Seasonal Variations of Pavement Layer Moduli Determined Using In Situ Measurements of Pavement Stress and Strain

Pavement design procedures have advanced a great deal in recent years, changing from empirical equations based on road tests in the 1950s to mechanistic-empirical design procedures developed in the past few years. The resilient moduli for the asphalt and soil layers of pavement sections are important properties necessary for pavement design, and an accurate method for determining moduli under different conditions is necessary. The stiffness of pavement section layers changes with the season, and typically, a road section will be the weakest during spring thaw due to loss of frozen soil stiffness, and increases in water content. This is critical to consider for roadways that are traveled by heavy truck traffic, where weight limits are implemented to reduce spring thaw damage. Resilient modulus is a form of the elastic modulus of soil. The value can be calculated using a variety of methods. AASHTO has a procedure for laboratory determination of resilient modulus, and correlations exist to estimate modulus based on other soil properties. The most widely used method of calculating pavement layer moduli is the backcalculation of moduli from deflection data obtained using a Falling Weight Deflectometer. The goal of this project was to collect in situ stress and strain data in an attempt to calculate resilient modulus directly in the field. Temperature data was also collected to help quantify the effect of freezing and thawing cycles on changes in modulus. A section of Rt. 15 in Guilford, Maine was instrumented with strain gages, stress gages, and climate related gages during the reconstruction of the roadway. Strain gages and thermocouples were installed in the asphalt layer, and strain gages, pressure cells, thermocouples, resistivity probes, and moisture gages were installed in the subbase and subgrade layers. A data acquisition system was set up on site to collect both high speed stress and strain responses, and static temperature, moisture, and resistivity responses. Data was collected during the winter, spring, and summer of 2006. Stress and strain responses were recorded for traffic loading due to normal truck traffic and controlled loading with a MaineDOT dump truck with a known weight. A Falling Weight Deflectometer was also used to acquire data for modulus backcalculation. Asphalt strain responses were used to estimate the value of Nf, the number of loading cycles required to cause fatigue cracking. Predicted and measured values of strain in the asphalt and the soil were compared. In situ moduli were calculated using recorded stresses and strains and related to FWD backcalculated moduli. These initial results from the instrumented site were used to observe the effect of freezing and thawing on pavement responses

Enhancement of ion cyclotron waves in hydrogen helium mixtures

Metastable helium atom addition to hydrogen plasma for ion cyclotron mode enhancemen

Disruption of Intrinsic Motions as a Mechanism for Enzyme Inhibition

AbstractClostridium difficile (C. diff) is one of the most common and most severe hospital-acquired infections; its consequences range from lengthened hospital stay to outright lethality. C. diff causes cellular damage through the action of two large toxins TcdA and TcdB. Recently, there has been increased effort toward developing antitoxin therapies, rather than antibacterial treatments, in hopes of mitigating the acquisition of drug resistance. To date, no analysis of the recognition mechanism of TcdA or TcdB has been attempted. Here, we use small molecule flexible docking followed by unbiased molecular dynamics to obtain a more detailed perspective on how inhibitory peptides, exemplified by two species HQSPWHH and EGWHAHT function. Using principal component analysis and generalized masked Delaunay analysis, an examination of the conformational space of TcdB in its apo form as well as forms bound to the peptides and UDP-Glucose was performed. Although both species inhibit by binding in the active site, they do so in two very different ways. The simulations show that the conformational space occupied by TcdB bound to the two peptides are quite different and provide valuable insight for the future design of toxin inhibitors and other enzymes that interact with their substrates through conformational capture mechanisms and thus work by the disruption of the protein’s intrinsic motions

1861-11-25 J.G. Swett asks that C.F. Nickerson be transferred from infantry to artillery

https://digitalmaine.com/cw_me_2nd_regiment_corr/1206/thumbnail.jp

Economic Analysis of Working Waterfronts in the United States

Waterfront communities in the United States, whether rural or urban, recreational or industrialized, have been subject to economic, technological, ecological, and demographic changes that challenge their continued existence or development. The purpose of this study is to document the current status, contribution to regional economies, and future prospects of U.S. coastal communities in order help promote their long‐term economic prosperity. A review of the relevant literature on economic valuation of waterfront and ocean‐related economic activities found that previous studies usually evaluated only one particular economic sector or specific region. The present study attempts to provide a comprehensive evaluation of all ocean‐related economic activity for all coastal regions of the United States

Voltage gated inter-cation selective ion channels from graphene nanopores

With the ability to selectively control ionic flux, biological protein ion channels perform a fundamental role in many physiological processes. For practical applications that require the functionality of a biological ion channel, graphene provides a promising solid-state alternative, due to its atomic thinness and mechanical strength. Here, we demonstrate that nanopores introduced into graphene membranes, as large as 50 nm in diameter, exhibit inter-cation selectivity with a ~20x preference for K+ over divalent cations and can be modulated by an applied gate voltage. Liquid atomic force microscopy of the graphene devices reveals surface nanobubbles near the pore to be responsible for the observed selective behavior. Molecular dynamics simulations indicate that translocation of ions across the pore likely occurs via a thin water layer at the edge of the pore and the nanobubble. Our results demonstrate a significant improvement in the inter-cation selectivity displayed by a solid-state nanopore device and by utilizing the pores in a de-wetted state, offers an approach to fabricating selective graphene membranes that does not rely on the fabrication of sub-nm pores

