RESUMO
Oxygen molecules accept electrons from the respiratory chain in the mitochondria and are responsible for energy production in aerobic organisms. The reactive oxygen species formed via these oxygen reduction processes undergo complicated electron transfer reactions with other biological substances, which leads to alterations in their physiological functions and cause diverse biological and pathophysiological consequences (e.g., oxidative stress). Oxygen accounts for only a small proportion of the redox reactions in organisms, especially under aerobic or hypoxic conditions but not under anaerobic and hypoxic conditions. This article discusses a completely new concept of redox biology, which is governed by redox-active supersulfides, i.e., sulfur-catenated molecular species. These species are present in abundance in all organisms but remain largely unexplored in terms of redox biology and life science research. In fact, accumulating evidence shows that supersulfides have extensive redox chemical properties and that they can be readily ionized or radicalized to participate in energy metabolism, redox signaling, and oxidative stress responses in cells and in vivo. Thus, pharmacological intervention and medicinal modulation of supersulfide activities have been shown to benefit the regulation of disease pathogenesis as well as disease control.
Assuntos
Oxirredução , Estresse Oxidativo , Espécies Reativas de Oxigênio , Transdução de Sinais , Sulfetos , Humanos , Animais , Sulfetos/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Metabolismo Energético , Mitocôndrias/metabolismoRESUMO
SUMMARY STATEMENT: Medical students have traditionally practiced painful procedures such as intravenous (IV) line insertion on each other. Recently, there has been more emphasis on learning through simulation. Our study investigated students' attitudes regarding IV line insertion training, focusing on their anxiety, expectation to learn empathy, learning preference, and litigiousness. A 24-question survey was taken regarding anxiety and empathy when learning IV placement on each other versus on mannequins.Many students believed that they could learn empathy skills and better appreciate patient discomfort by learning IV placement through person-based practice. However, students who reported feeling anxious about having a student practice IV placement on them believed they were less likely to learn empathy through having a student practice IV insertion on them. The preferred method of learning painful procedures, such as IV placement, may be through a combination of simulation and person-based practice to mitigate anxiety while also enhancing empathy skills.
RESUMO
INTRODUCTION: Site visits (SVs) are a common component of clinical education. The purpose of this paper was to explore clinicians' perspectives regarding SVs, including methods of communication used and their effectiveness, purposes of SVs, and the level of interaction between the stakeholders. REVIEW OF THE LITERATURE: Several communication methods are used to conduct SVs, with varying levels of "richness" and effectiveness. Previous studies have explored the perceptions of physical therapist (PT) students and Directors of Clinical Education regarding communication methods used during SVs, as well as reporting the purposes, effectiveness, and logistics. SUBJECTS: Clinicians, including clinical instructors (CIs) and Site Coordinators of Clinical Education, from across the United States, representing various geographical locations and settings were invited to participate. METHODS: An electronic survey was distributed to participants using information from 2 PT education programs and the Physical Therapist Clinical Performance Instrument database. RESULTS: A total of 273 responses were included in the analysis. Clinicians ranked in-person visits as their first choice of communication for future SVs (n = 157, 59.9%) and indicated that in-person communication was "very effective" (n = 143, 52.4%) when compared with videoconferencing (n = 55, 20.1%) and telephone (n = 49, 17.9%). Clinicians ranked verifying the competency level of the student and verifying site resources during the SV as "extremely important" or "important" (n = 257, 94.2% and n = 250, 91.5%, respectively). Answering CI's questions and providing support to the CI were also identified as "extremely important" or "important" (n = 262, 96% and n = 244, 89.4%, respectively). Analysis of open-ended responses revealed 5 themes: Communication is important, flexibility allows best fit for a situation, on-site visits offer a more complete picture, real-time dialog is preferred, and email can lead to misinterpretation. DISCUSSION AND CONCLUSION: Communication is a key component of the clinical-academic relationship. Although clinicians prefer in-person communication, flexibility is necessary when planning and conducting SVs. Future research recommendations include gathering student and clinician perceptions regarding faculty involvement in SVs, as well as gathering faculty perspectives regarding their participation in SVs. In addition, the impact of the pandemic on the future of SVs warrants further exploration.
