Usual Setups Research Articles

The anesthetists’ concerns regarding robotic surgery

Advancement of technology has great impact on medical field. With all its pros and cons its use can be practiced with minimizing the risk and maximizing its benefits for the wellness of patient. With all the goodness that it offers to the surgery; its demand for environment and changes in the physiology of patient remains concerning for the anesthetist and surgical team. Despite the progression, it's huge space occupying size and its extra costly investment makes it difficult for usual setups to initiate it's use for common man. The robotic system has been used in a range of specialist areas, including bariatrics, general surgery, & cardiothoracic and urological surgeries and gynecological surgeries. Here we discuss various issues faced by the anesthetist to accommodate the concerns of robot assisted surgeries for the better outcome of the patients. Keywords: Anesthesia; Robotic surgical procedures; Education; Training; Pakistan Citation: Raza S, Tabassum S. The anesthetists’ concerns regarding robotic surgery. Anaesth. pain intensive care 2024;28(5):788−790; DOI: 10.35975/apic.v28i5.2542 Received: August 06, 2024; Reviewed: September 14, 2024; Accepted: September 14, 20

STEM-Based Course Design: A Way to Develop Attitudes towards STEM and Science Course

The study aimed to investigate the effects of a STEM-based course design on students’ attitudes towards STEM and a science course. STEM activities were prepared per learning outcomes relating to the ‘illumination and sound technologies’ learning domain in the grade 4 science course. The study was carried out based on an experiment and control group quasi-experimental design. The study was carried out at a state school in Mersin in 2021. The experimental group of the study consisted of 32 and the control group consisted of 32 grade 4 students. STEM-based activities were performed in the experimental group. However, non-STEM activities were performed based on usual experimental setups in the control group. At the end of the study, the experimental and control group students’ attitudes towards STEM and science course were examined to determine whether there were statistically significant differences. As part of this study, student opinions on STEM were examined. A STEM Attitude Test and open-ended opinion form were used as data collection tools. Normality tests were conducted, and the homogeneity of variances was examined. Dependent and independent t-tests were conducted in quantitative data analysis and content analysis in the qualitative data analysis. The results suggested that STEM-based course design significantly increased students’ STEM attitudes and their attitudes towards science course more than the attitudes of students not exposed to STEM-based course design. In addition, students considered STEM practices fun and informative. Accordingly preparing STEM based course design for science course has been suggested.

Non-line-of-sight transient rendering

The capture and analysis of light in flight, or light in transient state, has enabled applications such as range imaging, reflectance estimation and especially non-line-of-sight (NLOS) imaging. For this last case, hidden geometry can be reconstructed using time-resolved measurements of indirect diffuse light emitted by a laser. Transient rendering is a key tool for developing such new applications, significantly more challenging than its steady-state counterpart. In this work, we introduce a set of simple yet effective subpath sampling techniques targeting transient light transport simulation in occluded scenes. We analyze the usual capture setups of NLOS scenes, where both the camera and light sources are focused on particular points in the scene. Also, the hidden geometry can be difficult to sample using conventional techniques. We leverage that configuration to reduce the integration path space. We implement our techniques in a modified version of Mitsuba 2 adapted for transient light transport, allowing us to support parallelization, polarization, and differentiable rendering.

Holographic complexity of quantum black holes

We analyze different holographic complexity proposals for black holes that include corrections from bulk quantum fields. The specific setup is the quantum BTZ black hole, which encompasses in an exact manner the effects of conformal fields with large central charge in the presence of the black hole, including the backreaction corrections to the BTZ metric. Our results show that Volume Complexity admits a consistent quantum expansion and correctly reproduces known limits. On the other hand, the generalized Action Complexity picks up large contributions from the singularity, which is modified due to quantum backreaction, with the result that Action Complexity does not reproduce the expected classical limit. Furthermore, we show that the doubly-holographic setup allows computing the complexity coming purely from quantum fields — a notion that has proven evasive in usual holographic setups. We find that in holographic induced-gravity scenarios the complexity of quantum fields in a black hole background vanishes to leading order in the gravitational strength of CFT effects.

