Spectroelectrochemical sensing based on attenuated total internal reflectance stripping voltammetry. 2. Determination of mercury and lead

Detection of lead and mercury by attenuated total internal reflectance spectroscopy coupled to stripping voltammetry is demonstrated. Changes in attenuation of light passing through an indium tin oxide optically transparent electrode (ITO-OTE) accompany the electrodeposition and stripping of lead and mercury on the electrode surface. The change in absorbance during stripping of electrodeposited metal constitutes the analytical response that enables detection over a range of 2.5 x 10(-7)-5 x 10(-5) and 5 x 10(-8)-5 x 10(-5) M for mercury and lead, respectively. The spectroelectrochemical responses of mercury and lead on the ITO surface are characterized and optimized with respect to solution conditions, the potential excitation signals used for deposition and stripping, and wavelength for detection. The deposited metals were examined by environmental scanning electron miscroscopy, and the electrodeposition pattern of lead and mercury was found to influence the optical response.     

Contents of Volume 111 (2001)

Volume Contents

Contents of Volume 111 (2001)     

Carabidae Semiochemistry: Current and Future Directions

Ground beetles (Carabidae) are recognized for their diverse, chemically-mediated defensive behaviors. Produced using a pair of pygidial glands, over 250 chemical constituents have been characterized across the family thus far, many of which are considered allomones. Over the past century, our knowledge of Carabidae exocrine chemistry has increased substantially, yet the role of these defensive compounds in mediating behavior other than repelling predators is largely unknown. It is also unclear whether non-defensive compounds produced by ground beetles mediate conspecific and heterospecific interactions, such as sex-aggregation pheromones or kairomones, respectively. Here we review the current state of non-exocrine Carabidae semiochemistry and behavioral research, discuss the importance of semiochemical research including but not limited to allomones, and describe next-generation methods for elucidating the underlying genetics and evolution of chemically-mediated behavior.     

Rare Gain-of-Function KCND3 Variant Associated with Cerebellar Ataxia,Parkinsonism, Cognitive Dysfunction,and Brain Iron Accumulation

Loss-of-function mutations in the K_V4.3 channel-encoding KCND3 gene are linked to neurodegenerative cerebellar ataxia. Patients suffering from neurodegeneration associated with iron deposition may also present with cerebellar ataxia. The mechanism underlying brain iron accumulation remains unclear. Here, we aim to ascertain the potential pathogenic role of KCND3 variant in iron accumulation-related cerebellar ataxia. We presented a patient with slowly progressive cerebellar ataxia, parkinsonism, cognitive impairment, and iron accumulation in the basal ganglia and the cerebellum. Whole exome sequencing analyses identified in the patient a heterozygous KCND3 c.1256G>A (p.R419H) variant predicted to be disease-causing by multiple bioinformatic analyses. In vitro biochemical and immunofluorescence examinations revealed that, compared to the human K_V4.3 wild-type channel, the p.R419H variant exhibited normal protein abundance and subcellular localization pattern. Electrophysiological investigation, however, demonstrated that the K_V4.3 p.R419H variant was associated with a dominant increase in potassium current amplitudes, as well as notable changes in voltage-dependent gating properties leading to enhanced potassium window current. These observations indicate that, in direct contrast with the loss-of-function KCND3 mutations previously reported in cerebellar ataxia patients, we identified a rare gain-of-function KCND3 variant that may expand the clinical and molecular spectra of neurodegenerative cerebellar disorders associated with brain iron accumulation.     

Field-Testing of Methyl Salicylate for Recruitment and Retention of Beneficial Insects in Grapes and Hops

Evidence for recruitment and retention of beneficial insects in grapes and hops using controlled-release dispensers of methyl salicylate (MeSA), a component of herbivore-induced volatile blends, is presented. In a replicated experiment conducted in a juice grape vineyard, sticky cards in blocks baited with MeSA captured significantly greater numbers of five species of predatory insects (Chrysopa nigricornis, Hemerobius sp., Deraeocoris brevis, Stethorus punctum picipes, Orius tristicolor) than unbaited blocks. Four insect families (Syrphidae, Braconidae, Empididae, Sarcophagidae) were also significantly more abundant in the MeSA-baited blocks, as indicated by sticky card captures. Canopy shake samples and sticky card monitoring conducted in a MeSA-baited, unsprayed hop yard indicated development and maintenance of a beneficial arthropod population that was nearly four times greater than that present in an unbaited reference yard. Four times as many S. punctum picipes and six times as many O. tristicolor were sampled in the MeSA yard. Similar contrasts in abundance of these predators and others were apparent when compared with levels recorded in the yard in previous years. The large population of predatory insects in the MeSA-baited hop yard was associated with a dramatic reduction in spider mite numbers, the major arthropod pest of hops, in late June, and subeconomic populations were maintained for the rest of the season. The evidence presented here is highly suggestive that the use of controlled-release MeSA in a crop could increase recruitment and residency of populations of certain beneficial insects. This strategy may have the potential to enhance the efficacy and reliability of conservation biological control in crop pest management.     

