Thiele Model Research Articles

Coarse-graining collective skyrmion dynamics in confined geometries

Magnetic skyrmions are magnetic quasi-particles with enhanced stability and different manipulation mechanisms using external fields and currents, making them promising candidates for future applications such as neuromorphic computing. Recently, several measurements and simulations have shown that thermally activated skyrmions in confined geometries, as they are necessary for device applications, arrange themselves predominantly based on commensurability effects. In this simulational study, based on the Thiele model, we investigate the enhanced dynamics and degenerate non-equilibrium steady state of a system in which the intrinsic skyrmion–skyrmion and skyrmion–boundary interaction compete with thermal fluctuations as well as current-induced spin–orbit torques. The investigated system is a triangular-shaped confinement geometry hosting four skyrmions, where we inject spin-polarized currents between two corners of the structure. We coarse grain the skyrmion states in the system to analyze the intricacies of arrangements of the skyrmion ensemble. In the context of neuromorphic computing, such methods address the key challenge of optimizing readout positions in confined geometries and form the basis for understanding collective skyrmion dynamics in systems with competing interactions on different scales. The findings are corroborated by experimental measurements.

THE MOST REALISTIC SURGICAL SIMULATION MODEL TO GAIN SKILLS IN LAPAROSCOPIC SURGERY IS THE CADAVERIC MODEL THIEL, ACCORDING TO OPINIONS OF DIFFERENT SPECIALIST SURGEONS

Abstract INTRODUCTION Laparoscopic procedures are still a challenge for the surgeon residents and young surgeon physicians. Different learning systems have been used without achieving a realism faithful to the lived in the operation room. All existing surgical simulation systems should be compared, with the aim of identifying the most realistic of them, for improving the surgical learning. MATERIAL AND METHODS An 18-item survey was sent to different specialized surgeons (general surgeons, gynecologists and urologists) who participated in international postgraduate laparoscopic surgery courses on cadavers embalmed by Thiel method. Participants were asked to the differences and improving skills in each surgical procedure, about the different surgical simulation models that the participants had already used. Surgeons were asked if they would recommend doing it during residency to improve their confidence in the operating room. RESULTS Attendees (n = 104) had a response rate of 92% (96 replies). The 91.8% surgeons recognized that Thiel model was more realistic than others simulation methods. The 97.9 % of respondents believed that had improved their surgical skills. Globally, 96.9% (93) of the participants surveyed recommended the conducting of these courses with Thiel cadavers to different colleagues of other specialties as a reliable simulation measure during the residency period. CONCLUSIONS Participants in the laparoscopic surgery course on the cadaver Thiel recognized that this is more realistic surgical simulation model than conventional models, one of the best ways to gain confidence and improve laparoscopic skills in operation room for inexperienced surgeons.

Analytical model of the deformation-induced inertial dynamics of a magnetic vortex

We present an analytical model to account for the deformation-induced inertial dynamics of a magnetic vortex. The model is based on a deformation of the vortex core profile based on the Döring kinetic field, whereby the deformation amplitudes are promoted to dynamical variables in a collective-coordinate approach that provides a natural extension to the Thiele model. This extended model describes complex transients due to inertial effects and the variation of the effective mass with velocity. The model also provides a quantitative description of the inertial dynamics leading up to vortex core reversal, which is analogous to the Walker transition in domain wall dynamics. Our work paves the way for a standard prescription for describing the inertial effects of topological magnetic solitons.

Qualitative and quantitative comparison of Thiel and phenol-based soft-embalmed cadavers for surgery training.

Surgical skills training has traditionally been limited to formalinembalming that does not provide a realistic model. The aim of this study was to qualitatively and quantitatively compare Thiel and phenol-based soft-embalming techniques: qualitatively in a surgical training setup, and quantitatively by comparing the mechanical and histomorphometric properties of skin specimens embalmed using each method. Thirty-four participants were involved in surgical workshops comparing Thiel and phenol-based embalmed bodies. Participants were asked to evaluate the utility of the different models for surgical skills training. In parallel, tensile elasticity evaluation was performed on skin flaps from six fresh-frozen cadavers. Flaps were divided into three groups for each specimen: fresh-frozen, Thiel, and phenol-based embalmed and compared together at 1month or 1year after embalming. A histological investigation of the skin structural properties was performed for each embalming type using haematoxylin and eosin and Masson's trichrome. All participants rated the phenol-based specimens consistently better or equivalent to Thiel for the evaluated parameters. Quantitatively, there were statistically significant differences for the tensile elasticity between the embalming techniques (p<.05). There were no significant differences for the tensile elasticity between phenol-based embalmed skin and fresh state (p=.30), and no significant difference between embalming time was reported (p=.47). Histologically, the integrity of the skin was better preserved with the phenol-based technique. Phenol-based embalming provides as realistic or better of a model as Thiel embalming for surgical training skills and was generally preferred over Thiel model. The phenol-based embalming better preserved the integrity of the skin.

