bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of ABCC6 Transporter Modifies Cytoskeleton and Reduces Motility of HepG2 Cells via Purinergic Pathway
Authors: Ostuni Angela , Carmosino Monica , Miglionico Rocchina , Abruzzese Vittorio , Martinelli Fabio , Russo Daniela , Laurenzana Ilaria , Petillo Agata , Bisaccia Faustino
Published: June 2020

ABCC6, belonging to sub-family C of ATP-binding cassette transporter, is an ATP-dependent transporter mainly present in the basolateral plasma membrane of hepatic and kidney cells. Although the substrates transported are still uncertain, ABCC6 has been shown to promote ATP release. The extracellular ATP and its derivatives di- and mono-nucleotides and adenosine by acting on specific receptors activate the so-called purinergic pathway, which in turn controls relevant cellular functions such as cell immunity, inflammation, and cancer. Here, we analyzed the effect of Abcc6 knockdown and probenecid-induced ABCC6 inhibition on cell cycle, cytoskeleton, and motility of HepG2 cells. Gene and protein expression were evaluated by quantitative Reverse Transcription PCR (RT-qPCR) and western blot, respectively. Cellular cycle analysis was evaluated by flow cytometry. Actin cytoskeleton dynamics was evaluated by laser confocal microscopy using fluorophore-conjugated phalloidin. Cell motility was analyzed by in vitro wound-healing migration assay. Cell migration is reduced both in Abcc6 knockdown HepG2 cells and in probenecid treated HepG2 cells by interfering with the extracellular reserve of ATP. Therefore, ABCC6 could contribute to cytoskeleton rearrangements and cell motility through purinergic signaling. Altogether, our findings shed light on a new role of the ABCC6 transporter in HepG2 cells and suggest that its inhibitor/s could be considered potential anti-metastatic drugs.
The Role of Hematopoietic Cell Transplant in the Glycoprotein Diseases
Authors: Naumchik Brianna M. , Gupta Ashish , Flanagan-Steet Heather , Steet Richard A. , Cathey Sara S. , Orchard Paul J. , Lund Troy C.
Published: June 2020

The glycoprotein disorders are a group of lysosomal storage diseases (α-mannosidosis, aspartylglucosaminuria, β-mannosidosis, fucosidosis, galactosialidosis, sialidosis, mucolipidosis II, mucolipidosis III, and Schindler Disease) characterized by specific lysosomal enzyme defects and resultant buildup of undegraded glycoprotein substrates. This buildup causes a multitude of abnormalities in patients including skeletal dysplasia, inflammation, ocular abnormalities, liver and spleen enlargement, myoclonus, ataxia, psychomotor delay, and mild to severe neurodegeneration. Pharmacological treatment options exist through enzyme replacement therapy (ERT) for a few, but therapies for this group of disorders is largely lacking. Hematopoietic cell transplant (HCT) has been explored as a potential therapeutic option for many of these disorders, as HCT introduces functional enzyme-producing cells into the bone marrow and blood along with the engraftment of healthy donor cells in the central nervous system (presumably as brain macrophages or a type of microglial cell). The outcome of HCT varies widely by disease type. We report our institutional experience with HCT as well as a review of the literature to better understand HCT and outcomes for the glycoprotein disorders.
Elements of the Endomucin Extracellular Domain Essential for VEGF-Induced VEGFR2 Activity
Authors: Hu Zhengping , Cano Issahy , Saez-Torres Kahira L. , LeBlanc Michelle E. , Saint-Geniez Magali , Ng Yin-Shan , Argüeso Pablo , D’Amore Patricia A.
Published: June 2020

Endomucin (EMCN) is the type I transmembrane glycoprotein, mucin-like component of the endothelial cell glycocalyx. We have previously shown that EMCN is necessary for vascular endothelial growth factor (VEGF)-induced VEGF receptor 2 (VEGFR2) internalization and downstream signaling. To explore the structural components of EMCN that are necessary for its function and the molecular mechanism of EMCN in VEGF-induced endothelial functions, we generated a series of mouse EMCN truncation mutants and examined their ability to rescue VEGF-induced endothelial functions in human primary endothelial cells (EC) in which endogenous EMCN had been knocked down using siRNA. Expression of the mouse full-length EMCN (FL EMCN) and the extracellular domain truncation mutants ∆21-81 EMCN and ∆21-121 EMCN, but not the shortest mutant ∆21-161 EMCN, successfully rescued the VEGF-induced EC migration, tube formation, and proliferation. ∆21-161 EMCN failed to interact with VEGFR2 and did not facilitate VEGFR2 internalization. Deletion of COSMC (C1GalT1C1) revealed that the abundant mucin-type O-glycans were not required for its VEGFR2-related functions. Mutation of the two N-glycosylation sites on ∆21-121 EMCN abolished its interaction with VEGFR2 and its function in VEGFR2 internalization. These results reveal ∆21-121 EMCN as the minimal extracellular domain sufficient for VEGFR2-mediated endothelial function and demonstrate an important role for N-glycosylation in VEGFR2 interaction, internalization, and angiogenic activity.
Emerin Phosphorylation during the Early Phase of the Oxidative Stress Response Influences Emerin–BAF Interaction and BAF Nuclear Localization
Authors: Cenni Vittoria , Squarzoni Stefano , Loi Manuela , Mattioli Elisabetta , Lattanzi Giovanna , Capanni Cristina
Published: June 2020

