Realizing a Superior Conversion Efficiency of ≈11.3% in the Group IV-VI Thermoelectric Module.

GeTe-based materials exhibit superior thermoelectric performance, while the development of power generation devices has mainly been limited by the challenge of designing the interface due to the phase transition in GeTe. In this work, via utilizing the low-temperature nano-Ag sintering technique and screening suitable Ti-Al alloys, a reliable interface with excellent connection performance has been realized. The Ti-Al intermetallic compounds effectively inhibit the diffusion process at Ti-34Al/Ge0.9 Sb0.1 Te interface. Thus, the thickness of the interfacial reaction layer only increases by ≈2.08 µm, and the interfacial electrical contact resistivity remains as low as ≈15.2 µΩ cm2 even after 30 days of isothermal aging at 773 K. A high conversion efficiency of ≈11.3% has been achieved in the GeTe/PbTe module at a hot-side temperature of 773 K and a cold-side temperature of 300 K. More importantly, the module's performance and the reliability of the interface remain consistently stable throughout 50 thermal cycles and long-term aging. This work promotes the application of high-performance GeTe materials for thermoelectric power generation.

The Rac-GEF Tiam1 Promotes Dendrite and Synapse Stabilization of Dentate Granule Cells and Restricts Hippocampal-Dependent Memory Functions.

The dentate gyrus (DG) controls information flow into the hippocampus and is critical for learning, memory, pattern separation, and spatial coding, while DG dysfunction is associated with neuropsychiatric disorders. Despite its importance, the molecular mechanisms regulating DG neural circuit assembly and function remain unclear. Here, we identify the Rac-GEF Tiam1 as an important regulator of DG development and associated memory processes. In the hippocampus, Tiam1 is predominantly expressed in the DG throughout life. Global deletion of Tiam1 in male mice results in DG granule cells with simplified dendritic arbors, reduced dendritic spine density, and diminished excitatory synaptic transmission. Notably, DG granule cell dendrites and synapses develop normally in Tiam1 KO mice, resembling WT mice at postnatal day 21 (P21), but fail to stabilize, leading to dendrite and synapse loss by P42. These results indicate that Tiam1 promotes DG granule cell dendrite and synapse stabilization late in development. Tiam1 loss also increases the survival, but not the production, of adult-born DG granule cells, possibly because of greater circuit integration as a result of decreased competition with mature granule cells for synaptic inputs. Strikingly, both male and female mice lacking Tiam1 exhibit enhanced contextual fear memory and context discrimination. Together, these results suggest that Tiam1 is a key regulator of DG granule cell stabilization and function within hippocampal circuits. Moreover, based on the enhanced memory phenotype of Tiam1 KO mice, Tiam1 may be a potential target for the treatment of disorders involving memory impairments.SIGNIFICANCE STATEMENT The dentate gyrus (DG) is important for learning, memory, pattern separation, and spatial navigation, and its dysfunction is associated with neuropsychiatric disorders. However, the molecular mechanisms controlling DG formation and function remain elusive. By characterizing mice lacking the Rac-GEF Tiam1, we demonstrate that Tiam1 promotes the stabilization of DG granule cell dendritic arbors, spines, and synapses, whereas it restricts the survival of adult-born DG granule cells, which compete with mature granule cells for synaptic integration. Notably, mice lacking Tiam1 also exhibit enhanced contextual fear memory and context discrimination. These findings establish Tiam1 as an essential regulator of DG granule cell development, and identify it as a possible therapeutic target for memory enhancement.

CALPHAD accelerated design of advanced full-Zintl thermoelectric device.

