Nonsymmetrical separations in thermal diffusion columns

The influence of the feed composition upon the actual degrees of separation attained at the top and bottom sections of a thermogravitational column is discussed using the classical phenomenological theory of Furry, Jones, and Onsager. It is shown that, except for a feed composition of C 0 = 0.5 (mass fraction), the separation profile is nonsymmetric, i.e., the separations in the top and bottom sections of the column are nonsymmetric with respect to the feed composition, the asymmetry increasing as the feed composition moves away from C 0 = 0.5. An equation for the determination of the optimum feed location as a function of the feed composition is derived.

Estudos citológicos em Hemíoteros da família Coreidae

A more or less detailed study of the spermatogenesis in six species of Hemiptera belonging to the Coreid Family is made in the present paper. The species studied and their respective chromosome numbers were: 1) Diactor bilineatus (Fabr.) : spermatogonia with 20 + X, primary spermatocytes with 10 + X, X dividing equationaliv in the first division and passing undivided to one pole in the second. 2) Lcptoglossus gonagra (Fabr.) : spermatogonia with 20 + X, primary spermatocytes with 10 + X, X dividing equationally in the first division and passing undivided to one pole in the second. 3) Phthia picta (Drury) : spermatogonia with 20 + X, primary spermatocytes with 10 + X, X dividing equationally in the first division and passing undivided to one pole in the second. 4) Anisocelis foliacea Fabr. : spermatogonia with 26 + X fthe highest mumber hitherto known in the Family), primary .spermatocytes with 13 + X, X dividing equationally in the first division an passing undivided to one pole in the second. 5) Pachylis pharaonis (Herbtst) : spermatogonia with 16 + X, primary spermatocytes with 8 + X. Behaviour of the heteroehromosome not referred. 6) Pachylis laticornis (Fabr.) : spermatogonia with 14 + X, primary spermatocytes with 7 + X, X passing undivided to one pole in the first division and therefore secondary spermatocytes with 7 + X and 7 chromosomes. General results and conclusions a) Pairing modus of the chromosomes (Telosynapsis or Farasynapsis ?) - In several species of the Coreld bugs the history of the chromosomes from the diffuse stage till diakinesis cannot be follewed in detail due specially to the fact that lhe bivalents, as soon as they begin to be individually distinct they appear as irregular and extremely lax chromatic areas, which through an obscure process give rise to the diakinesis and then to the metaphase chomosomes. Fortunately I was able to analyse the genesis of the cross-shaped chromosomes, becoming thus convinced that even in the less favorable cases like that of Phthia, in which the crosses develop from four small condensation areas of the diffuse chromosomes, nothing in the process permit to interpret the final results as being due to a previous telosynaptic pairing. In the case of long bivalents formed by two parallel strands intimately united at both endsegments and more or less widely open in the middle (Leptoglossus, Pachylis), I could see that the lateral arms of the crosses originate from condensation centers created by a torsion or bending in the unpaired parts of the chromosomes In the relatively short bivalents the lateral branches of the cross are formed in the middle but in the long ones, whose median opening is sometimes considerable, two asymetrical branches or even two independent crosses may develop in the same pair. These observations put away the idea of an end-to-end pairing of the chromosomes, since if it had occured the lateral arms of the crosses would always be symetrical and median and never more than two. The direct observation of a side- toside pairing of the chromosomal threads at synizesis, is in foil agreement with the complete lack of evidence in favour of telosynapsis. b) Anaphasic bridges and interzonal connections - The chromosomes as they separate from each other in anaphase they remain connected by means of two lateral strands corresponding to the unpaired segmenas observed in the bivalents at the stages preceding metaphase. In the early anaphase the chromosomes again reproduce the form they had in late diafcinesis. The connecting threads which may be thick and intensely coloured are generally curved and sometimes unequal in lenght, one being much longer than the other and forming a loop outwardly. This fact points to a continuous flow of chromosomal substance independently from both chromosomes of the pair rather than to a mechanical stretching of a sticky substance. At the end of anaphase almost all the material which formed the bridges is reduced to two small cones from whose vertices a very fine and pale fibril takes its origin. The interzonal fibres, therefore, may be considered as the remnant of the anaphasic bridges. Abnormal behaviour of the anaphase chromosomes showed to be useful in aiding the interpretation of normal aspects. It has been suggested by Schrader (1944) "that the interzonal is nothing more than a sticky coating of the chromosome which is stretched like mucilage between the daughter chromosomes as they move further and further apart". The paired chromosomes being enclosed in a commom sheath, as they separate they give origin to a tube which becomes more and more stretched. Later the walls of the tube collapse forming in this manner an interzonal element. My observations, however, do not confirm Schrader's tubular theory of interzonal connections. In the aspects seen at anaphase of the primary spermatocytes and described in this paper as chromosomal bridges nothing suggests a tubular structure. There is no doubt that the chromosomes are here connected by two independent strands