The significance of changes in Mytella falcata (Orbigny, 1842) gill filaments chronically exposed to polluted environments

The impact of pollutants in an organism can be observed by changes in functional complexity at different levels. Bivalve gills are suitable for histopathological analysis because of their structure and function. This study aimed at examining the morphology of Mytella falcata gill filaments from three sites in the Santos estuary (São Paulo, Brazil) with different levels of environmental degradation to identify possible changes in gill structure and discuss the significance of these alterations. For this purpose, histological, histochemical and ultrastructural techniques were used. The filaments of animals from site A (less impacted site) were intact, while in sites B and C, pathological changes were observed, such as: detachment of the epithelium in the intermediate zone, morphological changes of this epithelium, inflammatory process, increase in the number of mucous cells and cell turnover processes. These results suggest that the related changes are an attempt to prevent the entrance of pollutants through gill filaments into the entire organism and that cell turnover is the final way to compensate cell injury.     

Acute and subchronic exposure of diplopods to substrate containing sewage mud: Tissular responses of the midgut

Several discussions regarding the agricultural use of sewage mud have occurred; however, its use has been questioned due to the risks of soil contamination mainly by metals. Diplopods are saprophagous invertebrates, agile in colonizing several layers of soil. Due to the habit of this group, several researchers have proposed their use in ecotoxicological analyses. This study aimed to expose these invertebrates to substrate containing sewage mud of a STS (Sewage Treatment Station) from São Paulo State, Brazil and analyzed its toxic potential by morphological analysis of the midgut of the diplopod Rhinocricus padbergi, region of the digestive tube where digestion and nutrient absorption occur. The animals were exposed in mud concentrations at 1%, 10% and 50% mixed with soil from the collection site for periods of 7 (acute exposure), 15 (intermediary exposure) and 90 (subchronic exposure) days in each treatment. The animals from the control group did not present alterations at all the exposition times. As an acute response (7 days), it was observed in the animals exposed to mud at 1% and 10% an increase in the epithelial renovation and in the liberation of secretory vesicles of glycoprotein content. In the animals exposed to mud at 50%, the main alteration observed was the increase in the number of cytoplasmatic granules in the fat body cells; the epithelium seemed to be in reorganization process in all the observed individuals, suggesting an intense epithelial renovation. In the intermediary period of exposure (15 days), in the animals exposed to mud at 1% it was observed an increase in the number of haemocytes among the cells of the fat body, distributed both separately and grouped; the animals exposed to mud at 10% presented the same evidence of epithelial renovation observed in the animals exposed for 7 days at a concentration of 50% of mud; it was also observed an increase in the number of haemocytes, which reacted strongly to the PAS technique. Cytoplasmatic granules in the hepatic cells, fat body cells and haemocytes were also observed in great number, being that great part presented calcium in their constitution. In the animals exposed to mud at 50%, the alteration observed was the presence of numerous secretory vesicles of the apocrine type through all the epithelia of vacuolated aspect; hepatic cells with cytoplasmatic granules were also observed. As subchronic response (90 days), it was observed that all the fat body cells were completely taken by cytoplasmatic granules, into which it was, detected the presence of calcium; such granules were also observed in the apical region of the principal epithelial cells. These results suggest the existence of toxic agents in the analyzed mud sample, whose different concentrations trigger responses that occur in different manners, intensities and velocities that might prevent the entrance and action of toxic agents in the organism of the studied invertebrate.     

Energy variability of bottom reflections as an indicator of crossing the frontal zone by an acoustic path

A considerable energy variability is observed for quartets of doubly bottom-reflected signals when the acoustic path crosses the frontal zone of the Gulf Stream. The experimental curves exhibit a local increase by a factor of more than two in the energy of individual bottom-reflected signals. According to the data of numerical modeling, the position and magnitude of the energy maxima prove to be highly sensitive to the position of the frontal zone, its horizontal and vertical sizes, and the values of the horizontal sound speed gradients. A conclusion is drawn that the observed phenomenon can be used as an indicator of the position of the frontal zone and as a tool for estimating its parameters.     

Multiple lump molecules and interaction solutions of the Kadomtsev–Petviashvili I equation

In this paper, a modified version of the solution in form of a Gramian formula is employed to investigate a new type of multiple lump molecule solution of the Kadomtsev–Petviashvili I equation. The high-order multiple lump molecules consisting of M N-lump molecules are constructed by means of the Mth-order determinant and the non-homogeneous polynomial in the degree of 2N. The interaction solutions describing P line solitons radiating P of the M N-lump molecules are constructed. The dynamic behaviors of some specific solutions are analyzed through numerical simulation. All the results will enrich our understanding of the multiple lump waves of the Kadomtsev–Petviashvili I equation.     

