Shield Benefits Research Articles

Cardiovascular Effects of Cosmic Radiation and Microgravity.

Recent spaceflights involving nonprofessional people have opened the doors to the suborbital space tourism business. However, they have also drawn public attention to the safety and hazards associated with space travel. Unfortunately, space travel involves a myriad of health risks for people, ranging from DNA damage caused by radiation exposure to the hemodynamic changes that occur when living in microgravity. In fact, the primary pathogenetic role is attributed to cosmic radiation, since deep space lacks the protective benefit of Earth's magnetic shielding. The second risk factor for space-induced pathologies is microgravity, which may affect organ function and cause a different distribution of fluid inside the human body. Both cosmic radiation and microgravity may lead to the alteration of cellular homeostasis and molecular changes in cell function. These, in turn, might have a direct impact on heart function and structure. The aim of this review is to draw attention to the fact that spaceflights constitute a novel frontier in biomedical research. We summarize the most important clinical and experimental evidence regarding the cardiovascular effects of cosmic radiation and microgravity. Finally, we highlight that unraveling the mechanisms underlying how space radiation and microgravity affect the cardiovascular system is crucial for identifying potential countermeasures and developing effective therapeutic strategies.

The New Strategy of High-Tech Companies – Hidden Sources of Growth

The recent increase in the share of zero-leverage firms is most pronounced in the Software and Services, Hardware Equipment, and Pharmaceutical and Biotechnical industries. The reasons for these industries’ conservative debt policies are not fully disclosed. How companies in technological sectors manage to perform well attracting no debt and loosing debt tax shield benefits is a mystery. This study aims to determine why high-tech firms are less likely to have debt in the capital structure. On the basis of a sample of US-based firms from the RUSSELL 3000 index for 12 years, we show the factors leading to a zero-debt structure. After dividing the sample into high-tech and non-high-tech subsamples, we demonstrate the gap between zero-debt motives for technological and traditional sectors. We show that the common determinants of corporate structure cannot fully explain why high-tech firms choose a zero-debt policy. Testing the possible motives of debt financing avoidance, we find that high-tech firms are more financially constrained than non-high-tech firms. We further show that unconstrained high-tech firms may avoid debt to maintain their financial flexibility. On top of that, managerial entrenchment also adds to the zero-leverage choice of high-tech companies. The study results are helpful for executive management teams and investors since they shed light on the specific style of financing choice for technological firms.

To be or not to be all-equity for firms that eliminate long-term debt

Despite the advantages of debt, a significant number of firms that have an established leverage policy deliberately become all-equity. These firms eliminate a substantial amount of long-term debt as the average firm’s leverage ratio is approximately 30 percent at the year-end prior to debt elimination. Firm-level “shocks” such as CEO turnover and changes in credit ratings cannot explain the dramatic recapitalization decision. Consistent with the tradeoff theory, firms that eliminate debt have lower benefits (less tax shield benefits, agency costs) and higher costs (probability of financial distress, access to capital markets, etc.) of leverage in the three prior years compared to a matched sample. We also find that the factors influencing the decision to eliminate all debt is different from those to significantly reduce leverage or to have very low debt levels. Firms primarily finance the approximately $70 million of average long-term debt eliminated using proceeds from sales of relatively unproductive assets and from equity issues. Interestingly, over half of these firms issue significant amount of new debt within three years of becoming all-equity. Firms with lower liquidity and non-debt tax shields, higher potential overinvestment agency costs, and those that issue equity at the debt elimination year are more likely to relever quickly.

Is Sustainable Investing Driven by Altruism: Evidence from Shocks to Philanthropy

We test the conjecture that sustainable investing (SI) is driven by altruistic motives by examining the responses of charitable giving and SI flows to exogenous shocks to altruism. We find that while philanthropy responds strongly and significantly, SI flows do not. In addition, two further types of shocks to the reputation and tax shield benefits of philanthropy do not result in an increase in SI either. Our results contribute to understanding the channels behind SI and suggest that altruism is not as an important determinant as previously suggested.

