We speed up thermal simulations of quantum many-body systems in both one- (1D) and two-dimensional (2D) models in an exponential way by iteratively projecting the thermal density matrixρ^=e−βH^onto ...itself. We refer to this scheme of doublingβin each step of the imaginary time evolution as the exponential tensor renormalization group (XTRG). This approach is in stark contrast to conventional Trotter-Suzuki-type methods which evolveρ^on a linear quasicontinuous grid in inverse temperatureβ≡1/T. As an aside, the large steps in XTRG allow one to swiftly jump across finite-temperature phase transitions, i.e., without the need to resolve each singularly expensive phase-transition point right away, e.g., when interested in low-energy behavior. A fine temperature resolution can be obtained, nevertheless, by using interleaved temperature grids. In general, XTRG can reach low temperatures exponentially fast and, thus, not only saves computational time but also merits better accuracy due to significantly fewer truncation steps. For similar reasons, we also find that the series expansion thermal tensor network approach benefits in both efficiency and precision, from the logarithmic temperature scale setup. We work in an (effective) 1D setting exploiting matrix product operators (MPOs), which allows us to fully and uniquely implement non-Abelian and Abelian symmetries to greatly enhance numerical performance. We use our XTRG machinery to explore the thermal properties of Heisenberg models on 1D chains and 2D square and triangular lattices down to low temperatures approaching ground-state properties. The entanglement properties, as well as the renormalization-group flow of entanglement spectra in MPOs, are discussed, where logarithmic entropies (approximatelylnβ) are shown in both spin chains and square-lattice models with gapless towers of states. We also reveal that XTRG can be employed to accurately simulate the HeisenbergXXZmodel on the square lattice which undergoes a thermal phase transition. We determine its critical temperature based on thermal physical observables, as well as entanglement measures. Overall, we demonstrate that XTRG provides an elegant, versatile, and highly competitive approach to explore thermal properties, including finite-temperature thermal phase transitions as well as the different ordering tendencies at various temperature scales for frustrated systems.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM, UPUK
Magic-angle twisted bilayer graphene has recently become a thriving material platform realizing correlated electron phenomena taking place within its topological flat bands. Several numerical and ...analytical methods have been applied to understand the correlated phases therein, revealing some similarity with the quantum Hall physics. In this work, we provide a Mott-Hubbard perspective for the TBG system. Employing the large-scale density matrix renormalization group on the lattice model containing the projected Coulomb interactions only, we identify a first-order quantum phase transition between the insulating stripe phase and the quantum anomalous Hall state with the Chern number of ±1. Our results not only shed light on the mechanism of the quantum anomalous Hall state discovered at three-quarters filling, but also provide an example of the topological Mott insulator, i.e., the quantum anomalous Hall state in the strong coupling limit.
The Shimensi deposit (South China) is a newly discovered W-Cu-Mo polymetallic deposit with a reserve of 0.76 million tones WO3, one of the largest tungsten deposits in the world. We report elemental ...and Sr-Nd isotopic data for scheelites from the giant deposit, to determine the source region and genesis of the deposit. Scheelite is the most important ore mineral in the Shimensi deposit. Trace elements (including REEs) and Nd-Sr isotopic compositions of scheelites were used to constrain the origin of the mineralizing fluids and metals. Our data reveal that the REEs of scheelite are mainly controlled by the substitution mechanism 3Ca2+ = 2REE3++ ∎Ca, where ∎Ca is a Ca-site vacancy. Scheelites from the Shimensi deposit show negative Eu anomalies in some samples, but positive Eu anomalies in others in the chondrite-normalized REE patterns. The variation of Eu anomalies recorded the ore-forming processes. Considering the close spatial and temporal relationship between the mineralization and porphyritic granite, we think the negative Eu anomalies were inherited from the porphyritic granite and the positive ones from destruction of plagioclase of country rock during fluid-rock interaction. The variation of cathodeluminescence (CL) color of a single scheelite from red to blue and to yellow was likely associated with the increase of REE contents. The scheelites hosted in the Mesozoic porphyritic granite with negative Eu anomalies formed in a primitive ore-forming fluid, whereas the scheelites hosted in Neoproterozoic granite with positive Eu anomalies precipitated in an evolved ore-forming fluid. The high Nb, Ta, LREE contents, and LREE-enriched REE patterns of scheelites from the Shimensi deposit reveal a close relationship with magmatic hydrothermal fluids. The scheelites from the Shimensi deposit are characterized by low εNd(t) values (-6.1 ∼ -8.1) and unusually high and varied initial 87Sr/86Sr ratios (0.7230∼0.7657). The εNd(t) values of scheelites are consistent with those of the Mesozoic porphyritic granite, but the Sr isotopic ratios are significantly higher than those of the granites, and importantly, beyond the Sr isotopic range of normal granites. This suggests that the ore-forming fluids and metals cannot be attributed to the Mesozoic porphyritic granites alone, the local Neoproterozoic Shuangqiaoshan Group schists/gneisses with high Rb/Sr ratios and thus radiogenic Sr isotopic compositions should have contributed to the ore-forming fluids and metals, particularly, in a later stage of ore-forming process, by intense fluid-rock interaction. This is different from a commonly accepted model that the ore-forming fluids and metals were exsolved exclusively from the granite plutons.
