4,296 research outputs found
Thermalization, Viscosity and the Averaged Null Energy Condition
We explore the implications of the averaged null energy condition for thermal
states of relativistic quantum field theories. A key property of such thermal
states is the thermalization length. This lengthscale generalizes the notion of
a mean free path beyond weak coupling, and allows finite size regions to
independently thermalize. Using the eigenstate thermalization hypothesis, we
show that thermal fluctuations in finite size `fireballs' can produce states
that violate the averaged null energy condition if the thermalization length is
too short or if the shear viscosity is too large. These bounds become very weak
with a large number N of degrees of freedom but can constrain real-world
systems, such as the quark-gluon plasma.Comment: 28 pages, 3 figure
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The Epstein-Barr Virus Episome Maneuvers between Nuclear Chromatin Compartments during Reactivation.
The human genome is structurally organized in three-dimensional space to facilitate functional partitioning of transcription. We learned that the latent episome of the human Epstein-Barr virus (EBV) preferentially associates with gene-poor chromosomes and avoids gene-rich chromosomes. Kaposi's sarcoma-associated herpesvirus behaves similarly, but human papillomavirus does not. Contacts on the EBV side localize to OriP, the latent origin of replication. This genetic element and the EBNA1 protein that binds there are sufficient to reconstitute chromosome association preferences of the entire episome. Contacts on the human side localize to gene-poor and AT-rich regions of chromatin distant from transcription start sites. Upon reactivation from latency, however, the episome moves away from repressive heterochromatin and toward active euchromatin. Our work adds three-dimensional relocalization to the molecular events that occur during reactivation. Involvement of myriad interchromosomal associations also suggests a role for this type of long-range association in gene regulation.IMPORTANCE The human genome is structurally organized in three-dimensional space, and this structure functionally affects transcriptional activity. We set out to investigate whether a double-stranded DNA virus, Epstein-Barr virus (EBV), uses mechanisms similar to those of the human genome to regulate transcription. We found that the EBV genome associates with repressive compartments of the nucleus during latency and with active compartments during reactivation. This study advances our knowledge of the EBV life cycle, adding three-dimensional relocalization as a novel component to the molecular events that occur during reactivation. Furthermore, the data add to our understanding of nuclear compartments, showing that disperse interchromosomal interactions may be important for regulating transcription
The Deuterium Abundance and Nucleocosmochronology
We examine galactic chemical evolution models which reproduce the present-day
and pre-solar values of deuterium starting with a primordial value which is
consistent with a baryon-to-photon ratio of . We consider
various galactic chemical evolution models to determine the viability of
significant deuterium destruction and which provide a consistent age of the
galaxy at the time of the formation of the solar system and consequently its
present day age from nuclear chronometers. These models generally require some
amount of infall which we take with rates proportional to the gas mass as well
as exponentially decreasing rates and some initial disk enrichment which we
limit to the range of 0\% to 30\%. We present those models which give the
observed pre-solar value and present-day value of D/H and which lead to a
present-day gas fraction of . These models result
in a braod range for the age of galaxy between Gyrs.Comment: 16 pages, LateX, Figures available by anonymous ftp from
ast1.spa.umn.edu in the directory pub with filename deutfig.ps,
UMN-TH-1260/9
A critical review of the role of local excision in the treatment of early (T1 and T2) rectal tumors
The optimal treatment of early (T1 and T2) rectal adenocarcinomas remains controversial. Local excision and radical resection with total mesorectal excision are the two surgical techniques for excising early rectal cancer. Each has their respective benefits, with local excision allowing for decreased operative morbidity and mortality while radical resection provides an oncologically complete treatment through lymphadenectomy. Local excision can be accomplished via transanal endoscopic microsurgery or transanal excision. There is no significant difference in the recurrence rates (21% vs. 33%) or overall survival (80% vs. 66%) between the two local excision modalities; however, transanal endoscopic microsurgery does allow for a higher rate of R0 resection. Current selection criteria for local excision include well to moderately differentiated tumors without high-risk features such as lymphovascular invasion, perineural invasion, or mucinous components. In addition, tumors should ideally be \u3c3 cm in size, excised with a clear margin, occupy less than 1/3 of the circumference of the bowel and be mobile/nonfixed. Despite these stringent inclusion criteria, local excision continues to be plagued with a high recurrence rate in both T1 and T2 tumors due to a significant rate of occult locoregional metastases (20% to 33%). For both tumor groups, the recurrence rate in the local excision group is more than double compared to radical resection. However, the overall survival is not significantly different between those with and without metastases. With intense postoperative surveillance, these recurrences can be identified early while they are confined to the pelvis allowing for salvage surgical options. Recently, neoadjuvant therapy followed by local excision has shown favorable short and long-term oncological outcomes to radical resection in the treatment of T2 rectal cancer. Ultimately, the management of early rectal cancer must be individualized to each patient\u27s expectations of quality and quantity of life. With informed consent, patients may be willing to accept a higher failure rate and an increased post-operative surveillance regimen to preserve a perceived increased quality of life