Radiation Exposure During Transcatheter Valve Replacement: What Cardiac Surgeons Need to Know

Transcatheter aortic valve replacement (TAVR) and transcatheter mitral valve replacement expose operators to radiation. These procedures differ primarily in whether they are performed via a transfemoral (TF) or an alternative access (AA) approach. This study compared operator radiation exposure during transcatheter valve implantation when performed via a TF vs an AA approach, when performed in a catheterization lab vs a hybrid operating room (OR), and investigated the potential benefit of disposable shielding. Dosimeters were worn during TAVR-TF (n= 50) and TAVR-AA (n= 31) procedures by operators. All TAVR-AA procedures were performed in a hybrid OR and TF procedures were performed in either catheterization labs (n= 16) or a hybrid OR (n= 34). Disposable radiation shielding pads (RADPAD; Worldwide Innovations and Technologies, Inc, Kansas City) or a placebo were added in a randomized, blinded fashion. Team radiation exposure was higher after TAVR-AA vs TAVR-TF (median 15.1 mRad [interquartile range: IQR 8.6, 32.4] vs 5.5 mRad [IQR 2.4, 9.8], P < .001). TAVR-TF procedures required the same amount of fluoroscopy time regardless of where they were performed (20.3 ± 7.4 min in hybrid OR vs 19.0 ± 6.4 min in catheterization lab, P= .55). However, radiation exposure for TAVR-TF remained higher when performed in a hybrid OR (median 9.0 mRad [IQR 4.5, 11.9] vs 2.2 mRad [IQR 1.3, 2.8], P < .001). Radiation exposure was greatest for TAVR-AA (median 15.1 mRad [IQR 8.6, 32.4]). The use of RADPAD did not decrease radiation exposure (median 9.0 mRad [IQR 4.5, 14.7] vs 9.4 mRad [IQR 2.8, 19.5], P= .82). Procedures performed in the hybrid OR were associated with higher operator radiation exposure. In comparison with the TF approach, AA cases had thehighest levels of operator radiation. This is particularly important in cases of transcatheter mitral valve replacement that can only be done via an AA approach. The use of disposable radiation shielding in this series did not attenuate operator radiation exposure. Radiation shielding within hybrid ORs should be scrutinized in an effort to remain on par with that found within catheterization labs.

Firm-level investment, financing choices and corporate taxation management: evidence from panel of non-financial firms

This paper investigates the relationship between firm's financing choices, taxation benefits and investment in Pakistani listed firms. We apply the system generalised method of moments regression estimation on a sample of firms listed on Pakistan Stock Exchange during the period from 2001-2014. Our findings are that there is a positive relationship between leverage and investment accruing from the use of tax shield benefits which also are positively associated with the firm-level investment. Equity is also positively related to investment but the effect of leverage is more pronounced than equity. We also find that the positive relation between leverage and investment is stronger for firms with a medium level of debt, consistent with the trade-off theory argument of the existence of an optimal level of debt. Our results support the hypothesis that firms utilise debt to supplement investment in circumstances where alternate mechanisms of finance are not well developed.

The interaction of debt financing, cash grants and the optimal investment policy under uncertainty

Significant progress has been made toward understanding a levered firm's optimal investment policy under uncertainty. To date, however, not much work has concentrated on the time scale trade-off and collectively held real options. We employ a game-theoretic real option model between a firm and a government to analyze the effect of uncertainty and investment stimulus in the form of cash grants on optimal investment timing, financing and investment scaling. We find that the jointly held real option between the firm and the government leads to underinvestment, regardless of whether the firm has the possibility to issue debt. Subsidies, however, reduce the level of underinvestment. Notably, the results indicate that even though levered firms receive less support, they invest more than unlevered firms. This challenges recent findings that a firm's optimal investment level is not affected by the way it finances a project. Similarly, we find that for realistic parameter constellations the levered firm's optimal investment threshold can be higher than that of its unlevered counterpart. This indicates that the availability of tax shield benefits does not necessarily serve as an incentive to invest earlier. Finally, we show that the effect of cash flow uncertainty on the equilibrium level of grants is ambiguous and triggers the switch from a subsidy to non-subsidy regime.

