Observation of dichotomic field-tunable electronic structure in twisted monolayer-bilayer graphene.

Twisted bilayer graphene (tBLG) provides a fascinating platform for engineering flat bands and inducing correlated phenomena. By designing the stacking architecture of graphene layers, twisted multilayer graphene can exhibit different symmetries with rich tunability. For example, in twisted monolayer-bilayer graphene (tMBG) which breaks the C2z symmetry, transport measurements reveal an asymmetric phase diagram under an out-of-plane electric field, exhibiting correlated insulating state and ferromagnetic state respectively when reversing the field direction. Revealing how the electronic structure evolves with electric field is critical for providing a better understanding of such asymmetric field-tunable properties. Here we report the experimental observation of field-tunable dichotomic electronic structure of tMBG by nanospot angle-resolved photoemission spectroscopy (NanoARPES) with operando gating. Interestingly, selective enhancement of the relative spectral weight contributions from monolayer and bilayer graphene is observed when switching the polarity of the bias voltage. Combining experimental results with theoretical calculations, the origin of such field-tunable electronic structure, resembling either tBLG or twisted double-bilayer graphene (tDBG), is attributed to the selectively enhanced contribution from different stacking graphene layers with a strong electron-hole asymmetry. Our work provides electronic structure insights for understanding the rich field-tunable physics of tMBG.

Investigation and Modeling of the Behavior of Temperature Characteristics of 0.3-1.1 GHz Complementary Metal Oxide Semiconductor Class-A Broadband Power Amplifiers.

A power amplifier (PA) stands as a central module within the electronic information system (EIS), and any variation in a PA's specifications has a direct impact on the EIS's performance, especially in the face of temperature fluctuations. In examining the influence of PA specification changes on the EIS, we employed support vector machine (SVM) to model the behavior of the temperature characteristics of 0.3-1.1 GHz complementary metal oxide semiconductor (CMOS) class-A broadband PAs. The results show that the parameters of S11, S12, S21, and S22 can be effectively modeled. SVM outperforms Elman and GRNN in terms of combined modeling time and modeling accuracy. This research can be extended to modeling the behavior of other types of power amplifiers or devices and circuits.

Floquet Engineering of Black Phosphorus upon Below-Gap Pumping.

Time-periodic light field can dress the electronic states and lead to light-induced emergent properties in quantum materials. While below-gap pumping is regarded favorable for Floquet engineering, so far direct experimental evidence of momentum-resolved band renormalization still remains missing. Here, we report experimental evidence of light-induced band renormalization in black phosphorus by pumping at photon energy of 160 meV, which is far below the band gap, and the distinction between below-gap pumping and near-resonance pumping is revealed. Our Letter demonstrates light-induced band engineering upon below-gap pumping, and provides insights for extending Floquet engineering to more quantum materials.

CS-GA-XGBoost-Based Model for a Radio-Frequency Power Amplifier under Different Temperatures.

Machine learning methods, such as support vector regression (SVR) and gradient boosting, have been introduced into the modeling of power amplifiers and achieved good results. Among various machine learning algorithms, XGBoost has been proven to obtain high-precision models faster with specific parameters. Hyperparameters have a significant impact on the model performance. A traditional grid search for hyperparameters is time-consuming and labor-intensive and may not find the optimal parameters. To solve the problem of parameter searching, improve modeling accuracy, and accelerate modeling speed, this paper proposes a PA modeling method based on CS-GA-XGBoost. The cuckoo search (CS)-genetic algorithm (GA) integrates GA's crossover operator into CS, making full use of the strong global search ability of CS and the fast rate of convergence of GA so that the improved CS-GA can expand the size of the bird nest population and reduce the scope of the search, with a better optimization ability and faster rate of convergence. This paper validates the effectiveness of the proposed modeling method by using measured input and output data of 2.5-GHz-GaN class-E PA under different temperatures (-40 °C, 25 °C, and 125 °C) as examples. The experimental results show that compared to XGBoost, GA-XGBoost, and CS-XGBoost, the proposed CS-GA-XGBoost can improve the modeling accuracy by one order of magnitude or more and shorten the modeling time by one order of magnitude or more. In addition, compared with classic machine learning algorithms, including gradient boosting, random forest, and SVR, the proposed CS-GA-XGBoost can improve modeling accuracy by three orders of magnitude or more and shorten modeling time by two orders of magnitude, demonstrating the superiority of the algorithm in terms of modeling accuracy and speed. The CS-GA-XGBoost modeling method is expected to be introduced into the modeling of other devices/circuits in the radio-frequency/microwave field and achieve good results.

