bluuebunny/crossref_metadata_2025 huggingface dataset:
Letter to the Editor—Bounds for Simplifying Estimation of Elevator Running Times
Authors: Powell Bruce A.
Published: October 2008

The realism of an approximation to the running time of an elevator car during morning up-peak is studied. It is shown that the difference between maximum and minimum running times is very small for cases of practical interest. This small range not only verifies that the approximation gives realistic values for running time but also eliminates the need for complicated probability calculations for up-peak elevator studies.
Letter to the Editor—A Note on a Minimax Location Problem
Authors: Elzinga Jack , Hearn Donald W.
Published: October 2008

In a recent edition of this journal, Wesolowsky (Trans. Sci. 6, 103–113) presents a formulation of a multifoxility minimax location problem for rectilinear distances as a parametric linear program. It is shown here that a modification of Wesolowsky's approach will result in a nonparametric linear program, and further, that a different approach to the problem will yield a simpler formulation as a smaller linear program.
A Technique for the Solution of Massive Set Covering Problems, with Application to Airline Crew Scheduling
Authors: Rubin Jerrold
Published: October 2008

Recent set covering algorithms have been able to solve problems for which the constraint matrix has as many as 10 columns. Unfortunately, in certain applications, the number of columns is combinatorially dependent on the number of rows, and can reach many orders of magnitude greater, for 500–1,000 rows. For these problems, the constraint matrix cannot be generated, much less solved, unless severe ad hoc limitations are imposed. It stems clear that we must reluctantly abandon the search for the true mathematical optimum in such cases. One method of attack is to use a set covering algorithm repeatedly on much smaller matrices extracted from the overall problem, generating columns as needed. Such an approach has been used on an airline crew-scheduling problem, with excellent practical success on test cases involving close to 1,000 rows. It utilizes some techniques that are more generally applicable, and some that make use of the structure of the crew-scheduling problem, and that therefore are specific to it.
Minimum Cost Schedules for a Public Transportation Route—I. Theory
Authors: Hurdle V. F.
Published: October 2008

A fleet of vehicles carries passengers in one direction on a public transit route, then returns empty to the dispatch point after a round trip travel time T. The arrival rate of passengers is a known, deterministic, continuous, function of time and the objective is to devise a schedule that minimizes the total cost for passenger waiting time and vehicle operation. It is shown that the optimal dispatch rate at any time t is either equal to the arrival rate at t + kT where k is some integer (not necessarily positive) or proportional to the square root of the average of the passenger arrival rates at t − mT, t − (m − 1)T, …, t, …, t + nT where m and n are nonnegative integers (sometimes both zero). Furthermore, the optimal dispatch rate, expressed as a function of time, can be discontinuous only at tq + jT and at td, where tq is a time when a queue of waiting passengers forms, td is a time when a queue disappears, and j is an integer.
A Mathematical Model for Predicting the Number of Potential Conflict Situations at Intersecting Air Routes
Authors: Siddiqee Waheed
Published: October 2008

A mathematical model is developed for predicting the expected number of potential conflict situations at the intersection of air routes. Given the intersection angle of two routes and the average flows and speeds of aircraft, the model predicts the average number of potential conflict situations per unit of time. A concept of intersection capacity based on conflict situations is introduced, and a mathematical model of intersection capacity is developed. The models can be used in planning air route network geometry, as well as in providing guidelines to the establishment of suitable levels of traffic flow along various routes.
A Column Generation Algorithm for Optimal Traffic Assignment
Authors: Leventhal T. , Nemhauser G. , Trotter L.
Published: October 2008

A column generation algorithm for solving a class of nonlinear traffic assignment problems is presented. The fundamental advantage of the algorithm is that it does not require the a priori generation of all paths joining each origin-destination pair. The algorithm is capable of handling rather large networks. Computational experience that contrasts column generation with the a priori generation of all paths and compares two different quadratic programming algorithms is reported.
Strategic Air Deployment Resource Planning
Authors: Stowell R. L.
Published: October 2008

“Steady-state” methods have long been used to calculate unit closure times in military strategic air deployment planning studies. The development of a simple, yet powerful, simulation model (Airlift Fleet Evaluation Model) has allowed a significant advance in deployment analysis capability. Using a simplified NATO reinforcement scenario, minimum deployment times, as determined by two steady-state methods, are compared with simulation results and the applicability of the several approaches is discussed. Resource levels and allocations meeting typical mission requirements are determined. An assessment is made of the credibility of a published planning factor value for the time to deploy an Army division to Europe.
Toll Patterns for Multiclass-User Transportation Networks
Authors: Dafermos Stella C.
Published: October 2008

In this paper we apply the following general scheme to determine toll patterns for multiclass-user transportation networks: we modify the travel cost as perceived by the individual traveler by charging him a “toll.” Then we try to determine the toll pattern in such a way that the system-optimizing flow pattern becomes at the same time user-optimizing. We discuss two toll policies: (a) Tolls are collected on a link basis, (b) Tolls are collected on a path basis. The study shows that there is a degree of freedom in the path-toll collection policy. Alternative criteria are proposed for the exploitation of the degree of freedom such as: (i) that the tolls collected be nonnegative; (ii) that the personal cost of travelers, before and after the imposition of tolls, remains the same; (iii) that certain classes are treated discriminately in order to attain some social good.
Iso-Veloxic Traffic Sampled Jointly in Space and Time
Authors: Wright Christopher
Published: October 2008

