Do countercyclical-weekend effects persist in online retail markets?

Contrary to classical economic price theory, Warner and Barsky [Warner, Elizabeth J., and Barsky, Robert B. The timing and magnitude of retail store markdowns: Evidence from weekends and holidays. Quarterly Journal of Economics, 110, 2, 1995, 321–352.] show that in traditional off-line markets, prices on average tend to be lower on weekends despite higher aggregate demand. Their explanation for this effect is rooted in the existence of consumers’ search and transportation costs. We argue that since these costs are significantly reduced in many online retail market environments, this “weekend effect” should be weakened substantially. Our empirical evidence suggests that in fact, there are few statistically significant day-of-the-week price differences in the online markets we study, and the estimated magnitude of these differences is quite small.     

A multi-angular mass spectrometric view at cyclic nucleotide dependent protein kinases: in vivo characterization and structure/function relationships

Mass spectrometry has evolved in recent years to a well-accepted and increasingly important complementary technique in molecular and structural biology. Here we review the many contributions mass spectrometry based studies have made in recent years in our understanding of the important cyclic nucleotide activated protein kinase A (PKA) and protein kinase G (PKG). We both describe the characterization of kinase isozymes, substrate phosphorylation, binding partners and post-translational modifications by proteomics based methodologies as well as their structural and functional properties as revealed by native mass spectrometry, H/D exchange MS and ion mobility. Combining all these mass spectrometry based data with other biophysical and biochemical data has been of great help to unravel the intricate regulation of kinase function in the cell in all its magnificent complexity.     

Enhanced laser shutter using a hard disk drive rotary voice-coil actuator

Rotary voice-coil motors from computer hard disk drives make excellent mechanical shutters for light beams. However, the complexity of the necessary electronic driving circuit can hinder their application. A new design is presented here, using a single integrated circuit originally intended for controlling dc motors. A digital input signal switches a unipolar power supply bidirectionally through the voice coil. Short high-current pulses are generated on the transitions to ensure rapid shutter action, while a low holding current reduces the power requirement and heating of the actuator. The circuit can reverse the current to brake the shutter and reduce the impact at the end of its travel. With a focused laser beam, the shutter achieves rise times below 500 ns. A method for producing variable length pulses is also described, demonstrating durations as short as 700 ns.     

Microfabricated optofluidic ring resonator structures

We describe the fabrication and preliminary optical characterization of rugged, Si-micromachined optofluidic ring resonator (μOFRR) structures consisting of thin-walled SiO(x) cylinders with expanded midsections designed to enhance the three-dimensional confinement of whispering gallery modes (WGMs). These μOFRR structures were grown thermally at wafer scale on the interior of Si molds defined by deep-reactive-ion etching and pre-treated to reduce surface roughness. Devices 85-μm tall with 2-μm thick walls and inner diameters ranging from 50 to 200 μm supported pure-mode WGMs with Q-factors >10(4) near 985 nm. Advantages for eventual vapor detection in gas chromatographic microsystems are highlighted.     

Dutch performance-based approach to building regulations and public procurement

Along with the publication of the first set of performance-based regulations in 1991, the Netherlands Governmental Building Agency (GBA) introduced innovative performance-based procurement and tendering. A structurally different performance-based regulation document was published in 2001. A continuous research effort paralleled these developments, leading recently to the Policy Document on Building Regulations 2002-06 and the approval of a new national programme called Process and System Innovation in Building (PSIB). Actual and future developments are strongly influenced by the turmoil following the recent disclosure of the wide use of outlawed settlement of calculation cost and project 'rights' by the Dutch contractors. In addition, some blatant cases of fraudulent contract administration were revealed. By the end of 2003, key stakeholders within both the government and industry were in agreement that there was a need for radical change of the economic and social performance of the building and construction sector. The PSIB programme, in combination with a strong deregulation initiative, will be the major driver for the application of the performance approach in the sector.     

