2,141 research outputs found
Representational practices in VMT.
This chapter analyzes the interaction of three students working on mathematics problems over several days in a virtual math team. Our analysis traces out how successful collaboration in a later session was contingent upon the work of prior sessions, and shows how representational practices are important aspects of these participantsâ mathematical problem solving. We trace the formation, transformation and refinement of one problem-solving practiceâproblem decompositionâand three representational practicesâinscribe first solve second, modulate perspective and visualize decomposition. The analysis is of theoretical interest because it suggests that âsituated cognitionâ is contingent upon not only the immediate situation but also the chronologically prior resources and associated practices; shows how inscriptions become representations for the group through an interactive process of interpretation; and sheds light on âgroup cognitionâ as an interactional process that is not identical to individual cognition yet that draws upon a dynamic interplay of individual contributions
Investigating photoexcitation-induced mitochondrial damage by chemotherapeutic corroles using multimode optical imaging
We recently reported that a targeted, brightly fluorescent gallium corrole (HerGa) is highly effective for breast tumor detection and treatment. Unlike structurally similar porphryins, HerGa exhibits tumor-targeted toxicity without the need for photoexcitation. We have now examined whether photoexcitation further modulates HerGa toxicity, using multimode optical imaging of live cells, including two-photon excited fluorescence, differential interference contrast (DIC), spectral, and lifetime imaging. Using two-photon excited fluorescence imaging, we observed that light at specific wavelengths augments the HerGa-mediated mitochondrial membrane potential disruption of breast cancer cells in situ. In addition, DIC, spectral, and fluorescence lifetime imaging enabled us to both validate cell damage by HerGa photoexcitation and investigate HerGa internalization, thus allowing optimization of light dose and timing. Our demonstration of HerGa phototoxicity opens the way for development of new methods of cancer intervention using tumor-targeted corroles
Re-evaluation of mammary stem cell biology based on in vivo transplantation
Over nearly half a century, transplantation methods have been employed to regenerate the mammary gland in vivo. Recent highly cited reports claim to have demonstrated the regeneration of an entire functional mammary gland from a single mammary epithelial cell. Nevertheless, re-examination of the literature on the transplantation biology of mammary gland regeneration reveals that a complex, combinatorial interaction between variously differentiated mammary epithelial cells and the mammary fat pad stroma is indispensable to this process. In the present article, these issues are reviewed and discussed to provide a greater understanding of the complexity of these multiplex interactions
SIT 45: An interacting, compact, and star-forming isolated galaxy triplet
Acknowledgements. We thank our referee whose valuable comments have certainly
contributed to improve and clarify this paper. MAF and PVB acknowledge
financial support by the DI-PUCV research project 039.481/2020. MAF
also acknowledges support from FONDECYT iniciaciĂłn project 11200107 and
the Emergia program (EMERGIA20_38888) from ConsejerĂa de TransformaciĂłn
EconĂłmica, Industria, Conocimiento y Universidades and University of
Granada. UL and DE acknowledge support from project PID2020-114414GB-
100, financed by MCIN/AEI/10.13039/501100011033. DE also acknowledges
support from Beatriz Galindo senior fellowship (BG20/00224) financed by the
Spanish Ministry of Science and Innovation, and project PID2020-114414GB-
100 financed by MCIN/AEI/10.13039/501100011033. UL, SV and DE acknowledge
support from project P20_00334 financed by the Junta de AndalucĂa and
from FEDER/Junta de AndalucĂa-ConsejerĂa de TransformaciĂłn EconĂłmica,
Industria, Conocimiento y Universidades/Proyecto A-FQM-510-UGR20. MB
gratefully acknowledges support by the ANID BASAL project FB210003
and from the FONDECYT regular grant 1211000. SDP is grateful to the
Fonds de Recherche du QuĂ©bec â Nature et Technologies and acknowledges
financial support from the Spanish Ministerio de EconomĂa y Competitividad
under grants AYA2016-79724-C4-4-P and PID2019-107408GB-C44, from
Junta de AndalucĂa Excellence Project P18-FR-2664, and also acknowledges support from the State Agency for Research of the Spanish MCIU through
the âCenter of Excellence Severo Ochoaâ award for the Instituto de AstrofĂsica
de AndalucĂa (SEV-2017-0709). This research made use of Astropy, a
community-developed core Python (http://www.python.org) package for
Astronomy (Astropy Collaboration 2013); Ipython (PĂ©rez & Granger 2007);
Matplotlib (Hunter 2007); Numpy (Walt et al. 2011); Scipy (Jones et al.
