Impact of Age on the Occurrence of Vascular Complications in Patients Undergoing Anterior Lumbar Approach Surgery.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To investigate the impact of age on incidence of vascular complications in patients undergoing anterior lumbar approach surgery. SUMMARY OF BACKGROUND DATA: Anterior approach lumbar spinal surgery may facilitate use of intervertebral devices with larger endplate coverage and increased lordosis. Despite the advantages of this approach, risks related to vascular injury in older patients have been described in the literature. METHODS: In total, 751 consecutive patients with degenerative spinal pathology who underwent stand-alone anterior lumbar interbody fusion (ALIF), ALIF combined with posterior fusion and/or instrumentation (360), total disc replacement (TDR), or hybrid procedures (ALIF and TDR) were included. Data collected included general patient descriptive data, surgery details, intraoperative vascular injury, and post-operative vascular complications (deep vein thrombosis (DVT) and/or pulmonary embolism (PE)). Rates of vascular complications were compared across age groups. Additionally, the mean age of patients was compared between those with vs. without vascular complications. RESULTS: Overall mean age was 50.4 years (range 20-83 years). Mean estimated blood loss was 91.3 ml (range 10 to 2800 ml). A total of 15 patients, 2.0%, had vascular complications. There were 10 cases (1.3%) of intraoperative injury to iliac arteries or iliolumbar veins (mean blood loss was 721 mL and all were repaired intraoperatively). Postoperatively, 6 patients (0.8%) developed DVT and/or PE (one patient had both). With respect to age, there were no significant differences in rates of intra-operative, post-operative, or combined vascular complication rates across the age group (P>0.38). Additionally, there were no statistically significant differences in the mean ages of patients with vs. those without vascular complications (P>0.17). CONCLUSION: Overall incidence of vascular complications was 2.0%. No relationship between vascular complications and age was demonstrated. These data suggest that increased age may not necessarily be an absolute contraindication for anterior lumbar approach surgery.

Improvement of the anthropogenic emission rate estimate in Ulaanbaatar, Mongolia, for 2020-21 winter.

Ulaanbaatar (UB), the fast-growing capital of Mongolia, is known for its world's worst level of particulate matter (PM) concentrations in winter. However, current anthropogenic emission inventories over the UB are based on data from more than fifteen years ago, and satellite observations are scarce because UB is in high latitudes. During the winter of 2020-21, the first period of the Fine Particle Research Initiative in East Asia considering the National Differences (FRIEND), several times higher concentrations of PM in UB compared to other urban sites in East Asia were observed but not reproduced with a chemical transport model mainly due to the underestimated anthropogenic emissions. Therefore, we devised a method for sequentially adjusting emissions based on the reactivity of PM precursors using ground observations. We scaled emission rates for the inert species (CO, elemental carbon (EC), and organic carbon (OC)) to reproduce their observed ambient concentrations, followed by SO2 to reproduce the concentration of SO42-, which was examined to have the least uncertainty based on the abundance of observed NH3, and finally NO and NH3 for NO3-, and NH4+. This improved estimation is compared to regional inventories for Asia and suggests more than an order of magnitude increase in anthropogenic emissions in UB. Using the improved emission inventory, we were able to successfully reproduce independent observation data on PM2.5 concentrations in UB in December 2021 from the U.S. Embassy. During the campaign period, we found more than 50% of the SO42-, NO3-, and NH4+ increased in UB due to the improvement could travel to Beijing, China (BJ), and about 20% of the SO42- could travel to Noto, Japan (NT), more than 3000 km away. Also, the anthropogenic emissions in UB can effectively increase OC, NO3-, and NH4+ concentrations in BJ when Gobi dust storms occur.

Effects of volatile organic compounds and new particle formation on real-time hygroscopicity of PM2.5 particles in Seosan, Republic of Korea.

