Cartan's spiral staircase in physics and, in particular, in the gauge theory of dislocations

In 1922, Cartan introduced in differential geometry, besides the Riemannian curvature, the new concept of torsion. He visualized a homogeneous and isotropic distribution of torsion in three dimensions (3d) by the "helical staircase", which he constructed by starting from a 3d Euclidean space and by defining a new connection via helical motions. We describe this geometric procedure in detail and define the corresponding connection and the torsion. The interdisciplinary nature of this subject is already evident from Cartan's discussion, since he argued - but never proved - that the helical staircase should correspond to a continuum with constant pressure and constant internal torque. We discuss where in physics the helical staircase is realized: (i) In the continuum mechanics of Cosserat media, (ii) in (fairly speculative) 3d theories of gravity, namely a) in 3d Einstein-Cartan gravity - this is Cartan's case of constant pressure and constant intrinsic torque - and b) in 3d Poincare gauge theory with the Mielke-Baekler Lagrangian, and, eventually, (iii) in the gauge field theory of dislocations of Lazar et al., as we prove for the first time by arranging a suitable distribution of screw dislocations. Our main emphasis is on the discussion of dislocation field theory.Comment: 31 pages, 8 figure

Averaged control and observation of parameter-depending wave equations

We analyze the problem of averaged observability and control of wave equations.This topic is motivated by the control of parameter-dependent systems of wave equations. We look for controls ensuring the controllability of the averages of the states with respect to the parameter. This turns out to be equivalent to the problem of averaged observation in which one aims at recovering the energy of the initial data of the adjoint system by measurements done on its averages, under the assumption that the initial data of all the components of the adjoint system coincide.The problem under consideration is weaker than the classical notion of simultaneous observation and control.The method of proof uses propagation arguments based on H-measures or microlocal defect measures that reduce the problem to non-standard unique-continuation issues.Using transmutation techniques, we also derive some results on the averaged observation and control of parameter-dependent heat equations

Neurokernel: An Open Source Platform for Emulating the Fruit Fly Brain

We have developed an open software platform called Neurokernel for collaborative development of comprehensive models of the brain of the fruit fly Drosophila melanogaster and their execution and testing on multiple Graphics Processing Units (GPUs). Neurokernel provides a programming model that capitalizes upon the structural organization of the fly brain into a fixed number of functional modules to distinguish between these modules’ local information processing capabilities and the connectivity patterns that link them. By defining mandatory communication interfaces that specify how data is transmitted between models of each of these modules regardless of their internal design, Neurokernel explicitly enables multiple researchers to collaboratively model the fruit fly’s entire brain by integration of their independently developed models of its constituent processing units. We demonstrate the power of Neurokernel’s model integration by combining independently developed models of the retina and lamina neuropils in the fly’s visual system and by demonstrating their neuroinformation processing capability. We also illustrate Neurokernel’s ability to take advantage of direct GPU-to-GPU data transfers with benchmarks that demonstrate scaling of Neurokernel’s communication performance both over the number of interface ports exposed by an emulation’s constituent modules and the total number of modules comprised by an emulation

Notes on shape orientation where the standard method does not work

Copyright © 2006 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Pattern Recognition . Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Pattern Recognition, Vol. 39 Issue 5 (2006), DOI: 10.1016/j.patcog.2005.11.010Notes: This paper introduces a new method for shape orientation. This method, which uses Nth-order centralised moments (N>2), can be applied to cases, such as many-fold symmetric shapes, for which the standard method does not work. The paper proves several desirable properties of shape orientation defined in this way, and also corrects the previous approach where the central moments were treated equally independently of N. It shows that the situation is essentially different depending on whether N is an even or odd number. This corrects the previous work of Tsai and Chou (Pattern Recognition, vol. 24, pp.95-104, 1991), which up to then represented the state of the art in the field.In this paper we consider some questions related to the orientation of shapes with particular attention to the situation where the standard method does not work. There are irregular and non-symmetric shapes whose orientation cannot be computed in a standard way, but in the literature the most studied situations are those where the shape under consideration has more than two axes of symmetry or where it is an n-fold rotationally symmetric shape with n>2.n>2. The basic reference for our work is [W.H. Tsai, S.L. Chou, Detection of generalized principal in rotationally symmetric shapes, Pattern Recognition 24 (1991) 95–104]. We give a very simple proof of the main result from [W.H. Tsai, S.L. Chou, Detection of generalized principal in rotationally symmetric shapes, Pattern Recognition 24 (1991) 95–104] and suggest a modification of the proposal on how the principal axes of rotationally symmetric shapes should be computed. We show some desirable property in defining the orientation of such shapes if the modified approach is applied. Also, we give some comments on the problems that arise when computing shape elongation

Bioeconomic analysis of Engraulicypris sardella (USIPA) in South east arm of Lake Malawi

