Development of a self-consistent model of dust grain charging at elevated pressures using the method of moments

A model of dust grain charging is constructed using the method of moments. The dust grain charging process in a weakly ionized helium plasma produced by a 100-keV electron beam at atmospheric pressure is studied theoretically. In simulations, the beam current density was varied from 1 to 10⁶ μA/cm². It is shown that, in a He plasma, dust grains of radius 5 μm and larger perturb the electron temperature only slightly, although the reduced electric field near the grain reaches 8 Td, the beam current density being 10⁶ μA/cm². It is found that, at distances from the grain that are up to several tens or hundreds of times larger than its radius, the electron and ion densities are lower than their equilibrium values. Conditions are determined under which the charging process may be described by a model with constant electron transport coefficients. The dust grain charge is shown to be weakly affected by secondary electron emission. In a beam-produced helium plasma, the dust grain potential calculated in the drift-diffusion model is shown to be close to that calculated in the orbit motion limited model. It is found that, in the vicinity of a body perturbing the plasma, there may be no quasineutral plasma presheath with an ambipolar diffusion of charged particles. The conditions for the onset of this presheath in a beam-produced plasma are determined. __________ Translated from Fizika Plazmy, Vol. 29, No. 3, 2003, pp. 214–226. Original Russian Text Copyright ? 2003 by Filippov, Dyatko, Pal’, Starostin.     

Photoabatement by Anthocyanin Shields Photosynthetic Systems from Light Stress

Leaves and other chlorophyllous tissues of plants often show transient or permanent anthocyanin coloration. The question of whether anthocyanins can function as effective light screens to modulate photosynthesis in plants was addressed by comparing photosynthetic responses in reddish-purple pods with those in green pods of the ornamental leguminous tree Bauhinia variegata. For these comparisons the actinic radiation employed was either red radiation (RR) which was poorly absorbed by anthocyanin or blue-green radiation (BGR) which was strongly absorbed by anthocyanin. Photon yields of photosystem 2 (PS2) photochemistry and photochemical chlorophyll fluorescence quenching coefficients (q_p), measured over a range of photon flux densities (PFD) up to 1200 μmol m^-2 s^-1 at 23 °C and at five temperatures from 8 to 28 °C at a PFD of 260 μmol m^-2 s^-1, were almost identical in green pods irradiated with either RR or BGR and in purple pods irradiated with RR. However, q_p values remained much higher in purple pods irradiated with BGR, e.g., 0.80 in BGR versus 0.29 in RR at a PFD of 1200 μmol m-2 s^-1 at 23 °C, and 0.67 in BGR versus 0.28 in RR at a PFD of 260 μmol m^-2 s-1 at 8 °C. The higher values of q_p in BGR compared to RR indicated that photoabatement by anthocyanin allowed the first stable acceptor of PS2, Q_A, to be kept in a more oxidized state, thus decreasing the likelihood of photoinhibition. This was confirmed by demonstrating a lower susceptibility to photoinhibition in purple pods than in green pods in the sunlight, either naturally in pods on trees or in detached pods exposed to photoinhibitory conditions. We conclude that photoabatement by anthocyanin is a mechanism for allowing maintenance of higher oxidative levels of PS2 acceptor during episodes of high radiation stress, thereby minimizing photodamage to photosynthetic tissues. This revised version was published online in June 2006 with corrections to the Cover Date.     

Structures of the plasma channels in a Besselian beam

A mechanism for the formation of the structure of an optical discharge in Besselian laser beams is proposed on the basis of analyzing numerous experiments. The discharge structure is determined by the periodicity of the field of a Besselian beam in the radial and longitudinal directions and also depends on the power and duration of the heating pulse. In the initial stage of the plasma channel formation, the configuration of the channel inhomogeneities follows the discharge structure. If the spatial scale of the discharge structure is small, then the developing channel evolves into a homogeneous state. The time required for the structural inhomogeneities of the plasma channel to be smoothed out is estimated as a function of their scale length. __________ Translated from Fizika Plazmy, Vol. 27, No. 9, 2001, pp. 846–858. Original Russian Text Copyright ￠ 2001 by Pyatnitsky.     

