Measurement of surface area of stones

The surface area of stones can be quickly, accurately, and precisely estimated from linear regression equations of area on a two-dimensional term of the form (xy + yz + zx) where x, y, and z are either the axial dimensions or the axial perimeters of stones. Dimension measurements are made with calipers, and perimeters are measured with a tape measure or a mapping wheel. The best fit slopes for the equations are determined from a representative sample of stones whose surface areas are measured by mapping. Estimates of surface areas of river-worn cobbles by these methods had mean percentage absolute errors of about 4%, considerably better than other methods examined.     

Structure of the cross-striated adductor muscle of the scallop

The structure of the cross-striated adductor muscle of the scallop has been studied by electron microscopy and X-ray diffraction using living relaxed, glycerol-extracted (rigor), fixed and dried muscles. The thick filaments are arranged in a hexagonal lattice whose size varies with sarcomere length so as to maintain a constant lattice volume. In the overlap region there are approximately 12 thin filaments about each thick filament and these are arranged in a partially disordered lattice similar to that found in other invertebrate muscles, giving a thin-to-thick filament ratio in this region of 6:1.The thin filaments, which contain actin and tropomyosin, are about 1 μm long and the actin subunits are arranged on a helix of pitch 2 × 38.5 nm. The thick filaments, which contain myosin and paramyosin, are about 1.76 μm long and have a backbone diameter of about 21 nm. We propose that these filaments have a core of paramyosin about 6 nm in diameter, around which the myosin molecules pack. In living relaxed muscle, the projecting myosin heads are symmetrically arranged. The data are consistent with a six-stranded helix, each strand having a pitch of 290 nm. The projections along the strands each correspond to the heads of one or two myosin molecules and occur at alternating intervals of 13 and 16 nm. In rigor muscle these projections move away from the backbone and attach to the thin filaments.In both living and dried muscle, alternate planes of thick filaments are staggered longitudinally relative to each other by about 7.2 nm. This gives rise to a body-centred orthorhombic lattice with a unit cell twice the volume of the basic filament lattice.     

Hydration of krypton and consideration of clathrate models of hydrophobic effects from the perspective of quasi-chemical theory

Ab initio molecular dynamics (AIMD) results on a krypton-water liquid solution are presented and compared to recent XAFS results for the radial hydration structure for a Kr atom in liquid water solution. Though these AIMD calculations have important limitations of scale, the comparisons with the liquid solution results are satisfactory and significantly different from the radial distributions extracted from the data on the solid Kr/H(2)O clathrate hydrate phase. The calculations also produce the coordination number distribution that can be examined for metastable coordination structures suggesting possibilities for clathrate-like organization; none are seen in these results. Clathrate pictures of hydrophobic hydration are discussed, as is the quasi-chemical theory that should provide a basis for clathrate pictures. Outer shell contributions are discussed and estimated; they are positive and larger than the positive experimental hydration free energy of Kr(aq), implying that inner shell contributions must be negative and of comparable size. Clathrate-like inner shell hydration structures on a Kr atom solute are obtained for some, but not all, of the coordination number cases observed in the simulation. The structures found have a delicate stability. Inner shell coordination structures extracted from the simulation of the liquid, and then subjected to quantum chemical optimization, always decomposed. Interactions with the outer shell material are decisive in stabilizing coordination structures observed in liquid solution and in clathrate phases. The primitive quasi-chemical estimate that uses a dielectric model for the influence of the outer shell material on the inner shell equilibria gives a contribution to hydration free energy that is positive and larger than the experimental hydration free energy. The 'what are we to tell students' question about hydrophobic hydration, often answered with structural clathrate pictures, is then considered; we propose an alternative answer that is consistent with successful molecular theories of hydrophobic effects and based upon distinctive observable properties of liquid water. Considerations of parsimony, for instance Ockham's razor, then suggest that additional structural hypotheses in response to 'what are we to tell students' are not required at this stage.     