Usipa Engraulicypris sardella is the most abundant small pelagic species in Lake Malawi. It plays an important part in the lake communities’ economy and food security. However, much remains unknown on their stock status and bioeconomic importance. This study is carried out to estimate the maximum economic yield and maximum sustainable yield for Usipa fishery in the South-east arm of Lake Malawi. Structured quantitative questionnaire was used to collect information from 139 informants on the price of usipa landings and cost of fishing effort. Catch and effort data for Usipa were used in a biomass dynamic model (ASPIC) to estimate key parameters (r, q and k). A bioeconomic model was further developed based on the Gordon-Schaefer model using cost and revenues of the Usipa fisheries to derive the Maximun Sustainable Yield (MSY) and the Maximum Economic Yield (MEY). Model estimates of MSY and MEY were 9,228.8 and 8,227.1 tonnes, respectively. The corresponding fishing effort was estimated to be 40,000 net-hauls and 30,000 net-hauls at MSY and MEY, respectively. Revenues at MSY were estimated at MWK42.280 billion, while at MEY the revenues were MWK39.309 billion. The analysis shows that the current effort of 65,232 net-hauls has a yield of 6,000 tonnes, indicating that the Usipa fishery is currently overexploited over the optimum bio-economic level and even beyond the open access yield. We recommend reducing the fishing effort by 54% to realize the best economic benefits (Production at MEY) and end overfishing to protect the fishery from biological and economic collapses

Retropancreatic space - the key to remnants and septic recurrences in severe acute pancreatitis

Institutul Oncologic București, Clinica de Chirurgie Nr. 1, Al XI-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova și cea de-a XXXIII-a Reuniune a Chirurgilor din Moldova „Iacomi-Răzeșu” 27-30 septembrie 2011Autorii prezintă un punct de vedere asupra spațiului retropancreatic, zona topografică răspunzatoare de evoluția supurațiilor din pancreatita acută severț. În majoritatea cazurilor, chirurgia e restricționată la abordul limitat prin bursa omentală, folosită ca unica zonă de acces asupra pancreasului. De cele mai multe ori, însă, necrozele și supurațiile evoluează în aria compartimentelor retropancreatice și retroperitoneale, aproape imposibil de abordat prin bursa omentală. De aici survin debridările și drenajele insuficiente care lasă restanțe septice și permit recurente supurative ce reclamă reintervenții succesive, mai mult sau mai puțin programate. Există însă posibilitatea unei strategii planificate de abord retropancreatic, de prima intenție, în scopul unei toalete cat mai complete a acestui spațiu. În cadrul acestei strategii un rol de maximă importanță revine CT cu contrast oral și I.V., dar mai ales imagisticii prin reconstrucții în plan frontal și sagital. Acestea ar trebui să constituie regula explorării CT și să fie solicitate de către chirurg pentru a reuși să aleagă calea de abord adecvată pentru accesul confortabil în spațiul retropancreatic. În susținerea acestor afirmații, autorii prezintă compartimentarea spațiului retropancreatic, zonele de comunicare ale acestuia cu celelalte arii retroperitoneale, la distanța de pancreas, cât și căile de difuziune ale proceselor supurative. De asemenea, sunt puse în evidentță reperele anatomice CT care asigură orientarea corectă în analiza imaginilor standard, cât și a reconstrucțiilor. Devine astfel posibil un acces cât mai direct în zonele care, aproape de regulă, sunt neabordate chirurgical cu ocazia primei intervenții.The authors present a point of view on retropancreatic space, a topographic area responsible for the evolution of suppuration in severe acute pancreatitis. In the majority of cases, surgery is restricted to the limited approach through omental bursa, used as a unique access zone to the pancreas. However, in the majority of cases, necroses and suppurations progress in retropancreatic and retroperitoneal compartment area, which is almost impossible to approach through the omental pouch. This is the reason for debridations occurrences and for insufficient drainage that allow for septic remnants and suppurative reccurences requiring successive reinterventions more or less scheduled. There is, however, the possibility for a planned strategy for retropancreatic approach, as primary intention, for the purpose of a thorough as possible cleaning. As a part of this strategy, a role of maximum importance belongs to oral and intravenous contrast CT and especially to imagistic frontal and sagittal reconstructions. These should constitute the rule for CT exploration and should be requested by the surgeon to succeed in choosing the retropancreatic approach for comfortable access to this area. In sustaining these affirmations, in this paper, the authors present the compartmentation of retropancreatic space, its communicating zones to other retroperitoneal areas, further away from the pancreas, but also diffusion routes for suppurative processes. Also, CT anatomic landmarks that assure the wright orientation in the analysis of standard, but also reconstructed images, are highlighted here. Therefore, an as direct as possible access in the areas, that as a rule are not surgically approached during the first intervention, becomes feasible

A proof of uniqueness of the Gurarii space

We present a short and elementary proof of isometric uniqueness of the Gurarii space.Comment: 6 pages, some improvements incorporate