The hygroscopicity of PM2.5 particles plays an important role in PM2.5 haze in Northeast Asian countries by influencing particle growth and chemical composition. New particle formation (NPF) and atmospheric volatile organic compounds (VOCs) are factors that influence particle hygroscopicity. However, the lack of real-time hygroscopicity measurements has deterred the understanding of their effects on particle hygroscopicity. In this study, two intensive monitoring campaigns were conducted during the summer of 2021 and spring of 2022 using real-time aerosol instruments, including a humidified tandem differential mobility analyzer (HTDMA), in Seosan, Republic of Korea. The hygroscopicity parameter κ was calculated from the real-time HTDMA measurement data (κGf). The diurnal variations in κGf exhibited strong inverse linear correlations with the total concentration of VOCs (CTVOC) during the two campaigns. The higher atmospheric CTVOC in summer increased the growth rate of the particle diameter from 10 to 40 nm (6 nm/h) compared with that in spring (2.7 nm/h), resulting in a faster change in κGf for 40-nm particles in summer than in spring because of the increase in organic matter in the chemical compositions of particles. In addition, NPF events introduced additional tiny fresh particles into the atmosphere, which reduced the κGf of 40-nm particles and increased the intensity of the less hygroscopic peaks (κGf < 0.1) of κ-probability density functions (κ-PDF) in NPF days. However, 100-nm particles exhibited fewer changes in κGf than 40-nm particles, resulting in additional dominant hygroscopic peaks (κ âˆ¼ 0.2) of κ-PDFs in both NPF and non-NPF days. When κGf values measured in Seosan were compared with those in other Northeast Asian countries in the literature, the κ values for 40-nm particles were lower than those (κ > 0.2) measured in Beijing and Guangzhou, but those for 100-nm particles were close to those measured in the two cities.

The Effect of High-Normal Preoperative International Normalized Ratios on Outcomes and Complications After Anterior Cervical Spine Surgery.

Hematoma after anterior cervical spine surgery can result in neurologic and airway compromise. Current guidelines recommend an international normalized ratio (INR) <1.5 before elective spine surgery because of increased complications. The risk associated with an INR of 1.25 is not well studied. The purpose of this study was to determine the risk of complications associated with a preoperative INR >1.25 and ≤1.5 in patients undergoing elective anterior cervical spine surgery. The American College of Surgeons National Surgical Quality Improvement Program database was queried. Patients undergoing elective anterior cervical spine surgery from 2012 to 2016 who had an INR recorded within 24 hours of surgery were included. Outcomes of interest included postoperative hematoma requiring surgery, 30-day mortality, and 30-day readmissions and reoperations. A total of 2949 patients were included. The incidence of a postoperative hematoma that required surgical management was 0.2%, 0.6%, and 4.5% in the INR≤1, 11.25 and ≤1.5 before elective anterior cervical spine surgery is associated with significantly higher rates of postoperative hematoma formation as well as 30-day readmission and reoperation; there was a trend toward significance in mortality rate. [Orthopedics. 2024;47(1):e26-e32.].

Characterization of chemoresistant human non-small cell lung cancer cells by metabolic and lipidomic profiling.

INTRODUCTION: Lung cancer is one of the most malignant cancers and the leading cause of cancer-related deaths worldwide, while acquired chemoresistance would represent a major problem in the treatment of non-small cell lung cancer (NSCLC) because of the reduced treatment effect and increased rates of recurrence. METHODS: To establish the chemoresistant NSCLC cells, doxorubicin was treated to A549 cells over 3 months at gradually increasing concentrations from 0.03 to 0.5 µM. Real-time PCR and Western blotting were employed for investigating mRNA and protein expression of the glutathione peroxidase (GPX) protein family and multidrug resistance protein 1 (MRP1) in A549 and A549/CR cells. We also employed gas chromatography mass-spectrometry and nano electrospray ionization mass-spectrometry coupled with multivariate statistical analysis to characterize the unique metabolic and lipidomic profiles of chemoresistant NSCLC cells in order to identify potential therapeutic targets. RESULTS: Reactive oxygen species levels were decreased, and mRNA and protein levels of GPX2 and multidrug resistance protein 1 (MRP1) were increased in A549/CR. We identified 87 metabolites and intact lipid species in A549 and A549/CR. Among these metabolites, lactic acid, glutamic acid, glycine, proline, aspartic acid, succinic acid, and ceramide, alongside the PC to PE ratio, and arachidonic acid-containing phospholipids were suggested as characteristic features of chemoresistant NSCLC cells (A549/CR). CONCLUSIONS: This study reveals characteristic feature differences between drug-resistance NSCLC cells and their parental cells. We suggest potential therapeutic targets in chemoresistant NSCLC. Our results provide new insight into metabolic and lipidomic alterations in chemoresistant NSCLC. This could be used as fundamental information to develop therapeutic strategies for the treatment of chemoresistant NSCLC patients.

