Marginal Delay Research Articles

Granular analysis of pathways to care and durations of untreated psychosis: A marginal delay model.

An extensive international literature demonstrates that understanding pathways to care (PTC) is essential for efforts to reduce community Duration of Untreated Psychosis (DUP). However, knowledge from these studies is difficult to translate to new settings. We present a novel approach to characterize and analyze PTC and demonstrate its value for the design and implementation of early detection efforts. Type and date of every encounter, or node, along the PTC were encoded for 156 participants enrolled in the clinic for Specialized Treatment Early in Psychosis (STEP), within the context of an early detection campaign. Marginal-delay, or the portion of overall delay attributable to a specific node, was computed as the number of days between the start dates of contiguous nodes on the PTC. Sources of delay within the network of care were quantified and patient characteristic (sex, age, race, income, insurance, living, education, employment, and function) influences on such delays were analyzed via bivariate and mixed model testing. The period from psychosis onset to antipsychotic prescription was significantly longer (52 vs. 20.5 days, [p = 0.004]), involved more interactions (3 vs. 1 nodes, [p<0.001]), and was predominated by encounters with non-clinical nodes while the period from antipsychotic to STEP enrollment was shorter and predominated by clinical nodes. Outpatient programs were the greatest contributor of marginal delays on both before antipsychotic prescription (median [IQR] of 36.5 [1.3-132.8] days) and (median [IQR] of 56 [15-210.5] days). Sharper functional declines in the year before enrollment correlated significantly with longer DUP (p<0.001), while those with higher functioning moved significantly faster through nodes (p<0.001). No other associations were found with patient characteristics and PTCs. The conceptual model and analytic approach outlined in this study give first episode services tools to measure, analyze, and inform strategies to reduce untreated psychosis.

When to swing into high gear? A time-limit approach to problem escalation

In manufacturing and services, random problems arise that disrupt normal operations. Organizations must resolve these problems in a timely and cost-efficient manner—which can be a daunting task. A typical management response is assigning escalation routes whereby the lowest tier initially owns a problem that may later be escalated to higher tiers. To minimize the costs associated with these problems, we consider a management policy that specifies a time limit beyond which problems must move up a tier; the setting is formulated as a stochastic dynamic program. For scenarios involving a single problem type, we find that optimal time limits can exist when the problem service times are generally distributed or correlated and when the marginal delay cost increases with time; we also characterize the single–problem type, multi-tier optimal solution when the marginal delay cost is constant. When multiple types of problems are pooled together, we show that a time-limit–based approach is robust to various probability distributions of service times and performs reasonably well even when the problem type is unidentified ex ante. Finally, we derive comparative statics on how parameter values, problem characteristics, and the composition of problems each affect the optimal time limit.

Accurate Distributed Secondary Control for DC Microgrids Considering Communication Delays: A Surplus Consensus-Based Approach

The state-of-the-art dynamic consensus-based microgrid (MG) secondary controls suffer from the communication delay effect. Specifically, the system could not converge to the desired operating points with time-delayed communications. Such deviations are hard to detect in a decentralized manner and could destabilize the system. This paper proposes an accurate distributed secondary controller for DC MGs based on the surplus consensus algorithm. The proposed controller achieves accurate proportional power sharing and average voltage regulation among distributed generators (DGs) with the presence of variable and bounded communication delays. A surplus consensus-based observer is developed. The developed observer is proved robust against variable and bounded communication delays; it tracks the average of a group of dynamic states with zero steady-state deviations, which cannot be done using the conventional dynamic consensus-based observer. The convergence speed of the developed observer is analyzed and a parameter design procedure is presented. Moreover, the delay-dependent stability analysis of DC MG operation with the proposed secondary controller is derived. The marginal delay that leads the system to instability is calculated. At last, the performance of the proposed secondary controller and the developed stability analysis are validated under various scenarios using MATLAB/Simulink.

