A Stepwise Guide to Performing Shoulder Ultrasound: The Acromio-Clavicular Joint, Biceps, Subscapularis, Impingement, Supraspinatus Protocol.

Shoulder pain is a common and painful patient condition. Unfortunately, diagnostic imaging of shoulder pain in the emergency department (ED) is often limited to radiography. While diagnostic for fractures and dislocations, drawbacks of radiography include time delays and non-diagnostic imaging in the case of rotator cuff pathology. While bedside ultrasound has been incorporated into many procedural and diagnostic applications in the ED, its use for musculoskeletal complaints and specifically shoulder pain is infrequent among ED clinicians. The incorporation of shoulder ultrasound in the ED may improve diagnostic certainty while decreasing time to diagnosis and treatment, yielding patient and health system benefits. Herein, we present the ABSIS (Acromio-clavicular joint, Biceps, Subscapularis, Impingement, Supraspinatus) Protocol for performing bedside ultrasound of the shoulder including the rotator cuff and bony anatomy.

Characteristics of and Predictors for Apnea and Clinical Interventions During Procedural Sedation.

STUDY OBJECTIVE: We describe the characteristics of and predictors for apnea and clinical interventions during emergency department (ED) procedural sedation. METHODS: High-resolution data were collected prospectively, using a convenience sample of ED patients undergoing propofol or ketofol sedation. End tidal CO2 (etco2), respiratory rate, pulse rate, and SpO2 were electronically recorded in 1-second intervals. Procedure times, drug delivery, and interventions were electronically annotated. Kaplan-Meier curves were used to describe the onset of clinical interventions as a function of sedation time. The onset of apnea (15 consecutive seconds with carbon dioxide ≤10 mm Hg) and clinical interventions were estimated with a series of Cox proportional hazards survival models, with time to first apnea or clinical intervention as the dependent variable. Finally, we tested the association between apnea and clinical intervention. RESULTS: Three hundred twelve patients were analyzed (53% male patients). Apnea was preceded by etco2 less than 30 mm Hg or greater than 50 mm Hg at 30, 60, and 90 seconds before its onset. Clinical interventions were predicted by apnea, SpO2, and propofol use. Increasing age predicted both apnea and interventions. Apnea was not predicted by respiratory rate or SpO2. Apnea occurred in half of the patients and clinical interventions in a quarter of them. Clinical intervention was not predicted by abnormal respiratory rate or abnormal etco2 level. The majority of clinical interventions (85%) were minor, with no cases of assisted ventilation, intubation, or complications. CONCLUSION: Alterations in etco2 predicted apnea along a specific time course. Alterations in SpO2, apnea, and propofol use predicted clinical interventions. Increasing age predicted both apnea and clinical intervention.

Fractional quantum Hall phase transitions and four-flux states in graphene.

Graphene and its multilayers have attracted considerable interest because their fourfold spin and valley degeneracy enables a rich variety of broken-symmetry states arising from electron-electron interactions, and raises the prospect of controlled phase transitions among them. Here we report local electronic compressibility measurements of ultraclean suspended graphene that reveal a multitude of fractional quantum Hall states surrounding filling factors ν=-1/2 and -1/4. Several of these states exhibit phase transitions that indicate abrupt changes in the underlying order, and we observe many additional oscillations in compressibility as ν approaches -1/2, suggesting further changes in spin and/or valley polarization. We use a simple model based on crossing Landau levels of composite fermions with different internal degrees of freedom to explain many qualitative features of the experimental data. Our results add to the diverse array of many-body states observed in graphene and demonstrate substantial control over their order parameters.

Unconventional sequence of fractional quantum Hall states in suspended graphene.

Graphene provides a rich platform to study many-body effects, owing to its massless chiral charge carriers and the fourfold degeneracy arising from their spin and valley degrees of freedom. We use a scanning single-electron transistor to measure the local electronic compressibility of suspended graphene, and we observed an unusual pattern of incompressible fractional quantum Hall states that follows the standard composite fermion sequence between filling factors ν = 0 and 1 but involves only even-numerator fractions between ν = 1 and 2. We further investigated this surprising hierarchy by extracting the corresponding energy gaps as a function of the magnetic field. The sequence and relative strengths of the fractional quantum Hall states provide insight into the interplay between electronic correlations and the inherent symmetries of graphene.

