Difference of carrier dynamics in a semiconductor saturable absorber mirror with and without B+ ion-implantation.

Three samples whose growth temperatures were 450°C, 500°C, and 560°C for S E S A M 1, S E S A M 2, and S E S A M 3, respectively, were tested by femto-second time-resolved transient absorption spectroscopy. The results indicate that the carrier dynamics of excited state absorption were dominant, and the lifetimes of carriers trapped by defect levels were about tens of pico-seconds. To further study the influence of carrier dynamics and recovery time of samples by ion-implantation, B + ions of 80 and 130 KeV were implanted into the samples with dose of 1014/c m 2. The modified samples showed a dominance of ultra-fast carrier dynamics of ground-state bleaching and direct recombination, which lasted for hundreds of femto-seconds, over excited state absorption. Additionally, carrier fast trapping was observed to be competitive with the excited state absorption process. After ion-implantation, the carrier dynamics of carrier trapping were enhanced, which contributed to forming an ultra-short laser, while the carrier dynamics of absorption of the excited state were suppressed. The conclusion that defect levels were partially eliminated by B + ion-implantation can be drawn.

Trinuclear Cu-based covalent organic framework: π-conjugated framework regulating electron delocalization to promote photoreduction CO2.

Sunlight-driven CO2 reduction to value-added chemicals is an effective strategy to promote carbon recycling. The exploration of catalysts with efficient charge separation is crucially important for highly efficient CO2 photoreduction. In this work, the preparation of metal-cluster-based covalent organic framework (CuABD) integrated features from both metal organic frameworks (MOFs) and covalent organic frameworks (COFs) through the condensation of diamines and functionalized trinuclear copper clusters demonstrate a thoughtful design strategy. The reported yield of 1.3 mmol g-1 h-1 for formic acid (HCOOH) under simulated solar irradiation is impressive, surpassing the performance of many COF- and MOF-based catalysts previously reported. Compared to its isomorphic metal-free structure (named BDFTD) and bare trinuclear Cu cluster which present extremely poor catalytic activities, CuABD displays remarkably enhanced CO2 reduction activity. Experimental and theoretical investigations reveal that the efficient charge transfer between diamine monomer and cyclic trinuclear copper (I) units, and the electron delocalization of the π-conjugated framework are responsible for the appealing catalytic performance. In summary, the work presents a well-structured and scientifically sound exploration of a metal-cluster-based covalent organic framework for efficient CO2 reduction under sunlight.

The effects of contextual certainty on tension induction and resolution.

It is known that tension is a core principle of the generation of music emotion and meaning, and supposed to be induced by prediction in process of music listening. Using EEG and behavioral rating, the current research investigated how contextual certainty affects musical tension induction and resolution. The major results were that in the tension induction process, incongruent conditions elicited larger EN and P600 in ERP responses compared with congruent conditions, and the amplitude of P600, tension ratings were mediated by contextual certainty. In the tension resolution process, contextual certainty further affected the duration of P600 and tension ratings. For the certain conditions, tension ratings were higher, tension curves fluctuated faster, and a larger P600 was evoked in the incongruent condition compared with the congruent condition. For the uncertain conditions, there was no congruency effect on behavioral ratings and tension curves, but a larger P600 was elicited in the congruent condition. These results show that contextual certainty affects tension induction and resolution. Our findings provide a more comprehensive view on how musical prediction affects musical tension.

Effect of hip flexion angle on lower limb injuries of occupants in autonomous vehicle crashes.

This study aims to determine the influence of the hip flexion angle on the injury trends of lower limbs. An impact model was established using a hybrid human body model and an accurate vehicle model. Simulations were performed in two boundary environments of 25 and 40% overlap impacts under different hip flexion angles. The analysis of the dynamic responses indicated that the hip flexion angle significantly affected the injury trends. The maximum femur index of different overlaps was all found at the minimum hip angle, except for the left femur at 25% overlap rate. Meanwhile, the maximum acetabular stress was all found at the minimum hip angle (approximately 0.09-0.20 GPa). This study provides mechanistic insights into the lower limb injuries associated with complex human postures.