Microdialysis and nanofiltration allow to distinguish molecularly dissolved from colloid-associated drug concentrations during biomimetic dissolution testing of supersaturating formulations

Many new drug entities are poorly water-soluble and thus require solubility-enhancing formulations to ensure sufficient bioavailability. On the other hand, it is more and more accepted that not all “dissolved” states of a drug contribute equally to enhanced absorption, i.e. an increase in apparent solubility does not necessarily go in parallel with an increase in molecularly dissolved drug, the latter being regarded as the key driving force for absorption. Our study aimed to provide time-resolved information on the dissolution, supersaturation, and precipitation behavior of molecularly dissolved drug as released from an amorphous solid dispersion and a surfactant-containing crystalline suspension of Posaconazole (PCZ), a weakly basic and poorly water-soluble drug. Thereby, we aimed to gain a deeper mechanistic understanding of enabling formulation principles and possibly establish a dynamic biopharmaceutical assessment tool for molecularly dissolved drug released from enabling formulations.A two-staged dissolution test, with media transition from simulated gastric fluid (SGF) to fasted state simulated intestinal fluid (FaSSIF), was performed with three alternative sampling approaches in parallel: the classical bench centrifugation approach was used to assess total dissolved concentrations, while a nanofiltration method and a microdialysis setup were tested for their ability to discriminate molecularly and colloid-associated drug concentrations over time. For comparison, a single-stage dissolution setup was performed, where a marketed PCZ suspension was dispersed in biomimetic media with increasing amounts of solubilizing agents to understand their effect on the concentration of molecularly dissolved drug.It was demonstrated that the microdialysis setup allowed to follow the molecularly dissolved drug concentration in a time-resolved manner during the single-and two-stage dissolution tests with marginal delays. Interestingly, the PCZ concentrations measured by the nanofiltration approach differed from both, the molecularly dissolved (assessed by microdialysis) and apparently dissolved (assessed by centrifuge) PCZ concentrations, indicating that nanofiltration may allow to differentiate between different colloid-associated (apparently) dissolved drug species. Moreover, it was shown that the release of the molecularly dissolved drug from an amorphous solid dispersion did not correlate at all with the results obtained by the centrifugation method: While this conventional sampling revealed a classical spring and parachute concentration/time-profile with a high degree of (apparent) supersaturation, the concentration of molecularly dissolved drug (assessed by the microdialysis setup) indicated an initial short decline of PCZ concentration, followed by a prolonged (moderate) molecular supersaturation. This observation may give rise to a re-thinking of the current mechanistic understanding of how amorphous solid dispersions enhance oral bioavailability. In essence, the current study provides data which indicate a benefit of both the microdialysis sampling and nanofiltration approaches for the in vitro biopharmaceutical assessment of enabling drug formulations.

Arabidopsis WRKY71 regulates ethylene-mediated leaf senescence by directly activating EIN2, ORE1 and ACS2 genes.

Leaf senescence is a pivotal step in the last stage of the plant life cycle and is influenced by various external and endogenous cues. A series of reports have indicated the involvement of the WRKY transcription factors in regulating leaf senescence, but the molecular mechanisms and signaling pathways remain largely unclear. Here we provide evidence demonstrating that WRKY71 acts as a positive regulator of leaf senescence in Arabidopsis. WRKY71-1D, an overexpressor of WRKY71, exhibited early leaf senescence, while wrky71-1, the WRKY71 loss-of-function mutant, displayed delayed leaf senescence. Accordingly, a set of senescence-associated genes (SAGs) were substantially elevated in WRKY71-1D but markedly decreased in wrky71-1. Chromatin immunoprecipitation assays indicated that WRKY71 can bind directly to the promoters of SAG13 and SAG201. Transcriptome analysis suggested that WRKY71 might mediate multiple cues to accelerate leaf senescence, such as abiotic stresses, dark and ethylene. WRKY71 was ethylene inducible, and treatment with the ethylene precursor 1-amino-cyclopropane-1-carboxylic acid enhanced leaf senescence in WRKY71-1D but caused only a marginal delay in leaf senescence in wrky71-1. In vitro and invivo assays demonstrated that WRKY71 can directly regulate ETHYLENE INSENSITIVE2 (EIN2) and ORESARA1 (ORE1), genes of the ethylene signaling pathway. Consistently, leaf senescence of WRKY71-1D was obviously retarded in the ein2-5 and nac2-1 mutants. Moreover, WRKY71 was also proved to interact with ACS2 invitro and invivo. Treatment with AgNO3 and aminoethoxyvinylglycine and acs2-1 could greatly arrest the leaf senescence of WRKY71-1D. In conclusion, our data revealed that WRKY71 mediates ethylene signaling and synthesis to hasten leaf senescence in Arabidopsis.

