bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical thermal resistance model for calculating mean die temperature of eccentric quad flat no-leads packaging on printed circuit board
Authors: Wang Yongchao , Wei Xin , Zhang Guohao , Hu Zhengfa , Zhao Zhongwei , Wang Lei
Published: March 2021

Quad Flat No-leads (QFN) packaging is one of the most commonly used packaging types for microelectronic devices due to its outstanding thermal performance. However, it is difficult to analyze the thermal performance of QFN packaging because numerical simulations and experiments often require a large amount of time and resources. In this work, an analytical thermal resistance network model for calculating the mean die temperature of eccentric QFN packaging on the printed circuit board (PCB) is presented. Based on the heat dissipation path from the die to ambient, the thermal resistance network is established. The analytical solution of the mean die temperature of QFN packaging is obtained by the analytical expressions of each thermal resistance in the thermal resistance network. Simulations by commercial software ANSYS provide a reference for verification of the present model. The comparison of the results between simulation and analytical solution shows that the network model can calculate the mean die temperature of QFN packaging accurately over wide ranges of PCB’s thermal conductivity and heat transfer coefficient, and the maximum relative error is only 4.73%. The present model is fast and resource-saving to predict the mean die temperature of QFN packaging; moreover, it provides an optimization method for QFN packaging design to achieve good reliability.
Bending behaviors of flexible acoustic wave devices under non-uniform elasto-plastic deformation
Authors: Zhang Qian , Wang Yong , Li Dongsheng , Yang Xin , Xie Jin , Fu Yongqing
Published: March 2021

Flexible acoustic wave devices (FAWDs) have been explored in various applications where bending is inevitable. However, theoretical investigations of bending behavior of FAWDs hitherto are mostly done in the linear deformation regime. Herein, we develop a multi-sublayer model based on a stiffness matrix method for analysis of frequency shifts of surface acoustic waves and Lamb waves under elasto-plastic deformations. Using this model, we calculate the frequency shifts for the cases of both an elastic bending and an elasto-plastic bending. Experimental frequency shifts of ZnO/Al flexible devices show good agreement with the theoretical results in the elastic bending tests (with a relative error of strain sensitivity < 3%) and also show relatively good agreement with the qualitative theoretical predictions in the nonlinearly elasto-plastic bending. For three successive bending and recovery processes, the experimentally obtained frequency shifts show good repeatability in the elastic and elasto-plastic bending, demonstrating maximum relative errors of strain sensitivities less than 6.1% and 18.2%.
Ion-temperature determination with a baffled Langmuir probe
Authors: Finnegan S. M. , Koepke M. E. , Demidov V. I.
Published: March 2021

An electrostatic Langmuir probe for real-time measurements of parameters in magnetized plasma is tested in fully ionized, barium, Q-machine plasma. The small-diameter, long-length, tungsten wire sensor, i.e., the probe tip, oriented with its cylindrical axis perpendicular to the magnetic field (B), is partially shielded by ceramic baffles, or masks, that form sensor-access slots between the baffles. Adjusting the azimuthal orientation of the slots, by rotating the probe about its cylindrical axis, changes the fraction of proximity gyro-orbiting electrons, relative to the fraction of proximity gyro-orbiting ions, that can access the recessed sensor along the magnetic field. Thus, the ratio between the electron and ion saturation currents, Iesat and Iisat, can be adjusted without having affected the probe bias voltage Vb. When optimally shielded (Iesat/Iisat=1), accurate, real-time measurements of space potential Vs can be acquired. When maximally shielded (Iesat/Iisat≪1), accurate, real-time measurements of ion temperature Ti can be acquired. Subtracting the floating potential Vf of an optimally shielded baffled probe from Vf of a maximally shielded baffled probe yields Ti (and its fluctuation phase) in real time.
Design and analysis of a quasi-TM03 mode G-band extended interaction radiation source
Authors: Zu Yifan , Yuan Xuesong , Xu Xiaotao , Chen Qingyun , Cole Matthew , Yin Yong , Bi Liangjie , Li Hailong , Wang Bin , Meng Lin , Yan Yang
Published: March 2021

A disk-loaded coupled cavity structure operating in the quasi-TM03 mode has been used here to develop a high electron efficiency, high output power terahertz radiation source, demonstrating that it is possible to concentrate the axial field energy along the source’s central axis within a large cavity. Compared with traditional extended interaction devices operating at the same frequency band, the operating mode of this present device provides a sizable beam tunnel capacity that can support efficient energy conversion between the electron beam and the high frequency field. The developed electron optical system is based on a cylindrical electron beam of 0.3 mm radius and is capable of producing a beam current of 0.65 A at a bias of 16.4 kV. Particle in cell simulations show that such new design approaches can achieve kilowatt-level output power at 0.22 THz with a high electron efficiency of 11.5%.
Abnormal Seebeck effect in doped conducting polymers
Authors: Ge Yufei , Liu Ran , Shuai Zhigang
Published: March 2021

