Cyclooxygenase inhibition does not blunt thermal hyperemia in skeletal muscle of humans.

Acute heat exposure increases skeletal muscle blood flow in humans. However, the mechanisms mediating this hyperemic response remain unknown. The cyclooxygenase pathway is active in skeletal muscle, is heat sensitive, and contributes to cutaneous thermal hyperemia in young healthy humans. Therefore, the purpose of this study was to test the hypothesis that cyclooxygenase inhibition would attenuate blood flow in the vastus lateralis muscle during localized heating. Twelve participants (6 women) were studied on two separate occasions: 1) time control (i.e., no ibuprofen); and 2) ingestion of 800 mg ibuprofen, a nonselective cyclooxygenase inhibitor. Experiments were randomized, counter-balanced, and separated by at least 10 days. Pulsed short-wave diathermy was used to induce unilateral deep heating of the vastus lateralis for 90 min, whereas the contralateral leg served as a thermoneutral control. Microdialysis was utilized to bypass the cutaneous circulation and directly measure local blood flow in the vastus lateralis muscle of each leg via the ethanol washout technique. Heat exposure increased muscle temperature and local blood flow (both P < 0.01 vs. baseline). However, the thermal hyperemic response did not differ between control and ibuprofen conditions (P ≥ 0.2). Muscle temperature slightly decreased for the thermoneutral leg (P < 0.01 vs. baseline), yet local blood flow remained relatively unchanged across time for control and ibuprofen conditions (both P ≥ 0.7). Taken together, our data suggest that inhibition of cyclooxygenase-derived vasodilator prostanoids does not blunt thermal hyperemia in skeletal muscle of young healthy humans.NEW & NOTEWORTHY Acute heat exposure increases skeletal muscle blood flow in humans. However, the mechanisms mediating this hyperemic response remain unknown. Using a pharmacological approach combined with microdialysis, we found that thermal hyperemia in the vastus lateralis muscle was well maintained despite the successful inhibition of cyclooxygenase. Our results suggest that cyclooxygenase-derived vasodilator prostanoids do not contribute to thermal hyperemia in skeletal muscle of young healthy humans.

Neurophysiologic monitoring during cervical traction in a pediatric patient with severe cognitive disability and atlantoaxial instability.

Background: Surgical management of atlantoaxial instability (AAI) in pediatric patients with Down syndrome is associated with high neurological morbidity. Moreover, Down syndrome cognitive impairment coupled to AAI removes traditional verbal communication to relay evolving symptoms and aid in neurologic examination. It is not clear whether surgical adjuncts can alter clinical outcomes in this vulnerable population. Case Description: Herein, we report the case of a 6-year-old patient with significant developmental delay and severe AAI that was successfully managed by stabilization with guidance of neurophysiologic investigations in the perioperative phase. Conclusion: Perioperative neurophysiologic monitoring is safe, useful, and reliable in pediatric patients with trisomy 21 undergoing cervical traction and occipitocervical instrumented fusion for AAI.

Two-dimensional MoS2 2H, 1T, and 1T' crystalline phases with incorporated adatoms: theoretical investigation of electronic and optical properties.

Although there has been progress in studying the electronic and optical properties of monolayer and near-monolayer (two-dimensional, 2D) MoS2 upon adatom adsorption and intercalation, understanding the underlying atomic-level behavior is lacking, particularly as related to the optical response. Alkali atom intercalation in 2D transition metal dichalcogenides (TMDs) is relevant to chemical exfoliation methods that are expected to enable large scale production. In this work, focusing on prototypical 2D MoS2, the adsorption and intercalation of Li, Na, K, and Ca adatoms were investigated for the 2H, 1T, and 1T' phases of the TMD by the first principles density functional theory in comparison to experimental characterization of 2H and 1T 2D MoS2 films. Our electronic structure calculations demonstrate significant charge transfer, influencing work function reductions of 1-1.5 eV. Furthermore, electrical conductivity calculations confirm the semiconducting versus metallic behavior. Calculations of the optical spectra, including excitonic effects using a many-body theoretical approach, indicate enhancement of the optical transmission upon phase change. Encouragingly, this is corroborated, in part, by the experimental measurements for the 2H and 1T phases having semiconducting and metallic behavior, respectively, thus motivating further experimental exploration. Overall, our calculations emphasize the potential impact of synthesis-relevant adatom incorporation in 2D MoS2 on the electronic and optical responses that comprise important considerations toward the development of devices such as photodetectors or the miniaturization of electroabsorption modulator components.