Spectral Test Instrument for Color Vision Measurement

Common displays such as CRT or LCD screens have hmlted capabilities in displaying most color spectra correctly. The main disadvantage of these devices is that they work with three primaries and the colors displayed are the mixture of these three colours. Consequently these devices can be confusing in testing human color identification, because the spectral distribution of the colors displayed is the combined spectrum of the three primaries. We have developed a new instrument for spectrally correct color vision measurement. This instrument uses light emitting diodes (LEDs) and is capable of producing all spectra of perceivable colors, thus with appropriate test methods this instrument can be a reliable and useful tool in testing human color vision and in verifying color vision correction.     

A non-equilibrium thermodynamics model of reconstituted Ca2+-ATPase

A non-equilibrium thermodynamics (NET) model describing the action of completely coupled or `slipping' reconstituted Ca<sup>2+</sup>-ATPase is presented. Variation of the coupling stoichiometries with the magnitude of the electrochemical gradients, as the ATPase hydrolyzes ATP, is an indication of molecular slip. However, the Ca<sup>2+</sup> and H<sup>+</sup> membrane-leak conductances may also be a function of their respective gradients. Such non-ohmic leak typically yields `flow-force' relationships that are similar to those that are obtained when the pump slips; hence, caution needs to be exercised when interpreting data of Ca²⁺-ATPase-mediated fluxes that display a non-linear dependence on the electrochemical proton (Δμ˜_H) and/or calcium gradients (Δμ˜_Ca). To address this issue, three experimentally verifiable relationships differentiating between membrane leak and enzymic slip were derived. First, by measuring Δμ˜_H as a function of the rate of ATP hydrolysis by the enzyme. Second, by measuring the overall `efficiency' of the pump as a function of Δμ˜_H. Third, by measuring the proton ejection rate by the pump as a function of its ATP hydrolysis rate. Received: 19 June 1997 / Accepted: 3 December 1997     

Forms of iron in the oxygenated waters of Esthwaite Water,U.K.

Flow centrifugation at an acceleration of 18 000 × gravity of surface water samples of Esthwaite Water separates the iron into two fractions, the sediment (A) and the supernatant (B). The amounts of iron in A and B are approximately equal (40–60%) except during, and for a few months after, the annual overturn. At this time there is a large increase in the total iron concentration, the extra iron being found in fraction A. Electron microscopic examination and microprobe analysis of fraction A collected at times other than the overturn period show that the most prevalent form of iron in this fraction is amorphous iron (III) oxide. The oxide consists of approximately spherical, ellipsoidal or cylindrical particles, hardly any of which have a dimension >0.5 μm. In the lake, sedimentation of iron probably requires the particles to flocculate either by self-association or by association with other particulate matter. The particles contain highly variable amounts of Ca, also Si, P and S, and probably humic substances. Kinetic analyses of Fe (III) species, carried out by measuring rates of formation of Fe³⁺ on treatment with acid, show that fraction A contains a single slow-reacting species which can be equated with the amorphous iron oxide. Fraction B contains this species also, together with a component which reacts about 30 times faster, and which comprised approximately 15% of the iron in an unconcentrated surface water sample. The nature of the fast-reacting component is not clear. Possibly it consists of small unaged oxide polymers; alternatively it might be composed of iron-organic complexes.     

