230 research outputs found
Mr Bawa I suppose
No full textMr Bawa, I presume Giovanna Silva The title of the exhibition, “Mr Bawa, I presume”, comes from the inner dialogue which takes place every time the author is in front of one of Geoffrey Manning Bawa buildings. In her photographs Silva explores the fleeting edge where different worlds meet. Along these lines of accidental collision, the architectural language withdraws and gives way to places slowly shaped between our memory and vision. Focusing on the results that this collision produces, Giovanna Silva provides us an unusual perspective on architecture and landscape: “I start to take picture while the world still asleep; I manage to immerse the buildings in a suspended dimension. They seem inhabited, a part from the trace left by people the day before. The result is a photo of unclean architecture, apparently inanimate but instead dotted with objects testifying the secret life of architecture.” Working between script and gaze, the photographic sequences bring us into an invisible dimension, disclosing a narration that is alternative to the official history of architecture. At the center of her work is not just the architecture but also the personal story of the architect where she finds herself: “my pictures and my works always begin from a narrative inspiration more than a starting fact. I’ve read that after having worked as a lawyer, he decided to become architect and went back to study in England. I was fascinated by the fact that he changed his life when he was 38 years old, I’m nearly 39 years old. Then I discovered his obsessive side, leading him to consider in his entire life only black and white (not by chance he has chosen a Dalmatian as a dog), his tendency to consider the architectural experience a team work, a reason why he would involve in his project artists and friends.” The photographs will be showcased between CAMPO and the Leporello library, marking a path in the city where the work could meet the absent-minded look of the passer-by. The street is the place where Silva’s encounter with Bawa’s work can live again in each chance encounter between the photographs and the involuntary gaze of the viewer. Together with Silva we might think: “Mr Bawa, I presume”
Computer Simulation of the Responses of Human Motoneurons to Composite 1A EPSPS: Effects of Background Firing Rate
No full text Jones, Kelvin E. and Parveen Bawa. Computer simulation of the responses of human motoneurons to composite 1A EPSPS: effects of background firing rate. J. Neurophysiol. 77: 405–420, 1997. Two compartmental models of spinal alpha motoneurons were constructed to explore the relationship between background firing rate and response to an excitatory input. The results of these simulations were compared with previous results obtained from human motoneurons and discussed in relation to the current model for repetitively firing human motoneurons. The morphologies and cable parameters of the models were based on two type-identified cat motoneurons previously reported in the literature. Each model included five voltage-dependent channels that were modeled using Hodgkin-Huxley formalism. These included fast Na+ and K+ channels in the initial segment and fast Na+ and K+ channels as well as a slow K+ channel in the soma compartment. The density and rate factors for the slow K+ channel were varied until the models could reproduce single spike AHP parameters for type-identified motoneurons in the cat. Excitatory synaptic conductances were distributed along the equivalent dendrites with the same density described for la synapses from muscle spindles to type-identified cat motoneurons. Simultaneous activation of all synapses on the dendrite resulted in a large compound excitatory postsynaptic potential (EPSP). Brief depolarizing pulses injected into a compartment of the equivalent dendrite resulted in pulse potentials (PPs), which resembled the compound EPSPs. The effects of compound EPSPs and PPs on firing probability of the two motoneuron models were examined during rhythmic firing. Peristimulus time histograms, constructed between the stimulus and the spikes of the model motoneuron, showed excitatory peaks whose integrated time course approximated the time course of the underlying EPSP or PP as has been shown in cat motoneurons. The excitatory peaks were quantified in terms of response probability, and the relationship between background firing rate and response probability was explored. As in real human motoneurons, the models exhibited an inverse relationship between response probability and background firing rate. The biophysical properties responsible for the relationship between response probability and firing rate included the shapes of the membrane voltage trajectories between spikes and nonlinear changes in PP amplitude during the interspike interval at different firing rates. The results from these simulations suggest that the relationship between response probability and background firing rate is an intrinsic feature of motoneurons. The similarity of the results from the models, which were based on the properties of cat motoneurons, and those from human motoneurons suggests that the biophysical properties governing rhythmic firing in human motoneurons are similar to those of the cat. </jats:p