Does exposure to radiofrequency radiation (RFR) affect the circadian rhythm of rest-activity patterns and behavioral sleep variables in humans?

ABSTRACT We evaluated the effects of the exposure to radio-frequency radiation emanating from the base transceiver station (BTS) on the characteristics of circadian rest-activity rhythm and behavioral sleep variables in humans. We performed this exploratory field study in a sample of 89 healthy subjects randomly chosen out of 1434 individuals surveyed for the purpose. We divided 89 subjects into five groups, including the control, as a function of distance from the BTS. The E-field strength was higher in the groups of the inter-tower region and between 0 and 150 m away from the BTS. The E-field (distance) did not significantly affect the circadian rhythm parameters and behavioral sleep variables, except a marginal delay in the peak timings of the rest-activity rhythm of subjects in the inter-tower and 300–500 m groups. Notable secondary effects of the factor gender were noticed on circadian amplitude, sleep efficiency, dichotomy index, and wake after sleep onset. We concluded that exposure to radiation from the BTS did not modulate actigraphy-based behavioral sleep variables of people residing around BTS installations. We recommend more extensive field-based studies with rigorous longitudinal designs to validate the effects of radiation from the BTS in humans.

Design of an enhanced write stability, high-performance, low power 11T SRAM cell

ABSTRACT In the present era of diminishing technology nodes, stability and performance of SRAM cells deteriorate. To cope up with the above growing concerns, a new 11 T SRAM cell has been proposed which improves the stability in all operating modes of SRAM as well as the delay and power in the write mode. At worst process corner SS, the write 0 delay has been improved by 14.01%, 6.75%, 115.72% and 26.61% compared to 6 T, 8 TG, 10 TDiff and 11 T SRAM designs and write 1 delay has been improved by 9.2%, 88.639%, 13.69% and 71.42% compared to 6 T, 10 TDiff, DDS11T and 11 T designs at 0.9 V supply voltage. The impact of PVT variations has been studied on SNM, Write Margin, Read & Write delay, Leakage Power. The Monte Carlo simulation has been performed to study the effect of variability. P11T SRAM cell exhibits narrower spread in the distribution of majority design metrics. The removal of the half-select issue has been illustrated in the P11T SRAM cell using Monte Carlo simulations. Post-Layout simulation has been carried out to evaluate different design metrics at 45 nm technology node in Cadence Virtuoso.

The Helminth Parasite Heligmosomoides polygyrus Attenuates EAE in an IL-4Rα-Dependent Manner.

