Transverse light-shift in a spin-exchange relaxation-free co-magnetometer: measurement, decoupling, and suppression.

The transverse light-shift can induce non-negligible polarization error in the output signal of spin-exchange relaxation-free (SERF) co-magnetometer. In this paper, a novel method for rapid measurement of transverse light-shift based on the error of steady-state response of co-magnetometer is proposed firstly, then the sources of transverse light-shift in a compact SERF co-magnetometer is modeled and analyzed from three aspects: the non-ideal linear polarization of probe laser, the circular dichroism of the atomic spin ensembles, and the stress-induced birefringence effect of the cell wall. Furthermore, the decoupling and suppression methods of transverse light-shift based on a degree of circular polarization (DOCP) regulation scheme is presented, to realize the decoupling measurement of the transverse light-shift introduced by the whole co-magnetometer cell, and cancel it out with the non-ideal linear polarization of the probe laser. Eventually, the DOCP regulation scheme suggested in this paper achieves more than a 67% suppression ratio in transverse light-shift, and the short- and long-term performance of SERF co-magnetometer are improved due to the reduction of the coupling effect between the probe laser power and transverse field. Moreover, the measurement, decoupling and suppression methods provided in this paper also have the potential to be applied to other atomic sensors, such as the SERF magnetometers and nuclear spin co-magnetometers.

Fractional Exponential Feedback Control for Finite-Time Stabilization and its Application in a Spin-Exchange Relaxation-Free Comagnetometer.

This article is the first work to propose a series of control strategies for the longitudinal electron spin polarization of the spin-exchange relaxation-free comagnetometer system to ensure its ultrastable measurement. Two types of finite-time control strategies are presented for a nonlinear system with affine input. The first control strategy is finite-time fractional exponential feedback control (FEFC), which ensures that the trajectories of an autonomous system converge to an equilibrium state in a finite time that can be specified. The second control strategy is finite-time robust FEFC, which provides a finite-time stability of a nonautonomous system with unknown structures under disturbance and perturbations, and its upper bound of the settling time can be estimated. The theoretical results are supported by numerical simulations.

The Psychopathology of Worthlessness in Depression.

Background: Despite common dissatisfaction with the syndromic heterogeneity of major depression, investigations into its symptom structure are scarce. Self-worthlessness/inadequacy is a distinctive and consistent symptom of major depression across cultures. Aims: We investigated whether self-worthlessness is associated with self-blaming attribution-related symptoms or is instead an expression of reduced positive feelings overall, as would be implied by reduced positive affect accounts of depression. Methods: 44,161 undergraduate students in Study 1, and 215 patients with current Major Depressive Disorder (MDD) and 237 age-matched healthy control participants in Study 2 completed the well-validated Symptom Check List-90. Depression-relevant items were used to construct regularized partial correlation networks with bootstrap estimates of network parameter variability. Results: Worthlessness co-occurred more strongly with other symptoms linked to self-blaming attributions (hopelessness, and self-blame), displaying a combined edge weight with these symptoms which was significantly stronger than the edge weight representing its connection with reduced positive emotion symptoms (such as reduced pleasure/interest/motivation, difference in edge weight sum in Study 1 = 2.95, in Study 2 = 1.64; 95% confidence intervals: Study 1: 2.6-3.4; Study 2: 0.02-3.5; Bonferroni-corrected p < 0.05). Conclusions: This confirms the prediction of the revised learned helplessness model that worthlessness is most strongly linked to hopelessness and self-blame. In contrast, we did not find a strong and direct link between anhedonia items and a reduction in self-worth in either study. This supports worthlessness as a primary symptom rather than resulting from reduced positive affect.

Optimal Spin Polarization Control for the Spin-Exchange Relaxation-Free System Using Adaptive Dynamic Programming.

