146 research outputs found
Hierarchical accompanying and inhibiting patterns on the spatial arrangement of taxis' local hotspots
Due to the large volume of recording, the complete spontaneity, and the
flexible pick-up and drop-off locations, taxi data portrays a realistic and
detailed picture of urban space use to a certain extent. The spatial
arrangement of pick-up and drop-off hotspots reflects the organizational space,
which has received attention in urban structure studies. Previous studies
mainly explore the hotspots at a large scale by visual analysis or some simple
indexes, where the hotspots usually cover the entire central business district,
train stations, or dense residential areas, reaching a radius of hundreds or
even thousands of meters. However, the spatial arrangement patterns of
small-scale hotspots, reflecting the specific popular pick-up and drop-off
locations, have not received much attention. Using two taxi trajectory datasets
in Wuhan and Beijing, China, this study quantitatively explores the spatial
arrangement of fine-grained pick-up and drop-off local hotspots with different
levels of popularity, where the sizes are adaptively set as 90m*90m in Wuhan
and 105m*105m in Beijing according to the local hotspot identification method.
Results show that popular hotspots tend to be surrounded by less popular
hotspots, but the existence of less popular hotspots is inhibited in regions
with a large number of popular hotspots. We use the terms hierarchical
accompany and inhibiting patterns for these two spatial configurations.
Finally, to uncover the underlying mechanism, a KNN-based model is proposed to
reproduce the spatial distribution of other less popular hotspots according to
the most popular ones. These findings help decision-makers construct reasonable
urban minimum units for precise traffic and disease control, as well as plan a
more humane spatial arrangement of points of interest
Multi-band remote sensing based retrieval model and 3D analysis of water depth in Hulun Lake, China
Hulun Lake, a large lake located on the cold and arid Hulunbeir grassland in the Inner
Mongolia Autonomous Region, is the fifth largest in China and the largest in the north of
the country. However, the information on the lake’s characteristics (e.g., water depth versus
surface area) is scarce in literature. Based on the lake’s physiographic features, this study
developed and used a model that merges the sunlight reflection band with the thermal
infrared radiation band to simulate the lake’s characteristics. The model verification and
error analysis indicated an optimal model structure of logarithm. Thus, this logarithmic
model was selected to analyze the spectral data. The results indicated that the model did a
good job in reproducing observed water depths and accurately predicted the depths on 24
September 2007. This showed that this model can be reliably applied to the cold and arid
region. Subsequently, the results were used to generate a triangular irregular network (TIN)
model, which in turn was used to compute the functional relations between water level,
surface area, and volume. The correlation between water level and volume is superior to
that between water level and area. The regression equation developed in this study can be
used to estimate the volume when water elevation is knowninfo:eu-repo/semantics/publishedVersio
Analogs of the novel phytohormone, strigolactone, trigger apoptosis and synergize with PARP inhibitors by inducing DNA damage and inhibiting DNA repair
Precise Measurements of Branching Fractions for Meson Decays to Two Pseudoscalar Mesons
We measure the branching fractions for seven two-body decays to
pseudo-scalar mesons, by analyzing data collected at
GeV with the BESIII detector at the BEPCII collider. The branching fractions
are determined to be ,
,
,
,
,
,
,
where the first uncertainties are statistical, the second are systematic, and
the third are from external input branching fraction of the normalization mode
. Precision of our measurements is significantly improved
compared with that of the current world average values
Health-Promoting Properties of Common Herbs
Herbs have been used as food and for medicinal purposes for centuries. Research interest has focused on various herbs that possess hypolipidemic, antiplatelet, antitumor, or immune-stimulating properties that may be useful adjuncts in helping reduce the risk of cardiovascular disease and cancer. In different herbs, a wide variety of active phytochemicals, including the flavonoids, terpenoids, lignans, sulfides, polyphenolics, carotenoids, coumarins, saponins, plant sterols, curcumins, and phthalides have been identified. Several of these phytochemicals either inhibit nitrosation or the formation of DNA adducts or stimulate the activity of protective enzymes such as the Phase II enzyme glutathione transferase (EC 2.5.1.18). Research has centered around the biochemical activity of the Allium sp: and the Labiatae, Umbelliferae, and Zingiberaceae families, as well as flaxseed, licorice root, and green tea. Many of these herbs contain potent antioxidant compounds that provide significant protection against chronic diseases. These compounds may protect LDL cholesterol from oxidation, inhibit cyclooxygenase and lipoxygenase enzymes, inhibit lipid peroxidation, or have antiviral or antitumor activity. The volatile essential oils of commonly used culinary herbs, spices, and herbal teas inhibit mevalonate synthesis and thereby suppress cholesterol synthesis and tumor growth
Basal Immunoglobulin Signaling Actively Maintains Developmental Stage in Immature B Cells
In developing B lymphocytes, a successful V(D)J heavy chain (HC) immunoglobulin (Ig) rearrangement establishes HC allelic exclusion and signals pro-B cells to advance in development to the pre-B stage. A subsequent functional light chain (LC) rearrangement then results in the surface expression of IgM at the immature B cell stage. Here we show that interruption of basal IgM signaling in immature B cells, either by the inducible deletion of surface Ig via Cre-mediated excision or by incubating cells with the tyrosine kinase inhibitor herbimycin A or the phosphatidylinositol 3-kinase inhibitor wortmannin, led to a striking “back-differentiation” of cells to an earlier stage in B cell development, characterized by the expression of pro-B cell genes. Cells undergoing this reversal in development also showed evidence of new LC gene rearrangements, suggesting an important role for basal Ig signaling in the maintenance of LC allelic exclusion. These studies identify a previously unappreciated level of plasticity in the B cell developmental program, and have important implications for our understanding of central tolerance mechanisms
Collaborative Action of Brca1 and CtIP in Elimination of Covalent Modifications from Double-Strand Breaks to Facilitate Subsequent Break Repair
Topoisomerase inhibitors such as camptothecin and etoposide are used as anti-cancer drugs and induce double-strand breaks (DSBs) in genomic DNA in cycling cells. These DSBs are often covalently bound with polypeptides at the 3′ and 5′ ends. Such modifications must be eliminated before DSB repair can take place, but it remains elusive which nucleases are involved in this process. Previous studies show that CtIP plays a critical role in the generation of 3′ single-strand overhang at “clean” DSBs, thus initiating homologous recombination (HR)–dependent DSB repair. To analyze the function of CtIP in detail, we conditionally disrupted the CtIP gene in the chicken DT40 cell line. We found that CtIP is essential for cellular proliferation as well as for the formation of 3′ single-strand overhang, similar to what is observed in DT40 cells deficient in the Mre11/Rad50/Nbs1 complex. We also generated DT40 cell line harboring CtIP with an alanine substitution at residue Ser332, which is required for interaction with BRCA1. Although the resulting CtIPS332A/−/− cells exhibited accumulation of RPA and Rad51 upon DNA damage, and were proficient in HR, they showed a marked hypersensitivity to camptothecin and etoposide in comparison with CtIP+/−/− cells. Finally, CtIPS332A/−/−BRCA1−/− and CtIP+/−/−BRCA1−/− showed similar sensitivities to these reagents. Taken together, our data indicate that, in addition to its function in HR, CtIP plays a role in cellular tolerance to topoisomerase inhibitors. We propose that the BRCA1-CtIP complex plays a role in the nuclease-mediated elimination of oligonucleotides covalently bound to polypeptides from DSBs, thereby facilitating subsequent DSB repair
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