Últimos itens adicionados do Acervo: Harvard University

A Universidade de Harvard (em inglês: Harvard University) é uma universidade privada membro da Ivy League, localizada em Cambridge, Massachusetts, Estados Unidos, e cuja história, influência e riqueza tornam-a uma das mais prestigiadas universidades do mundo.

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#Autism Versus 299.0: Topic Model Exploration of Multimodal Autism Data

Ming, Joy Carol
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
Though prevalence and awareness for Autism Spectrum Disorder (ASD) has steadily increased, a true understanding is hard to reach because of the behavior-based nature of the diagnosis and the heterogeneity of its manifestations. Parents and caregivers often informally discuss symptoms and behaviors they observe from their children with autism through online medical forums, contrasting the more traditional and structured text of electronic medical records collected by doctors. We modify an anchor word driven topic model algorithm originally proposed by Arora et al. (2012a) to elicit and compare the medical concept topics, or “themes” from both modes of data: the novel data set of posts from autism-specific online medical forums and electronic medical records. We present methods to extract relevant medical concepts from colloquially written forum posts through the use of choice sections of the consumer health vocabulary and other filtering techniques. In order to account for the sparsity of concept data, we propose and evaluate a more robust approach to selecting anchor words that takes into account variance and inclusivity. This approach that combines concept and anchor words selection seeds the discussion about how unstructured text can influence and expand understanding of the enigmatic disorder...

National Leaders and Economic Growth: What Characteristics Matter?

Zhang, Howard
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
This paper uses data on more than 1000 national leaders between 1875 and 2005 to examine how four key individual characteristics – military experience, being a member of a political dynasty, belonging to the ethnic majority, and the number of daughters – influence the rate of economic growth. Following Jones and Olken (2005), I identify leadership transitions caused by natural deaths and illnesses to isolate the effect of leaders on economic growth, sidestepping the causality that runs between economic growth and the timing of leadership transitions. I find that even though leaders do seem to matter for economic growth, there does not seem to be substantial evidence that the identified characteristics systematically influence national growth. I then examine if these characteristics affect relevant policy outcomes. Although I do not find substantial evidence that the identified characteristics systematically influence the policy outcomes, I do find some evidence of a relationship between a leader’s ethnicity and the infant mortality rate, as well as between the number of daughters a leader has and the female and male adult mortality rates.

The Role of Cell Compaction in Radiation Therapy for Breast Cancer

Welbeck, Arakua Naa Korkoi
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN_GB
Physical compaction and accompanied collagen remodelling are required for normal organ development, while tumour cell compaction induces tumour angiogenesis and growth by changing expression of an angiogenic factor, Vascular Endothelial Growth Factor. Tumour cell compaction is involved in the resistance to chemotherapy in ovarian and breast cancer, and to radiotherapy in colon cancer. Here, we show that the modification of physical cell compaction, which changes the tumour microenvironment, is able to improve the response and to decrease resistance to radiotherapy in breast cancer. To investigate whether mechanical compression of breast cancer cells alters their response to irradiation, we first examined the effects of irradiation on 4T1 breast cancer cells in vitro. Irradiation of 4T1 cells causes DNA fragmentation 4 h after irradiation, which is partially recovered 24 h later. The expression of Platelet Derived Growth Factor-b (PDGF-b) decreases in the cells 4 h post-irradiation, while this decrease is attenuated 24 h after irradiation, suggesting that PDGF-b may mediate this recovery from radiation-induced DNA damage by increasing resistance. We then explored whether mechanical compression and subsequent changes in ECM structure contribute to these effects by plating breast cancer cells at different densities or by compressing tumour tissues in vitro. Tumour compression inhibits DNA fragmentation in vitro by stimulating a rise in PDGF-b expression...