YouTube as a source of information on pediatric scoliosis: a reliability and educational quality analysis.

PURPOSE: To assess the reliability and educational quality of YouTube videos related to pediatric scoliosis. METHODS: In December 2020, searches of "pediatric scoliosis", "idiopathic scoliosis", "scoliosis in children", and "curved spine in children" were conducted using YouTube. The first 50 results of each search were analyzed according to upload source and content. The Journal of the American Medical Association (JAMA) Benchmark Criteria were used to assess reliability (score 0-4), and educational quality was evaluated using the Global Quality Score (GQS; score 0-5) and Pediatric Scoliosis-Specific Score (PSS; score 0-15). Differences in scores based on upload source and content were determined by Analysis of Variance (ANOVA) or Kruskal-Wallis tests. Multivariate linear regressions identified any independent predictors of reliability and educational quality. RESULTS: After eliminating duplicates, 153 videos were analyzed. Videos were viewed 28.5 million times in total, averaging 186,160.3 ± 1,012,485.0 views per video. Physicians (54.2%) and medical sources (19.0%) were the most common upload sources, and content was primarily categorized as disease-specific (50.0%) and patient experience (25.5%). Videos uploaded by patients achieved significantly lower JAMA scores (p = 0.004). Conversely, academic or physician-uploaded videos scored higher on PSS (p = 0.003) and demonstrated a trend towards improved GQS (p = 0.051). Multivariate analysis determined longer video duration predicted higher scores on all measures. However, there were no independent associations between upload source or content and assessment scores. CONCLUSION: YouTube contains a large repository of videos concerning pediatric scoliosis; however, the reliability and educational quality of these videos were low. LEVEL OF EVIDENCE: V.

Prediction of Clinical Remission with Adalimumab Therapy in Patients with Ulcerative Colitis by Fourier Transform-Infrared Spectroscopy Coupled with Machine Learning Algorithms.

We aimed to develop prediction models for clinical remission associated with adalimumab treatment in patients with ulcerative colitis (UC) using Fourier transform-infrared (FT-IR) spectroscopy coupled with machine learning (ML) algorithms. This prospective, observational, multicenter study enrolled 62 UC patients and 30 healthy controls. The patients were treated with adalimumab for 56 weeks, and clinical remission was evaluated using the Mayo score. Baseline fecal samples were collected and analyzed using FT-IR spectroscopy. Various data preprocessing methods were applied, and prediction models were established by 10-fold cross-validation using various ML methods. Orthogonal partial least squares-discriminant analysis (OPLS-DA) showed a clear separation of healthy controls and UC patients, applying area normalization and Pareto scaling. OPLS-DA models predicting short- and long-term remission (8 and 56 weeks) yielded area-under-the-curve values of 0.76 and 0.75, respectively. Logistic regression and a nonlinear support vector machine were selected as the best prediction models for short- and long-term remission, respectively (accuracy of 0.99). In external validation, prediction models for short-term (logistic regression) and long-term (decision tree) remission performed well, with accuracy values of 0.73 and 0.82, respectively. This was the first study to develop prediction models for clinical remission associated with adalimumab treatment in UC patients by fecal analysis using FT-IR spectroscopy coupled with ML algorithms. Logistic regression, nonlinear support vector machines, and decision tree were suggested as the optimal prediction models for remission, and these were noninvasive, simple, inexpensive, and fast analyses that could be applied to personalized treatments.

