Publications by authors named "Dharshan Sivaraj"

18 Publications

  • Page 1 of 1

CVD Risk Factors in the Ukrainian Roma and Meta-Analysis of Their Prevalence in Roma Populations Worldwide.

J Pers Med 2021 Nov 2;11(11). Epub 2021 Nov 2.

Division of Cellular Therapy, Duke University, 2400 Pratt Street, Durham, NC 27708, USA.

The Roma population suffers from severe poverty, social exclusion, and some of the worst health conditions in the industrialized world. Herein, we report on cardiovascular disease (CVD) risk factors in the Ukrainian Roma and present a meta-analysis of the prevalence of CVD risk factors in 16 Roma populations worldwide. The meta-analyses of CVD risk factors in Roma ( = 16,552) vs. non-Roma majority population of the same country ( = 127,874) included publicly available data. Ukrainian field survey included 339 adults of both sexes and outcomes of interest were hypertension, body mass index (BMI), smoking, education, and employment status. Furthermore, 35.7% of the Ukrainian Roma were hypertensive, 69.3% unemployed, and 48.4% never went to school. Ukrainian Roma women were more likely to be underweight and more prone to be hypertensive, with odds of hypertension increasing with age, BMI, and positive smoking status. Meta-analyses showed that, in comparison with non-Roma worldwide, the Roma bear significantly higher risk factor loads related to smoking (OR = 2.850), diabetes (OR = 1.433), abdominal obesity (OR = 1.276), and metabolic syndrome (OR = 1.975), with lower loads for hypertension (OR = 0.607) and BMI ≥ 25 kg/m (OR = 0.872). To conclude, the CVD risk factors which are more common in Roma than in the majority population may reflect their poor health-related behaviors and inadequate access to health education.
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http://dx.doi.org/10.3390/jpm11111138DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8622536PMC
November 2021

A rare case of infection in California.

JAAD Case Rep 2021 Nov 30;17:55-57. Epub 2021 Sep 30.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, California.

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http://dx.doi.org/10.1016/j.jdcr.2021.09.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8526914PMC
November 2021

The Plane of Mesh Placement Does Not Impact Abdominal Donor Site Complications in Microsurgical Breast Reconstruction.

Ann Plast Surg 2021 11;87(5):542-546

From the Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Stanford, CA.

Background: Reinforcement of the abdominal wall with synthetic mesh in autologous breast reconstruction using abdominal free tissue transfer decreases the risk of bulging and herniation. However, the impact of the plane of mesh placement on donor site complications has not yet been investigated.

Methods: We performed a retrospective analysis of 312 patients who had undergone autologous breast reconstruction with muscle-sparing transverse rectus abdominis myocutaneous (MS-TRAM) flaps or deep inferior epigastric perforator (DIEP) flaps as well as polypropylene mesh implantation at the donor site. Donor site complications were compared among patients with different flap types and different mesh positions including overlay (n = 90), inlay and overlay (I-O; n = 134), and sublay (n = 88).

Results: Abdominal hernias occurred in 2.86% of patients who had undergone MS-TRAM reconstructions and in 2.63% of patients who had undergone DIEP reconstructions. When comparing patients with different mesh positions, donor site complications occurred in 14.4% of patients with overlay mesh, 13.4% of patients with I-O mesh, and 10.2% of patients with sublay mesh (P = 0.68). Abdominal hernias occurred in 4.44% of patients with overlay mesh, 2.24% of patients with I-O mesh, and 2.27% of patients with sublay mesh (P = 0.69). Multivariable logistic regression analysis did not identify a significant association between mesh position and hernia rates as well as wound complications.

Conclusions: Our data indicate that the plane of synthetic mesh placement in relation to the rectus abdominis muscle does not impact the rate of postoperative donor site complications in patients undergoing breast reconstruction with MS-TRAM or DIEP flaps.
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http://dx.doi.org/10.1097/SAP.0000000000002897DOI Listing
November 2021

Epidermal-Derived Hedgehog Signaling Drives Mesenchymal Proliferation during Digit Tip Regeneration.

J Clin Med 2021 Sep 20;10(18). Epub 2021 Sep 20.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.

