377 research outputs found
Alternative inversion strategies to resistivity data for targets with sharp boundaries
No full textEstimating the geometry and resistivity of archeological structures using resistivity models produced as a result of applying smoothness constraints in most inversion algorithms is difficult, especially when structures are closely spaced. However, such quantification is important to facilitate conservation and to minimize the potential of damage when excavations are undertaken. Alternative inversion approaches more appropriate for imaging such targets require either a priori information about the subsurface (e.g. disconnected inversion) or require two or more geophysical datasets to be collected at the same site (e.g. joint inversion). The research outlined in this dissertation presents three novel approaches to improve resistivity imaging of discrete targets without the need to incorporate a priori information in the inversion. The first approach combines an initial 2D smoothness constraint inversion coupled with a digital image processing technique known as a watershed algorithms and a second inversion step incorporating a disconnect in the regularization based on the output of the watershed algorithm. This approach has improved estimate of the geometries of individual targets, but it was not very effective at predicting the resistivity of the targets or resolving closely spaced targets. The second approach combines an initial 2D smoothness constraint inversion coupled with the watershed algorithm and a trained Artificial Neural Network (ANN). Although this approach has been proven effective for resolving widely and closely spaced archeological targets, the results depend largely on the quality of ANN training and on the accuracy of the watershed algorithm geometry prediction. Finally, the third strategy is an iterative approach that combines an initial 3D smoothness constraint inversion that is used only at the first iteration to recover a resistivity model that is fairly consistent with the measured data, from which an initial target location is estimated using an edge detector method and from which a disconnect in the inversion is identified. The disconnect defining the target outline is then progressively improved following each iteration of the inverse procedure. This approach has been proven more effective for resolving widely and closely spaced archeological targets over other approaches, but it is partially sensitive to artifacts in the initial smoothness constraint model.Ph.D.Includes bibliographical referencesIncludes vitaby Mehrez H. Elwasei
I-V characteristics and differential conductance fluctuations of Au nanowires
No full textElectronic transport properties of the Au nanostructure are investigated using both experimental and theoretical analysis. Experimentally, stable Au nanowires were created using a mechanically controllable break junction in air, and simultaneous current-voltage (I-V) and differential conductance δI/δV data were measured. The atomic device scale structures are mechanically very stable up to bias voltage Vb∼0.6 V and have a lifetime of a few minutes. Facilitated by a shape function data analysis technique which finger prints electronic properties of the atomic device, our data show clearly differential conductance fluctuations with an amplitude >1% at room temperature and a nonlinear I-V characteristics. To understand the transport features of these atomic scale conductors, we carried out ab initio calculations on various Au atomic wires. The theoretical results demonstrate that transport properties of these systems crucially depend on the electronic properties of the scattering region, the leads, and most importantly the interaction of the scattering region with the leads. For ideal, clean Au contacts, the theoretical results indicate a linear I-V behavior for bias voltage Vb<0.5 V. When sulfur impurities exist at the contact junction, nonlinear I-V curves emerge due to a tunneling barrier established in the presence of the S atom. The most striking observation is that even a single S atom can cause a qualitative change of the I-V curve from linear to nonlinear. A quantitatively favorable comparison between experimental data and theoretical results is obtained. We also report other results concerning quantum transport through Au atomic contacts
FIGURE 2 in Updated inventory and distribution of free-living flatworms from Tunisian waters
No full textFIGURE 2. Polyclads from Tunisian waters. Dorsal view in all panels, anterior to the left. a Leptoplana mediterranea. b Leptoplana tremellaris. c Echinoplana celerrima. d Theama mediterranea; the depicted specimen was collected in Calvi, Corse. e Imogine mediterranea. f Discocelis tigrina. g Cestoplana rubrocinta. h Comoplana agilis. i Prosthiostomum siphunculus. j Prostheceraeus moseleyi. k Thysanozoon brocchii. l Pseudoceros maximus. m Yungia aurantiaca n hatching in Leptoplana tremellaris. o hatched four-eyed juvenile of Leptoplana tremellaris. Scale bars: 2a–c, 2e–m: 5 mm; 2d, 2n–o: 100 microns.Published as part of Gammoudi, Mehrez, Garbouj, Myriam, Egger, Bernhard & Tekaya, Saïda, 2017, Updated inventory and distribution of free-living flatworms from Tunisian waters, pp. 120-138 in Zootaxa 4263 (1) on page 123, DOI: 10.11646/zootaxa.4263.1.5, http://zenodo.org/record/57256
FIGURE 4 in The genus Leptoplana (Leptoplanidae, Polycladida) in the Mediterranean basin. Redescription of the species Leptoplana mediterranea (Bock, 1913) comb. nov.
