Northwestern University
  • Evanston, IL, United States
Recent publications
Introduction The Lancet Commission on Global Surgery indicators for monitoring anesthetic and surgical care allow the identification of access barriers, evaluate the safety of surgeries, facilitate planning, and assess changes over time. The primary objective was to measure these indicators in all health facilities of a Peruvian region in 2020. Methods This was an ambispective observational study to measure the anesthetic and surgical care indicators in Piura, a region in Peru, between January 2020 and June 2021. Public and private health facilities in the Piura region that performed surgical care or had specialists from any surgical specialty participated in the study. Data were collected from all regional health facilities that provided surgical care to estimate the density of surgical workforce. Likewise, the percentage of the population with access to an operating room within 2 h was estimated using georeferenced tools. Finally, a public database was accessed to determine the surgical volume, the percentage of the regional population protected with health insurance. Results In 2020, 88.4% of the inhabitants of this Peruvian region had access to timely essential surgery. There were 18.4 surgical specialists and 1174 surgeries per 100,000 populations, and 91% of the population had health insurance. In addition, there was a rate of 2.1 working operating rooms per 100,000 inhabitants in 2021. Conclusions This Peruvian region presented an increasing trend with respect to the population's access to essential and timely surgical care, and health insurance coverage. However, the workforce distribution was inequitable among the provinces of the region, the surgical volume was reduced, and timely access was hindered because of the SARS-CoV-2 pandemic.
Introduction Patients admitted to intensive care units (ICUs) have high rates of mortality and morbidity. Improved communication between providers within ICUs may reduce morbidity. The goal of this study is to leverage a natural experiment of the temporally staggered implementation of a smart phone application for interprofessional communication to quantify the association with postoperative mortality and morbidity among critically ill surgical patients. Methods We conducted an observational case-control study and utilized a difference-in-difference model to determine the impact of temporally staggered implementation of an interprofessional communication smart phone application on mortality, postoperative hyperglycemia, malnutrition, venous thromboembolism (VTE), and surgical site infections. Our study included patients who underwent surgical procedures and were admitted to the ICU at one of three hospitals (one academic medical center, hospital A, and two community hospitals, hospitals B and C) in a single health system between March 2018 and April 2021. Results Our cohort consisted of 1457 patients, of which 1174 were hospitalized at hospital A and 283 at hospitals B and C. In the full cohort, 80 (5.6%) patients died during ICU admission. Difference-in-difference analysis demonstrated a relative difference in mortality of 4.8% [1.1%-8.5%] (P = 0.04) at hospitals B and C compared to hospital A after the implementation of the application. Our model demonstrated a 2.5% difference in VTEs [1.1%-3.8%], P = 0.03. There were no significant reductions in hyperglycemia, malnutrition, or surgical site infection. Conclusions The implementation of an interprofessional communication smart phone application is associated with reduced mortality and VTE incidence among critically ill surgical patients across three diverse hospitals.
In this paper, we compare different methods to extract skill demand from the text of job descriptions. We propose the fraction of wage variation explained by the extracted skills as a novel performance metric for the comparison of methods. Using this, we compare the performance of the word-counting method with three different dictionaries and that of three unsupervised topic-modeling techniques, the LDA, the PLSA and the BERTopic. We apply these methods to a U.K. job board dataset of 1,158,926 job advertisements from 35 industries collected in 2018. We find that each of the dictionary-based methods explain about 20% of the wage variation across jobs. The topic modeling techniques perform better as the PLSA is able to explain 36.5% of the wage variation, while BERTopic 32.6%. The best performing method is the LDA with 48.3% of the wage variation explained. Its disadvantage, however, is in the difficulty of interpretation of the skills extracted.