Dynamic Interface with Enhanced Visible-Light Absorption and Electron Transfer for Direct Photoreduction of Flue Gas to Syngas.

The direct usage of CO2 in the flue gas to produce fuels or chemicals is of great significance from energy-saving and low-cost perspectives, yet it is still underexplored. Herein, we report the photoreduction of CO2 from the simulated industrial exhaust by synergistic catalysis of TEOA and a metal-free composite (COF1-g-C3N4) fabricated via covalently grafting COF1 with g-C3N4. The hydrogen bond interaction between TEOA and hydrazine units on COF1 is detected in diluted CO2, which leads to significantly enhanced light absorption in the whole visible-light region. Also, the photo-induced electrons undergo fast transfer from COF1 to g-C3N4. This kind of dynamic interface with enhanced light absorption and electron transfer effects promotes the photosynthetic yield of syngas to 165.6 µmol·g-1·h-1 with the use of simulated exhaust gas as a raw material directly. The photosynthetic yield of syngas ranks among the highest of known metal-free catalysts in diluted CO2. This work provides a general rule for designing efficient catalysts via a controlled catalytic interface and new insights into the role of TEOA in photochemical CO2 reduction.

Investigation of lower limb injury under different contact stiffness for drivers during frontal crash.

Lower extremity injuries in AIS2+ were the most costly injuries through the statistic analysis of traffic accidents. This study aimed to investigate the response characteristics of the lower limb with different contact stiffness, in which knee cushion and foot cushion were applied. First, a model with a human body and a car was established, and the muscle function was activated in lower extremity of human model. Second, the deceleration pulse with a peak of 186 m/s2 was applied to the car to simulate the frontal crash. Then, four sets of simulations with different contact stiffness are conducted to obtain the lower limb responses. Results indicate that the maximum loading of the left and right legs during the impact wes 1.29 and 1.22 kN, respectively. Meanwhile, the maximum moment were 28.82 and 52.17 Nm, respectively. The maximum stress of lower extremity was 87.35 MPa, and the maximum tibia index was 0.230. It was demonstrated that the injury risk of the femur in the groups with equipment of knee cushion and foot cushion was low, but the injury risk of the tibia increased at the same time. This study could provide a reference to the study of lower limb injury in a frontal impact.

Contextual prediction modulates musical tension: Evidence from behavioral and neural responses.

Tension is a bridge between music structure and emotion. It is known that tension is affected by prediction in music listening as music unfolds. Combining behavioral and neural responses, the current research investigated how musical predictions influence tension in the process of prediction build-up based on musical context (anticipatory stage) and its integration with upcoming stimuli (integration stage). The results showed that, at the anticipatory stage, compared with high-prediction conditions, in low-prediction conditions tension curve changed faster and unstable, and a larger N5 in ERP response was elicited. Furthermore, at the integration stage, compared with congruent conditions, in incongruent conditions the behavioral rating of tension were higher regardless of the predictability of the final chord; a right negativity and P600 were elicited, and the amplitude of P600 was modulated by the predictability of the final chord. These results indicated that the effect of prediction on tension was modulated by contextual predictability. The findings provide a more comprehensive view on how musical prediction affects musical tension.

Synergetic effect of H+ adsorption and ethylene functional groups of covalent organic frameworks on the CO2 photoreduction in aqueous solution.

We prepare a novel COF for CO2 photoreduction with 99.9% CO selectivity in aqueous solution without a cocatalyst. DFT shows that the preferential adsorption of H+ on the COF results in increased CO2 adsorption energy providing an anchoring site of CO2, and with the cooperation of an ethylene group, CO2 reduction is triggered.

A ruthenium/polyoxometalate for efficient CO2 photoreduction under visible light in diluted CO2.

