Localization Of Foci Research Articles

Graphical Interface in MATLAB for design and analysis of reflectors for lighting systems or solar collectors on parabolic surfaces

This project introduces the successful development of a MATLAB graphical interface for the design and analysis of reflectors and solar concentrators on parabolic surfaces. The integration of spline techniques for precise modeling of these surfaces has been implemented, along with the capability to generate STL files for 3D printing. The interface not only enables detailed and adaptable design of reflectors but also includes an advanced simulator for projecting incident rays and analyzing their reflection on the parabolic surface, focusing specifically on the focal point location. This has led to a significant increase in the efficiency of solar concentrators and lighting systems by enabling the precise placement of absorbers to maximize energy transfer. The obtained results confirm the initial hypothesis, demonstrating that the interface enhances the precision and efficiency in the design of these systems, thereby offering a valuable tool in both educational and professional realms in the fields of solar energy and lighting.

Risk score for malignancy in patients with suspicious gallbladder lesions: Retrospective analysis of 175 cases.

Among cancers, carcinoma gallbladder has one of the most dismal prognosis. Early lesions are difficult to biopsy because of proximity to luminal structures and risk of biliary peritonitis. However, early surgery offers the only chance of a complete cure. Utilizing a risk score would allow characterization of the risk of malignancy and early referral to an oncology centre thereby resulting in better outcomes for patients with carcinoma gallbladder. The aim of this study was to develop a risk score for carcinoma in patients with suspicious gallbladder lesions based on clinical presentation and imaging. All patients with suspicious gallbladder lesions on radiological imaging who underwent surgery were analyzed. Patients were considered for scoring if the ultrasound showed the gallbladder wall thickening (more than 4mm) and computed tomography scan showed operable disease. Statistical analysis was done to derive a score for malignancy. Total 175 patients underwent an operation for suspicious gallbladder lesions from January 2005 to December 2014. The factors analyzed were clinical biochemical and imaging findings. Of these, 71 were benign on the final histopathology and 104 were malignant. The score was constructed with the following variables: female sex, high total bilirubin (≥ 1mg/dL), presence of a mass, focal location of the lesion, presence of gallbladder stones and nodal involvement in the hepatoduodenal region on imaging. A model score and modified score were obtained. In this modified score, score of more than 8 out of 20 predicted malignancy with a sensitivity of 78% and specificity of 70.4%. Receiver operating characteristic (ROC) curve constructed with these variables had an area under curve of 0.828. There was no statistically significant difference between the model score and the modified score. A pre-operative risk score was obtained for carcinoma gallbladder, which needs to be validated prospectively in future.

Optimization of Surface Finish of Plasma Metal Deposited Stainless Steel 316L Parts by Utilization of Plasma Beam Remelting (PBR) and Taguchi Methodology

The study aimed to optimize the Plasma Beam Polishing process for 316L stainless steel components to reduce anisotropy and poor surface roughness using statistical analysis. An experimental design investigated the impacts of managing factors on surface roughness, with scanning speed having the ultimate impact, followed by beam power and energy density. For lower values of plasma energy density and scanning speed, and a focal location without changes on the metal surface, there was a strong tendency for the estimated Ra to drop with increasing laser power. The process parameters were changed throughout a broad range of values, making it challenging to model the dependent variable across the whole range of experimental trials. The study supports the potential of PBP as a post-processing method for additive manufacturing components.

TÜRKİYE’NİN METROPOL ŞEHİRLERİNDEKİ BAZI ALIŞVERİŞ MERKEZLERİNİN IPA VE IPCA YÖNTEMLERİ KULLANILARAK KARŞILAŞTIRMALI ANALİZİ

