AOA Critical Issues Symposium: So, You Want to Be a Department Leader: Essentials for Success.

ABSTRACT: Most health systems are vertically integrated, and the leaders of orthopaedic surgery departments or service lines must have a comprehensive understanding of their role in the strategic plan of the health system. Orthopaedic surgery departments must be profitable while supporting the tripartite mission of excellence in clinical care, research, and education. This symposium had 4 specific objectives: to discuss how to (1) create synergy between the department or service line and the health system, (2) develop a strategy to enhance financial stability and revenue growth, (3) develop a comprehensive plan to enhance recruitment and retention of a diverse faculty, and (4) consider alternative strategies to foster education and research, even when the health system may be more focused on revenue generation.

A few-layer graphene for advanced composite PVDF membranes dedicated to water desalination: a comparative study.

Membrane distillation is envisaged to be a promising best practice to recover freshwater from seawater with the prospect of building low energy-consuming devices powered by natural and renewable energy sources in remote and less accessible areas. Moreover, there is an additional benefit of integrating this green technology with other well-established operations dedicated to desalination. Today, the development of membrane distillation depends on the productivity-efficiency ratio on a large scale. Despite hydrophobic commercial membranes being widely used, no membrane with suitable morphological and chemical feature is readily available in the market. Thus, there is a real need to identify best practices for developing new efficient membranes for more productive and eco-sustainable membrane distillation devices. Here, we propose engineered few-layer graphene membranes, showing enhanced trans-membrane fluxes and total barrier action against NaCl ions. The obtained performances are linked with filling polymeric membranes with few-layer graphene of 490 nm in lateral size, produced by the wet-jet milling technology. The experimental evidence, together with comparative analyses, confirmed that the use of more largely sized few-layer graphene leads to superior productivity related efficiency trade-off for the membrane distillation process. Herein, it was demonstrated that the quality of exfoliation is a crucial factor for addressing the few-layer graphene supporting the separation capability of the host membranes designed for water desalination.

A simple enzymatic assay for the quantification of C1-specific cellulose oxidation by lytic polysaccharide monooxygenases.

OBJECTIVE: The development of an enzymatic assay for the specific quantification of the C1-oxidation product, i.e. gluconic acid of cellulose active lytic polysaccharide monooxygenases (LPMOs). RESULTS: In combination with a ß-glucosidase, the spectrophotometrical assay can reliably quantify the specific C1- oxidation product of LPMOs acting on cellulose. It is applicable for a pure cellulose model substrate as well as lignocellulosic biomass. The enzymatic assay compares well with the quantification performed by HPAEC-PAD. In addition, we show that simple boiling is not sufficient to inactivate LPMOs and we suggest to apply a metal chelator in addition to boiling or to drastically increase pH for proper inactivation. CONCLUSIONS: We conclude that the versatility of this simple enzymatic assay makes it useful in a wide range of experiments in basic and applied LPMO research and without the need for expensive instrumentation, e.g. HPAEC-PAD.

Carbohydrate binding modules enhance cellulose enzymatic hydrolysis by increasing access of cellulases to the substrate.

Plant biomass is a low-cost and abundant source of carbohydrates for production of fuels, "green" chemicals and materials. Currently, biochemical conversion of the biomass into sugars via enzymatic hydrolysis is the most viable technology. Here, the role of carbohydrate binding modules (CBMs) in the disruption of insoluble polysaccharide structures and their capacity to enhance cellulase-promoted lignocellulosic biomass hydrolysis was investigated. We show that CBM addition promotes generation of additional reducing ends in the insoluble substrate by cellulases. On the contrary, bovine serum albumin (BSA), widely used in prevention of a non-specific protein binding, causes an increase in soluble reducing-end production, when applied jointly with cellulases. We demonstrate that binding of CBMs to cellulose is non-homogeneous, irreversible and leads to its amorphisation. Our results also reveal effects of CBM-promoted amorphogenesis on cellulose hydrolysis by cellulases.