DESAIN SARANA BAWA OLAHRAGA SUMPIT
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Menyumpit adalah sebuah kegiatan yang dilakukan suku Dayak untuk berburu. Di Kalimantan timur terdapat Festival Erau yang betujuan melestarikan budaya kutai. Di ajang perlombaan tersebut para peserta lomba menyumpit kesulitan membawa sumpit yang sangat panjang saat berlomba. Motif Dayak adalah merupakan perpaduan antara suatu pola dasar yang memiliki artinya masing-masing, kemudian dikreasikan dalam berbagai perpaduan beberapa motif dasar sehingga menjadi satu kesatuan rangkaian makna yang berarti. Penulis ingin mendesain tas sumpit, yaitu wadah untuk membawa peralatan sumpit tersebut. Metode perancangan yang dilakukan yaitu melakukan pengumpulan data, analisa data, menentukan konsep desain, membuat desain alternatif, mengembangkan desain alternatif, hingga desain akhir. Untuk itu dengan adanya “Desain Sarana Bawa Olahraga Sumpit”, peserta lomba dapat membawa sumpit dengan nyaman dan aman saat berlomba dengan desain yang ergonmis serta estetis, karena sarana bawa ini memiliki motif Dayak Kalimantan Timur. Dilengkapi dengan konfigurasi yang teratur dan rapi, dan mengutamakan kenyamanan dan keamanan bagi peserta lomba. Sehingga semua dapat terakomodir dalam tas.
Kata kunci: sumpit, tas, olahraga, dayak
Abstract
Blowguns are an activity that Dayak tribes do to hunt. In eastern Kalimantan there is the Erau Festival which aims to preserve the culture of Kutai. In contest, the competitors contend with the difficulty of carrying very long Blowguns while competing. Dayak motif is a combination of an archetype that has its own meaning, then creation in various combinations of several basic motives that become a unity meaning meaningful circuit. The author wants to design a Blowgun bag, the container to carry the Blowguns. The design method is to collect data, analyze the data, determine the design concept, create alternative design, develop alternative design, until the final design. For that with the "Design Of Blowgun Sport Bag", users can carry Blowguns comfortably and safely while competing with ergonomic and aesthetic designs, because the vehicle has East Dayak motifs. Equipped with an orderly and neat configuration, and prioritizes comfort and safety for the users. So that all can be accommodated in the bag.
Keywords: Blowguns, bags, sports, Daya
Effects of tetanic stimulation on monosynaptic and dorsal root reflexes in kittens
No full text The effects of tetanic stimulation of peripheral afferents were examined on monosynaptic reflexes and dorsal root reflexes in kittens of various ages. Concomitantly recorded monosynaptic and dorsal root reflexes resulting from the stimulation of muscle nerves showed similar post-tetanic changes, namely, predominantly post-tetanic depression in neonates and post-tetanic potentiation in older kittens or adults. However, the changes in post-tetanic responses expressed as a percentage of control in dorsal root reflexes were much smaller than those in monosynaptic reflexes. When dorsal root reflexes originating from muscle and cutaneous afferents were compared, dorsal root reflexes from the latter behaved quite differently. For all ages, post-tetanic effects on dorsal root reflexes arising from cutaneous afferents were either insignificant or very small. The possible mechanisms underlying differences in post-tetanic effects from muscle and cutaneous afferents in adults and neonates are discussed.Key words: cat, kitten, development, dorsal root reflex, monosynaptic reflex, spinal cord, post-tetanic potentiation. </jats:p
Interaction of excitatory and inhibitory inputs to motoneurons in man
No full text Two separate paradigms were used to study the interaction of excitatory and inhibitory inputs to the motoneuron pools of lower leg muscles in human subjects. During inhibition of tibialis anterior muscle from Ia soleus afferents, the probability of firing of the higher threshold unit decreased more than that of the lower threshold unit in 14 out of 18 pairs. When soleus motor units were recruited by tendon vibration reflex and the subject voluntarily inhibited one unit, the higher threshold unit was silenced first in 55 pairs, whereas the lower threshold unit ceased firing first in 29 pairs, and 16 showed inconsistencies. It is concluded that although under standard conditions there is orderly derecruitment of units which is the reverse of recruitment, vibration of the intact human tendon brings about synaptic effects in the spinal cord which affect the normal patterns of recruitment and derecruitment of motor units. </jats:p
Neural control of motor output : can training change it ?
