ABSTRACT
BACKGROUND: Cerebellar intracerebral hemorrhage (cICH) is often attributed to hypertension or cerebral amyloid angiopathy (CAA). However, deciphering the exact etiology can be challenging. A recent study reported a topographical etiologic relationship with superficial cICH secondary to CAA. We aimed to reexamine this relationship between topography and etiology in a separate cohort of patients and using the most recent Boston criteria version 2.0. METHODS: We performed a retrospective analysis of consecutive patients with primary cICH admitted to a tertiary academic center between 2000 and 2022. cICH location on brain computed tomography/magnetic resonance imaging scan(s) was divided into strictly superficial (cortex, surrounding white matter, vermis) versus deep (cerebellar nuclei, deep white matter, peduncular region) or mixed (both regions). Magnetic resonance imaging was rated for markers of cerebral small vessel disease. We assigned possible/probable versus absent CAA using Boston criteria 2.0. RESULTS: We included 197 patients; 106 (53.8%) were females, median age was 74 (63-82) years. Fifty-six (28%) patients had superficial cICH and 141 (72%) deep/mixed cICH. Magnetic resonance imaging was available for 112 (57%) patients (30 [26.8%] with superficial and 82 [73.2%] with deep/mixed cICH). Patients with superficial cICH were more likely to have possible/probable CAA (48.3% versus 8.6%; odds ratio [OR], 11.43 [95% CI, 3.26-40.05]; P<0.001), strictly lobar cerebral microbleeds (51.7% versus 6.2%; OR, 14.18 [95% CI, 3.98-50.50]; P<0.001), and cortical superficial siderosis (13.8% versus 1.2%; OR, 7.70 [95% CI, 0.73-80.49]; P=0.08). Patients with deep/mixed cICH were more likely to have deep/mixed cerebral microbleeds (59.2% versus 3.4%; OR, 41.39 [95% CI, 5.01-341.68]; P=0.001), lacunes (54.9% versus 17.2%; OR, 6.14 [95% CI, 1.89-19.91]; P=0.002), severe basal ganglia enlarged perivascular spaces (36.6% versus 7.1%; OR, 7.63 [95% CI, 1.58-36.73]; P=0.01), hypertension (84.4% versus 62.5%; OR, 3.43 [95% CI, 1.61 to -7.30]; P=0.001), and higher admission systolic blood pressure (172 [146-200] versus 146 [124-158] mm Hg, P<0.001). CONCLUSIONS: Our results suggest that superficial cICH is strongly associated with CAA whereas deep/mixed cICH is strongly associated with hypertensive arteriopathy.
Subject(s)
Cerebral Amyloid Angiopathy , Hypertension , Female , Humans , Aged , Male , Retrospective Studies , Cerebral Hemorrhage/diagnostic imaging , Cerebral Hemorrhage/epidemiology , Cerebral Hemorrhage/etiology , Cerebral Amyloid Angiopathy/complications , Cerebral Amyloid Angiopathy/diagnostic imaging , Cerebral Amyloid Angiopathy/pathology , Magnetic Resonance Imaging , Hypertension/complications , Hypertension/epidemiologyABSTRACT
OBJECTIVES: This systematic review and meta-analysis evaluated the diagnostic accuracy of CT and MRI for differentiating atypical lipomatous tumors and malignant liposarcomas from benign lipomatous lesions. METHODS: MEDLINE, EMBASE, Scopus, the Cochrane Library, and the gray literature from inception to January 2022 were systematically evaluated. Original studies with > 5 patients evaluating the accuracy of CT and/or MRI for detecting liposarcomas with a histopathological reference standard were included. Meta-analysis was performed using a bivariate mixed-effects regression model. Risk of bias was evaluated using Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2). This study is registered on PROSPERO, number CRD42022306479. RESULTS: Twenty-six studies with a total of 2613 patients were included. Mean/median reported patient ages ranged between 50 and 63 years. The summary sensitivity and specificity of radiologist gestalt for detecting liposarcomas was 85% (79-90% 95% CI) and 63% (52-72%), respectively. Deep depth to fascia, thickened septations, enhancing components, and