Probing the dark universe with gravitational lensing

Since its early success as an experimental test of the theory of general relativity in 1919, gravitational lensing has come a long way and is firmly established as an indispensable element for many astrophysical applications. In this thesis, we explore novel applications of gravitational lensing that further our understanding of the dark sectors of the cosmos and other astrophysical objects, namely dark matter nanostructure, black holes and the Galactic disk. We pay particular attention to developing concrete and optimal statistical methodologies and numerical implemen- tations for these novel probes. We start by developing a statistical framework to measure the dark matter power spectrum in the deep nonlinear regime, using transient weak lensing, and simultaneously measure the time delays for strongly lensed quasars. We then outline how observations of microlensing in optical and radio can unravel the structure, dynamics, and content of the Galactic disk, and in particular, be used to detect stellar mass black holes. Lastly, using the shadow images of the super-massive black holes caused by extreme lensing effect, we can learn about the structure of space-time, accretion flows and astrophysical jets. We present a Bayesian framework for analyzing the data from the Event Horizon Telescope Collaboration

Unique probe of dark matter in the core of M87 with the Event Horizon Telescope

We demonstrate the unprecedented capabilities of the Event Horizon Telescope (EHT) to image the innermost dark matter profile in the vicinity of the supermassive black hole at the center of the M87 radio galaxy. We present the first model of the synchrotron emission induced by dark matter annihilations from a spiky profile in the close vicinity of a supermassive black hole, accounting for strong gravitational lensing effects. Our results show that the EHT should readily resolve dark matter spikes if present. Moreover, the photon ring surrounding the silhouette of the black hole is clearly visible in the spike emission, which introduces observable small-scale structure into the signal. We find that the dark matter-induced emission provides an adequate fit to the existing EHT data, implying that in addition to the jet, a dark matter spike may account for a sizable portion of the millimeter emission from the innermost (subparsec) region of M87. Regardless, our results show that the EHT can probe very weakly annihilating dark matter. Current EHT observations already constrain very small cross sections, typically down to a few 10−31 cm3 s−1 for a 10 GeV candidate, close to characteristic values for p-wave-suppressed annihilation. Future EHT observations will further improve constraints on the DM scenario

Radiological protection in the Neonatal Intensive Care Units (NICUs): a retrospective and observational audit at two teaching hospitals

Introduction: Portable chest and abdomen x-rays are the most common x-ray procedures performed during hospitalization in the Neonatal Intensive Care Units (NICUs). These x-rays contribute to radiation exposure to several radiosensitive tissues, causing increased concerns about patients’ safety. This study aims to assess the status of radiological protection in the NICUs at two teaching hospitals supervised by Dezful University of Medical Sciences (DUMS), Dezful, Iran. Methods: A retrospective and observational study was performed at two teaching hospitals of DUMS comprising three NICUs. Six radiologic technology students were invited and agreed to participate in this audit. The students were asked to attend as observers in the NICUs and record the radiation safety principle observances specified in the checklist. We also supplemented data from an observational study with a retrospective survey of the images at the picture archiving and communication system (PACS) database. Results: 230 neonatal chest and abdomen x-rays from 65 hospitalized neonates were investigated during 57 work shifts in the observational survey. In all, 90.1%, 80% and 13% of the chest, abdomen and chest/abdomen x-rays had unsatisfactory beam restriction, respectively. The protective shielding tools were available; however, they were not commonly applied to the patients. Most of the personnel used fixed exposure parameters of 42 kVp and 3.2 mAs. In the retrospective study, 498 portable x-rays were retrieved from the PACS database, in which only 17.5% and 0.4% of images have adequate beam restriction and evidence of shielding, respectively. Conclusion: Our study is commensurate with previous literature and emphasizes that neonates in the investigated hospitals are receiving avoidable excessive radiation exposure, mainly due to inappropriate beam restriction

Comparison of Er:YAG Laser and Hand Instrumentation on the Attachment of Cultured Human Gingival Fibroblasts to Periodontally Involved Root Surfaces

BackgroundThe present study compared the effects of Er:YAG laser and hand instrumentation on the attachment of human gingival fibroblast (HGF) cells to periodontally involved root surfaces.MethodsA total of 40 tooth specimens were collected and treated in four distinct groups: scaled and root planed with hand instruments, treated with Er:YAG laser, treated with combination of hand instruments and Er:YAG laser and non-treated control group. The attachment and proliferation rate of HGF were assessed using MTT assay and the Scanning Electron Microscope (SEM) Examination was used for cell morphological evaluation.ResultsThe MTT assay showed significantly decrease in HGF cell viability in both hand instruments only and combination treated teeth specimens compared to control specimens (p<0.05), 24 hours after cell seeding. However, at time 48, the cell viability of attached cells in these two treated groups was almost similar to control.  In contrast, at 24 and 48 hours after cell seeding, viability of attached cells was higher than control in Er:YAG laser treated only specimens (p<0.05). According to SEM study, the laser treated specimens showed more surface roughness.ConclusionsEr:YAG laser increased attachment and proliferation of HGF cells in comparison with hand instruments method