2001); and Topcat (Taylor 2005). This research made use of Astrodendro,
a Python package to compute dendrograms of Astronomical data (http://
www.dendrograms.org/). This research has made use of the NASA/IPAC
Extragalactic Database, operated by the Jet Propulsion Laboratory of the California
Institute of Technology, un centract with the National Aeronautics and
Space Administration. Funding for SDSS-III has been provided by the Alfred P.
Sloan Foundation, the Participating Institutions, the National Science Foundation,
and the U.S. Department of Energy O ce of Science. The SDSS-III Web
site is http://www.sdss3.org/. The SDSS-IV site is http://www.sdss.
org. Based on observations made with the NASA Galaxy Evolution Explorer
(GALEX). GALEX is operated for NASA by the California Institute of Technology
under NASA contract NAS5-98034. This publication makes use of data
products from the Wide-field Infrared Survey Explorer, which is a joint project
of the University of California, Los Angeles, and the Jet Propulsion Laboratory
/California Institute of Technology, funded by the National Aeronautics and
Space Administration.Context. The underlying scenario of the formation and evolution of galaxy triplets is still uncertain. Mergers of galaxies in isolated triplets give us the opportunity to study the already complex merging process, with minimal contamination of other environmental effects that potentially allow and accelerate galaxy transitions from active star-forming to passive galaxies.
Aims. The merging system SIT 45 (UGC 12589) is one of 315 systems in the SDSS-based catalogue of Isolated Triplets (SIT); it is an unusual isolated galaxy triplet, consisting of three merging late-type galaxies. The main aims of this work are to study the dynamical evolution and star formation history (SFH) of SIT 45, as well as its dependence on its local and large-scale environment.
Methods. To study its dynamics, parameters such as the velocity dispersion (Ïv), the harmonic radius (RH), the crossing time (H0tc), and the virial mass (Mvir), along with the compactness of the triplet (S) were considered. To investigate the possible dependence of these dynamical parameters on the environment, the tidal force Q parameters (both local and large-scale) and the projected local density (ηk) were used. To constrain the SFH, we used CIGALE to fit its observed spectral energy distribution using multiwavelength data from the ultraviolet to the infrared.
Results. SIT 45 is one of the most compact triplets in the SIT, and it is also more compact than triplets in other samples. According to its SFH, SIT 45 presents star formation, where the galaxies also present recent (âŒ200 Myr) star formation increase, indicating that this activity may have been triggered by the interaction. Its dynamical configuration suggests that the system is highly evolved in comparison to the SIT. However, this is not expected for systems composed of star-forming late-type galaxies, based on observations in compact groups.