lesion size (≥ 10 cm) all demonstrated sensitivities ≥ 85%. Other imaging characteristics including heterogenous/amorphous signal intensity, irregular tumor margin, and nodules present demonstrated lower sensitivities ranging from 43 to 65%. Inter-reader reliability for radiologist gestalt within studies ranged from fair to substantial (k = 0.23-0.7). Risk of bias was predominantly mixed for patient selection, low for index test and reference standard, and unclear for flow and timing. CONCLUSION: Higher sensitivities for detecting liposarcomas were achieved with radiologist gestalt, deep depth to fascia, thickened septations, enhancing components, and large size. Combined clinical and imaging scoring and/or radiomics both show promise for optimal performance, though require further analysis with prospective study designs. CLINICAL RELEVANCE: This pooled analysis evaluates the accuracy of CT and MRI for detecting atypical lipomatous tumors and malignant liposarcomas. Radiologist gestalt, deep depth to fascia, thickened septations, enhancing components, and large size demonstrate the highest overall sensitivities. KEY POINTS: ⢠The summary sensitivity and specificity of radiologist gestalt for detecting liposarcomas was 85% (79-90% 95% CI) and 63% (52-72%), respectively. ⢠Radiologist gestalt, deep depth to fascia, thickened septations, enhancing components, and large tumor size (≥ 10 cm) showed the highest sensitivities for detecting atypical lipomatous tumors/well-differentiated liposarcomas and malignant liposarcomas. ⢠A combined clinical and imaging scoring system and/or radiomics is likely to provide the best overall diagnostic accuracy, although currently proposed scoring systems and radiomic feature analysis require further study with prospective study designs.
Subject(s)
Lipoma , Liposarcoma , Humans , Middle Aged , Reproducibility of Results , Prospective Studies , Magnetic Resonance Imaging , Liposarcoma/diagnostic imaging , Liposarcoma/pathology , Lipoma/diagnostic imaging , Lipoma/pathology , Tomography, X-Ray Computed , Sensitivity and SpecificityABSTRACT
BACKGROUND: There is a paucity of information regarding the mental health of midwives working in Ontario, Canada. Many studies have investigated midwives' mental health around the world, but little is known about how the model of midwifery care in Ontario contributes to or negatively impacts midwives' mental health. The aim of the study was to gain a deeper understanding of factors that contribute to and negatively impact Ontario midwives' mental health. METHODS: We employed a mixed-methods, sequential, exploratory design, which utilized focus groups and individual interviews, followed by an online survey. All midwives in Ontario who had actively practiced within the previous 15 months were eligible to participate. FINDINGS: We conducted 6 focus groups and 3 individual interviews, with 24 midwives, and 275 midwives subsequently completed the online survey. We identified four broad factors that impacted midwives' mental health: (1) the nature of midwifery work, (2) the remuneration model, (3) the culture of the profession, and (4) external factors. DISCUSSION: Based on our findings and the existing literature, we have five broad recommendations for improving Ontario midwives' mental health: (1) provide a variety of work options for midwives; (2) address the impacts of trauma on midwives; (3) make mental health services tailored for midwives accessible; (4) support healthy midwife-to-midwife relationships; and (5) support improved respect and understanding of midwifery. CONCLUSION: As one of the first comprehensive investigations into midwives' mental health in Ontario, this study highlights factors that contribute negatively to midwives' mental health and offers recommendations for how midwives' mental health can be improved systemically.
