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"Chen, Michael"
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Chinese scholars on Western ideas about thinking, leadership, reform and development in education
This collection of papers by a group of Chinese educational administrators came about through a graduate study program that facilitated comparisons of educational practices from other cultures against the backdrop of globalization. Collaborative international programs allow contrast and comparisons of practices, policies and educational principles but are not without barriers faced by candidates which can include but are not limited to culture shock and communication and language adjustments. Comparisons of international educational institutions are telling when examined through transfer credit policies, degree recognition, institutional accreditation and the value of academic credits in a globalized educational marketplace. China and Chinese educators recognize that movement and take it most seriously as demonstrated by the group of educational ambassadors who have contributed a variety of perspectives and interests to this volume. They are a new wave of thinkers whose studies embrace their native culture and open minds to alternative ways of understanding and acting on rapidly changing educational circumstances for learners, teachers and administrators.
Book
EEG correlates of time-varying BOLD functional connectivity
Recent resting-state fMRI studies have shown that the apparent functional connectivity (FC) between brain regions may undergo changes on time-scales of seconds to minutes, the basis and importance of which are largely unknown. Here, we examine the electrophysiological correlates of within-scan FC variations during a condition of eyes-closed rest. A sliding window analysis of simultaneous EEG–fMRI data was performed to examine whether temporal variations in coupling between three major networks (default mode; DMN, dorsal attention; DAN, and salience network; SN) are associated with temporal variations in mental state, as assessed from the amplitude of alpha and theta oscillations in the EEG. In our dataset, alpha power showed a significant inverse relationship with the strength of connectivity between DMN and DAN. In addition, alpha power covaried with the spatial extent of anticorrelation between DMN and DAN, with higher alpha power associated with larger anticorrelation extent. Results suggest an electrical signature of the time-varying FC between the DAN and DMN, potentially reflecting neural and state-dependent variations.
► We examined correlations between time-varying BOLD fMRI connectivity and EEG power. ► Connectivity between two major networks was inversely correlated with alpha power. ► EEG power also correlated with spatial anticorrelation extent between these networks.
Journal Article
Impact on patients with oral squamous cell carcinoma in different anatomical subsites: a single-center study in Taiwan
The incidence of oral cavity squamous cell carcinoma (OSCC) is particularly high in South Asia. According to the National Comprehensive Cancer Network, OSCC can arise in several subsites. We investigated survival rates and the clinical and pathological characteristics of OSCC in different anatomical subsites in the Taiwanese population. We retrospectively analyzed data for 3010 patients with OSCC treated at the Changhua Christian Hospital. Subsequently, we compared clinical and pathological features of OSCC in different subsites. Pathological T4 stage OSCCs occurred in the alveolar ridge and retromolar trigone in 56.4% and 43.7% of cases, respectively. More than 25% of patients with tongue OSCC and 23.4% of those with retromolar OSCC had lymph node metastasis. The prognosis was worst for hard palate OSCC (hazard ratio 1.848;
p
< 0.001) and alveolar ridge OSCC (hazard ratio 1.220;
p
= 0.017). Retromolar OSCC recurred most often and tongue OSCC second most often. The risk for cancer-related mortality was highest for hard palate OSCC, followed by alveolar ridge and retromolar OSCC. We found distinct differences in survival among the different subsites of OSCC. Our findings may also help prompt future investigations of OSCC in different subsites in Taiwanese patients.