in the first division of the spermatocytes and by a single one in the second. The manner in which the chromosomes separate supports the idea of transverse divion, leaving little place for another interpretation. c) Ptafanoeomc and chromatoid bodies - The colourabtlity of the plasmosome in Diactor and Anisocelis showed to be highly variable. In the latter species, one may find in the same cyst nuclei provided with two intensely coloured bodies, the larger of which being the plasmosome, sided by those in which only the heterochromosome took the colour. In the former one the plasmosome strongly coloured seen in the primary metaphase may easily be taken for a supernumerary chromosome. At anaphase this body stays motionless in the equator of the cell while the chromosomes are moving toward the poles. There, when intensely coloured ,it may be confused with the heterochromosome of the secondary spermatocytes, which frequently occupies identical position in the corresponding phase, thus causing missinterpretation. In its place the plasmosome may divide into two equal parts or pass undivided to one cell in whose cytoplasm it breaks down giving rise to a few corpuscles of unequal sizes. In Pachylis pharaonis, as soon as the nuclear membrane breate down, the plasmosome migrates to a place in the periphery of the cell (primary spermatocyte), forming there a large chromatoid body. This body is never found in the cytoplasm prior to the dissolution of the nuclear membrane. It is certain that chromatoid bodies of different origin do exist. Here, however, we are dealing, undoubtedly, with true plasmosomes. d) Movement of the heterochromosome - The heterochromosome in the metaphase of the secondary spermatocytes may occupy the most different places. At the time the autosomes prient themselves in the equatorial plane it may be found some distance apart in this plane or in any other plane and even in the subpolar and polar regions. It remains in its place during anaphase. Therefore, it may appear at the same level with the components of one of the anaphase plates (synchronism), between both plates (succession) or between one plate and tbe pole (precession), what depends upon the moment the cell was fixed. This does not mean that the heterochromosome sometimes moves as quickly as the autosomes, sometimes more rapidly and sometimes less. It implies, on the contrary, that, being anywhere in the cell, the heterochromosome m he attained and passed by the autosomes. In spite of being almost motionless the heterochromosome finishes by being enclosed in one of the resulting nuclei. Consequently, it does move rapidly toward the group formed by the autosomes a little before anaphase is ended. This may be understood assuming that the heterochromosome, which do not divide, having almost inactive kinetochore cannot orient itself, giving from wherever it stays, only a weak response to the polar influences. When in the equator it probably do not perform any movement in virtue of receiving equal solicitation from both poles. When in any other plane, despite the greater influence of the nearer pole, the influence of the opposite pole would permit only so a slow movement that the autosomes would soon reach it and then leave it behind. It is only when the cell begins to divide that the heterochromosome, passing to one of the daughter cells scapes the influence of the other and thence goes quickly to join the autosomes, being enclosed with them in the nucleus formed there. The exceptions observed by BORING (1907) together with ; the facts described here must represent the normal behavior of the heterocromosome of the Hemiptera, the greater frequency of succession being the consequence of the more frequent localization of the heterochromosome in the equatorial plane or in its near and of the anaphase rapidity. Due to its position in metaphase the heterochromosome in early anaphase may be found in precession. In late anaphase, oh the contrary ,it appears almost always in succession. This is attributed to the fact of the heterochromosome being ordinairily localized outside the spindle area it leaves the way free to the anaphasic plate moving toward the pole. Moreover, the heterochromosome being a round element approximately of the size of the autosomes, which are equally round or a little longer in the direction of the movement, it can be passed by the autosomes even when it stands in the area of the spindle, specially if it is not too far from the equatorial plane. e) The kinetochore - This question has been fully discussed in another paper (PIZA 1943a). The facts treated here point to the conclusion that the chromosomes of the Coreidae, like those of Tityus bahiensis, are provided with a kinetochore at each end, as was already admitted by the present writer with regard to the heterochromosome of Protenor. Indeed, taking ipr granted the facts presented in this paper, other cannot be the interpretation. However, the reasons by which the chromosomes of the species studied here do not orient themselves at metaphase of the first division in the same way as the heterochromosome of Protenor, that is, with the major axis parallelly to the equatorial plane, are claiming for explanation. But, admiting that the proximity of the kinetochores at the ends of chromosomes which do not separate until the second division making them respond to the poles as if they were a single kinetochore ,the explanation follows. (See PIZA 1943a). The median opening of the diplonemas when they are going to the diffuse stage as well as the reappearance of the bivalents always united at the end-segments and open in the middle is in full agreement with the existence of two terminal kinetochores. The same can be said with regard to the bivalents which join their extremities to form a ring.

