Dilepton and Photon Emission Rates from a Hadronic Gas

We analyze the dilepton and photon emission rates from a hadronic gas using chiral reduction formulas and a virial expansion. The emission rates are reduced to pertinent vacuum correlation functions, most of which can be assessed from experiment. Our results indicate that in the low mass region, the dilepton and photon rates are enhanced compared to most of the calculations using chiral Lagrangians. The enhancement is further increased through a finite pion chemical potential. An estimate of the emission rates is also made using Haag's expansion for the electromagnetic current. The relevance of these results to dilepton and photon emission rates in heavy-ion collisions is discussed.Comment: 7 pages, LaTeX using revTeX, 6 figures imbedded in text. Figures slightly changed, text left unchange

Instantons and Scalar Multiquark States: From Small to Large N_c

We study scalar quark-anti-quark and two-quark-two-anti-quark correlation functions in the instanton liquid model. We show that the instanton liquid supports a light scalar-isoscalar (sigma) meson, and that this state is strongly coupled to both $(\bar{q}q)$ and $(\bar{q}q)^2$. The scalar-isovector $a_0$ meson, on the other hand, is heavy. We also show that these properties are specific to QCD with three colors. In the large $N_c$ limit the scalar-isoscalar meson is not light, and it is mainly coupled to $(\bar{q}q)$.Comment: 24 page

Autoimmune and infectious skin diseases that target desmogleins

Desmosomes are intercellular adhesive junctions of epithelial cells that contain two major transmembrane components, the desmogleins (Dsg) and desmocollins (Dsc), which are cadherin-type cell–cell adhesion molecules and are anchored to intermediate filaments of keratin through interactions with plakoglobin and desmoplakin. Desmosomes play an important role in maintaining the proper structure and barrier function of the epidermis and mucous epithelia. Four Dsg isoforms have been identified to date, Dsg1–Dsg4, and are involved in several skin and heart diseases. Dsg1 and Dsg3 are the two major Dsg isoforms in the skin and mucous membranes, and are targeted by IgG autoantibodies in pemphigus, an autoimmune disease of the skin and mucous membranes. Dsg1 is also targeted by exfoliative toxin (ET) released by Staphylococcus aureus in the infectious skin diseases bullous impetigo and staphylococcal scalded skin syndrome (SSSS). ET is a unique serine protease that shows lock and key specificity to Dsg1. Dsg2 is expressed in all tissues possessing desmosomes, including simple epithelia and myocardia, and mutations in this gene are responsible for arrhythmogenic right ventricular cardiomyopathy/dysplasia. Dsg4 plays an important adhesive role mainly in hair follicles, and Dsg4 mutations cause abnormal hair development. Recently, an active disease model for pemphigus was generated by a unique approach using autoantigen-deficient mice that do not acquire tolerance against the defective autoantigen. Adoptive transfer of Dsg3−/− lymphocytes into mice expressing Dsg3 induces stable anti-Dsg3 IgG production with development of the pemphigus phenotype. This mouse model is a valuable tool with which to investigate immunological mechanisms of harmful IgG autoantibody production in pemphigus. Further investigation of desmoglein molecules will continue to provide insight into the unsolved pathophysiological mechanisms of diseases and aid in the development of novel therapeutic strategies with minimal side effects

DRIVER UNDERSTANDING OF SIMULTANEOUS TRAFFIC SIGNAL INDICATIONS IN PROTECTED LEFT TURNS

A comprehensive assessment of protected and permitted left-turn (PPLT) signal displays was performed considering safety, operational performance, and driver-understanding measures. The research focused on a study of driver understanding of protected left-turn indications. All currently used PPLT display arrangements and protected indication combinations were evaluated, including those with simultaneous green-arrow and red- or green-ball indications and those with the green-arrow indication only. Driver understanding was evaluated through a computer-based driver survey completed by 2,465 drivers. In total, 73,950 survey responses were received pertaining to the 200 different survey scenarios evaluated, 24,863 pertaining to protected left-turn indications. Findings show that the simultaneous illumination of the green-arrow and red-ball indications in a five-section PPLT signal display during a protected left-turn phase significantly reduces driver understanding and increases driver error. This finding is especially true for drivers over the age of 65. Simultaneous illumination of the green-arrow and green-ball indications also resulted in levels of driver understanding lower than the green-arrow-only indication; however, these differences were not statistically significant

DRIVERS\u27 UNDERSTANDING OF PROTECTED-PERMITTED LEFT-TURN SIGNAL DISPLAYS

A comprehensive assessment of protected-permitted left-turn (PPLT) signal displays was performed considering safety, operational performance, and driver understanding measures. The research focuses on a study of driver understanding of permitted left-turn indications. All currently used PPLT display arrangements and permitted indication combinations were evaluated, including those with flashing red and yellow permitted indications. Driver understanding was evaluated through a computer-based driver survey completed by 2,465 drivers. A total of 73,950 survey responses were received pertaining to the 200 different survey scenarios evaluated. The study results indicate that yellow or red flashing permitted indications may lead to higher levels of driver comprehension. Both the flashing red and yellow permitted indications had a significantly higher correct response rate than did the green ball permitted indication. Drivers over the age of 65 found the flashing ball permitted indications easier to comprehend and responded more quickly with fewer fail critical (turning left without the right-of-way) errors. Higher correct response rates with flashing permitted indications were also found in other important demographic groups, including inexperienced drivers and drivers with limited education