Subject(s)
Nurse Midwives , Occupational Stress , Mental Health , Midwifery , Nurse Midwives/psychology , Burnout, Professional , Ontario , Mental Health Services , Focus Groups , Qualitative Research , Humans , Male , Female , Adult , Middle Aged , AgedABSTRACT
BACKGROUND: Differentiating atypical lipomatous tumors (ALTs) and well-differentiated liposarcomas (WDLs) from benign lipomatous lesions is important for guiding clinical management, though conventional visual analysis of these lesions is challenging due to overlap of imaging features. Radiomics-based approaches may serve as a promising alternative and/or supplementary diagnostic approach to conventional imaging. PURPOSE: The purpose of this study is to review the practice of radiomics-based imaging and systematically evaluate the literature available for studies evaluating radiomics applied to differentiating ALTs/WDLs from benign lipomas. REVIEW: A background review of the radiomic workflow is provided, outlining the steps of image acquisition, segmentation, feature extraction, and model development. Subsequently, a systematic review of MEDLINE, EMBASE, Scopus, the Cochrane Library, and the grey literature was performed from inception to June 2022 to identify size studies using radiomics for differentiating ALTs/WDLs from benign lipomas. Radiomic models were shown to outperform conventional analysis in all but one model with a sensitivity ranging from 68 to 100% and a specificity ranging from 84 to 100%. However, current approaches rely on user input and no studies used a fully automated method for segmentation, contributing to interobserver variability and decreasing time efficiency. CONCLUSION: Radiomic models may show improved performance for differentiating ALTs/WDLs from benign lipomas compared to conventional analysis. However, considerable variability between radiomic approaches exists and future studies evaluating a standardized radiomic model with a multi-institutional study design and preferably fully automated segmentation software are needed before clinical application can be more broadly considered.
Subject(s)
Lipoma , Liposarcoma , Humans , Liposarcoma/pathology , Lipoma/diagnostic imagingABSTRACT
BACKGROUND: Hyperglycemia in the acute phase of intracerebral hemorrhage (ICH) has been associated with poor functional outcomes, however all interventions to lower glucose have yielded neutral or negative results. We attempt an explanation of the causal role of hyperglycemia in ΙCH outcome using generalized structural equation modeling. MATERIALS AND METHODS: Consecutive primary ICH patients admitted to an academic hospital between 2007 and 2018 were identified. Patients with missing baseline or follow up CT scans and without 90 day follow up status were excluded. We constructed a causal model accounting for pre-defined markers of ICH severity to evaluate the association between mean 72 h glucose and 90 day functional outcome measured by modified Rankin Scale, dichotomized as favorable ≤2 or unfavorable >2. RESULTS: Primary analyses included 410 patients (70.4 ± 13.8years, 43 % female). Mean 72 h glucose was 137.5 ± 33.4mg/dl and 102 (25 %) patients were diabetic. On univariable analysis, higher glucose levels were negatively correlated with favorable outcome (p < 0.0001). However in the structural equation model, this relationship was significantly attenuated (p = 0.06) after accounting for the causal effect of diabetes (p < 0.0001), hematoma volume (p < 0.0001), intraventricular extension (p = 0.01) and Glasgow coma scale (p = 0.001) on glucose levels. On secondary analyses stratifying by diagnosis of diabetes, higher glucose levels were negatively correlated with favorable outcome in patients without diabetes (p = 0.04), but not in patients with diabetes (p = 0.35). CONCLUSIONS: Hyperglycemia may be a downstream effect of other markers of ICH severity, particularly among patients without diabetes, suggesting a possible explanation for the limited evidence of glucose lowering interventions in outcome.
Subject(s)
Diabetes Mellitus , Hyperglycemia , Humans , Female , Male , Treatment Outcome , Hyperglycemia/complications , Hyperglycemia/diagnosis , Cerebral Hemorrhage/diagnostic imaging , Cerebral Hemorrhage/therapy , Cerebral Hemorrhage/complications , Glucose , Retrospective Studies , PrognosisABSTRACT
