On the complexity of the continuous unbounded knapsack problem with uncertain coefficients

In this paper, a linear-time algorithm is developed for the minmax-regret version of the continuous unbounded knapsack problem with n items and uncertain objective function coefficients, where the interval estimates for these coefficients are known. This improves the previously known bound of time for this optimization problem.     

The Muonic Hydrogen Lamb Shift Experiment at PSI

A measurement of the 2S Lamb shift in muonic hydrogen (μ⁻p) is being prepared at the Paul Scherrer Institute (PSI). The goal of the experiment is to measure the energy difference ΔE(2⁵ P _3/2−2³ S _1/2) by laser spectroscopy (λ≈6μm) to a precision of 30 ppm and to deduce the root mean square (rms) proton charge radius with 10⁻³ relative accuracy, 20 times more precise than presently known. An important prerequisite to this experiment is the availability of long-lived μp_2S -atoms. A 2S-lifetime of ∼1 μs – sufficiently long to perform the laser experiment – at H₂ gas pressures of 1–2 hPa was deduced from recent measurements of the collisional 2S-quenching rate. A new low-energy negative muon beam yields an order of magnitude more muon stops in a small low-density gas volume than a conventional cloud muon beam. A stack of ultra-thin carbon foils is the key element of a fast detector for keV-muons. The development of a 2 keV X-ray detector and a 3-stage laser system providing 0.5 mJ laser pulses at 6 μm is on the way. This revised version was published online in August 2006 with corrections to the Cover Date.     

Laser Ablation Synthesis of Gold Selenides by using a Mass Spectrometer as a Synthesizer: Laser Desorption Ionization Time‐of‐Flight Mass Spectrometry

Methods for the rapid construction of new chemical motifs have the potential to accelerate the development of nanoscience. The synthesis of new chemical entities by laser ablation has been systematically demonstrated by using mixtures of gold and selenium. The compounds generated are detected by time‐of‐flight mass spectrometry and, for selected compounds, the structure is investigated by using density functional theory optimization. In total, 67 new gold selenide clusters have been synthesized, demonstrating an unsuspected richness in gold chemistry. Chemical species generated in the gas phase might inspire new routes for the synthesis of novel compounds in the solid state.     

Enhancing the effect of repetitive I-wave paired-pulse TMS (iTMS) by adjusting for the individual I-wave periodicity

Background

The aberrant pyramidal tract (APT) refers to the collateral pathway of the pyramidal tract (PT) through the medial lemniscus in the midbrain and pons. Using diffusion tensor tractography (DTT), we investigated the characteristics of the APT in comparison with the PT in the normal human brain.

Results

In thirty-four (18.3%, right hemisphere: 20, left hemisphere: 14) of the 186 hemispheres, the APTs separated from the PT at the upper midbrain level, descended through the medial lemniscus from the midbrain to the pons, and then rejoined with the PT at the upper medulla. Nine (26.5%) of the 34 APTs were found to originate from the primary somatosensory cortex without a primary motor cortex origin. Values of fractional anisotropy (FA) and tract volume of the APT were lower than those of the PT (P < 0.05); however, no difference in mean diffusivity (MD) value was observed (P > 0.05).

Conclusion

We found that the APT has different characteristics, including less directionality, fewer neural fibers, and less origin from the primary motor cortex than the PT.     

Tetrazine Carbon Nanotubes for Pretargeted In Vivo “Click‐to‐Release” Bioorthogonal Tumour Imaging

The bioorthogonal inverse‐electron‐demand Diels–Alder (IEDDA) cleavage reaction between tetrazine and trans‐cyclooctene (TCO) is a powerful way to control the release of bioactive agents and imaging probes. In this study, a pretargeted activation strategy using single‐walled carbon nanotubes (SWCNTs) that bear tetrazines (TZ@SWCNTs) and a TCO‐caged molecule was used to deliver active effector molecules. To optimize a turn‐on signal by using in vivo fluorescence imaging, we developed a new fluorogenic near‐infrared probe that can be activated by bioorthogonal chemistry and image tumours in mice by caging hemicyanine with TCO (tHCA). With our pretargeting strategy, we have shown selective doxorubicin prodrug activation and instantaneous fluorescence imaging in living cells. By combining a tHCA probe and a pretargeted bioorthogonal approach, real‐time, non‐invasive tumour visualization with a high target‐to‐background ratio was achieved in a xenograft mice tumour model. The combined advantages of enhanced stability, kinetics and biocompatibility, and the superior pharmacokinetics of tetrazine‐functionalised SWCNTs could allow application of targeted bioorthogonal decaging approaches with minimal off‐site activation of fluorophore/drug.     

Maximin location: Discretization not always works

In this note we show by means of a simple example that, if the maximin problem with (nonlinear) concave increasing utility functions is solved by inspecting the extreme points of the (generalized) Voronoi diagram (as usually proposed), one may have to inspect an infinite number of candidate points. The research of the second and third authors is partially supported by Grant PB96-1416-C02-02 of Ministerio de Educación y Cultura, Spain     

Laser assisted chemical vapour deposition of silicon oxide layers

This paper focuses on the deposition of silicon oxide thin films, using laser assisted CVD based on a CO₂ laser, and on the feasibility of the process for coating porous silicon samples. Scanning electron and atomic force microscopy were used to analyse the morphology and microstructure of the films, while structure and chemical composition were determined by Fourier transform infrared and Rutherford backscattering spectroscopy. Two-wavelength ellipsometry was used for thickness and refractive index evaluation. The photoluminescence of SiO₂/PS was measured and compared with that of uncoated samples.