Radiation Exposure to Personnel Obtaining Equine Appendicular Radiographs Using a Handheld Generator

Knowledge of radiation exposure in equine radiography is very limited. A study evaluating operator exposure confirmed the benefits of shielding, but exposure to personnel holding cassettes was not evaluated. This is an analytic study with the objective to measure and compare radiation exposures to personnel using a handheld generator with and without lead shielding. A cadaveric hindlimb was suspended to mimic standing position. Two dosimeters were placed at each of six locations from the generator and cassette to mimic locations of hands, trunk, and thyroid of personnel. At each location, one dosimeter was unshielded and the other was shielded. Six anatomic projections were performed, including lateromedial projections of the foot, metatarsophalangeal joint, tarsus, and stifle, as well as caudolateral–craniomedial oblique and caudocranial stifle projections. Comparisons between radiographer versus cassette holder exposure values were compared using the Wilcoxon signed rank test. Exposure was significantly (P < .05) higher for the holder than for the radiographer. Proper shielding techniques and as low as reasonably achievable principles should always be applied with use of handheld generators and cassettes to lower the risk of adverse radiation effects.

Firm Leverage Policy Decisions: Does Consumer Behaviour Explain Sectoral-Level Corporate Debt Policy in the U.S?

This paper investigates the impact of consumer sentiment on firms’ debt policy decisions and identifies the channels through which consumer sentiment impacts the corporate debt policy of U.S. firms at the sectoral level. Using the panel frameworks, the overall findings suggest a clear link between consumer sentiment which reflects personal financial conditions, business conditions and buying conditions for major ticket items and the choice of debt financing after controlling for firms specific factors and macroeconomic factors. The results also show that the effects of consumer sentiment on firms leverage policy are primary conditioning factors, due to the interaction between optimism about economic outlook reflected in consumer sentiment index and firm profitability. Given no direct link between consumer sentiment and firm leverage policy, we also search for a link via the consumption channel. I find that consumer sentiment positively affects personal consumption expenditures, confirming a link between consumer sentiment and corporate debt policy. Further the results from quantile regressions highlight how the leverage distribution is differentially affected by changes in both consumer sentiment and other control variables. In particular, firms in lower leverage quantiles appear to increase leverage as consumer optimism increases, to reap tax shield benefits. Further, the findings are robust to different time horizons for the pre- and post-crisis periods and consistent across alternative measures of sentiment and debt policy.

Dosimetric effects of bolus and lens shielding in treating ocular lymphomas with low-energy electrons

Radiation therapy is an effective treatment for primary orbital lymphomas. Lens shielding with electrons can reduce the risk of high-grade cataracts in patients undergoing treatment for superficial tumors. This work evaluates the dosimetric effects of a suspended eye shield, placement of bolus, and varying electron energies. Film (GafChromic EBT3) dosimetry and relative output factors were measured for 6, 8, and 10 MeV electron energies. A customized 5-cm diameter circle electron orbital cutout was constructed for a 6 × 6-cm applicator with a suspended lens shield (8-mm diameter Cerrobend cylinder, 2.2-cm length). Point doses were measured using a scanning electron diode in a solid water phantom at depths representative of the anterior and posterior lens. Depth dose profiles were compared for 0-mm, 3-mm, and 5-mm bolus thicknesses. At 5 mm (the approximate distance of the anterior lens from the surface of the cornea), the percent depth dose under the suspended lens shield was reduced to 15%, 15%, and 14% for electron energies 6, 8, and 10 MeV, respectively. Applying bolus reduced the benefit of lens shielding by increasing the estimated doses under the block to 27% for 3-mm and 44% for 5-mm bolus for a 6 MeV incident electron beam. This effect is minimized with 8 MeV electron beams where the corresponding values were 15.5% and 18% for 3-mm and 5-mm bolus. Introduction of a 7-mm hole in 5-mm bolus to stabilize eye motion during treatment altered lens doses by about 1%. Careful selection of electron energy and consideration of bolus effects are needed to account for electron scatter under a lens shield.