Background Physical activity recovery after pediatric surgery can be assessed using objective measures such as step counts, but practice currently relies on subjective assessment by proxy. It is unclear how subjective and objective assessments of activity relate. We compared caregiver assessment of return to normal physical activity after pediatric appendectomy to step count recovery measured by a Fitbit. Methods Pediatric patients who underwent appendectomy were recruited between 2020 and 2022 to be monitored for 21 d with a Fitbit. Patients were grouped by the postoperative day (POD) (7, 14, or 21) their caregiver first reported their activity was “back to normal.” Objective return to normal step count was estimated for each group by modeling the inflection point from increasing steps to a plateau. These measures were determined discordant if the subjective report remained outside the modeled 95% confidence interval (CI) for the day the group plateaued. Results Thirty-nine simple appendicitis and 40 complicated appendicitis patients were recruited. Among simple appendicitis patients, daily steps plateaued on POD 10.8 (95% CI 7.4-14.3), POD 14.0 (95% CI 11.0-17.1), and POD 11.1 (95% CI 6.9-15.3) for the day 7, day 14, and day 21 groups, respectively. Complicated appendicitis groups plateaued on POD 12.8 (95% CI 8.7-16.9), POD 15.2 (95% CI 11.1-19.3), and POD 16.7 (95% CI 12.3-21.0), respectively. Significant discordance was observed between subjective and objective assessments for the day 7 and day 14 simple groups and for the day 7 complicated group. Conclusions There was significant discordance between caregiver and accelerometer-assessed activity recovery after pediatric surgery. Development of objective measures of recovery could help standardize assessment of children's recovery after surgery.
There is little question that new communication and transportation technologies have effectively “shrunk the world” for a great many activities. At the same time, the “death of distance” has been greatly exaggerated, especially in fields such as academic scholarship and knowledge development where the positive benefits of knowledge spillovers remain highly distance dependent. We analyze 17.6 million publications authored by 1.7 million scholars to examine how knowledge spillovers between scholars collaborating at different geographical distances impacts their future knowledge portfolios. Our results show that in 1975, scholars collaborating locally were 57 % more likely to learn from knowledge spillovers than similar scholars collaborating non-locally. We identify four factors that structure these findings. Individuals deriving the greatest learning premiums from local collaboration tend to be (1) in earlier stages of their career; (2) associated with lower-ranked institutions; (3) working with fewer collaborators; and (4) in STEM fields. The probability of learning drops with geographical distance and correspond to the number of institutional boundaries crossed during collaboration. We conclude that even in the 21st century, geographical distance still negatively impacts knowledge spillovers through collaboration. These findings have implications for debates in innovation and management studies concerning knowledge spillovers, the spatial organization of (knowledge-intensive) economic activity, regional innovation policies, structuring team-work and working-from-home vs. returning to office.
This study aimed to explore contemporary in-hospital outcomes and trends of transcatheter aortic valve implantation (TAVI) outcomes in patients with baseline right bundle branch block (RBBB) using data collected from a nationwide sample. Using the National Inpatient Sample, we identified patients hospitalized for an index TAVI procedure from 2016 to 2019. Primary outcomes included in-hospital all-cause mortality, complete heart block, and permanent pacemaker (PPM) implantation. A total of 199,895 hospitalizations for TAVI were identified. RBBB was present in 10,495 cases (5.3%). Patients with RBBB were older (median age 81 vs 80 years, p <0.001) and less likely to be female (35% vs 47.4%, p <0.001). After adjusting for differences in baseline characteristics and elective versus nonelective admission, patients with RBBB had a higher incidence of complete heart block (adjusted odds ratio [aOR] 4.77, confidence interval [CI] 4.55 to 5.01, p <0.001) and PPM implantation (aOR 4.15, CI 3.95 to 4.35, p <0.001) and no difference in-hospital mortality rate (aOR 0.85, CI 0.69 to 1.05, p = 0.137). Between 2016 and 2019, there was a 3.5% and 2.9% decrease in in-hospital PPM implantation in patients with and without RBBB, respectively. In conclusion, from 2016 to 2019, the rate of in-hospital PPM implantation decreased during index TAVI hospitalization in both patients with and without RBBB. However, in those with baseline RBBB, complete heart block complication rates requiring PPM implantation remain relatively high. Further research and advances are needed to continue to reduce complication rates and the need for PPM implantation.
Conspiracy theories have accrued around recent world events, and many of them have been endorsed by leaders seeking to garner support. Drawing from compensatory control theory, we argue a reduced sense of control will increase support for leaders who use conspiratorial rhetoric. Moreover, we posit that the congruence between one's political identity and a leader's conspiratorial rhetoric is an important consideration with regard to when this effect will emerge. Studies 1a and 1b established causality by directly manipulating sense of control and finding greater support for conspiratorial leaders in the lacking vs. having control condition. Studies 2 and 3 examined the effects of real-world events that are posited to reduce a sense of control, along with the moderating effect of political identity. Study 2 showed, in two waves collected before and during COVID-19 lockdowns, that the lockdowns reduced a sense of control. Congruently, individuals supported leaders espousing a COVID-19 conspiracy theory more during the lockdowns than before. In addition, for leaders espousing conspiratorial rhetoric related to paid protests, Republicans exhibited greater support during than before the lockdown; however, the lockdown did not affect Democrats' support. Study 3 showed, in two waves collected before and after the 2020 U.S. Presidential election, that Biden supporters felt greater control after the election and decreased their support for conspiratorial leaders. Trump supporters' sense of control did not change, and concurrently they did not change their support for conspiratorial leaders. Implications are discussed for leadership during times of crisis and beyond.