As part of a continuing general investigation into the fundamental relations of traffic flow, the sampling properties of the variables speed, flow, and concentration of an ideal traffic stream, measured in rectangular space/time domains according to Edie's definitions, are evaluated and discussed. Although the speeds of drivers are independently distributed and maintained constant regardless of the proximity of other vehicles, it is shown that the speed and flow and the speed and concentration are both marginally correlated. Analytical expressions for the serial and cross-correlations of the flow and concentration in consecutive samples are given, and it is shown that the flow and concentration are distributed with both discrete and continuous probability components, with variance/mean ratios less than one.
Recursive Estimation of Traffic Variables: Section Density and Average Speed
Authors: Nahi N. E. , Trivedi A. N.
Published: October 2008

Simultaneous recursive estimators for aggregate variables, section density, and mean speed, are derived. The estimators are simple and easily suitable for digital implementation. Performances of the estimators are evaluated utilizing the real traffic data obtained over a three-quarter mile section of the Long Island Expressway, New York, and data obtained from digital simulation of freeway traffic.
A Dual Decomposition Method for Minimizing Transportation Costs in Multifacility Location Problems
Authors: Love Robert F. , Kraemer Svend A.
Published: October 2008

This paper develops the dual program of the constrained multifacility location problem in which total transportation cost in the system is proportional to the sum of the weighted Euclidean distances between facilities. A decomposition solution method is presented in which the master program is linear and each subprogram is a nonlinear programming problem. Computation results are presented and discussed.
Minimum Cost Locations for Parallel Public Transit Lines
Authors: Hurdle V. F.
Published: October 2008

Passengers are to be carried to a rapid transit line by feeder transit lines perpendicular to the rapid transit line. How should the feeder lines be located and how should their schedules respond to a passenger arrival pattern that varies with location and time? These questions are answered for a system with a simple cost structure by using continuous functions to approximate the behavior of the system, then minimizing the cost by the methods of elementary calculus.
A Network Flow Solution to a Multifacility Minimax Location Problem Involving Rectilinear Distances
Authors: Dearing P. M. , Francis R. L.
Published: October 2008

The problem considered is to locate new facilities with respect to existing facilities so as to minimize the maximum cost; costs are incurred that are linearly proportional to the rectilinear distances between new and existing facilities, or to the rectinlinear distances between new facilities. Constraints on the distances between facilities are also included in the problem formulation. It is shown that the problem can be decomposed into two subproblems that have identical structure, and that may be solved independently. Each subproblem is solved efficiently by converting it into an equivalent network flow problem that is in turn solved by determining a simple chain of maximum “cost” to “weight” ratio.
Letter to the Editor—A Note on Delays Induced by Random Exogenous Events
Authors: Nakagawa Toshio , Osaki Shunji
Published: October 2008

In a contribution to this journal, Sivazlian (Trans. Sci. 5, 337–343) presents a convoy model and derives the delays induced by random exogenous events. This note shows that the convoy model corresponds to the sojourn time problem and his results are easily deduced from the famous ones of Takács under more generalized assumptions.
Comparison of Taxi and Dial-a-Bus Services
Authors: Gerrard M. J.
Published: October 2008

A probabilistic model of a conventional taxi service is formulated and analyzed. This model also applies to other queuing systems in which the servers must travel to the customers. The main assumptions are that demand is homogeneous and that the street network is uniform in a certain sense. Computer simulations incorporating these assumptions were made of both the taxi service and a many-to-many dial-a-bus system. It was found that small dial-a-bus vehicles (capacity 6–8) can serve 50 per cent more people than taxis with only a slight increase in travel-time. An attempt to carry more passengers leads to steadily greater travel-times. However dial-a-bus is generally less affected by changes in demand than taxis. The size of the region served has a pronounced effect on the efficiency of both dial-a-bus and taxi services.
An Algorithm for the Traffic Assignment Problem
Authors: Nguyen Sang
Published: October 2008

The traffic assignment problem associated with a given transportation network is the process of distributing zone-to-zone trips on links of the network. A number of methods have been proposed to solve this problem, but none have been found to be entirely satisfactory. This paper is concerned with the nonlinear mathematical model of the problem, where the link-traveling costs are increasing functions of the link flows and no explicit capacity constraint is imposed on individual links. An efficient algorithm is developed, using a node-arc formulation of the problem. It is an adaptation of the convex-simplex method that takes advantage of the very special network structure of the traffic assignment problem formulated in this way. Numerical results obtained with a moderate size street network are presented.
An Algorithm for the M-Median Plant Location Problem
Authors: Garfinkel R. S. , Neebe A. W. , Rao M. R.
Published: October 2008