High heat flux capabilities of the Magnum-PSI linear plasma device

Magnum-PSI is an advanced linear plasma device uniquely capable of producing plasma conditions similar to those expected in the divertor of ITER both steady-state and transients. The machine is designed both for fundamental studies of plasma–surface interactions under high heat and particle fluxes, and as a high-heat flux facility for the tests of plasma-facing components under realistic plasma conditions. To study the effects of transient heat loads on a plasma-facing surface, a novel pulsed plasma source system as well as a high power laser is available. In this article, we will describe the capabilities of Magnum-PSI for high-heat flux tests of plasma-facing materials.     

Sphingosine Kinase Interacting Protein is an A‐Kinase Anchoring Protein Specific for Type I cAMP‐Dependent Protein Kinase

The compartmentalization of kinases and phosphatases plays an important role in the specificity of second‐messenger‐mediated signaling events. Localization of the cAMP‐dependent protein kinase is mediated by interaction of its regulatory subunit (PKA‐R) with the versatile family of A‐kinase‐anchoring proteins (AKAPs). Most AKAPs bind avidly to PKA‐RII, while some have dual specificity for both PKA‐RI and PKA‐RII; however, no mammalian PKA‐RI‐specific AKAPs have thus far been assigned. This has mainly been attributed to the observation that PKA‐RI is more cytosolic than the more heavily compartmentalized PKA‐RII. Chemical proteomics screens of the cAMP interactome in mammalian heart tissue recently identified sphingosine kinase type 1‐interacting protein (SKIP, SPHKAP) as a putative novel AKAP. Biochemical characterization now shows that SPHKAP can be considered as the first mammalian AKAP that preferentially binds to PKA‐RIα. Recombinant human SPHKAP functions as an RI‐specific AKAP that utilizes the characteristic AKAP amphipathic helix for interaction. Further chemical proteomic screening utilizing differential binding characteristics of specific cAMP resins confirms SPHKAPs endogenous specificity for PKA‐RI directly in mammalian heart and spleen tissue. Immunolocalization studies revealed that recombinant SPHKAP is expressed in the cytoplasm, where PKA‐RIα also mainly resides. Alignment of SPHKAPs' amphipathic helix with peptide models of PKA‐RI‐ or PKA‐RII‐specific anchoring domains shows that it has largely only PKA‐RIα characteristics. Being the first mammalian PKA‐RI‐specific AKAP with cytosolic localization, SPHKAP is a very promising model for studying the function of the less explored cytosolic PKA‐RI signaling nodes.     

Sample comminution for mycotoxin analysis: Dry milling or slurry mixing?

A comparison was made between dry milling and slurry mixing as a comminuting step preceding mycotoxin analysis. Sample schemes of up to 30 kg are mandated by European Commission legislation. Cocoa, green coffee, almonds and pistachio samples of 10 kg were milled by a Romer analytical sampling mill and all three subsamples were analysed for aflatoxin B₁ or ochratoxin A content. The homogenization process was evaluated in terms of the analytical results, coefficients of variation for different mills and particle size distributions. Coefficients of variation for the comminuting step were higher for dry milling than for slurry mixing. This difference was explained based on measured particle size distributions for both milling types. Measurements also showed slight differences in mycotoxin content of samples based on milling procedures. This might lead to lots being wrongly accepted or rejected based on an erroneous subsample result. It was concluded that sample comminution was best performed by slurry mixing, which produced smaller particles and, consequently, homogeneous samples with lowest coefficients of variation. Additional data are given on analytical results in 10-kg subsamples that originate from the aggregate 30-kg sample as described in Commission Directive 98/53/EC.     

Impact of downscaling and poly-gate depletion on the RF noise parameters of advanced nMOS transistors

For the first time, the effects of poly depletion on the RF noise performance of advanced CMOS transistors are reported and analyzed. Based on measurements and physical device simulations we quantify the increasing danger of poly gate depletion with downscaling on the RF noise parameters of CMOS devices. While poly depletion does not affect the minimum noise figure, it results in a degradation of the noise matching freedom for RFIC designers. This trend worsens with technology downscaling.