Strain-induced phonon shifts in tungsten disulfide nanoplatelets and nanotubes

The relationship between structure and properties has been followed for different nanoscale forms of tungsten disulfide (2H-WS2) namely exfoliated monolayer and few-layer nanoplatelets, and nanotubes. The similarities and differences between these nanostructured materials have been examined using a combination of optical microscopy, scanning and high-resolution transmissionelectron microscopy (SEM and HRTEM) and atomic force microscopy (AFM). Photoluminescence (PL) and Raman spectroscopy have also been used to distinguish between monolayer and few-layer material. Strain induced phonon shifts have been followed from the changes in the positions of the A1g and E2g1 Raman bands during uniaxial deformation. This has been modelled for monolayer using density functional theory (DFT) with excellent agreement between the measured and predicted behaviour. It has been found that as the number of WS2 layers increases for few-layer crystals or nanotubes, the A1g mode hardens whereas the E2g1 mode softens. This is believed to be due to theA1g mode, which involves out of plane atomic movements, being constrained by the increasing number of WS2 layers whereas easy sliding reduces stress transfer to the individual layers for the E2g1mode, involving only in-plane vibrations. This finding has enabled the anomalous phonon shift behaviour in earlier pressure measurements on WS2 to be resolved, as well as similar effects in othertransition metal dichalcogenides, such as molybdenum disulfide (MoS2), to be explained. <br/

Hospital inpatient care utilization among patients with tuberculosis, Republic of Ireland, 2015-2018.

BackgroundThe Republic of Ireland (ROI) has a low incidence of TB. A reform of TB services in 2003 recommended that the delivery of care to patients with TB should primarily be in the outpatient setting, with limited indications for hospitalization. Three hospitals were designated as TB centres. Our aim was to describe the utilization of hospital inpatient care by patients with TB in the ROI.MethodsWe searched public hospital coding data to identify discharges between 01/01/2015-31/12/18 where TB was the principal diagnosis. The cost of TB episodes of care was calculated using payment rules for public hospitals in the ROI.ResultsWe identified 1185 discharges with TB as the principal diagnosis. Of these, 68% (801/1185) were emergency episodes of care and 32% (384/1185) were elective. We estimate that 65.1% (818/1257) patients with TB notified in the ROI from 2015 to 2018 who had an episode of care in a public hospital was 65.1% (818/1257) and that 50.8% (639/1257) of those notified had an emergency episode of care. The estimated mean annual cost of TB inpatient care per year in the ROI from 2015 to 2018 was €2,638,828-2,955,047, with emergency episodes of care having a mean annual cost of €2,250,926-2,557,397 per year.ConclusionsThe burden of TB on hospital inpatient care in the Republic of Ireland is significant

World Tuberculosis Day 2020: It’s time

The 24th of March was chosen as World Tuberculosis Day to raise public awareness about the disease. It is also the day Robert Koch announced his discovery of the Mycobacterium bacillus as the cause of tuberculosis (TB) in 1882. Latent tuberculosis infection (LTBI) is a state of persistent immune response to stimulation by Mycobacterium tuberculosis antigens with no evidence of clinically manifest active disease. The incidence of tuberculosis disease in Ireland is now low at 6.6/100,000 population. The World Health Organisation (WHO) has set the goal of a 90% reduction in global TB incidence by 2035 when compared to 2015. Unless improvements in TB prevention and control are made in Ireland it is unlikely we will achieve this target. The WHO End TB Strategy states that the systematic identification and management of LTBI in groups of people at high risk of reactivation is an essential part of TB elimination in low-incidence countries. The Health Protection Surveillance Centre (HPSC) Guidelines for the Prevention and Control of TB 2010 recommend the screening of people living with HIV, persons on immunosuppressive therapy, healthcare workers, people who use intravenous drugs, people who are homeless and people from countries with a high incidence of TB.</p

A feasibility assessment of an ambulatory care pathway for cellulitis at a tertiary referral centre in the Republic of Ireland.