The problem is to locate a given number of plants along a road network so as to minimize the total distance between plants and warehouses assigned to them. It is modeled as an integer programming problem and the relaxed LP is solved by decomposition. In cases of noninteger termination, the ILP is attacked using group theoretics and a dynamic programming recursion. Computational results are given, which contrast this procedure to a branch-and-bound approach.
Control of Pairing of Vehicles on a Public Transportation Route, Two Vehicles, One Control Point
Authors: Newell G. F.
Published: October 2008

If the time required for a vehicle (particularly buses or elevators) to load passengers is an increasing function of the number of passengers loaded, then, on a route served by more than one vehicle, the vehicles tend to form pairs. If a vehicle runs behind (ahead of) schedule, it typically will pick up more (less) passengers and get even further behind (ahead of) schedule. The following is concerned with a shuttle type of route having just two vehicles and serving passengers who arrive at a constant rate. There is one control point at which vehicles can be intentionally delayed. The object is to devise a strategy of control that will minimize the average waiting time of the passengers. The strategy must correct for random fluctuations in trip time so that the headways will not become sufficiently unequal as to initiate effects of pairing. An approximate solution of the optimization problem suggests that the optimal control involves sufficiently tight control that the pairing effect has little influence on the waiting times.
A Model for Optimal Operation and Design of Solid Waste Transfer Stations
Authors: Yaffe Harold J.
Published: October 2008

At a transfer station arriving trucks dump collected refuse, and larger capacity trucks haul the refuse to a final disposal point. Transfer of refuse from collection to haul trucks is direct at some such facilities, while at others a storage area serves as a buffer into which refuse is dumped and from which it is loaded for shipment. A (single) deterministic queuing model is formulated for idealized forms of both direct and indirect transfer. The model takes into account a time-dependent arrival rate of refuse, the number of haul trucks, the hauling time, the number of collection loads per haul load, the storage capacity, numbers of dumping and loading channels, and dumping and loading times. Arrivals and departures of both types of vehicles are treated as fluid flows. Mathematical relations that describe physical behavior are derived, and interpreted graphically. Quantities represented graphically include storage level, and queues and delays of both kinds of vehicles. Optimal haul schedules are obtained for “typical” examples. The San Francisco (indirect) and Orange County (direct) transfer stations are discussed, based on direct observation. The model is applied directly to the former facility; a variation of the model is outlined for the latter.
Minimum Cost Multicommodity Circulation Problem with Convex Arc-Costs
Authors: Ferland Jacques A.
Published: October 2008

The minimum cost multicommodity circulation problem with convex arc-costs is solved by using the negative directed cycles approach. This algorithm is used to compute equilibrium flows in a transportation network with elastic demands and congestion effects.
Decentralized Control of High-Speed Vehicular Strings
Authors: Chu Kai-ching
Published: October 2008

The automatic control of a string of high-speed, densely-packed vehicles is studied in a unified approach. Various input structures for the control schemes and their stability are studied and compared. The optimal decentralized regulation theory developed in a previous paper is applied to seek the best feedback control gains for various input structures. Value of information is defined to evaluate the relative merit of these inputs. The results can be easily applied for on-board computer designs in developing new transportation technology such as “personal rapid transit” systems.
An Operating Strategy for a Commuter Bus System
Authors: Clarens Gérard C. , Hurdle V. F.
Published: October 2008

The operator of a bus system wishes to determine when and where to send each vehicle in order to minimize the sum of operating and user costs incurred in carrying commuters from a central terminal to destinations dispersed over the city and its suburbs. Application of a continuum approximation approach to this problem leads to an objective function which is a function of one unknown variable, the zone size. Analytic solutions are obtained for a number of special cases. If the problem parameters do not vary with the time of day, the optimal zone size for suburban locations is inversely proportional to the square root of the density of passenger destinations if the vehicles are filled to capacity, but to the cube root if they are not completely filled. A numerical example of this special case is used to illustrate a technique for application of the results.
On the Combined Distribution-Assignment of Traffic
Authors: Florian Michael , Nguyen Sang , Ferland Jacques
Published: October 2008

It has been remarked that in the practice of transportation planning the distribution and assignment computations are treated sequentially as independent problems, although ideally they should be solved simultaneously. A case has been made by many practitioners for repeating the distribution and assignment computations in order to obtain more consistent results. The purpose of this paper is to shed some light on the eventual results of sequentially solving the distribution and assignment problem. Our conclusion, based on rigorous arguments, is that such practice does not lead to valid results. Also, we develop an approach to solving the distribution and assignment problem simultaneously and relate it to other methods that were proposed for this problem. A numerical example illustrates the conclusions drawn.
Elevator Systems for Tall Buildings Part I: Single-Mode Elevator Systems
Authors: Mitric Slobodan
Published: October 2008

Tail buildings result largely from the scarcity of land in the centers of towns. Provision of the vertical transportation involves a loss of some useful floor area in these buildings. The main objective of the research reported in this paper is to compare different design arrangements of elevator systems in terms of the floor area they consume, and to point out the implications for the limits to height of tall buildings. The research approach is to formulate models of several types of elevator systems, in which the area of elevator shafts and the useful area (on various floors and in total) are expressed as functions of building's height, inclusive of such parameters as: the base area of a building, duration of the peak period, density of a building's population, the cruise speed of elevators, etc. Solutions are found for the optimal height of buildings, when the objective is to maximize the total useful floor area. This part of the paper presents two simple models: the first is of an all-express system where each elevator serves only one floor, while the second is the familiar system where each elevator serves all floors.
Common Bus Lines
Authors: Chriqui Claude , Robillard Pierre
Published: October 2008