Comportamento do Heterocromossômio em alguns Ortópteros do Brasil

In the present paper the behavior of the heterochromoso-mes in the course of the meiotic divisions of the spermatocytes in 15 species of Orthoptera belonging to 6 different families was studied. The species treated and their respective chromosome numbers were: Phaneropteridae: Anaulacomera sp. - 1 - 2n = 30 + X, n +15+ X and 15. Anaulacomera sp. - 2 - 2n - 30 + X, n = 15+ X and 15. Stilpnochlora marginella - 2n = 30 + X, n = 15= X and 15. Scudderia sp. - 2n = 30 + X, n = 15+ X and 15. Posldippus citrifolius - 2n = 24 + X, n = 12+X and 12. Acrididae: Osmilia violacea - 2n = 22+X, n = 11 + X and 11. Tropinotus discoideus - 2n = 22+ X, n = 11 + X and 11. Leptysma dorsalis - 2n = 22 + X, n = 11-J-X and 11. Orphulella punctata - 2n = 22-f X, n = 11 + X and 11. Conocephalidae: Conocephalus sp. - 2n = 32 + X, n = 16 + X and 16. Proscopiidae: Cephalocoema zilkari - 2n = 16 + X, n = 8+ X and 8. Tetanorhynchus mendesi - 2n = 16 + X, n = 8+X and 8. Gryliidae: Gryllus assimilis - 2n = 28 + X, n = 14+X and 14. Gryllodes sp. - 2n = 20 + X, n = 10- + and 10. Phalangopsitidae: Endecous cavernicola - 2n = 18 +X, n = 94-X and 9. It was pointed out by the present writer that in the Orthoptera similarly to what he observed in the Hemiptera the heterochromosome in the heterocinetic division shows in the same individual indifferently precession, synchronism or succession. This lack of specificity is therefore pointed here as constituting the rule and not the exception as formerly beleaved by the students of this problem, since it occurs in all the species referred to in the present paper and probably also m those hitherto investigated. The variability in the behavior of the heterochromosome which can have any position with regard to the autosomes even in the same follicle is attributed to the fact that being rather a stationary body it retains in anaphase the place it had in metaphase. When this place is in the equator of the cell the heterochromosome will be left behind as soon as anaphase begins (succession). When, on the contrary, laying out of this plane as generally happens (precession) it will sooner be reached (synchronism) or passed by the autosomes (succession). Due to the less kinetic activity of the heterochromosome it does not orient itself at metaphase remaining where it stands with the kinetochore looking indifferently to any direction. At the end of anaphase and sometimes earlier the heterochromosome begins to show mitotic activities revealed by the division of its body. Then, responding to the influence of the nearer pole it moves to it being enclosed with the autosomes in the nucleus formed there. The position of the heterochromosome in the cell is explained in the following manner: It is well known that the heterochromosome of the Orthoptera is always at the periphery of the nucleus, just beneath the nuclear membrane. This position may be any in regard of the axis of the dividing cell, so that if one of the poles of the spindle comes to coincide with it, the heterochromosome will appear at this pole in the metaphasic figures. If, on the other hand, the angle formed by the axis of the spindle with the ray reaching the heterochromosome increases the latter will appear in planes farther and farther apart from the nearer pole until it finishes by being in the equatorial plane. In this way it is not difficult to understand precession, synchronism or succession. In the species in which the heterochromosome is very large as it generally happens in the Phaneropteridae, the positions corresponding to precession are much more frequent. This is due to the fact that the probabilities for the heterochromosome taking an intermediary position between the equator and the poles at the time the spindle is set up are much greater than otherwise. Moreover, standing always outside the spindle area it searches for a place exactly where this area is larger, that is, in the vicinity of the poles. If it comes to enter the spindle area, what has very little probability, it would be, in virtue of its size, propelled toward the pole by the nearing anaphasic plate. The cases of succession are justly those in which the heterochromosome taking a position parallelly to the spindle axis it can adjust its large body also in the equator or in its proximity. In the species provided with small heterochromosome (Gryllidae, Conocephalidae, Acrididae) succession is found much more frequently because here as in the Hemiptera (PIZA 1945) the heterochromosome can equally take equatorial or subequatorial positions, and, furthermore, when in the spindle area it does offer no sereous obstacle to the passage of the autosomes. The position of the heterochromosome at the periphery of the nucleus at different stages may be as I suppose, at least in part a question of density. The less colourability and the surface irregularities characteristic of this element may well correspond to a less degree of condensation which may influence passive movements. In one of the species studied here (Anaulacomera sp.- 1) included in the Phaneropteridae it was observed that the plasmosome is left motionless in the spindle as the autosomes move toward the poles. It passes to one of the secondary spermatocytes being not included in its nucleus. In the second division it again passes to one of the cells being cast off when the spermatid is being transformed into spermatozoon. Thus it is regularly found among the tails of the spermatozoa in different stages of development. In the opinion of the present writer, at least in some cases, corpuscles described as Golgi body's remanents are nothing more than discarded plasmosomes.