OBJECTIVES: This meta-analysis evaluated the diagnostic accuracy of dual-energy CT (DECT) for detecting bone marrow edema (BME) in the appendicular skeleton. METHODS: A systematic review of MEDLINE, EMBASE, Scopus, the Cochrane Library, and gray literature from inception through January 31, 2020, was performed. Original articles with > 10 patients evaluating the accuracy of DECT for detecting BME in the appendicular skeleton with a reference standard of MRI and/or clinical follow-up were included. Study details were independently extracted by two reviewers. Meta-analysis was performed using a bivariate random-effects model with multivariable meta-regression. Risk of bias (RoB) was evaluated with QUADAS-2. RESULTS: Twenty studies evaluating 790 patients for BME in the appendicular skeleton were included in analysis. The summary sensitivity, specificity, and AUC values for BME in the appendicular skeleton were 86% (95% confidence interval [CI] 82-89%), 93% (95% CI 90-95%), and 0.95, respectively. Quantitative analysis had a higher sensitivity than qualitative analysis on meta-regression (p = 0.01), but no difference in specificity (p = 0.28). No other covariates contributed to variability in accuracy (etiology (trauma vs non-trauma); location (upper vs lower extremity); and RoB). Studies demonstrated generally low or unclear RoB and applicability. Eight studies included index tests with high RoB when quantitative assessments used a retrospective cut-off value. CONCLUSIONS: DECT demonstrates a higher specificity than sensitivity and AUC > 0.9. In scenarios where MRI availability is limited or contraindicated, DECT could be an alternative to MRI for detecting BME in the appendicular skeleton. However, limitations in sources of variability and RoB warrant continued study. KEY POINTS: ⢠Twenty studies evaluating 790 patients for bone marrow edema in the appendicular skeleton with dual-energy CT were included in analysis. ⢠The summary sensitivity, specificity, and AUC values for detecting bone marrow in the appendicular skeleton were 86% (95% confidence interval [CI] 82-89%), 93% (95% CI 90-95%), and 0.95, respectively. ⢠In scenarios where MRI availability is limited or is contraindicated, DECT could be an alternative to MRI for detecting bone marrow edema in the appendicular skeleton.
Subject(s)
Bone Marrow , Tomography, X-Ray Computed , Bone Marrow/diagnostic imaging , Edema/diagnostic imaging , Humans , Retrospective Studies , Sensitivity and SpecificityABSTRACT
OBJECTIVE. This systematic review and meta-analysis evaluates the diagnostic accuracy of MRI for differentiating malignant (MPNSTs) from benign peripheral nerve sheath tumors (BPNSTs). MATERIALS AND METHODS. A systematic review of MEDLINE, Embase, Scopus, the Cochrane Library, and the gray literature from inception to December 2019 was performed. Original articles that involved at least 10 patients and that evaluated the accuracy of MRI for detecting MPNSTs were included. Two reviewers independently extracted clinical and radiologic data from included articles to calculate sensitivity, specificity, PPV, NPV, and accuracy. A meta-analysis was performed using a bivariate mixed-effects regression model. Risk of bias was evaluated using QUADAS-2. RESULTS. Fifteen studies involving 798 lesions (252 MPNSTs and 546 BPNSTs) were included in the analysis. Pooled and weighted sensitivity, specificity, and AUC values for MRI in detecting MPNSTs were 68% (95% CI, 52-80%), 93% (95% CI, 85-97%), and 0.89 (95% CI, 0.86-0.92) when using feature combination and 88% (95% CI, 74-95%), 94% (95% CI, 89-96%), and 0.97 (95% CI, 0.95-0.98) using diffusion restriction with or without feature combination. Subgroup analysis, such as patients with neurofibromatosis type 1 (NF1) versus those without NF1, could not be performed because of insufficient data. Risk of bias was predominantly high or unclear for patient selection, mixed for index test, low for reference standard, and unclear for flow and timing. CONCLUSION. Combining features such as diffusion restriction optimizes the diagnostic accuracy of MRI for detecting MPNSTs. However, limitations in the literature, including variability and risk of bias, necessitate additional methodologically rigorous studies to allow subgroup analysis and further evaluate the combination of clinical and MRI features for MPNST diagnosis.