Plenty of Room at the Top: A Multi-Scale Understanding of nm-Resolution Polymer Patterning on 2D Materials.

Lamellar phases of alkyldiacetylenes in which the alkyl chains lie parallel to the substrate represent a straightforward means for scalable 1-nm-resolution interfacial patterning. This capability has the potential for substantial impacts in nanoscale electronics, energy conversion, and biomaterials design. Polymerization is required to set the 1-nm functional patterns embedded in the monolayer, making it important to understand structure-function relationships for these on-surface reactions. Polymerization can be observed for certain monomers at the single-polymer scale using scanning probe microscopy. However, substantial restrictions on the systems that can be effectively characterized have limited utility. Here, using a new multi-scale approach, we identify a large, previously unreported difference in polymerization efficiency between the two most widely used commercial diynoic acids. We further identify a core design principle for maximizing polymerization efficiency in these on-surface reactions, generating a new monomer that also exhibits enhanced polymerization efficiency.

Oleylamine Impurities Regulate Temperature-Dependent Hierarchical Assembly of Ultranarrow Gold Nanowires on Biotemplated Interfaces.

Nanocrystals are often synthesized using technical grade reagents such as oleylamine (OLAm), which contains a blend of 9-cis-octadeceneamine with trans-unsaturated and saturated amines. Here, we show that gold nanowires (AuNWs) synthesized with OLAm ligands undergo thermal transitions in interfacial assembly (ribbon vs. nematic); transition temperatures vary widely with the batch of OLAm used for synthesis. Mass spectra reveal that higher-temperature AuNW assembly transitions are correlated with an increased abundance of trans and saturated chains in certain blends. DSC thermograms show that both pure (synthesized) and technical-grade OLAm have primary melting transitions near -5 °C (20-30 °C lower than the literature melting temperature range of OLAm). A second, broader melting transition (in the previous reported melting range) appears in technical grade blends; its temperature varies with the abundance of trans and saturated chains. Our findings illustrate that, similar to biological membranes, blends of alkyl chains can be used to generate mesoscopic hierarchical nanocrystal assembly, particularly at interfaces that further modulate transition temperatures.

One Nanometer Wide Functional Patterns with a Sub-10 Nanometer Pitch Transferred to an Amorphous Elastomeric Material.

Decades of work in surface science have established the ability to functionalize clean inorganic surfaces with sub-nm precision, but for many applications, it would be useful to provide similar control over the surface chemistry of amorphous materials such as elastomers. Here, we show that striped monolayers of diyne amphiphiles, assembled on graphite and photopolymerized, can be covalently transferred to polydimethylsiloxane (PDMS), an elastomer common in applications including microfluidics, soft robotics, wearable electronics, and cell culture. This process creates precision polymer films <1 nm thick, with 1 nm wide functional patterns, which control interfacial wetting and reactivity, and template adsorption of flexible, ultranarrow Au nanowires. The polydiacetylenes exhibit polarized fluorescence emission, revealing polymer location, orientation, and environment, and resist engulfment, a common problem in PDMS functionalization. These findings illustrate a route for patterning surface chemistry below the length scale of heterogeneity in an amorphous material.

Nonsurgical Management of Combined Occipitocervical and Atlantoaxial Distraction Injuries: A Case Report.

