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1.
Adv Exp Med Biol ; 1458: 315-334, 2024.
Article in English | MEDLINE | ID: mdl-39102206

ABSTRACT

Digital health has transformed the healthcare landscape by leveraging technology to improve patient outcomes and access to medical services. The COVID-19 pandemic has highlighted the urgent need for digital healthcare solutions that can mitigate the impact of the outbreak while ensuring patient safety. In this chapter, we delve into how digital health technologies such as telemedicine, mobile apps, and wearable devices can provide personalized care, reduce healthcare provider burden, and lower healthcare costs. We also explore the creation of a greenway of digital healthcare that safeguards patient confidentiality, enables efficient communication, and ensures cost-effective payment systems. This chapter showcases the potential of digital health to revolutionize healthcare delivery while ensuring patient well-being and medical staff satisfaction.


Subject(s)
Bibliometrics , COVID-19 , Telemedicine , COVID-19/epidemiology , Humans , SARS-CoV-2 , Mobile Applications , Wearable Electronic Devices , Delivery of Health Care , Pandemics/prevention & control , Digital Technology , Digital Health
2.
Cancers (Basel) ; 16(8)2024 Apr 15.
Article in English | MEDLINE | ID: mdl-38672588

ABSTRACT

Lung cancer is the leading cause of cancer-related deaths worldwide. Two of the crucial factors contributing to these fatalities are delayed diagnosis and suboptimal prognosis. The rapid advancement of deep learning (DL) approaches provides a significant opportunity for medical imaging techniques to play a pivotal role in the early detection of lung tumors and subsequent monitoring during treatment. This study presents a DL-based model for efficient lung cancer detection using whole-slide images. Our methodology combines convolutional neural networks (CNNs) and separable CNNs with residual blocks, thereby improving classification performance. Our model improves accuracy (96% to 98%) and robustness in distinguishing between cancerous and non-cancerous lung cell images in less than 10 s. Moreover, the model's overall performance surpassed that of active pathologists, with an accuracy of 100% vs. 79%. There was a significant linear correlation between pathologists' accuracy and years of experience (r Pearson = 0.71, 95% CI 0.14 to 0.93, p = 0.022). We conclude that this model enhances the accuracy of cancer detection and can be used to train junior pathologists.

3.
Cureus ; 16(1): e52045, 2024 Jan.
Article in English | MEDLINE | ID: mdl-38344576

ABSTRACT

Acute myocardial infarction is a fatal condition. Acute myocardial infarction requires appropriate timely reperfusion therapy to improve the outcomes. Fibrinolysis and percutaneous coronary intervention are the cornerstone strategies for managing such cases. In this review, our objective is to summarize the available evidence concerning the administration of prehospital fibrinolysis and its impact on patient outcomes in patients with acute myocardial infarction. We conducted a comprehensive literature search across PubMed, Cochrane Library, Scopus, and Web of Science databases. Our search strategy included the following terms: "Prehospital," "EMS," "Emergency Medical Services," "ambulance," "Fibrinolytic Therapy," "alteplase," "streptokinase," "reteplase," "tenecteplase," "Acute Myocardial Infarction," and "patient outcomes." We found prehospital administration of fibrinolysis may improve the outcomes and decrease the mortality rate. We found that some recommendations were to use prehospital fibrinolysis only if the percutaneous coronary intervention was not accessible within two hours. Additionally, we discussed recommendations to use newer prehospital fibrinolysis as they have better efficacy and safety outcomes. In conclusion, prehospital fibrinolysis decreases the total ischemic time and improves outcomes in acute myocardial infarction patients when timely percutaneous coronary intervention is not available. The guidelines strongly recommend it when the anticipated time for percutaneous coronary intervention exceeds two hours. Ongoing research optimizes patient selection, treatment tools, and prehospital systems of care.