In large cities operating an important public mass transit network, we are faced with the problem of ‘common bus lines’: some routes share common sections and the passenger must select the buses he will probably use. While most computer packages code the section as a unique link and disregard the precise assignment of passengers on the distinct routes, we give a solution to this operational assignment based on the “perceived” travel time. Formulated as an optimization problem within a probabilistic context, the optimal subset of routes “to be selected” is obtained. A more detailed treatment on uniform and exponential cases for the time of the first vehicle to arrive on a route concludes the paper.
Real-Time Merging of High-Speed Vehicular Strings
Authors: Sarachik Philip E. , Chu Kai-Ching
Published: October 2008

The problem of merging two strings of vehicles is considered and a complete merging strategy is presented. This strategy consists of a combination of a real time assignment algorithm with a decentralized control law. The real time assignment algorithm assigns vehicles to moving reference cells in order to provide for smooth merges at the junction of two guideways. The control law, which has the task of moving the vehicles to follow the reference positions in an optimum way, is implemented by fixed gain controllers aboard each vehicle. These controllers are designed to use information only about the vehicle itself and its nearest neighbors.
Analytical Models of Perceived Air Traffic Control Conflicts
Authors: Dunlay William J.
Published: October 2008

This paper describes two analytical models for estimating the expected number of perceived enroute air traffic control conflicts: one for crossing conflicts and one for overtake conflicts. The crossing conflicts model is derived in terms of the probability that controllers perceive various aircraft separations as potential violations of the 5-nmi minimum separation rule. The expected number of perceived overtake conflicts is shown to depend only on the relative speeds of in-trail aircraft. In both cases the expected number of conflicts is found to vary as the square of the aircraft flow rate. The epochs at which aircraft pass a point on an airway are assumed to define a stochastic point process. Both models for the expected number of conflicts are shown to depend only on the assumption that the point process is stationary. It is argued that the distribution of the number of conflicts of either type in a given time interval is approximately Poisson.
Letter to the Editor—Airline Overbooking: Fresh Approaches are Needed
Authors: Rothstein Marvin
Published: October 2008

This note, motivated by the paper of Shlifer and Vardi, is an attempt to set the problem of airline overbooking in proper perspective and to show why most of the operations research already carried out in regard to this problem may now be misdirected.
Elevator Banking for High Rise Buildings
Authors: Powell Bruce A.
Published: October 2008

Elevator service in multistory buildings has been improved by the concept of banking. A building is split into two or more groups of contiguous floors, and each group of floors is served by a different set of elevators. This paper presents an optimization procedure based on dynamic programming for determining good banking arrangements. The algorithm has solved the combinatorial problem of deciding on the number of banks and cars, floor splits, and car speeds that has up to now faced the elevator industry. The algorithm has been reduced to a FORTRAN computer program that requires very little computer time.
Optimization of Traffic Signal Settings by Mixed-Integer Linear Programming
Authors: Gartner Nathan H. , Little John D. C. , Gabbay Henry
Published: October 2008

Remits obtained in Part I are extended to include offsets, splits at each intersection, and a common cycle time for the network as simultaneous decision variables. In addition to the deterministic link performance function, the stochastic effects of overflow queues from one cycle to the next are modeled by means of a saturation deterrence function that enters as an additive component in the objective function. Computational results demonstrate the feasibility of using mixed-integer linear programming on problems of realistic size. Sensitivity analysis of cycle time shows it to have a strong influence on network performance.
Usefulness of adrenal scintigraphy in the follow-up of adrenocortical incidentalomas: a prospective multicenter study
Authors: Fagour Cédric , Bardet Stéphane , Rohmer Vincent , Arimone Yannick , Lecomte Pierre , Valli Nathalie , Tabarin Antoine
Published: October 2008

Objectives

Prognostic factors for progression of benign adrenocortical adenomas (AI) remain poorly known. We assessed the usefulness of 131I-6-β-iodomethylnorcholesterol scintigraphy (IMS) to predict the occurrence of adrenal hyperfunction or mass enlargement.

Design

Fifty-one consecutive inpatients with unilateral AI and normal 24-h urinary free cortisol (UFC) were enrolled in a multicenter observational prospective study to investigate the relationship between the scintigraphic pattern and the progression of biological abnormalities of the hypothalamo-pituitary–adrenal axis or tumor size.

Results

Biochemically defined ‘subclinical’ Cushing's syndrome (SCS) was found at baseline in 47% of patients. Unilateral uptake (UU) was significantly associated with SCS (P<0.05). During the follow-up (4.3±1.6-year): 53% of patients showed unchanged hormonal evaluation, 29% displayed intermittent SCS and 18% showed definitive hormonal progression of SCS but without overt biochemical hypercortisolism. UU was associated with persistence of SCS and hormonal progression (P<0.01). In multivariate analysis, UU and impaired 1 mg dexamethasone suppression were independently associated with hormonal progression. Three patients with UU developed clinical CS despite persistently normal UFC. Tumor size increased in 10% patients and was not associated with any scintigraphic pattern.

