Manipulation of live mouse embryonic stem cells using holographic optical tweezers

We report the ability to move and arrange patterns of live embryonic stem cells using holographic optical tweezers. Single cell suspensions of mouse embryonic stem cells were manipulated with holographic optical tweezers into a variety of patterns including lines, curves and circles. Individual cells were also lifted out of the sample plane highlighting the potential for 3D positional control. Trypan blue dye exclusion and Live/Dead? staining (CMFDA^?1, EthHD^?1) showed that the cells were still viable after manipulation with the optical tweezers. The ability to move individual stem cells into specific, pre-defined patterns provides a method to study how arrangement and associated small-scale interactions occur between neighbouring cells.     

In full retreat: the Canadian government's new environmental assessment law undoes decades of progress

The Canadian Environmental Assessment Act 2012, which came into force on 6 July 2012, virtually eliminates the core of federal-level environmental assessment in Canada. Under the new law, federal environmental assessments will be few, fragmentary, inconsistent and late. Key decision-making will be discretionary and consequently unpredictable. Much of it will be cloaked in secrecy. The residual potential for effective, efficient and fair assessments will depend heavily on requirements under other federal legislation and on the uneven diversity of provincial, territorial and Aboriginal assessment processes. This paper reviews the key characteristics of the new law in light of 10 basic design principles for environmental assessment processes, and considers the broader international implications of the Canadian retreat from application of these principles.     

Avoiding sustainability trade-offs in environmental assessment

Progress towards sustainability requires positive steps to meet all of the interdependent core requirements for sustainability – including biophysical system integrity and basic human well-being. Where these essentials are involved trade-offs should be avoided, unless all other options are worse. In environmental assessments, it is useful to identify major trade-offs and minimize them through selection of less bad alternatives or addition of mitigations or offsets. However, the more promising approach starts earlier and encourages planning that avoids invidious trade-offs, including through re-consideration of the initial purposes and alternatives.

This paper considers two historical cases of assessments that avoided significant trade-offs through processes that gave mandatory attention to purposes and alternatives, covered the full suite of sustainability considerations, empowered citizen participants and facilitated the bumping of cases up to a more strategic level where broader alternatives offered better trade-off avoidance. These long-advocated assessment design elements are still rarely applied as a full package in existing environmental assessment law and practice. Commitment to trade-off avoidance adds to the reasons for their general adoption.     

A Phenomenological Model for Tool Wear in Friction Stir Welding of Metal Matrix Composites

Friction stir welding (FSW) of metal matrix composites (MMCs) is advantageous because the solid-state nature of the process precludes formation of deleterious intermetallic phases which accompany melting. FSW of MMCs is complicated by rapid and severe wear of the welding tool, a consequence of contact between the tool and the much harder abrasive reinforcement which gives the workpiece material its enhanced strength. The current article demonstrates that Nunes’s rotating plug model of material flow in FSW, which has been successfully applied in many other contexts, can also help us understand wear in FSW of MMCs. An equation for predicting the amount of wear in this application is developed and compared with experimental data. This phenomenological model explains the relationship between wear and FSW process parameters documented in previous studies.     

Mass spectrometric analysis of muscle samples to detect potential antibiotic growth promoter misuse in broiler chickens

Mass spectrometric methods were developed and validated for the analysis in chicken muscle of a range of antibiotic growth promoters: spiramycin, tylosin, virginiamycin and bacitracin, and separately for two marker metabolites of carbadox (quinoxaline-2-carboxylic acid and 1,4-bisdesoxycarbadox), and a marker metabolite of olaquindox (3-methyl-quinoxaline-2-carboxylic acid). The use of these compounds as antibiotic growth promoters has been banned by the European Commission. This study aimed to develop methods to detect their residues in muscle samples as a means of checking for the use of these drugs during the rearing of broiler chickens. When fed growth-promoting doses for 6 days, spiramycin (31.4?μg?kg(-1)), tylosin (1.0?μg?kg(-1)), QCA (6.5?μg?kg(-1)), DCBX (71.2?μg?kg(-1)) and MQCA (0.2?μg?kg(-1)) could be detected in the muscle 0 days after the withdrawal of fortified feed. Only spiramycin could consistently be detected beyond a withdrawal period of 1?day. All analytes showed stability to a commercial cooking process, therefore raw or cooked muscle could be used for monitoring purposes.     