Neck fragmentation reaction mechanism

Based on a microscopic transport model, we study the origin of nonstatistical intermediate mass fragment (IMF) production in semicentral heavy ion collisions at the Fermi energies. We show that a fast, dynamical IMF formation process, the neck fragmentation mechanism, can explain the experimentally observed features: deviations from Viola systematics and anisotropic, narrow angular distributions. It may be regarded as the continuation of the multifragmentation mechanism towards intermediate impact parameters. Its relation to other dynamical mechanisms, the induced fission and the abrasion of the spectator zones, that can also contribute to mid-rapidity IMF production, is discussed. The dependence on beam energy and centrality of the collision is carefully analysed. The competition between volume and surface instabilities makes this mechanism very sensitive to the in-medium nucleon-nucleon interactions, from the cross sections for hard collisions to the compressibility and other equation of state (EOS) properties.

For charge asymmetric collisions the sensitivity of various observables to the symmetry energy is investigated. Of particular interest appears the isospin diffusion dynamics with no signal of isospin equilibration. However, in spite of the short time scales and of the dynamical aspects, we notice isoscaling features of the neck mechanism. We observe that isospin enrichment of the neck zone as well as the isoscaling parameters are sensitive to the density dependence of asymmetry term of EOS around and below saturation value.     

Histochemical technique for the detection of chloride cells in fish

Chloride cells are responsible for ionic exchanges in the fish gill. These cells have been widely studied, considering its importance in vital functions of the gill, and because they proliferate when exposed to unfavorable environments. One of the main characteristic of these cells is an acidic cytoplasm, which has been used for identification through histochemical techniques with dyes such as Toluidine Blue and Hematoxylin and Eosin. However, these techniques can be problematic, since epithelial cells can, in certain situations, acquire acidic characteristics similar to those of chloride cells, thus staining in a similar way. Among other functions, chloride cells play a role in calcium uptake from the environment, and therefore have a high concentration of this element. Based on this information, this study aims at developing a specific protocol for the identification of chloride cells. With this purpose, the Von Kossa method specific for calcium was used combined with Hematoxylin counterstaining. Chloride cells had cytoplasm slightly stained with Hematoxylin and the presence of dark stained granules dispersed in the cytoplasm resulted from the Von Kossa reaction due to the calcium present in these cells. This was not found in any other gill cell. Thus, the technique used in this study was specific and efficient to identify chloride cells in fish gills.     

Venom gland of Pachycondyla striata worker ants (Hymenoptera: Ponerinae). Ultrastructural characterization

Morphological data concerning the venom gland of worker ants of Pachycondyla striata revealed that this gland consists of three distinct regions: an external secretory portion, composed by a secretory filament that bifurcates in order to give rise to other two filaments; an internal secretory portion, represented by the convoluted gland; and a storage portion, represented by a sac-shaped reservoir. The ultrastructural analysis showed that the reservoir is enveloped by a simple pavementous epithelium, coated internally with a cuticle. The external secretory portion is composed by cells forming a simple cubic epithelium, in which the apical portion presents numerous microvilli while the basal portion of the cells shows infoldings of the plasma membrane containing numerous mitochondria. The convoluted gland possesses cells of irregular morphology with nuclei containing condensed chromatin, suggesting inactivity. However, these cells are in fact undergoing secretory activity, which is probably added to the final secretion produced by the gland. The cytoplasm of these cells contains several elements distributed therein, such as ribosomes and polyribosomes, lipid droplets, and protein inclusions in the form of crystals, thus suggestive of protein storage, which would be used by the insect when metabolically required.     

Dynamic supercoiling bifurcations of growing elastic filaments

Certain bacteria form filamentous colonies when the cells fail to separate after dividing. In Bacillus subtilis, Bacillus thermus, and Cyanobacteria, the filaments can wrap into complex supercoiled structures as the cells grow. The structures may be solenoids or plectonemes, with or without branches in the latter case. Any microscopic theory of these morphological instabilities must address the nature of pattern selection in the presence of growth, for growth renders the problem nonautonomous and the bifurcations dynamic. To gain insight into these phenomena, we formulate a general theory for growing elastic filaments with bending and twisting resistance in a viscous medium, and study an illustrative model problem: a growing filament with preferred twist, closed into a loop. Growth depletes the twist, inducing a twist strain. The closure of the loop prevents the filament from unwinding back to the preferred twist; instead, twist relaxation is accomplished by the formation of supercoils. Growth also produces viscous stresses on the filament which even in the absence of twist produce buckling instabilities. Our linear stability analysis and numerical studies reveal two dynamic regimes. For small intrinsic twist the instability is akin to Euler buckling, leading to solenoidal structures, while for large twist it is like the classic writhing of a twisted filament, producing plectonemic windings. This model may apply to situations in which supercoils form only, or more readily, when axial rotation of filaments is blocked. Applications to specific biological systems are proposed.     

