Search

Although the two active redox centers in Li-rich cathodes, including the anionic and cationic contributions, can enable Li-ion batteries to achieve outstanding specific energy, their behaviors at different current densities have not been clarified. Here, we provide a comparative study of transition metals (TMs) and oxygen redox activities by directly accessing their oxidation states in Li-rich materials operated at very different current rates. Our data reveal that the oxidation of oxygen in the near-surface region is at the same level for electrodes cycled with a wide range of current rates, indicating a reaction gradient of lattice oxygen redox reactions. The oxidation process of lattice oxygen is found to be dynamically compatible with that of the TMs. Combining the results of first principles calculations and complementary experimental findings, we propose a detailed mechanism of structural distortion from octahedral Li to tetrahedral Li and the role of oxygen vacancy in Li+ diffusion. It is found that fast delithiation occurring at high current densities can easily cause local structural transformation, leading to a limited Li+ diffusion rate and consequently suppressing rate capability.

Background: The lack of racial diversity in science, technology, engineering, and mathematics (STEM) disciplines is perhaps one of the most challenging issues in the United States higher education system. The issue is not only concerning diverse students, but also diverse faculty members. One important contributing factor is the faculty hiring process. To make progress toward equity in hiring decisions, it is necessary to better understand how applicants are considered and evaluated. In this paper, we describe and present our study based on a survey of current STEM faculty members and administrators who examined applicant qualifcations and characteristics in STEM faculty hiring decisions. Results: There are three key fndings of the present research. First, we found that faculty members placed diferent levels of importance on characteristics and qualifcations for tenure track hiring and non-tenure track hiring. For example, items related to research were more important when evaluating tenure track applicants, whereas items related to teaching and diversity were more important when evaluating non-tenure track applicants. Second, faculty members' institutional classifcation, position, and personal identities (e.g., gender, race/ethnicity) had an impact on their evaluation criteria. For instance, we found men considered some diversity-related items more important than women. Third, faculty members rated the importance of qualifcations with diversity, equity, and inclusion (DEI)-related constructs signifcantly lower than qualifcations that did not specify DEI-related constructs, and this trend held for both tenure track and non-tenure track faculty hiring. Conclusions: This study was an attempt to address the issue of diversity in STEM faculty hiring at institutions of higher education by examining how applicant characteristics are considered and evaluated in faculty hiring practices. Emphasizing research reputation and postdoctoral reputation while neglecting institutional diversity and equitable and inclusive teaching, research, and service stunt progress toward racial diversity because biases--both implicit and explicit, both positive and negative--still exist. Our results were consistent with research on bias in recruitment, revealing that afnity bias, confrmation bias, and halo bias exist in the faculty hiring process. These biases contribute to inequities in hiring, and need to be addressed before we can reach, sustain, and grow desired levels of diversity

Low mental health literacy is a public health concern in China and contributes to the low underutilization of mental health resources. We extended the current conceptualization of mental health literacy and developed a comprehensive self-report measure of mental health literacy in the Chinese context, the Mental Health Literacy Questionnaire (MHLQ). We generated items based on existing literature, extensive qualitative interviews with mental health professionals and community members. We revised these items based on expert review to examine content validity, after which we conducted a pilot test with a representative sample of 734 urban and rural community members to illicit feedback on wording clarity and select items within appropriate difficulty levels (i.e., correct rate). We then examined dimensionality and item performance using multidimensional item response theory analyses in a combined sample of mental health professionals (n = 122), community members (n = 121), and college students (n = 144). We concluded a six-factor structure for the MHLQ encompassing mental health knowledge, mental illness knowledge, attitudes towards mental health, attitudes towards mental illness, behaviors regarding mental health promotion, and behaviors regarding mental illness coping. The scale yielded adequate internal reliability estimates and test-retest agreement, and convergent evidence and known-group comparisons results in support of construct validity. The six-factor MHLQ largely supported our extended theoretical conceptualization of the mental health literacy in the Chinese context. Future studies are needed to further validate the factor structure and examine measurement invariance., Author(s): Jue Wu [sup.1] [sup.2] [sup.3] , Cixin Wang [sup.4] , Yun Lu [sup.5] , Xu Zhu [sup.1] [sup.2] [sup.3] , Yanqing Li [sup.1] [sup.2] [sup.3] , Guangda Liu [sup.1] [...]