With the influence of globalization and modernism, habits have begun to change in many areas. Especially in recent years, as a result of economic and social events, the urban lifestyle has also changed. As a result of the change, people have started to prefer multifunctional shopping centers where all kinds of products, in addition to their basic needs, are available together and where they can have more rest opportunities. Areas with this function, which are also considered urban attraction points, are increasing their share in the service sector day by day. There is a highly competitive environment among shopping malls that have a significant customer potential. Understanding the competitive position of these areas is vital for decision-makers. This study, conducted in Ankara and Istanbul samples, aims to analyze to what extent the physical features of shopping malls meet the preferences and expectations of users. These properties were evaluated using IPA and IPCA methods. In this context, the study presents a comparative analysis of Ankara, which was selected as the focal location, and Istanbul, which was selected as the rival location. As a result of the analysis, the criteria that Ankara and Istanbul have higher performance than each other and the features that should be prioritized in performance improvement studies to increase their competitiveness were determined. It has been concluded that shopping malls in Ankara are in a position to compete with Istanbul.

A theragnostic HIFU transducer and system for inherently registered imaging and therapy.

One big challenge with high intensity focused ultrasound (HIFU) is the difficulty in accurate prediction of focal location due to the complex wave propagation in heterogeneous medium even with imaging guidance. This study aims to overcome this by combining therapy and imaging guidance with one single HIFU transducer using the vibro-acoustography (VA) strategy. Based on the VA imaging method, a HIFU transducer consisting of 8 transmitting elements was proposed for therapy planning, treatment and evaluation. Inherent registration between the therapy and imaging created unique spatial consistence in HIFU transducer's focal region in the above three procedures. Performance of this imaging modality was first evaluated through in-vitro phantoms. In-vitro and ex-vivo experiments were then designed to demonstrate the proposed dual-mode system's ability in conducting accurate thermal ablation. Point spread function of the HIFU-converted imaging system had a full wave half maximum of about 1.2 mm in both directions at a transmitting frequency of 1.2 MHz, which outperformed the conventional ultrasound imaging (3.15 MHz) in in-vitro situation. Image contrast was also tested on the in-vitro phantom. Various geometric patterns could be accurately 'burned out' on the testing objects by the proposed system both in vitro and ex vivo. Implementation of imaging and therapy with one HIFU transducer in this manner is feasible and it has potential as a novel strategy for addressing the long-standing problem in the HIFU therapy, possibly pushing this non-invasive technique forward towards wider clinical applications.

Focus enhancement in long schlieren imaging systems using corrector lenses.

Long schlieren imaging systems, where the parallel light test section is longer than the focal length of the focusing schlieren optics, have a limited region in the test section in which any occluding object, such as a wind tunnel model, is in focus in the schlieren image. Corrector lenses are introduced here to alter the location in the test section where image focus is achieved. Corrector lenses with focal lengths varying from -1000 to -100m m were studied. Lens-type inline and z-type mirror schlieren systems were experimentally tested with multiple collecting optic focal lengths to characterize the changes in focal position. An automated image processing method was used to determine the plane of best focus from image sequences. The introduction of the corrector lens was observed to move the location of best focus within the schlieren system test section while also causing a decrease in the focal sharpness of the images and altering the magnification. The thin lens equation was found to provide a good estimate of the focal location change in the schlieren imaging systems with the addition of the corrector lens.

Technical note: Evaluation of the acoustic radiation force imaging for predicting HIFU focus with in vitro and ex vivo experiments.

High-intensity focused ultrasound (HIFU) is currently used for the treatment of various diseases, but it still lacks a reliable technique in the preoperative stage to accurately place its "energy blade" onto diseased targets. Acoustic radiation force imaging (ARFI) was recently introduced to tackle this issue, but its applicability and limitations were not clear. The aim of this study was to evaluate the performance of ARFI method in prediction of HIFU focal location at the preoperative stage. A point spread function (PSF) localization method, which was borrowed from the ultrasound super resolution field, was used to validate the core autocorrelation-based motion estimation algorithm in the ARFI procedure. Accuracy of the ARFI method for estimating the HIFU focus were tested with in vitro and ex vivo experiments with a clinically equivalent HIFU system. Comparisons were made between the estimated focal locations and those of the damaged area after the testing objects were cut open. Results showed that the PSF localization was able to serve as a validating method for motion detection only when the tissue displacement was large. With the ARFI method, location of the HIFU focus could be accurately predicted by a 2D motion map preoperatively, and the axial spatial errors were less than 0.5mm. However, the derived 2D motion maps can only be valuable when the acoustic stimulation in ARFI were strong enough, which was probably due to the fact that the HIFU focal locations were at large depths and the ultrasound imaging signal had low signal to noise ratio. The ARFI method was indeed an accurate technique for preoperatively predicting HIFU focus in vitro and ex vivo. If clinical applications were to be considered, particularly in deep tissues, efforts might need to be made to improve ability of the ultrasound motion estimation technique.

