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In methodology, WJMSCs were treated with a 0.4-T SMF. The cell viability was tested using the MTT assay. For the osteogenic analysis, the alkaline phosphatase activity assay and alizarin red S staining were performed. The osteogenic-related gene expression ofThe cell viability showed no significant difference between the SMF-treated group and the sham-exposed cells. However, the SMF-treated group exhibited significantly more mineralized nodule formation and higher ALP activity than their control counterparts (The results suggest that 0.4-T SMF treatment enhances the osteogenesis of WJMSCs at the early-to-middle stage of osteogenic differentiation by increasing the matrix vesicle secretion and mineralization.

The successful demonstration of Q-switched and mode-locked fiber-laser operations using a topological insulator (TI) as saturable absorber (SA) has opened an application window besides TI's originally expected features. However, to date, all-solid-state mode-locked lasers base on TISAs are still unavailable and became a desired goal not only due to their application as light sources, but also because of providing a way for deeper investigation of the nature of ultrafast dynamics present in TISAs. In this paper, the realization of a continuous-wave mode-locked all-solid-state laser with a repetition rate of around 1 GHz is reported using a high-quality TI SA mirror (TI-SAM) with ultralow saturation intensity, fabricated by a spin coating-co-reduction approach. An output power of 180 mW and pulse duration of 8 ps are observed. In addition, a 61 dB pulse-train quality from the radio frequency spectrum of mode-locked operation prove the feasibility of the proposed laser. To the best of our knowledge, this is the first experimental demonstration of a mode-locked solid-state laser based on TIs. In addition, this paper shows that the use of TISAs is a promising option for the realization of scaling solid-state mode-locked lasers with higher repetition rates, reaching order of GHz.

In this paper, by using the prepared topological insulator saturable absorber mirror, a GHz, mode-locked Nd:YVO 4 bulk laser is realized for the first time with the output power of 180mW and pulse duration of 8ps.

Purpose This study developed calcium phosphate bone substitutes and their microstucture and in vitro cell response were evaluated in comparison with commercial hydroxyapatite (HA). Materials HA powder was ball-milled and then sintered to transfer into the calcium phosphate bulks (CPB). The density, hardness, and microstructure of the CPB were investigated. The viability and proliferation of MG63 osteoblast-like cells on the commercial HA and the CPB were evaluated. Results The x-ray diffraction confirmed that the CPB consisted of α-tricalcium phosphate (α-TCP), CaO, and HA. The hardness, density, and α-TCP-to-HA ratio of the CPB decreased when increasing the sintering duration. Cell tests demonstrated that the CPB exhibited an earlier cell-spread response than the commercial HA. Conclusions This study demonstrated that a phase transformation of HA into α-TCP and CaO was achieved by sintering. The cell tests indicated that the CPB has favorable in vitro cellular performance, which implied that it presented potential as bone substitute.

Developed in the early 1990s, ultrathin whitetopping (UTW) is a relatively new technique for asphalt pavement rehabilitation. To evaluate the applicability of UTW pavement in Florida, in 1997, the Florida Department of Transportation (FDOT) constructed an experimental UTW pavement in a weigh station along I-10, located in north Florida. The performance of these test sections, however, was less than ideal, with the observation of some early cracking on the concrete surface, which developed into severe cracking with time. Therefore, a forensic investigation was conducted to determine the causes of the problems in these UTW sections, so that lessons could be learned from this experimental project, the use of UTW under Florida's conditions could be adequately assessed, and UTW technology could be properly applied in the future. The scope of work consisted of field evaluation, laboratory testing, and pavement design evaluation. Field evaluation included a pavement condition survey, pavement temperature measurement, nondestructive load testing using a falling weight deflectometer, and slab thickness determination. Laboratory tests were performed to determine concrete and asphalt material properties. Other design and traffic data were also acquired from FDOT. Data collected from the field evaluation and laboratory testing were used in conjunction with a mechanistic UTW pavement design/evaluation procedure to determine the possible causes for premature failure. From this comprehensive evaluation, the primary cause for the failure was found to be inadequate UTW pavement design. The inadequacy of the combination of thickness and slab dimensions contributed to the early cracking of the UTW pavement.