Traffic characteristics of protected/permitted left-turn signal displays

25 p. ; Prepared for the 79th Annual Meeting of the Transportation Research Board, Washington, D.C. January, 2000At least four variations of the permitted indication in protected/permitted left-turn (PPLT) control have been developed in an attempt to improve the level of driver understanding and safety. These variations replace the green ball permitted indication with a flashing red ball, a flashing yellow ball, a flashing red arrow, or a flashing yellow arrow indication. In addition, the "Manual on Uniform Traffic Control Devices" allows several PPLT signal display arrangements. The variability in indication and arrangement has led to a myriad of PPLT displays throughout the United States. The level of driver understanding related to each PPLT display type, and the associated impact on traffic operations and safety, has not been quantified. A study was conducted to evaluate the operational characteristics associated with different PPLT signal displays. Specifically, the study quantified saturation flow rate, start-up lost time, response time, and follow-up headway associated with selected PPLT displays. No differences in saturation flow rate and start-up lost time were found due to the type of PPLT signal display. Saturation flow rates ranged from 1,770 to 2,400 vehicles per hour of green per lane and were related to differences in driver behavior between geographic locations. The variation in start-up lost time and response time between locations was primarily related to differences in phase sequence. The flashing red permitted indications were associated with the longest follow-up headway times, since drivers are required to stop before turning left with a flashing red permitted indication. The shortest follow-up headway was associated with the five-section cluster display using a green ball indication

TRAFFIC CHARACTERISTICS OF PROTECTED/PERMITTED LEFT-TURN SIGNAL DISPLAYS

At least four variations of the permitted indication in protected/permitted left-turn (PPLT) control have been developed in an attempt to improve the level of driver understanding and safety. These variations replace the green ball permitted indication with a flashing red ball, a flashing yellow ball, a flashing red arrow, or a flashing yellow arrow indication. In addition, the Manual on Uniform Traffic Control Devices allows several PPLT signal display arrangements. The variability in indication and arrangement has led to a myriad of PPLT displays throughout the United States. The level of driver understanding related to each PPLT display type, and the associated impact on traffic operations and safety, has not been quantified. A study was conducted to evaluate the operational characteristics associated with different PPLT signal displays. Specifically, the study quantified saturation flow rate, start-up lost time, response time, and follow-up headway associated with selected PPLT displays. No differences in saturation flow rate and start-up lost time were found due to the type of PPLT signal display. Saturation flow rates ranged from 1,770 to 2,400 vehicles per hour of green per lane and were related to differences in driver behavior between geographic locations. The variation in start-up lost time and response time between locations was primarily related to differences in phase sequence. The flashing red permitted indications were associated with the longest follow-up headway times, since drivers are required to stop before turning left with a flashing red permitted indication. The shortest follow-up headway was associated with the five-section cluster display using a green ball indication

Traffic conflicts associated with protected/permitted left-turn signal displays

25 p. ; Paper prepared for the 79th Annual Meeting of the Transportation Research Board, Washington, D.C. January 2000.Several different protected/permitted left-turn (PPLT) signal displays are used in the United States, varying in configuration and permitted indication. Questions remain as to the safety implications of using each type of display. Since left-turn crash data do not contain information related to the type of signal display and permitted indication at the intersection, conflict studies are often used as a surrogate measure. This paper describes a study of 24 intersections in eight U.S. cities to evaluate traffic conflicts and events (safety implications) associated with selected PPLT signal displays. Based on the results of this study, there was no difference in the conflict rates associated with the PPLT signal displays evaluated. Conflict rates varied from 0.0 to 1.4 conflicts/1,000 entering vehicles. Conflicts attributed to driver misunderstanding of the signal display or indication were primarily associated with the green ball permitted indication. Most left-turn events were related to hesitation at the onset of the protected green arrow indication. Evaluating each event type individually suggested that the five-section horizontal display with both the green arrow and red ball illuminated was associated with a significantly higher rate of Type 1 (hesitate on green arrow indication) events. Currently, the Manual on Uniform Traffic Control Devices (MUTCD) requires simultaneous illumination of the green arrow and adjacent through movement indication in the PPLT signal display during the protected left-turn phase. This result demonstrated the increase in signal display complexity and driver workload with the simultaneous illumination of the green arrow and red ball indications

Use of protected/permitted left-turn signal control in the U.S.

14 p. ; Paper prepared for Transportation Frontiers for the Next Millennium: 69th Annual Meeting of the Institute of Transportation Engineers, Las Vegas, Nevada, August 1-4, 1999.The growing level of traffic demand on urban and rural roadways has led to increased use of protected/permitted left-turn (PPLT) signal control. PPLT signal phasing provides an exclusive phase for left turns as well as a permissive phase during which left turns can be made if gaps in opposing through traffic allow, all within the same signal cycle. The signal display most commonly used with PPLT signal phasing is a five-section signal display with a green arrow indication for the exclusive left-turn phase and a green ball for the permitted left-turn phase. However, many transportation agencies use different mounting locations, signal display arrangements, and permitted indications when implementing PPLT. In addition, there are at least four variations of the permitted indication, including the flashing red ball, flashing red arrow, flashing yellow ball, and flashing yellow arrow. This paper presents the results of a comprehensive agency survey sent to local, county, and state officials designed to determine the use of PPLT signal control in the United States. The first section presents general survey information, including the total number of surveys received and the total number of signalized intersections reported. This section also quantifies the number of signalized intersections containing PPLT signal displays. The second section presents the types of PPLT signal displays used by these agencies and typical signal display mounting practices. The third section presents intersection geometry and signal phasing practices most often used with PPLT signal phasing. Finally, the last section provides a brief summary of the results

Traffic control guidelines for urban arterial work zones. Volume I: Executive summary. Final report.

Texas Department of Transportation, AustinFederal Highway Administration, Washington, D.C.Mode of access: Internet.Author corporate affiliation: Texas Transportation Institute, College StationReport covers the period Sept 1989 - Aug 1991Subject code: CCCCSubject code: CDNCSubject code: HBSubject code: KBMSubject code: YE