2,461 research outputs found
Spectroscopic Investigation of Thermal Conductivity in Few-Layer Graphene
Get PDFCarbon is an extremely versatile element due to the ability of its electronic structure to allow strong bonds with many elements including other carbon atoms. This allows for the formation of many types of large and complex architectures, such as fullerenes and carbon nanotubes, at the nanoscale. One of the most fascinating allotropes of carbon is graphene, a two-dimensional honeycomb lattice with carbon in sp2 hybridization, which building block for layered graphite and other nanocarbons.[1] Because of its unique structure, graphene displays several interesting properties including high thermal[2â4] and electrical mobility and conductivity[1,5]. The initial studies on graphene were performed on mechanically exfoliated samples, which were limited to few microns in size. In the recent years, large areas of single- and few-layer graphene (~few cm x cm) are being produced by chemical vapor deposition technique for practical applications. However, chemical vapor deposition grown graphene is highly polycrystalline with interfaces such as edges, grain boundaries, dislocations, and point defects. This inevitable presence of defects in graphene influences its electrical and thermal transport. While many studies have previously focused on the influence of defects on electrical mobility and conductivity, there is little information on the influence of defects on the thermal properties of graphene. This study specifically investigates the effect of both intrinsic and extrinsic defects on the in-plane thermal properties of graphene using micro-Raman spectroscopy. The in-plane thermal conductivity of few-layered graphene (FLG) was measured using Raman spectroscopy, following the work of Balandin et al. [4]The thermal conductivity was estimated from a shift of the characteristic G-band of graphene as a function of the excitation laser power. The graphene samples were synthesized on nickel substrates using chemical vapor deposition, and transferred to copper TEM grids and scanned using a micro-Raman spectrometer. The density of defects in the samples was controlled using reactive-ion etching with monovalent Ar ions. Thermal conductivities were then calculated and compared to previous works. Defect amounts were also calculated and catalogued. Defects and thermal conductivities from the two grids used were compared to assess the impact of defects, both in the structure of the graphene itself and surface contamination, on the in-plane thermal conductivity. This work gives preliminary evidences that both intrinsic and extrinsic defects have a detrimental effect on the thermal conductivity of graphene. Intrinsic defects impede phonon mobility, which carries heat across the structure while extrinsic defects such as surface contamination open up more avenues for out-of-plane heat loss. The preliminary results presented in this work warrant the need for a detailed theoretical and experimental investigation of the influence of different defects (e.g., dopants) on the thermal conductivity of single- and few-layer graphene samples
When The Sheep Are In The Fold, Jennie Dear
Get PDFhttps://digitalcommons.library.umaine.edu/mmb-vp/4569/thumbnail.jp
Neatth The Old Acorn Tree, Sweet Estelle
Get PDFhttps://digitalcommons.library.umaine.edu/mmb-vp/4461/thumbnail.jp
Qualitative evaluation of a rapid rollout of home blood pressure monitoring in pregnancy during Covid-19
Get PDFIn March 2020, the World Health Organisation named the severe acute respiratory syndrome coronavirus 2 (Sars-CoV-2), which causes corona virus disease 2019 (COVID -19), as a pandemic. Pregnant women were considered at increased risk of developing severe COVID-19 after viral infection. In response maternity services reduced face-to-face consultations with high-risk pregnant women by supplying blood pressure monitors for supported self-monitoring. This paper explores the experiences of patients and clinicians of the rapid roll-out of supported self-monitoring programme in Scotland during the first and second wave of the COVID-19 pandemic. We conducted semi-structured telephone interviews with high-risk women and healthcare professionals who were using supported self-monitoring of blood pressure (BP) In four case studies during the COVID-19 pandemic. 20 women, 15 midwives and 4 obstetricians took part in the interviews. Interviews with healthcare professionals showed that while implementation occurred at pace and at scale across the National Health Service (NHS) in Scotland, implementation differed locally, resulting in mixed experiences. Study Participants observed several barriers and facilitators to implementation. Women value the simplicity of use and convenience of the digital communications platforms while health professionals were more interested in their impact on reducing workload for both women and health professionals largely found self-monitoring acceptable, with only a few exceptions. These results show that rapid change can occur in the NHS at a national level when there is a shared motivation. While self-monitoring is acceptable to most women, decisions regarding self-monitoring should be made jointly and on an individual basis
When the Whip-Poor-Will Sings Marguerite
Get PDFVERSE 1The whip-poor-will at twilightâs glow was singing,The cricket chirpâd itâs âGoodnightâ lullaby,The dear old village bells were sweetly ringing,As you held me in your arms and said, âGoodbye;âYou told me of a love that naught could sever,Of happy days when you and I should wed,You kissed my lips to part perhaps, forever.Then held my hand a moment while you said:
CHORUSWhen the whip-poor-will sings Marguerite,And forget-me-nots bloom at your feet,You may know though you yearn, that to you Iâll return,Loveâs old story again to repeat;So be true little girl I entreat,Till the time when again we shall meet,Let loveâs star brightly shine,Iâll return sweetheart mine,When the whip-poor-will sings Marguerite.
VERSE 2For weary days Iâve waited your returning,Iâve longed to see your dear face once again,The whip-poor-will is singing, I am yearning,For my longing and my waiting was in vain;âNeath dear old southern shies tonight youâre sleeping,The Swanee river flows upon its way,For old timeâs sake your love I still am keeping,At twilightâs glow, I seem to hear you say:
CHORU
- âŠ