Conclusion

Evolution of SCS toward overt biochemical CS in patients with AI is a rare event during a 4-year follow-up. UU is predictive for the occurrence of SCS, its persistence and progression within the spectrum of SCS. Further studies aiming to establish the clinical consequences of SCS are needed to recommend IMS as a complementary evaluation in patients with AI and biochemical SCS.
Quality of Care for Children Hospitalized With Asthma
Authors: Nkoy Flory L. , Fassl Bernhard A. , Simon Tamara D. , Stone Bryan L. , Srivastava Rajendu , Gesteland Per H. , Fletcher Gena M. , Maloney Christopher G.
Published: October 2008

OBJECTIVES. The goals were (1) to identify evidence-based clinical process measures that are appropriate, feasible, and reliable for assessing the quality of inpatient asthma care for children and (2) to evaluate provider compliance with these measures.

METHODS. Key asthma quality measures were identified by using a modified Rand appropriateness method, combining a literature review of asthma care evidence with a consensus panel. The feasibility and reliability of obtaining these measures were determined through manual chart review. Provider compliance with these measures was evaluated through retrospective manual chart review of data for 252 children between 2 and 17 years of age who were admitted to a tertiary care children's hospital in 2005 because of asthma exacerbations.

RESULTS. Nine appropriate, feasible, reliable, clinical process measures of inpatient asthma care were identified. Provider compliance with these measures was as follows: acute asthma severity assessment at admission, 39%; use of systemic corticosteroid therapy, 98%; use of oral (not intravenous) systemic corticosteroid therapy, 87%; use of ipratropium bromide restricted to <24 hours after admission, 71%; use of albuterol delivered with a metered-dose inhaler (not nebulizer) for children >5 years of age, 20%; documented chronic asthma severity assessment, 22%; parental participation in an asthma education class, 33%; written asthma action plan, 5%; scheduled follow-up appointment with the primary care provider at discharge, 22%.

CONCLUSIONS. Nine appropriate, feasible, reliable, clinical process measures of inpatient asthma care were identified. Provider compliance across these measures was highly variable but generally low. Our study highlights opportunities for improvement in the provision of asthma care for hospitalized children. Future studies are needed to confirm these findings in other inpatient settings.
Risk Factors for Unintentional Injuries in Children: Are Grandparents Protective?
Authors: Bishai David , Trevitt Jamie L. , Zhang Yiduo , McKenzie Lara B. , Leventhal Tama , Gielen Andrea Carlson , Guyer Bernard
Published: October 2008

OBJECTIVE. We sought to identify sociodemographic and familial correlates of injury in children aged 2 to 3 years.

METHODS. The Healthy Steps data set describes 5565 infants who were enrolled at birth in 15 US cities in 1996–1997 and had follow-up until they were 30 to 33 months of age. Data were linked to medical claims reporting children's medically attended office visits by age 30 to 33 months. Each claim was accompanied by a reason for the visit. An analytical sample of 3449 was derived from the children who could be effectively followed up and linked to medical charts. Missing data were imputed by using multiple imputation with chained equations. The analytical sample showed no systematic evidence of sample selection bias. Multivariate logistic regression was used to determine the odds ratios of injury events.

RESULTS. Odds of medically attended injuries were decreased for children who received care from grandparents. Odds were increased for children who lived where fathers did not co-reside or in households where the parents never married. Statistical results were robust to the addition of a variety of covariates such as income, education, age, gender, and race.

CONCLUSIONS. Children are at higher risk for medically attended injury when their parents are unmarried. Having grandparents as caregivers seems to be protective. Household composition seems to play a key role in placing children at risk for medically attended injuries.
Potential Impact of Acceleration of the Pertussis Vaccine Primary Series for Infants
Authors: Shinall Myrick C. , Peters Timothy R. , Zhu Yuwei , Chen Qingxia , Poehling Katherine A.
Published: October 2008

OBJECTIVE. This study estimates the potential impact, on rates of pertussis infections, hospitalizations, and deaths among infants in the United States, of administering the first dose of diphtheria and tetanus toxoids and acellular pertussis vaccine at 6 weeks rather than 2 months of age.

METHODS. We used existing data to estimate current US rates of pertussis infections, hospitalizations, and deaths according to age and infant population in 2004. We then estimated the potential impact of accelerating the administration of the first dose of diphtheria and tetanus toxoids and acellular pertussis vaccine from 2 months to 6 weeks of age, an alternative schedule consistent with current vaccination guidelines. We used Poisson distribution analysis to determine 95% confidence intervals for projected rates of pertussis disease.

RESULTS. Acceleration of administration of the first dose of diphtheria and tetanus toxoids and acellular pertussis vaccine from 2 months to 6 weeks of age is expected to prevent 1236 cases of pertussis, 898 hospitalizations, and 7 deaths attributable to pertussis per year in the United States. These decreases represent 9% reduction in cases, 9% reduction in hospitalizations, and 6% reduction in deaths attributable to pertussis among infants <3 months of age. Acceleration of the second and third doses by 2 weeks is expected to prevent an additional 923 cases, 520 hospitalizations, and 2 deaths attributable to pertussis each year.

