectly screened MCK models through duality arguments. A study of channel anisotropy under renormalisation flow reveals a series of quantum phase transitions due to the change in ground state degeneracy. Our work thus presents a template for the study of how a degenerate ground state manifold arising from symmetry and duality properties in a multichannel quantum impurity model can lead to novel multicritical phases at intermediate coupling.
Highly stable graphene oxide/nylon membrane for molecular separation
Authors: Alemayehu Haftu Gebrekiros , Hailu Rshan Beyene , Taddesse Paulos
Published: April 2023

Graphene oxide (GO), due to its one-atom-thick structure and enriched oxygenated functionalities, is a promising candidate material to develop nanofiltration membranes to tackle the current worldwide water shortage. However, the stability of the GO membrane in an aqueous environment and its long-term operation remains unresolved. These issues greatly affect the mass transfer in the GO membrane. Here, we fabricate an ultrathin GO membrane on a nylon substrate within 5 min with the help of vacuum filtration for molecular separation. Thus, GO/nylon membranes dried in an oven at temperatures of 70 °C show greater aqueous solution stability than those dried at room temperature. To validate the stability, both GO membranes were immersed in DI water for 20 d. As a result, the GO/nylon membrane dried at room temperature was completely detached from the substrate within 12 h, whereas the GO/nylon membrane that dried at 70 °C remained stable for more than 20 d without any physical damage. We suppose the enhanced stability is due to the thermally induced balance in electrostatic repulsion resulting in stabilizing of the GO membrane. This method improves the GO membrane’s operating time, selectivity, and permeability. Therefore, the optimized GO/nylon membrane shows higher rejection of organic dyes (∼100%) and good selectivity for sulfate salts such as Na2SO4 and MgSO4 (>80%). The membrane continuously operates for more than 60 h with only a 30% water permeability decline and 100% rejection of dyes. We believe that the drying of GO/nylon membranes at a moderate temperature is important for enhanced separation performance and stability. This drying technique can be applied to other applications.