Sparsity-Based Super Resolution for SEM Images

The scanning electron microscope (SEM) produces an image of a sample by scanning it with a focused beam of electrons. The electrons interact with the atoms in the sample, which emit secondary electrons that contain information about the surface topography and composition. The sample is scanned by the electron beam point by point, until an image of the surface is formed. Since its invention in 1942, SEMs have become paramount in the discovery and understanding of the nanometer world, and today it is extensively used for both research and in industry. In principle, SEMs can achieve resolution better than one nanometer. However, for many applications, working at sub-nanometer resolution implies an exceedingly large number of scanning points. For exactly this reason, the SEM diagnostics of microelectronic chips is performed either at high resolution (HR) over a small area or at low resolution (LR) while capturing a larger portion of the chip. Here, we employ sparse coding and dictionary learning to algorithmically enhance LR SEM images of microelectronic chips up to the level of the HR images acquired by slow SEM scans, while considerably reducing the noise. Our methodology consists of two steps: an offline stage of learning a joint dictionary from a sequence of LR and HR images of the same region in the chip, followed by a fast-online super-resolution step where the resolution of a new LR image is enhanced. We provide several examples with typical chips used in the microelectronics industry, as well as a statistical study on arbitrary images with characteristic structural features. Conceptually, our method works well when the images have similar characteristics. This work demonstrates that employing sparsity concepts can greatly improve the performance of SEM, thereby considerably increasing the scanning throughput without compromising on analysis quality and resolution.Comment: Final publication available at ACS Nano Letter

Improved nuclear localization of DNA-binding polyamides

Regulation of endogenous genes by DNA-binding polyamides requires effective nuclear localization. Previous work employing confocal microscopy to study uptake of fluorophore-labeled polyamides has demonstrated the difficulty of predicting a priori the nuclear uptake of a given polyamide. The data suggest that dye identity influences uptake sufficiently such that a dye-conjugate cannot be used as a proxy for unlabeled analogs. Polyamides capable of nuclear localization unaided by fluorescent dyes are desirable due to size and other limitations of fluorophores. Recently, a polyamide-fluorescein conjugate targeted to the hypoxia response element (HRE) was found to inhibit vascular endothelial growth factor (VEGF) expression in cultured HeLa cells. The current study uses inhibition of VEGF expression as a biological read-out for effective nuclear localization of HRE-targeted polyamides. We synthesized a focused library of non-fluorescent, HRE-targeted polyamides in which the C-terminus ‘tail’ has been systematically varied. Members of this library bind the HRE with affinities comparable or superior to that of the fluorescein-labeled analog. Although most library members demonstrate modest or no biological activity, two non-fluorescent polyamides are reported with activity rivaling that of the previously reported fluorescein-labeled polyamide. We also show evidence that promoter occupancy by HIF-1, the transcription factor that binds the HRE, is inhibited by HRE-targeted polyamides

Adjoint sensitivity analysis of a thermal hydraulic system undergoing phase change due to boiling transition. [BWR]

Sensitivity analysis of practical problems can be performed systematically and very efficiently by using adjoint functions. In areas of interest to nuclear reactors, this efficiency has been amply demonstrated on several widely used codes for neutronics and/or thermal hydraulic calculations. Applications of the adjoint method of sensitivity analysis to models involving phase transitions, where non-differentiability occurs, do not seem to have been reported to date. The purpose of this paper is to report results from a successful adjoint sensitivity analysis of a space- and time-dependent system where phase transition occurs due to boiling. The specific model chosen for this analysis is a simplified but representative model of a BWR pump-trip-type accident. This model is of particular importance to BWR safety, since pump failure is one of the most limiting hypothetical accidents in BWR's. This model simulates an exponential flow decay of initially subcooled FREON-114 flowing through a heated channel and undergoing boiling transition

Blood-brain barrier disruption in post-traumatic epilepsy

BACKGROUND: Traumatic brain injury (TBI) is an important cause of focal epilepsy. Animal experiments indicate that disruption of the blood-brain barrier (BBB) plays a critical role in the pathogenesis of post-traumatic epilepsy (PTE). OBJECTIVE: To investigate the frequency, extent and functional correlates of increased BBB permeability in patient with PTE. METHODS: 32 head trauma patients were included in the study, with 17 suffering from PTE. Patients underwent brain MRI (bMRI) and were evaluated for BBB disruption, using a novel semi-quantitative technique. Cortical dysfunction was measured using electroencephalography (EEG), and localised using standardised low-resolution brain electromagnetic tomography (sLORETA). RESULTS: Spectral EEG analyses revealed significant slowing in patients with TBI, with no significant differences between patients with epilepsy and those without. Although bMRI revealed that patients with PTE were more likely to present with intracortical lesions (p = 0.02), no differences in the size of the lesion were found between the groups (p = 0.19). Increased BBB permeability was found in 76.9% of patients with PTE compared with 33.3% of patients without epilepsy (p = 0.047), and could be observed years following the trauma. Cerebral cortex volume with BBB disruption was larger in patients with PTE (p = 0.001). In 70% of patients, slow (delta band) activity was co-localised, by sLORETA, with regions showing BBB disruption. CONCLUSIONS: Lasting BBB pathology is common in patients with mild TBI, with increased frequency and extent being observed in patients with PTE. A correlation between disrupted BBB and abnormal neuronal activity is suggested

Do symptoms moderate the association between participation and executive functions outcomes among people with schizophrenia?

Abstract Background Literature explains participation limitations among people with schizophrenia through the context of metacognitive limitations, specifically in symptoms and in executive functions (EF). Research has shown mixed results regarding associations between symptoms and participation, reporting association with negative symptoms, positive symptoms, or only metacognitive limitations. The aim of this study was to deepen understanding of the symptoms’ impact on the association between participation and executive function among people with schizophrenia. Methods Forty-three participants with schizophrenia received 8 group sessions of focused metacognitive intervention (MCG) aimed at promoting participation by focusing on EF components (e.g., analyzing individual cognitive strategy use). Three measures were administered: the Positive and Negative Syndrome Scale (PANSS) to evaluate symptoms, the Weekly Calendar Planning Assessment (WCPA) to assess EF, and the Activity Card Sort (ACS) to measure participation at the baseline and 12 weeks following completion of the intervention. Scores were compared to a matched control group of 41 people with schizophrenia who instead received treatment as usual. The role of PANSS as moderator was examined using multiple hierarchical regressions, entering interactions between the PANSS scores and WCPA change scores in the final regression step. Results Relationships were not significant for participants with high PANSS scores. A positive relationship existed between change in WCPA and change in ACS for participants with low PANSS scores. Conclusions These results demonstrate that low PANSS scores moderate the association between EF and participation and highlight the importance of symptoms as a predictor of participation following the MCG intervention. Trial registration The trial was retrospectively registered at clinical.trial.gov. ClinicalTrials.gov Identifier: NCT05556941. Clinicaltrial.gov registration date: 27/09/2022