Hand injuries often result in significant functional impairments and are rarely completely restored. The spontaneous regeneration of injured appendages, which occurs in salamanders and newts, for example, has been reported in human fingertips after distal amputation, but this type of regeneration is rare in mammals and is incompletely understood. Here, we study fingertip regeneration by amputating murine digit tips, either distally to initiate regeneration, or proximally, causing fibrosis. Using an unbiased microarray analysis, we found that digit tip regeneration is significantly associated with hair follicle differentiation, Wnt, and sonic hedgehog (SHH) signaling pathways. Viral over-expression and genetic knockouts showed the functional significance of these pathways during regeneration. Using transgenic reporter mice, we demonstrated that, while both canonical Wnt and HH signaling were limited to epidermal tissues, downstream hedgehog signaling (through Gli) occurred in mesenchymal tissues. These findings reveal a mechanism for epidermal/mesenchyme interactions, governed by canonical hedgehog signaling, during digit regeneration. Further research into these pathways could lead to improved therapeutic outcomes after hand injuries in humans.
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http://dx.doi.org/10.3390/jcm10184261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8467649PMC
September 2021

Inhibiting Fibroblast Mechanotransduction Modulates Severity of Idiopathic Pulmonary Fibrosis.

Adv Wound Care (New Rochelle) 2021 Nov 30. Epub 2021 Nov 30.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, California, USA.

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that affects 63 in every 100,000 Americans. Its etiology remains unknown, although inflammatory pathways appear to be important. Given the dynamic environment of the lung, we examined the significance of mechanotransduction on both inflammatory and fibrotic signaling during IPF. Mechanotransduction pathways have not been thoroughly examined in the context of lung disease, and pharmacologic approaches for IPF do not currently target these pathways. The interplay between mechanical strain and inflammation in pulmonary fibrosis remains incompletely understood. In this study, we used conditional KO mice to block mechanotransduction by knocking out Focal Adhesion Kinase (FAK) expression in fibroblasts, followed by induction of pulmonary fibrosis using bleomycin. We examined both normal human and human IPF fibroblasts and used immunohistochemistry, quantitative real-time polymerase chain reaction, and Western Blot to evaluate the effects of FAK inhibitor (FAK-I) on modulating fibrotic and inflammatory genes. Our data indicate that the deletion of FAK in mice reduces expression of fibrotic and inflammatory genes in lungs. Similarly, mechanical straining in normal human lung fibroblasts activates inflammatory and fibrotic pathways. The FAK inhibition decreases these signals but has a less effect on IPF fibroblasts as compared with normal human fibroblasts. Administering FAK-I at early stages of fibrosis may attenuate the FAK-mediated fibrotic response pathway in IPF, potentially mediating disease progression.
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http://dx.doi.org/10.1089/wound.2021.0077DOI Listing
November 2021

Disrupting biological sensors of force promotes tissue regeneration in large organisms.

Nat Commun 2021 09 6;12(1):5256. Epub 2021 Sep 6.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA, USA.

Tissue repair and healing remain among the most complicated processes that occur during postnatal life. Humans and other large organisms heal by forming fibrotic scar tissue with diminished function, while smaller organisms respond with scarless tissue regeneration and functional restoration. Well-established scaling principles reveal that organism size exponentially correlates with peak tissue forces during movement, and evolutionary responses have compensated by strengthening organ-level mechanical properties. How these adaptations may affect tissue injury has not been previously examined in large animals and humans. Here, we show that blocking mechanotransduction signaling through the focal adhesion kinase pathway in large animals significantly accelerates wound healing and enhances regeneration of skin with secondary structures such as hair follicles. In human cells, we demonstrate that mechanical forces shift fibroblasts toward pro-fibrotic phenotypes driven by ERK-YAP activation, leading to myofibroblast differentiation and excessive collagen production. Disruption of mechanical signaling specifically abrogates these responses and instead promotes regenerative fibroblast clusters characterized by AKT-EGR1.
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http://dx.doi.org/10.1038/s41467-021-25410-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8421385PMC
September 2021

Mechanical Strain Drives Myeloid Cell Differentiation Toward Proinflammatory Subpopulations.

Adv Wound Care (New Rochelle) 2021 Aug 27. Epub 2021 Aug 27.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, California, USA.