Study of the plasma in a preformed Z-pinch constriction

The development of a preformed constriction in cylindrical agar-agar loads at currents of up to 3 MA is studied experimentally. The loads 3–5 mm in diameter have a mass density of 0.1 g/cm³ and are filled with different materials. Due to the implosion of the constriction to a minimum size of 40–70 μm, a hot dense plasma (with the electron density n _e=10²² cm⁻³, electron temperature T _e=0.8–1.5 keV, and ion temperature T _i=3–12 keV) is produced. It is found that the ion temperature substantially exceeds the electron temperature. The lifetime of the high-temperature plasma determined from the FWHM of a soft X radiation (SXR) pulse is shorter than 5 ns, the radiation power of photons with energies of ≥1 keV is higher than 0.5×10¹⁰ W, and their total energy attains 50 J. High-speed photography in the VUV, SXR, and optical spectral regions indicates the protracted generation of the high-temperature plasma. Calculations by the two-dimensional ideal MHD model of the Z-pinch show that the most important consequence of the protracted plasma generation in the constriction region is that the current is intercepted by a freshly produced plasma. In the course of plasma generation, the current near the axis inside the region of radius 50 μm is at most one-half of the total current. After the plasma generation comes to an end, almost the entire current is concentrated in this region for several nanoseconds; this process is accompanied by a sharp increase in the plasma temperature. __________ Translated from Fizika Plazmy, Vol. 27, No. 12, 2001, pp. 1101–1110. Original Russian Text Copyright ? 2001 by Bakshaev, Blinov, Vikhrev, Gordeev, Dan’ko, Korolev, Medovshchikov, Nedoseev, Smirnova, Tumanov, Chernenko, Shashkov.     

Chemical characteristics of lakes in the High Tatra Mountains,Slovakia

The chemistry of 53 lakes at various stages of acidification and inhabited (at the presence and/or in the past) by pelagic Crustacea was studied in September 1984. Ten of these lakes were investigated in detail biannually (July and October 1987–1990). The July results reflect the influence of snowmelt and were compared with the October ones. The most important anion was sulphate with the average values of 98 and 104 μeq 1^-1 in 1984 and 1987–1990, respectively. High concentrations of nitrate (21–56 μeq 1^-1) were observed in lakes above the treeline. Mean relative composition of cations does not differ between July and October; small changes are in the mean relative composition of anions. Acidification of lakes, expressed as a decrease in alkalinity, is 100 μeq l^-1, and is equal to the increase in the sum of sulphate and nitrate. The values of total phosphorus and COD are the lowest in the range of pH 5–6.5. Alkalinity, sulphate, nitrate and pH do not show any trend with time over the last ten years.     

Waldenström macroglobulinemia – definition, symptoms, and treatment

Waldenstr?m macroglobulinemia (WM) is a low-grade lymphoplasmacytic lymphoma of mature IgM⁺ B-lymphocytes that remains incurable despite recent practice-altering therapeutic advances and refinements in patient care. Defining features of WM include symptoms that can either be attributed to the extent and site of tissue infiltration by tumor cells or the magnitude and immunological specificity of the monoclonal serum IgM (paraprotein). Current guidelines for the therapeutic stratification of patients with newly diagnosed WM recommend BR (bendamustin-rituximab) for bulky and/or symptomatic disease. DRC (dexamethasone-rituximab-cyclophosphamide) is a good treatment option for relapsed or refractory WM. Ibrutinib – a small-drug inhibitor of Bruton tyrosine kinase, approved for WM treatment in the United States and Europe in 2015 – is particularly effective for tumors that harbor the hallmark MYD88^L265P mutation. Plasma exchange is indicated in patients with IgM-dependent hyperviscosity syndrome. The potential development of novel drugs and combination regimens generates promise that the future of patients with WM is bright.     

