Appearance Of Symmetry Research Articles

Optimization of the calculation time in simulation using the GATE/GEANT4 Monte Carlo of radiotherapy treatment plans for small fields

Radiation therapy is one of the most widely used methods of treating cancer. One of the therapeutic gains of this method is to save in terms of calculation time during treatment planning, the variance reduction method is one of the most used to reduce the calculation time except that there are other alternatives to be able to optimize as much as possible, hence the interest of this study. In this work, we compared by Monte-Carlo simulation the flattened and unflattened 6 MV photon beams of the VARIAN Clinac 2100 linear accelerator. All the elements of the accelerator were simulated and allowed us to reproduce very close to reality. The doses obtained by simulation were taken in a tank of water under reference conditions, source to surface distance (SSD) of 100 cm, the arm at 0 ° and for a field variation of 2 x 2 cm2, 3 x 3 cm2, 4 x 4 cm2, 5 x 5 cm2, 10 x 10 cm2, 20 x 20 cm2, 30 x 30 cm2, 40 x 40 cm2. For each field, we calculated using a beam with a flattening filter (FF) and another beam with flattening filter-free (FFF). The calculation time of all these simulations was recorded. The results showed that the shape of the dose profiles changes according to the FF and FFF mode with a very interesting change for fields greater than 5 x 5 cm2 and almost similar profiles for the fields 2 x 2 cm2, 3 x 3 cm2, 4 x 4 cm2, 5 x 5cm2. The region between 80% and 100% of doses for beams with FF contributes to dose uniformity while for FFF fields gives the appearance of symmetry of dose distribution for all fields combined. On the depth dose curves (PDD) the dose at the entry into FFF mode was greater than that of FF mode leading to an increase in the influence of photons, the latter thus important on the increase in dose rate. The computation time in FF mode is higher by a proportion factor of 0.85 to 7.36 compared to the FFF mode respectively by going from the field 2 x 2 cm2 to 40 x 40 cm2. This comparison leads to being able to neglect the flattening filter for fields smaller than 5 x 5 cm2 since it has no impact on the processing field but has a great impact on the calculation time and to have a mode without this filter for fields smaller than 5 x 5 cm2 leads to an optimization of the computation time of 1.35 times compared to the FF mode.

Deep structure in the Acheulean adaptation: technology, sociality and aesthetic emergence

This article considers the adaptive setting and probable origins of human aesthetic capabilities, using evidence of the Acheulean tradition in the last million years, and highlighting the importance of the preceding and enveloping social and technological contexts. Acheulean bifaces, made from about 1.75 to 0.1 Ma, often with an appearance of symmetry, give windows on crucial interlocking aspects of human intellectual evolution. These have been seen as the domains of technology, sociality and aesthetics, following Leroi-Gourhan, or in near-equivalence the ‘technological’, ‘sociological’ and ‘ideological/philosophical’ of L.A. White. These domains can be analysed to have a reality, in the sense that social worlds of the apes far antedate technology, which in turn is generally taken to be far older than a sense of aesthetic appreciation. The bifaces are helpful in illustrating early developments because they can be made only through bringing together a set of concepts linking form, function and technology of manufacture, in a recurring ‘deep structure’. As there are at least 6 to 12 necessary concepts, perhaps significantly more, the artefacts are essentially multivariable or multivariate. They thus impose high cognitive requirements in manufacture, pressing towards effective sequencing of steps so that not too many variables will be involved simultaneously. Support of such a knowledge base has social requirements of shared or collective intention. Biomechanical and functional necessities also exert pressures on concepts: rules maintained by all these requirements entail a notion of ‘appropriateness’ or ‘rightness’ that may have been a prime factor in driving evolution of a sense of aesthetics and even the shaping of moral feelings. As the rules are variably expressed through time and space in the Acheulean, some of the best information comes from seeing how far particular variables are ‘locked’ in relationships which recur to give the impression of deep structure.