Conclusions. We conclude that SIT 45 is a system of three interacting galaxies that are evolving within the same dark matter halo; its compact configuration is a consequence of the ongoing interaction rather than being due to a long-term evolution (as suggested from its H0tc value). We consider two scenarios for the present configuration of the triplet, one where one of the members is a tidal galaxy, and another where this galaxy arrives to the system after the interaction. Both scenarios need further exploration. The isolated triplet SIT 45 is therefore an ideal system to study short timescale mechanisms (âŒ108 yr), such as starbursts triggered by interactions which are more frequent at higher redshift.DI-PUCV research project 039.481/2020FONDECYT iniciaciĂłn project 11200107Emergia program (EMERGIA20_38888) from ConsejerĂa de TransformaciĂłn EconĂłmica, Industria, Conocimiento y UniversidadesUniversity of GranadaProject PID2020-114414GB- 100, financed by MCIN/AEI/10.13039/501100011033Senior fellowship (BG20/00224) financed by the Spanish Ministry of Science and InnovationProject PID2020-114414GB- 100 financed by MCIN/AEI/10.13039/501100011033Project P20_00334 financed by the Junta de AndalucĂa and from FEDER/Junta de AndalucĂa-ConsejerĂa de TransformaciĂłn EconĂłmica, Industria, Conocimiento y Universidades/Proyecto A-FQM-510-UGR20ANID BASAL project FB210003FONDECYT regular grant 1211000Fonds de Recherche du QuĂ©bec â Nature et TechnologiesSpanish Ministerio de EconomĂa y Competitividad under grants AYA2016-79724-C4-4-P and PID2019-107408GB-C44Junta de AndalucĂa Excellence Project P18-FR-2664State Agency for Research of the Spanish MCIU through the âCenter of Excellence Severo Ochoaâ award for the Instituto de AstrofĂsica de AndalucĂa (SEV-2017-0709
Conformal windows beyond asymptotic freedom
We study four-dimensional gauge theories coupled to fermions in the fundamental and mesonlike scalars. All requisite beta functions are provided for general gauge group and fermion representation. In the regime where asymptotic freedom is absent, we determine all interacting fixed points using perturbation theory up to three loop in the gauge and two loop in the Yukawa and quartic couplings. We find that the conformal window of ultraviolet fixed points is narrowed down by finite-N corrections beyond the Veneziano limit. We also find a new infrared fixed point whose main features, such as scaling exponents, UV-IR connecting trajectories, and phase diagram, are provided. Both fixed points collide upon varying the number of fermion flavors Nf, and conformality is lost through a saddle-node bifurcation. We further revisit the prospect for ultraviolet fixed points in the large-Nf limit where matter field fluctuations dominate. Unlike at weak coupling, we do not find clear evidence for new scaling solutions even in the presence of scalar and Yukawa couplings
The use of quartz crystal microbalance with dissipation (QCM-D) for studying nanoparticle-induced platelet aggregation
Interactions between blood platelets and nanoparticles have both pharmacological and toxicological significance and may lead to platelet activation and aggregation. Platelet aggregation is usually studied using light aggregometer that neither mimics the conditions found in human microvasculature nor detects microaggregates. A new method for the measurement of platelet microaggregation under flow conditions using a commercially available quartz crystal microbalance with dissipation (QCM-D) has recently been developed. The aim of the current study was to investigate if QCM-D could be used for the measurement of nanoparticle-platelet interactions. Silica, polystyrene, and gold nanoparticles were tested. The interactions were also studied using light aggregometry and flow cytometry, which measured surface abundance of platelet receptors. Platelet activation was imaged using phase contrast and scanning helium ion microscopy. QCM-D was able to measure nanoparticle-induced platelet microaggregation for all nanoparticles tested at concentrations that were undetectable by light aggregometry and flow cytometry. Microaggregates were measured by changes in frequency and dissipation, and the presence of platelets on the sensor surface was confirmed and imaged by phase contrast and scanning helium ion microscopy
Hormone-induced protection of mammary tumorigenesis in genetically engineered mouse models
INTRODUCTION: The experiments reported here address the question of whether a short-term hormone treatment can prevent mammary tumorigenesis in two different genetically engineered mouse models. METHODS: Two mouse models, the p53-null mammary epithelial transplant and the c-neu mouse, were exposed to estrogen and progesterone for 2 and 3 weeks, respectively, and followed for development of mammary tumors. RESULTS: In the p53-null mammary transplant model, a 2-week exposure to estrogen and progesterone during the immediate post-pubertal stage (2 to 4 weeks after transplantation) of mammary development decreased mammary tumorigenesis by 70 to 88%. At 45 weeks after transplantation, analysis of whole mounts of the mammary outgrowths demonstrated the presence of premalignant hyperplasias in both control and hormone-treated glands, indicating that the hormone treatment strongly affects the rate of premalignant progression. One possible mechanism for the decrease in mammary tumorigenesis may be an altered proliferation activity as the bromodeoxyuridine labeling index was decreased by 85% in the mammary glands of hormone-treated mice. The same short-term exposure administered to mature mice at a time of premalignant development also decreased mammary tumorigenesis by 60%. A role for stroma and/or systemic mediated changes induced by the short-term hormone (estrogen/progesterone) treatment was demonstrated by an experiment in which the p53-null mammary epithelial cells were transplanted into the cleared mammary fat pads of previously treated mice. In such mice, the tumor-producing capabilities of the mammary cells were also decreased by 60% compared with the same cells transplanted into unexposed mice. In the second set of experiments using the activated Her-2/neu transgenic mouse model, short-term estradiol or estradiol plus progesterone treatment decreased mammary tumor incidence by 67% and 63%, and tumor multiplicity by 91% and 88%, respectively. The growth rate of tumors arising in the hormone-treated activated Her-2/neu mice was significantly lower than tumors arising in non-hormone treated mice. CONCLUSION: Because these experiments were performed in model systems that mimic many essential elements of human breast cancer, the results strengthen the rationale for translating this prevention strategy to humans at high risk for developing breast cancer
Anomalous Fluctuations of Directed Polymers in Random Media
A systematic analysis of large scale fluctuations in the low temperature
pinned phase of a directed polymer in a random potential is described. These
fluctuations come from rare regions with nearly degenerate ``ground states''.
