Expected Firm Performance and IPO Price Formation.

This study examines how accounting information influences investors’ evaluations of IPO firms. Specifically, I examine whether a simple financial statement analysis process that provides information about the future prospects of IPO firms is useful in explaining the investor feedback that issuing firms receive during the bookbuilding portion of the IPO process. I find that this information about an IPO firm’s prospects is not fully captured in the price that the underwriter proposes for the offering and that investors use the bookbuilding process to adjust the proposed price to more fully reflect this information. I also show that investors’ use of this accounting information improves the accuracy of IPO pricing. Finally, I show that this information is more likely to be fully impounded into the final offer price when there is greater participation from institutional investors in the bookbuilding process. These findings highlight the value that investors associate with an IPO firm’s accounting information and reveal that the price revision is much more predictable than suggested by the extant literature.PhDBusiness AdministrationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113325/1/bhendrix_1.pd

The Impact of Aging and Estrogen Therapy on Synaptic Mitochondrial Bioenergetics in an Alzheimer\u27s Mouse Model

Mitochondrial dysfunction, such as reductions in ATP production via oxidative phosphorylation, is a recognized pathological symptom of neurodegenerative diseases including Alzheimer\u27s disease (AD). One of the known risk factors for the development of AD is the inheritance of a specific genotype of a lipid transporting protein known as apolipoprotein E (apoE). How apoE contributes to the development and progression of AD is poorly understood. The purpose of this study was to determine if a relationship exists between mitochondrial dysfunction and genetic predisposition to AD via apoE. Mitochondrial bioenergetics and enzymatic activity were investigated in an AD mouse model (apoE KO) and in wild-type (WT) mice. Since AD develops with age, mitochondrial function was studied in both young (4-6 months old) and old (12-22 months old) mice. Additionally, estrogen therapy was utilized as a possible therapeutic to prevent mitochondrial dysfunction. We isolated mitochondria located in nerve cell terminals (synaptosomes) using Percoll gradient centrifugation from WT (C57BL/6J) and apoE KO (Apoetn1Unc) mice. Mitochondria were isolated from the following three treatment groups: mice possessing ovaries injected with vehicle control solution (Sham), ovariectomized mice with vehicle control injection (OVX), and ovariectomized mice with 50 ng/g injection of 17β-estradiol (OVX + E2). Mitochondrial function was evaluated based on oxygen consumption of permeabilized and non-permeabilized synaptosomes and was measured using the OROBOROS Oxygraph-2k at 37°C. Succinate dehydrogenase (SDH) and citrate synthase (CS) activity was also assayed to help elucidate the bioenergetic profile of the isolated synaptosomes. Our results revealed no significant differences in oxygen consumption from intact and permeabilized synaptosomes between Sham and OVX young WT and apoE KO mice. Additionally, no significant differences were detected in SDH and CS activity between young WT and apoE KO mice. However, estrogen treatment dramatically increased oxygen consumption and enzymatic activity in apoE KO for all respiration parameters, whereas, a minimal effect was observed in WT mice. No significant differences in oxygen consumption from permeabilized and intact synaptosomes were detected between young and old OVX and OVX + E2 treated mice, but old Sham mice had significantly higher oxygen consumption rates compared to young Sham mice for most all permeabilized parameters in both WT and apoE KO mice. Estrogen treatment had no effect on mitochondrial respiration in old mice, but estrogen treated old apoE KO mice had significantly higher SDH activity compared to its Sham. Increases in respiration and enzymatic activity prompted investigation of mitochondrial quantity via Western blot. We used the voltage dependent-anion-channel (VDAC) as a mitochondrial quantity marker. The results revealed that estrogen treatment increased mitochondrial quantity in estrogen treated young apoE KO and old Sham mice. We speculate that increases in mitochondrial quantity in young apoE KO mice and old Sham mice were due to estrogen and reactive oxygen species (ROS) induced mitochondrial biogenesis, respectively. Our data suggests that predisposition of AD via apoE inheritance is not an underlying source of mitochondrial abnormalities; however, the effectiveness of estrogen as a neuro-therapeutic may be dependent upon an individual\u27s apoE genotype, as well as, their age

The Impact of Aging and Estrogen Therapy on Synaptic Mitochondrial Bioenergetics in an Alzheimer\u27s Mouse Model

