Performance evaluation of inverted pavement structures

Pavements are an integral part of modern transportation infrastructure. Growing pavement networks, diminishing resources, and climate change create a need for higher performing, more economical, and more sustainable pavement designs. Inverted base pavements (“inverted pavement” or IBP) is the term for a flexible pavement design philosophy different from conventional designs used in the United States. Inverted pavements maximize the performance of their constituent materials by taking advantage of their inherent properties. In IBP, the asphalt concrete surface layer is underlain by an unbound aggregate base layer, followed by a bound layer of stabilized aggregate subbase. This arrangement provides greater confining stress to the base course, resulting in a stiffer, more resilient structure. The improved performance of inverted pavement can reduce the thickness of the entire structure as well as the surface layer when compared to conventional pavement structures. Inverted base pavements may provide a solution to poor-performing, expensive, and unsustainable pavements. The first goal of this thesis is to explore the long-term performance of inverted pavements in the United States. While they have a longer history of use in other countries, inverted pavements have not been widely accepted in the United States. After a review of relevant literature, a field evaluation was conducted on two test sections of inverted pavement in Georgia. Falling weight deflectometer (FWD) measurements and a surface distress survey were conducted on the sections at 21 and 13 years of age, respectively. Results showed that the test sections performed better than conventional pavements. FWD data revealed that inverted sections exhibited greater structural stiffness and resistance to deformation over the life of the roadways. Material properties backcalculated from FWD data provided useful parameters for the modeling effort conducted in this study. The survey of surface distresses showed that inverted pavement sections accumulate less permanent deformation and load-related cracking, indicating superior load distribution and fatigue resistance. The second goal of this research was to examine the suitability of IBP for aircraft traffic. Few previous studies have explored this application. A modeling effort was undertaken using a mechanistic-empirical pavement analysis software to evaluate inverted and conventional pavement under simulated airplane loading. The simulated test sections were designed using material properties and layer dimensions from the literature, the field study in this thesis, and the software default values. The results predicted IBP could bear a significantly greater amount of traffic in every climate tested, when compared to conventional sections designed for the same loading. Furthermore, many inverted designs outperformed conventional pavements despite having thinner cross sections and thinner asphalt concrete layers. This indicates that inverted pavements may provide a cheaper, more sustainable solution for airfield pavements without a decline in performance. These results demonstrate that inverted pavements have a place in the future transportation networks of the United States. Further research is required to provide greater insight into the structures’ response to loading, particularly in varying climates. Additionally, modeling efforts should be refined by considering the stress- and climate-dependent properties of pavement materials. Finally, full-sized field and lab efforts should be undertaken to explore the application of IBP as airfield pavements using modern materials characterization and instrumentation. While a more complete understanding of inverted pavements is needed, this study has confirmed that inverted pavements can improve the performance, economy, and sustainability of our transportation networks.M.S

Intramolecular integration within Moloney murine leukemia virus DNA

By screening a library of unintegrated, circular Moloney murine leukemia virus (M-MuLV) DNA cloned in lambda phage, we found that approximately 20% of the M-MuLV DNA inserts contained internal sequence deletions or inversions. Restriction enzyme mapping demonstrated tht the deleted segments frequently abutted a long terminal repeat (LTR) sequence, whereas the inverted segments were usually flanked by LTR sequences, suggesting that many of the variants arose as a consequence of M-MuLV DNA molecules integrating within their own DNA. Nucleotide sequencing also suggested that most of the variant inserts were generated by autointegration. One of the recombinant M-MuLV DNA inserts contained a large inverted repeat of a unique M-MuLV sequence abutting an LTR. This molecule was shown by nucleotide sequencing to have arisen by an M-MuLV DNA Molecule integrating within a second M-MuLV DNA molecule before cloning. The autointegrated M-MuLV DNA had generally lost two base pairs from the LTR sequence at each junction with target site DNA, whereas a four-base-pair direct repeat of target site DNA flanked the integrated viral DNA. Nucleotide sequencing of preintegration target site DNA showed that this four-base-pair direct repeat was present only once before integration and was thus reiterated by the integration event. The results obtained from the autointegrated clones were supported by nucleotide sequencing of the host-virus junction of two cloned M-MuLV integrated proviruses obtained from infected rat cells. Detailed analysis of the different unique target site sequences revealed no obvious common features