Automatic Piecewise Extreme Learning Machine-Based Model for S-Parameters of RF Power Amplifier.

This paper presents an automatic piecewise (Auto-PW) extreme learning machine (ELM) method for S-parameters modeling radio-frequency (RF) power amplifiers (PAs). A strategy based on splitting regions at the changing points of concave-convex characteristics is proposed, where each region adopts a piecewise ELM model. The verification is carried out with S-parameters measured on a 2.2-6.5 GHz complementary metal oxide semiconductor (CMOS) PA. Compared to the long-short term memory (LSTM), support vector regression (SVR), and conventional ELM modeling methods, the proposed method performs excellently. For example, the modeling speed is two orders of magnitude faster than SVR and LSTM, and the modeling accuracy is more than one order of magnitude higher than ELM.

Three-Field Versus Two-Field Lymphadenectomy in Minimally Invasive Esophagectomy: 3-Year Survival Outcomes of a Randomized Trial.

BACKGROUND: Minimally invasive esophagectomy (MIE) has been used widely for the treatment of esophageal cancer. However, the optimal extent of lymphadenectomy for esophagectomy in MIE remains unclear. This trial aimed to investigate the 3-year survival and recurrence outcomes in a randomized controlled trial comparing MIE with either three-field lymphadenectomy (3-FL) or two-field lymphadenectomy (2-FL). METHODS: Between June 2016 and May 2019, 76 patients with resectable thoracic esophageal cancer were enrolled in a single-center randomized controlled trial and randomly assigned to MIE that included either 3-FL or 2-FL at a 1:1 ratio (n = 38 patients each). The survival outcomes and recurrence patterns were compared between the two groups. RESULTS: The 3-year cumulative overall survival (OS) probability was 68.2 % (95 % confidence interval [CI], 52.72-83.68 %) for the 3-FL group and 68.6 % (95 % CI, 53.12-84.08 %) for the 2-FL group. The 3-year cumulative probability of disease-free survival (DFS) was 66.3 % (95 % CI, 50.03-82.57 %) for the 3-FL group and 67.1 % (95 % CI, 51.03-83.17 %) for the 2-FL group.. The OS and DFS differences in the two groups were comparable. The overall recurrence rate did not differ significantly between the two groups (P = 0.737). The incidence of cervical lymphatic recurrence in the 2-FL group was higher than in the 3-FL group (P = 0.051). CONCLUSIONS: Compared with 2-FL in MIE, 3-FL tended to prevent cervical lymphatic recurrence. However, it was not found to add survival benefit for the patients with thoracic esophageal cancer.

Optimization Modeling of Anti - breast Cancer Candidate Drugs.

To explore how to control the estrogen level in vivo by regulating the activity of the estrogen receptor in the development of breast cancer drugs, multiple-featured evaluation methods were first applied to screen the molecular descriptors of compounds according to the information of antagonist ERα provided in this study. Combining the methods of Extreme Gradient Boost (XGBoost), Light Gradient Boosting Machine (LightGBM) and Random Forest (RF), a stacking-integrated regression model for quantitatively predicting the ERα (estrogen receptors alpha) activity of breast cancer candidate drug was constructed, which considered the compounds acting on the target and their biological activity data, a series of molecular structure descriptors as the independent variables, and the biological activity values as the dependent variables. Then, three classification methods of XGBoost, LightGBM, and Gradient Boosting Decision Tree (GBDT) were selected and the voting strategy was applied to build five ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) classification prediction models. Finally, two schemes based on genetic algorithm (GA) were used to optimize the model and provide predictions for optimizing the biological activity and ADMET properties of ERα antagonists simultaneously. Results showed that the model prediction has strong practical significance, which can guide the structural optimization of existing active compounds and improve the activity of anti-breast cancer candidate drugs.

Pseudospin-selective Floquet band engineering in black phosphorus.