High-Fidelity Microsurgical Simulation: The Thiel Cadaveric Nerve Model and Evaluation Instrument.

With surgical education moving from a time-based to a competency-based model, developing high-fidelity simulation models has become a priority. The Thiel cadaveric model has previously been used for a number of medical and surgical simulations, including microvascular simulation. We aim to investigate the use of the Thiel model in peripheral nerve simulation and validate a novel evaluation instrument. Sixteen residents ranging from postgraduate years 1 to 6 participated in the study. Their nerve coaptations using Thiel cadaveric nerves were video recorded and evaluated by 5 fellowship-trained microsurgeons using the Micro-Neurorrhaphy Evaluation Scale (MNES). The intraclass correlation among the 5 evaluators was 0.75, revealing excellent interrater reliability. The Cronbach α was .77, underlining the internal consistency of the test items. Bivariate analysis revealed a significant association between the MNES scores and the participants' self-declared level of experience. This correlation was confirmed by mixed modeling. Our results validate the MNES and underscore the utility of the Thiel nerve tissue for peripheral nerve surgical simulation.

Optimal Kinetic Parameters of Trickle bed Reactor for Oxidation of 2-Proplymercaptan in Naphtha

The best kinetic of the reaction are estimated based on experimental data obtained from the literature using parameter estimation technique. The best mathematical model for oxidative 2-proplymercaption via oxygen is taking into account the apparent intrinsic kinetics considering internal diffusion and TBR hydrodynamic effect on the reaction process mainly , catalyst wetting efficiency, catalyst effectiveness factor, Thiele model and the effective diffusivity. The optimal operating condition for oxidative process is carried out utilizing. The optimization technique based upon the minimization of the sum squared error between experimental and predicted composition of naphtha oxidative process to determine the best parameters of kinetics models. The predicted product compositions for oxidation process found to be a good agreement with the experimental data for wide range of operating conditions (2.5-10 hr-1, 75-300 ppm and 293-353K) with minimum error 5% among all results

High Fidelity Microsurgical Simulation: The Thiel Model and Evaluation Instrument.

The Thiel embalmment method has recently been used in a number of medical simulation fields. The authors investigate the use of Thiel vessels as a high fidelity model for microvascular simulation and propose a new checklist-based evaluation instrument for microsurgical training. Thirteen residents and 2 attending microsurgeons performed video recorded microvascular anastomoses on Thiel embalmed arteries that were evaluated using a new evaluation instrument (Microvascular Evaluation Scale) by 4 fellowship trained microsurgeons. The internal validity was assessed using the Cronbach coefficient. The external validity was verified using regression models. The reliability assessment revealed an excellent intra-class correlation of 0.89. When comparing scores obtained by participants from different levels of training, attending surgeons and senior residents (Post Graduate Year [PGY] 4-5) scored significantly better than junior residents (PGY 1-3). The difference between senior residents and attending surgeons was not significant. When considering microsurgical experience, the differences were significant between the advanced group and the minimal and moderate experience groups. The differences between minimal and moderate experience groups were not significant. Based on the data obtained, a score of 8 would translate into a level of microsurgical competence appropriate for clinical microsurgery. Thiel cadaveric vessels are a high fidelity model for microsurgical simulation. Excellent internal and external validity measures were obtained using the Microvascular Evaluation Scale (MVES).

