241,449 research outputs found
A C++ Program for the Cramér-Von Mises Two-Sample Test
No full textAs larger sets of high-throughput data in genomics and proteomics become more readily available, there is a growing need for fast algorithms designed to compute exact p values of distribution-free statistical tests. We present a program for computing the exact distribution of the two-sample Cramér-von Mises test statistic under the null hypothesis that the two samples are drawn from the same continuous distribution. The program makes it possible to handle substantially larger sample sizes than earlier proposed computational tools. The C++ source code for the program is published with this paper, and an R package is under development.
Comment on "Berry phase correction to electron density in solids" by Xiao et al
No full textComment. 2 pages, no figures. Reference date corrected Affiliation of the first author expandedThe main result of Xiao et al. [ Phys. Rev. Lett. 95, 137204 (2005)] is shown to follow from Hamiltonian mechanics
Structure elucidation and absolute configuration determination of C , C and C tirucallane triterpenoids from the leaves of Picrasma quassioides (D. Don) Benn
No full textYang, Pei-Yuan, Zhao, Peng, Bai, Ming, Yu, Xiao-Qi, Ren, Hui, Liu, Qing-Bo, Lin, Bin, Song, Shao-Jiang, Huang, Xiao-Xiao (2021): Structure elucidation and absolute configuration determination of C , C and C tirucallane triterpenoids from the leaves of Picrasma quassioides (D. Don) Benn. Phytochemistry (112675) 184: 1-9, DOI: 10.1016/j.phytochem.2021.112675, URL: http://dx.doi.org/10.1016/j.phytochem.2021.11267
Tumor necrosis factor-related apoptosis-inducing ligand-induced death-inducing signaling complex and its modulation by c-FLIP and PED/PEA-15 in glioma cells.
No full textTumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can trigger apoptosis in some tumor cells but not other tumor cells. To explore the signal transduction events in TRAIL-triggered apoptosis and its modulation in nontransfected tumor cells, we analyzed TRAIL-induced death-inducing signaling complex (DISC) in TRAIL-sensitive and -resistant glioma cells. Caspase-8 and caspase-10 were recruited to the DISC, where they were proteolytically activated to initiate apoptosis in TRAIL-sensitive glioma cells. Caspase-8 and caspase-10 were also recruited to the DISC in TRAIL-resistant cells, but their further activation was inhibited by two antiapoptotic proteins termed cellular Fas-associated death domain-like interleukin-1beta-converting enzyme-inhibitory protein (c-FLIP) and phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes-15kDa (PED/PEA-15). Both long and short forms of c-FLIP were recruited to the DISC, where the long form c-FLIP was cleaved to produce intermediate fragments. Of the three isoforms of PED/PEA-15 proteins, only the doubly phosphorylated form was expressed and recruited to the DISC in TRAIL-resistant cells, indicating that the phosphorylation status of PED/PEA-15 determines its recruitment in the cells. Treatment with calcium/calmodulin-dependent protein kinase inhibitor rescued TRAIL sensitivity in TRAIL-resistant cells, providing a potential new approach to sensitize the cells to TRAIL-induced apoptosis
From supramolecular vanadate receptors to enzyme models of vanadium Haloperoxidase
No full textV-HPOs are enzymes catalyzing the halogenation of a variety of organic substrates using hydrogen peroxide and halide ions at slightly acidic condition[1-3]. The X-ray structure of V-HPO from Curvularia inaequalis[4, 5] reveals that the positively charged residues at the active site bind orthovanadate (HVO42-) through electrostatic interaction and hydrogen bonds, together with one coordinating bond from the nitrogen (N 2) of His496 to vanadium, which is the only direct bond from protein to metal center. Accordingly the coordination sphere at vanadium is trigonalbipyramidal, resembling the transition state of SN2-type reactions involving phosphates[6]. Apart from that, vanadate and phosphate are also very similar in the tetrahedral ground state. Thus, it is no surprise that vanadate is an inhibitor of various phosphate metabolizing enzymes[7]. Since the structural assignment and reaction mechanism of V-HPOs are still under debate, and no structural model reported so far shows high fidelity concerning the non-covalent binding fashion, we decided to prepare supramolecular models structurally related to the binding mode of HVO42- in the enzyme, and study the influence of the binding sphere of vanadate to its catalytic activity. The vanadate receptor tris-(2-guanidinium-ethyl)aminewas rationally designed and conveniently synthesized from tris-(2-aminoethyl)amine via single step. Its three guanidinium-arms can provide not only positive charges but also several hydrogen bond donor sites. The central nitrogen with pKa=2.48 for its conjugated acid, allows the V-N coordination to occur within a broad pH window. The X-ray structure ofreveals that it is already preorganized in a basket shape before binding vanadate, which verifies our design. NMR titration data from 51V of vanadate and 1H of the ligand give complementary
results. The ligand 1 binds vanadate as 1/1 complex 5 (Scheme 19) at pH 10.21 in
water solution, with Ka = 103 Mol-1. The complex 5 was also detected by ESI-MS.