Reactive Oxygen Species (ROS) are reactive molecules required for the maintenance of physiological functions. Oxidative stress arises when ROS production exceeds the cellular ability to eliminate such molecules. In this study, we showed that oxidative stress induces post-translational modification of the inner nuclear membrane protein emerin. In particular, emerin is phosphorylated at the early stages of the oxidative stress response, while protein phosphorylation is abolished upon recovery from stress. A finely tuned balance between emerin phosphorylation and O-GlcNAcylation seems to govern this dynamic and modulates emerin–BAF interaction and BAF nucleoplasmic localization during the oxidative stress response. Interestingly, emerin post-translational modifications, similar to those observed during the stress response, are detected in cells bearing LMNA gene mutations and are characterized by a free radical generating environment. On the other hand, under oxidative stress conditions, a delay in DNA damage repair and cell cycle progression is found in cells from Emery–Dreifuss Muscular Dystrophy type 1, which do not express emerin. These results suggest a role of the emerin–BAF protein platform in the DNA damage response aimed at counteracting the detrimental effects of elevated levels of ROS.
Phosphoinositide Profile of the Mouse Retina
Authors: Finkelstein Stella , Gospe Sidney M. , Schuhmann Kai , Shevchenko Andrej , Arshavsky Vadim Y. , Lobanova Ekaterina S.
Published: June 2020

Phosphoinositides are known to play multiple roles in eukaryotic cells. Although dysregulation of phosphoinositide metabolism in the retina has been reported to cause visual dysfunction in animal models and human patients, our understanding of the phosphoinositide composition of the retina is limited. Here, we report a characterization of the phosphoinositide profile of the mouse retina and an analysis of the subcellular localization of major phosphorylated phosphoinositide forms in light-sensitive photoreceptor neurons. Using chromatography of deacylated phosphatidylinositol headgroups, we established PI(4,5)P2 and PI(4)P as two major phosphorylated phosphoinositides in the retina. Using high-resolution mass spectrometry, we revealed 18:0/20:4 and 16:0/20:4 as major fatty-acyl chains of retinal phosphoinositides. Finally, analysis of fluorescent phosphoinositide sensors in rod photoreceptors demonstrated distinct subcellular distribution patterns of major phosphoinositides. The PI(4,5)P2 reporter was enriched in the inner segments and synapses, but was barely detected in the light-sensitive outer segments. The PI(4)P reporter was mostly found in the outer and inner segments and the areas around nuclei, but to a lesser degree in the synaptic region. These findings provide support for future mechanistic studies defining the biological significance of major mono- (PI(4)P) and bisphosphate (PI(4,5)P2) phosphatidylinositols in photoreceptor biology and retinal health.
The Stemness of Human Ovarian Granulosa Cells and the Role of Resveratrol in the Differentiation of MSCs—A Review Based on Cellular and Molecular Knowledge
Authors: Jozkowiak Malgorzata , Hutchings Greg , Jankowski Maurycy , Kulcenty Katarzyna , Mozdziak Paul , Kempisty Bartosz , Spaczynski Robert Z. , Piotrowska-Kempisty Hanna
Published: June 2020

Ovarian Granulosa Cells (GCs) are known to proliferate in the developing follicle and undergo several biochemical processes during folliculogenesis. They represent a multipotent cell population that has been differentiated to neuronal cells, chondrocytes, and osteoblasts in vitro. However, progression and maturation of GCs are accompanied by a reduction in their stemness. In the developing follicle, GCs communicate with the oocyte bidirectionally via gap junctions. Together with neighboring theca cells, they play a crucial role in steroidogenesis, particularly the production of estradiol, as well as progesterone following luteinization. Many signaling pathways are known to be important throughout the follicle development, leading either towards luteinization and release of the oocyte, or follicular atresia and apoptosis. These signaling pathways include cAMP, PI3K, SMAD, Hedgehog (HH), Hippo and Notch, which act together in a complex manner to control the maturation of GCs through regulation of key genes, from the primordial follicle to the luteal phase. Small molecules such as resveratrol, a phytoalexin found in grapes, peanuts and other dietary constituents, may be able to activate/inhibit these signaling pathways and thereby control physiological properties of GCs. This article reviews the current knowledge about granulosa stem cells, the signaling pathways driving their development and maturation, as well as biological activities of resveratrol and its properties as a pro-differentiation agent.
Chromatin Trapping of Factors Involved in DNA Replication and Repair Underlies Heat-Induced Radio- and Chemosensitization
Authors: Luzhin Artem V. , Avanesyan Bogdan , Velichko Artem K. , Shender Victoria O. , Ovsyannikova Natalia , Arapidi Georgij P. , Shnaider Polina V. , Petrova Nadezhda V. , Kireev Igor I. , Razin Sergey V. , Kantidze Omar L.
Published: June 2020