High-order harmonic generation of pulses with multiple timescales: selection rules, carrier envelope phase and cutoff energy

ABSTRACTHigh harmonic generation (HHG) is sensitive to the carrier envelope phase (CEP) of its driving laser field if it is a sufficiently short pulse (several-cycle pulse). Here we show that strong CEP effects can also be found in HHG from long duration multi-cycle pulses (up to 200 fs at 800 nm central wavelength). We find that HHG from multi-cycle pulses may be CEP dependent when the driving pulse exhibits two distinct timescales (multi-timescale pulse): (i) a short timescale associated with the average frequency, and (ii) a long timescale associated with the pulse’s temporal periodicity. The interplay of these timescales results in significant changes to both the cutoff frequency, and the appearance of symmetry allowed harmonics in the spectrum as function of CEP, similar to HHG from several-cycle pulses. We relate this effect to the multi-timescale intensity variations in the driving pulse, and construct an analytical condition to access the phenomenon. Lastly, we numerically demonstrate reconstruction of the CEP through HHG from long duration multi-timescale pulses. Our work may be useful in several areas of strong-field physics and attosecond science, for example, allowing spectroscopy of multi-timescale processes (e.g. HHG from vibrationally active media), and paving the way towards CEP characterisation using long pulses.

La casa de Halldor Gunnløgsson (1959). Una mirada a Oriente desde el Sund

Halldor Gunnlogsson´s own house, one of the most refined works of the Golden Age of modern Danish architecture, is the result of a strong will and personal artistic discipline. The detached flat roof suspended above a large paved platform –itself continuing the construction of the place– has great presence. In the interior, a single space, flows freely and extends to the landscape. There is an extraordinary sophistication of vernacular building; and a strong connection with traditional Japanese architecture, revealed by the desire of living in close contact with nature, the pursuit for refinement through moderation, the elimination of unnecessary items and the preoccupation with light and shade, where a parallel with the dark world of the Nordic winter is established. Its characteristic abstraction is an example of modernity. The building approaches to the classic beauty, by the proportions, the appearance of symmetry and order, but also for the soft treatment of the surfaces of materials. Rhythm is recognized in different dimensions. Scale is valued. Colors applied or inherent in the material, reach intensity. The experience of the architectural space is global. It is a magical and wonderful house.

The First Appearance of Symmetry in the Human Lineage: Where Perception Meets Art

Although symmetry may be important for understanding the selection of form in art over the historical period, this preference may have originally stemmed from certain basic perceptual mechanism that initially arose during prehistory. The first signs of an awareness to symmetry can be found in the archaeological record with the arrival of Acheulean handaxes, especially those dating from 500,000 years ago onwards, which are typified by a prodigious bilateral symmetry. As handaxes represent the earliest material record of an interest in symmetry by the human lineage, they provide a privileged means of understanding why this kind of form came to be valued by later human groups, particularly in relation to “art”. Although still controversial, the preference for symmetry at such an early date has been linked to various aspects of perception relating to enduring evolutionary factors. In this regard, it will be demonstrated how the preference for symmetrical Acheulean tools arose out of long standing perceptual correlates relating to ecological factors that predated the arrival of hominins.

Sedation with detomidine and acepromazine influences the endoscopic evaluation of laryngeal function in horses

Endoscopy of the upper airways of horses is used as a diagnostic tool and at purchase examinations. On some occasions it is necessary to use sedation during the procedure and it is often speculated that the result of the examination might be influenced due to the muscle-relaxing properties of the most commonly used sedatives. To evaluate the effect of detomidine (0.01 mg/kg bwt) and acepromazine (0.05 mg/kg bwt) on the appearance of symmetry of rima glottidis, ability to abduct maximally the arytenoid cartilages and the effect on recurrent laryngeal neuropathy (RLN) grade. Forty-two apparently normal horses underwent endoscopic examination of the upper airways on 3 different occasions, under the influence of 3 different treatments: no sedation (control), sedation with detomidine and sedation with acepromazine. All examinations were performed with a minimum of one week apart. The study was performed as an observer-blind cross-over study. Sedation with detomidine had a significant effect on the RLN grading (OR = 2.91) and ability maximally to abduct the left arytenoid cartilages (OR = 2.91). Sedation with acepromazine resulted in OR = 2.43 for the RLN grading and OR = 2.22 for the ability to abduct maximally. The ability to abduct maximally the right arytenoid cartilage was not altered. Sedating apparently healthy horses with detomidine or acepromazine significantly impairs these horses' ability to abduct fully the left but not the right arytenoid cartilage. This resulted in different diagnosis with respect to RLN when comparing sedation to no sedation. Since the ability to abduct the right arytenoid cartilage fully is not altered by sedation, it is speculated that horses changing from normal to abnormal laryngeal function when sedated, might be horses in an early stage of the disease. To confirm or reject these speculations, further studies are needed. Until then sedation during endoscopy should be used with care.