Ultralow friction of ink-jet printed graphene flakes.

We report the frictional response of few-layer graphene (FLG) flakes obtained by the liquid phase exfoliation (LPE) of pristine graphite. To this end, we inkjet print FLG on bare and hexamethyldisilazane-terminated SiO2 substrates, producing micrometric patterns with nanoscopic roughness that are investigated by atomic force microscopy. Normal force spectroscopy and atomically-resolved morphologies indicate reduced surface contamination by solvents after a vacuum annealing process. Notably, the printed FLG flakes show ultralow friction comparable to that of micromechanically exfoliated graphene flakes. Lubricity is retained on flakes with a lateral size of a few tens of nanometres, and with a thickness as small as ∼2 nm, confirming the high crystalline quality and low defects density in the FLG basal plane. Surface exposed step edges exhibit the highest friction values, representing the preferential sites for the origin of the secondary dissipative processes related to edge straining, wear or lateral displacement of the flakes. Our work demonstrates that LPE enables fundamental studies on graphene friction to the single-flake level. The capability to deliver ultralow-friction-graphene over technologically relevant substrates, using a scalable production route and a high-throughput, large-area printing technique, may also open up new opportunities in the lubrication of micro- and nano-electromechanical systems.

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures.

Vertical heterostructures combining different layered materials offer novel opportunities for applications and fundamental studies. Here we report a new class of heterostructures comprising a single-layer (or bilayer) graphene in close proximity to a quantum well created in GaAs and supporting a high-mobility two-dimensional electron gas. In our devices, graphene is naturally hole-doped, thereby allowing for the investigation of electron-hole interactions. We focus on the Coulomb drag transport measurements, which are sensitive to many-body effects, and find that the Coulomb drag resistivity significantly increases for temperatures <5-10 K. The low-temperature data follow a logarithmic law, therefore displaying a notable departure from the ordinary quadratic temperature dependence expected in a weakly correlated Fermi-liquid. This anomalous behaviour is consistent with the onset of strong interlayer correlations. Our heterostructures represent a new platform for the creation of coherent circuits and topologically protected quantum bits.

A clinical research integration special program (CRISP) for young women with primary ovarian insufficiency.

Large-scale medical sequencing provides a focal point around which to reorganize health care and health care research. Mobile health (mHealth) is also currently undergoing explosive growth and could be another innovation that will change the face of future health care. We are employing primary ovarian insufficiency (POI) as a model rare condition to explore the intersection of these potentials. As both sequencing capabilities and our ability to intepret this information improve, sequencing for medical purposes will play an increasing role in health care beyond basic research: it will help guide the delivery of care to patients. POI is a serious chronic disorder and syndrome characterized by hypergonadotrophic hypogonadism before the age of 40 years and most commonly presents with amenorrhea. It may have adverse health effects that become fully evident years after the initial diagnosis. The condition is most commonly viewed as one of infertility, however, it may also be associated with adverse long-term outcomes related to inadequate bone mineral density, increased risk of cardiovascular disease, adrenal insufficiency, hypothyroidism and, if pregnancy ensues, having a child with Fragile X Syndrome. There may also be adverse outcomes related to increased rates of anxiety and depression. POI is also a rare disease, and accordingly, presents special challenges. Too often advances in research are not effectively integrated into community care at the point of service for those with rare diseases. There is a need to connect community health providers in real time with investigators who have the requisite knowledge and expertise to help manage the rare disease and to conduct ongoing research. Here we review the pathophysiology and management of POI and propose the development of an international Clinical Research Integration Special Program (CRISP) for the condition.

A ballistic quantum ring Josephson interferometer.

We report the realization of a ballistic Josephson interferometer. The interferometer is made from a quantum ring etched in a nanofabricated two-dimensional electron gas confined in an InAs-based heterostructure laterally contacted to superconducting niobium leads. The Josephson current flowing through the structure shows oscillations with h/e flux periodicity when threading the loop with a perpendicular magnetic field. This periodicity, in sharp contrast with the h/2e one observed in conventional dc superconducting quantum interference devices, confirms the ballistic nature of the device in agreement with theoretical predictions. This system paves the way for the implementation of interferometric Josephson π-junctions, and for the investigation of Majorana fermions.