Perpetual Adaptation in a Perpetually Changing Environment as a Survival Strategy of Plants: A Case Study in Foraminifers Concerning Coral Reef Bleaching

Coral reef bleaching is a global phenomenon poorly understood today. We investigated during 7 d the photosynthetic behaviour of symbionts of coral reef and temperate foraminifers in hospite, by means of the JIP-test. By this screening test the fast fluorescence rise O-J-I-P, measured by a Plant Efficiency Analyser (PEA) with 10 μs time resolution and 12 bit signal resolution, was analysed. It informs about the structure and function of photosystem 2 being at different physiological states established by adaptation to different irradiance and temperature. The test needs a measuring time in vivo of only 1 to 5 s, and thus many samples can be analysed. The measurements can be done continuously even on a single cell in a test tube or on the reef. The reef foraminifers tested here were Amphistegina and Amphisorus, freshly collected in Mauritius. As a temperate foraminifer, Sorites from the Mediterranean Sea was tested. The cells are very sensitive to slight temperature changes (25 to 32 °C). The comparison showed that the more the foraminifers live in an environment with constant temperature the less they are able to respond to temperature changes and, thus, the less they can adapt. Rising the temperature increases in general the sensitivity to different stress factors, such as high irradiance, pH, CO₂, etc. After the test series, the cells recovered fully and were kept in an aquarium for long time observation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Three-dimensional biomagnetic Maxwell fluid flow over a stretching surface in presence of heat source/sink

The present paper deals with the study of three-dimensional boundary layer flow of biomagnetic Maxwell fluid over a plane horizontal surface stretched linearly along two mutually perpendicular directions. Basic principles of magnetohydrodynamics (MHD) and ferro-hydrodynamics (FHD) have been employed. The effect of heat generation/absorption has been taken into consideration. The study is theoretical and is conducted by using a combination of approximate and numerical techniques. By using the method of similarity transformation, the governing nonlinear partial differential equations are converted into a set of coupled ordinary differential equations. In the sequel, a suitable numerical method has been developed to solve the coupled differential equations. The accuracy of the numerical method has been checked by comparing the numerical results with those of an earlier study reported in available literatures. Effects of various parameters involved in the study, viz. the magnetohydrodynamic and ferromagnetic parameters, Deborah number, stretching ratio and heat generation on the fluid flow profiles are investigated and the results have been presented graphically. Variations of the skin friction, heat transfer rate and relative wall pressure with change in hydrodynamic and ferromagnetic parameters have also been illustrated. It is found that due to the influence of the Kelvin force, the velocity component in xx-direction is greater than the corresponding one in the hydrodynamic case, but the opposite is true for the velocity component in the yy-direction. We also found that the temperature of the fluid for hydrodynamic flow is greater than that for MHD or FHD flow. It is even greater for BFD flows. The numerical results of the study reveal that the characteristics of blood flow are significantly affected by the presence of a magnetic field.     

Site of synthesis and phylogenetic distribution of a hemolymph trophic factor of the tobacco hornworm,Manduca sexta

Summary Identification of fith instar larvalManduca sexta fat body and epidermis as sites of synthesis of a hemolymph protein (hemolymph trophic factor or HTF) was achieved using in vitro³H-leucine incorporation into protein and subsequent immunoprecipitation of tissue homogenates. Fat body is the primary site of HTF synthesis with a maximal rate on Day 1; epidermis is a secondary site with peak synthesis on Day 0. In vitro radiolabelling followed by TCA precipitation of general protein of fat body and epidermal homogenates suggest that fat body actively elaborates protein on Days 0–5 with peak rates on Days 1 and 4, while epidermis is active on Days 0–5 with a peak rate on Day 3. Based on Anti-HTF ELISA estimates, HTF [500 to 1000 μg/ml] was found in the hemolymph of representatives of the insect orders Blattodea, Hemiptera, Orthoptera, and Lepidoptera and in the class Crustacea, but not in the class Merostomata. These studies suggest a possible fundamental role for HTF among modern arthropods in cuticular deposition involving both epidermis and fat body. The physiological role of HTF is undetermined.     