4.
Eur J Dent ; 18(1): 55-64, 2024 Feb.
Article in English | MEDLINE | ID: mdl-37207679

ABSTRACT

People with disabilities experience inferior health and poor access to good quality health services as compared with the general population. Optimum oral health is associated with improvement in the quality of life in such patients. As oral diseases are largely preventable, good oral health education can have a positive impact on individuals with disabilities. So, the aim of the study was to review the effectiveness of oral health promotion among individuals with intellectual disabilities (IDs). Seven electronic databases were searched using keywords like intellectual disability/mental retardation/learning disability AND dental health education/health promotion. All records that were identified electronically from this search were subjected to a preliminary review to identify eligible papers. Identified studies were grouped into oral health promotion directed at individuals with IDs, and those aimed at caregivers of people with IDs. Interpretation of the outcomes included the effects on oral health knowledge, attitudes, and behaviors (either observed or self-reported). Eventually, 16 studies were included in the review including five studies that were randomized controlled trials, while the remaining 11 studies were pre-post single group oral health promotion studies. Critical appraisal of each study was conducted with the 21-item criteria by Kay and Locker (1997) to provide a numerical quantification and ranking of the evidence. Positive changes in the behaviors and attitudes were observed, while other studies reported a considerable improvement in the knowledge of caregivers for oral healthcare of individuals with IDs. However, such activities need to be done over a long period of time with constant monitoring.

5.
Front Public Health ; 11: 1186442, 2023.
Article in English | MEDLINE | ID: mdl-37404286

ABSTRACT

Objectives: Healthcare students went through a rough time in March 2022 due to extreme changes in the educational system (moving from online to stationary learning) and Ukrainian-Russian war circumstances. Our study aims to update knowledge about psychological distress and its impact on healthcare students in Poland after two years of the COVID-19 pandemic, followed by intense and political instability in Europe. Methods: We conducted a cross-sectional study on healthcare students from Poznan University of Medical Sciences, Poland, from March to April 2022. The questionnaire included subjective retrospective 5-point Likert-scales ratings of anxiety, stress, and depression and self-reported information on various psychological distress predictors. Results: The anxiety levels at the beginning of the COVID-19 pandemic were higher than in April 2022. There was no significant reduction in stress and depression. Females had higher initial anxiety levels than post-pandemic levels. Higher reported levels of anxiety, stress, and depression were significantly correlated with political instability in Eastern Europe (Spearman ranxiety = 0.178, rstress = 0.169, rdepression = 0.154, p ≤ 0.001, respectively). The concern about moving towards online education showed a significant association only with stress level (rstress = 0.099, p = 0.034). We also observed a positive correlation between anxiety, stress, and depression and deteriorating sleep quality (Spearman ranxiety,=0.325, rstress = 0.410, rdepression = 0.440, p < 0.001), the feeling of worsening relationships with family and peers (ranxiety = 0.325, rstress = 0.343, rdepression = 0.379, p < 0.001), and the sense of loss of efficient time management (ranxiety = 0.321, rstress = 0.345, rdepression = 0.410, p < 0.001). Conclusion: Throughout the progression of the Ukrainian war and the COVID-19 pandemic, females reported improved (lower levels) levels of anxiety. Nevertheless, the current levels of self-reported anxiety post-pandemic remain alarming, while stress and depression levels remained unchanged. Mental, psychological, and social support activities are required for healthcare students, especially those away from their families. Time management, academic performance, and coping skills in relation to the additional stressors of war and the global pandemic require further research in this group of students.