The Invar problem

After briefly reviewing the history and practical applications of Invar, we present results of recent total energy calculations as a function of the magnetic moment and atomic volume E(M, V). Based on these results, we analyze Invar-relevant physical properties for a broad variety of fcc ferromagnetic and antiferromagnetic 3d-alloy systems as a function of the electron concentration. The observed systematics can principally be understood within the framework of the band calculations mentioned. We also give an answer to the question, why close to the Invar range martensitic fcc-bcc transitions occur. Finally we show that a deeper understanding of all the observed anomalies results from an analysis of available data as a function of the lattice constant. Almost quantitative agreement between experiment and theory allows the conclusion that the moment-volume instabilities are undoubtedly responsible for the magnetic, magnetovolume and structural properties exhibited by 3d-alloy systems.     

Prestomal teeth of some flies of medical importance

Comparison of prestomal teeth of adult Chrysomya megacephala, Chrysomya rufifacies, Chrysomya nigripes, Lucilia cuprina, Parasarcophaga dux and Musca domestica was accomplished by use of scanning electron microscopy. The prestomal teeth of C. megacephala, C. rufifacies, L. cuprina and P. dux are all similar in appearance in having various degrees of bifurcation at their tips. In contrast, the tips of the prestomal teeth in C. nigripes are very shallowly serrated, but are comparatively more deeply serrated in M. domestica. These features may help account for the roles these flies may play in matters of medical or veterinary importance, such as causing physical irritation or acting as vectors of disease agents.     

Long-range sound propagation in the region of the subarctic front

The data of two experiments performed in the northwestern Pacific are presented. The propagation path crosses the northern boundary of the subarctic frontal zone. The influence of the frontal zone on the time structure and intensity of the sound field is studied. This influence most clearly manifests itself in the range dependence of the level of the normalized sound field at frequencies of 63–800 Hz. In the region of crossing the boundary of the frontal zone, a change of 1.5–2 dB in the sound field level is observed with localization in distance. In this region, a pronounced increase in the frequency-independent component of the exponential attenuation is also observed (by 0.015 dB/km for explosion-generated signals received at a depth of 600 m). At depths of 150–800 m, a zone of weak variations of the propagation loss is present in the vertical structure of the sound field at the 100-km part of the path in the region of crossing the front. In the experiment with explosion-generated signals, phenomena that are unrelated to the frontal zone are observed as well, namely, the appearance of reverberation forerunners (prereverberation) on separate parts of the path and the presence of bottom-reflected signals on one of the path fractions with a local bottom rise.     

地下组合受限空间火灾分区实验与数值分析

本论文对地下组合受限空间火灾初期的分区现象进行了模拟试验和数值分析。地下组合受限空间火灾呈现出特殊的分区现象。一般可分为燃烧区、新鲜空气补充区、烟气流区、过渡区和火焰后面的“惰化区”五区。有上下两层的地下复杂组合受限空间可分为燃烧区、烟气流区、新鲜空气补充区和“惰化区”4区。将数值模拟分析结果与实验结果进行了比较,二者吻合较好。研究表明,本文所采用的组合受限空间火灾三维模拟分析模型,是一种既能实现对实际结构复杂火灾现象的模拟分析又能在一定程度上满足实际工程要求的较好分析方法。     

青藏高原东北部闪电M变化多参量观测

利用闪电光通道高速摄像、 地面电场变化和峰值辐射强度同步资料, 对比分析了负地闪连续电流阶段和人工触发闪电放电过程中M变化特征. 结果表明, 通道亮度资料能够辅助地面电场波形来准确判断是否为真实的M过程. 在经典M变化产生前及其过程中会产生很多快速电场变化MP(称为预M变化)变化, 大量MP促成了M变化. MP变化和K变化在脉冲特征上没有太多差别, 产生的物理机制是相似的. MP变化是连续电流阶段快速电场变化, 是击穿过程引起的电荷快速流动的结果, 并伴有通道突然增亮和高强度辐射. M变化脉冲波形多数为单极性, 有正有负, 少数呈现不规则变化, 持续时间在0.1 ms之内.而经典M变化的U 形结构只适用于近闪, 波形是静电场所致, 持续时间约0.2–0.8 ms. MP和K变化都是击穿所致, 只是MP变化有电荷流入原回击通道, 而K变化没有. 关键词： 青藏高原 M变化')" href="#">M变化 MP变化')" href="#">MP变化 K变化')" href="#">K变化     

