Suspending test masses in terrestrial millihertz gravitational-wave detectors: a case study with a magnetic assisted torsion pendulum

Current terrestrial gravitational-wave detectors operate at frequencies above 10 Hz. There is strong astrophysical motivation to construct low-frequency gravitational-wave detectors capable of observing 10 mHz - 10Hz signals. While space-based detectors provide one means of achieving this end, one may also consider terretrial detectors. However, there are numerous technological challenges. In particular, it is difficult to isolate test masses so that they are both seismically isolated and freely falling under the influence of gravity at millihertz frequencies. We investigate the challenges of low-frequency suspension in a hypothetical terrestrial detector. As a case study, we consider a Magnetically Assisted Gravitational-wave Pendulum Intorsion (MAGPI) suspension design. We construct a noise budget to estimate some of the required specifications. In doing so, we identify what are likely to be a number of generic limiting noise sources for terrestrial millihertz gravitational-wave suspension systems (as well as some peculiar to the MAGPI design). We highlight significant experimental challenges in order to argue that the development of millihertz suspensions will be a daunting task. Any system that relies on magnets faces even greater challenges. Entirely mechanical designs such as Zollner pendulums may provide the best path forward.Comment: 6 pages, 4 figure

When is price discrimination profitable?

We analyze a model of a quality-constrained monopolist's product line decision that encompasses a variety of important examples of second-degree price discrimination, including intertemporal price discrimination, coupons, advance purchase discounts, versioning of information goods, and damaged goods. We derive necessary and sufficient conditions for price discrimination to be profitable that generalize existing results in the literature. Specifically, we show that when a continuum of product qualities are feasible, price discrimination is profitable if and only if the ratio of the marginal social value from an increase in quality to the total social value of the good is increasing in consumers' willingness to pay. Unlike third-degree price discrimination, we show that second-degree price discrimination may result in a Pareto improvement. However, in general the welfare effects are ambiguous

Semiclassical Gravity in the Far Field Limit of Stars, Black Holes, and Wormholes

Semiclassical gravity is investigated in a large class of asymptotically flat, static, spherically symmetric spacetimes including those containing static stars, black holes, and wormholes. Specifically the stress-energy tensors of massless free spin 0 and spin 1/2 fields are computed to leading order in the asymptotic regions of these spacetimes. This is done for spin 0 fields in Schwarzschild spacetime using a WKB approximation. It is done numerically for the spin 1/2 field in Schwarzschild, extreme Reissner-Nordstrom, and various wormhole spacetimes. And it is done by finding analytic solutions to the leading order mode equations in a large class of asymptotically flat static spherically symmetric spacetimes. Agreement is shown between these various computational methods. It is found that for all of the spacetimes considered, the energy density and pressure in the asymptotic region are proportional to 1/r^5 to leading order. Furthermore, for the spin 1/2 field and the conformally coupled scalar field, the stress-energy tensor depends only on the leading order geometry in the far field limit. This is also true for the minimally coupled scalar field for spacetimes containing either a static star or a black hole, but not for spacetimes containing a wormhole.Comment: 43 pages, 2 figures. Reference added, minor changes, PRD versio

How Sales Taxes Affect Customer and Firm Behavior: The Role of Search on the Internet

When a multichannel retailer opens its first retail store in a state, the firm is obligated to collect sales taxes on all Internet and catalog orders shipped to that state. This article assesses how opening a store affects Internet and catalog demand. The authors analyze purchase behavior among customers who live far from the retail store but must now pay sales taxes on catalog and Internet purchases. A comparable group of customers in a neighboring state serves as a control. The results show that Internet sales decrease significantly, but catalog sales are unaffected. Further investigation indicates that the difference in these outcomes is partly attributable to the ease with which customers can search for lower prices at competing retailers. The authors extend the analysis to a panel of multichannel firms and show that retailers that earn a large proportion of their revenue from direct channels avoid opening a first store in high-tax states. They conclude that current U.S. sales taxes laws have significant effects on both customer and firm behavior

LGBTQ Training for Aquatic Employees: Impact on Attitudes and Professional Competencies

This study examined the impact of a LGBTQ diversity training on the attitudes and professional competencies of aquatic employees within a campus recreational sports setting. While diversity training is often discussed as a key component of inclusive aquatic programming, little empirical research examining the outcomes associated with such trainings exists. As such, members of the research team developed, implemented, and evaluated a four-month long training program consisting of one in-person training session and monthly inclusion handouts discussing issues related to the inclusion of LGBTQ participants. A comparative quantitative research design was used to measure employee’s attitudes towards the LGBTQ population and inclusive-recreational sports aquatic professional competencies for both individuals who underwent the training and a control group of employees who did not participate in the training. Results indicate initial support for this training initiative with those who attended the training scoring higher on average in both attitudinal and competency-based measures

Evaluation of a Single Nucleotide Polymorphism Baseline for Genetic Stock Identification of Chinook Salmon (Oncorhynchus tshawytscha) in the California Current Large Marine Ecosystem