Remote focused encoding and decoding of electric fields through acoustoelectric heterodyning

Heterodyning of signals through physical multiplication is the building block of numerous modern technologies. Yet, it has been mostly limited to the interaction between electromagnetic fields. Here, we report that heterodyning occurs also between acoustic and electric fields in liquid electrolytes. We predict acoustoelectric heterodyning via computational field modelling, which accounts for the vector nature of the electrolytic acoustoelectric interaction. We then experimentally validate the spatiotemporal characteristics of the field emerging from the acoustoelectric heterodyning effect. The electric field distribution generated by the applied fields can be controlled by the propagating acoustic field and the orientation of the applied electric field, enabling the focusing of the resulting electric field at remote locations. Finally, we demonstrate detection of multi-frequency ionic currents at a distant focal location via signal demodulation using pressure waves in electrolytic liquids. As such, acoustoelectric heterodyning could open possibilities in non-invasive biomedical and bioelectronics applications.

A CASE SERIES ON ADULT INTUSSUSCEPTIONS IN A TERTIARY CARE HOSPITAL AND LITERATURE REVIEW

The invagination of one part of the bowel into a neighboring part is known as intussusception.In both the pediatric and adult populations,there are differences in the etiology,symptoms,diagnoses,and treatments.The majority of idiopathic cases in the pediatric population lead to the typical scenario of ileocolic intussusception.Anatomical characteristics of the developing gastrointestinal tract and viral effects are factors that contribute to causality. The intussusceptum in adults often develops as a result of a focal location of traction acting as a mucosal, intramural, or extrinsic lead point, drawing the proximal portion of the intestine into the peristalsing distal segment.Intussusception in the adult population poses a diagnostic problem prior to surgery; although surgical intervention is required, intraoperative care is still debatable

Blowing out a candle from a distance with high amplitude time reversal

Time reversal is a technique that allows the focusing of sound from a source to a remote location causing an impulsive focusing event. Using more sources and other amplitude-increasing techniques, the focusing of audible sound can reach over 200 dB peak. This can extinguish the flame on a single candle without affecting nearby lit candles. Most methods used to extinguish a flame using sound involve the nearfield and nonlinear airflow effects. Because time reversal focusing can occur far from the sources, the mechanism is different. Using high-speed video footage of the focal event, we can see the finer details of this millisecond scale focus interacting with the flame. Measuring the sound field during the focus event at and near the focal location also sheds light on the mechanism. So far, it has been seen that the focus pushes the flame outward, separating the plasma from its fuel source. The known formation of shock waves provides a possible explanation. Further research is being done to explore the cause of the extinguishing of the flame. This talk will show that not only is it possible to focus high amplitude sound waves but targeted flows of air as well.

High amplitude time reversal focusing of sound and vibration

Time reversal (TR) is a signal processing technique that can be used to focus high amplitude sound or vibration at a desired location. TR focusing can be done with sources placed far from the desired focal location and the technique excels in complex environments. The impulse response between each source and the desired focal location must be obtained prior to the focusing and the environment must remain relatively unchanged for successful focusing. Multiple scattering or reverberation of waves off of many reflecting surfaces in the environment can actually be used advantageously by exploiting those reflections as additional image sources. This talk will provide an introduction to TR and then focus on the use of TR to provide high amplitude focusing of sound and vibration. Applications of high amplitude TR include lithotripsy of kidney stones, histotripsy of lesions, and locating cracks and defects in structures such as in human teeth, spent nuclear fuel storage casks, airplane wings, and automotive bearing caps. Recently, high amplitude TR of airborne sound has been studied in a reverberation chamber to generate a focused difference frequency and to study the nonlinear acoustics of the peak sound levels of 200 dB that have been attained.

