Size and Strain of Zinc Sulfide Nanoparticles Altered by Interaction with Organic Molecules.

Nanosized zinc sulfides (nano-ZnS) have size-dependent and tunable physical and chemical properties that make them useful for a variety of technological applications. For example, structural changes, especially caused by strain, are pronounced in nano-ZnS < 5 nm in size, the size range typical of incidental nano-ZnS that form in the environment. Previous research has shown how natural organic matter impacts the physical properties of nano-ZnS but was mostly focused on their aggregation state. However, the specific organic molecules and the type of functional groups that are most important for controlling the nano-ZnS size and strain remain unclear. This study examined the size-dependent strain of nano-ZnS synthesized in the presence of serine, cysteine, glutathione, histidine, and acetate. Synchrotron total scattering pair distribution function analysis was used to determine the average crystallite size and strain. Among the different organic molecules tested, those containing a thiol group were shown to affect the particle size and size-induced strain most strongly when added during synthesis but significantly reduced the particle strain when added to as-formed nano-ZnS. The same effects are useful to understand the properties and behavior of natural nano-ZnS formed as products of microbial activity, for example, in reducing environments, or of incidental nano-ZnS formed in organic wastes.

Copper (Cu) speciation in organic-waste (OW) amended soil: Instability of OW-borne Cu(I) sulfide and role of clay and iron oxide minerals.

The geochemistry of copper (Cu) is generally assumed to be controlled by organic matter in soils. However, the role of clay and iron oxide minerals may be understated. Soil density fractionation, X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS) were combined to assess the long-term behavior of Cu in an agricultural soil subject to organic waste application. Two unprecedented molecular environments of natural Cu (i.e. Cu inherited from the parent rock) in soils are reported: Cu dimer in the interlayer of vermiculite and Cu structurally incorporated within hematite. Moreover, the soil naturally containing Cu-vermiculite, Cu-hematite, but also Cu-kaolinite (Cutotal = 122 mg·kg-1) was amended over 11 years with Cu-rich pig slurry in which Cu was 100 % Cu(I) sulfide. Natural Cu associated with clay and iron oxide minerals persisted in the amended soil, but the exogenous Cu(I) sulfide was unstable. The increase in Cu concentration in the amended soil to 174 mg·kg-1 was accounted for the increase of Cu sorbed to kaolinite and Cu bound to organic matter. These results are important for better understanding the natural occurrence of Cu in soils and for assessing the environmental impacts of organic waste recycling in agricultural fields.

Novel FGF9 variant contributes to multiple synostoses syndrome 3.

Multiple synostoses syndromes (SYNS) are autosomal dominant syndromes characterized by multiple joint fusions commonly involving the carpal-tarsal, interphalangeal, humeroradial, and cervical spine joints. They display genetic heterogeneity with pathogenic variants reported in four separate genes (NOG, GDF5, FGF9, and GDF6) defining four different SYNS forms. FGF9 variants have been reported in SYNS3, a SYNS with multiple synostoses, normal cognition, normal hearing, and craniosynostosis. Here, we report a novel FGF9 c.569G > C p.(Arg190Thr) variant identified by whole-exome sequencing in a patient with multiple bony abnormalities. The patient initially presented with elbow instability and decreased range of motion. Imaging revealed bilateral radial head deformities, carpal-tarsal fusions, brachydactyly, and osteoarthritis of the sacroiliac joints. In silico protein modeling of the identified FGF9 variant predicts decreased stability of ligand-receptor binding supporting the pathogenicity of this finding. This finding expands the repertoire of FGF9 variants and phenotypic information reported for SYNS3 and suggest that genotype phenotype correlations due to localization seem less likely and more so due to the consequence of the pathogenic variant on the receptor. This is useful in the counseling in families as more de novo variants emerge.

Multi-scale X-ray computed tomography to detect and localize metal-based nanomaterials in lung tissues of in vivo exposed mice.

In this methodological study, we demonstrated the relevance of 3D imaging performed at various scales for the ex vivo detection and location of cerium oxide nanomaterials (CeO2-NMs) in mouse lung. X-ray micro-computed tomography (micro-CT) with a voxel size from 14 µm to 1 µm (micro-CT) was combined with X-ray nano-computed tomography with a voxel size of 63 nm (nano-CT). An optimized protocol was proposed to facilitate the sample preparation, to minimize the experimental artifacts and to optimize the contrast of soft tissues exposed to metal-based nanomaterials (NMs). 3D imaging of the NMs biodistribution in lung tissues was consolidated by combining a vast variety of techniques in a correlative approach: histological observations, 2D chemical mapping and speciation analysis were performed for an unambiguous detection of NMs. This original methodological approach was developed following a worst-case scenario of exposure, i.e. high dose of exposure with administration via intra-tracheal instillation. Results highlighted both (i) the non-uniform distribution of CeO2-NMs within the entire lung lobe (using large field-of-view micro-CT) and (ii) the detection of CeO2-NMs down to the individual cell scale, e.g. macrophage scale (using nano-CT with a voxel size of 63 nm).

