Showing papers in "Naturwissenschaften in 1989"

Self-organized Shortcuts in the Argentine Ant

Abstract: Les fourmis I. humilis choisissent le chemin le plus court pour aller de la colonie au lieu d'approvisionnement

Does Drosophila have seven eyes

Abstract: Des mutants sans yeux reagissent a la lumiere. Ils ont encore des cellules dans les lobes optiques, non decrites jusqu'ici. Ces cellules sont identifiees par immunocytochimie en utilisant un anticorps monoclonal qui colore specifiquement les photorecepteurs. Morphologiquement ces cellules peuvent etre considerees comme des vestiges des ocelles lateraux des larves. L'etude montre que ces cellules constituent deux yeux additionnels dans l'appareil visuel de l'adulte

Resonant stimulation and control of nonlinear oscillators

Abstract: Generalized dimensions, entropies, Lyapounov exponents [1], and approximations of the flow vector field [2, 3] are used to describe the periodic and chaotic dynamics of nonlinear experimental systems. In addition to the passive observation of a nonlinear oscillator and the description of the measured data using statistical quantities, it is possible to characterize a nonlinear oscillator by an active method, namely by determining its response to specific driving forces [4]. Active methods, like resonance spectroscopy, are superior to passive methods, especially when the experimental system is a set of identical, weakly coupled oscillators, behaving incoherently. I f one gets without driving force a compound signal of all oscillators, small and complex due to interference, a strong response emerges at resonance. At resonance every single oscillator is forced to coherent oscillations, sychronized by the driving force. For example, when a damped nonlinear mechanical pendulum is perturbed by a sinusoidal force, the response is comparatively small in amplitude [5] and does not fulfill any well-defined resonance condition [6], even when the frequency of the driving force coincides with a peak(resonance) in the power spectrum of the dynamics of the unperturbed system [7]. Outside the region of entrainment the response is complicated, in many cases chaotic [8]. In order to obtain a large response, the frequency of the driving force has to be varied in such a way, that it coincides at all amplitudes with a characteristic frequency of the oscillator. The characteristic frequencies of a nonlinear oscillator depend on the amplitude. For example, a weekly damped, mechanical oscillator with an anharmonic potential

Reproductive dominance controlled by mutilation in the queenless ant Diacamma australe

Abstract: the latter will be aroused and will mount the female laterally. Stage 3: subsequently, the male settles on the female's dorsum in a parallel position for a period of 0.5 - 1.0 min, while the female (with the male on her dorsum) will commence walking. Stage 4: the male turns his body by ~ 180 ~ and transfers his gnathosoma and part of his idiosoma beyond the margin of the female's opisthosoma. The male will then attach himself to the latter by his anal and tarsal suckers. In this position both sexes remain linked for 128- 219 min, during which the aedeagus is in- serted to the bursa copulatrix. Copu- latory movements are usually per- formed for an average period of 30 min. Insemination involves the produc- tion and transfer of spermatophores to the receptaculum seminis of the female; this process has been described in detail [4,5]. The events of stage 1 suggest the in- volvement of a male-produced pher- omone causing the recognition of males by the females, while the events of stages 2 and 3 indicate the utilization of a female-produced pheromone which elicits mating activity in the males. The use of sex pheromones for mate finding appears particularly important for A. siro, as this species lacks the capability of visual perception. The above results were corroborated by the observed attractiveness of an ex- tract of male A. siro for conspecific females as well as the sexual stimula- tion of male flour mites by an extract of female A. siro. Figure la reveals that

Freely flying honeybees use image motion to estimate object distance

Abstract: Les abeilles en vol utilisent la vitesse apparente de l'image retinienne pour juger de la distance des objets

A new procedure for fast electrochemical analysis of solid materials

Abstract: equal to the realistic mean experimental time for complete replication of MDV1 RNA up to the point when the replica release takes place [8]. This time is taken to be 15 s in realistic conditions. The time-dependent probabilities p=p( t ) for the most probable secondary structures at a given time are displayed in Fig. 2. The refolding transition occurs when a new secondary structure emerges with a higher probability. These transitions are indicated by numbers in Fig. 2. The correlation between these transitions and the most significant pause sites is revealed in Fig. 1. The pause site is found by simply locating the nucleotide in the replica sequence corresponding to the instant when two probability curves cross or when a new secondary structure with higher probability emerges, as is the case with transition indicated by "7" in Fig. 2. One can infer f rom this analysis that the pause sites considered occur as a consequence of the partial relaxation of effective binding of the growing chain to the enzyme.