Mitochondrial dysfunction, such as reductions in ATP production via oxidative phosphorylation, is a recognized pathological symptom of neurodegenerative diseases including Alzheimer\u27s disease (AD). One of the known risk factors for the development of AD is the inheritance of a specific genotype of a lipid transporting protein known as apolipoprotein E (apoE). How apoE contributes to the development and progression of AD is poorly understood. The purpose of this study was to determine if a relationship exists between mitochondrial dysfunction and genetic predisposition to AD via apoE. Mitochondrial bioenergetics and enzymatic activity were investigated in an AD mouse model (apoE KO) and in wild-type (WT) mice. Since AD develops with age, mitochondrial function was studied in both young (4-6 months old) and old (12-22 months old) mice. Additionally, estrogen therapy was utilized as a possible therapeutic to prevent mitochondrial dysfunction. We isolated mitochondria located in nerve cell terminals (synaptosomes) using Percoll gradient centrifugation from WT (C57BL/6J) and apoE KO (Apoetn1Unc) mice. Mitochondria were isolated from the following three treatment groups: mice possessing ovaries injected with vehicle control solution (Sham), ovariectomized mice with vehicle control injection (OVX), and ovariectomized mice with 50 ng/g injection of 17β-estradiol (OVX + E2). Mitochondrial function was evaluated based on oxygen consumption of permeabilized and non-permeabilized synaptosomes and was measured using the OROBOROS Oxygraph-2k at 37°C. Succinate dehydrogenase (SDH) and citrate synthase (CS) activity was also assayed to help elucidate the bioenergetic profile of the isolated synaptosomes. Our results revealed no significant differences in oxygen consumption from intact and permeabilized synaptosomes between Sham and OVX young WT and apoE KO mice. Additionally, no significant differences were detected in SDH and CS activity between young WT and apoE KO mice. However, estrogen treatment dramatically increased oxygen consumption and enzymatic activity in apoE KO for all respiration parameters, whereas, a minimal effect was observed in WT mice. No significant differences in oxygen consumption from permeabilized and intact synaptosomes were detected between young and old OVX and OVX + E2 treated mice, but old Sham mice had significantly higher oxygen consumption rates compared to young Sham mice for most all permeabilized parameters in both WT and apoE KO mice. Estrogen treatment had no effect on mitochondrial respiration in old mice, but estrogen treated old apoE KO mice had significantly higher SDH activity compared to its Sham. Increases in respiration and enzymatic activity prompted investigation of mitochondrial quantity via Western blot. We used the voltage dependent-anion-channel (VDAC) as a mitochondrial quantity marker. The results revealed that estrogen treatment increased mitochondrial quantity in estrogen treated young apoE KO and old Sham mice. We speculate that increases in mitochondrial quantity in young apoE KO mice and old Sham mice were due to estrogen and reactive oxygen species (ROS) induced mitochondrial biogenesis, respectively. Our data suggests that predisposition of AD via apoE inheritance is not an underlying source of mitochondrial abnormalities; however, the effectiveness of estrogen as a neuro-therapeutic may be dependent upon an individual\u27s apoE genotype, as well as, their age

Development of an Open Rotor Cycle Model in NPSS Using a Multi-Design Point Approach

NASA's Environmentally Responsible Aviation Project and Subsonic Fixed Wing Project are focused on developing concepts and technologies which may enable dramatic reductions to the environmental impact of future generation subsonic aircraft (Refs. 1 and 2). The open rotor concept (also referred to as the Unducted Fan or advanced turboprop) may allow the achievement of this objective by reducing engine emissions and fuel consumption. To evaluate its potential impact, an open rotor cycle modeling capability is needed. This paper presents the initial development of an open rotor cycle model in the Numerical Propulsion System Simulation (NPSS) computer program which can then be used to evaluate the potential benefit of this engine. The development of this open rotor model necessitated addressing two modeling needs within NPSS. First, a method for evaluating the performance of counter-rotating propellers was needed. Therefore, a new counter-rotating propeller NPSS component was created. This component uses propeller performance maps developed from historic counter-rotating propeller experiments to determine the thrust delivered and power required. Second, several methods for modeling a counter-rotating power turbine within NPSS were explored. These techniques used several combinations of turbine components within NPSS to provide the necessary power to the propellers. Ultimately, a single turbine component with a conventional turbine map was selected. Using these modeling enhancements, an open rotor cycle model was developed in NPSS using a multi-design point approach. The multi-design point (MDP) approach improves the engine cycle analysis process by making it easier to properly size the engine to meet a variety of thrust targets throughout the flight envelope. A number of design points are considered including an aerodynamic design point, sea-level static, takeoff and top of climb. The development of this MDP model was also enabled by the selection of a simple power management scheme which schedules propeller blade angles with the freestream Mach number. Finally, sample open rotor performance results and areas for further model improvements are presented

