Virtually all organosulfur compounds react with Fe(0) carbonyls to give the title complexes. These reactions are reviewed in light of major advances over the past few decades, spurred by interest in ...Fe2(μ-SR)2(CO) x centers at the active sites of the FeFe-hydrogenase enzymes. The most useful synthetic route to Fe2(μ-SR)2(CO)6 involves the reaction of thiols with Fe2(CO)9 and Fe3(CO)12. Such reactions can proceed via mono-, di-, and triiron intermediates. The reactivity of Fe(0) carbonyls toward thiols is highly chemoselective, and the resulting dithiolato complexes are fairly rugged. Thus, many complexes tolerate further synthetic elaboration directed at the organic substituents. A second major route involves alkylation of Fe2(μ-S2)(CO)6, Fe2(μ-SH)2(CO)6, and Li2Fe2(μ-S)2(CO)6. This approach is especially useful for azadithiolates Fe2(μ-SCH2)2NR(CO)6. Elaborate complexes arise via addition of the FeSH group to electrophilic alkenes, alkynes, and carbonyls. Although the first example of Fe2(μ-SR)2(CO)6 was prepared from ferrous reagents, ferrous compounds are infrequently used, although the Fe(II)(SR)2 + Fe(0) condensation reaction is promising. Almost invariably low-yielding, the reaction of Fe3(CO)12, S8, and a variety of unsaturated substrates results in C–H activation, affording otherwise inaccessible derivatives. Thiones and related CS-containing reagents are highly reactive toward Fe(0), often giving complexes derived from substituted methanedithiolates and C–H activation.
Under the influence of Covid-19, most universities worldwide transitioned from face-to-face pedagogy to online hybrid learning. As a result, scholarly publications about this transition are rapidly ...accumulating. However, to date, there are few studies published in international journals investigating online education in Macau during the pandemic, particularly on the feeling of presence when Macau students study online. Using an instrumental case study at a university in Macau, this research explored online learning during the pandemic. The interviewees reported a lack of embodied presence in online learning. Nevertheless, many of them enjoyed this learning mode, as it provided a more reciprocal classroom, flexibility and convenience. The interviewees also believe the lack of physicality is not the determining challenge affecting online learning, suggesting that joint efforts and collaboration between peers, better-designed pedagogy for teachers, smoother teacher-student communication channels, the university’s online policymaking, and the support of infrastructure, online teaching quality could all be improved. This result questions the emphasis on bodily presence in the online learning environment and the drawing of a stark divide between online and offline. In contrast, it endorses the concepts of presence under a framework of a Community of Inquiry, which is a more post-digital view, welcoming the seamless combination of the online and offline world within contemporary society.
Plain language summary
What Types of Online Presence Truly Make a Difference for University Students?
Due to Covid-19, many universities worldwide have shifted from in-person teaching to a combination of online and offline learning. Consequently, there has been a surge in scholarly articles discussing this transition. However, few studies published in international journals investigate online education in Macau during the pandemic, particularly focusing on how Macau students feel about studying online. This research conducted an instrumental case study at a university in Macau to explore online learning during the pandemic. Interviewees mentioned feeling disconnected while learning online but enjoyed it because it created a more interactive classroom environment and offered flexibility and convenience. They also believed that collaborative efforts between peers, better-designed teaching methods for instructors, smoother communication channels between teachers and students, effective university policies for online education, and improved infrastructure support can enhance the quality of online teaching instead of physical presence being the main challenge affecting it. These findings question the importance placed on physical presence in an online learning environment and challenge the strict division between online and offline modes of education by endorsing the concept of presence within a Community of Inquiry framework that embraces seamless integration between both digital and non-digital aspects within contemporary society.
Neurotransmitters and neuromodulators have a wide range of key roles throughout the nervous system. However, their dynamics in both health and disease have been challenging to assess, owing to the ...lack of in vivo tools to track them with high spatiotemporal resolution. Thus, developing a platform that enables minimally invasive, large-scale and long-term monitoring of neurotransmitters and neuromodulators with high sensitivity, high molecular specificity and high spatiotemporal resolution has been essential. Here, we review the methods available for monitoring the dynamics of neurotransmitters and neuromodulators. Following a brief summary of non-genetically encoded methods, we focus on recent developments in genetically encoded fluorescent indicators, highlighting how these novel indicators have facilitated advances in our understanding of the functional roles of neurotransmitters and neuromodulators in the nervous system. These studies present a promising outlook for the future development and use of tools to monitor neurotransmitters and neuromodulators.
The cultural transmission of behaviour depends on the ability of the pupil to identify and emulate an appropriate tutor
. How the brain of the pupil detects a suitable tutor and encodes the behaviour ...of the tutor is largely unknown. Juvenile zebra finches readily copy the songs of the adult tutors that they interact with, but not the songs that they listen to passively through a speaker
, indicating that social cues generated by the tutor facilitate song imitation. Here we show that neurons in the midbrain periaqueductal grey of juvenile finches are selectively excited by a singing tutor and-by releasing dopamine in the cortical song nucleus HVC-help to encode the song representations of the tutor used for vocal copying. Blocking dopamine signalling in the HVC of the pupil during tutoring blocked copying, whereas pairing stimulation of periaqueductal grey terminals in the HVC with a song played through a speaker was sufficient to drive copying. Exposure to a singing tutor triggered the rapid emergence of responses to the tutor song in the HVC of the pupil and a rapid increase in the complexity of the song of the pupil, an early signature of song copying
. These findings reveal that a dopaminergic mesocortical circuit detects the presence of a tutor and helps to encode the performance of the tutor, facilitating the cultural transmission of vocal behaviour.