Due to their high specific capacities beyond 250 mA h g-1, lithium-rich oxides have been considered as promising cathodes for the next generation power batteries, bridging the capacity gap between traditional layered-oxide based lithium-ion batteries and future lithium metal batteries such as lithium sulfur and lithium air batteries. However, the practical application of Li-rich oxides has been hindered by formidable challenges. To address these challenges, the understanding of their electrochemical behaviors becomes critical and is expected to offer effective guidance for both materials and cell development. This review aims to provide fundamental insights into the reaction mechanisms, electrochemical challenges and modification strategies of lithium-rich oxides. We first summarize the research history, the pristine structures, and the classification of lithium-rich oxides. Then we review the critical reaction mechanisms that are closely related to their electrochemical features and performances, such as lattice oxygen oxidation, oxygen vacancy formation, transition-metal migration, layered to spinel transitions, 'two-phase mechanism', and lattice evolution. These discussions are coupled with state-of-the-art characterization techniques. As a comparison, the anionic redox reactions of layered sodium transition metal oxides are also discussed. Finally, after a brief overview of the correlation among the aforementioned mechanisms, we provide perspectives on the rational design of lithium-rich oxides with high energy densities and long-term cycling stability. This journal is

Cation-disordered Li-excess cathodes with oxygen redox reactions are promising candidates for high-energy-density Li ion batteries. Nevertheless, the oxygen redox process that is required for the high capacity often comes with the oxygen loss, which leads to severe capacity degradation and voltage decay. In this work, we have successfully synthesized a series of Li-excess cation-disordered cathodes (Li1.2Mn0.4+xTi0.4-xO2-xFx) (0 ​≤ ​x ​≤ ​0.2) with different fluorine (F) contents. The electrochemical performance results show that the Li1.2Mn0.55Ti0.25O1.85F0.15 (LMTOF0.15) exhibits the highest reversible capacity (275 mAh g-1, under 30 ​mA ​g-1), cyclability, and voltage retentions. The mapping of resonant inelastic X-ray scattering (mRIXS) and differential electrochemical mass spectroscopy (DEMS) results reveal that the fluorination enhances the reversible lattice oxygen redox reaction while suppressing irreversible gas release and surface reactions. The X-ray Absorption Spectroscopy (XAS) during the initial two cycles shows that F-substitution alleviates the reduction of the Mn valence state during the whole (dis)charge processes in the bulk and at the surface of the material, results in higher average discharge voltage. In addition, the introduction of F improves the structural stability and suppresses local lattice distortion of the material. Therefore, LMTOF0.15 is able to cycle with smaller polarization, less interfacial side reaction and Mn dissolution, and therefore results in enhanced cyclability. This work provides a comprehensive understanding of the fluorination effect on the cationic and anionic redox activities in cation-disordered Li-excess cathodes.

Redox (reduction and oxidation) chemistry provides the fundamental basis for numerous energy-related electrochemical devices. Detecting the electrochemical redox chemistry is pivotal but challenging because it requires independent probes of the cationic and anionic redox states at different electrochemical states. The synchrotron-based soft X-ray mapping of resonant inelastic X-ray scattering (mRIXS) has recently emerged as a powerful tool for exploring such states in electrochemical devices, especially batteries. High-efficiency mRIXS covers the energy range of the absorption edge with the extra dimension of information on the emitted photon energies. In this frontier article, we review recent representative demonstrations of utilizing soft X-ray mRIXS for detecting the novel chemical state during electrochemical operation and for quantifying the cationic redox reactions through inverse partial fluorescence yield analysis (mRIXS-iPFY). More importantly, the non-divalent states of oxygen in electrodes involving oxygen redox reactions could be reliably captured by mRIXS, with its reversibility quantified by the intensity variation of the characteristic mRIXS feature through a super-partial fluorescence yield analysis (mRIXS-sPFY). These recent demonstrations inspire future perspectives on using mRIXS for studying the complex phenomena in energy materials, with both technical and scientific challenges in RIXS theory, in situ/operando experiments, and spatially resolved RIXS imaging.

