Nonparametric maximum likelihood estimation is intended to infer the unknown density distribution while making as few assumptions as possible. To alleviate the over parameterization in nonparametric ...data fitting, smoothing assumptions are usually merged into the estimation. In this letter a novel boosting-based method is introduced to the nonparametric estimation in univariate cases. We deduce the boosting algorithm by the second-order approximation of nonparametric log-likelihood. Gaussian kernel and smooth spline are chosen as weak learners in boosting to satisfy the smoothing assumptions. Simulations and real data experiments demonstrate the efficacy of the proposed approach.
Summary
Activating mutation of FLT3 by internal tandem duplications (ITDs) in the juxtamembrane region is the most common molecular aberration found in acute myeloid leukaemia (AML). In this study, a ...lentiviral vector containing two promoters achieved consistent and efficient co‐expression of FLT3/ITD and GFP in transduced human CD34+ haematopoietic stem/progenitor cells (HSPCs). When cultured in medium containing stem cell factor, thrombopoietin and FLT3 ligand (FL), FLT3/ITD‐transduced cells demonstrated enhanced self‐renewal and survival potential, unaffected by the withdrawal of FL. These cells retained a CD34+CD38−/dim immunophenotype, typical of HSPCs. Compared to cells transduced with a vector expressing GFP alone, FLT3/ITD‐transduced HSPCs had a higher fraction of cells in active cell cycle. FLT3/ITD‐transduced HSPCs were more sensitive to the induction of cytotoxicity by CEP‐701, a selective FLT3 inhibitor, indicating a rapid ‘addiction’ to signalling through this oncogenic pathway. The FLT3/ITD‐transduced HSPCs showed increased expression of Pim‐1, c‐Myc and Cyclin D3 (CCND3), each of which may contribute to the altered genetic programme instituted by FLT3/ITD signalling. Taken together, these results indicate that FLT3/ITD mutations may contribute to leukaemic transformation of normal HSPCs by prolonging survival, promoting proliferation and partially blocking differentiation. CEP‐701 may act as a potent therapeutic agent for AML stem cells harbouring FLT3/ITD mutations.
To improve the dewatering performances of the waste slurry, a new Fe-Polyacrylamide (Fe-PAM) flocculant was synthesized. Comparative analysis with various ionic forms of polyacrylamide (PAM) reveals ...that the Fe-PAM flocculant has the shortest flocculation time, the lowest optimal shear gradient for flocculation, and the best filtration performance. The capillary suction time (CST) of Fe-PAM treated slurry was improved from 262.3 s (raw sample) to 6.0 s. Moreover, sludge treated with Fe-PAM exhibits the lowest porosity under the same consolidation pressure and the highest permeability at the same void ratio. In addition, mercury intrusion porosimetry (MIP) results indicated that the Fe-PAM-treated sample features the highest number of largesized inter-aggregate pores (average value of 184.2 nm and median value of 23.2 nm) and the greatest pore connectivity (60.55 %), contributing to its superior permeability. The effectiveness of Fe-PAM is further elaborated through a synergistic flocculation mechanism, encompassing the electrical neutralization effect of the inorganic metal Fe3+ and the adsorption bridging effect of PAM's long-chains. This study demonstrates the potential of the synthesized Fe-PAM flocculant to enhance the dewatering efficiency of high-water content slurry and offers valuable insights for synthesizing advanced flocculants in slurry treatment engineering.
•A novel organic-inorganic hybrid flocculant was synthesized.•Flocculant has the dual mechanism of electric neutralization and adsorption bridging.•The flocculation effect was compared with different ionic polyacrylamide.•Effectively reduce the bound water and accelerate the flocculation process.•The large pores in the soil samples after treatment increased significantly.