Subject(s)
COVID-19 , Psychological Distress , Female , Humans , COVID-19/epidemiology , COVID-19/psychology , Cross-Sectional Studies , Poland/epidemiology , Ukraine/epidemiology , Pandemics , Retrospective Studies , Mental Health , Stress, Psychological/epidemiology , Students/psychology , Delivery of Health Care
6.
J Pers Med ; 13(6)2023 Jun 07.
Article in English | MEDLINE | ID: mdl-37373951

ABSTRACT

BACKGROUND: In the past vicennium, several artificial intelligence (AI) and machine learning (ML) models have been developed to assist in medical diagnosis, decision making, and design of treatment protocols. The number of active pathologists in Poland is low, prolonging tumor patients' diagnosis and treatment journey. Hence, applying AI and ML may aid in this process. Therefore, our study aims to investigate the knowledge of using AI and ML methods in the clinical field in pathologists in Poland. To our knowledge, no similar study has been conducted. METHODS: We conducted a cross-sectional study targeting pathologists in Poland from June to July 2022. The questionnaire included self-reported information on AI or ML knowledge, experience, specialization, personal thoughts, and level of agreement with different aspects of AI and ML in medical diagnosis. Data were analyzed using IBM® SPSS® Statistics v.26, PQStat Software v.1.8.2.238, and RStudio Build 351. RESULTS: Overall, 68 pathologists in Poland participated in our study. Their average age and years of experience were 38.92 ± 8.88 and 12.78 ± 9.48 years, respectively. Approximately 42% used AI or ML methods, which showed a significant difference in the knowledge gap between those who never used it (OR = 17.9, 95% CI = 3.57-89.79, p < 0.001). Additionally, users of AI had higher odds of reporting satisfaction with the speed of AI in the medical diagnosis process (OR = 4.66, 95% CI = 1.05-20.78, p = 0.043). Finally, significant differences (p = 0.003) were observed in determining the liability for legal issues used by AI and ML methods. CONCLUSION: Most pathologists in this study did not use AI or ML models, highlighting the importance of increasing awareness and educational programs regarding applying AI and ML in medical diagnosis.

7.
Metabolites ; 13(4)2023 Apr 11.
Article in English | MEDLINE | ID: mdl-37110201

ABSTRACT

Glioblastoma is the most common malignant primary brain tumor in adults. Thalidomide is a vascular endothelial growth factor inhibitor that demonstrates antiangiogenic activity, and may provide additive or synergistic anti-tumor effects when co-administered with other antiangiogenic medications. This study is a comprehensive review that highlights the potential benefits of using thalidomide, in combination with other medications, to treat glioblastoma and its associated inflammatory conditions. Additionally, the review examines the mechanism of action of thalidomide in different types of tumors, which may be beneficial in treating glioblastoma. To our knowledge, a similar study has not been conducted. We found that thalidomide, when used in combination with other medications, has been shown to produce better outcomes in several conditions or symptoms, such as myelodysplastic syndromes, multiple myeloma, Crohn's disease, colorectal cancer, renal failure carcinoma, breast cancer, glioblastoma, and hepatocellular carcinoma. However, challenges may persist for newly diagnosed or previously treated patients, with moderate side effects being reported, particularly with the various mechanisms of action observed for thalidomide. Therefore, thalidomide, used alone, may not receive significant attention for use in treating glioblastoma in the future. Conducting further research by replicating current studies that show improved outcomes when thalidomide is combined with other medications, using larger sample sizes, different demographic groups and ethnicities, and implementing enhanced therapeutic protocol management, may benefit these patients. A meta-analysis of the combinations of thalidomide with other medications in treating glioblastoma is also needed to investigate its potential benefits further.