Correlational Harmonic Metrics: Bridging Computational and Human Notions of Musical Harmony

Freedman, Dylan
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
The goal of this paper is to show that traditional music information retrieval tasks with well-chosen parameters perform similarly using computationally extracted chord annotations versus ground-truth annotations. Using a collection of Billboard songs from the last 60 years with provided ground-truth chord labels, I use established automatic chord identification algorithms to produce a corresponding extracted chord label dataset. I devise methods to compare chord progressions between two songs on the basis of their optimal localized alignment scores, adapting traditional sequence alignment techniques for transposition-invariance and the chord alphabet. I create a set of chord progression comparison parameters defined by chord distance metrics, gap costs, and normalization measures and run a black-box global optimization algorithm to stochastically search for the best parameter set to perform chordal comparisons on collections of songs across two primary tasks—fully connected harmonic comparison and query by n-grams. The first task involves evaluating chord progression similarity between all pairwise combinations of songs, separately ranking results for ground-truth and extracted chord labels, and returning the Spearman rho rank correlation coefficient of the two resulting rankings. The second task harmonically compares random chord query sequences of different sizes to the songs in the datasets...

Experiments on Universal Rigidity of Bipartite Graphs

Alves, Deborah B.
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
Our goal is to characterize necessary and sufficient conditions for the universal rigidity of bipartite frameworks. Previous work describe ways to test universal rigidity through semidefinite program- ming using stress matrix as a tool. Also, it had been shown a relationship between rigidity of a bipartite framework and quadric separability of the two sets of vertices. In particular, previous work showed that given a complete bipartite framework, separability by a quadric implied non- rigidity of the framework. Based on this, a reasonable conjecture was that the reciprocal could also be true. Our goal was to develop experiments using semidefinite programming to validate this conjecture for complete bipartite framework, and observe the behavior of rigidity for incomplete bipartite frameworks.

Estimation of Asset Volatility and Correlation Over Market Microstructure Noise in High-Frequency Data

Yevstihnyeyev, Roman
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
Accurate measurement of asset return volatility and correlation is an important problem in financial econometrics. The presence of market microstructure noise in high-frequency data complicates such estimations. This study extends a prior application of a model-based volatility estimator with autocorrelated market microstructure noise to estimation of correlation. The model is applied to a high-frequency dataset including a stock and an index, and the results are compared to some existing models. This study supports previous findings that including an autocorrelation factor produces an estimator potentially less vulnerable to market microstructure noise, and finds that the same is true about the extended correlation estimator that is introduced here.

How to Win Ratings and Influence Reviewers: Preferential Attachment in Rating Systems

Chin-Lee, Jao-ke
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
In this paper we introduce the concept of preferential attachment in the context of recommendation and rating systems. We present several models incorporating different qualities that may manifest in such systems, such as inherent bias, and examine the resulting degree distributions (i.e. ratings) as snapshots and through time. We then take preliminary steps towards testing real-world feasibility with the Yelp Academic Dataset.

Assessing the Effectiveness of Scrubber Installation on Air Pollution Emissions Reductions Among Coal-Fired Power Plants: Application of Statistical Methods for Causal Inference

Hansen, John Barrett
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
The 1990 amendment to the Clean Air Act implemented a cap-and-trade system that required electricity-generating power plants to dramatically reduce Sulfur Dioxide (SO2) and Nitrogen Oxide (NOx) emissions. Plants impacted by this legislation had a variety of compliance options, including decreasing factory operation, purchasing carbon credits, installing scrubbers, and changing fuel inputs. Using data from 1997-2012 of 995 coal-burning power plants, we examine the effectiveness of scrubber installation in reducing SO2 and NOx emissions. Specifically, we employ two methods—a propensity score algorithm and a matching algorithm—to estimate: 1) the causal effect of scrubber installation prior 1997 on the emissions during 1997; and 2) the causal effect of scrubber installation at any time during the period 1997-2012 on emissions two months following scrubber installation. Using a propensity score method, we found that pre-1997 SO2 scrubbers reduced 1997 SO2 emissions by 68% (95% CI 58% to 76%), and pre-1997 NOx scrubbers reduced 1997 NOx emissions by 28% (16%, 38%). Additionally, installing SO2 and NOx scrubbers at any time during the period 1997-2012 reduces SO2 and NOx emissions by 89% (88%, 90%) and 21% (19%, 24%) two months following installation...