Adolescents' family obligation is a cultural strength that shows enduring prevalence in China. Given that the meaning of family obligation has undergone rapid changes in recent decades, it is crucial ...to examine the role of family obligation in adolescent adjustment in contemporary China. More importantly, although past research has investigated the consequences of family obligation on adolescents' adjustment, little is known about the antecedents of Chinese adolescents' family obligation. Using a two‐wave longitudinal sample of 450 Chinese adolescents (mean age = 13.78 years, SD = .71 years; 49% female) and their parents, the current research explored two questions. First, this study examined the role of family obligation in adolescents' academic achievement, externalizing problems, and internalizing problems over early adolescence. Second, this study explored the role of parents in predicting Chinese adolescents' family obligation, specifically whether parental expectations or parental acceptance was predictive of adolescents' family obligation over time. Third, this study investigated whether family obligation is an underlying mechanism between parenting and Chinese adolescents' adjustment. Results showed that Chinese adolescents' family obligation was longitudinally associated with increased academic achievement and reduced externalizing problems. Moreover, perceived parental acceptance, but not parental expectations, was longitudinally associated with Chinese adolescents' greater family obligation. Notably, family obligation mediated the longitudinal effect of parental acceptance on Chinese adolescents' externalizing problems. By studying both the consequences and antecedents of Chinese adolescents' family obligation, this study helps provide a comprehensive understanding of this cultural strength.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Carbon dots (CDs) have received an increasing amount of attention because of their significant advantages in terms of low toxicity, chemical inertness, tunable fluorescence, good water solubility, ...and physicochemical properties. Due to these desirable properties, they have been used in numerous fields, including chemo- and biosensing, fluorescence imaging, and drug delivery. In this review, we aim to demonstrate the recent progress in the green synthesis and formation mechanism of CDs, and provide guidance for developing CDs with the concepts of green chemistry. In addition, we discuss three kinds of most accepted luminescence origins: surface state, quantum confinement effect and molecular fluorescence. Finally, we systematically summarize the latest progress of CDs in fluorescence sensing applications, including both solution phase sensing and solid phase sensing. Furthermore, the challenges and future direction of CDs in this emerging field are discussed.
We systematically summarize the recent progress in the green synthesis and formation mechanism of CDs with the hope to provide guidance for developing CDs with the concept of green chemistry. In addition, we discuss and organize the current opinions on the fluorescence origin of CDs and the latest progress of CDs in fluorescence sensing applications.
Associations between parent–child relationships and adolescents' shyness are well documented, but relatively little is known about the role of siblings. This three‐wave longitudinal research examined ...reciprocal associations between parental and sibling warmth and adolescents' shyness in China. One hundred and fifty Chinese adolescents (Mage = 12.84 years; 56.7% girls) participated. Data were collected from multiple sources including self‐reports and peer assessments. Cross‐lagged model analyses revealed unique longitudinal paths from sibling warmth to adolescents' shyness and from adolescents' shyness to sibling warmth. Moreover, no cross‐lagged paths existed between fathers' and mothers' warmth and adolescents' shyness. The results suggest that sibling relationships may be a unique social context for socialization and development among Chinese adolescents.
Full text
Available for:
BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Introduction
Given that coronavirus disease 2019 (COVID‐19) has largely influenced adolescents' physical and mental health around the globe, it is important to identify protective factors that may ...promote adolescents' positive adjustment during the pandemic. This study aimed to examine the role of parental attachment and COVID‐19 communication in adolescents' health behavior and mental health during COVID‐19.