The Seebeck effect or thermopower relates the temperature gradient to the electric voltage drop. Seebeck coefficient α measures the transport entropy, which could either linearly increase with temperature T like metallic conducting or decrease as 1/T like semiconducting behavior. It could become more complicated in the temperature dependence for a number of disordered systems but still in a monotonic way. However, several recent experiments reported the “abnormal” non-monotonic temperature dependence of the Seebeck coefficient in doped conducting polymers, for instance, first increasing and then decreasing. Through a one-dimensional tight-binding model coupled with the Boltzmann transport equation, we investigate theoretically the doping effect for the Seebeck coefficient. We find that the abnormal behavior comes from multi bands' contribution and a two-band model (conduction or valence band plus a narrow polaronic band) can address such an abnormal Seebeck effect, namely, if there exists (i) a small bandgap accessible for thermal activation between the two bands; and (ii) a large difference in the bandwidth between the polaronic band and the conduction band (or valence band), then the Seebeck coefficient increases with temperature first, then levels off, and finally drops down.
Flux ramp modulation based MHz frequency-division dc-SQUID multiplexer
Authors: Richter Daniel , Hoibl Ludwig , Wolber Thomas , Karcher Nick , Fleischmann Andreas , Enss Christian , Weber Marc , Sander Oliver , Kempf Sebastian
Published: March 2021

We present a MHz frequency-division direct-current superconducting quantum interference device (dc-SQUID) multiplexer that is based on flux ramp modulation and a series array of N identical current-sensing dc-SQUIDs with tightly coupled input coil. By running a periodic, sawtooth-shaped current signal through additional modulation coils being tightly but non-uniformly coupled to the individual SQUIDs, the voltage drop across the array changes according to the sum of the flux-to-voltage characteristics of the individual SQUIDs within each cycle of the modulation signal. In this mode of operation, an input signal injected in the input coil of one of the SQUIDs and being quasi-static within a time frame adds a constant flux offset and leads to a phase shift of the associated SQUID characteristics. The latter is proportional to the input signal and can be inferred by channelizing and down-converting the sampled array output voltage. Using a prototype multiplexer as well as custom readout electronics, we demonstrate the simultaneous readout of four signal sources with MHz bandwidth per channel.
Plasmon-enhanced lateral photovoltaic effect observed in Ag-ZnO core–shell nanoparticles
Authors: Dong Xinyuan , Zheng Diyuan , Lu Jing , Niu Yiru , Liu Binbin , Wang Hui
Published: March 2021

The lateral photovoltaic effect (LPE) is widely used in sensitive position detectors. Discovering comprehensive mechanisms and continuously improving their sensitivity are the ongoing goals in this field. However, the limited absorption and rapid recombination are two major challenges in the traditional LPE. Here, surface plasmon-based approaches have been used to boost the energy conversion efficiency, and the Ag-ZnO core–shell nanoparticles (NPs) with enhanced LPE are prepared on the Si substrate through atomic layer deposition. Owing to the enhanced light absorption, prolonged hot electron generation, and plasmon-induced charge separation, this system exhibits good LPE performance with a maximum sensitivity of 122.1 mV/mm at 980 nm, which is about seven times larger than that observed in conventional Ag/Si (5.03 mV/mm) and ZnO/Si (76.13 mV/mm). Besides, its sensitivity can increase up to 114.7% by using rapid thermal annealing to change the shape and size of active plasmon Ag NPs. Furthermore, the surface-enhanced Raman scattering spectra and finite-difference time-domain electric field simulation prove the occurrence of localized surfaced plasmon resonance excitation. This infrared sensitive shell-isolated structure has great potential for applications in high sensitivity and stability photoelectric devices.
Strong static and dynamic Jahn–Teller and pseudo-Jahn–Teller effects in niobium tetrafluoride
Authors: Vasilyev Oleg A. , Nandipati Krishna R. , Navarkin Ilya S. , Solomonik Victor G. , Domcke Wolfgang
Published: March 2021

We present a first-principles study of the static and dynamic aspects of the strong Jahn–Teller (JT) and pseudo-JT (PJT) effects in niobium tetrafluoride, NbF4, in the manifold of its electronic ground state, 2E, and its first excited state, 2T2. The complex topography of the full-dimensional multi-sheeted adiabatic JT/PJT surfaces is analyzed computationally at the complete-active-space self-consistent-field (CASSCF) and multireference second-order perturbation levels of electronic structure theory, providing a detailed characterization of minima, saddle points, and minimum-energy conical intersection points. The calculations reveal that the tetrahedral (Td) configuration of NbF4 undergoes strong JT distortions along the bending mode of e symmetry, yielding tetragonal molecular structures of D2d symmetry with Td → D2d stabilization energies of about 2000 cm−1 in the X̃2E state and about 6400 cm−1 in the Ã2T2 state. In addition, there exists strong X̃2E−Ã2T2 PJT coupling via the bending mode of t2 symmetry, which becomes important near the crossing seam of the X̃2E and Ã2T2 potential energy surfaces. A five-state five-mode JT/PJT vibronic-coupling Hamiltonian is constructed in terms of symmetry-invariant polynomial expansions of the X̃2E and Ã2T2 diabatic potential energy surfaces in the e and t2 bending coordinates. The parameters of the Hamiltonian are determined by a least-squares fit of its eigenvalues to the CASSCF ab initio data. The vibronic spectra and the time evolution of adiabatic electronic population probabilities are computed with the multi-configuration time-dependent Hartree method. The complexity of the spectra reflects the effects of the exceptionally strong E × e and T2 × e JT couplings and (E + T2) × (e + t2) PJT coupling. The time evolution of the populations of the adiabatic electronic states after the initial preparation of the Ã2T2 state reveals the femtosecond nonadiabatic dynamics through a multidimensional seam of conical intersection. These results represent the first study of the static and dynamical JT/PJT effects in the X̃2E and Ã2T2 electronic states of NbF4.
Addressing the Frenkel and charge transfer character of exciton states with a model Hamiltonian based on dimer calculations: Application to large aggregates of perylene bisimide
Authors: Canola Sofia , Bagnara Giuseppe , Dai Yasi , Ricci Gaetano , Calzolari Alessandro , Negri Fabrizia
Published: March 2021