Chinook Salmon (Oncorhynchus tshawytscha) is an economically and ecologically important species, and populations from the west coast of North America are a major component of fisheries in the North Pacific Ocean. The anadromous life history strategy of this species generates populations (or stocks) that typically are differentiated from neighboring populations. In many cases, it is desirable to discern the stock of origin of an individual fish or the stock composition of a mixed sample to monitor the stock-specific effects of anthropogenic impacts and alter management strategies accordingly. Genetic stock identification (GSI) provides such discrimination, and we describe here a novel GSI baseline composed of genotypes from more than 8000 individual fish from 69 distinct populations at 96 single nucleotide polymorphism (SNP) loci. The populations included in this baseline represent the likely sources for more than 99% of the salmon encountered in ocean fisheries of California and Oregon. This new genetic baseline permits GSI with the use of rapid and cost-effective SNP genotyping, and power analyses indicate that it provides very accurate identification of important stocks of Chinook Salmon. In an ocean fishery sample, GSI assignments of more than 1000 fish, with our baseline, were highly concordant (98.95%) at the reporting unit level with information from the physical tags recovered from the same fish. This SNP baseline represents an important advance in the technologies available to managers and researchers of this species

Factores preditivos da formação de aderências pleurais e sucesso da pleurodese nos doentes com derrame pleural

RESUMO: As aderências pleurais podem complicar a realização da pleurodese por toracoscopia. Os autores decidiram realizar este estudo para determinar os factores preditivos da formação e extensão das aderências pleurais e do sucesso da pleurodese em doentes submetidos a toracoscopia e talcagem.Os doentes submetidos a toracoscopia no Georgetown University Medical Center entre Agosto de 1995 e Março de 2002 foram estudados retrospectivamente. Os autores registaram o n.° de toracenteses, a duração do derrame, a malignidade, a origem doença subjacente, a existência de irradiação torácica, a presença e extensão das aderências pleurais e o sucesso da pleurodese. Foram estudados 89 doentes que tinham todos estes dados registados.Numa análise global, só os derrames pleurais que tinham uma duração superior a 5 meses têm um valor preditivo na formação das aderências (p=0,037) e extensão das mesmas (p=0,038). No grupo dos derrames pleurais malignos com uma duração superior a 5 meses este aspecto também tem um valor preditivo na formação (p=0,020) e extensão (p=0,037) das aderências. No grupo particular dos derrames pleurais secundários ao cancro da mama, a duração superior a 5 meses também tem um valor preditivo na formação (p=0,008) e extensão (p=0,011) das aderências pleurais.A regressão estatística determinou que a duração dos derrames superior a 5 meses é neste estudo o único factor preditivo na formação das aderências pleurais e que não existem factores preditivos do sucesso da pleurodese. A duração do derrame pleural, independentemente da sua etiologia, está associada à formação de espessas aderências pleurais, particularmente naqueles que tem uma duração superior a 5 meses. COMENTÁRIO: Nos EUA, 1,5 a 2 milhões de doentes por ano tem um derrame pleural. Cerca de 1/3 são secundários a insuficiência cardíaca e 20% estão relacionados com pneumonias bacterianas. Quinze a 40% são derrames pleurais malignos e, destes, cerca de 30% a 40% são secundários ao cancro do pulmão e 25% ao cancro da mama.A rentabilidade da citologia do líquido pleural (50% a70%) e das biópsias pleurais (39% a 75%) não é satisfatória. Estes factos levam a considerar a toracoscopia o exame indicado nos derrames pleurais sem diagnóstico, pois permite a visualização directa das superfícies pleurais e a realização das biópsias directamente. A toracoscopia permite também realizar a insuflação de talco e a pleurodese.A presença de aderências pleurais dificulta a realização da toracoscopia. A efectividade da pleurodese é diminuída porque as aderências cobrem parcialmente a pleura visceral e a pleura parietal, dificultando a sua aderência.A referência na literatura que a produção de citocinas inflamatórias, a subsequente formação de fibrina e a eventual formação de aderências pleurais, estão relacionadas com o número de toracenteses realizadas previamente à toracoscopia e que poderão afectar o êxito da pleurodese, é um dos aspectos que levou os autores a realizarem este estudo.Os resultados contrariaram em parte estes conceitos. Os autores constataram que a formação das aderências e a sua extensão estavam em parte relacionadas com a gravidade da doença subjacente e com a duração do derrame pleural. Não conseguiram estabelecer relação entre número de toracenteses e a formação de aderências assim como com o êxito ou não da pleurodese.Estatiscamente, só conseguiram estabelecer como factor preditivo da formação e da extensão de aderências a duração do derrame pleural quando superior a 5meses. Em relação aos factores preditivos do sucesso da pleurodese, neste estudo os autores não conseguiram estabelecer; contudo, não foram analisados os valores do pH do líquido pleural que é considerado em algumas séries como factor preditivo (pH <7,20 é um sinal de insucesso da pleurodese).A existência de aderências pleurais não é um factor directo de insucesso da pleurodese, mas como dificulta a realização da toracoscopia e da eventual talcagem é sempre um aspecto a considerar no êxito da toracoscopia/talcagem. Palavras-chave: Derrame pleural, aderências pleurais, toracoscopia, talcage