8.
PLoS One ; 17(12): e0278311, 2022.
Article in English | MEDLINE | ID: mdl-36454976

ABSTRACT

Our study aims to update knowledge about psychological distress and its changes in the Polish group of academic medical teachers after two years of a global pandemic. During the coronavirus disease, teachers were challenged to rapidly transition into remote teaching and adapt new assessment and evaluation systems for students, which might have been a completely novel situation that was not addressed before, especially in medical universities in Poland. We conducted a cross-sectional study at Poznan University of Medical Sciences from March to April 2022. The questionnaire included self-reported information on anxiety, stress, and depression. We found that post-pandemic levels of anxiety, stress, and depression have significantly (p<0.001) improved compared to initial levels at the beginning of coronavirus disease. In multivariate models, females had higher odds of improving levels of anxiety (OR = 0.46; 95% CI = -1.58-(-0.03); p = 0.04), stress (OR = 0.36; 95% CI = -1.83-(-0.22); p = 0.01), and depression (OR = 0.0.37; 95% CI = -1.58-(-0.12); p = 0.03). Anxiety, stress, or depression were not significantly associated with years of experience, the number of taught subjects, and weekly teaching hours, but only with the academic work during COVID-19 (Spearman ranxiety = 0.37, rstress = 0.32, rdepression = 0.37, p<0.001). For the virtual learning concerns, 79% of teachers reported that students might engage less; and it was correlated with higher weekly teaching hours (r = 0.19, p<0.05). Even though only 29.8% reported cheating as a concern, it was correlated with a higher number of taught subjects (r = 0.2, p<0.05). Levels of anxiety, stress, and depression have improved as time passed, not affecting teachers' academic performance. Concerns about virtual learning have been raised, suggesting it may be conjoined with classroom learning but not as an alternative. Universities should highlight the importance of seeking psychological support and provide essential programs to employees. Teachers' coping skills with psychological distress should be further studied.


Subject(s)
COVID-19 , Psychological Distress , Female , Humans , COVID-19/epidemiology , Pandemics , Poland/epidemiology , Universities , Cross-Sectional Studies
9.
Ann Med Surg (Lond) ; 84: 104866, 2022 Dec.
Article in English | MEDLINE | ID: mdl-36536750

ABSTRACT

Background: Herniated lumbar disc is one of the common causes of back pain. Discectomy provides rapid relief of back pain and radicular pain. Few studies have been done in our setting to look for the outcome of discectomy. The purpose of this study was to assess the outcome of discectomy. Methods: This prospective cross-sectional hospital-based study was carried out on Soba Teaching Hospital and Future hospitals in Khartoum, Sudan. Sixty-one patients with lumbar discectomy were included in this study, collected data through a direct interviewing questionnaire and took some information from patients' files. Then collected data were analyzed using the statistical package for social science (SPSS) 24. Results: In sixty-one patients with lumbar discectomy of them, 24(39.3%) were within the age group 31-45 years old, 21(34.4%) were within the age group 46-50 years old, and 10(16.4%) were within age group 51-65years old. Results showed a male-to-female ratio of 1.5:1. The most common presenting symptoms were right Leg pain or numbness in 14(23%) patients. In the majority, 33(54.1%) of patients, the duration of symptoms was 6-12 months, 46(75.4%) underwent discectomy only, and 15(24.6%) underwent discectomy with fusion. Preoperatively, the majority of 30(49.1%) patients had a complete disability, 26(42.6%) had a severe disability, and 5(8.2%) had a moderate disability. In contrast, postoperatively, the majority, 35(57.4%) of patients, had mild disability, 24(39.3%) had no disability, and only 2(3.3%) had moderate disability (P value < .001). Moreover, there was a statistically significant association between the presence of co-morbidity and postoperative outcome (P value = .021). Conclusion: Discectomy is a gold stander procedure in the management of LDH. Patients showed excellent functional outcomes. The most common presenting symptoms were right leg pain or numbness. Patients postoperatively showed significant clinical improvement according to the mODI score.

