Chromosomal instability and its relationship to other end points of genomic instability

Chromosomal destabilization is one end point of the more general phenomenon of genomic instability. We previously established that chromosomal instability can manifest in clones derived from single progenitor cells several generations after X-irradiation. To understand the potential relationship between chromosomal destabilization and the other end points of genomic instability, we generated a series of chromosomally stable and unstable clones by exposure to X-rays. All clones were derived from the human-hamster hybrid line GM10115, which contains a single copy of human chromosome 4 in a background of 20-24 hamster chromosomes. These clones were then subjected to a series of assays to determine whether chromosomal instability is associated with a general "mutator phenotype" and whether it modulates other end points of genomic instability. Thus, we analyzed clones for sister chromatid exchange, delayed reproductive cell death, delayed mutation, mismatch repair, and delayed gene amplification. Statistical analyses performed on each group of chromosomally stable and unstable clones indicated that, although individual clones within each group were significantly different from unirradiated clones for many of the end points, there was no significant correlation between chromosomal instability and sister chromatid exchange, delayed mutation, and mismatch repair. Delayed gene amplification was found to be marginally correlated to chromosomal instability (P < 0.1), and delayed reproductive cell death (the persistent reduction in plating efficiency after irradiation) was found to be significantly correlated (P < 0.05). These correlations may be explained by chromosomal destabilization, which can mediate gene amplification and can result in cellular lethality. These data implicate multiple molecular and genetic pathways leading to different manifestations of genomic instability in GM10115 cells surviving exposure to DNA-damaging agents.     

Open‐Shell Donor–Acceptor Conjugated Polymers with High Electrical Conductivity

Conductive polymers largely derive their electronic functionality from chemical doping, processes by which redox and charge‐transfer reactions form mobile carriers. While decades of research have demonstrated fundamentally new technologies that merge the unique functionality of these materials with the chemical versatility of macromolecules, doping and the resultant material properties are not ideal for many applications. Here, it is demonstrated that open‐shell conjugated polymers comprised of alternating cyclopentadithiophene and thiadiazoloquinoxaline units can achieve high electrical conductivities in their native “undoped” form. Spectroscopic, electrochemical, electron paramagnetic resonance, and magnetic susceptibility measurements demonstrate that this donor–acceptor architecture promotes very narrow bandgaps, strong electronic correlations, high‐spin ground states, and long‐range π‐delocalization. A comparative study of structural variants and processing methodologies demonstrates that the conductivity can be tuned up to 8.18 S cm^?1. This exceeds other neutral narrow bandgap conjugated polymers, many doped polymers, radical conductors, and is comparable to commercial grades of poly(styrene‐sulfonate)‐doped poly(3,4‐ethylenedioxythiophene). X‐ray and morphological studies trace the high conductivity to rigid backbone conformations emanating from strong π‐interactions and long‐range ordered structures formed through self‐organization that lead to a network of delocalized open‐shell sites in electronic communication. The results offer a new platform for the transport of charge in molecular systems.     

Ultrasensitive Strain Gauges Enabled by Graphene‐Stabilized Silicone Emulsions

Here, an approach is presented to incorporate graphene nanosheets into a silicone rubber matrix via solid stabilization of oil‐in‐water emulsions. These emulsions can be cured into discrete, graphene‐coated silicone balls or continuous, elastomeric films by controlling the degree of coalescence. The electromechanical properties of the resulting composites as a function of interdiffusion time and graphene loading level are characterized. With conductivities approaching 1 S m^?1, elongation to break up to 160%, and a gauge factor of ≈20 in the low‐strain linear regime, small strains such as pulse can be accurately measured. At higher strains, the electromechanical response exhibits a robust exponential dependence, allowing accurate readout for higher strain movements such as chest motion and joint bending. The exponential gauge factor is found to be ≈20, independent of loading level and valid up to 80% strain; this consistent performance is due to the emulsion‐templated microstructure of the composites. The robust behavior may facilitate high‐strain sensing in the nonlinear regime using nanocomposites, where relative resistance change values in excess of 10⁷ enable highly accurate bodily motion monitoring.     

