Giant thermal spin-torque–assisted magnetic tunnel junction switching

Spin-polarized charge currents induce magnetic tunnel junction (MTJ) switching by virtue of spin-transfer torque (STT). Recently, by taking advantage of the spin-dependent thermoelectric properties of magnetic materials, novel means of generating spin currents from temperature gradients, and their associated thermal-spin torques (TSTs), have been proposed, but so far these TSTs have not been large enough to influence MTJ switching. Here we demonstrate significant TSTs in MTJs by generating large temperature gradients across ultrathin MgO tunnel barriers that considerably affect the switching fields of the MTJ. We attribute the origin of the TST to an asymmetry of the tunneling conductance across the zero-bias voltage of the MTJ. Remarkably, we estimate through magneto-Seebeck voltage measurements that the charge currents that would be generated due to the temperature gradient would give rise to STT that is a thousand times too small to account for the changes in switching fields that we observe.Using heat to create potential gradients and charge currents has been a very active area of research in thermoelectrics (1). Spin caloritronics (2, 3) adds a new dimension to this concept by considering the use of heat to create spin-dependent chemical potential gradients in ferromagnetic materials (4). Traditionally, electric-current-driven spin currents have been used to transport spin angular momentum to change the magnetization of a magnetic material––a phenomenon known as spin-transfer torque (STT) (5–7). Heat currents can also create spin currents in magnetic materials; the transfer of spin angular momentum through this process has been named thermal-spin torque (TST) (8, 9). A panoply of recent experiments that use spin currents generated by heat has been reported which includes the spin-Seebeck effect observed in ferromagnetic metals (10, 11), semiconductors (12) and insulators (13), thermal-spin injection from a ferromagnet into a nonmagnetic metal (14), the magneto-Seebeck effect observed in magnetic tunnel junctions (MTJ) (15–17), Seebeck spin tunneling in ferromagnet–oxide–silicon tunnel junctions (18), and several others (19, 20). On the other hand, whereas there have been several theoretical predictions (8, 9, 21, 22) of the TST, there have been few experiments to date. In one experiment, evidence of TST was established in Co–Cu–Co spin-valve nanowires (23). However, in this work the same current was used for both heating and probing the device, thus making it difficult to unravel the individual contribution of TST from the simultaneously generated STT.In our device, the heating current is distinct from the probing current, which helps to decouple pure temperature gradient effects from charge-current–driven STT effects. We find that a temperature gradient of ∼1 K/nm across a 0.9-nm-thick MgO tunnel barrier in an MTJ induces modest charge currents on the order of 1 × 10³ A/cm² along with large spin currents that induce significant TST. The TST is as large as the STT that would be created by a pure charge current density of 1 × 10⁶ A/cm² in these devices as well as previously reported similar devices (24). Furthermore, the TST is strongly dependent on the orientation of the free layer with respect to the reference layer. We show that the TST can be attributed to an asymmetry in the tunneling conductance across zero bias, which is consistent with the spin accumulation in the free layer of the MTJ due to the temperature gradient across the tunnel barrier.     

Esomeprazole enhances the effect of ionizing radiation to improve tumor control

The resistance of cancer cells to radiation-based treatment is a major clinical challenge confounding standard of care in cancer. This problem is particularly notable in many solid tumors where cancer cells are only partially responsive to radiation therapy. Combination of radiation with radiosensitizers is able to enhance tumor cell killing. However, currently available radiosensitizers are associated with significant normal tissue toxicity. Accordingly, there is an unmet need to develop safer and more effective radiosensitizers to improve tumor control. Here, we evaluated the radiosensitizing effect of the FDA-approved drug esomeprazole in normal and radioresistant human head and neck squamous cell carcinoma (HNSCC) cells in vitro, and in a mouse model of HNSCC. For the in vitro studies, we used cancer cell colony formation (clonogenicity) assay to compare cancer cell growth in the absence or presence of esomeprazole. To determine mechanism(s) of action, we assessed cell proliferation and profiled cell cycle regulatory proteins. In addition, we performed reverse phase protein array (RPPA) study to understand the global effect of esomeprazole on over 200 cancer-related proteins. For the in vivo study, we engrafted HNSCC in a mouse model and compared tumor growth in animals treated with radiation, esomeprazole, and combination of radiation with esomeprazole. We found that esomeprazole inhibits tumor growth and dose-dependently enhances the cell killing effect of ionizing radiation in wildtype and p53-mutant radioresistant cancer cells. Mechanistic studies demonstrate that esomeprazole arrests cancer cells in the G1 phase of the cell cycle through upregulation of p21 protein and inhibition of cyclin-dependent kinases (Cdks) type 1 (Cdk1) and type 2 (Cdk2). In vivo data showed greater tumor control in animals treated with combination of radiation and esomeprazole compared to either treatment alone, and that this was associated with inhibition of cell proliferation in vivo. In addition, combination of esomeprazole with radiation significantly impaired repair following radiation-induced DNA damage. Our studies indicate that esomeprazole sensitizes cancer cells to ionizing radiation, and is associated with upregulation of p21 to arrest cells in the G1 phase of the cell cycle. Our findings have significant therapeutic implications for the repurposing of esomeprazole as a radiosensitizer in HNSCC and other solid tumors.     