Thermoplastic wrapped lead sheet to reduce cardiac device cumulative dose

The objective of this project is to evaluate the percentage dose reduction in cardiac implantable electronic devices (CIEDs) using a thermoplastic wrapped lead sheet. The dose to CIED is evaluated in various situations with and without a lead shield. The efficiency of this type of shielding is supported by measurements made with a commercial plastic scintillation detector (PSD). Percentage depth dose (PDD) curve and lateral dose measurements (LDMs) were made with and without shielding for photon and electron beams. Photon LDMs were made at a depth of 0.5 cm. PSD measurements were compared with dose calculation from the treatment planning system (TPS). The benefit of shielding is greater at 23 MV than at 6 MV, with an average reduction of 71% and 59% of dose, respectively, for out-of-field distance range between 3 and 15 cm. Measurement of posterior beams shows there is no significant increase in skin dose due to backscatter from the lead sheet even when the field intercepts it. Large deviations between TPS calculation and measurements have been observed. The use of lead shielding with an anterior field is advised and provides an easy way to decrease the cumulative dose to CIEDs. Interception of shielding by an electron beam would increase significantly the cumulative dose to CIED for high energies or decrease the quality of the treatment. For a posterior out-of-field, shielding does not have a significant impact on CIED dose.

Determinants of the capital structure of Portuguese firms with investments in Angola

Background: This article seeks to complement the previous literature and clarify the particularities of the capital structure policy of firms with foreign direct investment in Angola.Aim: This article seeks to identify the determinants of the capital structure of Portuguese firms with direct investment in Angola and to understand whether the determinants normally considered by standard finance theory are in line with those used by firms when structuring their capital structure policy to participate in the specific market of Angola.Setting: This article examines 26 large Portuguese firms with investments in Angola using econometric panel data for the period 2006–2010.Methods: The study applied fixed and random effects methods and panel-corrected standard errors that maintain efficiency and unbiased behaviour even in the presence of panel-level heteroscedasticity and contemporaneous correlation of observations among panels.Results: The results provide evidence that the determinants normally considered by standard finance theory are in fact – in terms of sign and coefficient dimension – those used by firms for structuring their capital structure policy when involved in the internationalisation process of entering Angola. Specifically, age, asset structure, return on assets and tangibility have a positive influence on the capital structure of Portuguese firms that have invested in Angola, while non-debt tax shields and liquidity have a negative influence on these companies’ leverage ratios. When comparing our results with studies that have analysed the capital structure determinants of listed Portuguese firms – firms belonging to the PSI 20 Index and large firms in the Portuguese corporate sector – we found similarities in the sign and coefficient dimension of the determinants of capital structure. However, the profitability coefficient sign is in line with the trade-off framework (i.e. profitability is positively related to debt) but not with pecking order theory (i.e. profitability is negatively related to debt).Conclusion: Our results suggest that the high-growth Angolan market is seen by larger Portuguese firms as a low-risk diversification process because of the economic hardship Portugal has gone through, as well as cultural and linguistic similarities to Portugal. As such, the Angolan market is seen as an extension of the Portuguese domestic market that has increased potential. This scenario potentially reduces the firm default probability and the cost of debt. Maintaining the tax shield benefits of debt and decreasing the cost of debt – through a reduction in the default probability – have induced profitable firms to use more debt.

Is Foreign-Currency Denominated Debt Performance Enhancing? Evidence From French Non-Financial Firms

We investigate the impact of foreign currency debt on firm performance for a sample of nonfinancial French firms studied over the period 2002 to 2012. As foreign currency debt is both a financing and hedging instrument against foreign exchange risk, we mobilize optimal hedging theory and capital structure theory. When we study the impact on firm value, our main results show that before and after the financial crisis of 2008, foreign debt had the same behavior as domestic debt. We find that during the crisis period, foreign debt positively affects firm value. Investors perceive foreign debt as a natural hedging instrument that is likely to reduce the costs of underinvestment, alleviate cash flow volatility, limit the costs of financial distress, and generate tax shield benefits. In addition, our results show that foreign leverage negatively affects the firm performance proxied by ROA and ROE, during and after the financial crisis of 2008. However, this impact is positive on the pre-crisis period.

Capital structure decisions of LPTs in a small economy

Purpose – The existing literature on real estate investment trust (REIT) capital‐structure decisions implicitly excludes either interest payment tax shield benefits or a trust's growth potential. The purpose of this paper is to test the long‐term debt leverage decisions of listed property trusts (LPTs), but without excluding interest payment tax shield benefits and growth potential. A new variable, the exchange rate, is included in the tests, because financial products subject to globalization, such as SWAPs are currently used to support the funding of small economies.Design/methodology/approach – This paper uses a truncated regression and probit model to empirically test two competing hypotheses – the trade‐off theory and the pecking order theory. It also takes into account the implicit debt costs influenced by the exchange rate. The data for New Zealand LPTs are used.Findings – Unlike the existing literature, it is found that the trade‐off theory is supported, while the pecking order theory is rejected,...