Journal Article
Spatial and Seasonal Controls on Eddy Subduction in the Southern Ocean
Carbon export driven by submesoscale, eddy‐associated vertical velocities (“eddy subduction”), and particularly its seasonality, remains understudied, leaving a gap in our understanding of ocean carbon sequestration. Here, we assess mechanisms controlling eddy subduction's spatial and seasonal patterns using 15 years of observations from BGC‐Argo floats in the Southern Ocean. We identify signatures of eddy subduction as subsurface anomalies in temperature‐salinity and oxygen. The anomalies are spatially concentrated near weakly stratified areas and regions with strong lateral buoyancy gradients diagnosed from satellite altimetry, particularly in the Antarctic Circumpolar Current's standing meanders. We use bio‐optical ratios, specifically the chlorophyll a to particulate backscatter ratio (Chl/bbp) to find that eddy subduction is most active in the spring and early summer, with freshly exported material associated with seasonally weak vertical stratification and increasing surface biomass. Climate change is increasing ocean stratification globally, which may weaken eddy subduction's carbon export potential. Plain Language Summary Oceans play an important role in global climate by soaking up and sequestering atmospheric carbon dioxide. Photosynthetic activity at the surface turns carbon dioxide into organic carbon, and if this carbon leaves the surface to the deep ocean, it can be locked away from the atmosphere. One way this occurs is through the physical circulation associated with swirling eddies, which can rapidly transport organic carbon‐rich surface waters and “inject” them into deep waters. However, we still don't fully understand the seasonal timing of this process, or what drives its spatial distribution. We investigated this in the Southern Ocean, which is very important to global climate, using data collected by drifting robots. We find that this process is the most active in regions where eddies drive strong surface stirring, and during the spring, when weak stratification allows injections to penetrate deep into the ocean. Because this process is poorly represented in climate models, these findings will improve our understanding of how the ocean absorbs carbon. Key Points Eddy subduction in the Southern Ocean is observed as subsurface anomalies in spice and oxygen measured by autonomous profiling floats Spatial distribution is controlled by weak stratification and strong lateral buoyancy gradients, diagnosed using satellite altimetry Bio‐optical proxies suggest that eddy subduction is most active in spring/early summer, driven by weak vertical stratification
Journal Article
Thirst regulates motivated behavior through modulation of brainwide neural population dynamics
How is it that groups of neurons dispersed through the brain interact to generate complex behaviors? Three papers in this issue present brain-scale studies of neuronal activity and dynamics (see the Perspective by Huk and Hart). Allen et al. found that in thirsty mice, there is widespread neural activity related to stimuli that elicit licking and drinking. Individual neurons encoded task-specific responses, but every brain area contained neurons with different types of response. Optogenetic stimulation of thirst-sensing neurons in one area of the brain reinstated drinking and neuronal activity across the brain that previously signaled thirst. Gründemann et al. investigated the activity of mouse basal amygdala neurons in relation to behavior during different tasks. Two ensembles of neurons showed orthogonal activity during exploratory and nonexploratory behaviors, possibly reflecting different levels of anxiety experienced in these areas. Stringer et al. analyzed spontaneous neuronal firing, finding that neurons in the primary visual cortex encoded both visual information and motor activity related to facial movements. The variability of neuronal responses to visual stimuli in the primary visual area is mainly related to arousal and reflects the encoding of latent behavioral states. Science , this issue p. eaav3932 , p. eaav8736 , p. eaav7893 ; see also p. 236 Water deprivation establishes a brainwide activity state that gates how sensory stimuli produce behavioral responses. Physiological needs produce motivational drives, such as thirst and hunger, that regulate behaviors essential to survival. Hypothalamic neurons sense these needs and must coordinate relevant brainwide neuronal activity to produce the appropriate behavior. We studied dynamics from ~24,000 neurons in 34 brain regions during thirst-motivated choice behavior in 21 mice as they consumed water and became sated. Water-predicting sensory cues elicited activity that rapidly spread throughout the brain of thirsty animals. These dynamics were gated by a brainwide mode of population activity that encoded motivational state. After satiation, focal optogenetic activation of hypothalamic thirst-sensing neurons returned global activity to the pre-satiation state. Thus, motivational states specify initial conditions that determine how a brainwide dynamical system transforms sensory input into behavioral output.
Journal Article
Structural basis of G-quadruplex unfolding by the DEAH/RHA helicase DHX36
Guanine-rich nucleic acid sequences challenge the replication, transcription, and translation machinery by spontaneously folding into G-quadruplexes, the unfolding of which requires forces greater than most polymerases can exert
1
,
2
. Eukaryotic cells contain numerous helicases that can unfold G-quadruplexes
3
. The molecular basis of the recognition and unfolding of G-quadruplexes by helicases remains poorly understood. DHX36 (also known as RHAU and G4R1), a member of the DEAH/RHA family of helicases, binds both DNA and RNA G-quadruplexes with extremely high affinity
4
–
6
, is consistently found bound to G-quadruplexes in cells
7
,
8
, and is a major source of G-quadruplex unfolding activity in HeLa cell lysates
6
. DHX36 is a multi-functional helicase that has been implicated in G-quadruplex-mediated transcriptional and post-transcriptional regulation, and is essential for heart development, haematopoiesis, and embryogenesis in mice
9
–
12
. Here we report the co-crystal structure of bovine DHX36 bound to a DNA with a G-quadruplex and a 3′ single-stranded DNA segment. We show that the N-terminal DHX36-specific motif folds into a DNA-binding-induced α-helix that, together with the OB-fold-like subdomain, selectively binds parallel G-quadruplexes. Comparison with unliganded and ATP-analogue-bound DHX36 structures, together with single-molecule fluorescence resonance energy transfer (FRET) analysis, suggests that G-quadruplex binding alone induces rearrangements of the helicase core; by pulling on the single-stranded DNA tail, these rearrangements drive G-quadruplex unfolding one residue at a time.
A mechanism for the unfolding of guanine-rich DNA ‘quadruplexes’ by helicases is suggested, based on the structure of a DNA-bound helicase.
Journal Article