10.
Article in English | MEDLINE | ID: mdl-36554693

ABSTRACT

In previous studies, there was an apparent lack of health education about dengue fever (DF) among the Saudi population. Therefore, we conducted this study to assess the knowledge, attitude, and practices (KAP) about dengue fever among the Jazan region population, which is one of the most prevalent diseases in the region in Saudi Arabia (KSA). This was a cross-sectional and community-based study. The adult population was divided into governorates according to the regions that were close to each other, and then a convenient stratum was selected from each region. Next, random sampling was applied. Data were collected using a self-administered questionnaire. Exclusion criteria were young people (<18 years old) and health workers. Data analysis was performed using descriptive statistics, the Pearson's correlation coefficient, and multiple linear regression. Of the 392 participants in this cross-sectional study, 59.18% were male, 76.28% were aged 18-35 years, 72.96% had a university degree, and 63% had a monthly income of less than SAR 5000 (USD1 = 3.76). The scores (mean ± SD) for KAP regarding DF among the responders were 22.77 ± 7.9, 22.68 ± 7.24, and 25.62 ± 9.4, respectively. KAP constructs were positively correlated according to the Pearson's coefficient. In multiple linear regression analysis, males were favorably and substantially linked with attitude score (ß = 2.76, p = 0.001) and negatively associated with practice score (ß = -2.45, p = 0.023). No-degree participants scored lower on knowledge (ß = -2.78, p = 0.003). There is potential for more research in Saudi Arabia to increase the generalizability to reduce the impact of dengue epidemics.


Subject(s)
Dengue , Health Knowledge, Attitudes, Practice , Adult , Humans , Male , Adolescent , Female , Cross-Sectional Studies , Saudi Arabia/epidemiology , Dengue/epidemiology , Dengue/prevention & control , Surveys and Questionnaires
11.
Cancers (Basel) ; 14(21)2022 Oct 26.
Article in English | MEDLINE | ID: mdl-36358683

ABSTRACT

The revolution of artificial intelligence and its impacts on our daily life has led to tremendous interest in the field and its related subtypes: machine learning and deep learning. Scientists and developers have designed machine learning- and deep learning-based algorithms to perform various tasks related to tumor pathologies, such as tumor detection, classification, grading with variant stages, diagnostic forecasting, recognition of pathological attributes, pathogenesis, and genomic mutations. Pathologists are interested in artificial intelligence to improve the diagnosis precision impartiality and to minimize the workload combined with the time consumed, which affects the accuracy of the decision taken. Regrettably, there are already certain obstacles to overcome connected to artificial intelligence deployments, such as the applicability and validation of algorithms and computational technologies, in addition to the ability to train pathologists and doctors to use these machines and their willingness to accept the results. This review paper provides a survey of how machine learning and deep learning methods could be implemented into health care providers' routine tasks and the obstacles and opportunities for artificial intelligence application in tumor morphology.

12.
Vaccines (Basel) ; 10(8)2022 Aug 06.
Article in English | MEDLINE | ID: mdl-36016158

ABSTRACT

COVID-19 vaccines are crucial to control the pandemic and avoid COVID-19 severe infections. The rapid evolution of COVID-19 variants such as B.1.1.529 is alarming, especially with the gradual decrease in serum antibody levels in vaccinated individuals. Middle Eastern countries were less likely to accept the initial doses of vaccines. This study was directed to determine COVID-19 vaccine booster acceptance and its associated factors in the general population in the MENA region to attain public herd immunity. We conducted an online survey in five countries (Egypt, Iraq, Palestine, Saudi Arabia, and Sudan) in November and December 2021. The questionnaire included self-reported information about the vaccine type, side effects, fear level, and several demographic factors. Kruskal−Wallis ANOVA was used to associate the fear level with the type of COVID-19 vaccine. Logistic regression was performed to confirm the results and reported as odds ratios (ORs) and 95% confidence intervals. The final analysis included 3041 fully vaccinated participants. Overall, 60.2% of the respondents reported willingness to receive the COVID-19 booster dose, while 20.4% were hesitant. Safety uncertainties and opinions that the booster dose is not necessary were the primary reasons for refusing the booster dose. The willingness to receive the booster dose was in a triangular relationship with the side effects of first and second doses and the fear (p < 0.0001). Females, individuals with normal body mass index, history of COVID-19 infection, and influenza-unvaccinated individuals were significantly associated with declining the booster dose. Higher fear levels were observed in females, rural citizens, and chronic and immunosuppressed patients. Our results suggest that vaccine hesitancy and fear in several highlighted groups continue to be challenges for healthcare providers, necessitating public health intervention, prioritizing the need for targeted awareness campaigns, and facilitating the spread of evidence-based scientific communication.