A technique to study the electrochemistry of minerals

Abstract: Recently a new technique has been introduced to study the dectrochemistry of metals and alloys [1,2]. This socal led abrasive stripping voltammetry comprises a mechanical (abrasive) transfer of traces of the solid material onto the surface of a solid electrode and the following electrochemical oxidation or reduction of these traces with an appropriate measuring method (e.g., differential pulse voitammetry). It turned out that this technique is highly useful to study the electrochemistry of sparingly soluble salts, including a great variety of minerals. This method opens up new areas of research, not only because of the extreme fastness of measurements (including sample preparation) but also because of the superior quality of the voltammograms and the trace amounts of material (less than 1/tg) which are sufficient to perform the study. To know the electrochemistry of minerals is important for a deep understanding of the formation and transformation of minerals. It is not less important for a possible electrochemical metallurgy [3]. Last, but not at least, abrasive stripping voltammetry can develop toward an easy method for mineral identification [4] even in fieldwork. As an example the electrochemistry of the mineral boulangerite, PbsSb4SI1 (Neumtihle, Greiz, GDR) will be discussed here. This mineral belongs to the extensive group of sulfo-salt minerals [5]. Figure 1 depicts the differential pulse voltammograms obtained after abrasive transfer of trace amounts of the mineral onto the surface of a paraffine-impregnated graphite electrode. Curve A is the cathodic voltammogram with the reduction of boulangerite according to

The spectral sensitivity of a passerine bird is highest in the UV

Abstract: hind leg. Whether the females give preference to intact males over handicapped ones was counted from pairs copulating. These observations continued over a period of 2 months. The results, illustrated in Fig. 1, show a strong bias against mutilated males. They were involved in matings in only 11 070 of the observed copulations. Apparently the mating success of males with one hind leg is drastically reduced. We take these results as an indication that the female grasshopper Ch. biguttulus can base its choice of a partner upon specific characteristics o f the male's song.

Natural rain forest fires in Eastern Borneo during the Pleistocene and Holocene

Abstract: Lowland tropical rain forests have been generally regarded as ecosystems in which disturbance by natural fires was excluded due to fuel characteristics and moist climatic conditions []. However, recent findings demonstrate that climatic conditions during the past six millennia have favored the occurrence and spread of fires in the Amazon rain forest [2]. We are now able to show that natural fires have repeatedly occurred in the lowland dipterocarp rain forest of East Borneo since the late Pleistocene. Interannual climatic variability, associated with the \"El Niflo-Southern Oscillation\" (ENSO) phenomenon, leads to periodic droughts within great parts of Indo-Malesia. A distinct and well documented ENSO event occurred in 1982 83 and caused an extreme dry spell in the equatorial zone of insular South-East Asia [3]. A similar strong event was recorded and reported in Indonesia in 1877 -78 [4]. In Balikpapan (East Kalimantan) the rainfall between July 1982 and April 1983 was only onethird of the annual mean; the rainfall deficit was similar in other coastal areas of Borneo. The drought stress of the lowland rain forest vegetation led to the drying of vines and shedding of leaves by evergreen species, and the turf-like accumulation of organic matter in the peat swamp forests was desiccated up t o 2 m .

Pheromone blends of green stink bugs and possible parasitoid selection.

Abstract: It is confirmed from a literature review and new research that different pheromone strains exist in Nezara viridula from different geographical regions and that males from the sister genus Acrosternum emit bouquets of distinctive ratios of the same sesquiterpenes as in N. viridula. Many tachinid parasitoids use heteropteran pheromones as kairomones, and it is suggested that the chemical similarity of pheromones of N. viridula and Acrosternum has facilitated the adoption of N. viridula as a host by tachinids in the New World.

Honeybees can be recruited by a mechanical model of a dancing bee

Abstract: Une fausse abeille a ete construite, animee par des moteurs, qui simule la danse de recrutement. L'efficacite de ce dispositif est testee en etudiant le transfert d'information de distance et de localisation entre le modele et les ouvriers

[Biochemistry of thiol groups: the role of glutathione].

