Do new caledonian crows solve physical problems through causal reasoning?

The extent to which animals other than humans can reason about physical problems is contentious. The benchmark test for this ability has been the trap-tube task. We presented New Caledonian crows with a series of two-trap versions of this problem. Three out of six crows solved the initial trap-tube. These crows continued to avoid the trap when the arbitrary features that had previously been associated with successful performances were removed. However, they did not avoid the trap when a hole and a functional trap were in the tube. In contrast to a recent primate study, the three crows then solved a causally equivalent but visually distinct problem--the trap-table task. The performance of the three crows across the four transfers made explanations based on chance, associative learning, visual and tactile generalization, and previous dispositions unlikely. Our findings suggest that New Caledonian crows can solve complex physical problems by reasoning both causally and analogically about causal relations. Causal and analogical reasoning may form the basis of the New Caledonian crow's exceptional tool skills.

Infrared emission spectra: enhancement of diagnostic features by the lunar environment.

Information diagnostic of general rock type is available as a well-defined emission maximum (related to the Christiansen frequency), rather than as contrast-depleted minima, in the infrared spectra of particulate solids. The amount of spectral information varies directly with the sharpness of the thermal gradient at the sample surface. Lunar thermal conditions optimize this gradient, making the moon an excellent target for remote sensing.

Infrared images of tycho on dark moon.

Infrared images of the thermal anomaly associated with the lunar crater Tycho were obtained during the lunar night after Tycho had ceased to be illuminated by the Suin for as long as 97 hours. In agreement with results of previous studies, these measurements show that the crater is warmer than its surroundings during the lunar night, and that the temperature of the thermal anomaly gradually decreases with time, being no longer detectable after new moon. This work provides strong evidence that the steeper crater walls facing the Sun before local sunset are warmer throughout the cooling phase, and that the Tycho anomaly is thus produced by solar, rather than internal, heat.

Martian surface materials: effect of particle size on spectral behavior.

The presence of abundant limonite on Mars has long been the subject of controversy. Some advocates of abundant limonite also suggest that the albedo differences between Martian light and dark areas are caused by different sizes of particles in those areas. We show that the relative albedo is reversed from the blue to the red for samples of limonite with particles of different sizes. Observations of Mars reveal no blue-red albedo reversal between the light and dark areas. Consequently, the hypothesis of particle size control of albedo is incompatible with the presence of abundant limonite on Mars.

Lunar eclipse: infrared images and an anomaly of possible internal origin.

Infrared images of the lunar eclipse of 13 April 1968 were obtained and compared with infrared images of the 19 December 1964 eclipse. A similarity of apparent strength and distribution of most thermal anomalies on the maria is evident from inspection of these images, indicating that these features are not ephemeral. One new linear thermal anomaly was discovered, which is thermally enhanced during the lunar afternoon. Its close relation to a lunar crustal fracture line and other features of probable internal origin suggests that this anomaly may be of internal origin.

31P- and 1H-NMR investigations of the effect of n-alcohols on the hydrolysis by phospholipase A2 of phospholipid vesicular membranes.

31P- and 1H-NMR spectroscopy of small, unilamellar egg yolk phosphatidylcholine (PC) vesicles in the presence of the lanthanide ion Dy3+ have been used to study the effect of various n-alcohols on the permeability induced by the action of the enzyme phospholipase A2 (PLA2). The method allows the monitoring of the number of PC and lysoPC molecules in the outer and inner monolayers. The results indicate that the initial rate of hydrolysis of PC by PLA2 is increased by all the n-alcohols but in a chain-length dependent manner and that the maximum rate occurs at n = 8 (octan-1-ol). The subsequent rate is dependent upon the rate of transbilayer lipid exchange (flip-flop) of PC molecules from the inner to the outer monolayer. The vesicles only become permeable to the Dy3+ ions when lysoPC is mobilised in the flip-flop process of exchange of lipid molecules between the two monolayers. The n-alcohols affect both the time taken to initiate flip-flop of inner monolayer PC and the subsequent rate of permeability to Dy3+. The n-alcohols are seen to affect all the above rates in an identical chain-length dependent manner, indicating a common cause for all observations which we identify as the degree of clustering of the n-alcohol molecules in the bilayer. The results are discussed in terms of the chain-length dependent mechanism of n-alcohol interactions with the membrane and the mechanism by which the vesicles become permeable to Dy3+ ions.

