Orthogonally bifunctionalised polyacrylamide nanoparticles: a support for the assembly of multifunctional nanodevices

Polyacrylamide nanoparticles bearing two orthogonal reactive functionalities were prepared by reverse microemulsion polymerisation. Water-soluble photosensitisers and peptide or carbohydrate moieties were sequentially attached to the new nanospecies by orthogonal conjugations based on copper-catalysed azide-alkyne cycloaddition and isothiocyanate chemistry.     

Harmonizing electrotechnical standards in North America

The creation of the North American free trade zone, and possibly an Americas free trade zone, will permit the US to compete on an equal footing with the European and Australasian markets. Harmonization of the electrotechnical product standards, conformity assessment test standards, and the electrical installation codes will greatly facilitate trade between Mexico, Canada, and the United States, and improve the economies and the standards of living in all three countries. The paper discusses the electrotechnical organisation agreements, types of harmonisation, North American harmonisation activities, electrotechnical standards harmonisation and their acceptance     

Arthropod–Frog Connection: Decahydroquinoline and Pyrrolizidine Alkaloids Common to Microsympatric Myrmicine Ants and Dendrobatid Frogs

Neotropical poison frogs (Dendrobatidae) contain a wide variety of lipophilic alkaloids, apparently accumulated unchanged into skin glands from dietary sources. Panamanian poison frogs (Dendrobates auratus) raised in a large, screened, outdoor cage and provided for six months with leaf-litter from the frog's natural habitat, accumulated a variety of alkaloids into the skin. These included two isomers of the ant pyrrolizidine 251K; two isomers of the 3,5-disubstituted indolizidine 195B; an alkaloid known to occur in myrmicine ants; another such indolizidine, 211E; two pyrrolidines, 197B and 223N, the former known to occur in myrmicine ants; two tricyclics, 193C and 219I, the former known to occur as precoccinelline in coccinellid beetles; and three spiropyrrolizidines, 222, 236, and 252A, representatives of an alkaloid class known to occur in millipedes. The alkaloids 211E, 197B, and 223N appear likely to derive in part from ants that entered the screened cage. In addition, the frog skin extracts contained trace amounts of four alkaloids, 205D, 207H, 219H, and 231H, of unknown structures and source. Wild-caught frogs from the leaf-litter site contained nearly 40 alkaloids, including most of the above alkaloids. Pumiliotoxins and histrionicotoxins were major alkaloids in wild-caught frogs, but were absent in captive-raised frogs. Ants microsympatric with the poison frog at the leaf-litter site and at an island site nearby in the Bay of Panamá were examined for alkaloids. The decahydroquinoline (–)-cis-195A and two isomers of the pyrrolizidine 251K were found to be shared by microsympatric myrmicine ants and poison frogs. The proportions of the two isomers of 251K were the same in ant and frog.     

Monitoring River Ice Conditions Using Web-Based Cameras

It is necessary to monitor river ice conditions at many northern locations where river ice can pose a risk. Web cameras have been used to monitor real-time ice conditions at hydropower plants, navigation reaches, or locations of ice-related flooding. This study demonstrates how Web cameras can also be used to investigate river ice processes. Hourly images taken over three winters at the confluence of the Allegheny River and Oil Creek in Oil City, Pa. were analyzed. Each image was manually reviewed and classified according to surface ice conditions: stationary ice cover, frazil ice, brash ice, or open lead formation in an ice cover. The percentage of the channel width in the image covered by each ice condition was recorded. The time series of ice data are presented along with the concurrent hydrological and meteorological data. The Web cameras were operational during the 2000–2001, 2001–2002, and 2002–2003 winter seasons and provided an effective and relatively inexpensive means of monitoring and analyzing the river ice conditions.     

Physical and mechanical properties of pultruded composites containing fillers and low profile additives

This article deals with the effect of fillers and additives content on the physical and mechanical properties of unidirectional pultruded glass/polyester composites. The physical characterization consisted of determining the void volume fraction (Vv), density, shrinkage ratio, coefficient of thermal expansion (CTE), and dynamic mechanical properties. The mechanical tests consisted of three‐point‐bending tests under static, impact, and fatigue loading. The low profile additive (LPA) has been found to compensate the cure shrinkage by microvoid formation. Dynamic mechanical analysis measurements show that the LPA slightly lowers the glass transition temperature Tg and increases the internal damping Tan δ. The transverse coefficient of thermal expansion was found to be sensitive to the LPA content. Three‐point bending tests show that the interlaminar shear strength (ILSS) is slightly sensitive to the fillers and LPA content, but the flexural strength is not affected. Impact test results on short beam shear and flexural specimens show the same behavior as in the static tests except that the LPA content has a detrimental effect on the flexural impact properties. The fatigue tests performed show that the effect of fillers is not significant, while the LPA effect is mixed. It seems that there is an LPA content for which the fatigue resistance is maximized. Finally, the wide range of behaviors and span‐to‐depth ratios investigated suggest that the ILSS as measured according to the ASTM 2344 recommendations can be largely misleading because of the unavoidable compressive yielding under the loading nose. For the materials investigated, higher span‐to‐depth ratio are more representative of the ILSS. POLYM. COMPOS., 27:71–81, 2006. © 2005 Society of Plastics Engineers     