No full textLa recherche sur le recrutement des motoneurones indique clairement que , dans des conditions normales, les unités motrices des muscles des membres sont recrutées de manière ordonnée. On manque de données fiables concernant les effets de l'entraînement sur les diverses composantes du système nerveux impliqué dans le contrôle moteu
Posttetanic changes in the afferent and efferent activity of monosynaptic reflex in kittens
No full text Both the afferent volleys from the dorsal root and the monosynaptic reflex discharges from the corresponding ventral root were recorded with hook electrodes during stimulation of the nerves innervating the triceps surae muscles. The effects of conditioning high frequency tetanus on the magnitudes of these afferents and reflex volleys were examined in kittens of postnatal age 1–90 days and in adult cats. In young kittens under barbiturate anaesthesia, large-amplitude monosynaptic reflex discharge can be evoked without prior conditioning. The amplitude of this reflex discharge decreased with increasing age of the animal. Application of conditioning tetanic stimuli to the muscle nerves resulted in posttetanic depression followed by posttetanic potentiation of the monosynaptic reflex. The magnitude of posttetanic depression was much higher than that of potentiation in the first postnatal week. As the age increased, the magnitude of depression decreased while the magnitude of potentiation increased. The afferent volley showed a considerable posttetanic potentiation in older kittens and cats. No significant potentiation or depression was observed in the younger animals. Possible mechanisms contributing to posttetanic depression and potentiation are discussed. </jats:p
Mechanisms underlying firing in healthy and sick human motoneurons
No full textInternational audienceIn an address to the British Association for the Advancement of Science in Cambridge, Professor Sherrington introduced the terms " motor neurone " and " the final common path, " the latter term implying that all motor commands converge onto the motoneuron which integrates the incoming information and passes the net information to the muscle for contraction (Sherrington, 1904). The relative ease of access of the spinal motoneuron made it feasible to set up techniques for investigating the physiological, biophysical and molecular properties of these neurons. It became the most investigated neuron of the CNS in the twentieth century and the information gained from studies on motoneurons formed the basis for examining the other neurons of the CNS. Since the compound action potential of a muscle unit is strictly related one-to-one to the action potential arriving from the innervating motoneuron, the statistical analysis of muscle unit action potentials provides an investigator with an elegant way to probe the properties of motoneurons in behaving humans. In the following review the terms motoneuron and motor unit might be used interchangeably. Different aspects of human motoneuron investigations in health and disease are presented in 16 articles of this topic which are summarized below. An increase in the net excitatory synaptic input to the motoneuron pool results in an increase in the level of muscle contraction by recruitment of additional motor units (MUs) and an increase in firing rates of the already recruited units (Milner-Brown et al., 1973; Henneman et al., 1974). The principle of orderly recruitment of motoneurons by size was originally proposed by Henneman (1957) but was later questioned by other researchers presenting examples of selective, rather than orderly recruitment (e.g., Smith et al., 1980). These controversies are assessed by Bawa et al. (2014), and the opinion unifying the concept of orderly recruitment is presented. In humans, increases in firing rates of motor units have been shown to follow the " onion skin " pattern at lower levels of contraction, meaning that the lower-threshold motor units discharge with higher rates than higher-threshold ones. However, studies performed on the whole range of muscle forces indicated that for higher force levels the motor unit firing rate follows a " reverse onion skin " pattern. Hu et al. (2014) decided to approach this problem using small surface electrodes and step increases in force instead of the " ramp and hold " protocols used by previous authors. They showed that the " onion skin " pattern was preserved until 15% of maximal voluntary contraction, and from their results predict this pattern to be valid for the whole range of muscle forces, which is not supported by the previous published works. However, the reported rate saturation of the MUs discharging with higher rates implies that at the higher forces the " reverse onion skin " pattern may be expected. In another paper, Duchateau and Baudry (2014) show that during ballistic contractions the maximal discharge rates are higher than those observed in ramp contractions. It should be noted, however, that during ballistic contractions one deals with instantaneous rates, while during ramp and hold contractions one refers to tonic firing rates defined as the averag
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