Since thermoelectric materials have different physical and chemical properties, the design of contact layers requires dedicated efforts, and the welding temperatures are distinctly different. Therefore, a general interface design and connection technology can greatly facilitate the development of thermoelectric devices. Herein, we proposed a screening strategy for the contact materials based on the calculation of phase diagram method, and Mg2Ni has been identified as a matched contact layer for n-type Mg3Sb2-based materials. And this screening strategy can be effectively applied to other thermoelectric materials. By adopting the low-temperature sintering silver nanoparticles technology, the Zintl phase thermoelectric device can be fabricated at low temperature but operate at medium temperature. The single-leg n-type Mg3.15Co0.05SbBi0.99Se0.01 device achieves an efficiency of ~13.3%, and a high efficiency of ~11% at the temperature difference of 430 K has been realized for the Zintl phase thermoelectric device comprised together with p-type Yb0.9Mg0.9Zn1.198Ag0.002Sb2. Additionally, the thermal aging and thermal cycle experiments proved the long-term reliability of the Mg2Ni/Mg3.15Co0.05SbBi0.99Se0.01 interface and the nano-silver sintering joints. Our work paves an effective avenue for the development of advanced devices for thermoelectric power generation.

Motor-Cognitive Interventions May Effectively Improve Cognitive Function in Older Adults with Mild Cognitive Impairment: A Randomized Controlled Trial.

Mild cognitive impairment (MCI) is a syndrome that occurs in the preclinical stage of Alzheimer's disease. Early intervention can be effective in preventing Alzheimer's disease, but further research is needed on intervention methods. To identify interventions that are more suitable for Chinese characteristics and to investigate the effects of motor-cognitive intervention on the cognitive functions of older adults with MCI, we screened 103 community-dwelling older adults with MCI aged 65 years and older in Qingdao, Shandong, China; divided them into an intervention group and a control group; and administered a motor-cognitive intervention to the intervention group for 12 weeks. The study used the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA) to assess the initial cognitive level of the MCI participants and detect the effects of the intervention. We found that the cognitive abilities of the intervention group were significantly improved at the end of the intervention, as well as at the end of the follow-up, compared with the control group. The results of the current study suggest that the motor-cognitive intervention we used may improve the cognition of older people with MCI in the Chinese community.

Performance boost for bismuth telluride thermoelectric generator via barrier layer based on low Young's modulus and particle sliding.

The lack of desirable diffusion barrier layers currently prohibits the long-term stable service of bismuth telluride thermoelectric devices in low-grade waste heat recovery. Here we propose a new design principle of barrier layers beyond the thermal expansion matching criterion. A titanium barrier layer with loose structure is optimized, in which the low Young's modulus and particle sliding synergistically alleviates interfacial stress, while the TiTe2 reactant enables metallurgical bonding and ohmic contact between the barrier layer and the thermoelectric material, leading to a desirable interface characterized by high-thermostability, high-strength, and low-resistivity. Highly competitive conversion efficiency of 6.2% and power density of 0.51 W cm-2 are achieved for a module with leg length of 2 mm at the hot-side temperature of 523 K, and no degradation is observed following operation for 360 h, a record for stable service at this temperature, paving the way for its application in low-grade waste heat recovery.

Mechanisms for spatiotemporal regulation of Rho-GTPase signaling at synapses.

Synapses mediate information flow between neurons and undergo plastic changes in response to experience, which is critical for learning and memory. Conversely, synaptic defects impair information processing and underlie many brain pathologies. Rho-family GTPases control synaptogenesis by transducing signals from extracellular stimuli to the cytoskeleton and nucleus. The Rho-GTPases Rac1 and Cdc42 promote synapse development and the growth of axons and dendrites, while RhoA antagonizes these processes. Despite its importance, many aspects of Rho-GTPase signaling remain relatively unknown. Rho-GTPases are activated by guanine nucleotide exchange factors (GEFs) and inhibited by GTPase-activating proteins (GAPs). Though the number of both GEFs and GAPs greatly exceeds that of Rho-GTPases, loss of even a single GEF or GAP often has profound effects on cognition and behavior. Here, we explore how the actions of specific GEFs and GAPs give rise to the precise spatiotemporal activation patterns of Rho-GTPases in neurons. We consider the effects of coupling GEFs and GAPs targeting the same Rho-GTPase and the modular pathways that connect specific cellular stimuli with a given Rho-GTPase via different GEFs. We discuss how the creation of sharp borders between Rho-GTPase activation zones is achieved by pairing a GEF for one Rho-GTPase with a GAP for another and the extensive crosstalk between different Rho-GTPases. Given the importance of synapses for cognition and the fundamental roles that Rho-GTPases play in regulating them, a detailed understanding of Rho-GTPase signaling is essential to the progress of neuroscience.