End Group Functionality of 95-99%: Epoxide Functionalization of Polystyryl-Lithium Evaluated via Solvent Gradient Interaction Chromatography.

End group functionality is a key parameter of functional polymer chains. The end-capping efficiency of living polystyryl lithium with various epoxides, namely ethylene oxide (EO), ethoxy ethyl glycidyl ether (EEGE) and isopropylidene glyceryl glycidyl ether (IGG), is investigated with solvent gradient interaction chromatography (SGIC). Generally, end-capping efficiencies >95% are observed. Hydroxy functional polystyrene (PS-OH, PS-EEGE-OH, and PS-IGG-OH) with molar masses ranging from 13.8 to 15.0 kg mol-1 are obtained, with dispersities of 1.05-1.06. Deprotection of the acetal (PS-EEGE-OH) and ketal protective group (PS-IGG-OH) is investigated. Nearly quantitative deprotection (>99%) resulting in the corresponding multihydroxy functional PS (PS-(OH)2 and PS-(OH)3 ) are observed via SGIC. Esterification of PS-OH with succinic anhydride shows a conversion of 98% to the corresponding ester. A detailed picture of side reactions during the carbanionic polymer synthesis subsequent epoxide termination is obtained, demonstrating 95-99% terminal functionality. Depending on the polarity of the end group, an elution order of PS-OH < PS-(OH)2  < PS-(OH)3  < PS-COOH is obtained in SGIC. The study demonstrates both the analytical power of SGIC and the exceptionally high terminal functionalization efficiency of anionic polymerization methods.

Dysphagia May Attenuate Improvements in Postoperative Outcomes Following Anterior Cervical Discectomy and Fusion.

BACKGROUND: Past studies outline potential risk factors for dysphagia following anterior cervical discectomy and fusion (ACDF). Few studies explored the impact of dysphagia, as measured by the swallowing quality of life (SWAL-QOL), on postoperative patient-reported outcome measure (PROM) improvement. This study aimed to determine the relationship between dysphagia and improvement in pain, disability, physical function, and mental health following ACDF. METHODS: A retrospective review of patients undergoing primary 1- or 2-level ACDF was performed. Individuals without a completed preoperative SWAL-QOL were excluded. Outcomes were collected for visual analog scale (VAS) neck and arm pain, Neck Disability Index (NDI), Patient-Reported Outcome Measurement Information System Physical Function (PROMIS-PF), 12-Item Short Form Physical Component Score (SF-12 PCS), 9-Item Patient Health Questionnaire (PHQ-9), and SWAL-QOL. Postoperative improvement from preoperative values was evaluated using a paired t test. The impact of SWAL-QOL on each PROM was assessed using linear regression. RESULTS: A total of 91 patients were included. Mean preoperative SWAL-QoL was 90.4, which worsened at 6 weeks and resolved by 6 months (P ≤ 0.007, both). VAS neck and arm scores significantly improved postoperatively (P < 0.001), as did the NDI score (P < 0.001). Physical function significantly improved at 12 weeks and 6 months (P ≤ 0.021, both). Depressive symptoms improved at 6 weeks and 12 weeks (P ≤ 0.007, both). Preoperatively, SWAL-QOL demonstrated significant relationships with all PROMs (P ≤ 0.005, all). At 6 weeks, 12 weeks, and 6 months (P ≤ 0.048, all), SWAL-QoL again demonstrated a similar significant association with all PROMs. Multiple regression did not demonstrate common demographic or operative variables that were significant predictors of PROMs. CONCLUSION: Following ACDF, patients experienced a worsening of dysphagia but resolved by 12 weeks. All PROMs demonstrated significant improvements by the 6-month timepoint, except for PHQ-9. SWAL-QoL demonstrated a significant effect on all postoperative outcomes, which may suggest that this questionnaire could effectively evaluate dysphagia and predict positive or negative outcomes following ACDF. LEVEL OF EVIDENCE: 3 CLINICAL RELEVANCE: The severity of dysphagia has a significant association with pain, disability, mental health, and physical function patient-reported outcome measures in patients undergoing ACDF.