Hyperthermia has been used as an adjuvant treatment for radio- and chemotherapy for decades. In addition to its effects on perfusion and oxygenation of cancer tissues, hyperthermia can enhance the efficacy of DNA-damaging treatments such as radiotherapy and chemotherapy. Although it is believed that the adjuvant effects are based on hyperthermia-induced dysfunction of DNA repair systems, the mechanisms of these dysfunctions remain elusive. Here, we propose that elevated temperatures can induce chromatin trapping (c-trapping) of essential factors, particularly those involved in DNA repair, and thus enhance the sensitization of cancer cells to DNA-damaging therapeutics. Using mass spectrometry-based proteomics, we identified proteins that could potentially undergo c-trapping in response to hyperthermia. Functional analyses of several identified factors involved in DNA repair demonstrated that c-trapping could indeed be a mechanism of hyperthermia-induced transient deficiency of DNA repair systems. Based on our proteomics data, we showed for the first time that hyperthermia could inhibit maturation of Okazaki fragments and activate a corresponding poly(ADP-ribose) polymerase-dependent DNA damage response. Together, our data suggest that chromatin trapping of factors involved in DNA repair and replication contributes to heat-induced radio- and chemosensitization.
Megalencephalic Leukoencephalopathy with Subcortical Cysts Disease-Linked MLC1 Protein Favors Gap-Junction Intercellular Communication by Regulating Connexin 43 Trafficking in Astrocytes
Authors: Lanciotti Angela , Brignone Maria Stefania , Belfiore Marcello , Columba-Cabezas Sandra , Mallozzi Cinzia , Vincentini Olimpia , Molinari Paola , Petrucci Tamara Corinna , Visentin Sergio , Ambrosini Elena
Published: June 2020

Astrocytes, the most numerous cells of the central nervous system, exert critical functions for brain homeostasis. To this purpose, astrocytes generate a highly interconnected intercellular network allowing rapid exchange of ions and metabolites through gap junctions, adjoined channels composed of hexamers of connexin (Cx) proteins, mainly Cx43. Functional alterations of Cxs and gap junctions have been observed in several neuroinflammatory/neurodegenerative diseases. In the rare leukodystrophy megalencephalic leukoencephalopathy with subcortical cysts (MLC), astrocytes show defective control of ion/fluid exchanges causing brain edema, fluid cysts, and astrocyte/myelin vacuolation. MLC is caused by mutations in MLC1, an astrocyte-specific protein of elusive function, and in GlialCAM, a MLC1 chaperon. Both proteins are highly expressed at perivascular astrocyte end-feet and astrocyte-astrocyte contacts where they interact with zonula occludens-1 (ZO-1) and Cx43 junctional proteins. To investigate the possible role of Cx43 in MLC pathogenesis, we studied Cx43 properties in astrocytoma cells overexpressing wild type (WT) MLC1 or MLC1 carrying pathological mutations. Using biochemical and electrophysiological techniques, we found that WT, but not mutated, MLC1 expression favors intercellular communication by inhibiting extracellular-signal-regulated kinase 1/2 (ERK1/2)-mediated Cx43 phosphorylation and increasing Cx43 gap-junction stability. These data indicate MLC1 regulation of Cx43 in astrocytes and Cx43 involvement in MLC pathogenesis, suggesting potential target pathways for therapeutic interventions.
HIV Nef and Antiretroviral Therapy Have an Inhibitory Effect on Autophagy in Human Astrocytes that May Contribute to HIV-Associated Neurocognitive Disorders
Authors: Cheney Laura , Guzik Hillary , Macaluso Frank P. , Macian Fernando , Cuervo Ana Maria , Berman Joan W.
Published: June 2020

A significant number of people living with HIV (PLWH) develop HIV-associated neurocognitive disorders (HAND) despite highly effective antiretroviral therapy (ART). Dysregulated macroautophagy (autophagy) is implicated in HAND pathogenesis. The viral protein Nef, expressed even with suppressive ART, and certain antiretrovirals affect autophagy in non-CNS cells. Astrocytes, vital for CNS microenvironment homeostasis and neuronal health, require autophagy for their own homeostasis. We hypothesized that extracellular Nef and/or ART impact astrocyte autophagy, thus contributing to HAND. We studied in-bulk and selective autophagic flux in primary human astrocytes treated with extracellular Nef and/or a combination of tenofovir+emtricitabine+raltegravir (ART) using Western blotting, a tandem fluorescent LC3 reporter, and transmission electron microscopy/morphometry. We show that after 24 h treatment, Nef and ART decrease autophagosomes through different mechanisms. While Nef accelerates autophagosome degradation without inducing autophagosome formation, ART inhibits autophagosome formation. Combination Nef+ART further depletes autophagosomes by inducing both abnormalities. Additionally, extracellular Nef and/or ART inhibit lysosomal degradation of p62, indicating Nef and/or ART affect in-bulk and selective autophagy differently. Dysregulation of both autophagic processes is maintained after 7 days of Nef and/or ART treatment. Persistent autophagy dysregulation due to chronic Nef and/or ART exposure may ultimately result in astrocyte and neuronal dysfunction, contributing to HAND.
High Throughput strategies Aimed at Closing the GAP in Our Knowledge of Rho GTPase Signaling
Authors: Dahmene Manel , Quirion Laura , Laurin Mélanie
Published: June 2020

Since their discovery, Rho GTPases have emerged as key regulators of cytoskeletal dynamics. In humans, there are 20 Rho GTPases and more than 150 regulators that belong to the RhoGEF, RhoGAP, and RhoGDI families. Throughout development, Rho GTPases choregraph a plethora of cellular processes essential for cellular migration, cell–cell junctions, and cell polarity assembly. Rho GTPases are also significant mediators of cancer cell invasion. Nevertheless, to date only a few molecules from these intricate signaling networks have been studied in depth, which has prevented appreciation for the full scope of Rho GTPases’ biological functions. Given the large complexity involved, system level studies are required to fully grasp the extent of their biological roles and regulation. Recently, several groups have tackled this challenge by using proteomic approaches to map the full repertoire of Rho GTPases and Rho regulators protein interactions. These studies have provided in-depth understanding of Rho regulators specificity and have contributed to expand Rho GTPases’ effector portfolio. Additionally, new roles for understudied family members were unraveled using high throughput screening strategies using cell culture models and mouse embryos. In this review, we highlight theses latest large-scale efforts, and we discuss the emerging opportunities that may lead to the next wave of discoveries.
Host Gene Expression of Macrophages in Response to Feline Coronavirus Infection
Authors: Drechsler Yvonne , Vasconcelos Elton J. R. , Griggs Lisa M. , Diniz Pedro P. P. V. , Collisson Ellen
Published: June 2020