The absorption at 306 nm observed in UV difference spectrum is an indication of a VN
bond formation in agreement with coordination in V-HPO. The time dependent
DFT calculation both for enzyme and model system 5 provided in-depth evidence that
V-N coordination is responsible for this UV band.
5 is the first supramolecular structural model V-HPO. These model studies provided
for the first time evidence that the V-N bond of V-HPO is coordinative and not
covalent as original proposed[8].
A series of more rigid novel guanidinium-cryptands containing the key scaffold of 1
were synthesized (Scheme 20), the preorganization was expected to provide higher
affinity to vanadate. A general flexible synthetic strategy was developed which allows
the preparation of the guanidinium cryptands with different size and geometry.
However, spectroscopic studies failed to demonstrate any enhancement of binding
constant for encapsulating vanadate. The association of vanadate most likely occurres
not interior but outside of the cavity even for the largest cage receptor 35. Three pyrene moieties introduced to the terminal-N atoms of 1 not only improved the
solubility of the receptor in unpolar solvent, but also served as UV and fluorescence
sensor for vanadate recognition (see Scheme 21). In addition, the - stacking
interaction within pyrenes holds three arms together to further preorganize itself
favoring the binding of vanadate. This preorganization was demonstrated by
observing the pyrene excimer emission, which can be also observed for the neutral
analogue 53. The binding of vanadate to 36 and 53 is coupled with the significant UV and
fluorescence response in acetonitrile. Upon the addition of vanadate, the UV bands of
36 became broader and red shifted, together with a PET-type fluorescence quenching.
Therefore, deduced from the UV, fluorescence titration and additional 51V-NMR data,
36 exhibits an association constant >> 3 × 107 mol-1 with pyrovanadate (V2O7
4-, V2)
(Scheme 22) in acetonitrile, which is at least 4 times magnitude higher than that of 1 to vanadate (HVO4
2-, V1). The preference of 36 to bind V2 over V1 was also
confirmed in titration studies with the pyrophosphate and phosphate, the structure
analogue of V2 and V1 respectively. The neutral thiourea receptor 53 shows much lower binding constant and almost no
preference to any vanadate or phosphate species mentioned above, revealing the
importance of positive charge on the affinity and selectivity for anion binding.
Kinetic studies reveal that simple vanadate in acetonitrile is a more efficient
functional model than in water. The rate acceleration in acetonitrile is thought to be
originated from an enzyme-like hydrophobic environment for the catalytic species.
UV and fluorescence titration shows that the supramolecular receptor 36 exhibits high
affinity to the peroxovanadate as well, which verifies that vanadium core keeps being
bounded in the catalytical cycle. A competitive catalytic bromination experiment was
designed and successfully demonstrated the kinetic process for the catalytic
bromination of 1,3,5-tri-methoxy-benzene (TMB) and monochlorodimedone (MCD)
mixture substrates. The addition of 36 to the reaction system significantly enhances
the catalytic efficiency. The rate enhancement by 36 may be reasoned to the
increasing of Lewis acidity of vanadate by forming hydrogen bonds with positively
charged guanidiniums of 36. In addition, the central nitrogen atom of 36 may act as an
acid base catalyst, facilitating the protonation of peroxovanadate. All together, 36 is
an effective functional model for V-HPO based on the structural fidelity to the
supramolecular binding fashion of the enzyme
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Cordyceps poluscapitis X. C. Peng, Y. P. Xiao & T. C. Wen 2023, sp. nov.