Carbon Free Boston: Buildings Technical Report

Part of a series of reports that includes: Carbon Free Boston: Summary Report; Carbon Free Boston: Social Equity Report; Carbon Free Boston: Technical Summary; Carbon Free Boston: Transportation Technical Report; Carbon Free Boston: Waste Technical Report; Carbon Free Boston: Energy Technical Report; Carbon Free Boston: Offsets Technical Report; Available at http://sites.bu.edu/cfb/OVERVIEW: Boston is known for its historic iconic buildings, from the Paul Revere House in the North End, to City Hall in Government Center, to the Old South Meeting House in Downtown Crossing, to the African Meeting House on Beacon Hill, to 200 Clarendon (the Hancock Tower) in Back Bay, to Abbotsford in Roxbury. In total, there are over 86,000 buildings that comprise more than 647 million square feet of area. Most of these buildings will still be in use in 2050. Floorspace (square footage) is almost evenly split between residential and non-residential uses, but residential buildings account for nearly 80,000 (93 percent) of the 86,000 buildings. Boston’s buildings are used for a diverse range of activities that include homes, offices, hospitals, factories, laboratories, schools, public service, retail, hotels, restaurants, and convention space. Building type strongly influences energy use; for example, restaurants, hospitals, and laboratories have high energy demands compared to other commercial uses. Boston’s building stock is characterized by thousands of turn-of-the-20th century homes and a postWorld War II building boom that expanded both residential buildings and commercial space. Boston is in the midst of another boom in building construction that is transforming neighborhoods across the city. [TRUNCATED]Published versio

Strontium Isotopic Variations of Neoproterozoic Seawater: Implications for Crustal Evolution

We report high precision Sr isotopic data on carbonates from the Neoproterozoic Shaler Group, Victoria Island, Northwest Territories, Canada. Lithostratigraphic correlations with the relatively well-dated Mackenzie Mountains Supergroup constrain Shaler deposition to approximately 770-880 Ma, a range corroborated by 723 +/- 3 Ma lavas that disconformably overlie Shaler carbonates and by Late Riphean microfossils within the section. Samples with low Rb-87/Sr-86 ratios (< 0.01) were selected for Sr isotopic analysis. delta-O-18, Mn, Ca, Mg, and Sr data were used to recognize altered samples. The altered samples are characterized by high Mn/Sr (greater-than-or-equal-to 2) and variable delta-O-18; most are dolomites. The data indicate that between ca. 790-850 Ma the Sr-87/Sr-86 ratio of seawater varued between 0.70676 and 0.70561. The samples show smooth and systematic variation, with the lowest Sr-87/Sr-86 value of 0.70561 at ca. 830 Ma. The low Sr-87/Sr-86 ratio of carbonates from the lower parts of our section is similar to a value reported for one sample from the Adrar of Mauritania (almost-equal-to 900 Ma), West African Craton. Isotopic ratios from the upper part of the Shaler section are identical to values from the lower part of the Neoproterozoic Akademikerbreen Group, Spitsbergen. Although a paucity of absolute age determinations hinders attempts at the precise correlation of Neoproterozoic successions, it is possible to draw a broad outline of the Sr isotopic composition of seawater for this period. Indeed, the Sr isotope data themselves provide a stratigraphic tool of considerable potential. Data from this study and the literature are used to construct a curve of the Sr-87/Sr-86 ratio of Neoproterozoic seawater. The new data reported in this study substantially improve the isotopic record of Sr in seawater for the period 790-850 Ma. The Sr isotope composition of seawater reflects primarily the balance between continental Sr input through river input and mantle input via hydrothermal circulation of seawater through mid-ocean ridges. Coupling of Nd and Sr isotopic systems allows us to model changes in seafloor spreading rates (or hydrothermal flux) and continental erosion. The Sr hydrothermal flux and the erosion rate (relative to present-day value) are modeled for the period 500-900 Ma. The results indicate that the hydrothermal flux reached a maximum value at ca. 830 Ma. In contrast, a large peak in erosion rate is indicated at ca. 570 Ma. The peaks in hydrothermal flux and erosion rate are most likely related to developments in the Pan-African and related orogenic events, whose initial development is characterized by production of juvenile crust during supercontinental break up and rifting. The time ca. 570 Ma is characterized by continent-continent collision and production of recycled crust. Sr isotope data from Proterozoic carbonates offer a valuable resource for understanding large-scale crust dynamics.Earth and Planetary SciencesOrganismic and Evolutionary Biolog