13.
Healthcare (Basel) ; 10(2)2022 Feb 18.
Article in English | MEDLINE | ID: mdl-35206998

ABSTRACT

Soon after the coronavirus disease 2019 pandemic was proclaimed, digital health services were widely adopted to respond to this public health emergency, including comprehensive monitoring technologies, telehealth, creative diagnostic, and therapeutic decision-making methods. The World Health Organization suggested that artificial intelligence might be a valuable way of dealing with the crisis. Artificial intelligence is an essential technology of the fourth industrial revolution that is a critical nonmedical intervention for overcoming the present global health crisis, developing next-generation pandemic preparation, and regaining resilience. While artificial intelligence has much potential, it raises fundamental privacy, transparency, and safety concerns. This study seeks to address these issues and looks forward to an intelligent healthcare future based on best practices and lessons learned by employing telehealth and artificial intelligence during the COVID-19 pandemic.

14.
Environ Sci Pollut Res Int ; 29(2): 1677-1695, 2022 Jan.
Article in English | MEDLINE | ID: mdl-34689274

ABSTRACT

Biosensors are analytical tools that transform the bio-signal into an observable response. Biosensors are effective for early detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection because they target viral antigens to assess clinical development and provide information on the severity and critical trends of infection. The biosensors are capable of being on-site, fast, and extremely sensitive to the target viral antigen, opening the door for early detection of SARS-CoV-2. They can screen individuals in hospitals, airports, and other crowded locations. Microfluidics and nanotechnology are promising cornerstones for the development of biosensor-based techniques. Recently, due to high selectivity, simplicity, low cost, and reliability, the production of biosensor instruments have attracted considerable interest. This review article precisely provides the extensive scientific advancement and intensive look of basic principles and implementation of biosensors in SARS-CoV-2 surveillance, especially for human health. In this review, the importance of biosensors including Optical, Electrochemical, Piezoelectric, Microfluidic, Paper-based biosensors, Immunosensors, and Nano-Biosensors in the detection of SARS-CoV-2 has been underscored. Smartphone biosensors and calorimetric strips that target antibodies or antigens should be developed immediately to combat the rapidly spreading SARS-CoV-2. Wearable biosensors can constantly monitor patients, which is a highly desired feature of biosensors. Finally, we summarized the literature, outlined new approaches and future directions in diagnosing SARS-CoV-2 by biosensor-based techniques.


Subject(s)
Biosensing Techniques , COVID-19 , COVID-19/diagnosis , Humans , Immunoassay , Reproducibility of Results , SARS-CoV-2
15.
Nanotechnology ; 33(1)2021 Oct 20.
Article in English | MEDLINE | ID: mdl-34560680

ABSTRACT

Misfit strain in core-shell nanowires can be elastically released by nanowire bending in case of asymmetric shell growth around the nanowire core. In this work, we investigate the bending of GaAs nanowires during the asymmetric overgrowth by an InxGa1-xAs shell caused by avoiding substrate rotation. We observe that the nanowire bending direction depends on the nature of the substrate's oxide layer, demonstrated by Si substrates covered by native and thermal oxide layers. Further, we follow the bending evolution by time-resolvedin situx-ray diffraction measurements during the deposition of the asymmetric shell. The XRD measurements give insight into the temporal development of the strain as well as the bending evolution in the core-shell nanowire.

16.
Biophys Chem ; 277: 106663, 2021 10.
Article in English | MEDLINE | ID: mdl-34388678

ABSTRACT

Influenza (flu) is a serious global health threat. The Hemagglutinin (HA) protein binds the flu virus to the sialic acids at the surface of the host cells' membrane which allows the endocytosis of the virus. Therefore, potential inhibitors can attach to the active site of HA and block the virus life-cycle. In this study, the antiviral drug arbidol (ARB) and 16 HA-subtypes were docked and analyzed to represent different approaches in predicting the conformation of protein-ligand, protein-protein, and protein-glycan complex and its binding energy. Our findings show that ARB interacts with all HA subtypes, and H7 possesses the best affinity. The next influenza pandemic could be caused by H4, H5, H6, and H14 subtypes, which prompts further studies in investigating the interaction between these particular HA subtypes and other antiviral drugs to obtain higher efficacy.