The value of a desk study for building a national river obstacle inventory

This study evaluates two desk‐based approaches for building an inventory of man‐made river obstacles. The creation of a river obstacle inventory is a vital first step in developing a prioritization process for obstacle removal and/or modification. In this study, a desktop geographical information system analysis of two rivers and their tributary network was undertaken, using two different approaches. The first involved analysing historical maps, satellite imagery, and Ordnance Survey Ireland Discovery Series maps and producing a geo‐referenced layer of all the potential river obstacles. The second involved developing a geo‐referenced layer of potential river obstacles based on the intersections between elements of the transport network (roads and railways) and river systems. To determine the effectiveness of the desk studies, the located obstacles were cross‐referenced with actual obstacles verified through a field survey. The desk studies identified several thousand potential obstacles. The study utilizing a range of maps consistently located a greater number of actual obstacles than the desk study based on intersections between the transport and river networks. The results indicate that desk‐based research offers an efficient and effective method for locating river obstacles and can guide subsequent field surveys aimed at confirming the presence of obstacles. This is particularly useful for eliminating from study large stretches of rivers that would otherwise need to be walked to confirm the presence, or otherwise, of potential river obstacles. In this regard, desk‐based exercises can offer opportunities to save on both time and cost in larger river assessments.     

Controlling the Diameters of Nanotubes Self‐Assembled from Designed Peptide Bolaphiles

Controlling the diameters of nanotubes represents a major challenge in nanostructures self‐assembled from templating molecules. Here, two series of bolaform hexapeptides are designed, with Set I consisting of Ac‐KI₄K‐NH₂, Ac‐KI₃NleK‐NH₂, Ac‐KI₃LK‐NH₂ and Ac‐KI₃TleK‐NH₂, and Set II consisting of Ac‐KI₃VK‐NH₂, Ac‐KI₂V₂K‐NH₂, Ac‐KIV₃K‐NH₂ and Ac‐KV₄K‐NH₂. In Set I, substitution for Ile in the C‐terminal alters its side‐chain branching, but the hydrophobicity is retained. In Set II, the substitution of Val for Ile leads to the decrease of hydrophobicity, but the side‐chain β‐branching is retained. The peptide bolaphiles tend to form long nanotubes, with the tube shell being composed of a peptide monolayer. Variation in core side‐chain branching and hydrophobicity causes a steady shift of peptide nanotube diameters from more than one hundred to several nanometers, thereby achieving a reliable control over the underlying molecular self‐assembling processes. Given the structural and functional roles of peptide tubes with varying dimensions in nature and in technological applications, this study exemplifies the predictive templating of nanostructures from short peptide self‐assembly.     

Hierarchically Branched Siloxane Brushes for Efficient Harvesting of Atmospheric Water

Atmospheric water harvesting is considered a viable source of freshwater to alleviate water scarcity in an arid climate. Water condensation tends to be more efficient on superhydrophobic surfaces as the spontaneous coalescence-induced droplet jumping on superhydrophobic surfaces enables faster condensate removal. However, poor water nucleation on these surfaces leads to meager water harvest. A conventional approach to the problem is to fabricate micro- and nanoscale biphilic structures. Nonetheless, the process is complex, expensive, and difficult to scale. Here, the authors present an inexpensive and scalable method based on manipulating the water-repellent coatings of superhydrophobic surfaces. Flexible siloxane can facilitate water nucleation, while a branched structure promotes efficient droplet jumping. Moreover, ToF-SIMS analysis indicated that branched siloxane provides a better water-repellent coating coverage than linear siloxane and the siloxanes comprise hydrophilic and hydrophobic molecular segments. Thus, the as-prepared superhydrophobic surface, TiO₂ nanorods coated with branched siloxanes harvested eight times more water than a typical fluoroalkylsilane (FAS)-coated surface under a low 30% relative humidity and performed better than most reported biphasic materials.     