Provas adicionais da dicentricidade dos cromossômios dos Hemípteros

In order to test Piza's conclusions regarding the dicentricity of Hemipteran chromosomes, two species of bugs of the family Coreidae, namely, Anasa sp. and Leptoglossus stigma (Herbst), are studied in the present paper. a) Anasa sp. - The male of this species has 21 chromosomes, that is, 20 pairs of autosomes and a single sex chromosome. The latter divides equationally in the first division of the spermatocytes and passes undivided to one cell in the second division. In this it moves with its longer axis parallelly to the spindle axis and shows fibrillar connections with both poles. Special attention was paid to the behavior of the chromosomes in the anaphase of the spermatogonia. As it was previously stated (Piza 1946 and 1946a) with regard to other species, the chromosomes are here attached to the spindle by both ends and begin to move toward the poles strongly curved to them. No intercalary fibers could be detected although their existente may not be denied by theoretical reasons developed in another paper (Piza 1946). Mitoses in somatic tissues of the embryo were equally studied. Careful examination of anaphase chromosomes in a great number of cells showed that the chromosomes behave exactly as in the spermatogonia, being equally attached to the spindle by the extremities alone and moving with their ends looking to the pole. A weak median constriction sometimes replaced by a slightly clearer space was observed in prometaphase and even in metaphase chromosomes of the spermatogonia as well as the somatic cells, having already been referred to in the case of Diactor bilineatus. (Piza 1945). Hemipteran chromosomes being considered as iso-chromosomes originated by a longitudinal spliting of the monocentric chromosomes resulting from the second division of the spermatocytes, the median aspect just mentioned may be regarded as the point of union of the separated halves. (See origin of dicentricity in Piza 1946). b) Leptoglossus stigma - This species has spermatogonia provided with 20 pairs of autosomes and one sex chromosome whose behavior differs in nothing from what was stated in regard of the preceding species. In the primary spermatocytes nothing meriting special mention was observed. Orientation, connection with the poles and movements of the sex chromosome in the secondary spermatocytes confirm the views already developed.

Trophic ecology and foraging behavior of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata, Tropiduridae) in a caatinga area of northeastern Brazil

This study aimed to analyze the seasonal variation in diet composition and foraging behavior of Tropidurus hispidus (Spix, 1825) and T. semitaeniatus (Spix, 1825), as well as measurement of the foraging intensity (number of moves, time spent stationary, distance traveled and number of attacks on prey items) in a caatinga patch on the state of Rio Grande do Norte, Brazil. Hymenoptera/Formicidae and Isoptera predominated in the diet of both species during the dry season. Opportunistic predation on lepidopteran larvae, coleopteran larvae and adults, and orthopteran nymphs and adults occurred in the wet season; however, hymenopterans/Formicidae were the most important prey items. The number of food items was similar between lizard species in both seasons; however the overlap for number of prey was smaller in the wet season. Preys ingested by T. hispidus during the wet season were also larger than those consumed by T. semitaeniatus. Seasonal comparisons of foraging intensity between the two species differed, mainly in the wet season, when T. hispidus exhibited less movement and fewer attacks on prey, and more time spent stationary if compared to T. semitaeniatus. Although both lizards are sit-and-wait foragers, T. semitaeniatus is more active than T. hispidus. The diet and foraging behavior of T. hispidus and T. semitaeniatus overlap under limiting conditions during the dry season, and are segregative factors that may contribute to the coexistence of these species in the wet season.