A new physiological model for studying the effect of chest compression and ventilation during cardiopulmonary resuscitation: The Thiel cadaver

BackgroundStudying ventilation and intrathoracic pressure (ITP) induced by chest compressions (CC) during Cardio Pulmonary Resuscitation is challenging and important aspects such as airway closure have been mostly ignored. We hypothesized that Thiel Embalmed Cadavers could constitute an appropriate model. MethodsWe assessed respiratory mechanics and ITP during CC in 11 cadavers, and we compared it to measurements obtained in 9 out-of-hospital cardiac arrest patients and to predicted values from a bench model. An oesophageal catheter was inserted to assess chest wall compliance, and ITP variation (ΔITP). Airway pressure variation (ΔPaw) at airway opening and ΔITP generated by CC were measured at decremental positive end expiratory pressure (PEEP) to test its impact on flow and ΔPaw. The patient’s data were derived from flow and airway pressure captured via the ventilator during resuscitation. ResultsResistance and Compliance of the respiratory system were comparable to those of the out-of-hospital cardiac arrest patients (CRSTEC 42 ± 12 vs CRSPAT 37.3 ± 10.9 mL/cmH2O and ResTEC 17.5 ± 7.5 vs ResPAT 20.2 ± 5.3 cmH2O/L/sec), and remained stable over time. During CC, ΔITP varied from 32 ± 12 cmH2O to 69 ± 14 cmH2O with manual and automatic CC respectively. Transmission of ΔITP at the airway opening was significantly affected by PEEP, suggesting dynamic small airway closure at low lung volumes. This phenomenon was similarly observed in patients. ConclusionRespiratory mechanics and dynamic pressures during CC of cadavers behave as predicted by a theoretical model and similarly to patients. The Thiel model is a suitable to assess ITP variations induced by ventilation during CC.

Re-modeling &lt;em&gt;Chara&lt;/em&gt; action potential: I. from Thiel model of Ca&lt;sup&gt;2+&lt;/sup&gt;transient to action potential form

Thiel and colleagues demonstrated that the all-or-none nature of Chara action potential(AP) is determined by formation of a second messenger, probably inositol triphosphate (IP 3 ), whichin turn releases Ca 2+ from internal stores. The Ca 2+ -activated Cl – channels are the main agent of thedepolarization phase of the AP. Once the Ca 2+ is re-sequestered by the calcium pumps, the chlorideconductance drops and depolarization-activated outward rectifier current, the background current andthe proton pump current return the membrane potential difference (PD) to resting level. Departingfrom the Thiel model of transient increase of Ca 2+ concentration, we set up membrane PD rate ofchange equation to calculate the AP form by numerical integration. Compared to data, this model APdepolarized more gradually. We introduced a prompt Ca 2+ transient from the outside, achieving agood correspondence with the experimental AP. In Chara cells subjected to 50 mM NaCl/0.1 mMCa 2+ medium, the AP duration increased from 2 s to up to 50 s and the APs were often spontaneous.The lack of stimulating pulse revealed a sharp positive spike at the beginning of each AP, confirmingthat Chara plasma membrane may contain transient receptor potential (TRP)-like channels, possiblyactivated by another second messenger diacylglycerol (DAG) formed at the same time as IP 3 . Thelong duration of the saline AP can be modeled by decreasing the coefficients in the Hill equationdescribing the Ca 2+ pumps on the internal stores. The model provides new insights into the characeanAP and suggests a range of experiments.

PRF thermometry during MR-guided focused ultrasound ablation in a preclinical thiel model

Proton Resonance Frequency (PRF) MR Thermometry is a useful method for treatment planning with MR-guided Focused Ultrasound (MRgFUS), as it provides accurate, real-time temperature maps. Thiel is an embalming medium that retains physical properties and life-like characteristics of human and animal tissue. The aim of the present study was to determine the accuracy of PRF Thermometry during MRgFUS and to estimate the value of PRF coefficient of pre-clinical Thiel embalmed human and animal tissue, and compare to fresh tissue and gel phantom.