Pavement testing by integrated geophysical methods: Feasibility, resolution and diagnostic potential

This work is focused on the assessment of the diagnostic potential of several geophysical methods when applied to the investigation of a rigid airport pavement. The potential and limit of each technique are evaluated as well as the added value deriving from their integration. Firstly, we reconstruct a high-resolution image of the pavement by a large electromagnetic and georadar screening. An advanced processing of georadar data, implemented through the picking of the arrival times of reflections for each profile, provides a quantitative estimation of the deviation between the design and the as-built thickness of layers. Additionally, electrical tomography has been applied to unequivocally identify the anomalous zones, where higher values of resistivity would be associated to porous zones that are prone to degradation and failure. The seismic tomographic survey had the additional purpose to recover the mechanical properties of the pavement in terms of both P- and S-waves and consequently of elastic constants (Poisson's ratio), whose values were consistent with those recovered in literature. The anomalies detected by each technique are consistent in their indications and they can be correlated to failure phenomena occurring at layer interfaces within the pavement structure or to unexpected variations of the layer thicknesses. The cost-effective geophysical campaign has validated the four-layered system deduced from the original design and has been used to reconstruct a high-resolution map of the pavement in order to discriminate fractures, crack-prone areas or areas where the as-built differs from the original design

On the improvement of cosmological neutrino mass bounds

The most recent measurements of the temperature and low-multipole polarization anisotropies of the Cosmic Microwave Background (CMB) from the Planck satellite, when combined with galaxy clustering data from the Baryon Oscillation Spectroscopic Survey (BOSS) in the form of the full shape of the power spectrum, and with Baryon Acoustic Oscillation measurements, provide a $95\%$ confidence level (CL) upper bound on the sum of the three active neutrinos $\sum m _\nu< 0.183$ eV, among the tightest neutrino mass bounds in the literature, to date, when the same datasets are taken into account. This very same data combination is able to set, at $\sim70\%$ CL, an upper limit on $\sum m _\nu$ of $0.0968$ eV, a value that approximately corresponds to the minimal mass expected in the inverted neutrino mass hierarchy scenario. If high-multipole polarization data from Planck is also considered, the $95\%$ CL upper bound is tightened to $\sum m _\nu< 0.176$ eV. Further improvements are obtained by considering recent measurements of the Hubble parameter. These limits are obtained assuming a specific non-degenerate neutrino mass spectrum; they slightly worsen when considering other degenerate neutrino mass schemes. Current cosmological data, therefore, start to be mildly sensitive to the neutrino mass ordering. Low-redshift quantities, such as the Hubble constant or the reionization optical depth, play a very important role when setting the neutrino mass constraints. We also comment on the eventual shifts in the cosmological bounds on $\sum m_\nu$ when possible variations in the former two quantities are addressed.Comment: 9 pages, 3 figures, 2 table

Top management team and board attributes and firm performance in the Netherlands

We survey the evidence on the relationship between board and top management team attributes and firm performance in the Netherlands (sample of 94 listed firms). To this aim we develop hypotheses by using sources from the strategic management and the corporate governance literature. Dutch corporations generally have a two-tier board system. We use the size of the top management team (TMT) and their average age as well as the size of the supervisory board (RVC) and the percentage of outside members as attributes of corporate performance. Our base model consists of two performance indicators: a composite financial accounting measure (of ROA, ROS, and ROE) and a market- based indicator (standardized stock prize increase). Control variables are: log of total assets as an indicator of the size of a firm, leverage and adjusted cash flow/total assets as indicators of financial structure, coefficients of variation of sales and ROA as measures of environmental uncertainty (dynamics), and diversification as a measure of risk-spread. In general, we conclude for the year 1996, that by using the base model, direct linear and non-linear relationships between the TMT/board variables and performance are not existent. Also, the interaction effects with environmental dynamics as a moderating variable are tested. From this analysis it becomes evident that, although environmental uncertainty has a clear direct relationship with performance, it has no significance as a moderating variable. Only in one case the interaction with size of the board leads to a significant result. Indicating (instead of the hypothesized inverted U-shaped relationship) a U-shaped relationship between RVC and performance.