Microendoscopic Decompression for Lumbar Disc Herniations: An Analysis of Short and Long Term Patient Reported Outcome Measures.

INTRODUCTION: Endoscopic spine surgery is increasingly being used, and techniques, platforms, and applications are rapidly evolving. Despite substantial enthusiasm surrounding these techniques, there is a dearth of longer term patient-reported clinical outcomes. Within the United States in particular, there are yet to be reported large cohort studies with a notable follow-up. We sought to characterize the clinical outcomes of patients undergoing microendoscopic decompression (MED) for lumbar disk herniations. METHODS: The records of patients with symptomatic lumbar disk herniations who underwent MED from May 2018 to February 2021 within a single practice were reviewed. Paired outcomes scores were evaluated using Patient-Reported Outcomes Measurement Information System parameters. Basic perioperative data including length of stay, estimated blood loss, mean opioid use, complication rate, and rate of revision were tabulated. Paired sample Student t-tests and paired Wilcoxon sign tests were used to compare normally distributed and nonparametric data, respectively. RESULTS: Thirty-five patients with complete paired patient-reported outcome measures data and a minimum 6-month follow-up were included; 65.7% of the patients were male with a mean age of 47.1 years (SE 1.8). The mean follow-up was 590.6 days (SE 47.7). In total, 34 of the 35 patients (97.1%) were discharged on the day of their procedure. The estimated blood loss was <25 mL for each procedure. The mean opioid use after extubation and before discharge was 10.4 morphine milligram equivalents. At the 2-week follow-up, there were notable improvements in pain metrics and global health components. At the final follow-up, nearly all parameters showed notable improvement that exceeded minimally clinical important difference values. For most parameters, preoperative values outside of the "normal" range were within normal limits on postoperative testing. DISCUSSION: MED resulted in sustained notable improvement in patient-reported outcome measures that exceeded minimally clinical important difference values at the average follow-up approximating 2 years. These findings substantiate the utility of this technique and additional investment in endoscopic spine technology. DATA AVAILABILITY: Not publicly available; available upon request.

Field-scale investigation of nanoscale zero-valent iron (NZVI) injection parameters for enhanced delivery of NZVI particles to groundwater.

The effects of the injection parameters on delivery of nanoscale zero-valent iron (NZVI) to contaminated groundwater were investigated. The first two NZVI injections (gravity injection at low flow rates) resulted in NZVI being poorly mobile and gave total cumulative mass recoveries at the monitoring wells of 1.07%-2.43%. NZVI reached some wells (KDMW-3, MW-2, MW-4, and MW-7) earlier than the bromide tracer. The dominant travel directions for NZVI and the bromide tracer were very different. The NZVI transport characteristics suggested that targeted NZVI delivery requires preferential groundwater flow paths and local heterogeneity to be considered. In the gravity injection tests, the maximum NZVI concentrations and cumulative NZVI mass recoveries in the wells decreased markedly as the injected NZVI concentration and dose increased. In the third and fourth tests, in which NZVI was injected under pressure at high flow rates, NZVI was effectively delivered to the wells despite the injected NZVI concentration and dose being high. Relatively high cumulative mass recoveries of 26.0% and 74.5% were found for the third and fourth injections, respectively. Controlling the flow rate (pressure) and NZVI concentration and dose simply and effectively controlled NZVI mobility in the groundwater. The colloidal and electrostatic characteristics of the NZVI particles were monitored and modeled, and the results indicated that NZVI particles without Derjaguin-Landau-Verwey-Overbeek energy barriers were successfully delivered to the target zone and that decreased magnetic attractive forces between NZVI particles caused by iron corrosion probably decreased the degree of NZVI particle aggregation and therefore contributed to NZVI being delivered to the target zone.

Laboratory and field study on changes in water quality and increase in dissolved iron during riverbank filtration.