Feline coronavirus is a highly contagious virus potentially resulting in feline infectious peritonitis (FIP), while the pathogenesis of FIP remains not well understood, particularly in the events leading to the disease. A predominant theory is that the pathogenic FIPV arises from a mutation, so that it could replicate not only in enterocytes of the intestines but also in monocytes, subsequently systemically transporting the virus. The immune status and genetics of affected cats certainly play an important role in the pathogenesis. Considering the importance of genetics and host immune responses in viral infections, the goal of this study was to elucidate host gene expression in macrophages using RNA sequencing. Macrophages from healthy male cats infected with FIPV 79-1146 ex vivo displayed a differential host gene expression. Despite the virus uptake, aligned viral reads did not increase from 2 to 17 h. The overlap of host gene expression among macrophages from different cats was limited, even though viral transcripts were detected in the cells. Interestingly, some of the downregulated genes in all macrophages were involved in immune signaling, while some upregulated genes common for all cats were found to be inhibiting immune activation. Our results highlight individual host responses playing an important role, consistent with the fact that few cats develop feline infectious peritonitis despite a common presence of enteric FCoV.
Investigation the Stability of Water in Oil Biofuel Emulsions Using Sunflower Oil
Authors: Sahota Ravin S. , M. Dakka Sam
Published: June 2020

Targets to reduce CO2 emissions by 75% and NOx emissions by 90% by 2050 in aviation have been set by The Advisory Council for Aviation Research and Innovation in Europe. Sustainable fuels, e.g., emulsified biofuel, have demonstrated promise in reducing emissions and greenhouse gases. The aim of this project is to investigate the stability of a water in oil emulsion using sunflower oil. The primary objective is to achieve an emulsion which is stable for at least 4 days, and the secondary objective is to investigate how altering the emulsification parameter values of the surfactant hydrophilic-lipophilic balance (HLB), energy density and sonotrode depth in an ultrasonication procedure can impact the stability. The stability of each emulsion was measured over a period of 14 days. The main outcome is that two of the 14 emulsions made remained stable for at least 14 days using a surfactant HLB of five, which proved to be the optimum value from those tested. The results also show that, by using the sonotrode in a higher starting position, emulsions achieved a greater stability. Furthermore, over-processing of the emulsion was determined, with the point of over-processing lying between an energy density of 75 and 200 W.s/mL.
Sleep and Mental Health among Paramedics from Australia and Saudi Arabia: A Comparison Study
Authors: Khan Wahaj Anwar A. , Conduit Russell , Kennedy Gerard A. , Abdullah Alslamah Ahmed , Ahmad Alsuwayeh Mohammad , Jackson Melinda L.
Published: June 2020

Paramedics face many challenges while on duty, one of which is working different types of shifts. Shift work has been linked to a number of health issues such as insomnia, depression, and anxiety. Besides shift work, Saudi paramedics, a group that has not been investigated for sleep or mental health issues previously, may be facing more demands than Australian paramedics due to lower numbers of paramedics in comparison to the general population. The aim of this study was to investigate the prevalence of sleep and mental health disorders among paramedics in Saudi Arabia and Australia. Paramedics were invited to complete a survey to assess stress, post-traumatic stress disorder (PTSD), depression, anxiety, daytime sleepiness, insomnia, sleep quality, shift work disorder, obstructive sleep apnoea, fatigue, and general health. A total of 104 males Saudi paramedics (M age = 32.5 ± 6.1 years) and 83 males paramedics from Australia (M age = 44.1 ± 12.1 years) responded to the survey. Significantly higher rates of depression, PTSD, insomnia, and fatigue, along with significantly poorer physical functioning were observed among Saudi paramedics in comparison with Australian paramedics. However, Australian paramedics reported significantly poorer sleep quality and general health in comparison to Saudi paramedics. After removing the effect of driving and working durations, outcomes were no longer significant. The higher burden of depression and PTSD among Saudi paramedics may be explained by longer hours spent driving and longer work durations reported by this group. Taking into consideration the outcomes reported in this study, more investigations are needed to study their possible effects on paramedics’ cognition, performance, and safety.
Influence of Nitrogen Content and Bias Voltage on Residual Stress and the Tribological and Mechanical Properties of CrAlN Films
Authors: Tang Jian-Fu , Lin Ching-Yen , Yang Fu-Chi , Chang Chi-Lung
Published: June 2020

This study deposited CrAlN coatings from Al50Cr50 targets using high-power impulse magnetron sputtering, with a focus on the effects of nitrogen content and substrate bias voltage on the deposition rate, microstructure, crystal orientation, residual stress, and mechanical properties of the coating. The nitrogen content was adjusted by varying the N2/Ar flow ratio between 20% and 140%. Increasing the nitrogen flow rate during deposition led to corresponding decreases in the deposition rate and film thickness. X-ray diffractometer (XRD) analysis revealed that a low N2/Ar flow ratio (<40%) resulted in amorphous CrAlN, whereas a higher ratio (>40%) resulted in an face-centered cubic (FCC) phase. Bias voltage also had considerable influence on the residual stress and grain size. A refined grain structure and high internal stress resulted in hard CrAlN coatings. Among the various parameter combinations evaluated in this study, the highest hardness (35.4 GPa) and highest elastic modulus (426 GPa) were obtained using an N2/Ar flow ratio of 100% and a bias voltage of −120 V.
Enhancement of the Electrochemical Properties of an Open-Pore Graphite Foam with Electrochemically Reduced Graphene Oxide and Alternating Current Dispersed Platinum Particles
Authors: Fernández Javier , Bonastre José , Molina José Miguel , Cases Francisco
Published: June 2020

