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"Yan, James"
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Hands-On Data Science with Anaconda: Utilize the right mix of tools to create high-performance data science applications
2018
Hands-On Data Science with Anaconda gets you started with Anaconda and demonstrates how you can use it to perform data science operations in the real world. You will learn different ways to retrieve data from various sources and different visualization tools packages available in Python, R, and Julia.
Resonant inelastic X-ray scattering determination of the electronic structure of oxyhemoglobin and its model complex
by
Hodgson, Keith O.
,
Baker, Michael L.
,
Solomon, Edward I.
in
Absorption spectroscopy
,
Catalytic Domain
,
Chemistry
2019
Hemoglobin and myoglobin are oxygen-binding proteins with S = 0 heme {FeO₂}⁸ active sites. The electronic structure of these sites has been the subject of much debate. This study utilizes Fe K-edge X-ray absorption spectroscopy (XAS) and 1s2p resonant inelastic X-ray scattering (RIXS) to study oxyhemoglobin and a related heme {FeO₂}⁸ model compound, [(pfp)Fe(1-MeIm)(O₂)] (pfp = meso-tetra(α,α,α,α-o-pivalamido-phenyl)porphyrin, or TpivPP, 1-MeIm = 1-methylimidazole) (pfpO₂), which was previously analyzed using L-edge XAS. The K-edge XAS and RIXS data of pfpO₂ and oxyhemoglobin are compared with the data for low-spin FeII and FeIII [Fe(tpp)(Im)₂]0/+ (tpp = tetra-phenyl porphyrin) compounds, which serve as heme references. The X-ray data show that pfpO₂ is similar to FeII, while oxyhemoglobin is qualitatively similar to FeIII, but with significant quantitative differences. Density-functional theory (DFT) calculations show that the difference between pfpO₂ and oxyhemoglobin is due to a distal histidine H bond to O₂ and the less hydrophobic environment in the protein, which lead to more back-bonding into the O₂. A valence bond configuration interaction multiplet model is used to analyze the RIXS data and show that pfpO₂ is dominantly FeII with 6–8% FeIII character, while oxyhemoglobin has a very mixed wave function that has 50–77% FeIII character and a partially polarized Fe–O₂ π-bond.
Journal Article
Structural characterization of a non-heme iron active site in zeolites that hydroxylates methane
by
Zhao, Jiyong
,
Hodgson, Keith O.
,
Böttger, Lars H.
in
Absorption spectroscopy
,
Catalysis
,
Catalytic Domain
2018
Iron-containing zeolites exhibit unprecedented reactivity in the low-temperature hydroxylation of methane to form methanol. Reactivity occurs at a mononuclear ferrous active site, α-Fe(II), that is activated by N₂O to form the reactive intermediate α-O. This has been defined as an Fe(IV)=O species. Using nuclear resonance vibrational spectroscopy coupled to X-ray absorption spectroscopy, we probe the bonding interaction between the iron center, its zeolite lattice-derived ligands, and the reactive oxygen. α-O is found to contain an unusually strong Fe(IV)=O bond resulting from a constrained coordination geometry enforced by the zeolite lattice. Density functional theory calculations clarify how the experimentally determined geometric structure of the active site leads to an electronic structure that is highly activated to perform H-atom abstraction.
Journal Article
COVID-19 and the transition to virtual teaching sessions in an orthopaedic surgery training program: a survey of resident perspectives
by
Chan, Teresa
,
Yan, James R.
,
Kruse, Colin
in
Behavioral Objectives
,
Beliefs, opinions and attitudes
,
Blended Learning
2022
Background
COVID-19 has had a tremendous impact on medical education. Due to concerns of the virus spreading through gatherings of health professionals, in-person conferences and rounds were largely cancelled. The purpose of this study is the evaluate the implementation of an online educational curriculum by a major Canadian orthopaedic surgery residency program in response to COVID-19.
Methods
A survey was distributed to residents of a major Canadian orthopaedic surgery residency program from July 10
th
to October 24
th
, 2020. The survey aimed to assess residents’ response to this change and to examine the effect that the transition has had on their participation, engagement, and overall educational experience.
Results
Altogether, 25 of 28 (89%) residents responded. Respondents generally felt the quality of education was superior (72%), their level of engagement improved (64%), and they were able to acquire more knowledge (68%) with the virtual format. Furthermore, 88% felt there was a greater diversity of topics, and 96% felt there was an increased variety of presenters. Overall, 76% of respondents felt that virtual seminars better met their personal learning objectives. Advantages reported were increased accessibility, greater convenience, and a wider breadth of teaching faculty. Disadvantages included that the virtual sessions felt less personal and lacked dynamic feedback to the presenter.
Conclusions
Results of this survey reveal generally positive attitudes of orthopaedic surgery residents about the transition to virtual learning in the setting of an ongoing pandemic. This early evaluation and feedback provides valuable guidance on how to grow this novel curriculum and bring the frontier of virtual teaching to orthopaedic education long-term.