After injury, humans and other mammals heal by forming fibrotic scar tissue with diminished function, and this healing process involves the dynamic interplay between resident cells within the skin and cells recruited from the circulation. Recent studies have provided mounting evidence that external mechanical forces stimulate intracellular signaling pathways to drive fibrotic processes. While most studies have focused on studying mechanotransduction in fibroblasts, recent data suggest that mechanical stimulation may also shape the behavior of immune cells, referred to as "mechano-immunomodulation." However, the effect of mechanical strain on myeloid cell recruitment and differentiation remains poorly understood and has never been investigated at the single-cell level. In this study, we utilized a three-dimensional (3D) culture system that permits the precise manipulation of mechanical strain applied to cells. We cultured myeloid cells and used single-cell RNA-sequencing to interrogate the effects of strain on myeloid differentiation and transcriptional programming. Our data indicate that myeloid cells are indeed mechanoresponsive, with mechanical stress influencing myeloid differentiation. Mechanical strain also upregulated a cascade of inflammatory chemokines, most notably from the family. Further understanding of how mechanical stress affects myeloid cells in conjunction with other cell types in the complicated, multicellular milieu of wound healing may lead to novel insights and therapies for the treatment of fibrosis.
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http://dx.doi.org/10.1089/wound.2021.0036DOI Listing
August 2021

Hydrogel Scaffolds to Deliver Cell Therapies for Wound Healing.

Front Bioeng Biotechnol 2021 3;9:660145. Epub 2021 May 3.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA, United States.

Cutaneous wounds are a growing global health burden as a result of an aging population coupled with increasing incidence of diabetes, obesity, and cancer. Cell-based approaches have been used to treat wounds due to their secretory, immunomodulatory, and regenerative effects, and recent studies have highlighted that delivery of stem cells may provide the most benefits. Delivering these cells to wounds with direct injection has been associated with low viability, transient retention, and overall poor efficacy. The use of bioactive scaffolds provides a promising method to improve cell therapy delivery. Specifically, hydrogels provide a physiologic microenvironment for transplanted cells, including mechanical support and protection from native immune cells, and cell-hydrogel interactions may be tailored based on specific tissue properties. In this review, we describe the current and future directions of various cell therapies and usage of hydrogels to deliver these cells for wound healing applications.
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http://dx.doi.org/10.3389/fbioe.2021.660145DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8126987PMC
May 2021

Adipose-Derived Stromal Cells Seeded in Pullulan-Collagen Hydrogels Improve Healing in Murine Burns.

Tissue Eng Part A 2021 06 27;27(11-12):844-856. Epub 2021 May 27.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, California, USA.

Burn scars and scar contractures cause significant morbidity for patients. Recently, cell-based therapies have been proposed as an option for improving healing and reducing scarring after burn injury, through their known proangiogenic and immunomodulatory paracrine effects. Our laboratory has developed a pullulan-collagen hydrogel that, when seeded with mesenchymal stem cells (MSCs), improves cell viability and augments their proangiogenic capacity . Concurrently, recent research suggests that prospective isolation of cell subpopulations with desirable transcriptional profiles can be used to further improve cell-based therapies. In this study, we examined whether adipose-derived stem cell (ASC)-seeded hydrogels could improve wound healing following thermal injury using a murine contact burn model. Partial thickness contact burns were created on the dorsum of mice. On days 5 and 10 following injury, burns were debrided and received either ASC hydrogel, ASC injection alone, hydrogel alone, or no treatment. On days 10 and 25, burns were harvested for histologic and molecular analysis. This experiment was repeated using CD26/CD55 FACS-enriched ASCs to further evaluate the regenerative potential of ASCs in wound healing. ASC hydrogel-treated burns demonstrated accelerated time to reepithelialization, greater vascularity, and increased expression of the proangiogenic genes MCP-1, VEGF, and SDF-1 at both the mRNA and protein level. Expression of the profibrotic gene and proinflammatory gene was downregulated in ASC hydrogel-treated burns. ASC hydrogel-treated burns exhibited reduced scar area compared to hydrogel-treated and control wounds, with equivalent scar density. CD26/CD55 ASC hydrogel treatment resulted in accelerated healing, increased dermal appendage count, and improved scar quality with a more reticular collagen pattern. Here we find that ASC hydrogel therapy is effective for treating burns, with demonstrated proangiogenic, fibromodulatory, and immunomodulatory effects. Enrichment for CD26/CD55 ASCs has additive benefits for tissue architecture and collagen remodeling postburn injury. Research is ongoing to further facilitate clinical translation of this promising therapeutic approach. Impact statement Burns remain a significant public health burden. Stem cell therapy has gained attention as a promising approach for treating burns. We have developed a pullulan-collagen biomimetic hydrogel scaffold that can be seeded with adipose-derived stem cells (ASCs). We assessed the delivery and activity of our scaffold in a murine contact burn model. Our results suggest that localized delivery of ASC hydrogel treatment is a promising approach for the treatment of burn wounds, with the potential for rapid clinical translation. We believe our work will have broad implications for both hydrogel therapeutics and regenerative medicine and will be of interest to the general scientific community.
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http://dx.doi.org/10.1089/ten.TEA.2020.0320DOI Listing
June 2021

A Comparative Oncology Drug Discovery Pipeline to Identify and Validate New Treatments for Osteosarcoma.

