Why Leaves Turn Red in Autumn. The Role of Anthocyanins in Senescing Leaves of Red-Osier Dogwood

Why the leaves of many woody species accumulate anthocyanins prior to being shed has long puzzled biologists because it is unclear what effects anthocyanins may have on leaf function. Here, we provide evidence for red-osier dogwood (Cornus stolonifera) that anthocyanins form a pigment layer in the palisade mesophyll layer that decreases light capture by chloroplasts. Measurements of leaf absorbance demonstrated that red-senescing leaves absorbed more light of blue-green to orange wavelengths (495–644 nm) compared with yellow-senescing leaves. Using chlorophyll a fluorescence measurements, we observed that maximum photosystem II (PSII) photon yield of red-senescing leaves recovered from a high-light stress treatment, whereas yellow-senescing leaves failed to recover after 6 h of dark adaptation, which suggests photo-oxidative damage. Because no differences were observed in light response curves of effective PSII photon yield for red- and yellow-senescing leaves, differences between red- and yellow-senescing cannot be explained by differences in the capacities for photochemical and non-photochemical light energy dissipation. A role of anthocyanins as screening pigments was explored further by measuring the responses PSII photon yield to blue light, which is preferentially absorbed by anthocyanins, versus red light, which is poorly absorbed. We found that dark-adapted PSII photon yield of red-senescing leaves recovered rapidly following illumination with blue light. However, red light induced a similar, prolonged decrease in PSII photon yield in both red- and yellow-senescing leaves. We suggest that optical masking of chlorophyll by anthocyanins reduces risk of photo-oxidative damage to leaf cells as they senesce, which otherwise may lower the efficiency of nutrient retrieval from senescing autumn leaves.

Seabed photographs taken along OFOS profiles during POLARSTERN cruise PS96 (ANT-XXXI/2 FROSN)

Within the context of the overall ecological working programme Dynamics of Antarctic Marine Shelf Ecosystems (DynAMo) of the PS96 (ANT-XXXI/2) cruise of RV "Polarstern" to the Weddell Sea (Dec 2015 to Feb 2016), seabed imaging surveys were carried out along drift profiles by means of the Ocean Floor Observation System (OFOS) of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) Bremerhaven. The setup and mode of deployment of the OFOS was similar to that described by Bergmann and Klages (2012, doi:10.1016/j.marpolbul.2012.09.018). OFOS is a surface-powered gear equipped with two downward-looking cameras installed side-by-side: one high-resolution, wide-angle still camera (CANON® EOS 5D Mark III; lens: Canon EF 24 f/1.4L II, f stop: 13, exposure time: 1/125 sec; in-air view angles: 74° (horizontal), 53° (vertical), 84° (diagonal); image size: 5760 x 3840 px = 21 MPix; front of pressure resistant camera housing consisting of plexiglass dome port) and one high-definition color video camera (SONY® FCB-H11). The system was vertically lowered over the stern of the ship with a broadband fibre-optic cable, until it hovers approximately 1.5 m above the seabed. It was then towed after the slowly sailing ship at a speed of approximately 0.5 kn (0.25 m/s). The ship's Global Acoustic Positioning System (GAPS), combining Ultra Short Base Line (USBL), Inertial Navigation System (INS) and satellite-based Global Positioning System (GPS) technologies, was used to gain highly precise underwater position data of the OFOS. During the profile, OFOS was kept hanging at the preferred height above the seafloor by means of the live video feed and occasional minor cable-length adjustments with the winch to compensate small-scale bathymetric variations in seabed morphology. Information on water depth and height above the seafloor were continuously recorded by means of OFOS-mounted sensors (GAPS transponder, Tritech altimeter). Three lasers, which are placed beside the still camera, emit parallel beams and project red light points, arranged as an equilateral triangle with a side length of 50 cm, in each photo, thus providing a scale that can be used to calculate the seabed area depicted in each image and/or measure the size of organisms or seabed features visible in the image. In addition, the seabed area depicted was estimated using altimeter-derived height above seafloor and optical characteristics of the OFOS still camera. In automatic mode, a seabed photo, depicting an area of approximately 3.45 m**2 (= 2.3 m x 1.5 m; with variations depending on the actual height above ground), was taken every 30 seconds to obtain series of "TIMER" stills distributed at regular distances along the profiles that vary in length depending on duration of the cast. At a ship speed of 0.5 kn, the average distance between seabed images was approximately 5 m. Additional "HOTKEY" photos were taken from interesting objects (organisms, seabed features, such as putative iceberg scours) when they appeared in the live video feed (which was also recorded, in addition to the stills, for documentation and possible later analysis). If any image from this collection is used, please cite the reference as given above.