Development of a novel anemometry technique for velocity and temperature measurement

Hot-wire anemometry is a widely used measurement technique for obtaining local velocities or temperatures in a flow-field. Operated under constant temperature or constant current the small diameter wires can resolve high-frequency velocity or temperature fluctuations with a high degree of spatial and temporal resolution. Therefore, more or less sophisticated hardware, e.g. using a Wheatstone bridge for constant temperature anemometry (CTA), is used with relatively high acquisition costs. In this paper a new technique is used, where the wire temperature or current is digitally controlled via a FPGA unit. The electric circuit is simpler than the usual set-ups and the hardware used is very robust, allowing to operate the control unit under harsh environments. This allows also to reduce the cable lengths, and therefore, eventually to increase the frequency response of the hot wire. The application of this technique for measurements of aerodynamic and thermal boundary layers under varying Reynolds numbers for laminar and turbulent boundary layers is demonstrated. The results are compared to measurements with standard CTA system and show that similar results are obtained with this new technique.

Complex Impedance of Fast Optical Transition Edge Sensors up to 30 MHz

Optical transition edge sensors (TESs) are characterized by a very fast response, of the order of $$\upmu $$ s, which is $$10^3$$ times faster than TESs for X-ray and gamma-ray. To extract important parameters associated with the optical TES, complex impedances at high frequencies (> 1 MHz) need to be measured, where the parasitic impedance in the circuit and reflections of electrical signals due to discontinuities in the characteristic impedance of the readout circuits become significant. This prevents the measurements of the current sensitivity $$\beta $$ , which can be extracted from the complex impedance. In usual setups, it is hard to build a circuit model taking into account the parasitic impedances and reflections. In this study, we present an alternative method to estimate a transfer function without investigating the details of the entire circuit. Based on this method, the complex impedance up to 30 MHz was measured. The parameters were extracted from the impedance and were compared with other measurements. Using these parameters, we calculated the theoretical limit on an energy resolution and compared it with the measured energy resolution. In this paper, the reasons for the deviation of the measured value from theoretically predicted values will be discussed.

Modeling and specific growth rates estimation of a two-stage anaerobic digestion process for hydrogen and methane production

Production of hydrogen from anaerobic digestion of waste, also known as dark fermentative hydrogen production, is one the numerous alternatives to obtain this precious source of energy. In most usual experimental setups anaerobic digestion is known to produce small quantities of H2. In a comprehensive study Pakarinen, Kaparaju and Rintala have compared two-stage H2 and CH4 production and one-stage CH4 production. Simeonov, Denchev, and Chorukova recently announced a simple model of such a two-stage anaerobic digestion process for the production of hydrogen and methane. In the present communication we propose such a complete model along with estimation schemes of the specific growth rates of the involved bacteria that avoids the tedious work of empirical modeling and identification of these specific growth rates. At this stage only simulations are provided to illustrate the performance of these proposed estimation schemes.

Parameter Estimation of a Two-Colored Urn Model Class.

Though widely used in applications, reinforced random walk on graphs have never been the subject of a valid statistical inference. We develop in this paper a statistical framework for a general two-colored urn model. The probability to draw a ball at each step depends on the number of balls of each color and on a multidimensional parameter through a function, called choice function. We introduce two estimators of the parameter: the maximum likelihood estimator and a weighted least squares estimator which is less efficient, but is closer to the calibration techniques used in the applied literature. In general, the model is an inhomogeneous Markov chain and this property makes the estimation of the parameter impossible on a single path, even if it were infinite. Therefore we assume that we observe i.i.d. experiments, each of a predetermined finite length. This is coherent with the usual experimental set-ups. We apply the statistical framework to a real life experiment: the selection of a path among pre-existing channels by an ant colony. We performed experiments, which consisted of letting ants pass through the branches of a fork. We consider the particular urn model proposed by J.-L. Deneubourg et al. in 1990 to describe this phenomenon. We simulate this model for several parameter values in order to assess the accuracy of the MLE and the WLSE. Then we estimate the parameter from the experimental data and evaluate confident regions with Bootstrap algorithms. The findings of this paper do not contradict the biological literature, but give statistical significance to the values of the parameter found therein.

A tunable piezoelectric Fresnel mirror for high-speed lineshaping

We present the first tunable v-shaped mirror, also known as Fresnel mirror, that may be used to generate a quasi-nondiffracting line pattern, for example for applications in laser lithography or nanomachining with femtosecond lasers. The aperture of the device is 5 mm with a surface flatness of better than λ/10, and the range of the tilting angle is 1.3–38 mrad, resulting in a fringe spacing of 123 μm down to 4.2 μm for red light at 633 nm. In contrast to usual cantilever-comb setups, the mirrors are supported on a PDMS layer and tilted by a single piezoelectric actuator, providing a high resonance frequency of 5.1 kHz. The device is fabricated using laser rapid prototyping of silicon and a casting processes of soft polymers. We show the static and dynamic characterization of the mirror and the verification of the optical functionality.