Effect of field site hydrogeochemical conditions on the corrosion of milled zerovalent iron particles and their dechlorination efficiency.

Milled zerovalent iron (milled ZVI) particles have been recognized as a promising agent for groundwater remediation because of (1) their high reactivity with chlorinated aliphatic hydrocarbons, organochlorine pesticides, organic dyes, and a number of inorganic contaminants, and (2) a possible greater persistance than the more extensively investigated nanoscale zerovalent iron. We have used laboratory-scale batch degradation experiments to investigate the effect that hydrogeochemical conditions have on the corrosion of milled ZVI and on its ability to degrade trichloroethene (TCE). The observed pseudo first-order degradation rate constants indicated that the degradation of TCE by milled ZVI is affected by groundwater chemistry. The apparent corrosion rates of milled ZVI particles were of the same order of magnitude for hydrogeochemical conditions representative for two contaminated field sites (133-140mmolkg-1day-1, indicating a milled ZVI life-time of 128-135days). Sulfate enhances milled ZVI reactivity by removing passivating iron oxides and hydroxides from the Fe0 surface, thus increasing the number of reactive sites available. The organic matter content of 1.69% in the aquifer material tends to suppress the formation of iron corrosion precipitates. Results from scanning electron microscopy, X-ray diffraction, and iron K-edge X-ray adsorption spectroscopy suggest that the corrosion mechanisms involve the partial dissolution of particles followed by the formation and surface precipitation of magnetite and/or maghemite. Numerical corrosion modeling revealed that fitting iron corrosion rates and hydrogen inhibitory terms to hydrogen and pH measurements in batch reactors can reduce the life-time of milled ZVI particles by a factor of 1.2 to 1.7.

Virtual Reality Compared with Bench-Top Simulation in the Acquisition of Arthroscopic Skill: A Randomized Controlled Trial.

BACKGROUND: Work-hour restrictions as set forth by the Accreditation Council for Graduate Medical Education (ACGME) and other governing bodies have forced training programs to seek out new learning tools to accelerate acquisition of both medical skills and knowledge. As a result, competency-based training has become an important part of residency training. The purpose of this study was to directly compare arthroscopic skill acquisition in both high-fidelity and low-fidelity simulator models and to assess skill transfer from either modality to a cadaveric specimen, simulating intraoperative conditions. METHODS: Forty surgical novices (pre-clerkship-level medical students) voluntarily participated in this trial. Baseline demographic data, as well as data on arthroscopic knowledge and skill, were collected prior to training. Subjects were randomized to 5-week independent training sessions on a high-fidelity virtual reality arthroscopic simulator or on a bench-top arthroscopic setup, or to an untrained control group. Post-training, subjects were asked to perform a diagnostic arthroscopy on both simulators and in a simulated intraoperative environment on a cadaveric knee. A more difficult surprise task was also incorporated to evaluate skill transfer. Subjects were evaluated using the Global Rating Scale (GRS), the 14-point arthroscopic checklist, and a timer to determine procedural efficiency (time per task). Secondary outcomes focused on objective measures of virtual reality simulator motion analysis. RESULTS: Trainees on both simulators demonstrated a significant improvement (p < 0.05) in arthroscopic skills compared with baseline scores and untrained controls, both in and ex vivo. The virtual reality simulation group consistently outperformed the bench-top model group in the diagnostic arthroscopy crossover tests and in the simulated cadaveric setup. Furthermore, the virtual reality group demonstrated superior skill transfer in the surprise skill transfer task. CONCLUSIONS: Both high-fidelity and low-fidelity simulation trainings were effective in arthroscopic skill acquisition. High-fidelity virtual reality simulation was superior to bench-top simulation in the acquisition of arthroscopic skills, both in the laboratory and in vivo. Further clinical investigation is needed to interpret the importance of these results.

Surgeon-driven neurophysiologic monitoring in a spinal surgery population.

