Cities as emergent models: the morphological logic of Manhattan and Barcelona

This paper is set to unveil several particulars about the logic embedded in the diachronic model of city growth and the rules which govern the emergence of urban spaces. The paper outlines an attempt to detect and define the generative rules of a growing urban structure by means of evaluation techniques. The initial approach in this regards will be to study the evolution of existing urban regions or cities which in our case are Manhattan and Barcelona and investigate the rules and causes of their emergence and growth. The paper will concentrate on the spatial aspect of the generative rules and investigate their behaviour and dimensionality. Several Space Syntax evaluation methods will be implemented to capture the change of spatial configurations within the growing urban structures. In addition, certain spatial elements will be isolated and tested aiming to illustrate their influence on the main spatial structures. Both urban regions were found to be emergent products of a bottom up organic growth mostly distinguished in the vicinities of the first settlements. Despite the imposition of a uniform grid on both cities in later stages of their development these cities managed to deform the regularity in the preplanned grid in an emergent manner to end up with an efficient model embodied in their current spatial arrangement. The paper reveals several consistencies in the spatial morphology of both urban regions and provides explanation of these regularities in an approach to extract the underlying rules which contributed to the growth optimization process

Optical signatures of intrinsic electron localization in amorphous SiO2

We measure and analyse the optical absorption spectra of three silica glass samples irradiated with 1 MeV electrons at 80 K, where self-trapped holes are stable, and use ab initio calculations to demonstrate that these spectra contain a signature of intrinsic electron traps created as counterparts to the holes. In particular, we argue that optical absorption bands peaking at 3.7, 4.7, and 6.4 eV belong to strongly localised electrons trapped at precursor sites in amorphous structure characterized by strained Si–O bonds and O–Si–O angles greater than 132°. These results are important for our understanding of the properties of silica glass and other silicates as well as the reliability of electronic and optical devices and for luminescence dating

The effect of nuclear deformation on level statistics

We analyze the nearest neighbor spacing distributions of low-lying 2+ levels of even-even nuclei. We grouped the nuclei into classes defined by the quadrupole deformation parameter (Beta2). We calculate the nearest neighbor spacing distributions for each class. Then, we determine the chaoticity parameter for each class with the help of the Bayesian inference method. We compare these distributions to a formula that describes the transition to chaos by varying a tuning parameter. This parameter appears to depend in a non-trivial way on the nuclear deformation, and takes small values indicating regularity in strongly deformed nuclei and especially in those having an oblate deformation.Comment: 10 Pages, 6 figure

Being a mobile international postgraduate research student with family in the United Kingdom: conflict, contestation, and contradictions

The internationalisation of higher education has influenced the dramatic rise in the mobility of students, academics and knowledge across borders. There has been growing research interest focusing on international students studying abroad. While the student experience is an area of education that is often researched, most research focuses on experiences of undergraduate students. Also in the context of international students, greater research emphasis has been placed on the academic experiences and support available for undergraduates. While such research is important, less attention has been paid to the non-academic experiences of International Post-Graduate Research Students with Families (IPGRSF). This article seeks to fill this gap by focusing on the social worlds of IPGRSF in the UK, examining students’ nuclear family contexts that are often marginalised in discourse. The article legitimises the IPGRSF subaltern world by focusing on how students negotiate its demands; how they negotiate their roles as research students with their other roles as spouses and parents, and the interrelationships among these roles; and how the university as an institution interacts with the students’ subaltern world. The findings show that language plays a significant role in shaping the process of mobility as well as influencing the students’ and their families’ integration and networking in the host country. Also, the findings suggest that students often had positive experiences at departmental level, but felt let down by the wider university support