Ultimate Analytics: A study of elite teams' offenses

Zhang, David
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
Many traditional, powerhouse sports are currently undergoing an analytics revolution. While ultimate is a relatively young sport, it is certainly not immune to this revolution. Most ultimate data presently track basic summary statistics, but some more advanced work in the field on spatial analytics has been done. We stand on the brink of an explosion in advanced ultimate analytics. This paper attempts to progress that field, analyzing data from elite men's club teams, namely Denver Johnny Bravo, Boston Ironside, and San Francisco Revolver. We analyze how variables beyond just spatial location affect the probability of scoring. Our results demonstrate that elite teams should attack downfield to gain yards while prioritizing the creation of ``entropy"---throwing more passes rather than fewer and holding the disc as briefly as possible; once in the red zone, teams should modify their offense to maximize space while changing their points of attack by swinging the disc laterally. We propose two new end zone sets for offenses to run. Our method, when combined with conventional ultimate wisdom, provides a strong attempt at streamlining offenses to be more efficient at scoring.

Distinguishing Earth, Water, Fire, and Air: Factor Analysis to Determine the Four Fundamental Elements of State Capability

Drumm, Brian Richardson
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
While some states can send men to the moon and back, others cannot even muster the effectiveness to maintain order. Understanding what produces these differences in the capabilities of states to deliver outcomes to their citizens is central to understanding why these outcomes differ across states. But what are the fundamental determinants of state capability? This has not yet been investigated; though previous attempts have been made to understand what the most popular state capability index actually measures, these were made to determine its validity, not its fundamental determinants. I empirically determine that there are four fundamental determinants of a state’s capability to deliver outcomes for its citizens by using a rigorous application of factor analysis to four state capability indexes: Outcomes delivered by a state are determined by the ``Effectiveness'' by which states are able to implement their ``Political Gumption'' (their responsiveness and political resourcefulness to satisfy the demands of their citizens) in the face of pressures, represented by the ``Absence of Internal Pressures'' and ``Popular Support and Absence of External Pressures.'' These determinants drive the differences in the capabilities of states to deliver outcomes for its citizens...

Incommensurate Smectic Order at the Free Surface in the Nematic Phase of \(4-N-Heptylphenyl-4'-(4"-Nitrobenzoyloxy)Benzoate (DB7NO_2)\)

Ocko, B. M.; Pershan, Peter S.; Safinya, C. R.; Chiang, L. Y.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artigo de Revista Científica
EN_US
We report x-ray reflectivity measurements on the free surface of \(4-n-heptylphenyl-4'-(4"-nitrobenzoyloxy)benzoate (DB7NO_2)\) at the nematic to smectic-A phase transition, \(T_{NA}=99.9^{\circ}C\). The free surface in the nematic phase exhibits smecticlike ordering at two q vectors, one which is commensurate with the smectic-A monolayer q vector \(q_2\). The other q vector is incommensurate corresponding to ordering at \(\sim 0.59q_2\). The commensurate peak constructively interferes with the air-liquid interface while the incommensurate peak destructively interferes. These results are compared with bulk-phase x-ray scattering measurements.; Engineering and Applied Sciences

Those Who Study and Teach the Qur'an

Graham, William A.
Fonte: Ashgate Publishing Publicador: Ashgate Publishing
Tipo: Monograph or Book
EN_US

The Framingham Heart Study 100K SNP Genome-Wide Association Study Resource: Overview of 17 Phenotype Working Group Reports