Appearance of symmetry, beauty, and health in human faces

Symmetry is an important concept in biology, being related to mate selection strategies, health, and survival of species. In human faces, the relevance of left–right symmetry to attractiveness and health is not well understood. We compared the appearance of facial attractiveness, health, and symmetry in three separate experiments. Participants inspected front views of faces on the computer screen and judged them on a 5-point scale according to their attractiveness in Experiment 1, health in Experiment 2, and symmetry in Experiment 3. We found that symmetry and attractiveness were not strongly related in faces of women or men while health and symmetry were related. There was a significant difference between attractiveness and symmetry judgments but not between health and symmetry judgments. Moreover, there was a significant difference between attractiveness and health. Facial symmetry may be critical for the appearance of health but it does not seem to be critical for the appearance of attractiveness, not surprisingly perhaps because human faces together with the human brain have been shaped by adaptive evolution to be naturally asymmetrical.

The standard modes of aversion: fear, disgust and hatred

I have nothing to offer but (a) one very plain and unexciting thesis of asymmetry between the fundamental types of emotional responses (or responses and reactions) to objects: liking and disliking, or, say, pro and con, appreciative/appetitive and aversive: an asymmetry not just empirically encountered but analysable and explainable; and (b) a restricted and somewhat arbitrary triadic selection of modes of aversion on which to base a diffential analysis. I shall argue that no such fundamental division, that is, none exactly on the same logical footing with this, can be attempted in the vastly more variegated range of friendly responses; and shall also mildly try to uphold the fairly representative character of the chosen triad of fear, disgust, hatred. Certainly we are accustomed to such apparently symmetrical contrasts as like and dislike, pro and con, being pleased and displeased, appetite and repugnance, attraction and aversion, and hatred. That appearance of symmetry is near enough to evident truth so long as we stick closely to the highly general root concepts of pro and con, like and dislike, or acceptance and rejection. It tends, however, to break down as our interest turns to the specified forms of pro and con emotional attitudes. Is hatred a symmetrical opposite of love? In every language, the word love has a way of embracing the entire conceptual field of pro responses: hence the traditional trinity of amor complacentiae, amor concupiscentiae and amor benevolentiae. Hatred is confined within much narrower limits: its proper object is only a person or a collective of persons, or at any rate something strictly expressive of the attitudes or words of such. In other cases, loathing, detestation, or repugnance rather than hatred seems to be the fit counterpart of what may still quite properly be called love. I the ducks in the park; I would refuse to say that I hate the seagulls which infest it in wintertime. Again, disgust has its range of objects limited to live beings or their remains, products, vestiges or representations; there is no similarly classic counterpart to it on the pro side. Again, what is the opposite

Variables affecting symmetry of the nipple-areola complex.

Currently, little is known about which variables are most critical to the subjective appearance of symmetry of the nipple-areola complex. Clinical photographs were transferred onto a compact disc and then imported into a computer photoshop program. Alterations to the nipple-areola complex were then performed, creating 1 symmetrical image and 19 asymmetrical images. The asymmetries were produced by altering position, diameter, or pigmentation. The images were converted to 35-mm slides and shown to four separate panels of three members each. A "symmetry score" was given for each slide. Results showed that any deviation from symmetrical was reliably detectable by the observers. Changes in areola diameter were detected most easily, and the specific direction of positional change was not found to be a significant factor. Differences were seen between individual panel assessments. This study has shown an application for CD-ROM technology in analyzing well-identified variables and has helped in delineating which factors are most critical to the subjective impression of symmetry of the nipple-areola complex.

NEW PROPERTIES OF QUASIPERIODIC SOLUTIONS OF THE COMPLEX GINZBURG-LANDAU EQUATION

By using analytical and numerical methods the authors study one of the basic models of mathematical physics—the so-called complex Ginzburg-Landau equation [Formula: see text] with the provision that no fluxes exist at the segment boundaries. A new class of solutions is found for this equation. It is shown that among its solutions there are analogs of limiting cycles of the second kind. A value describing these analogs is introduced, and a scenario of its variation depending on the parameters of the problem is given. A new type of spontaneous appearance of symmetry is shown when we go from initial data in the general form to spatially symmetrical solutions describing quasiperiodic regimes.