Imaging spin dynamics on the nanoscale using X-Ray microscopy

The dynamics of emergent magnetic quasiparticles, such as vortices, domain walls, and bubbles are studied by scanning transmission x-ray microscopy (STXM), combining magnetic (XMCD) contrast with about 25 nm lateral resolution as well as 70 ps time resolution. Essential progress in the understanding of magnetic vortex dynamics is achieved by vortex core reversal observed by sub-GHz excitation of the vortex gyromode, either by ac magnetic fields or spin transfer torque. The basic switching scheme for this vortex core reversal is the generation of a vortex-antivortex pair. Much faster vortex core reversal is obtained by exciting azimuthal spin wave modes with (multi-GHz) rotating magnetic fields or orthogonal monopolar field pulses in x and y direction, down to 45 ps in duration. In that way unidirectional vortex core reversal to the vortex core 'down' or 'up' state only can be achieved with switching times well below 100 ps. Coupled modes of interacting vortices mimic crystal properties. The individual vortex oscillators determine the properties of the ensemble, where the gyrotropic mode represents the fundamental excitation. By self-organized state formation we investigate distinct vortex core polarization configurations and understand these eigenmodes in an extended Thiele model. Analogies with photonic crystals are drawn. Oersted fields and spin-polarized currents are used to excite the dynamics of domain walls and magnetic bubbles. From the measured phase and amplitude of the displacement of domain walls we deduce the size of the non-adiabatic spin-transfer torque. For sensing applications, the displacement of domain walls is studied and a direct correlation between domain wall velocity and spin structure is found. Finally the synchronous displacement of multiple domain walls using perpendicular field pulses is demonstrated as a possible paradigm shift for magnetic memory and logic applications.

PRF Thermometry during MR-guided Focused Ultrasound Ablation in a Preclinical Thiel Model

PRF Thermometry during MR-guided Focused Ultrasound Ablation in a Preclinical Thiel Model

Bone conduction in Thiel-embalmed cadaver heads

IntroductionSound can reach the inner ear via at least two different pathways: air conduction and bone conduction (BC). BC hearing is used clinically for diagnostic purposes and for BC hearing aids. Research on the motion of the human middle ear in response to BC stimulation is typically conducted using cadaver models.We evaluated middle ear motion of Thiel-embalmed whole-head specimens in terms of linearity, reproducibility, and consistency with the reported middle ear motion of living subjects, fresh cadaveric temporal bones, and whole-heads embalmed with a Non-Thiel solution of salts. MethodsWe used laser Doppler vibrometry to measure the displacement of the skull, the umbo, the cochlear promontory, the stapes, and the round window in seven ears from four human whole-head specimens embalmed according to Thiel's method. The ears were stimulated with a Baha® implanted behind the auricle. ResultsThe Thiel model shows promontory velocity similar to that reported in the literature for whole-heads embalmed with a Non-Thiel solution of salts (0- to 7-dB difference). The Thiel heads' relative velocity of the stapes with respect to the promontory was similar to that of fresh cadaver temporal bones (0- to 4-dB difference). The velocity of the umbo was comparable in Thiel-embalmed heads and living subjects (0- to 10-dB difference). The skull and all middle ear elements measured responded linearly to different stimulation levels, with an average difference less than 1 dB. The variability of repeated measurements for both short- (2 h; 4 dB) and long-term (4–16 weeks; 6 dB) repetitions in the same ear, and the difference between the two ears of the same donor (approximately 10 dB) were lower than the inter-individual difference (up to 25 dB). ConclusionThiel-embalmed human whole-head specimens can be used as an alternative model for the study of human middle ear mechanics secondary to BC stimulation. At some frequencies, differences from living subjects must be considered.

３次元集積回路電極用Ｓｉマイクロ孔内側壁に超臨界流体を利用してＣｕを堆積した際の被覆特性の検討

Supercritical fluids are high-pressure media possessing both high diffusivity and solvent capability. Metal thin films can be deposited in supercritical fluids from an organometallic compound (precursor) through thermochemical reactions. In this study, copper thin films were deposited in silicon microholes of 10 μm diameter and 350 μm depth to the fabricate through-silicon vias (TSVs) used in three-dimensional silicon integrated circuits. The fabrication temperatures and pressures were varied respectively within 180−280°C and 1−20 MPa, respectively. The maximum coating depth decreased with deposition temperature, although a peak maximum of the depth was observed at around 10 MPa. The dependence of temperature and pressure on the coating depth was discussed using a Thiele model, which describes the balance between diffusive transport and consumption of the precursor. The model results and experimental results showed good agreement. Diffusion constants of the precursor in the silicon microholes were estimated from the observed maximum coating depths.

Alternating motion of liquid in catalyst pores in a liquid/liquid–gas reaction with heat or gas production

A theoretical analysis of liquid–gas reactions with heat or gas production on a porous catalyst shows the possibility of pulsating motion of liquid in pores caused by the formation of bubbles inside pores due to gas or vapor generation. The criterion number determining the conditions under which such behavior occurs is given. Since the mass transfer and chemical reaction in pores take place under forced, oscillating motion, the description of such a phenomenon cannot be made by the Thiele model. The approach to modeling for such processes is being developed.

