scholarly journals Average unit cell for the Generalized Penrose Tiling

2014 ◽  
Vol 70 (a1) ◽  
pp. C88-C88
Author(s):  
Maciej Chodyn ◽  
Pawel Kuczera ◽  
Janusz Wolny
Keyword(s):  
Single Point ◽  
Analytical Formula ◽  
Unit Cell ◽  
The Body ◽  
Penrose Tiling ◽  
Shift Parameter ◽  
Decagonal Quasicrystal ◽  
Promising Alternative ◽  
Hypercubic Lattice ◽  
Average Unit

The Generalized Penrose Tiling (GPT) can be considered a promising alternative for Penrose Tiling (PT) as a model for decagonal quasicrystal refinement procedure, particularly in the statistical approach (also called the Average Unit Cell (AUC) approach) [1]. The statistical method using PT has been successfully applied to the structure optimization of various decagonal phases [2]. The application of the AUC concept to the GPT will be presented. In the higher dimensional (nD) approach, PT is obtained by projecting a 5D hypercubic lattice through a window consisting of four pentagons, called the atomic surfaces (ASs), in the perpendicular space. The vertices of these pentagons together with two additional points form a rhombicosahedron. The GPT is created by projecting the 5D hypercubic lattice through a window consisting of five polygons, generated by shifting the ASs along the body diagonal of the rhombicosahedron. Three of the previously pentagonal ASs will become decagon, one will remain pentagonal and one more pentagon will be created (for PT it is a single point). The structure of GPT will depend on the shift parameter, its building units are still thick and thin rhombuses, but the matching rules and the tiling changes. In the AUC concept the probability distribution for rhombuses of PT can be obtained as an oblique projection of the ASs on the physical space. This holds true also for the GPT. The derivation of the AUC distribution for a given type of rhomb in a given orientation of an arbitrarily chosen GPT will be presented. In the PT, these distributions are triangular, whereas in the case of the GPT they are triangular (originating from the pentagonal AS) or hexagonal (originating from the decagonal AS). The AUC of GPT for shift parameters 0.2 and 0.5 has been calculated. The derivation of the analytical formula for structure factor using AUC formalism, for the decorated GPT is made similarly to the calculation for the PT [3].

Generalized Penrose tiling as a quasilattice for decagonal quasicrystal structure analysis

2015 ◽  
Vol 71 (2) ◽  
pp. 161-168 ◽  
Author(s):  
Maciej Chodyn ◽  
Pawel Kuczera ◽  
Janusz Wolny
Keyword(s):  
Long Range ◽  
Physical Space ◽  
Range Order ◽  
Penrose Tiling ◽  
Long Range Order ◽  
Shift Parameter ◽  
Decagonal Quasicrystal ◽  
Final Formula ◽  
Higher Dimensional ◽  
Average Unit

The generalized Penrose tiling is, in fact, an infinite set of decagonal tilings. It is constructed with the same rhombs (thick and thin) as the conventional Penrose tiling, but its long-range order depends on the so-called shift parameter (s∈ 〈0; 1)). The structure factor is derived for the arbitrarily decorated generalized Penrose tiling within the average unit cell approach. The final formula works in physical space only and is directly dependent on thesparameter. It allows one to straightforwardly change the long-range order of the refined structure just by changing thesparameter and keeping the tile decoration unchanged. This gives a great advantage over the higher-dimensional method, where every change of the tiling (change in thesparameter) requires the structure model to be built from scratch,i.e.the fine division of the atomic surfaces has to be redone.

Construction of average unit cell for Penrose tiling

2002 ◽  
Vol 342 (1-2) ◽  
pp. 198-202 ◽  
Author(s):  
Janusz Wolny ◽  
Bartłomiej Kozakowski ◽  
Przemysław Repetowicz
Keyword(s):  
Unit Cell ◽  
Penrose Tiling ◽  
Average Unit

scholarly journals Li3Al2, eine neue Phase im System Li/Al / Li3Al2, a New Phase in the System Li/Al

1973 ◽  
Vol 28 (9-10) ◽  
pp. 600-605 ◽  
Author(s):  
Karl-Friedrich Tebbe ◽  
Hans Georg Schnering ◽  
Barbara Rüter ◽  
Gisela Rabeneck
Keyword(s):  
Unit Cell ◽  
The Body ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural Relation ◽  
New Phase