Helminth parasites are effective in biasing Th2 immunity and inducing regulatory pathways that minimize excessive inflammation within their hosts, thus allowing chronic infection to occur whilst also suppressing bystander atopic or autoimmune diseases. Multiple sclerosis (MS) is a severe autoimmune disease characterized by inflammatory lesions within the central nervous system; there are very limited therapeutic options for the progressive forms of the disease and none are curative. Here, we used the experimental autoimmune encephalomyelitis (EAE) model to examine if the intestinal helminth Heligmosomoides polygyrus and its excretory/secretory products (HES) are able to suppress inflammatory disease. Mice infected with H. polygyrus at the time of immunization with the peptide used to induce EAE (myelin-oligodendrocyte glycoprotein, pMOG), showed a delay in the onset and peak severity of EAE disease, however, treatment with HES only showed a marginal delay in disease onset. Mice that received H. polygyrus 4 weeks prior to EAE induction were also not significantly protected. H. polygyrus secretes a known TGF-β mimic (Hp-TGM) and simultaneous H. polygyrus infection with pMOG immunization led to a significant expansion of Tregs; however, administering the recombinant Hp-TGM to EAE mice failed to replicate the EAE protection seen during infection, indicating that this may not be central to the disease protecting mechanism. Mice infected with H. polygyrus also showed a systemic Th2 biasing, and restimulating splenocytes with pMOG showed release of pMOG-specific IL-4 as well as suppression of inflammatory IL-17A. Notably, a Th2-skewed response was found only in mice infected with H. polygyrus at the time of EAE induction and not those with a chronic infection. Furthermore, H. polygyrus failed to protect against disease in IL-4Rα−/− mice. Together these results indicate that the EAE disease protective mechanism of H. polygyrus is likely to be predominantly Th2 deviation, and further highlights Th2-biasing as a future therapeutic strategy for MS.

Technologies for congestion pricing

Congestion pricing of high-demand roadways seeks to influence travelers’ route choices, trip timing, modes, and destination choices, to keep vehicles moving and avoid excessive congestion. This paper describes the use of various technologies to enable more advanced and cost-effective congestion pricing applications, and a credit-based policy to ensure equitable network access for all travelers.Video-based systems require cameras to capture the state of traffic, plus some form of communication back to users. Both DSRC and cellular-based systems use GPS data to price roads and toll users based on traffic conditions. DSRC employs roadside units (RSUs) to receive and send messages to in-vehicle DSRC units. A cellular-based system could use communications from cellular towers in combination with a smartphone, on-board diagnostics port (OBD-II), or pre-installed cellular chip. DSRC is a valuable technology to pilot congestion pricing at highly congested locations, such as bridges and major highways, while cellular communications enable congestion pricing across entire networks.VMT fees can be relatively simple, or variable in space and time, facilitating transportation-agency cost recovery. A next step for roadway management is congestion pricing (CP), to better reflect the marginal delay costs of one's travel choices. When coupled with travel credits, CP can better ensure welfare gains for most travelers.

Establishing Trust in Online Advertising With Signed Transactions

Programmatic advertising operates one of the most sophisticated and efficient service platforms on the Internet. However, the complexity of this ecosystem is a direct cause of one of the most important problems in online advertising, the lack of transparency. This lack of transparency enables subsequent problems such as advertising fraud, which causes billions of dollars in losses. In this paper we propose Ads.chain, a technological solution to the lack-of-transparency problem in programmatic advertising. Ads.chain extends the current effort of the Internet Advertising Bureau (IAB) in providing traceability in online advertising through the Ads.txt and Ads.cert solutions, addressing the limitations of these techniques. Ads.chain is (to the best of the authors' knowledge) the first solution that provides end-to-end cryptographic traceability at the ad transaction level. It is a communication protocol that can be seamlessly embedded into ad-tags and the OpenRTB protocol, the de-facto standards for communications in online advertising, allowing an incremental adoption by the industry. We have implemented Ads.chain and made the code publicly available. We assess the performance of Ads.chain through a thorough analysis in a lab environment that emulates a real ad delivery process at real-life throughputs. The obtained results show that Ads.chain can be implemented with limited impact on the hardware resources and marginal delay increments at the publishers lower than 0.20 milliseconds per ad space on webpages and 2.6 milliseconds at the programmatic advertising platforms. These results confirm that Ads.chain's impact on the user experience and the overall operation of the programmatic ad delivery process can be considered negligible.