Combined Diffusion, Adsorption, and Reaction Studies of n-Hexane Hydroisomerization over Pt/H–Mordenite in an Oscillating Microbalance

Uptake experiments under full catalytic conditions have been performed using a tapered element oscillating microbalance. The effect of acid leaching on the diffusivity and reaction of n-hexane in Pt/H–mordenite has been established from these experiments. For acid-leached Pt/H–mordenite the hydroisomerization activity is four times higher than for untreated Pt/H–mordenite. Acid leaching gives rise to an acceleration of the uptake of n-hexane under reaction conditions. Analysis of the data implies the faster uptake to be predominantly accounted for by a shorter intracrystalline diffusion path length, as diffusivities are in the same range for both catalysts. The shorter path length results from the mesoporous structure of H-mordenite generated by acid leaching. From the diffusivities, from the path lengths, and by using the Thiele model, it is inferred that the intrinsic rate constant of acid-leached Pt/H–mordenite is twice that of the untreated Pt/H–mordenite. The facilitated transport of reactants and products doubles the effectiveness factor, thus also contributing to the overall activity enhancement for n-hexane hydroisomerization after acid leaching.

Diffusion limitations in fischer‐tropsch catalysts

AbstractThe extent of diffusion limitations in the catalytic conversion of synthesis gas to hydrocarbons by the Fischer‐Tropsch reaction has been established for a number of iron‐ and cobalt‐based catalysts. The studies were performed in a fixed‐bed microreactor system at temperatures in the range 473–523 K. Variation of catalyst particle size in the range 0.2–2.6 mm shows that the conversion of synthesis gas decreases considerably when the average particle size is increased. The effects of variation of particle size and pore diameter have been quantified with the Thiele model for diffusion limitations. Evidence has accumulated that the limited mobility of reactant molecules in the liquid‐filled pores of Fischer‐Tropsch catalysts is the main cause of retardation of the reaction rates. The experimentally determined reaction rates with various catalysts operated under different conditions show an excellent fit with the theoretical model.

Morphological Development and Intrinsic Reactivity for Combustion of Two Microporous Carbon Chars

Abstract In this paper, we consider the morphological development and intrinsic reactivity or two microporous carbon chars burning at conditions typical of a pulverized-fuel combustor (i.e., particle temperatures above 1300 K. and diameters below 200 μm). The model chars were chosen for their low ash and volatile matter contents to preclude the complicating effects of these components on the oxidation process. The partially oxidized samples (0 to 65% mass loss), which were collected in an entrained-flow reactor, are experimentally characterized by their total surface area, particle diameter, apparent density. pore volume distribution, and macroporous surface area. SEM photomicrographs of the external particle surface and refiected-light photomicrographs of the internal porosity of the particles are also presented. These measurements demonstrate that combustion occurs under Zone II conditions. The Thiele model of diffusion and reaction in a porous particle is used to calculate intrinsic combustion rates fr...

Analysis of the performance of a simulated counter‐current chromatographic system for fructose – glucose separation

AbstractThe adsorptive separation of fructose from glucose has been carried out in a simulated counter‐current chromatographic system using Zerolit‐25SCR14 ion exchange resin in Ca++ form as the adsorbent. Rate and equilibrium constants have been determined from chromatographic retention time measurements. The performance of a simulated counter‐current system comprising ten identical columns connected in series has been investigated and it is shown that the behaviour of such a system may be approximately represented by a simple McCabe–Thiele model. The HETP in the counter‐current system is higher than would be expected for an ideal plug flow system, showing that axial mixing is important. The McCabe–Thiele analysis may be easily extended to a four section ‘Sorbex’ system and a preliminary assessment of the performance of such a unit is made on the basis of the kinetic and equilibrium parameters derived from the experimental study.

Time Series Analysis in 1880: A Discussion of Contributions Made by T.N. Thiele

Summary We describe and discuss a paper of T.N. Thiele from 1880 where he formulates and analyses a model for a time series consisting of a sum of a regression component, a Brownian motion and a white noise. He derives a recursive procedure for estimating the regression component and predicting the Brownian motion. The procedure is now known as Kalman filtering. He estimates the unknown variances of the Brownian motion and the white noise by an iterative procedure that essentially is the EM-algorithm. We finally give a short account of an application of Thiele's model and method to the description of hormone production during normal pregnancy.