Generation and interaction of intense counterpropagating plasma flows

Results are presented from experimental studies of the parameters of two counterpropagating (colliding) plasma flows generated by discharges in crossed electric and magnetic fields. It is shown that the conversion efficiency of the energy deposited in the discharges into the energy of directed plasma flows is 0.3–0.6. For discharge current pulses with a duration of ∼10 μs, the energy flux density in the plasma flow reaches ∼10 J/cm² and the total energy of the flow is on the order of 300 J. The density of deuterons in the flows is ∼10¹⁵ cm⁻³, and the flow velocity is ≤2×10⁷ cm/s. The total number of particles carried by the flows is about 10¹⁹. The possibility of using counterpropagating plasma flows to study reactions involving light nuclei (dd, pd, dt, and dHe reactions) in the range of ultralow collision energies is discussed. __________ Translated from Fizika Plazmy, Vol. 29, No. 8, 2003, pp. 714–721. Original Russian Text Copyright ? 2003 by Dudkin, Nechaev, Padalko, Bystritsky, Stolupin, Bystritskii, Voznyak.     

Store-Dependent Entry of Ca<Superscript>2+</Superscript> into Sensory Neurons of the Rat

We studied store-dependent (activated by depletion of the endoplasmic reticulum, ER, store) entry of Ca²⁺ from the extracellular medium into neurons of the rat spinal ganglia (small- and medium-sized cells; diameter, 18 to 36 μm). Activation of ryanodine-sensitive receptors of the ER in the studied neurons superfused by Tyrode solutions containing Ca²⁺ or with no Ca²⁺ was provided by application of 10 mM caffeine. The decay phase of caffeine-induced calcium transients in a Ca²⁺-containing solution was significantly longer than that in a Ca²⁺-free solution. This fact allows us to suppose that such a phenomenon is determined by Ca²⁺ entry into the neuron from the extracellular medium activated by caffeine-induced depletion of the ER store. Substitution of Ca²⁺-free extracellular solution by Ca²⁺-containing Tyrode solution, after depletion of the ER stores induced by applications of 100 nM ryanodine, 200 μM ATP, or 1 μM thapsigargin, resulted in increases in the concentration of intracellular Ca²⁺. These observations allow us to postulate that store-dependent Ca²⁺ entry into the studied neurons is activated after depletion not only of the inositol trisphosphate-sensitive ER store but also of the ryanodine-sensitive store. This entry also occurs after blocking of ATPases of the ER by thapsigargin. The kinetic characteristics of the rising phase of store-dependent Ca²⁺ entry induced by depletion of the ER stores under the influence of various agents are dissimilar; this can be related to different mechanisms of activation of such signals and/or to a compartmental organization of the ER. Neirofiziologiya/Neurophysiology, Vol. 37, No. 3, pp. 277–283, May–June, 2005.     

Effects of particle concentration and season on the filtration rates of the freshwater clam,Sphaerium striatinum Lamarck (Bivalvia: Pisidiidae)

The effects of particle concentration and season on the filtration rates of the freshwater clamSphaerium striatinum Lamarck were assessed by measuring clearance rates of small (2.02 μm) latex beads from dilute suspensions. Filtration rates decreased as particle concentration increased over a range of 2–64 mg 1⁻¹, with rates decreasing in similar proportion for clams of all sizes. For a 1-mg clam, rates decreased from approximately 8.4 to 0.57 ml clam⁻¹ h⁻¹. Seasonal filtration rates for adult clams peaked during periods of greatest reproduction. The patterns for smaller clams are similar, though proportional changes in filtration rates differ for various sizes of clams. It is estimated that clams occupying 1 m² of stream substrate removed about 3.67 gCa⁻¹. This is equivalent to 0.0004% of the carbon that flows past them annually. Filter-feeding provided only 24% of the calculated energy needs of the population, suggesting that another mode of feeding (e.g. deposit-feeding) may provide an important energy source for these forms. Funded in part by a grant-in-aid to D. J. Hornbach from Sigma-Xi, The Research Society. Funded in part by a grant-in-aid to D. J. Hornbach from Sigma-Xi, The Research Society.     