Early transition, relaminarization and drag reduction in the flow of polymer solutions through microtubes

Experiments are performed to investigate the onset of early transition and drag reduction in the flow of polymer (polyacrylamide and polyethylene oxide) solutions through rigid microtubes of diameters in the range 0.49–2.84 mm. We measure friction factor variation with Reynolds number for varying polymer concentrations and tube diameters, and the Reynolds number, , at which the experimental data deviate from the laminar value represents the onset of transition. Crucially, owing to the high shear rates encountered in our experiments, we show that it is important to account for shear thinning of the fluid in the theoretical estimation of the friction factor in the laminar regime. We accomplish this using a Carreau model, and show that the use of laminar friction factor calculated without shear thinning leads to an erroneous overestimation of . The obtained from friction factor data in the present study is in good agreement with that inferred using micro particle image velocimetry analysis in Chandra et al. (J. Fluid Mech., vol. 844, 2018, pp. 1052–1083). For smaller concentrations of the added polymer, there is a marginal delay in the onset of turbulence, but as the concentration is increased further, the transition Reynolds number decreases much below , the usual value at which transition occurs in Newtonian pipe flows. Thus, the present study further corroborates the phenomenon of early transition leading to an ‘elasto-inertial’ turbulent state in the flow of polymer solutions. For concentrations such that there is a delay in transition, if is maintained above the for Newtonian fluids, the flow is transitional or turbulent in the absence of polymers. At such a fixed , if the concentration of the polymer is increased gradually, the friction factor decreases and the flow relaminarizes. With further increase in polymer concentration, the flow undergoes a transition due to elasto-inertial instability. The effect of addition of small amounts of polymer on turbulent drag reduction in the flow of water through microtubes is also investigated. Increase in polymer concentration, molecular weight and decrease in tube diameter causes an increase in drag reduction. The friction factor data for different polymer concentrations, molecular weights, tube diameters and , when plotted with , show a reasonable collapse, where is the Weissenberg number defined as the product of the longest relaxation time of the polymer solution and the average shear rate in the tube and is the ratio of solvent to total solution viscosity. Interestingly, the onset of the maximum drag reduction asymptote, for experiments using varying tube diameters and polymer concentrations, appears to occur at .

Familial glucocorticoid deficiency presenting with hyperpigmentation, gigantism, and motor development delay: a case report

BackgroundFamilial glucocorticoid deficiency is a rare autosomal recessive disorder characterized by isolated glucocorticoid deficiency. Most patients are diagnosed following episodes of hypoglycemia or convulsion. We report the case of an infant with familial glucocorticoid deficiency who presented with hyperpigmentation, gigantism, and motor developmental delay without documented hypoglycemia, convulsion, or circulatory collapse.Case presentationA 10-month-old Sri Lankan Sinhalese baby boy born to consanguineous parents presented with generalized hyperpigmentation and overgrowth since birth. He had marginal gross motor developmental delay. His weight, length, and head circumference were above normal range for his age. Investigations revealed low serum cortisol and high adrenocorticotrophic hormone levels with no cortisol response following adrenocorticotropin stimulation. Serum electrolytes and aldosterone levels were normal. A diagnosis of familial glucocorticoid deficiency was made based on isolated glucocorticoid deficiency, hyperpigmentation, and tall stature.ConclusionsThis case report highlights that glucocorticoid deficiency can present without documented hypoglycemia and circulatory collapse and a high degree of suspicion is needed in diagnosis.

A reliable adaptive forwarding approach in named data networking

Named Data Networking (NDN) is a new paradigm for the future Internet infrastructure based on routable named data. The NDN infrastructure consists of a new component called strategy layer. The strategy layer allows for dynamically selecting network interfaces taking into account network conditions such as delay to forward Interest messages toward a provider. However, defining proper criteria for selecting the best possible paths to forward Interest messages is challenging in this network because different parameters and conditions conflict one another when choosing the best interfaces. Moreover, in NDN, data can be retrieved from different sources. However, to the best of our knowledge, the previous forwarding strategy methods that can estimate from which path the valid data can be fetched have not considered an attacker who tries to inject fake data with the same name as valid data. Therefore, in this paper, we take a holistic, adaptive forwarding approach that takes into account various metrics: bandwidth, load, delay, and reliability. Especially, we propose a reliability metric that defines which path is more stable and reliable to retrieve legitimate data. Our evaluation demonstrates that the proposed method enables reliable message delivery against potential attackers that inject invalid data, in addition, our method introduces marginal delay compared with the conventional forwarding methods in NDN.