Besides ‘Li2Al’ which was recently shown to be the phase Li9Al4 there exists the phase Li3Al2 characterized by preparation and X-ray diffraction methods. It cristallizes with a rhomboedric unit cell, R3̄m, a = 4.508 Å, c = 14.26 Å and z = 3 formula units (hexagonal setting). The structure can be looked at as a variant of the body centred cubic packing with Αl-atom layers of puckered six membered rings. The structural relation of the phases LiAl, Li3Al2, Li9Al4, Li is discussed.

scholarly journals THE AXOSTYLE OF SACCINOBACULUS

1973 ◽  
Vol 56 (2) ◽  
pp. 304-323 ◽  
Author(s):  
J. Richard McIntosh ◽  
Edward S. Ogata ◽  
Story C. Landis
Keyword(s):  
Unit Cell ◽  
Leaf Spring ◽  
Average Unit ◽  
Dark Staining

The axostyle of the flagellate Saccinobaculus is a motile ribbon composed of microtubules, cross-bridged to form interconnected rows. We find a centriole-related row of dark-staining tubules near the nucleus at the anterior end of the axostyle. Other tubule rows bind parallel to this primary row, acquire ordered relationships, and become the tubules of the axostyle proper. The number of tubule rows is constant in Saccinobaculus lata from the region near the nucleus to within a few micrometers of the posterior tip of the cell. In Saccinobaculus ambloaxostylus a few tubule rows are added to the axostyle posterior to the nucleus, giving this axostyle a leaf spring construction. The tubules of S. lata are held in rows by links with a 140 Å periodicity along the tubule axis; bridges between rows of tubules are also seen but are not apparently periodic. Each tubule in S. ambloaxostylus shows an axial periodicity of 150 Å due to pairs of arms, one of which is always part of the intrarow link. Interrow bridges in this species run either from tubule to tubule or from tubule to the free arm, but as in S. lata they do not display an obvious axial periodicity. An average unit cell is presented for the axostyle of each species, and the relation of the intertubule links to the microtubule substructure is discussed.

scholarly journals Utility of Periurethral Electric Stimulation to Reduce Voiding Frequency in Rats

2009 ◽  
Vol 3 (2) ◽  
Author(s):  
A. Forrest ◽  
Y. Zhang ◽  
A. Bicek ◽  
G. Timm
Keyword(s):  
Electrical Stimulation ◽  
Electric Stimulation ◽  
The United States ◽  
The Body ◽  
Bladder Pressure ◽  
Urinary Continence ◽  
Sprague Dawley ◽  
Promising Alternative ◽  
Surgical Interventions ◽  
Stimulation Of

Urinary continence is maintained through coordination of electrical (nervous) and mechanical (muscles, ligaments and other structures) systems in the body. During micturition, the central nervous system sends a signal to the detrusor and sphincter muscles to coordinate voiding. Pathological problems can undermine either of the two systems and result in urinary incontinence (UI). Thirteen million people in the United States live with UI. Clinical treatments to date are largely mechanical in nature, restoring function through surgical interventions. However, electrically-based treatments, such as electric stimulation, offer a promising alternative. Here we investigate the utility of electrical stimulation of the periurethral neuromusculature to reduce voiding contractions in well-controlled animal experiments. Female Sprague Dawley rats were anesthetized with a ketamine/xylazine/acepromazine cocktail and the bladder was catheterized through a small incision in the bladder dome and was infused with saline. Continuous filling of the bladder triggered related cycles of voiding which was identified through bladder pressure increases and visual urination. The pubic symphysis bone was cut to expose the urethra and a stimulating electrode was placed in the periurethral region. The electrical stimulation parameters were 2.8 mA of current, 200 us pluses, and 20 Hz. The electrical stimulation was done in fifteen minute intervals. Statistically, the rats without electrical stimulation have an average contraction period of 63.1 sec (+/– 31.3 sec) and the rats with electrical stimulation have an average contraction period of 97.2 sec (+/– 43.0 sec). The results showed that the electrical stimulation of the periurethral neuromusculature in the group revealed 54.0% increase in average contraction period and decrease in voiding frequency. Electrical stimulation of the periurethral neuromusculature increases the voiding interval and void volume for the rats. This suggests the existence of an external urinary sphincter to the bladder inhibitory pathway and supports periurethral neuromusculature stimulation as an alternative to spinal nerve stimulation for the treatment of bladder overactivity.