Voltage decay,i.e., the voltage decrease during electrochemical cycling, has been a decade-long challenge for lithium-ion batteries. This issue not only leads to a substantial loss of energy density, but also raises challenges for the battery management system, hindering the commercial application of high capacity lithium-rich oxide. Here, we show that through a combination of electrochemical conditioning and thermal treatment, Li2MnO3, the parent compound of lithium-rich oxide, which typically displays severe voltage and capacity decay, could be converted into a new phase that essentially suppresses the voltage decay with improved capacity retention and rate performance. By combining atomic-sensitive nuclear magnetic resonance, differential electrochemical mass spectrometry and synchrotron-based resonant inelastic X-ray scattering, we disclose that treatment triggers the formation of three-coexisting phases,i.e., the lithium-rich layered, spinel and defect spinel phases, which enables improved reversibility of the oxygen redox activity and enhanced manganese redox reactions in the initial cycle. Our findings suggest the key role of the local structure in the voltage decay problem and provide insights for material optimizations towards lithium- and manganese-rich cathodes without the voltage decay.

Layered Li-rich Ni, Mn, Co (NMC) oxide cathodes in Li-ion batteries provide high specific capacities (>250 mAh/g) via O-redox at high voltages. However, associated high-voltage interfacial degradation processes require strategies for effective electrode surface passivation. Here, we show that an acidic surface treatment of a Li-rich NMC layered oxide cathode material leads to a substantial suppression of CO2 and O2 evolution, ∼90% and ∼100% respectively, during the first charge up to 4.8 V vs Li+/0. CO2 suppression is related to Li2CO3 removal as well as effective surface passivation against electrolyte degradation. This treatment does not result in any loss of discharge capacity and provides superior long-term cycling and rate performance in comparison to as-received, untreated materials. We also quantify the extent of lattice oxygen participation in charge compensation ("O-redox") during Li+ removal by a novel ex situ acid titration. Our results indicate that the peroxo-like species resulting from O-redox originate on the surface at least 300 mV earlier than the activation plateau region at around 4.5 V. X-ray photoelectron spectra and Mn L-edge X-ray absorption spectra of the cathode powders reveal a Li+ deficiency and a partial reduction of Mn ions on the surface of the acid-treated material. More interestingly, although the irreversible oxygen evolution is greatly suppressed through the surface treatment, O K-edge resonant inelastic X-ray scattering shows that the lattice O-redox behavior is largely sustained. The acidic treatment, therefore, only optimizes the surface of the Li-rich material and almost eliminates the irreversible gas evolution, leading to improved cycling and rate performance. This work therefore presents a simple yet effective approach to passivate cathode surfaces against interfacial instabilities during high-voltage battery operation.

As a parent compound of Li-rich electrodes, Li2MnO3 exhibits high capacity during the initial charge; however, it suffers notoriously low Coulombic efficiency due to oxygen and surface activities. Here, we successfully optimize the oxygen activities toward reversible oxygen redox reactions by intentionally introducing protons into lithium octahedral vacancies in the Li2MnO3 system with its original structural integrity maintained. Combining structural probes, theoretical calculations, and resonant inelastic X-ray scattering results, a moderate coupling between the introduced protons and lattice oxygen at the oxidized state is revealed, which stabilizes the oxygen activities during charging. Such a coupling leads to an unprecedented initial Coulombic efficiency (99.2%) with a greatly improved discharge capacity of 302 mAh g-1 in the protonated Li2MnO3 electrodes. These findings directly demonstrate an effective concept for controlling oxygen activities in Li-rich systems, which is critical for developing high-energy cathodes in batteries.

