An economic model of the last-mile internet Chaturvedi, Rakesh; Dutta, Souvik; Kanjilal, Kiriti
Journal of economic behavior & organization,
11/2021, Letnik:
191
Journal Article
Recenzirano
•Pricing decisions of an internet service provider (ISP) are studied in a demand-supply framework.•The framework has complementarity between broadband connection and content, congestion externalities ...and oligopoly.•When the ISP uses two-part tariffs, the equilibrium is sensitive to usage price level but is invariant to its structure.•With nonlinear pricing, it is shown how network congestion and complementarity bear on the pricing decisions of the ISP.•For the zero-price rule, a neutrality-of-policy result holds with two-part tariffs but not with nonlinear pricing.
Pricing decisions of an internet service provider (ISP) are studied in a model based on complementarity between broadband connection and content, congestion externalities on consumer side and oligopolistic externalities on content provider side. When consumers face two-part tariffs from the ISP, the equilibrium is sensitive to usage price level but is invariant to its structure on two sides. With nonlinear pricing, the markup of content providers affects consumer prices while congestion externalities and elasticity of content demand shape the price for providers. For the zero-price rule, a neutrality-of-policy result holds with two-part tariffs but not with nonlinear pricing.
Patients with severe chronic obstructive pulmonary disease (COPD) often have intrinsic positive end-expiratory pressure. Continuous positive airway pressure has been shown to decrease the inspiratory ...work of breathing and increases exercise capacity in these patients.
To determine whether continuous negative pressure (CNP) around the chest is able to bring the positive end-expiratory pressure closer to atmospheric pressure, thereby reducing the threshold load and increasing exercise capability.
A pilot study was undertaken with eight COPD patients who had been hospitalized for exacerbation and were close to discharge. For CNP, a shell (around the thorax from under the axillae to the mid abdomen) and wrap were used. Each of the eight patients was assessed with a 6 min walk test in three modes (in randomized order) with 30 min of rest in between: a control walk with no shell or wrap; a sham CNP in which the applied CNP was negligible; and CNP, with pressure chosen by the patient that provided maximal relief of dyspnea at rest.
At the end of each of the 6 min walk tests, there was no difference in heart rate, oxygen saturation or level of dyspnea among the three test modes. Respiratory rate was reduced with CNP compared with sham. The patients walked furthest with CNP compared with control (mean ± SD) (313 ± 66.2 m versus 257 ± 65.2 m; P<0.01) and compared with sham.
In the present pilot study, COPD patients improved their exercise performance with CNP.
We investigate the coexistence of an age optimizing network (AON) and a throughput optimizing network (TON) that share a common spectrum band. We consider two modes of long run coexistence: (a) ...networks compete with each other for spectrum access, causing them to interfere and (b) networks cooperate to achieve non-interfering access. To model competition, we define a non-cooperative stage game parameterized by the average age of the AON at the beginning of the stage, derive its mixed strategy Nash equilibrium (MSNE), and analyze the evolution of age and throughput over an infinitely repeated game in which each network plays the MSNE at every stage. Cooperation uses a coordination device that performs a coin toss during each stage to select the network that must access the medium. Networks use the grim trigger punishment strategy, reverting to playing the MSNE every stage forever if the other disobeys the device. We determine if there exists a subgame perfect equilibrium, i.e., the networks obey the device forever as they find cooperation beneficial. We show that networks choose to cooperate only when they consist of a sufficiently small number of nodes, otherwise they prefer to disobey the device and compete.
Aim: The aim of this study was to determine the midterm functional quality of life in octogenarians after open valvular surgery. Methods: One hundred and eighty‐five consecutive patients above age 80 ...had valvular surgery with or without coronary artery bypass grafting (CABG). Using the Karnofsky Performance score and Barthel Index, patients were evaluated for functional autonomy, living disposition, and leisure activity by a single telephone interview. Subgroup analysis was performed on the 49 cases of isolated aortic valve replacement (AVR). Results: Mean age of octogenarians undergoing valvular surgery was 82.7 years (range 80 to 92 years). Actuarial survival at one and three years was 71% and 59%, respectively, for the entire group, compared to 84% and 71%, respectively, for isolated AVRs. After a mean follow‐up of 38 months there were 110 survivors (59.5%). Among survivors, 66% were autonomous, 26% semiautonomous, and 8% deemed dependent. Seventy‐two percent were living at home, 19% in a residence, and 9% in a supervised nursing facility. Over 90% of patients pursued leisure activities in the social, cognitive, and physical domains. Conclusions: Valvular surgery in high‐risk octogenarians, can be performed with acceptable mortality rates, and provide patients with functional autonomy and an excellent quality of life. (J Card Surg 2012;27:408‐414)
Little attention is given to the mode of mechanical ventilation after cardiac surgery. Positive pressure ventilation with positive end-expiratory pressure (PEEP) has been shown to reduce cardiac ...output. We hypothesized that positive pressure ventilation with continual negative pressure applied to the chest through a cuirass would increase cardiac output in coronary artery bypass graft patients immediately after surgery.
