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OBJECTIVES: To compare outcomes and complications between non-operative and operative management of femur and tibia fractures in patients with paraplegia or quadriplegia from chronic spinal cord injury (SCI). METHODS: Design: Retrospective cohort study. SETTING: Three Level-1 Trauma centers. PATIENT SELECTION CRITERIA: All adult patients with paraplegia or quadriplegia due to a chronic SCI with operative or nonoperative treatment of a femoral or tibial shaft fracture from 01/01/2009 through 12/31/2019 were included. OUTCOME MEASURES AND COMPARISONS: Outcomes collected included range of motion, pain, return to baseline activity, extent of malunion and treatment complications (infection, pressure ulcers, nonunion, DVT/PE, stroke, amputation, death). Comparison between operative and nonoperative treatment were made for each outcome. RESULTS: Fifty-nine patients with acute lower extremity fracture in the setting of chronic SCI fulfilled inclusion criteria with a median age of 46 years in the operative group and 47 years in the non-operative group. Twelve patients (70.6%) in the nonoperative group were male with 32 (76.2%) male patients in the operative group. Forty-six patients (78%) presented as low energy trauma. Differences were seen between operative and non-operative management for pressure ulcers (19% vs 52.9%, p=0.009) and mean VAS pain score at first follow-up (1.19 vs 3.3, p=0.03). No difference was seen for rates of infection, nonunion, DVT/PE, stroke, amputation, death, return to baseline activity, and range of motion. CONCLUSIONS: Tibial and femoral shaft fractures commonly resulted from low energy mechanisms in patients with chronic SCI. Operative treatment seemed to decrease morbidity in these patients via lowered rates of pressure ulcers and decreased pain compared to non-operative management. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
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Possessing excellent electronic properties and high chemical stability, semiconducting n-type two-dimensional (2D) tin dioxide (SnO2) nanosheets have been featured in sensing and electrocatalysis applications recently. Derived from non-layered crystal structures, 2D SnO2 has abundant unsaturated dangling bonds existing at the surface, providing interfacial activity. How the surface chemistry alters the electronic properties of 2D SnO2 nanomaterials remains unexplored. In this study, we synthesised ultra-thin 2D SnO2 nanosheets using a liquid metal (LM) touch printing technique and investigated experimentally and theoretically how the interactions of organic solvents composed of alkyl and hydroxyl groups with the surface of LM-derived 2D SnO2 modulate the electronic properties. It was found that alkane solvents can physically absorb onto the SnO2 surface with no impact on the material conductivity. Alcohol-based solvents on the other hand interact with the SnO2 surface via chemical absorptions primarily, in which oxygen atoms of hydroxyl groups in the alcohols form bonds with the surface atoms of SnO2. The binding stability is determined by the length and configuration of the hydrocarbon chain in alcohols. As representative long-chain alcohols, 1-octanol and 1-pentanol attach onto the SnO2 surface strongly, lowering the binding energy of Sn4+ and reducing the electron transfer ability of SnO2 nanosheets. Consequently, the electronic properties, i.e. conductivity and electronic mobility of SnO2 nanosheet-based electronic devices are decreased significantly.
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Two-dimensional (2D) materials are promising platforms for future nanoelectronic technologies as they provide the building blocks for atomically thin devices, including switches, amplifiers, and oscillators. When 2D materials are layered on top of each other, forming van der Waals heterostructures (vdWHs), they can provide unique properties not possessed by the individual layers. Here we consider the vdWHs HfS2/MoTe2, HfS2/WTe2, 1T-HfS2/WTe2, TiS2/WSe2, TiS2/ZnO, and TiSe2/WTe2 as potential Esaki (or tunnel) diodes that can be incorporated into electronic devices. In this work, the strongly constrained and appropriately normed (SCAN) meta-generalised-gradient approximation (meta-GGA) functional is employed for the structural properties, whereas the Heyd-Scuseria-Ernzerhof (HSE) functional is used for the electronic properties. We establish that the band alignments in these systems form broken-band heterojunctions. We show that the electronic properties of the systems can be effectively modulated by applying lateral strain or an external electric field. Importantly, we demonstrate that the band gap of the vdWHs can be widened by up to 0.65 eV by applying an electric force field of -1 to +1 eV Å-1. This work demonstrates a set of 6 vdWHs with properties suitable for application as 2D Esaki tunnel diodes, 4 of which could be applied as multifunctional devices. These materials not only offer new device properties, but their small dimensions allow for the creation of ultrathin devices.