Assuntos
Comunicação , Humanos , Estados Unidos , Inquéritos e Questionários , Masculino , Feminino , Fisioterapeutas/educação , COVID-19/epidemiologia , Especialidade de Fisioterapia/educação , Docentes/psicologia , AdultoRESUMO
Reactive sulfane sulfur species such as persulfides (RSSH) and H2S2 are important redox regulators and closely linked to H2S signaling. However, the study of these species is still challenging due to their instability, high reactivity, and the lack of suitable donors to produce them. Herein we report a unique compound, 2H-thiopyran-2-thione sulfine (TTS), which can specifically convert H2S to HSOH, and then to H2S2 in the presence of excess H2S. Meanwhile, the reaction product 2H-thiopyran-2-thione (TT) can be oxidized to reform TTS by biological oxidants. The reaction mechanism of TTS is studied experimentally and computationally. TTS can be conjugated to proteins to achieve specific delivery, and the combination of TTS and H2S leads to highly efficient protein persulfidation. When TTS is applied in conjunction with established H2S donors, the corresponding donors of H2S2 (or its equivalents) are obtained. Cell-based studies reveal that TTS can effectively increase intracellular sulfane sulfur levels and compensate for certain aspects of sulfide:quinone oxidoreductase (SQR) deficiency. These properties make TTS a conceptually new strategy for the design of donors of reactive sulfane sulfur species.
Assuntos
Sulfeto de Hidrogênio , Piranos , Compostos de Sulfidrila , Sulfeto de Hidrogênio/metabolismo , Tionas , Sulfetos/metabolismo , Enxofre/metabolismo , Oxirredução , Proteínas/metabolismoRESUMO
Supersulfides, which are defined as sulfur species with catenated sulfur atoms, are increasingly being investigated in biology. We recently identified pyridoxal phosphate (PLP)-dependent biosynthesis of cysteine persulfide (CysSSH) and related supersulfides by cysteinyl-tRNA synthetase (CARS). Here, we investigated the physiological role of CysSSH in budding yeast (Saccharomyces cerevisiae) by generating a PLP-binding site mutation K109A in CRS1 (the yeast ortholog of CARS), which decreased the synthesis of CysSSH and related supersulfides and also led to reduced chronological aging, effects that were associated with an increased endoplasmic reticulum stress response and impaired mitochondrial bioenergetics. Reduced chronological aging in the K109A mutant could be rescued by using exogenous supersulfide donors. Our findings indicate important roles for CARS in the production and metabolism of supersulfides-to mediate mitochondrial function and to regulate longevity.
Assuntos
Longevidade , Proteínas de Saccharomyces cerevisiae , Mitocôndrias/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Enxofre/metabolismoAssuntos
Anemia Falciforme , Criança , Humanos , Fenótipo , Anemia Falciforme/genética , Anemia Falciforme/terapiaRESUMO
The onset of COVID-19 coincided with the peak growth of video game usage, with 2.7 billion gamers in 2020. During the pandemic, gaming and streaming platforms offered an entertaining, social, and safe alternative to recreation during severe lockdowns and social isolations. This study aimed to examine the impact of the COVID-19 pandemic on health-related outcomes in self-proclaimed video gamers based on the type of lockdown experienced and to discuss the potential role of video games during times of preventive lockdown measures. This was a cross-sectional international survey constructed by two academic institutions, NYIT (NY, USA) and McGill University (Montreal, Canada), and Adamas Esports (BC, Canada). The survey consisted of questions including demographics, multiple choice, ratings, and Likert scales relating to the periods prior to and during the COVID-19 lockdowns. There were 897 respondents from North America (72.7%), Europe (10.9%), Asia (4.9%), and other countries (11.5%), with a mean age of 22 years. Significant increases in game time were reported in casual and competitive gamers during the first months of the pandemic. The level of gaming, type of lockdown, and physical activity level prior to the pandemic were examined as potential moderating factors. Significant increases in sedentary behaviors (video game time and sitting time) were observed, while physical activity levels remained unchanged in most participants, regardless of the type of lockdown. Sleep time, but not sleep quality, increased, while mental health exhibited opposing effects, influenced by the type of lockdown and gaming competition levels. Video games, when played moderately, could offer a cost-effective, safe strategy to promote socialization and mental health and improve the overall well-being of the non-gaming and gaming population during pandemic times when strict lockdowns are in place.