Twenty patients with a normal left ventricular ejection fraction were studied 2 hours after coronary artery bypass graft surgery. The patients were ventilated with synchronized intermittent mandatory ventilation (SIMV) and PEEP. Hemodynamic variables and blood gases were studied using four modes of ventilation after 15 minutes in each mode: A (baseline 1) = SIMV and 5 cmH(2)O of PEEP; B = SIMV without PEEP; C = SIMV without PEEP and with continuous negative pressure applied to the thorax at -20 cmH(2)O; D (baseline 2) = SIMV and 5 cmH(2)O of PEEP. The results of the two baselines were averaged.
All patients were hemodynamically stable during the trial. Heart rate, blood pressure, and gas exchange were not affected by the changes in ventilatory modes. With continual negative pressure, the stroke volume index and cardiac index were significantly increased relative to ventilation with SIMV and PEEP by 3.21 mL x min(-1) x m(-2) (9.0%) and 0.45 L x min(-1) x m(-2) (13.8%), respectively. Continual negative pressure also reduced venous and wedge pressure.
Continual negative pressure attenuates the negative effects of positive pressure ventilation on cardiac output. Although the improvement in this cohort with normal ventricular function is modest, this pilot study demonstrates that the mode of ventilation may have potentially important effects on cardiac output.
With chronic obstructive pulmonary disease (COPD) exacerbations, continuous positive airway pressure (CPAP) has been used to overcome the threshold load provided by intrinsic positive end expiratory ...pressure and decrease the inspiratory work of breathing. In this pilot study, we observed whether a continuous negative pressure (CNP) around the thorax and upper abdomen with a shell and wrap would provide a similar level of relief in dyspnoea.
In eight patients with COPD in the intensive care unit receiving CPAP, CNP was alternated twice with CPAP (30 minutes each time). We measured heart rate, respiratory rate, blood pressure, arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2) pH and dyspnoea score, and asked each patient which system was more comfortable.
Comparing CPAP with CNP, we found no significant difference in all measured parameters except PaCO2 which was lower with CNP. Seven out of eight patients found that CNP was more comfortable.
The CNP was similar to CPAP except CNP was more comfortable.
Controlled mechanical ventilation (CMV) results in atrophy of the human diaphragm. The autophagy-lysosome pathway (ALP) contributes to skeletal muscle proteolysis, but its contribution to ...diaphragmatic protein degradation in mechanically ventilated patients is unknown.
To evaluate the autophagy pathway responses to CMV in the diaphragm and limb muscles of humans and to identify the roles of FOXO transcription factors in these responses.
Muscle biopsies were obtained from nine control subjects and nine brain-dead organ donors. Subjects were mechanically ventilated for 2 to 4 hours and 15 to 276 hours, respectively. Activation of the ubiquitin-proteasome system was detected by measuring mRNA expressions of Atrogin-1, MURF1, and protein expressions of UBC2, UBC4, and the α subunits of the 20S proteasome (MCP231). Activation of the ALP was detected by electron microscopy and by measuring the expressions of several autophagy-related genes. Total carbonyl content and HNE-protein adduct formation were measured to assess oxidative stress. Total AKT, phosphorylated and total FOXO1, and FOXO3A protein levels were also measured.
Prolonged CMV triggered activation of the ALP as measured by the appearance of autophagosomes in the diaphragm and increased expressions of autophagy-related genes, as compared with controls. Induction of autophagy was associated with increased protein oxidation and enhanced expression of the FOXO1 gene, but not the FOXO3A gene. CMV also triggered the inhibition of both AKT expression and FOXO1 phosphorylation.
We propose that prolonged CMV causes diaphragm disuse, which, in turn, leads to activation of the ALP through oxidative stress and the induction of the FOXO1 transcription factor.
Division of Cardiothoracic Surgery, Department of Surgery, McGill University Health Centre, McGill University, Montreal, Canada
*Corresponding author. Royal Victoria Hospital, 687 Pine Avenue West, ...Suite S8.30, Montreal, QC H3A 1A1, Canada. Tel.: +1(514) 843-1463; fax: +1(514) 843-1602. E-mail address : dr_turki{at}yahoo.com (T.B. Albacker).
Old age is a significant risk factor for perioperative morbidity and mortality following cardiac surgery and optimal myocardial protection strategy should be sought in this group of patients. We, therefore, reviewed the data on 295 consecutive patients older than 75 years who underwent any cardiac surgical procedure. Microplegia was used in 144 patients compared to 151 patients who had the standard 4:1 blood cardioplegia. Logistic regression analysis was used for propensity matching to balance the differences between the two groups. The microplegia group included more females and sicker patients as indicated by higher Parsonnet scores. There were differences in the pump time, aortic cross-clamp time, procedure type and surgeons between the two groups. These differences were balanced using the propensity matching. In-hospital mortality, acute renal injury and confusion were higher in the microplegia group (17%, 34%, 35%, respectively) compared to the standard 4:1 cardioplegia group (9%, 23%, 24%, respectively) ( P =0.04, 0.04, 0.04, respectively). These differences were not statistically significant after propensity matching. These results demonstrate that the use of microplegia is safe in patients older than 75 years who are undergoing cardiac surgery and results in similar in-hospital morbidity and mortality to the standard 4:1 blood cardioplegia.
Key Words: Microplegia; Cardioplegia; Myocardial protection; Morbidity; Mortality
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