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Using Market Forces for Social Good
The environment has traditionally been the domain of nonprofit organizations. For decades, nonprofit organizations have worked to reduce the negative impact of market-based activity on the environment. However, more recently nonprofits have started to adopt the methods and values of the market to achieve sustainability goals. One of the primary strategies that nonprofits use is to disclose, or pressure corporations to disclose, information about the environmental impact of their products and processes. These information disclosure strategies seek to help stakeholders make green purchases or invest in corporations that use green practices, thus incentivizing corporations to reduce their negative environmental impact. In this chapter, we review the benefits and the challenges encountered by nonprofits in their attempt to use information disclosure strategies
Investigating How Speech And Animation Realism Influence The Perceived Personality Of Virtual Characters And Agents
The portrayed personality of virtual characters and agents is understood to influence how we perceive and engage with digital applications. Understanding how the features of speech and animation drive portrayed personality allows us to intentionally design characters to be more personalized and engaging. In this study, we use performance capture data of unscripted conversations from a variety of actors to explore the perceptual outcomes associated with the modalities of speech and motion. Specifically, we contrast full performance-driven characters to those portrayed by generated gestures and synthesized speech, analysing how the features of each influence portrayed personality according to the Big Five personality traits. We find that processing speech and motion can have mixed effects on such traits, with our results highlighting motion as the dominant modality for portraying extraversion and speech as dominant for communicating agreeableness and emotional stability. Our results can support the Extended Reality (XR) community in development of virtual characters, social agents and 3D User Interface (3DUI) agents portraying a range of targeted personalities
A Case of Congenital Coronary Sinus Ostial Atresia with Persistent Left Superior Vena Cava
Introduction: The coronary sinus is responsible for venous drainage of the heart. Congenital anomalies of the coronary sinus are rare and typically associated with other anomalies, such as atrial septal defects or other congenital heart malformations.
Clinical Findings: We present a case of incidentally found atresia of the coronary sinus ostium with associated persistent left superior vena cava. This case involved a 52-year-old patient who initially presented with a supraventricular tachycardia and elevated troponin.
Clinical Course: The patient underwent cardiac workup with a coronary computed tomographic angiography scan. This scan showed no obstructive coronary artery disease, but did show congenital atresia of the coronary sinus and a persistent left superior vena cava.
Conclusions: This case shows that coronary computed tomographic angiography is an excellent modality for identifying anomalous coronary venous return and congenital abnormalities of the coronary sinus
Evaluating tree root distribution in a tree-based intercropping system with use of ground penetrating radar
Paper presented at the 13th North American Agroforesty Conference, which was held June 19-21, 2013 in Charlottetown, Prince Edward Island, Canada.In Poppy, L., Kort, J., Schroeder, B., Pollock, T., and Soolanayakanahally, R., eds. Agroforestry: Innovations in Agriculture. Proceedings, 13th North American Agroforestry Conference, Charlottetown, Prince Edward Island, Canada, June 19-21, 2013.Within agroforestry systems, tree root architecture is a driver of important ecological processes such as belowground nutrient flows and C storage. Yet the belowground component of trees remains largely under-studied due to methodological restraints. Conventional subsurface sampling can overlook the heterogeneity of root systems, while complete excavations are destructive and unrepeatable. Thus, there is a need to develop non-intrusive technologies, such as ground penetrating radar (GPR), to measure root systems in situ. In this study we used GPR to detect coarse root distributions below five tree species (Quercus rubra, Juglans nigra, Populus sp., Picea abies, and Thuja occidentalis) at a temperate tree-based intercropping site in Guelph, Ontario. GPR geo-imaged transects were collected in 4.5 _ 4.5m grids that were centered on 15 individual trees. Subsequently, tree roots were identified across all geo-images (visualized as radar signal reflections) providing 3-dimensional root distribution data for each target tree. Roots
detected by GPR accounted for approximately 80% of large coarse roots (�1cm) and 40% of small coarse roots (<1cm) that were later exposed in a subset of matched soil profiles. Significant inter-specific variations of coarse rooting depth preferences were detected. Additionally, preliminary analyses indicate different tree rooting patterns below the crop rows. To determine fine root distributions, fine roots were extracted from soil cores collected from the tree root study plots. Preliminary analysis indicates fine root length densities vary across species predominately in the upper 20cm. Limitations will be identified and applications will be discussed of GPR to answer ecological questions within agroforestry systems. Notably, we will highlight results from our complementary study that used the same GPR data to effectively estimate belowground biomass.Kira A. Borden (1), Marney E. Isaac (2) and Sean C. Thomas (1) ; 1. Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario, Canada, M5S 3B3. 2. Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada, M1C 1A4.Includes bibliographical references
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