Truth or meaning: Ricoeur versus Frei on biblical narrative

Truth or meaning: Ricoeur versus Frei on biblical narrative Of the theologians and philosophers now writing on biblical narrative, Hans Frei and Paul Ricoeur are probably the most prominent. It is significant that their views converge on important issues. Both are uncomfortable with hermeneutic theories that convert the text into an abstract philosophical system, an ideal typological structure, or a mere occasion for existential decision. Frei and Ricoeur seem knit together in a common enterprise; they appear to be building a single narrative theology. I argue that the appearance of symmetry is an illusion. There is a fundamental conflict between the ‘pure narrativism’ of Frei and the ‘impure narrativism’ of Ricoeur. I give reasons for thinking that Ricoeur’s is the stronger position.

Crystal symmetry and atomic interactions

A crystal-chemical model of atomic interactions has been suggested which considers the conditions necessary for the attainment by a crystal of the minimum potential energy, which provides the appearance of symmetry including the translation one. The model has been tested on crystal structures of elemental substances and 26 structural types of inorganic compounds. The appearance of crystals symmetry, including the translation one, is explained in terms of multiatomic interactions (cooperative effect) reducing the potential energy of a multiatomic system to its minimum.

Truth or Meaning: Ricoeur versus Frei on Biblical Narrative

Truth or meaning: Ricoeur versus Frei on biblical narrative Of the theologians and philosophers now writing on biblical narrative, Hans Frei and Paul Ricoeur are probably the most prominent. It is significant that their views converge on important issues. Both are uncomfortable with hermeneutic theories that convert the text into an abstract philosophical system, an ideal typological structure, or a mere occasion for existential decision. Frei and Ricoeur seem knit together in a common enterprise; they appear to be building a single narrative theology. I argue that the appearance of symmetry is an illusion. There is a fundamental conflict between the ‘pure narrativism’ of Frei and the ‘impure narrativism’ of Ricoeur. I give reasons for thinking that Ricoeur’s is the stronger position.

The Sigemund-Heremod and Hama-Hygelac Passages in Beowulf

The four-hundred-odd lines of Beowulf1 between the defeat of Grendel and the attack by Grendel's mother contain two brief digressive passages, set with some appearance of symmetry on either side of the longer Finn Episode (1071—1159): a lay by one of HroSgar's thanes, contrasting the glorious deeds of Sigemund with the downfall of Heremod (874-915); and a pair of allusions introduced by the poet through the device of the torque given to Beowulf, concerning a mysterious exploit of Hama and the fatal expedition of Hygelac (1197-1214). The four basic references which make up these two passages seem designed as piecemeal allusions to stories more or less lost to us—a fact that must necessarily deprive us of much that the lines were meant to convey. Yet even allusion, if it is developed at all, is normally developed in the direction of its intended meaning, so that its general drift can sometimes be understood without a full knowledge of its underlying story. In this paper I will try to show that the Sigemund-Heremod and Hama-Hygelac passages are each organized around a clear thematic contrast, closely related to its context in the narrative; that they are meaningfully related to one another, and together express a theme of importance in this part of the poem; and that their significance grows naturally out of the great heroic ideal of sapientia et fortitudo which I believe lies at the heart of Beowulf? Section I will analyze the two passages themselves and their immediate contexts; Section II will explore their relation to the poem and its governing ideal.

F2 Ionization and Geomagnetic Latitudes

While studying the relation between the anomalous distribution of F2 ionization in the ionosphere and the geomagnetic co-ordinates of various observatories, we found that Sir Edward Appleton had already published his results1 (that issue of Nature was not available to us until two months ago owing to post-war difficulties), showing clearly the symmetry of F2 critical frequencies with respect to the dip angles south and north of the magnetic equator. Later, Prof. S. K. Mitra gave reasons2 explaining the geomagnetic control of F2 ionization, and found that the location of maximum critical frequencies obtained from his calculation agrees very well with that shown by Appleton's result. In our work, the critical frequencies are plotted against the geomagnetic latitudes—Figs. 1 and 2 for March and September 1946. Compared with Figs. 3 and 4, where the critical frequencies are plotted against dip angles, they show a similar appearance of symmetry. I feel, however, that the dip angles as measured near the surface of the earth, inevitably influenced by local factors, may not represent at all well the geomagnetic effect in a region far above the earth such as the F2 region in the ionosphere.