Heterotic α\alpha'-corrections in Double Field Theory

We extend the generalized flux formulation of Double Field Theory to include all the first order bosonic contributions to the $\alpha '$ expansion of the heterotic string low energy effective theory. The generalized tangent space and duality group are enhanced by $\alpha'$ corrections, and the gauge symmetries are generated by the usual (gauged) generalized Lie derivative in the extended space. The generalized frame receives derivative corrections through the spin connection with torsion, which is incorporated as a new degree of freedom in the extended bein. We compute the generalized fluxes and find the Riemann curvature tensor with torsion as one of their components. All the four-derivative terms of the action, Bianchi identities and equations of motion are reproduced. Using this formalism, we obtain the first order $\alpha'$ corrections to the heterotic Buscher rules. The relation of our results to alternative formulations in the literature is discussed and future research directions are outlined.Comment: Published versio

Can Maquila Booms Reduce Poverty? Evidence from Honduras

This paper identifies and estimates the strength of the reduction in poverty linked to improved opportunities for women in the expanding maquila sector. A simulation exercise shows that, at a given point in time, poverty in Honduras would have been 1.5 percentage points higher had the maquila sector not existed. Of this increase in poverty, 0.35 percentage points is attributable to the wage premium paid to maquila workers, 0.1 percentage points to the wage premium received by women in the maquila sector, and 1 percentage point to employment creation. Given that female maquila workers represent only 1.1 percent of the active population in Honduras, this contribution to poverty reduction is significant.Trade liberalization; maquila; poverty; gender wage gap; Honduras

SYSTEMATICS AND EVOLUTION IN THE TRIBE SCHIZOPETALAE (BRASSICACEAE): A MOLECULAR, MORPHOLOGICAL, AND ECOLOGICAL ANALYSIS OF THE DIVERSIFICATION OF AN ENDEMIC LINEAGE FROM THE ATACAMA DESERT (CHILE)

As aridity has been identified as an active promoter of diversification in deserts, attempts to test organismal differentiation in the Atacama Desert have resulted particularly challenging. Most limitations are related to the recent origin of the extreme aridity in the Atacama Desert, which have stimulated a rapid process of diversification and obscured evidence of interspecific divergence. Based on its favorable biological attributes and high endemicity, genera from the tribe Schizopetalae (Mathewsia and Schizopetalon) emerge as a practical study group to conduct studies of diversification under rapid and recent diversification. The present dissertation focuses on exploring this issue, 1) solving the phylogenetic relationships in the tribe Schizopetalae, 2) describing patterns of interspecific divergence in a well-defined lineage of Schizopetalon from the Atacama Desert, and 3) searching and testing multiple highly variable nuclear loci for phylogenetic and phylogeographic purposes. The results confirmed the monophyletic status of the tribe Schizopetalae and genus Schizopetalon; nevertheless, genus Mathewsia requires to be redefined because the exclusion of M. nivea. Patterns of interspecific differentiation suggest a process of allopatric divergence promoted by ecological niche differentiation between the Andes and coastal ranges in the Atacama Desert. While this result is consistent with previous hypotheses of divergence by habitat differentiation, elements of hybridization, incomplete lineage sorting, and phenotypic plasticity obscured the identification of species limits and precluded a better inference of lineage isolation. The analysis of available genomic resources demonstrated the suitability of obtaining multiple low copy nuclear loci from already available genomic data in Schizopetalon. However, the use of these markers is yet limited, as the detection of multiple copies implies that further analyses are needed to discard paralogous copies. Overall, this dissertation sets the foundation for more elaborated studies, as more available genomic resources and intricate pattern of divergence can result promising to explore the consequences of local patterns of extreme aridity in the diversification and evolution of species of Schizopetalae

Empowerment of Foreign-Born Latino Students Through the Use of Digital Educational Technologies: A Collective-Case Study