An investigation of dehazing effects on image and video coding

This paper makes an investigation of the dehazing effects on image and video coding for surveillance systems. The goal is to achieve good dehazed images and videos at the receiver while sustaining low bitrates (using compression) in the transmission pipeline. At first, this paper proposes a novel method for single-image dehazing, which is used for the investigation. It operates at a faster speed than current methods and can avoid halo effects by using the median operation. We then consider the dehazing effects in compression by investigating the coding artifacts and motion estimation in cases of applying any dehazing method before or after compression. We conclude that better dehazing performance with fewer artifacts and better coding efficiency is achieved when the dehazing is applied before compression. Simulations for Joint Photographers Expert Group images in addition to subjective and objective tests with H.264 compressed sequences validate our conclusion.     

Chromium isotope fractionation during reduction of Cr(VI) under saturated flow conditions

Chromium isotopes are potentially useful indicators of Cr(VI) reduction reactions in groundwater flow systems; however, the influence of transport on Cr isotope fractionation has not been fully examined. Laboratory batch and column experiments were conducted to evaluate isotopic fractionation of Cr during Cr(VI) reduction under both static and controlled flow conditions. Organic carbon was used to reduce Cr(VI) in simulated groundwater containing 20 mg L(-1) Cr(VI) in both batch and column experiments. Isotope measurements were performed on dissolved Cr on samples from the batch experiments, and on effluent and profile samples from the column experiment. Analysis of the residual solid-phase materials by scanning electron microscopy (SEM) and by X-ray absorption near edge structure (XANES) spectroscopy confirmed association of Cr(III) with organic carbon in the column solids. Decreases in dissolved Cr(VI) concentrations were coupled with increases in δ(53)Cr, indicating that Cr isotope enrichment occurred during reduction of Cr(VI). The δ(53)Cr data from the column experiment was fit by linear regression yielding a fractionation factor (α) of 0.9979, whereas the batch experiments exhibited Rayleigh-type isotope fractionation (α = 0.9965). The linear characteristic of the column δ(53)Cr data may reflect the contribution of transport on Cr isotope fractionation.     

Erratum: Determination of Deterrent Profiles in Nitrocellulose Propellant Grains Using Confocal Raman Microscopy

Due to a technical error this article was published online with two DOI: (10.1002/prep.201000081 and 10.1002/prep.201100081). When citing or referring to this article, please use the following DOI: 10.1002/prep.201000081.     

QuaMeter: multivendor performance metrics for LC-MS/MS proteomics instrumentation

LC-MS/MS-based proteomics studies rely on stable analytical system performance that can be evaluated by objective criteria. The National Institute of Standards and Technology (NIST) introduced the MSQC software to compute diverse metrics from experimental LC-MS/MS data, enabling quality analysis and quality control (QA/QC) of proteomics instrumentation. In practice, however, several attributes of the MSQC software prevent its use for routine instrument monitoring. Here, we present QuaMeter, an open-source tool that improves MSQC in several aspects. QuaMeter can directly read raw data from instruments manufactured by different vendors. The software can work with a wide variety of peptide identification software for improved reliability and flexibility. Finally, QC metrics implemented in QuaMeter are rigorously defined and tested. The source code and binary versions of QuaMeter are available under Apache 2.0 License at http://fenchurch.mc.vanderbilt.edu.     

Magnesium- and strontium-co-substituted hydroxyapatite: the effects of doped-ions on the structure and chemico-physical properties

The present study is aimed at investigating the contribution of two biologically important cations, Mg²⁺ and Sr²⁺, when substituted into the structure of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂,HA). The substituted samples were synthesized by an aqueous precipitation method that involved the addition of Mg²⁺- and Sr²⁺-containing precursors to partially replace Ca²⁺ ions in the apatite structure. Eight substituted HA samples with different concentrations of single (only Mg²⁺) or combined (Mg²⁺ and Sr²⁺) substitution of cations have been investigated and the results compared with those of pure HA. The obtained materials were characterized by X-ray powder diffraction, specific surface area and porosity measurements (N₂ adsorption at 77?K), FT-IR and Raman spectroscopies and scanning electron microscopy. The results indicate that the co-substitution gives rise to the formation of HA and ??-TCP structure types, with a variation of their cell parameters and of the crystallinity degree of HA with varying levels of substitution. An evaluation of the amount of substituents allows us to design and prepare BCP composite materials with a desired HA/??-TCP ratio.