The Proterozoic Eon covers 40% of Earth's history, from 2500 to 541 Ma (million years ago), and was home to a series of major events in Earth's history. The tectonic configuration of the early stages of the Proterozoic is not known, but from 1500 Ma onwards there are reconstructions available. They are used here in a dedicated tidal model to simulate how the tides changed during the middle-late part of the Eon. We also revisit the Cryogenian period (715–630 Ma), when it has been proposed that Earth was home to vast near-global glaciations and extend the simulations into the later parts of the Eon. We show that the tides are far less energetic than today (about 40% of present-day tidal dissipation rates) for most of the period we could simulate, with the exception of a tidal maximum around 1250 Ma. The reason is that the period we simulated is home to the supercontinents Rodinia and Pannotia, and the results confirm the existence of a supertidal cycle linked to the supercontinent cycle.
The Phanerozoic Eon spans the past 541 Myr (million years) and includes present day. It was home to the assembly and breakup of the latest supercontinent, Pangea, and the subsequent scattering of the continents into Earth as we know it today. The changing face of the Earth is shown here, using a dedicated numerical tidal model and recent paleo-bathymetries, to have had a profound impact on the tides, with prolonged period of very weak tidal energy levels. These quiescent states were interrupted by tidal maxima lasting 5–20 Myr between the supercontinents; these were found around 430 Ma (million years ago), 150 Ma, and 20 Ma and we propose that Earth is currently on the way out of the most recent tidal maximum. We also present three case studies to highlight the importance of tides in the Earth system. These include the Devonian (~ 400 Ma) when key evolution events took place, the Turonian around 95 Ma when there was a marine extinction event due to anoxia, and the Eocene, 55 Ma, where it has been proposed that enhanced tidal dissipation rates could explain the reduced meridional temperature gradient found in proxies.
Lightweight materials design of friction parts promises aluminum matrix composites to achieve comparable anti-wear properties as steel. However, it is still challenging due to the limited effects of monotonous reinforcement. In this work, (TiB2-TiC)/Al-Cu-Mg composites were fabricated with particle content from 10 to 60 vol% and scaled from nano-sized to nano-/micron-sized. The microstructures, mechanical properties, elevated-temperature tribology behaviors and wear mechanisms of the Al-Cu-Mg composites reinforced by TiB2-TiC particles with tunable size and volume fractions were systematically investigated. Compared to the Al-Cu-Mg composite reinforced by nano-sized particles, the significant micron-/nano-sized effect and thicker mechanical mixture layer in the composites can weaken the influence of load on the composites and thus better protect the matrix. The incorporated particles evolved from single nano-sized to micron-/nano-sized hybridized, and the dominant wear mechanism transformed from severe adhesive and delamination wear (surface fatigue) to slight adhesive wear. 60 vol% micron-/nano-sized (TiB2-TiC)/Al-Cu-Mg composite showed the lowest wear rate (0.047 mm3/m) and coefficient of friction (0.38) at 473 K, 0.32 mm/s sliding velocity and 40 N load, reduced 24% and 20% than composite with 10 vol% nano-sized particles. This work provided a strategy for improving the wear resistance of aluminum matrix composites reinforced by size-tunable particles for their extended applications on structural components.
We show that exchange rate correlations tend to be explained by the global trade network while consumption correlations tend to be explained by productivity correlations. Sharing common trade linkages with other countries increases exchange rate correlations beyond bilateral linkages. We explain these findings using a model of the global trade network with market segmentation. Interdependent global production generates international comovements, while market segmentation disconnects the drivers of exchange rate correlations from the drivers of consumption correlations. Moreover, we show that the trade network generates common factors found in exchange rates. Our findings offer a trade-based account of the origins of international comovements and shed light on important frictions in international markets.