This dissertation followed four newcomer foreign-born Latino (FBL) at Frank Porter Graham Elementary School in North Carolina and examined how they engaged with critical educational technologies. I designed this collective case study to examine the relationships among the places, spaces, actors, and objects that affect their learning experiences and their engagement with digital educational technologies. Using qualitative methods of data collection, I observed and interviewed the four FBL students, and also interviewed other actors (i.e., teachers, peers and parents) and observed other spaces (i.e., classroom, afterschool program and home) relevant to their educational experiences. Using a constructivist grounded theory methodology, I examined each FBL student's (1) dual-socialization experience of acculturation and enculturation; (2) their use of digital educational technology in the classroom; and (3) their family dynamics at home. I developed a conceptual analysis of the participants' behaviors and responses with the goal of developing a grounded model based on their perspectives and experiences. I documented two different approaches to digital educational technology in the classroom: the one-to-one approach and the organic approach. The organic approach successfully resulted in the creation of empowering educational third spaces in the classroom; however, these spaces proved difficult to foster in home settings. The challenge of replicating educational third spaces at home was found to exceed general problems of access and to represent a larger pedagogical problem: that academic goals and expectations were largely based on middle-class, Anglo parenting standards. Further research is needed to assess how family dynamics affect students' engagement with digital educational technologies. In presenting the cases of these four FBL students I sought not only to understand their use of technology in classroom, but to better understand the empowering potential of digital educational technologies. In an era of digital dominance, digital nativity can be the key to Latino youth becoming the producers of their own future. Doctor of Philosoph

3D printing part orientation optimization: discrete approximation of support volume

In three-dimensional (3D) printing, due to the geometry of most parts, it is necessary to use extra material to support the manufacturing process. This material must be discarded after printing, so its reduction is essential to minimize manufacturing time and cost. An important parameter that must be defined before starting the printing process is the part orientation, which has repercussions on the quality, deposition path, and post-processing among others. Usually, the user sets up this parameter arbitrarily, so this paper takes advantage of it on optimization techniques and proposes an approximation of the volume be covered by the support material, which depends directly on the angle of the part to be printed and its geometry. Among mono-objectives optimization strategies, this work focuses on five of them. Their performance is compared by two metrics: support volume and execution time. Then, the best result is compared with commercial software

A Review of Digital Twins and their Application in Cybersecurity based on Artificial Intelligence

The potential of digital twin technology is yet to be fully realized due to its diversity and untapped potential. Digital twins enable systems' analysis, design, optimization, and evolution to be performed digitally or in conjunction with a cyber-physical approach to improve speed, accuracy, and efficiency over traditional engineering methods. Industry 4.0, factories of the future, and digital twins continue to benefit from the technology and provide enhanced efficiency within existing systems. Due to the lack of information and security standards associated with the transition to cyber digitization, cybercriminals have been able to take advantage of the situation. Access to a digital twin of a product or service is equivalent to threatening the entire collection. There is a robust interaction between digital twins and artificial intelligence tools, which leads to strong interaction between these technologies, so it can be used to improve the cybersecurity of these digital platforms based on their integration with these technologies. This study aims to investigate the role of artificial intelligence in providing cybersecurity for digital twin versions of various industries, as well as the risks associated with these versions. In addition, this research serves as a road map for researchers and others interested in cybersecurity and digital security.Comment: 60 pages, 8 Figures, 15 Table

The effects of armed conflict on forest cover changes across temporal and spatial scales in the Colombian Amazon

This paper's results show that conflict variables have positive relationships with deforestation in Colombia; yet, they are not among the main variables explaining deforestation

Melanotic Neuroectodermal Tumor of Infancy (MNTI) and Pineal Anlage Tumor (PAT) Harbor A Medulloblastoma Signature by DNA Methylation Profiling

MNTI is a rare tumor of indeterminate histogenesis and molecular signature. We performed methylation and copy number variation (CNV) profiles in patients with MNTI (n = 7) and PAT (n = 1) compared to the methylation brain tumor classifier v11b4 (BT-C) and the medulloblastoma (MB) classifier group 3/4 v1.0 (MB3/4-C). The patients’ mean age was 8 months (range: 4–48). The BT-C classified five MNTIs and one PAT (relapse) as class family MB-G3/G4, subclass group 3 (score: >0.9). The remaining two MNTIs and PAT (primary) were classified as class family plexus tumor, subclass pediatric (scores: >0.45). The MB3/4-C classified all MNTIs as high-risk MB-G3, Subtype II (score: >0.45). The primary PAT was classified as subtype III (score: 0.99) and its relapse as subtype II/III. MNTI and PAT clustered close to MB-G3. CNV analysis showed multiple rearrangements in one PAT and two MNTIs. The median follow-up was 54 months (four MNTIs in remission, one PAT died). In conclusion, we demonstrated that MNTI shares a homogenous methylation profile with MB-G3, and possibly with PAT. The role of a multipotent progenitor cell (i.e., early cranial neural crest cell) in their histogenesis and the influence of the anatomical site, tumor microenvironment, and other cytogenetic events in their divergent biologic behavior deserve further investigation