Alterations in juvenile diploid and triploid African catfish skin gelatin yield and amino acid composition: effects of chlorpyrifos and butachlor exposures

Skin is a major by-product of the fisheries and aquaculture industries and is a valuable source of gelatin. This study examined the effect of triploidization on gelatin yield and proximate composition of the skin of African catfish (Clarias gariepinus). We further investigated the effects of two commonly used pesticides , chlorpyrifos (CPF) and butachlor (BUC), on the skin gelatin yield and amino acid composition in juvenile full-sibling diploid and triploid African catfish. In two separate experiments, diploid and triploid C. gariepinus were exposed for 21 days to graded CPF [mean measured: 10, 16, or 31 mg/L] or BUC concentrations [Mean measured: 22, 44, or 60 mg/L]. No differences in skin gelatin yield, amino acid or proximate compositions were observed between diploid and triploid control groups. None of the pesticide treatments affected the measured parameters in diploid fish. In triploids, however, gelatin yield was affected by CPF treatments while amino acid composition remained unchanged. Butachlor treatments did not alter any of the measured variables in triploid fish. To our knowledge, this study is the first to investigate changes in the skin gelatin yield and amino acid composition in any animal as a response to polyploidization and/or contaminant exposure

Application of MOS gas sensors coupled with chemometrics methods to predict the amount of sugar and carbohydrates in potatoes

Five potato varieties were studied using an electronic nose with nine MOS sensors. Parameters measured included carbohydrate content, sugar level, and the toughness of the potatoes. Routine tests were carried out while the signals for each potato were measured, simultaneously, using an electronic nose. The signals obtained indicated the concentration of various chemical components. In addition to support vector machines (SVMs that were used for the classification of the samples, chemometric methods, such as the partial least squares regression (PLSR) method, the principal component regression (PCR) method, and the multiple linear regression (MLR) method, were used to create separate regression models for sugar and carbohydrates. The predictive power of the regression models was characterized by a coefficient of determination (R2), a root-mean-square error of prediction (RMSEP), and offsets. PLSR was able to accurately model the relationship between the smells of different types of potatoes, sugar, and carbohydrates. The highest and lowest accuracy of models for predicting sugar and carbohydrates was related to Marfona potatoes and Sprite cultivar potatoes. In general, in all cultivars, the accuracy in predicting the amount of carbohydrates was somewhat better than the accuracy in predicting the amount of sugar. Moreover, the linear function had 100% accuracy for training and validation in the C-SVM method for classification of five potato groups. The electronic nose could be used as a fast and non-destructive method for detecting different potato varieties. Researchers in the food industry will find this method extremely useful in selecting the desired product and samples

Decomposing socioeconomic inequality in poor mental health among Iranian adult population: results from the PERSIAN cohort study

Background Socioeconomic inequality in mental health in Iran is poorly understood. This study aimed to assess socioeconomic inequality in poor mental health among Iranian adults. Methods The study used the baseline data of PERSIAN cohort study including 131,813 participants from 17 geographically distinct areas of Iran. The Erreygers Concentration index (E) was used to quantify the socioeconomic inequalities in poor mental health. Moreover, we decomposed the E to identify factors contributing to the observed socioeconomic inequality in poor mental health in Iran. Results The estimated E for poor mental health was - 0.012 (95% CI: - 0.0144, - 0.0089), indicating slightly higher concentration of mental health problem among socioeconomically disadvantaged adults in Iran. Socioeconomic inequality in poor mental health was mainly explained by gender (19.93%) and age (12.70%). Region, SES itself, and physical activity were other important factors that contributed to the concentration of poor mental health among adults with low socioeconomic status. Conclusion There exists nearly equitable distribution in poor mental health among Iranian adults, but with important variations by gender, SES, and geography. These results suggested that interventional programs in Iran should focus on should focus more on socioeconomically disadvantaged people as a whole, with particular attention to the needs of women and those living in more socially disadvantaged regions. Keywords:Mental health; Socioeconomic inequality; Concentration index; Decompositio