Fragmentation characteristics of collision-induced dissociation in MALDI TOF/TOF mass spectrometry

The identification of proteins by tandem mass spectrometry relies on knowledge of the products produced by collision-induced dissociation of peptide ions. Most previous work has focused on fragmentation statistics for ion trap systems. We analyzed fragmentation in MALDI TOF/TOF mass spectrometry, collecting statistics using a curated set of 2459 MS/MS spectra and applying bootstrap resampling to assess confidence intervals. We calculated the frequency of 18 product ion types, the correlation between both mass and intensity with ion type, the dependence of amide bond breakage on the residues surrounding the cleavage site, and the dependence of product ion detection on residues not adjacent to the cleavage site. The most frequently observed were internal ions, followed by y ions. A strong correlation between ion type and the mass and intensity of its peak was observed, with b and y ions producing the most intense and highest mass peaks. The amino acids P, W, D, and R had a strong effect on amide bond cleavage when situated next to the breakage site, whereas residues including I, K, and H had a strong effect on product ion observation when located in the peptide but not adjacent to the cleavage site, a novel observation.     

Modeling the National Ignition Facility neutron imaging system

Numerical modeling of the neutron imaging system for the National Ignition Facility (NIF), forward from calculated target neutron emission to a camera image, will guide both the reduction of data and the future development of the system. Located 28 m from target chamber center, the system can produce two images at different neutron energies by gating on neutron arrival time. The brighter image, using neutrons near 14 MeV, reflects the size and symmetry of the implosion "hot spot." A second image in scattered neutrons, 10-12 MeV, reflects the size and symmetry of colder, denser fuel, but with only ～1%-7% of the neutrons. A misalignment of the pinhole assembly up to ±175?μm is covered by a set of 37 subapertures with different pointings. The model includes the variability of the pinhole point spread function across the field of view. Omega experiments provided absolute calibration, scintillator spatial broadening, and the level of residual light in the down-scattered image from the primary neutrons. Application of the model to light decay measurements of EJ399, BC422, BCF99-55, Xylene, DPAC-30, and Liquid A suggests that DPAC-30 and Liquid A would be preferred over the BCF99-55 scintillator chosen for the first NIF system, if they could be fabricated into detectors with sufficient resolution.     

Precisely positioning pallets in multi-station assembly systems

In multi-station assembly systems, common for mass-customization manufacturing strategies, the product being assembled is held in a fixture attached to a pallet, and the pallet is conveyed between workstations. In high-precision assembly systems, variation in the position of the pallet is one of the largest sources of variation within the error budget, reducing quality and yields. Conventional approaches to locating pallets use pins and bushings, and a method for predicting their repeatability is presented. This paper also presents an exact constraint approach using a split-groove kinematic coupling, which reduces variation in pallet location by an order of magnitude.     

Low Cost Home Ownership Initiatives in the UK

In common with many other countries, the UK has treated owner occupation favourably in comparison with other tenures in terms of tax and subsidy. However, the UK is distinctive in having encouraged the large-scale transfer of dwellings from the public rented sector to home ownership and in having developed a variety of low cost home ownership (LCHO) mechanisms to assist people at the margins into owner occupation. This paper evaluates these LCHO initiatives, considering value for money, sustainability and potential demand. Looking to the future, we see government policy and the level of demand as the most important determinants of the role of LCHO and discuss influences on demand and pointers to government policy.     

Urban renewal on the last frontier

After the Alaskan earthquake of 1964, the frontier fishing village of Seldovia was threatened by high tides along its picturesque downtown waterfront. The availability of federal reconstruction funds lured policy makers to opt for urban renewal rather than rehabilitation. The result was an economic, social and aesthetic disaster. The episode illustrates some of the difficulties of environmental management on the last U.S. frontier.     

