Mean Number Of Calls Research Articles

Doctorline: a private toll-free telephone medical information service. Five years of activity: old problems and new perspectives.

Introduction; Healthcare professionals need to continually update their knowledge to provide care based on scientific evidence. In some cases it can be difficult to gain access to the different sources of medical information. In an attempt to overcome these problems, a toll-free telephone medical information service (Doctorline) was established. To describe the development, aims, organization, and activities of this private service. Doctorline is an independent, unbiased, toll-free medical information service that provides information on clinical, pharmacologic, and toxicologic issues; bibliographic searches; full-text articles; public and private clinics; details of forthcoming congresses; and legislative documentation. The service is available Monday through Friday, 1000 to 2000. Staff members are physicians trained in communication techniques, literature evaluation methodologies, and computerized database use. The main on-line facilities are MEDLINE, Micromedex-CCIS, and the Italian Formulary on CD-ROM. Books, bulletins, national and international drug formularies, and property files (i.e., directory of Italian public and private clinics) are also available. In 5 years, Doctorline has received 65 258 calls. Nearly 34% of the calls were made by general practitioners, followed by cardiologists (22%), orthopedists (15%), pharmacists (14%), gastroenterologists (13%), and urologists (10%). From 1991 to 1996, nearly 20% of the calls concerned pharmacologic issues, 43% nonpharmacologic issues, while the rest of the calls were for nonclinical requests. Approximately 21% of all questions received an answer during the same phone call (on-line answers); for the other answers (off-line answers) the mean +/- SD waiting time was 7.8 +/- 10.4 days. Although the nature of the questions has been recorded since 1991, data about the exact number of physicians who used the service are available only from 1994. Data from 1994 indicate that of the 52,181 physicians who could access the service, only 8817 (16.9%) called at least once, with a mean number of calls per physician of 3.9 (range 3.0-5.6). The future of Doctorline will depend on the quality and validity of the information provided (i.e., based exclusively on scientific evidence, independent of the source of funds), the promotion of the aims, organization, and clinical utility of the service (especially among physicians who made little or no use of the service), and differentiation of the service activities in relation to the physician's specific needs.

The time-dependent Erlang loss model with retrials

We consider a generalization of the classical Erlang loss model with both retrials of blocked calls and a time?dependent arrival rate. We make exponential?distribution assumptions so that the number of calls in progress and the number of calls in retry mode form a nonstationary, two?dimensional, continuous?time Markov chain. We then approximate the behavior of this Markov chain by two coupled nonstationary, one?dimensional Markov chains, which we solve numerically. We also develop an efficient method for simulating the two?dimensional Markov chain based on performing many replications within a single run. Finally, we evaluate the approximation by comparing it to the simulation. Numerical experience indicates that the approximation does very well in predicting the time?dependent mean number of calls in progress and the times of peak blocking. The approximation of the time?dependent blocking probability also is sufficiently accurate to predict the number of lines needed to satisfy blocking probability requirements.

Potential Role of Vocalizations in West Indian Manatees

Although vocalizations have been relatively well studied in several groups of marine mammals, very little is known regarding the context and function of vocalizations of West Indian manatees (Trichechus manatus). Manatee vocalizations have been described by Schevill and Watkins (1965), Evans and Herald (1970), Sonoda and Takemura (1973), and Hartman (1979). Most of these authors presumed that the calls were primarily used for social reasons, such as maintaining cow/calf contact, rather than for navigation. While studying the ecology and behavior of manatees at Blue Spring Run (Volusia Co., Florida) and in the St. Johns River, Florida (Bengtson, 1981), manatees were heard vocalizing in a variety of behavioral contexts other than cow/calf interactions. In order to examine the importance of vocalizations during certain behaviors, we measured call rates during different activities. Recordings of manatees vocalizations were made opportunistically in Blue Spring Run and the St. Johns River using an Inter-Oceans Systems, Inc. R-130 hydrophone (frequency response range 20 Hz to 8 kHz) and a Panasonic RQ-309AS tape recorder. This equipment was well within the range of manatee vocalizations described by Schevill and Watkins (1965). The behavioral situations in which recordings were made included: 1) Natural feeding: grazing on submerged, rooted vegetation while moving slowly along the bottom; 2) Swimming: traveling in the St. Johns River while passing our anchored boat (not recorded in Blue Spring Run); 3) Bottom resting: resting or sleeping on the bottom of the waterway, rising periodically to the surface to breathe; 4) Artificial feeding: experimental presentation of plants to manatees by lowering a tray holding various plant species into Blue Spring Run. Sometimes two or more manatees jostled each other while attempting to gain access to the tray (Bengtson, 1983); 5) Milling: manatees grouped together but not cavorting (see below) as they moved slowly about; and 6) Cavorting: rolling, pushing, nuzzling, and embracing each other, sometimes with much chasing and splashing. There were several potential sources of error in the recordings and counts of manatees. Both the number of manatees present and the classification of different behaviors may have been misidentified outside the clear waters of Blue Spring (78% of the recordings were made in Blue Spring Run). In the St. Johns River, the number of manatees was estimated by counting their noses as they breathed. At night our estimates were poorer, based on the number of radio-tagged individuals and the breathing frequency. Another possible source of error was the vocalizations of nearby manatees involved in a different behavior. For example, in some cases when recordings were being made of individuals cavorting, others nearby might have been bottom resting or feeding. However, most recordings were made when an individual was alone or when individuals in a group of manatees were behaving similarly. The presence of cow/calf pairs (present in 18% of the samples) may have raised calling rates in our recordings. Rather than attempt to differentiate between calls (whistle-squeaks and chirps), all vocalizations were lumped together and reported as number of calls per unit time. Although both sexes were present during recordings, no differentiation was made between their vocalizations. A total of 3,744 calls was tallied during 21.5 h of recording on 19 days in February through April, 1979. Of these, 2,124 calls were selected for analysis on the basis of knowing manatees' behavior. Calls recorded during periods when the manatees' behavior was uncertain were discarded. Recordings were analyzed for average number of calls (discrete pulses) per 5-min interval for each taping session within a behavioral type. Because the number of manatees per session ranged between 1 and 20 and the length of observation period varied between sampling sessions, the mean number of calls per manatee per unit time was calculated for each behavioral category. These data were normalized using a square root transformation, which stabilized the variances among the different behaviors. A one-way analysis of variance and Tukey's Q test indicated significantly different call rates among behaviors (Fig. 1). Rates of vocalizations 816 Vol. 66, No. 4