To understand the influence of interchromophoric arrangements on photo-induced processes and optical properties of aggregates, it is fundamental to assess the contribution of local excitations [charge transfer (CT) and Frenkel (FE)] to exciton states. Here, we apply a general procedure to analyze the adiabatic exciton states derived from time-dependent density functional theory calculations, in terms of diabatic states chosen to coincide with local excitations within a restricted orbital space. In parallel, motivated by the need of cost-effective approaches to afford the study of larger aggregates, we propose to build a model Hamiltonian based on calculations carried out on dimers composing the aggregate. Both approaches are applied to study excitation energy profiles and CT character modulation induced by interchromophore rearrangements in perylene bisimide aggregates up to a tetramer. The dimer-based approach closely reproduces the results of full-aggregate calculations, and an analysis in terms of symmetry-adapted diabatic states discloses the effects of CT/FE interactions on the interchange of the H-/J-character for small longitudinal shifts of the chromophores.
Study of the Ar II spectral line shape in the cathode sheath region of glow discharge
Authors: Vasiljević M. M. , Spasojević Đ. , Konjević N.
Published: March 2021

We present the results of an experimental study of Ar II line shapes emitted side-on from the cathode sheath (CS) region of an abnormal glow discharge operating in pure argon with different cathode materials. The shape of Ar II lines is recorded side-on to the discharge axis and parallel to the plane cathode surface by using the optical emission spectroscopy technique. Our experimental line shape analysis shows that the atomic line shapes can be used for determination of the electric field strength distribution and the thickness of the CS region, whereas the broadened wings of the Ar II lines provide an insight into line shape formation as a result of electric field strength distribution, which is essential for discharge particle dynamics, and interaction with the discharge gas and sputtered cathode material. The results are summarized in two analytic formulas: one for the half width of wings as a function of the cathode distance from the recording position and the other for correlation between Ar II line width and electric field strength.
Narrowing of d bands of FeCo layers intercalated under graphene
Authors: Pacilè Daniela , Cardoso Claudia , Avvisati Giulia , Vobornik Ivana , Mariani Carlo , Leon Dario A. , Bonfà Pietro , Varsano Daniele , Ferretti Andrea , Betti Maria Grazia
Published: March 2021

We report on the electronic properties of an artificial system obtained by the intercalation of equiatomic FeCo layers under graphene grown on Ir(111). Upon intercalation, the FeCo film grows epitaxially on Ir(111), resulting in a lattice-mismatched system. By performing density functional theory calculations, we show that the intercalated FeCo layer leads to a pronounced corrugation of the graphene film. At the same time, the FeCo intercalated layers induce a clear transition from a nearly undisturbed to a strongly hybridized graphene π-band, as measured by angle-resolved photoemission spectroscopy. A comparison of experimental results with the computed band structure and the projected density of states unveils a spin-selective hybridization between the π band of graphene and FeCo-3d states. Our results demonstrate that the reduced dimensionality, as well as the hybridization within the FeCo layers, induces a narrowing and a clear splitting of Fe 3d-up and Fe 3d-down-spin bands of the confined FeCo layers with respect to bulk Fe and Co.
Titanium dioxide nanotubes: synthesis, structure, properties and applications
Authors: Rempel Andrey A. , Valeeva Albina A. , Vokhmintsev Alexander S. , Weinstein Ilya A.
Published: March 2021

Methods of synthesis of nanotubular structures based on titania of various phase and chemical compositions are described. A systematic account is given of known data about the influence of synthesis and subsequent treatment conditions on the amorphous and crystal structures, specific surface area, morphology and optical, luminescence and electro-physical properties of titania-based nanotubular oxide materials. The photocatalytic properties in the oxidation reactions of organic compounds and the performance characteristics of the memristive behaviour of TiO2-based nanotubular structures are considered in details. Their applications are discussed.

The bibliography includes 238 references.
The importance of small fires for wildfire hazard in urbanised landscapes of the northeastern US
Authors: Carlson Amanda R. , Sebasky Megan E. , Peters Matthew P. , Radeloff Volker C.
Published: March 2021

Frequent, small wildfires can pose dangers to homes in the wildland–urban interface, but are not often included in wildfire hazard models. We assessed patterns of small wildfire occurrence probability in the Northeast region of the United States, focusing on (1) spatial and seasonal variations; (2) differences between small and large fires (size threshold of 4 ha); and (3) how predicted probabilities are influenced by inconsistent wildfire definitions in urbanised landscapes. We analysed fire incident report data from 2005 to 2017 to parameterise maximum entropy (MaxEnt) models based on land cover, topography, climatic water deficit, soil moisture and road density. Overall, wildfire occurrence was highest in areas with lower agricultural cover and with more low-density urban development (explaining 53.5 and 28.6% of variance, respectively, in our region-wide model), while larger fires were concentrated in areas with intermediate levels of development, higher climatic water deficit and more rugged topography. These patterns were largely consistent when we assessed models for individual states, but differences in wildfire reporting patterns led to differences in the effect of urban development on fire probability. Our results provide novel understanding of small wildfire patterns in the Northeast and demonstrate the need to more reliably quantify these hazards.
DNA affinity purification sequencing and transcriptional profiling reveal new aspects of nitrogen regulation in a filamentous fungus
Authors: Huberman Lori B. , Wu Vincent W. , Kowbel David J. , Lee Juna , Daum Chris , Grigoriev Igor V. , O’Malley Ronan C. , Glass N. Louise
Published: March 2021