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Polar metals are challenging to identify spectroscopically because the fingerprints of electric polarization are often obscured by the presence of screening charges. Here, we unravel unambiguous signatures of a distortive polar order buried in the Fermi sea by probing the nonlinear optical response of materials driven by tailored terahertz fields. We apply this strategy to investigate the topological crystalline insulator Pb1-xSnxTe, tracking its soft phonon mode in the time domain and observing the occurrence of inversion symmetry breaking as a function of temperature. By combining measurements across the material's phase diagram with ab initio calculations, we demonstrate the generality of our approach. These results highlight the potential of terahertz driving fields to reveal polar orders coexisting with itinerant electrons, thus opening additional avenues for material discovery.
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We present evidence of a strong circular photon drag effect (PDE) in topological insulators (TIs) through the observation of helicity-dependent topological photocurrents with threefold rotational symmetry using THz spectroscopy in epitaxially-grown Bi2Se3 with reduced crystallographic twinning. We establish how twinned domains introduce competing nonlinear optical (NLO) responses inherent to the crystal structure that obscure geometry-sensitive optical processes through the introduction of a spurious mirror symmetry. Minimizing the twinning defect reveals strong NLO response currents whose magnitude and direction depend on the alignment of the excitation to the crystal axes and follow the threefold rotational symmetry of the crystal. Notably, photocurrents arising from helical light reverse direction for left/right circular polarizations and maintain a strong azimuthal dependence-a result uniquely attributable to the circular PDE, where the photon momentum acts as an applied in-plane field stationary in the laboratory frame. Our results demonstrate new levels of control over the magnitude and direction of photocurrents in TIs and that the study of single-domain films is crucial to reveal hidden phenomena that couple topological order and crystal symmetries.
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Magnetic transition metal chalcogenides form an emerging platform for exploring spin-orbit driven Berry phase phenomena owing to the nontrivial interplay between topology and magnetism. Here we show that the anomalous Hall effect in pristine Cr2Te3 thin films manifests a unique temperature-dependent sign reversal at nonzero magnetization, resulting from the momentum-space Berry curvature as established by first-principles simulations. The sign change is strain tunable, enabled by the sharp and well-defined substrate/film interface in the quasi-two-dimensional Cr2Te3 epitaxial films, revealed by scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry. This Berry phase effect further introduces hump-shaped Hall peaks in pristine Cr2Te3 near the coercive field during the magnetization switching process, owing to the presence of strain-modulated magnetic layers/domains. The versatile interface tunability of Berry curvature in Cr2Te3 thin films offers new opportunities for topological electronics.
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Few-layer black phosphorus (FLBP), a technologically important 2D material, faces a major hurdle to consumer applications: spontaneous degradation under ambient conditions. Blocking the direct exposure of FLBP to the environment has remained the key strategy to enhance its stability, but this can also limit its utility. In this paper, a more ambitious approach to handling FLBP is reported where not only is FLBP oxidation blocked, but it is also repaired postoxidation. Our approach, inspired by nature, employs the antioxidant molecule ß-carotene that protects plants against photooxidative damages to act as a protecting and repairing agent for FLBP. The mechanistic role of ß-carotene is established by a suite of spectro-microscopy techniques, in combination with computational studies and biochemical assays. Transconductance studies on FLBP-based field effect transistor (FET) devices further affirm the protective and reparative effects of ß-carotene. The outcomes indicate the potential for deploying a plethora of natural antioxidant molecules to enhance the stability of other environmentally sensitive inorganic nanomaterials and expedite their translation for technological and consumer applications.