河南大学校园鸟类初步调查

截至2010年12月,为期2年的河南大学校园鸟类调查共记录到鸟类44种,隶属11目、25科;其中雀形目鸟类28种,留鸟20种,夏候鸟18种,冬候鸟和旅鸟各3种,分别占总数的63.6%、45.5%、40.9%、6.8%和6.8%;区系分析表明东洋种9种,古北种16种,广布种19种,分别占总数的20.5%、36.4%和43.2%。整体表现出南北混杂,古北种鸟类较东洋种比例大,广布种鸟类较多的特点。在调查基础上,提出了一些校园鸟类保护的建议。     

An investigation of the sources of nonuniqueness in deterministic identifiability

While a choice of techniques exists for checking the deterministic (structural) identifiability of a specific linear, time-invariant model from a specific experiment, and some progress has been made towards topological criteria for identifiability, no method at present available allows quick and reliable checking of a range of models for globally unique identifiability from a range of experiments. Even individual cases are sometimes difficult and tedious to check. The reasons are examined by exhaustive case-by-case analysis of single-input experiments on all possible three-compartment models. All patterns of loss to the environment are covered, and all combinations of observed compartments. Catalogues of minimal observation sets for globally unique identifiability, and of nonuniquely identifiable cases, are presented. The structural causes of nonuniqueness are discussed by reference to examples from the latter catalogue. Methods are given for shortening the derivation of the structural equations giving rise to nonunique parameters. From the diversity of behavior found, it is concluded that the prospects of obtaining a comprehensive set of necessary and sufficient structural conditions for globally unique identifiability are poor.     

Mutants of Escherichia Coli with Increased Fidelity of DNA Replication

SINEs are short interspersed repeated DNA elements which are considered to spread throughout genomes via RNA intermediates. Polymorphisms with regard to the presence or absence of SINE are occasionally observed in a specific location of a genome. We modeled the evolution of SINEs with regard to this type of polymorphism. Because SINEs are rarely deleted, multiplication of elements is confined to a certain period, and a few master copies are considered to be responsible for their multiplication, the usual population genetic models of transposable elements assuming the equilibrium state are not applicable to describe the evolution of SINEs. Taking into account these properties and assuming selective neutrality, we computed conditional probabilities of finding a SINE at a specific site given that this site is first found because it is occupied by a SINE in an original sample. Using these probabilities, we investigated ways to estimate the multiplication period and infer relationships among populations. The latter inference procedures are shown to be strongly dependent on the multiplication period.     

The use of cultured hepatocytes to investigate the metabolism of drugs and mechanisms of drug hepatotoxicity

Hepatotoxins can be classified as intrinsic when they exert their effects on all individuals in a dose-dependent manner, and as idiosyncratic when their effects are the consequence of an abnormal metabolism of the drug by susceptible individuals (metabolic idiosyncrasy) or of an immune-mediated injury to hepatocytes (allergic hepatitis). Some xenobiotics are electrophilic, and others are biotransformed by the liver into highly reactive metabolites that are usually more toxic than the parent compound. This activation process is the key to many hepatotoxic phenomena. Mitochondria are a frequent target of hepatotoxic drugs, and the alteration of their function has immediate effects on the energy balance of cells (depletion of ATP). Lipid peroxidation, oxidative stress, alteration of Ca(2+) homeostasis, and covalent binding to cell macromolecules are the molecular mechanisms that are frequently involved in the toxicity of xenobiotics. Against these potential hazards, cells have their own defence mechanisms (for example, glutathione, DNA repair, suicide inactivation). Ultimately, toxicity is the balance between bioactivation and detoxification, which determines whether a reactive metabolite elicits a toxic effect. The ultimate goal of in vitro experiments is to generate the type of scientific information needed to identify compounds that are potentially toxic to man. For this purpose, both the design of the experiments and the interpretation of the results are critical.]     

Characterization of scientific studies usually cited as evidence of adverse effects of GM food/feed

GM crops are the most studied crops in history. Approximately 5% of the safety studies on them show adverse effects that are a cause for concern and tend to be featured in media reports. Although these reports are based on just a handful of GM events, they are used to cast doubt on all GM crops. Furthermore, they tend to come from just a few laboratories and are published in less important journals. Importantly, a close examination of these reports invariably shows methodological flaws that invalidate any conclusions of adverse effects. Twenty years after commercial cultivation of GM crops began, a bona fide report of an adverse health effect due to a commercialized modification in a crop has yet to be reported.     