Changes in the water quality by the riverbank filtration (RBF) process were investigated in the field-scale demonstration sites. The overall water quality was improved by RBF, but Fe2+ concentration significantly increased in the riverbank-filtered water more than in the river water. This result would be caused by the interaction between the iron minerals and the river water in the aquifer and the influx of the hinterland groundwater into RBF wells. Dissolution properties of iron from the aquifer soils cored at the sites were evaluated through incubation experiment considering various values of redox potential (Eh), dissolved oxygen (DO), and hydrogen-ion concentration exponent (pH). These results presented that at the incubator with the final Eh of 470 mV, DO of 3.4, and pH of 4.53, the iron from the aquifer soil was most dissolved, and the pyrite and siderite contents in the aquifer soil decreased significantly from 11.5 to 6.22% and from 50.8 to 24.5%, respectively. Based on changes of ion concentrations (such as Fe2+, Fe3+, SO42- and NO3-) and iron species in the incubators, it was believed that pyrite and siderite minerals in the aquifer soils cause an increase in the Fe2+ concentration with the absence of DO and an increase in the Fe2+ and Fe3+ concentrations with the presence of DO. The dissolution rates of iron minerals into Fe2+ and Fe3+ were dependent on Eh, pH, and DO and were more sensitive to Eh and pH than DO. The results of this study can provide information on RBF site selection and its operation.

Thoracolumbar Spinal Cord Stimulator Trial: Procedural Technique.

Spinal cord stimulator trials are indicated for the treatment of postlaminectomy syndrome with persistent severe back and limb pain which has failed conservative treatment options and where no further surgery is indicated. They are also indicated for refractory complex regional pain syndrome. This article details patient positioning and set up, step-by-step instructions for the procedure and postoperative management. Pearls and pitfalls are also discussed. In addition, an instructional procedure video, Supplemental Digital Content 1 (http://links.lww.com/CLINSPINE/A121) accompanies this paper.

Nonlinear rheometry of entangled polymeric rings and ring-linear blends.

We present a comprehensive experimental rheological dataset for purified entangled ring polystyrenes and their blends with linear chains in nonlinear shear and elongation. In particular, data for shear stress growth coefficient, steady-state shear viscosity, and first and second normal stress differences are obtained and discussed as functions of shear rate as well as molecular parameters (molar mass, blend composition and decreasing molar mass of linear component in blend). Over the extended parameter range investigated, rings do not exhibit clear transient undershoot in shear, in contrast to their linear counterparts and ring-linear blends. For the latter, the size of the undershoot and respective strain appear to increase with shear rate. Universal scaling of strain at overshoot and fractional overshoot (ratio of maximum to steady-state shear stress growth coefficient) indicates subtle differences in the shear-rate dependence between rings and linear polymers or their blends. The shear thinning behaviour of pure rings yields a slope nearly identical to predictions (-4/7) of a recent shear slit model and molecular dynamics simulations. Data for the second normal stress difference are reported for rings and ring-linear blends. While N 2 is negative and its absolute value stays below that of N 1 , as for linear polymers, the ratio -N 2 /N 1 is unambiguously larger for rings compared to linear polymer solutions with the same number of entanglements (almost by factor of two), in agreement with recent non-equilibrium molecular dynamics simulations. Further, -N 2 exhibits slightly weaker shear rate dependence compared to N 1 at high rates, and the respective power-law exponents can be rationalized in view of the slit model (3/7) and simulations (0.6), although further work is needed to unravel the molecular original of the observed behaviour. The comparison of shear and elongational stress growth coefficients for blends reflects the effect of ring-linear threading which leads to significant viscosity enhancement in elongation. Along the same lines, the elongational stress is much larger than the first normal stress in shear, and their ratio is much larger for rings and ring-linear blends compared to linear polymers. This conforms the interlocking scenario of rings and their important role in mechanically reinforcing linear matrices.

A Comparison of Surgical Outcomes Between Minimally Invasive and Open Thoracolumbar Corpectomy.

