Survival mediation analysis with the death-truncated mediator: The completeness of the survival mediation parameter

In medical research, the development of mediation analysis with a survival outcome has facilitated investigation into causal mechanisms. However, studies have not discussed the death-truncation problem for mediators, the problem being that conventional mediation parameters cannot be well-defined in the presence of a truncated mediator. In the present study, we systematically defined the completeness of causal effects to uncover the gap, in conventional causal definitions, between the survival and nonsurvival settings. We proposed three approaches to redefining the natural direct and indirect effects, which are generalized forms of the conventional causal effects for survival outcomes. Furthermore, we developed three statistical methods for the binary outcome of the survival status and formulated a Cox model for survival time. We performed simulations to demonstrate that the proposed methods are unbiased and robust. We also applied the proposed method to explore the effect of hepatitis C virus infection on mortality, as mediated through hepatitis B viral load

Propfan Test Assessment (PTA)

The objectives of the Propfan Test Assessment (PTA) Program were to validate in flight the structural integrity of large-scale propfan blades and to measure noise characteristics of the propfan in both near and far fields. All program objectives were met or exceeded, on schedule and under budget. A Gulfstream Aerospace Corporation GII aircraft was modified to provide a testbed for the 2.74m (9 ft) diameter Hamilton Standard SR-7 propfan which was driven by a 4475 kw (600 shp) turboshaft engine mounted on the left-hand wing of the aircraft. Flight research tests were performed for 20 combinations of speed and altitude within a flight envelope that extended to Mach numbers of 0.85 and altitudes of 12,192m (40,000 ft). Propfan blade stress, near-field noise on aircraft surfaces, and cabin noise were recorded. Primary variables were propfan power and tip speed, and the nacelle tilt angle. Extensive low altitude far-field noise tests were made to measure flyover and sideline noise and the lateral attenuation of noise. In coopertion with the FAA, tests were also made of flyover noise for the aircraft at 6100m (20,000 ft) and 10,668m (35,000 ft). A final series of tests were flown to evaluate an advanced cabin wall noise treatment that was produced under a separate program by NASA-Langley Research Center

Advanced turboprop testbed systems study. Volume 1: Testbed program objectives and priorities, drive system and aircraft design studies, evaluation and recommendations and wind tunnel test plans

The establishment of propfan technology readiness was determined and candidate drive systems for propfan application were identified. Candidate testbed aircraft were investigated for testbed aircraft suitability and four aircraft selected as possible propfan testbed vehicles. An evaluation of the four candidates was performed and the Boeing KC-135A and the Gulfstream American Gulfstream II recommended as the most suitable aircraft for test application. Conceptual designs of the two recommended aircraft were performed and cost and schedule data for the entire testbed program were generated. The program total cost was estimated and a wind tunnel program cost and schedule is generated in support of the testbed program

Propfan Test Assessment (PTA): Flight test report

The Propfan Test Assessment (PTA) aircraft was flown to obtain glade stress and noise data for a 2.74m (9 ft.) diameter single rotation propfan. Tests were performed at Mach numbers to 0.85 and altitudes to 12,192m (40,000 ft.). The propfan was well-behaved structurally over the entire flight envelope, demonstrating that the blade design technology was completely adequate. Noise data were characterized by strong signals at blade passage frequency and up to 10 harmonics. Cabin noise was not so high as to preclude attainment of comfortable levels with suitable wall treatment. Community noise was not excessive

Characteristics of phonon transmission across epitaxial interfaces: a lattice dynamic study

Phonon transmission across epitaxial interfaces is studied within the lattice dynamic approach. The transmission shows weak dependence on frequency for the lattice wave with a fixed angle of incidence. The dependence on azimuth angle is found to be related to the symmetry of the boundary interface. The transmission varies smoothly with the change of the incident angle. A critical angle of incidence exists when the phonon is incident from the side with large group velocities to the side with low ones. No significant mode conversion is observed among different acoustic wave branches at the interface, except when the incident angle is near the critical value. Our theoretical result of the Kapitza conductance $G_{K}$ across the Si-Ge (100) interface at temperature $T=200$K is 4.6\times10^{8} {\rm WK}^{-1}{\rmm}^{-2}. A scaling law $G_K \propto T^{2.87}$ at low temperature is also reported. Based on the features of transmission obtained within lattice dynamic approach, we propose a simplified formula for thermal conductanceacross the epitaxial interface. A reasonable consistency is found between the calculated values and the experimentally measured ones.Comment: 8 figure