Investigações sobre doenças de Psittacideos

The present paper colligates the notions acquired in previous investigations, already published, and new observations upon diseases of the psittacidae, liable to be confused with psittacosis of parrots. The author calls attention to the indifference with regard to this question shown by investigators, even by those who dealt with the study of this disease on the occasion of the latest outbreak of psittacosis, in flagrant contrast with the researches upon the alterations induced by pathogenic agents of other diseases transmissible to man, when these agents pass through animals or when the latter are depositaries of the virus. This remark considerably enhances the importance of the presence paper from a hygienic and epidemiologic point of view, representing moreover a contribution to general knowledge and to veterinary medicine. The researches carried out since the appearance of the latest outbreak of psittacosis,-which occurred simultaneously with an epizooty in parrots lodged in aviary of the park of Agua Branca (Directory of Animal Industry of the State São Paulo)-led to the verification of the frequent existence in these animals of various diseases liable to be confused with psittacosis. These diseases are due to two kinds of pathogenic agents: virus and bacteria. In the first group there are to be found the diseases occasioned by the virus of human psittacosis, discovered by Western, Bedson and Simpson, and the disease me with in parrots coming from traders in S. Paulo. The infections by bacteria of the genus Salmonella and by those of other genera belong to the second group. As differential characters of the two infections due to virus, delineated on the strength of notions drawn from a detailed experimental study and from the literature on this subject, the following are given: ¹ Samples of our virus were sent, for comparison, to various investigators of psittacosis. Amongst them, Prof. M. Rivers acceded to our request; he found its nature to be different from that of the virus of psittacosis studiedby him. We are very much obliged to him for the attention he paid to this verification. Virus of psittacosis - Infectiousness: man, monkey, rabbit, mouse, hen, canary. Neurotropic affinity. Inclusions: small, protoplasmic. Exsiccation: the virus has good power of preservation. Symptoms: inactivity, drowsiness, frequent diarrhoea, oculo-nasal discharge and cough, coma. Duration: 4 to 5 days. Bodily lesions: congestion of intestines, splenomegaly. Virus of S. Paulo - Infects only psittacidae, particularly those of the genus Amazona. No localization in the nervous system. Large, nuclear. Is rapidly destroyed. Inactivity, inappetency, adynamia (drooping of the wings, indifference, leaning its beak against the bars of the cage in order not to fall down); profuse diarrhoea, of whitish stools, at times enterorrhagia; prolonged coma. 2 to 8 days. Foci of yellowish necrosis in liver, spleen and lung. At times, congestion of intestines. Characteristic features common to the two viruses.-They act in great dilutions, filter through tight candles though being partly retained, are preserved under glycerine or Bedson's solution, are stable at 55°C. heat and are destroyed by physical and chemical agents. Both virus diseases are very seldom met with in psittacidae: only once, amongst numberless sick parrots, the author met with a disease of the virus differring from that of psittacosis. This disease, greatly transmissible to man, ought to be more frequent, if it were common in parrots. On the contrary, bacteria cause diseases in these animals with great frequency, presenting variable characters, from a severe epizootic form, rapidly mortal, to ambulatory or silent forms, for the most part developing towards a cure or assuming a chronic character. Amongst the bacteria which cause the infection of this group the salmonellae predominate and amongst them the bacterium discovered by Nocard, as well as a species which in the course of this study is characterized under the name of Salmonella nocardi. The author believes that in the epizooty from which Nocard isolated his bacterium there was association of the virus-disease inducing the epizooty of that epoch in Paris with the bacterial disease, as must have happened in Argentina, where the disease was transmitted to man, and Santillan, according to Barros, isolated from the sick parrots bacteria of the genus Salmonella. The diseases of the two groups, that due to virus and that due to bacteria, are differentiated: Virus-diseases - Evolution: rapid, nearly always followed by death. Symptoms: sadness, profuse diarrhoea, of whitish stools, at times enterorrhagia, complete inappetency, adynamia, indifference, prolonged coma. Clinical forms: acute and subacute. Lesions: Foci of necrosis in liver and spleen without cellular reaction around the focus, yellow liver, multiple serositis. Presence of protoplasmic or nuclear granulations. Bacteriology: Complete lack or inconstant presence of bacteria in the organs and blood. Infectiousness of the organs and blood after filtration: positive. Bacterial diseases - Varies from one week to a month or more, not always fatal. Sadness, partial inappetency, tremblings, intensive thirst, mucous or mucosanguineous diarrhoea, lack of adynamia (reacts to stimulations and moves well at any time of the disease, though showing little disposition to locomotion), soiling of feathers. Frustrate, acute, subacute and chronic. Hepatic and intestinal cogestion, foci of necrosis in liver, spleen and lung with cellular reaction around the focus. Lack of granulations. Constant presence of bacteria in the organs and blood. Negative. The analysis of the litterature shows that the characteristic features of the diseases in parrots referred to parrot psittacosis, more frequently approach the bacterial diseases here described of these animals, a hypothesis which is reinforced by the observation of the greater frequency of infections...

Forward induction and the excess capacity puzzle: An experimental investigation.

While the theoretical industrial organization literature has long argued that excess capacity can be used to deter entry into markets, there is little empirical evidence that incumbent firms effectively behave in this way. Bagwell and Ramey (1996) propose a game with a specific sequence of moves and partially-recoverable capacity costs in which forward induction provides a theoretical rationalization for firm behavior in the field. We conduct an experiment with a game inspired by their work. In our data the incumbent tends to keep the market, in contrast to what the forward induction argument of Bagwell and Ramey would suggest. The results indicate that players perceive that the first mover has an advantage without having to pre-commit capacity. In our game, evolution and learning do not drive out this perception. We back these claims with data analysis, a theoretical framework for dynamics, and simulation results.

Approximating subtree distances between Phylogenies

We give a 5-approximation algorithm to the rooted Subtree-Prune-and-Regraft (rSPR) distance between two phylogenies, which was recently shown to be NP-complete by Bordewich and Semple [5]. This paper presents the first approximation result for this important tree distance. The algorithm follows a standard format for tree distances such as Rodrigues et al. [24] and Hein et al. [13]. The novel ideas are in the analysis. In the analysis, the cost of the algorithm uses a \cascading" scheme that accounts for possible wrong moves. This accounting is missing from previous analysis of tree distance approximation algorithms. Further, we show how all algorithms of this type can be implemented in linear time and give experimental results.