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Antioxidantes , beta Caroteno , beta Caroteno/química , Antioxidantes/farmacología , Fósforo/química , Oxidación-ReducciónRESUMEN
The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 min was expected if the incident momentum from the DART spacecraft was directly transferred to the asteroid target in a perfectly inelastic collision1, but studies of the probable impact conditions and asteroid properties indicated that a considerable momentum enhancement (ß) was possible2,3. In the years before impact, we used lightcurve observations to accurately determine the pre-impact orbit parameters of Dimorphos with respect to Didymos4-6. Here we report the change in the orbital period of Dimorphos as a result of the DART kinetic impact to be -33.0 ± 1.0 (3σ) min. Using new Earth-based lightcurve and radar observations, two independent approaches determined identical values for the change in the orbital period. This large orbit period change suggests that ejecta contributed a substantial amount of momentum to the asteroid beyond what the DART spacecraft carried.
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Since the early 2000s, sea ice has experienced an increased rate of decline in thickness, extent and age. This new regime, coined the 'New Arctic', is accompanied by a reshuffling of energy flows at the surface. Understanding of the magnitude and nature of this reshuffling and the feedbacks therein remains limited. A novel database is presented that combines satellite observations, model output, and reanalysis data with sea ice parcel drift tracks in a Lagrangian framework. This dataset consists of daily time series of sea ice parcel locations, sea ice and snow conditions, and atmospheric states, including remotely sensed surface energy budget terms. Additionally, flags indicate when sea ice parcels travel within cyclones, recording cyclone intensity and distance from the cyclone center. The quality of the ice parcel database was evaluated by comparison with sea ice mass balance buoys and correlations are high, which highlights the reliability of this database in capturing the seasonal changes and evolution of sea ice. This database has multiple applications for the scientific community; it can be used to study the processes that influence individual sea ice parcel time series, or to explore generalized summary statistics and trends across the Arctic.
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Novel therapeutics to manage bacterial infections are urgently needed as the impact and prevalence of antimicrobial resistance (AMR) grows. Antivirulence therapeutics are an alternative approach to antibiotics that aim to attenuate virulence rather than target bacterial essential functions, while minimizing microbiota perturbation and the risk of AMR development. Beyond known virulence factors, pathogen-associated genes (PAGs; genes found only in pathogens to date) may play an important role in virulence or host association. Many identified PAGs encode uncharacterized hypothetical proteins and represent an untapped wealth of novel drug targets. Here, we review current advances in antivirulence drug research and development, including PAG identification, and provide a comprehensive workflow from the discovery of antivirulence drug targets to drug discovery. We highlight the importance of integrating bioinformatic/genomic-based methods for novel virulence factor discovery, coupled with experimental characterization, into existing drug screening platforms to develop novel and effective antivirulence drugs.
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Antibacterianos , Factores de Virulencia , Humanos , Flujo de Trabajo , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Virulencia/genética , Factores de Virulencia/genética , Estudios de Asociación GenéticaRESUMEN
Two-dimensional (2D) ferroelectric materials are providing promising platforms for creating future nano- and opto-electronics. Here we propose new hybrid van der Waals heterostructures, in which the 2D ferroelectric material CuInP2S6(CIPS) is layered on a 2D semiconductor for near-infrared (NIR) memory device applications. Using density functional theory, we show that the band gap of the hybrid bilayers formed with CIPS can be tuned and that the optical and electronic properties can be successfully modulated via ferroelectric switching. Of the 3712 heterostructures considered, we identified 19 structures that have a type II band alignment and commensurate lattice matches. Of this set, both the CuInP2S6/PbSe and CuInP2S6/Ge2H2heterostructures possess absorption peaks in the NIR region that change position and intensity with switching polarisation, making them suitable for NIR memory devices. The CuInP2S6/ISSb, CuInP2S6/ISbSe, CuInP2S6/ClSbSe and CuInP2S6/ZnI2heterostructures had band gaps which can be switched from direct to indirect with changing the polarisation of CIPS making them suitable for optoelectronics and sensors. The heterostructures formed with CIPS are exciting candidates for stable ferroelectric devices, opening a pathway for tuning the band alignment of van der Waal heterostructures and the creation of modern memory applications that use less energy.