Rashmdeep's Method: A Novel Method to Confirm Nasal Breathing

Mouth breathing has been a very prevalent oral habit, especially among children. Common etiologies behind this common occurrence can be physiologic enlargement of lymphoid tissue like adenoids leading to decrease nasopharyngeal airway or allergic rhinitis. The traditional or the latest methods used for diagnosing mouth breathing either are too subjective or cannot be performed in usual dental setups. This article presents an innovative method to confirm whether patient can breathe through the nose. This can also be used to diagnose any unilateral nasal blockade.

Dynamics of levitated nanospheres: towards the strong coupling regime

The use of levitated nanospheres represents a new paradigm for the optomechanical cooling of a small mechanical oscillator, with the prospect of realizing quantum oscillators with unprecedentedly high quality factors. We investigate the dynamics of this system, especially in the so-called self-trapping regime, where one or more optical fields simultaneously trap and cool the mechanical oscillator. The determining characteristic of this regime is that both the mechanical frequency ωM and single-photon optomechanical coupling strength parameters g are a function of the optical field intensities, in contrast to usual set-ups where ωM and g are constant for the given system. We also measure the characteristic transverse and axial trapping frequencies of different sized silica nanospheres in a simple optical standing wave potential, for spheres of radii r = 20–500 nm, illustrating a protocol for loading single nanospheres into a standing wave optical trap that would be formed by an optical cavity. We use these data to confirm the dependence of the effective optomechanical coupling strength on sphere radius for levitated nanospheres in an optical cavity and discuss the prospects for reaching regimes of strong light–matter coupling. Theoretical semiclassical and quantum displacement noise spectra show that for larger nanospheres with a range of interesting and novel dynamical regimes can be accessed. These include simultaneous hybridization of the two optical modes with the mechanical modes and parameter regimes where the system is bistable. We show that here, in contrast to typical single-optical mode optomechanical systems, bistabilities are independent of intracavity intensity and can occur for very weak laser driving amplitudes.

The Impact of Experimental Factors on Oxygen Semi-Permeation Measurements

Many recent studies have focused on the development of perovskite membranes with high oxygen semi-permeation performance. However, the usual experimental setups used to measure oxygen semi-permeation values may lead to significant errors in the actual performance of the membrane materials. In this paper, special attention is paid to the experimental conditions and the associated impacts on oxygen semi-permeation measurements collected from the membrane. Furthermore, the experimental setups described in the literature do not allow the direct identification of the limiting step for oxygen transport through the membrane, i.e., either through bulk oxygen diffusion or oxygen surface exchange on both membrane surfaces. In this work, a specific experimental setup is proposed for the discrimination of oxygen bulk diffusion and surface exchange phenomena.

Automated setup of functional electrical stimulation for drop foot using a novel 64 channel prototype stimulator and electrode array: Results from a gait-lab based study

Functional electrical stimulation is commonly used to correct drop foot following stroke or multiple sclerosis. This technique is successful for many patients, but previous studies have shown that a significant minority have difficulty identifying correct sites to place the electrodes in order to produce acceptable foot movement. Recently there has been some interest in the use of ‘virtual electrodes’, the process of stimulating a subset of electrodes chosen from an array, thus allowing the site of stimulation to be moved electronically rather than physically. We have developed an algorithm for automatically determining the best site of stimulation and tested it on a computer linked to a small, battery-powered prototype stimulator with 64 individual output channels. Stimulation was delivered via an 8×8 array adhered to the leg by high-resistivity self-adhesive hydrogel. Ten participants with stroke (ages 53–71 years) and 11 with MS (ages 40–80 years) were recruited onto the study and performed two walks of 10m for each of the following conditions: own setup (PS), clinician setup (CS), automated setup (AS) and no stimulation (NS). The PS and CS conditions used the participant's own stimulator with two conventional electrodes; the AS condition used the new stimulator and algorithm. Outcome measures were walking speed, foot angle at initial contact and the Borg Rating of Perceived Exertion.Mean walking speed with no stimulation was 0.61m/s; all FES setups significantly increased speed relative to this (AS p<0.05, PS p<0.01, CS p<0.01). Speed for PS (0.72m/s) was faster than both AS (0.65m/s, p<0.01) and CS (0.68m/s, p<0.05). Frontal plane foot orientation at heel-strike was more neutral for AS (0.3° everted) than in the NS (11.2° inverted, p<0.01), PS (4.5° inverted, p<0.05) and CS (3.1° inverted, p<0.05) conditions. Dorsiflexion angles for AS (4.2°) were larger than NS (−3.0°, p<0.01), not different to PS (4.3°, p>0.05) and less dorsiflexed than CS (6.0°, p<0.05).This proof of principle study has demonstrated that automated setup of an array stimulator produces results broadly comparable to clinician setup. Slower walking speed for automated and clinician setups compared to the participants’ own setup may be due to the participants’ lack of familiarity with responses different to their usual setups. Automated setup using the method described here seems sufficiently reliable for future longer-term investigation outside the laboratory and may lead to FES becoming more viable for patients who, at present, have difficulty setting up conventional stimulators.

