Context-dependent use of visual cues in the shell selection behaviour of the hermit crab Pagurus bernhardus

Animals avoid predator attack in different ways; some carry defensive structures to reduce predation, with the classic example being hermit crabs and their use of a mollusc shell as a portable refugium. During shell selection, various shell characteristics are investigated by the crab to determine their suitability. Here we consider the role of visual cues. Previous research suggests that some hermit crabs are more likely to initially choose a conspicuous shell but also to move to backgrounds against which they are less conspicuous, suggesting a short-term/long-term trade-off. Across experiments in which we manipulated shell and background colour, we show initially that Pagurus bernhardus prefer black shells over white but this preference was lost in the absence of visual cues. We then show that the strength of preference was dependent on background colour. We repeated this last experiment with red and yellow shells against red or yellow backgrounds to investigate whether this preference extended to chromatic hues. A preference for darker (red) shells was expressed, but preference alteration with background was not observed. P. bernhardus therefore discriminate between shells in terms of shell and background colour, and discrimination may be rooted in a preference for darker shaded shells.PostprintPeer reviewe

Quantifying effectiveness of chloride desalination treatments for archaeological iron using oxygen measurement

Alkaline deoxygenated aqueous treatments are employed to remove damaging chloride ions (Cl⁻) from excavated archaeological iron objects; however, their effectiveness is either qualitatively assessed or anecdotal. A novel oxygen measurement technique is used to assess pre- and post-treatment corrosion rates of individual archaeological iron objects; these rates are related to their Cl⁻ content before and after treatment. Ten archaeological iron nails were individually sealed in reaction vessels conditioned to 80% relative humidity (RH) at 20 ºC. The oxygen partial pressure inside each vessel was measured remotely over the course of 37 days using an OxyMini fibre-optic meter and a sensor spot inside each vessel. Control vessels containing nitrogen gas revealed negligible leakage. Objects were removed and treated for two weeks in an alkaline sulphite (0.1 M NaOH / 0.05 M Na2SO3) solution at 60 ºC and the extracted Cl⁻ was recorded quantitatively and then the objects were placed back in the oxygen measurement vessels (80% RH and 20 ºC). After recording oxygen consumption, nitric acid digestion was used to determine the residual Cl⁻ content. Half of the ten objects that were treated had their oxygen consumption rate reduced by 91% or more, with the oxygen consumption rate of the remaining reducing by 49-71%. Object Cl⁻ contents reduced from between 336-3487 parts-per-million (ppm) before treatment to a maximum of 364 ppm after treatment. A linear correlation between pre-treatment Cl⁻ content and oxygen consumption rate existed but was not apparent post-treatment, suggesting that the readily accessible soluble Cl⁻, which is removed by a single two-week bath, is the most significant driver for corrosion. Half of the objects were still measurably consuming oxygen after treatment but it is expected that this slower corrosion rate should significantly increase overall lifespan. A single, brief, alkaline deoxygenation treatment is a useful addition to preventive conservation strategies for vulnerable iron objects. Use of oxygen partial pressure measurement to assess corrosion rates provides a new insight into the effectiveness of treatments for quantifying corrosion risk, determining the success of conservation strategies, developing management procedures and cost benefit analysis

Residues of alkaline sulphite treatment and their effects on the corrosion of archaeological iron objects