Effects of changing diagnostic criteria on the risk of developing diabetes

OBJECTIVE: The American Diabetes Association (ADA) has recommended that the fasting plasma glucose (FPG) level used to diagnose diabetes be changed from 7.8 mmol/l (the level recommended by the National Diabetes Data Group [NDDG] in 1979) to 7.0 mmol/l. We examined the impact of this change on rates of progression to overt diabetes from different levels of FPG. RESEARCH DESIGN AND METHODS: Using the laboratory database of Mayo Clinic, we assembled a cohort of 8,098 nondiabetic Olmsted County residents 40 years of age or older on 1 July 1983. Subjects were followed for a median of 9 years. RESULTS: Among 7,567 individuals with follow-up FPG data, 778 (10.3%) progressed to ADA diabetes and 513 (6.8%; P < 0.0001) progressed to NDDG diabetes. The risk of developing ADA diabetes was 7, 19, and 39% for individuals with initial FPG values in the ranges of <5.6, 5.6-6.0, and 6.1-6.9 mmol/l, respectively. For progression to NDDG diabetes, the respective risks were 3, 11, and 25%. A clear gradient of risk was observed within the "normal" range of FPG (<5.6 mmol/l). Among the 793 individuals who developed ADA diabetes, 222 (29%) developed NDDG diabetes simultaneously and 291 (37%) developed NDDG diabetes later. In all FPG subgroups, progression to ADA diabetes occurred approximately 7 years sooner than progression to NDDG diabetes. CONCLUSIONS: The baseline level of FPG is a major predictor of an individual's risk of developing diabetes. The proposed change in the diagnostic criteria for diabetes will lead to earlier diagnosis among individuals who are destined to develop the disease.     

Area‐Preserving Parameterizations for Spherical Ellipses

We present new methods for uniformly sampling the solid angle subtended by a disk. To achieve this, we devise two novel area‐preserving mappings from the unit square [0,1]² to a spherical ellipse (i.e. the projection of the disk onto the unit sphere). These mappings allow for low‐variance stratified sampling of direct illumination from disk‐shaped light sources. We discuss how to efficiently incorporate our methods into a production renderer and demonstrate the quality of our maps, showing significantly lower variance than previous work.     

Deposition rate and temperature of carbon films during laser-induced CVD on a moving substrate

The feasibility of using pyrolytic laser-induced chemical vapor deposition (LCVD) to deposit carbon coatings on moving fused quartz substrates is investigated. This LCVD system uses a CO₂ laser to locally heat a substrate in open air to create a hot spot. Pyrolysis of hydrocarbon species occurs and subsequently deposits a layer of carbon film onto the substrate surface. The results of this study indicate that growth kinetics and the geometry of uniform carbon stripes deposited by pyrolytic LCVD strongly related to the laser power, the traverse velocity of the substrate, the type of hydrocarbon species used in deposition, and the diameter of the substrate. The deposition rate of carbon film increases exponentially with the laser power, while an increase in traverse velocity of the substrate will also increase the deposition rate until a maximum deposition rate is reached; further increases in the traverse velocity will decrease the deposition rate. We suspect that this optimal deposition rate is caused by substrate motion, which affects the substrate surface temperature, and consequently the effective surface area available for film deposition. The substrate temperature is observed to behave linearly with the deposition parameters considered in this study.     

Lipase-catalyzed glycerolysis of soybean oil in supercritical carbon dioxide

The transesterification of soybean oil with glycerol, 1,2-propanediol, and methanol by an immobilized lipase in flowing supercritical carbon dioxide for the synthesis of monoglycerides is described. A lipase from Candida antarctica was used to catalyze the reaction of soybean oil with glycerol, 1,2-propanediol, ethylene glycol, and methanol. Reactions were performed in supercritical carbon dioxide at a density of 0.72 g/L and at a flow rate of 6 μL/min (expanded gas). The substrates were added at flows ranging from 2.5 to 100 μL/min. Monoglycerides were obtained at up to 87 wt%, and fatty acid methyl esters at nearly 100 wt%. The reactivity of the alcohols paralleled the solubility of the substrate in liquid carbon dioxide. Glycerol has the slowest reaction rate, only 2% of that of methanol.