This paper considers a class of M/G/1 queueing models with a server who is unavailable for occasional intervals of time. As has been noted by other researchers, for several specific models of this type, the stationary number of customers present in the system at a random point in time is distributed as the sum of two or more independent random variables, one of which is the stationary number of customers present in the standard M/G/1 queue (i.e., the server is always available) at a random point in time. In this paper we demonstrate that this type of decomposition holds, in fact, for a very general class of M/G/1 queueing models. The arguments employed are both direct and intuitive. In the course of this work, moreover, we obtain two new results that can lead to remarkable simplifications when solving complex M/G/1 queueing models.

US troops were deployed to the Persian Gulf in what became known as the Gulf War. Upon their return, many Gulf War veterans from both the US and other allied forces began to report chronic, unexplained fatigue, pain, Author Affiliations are listed at the end of this article. Members of the VA Cooperative Study #470 Study Group and the data and safety monitoring board are listed in reference 14 of this article.

This paper extends the results of a previous paper in which two models of a system of queues served in cyclic order were studied. One model is an exhaustive service model, in which the server waits on all customers in a queue before proceeding to the next queue in cyclic order. The other is a gating model, in which a gate closes behind the waiting units when the server arrives, and the server waits on only those customers in front of the gate, deferring service of later arrivals until the next cycle. In the present paper, the Laplace—Stieltjes transforms of the order‐of‐arrival waiting time distribution functions and, for the exhaustive service model, the mean waiting time for a unit arriving at a queue, are obtained.

Thalidomide enhances rituximab-mediated, antibody-dependent, cell-mediated cytotoxicity. We therefore conducted a phase 2 study using thalidomide and rituximab in symptomatic Walden-strom macroglobulinemia (WM) patients naive to either agent. Intended therapy consisted of daily thalidomide (200 mg for 2 weeks, then 400 mg for 50 weeks) and rituximab (375 mg/m 2 per week) dosed on weeks 2 to 5 and 13 to 16. Twenty-five patients were enrolled, 20 of whom were untreated. Responses were complete response (n 1), partial response (n 15), and major response (n 2), for overall and major response rate of 72% and 64%, respectively, on an intent-to-treat basis. Median serum IgM decreased from 3670 to 1590 mg/dL (P < .001), whereas median hematocrit rose from 33.0% to 37.6% (P .004) at best response. Median time to progression for responders was 38 months. Peripheral neuropathy to thalidomide was the most common adverse event. Among 11 patients experiencing grade 2 or greater neuropathy, 10 resolved to grade 1 or less at a median of 6.7 months. Thalido-mide in combination with rituximab is active and produces long-term responses in WM. Lower doses of thalidomide (ie, < 200 mg/day) should be considered given the high frequency of treatment-related neuropathy in this patient population. This trial is registered at www. clinicaltrials.gov as #NCT00142116. (Blood. 2008;112:4452-4457) Introduction Monoclonal antibodies have been successfully used to treat patients with B-cell malignancies, including Waldenstrom macroglobu-linemia (WM). Most of these efforts have focused on the use of rituximab, a chimeric human IgG 1 monoclonal antibody, which targets CD20, which is widely expressed in WM. 1,2 Studies using standard-dose rituximab therapy have demonstrated activity in WM, with overall response rates of 27% to 35% and median durations of response from 8 to 27 months. 2-7 More recently, the use of extended schedule rituximab has been evaluated wherein patients received 8 infusions of rituximab (375 mg/m 2 per week) at weeks 1 to 4 and 12 to 16. Overall response rates of 44% to 48% were observed in these studies, with median durations of response from 16 to 29 months. 8,9 Among WM patients receiving rituximab as monotherapy, lower response rates have been observed in those patients with high serum IgM (6000 mg/dL) and beta-2 microglobulin (B 2 M; 3.0 mg/L) levels, as well as homozygous expression of phenylalanine at amino acid position 158 on CD16 (FcRIIIA-158). 8-10 Studies combining rituximab with chemotherapy have also been explored in WM. 11 The combination of nucleoside analogs plus rituximab has yielded major response rates of 70% to 90%, 12-15 whereas the combinations of CHOP-R (cyclophosphamide, adria-mycin, vincristine, prednisone, rituximab) or DC-R (dexametha-sone, cyclophosphamide, rituximab) have resulted in response rates of 80% to 90%. 16-18 Median time to progression (TTP) in excess of 3 years has been reported with these combinations. Although these combinations have produced more impressive responses, greater toxi...

Background: Patients submitted to coronary artery bypass graft (CABG) surgery present higher risk to develop pulmonary complications, such as atelectasia, pneumonia and pleural effusion. These complications may increase the time of hospitalization as well as the necessity of financial resources, and are also associated with the reduction of life quality and long-term functional capacity.

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If the uptake of fatty acids by liver is a physical, not a biological, process, then the size and location of the intrahepatic pool of fatty acids can be predicted from uptake rates and thermodynamic data. The purpose of the experiments in this paper was to test the accuracy of this idea. Rat livers were perfused with palmitate bound to albumin, and the total amounts of palmitate removed from the perfusate were measured at 3-s intervals. The intrahepatic pools of palmitate calculated from these data were 13.8 and 23.0 nmol/g of liver at ratios of palmitate/albumin (mol/mol) (afferent side) of 2/1 and 4/1, respectively, in the steady state. The intrahepatic pools of palmitate calculated from the distributions of palmitate between membranes, H2O, albumin, and fatty acid binding protein and the measured first-order rate constants for acyl-CoA ligases in mitochondria and microsomes were 12.1 and 34.6 nmol/g for perfusate ratios of palmitate/albumin of 2/1 and 4/1, in the steady state. Intrahepatic pools of palmitate measured after establishment of a steady-state rate of uptake were 15.0 and 31.8 nmol/g for these ratios of palmitate/albumin of 2/1 and 4/1.

Queueing theory has become an important subject to computer scientists because it forms the mathematical basis for research in computer system perlormance evaluation. This tutorial will attempt to explain the elements of queueing theory so that the audience will understand (I) the kind of assumptions usually made in the construction of queueing models, (2) the kind of mathematical tools ordinarily used in queueing theory, and (3) the strengths and limitations of queueing theory in the design and analysis of computer systems.In particular, we will cover (la) the properties of the Foisson process and the reasons for its use to describe the arrival process, (Ib) the properties of the exponential distribution and the reasons for its use to describe service times, and (Ic) the degree to which the solutions of queueing models are sensitive to these assumptions; (2a) the notation of standard queueing models, such as M/M/s and M/G/I, (2b) how to write and solve the birth-and-death equations that describe many queueing models, such as queueing networks, (2c) the reason for the introduction of such analytical tools as generating functions and Laplace-Stieltjes transforms) and (2d) the use of numerical analysis and simulation; (3a) examples of the successful application of queueing theory, such as telecommunications engineering and CPU scheduling algorithms) and (3b) problems that are too hard for mathematical analysis,