Assuntos
COVID-19 , Jogos de Vídeo , Humanos , Adulto Jovem , Adulto , Pandemias/prevenção & controle , Estudos Transversais , COVID-19/epidemiologia , COVID-19/prevenção & controle , Controle de Doenças Transmissíveis , Inquéritos e Questionários , Jogos de Vídeo/psicologiaRESUMO
BACKGROUND: Esport players require a high number of action moves per minute to play, with substantial contractions of the wrist extensor muscles. Players frequently suffer from acute fatigue. The purpose of this study was to examine the use of below the elbow compression sleeves on Sm02 during intense aim training. Secondly, to examine players' performance and perception with and without compression. METHODS: This study was conducted at the New York Institute of Technology and enrolled fifteen collegiate esport players, 2 women and 13 men (age 21.2 ± 2.2). All subjects signed written consent. Participants performed 3 high intensity bouts of an aim trainer followed by a 15-minute rest before doing another 3 bouts of high intensity training conducting the other arm of the study. The compression wear order was randomized. The primary outcome included Sm02 of the extensor carpi radialis longus using near-infrared spectrometry. Secondary outcomes included Kills Per Second (KPS), Score, Total Time to Kill (TTK), accuracy, and perceived performance. RESULTS: Following 15 min of recovery, there was a significant rise in Sm02 while wearing the compression sleeve compared to no compression sleeve (p = 0.004). No change in Sm02 was seen while gaming. In trials 1 and 2, wearing the compression sleeve resulted in a significant increase in KPS and score when compared to not wearing it (p = 0.002,0.006). Although TTK and accuracy did not alter, 46.7% of participants believed the compression sleeve aided their performance. CONCLUSIONS: This study provides support that wearing below the elbow upper body compression sleeves while performing high intensity gaming may reduce fatigue, improve muscle recovery and gaming performance. TRIAL REGISTRATION: Clinicaltrials.gov identifier NCT05037071. Registered 08/09/2021. URL: Arm Compression on Muscle Oxygen Saturation - Full Text View - ClinicalTrials.gov.
RESUMO
Significance: Persulfides/polysulfides are sulfur-catenated molecular species (i.e., R-Sn-R', n > 2; R-Sn-H, n > 1, with R = cysteine, glutathione, and proteins), such as cysteine persulfide (CysSSH). These species are abundantly formed as endogenous metabolites in mammalian and human cells and tissues. However, the persulfide synthesis mechanism has yet to be thoroughly discussed. Recent Advances: We used ß-(4-hydroxyphenyl)ethyl iodoacetamide and mass spectrometry to develop sulfur metabolomics, a highly precise, quantitative analytical method for sulfur metabolites. Critical Issues: With this method, we detected appreciable amounts of different persulfide species in biological specimens from various organisms, from the domains Bacteria, Archaea, and Eukarya. By using our rigorously quantitative approach, we identified cysteinyl-tRNA synthetase (CARS) as a novel persulfide synthase, and we found that the CysSSH synthase activity of CARS is highly conserved from the domains Bacteria to Eukarya. Because persulfide synthesis is found not only with CARS but also with other sulfotransferase enzymes in many organisms, persulfides/polysulfides are expected to contribute as fundamental elements to substantially diverse biological phenomena. In fact, persulfide generation in higher organisms-that is, plants and animals-demonstrated various physiological functions that are mediated by redox signaling, such as regulation of energy metabolism, infection, inflammation, and cell death, including ferroptosis. Future Directions: Investigating CARS-dependent persulfide production may clarify various pathways of redox signaling in physiological and pathophysiological conditions and may thereby promote the development of preventive and therapeutic measures for oxidative stress as well as different inflammatory, metabolic, and neurodegenerative diseases. Antioxid. Redox Signal. 39, 983-999.
Assuntos
Cisteína , Sulfetos , Animais , Humanos , Sulfetos/metabolismo , Oxirredução , Cisteína/metabolismo , Enxofre/metabolismo , Mamíferos/metabolismoRESUMO
Abundant formation of endogenous supersulfides, which include reactive persulfide species and sulfur catenated residues in thiols and proteins (supersulfidation), has been observed. We found here that supersulfides catalyze S-nitrosoglutathione (GSNO) metabolism via glutathione-dependent electron transfer from aldehydes by exploiting alcohol dehydrogenase 5 (ADH5). ADH5 is a highly conserved bifunctional enzyme serving as GSNO reductase (GSNOR) that down-regulates NO signaling and formaldehyde dehydrogenase (FDH) that detoxifies formaldehyde in the form of glutathione hemithioacetal. C174S mutation significantly reduced the supersulfidation of ADH5 and almost abolished GSNOR activity but spared FDH activity. Notably, Adh5C174S/C174S mice manifested improved cardiac functions possibly because of GSNOR elimination and consequent increased NO bioavailability. Therefore, we successfully separated dual functions (GSNOR and FDH) of ADH5 (mediated by the supersulfide catalysis) through the biochemical analysis for supersulfides in vitro and characterizing in vivo phenotypes of the GSNOR-deficient organisms that we established herein. Supersulfides in ADH5 thus constitute a substantial catalytic center for GSNO metabolism mediating electron transfer from aldehydes.