No full textFIGURE 4. Embryonic development in L. mediterranea. (A) Embryo at the 1-cell stage. (B) Contortion of the egg during restriction of the polar bodies (arrowhead). (C) Contortions (blebbing) of 1-cell stage embryos. (D) 2-cell stage. (E) 4-cell stage. (F) 8-cell stage. (G) 12-cell stage. (H) Presumptive mesentoblast (arrowhead). (I) Divided presumptive mesentoblast (arrowheads). (J) Two-eyed (arrowhead) embryo. (K) Four-eyed (arrowhead) embryo. (L, M) Six-eyed and ten-eyed embryo (N, O) Hatched twelve-eyed juvenile with yolk-filled gut branches (arrowhead). Anterior is left. b: prominent brain, ph: posterior pharynx. Scale bars: 0.05 mmPublished as part of Gammoudi, Mehrez, Egger, Bernhard, Tekaya, Saïda & Noreña, Carolina, 2012, The genus Leptoplana (Leptoplanidae, Polycladida) in the Mediterranean basin. Redescription of the species Leptoplana mediterranea (Bock, 1913) comb. nov., pp. 45-56 in Zootaxa 3178 on page 52, DOI: 10.5281/zenodo.21424
خارطة الكتابة: حوار مع أهداف سويف / The Map of Writing: An Interview with Ahdaf Soueif
No full text[After introducing the works of Ahdaf Soueif, her background, and critical response to her novels, Mehrez raises questions on Anglophone writing with the author. The following are excerpts from Soueif\u27s answers: The first language in which I read was English. My introduction to written stories was in English. I have truly not considered my reader till after the publication of In the Eye of the Sun... its reception in the Arab World and in the West and how people reacted to it. I imagine that one can explain or interpret The Map of Love as being a more accentuated awareness of my position as an Egyptian writer writing in English and addressing the Western reader to tell him our story with them from our point of view-an Egyptian Arab one. A quick glance at the world situation will suffice to show that we remain in the throes of certain kinds of colonialisms that have more effective power and are certainly an extention of older forms. A number of critics have written about an innovative aspect of my work that has to do with my use of the English language to relay an Arab context. The Arabic language... is my first and principle language. Consequently, I cannot allow the appearance of a translation of my work into Arabic. Rather, I feel the need to Arabize it, to rewrite it myself. The nomination to the Booker Prize... for a writer like myself, coming to the English language from the outside without belonging to its literary history is a recognition of considerable importance.
Impact of Microwave Assisted Infusion on the Quality and Volatile Composition of Olive Oil Aromatized with Rosemary Leaves
No full textOlive oil with rosemary leaves by microwave assisted infusion (MAI) as an alternative to conventional infusion (CI) was evaluated. Microwave heating was applied to the mixture in order to accelerate diffusion of the rosemary volatile compounds into the olive oil. The volatile components of the aromatized oils were quantified by HS-SPME/GC-MS, as well as several quality indexes such as free fatty acids (FFA), peroxide value (PV), specific coefficients of extinction, chlorophyll and carotenoid content, and color assessment. Fatty acid profiles of the oils aromatized by MAI were compared to those produced by CI. Results showed that the infusion time is reduced from 12 h to 10 min when utilizing MAI in place of CI. MAI treatment caused a slight increase in FFA levels, and specific extinction coefficient indices (K (232) and K (270)). PV during MAI remained unchanged for the first 3 min, after which there was an observable increase. All physico-chemical values were found to be well below the maximum permitted limits. The MAI treatment reduced chlorophyll and carotenoid levels during the final step of aromatization, thus affecting final color. The MAI aromatized oil was characterized by its clear green color (L*, a*, b* parameters). Fatty acid analysis showed that MAI slightly changed the fatty acid composition of the olive oil. This study indicates that MAI appears to be a viable and rapid method to flavor olive oil with rosemary leaves
Conductance of ferromagnetic nanowires
No full textThe conductance distribution obtained from an ensemble of stretching ferromagnetic nanowires or point contacts do not exhibit peaks near the integer multiples of 2e2/h. This observation has been interpreted as the absence of conductance quantization. In this report, we examine various features of electron transport through the Ni nanowires and clarify the behavior of conductance distribution that is different from gold and copper nanowires. Our study concludes that the tunneling through the closely spaced states near EF that originate from crystal field and spin split 3d states of Ni prevents the plateaus of conductance from forming in the course of stretch
An experimental investigation of the natural frequency statistics of a beam with spatially correlated random masses