Raman scattering at pure graphene zigzag edges.

Theory has predicted rich and very distinct physics for graphene devices with boundaries that follow either the armchair or the zigzag crystallographic directions. A prerequisite to disclose this physics in experiment is to be able to produce devices with boundaries of pure chirality. Exfoliated flakes frequently exhibit corners with an odd multiple of 30°, which raised expectations that their boundaries follow pure zigzag and armchair directions. The predicted Raman behavior at such crystallographic edges however failed to confirm pure edge chirality. Here, we perform confocal Raman spectroscopy on hexagonal holes obtained after the anisotropic etching of prepatterned pits using carbothermal decomposition of SiO(2). The boundaries of the hexagonal holes are aligned along the zigzag crystallographic direction and leave hardly any signature in the Raman map indicating unprecedented purity of the edge chirality. This work offers the first opportunity to experimentally confirm the validity of the Raman theory for graphene edges.

Graphene on a hydrophobic substrate: doping reduction and hysteresis suppression under ambient conditions.

The intrinsic doping level of graphene prepared by mechanical exfoliation and standard lithography procedures on thermally oxidized silicon varies significantly and seems to depend strongly on processing details and the substrate morphology. Moreover, transport properties of such graphene devices suffer from hysteretic behavior under ambient conditions. The hysteresis presumably originates from dipolar adsorbates on the substrate or graphene surface. Here, we demonstrate that it is possible to reliably obtain low intrinsic doping levels and to strongly suppress hysteretic behavior even in ambient air by depositing graphene on top of a thin, hydrophobic self-assembled layer of hexamethyldisilazane (HMDS). The HMDS serves as a reproducible template that prevents the adsorption of dipolar substances. It may also screen the influence of substrate deficiencies.

Hot phonons in an electrically biased graphene constriction.

Phonon-carrier interactions can have significant impact on device performance. They can be probed by measuring the phonon lifetime, which reflects the interaction strength of a phonon with other quasi-particles, in particular charge carriers as well as its companion phonons. The carrier phonon and phonon-phonon contributions to the phonon lifetime can be disentangled from temperature-dependent studies. Here, we address the importance of phonon-carrier interactions in Joule-heated graphene constrictions in order to contribute to the understanding of energy dissipation in graphene-based electronic devices. We demonstrate that gapless graphene grants electron-phonon interactions uncommon significance in particular at low carrier density. In conventional semiconductors, the band gap usually prevents the decay of phonons through electron-hole generation and also in metals or other semimetals the Fermi temperature is excessively large to enter the regime where electron-phonon coupling plays such a dominant role as in graphene in the investigated phonon temperature regime from 300 to 1600 K.

Raman spectra of epitaxial graphene on SiC and of epitaxial graphene transferred to SiO2.

Raman spectra were measured for mono-, bi-, and trilayer graphene grown on SiC by solid state graphitization, whereby the number of layers was preassigned by angle-resolved ultraviolet photoemission spectroscopy. It was found that the only unambiguous fingerprint in Raman spectroscopy to identify the number of layers for graphene on SiC(0001) is the line width of the 2D (or D*) peak. The Raman spectra of epitaxial graphene show significant differences as compared to micromechanically cleaved graphene obtained from highly oriented pyrolytic graphite crystals. The G peak is found to be blue-shifted. The 2D peak does not exhibit any obvious shoulder structures, but it is much broader and almost resembles a single-peak even for multilayers. Flakes of epitaxial graphene were transferred from SiC onto SiO2 for further Raman studies. A comparison of the Raman data obtained for graphene on SiC with data for epitaxial graphene transferred to SiO2 reveals that the G peak blue-shift is clearly due to the SiC substrate. The broadened 2D peak however stems from the graphene structure itself and not from the substrate.