Synthesis and Evaluation of Highly Inhibitory Oil Well Cement Retarders with Branched-Chain Structures.

Cementing at medium temperature and high temperature (90-150 °C) is facing challenges on account of the properties of the retarders. Except for the thermal stability, abnormal gelation, such as "bulging" and "stepping", often takes place and results in safety problems. In this article, the synthesis of a new retarder DRH-150 was introduced. First, a main chain with thermal-resistant groups, 2-acrylamido-2-methylpropanesulfonic acid-acrylic acid (AMPS-IA-AA) was prepared by free radical polymerization. Second, the retarder with a branched structure was synthesized by the grafting reaction. Evaluation of the construction performance showed that, within the temperature range from 90 to 150 °C, the initial viscosity of the cement slurry with DRH-150 was less than 15 Bc, exhibiting an adjustable thickening time and a dosage sensitivity of less than 20%. Meanwhile, no abnormal gelation phenomenon was observed. Referring to the static gelation, both the transition time and the starting strength time (1 MPa) were short. The overall results proved that the retarder DRH-150 might ensure the safety of well cementing and improve the wellbore sealing effect in deep wells, ultradeep wells, and complex wells.

Variable bandwidth, high efficiency microwave resonator for control of spin-qubits in nitrogen-vacancy centers.

Nitrogen-Vacancy (NV) centers in diamond are attractive tools for sensing and quantum information. Realization of this potential requires effective tools for controlling the spin degree of freedom by microwave (mw) magnetic fields. In this work, we present a planar microwave resonator optimized for microwave-optical double resonance experiments on single NV centers in diamond. It consists of a piece of wide microstrip line, which is symmetrically connected to two 50 Ω microstrip feed lines. In the center of the resonator, an Ω-shaped loop focuses the current and the mw magnetic field. It generates a relatively homogeneous magnetic field over a volume of 0.07 × 0.1 mm3. It can be operated at 2.9 GHz in both transmission and reflection modes with bandwidths of 1000 and 400 MHz, respectively. The high power-to-magnetic field conversion efficiency allows us to produce π-pulses with a duration of 50 ns with only about 200 and 50 mW microwave power in transmission and reflection, respectively. The transmission mode also offers capability for efficient radio frequency excitation. The resonance frequency can be tuned between 1.3 and 6 GHz by adjusting the length of the resonator. This will be useful for experiments on NV-centers at higher external magnetic fields and on different types of optically active spin centers.

Fast Quantum State Tomography in the Nitrogen Vacancy Center of Diamond.

Quantum state tomography is the procedure for reconstructing unknown quantum states from a series of measurements of different observables. Depending on the physical system, different sets of observables have been used for this procedure. In the case of spin qubits, the most common procedure is to measure the transverse magnetization of the system as a function of time. Here, we present a different scheme that relies on time-independent observables and therefore does not require measurements at different evolution times, thereby greatly reducing the overall measurement time. To recover the full density matrix, we use a set of unitary operations that transform the density operator elements into the directly measurable observable. We demonstrate the performance of this scheme in the electron-nuclear spin system of the nitrogen vacancy center in diamond.

Gold(I)-Catalyzed Tandem Intramolecular Methoxylation/Double Aldol Condensation Strategy Yielding 2,2'-Spirobi[indene] Derivatives.

The syntheses of 2,2'-spirobi[indene] derivatives based on a gold(I)-catalyzed tandem strategy involving intramolecular methoxylation/double aldol condensation were achieved. Examination of the scope of this tandem reaction by using a batch of alkynone substrates disclosed that the reaction possessed a good functional group tolerance. A cationic gold(I) catalyst/protonic acid-catalyzed mechanism for this tandem reaction is proposed.

EpiTopics: A dynamic machine learning model to predict and inform non-pharmacological public health interventions from global news reports.

Non-pharmacological interventions (NPIs) are important for controlling infectious diseases such as COVID-19, but their implementation is currently monitored in an ad hoc manner. To address this issue, we present a three-stage machine learning framework called EpiTopics to facilitate the surveillance of NPI. In this protocol, we outline the use of transfer-learning to address the limited number of NPI-labeled documents and topic modeling to support interpretation of the results. For complete details on the use and execution of this protocol, please refer to Wen et al. (2022).

Toward the Speed Limit of High-Fidelity Two-Qubit Gates.