A three-dimensional (3-D) finite element model for stress analysis of pavements with ultrathin whitetopping (UTW) under critical loading conditions was developed. The 3-D model developed was used to analyze the UTW test pavement sections at the Ellaville Weigh Station in Florida, which had less than satisfactory performance. The poorly performing UTW sections at the Ellaville Weigh Station were found to have relatively higher maximum computed stresses under critical loading conditions, which appeared to explain their poor performance and high percentages of cracked slabs. The 3-D model developed was also used to perform a parametric analysis to determine the effects of asphalt thickness, asphalt modulus, concrete thickness, concrete modulus, base stiffness, subgrade stiffness, slab dimension, temperature differential in the concrete, and applied load on the maximum stresses in UTW pavements under typical Florida conditions.

As part of a study sponsored by NCHRP, research was conducted to evaluate the variability of concrete materials data in the Long-Term Pavement Performance (LTPP) program. The following materials-related data were studied: ( a) compressive strength, ( b) flexural strength, ( c) split tensile strength, and ( d) modulus of elasticity. The variability was determined in terms of the standard deviation and coefficient of variability. The strength and stiffness data used came from the General Pavement Study (GPS) as well as the Specific Pavement Study (SPS) test sections. The analysis of data indicates that, in general, the LTPP program GPS test sections as well as the LTPP program SPS test sections exhibit characteristics of well-controlled construction projects with respect to the strength- and stiffness-related properties of concrete. The results of the analysis indicate that on well-controlled concrete pavement construction projects it would not be unreasonable to produce concrete that has a coefficient of variation of 15% or less for compressive strength, flexural strength, split tensile strength, and the modulus of elasticity. The findings from the analysis can be used to refine statistics-based quality assurance/quality control procedures for concrete acceptance and to define the measures of variability to be used in mechanistically based concrete design procedures.

To obtain a better understanding of ultrathin whitetopping (UTW) pavement behavior under traffic loading and environmental effects and to collect data for calibration and development of a mechanistic design procedure, a UTW test pavement was constructed, instrumented, and load tested. The UTW pavement test section is located at the Spirit of St. Louis Airport, a general aviation airport in Chesterfield, Missouri, and is designed to carry a light aircraft load of 56 kN. The results of analyses conducted on this test pavement and its performance to date are described. The UTW test section was constructed in February 1995 and consisted of six slabs with dimensions of 1.3 × 1.3 m and a design slab thickness of 89 mm. The load testing was conducted in May and September 1995. Load-induced strains, temperature distribution, and surface profiles were measured at different locations and at different times. Pavement core samples were also taken and subjected to laboratory testing. It was observed from the evaluation that ( a) there was very little vertical slab movement in spite of the temperature differential in the slabs, ( b) there was no apparent change in load-induced strains (stresses) with temperature changes, ( c) pavement exhibited high load transfer efficiencies across contraction joints, and ( d) an interface shear strength of 689 kPa was achieved by the commonly used technique for asphalt surface preparation, milling and cleaning. A recent performance review of this pavement also showed that it has performed extremely well after over 6 years in service. Of the 11620 m2 of UTW pavements (about 72,000 UTW panels), only 18 panels have cracked.

Since its inception in 1991, ultrathin whitetopping (UTW) has moved beyond the experimental stage and has become a viable pavement rehabilitation alternative. Development of the mechanistic design procedure in 1997 represented a milestone in the development of this technology. Over 150 UTW pavements have been built in the past decade. With the use of UTW rapidly increasing, the next logical step in the development of this technology is to develop UTW repair and rehabilitation techniques. How does one repair UTW pavements? Can conventional concrete pavement rehabilitation materials and methods be used for UTW pavements? Construction of the UTW test sections at the FHWA Turner-Fairbank Highway Research Center, subjected to accelerated loading tests, provided an excellent opportunity for evaluating potential UTW pavement repair methods. These test sections were constructed in April 1998 and were subjected to accelerated load testing with FHWA’s accelerated loading facility (ALF) from May 1998 until November 1999. Some UTW panels exhibited distresses, with corner cracking being the most prominent. After discussions with state agency staff and industry representatives, panel removal and replacement was selected to repair some of the distressed panels of these test sections. The repair work was done in April 2000 and the repaired test sections were load tested with ALF from May to August 2000. Based on the results of ALF testing, it was observed that panel removal and replacement is an effective method for UTW pavement repair. Guidelines for UTW pavement repair by this method are proposed. A strong bond between the concrete and asphalt layers, even for distressed (cracked) panels, was observed. The time required for UTW panel repair was also documented and can be used for planning UTW repairs.