This paper aimed to improve the electrochemical activity of a pitch-derived open-pore graphite foam (GF) by an electrochemical coating of reduced graphene oxide (RGO) and platinum particles without significantly affecting its 3D-structure. RGO was synthesized using cyclic voltammetry (CV) from a 3 g L−1 GO and 0.1 M LiClO4 solution. For the electrodeposition of Pt particles, an alternating current method based on electrochemical impedance spectroscopy (EIS) was used. A sinusoidal voltage from a fixed potential Ei was varied following a selected amplitude (ΔEac = ± 0.35 V) in a frequency range of 8 Hz ≤ fi ≤ 10Hz, where i = 500. This method proved its efficiency when compared to the traditional CV by obtaining more highly electroactive coatings in less synthesis time. For samples’ characterization, physical measures included permeability, pressure drop, and nitrogen adsorption isotherms. The electrochemical characterization was performed by CV. The surface morphology and chemical composition were examined using field emission electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. RGO improved the electron transfer rate constant of GF, and a more homogeneous coating distribution of reduced size Pt particles was obtained.
A Review of Memory Errors Exploitation in x86-64
Authors: Pirry Conor , Marco-Gisbert Hector , Begg Carolyn
Published: June 2020

Memory errors are still a serious threat affecting millions of devices worldwide. Recently, bounty programs have reached a new record, paying up to USD 2.5 million for one single vulnerability in Android and up to USD 2 million for Apple’s operating system. In almost all cases, it is common to exploit memory errors in one or more stages to fully compromise those devices. In this paper, we review and discuss the importance of memory error vulnerabilities, and more specifically stack buffer overflows to provide a full view of how memory errors are exploited. We identify the root causes that make those attacks possible on modern x86-64 architecture in the presence of modern protection techniques. We have analyzed how unsafe library functions are prone to buffer overflows, revealing that although there are secure versions of those functions, they are not actually preventing buffer overflows from happening. Using secure functions does not result in software free from vulnerabilities and it requires developers to be security-aware. To overcome this problem, we discuss the three main security protection techniques present in all modern operating system; the non-eXecutable bit (NX), the Stack Smashing Protector (SSP) and the Address Space Layout Randomization (ASLR). After discussing their effectiveness, we conclude that although they provide a strong level of protection against classical exploitation techniques, modern attacks can bypass them.
Topological Dirac Semimetal Phase in Bismuth Based Anode Materials for Sodium-Ion Batteries
Authors: Chiu Wei-Chi , Singh Bahadur , Mardanya Sougata , Nokelainen Johannes , Agarwal Amit , Lin Hsin , Lane Christopher , Pussi Katariina , Barbiellini Bernardo , Bansil Arun
Published: June 2020

Bismuth has recently attracted interest in connection with Na-ion battery anodes due to its high volumetric capacity. It reacts with Na to form Na 3 Bi which is a prototypical Dirac semimetal with a nontrivial electronic structure. Density-functional-theory based first-principles calculations are playing a key role in understanding the fascinating electronic structure of Na 3 Bi and other topological materials. In particular, the strongly-constrained-and-appropriately-normed (SCAN) meta-generalized-gradient-approximation (meta-GGA) has shown significant improvement over the widely used generalized-gradient-approximation (GGA) scheme in capturing energetic, structural, and electronic properties of many classes of materials. Here, we discuss the electronic structure of Na 3 Bi within the SCAN framework and show that the resulting Fermi velocities and s-band shift around the Γ point are in better agreement with experiments than the corresponding GGA predictions. SCAN yields a purely spin-orbit-coupling (SOC) driven Dirac semimetal state in Na 3 Bi in contrast with the earlier GGA results. Our analysis reveals the presence of a topological phase transition from the Dirac semimetal to a trivial band insulator phase in Na 3 Bi x Sb 1 − x alloys as the strength of the SOC varies with Sb content, and gives insight into the role of the SOC in modulating conduction properties of Na 3 Bi.
A Versatile THz Source from High-Brightness Electron Beams: Generation and Characterization
Authors: Chiadroni Enrica , Cianchi Alessandro , Ferrario Massimo , Mostacci Andrea , Pompili Riccardo , Shpakov Vladimir
Published: June 2020

Ultra-short electron bunches, such as those delivered by a high-brightness photo-injector, are suitable to produce high peak power THz radiation, both broad and narrow band, with sub-picosecond down to femtosecond pulse shaping. The features of this kind of source in the THz range of the electromagnetic spectrum are extremely appealing for frequency- and time-domain experiments in a wide variety of fields. The present manuscript will overview the method of generation and characterization of THz radiation produced by high-brightness electron beams, as those available at the SPARC_LAB test facility.
Tetrathiafulvalene: A Gate to the Mechanochemical Mechanisms of Electron Transfer Reactions
Authors: Chen Richard , Gokus Mehmet Kerem , Pagola Silvina
Published: June 2020