Postharvest light treatments increase skin blush in mango fruit

Skin colour is an important quality parameter that influences mango fruit marketability. The mango industry is interested in controlled induction of skin blush in mangoes. It is desirable to understand the control of anthocyanin accumulation in mango skin. Among environmental factors known to induce anthocyanin accumulation in plants, light is the most studied. Light exposure induces pigmentation in various fruits, including apple, strawberry and grape. The effect of different light qualities on skin blush in mango fruit has received relatively little attention. The objective of this study was to assess anthocyanin accumulation and blush in response to blue, red and far red light from light-emitting diodes (LEDs) as applied to harvested mango fruit skin during storage at 12°C. Except for red light, the other wavelengths induced anthocyanin accumulation and skin blush as compared to the dark control treatment. Anthocyanin concentration and a∗ values were highest in blue light exposed fruit skin. This wavelength enhanced phenylalanine ammonia lyase activity in the mango skin, which may be associated with increased pigmentation. LED light treatment did not affect other fruit quality parameters at 21 days of storage, including firmness, total soluble solids and titratable acidity. Overall, the findings suggest that postharvest treatment with blue light can induce skin blush in mango fruit, which potentially may enhance their commercial value.

Effects of light quality supplied by light emitting diodes (LEDs) on microalgal production

Dissertação de mestrado, Aquacultura, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2014

Increase in particle number emissions from motor vehicles due to interruption of steady traffic flow

We assess the increase in particle number emissions from motor vehicles driving at steady speed when forced to stop and accelerate from rest. Considering the example of a signalized pedestrian crossing on a two-way single-lane urban road, we use a complex line source method to calculate the total emissions produced by a specific number and mix of light petrol cars and diesel passenger buses and show that the total emissions during a red light is significantly higher than during the time when the light remains green. Replacing two cars with one bus increased the emissions by over an order of magnitude. Considering these large differences, we conclude that the importance attached to particle number emissions in traffic management policies be reassessed in the future.

Effect of optical aberrations on the colour appearance of small lights

Purpose: Small red lights (one minute of arc or less) change colour appearance with positive defocus. We investigated the influence of longitudinal chromatic aberration and monochromatic aberrations on the colour appearance of small narrow band lights. Methods: Seven cyclopleged, trichromatic observers viewed a small light (one minute of arc, λmax = 510, 532, 550, 589, 620, 628 nm, approximately 19 per cent Weber contrast) centred within a black annulus (4.5 minutes of arc) and surrounded by a uniform white field (2,170 cd/m2). Pupil size was four millimetres. An optical trombone varied focus. Longitudinal chromatic aberration was controlled with a two component Powell achromatising lens that neutralises the eye’s chromatic aberration; a doublet that doubles and a triplet that reverses the eye’s chromatic aberration. Astigmatism and higher order monochromatic aberrations were corrected using adaptive optics. Results: Observers reported a change in appearance of the small red light (628 nm) without the Powell lens at +0.49 ± 0.21 D defocus and with the doublet at +0.62 ± 0.16 D. Appearance did not alter with the Powell lens, and five of seven observers reported the phenomenon with the triplet for negative defocus (-0.80 ± 0.47 D). Correction of aberrations did not significantly affect the magnitude at which the appearance of the red light changed (+0.44 ± 0.18 D without correction; +0.46 ± 0.16 D with correction). The change in colour appearance with defocus extended to other wavelengths (λmax = 510 to 620 nm), with directions of effects being reversed for short wavelengths relative to long wavelengths. Conclusions: Longitudinal chromatic aberrations but not monochromatic aberrations are involved in changing the appearance of small lights with defocus.