The measurement of low pay in the UK labour force survey

Consideration of the National Minimum Wage requires estimates of the distribution of hourly pay. The UK Labour Force Survey (LFS) is a key source of such estimates. The approach most frequently adopted by researchers has been to measure hourly earnings from several questions on pay and hours. The Office for National Statistics is now applying a new approach, based on an alternative more direct measurement introduced in March 1999. These two measures do not produce identical values and this paper investigates sources of discrepancies and concludes that the new variable is more accurate. The difficulty with using the new variable is that it is only available on a subset of respondents. An approach is developed in which missing values of the new variable are replaced by imputed values. The assumptions underlying this imputation approach and results of applying it to LFS data are presented. The relation to weighting approaches is also discussed

Informed consent and medical ordeal: a qualitative study

Background Informed consent is a mainstay of clinical practice, with both moral and legal force. Material disclosure about extreme treatments, however, is unlikely to convey the full impact of the experience of treatment. Informed consent may be flawed under such cir-cumstances. Aims To compare expressed satisfaction with pre-treatment information to satisfaction af-ter experiencing autologous stem cell transplantation (ASCT) for recurrent lymphoma. Methods A qualitative, narrative-based cohort study has been conducted in a Teaching hospital Bone Marrow Transplant unit at Westmead Hospital, Sydney, Australia. The cohort consisted of ten transplant recipients and nine of their nominated lay carers. The Outcome measure was satisfaction expressed in narrative interviews at the time of transplantation and three months later. We used discourse analytic techniques to examine the narratives. Results Both patients and carers expressed high satisfaction with the information given by individual clinicians and by speakers at a formal Information Day held before transplanta-tion. At the first interview, neither patients nor carers commented much on the forthcom-ing ordeal of chemotherapy and bone marrow ablation, although all patients had under-gone previous chemotherapy. At the second interview, the ordeal dominated the narratives, and retrospective dissatisfaction with information was common. Conclusions This study suggests that information about treatment theories and protocols can be satisfactorily communicated, but personal experience of suffering defies communi-cation. This finding has serious implications for the practices involved in obtaining informed consent and for the very notion of informed consent. KEY WORDS Autologous stem cell transplantation; haematological malignancies; extreme treatment; medical communication; informed consent

Informed consent and medical ordeal: a qualitative study

Background Informed consent is a mainstay of clinical practice, with both moral and legal force. Material disclosure about extreme treatments, however, is unlikely to convey the full impact of the experience of treatment. Informed consent may be flawed under such cir-cumstances. Aims To compare expressed satisfaction with pre-treatment information to satisfaction af-ter experiencing autologous stem cell transplantation (ASCT) for recurrent lymphoma. Methods A qualitative, narrative-based cohort study has been conducted in a Teaching hospital Bone Marrow Transplant unit at Westmead Hospital, Sydney, Australia. The cohort consisted of ten transplant recipients and nine of their nominated lay carers. The Outcome measure was satisfaction expressed in narrative interviews at the time of transplantation and three months later. We used discourse analytic techniques to examine the narratives. Results Both patients and carers expressed high satisfaction with the information given by individual clinicians and by speakers at a formal Information Day held before transplanta-tion. At the first interview, neither patients nor carers commented much on the forthcom-ing ordeal of chemotherapy and bone marrow ablation, although all patients had under-gone previous chemotherapy. At the second interview, the ordeal dominated the narratives, and retrospective dissatisfaction with information was common. Conclusions This study suggests that information about treatment theories and protocols can be satisfactorily communicated, but personal experience of suffering defies communi-cation. This finding has serious implications for the practices involved in obtaining informed consent and for the very notion of informed consent. KEY WORDS Autologous stem cell transplantation; haematological malignancies; extreme treatment; medical communication; informed consent

Geophysics

Contains reports on three research projects