Dynamic control of excitatory synapse development by a Rac1 GEF/GAP regulatory complex.

The small GTPase Rac1 orchestrates actin-dependent remodeling essential for numerous cellular processes including synapse development. While precise spatiotemporal regulation of Rac1 is necessary for its function, little is known about the mechanisms that enable Rac1 activators (GEFs) and inhibitors (GAPs) to act in concert to regulate Rac1 signaling. Here, we identify a regulatory complex composed of a Rac-GEF (Tiam1) and a Rac-GAP (Bcr) that cooperate to control excitatory synapse development. Disruption of Bcr function within this complex increases Rac1 activity and dendritic spine remodeling, resulting in excessive synaptic growth that is rescued by Tiam1 inhibition. Notably, EphB receptors utilize the Tiam1-Bcr complex to control synaptogenesis. Following EphB activation, Tiam1 induces Rac1-dependent spine formation, whereas Bcr prevents Rac1-mediated receptor internalization, promoting spine growth over retraction. The finding that a Rac-specific GEF/GAP complex is required to maintain optimal levels of Rac1 signaling provides an important insight into the regulation of small GTPases.

Alpha-Zearalanol, a phytoestrogen for cardiovascular therapy.

Estrogen replacement therapy (ERT) is one of the most challenging issues women and their physicians have to face. Clinical and epidemiological studies have provided conflicting data regarding the cardiovascular benefit versus risk in women using ERT. Although ERT may improve several risk factors of coronary heart disease such as favorable changes in lipid profile, an associated increased incidence of uterine and breast tumors has jeopardized the clinical use of ERT. We reported here that the phytoestrogen alpha-zearalanol is effective against atherosclerotic development without overt growth-promoting effects in the uterus compared to estrogen. These results suggest clinical potential of this phytoestrogen as a "safe estrogen" with less risk of tumorogenesis.

Phytoestrogen alpha-zearalanol inhibits atherogenesis and improves lipid profile in ovariectomized cholesterol-fed rabbits.

Although favorable effects of estrogen replacement therapy on atherosclerosis have been recognized, the benefit versus risk of estrogen replacement on overall cardio- vascular health remains controversial. The main adverse effect jeopardizing the clinical usage of estrogen is the increased risk of breast and endometrial cancer. Zearalenone (ZEN) is a universal endogenous hormone possessing estrogen-like effects and facilitating plant growth. alpha-Zearalanol (alpha-ZAL), a new phytoestrogen, is a reductive product of ZEN. Our preliminary evidence suggested that alpha-ZAL is anti-atherosclerotic. The aim of this study was to examine the effect of alpha-ZAL on atherosclerotic formation and serum lipid profile. Adult female nulliparous rabbits were ovariectomized or sham-operated and fed a high-cholesterol diet with different doses of alpha-ZAL or 17beta-estradiol for 12 wk. The aortic intimal atherosclerotic plaque was significantly larger in the cholesterol-fed group compared to control and sham groups. alpha-ZAL and 17beta-estradiol treatments significantly reduced plaque formation and improved serum profile of lipid (TC, TG, HDL-C, and LDL-C) and lipoprotein (ApoAl and ApoB). Both alpha-ZAL and 17beta-estradiol reconciled ovariectomy-induced uterine atrophy, although alpha-ZAL was significantly less potent than 17beta-estradiol in stimulating uterine growth. Our findings indicate that the phytoestrogen alpha-ZAL has an important anti-atherogenic property, analogous to that of estrogen.