Cupples, L Adrienne; Arruda, Heather T; Benjamin, Emelia J; D'Agostino, Ralph B; Demissie, Serkalem; DeStefano, Anita L; Dupuis, Josée; Govindaraju, Diddahally R; Heard-Costa, Nancy L; Hwang, Shih-Jen; Kathiresan, Sekar; Laramie, Jason M; Larson, Martin
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
EN_US
Background: The Framingham Heart Study (FHS), founded in 1948 to examine the epidemiology of cardiovascular disease, is among the most comprehensively characterized multi-generational studies in the world. Many collected phenotypes have substantial genetic contributors; yet most genetic determinants remain to be identified. Using single nucleotide polymorphisms (SNPs) from a 100K genome-wide scan, we examine the associations of common polymorphisms with phenotypic variation in this community-based cohort and provide a full-disclosure, web-based resource of results for future replication studies. Methods: Adult participants (n = 1345) of the largest 310 pedigrees in the FHS, many biologically related, were genotyped with the 100K Affymetrix GeneChip. These genotypes were used to assess their contribution to 987 phenotypes collected in FHS over 56 years of follow up, including: cardiovascular risk factors and biomarkers; subclinical and clinical cardiovascular disease; cancer and longevity traits; and traits in pulmonary, sleep, neurology, renal, and bone domains. We conducted genome-wide variance components linkage and population-based and family-based association tests. Results: The participants were white of European descent and from the FHS Original and Offspring Cohorts (examination 1 Offspring mean age 32 ± 9 years...

Democratizing Education? Examining Access and Usage Patterns in Massive Open Online Courses

Hansen, John David Nadal; Reich, Justin
Fonte: American Association for the Advancement of Science Publicador: American Association for the Advancement of Science
Tipo: Artigo de Revista Científica
EN_US
Massive open online courses (MOOCs) are often characterized as remedies to educational disparities related to social class. Using data from 68 MOOCs offered by Harvard and MIT between 2012 and 2014, we found that course participants from the United States tended to live in more-affluent and better-educated neighborhoods than the average U.S. resident. Among those who did register for courses, students with greater socioeconomic resources were more likely to earn a certificate. Furthermore, these differences in MOOC access and completion were larger for adolescents and young adults, the traditional ages where people find on-ramps into science, technology, engineering, and mathematics (STEM) coursework and careers. Our findings raise concerns that MOOCs and similar approaches to online learning can exacerbate rather than reduce disparities in educational outcomes related to socioeconomic status.

Semiconductors with a loop of extrema

Rashba, Emmanuel
Fonte: Elsevier BV Publicador: Elsevier BV
Tipo: Artigo de Revista Científica
EN_US
Crystals with a Wurtzite-type structure are used as an example to show that owing to spin–orbit coupling a new type of band structure can arise. For this band structure the extrema are reached at a circle, a loop of extrema, rather than in isolated points of the Brillouin zone. Specific properties of such semiconductors are studied theoretically, in particular, the peculiarities of the cyclotron resonance at low temperatures. In strong magnetic fields, spin–orbit coupling results in absorption at the frequency of electron spin resonance but driven by the electric vector of electromagnetic wave (combined resonance).; Physics

Preface

Rashba, Emmanuel
Fonte: Elsevier BV Publicador: Elsevier BV
Tipo: Artigo de Revista Científica
EN_US
Physics

Impact of Host Heterogeneity on the Efficacy of Interventions to Reduce Staphylococcus aureus Carriage

