166 research outputs found
Variance in the Accuracy of Tidal Levels with Increasing Data Length
The Highest Astronomical Tide level (HAT) is derived from sea level datasets of sufficient length to encapsulate the lunar nodal cycle. HAT based on datasets of 35, 90, 180 and 400 days was determined for 14 sites. The difference between HAT based on short datasets and on 20-year datasets indicate that short datasets gave an average difference of 0.22 to 0.24 m. Increasing the length to 400 days decreased the difference to 0.06 m. Sites with diurnal form gave a larger difference of 0.4 to 0.9 metres. Inferring shallow water tidal constituents from the nearest longterm site reduced the difference to 0.15 to 0.19 m.La MĂĄxima Pleamar AstronĂłmica (HAT) se deriva a partir de conjuntos de datos del nivel del mar con longitud suficiente para englobar el ciclo nodal lunar. Se determinĂł la HAT para 14 sitios basĂĄndose en conjuntos de datos de 35, 90, 180 y 400 dĂas. La diferencia entre HAT basadas en conjuntos de datos cortos y en conjuntos de datos de 20 años indica que los conjuntos de datos cortos proporcionaron una diferencia media de 0.22 a 0.24 m. Aumentar la longitud a 400 dĂas redujo la diferencia a 0.06 m. Los sitios con forma diurna proporcionaron una diferencia mayor de 0.4 a 0.9 metros. Inferir los constituyentes de marea de aguas someras a partir del sitio a largo plazo mĂĄs cercano redujo la diferencia a entre 0.15 y 0.19 m.Le niveau de la plus haute mer astronomique (PHMA) est dĂ©rivĂ© de jeux de donnĂ©es sur le niveau de la mer d'une longueur suffisante pour englober le cycle nodal lunaire. La PHMA a Ă©tĂ© dĂ©terminĂ©e pour 14 sites, Ă partir dâensembles de donnĂ©es de 35, 90, 180 et 400 jours. La diffĂ©rence entre la PHMA basĂ©e sur des jeux de donnĂ©es courts et sur des jeux de donnĂ©es de 20 ans indique que les jeux de donnĂ©es courts ont donnĂ© une diffĂ©rence moyenne de 0,22 Ă 0,24 m. L'augmentation de la longueur Ă 400 jours a diminuĂ© la diffĂ©rence Ă 0,06 m. Les sites avec une forme diurne ont donnĂ© une plus grande diffĂ©rence de 0,4 Ă 0,9 mĂštres. LâinfĂ©rence dĂ©duction des composantes de la marĂ©e en eau peu profonde Ă partir du site Ă long terme le plus proche a rĂ©duit la diffĂ©rence Ă 0,15 Ă 0,19 m
A Coherent Tidal Datum for the Torres Strait
The Torres Strait is a complex waterway to the north of Australia linking the Arafura and Coral Seas. Sea level data from 13 islands were provided with the intention of validating the GPS extension of AUSGeoid98 to the Torres Strait. A comparison between the Australian Height Datum (AHD) determined from the AUSGeoid98 model and Mean Sea Level (MSL) identified differences of up to 1.57m. A coherent tidal datum was established with a seasonal adjustment to the long-term level from Thursday Island. The seasonally adjusted MSL from this study should be considered as an approximation of AHD in the Torres Strait.El Estrecho de Torres es un canal complejo al norte de Australia, que conecta los Mares de Arafura y Coral. Se proporcionaron datos del nivel del mar de 13 islas, con la intenciĂłn de validar la