Subject(s)
Magnetic Resonance Imaging/methods , Nerve Sheath Neoplasms/diagnostic imaging , Nerve Sheath Neoplasms/pathology , Diagnosis, Differential , Humans , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
PURPOSE: This systematic review and meta-analysis evaluated the diagnostic accuracy of dual-energy CT (DECT) for detecting bone marrow edema (BME) in adult patients with acute knee injuries. METHODS: A systematic review of MEDLINE, EMBASE, Scopus, the Cochrane Library, and gray literature was performed from inception to January 31, 2020, using PRISMA-DTA guidelines. The review included studies assessing the diagnostic accuracy of DECT for detecting BME in at least 10 adult patients with acute knee injuries and with an MRI reference standard. Study details were independently extracted by two reviewers. Meta-analysis was performed using a bivariate mixed-effects regression model with subgroup analysis performed to evaluate for sources of variability. Risk of bias (ROB) was evaluated using the QUADAS-2 tool. RESULTS: Eight studies evaluating 267 patients between the ages of 25-54 with acute knee injuries undergoing DECT and MRI were included in analysis. Summary sensitivity, specificity, and AUROC values for BME were 84% (95% confidence interval (CI) 74-91%), 96% (95% CI 93-98%), and 0.97 (95% CI 0.95-0.98), respectively. Bone-based characterization was found to have lower specificity than region-based characterization (83% (57-95%) versus 97 (96-98%), p < 0.05), but no difference in sensitivity. No other statistical differences were identified amongst study subgroups to account for presumed variability amongst studies. Most studies were rated low risk for bias and applicability concerns. CONCLUSION: DECT is specific and accurate for detecting BME in adult patients with acute knee injuries and can be used as an alternative to MRI, particularly when MRI is contraindicated or unavailable.
Subject(s)
Bone Marrow , Knee Injuries , Adult , Bone Marrow/diagnostic imaging , Edema/diagnostic imaging , Humans , Knee Injuries/diagnostic imaging , Middle Aged , Sensitivity and Specificity , Tomography, X-Ray ComputedABSTRACT
Background Lipid-poor angiomyolipomas (AMLs) are challenging to differentiate from other renal lesions at imaging and often necessitate biopsy or surgery. If sufficiently accurate, MRI may play a role as a replacement test for biopsy. Purpose To perform a systematic review to evaluate the diagnostic performance of MRI for lipid-poor AMLs in patients with renal masses. Materials and Methods A systematic review of MEDLINE, EMBASE, Scopus, the Cochrane Library, and the "gray literature" (conference proceedings) was performed without language restriction through July 18, 2019, with the assistance of a health sciences librarian. Original articles with more than 10 patients evaluating the diagnostic performance of MRI, with histopathologic findings used as the reference standard, for the diagnosis of lipid-poor AMLs in patients with renal masses were included. Studies including AMLs with macroscopic fat and studies with insufficient data were excluded. Patient, clinical, MRI, and diagnostic performance parameters were independently acquired by two authors. Meta-analysis was performed by using a random-effects or bivariate mixed-effects regression model depending on the number of studies. Risk of bias of individual studies was evaluated by using Quality Assessment of Diagnostic Accuracy Studies-2. Results Twenty-three studies with 2196 patients and 25 contingency tables were included. The pooled sensitivity, specificity, and area under the receiver operating characteristic curve were 83% (95% confidence interval [CI]: 72%, 90%), 90% (95% CI: 84%, 94%), and 0.93 (95% CI: 0.91, 0.95), respectively. Considerable variability was present for several variables, including MRI parameters; however, subgroup analysis did not identify MRI sequence or field strength as sources for variability. All studies were at high risk of bias for index test domain because no reported thresholds were prespecified. Conclusion MRI shows promising accuracy for detecting lipid-poor angiomyolipomas (area under the receiver operating characteristic curve, >0.9), indicating a potential role as a replacement test for biopsy in selected patients. Studies evaluating MRI accuracy with a pragmatic algorithm and prespecified threshold may be helpful to confirm this potential role in the management pathway. © RSNA, 2020 Online supplemental material is available for this article.