•Properties of Fe-Al IMCs were systematically calculated using the first-principle.•Lattice constants, mechanical properties and electronic structures were obtained.•Fe-rich phases are superior to ...Al-rich phases on the mechanical properties.•316L stainless steel and 6061 aluminum were laser welded using T-joint.•The calculated results were verified with the experiments.
To analyze the IMC (Intermetallic Compound) properties and their effects on steel/aluminum welding, the equilibrium lattice constants, mechanical properties and electronic structures of the intermetallic compounds Fe3Al, FeAl, Fe2Al5, FeAl2, FeAl3 and Fe4Al13 were systematically calculated using the first-principle methods. The results show that the calculated elastic constants of the IMCs satisfy the mechanical stability conditions. Fe3Al and FeAl2 exhibit plastic characteristics; FeAl, Fe2Al5, FeAl3, and Fe4Al13 exhibit brittle characteristics; Fe-Al binary compounds have typical metallic properties; and the 3d bands of Fe contribute most significantly to the total density of states. In the vicinity of the Fermi level, the 3d bands of Fe contribute together with the bands of Al; the Fe-Al binary compounds have weak ionicity, relatively high hardness and high melting points; additionally, the effects of Fe-rich phases on the mechanical properties of the joints are superior compared to Al-rich phases. To verify the first principle calculations, T-joint laser welding experiments were conducted on 316L stainless steel and 6061 aluminum alloy sheets. The microstructure, reaction phases, fracture morphologies and mechanical properties of the welded joint were analyzed by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and nanoindentation. According to the XRD and EDS analysis, Fe3Al, FeAl, Fe2Al5, FeAl2, FeAl3 and Fe4Al13 were formed; their properties and effects on the joint of these phases are consistent with the calculated results.
Sleep and wakefulness are homeostatically regulated by a variety of factors, including adenosine. However, how neural activity underlying the sleep-wake cycle controls adenosine release in the brain ...remains unclear. Using a newly developed genetically encoded adenosine sensor, we found an activity-dependent rapid increase in the concentration of extracellular adenosine in mouse basal forebrain (BF), a critical region controlling sleep and wakefulness. Although the activity of both BF cholinergic and glutamatergic neurons correlated with changes in the concentration of adenosine, optogenetic activation of these neurons at physiological firing frequencies showed that glutamatergic neurons contributed much more to the adenosine increase. Mice with selective ablation of BF glutamatergic neurons exhibited a reduced adenosine increase and impaired sleep homeostasis regulation. Thus, cell type-specific neural activity in the BF dynamically controls sleep homeostasis.
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•Genetically-encoded fluorescent sensors are essential for studying neurotransmission.•Today's sensors are limited in certain aspects, especially for in vivo applications.•GPCR is a ...versatile platform for engineering next-generation fluorescent sensors.
Measuring the precise dynamics of specific neurotransmitters and neuromodulators in the brain is essential for understanding how information is transmitted and processed. Thanks to the development and optimization of various genetically encoded sensors, we are approaching the stage in which a few key neurotransmitters/neuromodulators can be imaged with high cell specificity and good signal-to-noise ratio. Here, we summarize recent progress regarding these sensors, focusing on their design principles, properties, potential applications, and current limitations. We also highlight the G protein-coupled receptor (GPCR) scaffold as a promising platform that may enable the scalable development of the next generation of sensors, enabling the rapid, sensitive, and specific detection of a large repertoire of neurotransmitters/neuromodulators in vivo at cellular or even subcellular resolution.
The sleep cycle is characterized by alternating non-rapid eye movement (NREM) and rapid eye movement (REM) sleeps. The mechanisms by which this cycle is generated are incompletely understood. We ...found that a transient increase of dopamine (DA) in the basolateral amygdala (BLA) during NREM sleep terminates NREM sleep and initiates REM sleep. DA acts on dopamine receptor D2 (Drd2)-expressing neurons in the BLA to induce the NREM-to-REM transition. This mechanism also plays a role in cataplectic attacks-a pathological intrusion of REM sleep into wakefulness-in narcoleptics. These results show a critical role of DA signaling in the BLA in initiating REM sleep and provide a neuronal basis for sleep cycle generation.
•Innovative method is used to study mass transfer phenomena of direct-contact condensation.•Nonequilibrium liquid–vapor surface is constructed with temperature/pressure drop.•Non-negligible ...anisotropic region exists by liquid–vapor interface in preliminary stage.•Evaporation and condensation coefficients are not equal.•Modified Schrage relation shows better consistency with the MD results.
Direct-contact condensation plays an important role in both natural and engineering sciences. Nonequilibrium molecular dynamics (MD) simulations were conducted in this study to examine the mass transfer during transient direct-contact condensation. We designed an innovative method to construct a nonequilibrium liquid–vapor surface with sudden temperature and pressure drop between the two adjacent sides of the interface. This state was consistent with the initial state of real direct-contact condensation and verified the effectiveness of this method. The MD results indicated that a non-negligible anisotropic region existed near the liquid–vapor interface in the preliminary stage of direct-contact condensation when the nonequilibrium and transient phenomena were obvious. The velocity distributions of the vapor were time- and space-dependent, and the condensation and evaporation coefficients were not equal. Validation of the Schrage relation was conducted to calculate the net condensation rate. The results indicated that the Schrage relation modified by the temperature anisotropy and the evaporation coefficient shows better consistency with the MD results. For engineering applications, the time- and space-dependencies of velocity distributions are regarded having minimal influence on the validity of modified Schrage relation.
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