Experimental Test Site Research Articles

Cost-Effectiveness of Crack Sealing Materials and Techniques for Asphalt Pavements

Sealing or filling cracked asphalt pavements to prevent the intrusion of water into the pavement structure has long been an accepted practice of the Montana Department of Transportation. Attempts were made to establish the most economical and effective method of sealing pavement cracks for Montana and to better determine crack sealing’s role within Montana’s pavement management system (PvMS). Four experimental test sites were constructed within crack-sealing projects. The test sites included combinations of nine sealant materials and six sealing techniques. Monitoring of the test sites includes visual inspections (for all of the sites) and nondestructive structural readings and surface distress identification under Montana’s PvMS (for one test location). One expectation of the inspections is an estimation of crack sealing’s useful life. Information on project history and project methodology, including the methods used for evaluating the performance of sealed cracks, is presented. Interim conclusions are presented, most of which have been obtained from the two test sites that have been in service for 3 years. Similar performance has been observed for all materials with ASTM D5329 cone penetrations in excess of 90. In general, routing of transverse cracks improved the performance of the sealants. Routing did not appear necessary for centerline longitudinal cracks. Observations from the first year of service for the most recent installation are noted. Notably, router operators appear to prefer the shallow reservoir configuration over square reservoirs. The highest failure rates occur during the coldest period of the year, and much of this distress “heals” after exposure to the summer heat.

Site-specific subgingival colonization by Actinobacillus actinomycetemcomitans in orthodontic patients

A high prevalence of Actinobacillus actinomycetemcomitans (Aa) in subgingival plaque in patients for orthodontia already has been observed. The present study had the following aims: 1) to ascertain a direct relationship between the orthodontic appliance placement and the subgingival colonization by Aa , and 2) to determine whether the Aa growth specifically occurred on teeth with braces attached or whether the presence of orthodontic appliances could also cause the isolation of Aa in teeth free from therapeutic appliances. Twenty-four young systemically and periodontally healthy subjects with malaligned and crowded teeth in the anterior sextants of both dental arches participated in this study. After 1 session of ultrasonic scaling with oral hygiene instructions during the first experimental session, the mesiobuccal sites of the first molars and the distobuccal sites of the lateral incisors in both dental arches in each participant were subjected to clinical and microbiologic examination for the recovery of Aa . Clinical examination consisted of recording the presence of plaque and the examination of gingival bleeding on probing and probing depth. Microbiologic sampling was obtained with the insertion of 3 sterile paper points at the deepest part of each gingival sulcus. Altogether, 192 periodontal sites were examined. After the examinations, the patients received fixed orthodontic appliances in only 1 dental arch (test sites) and the other one was left free from appliances (control sites). Clinical examination and microbiologic sampling were repeated in the same experimental test and control sites after 4, 8, and 12 weeks. At the 12-week session, the orthodontic appliance was removed from the test arch, and, 4 weeks later, a further clinical and microbiologic examination was performed. The results showed that, during the period with orthodontic appliances, the presence of plaque scores and the gingival bleeding on probing scores were increased significantly and that Aa , initially absent from all but 1 subject, was isolated in 19 and 20 subjects after 4 and 8 weeks, respectively. Furthermore, no gingival sites from the control teeth (free from Aa colonization at baseline) showed positive results for the sought-after bacterium throughout the entire length of the study. It was concluded that the placement of orthodontic appliances promotes the subgingival growth of Aa ; this specific microbial change is specifically restricted to subgingival plaque from orthodontic appliance–bearing teeth. The presence of orthodontic bands and brackets therefore cannot affect the microbiologic condition of the whole mouth. (Am J Orthod Dentofacial Orthop 1999;115:423-8)

Seismic Flat Dilatometer Tests in Connecticut Valley Varved Clay

Abstract Downhole shear wave velocity measurements have been incorporated within a “Marchetti” flat dilatometer by placing a velocity transducer in a connecting rod just above the blade. The hybrid of combining downhole seismic with flat dilatometer, termed the seismic dilatometer test (SDMT), has the superior advantages of determining both the routine estimates of soil properties and stratigraphic information, while also measuring the small-strain stiffness within a single sounding. The SDMT is rapid, simple, and cost effective, requiring essentially no more time than a conventional dilatometer sounding. Results of seismic dilatometer testing in clays at the National Geotechnical Experimental Test Site (NGES) in Amherst, Massachusetts are presented and compare favorably with results from companion series of seismic cone penetrometer tests.