This report describes aspects of our previous studies of the mechanochemical synthesis of charge transfer complexes of the electron donor tetrathiafulvalene, which are relevant to the use of laboratory X-ray powder diffraction for ex situ monitoring of mechanochemical reactions toward investigating their mechanisms. In particular, the reaction of tetrathiafulvalene and chloranil was studied under neat mechanochemical conditions and liquid-assisted grinding with diethyl ether (1 μL/mg). The product in both cases is the green tetrathiafulvalene chloranil polymorph and the mechanism of the redox reaction is presumably the same. However, while the kinetic profile of the neat mechanochemical synthesis was fitted with a second-order rate law, that of the overall faster liquid-assisted grinding reaction was fitted with the Ginstling-Brounshtein 3D diffusion-controlled model. Hence, the diffusional processes and mass transfer bringing the reactants together and separating them from products must be different. Diffraction measurements sensitive to crystalline phases and amorphous material, combined with in situ monitoring by spectroscopic techniques, will ultimately afford a better understanding of mechanochemical reaction mechanisms, a hot topic in mechanochemistry.
In Situ X-ray Diffraction Study of Xe and CO2 Adsorption in Y Zeolite: Comparison between Rietveld and PCA-Based Analysis
Authors: Conterosito Eleonora , Lopresti Mattia , Palin Luca
Published: June 2020

New very fast and efficient detectors, installed both on laboratory instruments and synchrotron facilities, allow the monitoring of solid-state reactions from subsecond to minute scales with the production of large amounts of data. Traditional “one-by-one” pattern refinement needs complementary approaches, useful to handle hundreds to thousands of X-ray patterns. Principal-component analysis (PCA) has been applied to these fields in the last few years to speed up analysis with the specific goals of assessing data quality, identifying patterns where a reaction occurs, and extracting the kinetics. PCA is applied to the adsorption/desorption of Xe and CO2 within a Y zeolite. CO2 sequestration is a key issue in relation to climate change, while Xe is a critical raw material, and its purification is an important topic for the industry. At first, results were compared to traditional sequential Rietveld refinement. CO2-Y data were also compared with in situ single crystal data to investigate the different potentialities of PCA in the two cases. Two CO2 adsorption sites were confirmed, while three Xe sites were identified. CO2 showed a more linear adsorption trend with decreasing temperature, while Xe showed a more sigmoidal-like trend. Xe only showed site-dependent behavior in adsorption. Finally, PCA and correlation analysis, applied to analyze the parameters obtained from Rietveld refinement, highlighted finer details: in particular, this approach showed that the Y zeolite framework responded differently to CO2 and Xe adsorption.
Thin Films and Glass–Ceramic Composites of Huntite Borates Family: A Brief Review
Authors: Volkova Elena A. , Naprasnikov Daniil A. , Leonyuk Nikolay I.
Published: June 2020

Rare-earth aluminum borates, RAl3(BO3)4 (where R = Y, Pr–Lu), are of great interest because of their attractive multifunctional properties, depending on their structure and composition. The combination of desirable physical and chemical characteristics makes them promising materials for lasers and nonlinear optics. Research focusing on RAl3(BO3)4 (RAB) compounds and their solids solutions has continued for more than five decades and has been reflected in numerous articles and several reviews. The last decade’s enhanced interest is being conducted towards epitaxial layers because of the availability of other possible applications, for instance, as scintillators, visible emitting phosphors or optical waveguides and waveguide lasers. On the other hand, the tendency of borate melts to form glasses makes them attractive for research of micro-crystallization processes in these systems and can be effortless towards finding relatively inexpensive optical glass–ceramic materials with similar composition as alternative components to laser systems. This article reviews the recent progress carried out hitherto on epitaxial layers and glass–ceramic composites of huntite-type rare-earth aluminum borates.
Mechanical Properties of DO3 Based on First Principles
Authors: Zhang Qingdong , Huang Gang , Li Shuo
Published: June 2020

The elastic constants, ideal strength, band structure and electronic density state of Fe3Si (DO3) under triaxial tension and triaxial compression were studied using the first principle. The structural parameters calculated at zero pressure are consistent with the experimental results. The dependence of elastic constant and strain can be obtained using static finite strain technique. The ideal triaxial tensile and compressive strength of DO3 were studied by calculating the stress–strain relationship. The micro mechanism that affects the stability of the structure was analyzed using the results of electronic structure calculation. The results showed that the compressive strength of DO3 structure is higher than the tensile strength. When the stress of cell structure exceeds a limit, the covalent bond of Fe–Si is destroyed, resulting in the sudden decrease of G and E and the abnormal change of electronic density of state.
Synthesis and Experimental-Computational Characterization of a Copper/Vanadium Compound with Potential Anticancer Activity
Authors: Martínez-Valencia Beatriz , Corona-Motolinia Nidia D. , Sánchez-Lara Eduardo , Sánchez-Gaytán Brenda L. , Cerro-López Mónica , Mendoza Angel , Castro María Eugenia , Meléndez-Bustamante Francisco J. , González-Vergara Enrique
Published: June 2020

