331 research outputs found

    Parameterized model order reduction of delayed systems using an interpolation approach with amplitude and frequency scaling coefficients

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    When the geometric dimensions become electrically large or signal waveform rise times decrease, time delays must be included in the modeling. We present an innovative PMOR technique for neutral delayed differential systems, which is based on an efficient and reliable combination of univariate model order reduction methods, amplitude and frequency scaling coefficients and positive interpolation schemes. It is able to provide parameterized reduced order models passive by construction over the design space of interest. Pertinent numerical examples validate the proposed PMOR approach

    Signal Strength, Media Attention, and Resource Mobilization: Evidence from New Private Equity Firms

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    This is the author accepted manuscript. The final version is available from the Academy of Management via the DOI in this recordPast research has shown that new firms can facilitate resource mobilization by signaling their unobservable quality to prospective resource providers. However, we know less about situations in which firms convey multiple signals of different strengths—i.e., signals that are more or less correlated with unobservable firm quality. Building on a sociocognitive perspective, we propose that prospective resource providers respond differently to signals of different strengths and that the effectiveness of signals, especially weak signals, will be contingent on the media attention new firms receive. Empirically, we conduct a longitudinal analysis examining the ability of new private equity (PE) firms to raise a follow-on fund. Consistent with our theory, we find that unrealized performance, a relatively weak signal, positively influences fundraising. But we fail to find statistical evidence that its effect is weaker than that of realized performance, a relatively strong signal. Further, media attention strengthens the relationship between unrealized performance and fundraising, but media attention exerts less impact on the relationship between realized performance and fundraising. Taken together, our findings deepen our understanding of how new firms can mobilize resources with signals of different strengths and of how the media—as a key information intermediary—differently impacts their effectiveness.Richard M. Schulze Family Foundatio

    Toward a Harmonization for Using in situ Nutrient Sensors in the Marine Environment

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    Improvedcomparabilityofnutrientconcentrationsinseawaterisrequiredtoenhancethe quality and utility of measurements reported to global databases. SigniïŹcant progress has been made over recent decades in improving the analysis and data quality for traditional laboratory measurements of nutrients. Similar efforts are required to establish high-quality data outputs from in situ nutrient sensors, which are rapidly becoming integral components of ocean observing systems. This paper suggests using the good practices routine established for laboratory reference methods to propose a harmonized setofdeploymentprotocolsandofqualitycontrolproceduresfornutrientmeasurements obtained from in situ sensors. These procedures are intended to establish a framework to standardize the technical and analytical controls carried out on the three main types of in situ nutrient sensors currently available (wet chemical analyzers, ultraviolet optical sensors, electrochemical sensors) for their deployments on all kinds of platform. The routine reference controls that can be applied to the sensors are listed for each step of sensor use: initial qualiïŹcation under controlled conditions in the laboratory, preparation of the sensor before deployment, ïŹeld deployment and ïŹnally the sensor recovery. The fundamental principles applied to the laboratory reference method are then reviewed in termsofthecalibrationprotocol,instrumentalinterferences,environmentalinterferences, external controls, and method performance assessment. Data corrections (linearity, sensitivity, drifts, interferences and outliers) are ïŹnally identiïŹed along with the concepts and calculations for qualiïŹcation for both real time and time delayed data. This paper emphasizes the necessity of future collaborations between research groups, referenceaccredited laboratories, and technology developers, to maintain comparability of the concentrationsreportedforthevariousnutrientparametersmeasuredbyinsitusensors

    The effects of private equity investors on the governance of firms

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    Companies that receive external equity typically experience a separation of ownership and control, where owners who are not involved in the company (principals) have to rely on the management team (agents) for achieving expected goals and target levels. Theoretical literature argues that when ownership and control are separated, principals develop governance structures to reduce agency costs and align agents’ incentives (Berle and Means, 1932; Jensen and Meckling, 1976; Grossman and Hart, 1986; Zingales, 1995). Likewise, optimal financial structure design by financial intermediaries can effectively help to mitigate agency problems by identifying self-enforcing equilibria (Diamond, 1984; Fama and Jensen, 1985; Stiglitz, 1985; Bhattacharya and Thakor, 1993; Barry, 1994). In general terms, governance and financial devices can be thought of as either internal control mechanisms (such as the board) or external control mechanisms (such as the market for corporate control). An increasingly important external control mechanism affecting the governance of young and fast-growing companies worldwide is the emergence of institutional and private equity investors, as equity owners. Institutional investors have the potential to influence management’s activities directly through their ownership, and indirectly by trading their shares (Gillan and Starks, 2003). In this respect private equity investors are differentiated from institutional ones in the longer-term view and in the significantly more hands-on approach that they pursue when investing in a portfolio company. As a result, companies backed by private equity investors represent a fruitful environment to investigate the use and efficiency of a multitude of control mechanisms. The surge over the last 30 years in investment activity by private equity investors at large has given rise to an increased specialization of this class of investors conditional on the risk return profiles associated with different investment and firm life cycle stages. For instance, business angels supporting the archetypical ‘paper company’ start-up face a risk exposure that in terms of both magnitude and characteristics is significantly different from that incurred by a private equity investor acquiring control of a mature company. Yet, investors in this market share common traits such as a value maximization approach, risk‒return informed decisions, and a deep knowledge of governance mechanisms. As such their influence on portfolio company governance mechanisms is largely similar in terms of depth and breadth. In this chapter we aim at presenting an up-to-date review of the main theoretical contributions and empirical results in this active and growing field of research

    The effect of tightly-bound water molecules on scaffold diversity in computer-aided de novo ligand design of CDK2 inhibitors

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    We have determined the effects that tightly bound water molecules have on the de novo design of cyclin-dependent kinase-2 (CDK2) ligands. In particular, we have analyzed the impact of a specific structural water molecule on the chemical diversity and binding mode of ligands generated through a de novo structure-based ligand generation method in the binding site of CDK2. The tightly bound water molecule modifies the size and shape of the binding site and we have found that it also imposed constraints on the observed binding modes of the generated ligands. This in turn had the indirect effect of reducing the chemical diversity of the underlying molecular scaffolds that were able to bind to the enzyme satisfactorily
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