Significance

Microorganisms have evolved transcriptional networks to prioritize utilization of available nutrient sources. For filamentous fungi, such as
Neurospora crassa
, this entails distinguishing between a variety of organic and inorganic nitrogen sources. Here, we transcriptionally profiled the response of
N. crassa
to a variety of nitrogen sources and used DNA affinity purification sequencing to characterize the role of regulatory genes and their direct downstream targets. We identified a transcription factor responsible for regulating genes involved in amino acid and mannose metabolism. By comparing the genes regulated by transcription factors that regulate specific nitrogen utilization pathways and transcription factors that regulate utilization of all nitrogen sources that require metabolic processing before utilization, we revealed aspects of the nitrogen regulatory network.
A glutaminase isoform switch drives therapeutic resistance and disease progression of prostate cancer
Authors: Xu Lingfan , Yin Yu , Li Yanjing , Chen Xufeng , Chang Yan , Zhang Hong , Liu Juan , Beasley James , McCaw Patricia , Zhang Haoyue , Young Sarah , Groth Jeff , Wang Qianben , Locasale Jason W. , Gao Xia , Tang Dean G. , Dong Xuesen , He Yiping , George Daniel , Hu Hailiang , Huang Jiaoti
Published: March 2021

Significance

We report that androgen receptor (AR) promotes glutaminase 1 (GLS1) expression and glutamine utilization to support the survival of prostate cancer (PCa) cells. Hormonal therapy inhibits AR and decreases GLS1 expression and glutamine utilization to achieve therapeutic effect. Our results suggest that eventually the tumor cells switch GLS1 expression from the AR-dependent KGA isoform to the androgen-independent and enzymatically more potent GAC isoform, which increases glutamine utilization and can contribute to the development of castration-resistant PCa. Our work has discovered a previously unknown AR function, a metabolic mechanism of hormonal therapy and an important therapeutic target more specific than AR. Targeting GLS1 may achieve similar therapeutic efficacy but without the side effects resulting from inhibiting AR’s other important physiologic functions.
A highly selective and potent CXCR4 antagonist for hepatocellular carcinoma treatment
Authors: Song Jen-Shin , Chang Chih-Chun , Wu Chien-Huang , Dinh Trinh Kieu , Jan Jiing-Jyh , Huang Kuan-Wei , Chou Ming-Chen , Shiue Ting-Yun , Yeh Kai-Chia , Ke Yi-Yu , Yeh Teng-Kuang , Ta Yen-Nhi Ngoc , Lee Chia-Jui , Huang Jing-Kai , Sung Yun-Chieh , Shia Kak-Shan , Chen Yunching
Published: March 2021

Significance

A highly selective, safe, and potent CXCR4 antagonist, BPRCX807, has been designed and experimentally validated in various hepatocellular carcinoma models. Through combination therapy, it can synergize with either a kinase (e.g., sorafenib) or checkpoint inhibitor (e.g. anti–PD-1) to augment effectiveness of current anticancer treatments. With its unique mode of action, a new anticancer strategy for preventing cell migration and metastasis is provided.
Experimental competition induces immediate and lasting effects on the neurogenome in free-living female birds
Authors: Bentz Alexandra B. , George Elizabeth M. , Wolf Sarah E. , Rusch Douglas B. , Podicheti Ram , Buechlein Aaron , Nephew Kenneth P. , Rosvall Kimberly A.
Published: March 2021

Significance

Social challenges are thought to be embedded in the genome, but little is known about how this adaptive modification of gene activity occurs in nature. We experimentally generated competition among free-living female tree swallows (
Tachycineta bicolor
) and measured both transcriptomic and epigenomic changes in the brain. Social competition rapidly altered gene expression and methylation, with effects that were enriched for hormone- and neurotransmitter-related processes also being found two full days later. These persistent effects on gene activity were correlated with epigenetic patterns as well as the degree of aggression experienced during the peak of competition. Thus, a single day of competition in the wild is encoded in the brain, both during competition and days later.
ICOS ligand and IL-10 synergize to promote host–microbiota mutualism
Authors: Landuyt Ashley E. , Klocke Barbara J. , Duck Lennard W. , Kemp Keri M. , Muir Rachel Q. , Jennings Melissa S. , Blum Samuel I. , Tse Hubert M. , Lee Goo , Morrow Casey D. , Elson Charles O. , Maynard Craig L.
Published: March 2021

Significance

Both
IL10
and
ICOSL
are risk alleles for inflammatory bowel disease (IBD). The role of IL-10 in preventing gut inflammation is well established experimentally and clinically. However, it is unclear whether and how ICOSL functions in the intestines, and how it might impact susceptibility to gut inflammation. We found that in mice, the absence of ICOSL is associated with increased accumulation of IL-10–producing CD4 T cells but dramatic reductions in anti-commensal antibodies, resulting in limited recognition of antigens implicated in the progression of IBD. Simultaneous disruption of both pathways, either genetically or transiently, resulted in colitis. Therefore, we have identified an IBD-relevant axis in intestinal immune regulation predicated on the cooperative functions of ICOSL and CD4 T cell–derived IL-10.
Early-stage dynamics of chloride ion–pumping rhodopsin revealed by a femtosecond X-ray laser
Authors: Yun Ji-Hye , Li Xuanxuan , Yue Jianing , Park Jae-Hyun , Jin Zeyu , Li Chufeng , Hu Hao , Shi Yingchen , Pandey Suraj , Carbajo Sergio , Boutet Sébastien , Hunter Mark S. , Liang Mengning , Sierra Raymond G. , Lane Thomas J. , Zhou Liang , Weierstall Uwe , Zatsepin Nadia A. , Ohki Mio , Tame Jeremy R. H. , Park Sam-Yong , Spence John C. H. , Zhang Wenkai , Schmidt Marius , Lee Weontae , Liu Haiguang
Published: March 2021