CONCLUSION. Acceleration of administration of diphtheria and tetanus toxoids and acellular pertussis vaccine from 2 months to 6 weeks should reduce the burden of pertussis among young infants.
Barriers to Care and Primary Care for Vulnerable Children With Asthma
Authors: Seid Michael
Published: October 2008

OBJECTIVE. I tested the hypothesis that, for vulnerable children with asthma, barriers to care (pragmatics, skills, knowledge and beliefs, expectations of care, and marginalization) affect primary care experiences, after accounting for financial, potential, and realized access to care, demographic features, and asthma severity.

METHODS. Patients, recruited primarily from urban, federally qualified health centers, were between 3 and 12 years of age and had been diagnosed as having asthma. Bilingual, bicultural interviewers administered surveys in participants' homes. Validated instruments were used to measure barriers to care (Barriers to Care Questionnaire) and primary care experiences (Parent's Perceptions of Primary Care measure).

RESULTS. Of 252 families recruited, 56.6% of parents were monolingual Spanish speakers, 73.6% of mothers had not graduated from high school, and 24.5% of children were uninsured. Asthma severity was 27% mild persistent, 40.5% moderate persistent, and 32.5% severe persistent. In bivariate analyses, better access to care (being insured and having a regular provider) was related to better primary care experiences. Consistent with the hypothesis, multivariate regression analyses showed that fewer barriers (Barriers to Care Questionnaire scores) predicted better primary care (Parent's Perceptions of Primary Care total and subscale scores), after controlling for access to care, demographic features, and asthma severity (a 1-point change in Barriers to Care Questionnaire scores was associated with a 0.59-point change in Parent's Perceptions of Primary Care total scale scores). Having a regular doctor and not having experienced foregone care were also significant predictors of Parent's Perceptions of Primary Care scores in the multivariate analysis.

CONCLUSION. For vulnerable children with asthma, barriers to care explain variance in primary care characteristics beyond that explained by access, demographic factors, and disease severity.
Emergence of and Risk Factors for Methicillin-Resistant Staphylococcus aureus of Community Origin in Intensive Care Nurseries
Authors: Seybold Ulrich , Halvosa J. Sue , White Nancy , Voris Victoria , Ray Susan M. , Blumberg Henry M.
Published: October 2008

OBJECTIVE. The goal of this study was to define more clearly the impact of community-acquired methicillin-resistant Staphylococcus aureus clones (eg, USA300 and USA400) on colonization and infection in infants in intensive care nurseries and potential modes of transmission of community-acquired methicillin-resistant S aureus clones.

METHODS. Prospective surveillance for methicillin-resistant S aureus colonization and infection was performed among infants in the intensive care nurseries at Grady Memorial Hospital (Atlanta, GA) between 1993 and 2006. Beginning in September 2004, nares surveillance cultures were collected at admission. Methicillin-resistant S aureus isolates were genotyped by using pulsed-field gel electrophoresis and multiplex polymerase chain reaction assays for staphylococcal chromosomal cassette mec gene complex type and Panton-Valentine leukocidin genes. Prevalence of and risk factors for colonization with community-acquired versus health care-associated methicillin-resistant S aureus clones (eg, USA100) were assessed.

RESULTS. Between 1993 and 2006, 130 (3.5%) of 3707 infants were identified to be colonized with methicillin-resistant S aureus. Twelve (1.2%) of 996 admission nares cultures were positive for methicillin-resistant S aureus (since initiation of admission cultures in September 2004). Community-acquired methicillin-resistant S aureus clones were first recovered in 1998; the proportion of methicillin-resistant S aureus clones of community origin increased significantly between 1998 and 2004. Multivariate analysis identified vaginal delivery and maternal smoking, both among infants of mothers receiving systemic antibiotic treatment before delivery, as independent predictors for neonatal colonization with community-acquired methicillin-resistant S aureus. Systemic antibiotic therapy before delivery for nonsmoking mothers delivering through cesarean section and possibly endotracheal intubation were associated with the recovery of health care-associated methicillin-resistant S aureus clones.

CONCLUSIONS. Community-acquired methicillin-resistant S aureus clones have emerged as a major cause of methicillin-resistant S aureus colonization in high-risk newborns. Community-acquired methicillin-resistant S aureus recovery was associated with acquisition during birth, whereas health care-associated methicillin-resistant S aureus clones seemed to be transmitted nosocomially.
Office-Based Treatment and Outcomes for Febrile Infants With Clinically Diagnosed Bronchiolitis
Authors: Luginbuhl Lynn M. , Newman Thomas B. , Pantell Robert H. , Finch Stacia A. , Wasserman Richard C.
Published: October 2008

OBJECTIVES. The goals were to describe the (1) frequency of sepsis evaluation and empiric antibiotic treatment, (2) clinical predictors of management, and (3) serious bacterial illness frequency for febrile infants with clinically diagnosed bronchiolitis seen in office settings.