Dendritic microstructures are ubiquitous in nature and are the primary solidification morphologies in metallic materials. Techniques such as X-ray computed tomography (XCT) have provided new insights into dendritic phase transformation phenomena. However, manual identification of dendritic morphologies in microscopy data can be both labor intensive and potentially ambiguous. The analysis of 3D datasets is particularly challenging due to their large sizes (terabytes) and the presence of artifacts scattered within the imaged volumes. In this study, we trained 3D convolutional neural networks (CNNs) to segment 3D datasets. Three CNN architectures were investigated, including a new version of FCDenseNet which we extended to 3D. We show that using hyperparameter optimization (HPO) and fine-tuning techniques, both 2D and 3D CNN architectures outperform the previous state of the art. The 3D U-Net architecture trained in this study produced the best segmentations according to quantitative metrics (intersection-over-union of 95.56% and a boundary displacement error of 0.58 pixels), while 3D FCDense produced the smoothest boundaries and best segmentations according to visual inspection. The trained 3D CNNs are able to segment entire 852 × 852 × 250 voxel 3D volumes in only ∼60 s, thus hastening the progress towards a deeper understanding of phase transformation phenomena such as dendritic solidification.
We report time- and angle-resolved photoemission spectroscopy on SnSe which currently attracts great interest due to its extremely high thermoelectric performance. Laser-assisted photoemission signals are observed within ±20 fs of the pump pulse arrival. Around 30–50 fs after the photoexcitation, the conduction band minima are not populated by the photoexcited electrons while the valence bands are considerably broadened. In going from 90 fs to 550 fs after the photoexcitation, the photoexcited carriers are decayed into the multiple conduction band minima. The observed conduction bands are consistent with the band structure calculations. The multiple conduction minima suggest possibility of high and anisotropic thermoelectric performance of n-type SnSe single crystal if it is realized.
Background Adolescent dating violence (ADV) can have lasting effects on youth's well-being and development. However, few studies in Latin America have described its prevalence and risk factors for having experienced ADV. Methods We conducted a multisite, cross-sectional study using two-stage cluster sampling among adolescents (14–19 years) attending public high schools in the urban districts of Panama, San Miguelito, Colón, and Arraiján/La Chorrera from 2015 to 2018 (N = 2469). All completed a tablet-based, self-administered questionnaire. Random effects logistic regression was used to identify risk factors for each ADV type among adolescent boys and girls separately. Findings Participants reported experiencing a range of ADV at least once (girls: emotional 61.6%, physical 7.9%, sexual 21.0%; boys: emotional 73.4%, physical 24.1%, sexual 28.9%). In adjusted models, participants with a history of sexual intercourse had greater odds of ADV than those without such history across types (boys: emotional and sexual; girls: emotional, physical, and sexual). Additionally, participants who reported three or more romantic partners in the past year had greater odds of ADV than those with one partner (boys: emotional, physical; girls: physical). Girls with an earlier sexual debut (≤14 years vs ≥15 years) had greater odds of reporting ADV (emotional and sexual violence). No associations were found between reporting dating violence survival and the sex of romantic partners in the past year or the age of the current/most recent sex partner. Interpretation This study reveals a high prevalence of ADV among adolescents in urban public schools in Panama. These findings support the need for program implementation to address ADV. Funding Funding to undertake this study was acquired from Panama's Ministry of Economics and Finance, project number 009044.049.
Background While acute kidney injury (AKI) is a common complication in COVID-19, data on post-AKI kidney function recovery and the clinical factors associated with poor kidney function recovery is lacking. Methods A retrospective multi-centre observational cohort study comprising 12,891 hospitalized patients aged 18 years or older with a diagnosis of SARS-CoV-2 infection confirmed by polymerase chain reaction from 1 January 2020 to 10 September 2020, and with at least one serum creatinine value 1–365 days prior to admission. Mortality and serum creatinine values were obtained up to 10 September 2021. Findings Advanced age (HR 2.77, 95%CI 2.53–3.04, p < 0.0001), severe COVID-19 (HR 2.91, 95%CI 2.03–4.17, p < 0.0001), severe AKI (KDIGO stage 3: HR 4.22, 95%CI 3.55–5.00, p < 0.0001), and ischemic heart disease (HR 1.26, 95%CI 1.14–1.39, p < 0.0001) were associated with worse mortality outcomes. AKI severity (KDIGO stage 3: HR 0.41, 95%CI 0.37–0.46, p < 0.0001) was associated with worse kidney function recovery, whereas remdesivir use (HR 1.34, 95%CI 1.17–1.54, p < 0.0001) was associated with better kidney function recovery. In a subset of patients without chronic kidney disease, advanced age (HR 1.38, 95%CI 1.20–1.58, p < 0.0001), male sex (HR 1.67, 95%CI 1.45–1.93, p < 0.0001), severe AKI (KDIGO stage 3: HR 11.68, 95%CI 9.80–13.91, p < 0.0001), and hypertension (HR 1.22, 95%CI 1.10–1.36, p = 0.0002) were associated with post-AKI kidney function impairment. Furthermore, patients with COVID-19-associated AKI had significant and persistent elevations of baseline serum creatinine 125% or more at 180 days (RR 1.49, 95%CI 1.32–1.67) and 365 days (RR 1.54, 95%CI 1.21–1.96) compared to COVID-19 patients with no AKI. Interpretation COVID-19-associated AKI was associated with higher mortality, and severe COVID-19-associated AKI was associated with worse long-term post-AKI kidney function recovery. Funding Authors are supported by various funders, with full details stated in the acknowledgement section.