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While heterostructures are ubiquitous tools enabling new physics and device functionalities, the palette of available materials has never been richer. Combinations of two emerging material classes, two-dimensional materials and topological materials, are particularly promising because of the wide range of possible permutations that are easily accessible. Individually, both graphene and Pb1-xSnxTe (PST) are widely investigated for spintronic applications because graphene's high carrier mobility and PST's topologically protected surface states are attractive platforms for spin transport. Here, we combine monolayer graphene with PST and demonstrate a hybrid system with properties enhanced relative to the constituent parts. Using magnetotransport measurements, we find carrier mobilities up to 20â¯000 cm2/(V s) and a magnetoresistance approaching 100%, greater than either material prior to stacking. We also establish that there are two distinct transport channels and determine a lower bound on the spin relaxation time of 4.5 ps. The results can be explained using the polar catastrophe model, whereby a high mobility interface state results from a reconfiguration of charge due to a polar/nonpolar interface interaction. Our results suggest that proximity induced interface states with hybrid properties can be added to the still growing list of behaviors in these materials.
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The COVID-19 pandemic motivated research on antiviral filtration used in personal protective equipment and HVAC systems. In this research, three coating compositions of NaCl, Tween 20 surfactant, and NaCl-Tween 20 were examined on polypropylene spun-bond filters. The pressure drop, coverage, and crystal size of the coating methods and compositions were measured. Also, in vitro plaque assays of the Phi6 Bacteriophage on Pseudomonas syringae as a simulation of an enveloped respiratory virus was performed to investigate the antiviral properties of the coating. NaCl and NaCl-Tween 20 increased the pressure drop in the range of 40-50 Pa for a loading of 5 mg/cm2. Tween 20 has shown an impact on the pressure drop as low as 10 Pa and made the filter surface more hydrophilic which kept the virus droplets on the surface. The NaCl-Tween 20 coated samples could inactivate 108 plaque forming units (PFU) of virus in two hours of incubation. Tween 20 coated filters with loading as low as 0.2 mg/cm2 reduced the activity of 108 PFU of virus from 109 to 102 PFU/mL after 2 h of incubation. NaCl-coated samples with a salt loading of 15 mg/cm2 could not have antiviral properties higher than reducing the viral activity from 109 to 105 PFU/mL in 4 h of incubation.
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Antivirales , Polisorbatos , SARS-CoV-2 , Cloruro de Sodio , Tensoactivos , Antivirales/farmacología , Lipoproteínas , Polisorbatos/química , Polisorbatos/farmacología , Estudios Prospectivos , ARN Viral , SARS-CoV-2/efectos de los fármacos , Cloruro de Sodio/farmacología , Tensoactivos/química , Tensoactivos/farmacologíaRESUMEN
The ferroelectric material In2Se3 is currently of significant interest due to its built-in polarisation characteristics that can significantly modulate its electronic properties. Here we employ density functional theory to determine the transport characteristics at the metal-semiconductor interface of the two-dimensional multiferroic In2Se3/Fe3GeTe2 heterojunction. We show a significant tuning of the Schottky barrier height as a result of the change in the intrinsic polarisation state of In2Se3: the switching in the electric polarisation of In2Se3 results in the switching of the nature of the Schottky barrier, from being n-type to p-type, and is accompanied by a change in the spin polarisation of the electrons. This switchable Schottky barrier structure can form an essential component in a two-dimensional field effect transistor that can be operated by switching the ferroelectric polarisation, rather than by the application of strain or electric field. The band structure and density of state calculations show that Fe3GeTe2 lends its magnetic and metallic characteristics to the In2Se3 layer, making the In2Se3/Fe3GeTe2 heterojunction a potentially viable multiferroic candidate in nanoelectronic devices like field-effect transistors. Moreover, our findings reveal a transfer of charge carriers from the In2Se3 layer to the Fe3GeTe2 layer, resulting in the formation of an in-built electric field at the metal-semiconductor interface. Our work can substantially broaden the device potential of the In2Se3/Fe3GeTe2 heterojunction in future low-energy electronic devices.