Abstract: Glutathione (GSH) comprises the bulk of the pool of free thiol groups in biological systems. Since its first description as philothione 100 years ago, there have been repeated surprises in discoveries of novel functions. Just recently the important role of thioethers with products of the lipoxygenase reaction, i.e., the leukotrienes, was revealed as mediator of physiological and pathophysiological processes. Another major function resides in detoxication, GSH being cosubstrate in the GSH-peroxidase reaction for the reduction of hydroperoxides in the defense against oxidative stress. Interest also focuses on reactions of glutathionyl radicals in protection by thiols against DNA damage resulting from ionizing radiation.

Cleavage of dibenzofuran and dibenzodioxin ring systems by a Pseudomonas bacterium.

Abstract: Etude de la degradation du dibenzofurane, et du clivage de 2 des 3 cycles de la di-benzo-p-dioxine par une souche de Pseudomonas. Les produits obtenus sont purifies par chromatographie HPLC et identifies par spectroscopie RMN et spectrometrie de masse. L'elucidation des etapes metaboliques impliquees dans ce mecanisme permettront la construction de bacteries capables de degrader des composes toxiques

The skylight polarization patterns at dusk affect the orientation behavior of blackcaps,Sylvia atricapilla

Abstract: Avian nocturnal migrants have been shown to use a variety of orientat ional cues to select their migratory direction [11. Recently, Able [21 and Moore [31 called at tention to another relevant orientation factor: skylight polarization. At sunrise and sunset, a band of maximally polarized light with its evector perpendicular to the sun azimuth runs through the zenith at an axis 90 ~ from the sun [4]. This pat tern remains detectable through a polarizer up to 45 min after sunset, and provides a prominent cue for animals able to perceive polarized light and its e-vector direction. Able and Moore [2, 3] suggest that it is used as a compass by nocturnal migrants, as they could alter the orientation of their test birds by shifting the e-vector of incident plane-polarized light. Here we report findings with blackcaps, Sylvia atricapilla, which show that this species also responds to alterations in e-vector direction, but that the behavior with respect to an artificial e-vector differs markedly f rom that under natural , clear skies. The test birds were caught prior to autumn migration between July and midSeptember. They were housed individually in cages in the natural geomagnetic field at Frankfur t a .M. and in an artificial photoper iod simulating the natural one. Tests were per formed on clear evenings only ( < l/8 cloud cover) on the flat roof top of the Insti tute building, 25 m above the ground. The activity was recorded in Emlen funnels lined with typewriter correction paper [5]. The cages were covered with polarizers (Dodwell Hi-Tech, Tokyo, 40 • 40 cm; 0.40 mm thick) which allowed passage of no more than 0.01 o70 unpolarized light. They also at tenuated the intensity of incident light by 6 0 65 % (depending on wavelength) in the visible part of the spectrum and by almost 80 o70 in the near-UV below 400 nm. For control tests, we used clear Plexiglass 233 (3 mm thick) with a transmission of nearly 100070 in the visible. The birds were assigned at random to either experimental or control conditions, which were always run simultaneously. Tests were carried out f rom Sept. 18 to Nov. 4, 1985 with 8 birds, and from Sept. 10 to Sept. 30, 1986 with 10 birds. During the test periods, the azimuth of sunset changed from 277 ~ on Sept. 10 to 246 ~ on Nov. 4, and with it the band of maximal polar izat ion of the natural sky f rom 7 ~ ~ to 1 5 6 ~ ~ . Birds were put into the test cages after local sunset and retrieved 1 h later, i .e. , when the major stars became visible. Since no peripheral shields were used, the birds had an unobstructed view of the sky almost down to the horizon in-

Restricted hearing range in a subterranean rodent, Cryptomys hottentotus.

Abstract: 1. Alcock, J., Gwynne, D. T., Dadour I. A.: J. Insect Behav. (in press) 2. Bailey, W. J. : Nature 272, 444 (1978) 3. Blest, A. D., Collett, T. S., Pye, J. D.: Proc. R. Soc. Lond. B. 158, 196 (1963) 4. Fenton, M. B., Fullard, J. H." J. Comp. Physiol. 132, 77 (1979) 5. Fullard, J. H. : ibid. A. 155, 795 (1984) 6. Fullard, J. H., Thomas, D. W." ibid. 143, 363 (1981) 7. Moiseff, A., Hoy, R. R. : ibid. 152, 155 (1983) 8. Surlykke, A.: Physiol. Entomol. 11, 221 (1986) 9. Surlykke, A., Gogala, M.: J. Comp. Physiol. A. 159, 267 (1986) 10. Surlykke, A., Larsen, O. N., Michelsen, A. : ibid. A. 162, 367 (1988)