Assuntos
Aldeídos , Óxido Nítrico , Animais , Camundongos , Transporte de Elétrons , Catálise , GlutationaRESUMO
Supersulphides are inorganic and organic sulphides with sulphur catenation with diverse physiological functions. Their synthesis is mainly mediated by mitochondrial cysteinyl-tRNA synthetase (CARS2) that functions as a principal cysteine persulphide synthase (CPERS). Here, we identify protective functions of supersulphides in viral airway infections (influenza and COVID-19), in aged lungs and in chronic lung diseases, including chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF). We develop a method for breath supersulphur-omics and demonstrate that levels of exhaled supersulphides increase in people with COVID-19 infection and in a hamster model of SARS-CoV-2 infection. Lung damage and subsequent lethality that result from oxidative stress and inflammation in mouse models of COPD, IPF, and ageing were mitigated by endogenous supersulphides production by CARS2/CPERS or exogenous administration of the supersulphide donor glutathione trisulphide. We revealed a protective role of supersulphides in airways with various viral or chronic insults and demonstrated the potential of targeting supersulphides in lung disease.
Assuntos
COVID-19 , Fibrose Pulmonar Idiopática , Doença Pulmonar Obstrutiva Crônica , Animais , Camundongos , SARS-CoV-2 , Doença Pulmonar Obstrutiva Crônica/genética , Pulmão , Fibrose Pulmonar Idiopática/genéticaRESUMO
Background: Non-motor symptoms of Parkinson's disease (PD) such as cognitive impairment are common and decrease patient quality of life and daily functioning. While no pharmacological treatments have effectively alleviated these symptoms to date, non-pharmacological approaches such as cognitive remediation therapy (CRT) and physical exercise have both been shown to improve cognitive function and quality of life in people with PD. Objective: This study aims to determine the feasibility and impact of remote CRT on cognitive function and quality of life in patients with PD participating in an organized group exercise program. Methods: Twenty-four subjects with PD recruited from Rock Steady Boxing (RSB), a non-contact group exercise program, were evaluated using standard neuropsychological and quality of life measures and randomized to the control or intervention group. The intervention group attended online CRT sessions for one hour, twice a week for 10 weeks, engaging in multi-domain cognitive exercises and group discussion. Results: Twenty-one subjects completed the study and were reevaluated. Comparing groups over time, the control group (n = 10) saw a decline in overall cognitive performance that trended towards significance (p = 0.05) and a statistically significant decrease in delayed memory (p = 0.010) and self-reported cognition (p = 0.011). Neither of these findings were seen in the intervention group (n = 11), which overwhelmingly enjoyed the CRT sessions and attested to subjective improvements in their daily lives. Conclusions: This randomized controlled pilot study suggests that remote CRT for PD patients is feasible, enjoyable, and may help slow the progression of cognitive decline. Further trials are warranted to determine the longitudinal effects of such a program.
RESUMO
Reactive sulfur species, or persulfides and polysulfides, such as cysteine hydropersulfide and glutathione persulfide, are endogenously produced in abundance in both prokaryotes and eukaryotes, including mammals. Various forms of reactive persulfides occur in both low-molecular-weight and protein-bound thiols. The chemical properties and great supply of these molecular species suggest a pivotal role for reactive persulfides/polysulfides in different cellular regulatory processes (e.g., energy metabolism and redox signaling). We demonstrated earlier that cysteinyl-tRNA synthetase (CARS) is a new cysteine persulfide synthase (CPERS) and is responsible for the in vivo production of most reactive persulfides (polysulfides). Some researchers continue to suggest that 3-mercaptopyruvate sulfurtransferase (3-MST), cystathionine ß-synthase (CBS), and cystathionine γ-lyase (CSE) may also produce hydrogen sulfide and persulfides that may be generated during the transfer of sulfur from 3-mercaptopyruvate to the cysteine residues of 3-MST or direct synthesis from cysteine by CBS/CSE, respectively. We thus used integrated sulfur metabolome analysis, which we recently developed, with 3-MST knockout (KO) mice and CBS/CSE/3-MST triple-KO mice, to elucidate the possible contribution of 3-MST, CBS, and CSE to the production of reactive persulfides in vivo. We therefore quantified various sulfide metabolites in organs derived from these mutant mice and their wild-type littermates via this sulfur metabolome, which clearly revealed no significant difference between mutant mice and wild-type mice in terms of reactive persulfide production. This result indicates that 3-MST, CBS, and CSE are not major sources of endogenous reactive persulfide production; rather, CARS/CPERS is the principal enzyme that is actually involved in and even primarily responsible for the biosynthesis of reactive persulfides and polysulfides in vivo in mammals.