Ultrastructural and biochemical studies of the swelling of developing chick telencephalic slices

Summary An ultrastructural and biochemical study of the importance and localization of tissue swelling was performed on telencephalic slices of 1- and 30-day-old chicks incubated in an oxygenated or a non-oxygenated physiological medium. The swelling of slices is greater for 30-day-old chick material than for that from 1-day-old chicks. It also reaches higher values in the non-oxygenated than in the oxygenated medium. When the 30-day-old chick telencephalic slices are incubated in an oxygenated medium, swelling mainly affects astrocytes, and especially the astrocytic endfeet. When they are incubated in a non-oxygenated medium, the astrocytes and astrocytic endfeet are very swollen and in addition the swelling also affects the neurons and their organelles. Extracellular space is increased. When 1-day-old chick telencephalic slices are incubated in a non-oxygenated medium, the tissue structures are well preserved. Swelling predominantly affects astrocytes and astrocytic endfeet. Neurons are not affected and the extracellular space is reduced. However, when they are incubated in an oxygenated medium, tissue structures are greatly affected showing a high degree of disorganization. Extracellular space is greatly increased. This study thus indicates that the best incubation conditions are an oxygenated medium for 30-day-old chick telencephalic slices which are characterized by an aerobic metabolism, and a non-oxygenated medium for 1-day-old chick telencephalic slices which have a predominantly anaerobic metabolism.     

Group-theory classification of oscillations of plasma clusters

Normal oscillations of three-dimensional configurations of dust grains trapped in a spherically symmetric potential well are studied. All possible oscillations of a system consisting of 7–13 grains are classified in terms of group theory. For a Coulomb interaction potential, all the oscillation frequencies are calculated. The frequencies and polarizations of some oscillation modes are obtained for an arbitrary interaction potential.     

Possible evidence of predation in placoderms (Pisces) of the Evlanovo basin of central Russia

Two placoderms of different orders from a concretion of the Zyabrevo locality (Evlanovo Regional Stage, Frasnian) in central Russia are described. Five plates of the ventral and lateral sides of the trunk armor are assigned to a plourdosteid arthrodire. Three bones located in the region of its stomach are determined as a juvenile ptyctodontid, Ctenurella sp. Records providing actual evidence of predation in Devonian vertebrates are extremely scarce. Finds of this kind are listed for the first time.     

Comparison of floristic and structural classification of vegetation

A comparison is made between floristic and structural-physiognomic classifications of a tropical dry, semi-evergreen forest and thicket vegetation of south-eastern India. The classifications are strikingly similar in their main groupings which are ecologically meaningful; the differences between the classifications are virtually limited to allocation of some stands to different subcommunities. It is concluded that the use of structural-physiognomic criteria allows a detailed and ecologically significant classification of vegetation. Fairly advanced calculation facilities are necessary, however, to reach such a classification, since the structural-physiognomic differences between the resulting groupings are largely of a quantitative and not of a qualitative nature. This is a consequence of the general occurrence in all stands of the vegetation of the very great majority of the characters used in this study.Nomenclature follows Sprangers & Balasubramanian (1978) who give a complete list of authorities.     

Demonstration of rotational symmetries in alpha-keratin microfibrils of porcupine quill tip

Selected electron micrographs of transversely, obliquely and longitudinally sectioned microfibrils of transversely sectioned porcupine quill tip are shown to possess 2-fold radial, 3-fold radial and 5-fold polygonal rotational symmetries. These symmetries are verified with a rotation technique, and are similar to edge, corner and face projections of a pentagonal dodecahedron. The a-keratin microfibril is therefore suggested to be composed of a linear arrangement of morphologically identical microfibrillar subunits which approximate the shape of a pentagonal dodecahedron. The various line patterns present in electron micrographs of microfibrils are explained by different orientations of this three-dimensional shape within the thickness of the section. Previous electron microscopic models for the structure of the microfibrils are incompatible with these results. The image averaging methods used to arrive at these earlier models are discussed, and are thought to yield results which must differ from the demonstrated rotational symmetries.     

Energy of electrons emitted as a result of separation of surfaces

Experiments indicating acceleration of charged particles as a result of separation of solid surfaces are analyzed. As a possible mechanism of such acceleration, generation of surface charge on the separated surfaces of a cleaved ionic crystal is considered. The maximum electric field generated due to the charging of the separated surfaces and the energy of electrons accelerated in such a field are estimated. It is shown that, for the maximum attainable electric field, conditions are created for the generation of runaway electrons that, even at atmospheric pressure, electrons are accelerated to high energies, not experiencing collisions with gas particles.     

Anabolic steroids: a review of their effects on the muscles, of their possible mechanisms of action and of their use in athletics.