Time-periodic light field has emerged as a control knob for manipulating quantum states in solid-state materials1-3, cold atoms4 and photonic systems5 through hybridization with photon-dressed Floquet states6 in the strong-coupling limit, dubbed Floquet engineering. Such interaction leads to tailored properties of quantum materials7-11, for example, modifications of the topological properties of Dirac materials12,13 and modulation of the optical response14-16. Despite extensive research interests over the past decade3,8,17-20, there is no experimental evidence of momentum-resolved Floquet band engineering of semiconductors, which is a crucial step to extend Floquet engineering to a wide range of solid-state materials. Here, on the basis of time and angle-resolved photoemission spectroscopy measurements, we report experimental signatures of Floquet band engineering in a model semiconductor, black phosphorus. On near-resonance pumping at a photon energy of 340-440 meV, a strong band renormalization is observed near the band edges. In particular, light-induced dynamical gap opening is resolved at the resonance points, which emerges simultaneously with the Floquet sidebands. Moreover, the band renormalization shows a strong selection rule favouring pump polarization along the armchair direction, suggesting pseudospin selectivity for the Floquetband engineering as enforced by the lattice symmetry. Our work demonstrates pseudospin-selective Floquet band engineering in black phosphorus and provides important guiding principles for Floquet engineering of semiconductors.

Carbon nanotube electron blackbody and its radiation spectra.

An optical blackbody is an ideal absorber for all incident optical radiation, and the theoretical study of its radiation spectra paved the way for quantum mechanics (Planck's law). Herein, we propose the concept of an electron blackbody, which is a perfect electron absorber as well as an electron emitter with standard energy spectra at different temperatures. Vertically aligned carbon nanotube arrays are electron blackbodies with an electron absorption coefficient of 0.95 for incident energy ranging from 1 keV to 20 keV and standard electron emission spectra that fit well with the free electron gas model. Such a concept might also be generalized to blackbodies for extreme ultraviolet, X-ray, and γ-ray photons as well as neutrons, protons, and other elementary particles.

A newly designed femtosecond KBe2BO3F2 device with pulse duration down to 55 fs for time- and angle-resolved photoemission spectroscopy.

Developing a widely tunable vacuum ultraviolet (VUV) source with a sub-100 fs pulse duration is critical for ultrafast pump-probe techniques such as time- and angle-resolved photoemission spectroscopy (TrARPES). While a tunable probe source with a photon energy of 5.3-7.0 eV has been recently implemented for TrARPES by using a KBe2BO3F2 (KBBF) device, the time resolution of 280-320 fs is still not ideal, which is mainly limited by the duration of the VUV probe pulse generated by the KBBF device. Here, by designing a new KBBF device, which is specially optimized for fs applications, an optimum pulse duration of 55 fs is obtained after systematic diagnostics and optimization. More importantly, a high time resolution of 81-95 fs is achieved for TrARPES measurements covering the probe photon energy range of 5.3-7.0 eV, making it particularly useful for investigating the ultrafast dynamics of quantum materials. Our work extends the application of the KBBF device to ultrafast pump-probe techniques with the advantages of both a widely tunable VUV source and ultimate time resolution.

BPNN-Based Behavioral Modeling of the S-Parameter Variation Characteristics of PAs with Frequency at Different Temperatures.

To address the issue of frequency nonlinearity modeling of RF PAs, which is rarely seen in the literature, a BPNN is applied to model the frequency nonlinearity of RF PAs in this paper. The BPNN is used to model the frequency nonlinearity of the RF PA, based on the actual measured S-parameter data at different ambient temperatures. The modeling results show that BPNN shows the advantage of a high accuracy in modeling the frequency nonlinearity of RF PAs. It is expected that a BPNN will also show the advantages of a high accuracy in the modeling process of other RF devices or circuits.

An Experimental Investigation of the Degradation of CMOS Low-Noise Amplifier Specifications at Different Temperatures.

To investigate the relationship between the specifications degradation of a low-noise amplifier (LNA) and temperature, we experimentally investigated the degradation characteristics of the specifications of the LNA at different temperatures. The small-signal gain (S21) of the LNA decreases with increasing temperature. This paper discusses and analyzes the experimental results in detail, and the reasons for the degradation of LNA specifications with temperature changes are known. Finally, we have tried to use the structure already available in the literature for the PA temperature compensation circuit for the temperature compensation of the LNA. The results show that the existing circuit structure for PA temperature compensation in the literature can also effectively compensate for the S21 and NF degradation of the LNA due to the temperature increase.