Affirmative Action Policy and Effort Levels. Sequential-Move Contest Game Argument

In this paper we analyse a simple two-person sequential-move contest game with heterogeneous players. Assuming that the heterogeneity could be the consequence of past discrimination, we study the effects of implementation of affirmative action policy, which tackles this heterogeneity by compensating discriminated players, and compare them with the situation in which the heterogeneity is ignored and the contestants are treated equally. In our analysis we consider different orders of moves. We show that the order of moves of contestants is a very important factor in determination of the effects of the implementation of the affirmative action policy. We also prove that in such cases a significant role is played by the level of the heterogeneity of individuals. In particular, in contrast to the present-in-the-literature predictions, we demonstrate that as a consequence of the interplay of these two factors, the response to the implementation of the affirmative action policy option may be the decrease in the total equilibrium effort level of the contestants in comparison to the unbiased contest game.

Presença de material eletrodenso sob a membrana vitelina do ovo de Scaptotrigona postica latr. (Hymenoptera, Meliponinae) durante a fase inicial da embriogenese

The present paper reports the presence of an electrondense material of unknown nature distributed under the viteline membrane of Scaptotrigona postica egg. The dorsal side layer is thicker then the ventral one. In eggs newly oviposited the material is gradually distributed inside the plasmalema invaginations. Later on (12 hs after oviposition) when a blastoderm is already formed around the egg, the material moves to the intercellular space. On the sequence of the development there was no more indication of the material under the membrane.

Non-cooperative incentives to share knowledge in competitive environments

In this paper we study a model where non-cooperative agents may exchange knowledge in a competitive environment. As a potential factor that could induce the knowledge disclosure between humans we consider the timing of the moves of players. We develop a simple model of a multistage game in which there are only three players and competition takes place only within two stages. Players can share their private knowledge with their opponents and the knowledge is modelled as in uencing their marginal cost of e¤ort. We identify two main mechanisms that work towards knowledge disclosure. One of them is that before the actual competition starts, the stronger player of the rst stage of a game may have desire to share his knowledge with the "observer", be- cause this reduces the valuation of the prize of the weaker player of that stage and as a result his e¤ort level and probability of winning in a ght. Another mechanism is that the "observer" may have sometimes desire to share knowledge with the weaker player of the rst stage, because in this way, by increasing his probability of winning in that stage, he decreases the probability of winning of the stronger player. As a result, in the second stage the "observer" may have greater chances to meet the weaker player rather than the stronger one. Keywords: knowledge sharing, strategic knowledge disclosure, multistage contest game, non-cooperative games

Hàbits alimentaris en nens de 8 a 12 anys de la comarca d'Osona

Introducció: La dieta mediterrània és considerada un dels patrons alimentaris més saludables ja que diversos estudis epidemiològics mostren que protegeix front diverses malalties cròniques com ara les malalties cardiovasculars, la diabetis i alguns càncers. Malauradament al nostre país els patrons alimentaris estan canviant a conseqüència de la modernització de la societat i estan portant a l’allunyament del patró de dieta mediterrània. Això és especialment crític entre la població infantil i juvenil, fet que predisposa a que en un futur augmenti la prevalença de malalties cròniques entre la població adulta. Objectiu: avaluar els hàbits alimentaris i l’estat nutricional d’escolars de 8 a 12 anys de la comarca d’Osona. Mètodes: estudi de disseny observacional i transversal. La mostra estava constituïda per 191 escolars de 4rt i 5è d’ensenyança primària d’escoles de la comarca d’Osona. La informació sobre la dieta es va recollir a través d’una enquesta alimentària, un recordatori de 24 hores, un qüestionari de freqüència de consum alimentari i el test KIDMED. Les determinacions antropomètriques que es van realitzar van ser talla, pes, IMC (Índex de Massa Corporal), plec tricipital, perímetre braquial i perímetre abdominal. L’anàlisi estadística de totes les dades es va portar a terme mitjançant el programa estadístic SPSS per Windows versió 12.0. Resultats: quan es valora la qualitat de l’esmorzar, s’observa que només en el 16.8% dels casos la qualitat era bona, en el 68.6% dels casos la qualitat havia de millorar i en el 12.6% era de qualitat insuficient i en el 2.1% era de mala qualitat. També s’observa que la dieta que segueixen és desequilibrada quantitativament, concretament és baixa en hidrats de carboni, rica en greixos i lleugerament elevada en proteïnes. L’anàlisi qualitativa mostra que hi ha un molt baix consum de verdures i hortalisses i de fruita, mentre que s’arriba a les racions recomanades de carnis i d’olis i greixos. El test KIDMED mostra una puntuació mitjana de 7.21±1.96 punts, el que indica que la dieta de la població és de qualitat millorable. Pel que fa a l’estat nutricional s’observa que un 24,6% presenta valors de baix pes i un 17,8% sobrepès o obesitat, el que indica que un 42,4% de la població estudiada presenta un estat nutricional incorrecte. Conclusions: La dieta del col·lectiu estudiat s’allunya de les recomanacions de la SENC (Sociedad Española de Nutrición Comunitaria). Els resultats del test KIDMED indiquen que només un 44% de la població segueix un patró òptim de Dieta mediterrània i l’anàlisi de l’estat nutricional mostra que un 42,4% presenta un estat nutricional incorrecte, sigui per excés o per defecte de pes. Per tant, es fa necessari dissenyar estratègies d’educació alimentària adequades per millorar els hàbits alimentaris dels escolars i aconseguir en un futur un estat òptim de salut.