Anabolic steroids are synthetic molecules developed in the hope of obtaining a complete separation of the androgenic and myotrophic (anabolic) actions of testosterone. Such a goal has never been fully achieved. However, some synthetic steroids present a partial dissociation between these two activities. Since a single hormonal receptor apparently mediates the androgenic as well as the anabolic actions of testosterone, differences in patterns of androgen metabolization in the muscles and the sex accessory organs have been proposed as a possible cause of this phenomenon. Undoubtedly, androgens are able to exert a trophic effect on skeletal and cardiac muscle fibres in subjects with low circulating levels of testosterone such as prepubertal or hypogonadal males and females; however, the widespread use of anabolic steroids in male athletes to increase their physical performances poses the question of whether these compounds are active in the presence of normal circulating levels of testosterone. Most experimental animal studies indicate that anabolic steroids are ineffective in this situation. Since the results of the experiments performed in humans are largely contradictory, it is still not clear whether anabolic steroids are able to improve athletic performances. These and other relevant issues are reviewed.     

Morphology of the air-breathing stomach of the catfish Hypostomus plecostomus

Histological and ultrastructural investigations of the stomach of the catfish Hypostomus plecostomus show that its structure is different from that typical of the stomachs of other teleostean fishes: the wall is thin and transparent, while the mucosal layer is smooth and devoid of folds. The epithelium lining the whole internal surface of the stomach consists of several types of cells, the most prominent being flattened respiratory epithelial cells. There are also two types of gastric gland cells, three types of endocrine cells (EC), and basal cells. The epithelial layer is underlain by capillaries of a diameter ranging from 6.1-13.1 microm. Capillaries are more numerous in the anterior part of the stomach, where the mean number of capillary sections per 100 microm of epithelium length is 4, compared with 3 in the posterior part. The cytoplasm of the epithelial cells, apart from its typical organelles, contains electron-dense and lamellar bodies at different stages of maturation, which form the sites of accumulation of surfactant. Small, electron-dense vesicles containing acidic mucopolysaccharides are found in the apical parts of some respiratory epithelial cells. Numerous gastric glands (2 glands per 100 microm of epithelium length), composed of two types of pyramidal cells, extend from the surface epithelium into the subjacent lamina propria. The gland outlets, as well as the apical cytoplasm of the cells are Alcian blue-positive, indicating the presence of acidic mucopolysaccharides. Zymogen granules have not been found, but the apical parts of cells contain vesicles of variable electron density. The cytoplasm of the gastric gland cells also contains numerous electron-dense and lamellar bodies. Gastric gland cells with electron-dense cytoplasm and tubulovesicular system are probably involved in the production of hydrochloric acid. Fixation with tannic acid as well as with ruthenium red revealed a thin layer of phospholipids and glycosaminoglycans covering the entire inner surface of the stomach. In regions of the epithelium where the capillaries are covered by the thin cytoplasmic sheets of the respiratory epithelial cells, a thin air-blood barrier (0.25-2.02 microm) is formed, thus enabling gaseous exchange. Relatively numerous pores closed by diaphragms are seen in the endothelium lining the apical and lateral parts of the capillaries. Between gastric gland cells, solitary, noninnervated endocrine cells (EC) of three types were found. EC are characterized by lighter cytoplasm than the surrounding cells and they contain dense core vesicles (DCV) with a halo between the electron-dense core and the limiting membrane. EC of type I are the most abundant. They are of an open type, reaching the stomach lumen. The round DCV of this type, with a diameter from 92-194 nm, have a centrally located core surrounded by a narrow halo. EC of type II are rarely observed and are of a closed type. They possess two kinds of DCV with a very narrow halo. The majority of them are round, with a diameter ranging from 88-177 nm, while elongated ones, 159-389 nm long, are rare. EC of type III are numerous and also closed. The whole cytoplasm is filled with large DCV: round, with a diameter from 123-283 nm, and oval, 230-371 nm long, both with a core of irregular shape and a wide, irregular halo. EC are involved in the regulation of digestion and probably local gas exchange. In conclusion, the thin-walled stomach of Hypostomus plecostomus, with its rich network of capillaries, has a morphology suggesting it is an efficient organ for air breathing.     

