SCFSAP controls organ size by targeting PPD proteins for degradation in Arabidopsis thaliana

Control of organ size by cell proliferation and growth is a fundamental process, but the mechanisms that determine the final size of organs are largely elusive in plants. We have previously revealed that the ubiquitin receptor DA1 regulates organ size by repressing cell proliferation in Arabidopsis. Here we report that a mutant allele of STERILE APETALA (SAP) suppresses the da1-1 mutant phenotype. We show that SAP is an F-box protein that forms part of a SKP1/Cullin/F-box E3 ubiquitin ligase complex and controls organ size by promoting the proliferation of meristemoid cells. Genetic analyses suggest that SAP may act in the same pathway with PEAPOD1 and PEAPOD2, which are negative regulators of meristemoid proliferation, to control organ size, but does so independently of DA1. Further results reveal that SAP physically associates with PEAPOD1 and PEAPOD2, and targets them for degradation. These findings define a molecular mechanism by which SAP and PEAPOD control organ size

Highly accurate and reliable ultrasonic focusing capability in heterogeneous media using a spherical cavity transducer

Introduction: Focused ultrasound ablation surgery (FUAS) has been emerging to treat a wide range of conditions non-invasively and effectively with promising therapeutic outcomes. The focusing capability of an ultrasound transducer (i.e., focus shift, beam distortion, and acoustic pressure at the focus) determines the ablation effects. However, the focus shift and focal beam distortion after ultrasound propagating through multi-layered heterogeneous viscoelastic biological tissues become significant and are found to deteriorate the performance of FUAS in clinics.Methods: To achieve an accurate and reliable focal field among patients with large variations in the anatomical structures and properties, a spherical cavity transducer with open ends and sub-wavelength focal size (Li et al., APL, 2013,102:204102) was applied here. Both experimental measurements and numerical simulations were performed to characterize the acoustic fields of the spherical cavity transducer in water, the multi-layered concentric cylindrical phantom, and the heterogeneous tissue model (an adult male pelvis enclosed by porcine skin, fat, and muscle) and then compared with those of a conventional concave transducer at the same electrical power output.Results: It is found that standing-wave focusing using the spherical cavity transducer results in much less focus shift (0.25λ vs. 1.67λ) along the transducer axis and focal beam distortion (−6 dB beam area of 0.71 mm2vs. 4.72 mm2 in water and 2.55 mm2vs. 17.30 mm2 in tissue) in the focal plane but higher pressure focusing gain (40.05 dB vs. 33.61 dB in tissue).Discussion: Such a highly accurate and reliable focal field is due to the excitation at an appropriate eigen-frequency of the spherical cavity with the varied media inside rather than the reverberation from the concave surface. Together with its sub-wavelength focal size, the spherical cavity transducer is technically advantageous in comparison to the concave one. The improved focusing capability would benefit ultrasound exposure for not only safer and more effective FUAS in clinics, but also broad acoustic applications

Improving the emission efficiency of MBE-grown GaN/AlN QDs by strain control

The quantum-confined stark effect induced by polarization has significant effects on the optical properties of nitride heterostructures. In order to improve the emission efficiency of GaN/AlN quantum dots [QDs], a novel epitaxial structure is proposed: a partially relaxed GaN layer followed by an AlN spacer layer is inserted before the growth of GaN QDs. GaN/AlN QD samples with the proposed structure are grown by molecular beam epitaxy. The results show that by choosing a proper AlN spacer thickness to control the strain in GaN QDs, the internal quantum efficiencies have been improved from 30.7% to 66.5% and from 5.8% to 13.5% for QDs emitting violet and green lights, respectively

Family functioning as a moderator in the relation between perceived stress and psychotic-like experiences among adolescents during COVID-19

Background: The COVID-19 pandemic has increased psychological stress among adolescents, and the relation between perceived stress (PS) and psychotic-like experiences (PLEs) has been well-established. However, little is known about the role of family functioning (FF) in this relation, especially when adolescents experienced the extended lockdown period with family members. Methods: A total of 4807 adolescents completed this retrospective paper-and-pencil survey after school reopening between May 14th and June 6th, 2020 in Hunan Province, China. We measured PS with the Perceived stress scale (PSS-10), PLEs with the eight positive items from Community Assessment of Psychic Experiences (CAPE-8), and FF with the Family APGAR scale. We conducted subgroup analysis based on three FF levels (good, moderate, and poor) determined by previous studies. Finally, correlation and moderation analysis were performed to detect the effect of FF in the relation between PS and PLEs after adjusting for demographic variables. Results: Adolescents with poor FF had higher levels of PS and higher prevalence of PLEs compared to those with good FF (both p \u3c 0.001). FF was negatively associated with both PS (r = −0.34, p \u3c 0.001) and PLEs (r = −0.29, p \u3c 0.001). Higher FF significantly attenuated the effect of PS on PLEs after adjusting for sex and age (effect = −0.011, bootstrap 95% CI -0.018, −0.005). Conclusion: Our findings indicate that well-functioned family could protect against stress-induced PLEs among adolescents during this crisis. Thus family system could be an early interventional target for distressing psychotic-like experiences in youngsters

Failure Mechanism of Bolts and Countermeasures in Swelling Soft Rock Support

The effect of conventional bolt support is not ideal due to the large deformation character of soft rock. As an innovative bolt, constant resistance large deformation (CRLD) bolt has been successfully applied to swelling soft rock engineering, but the reinforcement mechanism is not yet clear. To investigate the interaction mechanism between bolt and surrounding rock, Nanshan Coal Mine of China was selected as the engineering background. The plastic zone of surrounding rock mass and the axial force of three bolts were obtained by theoretical analysis and FLAC3D numerical simulation. Failure processes of conventional pretension bolts in soft rock were reproduced, and the interaction between CRLD bolt and soft rock was investigated in comparison. The results indicate that: (1) The fracture zone of surrounding rock exceeds the anchorage range of the low pretension bolt, the bolt slides with surrounding rock and finally fails. (2) The fracture zone of surrounding rock does not exceed the anchorage range of the high pretension bolt. However, with the accumulation of deformation energy, stress concentration makes the bolt break. (3) CRLD bolt can effectively absorb the deformation energy released by soft rock and maintain constant support resistance. The conclusions obtained in this study provide significant references in the selection of bolts in soft rock engineering