Support Vector Machine-Based Model for 2.5-5.2 GHz CMOS Power Amplifier.

A power amplifier (PA) is the core module of the wireless communication system. The change of its specification directly affects the system's performance and may even lead to system failure. Furthermore, change in the PA specification is closely related to changes in temperature. To study the influence of PA specification change on the system, we used a support vector machine (SVM) to model the temperature characteristics of PA. For SVM modeling, the question of how much experimental data should be used for modeling to meet the requirements is a constant problem. To address this issue, we investigate the effect of different amounts of training data on the modeling of SVM models. The results show that only 75% of the experimental data needs to be used in the modeling process to satisfy the modeling requirements of the SVM model. The number of measurement points required in the PA specification degradation experiment can be reduced by 25%. The results of this paper serve as a guide for planning the number of experimental measurement points and reducing the measurement cost and measurement time.

On-Chip Temperature Compensation for Small-Signal Gain Variation Reduction.

Power amplifier (PA) specifications are closely related to changes in temperature; thus, the small-signal gain (S21) of PA decreases with the temperature increase. To compensate for the degradation caused by the decrease in S21, we present a compensation circuit that consists of two diodes and four resistors. At the same time, a differential stacked millimeter-wave wideband PA was designed and implemented based on this compensation circuit and 55 nm CMOS process. The post-layout simulation results showed that the fluctuation of S21 reduced from 2.4 dB to 0.1 dB in the frequency range of 25-40 GHz over the temperature range of -40 °C to 125 °C. Furthermore, the proposed on-chip temperature compensation circuit also applies to multi-stage cascaded microwave/mm-wave power amplifiers.

Experimental Investigation of Relationship between Humidity Conditions and Degradation of Key Specifications of 0.1-1.2 GHz PA in 0.18 µm CMOS.

The specification of power amplifiers (PA) is closely related to humidity variation, and few reports on the humidity properties of PA are available in the literature. Therefore, an experimental study of PA specifications was conducted under different humidity conditions to elucidate the relationship between the degradation of PA specifications and humidity conditions. This paper studies and provides results of the degradation of a PA subjected to different humidity levels. The experimental results show that the S21 and output power decrease with the increase in humidity. The main cause of this degradation is the decrease in oxide capacitance and increase in threshold voltage with increasing humidity, resulting in a reduction of transconductance and an increase in on-resistance. The results of this study can guide designers in designing compensation circuits to achieve some degree of compensation for the degradation of PA specifications.

Short-term outcomes of neoadjuvant sintilimab with chemotherapy in stage III non-small cell lung cancer: a case series.

Background: Neoadjuvant chemoimmunotherapy seems to be a promising treatment option for stage III non-small cell lung cancer (NSCLC). Sintilimab, as a programmed death receptor-1 inhibitor, has exhibited a fine performance in treating NSCLC. However, the efficiency of sintilimab combined with chemotherapy for stage IIIA/IIIB NSCLC remains inconclusive. The purpose of this study was to share our experience on sintilimab in neoadjuvant chemoimmunotherapy for stage III NSCLC. Methods: This study retrospectively reviewed patients who received surgical resection following 1-3 cycles of neoadjuvant sintilimab (200 mg) with chemotherapy for stage III NSCLC between June 2020 and March 2022 in our center. Patients characteristics, surgical factors, surgery-related complications 30 days postoperatively, and treatment-related adverse events (TRAEs) before surgery were recorded through reviewing medical record data and telephone follow-up. Results: A total of eight patients were enrolled, including six cases of squamous cell carcinoma and two cases of adenocarcinoma. All of the patients received 1-3 cycles of neoadjuvant therapy. There were no treatment-related surgical delays. All patients underwent lobectomy, among which two underwent sleeve lobectomy and one received bronchoplasty. Five patients underwent open thoracotomy. Fibrosis of the primary tumor and lymph nodes was observed in all the cases. There were no surgery-related complications > grade 2 at 30 days postoperatively. According to the radiographic findings, one patient had stable disease and all of the others achieved a partial response. The median of maximum standardized uptake value change from baseline was a 52.75% reduction (range, 37.2-68.8%). Five patients achieved a major pathological response. R0 resection was achieved in all eight cases. One grade 4 event was observed. Neutropenia was the most common TRAE > grade 2 (3/8). There were no cases of treatment discontinuation or dose reduction due to TRAEs. Conclusions: The current study found that neoadjuvant sintilimab plus chemotherapy bring a high rate of major pathological response and acceptable TRAEs. Even though it increased the difficulties of surgery, there is still no evidence suggesting that it will brings additional surgical death. We believe that neoadjuvant sintilimab plus chemotherapy might be feasible for stage III NSCLC.