BACKGROUND: This is a prospective observational study examining the use of a surgeon-driven intraoperative neurophysiologic monitoring system. Intraoperative neurophysiologic monitoring is becoming the standard of care for spinal surgeries with potential post-operative neurologic deficits. This standard applies to both adult and pediatric spinal surgery, but a shortage of appropriately trained and certified technologists and physiologists can compromise monitoring capabilities in some centers. A surgeon-driven, intra-operative monitoring system in the absence of a technologist or physiologist was examined for safety and efficacy. METHODS: One hundred thirty-five patients undergoing a variety of spinal procedures were monitored intra-operatively using a surgeon-driven neuro-monitoring system over a period of 80 months. Intraoperative monitoring included serial motor evoked potentials via an automated system that provided visual and audible feedback directly to the operative surgeon. Changes in monitoring and any corresponding surgical responses were evaluated and compared with postoperative neurological status. RESULTS: Of the 135 patients studied, intraoperative adjustments based on neuro-monitoring took place in four patients (3.0%): following reduction in spondylolisthesis, during instrumentation and fusion for a large kyphoscoliosis deformity, due to low hemoglobin, and because of traction. In all cases, surgical and/or anaesthetic modification restored MEPs toward baseline values. The accuracy of the neuro-monitoring results was sensitive to narcotics, benzodiazepines and changes in haemoglobin concentrations. No new postoperative deficits were observed in any patients in the cohort. CONCLUSIONS: The authors concluded that surgeon-driven neuro-monitoring was a safe and effective means of intraoperative neuro-monitoring during spinal surgery. It reliably detected intraoperative insults, which could potentially have resulted in postoperative neurologic compromise, and was not associated with any false-negative results in this cohort. Utility of surgeon-driven monitoring, using validated algorithms, may provide an option for this added safety measure even in cases where monitoring personnel are unavailable.

Microbial and mineral evolution in zero valent iron-based permeable reactive barriers during long-term operations.

Impacts of subsurface biogeochemical processes over time have always been a concern for the long-term performance of zero valent iron (Fe(0))-based permeable reactive barriers (PRBs). To evaluate the biogeochemical impacts, laboratory experiments were performed using flow-through glass columns for 210 days at controlled temperature (20 °C). Two different particle sizes of Fe(0) were used in the columns, and to simulate indigenous microbial activity, extra carbon source was provided in the two columns (biotic columns) and the remaining two columns were kept abiotic using gamma radiations. Heavy metals (Zn, As) were removed efficiently in all the columns, and no exhaustion of treatment capability or clogging was observed during our experimental duration. Newly formed Fe mineral phases and precipitates were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and micro-XRF techniques in solid phase at the end of the experiment. In addition, 16S rRNA gene extraction was used for microbial community identification in biotic columns. During the incubation, microbial population shifted in favor of Desulfosporosinus species (sulfate-reducing bacteria) from initial dominance of Acidithiobacillus ferrooxidans in sediments. Dominant mineral phases detected in biotic columns were mackinawite (FeS) and sulfate green rust, while in abiotic columns, magnetite/maghemite phases were more prevalent.

Molecular insights of oxidation process of iron nanoparticles: spectroscopic, magnetic, and microscopic evidence.

Oxidation behavior of nano-Fe(0) particles in an anoxic environment was determined using different state-of-the-art analytical approaches, including high resolution transmission electron microscopy (HR-TEM) combined with energy filtered transmission electron microscopy (EFTEM), X-ray absorption spectroscopy (XAS), and magnetic measurements. Oxidation in controlled experiments was compared in standard double distilled (DD) water, DD water spiked with trichloroethene (TCE), and TCE contaminated site water. Using HR-TEM and EFTEM, we observed a surface oxide layer (∼3 nm) formed immediately after the particles were exposed to water. XAS analysis followed the dynamic change in total metallic iron concentration and iron oxide concentration for the experimental duration of 35 days. The metallic iron concentration in nano-Fe(0) particles exposed to water, was ∼40% after 35 days; in contrast, the samples containing TCE were reduced to ∼15% and even to nil in the case of TCE contaminated site water, suggesting that the contaminants enhance the oxidation of nano-Fe(0). Frequency dependence measurements confirmed the formation of superparamagnetic particles in the system. Overall, our results suggest that nano-Fe(0) oxidized via the Fe(0) - Fe(OH)2 - Fe3O4 - (γ-Fe2O3) route and the formation of superparamagnetic maghemite nanoparticles due to disruption of the surface oxide layer.

Implementation of a novel night float call system: resident satisfaction and quality of life.