English Syntax I

This paper focuses on the description of several controversial properties of Negative Inversion (NI) in Standard English. The first topic is the fact that, according to some scholars, subject-auxiliary (subj-aux) inversion when there is preposed negative element is sometimes optional. Scholars agree that subject-auxiliary inversion is compulsory whenever the fronted negative element is an adjunct, but they differ when taking complements into account. Some state that subject-auxiliary (subj-aux) inversion is optional when the fronted negative element is a complement. However, others consider subject-auxiliary inversion to be compulsory all the time. In this paper I show that it is true that subject-auxiliary inversion is optional when the fronted negative element is a complement, as all the speakers asked accept non-inversion, and only half of them accept inversion in such environment. The next topic is whether NI behaves as a Root Phenomenon (RT) or not. Some scholars have stated that NI is in fact a RT, however, by analysing and comparing the environments where RTs and NI can appear, I get to the conclusion that, unlike Topicalization or Focalization (which are also considered RTs), NI does not follow all the requirements to be considered a RT. The last topic is the classification of Only Inversion as a subtype of NI, which I believe not to be accurate, as there are many differences between both phenomena, as the optionality of inversion and their monotonicity. I have approached all these topics from an empirical point of view, comparing what has been previously said in the literature with native English speakers’ grammaticality judgements gathered by an online survey, with the aim of getting clearer results. Keywords: Negative Inversion, Negative Preposing, Negative Constituent Preposing, Negative Adverbials, Interrogative Inversion, Subject-auxiliary inversion, Wh- questions, Focus Preposing, Topicalization, Only Inversion, Only Preposing, Only fronting, Root Phenomena

Thermal structure and exhumation history of the Lesser Himalaya in central Nepal

The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ~20 Myr. It now forms a significant fraction of the Himalayan collisional orogen. We document the kinematics and thermal metamorphism associated with the deformation and exhumation of the LH, combining thermometric and thermochronological methods with structural geology. Peak metamorphic temperatures estimated from Raman spectroscopy of carbonaceous material decrease gradually from 520°–550°C below the Main Central Thrust zone down to less than 330°C. These temperatures describe structurally a 20°–50°C/km inverted apparent gradient. The Ar muscovite ages from LH samples and from the overlying crystalline thrust sheets all indicate the same regular trend; i.e., an increase from about 3–4 Ma near the front of the high range to about 20 Ma near the leading edge of the thrust sheets, about 80 km to the south. This suggests that the LH has been exhumed jointly with the overlying nappes as a result of overthrusting by about 5 mm/yr. For a convergence rate of about 20 mm/yr, this implies underthrusting of the Indian basement below the Himalaya by about 15 mm/yr. The structure, metamorphic grade and exhumation history of the LH supports the view that, since the mid-Miocene, the Himalayan orogen has essentially grown by underplating, rather than by frontal accretion. This process has resulted from duplexing at a depth close to the brittle-ductile transition zone, by southward migration of a midcrustal ramp along the Main Himalayan Thrust fault, and is estimated to have resulted in a net flux of up to 150 m^2/yr of LH rocks into the Himalayan orogenic wedge. The steep inverse thermal gradient across the LH is interpreted to have resulted from a combination of underplating and post metamorphic shearing of the underplated units

The Sub-Surface Structure of a Large Sample of Active Regions

We employ ring-diagram analysis to study the sub-surface thermal structure of active regions. We present results using a large number of active regions over the course of Solar Cycle 23. We present both traditional inversions of ring-diagram frequency differences, with a total sample size of 264, and a statistical study using Principal Component Analysis. We confirm earlier results on smaller samples that sound speed and adiabatic index are changed below regions of strong magnetic field. We find that sound speed is decreased in the region between approximately r=0.99R_sun and r=0.995R_sun (depths of 3Mm to 7Mm), and increased in the region between r=0.97R_sun and r=0.985R_sun (depths of 11Mm to 21Mm). The adiabatic index is enhanced in the same deeper layers that sound-speed enhancement is seen. A weak decrease in adiabatic index is seen in the shallower layers in many active regions. We find that the magnitudes of these perturbations depend on the strength of the surface magnetic field, but we find a great deal of scatter in this relation, implying other factors may be relevant.Comment: 16 pages, 11 figures, accepted for publication in Solar Physic