Significance

Light-driven rhodopsin proteins pump ions across cell membranes. They have applications in optogenetics and can potentially be used to develop solar energy–harvesting devices. A detailed understanding of rhodopsin dynamics and functions may therefore assist research in medicine, health, and clean energy. This time-resolved crystallography study carried out with X-ray free-electron lasers reveals detailed dynamics of chloride ion–pumping rhodopsin (ClR) within 100 ps of light activation. It shows the dissociation of Cl
−
from the Schiff base binding site upon light-triggered retinal isomerization. This Cl
−
dissociation is followed by diffusion toward the intracellular direction. The results hint at a common ion-pumping mechanism across rhodopsin families.
Primary cilia and the reciprocal activation of AKT and SMAD2/3 regulate stretch-induced autophagy in trabecular meshwork cells
Authors: Shim Myoung Sup , Nettesheim April , Dixon Angela , Liton Paloma B.
Published: March 2021

Significance

The trabecular meshwork is the major tissue regulating intraocular pressure (IOP). Malfunction of this tissue results in ocular hypertension, the major risk factor for glaucoma. How IOP is regulated is still unknown, but it is accepted that mechanosensation and mechanotransduction are critical regulators. In this study, we report that primary cilia (PC) is a mechanosensor for stretch-induced autophagy in TM cells and identified a reciprocal activation of AKT1 and SMAD2/3 as a signaling pathway regulating the activation of autophagy by PC. Most importantly, we showed that PC-mediated autophagy plays a critical role in IOP homeostasis. These findings tremendously contribute to our understanding of TM biology and identify new potential targets for therapeutic strategies.
Shape anisotropy-governed locomotion of surface microrollers on vessel-like microtopographies against physiological flows
Authors: Bozuyuk Ugur , Alapan Yunus , Aghakhani Amirreza , Yunusa Muhammad , Sitti Metin
Published: March 2021

Significance

Controlled microrobotic navigation in blood vessels holds significant potential to revolutionize targeted drug delivery. Navigation on the surface of the blood vessels is advantageous because of decreased flow velocities; however, surface microtopography of blood vessels, in the size scale of the microrobots, is a major hurdle for robust locomotion of surface-rolling microrobots against the blood flow. Here, we show the effect of the body-shape anisotropy of the microrollers on their locomotion capability over vessel-like microtopographies. We demonstrate by experiments and simulations that the microrollers with slender bodies are more robust to locomote on biological microtopographies due to their favorable hydrodynamic interactions. Thus, such anisotropically shaped microrollers would be more viable and robust in future in vivo medical applications.
Staphylococcus aureus
adapts to the host nutritional landscape to overcome tissue-specific branched-chain fatty acid requirement
Authors: Teoh Wei Ping , Chen Xi , Laczkovich Irina , Alonzo Francis
Published: March 2021

Significance

Lipoylation is a posttranslational modification critical for the function of several metabolic enzymes. In the bacterial pathogen
Staphylococcus aureus
, lipoylation deficiency compromises growth and causes tissue-specific virulence defects. Perturbation of lipoylation causes attenuation in part due to disruption of the enzyme complex required for the synthesis of branched-chain fatty acids, an essential constituent of
S. aureus
membrane.
S. aureus
overcomes branched-chain fatty acid auxotrophy in the skin by acquiring host unsaturated fatty acids. This work underscores the adaptability of
S. aureus
when faced with nutrient scarcity and the relevance of lipoic acid sufficiency during infection. Our findings support the view that versatility in
S. aureus
membrane biogenesis must be considered when devising therapeutics.
The number of catalytic cycles in an enzyme’s lifetime and why it matters to metabolic engineering
Authors: Hanson Andrew D. , McCarty Donald R. , Henry Christopher S. , Xian Xiaochen , Joshi Jaya , Patterson Jenelle A. , García-García Jorge D. , Fleischmann Scott D. , Tivendale Nathan D. , Millar A. Harvey
Published: March 2021

Significance

The continuous replacement of enzymes and other proteins appropriates up to half the maintenance energy budget in microorganisms and plants. High enzyme replacement rates therefore cut the productivity of biosystems ranging from microbial fermentations to crops. However, yardsticks to assess what drives enzyme protein replacement and guidelines on how to reduce it are lacking. Accordingly, we compared enzymes’ life spans across kingdoms using a new yardstick (catalytic cycles until replacement [CCR]) and related CCR to enzyme reaction chemistry. We concluded that 1) many enzymes fail due to collateral damage from the reaction they catalyze, and 2) such damage and its attendant enzyme replacement costs are mitigable by engineering and are therefore promising targets for synthetic biology.
A localized adaptor protein performs distinct functions at the
Caulobacter
cell poles
Authors: Wang Jiarui , Moerner W. E. , Shapiro Lucy
Published: March 2021