RESUMO
There is a strong association between intracranial hypertension (IH) that occurs following the acute phase of traumatic brain injury (TBI) and negative outcomes. This study proposes a pressure-time dose (PTD)-based parameter that may specify a possible serious IH (SIH) event and develops a model to predict SIH. The minute-by-minute signals of arterial blood pressure (ABP) and intracranial pressure (ICP) of 117 TBI patients were utilized as the internal validation dataset. The SIH event was explored through the prognostic power of the IH event variables for the outcome after 6 months, and an IH event with thresholds that included an ICP of 20 mmHg and PTD > 130 mmHg * minutes was considered an SIH event. The physiological characteristics of normal, IH and SIH events were investigated. LightGBM was employed to forecast an SIH event from various time intervals using physiological parameters derived from the ABP and ICP. Training and validation were conducted on 1,921 SIH events. External validation was performed on two multi-center datasets containing 26 and 382 SIH events. The SIH parameters could be used to predict mortality (AUROC = 0.893, p < 0.001) and favorability (AUROC = 0.858, p < 0.001). The trained model robustly forecasted SIH after 5 and 480 minutes with an accuracy of 86.95% and 72.18% in internal validation. External validation also revealed a similar performance. This study demonstrated that the proposed SIH prediction model has reasonable predictive capacities. A future intervention study is required to investigate whether the definition of SIH is maintained in multi-center data and to ensure the effects of the predictive system on TBI patient outcomes at the bedside.
RESUMO
Objective: The purpose of this study was to investigate the association between academic success and changes in predictor variables of aerobic fitness, sleep, stress and quality of life (QOL) in students enrolled in the first year of a physical therapist education program. Participants: This prospective longitudinal cohort study utilized 37 first-year Doctor of Physical Therapy students. Methods: We investigated the association between grade point average (GPA) and the various predictor variables. A multiple logistic regression model with backward selection was used to predict GPA. GPA greater than or equal to 3.5 or below 3.5 out of a 4.0 scale were used as the dichotomous events. Results: The regression model with the selected-out predictors was a good fit (p = 0.011). About 60% of the variation in the outcome GPA binary can be explained by the selected predictors that were the changes in sleep and QOL. Conclusions: Achieving academic success can be affected by changes in sleep and QOL.
Assuntos
Sucesso Acadêmico , Humanos , Qualidade de Vida , Estudantes , Estudos Longitudinais , Estudos Prospectivos , Universidades , Instituições Acadêmicas , Modalidades de Fisioterapia , SonoAssuntos
COVID-19 , Nascimento Prematuro , Recém-Nascido , Humanos , Feminino , Nascimento Prematuro/epidemiologia , FamíliaRESUMO
BACKGROUND & AIMS: Weight loss and exercise intervention have been reported to increase the interaction between Bacteroides spp and Akkermansiamuciniphila (Am), although the underlying mechanisms and consequences of the interaction remain unknown. METHODS: Using a healthy Korean twin cohort (n = 582), we analyzed taxonomic associations with host body mass index. B vulgatus strains were isolated from mice and human subjects to investigate the strain-specific effect of B vulgatus SNUG 40005 (Bvul) on obesity. The mechanisms underlying Am enrichment by Bvul administration were investigated by multiple experiments: (1) in vitro cross-feeding experiments, (2) construction of Bvul mutants with the N-acetylglucosaminidase gene knocked out, and (3) in vivo validation cohorts with different metabolites. Finally, metabolite profiling in mouse and human fecal samples was performed. RESULTS: An interaction between Bvul and Am was observed in lean subjects but was disrupted in obese subjects. The administration of Bvul to mice fed a high-fat diet decreased body weight, insulin resistance, and gut permeability. In particular, Bvul restored the abundance of Am, which decreased significantly after a long-term high-fat diet. A cross-feeding analysis of Am with cecal contents or Bvul revealed that Am enrichment was attributed to metabolites produced during mucus degradation by Bvul. The metabolome profile of mouse fecal samples identified N-acetylglucosamine as contributing to Am enrichment, which was confirmed by in vitro and in vivo experiments. Metabolite network analysis of the twin cohort found that lysine serves as a bridge between N-acetylglucosamine, Bvul, and Am. CONCLUSIONS: Strain-specific microbe-microbe interactions modulate the mucosal environment via metabolites produced during mucin degradation in the gut.
