Managing highly innovative projects: the influence of design characteristics on project valuation

The climate change debate and economic recovery strategies in various industries demand highly innovative projects featuring stretched performance goals for developing clean technology. These projects face multiple sources of uncertainty in high risk situations, and require specialized know-how and longer periods for revenue growth than their counterparts in other industries. We use data from 207 clean technology projects funded by the U.S. Advanced Research Projects Agency-Energy to conduct a comparative study of how operations design can hedge risk and enhance project valuation in technology development and deployment stages. We find that deployment feasibility is significantly and positively related to project valuation. On the other hand, stretched technical performance goals, development feasibility and market growth targets are associated with lower valuation. We also find some significant differences for these results across institution types: mature firms, start-ups, universities, and research centers. We examine the risk profile of these projects by technology and institution type, and discuss the managerial and policy implications for these findings

Nilpotent normal form for divergence-free vector fields and volume-preserving maps

We study the normal forms for incompressible flows and maps in the neighborhood of an equilibrium or fixed point with a triple eigenvalue. We prove that when a divergence free vector field in $\mathbb{R}^3$ has nilpotent linearization with maximal Jordan block then, to arbitrary degree, coordinates can be chosen so that the nonlinear terms occur as a single function of two variables in the third component. The analogue for volume-preserving diffeomorphisms gives an optimal normal form in which the truncation of the normal form at any degree gives an exactly volume-preserving map whose inverse is also polynomial inverse with the same degree.Comment: laTeX, 20 pages, 1 figur

Shaping of melting and dissolving solids under natural convection

How quickly does an ice cube melt or a lump of sugar dissolve? We address the open problem of the shapes of solids left to melt or dissolve in an ambient fluid driven by stable natural convection. The theory forms a convective form of a Stefan problem in which the evolution is controlled by a two-way coupling between the shape of the body and stable convection along its surface. We develop a new model describing the evolution of such bodies in two-dimensional or axisymmetric geometries and analyse it using a combination of numerical and analytical methods. Different initial conditions are found to lead to different fundamental shapes and descent rates. For the cases of initially linear surfaces (wedges or cones), the model admits similarity solutions in which the tip descends from its initial position as t4/5 , where t is time. It is determined that the evolving shape always forms a parabola sufficiently near the tip. For steeply inclined bodies, we establish a general two-tiered asymptotic structure comprising a broad 4/3 -power intermediate near-tip region connected to a deeper parabolic region at the finest scale. The model results apply universally for any given relationship between density, viscosity, diffusivity and concentration, including two-component convection. New laboratory experiments involving the dissolution of cones of sugar candy in water are found to collapse systematically onto our theoretically predicted shapes and descent rates with no adjustable parameters

Nonlinear frequency mixing in quantum cascade lasers: Towards broadband wavelength shifting and THz up-conversion

Terahertz (THz) sideband generation on a near-infrared (NIR) carrier has been recently demonstrated using quantum cascade lasers (QCL), with potential applications in wavelength shifting and THz up-conversion. However, the NIR wavelength range and nonlinear efficiency were severely limited by absorption. Here we overcome this drawback through a novel reflection geometry, whilst preserving a large interaction area. As well as insights into the nonlinear mechanism, this allows a much large range of NIR pump energies, relaxing the criteria of using particular excitation wavelengths

Valsalva retinopathy in pregnancy: a case report

<p>Abstract</p> <p>Introduction</p> <p>Valsalva retinopathy is a unilateral or bilateral condition that occurs when increased intra-thoracic or intra-abdominal pressure transmitted to the eye causes a sharp rise in the intra-ocular venous pressure, and rupture of superficial retinal capillaries. The patient often gives a history of a recent strenuous physical act, which could have increased the intra-thoracic pressure. Pregnancy is known to be a risk factor for Valsalva retinopathy.</p> <p>Case presentation</p> <p>A 23-year-old woman in her seventh month of pregnancy presented with a history of decreased vision in her left eye of one-week duration. Examination of the affected eye showed best corrected visual acuity of 20/50, and fundus examination revealed a pre-retinal hemorrhage located in the macula. Based on clinical findings, the diagnosis of Valsalva retinopathy was made.</p> <p>Conclusion</p> <p>Retinal hemorrhages can be generated by Valsalva maneuvers. Pregnancy is a known risk factor for Valsalva retinopathy; however, the diagnosis should be made only after excluding other causes of retinal hemorrhages. It is a self-limited event. We report a case of Valsalva retinopathy complicating normal pregnancy and confirm that, to date, there is no evidence to indicate that there is a risk of recurrence following spontaneous vaginal delivery.</p

High-performance continuous-wave operation of superlattice terahertz quantum-cascade lasers