Teachers' perceptions of students' reading abilities: An examination of the relationship between teachers' judgments and students' performance across a continuum of rating methods.

Teacher perceptions about students' academic abilities are important for several reasons (e.g., instructional decision making, special education entitlement decisions). Not surprisingly, researchers have investigated the accuracy of teachers' decisions. Although some data reveal that teachers are relatively good judges of academic performance, other findings have suggested otherwise. A likely explanation for conflicting findings is the varying assessment methods (e.g., direct vs. indirect, norm-referenced vs. peer-independent) and different data analysis procedures that have been used across studies. The purpose of this study was to investigate a continuum of teacher-perception assessment methods as they corresponded to students' oral reading fluency performance. Participants included 10 teachers and 87 first, second, and third grade students from a suburban school in the northeast. Overall results suggested that teachers were generally accurate when estimating students' performance when students had strong oral reading fluency skills, but teachers had more difficulty judging students with average to low oral reading fluency. Further, data interpretation of teachers' judgment accuracy differed somewhat depending upon the statistical method employed. Implications, limitations, and suggestions for future research related to this study are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A general method for solving dynamically accelerating multiple co-linear cracks

We present a general method for analyzing dynamically accelerating multiple co-linear cracks that can be applied to the contexts of plane strain or antiplane shear in an elastic material. The difficulty in solving such problems lies in the fact that the space-time regions containing known data evolve as the crack propagates in an a priori unknown manner. Using an analog to a Dirichlet-to-Neumann map, we can find complete knowledge of the stress and displacement along the fracture plane, facilitating the application of fracture criteria that require these values away from the crack tip. The method is demonstrated for a semi-infinite or finite mode III crack as well as for a pair of cracks in elastic material, using a stress intensity factor fracture criterion for simplicity.     

Effects of Duct Types and Emulsifiable Oils on Bond and Friction Losses in Posttensioned Concrete

Emulsifiable oils are often used in posttensioned construction to reduce friction losses and provide temporary corrosion protection for tendons prior to grouting. This paper addresses the effects of two emulsifiable oils and three duct types on bond and friction losses. Bond test results indicate that corrugated galvanized steel ducts provide better anchorage than corrugated HDPE ducts. Rigid steel pipes performed poorly because of failure at the duct-concrete or grout-duct interface. Bond test results also indicate that the ultimate strength of posttensioned specimens with oiled tendons is similar to or better than the ultimate strength of specimens with unoiled tendons. However, specimens with oiled tendons experienced greater slip at a given load than specimens with unoiled tendons. Friction test results indicate that current recommended design values for the coefficient of friction for steel pipes and galvanized ducts are accurate. However, the measured coefficient for HDPE ducts is significantly less than the AASHTO-recommended value. Friction tests also indicate that lubrication of the tendon reduces the friction coefficient by 15% in rigid steel pipes and HDPE ducts if stressing occurs while the oil is fresh.     

Managing artificial intelligence projects: Key insights from an AI consulting firm

While organisations are increasingly interested in artificial intelligence (AI), many AI projects encounter significant issues or even fail. To gain a deeper understanding of the issues that arise during these projects and the practices that contribute to addressing them, we study the case of Consult, a North American AI consulting firm that helps organisations leverage the power of AI by providing custom solutions. The management of AI projects at Consult is a multi-method approach that draws on elements from traditional project management, agile practices, and AI workflow practices. While the combination of these elements enables Consult to be effective in delivering AI projects to their customers, our analysis reveals that managing AI projects in this way draw upon three core logics, that is, commonly shared norms, values, and prescribed behaviours which influence actors' understanding of how work should be done. We identify that the simultaneous presence of these three logics—a traditional project management logic, an agile logic, and an AI workflow logic—gives rise to conflicts and issues in managing AI projects at Consult, and successfully managing these AI projects involves resolving conflicts that arise between them. From our case findings, we derive four strategies to help organisations better manage their AI projects.