Significance

Asymmetric cell division yields two distinct daughter cells by mechanisms that underlie stem cell behavior and cellular diversity in all organisms. The bacterium
Caulobacter crescentus
is able to orchestrate this complex process with less than 4,000 genes. This article describes a strategy deployed by
Caulobacter
where a regulatory protein, PopA, is programed to perform distinct roles based on its subcellular address. We demonstrate that, depending on the availability of a second messenger molecule, PopA adopts either a monomer or dimer form. The two oligomeric forms interact with different partners at the two cell poles, playing a critical role in the degradation of a master transcription factor at one pole and flagellar assembly at the other pole.
PPARγ marks splenic precursors of multiple nonlymphoid-tissue Treg compartments
Authors: Li Chaoran , Muñoz-Rojas Andrés R. , Wang Gang , Mann Alexander O. , Benoist Christophe , Mathis Diane
Published: March 2021

Significance

Foxp3
+
CD4
+
regulatory T cells (Tregs) control both immune responses and tissue homeostasis. Dedicated Treg compartments occur in several nonlymphoid tissues—When, where, and how do they acquire specialized characteristics? A splenic Treg population expressing low levels of the transcription factor PPARγ contains precursors of Tregs in visceral adipose tissue. Since PPARγ, the “master regulator” of adipocyte differentiation, is required for the accumulation and function of Tregs in this tissue but not others, its expression in splenic precursors of adipose-tissue Tregs is not surprising. We show that the splenic PPARγ
lo
Treg population is transcriptionally heterogeneous and engenders Tregs in multiple additional nonlymphoid tissues. A general pool of splenic precursors of nonlymphoid-tissue Tregs opens possibilities for manipulating them experimentally or therapeutically.
Rapid hyperpolarization and purification of the metabolite fumarate in aqueous solution
Authors: Knecht Stephan , Blanchard John W. , Barskiy Danila , Cavallari Eleonora , Dagys Laurynas , Van Dyke Erik , Tsukanov Maksim , Bliemel Bea , Münnemann Kerstin , Aime Silvio , Reineri Francesca , Levitt Malcolm H. , Buntkowsky Gerd , Pines Alexander , Blümler Peter , Budker Dmitry , Eills James
Published: March 2021

Significance

Magnetic resonance imaging is hindered by inherently low sensitivity, which limits the method for the most part to observing water molecules in the body. Hyperpolarized molecules exhibit strongly enhanced MRI signals which opens the door for imaging low-concentration species in vivo. Biomolecules can be hyperpolarized and injected into a patient allowing for metabolism to be tracked in real time, greatly expanding the information available to the radiologist. Parahydrogen-induced polarization (PHIP) is a hyperpolarization method renowned for its low cost and accessibility, but is generally limited by low polarization levels, modest molecular concentrations, and contamination by polarization reagents. In this work we overcome these drawbacks in the production of PHIP-polarized [1-
13
C]fumarate, a biomarker of cell necrosis in metabolic
13
C MRI.
SPAAC-NAD-seq, a sensitive and accurate method to profile NAD
+
-capped transcripts
Authors: Hu Hao , Flynn Nora , Zhang Hailei , You Chenjiang , Hang Runlai , Wang Xufeng , Zhong Huan , Chan Zhulong , Xia Yiji , Chen Xuemei
Published: March 2021

Significance

The m
7
G cap is the canonical RNA cap in eukaryotes, but other noncanonical RNA caps exist, including the NAD
+
cap. NAD captureSeq has been widely used to profile NAD
+
-capped RNAs (NAD-RNAs) in prokaryotes and eukaryotes. However, NAD captureSeq reacts at a low level with m
7
G-RNAs and introduces copper ions that cause RNA fragmentation, resulting in reduced sensitivity and loss of full-length sequence information. To address these issues, we developed the copper-free SPAAC-NAD-seq, which utilizes the strain-promoted azide–alkyne cycloaddition reaction to capture NAD-RNAs followed by high-throughput sequencing. Compared to NAD captureSeq, SPAAC-NAD-seq is more sensitive and retains full-length sequence information. This optimized technique provides a useful tool to profile NAD-RNAs in prokaryotes and, when combined with m
7
G-RNA depletion, in eukaryotes.
Multiple migrations to the Philippines during the last 50,000 years
Authors: Larena Maximilian , Sanchez-Quinto Federico , Sjödin Per , McKenna James , Ebeo Carlo , Reyes Rebecca , Casel Ophelia , Huang Jin-Yuan , Hagada Kim Pullupul , Guilay Dennis , Reyes Jennelyn , Allian Fatima Pir , Mori Virgilio , Azarcon Lahaina Sue , Manera Alma , Terando Celito , Jamero Lucio , Sireg Gauden , Manginsay-Tremedal Renefe , Labos Maria Shiela , Vilar Richard Dian , Latiph Acram , Saway Rodelio Linsahay , Marte Erwin , Magbanua Pablito , Morales Amor , Java Ismael , Reveche Rudy , Barrios Becky , Burton Erlinda , Salon Jesus Christopher , Kels Ma. Junaliah Tuazon , Albano Adrian , Cruz-Angeles Rose Beatrix , Molanida Edison , Granehäll Lena , Vicente Mário , Edlund Hanna , Loo Jun-Hun , Trejaut Jean , Ho Simon Y. W. , Reid Lawrence , Malmström Helena , Schlebusch Carina , Lambeck Kurt , Endicott Phillip , Jakobsson Mattias
Published: March 2021