Proposal for detecting spin-chirality terms in Mott insulators via resonant inelastic x-ray scattering

We consider the question of whether resonant inelastic x-ray scattering (RIXS) can be used to detect many-body excitations that are coupled to the spin-chirality terms S_i . (S_j x S_k) in a Mott insulator. We find that while the spin-chirality terms are in general absent in the usual experimental setups of RIXS, there are prospects of realizing such terms if one considers instead the scattering near a pre-edge. We then perform detailed analyses for the square and the kagome lattices, and brief analyses for the triangular and the honeycomb lattices, in which we show that the spin-chirality terms are indeed present in all the above lattices, but that they occur at a higher order in our expansion for the kagome and the honeycomb lattices. The merit of using RIXS in addition to Raman spectroscopy to detect excitations that are coupled to the spin-chirality terms is also briefly discussed in the context of the emergent gauge boson in the U(1) Dirac spin liquid.

Formation of metamorphic core complex in inherited wedges: A thermomechanical modelling study

Metamorphic Core Complexes (MCCs) form when a thickened domain with a low-strength lower crust is submitted to extension. These structures are characteristic of post-orogenic extension, and field observations suggest that several MCCs rework a crustal nappe-stack emplaced before extension begins. These MCCs therefore develop within heterogeneous crusts that contain pre-existing dipping heterogeneities, such as thrust faults and dipping nappes in a crustal wedge. Although very common, this first order structural inheritance has never been considered in studies modelling MCCs. Our contribution therefore investigates the effect of an inherited crustal wedge structure on the dynamics and kinematics of formation of the MCCs, using fully coupled thermomechanical modelling. The wealth of petrological, structural and time informations available in the Cycladic MCCs (Aegean domain) allows setting up more realistic initial conditions for the experiments than usual flat-lying setups. It also allows the results of the numerical computation to be directly validated with final geometries, P–T paths and exhumation rates. The experiments using dipping heterogeneities are characterised by a much more complex evolution and final structure than their flat-lying layered equivalents. Dipping heterogeneities drive lateral strength contrasts and help to re-localise the deformation on successive detachments. The dip of the inherited wedge structures imposes kinematic constraints on the flow, which provides a model that explains the regional scale asymmetry of the Cycladic MCCs. The P–T paths, the exhumation rates and the final crustal structure that come out of an initial shallow-dipping wedge model provide a much more realistic comparison with their natural counter-parts than common flat-lying models. Other parameters, like crustal-scale density inversion, thermal structure and creep law parameters are of second order when compared to the initial wedge structure. Being little dependent on these second order parameters, the proposed model for the formation of MCCs within inherited crustal wedges is likely to be applied to other areas where the MCCs formed in a nappe stack involving continental basement.

An Optical Method for Pretilt and Profile Determination in LCOS VAN Displays

Pretilt angle and cell thickness are two extremely important parameters in predicting the behavior of vertically aligned negative nematic liquid crystal (LC) displays. The accurate estimation of pretilt angle and cell thickness is not a trivial task when these devices work in reflective mode, as in liquid crystal on silicon (LCOS) vertically aligned nematic (VAN) displays. Usual experimental setups are based on the proportionality between the retardation of the polarization components of the incident light and the product effective birefringence times thickness. However, any attempt to separate the two product variables is cancelled out by symmetry from reflection. This work shows a relatively simple method capable of separating both variables, allowing accurate, independent measurements of pretilt and thickness, as well as other configurations details, such as residual twist. A simulation model based on the properties of actual reflective displays has been developed. An experimental setup specifically designed for measuring LCOS VAN cells has been prepared. Initial comparisons between experimental measurements of intensity and theoretical results showed some discrepancies that could be explained assuming that the LC profile contains a residual twist from the manufacturing process. Including that twist in the model, an excellent agreement between theory and experiment has been achieved. Matching simulations and experimental results yield separate determinations of pretilt angle and thickness, and give good estimates for the residual twist angle.