extensiĂłn GPS de AUSGeoid98 al Estrecho de Torres. Una comparaciĂłn entre el Plano de Referencia Australiano (AHD) determinado a partir del modelo AUSGeoid98 y el Nivel Medio del Mar (MSL) identificĂł diferencias de hasta 1,57m. Se creĂł un Datum de Mareas coherente con un reajuste de nivel estacional a largo plazo a partir de la Isla Thursday. El MSL reajustado estacionalmente a partir de este estudio deberĂa ser considerado como una aproximaciĂłn del AHD en el Estrecho de Torres.Le dĂ©troit de Torres est une voie navigable complexe au nord de lâAustralie, qui relie les mers dâArafura et de Coral. Les donnĂ©es sur le niveau de la mer de 13 Ăźles ont Ă©tĂ© fournies dans lâintention de valider lâextension du GPS dâAUSGeoid98 au dĂ©troit de Torres. Une comparaison entre le systĂšme de rĂ©fĂ©rence australien (AHD) dĂ©terminĂ© Ă partir du modĂšle de AUSGeoid98 et le niveau moyen de la mer (MSL) a mis en Ă©vidence des diffĂ©rences allant jusquâĂ 1,57m. Un zĂ©ro des marĂ©es cohĂ©rent a Ă©tĂ© Ă©tabli avec une correction saisonniĂšre du niveau Ă long terme, Ă partir de Thursday Island. Le MSL corrigĂ© des variations saisonniĂšres de cette Ă©tude doit ĂȘtre considĂ©rĂ© comme une approximation du AHD dans le dĂ©troit de Torres
Forensic electrochemistry: indirect electrochemical sensing of the components of the new psychoactive substance "Synthacaine"
âSynthacaineâ is a New Psychoactive Substance which is, due to its inherent psychoactive properties,
reported to imitate the effects of cocaine and is therefore consequently branded as âlegal cocaineâ. The
only analytical approach reported to date for the sensing of âSynthacaineâ is mass spectrometry. In this
paper, we explore and evaluate a range of potential analytical techniques for its quantification and potential
use in the field screening âSynthacaineâ using Raman spectroscopy, presumptive (colour) testing, High
Performance Liquid Chromatography (HPLC) and electrochemistry. HPLC analysis of street samples
reveals that âSynthacaineâ comprises a mixture of methiopropamine (MPA) and 2-aminoindane (2-AI).
Raman spectroscopy and presumptive (colour) tests, the Marquis, Mandelin, Simonâs and Robadope test,
are evaluated towards a potential in-the-field screening approach but are found to not be able to discriminate
between the two when they are both present in the same sample, as is the case in the real
street samples. We report for the first time a novel indirect electrochemical protocol for the sensing of
MPA and 2-AI which is independently validated in street samples with HPLC. This novel electrochemical
approach based upon one-shot disposable cost effective screen-printed graphite macroelectrodes holds
potential for in-the-field screening for âSynthacaineâ.
Introduction
In the last few years there has been a striking increase in the
sale of âNew Psychoactive Substancesâ (NPSs) formerly known as
âlegal highsâ.1 These chemicals may be bought through the
internet at low cost and are sometimes pure compounds
which display highly similar chemical structures to existing
controlled substances within the phenethylamine class.