Bicarbonate: The Alternative Buffer for Peritoneal Dialysis

1996 ◽  
Vol 16 (1_suppl) ◽  
pp. 109-113 ◽  
Author(s):  
Jutta Passlick-Deetjen ◽  
Judith Kirchgessner
Keyword(s):  
Peritoneal Dialysis ◽  
Metabolic Acidosis ◽  
Cell Function ◽  
Multicenter Trial ◽  
The Body ◽  
Bicarbonate Concentration ◽  
Promising Alternative ◽  
Technical Problems ◽  
Cell Functions

For a long time bicarbonate, the physiological buffer of the body, was suggested to be the best buffer for peritoneal dialysis. However, since the production of bicarbonate containing solutions is associated with technical problems, lactate was favored. To avoid the well-known disadvantages of lactate solution concerning biocompatibility and possible metabolic side effects, different attempts have been made to use bicarbonate as a buffer in peritoneal dialysis. One of the major approaches was the total replacement of lactate by bicarbonate combined with storage of the fluid in a specially designed double-chamber bag. Further solutions of the above-mentioned problem were the on-line preparation of bicarbonate fluids for intermittent peritoneal dialysis, the addition of bicarbonate just before use, the combination of bicarbonate with organic acids, or its combination with the dipeptide glycylglycine as a stabilizing agent. By now, the beneficial effect of the neutral bicarbonate fluid, for example, on cell viability and cell functions, has been demonstrated in many different in vitro and animal studies. However, only few reports on clinical experience have been published. These investigations demonstrated independently that bicarbonate fluids diminish inflow pain, are well tolerated by the patients, and may correct metabolic acidosis of uremic patients. A controlled randomized multicenter trial using 34 mmol/L bicarbonate for at least three months confirmed that bicarbonate is as efficacious as lactate in equimolar concentrations. Concomitant investigations on energy metabolism and redox state of red blood cells and phospholipid secretion of mesothelial cells additionally demonstrated the improvement of cell function with bicarbonate solutions. For some patients with severe metabolic acidosis the bicarbonate concentration used in the multicenter trial seemed to be too low. Thus, a fluid containing a higher bicarbonate concentration was tested in a pilot study resulting in the expected significant increase of arterial bicarbonate levels. In summary, bicarbonate-containing peritoneal dialysis solutions are a promising alternative to lactate, especially if bicarbonate concentrations are adjusted individually to the patient's need.

A Pressure Modulating Sensorized Soft Actuator Array for Pressure Ulcer Prevention

2017 ◽  
Author(s):  
Wei Carrigan ◽  
Pavan Nuthi ◽  
Charu Pande ◽  
Caleb P. Nothnagle ◽  
Muthu B. J. Wijesundara
Keyword(s):  
Pressure Ulcer ◽  
Time Pressure ◽  
Soft Materials ◽  
Pressure Profile ◽  
The Body ◽  
Support Surface ◽  
Ulcer Formation ◽  
Interface Pressure ◽  
Promising Alternative ◽  
Pressure Modulation

Pressure ulcers are a serious reoccurring complication among wheelchair users with impaired mobility and sensation. It is postulated that external mechanical loading, specifically on bony prominences, is a major contributing factor in pressure ulcer formation. Prevention strategies mainly center on reducing the magnitude and duration of external forces acting upon the body. Seat cushion technologies for reducing pressure ulcer prevalence often employ soft materials and customized cushion geometries. Air cell arrays used in time-based pressure modulation techniques are seen as a promising alternative; however, this approach could be further enhanced by adding real-time pressure profile mapping to enable automated pressure modulation customizable for each user’s condition. The work presented here describes the development of a prototype support surface and pressure modulation algorithm which can monitor interface pressure as well as automatically offload and redistribute concentrated pressure. This prototype is comprised of arrays of sensorized polymeric soft air cell actuators which are modulated by a pneumatic controller. Each actuator’s pressure can be changed independently which results in a change to the interface pressure allowing us to offload targeted regions and provide local adjustment for redistribution. The pressure mapping, redistribution, and offloading capabilities of the prototype are demonstrated using pressure modulation algorithms described here.

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