Subject(s)
Angiotensin-Converting Enzyme Inhibitors , Indoles , Angiotensin Receptor Antagonists , Hemagglutinins
17.
J Appl Crystallogr ; 54(Pt 1): 80-86, 2021 Feb 01.
Article in English | MEDLINE | ID: mdl-33833642

ABSTRACT

This article reports on energy-dispersive micro Laue (µLaue) diffraction of an individual gold nanowire that was mechanically deformed in three-point bending geometry using an atomic force microscope. The nanowire deformation was investigated by scanning the focused polychromatic X-ray beam along the nanowire and recording µLaue diffraction patterns using an energy-sensitive pnCCD detector that permits measurement of the angular positions of the Laue spots and the energies of the diffracted X-rays simultaneously. The plastic deformation of the nanowire was shown by a bending of up to 3.0 ± 0.1°, a torsion of up to 0.3 ± 0.1° and a maximum deformation depth of 80 ± 5 nm close to the position where the mechanical load was applied. In addition, extended Laue spots in the vicinity of one of the clamping points indicated the storage of geometrically necessary dislocations with a density of 7.5 × 1013 m-2. While µLaue diffraction with a non-energy-sensitive detector only gives access to the deviatoric strain, the energy sensitivity of the employed pnCCD offers absolute strain measurements with a resolution of 1%. Here, the residual strain after complete unloading of the nanowire amounted to maximum tensile and compressive strains of the order of +1.2 and -3%, which is comparable to the actual resolution limit. The combination of white-beam µLaue diffraction using an energy-sensitive pixel detector with nano-mechanical testing opens up new possibilities for the study of mechanical behavior at the nanoscale.

18.
J Appl Crystallogr ; 53(Pt 5): 1310-1320, 2020 Oct 01.
Article in English | MEDLINE | ID: mdl-33117111

ABSTRACT

Core-shell nanowires (NWs) with asymmetric shells allow for strain engineering of NW properties because of the bending resulting from the lattice mismatch between core and shell material. The bending of NWs can be readily observed by electron microscopy. Using X-ray diffraction analysis with a micro- and nano-focused beam, the bending radii found by the microscopic investigations are confirmed and the strain in the NW core is analyzed. For that purpose, a kinematical diffraction theory for highly bent crystals is developed. The homogeneity of the bending and strain is studied along the growth axis of the NWs, and it is found that the lower parts, i.e. close to the substrate/wire interface, are bent less than the parts further up. Extreme bending radii down to ∼3 µm resulting in strain variation of ∼2.5% in the NW core are found.

19.
Nanotechnology ; 31(21): 214002, 2020 May 22.
Article in English | MEDLINE | ID: mdl-32050166

ABSTRACT

We report on the direct correlation between the structural and optical properties of single, as-grown core-multi-shell GaAs/In0.15Ga0.85As/GaAs/AlAs/GaAs nanowires. Fabricated by molecular beam epitaxy on a pre-patterned Si(111) substrate, on a row of well separated nucleation sites, it was possible to access individual nanowires in the as-grown geometry. The polytype distribution along the growth axis of the nanowires was revealed by synchrotron-based nanoprobe x-ray diffraction techniques monitoring the axial 111 Bragg reflection. For the same nanowires, the spatially-resolved emission properties were obtained by cathodoluminescence hyperspectral linescans in a scanning electron microscope. Correlating both measurements, we reveal a blueshift of the shell quantum well emission energy combined with an increased emission intensity for segments exhibiting a mixed structure of alternating wurtzite and zincblende stacking compared with the pure crystal polytypes. The presence of this mixed structure was independently confirmed by cross-sectional transmission electron microscopy.

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