Cancer represents a major worldwide public health problem. While significant advances in different fronts are being made to combat the disease, the development of new metal-based drugs with cytotoxic capabilities is of high relevance. This work presents a heterobimetallic molecule comprising two moieties with a structure similar to Casiopeina II-gly. One of them has a cyclotetravanadate anion that functions as an inorganic bridge coordinating two Cu (II) atoms resulting in a hexanuclear [Cu(phen)(Gly)-µ2-V4O12-Cu(phen)(Gly)]2− complex, which is counterbalanced by two isolated [Cu(phen)(Gly)(H2O)]1+ cations. Ten water molecules arranged in two sets of five-member chains also play an essential role in the 3D supramolecular structure of the compound. The molecule was designed to provide Cu and V, two metals with proven anticancer capabilities in the same molecular structure. The compound was synthesized and characterized by elemental analysis; visible, FTIR, and Raman spectroscopies; 51V Nuclear Magnetic Resonance; cyclic voltammetry; and monocrystalline X-ray diffraction. The structural, spectroscopic, and electronic properties of the compound were calculated through the density functional theory (DFT) using the Minnesota functional M06-2X and the Def2TZVP/LANL2TZ(f) basis sets with an effective core potential (ECP) for metals. Noncovalent interactions were analyzed using a natural population analysis (NPA) and Hirshfeld surfaces. The compound upon dissociation provides two metals that can interact with important biological targets in a variety of cancer cell models.
Highly Crystalline TiO2-MoO3 Composite Materials Synthesized via a Template-Assisted Microwave Method for Electrochemical Application
Authors: Kubiak Adam , Wojciechowska Wiktoria , Kurc Beata , Pigłowska Marita , Synoradzki Karol , Gabała Elżbieta , Moszyński Dariusz , Szybowicz Mirosław , Siwińska-Ciesielczyk Katarzyna , Jesionowski Teofil
Published: June 2020

TiO2-MoO3 composite systems were successfully prepared using a template-assisted microwave method at molar ratios TiO2:MoO3 = 8:2, 5:5 and 2:8. The synthesized material systems were comprehensively characterized, in terms of their crystalline structure (XRD and Raman spectroscopy), morphology (SEM, TEM and HRTEM analysis) and parameters of the porous structure (low-temperature N2 sorption). The materials exhibited highly crystalline phases: anatase and hexagonal molybdenum trioxide. Moreover, TEM analysis revealed hexagonal prism particles of MoO3 and nanocrystalline particles of TiO2. The proposed template-assisted microwave synthesis enabled the incorporation of TiO2 particles on the surface of hexagonal particles of MoO3, which resulted in a stable junction between titania and molybdenum trioxide. The values of BET surface area were 57, 29 and 11 m2/g for samples obtained at molar ratios TiO2:MoO3 = 8:2, 5:5 and 2:8 respectively. In electrochemical applications, titanium dioxide plays a crucial role as an intercalation intensifier, in which MoO3 is responsible for current conduction. Taking account of the potential electrochemical applications, the best system was obtained at the molar ratio TiO2:MoO3 = 5:5. The anode could maintain a capacity of 400 mAh/g at current densities in the range 100–1000 mA/g at potential values ranging from 1.00 to 3.30 V vs. Li/Li+. X-ray photoelectron spectroscopy (XPS) confirmed the effective intercalation of lithium ions into the TiO2-MoO3 composite materials.
Improving the Power Efficiency of Micro-LED Displays with Optimized LED Chip Sizes
Authors: Hsiang En-Lin , He Ziqian , Huang Yuge , Gou Fangwang , Lan Yi-Fen , Wu Shin-Tson
Published: June 2020

Micro-LED (light-emitting diode) is a potentially disruptive display technology, while power consumption is a critical issue for all display devices. In this paper, we develop a physical model to evaluate the power consumption of micro-LED displays under different ambient lighting conditions. Both power efficiency and ambient reflectance are investigated in two types of full color display structures: red/green/blue (RGB) micro-LEDs, and blue-LED pumped quantum dots color-conversion. For each type of display with uniform RGB chip size, our simulation results indicate that there exists an optimal LED chip size, which leads to 30–40% power saving. We then extend our model to analyze different RGB chip sizes, and find that with optimized chip sizes an additional 12% average power saving can be achieved over that with uniform chip size.
Growth and Structural Characterization of Doped Polymorphic Crystalline MgPc as an Organic Semiconductor
Authors: Hamui Leon , Sánchez-Vergara María Elena , Sánchez-Ruiz Rocio , Álvarez-Toledano Cecilio , Reyes-Rodriguez Jose Luis , Ponce Arturo
Published: June 2020

The doping and crystallization of the molecular semiconductor formed from the magnesium phthalocyanine (MgPc) and 1-(4-Methoxyphenyl)-2,2,6,6-tetramethyl-5-phenylhepta-3,4-dienedioic (MTPDA) acid was carried out in this work. The crystals obtained were characterized by using transmission electronic microscopy (TEM), Raman spectroscopy, and X-Ray diffraction (XRD), to later evaluate their optical behavior. Raman, IR, and UV–Vis results indicate that the MgPc has been doped with the MTPDA. A uniform material layer with particles is observed as a result of a two-stage process, nucleation and growth. The polycrystalline films are constituted by a mixture of α and β phases with crystalline sizes of ~7 nm, 14 nm, and 20 nm average sizes. The films exhibit a preferred orientation along the [001]. The MTPDA doping does not have an important effect on the molecule planar distances indicating that the MTPDA molecule is among the equivalent MgPc plane direction. A transparent region with a minimum at 483 nm is observed, also a B-band at 337 nm and a Q-band transition with a high-energy peak around 639 nm, and a low energy peak around 691 nm.
Crystal Structure of the N112A Mutant of the Light-Driven Sodium Pump KR2
Authors: Maliar Nina , Kovalev Kirill , Baeken Christian , Balandin Taras , Astashkin Roman , Rulev Maksim , Alekseev Alexey , Ilyinsky Nikolay , Rogachev Andrey , Chupin Vladimir , Dolgikh Dmitry , Kirpichnikov Mikhail , Gordeliy Valentin
Published: June 2020