SU-E-T-265: Reducing Pacemaker Doses with a Lead Sheet: A Multi-Detector Study.

Evaluate the usability of lead shielding to reduce the dose to pacemakers. The efficiency and risk of this type of skin block will be presented. A solid water phantom was used and all measurements were made at a depth of 0.5 cm for 6 MV and 23 MV photon beams. Measurements were performed with a parallel plate ion chamber and with a plastic scintillation detector (PSD) prototype. Measurements were made for fields of 10, 20 and 30 cm square. For every field, measurements were made in increment of 5 cm from the center of the field to the edge of the 60 cm long phantom for anterior and posterior beams. All measures have been made with and without a 1.6 mm of lead shielding wrapped in a thermoplastic. For all measurements, both detectors agree to 0.6%, well within the uncertainties of the detectors. With antero-posterior fields, the benefit of shielding is more important at 23MV (reduction of dose by65%) compared to 6MV (reduction of dose by 46%) when the shielding is out of the field. For distances larger than 35 cm, no benefits are measured. In the case were the lead is completely inside the fields, the dose is increased by the presence of shielding. The same observation is made for postero-anterior fields. For shielding out of field, the dose is slightly increased. The used of lead shielding with antero-posterior field is advised and provided an easy way to decrease dose to pacemaker. For a postero-anterior field, it is preferable to avoid shielding, but it could be used if it stays outside fields in the case of a multiple beams treatment. PSD has been shown to be an excellent candidate for in vivo monitoring dose to pacemakers and also site like foetus.

Does Security Choice Matter in Venture Capital? The Case of Venture Debt

The switch from equity to debt in venture capital-backed entrepreneurial firms is rare, but uniquely informative. Using a novel dataset of financing decisions, we find that entrepreneurial firms that raise debt financing suffer from an average 40% post-debt valuation drop and a 26% lower probability of successful exit (IPO/acquisition). Venture capitalists with equity stakes lend to lower quality entrepreneurial firms compared to outside lenders, and debt from both precedes deterioration in firm quality. Our results do not imply that debt causes negative outcomes. Rather, we argue that debt helps maintain incentive alignment after adverse shocks to firm quality. ∗Cox School of Business, Southern Methodist University and Tepper School of Business, Carnegie Mellon University. Corresponding author contact information: Michael Ewens (mewens@cmu.edu), Tepper School of Business, 5000 Forbes Ave. Pittsburgh, PA 15221, 412-423-8203. We thank Richard Green, Thomas Hellmann, Doron Levit, Nadya Malenko, Matthew Rhodes-Kropf, David Robinson, Luke Taylor, Rex Thompson, Michael Vetsuypens, Rebecca Zarutskie, and seminar participants at the 3rd Entrepreneurial Finance and Innovation Conference, Arizona State University, Darden Entrepreneurship Conference, Financial Intermediation Research Society Conference, MidAtlantic Research Conference, Harvard Business School, Southern Methodist University, and Tepper School of Business for their helpful comments. Chris E. Fishel and Paul Jaewoo Jung provided excellent research assistance. We are grateful to VentureSource and Correlation Ventures for access to the data. Empirical studies on the relationship between a firm’s prospects and its financing policy traditionally focus on publicly-traded firms. Due to data availability, the determinants of the security choices of young, private entrepreneurial firms are relatively unexplored. The financing environment of such firms is unique. Venture capital (VC)-backed entrepreneurial firms receive financing from inside investors who are informed about firm quality and help determine firm financing decisions. The environment contrasts with the setup of public firms that raise financing from arm’s length investors who face information asymmetry about firm prospects. In this paper, we seek to determine how these differences affect financing decisions and firm outcomes of VC-backed firms in particular and firms in general. Traditional explanations for debt financing do not easily apply in the VC setting. Since the investor is also an insider, the entrepreneur need not signal firm quality to the VC. Moreover, such firms rarely have taxable income, ruling out tax shield benefits as the motivation for debt issuance. Why then do VC-backed firms issue debt? Empirical research on capital structure suggests that leverage increase is positively related to firm value. In contrast, our analysis reveals that entrepreneurial firms that issue debt exhibit a reduction in firm value after obtaining debt and a lower probability of a successful exit (an initial public offering (IPO) or a private sale of the firm). We distinguish between two sources of debt: insiders, who are existing equity holders, and outsiders, who are new investors. Inside investors provide debt financing to lower quality firms than outside investors and debt from the former precedes significantly larger falls in valuation. If debt were causing the deterioration in firm prospects, then inside investors would not jeopardize their own firms more Brav (2009) studies private firm capital structure in the UK. Robb and Robinson (forthcoming) find that startups rely heavily on formal debt sources, such as bank financing. Venture capitalists possess in-depth knowledge of firm operations and industry expertise (see Lerner (1995) and Hellmann and Puri (2002)). See Masulis (1980) and Asquith and Mullins (1986), among others.

