Brain region-specific roles of brain-derived neurotrophic factor in social stress-induced depressive-like behavior

Brain-derived neurotrophic factor is a key factor in stress adaptation and avoidance of a social stress behavioral response.Recent studies have shown that brain-derived neurotrophic factor expression in stressed mice is brain region–specific,particularly involving the corticolimbic system,including the ventral tegmental area,nucleus accumbens,prefrontal cortex,amygdala,and hippocampus.Determining how brain-derived neurotrophic factor participates in stress processing in different brain regions will deepen our understanding of social stress psychopathology.In this review,we discuss the expression and regulation of brain-derived neurotrophic factor in stress-sensitive brain regions closely related to the pathophysiology of depression.We focused on associated molecular pathways and neural circuits,with special attention to the brain-derived neurotrophic factor–tropomyosin receptor kinase B signaling pathway and the ventral tegmental area–nucleus accumbens dopamine circuit.We determined that stress-induced alterations in brain-derived neurotrophic factor levels are likely related to the nature,severity,and duration of stress,especially in the above-mentioned brain regions of the corticolimbic system.Therefore,BDNF might be a biological indicator regulating stress-related processes in various brain regions.

Exploring the psychological impact of the 2022 SARS-CoV-2 Omicron variant outbreak in China

To the editor:The impact of the coronavirus disease 2019(COVID-19)pandemic in 2020 on mental health was substantialin Chinai2and various other countries.34 Beyond the direct consequences of COVID-19,the pandemic created an environment in which many determinants of mental health were affected.Issues associated with the pandemic,such as loss of livelihood,limited access to medical services,reduced social interactions,and economic downturn,could potentially have adverse effects on the population's mental well-being.5 In November 2021,the World Health Organization(WHO)designated the new variant of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),variant B.1.1.529,as a variant of concern and named it Omicron;its rapid mutation and spread raised a new global health concern.

Two material removal modes in chemical mechanical polishing:mechanical plowing vs.chemical bonding

With the rapid development of semiconductors,the number of materials needed to be polished sharply increases.The material properties vary significantly,posing challenges to chemical mechanical polishing(CMP).Accordingly,the study aimed to classify the material removal mechanism.Based on the CMP and atomic force microscopy results,the six representative metals can be preliminarily classified into two groups,presumably due to different material removal modes.From the tribology perspective,the first group of Cu,Co,and Ni may mainly rely on the mechanical plowing effect.After adding H_(2)O_(2),corrosion can be first enhanced and then suppressed,affecting the surface mechanical strength.Consequently,the material removal rate(MRR)and the surface roughness increase and decrease.By comparison,the second group of Ta,Ru,and Ti may primarily depend on the chemical bonding effect.Adding H_(2)O_(2)can promote oxidation,increasing interfacial chemical bonds.Therefore,the MRR increases,and the surface roughness decreases and levels off.In addition,CMP can be regulated by tuning the synergistic effect of oxidation,complexation,and dissolution for mechanical plowing,while tuning the synergistic effect of oxidation and ionic strength for chemical bonding.The findings provide mechanistic insight into the material removal mechanism in CMP.

AFM probe for measuring~10^(−5)ultra-low friction coefficient:Design and application

Superlubricity provides a novel approach to addressing friction and wear issues in mechanical systems.However,little is known regarding improving the atomic force microscope(AFM)friction coefficient measurement resolution.Accordingly,this study established the theoretical formula for the AFM friction coefficient measurement and deduced the measurement resolution.Then,the formula was applied to the AFM probe with a rectangular cross-section cantilever.The measurement resolution is associated with the dimensional properties of the AFM probe,the mechanical properties of the cantilever material,the properties of the position-sensitive detector(PSD),and probably the anti-vibration performance of the AFM.It is feasible to make the cantilever as short as possible and the tip as high as possible to improve the measurement resolution.An AFM probe for measuring an ultra-low friction coefficient was designed and fabricated.The cantilever’s length,width,and thickness are 50,35,and 0.6μm,respectively.The tip height is 23μm.The measurement resolution can reach 7.1×10^(−6) under the maximum normal force.Moreover,the AFM probe was applied to measure the superlubricity between graphene layers.The friction coefficient is 0.00139 under 853.08 nN.This work provides a promising method for measuring a~10^(−5) friction coefficient of superlubricity.

AFM probe with the U-shaped cross-sectional cantilever for measuring the ultra-low coefficient of friction of 10^(–6)

Accurately measuring the coefficient of friction(COF)is the fundamental prerequisite of superlubricity research.This study aimed to reduce the COF measurement resolutionΔμof atomic force microscopy(AFM).Based on the theoretical model,a distinctive strategy was adopted to reduceΔμby optimizing the cantilever’s cross-section of the AFM probe,inspired by civil engineering.Δμcan be reduced by decreasing the width of the horizontal side wR and the wall thickness t and increasing the width of the vertical side wH.Moreover,the I-shape demonstrates the highest reduction inΔμ,followed by the U-shape.Considering the processability,the AFM probe with the U-shaped cross-sectional cantilever was investigated further,and the dimensions are 35μm wR,3.5μm wH,0.5μm t,50μm l(cantilever length),and 23μm htip(tip height).The finite element analysis results confirm its reliability.After being fabricated and calibrated,the AFM probe achieves the minimalΔμof 1.9×10^(–6)under the maximum normal force so far.Additionally,the friction detection capability of the fabricated AFM probe improves by 78 times compared to the commercial tipless-force modulation mode(TL-FM)AFM probe with the conventional solid rectangular cross-sectional cantilever.This study provides a powerful tool for measuring 10^(–6)COF.