Criteria for the control of radioactive effluents

The risks to the population from the U.S. nuclear energy industry are considered to be very small in comparison with other environmental risks. However, they are not zero and, on the assumption that radiation damage increases linearly with the accumulated dose, they can be expected on a statistical basis to result in a few deaths in the exposed population. Thus, the routine operation of these nuclear power plants may cause about 18 deaths/yr and the serious accidents, which may occur at a frequency of once every 50 yr, may add another 6 deaths/yr on the average. This is considered to be a small price to pay relative to the real but less‐well‐defined environmental risks from atmospheric pollution caused by fossil fuel power plants. Assuming the proper selection of a reactor site and all practicable precautions in the design and operation of a nuclear power reactor, adequate radiation protection for nearby populations can be assured by concentrating health physics attention on the critical radionuclides, critical pathways and critical segments of the population.     

Dynamics of control in construction project teams

Control is pervasive in construction project environments. The management of projects through various planning and control tools has therefore been described essentially as rebureaucratization which increases control over individuals, teams and organizations through ideologies of efficiency and performativity. Yet certain characteristics of the project setting make it an ideal climate for the empowerment of individuals and teams. The manifestations of control in five construction project management teams involved in two ongoing construction projects in Hong Kong are examined. The interpretive and exploratory focus of the study favoured the use of a qualitative research design and the case study approach in particular. Control is viewed as all devices and systems employed to ensure that acts, behaviours, outcomes and decisions of individuals, teams and organizations are consistent with meeting organizational or project goals, objectives and strategies. The findings indicate that a portfolio of control modes is implemented in project teams comprising both formal (i.e. behaviour‐ and outcome‐based) and informal (i.e. clan‐ and self‐based) control mechanisms which are not necessarily incompatible. While formal control remains the primary control mode, a portfolio of control appears necessary to augment the inadequacies of formal control due to the evolving nature of the project environment.     

Synergistic Actions of Tailoring Enzymes in Pradimicin Biosynthesis

Three key tailoring enzymes in pradimicin biosynthesis: PdmJ, PdmW, and PdmN, were investigated. PdmW was characterized as the C‐6 hydroxylase by structural characterization of the corresponding product, 6‐hydroxy‐G‐2A. The efficiencies of the C‐5 and C‐6 hydroxylations, catalyzed respectively by PdmJ and PdmW, were low when they were expressed individually with the early biosynthetic enzymes that form G‐2A. When these two cytochrome P450 enzymes were co‐expressed, a dihydroxylated product, 5,6‐dihydroxy‐G‐2A, was efficiently produced, indicating that these two enzymes work synergistically in pradimicin biosynthesis. Heterologously expressed PdmN in Streptomyces coelicolor CH999 converted G‐2A to JX137a by ligating a unit of D ‐alanine to the carboxyl group. PdmN has relaxed substrate specificity toward both amino acid donors and acceptors. Through combinatorial biosynthesis, a series of new pradimicin analogues were produced.     

Direct exit-wave reconstruction from a single defocused image

We propose a direct, non-iterative method for the exact recovery of the complex wave in the exit-surface plane of a coherently illuminated object from a single defocused image. The method is applicable for a wide range of illumination conditions. The defocus range is subject to certain conditions, which if satisfied allow the complex exit-surface wave to be directly recovered by solving a set of linear equations. These linear equations, whose coefficients depend on the incident illumination, are obtained by analyzing the autocorrelation function of an auxiliary wave which is related to the exit-surface wave in a simple way. This autocorrelation is constructed by taking the inverse Fourier transform of the defocused image. We present an experimental proof of concept by recovering the exit-surface wave of a microfiber illuminated by a plane wave formed using a HeNe laser.     

New calibration technique for multiple-component stress wave force balances

The measurement of forces in hypervelocity expansion tubes is not possible using conventional techniques. The stress wave force balance technique can be applied in expansion tubes to measure forces despite the short test times involved. This article presents a new calibration technique for multiple-component stress wave force balances where an impulse response created using a load distribution is required and no orthogonal surfaces on the model exist. This new technique relies on the tensorial superposition of single-component impulse responses analogous to the vectorial superposition of the calibration loads. The example presented here is that of a scale model of the Mars Pathfinder, but the technique is applicable to any geometry and may be useful for cases where orthogonal loads cannot be applied.