CASE: A 41-year-old man sustained occipitocervical dislocation (OCD) and atlantoaxial dislocation (AAD) injuries in a motor vehicle collision. These injuries were treated nonoperatively with a hard cervical collar and activity restrictions with an excellent result at 4-year follow-up. CONCLUSION: OCD and AAD injuries require prompt diagnosis and immobilization. Standard of care for coexisting injuries is occipitocervical fusion; however, some patients have coexisting injuries which may prevent operative treatment. These polytrauma patients require a creative nonoperative approach with close follow-up to avoid neurologic decline.

Enhanced charge separation in TiO2/nanocarbon hybrid photocatalysts through coupling with short carbon nanotubes.

The interfacial contact between TiO2 and graphitic carbon in a hybrid composite plays a critical role in electron transfer behavior, and in turn, its photocatalytic efficiency. Herein, we report a new approach for improving the interfacial contact and delaying charge carrier recombination in the hybrid by wrapping short single-wall carbon nanotubes (SWCNTs) on TiO2 particles (100 nm) via a hydration-condensation technique. Short SWCNTs with an average length of 125 ± 90 nm were obtained from an ultrasonication-assisted cutting process of pristine SWCNTs (1-3 µm in length). In comparison to conventional TiO2-SWCNT composites synthesized from long SWCNTs (1.2 ± 0.7 µm), TiO2 wrapped with short SWCNTs showed longer lifetimes of photogenerated electrons and holes, as well as a superior photocatalytic activity in the gas-phase degradation of acetaldehyde. In addition, upon comparison with a TiO2-nanographene "quasi-core-shell" structure, TiO2-short SWCNT structures offer better electron-capturing efficiency and slightly higher photocatalytic performance, revealing the impact of the dimensions of graphitic structures on the interfacial transfer of electrons and light penetration to TiO2. The engineering of the TiO2-SWCNT structure is expected to benefit photocatalytic degradation of other volatile organic compounds, and provide alternative pathways to further improve the efficiency of other carbon-based photocatalysts.

Thermodynamic Surface Analyses to Inform Biofilm Resistance.

Biofilms are the habitat of 95% of bacteria successfully protecting bacteria from many antibiotics. However, inhibiting biofilm formation is difficult in that it is a complex system involving the physical and chemical interaction of both substrate and bacteria. Focusing on the substrate surface and potential interactions with bacteria, we examined both physical and chemical properties of substrates coated with a series of phenyl acrylate monomer derivatives. Atomic force microscopy (AFM) showed smooth surfaces often approximating surgical grade steel. Induced biofilm growth of five separate bacteria on copolymer samples comprising varying concentrations of phenyl acrylate monomer derivatives evidenced differing degrees of biofilm resistance via optical microscopy. Using goniometric surface analyses, the van Oss-Chaudhury-Good equation was solved linear algebraically to determine the surface energy profile of each polymerized phenyl acrylate monomer derivative, two bacteria, and collagen. Based on the microscopy and surface energy profiles, a thermodynamic explanation for biofilm resistance is posited.

Hierarchically patterned striped phases of polymerized lipids: toward controlled carbohydrate presentation at interfaces.

Complex biomolecules, including carbohydrates, frequently have molecular surface footprints larger than those in broadly utilized standing phase alkanethiol self-assembled monolayers, yet would benefit from structured orientation and clustering interactions promoted by ordered monolayer lattices. Striped phase monolayers, in which alkyl chains extend across the substrate, have larger, more complex lattices: nm-wide stripes of headgroups with 0.5 or 1 nm lateral periodicity along the row, separated by wider (∼5 nm) stripes of exposed alkyl chains. These anisotropic interfacial patterns provide a potential route to controlled clustering of complex functional groups such as carbohydrates. Although the monolayers are not covalently bound to the substrate, assembly of functional alkanes containing an internal diyne allows such monolayers to be photopolymerized, increasing robustness. Here, we demonstrate that, with appropriate modifications, microcontact printing can be used to generate well-defined microscopic areas of striped phases of both single-chain and dual-chain amphiphiles (phospholipids), including one (phosphoinositol) with a carbohydrate in the headgroup. This approach generates hierarchical molecular-scale and microscale interfacial clustering of functional ligands, prototyping a strategy of potential relevance for glycobiology.