Intrinsic Charge Trapping in Amorphous Oxide Films: Status and Challenges

We review the current understanding of intrinsic electron and hole trapping in insulating amorphous oxide films on semiconductor and metal substrates. The experimental and theoretical evidences are provided for the existence of intrinsic deep electron and hole trap states caused by the disorder of amorphous metal oxide films. We start from presenting the results for amorphous (a) HfO<sub>2</sub>, chosen due to the availability of highest purity amorphous films, which is vital for studying their intrinsic electronic properties. Exhaustive photo-depopulation spectroscopy (EPDS) measurements and theoretical calculations using density functional theory (DFT) shed light on the atomic nature of electronic gap states responsible for deep electron trapping observed in a-HfO<sub>2</sub>. We review theoretical methods used for creating models of amorphous structures and electronic structure calculations of amorphous oxides and outline some of the challenges in modelling defects in amorphous materials. We then discuss theoretical models of electron polarons and bi-polarons in a-HfO<sub>2</sub> and demonstrate that these intrinsic states originate from low-coordinated ions and elongated metal-oxygen bonds in the amorphous oxide network. Similarly, holes can be captured at under-coordinated O sites. We then discuss electron and hole trapping in other amorphous oxides, such as a-SiO<sub>2</sub>, a-Al<sub>2</sub>O<sub>3</sub>, a-TiO<sub>2</sub>. We propose that the presence of low-coordinated ions in amorphous oxides with electron states of significant p and d character near the conduction band minimum (CBM) can lead to electron trapping and that deep hole trapping should be common to all amorphous oxides. Finally, we demonstrate that bi-electron trapping in a-HfO<sub>2</sub> and a-SiO<sub>2</sub> weakens Hf(Si)-O bonds and significantly reduces barriers for forming Frenkel defects, neutral O vacancies and O<sup>2-</sup> ions in these materials. These results should be useful for better understanding of electronic properties and structural evolution of thin amorphous films under carrier injection conditions

Role of hydrogen in volatile behaviour of defects in SiO2-based electronic devices

Charge capture and emission by point defects in gate oxides of metal–oxide–semiconductor field-effect transistors (MOSFETs) strongly affect reliability and performance of electronic devices. Recent advances in experimental techniques used for probing defect properties have led to new insights into their characteristics. In particular, these experimental data show a repeated dis- and reappearance (the so-called volatility) of the defect-related signals. We use multiscale modelling to explain the charge capture and emission as well as defect volatility in amorphous SiO2 gate dielectrics. We first briefly discuss the recent experimental results and use a multiphonon charge capture model to describe the charge-trapping behaviour of defects in silicon-based MOSFETs. We then link this model to ab initio calculations that investigate the three most promising defect candidates. Statistical distributions of defect characteristics obtained from ab initio calculations in amorphous SiO2 are compared with the experimentally measured statistical properties of charge traps. This allows us to suggest an atomistic mechanism to explain the experimentally observed volatile behaviour of defects. We conclude that the hydroxyl-E′ centre is a promising candidate to explain all the observed features, including defect volatility

Modelling dependency networks to inform data structures in BIM and smart cities

The pervasive deployment of "smart city" and "smart building" projects in cities world-wide is driving innovation on many fronts including; technology, telematics, engineering and entrepreneurship. This paper focuses on the technical and engineering perspectives of BIM and smart cities, by extending building and urban morphology studies as to respond to the challenges posed by Big Data, and smart infrastructure. The proposed framework incorporates theoretical and modelling descriptions to verify how network-based models can act as the backbone skeletal representation of both building and urban complexity, and yet relate to environmental performance and smart infrastructure. The paper provides some empirical basis to support data information models through building dependency networks as to represent the relationships between different existing and smart infrastructure components. These dependency networks are thought to inform decisions on how to represent building and urban data sets in response to different social and environmental performance requirements, feeding that into void and solid descriptions of data maturity models. It is concluded that network-based models are fundamental to comprehend and represent the complexity of cities and inform urban design and public policy practices, in the design and operation phases of infrastructure projects

Antiretroviral therapy, CD4, viral load, and disease stage in HIV patients in Saudi Arabia: a 2001–2013 cross-sectional study

Introduction: The incidence of HIV/AIDS is increasing worldwide and in the Middle East. In this study, we analyzed the use of antiretroviral therapy (ART), the patterns of CD4 and viral load (VL), and stage of presentation. Methodology: Laboratory variables, ART use, and CD4 count were obtained and analyzed retrospectively. Results: A total of 997 cases from eight HIV/AIDS care providers were included. Of the total cases, 274 (28.3%) had a CD4 count of 5 log10. Of the total cases, 50% were on highly active antiretroviral therapy (HAART), and the majority of cases were asymptomatic (70%). Of those patients on ART, 247 (39.5%) took tenofovir/emtricitabine combined with either efavirenz (147; 14.7%) or lopinavir/ritonavir (100; 10%), and 158 (15.8%) were on lamivudine and zidovudine with either efavirenz (32; 3.2%) or lopinavir/ritonavir (126; 12.6%). Other combinations were used in 70 (7%) patients. The mean (± standard deviation) of baseline CD4 and viral load were 401 cells/mm3 (322 cells/mm3) and 4.6 log1010 (1.3 log10), respectively. At diagnosis, 72% of patients were asymptomatic; 50% had AIDS and 20% had CD4 count < 350. Conclusions: ART use was in line with international guidelines, but the number of patients receiving ART was lower than expected. Large proportions of cases presented late with AIDS at diagnosis or had CD4 < 350. Further data is needed to evaluate the medical care of patients with HIV/AIDS in the Kingdom of Saudi Arabia