New Complexity Results and Algorithms for the Minimum Tollbooth Problem

The inefficiency of the Wardrop equilibrium of nonatomic routing games can be eliminated by placing tolls on the edges of a network so that the socially optimal flow is induced as an equilibrium flow. A solution where the minimum number of edges are tolled may be preferable over others due to its ease of implementation in real networks. In this paper we consider the minimum tollbooth (MINTB) problem, which seeks social optimum inducing tolls with minimum support. We prove for single commodity networks with linear latencies that the problem is NP-hard to approximate within a factor of $1.1377$ through a reduction from the minimum vertex cover problem. Insights from network design motivate us to formulate a new variation of the problem where, in addition to placing tolls, it is allowed to remove unused edges by the social optimum. We prove that this new problem remains NP-hard even for single commodity networks with linear latencies, using a reduction from the partition problem. On the positive side, we give the first exact polynomial solution to the MINTB problem in an important class of graphs---series-parallel graphs. Our algorithm solves MINTB by first tabulating the candidate solutions for subgraphs of the series-parallel network and then combining them optimally

How equitable is vocational rehabilitation in Sweden? A review of evidence on the implementation of a national policy framework

Purpose. Under the national framework law in Sweden, all eligible people should have equal chances of receiving vocational rehabilitation. We aimed to review the evidence on (1) whether access to vocational rehabilitation is equitable in practice and (2) whether the outcomes vary for different groups in the population. Method. Systematic review of studies in Sweden that reported diagnostic or socio-demographic characteristics of people offered or taking up rehabilitation programmes and outcomes of such programmes for different diagnostic and socio-demographic groups. Searches of 11 relevant electronic databases, 15 organisational websites, citation searching and contact with experts in the field, for the period 1990–2009. Results. A total of 11 studies were included in the final review, six of which addressed review question (1) and seven addressed review question (2). All the six observational studies of access reported biased selection into vocational rehabilitation: greater likelihood for men, younger people, those with longer-term sick leave, those with lower income, employed rather than unemployed people and those with musculoskeletal and mental disorders or alcohol abuse. Having had a rehabilitation investigation also increased the likelihood of receiving vocational rehabilitation. Differential outcome of rehabilitation was reported in seven studies: outcomes were better for men, younger people, employed individuals, those with shorter sick leave and those with higher income. Selection into vocational rehabilitation was perceived as important for successful outcomes, but success also depended on the state of the local labour market. Conclusions. There is evidence of socio-demographic differences in access to and outcomes of vocational rehabilitation in Sweden, even though the national framework law is meant to apply to everyone. Few studies have deliberately measured differential access or outcomes, and there is a need for this kind of equity analysis of population-wide policies. Studies evaluating the effects of vocational rehabilitation must consider selection into the programmes for adequate interpretation of impact results

Specific mediator inhibition by the NO donors SNP and NCX 2057 in the peripheral lung: implications for allergen-induced bronchoconstriction

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to examine potential therapeutic effect of the two NO donors NCX 2057 (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid) 4-(nitrooxy)butyl ester) and SNP (sodium nitroprusside) on the early allergic airway response in the peripheral lung.</p> <p>Methods</p> <p>The experiments were performed in guinea pig lung parenchyma (GPLP) derived from ovalbumin (OVA) sensitized guinea pigs. The effects of NCX 2057 and SNP were evaluated by contractile responses and mediator release during OVA challenge. The generation of nitrite and nitrate was assessed by chemiluminescence. Statistical analysis was evaluated by ANOVA.</p> <p>Results</p> <p>Cumulatively increasing concentrations of OVA (1–10,000 ng/ml) induced concentration-dependent contractions of the GPLP that were reduced by NCX 2057 (100 μM, p < 0.001) and SNP (100 μM, p < 0.05). Antigen-induced eicosanoid release was decreased by NCX 2057 (100 μM, p < 0.001) but not by SNP (100 μM), whereas the release of histamine was reduced by SNP (100 μM, p < 0.001) but not by NCX 2057 (100 μM). In addition, NCX 2057 (0.1–100 μM), but not SNP (0.1–100 μM), relaxed leukotriene D₄(10 nM) precontracted GPLP (p < 0.01). The guanylyl cyclase inhibitor ODQ had no effect on the NCX 2057 mediated relaxation. SNP released significantly less nitrite than NCX 2057.</p> <p>Conclusion</p> <p>Although both SNP and NCX 2057 reduced the release of pro-inflammatory mediators, their profiles were distinctly different. Furthermore, NCX 2057 also induced smooth muscle dilation in the GPLP. The findings point to specific anti-inflammatory effects of different NO donors in the peripheral lung tissue.</p