Cancers (Basel) 2020 Nov 11;12(11). Epub 2020 Nov 11.

Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.

Background: Osteosarcoma is a rare but aggressive bone cancer that occurs primarily in children. Like other rare cancers, treatment advances for osteosarcoma have stagnated, with little improvement in survival for the past several decades. Developing new treatments has been hampered by extensive genomic heterogeneity and limited access to patient samples to study the biology of this complex disease.

Methods: To overcome these barriers, we combined the power of comparative oncology with patient-derived models of cancer and high-throughput chemical screens in a cross-species drug discovery pipeline.

Results: Coupling in vitro high-throughput drug screens on low-passage and established cell lines with in vivo validation in patient-derived xenografts we identify the proteasome and CRM1 nuclear export pathways as therapeutic sensitivities in osteosarcoma, with dual inhibition of these pathways inducing synergistic cytotoxicity.

Conclusions: These collective efforts provide an experimental framework and set of new tools for osteosarcoma and other rare cancers to identify and study new therapeutic vulnerabilities.
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http://dx.doi.org/10.3390/cancers12113335DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7696249PMC
November 2020

Characterization of Diabetic and Non-Diabetic Foot Ulcers Using Single-Cell RNA-Sequencing.

Micromachines (Basel) 2020 Aug 28;11(9). Epub 2020 Aug 28.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.

Recent advances in high-throughput single-cell sequencing technologies have led to their increasingly widespread adoption for clinical applications. However, challenges associated with tissue viability, cell yield, and delayed time-to-capture have created unique obstacles for data processing. Chronic wounds, in particular, represent some of the most difficult target specimens, due to the significant amount of fibrinous debris, extracellular matrix components, and non-viable cells inherent in tissue routinely obtained from debridement. Here, we examined the feasibility of single cell RNA sequencing (scRNA-seq) analysis to evaluate human chronic wound samples acquired in the clinic, subjected to prolonged cold ischemia time, and processed without FACS sorting. Wound tissue from human diabetic and non-diabetic plantar foot ulcers were evaluated using an optimized 10X Genomics scRNA-seq platform and analyzed using a modified data pipeline designed for low-yield specimens. Cell subtypes were identified informatically and their distributions and transcriptional programs were compared between diabetic and non-diabetic tissue. 139,000 diabetic and non-diabetic wound cells were delivered for 10X capture after either 90 or 180 min of cold ischemia time. cDNA library concentrations were 858.7 and 364.7 pg/µL, respectively, prior to sequencing. Among all barcoded fragments, we found that 83.5% successfully aligned to the human transcriptome and 68% met the minimum cell viability threshold. The average mitochondrial mRNA fraction was 8.5% for diabetic cells and 6.6% for non-diabetic cells, correlating with differences in cold ischemia time. A total of 384 individual cells were of sufficient quality for subsequent analyses; from this cell pool, we identified transcriptionally-distinct cell clusters whose gene expression profiles corresponded to fibroblasts, keratinocytes, neutrophils, monocytes, and endothelial cells. Fibroblast subpopulations with differing fibrotic potentials were identified, and their distributions were found to be altered in diabetic vs. non-diabetic cells. scRNA-seq of clinical wound samples can be achieved using minor modifications to standard processing protocols and data analysis methods. This simple approach can capture widespread transcriptional differences between diabetic and non-diabetic tissue obtained from matched wound locations.
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http://dx.doi.org/10.3390/mi11090815DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7570277PMC
August 2020

E-Cadherin Represses Anchorage-Independent Growth in Sarcomas through Both Signaling and Mechanical Mechanisms.

Mol Cancer Res 2019 06 12;17(6):1391-1402. Epub 2019 Mar 12.

Department of Medicine, Duke University Medical Center, Durham, North Carolina.