The effectiveness of traffic policing in reducing traffic crashes

Many governments throughout the world rely heavily on traffic law enforcement programs to modify driver behaviour and enhance road safety. There are two related functions of traffic law enforcement, apprehension and deterrence, and these are achieved through three processes: the establishment of traffic laws, the policing of those laws, and the application of penalties and sanctions to offenders. Traffic policing programs can vary by visibility (overt or covert) and deployment methods (scheduled and non-scheduled), while sanctions can serve to constrain, deter or reform offending behaviour. This chapter will review the effectiveness of traffic law enforcement strategies from the perspective of a range of high-risk, illegal driving behaviours including drink/drug driving, speeding, seat belt use and red light running. Additionally, this chapter discusses how traffic police are increasingly using technology to enforce traffic laws and thus reduce crashes. The chapter concludes that effective traffic policing involves a range of both overt and covert operations and includes a mix of automatic and more traditional manual enforcement methods. It is important to increase both the perceived and actual risk of detection by ensuring that traffic law enforcement operations are sufficiently intensive, unpredictable in nature and conducted as widely as possible across the road network. A key means of maintaining the unpredictability of operations is through the random deployment of enforcement and/or the random checking of drivers. The impact of traffic enforcement is also heightened when it is supported by public education campaigns. In the future, technological improvements will allow the use of more innovative enforcement strategies. Finally, further research is needed to continue the development of traffic policing approaches and address emerging road safety issues.

Examining Exposure of Motorcycles at Signalized Intersections

Crash statistics in Singapore from 2001 to 2005 have shown that motorcycles are involved in about 54% of intersection crashes. The overall involvement of motorcycles in crashes as the not-at-fault party is about 43% but at intersections, the corresponding percentage is increased to 57%. Quasi-induced exposure estimates show that the motorcycle exposure rate at signalized intersections is 41.7% even though motorcycles account for only 19% of the vehicle population. This study seeks to examine in greater details, the problem of motorcycle exposure at signalized intersections. In particular, the exposure arising from potential crashes with red light running vehicles from the conflicting stream at four signalized intersections is investigated. The results show that motorcycles are more exposed because they tend to accumulate near the stop-line during the red phase to facilitate an earlier discharge during the initial period of the green which is the more vulnerable period. At sites where there are more weaving opportunities because the lanes are wider or where there are exclusive right-turn lanes, the accumulation is higher and hence an increased exposure is observed. The analysis also shows that the presence of heavy vehicles tends to decrease motorcycle exposure as their weaving opportunities become restricted as well as there is a greater reluctance for them to weave past or queue alongside the heavy vehicles and their effects intensify for narrower lane width.

Electron-accepting conjugated materials based on 2-Vinyl-4,5- dicyanoimidazoles for application in organic electronics

We report the Heck coupling of 2-vinyl-4,5-dicyanoimidazole (vinazene) with selected di- and trihalo aromatics in an effort to prepare linear and branched electron-accepting conjugated materials for application in organic electronics. By selecting the suitable halo-aromatic moiety, it is possible to tune the HOMO - LUMO energy levels, absorption, and emission properties for a specific application. In this regard, materials with strong photoluminescence from blue → green → red are reported that may have potential application in organic light-emitting diodes (OLEDs). Furthermore, derivatives with strong absorption in the visible spectrum, coupled with favorable HOMO-LUMO levels, have been used to prepare promising organic photovoltaic devices (OPVs) when combined with commercially available semiconducting donor polymers.

A comparison of factors influencing perceived risk by French and Australian cyclists and drivers

Differences in the levels of risk perceived by cyclists and car drivers may contribute to the dangers in their interactions. Levels of perceived risk have been shown to vary according to personal and environmental factors and between countries. Cycling rates in France are higher than in Australia, particularly among women. This study investigated whether cultural differences between France and Australia are reflected in perceived risks for experienced adult cyclists and drivers in the two countries. In online surveys, regular cyclists (France 336, Australia 444) and drivers (France 92, Australia 151) were asked to rate the level of risk in six situations: failure to yield; going through a red light; not signalling when turning; swerving; tail-gating; and not checking traffic. The effects of type of interacting vehicle and participant type on perceived risk were similar in France and Australia. However, the influence of responsibility for the risky behaviour differed according to participant type, type of situation and nationality. When the bicycle rider committed the road rule violation, Australian cyclists and drivers gave higher risk ratings than French cyclists and drivers. In both countries, cyclists rated themselves significantly higher than drivers on the perceived control and overconfidence subscales of the perceived skill measure. The French cyclists rated themselves higher than Australian cyclists on these scales, which could be responsible for overall lower perceived risk levels when interacting with a bike. Australian cyclists rated themselves significantly lower than drivers on the incompetence subscale but French cyclists rated themselves higher than drivers. In both countries incompetence scores were positively related to levels of perceived risk. Weekly time was associated with perceived risk in Australia but not in France. Frequency of traffic violations was not associated with perceived risk in either country. In conclusion, levels of perceived risk differed between drivers and cyclists in both countries and were influenced by type of interacting vehicle, experience and perceived skill. However, some differences between the results from the two countries merit further investigation to shed light on potential improvements in safety and cycling participation.