Nitrogen and phosphorus limitation of oceanic microbial growth during spring in the Gulf of Aqaba

Bioassay experiments were performed to identify how growth of key groups within the microbial community was simultaneously limited by nutrient (nitrogen and phosphorus) availability during spring in the Gulf of Aqaba's oceanic waters. Measurements of chlorophyll a (chl a) concentration and fast repetition rate (FRR) fluorescence generally demonstrated that growth of obligate phototrophic phytoplankton was co-limited by N and P and growth of facultative aerobic anoxygenic photoheterotropic (AAP) bacteria was limited by N. Phytoplankton exhibited an increase in chl a biomass over 24 to 48 h upon relief of nutrient limitation. This response coincided with an increase in photosystem II (PSII) photochemical efficiency (F v /F m), but was preceded (within 24 h) by a decrease in effective absorption crosssection (σPSII) and electron turnover time (τ). A similar response for τ and bacterio-chl a was observed for the AAPs. Consistent with the up-regulation of PSII activity with FRR fluorescence were observations of newly synthesized PSII reaction centers via low temperature (77K) fluorescence spectroscopy for addition of N (and N + P). Flow cytometry revealed that the chl a and thus FRR fluorescence responses were partly driven by the picophytoplankton (æ10 μm) community, and in particular Synechococcus. Productivity of obligate heterotrophic bacteria exhibited the greatest increase in response to a natural (deep water) treatment, but only a small increase in response to N and P addition, demonstrating the importance of additional substrates (most likely dissolved organic carbon) in moderating the heterotrophs. These data support previous observations that the microbial community response (autotrophy relative to heterotrophy) is critically dependent upon the nature of transient nutrient enrichment. © Inter-Research 2009

Personality of political leader. Case study: presidents of the United States of America 1933-2001: antropological, psychological and politicological approach

У овом раду смо поставили циљ да истражимо мотивацију председника Сједињених Америчких Држава као политичких вођа и личности и покушали смо да је доведемо у везу са резултатима које су постигли у току и након вршења те функције. Узорак нашег истраживања чини 11 председника САД, у периоду од 1933. до 2001. године. На основу претходних истраживања изабрали смо четири мотива: мотив постигнућа, мотив моћи, мотив афилијације и мотив аутономије. У складу са ранијим истраживањима, поставили смо и две хипотезе: (1) да су мотиви постигнућа и моћи изражени код свих председника из узорка и (2) да, у зависности од јачине заступљености мотива афилијације, председници показују већи интерес (а) за успостављање једнаких права и за (б) економско управљање и благостање америчког народа и да, насупрот томе, ако је више изражен мотив аутономије, неће имати позитивне резултате на тим двема варијаблама. Прву хипотезу смо потврдили, док је друга хипотеза одбачена. Наиме, установили смо да се мотивација политичара о којима је реч развија на један начин док се не баве политиком, а да, када постану политичари у Конгресу, Сенату, гувернери и на крају председници САД, њихова улога постаје политичка и мотиви се одсликавају кроз призму интереса и очувања политичких позиција. То додаје нову димензију нашем истраживању Наше хипотезе смо проверавали путем истраживања које је спровео „C-SPAN“, у коме је 75 угледних историчара процењивало учинак председника САД на варијаблама – једнака права за све и економско управљање и благостање. Резултати истраживања указују на могућности предикције понашања политичара уколико се разматра више фактора на идндивидуалном нивоу у одређеној средини и друштвено-политичким околностима, уз комбинацију различитих метода и мултидисциплинарни приступ.My goal has been to research the motivation of Presidents of the United States of America, as representatives of political personalities and leaders, and I have tried to identify the link between motivation and achievements of selected US presidents in the period when they held that tenure. The sample consists of 11 US Presidents who held this position in the period from 1933 till 2001. Following previous research of political motives I have selected 4 motives to scrutinize: need for achievement, need for power, need for affiliation and need for autonomy. According to previous research I have set two hypotheses: (1) need for achievement and need for power will be largely represented in behavior of all presidents and (2) depending of the intensity of presence of need for affiliation, presidents will act for the benefit of equal justice and economic management or wellbeing of American people, and vice versa, depending on the intensity of need for autonomy, there will be no positive results on these two variables. The first hypothesis has been confirmed, but the second one has been rejected. Based on this sample I have concluded that motivation profiles develop separately in the period before they become politicians and afterwards (as Congressmen, Senators, Governors and finally Presidents of US). Their role is different and these motives are expressed through political interest and as the struggle for preservation of power. This adds new dimension to my research. My hypotheses has been controlled by research provided by “C-Span” in which 75 respectable historians assessed the results of US Presidents on these two variables: equal justice for all and economic management. Finally, the results point to a possibility of prediction of the behavior of politicians if one takes into consideration several factors, and if prediction is given for an individual case having in mind background and combining diverse methods and multidisciplinary approach