Subject(s)
Angiomyolipoma/diagnostic imaging , Kidney Neoplasms/diagnostic imaging , Magnetic Resonance Imaging , Adolescent , Adult , Aged , Female , Humans , Kidney/diagnostic imaging , Male , Middle Aged , Sensitivity and Specificity , Young AdultABSTRACT
BACKGROUND: The increase in the number of predatory journals puts scholarly communication at risk. In order to guard against publication in predatory journals, authors may use checklists to help detect predatory journals. We believe there are a large number of such checklists yet it is uncertain whether these checklists contain similar content. We conducted a systematic review to identify checklists that help to detect potential predatory journals and examined and compared their content and measurement properties. METHODS: We searched MEDLINE, Embase, PsycINFO, ERIC, Web of Science and Library, and Information Science & Technology Abstracts (January 2012 to November 2018); university library websites (January 2019); and YouTube (January 2019). We identified sources with original checklists used to detect potential predatory journals published in English, French or Portuguese. Checklists were defined as having instructions in point form, bullet form, tabular format or listed items. We excluded checklists or guidance on recognizing "legitimate" or "trustworthy" journals. To assess risk of bias, we adapted five questions from A Checklist for Checklists tool a priori as no formal assessment tool exists for the type of review conducted. RESULTS: Of 1528 records screened, 93 met our inclusion criteria. The majority of included checklists to identify predatory journals were in English (n = 90, 97%), could be completed in fewer than five minutes (n = 68, 73%), included a mean of 11 items (range = 3 to 64) which were not weighted (n = 91, 98%), did not include qualitative guidance (n = 78, 84%), or quantitative guidance (n = 91, 98%), were not evidence-based (n = 90, 97%) and covered a mean of four of six thematic categories. Only three met our criteria for being evidence-based, i.e. scored three or more "yes" answers (low risk of bias) on the risk of bias tool. CONCLUSION: There is a plethora of published checklists that may overwhelm authors looking to efficiently guard against publishing in predatory journals. The continued development of such checklists may be confusing and of limited benefit. The similarity in checklists could lead to the creation of one evidence-based tool serving authors from all disciplines.
Subject(s)
Biomedical Research/standards , Periodicals as Topic/standards , Checklist , HumansABSTRACT
OBJECTIVE. This systematic review and meta-analysis aimed to evaluate the diagnostic accuracy of limited MRI protocols for detecting radiographically occult proximal femoral fractures. MATERIALS AND METHODS. A systematic review of MEDLINE, Embase, Scopus, the Cochrane Library, and the gray literature through November 15, 2019, was performed. Original articles with 10 or more patients evaluating limited MRI protocols for the diagnosis of radiographically occult proximal femoral fractures compared with multiparametric MRI with or without clinical outcome as the reference standard were included in the analysis. Patient, clinical, MRI, and performance parameters were independently acquired by two reviewers. Meta-analysis was performed using a bivariate mixed-effects regression model. RESULTS. Eleven studies with 938 patients and 247 proximal femoral fractures met inclusion criteria, and five of these studies were included in the meta-analysis. The pooled and weighted summary sensitivity and specificity and the area under the summary ROC curve for limited MRI protocols in detecting radiographically occult hip fractures were 99% (95% CI, 91-100%), 99% (95% CI, 97-100%), and 1 (95% CI, 0.99-1), respectively. The aggregate sensitivity and specificity values for a single-plane T1-weighted sequence only, STIR sequence only, T1-weighted and STIR sequences, and T2-weighted sequence only were as follows: 97% (89/92) and 100% (76/76), 99% (126/127) and 99% (865/873), 100% (118/118) and 99% (867/874), and 86% (51/59) and 97% (137/141), respectively. Sensitivity was 100% (58/58) when images were acquired on 3-T scanners only and 99% (284/288) when interpreted only by certified radiologists. The mean scanning time for the limited MRI protocols was less than 5 minutes. CONCLUSION. Limited MRI protocols can be used as the standard of care in patients with a suspected but radiographically occult hip fracture. A protocol composed of coronal T1-weighted and STIR sequences is 100% sensitive.
Subject(s)
Fractures, Closed/diagnostic imaging , Hip Fractures/diagnostic imaging , Magnetic Resonance Imaging/methods , HumansABSTRACT
BACKGROUND: Radiology interest groups (RIGs) can serve as a means of increasing exposure of the radiology specialty early in the medical curriculum while also increasing educational opportunities. However, the organizational structure and various functions of individual RIGs in Canada are not well-documented. We performed a survey of all active RIGs in Canada for the purpose of better understanding their structure, function, and opportunities for improvement. METHODS: A 21-question survey was sent to current or recent former medical student leaders of all active RIGs in Canada during the 2016-2017 academic year. RESULTS: Radiology interest groups were identified in 88% (15/17) of Canadian medical schools. We received a 100% (15/15) response rate. Events held by RIGs consist mostly of lunch and learns (67%, 10/15), career panels (53%, 8/15), networking events (40%, 6/15), and curriculum-related events (40%, 6/15). General mentorship (93%, 13/14), shadowing opportunities (86%, 12/14), and research mentorship (63%, 8/14) were most often cited in their top 3 choices for opportunities for improvement. Sixty-six percent indicated that if a radiology society were to host a page for their interest group, they would be interested in posting content and/or links. CONCLUSIONS: Canadian RIGs offer increased early awareness and education about radiology in the medical curriculum. Radiology departments can facilitate improvement in Canadian RIGs through targeted institutional mentorship, research opportunities, and shadowing programs for their members.
