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We extend the Annually Recalculated Virtual Annuity (ARVA) spending rule for retirement savings decumulation (Waring and Siegel (2015) Financial Analysts Journal, 71(1), 91–107) to include a cap and a floor on withdrawals. With a minimum withdrawal constraint, the ARVA strategy runs the risk of depleting the investment portfolio. We determine the dynamic asset allocation strategy which maximizes a weighted combination of expected total withdrawals (EW) and expected shortfall (ES), defined as the average of the worst 5% of the outcomes of real terminal wealth. We compare the performance of our dynamic strategy to simpler alternatives which maintain constant asset allocation weights over time accompanied by either our same modified ARVA spending rule or withdrawals that are constant over time in real terms. Tests are carried out using both a parametric model of historical asset returns as well as bootstrap resampling of historical data. Consistent with previous literature that has used different measures of reward and risk than EW and ES, we find that allowing some variability in withdrawals leads to large improvements in efficiency. However, unlike the prior literature, we also demonstrate that further significant enhancements are possible through incorporating a dynamic asset allocation strategy rather than simply keeping asset allocation weights constant throughout retirement.
The problem of how to evaluate investments in airports has now been studied for over 50 years. This paper analyzes the use of different methods like cost–benefit analysis (CBA), economic impact analysis (EIA), and computable general equilibrium (CGE) models to address the question. It assesses the strength and weaknesses of each method, and it discusses which methods have been used in different countries. The paper argues that the CBA approach and the newer CGE modeling approach address the policy issue well and that both methods are appropriate, although improvements are possible, especially in the newer aspects of evaluation. Furthermore, more data intensive CGE models are able to analyze broader aspects of the evaluation question for which CBA has had difficulty. EIA does not address the problem satisfactorily, and it misleads air transport policy. But this evaluation contrasts sharply with practice. EIA has been extensively used to decide on airport investment. CGE approaches are very promising, though further work is needed for them to reach their full potential. This paper pays particular attention to the relationship between CBA and CGE in airport investment evaluation and also the possible role of wider economic benefits (WEBs) of aviation in evaluation.
We determine the optimal asset allocation to bonds and stocks using an annually recalculated virtual annuity (ARVA) spending rule for DC pension plan decumulation. Our objective function minimizes downside withdrawal variability for a given fixed value of total expected withdrawals. The optimal asset allocation is found using optimal stochastic control methods. We formulate the strategy as a solution to a Hamilton–Jacobi–Bellman (HJB) Partial Integro Differential Equation (PIDE). We impose realistic constraints on the controls (no-shorting, no-leverage, discrete rebalancing) and solve the HJB PIDEs numerically. Compared to a fixed-weight strategy which has the same expected total withdrawals, the optimal strategy has a much smaller average allocation to stocks and tends to de-risk rapidly over time. This conclusion holds in the case of a parametric model based on historical data and also in a bootstrapped market based on the historical data.
The Family Group Conference (FGC) is an approach to partnership working which brings together service users, their support network and care professionals in a family-led decision making forum. Evidence, though limited, indicates that that FGC can enhance outcomes for service providers and their users. This study aimed to evaluate the impact of the pilot FGC service, delivered to people with dementia and their families, in terms of the experience of care provision by families and care professionals involved in the project.
Focus group interviews were conducted with families and professionals participating in the pilot intervention.
FGC was perceived as having the potential to positively impact service users, their families, service providers and the wider culture of care. However, despite an overall positive evaluation the participants identified a number of challenges related to service implementation. Both the opportunities and challenges identified in this study are discussed in the context of the existing international evidence base.
This study contributes to a better understanding of the applicability of FGC as a strategy to support people with dementia and their families. Although promising in terms of potential outcomes for service users and providers, FGC presents challenges which need to be carefully managed in order to secure maximum benefit to all parties.
This paper estimates the potential economic effects on the Australian tourism industry from the introduction of an economy wide carbon tax to be introduced in July 2012. The manner in which the tax is expected to work is examined together with a discussion of some concerns that have been raised by the tourism industry regarding its impacts on Australia's destination competitiveness, industry profitability and employment. Dynamic computable general equilibrium (CGE) modelling projects that the tax will lead to changes in key macroeconomic variables, reducing growth in real GDP, real consumption and employment. The simulation results also indicate that while some tourism industries in Australia will gain from the tax, most will experience contractions in output relative to baseline values in line with a general shrinkage of the tourism sector as a whole. In the light of the modelling simulations, the paper concludes with an assessment of the validity of the main stakeholder concerns regarding the implications of the tax for the Australian tourism industry.
Chemoradiotherapy followed by monthly temozolomide (TMZ) is the standard of care for patients with glioblastoma multiforme (GBM). Case reports have identified GBM patients who experienced transient radiological deterioration after concurrent chemoradiotherapy which stabilized or resolved after additional cycles of adjuvant TMZ, a phenomenon known as radiographic pseudoprogression. Little is known about the natural history of radiographic pseudoprogression.
We retrospectively evaluated the incidence of radiographic pseudoprogression in a population-based cohort of GBM patients and determined its relationship with outcome and MGMT promoter methylation status.