METHODS. The Pediatric Research in Office Settings network conducted a prospective cohort study of 3066 febrile infants (<3 months of age with temperatures ≥38°C) in 219 practices in 44 states. We compared the frequency of sepsis evaluation, parenteral antibiotic treatment, and serious bacterial illness in infants with and without clinically diagnosed bronchiolitis. We identified predictors of sepsis evaluation and parenteral antibiotic treatment in infants with bronchiolitis by using logistic regression models.

RESULTS. Practitioners were less likely to perform a complete sepsis evaluation, urine testing, and cerebrospinal fluid culture and to administer parenteral antibiotic treatment for infants with bronchiolitis, compared with those without bronchiolitis. Significant predictors of sepsis evaluation in infants with bronchiolitis included younger age, higher maximal temperature, and respiratory syncytial virus testing. Predictors of parenteral antibiotic use included initial ill appearance, age of <30 days, higher maximal temperature, and general signs of infant distress. Among infants with bronchiolitis (N = 218), none had serious bacterial illness and those with respiratory distress signs were less likely to receive parenteral antibiotic treatment. Diagnoses among 2848 febrile infants without bronchiolitis included bacterial meningitis (n = 14), bacteremia (n = 49), and urinary tract infection (n = 167).

CONCLUSIONS. In office settings, serious bacterial illness in young febrile infants with clinically diagnosed bronchiolitis is uncommon. Limited testing for bacterial infections seems to be an appropriate management strategy.
Effects of Neonatal Dexamethasone Treatment on the Cardiovascular Stress Response of Children at School Age
Authors: Karemaker Rosa , Karemaker John M. , Kavelaars Annemieke , Tersteeg-Kamperman Marijke , Baerts Wim , Veen Sylvia , Samsom Jannie F. , van Bel Frank , Heijnen Cobi J.
Published: October 2008

OBJECTIVE. The goal was to investigate cardiovascular responses to a psychosocial stressor in school-aged, formerly premature boys and girls who had been treated neonatally with dexamethasone or hydrocortisone because of chronic lung disease.

METHODS. We compared corticosteroid-treated, formerly preterm infants with formerly preterm infants who had not been treated neonatally with corticosteroids (reference group). Children performed the Trier Social Stress Test for Children, which includes a public speaking task and a mental arithmetic task. Blood pressure was recorded continuously before, during, and after the stress test. Plasma norepinephrine levels were determined before the test, directly after the stress task, and after recovery.

RESULTS. Overall, in response to stress, girls had significantly larger changes in systolic blood pressure and mean arterial pressure and in stroke volume and cardiac output, compared with boys. Boys exhibited larger total peripheral resistance responses, compared with girls. The hydrocortisone group did not differ significantly from the reference group in any of the outcome measures. However, dexamethasone-treated children had smaller stress-induced increases in systolic and mean arterial blood pressure than did hydrocortisone-treated children. In addition, the dexamethasone group showed smaller increases in stroke volume and blunted norepinephrine responses to stress, compared with children in the reference group. Correction for gender did not affect these results.

CONCLUSIONS. The differences in cardiovascular stress responses between girls and boys are consistent with known gender differences in adult cardiovascular stress responses. Our data demonstrate that neonatal treatment with dexamethasone has long-term consequences for the cardiovascular and noradrenergic stress responses; at school age, the cardiovascular stress response was blunted in dexamethasone-treated children. Hydrocortisone-treated children did not differ from the reference group, which suggests that hydrocortisone might be a safe alternative to dexamethasone for treating chronic lung disease of prematurity.
Mental Illness in Young Adults Who Had Strabismus as Children
Authors: Mohney Brian G. , McKenzie Jeff A. , Capo Jason A. , Nusz Kevin J. , Mrazek David , Diehl Nancy N.
Published: October 2008

OBJECTIVE. We investigated the prevalence and types of psychiatric disorders diagnosed by early adulthood among patients who had common forms of strabismus as children.

METHODS. The medical records of children (<19 years) who were diagnosed as having esotropia (N = 266) or exotropia (N = 141) while residents of Olmsted County, Minnesota, between January 1, 1985, and December 31, 1994, were reviewed retrospectively for psychiatric disease diagnoses. Each case subject was compared with a randomly selected, individually birth- and gender-matched, control subject from the same population.

RESULTS. A mental health disorder was diagnosed for 168 (41.3%) of the 407 patients with a history of childhood strabismus, who were monitored to a mean age of 17.4 years, compared with 125 control subjects (30.7%). Children with exotropia were 3.1 times more likely to develop a psychiatric disorder than were control subjects when monitored to a mean age of 20.3 years. Children with esotropia were no more likely to develop mental illness than were control subjects when monitored for similar periods. Patients with intermittent exotropia also were significantly more likely to have greater numbers of mental health disorders, mental health emergency department visits, and mental health hospitalizations and to have suicidal or homicidal ideation.