Subject(s)
Group Processes , Radiology/education , Schools, Medical , Social Networking , Students, Medical , Canada , Curriculum , Education, Medical, Undergraduate , Humans , Internet , Mentors , Societies, Medical , Surveys and QuestionnairesABSTRACT
Self-assembly of nanocrystals is a promising route for creating macroscale materials that derive function from the properties of their nanoscale building blocks. While much progress has been made assembling nanocrystals into different superlattices, controlling the relative orientations of nanocrystals in those lattices remains a challenge. Here, we combine experiments with computer simulations to study the self-assembly of patchy heterostructural nanocrystals (HNCs), consisting of near-spherical quantum dots decorated with regular arrangements of small gold satellites, into close-packed superlattices with pronounced orientational alignment of HNCs. Our simulations indicate that the orientational alignment is caused by van der Waals interactions between gold patches and is sensitive to the interparticle distance in the superlattice. We demonstrate experimentally that the degree and type of orientational alignment can be controlled by changing ligand populations on HNCs. This study provides guidance for the design and fabrication of nanocrystal superlattices with enhanced structural control.
ABSTRACT
The self-assembly of nanocrystals into ordered superlattices is a powerful strategy for the production of functional nanomaterials. The assembly of well-ordered target structures, however, requires control over the building blocks' size and shape as well as their interactions. While nanocrystals with homogeneous composition are now routinely synthesized with high precision and assembled into various ordered structures, high-quality multicomponent nanocrystals and their ordered assemblies are rarely reported. In this paper, we demonstrate the synthesis of quantum dot-gold (QD-Au) heterodimers. These heterodimers possess a uniform shape and narrow size distribution and are capped with oleylamine and dodecyltrimethylammonium bromide (DTAB). Assembly of the heterodimers results in a superlattice with long-range orientational alignment of dimers. Using synchrotron-based X-ray measurements, we characterize the complex superstructure formed from the dimers. Molecular dynamics simulations of a coarse-grained model suggest that anisotropic interactions between the quantum dot and gold components of the dimer drive superlattice formation. The high degree of orientational order demonstrated in this work is a potential route to nanomaterials with useful optoelectronic properties.
ABSTRACT
Respectful maternity care research in Tanzania continues to increase. This is an overview of the literature summarizing research based on the domains which comprise this quality of care indicator, ranging from exploratory and descriptive to quantitative measurements of birth perinatal outcomes when respectful interventions are made. The domains of respectful care are reflected in the seven Universal Rights of Childbearing Women but go further to implicate facility administrators and policy makers to provide supportive infrastructure to allay disrespect and abuse.The research methodologies continue to be problematic and several ethical cautions restrict how much control is possible. Similarly, the barriers to collecting accurate accounts in qualitative studies of disrespect require astute interviewing and observation techniques. The participatory community-based and the critical sociology and human rights frameworks appear to provide a good basis for both researcher and participants to identify problems and determine possible solutions to the multiple factors that contribute to disrespect and abuse. The work-life conditions of midwives in the Global South are plagued with poor infrastructure and significantly low resources which deters respectful care while decreasing retention of workers. Researchers and policy-makers have addressed disrespectful care by building human resource capacity, by strengthening professional organizations and by educating midwives in low-resource countries. Furthermore, researchers encourage midwives not only to acquire attitudinal change and to adopt respectful maternity care skills, but also to emerge as leaders and change agents.Safe methods for conducting care while addressing low resources, skilled management of conflict and creative innovations to engage the community are all interventions that are being considered for quality improvement research. Tanzania is poised to evaluate the outcomes of education workshops that address all seven domains of respectful care.