Structural and spectroscopic characterisation of the holmium double-decker partially oxidised and bi-radical phthalocyanine complexes with iodine

Two crystals of holmium(III) double-decker iodine doped phthalocyanines, HoPc₂I_5/3 (I) and HoPc₂I (II), were grown directly in the reaction of holmium chips with 1,2-dicyanobenzene under versatile quantity of iodine at 180-160 °C. The complex I crystallises in the P4/mcc space group of tetragonal system, while the complex II crystallises in the P2/c space group of monoclinic system. The space group of P4/mcc and z = 1 requires that the Ho(III) atom is statistically disordered in the HoPc₂I_5/3 structure. The iodine atoms form linear symmetrical triiodide ions in I, while the I⁻ ions in II. Assignment of iodine species as in the HoPc₂I_5/3 and I⁻ in HoPc₂I complexes point to the +5/9 and +1 oxidation state of the HoPc₂ unit in these complexes. Thus one Pc macrocycle of the double-decker HoPc₂ units has a non-integer oxidation state of −1.222 in I, while both Pc-rings are one-electron oxidised radical Pc⁻ in II. Magnetic susceptibilities of HoPc₂I_5/3 and HoPcI at room temperature are 4.56 × 10⁻² and 5.12 × 10⁻² emu/mol and the calculated magnetic moments are 10.46 and 11.08 μ_B, respectively. UV-Vis spectroscopic measurement of I and II in benzene solution were carried out and discussed.     

Measuring the Surface Roughness of Stream Stones

Measuring the fine-scale heterogeneity of stones and other substrates is a challenge for benthic ecologists. I describe a method for measuring the roughness of stones that is based on the ratio of two surface area measurements: one that follows substrate contours and one based on a similar-sized modified spheroid. This roughness index is easily measured, assesses the entire surface of stones, and enables the measurement of replicate stones. Roughness measurements of 14 rock types demonstrated that values obtained were consistent with perceived roughness and porosity. Application of the roughness index to a published data set produced a curvilinear relationship between stone roughness and the biomass of algae in roughness-associated crevices.     

Robust hierarchical state-space models reveal diel variation in travel rates of migrating leatherback turtles

1. Biological and statistical complexity are features common to most ecological data that hinder our ability to extract meaningful patterns using conventional tools. Recent work on implementing modern statistical methods for analysis of such ecological data has focused primarily on population dynamics but other types of data, such as animal movement pathways obtained from satellite telemetry, can also benefit from the application of modern statistical tools. 2. We develop a robust hierarchical state-space approach for analysis of multiple satellite telemetry pathways obtained via the Argos system. State-space models are time-series methods that allow unobserved states and biological parameters to be estimated from data observed with error. We show that the approach can reveal important patterns in complex, noisy data where conventional methods cannot. 3. Using the largest Atlantic satellite telemetry data set for critically endangered leatherback turtles, we show that the diel pattern in travel rates of these turtles changes over different phases of their migratory cycle. While foraging in northern waters the turtles show similar travel rates during day and night, but on their southward migration to tropical waters travel rates are markedly faster during the day. These patterns are generally consistent with diving data, and may be related to changes in foraging behaviour. Interestingly, individuals that migrate southward to breed generally show higher daytime travel rates than individuals that migrate southward in a non-breeding year. 4. Our approach is extremely flexible and can be applied to many ecological analyses that use complex, sequential data.     

Nanomechanical force measurements of gliadin protein interactions

The strength and nature of interactions between monomeric gliadin proteins involving alpha-alpha, omega-omega, and alpha-omega interactions in 0.01M acetic acid, and the effect of urea has been investigated. It was shown by means of nanomechanical force measurements that the stretching events in the separation curve after adhesive phenomena originated from proteins. These stretching events displayed different responses of the alpha- and omega-gliadins to urea. While 2M urea caused the more globular alpha-gliadins to unfold, the beta-turn-rich omega-gliadins remained fairly stable even in 8M urea. This suggests different roles for gliadins in the formation of dough; while the omega-gliadins are still in a compact structure being responsible for the viscous flow, the alpha-gliadins have already started to participate in forming the network in dough.     

INCREASED RESIDUAL VARIANCE AT DEVELOPMENTAL SWITCH POINTS: STATISTICAL ARTIFACT OR INDICATOR OF EXPOSED GENOTYPIC INFLUENCE?