Methods
A total of 442 Chinese parent−adolescent dyads (mean age of adolescents = 13.35 years; 50% girls) completed two‐wave longitudinal surveys over the span of 2 months during the pandemic (Wave 1: July 2020; Wave 2: September 2020). At each wave, adolescents reported on their COVID‐19‐related health behavior, general health behavior, depressive symptoms, and anxiety symptoms. At Wave 1, parent−adolescent attachment security and COVID‐19 communication were also assessed.
Results
Adolescents' attachment security to parents was associated with their increased COVID‐19‐related and general health behavior as well as decreased depression and anxiety over 2 months during COVID‐19. Moreover, more frequent parent−adolescent COVID‐19 communication was associated with adolescents' increased COVID‐19‐related and general health behavior over time. Notably, attachment security's and COVID‐19 communication's associations with health behavior largely remained the same after taking into account both factors simultaneously. In addition, results from exploratory analyses suggest that more frequent COVID‐19 communication mediates the link between attachment security and increased health behavior.
Conclusions
These findings highlight the importance of promoting attachment security and COVID‐19 communication between parents and adolescents during the pandemic, which may play a positive role in adolescents' health behavior and mental health.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
8.
Carbon dot-based composites for catalytic applications Chen, Bin Bin; Liu, Meng Li; Huang, Cheng Zhi
Green chemistry : an international journal and green chemistry resource : GC,
01/2020, Volume:
22, Issue:
13
Journal Article
Peer reviewed
Carbon dots (CDs) have been regarded as prospective carbon nanomaterials for catalytic applications due to their advantages such as low toxicity, strong and broad optical absorption, high chemical ...stability, and rapid electron transfer properties. To further improve their function, CD-based composites or hybrid materials have been developed by integrating CDs into different functional nanomaterials such as inorganic nanostructures, biomaterials, polymers and so on. This review presents and discusses the current development of CD-based composites. After the introduction of the methods for the preparation of CD-based composites, we focus on the description of the factors affecting the synthesis of CD-based composites. Lastly, the advantages of CD-based composites in catalytic applications such as photocatalysis, chemical catalysis, peroxidase-like catalysis, Fenton-like catalysis and electrocatalysis are described.
We summarize the construction methods and influencing factors of CDs-based composites and discuss their catalytic applications, including photocatalysis, chemical catalysis, peroxidase-like catalysis, Fenton-like catalysis and electrocatalysis.
•The multi-regional network model for energy-water nexus is proposed.•The water-related energy and energy-related water are systemically inventoried.•System properties and dynamics are altered by the ...urban agglomeration nexus.
The nexus between energy and water introduces cross-sectoral vulnerabilities, which provides cross-cutting opportunities to mitigate urban energy and water demand pressure. The existing nexus research has generally been limited to inventorying energy-related water and water-related energy. In this study, we propose a hybrid framework to study the interwoven connections of energy consumption and water use for urban agglomerations. The energy-related water and water-related energy are also systematically inventoried with the multi-regional input–output method. Then, a multi-regional nexus network is established, based on ecological network analysis, to explore the structural properties and sectoral interactions between sectors within urban agglomerations. A case study of the Beijing–Tianjin–Hebei region shows the differences of direct energy/water and embodied energy/water consumption between sectors and regions. There are significant changes of control/dependence relationships between sectors and regions after considering the urban agglomeration nexus. Also, the effect of the nexus on water networks is smaller than energy networks. The nexus effect on energy and water networks for Beijing is bigger than those of Tianjin and Hebei. The recycling rates in water networks are around 20–23%, which are lower than those of energy networks (28–30%). The recycling rates of Tianjin and Beijing are higher than that of Hebei. According to the results of energy and water flows between regions, Beijing and Tianjin are dependent on Hebei for water and energy resources, while Hebei is more self-sufficient. The multi-regional network approach presents great potential for bridging nexus analysis with sustainable planning for urban agglomerations by simultaneously mitigating the energy and water burden.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This longitudinal study examined the reciprocal associations between paternal and maternal rejection and firstborn children's (Mage = 49.9 months; 55% boys) behavior problems across the transition to ...siblinghood in a sample of 120 families recruited from 2016 to 2018 from Shanghai, China. Parental rejection and behavior problems were assessed before (prenatal) and 1, 6, and 12 months after the birth of a baby sibling. Random intercept cross‐lagged panel models revealed positive relations between internalizing problems and both maternal and paternal rejection, and between externalizing problems and paternal rejection at the between‐person level (rs = .32–.37), but only cross‐lagged effects from children's internalizing and externalizing problems to maternal rejection at the within‐person level (βs = .30–.54).
Full text
Available for:
BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