Firm Valuation: Tax Shields &amp; Discount Rates

This paper proposes a new discounted cash flows’ valuation setup, and derives a general expression for the tax shields’ discount rate. This setup applies to any debt policy and any cash flow pattern. It only requires the equality at any time between the assets side and the liabilities side of the market value balance sheet, which has been introduced by Farber, Gillet and Szafarz (2006). This concept is extensively developed in the paper. This model encompasses all the usual setups that consider a fixed discount rate for the tax shields and require a fixed level of debt or a fixed leverage ratio, in particular Modigliani & Miller (1963) and Harris & Pringle (1985). It proposes an endogenized and integrated approach and modelizes the different market value discount rates as functions of both their relevant leverage ratio and the operating profitability of the firm. Among these rates are the cost of debt and the tax shields’ discount rate, which are usually assume constant. In this model, all the discount rates are likely to vary as soon as perpetuity cases are not considered. This setup introduces a new rate for the cost of levered equity without tax shields and develops the relation between the present value of tax shields and the market value of equity since debt tax shields entirely flow to equity. It only requires the risk free rate and the unlevered cost of capital as inputs but not the capital structure of the firm, as it tackles the circularity problem by considering an iterative approach. This fully dynamic model yields both theoretical and economic sensible results, and allows straightforward applications. It apparently solves the discrepancies of the usual setups and hopefully paves the way for further research.

Measuring Thickness and Pretilt in Reflective Vertically Aligned Nematic Liquid Crystal Displays

Pretilt angle is a parameter of the utmost importance in the ultimate performance of vertically-aligned negative nematic LC displays. When these devices work in reflective mode, as is the LCOS microdisplays, accurate measurement of pretilt angles becomes a difficult problem, since usual experimental setups based on retardation of the polarization components of the impinging light are proportional to the product effective birefringence (n eff − n o ) times thickness, and any attempt to separate these variables is cancelled out by symmetry. This work shows a relatively simple method capable of separating both variables. An experimental setup specifically aimed at vertically aligned reflective cells has been prepared. At the same time, a simulation model has been developed taking into account the properties of actual reflective displays. Comparison between experimental and theoretical results shows some discrepancies that can be explained assuming that the LC profile contains a residual twist. Including that twist in the model, an excellent agreement between theory and experiment has been achieved. Matching of simulations and measurements yields to the separate determination of pretilt angle and thickness and gives good estimates for the residual twist angle.

Sampling from compositional and directional distributions

This paper describes a method for sampling from a non-standard distribution which is important in both population genetics and directional statistics. Current approaches rely on complicated procedures which do not work well, if at all, in high dimensions and usual parameter set-ups. We use a Gibbs sampler which seems necessary in practical situations of high dimensions.

Option Pricing under Stochastic Volatility and Trading Volume

This paper presents a pricing formula for European options that is derived from a model in which changes in the underlying price and trading volumes are jointly determined by exogenous events. The joint determination of volume and price changes provides a crucial link between volatility of the price process and an observable variable. The model works as follows: the process of information arrival (news) is taken to be a point process that induces simultaneous jumps in price and trading volume. In addition, price has a diffusion component that corresponds to background noise, and the parameter that governs the volatility of this component is a continuously weighted average of past trading volume. This specification makes increments to the volatility process depend on the current level of volatility and news and thereby accounts for the observed persistence in volatility. Moreover, it makes volatility an observable instead of a latent variable, as it is in the usual stochastic volatility setups. Options can be priced as in the Heston framework by inverting the conditional characteristic function of underlying price at expiration. We find that the model accounts well for time varying volatility smiles and term structures and that out-of-sample price forecasts for a sample of stock options are superior not only to those of standard stochastic volatility models but even to the benchmark ad hoc procedure of plugging current implicit volatilities into the Black-Scholes formula.