Most implementations of quantum gate operations rely on external control fields to drive the evolution of the quantum system. Generating these control fields requires significant efforts to design the suitable control Hamiltonians. Furthermore, any error in the control fields reduces the fidelity of the implemented control operation with respect to the ideal target operation. Achieving sufficiently fast gate operations at low error rates remains therefore a huge challenge. In this Letter, we present a novel approach to overcome this challenge by eliminating, for specific gate operations, the time-dependent control fields entirely. This approach appears useful for maximizing the speed of the gate operation while simultaneously eliminating relevant sources of errors. We present an experimental demonstration of the concept in a single nitrogen-vacancy center in diamond at room temperature.

Comparison of treatments for hepatocellular carcinoma patients with portal vein thrombosis: a systematic review and network meta-analysis.

BACKGROUND: Sorafenib, hepatectomy, and transarterial chemoembolization (TACE) are the recommended treatment for portal vein tumor thrombosis (PVTT) patients. Therefore, the aim of the present study was to conduct a multi-treatment meta-analysis. The aim of the present study was to analyze the survival benefit of different treatments options on PVTT patients. METHODS: We systematically analyzed 12 randomized controlled trials (4,265 participants) from 2012 to 2019, which compared any of the following treatment options on PVTT patients: TACE, sorafenib, hepatectomy, sorafenib + TACE, hepatectomy + TACE, and sorafenib + hepatectomy. The main outcome was the 1-year survival rate of patients. RESULTS: The results of the rank probability of effectiveness showed that sorafenib + TACE was more likely to be the most effective treatment, sorafenib + TACE group was ranged rank 1 when compared with the others [hepatectomy group: odds ratio (OR): 0.79, 95% confidence interval (CI): 0.03-18.26; hepatectomy + TACE group: OR: 0.51, 95% CI: 0.01-13.59; sorafenib group: OR: 0.14, 95% CI 0.01-2.29, sorafenib + hepatectomy group: OR: 0.15, 95% CI: 0.00-24.88; and TACE group: OR: 0.51, 95% CI: 0.02-9.88]. The second most effect treatment option was hepatectomy alone. DISCUSSION: Sorafenib + TACE is more likely to be the most effective treatment option, while hepatectomy alone is the second effective treatment option.

Diabetes mellitus and postoperative blood glucose value help predict posthepatectomy liver failure in patients with hepatocellular carcinoma.

BACKGROUND: Many complications after hepatectomy can lead to perioperative death, among which posthepatectomy liver failure (PHLF) is the leading one. Existing studies suggest that one of the most important risk factors for PHLF is cirrhosis. Hepatitis B virus (HBV) infection is an important factor in the occurrence of cirrhosis, and the exact relationship between HBV infection and PHLF is not obvious. Diabetes mellitus and postoperative blood glucose are closely associated with liver regeneration, but its exact relationship with PHLF remains unclear. METHODS: We collected clinical indicators from 920 adult patients treated at the Liver Surgery and Transplantation Center of West China Hospital of Sichuan University from April 2009 and April 2019. We conducted a univariate analysis find out the risk factors of PHLF, follow by a multivariate analysis to ascertain the independent risk factors. Receiver operating characteristic (ROC) curves were plotted to evaluate the predictive efficiency of each risk factor. RESULTS: Following hepatectomy, 205 (22.2%) of patients were diagnosed with PHLF. Several variables were confirmed to related with PHLF significantly: diabetes [P<0.01, odds ratio (OR) =10.845, 95% confidence interval (CI): 5.450-21.579], HBV (P<0.01, OR =0.345, 95% CI: 0.187-0.635), blood glucose on the first postoperative day (post-BG1) (P=0.027, OR =1.059, 95% CI: 1.006-1.115), blood glucose on the third postoperative day (post-BG3) (P=0.021, OR =1.085, 95% CI: 1.012-1.162), blood glucose on the fifth postoperative day (post-BG5) (P=0.014, OR =1.119, 95% CI: 1.023-1.225), postoperative total bilirubin (post-TB) (P<0.01, OR =1.160, 95% CI: 1.133-1.187), and liver cirrhosis (P<0.01, OR =0.982, 95% CI: 0.561-1.717) identified to be independent risk factors of PHLF. CONCLUSIONS: Diabetes, HBV, post-BG1, post-BG3, and post-BG5 are related to the development of PHLF, and diabetes and post-BG can be used as predictors of the development of PHLF in patients with hepatocellular carcinoma (HCC).

Efficient Implementation of a Quantum Algorithm in a Single Nitrogen-Vacancy Center of Diamond.

Quantum computers have the potential to speed up certain problems that are hard for classical computers. Hybrid systems, such as the nitrogen-vacancy (NV) center in diamond, are among the most promising systems to implement quantum computing, provided the control of the different types of qubits can be efficiently implemented. In the case of the NV center, the anisotropic hyperfine interaction allows one to control the nuclear spins indirectly, through gate operations targeting the electron spin, combined with free precession. Here, we demonstrate that this approach allows one to implement a full quantum algorithm, using the example of Grover's quantum search in a single NV center, whose electron is coupled to a carbon nuclear spin.