No full textCordyceps poluscapitis X.C. Peng, Y.P. Xiao & T.C. Wen, sp. nov. (Fig. 2) Index Fungorum number: IF559584; Facesoffungi number: FoF13863 Etymology:— Fertile head is small. Holotype:— HKAS 122630 Parasitic on ants (Hymenoptera, Formicidae). Host 1.2 cm long, red-brown, with white mycelium on the surface. Sexual morph:— Stromata 11 mm long, stipitate, double, unbranched, arising from the head and thorax of ant, pale yellow to orange. Stipe 8–9 mm long, 0.2–0.4 mm diam., pale yellow to orange, fleshy, cylindrical. Fertile head 2.5 mm long, 0.5–0.8 mm diam., single, clavate, surface roughened, orange. Perithecia 250–300 × 130–210 μm (x = 273 × 148 µm, n = 10), superficial, pale yellow-orange, ovoid. Asci 63–114 × 1.4–3.6 μm (x = 87 × 2.4 µm, n = 10), narrow cylindrical, hyaline, with a thickened apical cap. Apical cap 1.4–2.4 × 2.1–3.1 μm (x = 1.8 × 2.7 µm, n = 15), hyaline. Ascospores as long as asci, 0.2–0.5 μm (x = 0.3 µm, n = 10) diam., filiform, hyaline. Culture characteristics:— colonies on PDA, attaining a diameter of 29–34 mm after 19 d at 20 ° C, dense, cottony, white, ringed, reverse yellowish. Hyphae smooth, septate, hyaline, 0.7–3.25 μm (x = 1.7 µm, n = 30) diam. Phialides 11–25 × 0.8–1.4 µm (x = 17.2 × 1.1 µm, n = 5), solitary, smooth, lancelate. Conidia 3.8–17.1 × 1.1–2.4 µm (x = 9.6 × 1.6 µm, n = 40), cylindrical, smooth, aseptate or 1–2 septate. Material examined:— CHINA. Guizhou Province: Chishui Waterfall, on dead ant (Hymenoptera; Formicidae), 4 April 2021, collected by Xing-Can Peng (holotype HKAS 122630; ex-type living culture CS21040411).Published as part of Peng, Xing-Can, Xiao, Yuan-Pin, Zhang, Yan, Chomnunti, Putarak, Tangtrakulwanich, Khanobporn & Wen, Ting-Chi, 2023, Cordyceps poluscapitis sp. nov., an ant-pathogenic fungus from Guizhou, China, pp. 239-251 in Phytotaxa 599 (4) on pages 245-247, DOI: 10.11646/phytotaxa.599.4.3, http://zenodo.org/record/803020
Extending the Technology Acceptance Model to Investigate Impact of Interactive Games on Learning of Xiao-zhuan(小篆)
No full text[[abstract]]This research focuses on topic of e-learning of Xiao-zhuan through digital Embodied games as a brand new way of creative
learning method for Xiao-zhuan. TAM, Technology Acceptance Model, is the methodology in this research. Theory of
perceived playfulness is also adopted to analyze the learning of Xiao-zhuan. Subjects in this research are 45 sophomores of
the Department of Chinese Literature in National Taiwan Normal University. This research adopts questionnaire survey
method, then refers to students’ paper scores on the test. The results of this research are as follows: Firstly, “Perceived
Usefulness” has the significant influence on “Learning Effectiveness” and “Attitude toward Using the Embodied games”.
Secondly, “Perceived Ease of Use” has the influence on “Perceived Playfulness”. Thirdly, “Perceived Playfulness” has the
significant influence on “Attitude toward Using the Embodied games”.
Improved AC conductance and Gray-Brown methods to characterize fast and slow traps in Ge metal–oxide–semiconductor capacitors
No full textWe use an improved AC conductance method and a modified Gray-Brown method to study fast interface traps and slow border traps in Ge-based MOS capacitors. The combined methods provide the corrected Fermi energy level (E) versus gate voltage (V-g) relationship, even in samples with high densities of traps that cause significant C-V distortion, the energy distribution of interface traps, their capture cross sections (sigma), as well as slow border traps. A wide range of sigma's in p-type Ge is found, indicating that there is more than one type of interface trap near the Ge valence band edge. In contrast, a constant sigma near the Ge conduction band edge is observed in n-type Ge. XPS results indicate that Ge suboxides near the interface are accountable for the detected slow border traps. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691898]This work is partially supported by the National Science
Foundation through MRSEC DMR 1119826, DTRA through
HDTRA 1-10-1-0042, and K. U. Leuven scholarship for the
first author Xiao Sun. Xiao Sun would also like to thank
AMSIMEC and EPI group in IMEC, Belgium for their help and
Benjamin Leung for his help in the preparation of this pape
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