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Antimicrobial resistance has rendered many conventional therapeutic measures, such as antibiotics, ineffective. This makes the treatment of infections from pathogenic micro-organisms a major growing health, social, and economic challenge. Recently, nanomaterials, including two-dimensional (2D) materials, have attracted scientific interest as potential antimicrobial agents. Many of these studies, however, rely on the input of activation energy and lack real-world utility. In this work, we present the broad-spectrum antimicrobial activity of few-layered black phosphorus (BP) at nanogram concentrations. This property arises from the unique ability of layered BP to produce reactive oxygen species, which we harness to create this unique functionality. BP is shown to be highly antimicrobial toward susceptible and resistant bacteria and fungal species. To establish cytotoxicity with mammalian cells, we showed that both L929 mouse and BJ-5TA human fibroblasts were metabolically unaffected by the presence of BP. Finally, we demonstrate the practical utility of this approach, whereby medically relevant surfaces are imparted with antimicrobial properties via functionalization with few-layer BP. Given the self-degrading properties of BP, this study demonstrates a viable and practical pathway for the deployment of novel low-dimensional materials as antimicrobial agents without compromising the composition or nature of the coated substrate.
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Antiinfecciosos/química , Antiinfecciosos/farmacología , Fósforo/química , Animales , Relación Dosis-Respuesta a Droga , Farmacorresistencia Bacteriana/efectos de los fármacos , Farmacorresistencia Fúngica/efectos de los fármacos , Humanos , RatonesRESUMEN
Brains demonstrate varying spatial scales of nested hierarchical clustering. Identifying the brain's neuronal cluster size to be presented as nodes in a network computation is critical to both neuroscience and artificial intelligence, as these define the cognitive blocks capable of building intelligent computation. Experiments support various forms and sizes of neural clustering, from handfuls of dendrites to thousands of neurons, and hint at their behavior. Here, we use computational simulations with a brain-derived fMRI network to show that not only do brain networks remain structurally self-similar across scales but also neuron-like signal integration functionality ("integrate and fire") is preserved at particular clustering scales. As such, we propose a coarse-graining of neuronal networks to ensemble-nodes, with multiple spikes making up its ensemble-spike and time re-scaling factor defining its ensemble-time step. This fractal-like spatiotemporal property, observed in both structure and function, permits strategic choice in bridging across experimental scales for computational modeling while also suggesting regulatory constraints on developmental and evolutionary "growth spurts" in brain size, as per punctuated equilibrium theories in evolutionary biology.
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Corteza Cerebelosa/citología , Simulación por Computador , Modelos Neurológicos , Red Nerviosa/citología , Neuronas/citología , HumanosRESUMEN
Vanadium pentoxide is the most important vanadium compound by being the precursor to most vanadium alloys. It also plays an essential role in the production of sulfuric acid as well as in metal-ion batteries and supercapacitors. In this paper, pulsed laser ablation in liquids is used to synthesize "naked" vanadium pentoxide nanostructures. The resulting particles take up "nearly-spherical" and "flower-like" morphologies, composed of α-V2O5 and ß-V2O5 crystalline phases. Even "naked", the nanostructures are stable in time with a zeta potential of -51 ± 7 mV. In order to maximize the production of vanadium pentoxide nanostructure, the optimal repetition rate was determined to be @ â¼6600 Hz when irradiating a pure vanadium target in DI-water. This corresponds to a cavitation bubble lifetime of around â¼0.15 ms. At that repetition rate, the production reached â¼10 ppm per minute of irradiation. Finally, from the characterization of the α-V2O5 and ß-V2O5 nanostructures, the surface energy of each phase has been carefully determined at 0.308 and 1.483 J cm-2, respectively. Consequently, the ß-phase was found to display a surface energy very close to platinum. The exciton Bohr radius has been determined at 3.5 ± 0.7 nm and 2.0 ± 0.6 nm for α-V2O5 and ß-V2O5 phases, respectively.