Source rupture characteristics of the September 5, 2022 Luding MS 6.8 earthquake at the Xianshuihe fault zone in southwest China

On September 5, 2022, at Beijing time 12:52 p.m., an MS 6.8 earthquake struck Luding County, Garze Tibetan Autonomous Prefecture, Sichuan Province. The epicenter of the earthquake was at the intersection of the Sichuan-Yunnan, Bayankala, and South China blocks. The tectonic background is extremely complex, and strong earthquakes occur frequently. Based on a predetermined focal location and focal mechanism solution for the earthquake, we reversed the focal depth and rupture process of the earthquake by fitting the teleseismic P and SH waves recorded by the global seismic network. The results show that the focal depth is 16 ​km, with the main rupture having a length of about 45 ​km near the epicenter, with a maximum displacement of 1.02 ​m. Although the rupture mainly propagates from the north–northwest (NNW) to the south–southeast (SSE) along the fault strike, there is a small-scale rupture slip zone at shallow depths in the north–northeast (NNE) direction along the epicenter of the seismogenic fault. This rupture image corresponds to the cluster distribution of aftershocks in the NNW and SSE directions starting from the epicenter, corresponding to the distribution of recorded landslides. The earthquake occurred on the Moxi fault, located in the southeastern section of the Xianshuihe fault. The major tectonic feature in this area is the southeastward movement of the Chuandian block relative to the Bayanhar block.

Analysis of the peaks of ship motions in linear and nonlinear focused waves

Three focused waves, which have almost identical temporal profiles, are successfully generated in a numerical wave tank with both linear and nonlinear methods, and they are utilized to act upon an LNG carrier to study the induced differences of the ship peak responses for the first time. The influences of focal location and incident wave direction are taken into account and the fundamental reason for the response difference is revealed from the perspective of energy variation. It can be concluded that when the LNG carrier encounters the same temporal focused waves, the peak motion responses can be different due to the different hydrodynamic characteristics under the focused crests, which can be further attributed to the distinct physical mechanisms involved in the energy concentration of these focused waves. The focal location and incident wave angle can further enlarge the corresponding discrepancy under some circumstances. From a spectral point of view, the motion discrepancy is mainly caused by the actions of the distinct fundamental wave components. Specifically speaking, the relatively high-frequency components of the nonlinear focused waves tend to induce a smaller heave response and the quasi-monochromatic wave component cannot trigger a larger pitch motion than the linear focused waves.

Design of HIFU Treatment Plans Using Thermodynamic Equilibrium Algorithm

High-intensity focused ultrasound (HIFU) is a non-invasive medical procedure, which is mainly used to ablate tumors externally by focusing on them with high-frequency ultrasound. Because a single ablation can process only a small volume of tissue, a succession of ablations is required to treat a large volume of cancerous tissue. In order to maximize the therapeutic effect and reduce side effects such as skin burns, careful preoperative treatment planning must be performed to determine the focal location and sonication time for each ablation. This paper proposes a novel optimization algorithm, called the thermodynamic equilibrium algorithm (TEA), inspired by the behavior of thermodynamic systems reaching their equilibrium states. Like other evolutionary algorithms, TEA starts with an initial population. Gas chambers at various thermodynamic states are employed as representatives of the population individuals, and the equilibrium state is regarded as the global minimum. The movement of thermodynamic parameters in the direction of reducing the temperature gradient forms the basis of the proposed evolutionary algorithm. During this movement, the second law of thermodynamics is checked to ensure that entropy will increase in each process. This movement leads to the state where most of the systems are at equilibrium. In this state, the systems are localized at the same position and have the same cost as the global minimum. The TEA was applied to several well-known unconstrained and constrained benchmark cost functions, and the performance was compared with other well-known optimization algorithms. The results showed that the TEA has high potential to handle various types of optimization problems with a good convergence rate and high precision. Finally, the suggested evolutionary approach is applied to HIFU treatment regimens adopting a map of patient-specific material properties and an accurate thermal model. High-quality treatment plans could be created using the suggested method, and the average amount of tissue that is over- or under-treated was less than 0.08 percent.