What is entropy

Abstract: The foundations of entropy and its significance in the thermodynamic description of the macroscopic world are discussed in the framework of the modern theory of nonequilibrium systems. Entropy production in open systems as the source for the formation of \"dissipative\" spatio-temporal structures is a fundamental principle in physics, chemistry, biology, and related fields of science. The article describes how entropy is connected with evolution, which requires irreversibility, probability, and coherence for producing new ordered phenomena; it also examines the role of entropy in the context of recent cosmological models. Introduction ~

Marangoni flow and the shapes of laser-melted pools

Abstract: The incidence of a concentrated flux of energy onto a conducting substrate which leads to localized melting as with a laser beam striking a metal is currently of interest in various material technologies, such as welding [1], in amorphous surface layer formation, as well as in the related problem of plasma disruptions on the first wall of projected thermonuclear fusion reactors [2]. Here we have modeled the process and consider the contribution of Marangoni or capillary gradient convection to the steady-state molten zone configuration. In the small-scale hydrodynamics involved in these phenomena and with high-surface-tension substances, Marangoni flow dominates over buoyancy flow. Tested on an important steel for laser powers up to 4 kW, the model predicts that the system capillarity, related to temperature and chemical composition, determines in a remarkable way the profile of the molten pool and explains observations made in metallurgical practice. This two-dimensional transient analysis refers to a model of a laser beam with a Gaussian power distribution normal to a flat substrate. Part of the incident radiation is reflected, while the absorbed part raises the temperature and produces a molten pool. Because of the steep temperature distribution, the surface tension decreases or increases radially from the center depending upon the surface chemistry of the system. Classical Marangoni flow arises from thermal or chemical capiUary gradients at the fluid surface, the direction of flow being from a locality of low to one of high surface tension. A detailed description of the present modeling will be published elsewhere. In summary, for the treatment of the flow hydrodynamics, we consider the Navier-Stokes governing equations with an additional relation expressing surface tension as a linear function of temperature. The analysis incorporates the problem of the moving boundary, as treated by Szekely [3] and exemplified in typical melting and solidification processes. Here, for a single-component system, the temperatures of the solid and the molten phases are equal at the meltsolid interface. In addition, a relationship has been established between the movement of the liquefaction front and the heat flux crossing the melt-solid interface. This is simply an expression of a balance between the heat flux arriving at the interface from the melt and passing into the solid, to the rate of advance of the interface. For the free surface, we consider the heat flux lost by evaporation, whereas heat losses by radiation and convection are neglected. Computations have been restricted to the case where the surface temperature never exceeds the boiling temperature. Furthermore, we assume at this stage as a first approximation, that the thermal conductivity and density are the same for both liquid and solid, that all physical properties such as viscosity and density of the liquid and solid are invariant with respect to temperature, and that the surface of the melt pool remains flat (a treatment under development will make allowance for a changing liquid/vapor interface). By considering cylindrical geometry, the governing equations have been discretized by finite difference methods using an unevenly spaced grid. As a starting point, a constant temperature field without fluid motion is considrently of interest as a candidate for first wall material for the next step of tokamak-type thermonuclear fusion reactor, where localized surface melting is expected to occur due to energy bursts resulting from plasma disruptions, a phenomenon which has been simulated by Schiller et al. [2] using electron beams. The present alloy has been studied in connection with anomalous welding behavior [4-8] and it has been demonstrated experimentally [1] that a steel with a high impurity content is associated with a deep, narrow weld pool (good penetrability) while the converse holds for a \"clean\" steel. The weld pool geometry is convincingly related to the sulfur impurity content of the steel. We apply the present model to test the notion that the role of the sulfur is through its effect on capillarity, which in turn influences the flow hydrodynamics. In essence, we attempt through the present model to predict the resulting pool shapes from the surface thermodynamic data. The surface tensions of this family of alloys have been measured recently by Mills et al. [1], using an elegant levitated molten-drop technique in a well controlled environment. These are currently the most rigorous data available on high-temperature alloy systems. We have applied the following quantities: Steel A (\"clean\" steel with very low impurity levels) which has a temperature coefficient of surface tension of -0 .30 mNm-lK -1 in a temperature range of 1400-1800 ~ Steel B, containing 140 ppm of sulfur (which displays good weld pool penetration) has a value + 0.36 mNm-lK -1. The negative coefficient for steel A is consistent with thermodynamic expectation for a system in which the bulk and surface compositions are identical; whereas the positive coefficient for steel B reflects

Different isotope compositions of C32 DPEP and C32 etioporphyrin III in oil shale: origin of etioporphyrin III from heme?