Patterning corrosion‐susceptible metallic alloys for digital image correlation in a scanning electron microscope

We investigate the self‐assembly of gold nanoparticles on the surface of magnesium functionalized with 3‐(aminopropyl)trimethoxysilane or 3‐(mercaptopropyl)trimethoxysilane. These nanoparticles served as a speckle pattern for high magnification deformation tracking via digital image correlation combined with scanning electron microscopy. Controlling the pH of the gold nanoparticle suspension to a specific basicity passivated corrosion in magnesium and in three of its alloys to enable proper nanoparticle bonding and self‐assembly. Magnesium was used as a model material as it is particularly difficult to modify for self‐assembly because of its propensity to quickly form a thick oxide, hydroxide, and carbonate layer in the presence of oxygen, water, and carbon dioxide, respectively. Moreover, it corrodes in acidic and slightly basic solutions, further complicating the self‐assembly process. Due to these difficulties, the successful self‐assembly of nanoparticles on magnesium has not previously been reported, to the best of the authors' knowledge. This technique is potentially amendable to other corrosion‐susceptible materials. Gold nanoparticles were self‐assembled in a uniformly dispersed random distribution on pure cast magnesium, cast AM60 (Mg‐6Al‐0.5Mn), rolled WE43 (Mg‐4Y‐3Nd/Gd), and extruded ZE20 (Mg‐2Zn‐0.2Ce).     

An Experimental Comparison of the Maintainability of Object-Oriented and Structured Design Documents

Several important questions still need to be answered regarding the maintainability of object-oriented design documents. This paper focuses on the following issues: are object-oriented design documents easier to understand and modify than structured design documents? Do they need to comply with quality guidelines such as the ones provided by Coad and Yourdon? What is the impact of such quality standards on the understandability and modifiability of design documents? Answers can be based on informed opinion or empirical evidence. Since software technology investments are substantial and contradictory opinions exist regarding design strategies, performing empirical studies on these topics is a relevant research activity. This paper presents a controlled experiment performed with computer science students as subjects. Results strongly suggest that quality guidelines based on Coad and Yourdon principles have a beneficial effect on the maintainability of object-oriented design documents. However, there is no strong evidence regarding the alleged higher maintainability of object-oriented design documents over structured design documents. Furthermore, results suggest that object-oriented design documents are more sensitive to poor design practices, in part because their cognitive complexity becomes increasingly unmanageable. However, because our ability to generalise these results is limited, they should be considered as preliminary, i.e., it is very likely that they can only be generalised to programmers with little object-oriented training and programming experience. Such programmers can, however, be commonly found on maintenance projects. As well as additional research, external replications of this study are required to confirm the results and achieve confidence in these findings.     

Retinopathy of prematurity screening, stress related responses, the role of nesting

AIMS/BACKGROUND: In a prospective study the degree of distress caused by retinopathy of prematurity (ROP) screening in a cohort of preterm infants was assessed and the modifying effects of nesting in reducing their discomfort was evaluated. METHODS: 38 preterm infants were included in the study. 19 infants were placed in a nest with boundaries (intervention group) and 19 infants were placed on a cot blanket (control group). Observations were made 2 minutes before, throughout, and 2 minutes after ROP examination. The factors observed were crying responses, neurobehavioural activity, and physiological changes (heart rate, oxygen saturation). Recordings were made using a video camera for crying and neurobehavioural activity and an Oxypleth monitor for heart rate and oxygen saturation. RESULTS: During ROP screening, the total group of 38 infants (nested and non-nested combined) displayed increased neurobehavioural activity (p < 0.01) and crying (p < 0.01). The increased activity and crying coincided with the invasive part of the procedure. The distress caused by ROP screening was significantly less for the nested group compared with the non-nested group for both movement activity (p < 0.01) and crying (p < 0.01). The physiological data, heart rate, and oxygen saturation were not statistically significant. CONCLUSION: ROP screening is distressing for preterm infants. Nesting can significantly reduce this discomfort. The findings in this study are of value in designing more optimal ROP examination schedules for infants.     

Maximum Impact Force of Woody Debris on Floodplain Structures

We collided woody debris (i.e., logs) with structures using flume and test basin laboratory facilities to investigate the maximum impact force that floodplain structures are exposed to from floating woody debris. The tests also investigated the influence of collision geometry, determined by the debris orientation on impact, on the maximum impact forces. We reviewed the three approaches that represent the existing guidance for estimating maximum impact forces. Each approach estimates the maximum impact force based on the debris velocity and mass. We show that all the existing approaches can be derived from a single-degree-of-freedom model of the collision and can be considered to be equivalent. The laboratory data show that the maximum impact force was associated with a log striking a rigid structure with its end. Oblique and eccentric collisions reduced the maximum impact load in a predictable and consistent manner. The approach we refer to as “contact stiffness,” a linear, one-degree-of-freedom model with no damping, was able to reproduce the laboratory results over the entire range of data, with an effective contact stiffness of 2.4 MN/m.