Involving students in the co-design of educational curricula and practices can benefit both students and teachers. Students who participate in co-design may show better learning or increased agency or engagement. In the present study, we investigated what kind of science knowledge or practices can be learned by student co-designers while engaging in co-design practices and how that learning happens with six high school students. We created a model to guide the analysis of students' learning with technology in co-designing processes. The results revealed that students learned engineering design process even if no explicit instruction on engineering learning was given. Also, our analysis suggested that co-designing with technology enabled learning of the engineering design process and potentially furthered learning of science because it promoted knowledge integration. The results have implications for understanding and enhancing engineering design and science learning through co-designing with technology.

The global COVID-19 is still in a pandemic state, and Omicron is still the dominant variant in the world, accounting for about 99% of the global gene sequence. Many regions around the world are experiencing the seventh wave of the epidemic. This round of epidemics is mainly caused by Omicron subvariants BA.4 and BA.5, but the epidemiological characteristics of Omicron subvariants BA.4 and BA.5 are still unclear, bringing great challenges to the prevention and control of the epidemic in countries and regions. In this study, discovery and epidemic status, the incubation period, transmissibility, clinical symptoms, case fatality rate, and the protective effect of vaccines of Omicron subvariants BA.4 and BA.5 were reviewed, in order to provide reference for scientific prevention and control of Omicron subvariants BA.4 and BA.5.

Layered Li-rich Ni, Mn, Co (NMC) oxide cathodes in Li-ion batteries provide high specific capacities (>250 mAh/g) via O-redox at high voltages. However, associated high-voltage interfacial degradation processes require strategies for effective electrode surface passivation. Here, we show that an acidic surface treatment of a Li-rich NMC layered oxide cathode material leads to a substantial suppression of CO2 and O2 evolution, ~90% and ~100% respectively, during the first charge up to 4.8 V vs. Li+/0. CO2 suppression is related to Li2CO3 removal as well as effective surface passivation against electrolyte degradation. This treatment does not result in any loss of discharge capacity and provides superior long-term cycling and rate performance compared to as-received, untreated materials. We also quantify the extent of lattice oxygen participation in charge compensation (“O-redox”) during Li+ removal by a novel ex-situ acid titration. Our results indicate that the peroxo-like species resulting from O-redox originate on the surface at least 300 mV earlier than the activation plateau region around 4.5 V. X-ray photoelectron spectra and Mn-L X-ray absorption spectra of the cathode powders reveal a Li+ deficiency and a partial reduction of Mn ions on the surface of the acid-treated material. More interestingly, although the irreversible oxygen evolution is greatly suppressed through the surface treatment, our O K-edge resonant inelastic X-ray scattering shows the lattice O-redox behavior largely sustained. The acidic treatment, therefore, only optimizes the surface of the Li-rich material and almost eliminates the irreversible gas evolution, leading to improved cycling and rate performance. This work therefore presents a simple yet effective approach to passivate cathode surfaces against interfacial instabilities during high-voltage battery operation.

Lithium cobalt oxide (LiCoO2) and graphite-based Li-ion batteries have been widely applied for consumer electronics because of the long cycle life and easy preparation. However, the limited capacity for traditional materials hampers the practical application for high energy-density battery. Conventional electrolyte system could not satisfy the need for high-capacity materials. Here, methylene methanedisulfonate (MMDS) was chosen as electrolyte additive for enhancing the available capacity for LiCoO2 and graphite-based battery. The effect of MMDS on the LiCoO2 cathode and graphite anode was investigated via multi electrochemical methods. It was found that the capacity for cells with MMDS electrolyte additive increases (from 142.6 mAh g−1 for pristine to 193.4 mAh g−1 on LiCoO2/Li battery, from 275.5 mAh g−1 for pristine to 407.0 mAh g−1 on graphite/Li battery). The experimental results indicate that improved capacity by MMDS electrolyte additive can be attributable to the stabilized interface on both cathode and anode sides, leading to superior interfacial Li+ kinetics and mitigated bulk structural degradation, which was further confirmed by the ex-situ electrochemical and structural characterization. [ABSTRACT FROM AUTHOR]