Abstract: Le schiste bitumineux Julia Creek (Cretace, Australie) est utilise pour etudier la relation entre les cycloalkanoporphyrines et les polyalkylporphyrines a partir d'une comparaison des compositions isotopiques

Discovery of copper chloride cancer in ancient Egyptian polychromic wall paintings and faience: A developing archaeological disaster

Abstract: We report the discovery of a disastrous and well advanced deterioration process of Egyptian Blue, Green Frit and Egyptian Faience in ancient Egyptian decorations and paintings. The process commences with the devitrification of copperand chlorine-bearing glass and glaze. Copper and chlorine ions are then leached out of the residual glass and gel into migrating solutions. Basic copper chloride (atacamite or paratacamite) precipitates through reactions of these solutions with calcium carbonate in the stucco or reactions between the leached copper ions with sodium chloride-rich solutions. Basic copper chloride deposits on the surface of the pigment layer or glaze, in its interstices, and in the stucco or plaster below the pigment layer. The original blue colour of the paint or glaze changes to faint green. The process leads to the development of highly friable and spongy pigment layers or glaze thus resulting in their desintegration to fine powder, denudation, ultimately final destruction, and hence bare reliefs. l ' n decorating tombs, temples, and their diverse sacral objects the ancient Egyptians definitely . sought eternal durability. This is probably a plausible explanation for their restlessness in manufacturing new pigments, introducing technical innovations, and their eagerness to improve the quality of their decorative products. Already in the Predynastic Period and the early Old Kingdom natural minerals were well known and used for decorations e.g. gypsum and calcite for white, ochre, haematite, and goethite for brown, red, and yellow. Compared to the decorations of other ancient cultures, the evolution of blue and green decorations in Egypt is unique. Blue and green Egyptian faiences are ubiquitous throughout the Egyptian history from the Early Dynastic Period to the Roman Period. In wall paintings no evidence was found for use of natural blue and green copper minerals (azurite, chrysocolla, and malachite) throughout the Egyptian history from the fifth Dynasty till the Roman Period [1, 2]. Information in the literature [3] about the use of these natural copper minerals are erroneous. This is a result of either misidentification of the nature of the pigment or insufficient knowledge whether the identified copper compound is an original paint or formed by a later deterioration process of the original pigment. In ancient Egyptian paintings, two synthetic compounds: Egyptian Blue and Green Frit were widely used as early as the fifth and sixth Dynasties. The manufacture of these pigments achieved high quality already in the Old Kingdom. The copper ingredient usually bronze was added to different mixtures of lime, and silica depending on whether Egyptian Blue or Green Frit (cuproan wollastonite) was to be manufactured [4]. The mixtures were then heated with salt flux or pottash and brought to fusion. The products are multiphase pigments. Egyptian Blue is a mixture of cuprorivaite (CaCuSi4010), silica phases (quartz, tridymite, cristobalite), a cuproan alkaliand chlorinebearing silicate glass, a copper oxide phase, and some unreacted bronze residues (depending on the time of manufacture arsenic, tin, and lead compounds) [4, 1, 2]. The Green Frit consists of cuproan wollastonite [(CaCu)SiO3, 0.6 wt. % CuO], a high content of a glass phase similar to that encountered in Egyptian Blue, and very few bronze residues [4]. Basic copper chlorides were reported from medieval paintings [5]. However, they were first detected in ancient Egyptian paintings from the Middle Kingdom by Terrace [6]. Subsequently Riederer [7] reported atacamite in stone reliefs from tombs of the 1 lth Dynasty in Deir el Bahari (1972). Riederer discussed in his report the various possibilities for the origin of basic copper chlorides. He considered it a pigment. However, he did not exclude the possibility of its formation by a