Risks and benefits of ovarian shielding in female patients undergoing TBI: a decision analysis

Risks and benefits of ovarian shielding in female patients undergoing TBI: a decision analysis

Introducing knowledge redundancy practice in software development: Experiences with job rotation in support work

Context Job rotation is a widely known approach to increase knowledge redundancy but empirical evidence regarding introduction and adoption in software development is scant. A lack of knowledge redundancy is a limiting factor for collaboration, flexibility, and coordination within teams and within the organization. Objective The scientific objective of this investigation was to explore benefits and challenges with improving knowledge redundancy among developers participating in job rotation. There were two practical objectives; (a) to establish customer support as a legitimate organizational function that would shield developers from support enquiries, and (b) to contribute to improved flexibility in project staffing by enabling overlapping product experience among developers. Method We used action research to integrate organizational change with scientific inquiry. During a period of eighteen weeks, nine developers rotated to customer support. We collected data throughout the period of collaboration; in meetings, from comprehensive interviews, and from customer support work logs. Results Perceptions of reduced efficiency and unnecessary redundancy outweighed benefits of shielding and learning about different products. Although there were strong indications of increased knowledge redundancy, the benefits were not sufficient to justify job rotation. Job rotation was abandoned after the trial period. Conclusions Job rotation can contribute to improved knowledge redundancy. Benefits of knowledge redundancy include innovation stemming from integration of different knowledge domains and improved appreciation of organizational concerns. However, knowledge redundancy incurs a collective cost that must be amortized and legitimized by the organization. An adoption process that accommodates open and trustful discussion among all involved stakeholders is therefore encouraged.

Influence of shielded insoluble anode layout on the consumption of bath additives

The benefi ts of anode shielding, either physically by an inert grid placed above the anode or by a grid electrically connected to the anode, are reviewed. During operation in practice and in laboratory investigations with a range of plating solutions, shielding has been found to reduce additive consumption and hence the need for bath regeneration, to reduce the effect on the active layer in pulse plating reverse mode, to reduce oxidation of cations, and to increase stability of performance over the life of the anode.

Optimal Capital Structure, Debt Structure, and Investment

We examine the optimal capital structure and priority structure of multiple classes of debt using a dynamic model where firms face a tradeoff between bankruptcy costs, interest tax shield benefits, and investment benefits. As a base case, we first analyze jointly optimal policies for a firm initially constrained to a single class of debt, which results in underinvestment in the growth option. Surprisingly, this standard case produces several novel predictions, such as, financial leverage ratios need not be inversely related to a firm's investment opportunities, and reliance on credit spreads to gauge agency costs of debt is inappropriate when it is hard to identify whether debt policy is endogenous or not. Relaxing the firm's constraint, we then study jointly optimal policies for initial debt and additional debt used to finance the growth option. Ironically, equityholders' optimal strategy in this unconstrained case results in overinvestment in the growth option. As a result, we obtain an interior optimum for priority structure as an important financial contracting device. One of the paper's key implications is that priority structure plays a critical and heretofore unrecognized role in helping to resolve bondholder-shareholder conflicts over investment policy. This financial contracting perspective offers other potentially fruitful insights to better understand the effects of optimal capital structure and debt structure on corporate investment policy.