Bright and Ultrafast Photoelectron Emission from Aligned Single-Wall Carbon Nanotubes through Multiphoton Exciton Resonance.

Ultrashort bunches of electrons, emitted from solid surfaces through excitation by ultrashort laser pulses, are an essential ingredient in advanced X-ray sources, and ultrafast electron diffraction and spectroscopy. Multiphoton photoemission using a noble metal as the photocathode material is typically used but more brightness is desired. Artificially structured metal photocathodes have been shown to enhance optical absorption via surface plasmon resonance but such an approach severely reduces the damage threshold in addition to requiring state-of-the-art facilities for photocathode fabrication. Here, we report ultrafast photoelectron emission from sidewalls of aligned single-wall carbon nanotubes. We utilized strong exciton resonances inherent in this prototypical one-dimensional material, and its excellent thermal conductivity and mechanical rigidity leading to a high damage threshold. We obtained unambiguous evidence for resonance-enhanced multiphoton photoemission processes with definite power-law behaviors. In addition, we observed strong polarization dependence and ultrashort photoelectron response time, both of which can be quantitatively explained by our model. These results firmly establish aligned single-wall carbon nanotube films as novel and promising ultrafast photocathode material.

Effect of Physical Parameters on Outcomes of Total Knee Arthroplasty.

BACKGROUND: Increasing body mass index (BMI) has been shown to correlate with increased rates of complications after total knee arthroplasty. To our knowledge, body surface area, body mass, and height have not been investigated in this manner. BMI and body surface area are affected differently by changes in height, and they are affected similarly by changes in weight. The purpose of this study was to quantify revision for any reason, mechanical failure, aseptic loosening, polyethylene wear, reoperation, and any infection after total knee arthroplasty using BMI, body surface area, body mass, and height as continuous variables. METHODS: Prospectively collected data from a single institution's total joint registry were used to analyze 22,243 consecutive knees, in 16,106 patients, treated with a primary total knee arthroplasty from 1985 to 2012. The Kaplan-Meier survival method was used to evaluate revision and other common complications, with outcomes assessed using Cox regression analysis. Smoothing spline parameterization was used on physical parameters in these models. RESULTS: Increasing BMI, body surface area, body mass, and height were associated with an increased risk of any revision surgical procedure, mechanical failure, and aseptic loosening after total knee arthroplasty. The risk of a revision surgical procedure was directly associated with each 1 standard deviation increase in BMI (hazard ratio [HR], 1.19; p < 0.01), body surface area (HR, 1.37; p < 0.01), body mass (HR, 1.30; p < 0.01), and height (HR, 1.22; p < 0.01). This association was especially demonstrated with revision for mechanical failure (BMI: HR, 1.15; p < 0.01; body surface area: HR, 1.35; p < 0.01; body mass: HR, 1.27; p < 0.01; and height: HR, 1.23; p < 0.01). The risk of failure in the subgroups of mechanical failure including a revision surgical procedure for aseptic loosening or polyethylene wear was also associated with increasing body surface area, body mass, and height. Increasing BMI (HR, 1.22; p < 0.01), body surface area (HR, 2.56; p < 0.01), and body mass (HR, 2.54; p < 0.01) were also associated with increased risk of any infection. CONCLUSIONS: Increasing BMI, body surface area, body mass, and height were strongly associated with the rates of revision, aseptic loosening, and other common complications following total knee arthroplasty. Body surface area and body mass appear to correlate more strongly with mechanical failure outcomes than BMI or height. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Spatially Controlled Noncovalent Functionalization of 2D Materials Based on Molecular Architecture.