Self-energy dynamics and the mode-specific phonon threshold effect in Kekulé-ordered graphene.

Electron-phonon interaction and related self-energy are fundamental to both the equilibrium properties and non-equilibrium relaxation dynamics of solids. Although electron-phonon interaction has been suggested by various time-resolved measurements to be important for the relaxation dynamics of graphene, the lack of energy- and momentum-resolved self-energy dynamics prohibits direct identification of the role of specific phonon modes in the relaxation dynamics. Here, by performing time- and angle-resolved photoemission spectroscopy measurements on Kekulé-ordered graphene with folded Dirac cones at the Γ point, we have succeeded in resolving the self-energy effect induced by the coupling of electrons to two phonons at Ω1 = 177 meV and Ω2 = 54 meV, and revealing its dynamical change in the time domain. Moreover, these strongly coupled phonons define energy thresholds, which separate the hierarchical relaxation dynamics from ultrafast, fast to slow, thereby providing direct experimental evidence for the dominant role of mode-specific phonons in the relaxation dynamics.

Investigation of the Specification Degradation Mechanism of CMOS Power Amplifier under Thermal Shock Test.

To investigate the critical specifications of a power amplifier (PA) under rapidly changing temperature conditions, we fabricated and tested a 0.3-1.1 GHz complementary metal-oxide-semiconductor (CMOS) PA under thermal shock tests. The results show that high- and low-temperature shocks can accelerate the degradation of critical specifications of PAs and that the critical specifications of PAs degrade with the increasing number of shocks. The main reason for the degradation of critical specifications of PAs with increasing thermal shock tests is the mismatch of thermal expansion coefficients of printed circuit boards (PCB) with FR-4 as a substrate. The results of this paper can provide a reference for the development of temperature-robust PAs design guidelines for the implementation of temperature-robust PAs using low-cost silicon technology.

Modeling of Key Specifications for RF Amplifiers Using the Extreme Learning Machine.

The amplifier is a key component of the radio frequency (RF) front-end, and its specifications directly determine the performance of the system in which it is located. Unfortunately, amplifiers' specifications degrade with temperature and even lead to system failure. To study how the system failure is affected by the amplifier specification degradation, it is necessary to couple the amplifier specification degradation into the system optimization design. Furthermore, to couple the amplifier specification degradation into the optimal design of the system, it is necessary to model the characteristics of the amplifier specification change with temperature. In this paper, the temperature characteristics of two amplifiers are modeled using an extreme learning machine (ELM), and the results show that the model agrees well with the measurement results and can effectively reduce measurement time and cost.

Ultrafast time- and angle-resolved photoemission spectroscopy with widely tunable probe photon energy of 5.3-7.0 eV for investigating dynamics of three-dimensional materials.

Time- and angle-resolved photoemission spectroscopy (TrARPES) is a powerful technique for capturing the ultrafast dynamics of charge carriers and revealing photo-induced phase transitions in quantum materials. However, the lack of widely tunable probe photon energy, which is critical for accessing the dispersions at different out-of-plane momentum kz in TrARPES measurements, has hindered the ultrafast dynamics investigation of 3D quantum materials, such as Dirac or Weyl semimetals. Here, we report the development of a TrARPES system with a highly tunable probe photon energy from 5.3 to 7.0 eV. The tunable probe photon energy is generated by the fourth harmonic generation of a tunable wavelength femtosecond laser source by combining a ß-BaB2O4 crystal and a KBe2BO3F2 crystal. A high energy resolution of 29-48 meV and time resolution of 280-320 fs are demonstrated on 3D topological materials ZrTe5 and Sb2Te3. Our work opens up new opportunities for exploring ultrafast dynamics in 3D quantum materials.