Subacute and chronic, non-specific back and neck pain: cognitive-behavioural rehabilitation versus primary care. A randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>In the industrial world, non-specific back and neck pain (BNP) is the largest diagnostic group underlying sick-listing. For patients with subacute and chronic (= full-time sick-listed for 43 – 84 and 85 – 730 days, respectively) BNP, cognitive-behavioural rehabilitation was compared with primary care. The specific aim was to answer the question: within an 18-month follow-up, will the outcomes differ in respect of sick-listing and number of health-care visits?</p> <p>Methods</p> <p>After stratification by age (≤ 44/≥ 45 years) and subacute/chronic BNP, 125 Swedish primary-care patients were randomly allocated to cognitive-behavioural rehabilitation (rehabilitation group) or continued primary care (primary-care group). Outcome measures were <it>Return-to-work share </it>(percentage) and <it>Return-to-work chance </it>(hazard ratios) over 18 months, <it>Net days </it>(crude sick-listing days × degree), and the number of <it>Visits </it>(to physicians, physiotherapists etc.) over 18 months and the three component six-month periods. Descriptive statistics, Cox regression and mixed-linear models were used.</p> <p>Results</p> <p>All patients: <it>Return-to-work share </it>and <it>Return-to-work chance </it>were equivalent between the groups. <it>Net days </it>and <it>Visits </it>were equivalent over 18 months but decreased significantly more rapidly for the rehabilitation group over the six-month periods (<it>p </it>< .05). Subacute patients: <it>Return-to-work share </it>was equivalent. <it>Return-to-work chance </it>was significantly greater for the rehabilitation group (hazard ratio 3.5 [95%CI1.001 – 12.2]). <it>Net days </it>were equivalent over 18 months but decreased significantly more rapidly for the rehabilitation group over the six-month periods and there were 31 days fewer in the third period. <it>Visits </it>showed similar though non-significant differences and there were half as many in the third period. Chronic patients: <it>Return-to-work share, Return-to-work chance </it>and <it>Net days </it>were equivalent. <it>Visits </it>were equivalent over 18 months but tended to decrease more rapidly for the rehabilitation group and there were half as many in the third period (non-significant).</p> <p>Conclusion</p> <p>The results were equivalent over 18 months. However, there were indications that cognitive-behavioural rehabilitation in the longer run might be superior to primary care. For subacute BNP, it might be superior in terms of sick-listing and health-care visits; for chronic BNP, in terms of health-care visits only. More conclusive results concerning this possible long-term effect might require a longer follow-up.</p> <p>Trial registration</p> <p>NCT00488735.</p

On the existence and uniqueness of first best tolls in networks with multiple user classes and elastic demand

System optimal (SO) or first best pricing is examined in networks with multiple user classes and elastic demand, where different user classes have a different average value of value of time (VOT). Different flows (and first best tolls) are obtained depending on whether the SO characterisation is in units of generalised time or money. The standard first best tolls for time unit system optimum are unsatisfactory, due to the fact that link tolls are differentiated across users. The standard first best tolls for the money unit system optimum may seem to be practicable, but the objective function of the money unit system optimum is nonconvex, leading to possible multiple optima (and non-unique first best tolls). Since these standard first best tolls are unsatisfactory, we look to finding common money tolls which drive user equilibrium flows to time unit SO flows. Such tolls are known to exist in the fixed demand case, but we prove that such tolls do not exist in the elastic demand case. Although common money tolls do not exist which drive the solution to the exact time system optimal flows, tolls do exist which can push the system close to time system optimum (TSO) flows

A toll pricing framework for traffic assignment problems with elastic demand

Abstract: This paper extends the notion of toll pricing and the toll pricing framework previously developed for fixed demand traffic assignment [4, 13] to the problem with elastic demand. The system problem maximizes net benefit to the network users [9, 20] and the user problem is the usual one of finding equilibrium with elastic demand. We define and characterize T, the set of all tolls for the user problem that achieve the system optimal solution. When solutions to the two problems are unique, T is a polyhedron defined by the optimal solution of the system problem, similar to the case in [4, 13]. The Toll Pricing Framework in [13] is also extended to allow optimization of secondary criteria over T. Examples include minimizing the number of toll booths and minimizing the maximum toll on any link. A numerical example illustrates the results. Keywords

Isolation and identification from Salvia officinalis of two diterpenes which inhibit t-butylbicyclophosphoro[35S]thionate binding to chloride channel of rat cerebrocortical membranes in vitro

Ethanolic extracts from dried leaves of sage (Salvia officinalis) showed inhibition of [35S]tertiary-butylbicyclophosphorothionate ([35S]TBPS) binding to rat brain membranes in vitro. This ligand is considered to bind to the chloride channel of the GABA/benzodiazepine receptor complex in brain tissue. Substances having inhibitory activity were purified and their chemical structure identified as the diterpenes carnosic acid and carnosol (IC50 values of 33 +/- 3 microM and 57 +/- 4 microM, respectively). The two compounds did not affect binding of the ligands [3H]muscimol and [3H]diazepam to the GABA/benzodiazepine complex in vitro. Saturation experiments of [35S]TBPS binding indicated that carnosic acid decreases the binding affinity

Solving Congestion Toll Pricing Models

: Recently a methodology for traffic networks has been developed which extracts congestion toll sets such that the tolled user equilibrium is system optimal. Properties of toll sets, such as convexity, are investigated, as well as relationships with other problems. For a given toll set, various objectives can be defined and optimized with respect to the tolls. Examples include minimizing the total tolls collected, minimizing the number of toll booths and constraining net tolls collected to be zero. We illustrate with an example and report on our computational experience with the Stockholm network. 1.1 INTRODUCTION Congestion toll pricing addresses the classic traffic assignment problem for which Wardrop enunciated two principles of traffic flow: user-optimal behavioral hypothesis and the notion and system-optimality. (See [7] for a recent review of the traffic assignment problem and [12] for a recent volume of papers on road pricing.) The traditional objective of congestion pricing h..