Phosphorus intensity determines short-term P uptake by pigeon pea (<Emphasis Type="Italic">Cajanus cajan</Emphasis> L.) grown in soils with differing P buffering capacity

Phosphorus (P) uptake by plant roots depends on P intensity (I) and P quantity (Q) in the soil. The relative importance of Q and I on P uptake is unknown for soils with large P sorption capacities because of difficulties in determining trace levels of P in the soil solution. We applied a new isotope based method to detect low P concentrations (<20 μg P l⁻¹). The Q factor was determined by assessment of the isotopically exchangeable P in the soil (E-value) and the I factor was determined by measurement of the P concentration in the pore water. A pot trial was set up using four soils with similar labile P quantities but contrasting P buffering capacities. Soils were amended with KH₂PO₄ at various rates and pigeon pea (Cajanus cajan L.) was grown for 25 days. The P intensity ranged between 0.0008 and 50 mg P l⁻¹ and the P quantity ranged between 10 and 500 mg P kg⁻¹. Shoot dry matter (DM) yield and P uptake significantly increased with increasing P application rates in all soils. Shoot DM yield and P uptake, relative to the maximal yield or P uptake, were better correlated with the P concentration in the pore water (R ² = 0.83–0.90) than with the E-value (R ²=0.40–0.53). The observed P uptakes were strongly correlated to values simulated using a mechanistic rhizosphere model (NST 3.0). A sensitivity analysis reveals that the effect of P intensity on the short-term P uptake by pigeon pea exceeded the effect of P quantity both at low and high P levels. However, DM yield and P uptake at a given P intensity consistently increased with increasing P buffering capacity (PBC). The experimental data showed that the intensity yielding 80% of the maximal P uptake was 4 times larger in the soil with the smallest PBC compared to the soil with the largest PBC. This study confirms that short-term P uptake by legumes is principally controlled by the P intensity in the soil, but is to a large extent also affected by the PBC of the soil. Section Editor: N. J. Barrow     

Evaluation of the different levels of variability in the underwater light field of a shallow estuary

The underwater light climate of a shallow estuary located at the southern coast of the Baltic Sea has been investigated, with special emphasis on the spectral irradiance composition and on short-term irradiance fluctuations caused by vertical mixing and wave focussing. The inherent optical properties of the water body were dominated by phytoplankton pigment absorption in the long-wavelength range and by coloured, dissolved organic matter (cDOM) absorption in the wavelength range <500 nm, including ultraviolet-A (UV-A) and ultraviolet-B radiation (UV-B). Pronounced particulate scattering combined with the absorption values to give very high attenuation coefficients, especially for the shorter wavelengths of UV-B radiation. Photosynthetically active radiation (PAR) was found to be reduced to 1% of the surface value within 0.8 m in the inner, hypertrophic end of the estuary and within 1.9 m in the outer, eutrophic parts of this system, with corresponding 1% penetration depths for UV-B of 0.13 and 0.31 m. During late winter and early spring, the period when reduced atmospheric ozone concentrations and enhanced UV-B have been reported over northern Europe, the irradiance levels in the water column were greatly reduced, due to strong attenuation by ice cover and overlying snow. cDOM concentration of the water was also found to remain at a high level during these periods, and indeed throughout the year, thus reducing the exposure of organisms to UV-R and PAR still further. A complex irradiance regime was found in this system, with irregular and high amplitude fluctuations caused by wind-induced vertical mixing and wave focussing being superimposed upon the solar-angle-dependent seasonal and daily cycles. The methods used to quantify the short-term fluctuations are described, and their relevance to phytoplankton physiology is discussed. The wave-focussing effect is unique to the aquatic environment, and measurements showed that average subsurface irradiances could be increased by up to 5 times for periods lasting for <1 s. The highest irradiances recorded during wave-focussing events reached over 9,000 μmol photons m^–2 s^–1. Received in revised form: 7 April 2000 Electronic Publication     