To provide accurate climatic data for pavements under the Long-Term Pavement Performance (LTPP) Program, a climatic database was developed in 1992 and subsequently revised and expanded in 1998. In the development of this database, up to five nearby weather stations were selected for each test site. Pertinent weather data for the selected weather stations were obtained from the U.S. National Climatic Data Center and the Canadian Climatic Center. With a 1/ R2 weighting scheme, site-specific climatic data were derived from the nearby weather station data. The derived data were referred to as “virtual”weather data. To evaluate the effect of environmental factors on pavement performance and design, automated weather stations (AWS) were installed at LTPP Specific Pavement Study Projects 1, 2, and 8 to collect on-site weather data. Since the virtual weather data were developed for all LTPP test sites and will be used for future pavement performance studies, it is essential that the derived virtual data be accurate and representative of the actual onsite climatic conditions. The availability of the AWS weather data has provided an opportunity to evaluate whether virtual weather data can be used to represent on-site weather conditions. Daily temperature data and monthly temperature and precipitation data were used in this experiment. On the basis of the comparisons made between the virtual and onsite measured (AWS) data, it appears that climatic data derived from nearby weather stations using the 1/R2 weighting scheme estimate the actual weather data reasonably well and thus can be used to represent on-site weather conditions in pavement research and design.

This paper presents the Findings of an effort undertaken by the Federal Highway Administration (FHWA) Long-Term Pavement Performance (LTPP) program to assess variability of distress data collected using a photographic method. The primary source of data used to characterize the film-derived distress data variability is the results of a distress survey conducted on 12 pavement test sections, including six asphalt concrete (AC) and six portland cement concrete (PCC) pavements. Distress surveys were performed by experts, individual raters, and two-person teams. A consensus survey on the pavements by a group of experts based on the photographic method was also conducted. Finally, a reference rating of the distress present on the same 12 test sections was performed using a consensus manual rating method by the same group of experts; data from these reference surveys were used as a surrogate of “ground-truth”. Based on the analyses of these data, variability of the film-derived distress data was evaluat...

The results of a laboratory testing program carried out to investigate the effect of coarse aggregate types on the elastic modulus of typical pavement concretes are presented. The elastic modulus was determined in both flexure and compression using static and dynamic means. Three different mixes, made using three different aggregates, were compared. The water-cement ratio was kept at 0.53 throughout the test program. The results showed that within the tested range, the aggregate type significantly affected the studied properties of concrete. Calera aggregate (a dense limestone) with its rough-textured surface and angular shape produced a concrete with higher strength and stiffness than those of concretes made with Brooksville aggregate (a porous limestone) and river gravel. In addition, the measured dynamic modulus in compression was significantly different from that in flexure. Also, in flexure, the dynamic modulus was higher than the static modulus by an average of 23 percent, whereas in compression, the dynamic modulus appeared to be in the same range as the static modulus. The change in frequency from 1 to 7 Hz did not have a significant influence on the dynamic modulus.

To study the seeding mechanism of ionospheric irregularity occurrences, a correlation study has been carried out between the global monthly/latitudinal (m/l) distributions of irregularity occurrences and the deep atmospheric convective clouds in the intertropical convergence zone (ITCZ) indicated by the outgoing longwave radiation (OLR) measurements. Seven longitude sectors - the African, Indian, West Pacific, Central Pacific, East Pacific, South American, and Atlantic sectors - are selected to study the correlations between the two distributions. The results indicate that good correlations exist only in the South American sector and to some extent in the African sector. For the other five sectors, no correlations are found in the m/l distributions between the irregularities and OLRs. This implies that the gravity wave induced in the ITCZ cannot be the sole seeding agent for the Rayleigh-Taylor (RT) instability in the global irregularity occurrences every season. We suspect that the post-sunset ionospheric electrodynamic perturbations could be the prevailing seeds for the RT instability globally year long. Together with the favorable post-sunset ionospheric condition, the global m/l distributions of irregularity occurrences could be adequately explained.