The structure of the fibrous tissue on the articular surface of the temporal bone in the monkey (Macaca mulatta)

The articulating surface of bones which ossify in mesenchyme, like the mandible, is covered by a layer of dense, fibrous tissue. The purpose of the present study was to examine the structure of the fibrous tissue on the surface of the articular surface of the temporal bone in the monkey. Young Rhesus monkeys (Macaca mulatta) were perfused with glutaraldehyde-paraformaldehyde. The specimens were demineralized in 0.5M EDTA. Small pieces of fibrous tissue and underlying bone were dissected out and processed for light and electron microscopy. The mandibular fossa is shallower and the articular eminence flatter in the monkeys as compared to humans. The articular part of the temporal bone is covered by a layer of avascular, soft tissue extending from the surface to the underlying bone. The tissue can be divided into three zones which gradually merge into one another. The zone facing the articular cavity consists of dense, fibrous tissue with layers of collagen fibers, oriented parallel to the articular surface, but at angles to each other. Fibers thought to be elastic fibers oriented parallel with the collagen fibers are also observed, particularly close to the surface, and their function is probably to impart resilience to the fibrous articular tissue. Between the fibers scattered cells with an ample rough endoplasmic reticulum are present. A thin layer of granular appearance is often observed on the surface. This layer may be of importance in joint lubrication. The second zone is more cell rich and the cells have long slender cellular processes and are surrounded by a dense collagenous matrix with an irregular orientation. These cells are probably precursor for the underlying cartilage but, not for the cells in the outer articular layer. In the third zone next to the bone the fibrous tissue gradually turns into cartilage. The cartilagenous zone is narrow, sometimes absent and is replaced by bone tissue. In some areas chondroclasts are observed, with forming osteons with osteoid seams. These observations indicate that remodeling is taking place and that cartilage is replaced by bone. The three zones observed correspond to findings in the mandibular condyle, but the zones are not as constant and distinct as in the condyle, and this reflects the adaptive role of the temporal bone in the growth of the temporomandibular joint.     

The venom gland of queens of Apis mellifera (Hymenoptera, Apidae): morphology and secretory cycle

The venom gland of queens of Apis mellifera was examined through light and transmission electron microscopy and subjected to electrophoretic analyses. Virgin queens exhibited prismatic secretory cells containing large amounts of rough endoplasmic reticulum with dilated cisternae, open secretory spaces, numerous vacuoles and granules scattered in the cytoplasm, and spherical nuclei with numerous nucleoli. The secretion produced was non-refringent under polarized light and the electrophoretic analysis of glandular extracts revealed five main protein bands. In mated queens, the venom gland exhibited a high degree of degeneration. Its secretion was refringent under polarized light and one of the main bands was absent in the electrophoretic pattern obtained. The morphological aspects observed are in agreement with the function of this gland in queens, given that virgin queens use venom in battles for the dominance of the colony, a situation that occurs as soon as they emerge, while fertilized queens rarely use venom.     

Morphological features and occurrence of degenerative characteristics in the hypopharyngeal glands of the paper wasp Polistes versicolor (Olivier) (Hymenoptera: Vespidae)

Different histochemical techniques were applied to examine the morphological features of the secretory cells of hypopharyngeal glands in the wasp Polistes versicolor. The results showed that most analyzed individuals present active glands with secretion stored in the cytoplasm. In some glands, morphological analyses revealed the presence of degenerative characteristics. Analyses of cellular integrity, however, did not detect dead cells. The results showed that, in P. versicolor, the development and regression of the hypopharyngeal glands were not age related, unlike glands of social bees.     

Existence and uniqueness of solutions to superdifferential equations

We state and prove the theorem of existence and uniqueness of solutions to ordinary superdifferential equations on supermanifolds. It is shown that any supervector field, X = X₀ + X₁, has a unique integral flow, Г: ^1¦1 x (M, A_M) → (M, A_M), satisfying a given initial condition. A necessary and sufficient condition for this integral flow to yield an ^1¦1-action is obtained: the homogeneous components, X₀, and, X₁, of the given field must define a Lie superalgebra of dimension (1, 1). The supergroup structure on ^1¦1, however, has to be specified: there are three non-isomorphic Lie supergroup structures on ^1¦1, all of which have addition as the group operation in the underlying Lie group . On the other extreme, even if X₀, and X₁ do not close to form a Lie superalgebra, the integral flow of X is uniquely determined and is independent of the Lie supergroup structure imposed on ^1¦1. This fact makes it possible to establish an unambiguous relationship between the algebraic Lie derivative of supergeometric objects (e.g., superforms), and its geometrical definition in terms of integral flows. It is shown by means of examples that if a supergroup structure in ^1¦1 is fixed, some flows obtained from left-invariant supervector fields on Lie supergroups may fail to define an ^1¦1-action of the chosen structure. Finally, necessary and sufficient conditions for the integral flows of two supervector fields to commute are given.     