Discussing the organization of developmental switches, West-Eberhard (2003) proposed the use of regression residual plots to locate the neutral point of the switch, which is characterized by maximum genotypic influence on the resulting phenotype. However, statistical artifacts due to measurement error in nonlinear models might account for a substantial proportion of the increase of residuals variance at the switch point. Simulations based on field data show that increases in residual variance occur as artifacts when normal amounts of measurement error are present, even in absence of any genotypic variance. The results suggest that interpretation of nonlinear variation in thresold traits is problematic and requires considering this statistical effect. A method to estimate the weight of genotypic contribution to residual variance is proposed, and its assumptions and limitations are discussed.     

Bivariate line-fitting methods for allometry

Fitting a line to a bivariate dataset can be a deceptively complex problem, and there has been much debate on this issue in the literature. In this review, we describe for the practitioner the essential features of line-fitting methods for estimating the relationship between two variables: what methods are commonly used, which method should be used when, and how to make inferences from these lines to answer common research questions. A particularly important point for line-fitting in allometry is that usually, two sources of error are present (which we call measurement and equation error), and these have quite different implications for choice of line-fitting method. As a consequence, the approach in this review and the methods presented have subtle but important differences from previous reviews in the biology literature. Linear regression, major axis and standardised major axis are alternative methods that can be appropriate when there is no measurement error. When there is measurement error, this often needs to be estimated and used to adjust the variance terms in formulae for line-fitting. We also review line-fitting methods for phylogenetic analyses. Methods of inference are described for the line-fitting techniques discussed in this paper. The types of inference considered here are testing if the slope or elevation equals a given value, constructing confidence intervals for the slope or elevation, comparing several slopes or elevations, and testing for shift along the axis amongst several groups. In some cases several methods have been proposed in the literature. These are discussed and compared. In other cases there is little or no previous guidance available in the literature. Simulations were conducted to check whether the methods of inference proposed have the intended coverage probability or Type I error. We identified the methods of inference that perform well and recommend the techniques that should be adopted in future work.     

Quantification and visualization of phosphoinositides by quantum dot-labeled specific binding-domain probes

Phosphoinositides (PI) play important regulatory roles in cell physiology. Localization and quantitation of PIs within the cell is necessary to understand their precise function. Currently, ectopic expression of green fluorescent protein (GFP)-fused PI-binding domains is used to visualize PIs localized to the cell membrane. However, ectopically expressed PI-binding domains may compete with endogenous binding proteins, thus altering the physiological functions of the PIs. Here, we establish a novel method for quantification and visualization of PIs in cells and tissue samples using PI-binding domains labeled with quantum dots (Qdot) as specific probes. This method allowed us to simultaneously quantify three distinct PIs, phosphatidylinositol 3,4,5-triphosphatase [PtdIns(3,4,5)P(3)), PtdIns(3,4)P(2), and PtdIns(4,5)P(2), in crude acidic lipids extracted from insulin-stimulated cells. In addition, the method allowed the PIs to be visualized within fixed cells and tissues. Sequential and spatial changes in PI production and distribution were detected in platelet-derived growth factor (PDGF)-stimulated NRK49F cells. We also observed accumulation of PtdIns(3,4)P(2) at the dorsal ruffle in PDGF-stimulated NIH3T3 cells. Finally, we found PtdIns(3,4,5)P(3) was enriched in lung cancer tissues, which also showed high levels of phosphorylated Akt. Our new method to quantify and visualize PIs is expected to provide further insight into the role of lipid signaling in a wide range of cellular events.     

Application of an induced field sensor for assessment of electromagnetic exposure from compact fluorescent lamps

The development of scientifically sound instrumentation, methods, and procedures for the electromagnetic exposure assessment of compact fluorescent lamps (CFLs) is investigated. The incident and induced fields from 11 CFLs have been measured in the 10 kHz–1 MHz range, and they are compared with the levels for incandescent and light emitting diode (LED) bulbs. Commercially available equipment was used to measure the incident fields, while a novel sensor was built to assess the induced fields in humans. Incident electric field levels significantly exceed the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) reference levels at close distances for some sources, while the induced fields are within the ICNIRP basic restrictions. This demonstrates the importance of assessing the induced fields rather than the incident fields for these sources. Maximum current densities for CFLs are comparable to the limits (in the range of 9% to 56%), demonstrating the need for measurements to establish compliance. For the frequency range investigated, the induced fields were found to be considerably higher for CFLs than for incandescent light bulbs, while the exposure from the two LED bulbs was low. The proposed instrumentation and methods offer several advantages over an existing measurement standard, and the measurement uncertainty is significantly better than the assessment of electric and magnetic fields at close distances. Bioelectromagnetics 33:166–175, 2012. © 2011 Wiley Periodicals, Inc.