Displacement of Biomfhalaria glabrata by thiara granifera under natural conditions in the Dominican Republic

After a study of the population dynamics of Biomphalaria glabrata snails in several breeding places in the Dominican Republic, the snail Thiara granifera was introduced in some B. glabrata habitats. T. granifera became established in one point in one habitat in the townof Quisqueya, in the east of the country. Around this point of establishment 6 points were selected in order to observe the population dynamics of both species of snails and the chemical and biological characteristics at each point. Four of these points already harbored B. glabrata. One control point was selected also harboring B. glabrata. After 14 months of observations, the results showed that T. granifera was competing with and displacing B. glabrata. This competition does not seem to be competition for food or vital space. Rather, B. glabrata avoids the presence of T. granifera and moves away to new areas, and this is possibly due to a chemical substance(s) secreted by T. granifera or by physical contact with the large number of individuals of T. granifera.

The analysis of approximate quickselect and related problems

Approximate Quickselect, a simple modification of the well known Quickselect algorithm for selection, can be used to efficiently find an element with rank k in a given range [i..j], out of n given elements. We study basic cost measures of Approximate Quickselect by computing exact and asymptotic results for the expected number of passes, comparisons and data moves during the execution of this algorithm. The key element appearing in the analysis of Approximate Quickselect is a trivariate recurrence that we solve in full generality. The general solution of the recurrence proves to be very useful, as it allows us to tackle several related problems, besides the analysis that originally motivated us. In particular, we have been able to carry out a precise analysis of the expected number of moves of the ith element when selecting the jth smallest element with standard Quickselect, where we are able to give both exact and asymptotic results. Moreover, we can apply our general results to obtain exact and asymptotic results for several parameters in binary search trees, namely the expected number of common ancestors of the nodes with rank i and j, the expected size of the subtree rooted at the least common ancestor of the nodes with rank i and j, and the expected distance between the nodes of ranks i and j.

Les symbioses agro-industrielles en Afrique de l'Ouest : évaluation du potentiel d'une nouvelle stratégie pour un développement durable