The probability distribution of their sizes is found to have a power law tail.
The rare regions in the tail dominate much of the physics. The analysis
presented here takes advantage of the mapping to the noisy-Burgers' equation.
It complements a phenomenological description of glassy phases based on a
scaling picture of droplet excitations and a recent variational approach with
``broken replica symmetry''. It is argued that the power law distribution of
large thermally active excitations is a consequence of the continuous
statistical ``tilt'' symmetry of the directed polymer, the breaking of which
gives rise to the large active excitations in a manner analogous to the
appearance of Goldstone modes in pure systems with a broken continuous
symmetry.Comment: 59 pages including 8 figures ( REVTEX 3.0 )E-mail:
[email protected]
Expression of MDM2 during mammary tumorigenesis
The MDM2 oncoprotein encodes a 90 kDa nuclear phosphoprotein capable of abrogating the growth suppressive functions of p53 and pRb tumor suppressor proteins by direct interaction. Alternative splicing of MDM2 protein coding sequences has been documented during tumor progression in human ovarian and bladder carcinomas. The aim of this study was to determine whether alternative splicing of MDM2 occurs during breast tumorigenesis in mice and humans and whether protein coding sequences were affected. Specimens representing normal and malignant breast tissues from the murine D2 mammary tumor model system and human breast carcinomas were examined. Three distinct mdm2 mRNA transcripts of 3.3, 1.6 and 1.5 kb were detected in normal and malignant murine mammary tissues by Northern blot analysis using a full-length mdm2 cDNA probe. Additional Northern blot analysis using a probe derived from exon 12 of murine mdm2 demonstrated that the 1.5 and 1.6 kb transcripts lack sequences encoding the C-terminus of the protein. No evidence of internal deletions of protein coding sequences of mdm2 was detected in any of the normal mammary tissues or D2 murine mammary tumors examined by reverse transcription PCR (RT-PCR). Three distinct MDM2 transcripts of 6.7, 4.7 and 1.9 kb were detected in malignant human breast tissue by Northern blot analysis using a cDNA probe specific for the complete open reading frame of human MDM2. However, a cDNA probe specific for the last exon of human MDM2 hybridized only to the 6.7 and 4.7 kb transcripts, demonstrating that the 1.9 kb transcript lacked protein coding sequences contained in exon 12. Similarly, no internal deletions were detected in a panel of malignant human breast tissues using RT-PCR and analogous primers within human MDM2. Therefore, breast tumors differ from other solid tumors reported previously in that no internal deletions of MDM2 protein coding sequences were observed. However, the data document the presence of multiple MDM2 mRNA transcripts in both normal and malignant breast tissues. A subset of MDM2 transcripts were shown to lack the last exon which contains sequences coding for the RING and zinc fingers and domains which are targets for caspase-3 mediated proteolytic degradation and are required to target p53 for proteosomal degradation. Int. J. Cancer 81:292-298, 1999. 1999 Wiley-Liss, Inc
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