Polymerizable amphiphiles can be assembled into lying-down phases on 2D materials such as graphite and graphene to create chemically orthogonal surface patterns at 5-10 nm scales, locally modulating functionality of the 2D basal plane. Functionalization can be carried out through Langmuir-Schaefer conversion, in which a subset of molecules is transferred out of a standing phase film on water onto the 2D substrate. Here, we leverage differences in molecular structure to spatially control transfer at both nanoscopic and microscopic scales. We compare transfer properties of five different single- and dual-chain amphiphiles, demonstrating that those with strong lateral interactions (e.g., hydrogen-bonding networks) exhibit the lowest transfer efficiencies. Since molecular structures also influence microscopic domain morphologies in Langmuir films, we show that it is possible to transfer such microscale patterns, taking advantage of variations in the local transfer rates based on the structural heterogeneity in Langmuir films. Nanoscale domain morphologies also vary in ways that are consistent with predicted relative transfer and diffusion rates. These results suggest strategies to tailor noncovalent functionalization of 2D substrates through controlled LS transfer.

Hierarchically Patterned Noncovalent Functionalization of 2D Materials by Controlled Langmuir-Schaefer Conversion.

Noncovalent monolayer chemistries are often used to functionalize 2D materials. Nanoscopic ligand ordering has been widely demonstrated (e.g., lying-down lamellar phases of functional alkanes); however, combining this control with micro- and macroscopic patterning for practical applications remains a significant challenge. A few reports have demonstrated that standing phase Langmuir films on water can be converted into nanoscopic lying-down molecular domains on 2D substrates (e.g., graphite), using horizontal dipping (Langmuir-Schaefer, LS, transfer). Molecular patterns are known to form at scales up to millimeters in Langmuir films, suggesting the possibility of transforming such structures into functional patterns on 2D materials. However, to our knowledge, this approach has not been investigated, and the rules governing LS conversion are not well understood. In part, this is because the conversion process is mechanistically very different from classic LS transfer of standing phases; challenges also arise due to the need to characterize structure in noncovalently adsorbed ligand layers <0.5 nm thick, at scales ranging from millimeters to nanometers. Here, we show that scanning electron microscopy enables diynoic acid lying-down phases to be imaged across this range of scales; using this structural information, we establish conditions for LS conversion to create hierarchical microscopic and nanoscopic functional patterns. Such control opens the door to tailoring noncovalent surface chemistry of 2D materials to pattern local interactions with the environment.

Ectopic expression of two AREB/ABF orthologs increases drought tolerance in cotton (Gossypium hirsutum).

Plants have evolved complex molecular, cellular and physiological mechanisms to respond to environmental stressors. Because of the inherent complexity of this response, genetic manipulation to substantially improve water deficit tolerance, particularly in agricultural crops, has been largely unsuccessful, as the improvements are frequently accompanied by slower growth and delayed reproduction. Here, we ectopically express two abiotic stress-responsive bZIP AREB/ABF transcription factor orthologs, Arabidopsis ABF3 and Gossypium hirsutum ABF2D, in G. hirsutum, to compare the effects of exogenous and endogenous AREB/ABF transgene overexpression on dehydration resilience. Our results show that ectopic expression of each of these orthologs increases dehydration resilience, although these increases are accompanied by slower growth. These phenotypic effects are proportional to the ectopic expression level in the GhABF2D transgenic plants, while the phenotypes of all of the AtABF3 transgenic plants are similar, largely independent of ectopic expression level, possibly indicating differential post-transcriptional regulation of these transgenes. Our results indicate that overexpression of exogenous and endogenous ABF homologs in G. hirsutum substantially increases drought resilience, primarily through stomatal regulation, negatively impacting transpiration and photosynthetic productivity.

Multimicrometer Noncovalent Monolayer Domains on Layered Materials through Thermally Controlled Langmuir-Schaefer Conversion for Noncovalent 2D Functionalization.