The formation of chemical residues on archaeological iron following its treatment in aqueous alkaline sulphite (NaOH/ Na2SO3) is simulated by evaporating selected ion mixtures to dryness. The residues are identified by X-ray diffraction (XRD) and their influence on iron corrosion is investigated by mixing them with iron powder and dynamically recording the weight change of these powder mixtures at fixed temperature and relative humidity (RH) in a climatic chamber.Ferrous chloride was dissolved in Na2SO4 to simulate Fe2+/Cl⁻ contaminated Na2SO4 solution. This formed FeSO4·4H2O/FeSO4·7H2O/NaCl upon evaporation. Evaporating a FeCl2/NaOH/Na2SO3 solution produced either Na2SO4/NaCl/γ- FeOOH or Na6(CO3)(SO4)2/Na2SO4/NaCl/γFeOOH mixtures according to ion concentration in the initial solution. Iron powder and various residues were mixed and exposed at 75% RH and 20oC; Na2SO4/Fe did not corrode iron; FeSO4·7H2O/Fe produced minimal corrosion of iron; during the hydration phase of FeSO4·4H2O to FeSO4·7H2O iron corroded; a NaCl/FeSO4·7H2O/FeSO4·4H2O mixture corroded iron rapidly. Overall, at 75% RH, soluble chloride residues offer a more immediate and significant corrosion risk to iron than Na2SO4 ,FeSO4·7H2O and FeSO4·4H2O

Floppy aortic graft reconstruction for germ cell tumor invasion of the infrarenal aorta

AbstractSignificant aortic invasion by metastatic nonseminomatous germ cell tumors can present difficult problems intraoperatively in attempted curative retroperitoneal lymph node dissection. Aortic replacement with Dacron graft has been a successful method of dealing with this predicament. We describe a new approach of intraoperative floppy aortic graft reconstruction in a young patient with testicular germ cell cancer in whom a 14 cm pseudoaneurysm involving the infrarenal aorta developed after four courses of preoperative chemotherapy. This technique prevents significant lower extremity and pelvic ischemia during resection of the aorta and retroperitoneal tumor while providing the urologic surgeon with excellent exposure and minimal interference from the aortic graft. (J Vasc Surg 2003;37:889-91.

Oligosaccharide recognition and binding to the carbohydrate binding module of AMP-activated protein kinase

AbstractThe AMP-activated protein kinase (AMPK) contains a carbohydrate-binding module (β1-CBM) that is conserved from yeast to mammals. β1-CBM has been shown to localize AMPK to glycogen in intact cells and in vitro. Here we use Nuclear Magnetic Resonance spectroscopy to investigate oligosaccharide binding to 15N labelled β1-CBM. We find that β1-CBM shows greatest affinity to carbohydrates of greater than five glucose units joined via α,1→4 glycosidic linkages with a single, but not multiple, glucose units in an α,1→6 branch. The near identical chemical shift profile for all oligosaccharides whether cyclic or linear suggest a similar binding conformation and confirms the presence of a single carbohydrate-binding site

Ketamine inhibits synaptic transmission and nicotinic acetylcholine receptor-mediated responses in rat intracardiac ganglia <i>in situ</i>

The intravenous anaesthetic ketamine, has been demonstrated to inhibit nicotinic acetylcholine receptor (nAChR)-mediated currents in dissociated rat intracardiac ganglion (ICG) neurons (Weber et al., 2005). This effect would be predicted to depress synaptic transmission in the ICG and would account for the inhibitory action of ketamine on vagal transmission to the heart (Inoue and König, 1988). This investigation was designed to examine the activity of ketamine on (i) postsynaptic responses to vagal nerve stimulation, (ii) the membrane potential, and (iii) membrane current responses evoked by exogenous application of ACh and nicotine in ICG neurons in situ. Intracellular recordings were made using sharp intracellular microelectrodes in a whole mount ICG preparation. Preganglionic nerve stimulation and recordings in current- and voltage-clamp modes were used to assess the action of ketamine on ganglionic transmission and nAChR-mediated responses. Ketamine attenuated the postsynaptic responses evoked by nerve stimulation. This reduction was significant at clinically relevant concentrations at high frequencies. The excitatory membrane potential and current responses to focal application of ACh and nicotine were inhibited in a concentration-dependent manner by ketamine. In contrast, ketamine had no effect on either the directly-evoked action potential or excitatory responses evoked by focal application of γ-aminobutyric acid (GABA). Taken together, ketamine inhibits synaptic transmission and nicotine- and ACh-evoked currents in adult rat ICG. Ketamine inhibition of synaptic transmission and nAChR-mediated responses in the ICG contributes significantly to its attenuation of the bradycardia observed in response to vagal stimulation in the mammalian heart