âSynthacaineâ is a slang term derived from âsyntheticâ and
âcocaine
Forensic electrochemistry: simultaneous voltammetric detection of MDMA and its fatal counterpart "Dr Death" (PMA)
The simultaneous detection of substances present in drugs of abuse is increasingly important since some materials are known for their high mortality rate. One drug that received considerable attention is para-methoxyamphetamine (PMA), commonly known as âDr Deathâ â this substance is linked with several deaths internationally and can often be found together with 3,4-methylenedioxymethamphetamine (MDMA) in drugs sold under the alias âecstasyâ, a very popular drug of abuse. This work reports for the first time the detection and quantification of MDMA and PMA simultaneously through an electrochemical technique using screen-printed graphite electrodes (SPEs). The electroanalytical sensing of MDMA/PMA, MDMA and PMA are explored directly at bare unmodified SPEs yielding a detection limit (3Ï) corresponding to 0.25 ÎŒg mLâ1/0.14 ÎŒg mLâ1 for MDMA/PMA, 0.04 ÎŒg mLâ1 MDMA and 0.03 ÎŒg mLâ1 PMA. Raman spectroscopy and presumptive colour tests were also performed on MDMA/PMA, MDMA and PMA using the Marquis, Mandelin, Simon's and Robadope tests but were found to not be able discriminate when PMA and MDMA are both present in the same samples. We report a novel electrochemical protocol for the sensing of PMA and MDMA which is independently validated in a synthetic (MDMA/PMA) sample with HPLC
Catalytic dehydrocoupling of Amine-Boranes Using Cationic Zirconium(IV)-Phosphine Frustrated Lewis Pairs
A series
of novel, intramolecular ZrÂ(IV)/P frustrated Lewis pairs
(FLPs) based on cationic zirconocene fragments with a variety of ancillary
cyclopentadienyl and 2-phosphinoaryloxide (âOÂ(C<sub>6</sub>H<sub>4</sub>)ÂPR<sub>2</sub>, R = <sup>t</sup>Bu and 3,5-CF<sub>3</sub>-(C<sub>6</sub>H<sub>3</sub>)) ligands are reported and their activity
as catalysts for the dehydrocoupling of dimethylamineâborane
(Me<sub>2</sub>NH·BH<sub>3</sub>) assessed. The FLP system [(C<sub>9</sub>H<sub>7</sub>)<sub>2</sub>ZrOÂ(C<sub>6</sub>H<sub>4</sub>)ÂP<sup>t</sup>Bu<sub>2</sub>]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]
is shown to give unprecedented turnover frequencies (TOF) for a catalyst
based on a group 4 metal (TOF â„ 600 h<sup>â1</sup>),
while also proving to be the most efficient FLP catalyst reported
to date. The mechanism of this reaction has been probed using analogous
intermolecular ZrÂ(IV)/P FLPs, permitting deconvolution of the reactions
taking place at both the Lewis acidic and basic sites. Elucidation
of this mechanism revealed an interesting cooperative two-cycle process
where one cycle is FLP mediated and the other, a redistribution of
a linear diborazane intermediate, relies solely on the presence of
a ZrÂ(IV) Lewis acid
Electroanalytical detection of pindolol: comparison of unmodified and reduced graphene oxide modified screen-printed graphite electrodes
Recent work has reported the first electroanalytical detection of pindolol using reduced graphene oxide
(RGO) modified glassy carbon electrodes [S. Smarzewska and W. Ciesielski, Anal. Methods, 2014, 6, 5038]
where it was reported that the use of RGO provided significant improvements in the electroanalytical
signal in comparison to a bare (unmodified) glassy carbon electrode. We demonstrate, for the first time,
that the electroanalytical quantification of pindolol is actually possible using bare (unmodified) screenprinted
graphite electrodes (SPEs). This paper addresses the electroanalytical determination of pindolol
utilising RGO modified SPEs. Surprisingly, it is found that bare (unmodified) SPEs provide superior electrochemical
signatures over that of RGO modified SPEs. Consequently the electroanalytical sensing of
pindolol is explored at bare unmodified SPEs where a linear range between 0.1 ÎŒMâ10.0 ÎŒM is found to
be possible whilst offering a limit of detection (3Ï) corresponding to 0.097 ÎŒM. This provides a convenient
yet analytically sensitive method for sensing pindolol. The optimised electroanalytical protocol using the
unmodified SPEs, which requires no pre-treatment (electrode polishing) or electrode modification step
(such as with the use of RGO), was then further applied to the determination of pindolol in urine samples.