Recent advances in induced pluripotent stem (iPS) cell research have significantly changed our perspective on regenerative medicine. Patient‐specific iPS cells have been derived not only for disease ...modeling but also as sources for cell replacement therapy. However, there have been insufficient data to prove that iPS cells are functionally equivalent to human embryonic stem (hES) cells or are safer than hES cells. There are several important issues that need to be addressed, and foremost are the safety and efficacy of human iPS cells of different origins. Human iPS cells have been derived mostly from cells originating from mesoderm and in a few cases from ectoderm. So far, there has been no report of endoderm–derived human iPS cells, and this has prevented comprehensive comparative investigations of the quality of human iPS cells of different origins. Here we show for the first time reprogramming of human endoderm‐derived cells (i.e., primary hepatocytes) to pluripotency. Hepatocyte‐derived iPS cells appear indistinguishable from hES cells with respect to colony morphology, growth properties, expression of pluripotency‐associated transcription factors and surface markers, and differentiation potential in embryoid body formation and teratoma assays. In addition, these cells are able to directly differentiate into definitive endoderm, hepatic progenitors, and mature hepatocytes. Conclusion: The technology to develop endoderm–derived human iPS cell lines, together with other established cell lines, will provide a foundation for elucidating the mechanisms of cellular reprogramming and for studying the safety and efficacy of differentially originated human iPS cells for cell therapy. For the study of liver disease pathogenesis, this technology also provides a potentially more amenable system for generating liver disease‐specific iPS cells. (HEPATOLOGY 2010;51:1810–1819)
Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, US Food and Drug Administration, USA
Rationale : Differentiation of hematopoietic stem cells from human induced ...pluripotent stem cells (iPSCs) has the potential to provide novel therapeutic options for a wide range of blood diseases; however, despite significant progress that has been made in driving iPSC differentiation, issues with limited differentiation potential and engraftment capability in vivo still persist. A better understanding of the key regulators of hematopoiesis is essential for the development of improved differentiation protocols. GATA-2, a transcription factor shown to be essential for hematopoiesis, has been examined to determine its role in both hematopoiesis and endothelial cell development. Mouse studies have described an early developmental Gata-2 hematopoietic-specific enhancer located 5′ to its distal first exon. Based on homology within this regulatory domain between mouse and human sequences, we hypothesize that this cis-regulatory region plays an essential role in human hematopoietic expression of GATA-2 and in endothelial-to-hematopoietic transition.
Methods : In this study, we use a genome editing approach and an in vitro human iPSC differentiation system to examine our hypothesis. A pair of CRISPR/Cas9 guide RNA was designed to recognize sequences of a DNase I hypersensitive site (DHS) within the putative enhancer region immediately upstream of the GATA-2 distal first exon. Human iPSCs were treated with CRISPR/Cas9 to create cell lines that have a deletion at this DHS. These genetically modified iPSC lines were compared to their isogenic parental controls, to examine functional consequences of the deletion. Both adherent culture-based and spin-embryoid body formation-based protocols were used for mesodermal differentiation, endothelial specification and hematopoietic induction.
Results : Screening of human iPSC clones after co-transfection of Cas9 and guide RNA-expression vectors has identified clones with ~400 bp deletion of the DNase I hypersensitive site that is conserved among vertebrates. When maintained in iPSC expansion condition, these iPSC clones display typical undifferentiated human iPSC morphology and expression of pluripotency-related markers such as TRA-1-60. Upon treatment with a Wnt signaling activator, BMP4, bFGF and VEGF, the genetically modified cells showed similar differentiation efficiency, compared to parental controls, to mesoderm and endothelial lineages. However, they exhibit a lower proliferation rate in endothelial expansion conditions. Preliminary studies also showed a deficiency of the modified cells in their ability to form capillary-like structures in tube formation assays. In hematopoietic differentiation experiments using the spin-EB method, these cells showed very low viability upon hematopoietic induction and failed to produce hematopoietic progenitor cells. These results suggest that the DNase I hypersensitive site upstream of GATA2 distal first exon plays an important role in human endothelial cell function including transition from hemogenic endothelium to hematopoietic cells upon stimulation.
Currently, experiments are being conducted to characterize the functionality of endothelial-like cells and to confirm previous observations in additional iPSC lines. Differential expression of GATA-2 between parental and genome edited cells at various developmental stages is being determined. Hematopoietic differentiation capacity of these iPSCs by stromal cell co-culture methods is being used to confirm observations from the spin-EB protocol. Defining the functional outcome of this targeted deletion, across several iPSC lines, will provide a system for understanding molecular regulations in the first steps of human hematopoietic stem cell generation.
No relevant conflicts of interest to declare.
Traditional methods of dividing petroleum reservoirs are inefficient. The machine learning method has been applied in the two-class and three-class tasks of the reservoir, but there is no research on ...the classification of all classes. In this paper, the GBDT (Gradient Boosting Decision Tree) model is proposed for the reservoir classification problem in argillaceous sandstone areas, and the model is implemented by XGBoost algorithm. The classification effect of this model is better than that of multiple-hidden-layer neural networks, and the macro-average AUC is 0.89.