No full textExperimental investigations into the dynamic response of structures with material or geometrical random fields usually depend upon an initial characterization of this variability, with very little control over the statistics at its early manufacturing stage. This provides the need of a minimal number of samples to generate an ensemble of dynamic responses, making such experimental data scarcely found in the literature. In this work, a cantilever beam with small masses attached along its length according to a given discrete random field has an ensemble of natural frequencies measured for a number of correlation lengths. The results can be used to investigate the effects of the correlation length on the subsequent natural frequency statistics. The experimental results are compared with a wave approximation for flexural waves using a continuous random field for the mass density, in order to approximate the mass distribution. Issues concerning this approximation are discussed. In addition, results are also compared with a simple added mass approximation with assumed modes from a FE solution
FIGURE 4. Marine triclads. a in Updated inventory and distribution of free-living flatworms from Tunisian waters
No full textFIGURE 4. Marine triclads. a Cleared whole mount of Procerodes dohrni. Note the presence of horn-shaped auricles in the anterior margin of body arrowheads. The pharynx ph is located in the second third of body. The testes (arrows) are distributed between intestinal ramifications ir. Penis papilla pp. b Cleared whole mount of Procerodes lobatus. Note the presence of flat auricles appearing as anterior marginal expansions (folds) arrowheads. The pharynx ph is located in the second half of body. Testes (arrows) are superimposed with intestine ramifications ir; penis papillae pp. c Cleared whole mount of Cerbussowia cerruti. The pharynx ph is located in the last third of body. A pair of oval shaped testes t and piriform ovaries ov are located anteriorly to the pharynx; vas deferens vd; intestine ramifications ir. d Procerodes lobatus. Dorsal view e Cercyra hastata. Ventral view showing everted pharynx ph and pigmented anterior end pae. f Cercyra hastata. Dorsal view. g Cleared whole mount of male specimen of Sabussowia dioica. The pharynx ph is located in the posterior part of the body. Testis (arrows) are distributed in all parts of the body. h Cleared whole mount of female specimen of Sabussowia dioica showing spermatophore (arrowhead) being impregnated to the marginal tissue of the body. Ovaries ov are located behind cerebral area. i Cleared whole mount of female specimen of Sabussowia dioica showing cocoon cc in uterus. Scale bars: 4a–c: 0.5mm; 4d: 0.5mm; 4e–f: 1mm; 4g–i: 1 mm.Published as part of Gammoudi, Mehrez, Garbouj, Myriam, Egger, Bernhard & Tekaya, Saïda, 2017, Updated inventory and distribution of free-living flatworms from Tunisian waters, pp. 120-138 in Zootaxa 4263 (1) on page 129, DOI: 10.11646/zootaxa.4263.1.5, http://zenodo.org/record/57256
FIGURE 3. Leptoplana tremellaris. a in Updated inventory and distribution of free-living flatworms from Tunisian waters
No full textFIGURE 3. Leptoplana tremellaris. a Dorsal view of anterior region showing the arrangement of eyes. Note the presence of two clusters of tentacular eyes te located posteriorly to two clusters of cerebral eyes ce. b Ventral view of anterior region showing confluent uteri ut filled with eggs. Tentacular eyes te, cerebral eyes ce. c Ventral view of posterior region showing male gonopore mg, genital pit gp and female gonopore fg. d Sagittal section of body wall. Note the presence of rhabdites rh among epithelial cells supported by basal lamina bl. The musculature is developed and organized in different layers, circular layer cl, oblique layer ol and longitudinal layer ll. e Section through uteri and ovaries showing uterine eggs ue and ovarian egg oe. f Section through male gonopore mg. The male atrium is provided with diverticulum d. Prostatic vesicle pv. g Section through seminal vesicle sv and ventral diverticulum of the prostatic vesicle dpv. Note the presence of mesenchyme separating seminal vesicle and prostatic vesicle. h Section through the entrance of vas deferens vd into the seminal vesicle. Note the presence of mesenchyme separating seminal vesicle sv and prostatic vesicle pv. i Section through female genital apparatus, the vagina is formed by vagina externa ve, vagina media vm and vagina interna vi. Female gonopore fg. Scale bars: 3a–b: 0.5 mm; 3c: 100 microns; 3d: 10 microns; 3e–i: 100 microns.Published as part of Gammoudi, Mehrez, Garbouj, Myriam, Egger, Bernhard & Tekaya, Saïda, 2017, Updated inventory and distribution of free-living flatworms from Tunisian waters, pp. 120-138 in Zootaxa 4263 (1) on page 124, DOI: 10.11646/zootaxa.4263.1.5, http://zenodo.org/record/57256
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