BACKGROUND: Minimally invasive (MIS) techniques have gained considerable attention for the management of degenerative spinal pathologies. However, few studies have compared the outcomes between MIS and open thoracolumbar corpectomies. The purpose of this study was to compare perioperative variables between MIS and open thoracolumbar corpectomy. METHODS: Retrospective review of 33 patients who underwent either an MIS or open thoracolumbar corpectomy by a single surgeon between 2005 and 2012 was performed. Patients were separated into anterior-posterior MIS (MIS AP), anterior-posterior open (AP), and posterior open (P) cohorts. Postoperative narcotic use was converted to oral morphine equivalents (OMEs). Demographics, comorbidity, perioperative variables, complications, and computed tomographic analyses were assessed. Fisher exact test was performed for categorical variables and Student t test for continuous variables. A P value of ≤ .05 denoted statistical significance. RESULTS: Thirty-three patients underwent an MIS AP, AP, or P thoracolumbar corpectomy (39.4% vs 15.2% vs 45.5%, respectively). MIS AP patients were younger with a lower comorbidity burden than either open cohorts. In addition, MIS AP patients demonstrated a decreased procedural time, lower blood loss, and shorter hospitalization than either open cohorts. MIS AP patients required less units of transfusion than P and AP patients while demonstrating lower postoperative narcotics consumption and reoperations rates than open AP patients. Surgical site infection rates, body mass index, intraoperative fluid requirements, and complication rates were similar between cohorts. All patients demonstrated successful arthrodesis at 1 year based upon computed tomography. CONCLUSIONS: MIS AP thoracolumbar corpectomy patients incurred decreased procedural times, shorter hospitalization, and lower blood loss compared with open patients. MIS AP patients demonstrated decreased postoperative narcotics consumption and reoperation rates compared with traditional AP patients. All patients demonstrated successful arthrodesis. CLINICAL RELEVANCE: The MIS approach to thoracolumbar corpectomies appears to be a safe and efficacious alternative when compared with traditional methods.

Lumbar Radiofrequency Ablation: Procedural Technique.

Lumbar radiofrequency ablation is indicated for the treatment of chronic axial low back pain that is mediated by facet arthropathy which has failed more conservative treatment options. This article details proper equipment and medications, patient positioning and setup, step-by-step instructions for multiplanar fluoroscopic visualization, cannula placement, and postoperative management. Pearls and pitfalls are also discussed. In addition, an instructional procedure video (Supplemental Digital Content 1, http://links.lww.com/CLINSPINE/A90) accompanies this paper.

Stress relaxation in symmetric ring-linear polymer blends at low ring fractions.

We combine linear viscoelastic measurements and modelling in order to explore the dynamics of blends of the same-molecular-weight ring and linear polymers in the regime of the low volume fraction (0.3 or lower) of the ring component. The stress relaxation modulus is affected by the constraint release (CR) of both rings and linear components due to the motion of linear chains. We develop a CR-based model of ring-linear blends that predicts the stress relaxation function in the low fraction regime of ring component in excellent agreement with experiments. Rings trapped by their entanglements with linear chains can only relax by linear-chain-induced constraint release, resulting in much slower relaxation of rings than of linear chains. The relative viscosity η ( ϕ R * ) / η L of the blend with respect to the linear melt viscosity η L at ring overlap volume fraction ϕ R * increases proportionally to the square root of ring molecular weight M w , R . Our experimental results clearly demonstrate that it is possible to enhance the viscosity and simultaneously the structural relaxation time of linear polymer melts by adding a small fraction of ring polymers. These results not only provide fundamental insights into the physics of the CR process but also suggest ways to fine-tune the flow properties of linear polymers by means of adding rings.

Investigation of factors controlling PM2.5 variability across the South Korean Peninsula during KORUS-AQ.