Efficient Quantum Gates for Individual Nuclear Spin Qubits by Indirect Control.

Hybrid quantum registers, such as electron-nuclear spin systems, have emerged as promising hardware for implementing quantum information and computing protocols in scalable systems. Nevertheless, the coherent control of such systems still faces challenges. Particularly, the lower gyromagnetic ratios of the nuclear spins cause them to respond slowly to control fields, resulting in gate times that are generally longer than the coherence time of the electron. Here, we demonstrate a scheme for circumventing this problem by indirect control: we apply a small number of short pulses only to the electron and let the full system undergo free evolution under the hyperfine coupling between the pulses. Using this scheme, we realize robust quantum gates in an electron-nuclear spin system, including a Hadamard gate on the nuclear spin and a controlled-NOT gate with the nuclear spin as the target qubit. The durations of these gates are shorter than the electron coherence time, and thus additional operations to extend the system coherence time are not needed. Our demonstration serves as a proof of concept for achieving efficient coherent control of electron-nuclear spin systems, such as nitrogen vacancy centers in diamond. Our scheme is still applicable when the nuclear spins are only weakly coupled to the electron.

Effect of the mobile phone-related background on inhibitory control of problematic mobile phone use: An event-related potentials study.

The present study aims to provide electrophysiological evidence for deficient inhibitory control in problematic mobile phone use and to investigate whether reduced inhibition is more pronounced during exposure to a mobile phone related background cue. A screen scale of smartphone addiction was completed by 227 college students, and finally an experimental group and a control group consisting of 20 problematic mobile phone users and 19 controls were included in the study. Event-related potentials were recorded during a backgrounded Go/NoGo task performed by those two groups, in which either a frequent Go signal (letter "M") or a rare NoGo signal (letter "W") was superimposed on three different background cues: neutral, mobile phone application-related and mobile phone using-related pictures. Results showed that problematic mobile phone users performed more commission errors than controls following mobile phone application background. Furthermore, problematic mobile phone users displayed a weaker NoGo P3 amplitude than controls on the mobile phone application background. The result might suggest that there is no general impairment of inhibitory control in problematic mobile phone use. The deficient inhibitory control on behavioral and psychophysiological level appeared merely in the mobile phone-related background. Such deficient stimuli-specific inhibitory control appears at the late stage of inhibitory control. Prevention programs should be designed to curtail exposure to the mobile phone-related stimulus and enhance cognitive control of potential problematic mobile phone users.

Experimental protection of two-qubit quantum gates against environmental noise by dynamical decoupling.

Hybrid systems consisting of different types of qubits are promising for building quantum computers if they combine useful properties of their constituent qubits. However, they also pose additional challenges if one type of qubits is more susceptible to environmental noise than the others. Dynamical decoupling can help to protect such systems by reducing the decoherence due to the environmental noise, but the protection must be designed such that it does not interfere with the control fields driving the logical operations. Here, we test such a protection scheme on a quantum register consisting of the electronic and nuclear spins of a nitrogen-vacancy center in diamond. The results show that processing is compatible with protection: The dephasing time was extended almost to the limit given by the longitudinal relaxation time of the electron spin.

Protected quantum computing: interleaving gate operations with dynamical decoupling sequences.

Implementing precise operations on quantum systems is one of the biggest challenges for building quantum devices in a noisy environment. Dynamical decoupling attenuates the destructive effect of the environmental noise, but so far, it has been used primarily in the context of quantum memories. Here, we experimentally demonstrate a general scheme for combining dynamical decoupling with quantum logical gate operations using the example of an electron-spin qubit of a single nitrogen-vacancy center in diamond. We achieve process fidelities >98% for gate times that are 2 orders of magnitude longer than the unprotected dephasing time T2.

Research on relationship among internet-addiction, personality traits and mental health of urban left-behind children.