Assuntos
Acetilglucosamina , Akkermansia , Humanos , Camundongos , Animais , Bacteroides/genética , Obesidade/metabolismo , Dieta HiperlipídicaRESUMO
Recently, bioactive glass nanoparticles (BGns) have been acknowledged for their ability to promote interactions with the periapical tissue and enhance tissue regeneration by releasing therapeutic ions. However, there have been no studies on calcium silicate sealers with bioactive glass nanoparticle (BGn) additives. In the present study, a premixed calcium silicate root canal sealer reinforced with BGn (pre-mixed-RCS@BGn) was developed and its physicochemical features and biological effects were analyzed. Three specimens were in the trial: 0%, 0.5%, and 1% bioactive glass nanoparticles (BGns) were gradually added to the premixed type of calcium silicate-based sealer (pre-mixed-RCS). To elucidate the surface properties, scanning electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy were used and flowability, setting time, solubility, and radiopacity were analyzed to evaluate the physical properties. Chemical properties were investigated by water contact angle, pH change, and ion release measurements. The antibacterial effects of the bioactive set sealers were tested with Enterococcus faecalis and the viability of human bone marrow-derived mesenchymal stem cells (hMSCs) with this biomaterial was examined. In addition, osteogenic differentiation was highly stimulated, which was confirmed by ALP (Alkaline phosphatase) activity and the ARS (Alizarin red S) staining of hMSCs. The pre-mixed-RCS@BGn satisfied the ISO standards for root canal sealers and maintained antimicrobial activity. Moreover, pre-mixed-RCS@BGn with more BGns turned out to have less cytotoxicity than pre-mixed-RCS without BGns while promoting osteogenic differentiation, mainly due to calcium and silicon ion release. Our results suggest that BGns enhance the biological properties of this calcium silicate-based sealer and that the newly introduced pre-mixed-RCS@BGn has the capability to be applied in dental procedures as a root canal sealer. Further studies focusing more on the biocompatibility of pre-mixed-RCS@BGn should be performed to investigate in vivo systems, including pulp tissue.
RESUMO
The polymorphism of nanostructures is of paramount importance for many promising applications in high-performance nanodevices. We report the chemical vapor deposition synthesis of Ga2S3 nanowires (NWs) that show the consecutive phase transitions of monoclinic (M) â hexagonal (H) â wurtzite (W) â zinc blende (C) when lowering the growth temperature from 850 to 600 °C. At the highest temperature, single-crystalline NWs were grown in the thermodynamically stable M phase. Two types of H phase exhibited 1.8 nm periodic superlattice structures owing to the distinctively ordered Ga sites. They consisted of three rotational variants of the M phase along the growth direction ([001]M = [0001]H/W) but with different sequences in the variants. The phases shared the same crystallographic axis within the NWs, producing novel core-shell structures to illustrate the phase evolution. The relative stabilities of these phases were predicted using density functional theory calculations, and the results support the successive phase evolution. Photodetector devices based on the p-type M and H phase Ga2S3 NWs showed excellent UV photoresponse performance.
RESUMO
We compare the adiabatic quantized charge pumping performed in two types of InAs nanowire double quantum dots (DQDs), either with tunnel barriers defined by closely spaced narrow bottom gates, or by well-separated side gates. In the device with an array of bottom gates of 100 nm pitch and 10 µm lengths, the pump current is quantized only up to frequencies of a few MHz due to the strong capacitive coupling between the bottom gates. In contrast, in devices with well-separated side gates with reduced mutual gate capacitances, we find well-defined pump currents up to 30 MHz. Our experiments demonstrate that high frequency quantized charge pumping requires careful optimization of the device geometry, including the typically neglected gate feed lines.