Post-disaster map builder: Crowdsensed digital pedestrian map construction of the disaster affected areas through smartphone based DTN

Constructing digital pedestrian maps of the disaster affected areas is a vital requirement for post-disaster relief operation. Digital maps help disaster management agencies in decision making and mobilizing the manpower and resources in the disaster affected areas. However, due to the intermittent connectivity after large scale natural disasters, the existing web based digital mapping systems remain inaccessible in the disaster affected areas. Moreover, the road networks in such areas change drastically because of disaster (for instance waterlogging due to flood, structural collapse or incidental destructions like a landslide). Hence, existing analog (paper based) route maps of such areas become obsolete. In this work, we propose Post-Disaster Map Builder, a crowdsenced digital pedestrian map construction system over smartphone based DTN. The proposed system generates digital pedestrian maps of the disaster affected areas using battery powered mobile handheld devices. Here, trajectory traces collected by the volunteers are periodically shared among the other volunteers of the disaster affected area through smartphone based DTN. Pedestrian maps of the disaster affected areas are gradually constructed in the mobile handheld devices of the volunteers by combining the collected traces over time. The proposed system is thoroughly evaluated through simulation and testbed implementation. The results reveal that our proposed system can automatically construct digital pedestrian maps of disaster affected areas with high accuracy at the cost of marginal delay.

Condensation Kinetics of Water on Amorphous Aerosol Particles.

Responding to changes in the surrounding environment, aerosol particles can grow by water condensation changing rapidly in composition and changing dramatically in viscosity. The timescale for growth is important to establish for particles undergoing hydration processes in the atmosphere or during inhalation. Using an electrodynamic balance, we report direct measurements at -7.5, 0, and 20 °C of timescales for hygroscopic condensational growth on a range of model hygroscopic aerosol systems. These extend from viscous aerosol particles containing a single saccharide solute (sucrose, glucose, raffinose, or trehalose) and a starting viscosity equivalent to a glass of ∼1012 Pa·s, to nonviscous (∼10-2 Pa·s) tetraethylene glycol particles. The condensation timescales observed in this work indicate that water condensation occurs rapidly at all temperatures examined (<10 s) and for particles of all initial viscosities spanning 10-2 to 1012 Pa·s. Only a marginal delay (<1 order of magnitude) is observed for particles starting as a glass.

WRKY71 Acts Antagonistically Against Salt-Delayed Flowering in Arabidopsis thaliana

Soil salinity affects various aspects of plant growth and development including flowering. Usually, plants show a delayed flowering phenotype under high salinity conditions, whereas some plants will risk their life to continue to grow, thereby escaping serious salt stress to achieve reproductive success. However, the molecular mechanisms of the escape strategies are not clear yet. In this work, we report that the transcription factor WRKY71 helps escape salt stress in Arabidopsis. The expression of the WRKY71 wild-type (WT) allele was salinity inducible. Compared with Col-0, high salt stress caused only a marginal delay in the flowering time of the activation-tagged mutant WRKY71-1D. However, flowering in the RNA interference (RNAi)-based multiple WRKY knock-out mutant (w71w8 + 28RNAi) was dramatically later than in the WT under high salinity conditions. Meanwhile, expression of FLOWERING LOCUS T (FT) and LEAFY (LFY) was greater in WRKY71-1D than in the WT, and lower in w71w8 + 28RNAi under salinity-stressed conditions. The suggestion is that WRKY71 activity hastens flowering, thereby providing a means for the plant to complete its life cycle in the presence of salt stress.

Gridding discretization-based multiple stability switching delay search algorithm: The movement of a human being on a controlled swaying bow.