The efficiency of chloride extraction from archaeological iron objects using deoxygenated alkaline solutions

Chloride-contaminated archaeological iron is unstable and problematic to store and display within museum collections. Reducing its chloride ion content using aqueous desalination followed by storage in controlled relative humidity offers one treatment option. This study reports a quantitative assessment of chloride extraction by aqueous deoxygenated alkaline desalination solutions from 120 individual archaeological iron nails. The three treatment methods comprised alkaline sulphite solution (0.1 M NaOH/0.05 M Na2SO3) at room temperature and at 60°C and sodium hydroxide solution (0.1 M) deoxygenated using a nitrogen gas positive pressure system at room temperature. Chloride extraction was monitored using a specific ion meter. The nails were digested after treatment to measure their residual chloride content. A wide range of extraction patterns emerged, with the majority of individual treatments extracting 60–99% of the chloride present. Residual chloride levels for 87% of the objects fell below 1000 ppm and 42% were below 200 ppm. Although no treatment extracted 100% of the chloride in the object, alkaline desalination produced very significant reductions in chloride content. The impact of this on future corrosion of the objects is discussed. This quantitative and statistically viable assessment of deoxygenated desalination treatments provides evidence to support their use in conservation practice, which will impact on procedures for the preservation and management of archaeological heritage

The impact of chloride desalination on the corrosion rate of archaeological iron

Although desalination of archaeological iron reduces its chloride concentration and enhances object stability, the reduction in corrosion rate that this produces has never been quantified. This study measures post-treatment corrosion rates in accelerated corrosion environments to identify the impact of removing chloride ions on corrosion rate. Thirty-five archaeological iron nails, treated individually in either alkaline sulphite or nitrogen-deoxygenated sodium hydroxide, were exposed to 75°C and 75% relative humidity together with 31 untreated objects from the same archaeological sites. Object weight change and visual examination of physical change before and after the test period were used to monitor corrosion. 77% of treated objects showed no weight gain and no visible signs of corrosion, while 90% of untreated objects did corrode. The impact of chloride on corrosion of untreated objects was clearly established by a significant linear correlation between chloride content and weight gain. Treated objects with <400 ppm chloride content showed no corrosion behaviour. Corrosion of treated objects was attributed to incomplete treatment: 93% of objects treated to <5 mg/l Cl− in the final solution bath displayed no corrosion behaviour. Based on these results, desalination of iron objects to enhance their stability offers a valuable option for reducing corrosion rates of archaeological iron, which should increase object lifespan. The results also raise the question of whether low levels of post-treatment residual chloride produce corrosion of any significance. Answering this will be an important step forward for managing the preservation of archaeological iron

Sterols in soil organic matter of sandy arable soils: Quantification using mass spectrometry and their relation to mineralizability of soil organic N

Lately, a significant negative correlation between proportions of the compound class of sterols from pyrolysis-field ionization mass spectrometry (Py-FIMS) and net N mineralizability of soil organic N was found. However, main plant sterols (?-Sitosterol, Stigmasterol, and Campesterol) cannot be clearly verified and quantified with Py-FIMS, and there are only very few studies on measuring concentrations in soils. Thus, the objective was the extraction, identification and quantification of typical plant sterols and their relation to net N mineralization rates. The three sterols were identified and quantified in lipid extracts (Soxhlet procedure) using gas chromatography - mass spectrometry (GC-MS). Concentrations were similar to few other available studies, but concentrations of the three sterols were not significantly correlated with net N mineralizability. As quantification was difficult due to co-elution, further optimization of the methodology is necessary. In addition, the underlying mechanisms also need to be clarified

Guidelines for the storage and display of archaeological metalwork

This is a guide for Heritage Professionals on how to control the corrosion of archaeological metal objects during storage and display. It is a practical guide with clear statement of the underpinning theory behind the strategies and procedures recommend, with the inclusion of the evidence base that supports them