A high-speed complementary silicon bipolar technology with 12-fJ power-delay product

A complementary silicon bipolar technology offering a substantial improvement in power-delay performance over conventional n-p-n-only bipolar technology is demonstrated. High-speed n-p-n and p-n-p double-polysilicon, self-aligned transistors were fabricated in a 20-mask-count integrated process using an experimental test site designed specifically for complementary bipolar applications. N-p-n and p-n-p transistors with 0.50- mu m emitter widths have cutoff frequencies of 50 GHz and 13 GHz, respectively. Two novel complementary bipolar circuits-AC-coupled complementary push-pull ECL, and NTL with complementary emitter-follower-display a significant advantage in power dissipation as well as gate delay when compared to conventional n-p-n-only ECL circuits. Record power-delay products of 34 fJ (23.2 ps at 1.48 mW) and 12 fJ (19.0 ps at 0.65 mW) were achieved for these unloaded complementary circuits, respectively. These results demonstrate the feasibility and resultant performance leverage of high-speed complementary bipolar technologies. >

Use of a phosphophoryn-Ca+2-collagen composition that mimics a mineralization front in unicortical defects in long bones

The present study was designed to ascertain if dynamic ionic matrices that mimic the mineralization front could be used as active scaffolds for bone repair. Dentinal phosphophoryn calcium salts were extracted from unerupted bovine dentine using chatopic buffers and EDTA. The phosphophoryns were subsequently isolated following precipitation with CaCl2. The phosphophoryn-Ca+2 salts were then mixed with pepsin solubilized bovine skin collagen and lyophilized into hardened sponges. Three groups of 4 beagle dogs were employed such that one leg served as an experimental test site for a mechanical wound, while the contralateral leg served as a control. Animals were sacrificed at 1,3, and 6 month intervals. The test specimens were harvested, fixed, and processed for routine histology, examined with image histomorphometric analysis, and scored. Tabulation of these data indicated that phosphophoryn-Ca(+2)-collagen enhances the repair of mechanically formed osseous defects in the distal femur of beagle dogs. This enhanced rate of bone repair was manifest by earlier filling of bony voids with osteoid and trabecular bone. Eventually, this process was followed by recortification of the surface defects. These data suggest that components derived from a mineralization front may influence bone formation in unicortical defects within long bones.

Chromium Migration Through Sludge‐Treated Soils

ABSTRACTThe Environmental Protection Agency and the Tanner's Council of America jointly initiated a five‐year project in September 1980 to investigate the feasibility of using land treatment to dispose of chromium tanning sludges. These sludges contain high concentrations of Cr, in the range of 21,000 to 55,000 ppm on a dry weight basis. Chromium could migrate in soil waters at a land treatment site as either a soluble Cr (VI) species, HCrO4 or CrO42, or as Cr (III) or Cr (VI) in soluble complexes with organic or inorganic substances. Field measurements of Cr fluxes at an experimental test site near Santa Cruz, California indicate that Cr in tannery sludges exhibits a very low mobility. Less than 0.1% of the total Cr applied to a test plot was transported through the upper soil zone during a three‐month period. However, the sludge applications introduced high concentrations of nitrates and major cations. Estimates of contaminant fluxes based on measured concentrations in soil water collected with porous cup samplers contain large uncertainties. In addition to potential errors in moisture flux computations, chemical reactions in the cups can significantly alter the composition of soil‐water samples.

The use of measurements to detect electrical problems in operational photovoltaic arrays

The U.S. Department of Energy has set a 20 year lifetime goal for terrestrial photovoltaic modules. In its capacity as a photovoltaics field tests and applications center, the Lincoln Laboratory, Massachusetts Institute of Technology, has established various experimental test sites throughout the U.S.A., ranging in size from 1.5 to 100 kW p. These sites contain modules from several manufacturers and serve as test beds for photovoltaic system components. Since May 1977, over 11 000 modules have been placed in service at these sites, of which a total of 250 have suffered electrical failures. In previous reports, emphasis has been placed on failure modes and the types of physical and electrical degradation found in modules. In this paper the methods used to detect failures in operational photovoltaic power-generating systems are reported for several Lincoln Laboratory test sites.

<title>Passive Ground-Based Electro-Optical Detection of Artificial Earth Satellites</title>

M.I.T. Lincoln Laboratory is supporting the Electronic Systems Division (ESD) of the Air Force Systems Command (AFSC) in the development of the Ground-based Electro-Optical Deep Space Surveillance (GEODSS) system. As part of this program, an Experimental Test Site (ETS) has been established in the White Sands Missile Range, New Mexico, to serve as a test-bed for the system. After a brief description of the GEODSS network, the ETS and its role are defined and illustrated. Next, the matter of sensor selection for the ETS is discussed. This is followed by the consideration of the general problem of point-source detection. Experimental data are discussed which indicate the point-source response of the ETS sensors. Then, a semi-empirical model for the point-source detection capabilities of these background-limited sensors is presented. Short dicussions of the satellite population and the peculiar problems associated with the passive detection of space objects by reflected sunlight are followed by conclusions based upon brightness measurements made at the ETS during approximately two years of operation.