Journal Article
Evaluation of a concerted vs. sequential oxygen activation mechanism in α-ketoglutarate–dependent nonheme ferrous enzymes
by
Christensen, Hans E. M.
,
Hodgson, Keith O.
,
Babicz, Jeffrey T.
in
Activation
,
Binding
,
Biochemistry
2020
Determining the requirements for efficient oxygen (O₂) activation is key to understanding how enzymes maintain efficacy and mitigate unproductive, often detrimental reactivity. For the α-ketoglutarate (αKG)–dependent nonheme iron enzymes, both a concerted mechanism (both cofactor and substrate binding prior to reaction with O₂) and a sequential mechanism (cofactor binding and reaction with O₂ precede substrate binding) have been proposed. Deacetoxycephalosporin C synthase (DAOCS) is an αKG-dependent nonheme iron enzyme for which both of these mechanisms have been invoked to generate an intermediate that catalyzes oxidative ring expansion of penicillin substrates in cephalosporin biosynthesis. Spectroscopy shows that, in contrast to other αKG-dependent enzymes (which are six coordinate when only αKG is bound to the FeII), αKG binding to FeII-DAOCS results in ∼45% five-coordinate sites that selectively react with O₂ relative to the remaining six-coordinate sites. However, this reaction produces an FeIII species that does not catalyze productive ring expansion. Alternatively, simultaneous αKG and substrate binding to FeII-DAOCS produces five-coordinate sites that rapidly react with O₂ to form an FeIV=O intermediate that then reacts with substrate to produce cephalosporin product. These results demonstrate that the concerted mechanism is operative in DAOCS and by extension, other nonheme iron enzymes.
Journal Article
Mechanism of selective benzene hydroxylation catalyzed by iron-containing zeolites
2018
A direct, catalytic conversion of benzene to phenol would have wide-reaching economic impacts. Fe zeolites exhibit a remarkable combination of high activity and selectivity in this conversion, leading to their past implementation at the pilot plant level. There were, however, issues related to catalyst deactivation for this process. Mechanistic insight could resolve these issues, and also provide a blueprint for achieving high performance in selective oxidation catalysis. Recently, we demonstrated that the active site of selective hydrocarbon oxidation in Fe zeolites, named α-O, is an unusually reactive Fe(IV)=O species. Here, we apply advanced spectroscopic techniques to determine that the reaction of this Fe(IV)=O intermediate with benzene in fact regenerates the reduced Fe(II) active site, enabling catalytic turnover. At the same time, a small fraction of Fe(III)-phenolate poisoned active sites form, defining a mechanism for catalyst deactivation. Density-functional theory calculations provide further insight into the experimentally defined mechanism. The extreme reactivity of α-O significantly tunes down (eliminates) the rate-limiting barrier for aromatic hydroxylation, leading to a diffusion-limited reaction coordinate. This favors hydroxylation of the rapidly diffusing benzene substrate over the slowly diffusing (but more reactive) oxygenated product, thereby enhancing selectivity. This defines a mechanism to simultaneously attain high activity (conversion) and selectivity, enabling the efficient oxidative upgrading of inert hydrocarbon substrates.
Journal Article
Risk Factors and Post-Resection Independent Predictive Score for the Recurrence of Hepatitis B-Related Hepatocellular Carcinoma
by
Seto, Wai-Kay
,
Chui, Ada Hang-Wai
,
Yuen, John Chi-Hang
in
Aged
,
Antiviral agents
,
Antiviral Agents - therapeutic use
2016
Independent risk factors associated with hepatitis B (HBV)-related hepatocellular carcinoma (HCC) after resection remains unknown. An accurate risk score for HCC recurrence is lacking.
We prospectively followed up 200 patients who underwent liver resection for HBV-related HCC for at least 2 years. Demographic, biochemical, tumor, virological and anti-viral treatment factors were analyzed to identify independent risk factors associated with recurrence after resection and a risk score for HCC recurrence formulated.
Two hundred patients (80% male) who underwent liver resection for HBV-related HCC were recruited. The median time of recurrence was 184 weeks (IQR 52-207 weeks) for the entire cohort and 100 patients (50%) developed HCC recurrence. Stepwise Cox regression analysis identified that one-month post resection HBV DNA >20,000 IU/mL (p = 0.019; relative risk (RR) 1.67; 95% confidence interval (C.I.): 1.09-2.57), the presence of lymphovascular permeation (p<0.001; RR 2.69; 95% C.I.: 1.75-4.12), microsatellite lesions (p<0.001; RR 2.86; 95% C.I.: 1.82-4.51), and AFP >100ng/mL before resection (p = 0.021; RR 1.63; 95% C.I.: 1.08-2.47) were independently associated with HCC recurrence. Antiviral treatment before resection (p = 0.024; RR 0.1; 95% C.I.: 0.01-0.74) was independently associated with reduced risk of HCC recurrence. A post-resection independent predictive score (PRIPS) was derived and validated with sensitivity of 75.3% and 60.6% and specificity of 55.7% and 79.2%, to predict the 1- and 3-year risks for the HCC recurrence respectively with the hazard ratio of 2.71 (95% C.I.: 2.12-3.48; p<0.001). The AUC for the 1- and 3-year prediction were 0.675 (95% C.I.: 0.6-0.78) and 0.746 (95% C.I.: 0.69-0.82) respectively.