New bacterial degradation of the biaryl ether structure

Abstract: We report here the oxygenolytic cleavage of the ether bond occurring as the initial enzymatic step of high regioselectivity in the course of the bacterial attack on such aromatic compounds. Their complete catabolism is achieved by subsequent cleavage of the aromatic rings and further known reactions

Hearing of the Australian whistling moth, Hecatesia thyridion

Abstract: ing, however, such variability in the motor output might have a fundamental biological role for a continuous process of self-adjustment and fine tuning of sensorimotor functions even in a \"simple\" nervous system like that of the locust. Interestingly, 17 years ago Weber [9] demonstrated a process of stabilizing and shaping the flight rhythm in the cricket by means of \"flight experience\". The important role of \"biological noise\" for flight steering in Drosophila has been pointed out by Heisenberg and Wolf [10]. According to their experiments in an optical flight simulator, Drosophila discriminates open-loop from closed-loop conditions by means of spontaneous fluctuations of the yaw torque. Although the time constants for such \"self-respective\" sensory evaluation probably differ between locust and fly, the basic neuronal algorithms may be similar and perhaps also existent in other insects. They remind one of the ability of the vertebrate nervous system to select and tune its wide repertoire of motor functions depending on whether a particular outcome is \"successful\" (closed loop) or \"frustrating\" (open loop), even though the neuronal implementation in invertebrates is certainly simpler than in vertebrates. On the other hand, the evidence does suggest that the functional principles of motor plasticity in \"higher\" and \"lower\" animals are probably more similar than was expected so far.

Sound localization in the barking treefrog.

Abstract: 1. Poggio, T., Reichardt, W.: Kybernetik 13, 223 (1973) 2. Hassenstein, B., Reichardt, W.: Z. Naturforsch. 11b, 513 (1956) 3. Reichardt, W., in: Principles of Sensory Communication, p. 303 (ed. Rosenblith, W. A.). New York: Wiley 1961; Buchner, E., in: Photoreception and Vision in Invertebrates, p. 561 (ed. All, M. A.). New York-London: Plenum 1984 4. Reichardt, W. : J. Comp. Physiol A 161, 533 (1987) 5. Reichardt, W., Egelhaaf, M. : Biol. Cybern. 58, 287 (1988) 6. Foster, D. H.: Kybernetik 8, 69 (1971); van Doom, A. J., Koenderink, J. J.: Exp. Brain Res. 45, 179 (1982); 45, 189 (1982) 7. van Santen, J., Sperling, G.: J. Opt. Soc. Am. A 1,451 (1984) 8. Wilson, H. R.: Biol. Cybern. 51, 213 (1985) 9. Egelhaaf, M., Reichardt, W.: ibid. 56, 69 (1987) 10. van Santen, J., Sperling, G.: J. Opt. Soc. Am. A 2, 300 (1985) 11. Adelson, E., Bergen, J. : ibid. A 2, 284 (1985) 12. Torre, V., Poggio, T.: Proc. R. Soc, Lond. B 202, 409 (1978) 13. Grzywacz, N., Koch, C.: Synapse 1,417 (1987) 14. Egelhaaf, M., Borst, A., Reichardt, W. : J. Opt. Soc. Am. A (submitted) 15. Hausen, K.: Biol. Cybern. 45, 143 (1982); 46, 67 (1982) 16. Egelhaaf, M., Borst, A.: J. Opt. Soc. Am. A (in press) 17. Emerson, R. C., et al. : J. Neurophysiol. 58, 33 (1987)

Comparison monoterpene volatilization and leaf-oil composition of conifers

Abstract: Dans le cadre de l'etude du role des monoterpenes dans la deposition des polluants atmospheriques, on etudie la concentration totale en monoterpenes ainsi que leur volatilisation chez l'epicea et le douglas

Native fluorescence of unstained cryo-sections of the skin with melanomas and nevi.

Abstract: To obtain more detailed information concerning the distribution of the fluorophore(s) in the skin in the case of nevi and malignant melanomas, 10-μm cryo-sections of these samples have been investigated by the fluorescence technique and, after HE staining, examined histologically, Moreover, these investigations might elucidate the molecular differences between nevi and malignant melanomas. A total of 27 skin samples obtained from patients with nevi (16) or superficial spreading melanomas (11) has been investigated

Neuropeptides--occurrence and functions in insects.

Abstract: Article de synthese sur les neuropeptides (de mammiferes et d'invertebres) identifies chez les insectes