Efficient and precise genome editing is crucial for realizing the full research and therapeutic potential of human induced pluripotent stem cells (iPSCs). Engineered nucleases including CRISPR/Cas9 ...and transcription activator like effector nucleases (TALENs) provide powerful tools for enhancing gene-targeting efficiency. In this study, we investigated the relative efficiencies of CRISPR/Cas9 and TALENs in human iPSC lines for inducing both homologous donor-based precise genome editing and nonhomologous end joining (NHEJ)-mediated gene disruption. Significantly higher frequencies of NHEJ-mediated insertions/deletions were detected at several endogenous loci using CRISPR/Cas9 than using TALENs, especially at nonexpressed targets in iPSCs. In contrast, comparable efficiencies of inducing homologous donor-based genome editing were observed at disease-associated loci in iPSCs. In addition, we investigated the specificity of guide RNAs used in the CRISPR/Cas9 system in targeting disease-associated point mutations in patient-specific iPSCs. Using myeloproliferative neoplasm patient-derived iPSCs that carry an acquired JAK2-V617F point mutation and α1-antitrypsin (AAT) deficiency patient-derived iPSCs that carry an inherited Z-AAT point mutation, we demonstrate that Cas9 can specifically target either the mutant or the wild-type allele with little disruption at the other allele differing by a single nucleotide. Overall, our results demonstrate the advantages of the CRISPR/Cas9 system in allele-specific genome targeting and in NHEJ-mediated gene disruption.
Human induced pluripotent stem (iPS) cells derived from somatic cells hold promise to develop novel patient-specific cell therapies and research models for inherited and acquired diseases. We and ...others previously reprogrammed human adherent cells, such as postnatal fibroblasts to iPS cells, which resemble adherent embryonic stem cells. Here we report derivation of iPS cells from postnatal human blood cells and the potential of these pluripotent cells for disease modeling. Multiple human iPS cell lines were generated from previously frozen cord blood or adult CD34+ cells of healthy donors, and could be redirected to hematopoietic differentiation. Multiple iPS cell lines were also generated from peripheral blood CD34+ cells of 2 patients with myeloproliferative disorders (MPDs) who acquired the JAK2-V617F somatic mutation in their blood cells. The MPD-derived iPS cells containing the mutation appeared normal in phenotypes, karyotype, and pluripotency. After directed hematopoietic differentiation, the MPD-iPS cell-derived hematopoietic progenitor (CD34+CD45+) cells showed the increased erythropoiesis and gene expression of specific genes, recapitulating features of the primary CD34+ cells of the corresponding patient from whom the iPS cells were derived. These iPS cells provide a renewable cell source and a prospective hematopoiesis model for investigating MPD pathogenesis.
Multi-agent path finding (MAPF) is an essential issue for warehouse automation, where multiple agents plan collision-free paths from the start to goal positions. Reinforcement learning (RL) has been ...employed to develop partially observable distributed MAPF methods that can be scaled to any number of agents. However, existing RL-based MAPF methods still have some limitations in handling redundant information and avoiding deadlock, resulting in a low success rate or longer makespan. This paper proposes a Priority-aware Communication & Experience learning method (PCE), which combines RL with a novel priority-aware multi-agent communication and a new priority-aware deadlock experience replay to tackle this challenge. To be specific, our innovation encompasses two-fold. Our proposed communication mechanism aims to handle redundant information, which establishes a dynamic communication topology based on agents' priorities and proposes a two-head priority-aware graph attention network to aggregate information. In order to help the agent avoid deadlock, we prioritize the expert experience that solves the deadlock when performing experience replay. We conduct multiple simulation experiments on warehouse-like structured grid maps. Compared with the state-of-the-art RL-based MAPF methods, PCE performs significantly better with a higher success rate and lower makespan in small and large MAPF and higher average throughput in the lifelong MAPF, which can further improve the efficiency of warehouse automation. Finally, we validate PCE using three Turtlebot3-Burger robots, which shows that PCE can be applied in real warehouse automation scenarios.
To determine the most robust and reproducible parameters for noninvasively estimating tumor cell burden in a murine model, we used real-time in vivo bioluminescent imaging to assess the growth ...kinetics and dissemination of luciferase-transfected Raji B-cell lymphoma. Bioluminescent signals were acquired every minute for 40 minutes after luciferin injection every other day post-tumor injection. The total 40-minute area under the curve (AUC) of photon intensity (photons/second) was calculated and compared with simplified fixed time point observations (every 5 minutes from 5 to 40 minutes after substrate injection). There was substantial variability in the shape of the time signal intensity curves at different stages of tumor growth in both the intravenous and subcutaneous models. The coefficient of variance in the AUC was 0.27 (intravenous) and 0.36 (subcutaneous) as values determined by fitting the curve, whereas the 20-minute time point measurement varied at 0.29 (intravenous) and 0.37 (subcutaneous). In both the subcutaneous and intravenous models, single time point measurements at 20 minutes had the highest correlation value with AUC. This simplified single time point measurement appears appropriate to estimate the total tumor burden in this model, but the substantial variance at each measurement must be considered in experimental designs.
PDF