Meanline Analysis of Turbines with Choked Flow in the Object-Oriented Turbomachinery Analysis Code

The prediction of turbomachinery performance characteristics is an important part of the conceptual aircraft engine design process. During this phase, the designer must examine the effects of a large number of turbomachinery design parameters to determine their impact on overall engine performance and weight. The lack of detailed design information available in this phase necessitates the use of simpler meanline and streamline methods to determine the turbomachinery geometry characteristics and provide performance estimates prior to more detailed CFD (Computational Fluid Dynamics) analyses. While a number of analysis codes have been developed for this purpose, most are written in outdated software languages and may be difficult or impossible to apply to new, unconventional designs. The Object-Oriented Turbomachinery Analysis Code (OTAC) is currently being developed at NASA Glenn Research Center to provide a flexible meanline and streamline analysis capability in a modern object-oriented language. During the development and validation of OTAC, a limitation was identified in the code's ability to analyze and converge turbines as the flow approached choking. This paper describes a series of changes which can be made to typical OTAC turbine meanline models to enable the assessment of choked flow up to limit load conditions. Results produced with this revised model setup are provided in the form of turbine performance maps and are compared to published maps

Commercial Supersonic Variable Cycle Engine Modeling with Application of Mixer-Ejector Nozzles

No abstract availabl

Electrical Cable Design for Urban Air Mobility Aircraft

Urban Air Mobility (UAM) describes a new type of aviation focused on efficient flight within urban areas for moving people and goods. There are many different configurations of UAM vehicles, but they generally use an electric motor driving a propeller or ducted fan powered by batteries or a hybrid electric power generation system. Transmission cables are used to move energy from the storage or generation system to the electric motors. Though terrestrial power transmission cables are well established technology, aviation applications bring a whole host of new design challenges that are not typical considerations in terrestrial applications. Aircraft power transmission cable designs must compromise between resistance-per-length, weight-per-length, volume constraints, and other essential qualities. In this paper we use a multidisciplinary design optimization to explore the sensitivity of these qualities to a representative tiltwing turboelectric UAM aircraft concept. This is performed by coupling propulsion and thermal models for a given mission criteria. Results presented indicate that decreasing cable weight at the expense of increasing cable volume or cooling demand is effective at minimizing maximum takeoff weight (MTO). These findings indicate that subsystem designers should update their modeling approach in order to contribute to system-level optimality for highly-coupled novel aircraft. Mobility (UAM) vehicles have the potential to change urban and intra-urban transport in new and interesting ways. In a series of two papers Johnson et al.1 and Silva et al.2 presented four reference vehicle configurations that could service different niches in the UAM aviation category. Of those, this paper focuses on the Vertical Take-off and Landing (VTOL) tiltwing configuration shown in Figure 1. This configuration uses a turboelectric power system, feeding power from a turbo-generator through a system of transmission cables to four motors spinning large propellers on the wings. Previous work on electric cable subsystems leaves much yet to be explored, especially in the realm of subsystem coupling. Several aircraft optimization studies1, 3, 4 only considered aircraft electrical cable weight and ignored thermal effects. Electric and hybrid-electric aircraft studies by Mueller et al.5 and Hoelzen et al.6 selected a cable material but did not investigate alternative materials. Advanced cable materials have been examined by a number of authors: Alvarenga7 examined carbon nanotube (CNT) conductors for low-power applications. De Groh8, 9 examined CNT conductors for motor winding applications. Behabtu et al.,10 and Zhao et al.11 examined CNT conductors for a general applications. There were some studies that examined the thermal effects of cables but they did not allow the cable material to change; El-Kady12 optimized ground-cable insulation and cooling subject constraints. Vratny13 selected cable material based on vehicle power demand, and required resulting cable heat to be dissipated by the Thermal Management System (TMS). None of these previous studies allowed for the selection of the cable material based on a system level optimization goal. Instead, they focused on sub-system optimality such as minimum weight, which comes at the expense of incurring additional costs for other subsystems. Dama14 selected overhead transmission line materials using a weighting function and thermal constraints. However, that work was not coupled with any aircraft subsystems like a TMS. The traditional aircraft design approach, which relies on assembling groups of optimal subsystems, breaks down when considering novel aircraft concepts like the tiltwing vehicle. In a large part, this is because novel concepts have a much higher degree of interaction or coupling between subsystems. For example, when a cable creates heat, this heat needs to be dissipated by the TMS, which needs power supplied by the turbine, and delivering the power creates more heat. The cable, the TMS, and the turbine are all coupled. A change to one subsystem will affect all the other subsystems, much to the consternation of subsystem design experts. Multidisciplinary optimization is the design approach that can address these challenges. However, to fully take advantage of this, we must change the way we think about subsystem design. Specifically, we must move away from point design, and focus on creating solution spaces. The work presented in this paper uses the multidisciplinary optimization approach with aircraft level models to study the system-level sensitivity of cable traits: weight-per-length and resistance-per-length. Additionally, we examined the effects of vehicle imposed volume constraints on these traits. This is useful for three purposes: (1) to demonstrate a framework that can perform a coupled analysis between the aircraft thermal and propulsion systems, (2) to provide a method by which future cable designs can be evaluated against each other given a system-level design goal, (3) to provide insight into what cable properties may be promising for future research. This last element is explored given the caveat that the models contained in this analysis do not represent high-fidelity systems. Thus, while we can demonstrate coupling in between systems, the exact system-level sensitivity to a given parameter may change if a subsystem model or the assumptions governing that model change. The organization of this paper is as follows, in Sec II we outline a method to combine the VTOL vehicle design and cable information in order to produce cables sensitivity studies. Results analysis and discussion are contained in Sec III. Conclusions are presented in Sec IV