A 1H-NMR investigation of the mechanism for the ionophore activity of the bile salts in phospholipid vesicular membranes and the effect of cholesterol.

A 1H-NMR method previously applied to ionophore-medicated transport is used to investigate a similar behaviour by the bile salts. The permeability of phosphatidylcholine vesicles to Pr3+ is increased by several orders of magnitude over the self-diffusion rate and the kinetics indicate a transbilayer movement of inverted micelles [Pr(bile salt)4]. In vesicles containing 40 mol% cholesterol the mechanism of permeability is radically altered and the di- and trihydroxy bile salts behave differently.

A 1H-NMR investigation of the effects of ethanol and general anaesthetics on ion channels and membrane fusion using unilamellar phospholipid membranes.

Using 1H-NMR of small unilamellar vesicles in the presence of the lanthanide probe ion Pr3+, the effects of ethanol, diethyl ether and chloroform on various mechanisms of channel-mediated transport were studied. The mechanisms include channel formation by the polypeptide Alamethicin 30 and vesicular lysis at the gel to liquid-crystal phase transition of the lipid. Channel stabilisation and membrane fusion induced by sub-critical micelle concentrations of Triton X-100 were also investigated. The observation that ethanol and diethyl ether increase membrane permeability and fusion while chloroform inhibits them suggests a common locus of action on the properties and structure of channel-associated water. This conclusion is discussed in terms of current theories of general anaesthesia.

Human-like, population-level specialization in the manufacture of pandanus tools by New Caledonian crows Corvus moneduloides.

The main way of gaining insight into the behaviour and neurological faculties of our early ancestors is to study artefactual evidence for the making and use of tools, but this places severe constraints on what knowledge can be obtained. New Caledonian crows, however, offer a potential analogous model system for learning about these difficult-to-establish aspects of prehistoric humans. I found new evidence of human-like specialization in crows' manufacture of hook tools from pandanus leaves: functional lateralization or 'handedness' and the shaping of these tools to a rule system. These population-level features are unprecedented in the tool behaviour of free-living non-humans and provide the first demonstration that a population bias for handedness in tool-making and the shaping of tools to rule systems are not concomitant with symbolic thought and language. It is unknown how crows obtain their tool behaviour. Nevertheless, at the least they can be studied in order to learn about the neuropsychology associated with early specialized and/or advanced population features in tool-making such as hook use, handedness and the shaping of tools to rule systems.

Rate-determining processes in the transport of Pr3+ ions by the ionophore A23187 across phospholipid vesicular membranes. A 1H-MR and theoretical study.

Rate constants and activation parameters have been determined for the transport of Pr3+ ions by the ionophore A23187 across dipalmitoyl phosphatidylcholine vesicular membranes. The novel method described depends on the measurement of changes in chemical shift of the 1H-NMR choline head-group signals as Pr3+ is transported from outside to inside the vesicles. The determined rates are directly proportional to A23187 concentration, suggesting that the rate-determining step involves the species [Pr(A23187)](2+). A theoretical analysis of the initial stages of Pr3+ transport leads to the conclusion that diffusion over the image potential barrier is the rate-determing step. Calculation of the form and height of this barrier for the non-equilibrium state gives results which agree well with the experimental activation energy and also correctly predict a two-fold reduction in rate of transport when 7 mol % decane is present in the bilayer.

The effect of n-alcohols on vesicular permeability induced at the lipid phase transition temperature: a 1H-NMR study.

The effect of a series of n-alcohols on the permeability of small, unilamellar dipalmitoyl phosphatidylcholine (DPPC), dimyristoyl phosphatidylcholine (DMPC) and distearoyl phosphatidylcholine (DSPC) vesicles at the gel-to-liquid crystal phase transition temperature was investigated. It was found that the permeability took the form of the transient lysis of a fraction of the population of vesicles. The effect on this lysis of the n-alcohols was seen to be very chain-length dependent, with a minimum at n = 8 (octan-1-ol) for DPPC vesicles. A similar minimum was observed in the presence of 0.1 mM Triton X-100, but the detergent could then interact with certain of the alcohols to produce permanent channels. The results are discussed in terms of the semi-empirical model of Brasseur et al. (1985) Biochim. Biophys. Acta 814, 227-236, for the interaction of the n-alcohols with a DPPC membrane. The effect of various n-alcohols on the outer and inner monolayers of DPPC vesicles was also studied and the results related to their fluidising effect, allowing channels to open at the phase transition temperature.