IntroductionThere is a need for the development of more ambulatory care pathways to reduce the number of bed-days utilized by ambulatory care sensitive conditions in hospitals in Ireland. Healthcare policy and strategy has changed to reflect this. Our aim was to determine if an ambulatory care pathway for the management of cellulitis would be feasible in our tertiary referral centre.MethodsWe searched hospital coding data to identify all admissions with cellulitis from 1/1/2018 to 31/12/2018 in our tertiary referral centre. We estimated the cost of cellulitis admissions using guidelines from the Healthcare Pricing Office in Ireland. We used guidance from the Department of Public Expenditure and Reform to calculate the cost of staff in a proposed ambulatory care model.ResultsWe identified 249 episodes of care with cellulitis in 2018. 89.6% (223/249) were emergency episodes of care. A total of 2372 bed-days was utilized by emergency episodes of care at a cost of €1,126,369–1,129,823. The median cost of an emergency episode of care due to cellulitis was €2291 (IQR 2291–5594) with a mean cost per bed-day of €475–476. Overall, there was neither sepsis nor a surgical intervention coded in 85.2% (190/223) of emergency episodes of care. We identified a cohort of 23.8% (53/223) of emergency episodes of care that had a length of stay of 1–3 days which could potentially have been managed using an ambulatory care pathway.ConclusionEven if only a small proportion of cases were ambulated there are significant savings in terms of bed-days and costs to be made. An ambulatory care pathway for cellulitis should be established in our tertiary referral centre and this methodology could be used to inform resourcing of pathways elsewhere.</div

A survey of latent tuberculosis screening and treatment practices in a tertiary centre

Aim  Knowledge of latent tuberculosis infection (LTBI) screening and treatment practices are lacking in Ireland, where LTBI is not programmatically surveyed or managed. The aim of this research was to describe current clinical practice when screening and treating patients for LTBI in a tertiary referral centre in Ireland.  Methods  A 17-question survey relating to LTBI screening and management practices with both open-ended questions and close ended multiple-choice questions was created using SurveyMonkey. The survey target sample was healthcare workers in the tertiary centre who direct LTBI screening and treatment for patients at risk of TB disease in their respective departments.  Results  The response rate to the survey was 45% (21/47). Seventy-one percent (15/21) of those surveyed responded to the question “What barriers exist to screening patients for latent TB in your clinical practice?”. Fifty-three percent (8/15) said that they found it difficult to access LTBI testing and 27% (4/15) cited accessing the interferon-gamma release assay (IGRA) result as a barrier. Forty-three percent (9/21) responded that there was not a clear referral pathway for patients that they would like specialist input on when diagnosing and managing patients with LTBI.  Conclusion  Access to LTBI testing, LTBI test results, TB specialist services and the use of rifamycin-based regimens should be improved in this tertiary centre. Consideration should be given to developing a national LTBI education programme for healthcare professionals and updating national LTBI treatment guidelines.</p

Plasmons in MoS2 studied via experimental and theoretical correlation of energy loss spectra

This paper takes a fundamental view of the electron energy loss spectra of monolayer and few layer MoS2. The dielectric function of monolayer MoS2 is compared to the experimental spectra to give clear criteria for the nature of different signals. Kramers-Krönig analysis allows a direct extraction of the dielectric function from the experimental data. However this analysis is sensitive to slight changes in the normalisation step of the data pre-treatment. Density functional theory provides simulations of the dielectric function for comparison and validation of experimental findings. Simulated and experimental spectra are compared to isolate the and + surface plasmon modes in monolayer MoS2. Singleparticle excitations obscure the plasmons in the monolayer spectrum and momentum resolved measurements give indication of indirect interband transitions that are excited due to the large convergence and collection angles used in the experiment

New single photon sources by optoelectronic tailoring of 2D materials using low energy ion implantation

Monolayer thick transition metal dichalcogenides (TMDCs) with the chemical formula MX2 (M=Mo, W; X=S, Se), constitute a new class of direct bandgap semiconductors. Their remarkable physical properties resulting from their two dimensional (2D) geometry and lattice symmetry make them an exciting platform for developing photonic devices with new functionalities [1]. Monolayer TMDCs can be easily incorporated into electrically driven devices, which in turn can be coupled to optical microcavities or photonic circuits [2]. This work constitutes a proof-of-principle study to incorporate implanted TMDCs into non-classical single photon emitting diodes [3]. The development of such devices has far-reaching implications for emerging technologies such as quantum cryptography and quantum metrology. In order to make such devices a reality, methods of material modification for these materials, such as ultra-low energy (10-25 eV) ion implantation, must be developed [4,5]. Post-growth doping [6] of TMDCs offers an expanded selection of possible dopants compared to the popular method of doping via CVD growth. The technique allows for highly pure, clean and selective substitutional incorporation of dopants [7] and is also compatible with standard semiconductor processing. Ultra-low energy ion implantation is carried out using the ADONIS mass-selected ion beam deposition system at the University of Gottingen [8]