Significance

A key link to understand human history in Island Southeast Asia is the Philippine archipelago and its poorly investigated genetic diversity. We analyzed the most comprehensive set of population-genomic data for the Philippines: 1,028 individuals covering 115 indigenous communities. We demonstrate that the Philippines were populated by at least five waves of human migration. The Cordillerans migrated into the Philippines prior to the arrival of rice agriculture, where some remain as the least admixed East Asians carrying an ancestry shared by all Austronesian-speaking populations, thereby challenging an exclusive out-of-Taiwan model of joint farming–language–people dispersal. Altogether, our findings portray the Philippines as a crucial gateway, with a multilayered history, that ultimately changed the genetic landscape of the Asia-Pacific region.
Syntactic parallelism and the co-production of syntactic units in Mandarin Chinese
Authors: Gao Yanmei , Ren Xiaohua
Published: March 2021

Cross-linguistic studies on co-production of syntactic units and compound sentence formats have found that the location of predicates affects the projectability of the language, in that languages like English allow early projections while languages like Japanese later projections. In Mandarin Chinese, we found that syntactic parallelism often occurs before co-constructions, impacting the projectability of syntactic structures in one way or another. Based on the theories of dialogic syntax (Du Bois 2007,2014) and the principles of interactional linguistics, this study explores the relationship between syntactic parallelism and co-production of syntactic structures across turns. The co-production of four syntactic and sentential structures were closely examined, namely,Copula V+Complement, (be) Adjectival Predicate, the conditionalIF X THEN Yconstruction(如果ruguo……就/会jiu/hui……), and compound sentences withto-clause of purpose. Also observed is the emergent new sequence as interactionally relevant syntax. Upon inspection, we found that turn units with parallel syntactic structures may help narrow down the category of the projected final component, thus inspiring the second speaker to come in early and jointly complete the syntax-in-progress. Apart from co-producing syntax-in-progress, co-produced structures can also develop into interactionally relevant sequences with independent internal structures, thereby executing new social actions.
Complex reaction behaviour of ceramic mould with the molten AZ91 alloy during investment casting
Authors: Motesadi Zarandi Fateme , Malekan Mehdi , Lotfpour Mehrab , Karimi Chavan Ali
Published: March 2021

The effects of different pouring temperatures on the reaction behaviour of the ceramic shell with the molten Mg-9%Al-1%Zn-0.4%Mn (all are in wt-%) (AZ91) alloy during investment casting were studied. The scanning electron microscopy (SEM) micrographs with energy dispersive spectroscopy (EDS) analysis illustrated a complex interaction behaviour of the alloy with the mould components at various pouring temperatures. The MgO + MgAl2O4 compounds were formed on the surface of investment cast alloy at the pouring temperature of 600°C. With increasing the temperature to 650°C, the MgO compounds with the Al2O3 particles were observed at the interface of metal/mould. The Al2O3 particles were the main compound on the surface of alloy at the pouring temperature of 700°C. The formation of Al2O3 particles instead of the MgO compounds on the surface was related to the increase of magnesium evaporation by enhancement of the pouring temperature and also diffusion of Al2O3 particles from the ceramic shell to the surface of the alloy.
How do Public Libraries Respond to Patron Queries about Opioid use Disorder? A Secret Shopper Study
Authors: Wong Vivien , Cannuscio Carolyn C. , Lowenstein Margaret , Feuerstein-Simon Rachel , Graves Rachel , Meisel Zachary F.
Published: March 2021

Background

Improving linkage to opioid use disorder (OUD) treatment and services is a public health priority. Public libraries, a community resource for health information, may be well positioned to support and guide people who use drugs, as well as their families and friends. In this study, we sought to evaluate the availability and types of resources offered to patrons inquiring about OUD information, OUD treatment, and naloxone access.

Methods

We conducted an audit (secret shopper) study from April 2019 to June 2019 in which an auditor anonymously called Pennsylvania public libraries. We used a purposive sampling strategy to select libraries located in geographically diverse regions across the urban-rural continuum. We categorized responses and verified via phone or website whether referrals to treatment centers and other organizations provided OUD treatment or services.

Results

We obtained responses from 100 public libraries located across 48 of the 67 counties in Pennsylvania. Among the libraries that responded, 57 provided health information resources (e.g., books, websites) and 82 provided “next step” referrals to an organization that could provide further assistance. Among the libraries that provided referrals, 39 were to treatment centers, of which 33 were specifically to treatment centers that offer medications for OUD. Of the responding libraries, 28 communicated information about naloxone access.

Conclusion

Public libraries can and do connect patrons to OUD treatment and support services; however, there is wide interlibrary variation in the resources presented, demonstrating opportunities for improvement in how libraries engage and refer patrons with substance use needs.
Trust in Research Physicians as a Key Dimension of Randomized Controlled Trial Participation in Clinical Addictions Research
Authors: Jaffe Kaitlyn , Nosova Ekaterina , DeBeck Kora , Hayashi Kanna , Milloy M.-J. , Richardson Lindsey
Published: March 2021

Background

In the development of pharmacotherapies for substance use disorders, willingness to participate in randomized controlled trials (RCTs) among people who use drugs (PWUD) is influenced by numerous social and structural factors. Considering the criminalization and stigma experienced by PWUD and range of experiences in healthcare and research, PWUD may vary in their trust of health providers, health research physicians, or medical research processes. We therefore examine associations between trust in these three domains and willingness to participate in a hypothetical RCT for a novel pharmacotherapy for stimulant use among PWUD.