This work demonstrates that the use of RGO modified SPEs have no significant benefits when compared
to the bare (unmodified) alternative and that the RGO free electrode surface can provide electro-analytically
useful performances
Extreme water levels, waves and coastal impacts during a severe tropical cyclone in northeastern Australia: a case study for cross-sector data sharing
Severe tropical cyclone (TC) Debbie made landfall on
the northern Queensland coast of Australia on 27 March 2017 after crossing
the Great Barrier Reef as a slow-moving Category 4 system. Groups from
industry, government and academia collected coastal hazard and impact data
before, during and after the event and shared these data to produce a
holistic picture of TC Debbie at the coast. Results showed the still
water level exceeded the highest astronomical tide by almost a metre. Waves
added a further 16 % to water levels along the open coast, and were
probably unprecedented for this area since monitoring began. In most places,
coastal barriers were not breached and as a result there was net offshore
sand transport. If landfall had occurred 2 h earlier with the high tide,
widespread inundation and overwash would have ensued. This paper provides a
case study of effective cross-sector data sharing in a natural hazard
context. It advocates for a shared information platform for coastal extremes
in Australia to help improve the understanding and prediction of TC-related
coastal hazards in the future.</p
Multiple order-up-to policy for mitigating bullwhip effect in supply chain network
This paper proposes a multiple order-up-to policy based inventory replenishment scheme to mitigate the bullwhip effect in a multi-stage supply chain scenario, where various transportation modes are available between the supply chain (SC) participants. The proposed policy is similar to the fixed order-up-to policy approach where replenishment decision âhow much to orderâ is made periodically on the basis of the predecided order-up-to inventory level. In the proposed policy, optimal multiple order-up-to levels are assigned to each SC participants, which provides decision making reference point for deciding the transportation related order quantity. Subsequently, a mathematical model is established to define optimal multiple order-up-to levels for each SC participants that aims to maximize overall profit from the SC network. In parallel, the model ensures the control over supply chain pipeline inventory, high satisfaction of customer demand and enables timely utilization of available transportation modes. Findings from the various numerical datasets including stochastic customer demand and lead times validate thatâthe proposed optimal multiple order-up-to policy based inventory replenishment scheme can be a viable alternative for mitigating the bullwhip effect and well-coordinated SC. Moreover, determining the multiple order-up-to levels is a NP hard combinatorial optimization problem. It is found that the implementation of new emerging optimization algorithm named bacterial foraging algorithm (BFA) has presented superior optimization performances. The robustness and applicability of the BFA algorithm are further validated statistically by employing the percentage heuristic gap and two-way ANOVA analysis
Genetically manipulated phages with improved pH resistance for oral administration in veterinary medicine
Orally administered phages to control zoonotic pathogens face important challenges, mainly related to the hostile conditions found in the gastrointestinal tract (GIT). These include temperature, salinity and primarily pH, which is exceptionally low in certain compartments. Phage survival under these conditions can be jeopardized and undermine treatment. Strategies like encapsulation have been attempted with relative success, but are typically complex and require several optimization steps. Here we report a simple and efficient alternative, consisting in the genetic engineering of phages to display lipids on their surfaces. Escherichia coli phage T7 was used as a model and the E. coli PhoE signal peptide was genetically fused to its major capsid protein (10A), enabling phospholipid attachment to the phage capsid. The presence of phospholipids on the mutant phages was confirmed by High Performance Thin Layer Chromatography, Dynamic Light Scattering and phospholipase assays. The stability of phages was analysed in simulated GIT conditions, demonstrating improved stability of the mutant phages with survival rates 102107 pfu.mL1 higher than wild-type phages. Our work demonstrates that phage engineering can be a good strategy to improve phage tolerance to GIT conditions, having promising application for oral administration in veterinary medicine.This work was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and under the scope of the Project PTDC/BBB-BSS/6471/2014 (POCI-01-0145-FEDER-016678). Franklin L. Nobrega and Ana Rita Costa acknowledge FCT for grants SFRH/BD/86462/2012 and SFRH/BPD/94648/2013, respectively. Melvin F. Siliakus acknowledges funding from the Biobased Ecologically Balanced Sustainable Industrial Chemistry (BE-BASIC) foundation. Electron microscopy work was performed at the Wageningen Electron Microscopy Centre (WEMC) of Wageningen University
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