Stable isotopes of cerium (Ce) and neodymium (Nd), two rare earth elements (REEs), have emerged recently as useful tracers for a range of geological and environmental processes, such as redox changes ...in environments or continental weathering. However, the coupled use of stable isotopes of two (or more) rare earth elements is often hampered by difficulties in sequential separation of individual REEs and analysis of their stable isotope ratios at high precision. Here, we report a new three-stage chromatographic procedure that allows for simultaneous separation of Ce and Nd from geological samples for high-precision analysis of their stable isotope ratios on MC-ICP-MS. This approach also allows for analysis of radiogenic
143
Nd/
144
Nd ratios at high precision. Sequential separation of Nd and Ce in our procedure was achieved and optimized using α-hydroxyisobutyric acid (α-HIBA) as an eluent. Possible Ce and Nd stable isotope fractionations induced by the α-HIBA column were quantified. Total procedural blanks of our three-stage separation are low for Ce (∼46 pg) and Nd (∼2 pg). Extensive tests were conducted on MC-ICP-MS under dry plasma conditions to evaluate matrix effects associated with common cationic impurities, acid concentration, analyte/dopant ratio, and concentration mismatch between the sample and the bracketing standards. The presence of α-HIBA, and, occasionally, aluminum (Al) can affect measurements of both stable Ce and Nd isotopes, and acid concentration mismatch may affect stable Nd isotope measurements. An iterative correction method was developed to considerably increase the tolerance of stable Ce isotope analysis to Nd isobaric interferences, thereby improving the robustness of our measurement. Based on the analysis of various reference materials, we demonstrate that our new method is suitable for routine high-precision stable Ce and Nd isotope measurements on geological samples with a wide range of matrix compositions, yielding a long-term precision of ≤0.04‰ (2SD) for
142
Ce/
140
Ce and ≤0.03‰ (2SD) for
146
Nd/
144
Nd. This method also permits accurate radiogenic
143
Nd/
144
Nd measurement with an external precision of ≤15 ppm (2SD). Because the α-HIBA column is known for its capability of separating individual REEs, our approach can be adapted to separate other REEs for high-precision stable and radiogenic isotope analysis with minor modifications.
Stable isotopes of cerium (Ce) and neodymium (Nd), two rare earth elements (REEs), have emerged recently as useful tracers for a range of geological and environmental processes, such as redox changes in environments or continental weathering.
This paper focuses on event-triggered consensus tracking control for nonlinear parametric strict-feedback multi-agent systems subject to unknown sensor failures. Different from existing state ...observer, a new gain-scheduled state observer is designed to estimate the unmeasured states and sensor failures simultaneously. On the basis of the adaptive observer, a sensor failure compensator is constructed to adaptively cancel the effects of sensor failures. Furthermore, the designed switching threshold event-triggered strategy effectively reduces the communication burden and balances system performance. Based on the Lyapunov function method and the backstepping technique, it is shown that output consensus tracking and global uniform boundedness of all the closed-loop signals are achieved. Additionally, the Zeno behavior is proven to be excluded. Finally, the obtained results are illustrated by means of two simulation examples.
Ferroptosis is the cell death induced by ferrous ions and lipid peroxidation accumulation in tumor cells. Targeting ferroptosis, which is regulated by various metabolic and immune elements, might ...become a novel strategy for anti-tumor therapy. In this review, we will focus on the mechanism of ferroptosis and its interaction with cancer and tumor immune microenvironment, especially for the relationship between immune cells and ferroptosis. Also, we will discuss the latest preclinical progress of the collaboration between the ferroptosis-targeted drugs and immunotherapy, and the best potential conditions for their combined use. It will present a future insight on the possible value of ferroptosis in cancer immunotherapy.
•We discuss the latest therapeutic progress of the collaboration between the ferroptosis-targeted drugs and immunotherapy.•We use the concepts of "cold tumor" and "hot tumor" innovatively to discuss the relationship between immunotherapy and ferroptosis.
Stable potassium (K) isotopes (
41
K/
39
K) have shown great promise as novel chemical tracers for a wide range of bio-, geo-, and cosmo-chemical processes, but high precision stable K isotope ...analysis remains a challenge for plasma source mass spectrometry due to intense argon-related interferences produced directly from argon plasma. Here we provide an assessment on the analytical figures of merit of a new generation collision-cell equipped multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS), Sapphire from Nu Instruments, for K isotope analysis based on our extensive tests over a duration of ∼8 months. Because use of helium and hydrogen as collision/reaction gases can reduce argon-related interferences to negligible levels at optimal flow rates, the collision-cell mode can operate at low mass resolution during K isotope analysis, providing >2 orders of magnitude higher K sensitivity (>1000 V per μg mL
−1
K), as compared to the widely used "cold plasma" method, and the capability for direct
40
K measurement. One challenge of the collision/reaction cell analysis on Sapphire is its higher susceptibility to matrix effects, requiring effective sample purification prior to analysis. Also, the collision-cell mode on Sapphire shows a pronounced effect associated with concentration (or ion intensity) mismatch between the sample and the bracketing standard during analysis, and this effect may not be fully eliminated through conventional concentration matching practice. Instead, we developed a correction method for this concentration/ion intensity mismatch effect. Our method reduces the burden to the operator and increases sample throughput. This method allows for accurate K isotope analysis with an intermediate precision of ≤0.05‰ (2SD) to be routinely achieved using the collision cell on Sapphire, representing a major advance to stable K isotope analysis.