A system containing polyoxometalate ([Co-POM]2-) and [Ru(bpy)3]2+ as constructed for visible-light-induced CO2 conversion to syngas. In diluted CO2, high efficiency of 56.8 mmol g-1 h-1 in syngas production was gained, exceeding that of reported systems with [Ru(bpy)3]2+ participation in similar conditions. Mechanism studies revealed efficient photo-induced charge separation is achieved in the system and CO2 reduction tends to occur on [Ru(bpy)3]2+.

Mn-doped CsPb(Br/Cl)3 mixed-halide perovskites for CO2 photoreduction.

Halide perovskites have been employed as photocatalysts for CO2 photoreduction due to their excellent optical properties and unique electronic structure. However, their photocatalytic performance is relatively poor. Herein, we demonstrate a new strategy with Mn-doped CsPb(Br/Cl)3 mixed-halide perovskites as catalysts to enhance the efficiency of CO2 photoreduction. By tuning the content of Mn, a series of CsPb(Br/Cl)3:Mn perovskites are obtained and show high efficiency in CO2 conversion to CO and CH4. For the optimum catalyst sample, especially, the yields of CO and CH4 reach 1917 µmol g-1 and 82 µmol g-1 which are 14.2 and 1.4 times higher than those of CsPbBr3. This work provides new insights into improving the reactivity of perovskites in CO2 photoreduction.

Highly Efficient Photoreduction of Low-Concentration CO2 to Syngas by Using a Polyoxometalates/RuII Composite.

At present, the fixation of CO2 always requires it to be extracted from the atmosphere first, which leads to more energy consumption. Thus, direct photoreduction of low-concentration CO2 to useful chemicals (e.g., syngas) under sunlight is significant from an energy-saving and environmentally friendly perspective. Here, the design and fabrication of a [Ru(bpy)3 ]/[Co20 Mo16 P24 ] composite is demonstrated for visible-light-driven syngas production from diluted CO2 (3-20 %) gas with a high yield of approximately 1000 TONs (turnover number of syngas). This activity is an order of magnitude higher than the reported system with [Ru(bpy)3 ]2+ participation. With evidence from ultrafast transient absorption, GC-MS, 1 H NMR spectroscopy and in situ transient photovoltage tests, a clear and fundamental understanding of the highly efficient photoreduction of CO2 by the [Ru(bpy)3 ]/[Co20 Mo16 P24 ] composite is achieved. Making use of the structure and property designable polyoxometalates towards the photo-fixation of CO2 is a conceptually distinct and commercially interesting strategy for making useful chemicals and environmental protection.

All-inorganic perovskite/graphitic carbon nitride composites for CO2 photoreduction into C1 compounds under low concentrations of CO2.

CsPbBr3 is widely used in solar cells and LEDs for its excellent photoelectric properties that are also attractive for CO2 photoreduction, but it is less used in the photocatalytic reduction of CO2 mainly owing to its limited charge separation efficiency. To alleviate this issue, herein, all-inorganic orthorhombic CsPbBr3 was combined with graphitic carbon nitride (g-C3N4) and the resultant composite (CsPbBr3@g-C3N4) showed enhanced activity in CO2 photoreduction. Under the irradiation of AM1.5 filter for 12 h, CO2 was converted into CH4 and CO with high selectivity to methane (91%) and the total amount of gaseous products up to ∼300 µmol g-1. This reactivity is 6-fold and 4-fold higher than that of pure g-C3N4 and CsPbBr3, respectively. CsPbBr3@g-C3N4 also shows excellent catalytic activity at low concentrations of CO2. Studies of energy band level and steady-state and transient photoluminescence spectroscopy indicated that the incorporation of CsPbBr3 and g-C3N4 increases charge separation, which may result in sharply enhanced catalytic efficiency. This study has provided opportunities for the combination of CsPbBr3 and other semiconductor catalysts for the photocatalytic reduction of CO2.