BACKGROUND: Compliance with Professional Association of Internes and Residents of Ontario duty hour guidelines has been problematic at our institution. To facilitate orthopedic residents' ability to go home postcall without significant disruption of ongoing clinical activities, a novel call system was adopted at our tertiary care centre. We sought to evaluate the satisfaction and quality of life of orthopaedic residents with that system. METHODS: We administered questionnaires to on-service residents. These included the Short Form-36 questionnaire and others addressing topics including education, stress, work-related problems and miscellaneous concerns. RESULTS: Seventeen residents were surveyed: 6 who had just completed a night float rotation, and 11 who were on a regular orthopedic service rotation while the night float system was in place. Quality of life was similar between residents on the night float block and those on the standard rotation; it was also similar to age-matched Canadian normative data. Eighty-nine percent of residents agreed that the presence of the night float rotation improved their quality of life on standard rotations, and 100% felt that their education was improved on standard rotations by having the night float system in place. CONCLUSION: This call system results in improved resident quality of life and widespread overall satisfaction, and may be considered as a viable alternative to traditional call formats. Follow-up data as more residents experience the night float block will be valuable.

CONTEXTE: La conformité aux lignes directrices de l'Association professionnelle des résidents et internes de l'Ontario en matière d'horaires de travail pose un problème dans notre établissement. Pour permettre aux résidents en orthopédie de retourner plus facilement à la maison après un appel, sans nuire significativement aux activités cliniques en cours, notre établissement de soins tertiaires s'est doté d'un nouveau système d'appel. Nous avons voulu mesurer la satisfaction des résidents en orthopédie à l'endroit de ce système et évaluer leur qualité de vie. MÉTHODES: Nous avons administré des questionnaires aux résidents de garde, incluant le questionnaire SF-36 (Short Form-36) et d'autres questionnaires sur la formation, le stress, les problèmes liés au travail et diverses autres questions. RÉSULTATS: Dix-sept résidents ont répondu aux questionnaires : 6 venaient de terminer leur garde dans une équipe de nuit et 11 travaillaient selon l'horaire régulier de l'orthopédie pendant que le système de garde de nuit était en place. La qualité de vie a été similaire entre les résidents de l'équipe de garde de nuit et ceux qui suivaient l'horaire régulier; elle s'est également révélée similaire en comparaison avec des données canadiennes assorties selon l'âge. Quatre-vingt-neuf pour cent des résidents se sont dits d'avis que la présence de l'équipe de nuit améliorait leur qualité de vie lors de leurs gardes régulières et 100 % ont estimé que leur formation se trouvait améliorée lors des gardes régulières du fait que le système de garde de nuit était en place. CONCLUSION: Ce système d'appel entraîne une amélioration de la qualité de vie des résidents qui s'en disent globalement satisfaits et pourrait être considéré comme une solution de rechange viable aux types de gardes habituels. À mesure que d'autres résidents participeront à l'équipe de nuit, des données de suivi se révéleront utiles.

Spinal curvature measurement by tracked ultrasound snapshots.

Monitoring spinal curvature in adolescent kyphoscoliosis requires regular radiographic examinations; however, the applied ionizing radiation increases the risk of cancer. Ultrasound imaging is favored over radiography because it does not emit ionizing radiation. Therefore, we tested an ultrasound system for spinal curvature measurement, with the help of spatial tracking of the ultrasound transducer. Tracked ultrasound was used to localize vertebral transverse processes as landmarks along the spine to measure curvature angles. The method was tested in two scoliotic spine models by localizing the same landmarks using both ultrasound and radiographic imaging and comparing the angles obtained. A close correlation was found between tracked ultrasound and radiographic curvature measurements. Differences between results of the two methods were 1.27 ± 0.84° (average ± SD) in an adult model and 0.96 ± 0.87° in a pediatric model. Our results suggest that tracked ultrasound may become a more tolerable and more accessible alternative to radiographic spine monitoring in adolescent kyphoscoliosis.

Spinal needle navigation by tracked ultrasound snapshots.

PURPOSE: Ultrasound (US) guidance in facet joint injections has been reported previously as an alternative to imaging modalities with ionizing radiation. However, this technique has not been adopted in the clinical routine, due to difficulties in the visualization of the target joint in US and simultaneous manipulation of the needle. METHODS: We propose a technique to increase targeting accuracy and efficiency in facet joint injections. This is achieved by electromagnetically tracking the positions of the US transducer and the needle, and recording tracked US snapshots (TUSS). The needle is navigated using the acquired US snapshots. RESULTS: In cadaveric lamb model, the success rate of facet joint injections by five orthopedic surgery residents significantly increased from 44.4% with freehand US guidance to 93.3% with TUSS guidance. Needle insertion time significantly decreased from 47.9 ± 34.2 s to 36.1 ± 28.7 s (mean ± SD). In a synthetic human spine model, a success rate of 96.7% was achieved with TUSS. The targeting accuracy of the presented system in a gel phantom was 1.03 ± 0.48 mm (mean ± SD). CONCLUSION: Needle guidance with TUSS improves the success rate and time efficiency in spinal facet joint injections. This technique readily translates also to other spinal needle placement applications.