Male and female cyclist and driver perceptions of crash risk

Many drivers and non-cyclists perceive cycling as an extremely risky activity with women in particular being concerned about the risk of injury. The low rates of cycling participation by women pose a threat to the achievement of government targets for cycling participation and restrict the potential transport, health and environmental benefits that increased levels of cycling could provide. This study seeks to extend earlier research in gender and cycling by comparing the risks perceived by female and male cyclists and drivers in specific on-road situations while accounting for other potentially gender-related factors such as travel patterns and experience, perceived skill, and risk taking behaviors. In an online survey, 444 regular cyclists and 151 (non-cyclist) car drivers rated the level of risk in six situations: Failing to yield; Going through a red light; Not signaling when turning; Swerving; Tailgating; and Not checking traffic. The study found that the higher levels of risk perceived by women are not completely accounted for by differences in cycling patterns or perceptions of skill. Compared to their male counterparts, female cyclists and car drivers had similarly elevated perceptions of risk suggesting that these gender differences are not specific to cycling, but reflect wider differences in risk perception. Not all of the gender differences were consistent across cyclists and drivers. Higher levels of perceived skill were evident for male cyclists but not for male car drivers. Further research is needed to explore the robustness and interpretation of this finding.

Polyacrylic Acid Assisted Synthesis of Cu2ZnSnS4 by Hydrothermal Method

Pure phase Cu2ZnSnS4 (CZTS) nanoparticles were successfully synthesized via polyacrylic acid (PAA) assisted one-pot hydrothermal route. The morphology, crystal structure, composition and optical properties as well as the photoactivity of the as-synthesized CZTS nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectrometer, UV-visible absorption spectroscopy and photoelectrochemical measurement. The influence of various synthetic conditions, such as the reaction temperature, reaction duration and the amount of PAA in the precursor solution on the formation of CZTS compound was systematically investigated. The results have shown that the crystal phase, morphology and particle size of CZTS can be tailored by controlling the reaction conditions. The formation mechanism of CZTS in the hydrothermal reaction has been proposed based on the investigation of time-dependent phase evolution of CZTS which showed that metal sulfides (e.g., Cu2S, SnS2 and ZnS) were formed firstly during the hydrothermal reaction before forming CZTS compound through nucleation. The band gap of the as-synthesized CZTS nanoparticles is 1.49 eV. The thin film electrode based on the synthesized CZTS nanoparticles in a three-electrode photoelectrochemical cell generated pronounced photocurrent under illumination provided by a red light-emitting diode (LED, 627 nm), indicating the photoactivity of the semiconductor material.

Evaluation of safety treatments at roadwork zones

A major 3-year research project to improve safety at roadworks has recently been completed by the Centre for Accident Research and Road Safety – Queensland (CARRS-Q) and industry partners. This project involved developing strategies to mitigate roadwork hazards including speeding. This paper presents three on-road evaluation studies on the effectiveness of some current and new safety treatments: use of pilot vehicles, variable message signage (VMS), police enforcement with and without VMS, and remote-controlled traffic control devices. The speed reduction potential of pilot vehicles was evaluated at a highway site. Results showed that pilot vehicles reduced average speeds within the work area, but not at a downstream location. Combinations of VMS and police enforcement were evaluated at a motorway site and results showed that police enforcement accompanied with VMS had greater effects on reducing speeds than either of these treatments alone. Three new remote-controlled traffic control devices—red and amber lights, red light and amber arrow, and a robotic stop/slow sign—were evaluated at a highway site. Results showed that the red light and amber arrow option produced consistent effects on the speeds at the approach to traffic controls and at a location inside the work area. This paper presents the first rigorous evaluations of these roadwork safety treatments in Queensland.