Adaptation of the photosynthetic apparatus of Nitellopsis obtusa to changing light intensity at the molecular level: different pathways of a singlet excitation quenching

The effect of prolonged illumination (60 min) with photosynthetically active monochromatic radiation of low intensity (3 μmol m⁻² s⁻¹) and high intensity (60 μmol m⁻² s⁻¹), corresponding to the physiological conditions and light stress conditions, respectively, was studied in the algae Nitellopsis obtusa. Illumination of Nitellopsis obtusa cells with strong light was associated with activation of the xanthophyll cycle, manifested by the deepoxidation of violaxanthin and accumulation of antheraxanthin and zeaxanthin. At the same time, the efficient singlet excitation quenching in the photosynthetic apparatus was activated, as demonstrated by the decrease in the intensity of the chlorophyll a fluorescence emission by ca 50 %. The difference of the fluorescence excitation spectra recorded before and after the light treatment match the difference absorption spectrum of the xanthophyll cycle pigments. The illumination with low light intensity resulted also in the chlorophyll a fluorescence quenching but the effect was very small (less than 10 %). The fluorescence quenching is interpreted in terms of the energy transfer between the Q_y energy level of chlorophyll a and the 2¹ A_g ⁻ energy level of zeaxanthin. The singlet energy levels of carotenoids, corresponding to the green spectral region, are also taken into consideration in the interpretation of the excitation energy exchange between the carotenoids and chlorophylls. Possible molecular mechanisms involved in the activation of the strong and the weak excitation quenching, including violaxanthin isomerization, and possible physiological functions of such pathways of energy transfer are discussed.     

Geochemistry and clay mineralogy of termite mound soil and the role of geophagy in chimpanzees of the Mahale Mountains,Tanzania

Earth from a termite mound in the Mahale Mountains National Park, Tanzania, eaten by chimpanzees, was analyzed to determine the possible stimulus, or stimuli, for geophagy. The termite mound sample contains relatively high aluminum (10.0%), iron (3.0%), and sodium (0.5%). This correlates well with the mineralogy of the clay (<2 μm) fraction, which is high in metahalloysite, a 1:1 (Si:Al=1:1) clay mineral similar in chemical composition to the clay mineral kaolinite, and smectite (montmorillonite), which is a 2:1 expandable clay mineral. The combination of metahalloysite and smectite produces a substance much like the pharmaceutical Kaopectate^™ widely used by humans as an anti-diarrheal agent. These analyses and preliminary observations linking geophagy with instances of severe diarrhea, and other signs of gastrointestinal upset in the Mahale chimpanzees, suggest that one function for the ingestion of this substance by chimpanzees may be to help provide temporary relief from gastrointestinal ailments. Further detailed investigations into the relationship between health and geophagy should provide important insights into the diverse roles of this behavior as a form of self-medication.     

The nest architecture of the ant, Pheidole oxyops Forel, 1908 （Hymenoptera： Formicidae）

Pheidole oxyops builds subterranean nests, with an external architecture that is distinctive and easily recognizable by its wide and specific entrance hole, measuring up to 12.2 cm in diameter, denoting a pitfall-trap. In order to study the nests＇ internal architecture, seven nests were excavated; four were identified with neutral talc, while the others were cast in cement and then excavated. Measurements were made in order to gain a better understand- ing of their structures, and a photographic documentation was obtained as well. The excavations revealed that the nests are perpendicular relative to the ground, beginning with a cylindrical channel with a mean length of 13.5 cm, containing irregular formations, and whose diameter becomes progressively narrower until the first chamber is formed. As the channel continues, dish-like chambers appear, interconnected by channels that become progressively narrower and longer, while the chambers are arranged at greater distances from each other as nest depth increases. Both channels and chambers are located on the vertical projection of the entrance hole. Nests may reach a depth of up to 5.09 m, with a number of chambers ranging between 4 and 14.