Out of 43 evaluable patients, 25 (58%) exhibited radiographic progression on the first MRI after concurrent treatment. Twenty of these went on to receive adjuvant TMZ, and subsequent investigation demonstrated radiographic pseudoprogression in 10 cases (50%). Median survival (MS) was better in patients with pseudoprogression (MS 14.5 months) compared to those with true radiologic progression (MS 9.1 months, p=0.025). The MS of patients with pseudoprogression was similar to those who stabilized/responded during concurrent treatment (p=0.31). Neither the extent of the initial resection nor dexamethasone dosing was associated with pseudoprogression.
These data suggest that physicians should continue adjuvant TMZ in GBM patients when early MRI scans show evidence of progression following concurrent chemoradiotherapy, as up to 50% of these patients will experience radiologic stability or improvement in subsequent treatment cycles.
The purpose of this study was to determine incidence, survival rate, and prognostic factors as well as the frequency of Collins’ Law Violators (CLVs) in an unselected population of medulloblastoma patients. Collins’ Law dictates that ’cure’ of a child with a tumor occurs after a period that includes the child’s age at diagnosis plus 9 months.
Using the Alberta Cancer Registry a population-based review identified 49 patients with medulloblastoma (19 adults, 30 children) diagnosed from 1975-96. Pathology was reviewed in all cases. All patients had surgical resection, followed by radiotherapy in 47 patients and chemotherapy in 17.
The overall 5-year survival was 50%. There was a trend for the extent of resection to be associated with a longer survival (Long rank test, p< 0.06) but this was not significant. Tumor recurrence occurred a median of 22.4 months (range, 6.4-192.3) after diagnosis and median survival after recurrence was 9.3 months (range, 0.4-64.9). The survival curve did not appear to plateau but was affected by tumor-related deaths in 3 (21.4%) of the 21 long-term survivors diagnosed in childhood. These three patients had recurrences a mean of 11.7 years after diagnosis and are designated as CLVs.
The survival rate in an unselected population of patients with medulloblastoma is poor. Aggressive resection of the tumors prolongs survival. The Collins’ Law Violators were relatively common and we suggest this concept be abandoned in medulloblastoma.
Leptomeningeal disease (LMD) is a late complication of malignant glioma, mostly of glioblastoma, that usually responds poorly to treatment and is rapidly fatal. A long surviving case led us to review our experience with LMD in patients with oligodendrogliomas.
A 15-year retrospective chart review was performed. Patients with both oligodendroglial tumors and LMD were identified. A single neuro-pathologist reviewed all histological sections, a single neuro-radiologist reviewed all available images and lp/19q status was assessed.
Seven out of 145 patients with oligodendroglioma were diagnosed with LMD. Six were male. Median age at tumor diagnosis was 41 years (range, 28-50). None had radiographic or pathological evidence of leptomeningeal or subependymal tumor at initial diagnosis. Most patients had pure anaplastic oligodendrogliomas (4/7); 6/7 had 1p/19q co-deletion. The median time to first relapse was 41 months (range, 19-127). The median time to LMD was 76 months (range, 19-151) from initial diagnosis and 28 months (range, 0-36) from first relapse, respectively. Leptomeningeal disease treatments included spinal radiation and intrathecal and systemic chemotherapy. After progression, some patients with LMD remained stable clinically. The median survival from initial diagnosis was 104 months (range, 19-183) and from LMD diagnosis was 32 months (range, 2-43).
Leptomeningeal disease is a complication of oligodendroglioma that may occur preferentially in long surviving patients with 1p/19q co-deletion. Leptomeningeal disease in patients with oligodendrogliomas appears to be relatively indolent which may have implications for their treatment and be related to 1p/19q status.
We conducted a clinical trial to determine if prophylactic anticonvulsants in brain tumour patients (without prior seizures) reduced seizure frequency. We stopped accrual at 100 patients on the basis of the interim analysis.
One hundred newly diagnosed brain tumour patients received anticonvulsants (AC Group) or not (No AC Group) in this prospective randomized unblinded study. Sixty patients had metastatic, and 40 had primary brain tumours. Forty-six (46%) patients were randomized to the AC Group and 54 (54%) to the No AC Group. Median follow-up was 5.44 months (range 0.13 -30.1 months).
Seizures occurred in 26 (26%) patients, eleven in the AC Group and 15 in the No AC Group. Seizure-free survivals were not different; at three months 87% of the AC Group and 90% of the No AC Group were seizure-free (log rank test, p=0.98). Seventy patients died (unrelated to seizures) and survival rates were equivalent in both groups (median survival = 6.8 months versus 5.6 months, respectively; log rank test, p=0.50). We then terminated accrual at 100 patients because seizure and survival rates were much lower than expected; we would need ≥ 900 patients to have a suitably powered study.
These data should be used by individuals contemplating a clinical trial to determine if prophylactic anticonvulsants are effective in subsets of brain tumour patients (e.g. only anaplastic astrocytomas). When taken together with the results of a similar randomized trial, prophylactic anticonvulsants are unlikely to be effective or useful in brain tumour patients who have not had a seizure.
The effect of TiN Anti-Reflective Coating (ARC) layer capping of metal, in a multilevel interconnect system, on the reliability of the tungsten (W) plug has been investigated. EM study on Kelvin via showed that the thin TiN ARC Kelvin via lifetime exhibited a reduction of one order of magnitude compared to that of the thicker ARC thickness (1000Å) when they were stressed in a certain direction. A new testing technique, used to investigate the effect of ARC thickness on the W-plug electromigration (EM) performance, is discussed. The simulation results of current distribution confirmed the proposed failure model of EM performance of W-plug via with different ARC thickness.
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