A Multidisciplinary Approach to Mixer-Ejector Analysis and Design

The design of an engine for a civil supersonic aircraft presents a difficult multidisciplinary problem to propulsion system engineers. There are numerous competing requirements for the engine, such as to be efficient during cruise while yet quiet enough at takeoff to meet airport noise regulations. The use of mixer-ejector nozzles presents one possible solution to this challenge. However, designing a mixer-ejector which will successfully address both of these concerns is a difficult proposition. Presented in this paper is an integrated multidisciplinary approach to the analysis and design of these systems. A process that uses several low-fidelity tools to evaluate both the performance and acoustics of mixer-ejectors nozzles is described. This process is further expanded to include system-level modeling of engines and aircraft to determine the effects on mission performance and noise near airports. The overall process is developed in the OpenMDAO framework currently being developed by NASA. From the developed process, sample results are given for a notional mixer-ejector design, thereby demonstrating the capabilities of the method

Influence network linkages across implementation strategy conditions in a randomized controlled trial of two strategies for scaling up evidence-based practices in public youth-serving systems.

BackgroundGiven the importance of influence networks in the implementation of evidence-based practices and interventions, it is unclear whether such networks continue to operate as sources of information and advice when they are segmented and disrupted by randomization to different implementation strategy conditions. The present study examines the linkages across implementation strategy conditions of social influence networks of leaders of youth-serving systems in 12 California counties participating in a randomized controlled trial of community development teams (CDTs) to scale up use of an evidence-based practice.MethodsSemi-structured interviews were conducted with 38 directors, assistant directors, and program managers of county probation, mental health, and child welfare departments. A web-based survey collected additional quantitative data on information and advice networks of study participants. A mixed-methods approach to data analysis was used to create a sociometric data set (n = 176) to examine linkages between treatment and standard conditions.ResultsOf those network members who were affiliated with a county (n = 137), only 6 (4.4%) were directly connected to a member of the opposite implementation strategy condition; 19 (13.9%) were connected by two steps or fewer to a member of the opposite implementation strategy condition; 64 (46.7%) were connected by three or fewer steps to a member of the opposite implementation strategy condition. Most of the indirect steps between individuals who were in different implementation strategy conditions were connections involving a third non-county organizational entity that had an important role in the trial in keeping the implementation strategy conditions separate. When these entities were excluded, the CDT network exhibited fewer components and significantly higher betweenness centralization than did the standard condition network.ConclusionAlthough the integrity of the RCT in this instance was not compromised by study participant influence networks, RCT designs should consider how influence networks may extend beyond boundaries established by the randomization process in implementation studies.Trial registrationNCT00880126