On injection of hydrate-forming gas into a gas-saturated snowy agglomerate while transition through the ice melting point

The paper considers the process of injection of hydrate-forming gas (methane) into a snowy agglomerate (ini-tially saturated with methane). The self-similar problem statement demonstrates that if the warm gas (T_e > 0 °C) is injected under a high pressure (p_e ≥ p_*, where the critical values are found from the initial temperature T₀, pressure p₀, volumetric snow saturation S_i0, and permeability of snow) into the filtration zone with phase transition, this produces four characteristic zones: the nearest zone with all snow transformed into hydrate, therefore, the aggregate filled only with gas and hydrate, the two intermediate zones where gas, snow or water and hydrate are in phase equilibrium state, and the distant zone filled only with gas and snow. The obtained analytical and numerical solutions give an analysis of the influence of key input parameters like initial state of the aggregate, gas injection rate, and its temperature, on the structure and the length of four filtration zones.     

Spin waves in nickel thin films

Dynamic susceptibility and spin waves in nickel thin films are investigated within the framework of the multiband model. Parameters of the model are chosen in such a way that one-electron ground-state results consistent with ab initio theories are obtained. The dispersion relation for spin waves which propagate in the plane parallel to the surface along the [1 0] and [1 1] directions is calculated. Acoustic surface mode is observed up to the Brillouin zone boundary for wave vector q along the [1 1] direction and localization of the mode in the surface layer gradually increases with increasing q. On the other hand, for q in the [1 0] direction acoustic surface mode appears only for low q values and it disappears in the band of bulk modes for greater values of q. Near the zone boundary only bulk modes are observed. It is suggested that the disappearance of the surface mode can be a result of crossing of spin-wave branches.     

半干旱采煤塌陷不同应力区典型植物高光谱特征分析

利用高光谱反演、监测植被生长状况的基础是光谱特征识别。以半干旱采煤塌陷区为样地，利用Field Spec 3地物光谱仪与SPAD-502叶绿素仪同步采集采煤地表塌陷形成的不同应力区(非采区、中性区、拉伸区、压缩区)典型植物叶片光谱反射率与叶绿素含量(SPAD值)，分析典型植物相同应力区SPAD值升高其光谱特征的变化，对比不同应力区典型植物SPAD值较高与较低时光谱特征的差异，并借助Matlab软件深入研究不同应力区典型植物SPAD值与差值指数、归一化指数的相关关系。结果表明：(1)不同应力区同种植物光谱曲线随着SPAD值不同变化规律相异，可见光波段区分明显，其余波段受应力影响的区域样本SPAD值不同，反射率比非采区波动更为剧烈与无序。可见光波段，糙隐子草、柠条、杨树、油蒿SPAD值低的样本光谱曲线绿峰缺失，SPAD值升高，绿峰出现但位置红移，SPAD值高于30时，为典型植被光谱曲线，油松样本SPAD值越高反射峰值越小；受应力影响的区域SPAD值低的样本谷、峰、边特征参数缺失更多，光谱变化规律不强。(2)400～700 nm波段，不同应力区糙隐子草、油蒿、油松、柠条样本SPAD值较低组反射率显著高于较高组，杨树样本相反；780～1 350 nm波段，拉伸区的糙隐子草、非采区的油蒿和柠条、压缩区的油松和杨树样本SPAD值较高组与较低组的反射率差异小；相较于非采区，受应力影响的糙隐子草、油蒿、柠条样本在所测波段SPAD值较高组与较低组的同波段反射率差值显著减小。(3)受应力影响的区域样本SPAD值与光谱指数相关性较之非采区在某些波段大面积增强。与非采区相比，中性区的油蒿、油松、柠条、杨树样本SPAD值与光谱指数的最大相关系数值均增大，糙隐子草相反；非采区植物SPAD值与NDVI最大相关系数均高于DI，波段组合多位于近红外，受应力影响区域的样本最大相关系数多数位于可见光波段。本研究为矿区不同应力区典型植物高光谱波段识别与植物健康状态监测、矿区生态环境精准治理提供了理论支撑。