CONCLUSIONS. Children diagnosed as having strabismus in this population, especially those with exotropia, were at increased risk for developing mental illness by early adulthood. Patients with intermittent exotropia seemed to be particularly prone to developing significant psychiatric diseases by the third decade of life.
Prophylaxis After First Febrile Urinary Tract Infection in Children? A Multicenter, Randomized, Controlled, Noninferiority Trial
Authors: Montini Giovanni , Rigon Luca , Zucchetta Pietro , Fregonese Federica , Toffolo Antonella , Gobber Daniela , Cecchin Diego , Pavanello Luigi , Molinari Pier Paolo , Maschio Francesca , Zanchetta Sergio , Cassar Walburga , Casadio Luca , Crivellaro Carlo , Fortunati Paolo , Corsini Andrea , Calderan Alessandro , Comacchio Stefania , Tommasi Lisanna , Hewitt Ian K. , Da Dalt Liviana , Zacchello Graziella , Dall'Amico Roberto ,   on behalf of the IRIS group
Published: October 2008

OBJECTIVES. Febrile urinary tract infections are common in children and associated with the risk for renal scarring and long-term complications. Antimicrobial prophylaxis has been used to reduce the risk for recurrence. We performed a study to determine whether no prophylaxis is similar to antimicrobial prophylaxis for 12 months in reducing the recurrence of febrile urinary tract infections in children after a first febrile urinary tract infection.

METHODS. The study was a controlled, randomized, open-label, 2-armed, noninferiority trial comparing no prophylaxis with prophylaxis (co-trimoxazole 15 mg/kg per day or co-amoxiclav 15 mg/kg per day) for 12 months. A total of 338 children who were aged 2 months to <7 years and had a first episode of febrile urinary tract infection were enrolled: 309 with a confirmed pyelonephritis on a technetium 99m dimercaptosuccinic acid scan with or without reflux and 27 with a clinical pyelonephritis and reflux. The primary end point was recurrence rate of febrile urinary tract infections during 12 months. Secondary end point was the rate of renal scarring produced by recurrent urinary tract infections on technetium 99m dimercaptosuccinic acid scan after 12 months.

RESULTS. Intention-to-treat analysis showed no significant differences in the primary outcome between no prophylaxis and prophylaxis: 12 (9.45%) of 127 vs 15 (7.11%) of 211. In the subgroup of children with reflux, the recurrence of febrile urinary tract infections was 9 (19.6%) of 46 on no prophylaxis and 10 (12.1%) of 82 on prophylaxis. No significant difference was found in the secondary outcome: 2 (1.9%) of 108 on no prophylaxis versus 2 (1.1%) of 187 on prophylaxis. Bivariate analysis and Cox proportional hazard model showed that grade III reflux was a risk factor for recurrent febrile urinary tract infections. Whereas increasing age was protective, use of no prophylaxis was not a risk factor.

CONCLUSIONS. For children with or without primary nonsevere reflux, prophylaxis does not reduce the rate of recurrent febrile urinary tract infections after the first episode.
Evaluation of Pediatric Patients With Mild-to-Moderate Hypertension: Yield of Diagnostic Testing
Authors: Wiesen Jonathan , Adkins Matthew , Fortune Sherwin , Horowitz Judah , Pincus Nava , Frank Rachel , Vento Suzanne , Hoffman Cathy , Goilav Beatrice , Trachtman Howard
Published: October 2008

OBJECTIVE. Children and adolescents with newly diagnosed hypertension undergo various tests to define the cause and target organ consequences of the elevated blood pressure. We tested the hypothesis that the diagnostic yield of individual components of the currently recommended assessment does not justify performance for all patients with mild-to-moderate hypertension.

METHODS. A retrospective chart review was conducted of patients who were referred between July 2002 and June 2007 for mild-to-moderate hypertension, defined as maximum blood pressure at ≥95% + 20/10 mmHg. The assessment included history and physical examination, nutritional assessment, urinalysis, biochemical and fasting lipid profile, renal ultrasound, echocardiogram, and 24-hour ambulatory blood pressure monitoring.

RESULTS. A total of 249 patients were identified, and charts for 220 (88%) were available for review. There were 156 boys and 64 girls aged 13.3 ± 4.4 years. BMI was 26.1 ± 6.7 kg/m2, and 143 (65%) had a BMI of ≥90%. Results of urinalysis and serum biochemical testing were clinically normal in all cases. Among those with a lipid profile, 59 (42%) had total cholesterol values of >170 mg/dL, and 26 (19%) had severe hypercholesterolemia (>200 mg/dL). Renal sonography revealed findings plausibly associated with hypertension in 14 (8%) patients; 4 (2%) had renovascular abnormalities. Yield of echocardiography was 17%. On ambulatory blood pressure monitoring, 47 (60%) children had systolic readings of >95% at least 20% of the time, and 28 (36%) had diastolic readings of >95% at least 20% of the time.

CONCLUSIONS. For children and adolescents with mild-to-moderate hypertension, on the basis of a cutoff of 5% to 20% abnormal results to define a useful test, the initial evaluation can range from a serum cholesterol level and ambulatory blood pressure monitoring to a panel that consists of a fasting lipid profile, renal ultrasound, echocardiogram, and ambulatory blood pressure monitoring. Additional assessment should be guided by specific clinical features and the nature of the patient population.