This study explores the transnational literacies that contribute to creating online social connections among migrant youth that may support their development and navigation of life across countries. We examine how social connectedness is semiotically constructed through time–space framing among two youth of Chinese descent who were participants of a larger study of the digital media practices of young people in an urban high school. We build on the concept of chronotope (Bakhtin, 1981) and scholarship of transnational literacies to understand the space–time dimensions of digital literacy practices, specifically how youth create the spatiotemporal context or frame of reference for their actions and positionings with others across geographical distances. Using a case study approach with data from interviews and observations, we analyzed how the youth depicted their transnational social relations within particular time–space frames. Qualitative and discourse analyses of the youths' narrative accounts show that they positioned themselves in proximity with their transnational peers within particular time–space contexts that supported their actions and emotions, and how they made sense of events, issues, practices, and their own identities as transnational individuals. The youths' ideas of schooling and education, and attunement to nationalistic ideologies, were developed through multiple chronotopes in their social connections across countries. This study offers implications for how an attention to the transnational spatiotemporal frame of youths' discourse and narrative may give us a more nuanced understanding of the subjectivity, knowledge, and perspective they derive from their experiences of movement and connection across borders. [ABSTRACT FROM AUTHOR]

Purpose. This study aimed to investigate nurses' perceptions of spirituality and spiritual care and perceived professional benefits in China and reveal the relationship between them. Design and Methods. In this study, 372 nurses (response rate: 93.47%) from a number of hospitals across China were surveyed using convenience sampling. The data were collected through online questionnaires, including a sociodemographic characteristics form, the Chinese version of the Spiritual Care-Giving Scale (C-SCGS), and the Nurses' Perceived Professional Benefits Questionnaire (NPPBQ). Findings. The total score of the NPPBQ was 136.88±20.13. A statistically significant relationship was found between the total score and subscale score of the C-SCGS and the total score and subscale score of the NPPBQ (R=0.217-0.475, P, Author(s): Xiaoying Zeng [1]; Jianhua Yang [1]; Yanjia Li [1]; Min Chen [2]; Jue Wu [3]; Yanli Hu [4]; Weinan Lu [1]; Jing Liu [1]; Qian Yang [1]; Wenqiong Guo [...]

The gender imbalance in computer science (CS) is one of the most challenging issues in American education. CS is the only science, technology, engineering, and mathematics (STEM) field in which women's representation has steadily declined in recent decades. In this study, we explored one potential approach that could be effective in increasing college women's participation in CS: participation in Women‐in‐Computing (WiC) groups. Through participant observation and individual interviews in a WiC group at a major research university, we investigated how students engage in WiC, the impacts of the WiC on identity and belonging, and the challenge of sustainability. The results were coded using a hybrid of grounded and deductive coding and indicate that WiC groups offer various programs and events that enable women in CS to fully participate, learn, and grow. WiC represents an identity, a community, a safe space, and a journey. The results also suggest that the WiC has had positive impacts on students' identity and belonging, as evidenced by increased self‐efficacy, reduced imposter syndrome, and enhanced sense of belonging and community. Furthermore, we outline three strategies employed by the WiC to ensure the group's sustainability. Our study sheds light on how WiC can encourage women to enter and persist in CS, and on some of the characteristics of a successful WiC. We demonstrate that WiC may be potentially effective in diversifying CS through identity‐based participation. Moreover, student leaders design both the structure of the group and the leadership continuity process to ensure sustainability. [ABSTRACT FROM AUTHOR]

Brain tumor is a severe cancer disease caused by uncontrollable and abnormal partitioning of cells. Recent progress in the field of deep learning has helped the health industry in Medical Imaging for Medical Diagnostic of many diseases. For Visual learning and Image Recognition, task CNN is the most prevalent and commonly used machine learning algorithm. Similarly, in our paper, we introduce the convolutional neural network (CNN) approach along with Data Augmentation and Image Processing to categorize brain MRI scan images into cancerous and non-cancerous. Using the transfer learning approach we compared the performance of our scratched CNN model with pre-trained VGG-16, ResNet-50, and Inception-v3 models. As the experiment is tested on a very small dataset but the experimental result shows that our model accuracy result is very effective and have very low complexity rate by achieving 100% accuracy, while VGG-16 achieved 96%, ResNet-50 achieved 89% and Inception-V3 achieved 75% accuracy. Our model requires very less computational power and has much better accuracy results as compared to other pre-trained models.