Protection against membrane damage: a 1H-NMR investigation of the effect of Zn2+ and Ca2+ on the permeability of phospholipid vesicles.

1H-NMR spectroscopy of small, unilamellar dipalmitoyl phosphatidylcholine (DPPC) vesicles in conjunction with the lanthanide shift reagent Pr3+ was used to study the effect of Zn2+ and Ca2+ ions on the permeability induced at the lipid phase transition temperature (Tc) of the vesicles and by the bee venom polypeptide melittin. In addition, the effects of Zn2+ and Ca2+ were studied on Triton X-100 stabilized channels at Tc and in the presence of n-alcohols. The results show that the presence of 10 mM Zn2+ and Ca2+ inhibited most of the forms of vesicular permeability investigated. The results are discussed in terms of the nature of the binding of the metal ions to the vesicles and support the proposal that one biological function of Zn2+ and Ca2+ is protection against membrane damage.

The modulation of ion channels by the inhalation general anaesthetics. A1H-NMR investigation using unilamellar phospholipid membranes.

The modulation of a variety of mechanisms of channel-mediated transport across unilamellar phospholipid membranes by a range of halogenated inhalation general anaesthetics (chloroform, enflurane, halothane and methoxyflurane) was investigated using 1H-NMR spectroscopy. Transport of the probe ion Pr3+ across egg yolk phosphatidylcholine (PC) and dipalmitoyl phosphatidylcholine (DPPC) vesicular membranes in the presence of the channel forming polypeptides alamethicin 30 and melittin, and the polyene antibiotic nystatin, as well as the degree of vesicular lysis at the gel to liquid-crystal phase transition of DPPC vesicles was monitored. The observation that the inhalation general anaesthetics inhibit such membrane permeability independently of the channel system or type of lipid used, suggests that hydrogen-bonded water structure and/or hydrogen-bonding centres at dipolar lipid-polypeptide interfaces, can be likely sites of action of the general anaesthetics.

Phosphatidic acid regulates the activity of the channel-forming ionophores alamethicin, melittin, and nystatin: a 1H-NMR study using phospholipid membranes.

The regulation of ion channels by phosphatidic acid (a proposed active metabolite in the phosphatidylinositol effect) was investigated using 1H-NMR spectroscopy and small unilamellar phospholipid vesicles. Transport across egg-yolk phosphatidylcholine (egg PC) and dipalmitoyl phosphatidylcholine (DPPC) vesicular membranes in the presence of the channel-forming ionophores alamethicin, melittin, and nystatin was monitored using the lanthanide probe ion Pr3+. In the absence of the ionophores, phosphatidic acid (PA) alone was found to have no ionophore properties, but in the presence of the ionophores the incorporation of 3 mol % phosphatidic acid in the bilayer markedly increased the rate of transport using melittin and nystatin, but decreased the rate using alamethicin, independent of the type of phosphatidylcholine used. The presence of PA in the bilayer also stimulated the production of lytic type channels, the extent of which were both ionophore- and lipid-dependent. These results are discussed in terms of possible molecular interactions between the PA, the individual ionophores, and type of lipid used.

Bites and stings of uncommon arthropods. 1. Spiders.

In addition to the Hymenoptera, less common arthropods, such as spiders and reduviids, can inflict injuries of medical importance. Identification of the source of the bite or sting may be difficult but is essential to proper treatment. Part 1 of this article describes recognition and treatment of the bites of various spiders; part 2, beginning on page 107, considers bites and stings of other arthropods.

Bites and stings of uncommon arthropods. 2. Reduviids, fire ants, puss caterpillars, and scorpions.

Arthropod bites and stings may cause intense pain, sometimes out of proportion to the size of the lesion. Severe reactions may arise from prior exposure and buildup of antibodies. Diagnosis often can be made from the clinical presentation if the physician is familiar with the effects of the uncommon bites and stings. Some uncommon bites, such as those of reduviids, can be treated symptomatically, but others, such as those of poisonous scorpions, call for antivenin therapy.