Methods

Data were derived from a cross-sectional questionnaire administered to participants using crack and/or cocaine from three cohort studies of PWUD in Vancouver ( N = 229).

Results

A majority of participants were “definitely” or “probably” willing to participate in an RCT. In multivariable ordinal regression, trust in research physicians was positively associated with willingness to participate, while trust in primary care providers or medical research processes were not significantly associated.

Conclusions

This data suggests trust in research physicians plays a role in RCT decision-making among PWUD, while trust in healthcare providers and research processes appears less relevant. These findings highlight opportunities for supporting RCT recruitment by building trust in research physicians.
Secondary Effects of an Opioid-Focused Academic Detailing Program on Non-Opioid Controlled Substance Prescribing in Primary Care
Authors: Saffore Christopher D. , Pickard A. Simon , Crawford Stephanie Y. , Fischer Michael A. , Sharp Lisa K. , Pointer Sarah , Lee Todd A.
Published: March 2021

Background

Educational outreach programs that focus on safe opioid prescribing and awareness of state prescription monitoring programs may modify clinicians’ prescribing behavior. The objective of this study was to evaluate the secondary effects of an opioid-focused academic detailing (AD) program on non-opioid controlled substance prescribing in primary care.

Methods

A quasi-experimental pre-post study of primary care clinicians exposed and unexposed to the AD program was conducted using data from the Illinois Prescription Monitoring Program from December 2017 to February 2019. Outcomes were mean monthly prescriptions for benzodiazepines (BZD), non-BZD sedative-hypnotics, and carisoprodol, per clinician. A difference-in-differences (DID) approach utilizing repeated-measures mixed-effects linear regression models was used to compare changes in outcomes six-months before and after the program.

Results

Mean monthly BZD prescriptions declined in both groups of clinicians (AD-exposed n = 151; controls n = 399) after implementation of the AD program. Although the mean monthly number of BZD prescriptions decreased in both groups after the AD program, BZD prescribing in the AD-exposed group declined at a slower rate following the AD program (DID = 0.73; 95% CI: 0.14, 1.31). The AD-exposed group had a 0.06 (95% CI: −0.11, −0.01) lower rate of mean monthly carisoprodol prescriptions compared to the control group following the AD program. There was no change in the rate of mean monthly non-BZD sedative-hypnotic prescriptions between the two groups.

Conclusions

The higher relative rate of BZD prescribing in the AD-exposed group compared to the control group following the AD program may be reflective of an unintended consequence of opioid-focused AD programs as clinicians learn to be cautious about opioid prescribing. Our findings may suggest the need for incorporation of targeted education on appropriate BZD prescribing into opioid-focused AD programs as a featured component. These findings warrant further consideration and investigation before large-scale implementation of opioid-focused educational outreach programs.
Superconductors for power applications: an executable and web application to learn about resistive fault current limiters
Authors: Riva Nicolò , Grilli Francesco , Dutoit Bertrand
Published: March 2021

High-temperature superconductors (HTS) can be superconducting in liquid nitrogen (77 K) at atmospheric pressure, which holds immense promises for our future such as nuclear fusion, compact medical devices and efficient power applications. In a power system, high short-circuit currents can exceed the operational current by more than ten times, putting many parts of the system at risk. Superconducting fault current limiters (SFCLs) can limit the prospective fault current without disconnecting the power system, and are thus becoming increasingly attractive for future grids. With a growing interest in modeling and commercializing SFCL, the question of how to teach and to explain their operation to students has arisen. In order to help students visualize the potential use and benefits of an SFCL, we created an executable and a web application using COMSOL Multiphysics. This executable allows students to investigate the electro-thermal response of a resistive SFCL. The executable solves a 1D electro-thermal model of the SFCL under AC fault conditions, evaluating important figures of merit such as the limited current, the prospective current and the maximum temperature reached within the tape. Finally, the geometrical parameters as well as the superconducting properties of the device can be modified. The importance of the amount of silver stabilizer necessary to protect the device from over-heating occurring during a fault current can be investigated. In addition, the effects of having a sharp nonlinear transition from the superconducting to the normal state (intrinsic property of the superconductor) to obtain a current limitation can be explored. The executable allows the users to learn about the benefits of superconductors in real-life applications, without the prerequisite of extensive modeling or experimental setup. The executable can be downloaded from the HTS modeling website and run on the most commonly used operating systems.
Electronic structure evolution of the transition metals substituted tetragonal graphene: a first-principles investigations
Authors: Sadhukhan Surasree , Kanungo Sudipta
Published: March 2021

Motivated by the possibilities of tuning the Fermi level of the metallic band structure of the planar tetragonal graphene (T-graphene), by using the transition metals (TMs) substitution (3d, 4d and 5d series), the electronic structure investigation has been carried out at low concentration level (≈2.7%) through ab initio density functional theory method. We have investigated the influence of the valence electrons of the TM on the evolution of the electronic structure and magnetization and the induced magnetic moments at the carbon atoms in the T-graphene network. The investigations also explored the possibilities of inducing long-range magnetic ordering. In the case of multi TMs substitutions we found the dominance signature of the antiferromagnetic correlations for most of the TM substituted cases. The critical analysis of the magnetization densities indicated the important role of the hybridization between the carbon π and σ orbitals with the TM-d states. We explored that the observed non-monotonic nature of the magnetization and evolution of electronic structure was due to the competing energy scales of electronic correlation, hybridization and crystal field splitting. This study opens up the route for further investigations towards the possibilities of using T-graphene as a potential polymorph of graphene for device applications.