Mutations in the Aristaless-Related Homeobox (ARX) gene cause structural anomalies of the brain, epilepsy, and neurocognitive deficits in children. During forebrain development, Arx is expressed in both pallial and subpallial progenitor cells. We previously demonstrated that elimination of Arx from subpallial-derived cortical interneurons generates an epilepsy phenotype with features overlapping those seen in patients with ARX mutations. In this report, we have selectively removed Arx from pallial progenitor cells that give rise to the cerebral cortical projection neurons. While no discernable seizure activity was recorded, these mice exhibited a peculiar constellation of behaviors. They are less anxious, less social, and more active when compared with their wild-type littermates. The overall cortical thickness was reduced, and the corpus callosum and anterior commissure were hypoplastic, consistent with a perturbation in cortical connectivity. Taken together, these data suggest that some of the structural and behavioral anomalies, common in patients with ARX mutations, are specifically due to alterations in pallial progenitor function. Furthermore, our data demonstrate that some of the neurobehavioral features found in patients with ARX mutations may not be due to on-going seizures, as is often postulated, given that epilepsy was eliminated as a confounding variable in these behavior analyses.

Addicted drugs like nicotine affect autonomic nervous system that results in arrhythmia and other cardiovascular diseases. Notable effects of Zen meditation on autonomic nervous system have been reported during the past decade. Holistic Detox Association (HDA) in Taiwan offered Zen-meditation program to drug addicts as the core scheme among a variety of drug addiction treatments. This paper reports the results of quantifying the cardiorespiratory interactions and autonomic nervous system function to evaluate the on-site effect of Zen meditation on drug rehab. Methods and schemes for quantifying time-domain heart rate variability were employed to electrocardiograph and respiratory signals. Peak-valley method was developed to quantify the respiratory sinus arrhythmia (RSA) behavior. Poincaré Plot Analysis was adopted to evaluate the cardiorespiratory functioning. Among 18 voluntary drug addicts during the 10-minute Zen meditation session, about two-third subjects have significant improvement in autonomic nervous system function characterized by heart rate variability (SDNN, RMSSD and pNN50). Group average of RSA increases from 33.43 ms(Rest) to 69.14 ms(AR Zen meditation). Poincaré-plot analysis reveals the improvement of SD1, SD2 and SD2/SD1 by respectively 14.7%, 19.8% and 8.8%. The group averages of all the parameters exhibit significantly positive changes in the 10-minute session of abdominal-respiration Zen meditation. Even the subject with heart transplant showed the improvement of all the quantitative indicators during the AR Zen meditation. Keywords: Cardiorespiratory interaction, Drug addiction, Heart rate variability, Respiratory sinus arrhythmia, Zen meditation

This study aimed to reveal potential roles of the phosphatidylinositol 3 kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling pathway in apoptosis and autophagy of astrocytes induced by methamphetamine (METH). A Cell Counting Kit-8 (CCK-8) was used to determine the reduction in proliferation of U-118 MG cells induced by METH. Hoechst 33258 and flow cytometry were used to observe the astrocytes. Western blot analysis was performed to evaluate protein expression and phosphorylation levels. METH inhibited the proliferation of U-118 MG cells and induced apoptosis and autophagy. Western blot analysis showed that the ratio of LC3-II/I was increased, whereas the expression of Bcl-2 was decreased. The phosphorylation cascade of kinases in the PI3K-Akt-mTOR signaling pathway was significantly inhibited by METH exposure, as were proteins downstream of mTORC1, such as p70s6k, rps6, 4EBP1 and eIF4E. METH inhibited proliferation of U-118 MG cells and induced apoptosis and autophagy. The PI3K-Akt-mTOR signaling pathway likely plays a critical role in these effects.