RésuméCette thèse traite de l'utilisation des concepts de Symbiose Industrielle dans les pays en développement et étudie le potentiel de cette stratégie pour stimuler un développement régional durable dans les zones rurales d'Afrique de l'Ouest. En particulier, lorsqu'une Symbiose Industrielle est instaurée entre une usine et sa population alentour, des outils d'évaluation sont nécessaires pour garantir que le projet permette d'atteindre un réel développement durable. Les outils existants, développés dans les pays industrialisés, ne sont cependant pas complètement adaptés pour l'évaluation de projets dans les pays en développement. En effet, les outils sont porteurs d'hypothèses implicites propres au contexte socio-économique dans lequel ils ont été conçus.L'objectif de cette thèse est de développer un cadre méthodologique pour l'évaluation de la durabilité de projets de Symbiose Industrielle dans les pays en développement.Pour ce faire, je m'appuie sur une étude de cas de la mise en place d'une Symbiose Industrielle au nord du Nigéria, à laquelle j'ai participé en tant qu'observatrice dès 2007. AshakaCem, une usine productrice de ciment du groupe Lafarge, doit faire face à de nombreuses tensions avec la population rurale alentour. L'entreprise a donc décidé d'adopter une nouvelle méthode inspirée des concepts de Symbiose Industrielle. Le projet consiste à remplacer jusqu'à 10% du carburant fossile utilisé pour la cuisson de la matière crue (calcaire et additifs) par de la biomasse produite par les paysans locaux. Pour ne pas compromettre la fragile sécurité alimentaire régionale, des techniques de lutte contre l'érosion et de fertilisation naturelle des sols sont enseignées aux paysans, qui peuvent ainsi utiliser la culture de biomasse pour améliorer leurs cultures vivrières. A travers cette Symbiose Industrielle, l'entreprise poursuit des objectifs sociaux (poser les bases nécessaires à un développement régional), mais également environnementaux (réduire ses émissions de CO2 globales) et économiques (réduire ses coûts énergétiques). Elle s'ancre ainsi dans une perspective de développement durable qui est conditionnelle à la réalisation du projet.A travers l'observation de cette Symbiose et par la connaissance des outils existants je constate qu'une évaluation de la durabilité de projets dans les pays en développement nécessite l'utilisation de critères d'évaluation propres à chaque projet. En effet, dans ce contexte, l'emploi de critères génériques apporte une évaluation trop éloignée des besoins et de la réalité locale. C'est pourquoi, en m'inspirant des outils internationalement reconnus comme l'Analyse du Cycle de Vie ou la Global Reporting Initiative, je définis dans cette thèse un cadre méthodologique qui peut, lui, être identique pour tous les projets. Cette stratégie suit six étapes, qui se réalisent de manière itérative pour permettre une auto¬amélioration de la méthodologie d'évaluation et du projet lui-même. Au cours de ces étapes, les besoins et objectifs en termes sociaux, économiques et environnementaux des différents acteurs sont déterminés, puis regroupés, hiérarchisés et formulés sous forme de critères à évaluer. Des indicateurs quantitatifs ou qualitatifs sont ensuite définis pour chacun de ces critères. Une des spécificités de cette stratégie est de définir une échelle d'évaluation en cinq graduations, identique pour chaque indicateur, témoignant d'un objectif totalement atteint (++) ou pas du tout atteint (--).L'application de ce cadre méthodologique à la Symbiose nigériane a permis de déterminer quatre critères économiques, quatre critères socio-économiques et six critères environnementaux à évaluer. Pour les caractériser, 22 indicateurs ont été définis. L'évaluation de ces indicateurs a permis de montrer que le projet élaboré atteint les objectifs de durabilité fixés pour la majorité des critères. Quatre indicateurs ont un résultat neutre (0), et un cinquième montre qu'un critère n'est pas atteint (--). Ces résultats s'expliquent par le fait que le projet n'en est encore qu'à sa phase pilote et n'a donc pas encore atteint la taille et la diffusion optimales. Un suivi sur plusieurs années permettra de garantir que ces manques seront comblés.Le cadre méthodologique que j'ai développé dans cette thèse est un outil d'évaluation participatif qui pourra être utilisé dans un contexte plus large que celui des pays en développement. Son caractère générique en fait un très bon outil pour la définition de critères et indicateurs de suivi de projet en terme de développement durable.SummaryThis thesis examines the use of industrial symbiosis in developing countries and studies its potential to stimulate sustainable regional development in rural areas across Western Africa. In particular, when industrial symbiosis is instituted between a factory and the surrounding population, evaluation tools are required to ensure the project achieves truly sustainable development. Existing tools developed in industrialized countries are not entirely suited to assessing projects in developing countries. Indeed, the implicit hypotheses behind such tools reflect the socioeconomic context in which they were designed. The goal of this thesis is to develop a methodological framework for evaluating the sustainability of industrial symbiosis projects in developing countries.To accomplish this, I followed a case study about the implementation of industrial symbiosis in northern Nigeria by participating as an observer since 2007. AshakaCem, a cement works of Lafarge group, must confront many issues associated with violence committed by the local rural population. Thus, the company decided to adopt a new approach inspired by the concepts of industrial symbiosis.The project involves replacing up to 10% of the fossil fuel used to heat limestone with biomass produced by local farmers. To avoid jeopardizing the fragile security of regional food supplies, farmers are taught ways to combat erosion and naturally fertilize the soil. They can then use biomass cultivation to improve their subsistence crops. Through this industrial symbiosis, AshakaCem follows social objectives (to lay the necessary foundations for regional development), but also environmental ones (to reduce its overall CO2 emissions) and economical ones (to reduce its energy costs). The company is firmly rooted in a view of sustainable development that is conditional upon the project's execution.By observing this symbiosis and by being familiar with existing tools, I note that assessing the sustainability of projects in developing countries requires using evaluation criteria that are specific to each project. Indeed, using generic criteria results in an assessment that is too far removed from what is needed and from the local reality. Thus, by drawing inspiration from such internationally known tools as Life Cycle Analysis and the Global Reporting Initiative, I define a generic methodological framework for the participative establishment of an evaluation methodology specific to each project.The strategy follows six phases that are fulfilled iteratively so as to improve the evaluation methodology and the project itself as it moves forward. During these phases, the social, economic, and environmental needs and objectives of the stakeholders are identified, grouped, ranked, and expressed as criteria for evaluation. Quantitative or qualitative indicators are then defined for each of these criteria. One of the characteristics of this strategy is to define a five-point evaluation scale, the same for each indicator, to reflect a goal that was completely reached (++) or not reached at all (--).Applying the methodological framework to the Nigerian symbiosis yielded four economic criteria, four socioeconomic criteria, and six environmental criteria to assess. A total of 22 indicators were defined to characterize the criteria. Evaluating these indicators made it possible to show that the project meets the sustainability goals set for the majority of criteria. Four indicators had a neutral result (0); a fifth showed that one criterion had not been met (--). These results can be explained by the fact that the project is still only in its pilot phase and, therefore, still has not reached its optimum size and scope. Following up over several years will make it possible to ensure these gaps will be filled.The methodological framework presented in this thesis is a highly effective tool that can be used in a broader context than developing countries. Its generic nature makes it a very good tool for defining criteria and follow-up indicators for sustainable development.