Several tumor, virological and biochemical factors were associated with a higher cumulative risk of HCC recurrence after resection. PRIPS was derived for more accurate risk assessment. Regardless of the HBV DNA level, antiviral treatment should be given to patients before resection to reduce the risk of recurrence.
Journal Article
Brown tumor causing pathologic fracture of the ipsilateral femur and pelvis in a pregnant woman: a case report
2025
We present the case of a 30-year-old pregnant woman who was found to have an aggressive-appearing osteolytic lesion of the left distal femur in the setting of hypercalcemia. Biopsy confirmed a brown tumor secondary to hyperparathyroidism. She underwent a successful parathyroidectomy followed by a Cesarean section. Postpartum, she sustained pathologic fractures of the ipsilateral femur and pelvis due to a fall, requiring operative fixation. She progressed to uncomplicated healing following surgical management. Although brown tumors can appear aggressive on imaging, they typically resolve following treatment of the underlying hyperparathyroidism. Pathologic fractures should be managed according to standard orthopedic principles. Clinicians should include brown tumors in the differential diagnosis when evaluating osteolytic lesions, particularly in the presence of hypercalcemia.
Journal Article
Hands-On Data Science with Anaconda
by
James Yan
,
Yuxing Yan
2018
Hands-On Data Science with Anaconda is your guide to harnessing the full potential of Anaconda, a powerful platform for data science and machine learning. With this book, you will learn how to set up Anaconda, manage packages, explore advanced data processing techniques, and create robust machine learning models using Python, R, and Julia.What this Book will help me doMaster data preprocessing techniques including cleaning, sorting, and classification using Anaconda.Understand and utilize the conda package manager for efficient package management.Learn to explore and visualize data using packages and frameworks supported by Anaconda.Perform advanced operations like clustering, regression, and building predictive models.Implement distributed computing and manage environments effectively with Anaconda Cloud.Author(s)Yuxing Yan and co-author None Yan are seasoned data science professionals with extensive experience in utilizing cutting-edge tools like Anaconda to simplify and enhance data science workflows. With a focus on making complex concepts accessible, they offer a practical and systematic approach to mastering tools that power real-world data science projects.Who is it for?This book is for data science practitioners, analysts, or developers with a basic understanding of Python, R, and linear algebra who want to scale their skills and learn to utilize the Anaconda platform for their projects. If you're seeking to work more effectively within the Anaconda ecosystem or equip yourself with efficient tools for data analysis and machine learning, this book is for you.
Impact of Tumour Biology on Outcomes of Radical Therapy for Hepatocellular Carcinoma Oligo-Recurrence after Liver Transplantation
by
Lo, Chung-Mau
,
Dai, Wing-Chiu
,
Fung, James Yan-Yue
in
Biology
,
Clinical medicine
,
Clinical outcomes
2022
It is uncertain whether tumour biology affects radical treatment for post-transplant hepatocellular carcinoma (HCC) oligo-recurrence, i.e. recurrence limited in numbers and locations amendable to radical therapy. We conducted a retrospective study on 144 patients with post-transplant HCC recurrence. Early recurrence within one year after transplant (HR 2.53, 95% CI 1.65–3.88, p < 0.001), liver recurrence (HR 1.74, 95% CI 1.12–2.68, p = 0.01) and AFP > 200 ng/mL upon recurrence (HR 1.62, 95% CI 1.04–2.52, p = 0.03) predicted mortality following recurrence. In patients with early recurrence and liver recurrence, radical treatment was associated with improved post-recurrence survival (early recurrence: median 18.2 ± 1.5 vs. 9.2 ± 1.5 months, p < 0.001; liver recurrence: median 28.0 ± 4.5 vs. 11.6 ± 2.0, p < 0.001). In patients with AFP > 200 ng/mL, improvement in survival did not reach statistical significance (median 18.2 ± 6.5 vs. 8.8 ± 2.2 months, p = 0.13). Survival benefits associated with radical therapy were reduced in early recurrence (13.6 vs. 9.0 months) and recurrence with high AFP (15.4 vs. 9.3 months) but were similar among patients with and without liver recurrence (16.9 vs. 16.4 months). They were also diminished in patients with multiple biological risk factors (0 risk factor: 29.0 months; 1 risk factor: 19.7 months; 2–3 risk factors: 3.4 months): The survival benefit following radical therapy was superior in patients with favourable biological recurrence but was also observed in patients with poor tumour biology. Treatment decisions should be individualised considering the oncological benefits, quality of life gain and procedural morbidity.
Journal Article