Chang, Qiuzhi; Lipsitch, Marc; Hanage, William P.
Fonte: Cambridge University Press (CUP) Publicador: Cambridge University Press (CUP)
Tipo: Artigo de Revista Científica
EN_US
BACKGROUND Staphylococcus aureus is a common cause of bacterial infections worldwide. It is most commonly carried in and transmitted from the anterior nares. Hosts are known to vary in their proclivity for S. aureus nasal carriage and may be divided into persistent carriers, intermittent carriers, and noncarriers, depending on duration of carriage. Mathematical models of S. aureus to predict outcomes of interventions have, however, typically assumed that all individuals are equally susceptible to colonization. OBJECTIVE To characterize biases created by assuming a homogeneous host population in estimating efficacy of control interventions. DESIGN Mathematical model. METHODS We developed a model of S. aureus carriage in the healthcare setting under the homogeneous assumption as well as a heterogeneous model to account for the 3 types of S. aureus carriers. In both models, we calculated the equilibrium carriage prevalence to predict the impact of control measures (reducing contact and decolonization). RESULTS The homogeneous model almost always underestimates S. aureus transmissibility and overestimates the impact of intervention strategies in lowering carriage prevalence compared to the heterogeneous model. This finding is generally consistent regardless of changes in model setting that vary the proportions of various carriers in the population and the duration of carriage for these carrier types. CONCLUSIONS Not accounting for host heterogeneity leads to systematic and substantial biases in predictions of the effects of intervention strategies. Further understanding of the clinical impacts of heterogeneity through modeling can help to target control measures and allocate resources more efficiently.

Legitimating status: perceptions of meritocracy and inequality among undergraduates at an elite British university

Warikoo, Natasha Kumar; Fuhr, Christina
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
EN_US
Given the frequent critiques of elite universities for admitting low numbers of state-school graduates and, more recently, British Afro-Caribbean students, how do students attending those universities make meaning of the admissions process? Through an analysis of 46 one-on-one in-depth interviews with undergraduates attending Oxford University, we show that students believe in the fairness of the admissions process, while lamenting the lack of opportunities for educational advancement faced by some disadvantaged youth in British society. Despite their understanding that many British youth do not have access to educational experiences that make Oxbridge an attainable goal, most students do not support changes to make access more equitable across class or racial/ethnic lines. This perspective, which legitimates the status students gain through matriculation at an elite university, supports the maintenance of unequal access to an Oxford education despite the advantages that education is known to confer to graduates. The findings demonstrate elites acknowledging the disadvantages of particular groups in society without acknowledging their own advantages in the same system. They do so by recognizing two elements of merit: (1) intelligence...

Colorblindness and Diversity: race frames and their consequences for white undergraduates at elite US universities

Warikoo, Natasha Kumar; de Novais, Janine
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
EN_US
In this paper we bring together the literatures on frame analysis, the meaning of race, and campus racial climate to analyze the race frames—lenses through which individuals understand the role of race in society—held by white students attending elite US universities. For most, the elite university experience coincides with a strengthening or emergence of the diversity frame, which emphasizes the positive benefits of cultural diversity. Still, many also hold a colorblind frame, which sees race groups as equivalent and racial identities as insignificant. We highlight the ambivalence these divergent frames create for student perspectives on affirmative action and interracial contact on campus. Our findings demonstrate the mutability of race frames, and we highlight the impact institutions may have on individuals’ race frames. The paper is based on in-depth interviews with 47 US-born white undergraduates attending Brown University and Harvard University.

Symbolic boundaries and school structure in New York and London schools

Warikoo, Natasha Kumar
Fonte: University of Chicago Press Publicador: University of Chicago Press
Tipo: Artigo de Revista Científica
EN_US
This article shows that an ethnically diverse student population leads to blurred ethnic and racial boundaries. Still, students in New York distinguish themselves much more along ethnic and racial lines than do London students. The evidence presented suggests that in addition to national-level differences, traditional British school structure, which provides continuity of peers through the Form Class as well as time for socializing, leads to less emphasis on ethnic and racial boundaries than in the anomic structure of traditional urban American public high schools. It follows that in order to promote ethnic and racial integration among teens, schools should not only serve integrated student bodies but also should maintain structures that present opportunities for students to bridge racial and ethnic boundaries. The study employs ethnographic data from schools in New York and London and 120 in-depth interviews.