AIM: In this research, we attempted at exploring the relationships among urban left-behind children's internet-addiction, personality traits and mental health. METHODS: In the form of three relevant questionnaires (Adolescent Pathological Internet Use Scale, Eysenck Personality Questionnaire, Children's Edition in Chinese and Mental Health Test), 796 urban left-behind children in China were investigated, concerning internet-addiction, personality traits and mental health. RESULTS: (1) The internet-addiction rate of urban left-behind children in China reached 10.8%-a relatively high figure, with the rate among males higher than that among females. In terms of internet-addition salience, the figure of urban left-behind children was obviously higher than that of non-left-behind children. (2) In China, the personality deviation rate of the overall left-behind children was 15.36%; while the personality deviation rate of the internet-addicted urban left-behind children was 38.88%, a figure prominently higher than that of the non-addicted urban left-behind children group, with the rate among females higher than that among males. (3) The mental health problem rate of the overall urban left-behind children in China was 8.43%; while the rate of the internet-addicted urban left-behind children was 27.77%, a figure significantly higher than that of the non-addicted urban left-behind children. (4) There were significant relationships among internet-addiction, personality traits and mental health. The total score of internet-addiction and its related dimensions can serve as indicators of personality neuroticism, psychoticism and the total scores of mental health.

Experimental implementation of assisted quantum adiabatic passage in a single spin.

Quantum adiabatic passages can be greatly accelerated by a suitable control field, called a counter-diabatic field, which varies during the scan through resonance. Here, we implement this technique on the electron spin of a single nitrogen-vacancy center in diamond. We demonstrate two versions of this scheme. The first follows closely the procedure originally proposed by Demirplak and Rice [J. Phys. Chem. A 107, 9937 (2003)]. In the second scheme, we use a control field whose amplitude is constant but whose phase varies with time. This version, which we call the rapid-scan approach, allows an even faster passage through resonance and therefore makes it applicable also for systems with shorter decoherence times.

Experimental implementation of encoded logical qubit operations in a perfect quantum error correcting code.

Large-scale universal quantum computing requires the implementation of quantum error correction (QEC). While the implementation of QEC has already been demonstrated for quantum memories, reliable quantum computing requires also the application of nontrivial logical gate operations to the encoded qubits. Here, we present examples of such operations by implementing, in addition to the identity operation, the NOT and the Hadamard gate to a logical qubit encoded in a five qubit system that allows correction of arbitrary single-qubit errors. We perform quantum process tomography of the encoded gate operations, demonstrate the successful correction of all possible single-qubit errors, and measure the fidelity of the encoded logical gate operations.

Digital quantum simulation of the statistical mechanics of a frustrated magnet.

Many problems of interest in physics, chemistry and computer science are equivalent to problems defined on systems of interacting spins. However, most such problems require computational resources that are out of reach with classical computers. A promising solution to overcome this challenge is quantum simulation. Several 'analogue' quantum simulations of interacting spin systems have been realized experimentally, where ground states were prepared using adiabatic techniques. Here we report a 'digital' quantum simulation of thermal states; a three-spin frustrated magnet was simulated using a nuclear magnetic resonance quantum information processor, and we were able to explore the phase diagram of the system at any simulated temperature and external field. These results help to identify the challenges for performing quantum simulations of physical systems at finite temperatures, and suggest methods that may be useful in simulating thermal open quantum systems.

Experimental quantum simulation of entanglement in many-body systems.

We employ a nuclear magnetic resonance (NMR) quantum information processor to simulate the ground state of an XXZ spin chain and measure its NMR analog of entanglement, or pseudoentanglement. The observed pseudoentanglement for a small-size system already displays a singularity, a signature which is qualitatively similar to that in the thermodynamical limit across quantum phase transitions, including an infinite-order critical point. The experimental results illustrate a successful approach to investigate quantum correlations in many-body systems using quantum simulators.

Experimental magic state distillation for fault-tolerant quantum computing.

Any physical quantum device for quantum information processing (QIP) is subject to errors in implementation. In order to be reliable and efficient, quantum computers will need error-correcting or error-avoiding methods. Fault-tolerance achieved through quantum error correction will be an integral part of quantum computers. Of the many methods that have been discovered to implement it, a highly successful approach has been to use transversal gates and specific initial states. A critical element for its implementation is the availability of high-fidelity initial states, such as |0〉 and the 'magic state'. Here, we report an experiment, performed in a nuclear magnetic resonance (NMR) quantum processor, showing sufficient quantum control to improve the fidelity of imperfect initial magic states by distilling five of them into one with higher fidelity.

Quantum simulation of a system with competing two- and three-body interactions.

Quantum phase transitions occur at zero temperature, when the ground state of a Hamiltonian undergoes a qualitative change as a function of a control parameter. We consider a particularly interesting system with competing one-, two-, and three-body interactions. Depending on the relative strength of these interactions, the ground state of the system can be a product state, or it can exhibit genuine tripartite entanglement. We experimentally simulate such a system in a NMR quantum simulator and observe the different ground states. By adiabatically changing the strength of one coupling constant, we push the system from one ground state to a qualitatively different ground state. We show that these ground states can be distinguished and the transitions between them observed by measuring correlations between the spins or the expectation values of suitable entanglement witnesses.