CDH1 (also known as E-cadherin), an epithelial-specific cell-cell adhesion molecule, plays multiple roles in maintaining adherens junctions, regulating migration and invasion, and mediating intracellular signaling. Downregulation of E-cadherin is a hallmark of epithelial-to-mesenchymal transition (EMT) and correlates with poor prognosis in multiple carcinomas. Conversely, upregulation of E-cadherin is prognostic for improved survival in sarcomas. Yet, despite the prognostic benefit of E-cadherin expression in sarcoma, the mechanistic significance of E-cadherin in sarcomas remains poorly understood. Here, by combining mathematical models with wet-bench experiments, we identify the core regulatory networks mediated by E-cadherin in sarcomas, and decipher their functional consequences. Unlike carcinomas, E-cadherin overexpression in sarcomas does not induce a mesenchymal-to-epithelial transition (MET). However, E-cadherin acts to reduce both anchorage-independent growth and spheroid formation of sarcoma cells. Ectopic E-cadherin expression acts to downregulate phosphorylated CREB1 (p-CREB) and the transcription factor, TBX2, to inhibit anchorage-independent growth. RNAi-mediated knockdown of TBX2 phenocopies the effect of E-cadherin on CREB levels and restores sensitivity to anchorage-independent growth in sarcoma cells. Beyond its signaling role, E-cadherin expression in sarcoma cells can also strengthen cell-cell adhesion and restricts spheroid growth through mechanical action. Together, our results demonstrate that E-cadherin inhibits sarcoma aggressiveness by preventing anchorage-independent growth. IMPLICATIONS: We highlight how E-cadherin can restrict aggressive behavior in sarcomas through both biochemical signaling and biomechanical effects.
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http://dx.doi.org/10.1158/1541-7786.MCR-18-0763DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6548594PMC
June 2019

Outcomes of Maintenance Therapy with Bortezomib after Autologous Stem Cell Transplantation for Patients with Multiple Myeloma.

Biol Blood Marrow Transplant 2017 Feb 14;23(2):262-268. Epub 2016 Nov 14.

Division of Cellular Therapy, Duke University, Durham, North Carolina.

Comprehensive recommendations for maintenance therapy after autologous stem cell transplantation (ASCT) for patients with multiple myeloma (MM) have yet to be defined. Bortezomib has been utilized as maintenance therapy after ASCT, but data attesting to the safety and efficacy of this agent compared with lenalidomide in the post-ASCT setting are limited. Therefore, we retrospectively analyzed the outcomes of 102 patients with MM who received maintenance therapy with bortezomib after ASCT at Duke University's adult bone marrow transplant clinic between 2005 and 2015. Maintenance with bortezomib was initiated between 60 and 90 days after ASCT as a single agent 1.3 mg/m once every 2 weeks (n = 92) or in combination with lenalidomide (10 mg/day) (n = 10). The median age at ASCT was 64 (range, 31 to 78). Of the 99 patients with molecular data available, 42% had high-risk cytogenetics (including d17p, t(4;14), +1q, and t(14;16) by fluorescein in situ hybridization). Overall, 46% of patients experienced side effects from maintenance therapy, with 31% of all patients experiencing peripheral neuropathy. In total, 2% of patients required discontinuation of bortezomib maintenance because of adverse events. No secondary malignancies were reported from the therapy. The median progression-free survival (PFS) for patients receiving maintenance therapy with bortezomib after ASCT was 36.5 months (95% confidence interval [CI], 21.3 to not available) and median overall survival was 72.7 months (95% CI, 63.9 to not available). The PFS of patients with high-risk cytogenetics was not statistically significantly different from those with standard-risk cytogenetics, suggesting that maintenance with bortezomib may help overcome the impact of high-risk cytogenetics on early progression. These results indicate that maintenance therapy with bortezomib represents a safe, well-tolerated, and efficacious option for patients with high-risk cytogenetics, renal insufficiency, an inability to tolerate lenalidomide, or a previous history of another cancer.
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http://dx.doi.org/10.1016/j.bbmt.2016.11.010DOI Listing
February 2017

Panobinostat for the management of multiple myeloma.

Future Oncol 2017 Mar 25;13(6):477-488. Epub 2016 Oct 25.

Division of Hematologic Malignancies and Cellular Therapy, Duke University Medical Center, Durham, NC, USA.

Multiple myeloma (MM) is the second most common blood cancer following non-Hodgkin's lymphoma. While the treatments for MM have improved over the past decade, for the most part, it remains an incurable disease. For this reason newer therapeutic agents are needed to combat this malignancy. Panobinostat is a pan-deacetylase inhibitor that impedes protein destruction by disturbing the enzymatic activity of deacetylases. It was US FDA approved in February 2015 for the management of relapsed/refractory MM in combination with bortezomib and dexamethasone. Several trials are ongoing, exploring the utility of panobinostat in various other settings for the management of MM. This review will detail the biology, clinical efficacy and potential future applications of panobinostat in the treatment of MM.
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http://dx.doi.org/10.2217/fon-2016-0329DOI Listing
March 2017
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