The light-driven sodium pump KR2, found in 2013 in the marine bacteria Krokinobacter eikastus, serves as a model protein for the studies of the sodium-pumping microbial rhodopsins (NaRs). KR2 possesses a unique NDQ (N112, D116, and Q123) set of the amino acid residues in the functionally relevant positions, named the NDQ motif. The N112 was shown to determine the Na+/H+ selectivity and pumping efficiency of the protein. Thus, N112A mutation converts KR2 into an outward proton pump. However, no structural data on the functional conversions of the light-driven sodium pumps are available at the moment. Here we present the crystal structure of the N112A mutant of KR2 in the ground state at the resolution of 2.4 Å. The structure revealed a minor deflection in the central part of the helix C and a double conformation of the L74 residue in the mutant. The organization of the retinal Schiff base and neighboring water molecules is preserved in the ground state of KR2-N112A. The presented data provide structural insights into the effects of the alterations of the characteristic NDQ motif of NaRs. Our findings also demonstrate that for the rational design of the KR2 variants with modified ion selectivity for optogenetic applications, the structures of the intermediate states of both the protein and its functional variants are required.
Comparative Study on the Activity of GaF3 and Ga2O3 Nanoparticle-Doped CsF-AlF3 Flux for Brazing 6061 Al/Q235 Steel Joints
Authors: Yao Zhen , Xue Songbai , Zhang Junxiong
Published: June 2020

The effect of trace amounts of GaF3 and Ga2O3 nanoparticles on the wettability and spreadability of CsF-AlF3 flux matched Zn-15Al filler metal were comparatively studied on 6061 aluminum alloy and Q235 low-carbon steel. The experimental results indicate that appropriate amounts of GaF3 and Ga2O3 added into the flux could significantly promote the Zn-15Al filler metal to wet and spread on the surface of 6061 aluminum alloy and Q235 low-carbon steel. The optimum ranges for GaF3 and Ga2O3 were 0.0075–0.01wt.% and 0.009–0.01 wt.%, respectively. Comparative analysis showed that the activity of CsF-AlF3 flux bearing GaF3 was higher than that bearing Ga2O3. The reason for this is that the former flux has a stronger ability to remove oxides of the base metal and reduce the interfacial tension of the molten filler metal and the base metal.
Sabella spallanzanii and Seafloor Biodiversity Enhancement in a Marine Soft-Sediment System
Authors: Douglas Emily J. , Townsend Michael , Tait Leigh W. , Greenfield Barry L. , Inglis Graeme J. , Lohrer Andrew M.
Published: June 2020

Predicting and managing the potential economic, social, and ecological impacts of bioinvasions is a key goal of non-indigenous species (NIS) research worldwide. The marine fan worm, Sabella spallanzanii, is an ecosystem engineering NIS that forms dense filter-feeding canopies on hard substrata and large clumps of individuals in soft sediment habitats. In this study, we investigated the epifaunal assemblages associated with Sabella clumps of increasing size and complexity from soft-sediment benthic ecosystems in Auckland Harbour, New Zealand. The diversity and abundance of epifaunal taxa increased with clump size. Species accumulation curves suggest that with further increases in Sabella clump size, diversity will continue to increase. There were no differential effects on taxa related to feeding mode or motility despite the potential for Sabella to reduce food to suspension feeders (through competition) and increase food supply to deposit feeders (through biodeposition). Our results provide an example of local biodiversity enhancement by an NIS, though some of the species benefitting from Sabella were themselves non-indigenous or of uncertain origin (cryptogenic/indeterminate). Longer term studies of the impacts of Sabella on native biodiversity and ecosystem functioning, including on food webs, are important next steps.
Plant Diversity and Composition Changes along an Altitudinal Gradient in the Isolated Volcano Sumaco in the Ecuadorian Amazon
Authors: Lozano Pablo , Cabrera Omar , Peyre Gwendolyn , Cleef Antoine , Toulkeridis Theofilos
Published: June 2020

The paramo is a unique and severely threatened ecosystem scattered in the high northern Andes of South America. However, several further, extra-Andean paramos exist, of which a particular case is situated on the active volcano Sumaco, in the northwestern Amazon Basin of Ecuador. We have set an elevational gradient of 600 m (3200–3800 m a.s.l.) and sampled a total of 21 vegetation plots, using the phytosociological method. All vascular plants encountered were typified by their taxonomy, life form and phytogeographic origin. In order to determine if plots may be ensembled into vegetation units and understand what the main environmental factors shaping this pattern are, a non-metric multidimensional scaling (NMDS) analysis was performed. In addition, species turnover was quantified in order to appreciate the quantity and sort of species which are responsible for the similarity or dissimilarity between vegetation units. Therefore, a SIMPER similarity percentage analysis was conducted. We encountered 68 plant species belonging to 54 genera and 31 families, of which three are Ecuadorian endemics. The most frequent life forms were erect herbs, rosette and tussocks, whereas the least were cushions. At genus level, 44% of the Sumaco paramo flora was of tropical origin, followed by temperate (33%) and finally cosmopolitan (22%). The neotropical montane element was the most represented with 15 species, followed by the Austral-Antarctic with ten, wide temperate with another ten and cosmopolitan with seven. Regarding vegetation, four floristically distinct groups were segregated being lower gradient (3250–3500 m a.s.l.) and high altitude (3500–3800 m a.s.l.)