The relation between antisaccade errors,fixation stability and prosaccade errors in schizophrenia

Whether antisaccade errors in schizophrenia are due to defects in implementing saccadic inhibition or difficulty in generating novel responses is uncertain. We investigated whether antisaccade errors were related to difficulty in inhibiting saccades when subjects were asked to maintain steady fixation, a situation that does not require a novel response. We examined the ocular motor data of 15 schizophrenia subjects and 16 healthy subjects. We assessed fixation in two situations: first, during the period before target onset during each saccadic trial, and second, during fixation trials that were interspersed with saccadic trials. We found that schizophrenia subjects had higher rates of fixation losses than control subjects in both situations. Second, both in healthy and schizophrenia subjects, antisaccade error rate was positively correlated with the frequency of fixation losses in the preparatory period of saccadic trials, but not with the frequency of fixation losses during fixation trials. Third, antisaccade errors were more likely to occur in trials with unstable fixation than in trials with stable fixation. Last, antisaccade error rate was also correlated with prosaccade error rate. We conclude that antisaccade errors are related to difficulties with implementing inhibitory control in the saccadic system. However, the finding of a correlation between the error rates for antisaccades and prosaccades suggests that this is not specifically concerned with inhibiting the automatic prosaccade, but a more general deficit in implementing goal-oriented behavior.     

Borderline tuberculoid leprosy misdiagnosed as Cheilitis Granulomatosa Miescher: A case report

Macrocheilia, as an initial manifestation of leprosy, is uncommon. We present a case of a 50‐year‐old female, with lower lip swelling, initially diagnosed as Cheilitis Granulomatosa Miescher. Unresponsiveness to local intralesional corticosteroids necessitated further evaluation. Repeat tissue sampling yielded a confirmatory diagnosis of borderline tuberculoid leprosy, which was managed successfully.     

Lifetime traumatic experiences and postpartum depressive symptoms in a cohort of women in South India

Archives of Women's Mental Health - Studies in western cultures have proposed mechanisms by which adverse childhood experiences can affect mental health, including mediating variables such as...     

Cardiovascular diseases display etiological and seasonal trend in human population: Evidence from seasonal cardiovascular comorbid diseases (SCCD) index

Seasonal changes in the human cardiovascular system are known to play an important role in the onset of many diseases. Confounding variables include behavioral and environmental factors; failing to address such variables makes measuring the true temporal impact of these diseases difficult. On the other hand, numerous clinical studies imply that only specific groups of people are more seasonal sensitive and that their maladaptation might contribute to various illnesses. As a result, it is critical to evaluate the etiological and seasonal sensitive patterns of cardiovascular diseases (CVD), which impact the majority of the human population. The hypothesis for this study formulated that cardiovascular and associated illnesses had substantial connections with seasonal and etiological variations. Thus in the present study, 4519 systematic screen-eligible studies were analyzed using data mining to uncover 852 disease association relationships between cardiovascular and associated disorders. A disease ontology-based semantic similarity network (DSN) analysis was performed to narrow down the identified CVDs. Further, topological analysis was used to predict the seven CVDs, including myocardial infarction (MI), in three clusters. Following that, Mann–Kendall and Cox–Stuart analyses were used to investigate the seasonal sensitivity and temporal relationship of these seven CVDs. Finally, temporal relationships were confirmed using LOESS and TBATS, as well as seasonal breakdown utilizing autocorrelation and fast Fourier transform results. The study provides indirect evidence of a severe etiological association among the three cardiovascular diseases, including MI, atrial fibrillation, and atherosclerosis, which are winter season sensitive in most of the world population. Hypertension has two seasonal falls and peaks due to its seasonal nature, that is, summer and winter hypertension. While, heart failure was also identified, with minor temporal trends. Hence, all five diseases could be classified as seasonal cardiovascular comorbid diseases (SCCD). Furthermore, these diseases could be studied for potential common risk factors such as biochemical, genetic, and physiological factors.     

Falls of newborn infants in a New Zealand hospital: A case series

Aim

The fall of a newborn baby to the hospital floor is a devastating experience for the family and staff caring for the mother and baby. The aim of this study was to report our experience in an ethnically diverse and socioeconomically disadvantaged community.

Methods

The study was a retrospective case series of all baby falls in the Counties Manukau Health (New Zealand) post-natal care wards, birthing suites and birthing units from 2015 to 2018. Information from the incident reporting system was used to identify the circumstances surrounding the fall. In addition, medical records of the mother and the baby were examined for the admission during which the fall occurred.

Results

There were 32 cases (rate 12.1/10 000 live births). Mothers of babies who fell were more likely to present late for antenatal care, to smoke and be obese. They were more likely to have delivered by caesarean. Falls were more likely to occur at night and around weekends. In most instances (84%) the mother fell asleep with baby on the bed while breastfeeding. There were no major injuries.

Conclusions

The rate of baby falls is considerably greater than previous reports. Recommendations are made to reduce this occurrence. These can be incorporated into safe sleep education.