Distribution of problematic localized facial infantile haemangiomas and their response to propranolol: a retrospective cohort study

The distribution and response to propranolol of problematic facial infantile haemangiomas (IHs) has rarely been described in the literature. To map problematic facial IHs and observe their response to propranolol. Eligible patients were categorized according to focal location and cohorts corresponding to these (buccal, medial, zygomatic, lateral and multiregional) were created. The primary efficacy variable was regression score ranging from 1 to 4, calculated using results of colour Doppler ultrasonography. In total, 104 patients met the inclusion criteria. There were 32 (30·8%) IHs located in the buccal area, 12 (11·5%) in the medial area, 49 (47·1%) in the lateral area and 1 (1·0%) in the zygomatic area, with 10 (9·6%) IH cases having multiregional lesions. We found that the distribution pattern of most IHs matched the surface projection of the trunk of the external carotid and the facial arteries. Further analysis showed that the median regression score in the buccal and medial groups were significantly lower than those in the lateral and multiregional groups. Treatment of buccal and medial haemangiomas tends to be more challenging and their distribution pattern mainly reflects the direction of the facial vessels.

S.M.A.R.T. F.U.S: Surrogate Model of Attenuation and Refraction in Transcranial Focused Ultrasound

Low-intensity focused ultrasound (LIFU) is an increasingly applied method for achieving non-invasive brain stimulation. However, transmission of ultrasound through the human skull can substantially affect focal point characteristics of LIFU, including dramatic attenuation in intensity and refraction of focal point location. These effects depend on a high-dimensional parameter space, making these effects difficult to estimate from previous work. Instead, focal point properties of LIFU experiments are often estimated using numerical simulation of LIFU sonication through skull. However, this procedure presents many entry barriers to even computationally savvy investigators and often requires expensive computational hardware, impeding LIFU research. We present a novel MATLAB toolbox (data: doi:10.5068/D1QD60; Matlab Scripts: https://doi.org/10.5281/zenodo.5811122) for rapidly estimating beam properties of LIFU transmitted through bone. Users provide specific values for frequency of LIFU, bone thickness, angle at which LIFU is applied, depth of the LIFU focal point, and diameter of the transducer used and receive an estimation of the degree of refraction/attenuation expected for the given parameters.

Generating patient-specific acoustic simulations for transcranial focused ultrasound procedures based on optical tracking information

During transcranial focused ultrasound (FUS) procedures, accurate targeting is important and neuronavigation with optically tracked tools is used to estimate the free-field focal location on pre-acquired images. Offline neuronavigation systems do not typically incorporate aberrating effects of the skull known to displace and distort the focus. Here, we developed a pipeline that integrated patient-specific acoustic simulations informed by transformations from optically tracked FUS procedures as a tool to evaluate transcranial pressure fields and demonstrated its use in three FUS scenarios: magnetic resonance imaging-guided (MR-guided) phantom experiments, MR-guided non-human primate (NHP) experiments, an offline behaving NHP experiments. Distance vectors between the estimated focus from optical tracking and peak intracranial location from simulations were less than 1 mm for all groups (Phantom: 0.6 ± 0.3 mm, NHP: 0.7 ± 0.3 mm, Behaving NHP: 0.5 ± 0.2 mm). Comparisons of the target registration error of MR measurements with the optically tracked focus (TRETracked) and simulated focus (TRESimulated) suggest that focal location errors are dominated by optical tracking errors rather than aberration through the skull in the NHP (Phantom: TRETracked: 3.3 ± 1.4 mm, Phantom TRESimulated: 3.3 ± 1.9 mm, NHP TRETracked: 3.9 ± 1.9 mm, NHP TRESimulated: 4.1 ± 1.6 mm). Our software pipeline provides patient-specific estimates of the acoustic field during transcranial FUS procedures.