A robust correction method is developed to significantly improve stable potassium isotope ratio measurement on a "Sapphire" collision-cell MC-ICP-MS.
An asymmetric unactivated alkene/CH bond difunctionalization reaction for the concomitant construction of CCF3 and CO bonds was realized by using a Cu/Brønsted acid cooperative catalytic system, ...thus providing facile access to valuable chiral CF3‐containing N,O‐aminals with excellent regio‐, chemo‐, and enantioselectivity. Mechanistic studies revealed that this reaction may proceed by an unprecedented 1,5‐hydride shift involving activation of unactivated alkenes and a radical trifluoromethylation to initiate subsequent enantioselective functionalization of CH bonds. Control experiments also suggested that chiral Brønsted acid plays multiple roles and not only controls the stereoselectivity but also increases the reaction rate through activation of Togni’s reagent.
En route: The title redox‐neutral reaction provides a convenient route to valuable enantioenriched trifluoromethylated N,O‐aminals in good to excellent yields and with excellent regio‐, chemo‐, and enantioselectivity. The reaction features a CuI/Brønsted acid system and broad substrate scope.
A chiral‐NHC‐catalyzed highly diastereo‐ and enantioselective dearomatizing double Mannich reaction of isoquinolines was developed that provides a powerful and straightforward synthetic route toward ...substituted tropane derivatives with four contiguous stereocenters. A unique feature of this strategy is the use of readily available isoquinolines to provide two reactive sites for dearomatization, thus opening up an unprecedented approach to tropane derivatives with excellent stereoselectivity. The four‐component reactions proceeded smoothly with good results. Thus, the present method is suitable for the diversity‐oriented synthesis of useful tropane derivatives with high efficiency.
Fab four: A highly stereoselective dearomatizing double Mannich reaction of readily available isoquinolines, which provided two reactive sites for dearomatization, smoothly produced substituted benzotropanes with four contiguous stereocenters. In particular as a four‐component reaction, this transformation shows high potential for the efficient diversity‐oriented synthesis of useful tropane derivatives (see scheme).
The adaptive fuzzy distributed optimization problem of nonlinear multiagent systems with unknown nonlinearities and uncertain disturbances is explored in this article. The unknown nonlinearities in ...the system model are determined by incorporating fuzzy logic systems. Rather than using the existing known gradient values of local objective functions, this article further takes into account the measured gradient values that are based on the output information. The bounded estimation method and well-defined smooth functions are used to account for the effects of uncertainties. To ensure that the output can asymptotically converge to the optimal solution, a new adaptive fuzzy distributed optimization controller is proposed using the Lyapunov function method and the adaptive backstepping technique. To demonstrate the effectiveness of the developed distributed optimization technique, two practical examples are used.
An unprecedented phosphine‐catalyzed remote β‐CH functionalization of amine derivatives triggered by trifluoromethylation of an alkene with Togni’s reagent was disclosed. This reaction proceeded ...through the highly selective and concomitant activation of an unactivated alkene and the β‐C sp 3H bond of an amine derivative, providing bistrifluoromethylated enamides in excellent yields with good regio‐, chemo‐, and stereoselectivity. Furthermore, the newly developed one‐pot protocol provides a facile and step‐economical access to valuable trisubstituted 5‐(trifluoromethyl)oxazoles. Mechanistic studies showed that this reaction may initiate with a novel phosphine‐catalyzed radical trifluoromethylation of unactivated alkene via a phosphorus radical cation.
The radical tandem functionalization of unactivated alkenes and the remote β‐C sp 3H bond of amine derivatives is achieved by phosphine catalysis. The one‐pot protocol provides facile access to bistrifluoromethylated enamides as well as trisubstituted 5‐(trifluoromethyl)oxazoles.
The problem of finite-time adaptive tracking control against event-trigger error is investigated in this article for a type of uncertain nonlinear systems. By fusing the techniques of command filter ...backstepping technical and event-triggered control (ETC), an adaptive event-triggered design method is proposed to construct the controller, under which the effect of event-triggered error can be compensated completely. Moreover, the proposed controller can increase robustness against uncertainties and event error in the backstepping design framework. In particular, we establish the finite-time convergence condition under which the tracking error asymptotically converges to zero in finite time with the aid of a scaling function. Detailed and rigorous stability proofs are given by making use of the improved finite time stability criterion. Two simulation examples are provided to exhibit the validity of the designed adaptive ETC approach.
The first Ni0/bis(oxazoline)‐catalyzed asymmetric denitrogenative transannulation of 1,2,3‐benzotriazin‐4(3H)‐ones with bulky internal alkynes to form novel axially chiral isoquinolones in an ...atroposelective manner has been developed. This method provides direct asymmetric access to axially chiral isoquinolones with excellent functional‐group tolerance in excellent yields and stereoselectivities from readily available starting materials under mild reaction conditions. These axially chiral isoquinolones exhibit high cytotoxicity against a number of human cancer cell lines. DFT calculations reveal the nature of the transition state in the key annulation step.
Getting the axe: Reported is the first enantioselective Ni0/bis(oxazoline)‐catalyzed asymmetric transannulation of 1,2,3‐benzotriazin‐4(3H)‐ones with internal alkynes in an atroposelective manner to form novel axially chiral isoquinolones. DFT calculations show data for the preferred transition state in the annulation step. The products show good cytotoxicity against cancer cell lines.