As functionalized 2D materials are incorporated into hybrid materials, ensuring large-area structural control in noncovalently adsorbed films becomes increasingly important. Noncovalent functionalization avoids disrupting electronic structure in 2D materials; however, relatively weak molecular interactions in such monolayers typically reduce stability toward solution processing and other common material handling conditions. Here, we find that controlling substrate temperature during Langmuir-Schaefer conversion of a standing phase monolayer of diynoic amphiphiles on water to a horizontally oriented monolayer on a 2D substrate routinely produces multimicrometer domains, at least an order of magnitude larger than those typically achieved through drop-casting. Following polymerization, these highly ordered monolayers retain their structures during vigorous washing with solvents including water, ethanol, tetrahydrofuran, and toluene. These findings point to a convenient and broadly applicable strategy for noncovalent functionalization of 2D materials in applications that require large-area structural control, for instance, to minimize desorption at defects during subsequent solution processing.

Risk Factors and Time to Recurrent Ipsilateral and Contralateral Patellar Dislocations.

BACKGROUND: Previous studies have reported variable rates of recurrent lateral patellar instability mainly because of limited cohort sizes. In addition, there is currently a lack of information on contralateral patellar instability. PURPOSE: To evaluate the rate of recurrent ipsilateral patellar dislocations and contralateral patellar dislocations after a first-time lateral patellar dislocation. Additionally, risk factors associated with recurrent dislocations (ipsilateral or contralateral) and time to recurrence were investigated. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: This population-based study included 584 patients with a first-time lateral patellar dislocation occurring between 1990 and 2010. A retrospective review was conducted to gather information about the injury, subsequent dislocations (ipsilateral or contralateral), and structural characteristics including trochlear dysplasia, patella alta, and tibial tubercle to trochlear groove (TT-TG) distance. Risk factors were assessed to delineate associations with subsequent dislocations and time to recurrence. RESULTS: At a mean follow-up of 12.4 years, 173 patients had ipsilateral recurrence, and 25 patients had a subsequent contralateral dislocation. At 20 years, the cumulative incidence of ipsilateral recurrence was 36.0%, while the cumulative incidence of contralateral dislocations was 5.4%. Trochlear dysplasia (odds ratio [OR], 18.1), patella alta (OR, 10.4), age <18 years at the time of the first dislocation (OR, 2.4), elevated TT-TG distance (OR, 2.1), and female sex (OR, 1.5) were associated with recurrent ipsilateral dislocations. Time to recurrence was significantly decreased in patients with trochlear dysplasia (23.0 months earlier time to recurrence; P < .001), elevated TT-TG distance (18.5 months; P < .001), patella alta (16.4 months; P = .001), and age <18 years at the time of the first dislocation (15.4 months; P < .001). Risk factors for subsequent contralateral dislocations included patella alta and trochlear dysplasia. CONCLUSION: At 20 years after a first-time lateral patellar dislocation, the cumulative incidence of recurrent ipsilateral patellar dislocations was 36.0%, compared with 5.4% for contralateral dislocations. Trochlear dysplasia, elevated TT-TG distance, patella alta, age <18 years at the time of the first dislocation, and female sex were associated with ipsilateral recurrence. Trochlear dysplasia, elevated TT-TG distance, patella alta, and age <18 years at the time of the first dislocation were predictive of a statistically significant decrease in time to recurrence.

Work function characterization of directionally solidified LaB6-VB2 eutectic.

With its low work function and high mechanical strength, the LaB6/VB2 eutectic system is an interesting candidate for high performance thermionic emitters. For the development of device applications, it is important to understand the origin, value, and spatial distribution of the work function in this system. Here we combine thermal emission electron microscopy and low energy electron microscopy with Auger electron spectroscopy and physical vapor deposition of the constituent elements to explore physical and chemical conditions governing the work function of these surfaces. Our results include the observation that work function is lower (and emission intensity is higher) on VB2 inclusions than on the LaB6 matrix. We also observe that the deposition of atomic monolayer doses of vanadium results in surprisingly significant lowering of the work function with values as low as 1.1eV.