Photoinduced DNA and Protein Cleavage Activity of Ferrocene-Conjugated Ternary Copper(II) Complexes

Ferrocene-conjugated ternary copper(II) complexes [Cu(L)(B)](ClO4)(2), where L is FcCH(2)N(CH2Py)(2) (Fc = (eta(5)-C5H4)Fe-II(eta(5)-C5H5)) and B is a phenanthroline base, viz., 2,2'-bipyridine (bpy, 1), 1, 10-phenanthroline (phen, 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 3), and dipyrido[3,2-a:2',3'-c]phenazine (dppz, 4), have been synthesized and characterized by various spectroscopic and analytical techniques. The bpy complex 1, as its hexafluorophosphate salt, has been structurally characterized by X-ray crystallography. The molecular structure shows the copper(II) center having an essentially square-pyramidal coordination geometry in which L with a pendant ferrocenyl (Fc) moiety and bpy show respective tridentate and bidentate modes of binding to the metal center. The complexes are redox active, showing a reversible cyclic voltammetric response of the Fc(+)-Fc couple near 0.5 V vs SCE and a quasi-reversible Cu(II)-Cu(I) couple near 0.0 V. Complexes 2-4 show binding affinity to calf thymus (CT) DNA, giving binding constant (K-b) values in the range of 4.2 x 10(4) to 2.5 x 10(5) M-1. Thermal denaturation and viscometric titration data suggest groove binding and/or a partial intercalative mode of binding of the complexes to CT DNA. The complexes show good binding propensity to the bovine serum albumin (BSA) protein, giving K-BSA values of similar to 10(4) M-1 for the bpy and phen complexes and similar to 10(5) M-1 for the dpq and dppz complexes. Complexes 2-4 exhibit efficient chemical nuclease activity in the presence of 3-mercapto-propionic acid (MPA) as a reducing agent or hydrogen peroxide (H2O2) as an oxidizing agent. Mechanistic studies reveal formation of hydroxyl radicals as the reactive species. The dpq and dppz complexes are active in cleaving supercoiled (SC) pUC19 DNA on photoexposure to visible light of different wavelengths including red light using an argon-krypton mixed gas ion laser. Mechanistic investigations using various inhibitors reveal the fort-nation of hydroxyl radicals in the DNA photocleavage reactions. The dppz complex 4, which shows efficient photoioduced BSA cleavage activity, is a potent multifunctional model nuclease and protease in the chemistry of photodynamic therapy (PDT) of cancer.

Observations of road safety behaviours and practices of motorcycle rickshaw drivers in Lahore, Pakistan

Motorcycle Rickshaws (MRs) are an informal paratransit mode in Pakistan. They are locally manufactured and very popular but there are concerns about their crash involvement and overall safety. The first study of the current PhD program revealed that rickshaws (both MRs and auto-rickshaws) were involved in 51,992 road crashes attended by emergency ambulances in Punjab province, Pakistan between 2011-2013. This study aims to examine the road safety behaviours and practices of Motorcycle Rickshaw Drivers (MRDs) that may be contributing to these crashes. MRDs were observed at 12 major signalised intersections in Lahore. Vehicle characteristics and driver behaviours were recorded using a paper-based survey between 9am-7pm for a full week in May 2015. Of the 500 MRDs observed, about 23.4% appeared to be younger than the minimum driver licensing age of 18 years. More than half (52.6%) of the MRDs entered on the red light and 17.4% crossed when the signal was turning from yellow to green or red. MR traffic conflicts were observed in 62.8% of cases and one crash and 15 near-miss crashes were witnessed. Additionally, about half of MRs were overloaded, no MRD wore a helmet, and 3.8% were using a mobile phone while driving. This study provides the first scientific evidence to substantiate public concerns regarding the safety of MRs. It demonstrates that about a quarter of MRDs are underage,almost half of MRs are overloaded and more than half disobey traffic signals. This research could inform authorities to manage MR related transport and road safety issues.