The Korea - United States Air Quality Study (May - June 2016) deployed instrumented aircraft and ground-based measurements to elucidate causes of poor air quality related to high ozone and aerosol concentrations in South Korea. This work synthesizes data pertaining to aerosols (specifically, particulate matter with aerodynamic diameters <2.5 micrometers, PM2.5) and conditions leading to violations of South Korean air quality standards (24-hr mean PM2.5 < 35 µg m-3). PM2.5 variability from AirKorea monitors across South Korea is evaluated. Detailed data from the Seoul vicinity are used to interpret factors that contribute to elevated PM2.5. The interplay between meteorology and surface aerosols, contrasting synoptic-scale behavior vs. local influences, is presented. Transboundary transport from upwind sources, vertical mixing and containment of aerosols, and local production of secondary aerosols are discussed. Two meteorological periods are probed for drivers of elevated PM2.5. Clear, dry conditions, with limited transport (Stagnant period), promoted photochemical production of secondary organic aerosol from locally emitted precursors. Cloudy humid conditions fostered rapid heterogeneous secondary inorganic aerosol production from local and transported emissions (Transport/Haze period), likely driven by a positive feedback mechanism where water uptake by aerosols increased gas-to-particle partitioning that increased water uptake. Further, clouds reduced solar insolation, suppressing mixing, exacerbating PM2.5 accumulation in a shallow boundary layer. The combination of factors contributing to enhanced PM2.5 is challenging to model, complicating quantification of contributions to PM2.5 from local versus upwind precursors and production. We recommend co-locating additional continuous measurements at a few AirKorea sites across South Korea to help resolve this and other outstanding questions: carbon monoxide/carbon dioxide (transboundary transport tracer), boundary layer height (surface PM2.5 mixing depth), and aerosol composition with aerosol liquid water (meteorologically-dependent secondary production). These data would aid future research to refine emissions targets to further improve South Korean PM2.5 air quality.

Threading-Unthreading Transition of Linear-Ring Polymer Blends in Extensional Flow.

Adding small amounts of ring polymers to a matrix of their linear counterparts is known to increase the zero-shear-rate viscosity because of linear-ring threading. Uniaxial extensional rheology measurements show that, unlike its pure linear and ring constituents, the blend exhibits an overshoot in the stress growth coefficient. By combining these measurements with ex-situ small-angle neutron scattering and nonequilibrium molecular dynamics simulations, this overshoot is shown to be driven by a transient threading-unthreading transition of rings embedded within the linear entanglement network. Prior to unthreading, embedded rings deform affinely with the linear entanglement network and produce a measurably stronger elongation of the linear chains in the blend compared to the pure linear melt. Thus, rings uniquely alter the mechanisms of transient elongation in linear polymers.

Factors controlling surface ozone in the Seoul Metropolitan Area during the KORUS-AQ campaign.

To understand the characteristics of air quality in the Seoul Metropolitan Area, intensive measurements were conducted under the Korea-United States Air Quality (KORUS-AQ) campaign. Trace gases such as O3, NOx, NOy, SO2, CO, and volatile organic compounds (VOCs), photochemical byproducts such as H2O2 and HCHO, aerosol species, and meteorological variables including planetary boundary layer height were simultaneously measured at Olympic Park in Seoul. During the measurement period, high O3 episodes that exceeded the 90 ppbv hourly maximum occurred on 14 days under four distinct synoptic meteorological conditions. Furthermore, local circulation such as land-sea breeze and diurnal evolution of the boundary layer were crucial in determining the concentrations of precursor gases, including NOx and VOC as well as O3. During such episodes, the nighttime NOx and VOC and daytime UV levels were higher compared to non-episode days. The overall precursor levels and photochemical activity were represented fairly well by variations in the HCHO, which peaked in the morning during the high O3 episodes. This study revealed that toluene was the most abundant VOC in Seoul, and its concentration increased greatly with NOx due to the large local influence under stagnant conditions. When O3 was highly elevated concurrently with PM2.5 under dominant westerlies, NOx and VOCs were relatively lower and CO was noticeably higher than in other episodes. Additionally, the O3 production efficiency was the highest due to a low NOx with the highest NOz/NOy ratio among the four episodes. When westerlies were dominant in transport-south episode, the nighttime concentration of O 3 remained as high as 40~50 ppbv due to the minimum level of NOx titration. Overall, the Seoul Metropolitan Area is at NOx-saturated and VOC-limited conditions, which was diagnosed by indicator species and VOC/NOx ratios.