Delay represents a significant phenomenon in the dynamics of many human-related systems—including biological ones. It has i.a. a decisive impact on system stability, and the study of this influence is often mathematically demanding. This paper presents a computationally simple numerical gridding algorithm for the determination of stability margin delay values in multiple-delay linear systems. The characteristic quasi-polynomial—the roots of which decide about stability—is subjected to iterative discretization by means of pre-warped bilinear transformation. Then, a linear and a quadratic interpolation are applied to obtain the associated characteristic polynomial with integer powers. The roots of the associated characteristic polynomial are closely related to the estimation of roots of the original characteristic quasi-polynomial which agrees with the system′s eigenvalues. Since the stability border is crossed by the leading one, the switching root locus is enhanced using the Regula Falsi interpolation method. Our methodology is implemented on—and verified by—a numerical bio-cybernetic example of the stabilization of a human-being′s movement on a controlled swaying bow. The advantage of the proposed novel algorithm lies in the possibility of the rapid computation of polynomial zeros by means of standard programs for technical computing; in the low level of mathematical knowledge required; and, in the sufficiently high precision of the roots loci estimation. The relationship to the direct search QuasiPolynomial (mapping) Rootfinder algorithm and computational complexity are discussed as well. This algorithm is also applicable for systems with non-commensurate delays.

A CONTINUOUS REVIEW MODEL WITH GENERAL SHELF AGE AND DELAY-DEPENDENT INVENTORY COSTS

We analyze a continuous review inventory model with the marginal carrying cost of a unit of inventory given by an increasing function of its shelf age and the marginal delay cost of a backlogged demand unit by an increasing function of its delay duration. We show that, under a minor restriction, an (r, q)-policy is optimal when the demand process is a renewal process, and a state dependent (r, q)-policy is optimal when the demand is a Markov-modulated renewal process. We also derive various monotonicity properties for the optimal policy parameters r* and r* + q*.

Reconciling quality and cost: A case study in interventional radiology.

To provide a method to calculate delay cost and examine the relationship between quality and total cost. The total cost including capacity, supply and delay cost for running an interventional radiology suite was calculated. The capacity cost, consisting of labour, lease and overhead costs, was derived based on expenses per unit time. The supply cost was calculated according to actual procedural material use. The delay cost and marginal delay cost derived from queueing models was calculated based on waiting times of inpatients for their procedures. Quality improvement increased patient safety and maintained the outcome. The average daily delay costs were reduced from 1275 € to 294 €, and marginal delay costs from approximately 2000 € to 500 €, respectively. The one-time annual cost saved from the transfer of surgical to radiological procedures was approximately 130,500 €. The yearly delay cost saved was approximately 150,000 €. With increased revenue of 10,000 € in project phase 2, the yearly total cost saved was approximately 290,000 €. Optimal daily capacity of 4.2 procedures was determined. An approach for calculating delay cost toward optimal capacity allocation was presented. An overall quality improvement was achieved at reduced costs. • Improving quality in terms of safety, outcome, efficiency and timeliness reduces cost. • Mismatch of demand and capacity is detrimental to quality and cost. • Full system utilization with random demand results in long waiting periods and increased cost.

A model for deceased-donor transplant queue waiting times

In many jurisdictions, organ allocation is done on the basis of the health status of the patient, either explicitly or implicitly. This paper presents a self-promoting queueing model for patient waiting times which takes into account changes in health status over time. In this model, most patients arrive as regular customers to the queue, but as the health of a patient degrades, their status is promoted to priority to reflect the increased urgency of the transplant. We model the queueing system as a level-dependent quasi-birth-and-death process, and the steady-state joint queue length distribution as well as the marginal delay distributions for each queue are computed via the use of matrix analytic techniques. The model is calibrated using liver transplantation wait-list data, provided by a regional health centre in Canada, which tracked approximately 1,100 patients over nearly 13 years. Blood-type-specific models are fit and performance measures, such as the mean and distribution of the time until transplant, are obtained and compared to empirical estimates calculated using the raw data.