Simultaneous Second Harmonic Generation and multiphoton excited photoluminescence in anatase TiO2 nano powders

Second Harmonic Generation (SHG) and Multiphoton Excited Photoluminescence (MEPL) are observed in retro-reflection mode from a 22 nm diameter anatase TiO2 nanoparticle powder. Depth intensity profiles are obtained by scanning the fundamental beam focal point through the TiO2 powder surface into its volume for the energy of the incident photons tuned around the anatase TiO2 band-gap energy of 3.2 eV. Evidence for the appearance of both SHG and MEPL is presented, their relative contribution depending on the conditions of photo-excitation, in particular the fundamental wavelength and the focal point depth location. MEPL dominates at fundamental photon energies matching the band-gap energy whereas below and above the band-gap SHG is clearly seen. Depth intensity profiles exhibiting a rising edge determined by the fundamental laser beam focusing conditions and a decreasing edge determined by extinction and multiphoton scattering strongly differ between SHG and MEPL, SHG profiles being by far narrower than that of MEPL. Re-absorption of the emitted SHG and MEPL light occurs due to the spectral proximity with the TiO2 band gap energy but excitation with fundamental light below band-gap further suggests that the intrinsic difference between the two SHG and MEPL processes is responsible for the contrasted depth profiles. This combined study where both SHG and MEPL occur presents perspectives in the study of the photonic properties of powder materials.

Numerical study on the vertical response of LNG carrier in abnormal waves generated with different mechanisms

To investigate the response difference of a ship encountering the same temporal abnormal waves formed with different physical mechanisms, three abnormal waves are generated with both linear and nonlinear focusing methods. These waves have the same crest height and trough-to-trough period as the New Year Wave. And the induced vertical responses of a LNG carrier are comparatively studied when these three abnormal waves focus at different sections of the ship hull moving with various speeds. Although the temporal profiles of abnormal waves are almost identical, their spatial profiles at the instant of focusing can be different, resulting in the distinct hydrodynamic characteristics between the linear and nonlinear focused abnormal waves. Consequently, the responses of LNG carrier are different, mainly due to the discrepancy in the Froude-Krylov forces. Besides, the focal location and ship forward speed can also significantly influence the peak response of LNG carrier for the given abnormal waves. Finally, some parameters associated with the spatial profile of abnormal wave seem to be more promising to work as indices to illustrate the corresponding generation mechanism and hydrodynamic property, as well as potentially induced extreme ship responses.

Seeing is visiting: discerning tourists’ behavior from landmarks in ordinary photos

The unprecedented development of the internet has compelled a growing number of tourists to share their photographs on social media. These images convey valuable memories and points of interest. As photography and content sharing have become commonplace among visitors, pictorial digital footprints represent a prevalent topic in tourism research. Studies on tourists’ movement trajectories hold great importance for destination management, marketing, and services. Flickr is a popular source in photo-based tourism research given the digital footprints embedded in photos’ metadata; however, the site’s bottlenecks (e.g. declining user activity, overly professional photographs) raise concerns. Scholars have instead gradually shifted their attention to emerging photo platforms such as Instagram—yet these pictures do not contain geographical information. Taking Beijing as a focal location, we introduce an approach in which landmark recognition complements the geographical cues in Instagram photos. Instagram check-in data and data identified through landmark recognition are validated. Ultimately, the recognized landmark information appears highly correlated with check-in data. This study demonstrates the feasibility of landmark recognition for extracting tourists’ footprints from ordinary content in user-generated photos. Findings also confirm that many photos from general social media platforms can serve as alternative and representative data sources in photo-based tourism research.