This work is the first to solve the 3-D spin polarization control (3DSPC) problem of atomic ensembles, which controls the spin polarization to achieve arbitrary states with the cooperation of multiphysics fields. First, a novel adaptive dynamic programming (ADP) structure is proposed based on the developed multicritic multiaction neural network (MCMANN) structure with nonquadratic performance functions, as a way to solve the multiplayer nonzero-sum game (MP-NZSG) problem in 3DSPC under the constraints of asymmetric saturation inputs. Then, we utilize the MCMANNs to implement the multicritic multiaction ADP (MCMA-ADP) algorithm, whose convergence is proven by the compression mapping principle. Finally, the MCMA-ADP is deployed in the spin-exchange relaxation-free (SERF) system to provide a set of control laws in 3DSPC that fully exploits the multiphysics fields to achieve arbitrary spin polarization states. Numerical simulations support the theoretical results.

Stress and Suicidal Ideation: The Role of State or Trait Anhedonia in a Moderated Mediation Model.

BACKGROUND: Recent works suggested taking into account the severity and the type of anhedonia when examining suicidal ideation. The present study investigated a moderated mediation model addressing the psychosocial mechanisms that account for the association between state or trait anhedonia and suicidal ideation. METHODS: State anhedonia was assessed using the Snaith-Hamilton Pleasure Scale, while trait anhedonia was assessed using the Temporal Experience of Pleasure Scale. A total number of 1,361 of undergraduates completed questionnaires at three different times, with one-year intervals. RESULTS: The direct effect of stress on suicidal ideation was significantly greater for those students who had lower trait anticipatory and consummatory anhedonia, whereas the indirect effect from stress on suicidal ideation through depression was significantly greater for those who had higher state anhedonia. Moreover, trait consummatory anhedonia moderated the relationship between stress and suicidal ideation after one year, and trait anticipatory anhedonia moderated the relationship between stress and suicidal ideation after two years. CONCLUSIONS: Low levels of trait anhedonia were associated with elevated suicidal ideation, while high levels of state anhedonia were associated with elevated suicidal ideation. Trait consummatory anhedonia was associated with short-term suicidal ideation, while trait anticipatory anhedonia was associated with long-term suicidal ideation.

Trajectories of state anhedonia and recent changes in anhedonia in college students: Associations with other psychiatric syndromes.

BACKGROUND: Recent works suggest recent changes in anhedonia may be specifically predictive of key elements of psychopathology. The present study aimed to identify the trajectories of state anhedonia and recent changes in anhedonia, and to investigate their associations with other psychiatric syndromes over time. METHODS: A total of 859 college students were assessed at three time points. State anhedonia was assessed using the Snaith Hamilton Pleasure Scale and recent changes in anhedonia were assessed with a subscale extracted from the Symptom Check-List-90. The Latent Growth Curve Modelling analysis was used to analyze trajectories. Associations with anhedonia were investigated with logistic regression models. RESULTS: Three state anhedonia trajectories and two recent changes in anhedonia trajectories were identified. The decreasing trajectory was the most prevalent class in both two types of anhedonia. Depression and suicidal ideation predicted recent changes in anhedonia whereas other psychiatric syndromes predicted state anhedonia. CONCLUSIONS: The current study highlighted the development trajectories of different measures of anhedonia. The results showed that the relationships between anhedonia and psychiatric syndromes were different according to the kind of anhedonia.

Differential effects of state and trait social anhedonia on suicidal ideation at 3-months follow up.

BACKGROUND: Recent work suggests that the social component of anhedonia is more associated with suicide ideation than the other component of pleasure. The present study investigated the differential effects of state and trait social anhedonia on suicidal ideation across two undergraduate samples based on the Interpersonal Theory and Three-Step Theory of Suicide. METHODS: State social anhedonia was assessed with a single item (Loss of Interest in People) extracted from the Beck Depression Inventory, while trait social anhedonia was assessed using the Anticipatory and Consummatory Interpersonal Pleasure Scale. Suicidal ideation was re-administered at a 3-month follow-up. RESULTS: In Study 1, higher state social anhedonia was associated with greater levels of suicidal ideation, while trait social anhedonia moderated the relationship between thwarted belongingness, perceived burdensomeness and suicidal ideation. In Study 2, state social anhedonia was margin significant predictor of suicidal ideation, while trait social anhedonia moderated the relationship between psychological pain and suicidal ideation. CONCLUSIONS: These findings confirmed the presence of two different effects on suicidal ideation in state and trait social anhedonia: state social anhedonia directly was associated with suicidal ideation, while trait social anhedonia was indirectly related through their effects on other risk factors of suicidality.