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Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that undergoes swarming motility in response to semisolid conditions with amino acids as a nitrogen source. With a genome encoding hundreds of potential intergenic small RNAs (sRNAs), P. aeruginosa can easily adapt to different conditions and stresses. We previously identified 20 sRNAs that were differentially expressed (DE) under swarming conditions. Here, these sRNAs were overexpressed in strain PAO1 and were subjected to an array of phenotypic screens. Overexpression of the PrrH sRNA resulted in decreased swimming motility, whereas a ΔprrH mutant had decreased cytotoxicity and increased pyoverdine production. Overexpression of the previously uncharacterized PA2952.1 sRNA resulted in decreased swarming and swimming motilities, increased gentamicin and tobramycin resistance under swarming conditions, and increased trimethoprim susceptibility. Transcriptome sequencing (RNA-Seq) and proteomic analysis were performed on the wild type (WT) overexpressing PA2952.1 compared to the empty vector control under swarming conditions, and these revealed the differential expression (absolute fold change [FC] ≥ 1.5) of 784 genes and the differential abundance (absolute FC ≥ 1.25) of 59 proteins. Among these were found 73 transcriptional regulators, two-component systems, and sigma and anti-sigma factors. Downstream effectors included downregulated pilus and flagellar genes, the upregulated efflux pump MexGHI-OpmD, and the upregulated arn operon. Genes involved in iron and zinc uptake were generally upregulated, and certain pyoverdine genes were upregulated. Overall, the sRNAs PA2952.1 and PrrH appeared to be involved in regulating virulence-related programs in P. aeruginosa, including iron acquisition and motility.IMPORTANCE Due to the rising incidence of multidrug-resistant (MDR) strains and the difficulty of eliminating P. aeruginosa infections, it is important to understand the regulatory mechanisms that allow this bacterium to adapt to and thrive under a variety of conditions. Small RNAs (sRNAs) are one regulatory mechanism that allows bacteria to change the amount of protein synthesized. In this study, we overexpressed 20 different sRNAs in order to investigate how this might affect different bacterial behaviors. We found that one of the sRNAs, PrrH, played a role in swimming motility and virulence phenotypes, indicating a potentially important role in clinical infections. Another sRNA, PA2952.1, affected other clinically relevant phenotypes, including motility and antibiotic resistance. RNA-Seq and proteomics of the strain overexpressing PA2952.1 revealed the differential expression of 784 genes and 59 proteins, with a total of 73 regulatory factors. This substantial dysregulation indicates an important role for the sRNA PA2952.1.
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Hierro/metabolismo , Pseudomonas aeruginosa/genética , ARN Bacteriano/fisiología , Virulencia , Proteínas Bacterianas/genética , Línea Celular , Supervivencia Celular , Genes Bacterianos , Humanos , Proteómica , Pseudomonas aeruginosa/patogenicidad , Pseudomonas aeruginosa/fisiología , Zinc/metabolismoRESUMEN
Model warming projections, forced by increasing greenhouse gases, have a large inter-model spread in both their geographical warming patterns and global mean values. The inter-model warming pattern spread (WPS) limits our ability to foresee the severity of regional impacts on nature and society. This paper focuses on uncovering the feedbacks responsible for the WPS. Here, we identify two dominant WPS modes whose global mean values also explain 98.7% of the global warming spread (GWS). We show that the ice-albedo feedback spread explains uncertainties in polar regions while the water vapor feedback spread explains uncertainties elsewhere. Other processes, including the cloud feedback, contribute less to the WPS as their spreads tend to cancel each other out in a model-dependent manner. Our findings suggest that the WPS and GWS could be significantly reduced by narrowing the inter-model spreads of ice-albedo and water vapor feedbacks, and better understanding the spatial coupling between feedbacks.
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Topological materials, such as the quintessential topological insulators in the Bi2X3 family (X = O, S, Se, Te), are extremely promising for beyond Moore's Law computing applications where alternative state variables and energy efficiency are prized. It is essential to understand how the topological nature of these materials changes with growth conditions and, more specifically, chalcogen content. In this study, we investigate the evolution of the magnetoresistance of Bi2TexSe3-x for varying chalcogen ratios and constant growth conditions as a function of both temperature and angle of applied field. The contribution of 2D and 3D weak antilocalization are investigated by utilizing the Tkachov-Hankiewicz model and Hakami-Larkin-Nagaoka models of magnetoconductance.