Char is formed as a significant product from the pyrolysis of biomass, and it is well reported that lignin is the greatest contributor to the production of char. The structures of lignin chars are well studied in literature; however, an elucidation on the lignin char formation mechanism is lacking and this is essential to achieve precise control of biomass thermal conversion. In this work, the char growth process from β-O-4 linkage derived lignin monomers was investigated using density functional theory (DFT) and validated by slow pyrolysis experiments and Nuclear Magnetic Resonance (NMR) analysis. It was shown that char forms in a two-step process, beginning with the aggregation of two mono-aromatic species to yield tricyclic species, which then participate in further ring forming reactions to yield larger aromatic clusters. The side products generated involve hydrogen, water, methanol, and formaldehyde. Insights from the proposed mechanism are important for guiding future research on char formation during biomass thermochemical conversion processes.
The large-scale synthesis of non-toxic, efficient quantum dots (QDs) is critical for expanding the practical application scope of QD-based photovoltaic (PV) devices. In this study, we synthesize ZnCuInSSe (ZCISSe) QDs on a gram scale (3.5 g) using a hybrid flow reactor method. This method is capable of producing QDs in gram quantities using solid-state chemicals. Additionally, by observing the composition, composition ratio, and reaction temperature, it is possible to produce ZCISSe QDs with highly controllable stoichiometry and a tuneable bandgap. Moreover, to improve the surface conditions of ZCISSe QDs, we propose for the first time the use of different types of surfactants with oleylamine (OAm) and S²⁻ surface ligands via ligand-exchange techniques. Subsequently, we validate the PV quality of the manufactured ZCISSe QDs. Additionally, we develop QD-based solar cells, in which the TiO2 film functions as an n-type semiconductor. The S²⁻-ligand-capped QD solar cell has a 25% higher power conversion efficiency than the OAm-ligand-capped QD solar cell.
Predictive constitutive equations that connect easy-to-measure transport properties (e.g., viscosity and conductivity) with system performance variables (e.g., power consumption and efficiency) are needed to design advanced thermal and electrical systems. In this work, we explore the use of fluorescent particle-streak analysis to directly measure the local velocity field of a pressure-driven flow, introducing a new Python package (FSVPy) to perform the analysis. Fluorescent streak velocimetry combines high-speed imaging with highly fluorescent particles to produce images that contain fluorescent streaks, whose length and intensity can be related to the local flow velocity. By capturing images throughout the sample volume, the three-dimensional velocity field can be quantified and reconstructed. We demonstrate this technique by characterizing the channel flow profiles of several non-Newtonian fluids: micellar Cetylpyridinium Chloride solution, Carbopol 940, and Polyethylene Glycol. We then explore more complex flows, where significant acceleration is created due to microscale features encountered within the flow. We demonstrate the ability of FSVPy to process streaks of various shapes and use the variable intensity along the streak to extract position-specific velocity measurements from individual images. Thus, we demonstrate that FSVPy is a flexible tool that can be used to extract local velocimetry measurements from a wide variety of fluids and flow conditions.
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15,471 members
Dina Simkin
  • The Ken and Ruth Davee Department of Neurology
Mohammed S.M. Elbaz
  • Departments of Radiology & Biomedical Engineering
Alexander V Misharin
  • Division of Pulmonary and Critical Care
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