Purification of Genomic DNA with Minimal Contamination of Proteins

The purification is based on a set of solutions and a simple centrifugation procedure. Protocols are designed for an easy extraction and purification of genomic DNA from a wide range of samples, including whole blood, buffy coat, bone marrow, body fluids, buccal cells, tissues, mouse tails, etc. RBCs are lysed by dilution into a hypotonic solution. Tissues are broken down and digested by proteinase K in the presence of an anion detergent to release genomic DNA. After precipitation of the detergent and proteins, unique beads that bind proteins, lipids, and RNAs are added to achieve the supreme purity. Genomic DNA is then separated by alcohol precipitation. A proprietary nucleic acid precipitation reagent is used to enhance DNA recovery from low concentration samples. No DNA-binding beads or columns are used in the method, eliminating the problem of low yield and the risk of shearing of genomic DNA. The purified samples are free of proteins, lipids, salts, and RNA contamination. Purified samples are also stable for storage and suitable for all downstream applications.     

The morphology and evolution of the female postabdomen of Holometabola (Insecta)

In the present article homology issues, character evolution and phylogenetic implications related to the female postabdomen of the holometabolan insects are discussed, based on an earlier analysis of a comprehensive morphological data set. Hymenoptera, the sistergroup of the remaining Holometabola, are the only group where the females have retained a fully developed primary ovipositor of the lepismatid type. There are no characters of the female abdomen supporting a clade Coleopterida + Neuropterida. The invagination of the terminal segments is an autapomorphy of Coleoptera. The ovipositor is substantially modified in Raphidioptera and distinctly reduced in Megaloptera and Neuroptera. The entire female abdomen is extremely simplified in Strepsiptera. The postabdomen is tapering posteriorly in Mecopterida and retractile in a telescopic manner (oviscapt). The paired ventral sclerites of segments VIII and IX are preserved, but valvifers and valvulae are not distinguishable. In Amphiesmenoptera sclerotizations derived from the ventral appendages VIII are fused ventromedially, forming a solid plate, and the appendages IX are reduced. The terminal segments are fused and form a terminal unit which bears the genital opening subapically. The presence of two pairs of apophyses and the related protraction of the terminal unit by muscle force are additional autapomorphies, as is the fusion of the rectum with the posterior part of the genital chamber (cloaca). Antliophora are supported by the presence of a transverse muscle between the ventral sclerites of segment VIII. Secondary egg laying tubes have evolved independently within Boreidae (absent in Caurinus) and in Tipulomorpha. The loss of two muscle associated with the genital chamber are likely autapomorphies of Diptera. The secondary loss of the telescopic retractability of the postabdomen is one of many autapomorphies of Siphonaptera.     

Mapping and ultrastructure of antennal chemosensilla of the wheat bug Eurygaster maura

Antennae of the wheat stink bug Eurygaster maura L. (Hemiptera: Scutelleridae) were investigated to elucidate structure and distribution of antennal chemosensilla in females. Five type of sensilla were identified and characterized using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Type 1 sensilla are mechanical and contact chemoreceptors with a single apical pore. Types 2 and 3 sensilla are multiporous chemoreceptors both with typical features of olfactory sensilla. Type 4 are multiporous peg-like sensilla, short and with a grooved surface. Type 5 are sensilla coeloconica with a smooth and aporous peg completely inserted in a sub-cuticular chamber. All types are distributed on the two flagellar segments, but we considered only the apical flagellomere in which the largest number of sensilla are located. The most abundant sensilla are type 3, while the less numerous are type 5. All types, except type 2, decreased in number from the tip to the base of the segment. The lower density of sensilla was recorded on the dorsal-internal part of the apical antennomere, while the higher density was recorded on the opposite side (external-ventral).     

Statistical Properties of the Number of Recombination Events in the History of a Sample of DNA Sequences

Some statistical properties of samples of DNA sequences are studied under an infinite-site neutral model with recombination. The two quantities of interest are R, the number of recombination events in the history of a sample of sequences, and RM, the number of recombination events that can be parsimoniously inferred from a sample of sequences. Formulas are derived for the mean and variance of R. In contrast to R, RM can be determined from the sample. Since no formulas are known for the mean and variance of RM, they are estimated with Monte Carlo simulations. It is found that RM is often much less than R, therefore, the number of recombination events may be greatly under-estimated in a parsimonious reconstruction of the history of a sample. The statistic RM can be used to estimate the product of the recombination rate and the population size or, if the recombination rate is known, to estimate the population size. To illustrate this, DNA sequences from the Adh region of Drosophila melanogaster are used to estimate the effective population size of this species.