Graphene field-effect transistors as room-temperature terahertz detectors.

The unique optoelectronic properties of graphene make it an ideal platform for a variety of photonic applications, including fast photodetectors, transparent electrodes in displays and photovoltaic modules, optical modulators, plasmonic devices, microcavities, and ultra-fast lasers. Owing to its high carrier mobility, gapless spectrum and frequency-independent absorption, graphene is a very promising material for the development of detectors and modulators operating in the terahertz region of the electromagnetic spectrum (wavelengths in the hundreds of micrometres), still severely lacking in terms of solid-state devices. Here we demonstrate terahertz detectors based on antenna-coupled graphene field-effect transistors. These exploit the nonlinear response to the oscillating radiation field at the gate electrode, with contributions of thermoelectric and photoconductive origin. We demonstrate room temperature operation at 0.3 THz, showing that our devices can already be used in realistic settings, enabling large-area, fast imaging of macroscopic samples.

About muscle insertions in man (Proposal for a new nomenclature of striated muscle).

Some plastic surgeons are limited in their technical knowledge on the mimetic muscle and conversely appear to vindicate a distinct priority in the problem of surgical rejuvenation, or, in general, in the effects of ageing, always involving the mimetic muscles included in the skin. Anatomists have worked better in research on mimetic muscles that we would like to indicate as not inserted, free to move in a different way from that of inserted or semi-inserted. Otolaryngologists and maxillo-facial surgeons, in the practice of surgery on the salivary glands, seem to have studied mimetic muscles before and in more detailed manner than plastic surgeons.

Two-dimensional Mott-Hubbard electrons in an artificial honeycomb lattice.

Artificial crystal lattices can be used to tune repulsive Coulomb interactions between electrons. We trapped electrons, confined as a two-dimensional gas in a gallium arsenide quantum well, in a nanofabricated lattice with honeycomb geometry. We probed the excitation spectrum in a magnetic field, identifying collective modes that emerged from the Coulomb interaction in the artificial lattice, as predicted by the Mott-Hubbard model. These observations allow us to determine the Hubbard gap and suggest the existence of a Coulomb-driven ground state.

Influence of femoral stem geometry, material and extent of porous coating on bone ingrowth and atrophy in cementless total hip arthroplasty: an iterative finite element model.

This work presents a computational model for the concurrent study of bone remodelling and ingrowth around cementless femoral stems in total hip arthroplasty. It is assumed that biological fixation depends upon the magnitude of relative displacement at the bone-stem interface as well as an ongoing updating of interface conditions during the remodelling process. The remodelling model determines the distribution of bone density by producing the stiffest structure for a given set of biological conditions at the point of equilibrium in bone turnover. Changes in bone density and patterns of ingrowth are compared for different stem geometries, materials and lengths of surface coating. Patterns of bone ingrowth on the tapered stem were independent of extent of porous coating, while ingrowth varied with the length of coating on the cylindrical stem. This model integrates knowledge of under what mechanical conditions bone ingrowth occurs on prosthetic stem surfaces with remodelling behaviour over time.

Filling factor dependence of the fractional quantum Hall effect gap.

We directly measure the chemical potential jump in the low-temperature limit when the filling factor traverses the nu=1/3 and nu=2/5 fractional gaps in two-dimensional (2D) electron system in GaAs/AlGaAs single heterojunctions. In high magnetic fields B, both gaps are linear functions of B with slopes proportional to the inverse fraction denominator, 1/q. The fractional gaps close partially when the Fermi level lies outside. An empirical analysis indicates that the chemical potential jump for an ideal 2D electron system, in the highest accessible magnetic fields, is proportional to q(-1) B(1/2).

Direct measurements of fractional quantum Hall effect gaps.