The cw operation of chirped-superlattice quantum-cascade lasers emitting at lambdasimilar to67 mum (4.4 THz) is analyzed. Collected (min. 33% efficiency) output powers of 4 mW per facet are measured at liquid helium temperatures and a maximum operating temperature of 48 K is reached. Under pulsed excitation at duty cycles of 0.5%-1%, slightly higher (10%) peak powers are reached, and the device can be operated up to 67 K. Low threshold current densities of 165 and 185 A cm(-2) are observed in pulsed and cw operation, respectively. The operation of the laser is examined using the Hakki-Paoli technique to estimate the net gain of the structure. (C) 2003 American Institute of Physics

Far-field engineering of metal -metal terahertz quantum cascade lasers with integrated horn antennas

The far-field of metal-metal terahertz quantum cascade lasers is greatly improved through integrated and stable planar horn antennas on top of the QCL ridge. The antenna structures introduce a gradual change in the high modal confinement of metal-metal waveguides and permit an improved far-field, showing a five times increase in the emitted output power. The two dimensional far-field patterns are measured at 77K and compared to electromagnetic simulations. The influence of parasitic high order transverse modes are restricted through the engineering of antenna structure (ridge and antenna width) to couple out the fundamental mode only

Monolithic echo-less photoconductive switches for high-resolution terahertz time-domain spectroscopy

Interdigitated photoconductive (IPC) switches are convenient sources and detectors for terahertz (THz) time domain spectroscopy. However, reflection of the emitted or detected radiation within the device substrate can lead to echoes that inherently limits the spectroscopic resolution achievable. In this work, we design and realize low-temperature-grown-GaAs (LT-GaAs) IPC switches for THz pulse generation and detection that suppresses such unwanted echoes. This is realized through a monolithic geometry of an IPC switch with a metal plane buried at a subwavelength depth below the LT-GaAs surface. Using this device as a detector, and coupling it to an echo-less IPC source, enables echo-free THz-TDS and high-resolution spectroscopy, with a resolution limited only by the temporal length of the measurement governed by the mechanical delay line used

Thermodynamics of a class of non-asymptotically flat black holes in Einstein-Maxwell-Dilaton theory

We analyse in detail the thermodynamics in the canonical and grand canonical ensembles of a class of non-asymptotically flat black holes of the Einstein-(anti) Maxwell-(anti) Dilaton theory in 4D with spherical symmetry. We present the first law of thermodynamics, the thermodynamic analysis of the system through the geometrothermodynamics methods, Weinhold, Ruppeiner, Liu-Lu-Luo-Shao and the most common, that made by the specific heat. The geometric methods show a curvature scalar identically zero, which is incompatible with the results of the analysis made by the non null specific heat, which shows that the system is thermodynamically interacting, does not possess extreme case nor phase transition. We also analyse the local and global stability of the thermodynamic system, and obtain a local and global stability for the normal case for 0<\gamma<1 and for other values of \gamma, an unstable system. The solution where \gamma=0 separates the class of locally and globally stable solutions from the unstable ones.Comment: 18 pages, version accepted for publication in General Relativity and Gravitatio

Celecoxib exerts protective effects in the vascular endothelium via COX-2-independent activation of AMPK-CREB-Nrf2 signalling

Although concern remains about the athero-thrombotic risk posed by cyclo-oxygenase (COX)-2-selective inhibitors, recent data implicates rofecoxib, while celecoxib appears equivalent to NSAIDs naproxen and ibuprofen. We investigated the hypothesis that celecoxib activates AMP kinase (AMPK) signalling to enhance vascular endothelial protection. In human arterial and venous endothelial cells (EC), and in contrast to ibuprofen and naproxen, celecoxib induced the protective protein heme oxygenase-1 (HO-1). Celecoxib derivative 2,5-dimethyl-celecoxib (DMC) which lacks COX-2 inhibition also upregulated HO-1, implicating a COX-2-independent mechanism. Celecoxib activated AMPKα(Thr172) and CREB-1(Ser133) phosphorylation leading to Nrf2 nuclear translocation. Importantly, these responses were not reproduced by ibuprofen or naproxen, while AMPKα silencing abrogated celecoxib-mediated CREB and Nrf2 activation. Moreover, celecoxib induced H-ferritin via the same pathway, and increased HO-1 and H-ferritin in the aortic endothelium of mice fed celecoxib (1000 ppm) or control chow. Functionally, celecoxib inhibited TNF-α-induced NF-κB p65(Ser536) phosphorylation by activating AMPK. This attenuated VCAM-1 upregulation via induction of HO-1, a response reproduced by DMC but not ibuprofen or naproxen. Similarly, celecoxib prevented IL-1β-mediated induction of IL-6. Celecoxib enhances vascular protection via AMPK-CREB-Nrf2 signalling, a mechanism which may mitigate cardiovascular risk in patients prescribed celecoxib. Understanding NSAID heterogeneity and COX-2-independent signalling will ultimately lead to safer anti-inflammatory drugs