We measure the chemical potential jump across the fractional gap in the low-temperature limit in the two-dimensional electron system of GaAs/AlGaAs single heterojunctions. In the fully spin-polarized regime, the gap for filling factor nu=1/3 increases linearly with the magnetic field and is coincident with that for nu=2/3, reflecting the electron-hole symmetry in the spin-split Landau level. In low magnetic fields, at the ground-state spin transition for nu=2/3, a correlated behavior of the nu=1/3 and nu=2/3 gaps is observed.

The optical visibility of graphene: interference colors of ultrathin graphite on SiO(2).

Monatomic layers of graphite are emerging as building blocks for novel optoelectronic devices. Experimental studies on a single graphite layer (graphene) are today possible since very thin graphite can be identified on a dielectric substrate using a normal optical microscope. We investigate the mechanism behind the strong visibility of graphite, and we discuss the importance of substrates and of the microscope objective used for the imaging.

Mechanical stimulation effects on functional end effectors in osteoblastic MG-63 cells.

Receptor activator of Nf-kappaB ligand (RANKL) and osteoprotegerin (OPG) have been implicated in bone metabolism. Specifically, the balance of these factors in conjunction with receptor activator of Nf-kappaB (RANK) is believed to be key in determining the rate of osteoclastogenesis and the net outcome of bone formation/resorption. While it is well accepted that mechanical loading in vivo affects bone formation/resorption and that alterations in the responsiveness of bone cells to mechanical loading have been implicated in metabolic bone diseases, the effect of in vitro mechanical loading on osteoblastic production of OPG and RANKL has not been extensively studied. Thus, in the current study, we developed an in vitro model to load human osteoblasts and studied levels of OPG, RANKL, PGE(2) and macrophage colony stimulating factor (M-CSF). We hypothesized that stimulating osteoblastic cells would increase the release of soluble OPG relative to RANKL favoring a bone-forming (and resorption-inhibiting) event. To accomplish this, we developed a small-scale loading machine that imparts via bending, well-defined substrate deformation to bone cells cultured on artificial substrates. Following 2h of loading and a 1h incubation period, media was collected and levels of soluble OPG, RANKL, PGE(2) and M-CSF were quantified using ELISA and western blotting. We found that mechanical loading significantly increased soluble OPG levels relative to RANKL at this 3h time point. Levels of soluble and cellular RANKL detected were not significantly affected by mechanical stimulation. The relative shift in abundance of OPG over RANKL associated with applied mechanical stimulation suggests the soluble OPG:RANKL ratio may be important in load-induced coupling mechanisms of bone cells.

Selective fluorescence recovery after bleaching of single E2GFP proteins induced by two-photon excitation.

We report the two-photon excitation and emission or a recently developed green fluorescent protein (GFP) mutant, E(2)GFP. Two main excitation bands are found at 780 and 870 nm. Blinking and irreversible and reversible bleaching were observed. Fluorescence blinking occurs in the millisecond range and has been ascribed to conversions between the neutral, anionic and dark zwitterionic states. Bleaching is observed after approximately 10 to 400 ms depending on the excitation power, and it is probably due to a conversion to a dark state. The striking feature of this GFP mutant is that the fluorescence can be recovered with very high efficiency only upon irradiation at 720 +/- 10 nm. This GFP mutant therefore seems promising as an almost permanent chromophore for two-photon excitation (TPE) microscopy or for applications in single-molecule memory arrays.

Multiphoton switching dynamics of single green fluorescent proteins.

Multi-photon driven photo-switching between dark and bright (fluorescent) states of a green fluorescent protein (GFP) mutant is demonstrated. A single-protein investigation shows the existence of two distinct bright states that display sharp two-photon cross-section bands peaked at 780 nm and at 870 nm. Fluorescence of these two species can be independently switched on and off. These results highlight a new photoconversion pathway for photochromic GFPs and can have significant applications in multi-photon confocal microscopy and in optical data-storage architectures.